& Digitized by the Internet Archive in 2016 ' v-.’ v. https://archive.org/details/manualofchemistrOOwebs y r ■ Tv 'IV MANUAL OF CHEMISTRY, CONTAINING THE PRINCIPAL FACTS OF THE SCIENCE, THE ORDER IN WHICH THEY ARE DISCUSSED AND ILLUSTRATED IN THE LECTURES AT HARVARD UNIVERSITY, N. E. AND SEVERAL OTHER COLLEGES AND MEDICAL SCHOOLS IN THE UNITED STATES. COMPILED AND ARRANGED AS A TEXT BOOK FOR THE USE OF STUDENTS, AND PERSONS ATTENDING LECTURES ON CHEMISTRY. THIRD EDITION, COMPRISING A SUMMARY OF THE LATEST DISCOVERIES AS CONTAINED IN THE WORKS OF BRANDE, TURNER, THOMSON AND OTHER DISTINGUISHED CHEMISTS, ILLUSTRATED WITH UPWARDS OF TWO HUNDRED ENGRAVINGS ON WOOD. BY JOHN W. WEBSTER, M. D. ERVING PROFESSOR OF CHEMISTRY AND MINERALOGY IN HARVARD UNIVERSITY. BOSTON: PUBLISHED BY MARSH, CAPEN, LYON AND WEBB. Entered according to Act of Congress, in the year 1839, By Marsh, Capen, Lyon and Webb, In the Clerk’s Office of the District Court of Massachusetts. TUTTLE, DENNETT AND CHISHOLM’S POWER PRESS, No. 17 School Street, Boston. i* TO JOHN GORHAM, M. D. LATE ERVING PROFESSOR OF CHEMISTRY, AND JAMES JACKSON, M. D . HERSEY PROFESSOR OF THE THEORY AND PRACTICE OF PHYSICK, IN HARVARD UNIVERSITY, EMERITUS, THE FOLLOWING PAGES ARE INSCRIBED. Harvard University, 1823. ADVERTISEMENT TO THE THIRD EDITION, The two former editions of this work were based upon the excellent Manual of Professor Brande, but the progress of chemical science has rendered it necessary to deviate so much from his arrangement, that in the present edition it has been entirely remodelled. In several institutions, where this work had been in use as a text book, it became necessary to seek for some other, in consequence of its having become out of print. Several editions of Dr Turner’s Elements of Chemistry having ap- peared in this country, under the able supervision of a gentleman eminent for his scientific attainments, that work was adopted in many institutions. As Dr Turner’s work was not so practical and elementary as was desirable, a new edition of it, calculated to meet the wants of beginners, was commenced by the compiler of this, but was subsequently relinquished on learning that Professor Bache was preparing a new edition of the former. In August, 1838, a part of this new edition was published, since that time no more of it has appeared. The delay was attributed to the decease of the author, but it was soon aftei; announced that the publication of the sixth edition of the Elements would be continued by the brother of Dr Turner and Professor Liebig. A portion of their joint work appeared in London, a part of which was republished in this country, and a few pages followed in England on organic chemistry. More than a year has elapsed and no more has been published. Under these circumstances, and at the repeated request of gentlemen connected with various colleges, a new edition of this Manual was commenced and has been completed, in which is incorporated much of the most important elementary part of Turner and Liebig’s work. It was deemed advisable to reduce the size of the work, and to embody more practical details and more copious experimental illustrations, than are generally given in the larger works. This edition has therefore been compiled from the volumes of Turner, Brande, Faraday, Liebig, Thomson, and others, and as an introduction to them, with no more alteration than was required to preserve uniformity and connexion.* The frequent references and designation of the writers’ * Numerous errors (probably of the press) in the English edition of Turner and Liebig’s work have been corrected. VI Advertisement. names by the initial letters, will enable those who are desirous of studying the subjects more in detail to turn to the originals. Chemical formulae have been largely employed in the present edition : those of Turner and Liebig, so far as they have been used in the three parts of the sixth English edition of Turner’s Elements that have appeared. Dr Thomson’s recent volume,* the most complete treatise on Organic Chemistry which we have in the English language, has been made the basis of the division to which it relates. In that work the author has, with vast labour, collected and embodied the materials that have been for several years accumulating from the labours of the French and German chemists, and which are scattered through so many of their works and journals. Although in Organic Chemistry the arrangement of Dr Thomson has been, for the most part, followed, it has not been rigidly adhered to, as it promised more advantage to the beginner to connect the description of some substances more immediately with the bodies affording them. As but a very limited portion of time is given to the department of what has been usually called Animal Chemistry, in most institutions and courses of lectures, it was concluded that a very concise chapter would answer the purpose. Many of the facts also that have usually been arranged in that division, are previously alluded to in the preceding chapters. It was therefore thought that the account of animal substances in the text book of Dr Reid, of Edinburgh, with some additions, would be sufficient. In regard to chemical analysis its details have now become so extended, that they require a distinct work, and as those who intend to prosecute them must very much rely upon their familiar acquaintance with chemical science, and refer to the treatises particularly devoted to this depart- ment, what related to that subject in former editions has been omitted. No one who intends to prosecute chemical analysis will fail to consult the ample details of Rose, Berzelius, Faraday, Dumas, and the various Journals and Transactions in which the original analyses and papers have appeared. Electricity and Electro-Magnetism, are now most usually discussed in collegiate courses of instruction in the department of Mechanical Phi- losophy. The description of complicated apparatus has been avoided, as such is seldom attainable by the pupil and not necessary for elementary study. So also has it been thought sufficient to refer, for abstruse points of theory, and description of complicated processes, to original papers, to which those who zealously undertake the study of chemistry will necessarily have recourse. The full descriptions of processes in the Chemical Arts , given by Dr Ure in his lately published Dictionary of Arts and Manu- factures , have rendered it unnecessary to retain many in the present edition of this work. Copious tables of chemical formulae and of atomic weights, which had been prepared, have been omitted, as it was found that their insertion Chemistry of Organic Bodies. London: 1838. pp. 1076. Advertisement . Vll would have materially increased the size and expense of the volume, and such are at hand in the larger works on the science. To the gentlemen who have aided the progress of the work, by public documents, valuable suggestions, or written communications, the compiler would express his obligations, especially to the Honorable John Quincy Adams, R. M. Patterson, Esq., of the U. S. Mint, Professor Silliman, A. A. Hayes, Esq., Drs C. T. Jackson and S. L. Dana, as also to Francis Peabody, Esq., of Salem, for his usual liberality in allowing several new instruments, from his richly appointed laboratory, to be copied and described. In accordance with a ,better taste which prevails among the scientific men of Europe, all titles have been omitted, it being deemed sufficient that the names quoted are considered as authorities . Harvard University, Cambridge, 1839. Note — All the articles of apparatus figured in this work are now manufactured or fur- nished by N. 13. Chamberlain, Philosophical Instrument Maker, School-street, Boston. The glass apparatus is beautifully made by the New-England Glass Company, and Electro-Mag- netic Apparatus by Daniel Davis, Jj Cornhill, Boston. NOTE. The letter D. refers to Davy’s Elements of Chemical Philosophy . H. “ Henry’s Chemistry. U. “ Ure’s Dictionary of Chemistry. M. “ Murray’s System of do. T. “ Turner’s 1st and 2d part. Tr5 “ “ Elements , 5th edition. T. and L. refer to Turner and Liebig’s continuation. T. in chap. ix. refers to Thomson’s Organic Chemistry. B. “ Brande’s Manual. F. “ Faraday’s Chemical Manipulation. EXPLANATION OF PLATES. Description of Frontispiece. Figs. 1 and 2 represent a modification of the Argand lamp, contrived by Dr C. T. Jack- son, and which he has called oxyalcohol and air blast lamp. Fig. 1. A, reservoir for alcohol containing JO oz. measures; B, connecting tube from reserv oir to burner ; C, burner containing the elevator and blow-pipe; D, blast tube for oxy- gen or air from the bellows or gasometer ; e e, inner cylinder or blow-pipe^ expanded to a trumpet form at top, where the opening may be regulated by turning the screw L t, so as to bring it nearer or farther from the interior lip of the elevator,//, the space ought to be ytW inch, g g. wick elevated by means of a spiral groove in the elevator, //, and the outer cylinder, h h, vylrieti has a slit and points to move it by turning the chimney-holder, i i. k k , chimney made of mica and supported' by two copper rings and strips, see Fig. 3. Fig. 2. The lamp ready for work. A, reservoir; B, burner ; C,. blast tube connected with the gasometer or bellows pipe, and controlled by a cock in order to shut off or let on the blast at pleasure; E, crucible of platina on a stand ring and support fixed by the clamps e and/; g , screw for fixing the lamp at any required height on the rod or stand ; A, brass retort ring for larger vessels used to support a retort, or for evaporations, digestions, &c. Fig. 3. Copper frame for a mica chimney. The mica being rolled it is inserted so that the lapping edges come under one of the copper strips, k k. When the ends of the copper strips are bent down and pressed tight so as to secure the mica in place : one frame will outlast many mica chimneys. Fig. 4. i, india-rubber cloth bag and weighty, for oxygen gas, when a gasometer is not at hand. When the lamp is to be used, the reservoir is charged with alcohol at 90° strength, and if oxygen gas is to be employed, a little “ spirit gas” may be added, but good alcohol is preferable. The cup is unscrewed from the bottom of the burner and tne lower orifice closed by a good cork. The blast tube is raised or depressed as required to produce thp best effect on the flame. The platinum crucible is heated to full redness by the natural current of air ; then^ having raised the wick, on urging a blast by means of bellows, a very intense heat will be obtained. This lamp is very powerful when used with’ oil and a blast of hot air, the air being heated in a copper tube over a charcoal fire in a wire grate ; ail the smoke is consumed. With this lamp a piece of lime or magnesia may be as intensely ignited as in Drummond's apparatus (251). By throwing a current of oxygen gas outside the flame, a more perfect combustion of oil takes place, but the wick will then require to be elevated by means of a rack and pinion. The outside current is, however, not wanted, a sufficiently high temperature for most pur- poses being obtained without it. These lamps are manufactured by Hooper and Blake, Boston. Fig. 5, represents an air pump constructed by Chamberlain, of Boston, for Harvard College. The internal length of the barrel is 13 inches, and the diameter 4 inches. The piston rod passes through an air-tigbtcollar, the upper part of which is concave, to receive oil, and into which the oil that is thrown out when the piston is elevated, is conveyed by a small bent tube passing out of the upper flange over the upper valve. The lower valve is formed by 6 small holes covered with leather, and there is a similar valve in the upper flange opening upwards. By this arrangement the atmospheric pressure is cut ofF, and after the first stroke by which the air above the piston is removed, the pump can be worked with great ease and rapidity. Within the receiver on the pump-plate, is represented a section of an improved method of exposing water to sulphuric acid (195/ The glass dish has an opening in its centre, on the elevated edge of which the small dish containing the water is securely supported. Fig. 6 and 8 represents the arrangement for covering the water with a brass plate, (see note page (>0,) while the exhaustion is making. The plate is then raised by means of the rod which passes through an air-tight cap, and the water freezes. X Description of Frontispiece. The piston is constructed of two plates of brass and one piece of leather , the lower f date being of the same diameter as the barrel, the upper plate is small enough to admit the eather turning up between it and the barrel ; the whole piston is only one half or five eighths of an inch thick. Fig. 6 is an enlarged section of the barrel and piston of the pump. Fig. 7, represents De Luc’s electrical columns, consisting of many hundred discs of sil ver-leaf and thin discs of zinc, alternating with writing paper, or silvered paper and zinc, or silvered paper and oxide of manganese, so arranged within the vertical and parallel glass tubes, that the dissimilar metals are in contact, and each pair thus formed, is separated by the paper. The tubes are terminated by small bells in metallic connexion with the upper discs. The series commences with silver in one tube and is terminated by zinc, or the other metal employed, while, in the other tube, the order of the discs is reversed. A deli- cate metallic clapper suspended between the columns, on a glass support, will be attracted and repelled. See page 92. Fig. 9, is a representation of Clarke’s electro-magnetic machine. A, horse-shoe magnets confined to the upright support by a clamp and screw. B is the armature, with coils of silked copper wire, which revolves in front of the poles of the magnets, mo- tion being communicated by the wheel C, which is turned by the hand. D H, Drake-pie- ces. The terminations of the coils are soldered to a brass cylinder, being insulated by a piece of hard wood attached to the brass stem. O O, iron wire springs pressing against the cylinder F, at one end Q, Q,, a metal spring that rubs upon the brake-piece H. T, a bent copper wire connecting brass straps, on the block L Thus E, if, Q,, P, N, are in connexion with the commencements of each coil, and F, O, M, with the ter- minations. Fig. 10 shows the arrangement for decomposing water by means of the above. Water is placed in a glass tube B, in a glass vessel A, through the bottom of which the platinum wires pass. To the glass vessel a brass cup is attached, from which proceed stout wires passing into holes in the brass straps on M and N. The wire Q, rubs on the break-piece H. When the armature is made to revolve the decomposition of the water takes place. For a more particular description see Clarke’s account of the instrument, &c. in Amer Jour. vol. xxx. 100. Fig. 11 represents a new self-registering thermometer, which was exhibited at the last meeting of the British Association. A is a glass tube filled with pure spirit of wine. B is a continuation of the same, but much smaller, which is to be about half full of quicksilver to support the spirit in the long tube. Upon the quicksilver at G, i9 a float supporting the wire C, which wire has a knee or bend in it, with a small eye, which runs upon the fixed wire D, carrying an index or pointer ; E is the scale whicn must be made experi- mentally. If any change takes place in the bulk of the spirit, the quicksilver is also af- fected, and with the silver the ivory float G, carrying the index or pointer, which shows at once the degree of temperature upon the scale ; this is the simple action of the thermome- ter - To make it register, the two light indexes or pointers F, move upon the wire D, their own friction keeping them wherever they are placed. To set it, the pointer F, below the thermometer’s index, must be pushed close up to it, and the pointer F, above, pushed down it ; and it is evident that if any change of temperature takes place, the thermometer’s in- dex will move the registering index eithei above or below, and leave it there, thereby showing the extreme rise and fall of the thermometer in any given time The action of the air upon the quicksilver is also provided against EigJuk Rep. Brit. Assoc. 1839 I PLATE 1 PLATE II. Plate I. Apparatus for the Solidification of Carbonic Acid , Fig. 1. A. A cylinder of wrought iron, 23 inches in length, 4 in diameter, terminated by cast iron hemispheres; supported by two gudgeons on an iron frame, upon which it revolves. d. A copper tube closed at bottom, for holding acid. D. The same j. brass hook for removing the acid holder. Fig. 2. B. Cylinder of wrought iron to receive the gas. Of the same size as A. h. A small tube passing down to within a short distance from the bottom, up which the lique- fied gas is forced by the pressure of the gas above. E. A brass box, 4 inches in diameter 4 in depth, to receive the solidified gas. o. The same without the cover, shewing the interior ; the horizontal pipe, (the mouth of which is also seen in E, under the upper clamp by which and the one below, the cover is confined when the box is used,) fits upon a short jet 3. The centre of each part of the box is pierced with several small holes communicating with the wooden handles, which are hollow and open to allow of the escaj e of the expanding gas- In front of the inner mouth of the horizontal pipe is a short curved slip oi sheet brass for tne purpose of preventing the solidified gas being too rapidly driven out of the handles. f. A copper pipe 16 inches in length and | inch in diameter, terminated by connecting pieces, by meansot which the two iron cylinders can be connected, for the transfer of the gas. g. A hold-fast of iron with a small projection that fits into the hole W in fig. 1. By this the cylinder can be secured from turning when the plug or valve is opened. li . A wrench for turning the plug i. Small brass wrench for turning the steel screw of the valve-plugs in the upper parts of the cylinders A. B. m. A vessel of zinc, holding the quantity of water required for each charge. n. A funnel of zinc for introducing the carbonate of soda into the cylinder A. Fig. 3- Section of one of the connecting screws and pipe ; the small projecting part on the flange of the pipe fits into the outlet of the screws of the valve plugs l and 2. The cylinder A may be called the Generator, B the Receiver. The materials employed for each charge of the Generator, are, Bicarbonate of Soda in powder 2| lbs. ; Water at 100° 6£ lbs.; Sulphuric acid 1 lb. 7^ oz. . „ The valve plugs are of brass and alike, but a section of one only is represented (in Fig. 1. A.) with a double cone of steel, which is accurately ground to its seat ; the stem is cut into a fine screw and passes through the upper part of the valve-plug, it is screwed up or down by means of the wrench i having a square hole into which the square end of the stem fits. It will be seen that when the cone is screwed up there is an outlet for any gas from the cylinder through the horizontal branch of the valve-plug, and when it is screwed down the passage is closed. The opening under the cone, through the lower part of the valve-plug, is one tenth of an inch diameter. When the cone is screwed up no gas can escape above it, as the upper part is also well ground to a conical cavity. To charo-e the generator. Unscrew the valve plug and remove it from the end ot the cylinder ; through the funnel n pour in the soda salt; add the warm water, remove the funnel, and with a stick stir the salt and water, breaking down any lumps. Pour the sulphuric acid into the copper acid holder D, and with the hooky introduce it into the generator. Remove the hook and having carefully cleaned all the screws with a tooth brush (not with a cloth) and oiled them, screw in the valve plu^ making it secure by the aid of ihe wrench and holdfast. Screw down the steel valve firmly.° Turn the generator and cause it to revolve several times, that the acid may be thrown upon the soda ; repeat this and occasionally allow the cylinder to remain with the valve downward. Let the generator remain 5 or 10 minutes in the position represented in the plate, until the gas has disengaged itself and collected in the upper part of the cylinder Haying pre- viously cooled the receiver in iced water (in which it should be immersed up to the valve) con- nect it with one end of the pipe/ securing the screw with a wrench. Connect the other end ol the pipe with the valve plug of Fig. 2. B also very firmly. Open the steel valve of the receiver by screwing it up entirely — then, slowly, and partially, open that of the generator. the S as will pass over and in about two minutes the pressure will be equalized, no more gas then pass- ing • close the steel valve of the receiver and then that of the generator. Disconnect the gen- erator, open the valve to allow the remaining gas to escape, having a vessel ready to receive the liquid which soon follows. When no more liquid passes out, remove the valve-plug, place it m a basin of clear water ; and having lifted out the acid holder, pour out the sulphate ot soda and wash out the inside of the generator with water. Repeat the charges in the same manner XIV Explanation of Plates. as long as any gas is heard to pass from the generator to the receiver. Nine charges I have ^usually found sufficient, which, if well managed, will completely till the box E with solid gas ‘several times. To obtain the solid. Having previously cooled the box in ice, wipe it dry and secure the top on with the clamps. Screw the coupling and short jet (3) upon the valve plug (as represented I) of the Receiver. Place the receiver between the knees, and the box upon the jet. Open the steel valve, slowly, until a white vapour issues from the handle^ of the box; gradually enlarge the opening, and when the brass box has become thickly covered with the condensed and frozen vapour of the apartment, the farther escape of the gas may be stopped by closing the valve. On removing the box and opening it, the while solid acid will be found within. The greatest care is necessary to avoid introducing any dirt, fibres of wood, cloth, &c. into the vessels, as they are liable to be forced under the valves and into the small tubes oud thus defeat the process. Plate II. Figs. I and 2 represent a method of washing precipitates : which will bo often found use ful. By this arrangement a column of pure water can be made continually to pass through a powder or precipitate. A flask, or bottle a, fig. 2, is filled with water and is closed by a cork, having a glass tube of the shape, fig. 1, passed through it. This tube may be about four inches in length and half an inch iu diameter. When the flask or bottle is inverted as in fig. 2 u, the water will run out only till the air within it is expanded to a certain degree, the capillarity of the tube a fig. I, not allowing the escape of any water into the air. But if the tube ham,f the water thus retained does not always appear to act this part, but to be in a peculiar state of combination. This he calls con- stitutional water ; being that which is essential to the existence of Constitu- tive salt. It differs from basic water, by not being removed even byjg 0 ^ wa ' the most powerful alkalies, but is readily removed, and its place as- sumed, by certain anhydrous salts. The character of water in these different states of combination will be understood from the following example. Crystals of phosphate of soda are composed of 1 propor- tion phosphoric acid, 2 soda, and 25 water. At the temperature of 212°, 24 proportions of the water are expelled ; but the 25th propor- tion is retained, and a red heat is required for its complete separation. By the loss of the 24 proportions the crystalline form and texture of the salt are destroyed, but the residual mass has all the properties of the common phosphate ; whereas, by the loss of the 25th proportion, an entirely different salt, the pyrophosphate of soda, is produced. 23. In some cases the proportion of water is removed by an equi- Water re- valeht of any base that supplies its place in the compound ; in others moyed> it is not affected by bases, but may be removed by certain anhydrous salts which occupy its place, and give rise to the formation of double salts. The former, as acting the part of a base, is the basic water ; the latter, as influencing the constitution of a salt, is the constitu- tional water. 24. The difference is denoted in symbols, by writing the basic Denoted by . ’ symbols. * Those crystals which effloresce by exposure to air, may often be conveniently pre- served, by slightly oiihig their surfaces. The best method is to soak the crystals in oil for a few hours., and then to wipe them and put them up in bottles. t Phil. Trans. Edin. , xii. 297. 6 Chap. I. Decrepita- tion. Watery fu sion. Crystal- lization promoted By a nu- cleus. Method of obtaining perfect crystals. Crystal- lization af- fected by circum- stances, By pres- sure. Attraction — Crystallization. water, as is the case with all bases, on the left side of the acid with which it is combined, and the constitutional water on the right. Hence the symbol of the crystals of phosphate of soda is 2NaO. HO, P0 5 +24Aq. 25. Salts, in crystallizing, frequently enclose mechanically within their texture particles of water, by the expansion of which, when heated, the salt is burst with a crackling noise into smaller frag- ments. This phenomenon is called decrepitation. Those crystals in which the water of crystallization is so abundant, as to liquefy them when its temperature is raised, are sometimes said to undergo the toatery fusion. 26. Some salts, in consequence probably of their strong attraction for the water that retains them in solution, cannot be brought to crys- tallize in the ordinary way. In such cases, crystallization may be effected by the addition of substances having a strong affinity for wa- ter, by which its attraction for the dissolved matters is weakened; thus alcohol, added to certain aqueous saline solutions, (as solution of nitre,) produces a separation of crystals, but they are generally small and indistinct. 27. Crystallization is accelerated by introducing into the solution a nucleus, or solid body, upon which the process begins ; and manu- facturers often avail themselves of this circumstance. Thus we see sugar-candy crystallized upon strings, and verdigris upon sticks. There are case^in which it is particularly advantageous to put a few crystals of the dissolved salt into the solution, which soon cause a crop of fresli crystals. In some instances, if there be two salts in solution, that will most readily separate of which the crystals have been introduced. 28. By placing a crystal of the same nature in a saturated solu- tion of a salt, and turning it daily, so that the different sides shall be successively exposed to the liquid, very large and perfect crystals may be obtained. 29. When two salts of different solubilities are present in the same solution, they often may be separated by crystallization, that which is least soluble constituting the earlier crop of crystals. 30. Sometimes crystallization is not effectual for the separation of salts. When the sulphates of iron and copper are in solution toge- ther, crystals will be obtained resembling those of sulphate of iron, but with very variable proportions of sulphate of copper in them, the latter salt being at times present in great quantity ; on other occa- sions triple salts arc formed. F. 254 . 31. The pressure of the atmosphere has been said to have consi- derable influence on crystallization. Thus a concentrated solution of sulphate of soda (Glauber’s salt), excluded from the air while hot, does not crystallize on cooling; but will generally crystallize when the air is admitted.* The theory of this phenomenon is not very ap- *The best method of exhibiting this, is to place several pounds of Glauber’s salt in a suitable vessel, and to pour upon it two parts of water to three of salt; boil it, and while hot strain the solution through a coarse cloth, into a tall, wide, thin glass jar, previously warmed ; over the mouth of the jar a piece of wet bladder is to be securely tied, and the whole left to cool. When quite cold, a puncture of the bladder with the point of a knife will often be followed by crystallization of the salt — if it should not commence, the introduction of a fragment of the salt will be required. The tempera- Primitive Forms. 1 parent. It does not depend upon atmospheric pressure, for the solution may be cooled in open vessels, without becoming solid, pro- vided its surface be covered with a thin film of oil ; and Turner succeeded with the same experiment without the use of oil, by caus- ing the air of the vessel to communicate with the atmosphere by means of a narrow tube. It appears from some experiments of Graham,^ that the influence of the air may be ascribed to its uniting chemically with water ; for he has proved that gases which are more freely absorbed than atmospheric air, act more rapidly in producing crystallization. 32. The presence of light also influences the process of crystalli- zation. Thus we see the crystals collected in camphor bottles in druggists’ windows always most copious upon the surface exposed to light ; and if we place a solution of nitre in a room which has the light admitted only through a small hole in the window shutter, crystals will form most abundantly upon the side of the basin most exposed to the aperture through which the light enters, and often the whole mass of crystals will turn towards it. Many saline solutions form arborescent crystalline pellicles, when left to spontaneous eva- poration, which slowly travel up the sides of the basin, and gradually proceed down upon the outside ;t this process also always begins on the side nearest the light, and is often confined to it 33. It is commonly observed, that crystallized bodies, affect one form in preference to others. The fluor spar of Derbyshire crystal- lizes in cubes : so does common salt. Nitre assumes the form of a six-sided prism, and sulphate of magnesia that of a four^sfded prism. These forms are liable to vary. Fluor spar and salt crystallize sometimes in the form of octohedrons ; and there are so many forms of carbonate of lime, that it is difficult to select that which most com- monly occurs. 34. Rome de Lisle referred these variations of form to certain truncations of an invariable primitive nucleus; and Gahn afterwards observed, that when a piece of calcareous spar was carefully broken, all its particles were of arhomboidal figure. This induced Bergman to suspect the existence of a primitive nucleus in all crystallized bo- dies.! This subject was more extensively prosecuted by Haiiy. He determined the primary forms of minerals, and showed how sec- ondary forms could be derived from them by simple laws of decre- ment.^ 35. Haiiy obtained his primary forms by mechanical division: thus hy the skilful division of a six-sided prism of calcareous spar, he reduced it to a rhomb, precisely resembling that which is known under the name of Iceland crystal. Other forms of calcareous spar were subjected to the same operation ; and, however different at the outset, finally agreed in yielding, as the last product, a rhomboidal solid. ture of the jar will rise during the change from the fluid to the solid state. If a glo- bular vessel, as a matrass, is employed, it will often be broken during the crystalliza- tion. The crystallization will olten take place on slight agitation without the access of air. * Phil. Trans. Edin. 1828- See also N. Edin. Jour. xiii. 309. + This may be prevented by smearing the edge of the vessel with oil. t Phys. and Cherti. Essays, Yol. II. p. 1. § TraiU de Min. Paris : 1801. Sect. 1. By light. Assume one form rather than another. Primitive nuclei. Hatty’s primitive forms. 8 Attraction — Crystallization. Chap. I. Daniell’s method. Wollas- ton’s theo- ry- Fig. 7. It was discovered also by Haiiy, that if we take a crystal of another kind (the cubic fluor spar, Derbyshire spar, for instance,) the nucleus obtained by its mechanical division, will have a different figure, viz. an octohedron.* 36. A method of developing the structure of crystals, has been described by Daniell.t It consists in exposing any moderately soluble salt to the slow and regu- lated action of a solvent. Thus if a lump of alum is placed in water, after some days, oetohedrons and sections of octohedrons will be seen in relief upon its lower part. (Fig. 7.) The crystal- line forms of metals may be in a similar manner developed by immersion in di- lute acids. 37. From the imperfect explanation of many of the appearances of crystals, afforded by the theory of Haiiy, Wollaston proposed to consider the primitive particles as spheres, which, by mutual attrac- tion, have assumed that arrangement which brings them as near as possible to each other. By the due application of spheres to each other, he has shown that a variety of crystalline forms may be pro- duced.f ♦The primary forms of HaOy are reducible to six; the paralleiopiped, fig. 1. which includes the cube, the rhomb, and all the solids which are terminated by six faces, parallel two and two ; the tetrahedron, fig. 2 ; the octohedron, fig. 3 ; the regular hexahe- Fig. 1. Fig. 2. I ig. 3. drnl prism, fig 4 ; the dodecahedron with equal and similar rhomltoidal planes, fig. 5 ; and the dodecahedron with triangular planes, fig. 6. Fig. 4. Fig. 6 Fig. 6. The instruments used for.mcasnring the angles at which the plaoes of crystals meet, or incline to each other, are called goniometers. For the description of these and the method of using them see Cleareland’s Mineralogy, chap. 2d. (edit. IS22-) Brooke's Crystallography, p. 25. t Jour, of Sd. and Arls, I. 24. t Philos. Trans. 1813, p. 51. Other and very different views of the subject of pri- mitive forms, have been taken by Brooke. Mohs and others. For more ample information on this subject consult the “ Familiar introduction to Crystallogra- phy, by H. J. Brooke”; Mohs’ Treatise on Mineralogy ; M Elements of Crystallo- graphy,'' hy G. Rose; or Whewell's Essay in the Phil. Trans. Lmd.. 1825 : “ She- s' Mineralogy ," aud " A System of Mineralogy including an (Mended Treatise on Crystallography , M by James D. Dana, M. D. New Haven : 1837. 9 Simple and Compound Forms. 38. The forms of crystals may be divided into simple and com- Sect- l pound; a simple form has all its faces equal and similar to each simple and other, while a compound form is bounded by at least two different compound classes of faces; thus figs. 8, 9, 10 are simple forms. Figs. 11, 12, furms ‘ Fig. 8. Fig. 9. Fig. 10. Fig. 11. Fig. 12. Fig. 13, six octagonal, and twelve quadratic. The lines round which the dif" Axes ferent parts of crystals are grouped, are called crystalline axes. It will be observed that in the figures 8, 9, 10, three right lines, which are equal in length and perpendicular to each other, may pass through the centre of the crystal ; in fig. 8 by joining the opposite angles, in fig. 9 by joining the centres of the opposite faces, and in fig. 10 by connecting the opposite angles formed by the meeting of four edges. These forms are thus connected by having the same axes of crystallization, and proceeding from these three equal and rectangular axes, either the octohedron, the cube, or the rhombic dodecahedron may be constructed, the resulting form depending solely on the law according to which planes are symmetrically arranged around the axes. 39. From the law that every plane shall pass through an extre- Laws. mity of each axis , results the octohedron fig. 8- This law limits the number of faces to eight, and as these intersect in the lines joining the extremities of the axes, each face is an equilateral triangle, and the resulting form is the regular octohedron. From the law that each plane shall pass through an extremity of one axis and be paral- lel to the other two> results the cube fig. 9. As each axis has two extremities, only six planes can be grouped around them, and by their intersection the hexahedron, or cube, is produced. In a similar manner may the rhombic dodecahedron, fig. 10, be shown to be formed according to the law that each plane shall pass through the extremities of two axes , and be parallel to the third. 40. Simple forms thus associated by being reducible from the same 2 10 Attraction — Crystallization. Cha P- i- axes, constitute what is termed a system of crystallization . Thus the Systems of octohedron, cube, and rhombic dodecahedron are three forms of the crystaUiza- octo ^ c< ^ ra ^ or re gular system. Such forms are connected still more intimately by the remarkable fact, that any substance which in crys- tallizing assumes one form of a system, may, and frequently does, as- sume other forms belonging to that system ; and what is still more remarkable, the same substance is not only capable of assuming dif- ferent forms of the same system, but during the act of crystallization, the faces of two, three, four, and in some cases even more, of these forms are simultaneously developed, whereby compound crystals of the greatest diversity of form and appearance are produced.* 41. A knowledge of all the simple forms of a system, as being those in which the same substance may occur, and which alone can give rise to compound crystals, is highly important. Haiiy first proved the existence of a mathematical connexion between them ; but we are indebted (o Weiss, of Berlin, for the distinction of the system of crystallization. He has shown that all crystalline forms may be brought under one of the six following systems, which may be distinguished as 1. The octohedrnl, or regular system. 4.. The oblique prismatic system. 2. The square prismatic system. 5. The square prismatic system. 3. The right prismatic system. 6. The rhombohedral system. 42. The octohedral system is characterized by the three equal and rectangular axes already described. If we suppose that two of the axes are horizontal, and the third vertical (figs. 8, 9, and 10), ? v c «i°«m dral the ^ aw symmetry is such, that if a face of a crystal be observed to bear a certain relation to one of the horizontal axes, other faces must fulfil the same condition to the other equal axes. From the perfect symmetry in the different parts of the crystal, this group is often called the regular system of crystallization. It consists of but few simple forms, the number being necessarily limited to the num- ber of different ways in which a plane can intersect the three axes. These are only seven. Number of 1. The plane may cut each at an equal distance from the centre, as in the octohedron (fig. 8). 2. The plane may cut two axes at an equal, and the third at a greater distance from the centre. The resulting- form is called the Triakisoctohedron. 3. The plane may cut two axes at an equal, and the third at a less distance from the centre. The resulting form is the Ikositetra- hedron. 4. The plane may cut all three axes unequally. The resulting form is the Herakisoctohedron. 5. The plane may cut two axes at unequal distances from the cen- tre, and be parallel to the third. The resulting crystal is the Tetrakishexahedron. 6. The plane may cut two axes in points equally distant from the system. forms. * Thus alum may crystallize in the form of a cube, or •'ctohedron. but the compound crystal, fig. II, is more common, where the faces of the cube truncate the angles of the octohedron. Fig. 12, is another form of the alum, where, in addition to the octo- hedron, the faces of the rhombic dodecahedron are also developed. Fig. 13 represents a combination of all three forms. Systems of Crystallization. 11 The form is the rhombic Sect. centre, and be parallel to the third, dodecahedron (fig. 10). 7. The plane may cut one axis, and be parallel to the other two. The form is the cube or hexahedron (fig. 9). Of these forms, 1, 6, and 7 are of frequent occurrence ; the others are usually found in combination. 43. The square prismatic system. The forms of this system Square are also characterized by three axes which intersect each other at prismatic right angles ; but they differ from those of the first system by two system ’ only out of the three, laeing equal. Let the third axis be supposed in a vertical po- sition (fig. 14), the octohedron formed is either longer or shorter in the direction of this axis, than in that of its horizontal’ axis. These octohedrons may be com- pared to a double four sided pyramid on a square base. The parts about the base are similar to each other, but differ from those about its upper or lower extremity; and this character distinguishes the system. 44. The right prismatic system. The crystals of this system are Right pris- Fig. 14, Fig. 15. Fig. 16. Fig. 17. malic sys- tem. like the preceding, characterized by three rectangular axes, and are distinguished from both by no two of these axes being equal. 45. The oblique prismatic system. The crys- tals of this system (fig. 18), differ from those of the last by the front and back parts being dissimilar. This is owing to two of the axes intersecting each other obliquely, while the third still remains perpendicular to both. Fig. 18. Oblique. 46. The double oblique system is readily re- cognized by the complete absence of all sym- metry in its crystalline forms. This results from all three axes intersecting each other obliquely ; owing to which the left and right sides, as well as the back and front, are of different crystalline values. Hence no two faces are connected except those which are parallel, and all symmetry of form disappears. Fig. 19. Double ob- lique. 12 Attraction — Isomorphism. Chap. I. Rhombohe- dral. Fig. 20. Discovery of Mitscher- lich. Isomorph- ism. Crystalli- zation and separation of isomor- phous sub- staucos. Advantages from iso- morphism, 47. The rhombokedral system. The forms of this system are, like the octohedral, characterized by three equal and si- milar axes ; but these axes intersect each other at equal, but not at right angles. Its most simple form is the rhombohedron (fig. 20), which is bounded by six equal and similar rhombic faces. The axes are obtained by joining the centre of the opposite faces.* 48. In the year 1819, a discovery, extremely important both to mineralogy and chemistry, was made by Mitscherlich of Berlin, relative to the connexion between the crystalline form and com- position of bodies. It appears from his researches,! that certain substances have the property of assuming the same crystalline form, and may be substituted for each other in combination without affect- ing the external character of the compound. Thus crystals pos- sessed of the form and aspect of alum may be made with sulphates of potassa and sesquioxide of iron, without a particle of aluminous earth; and a crystal composed of selenic acid and soda will have a perfect resemblance to Glauber’s salt. 49. To the new branch of science laid open by this discovery, the term isomorphism (from loos equal, and form) is applied : and those substances which assume the same figure, are said to be isomorphous. Of these isomorphous bodies, several distinct groups have been described by Mitscherlich.! 50. From the facts observed, the form of crystals is inferred to depend on their atomic constitution, and they at first induced Mits- cherlich to suspect that crystalline form is determined solely by the number and arrangement of atoms, quite independently of their na- ture, Subsequent observations, however, induced him to abandon this view ; and to incline to the opinion that certain elements, which are themselves isomorphous, when combined in the same manner with the same substance, communicate the same form. 51. Isomorphous substances crystallize together with great readi- ness, and are separated from each other with difficulty. Thus a weak solution of lime, which in pure water would be instantly indicated by oxalate of ammonia, is very slowly affected by that test when much sulphate of magnesia is present and Turner found that chloride of manganese cannot be purified from lime by oxalate of ammonia. The sulphates of zinc and copper, of copper and magnesium, of copper and nickel, of zinc and manganese, and of magnesium and manganese crystallize together, and have the same form as green vit- riol, without containing a particle of iron. These mixed salts may be crystallized over and over again without the ingredients being sepa- rated from each other. T. 418. 52. The tendency of isomorphous bodies to crystallize together, * For more minute details see Turner’s Elements , 6th edit. p. 409. t Ann. de Ch. ei dc Phys., vol. xiv. 172, xix. 350, and xxiv. 264 and 366. t For a table of isomorphous substances see Johnston's Report on Chemistry , in vol. 1st of Reports of British Association, 1831 — 2. § Daubeny, in Edin. Phil. Jour . vii. 108 - Chemical Attraction. 13 accounts for the difficulty of purifying mixtures of isomorphous salts Sect, n. by crystallization. The same property sets the chemist on his guard against the occurrence of isomorphous substances in crystallized minerals. It is a useful guide in discovering the atomic constitu- tion of compounds. For example, from the composition of the oxides of iron, and the compounds which this metal forms with other bodies, it is known that the sesquioxide consists of two atoms of iron and three atoms of oxygen; and, therefore, it is inferred that alumina, which is isomorphous with sesquioxide of iron, has a similar consti- tution.* 53. In connexion with chemistry, the theory of crystallization Connexion opens a new avenue to the science, and frequently enables us to a s- certain directly, that which, independent of such aids, could only be w ith chem- arrived at by an indirect and circuitous route. We frequently read istry- the chemical nature of substances, in their mechanical forms. In the arts, the process of crystallization is turned to very valuable account, in the separation and purification of a variety of substances. Section II. Heterogeneous Attraction , or Affinity. 54. Having considered attraction as disposing the particles of bo- Chemical dies to adhere so as to form masses or aggregates ; and in many i n . attraction stances, to arrange themselves according to peculiar laws, and to as- sume regular geometrical figures — we are now to regard this power as operating upon dissimilar particles ; as presiding over the com- position of bodies ; and as producing their chemical varieties. This is Chemical Attraction, or Affinity. 55. Chemical affinity, like the cohesive attraction, is effective on- Distin- ly at insensible distances ; but it is distinguished from the latter f r om h cohe- force, in being exerted between the particles or atoms of bodies of sive attrac- different kinds. The result of its action is a new compound, in tion - which the properties of the components have either entirely or part- ^^urac- ly disappeared, and in which new qualities are also apparent. tion. Thus, a piece of marble is an aggregate of smaller portions of marble attach- ed to one another by cohesion , and the parts so attached are the integrant parti- cles ; each of which, however minute, is as perfect marble as the mass itself. But the integrant particles consist of two substances, lime and carbonic acid, which are different from one another as well as from marble, and are united by chemical attraction. The integrant particles of a body are therefore aggregated togeth- er by cohesion ; the component parts are united by affinity. 56. The most simple instance of the exercise of chemical attrac- Instances, tion is afforded by the mixture of two substances with one another. Water and sulphuric acid, or water and alcohol combine readily. So when potassa is added to sulphuric acid chemical affinity is exerted, and they combine together. If the two last substances are examin- ed before being presented to each other, each will be found to be distinguished by peculiar properties. The potassa will convert the * Plesiomorphism (from the Greek near) is the term proposed by Miller to indicate the forms of substances that approximate but are not identical ; such have been brought forward by Brooke against the doctrine of isomorphism. See his essay, and the reply of Whewell, in Philos. Mag. and Ann. N. S- X. 161 & 401. 14 Attraction — Chemical. Chap i. Neutraliza tion, Distin- guished from satu- ration. The com- pound may nave dis- tinct pro- perties. Exp. 1. Exp. 2. Exp. 3. Results. blue colour of vegetable infusions* to green, the acid will turn them red. But if we gradually add the potassa to the acid, we shall obtain a liquid which will have neither the properties of the potassa or of the acid ; and which will no longer change the colour of the vegetable infusion, and the taste of which will have been converted into a bitter one. 57. In cases of this kind where chemical combination takes place, and the qualities of the component parts of a compound are no lon- ger to be detected in it ; the bodies combined are said to neutralize each other. 58. Neutralization is to be distinguished from saturation, (14) by which we express those weaker combinations where there is no re- markable alteration of qualities, as in cases of solution. — Water, for example, will dissolve successive portions of common salt, or sugar, until at length it refuses to take up more ; or is saturated; the so- lution retaining the saline or sweet taste and some other qualities of the salt or sugar. The only physical quality that is changed being that of cohesion. t 59. In many cases, the properties of the compounds resulting from chemical affinity differ essentially from those of their compo- nent parts, and a series of new bodies, possessed of distinct and pe- culiar characters, is produced. Thus when two volumes of nitric oxide gas (Deutoxide of Nitrogen) are mixed with one of oxygen, an orange-coloured gas results, very sour, ana soluble in wator, wheroas, the gases before mixture were colourless, tasteless, and insolu- ble in water. If into a glass vessel, exhausted of air, be introduced sulphur, and copper fi- lings, and heat he applied so as to melt the former, it will presently combine with the lattor. If we mix a quantity of iron filings and sulphur, nnd melt them in a crucible, we obtain a brittle mass which has properties different from those of either of its constituent parts. 60. We observe as the results of this attraction between these sub- stances, 1, that the substances produced have not the intermediate properties of their elements but that they present new characters , Te*t liquid. * An infusion of purple cabbage affords an economical and convenient liquid for this and similar purposes. For its preparation. <>no or more red cabbages should be cut into strips, and boiling water poured upon the pieces, a little dilute sulphuric acid is to be added, and the whole well stirred : it is then to be covered and kept hot as long as possible, or if convenient, should be heated nearly to boiling for an hour or two in a c »pper or earthen vessel. The quantity of water to be added at first should be sufficient to cover the cabbage, and the sulphuric acid should be in the proportion of about half an ounce of strong oil of vitriol bv measure to each good sized plant. This being done, the lluid should be separated and drained off. and as much more hot water poured on as will cover the solid residue, adding a very little sulphuric acid. The whole is to be closed up, and suffered to stand until cooled, and then the liquid poured off and added to the former infusion. The in fusion is to be evaporated to one half or one third its first bulk, poured into a jar, allowed to settle, and the clear red fluid decanted and preserved in bottles. This solution will keep a year. When required for use, the acid of a small portion of it should be neutralized by caustic potassa or soda, (not by ammonia.) when it will assume an intensely deep blue colour, andwill in most cases, require dilution with twelve or fourteen parts of water. Faraday. + Neutralizations are best effected with the assistance of heat, especially if a car- bonate be used, or if precipitation occur during the operation. The carbonic acid in the first case is dissipated, and in the latter the combination is more rapidly and perfectly effected. Evaporating basins are highly useful for these purposes, their contents being easily stirred, and the rod used for that purpose also applied to moisten the test paper when required. The solution to be neutralized should not be very strong, and the substance added should be diluted upon approaching the point of neutralization, if it be accurately required. F. 274. Change of Properties. 15 Solid pro- ducts. Fig. 21. 2, that in the second experiment much heat and light are evolved Sect, n. during the mutual action ; 3, that the substances will unite in cer- tain proportions only. 61. In liquids and gases, similar changes of properties may be exhibited, and, in many cases, a change of form or state results. Thus the combination of aeriform bodies produces a solid. Into a retort (fig. 21, a,) introduce a small quantity of liquid ammonia (volatile alkali,) and into another a little hydrochloric (muriatic) acid ; in- sert the beaks of the retorts into the extremities of a glass cylinder, b. The gases arising from the acid and ammonia, pass into the cylinder and unite to form a new solid compound, hydrochlorate of ammonia (sal am- moniac.) Exp. 1. If to a concentrated solution of hydrochlorate of lime, sulphuric acid or a sat- urated solution of carbonate ofpotassa be gradually added, a white solid will result. 62. In other cases the solids are converted into aeriform matter, of which the combustion of gunpowder is a familiar instance. — Gas- es also, form a liquid ; as when olefiant gas is mixed with chlorine. When certain liquids are presented to each other, gases are the result, as when to two parts of alcohol we add one part of nitric acid, an effervescence ensues, and aeriform matter is copiously evolved. Solids also produce liquids. Rub together in a mortar a few crystals of Glauber’s salt with nitrate of am- monia, the two solids will become fluid. Such operations are not confined to art. Nature presents them on an extended scale ; and in connexion with the functions of life, renders them subservient to the most exalted purposes. 63. The new chemical powers that bodies thus acquire in conse- quence of combination, are often extremely remarkable, and can on- ly be learned by experiment. It frequently happens that inert bodies produce inert compounds, and that active substances remain active when combined ; but the reverse often occurs : thus oxygen, sulphur, and water, in themselves tasteless and comparatively inert, produce sulphuric acid when chemically combined ; and potassa, which is a powerful caustic, when combined with sulphuric acid, forms a salt* possessing little activity. 64. The colours of bodies are altered by chemical action. Into a weak solution of nitrate of copper, drop liquid ammonia, a rich blue colour will be produced. Add gradually, on the end of a glass rod, a little sul- phuric acid, the liquid will become colourless. To an infusion of purple cabbage add a few drops of an acid, the colour will be changed to red. — The addition of liquid potassa, in quantity just sufficient to neutralize the acid, will restore the original colour. The addition of potassa alone, produces a green colour. Into a small jar of chlorine gas, confined by water, introduce a piece of lit- mus paper, the colour will be wholly destroyed. When sulphate of copper (blue vitriol,) and acetate of lead (sugar of lead) are rubbed together in a mortar; the new compound has a green colour. Calomel and potassa, both colourless, when rubbed in a mortar form a black compound. Eip. 2. Gaseous. Liquid. Exp. Changes produced by chemi- cal action. Exp. Exp. Exp. Exp. Exp. Exp. * The term salt in chemistry is not confined to those substances called salts in or- dinary discourse. 16 Attraction — Chemical. Chap. I. Exp. Change of specific gravity, And of tempera- ature. Kxp. Ignition. Rip. Eip. Chemical action pro- moted by mechanical division, Exp. By heat, Exp. Iodine, whose vapour is of a violet hue, forms a beautiful red compound with " mercury, and a yellow one with lead. 65. The specific gravity of bodies is altered by chemical action. Two bodies rarely occupy the same space after combination which they did separately. In general their bulk is diminished, so that the specific gravity of the new body is greater than the mean of its components. Thus a mixture of 100 equal measures of water and an equal quantity of sulphuric acid does not occupy the space of 200 measures, but considerably less. A similar contraction frequently attends the combination of solids. Gases often experience a re- markable condensation when they unite. But there are exceptions. The reverse happens in some metallic compounds ; and there are examples of combination between gases without any change in bulk. 66. A change of temperature generally accompanies chemical action. Caloric is evolved either when there is a diminution in the bulk of the combining substances without a change of form, or when a gas is condensed into a liquid, or when a liquid becomes solid (61. Exp. 2) ; and as when water is poured upon quicklime. When equal parts of sulphuric acid and water are mixed, the temperature is so much increased that if the mixture bo made in a phial about which tow is wrapped containing a few pieces of phosphorus, the phosphorus will be in- flamed.* 67. Ignition is a frequent attendant upon chemical action, (59. Exp. 2.) Mix, cautiously, a small quantity of sugar with about half its weight of the salt called chlorato of notnssa, form the mixture into a heap upon a plate of iron, and drop upon it from the extremity of a glass rod, a little sulphuric acid, it will bo inflamed. Drop a small piece of potassium into water, or upon ice, hydrogen gas will be disengaged and take fire. 68. As chemical action takes place among the ultimate or con- stituent elements of bodies, it must obviously be opposed by the co- hesion of their particles, and chemical attraction is often prevented by mechanical aggregation. Introduce a pieco of tho metal antimony into a jar of chlorine gas, it will be only slowly and superficially acted upon ; but if tire mechanical aggregation be previously diminished, by reducing tiro metal to powder, it in that state rapidly unites with the gas, and bums the instant that it is introduced. The influence of mechanical division in promoting the action of chemical affinity, and in favouring solution, will be obvious, if into a vessel containing dilute hydrochloric acid we drop a lump of mar- ble ; and into another vessel containing the same acid we pour an equal weight of marble reduced to powder. 69. The chemical energies of bodies, are increased by heat. To four ounce- measures of water, at the temperature of the atmosphere, add three ounces of sulphate of soda in powder, only part of the salt will be dissolv- ed, even after being agitated some time. Apply neat, and the whole of the salt will disappear. To this law, however, there are several exceptions ; for many salts are equally, or nearly equally, soluble in cold as in hot water ; as will be seen hereafter. The effects of heat are sometimes only referable to the diminution of adhesion by expansion, or liquefaction ; but in other cases they * As the phial is often broken, it should be placed upon a plate. Double Elective Affinity. 17 are peculiar and cmnplicated, and probably concerned in modnying Sect, u. the electrical energies of the acting substances. 70. Mechanical agitation, also favours the chemical action of And by Me- bodies. chanical Into a wine glass full of water, tinged blue with the infusion of cabbage let JL fall a small lump of solid tartaric acid. The acid, if left at rest, even during some hours, will only change to red that portion of the infusion, which is in immediate contact with it. Stir the liquid, and the whole will immediately become red. Sulphuric acid poured into alcohol will subside to the bottom, and chemical g action will take place only at the touching surfaces of the two substances — but it will be brought on through the whole mixture by agitation. 71. Some bodies evince no affinity for each other. Some * i i • Oil and water, or powdered chalk and water, may be agitated together, but v° n( !g they will not combine. On allowing the vessels containing them to remain at a ^ rest, the oil or water rises to the surface, and the chalk falls to the bottom. Exp. ^ 72. The intervention of a third body will sometimes promote the Union pro- union of two other bodies which have no affinity for each other. thir^body 1 Thus oil and water unite immediately on adding an alkali, as caustic potassa. Exp. 73. It very frequently happens, on the contrary, that the tenden- Or destroy- cy of two bodies to unite, or remain in combination together., is ed - weakened or destroyed by the addition of a third. Thus alcohol unites with water in such a manner as to separate most salts from it. A striking instance of this is seen in a saturated or strong solution of nitre in Exp. water. If to this there be added an equal measure of alcohol, the greater part of the nitre instantly falls down. Or, if to a solution of camphor in alcohol, water be added, the water will Exp. unite with the alcohol and the camphor will be separated. Oil has an affinity for the volatile alkali, ammonia, and will unite with it, g X p o forming a soapy substance called a liniment. But the ammonia has a still great- er attraction for sulphuric acid ; and hence if the acid be added to the -liniment* the alkali will quit the oil, and unite by preference with the acid.. 74. The affinity existing between any two bodies, is inferred from ^ o ® n j^ er their entering into chemical combination, and that this has happened, r ° d> n we have a proof in the change of properties. 75. From a great number of facts, it appears that some' bodies have a stronger tendency to unite than others, and that the union of a substance with another will often exclude, or even bring about the separation of a third substance which may have been previously united with one of them. This preference of uniting,, exhibited with regard to other bodies, has been called Elective Affinity. Thus’jj^)j* e To a solution of camphor in alcohol add water ; the camphor will be separa- g 5 p j ted, and the water and alcohol will unite. Add to water a few drops of sulphuric acid ; the addition of a solution of Exp. 2. baryta will cause the separation of the acid. The white substance that wil 1 subside will be a new compound of sulphuric acid and baryta. In these and many similar cases combination and decomposition occur. 76. When a compound is decomposed and but one substance is Single, separated, or brought into combination, the affinity has been called Single Elective. But the phenomena are often more complex. 77. When two compounds, each consisting of two ingredients, Double, are decomposed and two new compounds formed, we have an in- stance of Double Elective Affinity. 3 18 Attraction — Chemical. Cha p. 1. Exp. Dt compo- sition. Exp. Tables of affinity, Objections to. Diagrams. Mix together a solution of carbonate of ammonia and hydrochlorate of lime ; carbonate of lime and hydrochlorate of ammonia will be formed, 78. The knowledge of the affinities which bodies have for each other, enables us to separate them when united, or to perform the process of decomposition. Thus, In a solution of nitrate of silver (common lunar caustic) place a piece of polished copper; it will soon be covered with metallic silver. The solution will have been decomposed, and the silver precipitated. 79. The order in which decompositions take place has been ex- pressed in tables, of which the following, drawn up by Geoffroy, is an example : — SULPHUR IC ACID. Baryta, Strontia, Potassa, Soda, Lime, Ammonia, Magnesia. This table signifies, first, that sulphuric acid has an affinity for the substances placed below the horizontal line, and may unite separately with each ; and, secondly, that the base of the salts so formed will be separated from the acid by adding any of the alkalies or earths which stand above it in the column. Thusammouia will separate magnesia, lime ammonia, and potassa lime ; but none can withdraw baryta from sulphuric acid, nor can ammonia or magnesia decompose sul- phate of lime, though strontia or baryta will do so. Bergmann con- ceived that these decompositions are solely determined by chemical attraction, and that consequently the order of decomposition repre- sents the comparative forces of affinity; and this view, from the simple and natural explanation it affords of the phenomenon, was for a time very generally adopted. But it does not necessarily follow, because lime separates ammonia from sulphuric acid, that the lime has a greater attraction for the acid than the volatile alkali. Other causes are in operation which modify the action of affinity to such a degree, that it is impossible to discover how much of the effect is owing to that power. 80. Berthollet was the first to show that the relative forces of chemical attraction cannot always be determined by observing the order in which substances separate each other when in combination, and that the tables of Geoffrov are merely tables of decomposition, not of affinity. He likewise traced all the various circumstances that modify the action of affinity, and gave a consistent explanation of the mode in which they operate. He denied the existence of elective affinity as an invariable force, capable of effecting the perfect separa- tion of one body from another; he maintained that all the instances of complete decomposition attributed to elective affinity are in real- ity determined by one or more of the collateral circumstances that influence its operation. But here this acute philosopher went too far. Bergmann erred in supposing the result of chemical action to be in every case owing to elective affinity ; but Berthollet ran into the opposite extreme in declaring that the effects formerly ascribed to that power are never produced by it. 81. The chemical changes are often illustrated by diagrams, 19 Influence of Cohesion. which may either be constructed so as merely to show the result of . Sect * the change, or may exhibit the composition of the acting bodies. The addition of sulphate of soda to nitrate of baryta (both in solution), will be Exp. attended with the formation of sulphate of baryta and nitrate of soda. The following diagram exhibits the substances before mixture, on parallel lines ; after mixture, by diagonal lines : Nitric Acid. Baryta. Sulphuric Acid. . Soda. Or a more complete view of the change is given in the following diagram, where the bodies before mixture are placed upon the out- side of the perpendicular lines ; their component parts are shown within them ; and the new results on the outside of the horizontal lines. ^ Nitrate of Baryta. Nitrate of Soda. Nitric Acid. Soda. Baryta. Sulphuric Acid. Sulphate of Soda. Sulphate of Baryta. 82. Chemical affinity is influenced by various extraneous eircum- Circum- stances and forces. Of these the most important are, cohesion, elas- ® tance . s in ' ticity, quantity of matter, and gravity. To these may be added the affinity, agency of the imponderables. S3. The first obvious effect of cohesion is to oppose affinity, by c °hesion, impeding or preventing that mutual penetration and close proximity of the particles of different bodies, which is essential to the success- ful exercise of their attraction. For this reason, bodies seldom act chemically in their solid state. Liquidity, on the contrary, favours chemical action ; it permits the closest possible approximation, while the cohesive power is comparatively so trifling as to oppose no ap- preciable barrier to affinity. 84. Cohesion may be diminished in two ways, by mechanical How di- division, or by the application of heat. The former is useful by in- minished > creasing the extent of surface. Heat acts with greater effect, and never fails in promoting combination, whenever the cohesive power is a barrier to it. Its intensity should always be so regulated as to produce liquefaction. The fluidity of one of the substances fre- quently suffices for effecting chemical union, as is proved by the facility with which water dissolves many salts and other solid bodies. The reduction of both substances to the liquid state is the best me- * Various methods have been made use of to express chemical changes, and the re- sults of chemical actions, by means of diagrams, for which the student may consult Henry’s andBrande’s Chem., the Medical Chemistry of Paris, and Ure’s Dictionary , Art. Attraction. 20 Attraction — Chemical . Cha P- 1» thod for ensuring chemical action. The slight degree of cohesion possessed by liquids does not appear to cause any impediment to com- bination. It seems fair to infer, that very little, if any, affinity exists between two bodies which do not combine when they are intimately mixed in a liquid state. Agency in 85. The phenomena of crystallization are owing to the ascendancy tion tal * /a c °h es * on over affinity. When a large quantity of salt has been dissolved in water by the aid of heat, part of the saline matter gene- rally separates as the solution cools, because the cohesive power of the salt then becomes comparatively too powerful for chemical at- traction. Its particles begin to cohere together and are deposited in crystals, the process of crystallization continuing till it is arrested by the affinity of the liquid. A similar change happens when a solution made in the cold is gradually evaporated. The cohesion of the saline particles is no longer counteracted by the affinity of the liquid, and the salt, therefore, assumes the solid form. Affects re- 86. Cohesion plays a still more important part. It sometimes de- termines the result of chemical action, probably even in opposition to affinity. Exp. Its action in particu- lar cases. Exp. Thus, on mixing together a solution of two acids and one alkali, of which two salts may be formed, one soluble, and the other insoluble, the alkali will unite with that acid with which it forms the insoluble compound, to the exclusion of the other. This is one of the modifying circumstances employed by Berthollet to account for the phenomena of single Elective attraction, and is certainly appli- cable to many of tne instances to be found in the tables of affinity. 87. To comprehend the manner in which cohesion nets in some instances, it ia necessary to consider what takes place when in the same liquid two or more compounds are brought together, which do not give rise to an insoluble substance. Thus on mixing solutions of sulphate of potnssa and nitrate of soda, no precipi- tate ensues ; because the salts, capable of being funned by double decomposition, sulphate of soda and nitrate of potnssa, are likewise soluble. In this case it is possible either that each acid may be confined to one base, so as to constitute two neutral salts : or that each acid may be divided between both bases, yielding four neutral salts. It is difficult to decide this point in an unequivocal manner: but judging from many chemical phenomena, it is probable that the arrangement last mentioned is the most frequent, and is probably universal whenever the rela- tive forces of affinity are not very unequal. When two acids and two bases meet together in neutralizing proportion, it may, therefore, be inferred, that each acid unites with both the bases in a munnor regulated by their respective forces of affinity, and that four salts are contained in solution. In like manner the pre- sence of three acids and three bases will give rise to nine salts ; and when four of each are presont, sixteen salts will be produced. This view affords the most plausible theory of the constitution of mineral waters, and of the products which they yield by evaporation. T. Influence of 88. The influence of insolubility in determining the result of che- insolubil- m i ca l action may be readily explained on this principle. If nitric acid, sulphuric acid, and baryta, are mixed together in solution, the base may be conceived to be at first divided between the two acids, and nitrate and sulphate of baryta to be generated. The latter being insoluble is instantly removed beyond the influence of the nitric acid, so that for an instant nitrate of baryta and free sulphuric acid remain in the liquid ; but as the base left in solution is again divided between the two acids, a fresh quantity of the insoluble sulphate is generated ; and this process of partition continues, until either the baryta or the Influence of Heat. 21 sulphuric acid is withdrawn from the solution. Similar changes en- Seet. 11. sue when nitrate of baryta and sulphate of soda are mixed. ^ 89. The efflorescence of a salt is sometimes attended with a simi- of efflores- lar result. If carbonate of soda and chloride of calcium are mingled cence, together in solution, the insoluble carbonate of lime subsides. But if carbonate of lime and sea-salt are mixed in the solid state, and a certain degree of moisture is present, carbonate of soda and chloride of calcium are slowly generated , and since the former, as soon as it is formed, separates itself from the mixture by efflorescence, its production continues progressively. The efflorescence of carbonate of soda, which is sometimes seen on old walls, or which in some countries is found on the soil, appears to have originated in this manner. 90. From the obstacle which cohesion puts in the way of affinity, of elastic- the gaseous state, in which the cohesive power is wholly wanting, ity, might be expected to be peculiarly favourable to chemical action. The reverse, however, is the fact. Bodies evince little disposition to unite when presented to each other in the elastic form. Combina- tion does indeed sometimes take place in consequence of a very energetic attraction ; but examples of an opposite kind are much more common. This want of action seems to arise from the distance between the particles preventing that close approximation which is so necessary to the successful exercise of affinity. Hence many gases cannot be made to unite directly, which nevertheless combine readily while in their nascent state; that is- while in the act of as- suming the gaseous form by the decomposition of some of their solid or fluid combinations. Elasticity operates likewise as a decomposing agent. If two gases, the reciprocal attraction of which is feeble, suffer considerable con- densation when they unite, the, compound will be decomposed by very slight causes. Chloride of nitrogen affords an apt illustration of this principle, being distinguished for its remarkable facility of decomposition. 91. Many familiar phenomena of decomposition are owing to Of heat, elasticity. All compounds that contain a volatile and a fixed prin- ciple, are liable to be decomposed by a high temperature. The ex- pansion occasioned by heat removes the elements of the compound to a greater distance from each other, and thus by diminishing the force of chemical attraction, favours the tendency of the volatile prin- ciple to assume the form which is natural to it. The evaporation of water from a solution of salt is an instance of this kind. * The separation of salts by crystallization, from mineral waters or other saline mix- tures, is explicable by a similar mode of reasoning. Thus on mixing nitrate of potassa and sulphate of soda, four salts, according to this view, are generated, namely, the sulphates of soda and potassa, and the nitrates of those bases ; and if the solution be allowed to evaporate gradually, a point at length arrives when the least soluble of these salts, the sulphate of potassa, will be disposed to crystallize. As soon as some of its crystals are deposited, and thus withdrawn from the influence of the other salts, the constituents of these undergo a new arrangement, whereby an additional quantity of sulphate of potassa is generated ; and thijs process continues until the greater part of the sulphuric acid and potassa has combined, and the compound is re- moved by crystallization. If the difference in solubility is considerable, the separa- tion of salts may be often rendered very complete by this method. T. 22 Attraction — Chemical. Cha P* I- Many solid substances, which contain water in a state of intimate combination, part with it in a strong heat in consequence of the volatile nature of that liquid. The separation of oxygen from some metals, by heat alone, is explicable on the same principle. Heat may 92. It appears that the influence of heat over affinity is variable ; favour or for at one time it promotes chemical union, and opposes it at another. Its action, however, is always consistent. Whenever the cohesive power is an obstacle to combination, heat favours affinity either by diminishing the cohesion of a solid, or by converting it into a liquid. As the cause of the gaseous state, on the contrary, it keeps at a dis- tance particles which would otherwise unite ; or, by producing expansion, it tends to separate from one another substances which are already combined. Influence of 93. Some of the decompositions, which were attributed by Berg* ondecom- mann t0 l ^ e so ^ e influence of elective affinity, may be ascribed to positions, elasticity. If three substances are mixed together, two of which can form a compound which is less volatile than the third body, the last will, in general, be completely driven off by the application of heat. The decomposition of the salts of ammonia by the pure alkalies or alkaline earths, may be adduced as an example. On results 94. The influence of elasticity in determining the result of che- of chemical mical action in these instances, seems owing to the same cause action, which enables insolubility to be productive of similar effects. Thus, on mixing hydrochlorate of ammonia with lime, the acid is divided between the two bases; some ammonia becomes free, which, in consequence of its elasticity, is entirely expelled by a gentle heat. The acid of the remaining hydrochlorate of ammonia is again divided between the two bases ; and if a sufficient quantity of lime is pre- sent, the ammoniacal salt will be completely decomposed. 95. The influence of quantity of matter over affinity, is utiiver- Of quantity sally admitted. If one body a unites with another body b in several of matter, proportions, that compound will be most difficult of decomposition which contains the smallest quantity of b. Of the three oxides of lead, for instance, the peroxide parts most easily with its oxygen by the action of heat; a higher temperature is required to decom- pose the red oxide ; and the protoxide will bear the strongest heat of our furnaces without losing a^parlicle of its oxygen. 96. The influence of quantity over chemical attraction, may be hxample. f urt | ler illustrated by the phenomena of solution. When equal weights of a soluble salt are added in succession to a given quantity of water, which is capable of dissolving almost the whole of the salt employed, the first portion of the salt will disappear more readily than the second, the second than the third, the third than the fourth, and so on. The affinity of the water for the saline substance, dimi- nishes with each addition, till at last it is weakened to such a degree as to be unable to overcome the cohesion of the salt. The process then ceases, and a saturated solution is obtained.* * Quantity of matter is employed advantageously in many chemical operations. If, for instance, a chemist is desirous of separating an acid from a metallic oxide by means of the superior affinity of potassa for the former, he frequently uses rather more of the alkali than is sufficient for neutralizing the acid. He takes the precau- tion of employing an excess of alkali, in order the more effectually to firing every particle of the substance to be decomposed in contact with the decomposing agent. Measure of Affinity. 23 97. But Berthollet attributed a much greater influence to quanti- Sefct. II. ty of matter. It was the basis of his doctrine, developed in the Berthollet’? Statique Chimique , that bodies cannot be wholly separated from views ' each other by the affinity of a third substance for one element of a compound ; and to explain why a superior chemical attraction does not produce the effect which might be expected from it, he contend- ed that quantity of matter compensates for a weaker affinity. Berthollet confounded two things, namely, force of attraction and neutralizing power, which are really different, and ought -to be held distinct. M. Dulong has also found that the principle of Berthollet is not in accord with the results of experiment, t. i33. 98. The influence of gravity is perceptible when it is wished to influence make two substances unite, the densities of which are different. In °f gravity, a case of simple solution, a larger quantity of saline matter is found at the bottom than at the top of the liquid, unless the solution shall have been well mixed subsequently to its formation. In making an alloy of two metals, which differ from one another in density, a larger quantity of the heavier metal will be found at the lower than in the upper part of the compound ; unless great care be taken to counteract the tendency of gravity by agitation. This force obvious- ly acts, like the cohesive power, in preventing a sufficient degree of approximation. 99. Pressure has an important influence upon chemical action. It of pres- appears to operate both by bringing the particles into closer contact, sure, and by inducing elevation of temperature. As when chlorate of po- tassa and phosphorus are ignited by percussion. 100. The chemical agency of galvanism, and the effects of light and of impon- electricity, will be most conveniently stated in other parts of the derabies, work. t. 123 . 101. As the order of decomposition is not always a satisfactory Measure of measure of the force of affinity, when no disturbing causes operate, affinity, the phenomena of decomposition afford a sure criterion ; but when the conclusions obtained in this way are doubtful, assistance may be derived from other sources. The surest indications are procured by observing the tendency of different substances to unite with the same principle, under the same circumstances, and subsequently by marking the comparative facility of decomposition by the same de- composing agent. Thus, on exposing silver, lead, and iron, to air and moisture, the iron soon rusts, the lead is oxidized in a slight de- gree only, and the silver resists oxidation altogether. It is hence inferred that iron has the greatest affinity for oxygen, lead next, and silver the least. It is inferred from the action of heat on the carbo- nate of potassa, baryta, lime, and oxide of lead, that potassa has a stronger attraction for carbonic acid than baryta, baryta than lime, and lime than oxide of lead. 102. Of all chemical substances, our knowledge of the relative de- Of acids grees of attraction of acids and alkalies for each other is the most ^ alka " uncertain. Their action on one another is affected by so many, cir- cumstances, that it is in most cases impossible, with certainty, to re- fer any effect to its real cause, t. 103. Substances which unite chemically have been found to do so Substances in certain proportions. In some cases they are united in a great unite . in many proportions, in others only in a few. In a few instances combi- portions, 24 A ttr action — Chemical. Chap. I. Unlimited, Limited, Character of com- pounds of many pro- portions, Of few. Laws. First law. How ac- counted for. nation takes place unlimitedly in all proportions ; in others it occurs , in every proportion within a certain limit. The union of water with alcohol and the liquid acids, such as the sulphuric, hydrochloric, and nitric acids, affords instances of the first mode of combination ; the solutions of salts in water are examples of the second. One drop of sulphuric acid may be diffused through a gallon of water, or a drop of water through a gallon of the acid ; or they may be mixed to- gether in any intermediate proportions ; and in each case they ap- pear to unite perfectly with each other. A hundred grains of water, on the contrary, will dissolve any quantity of sea-salt which does not exceed forty grains. Its solvent power then ceases, because the cohesion of the solid becomes comparatively too powerful for the f &c - Proportional , and Chemical Equivalent , or Equivalent , to express them. The fatter term, introduced by Wollaston, was suggested by the circumstance that the combining proportion of one body is, as it were, equivalent to that of another body, and may be substitu- ted for it in combination. . 110. This law does not apply to elementary substances only, since lennTof compound bodies have their combining proportions or equivalents, compounds, which may likewise be expressed in numbers. Thus, since water is composed of one equivalent or 8 parts of oxygen, and one equiva- lent or 1 of hydrogen, its combining proportion or equivalent is 9. The equivalent of sulphuric acid is 40.1, because it is a compound of one equivalent or 16.1 parts of sulphur, and three equivalents or 24 parts of oxygen. The equivalent number of potassium is 39.15, and as that quantity combines with 8 of oxygen to form potassa, the equivalent of the latter is 39. 15— |— 8=47. 15. Now when these compounds unite, one equivalent of the one combines with one, two, three, or more equivalents of the other, precisely as the simple sub- stances do. The equivalent of sulphate of potassa will therefore be 40.1+47.15=87.25. 111. The composition of the salts affords a very instructive illus- Examples, tration of this subject; and to exemplify it still further, a list of the equivalents of a few acids and alkaline bases is annexed: — Hydrofluoric acid 19.68 Lithia 14.44 Phosphoric acid 71.4 Magnesia 20.7 Hydrochloric acid 36,42 Lime 28.5 Sulphuric acid 40.1 Soda 31.3 Nitric acid 54.15 Potassa 47.15 Arsenic acid 115.4 Strontia 51.8 - Selenic acid 63.6 Baryta 76.7 It will be seen at a glance that the neutralizing power of the dif- ferent alkalies is very different ; for the equivalent of each base ex- presses the quantity required to neutralize an equivalent of each of the acids. Thus 14.44 of lithia, 31.3 of soda, and 76.7 of baryta, combine with 54.15 of nitric acid, forming the neutral nitrates of lithia, soda, and baryta. The same fact is obvious with respect to the acids ; for 71.4 of phosphoric, 40.1 of sulphuric, and 115.4 of arsenic acid unite with 76.7 of baryta, forming a neutral phosphate, sulphate, and arseniate of baryta. 112. These circumstances afford a ready explanation of a curious N eutra i fact, first noticed by the Saxon chemist Wenzel ; namely, that when compounds, two neutral salts mutually decompose each other, the resulting com- pounds are likewise neutral. The cause of this fact is now obvious. If 71.4 parts of neutral sulphate of soda are mixed with 130.85 of 4 26 Attraction — Chemical. Chap. L Third law. Ratios. Whole numbers. Half equiv alents. nitrate of baryta, the 76.7 parts of baryta unite with 40.1 of sulphuric acid, and the 54.15 parts of nitric acid of the nitrate combine with the 31.3 of soda of the sulphate, not a particle of acid or alkali re- maining- in an uncombined condition. Sulphate of Soda. Nitrate of Baryta. Sulphuric acid . 40.1 54.15 Nitric acid, Soda . . . 31.3 76.7 Baryta, 71.4 130.85 It matters not whether more or less than 71.4 parts of sulphate of soda are added ; for if more, a small quantity of sulphate of so- da will remain in solution ; if less, nitrate of baryta will be in ex- cess ; but in either case the neutrality will be unaffected. 113. The third law of combination is, that when one body a unites with another body b in two or more proportions, the quanti- ties of the latter, united with the same quantity of the former, bear to each other a very simple ratio. The progress of chemical re- search, in discovering new compounds and ascertaining their exact composition, has shown that these ratios of b may be represented by one or other of the two following series : — 1st Series, a unites with 1, 2, 3, 4, 5, &c. of b. 2d Series, a unites with 1, 1£, 2, 24 , &c. of b. The first series is exemplified by the subjoined compounds : Water is composed of Hydrogen 1 Oxygen 8 , ) 1 Binoxide of hydrogen 'Do. 1 Do. 16 < is Carbonic oxide Carbon 6.12 Do. 8j 1 1 Carbonic acid Do. 6.12 . Do. 16 < 12 Nitrous oxide Nitrogen 14.15 Do. 8i I 1 Nitric oxide Do. 14.15 Do. 16 | 1 2 Hyponitrous acid . Do. 14.15 Do. 21 Y3 Nitrous acid Do. 14.15 Do. 32 | 4 Nitric acid Do. 14.15 Do. 40 J 1 5 It is obvious that in all these compounds the ratios of the oxygen are expressed by whole numbers. In water the hydrogen is com- bined with half as much oxygen as in the binoxide of hydrogen, so that the ratio is as 1 to The same relation holds in carbonic oxide and carbonic acid. The oxygen in the compounds of nitro- gen and oxygen is in the ratio of 1, 2, 3, 4, and 5. In like manner the ratio of sulphur in the two sulphurets of mercury, and that of chlorine in the two chlorides of mercury, is as 1 to 2. So, in bicar- bonate of potassa, the alkali is united with twice as much carbonic acid as in the carbonate ; and the acid of the three oxalates of po- tassa is in the ratio of 1, 2, and 4. The following compounds exemplify the second series : — Protoxide of iron consists of Iron 28 Oxygen s; [ 1 Sesquioxide or Peroxide . . Do. 28 Do. 12 < M4 Protoxide of manganese . Manganese 27.7 Do. 8 i >1 Sesquioxide* . Do. 27.7 Do. 12 ; Binoxide . Do. 27.7 Do. 16* 12 Arsenious acid . Arsenic 37.7 Do. 12 1 [14 Arsenic acid . Do. 37.7 Do. 20 < >24 Hypophosphorous acid Phosphorus 15.7 Do. 4 ] ) 4 Phosphorous acid Do. 15.7 Do. 12 ,14 Phosphoric acid Do. 15.7 Do. 20 * 124 ♦ The Latin sesqui , one and a half, is used when the elements of an oxide, chloride, &c., are as 1 to l£ or as 2 to 3. 27 Laws of Combination . Both of these series, which together constitute the third law of Sect, n. combination, result naturally from the operation of the second law. The first series arises from one equivalent of a body uniting with 1, 2, 3, or more equivalents of another body. The second series is a consequence of two equivalents of one substance combining with 3, 5, or more equivalents of another. Thus if two equivalents of phosphorus unite both with 3 and with 5 equivalents of oxygen, we obtain the ratio of 1£ to 2h ; and should one equivalent of iron com- bine with one of oxygen, and another compound be formed of two equivalents of iron to three of oxygen, then the oxygen united with the. same weight of iron would have the ratio, as in the table, of 1 to 1£. Still more complex arrangements will be readily conceived, More com- such as 3 equivalents of one substance to 4, 5, or more of another, plex But it is remarkable that combinations of the kind are very rare ; and even their existence, though theoretically possible, has not been decidedly established.^ 114. The utility of being acquainted with these important laws is Advanta- almost too manifest to require mention Through their aid, and by^° 1 es@ remembering the equivalents of a few elementary substances, the composition of an extensive range of compound bodies may be cal- culated with facility. Thus, by knowing that 6.12 is the equivalent of carbon and 8 of oxygen, it is easy to recollect the composition of carbonic oxide and carbonic acid ; the first consisting of 6.12 parts of carbon -j- 8 of oxygen, and the second of 6.12 carbon -j- 16 of oxygen. The equivalent of potassium is 39.15; and potassa, its protoxide, is composed of 39.15 of potassium -j- 8 of oxygen. From these few data, we know at once the composition of carbonate and bicarbonate of potassa; the former being composed of 22.12 parts of carbonic acid -j- 47.15 potassa, and the latter of 44.24 carbonic acid + 47.15 potassa. This method acts as an artificial memory, the advantage of which, compared with the common practice of stating the composition in 100 parts, will be manifest by inspecting the following quantities, and attempting to recollect them. Carbonic Oxide. Carbon 42.86 Oxygen 57.14 Carbonic Acid. 27.27 72.73 Carbonate of Potassa. Carbonic acid 31.43 Potassa 68.57 Bicarbonate of Potassa. 47.83 52.17 From the same data, calculation's, which would otherwise be diffi- cult or tedious, may be made rapidly and with ease, without refer- * The merit of establishing the first law of combination seems justly due to Wen- zel a Saxon chemist ; and the second law is also deducible from his expenments on the’ composition of the salts. His work, entitled Lehre der Verwandtschaft, was pub- lislied in 1777. The late Mr Higgins, also, in 1789, speculated on the atomic consti- tution of compound bodies; but it is to Dalton* that we are indebted for a theory of chemical union, embracing the whole science, and giving it a consistency and f before his time it had never possessed. Of all who have sum »sfol y Jabou ed in establishing the laws of combination, the most splendid contribution is that of the celebrated Berzelius, * New System of Chem. Philos. 1808. 28 Attraction — Chemical. Chap. I. Uses, In analysis. Numbers how deter- mined. Essential point. ence to books, and frequently by a simple mental process. The ex- act quantities of substances required to produce a given effect may be determined with certainly, thus affording information which is often necessary to the success of chemical processes, and of great consequence both in the practice of the chemical arts, and in the operations of pharmacy. 115. The same knowledge affords a good test to the analyst by which he may judge of the accuracy of his result, and even some- times correct an analysis which he has not the means of performing with rigid precision. Thus a powerful argument for the accuracy of an analysis is derived from the correspondence of its result with the laws of chemical union. On the contrary, if it form an excep- tion to them, we are authorized to regard it as doubtful ; and may hence be led to detect an error, the existence of which might not otherwise have been suspected. If an oxidized body be found to contain one equivalent of the combustible with 7.99 of oxygen, it is fair to infer that 8, or one equivalent of oxygen, would have been the result, had the analysis been perfect. The composition of a substance may sometimes be determined by a calculation, founded on the laws of chemical union, before an analysis of it has been accomplished. 116. The method of determining equivalent numbers will be an- ticipated from what has already been said. The commencement is made by carefully analyzing a definite compound of two simple sub- stances which possess an extensive range of affinity. Thus water, a compound of oxygen and hydrogen, is found to contain 8 parts of the former to 1 of the latter ; and if it be assumed that water con- sists of one equivalent of oxygen and one of hydrogen, the relative weights of these equivalents will be as 8 to 1. The chemist then selects for analysis such compounds as he believes to contain one equivalent of each element, in which either oxygen or hydrogen, but not both, is present. Carbonic oxide and hydrosulphuric acid are suited to his purpose : as the former consists of 8 parts of oxygen and 6.12 of carbon, and the latter of 1 part of hydrogen and 16.1 of sulphur, the equivalent of carbon is inferred to be 6.21, and that of sulphur 16.1. The equivalents of all the other elements may be determined in a similar manner.* 117. Since the equivalents merely express the relative quantities of different substances which combine together, it is in itself imma- terial what figures are employed to express them. The only essen- * In researches on chemical equivalents there are two kinds of difficulty, that every particle of matter, however small, m§y be divided into smaller portions, provided our instruments and organs were adapted to the operation. Their opponents contend, on the other hand, that matter is composed of certain ultimate particles or molecules, which by their nature are indivisible, and are hence termed atoms (from a not and veyveiv to cut). These opposite opinions have from time to time been keenly contested, and the progress of modern che- mistry has revived attention to this controversy. We have only to assume with Dalton, that all bodies are composed of ulti- mate atoms, the weight of which is different in different kinds of matter, and we explain at once the foregoing laws of chemical union ; and this mode of reasoning is, in the present case, almost decisive, because the phenomena do not appear explicable on any other supposition. 121. According to the atomic theory, every compound is formed * For description of this instrument, and a table of chemical equivalents of elemen- tary substances, see Appendix. See also Faraday’s Chemical Manipulation. 30 Attraction — Chemical. Cha P- L of the atoms of its constituents. An atom of A may unite with one, Form com- two, three, or more atoms of B. Thus supposing water to be com- pounds. posed of one atom of hydrogen and one atom of oxygen, binoxide of hydrogen will consist of one atom of hydrogen and two atoms of oxygen. If carbonic oxide is formed of one atom of carbon and one atom of oxygen, carbonic acid will consist of one atom of carbon and two atoms of oxygen. If, in the compounds of nitrogen and oxygen enumerated at (page 26,) the first or protoxide consist of one atom of nitrogen and one atom of oxygen, the four others will be regarded as compounds of one atom of nitrogen to two, three, four, and five atoms of oxygen. From these instances it will appear, that the law of multiple propor- tions is a necessary consequence of the atomic theory. There is also no apparent reason why two or more atoms of one substance may not combine with two, three, four, five, or more atoms of another ; but, on the contrary, these arrangements are necessary in explana- tion of the not unfrequent occurrence of half equivalents, as formerly stated. (Page 27.) Such combinations will also account for the complicated proportion noticed in certain compounds, especially in many of those belonging to the animal and vegetable kingdom. Use of the 122. In consequence of the satisfactory explanation which the laws term atom. 0 f chemical union receive by means of the atomic theory, it has become customary to employ the term atom in the same sense as combining proportion or equivalent. For example, instead of de- scribing water as a compound of one equivalent of oxygen and one equivalent of hydrogen, it is said to consist of one atom of each element. In like manner sulphate of potassa is said to be formed of one atom of sulphuric acid and one atom of potassa ; the word in this case denoting as it were a compound atom, that is, the smallest inte- gral particle of the acid or alkali, — a particle which does not admit of being divided, except by the separation of its elementary or con- stituent atoms. The numbers expressing the proportions in which bodies unite, must likewise indicate, consistently with this view, the relative weights #f atoms ; and accordingly these numbers are often Atomic called atomic weights. Thus, as water is composed of 8 parts of oxy- wdght. g. en an( j j 0 f hydrogen, it follows, on the supposition of water consisting of one atom of each element, that an atom of oxygen must be eight times as heavy as an atom of hydrogen. If carbonic oxide be formed of an atom of carbon and an atom of oxygen, the relative weight of their atoms is as 6.12 to 8; and in short the chemical equivalents of all bodies may be considered as expressing the rela- tive weights of their atoms. Arguments 123. The arguments in favour of the atomic constitution of matter in support become much stronger, when we trace the intimate connexion which of the the- su bsists, among many substances, between their crystalline form and chemical composition. The only mode of satisfactorily accounting for the striking identity of crystalline form observable, first, between two substances, and secondly, between all their compounds, which have an exactly similar composition, is by supposing them to consist of ultimate particles, possessed of the same figures, and arranged in precisely the same order. The phenomena presented by isomor- 31 Union of Gases. phous bodies (50), afford a powerful argument in favour of the atomic Sect. n. theory.^ T. 418. 124. Soon after the publication of Dalton’s views of the atomic Tiieor y of constitution of bodies,! a paper appeared by Gay-Lussac,! in which volumes, he proved that gases unite together by volume in very simple and definite proportions. It was found that water is composed precisely of 100 measures of oxygen gas and 200 measures of hydrogen ; and Gay-Lussac, being struck by this peculiary simple proportion, was induced to examine the combinations of other gases, with the view of ascertaining if any thing similar occurred in other instances. The first compounds which he examined were those of ammoniacal gas with hydrochloric, carbonic, and fluoboric acid gases. 100 vo- lumes of the alkali were found to combine with precisely 100 volumes of hydrochloric acid gas, and they could be made to unite in no other ratio. With both the other acids, on the contrary, two distinct com- binations were possible. These are 100 Fluoboric acid gas, with 100 Ammoniacal gas. 100 do. 200 do. 100 Carbonic acid gas 100 do. 100 do. 200 do. Various other examples were quoted, both from his own experi- ments and from those of others, all demonstrating the same fact. 125. From these and other instances Gay-Lussac established the u n i on 0 f fact, that gaseous substances unite in the simple ratio of 1 to 1, 1 to gases. 2, 1 to 3, &c. ; and this original observation has been confirmed by a multiplicity of experiments. Nor does it apply to gases merely, but to vapours also. 126. Another remarkable fact established by Gay-Lussac intheof com - same essay is, that the volumes of compound gases and vapours pound always bear a very simple ratio to the volumes of their elements. S ases * Thus, Volumes o f Elemen ts . Volumes o f resulting Compounds . 100 Nitrogen gas -j- 300 Hydrogen gas yield 200 Ammoniacal gas. 50 Oxygen “ -j- 100 Hydrogen “ . . . 100 Water. 50 Oxygen “ -j- 100 Nitrogen “ . . . ] 00 Protoxide of nitrogen gas. 100 Chlorine “ -f- 100 Hydrogen “ . . . 200 Hydrochloric acid “ 100 Iodine “ -|- 100 Hydrogen “ . . . 200 Hydriodic acid “ 100 Oxygen “ -j- 100 Nitrogen “ . . . 200 Binoxide of nitrogen “ * Dalton supposes that the atoms of bodies are spherical; and he has invented cer- tain symbols to represent the mode in which he conceives they may combine together, as illustrated by the following figures : 0 Hydrogen. - > O Oxygen. 0 Nitrogen. 9 Carbon. BINARY COMPOUNDS. O 0 Water. O 9 Carbonic oxide. TERNARY COMPOUNDS. O O O Binoxide of hydrogen. O • O Carbonic acid. &c. &c. &c. All substances containing only two atoms he called binary compounds ; those com- posed of three atoms, ternary compounds ; of four, quaternary, &c. For a more full account of the doctrine of atoms, see Daubeny on the Atomic Theory , and Prout’s Bridgewater Treatise. t New System of Chem. Philos. 1808. t Mem. d'Arcueil. 32 Jltttr action — Chemical. volumes. Volumes of Elements. 100 Nitrogen Chap. I. The law of multiples (page 26) is equally, demonstrable by means Combining of combining volumes as by combining weights. Thus, Resulting Compounds- eld Protoxide of nitrogen. Binoxide of nitrogen. Hyponitrous acid. Nitrous acid. Nitric acid. Water. Binoxide of hydrogen. Carbonic oxide. Carbonic acid. nation may equally well be 100 100 100 100 do. do. do. do. 100 Hydrogen 100 do. 100 Carbon vapour -j- 100 do t 50 Oxygen + 100 do. + 150 do. + 200 do. + 250 do. + 50 do. + 100 do. + 50 do. 4 - 100 do. Table of equivalent weights, &c. It thus appears that the laws of combi deduced from the volumes as from the weights of the combining substances, and that the composition of gaseous bodies may be ex- pressed as well by measure as weight. 127. The following table exhibitsa view of equivalent weights and volumes, to which are added the respective specific gravities in rela- tion both to air and hydrogen. Gasrs and Vapovhs. Specific Gravities. Chemical Equivalents. Air as 1. Hydrogen as 1. By Vol. By Weight. Hydrogen, ... M.ntW.i 1.00 100 1. Nitrogen, - 0.9727 14.15 100 14.15 Chlorine, ... 2.4700 35.42 100 35.42 Carbon, (hypothetical), 0.4215 6.12 100 6.12 Iodine, - 8.7020 126.30 100 126.3 Bromine, - 6.4017 78.40 100 78.4 Water, - Alcohol, .... 0.6201 9.00 100 9. 1.C009 23.24 100 23.24 Sulphuric ether, Light carburetted hydrogen, 2.5817 37.48 too 37.48 0.5593 8.12 100 8.12 Olefiant gas, ... Carbonic oxide, 0.9S08 14.24 100 14.24 0.9727 14.12 100 14.12 Carbonic acid, - l .6839 22.12 100 22.12 Protoxide of nitrogen, 1.5239 22.15 100 22.15 Sulphurous acid, 2.2117 32.10 100 32.1 Sulphuric acid, (anhydrous) 2.7629 40.10 100 40.1 Cyanogen, - Hydrosulphuric acid, 1.8157 26.39 100 26.39 1.1782 17.10 100 17.1 Binoxide of nitrogen, - 1 .0375 15.75 200 30.15 Mercury, - 6.9689 101.00 200 202. Ammonia, - 0.5897 8.75 200 17.15 Hydrochloric acid, - 1.2694 18.21 200 36.42 Hydriodic acid, - 4.3354 63.65 200 127.3 Hydrohromic acid, - 2 7353 39.70 200 79.4 Hydrocyanic acid, 0.9423 13.95 200 27.39 Arseniuretted hydrogen, - 2.7008 39.20 200 78.4 Sesquichloride of arsenic, * 6 3025 90.83 200 181.66 Sesquiodide of arsenic, - 15.6505 227.15 200 454.3 Protochloride of mercury, - 8.1939 118.71 200 237.42 Bichloride of mercury, - 9.4289 136.42 200 272.84 Bromide of mercury', - 9.6597 140.20 200 280.4 Bibromide of mercury, - 12.3606 179 40 200 353.8 Biniodide of mercury, 15.6609 227.30 200 454.6 Oxvgen, 1.1024 16.00 50 8. Arsenious acid, «- 13.6972 198.80 50 99.4 Phosphorus, ... 4.3269 62.80 25 15.7 Arsenic, - 10.3901 150.80 25 37.7 Sulphur, .... 6.6558 96.60 16.66 16.1 l.isulphuret of mercury, - 5.3788 78.06 300 234.2 Chemical Symbols. w 128. From the examination of the table it will be seen, 1st, that Sect - IL the combining volumes are either equal, or in the simple ratio of 1 to Ratios of 2, 1 to 3, &c. The same simplicity rarely exists among the equiva- lent weights. 2. The specific gravities and weights of the 18 first substances are seen to be identical. As these have the same uniting identity of volume as hydrogen, the assumed unit, and as the specific gravities specific are merely the weights of equal volumes, the numbers in the column f^ vlties of specific gravities and those in the column of weights coincide. 3. weights. The identity in the equivalent volumes of the elementary gases, hydrogen, nitrogen, and chlorine, led to the notion that the equivalent volumes of most other elements might also be identical. Assuming sp ec ifi c that identity, the specific gravity, for example, of the elements gravity hydrogen, carbon, and sulphur, in a gaseous state, may easily be calculate * calculated. Thus, taking 1, 6.12, and 16.1 as the equivalents of hydrogen, carbon, and sulphur, their specific gravities in the gaseous state, supposing combining volumes equal, will be in the same ratio of 1, 6.12 and 16.1. But such hypothetical numbers cannot be always confided in ; the real specific gravity of a vapour is, in some cases, as much greater than the hypothetical, as its equivalent volume is less than that of hydrogen.^ 129. The tables supply materials for calculating the specific gra- s ^*jJ c of vity of compound gases, and of verifying the accuracy of other con- compound elusions respecting their composition. The specific gravities of gases cal- certain gases being known, together with their uniting proportions culated ' by volumes, and the resulting volume, we can easily deduce the weight of 100 volumes of the compound gas that may be formed. 130. We can assume the specific gravity as the weight of 100 volumes, or the weight of 100 volumes as the specific gravity when the number of volumes is 100 ; then 50 volumes may be indicated by one half, 25 by a fourth, and 16.66 by a sixth of the specific gravity of 100 volumes. Thus the specific gravity of hydrosulphuric acid gas will be that of its constituents, viz. of 100 volumes of hydrogen -|- £th of 100 volumes of the vapour of sulphur.! 131. As vapours are easily condensed by cold, and in many cases exist as such only at high temperatures, their specific gravities may often be obtained by calculation more accurately than by experiment. 132. The impracticability of contriving convenient names expres- sive of the constitution of chemical compounds, suggested the em- ployment of symbols as an abbreviated mode of denoting the compo- Chemical sition of bodies. The symbols contrived by Berzelius are now 5 m0j - extensively used by chemists and mineralogists. These are also called chemical formula, and it is important that the chemical stu- dent should not be unacquainted with them. The following table includes the symbols of the elementary substances according to Berzelius. ♦The identity in the equivalent volumes of hydrogen, nitrogen, and chlorine, sug- gested the idea that the atoms of all the elements are of the same magnitude, and equal volumes of the elements in a gaseous state were supposed to contain an equal number of atoms. The late researches of Dumas and Mitscherlich have shown that this is not the fact. t For further examples see Turner’s Chemistry , 147. 5 34 Attraction — Chemical. Chap. I. TABLE OF SYMBOLS. Elements. Symb Elements. Symb. Elements. Symb. Aluminium Antimony (Stibium) Arsenic Barium - Bismuth Boron - , Bromine Cadmium Calcium Carbon - Cerium Chlorine - Chromium - Cobalt Columbium (Tanta- lum) Copper (Cuprum) Fluorine Glucinium A1 Sb As Ba Bi B Br Cd Ca C Ce Cl Cr Co Ta Cu F G Gold (Aurum) Hydrogen Iodine Iridium - Iron (ferrum) Lead (Plumbum) Lithium Magnesium Manganese Mercury (Hydrargy- rum) Molybdenum Nicae! - Nitrogen Osmium - Oxygen Palladium Phosphorus - Platinum - Au H I Ir Fe Pb L Mg Mn Hg Mo Ni N Os O Pd P Pt Potassium (Kalium) Rhodium - Selenium Silicium Silver (Argentum) Sodium (Natrium) Strontium - Sulphur - Tellurium - Thorium - Tin (Stannum) Titanium Tungsten (Wolfram) jUranium Vanadium Y r ttrium Zinc | Zirconium - K R Se Si n! Sr S Te Th Sn Ti W U V Y Zn Zr Explana- The foregoing symbols are intended to represent tbe chemical equivalents of the elements. Thus, the letters H, I, and Ba, stand for one equivalent of hydrogen, iodine, and barium ; and 2H, 3H, and 4H, for 2, 3, and 4 equivalents of hydrogen. Two equivalents of an element are often denoted by placing a dash through, or more commonly under its symbol : thus, H means 2H, and P signifies 2P. Certain compounds are often, for the sake of brevity, denoted by single symbols in the same manner as the elements ; thus, an equivalent of water, ammonia, and cyanogen, is sometimes expressed by Aq, Am, and Cy; but in general the formulae for compound bo- dies are so contrived as to indicate the elements they contain, and the mode in which they are united. This may be done in several ways ; but that which first suggests itself, is to connect together the symbols by the same signs as are used in Algebra. Thus the for- mula? K+O, Ca+O, Ba+O, Mn+O, Fe+O, 2Fe+30, 3H+N, 2H+2C, C+20, N+50, S+30,and H+Cl, denote single equiva- lents of potassa, lime, baryta, protoxide of manganese, protoxide of iron, sesquioxide of iron, ammonia, olefiant gas, carbonic acid, nitric acid, sulphuric acid, and hydrochloric acid. The formula K-j-N-j-60 indi- cates the elements which are contained in an equivalent of nitrate of potassa : in order to express further that the potassiu m is combined with only one equivalent of oxygen, the remaining oxygen with the nitro- gen, and the potassa with nitric acid, the symbols are placed thus, — (K+0)+(N+50), the brackets containing the symbols of those ele- ments which are supposed to be united. A number placed on the out- side of a bracket, multiplies the compound within it: thus (K— (-0)— (- (S-(-30) is sulphate of potassa, and (K-|-0)-|-2(S-f-30) is the bisul- phate. All the elements contained in a compound are thus visibly re- presented, and the chemist is able readily to trace all possible modes of combination, and to select that which is most in harmony with the Chemical Formula ?. 35 facts and principles of his science. He may, and often does, thereby Sect, n. detect relations which might otherwise have escaped notice. 133. Another advantage attributable to such formulas is, that they Advantage facilitate the comprehension of chemical changes, If hydrosulphuric of formulae, acid acts upon the protoxide of lead, it is easy to say that the sul- phur combines with the lead, and the hydrogen with the oxygen ; but the exact adaptation of the quantities for mutual interchange appears to be more clearly shown by symbols than by a description or a diagram. In the simple instance alluded to, H-j-S reacts on Pb-f-O, and the products are Pb-f-S and H-f-O. When hydrosul- phuric acid acts on bicyanuret of mercury, the result is bisulphuret of mercury and hydrocyanic acid ; the substances which interchange elements are2(H-j-S) andHg-f-2Cy; and the products are Hg-f-2S, and 2 (H-(-Cy). In more complicated changes the advantage of che- mical formulas Is still more manifest, examples of which kind will be found in other parts of this volume. 134. Useful as the algebraic chemical formulae are for the purpose of Abbrevia- studying chemical changes, they are sometimes found inconveniently ted - long where the object is merely to express the composition of bodies, and accordingly Berzelius has introduced several abbreviations. For instance, he indicates degrees of oxidation by dots placed over the symbol, writing K, C, N, instead of K-(-0, C-j-20, N-j-50, for potassa, carbonic acid, and nitric acid. In like manner he denotes compounds of sulphur by commas, writing K, Hg, H instead of K-f-S, Hg-f-2S, H-f-S, for sulphuret of potassium, bisulphuret of mercury, and hydrosulphuric acid. When the ratio is that of two to three he employs the symbol for two equivalents above stated ; thus, Fe, P, As is used instead of 2Fe-f-30, 2P-|-50, 2As-)-50, for an equivalent of sesquioxide of iron, phosphoric acid, and arsenic acid ; and similarly we have As, As instead of 2As-}-3S, 2As-j-5S for the sesquisulphuret and persulphuret of arsenic. These last formulae are sometimes used to indicate two equivalents instead of one ; but as, agreeably to the atomic theory, the smallest possible molecule of sesquioxide of iron consists of 2 atoms of iron and 3 of oxygen, the formula 2Fe-f-30 ought to stand for one equivalent only. Berzelius often dispenses with the sign -J-, and writes combined elements side by side, the sign of addition being understood instead of expressed. Thus he uses KS, CaC, BaN, KS-f-NiS, instead of K+S, Ca+C, Ba+N, (K+S)+(Ni+S), for sulphate of potassa, carbonate of lime, nitrate of baryta, and the double sulphate of potassa and oxide of nickel. Two or more equivalents of one consti- tuent of a compound are denoted by numbers placed in the same position as the indices of powers in algebra : thus NH 3 , NC 2 , Fe 2 H 3 is the abbreviation of N-f-3H, N-|-!2C, 2Fe-j-3H, for ammo- nia, cyanogen, and sesquihydrate of iron, a compound of 2 equiva- 36 Attraction — Chemical. Chap. I. Isomeric bodies. Modes of ascertain- ing the composi- tion of bodies. Ultimate and Proximate analysis. lents of sesquioxide of iron and 3 of water. A number used before symbols, like coefficients in algebra, multiplies all the following symbols not separated from it by a -f- sign. Thus in 8 Ca Si 3 -|-K Si 6 — j— 16 Aq (which is the formula for the mineral called apophyllite), the 8 denotes 8 equivalents of Ca Si 3 , or tersilicate of lime, which are united with 1 equivalent of sexsilicate of potassa, and 16 of water. Berzelius also expresses the vegetable and animal acids by the first letter of their name, with a dash over it. Thus T, A, C, B, G, F, are the symbols for tartaric, acetic, citric, benzoic, gallic, and formic acids. 135. It was formerly thought that the same elements united in the same ratio must always give rise to the same compound ; but examples have been discovered of two or even more substances con- taining the same elements in the same ratio, and yet exhibiting chemical properties distinct from each other. For such compounds Berzelius has suggested the general appellation of isomeric u from too; equal , and peqo ; part , expressive of equality in the ingredients. Isomerism is quite consistent with our theories of chemical union ; insomuch as the same elements may be grouped or combined in dif- ferent ways, and give rise to compounds essentially distinct.* Some bodies consist of the same elements in the same ratio, and yet differ in their equivalents. The nature of these compounds is at once detected by their equivalents being unlike, and by the volume which they occupy as gases compared with the volumes of the ele- ments of which they consist. Isomeric bodies of this kind are obvi- ously much less intimately allied than those above described. T. 153. 136. The proof which establishes the nature of chemical com- pounds, is of two kinds, synthesis and analysis . Synthesis consists in effecting the chemical union of two or more bodies ; and analysis, in separating them from each other, and exhibiting them in a sepa- rate state. The composition of sulphate of copper (blue vitriol) is synthetically demonstrated by uniting sulphuric acid to oxide of copper. When we have a compound of two or more ingredients, which are themselves compounded also, the separation of the com- pounds from each other may be called the proximate analysis of the body ; and the farther separation of these compounds into their most simple principles, its ultimate analysis. Thus the sulphuric acid of the sulphate of copper consists of sul- phur and oxygen, and oxide of copper consists of copper and oxygen ; consequently we should say that the ultimate component parts of blue vitriol are copper, sulphur, and oxygen. ♦Thus the elements of sulphate of potassa may perhaps be united indiscriminately with each other, as expressed by the formula KSCM ; or they may form KO-f SO 3 ; or KS+O'; or KO-H-SO 2 ; and other combinations might be made. The second of these is doubtless the real one ; but no one can say that the others are impracticable. Again, the elements of peroxide of tin, Sn and 20, may either form SnO 2 , or SnO+O; and those of the sesquioxide of iron, 2Fe and 30, may either be Fe 2 03 or FeO+FeOa, not to mention other possible combinations- The elements of alcohol are 2C, 3H, and O, which may be united indiscriminately as H 3 C 2 0, or H^Cs-l-O, or as H^-I-HO, besides others ; it is commonly considered a compound of olefiant gas and water, as indicated by the last formula. T. Caloric. 37 The proximate analysis of sulphate of potassa consists in resolving Sect, hi. it into potassa and sulphuric acid ; and its ultimate analysis is effected by decomposing the potassa into potassium and oxygen, and the sulphuric acid into oxygen and sulphur. When the analysis of any substance has been carried as far as possible, we arrive at its most simple principles or elements ; by which expression we are to understand, not a body that is incapable of further decomposition, but only one which has not yet been decom- posed. Section III. Heat or Caloric. 137. No sensations are more familiar to us than those of heat Sens^ations^ and cold. They are excited by bodies applied to our organs, and at° old< different times very different degrees of sensation are excited by the same body. The power of inducing these sensations does not de- pend upon the matter itself, which is applied to our organs ; for ev- ery shade of sensation is produced, without the qualities of that matter being permanently changed ; it is considered as depending on the operation of a certain subtle principle, present in bodies, and which, according to its quantity, gives rise to the power of exciting different sensations. 138. This principle, or power, has been distinguished by various Has receiv- appellations, as Fire, Heat, the matter of Heat, or the Igneous fluid ; names!° US terms which are either ambiguous, or which involve some hypothe- sis, and which are superseded by the unexceptionable appellation of Caloric, m. i. 183 .* 139. Caloric, so far as its chemical agencies are concerned, mayMaybe be chiefly considered under two views — as an antagonist to the co “ under two hesive attraction of bodies — and as concurring with, and increasing views, elasticity. By removing the particles of any solid to a greater dis- tance, from each other, their cohesive attraction is diminished ; and one of the principal impediments to their union with other bodies is overcome. On the other hand, caloric may be infused into bodies in such quantity, as not only to overcome cohesion, but to place their particles beyond the sphere of chemical affinity. In many cases, when two bodies are combined together, one of which is fixed, and the other becomes elastic by union with caloric, we are able, by its interposition alone, to effect their disunion. Thus carbonate of lime gives up its carbonic acid by the mere applica- tion of heat. 140. We may consider, then, all bodies in nature as subject to The state the action of two opposite forces, the mutual attraction of their par- £fflE 25 iced tides on the one hand, and the repulsive power of caloric on the by caloric, other ; and bodies exist in the solid, liquid, or elastic state, as one or the other of these forces prevails. Water, by losing caloric, has its cohesion so much increased, that it assumes the solid form of ice; adding caloric, we diminish again its cohesion, and render it fluid; and finally, by a still farther addition of caloric, we change it into va- * Or we may define caloric as the agent to which the phenomena of heat and com- bustion are ascribed. U. 38 Caloric — Expansion . Chap. I. It expands bodies. Prored by experi- ments. Principle upon which pyrometers are made. Expansion of solids. pour, and give it so much elasticity, that it may be rendered capable of bursting ' the strongest vessels. In many liquids, the tendency to elasticity is even so great, that they pass to the gaseous form by the mere removal of the weight of the atmosphere ; as is the case with ether in the exhausted receiver of the air pump. 141. Expansion is the most obvious and familiar effect of caloric and it takes place, though in different degrees, in all forms of mat- ter. When a body which occasions the sensation of heat on our organs, is brought into contact with another body which has no such effect, the result of their mutual action is that the hot body contracts, and loses to a certain extent its power of communicating heat, and the other body expands, and in a degree acquires this power. The expansion of solids may be made apparent by heating a rod of iron, of such a length as to be included, when cold, between two points, and the diameter of which is such, as barely to allow it to pass into an iron ring. When heated, it will have become sensibly larger ; and it will be found incapa- ble of passing through the ring. 142. This property of metals has been applied to the construction of an instrument for measuring temperature, called a pyrometer .* 143. The expansion of solids has engaged the attention of sever- al experimenters, t and the following results have been obtained : — I. Different solids do not expand to the same degree from equal ad- ditions of heat. 2. A body which has been heated from the tem- perature of freezing to that of boiling water, and again allowed to cool to 32° F., recovers precisely the same volume which it posses- sed at first. 3. The dilatation of the more permanent or infusible solids is very uniform within certain limits ; their expansion, for ex- Danlcll'* py- roin«tir. * Au instrument of this kind is repre- rcsented by fig. 22, which will be found very convenient for showing the expansi- bilities of bars of different metals, at tem- peratures not exceeding that of boiling water. Upon a flat piece of mahogany are tixed brass studs, g g, ou which the metallic bar,y f is placed. One end of „ , r this bar bears against a lever b at a point , very near its fulcrum; the other end of / {*«= this lever, which is bent, bears against another lever c, the lower extremity of which is an index. Beneath this index is a graduated arc d. When we wish to immerse the bar in hot water, or to apply heat gradually through the medium of water, the bar is passed through the brass box a, which has an aperture at each end. An open- ing is left in the board immediately under the box, to allow the application of a lamp. The small expansion of the metallic bar is magnified by the first lever in the pro- portion of the distances of the point of pressure from its plane, and from its other extremity ; and this magnified effect is again magnified by the other lever, so that an expansion of the tooth part of an inch corresponds to a whole inch on the scale. This pyrometer is liable to the objection that the distance of the points of pressure from the fulcrum and extremity of each lever is variable during the experiment. ( See Ferguson’s Led.) Daniell’s pyrometer is susceptible of great precision. Its indications result from a difference in the expansion and contraction of a platinum bar. and a tube of black lead ware, in which it is contained. These differences are made available by con- necting an index with the platinum bar, which traverses a circular scale fixed on to the tube. See a description of this instrument in Turner's Elements p. 26, Quart. Jour of Sd. xi. 309, and PhUos. Trans. 1330-1. t The Philosophical Transactions contain various dissertations on the subject by El- licot, Smeaton, Troughton, aud General Roy; and M. Biot, in his Trade de Physiaue , ha« given the results of experiments performed with great care by Lavoisier and La- place. 39 Relative Expansibilities of Liquids . ample, from the freezing point of water to 122°, is equal to what takes place betwixt 122° and 212°. The subsequent researches of Dulong and Petit, ^ prove that solids do not dilate uniformly at high temperatures, but expand in an increasing ratio ; that is, the higher the temperature beyond 212° the greater the expansion for equal additions of heat. It is manifest, indeed, from their experiments, that the rate of expansion is an increasing one even between 32° and 212° ; but the differences which exist within this small range are so inconsiderable as to escape observation, and, therefore, for most practical purposes may be disregarded. The subjoined table includes the most interesting results of La- voisier and and Laplace. (Biot, vol. 1. p. 158.) Names of Substances . Elongation when heated from 32° to 212° TiV& i ts length. T2"Vb 5^T 5ih- 1 FT¥ ¥T2- 3^7 1 8TTT 1 SSI 5TB ¥T2 BTT2 TT5T Glass tube without lead, a mean of three specimens English flint glass - Copper - Brass — mean of two specimens Soft iron forged Iron wire - Untempered steel - ' Tempered steel - Lead - - Tin of India - Tin of Falmouth - Silver - - Gold — mean of three specimens Platinum, determined by Borda 144. The expansion of liquids is seen by putting a common thermometer, made with mercury or alcohol, into warm water, Fig. 23, when the dilatation of the liquid will be shown by its ascent in the stem. The experiment is indeed illustrative of two other facts. It proves, first that the dilatation increas- es with the temperature ; for if the thermometer be plunged into several portions of water heated to different degrees, the ascent will be greatest in the hottest water, and least in the coolest portions. It demonstrates, secondly, that liquids more than solids. The glass bulb of the thermometer is itself ex- panded by the hot water, and, therefore, is enabled to contain more mercury than before ; but the mercury being dilated to a much greater extent, not only occupies the additional space in the bulb, but likewise rises in the stem. Its ascent marks the difference be- tween its own dilatation and that of the glass, and is only the ap- parent, not the actual, expansion of the liquid. 145. Liquids differ also in their relative expansibilities : ether is more expansible than spirit of wine, and spirit more than water, and water more than mercury. Those liquids are generally most ex- pansible which boil at the lowest temperature. Fig. 23. expand Sect. hi. Of liquids, Their rela tive expan- sibilities different. * An. de. Ckim. et de Phys. vn» 40 Caloric. Chap. I. Of mercu- ry, Liquids ex- pand in in- creasing ratio. This may be rendered evident by partially filling several glass tubes of equal diameters, furnished with bulbs, with the different liquids, and placing them in hot water; as the liquids expand, they will rise to different heights in the tubes. To render this more apparent the liquids may be tinged with some colouring matter. The tubes may be placed in a light frame, having a thin copper trough to contain water, which may be heated by a lamp. Fig. 24. Or they may be suspended as in Fig. 25. F ‘g-24. Fig. 25. 146. From the frequency with which mercury is employed in phi- losophical experiments, it is important to know the exact amount of its expansion. This subject has been investigated by several phi- losophers, but the experiments of Lavoisier and Laplace, and espe- cially of Dulong and Petit, are entitled to the greatest confidence. According to the former, the actual dilatation of mercury, in pas- sing from the freezing to the boiling point of water, amounts to of its volume ; but the result obtained by Dulong and Petit, who found it, - & VV?r is probably still nearer the truth. Adopting the last estimate, this metal dilates, for every degree of Fahrenheit’s thermometer, of the bulk which it occupied at the temperature of 32°. If the barometer, for instance, stand at 30 inches when the thermometer is at 32°, we may calculate what its elevation ought to be when the latter is at 60°, or at any other temperature. The ap- parent expansion of mercury contained in glass is of course less than the absolute expansion.* 147. All experimenters agree that liquids expand in an increasing ratio, or that equal increments of heat cause a greater dilatation at high than at low temperatures. Thus, if a fluid is heated from 32° to 122°, it will not expand so much as it would do in being heated from 122° to 212°, though an equal number of degrees is added in both cases. The nearer a liquid approaches its boiling point, the greater is its expansibility; hence those liquids appear most equably expansible which have the highest boiling points, and hence one of the great advantages of mercury in constructing thermometers. * Between the limits of 32° and 212 ° F. Lavoisier and Laplace estimate the apparent expansion at 5*3 and Dulong and Petit at f of its volume, being TT55T lor each degree of Fahrenheit's thermometer. Dulong and Petit state, that the mean total expansion of mercury from 32° to 572° F. for each degree is 9 - 5 * 3 ny ; and that the mean apparent expansion in glass from 32° to 572° F. for each degree is The temperature in tneir experiments was estimated by an air thermometer, which they consider more uniform in its rate of expansion than one of mercury. The tem- perature of 572° F. on the air thermometer corresponds to 536° in the mercurial one. T. 19. 41 Dilatation of Mr. 148. The expansion of air may be shown by inverting a tube se ct._ni ; terminated by a bulb, and partly filled with water (Fig. 26); the air confined in the bulb will expand when heated, and expel the water from the tube. Fig. 26. Fig. 27. Specific gravity al- 149. As heat increases the bulk of all bodies, it is obvious thatj, e h r ^ g ^ change of temperature is constantly producing changes in their den-tempera- sity or specific gravity, as may be easily demonstrated in fluids where ture > there is freedom of motion among the particles. If we apply heat to Of liquids, the bottom of a vessel of water, that portion of the fluid, which is nearest to the source of heat, is expanded, and becoming specifically lighter, ascends, and is replaced by a colder portion from above. This, in its turn, becomes heated and dilated, and gives way to a second colder portion ; and thus the process goes on, as long as the fluid is capable of imbibing heat. (Fig. 27. ) 150. In air, similar currents are continually pro- duced, and the vibratory motion observed over chim- ney pots, and slated roofs which have been heated by the sun, depends upon this circumstance': the warm air rises, and its refracting power being less than that -of the circumambient colder air, the cur- rents are rendered visible by the distortion of objects viewed through them. This is easily illustrated by placing a spiral of pasteboard upon a wire over an Argand lamp, or at the side of a stove pipe.^ The ventilation of rooms and buildings can only be perfectly effected by suffering the heated and foul air to pass off through apertures in the ceiling, while fresh air, of any desired temperature, is ad- mitted from below. t 151. As the particles of air and aeriform substances -are not held together by cohesion, they are found to dilate from equal additions of heat much more than solids or liquids. Now, 'chemists are in the habit of estimating the quantity of the gases employed in their expe- riments by measuring them ; and since the volume occupied by any * Advantage is taken of this in heating apartments by furnaces placed in cellars. Cold air being brought in contact with the surface of heated metal, and allowed to as- cend through pipes into the apartments. t Various contrivances have been resorted to, to prevent the passage of cold air from above downwards through the ventilator, which can only be completely eflected by keeping the ventilating tubes at a higher temperature than the surrounding air ; heating them, for instance, by steam ; passing them through a fire ; or placing a lamp beneath them, of sufficient dimensions to cause a strong current upwards. 6 Of air, Fig. 28. 42 Caloric . Chap I. Peculiar ef- fect of heat. gas is so much influenced by temperature, it is essential to accuracy that a due correction be made for the variations arising from this cause ; that they should know how much dilatation is produced by each degree of the thermometer, whether the rate of expansion is uniform at all temperatures, and whether that ratio is the same in all gases. 152. All gases undergo equal expansions by the same addition of heat, supposing them placed under the same circumstances ; so that it is sufficient to ascertain the law of expansion observed by any one gas, in order to know the law for all.* 153. There is a peculiarity in the effect of heat upon the bulk of some fluids, namely, that at a certain temperature, increase of heat causes them to contract, and its diminution makes them expand. This singular exception is only observable in those liquids which ac- quire an increase of bulk in passing from the liquid to the solid state, and is remarked only within a few degrees of temperature above their point of congelation. Water is a noted example of it. Ice swims upon the surface of water, and, therefore, must be lighter than it, which is a convincing proof that water, at the mo- ment of freezing, must expand. The increase is estimated by Boyle at about £th of its volume, which gives 900 as the specific gravity ♦It appears from the experiments of Gay Lussac, that 100 parts of air, in being heat- ed from 32° to 212° F., expand to 137.6 parts. The increase for ISO degrees is, therefore, 0 376 or 'W&ths of its bulk : and by dividing this number by 160, it is found that a given quantity of dry uir dilates to ninth of the volume it occupied at 32°, for every degree of Fahrenheit’s thermometer. This point being established, it is easv to ascertain what volume any given quantity of gas should occupy at any given temperature. Suppose a certain portion of gas to occupy 20 measures of a graduated tube at 32°, it may be desirable to determine what would be its bulk at 42°. For every degree of heat it has increased by T^oth of its original volume, and, therefore, since the increase amounts to ten degrees, the 20 measures will have dilated hy jV^jths. The expression will, therefore, be 20+20 xjVo =20.416. It must not be forgotten that the volume which the gas occupies at 32° is a necessary element in all such calculations. Thus, having 20.416 measures of gas at 42°, the corresponding bulk for 62° cannot be calculated by the formula 20.4 1 6+20.1 1 6 ; the real expression is 20+20. 4l6y 1 £°(j l because the increase is only ^S&ths of the space occupied at 32°, which is 20 measures.* A similar remark applies to the formula for estimating the effect of beat on the height of the barometer. The rate of expansion of atmospheric air at temperatures exceeding 212 has been examined by Dulong and Petit, and the following table contains the result o* their ob- servations. (An. de Ch. el de Ph. vii. 120.) Temperature by the Mercurial Thermometer. Corresponding volumes of a given volume of air. Fahrenheit. Centigrade. — 33 — 36 0 8650 32 0 1.0000 212 100 1.3750 302 160 1.6576 392 200 1.7389 462 250 1.8189 672 300 2.0976 Mercury boils 630 360 2.3125 * See Formula, Turner, 21. Temperature. 43 of ice, that of water being 1000.* Dalton estimates the specific gra- Sect m. vity of ice at 9.42. Water has attained its maximum of density at Water, its about 39°t, and if it be cooled below 39° it expands as the tempera- maximum ture diminishes, as it does when heated above that point. Immerse two thermometer tubes, one containing spirits of wine and the other Exp. water, into melting snow ; the former will sink till it indicates 32° F., but the latter, when it has nearly attained 39° F., will begin to expand, and continue to do so till it freezes. Or, fill a flask capable of holding three or four ounces, with water at the temperature of 60° F. and adapt a cork to it, through which passes a glass tube open at both ends, about the eighth of an inch wide, and ten inches long. After having filled the flask, insert the cork and tube, and pour a little wa- ter into the latter till the liquid rises to the middle of it. On immersing the flask in a mixture of pounded ice and salt, the water will fall in the tube, marking con- traction ; but in a short time an opposite movement will be perceived, indicating that expansion is taking place, while the water within the flask is at the same time yielding caloric to the freezing mixture on the outside of it. This anomaly in respect to water is productive of very important ^5*55!^ consequences, in preserving the depths of rivers and lakes of a tern- i n this J perature congenial to their inhabitants. anomaly. 154. The most remarkable circumstance attending this expansion, is the prodigious force with which it is effected. Boyle filled a brass L tube, three inches in diameter, with water, and confined it by means of a moveable plug ; the expansion, when it froze, took place with such violence as to push out the plug, though preserved in its situa- tion by a weight equal to 74 pounds. The Florentine Academicians burst a hollow brass globe, whose cavity was only an inch in diame- ter, by freezing the water with which it was filled ; and it has been estimated that the expansive power necessary to produce such an effect was equal to a pressure of 27,720 pounds weight. Major Williams gave ample confirmation of the same fact by some experi- ments which he performed at Quebec in the years 1784 and 17854 Glass bottles, lead and iron pipes, &c., in which water freezes, are often ruptured. 155. Water is not the only liquid which expands under reduction Other of temperature, as the same effect has been observed in a few others cases > which assume a highly crystalline structure on becoming solid : — fused iron, antimony, zinc, and bismuth are examples of it. Mer- cury is a remarkable instance of the reverse ; for when it freezes, it suffers a very great contraction (31 note.) 156. The cause of the expansion of water at the moment of freez- Cause, ing is attributed to a new and peculiar arrangement of its particles. Ice is in reality crystallized water, and during its formation the par- ticles arrange themselves in ranks and lines, which cross each other at angles of 60° and 120°, and consequently occupy more space than when liquid. This may be seen by examining the surface of water while freezing in a saucer. No very satisfactory reason can be as- signed for the expansion which takes place previous to congelation. 157. The state of a body with respect to its power of producing Tempera- the effects which arise from the operation of caloric, is termed its ture * Experiments on Cold. t Hallstrom An. de Chim. et Phys. xxviii, 90, whose experiments were made with great care. According to the more recent experiments of Stampfer 38.75 and to those of Crichton 38-97. Johnston’s Report in 1st Report of the British Association- t Phil. Trans. Ed. ii, 23. 44 Caloric. Principle on which the ther- mometer indicates tempera- ture. Thermom- eter. Chap, i. temperature. In every body the temperature depends on the quan- tity of caloric which it contains, and the temperature is said to be high or low as it respects another body, in proportion as it occasions an expansion or contraction of its parts. k m fvvn eCtly tem P erature bodies can be but imperfectly estimated from sensa- b>y the sensation of heat or cold they produce, the sensation being tion. modified by preceding impressions upon the sentient organ and other external circumstances. Hence the necessity of some common measure of temperature, as by means of the Thermometer . 159. The principle on which the thermometer indicates tempera- ture, is, that caloric has a tendency always to preserve an equilibri- um ; so that if two bodies at different temperatures, be brought into contact, it will pass from the one at the higher into that at the lower temperature, until the temperature of both is the same. Thus, if we mix equal quantities of the same fluid at different temperatures, the cold portion will expand as much as the hot portion contracts, and the resulting temperature is the mean ; so that it appears, that as much heat as is lost by the one portion is gained by the other. 160. A common thermometer consists of a tube terminated at one end by a bulb, and hermetically closed at the other. The bulb and part of the tube are filled with an appropriate liquid, which when designed to measure very low temperatures, is spirit of wine; under other circumstances quicksilver is better adapted for the purpose.* A graduated scalet is attached to the stem ; and whenever the instrument is applied to bodies of a higher tempera- ture, the mercury or spirit expands and rises in the lube. 161. In dividing the scale of a thermometer, the two fixed points usually resorted to are the freezing and boiling of water, which al- ways take place at the same temperature, when under the same at- mospheric pressure. The intermediate part of the scale is divided into any convenient number of degrees ; and it is obvious, that all thermometers thus constructed will indicate the same degree of heat when exposed to the same temperature. In the centigrade thermometer, this space is divided into 100° ; the freezing of water being marked 0°, the boiling point 100°. In this country we use Fahrenheit’s scale of which the 0° is placed at 32° below the freez- ing of water, which, therefore, is marked 32°, and the boiling point 212°, the intermediate space being divided into 180°. Another scale is Reaumur’s ; the freezing point is 0°, the boiling point 80°. These nre the principal thermometers used in Europe and this country.! Gradua- tion. * Quicksilver will indicate 500° F. but freezes at — 39°. t As the chemist will often have occasion to employ the thermometer for as- certaining the temperature of corrosive liquids, tne graduated scale should be provided with a hinge, so as to double back, and leave the bulb exposed, as shown in Fig. 29. t For the method of constructing thermometers sec Faraday’s Manipu- lation and for those of great sensibility, Quart. Jour, of Sd - vii- p. 183. Fig. 29i Thermometers . 45 162. Each degree of Fahrenheit’s scale is equal’to fths of a degree Sect, hi. on Reaumur’s : if, therefore, the number of degrees on Fahrenheit’s Rules for scale above or below the freezing of water be multiplied by 4 and divided by 9, the quotient will be the corresponding degree of ryt her- Reaumur. mometers. Fahrenheit. Reaumur. 68°— 32°= 36X4=144-7-9—16° 2 1 2°— 32°= 1 80 X 4=720-^-9=80°* 163. M. Bellain has observed that mercurial thermometers slowly Change of change their point of zero, which uniformly becomes higher than at^ ero ’ the time of graduation. This phenomenon appears owing to a di- minished capacity of the bulb due to the atmosphere continually pressing on its exterior, while a vacuum exists in the interior of the tube ; for it has not been noticed either in mercurial thermometers which are unsealed, or in thermometers made with alcohol. The principal contraction ensues soon after the tube is sealed, and hence some months should be permitted to elapse between the sealing and graduation of a thermometer.! 164. Air is sometimes resorted to as indicating very small Air ther- chang.es of temperature. The instrument employed by Sane- mometers ’ torio, to whom the invention of the thermometer is generally ascribed, was of a very simple kind, and measured variations of temperature by the variable expansion of a confined portion * To reduce the degrees of Reaumur to those of Fahrenheit, they are to be multi- plied by 9, and divided by 4. Reaumur. Fahrenheit. 1 6° X 9= 144-^4= 36°+32°= 68 80°X9=720-h4=180°+32°=212 Every degree of Fahrenheit’s is equal to fths of a degree on the centigrade scale ; the reduction therefore is as follows : Fahrenheit. Centigrade. 212—32=180X5=900^-9=100° Centigrade. Fahrenheit. 100X9=900-7-5=180+32=212° Corresponding degrees Fahr. Cent. Reaum. Fahr. Cent. Reaum. Fahr. Cent. Reaum. 212 100 80 113 45 36 14 -10 - 8 203 95 76 104 40 32 5 -15 -12 194 90 72 95 35 23 - 4 -20 -16 185 85 68 86 30 24 -13 -25 -20 176 80 64 77 25 20 -22 -30 -24 167 75 60 68 20 16 -31 -35 -28 158 70 56 59 15 12 -40 -40 -32 149 65 52 50 10 8 140 60 48 41 5 4 131! 55 44 32 0 0 122| 50 40 23 -5 -4 f An. de. Ch. et de Ph. xxi. 330. 46 Caloric. Chap. I. Advanta- ges of. Leslie’s. Howard's. O pair . of air. This instrument is represented in the margin. It consists of a glass tube, eighteen inches long, open at one end, and*Fig.3o. blown into a ball at the other. If a warm hand be applied to the ball, the included air will expand, and a portion be ex* pelled through the open end of the tube. And if in this state the aperture is quickly immersed in a cup filled with some coloured liquid, it will ascend in the tube, as the air in the ball contracts by cooling; and its altitude will in every case depend upon the degree of expansion which the air has previously undergone. In this manner it is prepared for use, and will indicate increase of temperature by the descent of its fluid, and vice versa. These effects may be exhibited, alternately by applying the hand to the ball, and then blowing on it with of bellows. The amount of the expansion or contraction is measur ed by a graduated scale attached to the stem of the instrument. 165. The advantages of the Air Thermometer consist in the great amount of the expansion of air, when compared with that of any liquid; by which it is enabled to detect minute changes of tempera- ture, which the mercurial thermometer would scarcely discover ; for air is increased in volume by a given elevation of temperature, about twenty times more than quicksilver. The advantages, however, which attend this excessive delicacy are counterbalanced by sever- al serious objections. It will be readily seen, for instance, that the air thermometer will not only be affected by changes of temperature, but by variations of atmospheric pressure. 166. Leslie, under the name of the Differential Ther- mometer, employed a modification of the air thermome- ter invented by Sturmius.* It consists of two glass- tubes of unequal length, each terminating in a hollow ball, as represented in Fig. 31, which are united by a bent tube containing coloured sulphuric acid. When- ever a hot body approaches one of the bulbs, it must ne- essarily drive the fluid towards the other. It is evident then that this instrument cannot be employed to measure variations in the temperature of the surrounding atmos- phere, because, as long as both balls are of the same temperature, whatever this may be, the air contained in both will have the same elasticity, and consequently, the included coloured liquor, being pressed equally in opposite directions, must remain stationa- ry. If, however, any change of temperature is effected in one of the balls, the instrument will immediately indi- cate this difference with the greatest nicety. The amount of this effect is ascertained by a graduated scale, the in- terval between freezing and boiling being divided into 100 equal degrees. This thermometer is peculiarly adapted to ascertain the difference of the temperatures of two contiguous spots in the same atmosphere. A differential thermometer has been contrived by How- ard resembling the above in its general form, (Fig. 32) but in Fig. 31. Fig. 3 2 . 1 o SJ * See a description and sketch in his Collegium Curiosum, p. 54 ; published in 1676. Thermometer. 47 which the degree of heat is measured by the expansive force of Sect, hi. the vapour of ether, or spirit of wine, in vacuo.*" It is intended to be applied, to the same purposes as that of Leslie, but is more sensible to changes of temperature, and the movement of the fluid follows instantaneously the application of the heating cause, whereas in the air thermometer some time is required before the effect takes place. 167. Different methods have been recommended for ascertaining Self-regis- the highest or lowest temperature that may occur during any parti- teving ther-* cular period, as during the night, when there is no one present to ob- mome serve it. The simplest contrivance of this kind is the following : It consists of two thermometers (Fig. 33), a Sp^t 0 f wine and a mercurial one the former for ascertaining the lowest, the latter the highest heat. In the tube of the Fig. 33 - former is placed a small piece of white ena- &) mel, which, as the fluid contracts, is brought along with it, but on its again expanding does not take it with it ; it leaves it at the place to which it had carried it, and thus the lowest temperature that had happened is pointed out. In the tube of the latter is placed a small piece of a needle, so as just to rest on the mercury. As the fluid expands, it pushes the needle before it and on again contracting, it leaves it at that part to which it had carried it, so that in this way the highest temperature is ascertained; These thermometers are fixed on a board, with the balls at opposite sides, the mercurial one horizontally, the one with spirit of wine with the ball inclined downwards, so that, when we wish to set them, by raising the side next the spirit ball, the enamel and needle will come to the surfaces of the fluids. Six’s thermometer (Fig. 34), has the bulb in the form of a long cylin- Fig. 34. der, the tube is bent down parallel with the cylinder and passing under Jsi^ it, rises in a parallel direction to the top on the other side ; the bulb is usually filled with spirits of wine, which is in contact with a portion of mercury occupying the lower part of the tube, and the mercury is suc- ceeded by a second portion of spirit. The mercury carries an index upon each of its surfaces; when the fluid in the cylinder contracts by cold, the index on the left side will be pressed upwards, as long as the heat decreases, and will be retained at its greatest height by a weak spring. When the fluid in the cylinder expands by heat, it must press upon the surface of the mercury in the left side of the tube, forcing it to rise higher in the right side : as long as the heat continues to increase, the index will rise on the surface of the mercury in the right side of the tube, and will be retained at the greatest height by its spring : it must be obvious, therefore, that the index on the side opposite the left hand will indicate the greatest degree of cold, in any given time, and the one on the right, the greatest degree of heat. The indexes being of iron or steel, may be brought back to their places by a magnet, applied to the outside of the tube. 168. Though the thermometer is a most valuable instrument, the Amount of sum of information which it conveys is very small. It only indicates that condition of bodies in which they affect the senses with an im- mometer pression of heat or cold, and which is expressed by the word temper- ature. It does indeed point out a difference in the temperature of two or more substances with great nicety ; but it does not indicate how much heat any body contains. We learn by it whether the temperature of one body is greater or less than that of another ; and if there is a difference, it is expressed numerically, namely, by the degrees of an arbitrary scale, selected for convenience, without any reference whatever to the actual' quantity of heat present in bodies. * Directions for constructing it are given in the 8th vol. of the Quart. Jour, of Sci. p, 219. 48 Caloric. Cha p. I. Specific ca loric. Exp. Exp. Different quantities of heat re quired by bodies. 169. The relative quantities of heat which different bodies in the . same state require to raise them to the same thermoinetric tempera- ture, is called their specific heat, and those bodies which require most heat are said to have the greatest capacity for heat. That the quantity of heat in different bodies of the same temperature is dif- ferent, was first shown by Black, in 1762. Mix together equal quantities of water, one portion being at 100° and the other at 50°, the temperature of the mixture will be the arithmetical mean or 75° ; that is, the 25 degrees lost by the warm water will exactly suffice to heat the cold water by the same number of degrees. It is hence inferred, that equal weights or measures of water of the same temperature contain equal quantities of heat; and the same is found to be true of other bodies. But if equal weights or equal bulks of different substances are employed, the result will be different. Thus, if a pint of mercury at 100° be mixed with a pint of water at 40 Q , the mixture will nave a temperature of 60°, so that the 4U degrees lost by the for- mer, heated the latter by 20 degrees only ; and when, reversing the experiment, the water is at 100° and the mercury at 40°, the mixture will be at 80°, the 20 degrees lost by the former causing a rise of 40 in the latter. The fact is still more strikingly displayed by substituting equal weights for measures. 170. k appears that the same quantity of heat imparts twice as high a temperature to mercury as to an equal volume of water ; a similar proportion is observed with respect to equal weights of sper- maceti oil and water; and that the heat which gives 5 degrees to water will raise an equal weight of mercury by 115 degrees, being the ratio of 1 to 23. Hence if equal quantities of heat be added to equal weights of water, spermaceti oil, and mercury, their tempera- tures in relation to each other will be expressed by the numbers 1,2, and 23 ; or, what amounts to the same, in order to increase the tem- perature of equal weights of those substances to the same extent, the water will require 23 times as much heat as the mercury, and twice as much as the oil. T. 29 . This may be illustrated by an inge- nious apparatus contrived by Bache. Three vessels of sheet iron, (Fig. 35) to contain equal iceights of mercury, alco- hol, and water, are attached to a frame, by which they can be dipped intothesame vessel containing hot water. An alcohol thermometer, with a large column of fluid, dips into each vessel. As the heat enters, the thermometer in the mercury rises with great ra- pidity, that in the alcohol more slowly, and that in the water still more so.* 171. The same knowledge may be obtained by reversing the pro- cess ; by noting the relative quantities of caloric which bodies give out in cooling ; for if water requires 23 times more caloric than mer- cury to raise its temperature 1 or more degrees, it must also lose 23 times as much in cooling. The calorimeter , invented and employed by Lavoisier and La Place, acts on this principle.! Fig. 35. * Cylinders of copper, coaled with a varnish of thickened linseed oil to protect the surface, may be substituted for the thermometers, phosphorus, placed on the top of each, will inflame first ou the cylinder in the liquid having the least capacity for heat. Amer. Jour, xxviii. 324. + See Lavoisier’s Elements of Chemistry. Specific Caloric. 49 172. The singular fact of substances of equal temperature, con- Sect, nr. taining unequal quantities of heat, naturally excites speculation about Cause, its cause, and various attempts have been made to account for it. The explanation deduced from the views of Black is the following. He conceived that heat exists in bodies in two opposite states : in one it is supposed to be in chemical combination, exhibiting none of its ordinary characters, and remaining as it were concealed, without evincing any signs of its presence; in the other, it is free and un- combined, passing readily from one substance to another, affecting the senses in its passage, determining the height of the thermometer, and in a word giving rise to all the phenomena which are attributed to this active principle.* 373. The capacities of bodies for heat have considerable influence Heating upon the rate at which they are heated and cooled. Those bodies which and cooling are most slowly heated and cooled, have generally the greatest ca P a ' -^fluenml city for heat. Thus* if equal quantities of water and quicksilver be by capac- placed at equal distances from' the fire, the quicksilver will be more by- rapidly heated than the water, and the metal will cool most rapidly when carried to a cold place. Upon this principle, Leslie ingeniously T es ]j e > s determined the specific heat of bodies, observing their relative times method, of cooling a certain number of degrees comparatively -with water, under similar circumstances. 174. The determination of the specific heat of gaseous substances Specific is a problem of importance, and has accordingly occupied the atten- heat of tion of several experimenters of great science and practical skill ; §ase8 ‘ but the inquiry is beset with so many difficulties that, in spite of the talent which has been devoted to it, our best results can be viewed as approximations only, requiringfo be corrected by future research. f 175. The circumstances which merit particular notice, concerning Circum- the specific heat of bodies, have been arranged by Turner under the stances lo eight following heads " be noticed. 1. Every substance has a specific heat peculiar to itself ; whence it follows, that a change of composition will be attended by a change of capacity for heat. 2. The specific heat of a body varies with its form. A solid has a smaller capacity for heat than the, same substance when in the state of a liquid. 3. When a given weight of any gas is made to vary in density and volume while its elasticity is unchanged, as when air confined in a tube over mercury is heated and suffered to expand without varia- tion of pressure, the specific heat is believed to remain constant. 4. Of the specific heat of equal volumes of the same gas at a vary- ing density and elasticity, as when air is forced into a bottle with different degrees of force,, nothing certain has been established. 5. The specific heat of equal weights of the same gas varies as the density and elasticity vary. 6. The specific heat of solids and liquids was formerly thought to be constant at all temperatures, so long as they suffer no change of form or composition. Dalton, however, {Chemical Philosophy, part * For objections to this theory, see note by Bache, p. 30, Turner’s Elements, Am. ed. t For a view of the experiments of Crawford, Lavoisier, Dulong, and others, on this subject, see Turner's Elements , p. 31. 7 50 Caloric. Chap. I. Dilatation of air, &c. Exp. I. p. 50,) endeavours to show that the specific heat of such bodies is greater in high than at low temperatures ; and Petit and Dulong have proved it experimentally with respect to several of them. It is difficult to determine whether the increased specific heat ob- served in solids and liquids at high temperatures is owing to the ac- cumulation of heat within them, or to their dilatation. It is ascribed in general to the latter. 176. Change of specific heat always occasions a change of tem- perature. Increase in the former is attended by diminution of the latter ; and decrease in the former by increase of the latter. Thus when air, confined within a flaccid bladder, is suddenly dilated by means of the air-pump, a thermometer placed in it will- indicate the pro- duction of cold. On the contrary, wnen air is compressed, the corres- ponding diminution of its specific heat gives rise to increase of tempera- ; nay, so much heat is evolved when the compression is sudden and ible, that tinder may be kindled by it. This is illustrated by a brass Fig. 36. ture ; fore syringe furnished at one end with a stop cock having a small cham- ber in which tinder, or what is better, a small piece of phosphorus wrapped in tow, is placed. By suddenly compressing the piston, the tinder takes fire on opening the stop cock. Or the tinder may be placed in a cavity, in the end of the piston. The explanation of these facts is obvious. In the first case, a quantity of heat becomes insensible, which was previously in a sensible state; in the second, heat is evolved, which was pre- viously latent. -U Relation of A curious relation between the specific heat of some ele- D® heat^and raenlar y substances and their atomic weight was discovered by Du- weight. long and Petit ; namely, that the product of the specific heat of each element by the weight of its atom is a constant quantity. Forma and 177. Heat has great influence on the forms or states of bodies, states of When we heat a solid it becomes fluid or gaseous, and liquids are fl^iKetTby converle( ^ i nt0 aeriform bodies or vapours. Black investigated this caloric. effect of heat with singular felicity.* During the liquefaction of bodies, a quantity of heat, which is essential to the state of fluidity, and which is therefore often called the heat of fluidity , is absorbed, without increasing the sensible or thermoinetric temperature. Con- sequently, if a cold solid body, and the same body hot and in a liquid state, be mixed in known proportions, the temperature after mix- ture will not be the proportional mean, as would be the case if both were liquid, but will fall short of it ; much of the heat of the hotter body being consumed in rendering the colder solid liquid , before it produces any effect upon its sensible temperature. 178. Equal parts of water at 32°, and of water at 212°, will pro- duce on mixture a mean temperature of 122°. But equal parts of ice at 32°, and of water at 212°, will only produce (after the lique- faction of the ice) a temperature of 52°, the greater portion of the heat of the water being employed in thawing the ice, before it can produce any rise of temperature in the mixture. To heat thus insensible or bric 0t Ca combined. Black applied the term latent heat. The actual loss of the thermometric heat in these cases was thus estimated ; a pound of ice at 32° was put into a pound of water at 172° , the ice melted, and the temperature of the mixture was 32°. Here the water was * Black’s Lectures. Freezing Mixtures . 51 cooled 140°, while the temperature of the ice was unaltered ; that is, .Sect, m. 140° of heat disappeared, their effect being not to increase tempera- ture, but to produce fluidity. 179. In all cases of liquefaction caloric is absorbed, and we pro- Cold pro- duce artificial cold, often of great intensity, by the rapid solution ^JaTdsofu certain saline bodies in water.^ Upon this principle the action of 80 freezing mixtures depends, some of which may frequently be conve- niently and economically applied to the purpose of cooling wine or water in hot climates, or where ice cannot be procured. Dilute a portion of nitric acid with an equal weight of water ; and, when the Exp. 1 . mixture has cooled, add to it a quantity of light fresh-fallen snow. On immers- ing the thermometer in the mixture, a very considerable reduction of tempera- ture will be observed. This is owing to the absorption, and intimate fixation of the free caloric of the mixture by the liquefying snow. Mix quickly together equal weights of fresh-fallen snow at 32°, and of com- Exp. 2. mon salt, cooled, by exposure to a freezing atmosphere, down to 32°. The two solid bodies, on admixture, will rapidly liquefy, and the thermometer will sink 32° or to 0°, or according to Blagden to 4+ lower. To understand this experiment, it must be recollected, that the snow Theory, and salt, though at the freezing temperature of water, have each a *FRIGORIFIC MIXTURES WITH SNOW* Mixtures. Parts hy weight. Sea-salt, ... 1 Snow, . ... 2 from any temperature rhermometer sinks to —5° Degree of Cold pro- duced. Sea-salt, ... 2 Hydrochlorate of ammonia, 1 Snow, .... 5 0 u to 0 Sea-salt, . . . .10 Hydrochlorate of ammonia, 5 Nitrate of potassa, . . 5 Snow, .... 24 0 1 CO 0 Sea-salt, . ... 5 Nitrate of ammonia, . 5 Snow, . . . .12 to —25° Diluted sulphuric acid,t 2 Snow, . . - .3 from +32° to —23° 55 degrees. Concentrated hydrochloric j g Snow, . . , .8 from 4-32° to —27° 59 Concentrated nitrous acid, 4 : Snow, . . . 7 from +32° to —30° 62 Chloride of calcium, . 5 Snow, .... 4 from 4-32° to —40° 72 Crystallized chloride of? 3 calcium, <> Snow, .... 2 from 4-32° to —50° 82 Fused potassa, . , 4 ; Snow, . ... 3 front 4-32° to —51° 83 But freezing mixtures may be made by the rapid solution of salts, without the use of snow or ice; and the following table, taken from Walker’s Essay in thePhilosoph- + Phil. Trans. Ixxviii. 281. *The snow should be freshly fallen, dry. and uncompressed. If snow cannot be had, finely powdered ice mpy be substituted for it. f Made of strong acid, diluted with half its weight of snow or distilled water. 52 Caloric. Chap, i. considerable portion of uncombined caloric. Now salt has a strong affinity for water ; but the union cannot take place while the water continues solid. In order, therefore, to act on the salt, the snow ab- sorbs all the free caloric required for its liquefaction ; and during this change, the free caloric, both of the snow and the salt, amount- ing to 32°, becomes latent, and is concealed in the solution. This solution remains in a liquid state at 0, or 4° below 0 of F. ; but if a greater degree of cold be applied to it, the salt separates in a con- crete form. Most neutral salts, also, during solution in water, absorb much ca- loric ; and the cold, thus generated, is sometimes so intense as to freeze water, and even to congeal mercury. The former experiment, however, (viz. the congelation of water,) may easily be repeated on a summer’s day. Exp. Add to 32 drachms of water, 11 drachms of hydrochlorate of ammonia, 10 of nitrate of potassa, and 16 of sulphate of soda, all finely powdered. The salts may icul Transactions for 1795, includes the most important of them. The salts must be finely powdered aud dry. Mixtures. Parts by weight- Hydrochlorate of ammonia. 5 Nitrate of potassa, 5 Water 16 Temperature falls from +50° to +10° Degree of Cold pro- duced. 40 degrees. Hydrochlorate of ammonia, 5 Nitrate of potassa, . . 5 Sulphate of soda, . 8 Water, . . 16 from +50° to +4° 46 Nitrate of ammonia, 1 Water 1 from +50° to 4-4° 46 Nitrate of ammonia, 1 Carbonate of soda, . . 1 Water, .... 1 from 4-50° to —7° 57 Sulphate of soda, . 3 Diluted nitrous acid,* 2 from 4-50° to —3° 53 Sulphate of soda, 6 Hydrochlorale of ammonia, 4 Nitrate of potassa, . 2 Diluted nitrous acid. 4 from 4-50° to — 10° 60 Sulphate of soda, . • 6 Nitrate of ammonia, 5 Diluted nitrous acid, 4 from 4-50° to — 14° 64 Phosphate of soda. . 9 k >iluted nitrous acid, . 4 from 4-50° to — 12° 62 Phosphate of soda. . 9 Nitrate of ammonia. . 6 Diluted nitrous acid. 4 from 4-50° to —21° 71 Sulphate of soda. . 8 Hydrochloric acid, 5 from +50° to 0° 50 1 Sulphate of soda, . 6 1 Diluted sulphuric acid.t 4 from 4-50° to 4-3° 47 These artificial processes for generating cold are mnch more effectual when the ma- terials are previously cooled by immersion in other frigorific mixtures. * Composed of fuming nitrous acid two parts in weight, and one of water — the mixture being allowed to cool before being used. f Composed of equal weights of strong acid and water, being allowed to cool before use. Latent and Sensible Heat. 53 be dissolved separately, in the order set down, A thermometer, put into the Sect. III. solution, will show, that the cold produced is at, or below freezing; and a little T ° water, in a thin glass tube, being immersed in the solution, will be frozen in **■ a few minutes. H. 1. 113,* Crystallized chloride of calcium, when mixed with snow, pro- Method of duces a most intense degree of cold. This property was discovered J^cury by Lovitz, and has bpen since applied to the congelation of mercury on a very extensive scale.! On a small scale, it may be sufficient to employ two or three pounds of the salt, Let a few ounces of mercury, in a very thin glass retort, be immersed, first Exp. in a mixture of one pound of each ; and, when this has ceased to act, let another similar mixture be prepared. The second will never fail to congeal the quick- silver.t 180. When fluids are converted into solids, their latent heat be- Latent ca- comes sensible. Water, if kept perfectly free from agitation, may bej^™.®^® cooled down, several degrees below 32° ; but, on shaking it, it imme- diately congeals, and the temperature rises to 32°. The evolution of caloric, during the congelation of water is well illustrated by the following experiment of Crawford. Into a round tin vessel put a pound of powdered ice; surround this by ag l mixture of snow and salt in a larger vessel ; and stir the ice in the inner one, till its temperature is reduced to + 4° F. To the ice thus cooled add a pound of water at 32°. One fifth of this will be frozen ; and the temperature of the ice will rise from 4° to 32°. In this instance, the caloric evolved, by the congela- tion of one fifth of a pound of water, raises the temperature of a pound of ice 28°. H. 1. 115. Dissolve sulphate of soda in water, in the proportion of one part to five, and „ surround the solution by a freezing mixture, it will cool gradually down to 31°. ' The salt, at this point, begins to be deposited, and stops the cooling entirely. * The results of some of Walker’s experiments on this subject, are given in the ta- bles of freezing mixtures. t The proportions, which answer best, are about equal weights of the salt finely powdered, and of fresh fallen and light snow. On mixing these together, and im- mersing a thermometer in the mixture, the mercury sinks with great rapidity. For measuring exactly the cold produced, a spirit thermometer, graduated to 50° below 0 of Fahrenheit, or still lower should be employed. A few pounds of the salt are suf- ficient to congeal a large mass of mercury. By means of 13 pounds of the chloride, and an equal weight of snow, Pepys and Allen froze 56 pounds of quicksilver into a solid mass. The mixture of the whole quantity of salt and snow, however, was not made at once, but part was expended in cooling the materials themselves. t Fig. 37, a very simple and cheap apparatus may be employed to freeze mercury. The outer vessel of wood may be twelve and a half inches square, and seven inches deep. It should have a wooden cover, rabbeted in, and furnished with a handle. Within this is placed a tin vessel b b, standing on feet which are one and a half inches high, and having a projection at the top, half an inch Fig. 37. broad and an inch deep, on which rests a shallow tin pan c c. Within the second vessel is a third d, made of un- tinned iron, and supported by feet two inches high. This vessel is four inches square, and is intended to con- tain the mercury. When the apparatus is used, a mix- ture of hydrocnlorate of lime and snow is put into the outer vessel a a, so as completely to surround the middle a vessel b b. Into the latter, the vessel d, containing the quicksilver to be frozen, pre- viously cooled down by a freezing mixture, is put ; and this is immediately surroun- ded by a mixture of snow and muriate of lime, previously cooled to 0 ° F. by an artificial mixture of snow and common salt. The pan c c is also filled with these materials, and the wooden cover is then put into its place. The vessels are now left till the quicksilver is frozen. A more elegant, but more expensive, apparatus, by Pepys, intended for the same purpose, is figured in an early volume of the Philosophi- cal Magazine. H. 1. 114. 54 Caloric. Chap, i. This evolution of calorie during the separation of a salt, is exactly the reverse of what happens during its solution.* When a solution of Glauber’s salt is made suddenly to crystal- lize, its temperature is considerably augmented ; (31 note) and when ^ water is poured upon quicklime, a great degree of heat is produced by the solidification which it suffers in consequence of chemical combination ; congelation, therefore, is to surrounding bodies a heating process, and liquefaction a cooling process. of7 V uid° n liquid* are heated they acquire the gaseous form, and into ‘the * become invisible elastic fluids, possessed of the mechanical proper- aeriform ties of common air. By a sufficiently intense heat every liquid and state. solid would probably undergo this change. A considerable number of bodies, however, resist the strongest heat of our furnaces without va- porizing. These are said to be fixed in the fire : those which, under the same circumstances, are converted into vapour, are called volatile . This effect of caloric is termed Vaporization. Vapours 182. Vapours are characterized by the readiness with which they are convertible into liquids or solids, either by a moderate increase of pressure, the temperature at which they were formed remaining the same, or by a moderate diminution of that temperature, without change of pressure. They retain this form or state as long as their temperature remains sufficiently high, but re-assume the liquid form when cooled again. Exp. i. Exp. 2. Fill a jar with water heated to 101° and invert it in a vessel of the same. Then introduce a little ether by means of a glass tube closed at one end. The ether will rise to the top of the jar, and, in its ascent will be changed into gas, filling the whole jar with a transparent, invisible, elastic fluid. On permitting the water to cool, the etiiereal gas is condensed, and the inverted jar again becomes filled with water. Or more beautifully thus. Fill a glass tube about thirty inches long and an inchin diameter, with quicksilver, and invert it in the mercurial trough. Pass up from a small bottle an ounce or more of ether ; after it has collected upon the surface of the quicksilver in the tube, it may be made to boil by the heat of the hand by grasping the tube at that part where the ether stands; which will pass to the state of vapour and depress the mercurial column. Difference 1S3. The disposition of various substances to yield vapour is very of density, different ; and the difference depends doubtless on the relative pow- er of cohesion with which they are endowed. Vapours occupy more space than the substances from which they were produced. According to the experiments of Gay Lussac, water, at its point of greatest density, in passing into vapour, expands to 1696 times its volume, alcohol to 659 times, and ether to 443 times, each vapour be- ing at a temperature of 212° F. and under a pressure of 29.92 inches of mercury. This shows that vapours differ in density. Watery vapour is lighter than air at the same temperature and pressure, in the proportion of 1000 to 1604 ; or the density of air being 1000, that of watery vapour is 625. The vapour of alcohol, on the contra- ry, is half as heavy again as air ; and that of ether is more than twice and a half as heavy. Dilatation 184. The dilatation of vapours by heat was found by Gay-Lus- of vapours. sac to follow the same law as gases, that is, for every degree of Fahrenheit, they increase by y^th of the volume they occupied at 32°. But the law does not hold unless the quantity of vapour con- Blagden, Phil. Trans. Ixxviii. 290. 55 Boiling Point. Sect. III. tinue the same. If the increase of temperature cause a fresh por- tion of vapour to rise, then the expansion will be greater than ^-gth for each degree ; because the heat not only dilates the vapour pre- viously existing to the same extent as if it were a real gas, but aug- ments its bulk by adding a fresh quantity of vapour. The contrac- tion of a vapour on cooling will likewise deviate from the above law, whenever the cold converts any of it into a liquid ; an effect which must happen, if the space had originally contained its maximum of vapour; The volume of vapour varies under varying pressure according to Influenced the same law as that of gases, provided always that the gaseous gu r ^ es ’ state is preserved. This law, discovered by Boyle and Mariotte, is more fully explained in the section on atmospheric air, and merely expresses the fact that the volume of gaseous substances at a constant temperature is inversely as the pressure to which they are subject. 155. The temperature at which vapour rises with sufficient free- Boiling dom for causing the phenomena of ebullition, is called the boiling point of point. The heat requisite for this effect varies with the nature of jifl ulds the fluid. Thus, sulphuric ether boils at 96° F. alcohol at 173° and pure water at 212° ; while oil of turpentine must be raised to 316°, and mercury to 662°, before either exhibits marks of ebullition. The appearance of boiling is owing to the formation of vapour at the bot- tom of the Vessel, and it escapes through the heated fluid above it. 186. The boiling point of the same liquid is constant, so long as Boiling the necessary conditions are preserved ; but it is liable to be affected P°jj^ by several circumstances. The nature of the vessel has some in flu- same cir _ ence upon it. Thus Gay Lussac observed that pure water boils pre- cumstan- cisely at 212° in a metallic vessel and at 214° in one of glass. It is ces ‘ likewise' affected by the presence of foreign substances. Bostock found that ether, heated in a glass vessel, had its boiling point lower- ed nearly 50° by introducing a few chips from a cedar pencil, and alcohol of s. g. 849 had its boiling point reduced by a similar cause between 30° and 40°. The boiling point of water, heated in a glass vessel, was brought down 4° or 5° by the same means. * By put- ting coils of wire into liquids, heated in glass vessels with a view to distillation, they are made to boil readily, quietly and some degrees lower than they would otherwise do. It is of course necessary to use a metal which will not be acted upon by the liquid. 187. A circumstance which has great influence over the boiling point and vaporization of fluids is variation of pressure. By the pres?ure . mere removal of atmospheric pressure, ether will be converted into vapour at the common temperature of the atmosphere. Into a glass tube, about six inches long, and half an inch in diameter, put a g xp teaspoonful of ether, and fill up the tube with water; then, pressing the thumb on the open end of the tube, place it, inverted, in a jar of water. Let the whole be set under the receiver of an air-pump, and exhaust the air. The ether will be changed into gas, which will expel the water entirely from the tube. On re-ad- mitting the air into the receiver, the gas is again condensed into a liquid form. From the experiments of the late Prof. Bobison it appears that Boiling liquids boil in a vacuum at a temperature 140° lower than in the P™ nt m va ' open air.t Thus water boils at 72° F., alcohol at 36,° and ether at — 44°. This proves that a liquid is not necessarily hot because it Ann. of Philos. N. S. ix. 196. t Black’s Lectures , Vol. i. p, 151. 56 Caloric. Chap. I Effect of chirtiges of density of the air. Altitudes determined by the boiling point. Example of diminished pressure fa- cilitating ebullition. Exp. boils. The heat of the hand is sufficient to Fi * ^ make ether boil in a vacuum, as is exem- pi i fied by the Pulse Glass. 188. Even the » ordinary variations in the weight of the air, as measured by the barometer, are sufficient to make a difference in the boiling point of water of several degrees. When the barometer is at 28 inches, water will boil at the temperature of 208,43°, when at 30 inches at 212°, and when at 31 at 213,76°. At the top of Mount Blanc, Saussure found that it boiled at 187°, so that the heights of mountains, and even of buildings, may be calculated by reference to the temperature at which water boils upon their summits.* The following apparently paradoxical experiment also illustrates the influence of diminished pressure in facilitating ebullition. Fig. 39. Insert a stop cock securely into the neck of a Florence flask, Fig. 39 ? containing a little water, and heat itover a lamp till the water boils, and the steam freely escapes by the open stop cock ; then suddenly remove the lamp and close the cock The water will soon cease to boil ; but if plunged into a vessel of cold water, ebul- lition instantly recommences, but ceases if the flask be held near the fire : the vacuum in this case being produced by the condensa- tion of the ste&m.t Example of 189. Water cannot be heated under common circumstances beyond ry^flbct'of 212° F. because it then acquires such an expansive force as enables it pressure, to overcome the atmospheric pressure, and to fly off in the form of vapour. But if subjected to sufficient pressure, it may be heated to any extent without boiling. The elasticity of steam increases in a greater ratio than the temperature at which it is produced . thus if it be 1 at 212° I 4 at 293.7 I 16 at 398.48 Fig. 49. it is 2 “ 250.5 | 8 “ 341.78 | 24 “ 435.57 G Or steam at these temperatures, has 2, 4, 8, 16, and 24 times the elastic force of steam at 212°. 4 * Wollaston has described the method of constructing a thermometer of extreme delicacy, applicable to these pur- poses.* t The experiment may be varied by placing the flask in an inverted position in the ring of a retort-stand and blow- ing upon it with a pair of bellows. M«rcei’« «ppa- * For making experiments on this suby ct, the apparatus, r«tu«. represented Fig. 40, contrived hy Marcet, will be found ex- tremely useful, o is a strong brass globe, composed of two hemispheres screwed together with flanches ; a portion of quicksilver is introduced into it, and it is then about half hlled with water, b is a barometer tube passing through a sleam-tight collar, and dipping into the quicksilver at the bottom of the globe, c is a thermometer graduated to ahout 400°, and also passing through an air-light collar, d is a stop cock, and e a large spirit lamp. The whole is supported upon the brass frame and stand f. Upon applying neat to this vessel, the stop cock being closed as soon as the water boils, it will be fouud that the temperature of the water and its vapour increases with the pressure, which is measured by the ascent of the mercury in the barometer tube. The thermometer under atmospheric pressure being at 212°, will be elevated to 217° under a pressure of five inches of mer- cury, and to 242° under a pressure of 30 inches, or therea- bouts ; each inch of mercury producing by its pressure a rise of about 1° in the thermometer. The barometer tube also serves the purpose of a safety-valve, the strength of the brass globe being such as to resist a greater pressure than that of one atmosphere. *Pk\l. Tmns. 1817. c 57 Freezing of Mercury. 190. Evaporation as well as ebullition consists in the formation of Sect, hi, vapour, and the only assignable difference between them is, that the Evapora- one takes place quietly, the other with the appearance nf boiling. tion - Evaporation occurs at common temperatures. This fact may be proved by exposing water in a shallow vessel to the air for a few days, when it will gradually diminish, and at last disappear entirely. Most liquids, if not all of them, are susceptible of this gradual dissi- pation ; and it may also be observed in some solids, as for example in camphor. Evaporation is much more rapid in some liquids than in others, and it is always found that those liquids, the boiling point of which is lowest, evaporate with the greatest rapidity. Thus alco- hol, which boils at a lower temperature than water, evaporates also more freely ; and ether, whose point of ebullition is yet lower than that of alcohol, evaporates with still greater rapidity. The chief circumstances that influence the process of evaporation are extent of surface, and the state of the air as to temperature, dry- ness, stillness, and density. 191. The conversion of a liquid into vapour is always attended Sensible, or with great loss of thermometric heat ; and as liquids may be regarded ela*^ as compounds of solids and heat, so vapours may be considered as. te nt. consisting of a similar combination of heat with liquids ; in other words, a great quantity of heat becomes latent during the formation^ of vapour. Moisten a thermometer with alcohol, or with ether, and expose it to the air, g t repeating these operations alternately. The mercury of the thermometer will ‘ " sink at each exposure, because the volatile liquor, during the evaporation, robs it of its heat. In this way, (especially with the aid of an apparatus, described by M. Cavallo, in the Philosophical Transactions, 1781, p. 509,) water may be frozen, in a thin and small glass ball, by means of ether. The same effect may be obtained, also, by immersing a tube, containing water at the bottom, in a glass of ether, which is to be placed under the receiver of an air pump ; or the ether may be allowed to float on the surface of the water. During the exhaustion of the vessel, the ether will evaporate rapidly, and, robbing the water of heat, will completely freeze it; thus exhibiting the singular spectacle of two fluids in contact with each other, one of which is in the act of boiling, and the other of freezing, at the same moment. By a little modification of the experiment, mercury itself, which Marcet’ requires for congelation a temperature of almost 40° below 0 of F. ? method of may be frozen, as was first shown by Marcet.'^ freezing mercury. Ah * A conical receiver, (Fig. 41,) open at the top, is placed on the Fig. 41. plate of an air-pump, and a small tube with a cylindrical bulb at its lower end, containing mercury, is suspended within the receiver, through the aperture, by means of a brass plate, perforated in its cen- tre, and fitting the receiver air-tight., when laid upon its open neck. The tube passes through this plate to which it is fitted by a leather adjustment, or simply by a cork secured withsealing wax. The bulb is then wrapped up in a little cotton wool, or, what is better, in a small bag of fine fleecy hosiery, in which a small spirit thermometer graduated below 40° F., may also be included, and after being dipped into sulphuret of carbon or ether,* the apparatus is quickly placed under the receiver, which is exhausted as rapidly as possible. In two or three minutes, the temperature sinks to about 45 Q below 0, at which moment the quicksilver in the stem suddenly descends with great rapidity. If it be desired to exhibit the mercury in a solid 1 ' state, common tubes may be used, which have originally been about an inch in diameter, but have been flattened by pressure, when softened by the blow- pipe. The experiment succeeds, when the temperature of the room is as high as + 40° Fahrenheit. H- 126. * In exhausting a vessel containing either of these fluids, the valves of the air pump should be metallic. 8 58 Caloric. Chap * *• 192. The loss of sensible heat attending the formation of vapour, Tempera- is proved by the well known fact that the temperature of steam is steam^ precisely the same as that of the boiling water from which it rises ; so that all the heat which enters into the liquid, is solely employed in converting a portion of it into vapour, without affecting the tem- perature of either in the slightest degree, provided the latter is per- mitted to escape with freedom. The heat which then becomes latent, to use the language of Black, is again set free when the vapour is condensed into water. The exact quantity of heat rendered insensi- ble by vaporization, may, therefore, be ascertained by condensing the vapour in cold water, and observing the rise of temperature which ensues. From the experiments of Black and Watt, conducted on this principle, it appears that steam of 212°, in being condensed into water of 212°, gives out as much heat as would raise the temperature of an % equal weight of water by 950 degrees, all of which had previously ex- isted in the vapour without being sensible to a thermometer. Latent heat The latent heat of steam and several other vapours has been exa- oi ‘ mined by Ure, whose results are contained in the following table. (Phil. Trans . 1818.) Latent Heat. Vapour of water at its boiling point Alcohol . Ether . Petroleum Oil of turpentine Nitric acid Liquid ammonia Vinegar, . 967 ° 442 302.379 177.87 177.87 531.99 837.28 875 * 193. The large quantity of heat, latent in steam, renders its ap- When a jet of liquid carbonic acid is directed upon mercury, it is so rapidly vaporized that the mercury is frozen. The pipes connected with the fountains from which soda water is drawn, are often closed by ice, formed on the sudden escape and expansion of the last portion of water and compressed gas. Henry’s appa- ratus. * The small boiler, represented in Fig. 42, taken from Henry’s Elements of Che- mistry , may be conveniently Fig. 42. employed in experiments on the latent heat ol steam. For this purpose the tubee must be screwed on the stop- cock b , and immersed into the glass of water f. The cock c being closed, the steam arising from the boiling water a will pass into the cold watery*, the temperature of which will be much augmented by its con* densation. Ascertain the in- crease of temperature and weight, and the result will show how much a given weight of water has had its tempera- ture raised by a certain weight of condensed steam. To ano- ther quantity of water of the same weight and temperature as that in the jar at the outset of the experiment, add a quan- tity of water at 212°, equal in weight to the condensed steam; it will be found, on comparing the resulting temperatures, that a given weight of steam has produced, by its condensation, a much greater elevation of temperature than the same quantity of boiling water. Steam . 59 plication extremely useful for practical purposes. Thus water may be Sect, iii. heated at a considerable distancefrom the conducting pipe e. (Fig. 42.) Economical This furnishes us with a commodious method of warming the water g t s e e a ^[ of baths, which, in certain cases of disease, it is of importance to have near the patient’s bed-room ; for the boiler, in which the water is heated, may thus be placed on the ground floor, or in the cellar of a house ; and the steam conveyed by pipes into an upper apartment. Steam may also be applied to the purpose of heating or evaporating water, by a modification of the apparatus.* In breweries and other in some manufactories, where large quantities of warm and boiling water are arts » consumed it is frequently heated by conveying steam into it, or by suffering steam-pipes to traverse the vessels or by employing double vessels, a plan adopted with particular advantage in the preparation of medicinal substances. Where a higher temperature than 212° is required it is necessary to employ steam under adequate pressure. 194. The perfect transparency of steam, and also two other impor- Steam is tant properties, on which depends its use as a moving power, viz. its J^ spa “ elasticity and its condensibility by a reduced temperature, are beau- tifully shown by a little apparatus contrived by Wollaston. It consists of a glass tube (Fig. 43) about 6 inches long and | inch bore, as cylindrical as possible, and blown out a little at the lower end. It has a wooden handle, to which is attached a brass clip embracing the tube ; and within is a piston, which, as well as its rod, is perforated, as shown by the dotted lines. This canal may be occasionally opened or closed by a screw at the top : and the piston rod is kept in the axis of the cylinder by being passed through a piece of cork fixed at the top of the tube. When the instrument is used, a little water is put into the bottom ; the piston is then introduced with its aperture left open ; and the water is heated over a spirit lamp. The common air is thus expelled from the tube, and when this may be supposed to be effect- ed, the aperture in the rod is closed by the screw. On ap- plying heat, steam is produced, which drives the piston up- wards. On immersing the bulb in water, or allowing it to * Fig 42, g represents the apparatus for boiling water by the condensation of steam, without adding to its quantity ; a circumstance occasionally of considerable importance. The steam is received between the vessel, which contains the water to be heated, and an exterior case ; it imparts its caloric to the water, through the substance of the vessel ; is thus condensed, and returns to the boiler by the perpendicular pipe. An altera- tion of the form of the vessel adapts it to evaporation (Fig. 42, h). This method of evaporation is admirably suited to the concentration of liquids, that are decomposed, or injured by a higher temperature than that of boiling water, such as medicinal ex- tracts ; to the drying of precipitates, &c. In the employment of either of these vessels, it is expedient to surround it with some slow conductor of heat. On a small sca'e a few folds of woollen cloth are sufficient ; and when the vessel is constructed of a large size for practical use, this purpose is served by the brick work in which it it. placed. H. 1. 135. A very convenient apparatus for drying precipitates, &c. by steam is described by Ure. tire’s drying A square tin box, about 18 inches long, 12 broad, and 6 deep, has its bottom hollowed a little by the hammer towards its centre, in which a round hole is cut of 5 or 6 inches diameter. Into this a tin tube, 3 or 4 inches long, is soldered. This tube is made to fit tightly into the mouth of a common teakettle, which has a folding handle. The top of the box has a number of circular holes cut. into it, of different diameters, in which evaporating capsules are placed. When the kettle, filled with water, and with its nozzle corked," is set on a stove, the vapour playing on the bottoms of the capsules, heats them, to any required temperature; and being itself continually condensed runs back into the kettle. The orifices not in use may be closed with tin lids. In drying- precipitates, the tube of the glass funnel should be corked up, and the funnel be placed, with its filter, directly into the proper sized opening. For drying red cabbage, violet petals, &c. a tin tray is provided, which fits close on the top of the box, within . the rim which goes about it. The round orifices are left open when this tray is applied. (Diet. Chem. 291.) Fig. 43, 60 Caloric. Chap. I. Reduction of tempera- ture by e- vaporation. Leslie’s method of freezing water. Wollas- ton’s Cryo- phorus. oool spontaneously, a vacuum is produced in the tube, and the piston is forced downwards by the weight of the atmosphere. These appearances may be alter- nately produced by repeatedly heating and cooling the water in the ball of the instrument. In the original steam engine, the vapour tvas condensed in the cylinder, as it is in the glass tube; but in the engine as improved by Watt, the steam is pumped into a separate vessel, and there con- densed ; by which the loss of heat, occasioned by cooling the cylin- der every time, is avoided. 195. Liquids assume the aeriform state much more rapidly under a diminished pressure, especially if the vapour which is formed, be condensed as soon as it is produced, so as to maintain the vacuum ; and the cold produced is very great. On this principle depends Leslie’s ingenious mode 0 / freezing water, in an atmosphere of any common temperature, by producing a rapid evaporation from the surface of the water itself. The water to be congealed is contained in a shallow porous vessel, which is sup- ported above another vessel, containing strong sulphuric acid, or dry chloride of calcium ; or even dried garden mould or parched oatmeal. Any substance, indeed, that powerfully attracts moisture, may be applied to this purpose. The whole is covered by the receiver of an air pump, which is rapidly exhausted ; and as soon as this is effected, crystals of ice begin to shoot in the water, and a considerable quan- tity of air makes its escape, after which the whole of the water be- comes solid. The rarefaction required is to about 100 times ; but to support congelation, after it has taken place, 20 or even 10 times are sufficient. The sulphuric acid becomes very warm ; and it is re- markable, that, if the vacuum be kept up, the ice itself evaporates. In fi ve or six days, ice of an inch in thickness will entirely disappear. The acid continues to act, till it has absorbed an equal volume of water.* In this interesting process, if it were not for the sulphuric acid, an atmosphere of aqueous vapour would fill the receiver; and, pressing on the surface of the water, would prevent the further production of vapour. But the steam, which rises, being condensed the moment it is formed, the evaporation goes on very rapidly, and has no limits but the quantity of the water, and the diminished concentration of the acid. 19G. It is on the same principle, that the instrument invented by Wollaston, and termed by him the Cryophorns , or Frostbearer , is founded. (Fig. 45.) When an instrument of this kind is well prepared, if the empty ball be immersed in a mixture of snow and salt, the water in ♦This beautiful experiment is not successful with pumps on the usual construction. Pumps are now made by Chamberlain of Boston, which produce the effect with ease and rapidity. See Frontispiece. An elegant manner of making the experiment is to cover the vessel of water (Fig. 44, a) with a plate of metal or glass, fixed to the end of a sliding wire b , which must pass through the neck of the receiver, and be at the same time air tight, and capable of be- ing drawn upwards. When the receiver is exhausted, the water will continue fluid, till the cover is removed, when, in less than five minutes, needle-shaped crystals of ice will shoot through it, and the whole will soon become frozen. Fig. 44. Effects of Evaporation. 61 the other ball, though at the distance of two or three feet* will be Sect. hi. frozen solid in the course of a very few minutes. # 197. The disappearance of heat that accompanies vaporization was explained by Black, in the way already mentioned under the head of liquefaction, (177.) The variation of volume and elasticity in vapours is attended, as in gases, with a change of specific heat and a consequent variation of temperature. Thus when steam, highly heated and compressed in a strong boiler, is permitted to escape by a large aperture, the sudden expansion is attended with a great loss of sensible heat : its tempera- ture instantly sinks so much, that the hand may be held in the cur- rent of vapour without inconvenience. The same principle accounts for the fact, first ascertained by Watt* that distillation at a low tem- perature is not attended with any saving of fuel. For when water boils at a low temperature in a vacuum, the vapour is in a highly expanded statej and contains more insensible heat than steam of greater density. 198. In many natural operations the conversion of water into va- pour, and the condensation of vapour in the form of dew and rain, is a process of the utmost importance, and tends considerably to the equalization of temperature over the globe. Water, as has been seen (192) in passing into vapour from heat, absorbs caloric without increasing in temperature; this vapour as- cends in the atmosphere ; when the heat diminishes, or when wafted to colder regions, it is condensed, and gives out the caloric it had ab- Tempera - sorbed. In seasons or situations where the cold becomes still more tl j r eo intense, water is congealed; and in suffering this change it evolves fqu a e ij Z ed. caloric (180) to moderate the progressive reduction of temperature. When warmth is restored, it returns to the liquid state, absorbs palo- ric, and retards the approaching heat. The transition of seasons is thus moderated ; sudden and extreme variations are guarded against, and the temperature of the globe everywhere preserved more uni- form. M. 1.480. 199. As evaporation goes on to a certain extent even at low tem- * It may be formed by taking a glass tube, having Fig. 45. an internal diameter about £th of an inch* the tube be- ing bent to a right angle at the distance of half an inch from each ball (Fig. 45). One of these balls should be about Jd filled with water, and the other should be as perfect a vacuum as can readily be obtained, the mode of effecting which is well known to those accustomed to blow glass. One of the balls is made to terminate in a capillary 3 tube; and when the water in the other ball has been boiled over a lamp a considerable time, till all the air is expelled, the capillary extremity, through which the steam is still issuing with violence, is held in the flame of the lamp, till the force of the vapour is so far reduced, that the heat of the flame has power to seal it hermetically. The experiment may be rendered even more striking, if per- formed according to Marcet’s modification of it : the empty ball cov- ered with a little moist flannel, is to be suspended in the manner shown in Fig. 46, within a receiver, over a shallow vessel of strong sulphuric acid, and the receiver is then to be exhausted. In both cases the vapour in the empty bail is condensed by the common opera- tion of cold ; and the vacuum produced by this condensation gives opportunity for a fresh quantity to arise from the opposite ball, with a proportional reduction of the temperature of its contents. Fig. 46. 62 Caloric. Hygrome- ters, Saussure’s, Chap. I. peratures, it is probable that the atmosphere is never absolutely free from vapour. The quantity of vapour present in the atmosphere is very variable, in consequence of the continual change of temperature to which the air is subject. But even when the temperature is the same, the quantity of vapour is still found to vary ; for the air is not always in a state of saturation. This variable condition of the atmosphere as to saturation is ascertained by the hygrometer. 200. A great many hygrometers have been invented ; but they may all be referred to three principles. The construction of the first kind of hygrometer is founded on the property possessed by some substances of expanding in a humid atmosphere, owing to a deposition of moisture within them ; and of parting with it again to a dry air, and in consequence contracting. Of these, none is better than the hu- man hair, which not only elongates freely from imbibing moisture, but, by reason of its elasticity, recovers its original length on drying. The hygrometer of Saussure is made with this material. The second kind of hygrometer points out the opposite states of dryness and moisture by the rapidity of evaporation. Water does not evaporate at all when the atmosphere is completely saturated with moisture ; and the freedom with which it goes on at other times, is in proportion to the dryness of the air. The hygrometric condition of the air may be determined, therefore, by observing the rapidity of evaporation. The most convenient method of doing this is by covering the bulb of a thermometer with a piece of silk or linen, moistening it with water, and exposing it to the air. The descent of the mercury, or the cold produced, will correspond to the quantity of vapour formed in a given time. Leslie’s hygrometer is of this kind. The third kind of hygrometer is on a principle entirely different from the foregoing. When the air is saturated with vapour, and any colder body is brought into contact with it, deposition of moisture immediately takes place on its surface. This is often seen when a glass of cold spring water is carried into a warm room in summer ; and the phenomenon is witnessed in the formation of dew, the moisture appearing on those substances only which are colder than the air. 201. Until the experiments of Wells* the deposition of dew and Hoar frost. ] 10ar f ro st had been supposed to depend entirely upon the reduction of temperature in the air during the night, and the consequent pre- cipitation of its moisture to the earth. Wells has shown that the deposition of dew and hoar frost, is the consequence of the radiation of caloric from the surface of the earth, and that, under favourable circumstances, the temperature of the ground, especially when its covering is formed of some substance that radiates freely, as grass, is several degrees below that of the atmospheric stratum, a few feet above it. It is this diminished temperature of the earth’s surface, that occasions the depositions of dew and hoar frost, which are always observed to be most abundantly formed under a clear un- clouded sky; a covering of clouds serves as a mantle to the earth, and prevents the free escape of radiant caloric, hence the advantage of snow and artificial coverings in protecting plants. Leslie’s. Dew and Eseay on Detr, <$y. Conducting Powers. 63 The temperature at which dew begins to be deposited is called the Sect, hi. dew point, for determining which a very ingenious instrument has Dewpoint, been contrived by Daniell.^ {Jour. Royal Institut. Yol. 8.) 202. When different bodies are exposed to the same source of Conducting heat, they suffer it to pass through them with very different degrees todies for of velocity, or they have various conducting powers in regard to heat, caloric, Among solid bodies, metals are the best conductors ; and silver, gold, tin and copper, are better conductors than platinum, iron, and lead. Next to the metals, we may, perhaps, place the diamond and topaz ; then glass ; then siliceous and hard stony bodies in general ; then soft and porous earthy bodies, and wood ; and lastly, down, feathers, wool, and other porous articles of clothing. 203. To exhibit the general fact, small cones of the different sub- Apparatus stances may be used about three inches high, and half an inch in [• ) „ g lllustra ' diameter at their bases : these may be tipped at the apex with a small piece of wax, and being placed on a heated metallic plate, will indicate the conducting powers by the relative times required to fuse the wax, which will be inversely, as the power of conducting heat.f The difference between the conducting power of the diamond and rock crystal or glass, is shown by applying the tongue to those sub- stances, when the former feels colder than the latter.! 204. Rumford’s experiments on the conducting power of several Conducting substances used as clothing, offer some interesting results.^ He ^° 0 Yh[ n g f found that a thermometer enclosed in a tube and bulb of the same substances, shape, but large enough to allow of an inch vacant space between the two, being previously heated, required 576 seconds to cool 135°. When 16 grains of lint were' diffused through the confined air, it took 1032 seconds to undergo the same change of temperature ; and 1305 seconds, with the same weight of eider down. The compres- sion of flocculent substances to a certain extent, renders them still inferior conductors ; thus, when the space which in the above expe- riments contained 16 grains of eider down was filled with 32, and then with 64 grains, the times required for the escape of 60 degrees of heat were successively increased ‘from 1305" to 1475" and 1615". On the other hand to show the effect of mere texture , similar Effect of comparative trials were made of the conducting powers of equal texture, weights of raw silk, of ravellings of white taffeta, and of common sewing silk, of which the first has the finest fibre, the second less fine, and the third, from being twisted harder, is much coarser. * A less expensive instrument is made by Pollock, of Boston ; it is a thermometer filled with ether, having two bulbs at the same extremity of the tube, the upper one being covered with muslin. When sulphuric ether is dropped upon the muslin, the temperature of the two bulbs falls, and a deposition of dew becomes visible on the lower and exposed bulb. The degree indicated by the thermometer at that instant is the dew point* * * § t This experiment may be varied by attaching small pieces of phosphorus to the cones. See on this subject ingenious experiments and apparatus by Bache, in Am. Jour., xxviii. 320. tFrom the experiments of Mayer, of Erlangen, (Ann. de Chirn. tom. xxx,) it would appear that the conducting powers of different woods are in some measure inversely as their specific gravities, water being assumed as= 1. § Phil. Trans. 1792. * See description of a Portable Hygrometer, Hayes, in Am. Jour . Sci. xvii. 351. 64 Caloric. Chap. I. Practical application. Sensations of heat and cold Liquids and gases im- perfect con- ductors. Exp. Exp, Exp. The difference between these three modifications of the same sub- stance is very striking, the raw silk detaining the heat for 1824", the taffeta ravellings 1469 1 and the silk thread only 947 1 205. The different conducting powers of bodies in respect to heat, are shown in the application of wooden handles to metallic vessels ; or a stratum of ivory or wood is interposed between the hot vessel and the metal handle. The transfer of heat is thus prevented. Heat is confined by bad conductors ; hence clothing for cold climates com sists of woollen materials ; hence, too, the walls of furnaces are composed of clay and sand. Confined air is a very bad conductor of heat ; hence the the advantage of double doors to furnaces, to pre- vent the escape of heat ; and of a double wall, with an interposed stratum of air, to an ice-house, which prevents the influx of heat from without. 206. From the different conducting powers of bodies in respect to heat, arise the sensations of heat and cold experienced upon ther ap- plication to our organs, though their thermometric temperature is similar. Good conductors occasion, when touched, a greater sensa- tion of heat and cold than bad ones. Metal feels cold because it readily carries off the heat of the body ; and we cannot touch a piece of metal immersed in air of a temperature moderate to our sense. 207. Liquids and gases are very imperfect conductors of heat, and heat is generally distributed through them by a change of specific gravity ; by an actual change in the situation of their particles. Take a glass tube, ten or twenty inches long, and four or six in diameter. Pour into the bottom part, for about the depth of five inches, water tinged with litmus, or cabbage, and fill up the tube with common water, pouring on the lat- ter extremely gently, so as to keep the two strata quite distinct. If the upper part of the tube be first heated, the coloured liquor will remain at bottom ; but if the tube be afterwards heated at bottom, the infusion will ascend, and will tinge the whole mass of fluid. A convenient method of exhibiting this has been contrived by Hare. (Fig. 47.) A glass jar, about 30 inches in height, is supplied with as much colourless water as will rise in it with- in a few inches of the brim. By means of a tube descending to the bottom, a small quantity of blue colouring matter is in- troduced belotd the colourless water, sq as to form a stratum, as represented at A in the annexed cut A stratum different- ly coloured, is formed in the upper part of the vessel, as at B. A tin cap, supporting a hollow tin cylinder, closed at the bot- tom, and about an inch less in diameter than the jar, is next placed as it is seen in the figure, so that the cylinder may be concentric with the jar, and descend about 3 or 4 inches into the water. If an iron heater H while red hot, be placed within the tin cylinder, the coloured water about it will soon boil ; but the heat penetrates only a very small distance be- ^ ^ low the tin cylinder, so that the colourless water, and the 1 ■ -*^R coloured stratum, at the bottom of the vessel, remain undisturbed, and do not mingle. But if an iron ring k be placed while red hot, upon the iron stand which surrounds the jar at S, S, the liquid soon rises, in beautiful clouds, until it en- counters the warmer and lighter particles which had been in contact with the tin cylinder.! Fill a jar with hot water ; and place a cake of ice on the surface of the water. The ice will soon be melted. This experiment is the more striking, if the water * Aiken’s Did. art. Caloric. t From Hares’s Engravings and description of Chemical Apparatus , &c. Part 1st, page 41. Fig. 47. Co) H Radiation , 65 used for forming the cake of ice, be previously coloured with litmus ; for, the Sec. Ill . descending currents of cold water are thus made apparent. Rumford’s Substituting water of the temperature of 11° for the boiling water used in this exper i„ experiment, Rumford found, that, in a given time, a much greater quantity of mep t 5- ice was melted by the cooler water. This appears, on first view, rather para T doxical. The fact, however, is explained by the remarkable property of water, viz. that when cooled, below 40°, it ceases to contract, and experiences on the contrary, an enlargement of bulk. Water, therefore, at 40° (at the bottom of which is a mass of ice at 32°,) is cooled by contact with the ice, and is expan- ded at the same moment. It therefore ascends, and is replaced by a heavier and warmer portion from above. 208. It is a consequence of the same property, that the surface of a deep lake is sometimes covered with ice, even when the water be- low is only cooled to 40°; for the superficial water is specifically light- er than the warmer water beneath it, and retains its place, till it is changed into ice. This property of water is one of the most remark- able exceptions to the law of expansion. (153.) 209. From the fact that heat applied to the upper surface of water, will with difficulty make its way downwards, (207), Rumford was induced to deny that water could conduct at all. Let an air thermometer be cemented into a glass funnel sup- ported as represented in Fig. 48 ; cover the bulb of the instru- ment with water, and upon the surface of the water pour a small quantity of ether,. The ether may be inflamed and the air thermometer will not be sensibly affected. 210. The inference that water is a complete non- conductor of caloric has been contradicted by the sub? sequent inquiries of Hope, Thomson, and Murray. Though they all admit that water and liquids in general, mercury excepted, possess the power of con- ducting caloric in a very slight degree. The follow- ing experiment made by Murray has been deemed con- clusive. If we carefully pour hot oil upon water in a tall glass jar, with delicate ther- „ mometers placed at different distances under the surface, it will be found that • P' those near the heated surface indicate increase of temperature. It might here be said that the heat was conducted by the sides of the jar, and so communicated to the water; to obviate such objection Murray made the experiment in a vessel of ice, which being con- verted into water at 32°, cannot convey any degree of heat above 32° downwards ; yet the thermometers were affected, as in the for- mer trial.* 211. It is extremely difficult to estimate the conducting power of Aeriform aeriform fluids. Their particles move so freely on each other, that fluids, the moment a particle is dilated by heat, it is pressed upwards vvith great velocity by the descent of colder and heavier particles, so that an ascending and descending current is instantly established. Be- sides, these bodies allow a passage through them by radiation. 212. There is yet another mode by which heat passes from one Radiation, body to another ; and as it takes place in all gases, and even in vacuo, it is inferred that the presence of a medium is not necessary to its passage. This mode of distribution is called Radiation of Heat, and the heat so distributed is called Radiant , ox Radiated Heat. A heated body suspended in the air cools, or is reduced to an equili- * See Matther’s Experiments in Amer. Jour, of Sci. xii. 368. 9 Fig- 48. Exp. Fluids irm %./ perfect cop? luctors- AJ 66 Caloric. Chap. J. Course of radiant caloric. Radiation, in vacuo Influenced by surface. Leslie’s ex- periments. Bache ; « appa-’ raius. brium with surrounding bodies, in three ways; first, by the conduct- ing power of the air, the influence of which is very trifling ; secondly, by the mobility of the air, in contact with it ; and thirdly, by radiation. 213. Radiant caloric passes from a hot body in all directions in right lines, like radii drawn from the centre to the circumference of a circle. When these rays fall upon the surface of a solid or liquid sub- stance, they may be disposed of in three different ways. By reflec- tion, by absorption, and by transmission. In the first and third cases the temperature of the body on which the rays fall is altogether unaffected, whereas in the second it is in- creased. 214. Radiation in the air-pump vacuum, may be shown by igniting charcoal, by means of the Voltaic battery, placed in the focus of a small mirror con- fined in the exhausted receiver of the air-pump. Davy found that the receiver being exhausted to the effect upon the thermometer in the opposite focus was nearly three times as great as when the air was in its natural state of condensation, Fig. 49, a is the receiver, b b the insulated wires connected with the voltaic apparatus igniting the charcoal in the focus of the upper mirror c. In the focus of the lower mirror d is the thermometer e. 215. The radiation of heat by hot bodies is singularly influenced by the nature and condition of their surfaces, a circumstance which was first examined by Leslie.* He made use of a canister of planished block tin, forming a cube of six or eight inches, having an orifice at the middle of its upper side. This orifice re- ceived a cap having a small hole, through which a thermometer was inserted, so that its bulb reached the centre of the canister. One side of the canister he covered with black paint ; destroyed the polish of another side, by scratching it with sand-paper ; tarnished a third with quicksilver ; and left the fourth bright. The vessel was filled with boiling water. The radiation of caloric from the blackened side was so much more abundant than from the others, as to be even sensible to the hand. He placed it before a reflector (Fig. 51) in lieu of the heat- ed iron ball described (220.) The thermometer, in the focus of the second re- flector, indicated the highest temperature, or most copious radiation of caloric, when the blackened side was presented to the reflector ; less, when the tarnish- ed or scratched side was turned towards it ; and least of all from the polished side.t * Essay on Heat, 1804. t The annexed figure represents an ingenious and much better apparatus for show- ing the different absorbing and radiating powers of different surfaces. A prism of any convenient number of sides, is made into an air thermometer, by placing a glass tube in it through a conical opening which can be made air tight ; the sides are variously coated. This is made to fit loosely into a prism of the same form, but wanting one side. To show the different absorbing powers of the different sub- stances, the vessels are placed as in the figure, before another, A, containing hot water, hot sand or any other convenient source of heat. If the side of the air thermometer which is the worst absorbent of heat is exposed to the source of heat, the air within is expanded, and the position of the liquid in the tube is marked by the index; abetter absorbent is ex- posed, and the liquid rises higher ; a worse and it falls below its original level. The outer sheath protects the sides which are not intended to be exposed, from the radiation of the ves- sel A and equalizes the radiation from the surfaces not ex- posed. To show the radiating powers of the surfaces, the sheath is turned so that the open side is exposed to the air. — Bache in Amer. Jour, xxviii. 326. Fig. 50. Fig. 49. 67 Reflection of Heat. 216. It follows from these researches that velocity of radiation de- Sect - pends more on the surface than the substance of a radiating body : Inferences, that the most imperfect radiators are to be sought among those bodies which are highly smooth and bright, such as polished gold, silver, tin, and brass ; but that these same metals radiate freely when their smoothness and polish are destroyed, as by scratching their surfaces with a file, or covering them with whiting or lampblack. A metal- lic surface seems adverse to radiation independently of its smooth- ness, since a highly polished piece of glass radiates far better than an equally polished metallic surface. Scratching a surface probably favours radiation by multiplying the number of radiating points. 217. Some interesting experiments by Stark of Edinburgh have stark’* appeared,^ illustrative of the connexion between radiation and the ex P eri * colour of surfaces. The bulb of a delicate thermometer was sue- ments ‘ cessively surrounded by equal weights of differently coloured wool, was placed in a glass tube, heated by immersion in hot water to 180°, and then cooled to 50° in cold water. The times of cooling were 21 minutes with black wool, 28 with red wool, and 27 with, white wool. Concurring results were obtained with flour of differ- ent colours. Likewise, black wool was found to collect more dew than an equal weight of white wool, other circumstances being alike. This is the first time that direct experiments, seemingly unexception- able, have been made in proof of the influence of colour over radia- tion. 218. It has been known for ages that the heat contained in the Reflection solar rays admits of being reflected by mirrors, and a like property °f caloric, has long since been recognized in the rays emitted by red-hot bo- dies ; but that heat emanates in invisible rays, which are subject to the same laws of reflection as those that are accompanied by light, is a modern discovery, noticed indeed by Lambert, but first decisive- ly established by Saussure and Pictet of Geneva. (220) This reflection of heat may be shown by standing at the side of a fire in such a position that the heat cannot reach the face directly, and then placing a plate of tinned iron opposite the grate, and at such an inclination as permits the observer to see in it the reflection of the fire: as soon as it is brought to this inclination, a distinct im- pression of heat will be perceived upon the face. If a line be drawn from a radiating substance to the point of a plane surface by which its rays are reflected, and a second line from that point to the spot where its heating power is exerted, the angles which these lines form with a line perpendicular to the reflecting plane are called the angles of incidence and reflection , and are invariably equal to each other. It follows from this law, that when a heated body is placed in the focus of a concave parabolic reflector, the diverging rays which strike upon it assume a parallel direction with respect to each other ; and that when these parallel rays impinge upon a second concave reflec- tor, standing opposite to the former, they are made to converge, so as to meet together in its focus. Their united influence is thus brought to bear upon a single point. * Edin. Phil. Trans. Part II. 1833. 68 Caloric. Chap. I. Pictet’s ex- periments. Apparent reflection of cold. 219. Those surfaces, that reflect light most perfectly are not equal- ly adapted to the reflection of caloric. Thus, a glass mirror, whicl reflects light with great effect when held before a blazing fire, scarce ly returns any heat, and the mirror itself becomes warm. On th* contrary, a polished plate of tin, or a silver spoOn, when similarly placed reflects, to the hand, a very sensible degree of warmth ; anc the metal itself remains cool. Metals, therefore, are much bettei reflectors of caloric than glass ; and they possess this property, ex* actly according to their degree of polish. 220. Caloric is reflected according to the same law that regulate* the reflection of light. This is proved by an interesting experimen of Pictet ; the means of repeating which may be attained at a moder ate expense. Provide two reflectors of planished tin, (a and 6, Fig. 51), which may be 1« inches diameter, and segments of a sphere of nine inches radius. Parabolic mirrors are still better adapted to the purpose, but their construction is less easy. Each of these must be furnished, on its convex side, with the means of support- ing it in a perpendicular position on a proper stand. Place the mirrors opposite to each other on a table, at the distance of from 6 to 12 feet. Or they may be placed in a horizontal position, as represented in the fourth plate to Davy’s Chemical Philosophy , an arrangement in some respects more convenient, in Fig. 51. the focus of one, let the ball of an air thermometer, or (which is still better) one of the balls of a differential thermometer, be situated ; and in that of the other, suspend a ball of iron, about four ounces in weight, and heated below ignition, or a small matrass of hot water ; having previously interposed a screen before the thermometer. Immediately on withdrawing the screen, the depression of the column of liquid, in the air thermometer, evinces an increase of tempera- ture in the instrument. In this experiment, the caloric flows first from the heated ball to the nearest reflector ; from this it is transmitted, in parallel rays, to the surface of the second reflector, by which it is collected into a fo- cus On the instrument. This is precisely the course that is followed by radiant light ; for if the flame of a taper be substituted for the iron ball, the image of the candle will appear precisely on that spot, (a sheet of paper being presented for its reception,) where the rays of caloric were before concentrated. 221. When a glass vessel, filled with ice or snow, is substituted for the heated ball, the course of the coloured liquid in the ther- mometer will be precisely in the opposite direction ; for its ascent will show, that the air in the ball is cooled by this arrangement. This experiment, which appears, at first view, to indicate the reflec- 69 Influence of Colours . lion of cold, presents, in fact, only the reflection of heat in an op- s , ect - In - posite direction ; the ball of the thermometer being, in this instance, the hotter body. 222. From what has been said concerning the communication Practical and radiation of heat, and of the circumstances that influence the useSi heating and cooling of bodies in these different ways, many useful practical observations may be drawn. Water continues much longer warm in a resplendent than in a blackened vessel. Hence metallic ones., with their surfaces polished, are employed for holding warm water, when we wish it to retain its heat for some time. It is a common remark, that tea is more easily infused in a silver than in an earthen tea-pot, which was at one time supposed to be owing to some property of the metal itself, but which is now accounted for by the laws of radiation, the bright metallic surface giving forth fewer rays than the other, and, of course, cooling the water less slowly. A metal is, however, a good conductor $ it is of advantage therefore, to' have not only a bad radiator, but also a bad conductor, that the heat given off from the surface by radiation, may be slowly sup- plied from the interior. Hence the frequent use of earthen ware covered with metallic matter, for holding warm fluids, as for jugs and tea-pots, the earthen ware being a bad conductor, and, by hav- ing its surface resplendent, becoming also a bad radiator, by which little heat is given off. 223. When, on the contrary, we wish to cool a fluid quickly, it must be put into a vessel which is a good conductor, as a metallic one, and with its surface blackened, to make it a good radiator. In conveying heated air, or steam, from one place to another, with the view of heating apartments, the tube ought to be made of bright metal, as tinned iron, that there may be little heat lost before the air reaches the place to be warmed. When, on the contrary, the steam is to be condensed, the tubes ought to be made of blackened metal, as sheet iron, so that a great deal of caloric may be given off, both by radia- tion and by communication. 224. When we have to guard a body from heat, we cannot employ a better protector than a plate of bright metal. Thus, in erecting a stove near woodwork, the latter ought to have a sheet of tinned iron placed near it, but not in contact with it, by which the greater part of the rays sent off from the stove are reflected. Should the metal it- self become warm, the layer of air between it and the wood, being a tery bad conductor, prevents in a great measure the transmission of the heat. Should stone be employed as the protector, it should be whitened, so that it may absorb as few of the rays as possible. 225. As the reflecting power is materially influenced by the na- ture of surfaces, the absorptive power must be so likewise. Those qualities of a surface which increase reflection are to the same extent adverse to absorption ; and those which favour absorption are pro- portionally injurious to reflection.* Colour has considerable influ- influence of ence, as is shown by the following very simple experiment of col °ur. Franklin. On a winter’s day, when the ground is covered with snow, take four pieces of Exp. woollen cloth, of equal dimensions, but of different colours, viz. black, blue, * See Ritchie’s experiments, Jour. Roy. Inst, v, 305 . 70 Caloric. Chap. I. brown, and white, and lay them on the surface of the snow, in the immediate neighbourhood of each other. In a few hours, the black cloth will have sunk considerably below the surface ; the blue almost as much ; the brown evidently less ; and the white will remain precisely in its former situation. Thus it appears that the sun’s rays are absorbed by the dark co- loured cloth, and excite such a durable heat, as to melt the snow un- derneath ; but they have less power of penetrating the white. Hence the preference, generally given to dark coloured clothes du- ring the winter season, and to light coloured ones in summer, appears to be founded on reason. ^Stark 16 * dependence of the absorptive power for simple heat on ° ’ colour has not till lately been noticed. From researches by Stark, it seems that differently coloured wools wound upon the bulb of a ther- mometer, and exposed within a glass tube to hot water, rose from 50° to 170 in the following times, — black wool in 4' 30", dark green in 5', scarlet in 5' 30", white in 8'. Of Nobili 227. An interesting connexion has been traced by Nobili and Mel- and Mel- loni between the absorbing and conducting power of surfaces,* and loni ‘ their researches, if free from fallacy, justify the inference that the radiating and absorbing powers of surfaces for simple heat are in the inverse order of their conducting powers, t. it. Transmi*- 228. Radiant heat passes with perfect freedom through a vacuum, sionof The air and gaseous substances present but a feeble barrier to its progress; so feeble, indeed, that the degree of impediment which they occasion has not yet been appreciated. Transparent media of a denser kind, on the contrary, such as the diamond, rock-crystal, glass, and water, even in thin strata, greatly interfere with its pas- sage, and when in moderately thick masses intercept it altogether. This last remark, however is only applicable to simple heat, that is, to heat unassociated with light. The solar rays pass readily through the substance of glass, both heat and light being refracted in their passage, as is shown by the operation of a burning-glass or lens ; and though much of the heat emitted by the flame of a lamp, or a red hot ball of iron, is arrested by glass, many calorific rays are di- rectly transmitted along with the light. But the result is different when the heated body is not luminous. Leslie denied that any rays of simple heat can pass by direct transmission through glass, and Brewster has supported this opinion by an argument suggested by his optical researches.! Several ingenious experiments have been made on this subject by Ritchie ; and it has lately been examined by Nobili and Melloni with the aid of their thermo-multiplier. Ail these experimenters concur in the belief of direct transmission. The total effect from this cause is, however, very small ; and with screens of moderate thickness it is wholly imperceptible. Heat polar- 229. The recent experiments of Forbesf have established the lzed ' polarization of heat under all the circumstances in which light is polarized, namely, by reflection, transmission, and double refraction. § Theories of 230. The tendency which all bodies evince to attain an equa- radiation. 0 f temperature by means of radiation, has given rise to two in- genious theories, suggested respectively by Pictet and Prevost. * An. de Chim. et dePhys. xlviii. 198. t Phil. Trans. 1816, p. 106 . $ laond. and Edin . Phil. Mag. vi. 134. § Edin. new Philos. Jour., No. 40. 71 Light . According to the former, bodies of equal temperature do not radiate Rect - 1V - at all ; and when the temperature is unequal, the hotter give calo- rific rays to the colder bodies till an equilibrium is established, at which moment the radiation ceases. Prevost, on the contrary, con- ceived radiation to go on at all times, and from all substances, whe- ther their temperature were the same or different from that of surrounding objects.^ Consistently with this view, the temperature of a body falls whenever it radiates more heat than it absorbs ; its temperature is stationary when the quantities emitted and received are equal ; and it grows warm when the absorption exceeds the radi- ation. A hot body surrounded by others colder than itself, affords an instance of the first case ; the second happens when all the sub- stances within the sphere of each other’s radiation have the same temperature ; and the third occurs when a body is introduced into a room which is warmer than itself. Of these theories the preference is very generally accorded to the latter. Most of the phenomena of radiation, indeed, admit of a satisfactory explanation by both ; but, on the whole, the theory of Prevost is more generally applicable, t. 12. 231. The sources of heat maybe reduced to six. 1 . The sun. Sources of 2. Combustion. 3. Electricity. 4. The bodies of animals during heat, life. 5. Chemical action. 6. Mechanical action. All these means of procuring a supply of heat, except the last, will be more conve- niently considered in other parts of the work. The mechanical me- thod of exciting heat is by friction and percussion. 232. Nothing is known of the nature or cause of heat. It has Nature of been by some considered as a peculiar fluid, to which the term eat * Caloric has been applied ; and many phenomena are in favour of the existence of such a fluid. By others, the phenomena above de- scribed have been referred to a vibratory motion of the particles of matter, varying in velocity with the perceived intensity of the heat. In fluids and gases the particles are conceived to have a motion round their own axes. Temperature , therefore, would increase with the velocity of the vibrations ; and increase of capacity would be produced by the motion being performed in greater space. The loss of tem- perature, during the change of solids into liquids and gases, would depend upon loss of vibratory motion, in consequence of the acquired rotatory motion. Upon the other hypothesis, temperature , is referred to the quantity of caloric present; and the loss of temperature, which happens when bodies change their state, depends upon the chemical combination of the caloric with the solid in the case of liquefaction, and with the liquid in the case of conversion into the aeriform state, b. Section IV. Of Light. 233. The minute investigation of the laws of light belongs to Mechanical Philosophy ; it is however requisite that some of them should partially be considered as bearing upon important questions of chemical inquiry. ... The phenomena of vision are produced either by bodies inherent- Vision. * Recherches sur la Chaleur. 72 Light. in right lines. Refraction. Cha P *■ ly luminous, such as the sun, the fixed stars, and incandescent sul> stances; or they are referable to the reflection of light from the sur- faces of bodies. Light 234. The manner in which the eye is affected by luminous bodies transmitted shows that light is transmitted in right lines, and every right line drawn from a luminous body to the eye is termed a ray of light, and as a congeries of rays possesses the same properties as the single ray, the same abstract term is frequently employed to designate the congeries. 235. Newton first discovered that certain bodies exercise on light a peculiar attractive force. When a ray passes obliquely from air into any transparent liquid or solid surface, it undergoes at entrance an angular flexure, which has been called refraction . The refrac- tion is towards the perpendicular when the ray passes into a denser medium, and from the perpendicular when it passes into a rarer me- dium. The medium in which the rays of light are caused to ap- proach nearest to the line perpendicular to its surface, is said to have the greatest refractive density. It was found by Newton, that unctuous, or inflammable bodies oc* casioned a greater deviation in the luminous rays than their attrac- tive mass, or density gave reason to expect. Hence he conjectured, that both diamond and water contained combustible matter. Ob- servation has since shown that oils and other highly inflamma- ble bodies, such as hydrogen, diamond, phosphorus, sulphur, amber, olive oil and camphor, have a refractive power which is from two to seven times greater than that of incombustible substances of equal density. 236. The refractive power of the same inflammable substance bears a proportion to its perfection, insomuch that this property may be used Refractive power of inflamma- ble bodies, May be used as a test of their purity, that that oil of genuine of an inferior as a test of its purity. Thus Wollaston found cloves has a refractive power of 1,535, while quality did not exceed 1,49S. The density of bodies is not the only circumstance that affects their refractive power ; it also depends on their chemical nature, and from the refractive power of bodies we may in many cases infer their chemical constitution. 237. The refractive power of compounds is not the mean deduced the meonof ^ rom components; which, however, it generally is in that of their mere mixtures. constitu 238. When the rays of light arrive at the surfaces of bodies, a part Reflected anc ^ sometimes nearly the whole, is thrown back, or reflec - e eC e ted , and the more obliquely the light falls upon the surface, the greater in general is the reflected portion. In these cases the angle of reflection is always equal to the angle of incidence. Depends on the chemi- cal nature as well as density, Of corn- light. Let a a represent pencils of light falling upon the surface of a polished piece of glass B, the perpendicu- lar pencil will pass on in a straight line to d. Of the oblique pencil, one portion will enter the glass and sutler refraction towards the perpendicu- lar as at b, and re-entering the atmosphere, it will bend from the perpendicular, and re-assume its former di- rection, as at c. Another portion of the oblique pencil will be reflected at an angle equal to that of its inci- dence, as at e. Fig. 52. Polarization . 73 239. When a ray of light passes through an oblique angular crys- Sect, iv. talline body, it exhibits peculiar phenomena; one portion is refracted in the ordinary way ; another suffers extraordinary refraction, in a plane parallel to the diagonal joining the two obtuse angles of t ^ ie Doublere . crystal ; so that objects seen through the crystal appear double. f ract j on< Transparent rhomboids of carbonate of lime, or Iceland crystal, ex- hibit this phenomenon of double refraction particularly distinct. If a ray of light, which has thus suffered double refraction, be re- ceived by another crystal, placed parallel to the first, there will be or di n ary no new division of the rays ; but if it be placed in a transverse di- refraction, rection, that part of the ray which before suffered ordinary refrac- tion will now undergo extraordinary refraction, and reciprocally that which underwent extraordinary refraction now suffers ordinary re- fraction. If the second crystal be turned gradually round in the same plane, Refracting when it has made a quarter of a revolution, there will be four di‘P°^^ de visions of the ray, and they will be reduced to two in the half of the j )en dentup- revolution ; so that the refracting power appears to depend upon on some some relation of the position of the crystalline particles. crystalline 240. When light is reflected from bodies, it retains, under many particles, circumstances, its former relations to the refractive power of trans- parent media ; but, in certain cases, at angles differing for different substances, the reflected rays exhibit peculiar properties, analogous to those which have suffered extraordinary refraction. Thps, if the flame of a taper reflected at an angle of 52° 4 5' from the surface of water, be viewed through a piece of double refracting spar, one of the images' will vanish every time that the crystal makes a quarter of a revolution. 241. When a ray of light is made to fall upon a polished glass Ang j e of surface, at an angle of incidence of 35° 25', the angle of reflection incidence will be equal to that of incidence. Let us suppose another plate of^qua^tothe glass so placed that the reflected ray will fall upon it at the same fle ;: tion> angle of 35° 25'; this second plate may be turned round its axis without varying the angle which it makes with the ray that falls upon it. A curious circumstance is observed as this second Curious in- glass is turned round. Suppose the two planes of reflection to be parallel to each other, in that case the ray of light is reflected from mission the second glass in the same manner as from the first. Let the sec- and reflcc- ond glass be now turned round a quadrant of a circle, so as to make |j, jbt the reflecting planes perpendicular to each other : now, the whole of the ray will pass through the second glass, and none of it will be reflected. Turn the second glass round another quadrant of a cir- cle, so as to make the reflecting planes again parallel, and the ray will again be reflected. When the second glass Is turned round, three quadrants, the light will be again transmitted, and none of it reflected. Thus, when the reflecting planes are parallel, the light is reflected, but when they are perpendicular the light is transmitted. This experiment proves, that, under certain circumstances, light can penetrate through glass when in one position, but not in another. PoIanza ' This curious fact was first observed by Malus, who accounted for it by supposing the particles of light to have assumed a particular po- sition as a needle does when under the influence of a magnet, and 10 tion. 74 Light. Chap. I. Analysis of light. Prismatic colours. Newton’s theory of colours. Seebeck’s experi- ments. Melloni’s. Influence over the chemical enemies of bodies. hence he called this property of light, its Polarization* It has since been studied with laborious diligence by Brewster, and by Arago and Biot.t 242. That a sunbeam, in passing through a dense medium, and especially through a triangular prism of glass, gives rise to a series of brilliant tints similar to those of the rainbow’, was known in the earliest ages, but it required the sagacity of Newton to develop the cause of the phenomenon. He inferred, that light consists of rays differing from each other in their relative refrangibilities ; and, gui- ded by their colour considered their number as seven : red, orange, yellow, green, blue, indigo, and violet. $ If the prismatic colours, or spectrum , be divided into 360 equal parts, the red rays will occupy 45 of these parts, the orange 27, the yellow 48, the green 60, the blue 60, the indigo 40, and the violet 80. Of these rays the red being least refrangible, fall nearest that spot which they would have passed to, had they not been refracted ; while the violet rays being most refrangible, are thrown to the greatest distance ; the interme- diate rays, possess mean degrees of refrangibility. 243. These differently coloured rays, w'hen collected into a focus reproduce white light. Upon these phenomena is founded the New- tonian theory of colours, which supposes them to depend upon the absorption of all rays, excepting those of the colour observed. 244. If a solar beam be refracted by a prism, and the coloured image received upon a sheet of paper it will be found, on moving the hand gently through it, that there is an evident difference in the healing power of the rays. Englefield, Davy and others, affirmed with Herschel, that the heat is greatest beyond the red ray ; while others contend that it is in the red ray itself. The observations of Seebeck^ have explained these contradictory statements, by showing that the point of greatest heat varies with the kind of prism employ- ed. These results have been confirmed by Melloni, who has suc- ceeded with a prism of rock salt in separating the spot of maximum heat from the coloured part of the spectrum by a much greater in- terval than had been done previously. The facts that have been arrived at, go far to prove that most, if not all, of the heating pow- er ascribed to light, is due, not to the absorption of luminous rays, but to that of the heat by which they are accompanied. 245. Light possesses considerable influence over the chemical en- ergies of bodies. If a mixture of equal volumes of the gases called chlorine and hydrogen be exposed in a dark room, they slowly com- bine, and produce hydrochloric acid gas ; but, if exposed to the di- rect rays of the sun, the combination is very rapid, and often accom- panied by an explosion. * See Fischer’s Elements of Natural Philosophy , page 336. Thomson’s System 1. p. 16. t Phil. Trans. 1813, 1814, 1815, 1816, 1817. — Ann. dc Chim. tom. 94. Traitt de Phys. t Wollaston found, however, that when a beam of light only inrth of an inch broad is received by the eye, at the distance of ten feet, through a clear prism of flint glass, only four colours are seen, viz. red, yellowish green, blue, and violet- Brewster has proved that the colours of the spectrum are occasioned by threo simple primary rays viz. the red, yellow and blue. § Edin. Jour, of Sci. 1 , 358. Photometer. lb Chlorine and carbonic oxide have scarcely any tendency to com- Sect, iv. bine, even at high temperatures, when light is excluded, but exposed to the solar rays they enter into chemical union. Chlorine has lit- tle action upon water, unless exposed to light, and, in that case, the water, which consists of oxygen and hydrogen, is decomposed. The hydrogen unites with the chlorine to produce hydrochloric acid, and the oxygen is evolved in a gaseous form. 246. These, and numerous other similar cases, show that solar Produces light influences the chemical energies of bodies, independent of its heating powers. Many important facts have been ascertained by Ritter, Wollaston, and Davy. Scheele* threw the prismatic spectrum upon a sheet of paper, moistened with a solution of nitrate of silver, a salt quickly decomposed by the agency of light. In the blue and violet rays the silver was soon reduced, producing a blackness upon the paper, but in the red ray scarcely any similar effect was observed. Wollaston and Ritter discovered that these chemical changes were most rapidly effected in the space which bounds the violet ray, and which is out of the visible spectrum. Davy has observed, that certain metallic oxides, when exposed to the violet extremity of the prismatic spectrum, undergo a ehange similar to that which would have been produced by exposure to a current of hydrogen ; and that when exposed to the red rays, they acquire a tendency to absorb oxygen. t 247. The more refrangible rays of light have been thought to Magnet- possess the property of rendering steel or iron magnetic. This pro- iz * n & a .v s - perty was announced by Morrichini of Rome; but as the experiment did not succeed in other hands, the subject was involved in some de- gree of uncertainty. The fact, however, appeared to be established by Mrs Somerville of London, in 1826, who gave an account of her researches to the Royal Society. Since that period the subject has been re-examined by Riess and Moser. They object to Mrs Somer- ville’s results, that her method of ascertaining the magnetic state of the needles used in the experiments, was not sufficiently precise : they deny the supposed magnetizing power of light. 4 248. The comparative intensities of light are measured by the in- photome- slrument called a Photometer : that which is known as Leslie’s is ter - constructed on the principle that light, in proportion to its absorption, produces heat. It is merely a very delicate and small differential thermometer, enclosed in a thin and pellucid glass tube. One of the bulbs is of black glass, which, when the instrument is suddenly ex- posed to light, becoming warmer than the clear bulb, indicates the effect by the depression of the fluids From the experiments of Turner and Christison this instrument does not appear applicable to lights which differ in colour, because the relation between the heat- ing and illuminating power of such light is exceedingly variable. Thus, the light emitted by burning cinders or red-hot iron, even after passing through glass, contains a quantity of calorific rays, which is out of all proportion to the luminous ones ; and, consequently, they may and do produce a greater effect on the photometer, than some * Experiments on Air and Fire , p. 78, &c. t Elements of Chem. Phil. Edin- Jour, of Sci. 2, 225. § Leslie on Heat , p. 424. 76 Chap. I. Perfect vegetation requires the influ- ence of solar rays. Drum- mond’s light. Phospho- rescent bodies. Solar phos- phori. Light. lights whose illuminating powers are far stronger. Leslie conceived that light when absorbed is converted into heat; but according to the experiments already referred to, the effect must be attributed, not so much to the light itself, as to the absorption of the calorific rays by which it is accompanied. A differential thermometer, containing the vapour of ether, may also, in certain experiments be advanta- geously used as a Photometric Thermometer 249. In nature the influence of the solar rays is very complex, and the growth, colour, flavour, and even the forms of many vegetables, are much dependent upon them. This is seen in many plants which are protected from the sun’s rays : celery and endive are thus culti- vated with the view of rendering them palatable ;t and plants which are made to grow in a room imperfectly illuminated, always bend towards the apertures by which the sun’s rays enter. The changes too which vegetables effect upon the circumambient atmosphere are influenced by the same cause. 250. In the animal creation, brilliancy of colour and gaudy plu- mage belong to the tropical climates ; more sombrous tints distin- guish the polar inhabitants ; and dull colours characterize nocturnal animals, and those who chiefly abide below the surface. 251. When bodies are rendered luminous by elevation of tem- perature, the light which they emit often appears dependent upon the heat to which they are subjected, and the common terms red-hot and white-hot are used to designate those appearances. There are, how- ever, certain bodies, which, at high temperatures, are remarkable for the quantity and extreme brilliancy of their light, independent of actual combustion ; this is the case with several of the earths, but more especially with lime, a small ball of which, £ inch in diameter, being ignited in the flame of alcohol urged by oxygen gas, emits light, having about thirtyseven times the intensity of an Argand’s lamp burner. $ 252. There are many substances which, when heated to a certain point, become luminous without undergoing combustion, and such bodies are said to be phosphorescent. The temperatures which they re- quire for this purpose are various ; it generally commences at about 400°, and may be said to terminate at the lowest visible redness. Some varieties of phosphate of lime, of fluor spar, of bituminous carbonate of lime, of marble, and sand, and certain salts, are the most remarka- ble bodies of this description. § Their luminous property may be best exhibited by scattering them in coarse powder upon an iron plate heated nearly to redness. Oil, wax, spermaceti, and butter, when yearly boiling, are also luminous. 253. Another class of phosphorescent bodies has been termed * Brande, Phil. Trans. 1820 . A photometer has been described by Ritchie, in the Quart. Jour. vol. 19, p. 299. For a description of Rumfont’s Photometer, see Phil. Trans, vol. 84. It determines the comparative strength of lights by a comparison of their shadows. ^ + The process is termed etiolation , or blanching, X Drummond, in Phil. Trans. 1826 . See figure and description of his apparatus in Brewster’s Edin. Jour, of Sci. v. § Wedgewood, Phil. Trans, vol. 82 . Light of Flames . 77 solar phosphor i, from becoming- luminous when removed into a dark ...- Sect ' 1 _ room after having been exposed to the sunshine.^ Of this descrip- tion are Canton’s, Baldwin’s, and the Bolognian phosphorus.! 254. A third set of bodies, belonging to this class, are those which Spontane- are spontaneously phosphorescent. Such are, especially, the flesh of oas P hos ’ salt-water fish just before it putrefies, and decayed wood. Thejg^gf" glow-worm and the lantern-fly are also luminous when alive ; and the hundred legged worm, and some others, shine brilliantly when irritated.! (See Bost. Jour. 2, 101.) 255. Percussion and friction are often attended by the evolution of Light from light, as when flint pebbles, pieces of sugar, and other substances, are percussion struck or rubbed together. The crystallization of some substances, or friction * * * § as benzoic acid, and acetate of potassa has been found to be attended with similar phenomena. § 256. From experiments in which air has been intensely heated, it Airin- has been concluded that gaseous matter is incapable of becoming ]u- ca P at >le of minous; for, though the temperature of air be such as to render lumincmsl solid bodies white-hot, it does not itself become visible.il Flame, however, may, in general, be regarded as luminous gaseous matter. Hydrogen gas, probably, furnishes the purest form of flame which can be exhibited; for the flames of bodies which emit much light, derive that power from solid matter which is intensely ignited and diffused through them, and which, in ordinary flames, as of gas, tallow, wax, oil, &c. consists of finely divided charcoal. 257. The intensity of the heat of flames which are but little lurni- Lio-ht and nous, as of hydrogen gas, spirit of wine, &c. maybe shown by tempera- introducing into them some fine platinum wire, which is instantly rendered white-hot in those parts where the combustion is most per- fect. It is even intensely ignited in the current of air above the * For practical directions for observing the phosphorescence of bodies, see Faraday’s Chemical Manipulation. t Cantonas phosphorus is prepared thus : — Calcine oyster-shells in the open fire for half an hour, then select the whitest and largest pieces and mix them with one third pound^* c ° m their weight of flowers of sulphur, pack the mixture closely into a covered crucible, ' and heat it t.o redness for an hour. When the whole has cooled, select the whitest pieces for use.* Baldwin’s phosphorus is prepared by heating nitrate of lime to a dull red heat, so as 7 to form it into a compact mass : and the Bolognian phosphorus, discovered by Vincen- th g Bosnian zio Cascariolo, a shoemaker of Bologna, is made by reducing compact sulphate of ha- phosphorus, ryta to a fine powder, which is formed into cakes with mucilage, and these are heated to redness. t Wilson has also made a variety of curious experiments on solar phosphori ; and he has discovered the simplest and most effectual of these bodies, which may be obtained Wi ! sor ^“ s cX ' by closely observing the following directions ; — Take the most flaming coals off a brisk pennnen s - fire, and throw in some thick oyster shells ; then replace the coals, and calcine them for an hour ; remove them carefully, and, when cold, it will be found that after expos- ing them for a few minutes to the light, they will glow in the dark, with most of the prismatic colours.? t It appears from the experiments of Canton and of Hulme,§ that sea-fish become luminous in about twelve hours after death, that it increases till putrefaction is evident, and then it decreases. Immersion in sea-water does not affect this luminous matter ; on the contrary, the brine is itself rendered luminous ; but it is extinguished by pure water, and by a variety of substances which act chemically upon the animal matter. § Brewster’s Journal , 3, 368. || Wedgewood, Phil. Trans. 17 92. * Phil. Trans. Vol. 58. f Aikin’s Diet. art. Phosphori. | Wilson on Phosphori, p. 20. § Phil. Trans. Vols. lix. xc. and xci. 78 Light. Chap. I. Exp. Exp. Exp. Eff ct nf wire gauze on flame. Davy’s S’ -tv lamp. Theory of phospho- rescence ami incan descence. flame, as may be shown by holding a piece of platinum wire over the chimney of an Argand lamp fed with spirit of wine; the high temperature of this current is also exhibited by the common expedi- ent of lighting paper by holding it in the heated air which rushes out of a common lamp-glass. The high temperature of flame is further proved by certain cases of combustion without flame. Thus, if a heated wire of platinum be introduced into any inflammable or explosive mixture, Fig. 53. it will become ignited , and continue so till the gas is consumed ; but inflammation will, in most cases, only take place when the wire becomes while-hot. This experiment is easily made by pouring a small quantity of ethor into the bottom of a deep wine-glass, or, what is better, a glass vessel, like that represented in Fig 53, and suspending in it a coil of heated platinum wire so as to be a little above the surface of the ether ; the wire becomes red hot, but does not inflame the vapour of the ether till it acquires an intense white heat. The same fact is exhibited by putting a small coil of fine platinum wire round the wick of a spirit lamp, (Fig. 54,) which, when heated, becomes red hot, and continues so, as long as the vapour of the spirit is supplied, the heat never becoming sufficiently in- tense to produce its inflammation. 25S. Such being the nature of flame, it is obvi- ous, that if we cool it by any means, we must at the same time extinguish it. This may be effected by causing it to pass through fine wire gauze, which is an excellent conductor and radia- tor of heat, and consequently possessed of great cooling power. If a piece of fine brass or iron wire-gauze be brought down upon the flame of a candle, or what answers better, upon an inflamed jet of oil gas, it will, as it were, cut the flame in half. That the cool gaseous matter passes through, may be shown by again lighting it upon the upper surfac?. The power, therefore, of a metallic tissue thus to extinguish flame, will depend upon the heat required to produce the combustion, as compared with that acquired by the tissue ; and the flame of the most inflammable substances, and of those that produce most heat in combustion, will pass through a metallic tissue that will interrupt the flame of less inflammable substances, or those that produce little heat in combustion ; so that different flames will pass through at different degrees of temperature. 259. The discovery of these facts, respecting the nature and prop- erties of flame, led Davy to apply them to the construction of the Miners' safety lamp , which will be explained under the article Light Carburetted hydrogen gas. 260. The phenomena exhibited by phosphorescent and incandes- cenf bodies, and in the process of combustion, have sometimes been explained upon the idea that the light and heat evolved were pre- viously in combination with the substances, and that they are after- wards merely emitted, in consequence of decomposition; and that the solar phosphori absorb light and again give it out unchanged; but the fact, that the colour of the light emitted is more dependent on the nature of the phosphorescent body than on the colour of the light to which it was exposed, seems inconsistent with this explana- Electricity. 79 lion. Chemical action is not connected with the phenomena ; for Sect, v. the phosphori shine in vacuo , and in gases which do not act on them, and some even under water.^ Section V. Electricity. 261. The term electricity is derived from the Greek word ehexjQov, Electrical amber , on account of the property which this substance was known excitement, to possess of attracting light substances when rubbed. If a piece of sealing-wax and of dry warm flannel be rubbed against each other, they both become capable of attracting and repelling light bodies. A dry and warm sheet of paper, rubbed with India rubber, or wool- len, or a tube of glass rubbed upon silk, exhibit the same phenomena. In these cases the bodies are said to be electrically excited ; and when in a dark room, they appear luminous. 262. If two pith-balls be electrified by touching them with the Repulsion sealing-wax or with the flannel, they repel each other; but if one and attrac_ pith-ball be electrified by the wax, and the other by the flannel, they 10n ’ attract each other. The same applies to the glass and silk. If one ball be electrified by sealing-wax rubbed by flannel, and another by silk rubbed with glass, those balls will repel each other. But if one ball be electrified by the sealing-wax and the other by the glass, they then attract each other.! 263. The terms vitreous and resinous electricity were applied to Dufay’s these two phenomena. According to Dufay the vitreous and resi- theory, nous electricities are distinct; an unexcited body contains both in a state of combination or neutralization, and cannot, therefore, exhibit any electrical attractions or repulsions. But friction disturbs this combination, or electric equilibrium, causing the vitreous electricity to accumulate in one body and the resinous in the other. They are both consequently in an excited state, and continue to be so till each recovers that kind of electricity which it had lost. A different explanation yvas proposed by Franklin, which is found- Franklin’* ed on the supposition that there is only one kind of electricity. tbeor J r - When bodies contain their natural quantity of electricity, they do not manifest any electrical phenomena ; but they are excited either by an increase or diminution in that quantity. Thus on rubbing a piece of glass with a woollen cloth, the electrical condition of both substances is disturbed ; the former acquires more, the other less than its natural quantity. These different states were expressed by the terms plus and minus, or positive and negative, the first corres- ponding to the vitreous, the second to the resinous electricity of Dufay.! * See Davy’s Elements 1,213, &c. — Murray’s System 1 , 570— Ure’s Did. article Caloric — Hare in Amer. Jour. iv. 12, &c. — Turner’s Elements, 69. f These experiments are conveniently performed with a large downy feather sus- pended by a dry thread of white silk. t As writers on chemistry continue to use the terms positive and negative , they are here retained. 80 Chap. I. Electrome- ter. Method of determin- ing the kind of electricity. Conductors and non- conductors. Electricity passes through rarefied air or a vacu- um. No con- stant rela- tion be- tween the state of bodies and their con- ducting powers. Some sub- stances be- come elec- tric by heat. Phenomena observed in using elec- trical ma- chines. Electricity. 264. Very delicate pith-balls, or strips of gold leaf, are usually employed in ascertaining the presence of electricity; and, by the way in which their divergence is affected by glass or sealing-wax, the kind or state of electricity is judged of. When properly suspended or mounted for delicate experi- ments, they form an electrometer or electroscope. (Fig. 55.) For this purpose the slips of gold leaf are suspended by a brass cap and wire in a glass cylinder ; they hang in contact when un-electrified; but when electrified they diverge.* 265. The kind of electricity by which the gold leaves are diverged may be judged of by approaching the cap of the instrument with a stick of excited sealing-wax ; if it be negative the divergence will increase ; if positive , the leaves will collapse, upon the principle of the mutual annihilation of the opposite electricities, or that bodies similarly electrified repel each other, but that when dissimilarly electrified they become mutually attractive. 266. Some bodies suffer electricity to pass readily along their sur- faces, and are called conductors. Others only receive it upon the spot touched, and are called imperfect or non-conductors. They are also called insulators.] The metals are all conductors ;t dry air, glass, sulphur, and resins, are non conductors. Water, damp wood, spirit of wine, damp air, and some oils are imperfect conductors. Rarefied air admits of the passage of electricity ; so does the Torricellian vacuum. 267. There appears to be no constant relation between the state of bodies and their conducting powers ; among solids, metals are conductors, but gums and resins are non-conductors; among liquids, strong alkaline, acid, and saline solutions, are good conductors ; pure water is an imperfect conductor, and oils are non-conductors ; wax and many other solids are imperfect conductors, but when fused are good ones. Conducting powers belong to bodies in the most op- posite states ; thus the flame of alcohol, and ice, are equally good conductors.^ Glass is a non-conductor when cold, but conducts when red-hot; the diamond is a non-conductor, but pure and well burned charcoal is among the best conductors. 268. There are many mineral substances which show signs of electricity when heated, as the tourmalin, topaz, diamond, boracite, &c. ; and in these bodies the different surfaces exhibit different elec- trical states. II 269. When an electrical machine is in good order, and the at- mospbtre dry, it produces a crackling noise when the plate or cylin- der is turned, and flashes or sparks of light are seen upon various * For other forms see Turner’s Chem. 81. t The insulation of substances is frequently required in electro-chemical experi- ments ; a plate of mica is the best substance for the purpose, then a plate of resin or wax, or iu their absence, a plate of warm glass. Faraday. t Of the metals, Harris found silver and copper to be the best conductors, and after these gold, zinc, platinum, iron, tin, lead, antimony, and bismuth — Phil. Trans. 1827. Part 1,21. § Biot, Traitdde Physique, tom. ii. p. 213. || For a description of Electrical machines and a more full account of Electricity, see Cambridge rial. Phil. vol. 2, Fischer’s Elements of Nat. Phil. p. 164. Brande's Chem. 69. Fig. 65. ia! A X 81 Faraday’s Views. parts of the glass passing from the cushion to the conductor ; if the sect. y. knuckle be held near the conductor, sparks pass to it through some inches of air, with a peculiar noise, and excite slightly painful sen- sation in the part upon which they are received. It is conjectured that the cause of the light thus perceived, is the sudden compres- sion of the air or medium through which the electricity passes, and j^ t; an it is always probably attended by a proportionate elevation of tem- perature, as is shown by the power of the spark to inflame spirit of wine, fulminating silver, and other easily inflammable compounds. 270. Another cause of excitement is proximity to an electrified body, which has a tendency to induce an electrical state opposite to its own. Thus an excited stick of sealing-wax attracts light bodies in its vicinity, and occasions them to be positively electrified. If an Electricity insulated conductor be electrified, and an uninsulated conductor bebymduc- opposed to it, there being between the two a thin stratum of air, tlon- glass, or other non-conductor, the uninsulated conductor, under such circumstances, acquires an opposite electrical state to that of the orig- inally electrified insulated conductor. In this case, the uninsulated body is electrified by induction, and the induced electricity remains evident, until an explosion, spark, or discharge happens, when the opposite electricities annihilate each other. Induced electricity may thus be exhibited through a long series of insulated conductors, pro- vided the last of the series be in communication with the earth. j c put Thus, in Fig. 56, Fig, 56- A, may represent the positive conduc- tor of the electrical machine ; b, c, and d. three insulated con ductors, placed at a little distance from each other, d , having a chain touching the ground ; then the balls 1, being posi tive, will attract the balls 2, which are rendered negative by induction. Under these circumstances, each of the conductors becomes polar, and the balls 3 are positive, while 4 are negative, 5 positive, 6 negative, &c. ; the central points of the conductors, bed, are neutral. \\i hen these opposite electrical states have arrived at a certain intensity*, sparks pass between the different conductors, and the electrical phenomena cease. B. 73. Illustra- tion. 271. The recent investigations of Faraday,! have led him to the Faraday’s inference that induction is essentially an action of contiguous parti- views, cles, through the intermediation of which the electric force, origi- nating or appearing at a certain place, is propagated to or sustained at a distance, appearing there as a force of the same kind exactly equal in amount, but opposite in its directions and tendencies. In- duction is considered as the essential function, both in the first de velopment and the consequent phenomena of electricity. He con ceives that induction consists in a certain polarized state of the par- ticles, into which they are thrown by the electrified body sustaining the action, the particles assuming positive and negative points or * Electricians generally employ the term quantity to indicate the absolute quanti- ty of electric power in any body, and the term intensity to signify its power of passing through a certain stratum of air or other ill-conducting medium, t P kilos. Trans. 1838. p. 1. 11 82 Chap. I. Specific in- ductive ca- pacity. Faraday’s differential ind udome- ter. Conse- quences of the theory. Electricity. parts, which are symmetrically arranged with respect to each other and the inducting surface or particles.* 272. For examining the specific inductive capncity of bodies, Faraday has contrived an apparatus, which he calls a Differential Inductometer. It consists of three insulated metallic plates, placed facing each other ; the centre one being fixed, and the other two moveable upon slides, by which they may be approximated to or withdrawn from the centre. When a charge is communicated to the centre plate under ordinary circumstances, the induction is equal on both sides and the gold leaves are not disturbed. But if after uninsulating them, and again insulating them, a thick plate of shel- lac or sulphur, be interposed between two of the plates, unequal in- duction will take place on the two sides, and the gold leaves will attract each other. By these means, Faraday has ascertained that, taking the specific inductive capacity of air to be I. That of Glass is 1.76 Shellac - 2. Sulphur - 2.24 The results obtained with spermaceti, oil of turpentine, and nap- tha, were higher than that of air, but their conducting powers inter- fered with the accuracy of the experiments. By another form of apparatus, he ascertained that all aeriform matter has the same power of sustaining induction ; and that no va- riations in the density or elasticity of gases produced any variation in their electric tension, until rarefaction is pushed so far as that dis- charge may lake place across them. No difference was found with hot, cold, dry or damp air. These experiments have established the important discovery of the princi- ple of specific inductive capacity. t 273. It is essential that the student should reflect carefully on the plain consequences of the theory of electricity, since the appli- cations of this knowledge are numerous. A few of these may now be enumerated — 1. An electrified body attracts light objects near it, because it in- duces in them a state opposite to itself. The attraction is most live- ly when the light object is a conductor, and in contact with the ground, since it then more completely assumes an electric state op- posed to that of the inducing body. A non-conductor is very im- perfectly electrified by induction, because the electric fluids cannot quit each other from inability to move through the non-conductor. 2. If a stick of sealing-wax, strongly negative, be presented to a thread or pith-ball which is also negatively, but feebly, excited, re- pulsion will ensue at a considerable distance, followed by attraction when the distance is small. This attraction is due to the strongly excited wax acting by induction on the feeble negative thread, there- by causing it to have an excess of positive electricity. * According to Faraday, bodies cannot be charged absolutely, but only relatively, and by a principle which is the same with that of induction : all charge is sustained by induction; all phenomena of intensity include the principle of induction; all excita tion is dependent on or directly related to induction; and all currents involve previous intensity and therefore previous induction, t See Lond. and Edin . Philos. Mag. Jan. and Feb. 1839. 83 Leyden Jar. 3. The positive electricity collected on the prime conductor of an Sect. v - electrical machine is by some ascribed, not to a transfer of that fluid from the glass to the prime conductor, but to a part of the combined electricities of the prime conductor being separated by induction, and the negative fluid being imparted to the positive glass. The same view is applicable to any system of conductors in contact with the prime conductor, as also to conductors connected with the rubber. It is difficult to say which explanation is the more correct, or wheth- er both may not be true. 4. On moving the hand towards the prime conductor of an excited electrical machine, the hand becomes negative by induction, and the spark ultimately obtained restores the equilibrium. In like manner a negatively electrified cloud renders positive a contiguous tree or tower, and then a stroke of lightning follows as a consequence of attraction between the two accumulated fluids. 5. The action of the Leyden Jar depends on the principle of in- Action of duced electricity. A gl^iss jar or bottle with a wide mouth is coat- the Leyden ed externally and internally with tinfoil, except to within three or jar * four inches of its summit ; and its aperture is closed by dry wood or some imperfect conductor, through the centre of which passes a me- tallic rod communicating with the tinfoil on the inside of the jar. On placing the metallic rod in contact with the prime conductor of an excited electrical machine, while the outer coating communicates with the ground, the interior of the jar acquires a charge of positive electricity, and the exterior becomes as strongly negative. If, the jar being 1 insulated, the metallic rod be placed close to the prime conductor, avoiding actual contact, while an uninsulated conductor be held at an equal distance from the outer coating, electric sparks in equal number and of equal size will pass between both intervals, and both sides of the jar are found to be in the same condition as before ; but no charge will be received wheu the inner coating com- municates with the prime conductor, and the outer coating is strictly insulated. From these facts it is inferred that the interior of the jar becomes positive, either by receiving positive electricity directly from the prime conductor, or, as is more probable, by communicating to it negative electricity ; and that the exterior then becomes nega- tive by the loss of a quantity of positive electricity equal to that on the interior. Unless means be afforded for the escape of the positive electricity from the exterior, no charge ought to be received ; and this conclusion is quite conformable to the fact above stated. 274. The opposite electric fluids accumulated on the opposite sides Leyden jar. of a charged Leyden jar exert a strong mutual attraction through the substance of the glass, and the presence of each secures the continu- ance of the other. The exterior of the jar may be freely handled, and its coating removed, without destroying the charge, provided no communication be made at the same time with the interior ; and if the exterior be insulated, the charge will be preserved, though the tinfoil of the interior be removed. But when a conductor communi- cates with both surfaces at the same instant, the two fluids rush to- gether with violence, and the equilibrium is restored. Whether in this and similar cases the two fluids coalesce entirely on the inter- mediate conductor, or whether each from its velocity may not in part 84 Chap.jl. Battery. Electropho rus. Mode of using it. The elec- trophorus used as an electric ma- chine. Electricity from change of tempera- ture. Other sources of electricity. Electricity. pass the other, and be projected to the opposite surface, is a question on which electricians are not agreed. 275. The Leyden jar affords the means of passing through bodies a large quantity of electricity. For not only may jars of any required size be employed, but it is easy so to arrange any number of such jars, that they shall all be charged and discharged at the same time, constituting what is termed an Electrical Battery. The arrange- ment is made, by placing a number of Leyden jars in a box lined with tinfoil, by which means their outer surfaces have free metallic communication with each other, and connecting their inner surfaces by wires. T. 78. 276. The operation of the instrument called the Electrophones (or bearer of electricity) is referable to the phenomena of induction. . The electrophorus (Fig. 57), consists of two metallic plates. Fig- 57. a a, with an intervening plate of resinous matter, 4, for which Q equal parts of shellac, resin, and Venice turpentine, are ge- nerally used, the mixture being carefully melted in a pipkin, L and poured, whilst liquid, into a wooden or metal hoop, of a l proper size, placed upon a polished surface of glass or marble, Jl from which it easily separates when cold ; it should be about half an inch thick, and the smooth surface being uppermost the lower side should bo covered with tinfoil, or attached to 1 -« any other metallic plate; a polished brass plate, with a glass handle c attached to it, is then placed upon the upper surface of trie resinous plate, and of rather smaller diameter. The resin is excited with a piece of dry fur, and the instrument will be found to exhibit the following phenomena : — Upon raising the brass plate by its insulating handle, it will be found very feebly electrical ; replace it, touch it with the finger an&again lift it off by its handle, and it will give a spark of positive electricity. This pro- cess may very often be repeated without fresh excitation.* The electrophorus may often be used for the same purpose as the electri- cal machine, and in the laboratory it furnishes a very convenient sub- ‘ stitute for that more expensive piece of apparatus.! 277. Electricity is excited also by change of temperature. The electric equilibrium is disturbed in metallic rods or wires when one extremity has a different temperature from that of the other, whether the difference be effected by the application of heat or cold. The experiment is usually made by heating or cooling the point of junc- tion of two metallic wires, which are soldered together; but Bec- querel has proved that the contact of different metals is not essential.! 278. There are many other sources of electricity. When glass is rubbed by mercury, it becomes electrified, and this is the cause of the luminous appearance observed when a barometer is agitated in a dark room, in which case flashes of light are seen to traverse the empty part of the tube. Even the friction of air upon glass is at- tended by electrical excitation. Whenever bodies change their forms, their electrical states are also altered. Thus during the con- gelation of melted resins and sulphur, electricity is rendered sensible. It is also developed during various natural processes; as evaporation * Ample directions for constructing this useful instrument, and for applying electri- city in tne laboratory, will be found in Faraday’s Cfiem. Manipulation, p. 436. tFor a more full account, see Turner’s Elements, Sect. 111. t An. de Chem. et de Phys. xli. 353, An. Philos., N. S., v. 427, and Phil. Mag. iii. Voltaic Circles , 85 and the condensation of vapour, which may aid in accounting for Sect, v. certain electrical phenomena of the atmosphere. Place a small iron cup, heated nearly to redness, over an electrometer ; on Exp. dropping into it a small portion of water, vapour will be produced, and the leaves of the electrometer will diverge. 279. Another reputed source of electricity is contact of different Electricity substances, especially of metals; a source originally suggested ^>y contact of Volta, who founded on it his theory of galvanism. When a plate of m etals. zinc furnished with a glass handle is brought into contact with one of copper or silver, it is found, after removal, to he positively electri- cal, and the silver or copper is left in the opposite state. The electricity thus developed was distinguished as Galvanism, Galvanism, from the circumstance that Galvani, an Italian physiologist, about the year 1789, observed the first striking phenomenon which led to the discovery. He observed it only in its power of affecting the ani- mal system. It was found that if the nerve of a recently killed frog was attached to a silver probe, and a piece of zinc was brought into contact with the muscles of the animal, violent contractions would be produced at every contact of the metals. Exactly the same effect is produced by an electric spark, or the discharge of a small Leyden phial. The following experiment produces a similar effect. Place a piece of zinc upon the tongue, and a piece of silver under it ; when- ever the projecting edges of these different metals are made to touch, a peculiar taste or sensation will be perceived, and if the pieces are large the contact will sometimes be accompanied by a flash of light. 280. From these and similar experiments Galvani concluded that Galvani’s the phenomena were owing to the communication of electricity ge- ypot esis ’ nerated by the animal system. Volta supposed that the electricity Volta’s was derived from the action exerted between the metal and the moist animal fibre, and soon discovered that it is evolved by arrange- ments wholly unconnected with any process of vitality. His disco- very of a method of augmenting the galvanic energy, and of thus enabling us to investigate its effects with more precision, has ac- quired for this form of electricity the epithet Voltaic. 281. The identity of the agent concerned in the phenomena of galvanism and of the common electrical machine, is now a matter of demonstration. The effects of common electricity are caused by a comparatively small quantity of electricity brought into a state of in- sulation, in which state it exerts a high intensity, as evinced by its remarkable attractive and repulsive energies, and by its power to force a passage through obstructing media. In galvanism the elec- tric agent is more intimately associated with other substances, is developed in large quantity, but never attains a high tension, and produces its peculiar effects while flowing along conductors in a con- tinuous current. 282. When a plate of zinc and a plate of copper are placed in a Simple vessel of water, and the two metals are made to touch each other, Y^Jj^ 0 either directly or by the intervention of a metallic wire, galvanism is C11C es * excited. The action is, indeed, very feeble, and not to be detected by ordinary methods ; but if a little sulphuric acid be added to the water, numerous globules of hydrogen gas will be evolved at the sur- face of the copper. This continues while metallic contact between the plates continues, in which state the circuit is said to be closed ; 86 Chap. I. Circle of metal and liquid. Zicc circle. Electricity — Voltaic. idi ! 1 1 • y _ but it ceases when the circuit is broken, that is, when metallic contact is interrupted. The hydrogen gas which arises from the copper plate results from water decomposed by the electric current, and its ceasing to appear indicates the moment when the current ceases. In this case the voltaic circle consists of zinc, copper, and interposed di- lute acid ; and the circle gives rise to a current only when the two metals are in contact. This arrangement is shown in Fig. 59, where metallic contact is readily made or broken by ^ Fig. 58. means of copper wires soldered to the plates. It is found that a current of positive electricity con- tinually circulates in the closed circuit from the zinc through the liquid to the copper, and from the copper along the conducting wires to the zinc, as indicated by the arrows in the figure. A current of negative electricity, agreeably to the theory of two electric fluids, ought to traverse the apparatus in a direction precisely re- versed ; but for the sake of simplicity the course of the positive cur- rent only will hereafter be indicated. 293. It matters not, so far as voltaic action is concerned, at what part the plates touch each other. Immersion of one plate only in the acid solution, however contact between the plates may be made, does not excite voltaic action ; nor does it suffice to have one plate in one vessel, and the other plate in another vessel. A plate of zinc soldered to one of copper, and plunged into dilute acid, gives a cur- rent passing from the zinc through the fluid round to the copper : but if the soldered plates are cemented into a box with a wooden bottom and metallic sides, so as to form two separate cells, as shown in a vertical section by Fig. 59, then the introduction of dilute acid to the cells will not excite a current unless the fluid of the cells be made to communicate by means of moistened fibres of twine, cotton, or some porous matter, or, as in the figure, by wires a b % soldered to the metallic sides which contain the dilute acid, or dipping into the acid itself. Then the positive current cir- culates in the direction shown by the arrows. Instead of a pair of plates being soldered together, they may be connected by a wire, and plunged into separate cells. 294. A simple voltaic circle may be formed of one metal and two liquids, provided the liquids are such that a stronger chemical action is induced on one side than on the other. Nay, the same acid solution may occupy both cells, provided some condition be introduced which shall cause one side of the zinc to be more rapidly dissolved than the other; as by the plate being rough on one side and polished on the other, or by the acid being hot in one cell ancl cold in the other. In this case, however, the result is the same as though two different liquids were used. 295 An interesting kind of simple voltaic circle is afforded by commercial zinc This metal, as sold in the shops, contains traces of tin and lead, with rather more than one per cent, of iron, which is mechanically diffused through its substance : on immersion in dilute sulphuric acid, these small particles of iron and the adjacent zinc Voltaic Circles. S7 form numerous voltaic circles, transmitting their currents through s e c. v. the acid which moistens them, and disengaging a large quantity of hydrogen gas.^ 286. While the current formed by the contact of two metals gives increased effect to the affinity of one of them for some element of the solution, the ability of the other metal to undergo the same change is proportionally diminished. Thus, when plates of zinc and copper touch each other in dilute acid, the zinc oxidizes more, and the cop- per less, rapidly than without contact. This principle was beauti- Davy . s fully exemplified by the attempt of Davy to preserve the copper protector, sheathing of ships. Davy found that the quantity of zinc required to form an efficient voltaic circle with copper was very small.! Un- happily, in practice, it is found that unless a certain degree of cor- rosion takes place in the copper, its surface becomes foul from the adhesion of sea-weeds and shell-fish. 287. Simple voltaic circles may be formed of various materials ; Other cir- but the combinations usually employed consist either of two perfect cles< and one imperfect conductor of electricity, or of one perfect and two imperfect conductors. The substances included under the title of perfect conductors are metals and charcoal, and the imperfect con- ductors are water and aqueous solutions. It is essential to the ope- ration of the first kind of circle, that the imperfect conductor act chemically on one of the metals : and in case of its attacking both, the action must be greater on one metal than on the other. It is also found generally, if not universally, that the metal most attacked is positive with respect to the other, or bears to it the same relation as zinc to copper.! 288. The presence of water has been shown by Faraday not to be Water not essential. A battery may be composed of other liquid compounds, essentia l* such as a fused metallic chloride, iodide, or fluoride, provided it is decomposable by galvanism, and acts chemically on one metal of the circle more powerfully than on the other. The following table of voltaic circles of the second kind is from Davy’s Elements of Chemical Philosophy : — * Mr Sturgeon has remarked that commercial zinc, with its surface amalgamated, which may be done by dipping a zinc plate iuto nitric acid diluted with two or three parts of water, and then rubbing it with mercury, resists the action of dilute acid fully as well as the purest zinc. This fact, of which Faraday in his late researches has made excellent use, appears due to the mercury bringing the surface of the zinc to a state of perfect uniformity, preventing those differences between one spot and another, which are essential to the production of minute currents ; one part has the same ten- dency to combine with electricity as another, and cannot act as a discharger to it (Fa- raday). t Phil. Trans. 1824. tDavy, in his Bakerian lecture for 1826 (Phil. Trans.), gave the following list of the first kind of arrangements, the imperfect conductor being either the common acids, alkaline solutions, or solutions of metallic sulphurets, such as sulphuret of potassium. The metal first mentioned is positive to those standing after it in the series. With common acids. — Potassium and its amalgams, barium and its amalgams, amalgam of zinc, cadmium, tin, iron, bismuth, antimony, lead, copper, silver, palladi- um, tellurium, gold, charcoal, platinum, iridium, rhodium. With alkaline solutions — The alkaligenous metals and their amalgams, zinc, tin, lead, copper, iron, silver, palladium, gold, and platinum. With solutions of metallic sulphurets.— Zinc, tin, copper, iron, bismuth, silver, pla- tinum, palladium, gold, charcoal. 88 Electricity — Voltaic. Chap I. Exp. Metals not essential. Circles most used. Solution of sulphuret of potassium Copper Nitric acid potassa Silver Sulphuric acid soda Lead Tin Zinc Other metals Charcoal Hydrochloric acid Any solutions contain- ing acid. The most energetic of these combinations is that in which the metal is chemically attacked on one side by sulphuret of potassium, and on the other by an acid. The experiment may be made by pour- ing dilute nitric acid into a cup of copper or silver, which stands in another vessel containing sulphuret of potassium. The following arrangements may also be employed : — Let two pieces of thick flannel be moistened, one with dilate acid and the other with the sulphuret, and then placed on opposite sides of a plate of copper, completing the circuit by touching each piece of flannel with a conducting wire : or, take two discs of copper, each with its appropriate wire, immerse one disk into a glass filled with dilute acid, and the other into a separate glass with alka- line solution, and connect the two vessels by a few threads of amianthus or cotton moistened with a solution of salt. A similar combination may be disposed in this order : let one disc of copper be placed on a piece of glass or dry wood ; on its upper surface lay in succession three pieces of flannel, the first moistened with dilute acid, the second with solution of salt, and the third with sulphuret of potassium, and then cover the last with the other disc of copper. ’ 2S9. Metallic bodies are not essential to the production of galvanic phenomena. Combinations have been made with layers of charcoal and plumbago, of slices of muscle and brain, and beet-root and wood; but the force of these circles though accumulated by the union of numerous pairs, is extremely feeble, and they are very rarely em- ployed in practice. 290. Of the simple voltaic circles above described, the one used for ordinary purposes is that composed of a pair of zinc and copper plates excited by an acid solution arranged as in Fig. 58. The form and size of the apparatus are exceedingly various. Instead of actu- ally immersing the plates in the solution, a piece of moistened cloth may be placed between them. Sometimes the copper plate is made into a cup for contaiping the liquid, and the Fig.60. zinc is fixed between its two sides, as shown by the accompanying transverse vertical section, Fig. 60 ; care being taken to avoid actual contact between the plates, by interposing pieces of wood, cork, or other imperfect conductor of electricity. T. 9i. Another con- trivance, which fs much more convenient, because the zinc may be removed at will and have its surface cleaned, is that represented by Fig. 61. An earthen pot a a is lined with a cylinder of thin copper, within which are one or more smaller cylinders of the same, connected at bottom by narrow pieces of cop- per. One, or more cylinders of zinc are placed in the space between the coppers, being somewhat shorter than the copper cylinders, and are support- ed on the edge of the pot by projecting pieces sol- dered to the upper edges. (Fig. 62.) Small cups [=3 Fig. 61. 4 Hare’s Calorimotor . 89 are attached to the two metals for receiv- ing a few drops of mercury, into which the ends of wires may be dipped and the circuit be closed or broken at pleasure. This apparatus is very serviceable in expe- riments on electro-magnetism. The liquid employed is a solution of sulphate of cop- per (blue vitriol) in water, and may be allowed to remain in the pot when the apparatus is not in use, all that is necessary is to remove the zinc cylinder. Another kind of circle may be formed by coiling a sheet of zinc and copper round each other, so that each surface of the zinc may be opposed to one of copper, and separated from it by a small inter- val. The contrivance of opposing one large connected surface of zinc to a similar surface of copper, originated with Hare of Phil- adelphia, who, from its surprising power of igniting metals, gave it the name of Calorimotor 291. Compound voltaic circles consist of a series of simple circles. The first combinations of the kind were described by Volta, and are Fig. 62. * A a, represent two cubical vessels, twenty inches square, inside, b b , a frame of wood containing 20 sheets of copper, and 20 sheets of zinc, alter- nating with each other, and about half an inch apart. T T It, masses of tin cast over the protruding edges of the sheets which are to communicate with each other. The small fig. on the right, represents the modem which the junc- tion between the various sheets and tin masses is effected. The zinc only is in contact with the tin on one side ; the copper alone touches on the other. At the back of the frame, ten sheets of copper and ten sheets of zinc are made to communicate, by a common mass of tin extending the whole length of the frame, between T T ; but in front, as in Fig. 63, there is an interstice between the mass of tin connecting the ten copper sheets, and that connecting the ten zinc sheets. The screw forceps, appertaining to each of the tin masses, may be seen on either side of the interstice ; and likewise a wire for igni- tion held between them. The application of the rope, pulley, and weights is obvi- ous. The frame can be swung round and lowered into the water in the' - vessel a, to wash off the acid, which, after immersion in the other vessel, might continue to act on the sheets, incrusting them with oxide. When the copper and zinc surfaces are united by an intervening wire, and the in- strument is immersed in the acid liquor in the vessel beneath, the wire becomes in- tensely ignited, and when hydrogen is liberated in sufficient quantity it usually takes fire producing a very beautiful corruscating flame upon the surface of the liquid.* Or the following method may be employed : cut the plates into the Fi 64 Fig. 65. form represented in Fig. 64, solder the zinc . . S ' — and copper together, bend them into the c TT form of Fig. 65 and arrange them in the 1 J trough as in Fig. 72. The zinc plates are kept from touching the copper plates by pieces of cork, and pieces of thick paper are interposed bet ween the contiguous surfaces of copper. Faraday, ‘ in Phil. Trans. 1835. * See Jhner. Jour . of Science, vol. i. 413. Sect. V. Circular arrange- ment. Compound circles. Hare’s im- prorement. Calorimoter- 12 90 Chap. I. Position of the metals. Trough. Electricity — Voltaic , now well known under the names of voltaic pile and crown of cups. (Fig. 66). In this apparatus the exciting so- Fig- 6G - lution is contained in separate glasses or cups ; each glass contains a pair of plates, and each zinc plate is attached to the cop- per of the next pair by a metallic wire. The voltaic pile is made by placing pairs of zinc and copper, or zinc and silver plates one above the other, as shown in Fig. 67, each pair separated from those adjoining by pieces of cloth rather smaller than the plates, and moistened with a saturated solution of salt. The relative position of the metals in each pair must be the same in the whole series ; that is, if the zinc be placed below the copper in the first pair, the same order should be observed in all the others. Without such precaution the apparatus would give rise to opposite currents, which would neutralize each other more or less accord- ing to their relative forces. The pile, which may con- sist of any convenient number of combinations, should be contained in a frame formed of glass pillars fixed into a piece of thick dry wood, by which it is both supported and insulated. Any number of these piles tnay be made to act in concert by establishing metallic communication between the positive extremity of each pile and the negative extremity of the pile immediately following. 292. The voltaic pile is now rarely employed, because we possess other modes of forming galvanic combinations which are far more powerful and convenient. The galvanic battery proposed by Cruik- shank, consists of a trough of baked wood, ab out 30 inc hes long, in which are placed at equal distances 50 pairs of zinc and copper plates previously soldered to- gether, and so arranged that the same metal shall always be on the same side. Each pair is fixed in a groove cut in the sides and bottom of the box, the points of junction being made water-tight by cement. The apparatus thus constructed is always ready for use, and is brought into action by filling the cells left between the pairs of plates with some convenient solution, which serves the same purpose as the moistened cloth in the pile of Volta. By means of Figs. 68 and 69 the mode in which the plates are arranged will easily be under- stood. 293. Other modes of combination are now in use, which facilitate the employment of the voltaic apparatus and increase its energy. Most of these may be regarded as modifications of the crown of cups. Instead of glasses it is more convenient to employ a trough of baked wood, (Fig. 69), or glazed earthenware, divided into separate cells by partitions of the same material ; and in order that the plates may be immersed into and taken out of the liquid conveniently and at the same moment, they are all attached to a bar of dry wood, the necessary connexion between Fig. 69. I Fig. 68. Compound Circles. 91 the zinc of one cell and the copper of the adjoining one being accomplished, as shown in figure 70, by a slip or wire of copper.^ 294. The size and number of the plates may be varied at pleasure. The common and most convenient size for the plates, is four or six inches square ; and when great power is required, a number of different batteries are united by establishing metal- lic communication between the positive extremity of one battery and the negative extremity of the adjoin- ing one. The great battery of the Royal Institution, with which Davy made his celebrated discovery of the compound nature of the al- kalies, was composed of 2000 pairs of plates, each plate having 32 square inches of surface. It is now recognized, however, that such large compound batteries are by no means necessary. Increasing the number of plates beyond a very moderate limit gives, for most purpos- es, no proportionate increase of power ; so that a battery of 50 or 100 pairs of plates, thrown into vigorous action, will be just as effective as one of far greater extent. 295. The electrical condition of compound voltaic arrangements is Condition similar to that of the simple circle. In the broken circuit no electric ’ ir _ current can be traced ; but in the -closed circuit, that is, when the c les. wires from the opposite ends of the battery are in contact, the galva- nometer indicates a positive electric current through the battery itself * A material improvement in the apparatus was made by- Wollaston, which consisted in extending the copper plate, so as to oppose it to every surface, of the zinc, as seen in Fig. 71. A is the rod of wood to which the plates are screwed ; b b the zinc plates connected as usual with the copper plates c c, which are doubled over the zinc plates, and opposed to them upon all sides, contact of the surfaces being prevented by pieces of wood or cork placed at d d. Hare adopted this with great advantage in his Deflagrator. (Fig. 72.) It consists of four troughs a a, b b, each 10 feet long. Each two of the troughs are joined lengthwise, edge to edge, so that when the sides of the two b b are vertical, those of the others a a are horizontal. The troughs are supported by a frame c c, and turn upon pi- vots d d. The pivots are made of iron coated with brass or copper, and a communi- Hare’s Defe- cation is made between these and the galvanic series within by strips of copper e. grator. Fig. 72. Fig. 73. Fig. 74. The galvanic series of 300 pairs of copper and zinc plates (connected as in Figs. 73 and 74, each zinc plate z being between two copper plates c c) are placed in the troughs a a,.* The acid liquor is contained in the troughs b b, and by a partial revolution of the apparatus is made to flow into the troughs containing the plates. * See Amer. Jour. iii. 347. 92 Electricity — Voltaic. Chap. I. Evolution of hydro- gen. Theories of Galvanism. Volta’s, Wollas- ton’s, and along the wires, as shown by the arrows in Figs. 66 and 68. The direction of the current appears at first view to be different from that of the simple circle; since in the latter the positive electric cur- rent flows from the zinc through the liquid to the copper, while in the compound circle its direction is from the extreme copper through the battery to the extreme zinc plate. This apparent difference arises from the compound circle being usually terminated by two superfluous plates. The extreme copper and extreme zinc plate of Fig. 68 are not in contact with the exciting fluid, and therefore con- tribute nothing to the galvanic action : removing these superfluous plates, which are solely conductors, there will remain four simple circles, namely, the three pair of soldered plates marked 2, 3, 4, which act as in Fig. 59, and the then extreme plates, 1, 1, which are related to each other as the plates in Fig. 58. When thus ar- ranged, the direction of the current will be seen to correspond with that of the simple circle. 296. During the action of a simple circle, as of zinc and copper, excited by dilute sulphuric acid, all of the hydrogen developed in the voltaic process is evolved at the surface of the copper. This fact is not apparent when common zinc plates are used, owing to the nu- merous currents which form on the surface of the zinc (285) ; but when a plate of amalgamated zinc and another of platinum are introduced into dilute sulphuric acid of specific gravity 1.068 or a little higher, no gas whatever appears until contact between the plates is made, and then hydrogen gas rises solely from the platinum, while zinc is tranquilly dissolved. The separation of one ingredient of the exciting solution at one plate, while the element previously combined with it unites with the other plate, seems essen- tial to voltaic action. It is in some way connected with the passage of the current across the exciting liquid. 297. Among the different kinds of voltaic apparatus is usually- placed the electFic column of De Luc, which is formed of successive pairs of silver and zinc, or silver and Dutch-metal leaf, separated by pieces of paper arranged as in a voltaic pile. It is remarkable for its power of exhibiting attractions and repulsions like common elec- tricity, but cannot produce chemical decomposition or any of the effects most characteristic of a voltaic current, and is rather an elec- trical than a voltaic instrument.* T. 94. 298. Several theories have been proposed for the explanation of galvanism and its effects. Volta conceived that electricity was set in motion and kept up, solely by the contact or communication be- tween the metals. He regarded the interposed solution merely as a conductor, by means of which the electricity of each pair of plates is conveyed from one part of the apparatus to the other. 299. The second theory is that of Wollaston, who assigned chemi- cal action as the cause of the electricity excited. He concluded that the process begins with the oxidation of the zinc, and that the con- De t.uc’ic*i- *Fig. 2, Frontispiece, represents De Luc’s columns, with a metallic ball suspended umn « between them. The glass tubes are packed with 1000 or 1500 pairs of zinc and silver disks, the series commencing with zinc in one, and with silver in the other; the co- lumns terminate at bottom in small bells, between which the ball is attracted and repelled for a considerable length of time, producing an irregular chime. See Singer’* Electricity , 452. Faraday^s Experiments . 93 Fig. 75, £■ Faraday’s Exp’ts. tact of the plates served only to conduct electricity. The third the- Sect, v. ory was that proposed by Davy, who maintained that, though not the primary movers of the electric current, the chemical changes are Davys ’ essential to the continued action of every voltaic circle. The elec- tric excitement was begun, he thought, by metallic contact, and main- tained by chemical action. 300. Conclusive evidence against the theory of Volta has very recently been obtained by Faraday.^ He proved metallic contact not to be essential to voltaic action, by procuring that action quite characteristically without contact. A plate of zinc, a, Fig. 75, about 8 inches long by £ an inch wide, Was cleaned and bent at a right angle : and a plate of platinum, oi the same width and three inches long, was soldered to a platinum wire, b s x, the point of which, x , rested on a piece of bibulous pa- per lying upon the zinc, and moistened with a solution of iodide of potassium. On introducing the plates into a vessel, c, filled with dilute sulphuric and nitric acid, a positive electric current instantly ensued in the direction of the arrow, as testified by the hydrogen evolved at the plate a, by the decomposed iodide of potassium, and by a galvanometer. We have thus a simple circle of the same con- struction and action as in Figure 58, except in the absence of me- tallic Contact. Another proof, aptly cited by Faraday, of electric ex- citement being independent of contact, is afforded by the spark which appears, when the wires of a pair of plates in vigorous action are brought into contact. The spark is occasioned by the passage of electricity across a thin stratum of air, and, therefore, its produc- tion proves that electro-motion really occurred while the wires were yet separated by a thin stratum of air, which permitted the electric current to pass, and anterior to their actual contact. This current in Faraday’s experiment, was so feeble compared with the one excited by the acid solution, that its influence was scarcely ap- Fig. 7 M Fig. 77. preciable ; but if the opposed currents had been of the same force, no action would have ensued. To illustrate this still fur- ther, Faraday fixed a plate of platinum, r, (Fig. 76) parallel and near to a plate of amal- y z gamated zinc, z. On placing a drop of dilute sulphuric acid at y, and making metallic contact between the plate at z p, a positive elec- tric current flowed in the direction of the arrows. If, in the same plates (Fig. 77), the acid be introduced at x, and metallic contact be made at p z, the cur- rent, passing as before from zinc through the liquid to the platinum, has a direction op- posed to that of Fig. 59, owing to the reversed position of the acid. If, then, in the same plate, (Fig. 78), a drop of acid be introduced at y and x, the conditions are obviously fulfilled for producing two opposite currents of positive electricity , each fluid act- ing as a substitute for metallic contact in conducting the current which the other tends to generate. If these opposing currents happen to be equal, they will annihilate the effects each separately would produce ; * The Philosophical Transactions contain a succession of essays on voltaic electri- city from the pen of Faraday, in which numerous errors have been exposed and new views of deep interest established. 94 Chap. I. Theory of compound circles. Quantity and intensi- ty. Energy es- timated. Nature of electricity. Electricity — Voltaic. Fig. 78. P X x and if unequal, the stronger current, as in Fig. 75, will annihilate the weaker, and, though with diminished power, impress its charac- ter on the circuit. 301. These considerations, made in reference to a simple circle, lead at once to the theory of the compound circle. For if, in Fig* 78, a drop of dilute acid, which acts solely on the zinc, be introduced at y, and a different liquid at z , capable of corroding platinum and not zinc, then the chemical action at y will cause a positive current from zinc to platinum, and that at z a similar current from platinum to zinc. The two cur- rents tend to circulate in the same direction, and each promotes the progress of the other. The same state of things exists in the batte- ries represented by Figs. 66 and 68. Chemical action taking place on the zinc of each pair of plates, there is a tendency to establish an equal number of positive currents all in the same direction ; and the simultaneous effort of all urges on the current with a force which it could not derive from a single pair of plates. It is now, also, appa- rent that all the zinc plates should have their surfaces towards one side, and those of copper towards the other : one reversed pair tends to establish a counter-current, which enfeebles the influence of the rest. On the same principle, the exciting liquid of a voltaic circle should act exclusively on one of the plates : if the copper is oxidized as fast as the zinc, opposite currents will be excited, which more or less completely counteract each other. For this reason, platinum and zinc act better than copper and zinc, especially when nitric acid is employed. 302. Electricians distinguish between quantity and intensity in galvanism as in ordinary electricity. Quantity , in reference to a voltaic circle, signifies the quantity of electric fluid set in motion ; and by tension or intensity is meant the energy or effort with which a current is impelled. The current of a single pair of plates, though variable in intensity according as the nature and strength of the ex- citing liquid varies, never attains a high tension. A compound circle dees not act by directly increasing the quantity of electricity, but by giving impetus or tension to that which is excited. 303. The energy of a voltaic circle is usually estimated either by the deflection which it causes on a magnetic needle, or by its power of chemical decomposition. Chemical decomposition depends on quantity and intensity to- gether, and affords a criterion of the increased tension of a com- pound circle due to an increase in the number of its plates. 304. Some conceive that what is called an electric current is not an actual transfer of anything, but a process of induction among the molecules of a conductor passing progressively along it. Others, denying independent materiality to electricity, may ascribe it to a wave of vibrating matter, just as the phenomena of optics are ex- plained by the undulatory theory. But whatever theory of the na- ture of electricity may be adopted, it seems necessary, after the ex- periments of Faraday on the identity of voltaic and common electrici- ty, that the nature of an electric and voltaic current is essentially the same. 95 Identity of Galvanism and Electricity. 305. When a zinc and copper plate are immersed in dilute acid, Sect, v. and the wire attached to the former is connected with a gold-leaf electrometer of sufficient delicacy, the leaves diverge with negative ga^anism electricity ; and on testing the wire of the copper plate in a smaller on electro-, manner, divergence from positive electricity is obtained. The effect m#ter - is so feeble with a single pair of plates, as to be scarcely apprecia- ble ; but with a battery of many pairs it is very distinct, though nev- er powerful. The condition of a battery which gives the greatest divergency to an electrometer is that of numerous plates ; small plates an inch square being just as effectual as large ones, 306. A Leyden jar may be charged from either wire of an un- Leyden jar broken circuit, provided the battery be in a state to supply a large charged ; quantity of electricity of high tension, as when formed of numerous four-inch plates excited by dilute acid. When the wires from such shock. a battery are brought near each other, a spark is seen to pass be- tween them ; and on establishing the communication by means of the hands, previously moistened, a distinct shock is perceived. On sending the current through fine metallic wires or slender pieces of plumbago or compact charcoal, these conductors become intensely heated, the wires even of the most refractory metals are fused, and a vivid white light appears at the points of the charcoal. If the com- ETect on munication be established by metallic leaves, the metals burn with metais > vivid scintillations. Gold-leaf burns with a white light, tinged with blue, and yields a dark brown oxide ; and the light emitted by silver is exceedingly brilliant, and of an emerald-green colour. Copper emits a bluish-white light attended with red sparks, lead a beauti- ful purple light, and zinc a brilliant white light inclining to blue, and fringed with red. (Singer.) 307. The phenomena seem to arise from the current passing Explained, along these substances with difficulty ; a circumstance which, as they are perfect conductors, can only happen when the quantity to be transmitted is out of proportion to the extent of surface over which it has to pass. It is, therefore, an object to excite as large a quantity of electricity in a given time as possible, and for this pur- pose a few large plates answer better than a great many small ones. A strong acid solution should also be used ; since energetic action, though of short continuance, is more important than a moderate one of greater permanence. A mixture of ten or twelve parts of water to one of nitric acid is applicable ; or, for the sake of economy, a mixture of one part of nitric to two parts of sulphuric acid may be substituted for pure nitric acid. 308. Most of the effects of galvanism are so similar to those of the identity of electrical machine, that it is impossible to witness and compare both galvanism series of phenomena without ascribing them to the same agent. ^" t d electn ‘ The question of identity early occupied the attention of Wollaston, who made some very beautiful and conclusive experiments to prove that the chemical effects of galvanism may be characteristically pro- duced by a current from the electrical machine.^ The subject has been examined anew by Faraday, who has subjected the effects of electricity and galvanism to a minute and critical comparison : he has obtained ample proof of the decomposing power of an electric * Phil. Trans. 1801 . 96 Chap. I. Chemical action of galvanism. Water de- composed. Other com- pounds. Davy's ex- periments. Electricity — Voltaic. current from an electrical machine, both by repeating the experi- ments of Wollaston and devising new ones of his own. These re- searches have led to a remarkable contrast between the quantity of electricity concerned in the production of voltaic and ordinary elec- trical phenomena. Faraday states, that the quantity of electric fluid employed in decomposing a single grain of water is equal to that of a very powerful flash of lightning. 309. The chemical agency of the voltaic apparatus, to which chemists are indebted for their most powerful instrument of analysis, was discovered by Carlisle and Nicholson. The substance first de- composed by it was water. When two gold or platinum wires are connected with the opposite ends of a battery, and their free extremi- ties are plunged into the same portion of water, (Fig. 79,*) but with- out touching each other, hydrogen gas is disengaged at the nega- tive and oxygen at the positive wire. By collecting the gases in separate tubes as they escape, (Fig. Sit) they are found to be quite pure, and in the exact ratio of two measures of hydrogen to one of oxygen. When wires of a more oxidable metal are employed, the result is somewhat different. The hydrogen gas appears as usual at the negative wire ; but the oxygen, instead of escaping, combines with the metal, and converts it into an oxide. 310. This important discovery led many able experimenters to make similar trials. Other compound bodies, such as acids and salts, were exposed to the action of galvanism, and all of them were decomposed without exception, one of their elements appearing at one side of the battery, and the other at its opposite extremity. An exact uniformity in the circumstances attending the decomposition was also remarked. Thus, in decomposing water or other com- pounds, the same kind of body was always disengaged at the same side of the battery. The metals, inflammable substances in general, the alkalies, earths, and the oxides of the common metals, were found at the negative wire ; while oxygen, chlorine, and the acids, went over to the positive surface. 311. Davy observed that if the conducting wires were plunged into separate vessels of water, made to communicate by some moist fibres of cotton or amianthus, the two gases were still disengaged in * Fig. 79. Shows the method of decomposing water in a glass tube. + Fig 81. Apparatus for collecting the gases in separate tubes ; the tubes h o , are filled with Fig. 79. Fig. 80. Fig. 81 water, and inverted in the globular vessel d } also containing water ; the tubes pass through holes in a wooden cover ; n p, are platinum wires passing through the globe to connect with the voltaic apparatus. Fig. 80 . Similar arrangement for collecting the mixed gases. 97 Faraday's Researches . their usual order, the hydrogen in one vessel, and the oxygen in the sect, v. other, just as if the wires had been immersed into the same portion of that liquid. This singular fact, and another of the like kind ob- served by Hisinger and Berzelius, induced him to operate in the same way with other compounds, and thus gave rise to his celebra- ted researches on the transfer of chemical substances from one ves- sel to another.^ In these experiments two agate cups, n and p, were cm- Fj g . g2. Exp. ployed, the first communicating with the negative, the second with the positive wire of the battery, and connected together by moistened amianthus. On putting a solution of sulphate of potassa or soda into n, and distilled water into p, the acid very soon passed over to the latter, while the liquid in the former, which was at first neutral, became distinctly alkaline. The process was reversed by placing the saline solution in p, and the distilled water in ra, when the alkali went over to the negative cup, leaving free acid in the other. That t.he acid in the first experiment, and the alkaline base in the second, actually passed along the amianthus, was obvious ; for on one occasion, when nitrate of oxide of silver was substituted for the sulphate of potassa, the amianthus leading to n was coated with a film of metal. A similar transfer was effected by putting distil- led water into n and p , and a saline solution in a third cup placed between the two others, and connected with each by moistened ami- anthus. In a short time the acid of the salt appeared in p , and the alkali in n. It was in pursuing these researches that Davy made his great discovery of the decomposition of the alkalies and earths, which till then had been regarded as elementary.! I 312. Such is a statement of the principal phenomena of electro- chemical decomposition according to the earlier experiments. The facts then observed were received as established truths of science. But Faraday, in his revision of this part of the science, has not only added much new matter, but proved that several points, which Faraday’s were considered as fundamental maxims, are erroneous. Before de- researches, scribing his results, however, it is necessary to define the new terms which he has had occasion to introduce. In order to decompose a compound, it is necessary that it should be liquid, and that an elec- tric current should pass through it, an object easily effected by dip- * Phil. Trans. 1807. + Ibib. 1808. t The transfer of acid and alkali may be shown by the fol- Fig- 83 - lowing arrangement: Fill the glass tubes a a, Fig- 83, which are closed at top and open at bottom, with infusion of violets, or purple cabbage, and invert them in the basins b b, containing a solution of Glauber’s salt, and connected by the glass tube c, also containing the solution ; p and n are platinum wires, which pass into the tubes nearly to the bottom, and which are to be connected with the positive and negative extremities of the Voltaic apparatus. It will be found that oxygen is evolved at the wire/), and hydrogen at n, derived from the decomposition of the water. The Glauber’s salt, which consists of sulphuric acid and soda, will also be decomposed: and the blue liquor will be ren- dered red in the positive vessel, by the accumulation of sul- phuric acid, and green in the negative, by the soda, while the acid and alkali will each traverse the tube c without uniting, in consequence of being under the influence of electrical attraction. 13 A Traniferof acid and alkali. 98 Chap. I. New terms, Anode and Cathode. Electro- lyze. Anions. Cations. Faraday’s results. All com pounds not electro- lytes. Secondary action. Electricity — Voltaic. ping into the liquid the ends of the metallic wires which communi- cate with the voltaic circle. These extremities of the wires are commonly termed poles, from a notion of their exerting attractive and repulsive energies towards the elements of the decomposing liquid, just as the poles of a magnet act towards iron; and each is further distinguished by the term positive or negative, according as it affects an electrometer with positive or negative electricity. Fara- day contends that these poles have not any attractive or repulsive energy, and act simply as a path or door to the current : he hence calls them electrodes , from vUxtqov, and dSog , a way. The electrodes are the surfaces, whether of air, water, metal, or any other sub- stance, which serve to convey an electric current into and from the liquid to be decomposed. The surfaces of this liquid which are in immediate contact with the electrodes, and where the elements make their appearance, are termed anode and cathode from dva, upwards, and ddog, the way in which the sun rises, and xara, downwards , the way in which the sun sets. The anode is where the positive cur- rent is supposed to enter, and the cathode where it quits, the de- composing liquid, its direction, when the electrodes are placed east and west, corresponding with that of the positive current which is thought to circulate on the surface of the earth. To electrolyze a compound, is to decompose it by the direct action of galvanism, its name being formed from nlenTQov and Xvo), to unloose, or set free ; and an electrolyte is a compound which may be electrolyzed. The elements of an electrolyte are called ions, from iov, going, neuter participle of the verb to go. Anions are the ions which appear at the anode, and are usually termed the electro-negative ingredients of a compound, such as oxygen, chlorine, and acids ; and the electro- positive substances, hydrogen, metals, alkalies, which appear at the cathode, are cations. Whatever may be thought of the necessity for some of these terms, the words electrode, electrolyze, and electro- lyte, are peculiarly appropriate. 313. The principal facts determined by Faraday, may be arrang- ed under the following propositions : — 1. All compounds, contrary to what has been hitherto supposed, are not electrolytes, that is, are not directly decomposable by an electric current. But in making this assertion it is necessary to distinguish between primary and secondary decomposition. Thus water is an electrolyte, its hydrogen being delivered up at the nega- tive and its oxygen at the positive electrode. Nitric acid is not an electrolyte, on subjecting it to voltaic action, the water of the solution is electrolyzed, and its hydrogen arriving at the negative electrode decomposes the nitric acid, water being there reproduced and ni- trous acid formed. Very numerous secondary actions are occasion- ed in this way, because the disunited elements are presented in a nascent form, which is peculiarly favourable to chemical action. By slow secondary actions, effected by very feeble currents, Becquerel, Crosse, and others, have procured several crystalline compounds ana- logous to minerals.* 2. Most of the salts which have been examined are resolvable into * See notice of Crosse’s experiments in Sixth Report of British Association , p. 47. 99 Faradaxfs Results. acid and oxide, apparently without reference to their proportions. Sect, v. But in compounds of two elements, the ratio of combination has an influence which has hitherto been wholly overlooked. No two ele- ments appear capable of forming more than one electrolyte. Sub- stances which consist of a single equivalent of one element and two or more equivalents of some other element, are not electrolytes: this is the reason why sulphuric and nitric acid and ammonia do not yield primarily to voltaic action. This principle bids fair to be- come very important in determining which of several compounds of two elements contain single equivalents, (116 note.) Water, which is remarkable for its easy decomposition, may hence be inferred to be a true binary compound. 3. It has been ascertained that most of the elements are ions , and Most ele- it is probable that all of them are so ; but there are several which are have not yet been proved to be so. 4. A single ion , that is, one ion not in combination with another, Character has no tendency to pass to either of the electrodes, and is quite in* i y ti c action, different to the passing current, unless it be itself a compound ion , and therefore electrolyzable. The character of true electrolytic ac- tion consists in the separation of ions , one passing to one electrode and another to the opposite electrode, and appearing there at the same instant, unless the appearance of one or both be prevented by some secondary action. 5. There is no such thing as a transfer of ions in the sense usual- No transfer ly understood. In order that the elements of decomposed water oflons * should appear at the opposite electrodes, there must be water be- tween the electrodes ; and for the similar separation of sulphuric acid and soda, there must be a line of particles of sulphate of soda extending from one electrode to the other. 6. Faraday has proved that even air may serve as an electrode. Air may be A current from the prime conductor of an electrical machine was ® r ”^ ec " made to pass from a needle’s point through air to a pointed piece of ro e ” litmus paper moistened with sulphate of soda, and then to issue from a similarly moistened point of turmeric paper. True electroly- tic action took place, the litmus becoming red and the turmeric paper brown, though both extremities of the decomposing solution commu- nicated solely with a stratum of air. 7. Electro-chemical decomposition cannot occur unless an elec- Electro- trie current is actually transmitted through it ; or, in other terms, an electrolyte is always a conductor of electricity. Water, which con- ducts an electric current, ceases to do so when it passes into ice, and then also resists decomposition — an observation equally true of all electrolytes in becoming solid. 8. Chemical compounds differ in the electrical force required for Force re- j * quired to decomposition. . , . , „ , decompose. 9. The conduction of the electric currents within the cells of a Electro . voltaic circle depends on chemical decomposition equally with that lytes only, between platinum electrodes. No substance not an electrolyte can exclte - serve to excite a voltaic apparatus, and for the passage of electricity from plate to plate through the intervening solution, the separation of substances previously combined in the required ratio is essential. 314. In experiments on decomposition the course of the electricity st ances"to should be facilitated by employing large electrodes and wires, and be regarded 100 Electricity — Voltaic. Cha p. I. in experi- ments on decomposi- tion. Electro- chemical equiva- lents. Quantity of electricity estimated- Exciting liquid. Volumeter. ] placing them at a short distance from each other in a good conduct- ing solution. It is important, also, that all the cells of a circle be excited with a liquid of the same strength.* 315. In a voltaic circle in which no zinc is oxidized but what con- tributes to excite an electric current, the quantity of zinc dissolved in a given time from each plate is in a constant ratio, not only to the hy- drogen gas evolved from the corresponding copper plate, but to the hy- drogen set free at the negative electrode. The ratio is such, that 32.3 parts of zinc are dissolved during the evolution of 1 part of hydrogen gas ; and the conclusion which Faraday has drawn from this and numerous similar experiments is, that the quantity of electricity set in motion by the oxidation of 32.3 grains of zinc exactly suffices for resolving 9 grains of water into its elements. If the same current, by means of 4 pairs of electrodes, be made to decompose water, chlo- ride of silver, chloride of lead, and chloride of tin, all in the liquid state, the quantities of hydrogen, silver, lead, and tin eliminated at the 4 negative electrodes will be in the ratio of 1, 108, 103.6, and 57.9 ; while, at one positive electrode, oxygen, and at the three others chlorine, in the ratio of 8 to 35.4, are separated. It thus dis- tinctly appears — and it is a new and important discovery — that elec- tro-chemical decomposition is perfectly definite, a given quantity of electricity evolving the ingredients of compound bodies in well de- fined and invariable proportions, to which Faraday has given the name of electro-chemical equivalents. The reader will at once see that these numbers are identical with the chemical equivalents (see table). Another connexion, then, closer than any before traced, is established between electricity and chemical attraction, showing a mutual dependence and similarity of effect between two agencies, such as almost forces a belief in their identity. T. 106 . 316. The definite nature of electro-chemical action, suggested to Faraday a ready mode of estimating the quantity of electricity circu- lating in a voltaic apparatus. The instrument is contrived to collect the gases evolved from acidulated water during a given interval, in a tube divided into equal measures, which then expresses de- grees of electricity, just as the expansion of a liquid in a thermom- eter indicates degrees of temperature. The instrument, as con- structed for this object, is called by Faraday a volta-electrometer. Various forms of it have been described by him, according as it is wished to collect oxygen or hydrogen separately or both logether.t * A mixture of a proper strength for galvanic troughs, is obtained by adding two parts in bulk of oil of vitriol and one part of common nitric acid to 100 parts of water, the whole being well stirred together until well mixed. Its power should be tested before it is poured into the troughs, by dipping a clean piece of zinc into a little of it in a glass, and observing the degree of action. A stream of bubbles should he disengaged, so small that their size can hardly be determined by the naked eye. If the action be strong, and bubbles of a considera- ble size are evolved, more water should be added. For full direc- tions for operating with voltaic apparatus, see Faraday’s Chem. Manip. 445. + See Faraday’s papers in Philos. Trans, (seventh series), 1834, p. 86. One of the most convenient forms is represented by Fig. 84. It is composed of three pieces, a wooden support, a glass tube, and chamber. The two latter are fitted with brass collars screw- ing into each other. The tube is 13| inches long, and 5-6ths of an inch in diameter, open at bottom, closed at top, and divided into cu- bic inches and parts. The chamber is 4* inches in diameter at the 101 Faraday's Theory. 317. The most celebrated attempt to explain the phenomena of sect, v. galvanism, was made by Davy in his essay on Some Chemical Agen- Theories of cies of Electricity {Phil. Trans. 1807), by means of an hypothesis electro- which has received the appellation of the electro-chemical theory. He jecomposi- considered that a certain electric condition, either positive or nega- tion, tive, is natural to the atoms or combining molecules of bodies ; that chemical union is the result of electrical attraction taking place be- tween oppositely excited atoms, and that ordinary chemical decom- position arises from two combined atoms being drawn asunder by the electric energies of other atoms more potent than those by which they were united. Davy regarded the metallic terminations or poles Davy ’ s > of a voltaic circle as two centres of electrical power, each acting re- pulsively to particles in the same electric state as itself, and by at- traction on those which were oppositely excited. The necessary result was, that if the electric energy of the battery exceeded that by which the elements of any compound subject to its action were held together, decomposition followed, and each element was transferred bodily to the pole by which it was attracted. Substances which ap- peared at the positive pole* such as oxygen, chlorine, and acids, were termed electro-negative substances ; and those electropositive bodies, which were separated at the negative pole. 318. Faraday contends that, between the electrodes and acting in Faraday’s, right lines, there is an axis of power which urges the electro-negative element of an electrolyte in the direction the positive current moves, and gives an opposite impulse to the electro-positive element. He adopts the opinion of Grotthuss, that the decomposing influence is not exerted on any single particle of the electrolyte, but that rows of particles lying between the electrodes are equally subject to its ac- tion. When a particle of oxygen is evolved at the positive electrode, the hydrogen with which it had been combined unites with the oxy- gen of a contiguous particle of water, on the side towards which the positive current is moving ; the second particle of hydrogen decom- poses a portion of water still nearer to the negative electrode ; and the same process of decomposition and reproduction of water con- tinues until it reaches the water in immediate contact with the nega- tive electrode, the hydrogen of which is disengaged. This operation, described as commencing at one electrode, takes place simultane- ously at both : a row of particles of oxygen suddenly lose their affinity for the hydrogen situated on the side next the negative elec- trode, in favour of those respectively adjacent to each on the other side ; while the affinity of a similar row of particles of hydrogen is diminished for the oxygen on the side of the positive electrode, and is base and in height. Through a short cylinder of wood, cemented into the bottom of the chamber, pass two platinum wires, prolonged by larger wires that dip into a small quantity of quicksilver in a cavity in the centre of the wooden support ; the cavity is divided by a partition, and each wire communicates with a separate portion of the quick- silver: wires pass to small brass cups, on the support, to contain quicksilver; thus the connexion with any apparatus is readily made. When prepared for use, the chamber is to be filled to about three fourths with dilute sulphuric acid of specific gravity 1 .336, or from that to specific gravity 1.25. The tube is then filled with the same liquid, and a piece of clean paper of a size to cover the open end, is pressed upon it. The tube can now be inverted and introduced, the paper withdrawn by a glass rod, and the tube screwed on. The connexion is now made, the evolved gases rise to the upper part of the tube, and their volumes are ascertained by inspection. This form of the appara- tus is an improvement on that of Fig. 9, in the paper above referred to. 102 Nomenclature. Chap II. Magnetic effects of galvanism. Old names. increased for those on their opposite side. Hence, for the elimina- tion of the elements of an electrolyte at the electrode, it is essential that the electrolyte itself should occupy the space between the elec- trodes, and be in contact with them. The theory, however, is at present incomplete. 319. The power of lightning in destroying and reversing the poles of a magnet, and in communicating magnetic properties to pieces of iron which did not previously possess them, was noticed at an early period of the science of electricity, and led to the supposi- tion that similar effects may be produced by the common electrical and voltaic apparatus. Attempts were made to communicate the magnetic virtue by means of electricity and galvanism ; but no re- sults of importance were obtained till the winter of 1819, when Oersted of Copenhagen made his famous discovery, which forms the basis of a new branch of science.* The fact observed by Oersted was, that the metallic wire of a closed voltaic circle, and the same is true of charcoal, saline fluids, and any conducting medium which forms part of a closed circle, causes a magnetic needle placed near it to deviate from its natural position, and assume a new one, the direction of which depends upon the relative position of the needle and the wire.t 320. In 1832 Forbes succeeded in obtaining a spark from a magnet without the aid of galvanism, and various methods have since been con- trived. By causing the armature of soft iron to revolve with rapidity in front of the poles of a powerful magnet, very remarkable results have been obtained. The voltaic currents are induced in one direc- tion as the armature approaches the magnetic poles, and are reversed a? it quits them ; so that the currents change their direction twice in each revolution. On all these occasions the source of the electricity is the same, being always induced in the silked wire or helix with which the armature is covered; it has all the characters of a voltaic current. It produces brilliant sparks, renders platinum wire red hot, and gives a strong shock. It readily explodes gunpowder, and a mixture of oxygen and hydrogen gases. It decomposes water ra- pidly; and though from the rapid reversal in the direction of the currents, both gases are given off at the same wire, Pixii succeeded in collecting them separately. $ (An. de Ch. et de Ph. li. 72.) CHAPTER II. Section I. Nomenclature. 321. The names formerly applied to chemical substances, were often fanciful and even absurd, but in 17S7 a new nomenclature was framed by the celebrated French chemists Lavoisier, Berthollet, * Ann. of Philos, xvi. 273. t On this subject, which belongs more to physics than chemistry, see the able outline in Turner’s Elements , p. 109. t For figures and description of magnetic electrical apparatus, see Amer. Jour. xxxiii- p. 213, and xxxiv p. 368. Oxides— Acids — Salts. 103 Morveau, and Fourcroy.t Such names as had been already given gee, i. to the known elementary substances, and the more familiar com- pounds were retained. To the newly discovered elements, names were given expressive of some striking property. To the beautiful element, to which the property of imparting acidity was believed ex- P f ri ^Pks clusively to belong, the name oxygen was given, from the Greek me nclature. o%tig acid, and yeweiv to generate : to inflammable air, which, with oxygen composes water, the name hydrogen was given, from tiding water, and ysvvsiv. New elementary substances have since been named on the same principle, as the green gas chlorine from xhwgog green ; iodine from its violet colour, ’I wdr/g violet, &c. 322. The act of combining with oxygen was called oxidation, and Oxidation, bodies which had united with it were said to be oxidized. Com- pounds, of which oxygen forms a part, were called acids or oxides , Acids^and according as they do or do not possess acidity. An oxide of copper 0X1 es ‘ or iron signified a combination of those metals with oxygen, which had no acid properties. The termination ide was also applied to simi- lar combinations of chlorine, iodine, &c., thus we have chlorides , iodides , fyc. 323. The combinations of the simple non-metallic substances, ei- xjrets. ther with one another, with a metal, or with a metallic oxide, were denoted by the termination uret. Thus sulphuret and carburet of iron, signify compounds of sulphur and carbon with iron. The dif- Oxides how ferent oxides or sulphurets of the same substance were distinguished dis . t1 "*, from one another by some epithet, which was commonly derived from the colour of the compound, as black and red oxides of iron, black and red sulphurets of mercury. Though this practice is still con- tinued occasionally, it is now more customary to distinguish degrees of oxidation by the use of derivatives from the Greek or Latin. Thus the protoxide of a metal denotes the compound containing the minimum of oxygen, or the first oxide which the metal is known to form, £moxide the second, ter or Zrifoxide the third ; and when per- oxide is employed, it denotes the highest degree of oxidation. The Sesquiox- Latin word sesqui, one and a half, is used as an affix to an oxide, ides - the oxygen in which is to that in the first oxide as 1£ to 1, or as 3 to 2. The sulphurets, carburets, &c., of the same substance are desig- nated in a similar way. 324. The name of an acid was derived from the substance acidi- Acids, fied by the oxygen, to which was added the termination in ic. Thus sulphuric and carbonic acids, signify acid compounds of sulphur and carbon with oxygen. If sulphur or any other body should form two acids, that which contains the least quantity of oxygen is made to terminate in ous , as sulphurous acid. 325. Compounds consisting of acids in combination with metallic Salts - oxides, or any alkaline bases, were termed salts , the names of which were so contrived as to indicate the substances contained in them. If the acidified substance contained a maximum of oxygen, the name of the salt terminated in ate ; if a minimum, the termination in ite was employed. Thus the sulphate, phosphate, and arseniate of po~ tassa, are salts of sulphuric, phosphoric, and arsenic acids ; while * For interesting biographies of these eminent men, see Thomson’s History of Chemistry , yoI. ii. 104 Nomenclature. Chap, ii. the terms sulphite, phosphite, and arsenite of potassa, denote combi- nations of that alkali with the sulphurous, phosphorous, and arseni- ous acids. 326. After the discovery of the laws of chemical combination, the Neutral, nomenclature was much improved. What were before called neutral salts , from the acid and alkali being in such proportions as to neu- Super-salts.tralize each other, swjoer-salts from the prevalence of acid, and sub- salts from the excess of alkali, were named from their atomic consti- Atomic tution. If the salt is a compound of one proportion of the acid and tkmmclVca o ener > c nama of the salt is employed without any te d. other addition ; but if two or more proportions of the acid are attached to one of the base, or two or more of the base to one of the acid, a numeral is prefixed so as to indicate its composition. The two salts of sulphuric acid and potassa are called sulphate and ^'sulphate ; the first containing an equivalent of the acid and the alkali, and the second salt, two of the former to one of the latter. The three salts of oxalic acid and potassa are termed the oxalate, fo'noxalate, and ^wadroxalate of potassa ; because one equivalent of the alkali is united with one equivalent of acid in the first, with two in the second, and with four in the third salt.* More ex- 327. The views of chemists in regard tq acids, alkalies, and salts, ▼lews of have been much extended. Several of the metals form acids with suits, &c. oxygen, and others alkalies. The acids and alkalies give rise to compounds more complex than themselves, containing at least three elements, and these are known by the name of salts ; most of them unite in definite proportions with certain substances, and, with other salts, forming double salts . Chemists are now inclined to consider as acids all compounds which unite with potassa or ammonia, and give rise to bodies similar in constitution and general character to the salts which the sulphuric or some admitted acid forms with those alkalies. Alkalies. 328. The characters of alkalies are exhibited most perfectly in potassa and soda; they are causticity, a peculiar pungent taste, alka- line reaction with test paper, and power of neutralizing acids, and especially of forming with them neutral saline compounds. Such Salifiable are ca ^ e ^ olkaline or salifiable bases , which unite definitely with ad- bases. mitted acids, and form compounds analogous in constitution to the salts from admitted alkalies and acids. Salts are 329. The salts are now viewed as compounds of oxidized bodies, compounds b 0 th ^e ac id an( J base containing oxygen. Ammonia, though not bodies. 1ZCd an oxide, has all the characters of an alkali, and its compounds with acids are admitted as salts. Orders. 330. Salts have been divided by Turner into four orders, viz. 1. oxy - salts ; 2. hydro-salts ; 3. sulphur-salts ; and 4. haloid-salts. In the first, the acid or base is an oxidized body, in the second it contains hydrogen, in the third the electro-positive or negative ingredient is a sulphuret, and in the fourth it is haloidal. The nomenclature of the hydro salts is framed on the same princi- , * As the numerals which denote the equivalents of the acid in a super salt are de- ni«thod°, n ' rived from the Latin, it has been proposed by Thomson to employ the Greek numerals dis , tris , tctrakis . to signify the equivalents of alkali in a subsalt. Turner has extended this by distinguishing two or more equivalents of the negatively electrical element by Latin numerals, and the positive element by Greek numerals. Thus a bichloride de- notes a compound which contains two equivalents of the negative element chlorine ; and dichloride indicates one equivalent of chlorine with two of some positive body. Salts — Gas. 105 pies as those applied to salts which contain oxygen. No general Sect, i. principle of nomenclature has yet been agreed upon with respect to the third and fourth order. Berzelius has extended to them the same nomenclature which he employs for the oxy-salts. 331. The haloid - salts of Berzelius (from &lg Sea-salt, and sldog form) are those which, in constitution, are analogous to sea-salt. sa J t “ They are, for the most part, bi-elementary, consisting of a metal, and of chlorine, iodine, bromine, fluorine and the radicals of the hydr- acids.^ The haloid-salts are analogous to oxides and sulphurets.t 332. In the compounds of metallic sulphurets (double sulphurets) Berzelius has found an exact analogy with the salts, and called them sulphur-salts. The union of simple sulphurets forms a sulphur-sa\t Sulphur analogous in constitution to acids and alkaline bases, and which, like them, are capable of assuming opposite electric energies in relation us> to each other. Electro-positive sulphurets are termed sulphur ■* bases, and are usually the protosulphurets of electro-positive me- tals, corresponding to the alkaline bases of those metals. Electro- negative sulphurets, sulphur acids , are the sulphurets of electro- negative metals, and are proportional in composition to the acids which the same metals form with oxygen. Hence if the sulphur of a sulphur-salt were replaced by an equivalent of oxygen, an oxy-salt would result. 333. Most salts a re solid at common temperatures and susceptible characters of crystallization ; they vary in colour. The soluble salts are more of salts, or less sapid, the insoluble are insipid ; few of them possess odour. They differ in their affinity for water (page 5), and in solubility. Some dissolve in less than their weight of water ; others require se- veral hundred times their weight ; others are quite insoluble ; this difference depends on their affinity for water, and on their cohesion ; their solubility being in direct ratio with the first, and in inverse ratio with the second. 334. The relative degrees of affinity of salts for water may be Affinity of estimated by dissolving, equal quantities of salts in equal quantities sal * s for of water, and heating the solution. That salt which has the great- ^i-mined" est affinity for the menstruum will retain it with most force, and will, therefore, require the highest temperature for boiling.! 335. The term gas is applied to those elastic fluids, except the at- Gas, what, mosphere, which retain their aeriform state at common temperatures, and which cannot be made to change their form unless by much greater pressure than they are naturally exposed to. They differ from vapours in the relative forces with which they resist condensation. *The metallic chlorides, iodides, bromides, and fluorides, the cyanurets, sulphocy- anurets, and ferrocyanurets, are included by Berzelius among the haloid salts. (Ann. de Chim . et de Phys. xxxii. 60.) t On this subject consult Turner’s Elements , 404. The haloid salts of Berzelius are the haloid acids and bases of Turner, and the double haloid salts of the former are the haloid salts of the latter chemist. t Gay Lussac, An. de Chim. lxxxii. 14 V 106 Apparatus and Manipulation. -Chap. II. Apparatus. Gas bottles. Apparatus for gases, requiring red heat. Coating of ?c*- ■• 1 *. Section II. Apparatus and Manipulation. 336. For performing experiments on gases, several articles of apparatus are ne- cessary, consisting partly of vessels fitied for containing the materials that afford them, and partly of vessels adapted to the reception of gases, and for submitting them to experiment. For procuring such gases as are producible without a very strong heat, glass vessels, furnished with ground stoppers and bent tubes are sufficient Of these, several will be required of different sizes and shapes. A Florence flask, with a Fig. 85. Fig. 86. Fig. 87. cork perforated by a bent glass tube, or even a tin pipe, will serve, for obtaining some of the gases. Those gases that require for their liberation a red heat, may be procured by exposing to heat the substances capable of affording them, in coated earthen retorts or tubes," or in a gun barrel, the touch-hole of which has been accurately closed by an iron pin. To the mouth of the barrel must be af- fixed a tube bent so as to convey the gas where it may be requisite. + A very convenient apparatus for obtaining such gases as cannot be disengaged without a red heat, consists of a cast-iron retort (Fig 89). This may have a jointed metallic conducting tube fitted to it by grinding (Fig. 90). It is repre- sented as placed, when in actual use, within the bars of a common fire-grate, 13. (Fig. 102.) The wrought iron bottles in which quicksilver is imported, form conve- nient retorts for this purpose, a gun barrel being screwed into the neck of the bottle. When these are used (as for obtaining oxygen gas), the fuel should be charcoal ; they are liable to melt if anthracite coal is used. ♦When a coating must sustain a very high temperature, it should be made of the best Stourbridge clay, made into a paste, beaten uutil perfectly elastic and uniform. A portion should be flattened out into a cake of the required thickness and size adapt- ed to the vessel. If the vessel he a retort or flask, it should be placed in the middle of the cake, and the edge of the latter be raised on all sides, and gradually moulded and applied to the glass ; if it be a tube, it should be laid upon one edge of the plate, and then applied by slowly rolling the tube forward. In all cases the surface to be coated should be rubbed over with a piece of the lute dipped in water, for the purpose of moistening, and leaving a little of the earth upon it; and if any part of the surface becomes dry before the lute is applied, it should be remoistened. The lute should be pressed and rubbed down upon tne glass, successively, from the part where the contact was first made to the edges, until all air bubbles are excluded, and an intimate adhe- sion effected. Care must be taken to exclude all air from between the glass and lute, and the edges should he moistened, made thin, and joined with great care. The ge- neral thickness may be from one fourth to one third of an inch. The vessels are af- terwards to be placed in a warm situation over the sand bath, or in the sun’s rays: they should dry slowly and regularly. To prevent cracking, horse dung, chopped hay, horse hair, and tow cut short may be incorporated with the lute. The addition of sand, renders the lute more fusible, and is not applicable when very high temperatures are to be sustained. In such cases fragments ef broken glass pots, or of broken cruci- bles, may be used, being first well pulverized ; but crucibles, soiled by flux or other impurities must not be so employed. For various kinds of lutes and cements, and di- rections for their application, &c., see Faraday’s Chem. Manip. p. 467. t Great convenience often arises from prolonging the tube by means of flexible tubes or hoses 5 and any num- ber of them may be cohnect- ed by the attached screw’s Fig. 95. Gasometers. 107 For receiving the gases, glass jars of various'sizes are required, some of which Apparatu* should be furnished with necks* at the top, fitted with ground stoppers, or to for receir- which a circular plate of brass is well ground. (Fig. 91 and 92.) in S gase*. Fig. 91. Fig. 92. Others should be provided with brass caps and screws for the reception of air cocks. (Fig. 9'd.) Of these air cocks several will be necessary, and to some of them bladders, (Fig. 94, a,)* or elas- tic bottles, should be firmly tied for the purpose of transferring Fig. 93. Fig 94. * A bladder may be made to continue tight for a considerable period by pouring a little oil into it at first, and allowing it to become saturated. Bladders are not per- fectly tight to gases, and are less so when dry than when moist ; consequently gases shou'd not be retained long in them, and never longer than is absolutely necessary. Hydrogen gas passes more rapidly through them than any other gas. Gas bags are made of oiled silk, or of two layers of woven material, haying between them a thick layer of caoutchouc. Those made of oiled silk are seldom tight, and ra- pidly increase in porosity. F. 108 Chap. II. Pneumatic trough. Graduated tubes. Gasometer. Transfer- ring of gases. •Apparatus and Manipulation. a few gallons of water. This is best made of copper, (Fig. 96, 6,) if of siderable size; or if small, of tin, japanned or painted; //, ezhibi con- ezhibits a Fig. 96. Fig- 97. section of this apparatus, which has been termed the pneumato-cbemical trough, or pneumatic cistern. Its size»may vary with that of the jars employed ; and, about one or two inches from the top, it should have a shelf on which the jars may be placed when filled with air, without the risk of being over- set. In this shell* should be a few small holes, to which inverted funnels may be soldered. Fig. 97 represents a very convenient Fig. 98. form of' this apparatus. A glass tube, Fig. 98, about l t t t 1 ( t IS inches long and three fourths of an inch in diam- 1 ' 1 - 1 1111 1 J eter, closed at one end, and di\ ided into cubic inches and tenths of inches will be 5 p 1 small measure, containing about two cubic inches, and similarly Fig graduated. Glass tubes about five inches long, and half an inch wide, divided decimally, are also necessary. Besides these, the experi- mentalist should be furnished with air funnels, (Fig. 99). for tram ’ ring gases from wide to narrow vessels. 337. An apparatus almost indispensable in experiments on this class of bodies, is a Gasometf.r, which enables the chemist to collect and to preserve large quantities of gas, with the aid of only a few pounds of water. In the form of this apparatus there is considerable variety ; its general construction and use is inch n peri- isfer- f \ as follows. It consists of an outer fixed vessel d, (Fig. 100), and an inner movable one c, both of copper or japanned iron. The latter slides easily up and down within the other, and is suspended by cords passing over pullics, to which are attached the counterpoises e e. To avoid the incumbrance of a great weight of water, the outer vessel d is made double, or is composed of two cylinders, the inner one of which is closed at the top and at the bottom. The space of only about half an inch is left between the two cylinders, as shown by the dotted lines. In this space the vessel c may move freely up and down. The interval is filled with wa- ter ns high as the top of the inner cylinder. The cup, or rim, at the top of the outer vessel, is to prevent the water from overflowing, wdien the vessel c is forcibly pressed Fig. 100. \4 'gj- 1 l| to be collected. The gas enters from the vessel in which it is produced, by the communicating pipe &, and passes along the perpendicular pipe, marked by dot- ted lines in the centre, into the cavity of the vessel c, which continues rising till it is full. 338. To transfer the gas or to apply it to any purpose, the cock b is to be shut, and an empty bladder, or bottle of elastic gum, furnished with a stop-cock, to be screwed on, a. When the vessel c is pressed down with the hand, the gas passes down the central pipe, which it had before ascended, and its escape at b being prevented, it finds its w'av up a pipe which is fixed to the outer surface of the vessel, and which is terminated by the cock a. By means of an ivory mouth-piece screwed upon this cock, the gas, included in the instrument, may be respired ; the nostrils being closed by the fingers. When it is re- quired to transfer the gas into glass jars standing inverted in water, a crook- Gas-holders , 109 ed tube may be employed, one end of which is screwed upon the cock b ; while the other aperture is brought under the inverted funnel, fixed into the shelf of the pneumatic trough. 339. When large quantities of gas are required, (as at a public lecture), the gas-holder (Fig. 101) will be found extremely useful. It is made pig. ioj. of copper or tinned iron-plate, japanned botli within and with- out. Two short pipes, a and c, terminated by cocks, proceed from its sides, and another, ft, passes through the middle of the top or cover, to which it is soldered, and reaches within half an inch of the bottom. It will be found convenient also to have an air cock with a very wide bore, fixed to the funnel at b. When gas is to be transferred into this vessel from the gasometer, the vessel is first completely filled with water through the funnel, the cock a being left open and c shut. By means of a horizon- tal pipe, the aperture a is connected with a of the gasometer. The cock b being shut, a and c are open, and the vessel c of the gasometer (Fig. 100), gently pressed downwards with the hand. The gas then descends from the gasometer till the air-holder is full, which may be known by the water ceasing to escape through the cock All the cocks are then to be shut, Fi 1Q2 and the Vessels disunited. To ap- ply this gas to any purpose, an empty bladder may be screwed on a ; and water being poured through the funnel b , a corresponding quan- tity of gas is forced into the blad- der. By lengthening the pipe 6, the pressure of a column of water may be added : and the gas, being forced through a with considerable velocity, may be applied to the purposes of a blow-pipe, &c. &c. The apparatus admits of a variety of modifications. The most useful one appears to be that contrived by Pepys, consisting chiefly in the ad- dition of a shallow cistern (Fig. 102, c) to the top of the air-holder, and of a glass register tube /, which shows the height of the water, and ( consequently the quantity of gas, in the vessel. When a jar is intended to be filled with gas from the reservoir, it is placed, filled with water, and inverted in the cistern c. The cocks 1 and 2 being opened, the water descends through the pipe attached to the latter, and the gas rises through the pipe e. By raising the cistern a to a greater elevation, any degree of pressure may be obtained ; and a blow-pipe may be screwed on the cock at the left side of the vessel.* 340. A very convenient apparatus was contrived by Hope, for receiving and storing large quantities of gases most in use, from which a supply may be easily procured as wanted. It consists of a large oil of vitriol bottle a, or carboy, (Fig 103 . ) in which two tubes with stop-cocks are fitted, water being introduced and forced out again when necessary by one, and gas by the other. In the figure i * It is necessary to be aware of the possible entrance of common air with the water, even when there is considerable depth in the cistern. When the gas is passing ra- pidly r out at the lateral stop-cock, and consequently the water rapidly descending through the tube, it will, if unattended to, frequently acquire a rotary motion, which, from mechanical causes easily explained, will at last produce an aperture commencing at the surface of the water and descending to the very bottom of the tube. Down this, air is rapidly carried by the descending water, which, mixing with the gas in the in- strument, deteriorates it, and with inflammable gases may lead to dangerous results. Hence this rotary motion when observed, should be disturbed. The formation of the central channel for air may easily be prevented by allowing a large bung or piece of light wood to swim on the surface of the water. If rotation does take place, it will draw the floating mass to the centre, and prevent the air from passirg down by hin- dering the formation of a channel, if water be plentifully supplied. F. 362. Sect. II. Gas-holder. Hope’s gas-hold er. Precaution*. 110 Chap. II. t Transfer- ring from. Mercurial gasome- ters. Nermann’* mercurial trough. Apparatus and Manipulation. may be supposed in connexion with the extremity of a bent gun barrel fixed in an iron retort, from which oxygen is passing To prevent accident and render it more easily movable when full of water, it should be placed in a tub, the space between the bottle and sides as well as the bottom are packed with saw dust. After filling it with water, a bent tube is connected with the gun barrel by a flexible lead or tin pipe two or three feet in length. No gas is allowed to pass in unless pure, the stop-cock at the extremity of the gun barrel, //, being kept shut, while the other one c, is open. The gas first passing over can be collected by means of a bent tube d fitted to it, in a small jar over water, so that its purity can be tested. When it is thought proper to commence collecting it, the stop-cock c is to be shut and the other b opened. As the gas enters, the water will be forced up the tube seen in the interior of the bottle continuous with the stop-cock e at- tached to the cap of the carboy ; and another bent tube being placed over it a syphon will bo formed, through which the water will continue to flow as the gas enters. By using a large quantity of materials at a time, several bottles may be filled successively without undoing any part of the apparatus, except the leaden pipe that connects them directly with the gun barrel ; one bottle may be detached and another attached in a few seconds. If wanted, jars of gas may be collected from the tube d in the pneumatic trough. To transfer a gas from this apparatus, detach the syphon, place a tin funnel z, (Fig. 10-1,) above the stop-cock e, pour in water and open the stop-cocks; it will descend and force the gas out at the stop- cock g, to which a flexible pipe may be attached. In the same manner the air is expelled and the carboy filled with w r ater before connecting it with the retort furnishing the gas. 341. The gasometers already described, are fitted only for the reception of gases that are confinable by water ; because quick- silver would act on tho tinning and solder of the vessels ; and would not only be spoiled itself, but would destroy the apparatus. Yet an in- strument of this kind, in which mercury can be employed, is peculiarly desira- ble, on account of the great weight of that fluid ; and two varieties of the mer- curial gasometer have therefore been invented. In that invented by Pepys, the cistern for the mercury is of cast iron. Newmann has joined a gasometer of this kind to an improved mercurial trough, by means of which the advantage of both are obtained with only CO or 70 pounds of quicksilver.* Fig. 105. Fig. 104. Fig. 103. * It is not more than 18 inches in length and height; and it is placed in a large jap- panned tray to collect scattered mercury. When gas is to be collected in the Fig. 105. gasometer, the beak of the retort is placed below the surface of the mercu- ry, in the cup at the bottom of the ap- paratus, and bavin" a bell shaped ves- sel immersed in the mercury imme- diately over it. The trough has a cavity in the middle, large enough to fill a jar 10 inches long, and 24 wide ; and there is a shelf on each side, three inches in width, to support vessels con- taining gas. Opposite to three inden- tations op the edge of the trough, are three holes in one of the shelves, into which the beaks of retorts libera- ting gas are to be introduced; or a sli- ding shelf with apertures may be fit- ted across the cavity for the same pur- pose. The gasometer is at one end, a, and sunk below the level of the trough. It is capable of containing 50 cubic inches. A tube, connected with the gasometer at the lower part is r- made to ascend, and passing up \. through the mercury in a corner of the trough, at about an inch above it bends down again and termiuates beneath its surface. If the gas is contained in the gasometer, it Furnaces. Ill For the mere exhibition of a few experiments, a small trough, eleven inches Sect. II. long, two wide, and two deep, cut out of a solid block of mahogany, (or soap- stone) is sufficient. 342. The'materials from which some gases are to be obtained, require the aid of a high temperature and a suitable furnace. Various kinds of furnaces are required by the chemist, of which figures and descriptions will be seen in Fara- day’s Chemical Manipulation* * For many processes a very convenient furnace may be formed out of the large Furnaces, crucibles known as blue pots , and may be had of almost every size less than the height of 22 inches, and of 12 to 14 inches diameter at the top. One of these vessels, of the height of 12 inches, and 7 inches wide at the top, will make a very useful furnace for the igniting of a small crucible, heating a tube, or small retort. Fig. 107. A number of holes are pierced in it, by a gim- Fig. 107. let or brad awl, and enlarged by a round rasp. The pot is now bound round with iron or copper wire, to strengthen and hold it together when it cracks, an effect which is sure to take place after it has been a few times heated. This wire should be carried round in three differ- ent places, and secured by notches made in the pot with the edge of a rasp, and the ends should then be twisted together. It is also con- venient to have a handle to these furnaces. A movable grate like that figured in the wood cut, makes this furnace com- plete for many operations. Fig. 108. If it be required to heat a crucible, the grate should be of such a size as to drop into the furnace, and rest between the bottom and the second row of holes. The part below then forms the Fig. 108. ash-pit to be supplied with air by the four holes; and the part above forms the body of the furnace to receive the fire and the crucible. If a shallow fire only is wanted, as in the process of distillation or the heating of tubes, the grate should be of such size as, when dropped may be transferred to air-jars in the trough, by filling them with mercury, Fig.106. placing them over the end of the bent tube, and giving pressure to the gasom- eter. The air will pass from it along the tube into the jar. By the bend in the tube, the mercury is prevented from passing into the lower part of the gasometer, while at the same time the gas is allowed a free passage. All inconvenience is prevented by means of a stop-cock, which shuts off the communication between the receiver and the trough, preventing at the same time the escape of air from the gasometer, and of mercury into it. A sliding shelf is fixed beneath the trough to support a spirit-lamp under a retort, or for other purposes. A detonating tube b, (Fig 106) and spring are also at- tached to the apparatus by a clamp and screws, and may be fixed on any side of the trough. The whole apparatus is of iron, excepting sometimes the pillars which support it, and which maybe of brass. See another form Fig. no. * A work which should be in the possession of every chemical student. A furnace for general laboratory use which has been found powerful and convenient, was orig- inally constructed for the Royal Institution* of the form and section represented in the annexed figures. It warms and airs the laboratory, heats water, tubes, gas bottles, a sand bath, &c. The principal part is of brick work, the top plate A B, sand bath, plate under the same and front may be of iron or soap stone. The flue is carried horizontally under the sand bath, and a warm chamber is left beneath, which is closed by doors, in which crucibles or other vessels may be kept warm, ready for introduction into the furnace, and slow evaporations be carried on. The circular opening in front, over the fire chamber, is adapted to receive various vessels, by means of concentric iron rings of various diameters, on a cast iron pot. _ * Furnaces of this kind have for several years past, been in use in the laboratory of the Univer- sity at Cambridge, and in that of the Medidal College in Boston, and proved admirably adapted for all purposes. For minute description see Faraday, p. 90. 112 * Apparatus and Manipulation. Chap. II. into the furnace, to descend only a little below the first tier of holes, the ash-pit having two tiers of holes entering it. Half a dozen of these small grates will be required in the laboratory, for the purpose of fitting at different times into different parts of the same furnace, and also for use in different sized furnaces of the kind now described. When we wish to diminish the intensity of the fire, the holes or a portion of them may be closed with soft brick or clay stoppers. On the contrary, when it is desirable to increase the temperature, or to increase the body of fuel, additions are made at the top of the furnace. A very useful one consists of the upper part of an old crucible cut off so as to form a ring, (Fig. 109,) which should be bound round with wire, as was directed in regard to the furnace. A most useful accompaniment to these small portable furnaces, is a piece of straight funnel pipe, about two feet long, four inches in width, and opening out below until it is about eight inches in diame- ter. Fig 110. This will easily rest upon any furnace not more than c* eight inches nor less than four or five inches wide ; is quickly put on or otf; stands steadily of itself, and increases the draught power- fully. A wooden handle may be attached to it for convenience ; or without it, the tongs will serve to remove it. It may either be taken off’ when the fire requires to be made up, or the pieces of charcoal may be dropped in from above. There is no difficulty in raising a crucible two inches and a half in diameter to a white heat, by a furnace of this kind, and that in any situation which may be convenient, upon the tables or the floor, and with all the advantage of arrunirinf a piece of glass ^uUienT" tube, about half an inch in diameter and five inches long, attached Fig. no. ^ or lrans _ to a piece of smaller diameter, which, after bending as in Fig. 112, q ference terminates in a chamber at a, which being cylindrical for the greater, part of its length, terminates in a capillary tube and aper- ture. A small piston, rendered air-tight by tow and tallow, is fitted into the cylindrical tube ; it is moved by a rod and ring, the rod passing through a box which closes the upper aperture of the A instrument, but which should not be air-tight. A portion of mer- ^/j ^ cury is placed above the piston, the space between it and the W JJ capillary opening of the chamber, is filled with the same metal when the piston is in the position depicted. Upon raising the piston, the mer- cury follows it, and descends into the chamber a, the space left by it being im- mediately filled with the air or gas Which has access to the capillary opening. The rod has a graduation upon it, by which it is known when a tenth of a cubical inch of air has entered the chamber. F. 340. 347- The manipulation with jars and glasses is comparatively easy to that which occurs in transference from them to tubes, or from tubes to each other. Manipula- One circumstance with tubes which occasions difficulty, in addition to the nar- 11011 Wlt h rowness of their mouths, is, their contracted capacity within, by which the easy tu °es. * In collecting and transferring gases over quicksilver, especially where the quick- silver is impure or dirty, the gas will escape on the outside of the jar, there being so little adhesion between the quicksilver and the glass; this, I have found, may be partially guarded against by slightly smearing the edge of the jar with pomatum. W. 15 114 Chap. IL Transfer- ring from large to small tubes, From jars. Removing tubes con- taining gas Specific gravities. « Apparatus and Manipulation. passage of a bubble of gas upwards, and water downwards, at the same time, is interfered with ; this effect is greatest in tubes of the smallest diameters. No great difficulty will occur in the transference of gas from a tube to another that is wider. (Fig. 113.) The second tube is to be filled in the usual manner with water, and held in the well of the trough, in a consi- derably inclined position : the tube containing the gas is to be brought near it, the upper edge of its mouth inserted as it were into the mouth of the first, and then its position slowly altered, until the gas passing to- wards the mouth be gradually delivered in distinct bubbles into the first tube. During this transfer, the should be retained as much as possible within the first ; the latter should not be raised to a perpendicular position, but be considerably inclined, for then the edges of its mouth meet better with, and are adapted to, those of the second tube, so as to oonfine the gas, and the motion of the bubbles is less sudden and less subject to derangement. Occasionally it is advantageously placed in almost a horizontal position, its closed extremity being but little raised. One bubble of gas should be allowed to rise to some height in the tube before another is permit- ted to follow. 348. When the delivering tube is larger than the receiving tube, more care is required in the transfer. The first tube should be inclined as before, and the upper edge of the mouth of the second placed within it, and to assist in uniting as it were the two tubes for the moment, the finger and thumb of the left hand (which holds the receiving tube) should be applied at the sides of the junction, so as to confine the gas and prevent its escape laterally. For this purpose, and ge- nerally in tube transference, the tube is best held in the hand, with its open ex- tremity passing out between the thumb and fore finger, so that when sustained in the water in an inclined position the back of the hand may be upwards, the hand being as it were over the vessel ; the tube is then easily supported by the two or three last fingers of the hand, and the fore finger and thumb are left at liberty to guide the mouths of the vessels or to close the lateral opening, as has been just described. At other times it may be held as a pen is retained in the hand, the mouth being confined and guided between the thumb and two fore fingers. The tubes should at all times be retained by a light and easy, though secure hold, and not in a stiff' rigid manner, and the arms may often be allowed to rest with advantage on the edge of the trough, whilst the hands are immersed in the water. 349. An intermediate lipped glass should be used for the transference of gas from a large jar to a lube. The tube being filled with water is to be held under the surface as before described (347) ; the lip is to be introduced into it, the junc- tion made by the fingers if necessary, as in the former case, and the gas allowed to pass in distinct bubbles. It will be found easier to transfer from a glass that is from a third to five-sixths full of gas, than from one containing more or less. When a glass is nearly empty, it is often exceedingly difficult to transfer from it into a narrow tube. Advantage may therefore occasionally be taken of the cir- cumstance above mentioned, to replenish the glass with gas. 350. Tubes containing gases are easily transferred from one trough to another, or to other situations, merely by closing their mouths with the finger or thumb, • and carrying them to the required situation. The student should very early at- tain the habit of closing the mouth of a tube by the finger with facility and secu- rity. The accurate manipulation of gas in tubes, so that none shall escape and be lost, is often essential in experiments of research, where only small portions of gas are evolved for examination as to many of its properties. F. 326. Section III. Methods of estimating Specific Gravities. 351. Water has been fixed upon as the standard of comparison in estimating specific gravities; and its specific gravity has been called 1. 352. In all experiments for ascertaining the specific gravities of different sub- stances, particularly of gases, great attention must be paid to the temperature, as their volume varies with the degree of heat to which they are exposed. Fig. 1 .3. mouth of the second tube 115 Specific Gravity. 353. To find the specific gravity of a solid body heavier than water, — First, Sect. III. weigh the solid in air; then weigh it in water by a hy- Fig. Ilf ~ ^ drostatic balance in tbe manner represented in Fig. 114, gmvitvof using a very fine thread, or a hair to suspend it from the H solids^ bottom of one of the scales. The difference in the results will express the weight of a quantity of water equal in bulk to the solid whose specific gravity is to be determined, and the following proportion will give its specific gravity in relation to water : As the weight of the water equal in bulk to that of the solid is to the weight of the solid itself, so is the specific gravity of wa- ter to the specific gravity of the solid. Thus, If the solid weigh 100 grains in air, and 60 grains in wa- ter, then 100 — 60, or 40 : 100 : : L: 2.5. The specific gravity of the solid is therefore 2.5 compared with that of water. 354. If the solid should be lighter than water, a more complicated process will Of light be necessary. Attac : h to the light solid by a slender thread another body of such bodies, a weight that when tied together they shall sink in water, having previously weighed the heavier solid in water, and each in air; then weigh them together in water, and from the difference between their weight in water and their weight in air, subtract the difference between the weight of the heavy solid in air and its weight in water ; the remainder will show the weight of a quantity of water equal in bulk to the light body, and we can then find its specific gravity in the way directed above. Thus, If the weight in air of the light solid be 10 and of the heavy solid 20 ; and if the weight of the heavy solid in water be 18, and of the two together 7, — then From their weight in air, . . . . 20 -f- 10 = 30 Substract their weight in water, ... 7 And from this substract 20 — 18= 2 23 2 The remainder 21 expresses the weight of a quantity of water equal in bulk to the light solid, and the following proportion will give us its specific gravity, 21 : 10 : : 1. : 0.47619, — the specific gravity of the lighter solid. 355. Where a hydrostatic balance cannot; be procured, the following method may be adopted : Weigh the solid and put it into a vessel full of ! water, the Another weight of which with the water is known; the solid will displace a quantity of method, water equal in bulk to its own ; weigh the vessel again, having either taken out the solid body, or put an equal weight in the opposite scale ; — the difference be- tween the present weight of the vessel and its former weight will express the weight of a quantity of water equal in bulk to the solid body, from which, by the same proportion as in the former instances, we can estimate the specific gravity of the solid body. Thus, if the vessel when full of water weighed 1000, and after some of the water had been displaced by the solid body and the solid re- moved, or a counterpoise placed in the opposite scale, it weighed 900 grains, — 100 grains of water were displaced by the solid body — and if the solid body in air weighed 300 grains, then the following proportion will give its specific gravity : 100 : 300 : : 1 : 3. 356. If the solid body be soluble in water, some other fluid, as oil, alcohol, ether, or a saturated solution of the substance itself must be used, its specific gra- of soluble vity being previously ascertained. We must first find the specific gravity of the k oc q es solid, considering the fluid used as a standard of comparison, and making the ' number representing its specific gravity the third term in the proportion, in the same manner as when water is used ; and then, by simple proportion, reduce the product to the standard of water. Thus, if the specific gravity of the fluid used be 1.2, and, considering it as a standard of comparison, the specific gravity of the solid be 1.8, then the following proportion will give us its real specific gravity : 1.2 : 1.8 : : 1. : 1.5. 357. When the substance, the specific gravity of which is to be ascertained, is Of pow- in the form of a powder, the following method, recommended by Leslie, will ders, be found most convenient. (Fig. 115.) Take a glass tube b /, three feet in 116 Chap. II. Ofliquids. Areometer. Lovi’s heads. Of Gases. Apparatus and Manipulation. length, and open at both ends. The wide part b e is to be about Fig- 115 . of an inch in diameter, and the narrow part c / about com- flO municating with each other by a very small aperture at c, which n — allows air to pass, but is sufficiently small to prevent any powder 0 from going through. The upper opening at b is to be ground, so that it can be accurately closed by a glass plate a. The substance whose specific gravity is to be determined, is put into the wide part of the tube b c , which is then to be placed in a wider tube containing mer- cury g , making it descend till the fluid metal shall have reached the , aperture at c. Then fix the cover, making it air-tight with a very a small quantity of lard, and lift it perpendicularly out of the mercury, ^ till the aperture at c shall have been raised above the surface of the mercury in the tube to a height exactly equal to half the height of the /. barometer at the time the experiment is made, and mark the point at J which the smaller tube is cut by the fluid, w hich we shall suppose in the present instance to bo d. The air within that part of the tube in which the powder has been placed being now subjected to the pressure of only half an atmosphere, it expands to double its former volume, one half still remaining within b c, w hile the rest occupies c d, the space it includes representing therefore the total bulk of air included at first along with the powder in b c at the ordinary pressure. The powder is now withdrawn, and the process repeated with b c full of air only, when it is obvious that the mercury will not stand so high within the tube cf as before, and supposing it to rise only to e, then the space c c will contain a quan- tity of expanded air, equal in bulk exactly to w r hat w ould be contained in b c be- fore lifting up the tube. Since c e then represents a space exactly equal to that within b c, and c d a space equal to the volume of air in be when the powder w r as in it, then d e } the difference between them, shows the spaee occupied by the powder when it was in b c. In this manner, then, we are enabled to find out a space exactly equal in bulk to that of the solid matter in the pow’der, and if the stem be graduated so as to express in grains the quantity of water which it can contain, we have only to weigh the powder in air and compare its weight with that of the equal bulk of water to ascertain its specific gravity. 358. Take a bottle of a known weight, fill it with distilled water, and weigh it carefully; then pour out the water, and after drying the bottle, fill it with the liquid to be tried. The following proportion will give its specific gravity : As the weight of the distilled water is to the weight of the liquid, so is 1 to the spe- cific gravity required. Thus, if the weight of the distilled water be 300 grains, and that of the liquid 600, the following is the proportion w r e must use : — 300 : 600 : : 1. : 2. The areometer is a convenient instrument for ascertaining the specific gravities of liquids. It consists of a long, straight, graduated stem, on which numbers are marked at the points to which the instrument sinks in liquids of the specific gravities marked at these points. Thus, in distilled water it will sink to 1, and in nitric acid to 1.48. It is made of different materials according to the nature of the liquids whose specific gravities are to be ascertained with it. Lovi’s beads are also very useful for ascertaining the specific gravities of liquids. These are small balls made of glass, with numbers marked on them in- dicating the specific gravity of those liquids in which they float without any ten- dency either to sink or rise to the top. Those that float on the surface show that the liquid has a greater specific gravity than the number marked on them expresses, while those that sinlv indicate tiie reverse, being heavier than an equal bulk of the fluid. 350. Atmospheric air is taken as a standard of comparison in estimating the specific gravitv of gases, and represented by the number 1. Their specific gra- vities are found out in the same manner as those of other substances, viz. by comparing the w eight of equal bulks of them and of the substance which is taken as a standard of comparison. For this purpose, a flask provided with a stop-cock is accurately weighed and attached to an air-pump or exhausting syringe, which is worked in the usual manner ; and, wffien the gas whose specific gravity is to be tried has no action on atmospheric air, it is not necessary to exhaust it to a very great degree. The stop-cock fixed to the flask is then turned, w T hen it is weighed again to ascertain the quantity of air extracted. It is then screwed on to a jar (placed over a pneu- matic trough) containing the gas whose specific gravity is to be determined, and on opening the stop-cock, a quantity of gas is forced by the pressure of the atmos- phere into the flask, exactly equal in bulk to the air which had been withdrawn, if the jar be depressed in the liquid till it shall be level both within and without. Liquefaction of Gases. 117 If the flask be then detached from the jar, it is obvious that by weighing it again Sect- lit. we can find out the weight of a measure of gas exactly equal in bulk to that of the air whose weight was found out by the first operation. For example, if the flask should weigh 570 grains when full of air, and 560 Example, after the exhaustion, then the quantity of air which has been withdrawn weighs 10 grains, «, W eight of flask with air ..... 570 grains. Weight of flask aftpr exhaustion .... 560 do. Weight of air withdrawn, . ... 10 do. And if it shall weigh 580 grains after admitting an equal volume of the gas whose specific gravity is to be determined, then it must be twice as heavy, or its specific gravity must be twice as great as that of atmospheric air. Weight of flask with gas . . . . . . 580 grains. Weight of flask after exhaustion, , 560 do. Weight of gas introduced 20 do. When the gas whose specific gravity is to be ascertained acts chemically on atmospheric air, the latter must be withdrawn as completely as possible by re- peated exhaustions, filling it after each with some gas which is not affected by the other, and then proceeding in the usual manner. 360. In operating with gases, it is also necessary to attend to the pressure of the atmosphere as indicated by the barometer, and the quantity of watery vapour which thby may contain. Formulas have been given for making correc- tions when the barometer is not at the point adopted as the standard of compari- son, and for the quantity of watery vapour which the gases may contain, for which see Faraday’s Chem. Manip. 375, and Turner, 48. 361. It may be necessary, to remark, that when the specific gravity of a gas is ascertained, and no variation in the pressure of the atmosphere of any consequence takes place in the short space of time necessary for this purpose, and equal bulks of air and the gas whose, specific gravity is to be found out having been weighed in this manner, precisely under the same circumstances with respect to pressure, no corrections on this account are required.* 362. Many operations upon the gases may be performed in appa- Tub ratus formed partly or altogether of glass tube, for a particular de-ratus. P scription of which, the precautions to be attended to in taking specific gravities, and many other details, the student is referred to Faraday’s Chemical Manipulation. 363. The experiments of Davy and Faraday have shown that many substances, which had previously been known, when uncom- bined, only as gases, may be obtained in a liquid state by generating them under pressure. When thus compressed, a very moderate heat is sufficient to make Liquefac- them boil ; and on the removal of pressure they re-assume the elas- tion of tic form, most of them with such violence as to cause a report like gases- an explosion, and others with the appearance of brisk ebullition. An intense degree of cold is produced at the same time, in conse- quence of caloric becoming latent. The process for condensing the gases consists in exposing them Process, to the pressure of their own atmospheres.! The materials for producing them are put into a strong glass tube about eight inches long, which is afterwards sealed hermetically ; then, being softened in the flame of a lamp,\ at about five inches from the closed end, it is to be bent, not sharply, but obtusely and roundly, until the two limbs make an angle of about 130° or 140°. The gas is generated, if necessary, by the application of heat, * Reid’s Elements of Pr act. Chem. t See Carbonic Acid. ]18 Cha p. III. Pressures required. Discovery. How ob* la ined. Theory. Oxygen. and when the pressure becomes sufficiently great, the liquid forms and collects in the free end of the tube, which is kept cool to facilitate the condensation.* The pressure required to liquefy the gases is very variable, as will appear from the following table of results obtained by Faraday : Sulphurous acid gas . Sulphuretted hydrogen gas Carbonic acid “ Chlorine “ Nitrous oxide “ Cyanogen “ Arnmoniacal “ Muriatic acid w Atmospheres. 2 at 45° F 17 “ 50° . 36 “ 32° 4 « 60° . 50 “ 45° 3,6 “ 45° 6,5 “ 50° . 40 “ 50° CHAPTER III. INORGANIC CHEMISTRY. Section I. Oxygen. Sip lib. Sp. Gr. Equip. O 1.1024 air =1 By Vol. 50. 1C. 00 Hyd.=t “ Wgt. 8. 364. Oxygen has never been obtained in a state of complete sepa- ration. In the state of gas, it was discovered in 1774 by Priestley, who gave it the name of dephlogisticated air. It was called Empy- real air , by Scheele, and Vital air by Condorcet. 365. It may be obtained from various substances. 1. From the black or peroxide of manganese, heated to redness in a gun-barrel, or in an iron retort (Fig. 89) ; or from the same oxide, heated by a lamp in a retort, (Fig. 96, c,) or gas bottle, (Fig. 87,) with half its weight of strong sulpuric acid. One pound of manganese is capable of furnishing from 40 to 50 wine pints of gas. But as man- ganese is often contaminated with a small proportion of carbonate of lime, it is advisable, before using it, to wash it with hydrochloric acid diluted with 15 or 20 parts of water; then with distilled water; and afterwards to dry it at a moderate heat. To understand the theory of these processes, it is necessary to bear in mind the composition of the three following oxides of manganese : Manganese. Oxygen. Protoxide . 27.7 or 1 equiv. -}- 6 . =35 7 Sesquioxide 27 7 . . -f 12 . =39.7 Peroxide 27.7 . . — 16 . =43 7 On applying a red heat to the last, it parts with half an equivalent of oxygen, and is converted into the sesquioxide. Every 43.7 grains of the peroxide will, therefore, lose, if quite pure, 4 grains of oxygen, or nearly 12 cubic inches ; and one ounce will yield about 12S cubic inches of gas. The action of sulphuric acid is different. The per- oxide loses a whole equivalent of oxygen, and is converted into prot- oxide, which unites with the acid, forming a sulphate of the protoxide of manganese. Every 43.7 grains of peroxide must consequently yield 8 grains of oxygen and 35.7 of protoxide, which by uniting with one equivalent (40.1) of the acid, forms 75.8 of the sulphate. The first of these processes is the most convenient in practice. ♦These experiments are dangerous and should not be undertaken without attending to the directions given by Faraday tn Sect. xvi. Chem. Manip. 119 Properties and Effects. 2. From various other oxides, as will be hereafter mentioned. 3. From nitrate of potassa (common saltpetre) made red-hot in a gun-barrel, or in a coated earthen retort. 4. From the salt called chlorate of potassa. For this purpose, the salt should be put into a retort of green glass, or of white glass made without lead, and be heated nearly to redness. It first becomes liquid, though quite free from water, and then, on increase of heat, is wholly resolved into pure oxygen gas, which escapes with effervescence, and into a white compound, called chloride of potassium, which is left in the retort. The composition of the chloric acid and potassa which constitute the salt, is stated below ; — Chlorine . 35.42 or 1 eq. Potassium . 39.15 or 1 eq. Oxygen . 40 or 5 eq. Oxygen . 8 or 1 eq. Chloric acid 75.42 or 1 eq. Potassa . 47.15 or 1 eq. Hence the oxygen which passes over from the retort, is derived partly from the potassa and partly from the chloric acid ; while chlo- rine and potassium enter into combination. Thus are 122.57 grains of the chlorate resolved into 74.57 grains of chloride of potassium, and 48 grains, or about 161 cubic inches, of pure oxygen. 366. Oxygen gas is insipid, colourless, and inodorous. It is so Properties sparingly absorbed by water, that when agitated in contact with it, ° x yo ei1 no perceptible diminution takes place. 100 cubical inches at mean s temperature and pressure, weigh 34.1872 grains. It refracts the Effect of rays of light less than any other gas. When suddenly and strongly s°<^ res ’ compressed, heat is evolved, and a luminous appearance observed from the combustion of the oil with which the compressing tube is lubricated.* 367. It is a powerful supporter of respiration and combustion. Supports No animal can live in an atmosphere which does not contain a cer- res P iratlon tain portion of uncombined oxygen ; for an animal soon dies if put Effect on into a portion of air from which the oxygen has been previously re- animals, moved by a burning body. It may, therefore, be anticipated that oxygen is consumed during respiration. Respiration and combus- tion have the same effect. An animal cannot live in an atmosphere which is unable to support combustion ; nor, in general, can a can- dle burn in air which contains too little oxygen for respiration. It is singular that, though oxygen is necessary to respiration, in a state of purity it is deleterious. When an animal is supplied with an atmosphere of pure oxygen gas, no inconvenience is at first per- ceived ; but after the interval of an hour or more, the circulation and respiration become very rapid, and the system in general is highly excited. Symptoms of debility subsequently ensue, followed by insensibility: and death occurs in six, ten, or twelve hours. On examination after death, the blood is found highly florid in every part of the body, and the heart acts strongly even after the breathing has ceased. t The absorption of oxygen gas by the blood, and the change of colour that results, may be shown by passing up a little dark venous blood into a jar filled with the gas, or by agitating a portion in a phial filled with it. *Thenard. + Broughton. 120 Oxygen. chap, hi. All combustible bodies burn in oxygen gas with greatly increased splendour. A lighted wax taper, fixed to an iron wire, and plunged into a ves- sel of this gas, burns with great brilliancy. (Fig. 116.) If the taper be blown out, and let down into a vessel of the gas while the snuff re- mains red hot, it instantly rekindles, with a slight explosion. A red-hot bit of charcoal, fastened to a copper wire, and immersed in the gas throws out beautiful sparks. The light of phosphorus burning in this gas, is exceed- ingly bright. Supports combus- tion. Exp. Combus- tion of phospho- rus, Exp. Let the phosphorus be placed in a small hemispherical tin cup, which may bo raised by means of a wire stand, (Fig. 117,) two or three inches above the sur- face of water contained in a broad shallow dish. Fill a bell- shaped receiver, having an open neck at the top, to which a stopper is ground, with oxygen gas ; and as it stands inverted in water, press a circular piece of pasteboard, rather exceeding the jar in diameter, over its mouth. Cover the phosphorus instantly with the jar of oxygen gas, retaining the pasteboard in its place, till the jar is immediately over the cup. When this has been skilfully managed, a very small portion only of ^ the gas will escape. The stopper may now be removed, when the water will rise to the same level within as without the jar, and the phospho- rus may be kindled by a heated copper wire.* Substitoto for the phosphorus a small ball formed of turnings of zinc, in which about a grain of phosphorus is to be enclosed. Set fire to the phosphorus as be- “ul white fore. 'I’he zinc will be inflamed, and will burn with a beautiful white light. A Of zinc and similar experiment may be made with metallic arsenic, which may be moistened other met- with spirit of turpentine. The filings of various metals may also be inflamed, by als, placing them in a small cavity, formed in a piece of charcoal, igniting the char- coal, and blowing, on the part containing the metal, a stream of oxygon gas from Of Iron. The combustion of iron or steel w ire in this gas is remarkably brilliant. The wire best suited for this experiment is the fine guitar wire ; it should he doubled several times so as to form a bundle, which is easily done by passing it round two nails fixed in the table about eighteen inches apart, and securing the bunch by loosely winding the last turn round it. Before removing it from the nails, the flame of a spirit lamp should be slowly passed along the wire so as Fig. 118- to give a low red heat to every inch, and thus diminish its elasticity. When cool, the bunch is to be coiled round a lube or rod of about ijths of an inch in diameter. Attach one end to a metallic plate, t and to the other fix a small piece of cotton dipped in melted sulphur. A large jar (Fig. 118) having been filled with the gas, remove the stopple, light the sulphur, and introduce the coil.t The iron will burn with a most brilliant light, throwing out a number of sparks, which fall to the bottom ; if a bottle is used the bottom is liable to be broken, this accident, however, may frequently be prevented by pouring sand into the bottle, so as to lie about half an inch deep on the bottom. By directing the flame of a spirit lamp, by means of a current of oxygen gas, upon a small ball of lime, the most intense light is produced. An apparatus lor this purpose has been described by Drummond in Edin Jour, of Sci. v. 31 9. § A little of Homberg's pyrophorus, a substance to be hereafter described, when poured into a bottle full of this gas, immediately flashes like inflamed gun- powder. 11.1.208. 363. During every combustion in oxygen gas it suffers a consi- bustion COm " ^ era ^ e diminution.il The fact may be shown by the combustion of ♦For Hare's apparatus see his Compendium, p. 103. + The wire should never he suspended from a cork, as it may take fire. t Watch springs, partially deprived of their elasticity in the same way, may be used. § The light and heat of an Argatid lamp supplied with oxygen, as contrived by Dr C. T. Jackson, are intense. See plate second. || To exhibit this, experimentally, in a manner perfectly free from all sources of er- ror, would require such an apparatus as few beside adepts in chemistry are likely to possess. The apparatus required for this purpose, is described in the 6th chapter of Lavoisier’s Elements. Exp. Oxygen di minisbes Theories of Combustion . phosphorus, in the manner which has been already described. The first effect of the combustion will be a depression of water within the jar ; but when the combustion has ceased, and the vessel has cooled, a considerable absorption vvill be found to have ensued.* In this process a white dense vapour is produced, which condenses on the inner surface of the jar in solid flakes. This substance has strongly acid properties ; and, being formed by the union of oxygen with phosphorus, is termed the phosphoric acid. In the instance of charcoal, though that substance undergoes combustion, no absorption ensues ; because, as will appear in the sequel, the product is a gas, occupying exactly the same bulk as the oxygen gas submitted to ex- periment. 369. The phenomena of combustion were referred by Stahl and his associates, to a peculiar principle which they called phlogiston ; it was supposed to exist in all combustibles, and combustion was said to depend upon its separation ; but this explanation was absurdly at variance with the well known fact, that bodies during combustion increase in weight. 370. All bodies, by combustion in oxygen gas, acquire an addi- tion to their weight ; and the increase is in proportion to the quantity of gas absorbed, viz. about one third of a grain for every cubic inch of gas. — To prove this by experiment, requires a complicated appa- ratus. But sufficient evidence of this fact may be obtained by the following very simple experiment. Fill the bowl of a common tobacco pipe, with iron wire coiled spirally, and of known weight : let the end of the pipe be slipped into a brass tube, which is screwed to a bladder filled with oxygen gas : heat the bowl of the pipe, and its contents, to redness in the fire, and then force through it a stream of oxygen gas from the bladder. The iron wire will burn ; will be rapidly oxidized ; and will be found, when weighed, to be considerably heavier than before. When com- pletely oxidized in this mode, 100 parts of iron wire gain an addition of about 30. 371. After the discovery of oxygen gas, it was adopted by Lavoi- sier as the universal supporter of combustion. The basis of the gas was supposed to unite to the combustible, and the heat and light which it before contained in the gaseous state, were said to be evolved in the form of flame. But in this case, several requisites are not fulfilled ; the light depends upon the combustible, and not upon the quantity of oxygen consumed ; and there are very numerous in- stances of combustion, in which oxygen, instead of being solidified, becomes gaseous during the operation ; and, lastly, in others, no oxygen whatever is present. Combustion, therefore, cannot be regarded as dependent upon any peculiar principle or form of matter. Berzelius, in adopting the electro-chemical theory, regards the heat of combination as an electrical phenomenon, believing it to arise from the oppositely electrical substances neutralizing one ano- ther, in the same manner as the electric equilibrium is restored during the discharge of a Leyden jar. There are, indeed, strong grounds for believing that electrical action is an essential part of every che- mical change, and it is probable that the heat developed during the latter may be due to the former ; but this part of science is as yet too imperfect for indicating the precise mode by which the effect is * Thq^e persons who are possessed of a mercurial apparatus may repeat this expe- riment in a less exceptionable manner, as described in Henry’s Chemistry, l. 210. 16 121 Sect. I. Stahl’s idea of combus- tion. Bodies in- crease in weight. iXp. Theory of Lavoisier, Insuffi- cient. Berzelius’ view. 122 Hydrogen , Chap in. produced. The heat emitted during combustion varies with the na- ture of the material.* T. 157 . Products. 372. The substances, capable of uniting with oxygen, afford acids and oxides . 373. The name oxygen, from acid , and yew&w I generate , was proposed by Lavoisier, from the supposition that it was the sole Oxygen not cause °f acidity. But oxygen is not essential to the acidity of a essential to compound, for some bodies are rendered acid by union with chlorine, acidity. others by hydrogen ; and the theory of Lavoisier which consid- ered oxygen as the essential principle of acidity, can no longer be received as correct. In many instances, a combustible body, which affords an acid when united with a certain quantity of oxygen, gives an oxide when combined with a less quantity ; and the acid may be brought back to the state of an oxide by separating part of its oxygen. Some of the metals also, combined with a small proportion of oxygen, give ox- ides capable of uniting with acids and of composing salts , and again united with more oxygen yield an acid which is susceptible, with oxides, of forming saline compounds. Action of 374. When acids, containing much oxygen, are poured on sub- faining°ox- stances that have a great affinity for this element, as metals and ygen. some inflammable bodies, oxygen is rapidly taken from them. The combination with the liberated oxygen is, in some cases, so rapid, as to give rise to combustion ; as when nitric acid is poured upon spirits of turpentine, or phosphorus. See nitric acid. Oxidation'' 375. Mercury is speedily oxidized by the same acid, and also if of mercury. b 0 i} e( i i n sulphuric acid. In both cases, however, the oxide formed by the decomposition of one portion of the acid unites with another portion that has not been decomposed, and the resulting products are a nitrate and a sulphate of the oxide of mercury. Deoiida- 376. When oxygen is to be removed from any substance which tion. does not part with it on exposure to heat, the substance is often mixed with charcoal, which, at a high temperature, has a much greater affinity for oxygen than most other substances. It is in this manner that most of the common metallic oxides are deoxidized, and their bases procured in a metallic form ; the carbon combining with the oxygen and passing off in the form of carbonic acid gas. F. Section II. Hydrogen. Symb. Sp. Gr. Chem. Equiv. H. 0.0689 air =1 By Vol. 100 1. 00 Hyd.=l “ Wgt. 1 Discovery , 377 This gas was formerly termed inflammable air , from its combustibility, and phlogiston , from the supposition that it was the matter of heat ; but the name hydrogen , from vSmq water, and yevvetv to generate, has now become general. Its nature and leading properties were first pointed out in the year 1766 by C-aven- dish.t The most simple form in which it has hitherto been obtained, is in that of a gas. Of its nature we know but little, but as it has not yet * S«e Dalton’s Chem. Philos. 11. 309. t Phil. Trans, lvi. 144. Methods of Procuring. 123 been resolved into any more simple form, it is still arranged among Sect.n. elementary bodies, 378. To procure hydrogen gas, let sulphuric acid, previously di- Method of luted with five or six times its weight of water, be poured on iron JJ^Jogen filings, or on small iron nails ; or (what is still better) pour sulphuric gas. acid diluted with eight parts of water, on zinc, granulated by pour- ing it melted into cold water, and contained in a gas bottle, Figs. 86, 87, or small retort. An effervescence will ensue, and the escaping gas may be collected in the usual manner over water. 379. An ingenious apparatus for obtaining it instantaneously in a Inflamma- laboratory, was contrived by Gay-Lussac. ble air lamp. It consists of a three necked glass bottle, (Fig. 119,) one of whose openings has a stopper, from which is suspended a small cylinder of zinc a. To the opposite aperture is fixed a bent brass tube furnished with a stop-cock, on which may be screwed either a small jet for burning the gas, or a tube to conduct it wherever it may be required. The upper vessel is of glass, and ground to fit the middle neck, its pipe reaching within a small distance of the bottom of the bottle. To use the apparatus, the lower vessel is filled with sulphuric acid properly diluted, aud the zinc cylinder is then introduced, the stopper being closed to which it is affixed, and the cover of the upper vessel removed. The gas which is generated drives the diluted acid into the upper vessel, and the further produc- tion of it ceases, when the zinc is completely uncovered. We have then the bottle filled with gas ; and can at any time expel it by opening the cock, and allowing the atmosphere to press on the surface of the liquid in the globular vessel. A more convenient modification of this apparatus has been contrived by Hare Self-remi- (Fig. 120.) It consists of two vessels, one withinthe Fig. 120 other, the inner one having no bottom is furnished with a stop-cock at the upper part, A piece of zinc is suspended in the inner vessel; acid and water, previ- ously cooled, being poured into the space between the two vessels, (the stop-cock being open,) will expel the air and rise in the inner vessel ; coming in com tact with the zinc, hydrogen will be given off. The gas should be allowed to escape until all the air has been expelled from the inner vessel. The stop-cock being now closed, the hydrogen will accumulate in the inner vessel, press upon the acid and water, and force it into the space between the two vessels. This will go on until the zinc is no longer in contact with the liquid. The inner vessel will be a reservoir of hydrogen, from which any desired quantity can be drawn on opening the stop-cock. A straight pipe, or flexible tube, being screwed upon the stop-cock, the gas may be conveyed into any other piece of apparatus. As the gas passes out, the acid and water rise in the inner vessel, and again come in contact with the zinc, and more hydrogen is obtained. 380. Hydrogen gas, thus obtained, is not, however, to be consi- Impure as dered as absolutely pure.^ commonly J 1 obtained. * The gas may be partially purified by passing it through a solution of pure potassa, or obtained purer by using distilled zinc. In order to purify the zinc. Thomson ex- poses it to a white heat in a stone ware retort, luted to a receiver nearly filled with water. At this temperature, the zinc is sublimed and freed from all its impurities, except a trace of cadmium too minute to occasion any sensible error. The zinc thus distilled over is melted in a crucible and poured upon the surface of a clean smooth sandstone, upon which it forms a thin sheet which can be easily broken into small pieces. T. First Prin. 1. 52. 124 Hydrogen. Chap, in. 381. Hydrogen is an aeriform fluid, but very slightly absorbable Properties, by water. It has no taste, and may be respired for a short time, though it is fatal to small animals. As usually prepared, it has a disagreeable odour, but when pure has none. # It may be breathed a few times with safety, and if the experimenter speak immtdiutely on removing his lips from the mouth-piece of the bag or bladder, a remarkable change in the voice is perceived. Weight and specific gravity. 382. It is the lightest body known, and is therefore conveniently assumed as unity in speaking of the specific gravity of gases, as well as in referring to the proportions in which bodies combine. 100 cu- bic inches weigh 2.1367 grains. It is 16 times lighter than oxygen. 383. The levity of hydrogen may be proved by experiment. Exp. Let a jar filled with this ga6 stand, for a few seconds, with its open mouth up- wards. On letting down a candle, the gas will be found to have escaped. E X p Place another jar of the gas inverted, or with its mouth downwards. The gas will now be found to remain a short time in the jar, being prevented from escap- ing upwards by the bottom and sides of the vessel. Exp. Exp. Inflamma- ble. 354. Hydrogen, in consequence ployed for filling air-balloons. Fill with hydrogen gas, a bladder fur- nished with a stop-cock, (Fig J21 ;) and adapt to this a common tobacco pipe. Dip the bowl of the pipe into a lather of soap, and, turning the cock, blow up the lather into bubbles ; instead of falling to the ground like those commonly blown by children, they will rise rapidly into the air. The experiment may be varied by filling the bladder with a mixture of two parts of hydrogen gas and one of oxygen gas. Bubbles, blown with this mixture, take firo on the approach of a lighted candle, and detonate with a loud report. It is proper, however, not to 6et them on fire till they are completely detached from the bowd of the pipe. 355. Hydrogen is inflammable, and when pure burns with a lam- bent blue flame at the surface in contact with the air. of its extreme lightness, is em- Fig. 121. Exp. Exp. Exp. Exp. Fill a small jar with the gas, and, holding it with the mouth downwards, bring the gas into contact with the flame of a candle. Fill with this gas a bladder which is furnished with a stop-cock, and with a small pipe, of diameter less than that of a common tobacco pipe. Press the air out through the pipe, and on presenting a lighted candle, the stream will take fire, and continue to burn with a pale and leeble flame. 3S6. Hydrogen gas does not support combustion. Remove ajar, filled with the gas, from the shelf of the pneumatic trough, upon a plate ; bring it near a lighted candle, and expedi- tiously removing the plate, cover the candle ; it will be extinguished. At first there will be a slight explosion, from the gas at the mouth of the jar mixing with atmospheric air. Suspend a long tube or jar (Fig. 122), with its mouth downward, containing hydrogen gas ; remove the stopple and introduce a light- ed taper attached to a long wire. The flame of the taper may be extinguished and relighted many times, as the taper is passed up into the eas, or brought down slowly through the portion burning at the mouth of the jar Care should obviously be taken, that w ater does not remain about the mouth of the jar. * Herzelius has shown that the gas generated from iron filings and di- lute sulphuric acid, loses its odour by being passed through pure alcohol, and when the alcohol is diluted with water and is kept a few days, an odorous volatile oil is separated, which caused the smell of the gas. Fig. 122. Detonation with Oxygen. 125 Persons who are provided with the jars represented Fig. 94, a , may screw to sec. II. the cook a brass pipe with a small aperture. On pressing the jar, filled with hy- ~ ~ drogen gas, into the water, and opening the cock, the gas will be forced out in a^ x P ? stream, which may be set on fire. On this principle are founded the artificial fireworks without smell or smoke. They consist of pipes, having variously sized apertures, some of which have a rotary motion. Or the gas may be condensed, by means of a syringe, into a strong copper globe furnished with a stop-cock, to which, on removing the syringe, a brass tube can be screwed, and a variety of jets and revolving burners be attached. 387. It has been found by Doebereiner, that when a stream of hy- Doeberein- drogen is directed upon spongy platinum, the platinum soon becomes er ’ s red hot, and the hydrogen is inflamed.^ gen a This discovery has led to various modifications of the in- flammable air lamp. A very convenient and ornamen- tal form of which is represented in Fig. 123. It is com- posed of two glass vessels fitted to each other by grinding, as m the apparatus of Gay Lussac. The tube a, of the upper vessel, is encompassed by a cylinder of zipc, which is sup- ported by a ring of cork on the lower part of the tube- The platinum sponge is contained in a small brass box A, attached to a brass wire passing through a collar of leather and which can be placed at any distance from the jet c When a light is required the cock d is turned, and the pressure of the acid liquor in the upper vessel expels the hydrogen, as in the ap- paratus already described.! 388. If mixed with common air, hydrogen burns rapidly with de- Detonates tonation. with air. Fig 123. Into a strong phial, capable of holding about 6 ounces of water introduce one part of hydrogen and three parts of common air. On applying a lighted candle or a red hot wire, the mixture will explode. This experiment may be performed by means of an apparatus called the in- Inflamma- flammable air pistol. (Fig. 124.) This instrument consists of pjg. 124 . ble air pis- a cylinder of brass, about three fourths of an inch in diameter, CL ^ tol. and six inches long, in the form of a small cannon or pistol- barrel, properly mounted, and having a wire a, passing through a tube of ivory, 6, and not quite touching the interior of the cylinder, at the part usually occupied by the touch- hole; an electric spark communicated to this wire inflames the mixture of hydro- gen and atmospheric air in its interior. It may be charged, by holding it for a moment over the open jet of the instrument (Fig. 119), always taking care that there is a due admixture of atmospheric air, otherwise the electric spark will not inflame it. 389. If the experiment be repeated with oxygen gas instead of Detonates atmospherical air; changing the proportions, and mixing only one with oxy- part of the oxygen gas with two of hydrogen, the report will be con- gen » siderably louder. The bottle should be a strong one, and should be wrapped round with cloth, to prevent accident. It may be exploded by igniting a fine platinum wire within a strong glass vessel (Fig. 125, b ); the wire may be an inch in length, and connected with two stout copper wires a a passing in at the sides through a cork : the copper wires should be attached to the vices of a small calorimotor c. The acid liquor being contained in a glass or other suitable vessel d, is to be raised up suffi- ciently to have the plates immersed. See Gal- vanism. * A convenient tinder may be prepared from a piece of cotton cloth, dipped in the solution from which the sponge is obtained, (see Platinum ,) and then inflamed ; it ignites as rea- dily as the platinum sponge ; the sponge and tinder should be perfectly dry. W. t See the subject of Eudiometry. Fig. 125. 126 Cha p. III. Exp. And by means of the electric spark. Explosion by electrici- ty, flame, &c. Hydrogen, A bladder, filled with hydrogen and oxygen, may be exploded with safety by suspending it from the ceiling, and piercing it with a sharp wire at the end of a long stick, with a little tow about it, dipped in spirits of turpentine and burning. 390. The same experiment may be made over water, by means of the electric spark. Procure a strong tube, about three quarters of an inch in diame- ter, and 12 inches long, closed at one end. (Fig. 126 ) About a quarter or half an inch from the sealed end, let two small holes be drilled, opposite to each other, ,and into each of these let a brass conductor be cemented, so that the two points may be dis- tant from each other, within the tube, about one eighth of an inch. An apparatus, serving the same purpose, and much more easily constructed, may be formed by hermetically sealing a piece of brass wire, or still better, platinum wire, into the end of a glass tube. With this conductor, an interrupted circuit may be formed by introducing into the tube a longer wire, one end of which ter- minates one tenth of an inch from the upper one, while the other extends beyond the aperture of the tube. (See Fig. 127, c.) Into Fig. 126. this tube, standing over water, pass about half a mixture of hydrogen and oxygen gases ; in the proportion of two measures of the former to one of the latter. Hold the tube firmly, and pass an electric spark through the mixed gases. For re- lieving the shock, which is sometimes considera- ble on firing, an ingenious contrivance of Davy may be employed.* The first effect of the com- bustion is a sudden and considerable enlargement of volume, which, from some experiments of Davy probably amounts to 15 times the original bulk of the mixture. After this the gases, if per- fectly pure and in the proper proportion, will be found to have disappeared entirely. H. 1. 235. cubic inch of a 391. The power of flame and electricity, in causing a mixture of hydrogen with air or oxygen gas to explode, is limited; flame occa- sions a very feeble explosion when the hydrogen is mixed with nine times its bulk of air; and a mixture of four measures of hydrogen with one of air does not explode at all. An explosive mixture, form- ed of two measures of hydrogen and one of oxygen gas, explodes from all the causes above enumerated. Biot found that sudden and violent compression likewise causes an explosion, apparently from the heat emitted during the operation ; for an equal degree of con- densation, slowly produced, has not the same effect. The electric spark ceases to cause detonation, when the explosive mixture is di- luted with twelve times its volume of air, fourteen of oxygen, or nine of hydrogen ; or when it is expanded to sixteen times its bulk by di- minished pressure. Spongy platinum acts just as rapidly as flame or the electric spark in producing explosion, provided the gases are quite pure and mixed in the exact ratio of two to one.t Fara- day finds that platinum foil, if perfectly clean, produces gradual though rather rapid combination of the gases, often followed by ex- plosion.! * Phil. Mag. xxxi. 3. t For a variety of facts respecting the causes which prevent the action of flame, elec- tricity, and plaiinum in producing detonation, the reader may consult the essay of Grotthus in the Ann. de Chimie vol. lxxxii. ; Davy’s work on Flame ; Henry’s essay in the Phil. Trans, for 1824; and a paper by Turner in the Edin. Philos. Jour, for the same year. t Phil. Trans. 1834. 127 Hare’s Compound Blow-pipe. 392. When the action of heat, the electric spark, and spongy plati- sect, ii. nurn no longer causes explosion, a silent and gradual combination be-siow com- tween the gases may still be occasioned by them. Davy observed that bination, oxygen and hydrogen gases unite slowly with one another, when they are exposed to a temperature above the boiling point of mercury, and below that at which glass begins to appear luminous in the dark. An explosive mixture, diluted with air to too great a degree to ex- plode by electricity, is made to unite silently by a succession of electric sparks. Spongy platinum causes them to unite slowly though mixed with one hundred times their bulk of oxygen gas. T.160. 393. A current of hydrogen may be inflamed when issuing from a Musical small aperture, and if a tube of eighteen or twenty inches in length be held over the flame, a peculiar musical tone is produced. This combustion effect is not peculiar to hydrogen, but is produced by a variety of of hydro- other flames, and is referable to the succession of explosions pro- gen ' duced by the combustion of the gas in the tube. 394. The tendency which gaseous fluids have to become com- Gases have pletely mixed under all circumstances, and as it were to penetrate tendency to each other, is well illustrated where hydrogen is employed. Thus, mix to- if two small phials, the one containing oxygen and the other hydro- S elher - gen, be connected perpendicularly by a long glass tube, of small bore, it will be found, that although the hydrogen be uppermost, and much lighter than the oxygen* it will, in the course of a few hours, have perfectly mixed with the oxygen, and the gases will be found in equal proportions in both phials. Dalton has shown that gases, un- like other fluids, do not remain upon each other without admixture.^ 395. The flame of hydrogen is occasionally employed for exciting Hare’s intense heat ; and it has been found when mixed with oxygen and blow-pipe, burned as the mixture issues from a small jet, to excite a tempera- ture nearly equal to that of the arc of flame in the Voltaic circuit. A blow-pipe upon this construction was first made by Hare : It consists of a cylindrical vessel of tin, (Fig. 128, a ,) or what is preferable copper, divided in the middle by two partitions, so as to form two distinct reservoirs, one for oxygen and the other for hydrogen. Into the lower part of each reservoir, a tube b, is inserted somewhat obliquely, as in the common gas-holder. Above the reservoirs is a conical tin funnel c, furnished with a stop- cock and connected with a tube which immediately be- low divides into two, one passing to each reservoir. A tube passes out from each reservoir, meeting in a cone d (a section of which is represented at e). The gases are thus mingled and are then made to issue through a capillary tube drilled through a wire of silver and inserted into the cone. t The lower tubes being closed, the apparatus is filled with water, and the gases introduc- ed, as in the usual method of filling a gas-holder. The re- Fig. 128. * Manchester Memoirs, vol. i. New Series. t The arrangement, consisting of two separate reservoirs for the gases, is perfectly safe and convenient : the jet may be formed of two concentric cones. In 1824 I devised a jet, which was made for me by Newman of London, to whom I sent a drawing and de- scription. It is the only jet I have been in the habit of using since that time, and it has proved, as anticipated, perfectly safe. It consists of two concentric tubes of brass (Fig. 129), each ter- minated by platinum, a space being left between the two. By one stop-cock, opening into the space, and another into the cavity of the inner tube, the two gases RwJLj^I Fig. 129. 128 Chap. III. Brooke’s blow-pipe. Hemming’! safety tube, Burns un- der water. Hydrogen * * servoirs being filled, the lower tubes are closed, and water poured into the funnel 'on opening the stop-cocks the gases are propelled through the jet. When sub- stances are to be exposed to the action of this instrument, the stop-cock connect- ed with the reservoir of hydrogen should be first opened and the gas may be inflamed ; the other stop-cock is then gradually opened, and the oxygen mixing with the hydrogen, an intensely high temperature is obtained. With this instrument Hare and Silliman first effected the fusion of some of the most refractory substances in nature.* 396. The blow-pipe invented by Brooke depends for its action on the elasticity of compressed air, and consists of a strong copper box (Fig. 130), into which several atmospheres are crowded by means of a condensing sy- ringe. Various expedients have been adopted to render this a safe substitute for the oxy-hydrogen blow-pipe of Hare. It may be done by interposing between the flame and the main reservoir of gases, a cylinder containing a little water or oil, through which by means of a valve at the bottom, the gases are allowed to pass. The safety of the instrument is increased by the safety tube, lately proposed by Hem- ming. It consists of a brass cylinder, about six inches long, and three fourths of an inch wide, filled with very fine brass wire, in length equal to that of the tube. A pointed rod of metal, one eighth of an inch thick, is then forcibly inserted through the centre of the bundle of wires in the tube, so as to wedge them tightly together. The interstices between the wires thus constitute very fine metallic tubes, the conducting power of which is so great as entirely to intercept the passage of flamed J 397. The flame produced by the oxy-hydrogen blow-pipe continues to burn when submersed in, and in actual contact with, water, with the same splendour as in the atmosphere ; the only difference being that under water its figure is conglobated, whereas in air it assumes that of a long, slender, conical pencil. Care is required to introduce the flame slowly into the water. A piece of pine wood or cork when brought within the action of the submerged flame gives out a bril- liant light. are conveyed along the jet without mingling until they arrive at the orifice where they are burned. Either gas may he made to surround the other at pleasure merely by changing the connexion with’the reservoirs In the Phil. Mag. ii. third series, Daniell has described a similar jet. I was not aware until these pages were passing through the press that a jet of similar construction had been early employed by Hare. W. * Amer. Jour, of Sci. vol. ii. p. 281 , &c. t Phil. Mag. third series, i. 82 . t In some recent experiments with mixtures of the gases, contained in bladders at- tached to the extremities of this tube. I have found it impossible to explode both by firing one, and. have been led to attach it to a large globe of copper in which the gases are condensed, and with a simple jet at the other extremity, use the apparatus with perfect safety. W. Fig. 130. 129 Water -—Theory. Hydrogen and Oxygen. Protoxide of Hydrogen — Water. Sect. 11 . Composition* Symb. H+O or H, By Wght . By Vol. sometimes acj. Hyd. Oxy- Equiv. Hyd. Oxy. from aqua. 1 or 1 eq. -f- 8 or 1 eq. =9 100 50 398. Hydrogen and Oxygen , Water. — When two volumes of hy- drogen gas are mixed with one volume of oxygen gas, and the mix- Union with ture inflamed in a proper apparatus by the electric spark, the gases oxygen gas, totally disappear, and the interior of the vessel is covered with drops water* CeS of pure water, equal in weight to that of the gases consumed. 399* If pure water be exposed to the action of Voltaic electricity, it is resolved into two volumes of hydrogen, and one volume of oxy- Decomposi- gen, so that water is thus proved by synthesis and analysis, to con- tion of wa- sist of two volumes of hydrogen combined with one volume of by elec - J ° tricity, oxygen. 400. Cavendish demonstrated the composition of water by burning oxygen and hydrogen gases in a dry glass vessel ; when a quantity B com _ of pure water was generated, exactly equal in weight to that of the bustion. gases which had disappeared. This experiment, which is the syn- thetic proof of the composition of water, was afterwards made on a much larger scale in Paris by Vauquelin, Fourcroy, and Seguin. Lavoisier first demonstrated its nature analytically. The composition of water by weight was determined with great care by Berzelius and Dulong ; and their result is regarded as a nearer approximation to the truth than that of any of their predeces- tiorTIJy* 1 " sors. They state, as a mean of three careful experiments,^ that weight. 100 parts of pure water consist of 11.1 of hydrogen and S8.9 oxy- gen, which is the ratio of 1 to 8.009, very nearly that of 1 to 8 above stated. 40 1. The processes for procuring hydrogen gas will now be intelli- gible. The first is the method by which Lavoisier made the analysis of water. It is founded on the fact, that iron at a red heat decomposes fofmaUorf water, the oxygen of that liquid uniting with the metal, and the hy- of hydro- drogen gas being set free. The hydrogen which is evolved when £ en - zinc or iron is put into dilute sulphuric acid must be derived, from the same source. The product of the operation, besides hydrogen, is sulphate of the protoxide of iron, if iron is used, or of the oxide of zinc, when zinc is employed. The knowledge of the combining pro-’ portions of these substances will give the exact quantity of each pro- duct. These numbers are— Water (8 oxy q_ 1 hyd. ..... 9 Sulphuric acid ...... 40.1 Iron 28 Protoxide of iron (28 iron + 8 oxygen) . 36 Sulphate of the protoxide of iron (40.1+36) . 76.1 Hence for every 9 grains of water which are decomposed, 1 grain of hydrogen will be set free ; 8 grains of oxygen will unite with 28 grains of iron, forming 36 of the protoxide of iron ; and the 36 grains of protoxide will combine with 40.1 grains of sulphuric acid, yielding 76.1 of sulphate of the protoxide of iron. A similar calculation may be employed when zinc is used, merely by substituting the equiva- * Ann. de Chim. et de Phys. vol. xv . 17 130 Hydrogen and Oxygen. Chap. III. Action of zinc, &c. Exp. Burns with OX^ KD gas and forms water, The mix* ture ex- plodes. Exp. Exp. Water a compound of the bases of the gases. lent of zinc (32.3) for that of iron. According to Cavendish, an ounce of zinc yields 676 cubic inches, and an equal quantity of iron 782 cubic inches of hydrogen gas. 402. The action of dilute sulphuric acid on metallic zinc affords an instance of what was once called Disposing Affinity. Zinc decom- poses pure water at common temperatures with extreme slowness ; but as soon as sulphuric acid is added, decomposition of the water takes place rapidly, though the acid merely unites with oxide of zinc. The former explanation was, that the affinity of the acid for oxide of zinc disposed the metal to unite with oxygen, and thus enabled it to decompose water; that is, the oxide of zinc was supposed to produce an effect previous to its existence. The obscurity of this explanation arises from regarding changes as consecutive, which are in reality simultaneous. There is, as it were, but one chemical change, which consists in the combination at one and the same moment of zinc with oxygen, and of oxide of zinc with the acid : and this change occurs be- cause these two affinities, acting together, overcome the attraction of oxygen and hydrogen for one another. T. 403. The experiments illustrating the composition of water may be divided into synthetic and analytic. Among these the following may be selected. Fig. 131. Burn a current of hydrogen under the funnel a, (Fig 131), by uniting with the oxygen of the atmosphere it will produce aqueous vapour, which passing into the glass cylinder i, will condense in drops. Fig. 132 represents an apparatus for showing the production of water by burning a current of hydrogen in an at- mosphere of oxygen, a is a glass cyl- inder, which, after having been exhaust- ed upon an air-pump, is filled with pure oxygen, b is a receiver of hydrogen immersed in the vessel of water c, by which the gas is compressed, so as to be urged through the capillary opening/, when the stop-cocks d d are open, e is a platinum wire by which the gas may be infiamed by an electric spark. It burns with the production of Intense lieat, and water is soon collected in drops upon the inte- rior of the cylinder. Jf. two measures of pure hydrogen be mixed with one of pure oxy- gon, and detonated in the graduated glass tube a, (Fig. lOti), stand- ing over water, by an electric spark passed through the Dlatinum wires Fig. 133. ft ft, the gases will entirely disappear. It there be any vill Cl excess of either of the gases, the portion in excess w remain unconsumed. The same experiment may be thus varied : Fig. 133 is a very strong glass vessel, capable of holding about half a pint and furnished (besides the proper contrivance at top for taking the electric spark in it) with a brass cap and cock, by means of which it can be screwed to the transfer plate of an air pump. When exhaust- ed, it may be filled with a mixture of oxygen and hydrogen gases, in the proportion of one measure of the former to two of the latter, and an electric spark maybe passed through the mixture. After the explosion, when time has been given to the vessel to cool, a sensible quantity of moisture will have condensed on the inner surface of the vessel, and by repeating the operation frequently, a sufficient quantity of fluid may be collected to show that water is the only product. 404. The water produced in this mode, is not, however, to be considered as a compound of the two gases, but Analysis of Water. 131 only of their bases, for the light and caloric, which constitute the Sect- 11 . gases, escape, in considerable part during the combustion. Every gas, it must be remembered, has at least two ingredients ; the one, gravitating matter, which, if separated, would probably exist in a solid or liquid form ; the other, an extremely subtile fluid, termed caloric and perhaps electricity and light. The compound, water, is therefore said to be composed of hydrogen and oxygen, the bases of the gases, and not of the hydrogen and oxygen gases. 405. Water may be decomposed or resolved into its elements by Analysis of a variety of processes, the most important of which are the fol- water » lowing : Fie. 134. Fig. 134, a, is a glass retort, into which is introduced a given weight of water ; b b, a small furnace through which passes the earthen, or iron, tube c c, which terminates in the spiral pewter tube d d , immersed in water. A given weight of pure iron coiled up, is introduced into the tube c, and the whole made red-hot ; the water in a is then made to boil, and the vapour, on coming into contact with the red hot iron, is in part decomposed ; the oxygen is retained by the iron, and the hydrogen escaping through the tube f , may be collected as usual. Any un- decomposed portion of water is condensed in the worm pipe d , and drops into the vessel e. By iron, Exp. After this experiment the iron will be found to have increased in weight; and if attention be paid to the quantity of water which has collected in e, and to the weight of the hydrogen gas evolved, it will be found that the weight gained by the iron, added to that of the hy- drogen, will be equal to the weight of the water which has disap- peared. 406. The processes, by which the elementary parts of water are separated from each other, and are both obtained in an aeriform state, as a mixture of hydrogen and oxygen gases, are dependent on the agency of electricity. The first of these experiments requires for its performance the aid Byelectri- of a powerful electrical machine. This fact was the discovery of a cit yj society of Dutch chemists ; and the principal circumstance in the ex- periment, is the transmission of electrical shocks through a confined portion of water. If these shocks be sufficiently strong, bubbles of air will be formed at each explosion, and the mixed gases being ex- ploded, the water will rise again in the tube, a very small quantity of gas remaining. In this experiment we may safely infer, that the evolved hydrogen and oxygen gases arise from decomposed water. 407. The decomposition of water by galvanic electricity is a pro- By voltaic cess singularly adapted to demonstrate the fact in Fig 135- electricity, a simple and elegant manner, since it exhibits both the oxygen and hydrogen in the gaseous form. Fig 135 represents a section of an apparatus for this pur- pose. It is a glass vessel containing water, having two wires of platinum passing through its bottom : over these are invert- ed the tubes, also filled with water. The wires are connected with a moderately powerful Voltaic apparatus. Oxygen is evolved at the positive wire, and hydrogen at the negative wire, which gases rise into the tubes, and it is seen that one 132 Chap. III. By living vegetables. Exp. Impurities of water. Properties. Standard oJ specific gravity. Hydrogen and Oxygen. volume of oxygen, o, and two volumes of hydrogen, h , are the constant results. If these gases be mixed and detonated, pure water is again formed. 408. Another mode of effecting the decomposition of water, is by the action of living vegetables, either entire or by means of their leaves only. Fill a clear glass globe with water, and put into it a number of green leaves from almost any tree or plant. A sprig or two of mint will answer the purpose perfectly well. Invert the glass, or place it, with its mouth downwards, in a vessel of water. Expose the whole apparatus to the direct light of the sun, which will then fall on the leaves surrounded by water. Bubbles of air will soon begin to form on the leaves, and will increase in size, till at last they rise to the top of the vessel. This process may be carried on as long as the vegetable con- tinues healthy ; and the gas, when examined, will prove to be oxygen gas. In this experiment, the hydrogen combines with the plant to the nourishment and support of which it contributes, while the oxygen is set at liberty. H. 1 . 253 . 409. Water, in its ordinary state, such as spring and river water, is always so far contaminated with foreign substances as to be unfit for any chemical purposes, and frequently as will be more fully shown hereafter, even for domestic use. Rain water is much more pure, but it always contains a portion of carbonic acid and of the elements of atmospheric air, besides appreciable traces of vegetable or animal matter ;* to the latter it owes its property of becoming pu- trid when kept. The distinction of water into hard and soft has reference to its less or greater purity. The impurities of water are partially separated by distillation. t 410. Distilled Water , as commonly prepared, always affords mi- nute traces of foreign matter, especially when subjected to Voltaic decomposition, and can only be considered as perfectly pure when re-distilled at a low temperature in silver vessels. 411. Pure water is transparent, and without either colour, taste or smell. In consequence of the facility of obtaining it pure, it is as- sumed as a standard to which the relative weight of all other bodies may be compared, its specific gravity being called = 1,000, and hence the importance of estimating its weight with precision. At the temperature of 62° F., barom. 30, a cubic inch of distilled water weighs 252.458 grains . t * The existence of organic matter in atmospheric water, has been ascribed by Eh- renberg to the ova of a particular class of infusoria, and to them the presence of the substance termed pyrrhine. There is evidence also of the presence of salts and of acids. See Daubeny’s Report on Water, in Vol. v. of Reports of Brit. Assoc. + This process is usually conducted upon the large scale in a copper boiler, (Fig. 136,) placed ei- ther in a portable furnace, or set in brickwork, ac- cording to its dimensions, to which is annexed a head b, of the same material, or of pewter, connect- ed with a spiral tube or worm, which is immersed in the worm-tub, or refrigerator d, its lower end passing out. The water in the worm-tub must al- ways be retained of a low temperature to effect the condensation of the vapour in the spiral tube. t According to the parliamentary standard of Great Britain, the pint of water con- sists of 8750 grains of water at 62° F. barometer at 30 inches, and the cubic inch of 252,458 grains. The gallon contains 277,274 cubic inches, or 70,000 grains of distilled water ; the pint 34,65925 inches, or 8750 grains. Fig. 136. Water — absorbing power of. 133 412. At the temperature of 32° water congeals into ice, which, if Sect, n. slowly formed, produces needles crossing each other at angles of 60° i ce . and 120°. The specific gravity of ice is 0,94. Exposed to the air, ice lo$es considerably in weight by evaporation. 413. Water is susceptible of compression, as was originally shown Compressi- by Canton, and more lately by Perkins, who has estimated, in an ble. ingenious series of experiments, the rate of its compression.^ If submitted to very sudden compression, water becomes luminous, as has been shown by Desaignes.f According to Despretz the com- pression of water by a force equal to 20 atmospheres, causes the evolution of ^g-th part of a degree of heat. 414. Water enters into combination with a variety of substances, State of and is retained with various degrees of force. Sometimes it is con- t° 0 ™ bina " tained in a variable ratio, as in ordinary solution ; in other com- pounds it is present in a fixed definite proportion, as in its union with several of the acids, the alkalies, and all salts that contain water of crystallization. These combinations have been termed hydrates. Hydrates. 415. Water, which has been exposed to the atmosphere, always Water con- contains a portion of air, as may be proved by boiling it, or by ex- tains air. posing it under the exhausted receiver of the air-pump. To sepa- rate the air, the water must be boiled for about two hours. It absorbs oxygen gas in preference to atmospheric air or nitrogen, and when the air is expelled by boiling, the last portions contain more oxygen than those first given off.! 416. Every gas is absorbed by water, which has been deprived of Absorption all or the greatest part of its air by long boiling. The quantity, of gases by however, which water is capable of absorbing, varies considerably water ‘ with respect to the different gases. Those gases, of which only a small proportion is absorbed, require violent and long continued agi- tation in contact with water. H. 1 . 253 . In the common process of manufacturing soda-water a large quantity of carbonic acid gas is absorbed by the water, and an additional portion is mechanically united with it by powerful compression. § * Phil. Trans. 1820. tThenard, TraiU de Chimie s i. 432. t Humboldt and Gay-Lussac, Jour, de Phys. 1805. § The following table from Henry’s Chemistry shows the absorbability of different gases by water deprived of all its air by ebullition. 100 cubic inches of such water, at the mean temperature and pressure, absorb of Sulphuretted hydrogen Dalton and Henry. 100 cubic inches Saussure. 253 Carbonic acid - - 100 “ CC 166 Nitrous oxide - . „ 100 Ct 76 Olefiant gas ... - 12,5 “ a 15,3 Oxygen - - - 3,7 “ u - 6,5 Carbonic oxide - . . 1,56 “ a 6.2 Nitrogen - . . 1,56 “ “ - 4,1 Hydrogen - - 1,56 “ “ - 4,6 The estimate of Saus?ure is in general too high. That of Dalton and Henry for ni- trous oxide is considerably beyond the truth, according to the experiments of Davy. T. 134 Chap. Ill- Properties. Actiou of metals, Use. Discovery. How ob- tained. Nitrogen , Binoxide or Peroxide of Hydrogen. Composition. By Wght. By Vol. Chem. Symb. Hyd. Oxy. Equiv. Hyd. Oxy. pounded of oxygen and an unknown base. This base, however, is purely hypothetical ; and has never yet been exhibited in a separate state. Berzelius has proposed for it the name of nitricum. 424. Nitrogen and oxygen . — When nitrogen and oxygen gases General —— ; ; — ; — view of the It appears from the remarks of Daubeny, that nitrogen gas is given off from many compounds thermal springs.— Report on mineral and thermal waters in vol. v. of Rep. Brit, of nitrogen Assoc 39. andoxy- + Johnson’s report in Rep. Brit. Assoc. 1331-2. 455. gen. • t Roy. Instit. Jour. 1 384. 136 Chap. III. Atmosphe- ric air. Weight. Barometer. Density of the atmos- phere indi- cated. Nitrogen and Oxygen. are mingled together, no combination ensues. The result is a sim- ple mixture of the two gases, which do not, like inelastic fluids, separate on standing, but remain diffused through each other for an indefinite length of time. When, however, either one or both of these elements is in a condensed state, they unite and form com- pounds, distinguished by very striking properties. According to the proportions in which the oxygen and nitrogen exist in these com- pounds, their qualities undergo a remarkable variation ; so that from two elementary bodifes, variously united, we have several compounds, totally unlike each other in external qualities, as well as in their chemical relations. 425. Nitrogen and oxygen are the two most important constitu- ents of the atmosphere ; the thin, transparent and elastic fluid which surrounds our planet. 426. The atmosphere reaches to a considerable height, probably about 45 miles.* It may be diminished in volume to a great extent by compression. That air is a ponderous body, was first suspected by Galileo, who found that a copper ball, in which the air had been condensed, weighed heavier than when the air was in its ordinary state of ten- sion. The fact was afterwards demonstrated by Toricelli. In 1643, he filled a glass tube, three feet long, and closed at one end with quicksilver, and inverted it in a basin of the same fluid ; he found that the mercury fell about six inches, so that the atmos- phere appeared capable of counterbalancing a column of mercury 30 inches in height. The empty space, in the upper part of the tube, has hence been called the Torricellian vacuum, and is the most perfect that can be formed. Paschal and Toricelli afterwards observed, that upon ascending a mountain, the quicksilver fell in the tube, because there was less air above to press upon the surface of the metal in the basin ; and thus a method of measuring the heights of mountains by the barometer , as the instrument is now called, was devised. 428. The barometer indicates, by its rise and fall, a corresponding change in the density of the atmosphere.! At the surface of the earth, the mean density or pressure is considered equal to the sup- port of a column of quicksilver 30 inches high.! * See Wollaston “ on the Finite Extent of the Atmosphere Bost. Jour. 1 . 15. t From causes at present not understood, the pressure varies at the same place. On this depend the indications of the barometer as a weather-glass ; the weather is commonly fair and calm when the barometer is high, and usually wet and stormy when the mercury falls. Inches. t At 1000 feet above the surface the column falls to 28,91 2000 27,86 3000 26.85 4000. 25.87 5000 24,93 1 Mile 24,67 2 20,29 3 16,68 4 13,72 5 11,28 in 4,24 15 1,60 20 0,96 See Camb. Me- chanics , page 351 . Eudiometry. 137 428. The general mechanical properties of the air are best illus- Sect, hi. trated by the air pump the construction of which much resembles Air-pump, that of the common pump used for raising water, excepting that all the parts are more accurately and nicely made, the object being to exhaust the air as completely and expeditiously as possible.! 429. The specific gravity of atmospheric air, at mean temper- Specific ature and pressure, that is, the thermometer being at 60°, and the S ravlt Y- barometer at 30 inches, is, usually considered as == 1. It is about 815 times as light as its bulk of water, 100 cubical inches weighing 31,0117 grains. 430. Atmospheric air has already been stated to consist essen- tially of oxygen and nitrogen gases : whether it should be consider- ed a mere mixture or a chemical compound, is a question which has been much discussed.! The oxygen seems to be the only ingre- C^emicaJ dient on which the effects of the air, as a chemical agent, depend, pendent on Hence combustible bodies burn in atmospheric air, only in conse- oxygen, quence of the oxygen gas which it contains ; and when this is ex- hausted, air is no longer capable of supporting combustion. Its analysis is satisfactorily demonstrated by the action of heated mer- cury, but the process is tedious. § By exposure, during 12 days to Lavoisier’s mercury heated in a retort, a given quantity of atmospheric air was ^ e P Q t r g‘ found to be diminished in bulk, and to have lost its property of sup- porting combustion. The mercury was changed into red scaly par- ticles, and it had acquired an increase of weight. When these red particles were submitted to heat, in a retort, oxygen gas was evolved equal in bulk to what the air had lost in the first part of the experi- ment. 431. There are various ways of learning the proportion which the oxygen bears to the nitrogen ; and as the relative fitness of the air for breathing has sometimes been considered as depending upon the quantity of oxygen contained in a given volume, the instruments used in these experiments have been called eudiometers. Eudiome- 432. From facts already stated it is obvious, that if atmospheric tr y- air, mixed with a certain quantity of hydrogen, be detonated by the electric spark, the absorption will be proportionate to the quantity of oxygen present. When 100 measures of pure hydrogen are mixed with 100 of pure oxygen, the diminution of bulk after detonation will amount to 150 parts, that is, one volume of oxygen requires for its saturation two of hydrogen. If we introduce into the graduated detonating tube (Fig. 106) 300 measures of common air, and 200 of pure hy- drogen, there will remain, after detonation, 305 measures ; so that 195 measures will have disappeared, of which one third may be es- timated as pure oxygen ; hence 300 parts of air have thus lost 65 of oxygen, or about 21 per cent. 433. The general rule, therefore, for estimating the purity of air General by hydrogen gas may be stated as follows: — Add to 3 measures of Wie- the air under examination 2 measures of pure hydrogen ; detonate ; * See Frontispiece. t See statement in Turner , 171. t See Camb. Mechanics , page 403. § See Lavoisier’s Elements, chap. iii. 18 138 Nitrogen and Oxygen . Cha P- in - and, when the vessel has cooled, observe the absorption ; divide its amount by 3, and the quotient is the quantity of oxygen. 434. Upon the same principle, detonation of mixtures of oxygen other^ ases anc ^ hydrogen often resorted to, with a view of ascertaining the ascertain 8 - 68 Parity of those gases. ed - To ascertain the purity of hydrogen, it may be detonated with excess of pure oxygen. Thus, if we add 100 of pure oxygen to 100 of hydrogen, and detonate, there will be a diminution equal to two thirds, or 150 parts if the hydrogen be pure. If, however, we suppose 100 of pure oxygen, mixed with 100 of hydrogen, to produce, after detonation, a residue of 80 measures, the diminution will then nave been only 120 measures, of which two thirds, or 80 measures, are hydro- gen ; so that the inflammable, gas will have contained 20 per cent, of some other gaseous body, not condensable by detonation with hydrogen. 1 * 435. This mode of ascertaining the purity of atmospheric air Eudiomc- was fi rsl re sorted to by Volta, and it is susceptible of great accura- ter of Volta. , , J , 1 i j + cy, since pure hydrogen and pure oxygen are easily procured.! * For a particular description of several points iu eadiometry, see Faraday’s Chem. Manip . sect. xvii. paragraph 919, &c. t In the eudiometer of Ure, the atmospheric air, the most elastic and economical of Ur^enJiuma. all springs, is employed to receive and deaden the recoil. This eudiometer consists ler - of a glass syphon (Fig. 139), having an interior diameter of from 2-lOtbs to 4-10ths of an inch. Its legs are of nearly equal length, each being from six to nine inches long. The open extremity is slightly funnel-shaped, the other hermetically sealed ; and has inserted near it, by the blow pipe, two platinum wires. The outer end of the one wire is incurvated across, so as nearly to touch the edge of the aperture ; that of the other is formed into a little hoolc. to allow a small spherical button to be at- tached to it when the electrical spark is to he transmitted. The two legs of the syphon are from one-fourth to one-half inch as- under. The sealed leg is graduated by introducing successive- ly equal weights of mercury from a measure glass tube. Sev- en ounces troy and 66 grains, occupy the space of a cubic inch ; and 34 1-4 grains represent part °f that volume. The other leg may be graduated also, though this is not necessary. To use this instrument, we first fill the whole syphon with mercury or water ; the open leg is then plunged into a pneumatic trough, and any convenient quantity of the gases is introduced from a glass measure tube containing them in determinate pro- portions. Applying the finger to the orifice we next remove it from the trough, like a simple tube, and by a little dexterity transfer the gas into the sealed leg of the sy- phon. When we conceive enough has beeu passed up, the finger is removed and the mercury brought to a level in both legs, either by the addition of a few drops, or by the displacement of a portion, by thrusting down into it a small cylinder of wood. We now ascertain, by careful inspection, the volume of included gas. Applying the forefinger again to the orifice, so as also to touch the end of the platinum wire, we then approach the ball to the electrical machine, and transmit a spark, but a slight push or pressure on the tip of the finger is felt, even when the gas is in considerable quantity and of a strongly explosive power. After explosion on gradually sliding the finger to one side and admitting the air, the mercurial column in the sealed leg will rise more or less above that in the other. The equilibrium is then restored by adding mercury, when we read off, without any reduction, the true resulting volume of gas. As two inches or more of air should always be left between the finger and the mercury, this atmospheric column serves as a perfect recoil spring, enabling us to explode very large quantities without danger. We may analyze the residual gaseous matter, by introducing, either a liquid or solid re-agent. We first fill the open leg nearly to the brim with quicksilver, and then place over it the substance whose action on the gas we wish to try. If liquid, it may be passed round into the sealed leg among die ga6; but if solid the gas must be brought round into the open leg, its orifice having been previously closed with a cork or stopper. After a proper interval the gas having been transferred back into the graduated tube, the change of its volume may be accurately determined.— Ure's Diet. A\0—Edin. Phil. Trans. 1818.— See, also, Faraday, p. 434. Several new eudiome- ters have been described by Hare, in the Amcr. Jour, of Sci. vols. ii. and x- 139 Composition of Air . 436. Instead of electricity, spongy platinum may be employed for Sect, hi. causing the union of oxygen and hydrogen gases ; and while its in- Analysis dications are very precise, it has the advantage of producing the ef- plati- fect gradually and without detonation. The most convenient mode of employing it with this intention is the following : A mixture of spongy platinum and pipe-clay, in the proportion of about Process, three parts of the former to one of the latter, is made into a paste with water, and then rolled between the fingers into* * * a globular form. In order to pre- serve the spongy texture of the platinum, a little hydrochlorate of ammonia is mixed with the paste ; and when the ball has become dry, it is cautiously ignited at the flame of a spirit-lamp. The sal ammoniac, escaping from all parts of the mass, gives it a degree of porosity which is peculiarly favourable to its action. The ball, thus prepared, should be protected from dust, and be heated to redness just before being used. To insure accuracy, the hydrogen employed should be kept over mercury for a few hours in contact with a platinum ball and a piece of caustic potassa. The first deprives it of traces of oxygen which it commonly contains, and the second of moisture and hydrosulphu- ric acid. The. analysis must be performed in a mercurial trough. The time required for completely removing the oxygen depends on the diameter of the tube. If the mixture is contained in a very narrow tube, the diminution does not arrive at its full extent in less than twenty minutes or half an hour ; while in a vessel of an inch in diameter, the effect is complete in the course of five minutes.^ 437. When nitric oxide gas, (binoxide of nitrogen) and atmos- method? § pheric air are mixed, there is a production of nitrous acid, in conse- quence of the union of oxygen with the oxide ; and if the mixture be made over water, an absorption ensues. Upon this principle this gas was used in eudiometrical experiments, by Priestley and Cavendish.! There are, however, several sources of error for which, and the precautions required to ensure accuracy, see Binoxide of Nitrogen , ! (454.) 438. If a stick of phosphorus be confined in a portion of atmos- L avo i- pheric air it will slowly absorb the oxygen present. The rapid sier’s,&c. combustion of the same substance may also be conveniently resort- ed to. These eudiometrical methods were used by Lavoisier, Berthollet, and Seguing _ Uniformity 439. The analyses of atmospheric air, collected at various eleva- i n compo- tions and in different latitudes, show that the proportion of oxygen sitionofair. is between 20 and 21 volumes, and of nitrogen 79 or 80. The av- erage of a number of analyses by Hare’s eudiometer, gave the pro- portion of oxygen at 20,66 per cent. The air which Gay-Lussac brought from an altitude of 21,735 feet above the earth, had the same composition as that collected near its surface. But Faraday found a decided difference between the air from the arctic regions and that of London. Dalton has inferred that the proportion of oxygen to nitrogen in the air on the surface of the earth, is not pre- * See Henry’s Essay in Philos. Trans. 1824. — Henry’s Chemistry, 1.237. t Phil. Trans. 17 83. t See Dalton’s Remarks,. Phil. Mag. Vol. xxviii. For the details of this process see Henry’s Chemistry, vol, 1. p. 312, edit. 10th. § Ann. de Chim. tom. ix. and xxxiv. 140 Chap. III. Carbonic acid in air. Water in air, Its quanti- ty- Slate in which eonv ponents of the air ex- ist, Dalton’s ▼iew, Graham’s experi- ments. Nitrogen and Oxygen. cisely the same at all places and times, and that in elevated regions, the proportion is somewhat less. The miasmata of marshes and the effluvia of infected places, are supposed to owe their noxious qualities to some peculiar subtle prin- ciple, and not to a deficiency of oxygen.* 440. Though oxygen and nitrogen are the essential component parts of atmospheric air, it contains other substances, which, however, may be regarded as adventitious, and the quantity of which is liable to vary : of these, carbonic acid and aqueous vapour are the most im- portant and constant. The quantity of the former may usually be considered as amounting to less than 1 per cent. 441. The presence of aqueous vapour in the atmosphere is shown in a variety of ways, but most easily by exposing to it certain de- liquescent substances which liquefy and increase in weight, in con- sequence of its absorption. t The quantity of water contained in air and gases is subject to va- riation. From the experiments of Saussure and Dalton, it appears that 100 cubic inches of atmospheric air at 57°, are capable of re- taining 0,35 grains of watery vapour ; in this state the air may be considered at its maximum of humidity: it would also appear that all the gases take up the same quantity of water when under similar circumstances, and that it consequently depends, not upon the den- sity or composition, but upon the bulk of the gaseous fluid. 442. Berthollet considered that the elements of the air are retain- ed together by chemical attraction ; but Dalton maintains that they are merely mechanically mixed, and proved that gases mingle me- chanically that have no attraction, and that even carbonic acid rises through a small tube into a bottle of hydrogen placed above it, though much heavier, a corresponding quantity of hydrogen des- cending into the carbonic acid bottle. This proves a power of diffu- sion among the gases. Dalton concluded that particles of the same gases repel each other, but that those of different gases do not, and that one gas acts as a vacuum to another, though they diffuse them- selves more slowly through each other than in a vacuum. 443. Graham has ascertained that each gas has a diffusiveness pe- culiar to itself, which is inversely proportional to the square root of its density, and has drawn up tables representing their diffusive pow- er, air being taken as a standard of comparison. t He used a tube with the gas under examination, open at one end, and closed with plaster-of-paris at the other, the diffusion taking place readily through the pores of this substance when moderately dry ; it also takes place through membranes, small cracks in glass vessels, and through numerous porous bodies.^ From all these considerations, ♦According to Prout there was a peculiar state of the air during the prevalence of the cholera in London, in 1832. See Reports of Brit. Assoc. 1832. + As the gases in general, unless artificially dried, also contain vapour, it is neces- sary, in delfcate experiments, and in ascertaining their specific gravity, to take this ingredient into the account, or to separate it by proper means, such as exposure to very deliquescent substances, among which fused chloride of calcium is especially useful. t Phil. Trans. Edin. 1831. § See Mitchell’s experiments in Amer. Jour. Med. Sci • vii. 36. 141 Protoxide of Nitrogen . Dalton’s view of the constitution of the air is now generally adop- Sect, in. ted. R. 54. 444. Hygroscopes and Hygrometers are instruments which show the presence of water in the air, its variation in quantity, and its Hygrorne . actual quantity existing in a given bulk of air at any given time. ters. Daniell's hygrometer shows the constituent temperature of the mois- ture in the atmosphere, by its precipitation upon a cold surface.! 445. Since oxygen is necessary to combustion, to the respiration L osso fox- of animals, and to various other natural operations, by all of which ygen, how that gas is withdrawn from the air, it is obvious that its quantity compeusa- would gradually diminish, unless the tendency of those causes were counteracted by some compensating process. The only source by which oxygen is known to be supplied, is the action of growing veg- etables. A healthy plant absorbs carbonic acid during the day, ap- propriates the carbonaceous part of that gas to its own wants, and evolves the oxygen with which it was combined. During the night, indeed, an opposite effect is produced. Oxygen gas then disappears, and carbonic acid is eliminated ; but it follows from the experiments of Priestley, Davy, and Daubeny, that plants during 24 hours yield more oxygen than they consume. Whether living vegetables make a full compensation for the oxygen removed from the air by the pro- cesses above mentioned, is uncertain. Nitrogen and Oxygen. Protoxide of Nitrogen — Nitrous Oxide. Composition. Symb. Sp. Gr. Nit. Oxy. Chem. Equiv. N + OorN 1.5239 Air =1 By Vol. 100 + 50 100 22.15 Hyd. =1 “ Wght. 14.15 + 8 22.15 446. This gas was termed, by its discoverer, Priestley, dephlogisti- cated nitrous air; by the Dutch chemists gaseous oxide of azote. It is obtained by several processes, but that most usually adopted is the following. The salt obtained by neutralizing nitric acid with carbonate of ammonia, called Nitrate of Ammoniat is heated in a glass retort. When all the salt is liquefied, it should be kept gently simmering, avoiding violent ebullition. The temperature should not Process f be raised above 500° F. If a white cloud appears within the retort, due to some of the salt subliming undecomposed, the heat should be checked. § The management of the heat is to be carefully at- tended to ; when the heat is too great, the gas is apt to be im- pure. 447. The gas may be collected over water and allowed to stand Collected an hour or two before it is used, during which time it will deposit a over watel » t See Quart. Jour. Sci. vols. viii. ix. x. t See Nitrate of Ammonia. § A chauffer with ignited charcoal affords the best heat, and the retort is less liable to be broken than when a lamp is employed. An iron or tin plate will be found use- ful to check the ebullition if too great, as it can be interposed between the chauffer and the retort, and withdrawn at pleasure. 142 Ch.ip. III. Theory of the process Properties. May be re- spired. Supports combus- tion. Detonates with hydro- gen. Nitrogen and Oxygen. white substance and become transparent. When a large quantity is wanted, it may be received in a gasholder, and much gas will be saved if the vessel be filled with water which has been once used for the same purpose. 448. The products of this operation, when carefully conducted, are water and protoxide of nitrogen. The nature of the change will be understood by comparing the composition of nitrate of am- monia with that of the products derived from it. These, in round numbers, are as follows : Nitric Acid. Ammonia. Water. Prot. of NiWogen . Nitrogen 14 or 1 eq. Nitrogen 14 or 1 eq. Hyd. 3 or 3 eq. Nit. 28 or 2 eq. Oxygen 40 or 5 eq. Hydrogen 3 or 3 eq. Oxy. 24 or 3 eq. Oxy . 16 or 2 eq. 54 17 27 44 The same expressed in symbols is N+50; N+3H; | 3(H+0) ; 2(N+0). The hydrogen in the ammonia takes so much oxygen as is suffi- cient for forming water, and the residual oxygen converts the nitro- gen both of the nitric acid and of the ammonia into protoxide of ni- trogen : 71 grains of the salt will thus yield 44 grains of protoxide of nitrogen and 27 of water. 449. Protoxide of nitrogen is a colourless gas, which does not affect the blue vegetable colours, even when mixed with atmospheric air. Kecently boiled water, which has cooled without exposure to the air, absorbs nearly its own bulk of it at 60° F. and gives it out again unchanged by boiling. The solution, like the gas itself, has a faint agreeable odour and sweet taste. The action of water affords a ready means of testing its purity ; removing it readily from all other gases, such as oxygen and nitrogen, which are sparingly ab- sorbed by that liquid. 450. Davy discovered that this gas may be taken into the lungs with safety,* and that it supports respiration for a few minutes. A few deep inspirations of it are followed by feelings of excitement, similar to the early stages of intoxication. The experiment, how- ever, cannot be made with impunity by all persons, especially by those who are liable to a determination of blood to the head.f 451. Protoxide of nitrogen supports combustion, and a taper in- troduced into it has its flame much augmented and surrounded by a purplish halo. Phosphorus and sulphur, when introduced in a state of vivid ignition into this gas, burn with the same appearance nearly as in oxygen ; but, if when put into the gas, they are merely burn- ing dimly, they do not decompose it and are extinguished, so that they may be melted in the gas, or even touched with a red-hot wire without inflaming, (but when wire intensely heated, or made white- hot, is applied, the phosphorus burns, or rather detonates, with pro- digious violence. H.) Charcoal, and many of the metals, also de- compose protoxide of nitrogen at high temperatures. 452. A mixture of this gas with an equal bulk of hydrogen gas detonates, on applying a lighted taper, or passing an electric spark, * Researches on the nitrous oxide • 4 See report of remarkable cases ia Amer. Jour. vol. v. Binoxide of Nitrogen. 143 and is decomposed also by spongy platinum at common tempera- sect. ni. tures. The product of the combustion is the same as when oxygen ~ gas or atmospheric air is used. The protoxide is decomposed ; the combustible matter unites with its oxygen, and the nitrogen is set free. 453. At a red heat this gas is decomposed and converted into Decompo- nitrogen, oxygen and nitrous acid.* It was analyzed by Davy, by sltlon - means of hydrogen gas. He mixed 39 measures of the former with 40 measures of hydrogen, and fired the' mixture by the electric spark. Water was formed ; and the residual gas, which amounted to 41 measures, had the properties of pure nitrogen. As 40 mea- sures of hydrogen require 20 of oxygen for combustion, it follows that 39 volumes of the protoxide of nitrogen contain 41 of nitrogen and 20 of oxygen. According to Gay-Lussac's law of gaseous com- bination, it may be inferred that protoxide of nitrogen contains its Analysis, own bulk of nitrogen and half its volume of oxygen. The analy- sis of this compound by Henry,! by means of carbonic oxide gas, has proved beyond a doubt that this is the exact proportion. Now, 100 cubic inches of nitrogen gas weigh - 30.1650 grains 50 do. oxygen - - - 17.0936 “ These numbers added together amount to - • 47.2586 which must be the weight of 100 cubic Inches of the protoxide ; and its specific gravity is, therefore, 1.5239. Its composition by weight is determined by the same data, being 17.0936 of oxygen to 30.1650 of nitrogen, or as 8 to 14.117, nearly the number already sta- ted. T. Syrrib. N+20 or N Binoxide of Nitrogen — Nitric Oxide. Composition. Sp. Gr. Nit. Oxy 1,0375 air=l By Vol. 15.75 air = Hyd.: Wght. too 14.15 Chem. Equiv. — 200 = 30.15 454. This gas, discovered by Hales, was first examined by Priest- ley, and called by him nitrous air a term afterwards changed to ni- trous gas, then to nitric oxide, and more lately to Binoxide of Nitro- gen, which last appears to be its most appropriate title. It is more generally known, however, under the name of nitrous gas. 455. It is usually obtained by presenting certain substances to ni- tric acid, which abstract a portion of its oxygen, leaving the remain- ing elements in such proportions as to constitute the gas in ques- la P^ d ^ >- tion ; for this purpose copper may be put into a gas bottle, (Fig. 87) * For experiments of this Fig. 140. kind the following simple apparatus may be used : It consists of two bladders, I Fig. 140,) one of which is /y filled with the gas, and the ff/y other empty, attached to the extremities of a porcelain tube which traverses the body of a furnace, ders are supplied with stop-cocks, and the gas is squeezed from one to when the tube is red hot. t Ann. of Phil. viii. 299, N. S. The blad- the other 144 Chap. III. Theory of the process. Effect of oxygen, Exp. Exp. Analysis. Properties. Nitrogen and Oxygen. with nitric acid, diluted with thrice its bulk of water; an action en- ' sues, red fumes are produced, and there is a copious evolution of the gas, which may be collected and preserved over water. The first portions should be rejected. It is presently recognised by the red fumes which it produces when brought into the contact of air. During this process part of the nitric acid gives oxygen to the cop- per; and passes to the state of binoxide of nitrogen, the remaining acid unites with the oxide of copper, and composes a nitrate of that metal. Quicksilver may be substituted for the copper ; but in the latter case it will be found necessary to apply heat to the materials. 450. When mixed with oxygen gas red fumes arise, heat is evolv- ed, a diminution takes place, and if the two gases be in proper pro- portion, and perfectly pure, they disappear entirely. The product of this union is possessed of acid properties, which may be shown by the following experiments. 1 . Paste a slip of litmus paper within a glass jar, near the bottom ; and into the jar, filled with and inverted in water, admit as much of the gas, previously well washed, as will displace the water below the level of the paper. The colour of the litmus will remain unchanged ; but on adding oxygen gas it will be im- mediately reddened. 2. Puss up into ajar filled with the vegetable infusion, (56 Note) a quantity of oxygen gas sufficient to displace about one half of the infusion ; to this admit biuoxide of nitrogen, absorption and reddening will ensue. 457. Binoxide of nitrogen is rather heavier than common air. It is partially resolved into its elements by being passed through red- hot tubes. A succession of electric sparks has a similar effect. It is converted into protoxide of nitrogen by substances which have a strong affinity for oxygen. Davy ascertained its composition by the combustion of charcoal.* Two volumes of the binoxide yielded one volume of nitrogen, and about one of carbonic acid, whence it was inferred to consist of equal measures of oxygen and nitrogen gases united without any condensation. Gay-Lussac also proved that this proportion is exact. He decomposed 100 measures of the gas, by heating potassium in it; when 50 measures of pure nitro- gen were left, and the potassa formed corresponded to 50 measures of oxygen. The same fact has been lately proved by Henry. t Hence, as 50 cubic inches of oxygen gas weigh - - 17.0936 grains. 50 do. nitrogen - - - 15.0825 “ 100 cubic inches of the binoxide must weigh 32.17C1 Its composition stated at page 143 is drawn from these facts. Its density ought to be 1.0375, which closely agrees with the direct ex- periments of Davy, Thomson, and Berard. T. 453. When washed with water it is not acid. Water absorbs the binoxide sparingly ; 100 measures of that liquid, cold and re- cently boiled, takeup about 11 of the gas. It extinguishes most burning bodies ; but phosphorus readily burns in it if introduced in intense ignition. It is quite irrespirable, exciting strong spasms of the glottis, as soon as an attempt is made to inhale it. The experi- ment, however, is a dangerous one. * Elem. Chem. Phil. p. 200. t Ann. of Phil. N. S. viii- 299. Hyponitrous Acid , 145 459. It is decomposed by exposure to almost all bodies that attract s , ec - n L oxygen ; thus iron filings decompose it, and become oxidized, afford- Decompose ing a proof of the presence of oxygen in it. During this process, hon, water, ammonia, and protoxide of nitrogen are generated. Mixed with sulphurous acid, it is decomposed, and this acid is changed into the sulphuric, but not unless water is present. With an equal bulk of hydrogen, it forms a mixture which cannot be made to explode, but which is kindled by contact with a lighted candle, and burns rapidly with a greenish white flame, water and pure nitrogen gas being the sole products. The action of freshly ignited spongy platb num on a mixture of hydrogen and binoxide of nitrogen gases leads to the slow production of water and ammonia. 460. From the formation of red coloured acid vapours, whenever Use in Eu« binoxide of nitrogen and oxygen are mixed, these gases detect the pre- lome r L sence of each other ; and since the product is wholly absorbed by wa- ter, either of them may be entirely removed from any gaseous mixture by adding a sufficient quantity of the other. Priestley, who first ob- served this fact, supposed that combination takes place between them in one proportion only; and inferring on this supposition, that a given absorption must always indicate the same quantity of oxygen, he was led to employ binoxide of nitrogen in Eudiometry. But in this opinion he was mistaken. Dalton and Gay-Lussac have described the precautions which are required to insure accuracy.^ Hyponitrous Acid. Composition. Symb. Nit.. Oxy. Equiv. By Vol. 100 + 150 N+30 or N “ Wght. 14.15 + 24 = 38.15 461. On adding binoxide of nitrogen in excess to oxygen gas, p rocess> confined in a giass tube over mercury, Gay-Lussac found that 100 measures of the latter combine with 400 of the former forming an acid which unites with the potassa. The compound so formed is hypo- nitrous acid. 462. The anhydrous liquid acid is colourless at 0° F. and green at Properties, common temperatures. It is so volatile, that in open vessels the green fluid wholly and rapidly passes off in the form of an orange vapour, which is said to have a density of 1.72. On admixture with water it is converted into nitric acid and binoxide of nitrogen, the latter escaping with effervescence ; but when much nitric acid is present, the hyponitrous is changed into nitrous acid, which imparts * Dalton in Ann. of Phil. x. 38; and further directions have been published MelhodofGay , by Henry in his -Elements. Instead of employing a narrow tube, such as is com- Lussac. monly used for measuring gases, Gay -Lussac advises that 100 measures of air should be introduced into a very wide tube or jar, and that an equal volume of binoxide of nitrogen should then be added. The red vapours, which are insfa&tl'y produced ; dis-, appear very quickly ; and the absorption after half a minute, or y minute at the most,, may be regarded as complete. The residue is then transferred into a graduated tube and measured. The diminution almost always, according to Gay-Lussac, amounts to 84 measures, one-fourth of which is oxygen. Gay-Lussac has applied this. process to the analysis of various mixed gasbs, in which the oxygep was sometimes in a. greater, at others in a less proportion than in the atmosphere, and the indications were al - ways correct. For other details see Turner’s Elements, 177, and Dana on, Nitrous , Gas, Amer. Jour., vii. 338. 19 146 I Chap. III. Action of sulphuric acid. Nitrous acid gas. Exp. Not easily- examined. ;Properties. Liquid ni- trous acid. From ni- trate of lead. Nitrogen and Oxygen. _ several shades of colour, orange, yellow, green, and blue, according to its quantity. One equivalent of hyponitrous and one of nitric acid, yield two equivalents of nitrous acid : thus N-)-30 and N-}-50 contain the elements for forming 2(N-f-40). 463. Hyponitrous acid does not unite directly with alkalies, being then resolved principally into nitric acid and binoxide of nitrogen ; but the hyponitrites of the alkalies and alkaline earths may be ob- tained by heating the corresponding nitrates to a gentle red heat. 464. Hyponitrous acid forms with water and sulfuric acid a crystalline compound, which is generated in large quantity during the manufacture of sulphuric acid, and the production of which is an essential part of that process. It is generated whenever moist sul- phurous acid gas and nitrous acid vapour are intermixed, being instantly deposited in the form of white acicular crystals. T. 179 . Nitrous Acid. Composition. Symb. Nit. Oxy. Equiv. By Vol. 100 + 200 N+40 or N “ Wglit. 14.15 + 32 = 46.15 465. When binoxide of nitrogen is presented to oxygen, the two gases combine, and a new gaseous compound of a deep orange colour results. Into a large glass globe, or other convenient vessel, previously filled with wa- ter, introduce sufficient nitrous gas to displace about two thirds of the water. On passing into it oxygen gas the vessel will become filled with deep orange coloured nitrous acid gas. This compound is absorbed both by quicksilver and water, so that to preserve it for examination, we are obliged to resort to exhausted glass vessels. When we thus mix two volumes of binoxide of ni- trogen with one volume of oxygen, the gases become condensed to one third their original volume, and form nitrous acid vapour. 466. This gas supports the combustion of the taper, of phosphorus, and of charcoal, but extinguishes sulphur.* 100 measures of nitrous acid vapour contain 100 of nitrogen gas and 200 of oxygen. The spe- cific gravity of this vapour ought to be 3.1775, formed of 0.9727 the sp. gr. of nitrogen-f-2.2048 twice the sp. gr. of oxygen. 467. Nitrous acid may exist in the liquid as well as in the gase- ous form. To form liquid nitrous acid, its vapour may be con- densed by a freezing mixture. It is readily absorbed by water ; the water becomes first green, then blue, and finally an orange colour, more or less deep. The latter may be brought to the state of green or blue by adding more or less water. Hence the colour depends partly on the circumstance of density ; but there can be little doubt that it is materially affected also b'y the proportions of nitric, nitrous, and hyponitrous acids, which according to Gay-Lussac, compose ni- trous acid, as it is ordinarily obtained in a liquid state. H. 1 . 321 . 468. It may be procured by exposing nitrate of lead carefully dried to a heat sufficient to decompose the salt. The nitric acid of the salt is resolved into nitrous acid and oxygen ; and if the products * It reddens litmus paper, has a sour taste, a strong smell, and turns animal sub- stances yellow. Nitric Acid. 147 are received in vessels kept moderately cool, the greater part of the Sect. m. former condenses into a liquid. This substance was first obtained by Gay-Lussac. 469. The liquid anhydrous acid is powerfully corrosive, has a Properties, strong acid taste and pungent odour, and is of a yellowish orange colour. Its density is 1.451. It remains liquid at ordinary tempe- ratures and pressure, and boils at 82° F. Exposed to the air it eva- porates with great rapidity, forming the common nitrous acid vapours, which, when once mixed with air or other gases, require an intense cold to condense them. 470. Nitrous acid is a powerful oxidizing agent, readily giving Oxidizes, oxygen to the more oxidable metals, and to most substances which have a strong affinity for it. The acid is decomposed at the same time, being commonly changed into binoxide of nitrogen, though sometimes the protoxide and even pure nitrogen, gases are evolved. When transmitted through a red hot porcelain tube, it suffers decom- position, and a mixture of oxygen and nitrogen gases is obtained. When nitrous acid is mixed with a considerable quantity of water, Action of it is instantly resolved into nitric acid, which unites with the water, ^ ater * and binoxide of nitrogen which escapes with effervescence. Nitric Acid . Composition. Symb. Nit. Oxy. Equiv. VJ-Lrn N ByVol. 100 + 250 N+oOor N “ Wght. 14.15 4- 40 = 54.15 471. If a succession of electric sparks be passed through a mixture of oxygen and nitrogen gases confined in a glass tube over mercury, a little water being present, the volume of the gases will gradually diminish, and the water after a time will be found to have acquired acid properties. On neutralizing the solution with potassa, or what is better, by putting a solution of pure potassa, instead of water, into the tube, a salt is obtained which possesses all the properties of the nitrate of potassa (nitre.) This experiment was performed by Ca- vendish in 1785, who inferred from it that nitric acid is composed of oxygen and nitrogen. The nitric acid may be formed more conveniently by adding bi- noxide of nitrogen slowly over water to an excess of oxygen gas. It cannot exist in an insulated state. The most simple form under which chemists have hitherto procured nitric acid is in solution with water. It is usually obtained by the distillation of purified nitre with sulphuric acid, of which materials different proportions are em- ployed. Into a glass retort, which may be either tubulated or not, put four parts by weight of nitrate of potassa, reduced to a coarse powder, and pour upon it three parts of concentrated sulphuric acid. Apply a tubulated receiver of large capa- city between which and the retort, an adopter may be interposed ; these junc- tures being luted with a mixture of pipe-clay, sifted sand, and cut tow or flax. To the tubulure of the receiver, a glass tube may be fixed by means of the fat lute,* and may terminate in another receiver, containing a small quantity of Nitric acid formed. Usual process for obtaining nitric acid. * Formed by heating perfectly dry and finely sifted tobacco pipe clay, with painters' drying oil. 148 Chap. III. On the large scale. Purification of nitric acid. Preparation of nitrous acid, or aquafortis Nitrogen and Oxygen. If the operator wishes to collect the gaseous products also, this second receiver should be provided with a tubulure, to which a bent pipe may be luted, termi- nating under one of the inverted funnels in the shelf of the pneumatic trough. Apply heat to the retort, through the intervention of the sand-bath. The first product that passes into the receiver, is generally of a red colour, and of a smok- ing quality. These appearances gradually diminish; and if the materials used were clean, the acid will come over pale, and even colourless. Afterwards it gradually re-assumes a red colour, and smoking property; which appearances go on increasing till the end of the operation ; and the whole product mingled to- gether, has either a yellow or an orange colour, according to the temperature employed. H. 1.318. 472. The nitric acid of commerce, which is generally red and fuming in consequence of the presence of binoxide of nitrogen, is procured by the distillation of two parts of nitre with one of sulphu- ric acid ; these proportions afford about one part of orange -coloured nitric acid of the specific gravity of 1.48.* 473. The nitric acid of commerce, as usually obtained is impure. It frequently contains portions of sulphuric and hydrochloric acid. The former is derived from the acid which is used in the process ; and the latter from sea-salt, which is frequently mixed with nitre. These impurities may be detected by adding a few drops of a solution of chloride of barium and nitrate of silver to separate portions of ni- tric acid, diluted with three or four parts of distilled water. If chlo- ride of barium cause a cloudiness or precipitate, sulphuric acid must be present ; if a similar effect be produced by nitrate of silver, the presence of hydrochloric acid may be inferred. Nitric acid is puri- fied from sulphuric acid by redistilling it from a small quantity of nitrate of potassa, with the alkali of which the sulphuric acid unites, and remains in the retort. To separate hydrochloric acid, it is ne- cessary to drop a solution of nitrate of silver into the nitric acid as long as a precipitate is formed, and draw off the pure acid by distil- lation.! * Upon the large scale 112 lbs. of nitre, and 56 of sulphuric acid yield from 50 to 52 lbs. of nitric acid. Some manufacturers employ three parts of nitre and two of sul- phuric acid, and the London Pharmacopoeia directs equal weights, by which a nearly colourless nitric acid is afforded. t The distillation of nitric acid may be conducted upon the small scale in a tabulated glass retort a, with a tubulated receiver b, passing into the bottle c, (Fig. 141.) The requisite heat is obtained by the lamp d ) and the whole apparatus supported by the brass stands with sliding rings c e. Fig. 141. Fig. 142. The manufacturer who prepares nitric acid upon a large scale, generally emplovs dis- tillatory vessels of stone ware. Fig. 142 represents the arrangement of the distillatory apparatus, employed at Apothecaries’ Hall, London, for the production of common aqua-fortis : it consists of an iron pot, set in brick-work, over afire-place ; an earthen- ware head is luted upon it, communicating with two receivers of the same material, furnished with earthen ware stop cocks, the last of which has a tube of safety dipping into a basin of water. 149 Nitric Acid — Effect of Light. For pharmaceutical purposes, the ordinary acid is generally suffi- Sect.m. ciently pure. If, however, pure nitre, and pure sulphuric acid be employed in its production, and the latter not in excess, there is little apprehension of impurity in the resulting acid. 474. Liquid nitric acid is heavier than water, in the proportion of Specific 1.5 or upwards to 1. The specific gravity of real nitric acid, which gravity, cannot, however, be obtained separately, may be calculated at 1.75. In its heaviest form, it still contains a portion of water, which is es- sential to its existence in a liquid state. In acid of the sp. gr. 1.5 the water amounts to 20 per cent. It possesses acid properties in an em- inent degree. A few drops of it diluted with a considerable quantity of water form an acid solution, which reddens litmus paper permanently. It unites with and neutralizes alkaline substances, forming with them salts which are called nitrates. 475. Nitric acid is usually coloured by nitrous acid. To expel which, put the acid into a retort to which a receiver is applied, the Coloured two vessels not being luted, but joined merely by paper. Apply a very gentle by nitrous heat for several hours to the retort, changing the receiver as soon as it becomes acid gas. filled with red vapours. The nitrous gas will thus be expelled, and the nitric acid will remain in the retort limpid and colourless. It must be kept in a bottle secluded from light. H. 327. 476. Nitric acid emits white fumes when exposed to the air, and Decompo- is extremely sour and corrosive. It effects the decomposition of ani- matters^* 1 mal matters. The cuticle and nails receive a permanent yellow stain when touched with it ; and if applied to the skin in sufficient quantity it acts as a powerful cautery, destroying the organization of the part entirely. 477. It boils at 248° F., and may be distilled over without any Boiling essential change. An acid, weaker than 1.42, is strengthened by p01nt ’ being boiled; while an acid, stronger than 1.42, becomes weaker by boiling. All the varieties of nitric acid, therefore, are brought, by sufficient boiling, to the specific gravity, 1.42, which appears to be the most energetic combination of acid and water. 478. Nitric acid may be frozen by cold. The temperature at Freezing, which congelation takes place, varies with the strength of the acid. The strongest acid freezes at about 50° below zero. When diluted with half its weight of water, it becomes solid at — 1 F. By the addition of a little more water, its freezing point is lowered to— 45° F. Strong nitric acid absorbs moisture from the atmosphere ; in consequence Absorbs of which it increases in weight, and diminishes in specific gravity. mmsture - 479. When two parts of the acid are suddenly diluted with one of Mixed with water, an elevation of temperature is produced to about 120° F. ; water, and the admixture of 58 parts by weight of acid of specific gravity ture P r!ses. 1.50 with 42 parts of water, both at 60° F., gives a temperature of 140°. * When more water is added to this diluted acid, its tempera- ture is reduced. Snow or ice added to the cold dilute acid is in- stantly liquefied and an intense degree of cold produced. 480. Wffieri very concentrated it becomes coloured by exposure to Effect of the sun’s light, passing first to a straw colour, and then to a deep solar ]i § ht * orange. This effect is produced by the union of the light of the sun * Ure. See table of strength of diluted acid in Appendix. 150 Chap. III. Affords ox- ygen. Decompos- ed by com- bustibles, Exp. Action on phospho- rus, Exp. Caution. Metals, and by a red heat. Nitrogen and Oxygen. with oxygen, in consequence of which the proportion of that princi- . pie to the nitrogen is diminished. By exposing it to the sun’s rays in a gas bottle, the bent tube of which terminates under water, oxy- gen gas may be procured. H. i. 321 . 481. This acid retains its oxygen with but little force, and hence is much employed by chemists for bringing bodies to their maximum of oxidation. It is decomposed by all combustible bodies, which are oxygenized by it, with more or less rapidity in proportion to their affinity for oxygen. Poured on perfectly dry and powdered charcoal it excites the com- bustion of the charcoal, which becomes red-hot, and emits an im- mense quantity of fumes. Its action on phosphorus is often extremely violent, and great Fig* 143. care should be taken to avoid accident. A few pieces of phos- 1 phorus may be placed in the bottom of a tall and strong glass, and the acid be poured upon it from a vessel attached to the end of a long rod of wood.* (Pig. 143.) All vegetable substances are decomposed by it. In general the oxygen of the nitric acid enters into direct combination with the hydrogen and carbon of those compounds, forming water with the former, and car- bonic acid with the latter. This happens remarkably in those compounds in which hydrogen and carbon are predominant, as in alcohol and the oils. ==k£===4=» It inflames essential oils when suddenly poured on them. Into a gallipot, placed upon a hearth and containing about a table spoonful of oil of turpentine, pour about half the quantity of the strong acid, previously mixed with a few drops of sulphuric acid. The moment the aeids come in con- tact with the turpentine, a large quantity of dense smoke will be produced, often accompanied with flame. The acid should be poured from a bottle tied to (he end of a long stick, otherwise the operator’s eyes may be severely injured. 482. It is also decomposed by metals, with different phenomena, according to the affinity of each metal for oxygen. This may be seen by pouring some strong nitric acid on iron filings, or powdered tin. The acid must be of greater density than 1.48, otherwise it will not produce the effect. Violent heat, attended with red fumes, will be produced, and the metals will be oxidized. When oxidation is effected through the medium of nitric acid, the acid itself is commonly converted into binoxide of nitrogen. This gas is sometimes given oflf nearly quite pure ; but in general some nitrous acid, protoxide of nitrogen, or pure nitrogen, is disengaged at the same time. 483. Nitric acid maybe decomposed by passing its vapour through a red hot porcelain tube ; oxygen is given off, nitrous acid gas is produced, and a quantity of diluted acid passes over into the receiver, having escaped decomposition ; so that it is thus proved to consist of nitrous acid gas, oxygen and water. For experiments of this kind the form of apparatus, described for the decomposition of water by iron (405), may be employed, omitting the condensing worm-pipq, and substituting a porcelain tube. 484. All the salts of nitric acid are soluble in water, and, there- *See Hare’s Compend , 171. Carbon — Diamond . 151 fore, it is impossible to precipitate that acid by any re-agent. The Sect, iv. presence of nitric acid, when uncombined, is readily detected by its strong action on copper and mercury, emitting ruddy fumes of nitrous acid, and by its forming with potassa a neutral salt, which crystallizes in prisms, and has all the properties of nitre. Gold-leaf is a still more Tests of, delicate test. When hydrochloric acid is added to the solution of a nitrate, chlorine is disengaged, and the liquid hence acquires the property of dissolving gold-leaf ; but as the action of hydrochloric acid on the salts of Chloric, bromic, iodic, and selenic acids likewise yields a solution capable of dissolving gold, no inference can be drawn from the experiment, unless the absence of these acids shall have been previously demonstrated. A very delicate test has been pro- posed by O’Shaugnessy, founded on the orange-red followed by a yellow colour, which nitric acid communicates to morphia. The supposed nitrate is heated in a test tube with a drop of sulphuric acid, and then a crystal of morphia is added. ^ It is advisable to try the process in a separate tube with the sulphuric acid alone, in order to prove the absence of nitric acid. T. 485. Nitric acid is of considerable use in the arts. It is employed Uses * for etching on copper, as a solvent of tin to form with that metal a mordant for some of the finest dyes ; in metallurgy and assaying ; in various chemical processes, on account of the facility with which it parts with oxygen and dissolves metals; in medicine as a tonic, &c. For the purposes of the arts it is commonly used in a diluted . state, and contaminated with the sulphuric and hydrochloric acids, by fortis. the name of aquafortist Section IV. Carbon . Symb. Sp. Gr. ( hypothetical .) Chem. Equiv. C. 0.4215 air =1 By Vol. 100 6.12 Hyd.=l “ Wght. 6.12 486. The purest form of carbon is the diamond ; from its powers Purest of refracting light, Newton inferred that it was a combustible body. form ’ The diamond is the hardest substance in nature. Its texture is crystalline in a high degree, and its cleavage very perfect. Its pri- mary form is the octohedron. Its specific gravity is 3.52. Acids- and alkalies do not act upon it; and it bears the most intense heat in close vessels without fusing or undergoing any perceptible change. Heated to redness in the open air, it is entirely consumed. Lavoisier first proved it to contain carbon by throwing the sun’s rays, concentrated by a powerful lens, upon a diamond contained in a vessel of oxygen gas. The diamond w&s consumed entirely, oxy- gen disappeared, and carbonic acid was generated. It has since been demonstrated by the researches of others, that carbonic acid is the product of its combustion.! * Lancet, 1829—30. + This is often prepared by mixing common nitre with an equal weight of sulphate of iron, and half its weight of the same sulphate calcined, and distilling the mixture; or by mixing nitre with twice its weight of dry powdered clay, and distilling in a reverberatory furnace. Two kinds are found in the shops, one called double aqua- for- tis, which is about half the strength of nitric’acid ; the other simply aqua-forlis, which is half the strength of the double. t For a description and plates of the various forms of apparatus contrived for the combustion of the diamond, see Henry’s and Brande’s vols. i. ; also 1st and 2d editions of this Manual . 152 Carbon. Chap. III. Charcoal. Method of preparing charcoal. Lamp- black. Animal charcoal. Its proper- ties. Combus- tion in ox- ygen. Absorbing power. 487. Guyton-Morveau inferred from his experiments that the dia- mond is pure carbon, and that charcoal is an oxide of carbon. Ten- nant burned diamonds by heating them with nitre in a gold tube; and comparing his own results with those of Lavoisier on the com- bustion of charcoal, he concluded that equal weights of diamond and pure charcoal, in combining with oxygen, yield precisely equal quantities of carbonic acid. He was thus induced to adopt the opin- ion, that charcoal and the diamond are chemically the same sub- stance ; and that the difference in their physical character is solely dependent on a difference of aggregation.* This conclusion was confirmed by the experiments of Allen and Pepys,t and Davy.t § Another form of carbon is charcoal, the purest variety of which is lamp-black. II 488. Charcoal may be prepared by heating pieces of wood, cover- ed with sand, to redness, and keeping them in that state for about an hour. They are converted into a black brittle substance, which appears to be the same from whatever kind of wood it has been pro- cured. Lamp-black is prepared from refuse and residuary resin. When lamp-black has been heated red-hot in a close vessel, it may be con- sidered as very pure carbon. A very pure charcoal is obtained from spirits of wine. Animal charcoal, or ivory black , is a mixture of charcoal and phos- phate of lime, prepared by exposing bones to heat in a close vessel. The quantity of charcoal obtained from different kinds of wood is liable to much variation. 489. Charcoal is black, insoluble, inodorous, insipid, and brittle ; an excellent conductor of electricity, but a bad conductor of heat ; un- changed by the combined action of air and moisture at common tem- peratures ; and easily combustible in r oxygen gas. The combustion of charcoal in oxygen has been already noticed. (367) The product of the combustion is carbonic acid gas, the oxygen neither increasing nor diminishing in volume, but becoming heavier by the quantity of carbon which combines with it ; every sixteen parts of oxygen take up six of carbon. 490. Charcoal likewise absorbs the odoriferous and colouringprin- ciples of most animal and vegetable substances. When coloured infusions of this kind are digested with a due quantity of charcoal, a solution is obtained, which is nearly if not quite colourless. Tainted flesh may be deprived of its odour by this means, and foul water be purified by filtration through charcoal. The substance commonly employed to decolorize fluids is animal charcoal reduced to a fine powder. It loses the property of absorbing colouring matters by use, but recovers it by being heated to redness. * Phil. Trans, for 1797. Ibid, 1807. i Ibid, 1814. § The latter chemist did indeed observe the production of a minute quantity of water during the combustion of the purest charcoal, indicative of a trace of hydrogen; but its quantity is so small, that it cannot he regarded as a necessary constituent. It proves only that a trace of hydrogen is retained by charcoal with such force, that it cannot be expelled by the temperature of ignition. T. || Graphite , or, as commonly called black lead , is a natural compound of carbon and iron ; some varieties appear to he a peculiar form of carbon, leaving very little residu- um when burned. Anthracite is another variety. Carbonic Acid. 153 491. The charcoal of wood, besides its use as a fuel, is necessary Sect, iv. to the preparation of that kind of iron which is used for wire ; to the Use in the cementation of steel; and to the preparation of gunpowder. From arts * the powerful affinity which it has for oxygen at a high temperature, it is constantly employed for deoxidating the metals and many other substances. The charcoal prepared from pit-coal, called coke, is less pure, and, Coke, besides other substances, generally contains sulphur, but it has the advantage of being heavier and more compact, in consequence of which it is better adapted for burning in furnaces in which there is a powerful blast of air. H. i. 330. 492. When large quantities of charcoal, in a state of minute divi- Spontane- sion, are left undisturbed, spontaneous combustion generally ensues, and occasionally with charcoal in fragments of considerable size, charcoal. This has been attributed to the action of air and moisture on minute quantities of potassium present in the coal.^ 493. The hypothetical density of the vapour of carbon, calculated Density, as explained at page 33, is 0.4215, and 100 cubic inches of it should weigh 13.0714 grains. Carbon and Oxygen. 494. There are two compounds of carbon and oxygen ; carbonic oxide and carbonic acid gases. Carbonic oxide gas is theoretically Compounds considered as a compound of 100 measures of the vapour of carbon ^ a ^ on and 50 of oxygen condensed into 100 measures ; and carbonic acid ge n .° xy gas, of 100 measures of the vapour of carbon and 100 of oxygen condensed into 100 measures. The composition of these compounds of carbon is as follows Carbon. Oxygen. Equiv. Formula. Carbonic oxide 6,12 or 1 eq. -f- 8 or 1 eq. = 14.12 C-f-O or C. Carbonic acid 6.12 or 1 eq. -f- 16 or 2 eq. = 22.12 C-f-20 or C. Carbonic Acid. 495. Carbonic acid was discovered by Black in 1757, and scribed by him under the name of fixed air. He observed the exist- aem " ence of this gas in common limestone and magnesia, and found that it may be expelled from these substances by the action of heat. It may be obtained by burning carbon, either pure charcoal or the dia- mond, in oxygen gas. The best mode of procuring it for experiment consists in acting upon marble [carbonate of lime) by dilute hydro- Processes, chloric acid. The hydrochloric acid takes the lime, and carbonic acid gas escapes with effervescence. For this purpose the marble, in fragments, is placed in the gas bottle (Fig. 85 or 86) and hydrochloric acid, previously diluted with water, poured upon it : im- * See Aubert’s .paper on this subject in Phil. Mag. and Ann. N. S., Vol. ix. 148, and Hadfield’s and Davies’s papers in Lond. and Edin. Phil. Mag. iii. 20 Composi- tion, de- Carbonic 154 Carbon and Oxygen. W a 145, Chap. Iir. mediate effervescence ensues, and the gas.is Fig. 144. conveyed by the bent pipe to an inverted jar on the shelf of the pneumatic trough, (Figs, 96, 97.) When the action ceases, it may be renewed by the addition of fresh acid until the marble is dissolved. Or the apparatus, (Fig. 144,) may be em- ployed, the acid being poured down the tube 0 , which passes to the bottom of the two necked bottle, a. As carbonic acid gas is heavier than at- mospheric air it may also be obtained by means of the apparatus, (Fig. 145) ; a is a long glass tube proceeding from the bottle contain- ing the marble and acid, and passing down to the bottom of the jar b, which stands with its mouth uppermost. The car- bonic acid will expel the common air from the jar. Properties. 496. Carbonic acid, as thus procured, is a colour- less, inodorous, elastic fluid, which possesses all the physical characters of the gases in an eminent degree, and requires a pressure of thirtysix atmos- pheres to condense it into a liquid. The exact know- ledge of its density is still an important desidera- tum: it is estimated at 1.524 by Dulong and Berzelius, and at 1.5277 by Thomson.* If its specific gravity is es- timated as 1.5239, 100 cubic inches should weigh 47.2586 grs. T. 497. Carbonic acid may be collected over water, but must be pre- served in vessels with glass-stoppers, since water, at common tempe- rature and pressure, takes up its own volume. Fill partly a jar with this gas, and let it stand a few hours over water. An absorption will gradually go on, till at last none will remain. This absorption is infinitely quicker when agitation is used. Repeat the above experiment, with this difference, that the jar must be shaken strongly. A very rapid diminution will now take place. In this manner, water may be charged with rather more than its own bulk of carbonic acid gas ; and it acquires, when thus saturated, a brisk and pleasant taste. Water im- 498. The effervescent quality, and brisk, pungent taste of ferment- pregnated. e( j liquors is due to the presence of this gas, as is likewise that of many mineral waters. The latter are often imitated by condensing carbonic acid into water, either by a condensing pump, of which a description is given by Pepy’s,! or by a Nooth’s apparatus, as repre- sented in Fig. 1464 Absorbed by water. Exp. Nooth’s appa- ratus. * First Principles , i. 143. + Quar. Jour, of Sci. and the Arts, vol. iv. p. 305. t It consists of three vessels, the lowest, a, flat and broad, so as to form a steady support : it contains the materials for evolv- ing the gas, such as pieces of marble and dilute hydrochloric acid, of which fresh supplies may occasionally be introduced through the stopped aperture. The gas passes through the tube b, in which is a glass valve opening upwards, into the vessel c, contain- ing the water or solution intended to be saturated with the gas, and which may occasionally be drawn off by the glass stop-cock. Into this dips the tube of the uppermost vessel d, which occa- sions some pressure on the gas in c, and also produces a circulation and agitation of the water. At the top of d is a conical siopper, which acts as an occasional valve, and keeps up a degree of pressure in the vessels. Fig. 146. 155 Carbonic Acid— properties of. The escape of carbonic acid from fermented liquors may be shown by placing three or four ounces of ale or porter in a jar or tube, (Fig. 147) twenty or more inches in height, on the plate of the air-pump, covering it with a tall receiver, and exhausting the air. The foam will rise and entirely fill the jar or tube. Under a pressure of two atmospheres water dissolves twice its volume of this gas, and so on. It thus becomes brisk and tart, and red- dens delicate vegetable blues. By freezing, boiling, or exposure to the vacuum of the air- pump, the gas is given off. Place a tumbler of water which has been impregnated with this gas (the soda-water of the shops for example) under the receiver of the air-pump, and exhaust it ; the gas will escape so rapidly as to present the appearance , of ebullition ; and will be much more remarkable than “ pi* ~ “ the discharge of air from another vessel of common spring water, confined at the same time under the receiver. 499. If the impregnated water be rapidly congealed, by surround- Expelled ing it with a mixture of snow and salt, the frozen water has more by freezing, the appearance of snow than of ice, its bulk being prodigiously in- creased by the immense number of air bubbles. When water, thus congealed, is liquefied again, it is found, by its taste, and other pro- perties, to have lost nearly the whole of its carbonic acid. 500. Carbonic acid extinguishes burning substances of all kinds, Does not and the combustion does not cease from the want of oxygen only. ItcoSbus- exerts a positive influence in checking combustion, as appears fromtion. the fact that a candle cannot burn in a gaseous mixture composed of four measures of atmospheric air and one of carbonic acid. This may be shown by setting a vessel filled with the gas, with the mouth up- Exp. wards, and letting down a lighted candle. The experiment may be varied by placing near the vessel containing the carbonic acid gas, a similar one filled with oxygen gas, and if the candle, after being extinguished by the carbonic acid be speedily immersed in the oxygen gas it will be relighted, and this may be repeated as long as the gases remain in the vessels. 501. It is not better qualified to support the respiration of animals ;Fata!j» for its presence, even in moderate proportion, is soon fatal.* An ani- ammas “ mal cannot live in air which contains sufficient carbonic acid for ex- tinguishing a lighted candle ; and hence the practical rule of letting down a burning taper into old wells or pits before any one ventures to descend. If the light is extinguished, the air is certainly impure; and there is generally thought to be no danger if the candle conti- nues to burn. But instances have been known of the atmosphere being sufficiently loaded with carbonic acid to produce insensibility, and yet not so impure as to extinguish a burning candle. t When an attempt is made to inspire pure carbonic acid, violent spasm of * By means of this gas, butterflies, and other insects, the colours of which it is de- sirable to preserve, for the purpose of cabinet specimens, may be suffocated better than by the common mode of killing them by the fumes of sulphur. H. t Christison on Poisons, 2d ed. 707. Two instances recently occurred at Cambridge, where a candle continued burning sn an apartment in which two men were found insensible, one was with great diffi- culty recovered, the other died. W. Fig. 147. Sect. IV. Exp. 1 § £ 2 ) Exp. 156 Chap. III. Heavier than atmos pheric air. Exp. Possesses acid pro- perties. Carbon and Oxygen. . the glottis takes place, which prevents the gas from entering the lungs. If it be so much diluted with air as to admit of its passing the glottis, it then acts as a narcotic poison on the system. It is this gas which has often proved destructive to persons sleeping in a con- fined room with a pan of burning charcoal. 502. Carbonic acid gas is heavier than atmospheric air, and may be poured from one vessel into another like water. Place a lighted taper at the bottom of a tall glass jar, and pour the gas out of a bottle into it; it descends and extinguishes the flame, and will remain a long time in the lower part of the jar. Hence in wells and in some caverns, carbonic acid gas frequently occupies the lower parts, while the upper parts are free from it. The miners call it choaJc damp. 503. When combined with water this gas reddens vegetable co- lours. This may be shown by dipping into water, thus impregnated, a bit of litmus paper, or by mixing, with a portion of it, about an equal bulk of the infusion of litmus. This establishes the title of the gas to be ranked among acids. When an infusion of litmus which has been thus reddened, is either heated, or exposed to the air, its blue colour is restored, in consequence of the escape of the carbonic acid. This is a marked ground of distinction from most other acids, the effect of which is permanent, even after boiling. 504. Carbonic acid gas precipitates lime-water — this character of the gas affords a ready test of its presence, whenever it is suspected. Pass the gas as it proceeds from the materials, through a portion of lime-water. This, though perfectly transparent before, will grow milky : Or, mix equal mea- sures of water saturated with carbonic acid, and lime-water. By means of lime-water, the whole of any quantity of carbonic acid, existing in a mixture of gases, cannot, however, be removed, but recourse must be had, in order to effect an entire absorption, to a so- lution of caustic potassa or soda.^ 505. As all common combustibles, such as coal, wood, oil, wax, tallow, &c. contain carbon as one of their component parts, so the combustion of these bodies is always attended by the production of carbonic acid. 1. Let the chimney of a portable furnace, in which charcoal is burning ter- minate, at a distance sufficiently remote to allow of its being kept cool, in the bottom of a barrel, provided with a moveable top, or of a large glass vessel, having two openings. A small jar of lime-water being let down into the tube or vessel, and agitated, the lime-water will immediately become milky. The gas will also extinguish burning bodies, and prove fatal to animals that are confined in it. 2. Fill the pneumatic trough with lime-water, and burn a candle, in a jar filled with atmospheric air, over the lime-water till the flame is extinguished. On agitating the jar, the lime-water will become milky. The same appearances will take place, more speedily and remarkably if oxygen gas be substituted for common air. H. 1.351. And of res- 506. It is also produced by the respiration of animals ; hence it is piration. detected often in considerable proportion, in crowded and illuminated rooms, which are ill-ventilated, and occasions difficulty of breathing, giddiness, and faintness. Test of its presence. Exp. A product of combus- tion, Exp. Exp. * If excess, either of the gas or of its aqueous solution, be added to the lime-water, the precipitate is re-dissolved, carbonate of lime being soluble in carbonic acid. Carbonic Acid — solidified . 157 The production of carbonic acid, by respiration, may be proved by Sect, i v. blowing the air from the lungs, with the aid of a quill, through lime- water, which will become milky. 507. Carbonic acid retards the putrefaction of animal substances. Retards pu- It exerts powerful effects on living vegetables. These effects, j^fefocts' however, vary according to the mode of its application. Water sa- onve g eta _ turated with this gas, proves highly nutritive when applied to the bles. roots of plants. The carbonic acid is decomposed, its carbon form- ing a component part of the vegetable, and its oxygen being liberated in a gaseous form. On the contrary, carbonic acid, when a living vegetable, is con- fined in the undiluted gas over water, is injurious to the health of the plant, especially in the shade. It is this process of nature that appears to be the principal means of preventing an excess of carbonic acid in the general mass of the atmosphere, which, without some provision of this kind, must gradu- ally, in the course of ages, be rendered less and less fit for respira- tion. 508. Carbonic acid was first obtained in a liquid form by Faraday, Liquefac- from carbonate of ammonia and sulphuric acid. Very strong tubes carbonic are required, and even those which have held fluid carbonic acid for acid, many days, have, upon a slight elevation of temperature, spontane- ously exploded with great violence. Great care is necessary, and the protection of a glass mask, goggles, &c., in repeating the pro- cess with glass tubes. The liquid acid is a limpid, colourless body, extremely fluid, distilling readily at the difference of temperature between 32° and 0°. Its refractive power is much less than that of water. Its vapour exerts a pressure of thirtysix atmospheres at a temperature of 32°.^ A safer method of obtaining the liquid acid as contrived by Thil- Solidifica- lorier, is with the aid of a strong metallic apparatus in which it may tioa of * be condensed mechanically. When allowed to escape from a stop- cock attached to the receiver, the liquid gas expands with so much rapidity that great absorption of caloric attends, and a part of the gas is rendered solid, resembling snow. A reduction of temperature to — 162° is said to have been obtained by this means ; hence mercury can be readily frozen by it.f * Faraday, Phil. Trans. t See Lond. and Edin. Phil. Mag. x. 158. The experiments of Thillorier have been repeated by Mitchell of Philadelphia, by means of an apparatus consisting of two strong vessels of cast iron. The two vessels can be firmly attached, a stop-cock being interposed. The, gas is generated in the larger vessel. The materials employed, are Ulbs. of bicarbonate of soda, 24 ounces of water, and 9 ounces of sulphuric acid ; the latter, being placed in a smaller vessel which is enclosed in the cylinder, is not allowed to come in contact with the bicarbo- nate of soda until the aperture by which it is introduced has been firmly secured, when the cylinder is brought to a horizontal position and the liquids are mingled. The re- ceiver, previously cooled by ice, is now attached, and the liquid carbonic acid allowed to pass into it, from which it may be permitted to escape as wanted. The pressure at 32° was found by Mitchell to be 36 atmospheres, at 66°, 60 atmos- pheres, and at 86°, 72 atmospheres. The condensed acid obtained by Mitchell, when recently formed was about the weight of carbonate of magnesia, perfectly white, and of a soft and spongy texture. It evaporates rapidly, becoming colder, and the mass may be kept for some time. A quantity weighing 346 grains lost from three to four grains per minute at first, but did not entirely disappear for three hours and a half. The na- 158 Carbon and Oxygen. Chap, hi. 509. Carbonic acid combines with bases, and the compounds are Carbon- termed carbonates : as it is usually retained in combination by very ates. feeble affinity, so it is evolved from most of the carbonates by the simple operation of heat. Thus chalk, when heated, gives out car- Efferves- bonic acid, and becomes quicklime. It is also evolved from its com- cence. binations by most of the other acids, with effervescence. ascertain ° f The quantity of carbonates in any saline mass, may be as- ingquanti- certained by noting the quantity of carbonic acid disengaged. This ties of car- may be done by measuring the volume of gas, or by ascertaining its bonic acid. we f ght> y * In the first case, the easiest method of proceeding is to fill a long tube (closed at one end, and capable of containing two or three cubic inches), nearly full of mercury, filling it completely afterwards with hydrochloric acid diluted with an equal quantity of water. The thumb is placed over this, after dipping it in oil, or rubbing it over with a little gas lute,* the tube inverted, and placed in a cup of mercury. One or two grains of the solid salt are then introduced into the tube, (the experiment is most easily performed with a fragment of some carbonate,) and the moment it rises to the top, and comes in contact with the acid, the car- bonic acid is disengaged with effervescence, depressing the mercury, and its amount is estimated by examining the volume which it occupies and making the usual corrections ; one equivalent of carbonic acid indicating one equivalent of a carbonate, whatever may be the nature ot the base. In the other method, a thin glass flask or bottle, of the form shown in Fig. 148, is placed on one of the scales of a balance with some hydrochloric acid, big. 148. and accurately counterpoised along with a given weight of the sub- stance under examination, and the bent tube passing through a cork, which fits to the mouth of the flask. This tube is put in when the acid and carbonates are mixed together, to prevent any loss from particles of liquid that may be thrown up during the effervescence, and it is evident that, by adding weights to the scale on which the glass vessel is placed (when the effervescence has finished), till it is again counterpoised, they will indicate the quantity of carbonic acid that has been evolved ; before weighing it the second time, the cork and tube should be taken out till the car- bonic acid gas in the interior has been blown out gently by a pair of bellows. t A convenient mode is by means of an alltalimeter. Into a tube sealed at one end, 9£ inches long, |ths of an inch in diameter, and as cylindrical as possi- Alkalime- ble in its whole length, pour 1000 grains of water, and with a file or diamond, mark ter. the place where its surface reaches, divide the space occupied by the water into tural temperature was 76°— 79°. The temperature of the mass continued to decrease, which was accelerated by any means for increasing the evaporation. At its formation the carbonic snow depressed the thermometer to about— 85. The greatest cold pro- duced hy the solid acid in the air was — 109°, under an exhausted receiver — 136°. Mercury placed in a cavity in it and covered up with the same substance, was frozen in a few seconds. At about — 110° liquid sulphurous acid was frozen, and at — 130° alcohol of .793 assumed a viscid and oily consistence, and at — 146° was like melted wax. Alcohol of .820 froze readily. A piece of solid carbonic acid applied to the skin produced a ghastly white spot, and in fifteen seconds raised a blister. Its specific gravity at 32° F. was .93, at 43° 5, .8325. Liquid carbonic acid did not appear to act upon any of the metals or oxides. When the liquid acid has been frozen in a tube of glass, the lube may be melted off and hermetically sealed. Such a tube will always retain the liquid, or gas; the former, if in sufficient quantity, at all tem- peratures, if not, th,e latter alone will be found in it at high temperatures. In such a tube moisture appears at 56°, and a constantly elongating cylinder of liquid forms as the coldness increases: at 32° the cylinder is about half an inch in length. See Mitchell’s paper and plate in the Jour, of Franklin Institute , vol. xxii, and Amer. Jour. xxxv. 346. * This is a very convenient lute for rendering joints in apparatus tight, and is com- posed of one part of wax and three of lard heated together until of uniform consistence. t Reid. Carbonic Oxide. 159 100 equal parts, as shown in Fig. 140. Opposite to the numbers 23, 44, 48, 96, 54, 63, and 65 draw a line, and at the first write soda, at the second potassa, at the third carbonate of soda, and at the fourth carbonate of potassa. Prepare a dilute acid having the specific gra- vity of 1.127 at 60°, which may be made by mixing one measure of concentrated sulphuric acid with four measures of distilled water. This is the standard acid to be used in all the experiments, being of — such strength that when poured into the tube till it reaches either of the four marks just mentioned, we shall obtain the exact quantity necessary for neutralizing 100 grains of the alkali written opposite to it. If, when the acid reaches the words carb. potassa , and when, _t consequently, we have the exact quantity which will neutralize 100 — grains of that carbonate, pure water be added until it reaches 0, or the beginning of the scale, each division of this mixture will neutral- ize one grain of carbonate of potassa. All that is now required, in order to ascertain the quantity of real carbonate in any specimen of pearlash, is to dissolve 100 grains of the sample in warm water, filter to remove all the insoluble parts, and add the dilute acid in succes- sive small quantities, until, by the test of litmus paper, the solution is exactly neutralized. Each division of the mixture indicates a grain of pure carbonate. It is convenient in conducting this process, to set aside a portion of the alkaline liquid, in order to neutralize the acid, in case it should at first be added too freely.* Carbonic Oxide A 511. Carbonic Oxide , discovered by Priestley, is usually obtained Carbonic by subjecting carbonic acid to the action of substances which abstract oxide ’ a portion of its oxygen. Upon this principle, carbonic oxide gas is produced by heating in an iron retort a mixture of chalk and char- coal ; or of equal weights of chalk and iron or zinc filings. It is also obtained by the distillation of the white oxide of zinc with one Howob- eighth of its weight of charcoal, in an earthen or glass retort ; from tained > the scales which fly from iron in forging, mixed with a similar pro- portion of charcoal ; from the oxides of lead, manganese, or, indeed, of almost every imperfect metal, when heated in contact with pow- dered charcoal. It may also be obtained from the substance which remains after preparing acetic acid from acetate of copper. But the mixture that affords it most pure, is equal parts of carbonate of ba- ryta and clean iron filings ; these should be introduced into a small earthen retort, so as nearly to fill it, and exposed to a red heat : the first portion of gas being rejected as mixed with the air of the retort, it. may afterwards be collected quite pure. 512. A very elegant mode of preparing carbonic oxide has been Dumas’s suggested by Dumas. t The process consists in mixing binoxalate process, of potassa with five or six times its height of concentrated sulphuric acid, and heating the mixture in a retort or other convenient glass vessel. Effervescence soon ensues, owing to the escape of gas, con- sisting of equal measures of carbonic acid and carbonic oxide gases ; and on absorbing the former by an alkaline solution, the latter is left in a state of perfect purity. To comprehend the theory of the pro- cess, it is necessary to premise, that oxalic acid is a compound of carbonic acid and carbonic oxide, or at least its elements are in the proportion to form these gases ; and that it cannot exist unless in combination with water or some other substance. Now the sulphu- ric acid unites both with the potassa and water of the binoxalate, Fig. 149. O Sect. IV. Q 5 10 15 20 25 30 35 40 45 5 O 55 60 65 70 75 80 85 90 95 100 * Faraday’s Chem. Manip. t Edin. Jour, of Sci. vi. 350. t For Composition, &,c. see (494.) 160 Chap III. Properties. Explodes witn oxy- gen. Density. Analysis. And spongy platinum. Carbon and Oxygen. and the oxalic acid being thus set free, is instantly decomposed. Oxalic acid may be substituted in this process for binoxalate of potassa. It may also be obtained by transmitting carbonic acid gas over charcoal ignited in a porcelain tube. The acid gas combines with an additional dose of charcoal, loses its acid properties, and is con- verted into carbonic oxide. 513. Carbonic oxide gas is colourless and insipid. It does not affect the blue colour of vegetables in any way ; nor does it combine, like carbonic acid, with lime or any of the pure alkalies. It is very sparingly dissolved by water. Lime-water does not absorb it, nor is its transparency affected by it. 514. The nature of this gas was first made known by Cruickshank, of Woolwich, in 1S02,* and about the same time it was examined by Clement and Desormes.t It extinguishes flame, and burns with a pale blue lambent light, when mixed with, or exposed to atmospheric air. The temperature of an iron wire heated to dull redness was found by Davy sufficient to kindle it. 515. A mixture of carbonic oxide and oxygen gases may be made to explode by flame, by a red-hot solid body, or by the electric spark. If they are mixed together in the ratio of 100 measures of carbonic oxide and rather more than 50 of oxygen, and the mixture is inflam- ed in Volta’s eudiometer by electricity, so as to collect the product of the combustion, the whole -of the carbonic oxide, together with 50 measures of oxygen, disappears, and 100 measures of carbonic acid gas occupy their place. From this fact, first ascertained by Berthollet, and since confirmed by subsequent observation, it follows that carbonic oxide contains half as much oxygen, aud as much carbon, as carbonic acid. Accordingly its density should be 0.4215 (sp. gr. of carbon va- pour)-|-0.5512 (half the sp. gr. of oxygen gas) =0.9727, which is the number found experimentally by Dulongand Berzelius. Hence 100 cubic inches should weigh 30.1650 grains. T. 516. It is extremely noxious to animals, and fatal to them if con- fined in it. When respired for a few minutes it produces giddiness and fainting. If pure it almost instantly causes profound coma. 517. When a mixture of hydrogen and carbonic acid gases is electrified, a portion of the latter yields one half of its oxygen to the former; water is generated, and carbonic oxide produced. On elec- trifying a mixture of equal measures of carbonic oxide and protoxide of nitrogen, both gases are decomposed without change of volume, and the residue consists of equal measures of carbonic acid and ni- trogen gases. The carbonic oxide should be in very slight excess, in order to ensure the success of the experiment. On this fact is founded Henry’s method of analyzing protoxide of nitrogen. 518. When a mixture of carbonic oxide with more than half its volume of oxygen gas, is exposed over mercury, in contact with spongy platinum, to a temperature between 300° and 310° F., it be- gins to be converted into carbonic acid, and at a heat of a few de- * Nicholson’s 4to Jour. v. t Ann. de Chim. xxxix. 161 Sulphur. grees higher, is wholly acidified in the course of a few minutes. Sect, v. Mixtures of these two gases are, howfever, very slowly acted upon by the platinum sponge at common temperatures.^ 519. None of the metals exert any action upon this gas, except By potassi- potassium and sodium, which at a red heat, burn in it by abstracting so ' its oxygen, and carbon is deposited. Section V. Sulphur. Symb. Sp. Gr.i Equiv. S. 6.6558 air =1 By Vol. 16.66 96.60 Hyd.= I “ Wght. 16.1 520. Sulphur is a brittle substance, of a pale yellow colour ; insi- Properties, pid and inodorous, but exhaling a peculiar smell when heated. Its specific gravity is 1.99. It becomes negatively electrical by heat and by friction. Sulphur is principally a mineral product,! and occurs massive and crystallized in the form of an oblique rhombic octohedron. Its crys- tals are in a high degree doubly refractive. Massive sulphur is chiefly brought from Sicily ; it occurs native, Native sul- and is found associated with sulphate of lime, sulphate of p u ’ strontia, and carbonate of lime : it is common among volcanic products. Sulphur occurs also in some mineral waters, partly in a free and partly in a combined state, in combination with soda.§ Roll-sulphur is chiefly obtained from native metallic sulphurets, Roll, which are roasted and the fumes received into a long chamber of brick-work, where the sulphur is gradually deposited : it is then pu- rified by fusion, and cast into sticks. It conducts heat imperfectly, and, if grasped by the warm hand, splits with a crackling noise. 521. The fusing point of sulphur is 216° F. Between 230° and Action of 280° it is as liquid as a clear varnish, and of the colour of amber ; tieat ‘ at about 320° it begins to thicken, and acquire a red colour; on in- creasing the heat, it becomes so thick that it will not pour. From 482° to its boiling point it becomes thinner, but never so fluid as at 248°. When the most fluid sulphur is suddenly cooled, it becomes brit- tle, but the thickened sulphur, similarly treated, remains soft, and more soft as the temperature has been higher. In this state it is ap- Use. plied to taking impressions from engraved stones, &c.|| 522. Fused sulphur has a tendency to crystallize in Cooling, and Crystalli- by good management regular crystals may be obtained. zation of, For this purpose several pounds of sulphur should be melted in a crucible ; and when partially cooled, the outer solid crust should be pierced, and the cruci- ble quickly inverted so that the fluid portion within may gradually flow out, on breaking the solid mass, when quite cold, crystals of sulphur will be found in the interior. Fused sulphur will remain fluid at common temperatures, and so- lidify when touched by a fragment of sulphur or a thread of glass. * Phil. Trans. 1824, p. 271. t In state of vapour. t It is said to have been detected in several vegetables and in gum arabic. — Jame- son’s Jour. xiv. 172. § Johnson’s report, Rep. Brit. Assoc. 1832. II See directions in Dumas’s Traitd de Chinn. 1 . 135. 21 162 Sulphur. Cha p. III. Vaporiza- tion of. Lac sul- phuris. Contains hydrogen. Density of its vapour. Test of the purity of sulphur. Products of its combus- tion. Equivalent. 52 3. Sulphur is very volatile. It begins to rise slowly in vapour even before it is completely fused. At 550° or 600° F. it volatilizes rapidly, and condenses again unchanged in close vessels. Common sulphur is purified by this process; and if the sublimation be con- ducted slowly, the sulphur collects in the receiver in the form of de- tached crystalline grains, called fioioers of sulphur. In this state however, it is not quite pure ; for the oxygen of the air within the apparatus combines with a portion of sulphur during the process, and forms sulphurous acid. The acid may be removed by washing the flowers repeatedly with water. 524. Sulphur is insoluble in water, but has been supposed to unite with it under favorable circumstances, forming what has been called Lac snlphuris and hydrate of sulphur, but which is consider- ed by Berzelius as sulphur with a minute portion of hydrogen. It dis- solves in boiling oil of turpentine, and is also soluble in alcohol if both substances are brought together in the form of vapour. The sulphur is precipitated from the solution by the addition of water. 525. Sulphur retains a portion of hydrogen so obstinately that it cannot be wholly freed from it either by fusion or sublimation. Davy detected its presence by exposing sulphur to Voltaic electricity, when some hydrosulphuric acid gas was disengaged. The hy- drogen, from its minute quantity, can only be regarded as an acci- dental impurity, and as not essential to the nature of sulphur. 526. The density of sulphur vapour was found by Dumas to lie between 6.51 and 6.617, and by Mitscherlich to be 6.9 its density by calculation (page 32) is 6.6558. Hence, could the vapour con- tinue as such at 60° F. and 30 bar., 100 cubic inches should weigh 206.4076 grains. 527. The purity of sulphur may be judged of by heating it gradu- ally upon a piece of platinum leaf ; if free from earthy impurities, it should totally evaporate. It should also be perfectly soluble in boil- ing oil of turpentine. t 528. When sulphur is heated in the open air to 300° or a little higher, it kindles spontaneously, and burns with a faint blue light. In oxygen gas its combustion is far more vivid ; the flame is much larger, and of a bluish white colour. Sulphurous acid is the pro- duct in both instances ; — no sulphuric acid is formed even in oxygen gas unless moisture be present. The oxygen in the oxide and acid of neutral sulphates is in the ratio of 1 to 3 ; so that when the composition of a metallic oxide, and the quantity of acid by which it is neutralized are known, the equivalent of sulphur may be calculated. On this principle has Berzelius inferred, from the composition of sulphate of the oxide of lead, that the equivalent of sulphur is 16.12; and the number ob- tained by Turner in the same way from the same salt and from sul- phate of baryta, is 16.09. As a mean of these results, 16.1 may be taken as the equivalent of sulphur. The number 16 is, for many purposes, a sufficient approximation. * Ann. de Chim • et de Phys. lv. 8. tAikin’s Did ■ article Sulphur. It sometimes contains arsenic, for detecting which see Brande’s Jour. N. S. v. Sulphurous Acid. 163 Sulphur and Oxygen. Sulphurous Acid. Composition. Form. Sp. Gr. Chem. Equiv. Sul. Oxy. Equiv, S-j-20 or S 2 . 2117 air =?l By Vol. 100 . 16.1 or 1 eq.4-16 or 2 eq. = 32.1 32.10 Hyd.=l “ Wght. 32.1. Sect. V. 529. Sulphurous acid is a gaseous body and may bd obtained by How ob. burning sulphur in common air or oxygen gas under a bell glass. tained * It is also procured by abstracting part of the oxygen from sulphuric acid. This may be done in several ways. If chips of wood, straw, or cork, oil or other vegetable matters be heated in strong sulphuric acid, the carbon and hydrogen of those substances deprive the acid of a part of its oxygen, and cpnvert it into sulphurous acid. Nearly all the metals, with the aid of heat, have a similar effect. 530. The most usual method is by putting two parts by. weight, of mercury, and three of sulphuric acid into a glass retort, and then raising the heat; sulphurous acid gas is formed, and may be col- lected and preserved over quicksilver. Half an ounce of mercury is sufficient for the production of several pints of the gas. This gas may also be obtained by introducing powdered charcoal into a retort and pouring over it concentrated sulphuric acid, until on shaking it, the mass appears moist. On heating, a constant stream of a mixture pf two volumes sulphurous acid and one of carbonic acid gases is given off, which continues till the mass becomes dry, 5 ^ As this gas is heavier than air, when a mercu- rial trough is not at hand, the student may collect it in bottles, by the arrangement shown in Fig. 150. The bent tube passes loosely through the neck of the' receiver, but is fixed to the gas bottle by means of plaster-of-paris and water. 531. Water takes up 33 times its bulk of this gas, it must therefore be collected in jars or bot- tles filled with mercury and over the mercurial trough, t * Knezaurek in Baumgartner’s Zeitschrift, lx. t The apparatus for collecting this and other gases which are absorbed by water, is similar to that for collecting other gases. The trough may be made of wood, marble, soapstone, or, what is preferable, cast-iron, well varnishsd to prevent its rusting. Fig- 151 represents a convenient mer^- curial trough 3 whieh may be 17 inches long, 7 broad, and 5 deep. The mercury does notrpass under the shelf, so that the body of the trough is only about half as broad below the shelf as above, and it is rounded at the bottom to save an unneces- sary quantity of mercury. The four niches' a a a a, at the edge of. the shelf, are to receive the beaks of retorts, the jars being placed over them 3 the rods attached to two of the sides of the trough are intended tr> steady any tall jar left upon the shelf. Such a trough requires about 140 pounds of mercury, when a number of jars are used. Also see Fig. 105. The jars for the mercurial trough should he at least One tenth of an inch in thick- ness, though not more tban-two inches in diameter; they ought also to be ground at the edges that they may be removed easily, when full of gas, on a flat glass plate rub- bed over with a little gas r lute, without losing auv of their contents. The mercurial trough should be placed in a large sheet iron tray, to prevent the loss of mercury. Blotting paper is constantly required to remove any acid or water that may collect on the surface of the mercury, and. after auy gcicl gas has been prepared over it, the mer- 164 Chap. III. Exp. Exp. Bleaches. Exp. Noxious. Davy’s an- alysis. Decomposi- tion. Converted into sul- phuric acid. Sulphur and Oxygen. Remove a jar, filled with the gas, by means of a flat glass plate held firmly to it, or place the thumb or finger on the mouth of a small bottle or tube filled with the gas, and take it oft under water. The gas will be absorbed and the water be forced up the vessel with violence. The acid property of the gas will also be evident if the water be coloured with purple cabbage. The experiment may be varied by inverting the vessel over mercury, and pass- ing a small quantity of water up through the mercury ; the latter will rise, and the water will be seen to absorb many times its own bulk of the gas. 532. Sulphurous acid has considerable bleaching properties. It reddens litmus papeT, and then slowly bleaches it. Most vegetable colouring matters, such as those of the rose and violet, are speedily removed, without being first reddened. It is remarkable that the colouring principle is not destroyed ; for it may be restored either by a stronger acid or by an alkali. Prepared by the combustion of sul- phur, it is much used for bleaching cotton goods* * and also for whit- ening silk and wool ; in wine countries it is sometimes used to check vinous fermentation. It restores the colour of sirup of violets, which has been reddened by other acids. A pleasing instahee of its efTect on colours, may be exhibited by holding a red rose over the blue flame of a common match, by which the colour will be discharged wherever the sulphurous acid comes in contact with it, so as to ren- der it beautifully variegated, or entirely white. If it be then dipped into water, tlto tedness, after a short time will be restored. 533. This gas has a suffocating nauseous odour, and an astrin- gent taste ; it extinguishes flame, and kills animals ; it is exceed- ingly deleterious to vegetables, even in very minute quantity and proportion.! 534. Davy proved that sulphurous acid gas contains exactly its own volume of oxygen,! and consequently the difference in the weights or specific gravity of these gases (2.2117 — 1.1024=1.1093), gives the weight of sulphur combined with the oxygen. The sul- phur and oxygen are thus found to be in the ratio of 1.1093 to 1.1024 or 16.1 to 16. T. 535. Sulphurous acid suffers no change at a red heat, but if mixed with hydrogen, and passed through a red-hot tube, water is formed and sulphur deposited ; under the same circumstances, it is also de- composed by charcoal, by potassium and sodium, &c. 536. Sulphurous acid is converted to the state of sulphuric acid by restoring oxygen to it. A mixture of oxygen and sulphurous acid gases, both perfectly dry, and standing over mercury, is not diminished during some months ; but if a small quantity of water be added, the mixture begins to diminish, and sulphuric acid is formed. Or if water impregnated with sulphurous acid be exposed to oxygen gas in a tube, the oxy- gen in 10 or 14 days is imbibed and sulphuric acid formed. The cury should always he washed with water, and dried with a towel and blotting paper. A red-hot poker held for a short lime in the mercury enables this to be done more effectually ; it is in this manner also, that mercury is most conveniently brought to a proper temperature when it is required to be heated for particular experiments The beak of the retort must be placed near the surface of the mercury, that the gas may have to overcome as little resistance as possible in rising through the heavy fluid j should this not he attended to. the retorts may he hroken by the pressure from within. No gas should he collected till the atmospheric air has been all expelled from the re- tort. See Reid’s Elements of Prac. Chem. * Quart. Jour, of Sci. iv. 196. + See Turner’s experiments on the effect of gases on vegetables , Brewster’s Jour m Jan. 1828. t Elements, 273, 165 Sulphuric Acid. same gases in a state of mixture, by the action of electricity or by sect, v being driven through a red-hot porcelain tube, afford sulphuric acid. The proportions required for mutual saturation are two measures of sulphurous acid and one of oxygen gas. To a portion of water saturated with sulphurous acid gas add a little oxide Exp. of manganese, a substance that contains much oxygen loosely combined ; the pungent smell of the water, and the other characteristics of sulphurous acid will soon disappear. H. 1. 385. 537. Sulphurous acid combines with metallic oxides, and forms salts which are called sulphites , which are decomposed by sulphuric acid, and then emit the characteristic odour of sulphurous acid. 538. Liquid sulphurous acid is obtained by transmitting the dry Liquid pure gas through a glass tube surrounded by a freezing mixture of aci ' snow and salt. It boils at 14°, and from the rapidity of its evapora- tion causes intense cold.^ 539. Faraday, by producing sulphurous acid from mercury and Liquefac- concentrated sulphuric acid sealed up in a bent tube, obtained it in a liquid state, very limpid and fluid, and quite colourless. Its refrac- acid gas. tive power appeared to be nearly equal to that of water. It does not solidify at a temperature of 0° F. When a tube containing it is opened, it does not rush out as with an explosion, but a portion of the liquid evaporates rapidly, cooling another portion so much as to leave it in a liquid state under common barometric pressure. It ra- pidly dissipates, however, without appearing invisible fumes, but with a strong odour of sulphurous acid, leaving the tube perfectly dry, A piece of ice dropped into the fluid instantly made it boil from the heat communicated to it. The specific gravity of liquid sulphurous acid is about 1.42, at 45° F. it exerts a pressure of about two atmospheres.! Sulphuric Acid. Composition. Form. Sp . Gr. ( anhydrous ) Chem. Equiv. Sulph. Oxy. Equiv . ... 2.7629 air =1 By Vol. 100. 16.1 or 1 eq.-p24 or 3 eq— 40.1 S+30 or S 40.40 Hyd.^i “ Wght. 40 1. 540. Sulphuric acid has been long known under the name of oil Fuming of vitriol, and is supposed to have been discovered by Basil Yalen- Nordhau- tine in the 15th century. It is prepared in large quantities for the sen. purposes of the arts. At Nordhausen, in Germany, the sulphate of oxide of iron (green vitriol) is decomposed by heat, and a dense oily liquid of a dark colour is obtained, which, from its emitting white fumes, is known as fuming sulphuric acid. It has a specific gravity of 1.896 or 1.90.4 541. In the United States and most other places, sulphuric acid is Usual pro- manufactured from sulphur and nitrate of potassa. cess, The mixture is burned in a large room or chamber lined with lead and cover- ed to the depth of several inches with water. The sulphur is converted into sulphurous acid during its combustion, and a portion of it into sulphuric acid by combining with some of the oxygen of the nitre, nitrous acid and binoxide of nitro- gen being disengaged. The sulphurous acid combines with the nitrous acid and some watery vapour, forming a crystalline compound which is decomposed by * See Bussy’s process in Bost. Jour, of Philos, ii. 359. t Phil. Trans. 1823, p. 190. Sulphurous acid is employed in some diseases under the name of “ Sulphur baths/’ fora description c.f which, see Dumas’ Traits, v ol. i. 152. ? For details see Turner 194, and Amer. Jour Sci. xx. 347. 166 Chap. III. Theory illustrated. Impurities. Arsenious acid. Detected. Sulphur and Oxygen. the water at the bottom of the chamber, being converted into sulphuric acid, * which remains in combination with the water, and binoxide of nitrogen gas, which is disengaged. All the binoxide rises in the chamber, and mixing with a fresh quantity of atmospheric air, combines with the oxygen and forms a dense ruddy vapour (nitrous acid), which immediately falls down in consequence of its great specific gravity, and meeting with more sulphurious acid and watery vapour, a crystalline compound is again formed, which is resolved as before into sulphuric acid and binoxide of nitrogen. In this manner, a small quantity of nitre is made to communicate or hand over, as it were, a large quantity cf oxygen from the air to the sulphurous acid, and the same series of combinations and decompositions goes on till the water at the bottom of the chamber has become strongly acid. It is then boiled in leaden vessels to expel a part of the water, and the concen- tration finished in large glass retorts in a sand bath, or in platinum retorts placed over the open fire. 542. The theory of the preparation of sulphuric aeid may be illus- trated very beautifully on the small scale by making sulphurous acid and nitrous acid meet together in a glass vessel, and as the experi- ment is intended solely for illustration, the sulphurous acid may be prepared by the decomposition of sulphuric acid. Into one of the small retorts, (Fig 152,) which should be large enough to hold about three or four ounces of water when full, — put 400 grains of mercury and <>00 grains of sulphuric acid, and into the other bO or 90 grams of sugar, lleat the first retort by a chauffer, and when the sulphu rous acid begins to come over, pour 300 grains of nitric acid over the sugar, previ- ously diluted with an equal bulk of water, and heat the retort gontly till the nitrous acid fumes begin to come over, which are formed by the sugar attracting oxygen from the nitric acid. When the gases meet in the large jar, (into which the re- torts are fixed by being ground to the tu- bulures, or having their beaks passed through corks fitted to them,) a crystalline compound is soon deposited on the sides of the vessel in beautiful dendritical crystals, which often cover its whole surface. Remove the retorts when either the sulphurous or nitrous acid ceases to come over, and pour a little water into the vessel , a brisk effervescence will take place wherever it comes in contact with the crystalline compound, which is resolved into binoxide of nitrogen and sulphuric acid, the former producing ruddy coloured fumes as it comes into contact with the air, and the latter being retained in combination with the water. Reid. 543. Sulphuric acid obtained by the usual process is not pure, being contaminated by potassa and the oxide of lead, and sometimes iron, the first derived from the nitre, and the two latter from the leaden chamber. To separate them the acid should be distilled from a glass or platinum retort. The former may be safely used by putting into it some pieces of platinum leaf, which causes the acid to boil freely on applying beat, without danger of breaking the ves- sel. Arsenious acid, derived from arsenic in the sulphur used in the manufacture, has been lately detected in most of the oil of vitriol made in Germany, and from that source arsenic is introduced into preparations for which such acid is employed, as into phosphorus and hydrochloric acid. It is discovered by diluting with water and trans- mitting through the solution hydrosulphuric acid gas, which causes orpiment to be formed. The oil of vitriol may be purified from ar- senious acid by adding a little hydrated peroxide of iron before dis- tilling. T. Fig. 152. 167 Sulphuric Acid— Analysis of. j The oil of vitriol of commerce often contains sulphate of lead, Sect, v. which may be detected in the cold acid, by adding- a few drops Hayes’s of hydrochloric acid. The precipitate is allowed to subside and the test f°r sul- clear acid decanted* feld 544. Sulphuric acid of commerce is a limpid, colourless fluid, of properties, a thick and oily consistence, having a specific gravity of 1.84; it is acrid and caustic, and even when largely diluted with water produc- es a very sour liquid. 545. It boils at 620° and freezes at — 15°, contracting at the same Boiling time considerably in its dimensions. But the temperature at which point ' the diluted acid congeals is singularly modified by the quantity of water which it contains. At the specific gravity of 1.780 it freezes at 45° ; but if the density be either increased or diminished, a great- er cold is required for its congelation.! Its boiling point diminish- es with its dilution. 546. It is acrid and caustic, and when diluted with water, pro- duces a very sour liquid. Whep mixed suddenly with water, (66) Mixture considerable heat is produced. Four parts by weight, of concentra- w dh water, ted sulphuric acid, and one of water, when mixed together, each at the temperature of 50° F. have their temperature raised to 300°. The greatest eleyation of temperature, lire finds to be occasioned by the sudden mixture of 73 parts by weight of strong sulphuric acid with 27 of water. 547. It rapidly absorbs water from the atmosphere. Even a Im h lbes boiling temperature, when it is concentrated, does not prevent its 018 me * taking up moisture from the air ; hence it cannot be concentrated so well in an open ;as in a close vessel, on which account, retorts of glass or platinum, are used for the last stage of its concentration by the manufacturers. It chars animal and vegetable substances, and is apt to acquire a brown tinge from any small particles of straw, resin, or other mat- ters that may accidentally have fallen into it. 548. The strength of sulphuric acid is best judged of by diluting a known weight of the acid moderately with water, and while i ng t h e warm, adding pure anhydrous carbonate of soda, until the solution strength of is exactly neutral. Every 53.42 parts of the carbonate required to acid 1 ™” 0 produce this effect, correspond to 40.1 parts of real sulphuric acid. For common purposes the strength of the acid may be estimated from its specific gravity.! 549. The decomposition of sulphuric acid may be effected by pas- sdphurfc 0 sing it through a red-hot platinum tube, when it is resolved into sul- add, phurous acid, oxygen and water. When heated with charcoal, sulphuric acid gives rise to the pro- duction of carbonic and sulphurous acids ; with phosphorus it. pro- duces phosphoric and sulphurous acids; and, with sulphur, sul- phurous acid is the only product. It is decomposed by several of the metals, which become oxidized, and evolve sulphumus acid, as shown in the production of this acid, by boiling sulphuric acid with mercury (530), tin, lead, &c. * Hayes in Amer. Jour. xvii. 195. t Keir, Irish Phil. Trans, iv. 88. t For table of strength of this acid of different densities, see Appendix. 168 Chap. III. By galvan- ism. Uses. Tests. How ob- tained. Peculiar relations. Process. Sulphur and Oxygen. The liquid acid is also decomposed by platinum wires, communi- cating with the extremities of a galvanic pile. 550. Sulphuric acid is largely consumed in a variety of manu- factures. It is used by the makers of nitric, hydrochloric, citric, and tartaric acids ; by bleachers, dyers, tin-plate makers, brass-founders, gilders, &c. 551. Baryta in solution detects the presence of sulphuric acid, a white insoluble sulphate of baryta being precipitated. The precipi- tate heated with charcoal before the blow-pipe is decomposed ; on moistening it with water and touching it with a solution of a salt of lead, the sulphur renders the lead black. This acid gives a copious white precipitate with soluble salts of lead. Hyposulphurous Acid. Composition. Form. Sulph. Oxy. Equiv. 2S+20 or de of 602. This compound is formed by heating selenium in a limited quantity of atmospheric air, and by washing the product to separate selenious acid, which is generated at the same time. It is a colour- less gas, very sparingly soluble in water, and is the cause of the pe» culiar odour which is emitted during the oxidation of selenium. 180 Chlorine . Chap. Ill, Selenious add. Decompo- sed. Selenic acid. Properties. Action itpon metals. Time or discovery. Synonyms. Selenious Acid. Form. Selen. Oxy. .Se+20 39.6 +16 or 2 eq.=55.8 603. This acid is prepared by digesting selenium in nitric or nitro- hydrochloric acid till it is completely dissolved. On evaporating the solution to dryness, a white residue is left, which is selenious acid. By increase of temperature, the acid itself sublimes, and condenses again unchanged into long four-sided needles. It attracts moisture from the air, and dissolves in alcohol and water. It has distinct acid properties, and its salts are called selenites. 604. Selenious acid is readily decomposed by all substances which have a strong affinity for oxygen. Selenic Acid. Se+30 39.6 -1-24 or 3 eq =63.6 605. This acid is prepared by fusing nitrate of potassa or soda with selenium, a metallic seleniuret, or with selenious acid or any of its salts.* 606. Selenic acid is a colourless liquid, which may be heated to 536° without appreciable decomposition ; but above that point de- composition commences, and it becomes rapid at 554°, giving rise to disengagement of oxygen and selenious acid. When concentrated by a temperature of 329° its specific gravity is 2.524; at 5l2° it is 2.60, and at 545° it is 2.625, but a little selenious acid is then present. Selenic acid has a powerful affinity for water, and emits as «nuch heat in uniting with it as sulphuric acid does. Like this acid it is not decomposed by hydrosulphuric acid, and hence this gas may he employed for decomposing seleniate of the Oxides of lead or cop- per. Selenic acid dissolves zinc and iron with disengagement of hydrogen gas, and copper with formation of selenious acid. It dis- solves gold also, but not platinum. Sulphurous acid has no action on selenic acid, whereas selenious acid is easily reduced by it. Con- sequently, when it is wished to precipitate selenium from selenic acid, it must be boiled with hydrochloric acid before sulphurous acid is added. Selenic and sulphuric acids are not only analogous in composi- tion and in many of their properties, but the similarity runs through their compounds with alkaline substances, their salts resembling each other in chemical properties, constitution, and form. T. Section X. Chlorine. Symb. Sp. Gr. Chem. Equiv. Cl 2.4700 Air = t By Vol. 100 35.42 Hyd. = I “ Wght. 35.42 607. Chlorine was discovered by Scheele in 1774 ; it was called by him dephlogisticated marine acid. The term oxy-muriatic acid was afterwards applied to it by the French chemists. From its colour the name by which it is now known, was given to this gas by Davy* from the Greek /haqoq green. * For a description of the process, see Turner’s Elements 6th ed. p. 209. Chlorine collected. l&l 608. Chlorine gas may be formed by either of the following pro- Sect, x. cesses : Method of The most convenient method ofpreparing it is by mixing concentrated hydro- obtaining chloric acid, contained in a glass flask or tubulated retort, with half its weight of c onne * finely powdered peroxide of manganese. Effervescence, owing to the escape of chlorine, takes place even in the cold ; but the gas is evolved much more freely by the application of a moderate heat. It should be collected in inverted glass bottles filled with warm water ; and when the water is wholly displaced by the gas, the bottles should be closed with a well ground glass stopper. As some hy- drochloric acid gas commonly passes over with it, the chlorine should not be considered quite pure, till after being transmitted through water. 609. The theory of this process will be readily understood by first Theory, viewing the elements which act on each other, namely : — Chlor. . 70.84 or 2 eq. 2C1 Hyd. . 2 or 2 eq. 2H Hydroch. ac. 72.84 or 2 eq. 2(H-f-Cl)j derived from them, namely, Chlor. 35.42 or 1 eq. Oxy . lb ^ Chloride of mang. 63.12 Water 18 In symbols Mn-j-20, and 2(H-j-Cl), yield Mn-J-Cl, 2(H-f O), and Cl. The affinities which determine these changes are the mutual attrac- tion of oxygen and hydrogen, and of chlorine and manganese. 610. When it is an object to prepare chlorine at the cheapest rate, Cheaper as for the purposes of manufacture, the preceding process is modified P rocess - in the following manner : — - Three parts of sea-salt are intimately mixed with one of peroxide of manganese, and to this mixture two parts of sulphuric acid, diluted with an equal weight of water, are added. By the action of sulphuric acid on sea-salt, hydrochloric acid is disengaged, which reacts as in the former case upon the peroxide of manga- nese ; so that, instead of adding hydrochloric acid directly to the manganese, the materials for forming it are employed. In this process, however, the sulphates of soda and protoxide of manganese are generated, instead of chloride of manga- nese. Thus the materials which act on each other are MnO 2 , NaCl and 2S0 3 ; and the products MnO, SO 3 , NaO, SO 8 and Cl. 611. The gas should be received, when it is intended to be kept, Method of in bottles filled with, and inverted in, water of Fig. 157. collecting, the temperature of 80° or 90° F., and provided with accurately ground stoppers. It will be found also much to diminish the loss of gas by absorp^ tion, if it be made to issue from a gas bottle, the tube of which is sufficiently long to reach nearly to the bottom of the inverted receiving bottle, as in Fig. 157. The stopper must be introduced under water, while the bottle remains quite full of the gas and in- verted, and no water must be left in the bottle, along with the gas. Cold recently boiled water, at the common pressure, absorbs twice its volume of chlorine, and yields it again when heated. 612. Chlorine is an elastic, gaseous fluid, it has a pungent disa- greeable odour, and is highly injurious when respired even largely Pro P erties ‘ Mang. . 27.7 or 1 eq. Mn Oxy. . 16 2 eq. 20 Perox. of mang. 43.7 or 1 eq. Mn-|-20 and then inspecting the products Mang. . . 27.7 Chlor. . . 35.42 . 182 Chlorine. Chap HI. Weight. Destroys vegetable colours. Bleaching property il- lustrated. Exp. Hydrate of chlorine. Effect of light. Supporter of combus- tion. diluted with atmospheric air.* When the hand is immersed in the gas a distinct sensation of heat is perceived. Its colour is greenish yellow. According to Davy 100 cubic inches of dry chlorine, at 30 Bar. and 60° F. weigh between 76 and 77 grains. Gay-Lussac and Thenard found the density of pure and dry chlorine to be 2.47, which gives 76.59S8 grains as the weight of 100 cubic inches at 60° F. and 30 Bar. 613. Chlorine gas, in its ordinary state, destroys all vegetable colours. This may be shown by passing into the gas confined by water, a piece of paper stained with litmus, the colour of which will immediately disappear. Hence the application of this gas to the purpose of bleaching, its power of effecting which may be shown by confining, in the gas, a pattern of unbleached calico, which has been previously boiled in a weak solution of caustic potassa, and then washed in water, but not dried. Chlorine gas, however, which has been carefully dried by solid chloride of calcium, and into which perfectly dry litmus paper is introduced, produces no change of col- our in the litmus, a sufficient proof that its bleaching power depends on the presence and decomposition of waters 614. The bleaching property may be shown by water impregna- ted with the gas. For this purpose fill a small bottle with cold water, and invert it on the shelf of the pneumatic trough, pass up chlorine until about one half the water is dis- placed from the bottle ; close its mouth with the thumb under water — agitate the water and gas together — invert the bottle in a basin of cold water and remove the thumb. VVatcr will rush in to supply the place of that absorbed; more gas may be then passed up and the process repeated three or four times. Strips of . calico immersed in this solution will soon be bleached. 615. Dry chlorine, is not condensable by a cold of — 40° F. ; but either the moist gas, or a solution of chlorine in water, crystallizes at 32°. The crystals may be obtained by introducing into a clean bottle of the gas, a little water, and exposing the bottle for a few days to a temperature at or below freezing, in a dark place. A sol- id compound of chlorine and water is formed, which, in a day or two, sublimes and shoots into delicate prismatic needles, extending from half an inch to two inches into the atmosphere of the bottle. These crystals are composed, according to Faraday, of 35.42 or 1 atom of chlorine + 90 or 10 atoms water.* 616. Light does not act on dry chlorine ; but if water be present, the chlorine decomposes that liquid, unites with the hydrogen to form hydrochloric acid, and oxygen gas is set at liberty. This change takes place quickly in sunshine, more slowly in diffused daylight, and not at all when light is wholly excluded. Hence the necessity of keeping moist chlorine gas, or its solution, in a dark place. Chlorine unites with some substances with evolution of heat and light, and is hence termed a supporter of combustion. If a lighted taper be plunged into chlorine gas, it burns for a short time with a * In case chlorine should escape into the apartment and be inhaled, relief will be found by opening a bottle of aq. ammonia and hreathing over it. Breathing the vapour of spirits of wine or swallowing lumps of sugar steeped in alcohol, is said to be ef- fectual. Effect of Heat. 183 •o Fisr. 159. small red flame, and emits a large quantity of smoke. Phosphorus takes fire in it spontaneously, and burns with a pale white light. Several of the metals, such as tin, copper, arsenic, antimony, and zinc, when introduced into chlorine in the state of powder or in fine leaves, are suddenly inflamed.* In all these cases the combustible substances unite with chlorine. Fill a narrow jar 18 or 20 inches in length with chlorine, and sprinkle into it powdered antimony; a beautiful shower of the ignited metal will be perceived until the jar becomes filled with dense white fumes, which should as far as pos- sible be prevented from escaping into the room. Fi ? . 158. Put some mercury into a copper cup, attached to a thin plate of cop- >■ — - per, (Fig. 158,) and rubbed over with a little gas-lute to prevent the met- als from combining, and place it in a bottle of the gas, after heating it in the flame of a spirit lamp. It will take fire and combine with the chlorine. The most elegant way of making these experiments consists in introducing the phosphorus or metallic leaves into a retort furnished with a stop-cock, and exhausted upon the air-pump ; (Fig. 159.) it is then screw- ed into the cap of an air jar of chlorine also furnished with a stop-cock, and standing over water in the pneumatic trough. Upon opening the cocks the gas rushes from the jar into the retort, and the phospho- rus or leaves immediately burn. A small quantity only of the metals should be used, as the heat is sudden and often sufficient to crack the retort. As retorts are very liable to break while exhausting, it is ad- visable to cover them with a cloth during the process. B. 139. 617. Chlorine has a very powerful attraction for hy- drogen ; and many of the chemical phenomena, to which chlorine gives rise, are owing to this property. A striking example is its power of decomposing water by the action of light, or at a red heat ; and most com- pound substances, of which hydrogen is an element, are deprived by it of that principle. For the same reason, when chlorine, water, and some other body which has a strong affinity for oxygen, are presented to one another, water is usually resolved into its elements, its hydrogen attaching itself to the chlorine, and its oxy-’ gen to the other body. Hence it happens that chlorine is, indirectly, one of the most powerful oxidizing agents which we possess. 618. It is not altered by exposure to very high terfii- peratures. By means of the apparatus, (Fig. 160,) Davy exposed it to the continued action of charcoal intensely ignited by voltaic electricity, without the smallest change in its properties. A glass globe a, of about four inches diameter, has at its upper part a sliding wire passing air-tight through a ground collar b, to the lower end of which is attached a piece of well burned charcoal c : at the bottom is a stop-cock supporting a pair of brass pincers, in which is another pointed piece of charcoal c; the globe is exhausted upon the air-pump, filled with chlorine, and the stop- cock d and sliding wire e attached to the extremities of the Voltaic apparatus ; the charcoal points are then brought into contact by pushing down the upper wire, and they are thus retained as long as necessary in intense ignition. B, Sect. X. Combus- tion of metals, Exp. l. Of mercury. Exp. 2. Exp. Union wilh hydrogen. Unaltered in high tempera- tures. Exp. * This is seen to most advantage when a very tall narrow jar is employed. 184 Chlorine and Hydrogen. Chap, in. Effect of pressure. Liquefac- tion of chlo Used in fumigation. Recog- nised. Exp. 619. When chlorine is suddenly and considerably condensed by mechanical pressure, not only heat is evolved, as from all other gas- es, but it emits a weak violet coloured light also. Under the pressure of about four atmospheres Faraday discover- ed that chlorine is a limpid liquid of a bright yellow colour, which does not freeze at the temperature of zero, and which assumes the gaseous form with the appearance of ebullition when the pressure is removed. 620. Chlorine is useful for the purposes of fumigation, in destroy- ing the volatile principles given off by putrefying animal matter and contagious effluvia. A peculiar compound of chlorine and so- da, the nature of which will be considered in the section on sodium, has been lately introduced for this purpose by Labarraque. 621. Chlorine is in general easily recognised by its colour and odour. Chemically it may be detected by its bleaching property, added to the circumstance that a solution of nitrate of oxide of silver occasions in it a dense white precipitate (a compound of chlorine and metallic silver,) which becomes dark on exposure to light. Into a weak solution of common lunar caustic, drop a small quantity of the water impregnated with chlorine. Those compounds of chlorine, which are not acid, are termed chlorides or chlorurets. Muriatic acid gas. Form. H+Cl Hydrogen and Chlorine — Hydrochloric Acid. Composition. Sp. Gr. Chlor. Hyd. Gr. 1.2694 Air = 1 18.21 Hyd. = 1 Chlor. 35.42 -f Equiv. By Vol. 200 “ Wgt. 36.42 Explosion of chlorine 622. When equal volumes of hydrogen and chlorine gases are mixed and exposed to light, they combine and produce a sour com- pound commonly called muriatic acid gas ; or in conformity to more modern nomenclature hydrochloric acid gas. 623. Chlorine and hydrogen gases act with considerable energy upon each other, and with different phenomena accordingly as the experiment is conducted. If a phial be entirely filled with a mixture of hydrogen and chlorine gases in equal proportions, and a well ground stopper be introduced, 'no action takes and hydro- place, provided light be carefully and completely excluded, even by standing S en * some time ; but on applying a lighted taper, the gases immediately explode. Into a small but strong vessel, guarded from the light, introduce equal volumes of the two gases, and inflame the mixture by the electric spark, hydrochloric acid gas results. The' apparatus shown at Fig. 133, may be used for the purpose. The vessel should be previously exhausted by the air pump,* and then filled with the mixed gases. An electric spark may now be passed through the mix- ture, when a detonation will ensue, to avoid any injury from which, the vessel should be wrapped in several folds of cloth. If the cock, attached to the ves- sel, be opened under mercury in about a quarter of an hour, very little of that fluid will enter, proving that the volume of gas after the experiment is scarcely diminished; that it is diminished at all, is owing to a small portion of air being Exp. * The foot a being unscrewed, and the end of the stop-cock connected with the pump plate. Hydrochloric Acid . 185 mingled with the other gases : and it was found by Davy that the more perfectly g eet . x. this is excluded, the less is the amount of the contraction of volume. If the cock be now opened under water, and left there for a few minutes, the water will be found to have ascended and entirely filled the vessel. 624. If a phial containing the mixed gases be exposed to the Effect of sun’s rays a detonation will ensue, which will probably drive out the hght stopper. But if this should not happen the stopper may be removed under water, which will ascend and completely fill the phial as in the former experiment. The agency of light may be beautifully shewn by filling a tube about half an Exp. inch diameter, and ] 2 inches long, with the mixed gases, and alternately shading it with an opaque cover, and exposing it to the sun’s rays. The moment the tube is exposed even to the diffused light of day, a cloudiness will appear within it, and the water will ascend more or less rapidly according to tire intensity of the light. The effect even of a passing cloud is distinctly seen in retarding the rapidity of the combination, which is very striking in the full solar light.* 625. The intense light issuing from charcoal points connected with a powerful galvanic battery is as effectual as solar light in act- ing on hydrogen and chlorine gases ; showing a curious analogy between electric and solar light ; for ordinary artificial light does not accelerate the combination. f 626. Hydrochloric acid gas differs essentially from either of its Hydro- components, and especially in being instantly absorbed by water. To chloric acid preserve it, therefore, in a gaseous state, it is necessary to confine it gas ‘ by quicksilver. 627. It was generated by Faraday in close tubes, from hydrochlo- Liquid, rate of ammonia and sulphuric acid, in a liquid state, and its refrac- tive power was found inferior to that of water. The pressure of its vapour at 50° F. was equal to about 40 atmospheres. 628. To obtain hydrochloric acid gas in sufficient quantity for the p roC ess for exhibition of its properties, the direct combination of chlorine and obtaining, hydrogen gases is not an eligible process. It maybe procured much more conveniently by the action of sulphuric acid on sea-salt. Let the tubulated gas bottle, (Fig. 87, a,) be about one fourth or one third,, filled with well dried sea-salt, in lumps, not in pow^der. To this adapt the acid holder, 6, filled with concentrated sulphuric acid; and let the aperture of the bent pipe c, terminate under a jar filled with, and inverted in quicksilver. Open the communication between the acid and the salt, by turning the cock, d; and immediately on the contact of these two bodies, an immense quantity of hy- drochloric acid gas will be disengaged. A common or tubulated gas-bottle, or tubulated retort will answer sufficiently well for procuring the gas. The first portions that come over, may be allowed to escape under a chimney ; because they are contaminated by the admixture of common air present in the bottle. The subsequent portions may be preserved for use. 629. This gas was first obtained pure by Priestley, but its compo- *p^ eor y sition was discovered by Scheele, and has since been most ably in- vestigated by Davy. Sea-salt was formerly supposed to be a com- pound of hydrochloric acid and soda ; and, on this supposition, the * It had been supposed that the direct beams of the sun were necessary to explode caution, a mixture of chlorine and hydrogen gases ; but Silliman has related the accidental ex- plosion of a mixture of the gases, in the quantity that filled a Florence oil flask, not only when no direct solar light fell upon it, but when the diffuse light of day was ren- dered more feeble than common by a thick snow-storm.* This fact furnishes a cau- tion against mixing the two gases in considerable quantities, t Brande^ Phil. Trans. 1820. * See Amor. Jour, of Sei, iii. 342. 186 Chap. III. Properties. Extin- guishes name. Absorbed by water. Exp. Exp. Exp. Analysis. Chlorine and Hydrogen . soda was believed merely to quit the hydrochloric and unite with sulphuric acid. But the researches of Gay-Lussac, Thenard, and Davy proved that it consists of chlorine and sodium combined in the ratio of their equivalents. The nature of its action with sulphuric acid will be understood by comparing 1 the elements concerned in the change before and after it has occurred : — Hydrous Sulp. Acid. Chloride of Sodium. Sulp. of Soda. Real acid 40.1 Chlor. 35.45 Acid w ^[oI y d : 1 8 Sodium 23.3 Soda £ 40.1 23.3 8 Hydrochloric Acid. Chlor. 35.42 Hyd. 1 Or in symbols, (S+30)-f-(H-f-0), and Na-fCl, yield (Na-f 0)+(S+30), and H-f-Cl. Thus it appears that single equivalents of water, sulphuric acid, and chloride of sodium, yield sulphate of soda and hydrochloric acid. The water of the sulphuric acid is essential; so much so, indeed, that chloride of sodium is not decomposed at all by anhydrous sul- phuric acid. 630. It has a very pungent smell ; and is sufficiently caustic to blister the skin, when applied to it for some time. When brought into contact with common air, it occasions a white cloud, owing to its union with the aqueous vapour, which is always present in the atmosphere. It is heavier than common air. 631. It extinguishes a lighted candle. Before the flame goes out, the upper part of it assumes a greenish hue. A white vapour also surrounds the extinguished wick, owing to the combination of water, produced by the combustion of the candle, with the acid gas. 632. Hydrochloric acid gas is greedily absorbed by water, which at 40° F. Davy found to take up about 480 times its bulk, forming a solution of specific gravity 1.2109.* Fill a narrow jar, or tube closed at one end, with the acid gas, over mercury, and through the latter pass up a few drops of water; the gas will be rapidly ab- sorbed, and the mercury will rise in the vessel. The *acid property of the solution may be shown as follows: — Take a long tube filled with the gas at the mercurial trough, close it with the thumb or finger, transfer it to a basin of water coloured blue by an infusion of cabbage, and remove the finger under the surface of the water; the gas is imme- diately condensed, the coloured water is forced up the tube by atmospheric pres- sure, and reddened at the same time by the acid gas. Into a similar vessel filled with the gas introduce a piece of ice ; it will be li- quefied, almost as rapidly as if touched with a red-hot iron, and the gas will be absorbed. The quantity of real acid contained in solutions of different densi- ties may be determined by ascertaining the quantity of pure marble dissolved by a given weight of each. Every 50.6 grains of marble correspond to 36.42 of real acid. 633. When a mixture of oxygen and hydrochloric acid gases is either electrified or transmitted through a red-hot porcelain tube, the oxygen unites with the hydrogen of the acid, and the chlorine of the latter is set at liberty. A similar mixture Henry found to be also decomposed by being exposed, at a temperature of 250° F. to * Elements , p. 252. For table of specific gravity of acid of different strengths, see Appendix. 187 Liquid Hydrochloric Acid . contact with the platinum sponge. Water is formed and the disen- gaged chlorine acts on the mercury used to confine the gas.^ H. 1- 268. 634. It is in the state of watery combination that hydrochloric acid is kept for chemical purposes, and all the processes for preparing the liquid acid have for their object the disengagement of the acid gas, and its absorption by water. For saturating water with this gas we commonly employ Woulfe’s apparatus.! The retort being furnished with the bent tube, a, Fig. 161, and placed in asand bath, the junctures should be carefully luted, and the acid should be added to the salt in the retort at intervals. The water employed may amount to half the weight of the salt, and may be equally distributed between the bottles. These it * Phil. Trans. 1824. t In several instances, the substance raised by distill&tion is partly a condensable li- quid, and partly a gas, which is not condensed, till it is brought into contact with water. To effect this double purpose, a series of receivers, termed Woulfe’s apparatus, is " employed. The first receiver (a, Fig. 161) has a right-angled glass tube, open at both Fig. 161. ends, fixed into its tubulure ; and the other extremity of the tube is made to terminate- beneath the surface of distilled water, contained, as high as the horizontal dotted line,, in the three-necked bottle c. From another neck of this bottle, a second pipe proceeds, which ends, like the first, under water, contained in a second bottle d. To the centra! neck, a straight tube open at both ends, is fixed, so that its lower end may be a little- beneath the surface of the liquid. Of these bottles any number may be employed that is thought necessary. The materials being introduced into the retort, the arrangement completed, and tlie joints secured, the distillation is begun. The condensable vapour collects in a liquid form in the balloon b, while the evolved gas passes through the bent pipe, beneath the surface of the water in c, which continues to absorb it till saturated. When the water of the first bottle can absorb no more, the gas passes, uncondensed, through the-second right-angled tube, into the water of the second bottle, which, in its turn, becomes satu- rated. Any gas that maybe produced, which is nojt absorbable by water, escapes through the bent tube e, and may be collected, if necessary. Supposing the bottles to be destitute of the middle necks, and, consequently, without the perpendicular tubes, the process would be liable to be interrupted by an accident: for if, in consequence of a diminished temperature, an absorption or condensation of gas should take place in the retort, and, of course, in the balloon b, it must necessarily ensue that the water of the bottles c and d would be forced, by the pressure of the at- mosphere into the balloon, and possibly into the retort ; but with the addition of the central tubes, a sufficient quantity of air rushes through them to supply any accidental vacuum. This inconvenience, however, is still more conveniently obviated by Wel- ther’s tube of safety, e, which supersedes the expediency of three-necked bottles. The apparatus being adjusted, as shown by the figure, a small quantity of water is poured into the funnel, so as to about half fill the hall d. When any absorption happens, the fluid rises in the hall, till none remains in the tube, when a quantity of air immediately rushes in. On the other hand, no gas can escape, because any pressure from within is instantly followed by the formation of a high column of liquid in the perpendicular part, which resists the egress of gas. — A convenient apparatus for this and similar purposes is described in Brewster’s Edin. Jour, viii- p. 3. Sect. X. Liquid hy- drochloric acid, how obtained. Woulfe'a appa- ratus, 188 Chap. Ill, Impurities. Properties of the liquid acid. Combines with alka- lies. Aqua regia. Chlorine and Hydrogen. is better to surround with cold water, or, still preferably, with ice or snow ; be- cause the condensation of the gas evolves considerable heat, which prevents the water from attaining its full impregnation. When the whole of the sulphurio acid has been added, and the gas no longer issues, let a fire be lighted in the fur- nace beneath the sand bath, removing the bent tube a, and substituting a well ground glass stopper. This will renew the production of gas ; and the tempera- ture must be preserved, as long as gas continues to be evolved. At this period it is necessary to keep the luting which connects the retort and receiver, perfectly cool.* Towards the close of the process, a dark coloured liquid is condensed in the first receiver, consisting of a mixture of sulphuric and hydrochloric acids. When nothing more comes over, the operation may be suspended, and the liquid in the two receivers must be preserved in bottles with ground stoppers. It con- sists of liquid hydrochloric acid. H. 272. 635. When hydrochloric acid is thus dissolved in water, it forms the liquid muriatic acid , or spirit of salt. When pure it is perfectly colourless, but it is generally impure. Its usual impurities are nitric acid, sulphuric acid, and oxide of iron. The presence of nitric acid may be inferred if the hydrochloric acid has the property of dissolv- ing gold-leaf. Iron may be detected by ferrocyanuret of potassium, and sulphuric acid by chloride of barium, the suspected hydrochloric acid being previously diluted with three or four parts of water. The presence of nitric acid is provided against by igniting the sea-salt, in order to decompose any nitre which it may contain. The other impurities may be avoided by employing YVoulfe’s apparatus. 636. Liquid hydrochloric acid emits white suffocating fumes, con- sisting of hydrochloric acid gas, which become visible by contact with the moisture of the air (630). When heated in a retort, the gas is disengaged, and may be collected. It is not decomposed by the contact of charcoal, or other combustible bodies. When diluted with water, an elevation of temperature is produced, less remarkable, however, than that occasioned by diluting sulphuric acid (66) ; and when the mixture has cooled to its former temperature, a diminution of volume is found to have ensued. 637. Hydrochloric acid combines readily with alkalies, and with most of the oxides both in their pure and carbonated state.! H. i. 272. A mixture of nitric and hydrochloric acids, in the ratio of one measure of the former to two of the latter, has long been known under the name of aqua regia , as a solvent for gold and platinum. When these acids are mixed together, the solution instantly becomes yellow; and on heating the mixture, pure chlorine is evolved, and the colour of the solution deepens. On continuing the heat, chlorine and nitrous acid vapors are disengaged. At length the evolution of chlorine ceases, and the residual liquid is found to be a solution of hydrochloric and nitrous acids, which is incapable of dissolving gold. The explanation of these facts is, that nitric and hydrochloric acids decompose one another, giving rise to the production of water and nitrous acid, and the separation of chlorine; while hydrochloric and nitrous acids may be heated together without mutual decompo- * The clay and sand lute is the best for this juncture. + For a full account of the opinions which have been maintained concerning the nature of chlorine and hydrochloric acid, the reader is referred to the controversy be- tween Murray and J. Davy, in the 34lh vol. of Richoi son's Jour. \ to Davy’s paper in the Phil. Trans, for ISIS. p. 169 ; to the Sth vol. of Trans. Roy. Soc. Edin. ; the Ann. of Philos, xii. 379 and xiii. 26, 285 ; and to a paper by Phillips, in the new series of that work. vol. i. p. 27, on the action of chlorides on water. 189 Chlorine and Oxygen. sition. It is hence inferred that the power of nitro-hydrochloric acid Sect, x. in dissolving gold is owing to the chlorine which is liberated.^ 638. Hydrochloric acid is distinguished by its odour, volatility, Hydrochlo- and strong acid properties. With nitrate of oxide of silver it yields ricaciddis- the same precipitate as chlorine; but there is no difficulty in dis- tin S uistle ^- languishing between them ; for the bleaching property of the former is a sure ground of distinction. 639. The experiments of Davy, and Gay-Lussac and Thenard Composi- concur in proving that hydrogen and chlorine gases unite in equal tion. volumes, and that the hydrochloric acid, which is the sole and con- stant product, occupies the same space as the gases from which it is formed. From these facts the composition of hydrochloric acid is easily inferred. For, as 50 cubic inches of chlorine weigh . . 38.2994 grains, 50 “ hydrogen . . 1.0683 “ 100 cubic inches of hydrochloric acid gas must weigh 39.3677 These numbers are nearly in the ratio of 1 to 35.42, being that of single eq. of chlorine and hydrogen. Hence its eq. is as already stated. Compounds of Chlorine and Oxygen , 640. The leading character of these compounds is derived from Leading the circumstance that chlorine and oxygen, the attraction of which character - for most elementary substances is so energetic, have but a feeble affinity for each other. They cannot be made to combine directly, and very slight causes effect their separation. Two volumes of chlorine, as also two of hydrogen and of nitro- gen correspond to one equivalent or atom.! Hypocklorous Acid. Composition. Form, Sp, Gr, Chlor. Oxy. Ckem. Equiv. CHO, Cl, or CIO 3.0212 Bv Wght. 35.42 = 8 43.42 “ Vol. 2 = 1 641. This gas was discovered in 1811 by Davy and describ- Discovery, ed under the name of EuchlorineX Until recently it has been con- sidered to be the protoxide of chlorine. 642. It is obtained by the action of hydrochloric acid on chlorate Process, of potassa. Twelve parts of acid diluted with an equal weight of water may be poured upon five parts of the salt (50 or 100 grains will be sufficient); a very gentle heat is to be applied by a small spirit lamp, and the gas may be collected over mercury. 643. This gas is generally, if not always, best made in a tube retort, formed from a piece of plain glass tube, about half an inch in diameter, two or three * Davy in Quart . Jour. vol. 1. + Berzelius considers the atoms of all elements as possessing the same vo’ume, and regards the compounds of chlorine and oxygen as composed of two equiv. of chlorine and one, four, five and seven of oxygen. t Philos . Trans. 190 Chap. III. Caution. Theory. Chlorine and Oxygen. inches in length, according to circumstances, and closed at one ~ end. (Fig. 102.) The mouth should be fitted with a good perfora- ted cork, having a small tube fixed into it, which, after proceed- ing about an inch upwards from the cork, is to turn on nearly at right angles for about three inches, and then return to its first direction for about the eighth of an inch. This piece of tube is the neck of the retort, whilst the wide short piece is the body ; the latter having received its charge, the cork is to be __ put in and made tight by cement, when the distillation may be proceeded with, and the gas evolved and collected. F. Great care should be taken in preparing this gas, as it explodes violently when exposed to a moderate heat, though nothing is mixed with it ; when the spirit lamp is used, it should be held immediately below the retort, so as not to play on its sides, and the gas should then come slowly away, producing a very moderate effervescence.* 644. When the object is merely to notice a few F *s- 163 - of the properties of the gas, it may be obtained from materials placed in a glass tube, 15 or 16 inches in length and about an inch in diameter, sur- rounded by water and heated, as in the Fig. 163. 645. The production of this gas is explicable by the fact, that hydrochloric and chloric acids mutual- ly decompose each other. When hydrochloric acid and chlorate of potassa are mixed together, more or less of the po- tassa is separated by the hydrochloric acid from the chloric acid, and the latter being set at liberty, reacts on free hydrochloric acid. The result depends upon the relative quantities of the materials. If hy- drochloric acid be in excess, the chloric acid undergoes complete de- composition. For each eq. of chloric acid, five eq. of hydrochloric acid are decomposed : the five eq. of oxygen contained in the former, unite with the hydrogen of the latter, producing five eq. of water ; while the chlorine of both acids is disengaged. If, on the contrary, chlorate of potassa be in excess, the chloric acid is de- prived of part of its oxygen only ; the products are water and the euchlorine of Davy. 646. The chloric and hydrochloric acids react on each other in the ratio of one eq. to two, or, what is the same thing, in that of four eq. to eight eq. ; thus 4 (Cl+50) . u 8 (H+O) and 8 (H +C1 ) yleld 12 (Cl+O) * In reference to the distillation of this gas, and of all other explosive substances, the student should be aware of the caution required to prevent accidents, in case explo- sion should occur. Whenever such an effect is probable, the vessel should be sur- rounded with low or cloth, that if it break, the fragments may be retained ; and during distillation the side of the apparatus, or that part which is guarded by the tow, is to be turned towards the eyes, that they at least may be out of danger. It is not easy to wrap tow regularly and tightly round a clean glass tube, from its tendency to slip over the surface ; but the difficulty is easily obviated, by rubbing the outside of the tube with soft cement, or a very little turpentine with a piece of tow or cloth, so as to ren- der it slightly adhesive to the fingers. Faraday p. 409. Silliman prefers placing the materials for producing the gas in a small glass flask furnished with a tube bent twice at right angles, and passing to the bottom of any clean dry phial, flask, or tube, rather deep with a narrow neck, a gentle heat, applied beneath the flask, soon disengages the euchlorine gas, which, by its great weight, dis- places the common air from the recipient, and takes its place. By using tongs, pro- perly curved, so as to embrace the phials or tubes filled with the gas, the operator may perform all the necessary experiments, without danger of causing an explosion by the warmth of the hand. Amer. Jour. vi. 165. Chlorous Acid . 191 The gas thus obtained, is not a distinct compound, but a mixture Sect, x. of chlorine and chlorous acid. T. 218. 647. The process for obtaining the pure acid, is to pour into bot- Process for ties filled with chlorine gas, peroxide of mercury in fine powder, and ^ d pure mixed with twice its weight of distilled water ; by brisk agitation the chlorine is rapidly and completely absorbed, if a slight excess of the peroxide be used. By this process one portion of the peroxide of mercury, HgO 2 , is decomposed, both its constituents combining with chlorine ; the mercury forming corrosive sublimate HgCl 2 , and the oxygen hypochlorous acid. The latter remains in solution in the water ; while the former, by combining with undecomposed per- oxide of mercury, forms the sparingly soluble oxychlUride of mer- cury, which is separated by filtration. The hypochlorous acid being volatile, is obtained pure by distillation ; the temperature being kept below 212° as the acid decomposes at that heat. The process is best performed under reduced pressure. 648. As thus obtained, hypochlorous acid is a transparent liquid properties, of a slightly yellow colour ; when concentrated, with a strong pene- trating odour, similar to that of chlorine. It acts powerfully upon the skin, and bleaches. It is easily decomposed, chlorine being evolved and chloric acid produced ; a change effected by light and instantly by the direct rays of the sun. It is also decomposed by angular bodies, as by pounded glass. 649. It is one of the most powerful oxidizing agents ; its action, Oxidizes, however, is various and is principally observed in relation to the sim- ple non-metallic elements. Its action on the more perfect metals is slight, with the exception of iron and silver, which in a state of mi- nute division instantly decompose it. 650. Hypochlorous acid has also been obtained in the gaseous Another form, by introducing a small quantity of its concentrated solution process, into a bell glass over mercury and adding fragments of dry nitrate of lime. The latter unites with the water and the acid gas escapes. The gas is of a yellowish green colour ; it unites rapidly with water which absorbs at least 100 times its volume. 651. It detonates by a slight increase of temperature, and oxygen Specific and chlorine are the results ; 100 measures produce 100 of chlorine g ravit Yj &c - and 50 of oxygen.^ From these data its sp. gr. is 3.0212 ; its eq. 43.42 ; eq. vol. == 100 ; symb. Cl+O, Cl, or CIO. (T.) Chlorous Acid. Composition. Chi. Oxy. Equiv. Equiv. Vol. Bv Wght. 35.42 32 67.42 = 200 “ Vol. 2 4 652. This compound was discovered by Davy in 1815, and soon after by Count Stadion of Vienna. It has heretofore been described as the peroxide of chlorine , but having been found to possess acid properties, and to form definite compounds with alkaline bases, it Symb. Sp. Gr. Cl+40, Cl or CIO 4 2.3374 * Balard Ann. de Chim. et de Phys. lvii. 225. 192 Chap. 111. Method of obtaining. Theory. Salts of, Decompo- sed by phosphorus and neat. Process. Properties. Decompos- ed. * Chlorine and Oxygen. must now be called chlorous acid. It is formed by the action of sul- phuric acid on the chlorate of potassa. To procure it, 50 or 60 grains of the powdered chlorate of potassa, are to be mixed with a small quantity of concentrated sulphuric acid. When thor- oughly incorporated, a solid mass will result, of a bright orange colour. This is to be introduced into a very small retort of glass, or a bent tube, which hs to be exposed to the heat of water gradually warmed, but prevented from attaining the boiling point, by an admixture of spirit of wine. 653. In this process the sulphuric acid decomposes some of the chlorate of potassa, and sets chloric acid at liberty. The chloric acid at the moment of separation, resolves itself into chlorous acid and oxygen ; the last of which, instead of escaping as free oxygen gas, goes over to the acid of some undecomposed chlorate of potassa, and converts it into perchloric acid. The products are bisulphate and perchlorate of potassa, and chlorous acid. It is probable that every three eq. of chloric acid yield one eq. of perchloric and two eq. of chlorous acid. T. 654. This acid readily unites with the alkalies and alkaline earths, and the union is effected by transmitting the gas into the alkaline solutions. The salts are soluble in water and bleach. 655. It is decomposed, at common temperatures, by phosphorus, which occasions an explosion when introduced into it. It explodes violently at 212°, and great care is necessary in operating with it. Chloric Acid. Composition. Chlor. Ory. Equit. By Wght. 35.42 40 75.42 “ Vol. 2 5 656. When a current of chlorine gas is passed into a strong solu- tion of pure potassa, part of the alkali is decomposed and chloride of potassium and hypochlorite of potassa are generated. On bringing the solution to the boiling point, the latter salt is decomposed. The changes are complicated ; from experiments* nine eq. of hypochlo- rite of potassa produce one eq. of chlorate of potassa, eight eq. of chloride of potassium, and twelve eq. of oxygen : or thus 9 (KO+CIO) yield (KO+CIO*), 8KC1 and 120 657. When weak sulphuric acid is added to a dilute solution of chlorate of baryta, exactly sufficient for combining with the baryta, sulphate of baryta subsides, and pure chloric acid remains in the liquid. 658. This acid was first obtained by Gay-Lussac. It reddens vegetable blue colours, has a sour taste, and forms neutral salts, cal- led chlorates (formerly hy per oxy muriates.) It has no bleaching prop- erties, nor does it afford a precipitate with solution of nitrate of oxide of silver. 659. Chloric acid is easily decomposed by oxidizing agents ; and it is easily known by forming a salt with potassa, which crystallizes fbrm. 01+50,01,’ or C105 * Of Morin, Soubeirain. and Balard. 193 Chlorine and Nitrogen . in tables and has a pearly lustre, deflagrates on burning coals, and Sect, x. yields chlorous acid by the action of concentrated sulphuric acid. Perchloric Acid. Composition. Form. Chi. Oxy. Equiv. CI+70, Cl or ClOr By Wght. 35.42 . 56 91.42 “ Vol. 2 7 660. The saline matter which remains in the retort after forming p rocess chlorous acid, is a mixture of perchlorate and bisulphate of potassa, and by washing it with cold water, the bisulphate is dissolved and the perchlorate is left. This acid may be prepared from the salt by mixing it in a retort with half its weight of sulphuric acid, diluted with one third water, and applying heat to the mixture. At the temperature of about 284° F. white vapours rise, which condense as a colourless liquid in the receiver. This is a solution of perchloric acid. Stadion, its discoverer, found it to be a compound of 1 eq. chlo- Composi- rine -f- 7 eq. oxygen, and his analysis has been confirmed by Gray- tion - Lussac and others. 661. When concentrated it has a density of 1.65 in which state it Properties, emits vapour on exposure to the air, absorbs moisture, and boils at 392°. It hisses when thrown into water like a red-hot iron when quenched. 662. It forms a salt with potassa, requiring 65 times its weight of water at 60° for solution. The perchlorate of potassa is dis® tinguished from the chlorate by not acquiring a yellow tint on the addition of hydrochloric acid. Quadrochloride of Nitrogen — Chloride of Nitrogen » Sp. Gr. 1,653. 663. Quadrochloride of nitrogen, discovered in 1811 by Dulong,* Properties, is one of the most explosive compounds yet known, having been the cause of serious accidents both to its discoverer and to Davy.f It does not congeal in the intense cold produced by a mixture of snow and salt. It may be distilled at 160° ,; but at a temperature between 200 and 212° it explodes. Its mere contact with some substances of a combustible nature causes detonation even at common temperatures. This result ensues particularly with oils, both volatile and fixed. The products of the explosion are chlorine and nitrogen. £ 664. It is prepared by inverting a jar or wide-mouthed bottle, (capable of con- p rocess> taining about 12 or 14 ounces) full of chlorine, over a dilute solution of the hy- drochlorate of ammonia, (sal ammoniac) made by dissolving an ounce of the salt in 10 or 12 ounces of water ; the bottle is placed on a very strong shallow leaden cup, which rests on a deep plate containing the solution previously heated to the temperature of 90°. One portion of the chlorine takes the hydrogen of the ammo- nia, § forming hydrochloric acid, and the other, combining with the nitrogen, is converted into the quadrochloride, which collects in the form of an oil on the surface of the liquid, and drops through it into the leaden cup : an additional quantity of the solution must be ready to fill up the plate as the absorption of the chlorine proceeds. 665. Great care must be taken not to shake the bottle, and any Caution. * Ann. de Ch. Ixxxvi. t Phil. Trans. 1813. } Nicholson’s Jour, xxxiv. § Ammonia consists of hydrogen and nitrogen. 25 194 Chlorine and Carbon. Cha P- greasy or oily matter adhering to it must be removed by washing it with a dilute solution of potassa before it is filled with chlorine. When the oil has fallen into the leaden cup, the bottle is carefully moved from the cup to the plate, and the leaden cup taken cautiously away. The liquid remaining above the quadrochloride in the cup is with- drawn by dipping small pieces of filtering paper into it. The oily looking globules may be conveniently removed by drawing Fig. 164 . them into a small and perfectly clean glass syringe, made of a glass tube drawn to a pointed orifice, and having a cop- per wire with a piece of clean tow wrapped round it for a piston, (Fig. 164) ; in this way a globule may be drawn into the tube, and transferred to any other vessel. Precautions 666. In making these experiments, a small globule of in “xperi- the compound, about the size of a mustard-seed, should be menting cautiously transferred to a clean porcelain basin, half filled with water. The basin should be covered with a wire safe- guard. A very small piece of phosphorus, fixed to the end of a long rod with the extremity dipped in oil, may be then brought into contact with the globule, which instantly explodes, dis- persing the water and breaking the basin. The same compound may be obtained by suspending a fragment of sal ammoniac in a solution of hypochlorous acid. T. Analysis. 667. Davy analyzed this compound by means of mercury, which unites with chlorine, and liberates the nitrogen. He inferred from his analysis that its elements are united in the proportion of four measures of chlorine to one of nitrogen ; and it hence follows that, by weight, it consists of four equivalents of chlorine, and one equi- valent of nitrogen. Its odour is extremely penetrating and almost insupportable, affecting the eyes very much on leaning over it even for a second or two. It is very volatile. Per chloride of Carbon. Symb. Equiv. 2C+3C1, or C^t 8 . 1 IS. 5 Discovery 668 . The discovery of this compound is due to Faraday. When olefiant gas (a compound of carbon and hydrogen) is mixed with chlorine, combination takes place between them, and an oil-like liquid is generated, which consists of chlorine, carbon and hydrogen. On exposing this liquid in a vessel full of chlorine gas to the direct solar rays, the chlorine acts upon and decomposes the liquid, hydro- chloric acid is set free, and the carbon, at the moment of separation, unites with the chlorine.* p . 669. Perchloride of carbon is solid at common temperatures, has an roper ies. aromat j c 0( j 0ur approaching to that of camphor, is a non-conductor of electricity, and refracts light very powerfully. Its specific gravity is exactly double that of water. It fuses at 320°, and after fusion it is colourless and very transparent. It boils at 360°. Perchloride of carbon burns with a red light when held in the flame of a spirit-lamp, giving out acid vapours and smoke. t * Phil. Trans. 1821 . t Protochloride of Carbon. Symb. C-f-Cl, or CC1. Equiv. 41.64 Discovered by Faraday in decomposing perchloride of carbon. It is liquid, colourless, and boils 195 Nature of Chlorine. 670. Chlorine was long regarded as a compound of muriatic acid Sect, x. and oxygen, an opinion ably defended by Murray : the phenomena Nature of which it presents are all explicable on this supposition, though the chlorine, view proposed by Davy, Gay-Lussac and Thenard, of its elementary nature, is considered more in accordance with actual experiment, and now generally adopted.^ at 170°. Its density is 1.5526. Does not congeal at 0 ° F. Analogous to perchloride of carbon in its chemical relations. Dichloride of Carbon. Symb. 2C+C1, or C 2 C1. Eq. 47.66. Obtained during the dis- tillation of nitric acid from crude nitre and sulphate of iron, in soft, adhesive fibres of a white colour and peculiar odour. Boils between 350°, and 460 °, sublimes at 250. So- luble in hot oil of turpentine or alcohol. Burns with a red flame. Dichloride of Sulphur • Symb. 2 S-fCl, or 8201. Density 1.687. Discovered by Thomson.* Prepared by passing chlorine over flowers of sulphur. Liquid, vola- tile below 200 °, boils at 280 p . Emits acrid fumes. Consists of 35.42 parts or l eq. chlorine, and 32.2 parts or 2 eq. sulphur. + Perchloride of Phosphorus. Symb. 2P+5C1, or P 2 C1 5 Equiv. 208.5. There are two definite compounds of chlorine and phosphorus, the nature of which was first satisfactorily explained bv Davy.t When phosphorus is introduced into a jar of dry chlorine, it inflames, and on the inside of the vessel a white matter collects, which is perchloride of phosphorus. It is very volatile, a temperature much below 212° being sufficient to convert it into vapour. Under pressure it may be fused, and it yields transparent prismatic crystals in cooling. Sesquichloride of Phosphorus , Symb. 2 P— j-3Cl , or P 2 CI 3 ; Equiv. 137.66, may be made by heating the perchloride with phosphorus, or by passing the vapour of phos- phorus over corrosive sublimate contained in a glass tube. It is a clear liquid Pike water, of specific gravity 1.45 ; emits acid fumes when exposed to the air, owing to the decomposition of watery vapour 5 but when pure it does not redden dry litmus paper. It appears to consist of 31.4 parts or two equivalents of phosphorus, and 106.26 parts or 3 eq. of chlorine. Chlorocarbonic Acid Gas. Symb. CO+Gl, or CO, Cl Equiv. 49.54. This com- pound was discovered in 1812by Dr Davy, who described it in the Philos. Trans, under the name of phosgene gas. (From

and the gas absorbed. t 733. None of the ammoniacal salts can sustain a red heat without Effect of being dissipated in vapour or decomposed, a character which arises eaU * Faraday, Phil. Tran e. 1834 . t A vessel of water or mercury should be at hand to supply the loss in the dish in which the tube is placed and prevent the entrance of air. 27 210 Chap. III. Decompo- sition. Action of chlorine, Phenomena attending. Exp. How re- cognised. Exp. Liquor ammonise. Phillips’ process. Hydrogen and Nitrogen. from the volatile nature of the alkali. If combined with a volatile acid, such as the hydrochloric, the compound itself sublimes un- changed by heat. 734. Hydrogen and nitrogen gases do not unite directly, but the composition of ammoniacal gas lias been determined by analysis with electricity, and by passing it through red-hot tubes. If passed over a coil of iron or copper wire in a red-hot porcelain tube, the metals become brittle, but their weight is not altered. The expan- sion which the gas suffers in being thus resolved into its constituents, is a singular instance of change of properties in consequence of che- mical combination. The bladder a, (Fig. 169,) is filled with ammo- nia, which may be F »e- 169 - passed through the tube b , in the furnace c, the hydrogen and nitrogen may be col- lected in d. 735. Ammonia is decomposed by chlorine, hydrochloric acid is formed by the union of the chlorine with its hydrogen, and if an ex- cess of the gas is present, hydrochlorate of ammonia is obtained. When the two gases are suddenly mixed they act upon each other so powerfully as sometimes to produce detonation. Invert a matrass with a conical neck and wide mouth, over another Fig- J '0. with a taper neck containing a mixture of sal ammoniac and lime, heat- ed by a lamp. As soon as the upper vessel seems to be full of ammonia, ( by the overflow of the pungent gas, it is to be cautiously lifted up, and \ J inserted, in a perpendicular direction, into a wide mouthed glass decan- \ / ter, or flask, nlled with chlorine. On seizing the vessels thus joined, with the two hands, covered with gloves, and suddenly inverting them ijtt like a sand-glass, the heavy chlorine and light ammonia, rushing in op- 7\ posite directions, unite, with the evolution of flame, 1 \ 736. Ammonia is readily recognised by its odour, and by I \ the white fumes which are given off when a rod dipped in ly hydrochloric acid is brought in contact with it. This will be evident if we moisten the inside of a glass jar with hydrochloric acid, and pass into it a small quantity of ammonia; dense clouds of hydrochlorate of ammonia will immediately form. 737. The usual state in which ammonia is employed is in solu- tion, both in chemistry and medicine. This solution bears the name of Aqua Ammonice in the Pharmacopoeia. It may be obtained by passing the gas into water in a proper apparatus, (Fig. 171,) or by distilling over the water Fig. m. and gas together. The following process, recommended by Phil- lips, answers well. On 9 ounces of well burn- ed lime pour half a pint of water, and when it has re- mained in a well closed ves- sel for about an hour, add 12 ounces of hydrochlorate of ammonia in powder and three pints and a half of boiling water ; when the mix- ture has cooled, pour off the clear portion, and distil from a retort 20 fluid ounces. 211 Light Carburetted Hydrogen. The sp, gr. of this solution, which is sufficiently strong for most purposes, is Sect. XV. 0 , 954 .* 738. Liquid ammonia should be preserved in well-stopped glass How pre- bottles, since it loses ammonia and absorbs carbonic acid, when ex- serve(L posed to air ; when heated to about 140°, ammonia is rapidly given off by it. When concentrated it requires to be cooled to —40° before it congeals, and then it is apparently inodorous.! t Section XV. Compounds of Hydrogen and Carbon. 739. Two compounds of hydrogen and carbon have long been Com- known, and late researches have brought to light others of much in- hydrogen terest. They are remarkable for their number ; for supplying some and carbon, instructive instances of isomerism; for their tendency to unite with and even neutralize powerful acids, without, in their uncombined state, manifesting any ordinary signs of alkalinity. 740. Several of them are particularly distinguished by their che- Distin- mical affinities ; for although compound, they exhibit in their com- binations with other substances, the characteristics of an element. They have hence been called compound radicals. In organic che- mistry they hold a place as the roots or radicals of the various organic products, and in inorganic chemistry as compounds formed by the direct union of two elements.! T. Light Carburetted Hydrogen. Composition. Form „ Sp. Gr „ Hyd- Carb. Equiv. Eq.Vol. H2C 0.5593 Air = 1 2 + 6.12 == $.12 100 8.12 Hyd. == 1 741. This gas is sometimes called heavy inflammable air , the in- flammable air of marshes , and hydrocarburet. It is generally termed light carburetted hydrogen. It may be collected, mixed however with carbonic acid and nitro- Collected, gen gases, by stirring the bottom of almost any stagnant pool of water, especially if formed of clay. It should be washed, when col- lected, with lime water or liquid potassa, to remove the carbonic * Or two parts of lime and three of sal ammoniac may be mix- Pig- 172. ed, after the former has been slaked with a half of its weight of water and allowed to cool 5 they should both be in fine powder, and intimately blended, taking care to avoid the pungent fumes that are disengaged. The mixture is then put into an iron retort and placed in a sand bath. (Fig. 172.) The beak 6f the retort is then luted to a quilled globe, making the joining tight with plas- ter*of-paris ; water, equal in weight to £ of the salt used, is put into a bottle or receiver. The tube from the globe should reach to the bottom of the bottle, which should not be more than half full, when the proper quantity of water has been put in. The use of the glass globe is to allow air to pass into the retort as the apparatus becomes cold, and prevent any of the water of ammonia from being carried along with it ; for when the gas ceases to come and all the liquid in the bottle has been forced into the globe by the pressure of the atmos- phere, air will enter by the quill tube and pass through the water to the retort, t For a table of the quantity of ammonia in solutions, see Davy’s Elements. t Those, which from their atomic constitution, or from being the products of the organic kingdom, belong to that department, will be described under that division. Another pro- cess- 212 Hydrogen and Carbon . Chap, m. acid, of which it contains This is the only convenient method of obtaining it. Properties. 742. Light carburetted hydrogen is nearly inodorous, and without colour or taste. Water absorbs about ^ of its volume. It does not support combustion or life, but is highly inflammable, burning wit.h a yellowish flame. Detonation 743. Mixed with atmospheric air it may be kindled by a lighted with air taper, and explodes with violence, provided it forms not less than and oxygen 0 f the mixture, and does not exceed With oxygen gas the detonation is louder and more violent ; but it is necessary that oxygen should rather exceed the inflammable gas in volume, and yet should not be more than 2^ times its bulk. For its perfect combus- tion more than twice its volume of oxygen gas is required, of which exactly two volumes are consumed, and carbonic acid is produced, equivalent in volume to the inflammable gas. 744. One hundred measures of carbonic acid gas, contain 100 of carbon vapour and 100 of oxygen, just half the oxygen employed ; the remaining oxygen requires 200 measures of hydrogen to form water. Hence at G0° F. and 30 inches barom. — 100 cubic inches of carbon vapour weigh 13.0714 grs. 200 “ “ hydrogen gas . . 4.2734 “ 100 “ “ light carb. hyd. must weigh 17.3448 “ being in the ratio of 2 to 6.12 and the sp. gr. ought to be 0.5593 which agrees nearly with experiment. T. 745. Chlorine and carburetted hydrogen do not act on each other at common temperatures, when quite dry, even if they are exposed to the direct solar rays. If the gases are moist, and the mixture is kept in a dark place, still no action ensues ; but if light be admitted decomposition follows. The nature of the products depends on the proportion of the gases. If 4 measures of chlorine and 1 of carbu- retted hydrogen are present, carbonic and hydrochloric acid gases will be produced. When three measures of chlorine are present carbonic oxide is formed, one half less water being decom- posed. H. 746. The gaseous matter that often issues in large quantity from coal mines, between beds of coal, and collects in the mines mixed with the at- mospheric air, forms an explosive mixture that has been the cause of many fatal accidents ; the first unprotected light that approaches sets fire to the whole mixture. The frequent loss of life from the explo- Fire damp, sion of this fire damp , led Davy to the construction of the safety lamp.* Davy’s ex- 747. In the course of his experiments Davy found that the explo- periments. sive power varies with the proportions of carburetted hydrogen and air ; thus with three or four times its volume of air there is no ex- plosion, with seven or eight times its bulk of air the explosion is powerful ; with fourteen times its volume it is still explosive, but with a larger quantity a taper burns in the mixture only with ♦ For a full account of the elaborate experiments, &c. on this subject, the student is referred to Davy’s Essay on Flame , and the biographies of him by Paris and Dr Davy. Composi- tion and sp. gr. Action of chlorine. Present in 213 Olefiant Gas. Theory of the safety lamp, an enlarged flame. He also ascertained that the temperature re- Sect, xv. quired for" explosion was very high ; and that flame cannot pass through a narrow tube, or a tissue of wire-gauze> 748. Flame is gaseous matter heated so intensely as to be luminous* Flame When it comes in contact with the sides pf minute apertures, as when wire-gauze is held upon a burning jet of coal gas, or the flame of a spirit lamp, it is deprived of so much heat that its temperature in- stantly falls below the degree at which gaseous matter is luminous, though the gas itself passes freely through the interstices and is still very hot. This will be seen on bringing a frig- Exp, piece of wire-gauze down upon the flame ; as at a, (Fig. 173,) the gas will be found to pass through and may be ignited above the gauze as atB. 749. If the flame of a com- mon lamp be everywhere pro- perly surrounded with a wire- gauze, and in that state immersed into an explosive gaseous mixture* it will be inadequate to its inflammation, that part only being burned which is within the cage, communication to the inflammable air without being prevented by the cooling power of the metallic tissue ; so that by such a lamp the explosive mixture will be consumed, but hot exploded. Fig. 174 is a representation of the safety lamp, a is a cylinder of wire-gauze, with a double top, securely and carefully fastened, by doubling over to the brass rim b , which screws on the lamp c. The whole is protected and rendered convenient for carrying, by the frame and ring d. If the cylinder be of twilled wire-gauze, the wire should be at least of the thickness of one fortieth of an inch, and of iron or copper* and 30 in the warp, and 16 or 18 in the weft. If of plain wire-gauze, the wire should not be less than one sixtieth of an inch in thick- ness, and from 28 to 30 both warp and woof.* The operation of this lamp may be shown on a small scale, by suspending it in an inverted glass jar, and then admitting a sufficient stream of coal gas from a gas-holder by a tube entering below, (Fig. 175,) to render the enclosed atmosphere explosive. The flame of the lamp first enlarges, and is then extinguished, the whole of the cage being filled with a lambent blue light ;t on turning off the supply of the gas this appearance gradually ceases, and the wick becomes rekindled, when the atmosphere returns to its Fig. 174. A Fig. 175, Illustrated. natural state.! Form. 2H+2C, or H (X Olefiant Gas. Hyd. 2 + Carb. 12.24 2 eq. Equiv. = 14.24 Eq. Vol. 100 Sp. Gr. 0 9808 Air = l 14.24 Hyd. = 1 750. This gas was discovered in 1796, by some associated Dutch Olefiant chemists, and was termed by them olefiant gas , from its property of gas * * To increase the safety of the lamp when exposed to a strong current of an explo- sive atmosphere, the addition of a glass cylinder and allowing the air to enter only through fine apertures below, has lately been resorted to with success. t The platinum coil within will continue red-hot. (257)'. t The explosion may be safely exhibited, previously, by suspending the lamp with- out the wire-gauze cylinder from a piece of pasteboard covering the jar, and admitting coal or oil gas. W. 214 Chap. III. How ob- tained. Process. Properties. Decompo-j sed. Action of chlorine. Exp. Hydrosul- phuric acid. Processes- Hydrogen and Sulphur. forming an oily looking liquid with chlorine. It has been called by Thomson hydroguret of carbon. 751. It is usually obtained by the decomposition of alcohol by sulphuric acid. For this purpose four parts of the acid and one of alcohol are put into a capa- cious retort, and heated by a lamp. The -acid soon acts upon the alcohol, effervescence ensues and olefiant gas passes over. The retort should not be more than one third full, and the acid and alcohol should be shaken together before the heat is applied. A little ether is formed at first, the solution becomes dark, sulphu- rous acid and carbonic oxide are formed, and carbon deposited-* * * § 752. This gas is colourless and inodorous. Water absorbs about £ of its volume. It extinguishes flame, and does not support life. It is inflammable, burning with a bright yellowish white flame. When mingled with oxygen gas, it explodes with great violence. One part by volume requires, for perfect combustion, three of oxygen ; and two of carbonic acid are produced. 100 cubic inches weigh 30.4162 by calculation, and its sp. gr. is as stated.! Olefiant gas is decomposed by electricity, and by transmission through red-hot tubes. 753. When this gas is mixed with chlorine, in the proportion of 1 to 2 by vol. the mixture, on inflammation, produces hydrochloric acid, and charcoal is abundantly deposited. If the gases be well mixed, and then inflamed in a tall and narrow glass jar, (about two feet high and four inches in diameter), placed with its mouth up- wards, the experiment is very striking; a deep flame gradually descends through the mixture, and a dense black cloud of carbon rises into the atmosphere ; fumes of hydrochloric acid are at the same time formed, and a peculiar aromatic odour is evolved. If instead of inflaming the gases, the jar be inverted in a basin of water, or if they be mixed in a clean and dry glass globe exhausted of air, they act slowly upon each other, and a peculiar fluid is formed, which appears like a heavy oil ; hence the name, olefiant gas. B. 1. 321. Section XVI. Compounds of Hydrogen and Sulphur. Hydrosvlphuric Acid — Sulphuretted Hydrogen. Composition. Form. Sp. Gr. Iiyd. Sul. Equiv. Eq. Vol. HS I- 1782 Air =1 l + 16.1 = 17-1 100 17.10 Hyd. = 1 754. This gaseous compound of sulphur and hydrogen was first investigated by Scheele in 1777. It may be obtained by presenting sulphur to nascent hydrogen, which is the case when protosulphuret of iron is acted upon by dilute sulphuric acid. The sulphuret of iron may be prepared by heating a bar of iron to a white or welding heat, and, in this state, rubbing it with a roll of sulphur. The metal and sulphur unite, and form a liquid compound, which falls down in drops.t These soon congeal ; and the compound must be preserved in a well closed phial. Or a mixture of two parts of iron filings and rather more than one part of sulphur, may be heated to redness in a covered crucible. § A portion of this may be in * The changes are complicated ; for the theory, see Alcohol, i Its density by experiment is 0.97. (Thomson.) t They should be received in an iron basin filled with water. § The gas which this affords is mixed with a good deal of hydrogen gas- Hydrosulpharic Acid . 215 troduced into a retort or gas bottle and diluted sulphuric acid poured upon it, as sect. XVI. in the process for obtaining hydrogen gas (378). It may also be conveniently “ : ^ obtained from bruised sesquisulphuret of antimony (crude antimony of the shops) with five or six times its weight of hydrochloric acid (sp.gr. 1.160 or thereabouts) contained in a retort or gas bottle, and heated by a lamp. 755. In the first process the sulphuret and water interchange ele- Theories, ments, hydrosulpharic acid and protoxide of iron are generated ; the latter unites with sulphuric acid and the former escapes. In the process with antimony the elements concerned are — 1 eq. sesquisulphuret and 3 eq. hydrochloric acid 2Sb+3S 3(H+C1) which yield 3 eq. hydrosulphuric acid and L eq. sesquichloride of antimony 3(H+S) 2Sb+3Cl 756. The gas may be collected over water, though, by agitation, Absorbed that fluid absorbs nearly thrice its bulk ; it should be received into by water ' bottles provided with glass stoppers, and after filling them entirely with the gas, the stopper should be introduced. 757. Faraday obtained it in a liquid form by producing it under Liquefac- pressure. It was colourless, limpid, and with a refractive power tio n of sul- greater than that of water. The pressure of its vapour was nearly hydrogen equal to 17 atmospheres at the temperature of 50° F. Its specific gravity appeared to be 0.9. 758. When in the form of gas, the smell is extremely offensive, Properties, resembling that of putrefying eggs, or of the washings of a gun- barrel, to which indeed it imparts their offensive odour. It exists in some mineral waters. 759. It appears to be one of the most unrespirable of all the gases, Unrespira- for a small bird died immediately in air containing x of its vo- ble ’ lume of hydrosulphuric acid gas ; a dog perished in air mingled with ■g-^, and a horse in air containing 760. It tarnishes silver, mercury, and other polished metals, and Action on instantly blackens white paint and solution of acetate of lead. By metals, direct experiments, Henry has found that one measure of this gas, mixed with 20.000 measures of hydrogen, or of carburetted hydro- gen, or common air, produces a sensible discoloration of white lead, or of oxide of bismuth, mixed with water, and spread upon a piece of card. 761. It is inflammable, burning with a pale blue flame, but does inflnmma- not support the combustion of other bodies. Water and sulphurous ble. acid are the products of its combustion, and sulphur is deposited. 762. Hydrosulphuric acid contains its own vol. of hydrogen gas, Coinposi- and 16.66 of the vapour of sulphur; and since tion - 16.66 cub. inches of the vapour of sulphur weigh . . 34.4012 grs. 100 ^ “ hydrogen gas “ . . 2.1367 100 “ “ hydrosulphuric acid gas must weigh . 36.5379 T. 763. The salts of hydrosulphuric acid are called hydrosulphates or Salts of. hydrosulphurets. They are decomposed by sulphuric or hydrochlo- ric acids. This acid rarely unites directly with metallic oxides ; but in most cases its hydrogen combines with the oxygen of the oxide, and its sulphur with the metal. *Thenard, iii. 601. 216 Cha p. III. Use. Solution decompo- sed. Process. Theory. Properties. Composi- tion. Hydrogen and Sulphur. 764. Hydrosulphuric acid, both in the state of a gas and of watery solution, precipitates most metallic solutions, and is hence an ex- ceedingly delicate test of the presence of most of the metals. Water impregnated with this gas, when exposed to the atmos^ phere, becomes covered with a pellicle of sulphur. Sulphur is even deposited when the water is kept in well closed bottles. Chlorine, iodine and bromine decompose it with separation of suh phur, and an atmosphere charged with the gas may be speedily pu- rified by chlorine. Per sulphur et of Hydrogen. Composition. Form. Hydr. Sulph. Equiv. HS 2 • 1 1 eq. + 32.2 2 eq. — 33.2 765. This compound was discovered by Scheele and described by Berthollet.* When protosulphuret of potassium (or of any metal of the alkalies and alkaline earths) is mixed in solution with sul- phuric acid, the oxygen of water unites with potassium and its hy- drogen with sulphur.! 7 66. Persulphuret of hydrogen is conveniently made by boiling equal parts of recently slaked lime and flowers of sulphur with 5 or 6 parts of water for half an hour, when a deep orange-yellow solution is formed, which contains persulphuret of calcium. Let this liquid be filtered, and gradually added cold to an excess of hydrochloric acid diluted with about twice its weight of water, stirring it briskly. A copious deposit of sulphur falls (the Sulphur Pracipitatuvn of the Lond. Pharmacop.) and persulphuret of hydrogen gradually subsides in the form of a yellowish semi-fluid matter like oil. 767. The change which ensues in the formation of the yellow so- lution may be theoretically represented thus : — 2 eq. lime and 6 eq. sulph. 2 1 eq. hyposulphs. acid and 2 eq. bisulphuret of calcium. 2(Ca+0) 6S .2 2S+20 2(Ca+2S). The hyposulphurous acid exists in solution united with lime, and is decomposed when hydrochloric acid is added, resolving itself into sulphurous acid and sulphur. 76S. At common temperatures it is a viscid liquid of a yellow colour, with a density of about 1.769, and a consistence varying be- tween that of a volatile and fixed oil. It has the peculiar odour and taste of hydrosulphuric acid, though in a less degree. Its ele- ments are so feebly united, that in the cold it gradually resolves it- self into sulphur and hydrosulphuric acid, and suffers the same change instantly by a heat considerably short of 212° F. Decom- position is also produced by the contact of most substances, especial- ly of metals and oxides. 769. The composition of persulphuret of hydrogen has been va- riously stated. According to Dalton it is a bisulphuret. But The- nard found its constituents to vary; whence it is probable that hy- drogen is capable of uniting with sulphur in several proportions. It is sometimes regarded as an acid. * Ann. de Chim. xxv. t See Turner, 254. Phosphuretted Hydrogen. 217 Section XVI L Hydrogen and Selenium. Seleniuretted Hydrogen. 770. These bodies combine to form a gaseous compound termed Seleniuret- seleniuretted hydrogen or hydroselenic acid. It may be obtained by ted hydrog. "dissolving protoseleniuret of iron in hydrochloric acid. 771. It is a colourless gas, highly irritating to the lining mem- Properties, brane of the nose, and for a time destroying the power of smelling. Its solution smells and tastes somewhat like hydrosulphuric acid ; it reddens litmus and tinges the skin brown. It is decomposed by the air, nitric acid and chlorine, and selenium is deposited. It occa- sions precipitates in solutions of neutral metallic salts, which are black or dark brown, with the exception of those from zinc, manga- nese and cerium, which are flesh-coloured. 772. Seleniuretted hydrogen is easily decomposed by the action ^ e d compo ’ of air and water ; it is absorbed by moist substances and communi- cates to them a red colour. The selenium is thus remarkably de- posited throughout the texture of organic bodies. A piece of moist paper is penetrated by the red colour. Moist wood and even a thin piece of caoutchouc became in the same way red throughout. B. 292. Hydroselenic acid consists of 39.6 or 1 eq. of selenium and I of hydrogen ; its equiv. is 40.6 and its formula H-f-Se or HSe. Section XVIII. Compounds of Hydrogen and Phosphorus. 773. The two compounds of hydrogen and phosphorus which ^ und s° m ' have heretofore been known as phosphuretted and perphosphuretted hydrogen, have been found by Rose to be isomeric, identical in com- position, and to differ only by the one being spontaneously inflam- mable and the other not so. Leverrier* has proved that perphosphu- retted hydrogen is a mixture of phosphuretted hydrogen with about fjy of its volume of a spontaneously inflammable compound of 31.4' g^ ^ parts or 2 eq. of phosphorus, and 2 parts or 2 eq. of hydrogen. In ^yd. the same paper he establishes the existence of a solid compound of 2 eq. of phosphorus and 1 eq. of hydrogen. The latter is deposited on the sides of the glass vessel when moist phosphuretted hydrogen gas, recently prepared, is exposed to strong light. Phosphuretted Hydrogen. tSyrrib. Density . Equiv. Eq. V'ol. 2P+3H or P 2 H 3 1.1850 34.4 200 774. Phosphuretted hydrogen was discovered by Davy in 1S12, oiseov er y, by heating hydrated phosphorous acid in a retort ; and it &c. is evolved from hydrous hypophosphorous acid by similar treat- ment. It is also formed, according to Dumas, by the action of strong hydrochloric acid on phosphuret of calcium. 775. It may also be obtained, in an impure state, by boiling phos- p rocegs phorus with a solution of potassa, or milk of lime. Water is de- composed, the oxygen and hydrogen of which unite with different portions of phosphorus, and phosphoric acid, hypophosphorous acid, and phosphuretted hydrogen are generated. * See the papers of Dumas, Buff, Rose, and Graham, in An • de Ch. ei de Phys. xxxi. 113, xli. 220, and xli. 5, Phil. Mag. v. 401. 218 Chap- III. Explodes with air, &c. Process. Another. Properties. Mitchell’s method of pre- paring phos- phuret of catct- Uffl, Hydrogen and Phosphorus. 776. When the gas is obtained pure from hydrated phosphorous or hypophosphorous acids, it may be mixed with air or oxygen gas at common temperatures without danger ; but the mixture detonates with the electric spark or at a temperature of 300°. Even dimin- ished pressure causes an explosion, an effect which in operating with the mercurial trough is produced simply by raising the tube, so that the level of the mercury within may be a few inches higher than at the outside. 777. In preparing the gas from phosphorus and solution of po- tassa in a glass retort, the atmospheric air should be removed, other- wise explosion may occur. A retort holding a pint may be employed. About a quarter of an ounce of phosphorus may be placed in the retort and a moderately strong solution ofpotas- sa poured upon it until the neck and body of the retort are completely filled. The finger being placed over the beak it is next immersed under the surface of a portion of the same so- lution, contained in a glass dish or a small pneumatic trough, and the finger is then removed. The retort may be attached to a block of wood or supported securely upon the rings of a retort stand. (Fig. 17G.) The su- perfluous solution may then be removed by passing up hydrogen gas.* The neat of a lamp is carefully applied and soon after the solution boils, the gas is evolved in abundance, and inflames on escaping into the air. Forty grains of phosphorus, fifty of caustic potassa, and sixty drops of water, give this gas very readily when gently heated in a small retort, (capable of holding an ounce and a half or two ounces when quite full,) and with very little trouble. The readiest mode of procuring this gas is by means of phosphu- ret of calcium ;t lumps of which may be dropped into water acid- ulated with hydrochloric acid. The retort or gas bottle may be placed wholly beneath the water in the pneumatic trough, and the combustion of the bubbles of gas will take place at the surface. 778. This gas is colourless, has a nauseous odour like onions, a very bitter taste, and inflames when mixed with air, a property * This may be done from a gas bottle having a long and slender leaden pipe at- tached to it, or by a pipe and flexible tube proceeding from the apparatus (Fig. 120.) It will be found necessary after all the solution has been expelled from the neck to incline the body of the retort so as to allow a part of what remains in the body to flow into it, which is to be expelled as at first. A very simple method of avoiding all danger, is to moisten the interior of the re- tort with ether. t.The following method of obtaining this compound has been described by Mitchell.* I employ two Hessian crucibles, some of the inner members of a nest. The larger of the two has a hole bored through its bottom, and a test tube of a suitable size luted in with clay. The phosphorus is put into the test tube ; the top of which is loosely covered with a piece of broken crucible to prevent the pieces of quicklime from running down into it. The lime is then put in so as to fill this crucible and partly fill the upper one, which serves as a cover to it, and is luted on with some fine clay a little moisten- ed. The cover has also a small hole in its top to afford an outlet for the air, &c. The whole is placed upon the grate of a furnace, with the test tube projecting through it below, and a charcoal fire is kindled around it. The phosphorus may be kept cool, if necessary, by making the tube dip into water contained in a tin cup attached to the end of a stick. When the crucibles and contents are thoroughly red-hot, a chafing dish is substituted for the tin cup, and the phosphorus rising in vapour produces the desired change. The phosphuret should be preserved in a sealed phial. * Mitchell in Jimer. Jour. xvii. 349, Fig. 176. 219 Cyanogen Gas , which it loses by being kept over water ; water takes up two per cent, of the gas, and acquires a bitter taste and the smell of onions. 779. If the beak of the retort (776) is plunged under water, the successive bubbles of gas as they escape, burst into flame and form rings of dense white smoke which enlarge as they ascend, retaining their shape if the air is tranquil. The wreaths are formed of meta- phosphoric acid and water. 780. When bubbles of phosphuretted hydrogen are let up into a jar of oxygen, they burn with greatly increased splendour. They should be received in a large jar, but half filled with oxygen, and care must be taken not to allow them to accumulate in the jar. The safest me- thod is to collect a few bubbles in a small phial and pass them up from that into the large jar, a bubble at a time. Similar experiments may be made with chlo- rine. 781. One hundred measures of phosphuretted hydrogen gas con- tain 150 of hydrogen and 2 5 of vapour of phosphorus, hence as 150 eub. inches of hydrogen gas weigh .... 3.2050 grs. 25 “ “ phosphorus vapour .... 33.5461 “ ]00 “ “ phosphuretted hydrogen gas should weigh 36.7511 and its calculated density should be 1.1850, which is nearly a mean of the observations of Dumas and Rose. 782. According to Leverrier, it is probable that the compound of phosphorus and hydrogen composed of two equiv. of each of its ele- ments, which is spontaneously inflammable, communicates that pro- perty to phosphuretted hydrogen gas. This opinion is grounded on the fact that when spontaneously inflammable phosphuretted hydro- gen is kept for any length of time in the dark it suffers no change, but in a strong light, solid phosphuretted hydrogen is deposited, and the residual gas is no longer spontaneously inflammable. Thus it appears that by the action of light P 2 H 2 is decomposed, and P 2 H and P 2 H 3 are formed. T. 258 . Section XIX. Compounds of Nitrogen and Carbon. Bicarburet of Nitrogen-— Cyanogen Gas . Composition. Form,. Sp. Gr. Nit. Car. Equiv. N+2C, or NC 2 , or Cy. 1,8157 Air = 1 14.15 1 eq. 12.24 2 eq. 26.39 by Wght. 25.39 Hyd. =1 100 “ Vol. 783. This gaseous compound was discovered by Gay-Lussac, in 1815, ^ and was called cyanogen from yvavos, blue , and yew&oj, I ge- nerate, because it is an essential ingredient of Prussian blue. 784. It is obtained by heating dried bicyanuret of mercury in a small glass retort! This cyanpret, formerly called prussiate of mercury , is composed of metallic mercury and cyanogen. On expo- sure to a low red heat, it is. resolved into its elements; the cyanogen passes over in the form of gas, and the metallic mercury is sublimed. The heat applied should be sufficient to expel the cyanogen slowly and steadily, as it is liable ;to be decomposed by a high temperature. Towards the end of the process, a black substance is procured, aris- Sect. XIX. Rings. Combus- tion in ox- ygen. Exp. Composi- tion and density. Effect of light. Cyanogen. Process. * Ann. de Ckim. xcv. t For the method of preparing : tjiis cyanu.ret, see Mercury. 220 Nitrogen and Carbon. Chap hi. ing from the decomposition of part of the cyanogen, consisting of the same ingredients as the gas itself. T. Properties. 785. Cyanogen has a strong, penetrating, and disagreeable smell, resembling that of bitter almonds. It burns with a bluish flame mixed with purple, which can be shown by igniting it at the beak of the retort, which may be drawn out to a fine point before the blow-pipe. 786. It must be collected over mercury, as water absorbs 4.5 times ° ected. vo | ume 0 f t | ie g as . ^he aqueous solution reddens litmus paper, an effect, however, not to be ascribed to the gas, but to acids ge- nerated by the mutual decomposition of cyanogen and water. 787. Cyanogen contains its own bulk of nitrogen and twice its volume of the vapour of carbon ; and since 100 cubic inches of nitrogen gas weigh . . . 30.1650 grs. 200 “ “ vapour of carbon “ ... 26.1428 “ 100 “ “ cyanogen gas must weigh . . 56.3078 “ The ratio ofits elements by weight is, Nitrogen 30.1650 . . . 0.9727 14.15 1 eq. Carbon 26.1428 . . . 0 8430(2+0.4215) . . . 12.24 2 eq. Sp. gr. The sp. gr. of a gas so constituted is 0.9727-f-0.843= 1.8157, which is near 1.8064 the number found experimentally by Gay-Lussac. Cyanogen is a bicarburet of nitrogen ; but its most convenient name, cyanogen , may be expressed by Cy.* t. 259 . Section XX. Compounds of Sulphur with Carbon , fyc. Bisulphuret of Carbon. Composition. Carbon and sulphur, bi- sulphuret, or alcohol of sulphur. How ob- tained. Properties, Form. Carb. Sul. Equiv. Eq. Vol. C+2SorCS 2 6.12 + 32.2 = 38.32 100 788. This substance was discovered in 1796 by Larnpadius who regarded it as a compound of sulphur and hydrogen, and termed it alcohol of sulphur. 789. It may be obtained by heating in close vessels the native bi- sulphuret of iron (iron pyrites) with one fifth of its weight of well dried charcoal, or by passing the vapour of sulphur over fragments of charcoal heated to redness in a tube of porcelain.! 790. The bi-sulphuret of carbon is eminently transparent, and perfectly colourless. Sometimes, immediately after distillation, the * Paracyanogen. Symb. N 4 C 8 . Eq. 105.56? The brown matter left in the retort in the foregoing process (784) is a solid bicarburet of nitrogen, isomeric with cyanogen, but differing from it in its physical and chemical relations. Heated in the open air, several definite compounds of carbon and nitrogen may be obtained.* It is soluble in nitric and sulphuric acids and forms a compound with oxygen in which one eq. of ox- ygen is combined with four eq. of nitrogen and eight eq. of carbon. Mellon. Symb. N 4 C 6 . Eq. 93.32. It is a lemon yellow coloured Dowder, insolur ble in water and alcohol, but soluble and decomposable by acids ana alkalies. By heat it affords one vol. of nitrogen and three of cyanogen. It is one of the compound radicals. T. Compound of Phosphorus and Nitrogen. Phosphuret of Nitrogen. Symb. N+2P, or NP 2 . Eq. 45.55. When either of the chlorides of phosphorus is saturated with dry amrnoniacal gas, a white solid mass is obtained, which on exposure to a strong heat, gives rise to the formation of phosphuret of nitrogen, and hydrochloric acid gas. It is a light snow white powder, insoluble in water. It is composed of 31.4 parts or 2 eq. of phosphorus, and 14.15 or one eq. of nitrogen. t A porcelain tube an inch or more in diameter is coated with clay and wrapped round • Brewster 1 * Jour. N. S. 1. 75. 221 Sulphuret of Phosphorus. oily liquid appears a little opaque and milky ; but the next day it is Sect, xx. found to have become completely limpid. It has an acrid, pungent, and somewhat aromatic taste ; its smell is nauseous and fetid. It is soluble in alcohol and ether ; its refractive power in regard to light is very considerable. Its sp. gr. is 1.272 ; of its vapour 2.668. It boils at 110°, and does not freeze at — 60°. It is very volatile, and the cold which it produces during evaporation is so intense, that by exposing a thermometer bulb, covered with fine lint, moistened with it, in the receiver of an air-pump, the temperature sunk, after ex- haustion to —80°. When a mercurial thermometer is used, the metal freezes. When a few drops of this liquid are poured on the surface of a glass of water, the temperature of which is 32° F. plumose branches of ice dart to the bottom of the vessel, and the whole water is suddenly frozen. At the same time, the sulphuret becomes volatilized ; and the spiculae of ice beautifully exhibit the colours of the solar spectrum. 791. Bisulphuret of carbon is a sulphur-acid, that is, it unites with A su ] p h ur . sulphur bases to constitute compounds analogous to ordinary salts, acid, and hence called sulphur-salts. Thus bisulphuret of carbon unites with sulphuret of potassium, forming a sulphur salt, in which the former acts as an acid and the latter as a base. T. Sulphuret of Phosphorus . 792. Sulphur and fused phosphorus unite frequently with vio-p rocess lence. The experiment should not be made with more than 30 or 40 grs. of phosphorus. The phosphorus is placed in a glass tube 5 or 6 inches long, and about half an inch wide, when by a gentle heat it is liquefied, the sulphur is added in successive small portions. The compound is highly combustible.* * with iron wire. It is then filled with frag- Fig. 177. ments of charcoal, taking care to leave room for the passage of vapour, and made to traverse a furnace as represented in Fig. 177. A retort filled about a third full of sulphur is then fitted to one end of the tube, supporting it by a retort stand, and using a mixture of clay and sand to make the join- ing air-tight. A bent glass tube about half an inch or rather less in diameter is attach- ed in the same manner to the ether extre- mity of the porcelain tube, anci connected with a glass globe terminating in a small tube placed in a receiver half full of water, which must be kept cold. When everything has been properly ad- justed, fire is put into the furnace, and the tube with the charcoal brought gradually to a strong red heat. The sulphur in the retort is then made to pass over it in vapour, and as they combine, the bisulphuret which is formed condenses in drops that fall to the bottom of the water in the receiver. The use of the globe is to prevent any water passing back to the porcelain tube. The charcoal should be well prepared, and not mixed with any unchanged woody fibre. Reid. * Bisulphuret of Selenium is of an orange colour, and fuses at a heat a little above 212°. Selenium also combines with phosphorus and forms a seleniuret which is very fusible. Sulphuret of Nitrogen is formed by the reaction of chloride of sulphur on a solu- tion of ammonia, aud contains from 92 to 93 percent, of sulphur, and 7 to 8 of ni- trogen. Seleniuret of Phosphorus may be made in the same manner as sulphuret of phos- phorus. It is very fusible and decomposes water when digested in it. Sulphuret of Nitrogen is formed by the reaction of chloride of sulphur on a solu- 222 Metals. Chap. IV. Number. CHAPTER IV. METALS. Section I. General Properties , and Combinations. 793. Many of the metals have been long known, while some have been recently discovered. There are fortytwo bodies of this class; they are incapable of being resolved into more simple parts, and are therefore regarded as elementary. Most of them are remarkable for their specific gravity; they are conductors of electricity and heat, they are positive electrics, opaque, possess a peculiar lustre, and are in general good reflectors of light. 794. The following table contains their names, date of discovery, specific gravity at 60° F., and symbols. Names of Metals. Dates of the Discovery. Specific Gravity. S/mb. Gold, m. Silver, m. . 19.267 . . . Au. • • • • . 10.474 . . . Ag. Iron, m. Copper, m. . 7.788 . . . Fe. . 8.895 . . . Cu. Mercury, . 13.568 . . . Hg- Lead, m. . 11.352 . . . Pb. Tin, m. J . 7.291 . . . Sn. Antimony, 1490 . . . 6.702 . . . Sb. Bismuth, 1530 . . . 9.822 . . . Bi. Zinc, m. 16th century. . . 6.861 to 7.1 Zn. Arsenic, i ► 1733 ' ■ . 5.8843 . . . As. Cobalt. j . 7.834 . . . Co. Platinum, m. 1741 . . . 20.98 . . . Pt. Nickel, m. 1751 . . . 8.279 . . , Ni; Manganese, 1774 . . . 8.013 . . . Mn. Tungsten, 1781 . . . 17.6 . . . W. Tellurium, Molybdenum, 1782 . . 6.115 . . . Te. 1782 . . . 8.615 to 8.636 . Mo. Uranium, 1789 . . . 9.000 . . . U. Titanium, 1791 . . .5.3 ... Ti. Chromium, 1797 . . .5+ ... Cr. Columbium, 1802 . . Ta. Palladium, m. ) Rhodium, S 1803 • * . 11.3 to 11.8 . . Pd. R. Iridium, 1803 *. *. . 18.68 .... Ir. Osmium, 1803 . . Os. Cerium, 1804 . . Ce. Potassium, m. } . 0.865 . '. . K. Sodium, m. . 0.972 . . . Na. Barium, Strontium, 1307 ! ! Ba. Sr. Calcium, Ca. Cadmium, m. 1818 . . . 8.604 , . . Cd. Lithium, 1818 . . L. Zirconium, 1824 . . Zr. Aluminium, J ) Al. Glucinium, > 1823 . . G. Yttrium, ‘ ) . Y. Thorium, Magnesium is29 ! ! Th. 1829 . . Mg. Vanadium Latanium, 1830 . . 1839 . . V. tion of ammonia. It is a colourless powder. Its alcoholic solution gives with potassa a fine purple colour which is fugitive. It contains from 92 to 93 per cent, of sulphur, and 7 or 8 of nitrogen. T. 223 Fusibility of Metals . 795. Malleability and ductility are important properties of metals.* Those metals which are remarkable for ductility are gold, silver, platinum, iron, and copper. 796. The metals also differ in tenacity, in which property iron surpasses all others. Their hardness also varies, some as titanium, iron, &c., are very hard ; others, as lead, are soft, and a few, as po- tassium, yield to the pressure of the fingers. 797. Some of the malleable and ductile metals have, also, a high degree of elasticity. This property fits them for being applied to the mechanical purpose of springs. Steel and iron are in this re- spect, superior to all other metals. Upon the properties of elasticity and hardness, appears also to depend that of fitness for exciting sound. 798. Many of the metals have a distinct crystalline structure, and not only occur in nature in distinct crystals, but can be obtained in that state by careful fusion and cooling. Thus bismuth, melted in a crucible, and suffered to cool, becomes covered with a crUst, and when this is pierced, and the fluid be- neath allowed to flow out, the cavity is found studded with beautiful- ly regular cubic crystals. 799. Metals, with the exception of mercury, are solid at common temperatures ; but they may all be liquefied by heat. The degree at which they fuse, or their point of fusion , is very different for dif- ferent metals, as appears from the following table. Fusible below a red heat Infusible below a red heat. Table of the Fusibility of different Metals. Fahr. Mercury Potassium Sodium Cadmium Tin, . Bismuth Lead . Tellurium — rather fusible than lead. Arsenic — undetermined . Zinc .... Antimony a little below a red heat. Silver about less 773 Different chemists. Gay-Lussac and Thenard. Stromeyer. Crichton. Klaproth. Daniel!. Copper Gold . Iron, cast Iron, malleable Manganese Cbbalt — rather less fu- sible than iron. Nickel — nearly the same as cobalt. Palladium DanielL 1873 1996 2016 2786 [ _ Requiring the highest heat of a smith’s forge. Molybdenum Uranium Tungsten Chromium Titanium Cerium Osmium Iridium )> Rhodium I Platinum j Columbium j > Almost infusible, and not to be procured in but- tons by the heat of a smith’s forge. Fusible be- fore the oxy- hydrogen blow-pipe. Infusible in the heat of a smith’s forge, but fusible before the oxy-hydrogen blow-pipe- Sect. I. Tenacity. Elasticity. Structure. Crystalli- zation. Fusibility of Metals. * The malleable metals are designated in the table by the letter m., to which may be added frozen mercury. 224 Metals . Chap. IV. Volatile. Action of metals up- on each other. Alloys. Amalgams. Characters of alloys. Union with other bo- dies. Combusti- ble. Product. 800. Some metals are volatilized by heat, others may be exposed to the intense heat of a wind furnace without being raised in va- pour. The metals may for the most part be combined with each other, forming a very important class of compounds, the metallic alloys. The word alloy is a general term for all combinations of metals with each other ; and the specific name is derived from that of the metal, which prevails in the compound. Thus in the alloy of gold with silver , the gold is to be understood as being in greatest propor- tion ; in the alloy of silver with gold , the silver is the principal in- gredient.* The compounds of mercury with other metals, at a very early pe- riod of chemistry, were called amalgams, and the term is still retained. 801. When metals are alloyed their properties are more or less affected. 1. We observe a change in the ductility, malleability, hardness, and colour. Malleability and ductility, are usually impaired, and often in a remarkable degree. *2. The specific gravity of an alloy is rarely the mean of its com- ponent parts ; in some cases an increase, in others a diminution of density having taken place. 3. The fusibility of an alloy is generally greater than that of its components. 4. Alloys are generally more oxidizable than their constituents, taken singly. 802. The metals, although they readily unite with the elementary substances, are little disposed to combine in the metallic state, with compound bodies, such as an oxide or an acid. Their union with the simple non-raetallic substances, such as oxygen, chlorine, and sulphur, gives rise to new bodies in which the metallic character is wholly wanting. In all these combinations the tendency to unite in definite proportions is conspicuous ; the chemical changes are regu- lated by the same general laws already described, and the same nomenclature is applicable. 803. Metals are of a combustible nature; that is, they are not only susceptible of slow oxidation, but, under favorable circumstan- ces, they unite rapidly with oxygen, giving rise to all the phenomena of real combustion. Zinc burns with a brilliant flame when heated to full redness in the open air; iron emits vivid scintillations on be- ing inflamed in an atmosphere of oxygen gas; and the least oxida- ble metals, such as gold and platinum, scintillate in a similar man- ner when heated by the oxy-hydrogen blow-pipe. S04. The product either of the slow or rapid oxidation of a met- al, when heated in the air, has an earthy aspect, and was called a * Various processes are adopted in the formation of alloys depending upon the na- ture of the metals. Many are prepared by simply fusing the two metals in a cov- ered crucible ; but if there be a considerable difference in the specific gravity of the metals, the heavier will often subside, and the lower part of the bar or ingot, will differ in composition from the uppeT ; this may be prevented by agitating the alloy till it solidifies. When one of the metals is very volatile, it should generally be added to the other after its fusion j and if both metals be volatile, they may be sometimes united by dis- tilling them together. Action of Chlorine. 225 calx by the older chemists, the process of forming it being expressed Sect. 1 by the term calcination. Another method of oxidizing metals is by deflagration ; that is, by mixing them with nitrate or chlorate of po- tassa, and projecting the mixture into a red-hot crucible. Most met- als may be oxidized by digestion in nitric acid; and nitro-hydro- chloric acid is an oxidizing agent of still greater power. 805. Some metals unite with oxygen in one proportion only, but Union with most of them have two or three degrees of oxidation. Metals differ ox ^ e remarkably in their relative forces of attraction for oxygen. Potas- sium and sodium, for example, are oxidized by mere exposure to the air ; and they decompose water at all temperatures, the instant they come in contact with it. Iron and copper may be preserved in dry air without change, nor can they decompose water at common tem- peratures ; but they are both slowly oxidized by exposure to a moist atmosphere, and combine rapidly with oxygen when heated to red- ness in the open air. Iron has a stronger affinity for oxygen than copper ; for the former decomposes water at a red heat, whereas the latter cannot produce that effect. Mercury is less inclined than cop- per to unite with oxygen. Thus it may be exposed without change to the influence of a moist atmosphere. At a temperature of 650° or 700° it is oxidized ; but at a red heat it is reduced to the metallic state, while oxide of copper can sustain the strongest heat of a blast furnace without losing its oxygen. The affinity of gold for oxygen is still weaker than that of mercury ; for it will bear the most in- tense heat of our furnaces without oxidation. 806. Metallic oxides may be reduced to the metallic state by heat Reduction alone, by the united agency of heat and combustible matter, as in 0 0X1 es ‘ metallurgy when metals are extracted from their ores with the aid of charcoal, &c., by galvanism, and by the action of deoxidizing agents on metallic solutions, as when one metal is precipitated by another. To a solution of the nitrate of oxide of silver, add a small quantity of Exp. mercury, the silver will be thrown down in a metallic form, and oxide of mer- cury be dissolved in the nitric acid and water. From this solution the mercury may be separated by placing in it a polished rod of copper, and a solution of nitrate of oxide of copper will be obtained, from which the copper may be precipitated by a rod of iron. S07. Metals, like the simple non-metallic bodies, may give rise to Acids from oxides or acids by combining with oxygen. The former are the metals, most frequent products. The acids contain a larger quantity of oxy- gen than the oxides of the same metal. 808. Many of the metallic oxides have the property of combining Oxides and with acids. In some instances all the oxides of a metal are capable acids - of forming salts with acids, as is exemplified by the oxides of iron : but, generally, the protoxide is the sole alkaline or salifiable base. Most of the metallic oxides are insoluble in water- Oxides some- times unite with each other and form definite compounds. 809. The metals combine with chlorine, and the compounds are Action of termed chlorides. In some instances the application of heat is re- chlorine, quir'ed : the combination is in some cases slow and in others rapid, attended with the evolution of light. The attraction of chlo- rine for the metals is superior to that of oxygen ; hence when chlorine is brought into contact with their oxides, the oxygen is libe- rated and a chloride of the metal is obtained, the elements of which 29 226 Metals. Chap. IV. C haracters of chlo- rides, Decompo- sition of, Procured. Action of iodine, Of bromine, Of fluorine, Of sulphur. Action of heat on sul- phurets. are so strongly united, that in some cases they are not separated by intense heat. 810. The metallic chlorides are mostly solid at common tempera- tures, fusible, and susceptible of crystallization ; several of them are volatile ; most of them are soluble. They are of nearly all colours. 811. The chlorides of the common metals are decomposed at a red heat by hydrogen gas, hydrochloric acid being disengaged and the metal set free. When in solution they may be recognised by yield- ing with nitrate of oxide of silver a white precipitate, which is chlo- ride of silver. Several of them decompose water, giving rise to the formation of hydrochloric acid and an oxide (617), or in some cases to a hydrochlorate.* 812. Metallic chlorides are frequently procured by dissolving me- tallic oxides in hydrochloric acid, evaporating to dryness, and apply- ing heat so long as any water is expelled. S13. The same metal often forms more than one compound with chlorine, and these compounds are designated as the oxides. 814. Iodine has a strong attraction for metals ; and most of the compounds which it forms with them sustain a red heat in close ves- sels without decomposition. But in the degree of its affinity for me- tallic substances it is inferior to chlorine and oxygen. The metallic iodides are generated under circumstances analogous to those men- tioned for procuring the chlorides. The action of iodine on metallic oxides, when dissolved or sus- pended in water, is precisely analogous to that of chlorine. On adding iodine to a solution of the pure alkalies or alkaline earths, an iodide and iodate are generated. 815. Bromine, in its affinity for metallic substances, is intermedi- ate between chlorine and iodine ; for while chlorine disengages bromine from its combination with metals, metallic iodides are de- composed by bromine. The same phenomena attend the union of bromine with metals, as accompany the formation of metallic chlo- rides. The nature of the action of fluorine upon the metals is im- perfectly known ; it exerts an extremely powerful affinity for them, which is the great obstacle to obtaining it in an insulated form. 816. Sulphur has a strong tendency to unite with metals. The metallic sulpkurets are in some cases formed by heating the metal with sulphur ; in others, by decomposing the sulphates ; and in oth- ers, by the action of hydrosulphuric acid. The sulphurets are in general brittle; some have a metallic, lustre; others are without lus- tre. Some are soluble, others insoluble in water. 817. Most of the protosulphurets support an intense heat without decomposition ; but, in general, those which contain more than one equivalent of sulphur, lose part of it when strongly heated. They are all decomposed without exception by exposure to the combined agency of air or oxygen gas and heat; and the products depend en- tirely on the degree of heat and the nature of the metal. The action * A difference of opinion exists among chemists as to the action of the chlorides upon water, some supposing them to become hydrochlorates when dissolved, others main- tain that some metallic chlorides dissolve as such. The latter opinion has been adopt- ed by Turner from considerations for which see his Elements , 272. See also Brande, 1 . 370. Union of Metals. 227 of heat and air in decomposing metallic sulphurets is the basis of Sect - *• several metallurgic processes. The metallic bases of the alkalies and alkaline earths agree with the common metals in their disposi- tion to unite with sulphur. 818. If a sulphate be decomposed by hydrogen or charcoal, or Decompose sulphur ignited with an alkali or alkaline earth, a metallic sulphuret is always the product. Direct combination between sulphur and a metallic oxide is a very rare occurrence, nor has the existence of such a compound been clearly established.^ 819. The metallic seleniurets have a resemblance in their chemi- Seieniurets, cal relations to the sulphurets. They may be prepared either by bringing selenium in contact with the metals at a high temperature, or by the action of hydroselenic acid on metallic solutions.! 820. Phosphorus combines with the greater number of the metals, Action of forming a series of metallic phosphurets. There are three methods *; lls p of forming them ; either by heating a mixture of phosphorus and the metal, or projecting phosphorus upon the metal previously heated to redness; or by heating a mixture of the metal or its oxide, with phosphoric acid and charcoal, or by passing phosphuretted hydrogen over the heated metallic oxide. These phosphurets have a metallic lustre ; if they contain a difficultly fusible metal they are more fusi- ble than the metal they contain ; if an easily fusible metal, less so.t 821. When phosphorus is introduced into the solutions of those ^metajlic metals which have but a feeble attraction for oxygen, it reduces 0 u 1 * them to the metallic state. Thus gold, silver, and platinum are thrown down by immersing a stick of phosphorus into their respec- tive solutions. 822. Carbon unites to very few of the metals, and of the metallic Action of carburets, one only is of importance, namely, carburet of iron, or carbon, steel. 823. Hydrogen forms compounds with but a few of the metals, Ofhydro- which are termed hydrogurets or hydrurets, gen ' 824. The metals may, for the most part, be combined with each Action of other, forming a very important class of compounds, the metallic al- metals on loys. Various processes are adopted in the formation of alloys de- ^ a< j 0 er ’ pending upon the nature of the metals. Many are prepared by oys ’ simply fusing the two metals in a covered crucible ; but if there be a considerable difference in their specific gravity, the heavier will sub- side, and the lower part of the bar or ingot will differ in composition from the upper ; this may be to a great extent prevented by agitating the alloy till it solidifies. 825. Where one of the metals is very volatile, it should be added Of volatile to the other after its fusion ; and if both metals be volatile, they may metals, be sometimes united by distilling them together. 826. Metals appear to unite with one another in every proportion, Union in thus there is no limit to the number of alloys of gold and copper. It definite is certain, however, that metals have a tendency to combine in defi- ^ons^ * See Turner, p. 270. t For the different opinions in regard to these compounds see Ibid, p. 272. t Phosphorus is said to unite with metallic oxides, as when phosphuret of lime is said to be formed by passing the vapour of phosphorus over lime at a low red heat ; hut it is probable that part of the metallic oxide is decomposed, and that phosphuret of calcium and phosphate of lime are formed. T. 228 Metals. Chap. IV. Characters of allays. Oxidation of alloys, Action of acids. Classifica- tion of met- als. 1st order, 2d, 3d. nite proportions ; for several atomic compounds of this kind occur native.* 827. When metals are alloyed they undergo great change of pro- perties, their malleability and ductility are usually impaired, and the colours changed. The hardness is in general increased, and the elasticity and sonorousness frequently improved. The specific gra- vity of an alloy is rarely the mean of its component parts, sometimes greater and sometimes less.T The fusibility of an alloy is generally greater than that of its components. Thus platinum, when alloyed with arsenic is very fusible, and an alloy of 8 parts of bismuth, 5 of lead, and 3 of tin liquefies at 212°, 828. Alloys are generally more oxidizable than their constituents, taken singly ; a property which is, perhaps, partly referable to the formation of an electrical combination. Thus the oxidability of zinc is increased by the presence of small quantities of iron. 829. The action of acids upon alloys may generally be anticipated by a knowledge of their effects upon the constituent metals; but if a soluble metal be alloyed with an insoluble one, the former is often protected by the latter from the action of the acid. Thus, silver, al- loyed with a large quantity of gold, resists the action of nitric acid in consequence of the insolubility of the latter metal in that acid ; and in order to render it soluble, it should form about one fourth part of the alloy, B. l. 382. 830. To those alloys of which mercury is a constituent the term amalgam is applied. 831. The metals may be divided into two classes, viz : 1, those which by oxidation yield alkalies or earths, and, 2, those the oxides of which are "neither alkalies nor earths. These classes maybe subdivided as follows : 1st. Metals that decompose cold water at the moment of contact, combining with its oxygen and liberating hydrogen. The resulting oxides are caustic, soluble in water, and possess alkaline properties. They are called alkalies , and their metallic bases alkaline or alkali - genous metals. They are, Potassium, Sodium, Lithium. 2d. Metallic bases of the alkaline earths. These, with the excep- tion of magnesium, decompose water at common temperatures. They are, Barium, Strontium, Calcium, Magnesium. 3d. Metallic bases of the pure earths. Aluminium, Yttrium, Zir- conium, Glucinium, Thorium. The second class includes the greater number of the metals. They unite with oxygen, generally in more than one proportion. Their protoxides have an earthy appearance, but with few excep- tions are coloured, and are insoluble in water. Most of them act as salifiable bases in uniting with acids, and forming salts ; but in this respect they are much inferior to the alkalies and alkaline earths, by which they may be separated from their combinations. Several of these metals are capable of forming with oxygen, compounds, which possess the characters of acids. They may be arranged as follows : * This view is supported by late experiments of Rudberg, Ann. de Cfi. et de Phys. xlviii. 363. T. 398. t For a table exhibiting this see Thenard TraiU de Chim. 1 . 394. Potassium . 229 1. Metals which decompose water at a red heat. They are seven Sect - n in number; namely, Subdivi- Manganese, Cadmium, Cobalt, Iron, Tin, Nickel, Zinc. 2. Metals which do not decompose water at any temperature, and the oxides of which are not reduced to the metallic state by the sole action of heat. Of these there are fourteen in number; namely, Arsenic, Chromium, Vanadium, Molybdenum, Tungsten, 3, Metals, the oxides of a red heat. These are Columbium, Antimony, Uranium, Cerium, Bismuth, Titanium, Tellurium, Copper, Lead. which are reduced to the metallic state by Mercury, Silver, Gold, Platinum, Osmium, Palladium, Iridium. Rhodium, T. Section II. Metallic Bases of the Alkalies. 832. Potassium , K. eq. 39.15, was discovered in 1807 by Davy.^ Potassium. He obtained it by submitting caustic potassa, or potash, to the action of Voltaic electricity : the metal was slowly evolved at the negative pole. From the facts which have become’known respecting the powers Its exist . of electrical decomposition, it appeared to be a natural inference, e nce how that the same powers applied in a state of the highest intensity, inferred, might disunite the elements of some bodies, which had resisted all other instruments of analysis. 833. In his first experiments, Davy failed to effect the decomposi- p avy , s ex _ tion of potassa, owing to his employing the alkali in a state of aque- petiments. ous solution, and to the consequent expenditure of the electrical energy in the mere decomposition of water. 834. The chief difficulty in subjecting potassa to electrical action Met j lof]o f is, that, in a perfectly dry state, it is a complete non-conductor of obtaining electricity. When rendered, however, in the least degree moist by potassium breathing on it, it readily undergoes fusion and decomposition, by by electnci the application of strong electrical powers. For this purpose, a piece of potassa, weighing from 60 to 70 grains, may be placed on a small insulated plate of platinum, and may be connected, in the way already described, with the opposite end of a battery, containing not less than 100 pairs of six inch plates. On establishing the connexion, the potassa will fuse at both places, where it is in contact with the platinum. A violent effervescence will be seen at the upper surface, arising from the escape of oxygen gas. At the lower or negative surface, no gas will be liberated ; but small bubbles will appear, having a high metallic lustre, and being precisely similar in visible cha- racters to quicksilver. Some of these globules burn with art explosion and bright flame ; while others are merely tarnished, and are protected from further change by a white film, which forms on their surface. This production of metallic globules is entirely independent of the * Phil . Trans. 1808. 230 Mttals — Potassium. Chap. IV. How pre- served. Reasons for considering it a metal, . Other pro- cesses for obtaining potassium. Curaudau’s. Wohler’s. Properties. action of the atmosphere ; for Davy found, that they may be pro- duced in vacuo. 835. To preserve this new substance, it is necessary to immerse it immediately in a fluid which does not afford oxygen. If exposed to the atmosphere it is rapidly converted back again into the state of pure potassa. 836. Nothing could be more satisfactory than the evidence fur- nished by Davy’s experiments, of the nature of one of the fixed alka- lies. We have the evidence, both of analysis and synthesis, that potassa is a compound of oxygen with a peculiar inflammable basis. 837. In assigning to this newly discovered substance a fit place among the objects of chemistry, Davy was induced to class it among the metals, because it agrees with them in opacity, lustre, malleabi- lity, conducting powers as to heat and electricity, and in its qualities of chemical combination. 838. In giving names to the alkaline bases, that termination was adopted which, by common consent, has been applied to other newly discovered metals. The base of potassa was called potassium, and the base of soda sodium ; and these names have met with universal acceptation. 839. It is not, however, by electrical means only that the decom- position of potassa has been accomplished. Soon after Davy’s dis- coveries were known at Paris, Gay-Lussac and Thenard succeeded in their attempts to decompose both the fixed alkalies, without the aid of a Voltaic apparatus, merely by the intervention of chemical affini- ties. Their process, though it affords the alkaline bases of less pu- rity, yields them in much larger quantity, than the electrical analysis. It consists in bringing the alkalies into contact with intensely heated iron, which, at this temperature, attracts oxygen more strongly than the alkaline base retains it. Potassium may also be prepared, as first noticed by Curaudau, by mixing dry carbonate of potassa with half its weight of powdered charcoal, and exposing the mixture, contained in a gun-barrel or spheroidal iron bottle, to a strong heat. An improvement on both processes has been made by Brunner, who decomposes potassa by means of iron and charcoal. From eight ounces of fused carbonate of potassa, six ounces of iron filings, and two ounces of charcoal mixed intimately and heated in an iron bottle, he obtained 140 grains of potassium.* A modification of this process has been described by Wohler, who effects the decomposition of the potassa solely by means of charcoal. The material employed for the purpose is carbonate of potassa, pre- pared by heating cream of tartar to redness in a covered crucible. f 840. Potassium is a white metal of great lustre. It exists in small globules, which possess the opacity, and general appearance of mercury ; so that when a globule of mercury is placed near one of potassium the eye can discover no difference between them. It in- * Quart. Jour. xv. 379. See also Henry’s Chcm. vol. i. Hare in Avxer. Jour. xxiv. 312, and Gale’s method ibid, xxi. 60. Very full practical directions are given in Reid’s Ele. of Prac. Chern. p. 221. t PoggendorfTs Annalen , iv. 23, and Brande’s Jour. xxii. 231 Protoxide of Potassium — Potassa. stantly tarnishes by exposure to air. It is ductile, and of the con- ^ct. u. sistency of soft wax. Its specific gravity is 0.865. At 150° it enters into perfect fusion ; and at a bright red heat rises in vapour. At 32° it is a hard and brittle solid. If heated in air it burns with a brilliant white flame. It is an excellent conductor of electricity and of heat. S41. Its most prominent chemical property is its great affinity for Prominent oxygen. It oxidizes rapidly in the air, or by contact with fluids cbaracter * which contain oxygen. On this account it must be preserved either in glass tubes hermetically sealed, or under the surface of liquids, of which oxygen. is notan element, such as naptha, or what is better the essential oil of copaiva. 842. If heated in the open air, it takes fire and burns with a pur- Decompo- ple flame and great evolution of heat. It decomposes water on the ses water * instant of touching it, and so much heat is disengaged, that the po- tassium is inflamed, and burns vividly while swimming upon its surface. The hydrogen unites with a little potassium at the moment of separation ; and this compound takes fire as it escapes, and thus augments the brilliancy of the combustion. When potassium is plunged under water, violent reaction ensues, but without light, and pure hydrogen gas is evolved. Take a small piece of potassium, remove the naptha adhering to it by blotting Exp. paper, and drop it into water ; after the combustion, add to the water infusion of purple cabbage, which will become green. Place another piece upon a lump of ice, the same action takes place. Exp. Gunpowder may be ignited by placing upon it a piece of potassium and touch- Exp. ing the metal with a drop of water on a rod, or with ice. Introduce a piece of the metal, wrapped up in paper, quickly into a test tube Exp. inverted in and full of water. It will rise to the top, and when the water reaches it through the paper, it will be decomposed and hydrogen be found in the upper part of the tube, which may be inflamed in the usual way. A small piece may be dropped into a little sulphuric acid, contained in ajar 3 Exp. or 4 inches in diameter and about 10 or 12 inches deep : potassa is formed and heat and light are at the same time evolved. Care must be taken that none of the acid is thrown into the eyes. Put 4 grains of iodine into a test tube about 4 or 5 inches long, throw a grain Exp. of potassium upon it, and hold the sealed end of the tube for a second or two in the flame of a spirit lamp. The iodine and potassium will rapidly combine with a brilliant light. The hand should be protected with a glove as the tube is usu- ally broken. A similar experiment may be made with half a grain of sulphur and a grain of Exp. potassium. 843. The combining weight or equivalent of potassium is easily Equivalent, deduced from the composition of potassa and chloride of potassium, which are admitted to consist of single equivalents of their elements. Berzelius analyzed chloride of potassium by means of nitrate of oxide of silver, and inferred that 39.15 is the equivalent of potassium. Compounds of Potassium. 844. Protoxide of Potassium — Potash, or Potassa , K-f-O, K or Protoxide KO, 39.15 1 eq. potas. -f* 8 1 eq. oxy. = 47.15 equiv., is formed or potassa. when potassium is put into water, or exposed to dry air or oxygen gas ; formed in the latter way it is anhydrous. It is a white caus- tic solid, fusing at a temperature above redness, and not decomposed by the heat of a wind furnace. It has a great affinity for water. 232 Metals — Potassium. Chap. IV. Protohy- drate, soda, which deliquiates more slowly than that formed on potassium. It is not changed, however, by air that has been artificially dried. 857. It combines with oxygen, slowly and without luminous ap- Of oxygen, pearance, at all common temperatures. When heated to its fusing point, the combination becomes more rapid ; but no light is emitted till it becomes nearly red hot. The flame which it then produces, is white, and it sends forth bright sparks, exhibiting a very beautiful effect. In common air, it burns with a similar colour to charcoal, but with much greater splendour. 858. When thrown on cold water, it swims, and is rapidly oxi- Action on dized, though in general, without inflaming, but with hot water it water > scintillates, or even takes fire. If the sodium is confined to one spot and the water rests on a non-conducting substance, as charcoal, the heat rises high enough for inflammation.^ In each case soda is formed, and the water acquires an alkaline reaction. 859. Its action on alcohol, ether, volatile oil, and acids, is similar alcohol to that of potassium ; but with nitric acid a vivid inflammation is & c . * produced. 860. Protoxide of Sodium , Na-f-O, Na or Nao, 23.3 1 eq. sod. Protoxide, + 8 1 eq. oxy. == 31.3 equiv., commonly called soda, and by the°r sotla > Germans natron, is formed by the oxidation of sodium in air and wa- ter, as potassa is from potassium. In its anhydrous state it is a gray solid, difficult of fusion, and very similar in its characters to potassa. With water it forms a solid hydrate, easily fusible by heat, very caustic, soluble in water and alcohol, has powerful alkaline proper- ties, and in all its chemical relations is exceedingly analogous to po- tassa. It is prepared from the solution of pure soda, in the same manner as the corresponding preparation of potassa. The solid hy- drate is composed of 31-3 parts or one equivalent of soda, and 9 parts or 1 equivalent of water. 861. Soda is readily distinguished from other alkaline bases by Distin- the following characters. 1. It yields with sulphuric acid a salt, §> uished - which by its taste and form is easily recognised as Glauber’s salt, or sulphate of soda. 2. All its salts are soluble in water, and are not precipitated by any reagent. 3. On exposing its salts by means of platinum wire to the blow-pipe flame, they communicate to it a rich yellow colour. 862. Sesquioxide of Sodium, 2Na-|-30 Na, or Na 2 03, 46.6 2 Sesquiox- eq. sod. — |— 24 3 eq. oxy. = 70.6 equiv., is formed when sodium is heated to redness in an excess of oxygen gas. It has an orange colour, has neither acid nor alkaline properties, and is resolved by water into soda and oxygen. * Ducatel jq Ajner. Jour, xxy , 90. 236 Metals — Sodium . Chap. I V. Chloride, How ob» tained. Common salt. Solution. lodlda. Bromide. Fluoride, 863. Chloride of Sodium , Na-j-Cl or NaCl, 23.3 1 eq. sod. -f- 35.42 1 eq. chlor. = 58.72 equiv. Sodium, when heated in chlorine, burns and produces a white compound, of a pure saline flavour. It may also be formed by heating sodium strongly in hydrochloric acid gas ; the hydrogen of which is liberated, while the chlorine combines with the metal. 864. Or it may be formed by saturating carbonate or hydrate of soda with hydrochloric acid, and evaporating the liquid, which yields chloride of sodium in a solid form. This chloride, also, is an abun- dant product of nature, being that well known substance, common salt. For purposes of experiment, the common salt maybe em- ployed which is to be found in the shops. This maybe purified, by adding to a solution of it in water a solution of carbonate of soda, as long as any milkiness ensues ; filtering the solution, and evaporating it till it crystallizes. 865. It crystallizes in solid regular cubes, or, by hasty evapora- tion, in hollow quadrangular pyramids, which, when the salt is pure, are but little changed by exposure to the air. The common salt of the shops, however, being impure, acquires an increase of weight, in consequence of the absorption of moisture. The various forms un- der which it appears, of stoved salt, fishery salt, bay salt, &c. arise from modifications in the size and compactness of the grain, rather than from any essential difference of chemical composition. Com- mon salt always contains small quantities of sulphate of magnesia and lime, and chloride of magnesium. These may be precipitated as carbonates by boiling a solution of salt for a few minutes with a slight excess of carbonate of soda, filtering the liquid and neutraliz- ing with hydrochloric acid. 866. It requires for solution, twice and a half its weight of water, at 60° F., and hot water takes up very little more. Hence its solu- tion crystallizes, not like that of nitre, by cooling, but by evaporation. When heated gradually it fuses, and forms, when cold, a solid com- pact mass. If suddenly heated as by throwing it on red-hot coals, it decrepitates. Its uses are well known. ^ 867. Protosulphuret of Sodium . Na-f-S, or NaS, 23.3 1 eq. sod. -f-16.1 1 eq. sulph = 39.4 equiv. The protosulphuret is obtained by processes similar to those for protosulphuret of potassium, to which in its taste and chemical relations it is very similar.! * Iodide of Sodium. Na+I, or Nal, 23.3 1 eq. sod.+ 126.3 1 eq. iod.=149.6 equiv. Obtained pure by processes similar to those for preparing iodide of potassium ; but it is contained in sea-water, in many salt springs, and in the residual liquor from kelp (673). Bromide of Sodium. Na+Br, or NaBr, 23.3 1 eq. sod. + 78.4 1 eq. brom. = 101.7 equiv. This compound is very analogous to sea-salt, and is associated with it in sea- water and most salt springs. Fluoride of Sodium. Na+F, or NaF, 23.3 1 eq. sod. + 18.68 1 eq. flu. =41*98 equiv. This compound is formed by neutralizing hydrofluoric acid by soda, and by igniting the double fluoride of sodium and silicon, when the fluoride of silicon is ex- pelled. * According to Gmelin of Tubingen, sulphuret of sodium is the colouring principle of lapis lazuli !, to which the colour of ultra-marine is owing; and he has succeeded in preparing artificial ultra-marine by heating sulphuret of sodium with a mixture of sili- cic acid and alumina. Ann. de Ch. et de Ph. xxxvii. 409* Barium, 237 Lithium . _bect 1 m 1 Symb. L. Equiv. 6.44. 868. In the year 1818, in the analysis of a mineral called petalite, Discovery. Arfwedson discovered about three per cent, of an alkaline substance, which was at first supposed to be soda; but, the further prosecution of his inquiries fully demonstrated that it possessed peculiar proper- ties. The minerals called spodumene , and lepidolite , also afford the same substance, to which the term lithia, deduced from its lapideous original has been applied. 869. For preparing lithia, One part of petalite or spodumene, in fine powder, is intimately mixed with Method of two parts of fluor spar, and the mixture is heated with three or four times its obtaining weight of sulphuric acid, as long as any acid vapours are disengaged. The silicic lithia. acid of the mineral is attacked by hydrofluoric acid, and is dissipated in the form of fluosilicic acid gas, while the alumina and lithia unite with sulphuric acid. After dissolving these salts in water, the solution is boiled with pure ammonia to precipitate the alumina, filtered, evaporated to dryness and then heated to red- ness to expel the sulphate of ammonia. The residue is sulphate of lithia.* T. 28(5. 870. When lithia is submitted to the action of the Voltaic pile, it Action of is decomposed with the same phenomena as potassa and soda ; a g alvan i sm » brilliant white and highly combustible metallic substance is separat- ed, which is lithium. 871. Lithia. L-j-O, L, or LO, 6.44 1 eq. lith. -|- 8 1 eq. oxy. — Distin- 14.44 equiv. Lithia is allied to potassa and soda, but distinguished f^^potas- by its greater neutralizing power, by its salts tinging the flame of thesa,&c. blow-pipe of a red colour. It attacks platinum when fused upon it, leaving a dull yellow trace. It is distinguished from baryta, strontia and lime by forming soluble salts with sulphuric and oxalic acids. t Section III. Metallic Bases of the Alkaline Earths. 872. Barium, Ba. eq. 68.7, was discovered by Davy, in 1808, by Barium 5 means of galvanism. He placed a globule of mercury in a hollow discover y° made in a paste of carbonate of baryta, on a platinum tray commu- nicating with the positive pole of a battery of 100 double plates, while the negative wire was in contact with the mercury. The baryta was decomposed, and its barium combined with mercury. An amalgam was obtained, from which the mercury was separated by heat in a vessel free from air, and barium was left in a pure form. 873. It is a dark gray colored metal, with a lustre inferior to that Properties. * For other methods see Henry’s Chemistry , 1 . 572. + For an analysis of lithion micas and the distinguishing properties of lithia, see Turner’s papers, Edin . Jour. iii. 137, 261, &c. ; and lor Berzelius’ method ol disco- vering lithia in any solution, see Edin. Philos. Jour. iv. 128. Chloride of Lithium. L+CL, or LC1, 6.44 1 eq. lith. + 35.42 1 eq. chlo. = 41.86 equiv. Fluoride of Lithium. L+F, or LF, 6.44 1 eq. lith. + 18-68 1 eq. flu. =25.12 equiv. 1 238 Metals — Barium. Chap. IV. Protoxide. How ob- tained. Properties. Solution. Affinity for carbonic acid, Exp. Takes it from other bodies. Exp. Alkaline properties. of cast-iron. It is far denser than water and sinks in sulphuric acid. It greedily absorbs oxygen and is converted into baryta. 874. Protoxide of Barium , Ba-f-O, Ba, or BaO, 68.7 1 eq. bar. + 8 1 eq. oxy. = 76.7 equiv., Barytes , or Baryta , so called from the great density of its compounds, (from ficiQvs, heavy,) was disco- vered in the year 1744 by Scheele. It is the sole production of the oxidation of barium in air and water. It is obtained by exposing the crystals of nitrate of baryta for some time to a bright red heat. It may also be obtained by decomposing the native carbonate of baryta. Let this be powdered, and passed through a fine sieve. Work it up with about an equal bulk of wheaten flour or tar into a ball, adding a sufficient quantity of water. Fill a crucible of proper size, about one third its height, with powdered charcoal ; place the ball on this ; and surround and cover it with the same pow- der, so as to prevent its coming into contact with the sides of the crucible. Lute on a cover ; and expose it, for two hours, to the most violent heat that can be raised in a wind furnace. Let the ball be removed when cold. On the addition of water, it will evolve great heat, and the baryta will be dissolved. The fil- tered solution, on cooling, will shoot into beautiful crystals.* 875. Baryta is of a gray colour, and very difficult of fusion. Its sp. gr. is about 4, being the heaviest of the substances usually called earths. It eagerly absorbs water, and slakes like lime. A white hydrate is formed, composed of 76.7 parts, 1 eq. of baryta, and 9 parts or 1 eq. of water. 876. Hydrate of baryta dissolves in three times its weight of boil- ing water, and in twenty parts of water at the temperature of 60° F.f A saturated solution of baryta in boiling water deposits, in cooling, transparent, flattened prismatic crystals, which are composed of 76.7 parts or one equivalent of baryta, and 90 parts or 10 equivalents of water. The aqueous solution of baryta is an excellent test of the presence of carbonic acid in the atmosphere or in other gaseous mixtures. The carbonic acid unites with the baryta, and a white insoluble pre- cipitate, carbonate of baryta, subsides. Let a solution of pure baryta be exposed to the atmosphere. It will soon be covered with a thin white pellicle ; which, when broken, will fall to the bottom of the vessel, and be succeeded by another. This may be continued, till the whole of the baryta is separated. The effect arises from the absorption of Car- bonic acid, which is always diffused through the atmosphere, and which forms, with baryta, a substance, viz. carbonate of baryta, much less soluble than the pure earth. Or if the air from the lungs be blown, by means of a quill, or tube^ through a solution of baryta, the solution will immediately become milky, in consequence of the production of an insoluble carbonate. The same effect will be produced by mingling with a solution of pure baryta, a little water, impregnated with car- bonic acid. 877. Baryta has so strong an affinity for carbonic acid as even to take it from other bodies. If to a solution of a small portion of carbonate of potassa, of soda, or of ammo- nia we add the solution of baryta, the earth will detach the carbonic acid from the alkali, and will fall down in the state of a carbonate. By adding a sufficient quantity of a solution of baryta in hot water, the whole of the carbonic acid may thus be removed from a carbonated alkali. H. 1. 578. 878. As baryta, like the alkalies, converts vegetable blues to green, and serves as an intermedium between oil and water, it has * For other processes see Sulphate and Nitrate of Baryta. + Davy. Strontium. 239 been called an alkaline earth. It has a very acrid, caustic taste, and Sect, m. is highly poisonous. It exists in two natural combinations only, viz. as sulphate and carbonate. 879. Peroxide of Barium. Ba-f-20, or BaO a -f-6Aq, 68.7 1 eq. p erox id e . bar. -f- 16 2 eq. oxy. = 84.7 equiv. When dry oxygen gas is con- ducted over pure baryta at a low red heat this oxide is formed. It is employed in preparing peroxide of hydrogen, page 134. An easier Process process is to heat pure baryta to low redness in a platinum cruci- v ble, and then gradually to add chlorate of potassa in the ratio of about one part of the latter to four of the former. 880. The oxygen of the chlorate goes over to the baryta, and Theory chloride of potassium is generated. Cold water removes the chlo- ride and the peroxide of barium is left as a hydrate with 6 eq. of water. 881. Chloride of Barium . Ba-j-Cl, or BaCl, 68.7 1 eq. bar. -f- 35.42 1 eq. chlor. = 104.12. Chloride of Barium may be obtained Chloride, by heating baryta in chlorine, in which case oxygen is evolved : or, more easily, by dissolving carbonate of baryta in diluted hydrochlo- ric acid. When filtered and evaporated, the solution yields regular crystals, which have most commonly the shape of flat four sided ta- bles, very like those of heavy spar. They contain 104.12 or 1 eq. of chloride of barium and 18 parts or 2 eq. of water ; formula BaCl -|-2Aq. 100 parts of water dissolve 43.5 at 60°, and 78 at 222° which is the boiling point of the solution.^ 882. Protosulphuret of Barium } Ba-f-S or Bas, 68.7 1 eq. bar. sulphuret. -f- 16.1 1 eq. sulp. = 84.8 equiv., is formed when dry hydrosul- phuric acid gas is passed over pure baryta at a red heat, and by the action of hydrogen gas or charcoal on sulphate of baryta (818.) It is very soluble in hot water, and the solution supplies a ready mode of obtaining pure baryta and its salts, when the carbonate can- So ^ utlon - not be obtained. Thus its solution, boiled with black oxide of cop- per until it ceases to precipitate a salt of lead black, yields pure bary- ta, which should be filtered while hot to separate the sulphuret of copper : it is apt to retain traces of oxide of copper. With a solu- tion of carbonate of potassa, carbonate of baryta falls, and sulphuret of potassium remains in solution ; and with hydrochloric acid it in- terchanges elements, by which hydrosulphuric acid and chloride of barium are formed. T. Strontium. Symb. Sr Equiv. 43.8 883. This metal was discovered by Davy in strontia , by the same Discovery, process as barium, which it resembles. 884. Protoxide of Strontium , Sr-f-0, Sr, or SrO, 43.8 1 eq. Strontia. stron. -f- 8 1 eq. oxy. = 51.8 equiv., or the earth Strontia , is so * Iodide of Barium. Ba+I, or Bal, 68.7 1 eq. bar. + 126.3 1 eq. iod. = 195 equiv. iodide. Bromide of Barium. Ba+Br, or BaBr, 68.7 1 eq. bar. + 78.4 1 eq. brom. = 147.1 equiv. Fluoride of Barium. Ba+F, or BaF, 68.7 1 eq. bar. + 18.68 1 eq. flu. =87.38 240 Metals — Calcium . Cha P- IV - called from Strontian in Scotland, where it was first discovered in combination with carbonic acid. How ob- tained. Composi- tion. Properties. Salts. Chloride. It may be prepared either by subjecting the carbonate to a strong heat in a crucible, or by igniting the nitrate in a porcelain retort or other close vessel. A gray substance remains which becomes very hot on the affusion of water ; and when more water is added and heat applied, a considerable proportion of the earth is dissolved. On cooling, the solution deposits regular crystals; but the shape of these differs considerably from that of barytic crystals. The crystals of strontia are thin quadrangular plates. 885. The hydrate consists of 51.8 parts or 1 eq. of strontia, and 9 parts or 1 eq. water. The crystals contain 10 eq. water and 1 strontia. It requires 50 times its weight of water for solution. 886. Pure strontia has a pungent, acrid taste, and when powder- ed in a mortar, the dust that rises irritates the lungs, and nostrils. Its specific gravity approaches that of baryta. 887. The salts of strontia are best prepared from the native car- bonate. Like those of baryta, they are precipitated by alkaline car- bonates, and by sulphuric acid or soluble sulphates. But sulphate of strontia is less insoluble than sulphate of baryta : on adding sul- phate of soda in excess to a barytic solution, baryta cannot after- wards be found in the liquid by any precipitant; but when strontia is thus treated, so much sulphate of strontia remains in solution, that the filtered liquid yields a white precipitate with carbonate of soda. The salts of strontia are not poisonous ; and most of them, when heated on platinum wire before the blow-pipe, communicate to the flame a red tint.* 888. Chloride of Strontium, Sr— (—Cl, or SrCl, 43.8 1 eq. stron. -f- 35.42 1 eq. chlor. — 79.22 equiv. This compound is formed by processes similar to those for preparing chloride of barium, and crys- tallizes in colourless prismatic crystals, which deliquesce in a moist atmosphere, require only twice their weight of water at 60° for so- lution, and still less of boiling water, and are soluble in alcohol. The alcoholic solution, when set on fire, burns with a red flame. These characters afford a certain mode of distinguishing strontia from baryta. The crystals consist of 79.22 parts or 1 eq. of chloride of strontium, and 81 parts or 9 eq. of water, which are expelled by heat. The anhydrous chloride fuses at a red heat, and yields a white crystalline brittle mass on cooling.! Calcium. Symb. Ca Eq. 20.5 How ob- 8S9. When lime is electrized negatively in contact with mercury, tained. an amalgam is obtained, which, by distillation, affords a white met- * Peroxide of Strontium, Sr+20 or SrO 2 . 43 S 1 eq. stron. + 16 2 eq. oxy = 59.8 eroxide. equiv., is prepared in the same way as peroxide of barium, and like it, is resolved by dilute acids into strontia and oxygen, the latter of which forms peroxide of hydro- gen with the water. iodide. t Iodide of Strontium, Sr+I, or Sri, 43.8 1 eq. stron. + 126.3 1 eq. iod. = 170.1 equiv., may be prepared in the same manner as that of barium. It is very soluble in water. Fluoride of Strontium and Protosulphur et of Strontium , Sr+F or SrF, 43.8 1 eq. stron. -|- 18.68 1 eq. fluor. = 62.48 equiv. and Sr-fS or SrS, 43.8 1 eq. stron. 16.1 l eq. sulp. = 59.9 equiv. are obtained like those of barium. Lime Watfir. 241 al. It has been called calcium , and when exposed to air, and gently Sect, m. heated, it burns and produces the oxide of calcium or lime. 890. Protoxide of Calcium , Ca-j-O, Ca, or CaO, 20.5 1 eq. calc. Protoxide 8 1 eq. oxy. = 28.5 equiv. This compound, commonly known by " the name of lime and quicklime , is obtained by exposing carbonate of lime to a strong red heat, so as to expel its carbonic acid. If lime of great purity is required, it should be prepared from pure carbonate of lime, such as Iceland spar or Carrara marble. Its colour is gray, it is acrid and caustic ; its sp. gr. is about 2.3. 891. It is very difficult of fusion, but remarkably promotes the Fusibility, fusion of most other earthy bodies, and is therefore used in several metallurgic processes as a cheap and powerful flux. When quite pure it can only be fused in very minute particles by the oxy-hydro- gen blow-pipe, or by the Voltaic flame. It is an essential ingredient in Uses mortar, and other cements used in building. Exposed to air it becomes white by the absorption of water and a little carbonic acid. 892. It has a powerful affinity for water. When a small quantity of water is poured upon lime, there is a great rise of temperature resulting from the solidification of a portion of the water, and white powder is obtained, called slaked lime y which is a hydrate , and appears to consist of one eq. water = 9-f-one eq. lime = 28.5. Some care is necessary in its preparation, lest more water should be added, than is essential to its constitution. It affords a very con- venient form of keeping lime, for occasional use in a laboratory ; for the hydrate may safely be preserved in glass bottles, which are almost constantly broken by the earth, if enclosed in its perfectly dry state. 893. The degree of heat produced by the combination of lime Heat, with water, is supposed by Dalton to be not less than 800°, and is sufficient to set fire to some inflammable bodies. Place a large lump of well burned quicklime on an iron dish and add Exp. a small quantity of water, a piece of phosphorus resting on it will be ignited. Hydrate. When a large quantity of lime is suddenly slaked in a dark place, even light, according to Pelletier, is sometimes evolved. 894. When a sufficient quantity of water has been added to re- Milk of duce lime into a thin liquid, this is called milk or cream of lime. By the addition of more water the solution known as lime water Water of, is obtained. When sufficiently cool it should be poured into a well stopped bottle until the undissolved parts have subsided, and be then decanted and kept from the air. Lime is very sparingly soluble in water, viz. in the proportion of about 1 to 778.* 895. Lime-water is limpid and colourless ; its taste is nauseous, ^F r ^ ies acrid, and alkaline, and it converts vegetable blues to green. When wa ter. exposed to the air, a pellicle of carbonate of lime forms upon its sur- face, which, if broken, is succeeded by others, until the whole of the * According to Thomson 1 to 75S. The experiments of Dalton tend to establish a curious fact respecting the solubility of lime, viz. that it dissolves more plentifully in cold than in hot water 5 he found that at 60° F. 778 grains of water dissolve l grain of lime, and at 212°, 1270 grains were required. He further infers that at the freezing point water would probably take up nearly twice as much lime as is dissolved by boiling water — this has been confirmed by Phillips. — Ann. Philos. N. S. 1. 107. 31 242 Metals — Calcium. Uses. Exp. Test of. Chap. iv. li me i s thus separated in the form of an insoluble carbonate. It is used in medicine as an antacid, and is a good test of the presence of carbonic acid gas. Into transparent lime water pass carbonic acid, or breathe into it by means of a glass tube, it will become milky and opaque from the formation of carbonate of lime. If an excess of carbonic acid is added the carbonate is dissolved and transparency restored. 896. The most delicate test of the presence of lime is oxalate of ammonia or potassa ; for of all the salts of lime, the oxalate is the most insoluble in water. This serves to distinguish lime from most substances, though not from baryta and strontia ; because the oxa- lates of baryta and strontia, especially the latter, are likewise spar- ingly soluble.* Chloride of 897. Chloride of Calcium , Ca-f-Cl, or CaCl, 20.5 1 eq. calc. calcium. 35.42 1 eq. chlor. = 55.92 equiv., is produced by heating lime in chlorine, in which case oxygen is evolved ; or by evaporating hydro- chlorate of lime to dryness, and exposing the dry mass to a red heat in close vessels. In this case the hydrochloric acid is decomposed ; its hydrogen uniting with the oxygen of the lime, escapes in the state of water ; and the chlorine unites with the calcium. S98. This compound has a strong attraction for water ; it deli- quesces when exposed to the air, and becomes what used to be cal- led oil of lime. It is difficultly crystallizable from its aqueous solu- tion ; with care, however, it may be obtained in irregular prisms, consisting of 55.92 parts or 1 eq. of chloride of calcium, and 54 parts or 6 eq. water. Its taste is bitter and acrid ; one part of water at 60° dissolves four parts of the chloride. Its solubility, however, is greatly influenced by temperature. It is copiously soluble in al- cohol, and much heat is evolved during the solution. When fused it acquires a phosphorescent property as was first observed by Hom- Homberg’s berg, and is hence termed Homberg's phosphorus. It is abundantly phospho- produced in the manufacture of carbonate of ammonia, from the decomposition of hydrochlorate of ammonia by lime. 899. It is used for frigorific mixtures with snow, and for this pur- pose the hydrous chloride is preferable, prepared by evaporating its solution so far that the whole becomes a solid mass on removal from the fire. It should be kept in bottles well secured from the air. In its fused state this compound is very useful for drying certain gaseous bodies, but where the quantity of the gas is to be ascertain- ed, its powers of absorption in certain cases must not be overlooked. Pelletier has stated, that if carbonic acid be passed through a solu- tion of hydrochlorate of lime, the whole becomes a hard solid mass. If sulphuric acid be poured into a strong solution of hydrochlorate of lime, the whole congeals into a solid mass of sulphate of lime (61). Composi- tion and properties. Uses. * All these oxalates dissolve readily in water acidulated with nitric or hydrochloric acid. It is distinguished from baryta and strontia by the fact, that nitrate of lime yields prismatic crystals by evaporation, is deliquescent in a high degree, and very so’uble in alcohol j while the nitrates of baryta and strontia crystallize in regular octohedrons or segments of the octohedron, undergo no change on exposure to the air, except when it is very moist, and do not dissolve in pure alcohol. T. Peroxide of Calcium. Ca+20, or CaO 2 , 20.5 1 eq. calc. + 16 2 eq. oxy. = 36.6 equiv. It is prepared in the same way as peroxide of barium, and is similar in its properties. Bleaching Powder. 243 900 It absorbs large quantities of ammoniacal gas, during which Sect, m. it swells, cracks, and at last crumbles down into a white powder. Absorbs With water it forms a strong alkaline solution. Heated it gives ofT amrnon * a - ammonia and the chloride remains. Immersed in chlorine, the am- monia burns off with a pale yellow flame. Twenty grains of the compound furnish, when heated, about 20 cubic inches of ammonia ; Faraday availed himself of it for the liquefaction of ammonia.* 901. The chloride of lime is abundantly employed as a bleaching Bleachi material, and known by the name of bleaching powder ; it is manu- powder. g factured by passing chlorine into leaden chambers containing hy- drate of lime in fine powder, by which the gas is copiously absorbed with evolution of heat. When heated it gives off a large quantity of oxygen, and a chloride of calcium results, showing the superior at- traction of calcium for chlorine compared to oxygen, the latter being expelled from the lime. The composition of bleaching powder has been variously stated. Composi- Dalton considers it as a hydrated subchloride of lime, containing two tion ° proportions of lime and one of chlorine ;t and the same opinion is adopted by Thomson,! and by Welter.^ According to Urell the quantity of chlorine absorbed is variable. That manufactured at Glasgow is stated by Thomson to be a compound of one atom of chlo- rine and one of lime. If * Faraday in Jour. Roy • Inst. v. 74. IfAnn. of Philos, i. 15 and ii. 6 . £ lb. xv. 401. §Ann. de Chim. et Phys. vii. 383. || Quart. Jour. xiii. 21 . IT As the value of chloride of lime depends on the quantity of chlorine which it con- tains, and as this varies considerably, several methods for ascertaining its strength have been proposed. One consists in adding a given quantity of the diluted solution to a solution of indigo in sulphuric acid of a known strength ;■*. the strength of the chlorine being indicated by the quantity of the solution which it can decolorize. Mo- rin has proposed a solution of the hydrochlorate of manganese as a substitute for this, as giving more accurate indications, the lime combining with the hydrochloric acid, and precipitating the brown oxide of manganese, while the chlorine is disengaged 5 the quantity of the hydrochlorate decomposed corresponding with the chlorine set at liberty. f It has also been proposed to ascertain the quantity of chlorine by observing the quantity of nitrogen gas which is disengaged when it is made into a paste or cream with water and mixed with fragments of hydrochlorate of ammonia ; the lime combining with the hydrochloric acid and forming hydrochlorate of lime, while the chlorine takes hydrogen from the ammonia and disengages nitrogen (420). An instrument for the speedy analysis of this substance has been described by Ure.t It consists of a glass tube, (Fig. 178,) of about five cubic inches capa- Fig 178. city, graduated into cubic inches and tenths. It is closed at top with a brass screw cap, and at. its recurved end below, with a good cork. Pour mercury into the upper orifice, till the tube be nearly full, leaving merely space to insert ten grains of the bleaching powder, made into a pellet form with a drop of water. Screw in the cap-plug rendered air- tight by leather. Remove now the cork from the lower end, (also full of mercury,) and replace a little of the liquid metal by dilute hydro- chloric acid (sp. gr. l.l). By dexterous inclination of the instrument, the acid is made to flow up through the mercury. Instantly on its co- ming in contact with the pellet, the chlorine is disengaged, the mercury flows out into a basin ready to receive it, while the resulting film of hydrochlorate of lime protects the surface of the metal almost com- pletely from the gas. The same instrument may be employed for ascertaining the quantity of carbonic acid in limestone, &c.§ Estimating a cubic inch of chlorine in round numbers at I of a grain, we may expect 10 grains of bleaching powder to yield from 3 to 4 cubic inches of that gas, or by weight, from 20 to 30 per cent. Ure. Ure’s method of analysis. * As the quantity of indigo varies, this test cannot be relied upon. See Amer- Jour. xvii. 170. f Jour. Roy. Inst. vi. J Jour. Roy. Inst. xiii. 21. $See Ure’s Chem Diet, article Carbonate. 244 Metals — Calcium. Chap, iv. 902. Fluoride of Calcium — Fluor Spar. Ca-f-F, or CaF, 20.5 1 eq. cal. -f- 18.68 1 eq. flu. = 39.18 equiv. Fluor spar is a mineral found in many parts of the world, but in great beauty and abundance in England, and especially in Derbyshire. Here it is commonly called Derbyshire spar , or by the miners of that Fluor spar, county blue John* It is usually found in cubic crystals, which may easily be cleaved into octohedra, sometimes considered as its primitive form. Its colours are extremely various. Its specific gravity is 3.15. It is perfectly tasteless and insoluble in water. When thrown in powder upon a plate of iron heated below redness in a dark place, it emits a phosphorescent light.! Properties. 903. piuorjde 0 f calcium fuses at a red heat without farther change. It is insoluble in water, slightly soluble in hot diluted hy- drochloric acid, and is decomposed by sulphuric acid aided by gentle heat, affording hydrofluoric acid (715).! Protosul’ 904 Protosulphur et of Calcium. Ca-(-S, or CaS, 20.5 1 eq. cal. phuret. 16.1 1 eq. sulph. = 36.6 equiv. This compound may be prepared by reduction from the sulphate by hydrogen or charcoal, and when pure is white with a reddish tint, and is very sparingly soluble in water. It has the property, in common with sulphuret of barium, of being phosphorescent after exposure to light, and appears to be the essential ingredient of Canton’s phosphorus. When 3 parts of slaked lime, I of sulphur, and 20 of water, are ret U PhU boiled together for an hour, and the solution, without separation from the sediment, is set aside in a corked flask for a few days, a copious deposite of orange-coloured crystals takes place, which, when slowly formed, are flat quadrilateral prisms. These, from the analysis of Herschel,§ appear to be bisulphuret of calcium with 3 eq. of water. They are decomposed by exposure to the air, and are of sparing so- lubility in water. When either of the foregoing sulphurets is boiled in water along with sulphur, a yellow solution is formed containing calcium com- bined with five equivalents of sulphur.|| 905. Phosphuret of Calcium. Ca-j-P, or CaP, 20.5 1 eq. cal. -f- Phosphu- 15.7 1 eq. phos. = 36.2 equiv. It is formed by passing the Tet * vapour of phosphorus over fragments of quicklime at a low red heat ;1T when a brown matter is formed, consisting of phosphate of * It occurs in various parts of the United States— that from Shawneetown, Illinois, is particularly beautiful. For other localities see Cleaveland’s and Dana’s Mineralogy. t It may be prepared artificially by digesting moist, recently precipitated, carbonate Proceu. jj me j n au excess 0 f hydrofluoric acid ; or by mixing a solution of chloride of calci- um with fluoride of potassium or sodium. As prepared in the latter mode, it is a bulky gelatinous mass, which it is very difficult to wash ; whereas the former method gives it in the state of a granular white powder, which may be washed with ease. t Iodide of Calcium. Ca+I, or Cal, 20.5 l eq. cal.+126.3 1 e q. iod. = 146.8 equiv. Bromide' of Calcium. Ca+Br. or CaBr, 20.5 1 eq. cal. + 78.4 1 eq. brom. = 93.9 equiv. § Edin. Philos. Jour. 1. p. 11, &c. || Bisulphuret of Calcium. Ca+2S, or CaS*, 20.5 1 eq. cal. + 32.2 2 eq. sulph. = 52.7 equiv. Quintosulphurel of Calcium. Ca+5S, or CaS 5 , 20.5 1 eq. cal. + 80.5 5 eq. sulph. = 101 equiv. „ if Select a green glass, or porcelain tube, closed at one end, and about 18 inches long, How prepared. ^ ^ diameter) and care fully cover it with a clay lute containing a very little Magnesium . lime and phosphuret of calcium. When put into water, mutual Sect - I1L decomposition ensues, and phosphuretted hydrogen, hypophospho- rous acid, and phosphoric acid are generated (777). Drop a small piece of it into a wine-glass of water, and in a short time bubbles Exp. of phosphuretted hydrogen gas will be produced ; which, rising to the sur- face will take fire, and explode. If the phosphuret of lime be not perfectly fresh, it may be proper to warm the water to which it is added. Into an ale-glass put one part of the phosphuret in pieces of about the size of Exp. a pea (not in powder), and add to it half a part of chlorate of potassa. Fill the glass with water, and put into it a funnel, with a long pipe, or narrow glass tube, reaching to the bottom. Through this pour three or four parts of strong sulphu- ric acid, which will decompose the chlorate ; and, the phosphuret also decom- posing the water at the same time, flashes of fire dart from the surface of the fluid, and the bottom of the vessel is illuminated by a beautiful green light. Magnesium. Symb. Mg Equiv. 12.7* 906. The existence of this metal was demonstrated by Davy, but Di SC0V ery. it was first obtained in any quantity by Bussy, in 1830 by means of potassium. 907. For this purpose five or six pieces of potassium, of the size of peas, were p rocess f or . introduced into a glass tube, the sealed extremity of which was bent into the form of a retort, and upon the potassium were laid fragments of chloride of mag- nesium. The latter being then heated to near its point of fusion, a lamp was applied to the potassium, and its vapour transmitted through the mass of heated chloride. Vivid incandescence immediately took place, and on putting the mass, after cooling, into water, the chloride of potassium with undecomposed chloride of magnesium was dissolved, and metallic magnesium subsided. These results have been since confirmed by Liebig.t 908. Magnesium has a brilliant metallic lustre, and a white colour p rope rties. like silver ; is very malleable, and fuses at a red heat. Moist air ox- idizes it superficially ; but it undergoes no change in dry air, and may be boiled in water without oxidation. Heated to redness in air or oxygen gas, it burns with brilliancy, yielding magnesia ; and it inflames spontaneously in chlorine gas. It is readily dissolved by dilute acids with disengagement of hydrogen, and the solution is found to contain a pure salt of magnesia. 909. Protoxide of Magnesium . MG-j-O, Mg, or MgO, 12.7 1 borax. Put an ounce of phosphorus broken into small pieces into the lower end, and fill it up with pieces of clean quicklime, about the size or large peas ; place it in an in- clined position in a furnace, so that the end containing the phosphorus may protrude, while the upper part of the tube is heating to redness 5 then slowly draw the cool part into the fire, by which the phosphorus will be volatilized, and passing into the red-hot lime, convert a portion of it into phosphuret. Care should be taken that no conside- rable portion of phosphorus escapes and burns away at the open end of the tube, Properties, which after the process, should be corked and suffered to cool. Its contents may then be shaken upon a sheet of paper, and the brown pieces picked out and carefully pre- served in a well stopped phial 3 the white pieces, or those which are only pale brown, must be rejected. An easier method is, by throwing a piece of dry phosphorus into a crucible with a few fragments of lime (each about the size of a pea), at the bottom, and at a bright red heat, an assistant putting on a cover, or inverting it immediately on a flat plate of iron, at the same time throwing a quantity of sand round it to close any aperture. The experiment may be made with 20 or 30 grains of phosphorus, and about 60 or 70 of lime in a small crucible. R. See Mitchell’s process, page 218, Note. * Inferred by Berzelius from the quantity of sulphate obtained from a known weight of pure magnesia. t Ann. de Ckim. et de Pkys. xlvi. 435. 246 Chap. IV. Protoxide or magne- sia. Action of water. Solution. Properties. Process. Calcined mag- nesia. Metals — Magnesium. eq. mag. + 8 1 eq. oxy. = 20.7 equiv. This, the only known oxide of magnesium, commonly known by the name of magnesia, is best obtained by exposing carbonate of magnesia to a very strong red heat, by which its carbonic acid is expelled. It is a white, friable powder, of an earthy appearance ; and, when pure, it has neither taste nor odour. Its specific gravity is about 2.3, and it is exceed- ingly infusible. Brande once succeeded in agglutinating a small portion of this earth in the Voltaic flame, and whilst exposed to this high temperature, it was perfectly fused by directing upon it the flame of oxygen and hydrogen. 910. It has a weaker affinity than lime for water; for though it forms a hydrate when moistened, the combination is effected with hardly any disengagement of caloric, and the product is readily de- composed by a red heat.* Magnesia dissolves very sparingly in water. According to Fyfe, it requires 5142 times its weight of water at 60°, and 36.000 of boiling water for solution. The resulting liquid does not change the colour of violets ; but when pure magnesia is put upon moistened turmeric paper, it causes a brown stain. From this there is no doubt that the inaction of magnesia with respect to vegetable co- lours, when tried in the ordinary mode, is owing to its insolubility. It possesses the still more essential character of alkalinity, that, namely, of forming neutral salts with acids, in an eminent degree. It absorbs both water and carbonic acid when exposed to the atmos- phere, and, therefore, should be kept in well closed phials. 911. Magnesia is characterized by the following properties. With nitric and hydrochloric acid it forms salts which are soluble in alco- hol, and exceedingly deliquescent. The sulphate of magnesia is very soluble in water, a circumstance by which it is distinguished from the other alkaline earths. Magnesia is precipitated from its salts as a bulky hydrate by the pure alkalies. It is precipitated as carbonate of magnesia by the carbonates of potassa and soda ;t but the bicar- bonates and the common carbonate of ammonia do not precipitate it in the cold. If moderately diluted, the salts of magnesia are not precipitated by oxalate of ammonia. By means of this reagent magnesia may be both distinguished and separated from lime. 912. Chloride of Magnesium. Mg-{-Cl, or MgCl, 12.7 1 eq. mag. 35.42 1 eq. = 43.12 equiv. This may be prepared by trans- mitting dry chlorine gas over a mixture of magnesia and charcoal at a red heat ; but Liebig has given an easier process, which consists in dissolving magnesia in hydrochloric acid, evaporating to dryness, mixing the residue with its own weight of hydrochlorate of ammo- nia, and projecting the mixture in successive portions into a platinum crucible at a red heat. As soon as the ammoniacal salt is wholly expelled, the fused chloride of magnesium is left in a state of tranquil * The native hydrate is found at Hoboken, N. J., it consists of 70 magnesia and 30 water. + The carbonate of magnesia, used in medicine, and for experimental purposes, is prepared by mixing hot solutions of carbonate of potassa and sulphate of magnesia (Ep- som salts). The carbonic acid is expelled by moderate heat, and the residue is pure magnesia ; being prepared by calcination, it is known as calcined magnesia. When incautiously used for a long time it may produce very serious evils, a remarkable case has been reported by Brande in Jour. Roy. Instil, i. Aluminium . 247 fusion, and on cooling becomes a transparent colourless mass, which Sect- tv. is highly deliquescent, and is very soluble in alcohol and water. ^ Section IV. Metallic Bases of the Earths. 913. Aluminium . Al. eq. 13.7. Alumina constitutes some of the Aluminous hardest gems, such as the sapphire and ruby ; and combined with minerals - water, it gives a peculiar softness and plasticity to some earthy com- pounds, such as the different kinds of clay. — The experiments of Davy afforded a strong presumption that alumina is a metallic oxide ; Alumi- but its base, aluminium , he did not obtain in such a state as to nlum * * * § make its properties an object of investigation. Yet alloys were formed which gave sufficient evidence of its existence, and the presence of oxygen in alumina was proved, by its changing potas- sium into potassa, when ignited with that metal. 914. Aluminium has since been procured by Wohlert by decom- posing the chloride by means of potassium. The action is very vio- lent, and accompanied with such intense heat that a crucible of pla- Processfor ” tinum is required. 915. The aluminium is generally in small scales of a metallic properties, lustre, or in slightly coherent spongy masses with the lustre of tin. It conducts electricity in its fused state, but in the form of powder it does not. Its fusing point is higher than that of cast iron. At a p us j|,j]j t y red heat it takes fire in the air, and alumina is formed; in oxygen gas it burns with intense light and heat. It is not oxidized by water at common temperatures; oxidation Action of commences when the water is near its boiling point, but even after water, continued boiling it is very slight 916. Sesquioxide of Aluminium. 2Al-|-30, Al, or A1 2 0 3 , 27.4 Alumina. 2 eq. alum. — |— 24 3 eq. oxy. = 51.4equiv. This is one of the most abundant earths in nature, being a constituent of many rocks, the different kinds of clay, and of some of the hardest gems, as the ruby and sapphire. 917. Alumina may be obtained by dissolving purified alumt in four or five Obtained, times its weight of boiling water, adding a slight excess of carbonate of potassa, and after digesting for a few minutes, the bulky hydrate of alumina may be col- lected on a filter and well washed with hot water. If an excess of alkali is not employed the precipitate will retain some sulphuric acid.§ 918. Alumina is destitute of taste and smell; moistened with properties, water, it forms a cohesive and ductile mass, susceptible of being kneaded into a regular form. It is not soluble in water ; but retains a considerable quantity, and is, indeed, a hydrate, containing when dried at the temperature of the atmosphere, almost half its weight of *For other compounds see Turner’s Chem. + Edin. Jour, of Sci. No. xvii. 178. t This salt, as purchased in the shops, is frequently contaminated with peroxide of iron, and consequently unfit for many chemical purposes ; but it may be separated from this impurity by repeated crystallization. Its absence is proved by the alum being soluble without residue in a solution of pure potassa ; whereas when peroxide of iron is present, it is either left undissolved in the first instance, or deposited after a few hours in yellowish-brown flocks. § But the alumina, as thus prepared, is not yet quite pure; for it retains some of the alkali with such force, that it cannot be separated by the action of water. For this 248 Metals — Glucinium. Chap. IV. Effect of heat. Recognis- ed. Sesqui- chloride. Wohler’s process. Properties. Glucinium. water. Even after ignition, alumina has such an affinity for moist- ure, that it can hardly be placed on the scale without acquiring weight.* It is dissolved by the liquid fixed alkalies, and is precipi- tated by acids unchanged. In ammonia it is very sparingly soluble. 919. Alumina has the property of shrinking considerably in bulk, when exposed to heat. On this property was founded the pyrometer of Wedgwood, designed to measure high degrees of heat by the amount of the contraction of regularly shaped pieces of China clay. 920. Alumina is easily recognised by the following characters. 1. It is separated from acids, as a hydrate, by all the alkaline carbo- nates, and by pure ammonia. 2. It is precipitated by pure potassa or soda, but the precipitate is completely redissolved by an excess of the alkali. 921. Sesquichloride of Aluminium , 2 Al— )— 3C1 or AP Cl 3 , 27.4 2 eq. alumin. -{- 106.26 3 eq. chlor. = 133.66 equiv., was obtained by Oersted, by transmitting dry chlorine gas over a mixture of alu- mina and charcoal heated to redness. It was afterwards prepared by Wohler as follows. 922. He precipitated aluminous earth from a hot solution of alum by means of potassa, and mixed the hydrate, when dry, with pulverized charcoal, sugar, and oil, so as to form a thick paste, which was heated in a covered crucible until all the oiganic matter was destroyed. By this means the alumina was brought into a state of intimate mixture with finely divided charcoal, and while yet hot, was introduced into a tube of porcelain, fixed in a convenient furnace. After expelling atmospheric air from the interior of the apparatus by a current of dry chlorine gas, the tube was brought to a red heat. The formation of sesquichlo- ride of aluminium then commenced, and continued, with disengagement of car- bonic oxide gas, during an hour and a half, when the tube became impervious from sublimed sesquichloride collected within it. The process was then ne- cessarily discontinued. 923. It is of a pale greenish colour, translucent, lamellated, and like talc. Exposed to air, it emits fumes having an odour like hy- drochloric acid, and deliquesces. It dissolves in water with a hiss- ing noise and much heat. It is volatile a little above 212° and fu- ses.t Glucinium. St/mb. G. Equiv. 26.5. 924. This is the metallic base of the earth glucina, and was obtained in 1S2S by Wohler, by the action of potassium on the chloride, as in the case of the last described metal ; it appeared as a gray powder but acquired a metallic lustre by burnishing, and was easily oxidized. $ reason the precipitate must be re-dissolved in dilute hydrochloric acid, and thrown down by means of pure ammonia, or its carbonate. This precipitate, after being well washed and exposed to a white heal, yields pure anhydrous alumina. -Ammonia can- not be employed for precipitating aluminous earth directly from alum, because sul- phate of alumina is not completely decomposed by this alkali. (Berzelius.) An easier • process, proposed by Gay-Lussac, is to expose sulphate of alumina and ammonia to a strong heat, so as to expel the ammonia and sulphuric acid. For other processes see Ure’s Diet. 3. 147. * Berzelius found, that 100 parts of alumina, after being ignited gained 15J from a dry atmosphere, and 33 from a humid one. For a full saturation, 100 grains of alu- mina, he ascertained, require 54 of water.* It does not affect vegetable colours. t Aluminium combines with sulphur, phosphorus and selenium, for which see Tur- ner, 299. t Phil. Mag. and Annals, v. 392. * Jinn, dt CAtm, et Phys. v. 101. Yttrium. 249 925. Sesquioxide of Glucinium or Glucina , 2G4-30, G, or G 2 03, — Sesquiox- was discovered by Vauquelin in the beryl, emerald and euclase. ide or glu- The process proposed by Berthier for obtaining it, is to mix the beryl in fine Clna ’ powder with its own weight of marble and expose the mixture in a crucible to a Process for, strong heat. A glass is obtained which when in fine powder is attacked by hy- drochloric or sulphuric acid. The mass is then dissolved in dilute hydrochloric acid, and the solution evaporated to perfect dryness ; by which means the silicic acid is rendered quite insoluble. The alumina and glucina are then redissolved in water acidulated with hydrochloric acid, and thrown down together by pure ammonia. The precipitate, after being well washed, is macerated with a large excess of carbonate of ammonia, by which glucina is dissolved ; and on boiling the filtered liquid, carbonate of glucina subsides. By means of a red heat its carbonic acid is entirely expelled. 926. Glucina is a white powder, which has neither taste nor Properties, odour, and is quite insoluble in water. Its sp. gr. is 3. Vegetable colours are not affected by it. The salts which it forms with acids have a sweetish taste, a circumstance which distinguishes glucina from other earths, and from which its name is derived. (From yXvxrjs, sweet.) 927. Glucina may be known chemically by the following charac- Distin- ters. 1. Pure potassa or soda precipitates glucina from its salts, but guished, an excess of the alkali redissolves it. 2. It is precipitated perma- nently by pure ammonia as a hydrate, and by fixed alkaline carbo- nates as a carbonate of glucina. 3. It is dissolved completely by a cold solution of carbonate of ammonia, and is precipitated from it by boiling. By means of this property, glucina may be both distin- guished and separated from alumina. T. Yttrium. Syrnb. Y 928. Yttrium is the metallic base of an earth which was discov- ered in the year 1794 by Gadolin, in a mineral found at Ytterby in Sweden, from which it received the name of yttria. The metal it- ^ Urium , self was prepared by Wohler in 1828, by a process similar to that above described. 929. Its texture, by which it is distinguished from glucinium and Properties, aluminium, is scaly, its colour grayish black, and its lustre perfectly metallic. In colour and lustre it is inferior to aluminium, bearing in these respects nearly the same relation to that metal, that iron does to tin. It is a brittle metal, while aluminium is ductile. It is not oxidized either in air or water; but when heated to redness, it burns with splendour even in atmospheric air, and with far greater brilliancy in oxygen gas. The product, yttria, is white, and shows unequivocal marks of fusion. It dissolves in sulphuric acid, and also, though less readily, in solution of potassa ; but it is not attack- ed by ammonia. It combines with sulphur, selenium, and phospho- rus.^ 930. The salts of yttria have in general a sweet taste, and the Characters sulphate, as well as many of its salts, has an amethyst colour. It is ofltssalts > precipitated as a hydrate by the pure alkalies, and it is not redis- solved by an excess of the precipitant ; but alkaline carbonates, es- * Phil. Mag. and Annals , v. 393. 32 250 • Metals — Zirconium. Chap. IV. Equivalent. Discovery, Process for, Oxidation of, Thorina, Properties, Distin- guished- Zirconium, pecially that of ammonia, dissolve it in the cold, though less freely than glucina, and carbonate of yttria is precipitated by boiling. Of all the earths it bears the closest resemblance to glucina; but it is readily distinguished from it by the colour of its sulphate, by its in- solubility in pure potassa, and by yielding a precipitate with ferro- cyanuret of potassium.* 931. The equivalent of yttrium, as deduced by Berzelius, is 32.2 ; and that of yttria, which is probably a protoxide, is 40.2. T. Thorium. Symb. Th Equiv. 69. 6 932. The earthy substance formerly called thorina , was found by Berzelius to be phosphate of yttria; but in 1828 he discovered a new earth, so similar in some respects to what was formerly called thorina, that he applied this term to the new substance. 933. The metallic base of thorina (thorium) was procured by the action of potassium on chloride of thorium, decomposition being ac- companied with a slight detonation. On washing the mass, thorium is left in the form of a heavy metallic powder, of a deep leaden-gray colour ; and when pressed in an agate mortar, it acquires metallic lustre and an iron-gray tint. 934. Thorium is not oxidized either by hot or cold water; but when gently heated in the open air, it burns with great brilliancy, comparable to that of phosphorus burning in oxygen. The resulting thorina is as white as snow, and does not exhibit the least trace of fusion. It is not attacked by caustic alkalies at a boiling heat, is scarcely at all acted on by nitric acid, and very slowly by the sul- phuric; but it is readily dissolved with disengagement of hydrogen gas by hydrochloric acid. T. 935. Thorina was procured from a rare mineral from Norway, called thorite , of which it constitutes 57.91 per cent. 936. Thorina is a white earthy substance, of sp. gr. 9.402 inso- luble in all the acids except the sulphuric it dissolves even in that with difficulty. It is precipitated from its solutions by the caustic alkalies as a hydrate, and in this state absorbs carbonic acid from the atmosphere, and dissolves readily in acids. Its exact composi- tion is not known ; but its equivalent is about 67.6. 937. Thorina is distinguished from alumina and glucina by its insolubility in pure potassa ; from yttria by forming with sulphate of potassa a double salt which is quite insoluble in a cold saturated solution of sulphate of potassa. Zirconium. Symb. Zr Eq. about 33.7? 938. The experiments of Davy proved zirconia to be an oxidized body, and afforded a presumption that its base, Zirconium , is of a metallic nature. When potassium was brought into contact with zirconia ignited to whiteness, potassa was formed, and dark particles of a metallic aspect were diffused through the alkali. The decom- position of this earth, however, had not been effected in a satisfactory * Berzelius. Manganese. manner until the year 1824, when Berzelius succeeded in obtaining Sect. zirconium in an insulated state. 939. Zirconium is procured by heating a mixture of potassium with the dou- How pro- ble fluoride of zirconia and potassa, carefully dried, in a tube of glass or iron, by cured, means of a spirit lamp. The reduction takes place at a temperature below red- ness, and without emission of light. The mass is then washed with boiling wa- ter, and afterwards digested for some time in dilute hydrochloric acid. A small portion of hydrate of zirconia however still adheres to the zirconium. 940. Zirconium thus obtained, is in the form of a black powder, Properties, which may be boiled in water without being oxidized, and is attacked with difficulty by the sulphuric or nitro-hydrochloric acids ; but is dissolved readily, and with disengagement of hydrogen by hydro- fluoric acid. 941. Heated in the open air it takes fire at a temperature far below Combus- incandescence, burns brightly and is converted into zirconia. tion °** 942. Zirconium may be pressed out into thin shining scales of a dark gray colour, and of a lustre which may be called metallic, but its particles adhere together very feebly. It is a non-conductor of electricity. 943. Sesquioxide of Zirconium , or Zirconia , 2Zr-|-30, Zr, or Sesquiox- Zr 2 0 3 , was discovered in 1789 by Klaproth. It is obtained from the j*® zir ' zircon or jargon of Ceylon. The zircon in fine powder may be fused with litharge in the ratio of 17 to 21, when a glass is obtained which is soluble in acids. 944. Zirconia is in the form of a fine white powder, which, Properties, when rubbed between the fingers, has somewhat of the harsh leel of silica. It is entirely destitute of taste or smell. Its specific gravity exceeds 4. It is insoluble in water, yet appears to have some affi- nity for that fluid, retaining when slowly dried after precipitation, one third its weight, and appearing like gum arabic. 945. Exposed to a strong heat, zirconia fuses, assumes a light Effect of gray colour; and such hardness, on cooling, as to strike fire with heat, steel, and to scratch even rock crystal.* Section V. Metals , the Oxides of which are neither Alkalies nor Earths. I. METALS WHICH DECOMPOSE WATER AT A RED HEAT. Manganese. Symb. Mn Equiv. 27.7 946. The common ore of manganese is the black or peroxide, which is found native in great abundance. The metal is obtained by mixing this oxide, finely powdered, with pitch, p rocess f or making it into a ball, and putting this into a crucible, with powdered charcoal, obtaining one tenth of an inch thick on the sides, and one fourth of an inch deep at the metallic bottom. The empty space is then to be filled with powdered charcoal, a cover manganese, is to be luted on, and the crucible exposed, for one hour, to the strongest heat that can be raised. Manganese is a hard brittle metal, of a grayish-white colour, and granular texture. When exposed to air it becomes an oxide. Its specific gravity is 8.013. It is not attracted by the magnet, except when contaminated with iron. * For other characters see Turner’s Elements , 303. 252 JWetals — Manganese . Chap, iv. 947. It slowly decomposes water at common temperatures, and Equivalent- rapidly at a red heat. Oxides of Manganese * Protoxide, 948. Protoxide Mn+O, Mn, or MnO, 27.7 1 eq. mang. -f- 8 1 eq. oxy. = 35.7 equiv., is that oxide of manganese which is a strong salifiable base present in all the ordinary salts of this me- tal, and which appears to be its lowest degree of oxidation. Process for ma ^ ^ orme( ^ by exposing the peroxide, sesquioxide, or red oxide of man- ’ ganese to the combined agency of charcoal and a white heat ; or by exposing ei- ther of the oxides of manganese, contained in a glass or iron tube, to a current of hydrogen gas at a high temperature. For this purpose the red oxide, prepared from the nitrate of oxide of manganese, is the best. Another, Properties. Salts. It is also obtained by fusing the chloride in a platinum crucible with about twice its weight of carbonate of soda and dissolving the chloride of sodium in water. 949. It is of a green colour, and, according to some, attracts ox- ygen rapidly from the air, but in Turner’s experiments was very permanent, undergoing no change during nineteen days.t It oxi- dized at 600°. It unites with acids producing the same salts as the carbonate. If quite pure it should dissolve in cold dilute sulphuric acid.t 950. The salts of manganese are in general colourless if pure, but often have a shade of pink from the presence of red oxide or permanganic acid. The alkalies precipitate the protoxide as a white hydrate, the carbonates give a white carbonate, and ferrocyanuret of potassium gives a white ferrocyanuret of manganese, a character by which the absence of iron may be demonstrated. The white precipitates become brown from absorption of oxygen. Sesquiox- ide, Properties. Peroxide, 951. Sesquioxide 2Mn-|-30, Mn, or Mn 2 0 3 , 55.4 2 eq. mang. + 24 3 eq. oxy. = 79.4 equiv., occurs nearly pure in nature, and is found as a hydrate at Ilefeld in the Hartz. It may be formed artificially by exposing peroxide of manganese for a conside- rable time to a moderate red heat, and, therefore, is the chief residue of the usual process for procuring a supply of oxygen gas. 952. The colour varies with the source from which it is derived. That which is procured by means of heat from the native peroxide or hydrated sesquioxide has a brown tint; but when prepared from nitrate of oxide of manganese, it is nearly as black as the peroxide, and the native sesquioxide is of the same colour. With sulphuric and hydrochloric acids, it yields oxygen and chlorine gases. It is more easily attacked than the peroxide by cold sulphuric acid. With strong nitric acid, it yields a soluble protonitrate and the peroxide. 953. Peroxide Mn-f-20, 27.7 1 eq. mang. — |— 16 2 eq. oxy. = 43.7 equiv. This is the well known ore commonly called * In studying metallic oxides, it is necessary, as remarked by Turner, to distinguish oxides formed by the direct union of oxygen and a metal, from those that consist of two other oxides united with each other, and which therefore) in composition, partake of the nature of a salt rather than of an oxide. + Phil. Trans. Edin. 1828, and Phil. Mag. iv. t For the method of preparing pure salts from common peroxide of manganese, see Turner’s Elements, 6th ed., p 305. 253 Red Oxide of Manganese . from its colour the black oxide. It generally occurs massive, of an Sect, v. earthy appearance, and mixed with other substances, such as sili- ceous and aluminous earths, oxide of iron and carbonate of lime. It also occurs crystallized, with an imperfect metallic lustre. It may be made artificially by exposing the nitrate of manganese to a com- mencing red heat, until the whole of the nitric acid is expelled. 954. The peroxide of manganese undergoes no change on expo- Properties, sure to the air. It is insoluble in water, and does not unite either with acids or with alkalies. When boiled with sulphuric acid, it yields oxygen gas, and a sulphate of the protoxide is formed (365). With hydrochloric acid, a hydrochlorate is generated, and chlorine is evolved (608). On exposure to a red heat, it is converted with evolution of oxygen gas, into the sesquioxide of manganese. 955. The peroxide of manganese is employed in the arts, in the Uses, manufacture of glass, and in preparing chlorine for bleaching. In the laboratory it is used for procuring chlorine and oxygen gases, and in the preparation of the salts of manganese. 956. The hydrated peroxide of manganese which is sometimes Black wad, called black wad , and which occurs in froth-like coatings on other minerals, is remarkable for its spontaneous inflammation with oil. If half a pound of this be dried before a fire, and afterwards suffered to cool Spontane- for about an hour, and it be then loosely mixed or kneaded with two ounces of ous infiam- linseed oil ; the whole, in something more than half an hour, becomes gradually niation °f* hot, and at length bursts into flame. U. 573. 957. Red oxide Manganese. Mn0-)-Mn 2 0 3 , or 2Mn0~{-Mn0 2 , Red 0X1£{e > 83.1 3 eq. mang. + 32 4 eq. oxy. == 115.1 equiv. The substance called red oxide of manganese, oxidum manganoso-manganicum of Arfwedson, occurs as a natural production, and may be formed artifi- cially by exposing the peroxide or sesquioxide to a white heat either in close or open vessels. It is also produced by absorption of oxygen from the atmosphere when the protoxide is precipitated from its salts by pure alkalies, or when the anhydrous protoxide or carbonate is heated to redness. 958. Fused with borax or glass it communicates a beautiful Fused, &c. violet tint, a character by which manganese may be easily detected before the blow-pipe ; and it is the cause of the rich colour of the amethyst. By cold concentrated sulphuric acid it is dissolved in small quantity. The liquid has an amethyst tint, which disappears when heat is applied, or by the action of deoxidizing substances. 959. It may be doubted whether the red oxide is not rather a Composi- kind of salt composed of two other oxides, than a direct compound of tion - manganese and oxygen. From the ratio of its elements it may con- sist either of Sesquioxide . . 79.4 or one eq. ) C Peroxide Protoxide . . 35.7 or one eq. ) ° r < Protoxide . . 43 7 or one eq. . 71.4 or two eq. 115.1 It contains 27.586 per cent, of oxygen, and loses when converted into the green or protoxide.^ T. 145.1 6.896 per cent. * Varvicite. Mn^0 3 -f2Mn0 2 (probably), 110-8 4 eq. mang. + 56 7 eq.oxy. = 166.8 Varvicite. equiv. This compound is known only as a natural production, having been first no- ticed a few years ago by Phillips among some ores of manganese found at Hartshill, in Warwickshire. The locality of the mineral suggested its name. Varvicite was at 254 Metals — Manganese. Chap IV. Manganic acid. Mineral chameleon. Exp. Theory. Manganate oi potassa. Permanga- nic acid. Wohler’s process. 960. Manganic Acid. Mn+30, M, or MnO 3 , 27.7 1 eq. mang. -f- 24 3 eq. oxy. = 51.7 equiv. Manganese is capable of forming an acid with oxygen. Manganate of potassa is generated when hy- drate or carbonate of potassa is heated to redness with peroxide of manganese ; and nitre may be used successfully, provided the heat be high enough to decompose the nitrate of potassa.* 961. The materials absorb oxygen from the air when fused in open vessels ; but manganate of potassa is equally well formed in close vessels, one portion of oxide of manganese then supplying oxy- gen to another. The product has been long known under the name of mineral chameleon , from the property of its solution to pass rapidly through several shades of colour : on the first addition of cold water, a green solution is formed which soon becomes blue, purple, and red ; and ultimately a brown flocculent matter, hydrated peroxide of manganese, subsides, and the liquid becomes colourless.! Put equal quantities of this substance into two separate glass vessels, and pour on the one hot, and on the other cold water. The hot solution will have a beau- tiful green colour, and the cold one a deep purple. The same material, with wa- ter of different temperatures, assumes various shades of colour. The phenomena are owing to the formation of manganate of po- tassa of a green colour, and to its ready conversion into the red per- manganate of potassa, the blue and purple tints being due to a mix- ture of these compounds. Manganic acid itself cannot be obtained in an uncombined state, because it is then resolved into the hydrated peroxide and oxygen. 962. Manganate of potassa is obtained in crystals by forming a concentrated solution of mineral chameleon in cold water, very pure and free from carbonic acid, allowing it to subside in a stoppered bottle, and evaporating the clear green solution in vacuo with the aid of sulphuric acid. All contact of paper and other organic matter must be carefully avoided, since they deoxidize the acid, and the process be conducted in a cool apartment. The crystals are anhy- drous, and permanent in the dry state ; but in solution the carbonic acid of the air suffices to decompose the acid, or even simple dilution with cold water. Mixed with a solution of potassa, the manganate may be crystallized a second time in vacuo without change. 963. Permanganic Acid or'btWOl , 55.4 2 eq. mang. — |— 56 7 eq. oxy. = 111.4 equiv., is obtained by heating a solution of mineral chameleon. The process of Wohler consists in fusing chlorate of potassa in a platinum cru- cible, and adding peroxide of manganese in fine powder. Gregory has improved this ; he mixes 4 parts of the peroxide with parts of the chlorate, adds it to 5 parts of hydrate of potassa dissolved in a small quantity of water, evaporates to first mistaken for peroxide of manganese, but is readily distinguished by its stronger lustre, greater hardness, more lamellated texture, and by yielding water freely when heated to redness. Itssp. gr. is 4 . 531 . When strongly hehted it is converted into red oxide, losing 5.725 per cent, of water, and 7.335 of oxygen. * One part of manganese well mixed with three or four of nitre may be exposed to a bright red heat for half an hour in a crucible. The crucible should be but one third full. + These changes, which are more rapid by dilution and with hot water, have been suc- cessively elucidated byChevillot and Edwards, Forchammer and Mitscherlich. An. de Ch. et de Ph. viii. and xlix. 113 , and An. of Phil. xvi. 255 Perfluoride of Manganese. dryness, and exposes the fine powder in a platinum crucible to a low red heat. Sect. V. The mass not fused is again powdered and added to a large quantity of boiling water ; when this is clear it is to be decanted, rapidly concentrated, and crystal- lized. The crystals are to be washed in a little cold water and redisso'ved in the smallest possible quantity of boiling water. The acid may be obtained by adding to a solution of permanga- Acid ob- nate of baryta dilute sulphuric acid to precipitate the baryta. tained, 964. This acid has a rich red colour ; contact with paper or linen Properties, as in filtering, particles of cork, organic particles floating in the at- mosphere decompose it rapidly; colouring matters are bleached by it ; and in pure water its decomposition begins at 86°, and is com- plete at 212°. On these occasions oxygen gas is abstracted or given out, and hydrated peroxide of manganese subsides. 965. The salts of permanganic acid are more permanent than the Its salts, free acid ; so that most of them may be boiled in solution, especially if concentrated. When heated they give out oxygen gas ; they de- flagrate like nitre, and detonate powerfully with phosphorus. 966. In constitution this acid bears a remarkable analogy to per- Composi- chloric acid.^ llon ' 967. Perchloride of Manganese. 2Mn-f-7Cl, or Mn 2 Cl 7 , 55.4 2 Perchlo- eq. mang. -|- 247.94 7 eq. chlor. — 303.34 equiv. This compound ride > is formed by putting a solution of permanganic into strong sulphuric acid, and then adding fused sea-salt. The best mode of preparation is to form the green mineral chameleon, and aci- dulate with sulphuric acid : the solution, when evaporated, leaves a residue of sulphate and permanganate of potassa. This mixture, treated by strong sulphuric acid, yields a solution of permanganic acid, to which are added small fragments of sea-salt, as long as coloured vapour continues to be evolved. t 96S. The perchloride, when first formed, appears as a vapour of Properties, a copper or greenish colour ; but on traversing a glass tube cooled to — 4°, it is condensed into a greenish-brown coloured liquid. When generated in a capacious tube, its vapour gradually displaces the air, and soon fills the tube. If it is then poured into a large flask, the sides of which are moist, the colour of the vapour changes in- stantly on coming into contact with the moisture, a dense smoke of a pretty rose tint appears, and hydrochloric and permanganic acids are generated. It is hence analogous in composition to permanganic acid, its ele- Composi- ments being in such a ratio that tlon ‘ 1 eq. perchloride and 7 eq. water 2 1 eq. permang. acid and 7 eq. hydrochloric acid. 2Mn+7Cl 7(H+0) -g, 2Mn-+70 7(H+C1). 969. Perfluoride of Manganese. 2Mn-|-7F, or Mn 2 F 7 , 55.4 p . . 2 eq. mang. 130.76 7 eq. oxy. = 186.16 equiv. This gase- er U ° n e ous compound! is formed by mixing common mineral chamele- on with half its weight of fluor spar, and decomposing the mixture in a platinum vessel by fuming sulphuric acid. The fluoride is then * Protochloride of Manganese, Mn-f Cl, or MnCl, 27.7 1 eq. mang. 4-35.42 1 eq. chlor. == 63,12 equiv., is best prepared by evaporating a solution of the chloride to Protochloride, dryness by a gentle heat, and heating the residue to redness in a glass tube, while a current of hydrochloric acid gas is transmitted through it. The heat of a spirit-lamp is sufficient for the purpose. It fuses readily at a red heat, and forms a pink-coloured lamehated mass on cooling. It is deliquescent, and of course very soluble in water. + Edin. Jour, of Sci. viii. 179. t Discovered by Dumas and Wohler, Edin. Jour . of Sci. ix. 256 « Metals — Iron. Chap. IV. Iron. Native. Properties. Combines ■with oxy- gen. Effect of water, at common tempera- tures. Of steam. Protosulphuret. disengaged in the form of a greenish-yellow gas or vapour, of a more intensely yellow tint than chlorine. When mixed with atmospheric air, it instantly acquires a beautiful purple-red colour; and it is freely absorbed by water, yielding a solution of the same red tint. It acts instantly on glass, with formation of fluosilicic acid gas, a brown matter being at the same time deposited, which becomes of a deep purple-red tint on the addition of water.* Iron. Symb. Fe Equiv. 28 1 970. The most important native combinations of iron, whence the immense supplies for the arts of life are drawn, are the oxides. Iron is also found combined with sulphur, and with several acids ; it is so abundant that there are few fossils free from it. It is also found in some animal and vegetable bodies, and in several mineral waters. Iron is sometimes found native,! and is usually regarded as of meteoric origin, for it is invariably alloyed by a portion of the metal nickel, and a similar alloy is found in meteoric atones. Native Iron is flexible, cellular, and often contains a green substance of a vitreous appearance. It has been found in Africa, in America, and in Sibe- ria, where a mass of it weighing 1600 lbs. was discovered by Pallas. The mass found in Peru, described by Don Rubin de Celis, weighed 15 tons. 971. Iron is a metal of a blue white colour, fusible at a white heat. Its specific gravity is 7.88. It has not been so long known as many of the other metals ; it was, however, employed in the time of Mo- ses for cutting instruments. It is extremely ductile, but cannot be hammered out into very thin leaves. 972. Exposed to heat and air iron quickly oxidizes, or in common language, rusts. If the temperature of the metal be raised, this change goes on more rapidly, and when made intensely hot, takes place with the appearance of actual combustion. Thus the small fragments, which fly from a bar of iron during forging, undergo a vivid combustion in the atmosphere ; and iron filings, projected upon the blaze of a torch, burn with considerable brilliancy. The oxide, obtained in these ways is of a black colour, and is still attract- ed by the magnet. 973. By contact with water at the temperature of the atmosphere, iron becomes slowly oxidized, and hydrogen gas is evolved. When the steam of water is brought into contact with red-hot iron, the iron is converted into black oxide ; and an immense quantity of hydrogen gas set at liberty (405). The iron is afterward found to have lost all its tenacity, and may be crumbled down into a black powder, to which the name o { finery cinder was given by Priestley. * Protosufphuret of Manganese, Mn+S, or MnS. 27.7 1 eq.fmang -f 16.1 1 eq. sulph. = 43.8 equiv., may lie procured by igniting the sulphate with one sixth of its weight of charcoal in powder.* It is also formed by the action of hydrosulphuric acjd gas on the protosulphate at a red beat.t It occurs native in Cornwall, and at Nagyag in Transylvania. It dissolves completely in dilute sulphuric or hydrochloric acid, with disengagement of very pure hydrosulpnuric acid gas. t Native iron of terrestrial origin has been observed at Canaan, Conn., and in Guil- ford Co. N. C. J. D. Dana’s System of Mineralogy, 1837. * Berthier. t Arfwedson in .9nn. of Phil. voi. vii. N. 8. 267 Sesquioxide of Iron . 974. When iron is dissolved in dilated sulphuric acid, the acid is Sect, v. not decomposed ; but the metal is oxidized at the expense of the wa- of sulphu- ter and hydrogen gas is obtained (378).^ ric acid. The eq. of iron has not been determined with accuracy. 975. Protoxide of Iron , Fe-(-0, Fe, or FeO, 28 L eq. iron -(- Protoxide, 8 1 eq. oxy. = 36 equiv. This oxide is the base of the native car- bonate of iron, and of the green vitriol of commerce. It is doubtful if it has ever been obtained in an insulated form. Its salts, particu- larly when in solution, absorb oxygen from the atmosphere with such rapidity that they may even be employed in eudiometry. This protoxide is always formed with evolution of hydrogen gas when metallic iron is put into dilute sulphuric acid ; and its compo- sition may be determined by collecting and measuring the gas which is disengaged. 976. Protoxide of iron i£ precipitated from its salts as a white hy- Precipita- drate by pure alkalies, as a white carbonate by alkaline carbonates, ted ‘ and as a white ferrocyanuret by ferrocyanuret of potassium. The two former precipitates become first green and then red, and the lat- ter, green and blue by exposure to the air. The solution of gall- nuts produces no change of colour. Hydro-sulphuric acid does not act if the protoxide is united with any of the stronger acids; but alkaline hydrosulphates cause a black precipitate, protosulphuret of iron. 977. Sesquioxide of Iron. 2Fe-[-30, Fe, or Fe 2 0 3 , 56 2 eq. iron Sesquiox- —f- 24 3 eq. oxy. = 80 equiv. The red or sesquioxide is a natural ide ' product, known as red hcematite. It occurs massive and fibrous. It may be made by dissolving iron in nitro-hydrochloric acid, and add- ing an alkali. The hydrate of the red oxide, consists of 80 parts or one eq. of the sesquioxide, and 18 parts or two eq. of water. 97S. It is not attracted by the magnet. Fused with vitreous sub- p ropert i es . stances, it communicates to them a red or yellow colour. It com- bines with most of the acids, forming salts, the greater number of which are red. Its presence may be detected by very decisive tests, The pure alkalies, fixed or volatile, precipitate it as the hydrate. Alkaline carbonates have a similar effect, peroxide of iron not form- ing a permanent salt with carbonic acid. With ferrocyanuret of potassium it forms Prussian blue. Sulphocyanuret of potassium causes a deep blood-red ; and infusion of gall-nuts, a black colour. Hydrosulphuric acid converts the sesquioxide into protoxide of iron, with deposition of sulphur. These reagents, and especially ferrocy- anuret and sulphocyanuret of potassium, afford an unerring test of the presence of minute quantities of sesquioxide of iron. On this account it is customary, in testing for iron, to convert it into the * The action of nitric acid on iron is attended by a series of very remarkable phenome- Action of nitrie na, which have been recently observed by ScliOnbein. He observed that this acid of sp. acid > gr. 1.35 though capable of acting with violence on ordinary iron, was inert on an iron wire, one extremity of which had been previously made red-hot. He found, too, that this indifference to nitric acid, may be communicated, by mere contact, from one iron wire to another, by submersion for a few moments into strong nitric acid, or by making it the positive electrode of a galvanic current, the negative electrode having been pre- viously introduced into the acid. Under these circumstances the wire does not com- bine with the oxygen liberated. Faraday has found that the same property is given to iron by contact with platinum, and that the effect is not limited to nitric acid. See the original papers in Phil. Mag. and Aim. ix- 53, x. 133, &c. 258 Metals — Iron. Chap, iv. sesquioxide, an object which is easily accomplished by boiling the solution with a small quantity of nitric acid. 979. Black , or Magnetic Oxide. Fe0+Fe 2 0 3 , 36 1 eq* protox. iron + 80 1 eq. sesquiox. iron = 1 16 equiv. This substance, the oxidum ferrosoferricum of Berzelius, long supposed to be protoxide of iron, contains more oxygen than the protoxide, and less than the red oxide. It cannot be regarded as a definite compound of iron and oxygen ; but it is composed of the two real oxides. It occurs native, frequently crystallized in the form of a regular octohedron ; and it is not only attracted by the magnet, but is itself sometimes magnetic. It is always formed when iron is heated to redness in the open air ; and is likewise generated by the contact of watery vapour with iron at elevated temperatures. 990. The composition of the product, however, varies with the duration of the process and the temperature which is employed. Thus, according to Buchholz, Berzelius, and Thomson, 100 parts of iron, when oxidized by steam, unite with nearly 30 of oxygen ; whereas in a similar experiment performed by Gay-Lussac, 37.8 parts of oxygen were absorbed. 991. The nature of the black oxide is farther elucidated by the action of acids. On digesting the black oxide in sulphuric acid, an olive-coloured solution is formed, containing two salts, sulphate of the sesquioxide and protoxide, which may be separated from each other by means of alcohol.* The solution of these mixed salts gives green precipitates with alkalies, and a very deep blue ink with infu- sion of gall-nuts. The black oxide of iron is the cause of the dull green colour of bottle glass. yiuwui . tu 982. Protochloride of Iron. Fe+Cl, or FeCl, 28 1 eq. iron -f- ride, 35.42 1 eq. chlor. = 63.42 equiv. This compound is formed by transmitting dry hydrochloric acid gas over iron at a red heat, when hydrogen gas is evolved and the surface of the iron is covered with a white crystalline protochloride which at a stronger heat is sub- limed. Also, on acting with hydrochloric acid on iron, which is dissolved with evolution of hydrogen gas, evaporating to dryness, and heating to redness in a tube without exposure to the air. Solution. 983. Protochloride of iron dissolves freely in water, yielding a pale green solution, from which rhomboidal prisms of the same co- lour are obtained by evaporation. The crystals contain several equivalents of water of crystallization, deliquesce by exposure to the air, owing to the formation of sesquichloride, and are soluble in alcohol as well as water. The aqueous solution absorbs oxygen from the air, and becomes yellow from the formation of sesquichloride of iron : one portion of iron takes oxygen from the air, and yields its chlorine to another portion of iron, whereby sesquichloride and sesquioxide of iron are generated, and the latter falls as an ochreous sediment com- bined with some of the sesquichloride. Sesquichlo- 984. Sesquichloride of Iron, 2Fe-j-3CI, or Fe 2 CI 3 , 56 2 eq. iron ride. _|_ 106.26 3 eq. chlor. = 162.26 equiv., is formed by the combustion of iron wire in dry chlorine gas, and by transmitting that gas over iron moderately heated ; when it is obtained in small iridescent plates of a red colour, which are volatile at a heat a little above 212% Black or magnetic oxide, Composi- tion, Action of acids on. * Proust and Gay-Lussac. 259 Protosulphuret of bon . deliquesce readily, and dissolve in water, alcohol, and ether. On Sect, v. agitating ether with a strong aqueous solution of the sesquichloride, the ether abstracts a part of it, and acquires a gold-yellow colour. The readiest mode of obtaining a solution of the sesquichloride is to p rocess dissolve sesquioxide of iron in hydrochloric acid. On concentrating to the consistence of syrup and cooling, it separates as red crystals, which by distillation yield at first water and hydrochloric acid, and then anhydrous sesquichloride of iron, leaving a compound of sesqui- oxide and sesquichloride of iron in crystalline laminse. 985. Protiodide of Iron. Fe-j-I, or Fel, 28 1 eq. iron -}~ 126.3 Protiodide, 1 eq. iod. = 154.3 equiv. It exists as a pale green solution when iodine is digested with water and iron wire, the latter being in ex- cess ; and on evaporating the solution, without exposure to the air, to dryness, and heating moderately, the protiodide is fused, and on cooling becomes an opaque crystalline mass of an iron-gray colour and metallic lustre. It is deliquescent and very soluble in water and alcohol. 986. Its aqueous solution attracts oxygen rapidly from the air, un- Solution, dergoing the same kind of change as the protochloride: to preserve a solution of protiodide as such, a long piece of iron wire should be kept permanently in the liquid. This compound has been very sue- Use. cessfully employed in medical practice.* 987. Sulphurets of Iron. These elements have for each other a Sulphurets, remarkably strong affinity, and unite under various circumstances and in several proportions. The two lowest degrees of sulphura- tion, the tetrasulphuret and disulphuret, were prepared by Arfwed- son by transmitting a current of hydrogen gas, at a red heat, over the anhydrous disulphate of sesquioxide of iron to procure the tetrasu;- phuret, and over anhydrous sulphate of protoxide of iron for the disulphuret. In both cases sulphurous acid and water are evolved, and the resulting sulphurets are left as grayish-black powders, sus- ceptible of a metallic lustre by friction. They both dissolve in dilute sulphuric acid with evolution of hydrogen and hydrosulphuric acid gases.t 988. Protosulphuret of Iron , Fe-j-S, or FeS, 28 1 eq. iron -f- Protosul- 16.1 1 eq. sulph. == 44.1 equiv., is prepared by heating thin laminse P hurel ° * Sesquiodide of Iron, 2Fe+3l, or Fe 2 ! 3 , 56 2 eq. iron + 378 9 3 eq. iod- = 434 9 «quiv.,of a yellow or orange colour according to the strength of the solution, is obtain- ed by freely exposing a solution of the protiodide to the air, or digesting iron wire with excess of iodine, gently evaporating and suhliming the sesquiodide. It is a vola- tile red compound, deliquescent, and soluble in water and alcohol. The bromides of iron are formed under similar conditions to the chlorides and iodides, and are very analogous to them in their properties. ProtoJLuoride of Iron, 28 1 eq. iron + 18.68 l eq. floor. = 46.68 is best pre- pared by dissolving iron in a solution of hydrofluoric acid, out of which it crystallizes as the acid becomes saturated, in small white square tables, which are sparingly soluble in water, and become pale yellow by the action of the air. By heat they part with their water of crystallization, and afterwards bear a red heat without decomposition. Berzelius. Sesquifluoride of Iron , 2Fe+3F, or Fe 2 F3, 56 2 eq. iron + 56.04 3 eq. fluor. = 112.04 equiv., is formed by dissolving sesquioxide of iron in hydrofluoric acid and yields a colourless solution even when saturated. By evaporation it is left as a crystalline mass of a pale flesh-colour, and of a mild astringent taste. It is sparingly soluble in water. t Tetrasulphuret of Iron. 4Fe+S, or Fe 4 S, 112 4 eq. iron + 16.1 1 eq. sulph. = 128.1 equiv. Disulphuret of Iron. 2Fe+S„ or Fe 2 S, 56 2 eq. iron +16,1 1 eq. sulph. = 72.1 equiv. 260 Metals — Iron. Chap. IV. Sesquisul- phuret. Bisulphu- ret. Action of acids. Magnetic. Diphoiphuret. of iron to redness with sulphur in a covered Hessian crucible, and continuing the heat until any excess of sulphur is expelled. The iron is found with a crust of protosulphuret, which is brittle, of a yellowish-gray colour and metallic lustre, and is attracted by the magnet. When pure it is completely dissolved by dilute sulphuric acid, yielding pure hydrosulphuric acid (754). The protosulphuret of iron exists in nature as an ingredient in variegated copper pyrites ; and it falls on mixing hydrosulphate of ammonia with sulphate of pro- toxide of iron as a black precipitate, which oxidizes rapidly by absorbing oxygen from the air, as soon as the excess of hydrosul- phate of ammonia is removed by washing. 989. Sesquisulphuret of Iron , 2Fe-j-3S, or Fe 2 S 3 , 56 2 eq. iron -f- 48.3 3 eq. sulph. = 104.3 equiv., is formed in the moist way by adding sesquichloride of iron drop by drop to hydrosulphate of am- monia or sulphuret of potassium in excess, and falls as a black preci- pitate, which is oxidized readily by the air. In the dry way it is slowly produced by the action of hydrosulphuric acid gas on sesqui- oxide of iron at a heat not exceeding 212°, water being also formed ; and by the action of the same gas on the hydrated sesquioxide at common temperatures. This sulphuret, when anhydrous, has a yellowish-gray colour, is not attracted by the magnet, and dissolves in dilute sulphuric or hydrochloric acid, yielding hydrosulphuric acid and a residue of bisulphuret of iron.* 990. Bisulphur et of Iron. Fe-(-2S, or FeS 2 , 2S 1 eq. iron -f- 32.2 2 eq. sulph. = 60.2 equiv. This, the iron pyrites of mineralo- gists, exists abundantly in the earth. It occurs in cubes or some allied form, has a yellow colour, metallic lustre, a density of 4.981, and is so hard that it strikes fire with steel. Some varieties have a white colour; but these usually contain arsenic. Others occur in rounded nodules, have a radiated structure divergent from a common centre, are often found in beds of clay and are much disposed by the influence of air and moisture to yield sulphate of protoxide of iron. 991. Bisulphuret of iron is not attacked by any of the acids ex- cept the nitric, and its best solvent is the nitro-hydrochloric acid. Heated in close vessels it gives off' nearly half its sulphur, and is converted into magnetic iron pyrites. 992. Magnetic Pyrites. 5FeS-|-FeS 2 , 60.2 1 eq. bisulph. of iron -f- 220.5 5 eq. protosuph. of iron = 280.7 equiv. This is a natural product, termed magnetic pyrites from being attracted by the magnet, and was formerly regarded as protosulphuret of iron ; but it may be regarded as a compound of bisulphuret and protosulphuret. It is formed by heating the bisulphuret to redness in close vessels, by fusing iron filings with half their weight of sulphur, or by rubbing sulphur upon a rod of iron heated to whiteness (754). It yields hy- drosulphuric acid gas.t * Berzelius. + Diphosphuret of Iron. 2Fe+P, or Fe 2 P, 56 2 eq. iron +15.7 1 eq. phosph. = 71.7 equiv. It is prepared by exposing the phosphate of protoxide of iron to a strong heat iu a covered crucible lined with charcoal, the excess of phosphorus being dissi- pated in vapour. It is a fused granular mass, of tne colour and lustre of iron, but very brittle, and is not attacked by hydrochloric acid. It is sometimes contained in metal- lic iron, to the properties of which it is very injurious by rendering it brittle at com- mon temperatures. Perphos. of Iron. 3Fe+4P, or Fe 3 P 4 , 84 3 eq. iron+62.8 l eq. phosph. = 146.8 equiv. Cast Iron . 261 993. Carburets of Iron. Iron combines with carbon in various Sect, v. proportions ; and the varieties of proportion occasion great differ- Carburets, ences of properties in the compounds. On these varieties, and the occasional combination of a small proportion of oxygen, depend the qualities of the different kinds of iron used in the arts, as cast-iron, steel, &c. &c. 994. The substance termed Graphite, Plumbago , and Black lead , is Graphite, a mechanical mixture of charcoal and iron ; the artificial graphite is a real carburet. The last may be formed by exposing iron with excess of charcoal to a violent and long continued heat. The first is not an uncommon mineral, though rarely found of Uses, sufficient purity for the manufacture of pencils the coarser kinds and the dust, are melted with sulphur to form common carpenters’ pencils : crucibles are sometimes made of it, and it forms an ingredi- ent in compositions for covering cast-iron, and for diminishing fric- tion in machines. It contains from 4 to 10 per cent, of iron. 995. Plumbago burns with great difficulty : when intensely heat- Effect of ed in a Toricellian vacuum by a Voltaic battery, Davy found that its heat, &c. characters remained wholly unaltered, neither could any evidence of its containing oxygen be derived from the action of potassium. But when exposed to the focus of a powerful burning lens in oxygen gas, it was observed that the gas became clouded, and that dew was de- posited, indicating the presence of hydrogen or of water.! 996. An extremely important part of the chemical history of iron varieties relates to the varieties of the metal which are found in commerce, of iron, These are much too numerous to be dwelt upon here ; the principal of them are cast iron , wrought iron , and steel. Of cast iron, there are two principal varieties, distinguished by the Cast iron, terms ivhite and gray. The first is very hard and brittle, and when broken, of a radiated texture. Acids act upon it but slowly, and exhibit a texture composed of a congeries of plates, aggregated in va- rious positions. Gray or mottled iron is softer and less brittle ; it may be bored Gray iron, and turned in the lathe. When immersed in dilute hydrochloric acid, it affords a large quantity of black insoluble matter, which Daniell considers as a triple compound of carbon, iron, and silicon, and which has some very singular properties. The texture of the metal resembles bundles of minute needles. Cast iron always contains impurities, such as charcoal, undecom- posed ore, and earthy matters, which are often visible by mere in- spection; and sometimes traces of chromium, manganese, sulphur, phosphorus and arsenic are present. It fuses readily at 2786° F.,t which is a full red heat, and in cooling it acquires a crystalline gra- nular texture. 997. Cast iron is converted into wrought iron by a curious pro- cess, called puddling. The cast iron is put into a reverberatory fur- Process of nace, and when in fusion is stirred, so that every part may be ex- puddling, posed to the air and flame. After a time the mass heaves, emits a * See a description of the mine at Borrowdale, in Bost. Jour . Philos, ii. 332. t On the fusion of plumbago by means of Hare ? s deflagrator, see Amer. Jour . vi. 344, &c. t Daniell. 262 Metals — Iron. Chap. IV. Difference in quality. Structure of wrought iron. Steel. Properties. Temper- ing. _ blue flame, and gradually grows tough and becomes less fusible, and at length congeals. In that state it is passed successively between rollers, by which a large quantity of extraneous matter is squeezed out, and the bars are now malleable. They are cut into pieces, placed in parcels in a very hot reverberatory furnace, and again hammered and rolled out into bars. They are thus rendered more tough, flexible and malleable, but much less fusible. 998. The difference in the quality of the two kinds of cast iron, appears owing to the mode of combination, rather than to a differ- ence in the proportion of carbon. According to Karsten, the carbon of the white is combined with the whole mass of iron, and amounts as a maximum to 5.25 per cent. ; the gray, on the contrary, con- tains from 3.15 to 4.65 per cent, of carbon, of which about three fourths are in the state of graphite. 999. A bar of wrought iron, when its texture is examined in the mode pointed out by Daniell, presents a fasciculated appearance, the fibres running in a parallel and unbroken course throughout its length. This structure may be well seen by tearing a bar of wrought iron asunder. 1000. Steel is commonly prepared by the process of cementation, which consists in filling a large furnace with alternate strata of bars of the purest malleable iron and powdered charcoal, closing every aperture so as perfectly to exclude atmospheric air, and keeping the whole during several days at a red heat. By this treatment the iron gradually combines with from 1.3 to 1.75 per cent, of carbon, its texture is greatly changed, and its surface is blistered. It is sub- sequently hammered at a red heat into small bars and beaten, it is then called tilted steel; and this broken up, heated, welded and again drawn out into bars, forms shear steel. Mackintosh of Glas- gow, has introduced an elegant process of forming steel by exposing heated iron to a current of coal gas; when carburetted hydrogen is decomposed, its carbon enters into combination with iron, and hy- drogen gas is evolved. 1001. In ductility and malleability it is far inferior to iron ; but exceeds it greatly in hardness, sonorousness, and elasticity. Its texture is also more compact, and it is susceptible of a higher polish. It sustains a full red heat without fusing, and is, therefore, less fusi- ble than cast iron ; but it is much more so than malleable iron. By fusion it forms cast steel, which is more uniform in composition and texture, and possesses a closer grain than ordinary steel. 1002. When steel is heated to a cherry-red colour, and then plunged into cold water, it becomes so extremely hard and brittle, as to be unfit for almost any practical purpose. To reduce it from this extreme hardness, is called by the workmen tempering , and is ef- fected by again heating the steel to a certain point. The surface being a little brightened exhibits, when heated, various colours which constantly change as the temperature is increased, and by these colours it has been customary to judge of the temper of the steel.* * For more extended accounts of iron and steel, see Braude’s Chem. ii. 35 — Aikin’s Did. art. Iron— Phil. Mag. ii.— Supplement to Encydop. Brit.— Report of Brit. Assoc. 1S37— Dumas’ Trail'd de Chim. iv. 599, and Thomson’s Inorg. Chem. i. 481,496. Zinc— Ch loride . 263 1003. Steel admits of being alloyed with several other metals, and rf«ct. v. the alloys, as appears from a recent investigation of Stodart and Alloys. Faraday* are applicable to various uses. Zinc * Symb. Zn Equiv. 32.3 1004. This metal is obtained from carbonate of zinc or calamine Ore, and from the native sulphuret or blende. f The zinc of commerce or spelter , is generally impure, containing sulphur, lead, arsenic, cop- per, &c. It may be freed from these by distillation at a white heat Reduction in an earthern retort, to which a receiver full of water is adapted ; of. but the first portions should be rejected as liable to contain arsenic and cadmium. 1005. Zinc is a bluish white metal, its specific gravity varies from properties 6.8 to 7.1, it is malleable at 300°, but very brittle when its tempera- °f zinc - ture approaches that of fusion, which is about 773°. I It is some- what ductile, but its wire possesses little tenacity. At a red heat it takes fire, burns with a bright flame, and is con- verted into a white flocculent substance, formerly called pompholix , nihil album , and flowers of zinc . It is also oxidized by dilute sulphuric or hydrochloric acid, and Oxidized, the hydrogen evolved contains a small quantity of metallic zinc in combination.^ 1006. Protoxide of Zinc. Zn~j-0,Zn, or ZnO, 32.3 1 eq. zinc Protoxide. -J-8 1 eq. oxy. == 40.3 equiv. This is the only oxide of zinc which acts as a salifiable base, and the only one of known composition. It is generated during the solution of zinc in dilute sulphuric acid, and may be obtained in a dry state by collecting the flakes which rise during the combustion of zinc, or by heating the carbonate to redness. At common temperatures it is white ; but when heated to low redness, it assumes a yellow colour, which gradually disap- pears on cooling. It is quite fixed in the fire. It is insoluble in water. 1007. The protoxide is precipitated from its solutions as a white hydrate by pure potassa or amtnonia, and as carbonate by carbonate of ammonia, but is completely redissolved by an excess of the pre- cipitant. The fixed alkaline carbonates precipitate it permanently as white carbonate of protoxide of zinc. When metallic zinc is exposed for some time to air and moisture, Action of or is kept under water, it acquires a superficial coating of a gray water * matter, which Berzelius describes as a sub*oxide. It is probably a mixture of metallic zinc and the protoxide. 1008. Chloride of Zinc. Zn-f-Cl, or ZnCl, 32.3 1 eq. zinc + Chloride. 35.42 1 eq. chlor. s= 67.72 equiv. This compound is formed, with evolution of heat and light, when zinc filings are introduced into chlorine gas ; and it is readily prepared by dissolving zinc in hy- * Phil. Trans. 1822, and Boston Jour. Philos, i. 130. t For the process see Brande ii. 48. t Daniell. § Zinc may be obtained in small fragments for introduction into a retort in pre- paring hydrogen gas, by dropping it in fusion into cold water. A preferable method is to cast it into bars of about quarter of an inch in diameter and afterwards break them into pieces of about half an inch in length. W. 264 Metals — Cadmium. Chap. IV. Sulphuret or blende. Uses of zinc. Cadmium, Separation of, Properties. _ drochloric acid, evaporating to dryness, and heating the residue in a tube through which dry hydrochloric acid gas is transmitted. It is colourless, fusible at a heat a little above 212°, has a soft consis- tence at common temperatures, hence called butter of zinc , sublimes at a red heat, and deliquesces in the air. 1009. Sulphuret of Zinc. Zn-J-S, or ZnS, 32.3 1 eq. zinc -f- 16.1 1 eq. sulph. = 49.4 equiv. This compound is well known to mineralogists under the name of zinc blende , and occurs in dode- cahedral crystals or some allied form. Its structure is lamellated, lustre adamantine, and colour variable, being sometimes yellow, red, brown, or black. It may be formed artificially by igniting, in a closed crucible, a mixture of oxide of zinc and sulphur, or sulphate of oxide of zinc and charcoal, or by drying the hydrated sulphuret of zinc. Zinc combines also with Iodine, Bromine and Fluorine. 1010. It has been proposed to apply zinc to the purpose of culi- nary vessels, pipes for conveying water, sheathing for ships, &c. ; but it is rendered unfit for the first object, by the facility with which the weakest acids act upon it, and for the remaining ones, by its con- siderable though slow oxidation, when exposed to the operation of air and moisture.* Cadmium . Symb. Cd Equiv. 55.8 1011. This metal discovered by Stromeyer in 1817, is contained in certain ores of zinc, and especially in the black fibrous blende of Bohemia. It has been detected in the calamine of Derbyshire, and in the zinc of commerce,! and in the sublimate which in the process for obtaining zinc, rises before that metal, forming what the workmen call the brown blaze.% It was called cadmium from xadpeia, a term applied both to calamine and to the volatile matters which rise from the furnace in preparing brass. 1012. A very elegant process for separating zinc from cadmium was proposed by Wollaston. The solution of the mixed metals is put into a platinum capsule, and a piece of metallic zinc is placed in it. If cadmium is present, it is reduced, and adheres so tena- ciously to the capsule, that it may be washed with water without danger of being lost. It may then be dissolved either by nitric or dilute hydrochloric acid.§ 1013. Cadmium, in colour and lustre, has a strong resemblance to tin, but is somewhat harder and more tenacious. It is very ductile and malleable. Its sp. gr. is 8.604 before being hammered, and 8.694 afterwards. It melts at about the same temperature as tin, and is nearly as volatile as mercury. When heated in the open * It has been employed in the U. S. as a covering for the roofs of buildings, but is in many situations quite unfit for that purpose. See a paper on this subject by Gale, in Amer. Jour. vol. xxxii. 315. + Ann. of Philos, xv. 272, and N. S. iii. 123. t Ann. Philos, iii. 435. Some portions of this substance yielded from 12 to 20 per cent, of cadmium. Ann. of Philos, xiv. and xvii. § For Stromeyer’s process see Turner, p. 321. Tin. 265 air. it absorbs oxygen, and is converted into an oxide, and is readily Sec> y. oxidized and dissolved by nitric acid, which, is its proper solvent.* Tin. Syrnb . Sn Equic. 58.9 1014. The properties of tin must he examined in the state of T i°- grain-tin or block tin ; what is commonly known by the name of tin, being nothing more than iron plates with a thin covering of this metal. Several varieties of tin are met with in commerce.! 1015. This metal has been kuown from the remotest ages. It was in common use in the time of Moses, and was obtained at a very earh* period from Spain and Britain by the Phoenicians.! The native oxide, found in Cornwall and some other counties, is the principal ore of tin ;9 the metal is obtained by heating it to red- To obtain ness with charcoal. To obtain pure tin the metal should be boiled P are tin - in nitric acid, and the oxide which falls down reduced by heat in coutact with charcoal in a covered crucible. U. 1016. Tin has a silvery white colour, is considerably harder than lead, scarcely at all sonorous, very malleable, though not very te- Properties, nacious. Under the hammer it is extended into leaves, called tin- foil, which aTe about y &o ts an i nc h thick. Its sp. gr. is about 7.291. It melts at 442 = , and by exposure to heat and air is grad- ually converted into a gray protoxide.** Placed upon ignited char- coal under a current of oxygen gas, it burns very brilliantly. * Oxide of Cadmium.. CcH-O. Cd. or CdO, 55.8 1 eq. cad. -f 8 1 eq. osv. = 63.3 equiv. The only known oxide of cadmium, is prepared by igniting its carbonate, has an orange colour, is fixed in the fire, and is insoluble in water. ; Sulphured of Cadmium. Cd-rS. or CdS. 55.3 1 eq. cad. —15.1 1 eq. sulph. = 7i.§ equiv, It occars in mixture or combination in some kinds of zinc blende. Cadmium combines with Chlorine. Iodine and Fluorine. t For the discrimination of which and the means of judging of its purity. Yauqueiia has given useful instructions in the 77th vol. of the Ann. de Chim and an interest- ing account of the ores of tin. and of the processes for extracting the metal in Cornwall, has been given by Taylor in the 5th vol. of the Trans. Geolog. Sac. bond. i Pliny, lib. iv. cap. 34. and xxxiv, cap. 47. § In some of the valleys of Cornwall, tin is found in rounded nodules, of various sizes, mixed with pebbles and rounded fragments of rocks. To separate the tin from the alluvial matter, currents of water are passed over it. arid hence these deposits have been called stream works, and the tin ore. stream tin. A modification of stream tin is called wood tin. It usually appears in small banded fragments of globular masses. !i The process is described at length in Aikin's Diet Art. Tin. IT The process of making tin-foil consists simply in hammering out a number cf plates of the metal, laid together upon a smooth block or plate of iron. The smallest sheets are the thinnest. ** A preparation under the name of powdered tin is sometimes directed to be pre- pared for pharmaceutical use, by shaking the melted meml in a wooden box robbed with chalk on the inside: tin flings have also a place in some Pharmacopceiee. and have heen used as a vermifuge These preparations are. however, both dangerous, the metal being rendered poisonous in the former case by a slight oxidation,* and often creating very dangerous irritation when giving in filings. The moiree metaUique , or crystallized tin plate as it is called, is prepared as fol- lows. The sheet or plate of tinned iron is heated until a drop of water allowed to fall upon its surface begins taboil immediately: one of the si.les is then washed with a mixture of 4 parts by” measure of water, l of nitric and l of hydrochloric acid. The P.'Til *d tin. 32’JL- * Or£la, Trmu css Poisons, T. i. 2me parue, p. IS. 34 266 Metals— Tin. ChapJV_ 1017 _ p rotoxide 0 f Tin _ g n+0i g ni or g n0i 539 J eq tini _|_ g Protoxide, j eq. oxy, = 66.9 equiv. When protochloride of tin in solution is mixed with an alkaline carbonate, hydrated protoxide of tin falls, which may be obtained as such in a dry form by washing with warm water, and drying at a heat not above 196°, with the least possible exposure to the air. The best mode of obtaining the anhy- drous protoxide is by heating the hydrate to redness in a tube from which air is excluded by a current of carbonic acid gas. The same oxide is formed when tin is kept for some time fused in an open ves- sel. T. 323. Properties, 1018. Protoxide of tin has a sp. gr. of 6.666. At common tem- peratures it is permanent in the air, but if touched by a red hot body, it takes fire and is converted into the binoxide. It is dissolved by the sulphuric and hydrochloric acids, as also by dilute nitric acid ; and the pure fixed alkalies likewise dissolve it. From the alkaline solution, metallic tin is gradually deposited, and binoxide of tin remains in solution. Chafers 1019. Its salts are remarkably prone to absorb oxygen, both from o its sa ts. t jj e a j r an( j f rom com p 0Un( j s which yield oxygen readily. Thus it converts sesquioxide of iron into protoxide, and throws down mer- cury, silver, and platinum in the metallic state from their salts. Cassius° f With a solution of gold it causes a purple precipitate, the purple of Cassius , which appears to be a compound of binoxide of tin and pro- toxide of gold. 1 * By this character protoxide of tin is recognized with certainty. It is thrown down by hydrosulphuric acid as black protosulphuret of tin. Sesquiox* 1020. Sesquioxide of Tin, 2 Sn+ 30 , Sn, or Sn 2 0 3 , 117.8 2 eq. ide - tin -)- 24 3 eq. oxy. == 141.8 equiv., may be made by mixing re- cently precipitated and moist hydrated sesquioxide of iron with a solution of protochloride of tin. Its solution in hydrochloric acid strikes the purple of Cassius with gold. Binoxide. 1021. Binoxide of Tin , Sn-f-20, Sn, or SnO 2 , 58.9 1 eq. tin -f- 16 2 eq. oxy. — 74.9 equiv., is most conveniently prepared by the action of nitric acid on metallic tin. Nitric acid, in its most concen- trated state, does not act easily upon tin ; but when a small quantity of water is added, violent effervescence takes place owing to the evo- lution of nitrous acid and binoxide of nitrogen, and a white powder, the hydrated binoxide is produced. On edulcorating this substance, and heating it to redness, watery vapour is expelled, and the pure binoxide, of a straw-yellow colour, remains. In this process ammo- surface assumes a beautiful crystalline appearance, and by heating the plate at par- ticular parts with the blow-pipe, or exposing different parts to higher and lower tem- peratures, a great variety of figures may be produced, which will he seen on washing the plate with water. The various colours which it is made to assume are commu- nicated by giving it a coating of different coloured varnishes. The tin plates used for this purpose should have a good coating of metallic tin, or the iron below will be exposed. Purple of Cas- * This compound is used to colour glass of a purple colour, and is made by dissolv- ,l0i - ing a lew grains of tin in hydrochloric acid, diluting the solution with a large quan- tity of distilled water, as a gallon to a drachm measure of the solution, and dropping into the diluted liquid 20 or 30 drops of the solution of gold in nitro-hydrochloric acid (637) to each gallon. In the space of three or four days, a purple precipitate is obtained, which is separated by filtration, washed and dried. Gray’s Operative Chem , 720. Sulphurets of Tin , 267 nia is generated, a circumstance which proves water as well as nitric Sect, v. acid to be decomposed. Binoxide of tin may likewise be obtained by precipitation from a solution of bichloride of tin, by potassa, am- monia, or alkaline carbonates. 1022. It is apt to separate from acids spontaneously as a gelati- nous hydrate. It acts the part of a ! feeble acid and forms soluble compounds with the alkalies called stannates. When melted with Stannates. glass it forms white enamel. 1023. Protochloride of Tin , Sn-f-Cl, or SnCl, 58 9 1 eq. tin Protochlo- 35 42 1 eq. chlor. — 9432 equiv., is obtained by transmitting hv- n e ’ drochloric acid gas over tin heated in a glass tube, and hydrogen gas is evolved : or by distilling a mixture of granulated tin, with an equal weight of bichloride of mercury, or of an amalgam of tin with calomel, urging the heat till the mercury is expelled. A gray fusi- ble solid of a resinous lustre is obtained. It is obtained also in crys- tals from a concentrated solution of the chloride. 1024. A solution of protochloride of tin is obtained by heating Solution, granulated tin in strong hydrochloric acid as long as hydrogen gas continues to be evolved. This solution is much employed as a de- oxidizing agent. 1025. Bichloride of Tin. Sn-f-2Cl, or SnCP, 58.9 1 eq. tin -j- Bichloride, 70. S4 2 eq. chlor. == 129.74 equiv. When protochloride of tin is heated in chlorine gas, or on distilling a mixture of 8 parts of granu- lated tin with 24 of bichloride of mercury, a very volatile, colourless liquid passes over, which is bichloride of tin. In an open vessel it emits dense white fumes, caused by the moisture of the air, and hence it was formerly called the fuming liquor of Libavius, who discovered it. At 248° it boils, and the sp. gravity of its vapour was found by Dumas to be 9.1997. With one third of its weight of wa- ter it forms a solid hydrate, and in a larger quantity of water dis- solves. 1026. The solution commonly called per muriate of tin , is much Solution or used in dyeing, and is prepared by dissolving tin in nitro-hydrochlo- permuriate. ric acid. The process requires care ; for if the action be very rapid, as is sure to happen if strong acid be employed and much tin added at once, the peroxide will be spontaneously deposited as a bulky hy- drate, and be subsequently redissolved with great difficulty. But the operation will rarely fail if the acid is made with two measures of hydrochloric acid, one of nitric acid, and one of water, and if the tin is gradually dissolved, one portion disappearing before another is added. The most certain mode of preparation, however, is to pre- pare a solution of the protochloride, and convert it into the bichloride either by chlorine, or by gentle heat and nitric acid. 1027. Protosulphuret of Tin , Sn-j-S, or SnS, 58.9 1 eq. tin Sulphurets, 16.1 1 eq. sulph. — 75 equiv., is prepared by pouring melted tin up- on its own weight of sulphur, and stirring rapidly with a stick during the action; as some tin usually escapes the sulphur from the latter being rapidly expelled, the product should be pulverized, mixed with its weight of sulphur, and projected in successive portions into a hot Hessian crucible, and then heated to redness, it is a brittle com- pound, of a bluish-gray, nearly black colour, and metallic lustre, which fuses at a red heat, and acquires a lamella ted texture in 268 Metals — Cobalt. Chap. IV. Aurum mu- sivum, Properties, Of its salts. Alloys. Cobalt, How ob- tained pure. 8eiqniaulphu- nt. cooling. It is dissolved by hydrochloric acid with evolution of hy- drosulpburic acid.* 1028. Bisulphuret of Tin, Sn-|-2S, or SnS 2 , 58.9 1 eq. tin -f- 32.2 2 eq. sulph. = 91.1 equiv., ( aurum musivum,) is formed by heating sulphur with peroxide of tin, or, by heating in a matrass a powdered amalgam of 12 parts’of tin and 6 of mercury, mixed with 7 parts of flowers of sulphurand6 of hydrochlorate of ammonia.f A gen- tle heat is to be applied till the white fumes cease to appear, when the heat is to be raised to redness, and kept so for some time. On cooling, the aurum musivum (or Mosaic Gold) may be obtained by breaking the matrass. It is of a beautiful gold coibur, and flaky in its structure. 1029. It has no taste, is not soluble in water, acids or alkaline so- lutions. It is used as a pigment for giving a golden colour to small statue or plaster figures. It is likewise said to be mixed with melted glass to imitate lapis lazuli. 1030. The salts of tin are mostly soluble in water ; they are pre- cipitated of an orange colour, byhydriodic acid and by hydrosulphu- ret of ammonia, provided no excess of acid be present. 1031. Tin forms useful alloys with many of the metals. Pewter is one of these ; and the best kind of it is entirely free from lead, being composed chiefly of tin with small proportions of antimony, copper, and bismuth. An amalgam formed by gradually adding three parts of mercury to twelve of tin melted in an iron ladle, and stirring the mixture, is much used in silvering looking glasses. With potassium and sodium, tin forms brittle white alloys. Its alloy with manganese is not known. It does not readily combine with iron, but tin-plate may be considered as an imperfect alloy of those metals. With zinc it forms a hard brittle alloy. I Cobalt .§ Symb. Co Equiv. 29.5 1032. This metal occurs combined with arsenic, sulphur, iron and nickel ; and according to Stromeyer is a constant ingredient in meteoric iron. It is chiefly obtained in Saxony. 1033. it may be obtained from the znffrc of commerce which is an impure ox- ide, and which, heated with a mixture of sand and potash, affords the beautiful blue glass known, in powder, as smalt. Dissolve zaffre in hydrochloric acid and transmit through the solution a current of hydrosulphuric acid gas until the arse- nious acid is completely separated in the form of orpiment. The filtered liquid is then boiled with a little nitric acid, in order to convert the protoxide into sesqui- oxide of iron, and an excess of carbonate of potassa is added. The precipitate, * Sesquisidphuret of Tin, 2Sn-l-3S, or Sn-S 3 , 117.8 2 eq. tin -|- 48.3 3 eq. sulph. = 166.1 equiv., is formed by mixing the protosulphuret in fine powder with a third of its weight of sulphur, and heating the mixture to low redness until sulphur ceases to es- cape. Its colour is of a deep grayish-yellow; it is reconverted by a strong heat into the protosulphuret, and dissolves in hydrochloric acid gas, yielding hydrosulphuric acid gas ana a residue of bisulphuret of tin. t Or heat two parts of binoxide of tin, two of sulphur, and one of sal ammoniac to a low red heat as long as sulphurous acid rises. t On the alloys of tin, a memoir of Dussaussoy may he consulted in the 5th vol. of Ann. de Chim. el Phys . ; and Chaudet’s paper in the same, and in the 7 th volume. § Its name is derived from the term Kobold , an evil spirit , applied to it by the Ger- man miners at a time when they were ignorant of its value, and considered it unfa- vourable to the presence of valuable metals. 269 Chloride of Cobolt . consisting of sesquioxide of iron and carbonate of protoxide of cobalt, after being Sect. V. well washed with water, is digested in a solution of oxalic acid, which dissolves the oxide of iron and leaves the oj^de of cobalt in the form of an insoluble oxa- late.* On heating this oxalate in a’ retort from which atmospheric air is excluded, a large quantity of carbonic acid is evolved, and a black powder, metallic cobalt, is left.t The pure metal is easily procured also by passing a current of dry hydrogen gas over oxide of cobalt heated to redness in a tube of por- celain. In this state it is porous, and if formed at a low tempera- ture it inflames spontaneously. 1034. Cobalt is a brittle metal, of a reddish-gray colour, and weak Properties, metallic lustre. Its density, according to Turner, is 7.834. It fuses at a heat rather lower than iron, and when slowly cooled it crystallizes. It has usually been considered to be attracted by the magnet, but the pure metal is not so.$ 1035. By exposure to the atmosphere cobalt is tarnished, but not oxidized to any extent. In an intense heat it burns with a red flame ; but, if pure, it is not easily oxidized by a moderate temperature. It is oxidized by nitric acid, and decomposes water at a red heat. 1036. Protoxide of Cobalt. Co-j-O, Co, or CoO, 29.5 1 eq. cob. Protoxide, -j- 8 1 eq. oxy. == 37.5 equiv. This oxide is of an ash-gray colour, and is the basis of the salts of cobalt, most of which are of a pink hue. When heated to redness in open vessels it absorbs oxygen, and is converted into the sesquioxide. It may be prepared by de- composing carbonate of the protoxide by heat in a vessel from which atmospheric air is excluded. It is recognised by giving a blue tint to borax when melted with it ; and is employed in the arts in the form of smalt, for communicating a similar colour to glass, earthen- ware, and porcelain. 1037. Protoxide of cobalt is precipitated from its salts by pure Precipita- potassa as a blue hydrate. Pure ammonia likewise causes a blue ted ’ precipitate, which is redissolved by the alkali if in excess. It is thrown down as a pale pink carbonate by carbonate of potassa, soda, or ammonia; but an excess of the last redissolves it with facility. Hydrosulphuric acid produces no change, unless the solution is quite neutral, or the oxide is combined with a weak acid. Alkaline hy- drosulphates precipitate it as a black protosulphuret.§ 1038. Chloride of Cobalt . Co+Cl, or CoCl, 29.5 1 eq. cob. + Chloride. 35.42 1 eq. chlor. = 64.92. equiv. It is obtained in solution on dis- solving metallic cobalt, its protoxide, or either of the other oxides in hydrochloric acid, with evolution of hydrogen gas with the first and of chlorine with the latter. It yields a pink-coloured solution, and by evaporation small crystals of the same colour containing water of crystallization. When deprived of water its colour is blue, a cha- racter on which is founded its use as a sympathetic .ink : when let- ters are written with a dilute solution of the chloride, the colour is so pale that it is invisible in the cold ; but on heating gently, the letters * Laugier. t Thomson in Ann- of Philos., N. S. i. + Faraday. § When a salt of cobalt is treated with pure ammonia in close vessels, part of the co- balt is dissolved, and part subsides in form of a blue powder. On admitting atmos- pheric air, this substance passes to a higher state of oxidation, and is gradually dissolved. If nitrate of cobalt is used, a double salt may be obtained in crystals, which L- Gmelin believes to consist of nitrate and ccbaltate of ammonia. The exist- ence of this acid, hb'WteV'er, has not ytet been established. 270 Metals — Nickel. Chap. IV. Alloys. Ores, Reduced. Properties. Sympathetic ink. Wollaston'* proce** for de- tecting nickel. appear of a blue colour, and disappear as soon as the chloride has recovered its moisture from the atmosphere. When iron or nickel is present, the dry chloride of cobalt is green instead of blue.* * * § 1039. The alloys of cobalt are unimportant. The chief use of this metal is in the state of oxide as a colouring material for porce- lain, earthenware, and glass ; it is principally imported from Ger- many in the state of zaffre and smalt , or azure. Smalt and azure are made by fusing zaffre with glass or by calcining a mixture of equal parts of roasted cobalt ore, common potash, and ground flints. A blue glass is formed which, while hot, is dropped into water, and afterwards reduced to a very fine powder. Nickel. Symb. Ni Equiv. 29.5 1040. Nickel is found native, and is a constituent of meteoric iron.t It occurs likewise in the copper-coloured mineral of Westphalia, termed copper-nickel , a native arseniuret of nickel, which in addition to its chief constituents, contains sulphur, iron, cobalt and copper. The combinations of nickel may be prepared from its ore, or from the artificial arseniuret called speiss.X The metal may be procured by heating the oxalate in close ves- sels, or by the combined action of heat and charcoal, or hydrogen, on protoxide of nickel. $ 1041. Crystals of nitrate of nickel, when placed in a cavity scoop- ed out of a piece of charcoal, and exposed to the oxy-hydrogen blow-pipe, afford a bead of metallic nickel. This, however, is a process obviously adapted to yield only very minute quantities of nickel. 1042. Nickel is of a white colour between that of tin and silver, with a strong lustre, and is ductile and malleable. It is attracted by * This solution has been termed Hellot's sympathetic ink. It may be prepared as follows : One part of cohalt, or, still better, of zaffre, may be digested in a sand heat, for some hours, with four parts of nitric acid. To the solution, add one part of sea- salt; and dilute with four parts of water. Characters written with this solution are illegible when cold ; but when a gentle heat is applied, they assume a beautiful blue or green colour. This experiment is reudered more amusing by drawing the trunk and branches of a tree in the ordinary manner; and tracing the leaves with the solu- tion. The tree appears leafless, till the paper is heated, when it suddenly becomes covered with heautilul foliage. The addition of a little nitrate o( copper to the solution forms a sympathetic ink, which by heat gives a rich greenish yellow co- lour. When a small quantity of hydrochlorate of soda, of magnesia, or of lime, is added to the ink, its traces disappear very speedily on removal from the fire. U. 346. t For an account of meteoric stones, masses of iron, &c. which have fallen from the heavens, from the earliest period down to 1 S 1 9, see Edln. Philos Jour. vol. i. p. 221. See also Cleaveland’s Mineralogy , p. 773, and Braude's Chem. ii. 149. t For details see Thomson’s Chemistry of Inorganic Bodies , ii 526, &c., and Tur- ner, 329. § For other processes see Thomson, ii., Henry, ii. 169, Quart. Jour. xliv. 396, and N. S. iii. 209. To detect the presence of nickel in iron, Wollaston recommends that a small por- tion, which need not exceed .01 of a grain, should be filed from the sample, and dis- solved in a drop of nitric acid ; evaporate this to dryness, and add a drop or two of liquid ammonia, whicn, when gently warmed, will dissolve any oxide of nickel that may he present. The transparent part of the fluid is then to be conducted by the end of a glass rod to a small distance from the precipitated oxide of iron, and mixed with a drop of ferrocyanate of poiassa, which, if nickel be present, will cause an immedi- ate milkiness, not discernible in a solution of common iron, formed and treated in the same way. B. ii. 148 Arsenic. 271 the magnet, and may like iron be rendered magnetic, but loses this Sect, vi. power at 630°. # Its sp. gr. is about 8.279. It is very infusible, Fusibility, suffers no change by exposure, but at a red heat absorbs oxygen, and decomposes water. It is oxidized by nitric acid. Its eq. is esti- mated at 29.5. 1043. Protoxide of Nickel. Ni-f-O, Ni, or NiO, 29.5 1 eq. nick. Protoxide. + 8 1 eq. oxy. = 37.5 equiv. This oxide may be formed by heating the carbonate, oxalate, or nitrate to redness in an open ves- sel, and is then of an ash-gray colour; but after exposure to a white heat, its colour is a dull olive-green. It is not reducible by heat unaided by combustibles. It is not attracted by the magnet. It is a strong alkaline base, and nearly all its salts have a green tint. It is precipitated as a hydrate of a pale-green colour by the pure alkalies, but is redissolved by ammonia in excess ; as a pale-green carbonate by alkaline carbonates, but is dissolved by an excess of carbonate of ammonia; and as a black sulphuret by alkaline hydrosulphates. Hydrosulphuric acid occasions no precipitate, unless the solution is quite neutral, or the oxide combined with a weak acid.t Section VI. Metals which do not Decompose Water at any Tem - perature , and the Oxides of which are not reduced to the Metallic State by the sole action of Heat. 1044. Arsenic. As, 37.7 eq. Metallic arsenic occurs native, but Arsenic more commonly in combination with other metals. The substance known in the shops by the name arsenic, is an oxide, from which the metal may be obtained by mixing it w T ith half its weight of black flux, I and introducing the mixture into a Florence flask, placed in a sand bath gradually raised to a red heat; a brilliant metallic sublimate of pure arsenic collects in the upper part of the flask. Or mix it with about twice its weight of charcoal, both perfectly dry, and ex- Obtained, pose the mixture to heat in a crucible, luting another over it in an inverted posi- tion to collect the product. § * Faraday. t Sesquioxide of Nickel , 2Ni+30, Ni, or Ni 2 0 3 , 59 2 eq. nick, -f 24 3 eq. oxy. = 83 equiv. , has a black colour, and is formed by transmitting chlorine gas through wa- Sest i ul0xlde ’ ter in which the hydrate of the protoxide is suspended, does not unite with acids, is decomposed by a red heat, and with hot hydrochloric acid lorms the chloride with dis- engagement of chlorine gas. Chloride of Nickel, Ni+Gl, or NiCl, 29.5 1 eq. nick + 35.42 I eq. chlor. s= 64.92 equiv., is formed by acting with hydrochloric acid on metallic nickel, its protoxide, or Chlori ®‘ sesquioxide ; hydrogen gas being evolved with ihe former, and chlorine with the latter. It forms an emerald-green solution, and by evaporation yields crystals of the same tint, which lose water or deliquesce, according as the air is dry or moist. Protosulpkuret of Nickel, Ni+S, or NiS, 29.5 l eq nick. -f 16.1 1 eq. sulph. = 45.6 equiv., is formed by processes similar to those for preparing protosulphuret of cobalt. The precipitated sulphuret is dark brown or nearly black. t This is an extremely useful compound for effecting the reduction of many of the metallic oxides. It consists of charcoal and subcarbonate of potassa, and is best pre- Black flui> pared by deflagrating in a crucible a mixture of one part of nitre and two of powdered tartar. The mixture remains in fusion at a red heat, and thus suffers the small glo- bules of reduced metal to coalesce into a button. § A small opening should be left for the escape of gaseous matters. The lower cru- cible should be placed in a sand bath furnace, and the upper one be kept as cool as possible and completely out of the sand 3 the process may be easily conducted with a small chauffer. Care must be taken not to inhale the vapour. 272 Metals — -Arsenic . Chtlp IV. Characters. Fly-pow- der. Arsenious acid, How ob- tained, Properties, Dimor- phous. Solubility. Poisonous effects. 1045. Arsenic is of a steel-blue colour, quite brittle, and of a spe- cifie gravity = 5.884. It readily fuses, and in close vessels may be distilled at a temperature of 360°, which is lower than its fusing point. Its vapour has a very strong smell, resembling that of garlic. Heated in the air it easily takes fire, burns with a blue flame, and produces copious white fumes of oxide. In general it speedily tarnishes by exposure to air and moisture, acquiring upon its surface a dark film, which is extremely superficial ; but Berzelius remarks that he has kept some specimens ir^open ves- sels for years without loss of lustre, while others are oxidized through their whole substance, and fall into powder. The product of this spontaneous oxidation, which is known under the name of Jly-powder, is supposed by Berzelius to be an oxide; but it is more generally re- garded as a mixture of white oxide and metallic arsenic. 1046. Arsenious Acid , 2As-|-30, As, or As 2 0 3 , 75.4 2 eq arsen. -f- 24 3 eq. oxy. = 99.4 equiv., or, as it is commonly called, white arsenic , or white oxide of arsenic , is the best known, and most com- monly occurring compound of this metal; and as cases of poison- ing by it are frequent, every person should be well acquainted with its characteristic properties. 1047. Arsenious acid may easily be procured by the combustion of the- metal ; but as it is formed during certain tnetallurgic proces- ses, that mode is rarely, resorted to. It is abundantly prepared in Bohemia, from arsenical cobalt ores, which are roasted in reverbera- tory furnaces, and the vapours condensed in a long chimney, the contents of which, submitted to a second sublimation, afford the white arsenic of commerce. 1048. Arsenious acid is white, semi-transparent, brittle, and of a vitreous fracture. Its sp. gr. is 3.7. Its taste has been usually de- scribed as acrid, but it appears that this is incorrect. It excites a very faint impression of sweetness and perhaps of acidity.* 1049. Arsenious acid is dimorphous , that is, susceptible of assum- ing two crystalline forms belonging to different systems of crystalli- zation. By slow sublimation in a glass tube, it is always obtained in distinct octohedral crystals of adamantine lustre and perfectly transparent. Its unusual form is that of six-sided scales derived from a rhombic prism. 1050. According to Klaproth and Buchholz, 1000 parts of water at 60° dissolve 2.5 of white arsenic,! 1000 parts of water at 212°, dissolve rather more than 77 parts, and about 30 parts are retained in permanent solution. Guibourt has lately observed that the transparent and opaque va- rieties of arsenic differ in solubility. He found that 1000 parts of temperate water dissolve, during 36 hours, 9.6 of the transparent, and 12 5 of the opaque variety : that the same quantity of boiling water dissolves 97 parts of the transparent variety, retainin 18 * See Cristison’s experiments. Edin. Philos Jour. xiv. 330. t It would take a loner time to prepare a saturated aquwus solution of white arsenic, by contact of the powder with water, or even by agitation ; but by hoi ling the water with the powder for half an hour, leaving it to cool, and afterwards filtering.it, a sat- urated solution will be at once obtained. Faraday, Chem. Manip . 174. Tests of Arsenic. 278 when cold, but takes up 115 of the opaque variety, and retains 29 Sect, vi. on cooling. By the presence of organic substances, such as milk or tea, its solubility is materially impaired.* 1051. It is virulently poisonous, producing inflammation and gan- p 0 i sonous grene of the stomach and intestines; it also proves fatal when ap- effects, plied to a wound ; and as the local injury is in neither case sufficient to cause death, it is probable that an induced affection of the nervous system and of the heart is the cause of the mischief. To get rid of the poison by producing copious vomiting and purging, and to pursue the usual means of subduing and preventing inflammation, are the principal points of treatment to be adopted in cases where this poison has been taken.! 1052. As arsenic either accidentally or intentionally taken, is a Methods of very frequent cause of death, and often the subject of judicial in- arsenic^ quiry, it becomes of importance to point out the most effectual modes ’ of discovering its presence. Where arsenic proves fatal, it is very seldom found in the contents of the stomach after death, but is gen- erally previously voided by vomiting or by stool ; and we often can detect it in the matter thrown ofF the stomach, in the form of a white powder, subsiding in water. The inflammation of stomach which results is generally a secondary effect, and takes place equal- ly, whether the poison be swallowed or applied to a wound. 1053. Several tests have been proposed for detecting minute Tests of. quantities of arsenic in the fluids likely to be met with in the stom- ach, the most valuable are the ammoniaco-nitrate of silver, ammo- niaco-sulphate of copper, hydrosulphuric acid and hydrogen gas. 1054. The first object is to obtain a concentrated solution of the Methods of substances ejected, or, in case of death, of the liquids contained in P roceed i n g* the stomach, or of any that may adhere to its interior surface. This is to be effected by means of washing in pure water, filtration, and evaporation. A solution having been obtained, the tests are to be applied, it having been previously ascertained that they are perfectly pure, as also the vessels in which the experiments are to be made. 1. The ammoniacal-nitrate of silver is made by dropping into a Ammonia- rather strong solution of lunar caustic, ammonia, till the oxide of of silver 16 silver at first thrown down is nearly all dissolved. This liquid contains the precise quantity of ammonia required to neutralize the nitric acid of the nitrate of silver. On dropping it into the suspected liquid, if arsenic is presented yellow insoluble arsenite of silver will be formed. 2. Ammoniacal-sulphate of copper, is made by adding ammonia Ammonia- to a solution of sulphate of protoxide of copper, until the precipitate is nearly all dissolved. This test affords a green precipitate with ar- senious acid, which has long been known as Scheele's green. 3. The hydrosulphuric acid gas, is to be obtained from the usual ^^icacid materials (754) and conducted by means of a suitable glass tube into p uncaci the suspected liquid ; if arsenious acid is present, the liquid be- comes yellow and turbid from the formation of orpiment or sesqui- sulphuret of arsenic.! On drying the sulphuret, mixing it with black flux, and heating * Christison on Poisons. + See Christison’s Experiments, Edin. Philos. Jour. xiv. 380. I The apparatus (Fig. 166), page 200, will be found convenient. 35 274 Metals — Arsenic. Chap, iv. the mixture contained in a glass tube to redness by means of a spirit- Reduction. lamp, decomposition ensues, and a metallic crust of an iron-gray colour externally, and crystalline on its inner surface, is deposited on the cool part of the tube. This character alone is quite satisfac- tory ; but it is easy to procure additional evidence, by reconverting the metal into arsenious acid, so as to obtain it in the form of re- splendent octohedral crystals. This is done by holding that part of the tube to which the arsenic adheres about three-fourths of an inch above a very small spirit-lamp flame, so that the metal may be slowly sublimed. As it rises in vapour it combines with oxygen, and is deposited in crystals within the tube. The character of these crystals, with respect to volatility, lustre, transparency, and form, is so exceedingly well marked, that a practised eye may safely identify them, though their weight should not exceed the 100th part of a grain. This experiment does not succeed unless the tube be quite clean and dry.* 4. For the application of hydrogen we are indebted to Marsh of Woolwich. t Its utility depends on the fact that, whenever nascent hydrogen is brought into contact with any compound of oxygen and arsenic, water and arseniuretted hydrogen are formed. If the gas be inflamed as it escapes into the air from a fine tube, it burns with the production of watery vapour, and the deposition of me- tallic arsenic. By holding a piece of clean glass over the flame, its surface is instantly covered with a thin coating of metallic arse- nic ; and if the flame be made to burn in the centre of a glass tube open at both extremities, so as to admit a larger supply of atmos- pheric oxygen, it is covered in half a minute with arsenious acid. Marsh’s E rocess by ydrogen gas. Liebig’s improve- ment. The hydrogen is obtained by introducing a portion of the suspected liquid into a tube about thirteen inches in length and three fourths of an inch internal diameter, or the glass bucket c, in which is a small piece of pure zinc b, sulphuric acid is added and the gas passes out through the jet a, while the stop-cock is open. When it is closed the gas accumulates in the upper part of the short leg; on opening the stop- cock, the liquor descends from the longer leg and drives out the gas. When large quantities of the suspected liquid can be obtained, the apparatus (Fig. 180) is employed ; see 379. Liebig recommends that a fragment of porce- as better Fig. 179. 181. be held in the flame instead of the glass, lain a very thin film of metallic arsenic seen on the white opaque ground of the former. To avoid the deposition of other metals, that may be carried up by the hydrogen, he recom- mends that the gas be transmitted through a fine tube of difficultly fusible glass, instead of <®Bp * A tube of the annexed form (Fig. 181,) has been recommended by Berzelius, it should be perfectly dry, and the mixture introduced by means of a small funnel descending within the ball, through which the mixture may be passed without soiling the tube, t Edin. Philos. Jour. Oct. 1836, and Trans ■ Soc. Arts, Li. 0 275 Eesquichloride of Arsenic . burning it at the jet ; on bringing, a part of the glass to a red heat by a spirit-lamp, the arseniuretted hydrogen is decomposed as it passes, and the metallic arsenic is deposited just beyond the heated part of the glass, while other metals are deposited in the hot parts themselves.^ 1055. The extreme delicacy of this method of testing for arsenic has been fully confirmed, but it also has been ascertained that it is not the only one to be relied upon. Other metals may be present, as antimony, which has been found to form a gaseous compound, and to give results that resemble those with arsenic. By decom- posing the gases while passing through a fine tube, as proposed by Liebig, and obtaining the metals, they can readily be distinguished.! 1056. Arsenic Acid. 2AS+50, As, or As 2 0 3 , 75.4 2 eq. arsen. 4" 40 5 eq. oxy. = 115.4 equiv. This compound is made by dis- solving arsenious acid in concentrated nitric, mixed with a little hy- drochloric acid, distilling in glass till it acquires the consistence of syrup, and then exposing it in a platinum crucible for some time to a heat somewhat short of low redness to expel the nitric acid. The acid thus prepared has a sour metallic taste, reddens vegetable blue colours, and with alkalies forms neutral salts, which are termed arseniates. It is much, more soluble in water than arsenious acid. It is an active poison. 1057. Arsenic acid is decomposed by hydrosulphuric acid gas, and yields a sulphuret of arsenic very like orpiment in colour, but containing a greater proportional quantity of sulphur. The soluble arseniates, when mixed with the nitrates of lead and silver, form insoluble arseniates, the former of which has a white, and the latter a brick-red colour.! 1058. Sesquickloride of Arsenic , 2As-{-3Cl, or As 2 Cl 3 , 75.4 2 eq. arsen. -j- 106.26 3 eq. chlor. — 181.66 equiv. When arsenic in * Liebig Ann. xxiii. 217 . t For minute details, the manipulation, precautions, sources of error, &c., the stu- dent must be referred to Turner’s Elements p. 333 ; Christiscn on Poisons ; Marsh on the separation of arsenic ; Trans. Soc. of Arts. Li. and Edin. Philos. Jour . Oct. 1836; Reid’s Prac. Chem. 341 5 Henry’s Elem. of Chem,. vol. ii. p.588, 10th edit.; to Murray’s System , vol. iii. p. 441, 4th edit.; to Bostock’s Paper in the Edin. Med. and Surg. Jour. vol. v. p. 166 ; Hume’s Essay in the Phil. Mag. vol. xxxiii.; and Bond. Med. and Pkys. Jour. vol. xxiii.; Marcet’s Paper, in the Medico- Chirurg. Trans, vol. ii. ; Sylvester’s Observations in Nicholson's Jour. vol. xxxiii. ; Beck’s Med. Juris, vol. ii. ; Traill’s Paper , in Boston Jour, of Philos. 1, 543 ; Edin. Medico. Chirurg. Trans, vol. ii. From late investigations arsenic possesses the property of preserving from decay the bodies of those poisoned with it. The antiseptic effects sometimes extend only to the stomach and intestines, that is, to the parts directly in contact with it ; but in some instances the whole body is preserved. The stomach and in- testines of persons killed with arsenic have been found entire and firm at the dis- tance of five, six, and fourteen months, or even of two years and a half after death ; and in some of these instances the poison itself was detected. Edin. Philos. Jour. vii. 381. A voltaic battery made to act on a little arsenious solution placed on a bit of glass, develops metallic arsenic at the negative pole, and if this wire be copper, it will be whitened like tombac. t Protochloride of Arsenic. As+Cl, or AsCl, 37.7 1 eq. arsen. + 35.42 1 eq. chlor. 73.12 equiv. It is prepared by introducing into a tubulated retort a mixture of arsenious acid with ten times its weight of concentrated sulphuric acid ; and after raising its temperature to near 212°, fragments of sea-salt are thrown in.* * See Quart. Jour. a mineral found at Bastnas in Sweden, to which they have given the ores ' name of Cerite.% It is also contained in Allanite , a mineral from Greenland, first distinguished as a peculiar species by Allan, of Edinburgh. It contains, according to Thomson’s analysis, about 40 per cent, of oxide of cerium. This oxide is extremely difficult of reduction. Children succeeded in fusing it by the aid of his powerful Voltaic apparatus, and when intensely heated it burned with a vivid flame, and was partly vol- atilized. 1134. The attempts of Vauquelin to reduce the oxide of cerium Vauque- produced only a small metallic globule, not larger than a pin’s r/ment? 6 " head. This globule was not acted upon by any of the simple acids ; but it was dissolved, though slowly, by nitro-hydrochloric acid. 1135. Protoxide of Cerium, Ce-[-0, Ce, or CeO, 46 1 eq. cerium, p ro toxide. + 8 1 eq. oxy. = 54 equm This oxide is a white powder, inso- luble in water, forming salts with acids, all of which, if soluble, * Named after the new planet, discovered in that year and called Uranus. + Buchholz, in Mem. Acad. Sci. of Stockholm, 1S22. t The name Cerium was given to this metal from the planet Ceres , discovered about the same period. See Nicholson’s Jour. xii. 105. 37 290 Metals — Bismuth. Chap. IV. - Sesquiox- ide. Native. Properties. Process for obtaining crystals. Oxide. Protoxide. Magistery. have an acid reaction. Heated in open vessels, it absorbs oxygen, and is converted into the sesquioxide. It is precipitated as a white hydrate by pure alkalies ; as a white carbonate by alkaline carbo- nates, but is redissolved by the precipitant in excess ; and as a white oxalate by oxalate of ammonia. 1136. Sesquioxide of Cerium , 2Ce-|-30, Ce, or Ce 2 0 3 , 92 2 eq. cerium, — (— 24 3 eq. oxy. = 116 equiv., has a fawn red colour ; it is dissolved by several of the acids, but is a weaker base than the pro- toxide. Digested in hydrochloric acid, chlorine is disengaged and a protochloride results. It is most readily extracted from cerite by a process of Laugier.* Bismuth. Symb. Bi Eq. 71 1137. This metal is found native; combined with oxygen; and with arsenic and sulphur. Native Bismuth occurs crystallized in octohedra and cubes, and in addition to arsenic generally contains cobalt. 1138. Bismuth has a reddish white colour, and is composed of broad brilliant plates adhering to each other. Its sp. gr. is 9.822, but is increased by hammering. It breaks, however, under the hammer, and hence cannot be considered as malleable ; nor can it be drawn out into wire. The bismuth of commerce is not quite pure. 1139. Bismuth is one of the most fusible metals, melting at 476° F., and it forms more readily than most other metals, distinct crys- tals by slow cooling. It may be obtained in regular crystals, by fusing a quantity of it in a crucible, and allowing it to cool till a crust is formed on the surface ; the extremity of the crucible may then be broken off, and the fluid metal beneath be allowed to escape. The under surface of the crust will be found beautifully crystallized. 1140. When bismuth is exposed to heat and air it oxidizes. If the heat be increased by directing a current of oxygen upon the metal, it burns with much brilliancy, and produces abundant yellow fumes of protoxide. It is readily oxidized and dissolved by nitric acid. 1141. Protoxide of Bismuth , Bi— [-0, Bi, or BiO, 71 1 eq. bism. — |— 8 1 eq. oxy. = 79 equiv. This compound is readily prepared by heating to redness the nitrate or subnitrate of protoxide of bis- muth. Its colour is yellow ; at a full red heat it is fused into a brown liquid, which on cooling becomes a yellow transparent glass of sp. gr. 8.211. At intense temperatures it is sublimed. It unites with acids, and most of its salts are white. 1142. When nitrate of protoxide of bismuth, either in solution or in crystals, is put into water, a copious precipitate, the subnitrate, of a beautifully white colour, subsides, which was formerly called * For which see Turner’s Chem. 362. Titanium. 291 the magistery of bismuth and r pearl white. From its whiteness it is Sect, v-i. sometimes employed as a paint for improving the complexion.* If the nitrate with which it is made contains no excess of acid, white ox- and a large quantity of water is employed, nearly the whole of the i( *e. bismuth is separated as a subnitrate, White oxide of the Pharmaco- poeia. By this character bismuth may be both distinguished and separated from other metals, 1143. Sesquioxide of Bismuth , 2Bi-|-30j Bi, or Bi 2 0 3 , 142 2Sesquiox= eq. bism. 24 3 eq. oxy. = 166 equiv. This oxide is generated when hydrate of potassa is fused at a moderate heat with protoxide of bismuth ; but the best mode of preparation is first to prepare the protoxide by igniting the subnitrate, and then gently heating it for some time in a solution of chloride of potassa or soda. After wash- ing with water, any unchanged protoxide is dissolved by a solution made with 1 part of nitric acid (quite free from nitrous acid) and 9 of water. 1144. As thus prepared, sesquioxide of bismuth is a heavy powder Properties, of a brown colour, with little disposition to unite either with acids or alkalies. Heated with sulphuric or phosphoric acid, it gives off oxygen gas, and with hydrochloric acid, chlorine is evolved, and the protochloride produced.! 1145. Chloride of Bismuth , Bi— j— Cl , or BiCl, 71 1 eq. bism. -j- Chloride. 35.42 1 eq. chlor. — 106,42 equiv. When bismuth in fine powder is introduced into chlorine gas, it takes fire, burns with a pale blue light, and is converted into a chloride, formerly termed butter of bis- muth. It may be prepared conveniently by heating two parts of corrosive sublimate with one of bismuth, and afterwards expelling the excess of the former, together with the metallic mercury by heat. 1146. Chloride of bismuth is of a grayish-white colour, opaque, properties, and of a granular texture. It fuses at a temperature a little above that at which the metal itself is liquefied, and bears a red heat in close vessels without subliming. 1147. Bismuth also combines with bromine, and with sulphur, the sulphuret is found native. Titanium.% Symb. Ti Eq. 24.3 1148. Titanium, in the metallic state, was discovered by Wollas- £)j scover y # ton in 1822, in the slag at the bottom of an iron smelting-furnace in South Wales. § It has been since found in several other places in Europe. It has the form of small smooth cubes, having a red col- cur exceedingly similar to that of copper. The cubes are hard enough to scratch rock crystal, and cannot be fused by the highest temperature which can be raised by the blow-pipe. The sp. gr. is * If a small portion of hydrochloric acid be mixed with the nitric, and the preci- pitate be washed with but a small quantity of cold water, it will appear in minute scales, constituting th q pearl-powder of perfumers ; but it is an inconvenient pigment, owing to the facility with which it is blackened by hydrosulphuric acid, t An. de Ch. et de Pfi. li. 267. t Named by Klaproth after the Titans of ancient fable. § Philos. Trans. 1823. 292 Metals — Titanium. [Chap. IV. Prepared. Oxide. Prepared. Titanic acid. Process. Properties. Solubility, &c. 5.3.^ It does not appear, however, to be absolutely free from iron. Wollaston found that when suspended by a fine thread a magnu drew it about 20 degrees from the perpendicular. He succeeded in detecting the presence of iron in it, and calculated the amount of that metal at part of the weight of the titanium. f 1 149. Metallic Titanium may be obtained by putting fragments of recently made chloride of titanium and ammonia into a glass tube half an inch wide and two or three feet long, transmitting through it a current of perfectly dry ammonia, and, when atmospheric air is entirely displaced, applying heat until the glass softens. Com- plete decomposition ensues, nitrogen gas is disengaged, hydrochlo- rate of ammonia sublimes, and metallic titanium is left in the state of a deep blue-coloured powder. If exposed to the air while warm, is apt to take fire. 11*50. Oxide of Titanium , (probably) Ti— |— 0, or TiO, 24.3 1 eq. titan, -f 8 1 eq. oxy. = 32.3 equiv., is prepared by exposing titanic acid to a strong heat in a black lead crucible ; the exterior of the mass obtained consists of metallic titanium, the interior is supposed to be the oxide. It may be formed in the moist way by acting upon a solution of titanic acid in hydrochloric acid by zinc or iron. The titanic acid is thrown down as a purple powder, but cannot be col- lected. 1 151. Titanic Acid , or Peroxide of Titanium , Ti-|-20, Ti, or TiO 2 , 24.3 1 eq. titan. -f- 16 2 eq. oxy. == 40.3 equiv., occurs nearly pure in the minerals anatase and rutile; it exists also in several other minerals. It may be obtained from rutile, or titaniferous iron exposed in a porcelain tube to a very strong red heat and a current of hydrosulphuric acid gas, which gives rise to water and sulphuret of iron. When the water ceases to appear, the mass is removed and digested in hydrochloric acid to remove the iron, and the titanic acid is separated from adhering sulphur by heat.* 1152. Titanic acid is quite white, exceedingly infusible and diffi- cult of reduction ; after being once ignited it ceases to be soluble in acids, except in the hydrofluoric. In its chemical relations it is ana- logous to silicic acid, being a feeble acid, but combining with metal- lic oxides. In the state of hydrate, it has a singular tendency to pass through the pores of a filter when washed with pure water ; but the presence of a little acid, alkali, or a salt, prevents this inconve- nience. 1153. If previously ignited with carbonate of potassa, titanic acid is soluble in dilute hydrochloric acid ; but it is retained in solution by so feeble an attraction, that it is precipitated merely by boiling. It is likewise thrown down by the pure and carbonated alkalies, both fixed and volatile. A solution of gall-nuts causes an orange-red co- lour, which is very characteristic of titanic acid. When a rod of zinc is suspended in the solution, a purple-coloured powder, probably the oxide, is precipitated, which is gradually converted into titanic acid. * From the extreme infusibility of the cubes of metallic titanium, Wollaston infers that they have not been formed by crystallization in cooling from a state of fusion ; but from the reduction of the oxide dissolved in the slag around them, t Phil. Trans, p. 200. Thomson’s First Prindp. 2. 80. tRose, An. de Ch. et de Ph. xxiii. and xxxviii. ] 31 . Tellurium * 293 1154. Bichloride of Titanium. Ti-f-2Cl, or TiCl 2 , 24.3 1 eq. g eC t. vi. titan. + 70.S4 2 eq. chlor. = 95.14 equiv. This substance was Bichloride, discovered in the year 1824 by transmitting dry chlorine gas over metallic titanium at a red heat. 1155. At common temperatures it is a transparent colourless fluid Properties, of considerable specific gravity, boils violently at a temperature a little above 212°, and condenses again without change. Dumas has shown that the density of its vapour may be estimated at 6.615. In open vessels it is attacked by the moisture of the atmosphere, and emits dense white fumes of a pungent odour similar to that of chlo- rine, but not so offensive. On adding a few drops of water to a few drops of the liquid, combination ensues with almost explosive vio- lence, from the evolution of intense heat; and if the water is not in excess a solid hydrate is obtained. On exposure, and on adding water, the greater part is dissolved. Tellurium. Symb. Te Equiv. 64.2 1156. Tellurium is a rare metal, found in the gold mines of Tran- Discovery. sylvania,and in Connecticut, U. S in small quantity. Its existence was inferred by Muller in the year 1782, and fully established in 1798 by Klaproth, who gave it the name of tellurium , from tellies, the earth , suggested by the source from which he drew the name of uranium.! It occurs in the metallic state, chiefly in combination with gold and silver. 1157. Tellurium is of a bright gray colour, brittle, easily fusible, Properties and very volatile. Its specific gravity is 6.17. 1158. It is oxidized when heated in contact with the air ; and Oxide, burns with a sky-blue flame, edged with green. Upon charcoal, before the blow-pipe, it inflames with a violence resembling detona- tion ; exhibits a vivid flame ; and entirely flies off in a gray smoke, having a peculiarly nauseous smell.! This smoke, when condensed, and examined in quantity, is found to be white with a tint of yellow. It is fusible by a strong heat, and volatile at still higher temperature. 1159. Tellurous Acid. Te-f-20, Te, or TeO 2 , 64.2 1 eq. tellur. -|- 16 2 eq. oxy. '= 80.2 equiv. This compound, also called oxide q/Tellurous tellurium, is generated by the action of nitric acid on tellurium, by acid - which acid it is dissolved ; but the solution possesses such little per- manence that mere affusion of water precipitates part of it, and the rest is obtained by evaporating to dryness. In this state, it is a white granular anhydrous powder, which slowly reddens moist lit- mus paper. 1160. Its aqueous solution reddens litmus paper ; it becomes tur- bid at 68°, and the acid which falls is no longer soluble in acids. Properties. In these properties tellurous acid closely resembles the titanic and several other feeble acids, which have a soluble hydrated state easily convertible into an insoluble anhydrous one. Its salts are precipitated black by hydrosulphuric acid, bisulphuret of tellurium being formed. § * Amer. Jour. i. 405. + Contributions, iii. t Ascribed by Berzelius to the presence of selenium. § Hydrotelluric Acid. Te+H, or TeH, 64.2 1 eq. tellur. + l l eq. hyd. — 65.2 294 Chap IV. Ores of copper ; Native copper. Meta) ob- tained pure. Properties. Action of air. Combus- tion of cop- per. Exp. Effect of heat. Equivalent. Metals — Copper . Copper. Symb. Cu Equiv. 31.6 1161. This metal was known in the early ages of the world, and was the principal ingredient in domestic utensils, and in the instru- ments of war, previous to the discovery of malleable iron.* * It is found native, and in various states of combination. Native copper is by no means uncommon, being found more or less in most copper mines. It occurs in a variety of forms; massive, dendritic, granu- lar. and crystallized in cubes, octohedra, &c. It is found in Corn- wall, Siberia, and other parts of Europe. Large masses have been found in various parts of America ; one of which, about 30 miles from Lake Superior, described by Schoolcraft, weighs hy estimation 2000 lbs.t The copper of commerce is extracted chiefly from the native sulphuret ; especially from copper pyrites, a double sulphuret of iron and copper. 1162. The metal may be obtained by dissolving the copper of commerce in hydrochloric acid ; the solution is diluted and a plate of iron immersed, upon which the copper is precipitated. It may be fused into a button, after having been previously washed in dilute sulphuric acid to separate a little iron that adheres to it. 1163. Copper has a fine red colour, and much brilliancy ; it is very malleable and ductile, and has a peculiar smell when warmed or rubbed. It melts at a cherry-red or dull white heat, 1996° F. Its sp. gr. varies, being increased by hammering ; when fused, its density is 8.S95. Under a flame urged by oxygen gas, it takes fire, and burus with a beautiful green light. 1164. Copper is oxidized by air. This may be shown by heating one end of a polished bar of copper, which will exhibit various shades of colour, according to the intensity of the heat. It burns with great splendour before the compound blow-pipe, upon charcoal. The white-hot globule being thrown from the charcoal into a tall jar or wide tube filled with water, it will pass in full ignition, through a column of the fluid two feet high, and will remain for some time ignited on the bottom, which should be protected by a layer of sand-I A plate of copper, exposed for some time to heat, becomes covered with protoxide, which breaks off in scales when the copper is ham- mered. 1165. From the experiments of Berzelius, eight parts of oxygen unite with 31.6 parts of copper to constitute the black oxide, and therefore if this oxide be formed of an atom of oxygen united with an atom of copper the eq. of this metal will be 31.6. This is adopted equiv. By acting on an alloy of tellurium with zinc or tin, by hydrochloric acid, Davy discovered this gas in 1809. It has the properties of a feeble acid. Telluric Acid , Te+30. Te, or Te03, 64-2 1 eq. tellur, -j- 24 3 eq. oxy. =88.2 equiv. For other compounds of tellurium see Turner, 368. See also Berzelius on Tellurium , in Ann. des Mines, v. 381, and Arner. Jour, xxviii. 137. * The word copper is derived from the island of Cyprus, where it was first wrought by the Greeks. t Stromeyer has lately discovered it in several specimens of meteoric iron, but in a quantity not exceeding of the mass. See other localities in Cleaveland’s Mi- neralogy, p. 554, and J. D. Dana’s System. X Silliman. 295 Protoxide of Copper. by many chemists, others regard it as a binoxide, and the red as the Sect, vi. protoxide, and take twice 31.6, or 63.2, as the eq. of copper. 1166. Red , or Dioxide of Copper , 2Cu-|-0, or Cu 2 0, 63.2 2 eq. Red oxide. :opper + 8 1 eq. oxy. = 71.2 equiv., occurs native in the form of Dctohedral crystals, and is found of peculiar beauty in the mines of Cornwall, it may be prepared artificially by heating, in a covered crucible, a mixture of 31.6 parts of copper filings with 39.6 of the black oxide ; or, still better, by arranging thin copper plates one above the other, with interposed strata of the black oxide, and ex- posing them to a red heat carefully protected from the air. Another Process, method is by boiling a solution of acetate of protoxide of copper with sugar, when the dioxide subsides as a red powder ; and another is to fuse at a low red heat the dichloride of copper with about an equal weight of carbonate or bicarbonate of soda, subsequently dis- solving the sea-salt by water, and drying the red powder.* In this case, by an interchange of elements, 1 eq. dichloride of copper 2Cu-f-Cl 2 1 eq. red oxide . . 2Cu-f-0 Theory, and 1 eq. soda . . Na-f-O and 1 eq. chloride of sodium Na-j-Ci 1167. The red or dioxide of copper has a density of 6.093, and in properties, colour is very similar to copper. At a red heat it absorbs oxygen, and is converted into the protoxide. Dilute acids act on it very slowly ; resolving it into metal and a protoxide. 1168. With strong nitric acid it is oxidized, binoxide of nitrogen Action of escapes, and a nitrate of the black oxide is formed. Strong hydro- acids, chloric acid forms with it a colourless solution. The red oxide of copper is soluble in ammonia, and the solution is quite colourless ; but it becomes blue with surprising rapidity by free exposure to air, owing to the formation of the black oxide. Put a small quantity of this oxide into a small bottle, nearly full of water of' ammonia, and shake it frequently, the solution will have a rich blue colour. If ^ X P* a quantity of copper filings be added and the bottle well closed so as completely to exclude the air, the solution will become colourless in a few days. If the cork be withdrawn, the blue colour will again return as oxygen is absorbed. 1169. Black or Protoxide. Cu-j-O, Cu, or CuO, 31.6 1 eq. cop. B i ack -f 8 1 eq. oxy. = 39.6 equiv. This oxide of copper occurs na- tive, by the spontaneous oxidation of other ores of copper ; it is the copper black of mineralogy. 1170. It may be prepared artificially by calcining metallic copper, Artificial, by precipitation from the salts of copper by means of pure potassa, and by heating nitrate of copper to redness. 1171. It varies in colour from a dark brown to a bluish-black, ac- Properties, cording to the mode of formation, and its density is 6.401. It under- goes no change by heat alone, but is readily reduced to the metallic state by heat and combustible matter. It is insoluble in water. It combines with nearly all the acids, and most of its salts have a green or blue tint. With ammonia, it forms a deep blue solution, by which it is distinguished from all other substances. * The following process is recommended by Malaguti : 109 parts of sulphate of cop- Maiaguti\ per and 57 of carbonate of soda, both in crystals, are fused with a gentle heat j and the process- mass left, when all water is expelled, is pulverized and mixed with 25 parts of copper filings. The mixture is pressed into a crucible and exposed for twenty minutes to a white heat. The result is again pulverized and washed. .Ann. de Chim. et de Phys. liv. 216. 296 Chap. IV. Salts recog- nised. Antidote. Metal sepa- rated. Detected. Dichloride. Properties. Sulphurets. Disulpbu- ret formed. Metals — Copper. 1172. Its salts are distinguished from most substances by their colour, and are easily recognised by reagents. Pure ammonia throws down the disulphate when carefully added ; but an excess of the alkali instantly redissolves the precipitate, and forms a deep blue solution. Alkaline carbonates cause a bluish-green precipitate. It is precipitated as a dark brown sulphuret by hydrosulphuric acid, and as a reddish-brown ferrocyanuret by ferrocyanuret of potassium. 1173. It is thrown down of a yellowish white colour by albumen, and Orfila has proved that this compound is inert, so that albumen is an antidote to poisoning by copper.* 1174. Copper is separated in the metallic state by a rod of iron or zinc. The copper thus obtained, after being digested in a dilute so- lution of hydrochloric acid, is almost chemically pure. 1175. The best mode of detecting copper, when supposed to be present in mixed fluids, is by hydrosulphuric acid. The sulphuret, after being collected, and heated to redness in order to char organic matter, should be placed on a piece of porcelain, and be digested in a few drops of nitric acid. Sulphate of protoxide of copper is formed, which, when evaporated to dryness, strikes the characteristic deep blue tint on the addition of ammonia.! 1176. Bichloride of Copper. 2Cu+Cl, or Cu 2 Cl, 63.2 2 eq. copper -f- 35.42 l eq. chlor. = 98.62 equiv. When copper filings are introduced into an atmosphere of chlorine gas, the metal takes fire spontaneously, and both the chlorides are generated. The di- chloride may be conveniently prepared by heating copper filings with twice their weight of corrosive sublimate. It is slowly deposited in crystalline grains, when the green solution of protochloride of copper is kept in a corked bottle in contact with metallic copper. 1 177. The dichloride of copper is fusible at a heat just below red- ness, and bears a red heat in close vessels without subliming. It is insoluble in water, but dissolves in hydrochloric acid. Its colour va- ries with the mode of preparation, being white, yellow, or dark brown. t 1178. Sulphurets of Copper. The disvlphur et y 2Cu+S, orCu 2 S, 63.2 2 eq. copper 4- 16.1 1 eq. sulph. — 79.3 equiv., is a natural production, the copper glance of mineralogists, and in combination with protosulphuret of iron, it is a constituent of variegated copper ore.$ 1179. It is formed by heating copper filings with a third of their weight of sulphur; when the sulphur is raised a little above its melt- * Superoxide of Copper. Cu+20, C u , or CuO 2 , 31.6 1 eq. cop. + 16 2 eq. oxy. = 47.6 equiv. + The action of ammonia may he taken advantage of in cleaning (or colouring, as it is termed by jewellers) gold trinkets, such as chains, &c. which are often made of a very inferior alloy. Artists make use of weak nitric acid, or of the materials from which the acid is produced, and which often destroys the finer kinds of workmanship by dissolving the copper of the alloy to some depth on the surface ; the gold not being acted upon, the trinket appears as if newly gilded. Boiling in ammonia is a safe sub- stitute for this process, and the operation may be performed by any person without the assistance of the artist. Brewster’s Jour. i. 75 ; Bost. Jour. ii. 206. t Protochloride of Copper. Cu+Cl, 31.6 1 eq. copper + 35.42 1 eq. chlor. = 67.02 equiv. t For an outline of the process of reducing the ores of copper, see Brande, ii. 67, and Vivian, in Ann. Philos. N. S. v. 113. 297 Jliloys of Copper. ing point, combustion suddenly pervades the whole mass. The ex- Sect, vl pertinent succeeds equally well in vacuo or in azote, u. 370 . Copper leaf burns in gaseous sulphur as brilliantly as iron wire in oxygen gas.* * * § 1180. Many of the alloys of copper are important. With gold it Alloys forms a fine yellow ductile compound, used for coin and ornamental work. With silver it forms a white compound, used for plate and coin.! Lead and copper require a high red heat for union ; the alloy is gray and brittle. Of the alloys of copper with the metals already described the most important are brass and bell-metal. It forms white compounds with potassium and sodium ; a reddish alloy with manganese ; and a gray one with iron. 1181. Brass is an alloy of copper and zinc. The metals are usu- Brass, ally united by mixing granulated copper with calamine (1004) and charcoal : the mixture is exposed to heat sufficient to reduce the calamine and melt the alloy, which is then cast into plates. The relative proportions of the two metals vary in the different kinds of brass ; the best brass consists of four parts copper to one of zinc. This alloy is malleable and ductile when cold ; and its colour and little liability to rust, recommend it in preference to copper for many purposes of the arts.l 1182. Tutenag is said to be an alloy of copper, zinc, and a little Tutenag, iron ; and Tombac , Dutch gold, Similor, Prince Rupert's metal&nd pinchbeck, Pinchbeck , are alloys, containing more copper than exists in brass, &c * and consequently made by fusing various proportions of copper with brass. According to Wiegleb, Manheim gold consists of three parts of copper and one of zinc. A little tin is sometimes added, which, though it may improve the colour, impairs the malleability of the alloys 1183. Bell-metal and bronze are alloys of copper and tin ; they Bell-metal are harder and more fusible, but less malleable than copper. The an ronze * best bell-metal is . composed of three parts copper and one of tin ; the Indian gong, celebrated for the richness of its tones, contains copper and tin in this proportion. A little zinc is added to small shrill bells. Bronze consists of from 8 to 12 of tin with 100 of copper. 1184. Dalton finds that into all the alloys of copper which are Alloys characterized by useful properties, the ingredients enter in atomic definite proportions ; and it is probable that by attention to these proportions, com P oun ^ s “ the manufacture of the artificial alloys may be greatly improved. * Berzelius, Ann de Chim. See also Vauquelin on Sulphurets of Copper , lxxx. 265. + See Gold and Silver. '+ According to Sage, a very beautiful brass may be made by mixing 50 grains of ox- ide of copper, 100 of calamine, 400 of black flux, and 30 of charcoal powder 3 melt these in a crucible till the blue flame is no longer seen round the cover; and, when cold, a button of brass is found at the bottom, of a golden colour, and weighing one sixth more than the pure copper obtained from the above quantity of oxide. § An alloy, which, from the resemblance it has in colour to gold, is called Mosaic gold , has been latelv prepared from equal parts of copper and zinc melted at the lowest temperature at which copper will fuse. Speculum metal is an alloy of copper and tin, with a little arsenic ; about 6 copper, 2 tin, l arsenic. On this subject the reader is referred to Edwards’s experiments. Nicholson’s Jour. 4to. iii. 38 298 Metals — Lead. Chap. IV. Ores. To obtain pure lead- Properties. Action of water, Of acids. Protoxide. 1185. Vessels of copper used for culinary purposes are usually coated with tin, to prevent the food being contaminated with copper. Their interior surface is first cleaned, then rubbed over with sal- ammoniac to prevent oxidation ; the vessel is heated, a little pitch or rosin spread over the surface, and a bit of tin rubbed over it, which instantly unites with and covers the copper.* Lead. Symb. Pb Equiv. 103.6 1 186. Lead appears to have been known in the earliest ages of the world. The natural compounds of this metal are very numerous. The most important is the sulphuret, or galena , from which the pure metal is chiefly procured. Lead is also found combined with vari- ous acids, with oxygen, chlorine, &c. 1187. To obtain lead perfectly pure, Berzelius dissolved it in ni- tric acid, and crystallized the salt several times, till the mother liquor, on adding carbonate of ammonia, gave no traces of copper. The pure nitrate of lead, mixed with charcoal, was strongly heated in a Hessian crucible; and the lead, which separated, was kept for some time in fusion, in order to free it entirely from charcoal. The lead, thus obtained, when re-dissolved in nitric acid, gave no trace of any other metal. 1188. Its colour is bluish-white; it is soft, flexible, malleable and ductile. It melts at about 612° and by slow cooling may be ob- tained in octohedral crystals. Its sp. gr. is 11.352. At high tempe- ratures it absorbs oxygen, and when in fusion a gray film is formed on its surface, which is a mixture of metallic lead and protoxide ; by increasing the heat it is dissipated in fumes of the protoxide. 1189. Lead undergoes no change in distilled water in close ves- sels, but in open vessels is oxidized ; the oxide combines also with carbonic acid present in the air. The presence of saline matter in the water retards the oxidation, and some salts, even in minute quan- tity, prevent it altogether. Many kinds of spring water, owing to the salts which they contain, do not corrode lead.t 1 190. Lead is not attacked by hydrochloric, or the vegetable acids, though their presence often accelerates the absorption of oxygen. The only proper solvent for lead is nitric acid ; it oxidizes it and forms a salt of the protoxide. 1191. Protoxide of Lead. Pb-f-O, Pb, or PbO, 103.6 1 eq. lead -f- 8 1 eq. oxy. = 111.6 equiv., is prepared on a large scale by collect- ing the gray film which forms on the surface of melted lead, and exposing it to heat and air until it acquires a uniform yellow colour. In this state it is the massicot of commerce ; and when partially fused * The oxidation of copper plates is a matter of very great importance in the arts, and in the case of great and expensive works where few impressions of an engraving are taken and the plates laid aside for a considerable length of time, a serious injury to the plates is sustained by the necessity of cleaning them from oxide, when they are to be again used. This may he prevented by varnishing the plates with common lac varnish, which can easily be removed, when requisite, by spirits of wine. Brewster’s Jour. i. 76 ; Bost. Jour. ii. 206. For method of analysis of these alloys, see Brande, xi. 74; and for other details Thomson’s System— Inorganic Bodies , i. 601 ; Dumas’ Traits de Chim- iii. 605. t Se« this subject discussed in Christison’s Treatise on Poisons. 299 Red Oxide of Lead. the term litharge is applied to it. As thus procured it is al- Sect - VL ways mixed with red oxide. It may be obtained pure by adding ammonia to a cold solution of nitrate of protoxide of lead until it is faintly alkaline, washing the precipitated subnitrate with cold water, and, when dry, heating it to redness for an hour in a platinum cru- cible. An open fire should be used, and great care taken to prevent combustible matter in any form from contact with the oxide. 1192. Protoxide of lead is red while hot, but has a rich lemon- pro P erlies * yellow colour when cold, is insoluble in water, fuses at a bright red heat, and is fixed and unchangeable in the fire. Its sp. gr. is 9.4214. The fused protoxide has a highly foliated texture, and is very tough, so as to be pulverized with difficulty. By transmitted light it is yellow; but by reflected light it appears green in some parts and yellow in others. Heated with combustible matters, the protoxide parts with oxygen and is reduced. It unites with acids, and is the base of all the salts of lead, most of which are of a white colour. 1193. Protoxide of lead is precipitated from its solutions by pure alkalies, as a white hydrate, which is redissolved by potassa in ex- cess ; as a white carbonate, which is the well known pigment white Whit«le&d. lead , by alkaline carbonates ; as a white sulphate by soluble sul- phates.; as a dark brown sulphuret by hydrosulphuric acid ; and as yellow iodide of lead by hydriodic acid or iodide of potassium. 1 * The best method of detecting the presence of lead in wine or other Testo f suspected mixed fluids is by means of hydrosulphuric acid.f (Fig. Lead. 166.) 1194. Protoxide of lead unites readily with earthy substances, forming with them a transparent colourless glass, and is much em- ^nio nofPb ployed for glazing earthenware and porcelain. It enters in large bodies, quantity into the composition of flint glass, $ which it renders more fusible, transparent, and uniform. 1195. Lead is separated from its salts in the metallic state by iron Separated, or zinc. The best way of demonstrating this fact is by dissolving in a tall jar or bottle 1 part of acetate of protoxide of lead in 24 of water, and suspending a piece of zinc in the solution by means of a thread. The lead is deposited upon the zinc in a peculiar arborescent form, giving rise to the appearance called arbor Saturni 1196. Red Oxide of Lead. 3Pb+40, or 2Pb0+Pb0 2 , 310.8 3 Red oxide, eq. lead — f— 32 4 eq. oxy., or 223.2 2 eq. prolox. -(- 119.6 1 eq. perox. or minium. s= 342.8 equiv. This compound, the minium of commerce, is em- ployed as a pigment, and in the manufacture of flint glass. * With regard to the poisonous property of the salts of lead, the carbonate is by far the most virulent poison. Any salt of lead which is easily convertible into the carbo- P«i«onom. nate, as for instance the subacetate, is also poisonous. Acetate of protoxide of lead, mixed with vinegar to prevent the formation of any carbonate, maybe freely and safely administered in medical practice. (Dr A. T. Thomson.) t The sulphuret of lead, after being collected on a filter and washed, is to be digest- ed in nitric acid diluted with twice its weight of water, until the dark colour of the sulphuret disappears. The solution of the nitrate should then he brought to perfect dryness on a watch-glass, in order to expel the excess of nitric acid, and the residue be redissolved in a small quantity of cold water- On dropping a particle of iodide of potassium into a portion of this liquid, yellow iodide of lead will instantly appear. t Hence flint glass retorts are less suitable for some chemical processes than those of green glass without lead ; the latter are also less fusible. W. SDinoxide of Lead. 2Pb-fO, or Pb^O, 207.2 2 «q. lead 8 1 aq. oxy. a* Sig.S equiv, 300 Metals — Lead . Chap. IV. Peroxide. Properties. Chloride. Alloys. Solders. Eliquation. It is formed by oxidizing lead by heat and air without allowing it to fuse, and then exposing it in open vessels to a temperature of 600 ° or 700 °, while a cur- rent of air plays upon its surface. It slowly absorbs oxygen and is converted into minium. This oxide does not unite with acids. When heated to redness it gives off pure oxygen gas, and is reconverted into the protoxide. When digested in nitric acid it is resolved into protoxide and perox- ide of lead, the former of which unites with the acid, while the latter remains as an insoluble powder. From the facility with which this change is effected even by acetic acid, most chemists consider red lead not so much as a definite compound of lead and oxygen, but as a salt composed of the protoxide and peroxide.* 1197. Peroxide of Lead. Pb-f-20, Pb, or PbO’, 103.6 1 eq. lead + 16 2 eq. oxy. = 119.6 equiv. This oxide may be obtained by the action of nitric acid on minium, as just mentioned ; by fusing protoxide of lead with chlorate of potassa, at a temperature short of redness, and removing the chloride of potassium by solution in water ; and by transmitting a current of chlorine gas through a solution of acetate of the protoxide of lead. The chloride formed is removed by washing with warm water. 1 198. Peroxide of lead is of a puce colour, is insoluble in water, and is resolved by strong ox-acids, such as the sulphuric and nitric, into a salt of the protoxide and oxygen gas. With hydrochloric acid it yields chlorine gas and chloride of lead. At a red heat it emits oxygen gas and is converted into the protoxide. 1199. Chloride of Lead. Pb+Cl, or PbCl, 103.6 1 eq. lead + 35.42 1 eq. chlor. = 139.02 equiv. This compound, sometimes called horn lead , is slowly formed by the action of chlorine gas on thin plates of lead, and may be obtained more easily by adding hy- drochloric acid or a solution of sea-salt to acetate or nitrate of oxide of lead dissolved in water. This chloride dissolves to a considerable extent in hot water, especially when acidulated with hydrochloric acid, and separates on cooling in small acicular anhydrous crystals of a white colour. It fuses at a temperature below redness, and forms as it cools a semi-transparent mass, which has a density of 5.133.1 1200. Alloys of Lead. The most important are those with tin. Common pewter consists of about 80 parts of tin and 20 of lead. Fine solder consists of 2 parts of tin and 1 of lead ; it fuses at about 360°, and is much employed in tinning copper. Coarse solder con- tains one fourth of tin, fuses at about 500°, and is used by plumbers. Pot metal is an alloy of lead and copper. 1201. If lead be heated so as to boil and smoke, it soon dissolves pieces of copper thrown into it; the mixture, when cold, is brittle. The union of the two metals is remarkably slight ; for, upon expos- ing the mass to a heat no greater than that in which lead melts, the lead almost entirely runs off by itself. This process is called eliqua- tion. The coarser sorts of lead, which owe their brittleness and gra- * This was long considered as a sesquioxide, an error corrected by Dalton, I\ew System, of Che vi. ii. 41. T. t For other compounds see Turner’s Elements, 376. Mercury. inflated texture to an admixture of copper, throw it up to the sur- Sect, vn. face on being- melted by a moderate heat.* Section VII. — Metals , the oxides of which are reduced to the metal - lie state by a red heat . 1202. Mercury or Quicksilver , Hg. 202 eq.,t is the only one of Mercury, the metals that retains a fluid form at the ordinary temperature of the atmosphere* The principal ore of this metal is the sulphuret, or native cinna- Ore. bar , from which the mercury is separated by distillation with quick- lime or iron filings. 1203. Mercury is a brilliant white metal, having much of the Boiling colour of silver, whence the terms hydrargyrum , argentum vivum, P omt - and quicksilver. It has been known from very remote ages. Ac- cording to Crichton it boils and becomes vapour at 656° F., 680° according to Petit and Dulong, 670° Brande, and 662° T. It also rises in vapour in small portions at the common, tempera- ture of the atmosphere, particularly in a vacuum. 1204. When the temperature of mercury is considerably increas- Vapour ed above its boiling point, the vapour acquires great expansive force, and the power of bursting the strongest vessels. Gay-Lussac has calculated that the vapour of mercury is 12.01 more dense than oxygen gas, and that the liquid metal in becoming gaseous, increase* in volume 961 times. 1205. When the temperature of mercury is reduced to about Freezing. — 39° or 40° F., it becomes solid and malleable. By congelation it acquires an increase of sp. gr. ; and, therefore, unlike other metals, the congealed portion sinks to the bottom of a fluid mass of mercury. Its sp. gr. at 47° above 0 F. being 13.568, it is increased by congelation, to 15.612. Mercury, if quite pure, is not tarnished in the cold by exposure to air and moisture ; but if it contain other metals, the amalgam of those metals oxidizes readily, and collects a film upon its surface. 1206. Mercury is sometimes adulterated with the alloy of lead Adultera* and bismuth, a fraud easily detected by the want of its due fluidity, Jete’aetT and by its not being perfectly volatile, but leaving a residuum when boiled in a platinum or iron spoon . t * Lead combines with Iodine, Fluorine, &c., for which see Turner, Brande, Thomson and others. + Turner, Phil. Trans., 1833, part ii. t Mercury which is chemically impure will soon acquire adhesive films on its sur- face, even when cleansed of mechanical impurities, and with a rapidity dependent on the agitation of the metal or extension of surface. These interfere chemically when the metal is to be used in forming combinations, and mechanically in its uses in the trough in electro-magnetic experiments, and in the construction of barometers and thermometers. The purification of mercury from metals by distillation should be performed in an iron retort, a portion of clean iron and copper filings having been introduced with the p ur ifi e d. mercury, which should be condensed and received in clean water. This process, however, is not wholly unobjectionable, as both zinc and arsenic will pass over, and these metals are often present. A very useful method is to put from naif an inch to an inch in depth of mercury, mto a large earthenware pan, and to pour over it sulph- uric acid diluted with twice its weight of water. The substances should be left to- gether for a week or two, being frequently agitated. The metal and acid ara then to 302 Chap IV. Action of acids. Protoxide. Properties. Peroxide, or red pre- cipitate. Process. Properties. Metals — Mercury « 1207. The only acids that act on mercury are the sulphuric and nitric, the former requires the aid of heat and sulphurous acid is disengaged (530) ; the latter acts at all temperatures and binoxide of nitrogen is evolved (455). 1208. Protoxide of Mercury , Hg-(-0, Hg, or HgO, 202 1 eq. mere. 8 1 eq. oxy. = 210 equiv. This oxide which is a black powder, insoluble in water, is best prepared by the process recom- mended by Donovan.* This consists in mixing calomel briskly in a mortar with pure potassa in excess, so as to effect its decomposition as rapidly as possible : the protoxide is then washed with cold water, and dried spontaneously in a dark place. These precautions are rendered necessary by the tendency of the protoxide to resolve it- self into the peroxide and metallic mercury, a change which is easily effected by heat, by the direct solar rays, and even by day- light. It is on this account very difficult to procure protoxide of mercury in a state of absolute purity. 1209. It is a black powder, insoluble in water, uniting with acids, but a weak alkaline base. The alkalies precipitate it from solutions of its salts as the black protoxide. It is thrown down as a white carbonate by alkaline carbonates, but soon becomes dark from loss of its carbonic acid ; as calomel by hydrochloric acid or any soluble chloride, and as black prolosulphur- et by hydrosulphuric acid ; this last is the best test of its pres- ence. 1210. Peroxide of Mercury , Hg+20, Hg, or HgO 2 , 202 1 eq. mere. -\- 16 2 eq. oxy. = 218 equiv. This oxide may be formed either by the combined agency of heat and air, or by dissolving mercury in nitric acid, and exposing the nitrate so formed to a temperature just sufficient for expelling the whole of the nitric acid.t It is commonly known by the name of red precipitate. X 1211. When prepared by heat the process may be conducted by intro- ducing into a flat-bottom matrass, (Fig. 182,) about 4 ounces of mercury, and placing it in a sand-bath, heated to the boiling point of the metal. In about a month's time nearly the whole is converted into oxide. Air is freely admitted by the tube, while its length prevents the escape of mercurial vapour, which condenses and falls back into the body of the vessel; the remaining portion of running mercury may be driven off by exposing it in a basin to a heat just below redness. 1212. Peroxide of mercury, thus prepared, is commonly in the form of shining crystalline scales of a nearly black colour while hot, be separated, the latter preserved for a similar operation in future, and the former washed, dried and cleansed mechanically, by squeezing through sbamois leather, by agitation with damp loaf sugar, passing through a paper funnel, &c. — See Faraday’s Chem. Manip. sect. xx. * Ann. of Phil. xiv. + The peroxide prepared from the nitrate almost always contains a trace of nitric acid, which may he detected by heating it in a clean glass tube by means of a spirit- lamp ; a yellow ring, formed of subnitrate of peroxide of mercury, collects within the tube just above the part which is heated. (Clarke.) t H'jdrargyri oxidum rubrum of the Pharmacop. In the manufacture of this com- pound at Apothecaries’ Hall (Loud.) 100 lhs. of mercury are boiled with 48 lbs. of nitric acid (sp. gr. 1.43) and by proper evaporation and application of a dull red heat, 112 ibs. of the hydrarpryri niirico oxidum are obtained. B 303 Protochloride of Mercury. but red when cold: when very finely levigated, the peroxide has Sect, vii. in orange colour. It is soluble to a small extent in water, forming i solution which has an acrid metallic taste, and is poisonous. When heated to redness, it is converted into metallic mercury and ixygen. Long exposure to light has a similar effect.* 1213. Some of the neutral salts of this oxide, such as the nitrate Action of md sulphate, are converted by water, especially at a boiling tern- wa er > c ' jerature, into insoluble yellow subsalts, leaving a strongly acid so- ution, in which a little of the original salt is dissolved. The oxide :s separated from all acids as a red, or when hydratic as a yellow precipitate, by the pure and carbonated fixed alkalies. Ammonia ind its carbonate cause a white precipitate, which is a double salt, consisting of one equivalent of the acid, one equivalent of the pe- roxide, and one equivalent of ammonia. The oxide is readily re- iuced to the metallic state by metallic copper. 1214. Protochloride of Mercury , Hg-[-Cl, or HgCl, 202 1 eq. Protochlo- merc. -(- 35.42 1 eq. chlor. = 237.42 equiv. This compound, com- ^’j or cal " rnonly termed calomel , is first mentioned by Crollius, early in the seventeenth century.! 1215. It is always generated when chlorine comes in contact with Obtained, mercury at common temperatures ; and also by the contact of me- ;allic mercury and the bichloride. It may be made by precipitation, by mixing nitrate of protoxide of mercury in solution with hydro- chloric acid or any soluble chloride. It is more commonly prepared by sublimation. This is conveniently done by mixing 272.84 parts cr one equivalent of the bichloride with 202 parts or one equiva- lent of mercury, until the metallic globules entirely disappear, and then subliming. When first prepared it is always mixed with some corrosive sublimate, and, therefore, should be reduced to powder and well washed, before being employed for chemical or medical purposes.! 1216. When obtained by sublimation it is in semi-transparent Properties, crystalline cakes ; but as formed by precipitation, it is a white pow- der. Its density is 7.2. At a heat short of redness, but higher than the subliming point of the bichloride, it rises in vapour with- out previous fusion ; but during the sublimation a portion is always * Guibourt. t The first directions for its preparation are given by Beguin, in the Tyrocinium Chemicum, published in 1608. He calls it draco mitigatus. Several other fanciful names have been applied to it, such as aquila mitigata , manna metallorum, panchy- magogum minerale, sublimatum dulce, mercurius didcis, fyc. $ It was formerly the custom to submit calomel to very numerous sublimations, under the idea of rendering it mild; but these often tended to the production of cor- cusora - rosive sublimate; and the calomel of the first sublimation, especially if a little ex- cess of mercury be found in it, is often more pure than that afforded by subsequent operations. The following are the directions given in the hand. Pharmacop. “ Take of oxymuriate of mercury, 1 lb. purified mercury, by weight , 9 oz. Rub them together until the metallic globules disappear ; then sublime : take out the sublimed mass, reduce it to powder, and sublime it in the same manner twice more successively; bring it to the state of a very fine powder; throw this into a large vessel, full of water; then stir it, and, after a short interval, pour the superna- tant turbid solution into another vessel, and set it by, that the powder may subside. Lastly, having poured away the water, dry the powder.” ; It will be observed that in these processes the operation consists in reducing the bichloride to the state of protochloride by the addition of mercury. 304 Chap. IV. Bichloride, or corrosive sublimate. Theory. Characters. Action of light, Of alkalies, Proceu. Metals — Mercury . resolved into mercury and the bichloride. It is yellow while warm, but recovers its whiteness on cooling. It is distinguished from the bichloride by not being poisonous, by having no taste, and by being exceedingly insoluble in water. Acids have little effect upon it ; but pure alkalies decompose it, separating the black protoxide of mercury. 1217. Bichloride of Mercury, Hg-}-2Cl, or HgCP, 202 1 eq. mere, -f- 70.84 2 eq. chlor. = 272.84 equiv. When mercury is heated in chlorine gas, it takes fire, and burns with a pale red flame, form- ing the well known medicinal preparation and virulent poison corrosive sublimate , or bichloride of mercury. It is prepared for medical purposes by subliming a mixture of bisulphate of the per- oxide of mercury with chloride of sodium or sea-salt.* The ex- act quantities required for mutual decomposition are 298.2 parts or one equivalent of the bisulphate, to 117.44 parts or two equivalents of the chloride. Thus, 1 eq. Bisulphate of Mercury. | 2 eq. Chloride of Sodium. Sulphuric Acid 80.2 or 2 eq. 2P>0 3 | Chlorine . 7(1.84 or 2 eq. 2C1. Perox. of Merc. . 218 or 1 eq. HgO-’ | Sodium 46.6 or 2 eq. 2Na 298.2 HgO*q-2S0 3 | 117.44 2 (Na+Cl) and by mutual interchange of elements they produce 1 eq. Bichloride of Mercury. Mercury . . 202 or 1 eq. Hg. Chlorine . - 70.84 or 2 eq. 2C1 272.84 Hg-f2Cl 2 eq Sulphate of Soda Soda 62.6 or 2 eq. 2NaO Sulph. Acid . 80.2 or 2 eq. 2S0 3 142.8 2 (NaO-fSO 3 ) The products have exactly the same weight (272.84 -j- 142.8 = 415.64) as the compounds (298.2 -|- 117.44 = 415.64) from which they were prepared. 1218. Bichloride of mercury is usually seen in the form of a per- fectly white semi-transparent mass, exhibiting the appearance of im- perfect crystallization. It is sometimes procured in quadrangular prisms. Its sp. gr. is 5.2, its taste is acrid and nauseous, leaving a peculiar metallic and astringent flavour upon the tongue. It dis- solves in 20 parts of water at 60°, and but twice its weight at 212°. It is more soluble in alcohol than in water. When heated, it readi- ly sublimes in the form of a dense white vapour, strongly affecting the nose and mouth. It dissolves without decomposition in hydro- chloric, nitric, and sulphuric acids : the alkalies and several of the metals decompose it. 1219. Its aqueous solution is gradually decomposed by light, cal- omel being deposited. The pure and carbonated fixed alkalies throw down the peroxide of mercury from a solution of corrosive sublimate ; ammonia on the * The following is the process followed at Apothecaries Hall, (Lnnd.^ 50 lbs. of mercury are boiled with 70 lbs. of sulphuric add, to dryness, in a cast-iron vessel j 62 lbs. of the dry salt are triturated with 40 1-2 lbs. of mercury, until the globules disappear, and 34 lbs of common salt are then added. This mixture is submitted to heat in earthen vessels, and from 95 to 100 lbs. of calomel are the result. It is to be washed in large quantities of distilled water, after having been ground to a fine and inapelpable powder. 305 Iodides of Mercury. contrary, causes the deposition of a white matter which is common- Sect, vn. Jy known as white precipitate * White pre- 1220. The presence of mercury in a fluid, supposed to contain cipitate. corrosive sublimate, may be detected by concentrating and digesting D. e ^tion it with an excess of pure potassa. Peroxide of mercury, which 0 mercul Ti subsides, is then sublimed in a small glass tube by means of a spirit- lamp, and obtained in the form of metallic globules. When the bichloride is mixed with organic substances, Christison recommends that the liquid, without previous filtration, be agitated with a fourth of its volume of ether, which separates the poison from the aqueous part and rises to the surface. The ethereal solution is then evapora- ted on a watch-glass, the residue dissolved in water, and the mercu- ry precipitated in the metallic state by protochloride of tin at a boiling temperature.! 1221. Avery elegant method of detecting the presence of mer- Sylvester’s cury is to place a drop of the suspected liquid on polished gold, and method, to touch the moistened surface with a piece of iron wire or the point of a penknife, when the part touched instantly becomes while, owing to the formation of an amalgam of gold. This process was orig- inally suggested by Sylvester, and has since been simplified by Paris.! 1222. Many animal and vegetable solutions convert bichloride of Action of mercury into calomel. Some substances effect this change slowly ; a umen ' while others, and especially albumen, produce it in an instant. Into a solution of corrosive sublimate drop a solution of albumen, made by Exp. mixing a portion of white of egg with water, a white flocculent precipitate subsides, which Orfila has shown to be a compound of calomel and albumen, and which he has proved experimentally to be inert.* Consequently, a solu- tion of the white of eggs is an an antidote to poisoning by corrosive sublimate. 1223. Protiodide of Mercury , Hg-f-I, or Hgl, 202 1 eq. mere, -f- Protiodide. 126.3 1 eq. iod. ±= 328.3 equiv., is obtained by mixing nitrate of protoxide of mercury in solution, with iodide of potassium ; when the latter is added to the mixed nitrates of the protoxide and perox- ide of mercury, the latter in excess, the sesquiodide falls. 1224. Biniodide of Mercury^ Hg-j-21, or Hgl 2 , 202 1 eq. mere. Biniodide. -j-252.6 2 eq. iod. = 454.6 equiv. This compound is formed by mixing nitrate of the peroxide or bichloride of mercury with iodide of potassium in solution, and falls as a rich red-coloured powder of a tint which vies in beauty with that of vermilion, though unfortu- * This substance has been recently examined.* It was found that a slight excess of ammonia being added, just one half the chlorine of the corrosive sublimate was separated, the other half remaining in the solution with the ammonia. The precipitate, nevertheless, did not contain calomel. It was found to be composed of Mercury . . 78.6 Ammonia . . 6.77 Chlorine . . 13.S5 Hygrometric water > 73 loss and oxygen, $ Its atomic constitution would appear from this analysis to contain the compound radical which is the base of the amides, + If. as is probable, most of the poison is already converted into calomel, and thereby rendered insoluble, as many vegetable fibres should be picked out as possible, and the whole at once digested with protcchloride of tin. The organic substances are then dissolved in a hot solution of caustic potassa, and the insoluble parts washed and sublimed to separate the mercury, t t Medical Jurisprudence, by Paris and Fonblanque. § Toxicologie , vol, i, * Kane in I vans. Irish ,$sad. xvii, f Christison on Poisons . 39 ' 306 Chap. IV. Effect of heat. Sulphurets. Bisulphu- ret, or cin- nabar. Procei*. Metals — Mercury . nately, the colour is less permanent. Though insoluble in water, it dissolves freely in an excess of either of its precipitants. If taken up in a hot solution of nitrate of peroxide of mercury, the biniodide crystallizes out on cooling in scales of a beautiful red tint. The same crystals separate from a solution in iodide of potassium; but if the liquid be concentrated, a double iodide of mercury and po- tassium subsides. 1225. The biniodide, when exposed to a moderate heat, gradually becomes yellow ; and the particles, though previously in powder, acquire a crystalline appearance. At about 400° it forms a yellow liquid which slowly sublimes in small transparent scales, or in large rhombic tables, when a considerable quantity is sublimed. The crystals retain their yellow colour at 60° if kept very tranquil ; but if the temperature be below a certain point, or they are rubbed or touched, they quickly become red.* This phenomenon is entirely due to a change in molecular arrangement: the different colours so often witnessed in the same substances at different temperatures, as in peroxide of mercury and the protoxides of lead and zinc, appear to be phenomena of the same nature.! 1226. Protosulphuret of Mercury , Hg-f-S, or HgS, 202 1 eq. mere. + 16.1 1 eq. sulph. = 218.1 equiv., may be prepared by transmitting a current of hydrosulphuric acid gas through a dilute solution of nitrate of protoxide of mercury, or through water in which calomel is suspended. It is a black-coloured substance, which is oxidized by digestion in strong nitric acid. When exposed to heat it is resolved into the bisulphuret and metallic mercury. 1227. Bisulphuret of Mercury , Hg-|-2S, or HgS 2 , 202 1 eq. mere. + 32.2 2 eq. sulph. = 234.2 equiv., is formed by fusing sulphur with about six times its weight of mercury, and subliming in close vessels. When procured by this process it has a red colour, and is known by the name of factitious cinnabar X Its tint is great- ly improved by being reduced to powder, in which state it forms the beautiful pigment vermilion. It may be obtained in the moist way by pouring a solution of corrosive sublimate into an excess of hydrosulphate of ammonia. A black precipitate subsides, which acquires the usual red colour of cinnabar when sublimed. 1228. Cinnabar is not altered by exposure to air or moisture; when heated to dull redness in an open vessel, the sulphur forms sulphurous acid, and the mercury escapes in vapour. It is decom- posed by distillation with fixed alkalies, lime, and baryta, and by * This appears to have begn first noticed by Hayes, who has given an economical process for preparing the compound in Amer. Jour. xvi. 174. + Sesquiodide of Mercury, 2Hg+3l, or Hg 2 I 3 , 404 2 eq. mere. -+- 378.9 3 eq. iod. = 782.9 equiv. Protobromide of Mercury, Hg-fBr, or HgBr, 202 1 eq. mere, -f- 78.4 1 eq. brom. = 280.4 equiv. Bibromide of Mercury, Hg+2Br. or HgBr 2 , 202 1 eq. mere, -f 156.8 2 eq. brom. =358.8 equiv. t In the manufacture of cinnabar 8 parts of mercury are mixed in an iron pot with one of sulphur, and made to combine by a moderate heat, and constant stirring ■, this compound is then transferred to a glass subliming vessel, (on a small scale a Flor- ence flask answers perfectly,) and heated to redness in a sand-bath ; a quantity of mercury and of sulphur evaporate, and a sublimate forms which is removed, and rub- bed or levigated into a very fine powder. Silver . 307 several of the metals. When adulterated with red lead it is not en- Sect, vn. tirely volatile. 1229. Native Cinnabar is the principal ore of mercury; it occurs Native cin- massive and crystallized of various colours, sometimes appearing nabar ’ steel-gray, at others bright red. Native mercury and native amal- gam of silver sometimes accompany it. 1230. When equal parts of sulphur and mercury are triturated together until metallic globules cease to be visible, the dark coloured Ethiops. mass called ethiops mineral results, which Brande has proved to be a mixture of sulphur and bisulphuret of mercury.^ 1231. Mercury combines with most of the other metals, and forms Amalgams, a class of compounds which have been called amalgams. These are generally brittle or soft. One part of potassium with 70 of mercury produces a hard brittle compound. If mercury be added to the liquid alloy of potassium and sodium, an instant solidification ensues, and heat enough to inflame the latter metal is evolved. The amalgams of gold and silver are employed in gilding and silvering. An amalgam of 2 parts of mercury, 1 of bismuth, and 1 of lead, is fluid, and when kept for some time, deposits cubic crystals of bis- muth.! 1232. By combination with mercury, metals that are not easily Oxidation oxidized, acquire a facility of entering into union with oxygen, Thus gold and silver, when combined with mercury, are oxidized by bymercury, ignition in contact with air. This fact furnishes a striking illustra- tion of the effect of overcoming the aggregative affinity of bodies in promoting chemical union. 1233. When mercury is negatively electrized in a solution of am- monia, or when an amalgam of potassium and mercury is placed upon moistened hydrochlorate of ammonia, the metal increases in volume, and becomes of the consistency of butter, an appearance which has sometimes been called the metallization of ammonia. It has suggested some hypotheses concerning the nature of ammonia and the metals (731 ). t Silver. Symb. Ag Equiv. 108 1234. Silver is found native , and in a variety of combinations ; it Silver, was known to the ancients. Native silver occurs crystallized in oc- tahedral or cubic crystals, arborescent and capillary. It is seldom pure, but contains small portions of other metals, which affect its colour and ductility. It is chiefly found in primitive countries. In Peru and Mexico are the richest known mines of native silver. 1235. Pure silver may be obtained from goldsmiths’, or standard Pure, pro- silver, by dissolving it in nitric acid and precipitating by means of a cess for - * Jour, of Sci. vol. xviii. p. 294. loduretted Bichloride of Mercury. 20HgCl 2 +I, 6456.8 20 eq. bichlor. + 126.3 1 eq. iodine = 5583.1 equiv. Iodobichloride of Mercury. 40HgC12-|-HgI 2 , 10913.6 40 eq. bichlor. + 454.6 1 eq. biniodide = 11368.2 equiv. t For the method of making an amalgam of copper see Aikin’s Did., art. Mercury , p. 92; Thomson’s Chem. oflnorg. Bodies, i. 626. t Upon this subject the student may consult Gay-Lussac and Thenard ( Recherche s Phys. Chim. vol. i.) ; and Berzelius (Lehrbuch 1). 308 Metals — Silver. _Ohap.iv. clean piece of copper, washing with pure water, and then digesting in ammonia, to remove the copper. Another. 1236. A better process is to decompose chloride of silver by means of carbonate of potassa. For this purpose precipitate a solution of nitrate of oxide of silver with chloride of sodium, wash the precipitate with water, and dry it. Then put twice its weight of carbonate of potassa into a clean Hessian or black lead crucible, heat it to redness, and throw the chloride by successive portions into the fused alkali. Effervescence takes place from the evolution of carbonic acid and oxygen gases, chloride of potassium is generated, and metallic silver subsides to the bottom. The pure metal may be granulated by pouring it while fused from a height of seven or eight feet into a vessel of water.* Characters. 1237. Silver has a pure white colour, and considerable brilliancy. Its sp. gr. is 10.51 (hammered). It is so malleable and ductile, that it may be extended into leaves not exceeding a ten thousandth of an inch in thickness, and drawn into wire finer than a human hair. Properties. 1238. It melts at a bright red heat, 1873° F., and when in fusion appears extremely brilliant. It resists the action of air and moisture, and does not oxidize ;t the tarnish of silver is occasioned by sulphu- rous vapours ; it takes place very slowly upon the pure metal, but more rapidly upon the alloy with copper used for plate, and was found by Proust to consist of sulphuret of silver. Effect of 1239. Pure water has no effect upon the metal; but if the water water, &c. conta j n vegetable or animal matter, it often slightly blackens its sur- face in consequence of the presence of sulphur. If an electric explo- sion be passed through fine silver wire, it burns into a black powder, which is an oxide of silver. In the Voltaic circle it burns with a fine green light, and throws off abundant fumes of oxide. Exposed to an intense white heat, it boils and evaporates. If suddenly cooled, it crystallizes during congelation, often shooting out like a cauli- flower, and throwing small particles of the metal out of the crucible. Cupella- 1240. Silver is not unfrequently obtained in considerable quanti- ties from argentiferous sulphuret of lead, which is reduced in the usual way and then cupelled ; the oxide of lead thus procured is af- terwards reduced by charcoal. t * Thomson found it difficult to obtain silver free from copper, even when reduced from the chloride, hut accomplished the object by first washing the chloride with di- luted nitric acid, which removed the copper. First Principles, ii. 436. t When fused in open vessels it absorbs oxygen amounting sometimes to twentytwo times its volume, but parts with it in the act of becoming solid. T. t The principle of its separation from lead is founded on the different oxidability of lead and silver, and on ihe ready fusibility oflitharge. The lead obtained from those kinds of galena which are rich in sulphuret of silver is kept at a red heat in a flat fur- nace, with a draught of air constantly playing on its surface; the lead is thus rapidly oxidized; and as the oxide, at the moment of its formation, is fused, and runs off through an aperture in the side of the furnace, the production of litharge goes on un- interruptedly unt'l all the lead is removed. The button of silver is again fused in a smaller furnace, resting on a porous earthen dish, made with bone-ashes, Fig.183. called a test or cupel , the porosity of which is so great, that it absorbs any remaining portions of litharge which may be formed on the silver. The cupel is easily prepared by driving pounded bone ashes into a small brass mould, by means of a pestle (Fig. 183), struck forcibly by a wooden Fig. 181. mallet. It must then he removed cautiously, placed on a piece o' paper and dried. The mould is open above and below. In the process the cupel is placed in a muf- Jle (Fig. 184), which is made of me clay used for cruci- bles, arched above and closed at every side except in r "1 front, so that it may be exposed to a high temperature, 7 — ' and air be at the same time admitted. The cupel in which is the Oxide of Silver . 309 Some of the silver ores, especially the sulphurets, are reduced by Sect, vit. amalgamation. These ores, when washed and ground, are mixed Amalga- wiih a portion of common salt and roasted; then powdered and mation. mixed by agitation with mercury, and the amalgam thus formed is distilled.* 1241. The only pure acids that act upon silver, are the sulphuric Action of and nitric, the latter is its proper solvent, forming with its oxide a salt, acicls - which, after fusion, is known as lunar caustic, 1242. Oxide of Silver , Ag-f-O, Ag, or AgO, 108 1 eq. silver -j- Oxide. 8 1 eq. oxy. == 116 equiv., may be procured by mixing a solution of pure baryta with nitrate of oxide of silver dissolved in water. It is of a brown colour, insoluble in water, and is completely reduced by a red heat. 1243. Silver is separated from its solution in nitric acid by pure Action of alkalies and alkaline earths as the brown oxide, which is redissolved alkalies, by ammonia in excess; by alkaline carbonates as a white carbonate, c ’ soluble in an excess of carbonate of ammonia ; as a dark brown sul- phuret by hydrosulphuric acid ; and as a white curdy chloride of silver, which is turned violet by light and is very soluble in ammonia, by hydrochloric acid or any soluble chloride. By the last character, silver may be both distinguished and separated from other metallic bodies. 1244. Silver is precipitated in the metallic state by most other Arbor Di- metals. When mercury is employed the precipitation is very slow, an8e ’ and produces a peculiar symmetrical arrangement, called the arbor lead and silver, is placed in the muffle, in the cupelling furnace. (Fig. 185.) This furnace has an opening in one of its sides to receive the muffle. This is an important process and much used by refiners and assay- ers in the analysis of alloyed silver. Supposing that an alloy of silver and copper is to be assayed, or analyzed, by cupellation, the lollowmg is the mode of proceeding. A clean piece of the metal, weighing about 30 grains, is laminated, and accurately weighed in a very sensible balance. It is then wrapped up in the re- quisite quantity of sheet lead, (pure and reduced from litharge,) and placed upon a small cupel , or shallow crucible, made of bone earth, which has been previously heated. The whole is then placed under the muffle, heated to bright redness ; the metals melt, and by the action of the air which plays over the hot surface, the'jead and copper are oxidized and absorbed by the cupel, and a button of pure silver ulti- mately remains, the completion of the pyocess being judged of by the cessation of the oxidation and motion upon the surface of the globule, and by the very brilliant appear- ance assumed by the silver when the oxidation of its alloy ceases. The button of pure metal is then suffered to cool gradually, and its loss of weight will be equivalent to the weight of the alloy, which has been separated by oxidation. To perform this process with accuracy, many precautions are requisite, and nothing but practice can teach these, so as to enable the operator to gain certain results. A muffle 10 inches in length, 5 broad, and about 4^ nigh, answers for most operations. It should never be exposed suddenly to a strong heat, as it is very apt to be cracked ; the fire should also be raised very gradually, at first with little more than may prevent it from going out. The fuel is introduced from an opening above, and care must be taken not to allow any of it to fall directly upon the muffle. The bottom should rest on a fire brick, and its sides be at least 2 inches from the walls of the furnace. *The old process of eliquation is now scarcely used 5 it consisted in fusing alloys of copper and silver with lead ; this triple alloy was cast into round masses which were set in a proper furnace upon an inclined plane of iron with a small channel groov- ed out, and heated red-hot, during which the lead melted out, and in consequence of its attraction for silver, carrried that metal with it, the copper being left behind in a reddish-black spongy mass.* * Aikin’e Diet. art. Silver, 3 10 Chap IV. How made. Fulmina- ting silver. Process. Caution. Chloride. Effect of light. Metals — Silver. Diance. It was first remarked by Lemery. To obtain this crystal- lization in its most perfect state, the solution should contain a little mercury, and the mercury put into it should be alloyed with a little silver. Make an amalgam, without heat, of four drachms of silver leaf with two drachms of mercury. Dissolve the amalgam in four ounces or a sufficient quantity of pure nitric acid of a moderate strength ) dilute this solution in about a pound and a half of distilled water ; agitate the mixture, and preserve it for use in a glass bottle with a ground stopper. When this preparation is to be used, the quantity of one ounce is put into a phial, and the size of a pea of amalgam of gold, or silver, as soft as butter, is to be added ; after which the vessel must be left at rest. Soon afterwards, small filaments appear to issue out of the ball of amalgam, which in- crease and shoot out branches in the form of shrubs. U. 703. According to Proust all that is required is to throw mercury into nitrate of silver very much diluted. 1245. When oxide of silver, recently precipitated by baryta or lime-water, and separated from adhering moisture by bibulous paper, is left in contact for ten or twelve hours with a strong solution of ammonia, the greater part of it is dissolved ; but a black powder re- mains which detonates violently from heat or percussion. This substance, which was discovered by Berthollet, # appears to be a compound of ammonia and oxide of silver ; for the products of its detonation are metallic silver, water, and nitrogen gas. Precipitate nitrate of silver by lime-water, and thoroughly edulcorate and dry the precipitate. Let this be afterward put into a vessel of the purest liquid am- monia, in which it may remain for ten or twelve hours. It will then assume the form of a black powder, from which the fluid is to be decanted, and the black substance left to dry in the air. This is the celebrated compound termed fulminating silver , which explodes with the gentlest heat, and even with the slightest friction. 1246. It should be made in very small quantity at a time, and dried spontaneously in the air.t When once prepared, no attempt must be made to enclose it in a bottle, and it must be left undisturbed in the vessel in which it was dried. Great caution is necessary in the preparation of this substance, for in making experiments on it several fatal accidents have been produced by indiscretion in its use. It even explodes, when moist, on the gentlest friction . t The liquid when gently heated, affords a still more dangerous compound. Another detonating compound, less dangerous, may be prepared by dissolving silver in nitric acid, and adding the solution to alcohol. It is this which is used in the little balls known by the name of torpedoes A 1247. Chloride of Silver , Ag+Cl, or AgCl, 10S 1 eq. silver -|- 35.42 1 eq. chlor. = 143.42 equiv., occurs in nature and is the horn silver of mineralogists. It is generated when silver is heated in chlorine gas, arid may be prepared conveniently by mixing hydrochloric acid, or any soluble chloride, with a solution of nitrate of oxide of silver. As formed by precipitation it is quite white ; but by exposure to the * Ann. de Chim. i. t The student cannot be too careful in preparing this dangerous substance, which has caused several fatal accidents. See Bruce’s Min . Jour., i. j and for details Silli- man’s Chen ., ii. 336. *See Count Rumford’s papers, Phil. Trans., 1798. §For processes see Silliman’s Chem ., ii. Alloys of Silver. 311 direct solar rays it becomes violet, and almost black, in the course of Sect, vil a few minutes ; and a similar effect is slowly produced by diffused day-light.^ According to Berthollet, the dark colour is owing to se- paration of oxide of silver.! 1248. It is insoluble in water, and is dissolved very sparingly by Of acids, the strongest acids ; but it is soluble in ammonia. Hyposulphurous acid likewise dissolves it. At about 500° it fuses, and forms a semi- transparent horny mass on cooling, which has a density of 5.524. It bears any degree of heat, or even the combined action of pure charcoal and heat, without decomposition ; but hydrogen gas decom- poses it readily. 1249. Chloride of silver is very soluble in ammonia, by which it Action of is usefully distinguished from some other chlorides, which, like it, ammonia * are white, and formed by precipitation.! 1250. As chloride of silver is insoluble in water, and very readily Uses, formed, it is often employed in analysis, as a means of ascertaining the proportion of chlorine present in various compounds. § 1251. Sulphuret of Silver. Ag+S, or AgS, 108 1 eq. silver Sulphuret. + 16.11 eq. sulph. = 124.1 equiv. Silver has a strong affinity for sulphur. This metal tarnishes rapidly when exposed to an at- mosphere containing hydrosulphuric acid gas, owing to the forma- tion of a sulphuret. On transmitting a current of this gas through a solution of lunar caustic, a dark brown precipitate subsides, which is a sulphuret of silver. The silver glance of mineralogists is a similar compound, and the same sulphuret may be prepared by heating thin plates of silver with alternate layers of sulphur. This sulphuret is remarkable for being soft and even malleable.il 1252. Alloys of Silver. Silver unites with most other metals, Alloys, and suffers greatly in malleability and ductility by their presence. When silver and steel are fused together, an alloy is formed, which appears perfect while in fusion, but globules of silver exude from it on cooling, which shows the weak attraction of the metals. At a very high temperature the greater part of the silver evaporates, but a portion equal to about 1 in 500 remains, forming a perfect alloy, admirably adapted to the formation of cutting instruments. IT 1253. Silver readily combines with zinc and tin, forming brittle alloys. The alloy of silver with copper is of the most importance, as it constitutes plate and coin. By the addition of a small proportion of copper to silver, the metal is rendered harder and more sonorous, * Advantage has been taken of this in obtaining copies of paintings, engravings, &c., see Talbot on Photogenic Drawing , in Lond. and Edin. Philos. Jour. xiv. 197. t Stat. Chim. vol. i. p. 195. tWe should be cautious in applying heat to the ammoniacal solution, as it some- times forms a fulminating precipitate. §In these cases some excess of the precipitant should be used, and the precipitate CircnmetAnces allowed to subside previous to separating it upon the filter; if the supernatant li- u ) ,r be a a 1 uend«d* quor become perfectly clear, the whole of the silver has fallen ; if it remain opalescent, t0 - a portion is probably retained. When the precipitate remains long suspended, its deposition may be accelerated by warmth, or by adding a little nitric acid. The chlo- ride in these cases should be perfectly dried in a silver crucible, up to incipient fusion. B. ii. 180. || Iodide of Silver. Ag-4-I, or Agl, 1081 eq. silver-)- 126.3 1 eq. iodine = 234.3 equiv. TT Stoddart and Faraday, on the Alloys of Steel. Quart. Jour. ix. 5 Bost. Jour . 312 Metals — Gold. Chap IV. Silvering for dials. Native gold. Separation or quarta- tion. Method of obtaining pure gold. Characters. Malleabili- ty- while its colour is scarcely impaired. With lead the alloy is gray and brittle, as also with antimony, bismuth, cobalt, and arsenic.^ 1254. Amalgam of silver is sometimes employed for plating ; it is applied to the surface of copper, and the mercury being evaporated by heat, the remaining silver is burnished. The better kind of plating, however is performed by the application of a plate of silver to the surface of the copper, which is afterwards beaten or drawn out. 1255. A mixture of chloride of silver, chalk, and pearlash, is em- ployed for silvering brass ; the metal is rendered very clean, and the above mixture moistened with water rubbed upon its surface. In this way thermometer scales and clock dials are usually silvered. Gold. • Symb. Au Equiv. 199.2 1256. Gold occurs in nature in a metallic state, alloyed with a little silver or copper, and in this state is called native gold. Its co- lour is various shades of yellow ; its forms are massive, ramose, and crystallized in cubes and octohedra. Large quantities of this metal are collected in alluvial soils and in the beds of certain rivers, more especially those of the west coast of Africa and Peru, Brazil and Mexico. It is found in various parts of Europe, in the Uralian mountains, and in North America. t 1257. Gold is generally separated by amalgamation and cupella- tion. The best mode is by fusing the gold with so much silver, that the former may constitute one fourth of the mass; nitric acid will then dissolve all the silver and leave the gold. This process is termed quartation. 1258. Gold may be obtained pure by dissolving standard gold in nitro-hydrochloric acid, 4 evaporating the solution to dryness, re-dis- solving the dry mass in distilled water, filtering, and adding to it a solution of sulphate of protoxide of iron ; a black powder falls, which, after having been washed with dilute hydrochloric acid and distilled water, affords on fusion a button of pure gold. 1259. Gold is of a deep yellow colour. It melts at a bright red heat, 2016° Daniell, and when in fusion appears of a brilliant green colour. Its specific gravity varies a little according to the mechani- cal processes which it has undergone ; but it may be stated on the average at 19.257. 1260. Gold is so malleable that it may be extended into leaves which do not exceed of an inch in thickness. It is also very * The standard silver of Great Britain consists of ll^y of pure silver, and cop- per. A pound troy therefore is composed of 11 oz. 2 dwts. pure silver, and 13 dwts. of copper, and it is coined into 66 shillings. B. The standard silver of the United States is such that of 1000 parts by weight, 900 are pure and 100 alloy j the alloy being of copper. The dollar weighs 412£ grs., the dime 4 If grs. t For an account of the gold mines of North Carolina see Amer. Jour, of Sci. iv. 5. The gold received at the United States’ mint from N. Carolina, in 1836, amounted to 148,100 dollars in value, and that from all the workings in United Stales to 467,000 dollars. 4 Composed of two measures hydrochloric and one of nitric acid. Fulminating Gold . 313 ductile and considerably tenacious ; for a wire only °f an inch Sect, vii. in diameter will sustain a weight of 150 lbs. 1261. It shows no tendency to unite to oxygen even when exposed Effect of to its action in a state of fusion ; but if an electric discharge be electricit y» passed through a very fine wire of gold, a purple powder is pro- duced, which has been considered as an oxide. Chlorine appears to Of chlorine, be the active agent in dissolving gold. 1262. Protoxide of Gold, Au-|-0, Au, or AuO, 199.2 1 eq. gold Protoxide, -f- 8 1 eq. oxy. .= 207.2 equiv., is obtained by the action of a cold solution of potassa on the protochloride. It is precipitated of a green colour. It undergoes spontaneous change into metallic gold and teroxide. The purple oxide formed by the combustion of gold is supposed to be the binoxide .* 1263. Teroxide of Gold, Au-j-30, Au, or AuO 3 , 199.2 1 eq. gold. Teroxide. + 24 3 eq. oxy. = 223.2 equiv., the only well known oxide of gold, may be prepared by the following process : Dissolve 1 part of gold in the usual way, render it quite neutral by evapora- Process, don, and redissolve in 12 parts of water : to the solution add 1 part of carbonate of potassa dissolved in twice its weight of water, and digest at about 170°. Car- bonic acid gradually escapes, and the hydrated teroxide of a brownish-red colour subsides. After being well washed it is dissolved in colourless nitric acid of sp. gr» 1.4, and the solution decomposed by admixture with water. The hydrated teroxide is thus obtained quite pure, and is rendered anhydrous by a temperature of 212° F. 1264. Teroxide of gold is yellow in the state of hydrate, and Properties, nearly black when anhydrous, is insoluble in water, and completely decomposed by solar light or a red heat. It combines with alkaline bases, such as potassa and baryta, apparently forming regular salts, in which it acts the part of a weak acid. This property, induced Aurates Pelletier to propose for it the name of auric acid, its compounds with alkalies being called aurates . t 1265. When recently precipitated teroxide of gold is kept in Action of strong ammonia for about a day, a detonating compound of a deep Ammonia, olive colour is generated. According to the analysis of Dumas, its elements are in the ratio of one equivalent of gold, two of nitrogen, six of hydrogen, and three of oxygen. With regard to the mode in which these elements are arranged, different opinions may be formed. It appears most simple to consider it as a diaurate of ammonia, ex- pressed by the formula 2(3H-f-N)~|~Au0 3 . t. 387 . 1266. The compound known as Fulminating Gold, is similar to Fulmina- the above, and is obtained by digesting terchloride of gold with an ting soldl excess of ammonia. To obtain this compound add a solution of ammonia in water, or the pure p rocess f or „ liquid ammonia, to the diluted chloride ; a precipitate will appear, which will be re-dissolved if too much alkali be used. Let the liquor be filtered and wash the sediment which remains on the filter with several portions of warm water. Dry it by exposure to the air, without any artificial heat, and preserve it in a wide mouthed bottle, in small packets of paper, closed, not with a glass stopper, but merely by a cork. A small portion of this powder, less than a grain in weight, being * Binoxide of Gold. Au+20, or AuO 2 , 199.2 1 eq. gold 4- 16 2 eq. oxy. = 215.2 equiv. t An. de Ch . et de Ph. xv. 40 314 Metals — Gold. Chap. IV. Chlorides. Terchlo- ride, Pure gold from. Ethereal solution. Action of tin. placed on the point of a knife and held over a lamp, detonates vio- lently. The precise temperature which is required is not known, but it appears to be about 290° F. At the moment of explosion, a transient flash is observed. Two or three grains, exploded on a pretty strong sheet of copper, will force a hole through it. Neither electricity nor a spark from the flint and steel are sufficient to occa- sion its detonation ; but the slightest friction explodes it, and serious accidents have happened from this cause. 1267. Chlorides of Gold. The terchloride is obtained in ruby-red crystals by concentrating the solution of gold. It is soluble in alco- hol and ether, the latter removing it from the aqueous solution. It loses chlorine at about 400° F., and is changed into a mixture of protochloride * and terchloride, soluble in water. 1268. Terchloride of Gold , Au-f-3Cl, or AuCl 3 , 199.2 1 eq. gold -f- 106.26 3 eq. chlor. = 305.46 equiv., is the usual and most con- venient form of obtaining a solution of gold. On adding to the so- lution sulphate of protoxide of iron, a brown precipitate ensues, which is gold in very fine division, and the solution contains tersul- phate of sesquioxide, and sesquichloride of iron. The action is such that G eq. sulphate of protoxide of iron . . 6(Fe-}-S) and 1 eq. terchloride of gold Au-f-oCl yield 2 eq. tersulphate of sesquioxide of iron 1 eq. sesquichloride of iron and 1 eq. gold ..... 2(Fe-f3S) 2Fe+3Cl Au 1269. The precipitate, washed with dilute hydrochloric acid to se- parate adhering iron, is gold in a state of perfect purity. A similar reduction is effected by most of the metals. When a piece of char- coal is immersed in a solution of gold, and exposed to the direct solar rays, its surface acquires a coating of metallic gold, and ribands may be gilded by moistening them with a dilute solution of gold, and ex- posing them to a current of hydrogen or phosphuretted hydrogen gas. 1270. When a strong aqueous solution of gold is shaken in a phial with an equal volume of pure ether, two fluids result, the lighter of which is an ethereal solution of gold. From this liquid flakes of metal are deposited on standing, especially by exposure to light, and substances moistened with it receive a coating of metallic gold.t 1271. When protochloride of tin is added to a dilute aqueous so- lution of gold, a purple-coloured precipitate, called the purple of Cassius , is thrown down ; and the same substance may be prepared by fusing together 150 parts of silver, 20 of gold, and 35.1 of tin, and acting on the alloy with nitric acid, which dissolves out the sil- ver and leaves a purple residue, containing the tin and gold which were employed. To prevent the oxidation of the tin during fusion, the three metals should be projected into a red-hot black-lead cruci- ble, which contains a little melted borax. * Protochloride of Gold. Au-j-Cl, or AuCl, 199.2 1 eq. gold -|- 35.42 l eq. chlor. = 234.62 equiv. + $ee an Essay on Combustion by Mte Fulhome, and a paper by Rumford is the PkU. 7Vun». Ayr 1798. 315 Alloys of Gold . 1272 . When the powder of Cassius is fused with vitreous sub- Sect, vii. stances, such as flint-glass, or a mixture of sand and borax, it forms Purple of with them a purple enamel, which is employed in giving pink co- ^ assius * [ours to porcelain. The essential cause of the colour is probably a Uses * compound of the purple or supposed binoxide of gold with earthy natters, similar to the enamel formed by glass and oxide of silver.* 1273. Alloys of GoldA The alloy of gold and iron is malleable With po- ind ductile, and harder than gold, its colour dull white, and its spe- ^® slum > fific gravity 16.885. The metals expand by union. 1274. With zinc the compound is brittle and brass-coloured. With zinc. Specific gravity 16.937. The metals contract a little in uniting. The fumes of zinc in a furnace containing fused gold, make it brittle. 1275. Tin forms a whitish alloy, brittle when thick, but flexible in With tin. ;hin pieces. Specific gravity 17.307. There is considerable con- ;raction. The old chemists called tin diabolus metallorum, from its property of rendering gold brittle, but Bingley’s experiments quoted by Hatchett, show that of tin does not render gold brittle. 1276. The alloy of lead is very brittle when that metal only con- With lead, stitues '^27 of the alloy; even the fumes of lead destroy the duc- tility of gold. The sp. gravity is 18.080 ; and 1000 parts become 1005. 1277. With copper (standard gold) the alloy is perfectly ductile With cop- and malleable, but harder than pure gold, and resists wear better per ‘ than any other alloy except that with silver. Its specific gravity is 17.157.4 1278. Arsenic and antimony, when alloyed in very small pro- portions with gold, destroy its colour and render it quite brittle. 1279. The analysis of most of the alloys of gold is performed by ^noysof cupellation. The triple alloy of gold, silver, and copper, may be analyzed by digesting it in nitric acid, which takes up the silver and copper, and leaves the gold in the form of a black powder, which may be fused into a button and weighed. The silver may be thrown down in the state of chloride by solution of common salt, and the copper precipitated by iron. * Iodides of Gold are formed by the action of iodide of potassium on the terchloride of gold. Protiodide of Gold . Au+I, or Aul, 199.2 1 eq. gold -1- 126.3 1 eq. iod. = 325.5 equiv. Teriodide of Gold. Au+3l, or Aul 3 , 199-2 l eq. gold + 378.9 3 eq. iod. = 578. 1 equiv.* t A very curious series of experiments upon the alloys of gold has been published in the Phil. Trans . for 1803, by Hatchett. See also Thomson’s Inorgi Chem., i 654. t The standard gold of the United States contains in 1000 parts by weight 900 of E ure metal and 100 alloy composed of copper and silver, the latter not exceeding one alf of the whole alloy. The legal weight of the American eagle is 253 grs The legal standard of the British sovereign is 22 carats — 916| thousandths. Forty pounds Troy are made into 1869 sovereigns, the weight of each = 123.2744 grs. The value of the sovereign in gold of United States, should be 4 .8665. Numerous exami- nations of British gold at the U. S. mint show that the actual quality of the gold does not average more than 915^, or the average weight more than 122.88 grs. The exa- mination of 104,960 sovereigns (the Smithsonian legacy) at the mint, produced an average of 4-84 T 4 T per sovereign. * See Johnston’s experiments in Phil. Mag', and Ann. ix. 266. TevsUlplturet of Chid. Au-f&S or Au83, 1P9.2 1 eq gold -f 48. S 3 eq. suiph. => 947.5 equi?. 316 Metals — Platinum . Chap. IV. Assay. Water gild- ing. Carats. Ores. Characters. Action of heat and air. Spongy platinum. 1280. The assay of gold is more complicated than that of silver, in consequence of the high attraction which it has for copper, and which prevents its complete separation by mere cupellation. An al- loy, therefore, of copper with gold, is combined with a certain quan- tity of silver, previous to cupellation ; this is then cupelled with lead ih the usual way, and the silver is afterwards separated by the ac- tion of nitric acid.* 1281. Mercury and gold combine with great ease, and produce a white amalgam much used in gilding. For this purpose the amal- gam is applied to the surface of the silver; the mercury is then driven off by heat, and the gold remains adhering to the silver, and is burnished. This process is called water gilding. 1282. In gilding porcelain, gold powder is generally employed, obtained by the decomposition of the chloride ; it is applied with a pencil, and burnished after it has been exposed to the heat of the porcelain furnace. 1283. The degree of purity of gold is expressed by the number of parts of that metal, contained in the 24 parts of any mixture. Thus gold, which in 24 such parts (termed carats ,) contains 22 of the pure metal is said to be 22 carats fine. Absolutely pure gold, using the same language, is 24 carats fine ; and gold alloyed with an equal weight of another metal, 12 carats fine.f Platinum. Symb. Pt Equiv. 98. 8 1284. This valuable metal occurs in Brazil, Peru, and other parts of South America in rounded or flattened grains mingled with seve- ral other metals. In 1826 it was discovered by Bousingault in a sienitic rock in the province of Antioquia, in South America, and since then it has been found in larger quantity in the Uralian moun- tains. t 1285. It is a white metal, much resembling silver, and is the heaviest metal known ; after forging its density being about 21.25, and in the state of wire 21.5. It is malleable, and may be drawn into wire the diameter of which does not exceed the two thousandth part of an inch. It is soft, and has the valuable property of welding. It is a less perfect conductor of heat than several other metals. § 1286. It is unaltered by the joint action of heat and air ; but small wires of it are fused and burn in the Voltaic circuit, and before the oxyhydrogen blow-pipe. No pure acids attack it. Its solvents are chlorine, or solutions that supply chlorine, as nitrohydrochloric acid. 1287. Spongy platinum has been discovered by Dobereiner to have * The real quantity of gold or silver taken for an assay is very small ; from 18 to 36 grains, for instance, for silver, and from 6 to 12 for gold ; whatever the quantity may be it is called the assay pound. The silver assay pound is divided into 12 ounces, ana each ounce into 20 pennyweights. The gold assay pound is subdivided into 24 carats, and each carat into 4 assay grains. Aiken’s Dicl ., art. Assay. t Many curious facts relating to the properties of gold, and its uses in the arts, will be found m Lewis’s Phil. Com. of the Arts. J Edin. Jour, of Sci., v. 323. § For many important details respecting platinum, see Wollaston’s paper in Phil. Trans ., 1829, and Brande’s Manual , ii. 20C. 317 Protochloride of Platinum . the remarkable property of causing the union of oxygen and hydro- Sect, vn. , gen gases (387) ; and Dulong and Thenard have shown that the same effect takes place, though in a lower degree, with platinum foil and wire.^ 1288. According to Faradayf the gases must be pure and the pla- tinum free from foreign matters, pure water excepted, which is ef- t i ons . fected by fusing pure potassa on its surface, washing, then dipping the platinum in hot oil of vitriol, and again washing with pure water. 1289. In this state platinum foil acts so rapidly at common tern- Action of. peratures on oxygen and hydrogen gases mixed in the ratio of 1 to 2, that it often becomes red-hot and kindles the mixture. Handling the platinum, wiping it with a towel, or exposing it to the atmos- phere for a few days, suffices to soil the surface of the metal, and thereby diminish or prevent its action. 1290. These phenomena are supposed to result from the concur- Theory of. ring influence of two forces, the self-repulsive energy of similar gaseous particles, and the adhesive attraction exerted between them and the platinum. Each gas, repulsive to itself and not repelled by the platinum, comes into the most intimate contact with that metal, and both gases are so condensed upon its surface, that they are brought within the sphere of their mutual attraction and combine. 1291. Protoxide of Platinum, Pt-f-O, Pt, or PtO, 98.8 1 eq. plat. Protoxide. + 8 1 eq. oxy. == 106.8 equiv., is prepared by digesting protochlo- ride of platinum in a solution of pure potassa, avoiding a large ex- cess of the alkali, since it dissolves a portion of the oxide, and thereby acquires a green colour. In this state it is a hydrate which loses first its water and then oxygen when heated, and dissolves slowly in acids, yielding solutions of a brownish-green tint. 1292. Binoxide of Platinum . Pt-f-20, Pt, or PtO 2 , 98.8 1 eq. Binoxide. plat, -f- 16 2 eq. oxy. i== 114.8 equiv. This oxide is prepared with difficulty. Berzelius recommends that it should be prepared by ex- actly decomposing sulphate of binoxide of platinum with nitrate of baryta, and adding pure soda to the filtered solution, so as to precipi- tate about half of the oxide ; since otherwise, a sub-salt would sub- side. The oxide falls in the form of a bulky hydrate, of a yellowish- brown colour ; it resembles rust of iron when dry, and is nearly black when rendered anhydrous. $ 1293. Protochloride of Platinum. Pt— |— Cl, or PtCl, 98.8 1 eq. Protochlo- plat. -j- 35.42 1 eq. chlor. = 134,22 equiv. When the bichloride ride - is heated to 450°, half of its chlorine is expelled, and the protochlo- ride of a greenish-gray colour remains. It is insoluble in water, sulphuric acid, and nitric acid ; but hydrochloric acid partially dis- solves it, yielding a red solution. At a red-heat its chlorine is dri- ven off, and metallic platinum is left. It is dissolved by a solution of the bichloride. * Ann. de Chim. et de Phys ., xxiii. and xxiv. + Phil. Trans. 1834, part i. t Sesquioxide of Platinum. 2PH-30, or Pt 2 0 3 , 197.6 2 eq. plat. + 24 3 eq oxy. = s«aquioxide. j 221. 6, equiv. This oxide, of a gray colour, is prepared according to its discoverer, E. Davy, by heating fulminating platinum with nitrous acid ; but the nature of the com- pound so formed has not yet been decisively determined. Phil, Trans , 1820. 318 Metals — Platinum. Solutions recognized . chap, iv. 1294. Bichloride of Platinum. Pt-f-2Cl, or PiCP, 98.8 1 eq. Bichloride, plat. -J- 70.84 2 eq. chlor. = 169.64 equiv. This chloride is ob- tained by evaporating the solution of platinum in nitro-hydrochloric acid to dryness at a very gentle heat, when it remains as a red hy- drate, which becomes brown when its water is expelled. It is deli- quescent, and very soluble in water, alcohol, and ether ; its solution, if free from the chlorides of palladium and iridium, being of a pure yellow colour. Its ethereal solution is decomposed by light, metal- lic platinum being deposited. 1295. A solution of platinum is recognized by the following cha- racters. When to an alcoholic or concentrated aqueous solution of the bichloride, a solution of chloride of potassium is added, a crys- talline double chloride of a pale yellow colour subsides, which is insoluble in alcohol, and sparingly soluble in water ; at a red heat it yields chlorine gas, and the .residue consists of metallic platinum and chloride of potassium. With a solution of hydrochlorate of ammo- nia a similar yellow salt falls, which when ignited leaves pure pla- tinum in the form of a delicate spongy mass, the power of which in kindling an explosive mixture of oxygen and hydrogen gases has already been mentioned* (1287). Biniodide. 1296. Biniodide of PlatiJium, Pt-f-2I, or PtP, 98.8 1 eq. plat, -f- 252.6 2 eq. iod. = 351.4 equiv., prepared by the action of iodide of potassium on a rather dilute solution of bichloride of platinum. At first the liquid acquires an orange-red and then a claret colour, without any precipitation ; but when the solution is boiled, a black precipitate subsides, which should be washed with hot water and dried at a heat not exceeding 212°. This biniodide is a black pow- der, sometimes crystalline, is tasteless and inodorous, insoluble in water, and may be boiled in water without change. By alcohol it is sparingly dissolved, especially when heated. Acids act feebly upon it ; but it is decomposed by alkalies ; and begins to lose iodine at 270°. t Protosul- phuret. Bisulphu- ret. Fulmina- ting. 1297. P rotosulphuret of Platinum , Pt-j-S, or PtS, 9S.8 1 eq. plat, -f- 16.1 1 eq. sulph. '= 114.9 equiv., is formed by heating the ammoniaeal chloride with half its weight of sulphur, until all the sal ammoniac and excess of sulphur are expelled. 1298. Bisulphuret of Platinum , Pt-j-2S, or PtS 2 , 98.S 1 eq. plat, -f- 32.2 2 eq. sulph. = 131 equiv., is formed by dropping a solution of bichloride of platinum into a solution of sulphuret of potassium, or by transmitting hydrosulphuric acid gas into a solution of the double chloride of platinum and sodium. It should be dried in vacuo. 1299. Fulminating platinum may be prepared by the action of ammonia in slight excess on a solution of sulphate of protoxide of platinum. When boiled in potassa, washed and dried, it was found by E. Davy to explode at about 420° with a very loud report.^ One grain laid on a thin sheet of copper and exploded produces a report * Protiodide of Platinum , Pt+I.or PtI, 98.8 1 eq. plat. + 126 3 1 eq. iod. =225.1 equiv., prepared by digesting the protochloride of platinum in a rather strong solution ot iodide of potassium, when the protiodide gradually appears in the form a black powder, which is insoluble in water and alcohol It is unchanged by the sulphuric, nitric, and hydrochloric acids, decomposed by the alkalies, and at a red heat gives on its iodine. t An. de Oh. etdt PA.,li. 113. t Phii. Trans. lSlf. Osmium and Iridium . 319 louder than that of a pistol, and the copper is deeply indented. It is Sect, vn. incapable of being exploded by percussion. 1300. Palladium , Rhodium , Osmium , and Iridium. These metals Associated are found associated in the ore of platinum, and have been procured meta s ‘ but in small quantity. 1301. Palladium, Pd, 53.3 eq., was discovered by Wollaston ; it Palladium, resembles platinum in colour and lustre; it is ductile and malleable; its sp. gr. is 11.3 to 118. 1302. In fusibility it is intermediate between gold and platinum, Properties, and is dissipated in sparks when intensely heated by the oxy hydro- gen blow-pipe. At a red heat in oxygen gas, its surface acquires a fine blue colour, owing to superficial oxidation ; but the increase of weight is so slight as not to be appreciated. 1303. Palladium is oxidized and dissolved by nitric acid, and even Action of the sulphuric and hydrochloric acids act upon it by the aid of heat; acids * but its proper solvent is nitro-hydrochloric acid. Its protoxide forms beautiful red-coloured salts, from which metallic palladium is preci- pitated by sulphate of protoxide of iron, and by all the metals de- scribed in the foregoing sections, excepting silver, gold, and pla- tinum. 1304. Rhodium , R, 52,2 eq., was discovered by Wollaston at the Rhodium time he was occupied with the discovery of palladium. He obtained oblained > it in the form of a black powder, which requires the strongest heat that can be produced in a wind furnace for fusion, and when fused has a white colour and metallic lustre. 1305. It is brittle, is extremely hard, and has a specific gravity of Properties, about 11. It attracts oxygen at a red heat, a mixture of peroxide and protoxide being formed. It is not attacked by any of the acids when in its pure state , but if alloyed with other metals, such as copper or lead, it is dissolved by nitro-hydrochloric acid, a circum- stance which accounts for its presence in the solution of crude pla- tinum. 1306. It is oxidized by being ignited either with nitre, or bisul- Oxidized, phate of potassa. When heated with the latter, sulphurous acid gas is evolved, and a double sulphate of peroxide of rhodium and potassa is generated, which dissolves readily in hot water, and yields a yel- low solution. The presence of rhodium in platinum, iridium, and osmium may thus be detected, and by repeated fusion a perfect se- paration be accomplished-^ Most of its salts are either red or yellow. 1307. Osmium and Iridium. Os, 99.7 eq. These metals were Osmium discovered by Tennant in the year 1803, t and the discovery of iridi- Indl " um was made about the same time by Descotils in France. Wol- laston detected them as an alloy in the black powder accompanying the ore of platinum. Osmium acquires a metallic lustre by friction ; its sp. gr. is 7 to 10. It takes fire when heated in the open air, and is readily oxidized and dissolved by fuming nitric acid. 1308. The highest stage of oxidation of Os. is the volatile compound Osmicacid, Osmic Acid, Os+40, or OsO 4 , 99.7 1 eq. osmium + 32 4 eq. oxy. = 131.7 equiv., which is the product of the oxidation of osmium by * Berzelius, t Phil. Trans. 1804. 320 Salts . Chap. V. Iridium. Latanium, Oxide of, Salts of. Application of the term salt* ft Orders. Oxysalts, what. . acids, by combustion, or by fusion with nitre or alkalies. Its vapour is very acrid, exciting cough, irritating the eyes, and producing a copious flow of saliva; its odour is disagreeable and pungent, some- what like that of chlorine, hence the name osmium from oo/tTj, odour. With infusion of gall nuts it gives a purple solution, which after- wards acquires a deep blue lint, a delicate test of the acid. 1309. Iridium is a brittle metal, apt to fall to powder when burnished, but with care may be polished and then resembles platinum. It is the most infusible of all metals ; sp. gr. 15.8629 ; equiv. 98.8. It forms with oxygen 4 oxides, and with chlorine 4 chlorides. 1310. $These metals combine with oxygen, chlorine, and sulphur, for an account of the compounds the student is referred to Turner’s Elements, and Brande’s Manual. 1311. Latanium. In submitting the cerite of Bastnaes to exami- nation Mosander has very recently obtained this new metal, and which was named from its being, as it were, hidden by the cerium. It was prepared by calcining the nitrate of cerium mixed with nitrate of latanium. The oxide of cerium loses its solubility in weak acids ; j and the oxide of latanium, which is a very strong base, may be sepa- rated by nitric acid, mixed with 100 parts of water. 1312. The oxide is of a brick-red colour, owing to the presence of oxide of cerium ; it is converted by hot water into a white hydrate which restores the blue colour of litmus paper: it is rapidly dis- solved by dilute acids, and when used in excess is converted into a sub-salt. 1313. Its salts have an astringent taste, without any mixture of sweetness ; and the crystals are of a rose-red colour. The atomic , weight of latanium is smaller than that of cerium.* CHAPTER V. Section 1. Salts. 1314. The term salt has been applied to a very extensive range of compounds, where acids are combined with oxides, or other com- pounds having similar properties. The oxide or other substance united with the acid is called a base or salifiable base. Each acid, with few exceptions, is capable of-uniting with every alkaline base, and frequently in two or more proportions. 1315. The class of salts has been divided into four orders (330), and many of their characters have been already described. t Order lsL Oxysalts. 1316. Of the common salts, a large proportion contain oxygen both in the acid and in the base, thus in the phosphate of soda it is associated with phosphorus in the phosphoric acid, and with sodium in the soda, and hence such are termed oxysalts. * Lond. and Edin. Phil. Mag., May, 1839. t Graham has been led to the conclusion that all salts are neutral in their constitu- tion, with the exception of certain classes. See Turner, 403. Thomson has divided the salts into nine classes. See Chem. of Inorg. Bodiet , vol. ii. 378. Sulphates . 321 1317. Those salts which consist of the same acid united with dif- Sect, i. ferent salifiable bases, possess certain characters in common, and may be considered as constituting one family. The combination of salts with one another gives rise to compounds Double which were formerly called triple salts ; but the term double salt, salts, proposed by Berzelius, gives a more correct idea of their nature and constitution. These salts may be composed of one acid and two bases, of two acids and one base, and of two different acids and two different bases. Most of the double salts hitherto examined consist of the same acid and two different bases. 1318. All the powerful alkaline bases, excepting ammonia, are the protoxides of an electro-positive metal, such as potassium, barium or iron ; so that if M represent an eq. of any one of those metals M-j-O, or MO is the strongest alkaline base, and often the only one which that metal can form. A single eq. of acid neutralizes MO, forming with it a neutral salt. Thus, indicating an equivalent of sulphuric and nitric acid by the signs SO 3 and NO 5 , all the neutral sulphates and nitrates of protoxides are indicated by MO-j-SO 3 and MO-j-NO 5 . There is, therefore, in the neutral protosalts of each fa- R ema rka- mily, a constant ratio in the oxygen of the base and acid, resulting blelaw. from the composition of each acid, that ratio for sulphates being as 1 to 3, and for nitrates as 1 to 5. If the metal M of a neutral sul- phate pass into a higher grade of oxidation, becoming a binoxide MO 2 , then will that binoxide be disposed to unite with two eq. of acid, and form a bisalt, MQ 2 -|-2S0 3 , in which the oxygen of the base and acid is still as 1 to 3 ; and if the metal yield a sesquioxide, M 2 0 3 , then, if sufficient acid be supplied, the resulting salt will con- sist of M 2 0 3 -(-3S0 3 , the ratio of 1 to 3 being preserved.* Sulphates. 1319. The acid of the sulphates is readily detected by chloride of Sulphates barium (551). An insoluble sulphate may be detected by mixing it, detec ted in fine powder, with three times its weight of carbonate of potassa or soda, and exposing the mixture to a red heat for half an hour, in a platinum crucible. Double decomposition ensues ; and on digest- ing the residue in water, filtering the solution, neutralizing the free alkali by pure hydrochloric, nitric, or acetic acid, and adding chlo- ride of barium, the insoluble sulphate of that base is precipitated. 1320. Many sulphates exist in nature, and those of lime and ba- Natural, ryta are the most abundant. They may all be formed by the action Arl j ficia j of sulphuric acid on the metals, their oxides or their carbonates, or by double decomposition. They vary in solubility in water ; most Solubility, of them are decomposed by a white heat with the escape of one part of the sulphuric acid, while the other part is resolved into sulphurous acid and oxygen. They are decomposed by carbonaceous mat- ^ com P°* ter with the aid of heat, carbonic acid being formed and a sulphuret of the metal. 1321. The composition of neutral protosulphates is expressed by Composi- the formula MQ-f-SQ 3 ; the acid containing three times as much j‘a?sul- eU — — ; = phates ex- * This curious law relative to oxy-salts, which is very general, was first noticed by pressed. Gay Lussac {Mem. d'Arcueil , ii.), and Berzelius has found it to hold in earthy mine - rals, and employed it as a guide in studying their composition. T. 41 322 Salts — Sulphates. chap, v. oxygen as the base ; and if both were deprived of it a metallic pro- tosulphuret would result, M-f-S.* Sulphate of 1322. Sulphate of Potassa. KO+SO 3 , 47.15 1 eq. base + 40.1 1 eq. acid = 87.25 equiv. The sal de duohus of the old chemists, potasscB sulphas of the Pharmacop. This salt is the result of several chemical operations in the arts ; and is procured abundantly by neu- tralizing with carbonate of potassa the residue of the operation for preparing nitric acid (471). 1323. Its taste is saline and bitter. Its crystals belong to the right prismatic system ; they are unchanged by exposure to the air, but decrepitate when heated. Soluble in sixteen times their weight of water at 60°, and five of boiling water. 1324. Intensely heated with one fifth its weight of powdered char- coal, it produces sulphuret of potassium. About two parts of sulphate of potassa and one of lampblack intimately mixed in fine powder, heated to redness in a coated phial, with great care to exclude the air during cooling, afford a compound which takes fire on exposure to the air. It appears to contain a compound of potassium which powerfully attracts oxygen, and thus excites heat enough to inflame the charcoal and sulphur. Gay Lussac attributes the combustibility of common pyrophorus to this compound. 1325. Bisulphate of Potassa. K0-|-2S0 3 , eq. 127.35 ; with 1 water 136.35. This salt is formed by adding S to a hot so- potassa, Properties, Effect of heat and carbon, Bisulphate formed, eq weight of S in a Properties. Old names. lution of KO-f-SO s , or by boiling it with half its platinum crucible, till none of the acid escapes when the heat ap proaches redness. It is obtained in crystals from a concentrated solution at high temperatures, as in the cold the neutral sulphate is formed. The form is a right rhombic prism, generally tabular. Ac- cording to Graham they contain 1 eq. water (basic), the bisulphate being a double sulphate of water and potassa. 1326. It has a sour taste, and is more soluble than the neutral sulphate, requiring only twice its weight of water at 60°, and less than an equal weight at 212°. 1327. It is formed in the process for nitric acid (471), and is called sal enixum — formerly arcanum duplicatum and panacea Hoi - satica. It is used for cleaning coin and other works in metal. Sulphate of 132S. Sulphate of Soda — Glauber's Salt. NaO-f-SO 3 , 31.3 1 eq. soda. base — |— 40. 3 1 eq. acid = 71.4 equiv. ; in crystals with 10 eq. water, 161.4 eq. This salt occurs in the earth and in the waters of certain springs. It may be obtained by saturating sulphuric acid with carbo- nate of soda. Large quantities are obtained as the residuum in the processes for hydrochloric acid and chlorine (610, 629). Properties. 1329. Its crystals belong to the right prismatic system, containing ten eq. of water, which is lost by efflorescence on exposure to the air ; by heat they undergo the watery fusion. The taste is bitter, cooling, and saline. 100 parts of water at 32° dissolve 12 parts of the crystals; at 64.5° 48 parts; at 77° 100 parts; at 91.5° 322 parts. Clau of iul- In accordance with the views of Graham (22), the sulphates may be divided into phate* accord- three classes : 1st, anhydrous sulphates without the eq. of constitutional water ; 2d, mg to Graham, ^ose j n which it is an essential part ; 3d, double salts, produced from the second by the eq. of constitutional water being replaced by an eq. of a sulphate of the first class. T. 323 Sulphate of Baryta . 1330. Sulphate of soda is sometimes decomposed for the purpose Sect, i. of obtaining soda, by igniting it with chalk and charcoal.* * * § Its Uses, principal use is in pharmacy and in the manufacture of glass. 1331. Sulphate of Lithia. LO-f-SO 3 , 14.44 1 eq. base -f- 40.1 1 Sulphate of eq. acid == 54.54 eq. in crystals with 9 1 eq. water. This salt is kthia, very soluble in water, fuses by heat more readily than the sulphates of the other alkalies, and crystallizes in flat prisms resembling sul- phate of soda, but not efflorescent. Taste saline. 1332. Sulphate of Oxide of Ammonium — Sulphate of Ammonia. Of ammo- H 4 N0-f-S0 3 , 26.15 I eq. base -f- 40.1 1 eq. acid == 66.25 eq., in nia » crystals with 9 or 1 eq. water = 75.25. It is obtained by neutral- izing sulphuric acid with carbonate of ammonia ; or by decomposing hydrochlorate of ammonia by sulphuric acid. 1333. It is important as a source of the hydrochlorate of ammonia use. which is obtained from a mixture of common salt and sulphate of ammonia by sublimation ; by this process sulphate of soda is also formed.! It is contained in the soot from coal. 1334. It crystallizes in long flattened six sided prisms ; dissolves properties, in two parts of water at 60°, and in an equal weight of boiliqg water. In a warm dry air it effloresces, losing 1 eq. of water. Sharply heated it fuses and is decomposed, yielding nitrogen gas, water, and sulphate of oxide of ammonium. 1335. Native Sulphate of Ammonia is sometimes found in volcanic Native, countries ; it has been procured from fissures in the earth near cer- tain small lakes in Tuscany, and is known by the name of Mascag- nine.t 1336. Sulphate of Baryta — heavy spar. BaO-j-SO 3 , 76.7 1 eq. Sulphate of base -f- 40.1 1 eq. acid = 116.8 eq. This is an abundant natural Bai 7 ta - product, insoluble in hot and cold water, and precipitated when sul- phuric acid or any soluble sulphate is added to any soluble salt of baryta (551). So extremely delicate is baryta as a test of sulphuric acid, that it shows the presence of 1 part of sulphate of soda in JJ® as a 400,000 of water.§ 1337. Heavy spar occurs associated with metallic ores, especially Occurs in those of lead, massive and crystallized. The form of the crystals is naure ' variable, being sometimes prismatic and sometimes tabular, deducible from a right rhombic prism. Its density is about 4.4. It is easily formed by double decomposition. 1338. When native sulphate of baryta is heated it decrepitates, Bologna and, at a high temperature, fuses into an opaque white enamel; it P^ospho- was employed in the manufacture of jasper ware , by Wedgwood. When heated to redness, it acquires the property of phosphores- cence. This was first ascertained by Vincenzo Cascariolo, of Bologna, whence the term Bologna phosphorus is applied to it. II *For a full account of the processes for decomposing this salt see Aiken’s Did. art. Mur. Soda, and Brande’s Manual, i. 426. t In the arts it is obtained by treating sulphate of lime with the carbonate of ammo- nia procured from animal matter by distillation. t From the name of its-discoverer. § Sulphate of baryta is sometimes very obstinate in subsiding from water, and will not only long remain suspended, but even pass through filtering paper 5 heat and a little excess of acid generally facilitate its deposition. B. || To prepare this substance the native sulphate, powdered after being ignited, is to 324 Salts — Sulphates . Cha P v - This kind of phosphorus, after being exposed for a few minutes to the sun’s rays, shines in the dark sufficiently to render visible the dial of a watch. This property is lost by repeated use, in conse- quence of the oxygenation of the sulphur ; but it may be restored by a second calcination.* 1339. As the native sulphate is a common and abundant com- Methods of pound, several processes have been contrived for obtaining from it obtaining p Ure baryta, pure baryta . J from native This may be effected by reducing the crystallized sulphate to a fine powder, sulphate. and heating it red-hot for half an hour in a silver crucible with three parts of carbonate of potassa, the fused mass is then boiled repeatedly in water, till it no longer affords anything soluble in that liquid; the insoluble residue, consisting chiefly of carbonate of baryta, may be digested in dilute nitric acid, by which ni- trate of baryta is formed, and which will yield the pure earth by exposure to heat. Henry’s The following method has been recommended by Henry. The sulphate of process. baryta is to be finely powdered, mixed with three or four times its weight of car- bonate of potassa, and boiled with a proper quantity of water for a considerable time, in an iron kettle, stirring it, and breaking down the hard lumps, into which it is apt to run, by an iron pestle. It is then to be washed with boiling water, as long as this acquires any taste. On the addition of dilute hydrochloric acid, a violent effervescence will ensue, and a considerable portion of the earth, probably along with some metals, will be dissolved. To the saturated solution, add solu- tion of pure baryta in water, as long as it disturbs the transparency of the liquor. This will throw down any metals that may be present; and the excess of baryta may afterwards be precipitated in the state of a carbonate by a stream of carbonic acid. Decompose the hydrochloric solution by any alkaline carbonate ; let the precipitated earth be well washed with distilled water ; and if the pure baryta is to be obtained from it, let it be treated as directed page 238. Another. Another method consists in exposing to a red heat, in an earthen crucible, a mixture of six parts of finely powdered sulphate of baryta, with one of powdered charcoal, for half an hour. This converts the sulphate into sulphuret which is to be dissolved in hot water, the solution filtered and mixed with solution of car- bonate of soda as long as it occasions a precipitate, which when washed and dried, is carbonate of baryta. Or, by adding hydrochloric acid to the liquid sul- phuret, sulphur is thrown down, hydrosulphuric acid gas evolved, and hydro chlorate of baryta formed, which maybe filtered off, and if required, decomposed by carbonate of potassa. Or the sulphuret, as it comes out or the crucible, may be thrown into dilute nitric acid, by which hydrosulphuric acid gas is evolved, and a nitrate of baryta formed, which may be separated from the remaining im- purities by copious washings with hot water. strontfa 6 1340. Sulphate of Strontia. SrO+SO 3 , 51.8 l eq. base -f- 40.1 1 eq. acid = 91.9equiv. This salt occurs native. It is nearly in- soluble, 1 part requiring for solution 4000 parts of cold, and 3840 of hot water. Heated with charcoal, its acid is decomposed and sul- phuret of strontium is formed, which affords nitrate of strontia by the action of nitric acid. This process, equally practicable upon sul- phate of baryta (884), is adopted to obtain strontia. Native. 1341. Native Sulphate of Strontia is sometimes of a blue tint, and has hence been called celestine. Sometimes it is colourless and transparent. It occurs of great beauty in Sicily associated with sul- be formed into a paste with mucilage of gum arabic, and divided into cylinders or pieces of one fourth of an inch in thickness. These, after being dried in a moderate heat, are to be exposed to the temperature of a wind furnace, placed in the midst of the charcoal. When the fuel is half consumed, it must be replenished, and suffered to burn out. The pieces will be found, retaining their original shapes, among the ashes, from which they may be separated by the blast of a pair of bellows. They must be preserved in a well-stopped phial. H. 1 . 584 . * The artificial sulphate of baryta is used as a pigment, under the name of perma- nent white. It is very useful for marking phials and jars in the laboratory. 325 Sulphate of Magnesia. phur, in anhydrous prismatic crystals. Magnificent crystals have Sect, i. been met with on Strontian Island in Lake Erie.* 1342. Sulphate of Lime. CaO-j-SO 3 , 28.5 1 eq. base -f- 40-1 Sulphate of 1 eq. acid = 68.6 eq. ; as gypsum with 18 or 2 eq. of water = 86.6. iime > This salt is easily formed by mixing in solution a salt of lime with any soluble sulphate (61, exp. 2). It occurs abundantly as a natural production. The mineral called anhydrite is anhydrous sulphate of Anhydrite, lime, and all the varieties of gypsum are composed of the same salt Gypsum, united with water. The pure crystallized specimens are called sele- nite , and the white compact variety is known as alabaster. Alabaster, 1343. The crystals of anhydrite belong to the right prismatic sys- Crystalline tern, and are isomorphous with the sulphates of baryta and strontia, f° rms i while the forms of gypsum are oblique prismatic. They contain 2 eq. water, one only of which is considered by Graham to be water of crystallization, the other being constitutional. The former is readily lost by exposing pounded gypsum to a temperature of 212° in vacuo , and the whole water is expelled by a temperature below 300°. Thus dried, it constitutes the well known plaster of Paris, which, when mixed piaster of with a proper proportion of water, rapidly becomes dry and solid, Paris, owing to the reproduction of gypsum.f 1344. Nearly all spring and river waters contain this salt, and in Contained those waters which are termed hard it is abundant. It gives them a slightly nauseous taste. Pour a quantity of hard water into two glasses, solution of baryta dropped into Exp. one will detect the sulphuric acid, and a solution of oxalic acid dropped into the other, will detect the lime. 1345. Sulphate of lime has hardly any taste. It is more soluble Solubility, than sulphate of baryta or strontia, requiring for solution about 500 parts of cold, and 450 of boiling water. rf 1346. Sulphate of Magnesia — Epsom Salt. MgO-}-S0 3 HO, Epsom 20.7 1 eq. base -f- 40.1 1 eq. acid 9 aq. 1 eq. = 69.8 ; in crys- salt > tals with 54 6 eq. water = 123.8 eq. This salt is usually obtained Bowob- from sea-water, the residue of which, after the separation of common tained. salt, is known by the name of bittern, and contains sulphate and hy- drochlorate of magnesia ; the latter is decomposed by sulphuric acid ; a portion of the hydrochlorate often remains in the sulphate and renders it deliquescent : it is also occasionally obtained from saline springs ; and sometimes by the action of sulphuric acid on magnesian lime- stone. It was procured from the springs of Epsom, in England, and hence called Epsom salt. It has been found native, constituting the bitter salt and hair salt of mineralogists: it not unfrequently oc- curs as a fine capillary incrustation upon the damp walls of cellars and new buildings. I * Discovered by Delafield, see Amer. Jour. iv. 279. tit is remarkable that gypsum which has lost only 1 eq. water, as well as that which is dried by a heat exceeding 270° will not act in a similar manner. In the lat- ter case the powder is a perfect anhydrite. (Phil. Mag. vi. 417.) Raw gypsum, ac- cording to Ernmet, finely pulverized, is capable of undergoing immediate and perfect solidification when mixed with certain solutions of potassa. See Auier. Jour, xxiii. 209. tThe sulphate of magnesia of commerce is occasionally adulterated with small crystals of sulphate of soda 5 the fraud is detected by the inferior weight of the preci- 326 Salts — Sulphates . Cha P- v - 1347. Sulphate of magnesia may be made by neutralizing dilute Taste and sulphuric acid with carbonate of magnesia. It has a saline, bitter, form talline a . nauseous taste > and crystallizes in small quadrangular prisms, which effloresce slightly in a dry air. It is obtained also in larger crystals, the principal form of which is a right rhombic prism. Solubility. 1348. The crystals are soluble in an equal weight of water at 60°, and in three fourths their weight of boiling water. They undergo the watery fusion, and the anhydrous salt is deprived of a portion of its acid at a white heat. Dried at 212° it retains 2 eq. of water, but one of these is expelled at 270°, while the other is retained till the temperature rises to 460°. * of alumina, 1349. Sulphate of Alumina. A1 2 0 3 +S0 3 , 51.4 1 eq. base -f- ’40.1 1 eq. acid = 91.5; in crystals with 81 9 eq. water = 172.5. Ter sulphate. A1 2 0 3 +3S0*, 51.4 acid -f 120.3 3 eq. base = 171.7 eq. ; in crystals with 162 18 eq. water = 333.7 eq. Tersul- The tersulphate is prepared by saturating dilute sulphuric acid phate. with hydrated alumina, and evaporating. It crystallizes in thin flex- ible plates of a pearly lustre, containing 18 eq. of water and soluble in twice their weight of water. Hydrated 1350. The hydrated disulphate is known to mineralogists under sulphate, t h e name 0 f aluminite. t Sulphates 1351. Sulphate of Protoxide of Iron. FeO-f-S0 3 HO, 36 1 eq. of iron, base -f- 40.1 1 eq. acid -f- 9 aq. 1 eq. =85. 1 ; in crystals with 45 5 eq. water = 130.1. Sulphuric acid with the protoxide of iron forms sulphate of the protoxide , green vitriol , or copperas.X It is Copperas, prepared in large quantities for commercial purposes, by exposing the native protosulphuret of iron to air and moisture, the iron being con- verted into an oxide, and the sulphur into sulphuric acid by attract- ing oxygen. Process. On the small scale it may be prepared by mixing C parts of iron with 10 of S and 00 of water, evaporating the solution in a glass or earthen vessel, after the effervescence lias ceased, and continuing the heat, till a rod dipped into it pre- sents appearances of crystallization, when taken out and held in the air. The solution may then bo filtered, and green crystals of the sulphate will be formed as it cools. Properties. 1352. This salt has a strong styptic taste. When pure it does not change vegetable blue colours, though generally stated to do so, the reddening effect being only produced when some of the iron pitate, occasioned by adding carbonate of potassa ; 100 parts of pure crystallized sul- phate of magnesia furnishing a precipitate of about 40 parts of dry carbonate. B. Much of the sulphate found in the shops contains some hydrochlorate ofmagnesia,\vhich renders it deliquescent, and consequently, it requires to be preserved iu close and co- vered jars. It is often adulterated with Glauber’s salt, which is made to resemble Epsom salt, by stirring it briskly, when it is about to crystallize. It may be detected by precipitating the magnesia by pure ammonia, aiding by heat; filtering and evapo- rating the filtered fluid to dryness by a heat sufficient to volatilize the sulphate of am- monia ; if it contains Glauber's salt the soda will remain fixed. Or it may be detected by no precipitation ensuing, on adding carbonate of potassa to the solution. Hydro- chlorate of lime is detected by the oxalic acid. Thomson’s Lond. Disp. 407. ♦On the manufacture of this salt from magnesite see Amer. Jour. iv. 22, and xiv. 10. t Sulphate of Protox. Manganese. MnO+S0 3 HO, 35.7 1 eq. base -f 40.1 1 eq. acid + 9 aq- 1 eq. = 84.8 eq. t Native Green Vitriol is frequently found associated with iron pyrites, being pro- duced by its decomposition ; it occurs in some coal mines. Sulphate of Zinc. 327 passes into a higher state of oxidation. This is prevented by a few sect, i. drops of sulphuric acid in excess, and the resulting crystals have a distinctly blue colour. The common green tint is a delicate test of •the presence of sesquioxide of iron.* The crystals belong to the oblique prismatic system, and contain 6 Crystalline eq. of water, one of which is retained, according to Graham, till the form - temperature rises to 535°. By operating carefully it may be ren- dered anhydrous without the loss of acid. It is soluble in two parts of cold, and in three fourths its weight of boiling water. This salt is employed in the manufacture of fuming sulphuric acid (540). 1353. When heated it fuses, and at a high temperature evolves a Effect of mixture of sulphurous and sulphuric acids, and the oxide remaining ileat " was formerly called caput mortuum vitrioli , or colcothar. Colcothar. 1354. Tersulphate of the Sesquioxide , Fe 2 0 3 -f-3S0 3 , 80 1 eq. base Tersul- + 120.3 3 eq. acid = 200.3 eq., is formed by mixing a solution of P hale - the protosulphate with half as much S as that salt contains, and adding to the mixture in a boiling state successive portions of nitric acid until N fumes cease to appear. The solution is then evaporated to dryness to expel the excess of N, and the tersulphate remains as a white salt. 1355. It dissolves in water, after being strongly heated ; and at a Solubility, red heat gives out all its acid, sesquioxide of iron remaining. Its &c. solution in water is yellow.t 1356. Sulphate of Protoxide of Zinc — White Vitriol, ZnO + Sulphate of S0 3 HO, 40.3 1 eq. base + 40.1 1 eq. acid + 9aq. 1 eq. = 89.4; *inc. in crystals with 54 6 eq. water = 143.4. This salt is the residue of the process for obtaining hydrogen gas, (378.)t It is also made for the purposes of commerce, by roasting native sulphuret of zinc. 1357. Its crystalline form is a flattened four sided prism of the Crystalline right prismatic system, and isomorphous with Epsom salt. The form, solu- crystals dissolve in 2£ parts of cold, and are still more soluble in bi,lt y> &c - boiling water. Its taste is strongly styptic. It reddens vegetable blue colours, though a neutral salt. 1358. This salt is almost always contaminated with iron, and i m p U rites often with copper and lead. Hence the yellow spots which are vis- removed, ible on it ; and hence also the reason why its solution in water lets fall a dirty brown sediment. It may be purified by dissolving it in water, and putting into the solution a quantity of zinc filings ; ta- king care to agitate occasionally. The zinc precipitates the foreign metals and takes their place. The solution is then to be filtered *BonsdorfFin Pogg. Ann., xxxi. 81. t The disulphate of the sesquioxide falls as a hydrate of an ochreous colour, when a solution of the protosulphate is kept in an open vessel. t Hydrogen gas holding zinc in solution, may be obtained by a process of Vauque- Hydmincic lin. A mixture of the ore of zinc, (blende, or calamine) with charcoal, is to be put gas. into a porcelain tube, which is to be placed horizontally in a furnace, and when red- hot, the vapour of water is to be driven over it. The gas produced is a mixture of carbonic acid, carburetted hydrogen, and a solution of zinc in hydrogen gas, which has been called hydrozincic gas. The zinc is deposited on the surface of the water, over which this gas is kept ; but if burned when recently prepared, the gas exhibits, in consequence of this impregnation, a distinctly blue flame. 328 Chap. V. Sulphate of nickel. Sulphate of cobalt. Sulphate of copper. Process. Disulphate, Sulphate of protox. cop. and ammonia. Salts — Sulphates. and the sulphate of zinc may be obtained from it in crystals by proper evaporation.* 1359. In the dose of a scruple or a drachm, sulphate of zinc is one of the most immediate emetics we possess ; and it is to be inferred, that if larger doses are rejected, as is the fact, with equal rapidity, they will in general cause no more harm than the medicinal dose. In some instances, however, persons have suffered severely from over- doses of this salt, and a few have even perished. It has also been said to have proved fatal when applied externally. t 1360. Sulphate of Protoxide of Nickel , NiO-f-SO s HO, 37.5 base 1 eq. -f- 40.1 acid 1 eq. + 9aq. = 86.6, like most of the salts of nickel this of a green colour, and crystallizes from its solution in pure water in right rhombic prisms, similar to the sulphates of zinc and magnesia. If an excess of acid is present the crystals are square prisms, containing less water and more acid than the prece- ding.t Soluble in about three times its weight of water at 60°. 1361. Sulphate of Protoxide of Cobalt , CoO-{-S0 3 HO, 37.5 1 eq. base -f- 40.1 1 eq. acid — |— 9 aq. 1 eq. =86.6, is obtained by di- gesting protoxide of cobalt in dilute S, evaporation and crystalliza- tion. The crystals are red, and isomorphous with Fe0-j-S0 3 H0.§ 1362. Sulphates of the Oxides of Copper. — Blue Vitriol , CuO-(- S0 3 H0, 39.6 1 eq. base -f- 40.1 1 eq. acid — 9aq. 1 eq. = 88.7 eq. in crystals with 36 4 eq. water = 124.7. The sulphate of the black or protoxide of copper is made by roasting the native sulphu- ret, or by dissolving the protoxide in dilute S and crystallizing by evaporation. It forms crystals of a blue colour, which contain 5 eq. of water, 4 of which are lost at 212° in dry air, but the fifth is re- tained till the temperature exceeds 430°. It is then a white powder, combining readily with water with development of heat. It is iso- morphous with MnO-f-S0 3 HO. 1363. In the large way the the copper is oxidized by igniting it in an oven ; the scale of oxide is then beaten off and the copper is heated again till the whole is thus oxidized ; the scales heated in the acid will partially dissolve without decomposing the latter.|| 1364. When pure potassa is added to a solution of this salt, in a quantity insufficient for separating the whole of the acid, the disul- phate, of a pale bluish green colour, is thrown down. 1365. By adding cautiously, a solution of ammonia to the sul- phate, until the subsalt thrown down is nearly all dissolved, sulphate of protoxide of copper and ammonia is generated. The solution is a rich blue from which crystals are deposited by the addition of al- cohol. It may be formed also by triturating carbonate of ammonia * Thomson’s Intrg. Chem. ii, 610. + Christison on Poisons, 375. For method of detecting in contents of the stomach see ibid, 374. t Ann. Philos, xxii. 439. § Brooke in Ann. Philos. NS. vi. 120. They are insoluble in alcohol, but dissolve in about 24 parts of cold water. || The composition of these scales is variable, they are often a pure protoxide, and when treated with hot S become peroxide of copper, which dissolves and finely di- vided metallic copper subsides. Their texture is crystalline and they readily dissolve in ammonia, and give, in close vessels, a colourless solution. ( Hayes.) Sulphate of Silver. 329 with crystals of sulphate of copper; carbonic acid is disengaged and Sect, i. the mass becomes moist, the water of the blue vitriol being liberated. This is the cuprum ammoniatum of the U. S. Phar. and contains S, Cu-j-0 and NH 3 ? It loses NH 3 by exposure to the air. 1366. Sulphates of the Oxides of Mercury. Sulphate of the Pro - Sulphates toxide HgO-f-SO 3 210 l eq. base + 40.1 1 eq. acid = 250.1 eq., is ofMercul 7- obtained when two parts of mercury are gently heated in three parts of strong S, so as to cause effervesence (530). 1367. If a strong heat is employed so as to excite brisk efferves- Effect of cence, and the mixture is brought to dryness, a bisulphate of the pe- heat - roxide results, both being anhydrous.^ This salt is employed in making corrosive sublimate (1217). Turpeth When thrown into hot water, it is decomposed, and a yellow sub- mmera ' salt, formerly called Turpeth mineral ,t subsides, according to Phil- lips it consists of 3 eq. of acid and 4 eq. of peroxide. 1368. Sulphate of Oxide of Silver. AgO-j-SO 3 , 116 1 eq. base Sujphate of — |— 40. 1 1 eq. acid = 156.1 eq. This salt is deposited when sul- phate of soda is mixed with nitrate of silver. It is also formed by boiling silver with its weight of sulphuric acid. 1369. It is white and easily fusible, requiring about 80 times its Properties, weight of hot water for solution, and the greater part is deposited in small needles on cooling. X ■ 1370. A compound acid, which may be called nitro-sulphuric, consisting of one part of nitre dissolved in about ten of S, dissolves silver at a temperature below 200°, and the solution admits of mode- rate dilution before sulphate of silver separates from it. This acid scarcely acts upon copper, lead, or iron, unless diluted with water ; it is, therefore, useful in separating the silver from old plated arti- cles : the precious metal may afterwards be separated either in the form of chloride, by adding common salt ; or by diluting the acid and continuing the immersion of the pieces of copper which have lost their silvering, and which will now dissolve in the diluted acid and occasion the precipitation of metallic silver.^ 1371. Sulphate of oxide of silver forms with ammonia a double Action of salt, which crystallizes in rectangular prisms, the solid angles and ammonia, lateral edges being replaced by tangent planes. It consists of 1 eq. AgO, 1 acid, and 2 NH 3 ; it is formed by dissolving AgO-f-SO 3 in a hot concentrated solution of ammonia, from which, on cooling, the crystals are deposited. It is isomorphous with the double chromate and seleniate of oxide of silver and ammonia.il * Donovan in Arm. Philos, xiv. + Hydrarg. sulphas flavus of the U. S. Pharm. JUpon the large scale small portions of gold may be economically separated from Economical . . _ method of sepa* large quantities of silver, by heating the finely granulated alloy in S; the gold remains rating gold, in the form of a black powder, and the sulphate of silver may be decomposed by the action of metallic copper 5 the silver is precipitated in a pulverulent state, and, with a little borax or other vitrifiable flux, is fused, and cast into ingots 3 the sulphate of copper is easily obtained in the crystallized state by evaporating the residuary liquor. B. ii. 187. § Keir in Phil. Trans, lxxx. || Mitscherlich in Ann. de Chim. el de Phys., xxxviii. 62, 42 330 Chap. V. Glauberite. Alum, Process for, Properties, Crystalline form, Pyropho- TUS, Process, Hare’s, Theory of its combus lion, Salts — Double Sulphates. Double Sulphates. 1372. Sulphate of Soda and Lime. NaO, S0 3 -f-CaO, SO 3 , 71.4 1 eq. sulph. sod. 6S.6 1 eq. sulp. lime = 140 eq. This salt, de- scribed by mineralogists under the name of Glauberite , is found in the salt mines of New Castile. It may be made by fusing together its constituents in the ratio of their equivalents.* 1373. Sulphate of Potassa and Alumina — Alum. KO, S0 3 -|- A1 2 0 3 , 3S0 3 , 87.25 1 eq. sulph. potassa -j- 171.7 1 eq. tersulph. alu. = 258.95 eq. ; do. with 216 or 24 eq. water = 474.95. Common alum is prepared by roasting and lixiviating certain clays containing iron pyrites ; to the leys a proper quantity of sulphate of potassa is added, and the salt is obtained by crystallization. In Italy it is made from alum stone which occurs at Tolfa near Rome. It occurs in volcanic countries, being probably formed by the action of sulphu- rous acid vapours on felspathic rocks.t 1374. Alum has a sweetish taste. It is soluble in five parts of water at 60°, and a little more than its own weight of boiling water . X 1375. Alum crystallizes readily in octohedrons or in segments of octohedrons. When the crystals are heated, they froth up, parting with their water and forming anhydrous alum, alumen exsiccatum of the U. S. Pharmacop. 1376. When alum is ignited with charcoal, a spontaneously in- flammable compound results, which has long been known under the name of Homberg’s Pyrophorus. It is made by mixing equal weights of alum and brown sugar, and stirring the mass over the fire in an iron ladle till quite dry. It is then reduced to powder and introduced into a phial coated with clay in a crucible filled with sand.§ The whole is heated to redness, and when a blue flame appears at the neck of the phial, allow it to burn about five minutes, then remove it from the fire ; stop the phial with a piece of soft clay, and when cool substitute a good cork, to exclude the air. Hare recommends the following method, which affords a pyrophorus that rarely fails. Take 3 parts of lampblack, 4 of calcined alum, and 8 of pearlashes ; mix them thoroughly, and heat them in an iron tube to a bright cherry red for one hour. On removal from the fire the tube should be carefully stopped- \\ hen well prepared and poured out upon a glass plate, and especially when breathed upon, the pyrophorus kindles with a series of small explosions. This pyropho- rus should be removed from the tube with great caution, as it has been found to explode violently on the introduction of a rod for the purpose of loosening it.|| 1377. From some experiments by Gay-Lussac, it appears that ' the essential ingredient of Homberg‘s pyrophorus is sulphuret of * Sulphate of Potassa and Magnesia , KO, SOH-MgO, SO 3 , 87.25 1 eq. sulph. pot. + 60.8 1 eq. sulph. magnes. = 148.05 eq., is formed on mixing solutions of the two salts ; the crystals belong to the oblique prismatic system. Sulph . Ox. Ammon, and Magnes. H-iNO, S03+MgO, SO 3 , 66.25 l eq. sulph. ox. ammon. + 60.8 1 eq. sulph. mag. = 127.05 eq. ; do. with 54 or 6 eq- of water = 181.05- + Large quantities are manufactured in the United States from the purer clays, as that of Martha’s Vineyard. t The variable solubility of alum as stated by different chemists, may have arisen from the want of care in selecting specimens for trial. Hayes informs me that we have several varieties of alum in commerce, which vary in "solubility ; he finds that the pure potash alum is not more soluble than has been stated by Ure, (1 in 16 water at 60°). W. § I usually prefer a small cast iron bottle, or retort. W. || Silliman in Amer. Jour. o fSci x. 367 Alum — Varieties. 331 potassium in a state of minute division. The charcoal and alumina Sect, i. act only by being mechanically interposed between its particles; but when the mass once kindles, the charcoal takes fire and continues the combustion. He finds that an excellent pyrophorus is made by mixing 27 parts of sulphate of potassa with 15 parts of calcined lamp- black, and heating the mixture to redness in a common Hessian cru- cible, of course excluding the air at the same time.* * * § 1378. Alum is of extensive use in the arts, more especially in u ses , dyeing and calico-printing, in consequence of the attraction which alumina has for colouring matter. 1379. Alum, having the same form, composition, appearance, and Other al- taste as the salt just described, maybe made with ammonia,! the ums - sulphate of which replaces sulphate of potassa. It is met with occa- sionally as a natural product, and may be prepared by evaporating a solution of sulphate of ammonia with tersulphate of alumina. A soda alum may also be prepared, similar in form and composi- tion to the preceding alums, except that it contains twentysix equi- valents of water.! This salt is disposed to effloresce in the air.§ 1380. Iron Alum. By mixing sulphate of potassa with tersul- Iron alum, phate of sesquioxide of iron, and crystallizing by spontaneous evapo- ration, crystals are obtained similar to common alum, in form, colour , taste, and composition. This salt has often a pink tint, but is some- times quite colourless. A similar double salt, quite colourless, may be made with ammonia instead of potassa. In both these alums the alumina is simply replaced by an equivalent quantity of oxide of iron. 1381. Chrome Alums. The tersulphate of sesquioxide of chromi- Chrome al- um forms with the sulphates of potassa and ammonia double salts which are exactly similar in form and composition to the preceding varieties of alum. They appear black by reflected, but ruby-red by transmitted light. 1382. Manganese Alum. Mitscherlich obtained this salt by mix- Manganese ing a solution of tersulphate of sesquioxide of manganese with sul- alum * phate of potassa, and evaporating to the consistence of syrup by a very gentle heat.|| 1383. The salts to which the term alum is applied,. are character- Character- ized by two common properties ; they all crystallize in the octohedral peJtiesof system, and they are all constituted as represented by the formula alum. R0S0 3 +R 2 0 3 3S0 3 -|-24Aq. ; where RO represents an eq. of po- tassa, or oxide of ammonium, and R'O 3 any one of the isomorphous sesquioxides of aluminium, iron, manganese, and chromium. As remarked by Berzelius, the formula and crystalline form serve to determine the genus alum, and the oxidized bases its species. IT t. and L. 667. * An. de Ch. et de Ph., xxxvii. 415* + H 4 NO, S0 3 +A1 2 0 3 , 3S0 3 , 66.25 1 eq. sulph. ox. ammon. + 171.7 1 eq. tersulph. alumina = 237.95 eq. 5 do. with 216 or 24 eq. water = 453.95. t Berzelius. § NaO, S0 3 +A1 2 0 3 3S0 3 , 71.4 1 eq. sulph. soda + 171-7 1 eq. tersulph. alumina = 243.1, eq. 5 do- with 234 or 26 eq. water = 477.1. || KO, S0 3 +MnO, SO 3 , 87.25 1 eq. sulph. potassa + 75.8 1 eq. sulph. protox. mang. = 163.05 eq. ; do with 54 or 6 eq. water = 217.05. IT For Sulphates of Protoxide of Iron and Alumina and remarks on Anhydrous Sulphates with Ammonia, see Turner and Liebig’s Chem., 667. 332 Salts — Nitrates. Chap. V. Sulphites. J Effect of heat. Nitrates. Effect of heat, &c. Oxidize. Deflagra- tion. Sulphites. 1384. The salts of sulphurous acid have not hitherto been mi- nutely examined. The sulphites of potassa, soda, and ammonia, made by neutralizing those alkalies with sulphurous acid, are solu- ble in water, but most of the other sulphites are of sparing solubili- ty. The sulphites of baryta, strontia, and lime are very insoluble. The stronger acids decompose all the sulphites with effervescence, owing to the escape of sulphurous acid, which may easily be recog- nised by its odour. Nitric acid, by yielding oxygen, converts the sulphites into sulphates. 1385. When the sulphites of the fixed alkalies and alkaline earths are strongly heated in close vessels, a sulphate is generated, and a portion of sulphur sublimed. In open vessels at a high tempera- ture they absorb oxygen, and are converted into sulphates ; and a similar change takes place even in the cold, especially when they are in solution. The kyposulphates and hyposulphites are of little practical impor- tance.* Nitrates. 13S6. The nitrates may be prepared by the action of nitric acid on metals, on the salifiable bases themselves, or on carbonates. As nitric acid forms soluble salts with all alkaline bases, the acid of the nitrates cannot be precipitated by any reagent. They are readi- ly distinguished from other salts, however, by the characters already described. (484.) 1387. All the nitrates are decomposed without exception by a high temperature; but the changes which ensue are modified by the nature of the oxide. Nitrate of oxide of palladium is decomposed at a moderate temperature. Nitrate of protoxide of lead requires a red heat, by which it is resolved into oxygen and nitrous acid. In some instances the changes are more complicated. 1388. As the nitrates are easily decomposed by heat alone, they must necessarily suffer decomposition by the united agency of heat | and combustible matter. The nitrates on this account are much I employed as oxidizing agents, and frequently act with greater effica- cy even than nitro-hydrochloric acid. The efficiency of nitre, which is the nitrate usually employed for the purpose, depends not only on the affinity of the combustible for oxygen, but likewise on that of the oxidized body for potassa. The process for oxidizing substances by means of nitre is called deflagra- tion , and is generally performed by mixing the inflammable body with an equal weight of the nitrate, and projecting the mixture in small portions at a time into a red-hot crucible. All the neutral nitrates of the fixed alkalies and alkaline earths, together with most of the neutral nitrates of the common metals, are composed of one equivalent of nitric acid, and one equiv- alent of a protoxide. Consequently, the oxygen of the oxide and acid in all such salts must be in the ratio of 1 to 5, the general for- mula being MO-f-NO 5 . * For their characters see T. & L. Elem. 307, and Heeren in Ann. de Chirn. et Phys, ad. 30. Nitrate of Potassa. 333 The only nitrates found native are those of potassa, soda, lime, Sect, i. and magnesia. 1389. Nitrate of Potassa — Nitre , KO+NO 5 , 47.15 1 eq. base-f- Nitrate of 54.15 1 eq. acid =101.3 eq. This salt is an abundant natural pro- potassa. duct, and is principally brought to this country from the East Indies, where it is produced by lixiviation of certain soils.* * * § The rough nitre is in broken crystals, of a brown colour, and more or less deliquescent: exclusive of other impurities, it often contains a very considerable proportion of common salt, which reacting upon the nitre, induces the production of nitrate of soda and chloride of potassium. 1390. In Germany and France it is artificially produced in what Artificial are termed nitre-beds. t Thenard has described the French process production at length. ofwlre - It consists in lixiviating old plaster rubbish , t which when rich in nitre, affords about five per cent. Refuse animal and vegetable matter which has putrefied in contact with calcareous soils produces nitrate of lime, which affords nitre by mixture with subcarbonate of potassa. In the same way it is abundantly pro- duced in some parts of Spain. Exudations containing saltpetre are not uncom- mon upon new walls, where it appears to arise from the decomposition of ani- mal matter contained in the mortar. It was long ago shown by Glauber, that a vault plastered over with a mixture of liriie, wood-ashes, and cows’ dung, soon becomes covered with efflorescent nitre, and that after some months, the mate- rials yield, on lixiviation, a considerable proportion of that salt. 1391. Nitre crystallizes in six-sided prisms, it dissolves in 7 parts Properties, of water at 60° and in its own weight at 212°. Its taste is cooling and peculiar. It contains no water of crystallization, but its crys- tals are never quite free from water lodged mechanically within them. 1392. When exposed to a white heat, nitre is decomposed into Effect of oxygen, (365) nitrogen, and dry potassa. By distilling it in an earth- heat - en retort, or in a gun-barrel, oxygen gas may be obtained in great abundance, one pound of nitre yielding about 12,000 cubic inches, of sufficient purity for common experiments, but not for pur- poses of accuracy. It fuses at a heat below redness, and congeals on codling into cakes called sal prunelle. If the temperature of nitre be so far increased as to allow a por- tion of oxygen to escape, the remaining salt, as Scheele first observed, remains neutral, and in this state it has been considered as forming a nitrite of potassa. 1393. It is decomposed by charcoal at a red heat, and if excess Decompo- sed by of charcoal be used the results are C, C, N and KO-j-CO. It is charcoal, also decomposed by sulphur with different results, according to the temperature and proportions employed. This may be shown by mixing two parts of powdered nitre with one of powdered charcoal, and setting fire to the mixture in an iron vessel under a chimney. § * In Kentucky and other parts of the U. S. the caverns in limestone afford abun- dant supplies of nitrate of lime from which nitre is obtained. The potassa is ob- tained from wood ashes. In some places 1 bushel of the earth yields from 3 to 10 lbs. of the salt. Amer. Jour. 1 . 321. + TraiU de Chim. Elem. ii. 511. t The greater part of the nitre made in France is thus obtained, § The residuum is known as white flux. 334 Salts — JVitrutes. Chap v. Exp. Exp. Combus- tion with phospho- rus, &c. Fulmina- ting pow- der. Use of nitre in chemistry, In the arts. Composition of gunpowders. Mix powdered nitre and sulphur, and throw the mixture, by a little at a time, ' into a red-hot crucible. The sulphur will unite with the oxygen of the nitric acid, and form sulphuric acid; which, combining with the potassa, will afford sulphate of potassa. The production of the latter salt will be proved by dissolv- ing the mass remaining in the crucible, and crystallizing, when a salt will be obtained exhibiting the characters of the sulphate. Mix a portion of sulphur with one sixth or one eighth its weight of nitrate of potassa ; put the mixture into a tin cup ; and raise it, by a small stand, a few inches above the surface of water, contained in a flat shallow dish. Set fire to the mixture, and cover it with a bell-shaped receiver. In this case, also, sulphu- ric acid will be formed; but it will not combine, as before, with the alkali of the nitre, which alkali is present in sufficient quantity to absorb only a part of the acid produced. The greater part of the acid will be condensed on the inner sur- face of the glass bell, and by the water, which will thus become intensely acid. The operation may be repeated three or four times, using the same poriion of water. When the water is partly expelled, by evaporation in a glass dish, con- centrated sulphuric acid remains. II. 1. 520. When phosphorus is thrown upon nitre, and inflamed, a vivid combustion ensues, and a phosphate of potassa is formed. Sulphur sprinkled upon hot nitre burns, and produces a mixture of sulphate and sulphite of potassa. This salt used formerly to be employed in medicine, under the name of Glaser's polyckrest salt. Most of the metals, when in filings or powder, detonate and burn when thrown on red-hot nitre ; some of the more inflammable metals produce in this way a considerable explosion. 1394. A mixture of three parts of nitre, two of dry subcarbonate of potassa, and one of sulphur, forms fulminating powder .* If a little of this compound be heated upon a metallic plate, it blackens, fuses, and explodes with much violence, in consequence of the rapid action of the sulphur upon the nitre. 1395. Nitre is employed in chemistry as an oxidizing agent, and in the formation of nitric acid (471). It is employed in the East Indies for the preparation of cooling mixtures ; an ounce of nitre dissolved in five ounces of water reduces its temperature 15°. It is highly antiseptic and much used in the preservation of animal sub- stances. 1396. Its chief use in the arts is in making gunpowder, which consists of a very intimate mixture of nitre, sulphur, and charcoal.t ♦Or nitre 2 parts, neutral carbonate of potassa 2, sulphur 1, and sea-salt 6, all in fine powder. Ferussac’s Bulletin , 1828. + The proportions vary. For a description of the manufacture, &c., see Ure’s Diet. Arts and Manuf. p. 620, from which the following table of composition of different gunpowders is taken. Nitre. Charcoal. Sulphur. Royal Mills, Waltham Abbey, - France, national establishment, French, for sportsmen, “ “ mining, - U. S. of America, Prussia, ------- Russia, - -- -- -- - Austria (musquet), Spam, Sweden, Switzerland (a round powder), - Chinese, * Theoretical proportions, 75 75 78 65 75 75 73.75 72 76.47 76 76 75 75 15 12.6 12 15 12.5 13.5 13.59 17 10.78 15 14 14.4 13.23 10 12.5 10 20 12.5 11.5 12.63 16 12.75 9 10 9.9 11.79 335 Nitrate of Baryta. 1397. Gunpowder explodes at 600° F. The violence of the eX- Sect. i. plosion depending upon the sudden production of gaseous matter Products of resulting from the action of the combustibles upon the nitre. ^ explosion C, C, N, and S are the principal gaseous results. der\ UnP ° W 1398. Gunpowder maybe inflamed by a violent blow ; if mixed Inflamed with powdered glass, or any other harder substance, and struck with b Y fnctlon * * a heavy hammer upon an anvil, it almost always explodes. 1399. Nitrate of Soda. NaO-j-NO 5 , 31.3 1 eq. base -f- 54.15 1 Nitrate of eq. acid = 85.45 eq. This salt, the cubic nitre of old writers, soda ’ is analogous in chemical properties to the preceding. It crystallizes in oblique rhombic prisms ; but more commonly in the form of an obtuse rhombohedron. It occurs in the soil of India, and covers large districts in Peru. 1400. Mixed with charcoal and sulphur it burns, but more slowly than nitre. It may be advantageously used in the manufacture of both S and N. 1401. Nitrate of Oxide of Ammonium. H 4 N0-f-N0 5 , 26.15, Of ammo- base -J- 54.15 acid — 80.3 eq. This salt may be procured by the nia ’ direct union of ammonia with nitric acid; or more easily by satu- rating dilute N with carbonate of ammonia, and evaporating the so- lution. The state of the salt varies with the temperature at which the evaporation is carried on.t At 100° it is obtained in prismatic crystals isomorphous with nitre ; at 212° it is fibrous, at 300° it forms a compact mass on cooling. The fibrous and compact varie-. ties still contain water, the former 8.2 per cent., and the latter 5.7. All the varieties deliquesce and are very soluble. 1402. It is the source of N (446). When heated to 600 it ex- Use. plodes,$ being resolved into water, N, N, and N. The fibrous vari- ety yields the largest quantity of N ; from one pound of the salt nearly three cubic feet of gas may be obtained. 1403. Nitrate of Baryta. BaO-f-NO 5 , 76.7 1 eq. base -J- 54. 15 Nitrate of 1 eq. acid = 130.85 eq. It maybe obtained by dissolving car- bar Y ta - bonate of baryta in N, evaporating to dryness, redissolving and crystallizing ; it forms transparent anhydrous octohedrons, and is apt The portfire used for firing artillery is mane of three parts of nitre, two of sulphur, and one of gunpowder, well mixed and rammed m cases. Signal lights are generally composed ot mire and sulphur, with a small quantity of nalUohu some metallic sulphuret, as that of arsenic or antimony. Mix 600 grains of nitre with i,sna 18 200 of sulphur and 100 of the yellow sulphuret of arsenic ; put the mixture into a cone of paper, and touch it (out of doors or under a large chimney), with a red-hot iron ; it will hum rapidly with a brilliant white light. Mix 1 0ft or 20Q grains of sulphuret of antimony with the same proportions of nitre and sulphur ; it will burn with a vivid light having a bluish tinge. For other compo- sitions used in pyrotechny, see Ure’s Did. and Gray’s Oper. Chem. 496. * The volume of gases produced from gunpowder is at 60°, 250 times, and at the mo- ment of discharge 1000 times greater than that of the powder;* as each additional of ex ' vol. of gas exerts a force equal to that of the atmosphere, 1000X 15=15.000 lbs. on a pansi0n ’ square inch, which -will project a bullet with a force of 2000 feet in a second. (Murray.) Ure estimates it theoretically at upwards of 2000 times Did. 627. + Davy’s Researches. * Hence it was formerly called nitrum Jlammans . * Robbins’ Essay on Gunnery , and Nicholson’s Jour. iv. 258. 336 Salts — Nitrates. Chap. V. Nitrate of strontia. Nitrate of lime Nitrate of copper. Effect of heat. Exp. Green fire. Red fire. to decrepitate by heat unless previously reduced to powder. It re- quires 12 parts of water at 60° and 3 or 4 of boiling water for solu- tion. It is used as a reagent,* * * § and for preparing pure baryta. t 1404. Nitrate of Strontia. SrO-f-NO 5 , 51.8 1 eq. base -f- 54.15 l eq. acid = 105.95 eq. ; in prisms with 45 or 5 eq. water = 150.95 eq. This salt may be made from the sulphate or carbonate of strontia in the same manner as the preceding. It crystallizes in anhydrous octohedons ; it sometimes contains 30 per cent, of water of crystallization and then assumes the form of the oblique prismatic system.! 1405. Nitrate of Lime. CaO-f-NO 5 , 28.5 1 eq. base -|- 54.15 l eq. acid = 82.65 eq. Nitrate of lime is a deliquescent salt, soluble in 4 parts of water at 60°. it is found in old plaster and mortar, from the washings of which, nitre is procured by the addition of carbonate of potassa (1381). When moderately heated it fuses, and on cooling concretes into a semitransparent mass known as Bald - loin's phosphorus 1406. Nitrate of Protoxide of Copper , CuO+NO 5 39.6 1 eq. base 4- 54.15 acid = 93.75 eq., is obtained by the action of N on copper (455). It crystallizes in prisms of a deep blue colour, soluble in water and alcohol, and deliquescent. By exposure to a heat of 400°, a green insoluble subsalt is obtained.il 1407. When this salt is heated to redness, it yields pure oxide of copper. It is sometimes used as an escharotic. It is decomposed by tin with the evolution of heat and N. Spread a drachm or two of the salt in coarse powder on a piece of tin-foil, se- veral inches square, moisten it with a few drops of water, fold it up quickly, and lay it upon a plate ; much heat will be evolved and the metal often takes fire. IT 1408. Nitrates of the Oxides of Mercury — Nitrate of the Pro- toxide, , HgO+NO 5 , 210 base 1 eq. + 54.15 1 eq. acid = 264.15; in crystals with 18 or 2 eq. water = 282.15 eq. * If a moderately strong solution of this salt he added to N, a precipitation of nitrate of baryta lakes place, in consequence of the insolubility of the nitrate in the acid ; hence in using nitrate of baryta as a test of S, the latter should be considerably diluted previous to its application. B. t This salt is employed in pyrotechny to impart a green colour to flame. The green fire is composed of 13*parts sulphur, 77 nitrate of baryta, chlorate of potassa 5, arsenic 2, and charcoal 3. The nitrate should be well dried, powdered, and mixed with the other ingredients, the powdered chlorate being added afterwards, and mixed, with caution, on a sheet of paper, and with an ivory or wooden spatula. tThis salt is used in the red, fire employed at the theatres, which consists of 40 parts dry nitrate of strontia, 13 sulphur, 5 chlorate of potassa. and 4 sulphuret of anti- mony. The chlorate and sulphuret should be separately powdered, and mixed on pa- per with the other ingredients j a very small quantity of powdered charcoal may also be added. § Birch’s Hist of Roy. Soc., iii. 323. H The neutral salt contains 3 eq. of constitutional water, and may be represented by the formula CuO NO’ 3 HO ; the subsalt is supposed to be similarly constituted, being a nitrate of water with 3 eq. of constitutional oxide of copper, and may be represented by the formula HO NOo 3CuO. T. 673. IT Nitrate of Protoxide of Lead PbO+NO 5 , 111.6 1 eq. base -f 54.15 1 eq. acid = 165.75 eq., is formed by digesting litharge in dilute N. Nitrate of Silver. 337 Sect. T. Protoni- trate of mercury. Pernitrate of mercury. Nitrate of the Peroxide, Hg0 2 -)-N0 5 , 218 1 eq. base -f- 54.15 acid = 272.15. Dinitrate , 2HgQ 2 -|-N0 5 , 436 2 eq. base -f- 54.15 acid — 490.15 eq. The protonitrate is obtained by digesting mercury in N, diluted with 3 or 4 parts of water, until the acid is saturated, and then al- lowing the solution to evaporate spontaneously in an open vessel. The solution always contains, at first, some nitrate of the peroxide ; but if metallic mercury is left in the liquid, a pure protonitrale is gradually deposited.* * * § 1409. When mercury is heated in an excess of strong N, it is dissolved with brisk effervescence, owing to the escape of N, and transparent prismatic crystals of the pernitrate are deposited as the solution cools. When put into hot water it is resolved into a solu- ble salt the composition of which is unknown, and into a yellow dinitrate of the peroxide ;t this is the nitrous turpeth of old wrh ters.l 1410. Nitrate of Oxide of Silver , AgO-f-NO 5 , 116 1 eq. base -j- 54.15 1 eq. acid — 170.15. Nitric acid diluted with three parts of water, readily dissolves silver, with the disengagement of N. If the acid contain the least portion of hydrochloric, the solution will be turbid, and deposit a white powder ; and if the silver contain copper, it will have a permanent greenish hue ; or if gold, that met- al will remain undissolved in the form of a black powderA The solution should be perfectly clear and colourless ; it is caus- tic, and tinges animal substances of a deep yellow, which, by ex- posure to light, becomes a deep purple, or black stain, and is indeli- ble, or peels off with the cuticle : it consists of reduced silver. 1411. It may be obtained in transparent tabular crystals, by evap- Crystals, oration. These crystals, which are anhydrous, undergo the igneous fusion at 426°, and yield a crystalline mass on cooling ; but at 600° or 700°, complete decomposition ensues, the acid being resolved into O and N, and metallic silver is left. 1412. When heated in a silver crucible it fuses, and if cast into Lunar small cylinders, forms the lapis infernalis , or lunar caustic of causUc - Nitrate of silver. * According to Mitscherlich, it is a sub-salt, in which the protoxide and acid are in the ratio of 20S to 36. The neutral protonitrale is said to be obtained in crystals, by dissolving the former salt in pure water, acidulated with N, and evaporating sponta- neously without the contact of metallic mercury or uncombined oxide. Pog. Ann. ix. 387. t Ann. de Ch. et Phys. xix. t In preparing these salts for different purposes, great attention should be paid to the strength of the acid employed, the temperature, and the relative proportions, as all these circumstances have an important influence upon the oxidation of the mercu- ry and the nature of the resulting salt. R. § A very useful solvent of silver is formed by dissolving one part of nitre in about Nit r 0 -suiphim eight or ten parts by weight of concentrated sulphuric acid* This compound (which acid, may be called nitro-sulphuric acid) when heated to between 100° and 200° F. dis- solves one fifth or one sixth its weight of silver, with an extrication of nitrous gas ; and leaves untouched, any copper, gold, lead, or iron, with which the silver may be combined. Hence it is a most useful agent in extracting silver from old plated goods. The silver may be recovered from the solution by adding common salt, and the chloride of silver formed may be decomposed by carbonate of soda. 43 338 Salts — Nitrates. Chap V. Solubility. Effect of light. Action of sulphur, &c. Exp. Exp. Exp. Arbor Di- anas. Indelible ink. pharmacy ; the argenti nitras of the Pharmacop. In forming this preparation, care should be taken not to overheat the salt, and the moulds should be warmed. When pure it is white and transparent, and does not deliquesce on exposure to the air ; but common lunar caustic is often dark and opaque, and dissolves imperfectly in water, owing to some of the nitrate being decomposed during its prepara- tion. It is impure, also, containing nitrate of protoxide of copper, and traces of gold. 1413. The pure salt is soluble in its own weight of cold and in half its weight of hot water. It dissolves also in 4 times its weight of alcohol. Its aqueous solution, if preserved in clear glass ves- sels, undergoes little or no change even in the direct rays of the sun ; but when exposed to light, especially to sunshine, in contact with paper, the skin, or any organic substance, a black stain is pro- duced, owing to decomposition of the salt and reduction of its oxide to the metallic state. This change is so constant, that this salt constitutes an extremely delicate test of the presence of organic matter. Its solution is a delicate test also of chlorine and hydro- chloric acid. 1414. Sulphur, phosphorus, charcoal, hydrogen, and several of the metals, decompose this nitrate. A few grains mixed with a little sulphur, and struck upon an anvil with a heavy hammer, produce a detonation ; phosphorus occasions a violent explosion when about halt a grain of it is placed upon a crystal of the nitrate, upon an anvil, and struck sharply with a hammer; and if heated with charcoal, it defla- grates, and the metal is reduced. If a piece of silk dipped into a solution of nitrate of silver be exposed while moist to a current of hydrogen gas, it is first blackened, and afterwards becomes iridescent from the reduction of portions of the metal/ * A stick of clean phosphorus, introduced into a solution of nitrate of silver, soon becomes beautifully incrusted with the metal, which separates upon it in arborescent crystals. A plate of copper occasions a brilliant precipitation of silver, and the copper is oxidized and dissolved by the acid. The precipitation of silver by mercury produces a peculiar ar- rangement, called the arbor Diana (1244.) 1415. Nitrate of silver is employed for writing upon linen under the name of indelible or marking ink , t and is an ingredient in many of the liquids which are sold for the purpose of changing the col- our of hair; but, when thus employed, it should be very much di- luted, and used with extreme caution. 1416. White paper, or white leather, when stained with a solution of nitrate of silver, in the proportion of ten parts of water to one of the salt, undergoes no change in the dark; but when exposed to the light of day, it gradually ac- quires colour, and passes through a succession of changes to black. The com- mon sun-beams, passing through red glass, have very little effect upon it; yellow and green are more efficacious; but blue and violet produce the most decidedly powerful effects. Hence this property furnishes a method of copying paintings on glass, and transferring them to leather or paper. t ♦See Mrs Fulhame’s Essay on Combustion. + 100 grs. of the nitrate may be dissolved in distilled water, and 2 or 3 drachms of mucilage be added. The preparatory liquid maybe made with half an ounce of car- bonate of soda dissolved in 2 or 3 ounces of water, adding half an ounce of mucilage. This ink is discharged by chlorine and ammonia. t See description of the process by Wedgwood in Nicholson’s Jour. iii. 167, and Talbot on Photogenic drawing, Lond. and Edin. Phil. Mag. xiv. 339 Chlorate of Potassa. By a similar process, ivory may be covered with silver. Let a slip of ivory Sect. I.' be immersed in a dilute solution of pure nitrate of silver, till the ivory has ac- g-| ver j n In- quired a bright yellow colour. Then remove it into a tumbler filled with dis- • ° tilled water, and expose it to the direct light of the sun. After two or three hours’ exposure, it will have become black ; but on rubbing it a little, the sur- face will be changed into a bright metallic one, resembling a slip of pure silver. As the solution penetrates deep into the ivory, the bright surface when worn away, is replaced by a succession of others. H. 2. 124. 1417. Nitrites . — Our knowledge of the compounds of nitrous acid with alkaline bases is imperfect. 1418. Chlorates . — The salts of chloric acid are very analogous to chlorates, the nitrates. As the chlorates of the alkalies, alkaline earths, and most of the common metals, are composed of 1 eq. of chloric acid and 1 eq. of a protoxide, M0-|-C10 5 , it follows that the oxygen of the latter to that of the former is in the ratio of 1 to 5. 1419. The chlorates are decomposed by a red heat, nearly all of Decompo- thern being converted into metallic chlorides, with evolution of pure sedbyheat. oxygen gas. They deflagrate with inflammable substances with greater violence than nitrates, yielding oxygen with such facility that an explosion is produced by slight causes. Mix a few grains of sulphur with three times its weight of chlorate of potas- g X p sa, wrap the mixture in tin foil, and strike it forcibly upon an anvil.* 1420. All the chlorates are soluble in water, and are distin- solubility guished by the action of strong hydrochloric and sulphuric acids, the ofchlo- former of which occasions the disengagement of chlorine and pro- rates - toxide of chlorine (641), and the latter of peroxide of chlorine (652). t. 1421. Chlorate of Potassa. This salt, formerly called oxymuriate Chlorate of or hyper -oxijmuriate of potassa , is formed by passing chlorine potassa. through a solution of potassa. Chloride of potassium is one of the results, the other is the chlorate of potassa. This salt is prepared, upon the large scale, by charging Woulfe’s bottles (634 jq ow 0 b_ note), with solution of carbonate of potassa, and passing chlorine slowly through tained. it :t the gas is absorbed, and the liquor effervesces chiefly from the escape of car- bonic acid; when this has ceased, the liquor may be put aside in a cold dark place for about 24 hours, when it will be found to have deposited a considerable portion of the crystallized chlorate which may be taken out, drained, and purified by solution in hot water, which, during cooling again, deposits the salt in white crystalline scales. The liquor is generally of a pinkish hue, from the pre- sence of manganese. 4 1422. The crystals are four and six sided scales, of a pearly lustre. Crystals. Its forms, according to Brooke, belong to the oblique prismatic sys- tem. It is soluble in 16 times its weight of water at 60°, and in two and a half of boiling water. It is anhydrous, and when exposed to a temperature of 400° or 500°, fuses. By an increase of heat, nearly 4) to redness, pure oxygen gas is disengaged (365-4). 1423. It acts very energetically upon many inflammables. onlnflam' Rub two grains into powder in a mortar, and add one grain of sulphur. Mix ma bi eg , them very accurately, by gentle triture, and then, having collected the mixture Exp. * This experiment requires caution, and is made more safely by placing the mix- ture under a long bar of wood, fitted to a groove, which can be driven down by a smart blow. W. t The tube which is immersed in the alkaline solution, should be at least half an inch in diameter, to prevent its being choaked by crystals that may form, t See another process by Hayes in Amer. Jour., xvii. 408. 340 Salts — Chlorates. Chap. V. Exp. Action of sulphuric acid. Exp. Exp. Caution. Chlorate of baryta, Process. Crystals. M&tchr*. Percussion powder. Snbititu'ed for nitre in gun- powder. to one part of the mortar, press the pestle down upon it suddenly, and forcibly. A loud detonation will ensue. Mix five grains of the salt with half the quantity of powdered charcoal in a similar manner. On triturating the mixture strongly, it will inflame, especially with the addition of a grain or two of sulphur, but not with much noise. 1424. When sulphuric acid is poured upon mixtures of this salt and combustibles, instant ignition ensues in consequence of the evo- lution of peroxide of chlorine; and when sulphuric or nitric acids are poured upon similar mixtures under water by means of a long funnel, inflammation also ensues. Mix a 9mall quantit)' of sugar with half its weight of the salt, and on the mix- ture pour a little sulphuric acid.* A sudden and vehement inflammation will be produced. Phosphorus may be inflamed under the surface of the water, by means of this salt. Put into a tall wine glass, one part of phosphorus with two of the salt ; fill it nearly with water, and slowly pour in, by means of a glass tube, reaching to the bottom, three or four parts of sulphuric acid. The phosphorus takes fire, and burns vividly under the water. These experiments require caution lest the in- flamed substances should be thrown into the eyes. Oil may also be thus in- flamed on the surface of water, the experiment being made with the omission of the phosphorus, and the substitution of a little olive or linseed oil. 1425. Chlorate of potassa should not be kept mixed with sulphur in considerable quantity, as the mixture may explode spontane- ously.! 1426. A few grains of chlorate of potassa put into a tea-spoonful of hydrochloric acid, and then diluted with water, form an extempo- raneous bleaching liquor. 1427. Chlorate of Baryta is the compound employed in the for- mation of chloric acid (657.) The readiest mode of preparing it is, to digest for a few minutes a concentrated solution of chlorate of potassa with a slight excess of silicated hydrofluoric acid, the alkali is precipitated in the form of an insoluble double fluoride of silicon and potassium, while chloric acid remains in solution. The liquid after filtra- tion is neutralized by carbonate of baryta, which throws down the excess of sili- cated hydrofluoric acid, and chlorate of baryta is left in solution By evaporation it yields prismatic crystals, requiring for solution four times their weight of cold, and a still smaller quantity of hot water. They are composed of 76.7 parts 1 eq. of baryta, 75.42 I eq. of chloric acid, and 9 or 1 eq. of water. T. 677. * A mixture of this kind is the basis of matches, for the purpose of procuring instan- taneous light- The bottle into which they are dipped, contains concentrated sulphuric acid which is prevented from escaping by a quantity o! finely spun glass or the fibres of amianthus. 30 parts of powdered chlorate of potassa, 10 cf powdered sulphur, 8 of sugar, 5 of gum arahic. and a little cinnabar. Tne sugar, gum, and salt are first rub- bed together into a paste with sufficient water; the sulphur is then added, and the whole being well beaten together, small brimstone matches are dipped in, so as to retain a thin coat of the mixture upon their sulphuretted points. ^ A very convenient method of obtaining a flame, is to dip the end of a piece of paper “ in spirits of turpentine, drop upon it a few scales of the salt, aud then a drop of sul- phuric acid One of the compounds occasionally employed in percussion gun-locks contains this salt ; 10 parts of gunpowder are rubbed with water, and the soluble part poured off; the remaining paste is then mixed with 5 $ parts of finely powdered chlorate of potassa, and a drop of it put into each of the small copper caps adapted to the peculiar touch- hole of the gun. The great disadvantage of this compound is that it forms products which corrode the toucnhole; lulminating mercury is preferable. t It was proposed by Berthollet to substitute this salt for nitre, in the preparation of gunpowder and the attempt was made at Essone in 1788 ; but, as might have been expected, no sooner was the mixture of the chlorate with the sulphur and charcoal submitted to trituration than it exploded with violence, and proved fatal to several people. Iodates. 341 1428. Perchlorates. The neutral proto-salts of perchloric acid Sect - r consist of 1 eq. acid and base, as is expressed by the formula MO+ Perchlo- C1 2 0 7 . Most of these salts are deliquescent, very soluble in water, rates - and soluble in alcohol. Heated to redness they yield oxygen gas Effect of and metallic chlorides ; and they are distinguished from the chlorates heat. by not acquiring a yellow tint on the addition of hydrochloric acid. 1429. The solubility in alcohol of the perchlorates of baryta, soda, Solubility and oxide of silver, is a property which the analytical chemist may a f( ^° ° avail himself of in analysis, for the separation of potassa and soda from each other. 1430. Chlorites. The alkaline salts of chlorous acid are readily Chlorites, made by transmitting a current of chlorous acid gas into a solution of the pure alkalies. They are soluble in water, and are remarkable for their bleaching and oxidizing properties. By the latter proper- Recog- ties and the evolution of chlorous acid on the addition of any of the nised. stronger acids their presence is readily recognised. 1431. Hypochlorites. The hypochlorites may be produced by the Hypochlo- addition of chlorine gas on the salifiable bases. The most impor- rites, tant of them is hypochlorite of lime, the well known bleaching powder (901). During absorption of the chlorine, chloride of calci- um and hypochlorite of lime are produced in equivalent propor- tions.^ 1432. It is a dry white powder, with the odour of chlorine and a Bleaching strong taste. It dissolves partially in water and the solution bleaches ; powder, it contains both chlorine and lime; the undissolved portion is hy- drate of lime, retaining a small quantity of chlorine. The solution is decomposed by exposure, its chlorine being set free, and carbonate of lime generated. 1433. It is largely employed in bleaching, for the purpose of re- Uses, moving offensive odours, and of arresting putrefaction.! With hy- drochlorate of ammonia it affords nitrogen gas from the decomposi- tion of the ammonia (420). Into a small tubulated retort introduce the bleaching salt, add sufficient water to bring it to the consistence of cream; drop in lumps of the hydrochlorate of ammonia ; effervescence will take place, and the nitrogen be disengaged. 1434. Iodates. The general character of the iodates is similar to Iodates, that of the chlorates. In all neutral protiodates the oxygen contained ^j e c ^| r e a n c er ' in the oxide and acid is in the ratio of 1 to 5. They deflagrate with ler) combustibles, and yield oxygen gas at a red heat, a metallic iodide remaining. 1435. The iodates are recognised by the facility with which their B ycog- acid is decomposed by deoxidizing agents. Hydrosulphnric acid oc- ruse casions the formation of hydriodic acid, by y^ielding hydrogen to the iodine. Hence an iodate of potassa may be converted into the iodide by transmitting a current of HS through its solution. The iodates are very sparingly soluble, or actually insoluble in water, excepting the iodates of the alkalies. 1438. Iodate of Potassa may be procured by adding iodine to a Todate of concentrated hot solution of pure potassa, until the alkali is com-P° tassa ’ pletely neutralized. * Turner. t For details respecting its manufacture, &c., see Ure’s Did. of Arts, &c., and for the methods of estimating the value of this substance, see page 243. 342 Chap. V. Process, Another. Henry’s. Use. Phos- phates. Three fam- ilies. Protophos- phates. Triphos- phates. Effect of heat. Soluble phosphates detected, FcrrtuU. W Her a base. Test of phos- phoric aciJ. Salts — Phosphates. The liquid, which contains an iodate and iodide is evaporated to dryness by " a gentle heat, and the residue, when cold, is treated by repeated portions of boil- ing alcohol. The iodate, which is insoluble in that menstruum, is left, while the iodide of potassium is dissolved. A better process is founded on the property which iodide of potassium pos- sesses, of absorbing oxygen while in the act of escaping from decomposing chlo- rate of potassa. For this purpose, Iodide of potassium is fused in a capacious Hessian crucible, and when, after removal from the fire, it is yet semi-fluid, successive portions of pulverized chlo- rate of potassa are projected into it, stirring well after each addition. The ma- terials froth up considerably, and when the action is over, a white, opaque, cellular mass remains, easily separable from the crucible; tepid water dissolves out the chloride of potassium, and leaves the iodate. Convenient proportions are one part of iodide of potassium and rather more than one and a half of chlo- rate of potassa.* 1437. From this salt all the insoluble iodates may be procured by double decomposition. Thus iodate of baryta may be formed by* | mixing chloride of barium with a solution of iodate of potassa. The Bromates have many characters in common with the chlo- rates and iodates. t. 1438. Phosphates. As there are three isomeric modifications of 1 the same acid, which have been described under the names of phos- phoric, pyrophosphoric , and vietaphosphoric acid (page 174), it is ne- cessary to have three corresponding families of salts, the phosphates, i pyrophosphates and metaphosphates .t 1439. All the protophosphates which are neutral in composition are soluble in water, and redden litmus paper ; whence they are com- monly called superphosphates. The triphosphates, except those j of the pure alkalies, are either sparingly soluble or insoluble in wa- ter ; but they are all dissolved bv dilute nitric or phosphoric acid, being converted into the soluble phosphates. All the triphosphates with fixed and strong bases bear a red heat without change ; but the phosphates and diphosphates, to judge from experiments on the soda : salts, are converted into metaphosphates and pyrophosphates. Most of the phosphates of the second class of metals are resolved into | phosphurels by the conjoint agency of heat and combustible matter. The phosphates of the alkalies are only partially decomposed un- der these circumstances, and the phosphates of baryta, strontia, and lime, undergo no change. 1440. The presence of a soluble phosphate may be distinguished by the test for phosphoric acid-t The insoluble phosphates are decomposed when boiled with a * Jour, de Phar., July, 1832 t An cquiv. of each of the three acids, is a compound of 31. 4 parts or 2 eq. of phos- J ihorus -f- 40 parts or 5 eq. of oxygen = 71.4, expressed by the formula P 2 !) 5 . To brm a salt neutral in composition 1 eq. of an alkaline base is requisite, and in the case of any protoxide, indicated by MO. the general formula will be MO-f-FHJ 5 . If 2 eq. of a protoxide are united with one of the acid, we have a disalt, 2MCH-P 2 0 5 ; and if 3 eq. of a base combine with 1 eq. of the acid, it is a trisalt , 3M04-P 2 0 5 . It seems also that water plays the part of an alkaline base towards each of the three acids, either alone or conjointly with another base; the salts with such compound bases can scarcely he viewed in the light of double salts, since the two bases act together as one electro-positive element. t When phosphoric acid is neutralized by ammonia and mixed with nitrate of oxide of silver, the yellow phosphate of that oxide subsides, a character by which it is dis- tinguished from all adds, except the arsenious. T. 316. 343 Triphosphates . strong solution of carbonate of potassa or soda, the acid uniting with Sect, i. the alkali so as to form a soluble phosphate ; the earthy phosphates Insoluble, require continued ebullition, and should preferably be fused with an decompo- alkaline carbonate, like an insoluble sulphate, t. 1441. Triphosphate of Soda. 3N0-j-P 2 0 5 , 93.9 3 eq. base -f- . 71.4 1 eq. acid = 165.3 ; in crystals with 216 or 24 eq. water = Soda,° S 381.3. This salt is made by adding pure soda to a solution of the Process, succeeding compound until the liquid feels soapy to the fingers, an excess of soda not being injurious. The liquid is then evaporated until a pellicle appears, and the crystals which form on cooling are quickly redissolved in water and recrystallized. 1442. The crystals are colourless six-sided prisms, with a strong properties, alkaline taste and reaction, requiring five times their weight of wa- ter at 60° for solution. They fuse at 170°, and may be exposed to a red heat, without losing their characters of a phosphate. The feeblest acids deprive the salt of one third of its soda. 1443. Triphosphate of Soda and Basic Water. 2NaO.HQ-|- Triphos- P O 5 , 62.6 2 eq. soda, 9 l eq. water -f- 71.4 1 eq. acid = 143 ; in goda^and crystals with 216 or 24 eq. water =' 359, with 135 or 15 eq. water basic wa- — 278. This salt is the most common of the phosphates, .'being' p^ cess manufactured on a large scale by neutralizing with carbonate of soda the acid phosphate of lime procured by the action of sulphuric acid on burned bones (p. 169). It is generally described as the neutral phosphate of soda. 1444. It crystallizes best out of an alkaline solution ; but however crystals, prepared is always alkaline to test paper. The crystals effloresce, and require four times their weight of cold, and twice their weight of hot water for solution. 1445. Acid Triphosphate of Soda and Basic Water. NaO. 2HO AcidTriph. -f-P 2 0 5 , 31.3 1 eq. sod. 18 2 eq. water -f- 71.4 1 eq. acid *= 120.7 ; and in crystals with 18 or 2 eq. water = 138 t 7. This salt, commonly water ‘ called biphosphate of soda, may be formed by adding phosphoric acid to a solution of carbonate of soda, or to either of the preceding phos- phates, until it ceases to give a precipitate with chloride of barium. Crystals. Being very soluble in water, the solution must be concentrated in order that it may crystallize. This salt is capable of yielding two different kinds of crystals without varying its composition.^ 1446. Triphosphate of Soda, Oxide of Ammonium, and Basic Water, NaO., H 4 NO. HG+P 2 0 5 , 31.3 1 eq soda, 26.15 1 eq. ox. am. 9 1 eq. water -j- 71.4 1 eq. acid .== 137.85 eq. ; in crystals with 72 or 8 eq. water =209.85. Prepared by mixing 1 eq. of hydrochlorate of ammonia and 2 eq. of the neutral phosphate of soda, each being previously dissolved in a .small quantity of boiling water. It has been long known as microcosmic salt, and is much mic salt*" * For which see Liebig and Turner’s Elem. 684. Triphosphate of Potassa. 3KO+P20 5 , 141.45 3 eq. base + 71.4 1 eq. acid = 212.85. Formed by adding caustic potassa in excess lo a solution of phosphoric acid. Triphosphate of Potassa and Basic Water. 2K0.HQ+P 2 0 5 , 94.3 2 eq. KO, 9 1 eq. HO -j- 71.4 1 eq. acid — 174.7. Prepared by neutralizing the superphosphate of lime from bones with carbonate of potassa. Acid Triphosphate of Potassa and Basic Water. KO 2 HO+P 2 O 5 , 47.15 1 eq. pot. 18 2 eq. water + 71.4 1 eq. acid — 136.55 eq. Formed by adding phosphoric acid to carbonate of potassa until the liquid ceases to give a precipitate with chloride of bari- um, and setting aside to crystallize. 344 Chap. V. Phosphates of lime, Triphos- phate, Acid tri- phosphate and basic water. Of magne- Phosphate of ammonia and magne- sia. Salts — Triphosphates. employed in experiments with the blotv-pipe. When heated it parts with its water and ammonia, and a very fusible metaphosphate of soda remains.* 1447. Phosphates of Lime. The peculiar compound called the bone phosphate ,t exists in bones after calcination, and falls as a gela- tinous precipitate on pouring chloride of calcium into a solution of the rhombic phosphate of soda, or on adding ammonia to a solution of any phosphate of lime in acids. t 1448. Triphosphate of Lime and Basic Water , 2CaO. HO-f- FO 5 , 57 2 eq. lime, 9 1 eq. water -f- 71.4 1 eq. acid = 137.4 eq. This salt is commonly called neutral phosphate ; it falls as a granular precipitate when the rhombic phosphate of soda is added drop by drop to chloride of calcium in excess. The triphosphate of lime occurs in the mineral called apatite. 1449. Acid Triphos. of Lime and Basic Water , Ca02H0 -j- FO 3 , 28.5 1 eq. lime, IS 2 eq. water -(-71.4 1 eq. acid = 117.9. This is called the biphosphate from its acid reaction, and is formed by dissolving either of the preceding salts in a slight excess of phos- phoric acid. It exists in the urine. 1450. Triphosphate of Magnesia and Basic Water, is formed by mixing hot saturated solutions of the rhombic phosphate of soda and sulphate of magnesia, and separates on cooling in small crys- tals which contain 13 eq. of water to 1 of the salt. 1451. The phosphate of ammonia and magnesia , subsides as a pulverulent granular precipitate from neutral or alkaline solutions, containing phosphoric acid, ammonia, and magnesia. It is readily dissolved by acids and is sparingly soluble in pure water, especially when carbonic acid is present ; but it is insoluble in a solution of most neutral salts, such as hydrochlorate of ammonia. It consti- tutes one variety of urinary concretions, according to Berzelius it consists of Phosphoric acid . 71.4 Magnesia . 41.4 Ammonia . 34.3 Water 90 1 eq. 2 eq. 10 eq. POo. 2MgO. 2H3N. 1HO. Effect of beat. Triphos- phate of silver. 1452. By a red heat it loses its water and ammonia, and the residue is diphosphate of magnesia, which contains 36.67 per cent, of pure magnesia. At a strong red heat it fuses, and appears when cold as a white enamel. 1453. Triphosphate of Oxide of Silver subsides, of a character- istic yellow colour, (1440) when the rhombic phosphate of soda is mixed in solution with nitrate of oxide of silver, N being set free at the same time. This salt is very soluble in N and P, forming the * Triphosphate of Oxide of Am. and Basic M ater, 2IPNO- HO P 2 0 5 , 52.30 2 eq. ox. Am. 9*1 eq water + 71.4 l eq. acid = 132-70 eq., formed hy adding ammo- nia to concentrated phosphoric acid until a precipitate appears. On applying heat, the precipitate is dissolved, and on abandoning the solution to itself, the neutrai salt crystallizes- The crystals are oblique rhombic prisms, the smaller angle being 84° 30/. t Bone Phosphate of Lime , 8Ca0-f-3P-*05, 2 23 8 eq. base + 214.2 3 eq. acid = 442.2 eq. t Triphosphate of Lime, 3Ca0+P 2 0 5 , 85.5 3 eq. base + 71.4 1 eq. acid = 156.9. Chromates . 345 soluble phosphate and in ammonia. It is blackened by exposure to Sect, i. light. 1454. When phosphoric acid, with the aid of heat is made to combine with 2 eq. either of water or some fixed base, the modifica- tion of phosphoric acid, termed pyrophosphoric (569) is procured. Pyrophos- Combined. with bases it forms pyrophosphates* phates. 1455. The oxides of most metals of the second class yield with this acid insoluble or sparingly soluble salts, which may be pre- pared by double decomposition with dipyrophosphate of soda-t 1456. Arseniates . Arsenic acid resembles the phosphoric in com- Arseniates. position and in many of its properties. It forms tribasic salts. Those with 2 eq. of basic water are soluble in water and redden litmus; with 1 eq. of basic water, in which the oxygen of the alkaline base and acid is as 2 to 5, the salt is usually called a neutral arseniate. When no basic water is present, the salt is usually described as a subarseniate. 1457. Many of the arseniates bear a red heat without decomposi- Effect of tion, but they are all decomposed when heated to redness along with heat - charcoal, metallic arsenic being set at liberty. The soluble arseniates are easily recognised by the tests for arsenic Arseniates (1053), and the insoluble arseniates, when boiled in a strong solu- recognised, tion of the fixed alkaline carbonates, are deprived of their acid, which may then be detected in the usual manner. The free alkali, however, should first be exactly neutralized by pure nitric acid. 1458. Arsenites. The arsenites of potassa, soda, and ammonia, Arsenites. may be prepared by acting with those alkalies on arsenious acid; they are very soluble in water, have an alkaline reaction, and have Pro P erties * not been obtained in regular crystals. Most of the other arsenites are insoluble, or sparingly soluble, in pure water ; but they are dis- solved by an excess of their own acid, with great facility by N, and by most other acids with which their bases do not form insoluble compounds. The insoluble arsenites are easily formed by double decomposition. 1459. All the arsenites are decomposed when heated in close vessels, the arsenious acid being either dissipated in vapour, or con- verted, with disengagement of some metallic arsenic, into arseniates. Heated with charcoal or black flux, the acid is reduced (1054.) 1460. The soluble arsenites, if quite neutral, are characterized by Soluble ar- forming a yellow arsenite of oxide of silver when mixed with the senites dis- nitrate of that base, and a green arsenite of protoxide of copper, tinguis e Scheele's green , with sulphate of that oxide. When acidulated with Schoeie , s acetic or hydrochloric acid, hydrosulphuric acid gas causes the forma- tion of orpiment. The insoluble arsenites are all decomposed when boiled in a solution of carbonate of potassa or soda. The arsenite of potassa is the active principle of Folder's arsenical solution. 1461. Chromates. The salts of chromic acid are mostly either Chromates, of a yellow or red colour, the latter tint predominating whenever * For which see Turner and Liebig’s Elem. 687. + For description of Metaphosphates see T. and L. Elem. 6S9 ; and Graham in Philos. Trans. 1833, part 2d. 44 346 Salts — Borates. Chap V. Effect of heat, Anil com- bustibles. Distin- guished. Chromate of poiassa. Properties. Bichro- mate. Crystals. Insoluble chromates. Chromate of lead. Borates. Dichromate. Process. the acid is in excess. The chromates of oxides of the second class of metals are decomposed by a strong red heat, by which the acid is resolved into the green oxide of chromium and oxygen gas ; but the chromates of the fixed alkalies sustain a very high temperature without decomposition. They are all decomposed by the united agency of heat and combustible matter. The neutral chromates of protoxides are similar in constitution to the sulphates, being formed of 1 eq. of the base and l of chromic acid, the formula being MO+ CrO 3 . 1462. The chromates are in general sufficiently distinguished by their colour. They may be known chemically by the following characters : on boiling a chromate in hydrochloric acid mixed with alcohol, the chromic acid is at first set free, and is then decomposed, a green solution of the chloride of chromium being generated. 1463. Chromates of Potassa. The neutral chromate from which all the compounds of chromium are directly or indirectly prepared, is made by heating to redness the native oxide of chromium and iron, chromate of iron, with nitrate of potassa (1077), when chromic acid is generated, and unites with the alkali of the nitre. 1464. Chromate of potassa has a cool, bitter and disagreeable taste ; it is soluble to great extent in boiling water, and in twice its weight of that liquid at 60°; but it is insoluble in alcohol. Ac- cording to Thomson it is neutral in composition, consisting of 52 parts or 1 eq. of chromic acid, and 47.15 parts or 1 eq. of potassa.* 1465. Bichromate of Potassa is made in large quantity for dye- in?* .by acidulating the neutral chromate with sulphuric, or still bet- ter with acetic acid, and allowing the solution to crystallize by spontaneous evaporation. When slowly formed it is deposited in four-sided tabular crystals, the form of which is an oblique rhombic prism. They have a rich red colour, are anhydrous, and consist of 1 eq. of the alkali, and 2 eq. of chromic acid.t They are soluble in about ten times their weight of water at 60°, and the solution reddens litmus paper. 1466. The insoluble salts of chromic acid such as the chromates of baryta and oxides of zinc, lead, mercury and silver, are prepared by mixing the soluble salts of those bases with a solution of chro- mate of potassa. The yellow chromate of lead is much used as a pigment, it consists of 1 eq. of acid and 1 eq. of oxide. t 1467. Borates. Boracic acid is a feeble acid and neutralizes im- perfectly, hence the borates of soda, potassa and oxide of ammo- nium hare always an alkaline reaction. For the same reason, when the borates are digested in any of the more powerful acids, the bo- * Ann. of Philos, xvi. t Thomson. t The chromate of oxide of zinc may be used for the same purpose. A dichromate composed of 1 eq. chromic acid and 2 ea- protox. lead, may be formed by boiling the carbonate of that oxide with excess of chromate of potassa. It is of a beautiful red colour, and has been recommended as a pigment {Ann. Philos, xxv. 303.) It may also be made by boiling the neutral chromate with ammonia or lime water ; or by fusing nitre at a low red heat, and adding chromate of oxide of lead by degrees un- til the nitre is nearly exhausted. The chromate of potassa and nitre are then re- moved by water, and the dichromate is left crystalline in texture, and of a beautiful tint. ( Pog . An. xxi. 580.)* * For Chromates of Silver, and of Chloride of Potassium, see T. and L. Elem. 695. 347 Carbonate of Potassa. tacic acid is separated from its base. But at a red heat this acid Se&t - l - decomposes all salts, the acid of which is volatile. 1463. The borates of the alkalies are soluble in water, but most Properties, of the salts of this acid are of sparing solubility. They are not de- &c - composed by heat, and the alkaline and earthy borates resist the action of heat and combustible matter. They are remarkably fusi* ble, a property owing to the great fusibility of the acid itself. 1469. The borates are distinguished by the following character : Distin- by digesting any borate in a slight excess of strong sulphuric acid, S uis hed. evaporating to dryness, and boiling the residue in strong alcohol, a solution is formed which has the property of burning with a green flame. 1470. Biborate of Soda— -Borax. This salt, which has been Borax, very long known, is imported from India in the impure state, under the name of Tincal , which, after being purified, constitutes the refined borax of commerce. It is frequently called sub-borate of soda. 1471. It crystallizes in prisms of the oblique system, which efflor- Crystals, esce ; they require 20 parts of cold, and 6 of boiling water, for so- lution. Exposed to heat the crystals lose their water of crystalliza- tion, fuse, and then form a vitreous substance called glass of borax. The crystals are composed of 69.8 parts or 2 eq. of acid, 31.3 or 1 eq. soda, and 90 or 10 parts of water. 1472. The chief use of borax is as a flux, and for the preparation Use. of boracic acid.^ 1473. Carbonates . The carbonates are distinguished by being de- Carbon- composed with effervescence, owing to the escape of C, by nearly actersof, all the acids ; and all of them, except the carbonates of potassa, so- da and lithia, may be deprived of their acid by heat. The carbo- nates of baryta and strontia, especially the former, require an in- tense heat for decomposition ; those of lime and magnesia are re- duced to the caustic state by a full red heat ; and the other carbo- nates part with their carbonic acid when heated to dull redness. 1474. All the carbonates, except those of potassa, soda and am- Solubility, monia, are of sparing solubility in pure water; but all of them are more or less soluble in an excess of carbonic acid, owing probably io the formation of supersalts. Several of the carbonates occur na- tive. , 1475. Carbonate of Potassa, KO+CO ! , 47.15 1 eq. base+22.12 1 eq. acid = 69 27 eq. This is a salt of great importance in many arts and manufactures, and is known in commerce in differ- ent states of purity, under the names of wood-ash , pot-ash, and pearl- ash. It is the subcarbonate of potassa of the U. S. Pharmacop. The simplest mode of showing the absorption of carbonic acid by potassa, is Exp. the following : Fill a common phial with carbonic acid gas over water ; and * The Boracite of mineralogists is a biborate of magnesia. A new biborate of New biborate of soda, containing half as much water of crystallization as the above, has been des- ssda. cribed. It is harder and denser than borax, is not efflorescent, and crystallizes in oc- tohedrons. It is made by dissolving borax in boiling water until the sp. gr. of the Process solution is at 30° or 32° of Beaume’s hydrometer 5 the solution is then very slowly cooled, and when the temperature falls to about 133° the salt is deposited. It is found to be more convenient for the use of jewellers than common borax. Ann. de Chim. et Phy. xxxvii. 419. 348 Sa Its — Carbonates . Chap. V. Exp. Effect of heat. Sources of potassa. Bicarbon- ate, Formed. Properties. Carbonate of soda. Sources of. when full, stop it by applying the thumb. Then invert the bottle in a solution of pure potassa contained in a cup, and rather exceeding in quantity what is sufficient to fill the bottle. The solution will rise into the bottle, and if the gas be pure, will fill it entirely. Pour out the alkaline liquor, fill the bottle with wa- ter, and again displace it by the gas. Proceed as before, and repeat the process several times. It will be found that the solution will condense many times its bulk of the gas ; whereas water combines only with its own volume. This experiment may be made in a much more striking manner, over mercu- ry, by passing into ajar, about three fourths filled with this gas, a comparative- ly small bulk of a solution of pure potassa, which will condense the whole of a large quantity of the gas. If dry hydrate of potassa be substituted in this ex- periment, no change will ensue ; which proves that solution is essential to the action of alkalies on this gas. A solution of potassa, which has condensed all the carbonic acid it is capable of absorbing, when evaporated to dryness, af- fords carbonate of potassa. H. 1.541. 1476. This salt is fusible without decomposition, at a red heat : it is very soluble in water, and deliquesces by exposure to air, forming a dense solution, once called oil of tartar per deliquium. Its taste is alkaline, and it renders vegetable blues green. The solution of carbonate of potassa will be found to have a much milder taste than the pure alkali, and no longer to destroy the texture of woollen cloth ; but it still turns to green the blue infusion of vegetables. 1477. The great consumption of this article in various manufac- tures is exclusively supplied by the combustion of vegetables, and consequently its production is almost limited to those countries which require clearing of timber, or where there are vast natural forests. The English market is chiefly supplied from North America. If any vegetable growing in a soil not impregnated with sea-salt be burned, its ashes will be found alkaline from the presence of car- bonate of potassa. If the ashes be submitted to heat, so as to burn away the carbonaceous matter entirely, they become a white mass generally termed pearl-ash .* 1478. Bi-carbonate of Potassa , K0-)-2C0 2 , 47.15 1 eq. base + 44.24 2 eq. acid = 91.39 eq. ; in crystals with 9 or 1 eq. water = 100.39. This salt is formed by passing a current of C into a solu- tion of the carbonate ; or by evaporatings mixture of the carbonates of ammonia and potassa, the ammonia being dissipated in a pure state. By slow evaporation, the bicarbonate is deposited from the liquid in hydrated prisms with eight sides, terminated with dihedral summits. 1479. This salt is milder than the carbonate. It does not deli- quesce on exposure. It requires 4 times its weight of water at 60° for solution. At a low red heat it is converted into the carbonate. 14S0. Carbonate of Soda , NaO+CO 2 31.3 1 eq. base + 22.12 1 eq. acid = 53.42 eq. ; in crystals with 90 or 10 eq. water =143.42, with 63 or 7 eq. water = 116.42 eq., is chiefly obtained by the com- bustion of marine plants, the ashes of which afford, by lixiviation, the impure alkali called soda. Two kinds of rough soda occur in the market : barilla and kelp ; besides which, some native carbonate of soda is also imported. Barilla is the semifused ash of the salsola * For ascertaining the quantity of real ( 510 .) the value of different samples of pearlash, that is to determine carbonate of potassa in a given weight of impure carbonate, see 349 Carbonate of Ammonia. soda, which is largely cultivated upon the Mediterranean shore Sect. i. of Spain, in the vicinity of Alicant. Kelp consists of the ashes of sea-weeds, which are collected upon the sea coast and burned in kilns, or merely in excavations made in the ground and surrounded by stones. It seldom contains more than 5 per cent, of carbonated alkali, and about 24 tons of sea-weed are required to produce one ton of kelp. The best produce is from the hardest fuel, such as the serraius , digitatus, nodosas , and vesicnlosus * * * § The rough alkali is contaminated by common salt, and impurities, from which it may be separated by solution in a small portion of water, filtrating the solu- tion, and evaporating it at a low heat ; the common salt may be skimmed off as its crystals form upon the surface. t 1481. It crystallizes in rhombic octohedrons, the acute angles ge- Crystals, nerally truncated. The crystals effloresce, and when heated dissolve in their water of crystallization. By continued heat they are ren- dered anhydrous without loss of carbonic acid. They dissolve in s °lubility. about two parts of cold, and rather less than their weight of boiling water; the solution being alkaline. The crystals usually contain 10 eq. of water . t 1482. Bicarbonate of Soda. Na0-|-2C0 2 , 31.3 1 eq. base -f- Bicarbon- 44.24 2 eq. acid = 75.54 ; in crystals with 9 or 1 eq. water == ate - 84.54 eq. This salt is made by the same processes as bicarbonate of potassa, and is deposited in hydrated crystalline grains by evapo- ration. It is milder than the carbonate and less soluble, requiring about ten times its weight of water at 60° for solution. It is con- verted into the carbonate by a red heat. 1483. Sesquicarbonate , 2NaO. 3C0 2 -f-4H0, occurs native in Afri- Sesquicar- ca, on the banks of soda lakes, and is called Trona .§ bonate. 1484. Carbonate of Ammonia. H 3 N-f-C, 17.15 1 eq. base -f- 22.12 1 eq. acid — 39.27 eq. The only method of obtaining the Carbonate substance so called is by mixing perfectly dry C and NH 3 . In what- n j a . * McCulloch’s Western Islands , i. 122. + The crystals of soda-carb. as well as the soda-ash of G. B. are made by the de- composition of sea-salt ; for a description of the process see lire’s Diet. Arts and Man. 1151. t The purity of barilla or other carbonates of soda, may be ascertained by the alka- limeter (510). In the analysis of barilla and kelp, to ascertain the relative proportion of soda, it may be useful to know that 100 parts of dilute nitric acid, specific gravity 1.36, will saturate 50 parts of dry carbonate of soda, which are equivalent to about 29 of pure soda. § Phillips in Jour. Sci. vii. Soda water is a solution of soda highly charged with carbonic acid gas, whereby it soda water, acquires a sparkling appearance, and agreeable pungent taste, and certain medicinal powers. For a plan and description of the apparatus see Ure’s Diet. Arts and Man. 1156. To make seltzer water, for each 12 lbs. Troy take 55 grs. carb. soda, 17 carb. lime, Seltzer water. 18 carb. magnesia, 3^ subphosphate alumina, 3 chloride potassium, 155 chlor. sodium, and 3 of finely precipitated silica, this solutionis charged with 353 cubic inches of carb. acid gas. Ibid , 1155. The disinfecting soda liquid of Labarraque is prepared by the following process, i.abarraque’a Dissolve 2800 grains of crystallized carbonate of soda in 1.28 pints of water, having liquid, placed the solution in a Woulfe’s apparatus, pass through it a current of chlorine gas evolved from a mixture of 957 grains of salt, and 750 of oxide of manganese, acted upon by 967 grains of oil of vitriol previously diluted with 750 grains of water. The operation should be conducted slowly. For most purposes the common bleaching 'powder sprinkled about or dissolved in water is quite as effectual and more economical, but for medical uses the preparation should be more nicely attended to. See Quart. Jour, of Sci., &c. N. S. i- 236— ii. 460 — iii. 84 ; and Amer. Jour. &c. xiv. 251. 350 Salts — Carbonates. Cha P- v - ever proportion the two gases be mixed, they unite only in the ratio of 1 vol. of the former to 2 of the latter, and condense into a white powder. It is decomposed by water into ammonia and the sesqui- carbonate. Bicarbon- 1485. Bicarbonate of Oxide of Ammonium is formed by trans- arnmonf- ,de m i u i n g a current of C through a solution of the common carbonate um. of ammonia. On evaporating the liquid by a gentle heat, the bicar- bonate is deposited in small prisms of the right rhombic system ? having no smell, and very little taste. It contains twice as much C as the carbonate. It cannot exist without the presence of water, of which it contains 22.7 percent.,* or 2 eq. It may therefore be con- sidered as carbonate of basic water and carbonate of oxide of ammo- nium, or H0.C0 2 +H 4 N0.C0 2 . Sesqui- 1486. Sesquicarbonate of Oxide of Ammonium. The common of oxide^f car ^ onate ammonia of the shops, Sub-carbonas Ammonia of the ammom- 0 Pharmacop., is different from both these compounds. It is prepared um. by heating a mixture of one part of hydrochlorate of ammonia with one part and a half of carbonate of lime, carefully dried. Double decomposition ensues during the process ; chloride of calcium re- mains in the retort, and hydrated sesquicarbonate of ammonia is sublimed. The carbonic acid and ammonia are, indeed, in proper proportion in the mixture for forming the real carbonate : but, owing to the presence of water, generated by the combination of the oxygen of the lime with the hydrogen of the hydrochloric acid, part of the ammonia is disengaged in a free state. 1487. The salt thus formed consists of 34.3 parts or 2 eq of am- monia, 66.36 parts or 3 eq. of carbonic acid, and 18 parts or 2 eq. of water. It is, therefore, anhydrous sesquicarbonate of oxide of am- monium, or 2H 4 NO-f~3CO\ When recently prepared, it is hard, compact, translucent, of a crystalline texture, and pungent ammoni- acal odour; but if exposed to the air, it loses weight rapidly from the escape of pure ammonia, and becomes an opaque brittle mass, which is the bicarbonate. Carbonate 1488. Carbonate of Baryta, BaO-j-CO 7 , 76.7 1 eq. base + 22.12 of baryta. 1 e q. acid = 98.82 eq., occurs abundantly in the lead mines of the north of England, where it was discovered by Withering, and has hence received the name of I Vitherite. It may be prepared by way of double decomposition, by mixing a soluble salt of baryta with any of the alkaline carbonates or bicarbonates. It is anhydrous, exceed- ingly insoluble in distilled water, requiring 4300 times its weight of water at 60°, and 2300 of boiling water for solution ; but when re- cently precipitated, it is dissolved much more freely by a solution of carbonic acid. It is higly poisonous. Carbonate 1489. Carbonate of Strontia, SrO-f-CO', 5I.S 1 eq. base-)- 22.12 of strontia. 1 eq. acid = 73.92 eq., occurs native at Strontian in Argyleshire, and is known by the name of Strontianite ; it may be prepared in the same manner as carbonate of baryta. It is anhydrous, and very inso- luble in pure water, but is dissolved by an excess of carbonic acid. Carbonate 1490. Carbonate of Lime. CaO-f-CO 2 , 28.5 1 eq. base + 22.12, of lime. ac -j __ 50 00 e q t This salt is a very abundant natural production * Berzelius. 351 Carbonate of Magnesia . and occurs under a great variety of forms, such as common limestone, Sect, i. chalk, marble, and Iceland, spar, and in regular anhydrous crystals, the density of which is 2.7. Though sparingly soluble in pure water, it is dissolved by carbonic acid in excess ; and hence the spring-water of limestone districts always contains carbonate of lime, which is deposited when the water is boiled. 1491. Lime has a strong attraction for carbonic acid, but not when Carbonate, perfectly dry ; for if a piece of dry quicklime be passed into a jar of carbonic acid gas over mercury, no absorption whatever ensues. But if a bottle, filled with carb. acid gas, be inverted over a mixture of lime and g X p. water of the consistence of cream, a rapid absorption will be observed, especially if the bottle be agitated ; or if a jar or bottle, filled with carbonic acid, be brought over a vessel of lime water, on agitating the vessel, a rapid diminution will ensue, and the lime water will become milky. 1492. When a shallow vessel of lime water is exposed to the Action of air, a white crust forms on the surface, and this, if broken, falls to air - the bottom, and is succeeded by another till the whole of the lime is precipitated from the solution. This is owing to the absorption of carbonic acid gas from the air by the lime, which is thus rendered insoluble in water. Dry lime, also, when exposed to the atmosphere, first acquires moisture, and having become a hydrate, next absorbs carbonic acid. In a sufficient space of time, all the characters dis- tinguishing it as lime disappear, and it acquires the property of effervescing with acids. The strong affinity of lime for carbonic acid enables it to take this acid from other substances. Thus carbonates of alkalies are decomposed by lime. h. i. 58 7 . 1493. The carbonic acid existing in carbonate of lime is expelled Carbonic by a strong red heat. If distilled in an earthen retort, carbonic acid 1 ex P el ; gas is obtained, and lime remains in the retort in a pure or caustic state. By this process carbonate of lime loses about 45 per cent. 1494. Carbonate of Magnesia. MgO-|-C0 2 , 20.7 1 eq. base -j- Carbonate 22.12 1 eq. acid == 42.82 eq. ; in crystals, with 27 or 3 eq. water = °f ma §> ne ' 69.82. It is met with occasionally in rhombohedral crystals, and in a pulverulent earthy state, but more commonly as a compact mineral of an earthy fracture called magnesite. It is abundant in the East Indies, of a snow-white colour, of density 2.56, and so hard that it strikes fire with steel.* It is obtained in minute transparent hexa- gonal prisms with three eq. of water, when a solution of bicarbonate of magnesia evaporates spontaneously in an open vessel. The crys- tals lose their water and become opaque by a very gentle heat, and even in a dry air at 60°. By cold water they are decomposed, yielding a soluble bicarbonate, and an insoluble white compound of hydrate and carbonate of magnesia ; and hot water produces the same change with disengagement of carbonic acid, without dissolv- ing any magnesia.! 1495. When carbonate of potassa is added in excess to a hot solu- tion of sulphate of magnesia, a white precipitate falls, which after being well washed has been long considered as pure carbonate of magnesia ; but Berzelius has shown that it consists of the following ingredients : — * Ann. of Philos, xvii. 252. t Berzelius. 352 Salts — Carbonates. Chap. V. Magnesia Carbonic acid Water 44.75 35.77 19.48 82.8 or 4 eq. CG.36 or 3 eq. 3(i or 4 eq. Probable formula is M gO .4 Ii 0-(-3Mg0C0 2 100.00 185.16 or 1 eq. This compound is said to require 2493 parts of cold, and 9000 of hot water for solution. It is freely dissolved by a solution of carbo- nic acid, bicarbonate of magnesia being generated ; but on allowing the solution to evaporate spontaneously, carbonic acid is given off, and crystals of the hydrated carbonate above mentioned are ob- tained. Carbonate 1496. Carbonate of Protoxide of Iron. FeO-fCO 2 , 36 1 eq. base of iron° Xi(le H“ 22.12 1 eq. acid = 58.12 eq. Carbonic acid, with the protoxide of iron, constitutes a salt which is an abundant natural production, occurring sometimes massive, and at other times crystallized in rhombohedrons. This protocarbonate is contained also in most of the chalybeate mineral waters, being held in solution by free carbo- nic acid ; and it may be formed by mixing an alkaline carbonate with the sulphate of protoxide of iron. When prepared by precipi- tation it attracts oxygen rapidly from the atmosphere, and the pro- toxide of iron, passing into the state of sesquioxide, parts with carbonic acid. For this reason, the carbonate of iron of the Phar- macop. is of a red colour, and consists chiefly of the sesquioxide. Dicarbon 1497. Dicarbonate of Protoxide of Copper. 2CuO-f-CO‘ 2 , 79.2 2 ate of pro- e q. base -f- 22.12 1 eq. acid = 101.32 eq.* It occurs as a hydrate copper beautiful green mineral called malachite ; and the same com- pound, as a green powder, the mineral green of painters, may be obtained by precipitation from a hot solution of sulphate of protoxide of copper, by carbonate of soda or potassa. When obtained from a cold solution, it falls as a bulky hydrate of a greenish-blue colour, which contains more water than the green precipitate. By careful drying its water may be expelled. When the hydrate is boiled for a long time in water, it loses both carbonic acid and combined water, and the colour changes to brown. The rust of copper, prepared by exposing metallic copper to air and moisture, is a hydrated di- carbonate. The blue pigment called verditer, prepared by decomposing ni- trate of protoxide of copper with chalk, has a similar composition. t 149S. Carbonate of Protoxide of Lead. 111.6 1 eq. base -|- 22.12 I eq. acid = 133.72 eq. This salt, which is the white lead or ceruse of painters, occurs native in white prismatic crystals de- rived from a right rhombic prism, the sp. gr. of which is 6.72. It is obtained as a white pulverulent precipitate by mixing solutions of an alkaline carbonate with acetate of protoxide of lead ; and it is pre- pared as an article of commerce from the subacetate by a current of Carbon- ate of pro toxide of lead. * In Malachite with 9 or i eq water eq. 110.32. Refiner’, rerdi- + There is a fine blue cupreous preparation, called Refiner's Verditer, principally made ter. by silver refiners. It consists, according to Phillips, of three proportionals of oxide, fourof carbonic acid, and two of water. (Quart. Jour, of Sci. iv. 277.) According to Pelletier, a good verditer may he obtained as follows : add a sufficient quantity of lime to nitrate ot copper to throw down the oxide ; it gives a greenish pre- cipitate'that is to be washed and nearly dried upon a strainer; then incorporate it with from eight to ten per cent, of fresh lime, which will give it a blue colour, and dry it carefullv. For processes see Ure^s Dtct. Arts, and Man. 1274. 353 Hydrochlorate of Ammonia . carbonic acid ; by exposing metallic lead in minute division to air Sect, n. and moisture ; and by the action on thin sheets of lead of the va- pour of vinegar, by which the metal is both oxidized and converted into a carbonate. 1499. Double Carbonates. One of the most remarkable of these Double car- is the double carbonate of lime and magnesia,* which constitutes the bonates - minerals called bitter-spar, pearl-spar, and Dolomite. The two for- mer occur in rhombohedrons of nearly the same dimensions as car- bonate of lime. Some specimens consist of the two carbonates in the ratio of their equivalents; but this ratio is very variable, since iso- morphous substances crystallize together in all proportions, t. & L. 706 . Section II. Ordered. Hydro- Salts. This section includes those salts, the acid or base of which con- Hydro- tains hydrogen. The salts formerly called muriates or hydrochlorates salts * of metallic oxides, have been already described as chlorides of metals ; as also those of hydriodic and other hydracids; the neutralizing power of the acids being considered as due to the direct union of the chlorine, iodine, &c., with the metal itself. Some of these com- pounds may be more properly placed in the fourth section, as in them the hydracid acts rather as a base or electro-positive ingredient, than as an acid or electro-negative substance.! 1500. The compounds of ammonia with the hydracids may be Ammoni- described as chlorides of the hypothetical radical ammonium. aca sa ts ' 1501. Ammoniacal Salts are recognized by the addition of pure potassa or lime, when the odour of ammonia may be perceived. Those which contain a volatile acid may in general be sublimed without decomposition ; but the ammonia is expelled by heat from those acids which are much more fixed than itself. 1502. Hydrochlorate of Ammonia , H 3 N-f-HCl, 17.15 1 eq. base Hydrochlo- + 36.42 1 eq. acid = 53.57. This salt,saZ ammoniac of commerce, rate of am- was formerly imported from Egypt, where it is procured by subli- moma ’ mation from the soot of camel’s dung; but it is now manufactured by several processes. The most usual is to decompose sulphate of ammonia by the chloride either of sodium or magnesium, when double decomposition ensues, giving rise in both cases to hydro- chlorate of ammonia, and to sulphate of soda when chloride of so- dium is used, and to sulphate of magnesia when chloride of mag- nesium is employed. The sal ammoniac is afterwards obtained in a pure state by sublimation. The method now generally used for obtaining sulphate of oxide of ammonium is to decompose with sulphuric acid the hydrosulphate and hydrocyanate of ammonia which is collected in the manufacture of coal-gas; but it may also be procured either by lixiviating the soot of coal, which contains sulphate of oxide of ammonium in considerable quantity, or by di- gesting with gypsum impure sesquicarbonate of oxide of ammonium, carbonate of ammonia, procured from the destructive distillation *Mg0C0 2 +Ca0C0 2 . 50.62 1 eq- carb. lime + 42.82 I eq. carb. mag. — 93.44 eq. + See Kane’s observations in Dublin Jour, of Sci. i. 265. 45 354 Chap. V. Properties. Native. Origin of the name. Formation illustrated. Uses, Hydroflu- ate of am- monia. Hydrosul- pbate of ammonia. Salts — Hydro - Salts. of bones and other animal substances, so as to form an insoluble carbonate of lime and a soluble sulphate of oxide of ammonium. 1503. Hydrochlorate of ammonia has a pungent saline taste, a density of 1.45, and is tough and difficult to be pulverized. It is so- luble in alcohol and water, requiring for solution three times its weight of water at 60°, and an equal weight at 212°. It usually crystallizes from its solution in feathery crystals, but sometimes in cubes or octohedrons. At a temperature below that of ignition it sublimes without fusion or decomposition, and condenses on cool surfaces as anhydrous salt, which absorbs humidity in a damp at- mosphere, but is not deliquescent. In commerce it usually occurs as procured by sublimation, in white cakes, hard and somewhat elastic. 1504. Native Hydrochlorate of Ammonia , occurs massive and crystallized, in the vicinity of volcanoes, and in the cracks and pores of lava, near their craters. An efflorescence of native sal ammoniac is sometimes seen upon pit-coal. Its colour varies from the admixture of foreign matter, and it is frequently yellow from the presence of sulphur. It is said that considerable quantities of native sal-ammo- niac are also found in the country of Bucharia, where it occurs with sulphur in rocks of indurated clay. The ancients, according to Pliny, called this salt ammoniac , because it was found near the tem- ple of Jupiter Ammon, in Africa. 1505. This salt may be produced di- rectly by means of the apparatus (Fig. 186.) Into one of the retorts a small quantity of hydrochloric acid or the materials from which the acid gas is usually obtained (628,) is introduced ; and into the other liquid ammonia (or the mixture of lime and hydrochlo- rate of ammonia (729.) The evolved gases passing into the globe unite producing dense clouds of hydrochlorate of ammonia which concrete upon the inner surface. We may also form it by mixing over mercury, equal measures of ammoniacal gas, and hydrochloric acid gas, which are entirely condensed into a white solid. 1506. Sal-ammoniac is used in the arts for a variety of purposes, especially in certain metallurgic operations. It is used in tinning, to prevent the oxidation of the surface of copper ; and small quan- tities are used by dyers. Dissolved in nitric acid, it forms the aqua regia of commerce, used for dissolving gold, instead of a mixture of nitric and hydrochloric acids (637.)* 1507. Hydrofluate of Ammonia , H 3 N-|-HF, 36.83 eq. It is pre- pared by mixing 1 part of sal ammoniac with 2i of fluoride of so- dium, both dry and in fine powder, gently heating the mixture in a platinum vessel, and receiving the sublimed salt in a second pla- tinum vessel, the temperature of which is not allowed to exceed 212 °. 1505. Hydrosulphate of Ammonia . H 3 N-|-HS, 17.15 1 eq. base — |— 17. 1 1 eq. acid = 34.25. This salt, also called hydrosulphuret of ammonia, and formerly the fuming liquor of Boyle , is prepared by heating a mixture of one part of sulphur, two of sal ammoniac, * Hydriodate, H 3 N+HI, 17.15 base + 127.3 1 eq. acid = 144.45 eq., and Hydro- bromate of amvionia, may be formed by similar processes. Fig. 186. Sulphur- Salts . 355 and two of unslaked lime. The volatile products are ammonia and hydrosulphate of ammonia ; and the fixed residue consists of sul- phate of lime with chloride and sulphuret of calcium. The hy- drosulphuric acid is formed from the hydrogen of hydrochloric acid uniting with sulphur, and the oxygen of the sulphuric acid is de- rived from decomposed lime, the calcium of which is divided be- tween the chlorine of the hydrochloric acid and the sulphur. Hy- drosulphate of ammonia may also be formed by the direct union of its constituent gases, and if they are mixed in a glass globe kept cool by ice, the salt is deposited in crystals. It is much used as a reagent, and for this purpose is usually prepared by saturating a so- lution of ammonia with hydrosulphuric acid gas.^' 1509. Salts of Phosphuretted Hydrogen. Phosphu retted hydro- gen is a feeble alkaline base, which combines with some of the hy- dracids. The salt best known is the hydriodate of phosphuretted hydrogen, first noticed by Gay-Lussac, which is formed of 127.3 parts or 1 eq. of acid and 34.4 parts or 1 eq. of base, and crystallizes in cubes. Sect. III. Use. Section III. Order 3 d. Sulphur- Salts. The compounds described in this section are double sulphurets, Sulphur* just as the oxy-salts in general are double oxides. Their resem- salts, blance in composition to salts is perfect. The principal sulphur-ba- ses are the protosulphurets of potassium, sodium, lithium, barium, strontium, calcium, and magnesium, and hydrosulphate of ammo- nia ; and the principal sulphur-acids are the sulphurets of arsenic, antimony, tungsten, molybdenum, tellurium, tin, and gold, together with hydrosulphuric acid, bisulphuret of carbon, and sulphuret of selenium. The sulphur-salts with two metals are so constituted, that if the sulphur in each were replaced by an equivalent quantity of oxygen, an oxy-salt would result. The analogy between oxy- salts and sulphur-salts is rendered still closer by the circumstance that hydrosulphuric and hydrosulphocyanic acids have the charac- teristic properties of acidity, and unite both with ammonia and with sulphur-bases. The sulphur-salts may be divided into families, characterized by Di v j s j on 0 f Fie. 187. * Fig. 187, represents the disposition of the apparatus for this process : a , a small furnace ; 6, a tubulated earth- ern retort containing the a- bove materials ; c, an adap- ting tube ; e, a glass balloon for condensing the vapour; / a receiver ; g, a bottle of water, into which the glass tube, issuing from the upper part of the receiver, e, is made to dip about half an mch. The product in the bottle/, may be mixed with the water mg-, and the whole used for washing out the receiver e. It is retained in the pharmacopaeia, and may be extemporaneously made by passing hydrosulphuric acid gas from an oil flask with a bent tube jinto aqua am- moniac kept cold. sulphur- salts. 356 Salts — Sulphur- Salts. Chap. V. Hydro- sulphurets. Hydro-sul- phuret of potassium. Process. Hydro-sul- E huret of arium. Carbo- sulphurets. Carbo-sul- phuret of potassium. containing the same sulphur-acid. For the purpose of indicating that such salts are double sulphurets, as well as to distinguish them readily from other kinds of salts, the generic name of each family may be constructed from the sulphur-acid terminated with sulphuret. Thus the salts which contain persulphuret of arsenic or hydrosul- phuric acid as the sulphur-acid are termed arsenio-sulphurets and hydro-sulphurets ; and a salt composed of each of these sulphur- acids with sulphuret of potassium is termed arsenio-sulphuret and hydro-sulphuret of sulphuret of potassium. For the sake of brevity the metal of the base may alone be expressed, it being understood that the positive metal in a sulphur-salt enters as a protosulphuret into the compound. 1510. Hydro- Sulphurets. The sulphur-salts contained in this group have hydro-sulphuric acid for their electro-negative ingredient. Most of them which have been studied are soluble in water, and may be obtained in crystals by evaporation. They are decomposed by exposure to the air, yielding at first bisulphurets of the metal, and then a hyposulphite. By acids the hydrosulphuric acid is ex- pelled with effervescence. 1511. Hydro-sulphuret of Potassium , KS-f-HS, 55.25 1 eq. sul- phur-base -f- 17.1 1 eq. sulphur acid = 72.35 eq. This salt is ob- tained in the anhydrous state by introducing anhydrous carbonate of potassa into a tubulated retort, transmitting through it a current of hydrosulphuric acid gas, and heating the salt to low redness. The same salt is prepared in the moist way by introducing a solution of pure potassa, free from carbonic acid, into a tubulated retort, expelling atmospheric air by a current of hydrogen gas, and then saturating the solution with hydro- sulphuric acid. At nrst the potassa, as in the former process, interchanges ele- ments with the gas, yielding water and protosulphuret of potassium ; after which the protosulphuret unites with hydrosulphuric acid. The solution should be evaporated in the retort to the consistence of syrup, a current of hy- drogen gas being transmitted through the apparatus the whole time ; and on cooling the salt crystallizes in large four or six sided prisms, which are colour- less if air was perfectly excluded. 1512. Hydrosulphuret of Barium , BaS-|-HS, 84.8 1 eq. sulphur base, -(-17.1 acid = 101.9 eq. It is prepared by the action of hydrosulphuric acid on a solution of baryta with the precautions al- ready mentioned for excluding atmospheric air, and crystallizes by evaporation in four-sided prisms, which are very soluble in water.* 1513. Car bo-sulphur ets. The acid of these sulphur-salts is bi- sulphuret of carbon. 1514. Carbo-sulphuret of Potassium , KS-f-CS 5 , 55.25 sulphur -f- 38.32 sulphur acid = 93.57 eq. On agitating bisulphuret of car- bon with a strong alcoholic solution of protosulphuret of potassium, the liquid when set at rest separates into three layers, the lowest of which is carbo-sulphuret of potassium, and is of the consistence of syrup. Another process is to digest bisulphuret of carbon at 86° in a corked bottle full of a strong aqueous solution of proto- sulphuret of potassium, until the latter is saturated. A concen- trated solution of this salt is of a deep orange, almost red colour; * For other hydrosulphurets and carbo-sulphurets see Turner and Liebig’s Elem. 713 . Molybdo- Sulphur ets. 357 and when evaporated at 86° to the consistence of syrup, a deliques- Sect- hi. cent yellow crystalline salt is deposited, which is sparingly soluble in alcohol. 1515. Carbo- sulphur et of Hydro sulphate of Ammonia , (H 3 N-|- Carbo-sul- HS) + CS 2 , 34.25 1 eq. sulphur + 38.32 1 eq. sulphur acid = 72.57 eq. This salt is prepared by filling a bottle with 10 mea-phateof sures of nearly absolute alcohol saturated with ammoniacal gas and ammonia. I measure of bisulphuret of carbon, and inserting a tight cork. As Process, soon as the liquid has acquired a yellowish brown colour, the bottle is plunged into ice-cold water, when the carbo-sulphuret is deposited either in yellow penniform crystals or as a crystalline powder. The whole is thrown upon a linen filter, and the salt after being washed first with absolute alcohol and then with ether, is dried by pressure within folds of bibulous paper. 1516. This salt is very volatile and can only be preserved in well Volatile, corked bottles. Exposed to the air it absorbs humidity and ac- quires a red colour. 1517. Arsenio-sulphurets. Berzelius finds that each of the three Arsenio- sulphurets of arsenic (page 276) is capable of acting as a sulphur- sulphurets. acid, giving rise to three distinct families of sulphur-salts, distin- guishable by the terms ar senio -per sulphur et s , arscnio-sesquisulphur- ets , and ar senio -proto sulphurets. 1518. Persulphuret of Arsenic , is a very powerful sulphur-acid, violently displacing hydrosulphuric acid from its combinations with sulphur-bases, even at common temperatures ; and when digested with earthy or alkaline carbonates, it expels carbonic acid. The salts of this sulphur-acid may be prepared by several methods.^ 1519. Most of the arsenio-persulphurets of the second class of Characters, metals are insoluble ; but those of the metals of the alkalies and al- kaline earths are very soluble in water, have, a lemon-yellow colour in the anhydrous state, and are colourless when combined with water of crystallization or in solution. When exposed to heat in close vessels they give off sulphur, and an arsenio-sesquisulphuret is gene- rated. In the solid state they are very permanent in the air, and even in solution oxidation takes place with great slowness. When decomposed by an acid, persulphuret of arsenic subsides, hydrosul- phuric acid gas escapes, and a salt of the alkali is generated. The salts in which sesquisulphuret of arsenic acts as an acid, re- semble those of the persulphuret both in their general characters and mode of formation. 1520. Molybdo- Sulphurets. The electro-negative ingredient of Molybdo- these salts is the tersulphuret of molybdenum, and the most remark- sulphurets. able of them is the molybdo-sulphuret of potassium, which is readily formed by decomposing with hydrosulphuric acid gas a rather strong solution of molybdate of potassa. If no iron is present, the liquid acquires a beautiful red colour, like the solution of bichromate of potassa, and on evaporation prismatic crystals with four and eight sides are deposited. Berzelius describes this compound as one of the most beautiful which chemistry can produce ; the crystals, by transmitted light, are ruby-red, and their surfaces, while moist with * For which see Turner and Liebig’s Elem. 715. 358 Chap. V. Antimonio- sulphureta. Tunpto- sulphurets. Haloid salts. Hydrareo- chlorides. Auro chlo- rides. Platino- chlorides. Palladio- chlorides. Sails — Haloid Salts. the solution which yielded them, shine like the wings of certain insects with a metallic lustre of a rich green tint. The crystals are anhydrous, dissolve readily in water, but are insoluble in alcohol. On the addition of sulphuric or any of the stronger acids, a salt of potassa is generated with escape of hydrosulphuric acid, and preci- pitation of tersulphuret of molybdenum. 1521. Antimonio- Sulphur ets. When two parts of carbonate of potassa are intimately mixed with four of sesquisulphuret of antimo- ny and one part of sulphur, and the mixture is fused, an antimonio- persulphuret of potassium is generated. On digesting in water, a subantimonio-persulphuret is dissolved, and is deposited by gentle evaporation in large colourless tetrahedrons, which become yellow on exposure to the air. 1522. Tung sto- Sul phurcts. The best known of these salts is that of potassium, in which tersulphuret of tungsten is combined with pro- tosulphuret of potassium. It is formed when a solution of tungstate of potassa is decomposed by hydrosulphuric acid, and crystallizes by evaporation in flat quadrilateral prisms, which are anhydrous, and are of a pale red colour. Section IV. Order 4th. Haloid Salts. 1523. Under this order are included substances composed like the preceding salts of two bi-elementary compounds, one or both of which are analogous in composition to sea-salt. The principal groups consist of double chlorides, double iodides, and double fluorides. In these the haloid bases belong usually to the electro-positive metals, and the haloid acids to the metals which are electro-negative. The same principles of nomenclature are applied to them as to the sul- phur salts. 1524. Hydrar go chlorides. The haloid acid of this family is bichloride of mercury, which reddens litmus paper, and loses the property when a haloid base is present, thus bearing a close analogy to ordinary acids. They are obtained by mixing the ingredients in the ratio for combining, and setting aside the solution to crystallize. The ammoniacal salt has long been known under the name of salt of alembroth. 1525. Auro-chlorides. The electro-negative ingredient of these salts is the terchloride of gold. They are prepared by mixing the chlorides in atomic proportions and setting aside the solution to crys- tallize. Most of them have an orange or yellow colour, and consist of single equivalents of their constituent chlorides. 1526. P latino-chlorides. Both the protochloride and bichloride of platinum act as haloid acids. The platino-protochloride of potassium is made by mixing chloride of potassium with a solution of proto- chloride of platinum in hydrochloric acid. It crystallizes in red, an- hydrous' prisms and consists of single equivalents of its constitu- ent chlorides. 1527. The Platino-bichloride of Hydrochlorate of Ammonia falls as a lemon-yellow powder, when sal ammoniac is mixed with a strong solution of bichloride of platinum. 1528. Palladio-chlorides are those in which the chlorides of palla- Chlorides with Ammonia. 359 dium act as haloid acids, combining with many of the metallic chlo- Sect, iv. rides, when their respective solutions are mixed and evaporated. 1529. Rhodio-chlorides are formed when sesquichloride of rho- R^°dio- dium combines with the chlorides of potassium and sodium. The chlorides of iridium and osmium act as haloid acids and pro- duce iridio-chlorides and osmio-chlorides. 1530. Oxy -chlorides. Chemists are acquainted with a considera- Oxy-chlo- ble number of compounds in which a metallic oxide is united with rides. a chloride either of the same metal, which is the most frequent, or of some other metal. These compounds are commonly termed sub- muriate, s, on the supposition that they consist of hydrochloric acid combined with two or more eq. of an oxide. 1531. Oxy -chlorides of Iron. When the crystallized protochloride Oxy-chlo- of iron is heated without exposure to the air, the last portions of its Tjjjes of water exchange elements with part of the chloride of iron, yielding hydrochloric acid, which is evolved, and protoxide of iron. On raising the heat so as to expel the pure chloride of iron, a deep green oxy-chloride in scaly crystals remains.* 1532. The ochreous matter which falls when a solution of the protochloride of iron is exposed to the air, is hydrated sesquioxide of iron combined with some sesquichloride. A similar hydrate is ob- tained by mixing with a solution of the sesquichloride of iron a quantity of alkali insufficient for complete decomposition. When a solution of the sesquichloride is evaporated to dryness without expo- sure to the air, the last portions of water exchange elements with the sesquichloride, hydrochloric acid is disengaged, and after subliming the pure anhydrous sesquichloride, a compound in large, brown, shining laminas is left, which consists of sesquioxide and sesquichlo- ride of iron.t 1533. Oxy-chloride of Copper falls as a green hydrate when po- Oxy-chlo- tassa is added to a solution of chloride of copper insufficient for its rides of complete decomposition. When its water is expelled it becomes 0 f co PP er ' a liver-brown colour. According to Berzelius it consists of 1 eq. chloride and 3 eq. oxide of copper. 1534. It is used as a pigment under the name of Brunswick green , Brunswick being prepared for that purpose by exposing metallic copper to hy- S reen - drochloric acid or a solution of sal-ammoniac. The same compound is generated during the corrosion of copper in sea-water. 1535. Oxy-chloride of Lead is prepared by adding pure ammonia Oxy-chlo- to a hot solution of chloride of lead. Another is known under the j^ of name of mineral ox patent yellow, and is prepared by the action of p atent moist sea-salt on litharge, by which means portions of the protoxide i ow . and sea-salt exchange elements, yielding soda and chloride of lead. After washing away the alkali, the mixed oxide and chloride are dried and fused. 1536. Chlorides with Ammonia. The perchlorides of tin and a Chlorides few other metals absorb ammonia at common temperatures, and most with am- of the other chlorides absorb it when gently warmed. Calomel moma * absorbs half an equiv. and forms a black compound, but on exposure to the air the ammonia flies off, and pure white calomel remains. * Berzelitjs. t Ibid. 360 Salts — Oxy-iodides. >huretted lydrogen. Double io- dides. Chap v. Corrosive sublimate, by the aid of heat, rapidly absorbs half an eq. and forms a white compound which is insoluble in water, and bears a considerable temperature without decomposition ; the white preci- pitate of pharmacy is probably analogous in nature, though the ratio of its ingredients is different. 1537. Most of these compounds lose their ammonia by mere ex- posure to the air, and it is expelled from nearly all of them by a very moderate heat. Chlorides 1538. Chlorides ivith phosphuretted hydrogen. Rose has traced a with pbos- remarkable analogy between ammonia and phosphuretted hydrogen, especially in the compounds which they form with metallic chlorides. The phosphuretted hydrogen is readily displaced by water, or a so- lution of ammonia, from the compounds of phosphuretted hydrogen and the perchlorides of tin, titanium, antimony, iron, and alumina, all of which correspond to ammoniacal chlorides of similar composi- tion. 1539. Double Iodides. These compounds have not yet been closely studied ; but there is no doubt that the iodides are capable of forming with each other an extensive series of compounds. A vari- ety of double iodides have been described by Boullay, and among them a compound of biniodide of mercury and hydriodic acid.* in general the double hydrargo-biniodides contain single equivalents of the respective iodides. Liebig obtained a compound of the bichlo- ride and biniodide of mercury, consisting of two eq. of the former to one eq. of the latter, as indicated by the formula, Hgl 2 -|-2HgCl 2 . Several compounds of biniodide of platinum with other iodides have been studied by Kane and Lassaigne.t 1540. Platino-biniodide of Potassium , is prepared by digesting an biniodide of excess of biniodide of platinum in a rather concentrated solution of potassium, iodide of potassium. By spontaneous evaporation it crystallizes in small rectangular plates surmounted sometimes with a four-sided pyramid, which are anhydrous, unchanged in the air, and insoluble in alcohol. The colour of the crystals is black with a metallic lustre, and they yield a deep claret-coloured solution with water. The biniodide of platinum appears to combine also with the iodide of pla- tinum ; but the compound has only been obtained in solution. Platino- 1541. Platino-biniodide of Hydrogen. This compound consists bimodide of of hydriodic acid and biniodide of platinum, in which the former is Platino- hydrogeu. Oxy-io- dides. regarded as the electro-positive element. It is prepared by acting on biniodide of platinum with a cold dilute solution of hydriodic acid, which gradually acquires a deep claret colour, and by evapora- tion under a bell-jar with quicklime, deposits black acicular crystals. The crystals become moist by exposure to the air. 1542. Oxy-iodides. The principal oxy-iodides at present known to chemists are those formed by the oxide and iodide of lead. When iodide of potassium is mixed with acetate of oxide of lead in excess, the yellow iodide at first formed combines with oxide of lead and ac- quires a white colour ; and the same compound is obtained directly by employing a subacetate. Denot finds that there are three oxy- * Ann. de Chem. et de Phys. xxxiv. t Dublin Jour, of Sci. i. 304, and Ann. de Chim. et de Phjys. li. 125. Tit ano fluorides. 361 iodides, in which 1 eq. of iodide of lead is united with one, two, and Sect, iv. five equivalents of oxide of lead. 1543. Double Fluorides . The researches of Berzelius have led to Double the formation of several extensive families of double fluorides, in duorides - which the fluorides of boron, silicon, titanium, and of other electro- negative metals are the acids, and the fluorides of electro-positive metals are bases. In some instances hydrofluoric acid is a haloid acid; but more commonly it acts the part of a base. 1544. Hydrofluorides. In this family hydrofluoric acid is com- Hydro- bined with the fluorides of electro-positive metals. If an equivalent fluorides, of any electro-positive metal be indicated by M, then the general for- mula for this family is MF-f-HF. 1545. Boro-fluorides. When the terfluoride of boron (fluoboric Boro-fluo- acid gas) is acted upon by water, one out of every four eq. of the rides - gas interchanges elements with water, giving rise to hydrofluoric and boracic acids, the former of which combines as a haloid-base with undecomposed terfluoride of boron, constituting the boro-hydro- fluoric acid, but which may be viewed as the boro-fluoride of hydro- gen. This change is such that 4 eq. terfluoride of boron 4 (B-|-3F) -c 3 eq. terfluoride of boron 3(B-j-3F) ^3 3 eq. hydrofluoric acid 3(H-f-F) and 3 eq. of water 3 (H-f-O) ^ and 1 eq. boracic acid B-f-30 By careful concentration and cooling, the boracic acid separates as a crystalline powder, and the boro-fluoride of hydrogen remains in so- lution. It is strongly acid to test paper, and its composition is indi- cated by the formula HF-f-BF 3 being an equiv. of each fluoride. 1546. Boro-fluoride of Potassium. It is prepared by dropping Boro _ fluo _ boro-fluoride of hydrogen drop by drop into a solution of a salt of ride of po- potassa, and falls as a gelatinous transparent hydrate, which is a tassium - white very fine powder -when dried. It has a slightly bitter taste, and is quite neutral to test paper, is very sparingly soluble in alcohol and cold water, but is dissolved freely by hot water, and subsides on coolingin small, brilliant, anhydrous crystals. At a strong red heat it gives off the terfluoride of boron and fluoride of potassium re- mains. 1547. Silico fluorides. The acid solution, called silico -hydrofluoric Silico-fluo- acid may be viewed as the subsesqui-silico fluoride of hydrogen , a ndes - compound of 157.16 parts or 2 eq. of fluoride of silicon and 59.04 or 3 eq. of fluoride of hydrogen (hydrofluoric acid), as indicated by the formula 3HF-|-2SiF 3 . When the solution is neutralized with po- tassa, the alkali interchanges elements with the fluoride of hydrogen, water and fluoride of potassium are generated, and the latter com- bines with the fluoride of silicon. This double fluoride consists, therefore, of 157.16 parts or two eq. of fluoride of silicon, and 173.49 or 3 eq. of fluoride of potassium, the formula of which is 3KF+2SiF 3 . A similar change ensues with the protoxides of most other metals, and hence the general formula of the silico-fluorides is 3MF^}-2SiF 3 . On exposing these compounds to a red heat, fluo- ride of silicon is disengaged. 1548. Tit ano fluorides. Hydrofluoric acid dissolves titanic-acid, Titano-flo- and forms with it an acid solution which may be viewed as the rides - titano-fluoride of hydrogen. When mixed with potassa, water and 46 362 Chap. VI. Vegetable principles. Com- pounds. Simple bodies. Com- pounds of two ingre- dients, Of three, Of four, Supposed difference in affinities of atoms of organized and unor- ganized bodies, Organic Chemistry. fluoride of potassium are generated, and the titano-fluoride of po- tassium results, the formula of which is KF-f-TiF 2 . By substitu- ting most other protoxides for potassa, similar salts may be prepar- ed, the general formula being MF-)-TiF 2 . CHAPTER VI. ORGANIC CHEMISTRY. Section I. Vegetable Bodies. 1549. The chemical principles of which animals and vegetables are Composed are exceedingly numerous.* We can seldom obtain these principles in a state of such purity as to enable us to examine their properties with accuracy, unless when they are capable of crystallizing, or of entering into definite compounds with acids or alkalies. 1550. These principles are all compounds, and consist sometimes of two, sometimes of three, and sometimes of four, simple bodies uni- ted together ; but seldom of more. These simple bodies are hydrogen, carbon, oxygen and nitrogen, which may be considered as constituting in a great measure, the basis of the animal and vegetable kingdoms. 1551. Organized principles composed of two ingredients are of four kinds. 1, composed of hydrogen and carbon, as oil of turpen- tine ; 2, of hydrogen and oxygen, as water; 3, of carbon and oxy- gen, as oxalic acid; 4, of carbon and nitrogen, as cyanogen. 1552. Those composed of three constituents are much more nu- merous. The most common constituents are carbon, hydrogen and oxy- gen. The greater number of the acids, alcohol, ethers, sugars, gums, &c., are thus constituted. Some few organized bodies are composed of carbon, hydrogen, and nitrogen. Some are supposed to be composed of carbon, nitro- gen and oxygen. 1553. The organic principles composed of four constituents, con- sist of carbon, hydrogen, nitrogen and oxygen, united in various proportions. The number of atoms of nitrogen contained in these compounds is generally small compared with that of the other three constituents, agd there is almost always a great preponderance in the atoms of carbon and hydrogen over those of nitrogen and oxygen. 1554. It has been supposed by some chemists that there is an essential difference between the affinities which unite the atoms * The number of discoveries which have of late been made in this department of chemistry, is such that the limits of this work will not allow of a full account of them. For minute details the student must be referred to the recent elaborate work of Thomson : Chemistry of Organic Bodies. Vegetables. London, 1838, p. 1076, and the third part of Liebig and Turner’s Elements ; as the former is complete, and comprises an account of all the recent researches of the European chemists in this department, it will be employed as the basis of this chapter. Of Liebig’s continua- tion of Turner’s Elements , but 100 pages have appeared. The letter T will refer to the first and L to the second. Vegetable Principles . 363 constituting- organic principles, and those which unite the atoms of Sect. 1 . unorganized bodies ; that there is some unknown power besides chemical affinity, which interferes with, and regulates the combina- tions and decompositions of organized bodies, which is wanting in those that are unorganized. The great difference between the two classes of bodies consists in this, that the organized are much more numberof complicated in their structure, containing a much greater number atoms, of atoms than the unorganized. Hence they are much more unsta- ble, much more easily decomposed, and much more liable to decom- position than unorganized bodies. 1555. The prevailing opinion is that binary compounds alone ex- prevailing ist : that is to say, that one electro-negative atom is only capable of opinion, combining with one electro -positive atom. Two of these binary compounds may combine together, making a new binary compound of four atoms. Two of these binary compounds may combine with each other, making a new binary compound of eight atoms. And in this way binary compounds may be formed as complicated as any that exist.* T. 3. 1556. Many of the principles or definite compounds which exist Crystalli- in the vegetable kingdom, or which may be formed from vegetable zable > bodies, are capable of crystallizing, and in this way may be procur- ed in a state of purity. Others are volatile, and are formed or driv- y olati]e en off at particular temperatures. Frequently several of these vola- principles, tile bodies occur together, and in such cases we have scarcely the means of obtaining them in a state of purity unless when they en- ter into definite and crystallizable compounds with some other sub- stance. 1557. It is not unlikely that all the vegetable principles may be All may found hereafter to be capable of entering into definite compounds form defi- with other bodies, and that they will ultimately be possessed of the pou n j° s m ' character of acids or bases. But there are many which, so far as our present knowledge extends, do not seem capable of forming any such definite compounds, thus caoutchouc neither combines with acids nor bases. We must consider such bodies as neutral. 1558. There are also several groups of bodies which have been Groups dis- distinguished by a common name, some of which neutralize acids, tinguished. and therefore ought to constitute bases, while others of the same group neutralize bases, and therefore ought to constitute acids ; while a considerable number has been so imperfectly examined that we do not know whether they be acids or alkalies. This is the case with the group of bodies distinguished by the name of vola- tile oils. 1559. Inconsequence of the imperfect state of our knowledge Temporary of these and various other groups similarly circumstanced, a tempo- ^medfate" rary class may be formed under the name of intermediate bodies, bodies, which will disappear, when the investigation of vegetable principles has made greater progress. 1560. All the vegetable principles may be arranged under the Four class- * Thomson dissents from this, and remarks that at present we have no means of knowing how the numerous atoms that constitute organic principles are grouped to- gether. 364 Chap. VI. Theory of amides. Amide, how applied. Liebig’s application of amide. Organic Chemistry. four following classes : — l. Acids. 2. Alkalies. 3. Intermediate principles. 4. Neutral principles. 1561. Before describing- the characters of the various principles, and to render the new terms intelligible, it will be proper to notice the results of the late investigations of Wohler, Liebig, Pelouse and Dumas. 1562. Theory of Amides , or Amidets. If we represent the com- position of oxalic acid by the formula C 2 0 3 , and that of ammonia by NH 3 , we rrlay represent oxalate of ammonia by C 2 0 3 -)-NH3. It was observed by Dumas, that when crystallized oxalate of ammonia is distilled there is obtained, among other products, a white tasteless powder, which he distinguished by the name of oxamide .* On an- alyzing this he found it composed of C 2 0 2 +NH 2 . It is therefore oxalate of ammonia deprived of an atom of water. When heated with potassa, ammonia is disengaged, and oxalate of potassa formed. By this treatment, therefore, it converted into oxalate of ammo- nia, and of course must have resumed the atom of water which it had lost. 1563. The term amide , has been generalized and is applied to all those anhydrous compounds of an acid and ammonia which by heat may be deprived of an atom of water ; or to all those compounds, which, by the addition of an atom of water, can be converted into a salt of ammonia. Benzoic aqid consists of C14H5O3 Ammonia . , t ' - H 3 N Benzoate of Ammonia of C14H5O3+H3N Now Wohler and Liebig obtained a substance to which they gave the name of Benzamide , composed of C u H 5 0.-|-H 2 N, so that it dif- fered from benzoate of ammonia by containing HO or an atom of water less. Now as oxalate of ammonia and benzoate of ammonia are in all probability binary compounds, it has been inferred that ox- amide and benzamide are also binary compounds, thus Oxamide .... CX)*fH 2 N Benzamide .... ChHsO^HsN If this be admitted, it will follow that C 2 0 2 and C M H s 0 2 are com pounds capable of existing and of combining with other bodies ; and likewise that there is such a compound as H 2 N. 1564. Liebig applies the name amide to the hypothetical com- pound of two atoms of hydrogen and one atom nitrogen. If potassi- um is heated to the point of fusion and a current of dry ammonia passed over it, hydrogen gas is eyolved, and the potassium at first increases in bulk, loses, the metallic lustre, and is converted into a clear liquid, which on cooling concretes into a gray silky mass; it is instantly converted into potassa and ammonia on the addition of water. It is called potassamide , or a compound of 1 atom potassium . . . . K 1 “ of, H 2 N Potassamide ..... K-j-H«jN * A contraction of oxalate of ammonia. Theory of Ethers. 365 Add 1 atom water . . . , HO Sect. 1 . and we have .... KO-I-H 3 N or an atom of potassa and an atom of ammonia/ 1565. Dumas has given to these compounds the name of arnidet . Amidets Thus oxamide he calls amidet of oxide of carbon H 2 N-j-C 2 0 2 ; C 2 0 2 °* * * § ^ umas - being a compound similar in constitution to oxide of carbon, which is CO.t 1566. Theory of Benzoyl. A remarkable train of discoveries has Theory of been made by Wohler and Liebig while investigating the volatile benzoyl ’ oil of bitter almonds. They have led to the inference that the basis of benzoic acid is a substance, to which they have given the name of benzoyl composed of C 14 H 5 0 2 . The oil of bitter almonds is a hydret ; or . . C 14 H 5 O 2 +H Benzoic acid is an oxide, or Ci 4 H 5 0 2 +0 They obtained also chloride, bromide, sulphuret and cyanide of benzoyl. These discoveries render it almost certain that benzoyl exists as a separate compound, and that it is capable of combining with the sup- porters of combustion and cyanogen, also with hydrogen, sulphur, and doubtless other simple substances or compounds. Similar com- pounds have been discovered by Lowig in the volatile oil of spiraea ulmaria, which is a hydret of spiroil.l Analogy leads to the infer- ence that other (probably all the) vegetable acids have, like the ben- zoic, a base, and that the acid is a compound of that base with oxygen. 1567. Theory of Ethers. According to Dumas the base of ether Theory of is C 4 H 4 .§ Sulphuric ether is C 4 H 4 +HO ; oxalic ether is (C 4 H 4 -)- ethers. H0)-f-C 2 0 3 and so on of the others. According to Liebig, the radical of ether isCjH 5 . Sulphuric ether Liebig’s, is an oxide of C 4 H 5 , and is represented by C 4 H 5 -(-0, or (for shortness sake) by C 4 H 5 0. Alcohol is a hydrate of sulphuric ether, or C 4 H 5 0+H0. The radical of ether is capable of combining with chlorine, bro- mine, and iodine, and forms chloric, bromic, and iodic ethers, com- posed as follows : Chloric ether .... C 4 H 5 -(-2Cl Bromic ..... C 4 Hs+2Br Iodic ..... C 4 H 5 -b 2 I All the oxygen-acid ethers are combinations of an atom of sulphuric ether, which possesses the characters of a base with an atom of the acid. 1568. What have been considered as alcohol acids are merely Alcohol combinations of one atom of ether acting as a base with two atoms of acids, the acid. They ought rather to be considered as salts, consisting of two atoms acid united to one atom base, than as acids sui generis. || * According to Kane white precipitate, of the Pharnmcop., is a morcuramide, or a compound of Hg+H 2 N. + For other examples see Thomson. 7, and Dumas’ Chim. appliqut , v. S3. t A supposed base. § Called by Thomson in Chem. of Inorg. Bodies, Tetarto-carbohydrogen. || Thomson is disposed to prefer the theory of Liebig as the simplest, and as agree- ing best with the phenomena. Liebig has extended his theory much farther, and made it to apply to sugars, &c. T. 9. 366 Organic Chemistry. Cha P vt - 1569. Theory of Pyr acids. There are several vegetable acids Theory of which, when distilled, undergo decomposition, and new acids are pyracids. generated by the process, which have been distinguished by the name o (pyracids. Thus tartaric acid when so treated, yields pyro- tiorTaffect 1 * tariaric ac ^’ £ a U‘ c > pyrogallic, &c. It has been observed by ed by heat. Pelouze, that the nature of the decomposition is regulated by the degree of heat applied. When the heat is not too high, the acid is resolved into a pyracid, carbonic acid and water, or sometimes into a pyracid, and one or other of the two last products. Thus when tannin is distilled at a heat of 4S2° it is resolved into carbonic acid, water, and metagallic acid. Tannin being C 18 H 3 0,2 three atoms of tannin are Now these three atoms are resolved by the heat into 6 atoms carb. acid . . =Cs O12 8 “ water . = H* 0« 8 “ metagallic acid . =C4*Hi6 0 ig C54 H24 0 3 6 When gallic acid is distilled at 419 °, it is converted into pyrogallic acid and carbonic acid, Gallic acid is . . . C7 H3 O5 Pyrogallic acid is . Carb. M is . C 6 Hj O3 C o 2 C 7 H 3 Os At the 482 ° no pyrogallic acid is formed, but only metagallic acid, water, and carbonic acid, 1 atom gallic acid is C7 H 3 O5 1 “ metagallic “ 1 “ carb. acid “ 1 “ water =C 6 Il 2 0 2 =C O2 = HO Theory of substitu- tions. Dumas’s conclu- sions. C 7 h 3 o 5 Sometimes the saturating power of a vegetable acid is not altered by converting it into a pyroacid ; sometimes, according to Pelouze, it is reduced one half.* From these observations it has been inferred that gallic acid is a compound of pyrogallic acid and water, and so of others. t 1570. Theory of Substitutions. Oxygen, chlorine, bromine, and iodine may be made to unite with various compound bodies, while at the same time these bodies give out hydrogen. Thus when dry chlorine gas is passed into pure oil of bitter almonds, which is com- posed of C u H 5 Oo-|-H, it loses its atom of hydrogen which con- stituted it a hydret, for which an atom of chlorine is substituted, making a compound consisting of C 14 H 5 0 2 -|-CI, which is a chloride of benzoyl. This and analogous facts have been generalized by Du- mas, who has drawn from them the following general conclusions. 1571. 1. When a body containing hydrogen is subjected to the * Ann. de Chim. et Phys. Ivi. 303 . + Thomson does not agree in this opinion and thinks it more probable, that by the temperature applied, a certain portion cf the carbon, or hydrogen, or of both, under- goes combustion, and that the remaining atoms arrange themselves so as to constitute the pyroacids- Compound Radicals. 367 dehydrogenizing action of oxygen, chlorine, bromine, or iodine, for Ssct. i. every atom of hydrogen that it loses it gains an atom of oxygen, chlorine, bromine, or iodine. 2. When the hydrogenous body con- tains water, this last body loses its hydrogen without anything being replaced. If, after this, any hydrogen be abstracted, it is replaced by a corresponding number of atoms of oxygen, chlorine, &c.* t. 1572. Laurentf considers the base or radical of every organic Laurent’s body to be a compound of carbon and hydrogen united together, so view, that the atoms of the carbon bear a simple relation to those of the hydrogen. When these radicals are subjected to a dehydrogenizing process, as by passing a current of chlorine through them, they gra- dually lose their hydrogen or a part of it, but gain as many atoms of the dehydrogenizing body as they lose of hydrogen. So that if we add the number of atoms of the new body to those of hydrogen re- maining, the sum will make up the number of atoms of hydrogen originally present in the radical. 1573. The dehydrogenizing body, or a part of it, being converted into water, nitric acid, hydrochloric acid, &c., may either be disen- gaged or remain combined with the new compound formed. 1574. The fundamental radical and its derivatives will be neutral Neutral or alkaline, whatever be the portion of oxygen, hydrogen, &c. enter- ing into it. But when the oxygen, &c. enters into combination with Acid< the radical, it renders it acid , how small soever the uniting portion Effect of may be. Those bodies which enter into combination without being heat. a part of the radical, may be removed by heat, alkalies, &c., without being replaced by anything else. But when a body constitutes a part of the radical, this cannot be done. T. 13. 1575. Liebig has termed certain compound bodies, which have the Compound property of uniting with simple bodies, compound radicals. Those J a . c, ^ c . als of which unite with hydrogen give rise to hydracids. He has arranged Lle lg ‘ these combinations in groups, according to the radical of each ; the individual members of each group arising from the combinations of the radical with the elements, and from the union of the compounds thus formed with other compound bodies. 1576. Whenever one or more of the constituent parts is removed New com- from any of these, a new compound of another radical is produced, pounds. When the oxygen has been removed, and its place supplied by its Oxygen re- equivalent of sulphur, a sulphur-compound of the same radical is moved - formed, and its properties are similar to those of the oxygen-com- pound. When the hydrogen is displaced, and its position occupied by its Hydrogen, equivalent of chlorine or oxygen, there will be formed either a similar compound of a similarly constituted radical, or several new com- pounds of a more simple radical. 1577. All combinations of compound radicals not containing nitro- Combina- gen, are reduced when exposed to the action of oxygen to oxides of compound more simple radicals, the higher or lower degree of oxidation being radicals not dependent upon the quantity of oxygen present. containing * For examples see T. Org. Chem. 1 1 . t Ann. de Grim, et Phys. Ixi. 128. 368 Chap. VI. Decompo- sed. Action of strong acids. Action of potassa, on compounds not con- taining ni- trogen. Products. Action on those con- taining ni- trogen. Products: Destructive distillatiou, products. Organic Chemistry. 1578. Organic compounds not containing nitrogen, may be de- composed in three different ways, when brought into contact with concentrated or anhydrous sulphuric acid ; firstly, the acid may withdraw water from the compound, or at least oxygen and hydro- gen in the proportions in which they form water; in this case the other component parts unite into one or more new compounds ; thus oxalic and sulphuric acids give rise to the formation of water, of car- bonic oxide and of carbonic acid ; or, secondly, the acid may at the same time give oxygen to a part of the carbon of the compound, when the above products, together with sulphurous acid, will be pro- duced; or, thirdly, the acid may give oxygen to the hydrogen of the compound, and iu this case be converted into hyposulphurous acid, which usually enters into very intimate combination with the organic substance thus modified. 1579. By the action of strong acids upon substances containing nitrogen, there is frequently produced through the medium of the constituents of water, on the one hand ammonia, which combines with the acid, and on the other an oxide of a new radical, in which all the carbon of the original compound is present. Hydrocyanic acid and hydrochloric acid ; oxamid, urea, and sulphuric acid, &c. &c. 1580. All organic compounds not containing nitrogen, are decom- posed by being fused with hydrate of potassa, and if the latter be present in sufficient quantity, the decomposition is not attended with the separation of carbon ; the products which are formed are the same as those resulting from the action of powerfully oxidizing’ agents; water is generally decomposed, its oxygen unites with the carbon and hydrogen of the substance, while its hydrogen is liberated, and either escapes in the form of gas, or enters into some new combination. The resulting products of this decom- position may be either ulmic, acetic, and oxalic acids, oxalic acid alone, or solely carbonic acid, according to the degreeof temperature to which the mixture is exposed. 1581. All organic compounds containing nitrogen are decomposed by being boiled in a solution of caustic potassa, or by being fused with the hydrate; the products are generally the same as those ge- nerated by the action of a strong acid upon the same substances, only that with potassa the ammonia is liberated, while the oxide of the new carbonized radical enters into combination with the potassa. Many substances which are very rich in nitrogen are converted, with the separation of a part of the nitrogen as ammonia, and the absorption of oxygen, into cyanic acid, and this, by uniting with the potassa escapes further decomposition ; in this case the fused resi- due is completely decomposed into ammonia and carbonic acid by bein? dissolved in a little water and boiled. 15S2. When organic bodies are exposed to the destructive distil- lation, their constituents give rise to the production of new volatile compounds of more simple radicals, either with or without the depo- sition of carbon. The products vary with the temperature, which gives rise to the division of the distillation into several periods. In the first are produced organic acid of more simple radicals, carbonic acid, water, and combustible fluids, which admit of being mixed with 869 Vegetable Acids. water. Jn the second period, the products of the decomposition of Sect, u. the new substances formed during the first, are generated ; the acids disappear, their oxygen unites with a part of their hydrogen and carbon, forming more simple compounds, as carbonic oxide, carbonic- acid, and water, a portion of the carbon is generally deposited, while the rest unites with hydrogen, giving rise to volatile or fixed oleagi- nous substances. In the last period, only charcoal and gases are obtained ; the latter generally consisting of a mixture of carbonic oxide, olefiant and light carburetted hydrogen gases. Substances containing nitrogen form, under the same circum- stances, ammonia, and sometimes cyanic acid ; in the last period, cyanogen and hydrocyanic acid. 1583. When an organic compound is exposed to a similar decom- Effect of position in contact with a strong base, which is not reduced by a red j^ r ° e n ^ c heat, it is generally decomposed into carbonic acid, which remains ’ in combination with the baseband into one or more new substances. Should these latter contain oxygen, they may be entirely deprived of Oxygen re* it by a new distillation with the base, the oxygen giving rise to ano- moved - ther portion of carbonic acid, while the other constituents of the sub- stance are obtained in the form of solid, fluid, or gaseous compounds of carbon and hydrogen, l. 738 . Section II. Vegetable Acids. 1584. These acids may be divided into seven sets — 1. Volatile Thomp- _ Acids, or those which may be volatilized without decomposition ; 2. s°o n s 0 f lvl Fixed Acids , such as cannot be volatilized or distilled over without acids, decomposition ; and these may be subdivided into such as are de- composed when exposed to heat, but furnish at the same time pyr- acids ; and, 3, into those whose pyracids are unknown. 4. Oily Acids, or those into which oils or wax are converted, when boiled with potassa or soda. The combination with the alkali constituting soap. 5. Acids containing nitrogen. 6. Acids imperfectly exa- mined. 7. Compound Acids , consisting of a vegetable principle united to a strong mineral or vegetable acid. 1585. Oxalic Acid , 2 C0-|-0, 2 eq. carb. oxide 1 oxy.= Oxalic 36.24. (L.) C 2 0 3 =36. (T.) This acid was discovered by Scheele in acid - 1776. It occurs in several plants, particularly of the genera oxalis, rumex, &c ; combined with potassa in roots and with lime in several kinds of lichens.* Oxalate of lime is also an ingredient of several uri- nary calculi ; the acid is a product of the decomposition of uric acid, of all organic compounds not containing nitrogen when oxidized by ni- tric acid, or acted upon by hydrate of potassa, or by permanganic acid ; it is also formed by the decomposition of cyanogen with water and ammonia. L. 1586. It is obtained by digesting by aid of gentle heat one part of sugar, or p rocess better still, of potato starch, in 5 parts of nitric acid of sp. gr. 1.42, diluted with 10 parts of water, as long as gaseous products are evolved ; by evaporation the acid is obtained in crystals, which may be purified by a second crystallization after being well dried on paper or porous earthen ware. * Said to occur in Humboltine with oxide of iron by Rivero — not confirmed by Thomson’s analysis. See his Mineralogy , ii. 469. 47 370 Chap. VI. Process 2. Theory. Crystals, How dis- tinguished from Ep- som salts. Vegetable Acids . When prepared on the large scale the process is conducted in cylindrical ves- ' sels of earthern ware, which are heated Ity being surrounded with warm water ) on a small scale it may be made in a porcelain dish. From 12 parts of potato starch 5 of the acid are obtained. The mother liquor should be treated with an additional quantity of acid, and again warmed, when a second crop of crys- tals will be formed ; this is repeated until the solution is quite exhausted. On account of the cheapness of nitric acid, this is the usual process now adopted in the manufactories. Any N adhering to the crystals, may be removed by gently heating them in a porcelain dish, or by repeated crystallization.* L. It may also be obtained by precipitating a solution of the superoxalates of po- tassa by acetate of lead or sulphuret of barium, carefully washing the precipitate, and decomposing it while yet moist by dilute S. Filter and evaporate. To de- compose the oxalate of lead or baryta five parts of strong S must be employed diluted with ten of water for every seven parts of the binoxalate of potassa. Nine tenths of the dilute S is to be added in successive portions to the moist lead or barytic precipitate ; sulphate of lead or baryta is instantly formed, and the ox- alic acid is dissolved by the water. After the mixture has stood some hours, the clear liquid should be poured from tiie precipitate, which should be repeatedly washed. The solution yields upon evaporation, crystals of pure oxalic acid ; any trace of lead may be removed by hydrosulphuric acid gas. The residue of i sulphate of lead or baryta, which still contains some undecomposed oxalate, , must be treated with the remaining tenth of the dilute S, and heated with a little more water ; in this manner an additional quantity of impure oxalic acid is obtained, but the 8 may be separated from the crystals by washing. 1537. The production of oxalic acid from organic matter is a con- sequence of the oxidation of the elements of the latter by the oxy- gen of the N ; hence those substances give it in greatest quantity , which contain oxygen and hydrogen in the same proportion as I water. In the second process sulphuret of potassium and oxalate of I baryta, or acetate of potassa and oxalate of lead are formed. The ] oxalate of baryta or lead is decomposed by S, giving rise to free 1 oxalic acid and sulphates of lead or baryta. L. 1558. The crystallized acid is, according to Liebig, a compound of I the hydrate with water of crystallization. The crystals are trans- I parent oblique rhombic prisms, with one or two terminal planes, one U pair of the lateral edges of the latter is sometimes truncated. 1559. This acid has no odour; tastes and reacts strongly acid, ■ and is poisonous, and from the resemblance which the crystals bear ■ to those of Epsom salt, many fatal mistakes have arisen. The acid ■ taste is in itself a sufficient mark of distinction ; or without tasting J| it, if a few drops of water be placed on a slip of the dark blue pa- 1 per which is commonly wrapped round sugar loaves, and a small I quantity of the suspected crystals be added, if it be oxalic acid iu I will change the colour of the paper to a reddish brown. The so- I lution also of a small quantity of this acid in a tea-spoonful of water, will effervesce with a little scraped chalk or whiting. H. When the acid has been swallowed, copious draughts of lime water, j 1 or magnesia and water, should be administered, and vomiting exci- ted as speedily as possible. * If shavings of wood be mixed with caustic potassa, and exposed to a heat consid- erably higher than that of boiling water, the wood suffers decomposition, and is f mrtly converted into oxalic acid, which combines with the potassa ; a process fol owed by some manufacturers of this acid. T. 371 Binoxalate of Potassa. 1590. The crystals when heated fall into powder, and lose 28 per Sect - 11 • cent. = 2 eq. of water of crystallization; the hydrate of oxalic Effect of acid is left. When rapidly heated to the temperature of 350°, they heat * fuse and lose their water of crystallization, a part of them decom- posing, while another portion sublimes as hydrate in dense white fumes of a strong odour, which cover the surface of the fused acid in the form of a woolly crystalline mass. If heated in a retort to 310° it is decomposed into C, C and formic acid. 1591. Heated in strong S, it is decomposed into C, C and water. Decompo- The anhydrous oxalic acid may be considered as a compound of 1 se ^by s eq. C — | — 1 eq. C, which accounts for the production of equal vols. of the two gases whenever the pure acid or any of its salts is heated in strong S (512). 1592. The crystals dissolve in eight parts of water at 60°, in their Solubility, own weight of boiling water, and in four parts of alcohol at 60°. When pure it should give a precipitate with salts of baryta that is Test of perfectly soluble in N, if it contain lead it is blackened by hydrosul- phuric acid gas: it should sublime without leaving a residue. 1593. This acid and its soluble salts are important reagents for detecting and separating lime.^ 1594. By distilling oxalate of ammonia, or oxalates, with am- Oxamide. moniacal salts, a substance has been obtained by Dumas which he has called oxamide, t which will be noticed hereafter. 1595. Oxalate of Ammonia. NH 4 0C 2 0 3 +aq. crystals. This is Oxalate of a very useful salt for the purpose of separating lime from magnesia, ammonia * and generally for precipitating lime from its solutions. It is obtained by neutralizing a solution of pure oxalic acid by Obtained, caustic or carbonate of ammonia, or by decomposing the oxalate of lead by sulphuret of ammonium, and evaporating the solution to crystallization. It may also be prepared by neutralizing the bin- or quadroxalate of potassa with carb. of ammonia ; the first crop of crystals consists of oxalate of ammonia, which may be completely freed from potassa by repeated crystallization, the mo- ther liquor contains the neutral oxalate of potassa. 1596. The crystals are long, colourless, transparent prisms, of the Crystals, right prismatic system ; with a strong saline taste, less soluble than the oxalic acid and efflorescent, losing 12.6 per cent, of water of crystallization. By heat it is decomposed, giving rise to oxamide. 1597. Binoxalate of Potassa. H0.C 2 0 3 ,K0.C 2 0 3 ~|-2 aq. eq. = Binoxalate 155.63. This salt is used and sold as the essential salt of lemons , of potassa. * In the neutral salts of oxalic acid, the oxygen of the base is to that of the anhy- drous add in the proportion of l : 3. If the oxygen of the metallic oxide be consid- ered as a part of the acid, the compound contains C and a metal. Many salts of oxalic acid, whose bases are oxides easily reduced to the metallic state, are decomposed by heat into C and metal (oxalate of silver with a slight explosion). The oxalates of the alkalies under the same circumstances evolve C, and are converted into carbo- nates. Many metallic oxides when heated with an oxalate are reduced by the C evolved. There exist both neutral and acid salts of this acid, the latter contain dou- ble, and sometimes four times as much acid as the former. (Liebig.) t Abbreviated from oxalic acid and ammonia. 372 Vegetable Jlcidt. Chap, vi. for removing iron-moulds and other metallic stains (ink, &c). It exists ready formed in the juice of the oxalis acetosella or wood sor- rel, from which it was formerly procured. Prepared. 1598. It may be made by neutralizing one part of crystallized ox- alic acid by carbonate of potassa, and afterwards adding to the neutral salt another part of oxalic acid and crystallizing. The crystals are transparent oblique rhombic prisms, with an acid taste and reaction. Properties. It is poisonous. Soluble in 40 parts of cold and 6 of boiling water. 1599. When pure it should fuse and decompose without emitting a burnt odour, and the residue should be of a gray, not of a black colour.* Quadroxa- 1600. Quadroxalate of Potassa is sold in commerce as binoxalate. late< It is procured by dissolving the binoxalate in hydrochloric acid and crystallizing; it is made on the large scale by neutralizing one part of crystallized oxalic acid and adding to the solution three parts of the pure acid. Crystals. 1601. Its crystals are transparent prisms of the doubly oblique prismatic system ; at 262° it loses two atoms or fourteen per cent, of water, at higher temperatures oxalic acid passes off and it is decomposed. If pure its reaction when heated is similar to that of the binoxalate; if three parts are converted into carbonate by a red heat, and added to a solution of one part, the neutral oxalate should be obtained. Oxalate of 1602. Oxalate of Lime , Ca0.C 2 0 3 -j-2 aq. = S2.74, occurs in se- lime. veral species of lichen, of which it forms the firm, hard skeleton, so that many of them may be used for preparing oxalic acid, but not very advantageously.! Distin- 1603. The insolubility of this salt in water, ammonia, and acetic guished. acid, an( j j ts so l u bility in the nitric and hydrochloric acids, distin- guishes it from most other precipitates. Advantage is taken of this to detect lime in solutions from which all other precipitable metallic oxides hare been separated by other means, the alkaline oxalates being the best reagents for this purpose; thus these oxalates are used to separate lime from magnesia, with the latter of which they form soluble double salts. On the other hand, lime may be used to detect oxalic acid.t Colour, &c. 1604. Recently precipitated oxalate of lime is a snow-white floc- culent powder, insoluble in acetic acid, readily dissolved by free nitric or hydrochloric acid, and by a red heat is converted, without being perceptibly blackened, into carbonate of lime ; from the weight of which, either the oxalic acid or the lime may be calculated. L. 750. imparities da- *The presence of cream of tartar is recognised by the carbonaceous residue, and the ucted. peculiar odour which it emits on burning ; that of sulphate of potassa by the common tests of S. If of two equal parts by weight, of the salt, the one be exposed to a red Irat, and the other be dissolved in water, the solution of the latter should be deprived of its acid reaction by the addition of the residue of the former; if this does not hap- pen, it is not the binoxalate but the quadroxalate, which is met with in commerce un- der that name. (Liebig.) t See Braconnot’s process Ann. do Chim.et Phys. xxviii. 318, and Quart. Jour. xix. t It should be remembered that oxalic acid is imperfectly precipitated by salts of lime from a solution which contains the oxides of chromium, iron, or manganese. (Liebig.) Formic Acid. 373 1605. j Rhodizonic Acid. C 7 H 3 O 10 . When a stream of dry carbonic Sect. 11 . oxide gas is transmitted over a portion of fused potassium, the gas is Rhodizonic absorbed in large quantity; the potassium coats the surface of the acid * glass tube, becomes green, and at last a black porous mass is ob- tained, which, if exposed to the air when warm, inflames, and if covered with water dissolves with the rapid evolution of a combusti- ble gas ; if moistened with water it burns, and forms a red solution which contains rhodizonate of potassa. 1606. This compound of potassium and carbonic oxide was Howob- obtained by Gmelin in considerable quantity as a secondary product taincd. during the preparation of potassium by Brunner’s process (839), when it separates from the gases evolved in the form of a gray pow- der, which may be readily collected. Exposed to moist air it ab- sorbs water, and is converted, without combustion, into rhodizonate of potassa of a scarlet- colour ; by being treated with alcohol, in which it is soluble, the free potassa may be separated. All its com- pounds are of a red colour, or, in the dry state, of a brilliant metallic green. 1607. The changes which are produced on rhodizonate of potassa Remarka- when Its aqueous solution is heated, are very remarkable; without ble the evolution of gases it is decomposed into free potassa, oxalate 0 f chan £ es * potassa, and into the potassa salt of a new acid, which has been called by Gmelin the croconic acid. l. 752. 1608. Croconic Acid. C 5 0 4 = 62. The croconic acid is prepared Croconic by adding hydrofluosilicic acid to a solution of its potassa salt, and eva- acid - porating to dryness ; the pure acid is removed from the yellow resi- due by water; it is yellow,* readily crystallized, tastes and reacts strongly acid, is soluble in water and alcohol ; all its salts are yellow, and, with the exception of the ammoniacal salts, are all of them insoluble in alcohol. 1609. Croconate of Potassa crystallizes in long six-sided prisms, Croconate of an orange-yellow colour, tastes similar to nitre, and is neutral with of potassa. respect to vegetable colours. When heated it loses 15 per cent. = 2 eq. winter and becomes of a lemon-yellow colour. It burns like tinder into a mixture of carbonate of potassa and carbon, with evolu- tion of C and C ; it is decomposed by chlorine and N with effer- vescence into peculiar salts. 1610. Formic Acid. C 2 H 0 3 = 37. This acid was first noticed by p orm i c Ray, in 1671, t in an account of the acid spontaneously given out by acid, ants, and which they yielded when distilled. In 1812 Gehlen examined History, it and pointed out some of its characters. It has been since ana- lyzed by Berzelius, and an artificial method of preparing it discover- ed by Dobereiner. 1611. It may be obtained from ants by the following process : Any quantity of ants may be infused in about thrice their weight of water, put _ the mixture into a silver, or tinned copper still, and draw off the water by distillation ” roceS3 or ” as long as it continues to come over without any burnt smell ; the distillation must be stopped as soon as that is perceived Saturate the water in the receiver with carbonate of potassa, and evaporate to dryness. Mix the white mass thus ob- tained with as much sulphuric acid, previously diluted with its weight of water, as is sufficient to saturate the potassa. Introduce the mixture into a retort, and * Hence its name from crocus, saffron . t Phil. Trans. 374 Chap. VI. Obtained from sugar &c. Process. Concentra- ted. Emmet’s process. Detected. Liebig’s acid. Properties. Vegetable Jlcids. distil slowly to dryness. The liquid which comes over into the receiver is to be ' again rectified by a very moderate heat, to get rid of any portion of sulphuric acid that may be present. 1612. It may be prepared from sugar and many other vegetable » substances, when treated with binoxide of manganese and sulphuric acid. The following process has been pointed out by Dobereiner. Dissolve 1 part of sugar, starch, &c., in 2 parts of water, mix the solution (in a large. vessel) with or three parts of binoxide of manganese in fine powder. Heat the mixture to 140°, add, by little and little at a time, 3 parts of concen- trated sulphuric acid, previously diluted with its own weight of water, care- fully agitating the mixture after every addition, with a wooden rod. After the addition of the first third of the acid so violent an effervescence takes place, that unless the vessel be at least 15 times the bulk of the mixture, a portion will run over.* 1613. A pound of sugar yields a quantity of the acid, capable of saturating five or six ounces of carbonate of lime. To obtain the formic acid in a concentrated state, evaporate the formate of lime to dryness, and mix seven parts of this dry salt, in powder, with ten parts of concentrated sulphuric acid and four parts of water, and dis- til in a retort If we substitute six parts of alcohol for the four parts of water and distil, we obtain formic ether. 1614. The following process has been given by Emmet, t who af- firms that the oxide of manganese is of no use in the process. Mix together in a retort equal measures of water, oil of vitriol, and clean, but unground rye, or cracked maize; let them be heated to the boiling point, and as soon as the mass has become thoroughly blackened, add another measure of water and distil otf one measure of formic acid. The addition of more water, and fresh distillation will afford an additional quantity of a weaker acid. 1615. The presence of formic acid may be easily ascertained. When the acid or formate of soda is put into a solution of any salt of gold, platinum, or silver, an effervescence takes place, C is given off, and the metal is deposited.! When formate of soda is mixed with a solution of corrosive sublimate, calomel is deposited. When the acid is added to a solution of nitrate of lead, crystals of formate of lead in needles are deposited. 1616. Liebig has found that formic acid maybe obtained, contain- ing only one atom water, by decomposing dry formate of lead by hy- drosulphuric acid. When of this strength it is much more corrosive than concentrated S. The smallest drop applied to the skin occa- sions a sensation like that produced by red-hot iron. A sore is produced, which is long in healing. This hydrate crystallizes at 32° and boils at 212° like water. The common acid, which is a bi- hydrate, crystallizes at 5° and boils at 226£°.§ Formic acid has a * The effervescence is owing to carbonic acid. Pungent vapours of formic acid are exhaled. To preserve these, the mixture should be made in a copper alembic the top of which should be put on and connected with the worm in the refrigeratory. When the violence of the effervescence is over, the rest of the sulphuric acid is to be added, the mixture is to be agitated, and the whole distilled over almost to dryness. A lim- pid acid liquid is obtained, having a strong smell, and consisting of water, formic, acid, and nn etherial liquor. Saturate the formic acid with carbonate of lime, and distil the liquor a second tune to preserve the etherial liquid which comes over with the water, and from which it may be afterwards separated by distilling it off fused chloride of calcium. T. t See his interesting paper in Amer. Jour, xxxii. 140. i Ann. d* Chim. et de Phys. lii. 107. § Jour, de Pharm. xxi. 381 Succinic Acid . 375 considerable resemblance to acetic. Very dilate formic acid is said sect, n. to undergo spontaneous decomposition like vinegar.* 1617. Mellitic Acid. C 4 0 4 -(-H = 57.48. (L.) Combined with alu- MeUitic niina this acid constitutes a rare mineral, mellite or honey-stone. It ac may be obtained by the following process of Wohler. Reduce mellite to fine powder, digest in a solution of carbonate of ammonia; Process, after the liquid has taken up all the mellitic acid, the excess of ammonia is ex- pelled by boiling; filter, evaporate until crystals appear. The crystals are then dissolved in water, and acetate of lead added. The mellitate of lead is decom- posed by hydrosulphuric acid. The solution separated by filtration from the sul- phuret of lead yields, on evaporation, a white slightly crystalline powder ; it is soluble in alcohol, from which it may be obtained by very slow evaporation in radiated groups of acicular crystals. 161S. The dry acid is not changed by boiling in N or S. The Effect of aqueous solution tastes and reacts strongly acid. Boiled in alcohol, heat > &,c * it seems to form an acid mellitate of ether. It forms salts by uniting with the base ; its alkaline salts are soluble, and may be obtained in crystals, but with the other metallic oxides it forms either insoluble or very sparingly soluble compounds. These salts are decomposed by heat, but the silver salt suffers in the first instance a peculiar change ; at 356° 1 eq. of water is separated.! 1619. Succinic Acid. C 4 H 2 0 3 , = 50. (T.) This acid is obtained Succinic from amber ( succinum ), and hence its name. acid> Fill a retort half way with powdered amber, and cover the powder with a Process, quantity of drj' sand ; lute on a receiver, and distil in a sand-bath without em- ploying too much heat. The succinic acid attaches itself to the neck of the retort. It is purified by dissolving in hot water and putting in the filter a little cotton, previously moistened with oil of amber, which retains most of the oil, and allows the solution to pass clear. It is subsequently crystallized by gentle evaporation, and this process is to be repeated till the acid is sufficiently pure. 1620. Succinic acid maybe obtained in three states: 1. com- May be ob- bined with an atom of water; 2. with half an atom; and, 3. anhy-^gg drous. states. The first is the crystallized acid of the shops, when pure. It is soluble in water, but less so in alcohol, and scarcely at all in ether. It melts at 356° and boils at 455°. When the crystallized acid is kept for a long time in a retort at a temperature between 266° and 284°, it undergoes a remarkable change. A great number of white needles are deposited and a little water is disengaged. These nee- dles consist of succinic acid deprived of half its water, while the por- tion in the retort remains unaltered. 1621. The anhydrous acid may be obtained by distilling a mix- Anhydrous ture of dry phosphoric acid with crystallized succinic acid. The acid * best method is to fuse the succinic acid in a retort, and then add the phosphoric acid, and distil slowly. Succinic acid dissolves in 96 parts of water at 50°, in 24 parts at Solubility. * Thomson states that he has preserved for several years, formic acid prepared by Dobereiner’s process, dilute, but stronger than vinegar. + Since the silver salt, dried at 212°, can retain no water, it is probable that the water is first formed at the above heat by the hydrogen of the acid, and the oxygen of the oxide of silver, when the salt passes into a combination of silver and carbonic ox- ide C 4 O 4 , the latter acting the part of chlorine or any other haloid substance. (Liebig.) 376 Vegetable Acids. Chap. Vf. Succinates. Acetic acid. Vinegar. Distilled or acetous acid. Acetic acid. Obtained. Pyroligne- ous acid. Properties of acetic acid. 52°, and in 2 parts at 212°. The anhydrous acid is less soluble in water than the hydrous, but more soluble in alcohol and ether. 1622. The compounds which this acid forms with bases are termed succinates. The alkaline succinates are soluble in water. This is not the case with succinate of baryta, hence baryta is preci- pitated from a neutral solution by succinate of ammonia. This salt likewise precipitates mercury and lead. It throws down iron from all solutions provided the iron be in the state of peroxide and there be no excess of acid present. 1623. Acetic Acid, C 4 H 3 0 3 = 51. (T.) This acid is employed in three different states. When first prepared it is called vinegar ; when purified by distillation it assumes the name of distilled vine gar, usually called acetous acid by chemists; when concentrated as much as pos- sible it is called radical vinegar and acetic acid. 1624. Vinegar is usually prepared by subjecting liquids that have undergone the vinous fermentation, to the action of air ; much oxygen is then absorbed. Many solutions of vegetable matter produce vinegar.* When distilled at a temperature not exceeding that of boiling wa- ter, till about two thirds or five sixths of it have passed over, most of the impurities are left behind and the product is pure acid, diluted with water. Distilled vinegar or acetous acid is transparent and colourless, of a strong acid taste and an agreeable odour. 1625. To obtain acetic acid, or, as it has been sometimes called, radical vinegar , distilled vinegar may be saturated with some me- tallic oxide, and the acetate thus obtained, subsequently decomposed. It is thus procured by distilling acetate of copper , or crystallized ver- digris , in a glass retort heated gradually to redness : it requires re-distillation to free it from a little oxide of copper which passes over in the first instance. Acetic acid may also be obtained by distilling acetate of soda or acetate of lead with half its weight of sulphuric acid : or from a mixture of equal parts of sulphate of cop- per and acetate of lead ; in these cases, the acid passes over at a moderate temperature. 1626. A considerable quantity of acetic acid is also now procured by the distillation of wood in the process of preparing charcoal for the manufacture of gunpowder. The liquor at first procured is usu- ally termed pyroligneous acid ; it is empyreumatic and impure, and several processes have been contrived to free it from tar and other matters which it contains. It may be saturated with chalk and evaporated, by which an impure acetate of lime will be obtained, and which, mixed with sulphate of soda, furnishes, by double decom- position, sulphate of lime and acetate of soda ; the latter distilled with sulphuric acid affords a sufficiently pure acetic acid, which by dilution with water may be reduced to any required strength. The purification of this acid has been brought to great perfection.! 1627. Acetic acid obtained by the processes described is transpa- rent and colourless, its odour highly pungent and it blisters and excoriates when applied to the skin. Its specific gravity is 1.060. * For other details see Fermentation • t For a full account of the processes see Ure’s Did. Arts and Man. 8. Acetic Acid . 377 It is extremely volatile, and its vapour readily burns. It combines Sect, n. in all proportions with water, and when considerably diluted resem- bles distilled vinegar. When highly concentrated, it crystallizes at the temperature of 40° F., but liquefies when its heat is a little above that point. In this state it is called glacial acetic acid. 1628. Liquid acetic acid, consisting of one atom acetic acid, and one of water, which has a specific gravity of 1.06296, does not Properties, redden litmus paper. It may be kept in contact with dry carbonate of lime, or even boiled over it without disengaging a single bubble of C gas, or combining with the lime, yet it dissolves quicklime in- stantly. It decomposes carbonate of potassa, soda, lead, zinc, strontia, baryta and magnesia, disengaging C. When mixed with several times its volume of alcohol, it loses its action upon these carbonates.* 1629. Acetic acid possesses but little energy in combining with Combining ‘bases, being displaced by most of the other acids. It forms with power, bases a class of salts called acetates , several of which are important. They are all soluble in water.f 1630. When the vapour of alcohol is brought into contact in the atmosphere with the black powder obtained by mixing hydrochlorate of platinum, potassa and alcohol, vinegar is rapidly formed. It is thus prepared in Germany.^ *Pelouze, Ann. de Chim , et de Phys. L 314i t Thomson’s Org. Cham. t The powder is called Platina Mohr and is thus made : melt platinum ore with dou- P] ttt j na .Mohr b!e its weight of zinc, reduce the alloy to powder, and treat it at first with dilute Process for. S, and next with dilute N, to oxidize and dissolve out all the zinc, which is somewhat difficult, even at a boiling heat. The insoluble black-gray powder contains some os- miuret of iridium united with the crude platinum. This compound acts like simple platina-black after it has been purified by digestion in potash ley, and washing with water. Its oxidizing power is so great as to transform not only formic acid into the carbonic, and alcohol into vinegar, but even some osmic acid, from the metallic osmi- um. This powder explodes by heat. When the platina-mo/tr, prepared by means of zinc, is moistened with alcohol, it ^ ctionupon al . becomes incandescent, and emits osmic acid; but if it be mixed with alcohol into a cohoi produces paste, and spread upon a watch-glass, nothing but acetic will be disengaged ; afford- a cet‘cacid. ing an elegant means of diffusing the odour of vinegar in an apartments With this powder vinegar may be made in the following manner : Under a large case, which, for experimental purposes may be made of glass, several saucer-shaped dishes of pottery or wood are to be placed in rows, upon shelves over each other, a few inches apart. A portion of the black platina powder moistened being suspended over each dish, let as much vinous spirits be put into them as the oxygen of the included air shall be adequate to acidify. This quantity may be inferred from the fact, that 1000 cubic inches of air can oxygenate 110 grs. of absolute alcohol, converting them into 122 grs. of absolute acetic acid and 64^ grs. of water. The above apparatus is to be set in a light place (in sunshine, if convenient), at a temperature of from 68° to 86° F., and the evaporation of the alcohol is to be promoted by hanging several leaves of porous paper in the case, with their bottom edges dipped in the spirit. In the course of a few minutes the mutual action of the platina and the alcohol will be displayed by an increase of temperature, and a generation of acid va- pours, which, condensing on the sides of the glass case, trickle in streams to the bot- tom. This, continues till all the oxygen of the air is consumed. If we wish to renew the process, the case must be opened, and replenished with air. With a box of 12 cubic feet in capacity, and with 7 or 8 ounces of the platina powder we can in the course of a day, convert one pound of alcohol into pure acetic acid, fit for every pur- pose, culinary or chemical. With from 20 to 30 lbs. of the powder (which does not waste), we may transform, daily, nearly 300 lbs. of bad spirits into the finest vinegar. 589.64 parts by weight of alcohol . . = H 12 C 4 Os consist of 74.88 of hydrogen . . == H 12 305.76 of carbon . . = C4 200.00 of oxygen . . =02 48 378 Vegetable Acids. Chap, vi. The following are among the most important of the acetates : Acetate of 1631. Acetate of Ammonia is a very deliquescent, soluble salt, and ammonia, extremely difficultly crystallizable. In solution, obtained by satu- rating distilled vinegar with carbonate of ammonia, it constitutes the ammonia, acetas liquidus of the U. S. P. which has long been used in medicine as a diaphoretic, under the name of spirit of Mindererus . Of potassa, 1632. Acetate of Potassa is usually formed by saturating distilled vinegar with carbonate of potassa, and evaporating to dryness. If this salt be carefully fused, it concretes into a lamellar deliquescent mass on cooling. It is the terra foliata tartaric and febrifuge salt of Sylvius of old pharmacy. It dissolves in its own weight of water at 60°, and the solution has an acrid saline taste. Of lime, 1633. Acetate of Lime, is a difficultly crystallizable salt, readily soluble in water, and of a bitter saline taste consisting of 1 at. lime, 1 at. acid, and 6 at. water.* It is sometimes obtained by saturating the vinegar formed during the distillation of wood, and employed in the preparation of acetate of alumina, which is used by the calico- printers as a mordant. Of iron, 1634. Acetate of Iron. The protacetate is formed by digesting sulphuret of iron in acetic acid ;t it yields green prismatic crystals, of a styptic taste, and readily soluble in water ; the solution becomes brown by exposure to air, and passes into peracetate , which is un- crystallizable, and obtained by digesting iron in acetic acid. This compound is used by calico-printers, who prepare it either by digest- ing iron in pyroligneous acid, or by mixing solution of acetate of lead with sulphate of iron, and exposing the filtered solution to air. Of zinc, 1635. Acetate of Zinc , 1 at. acid, 5 ox. zinc, 7 water, (T.) is form- ed either by dissolving oxide of zinc in acetic acid, or by mixing a solution of sulphate of zinc with one of acetate of lead. It crystal- lizes in thin shining plates of a bitter and metallic taste, very soluble, but not deliquescent. This salt is sometimes used in pharmacy, chiefly as an external application. t Of tin, 1636. Acetate of Tin. This mineral is slowly acted on by acetic acid, but a protacetate and peracetate of tin may be made by mixing acetate of lead with saturated solutions of the protochloride and per- chloride of tin. These solutions have been recommended as mor- dants for the use of dyers. The protacetate is crystallizable. Vine- gar kept in tin vessels dissolves a very minute portion of the metal ; and in pewter vessels it likewise dissolves a small portion of the lead, where in contact both with the vinegar and air ; hence distilled if we combine with this mixture 400 parts of oxygen = O 4 we have of water 337.44 . . = H6 O 3 acetic acid 643.20 • = He C 4 O 3 Hence 100 parts by weight of alcohol take 68.89 parts of oxygen, and there are pro- duced 58.11 parts of water, and 110.78 of acetic acid. Ure’s Diet, of Arts and Manuf. 2 and 1001. * Thomson + According to Thomson it consists of 1 atom acetic acid, 1 protoxide of iron, 3 atoms water. t According to Messrs Aikin, the specific gravity of a saturated solution of acetate of zinc, made by digesting the salt in distilled vinegar, is 1055. Of this solution 900 grains contain 53 of dry, or 82.6 of crystallized acetate. One ounce by measure of the solution weighs 506 grains, and contain 29.8 grains of dry, or 46.5 grains of crystallized salt. Acetates . 379 vinegar, which has been condensed in a pewter worm, affords gene- Sect - IL rally traces of both metals.^ 1637. Acetate of Copper. By exposing copper to the fumes of Acetate of vinegar, it becomes gradually incrusted with a green powder called copper, verdigris, t which is separable by the action of water into an insolu- ble subacetate of copper , and a soluble acetate. Acetate of copper may be obtained by digesting verdigris, or oxide of copper, in acetic acid ; by evaporating this solution, it is obtained in prismatic crystals of a fine green tint. It dissolves sparingly in water and alcohol, and communicates a beautiful blue-green colour to the flame of the latter ; by distillation it affords a very pure acetic acid. 1638. Acetate of Lead. 1 at. acid, 1 protox. lead, 3 water (T). of lead, This is the Sugar of Lead , and Salt of Saturn of the old chemists : it may be regarded as the most important of the acetates ; it is used in pharmacy, and by dyers and calico-printers for the preparation of acetate of alumina and of iron, which are formed by mixing its solu- tion with that of the sulphates of those metals, an insoluble sulphate of lead being at the same time produced. Acetate of lead is formed by digesting the carbonate in distilled vinegar, or in the acetic acid obtained by the destructive distillation of wood ; it usually occurs in masses composed of acicular crystals ; the crystalline form is an oblique angled prism. I Its taste is sweet and astringent, and it is soluble in about four parts of water at 60°. When exposed to the air it undergoes no change. When dissolved in water, a small quantity of white powder falls, which is a carbo- nate of lead, formed by the carbonic acid which usually exists in water, or a sulphate when sulphuric acid is present. If carbonate of lead is formed a slight addition of acetic acid renders the solution clear. 1639. The sub-acetate of lead, § commonly called extr actum saturni, Sub-acetate is prepared by boiling acetate of lead with litharge. This salt is less of iead ’ sweet and less soluble in water than the acetate, has an alkaline re- action and crystallizes in white plates by evaporation. It is decom- posed by a current of carbonic acid, with production of pure carbonate of lead ; and forms a turbid solution. It appears from the analysis of Berzelius to consist of 1 atom of acid and 3 atoms of the oxide of lead. Acetates of 1640. Protacetate of Mercury is formed by mixing a solution of ni- mercury. ° trate of mercury with acetate of potassa. * Vauquelin, Ann. de Chim. xxxii. t Diacetate of Thomson, L atom acid, 2 oxide of copper, 6 water. According to Ure, verdigris is a mixture of crystallized acetate and subacetate in varying proportions. See description of the manufacture in Ure’s Diet. 1273. The composition of the acetate, as stated by Thomson, is 1 at. acid, 1 oxide copper, 1 water. Phillips has given the following comparative statement of the composition of the different kinds of verdigris : Blue Crystals. French Verdigris. English. Acetic acid . 28.30 29.3 29.62 Peroxide copper . 43.25 43.5 42.25 Water 28.45 25.2 27.51 Impurity 0 2.0 0.62 100 100 100 t Brooke, in Ann . Philos. (2d series) vi. 374. § Trisacetate of Thomson who has described several acetates of lead, for an account of which see Inorg, Chem. ii. 642, 380 Vegetable Acids . Chap. VI. Acetate of alumina. Lactic acid. Effect of heat. For this purpose dissolve three ounces of mercury in about four ounces and a half of cold nitric acid, and mix this solution with three ounces of acetate of po- tassa previously dissolved in eight pints of boiling water, and set the whole aside to crystallize, which takes place as the liquor cools, and the acetate of mercury then separates in the form of micaceous crystalline plates, which are to be washed in cold water, and dried on blotting-paper.* * * § This salt has an acrid taste, and is very difficultly soluble in water, requiring, according to Braconnot.t 600 parts of water. It is inso- luble in alcohol. It was once used in medicine. 4 The peracetate is formed by dissolving red oxide of mercury in acetic acid, and boiling the solution on fresh oxide till the acid is saturated. 1641. Acetate of Alumina. This salt is extensively employed by calico-printers as a mordant or basis for fixing colours ; they pro- duce it by mixing solutions of alum and acetate of lead : about three pounds of alum are dissolved in eight gallons of water, and a pound and a half of sugar of lead stirred into it; a copious formation of sul- phate of lead ensues which is allowed to subside, and the clear liquor holding acetate of alumina and a portion of undecomposed alum in solution, is then drawn off, a portion of pearlash and chalk being added to it previous to use, in order to saturate any excess of acid. 1642. Acetate of alumina, formed by digesting recently precipitated alumina in acetic acid, may be procured in deliquescent acicular crys- tals of an astringent taste, and containing, according to Richter, 73.81 acid -(- 26.19 alumina : hence it is probably a binacetate. This salt is also produced by the mutual decomposition of acetate of lime and alurn. A gallon of a solution of the acetate, of a sp. gr. of about 1.050, equivalent to nearly half a pound avoirdupois of dry acetic acid, is employed for every 2£ lbs of alum.$ 1643. Lactic Acid. C 6 H 4 0 4 = 72. When milk is kept for some time it turns sour, and to the acid evolved Scheele gave the name lactic ; it has since been obtained from several vegetable bodies left to spontaneous fermentation. Gay-Lussac and Pelouze have obtained it from the beet root juice. II It is colourless, of a syrupy consistence, and at 69° has a sp. gr. of 1.215. It has no smell, but is extremely sour. Water and alcohol dissolve it. Boiled with concentrated N it is converted into oxalic acid. It dissolves the phosphate of lime of bones rapidly ; boiled with acetate of potassa, it disengages the acetic acid. 1644. The concentrated acid, heated gradually, becomes more fluid, darker, and gives a white solid, which when pure dissolves in boiling alcohol, from which crystals are deposited on cooling. The crystals fuse at 125°, and boil at 4S2° : they give out white irritating vapours, which condense upon cold surfaces and recrystallize : they are inflammable. The salts formed with this acid are termed lac- tates .IF * Eklin. Pharmacop. In preparing this salt, the quantity of water for dissolving the acetate need not he so large as above directed, one pint being sufficient, but it is necessary to pour the mercurial solution into the acetate. + Ann. de Chim. Ixxxvi. 92. + Proust, Jour, de Phys • lvi. § Ure’s Diet. — art. Alumina. || For details of the process see Thomson’s Chem. of Org. Bodies , 1.22. H Liebig has shown that the acid in sauer kraut is the lactic. Ann. de Pharm., xx til. 113. Benzoic Acid . 381 1645. Benzoic Acid. This acid exists in gum benzoin, in dragon Sect, n. blood, &c. ; it is formed according to Liebig by the oxidation of the Benzoic hyduret of benzule^ in the air, and by the decomposition of many ^id- compounds of benzule and of hippuric acid and amygdaline by oxidi- zing agents ; by the action of potassa on the essential oils, cinnamon oil, &c. Gum benzoin, in coarse powder, alone or mixed with an equal weight of sand. Process, is spread upon the bottom of a round vessel of iron, the sides of which should not be more than three inches high. A sheet of dry bibulous paper is stretched tightly over the opening, and fastened to the sides of the vessel by a little paste. A hat made of thick paper, and of the common form of a man’s hat, is made to co- ver the whole, and tightly tied to the sides of the vessel by a strong string. The vessel is now placed upon sand spread upon an iron plate, below which a fire is kept for 3 — 4 hours. The vapours of the sublimed benzoic acid pass readily through the pores of the bibulous paper, and are deposited in crystals upon the hat ; the crystals are prevented from falling back into the iron vessel by the pa- per which closes its opening.t This is continued as long as a deposite of crys- tals is observed. Or in the moist way ; equal parts of finely powdered benzoin and The moist hydrate of lime are most intimately mixed, and then boiled for se- Udy ' veral hours in 40 parts of water; the filtered liquid must then be evaporated to one fifth its vol. and treated with hydrochloric acid, when the benzoic acid will crystallize as the solution cools. $ Or hippuric acid§ is boiled for one quarter of an hour in nitric acid Another, of sp. gr. 1.42, after which water is added and the solution allowed to crystallize. The acid obtained from gum benzoin is purified either by a second sublimation, or being boiled in nitric acid, or by passing chlorine gas through its boiling aqueous solution. 1646. The benzoic acid exists ready formed, and principally in a Ready free state, in the gum benzoin, from which it is separated by subli- ^ r ^^ n in mation. On boiling hydrate of lime with gum benzoin, the benzoic acid is dissolved, and the resinous parts left ; by a strong acid the benzoate of lime is decomposed, and the benzoic acid separated.]! 1647. This acid crystallizes in soft white scales, which are flexi- Properties, ble, transparent, and of a pearly lustre ; or in hexagonal needles. When pure it is inodorous, but if gently warmed it smells like gum benzoin ; it has a slightly biting but sweetish taste, produces a burn- ing sensation in the throat, reddens litmus feebly, fuses at 250°, sub- Suberic Acid , CsHeOs, is obtained by digesting cork in nitric acid. Naphthalic Acid, see Naphthaline. * Benzule denotes the hypothetical radical of a series of compounds which are produced from the volatile oil of the bitter almond , or are connected with it by certain relations. The oil of bitter almonds itself is always a product of the decomposition of amygdalin, which exists in the kernels of most stone fruits, and in the leaf of the lauro- cerassus, from which it may be obtained in a variety of ways. Its formula is C 14 H 5 O 2 3 symb. = Bz 3 eq. = 106.68. Liebig and Turner’s Elem. 823. Benzule has not been obtained in a free state, but may be separated from one sub- stance and transferred to another in numerous combinations. t Mohr. t If less lime betaken, or if a perfect admixture be neglected, the whole will bake into a solid mass in the boiling water 3 in this case the hard fragments, after the whole has cooled, must be again mixed with hydrate of lime. § An acid obtained from the urine of the horse, convertible into benzoic acid, see process in Thomson’s Org . Chem. 47. || For an economical method of purifying the acid see Ann. de Chim. et Phys., lvi. 443, and Thomson’s Org. Chem • 42. 382 Chap. VI. Action of chlorine, &c. Benzoate of ammo- nia. Soluble and insoluble beuzoate. Malic acid. Process. Vegetable Acids . limes at 300°, (an appearance of light is frequently observed in the dark,) boils at 462°, yielding a vapour of sp. gr. 4.27. The sublimation may be beautifully seen by suspending a small Fig. 188. branch of a shrub within a tall glass without a bottom, placing a small quantity of the acid upon a plate of metal on a stand, cover- ing it with the jar and applying the heat of a lamp to vaporize the acid ; the branch will be covered with delicate white crystals of the acid. 1648. It is not changed by chlorine, or by being boiled with dilute N, but by the fuming acid it is converted into a yellow resinous substance of a strongly bitter taste. It is dissolved by concentrated S, but falls upon the addition of water. It is soluble in 200 parts of cold and 25 parts of. boiling water. Its formula is C H H 5 0 3 -f-aq., or BzO-f-aq. ; eq. =123.68. 1649. Benzoate of Ammonia , NH 4 0, BzO, is prepared by dis- solving benzoic acid in pure concentrated ammonia, by the aid of heat, till the latter is saturated, when it is allowed to cool. It forms feathery acicular crystals, which deliquesce in a moist air, and are soluble in absolute alcohol. The acid salt is formed by boiling and exposing to spontaneous evaporation the neutral salt, with the loss of ammonia, it is deposited in large regular crystals. 1650. The soluble benzoates of metallic oxides have a strong biting saline taste, and are decomposed by most other acids with the sepa- ration of benzoic acid ; the same change occurs with the insoluble salts, when the acid which is added forms a soluble salt with the metallic oxide. The benzoates of the alkalies are decomposed by destructive distillation into carbonates, and a variety of new products. Exposed to a red heat with an excess of hydrate of lime, the acid is decomposed into benzole,* and carbonic acid which unites with the lime.t L. Fixed Acids. 0 1651. Malic Acid. C 4 H a 0 4 , eq. 60.0. The existence of a peculiar acid in the juice of apples, was shown by Scheele, in 1785. He ob- tained it by adding solution of acetate of lead to the expressed juice of unripe apples, by which a malate of lead was formed, and after- wards decomposed by sulphuric acid. Vauquelin obtained it by a similar process from the juice of the house-leek. The same acid ex- ists in the berries of the mountain-ash , from which it was first obtained by Donovan in 1815, and called by him sorbic-acid ; he has given the following process for its preparation. $ Express the juice of the ripe berries, and add solution of acetate of lead, filter, and wash the precipitate with cold water, then pour boiling water upon the filter, and allow it to pass through the precipitate into glass jars ; after some hours crys- tals are deposited, which are to be boiled with 2.3 times their weight of sulphuric acid, specific gravity 1.090. The clear liquor is to be poured off, and, while still *73.44 carb.+6 hyd. = 79.44; C 12 H 6 . (Liebig.) t For description of benzoates see Turner and Liebig’s Elem. 827. Cinnamomic Acid was obtained by Dumas and Peligot from oil of cinnamon, which they consider a compound of hydrogen and tbe base of this acid or cinnamoyl. The oil they term hydrct 0 / cinnamoyl. This acid occurs in old oil of cinnamon in large yellow crystals, soluble in boiling water. Esculic Acid is obtained from the horse-chestnut ( Esculus hippocastatum). t Phil. Trans. ISIS'. Tartaric Acid . 383 hot, a stream of sulphuretted hydrogen is to be passed through it, to precipitate Sect. II. the remaining lead ; the liquid is then filtered, and when boiled so as to expel the sulphuretted hydrogen, is a solution of the pure vegetable acid. Malic acid may also be obtained by steeping sheet-lead in the juice of apples ; in a few days, crystals of rnalate of lead form, which may be collected and decomposed by dilute sulphuric acid.^ 1652. Malic acid, when carefully prepared, is colourless and very p sour. It forms crystallizable salts with many of the metallic oxides, and its salts are termed malates. t 1653. Citric Acid , C 4 H 2 0 4 , eq. 60.0, is obtained by the following Citric acid, process from lemon or lime juice : Boil the expressed juice for a few minutes, and when cold, strain it through How pre- fine linen; then add powdered chalk as long as it produces effervescence, heat p arec j. the mixture, and strain it as before : a quantity of citrate of lime remains upon F the strainer, which, having been washed with cold water, is to be put into a mix- ture of sulphuric acid with twenty parts of water : the proportion of acid may be about equal to that of the chalk employed. In the course of twentyfour hours the citrate of lime will have suffered decomposition, and sulphate of lime is formed, which is separated by filtration. The filtered liquor, by careful evapo- ration, as directed for tartaric acid, furnishes crystallized citric acid.t In different states of purity it is employed by the calico-printers, and used for domestic consumption. The proportion of citric acid afforded by a gallon of good lemon-juice, is about eight ounces. § 1654. Citric acid may be obtained from currants by the following Process process : with cur ' rants. Pound the currants and cause them to ferment ; when this is over, distil to separate the alcohol. Saturate the hot liquid with chalk ; wash the citrate of lime with water, and press. Mix the citrate of lime with water, and reduce to the consistence of syrup ; decompose by sulphuric acid diluted with twice its weight of water. Saturate the citric acid, thus obtained, with carbonate of lime ; press and treat as before with sulphuric acid. Remove the colour by animal charcoal and evaporate. || 1655. Citric acid forms prismatic crystals of a very sour taste, Characters, very soluble in water, and containing, according to Berzelius, 1 atom real acid -j- 2 atoms water, a portion of which it loses by exposure to heat. 1656. Exposed to heat, the crystals undergo the watery fusion, and the acid is itself decomposed.1T r Derivative A.cids nt 1657. Tartaric Acid. C 4 H 2 0 5 , eq. 66.24. 5 Pyrotartaric. ac id tanC (_ Pyruvic. This acid exists in several vegetable substances ; it is one of the sour principles of many fruits, and is said to be abundant in the po- tato-apple. Tartaric acid is generally obtained from the bi-tartrate of pot assa, {purified cream of tartar.) Mix 100 parts of this salt in fine powder with 30 of powdered chalk, and gra- dually throw the mixture into 10 times its weight of boiling water; when the "? • . liquor has cooled, pour the whole upon a linen strainer, and wash the white 0 ainln £* * * § * For other processes, &c., see Thomson’s lnorg. Bodies , ii. 76. t For an account of which, and of the acids derived from the decomposition of malic acid, see T. Org. Bodies , 63. t For a mode of obtaining it from gooseberries see Ann. Philos. N. S. iv. 152. Many circumstances which have not here been alluded to, are requisite to ensure complete success in the operation ; these have been fully described by Parkes, in his Chem. Essays. § Twenty gals, of good lemon-juice afford 10 lbs. of crystals. (Ure.) j| Tillog in Ann. de Chim. et de Phys. xxxix. 222. IT For derivative acids see T. or B. 62, and for Citrates , B. ii. 515. 384 Chnp VI. Properties. Forms dou- ble salts. Tartrate of potassa. Bilartrate, or crude tartar. Tartaric acid test for potassa- Impurities. Acts as a simple acid. Vegetable Acids. powder which remains with cold water; this is a tartrate of lime; diffuse it through a sufficient quantity of water, add sulphuric acid equal in weight to the chalk employed, and occasionally stir the mixture during 24 hours ; then filter, and carefully evaporate the liquor to about one fourth its original bulk ; filter again, and evaporate with much care nearly to dryness; re-dissolve the dry mass in about 6 times its weight of water, render it clear by filtration, evaporate slowly to the consistency of sirup, and set aside to crystallize. By two or three successive solutions and crystallizations, tartaric acid will be obtained in colourless crystals, soluble in 6 parts of wa- ter at 60°. Their primary form is an oblique rhombic prism.* 1658. The crystals melt at a heat a little exceeding 212° into a fluid which boils at 250° and leaves a semi-transparent mass on cooling, slightly deliquescent. The aqueous solution of tartaric, in common with the other vege- table acids, soon becomes mouldy, and suffers decomposition. 1659. Tartaric acid has a great tendency to combine at once with two bases and form double salts. In consequence of this property it prevents antimony from being precipitated as usual by water, and even hinders alkaline bodies from precipitating solutions of the me- tal in acids as they usually do. t. 1660. Tartrate of Potassa , (formerly soluble tartar ) is formed by saturating the excess of acid in tartar by potassa, and boiling. Ac- cording to Phillips,! 100 parts of tartar require 43.5 of sub-car- bonate of potassa. The resulting salt is soluble in less than twice its weight of water ; it forms large prismatic crystals. These contain 1 atom acid, I potassa, and water. This salt is used in pharmacy as an aperient ; it is the potasses tartras of the Pkarmacop. Its taste is saline, and somewhat bitter. 1661. Bi-tartrate , or Supertartrate of Potassa. Tartar. This substance exists in considerable abundance in the juice of the grape, and is deposited in wine casks, in the form of a crystallized incrus- tation : called argol or crude tartar. It is purified by solution and crystallization, which renders it perfectly white;! when in fine pow- der it is termed cream of tartar. It may also be formed by adding excess of tartaric acid to a solu- tion of potassa. The mixture presently deposits crystalline grains, and furnishes a striking example of the diminution of solubility by increase of acid in the salt. Upon this circumstance the use of tar- taric acid as a test for potassa depends, for soda forms an easily soluble supertartrate and consequently affords no precipitate, b. Its constituents are 2 at. acid, 1 potassa, 2 water, t. 1662. The tartar of commerce is never quite pure. According to Thomson it contains five per cent, of tartrate of lime.§ It is some- times adulterated by the addition of pounded quartz, and by calca- reous spar ; the former may be detected as an insoluble residue by boiling the powdered tartar with half its weight of potassa or of bo- rax in eight parts of water; the latter produces effervescence with dilute hydrochloric acid. 1663. Bi-tartrate of potassa, it is observed by Gay-Lussac, acts, in * Brooke in Ann. Philos, vi. N. S. t Remarks on Pharmacop. t See process B. ii. 600, and Jour, de Phys. i. 67. § Inorg. Chem. ii. 433. When present it separates in tufts ot acicular crystals from the hot solution. B. 502. Tartaric Acid — Tartrates . 385 many cases, like a simple acid, and even dissolves oxides that are Sect, n. insoluble in the mineral acids and in the tartaric acid. He proposed its use, therefore, in mineral analysis. 1664. When exposed to heat, tartar fuses, blackens, and isdecom- posed : and carbonate of potassa is the remaining result. Provided nea ’ c ‘ the tartar be free from lime, which however is seldom the case, this furnishes a good process for obtaining pure carbonate of potassa. The aqueous solution of tartar becomes mouldy when exposed to air, and the tartaric acid being entirely decomposed leaves a weak solu- tion of carbonate of potassa. The component parts of tartar render it an excellent flux in the reduction of metallic ores upon a small scale, its alkali promoting se> their fusion, and the carbonaceous matter tending to reduce the oxides. 1665. Tartrate of Potassa and Soda is prepared by saturating Tartrate of the excess of acid in tartar, with carbonate of soda ; it is the tartras potassa and potasses et sodee of the Pharmacop. ; it forms prismatic crystals.* It soda? has long been used in pharmacy under the name of Rochelle Salt and Sel de Seignette. It consists of 1 atom of the tartrate of potassa, 1 atom of the tartrate of soda, and 10 atoms of water, t. i 1 . 793 . It is frequently made extemporaneously by dissolving equal weights of tartaric acid and the sesquicarbonate of soda in separate portions of water, and then mixing the solutions.! 1666. Tartrate of Iron and Potassa. This is the Ferrum tarta - Of iron and risatum of the London Pharmacop but it is most conveniently em- P otassa - ployed as a medicine in solution, which may be formed by digesting 1 part of soft iron filings with 4 of tartar. This mixture should be made into a thin paste with water, and digested for some weeks, till the acid is neutralized, fresh portions of water being occasion- ally added to prevent exsiccation. The solution of this compound which con- tains the iron in the state of peroxide, is possessed of some curious properties, first pointed out by Phillips . t 1667. Tartrate of Potassa and Copper is formed by boiling oxide Brunswick of copper and tartar in water: the solution yields blue crystals on g reen - evaporation ; or if boiled to dryness, furnishes one of the pigments called Brunswick green. 1668. Tartrate of Antimony and Potassa — Emetic Tartar. This Tartrate of compound may be obtained by boiling protoxide of antimony, with antimony pure supertartrate of potassa. It is the antimonium tartarizaium of aad P otas ' the London and U. S. Pharmacop. Emetic tartar may be prepared by boiling a solution of 100 parts of tartar with p re p ara _ 100 parts of finely levigated glass of antimony, or of the sesquioxide ; the ebulli- ti on 0 f tion should be continued for half an hour, and the filtered liquor evaporated to emetic tar- about half its bulk, and set aside to crystallize ; octohedral and tertrahedral crys- tar. tals of the emetic salt are thus obtained ; and there is generally formed along with them a portion of tartrate of lime and potassa, which is deposited in small * The forms of its crystals arising from the modification of a right rhombic prism, are represented by Brooke in Ann. Philos. N. S. v. 451. t Soda or Sodaic powders of the shops are packed in two distinct papers, the one blue goda derg and the other white, the blue containing half a drachm of carbonate of soda, the white 0 apow er8, gr. xxv. of tartaric acid: when dissolved and mixed, effervescence takes place, but the liquid is by no means similar to “ soda water.” ? Experimental Examination of the London Pharmacop. 98. 49 386 Vegetable Acids. Chap. VI. tufts of a radiated texture, and which may easily be separated when the mass is dried.* 1669. Emetic tartar is a white salt, slightly efflorescent, soluble in about 14 parts of cold and 2 parts of boiling water. It is decomposed by the alkalies, and when heated with ammonia, a portion of protox- ide of antimony is thrown down, and a very soluble compound remains in the liquor. Hydrosulphuric acid gas produces an orange- coloured precipitate in its solution. It is decomposed by bitter and astringent vegetable infusions, but they do not render it inactive as a medicine. t Phillips has shown that emetic tartar consists of 1 atom bi-tartrate of potassa, 3 sesquioxide of antimony, 3 water. According to Thomson emetic tartar consists of 2 atoms tartaric acid, 3 atoms sesquioxide of antimony, 1 atom of potassa and 2 atoms of water.! C Derivative Acids. 1670. Meconic And. C 7 H 2 0 7 eq. 100.00. < Pyromeconic C 10 H 3 O 4 . f ftlelameconic C 12 H 4 O 10 . This acid exists in opium and was discovered by Serturner and called meconic acid from the Greek poppy. It is procured by se- veral processes of which the following is recommended by Thom- son^ as the easiest. Make an infusion of opium in water acidulated with sulphuric acid. The in- Processfor. fusion is mixed wilh chloride of calcium in sufficient quantity to throw down the sulphuric and meconic acids in combination with lime. This precipitate is washed, first with cold water, and afterwards with boiling alcohol. It is next mixed with ten times its weight of water, and heated to about 194°. Add by little and little, agitating violently, a quantity of hydrochloric acid, sufficient to dissolve the meconnte of lime, which constitutes the greater part of the precipi- tate. Pour the liquid upon a filter, previously washed wilh hydrochloric acid. On cooling, light and brilliant crystals of bimeconate of lime are deposited, which are to be dried between the folds of a cloth ; dissolve them in hot water, and add a sufficient quantity of hydrochloric acid to decompose the salt. Keep the liquid for some time hot, but under 212° j on cooling, crystals of meconic acid are deposited. || To deprive it of colour, saturate by a dilute solution of caustic potassa. Dis- solve the meconate of potassa formed, in a small quantity of hot water ; let it cool, and expose the resulting magma to pressure. Dissolve and crystallize anew, and finally decompose the salt by hydrochloric acid. Hare’s. Hare has given the following process :1T To an aqueous infusion of opium add acetate of lead, collect the meconate of lead by a niter, and expose it to hydro- sulphuric acid gas ; the meconic acid will be set free. The solution is of a red- dish amber colour, and furnishes, by evaporation, crystals of the same hue. Instead of hydrosulphuric acid, sulphuric acid may be used to liberate the meco- nic acid. Properties. Analysis. Meconic acid. Properties. 1671. Meconic arid crystallizes in white transparent scales. It is not altered by cold S or hydrochloric acid ; dilute N converts it * Phillips, in his Experimental Examinations of the London Pharmacop ., has stated several facts respecting the formation of this salt, which will be found useful to the manufacturer. See Bigelow’s Sequel, 75. t According to Orfila, the compound of tannin and oxide of antimony is inert, and he recommends adecoctiou of ciucbona bark as an antidote. t Inorg. Chem. 11.799. For an account of racemic acid and remarks on its com- pounds see T. Org. Chem. 67. § Org. Bodies , 80. || If the crystals are mixed with bimeconate of lime, repeat the treatment with hy- drochloric acid, or separate the crystals of bimeconate, which are much lighter, by levigation. T. Chem. Org. Bodies , 80. IT Amer. Jour. xii. 293. For other processes, see B. 11, 535. Gallic Acid . 387 into oxalic acid. It is soluble in 4 times its weight of hot water ; Sect - IL when long boiled the solution becomes yellowish, then red, and at last deep brown, at the same time C is disengaged, and the acid is changed into metameconic acid, which is no longer altered by the water. This change may be produced by the action of a water-bath continued for several days. The new acid precipitates during the cooling. It consists, according to Liebig, of carbon 41.54, hydrogen 2.07, oxygen 56.39. 1672. Meconic acid combines with bases in three proportions and Forms it forms with them neutral salts ; the bisalts strike a very deep red salts, with the persalts of iron, which disappears when the iron is reduced to protoxide, but re-appears when the iron is again peroxidized. The meconates are, in general, insoluble in alcohol. 1673. When nitrate of silver is poured into a solution of meconic Action of acid, and a little more N added than is sufficient to dissolve the me- silver? ° f conate of silver, if we heat the liquid the salt is converted into cya- nide of silver. The liquid, at first limpid, becomes gradually filled with flocks of cyanide. It contains also oxalate of silver in solution. If too much N be added, much oxalate of silver is formed, but no cyanide.* C Derivative Acids. 1674. Gallic Acid. C 7 H 3 0 5 , eq. 85.00. ] Pyrogallic Ce H 3 0 3 £This 4 ( Metagallic Ci 2 H 3 0 3 > acid derives its name from the gallnut , whence it was first procured by Scheele. It may be obtained by several processes,! among which the following deserve notice : Gallic acid. % Moisten bruised gallnuts, and expose them for four or five weeks, to How ob- a temperature of about 80°. A mouldy paste is formed, which is to be squeezed tained. dry, and digested in boiling water; it then affords a solution of gallic acid, which may be whitened by animal charcoal, and which, on evaporation, yields gallic acid, crystallized in white needles.? Boil an ounce of powdered galls in 16 ounces of water down to 8, and strain ; dissolve 2 ounces of alum in water, precipitate the alumina by carbonate of po- tassa, and, after edulcorating it, stir it into the decoction ; the next day filter the mixture ; wash the precipitate with warm water, till this will no longer blacken sulphate of iron ; mix the washing with the filtered liquor, evaporate, and the gallic acid will be obtained in acicular crystals.§ 1675. Gallic acid when pure is in snow-white needles, requiring p ropert i es . 100 times their weight of cold water to dissolve them. When dropped into a solution of persulphate of iron, a deep blue precipitate falls, which dissolves slowly in the liquid, and after an interval of some days, the liquid becomes almost colourless. Sulphuric acid removes nearly all the iron and protosulphate of iron crystallizes. The same changes are quickly produced by boiling, with the disen- gagement of C. 1676. Gallic acid forms white precipitates with baryta, strontia, Precipi- and lime water which redissolves in an excess of acid. Acetate or tates - nitrate of lead produces a white precipitate, not altered in colour by exposure to the air. II * Liebig. t For others see T. Inorg : Bodies , ii. 99, and B. 519. t Braconnot, Ann. de Chim. et Phys. ix. 181. § Fiedler in Nicholson’s Diet. 1.236. II Pelouze in Ann. de Chim. et Phys. liv. 348. 388 Vegetable Acids. Cha P VL 1677. The characteristic property of gallic acid is to strike a deep Character- blue with the salts of iron, particularly the sulphate. The tannin, perty Pr ° which is another constituent of nutgalls, possesses the same property. 1678. Gallic acid and tannin are of great importance in the forma- tion of ink, and the precipitate formed is retained in suspension by mucilage.* Kinicacid. 1679. Kinic Acid. C 15 H 9 0 9 , eq. 171.00. \ j Kinicacid derives its name from having been discovered in Peruvian bark. A watery infusion of the bark evaporated to a syrup and treated with alcohol, leaves a viscid mass containing kinate of lime and gum. Obtained ^ solution and crystallization, kinate of lime may be procured in crystals, from which the lime may be separated, by dissolving the kinate in water, and adding sulphuric or oxalic acid. It forms solu- ble salts with alkalies, and metallic oxides.t 1680. Tannic Acid — Tannin. Ci S H 8 0i2, eq. 212. This substance Tannic acid. exists in an impure state in the excrescences of several species of oak, called gallnuts; in the bark of most trees; in some inspissated juices, such as kino and catechu ; in the leaves of the tea-plant, su- Sources mach and whortleberry (uva ursa), and in astringent plants generally, being the chief cause of the astringency of vegetable matter. It is frequently associated with gallic acid, as in gallnuts, in most kinds of bark, and in tea ; but in kino, catechu, and cinchona bark, little or no gallic acid is present. It may be prepared pure from nutgalls by the following process : Obtained. Into the mouth of a flask, fit, by grinding, a narrow glass vessel, fitted with a cork, or stopper, at the upper end. Fill the bottom of the long narrow glass ves- sel, where it enters the flask, with a little cotton, and place above the cot- ton a quantity of nut-galls, in fine powder, filling about half the vessel. Pour over this a sufficient quantity of the common sulphuric ether of commerce to fill the rest of the vessel. Put in the stopper and set the whole aside. The follow- ing day, there will be found in the flask two distinct layers of liquid : one very light and fluid in the upper part ; the other heavier, of a light amber colour, occupying the bottom. Pour the whole into a funnel, stopping the bot- tom with the finger ; let it remain at rest for a few minutes, till the two liquids * To make twelve gallons of good ink, we may take nutgalls 12 lbs., green sulphate jjjjj of iron 5 lbs., gum Senegal 5 lbs., water 12 gals. The nutgalls are to be put into a cylindrical copper, of a depth equal to its diameter, and boiled, during three hours with three fourths of the above quantity of water, adding fresh water to replace what is lost by evaporation. Empty the decoction into a tuo, draw off the clear liquor and drain the lees. Dissolve the gum in a small quantity of hot water, filter, and add to the clear decoction. The sulphate of iron must be separately dissolved and mixed. The colour darkens by exposure. But ink is more durable when used pale, lire’s Diet. Arts and Alan. 677. The following gives a good ink. Bruised galls 8 oz., sulphate of iron 4 oz., gum arabic 3 oz., sugar candy 1 oz. Boil the galls in twelve pints of water down to six, strain, and add the other ingredients, stirring till dissolved. After twentyfour hours decant and bottle. See other methods in B. 11.523. The tendency of the ink to become mouldy is much diminished by keeping a few cloves in the ink bottle, or by dissolving in each pint of the ink about three grains of corrosive sublimate. The colour of common writing ink is apt to fade, in consequence of the decomposi- tion of its vegetable matter ; and when thus illegible, it may often be restored by wash- ing the writing with vinegar, and subsequently with infusion of galls. Acids also destroy its colouring matter, and those inks which resist their actiou contain some other colouring principle, usually finely powdered charcoal. Common writing ink is, for this reason, much improved by dissolving in the quantity above-mentioned about an ounce of Indian Ink, which is lamp-black made into a cake with isinglass. See Macculloch on Indelible Ink, &c. Brewster’s Jour. i. 318, and Bost. Jour. ii. 344. t For details, and other fixed acids, see T. Org. Bodies, 89. Tannic Acid. 389 separate ; allow the heavier to fall into a capsule, and set the lighter portion Sect. II. aside in order to recover the ether, of whichit principally consists, by distillation. Wash the dense liquid two or three times with sulphuric ether ; then dry it in a stove, or, in vacuo , over sulphuric acid. Much vapour of ether and water is disengaged ; the bulk increases, and a spongy residue is left, brilliant, and some- times colourless, though usually yellowish. This substance is tannin in a pure state. T. 109. 1681. Pure tannic acid is colourless and inodorous, has a purely astringent taste without bitterness, and may be preserved without Froperties * change in the solid state, very soluble in water, reddens litmus, and decomposes alkaline carbonates with effervescence. Alcohol and ether dissolve tannic acid, but more sparingly than water. Solutions of tannic acid do not affect pure protosalts of iron, but strike a deep blue precipitate with the persalts : a strong solution of it yields a copious white precipitate with the sulphuric, nitric, hydrochloric, phosphoric, and arsenic acids, but none with the oxalic, tartaric, lac- tic, acetic, citric, succinic, and selenious acids. It is precipitated also by the carbonates of potassa and ammonia, by the alkaline earths, alumina, and many solutions of the second class of metals. With cinchonia, quinia, brucia, strychnia, codeia, narcotina, and morphia, it yields white tannates, which are sparingly soluble in pure water, but are dissolved readily by acetic acid. By digestion with nitric acid it yields oxalic acid. 1682. A solution of tannic acid may be preserved without change, Absorb§ provided it be excluded from oxygen gas ; but in open vessels, it gra- oxygen, dually absorbs oxygen, an equal volume of carbonic acid is evolved, it becomes turbid, and deposits a crystalline matter of a gray colour, nearly all of which is gallic acid. After digestion with a little ani- mal charcoal, the gallic acid is perfectly white and pure. There is no doubt, therefore, of the conversion of tannic into gallic acid. 1683- Tannic acid is distinguished from all substances, except gal- lic acid, by forming a deep blue precipitate with persalts of iron, and 5]^^ from gallic acid, by yielding with a solution of gelatin a white flaky precipitate, which is soluble in a solution of gelatin, but insoluble in water and gallic acid. This substance, to which the name of tanno - gelatin has been applied, is the basis of leather, being always formed Leather ” when skins are macerated in an infusion of bark. When dried it becomes hard and tough, and resists putrefaction. Its composition is apt to vary, according to the relative quantities of the materials used in its formation. To a strong solution of gelatin (common glue answers) add a strong infusion of £ xp gallnuts, the white precipitate may be collected upon a glass rod and pressed together, forming a tough extensible mass resembling new leather. 1684. From the experiments of Davy, it appears that the inner cortical layers of bark are the richest in tannic acid. Its quantity is greatest in early spring, and smallest during winter. Of all the varieties of bark which he examined, that of the oak contains the largest quantity of tannic acid. 1685. The various kinds of tannic acid obtained from cinchona bark, kino, and other sources, correspond in most respects with that above described ; but at the same time some difference is observable, some kinds striking a green instead of a deep blue colour with the 390 Vegetable Jlcids . chap, vi. persalts of iron.* The tannic acid from catechu is less highly oxi- dized than that from gallnuts. 1686. Artificial Tannic Acid. This substance was discovered by Artificial I ^ Hatchett, and is prepared by the action of nitric acid on charcoal.! For this purpose 100 grains of charcoal in fine powder are digested in an ounce of nitric acid, of density J .4, diluted with two ounces of water, with a gentle heat, until the charcoal is dissolved. The reddish-brown solution is then evaporated to dryness, in order to expel the nitric acid, the temperature being carefully regu- lated towards the close of the process, so that the product may not be decom- posed. Properties. Artificial tannic acid is a brown fusible substance of a resinous fracture, astringent taste, and acid reaction ; soluble in cold water and in alcohol. With a salt of iron and solution of gelatin it acts pre- cisely in the same manner as natural tannic acid. It differs, how- ever, from that substance in not being decomposed by the action of strong nitric acid. 1687. Artificial tannic acid is generated by the action of nitric acid, both on animal or vegetable, charcoal, and on pit-coal, asphal- tum, jet, indigo, common resin, and several other resinous substances. It is also procured by treating common resin, elemi, assafaetida, cam- phor, balsams, &c., first with sulphuric acid, and then with alcohol. Oily Acids . Oily acids. 16S8. These acids are so called, because they are formed from oils or fat, and enter into the composition of soaps, or because they possess many of the characters of oils.! Margaric 16S9. In 1S13 Chevreul made Unown an acid substance which acid ‘ enters into the composition of soaps, to which he gave the name of margarine and afterwards distinguished it as margaric acid. He found that this acid extracted from different bodies existed in two differ- ent states, and as the one contained more oxygen than the other, he distinguished them at first by the name of margarous and margaric acids. But he afterwards thought better to give to margarous acid the name of stearic acid,$ and to retain the term margaric acid for the latter. Stearic 1690. The method of procuring stearic acid is as follows : acid, Make a soap by boiling mutton 6uet and caustic potassa together, with a suffi- Processfor, c j en t quantity of water, till the whole is converted into soap. Dissolve one part of this soap in 6 parts of warm water, and mix the solution with about 40 parts of cold water, and leave it for some time in a temperature about 60°, or between 60° and 70°. A substance precipitates of a pearly lustre, which is a mixture of bistearate of potassa and margarate of potassa. Collect this on a filter and wash it. The liquid that has passed through the filter being mixed with a little acid to saturate the potassa, will yield an additional quantity of this two-fold soapy salt. By repeaUng this process several times, all the bistearate and margarate of potassa is obtained, and the water retains only the oleate of potassa. The bi- stearate and margarate of potassa is to be dried and dissolved in about 20 times its weight of hot alcohol of 0.82. When the alcohol cools, a quantity ofbistear- * These have been distinguished by names formed from that of the substances which afford them. See Thomson, Org. Bodies , 112. i Phil. Trans. 1805—6. t Thomson includes twentythree acids in this group. They were first distinguished by Chevreul. who devoted ten years to tbe assiduous study of fixed oils and fats. A few only of the most important will be described in the following pages, referring to Thomson’s work for the study of the greater number. § From 15S°. When it is distilled with lime, a soft matter is obtained, which • when pressed between folds of blotting paper, gives out oil, and a white substance remains which has been named margarone. 1693. To obtain pure margarone it is to be repeatedly dissolved Obtained, in alcohol, and allowed to separate by crystallization. It is white, brilliant, and has a pearly lustre. It is a non-conductor of electricity and becomes electric by friction and pressure. It dissolves in fifty times its weight of boiling alcohol, of sp. gr. 0.S36 but is mostly de- posited on cooling; is incapable of forming a soap. It differs from margaric acid by wanting an atom of carbonic acid. 1694. Oleic Acid , C 70 H 62 O 7 , eq. 538, is obtained from soap made Oleic acid, with linseed or hemp oil with potassa. It is somewhat coloured and has an etherial smell, is insoluble in water, but soluble in alcohol. It decomposes the alkaline carbonates, reddens litmus, and forms salts, or rather soaps, to which the name of oleates is given. It burns like the fixed oils. 1695. When olive oil is treated with half its weight of concen- Action ?f trated sulphuric acid three acids are obtained, one of which has been ac jJ # called sulpho-oleic,\ and this decomposed affords hydro-oleic acid. From the last named acid two liquids have been obtained having the same composition as olefiant gas, one of these boils at 131°, the other at 230°. The first has been recently called Olein, the second Elain. Olein. 1696. Olein is white, very liquid, and lighter than water, with a strong odour, very combustible, and burning with a greenish flame. Its vapour appears to be poisonous. Elain is less soluble in alcohol, and burns with a fine white flame. ain ‘ According to Thomson, olein is composed of 6 carbon and 6 hydro- gen, and elain of 9 carbon and 9 hydrogen4 Acids containing Nitrogen .§ 1697. Azulmic Acid . C S H 4 N 40 4 . eq. 140. Boullay has given this Azulmic name to an acid obtained from cyanogen gas that has undergone spon- taneous decomposition. It is insoluble in water, but is dissolved by ni- tric acid and assumes a beautiful aurora-red colour. By heat it is *From [iMQyaQnrjs a pearl. tFremy, Ann. de Pharm. xx. 50. t Chlorophenisic and chlorophenesic acids have been obtained from coal-tar by Lau- rent, by the action of chlorine, and were named from a supposed base, phene (from (petty on I shine), from their supposed existence in oil gas. Ann. de Chim. et de Phys. lxiii. 27. For details see T. Org. Bodies , 129. § Of these Thomson describes eight. 392 Vegetable Jlcids. Chap, vi. converted into hydrocyanate of ammonia, and a gas is evolved which burns with a blue flame and the odour of cyanogen. acid g ° tiC 1698. Indigotic Acid. C.^H7£N1^0 15 . This acid is obtained by boiling indigo in rather dilute nitric acid, formed by mixing nitric acid of sp. gr. 1.2 with an equal weight of water. To the solution, kept boiling, indigo, in coarse powder is gradually added, as long as effervescence continues ; and hot water is occasionally added to sup- ply loss by evaporation. The impure indigotic acid, deposited in cooling, is boiled with oxide of lead and filtered, in order to separate resin ; and the clear yellow solution is decomposed by sulphuric acid, and again filtered at a boiling temperature. On cooling, the acid crystallizes in yellowish-white needles. In order to purify them # completely, they were digested in water with carbonate of baryta; and the indigotate of baryta, deposited from the hot filtered solution in cooling, was dissolved in hot water, and decomposed by an acid. Indigotic acid was thus obtained in acicular crystals, of snowy whiteness, which contracted greatly in drying, and lost their crystal- line aspect ; but the dry mass was dazzling white, and had a silky lustre. Properties. 1699. Indigotic acid decomposes carbonates, but is a feeble acid, and reddens litmus faintly. It requires 1000 times its weight of cold water for solution, but is soluble to any extent in hot water and alco- hol. Heated in a tube it fuses, and sublimes without decomposition; and the fused mass, in cooling, crystallizes in six-sided plates. When heated in open vessels, it is inflamed, and burns with much smoke.* Carhazotic 1700. Carbazotic Acid. C, 5 N 3 0 15 , eq. 252. This name has been acid » applied by Liebig to a peculiar acid formed by the action of nitric acid on indigo. It i9 made by dissolving small fragments of the be9t indigo in 8 or 10 times their weight of moderately strong nitric acid, and boiling as long as nitrous acid fumes are evolved. During the action, carbonic, hydrocyanic, and nitrous acids are evolved ; and in the liquid, besides carbazotic acid, is found a resinous matter, artificial tannin, and indigotic acid. On cooling, carbazotic acid is freely depo- sited in transparent yellow crystals ; and on evaporating the residual liquid, and adding cold water, an additional quantity of the acid is procured. To render it quite pure, it should be dissolved in hot water, and neutralized by carbonate of polassa. As the liquid cools, carbazotate of potassa crystallizes, and may be puri- fied by repeated crystallization. The acid may be precipitated from this salt by sulphuric acid. Properties, 1701. Carbazotic acid is sparingly soluble in cold water ; but it is dissolved much more freely by the aid of heat, and on cooling yields brilliant crystalline plates of a yellow colour. Ether and alcohol dissolve it readily. It is fused and volatilized by heat without de- composition ; but when suddenly exposed to a strong heat, it inflames without explosion, and burns with a yellow flame, with a residue of charcoal. Its solution has a bright yellow colour, reddens litmus paper, is extremely bitter, and acts like a strong acid on metallic ox- ides. It is said to be poisonous.! Salts of. 1702. The salts of carbazotic acid are for the most part crystal- * From the analysis by Dumas, Thomson considers it as merely indigo, containing five times as much oxygen as that pigment does. T. 142 . t Jour, of Sci. ii. 210. Pectic Acid . 393 lizable, of a yellow colour, and brilliant lustre. They have the pro- Sect, n. perty, when rapidly heated, either of detonating like fulminating silver, or of burning rapidly with scintillations. The sparing solu- bility of carbazotate of potassa is the cause of carbazotic acid being used as a test of that alkali. 1703. Carbazotic acid is generated by the action of nitric acid on many substances, both animal and vegetable, especially on those which contain nitrogen. The bitter principle, . formed with nitric acid and silk by Welter, is carbazotic acid. Acids Imperfectly Examined. 1704. Pectic Acid. C a H 7 O 10 , = 153 eq. Braconnot has given this Pectic acid, name* to a principle found in several plants which has the property of being coagulated by alcohol, metallic solutions, the acids, &c. It appears to be the same substance previously discovered by Torrey in the Tuckahoe, Sclerotium giganteum,i a fungus common in the sandy barrens of the southern states, and to which he gave the name Sclerotin. It is readily soluble in a solution of caustic potassa, and this solution is gelatinized by almost every known body. 1705. Braconnot’s process for obtaining this substance is as fol- ta ?^ d ° " lows : If roots containing starch be operated upon, such as those of celery and carrot, they are to be reduced to pulp by rasping, the juice expressed, the residue boiled in water, slightly acidified with hydrochloric acid, then washed, and afterwards heated with a very dilute solution of potassa or soda. A thick mucilaginous liquid results, slightly alkaline, from which hydrochloric acid separates the acid in the form of an abundant jelly, which should then be well washed. 1706. It forms a very soluble salt with potassa, which may be ob- Union with tained in the state of a transparent jelly, by adding weak alcohol, p as which removes the excess of alkali and colouring matter, if there be any present. This jelly washed on a cloth with alcoholized water, pressed and dried, swells and dissolves in water, and leaves upon evaporation a transparent mass, resembling gum arabic. Its taste is insipid. 1707. In consequence of the property which this acid has of gela- Use. tinizing large quantities of water, it has been proposed as a means of preparing jellies. Boil a little pectic acid in the quantity of water which is to be converted into jelly ; dissolve in the water a sufficient quantity of sugar previously seasoned by being rubbed over the skin of an orange, or by any other wished for seasoning, or add to the water a little alcohol previously seasoned In either case the whole assumes the form of a jelly, the flavour of which will of course depend upon the nature of the seasoning employed. 1708. There is a substance in many acid fruits, as currants and Pectin, gooseberries, which gelatinizes. It has very intimate connexion with pectic acid, being instantly converted into that acid by the smallest quantity of a fixed alkali. This substance has been distin- guished by Braconnot, by the name of pectin. 1709. It may be obtained from all fruits by means of alcohol. Process. Mix together the clear expressed juice of currants, with the equally clear juice * From TtexTLQ coagulum. Ann. de Chim. xxviii. 173, and Bost. Jour. iii. 132. t Torrey’s analysis of the Tuckahoe was published in the N. Y* Med. Rep. 1820. 50 394 Chap. VI. Cieuic acid. Properties. Apocrenic acid. In waters. Compound acids, Two sets. Althionic acid. Vegetable Acids. of sour cherries. Pectin falls down. Decant off the liquid, and wash the pectin with water, as long as the liquid abstracts any colour/ The analysis of pectic acid by Regnault gave, carbon 42.71, hy- drogen 4.73, oxygen 52.56. t 1710. Crenic Acid , 108.1 (T.)» was discovered by Berzelius in 1832, in the water of Porla well, in Sweden, to which it imparted a yellow colour and disagreeable taste. On exposure to the air, an ochrey sediment was deposited which consisted chiefly of crenated peroxide of iron.§ 1711. Crenic acid is yellow and transparent. It has no odour, but a sharp followed by an astringent taste. When in solution the latter only can be perceived. When the solution is exposed to the air, it becomes brown, and apocrenic acid is formed. 1712. It is very soluble in water and alcohol. Its salts resemble extracts, and are insoluble in absolute alcohol, but become more and more soluble as water is added. They become rapidly brown in the air, and apocrenates are formed. 1713. Crenic acid dissolves in nitric acid without change. Its salts are termed crenates. They resemble extracts in appearance, and are incapable of crystallizing. 1714. Apocrenic Acid. 132. (T.)« This acid was obtained by di- gesting the ochre from Porla well with potassa, to extract the crenic acid, and then precipitating the acid by means of acetate of copper. The apocrenate of copper falls, from which the acid is separated by the action of hydrosulphuric acid gas, absolute alcohol and potassa. 1715. Apocrenic acid is brown, and resembles a vegetable ex- tract. It is but slightly soluble in water, from which it is precipi- tated by sal ammoniac. 1716. These acids are supposed by Berzelius to occur frequently in water, and he is of opinion that the substances so often described as existing in mineral waters, and which have been distinguished by the name of extractive, in reality consist of these acids. He thinks too that they exist abundantly in bog iron-ore. Compound Acids. 1117. The compound acids consist of a vegetable principle, united to a strong mineral or vegetable acid. They have been divided by Thomson into two sets. The first set consists of two atoms of an acid, combined with one atom of abase, which may be driven ofFby a stronger base. They are, strictly speaking, not acids, but acidu- lous or super-salts. The second set contains hyposulphuric acid, combined with an organic substance, not acting the part of a base, and not capable of being expelled by a stronger base. 1718. Althionic Acid.W 2(S0 3 )+C 4 H 5 0-{-H0, 126 eq. This nam j is given by Magnus to what was formerly called sulphovinic acid. It is formed by the action of strong sulphuric acid and alcohol, and * Jour, dc Phar. xx. 467. For other acids of this group see Thomson, Chem. Inorg. Bodies , ii. and Org. Bodies, 146. t Jour, de Phar. xxiv. 201. t From xqtjvj] a fountain. S For details of the analysis see T. 148. || From Osiov, sulphur and alcohol. Formo-benzoilic Acid. 395 plays an important part in the formation of ether. When the ingre- Sect. 11 . dients for forming ether are mixed, and before heat is applied, much of the acid exists in the state of this acid, and may be separated by neutralizing the mixture with carbonate of baryta, when an althio- nate of baryta is formed which may be obtained in crystals. 1719. From the experiments of Magnus it seems that when equal Exp ® ri "^ weights of concentrated sulphuric acid and absolute alcohol are mixed, Magnus, one half of the acid deprives the other half of all its water, while every two atoms of the anhydrous acid thus formed unites with C 4 H 5 0+H0 (or alcohol). It is considered by Thomson as a bisalt, or a bisulphate of ether.* It forms with bases, althionates.f 1720. Ethionic Acid. S^-j-C^O-f-HOT This is one of the^j onic compound acids, containing an acid combined with an organic sub- stance, not acting the part of a base and not capable of being expelled by a stronger base. It was obtained by Sertuerner by the action of sulphuric acid and alcohol.^ Sulpho- 1721. Sulpho-naplithalic Acid. S 2 0 5 +C 2 oH 7 , — 199.024 eq. Dis- naphthalic covered by Faraday in 1826. acid > It is made by melting naphthaline with half its weight of strong sulphuric acid, Process, when a red-coloured liquid is formed, which becomes a crystalline solid in cool- ing. The mass is soluble in water, and the solution contains a mixture of sul- phuric and sulphonaphthalic acids. On neutralizing with carbonate of baryta, the insoluble sulphate subsides, while the soluble sulphonaphthalate remains in solu- tion ; and on decomposing this salt by a quantity of sulphuric acid precisely suf- ficient for precipitating the baryta, pure sulphonaphthalic acid is obtained, 1722. The aqueous solution of the acid, as thus formed, reddens Properties, litmus paper powerfully, and has a bitter acid taste. On concentrat- ing by heat, the liquid at last acquires a brown tint, and if then taken from the fire becomes solid as it cools. If the concentration is effected by means of sulphuric acid in an exhausted receiver, the acid becomes a soft white solid, apparently dry, and at length hard and brittle. Sulphonapthalic acid is readily soluble in water and alcohol, and F°J ms is also dissolved by oil of turpentine and olive oil, in proportions de- sa s " pendent on the quantity of water which it contains. By the aid of heat it unites with naphthaline. It combines with alkaline bases, and forms neutral salts, which are called sulpkonaphtholates. All these salts are soluble in water, and most of them in alcohol, and .when- exposed: to heat in the open air, take fire. j| 1723. Sulpho-indigotic and Hypo-sulpho-indigotic Acids are ob- Other acids tained from indigo dissolved in sulphuric acid. ™ in 1= Sulpho-indigotate of Potassa has received various names, ns pre- cipitated indigo , soluble indigo , and carmine of indigo. Crum showed that it was a compound of indigo and sulphate of potassa. He gave the name of cerulin, from its blue colour, to the soluble indigo Cerulin. contained in it, and that of ceruleo-sulphates to the salts consisting of this substance united with sulphates.- 1724. Formo-benzoilic acid may be obtained by mixing the water ^ e °n™il*ic distilled off bitter almonds with hydrochloric acid, and evaporating. a cid. * Organic Bodies , 169. t Phosphovinic Acid is obtained by distilling a mixture of phosphoric acid and Phosphovini® alcohol. t Liebig. % Ann. de Chim. et Phys. xiii. 62. It The sulpho-naphthalate of baryta has been found by Berzelius to be a mixture of two salts difficult to separate ; one containing sulpho-naphthalic and the other hypo- sulpho-naphthalic acid 2(S0 3 )-fCnH45. 396 Chap. VI. Composi- tion. Cyanogen, a com- pound rad- ical. Mellon, Obtained. Melamin, Cyanogen and its Compounds. It remains in crystalline masses mixed with sal ammoniac, from which it is freed by ether, which dissolves the new acid. It is white, very soluble in water, has a strong acid taste, neutralizes bases and forms salts with oxides of silver and copper. It is decomposed by heat, leaving charcoal, and giving out the odour of peach blossoms. Thomson considers it a compound of 1 atom formic acid 1 “ hydret of benzoil - c 2 h o 3 CuH 6 O2 C1&H7 O5 The hydrocyanic acid and water of the bitter almonds is decomposed into for- mic acid and ammonia, for 1 atom of hydrocyanic acid - - C^II N 3 “ water - - - H 3 O 3 1 “ formic acid - I “ ammonia * c 2 h 4 no 3 C 2 H 0 3 h 3 n CalLNOa This constitutes an acid formed by the combination of two organic bodies pos- sessing the characters of acids, and capable of being formed at pleasure.* Section III. Cyanogen and its Compounds. 1725. Cyanogen is considered by Liebig as a compound radical, and as such uniting with oxygen, hydrogen, and most other non- metallic elements, and also with the metals ; many of the latter being similar to haloid salts, while others possess a very different character. In describing the compounds of cyanogen,! it will be necessary to employ new terms, and refer to several substances which have not been described in the foregoing pages, a brief account of them is therefore introduced in this place. 1726. Mellon , C 6 N 4 , eq. =93.32, t is a yellow powder, insoluble in water, alcohol, and dilute hydrochloric and sulphuric acids, but solu- ble with decomposition in nitric acid and the caustic fixed alkalies, decomposable by a strong heat, into three vols. cyanogen, and one vol. nitrogen gas. It unites with potassium forming, mellonuret of potassium, with hydrogen forming hydromellonic acid.$ Discovered by Liebig, and considered by him a compound radical. It is obtained when dry sulpho-cyanogen is heated in a retort to redness, the products of the decomposition being sulphuret of carbon, sulphur and inellou. 1727. Melamin , C 6 N 6 H 6 , eq. =121.62, is a saline base discovered by Liebig, being a product of the decomposition of melam (1729) by alkalies and dilute acids. It crystallizes in colourless or slightly yellow rhombic octohedrons, transparent, anhydrous, sparingly soluble in * T. Organic Bodies, 206. t These compounds constitute the Second Series of Liebig. For details, see Thom- son, Org. Bodies , 768, and Liebig, Org. Chem. 755. t The formulas are those of Liebig. § By dissolving mellonuret of potassium in boiling water and adding hydrochloric, sulphuric, or nitric acid, hydromellonic acid is obtained. It is decomposed by metal- lic oxides. See L. 796. Jlmmdin. 397 cold but pretty freely in boiling water, insoluble in alcohol and ether. Sect, hi. It fuses when heated, and sublimes, partially decomposed into mellon and ammonia. Decomposed by concentrated nitric acid and sulphu- ric acid with the aid of heat into ammonia and ammelid or ammelin ; fused with hydrate of potassa, the elements of 3 eq. of water add themselves to its constituents and form 6 eq. of ammonia, which are evolved, and 3 eq. cyanate of potassa are left. 1728. Melamin combines with dilute acids to crystallizable salts, Combina- all of which have an acid reaction, excepting the double salts. The acetate and formate of melamin are very soluble ; it precipitates magnesia from hot solutions of its salts, owing to the formation of a double salt. Melamin combines directly with the anhydrous hydra- cids, all its salts with the oxacids correspond to the ammoniacal salt in containing an equiv. of water, without which they cannot exist; it forms double basic salts in which this equiv. of water is replaced by a metallic oxide. 1729. Melam. C 12 NnH 9 , eq. = 238.09. This product of the de- Melam. composition of sulphocyanuret of ammonium, was also discovered by Liebig. When the sulphocyanuret of ammonium, or a mixture of two parts of sal ammoniac and one of sulphocyanuret of potassium are heated to the point of fusion of the latter, the sulphocyanuret of ammonium is decomposed into three gaseous and one solid product. The former are ammonia, hydrosulphuric acid, and the sulphuret of carbon ; the latter is melam, which is left in the retort mixed with chloride of potassium, and is separated by washing with water. 1730. It is a white powder, insoluble in water, alcohol and ether ; Properties, but dissolved by hot potassa, a part being decomposed, but another portion is deposited again unchanged as the solution cools. It is also soluble in hot concentrated sulphuric and nitric acids, from which alco- hol and water throw down ammelid. If the solution in these acids Solutions be boiled, it is completely converted into cyanuric acid and ammonia ; ? onverted I eq. melam and 12 eq. water, contain the elements of 2 eq. of cya-ric acid, nuric acid and 5 eq. ammonia. It is dissolved in hydrochloric and dilute nitric acids and potassa with the formation of ammelin and melamin ; fused with hydrate of potassa, ammonia is evolved, and cyanate of potassa produced ; and with potassium the mellonuret of potassium is formed. When heated, it decomposes into mellon and ammonia. 1731. On heating 8 eq. sulphocyanuret of ammonium, they are Explana- decomposed into 1 eq. melam, 10 eq. ammonia, 4 eq. sulphuret of tlon * carbon, and 8 eq. of hydrosulphuric acid ; 1 eq. of melam, on being fused with 6 eq. of hydrate of potassa, give rise, by the addition of the elements of 6 eq. water, to 6 eq. cyanate potassa and 5 eq. am- monia. By long application of heat to melam in caustic potassa, it is decomposed, together with 2 eq. of water, into 1 eq. melamin and 1 eq. ammelin. Melam is converted into ammelid by the addition of the elements of 6 eq. water, which form 1 eq. ammelid and 2 eq. ammonia. 1732. Ammelin. C 6 N 5 H 5 0 2 , eq. =128.47. A saline base, disco- Ammelin, vered by Liebig. A product of the decomposition of melam and mela- min by acids and alkalies. It is precipitated from the alkaline solution from which melamin is deposited, by neutralization with acetic acid. 398 Chap. Vf. Forms salts. Nitrate. Ammelid. Theory of the compo sition of melamin, &c. Explana- tion. Cyanuric acid, Ate. compared. Cyanic acid. Cyanogen and Oxygen . It is white, insoluble in alcohol and ether, soluble in caustic alkalies, yields by distillation a crystalline sublimate and ammonia, with a resi- due of pure mellon. By long boiling in dilute acids, or on being dissolved in concentrated sulphuric acid, it is decomposed by the ad- dition of 1 eq. of water, into ammonia and ammelid. By fusion with caustic potassa 1 eq. of water is decomposed, and it is converted into ammonia and cyanate of potassa. 1733. Ammelin is a weak salifiable base, and forms only with the strong, and not with the organic acids, crystallizable salts, which have an acid reaction, and are partially decomposed by water with the deposition of ammelin. The salts of ammelin with the oxacids contain, like the ammonia salts, 1 eq of water, without which they cannot exist; the double salts are anhydrous. 1734. Nitrate of ammelin crystallizes in large broad plates, or in long quadrangular prisms. When heated it fuses and ammelid is left, nitric acid and the products of the decomposition of nitrate of ammonia are evolved. 1735. Ammelid. C^NyHaOc, eq. =257.79. A product of the de- composition of melam, melamin, and ammelin by concentrated acids. It is a white powder, insoluble in water, alcohol, and ether, but soluble in alkalies and strong acids ; by continued boiling in dilute nitric or sulphuric acid it is decomposed into cyanuric acid and ammonia, l. 1736. Liebig has given the following explanation of the basic qualities of melamin, ammelin, and ammelid, and of their connexion with ammelid and cyanuric acid. It is assumed that these substances contain the same radical as cyanuric acid, together with a com- pound of nitrogen and hydrogen, which is composed of equal vols. of these elements, and which are supposed to be denoted by the symbol 2M=HN ; the compounds may then be represented in the following form : Cyanuric acid - - - Cy3 Oj -+- H3 Melamin - - - Cys Me + H 3 Ammelin .... Cy 3 M 4 O* + H3 Ammelid - Cy 3 M3 O3 H3 Cyanuric acid - - - Cy 3 O3 O3 + H3 1737. The cyanuric acid is, as may be seen, both the commence- ment and termination of the series ; in melamin, the 6 eq. of oxygen are replaced by 6M(N 3 H 3 ), and in ammelin 4 eq. by 4M; both of them are saline bases. The ammelid has no basic properties, and in it one half of the oxygen of the cyanuric acid is replaced by 3M, and by the further removal of all M cyanuric acid is again produced. The basic properties of these bodies decrease as the quantity of oxy- gen which combines with the radical is increased. 173?. The cyanuric acid may be compared with the phosphoric acid, and melamin with phosphuretted hydrogen or ammonia ; am- melin and melamin enter into direct combination with the hydracids and without the intervention of water, but with the oxacids only by the intervention of 1 eq. of water, which must be in the same state of combination as in the ammoniacal salts. L. 803 . Cyanogen and Oxygen. 1739. Cyanic Acid. CyO, 26.39 1 eq. cy. + 8 1 eq. oxy. = 34.39 equiv. This acid was discovered by Wohler, and is formed when 399 Cyanaies of Ammonia. ■cyanogen is transmitted over carbonate of potassa at a red heat, or Sect, nr. into an alkaline solution ; by exposing compounds of cyanogen at a red heat to the action of the air, of nitre, or of peroxide of manga- nese ; by fusing ammelin, melamin, or ammelid with hydrate of potassa; it is a frequent product of the decomposition of compounds of nitrogen. It is not known in the anhydrous state. Obtained as hydrate, by distilling dry cyanuric acid or cyamelide* Obtained, in a retort, when the latter is converted into hydrate of cyanic acid, which must be collected in a receiver well cooled by ice. 1740. A clear transparent fluid of a strong penetrating odour, Properties, similar to that of acetic or formic acid, exceedingly volatile, and causes blisters on the skin, which are accompanied by great pain. Mixes readily with water. Decomposes with the production of great heat shortly after its formation into a white solid of the same com- position per cent, (cyamelide) ;t its aqueous solution reddens vege- table colours strongly ; it decomposes in the course of a few minutes, together with 2 eq. of water, into bicarbonate of ammonia ; Hydrated cyanic acid = C 2 NO+HO >_ C 2 eq. carb. acid . =2C02 Two eq. water . = 2H0 } — ( 1 eq. ammonia . = NH 3 C 2 N H 3 O 4 C 2 NH 3 O 4 1741. This acid forms only one series of salts with the bases ; Forms they are readily recognised by the peculiar decomposition produced sa ls " by dilute mineral acids. A few moments after mixing the salt with the acid, a rapid effervescence, accompanied by the strong penetrat- ing odour of cyanic acid, is observed, and the solution by being mixed with hydrate of lime evolves ammonia abundantly, which previous to the decomposition cannot be detected. Its salts with the alkaline bases and with ammonia are soluble, the others are insoluble ^ the former, with the exception of the ammoniacal salt, are decomposed, when their solutions are boiled, into ammonia and carbonates. 1742. Cyanates of Ammonia . Cyanic acid forms with ammonia Cyanatesof two compounds, one of which is particularly remarkable from its ammonia, identity with urea. 1. Basic Cyanate of Ammonia. When dry ammoniacal gas and the Basic cya ^ vapour of hydrated cyanic acid are simultaneously conducted into anateofam- dry vessel, they unite, forming a white woolly crystalline compound, monm > which contains more ammonia than corresponds to the constitution of a neutral cyanate. It is similar in all its properties to any other salt of cyanic acid ; treated with an acid it is decomposed with effer- vescence, and alkalies effect the evolution of ammonia ; but if on the contrary it be gently warmed, whether dry or in solution, or if it be left for some time exposed to the air, ammonia is given off, it loses all the above-mentioned properties, and is converted into urea. 2. Anomalous Cyanate of Ammonia ; XJrea. Discovered by Four- Urea, croy and Vauquelin in urine, by Wohler as the first organic compound * Insoluble Cyanuric Add ( 1767 ). + This decomposition with water is the cause of the impossibility of obtaining the free acid from the aqueous solutions of its salts by the action of a stronger acid, although a small quantity, as may readily be recognised by the peculiar odour which accompa- nies the carbonic acid evolved, does escape. 400 Chap. VI. Process, Another, Properties. Com- pounds, Decom- posed, Caution. Cyanogen and its Compounds. artificially produced. It is a constituent of uric acid, and is con- tained in the urine in combination with lactic acid.* It is obtained, 1743. By mixing fresh urine evaporated to the consistence of a syrup at a gentle heat, which should never reach that of ebullition, when quite cold, with its own volume of colourless nitric acid of sp. gr. = 1.42. If the evaporation has been carried sufficiently far, the whole will form a thick crystalline mass; to en- sure this, a small portion of the urine should be tried from time' to time. The crystalline mass consists of a compound of nitric acid and urea, which is sparingly soluble in nitric acid.t The impure crystals of nitrate of urea are to be carefully washed with dilute nitric acid, strongly pressed between folds of bibulous paper, dried upon a porous tile, and redissolved in warm water ; the solution, after being freed of its colour by recently prepared charcoal, is evaporated to crystallize. A solution of the colourless crystals of the nitrate of urea is treated with car- bonate of baryta until it is rendered perfectly neutral ; on evaporating, crystals of nitrate of baryta, and then of urea, will be obtained. The crystals of the latter, by being redissolved in a little cold water, are freed from the last portions of the nitrate of baryta ; the solution in alcohol gives crystals of pure urea.t 1744. Instead of using nitric acid, the concentrated urine may be added to a boiling saturated solution of oxalic acid, when the spar- ingly soluble oxalate of urea falls, which, after being deprived of its colour by charcoal, may be decomposed into the insoluble oxalate of lime and pure urea, by being digested with pounded chalM It can also be prepared by the decomposition of the cyanate of oxide of sil- ver by sal-ammoniac, or of the cyanate of oxide of lead by pure or carbonate of ammonia. 1745. Crystallizes in colourless, transparent, four-sided, somewhat flattened prisms of the sp. gr. 1 35, is soluble in its own weight of cold, and in every proportion in hot water, in 4.5 parts of cold, and in 2 parts of boiling alcohol : the aqueous solution has a cooling bitter taste like nitre ; when pure it is perfectly permanent in the air, is not deliquescent, fuses at 250° into a colourless liquid, is decom- posed by a higher temperature into ammonia, cyanate of ammonia, and dry solid cyanuric acid. Alkalies do not cause the separation of ammonia in the cold. 1746. Unites with several acids without decomposition to crystal- lizabie saline compounds : by evaporating its solution with nitrate of silver or acetate of lead it is decomposed ; the products being, with the first, nitrate of ammonia and crystalline cyanate of silver; with the second, acetate of ammonia and carbonate of lead. With hypo- nitrous acid it is instantly decomposed into nitrogen and carbonic acid gases, which are evolved in equal volumes; with chlorine it forms hydrochloric acid, nitrogen and carbonic acid. When fused with the hydrated alkalies, or heated in concentrated sulphuric acid, it is decomposed together with the constituents of 3 eq. of water into carbonic acid and ammonia. Urea contains the elements of cyanate ofamm onia (NH 4 0+C 4 N0) ; it may also be considered, according * Henry. t Since the urine contains metallic chlorides, which with the nitric acid by the aid of heat are decomposed, and give rise to the production of chlorine and nitrous acid, both of which act powerfully in destroying urea, all increase of temperature must be most carefully avoided. t Wohler. § Berzelius. Fulminic Acid. 401 to Dumas, as a second compound of carbonic oxide and amide,* in Sect, in. which the quantity of the latter is double that in oxamide C 2 0 2 -f~ 2NH 2 . 1747. Nitrate of Urea. This compound, when recently precipi- Nitrate of tated from urine, appears in the form of fine crystalline plates of a urea * brown colour and mother-of-pearl lustre ; the purer they are, the more they lose this appearance ; a solution of pure urea treated with nitric acid gives a granular white crystalline precipitate, which is soluble in 8 parts of cold, but more freely in hot water, from which it crystallizes in broad, scarcely translucent plates ; is sparingly so- luble in nitric acid, with which it may be boiled without decomposi- tion. Is composed of l eq. of nitric acid, 1 of urea, and 1 of water.! 1748. Cyanate of Potassa. KOCyO ; eq. = 81.54. By roasting Cyanate of at a red heat dry ferrocyanuret of potassium in fine powder upon an potassa “ iron plate, the powder being constantly stirred ; the cyanuret of po- tassium contained in the salt is thus converted, by absorbing the ox- ygen of the air, into cyanate of potassa. As soon as it is baked into one mass, owing to the fusion of the cyanate of potassa forming, it must be reduced to a fine powder and digested in boiling alcohol, from which, as the solution cools, crystals of the cyanate are depo- sited. A mixture of two parts of ferrocyanuret of potassium, and one of peroxide of Process, manganese, may be treated in the same way. This mixture may be kindled by a red-hot body, when it smoulders away into a brown mass which contains cya- nate of potassa, carbonate of potassa, and sesquioxide of manganese. This salt may also be procured of great purity, but not so economically, by fusing the hydrate of potassa in a silver vessel, and adding melam, ammelin, or ammelid in successive portions as long as they are dissolved ; the fused transparent mass congeals, on cooling, to a pure crystalline cyanate of potassa. 1749. Crystallizes from the alcoholic solution in transparent an- Properties hydrous plates, which closely resemble chlorate of potassa, but by exposure to a moist air are gradually converted, without any change of form, into bicarbonate of potassa, while ammonia is evolved. It is dissolved by cold water, in which it decomposes into bicarbonate of potassa and ammonia ; a change accelerated by heat. Fuses at a high temperature without loss of weight to a clear liquid, which, upon cooling, forms an opaque crystalline mass. If a concentrated solu- tion be partially decomposed by acetic acid, or a dilute mineral acid, the acid cyanuret of potassa is precipitated. 1750. Cyanates of oxides of silver and lead , AgOCyO, and ^de^of ° f PbOCyO, are white anhydrous salts, which are insoluble in water, silver and and are obtained by precipitating the cyanate of potassa by a neutral lead ' salt of lead or silver. Both consist of an eq. of acid and one of me- tallic oxide; the silver salt is soluble in ammonia, with which it forms a white crystalline compound, but by heat the ammonia is Products of again evolved, and the pure cyanate of silver remains ; decomposed dec C«y 2 0 2 is obtained ; from this the baryta, may be precipita- ted by free sulphuric acid, and the acid fulminate of zinc remains in solution, which has been described by E. Davy as pure fulminic acid, but the presence of the zinc may be shown after the decompo- sition of the fulminic acid by the sulphuret of ammonium and the known reagents. 1 ^ 1760. Hydro-chloro-cyanic Acid , is the product of the decompose- pjydro- tion of fulminate of silver by hydrochloric acid. This substance has chloro-cya* a biting but sweetish acid taste, does not precipitate silver salts, and moacid - is decomposed by heat into carbonate of ammonia and other new products. It contains 5 eq. of chlorine, and its constitution is most probably represented by the formula C 2 NCl 5 -f“H 2 . 1761. Cyanuric Acid. Described by Scheele as pyrouric acid, by Cyanuric Serullas as cyanure, but its nature was first pointed out by Wohler acid, and Liebig. * On the preparation of this acid, see Fehling in JLond . . and Edin. Philos Jour » July, 1839. 404 Cyanogen and Compounds. Chap. VI. Process. Explaua lion. Properties, Cyanu- rates. Cyanurate of potassa. Cyanurate of silver. It is a product of the decomposition of the solid chloride of cyano- gen by water, of the soluble cyanates by dilute acids (acetic, &c.), of urea by heat, of uric acid by the destructive distillation, and of me- lam, melamin, ammelid, and ammelin by acids. It is best prepared by dissolving dry melam in strong sulphuric acid, by aid of a gentle heat, throwing the solution into 20—30 parts of water ; the mixture must be kept for several days at near its boiling heat, until upon trial it no longer gives a white precipitate with ammonia, when the solution may be evaporated to crys- tallize ; the crystals should be purified by a second crystallization. Or it may be made by heating urea beyond its point of fusion, until it is converted with the evolution of ammonia into a white or grayish-white dry mass; this must then be dissolved in concentrated sulphuric acid, the solution treated with nitric acid added drop by drop until it becomes colourless, and then added to an equal vo- lume of water ; when cold, crystals of pure cyanuric acid are deposited. 1762. By dissolving melam in strong sulphuric acid it is converted into ammelid, which, by being further heated, is converted into am- monia and cyanuric acid. Three atoms of urea contain the elements of 1 eq. of cyanuric acid, and 3 eq. of ammonia ; at a high tempera- ture the greater part of the ammonia is evolved as a gas, while a small portion remains in combination with the cyanuric acid. 1763. Colourless, inodorous, a slight taste, reddens litmus feebly, sparingly soluble in cold, but taken up by 24 parts of boiling water; the crystals from the aqueous solution contain 21.66 per cent. =4 eq. water, which they Jose at common temperature when exposed to the air, but more rapidly when heated, and fall into powder. They are oblique rhombic prisms. The dry acid contains 3 eq. of water ; it may be obtained in crystals free from water of crystallization from a hot saturated solution in nitric or hydrochloric acid. The hydrate when heated is converted into 3 eq. of hydrated cyanic acid, the constituents of which it contains. It is soluble in the strongest acids without decomposition, but by long-continued boiling is converted into ammonia and carbonic acid. It is a tribasic acid ; its hydrate is Cy 3 0 3 -|-3H0 ; eq. = 130.17. 1764. Cyanurates. The salts of cyanuric acid contain three atoms of base, which are represented in the hydrate by three atoms of wa- ter. All cyanurets are decomposed by hydrochloric, nitric acids, & c. ; the cyanuric acid crystallizes out of the solutions without re- taining a trace of the metallic oxide with which it was united. Its alkaline salts fuse when heated, leaving a cyanate of the alkali, while cyanate of ammonia, cyanic and carbonic acids, are evolved. 1765. Cyanurate of Potassa. The salt < | -f“Cy 3 0 3 is made by neutralizing a boiling saturated solution of cyanuric acid by po- tassa; it falls in the form of white brilliant cubes. If these crystals be dissolved in a solution of caustic potassa, the addition of alcohol precipitates the cyanurate of potassa with two equivalents of fixed base, | oj^q j +Cy 3 0 3 , in white acicular crystals. On being re- dissolved in water and evaporated, it is decomposed into free potassa and the former salt. 1766. Cyanurate of Silver. If nitrate of silver be added to either of the above salts of potassa, a white precipitate is obtained, which is cyanurate of silver, with 2 eq. oxide of silver and 1 eq. water, Hydrocyanic Acid. 405 2A^O I Cy 3 0 3 ; this salt Seated in the dr y state evolves hydrated cyanic acid. But if a solution of silver be added to a boiling solu- tion of cyanurate of ammonia, containing ammonia in excess, the cyanurate with 3 eq. of oxide of silver is formed, 3Ag0,Cy 3 0 3 ; it is insoluble in water; very sparingly soluble in dilute nitric acid; may be heated to 600° without decomposition ; is white, is not blackened by light, emits carbonic acid and nitrogen gases, at a red heat, leav- ing the cyanuret of silver as a residue. 1767. Cyamelid , or Insoluble Cyanuric Acid. Probable formula C 2 0 2 +NH ; eq. == 43.39. The hydrate of cyanuric acid, when free from water of crystallization, hardens shortly after its prepara- tion into a white porcelain-like body, which is insoluble in water, dilute acids, alcohol, and ether ; but is dissolved with decomposition by the caustic alkalies ; ammonia is evolved, and cyanate and cya- nurate of the alkali formed. Concentrated sulphuric acid dissolves it with the aid of heat, when with the elements of 2 eq. water it is decomposed into carbonic acid and ammonia ; submitted to the de- structive distillation, it is converted into hydrated cyanic, a change which is very readily accounted for, since its composition is the same as that of the hydrated acid. Cyanogen and Hydrogen. 1768. Hydrocyanic Acid , Prussic Acid. Discovered by Scheele ; for a knowledge of its nature and chemical properties we are in- debted to Gay-Lussac : it is a constituent of the water distilled from the leaves and blossoms of several stone-fruits ; is formed by the de- structive distillation of many substances containing nitrogen, by the decomposition of formate of ammonia by heat, and of the metallic cyanurets by acids. 1769. Anhydrous Hydrocyanic Acid. Fifteen parts of crystalline ferrocyanuret of potassium are distilled in a retort, at a very gentle heat, with a mixture of 9 parts of sulphuric acid and 9 parts of water, and the products collected in a well- cooled receiver, containing 5 parts of chloride of calcium in coarse fragments : the mixture of acid and water should not be used till perfectly cold. The distil- lation is stopped as soon as the chloride of calcium is perfectly covered by the fluid collected in the receiver. It is then poured off into a strong glass vessel with a good stopper.* The ferrocyanuret of potassium contains the cyanuret of potassium, which is decomposed by the hydrous sulphuric, acid into sulphate of potassa and hydrocyanic acid ; the latter passes over with a little water into the receiver, but this is absorbed by the chloride of calci- um. It can also be prepared by decomposing the bicyanuret of mer- cury by strong hydrochloric or dry hydrosulphuric acid gas. l. 766. The bicyanuret may be heated gently in a tube of about 18 inches in length and at least half an inch in diameter internally, nearly filled with that substance, and placed horizontally, as in Fig. 189. the cut (Fig. 189). The gas is *L passed over until the contents of ^ the tube have become black; none of the gas escaping from the other extremity of the tube, till all the bicyanuret is decom- Sect. III. Cyamelid. Prussic acid. Anhydrous Hydrocya- nic acid. Process, Explained. Process. * Trautwein. 406 Chap. VI. Properties. Freezing point. Decom- posed by light, &c. Action of potassium. Hdyrous hydrocya- nic acid. Process. Cyanogen and Hydrogen. posed. Whenever the odour of the gas is perceived at the mouth of the receiv* ' er, the tube a, connected with the apparatus in which the gas is produced, is withdrawn, and the extremity of tne tube closed with plaster of Paris. It is heated gently when the lute has set, and the hydrocyanic acid which has been formed is volatilized and condensed in a small receiver placed in a freezing mix- ture. 1770. At common temperatures, a clear limpid fluid, very combus- tible, burning with a reddish flame, of sp. gr. = 0.6969 at 64°. It congeals at 5° to a solid fibrous mass, boils at 80°, may be mixed in every proportion with water, ether, and alcohol; the sp. gr. of the vapour is 0.9476 : scarcely reddens litmus paper. It has a peculiar penetrating odour, similar to that of bitter almonds, checks the breathing, and causes a flow of tears ; it possesses a penetrating taste, which is somewhat burning, and strongly bitter; its vapour, when inhaled, acts instantly as a most powerful poison. The anti- dotes are ammonia, as likewise chlorine, which, however, must be administered with caution. 1771. The congelation of the acid at 5° is, according to Schulz, owing to small quantities of water ; he states the perfectly anhy- drous acid as still liquid at — 64°. 1772. Decomposes when perfectly pure with the greatest facility under the influence of light, with the formation of a brown substance and ammonia ; small quantities of acids prevent this decomposition ; by concentrated mineral acids it is very rapidly converted, together with the elements of water, into formic acid and ammonia ; 3 eq. of water and l of hydrocyanic acid, a strong acid being present, suffer mutual decomposition, and are converted into ammonia which unites with the acid, and into formic acid. 1 eq. hydrocy. acid NC 2 H 1 _ 5 * e( l- amm * N H 3 3 eq. water H 3 0 3 $ — ( 1 eq. formic acid C 2 H0 3 NC 2 H 4 0 3 nc 2 h 4 o 3 1773. Potassium heated in the vapour of the acid unites with the cyanogen, and liberates the hydrogen ; lime and baryta, when heated in the vapour, also liberate hydrogen and give rise to cyanates ; it is decomposed by chlorine with the formation of hydrochloric acid and chloride of cyanogen. 1774. Hydrous Hydrocyanic Acid. CyH, eq. 27.39. One part of bicyanuret of mercury dissolved in 8 parts of water is treated with a stream of hydrosulphuric acid gas till the latter is in slight excess ; the free hydrosulphuric acid removed by a little carbonate of lead, and filtered. The clear liquid contains T \j of anhydrous hydrocya- nic acid. By the decomposition of the bicyanuret of mercury the fluid becomes black like ink, and it frequently only becomes clear after the addition of a small quantity of a free mineral acid ; it con- tains too, very generally, small quantities of hydro-sulphocyanic acid- 1775. It may be prepared of the same strength and perfectly pure, according to Geiger, By distilling 4 parts of crystallized ferrocyanuret of potassium with 18 parts of water and 2 of strong sulphuric acid ; 20 parts of water are placed in the receiver, and the distillation is conducted until 38 parts have collected. The distillation is best conducted in a chloride of calcium bath, and the vapours should be con- densed by a condensing apparatus of glass. The product is collected in a cylin- drical bottle, which is marked at the point corresponding to 38 parts. Hydrocyanic Acid. 1776. According to Clark, it may be prepared by dissolving 1 Sect - In - part of tartaric acid in 40 parts of water, and adding 2§ parts of Clark’s pure cyanuret of potassium in coarse fragments to the solution. The process, fluid must be kept very cold, and shaken from time to time ; this acid contains 3 per cent, anhydrous acid, and to 3 grs. of bitartrate of potassa in the ounce.^ 1777. Magendie states that the medicinal hydrocyanic acid ispre- Magenche’s pared by mixing 1 part by volume of the anhydrous acid with 6 parts of water ; or by weight, 1 part of the acid with 8^- of water. 1778. All methods in which hydrocyanic acid is obtained by dis- Strength tillation never yield this energetic preparation of the same quality and strength; even with the application of every possible precaution, the product never contains more than four fifths of the small quan- tity of acid which, according to the calculation, ought to be procured-; this arises, when ferrocyanuret of potassium is used, from a portion of the cyanuret entering into combination with the protocyanuret of iron during the decomposition of the yellow salt, or from the impos- sibility of effecting an absolute condensation of so volatile a substance during the distillation. 1779. It is therefore greatly preferable to prepare a stronger acid How in- in the first instance, to determine by experiment the quantity of an- hydrous acid contained in it ; and by the addition of water to bring it to that degree of dilution which is prescribed by the physician, or by the medical laws of the land.t The method described in the note may be used for testing the strength of any solution of hydrocyanic acid ; 100 grains of an acid which contains 3 per cent, anhydrous prussic acid should, when precipitated by the nitrate of silver, give 15 grains of the cyanuret. This method is independent of all acci- Strength dents which can possibly have an influence upon the activity of the teste * preparation ; it is so very simple that it will yield accurate results in every hand. The peroxide of mercury, which is readily dissolved as cyanide at common temperatures, may also be used to test the strength of the aqueous acid ; a drop or two of caustic potassa is ad- * Glasgow Med. Jour. 14. t For example 2 parts of crystalline ferrocyanuret of potassium are distilled with 1 Method of test- part of sulphuric acid and 2 of water to dryness in a chloride of calcium bath ; and iu s- the product, well cooled by the condensing tube apparatus, collected in a narrow- mouthed bottle, into which 2 parts of water have been placed. The quantity obtained generally amounts to 4— 4£ parts by weight of liquid, containing, according to the more or less perfect cooling, from 17 — 20 per cent, of anhydrous hydrocyanic acid. The exact quantity is determined in the following manner:— One drachm=60 grs. of the dilute acid is added to a carefully balanced glass vessel, which contains a dilute solution of nitrate of silver,* and the increase of weight accurately determined ; by way of precaution, a trial is made to see whether the addition of the silver solution causes a further precipitation, the precipitate collected upon a weighed filter, washed, dried, and the quantity of cyanuret of silver determined by a second weighing. Five parts of the precipitate correspond to 1 part of the hydrocyanic acid. If, for example 52 grains of cyanuret of silver be obtained, the 60 grains of dilute acid would have consisted of 10.4 grains of anhydrous acid, and of 49.7 grains of water. Were it de- sired, according to the prescription of any pharmacopoeia, to make a hydrocyanic acid containing 3 per cent, of anhydrous acid, and consequently 97 per cent, of water, it is done in the following manner: — 3 hydrocyanic acid is to 97 water as 10.4 acid is to X = 336.2 water: to 10.4 grains of anhydrous acid 336.2 grains of water must be ad- ded, in order to form a mixture which shall contain 3 per cent, of anhydrous acid. To each drachm of the product, therefore, since it consists of 10.4 grains of anhydrous acid and 49.6 of water, 336.2 — 49.6 = 286.6 grains of water must be added. * Nitrate of silver is an exceedingly delicate test of the presence of this acid- 408 Cyanogen and Hydrogen. Chap. VI. Properties. How pre- served. Detection of hydrocy- anic acid. Scheele's process. Las- saigne's process. ded to the solution, which is then treated with a known weight of the peroxide in fine powder ; every 4 parts of the oxide dissolved corresponds to one of the anhydrous acid. 1780. The properties of the aqueous acid are similar to those of the concentrated, with the difference of taste, odour, and poisonous and combustible properties, which are dependent on a higher or lower degree of concentration ; it decomposes when perfectly pure as readily as the anhydrous acid, becoming brown, and at last black. 1781. Like the anhydrous acid, however, it may be preserved by ad- ding a trace of a strong mineral acid ; a slight permanent reddening of litmus paper should not therefore be considered a sufficient reason for rejecting an acid ; it should be clear and colourless, leave no residue on evaporation, nor be precipitated or blackened by hydrosulphuric acid gas (lead or mercury). Treated with ammonia, and evaporated in a water-bath, the dry residue should not exceed one quarter per cent. ; nor should it become brown when heated, this indicating the presence of formic acid, which may also be detected by the tests hereafter to be mentioned. Sulphuric acid is detected by baryta ; hydrochloric acid by evaporating in a water-bath till all odour of prussic acid is gone, and then adding a salt of silver. By careful rectification over chalk, an excess of mineral acids may readily be corrected ; but in this case a trace of hydrochloric or sulphuric acid must be added afterwards, to give stability to the acid. L. 769 . 1782. As this acid is a very powerful poison, all experiments with it must be performed with the greatest caution. Several fatal acci- dents have occurred ; even the fumes, incautiously inhaled, produce severe head-ache, nausea, and fainting. A single drop introduced into the throat of a large dog, kills the animal. According to Herbst, the best antidote is the cold affusion. 1783. The presence of the free acid is recognized by its odour. Its presence in the stomach after death may be detected in several ways. The sulphate of copper forms when rendered alkaline by a little potassa, a greenish precipitate, which becomes nearly white, on the addition of hydrochloric acid, but this is of less value than the formation of Prussian blue as proposed by Scheele : To the liquid supposed to contain hydrocyanic acid, add a solution of green vitriol,* throw down the protoxide of iron by a slight excess of pure potassa, and acidulate with hydrochloric or sulphuric acid, so as to redissolve the precipitate. Prussian blue will then make its appearance, if hydrocyanic acid had been originally present. The presence of protoxide of iron is essential. 1784. The subject has been investigated experimentally by Leuret and Lassaigne, and the process they have recommended is the fol- lowing : The stomach or other substances to be examined are cut into small fragments, and introduced into a retort along with water, the liquid being slightly acidulated with sulphuric acid. The distillation is then conducted by the heat of boiling water, till about one eighth part of the water has passed over into the receiver. To the distilled liquid add a drop of caustic potassa, and immediately after a very small quantity of the solution of sulphate of copper. A small quantity of matter will be disengaged by the action of the alkali on the copper solution. Then add one or two drops of hydrochloric acid. If no hydrocyanic acid be present, the * Liebig disapproves of this test. 409 Cyanuret of Potassium. precipitate will be dissolved and the liquid become transparent ; but if any of the Sect. III. acid is present it will remain undissolved and white. By this method ^ otnr part of the acid may be detected. There is, however, a source of ambiguity ; the same white precipitate will remain if the liquid should contain hydriodic acid. Sulphate of iron when substituted for sulphate of copper will detect to - - . trou °f the weight of the acid, but it has the advantage of being characteristic in conse- quence of the formation of Prussian blue.* 1785. Hydrocyanate of Ammonia , Cyanuret of Ammonium. Hydrocya- NH 4 Cy, eq. = 44.54. Prepared by distilling dry ainmoniacal salts nateofam- with metallic cyanurets, or by bringing anhydrous hydrocyanic acid into contact with ammoniacal gas, when the compound is produced in the form of bright crystalline plates. It is almost as volatile as the acid itself; decomposes very rapidly in water, is poisonous, and has a strong peculiar smell. 1786. On bringing hydrocyanic acid into contact with metallic ox- Hydrocya- ides which retain their oxygen by a feeble affinity, as in the oxides ofnieacid mercury, silver, palladium, they suffer mutual decomposition, giving j^oxides ' rise to the formation of water and a metallic cyanuret ; if no water be present, the decomposition is accompanied by so great an evolution of heat as to cause an explosion. The alkaline oxides unite with the acid without decomposition ; in this class of com- pounds also the decomposition of the acid and alkali is instantly effected, when the solution is treated with another metallic cyanuret, with which they form a double compound. With many peroxides, as, for example, with the peroxide of copper, the hydrocyanic acid gives rise to a corresponding percyanuret ; but this is decomposed either instantly, or after a short time, into cyanogen gas, and a pro- tocyanuret; with the peroxide of lead the protocyanuret is formed, and cyanogen liberated. 1787. The compounds of cyanogen with silver, mercury, and Withsil- tnost heavy metals, are not decomposed by dilute ox-acids, and are ver ’ ^ c ' with difficulty decomposed by concentrated nitric acid at a boiling temperature; many of them with great facility by hydrosulphuric and hydrochloric acid into hydrocyanic acid, and a metallic sul- phuret or chloride (cyanurets of mercury, silver). The cyanurets of the precious metals (silver, mercury) are decomposed by heat like the corresponding, oxides into cyanogen and metal ; the cyanurets of the heavy metals into a carburet and free nitrogen ; the cyanurets of the alkaline metals, if protected from the action of the air and moisture, will bear a very high temperature without decomposition. 1788. All insoluble cyanurets of the heavy metals may be formed insoluble by adding hydrocyanic acid to the acetate. They are decomposed cyanurets on being heated in a large excess of hydrochloric acid or in hydrate of potassa into a metallic chloride, or into an oxide, ammonia, and formic acid ; the latter is the case with the alkaline cyanurets when boiled in an excess of alkali. All metallic cyanurets, the correspond- ing oxides of which do not retain carbonic acid at a red heat, evolve, when burnt with oxide of copper, nitrogen and carbonic acid gases in the proportion 1 : 2 by volume. 1789. Cyanuret of Potassium. KCy eq. 65.54. Formed, when Cyanuret potassium is heated in cyanogen gas with the appearance of com- of P otassi - 52 * Ann. de Chim. et Phys. xxvii. 200. 410 Chap. VI. Prepared. Properties. Action of water. Cyanuret oi iron. Cyanogen and its Compounds . bustion, by heating potassium with anhydrous substances containing nitrogen, by heating the carbonate of potassa to redness with matter containing carbon and nitrogen. By adding hydrocyanic acid in excess to a recently prepared concentrated so- lution of caustic potassa, evaporating the solution in a retort at a boiling heat till crystallization commences, when it must be poured into a porcelain dish and fused at a low red heat. Or a saturated alcoholic solution of hydrate of f iotassa is treated with strong hydrocyanic acid in successive portions as ong as it throws down a white crystalline precipitate, which should be washed with alcohol and dried. An additional quantity is obtained by eva- porating the liquid in a retort. Or better by heating the ferrocyanuret of po- tassium, carefully dried and reduced to a fine powder, in an iron vessel or well- closed crucible to a strong red heat, exposure to the air being carefully avoided till auite cold ; the semi-fused or black porous mass must then be reduced to a nne powder, placed in a funnel, moistened with a little alcohol, and then washed with cold water. The first concentrated colourless solution which passes off, is rapidly brought to dryness and fused in a porcelain dish. The pounded fused mass may also be boiled in spirit when the cyanuret is depo- sited in crystals on cooling. Alcohol of 60 per cent, dissolves at the boiling temperature a considerable quantity of the cyanuret, almost the whole of which is again deposited as the solution cools; if it be stronger or weaker, this does not occur. The application of warm water in the preparation must be altogether avoided, as when air is present it at once colours the so- lution yellow, owing to the reproduction of the ferrocyanuret of potassium. 1790. Colourless, crystallizes in transparent cubes, or other forms of the oetohetlral system, without odour, but of a sharp biting alka- line and bitter-almond taste ; fuses readily to a clear transparent liquid, and will bear a white heat without decomposition in close vessels ; exposed to oxygen, on the contrary, it is converted into cy- anate of potassa. On exposure the crystals become opaque, deli- quesce in a moist atmosphere, are very soluble in water, the solution is decomposed even by the carbonic acid of the air, and smells of prussic acid. Even kept in close vessels it decomposes in a shorter or longer time. 1791. The cyanuret of potassium is converted, when dissolved in water, into hydrocyanate of potassa ; if the solution be evaporated with an excess of potassa, the whole of the nitrogen is evolved as ammo- nia, and formate of potassa remains. Effervescence on the addition of an acid proves the presence of carbonic acid ; a yellow colour, that of iron ; and a blackening when heated, the admixture of salts of formic acid. It may be used instead of the hydrocyanic acid. 1792. Cyanuret of Iron. FeCy ; eq.=54.39. This compound, remarkable from its tendency to form a very peculiar class of double compounds by uniting with other cyanurets, would appear as inca- pable of existing in a free state as the corresponding protoxide. On adding a proto-salt of iron to a solution of cyanuret of potassium, a yellowish-red precipitate is formed, which is redissolved by an ex- cess of the cyanuret into a yellow liquid, the ferrocyanuret of potas- sium. On heating dry ferrocyanuret of ammonium, cyanuret of ammonium is evolved, and a gray insoluble powder, which has been considered as this compound, is the residue obtained. It is also produced, according to Robiquet, by pouring a saturated solution of hydrosulphuric acid over recently precipitated Prussian blue con- tained in a well-stoppered vessel ; the Prussian blue becomes white, 411 Cyanuret of Palladium . and the solution contains hydrocyanic acid.^ The properties of Sect, m. these preparations differ too widely to allow of their being considered as identical.! 1793. Bicyanuret of Mercury. HgCy 2 , eq. =254.78. An aque- Bicyanuret ous solution of prussic acid is treated with finely powdered peroxide 0 mercur y* of mercury until all odour of the former disappears ; the liquid yields on evaporation perfectly pure crystals of the bicyanuret. For this purpose the acid prepared as recommended by Geiger is most conve- Process, nient ; it should be introduced into a well-stopped bottle, and the combination with the oxide of mercury promoted by frequent agitation. It must always be remembered, that the compound can only be produced when water is present in sufficient quantity to dissolve the whole of the cyanuret; water must therefore be added, should it be observed that the liquid smells of prussic acid, while any portion of the oxide of mercury remains undissolved. Or by adding to a solution of 2 parts of ferrocyanuret of potassium in 15 parts of boiling water, 3 parts of perfectly dry bisulphate of the peroxide of mercury ; boil the mixture for a quar- ter of an hour, and separate the clear liquid while boiling hot from the precipitate by filtration ; as the solution cools, the bicyanuret crystallizes. The mother- liquor yields a second crop of crystals by further concentration ; or it may be evaporated to dryness, and the cyanuret obtained from the residue by boiling al- cohol. The first crystals from the aqueous solution are purified by a second crystallization. 1794. The formation of the cyanide in this process is owing to Explained, the mutual decomposition between the 2 eq. of cyanuret of potassium of the ferrocyanuret and 2 eq. of persulphate of mercury into bicya- nuret of mercury and sulphate of potassa, while the cyanuret of iron is precipitated. 1795. Crystallizes in colourless transparent regular four or six- Properties, sided prisms ; they are anhydrous, permanent in the air, of a very disagreeable metallic taste, and are very poisonous. Is dissolved by 8 parts of water at 60°, but is more soluble in boiling water, and in alcohol. Peroxide of mercury decomposes all soluble metallic cyanurets with the formation of an oxide and double cyanurets of mercury and other metals.! 1796. Cyanuret of Silver. AgCy, eq. 134.39. Falls, on mixing Cyanuret a soluble salt of silver with hydrocyanic acid, in the form of a bril- si * ver ‘ liant white curdy precipitate ; is decomposed by all hydracids, but with great difficulty by other mineral acids ; strong boiling nitric acid alone can dissolve it ; suffers no change by the caustic fixed al- kalies, is readily dissolved by ammonia. Is soluble in a concen- trated solution of the nitrate of silver, forming with it a compound, which may be obtained in crystals, but is not permanent in water. It gives rise to double compounds with all cyanurets of the alkaline metals. 1797. Cyanuret of Palladium. PdCy, eq. 79.69. The affinity Cyanuret of palladium for cyanogen surpasses that of all other metals ; they * Berzelius. t Sesqui, and Proto cyanurets of Iron, FeCy-fFe2Cy3-)-4 aq. $ If the bicyanuret be boiled with an excess of peroxide of mercury, the latter is dis- solved in large quantity (3 eq. Kuhn), and the solution on evaporation deposits a compound in fine acicular crystals; these are more soluble in cold water than the bi- cyanuret, and have an alkaline reaction on vegetable colours. The formation of this compound, during the preparation of the bicyanuret, must be carefully avoided, or only a white saline mass may be obtained. This is best done by the careful addition of hydrocyanic acid until its odour is slightly perceptible. 412 Chap. VI. Percyanu- ret of gold. Double cy- an urets of the metals. Constitu- tion of the double compounds of iron and cyanogen. Hydro-fer- rocyanic acid. Process. Cyanogen and its Compounds. combine, whenever hydrocyanic acid or any soluble cyanuret is ad- ded to a salt of the oxide of palladium, in the form of a light chest- nut precipitate, which has a greenish tint if copper be present ; gives rise to double salts with ammonia, cyanuret of potassium, and nitrate of the oxide of palladium. 1798. Per cyanuret of Gold. AuCy 3 ,eq. =278.17. This compound has recently been used medicinally. A solution of gold in aqua iegia, carefully deprived of all free acid by evapo- ration, is precipitated by a recently prepared solution of caustic potassa to which hydrocyanic acid has been added in excess ; care must be taken that a small quan- tity of the chloride of gold remain in the solution. The yellowish-white preci- pitate is collected, washed, and dried. An excess of cyanuret of potassium dissolves the precipitate, and the solution has a yellowish-red colour, but in this case it is re-precipitated by the addition of an acid. It may also be prepared by adding to 16 parts of gold dissolved in aqua regia by the aid of heat a boiling so- lution of 24 parts of bicyanuret of mercury, evaporating to dryness, and washing with pure water. 1799. All insoluble metallic cyanurets (the heavy metals) combine with the soluble (the alkaline metals) to peculiar generally crystal- lizable double compounds, which are very similar in their general properties to the combinations of the soluble and insoluble metallic sulphurets. On mixing a double cyanuret of potassium or sodium with a metallic salt, the basis of which is an oxide of a heavy metal, a new double compound is generally formed, arising from the re- placement of the alkali by its equivalent of the heavy metal. The double cyanuret of silver and potassium, KCy-|-AgCy, forms, with acetate of lead, PbOA, the double cyanuret of silver and lead, PbCy -)-AgCy, and acetate of potassa. 1800. The composition of these compounds is best explained by supposing the existence of a radical, which contains 1 eq. of iron in combination with carbon and nitrogen in the same proportion as they exist in cyanogen, but in such quantity as would form 3 eq. of the latter, and which, by uniting with 2 eq. of hydrogen, form a bibasic acid. The radical itself may be called ferrocyariogen ; the acid, hydro-ferrocyanic acid ; and the compounds of the radical with the metals by the same adjuncts to ferrocvanuret as are used lor the corresponding oxides. The ferrocyanogen is composed of 3 eq.' nUrogen \ =3 eq c y auo Sen+l eq. iron=l eq ferrocyanogen j symb. Cfy. Compounds of Ferrocyanogen. 1801. Hydro- Ferrocyanic Acid. Cfy-j-2H, eq.=109.17. Disco- vered by Porrett. Prepared by decomposing recently precipitated ferrocyanuret of lead or copper by sulphuretted hydrogen ; filter to separate the metallic sulphuret, and evapo- rate over sulphuric acid in vacuo.* Or by mixing pure Prussian blue with ten times its volume of concentrated hydrochloric acid, and as soon as the blue colour has disappeared, and the insoluble portions have become yellow or brown, washing it well with fresh portions of the concentrated acid ; the moi9t mass should be spread out upon a clean tile, placed under a bell-jar with quick lime, and when dry dissolved in alcohol, and the solution spontaneously eva- porated.t * Berzelius. t Robiquet. 413 Ferrocyanuret of Potassium . 1802. A white distinctly crystalline mass, or small granular, some- Sect, m. times acicular crystals, which acquire a blue colour by exposure to Properties, the air. The aqueous solution is decomposed by boiling into hydro- cyanic acid, and a white, but after exposure in open vessels blue, precipitate. The hypothetical radical of the acid can (probably) not be isolated. 1803. Ferrocyanuret of Ammonium. It may be formed by digest- Ferrocyan- ing at a gentle heat the ferrocyanuret of lead with carbonate of am- uret of am- monia; filtering to separate tbe carbonate of lead, and evaporating rnomum ' to crystallization. It is isomorphous with the ferrocyanuret of po- tassium ; the crystals are white, or yellowish-white, transparent, permanent in the air, very soluble in cold, but decomposed by boiling water into cyanuret of ammonium and cyanuret of iron, insoluble in alcohol. It forms with sal ammoniac a double salt, which is obtain- ed by boiling a solution of equal parts of ferrocyanuret of potassium and sal ammoniac in 6 parts of water, when it forms, on cooling, large lemon-yellow crystals, which are very brittle and permanent in the air. They are composed of an eq. of ferrocyanuret of ammo- nium, 1 of sal ammoniac, and 3 eq. water.^ 1804. On bringing the hydro-ferrocyanic acid into contact with Hydro-fer- metallic oxides, the latter are reduced by the hydrogen of the acidj.^y^J water, and a compound of the metal with the radical of the acid be- metallic ox- ing formed ; as 1 eq. of the acid contains 2 eq. of hydrogen, it fol- ides, lows as a necessary consequence that it decomposes 2 eq. of the most numerous class of oxides, in which 1 eq. of oxygen is present in 1 eq. of the oxide. 1805. The ferrocyanurets are, without exception, decomposed Decompos- when exposed to a red heat in close vessels ; those which contain an ed by heat ' alkaline metal give rise to the formation of the cyanuret of that metal, a carburet of iron, and the evolution of nitrogen gas ; all others yield mixtures of metals and metallic carburets, with or without the evolution of cyanogen. All the soluble ferrocyanurets are decom- posed by being boiled with peroxide of mercury into perycyanuret of mercury, free alkali, and oxy-cyanuret of iron. The ferrocyanurets of potassium and sodium are converted by being calcined in open ves- sels into alkaline cyanates, and the black oxide or carburet of iron. 1806. Most of the ferrocyanurets contain water of crystallization, Properties, which they lose when heated. Those of zinc, copper, and mercury unite with ammonia to peculiar crystalline double compounds.! Most of them are soluble in concentrated sulphuric acid without decompo- sition ; or they unite with it, when they lose their colour, to saline combinations in which the ferrocyanuret acts the part of a base. By nitric acid they are decomposed, many of them with the evolution of cyanogen and the formation of metallic ferrid-cyanurets. When those which are soluble in water are boiled with dilute acids, the hydro-ferrocyanic acid is separated, and at that temperature decom- posed into hydrocyanic acid which escapes, and into the white but impure protocyanuret of iron, which, on exposure to the air, absorbs oxygen and becomes blue. 1807. Ferrocyanuret of Potassium. In crystals K 2 Cfy-|-3 aq., eq. Ferrocya- =185.47. This compound occurs of great purity in commerce, and is potassium. * Bunsen. + Ibid. 414 Chap VI. Process. Explained. Effect of air. Air exclud- ed. Properties. Protoiulphatf of iron useful. Cyanogen and its Compounds. prepared on a large scale by fusing substances which are rich in ni- trogen, as horn, hoof, and dried blood, with 2 — 3 parts of carbonate of potassa in iron vessels ; the mass after perfect fusion is allowed to cool, the soluble parts removed by boiling water from which the fer- rocyanuret is obtained by crystallization. It may be obtained on a small scale by boiling Prussian blue in carbonate of potassa. 1808. By the fusion of substances containing carbon and nitrogen with carbonate of potassa at a red heat, the potassa is reduced by a portion of the carbon to potassium, by the reaction of which on the rest of the materials cyanuret of potassium as the principal product is formed. The red-hot fused mass does not contain a particle of the ferrocyanuret, but it contains, in the form of a black slime, a large quantity of finely divided metallic and carburetted iron. If the mass be treated with cold water, and the solution evaporated, no ferrocyanuret is obtained ; but if, while covered with water, it is freely exposed to the air and gently warmed for some hours, oxygen is rapidly absorbed, and a yellow solution is obtained, which is rich in ferrocyanuret of potassium; this arises from the solution of pure cyanuret of potassium dissolving iron when oxygen is present with the formation of potassa; the potassium, therefore, of the cyanuret, by uniting with oxygen, gives the cyanogen to the iron, by which the latter is converted into cyanuret, and thus acquires the property of uniting with undecomposed cyanuret of potassium to the ferrocy- anuret. 1809. In close vessels the solution of iron by cyanuret of potassi- um is attended with the evolution of hydrogen, owing to the decom- position of water, the oxygen of which unites with the potassium, while the cyanogen passes over to the iron. The fused mass con- tains a large quantity of free potassa, which, by being boiled with the cyanuret of potassium, causes the decomposition of the latter into formate of potassa and ammonia ; if the animal substances be fused in open vessels with the potassa, a portion of the cyanuret of potas- sium is burnt into cyanate of potassa, the solution of which is decom- posed by boiling into ammonia and bicarbonate of potassa. The ammonia arises in every case from the decomposition of the cyanuret of potassium ; its formation is consequently always accompanied by a corresponding loss, and should be most carefully avoided.* 1810. Crystallizes in large quadrangular tables or short prisms with truncated edges and angles, which belong to the square pris- matic system ; is of a lemon-yellow colour, of sp. gr. 1.832 ; has at first a sweetish bitter, but afterwards saline taste ; is permanent in the air, loses at 212° 12.82 per cent.=3 eq. of water, and becomes white ; is soluble in 4 parts of cold and in 2 parts of boiling water ; is insoluble in alcohol, by which it is precipitated from its aqueous * It is best to treat one third either by volume or weight of a cold solution of the raw mass with pr >tosulphate of iron as long as a precipitate falls, then add the remaining two thirds of the solution, and bring the whole to the boiling point} it must always be remembered that the solution must contain free potassa. In this manner sulphate of potassa is obtained, and all the cyanuret of potassium is converted without any loss into the ferrocyanuret ; the solution can be evaporated without decomposition, and the sulphate of potassa is easily separated by crystallization. The raw solution generally contains some sulphocyanuret of potassium, sulphuret of potassium, formate and car- bonate of potassa, all of which remain in the mother liquor. 415 Sesqui-ferrocyanuret of Iron . solution in brilliant yellow flakes. Is converted by nitric acid, with Sect, in. the escape of cyanogen, and by chlorine, into the ferrid-cyanuret of potassium. At a red heat it is decomposed into the carburet of iron and cyanuret of potassium, but by the action of atmospheric air the latter is converted into cyanate of potassa. 1811. The ferrocyanuret of potassium forms double compounds Use. with other ferrocyanurets. It is used as a test for the oxide of iron in solution. When thus employed, however, it must be remem- bered that the solution must not have an alkaline reaction, for all solutions of oxide of iron which contain free ammonia are not preci- pitated by the ferrocyanuret of iron. It is used for the preparation of hydrocyanic acid, percyanuret of mercury, Prussian blue, &c. ; taken in largo doses is purgative and not poisonous.* 1812. Ferrocyanuret of Mercury. On mixing a solution either Ferrocya- ofpro- or peroxide of mercury with ferrocyanuret of potassium a white nuret of precipitate falls, which spontaneously decomposes into cyanuret 0 f mercui T* mercury which is re-dissolved, and into cyanuret of iron. This change is rendered more rapid by the aid of heat, and metallic mer- cury is separated when a proto-salt of mercury has been used. 1813. Ferrocyanuret of potassium produces white precipitates with Colour of the salts of silver, zinc, and bismuth, a greenish-white with those of nickel, and green with cobalt ; but the latter, by taking up water, become reddish-gray ; with salts of protoxide of manganese a white precipitate is first formed, but it afterwards acquires the colour of peach-blossoms. 1814. Sesquiferrocyanuret of Iron. Discovered by Diesbach in p russ i an Berlin in 1710, from which it became generally known as Prussian blue. or Berlin blue- It is formed whenever a salt of peroxide of iron is added to a soluble metallic ferrocyanuret ; compounds similar in co- lour, but different in constitution, although likewise known by the name of Prussian blue, may be obtained by precipitating the ferrid- cyanuret of potassium by a salt of the protoxide of iron, or by preci- pitating the ferrocyanuret of potassium by a proto-salt of iron, adding an acid, and exposing the precipitate to the air until it becomes blue. By precipitating a solution of perchloride or pernitrate of iron by ferrocyanuret Process, of potassium, care being taken to avoid an excess of the latter. Or by dissolving 6 parts of green vitriol and (5 parts of ferrocyanuret of potassium each by itself in 15 parts of water, mixing the two solutions, and then adding to them 1 part of concentrated sulphuric acid and 24 parts of fuming hydrochloric acid un- der constant stirring. After some hours the whole should be treated with a clear solution of 1 part of bleaching-powder in 80 of water, added in successive portions, care being taken to stop the addition of the bleaching liquid as soon as an effervescence arising from the escape of chlorine gas is observed. After stand- ing some hours, the precipitate, should be thoroughly washed! and dried, either at common or high temperatures. Or the precipitate may be treated with dilute nitric acid till it is rendered of a deep blue colour. This yields the finest pro- duct.! 1815. Prussian blue dried at common temperatures is a ligh.t po- Properties, rous body of a deep velvet-blue colour; dried, on the contrary, at high temperatures, it has a deep copper-red colour, but the powder * For other ferrocyanurets see Liebig and Turner’s Elements , 780 . t Hochstatter. t For details of the manufacture, see lire’s Did. Arts and Manuj. 1040 , 416 Chap. VI. Chemical constitu- tion. Effect of light. Ferrocya- nurets with two basic metals. Ferrocya- nuret of po- tassium and iron. Cyanogen and its Compounds. is blue ; it is tasteless, insoluble in water and dilute acids, and is not poisonous. The painter’s Prussian blue of commerce contains vari- able quantities of earthy matter. When heated in close vessels, water, hydrocyanic acid, and carbonate of ammonia are evolved, and carburet of iron is the residue ; it may be kindled in the air by a red-hot body, when it burns slowly to oxide of iron; it is decomposed by fuming nitric acid, but strong sulphuric acid unites with it, form- ing a white mass of the consistence of paste. Concentrated hydro- cyanic acid deprives it of its iron, and liberates the hydro-ferrocyanic acid; sulphuretted hydrogen whitens it, but the colour returns on exposure to the air ; metallic zinc and iron have a similar action. By peroxide of mercury it is decomposed into percyanuret of mer- cury, and an insoluble mixture of oxide and cyanuret of iron ; by alkalies, into soluble ferrocyanurets and peroxide of iron. 1816. In reference to the constitution of this compound, it is known with certainty that it differs from all other ferrocyanurets. It contains hydrogen and oxygen, which cannot be separated without the decomposition of the compound, so that it must be considered as formed by the union of hydro-ferrocyanic acid with the peroxide of iron combined without reduction. According to the experiments of Berzelius, the weight of the iron of the hydro-ferrocyanic acid is to that of the oxide as 3 : 4 ; from this it may be concluded that its forma- tion is owing to the decomposition of 3 eq. of ferrocyanuret of po- tassium, and 2 eq. of peroxide of iron, into 6 eq. of a potassa salt and into Prussian blue. S+60 | =(3Cfy+2Fe a )+6KO. IS17. Prussian blue becomes white in the direct rays of the sun, and cyanogen is evolved ; but in the dark it absorbs oxygen and re- covers its colour.* This change of colour in substances dyed with Prussian blue in solar light, arises from a peculiar decomposition ; the recovery of the colour is owing to the formation of the so-called basic Prussian blue. 1818. When concentrated solutions of the salts of baryta, strontia, lime, magnesia, protoxide of iron, protoxide of manganese, copper, &c., are added to a solution of the ferrocyanurets of potassium, white bulky, frequently crystalline, precipitates are formed, which arise from the replacement of 1 eq. of potassium by 1 eq. of the other metal. These double ferrocyanurets which contain an alkaline me- tal, although with difficulty, are nevertheless soluble in water; they contain water of crystallization ; when dried at a high temperature they glow with a brilliant light, and cyanate of potassa is formed. t 1819. Ferrocyanuret of Potassium and Iron is obtained in the form of a bluish-white precipitate when a salt of the protoxide of iron is added to a solution of the ferrocyanuret of potassium. By the action of chlorine or nitric acid 3 eq. of potassium and 1 eq. of iron are removed from 3 eq. of the compound ; Prussian blue is left. Ex- posed to the air it absorbs oxygen and becomes blue ; when washed, the ferrocyanuret of potassium is dissolved, and after all soluble salts are removed the following compound is left. * Chevreul. t Campbell. 417 Hydro-ferridcyanic Acid. 1820. Basic Sesqui-ferrocyanuret of Iron. By continued washing Sect, hi. the preceding salt dissolves, without leaving any residue of oxide of Basic ses- iron, to a beautiful deep blue solution, which may be again evapo- rated to dryness without decomposition. The addition of any salt j ron . causes the separation of the compound ; the precipitate may be re- dissolved in pure water, and is not throvvn down by alcohol.* The formation of this soluble salt is prevented by the presence of a strong acid, which unites with the peroxide of iron, and Prussian blue is left. 1821. Ferrocyanuret of Potassium — Sesqui-ferrocyanuret of Iron. Ferrocya- The blue precipitate which falls when a salt of the peroxide of iron ta S r s e ium. P °" is added to a solution of ferrocyanuret of potassium, always contains, when the iron salt is in excess, variable quantities of the ferrocyanu- ret of potassium; the latter may, by continued washing with water, gradually, although with great difficulty, be removed, which ac- counts for the constant presence of potassium in the Prussian blue of commerce ; it varies from 2 to 9 per cent.! 1822. Ferrocyanuret of Potassium — Ferrocyanuret of Zinc , is ob- Ferrocya- tained by precipitating any salt of zinc, which is free from iron, by n ! lretof ferrocyanuret of potassium, and then washing and drying the preci- pitate. It is a white, tasteless powder, is insoluble in dilute acids, and contains 2 eq. of ferrocyanogen, 1 eq. potassium, 3 eq. of zinc, and 12 eq. of water =-2Cfy -j- j j -j- 12 aq. A blue tint shows the presence of Prussian blue. It is used in medicine. 1823. Ferrid-cyanogen. By treating a solution of ferrocyanuret Ferrid-cya- of potassium with chlorine a new compound of potassium is formed, nogen ‘ the radical of which contains twice as much cyanogen and iron as exists in ferrocyanogen. It may be called ferrid-cyanogen ; it unites with 3 eq. of hydrogen and forms a tribasic acid. Its formula is 6Cy+2Fe ; symb.=Cfdy ; ec[. =214. 34. The formula of hydro-ferridcyanic acid is - Cfdy + 3H ferridcyanuret of potassium - - Cfdy + 3K ferridcyanuret of iron (Prussian blue) Cfdy + 3Fe 1824. Hydro-ferridcyanic Acid unites with metallic oxides, form- Hydro-fer ing w r ater and a metallic ferridcyanuret; of these the compounds ^^ancf with the metals of the alkaline earths* as also that corresponding to metallic the peroxide of iron, are soluble in water ; all others are insoluble oxides. * Two eq. ferrocyanuret of potassium and iron contain 1 eq. of ferrocyanuret of po- tassium and 3 eq. of ferrocyanuret of iron (6Fe+3Cfy) ; of these 6 eq. of iron, 2 are converted into peroxide by the absorption of oxygen, and the ferrocyanuret of potassi- um is dissolved* so that the soluble blue compound must be represented by the formula j 2 p®|o s \ + 3 Cfy, which corresponds to a compound of L eq. of Prussian blue and 1 eq. of peroxide of iron. t If, instead of the salt of peroxide of iron, the ferrocyanuret of potassium be in ex- cess, the precipitate is likewise blue, but it is a mixture of Prussian blue with a com-* pound composed of Prussian blue and ferrocyanuret of potasssium eq. to eq. 2Cfy-}- ^■ e2 ^ . On washing, the latter is dissolved, giving a deep blue solution, which may be evaporated without decomposition, when it is obtained as a deep blue mass pos- sessed of a strong lustre- It is precipitated by the addition of a salt to its solution, without however losing its solubility in pure water; it is distinguished from the solu- ble basic Prussian blue by being precipitated from its solution by alcohol. 53 418 Chap. VI. Ferridcya- nuret oi potassium. Properties. Ferrid-cya- nuret of iron. Turnbull's blue. Constitu- tion of the ferrocyanu rets accor- ding to Berzelius, According to Graham, Cyanogen and its Compounds . in water. The latter may be prepared by the mutual decomposition of a soluble ferrideyanuret and the corresponding metallic salt. 1825. Ferrideyanuret of Potassium. K 3 Cfdy; eq.=331.79. Dis- covered by L. Gmelin, is prepared by passing a stream of chlorine gas through a solution of ferrocyanuret of potassium, until it no longer gives a blue precipitate with salts of the peroxide of iron ; the solution is then evaporated, and the crystals obtained by cooling pu- rified from the admixture of chloride of potassium by re-crystalliza- tion.* 1826. They are transparent right rhombic prisms of a red colour and high lustre, anhydrous, permanent in the air, and soluble in 3.8 parts of cold, but more freely in hot water; burn when held in the flame of a candle with brilliant scintillations ; heated in close ves- sels, cyanogen and nitrogen gases are evolved, a mixture of carburet of iron and ferrocyanuret of potassium is the residue. The aqueous solution is decomposed by hydrochloric or sulphuric acid ; in the last case, sulphur and cyanuret of iron are precipitated, and ferrocyanu- ret of potassium and prussic acid are formed. It is one of the most delicate tests for the protoxide of iron, with which it forms a precipi- tate similar to Prussian blue ; peroxide of iron is not precipitated. 1827. Ferrideyanuret of Iron. This compound is likewise sold in commerce as Prussian blue, but it is of a lighter colour and differs from it altogether in constitution. It is prepared by precipitating a solution of the protosulphate of iron by ferrideyanuret of potassium, or by a mixture of ferrocyanuret of potassium and hypochlorite of soda, to which a certain quantity of hydrochloric acid has been ad- ded. In this kind of Prussian blue the three equivalents of potassi- um of the ferrideyanuret of potassium are replaced by 3 eq. of iron. 1828. The peculiarly beautiful Prussian blue sold in commerce under the name of Turnbull’s blue, is the ferrideyanuret of iron ; it is easily recognised by its action on ferrocyanuret of potassium, for being boiled in a solution of the latter it is decomposed into ferrid- eyanuret of potassium, which is dissolved, and into an insoluble gray residue of ferrocyanuret of iron and ferrocyanuret of potassium. t 1829. According to Berzelius, the cyanurets form, by uniting with each other, double compounds similar to the double salts, which are produced by the oxacids; in these compounds, therefore, 1 eq. of cyanuret of iron is united with 2 eq. of another cyanuret, the consti- tution being such, if the metals be considered united with oxygen, as would be expressed by saying that the oxygen in the protoxide of iron is equal to one half that in the other metallic oxides. 1S30. According to Graham, the ferrocyanurets are formed from a peculiar acid, the eq. of which is triple of that of the hydrocyanic acid ; it contains 3 eq. of cyanogen, which constitutes a radical called prussine in combination with 3 eq. of hydrogen. This acid is accordingly a tribasic hydracid corresponding to the cyanuric acid; in uniting with a metallic oxide three eq. of hydrogen are replaced by their eq. of the metals. ♦ Its formation is owing to the decomposition of 2 eq, of ferrocyanuret of potassium, 2 Cfy 4- 4 K, by 1. eq. of chlorine into L eq. of ferrideyanuret, Cfdy + 3 K, and 1 eq. of chloride of potassium, KC1. t Cambell. For Cobalto- Cyanurets, see T. and L. Elem. 786. 419 Iodide of Cyanogen. 1331. Chloride of Cyanogen. Two compounds of chlorine with Sect, m. cyanogen are known, and these are isomeric in their constitution. Chloride of The one, which at common temperatures is gaseous, was discovered Cyanogen, by Gay-Lussac; the other, which is a crystalline solid, by Serullas. 1832. Gaseous Chloride of Cyanogen , CyCl ? is formed when Gaseous chlorine gas is transmitted into hydrated prussic acid, when moist gJJnogen*' bicyanuret is placed in an atmosphere of chlorine in the dark, or when mellon is heated in dry chlorine gas. 1833. This compound, which is gaseous at common temperatures, Pr°P® r fi es » has a most powerful penetrating odour, excites the eyes to a copious flow of tears, becomes solid at 0°, and forms long acicular needles, which fuse at 5° and boil at 10° ; but, under a pressure of four at- mospheres, it is still liquid at 70.° If the liquid be introduced into glass tubes and hermetically sealed, it is gradually converted into the solid chloride, and regular crystals of the following compound aie obtained. 1834. Water dissolves 25, alcohol 100, and ether 50 times its vo- Action^f lume of the gas without change. It is decomposed by the alkalies ; e * salts of the protoxide of iron are rendered of a deep green colour when an alkajj is added to the mixture. 1835. If moistened bicyanuret of mercury in chlorine gas be ex- Of light, posed to solar light, a heavy oily liquid of a yellow colour is formed, which is insoluble in water, and has the same odour as the gaseous: chloride ; the same substance appears to be formed by the action of chlorine upon the fulminate of silver. If it be dissolved in alcohol;,. and its solution thrown into water, a crystalline substance like cam- phor is precipitated ; on exposing a mixture of moist chlorine and chloride of cyanogen gases to the sun’s rays, two other solid corn?* pounds appear to be formed. 1836. Solid Chloride of Cyanogen. Discovered by Serullas. It SoHdehlo- is formed by exposing dry chlorine gas and anhydrous hydrocyanic noggn. ° y acid to the sun’s light; hydrochloric acid and the solid chloride, which is deposited in crystals, are formed. It may also be formed by heating sulphocyanuret of potassium in a stream of dry chloriiip , gas. 1837. In the pure state it is white, sublimes in long transparent. Properties, crystals, has a penetrating odour similar to the excrement of mice, and a sweet biting taste; its sp. gr.=1.32 ; fuses at 284°, sublimes at 374°. By digestion in water at a gentle heat, it is decomposed into cyanuric and hydrochloric acids, from which its constitution must be represented by the formula Cy 3 Cl 3 . It is soluble in absolute alcohol and ether without decomposition. 1838. Iodide of Cyanogen. Cyl. Formed by heating dry cyanuret Iodide of of mercury or silver with iodine;^ most conveniently by heating a c y ano S en ‘ mixture of bicyanuret of mercury, iodine, and water, in a retort,! when at a gentle temperature the iodide sublimes, and collects in the neck of the retort as a fine crystalline snow, or in long needles. The crystals have a penetrating odour, which excites a flow of tears, may be dissolved in alcohol, ether, and water without decomposition, and are perfectly volatilized at 100°. * Wohler. t Mitscherlich. 420 Cyanogen and its Compounds. Chap. VI. Cyanogen phur. Hydrosul- phocyanic acid. Obtained. Properties Sulphocy- anurct of ammoni- um.* Metallic sulphocya- nurets. 1839. Cyanogen and Sulphur . — Sulpho-cyanogen , Bisulphuret of Cyanogen. Cy-f-2S, Symb.=Csy ; eq.=58.59. Discovered by Lie- big. Prepared by saturating a concentrated solution of a metallic sul- phocyanuret with chlorine, or by heating it with nitric acid ; it falls in the form of a deep yellow, amorphous powder, which retains its colour when dry ; is light, porous ; is insoluble in water, alcohol, and ether, but is dissolved by strong sulphuric acid from which it is precipitated by water. It is decomposed by nitric acid and by potassium with the aid of heat, giving rise to the formation of the sulphuret, cyanuret, and sulphocyanuret of potassium. Its decomposition by the action of heat is peculiarly remarkable, the products of its destructive distilla- tion being sulphuret of carbon, sulphur, and the residue mellon, which at a high temperature is decomposed into nitrogen and cyano- gen gases. 1540. Hydro-sulphocyanic Acid. Csy-|-H, eq. 59.53. Discover- ed by Rink. Occurs in the seeds and blossoms of the Cruciferse (Se- napis, &c.), and in the saliva of man and sheep. 1541. By decomposing the basic sulphocyanuret of lead by dilute sulphuric acid, care being taken to leave some lead in the solution, which is afterwards separated by hydrosulphuric acid gas; or by decomposing sulphocyanuret of silver in 10 volumes of water by the same gas. 1842. A colourless fluid of a pure acid taste, which by the action of the air, and on being heated, readily decomposes into a variety of products; one of these deposits itself from the acid as a lemon-yel- low, in water insoluble, powder. It cannot exist without water; on treating the aqueous acid with chlorine or nitric acid, it is deprived of hydrogen, and sulpho-cyanogen is precipitated: by a further ac- tion cyanic and sulphuric acids are formed, but the former is at once decomposed into carbonic acid and ammonia. It colours the salts of peroxide of iron blood-red, and is not poisonous. 1843. Hydro-sulphocyanic Acid and Ammonia — Sulphocyanuret of Ammonium. NH 4 +CyS a ; eq.=75 74. By saturating the acid with ammonia and gently evaporating, a semi-fluid saline mass is obtained, which, at a higher temperature, suffers a peculiar decom- position. At first, ammoniacal gas is evolved, then sulphuret of carbon, and at last the protosulphuret of ammonium is sublimed. The residue, when the heat has not been driven too far, consists of melam, or of a mixture of melam with mellon. Sulphocyanuret of ammonium is also formed by adding sulphuret of carbon to alcohol, which has been saturated with ammonia. 1844. Metallic sulphocyanurets. The hydro-sulphocyanic acid must be considered as a compound analogous in its constitution to the hydrated cyanic acid, the oxygen of the latter having been replaced by its equivalent of sulphur. Considered as a hydracid, the formula of the hydrated cyanic acid would be Cy0 2 +H, corresponding to that of the hydro-sulpho- cyanic acid, CyS a -j-H. On its being brought into contact with the metallic oxides, the hydrogen is replaced by 1 eq. of the metal. The soluble metallic sulphocyanuret may be formed : — by the action of the acid on the metallic oxide, by heating the higher sulphurets of the alkaline me- 421 Cyanogen and Water . tals to redness in cyanogen gas, or by conducting cyanogen gas into Sect, hi. their solution, by heating or fusing the soluble metallic cyanurets with sulphur, or the insoluble cyanurets with the soluble sulphuret. 1845. The soluble metallic sulphocyanurets colour the salts °f ofsofubl? peroxide of iron blood-red ; are decomposed, when heated in dry m eta iii c hydrochloric acid gas, into metallic chlorides and anhydrous hydro- sulphocya- sulphocyanic acid, but the latter instantly decomposes into other pro- nurets - ducts. The sulphocyanurets of the alkaline metals, when dry, bear a strong heat without decomposition, but, if oxygen be present, they are converted, with the evolution of sulphurous acid, into salts of cyanic and sulphuric acids ; those of the heavy metals are decom- posed by the red heat into mixtures of metallic sulphurets and mel- lon, this change being generally accompanied by the evolution of sulphuret of carbon and sulphur ; at a higher temperature the resi- due evolves cyanogen and nitrogen gases in the proportion of 3 : 1. Heated to redness in chlorine gas, they give rise to metallic chlo- Action of rides, mellon, chlorides of sulphur and cyanogen, and a small quan- tity of the sulphuret sublimes unchanged ; they are most of them soluble in alcohol. The proto-salts of mercury are decomposed by the soluble sulphocyanurets into metallic mercury which is deposi- ted, and into the soluble bisulphocyanuret. All the soluble sulpho- cyanurets form with the bicyanuret of mercury double compounds, which are readily obtained in crystals. 1846. Sulpkocyanuret of Potassium. KCsy ; eq. 97.74. Fer- nuretY* rocyanuret of potassium, gently roasted to drive off water of crystal- potassium, lization, is mixed in the form of a fine powder with half its weight of flowers of sulphur, and the mixture fused in an iron vessel at a low red heat, until the bubbles of gas which escape through the melted mass inflame in the air and burn with a red light. The mass when cold is dissolved in boiling water, and treated with a solution of carbonate of potassa as long as a turbidity is produced ; the whole is then boiled for a quarter of an hour, and the clear liquid separated from the precipitated iron by filtration. On evaporation crystals are obtained, which are separated from the admixture of carbonate of potassa by being re-dissolved in alcohol. 1847. Crystallizes in long striated colourless prisms, which are Properties, anhydrous, of a cooling, somewhat biting taste, fuse much below the red heat to a clear liquid ; deliquesces in a moist atmosphere, very soluble in hot alcohol, from which it crystallizes on cooling.^ 1848. Cyanogen and Water. A solution of cyanogen in water ? ro ^ u ^ ts of acquires rapidly in the light, but more slowly in the dark, a brown position colour, and a brown flocculent precipitate falls ; the solution is then cyanogen found to contain carbonic acid, prussic acid, ammonia, urea, and ox- andlts alate ot ammoma.T pounds. 1849. The different products, which arise from the reaction of cyanogen cyanogen and water, are without doubt the results of several perfectly and water, independent decompositions. One eq. of cyanogen and 3 eq. water contain the elements of 1 eq. of anhydrous oxalate of ammonia ; 2 eq. cyanogen and 1 eq. water, the elements of 1 eq. of cyanic and 1 eq. of hydrocyanic acid. Carbonate of ammonia is formed from the * For others, see T. and L. 794. + Wohler. 422 Chap. VI. Cyanogen and ammo- nia. Paracyan- ogen. Cyanilic acid. Cyanogen and hydro- sulphuric acid Prepared. Properties, Hydrosul- phocyanic acid and hydrosul- phuric acid Cyanogen and its Compounds . decomposition of cyanic acid, and three equivalents of water ; urea, by the union of cyanic acid with ammonia and water. 1850. Cyanogen and Ammonia. If cyanogen gas be conducted into liquid ammonia, a decomposition similar to that produced by water ensues, but in a much shorter time. A large quantity of a brown substance, which contains ammonia in chemical combination, is deposited. By heating this brown precipitate to redness, paracyanogen, water, and carbonate of ammonia are obtained ; this decomposition is rea- dily explained, when it is considered that this product may be con- sidered as a compound of cyanogen (C 4 N 2 ) with ammonia and cyanic acid ; the latter of which, by decomposing with 3 eq. water, forms 2 eq. of carbonic acid and 1 eq. of ammonia. 1851. Paracyanogen. Discovered by Johnston. Formed by heating to redness the brown precipitate formed by the decomposi- tion of cyanogen with water or ammonia ; left in small quantity on decomposing bicyanuret of mercury in a retort by heat.* 1852. Cyanilic Acid. By a long-continued boiling of mellon in dilute nitric acid, a solution is effected with the evolution of gaseous products, and the liquid yields on evaporation colourless, transparent, octohedral crystals ; by resolution in hot water, hydrated cyanilic acid in soft tabular crystals of a mother-of-pearl lustre are obtained. This acid has the same composition as the crystalline cyanuric acid ; contains, like the latter, 4 eq. water of crystallization, which it loses at 212°, when it becomes opaque and falls to a white powder. By the destructive distillation it is converted into hydrated cyanic acid ; by solution in sulphuric acid and caustic potassa into cyanuric acid. 1853. Cyanogen and Hydro sulphuric Acid. Cy 3 S 0 H 6 -f- aq. Two compounds of cyanogen and hydrosulphuric acid are known, neither of which are formed when the gases are mixed in a dry state, but are generated by the direct combination of the gases when water is present. The one discovered by Gay-Lussac is obtained by mix- ing one volume of cyanogen with one and a half volume of sulphu- retted hydrogen, a small quantity of water being present; both the gases are absorbed by the water, and on evaporation it deposits long yellow acicular crystals, a solution of which is not precipitated by salts of lead. The other compound was discovered by Wohler. It is prepared by conducting sulphuretted hydrogen into a saturated solution of cyanogen in alcohol, by which the latter is rendered yellow, and on being artifi- cially cooled deposits this compound of cyanogen and sulphuretted hydrogen in bright orange-red crystals. 1854. Insoluble in cold, slightly soluble in boiling water. Very soluble in hot alcohol, from which it may again be obtained in crys- tals ; soluble by alkalies in the cold, and precipitated unchanged from the solution by acids ; but on the application of heat a mixture of a metallic sulphuret and a sulphocyanuret is formed ; its solution pre- cipitates salts of silver, lead, and copper. 1S55. Hydro-sulphocyanic Acid arid Hydrosulphuric Acid. Dis- covered by Zeise. Prepared by saturating 1 volume of absolute alcohol at the temperature of 50° with ammoniacal gas, and adding ♦For products of the decomposition of sulphocyanogen, mellon (1726), hydromello- nic acid, &c. see T. and L. Elem. 796. Uric Acid. 423 to the solution a mixture of 0.16 vol. of bisulphuret of carbon, and Sect, iv. 0.4 vol. of alcohol ; the whole should be placed in a well-stopped glass vessel, which is kept perfectly full at the temperature of 60°. Two products are thus produced, of which the one is a compound of ammonia with an acid formed of sulphuret of carbon and sulphuret- ted hydrogen; this ammoniacal salt separates in the course of some hours as a crystalline deposit, and the residual liquid contains ano- ther ammoniacal salt, the acid of which may be considered as a compound of hydro-sulphocyanic acid and hydro-sulphuric acid. Section IV. Hypothetical Compounds of Cyanogen and Carbonic Oxide . 1856. Under these compounds the uric acid and the products of^|P^ eti ‘ its decomposition are described. These substances are distinctly pounds of separated from all known bodies by their chemical relations ; an cyanogen explanation of their formation can only be developed by making cer- ^ic oxides", tain hypotheses, of which the assumption that they contain cyanogen and carbonic oxide is a deduction drawn from their analyses. The compounds belonging to this group are uril, uric acid, alloxan, al- loxantin, and uramil. (Liebig, so4.) 1857. The uril, or urilic acid, which may from its composition be Uril * also called the cyan-oxalic acid, is an hypothetical compound of ni- trogen, carbon, and oxygen, according to the formula C 8 N 2 0 4 ; it may be considered as a compound of cyanogen and carbonic oxide 2Cy-(-4CO, or as oxalic acid, in which the oxygen which unites with the radical, carbonic oxide, has been replaced by its eq. of cyanogen. C 2 0 2 -f-0 . . . Oxalic acid. 2(C 2 0 2 -f-Cy) . . . Cyan-oxalic acid. If this acid be represented by the symbol Ul, the compounds are represented by the formula : Rational formula. 2U1+1 eq. urea . =Uric acid 2UI-f OM-4 aq. . = Alloxan 2Ul-fO +5 aq. . = Alloxantin 2U1-J-1 eq. amm.-+2 aq. =Uramil Empirical formula. C10N4 H4 Oo Cs N2 H 4 Oie C 8 N 2 H s O10, Ci N 3 Hg Og. 1858. Uric Acid. Ci 0 N 4 H 4 O(;, or 2 Ul-f-(C 2 0 2 +2NH 2 ). Discover- Uric acid, ed by Scheele ; first pointed out as existing in the excrement of snakes by Vauquelin, in the excrement of silkworms by Brugnatelli, and in cantharides byRobiquet. Is a product of secretion of all carnivorous animals, of birds, and of many insects ; is deposited from human urine generally in combination with ammonia, as it cools, as a yellow or brownish powder ; the stone-like concretions in the joints of persons labouring under gout contain uric acid in combination with soda or ammonia ; it is the basis of most calcareous deposits in the hu- man bladder. The semi-fluid urine of serpents and birds is princi- pally composed of urate of ammonia. The guano (the decomposed Guano, excrement of aquatic birds, which covers the surface of many of the smaller islands of the South Sea, and is used as manure,) is also composed in greater part of urate of ammonia. 1859. Urinary calculi, or the white 'chalk-like excrement of ser- Process. 424 Chap. VI. Properties. Product of destructive distillation. Action ol nitric acid. Uric acid and metal- lic oxides. Urate of potassa. Urate of soda. Hypothetical Compounds of Cyanogen. pents, is reduced to a fine powder and dissolved in a solution of caustic potassa by boiling ; the solution is treated with hydrochloric acid in excess, boiled for one quarter of an hour, and the precipitate well washed. It is obtained perfectly pure by decomposing a satu- rated boiling solution of urate of potassa by hydrochloric acid. 1860. Crystallizes in fine scales of a brilliant white colour and silky lustre, is tasteless and inodorous, heavier than water, almost in- soluble in cold, slightly soluble, in small quantity, in boiling water ; the solution reddens feebly the vegetable colours. It is dissolved by concentrated sulphuric acid, from which it is precipitated by water ; in strong hydrochloric acid, it is somewhat more soluble than in pure water. 1861. Exposed to the destructive distillation, the products of the decomposition of urea are obtained, namely, urea, cyanuric acid, and cyamelid (the insoluble cyanuric acid) ; also, hydrocyanic acid, a litle carbonate of ammonia, and, as a residue, a brown carbonaceous substance which is rich in nitrogen. In this decomposition the hy- drated cyanic acid in combination with ammonia is deposited in the neck of the retort as urea ; the cyamelid dissolved in potassa forms cyanurate of potassa. 1S62. Dissolves in dilute nitric acid with the evolution of equal volumes of pure carbonic acid and nitrogen ; the solution contains alloxan, alloxantin, parabanic acid, and ammonia ; evaporated and treated with ammonia in excess, it acquires a purple-red colour, a test by which uric acid may be recognised. Fused with hydrate of po- tassa, carbonic acid, and cyanate of potassa, and cyanuret of potassium are obtained ; boiled with peroxide of lead in water, it is decomposed into allantoin and oxalic acid, and urea is separated. Is insoluble in ether and alcohol. With sulphuric acid it forms a crystalline compound.* 1863. Uric Acid and the Metallic Oxides. The uric acid appears to unite with the metallic oxides without, as in the other acids, the separation of an eq. of water ; its salts, with the fixed alkalies and alkaline earths, are sparingly dissolved by cold, but more freely by boiling water; with ammonia and the other oxides, insoluble com- pounds, generally of a white colour, are formed. All urates are de- composed by other acids, even by acetic acid ; the uric acid is at first separated as a bulky gelatinous mass, but it shortly afterwards chan- ges into a fine crystalline powder. 1864. Urate of Potassa. Impure urate of ammonia (the excre- ment of serpents) is dissolved by boiling in a dilute solution of caus- tic potassa ; and the clear liquid, obtained by separating the insolu- ble portions by filtration, is evaporated. On cooling, the urate of potassa separates as a white crystalline mass, which, when washed by cold water and dried, yields a powder composed of fine acicular crystals of a silky lustre ; these crystals are very sparingly soluble in cold water, and the alkaline reaction is scarcely perceptible. Uric acid is more soluble in carbonate of potassa than in pure water ; and one half of the carbonate is decomposed. 1S65. Urate of Soda. The action of uric acid upon pure and carbonate of soda is the same as above described for potassa ; this Fntszche. Alloxan . 425 salt may also be formed by boiling uric acid in a solution of borax ; sect, iv, it is the principal constituent of gouty concretions.^ 1866. Allantoin. Frequently called allantoic acid. Occurs ready Allantoin. formed in the allantoic fluid of the cow ;t it is formed when uric acid is boiled in water with peroxide of lead ! One part of uric acid is boiled in 20 parts of water, and recently prepared and Process, well- washed peroxide of lead is added in successive portions to the boiling liquid as long as its colour is observed to change. The hot liquid should be filtered, and evaporated until crystals are observed to form upon its surface. The crys- tals which have deposited when the solution has become quite cold, are purified by recrystallization. Or the allantoic fluid of the cow may be evaporated to one quarter its volume, and the crystals formed on cooling and long standing are pu- rified by animal charcoal. 1867. Small transparent and colourless prisms of the right rhom- Properties, bic system, which have a. glassy lustre, are tasteless, have no action on vegetable colours, and are soluble in 160 parts of cold, but more freely in hot water. It is soluble in nitric acid, and is decomposed by it when the solution is boiled without the evolution of nitrous fumes. Its composition is such, that it contains the elements of an- hydrous oxalate of ammonia minus 3 eq. water ; this explains its de- composition by the alkalies, by which it is reduced at the boiling heat into an oxalate and ammonia. 1868. Gently heated in concentrated sulphuric acid, it is decom- Action of posed into carbonic oxide, carbonic acid and ammonia ; but if a strong heat be rapidly applied, the acid is blackened. It is soluble in caus- 5 * tic and carbonated alkalies by the aid of a gentle heat, and may be again obtained unchanged by crystallization. A solution of allan- toin in hot water, to which a little ammonia has been added, pro- duces, with the nitrate of silver, a white precipitate, which contains 43,56 per cent, of oxide of silver, and is composed as represented by the formula, C d N 4 H 5 0 5 -l-Ag0 ; it consequently contains 2 eq. allan- toin, C s N 4 H 6 0 6 — 1 eq. water, HO-f-1 eq. oxide of silver. 1869. In the decomposition of uric acid by the peroxide of lead, 2 eq. of oxy- Explained, gen derived from 2 eq. of the peroxide, and 3 eq. water, attach themselves to the constituents of the cyanoxalic acid, by which the latter is decomposed into 2 eq. oxalic acid and 1 eq. allantoin, and the urea is set free. C 4 0 4 +N 2 C 4 _ ( 1 eq. cyanoxalic acid ) , • •. 2PbO+ 0 2 +H 3 0 3 — X 1 eq. urea $ ~ 1 e( *’ UnC aclcL 2 eq. oxalate of lead +1 eq. allantoin-fl eq. urea. Its formula is C 4 H 3 N 2 03 , or 2 Cy+3110. 1870. Alloxan. The erytbric acid of Brugnatelli : rediscovered Alloxan, by Wohler and Liebig. One of the products of the decomposition of uric acid by nitric acid. One part of dry uric acid is added in successive portions to 4 parts of p roce ss. nitric acid of sp. gr. 1.45 to 1.5, by which it is dissolved with efferves- cence and the production of heat ; the, production of a high temperature must be avoided as much as possible by artificial cooling, and by adding the uric acid slowly. Small granular crystals of a strong lustre are thus formed, and by degrees the whole liquid is converted into a solid mass. This should then be placed in a glass funnel ; and after the fluid parts have thus drained off, it should be spread upon a porous tile, where it is rendered perfectly dry. It is purified by solution in hot water and recrystallization. 1871. On the cooling of a warm but not perfectly saturated solu- Properties. * Wollaston. 54 t Vauquelin and Buniva. t Wohler and Liebig. 426 Chap. VI. Solubility. Action of zinc, fee* Theory. Alloxanic acid. Cyanogen and its Compounds. tion of alloxan, it is obtained in large colourless and transparent crys- tals of the right prismatic system, and of a strong adamantine lustre ; these crystals effloresce rapidly, losing 25 per cent.=6 eq. water, and are converted when gently warmed, with the loss of water, into anhydrous alloxan. If a hot saturated solution be allowed to crys- tallize in a warm place, anhydrous alloxan is deposited directly from the solution in oblique prisms, on the extremities of which truncated rhomboidal octohedrons are seen. 1872. It is very soluble in water, has a disagreeable odour, and a slightly saline astringent taste, reddens vegetable colours, and causes a purple stain on the skin. Treated with alkalies, alloxanic acid is formed ; but on boiling it is decomposed into urea and mesoxalic acid. Heated with peroxide of lead, it is decomposed into urea and carbonate of lead, with which a few traces of oxalate of lead are mixed. 1873. When brought into contact with zinc and hydrochloric acid, with chloride of zinc or sulphuretted hydrogen, alloxantin is produced ; it is decomposed by free ammonia into mykomelinic acid, by nitric acid into parabanic acid, by sulphuric and hydrochloric acids into alloxantin, by sulphurous acid and ammonia into thionurate of am- monia, with alloxantin and ammonia into murexid. With a proto- salt of iron and an alkali, it forms an indigo-blue solution. Does not unite without decomposition with the metallic oxides. 1874. The formation of alloxan and the other products which arise at the same time, is dependent upon two perfectly independent decompositions; namely, upon the conversion of cyanoxalic acid into alloxan, and upon the mutual de- composition of urea and hyponitrous acid. To 1 eq. of cyanoxalic acid are added the elements of 4 eq. water, and 2 eq. oxygen from 1 eq. nitric acid, by which 1 eq. alloxan and 1 eq. hyponitrous acid are formed. The latter combines with the ammonia of the urea, and liberates cyanic acid ; the hyponitrite of ammonia is decomposed by heat into nitrogen and water, and the cyanic acid with water is resolved into carbonic acid ana ammonia, which unites with the free nitric acid. Cyanoxalic acid=C 8 N 2 0 4 4 eq. water ~H 4 0 4 2 eq. oxygen 0 2 1 eq. alloxan = C 8 N 2 H 4 Oio U rea =C 2 N 2 H 4 0 2 Hyponitrous acid= N 0 3 c 2 n 3 h 4 o7=c 2 o 4 + n 2 + nh 3 + ho Carbonic acid. Nitrogen. Ammonia. Water. It frequently happens that on dissolving the impure alloxan, for the purpose of purifying by a second crystallization, a portion of alloxantin is obtained ; it may be easily separated from the alloxan- tin by cold water. (See Alloxantin.) 1875. Alloxanic Acid. C s N 2 H 2 0 8 -|-2 eq. Discovered by Wohler and Liebig. Produced by the decomposition of alloxan by alkalies. It is prepared by decomposing alloxanate of baryta by sulphuric acid. A strongly acid fluid is obtained, which by gentle evaporation crys- tallizes in radiated groups of acicular crystals ; it is a bibasic acid, dissolves zinc with the evolution of hydrogen, is unchanged by sul- phuretted hydrogen, and precipitates the salts of silver, baryta, and lime. The anhydrous alloxanic acid contains the constituents of half an equivalent of alloxan minus 1 eq. water. 427 Mykomelinic Acid. 1876. Alloxanic acid neutralizes the alkalies perfectly, decom- Sect, iv. poses the carbonates, and forms, when neutralized by ammonia, with Alloxanic the salts of silver a white precipitate, which by boiling becomes first yellow and then black, the change being accompanied by a rapid ef- ox ides. fervescence ; treated with ammonia in excess, it produces white gela- tinous precipitates with the salts of lime, strontia, and baryta ; but the precipitate is redissolved by a large excess of water, and readily by an acid. The solutions of the neutral alloxanate of lime, stron- tia, and baryta, become turbid when boiled, the bases are precipitated, and urea and mesoxalic acid are formed.* 1877. Mesoxalic Acid. When a saturated solution of alloxanate of Mesoxalic baryta or strontia is heated to the boiling point, a precipitate falls aci consisting of the carbonate, mesoxalate, and alloxanate of baryta or strontia. The solution, on evaporation, yields a crystalline crust, from which urea is separated by treating it with alcohol, and mesox- alate of baryta remains. If a solution of alloxan be added, drop by drop, to a boiling solution of acetate of lead, a very heavy granular precipitate of mesoxalate of lead is formed, and urea remains as the only other product in the solution. The mesoxalic acid may be ob- tained by decomposing this lead salt by sulphuric acid ; it is a strongly acid solution, reddens vegetable colours, and forms, like the alloxanic acid, on the addition of ammonia, precipitates with the salts of baryta and lime, which are soluble in acids and a large ex- cess of water ; it may be boiled and evaporated without change. Its action on the salts of silver is characteristic ; it forms with them, after being neutralized by ammonia, a yellow precipitate, which on being gently heated is reduced to the metal with a rapid efferves- cence. 1878. The above-mentioned lead salt yields, on analysis, 80.4 percent, of oxide of Analysis lead ; it contains a slight admixture of a substance containing nitrogen, probably and compo- cyanate or cyanurate of lead, from which it cannot be perfectly purified. The sition. composition of the lead salt is very probably expressed by the formula C 3 0 4 + 2PbO, in which case its formation from alloxan and alloxanic acid admits of a ready explanation. From 1 eq. alloxan 1 eq. urea is separated, by which 2 eq. of anhydrous mesoxalic acid is left. 1 eq. alloxan suCsN^H^Oio — 1 eq. urea — C 2 N 2 H 4 O 2 =2 eq. mesoxalic acid =Cg O g The above-mentioned mesoxalate of baryta contains 56 per cent, of baryta, from which its constitution is probably represented by the formula C 3 0 4 -f ^ 1879. Mykomelinic Acid. C 8 N 4 H 5 05 ? Discovered by Wohler Mykome- and Liebig. Product of the decomposition of alloxan by ammonia. linic acid * It is prepared by heating to 212° a solution of alloxan with an excess of ammo- Process, nia, then neutralizing with an excess of dilute sulphuric acid and boiling for a few minutes. The mykomelinic acid falls as a yellow gelatinous precipitate, which dries to a yellow porous powder; it is with difficulty dissolved by cold, but more readily by hot water. 1880. Its solution has a distinctly acid reaction ; it decomposes the carbonated alkalies and is easily dissolved by the caustic alka- lies, but on being boiled with them is decomposed with the evolution of ammonia ; it forms, with the oxide of silver, a yellow compound, ♦For Alloxanates , see T. and L. 810. 428 Cyanogen and its Compounds. Chap. VI. Parabanic acid. Properties. Theory. Oxaluric acid. Properties, Theory. Oxalurate of ammo* nia. Process. which is insoluble in water. It is produced by the decomposition of 1 eq. alloxan and 2 eq. ammonia into 1 eq. mykomelinic acid and 5 eq. water. 1881. Farabanic Acid. C G N 2 0 4 -|-2 aq. Discovered by Wohler and Liebig. Product of the decomposition of uric acid and alloxan by nitric acid. Prepared by treating 1 part of uric acid, or 1 part of alloxan, in 8 parts of pretty strong nitric acid, evaporating to the consistence of a syrup, and allowing it to stand for some time, when it yields colourless crystals which may be purified by a second crys- tallization. 1882. Colourless, transparent, thin, hexagonal prisms; has a strong acid taste, very similar to that of oxalic acid; is very soluble in water, does not effloresce either in the air or in a warm room ; fuses if heated, when a portion sublimes unchanged, but another part decomposes with the evolution of hydrocyanic acid. The cold solu- tion neutralized by ammonia, produces a white precipitate in the salts of silver, which contains 70.62 per cent, of the oxide ; when treated with ammonia it is converted into oxaluric acid. 1883. It is formed by the decomposition of 1 eq. of uric acid, which, by the addition of 2 eq. of water and 4 eq. oxygen from the nitric acid, is resolved into 2 eq. carbonic acid, 1 eq. parabanic acid, and 1 eq. urea ; the latter is decomposed as before-mentioned by the hyponitrous acid. One eq. alloxan with 2 eq. oxygen is resolved into 2 eq. carbonic acid, 4 eq. water, and 1 eq. parabanic acid. 1SS4. Oxaluric Acid. C fl N 2 H,}0 7 -(-aq. Discovered by Wohler and Liebig. Produced by the decomposition of parabanic acid. Prepared by adding dilute sulphuric or hydrochloric acid to a saturated solu- tion of oxalurate of ammonia in not water, and rapidly cooling the mixture when the oxaluric acid falls as a white crystalline powder; this should be washed with cold water as long as the washing, when neutralized by ammonia, causes with the salts of lime a precipitate which is perfectly redissolved by heat, or by an ad- ditional quantity of water. 18S-5. It is a white, or slightly yellow crystalline powder of an acid taste, reddens the vegetable colours, and, when neutralized hy ammonia, forms with silver salts a white precipitate which is per- fectly redissolved by boiling. By boiling in water it is completely decomposed into free oxalic acid and oxalate of urea. 1886. The oxaluric acid is formed bv the addition of2 eq. water to the consti- tuents of the parabanic acid. It contains further the elements of 2 equivalents of oxalic acid and 1 eq. urea ; it may be considered as uric acid in which the cya- noxalic acid has been replaced by the oxalic acid. 1887. Oxalurate of Ammonia , NH 4 0 -|-C 6 N 2 H.i 07 , may be formed by heating a solution of parabanic acid with ammonia, or more advantageously by treating a recently prepared solution of uric acid in dilute nitric acid with an excess of ammonia and evaporating. The liquid acquires at first a purple colour, which disappears during the evaporation, and if allowed to cool when arrived at a certain degree of concentration, it deposits radiated groups of hard acicular yel- low crystals ; they are obtained colourless by charcoal and recrystallization. Properties. 1888. The oxalurate of ammonia crystallizes in radiated groups of fine acicular crystals, which have a silky lustre, and are readily dissolved by hot, but with difficulty by cold water; the solution has no reaction on vegetable colours, and may be boiled and evaporated without change ; the dry salt loses no weight at 250°, but at a higher Uramil. 429 temperature it is decomposed with the rapid evolution of hydrocya- Sect, tv. nic acid. Acids separate from a concentrated solution the oxaluric acid as a crystalline powder. 1889. The oxaluric acid forms with the alkalies very soluble, but Oxaluric with the alkaline earths sparingly soluble salts. If concentrated so- aad lutions of oxalurate of ammonia, chloride of calcium or barium be ^ d g S | c mixed with each other, after standing some time, brilliant transpa- rent scales or needles of oxalurate of baryta or lime will be deposited ; a solution of the latter in water when treated with an excess of am- monia gives a basic salt in the form of a transparent gelatinous pre- cipitate, which is redissolved by a large quantity of water. 1890. Thionuric Acid. C 8 N3H 7 0 14 S2. A bibasic acid. Discovered Thionuric by Wohler and Liebig. Is formed by the action of sulphurous ac ‘ d - acid on alloxan. It is prepared by decomposing the thionurate of lead by hydrosulphuric acid. A white crystalline mass, is perma- nent in the air, and readily dissolved by water ; of an acid taste, reddens vegetable blues strongly; its saturated solution, when heated to the boiling point, congeals to a semi-fluid crystalline mass of uramil, and the fluid when this has deposited is found to contain free sulphuric acid. 1S91. The thionuric acid contains the elements of 1 eq. alloxan, Theory. 1 eq. ammonia, and 2 eq. sulphurous acid ; the uramil may be con- sidered as a compound of ammonia with alloxan minus 2 eq. oxygen, or of cyanoxalic acid with 1 eq. ammonia and 2 eq. water. On heating the solution of thionuric acid 2 eq. oxygen are given by 1 eq. alloxan to the 2 eq. of sulphurous acid, which is thus converted into sulphuric acid, while the elements of cyanoxalic acid, ammonia, and water combine to uramil. 1892. Thionuric acid forms with the alkalies very soluble salts ; Thionuric with the alkaline, earths either insoluble or sparingly soluble salts, ^etallicox- which are however readily dissolved by dilute acids; they generally ides. are formed of 1 eq. of acid and 2 eq. of the metallic oxide. All these salts evolve sulphurous acid abundantly when treated with concen- trated sulphuric acid ; when fused with hydrate of potassa, sulphite of potassa is formed. 1893. Uramil. C 8 N 3 H 5 0 6 ; eq.= 144.41. Discovered by Wohler Uramil. and Liebig. A product of the decomposition of thionuric acid. A cold saturated solution of thionurate of ammonia is made boiling hot, and then treated with hydrochloric acid till it has a strongly acid reaction, when it is again heated till a slight turbidity is observed, and allowed to cool slowly ; or a boiling saturated solution of the same salt may be mixed with hydrochloric or dilute sulphuric acid, and then kept boiling until the whole is converted to a semifluid mass. It is obtained in a plume-form aggregation of fine but hard needles, or as a fine porous powder, consisting of fine needles which have a silky lustre, and are permanent in the air, but acquire a pink tint when heated. 1894. It is insoluble in cold, but taken up in small quantity by Properties, boiling water ; soluble in ammonia and the caustic alkalies in the cold, from which it is precipitated by acids unchanged. The solu- tion of uramil in ammonia and caustic potassa acquires a purple co- lour by exposure to the air, and deposits green acicular crystals, of a brilliant metallic lustre; if boiled in the caustic potassa, it is decom- posed into uramilic acid with the evolution of ammonia. It is solu- ble in concentrated sulphuric acid, from which it is again precipi* 430 Chap. VI. Action of nitric acid. Uramilic acid. Prepara- tion. Properties. Salts of uramilic acid. Alloxantin. Prepara- tion. Properties. Cyanogen and its Compounds. tated by water ; by boiling in dilute acids it suffers the same change as in caustic potassa. By boiling with the oxides of silver and mer- cury it is converted into murexid, and the oxide is reduced. 1895. With concentrated nitric acid it is resolved into alloxan, with the evolution of hyponitrous acid, and the formation of nitrate of ammonia. The above decomposition of the thionurate of ammo- nia consists in the separation of the elements of 2 eq. of sulphate of ammonia. Uramil may be considered as uric acid, in which the urea is replaced by 1 eq. ammonia and 2 eq. water. 1896. Uramilic Acid. C^NsH^O^. Discovered by Wohler and Liebig. A product of the decomposition of uramil. A saturated solution of thionurate of amraonia in cold water is added to a small quantity of sulphuric acid, and the mixture evaporated in a water-bath, when the uramilic acid is slowly deposited in transparent prisms of a glassy lustre. If a white amorphous deposit, which is soluble in hot water, be at the same time ob- tained, it arises from the presence of undecomposed acid thionurate of ammonia; this is again dissolved in water mixed with sulphuric acid, and treated as before. 1897. Colourless four-sided prisms, or fine silky needles ; is so- luble in 6 — 8 parts of cold, and in 3 parts of boiling water ; loses no weight when heated to 212°, but acquires a slightly pink colour; the solution has a feeble acid reaction. It is soluble in concentrated sulphuric acid with effervescence, but without colouring the acid. By boiling in strong nitric acid, a yellow solution is obtained, which yields on evaporation white crystalline and sparingly soluble scales or granular crystals; they are dissolved by alkalies, and again pre- cipitated by acetic acid. In its formation 2 eq. of uramil lose the elements of 1 eq. of ammonia, which are replaced by 3 eq. of water. 1898. The uramilic acid forms with ammonia and the fixed alka- lies soluble crystallizable salts ; lime and baryta are not thrown down from their saline solution by the free acid ; but on the addition of ammonia a white precipitate is formed, which again disappears in a large quantity of water. Uramilate of ammonia produces with ni- trate of silver a dense white precipitate, which contains from 63 — 64 per cent, of silver. 1899. Allorantin. C.(N 2 H 5 0,o ; eq. =162.26. First observed by Prout as a product of the decomposition of uric acid by nitric acid ; it is also formed by the action of chlorine on uric acid, as likewise from alloxan by the action of deoxidizing agents. 1900. From uric acid . one part of uric acid is added to 32 parts of water, which is brought to the boiling point, and then treated with dilute nitric acid in successive portions till a perfect solution is obtained ; it should then be evapo- rated to two thirds of its volume, when, after standing for some hours, or a day, crystals of alloxantin will be deposited, w’hich should be purified by recryetal- lization. From aUoxan : it is obtained in large quantity by transmitting a stream of hydrosulphuric acid gas through a solution of alloxan, when first sulphur, and then a crystalline mass of alloxantin is deposited ; it is separated from the sul- phur by solution in hot water, which yields by evaporation and cooling pure crystals of alloxantin. It may also be formed by adding zinc and hydro- chloric acid to a solution of alloxan, but here an excess of acid must be care- fully avoided ; or by boiling alloxan in moderately strong sulphuric acid, when it is deposited as the solution cools. If a solution of alloxan be exposed to the action of a galvanic battery, oxygen is evolved at the positive electrode, while the negative is covered with a crystalline crust of alloxantin. 1901. Short oblique four-sided prisms of the oblique prismatic system, the obtuse angle of the prism being 105°. The crystals are Murexid, 431 colourless, or have a slightly yellow tint ; in an ammoniacal atmos- sect, iv. phere they become red, acquire a greenish metallic lustre, and are readily reduced to powder ; exposed to 212° they undergo no change of weight, but at 300° lose 15.4 per cent.^S eq. water ; sparingly soluble in cold, more freely in boiling water. The solution reddens litmus ; is converted into alloxan by being warmed with nitric acid, or by a solution of chlorine ; forms with the salts of silver a black precipitate of metallic silver ; it is decomposed by alkalies ; barytic water causes a violet-blue precipitate, which is first rendered colour- less by heat and then disappears ; by adding an excess of baryta to this solution a brilliant white precipitate is formed. 1902. If a solution of alloxan, instead of being left in contact with zinc and hydrochloric acid at common temperature, be heated to the boiling point, and kept at that temperature for some time, it deposits, on cooling, yellow granular crystals of a brilliant lustre and sparing solubility in boiling water, and of characters essentially different from alloxantin. 1903. If a stream of hydrosulphuric acid gas be passed through a Products of boiling solution of alloxantin, a further precipitation of sulphur en- sues, and the solution acquires a strongly acid reaction ; if neutralized afloxantin. by carbonate of ammonia, it deposits on cooling an abundant crop of white silky acicular crystals of an ammoniacal salt, which, when heated to 212° in the air, becomes of a blood-red colour; its compo- sition is represented by the formula C 8 N 3 H 2 0 8 , and it may therefore be considered to be a compound of cyanoxalic acid with 1 eq. ammo- nia and 4 eq. water. The acid in this salt appears in the moment of its separation from the ammonia with which it was combined to be decomposed into a variety of new products. It is proposed to call this acid the dialuric acid, since its properties appear to differ from those of the cyanoxalic, 1904. If a hot saturated solution of alloxantin be treated with a so- Action of lution of sal ammoniac, it instantly acquires a purple-red colour, ammonia, which disappears after a few moments, while the solution becomes turbid, and deposits brilliant white scales of uramil, but they are pink when dried ; the same occurs with the acetate, the oxalate, and other ammoniacal salts ; the solution contains, after the decomposi- tion, alloxan and free hydrochloric acid. 1905. Two eq. alloxantin and 1 eq. ammonia contain the elements of 1 eq. mL uramil, 1 eq. alloxan, and 4 eq. water. By heating a solution of alloxantin in pure ammonia, the products first formed are uramil and mykomelinate of ammo- nia, both of which suffer further changes by the continued action of ammonia and the atmospheric air. If a solution of alloxantin in ammonia, which has been prepared in the cold, be spontaneously evaporated by exposure to the air, oxygen is absorbed, and crystals of the oxalurate of ammonia are obtained : 3 eq. alloxantin, 7 eq. oxygen, and 6 eq. ammonia, contain the elements of 4 eq. oxa- lurate of ammonia and 5 eq. water. 1906. If oxide of silver be heated in a solution of alloxantin, a por- Action 0 f tion of the former is reduced with effervescence, and the solution oxide of contains pure oxalurate of silver. In this reaction 3 eq. oxygen silver, from the oxide of silver decompose l eq. alloxantin into 1 eq. water, 2 eq. carbonic acid, and 1 eq. oxaluric acid, which last unites with some undecomposed oxide of silver. 1907. Murexid. C 12 N 5 H 6 0 8 ; eq.= 197.19. The purpurate of Murexid. ammonia discovered by Prout. 432 Chap. VI. Processes. Theory. Properties. Cyanogen and its Compounds. By heating a mixture of equal parts of peroxide of mercury and uramilic acid in 3ti — 40 parts of water, with the addition of an exceedingly small quantity of ammonia ; as soon as the liquid has acquired a deep purple colour, it is filtered and allowed to rest, when the murexid crystallizes ; or by dissolving uramil by the aid of heat in ammonia, and when the solution has cooled to lfi0°, alloxan is added until a very slight alkaline reaction is observed. Or a solution of uric acid in dilute nitric acid is evaporated until it acquires a flesh-red colour, when it is allowed to cool to 100°, and is then treated with a dilute aqueous solution of ammonia, till the presence of free ammonia is re* marked by the odour ; the solution is then diluted with half its volume of boiling water, and allowed to cool.* Or a boiling saturated solution of alloxantin in water is treated with ammonia in excess till the precipitated uramil is redissolved, when a solution of alloxan is added, so that only a slight alkaline reaction is left, and the whole is allowed to cool. Or by heating alloxantin with sal ammoniac or oxalate of ammonia, and after the formation of uramil adding ammonia till the former is redissolved, and then alloxan. Murexid may be formed by a number of other processes, by bringing together many of the products of uric acid with ammonia, with or without the presence of atmospheric air. 1908. When the oxygen from ]£ eq. of peroxide of mercury is added to 2 eq. uramil, they may give rise to the formation of 1 eq. murexid, 1 eq. alloxanic acid, and 3 eq. water. Alloxan appears to have the same action upon a solution of uramil in ammonia as the peroxide of mercury. One eq. alloxan, 2 eq. alloxantin, and 4 eq. ammonia, contain the elements of 2 eq. murexid and 14 eq. water. The solution of uric acid in dilute nitric acid contains principally alloxantin, urea, and nitrate of ammonia : evaporated until the flesh- red colour appears, a portion of the alloxantin is converted by the action of free nitric acid into alloxan, a portion of which, by a further action, gives rise toparabauic acid. But when alloxan and alloxantinare simul- taneously present in a solution, an excess of ammonia produces a deep purple-red liquid from which murexid is deposited. If the solution contain an excess of alloxantin, the crystals of murexid are mixed with uramil ; with an excess of alloxan, mykomelinate of ammonia is formed, which also falls with the murexid. The parabanic acid present passes, when the solution of uric acid is saturated with am- monia, into oxaluric, which is obtained in crystals of oxalurate of ammonia by evaporating the mother-liquor. 1909. Murexid crystallizes in short four-sided prisms, two faces of which, like the upper wings of the cantharides, reflect a green metallic lustre. The crystals are transparent, and by transmitted light are of a garnet-red colour. It forms a brownish-red powder, which, under the polishing steel, acquires a brilliant metallic green colour. It is insoluble in ether and alcohol; sparingly soluble in cold, but more readily in boiling water, on the cooling of which it crystallizes unchanged ; insoluble in a saturated solution of carbo- nate of ammonia, soluble in caustic potassa with a beautiful indigo- blue colour, which disappears on the application of heat with the evolution of ammonia. * In applying this method of preparation, it is advisable to test a small quantity of the solution of uric acid from time to lime by saturating it with ammonia ; if it be rendered turbid by the ammonia, and a red powder falls, a small quantity of nitric acid must be added to the hot solution of the uric acid ; but if a yellow slimy precipi- tate be formed, the solution will only give rise to the formation of murexid after a stream of hydrosulphuric acid gas has been transmitted through it. 433 Cystic Oxide. 1910. It is decomposed either in the solid state or in solution by Sect, iv. all the mineral acids, with the separation of brilliant scales of mu- Decom- rexan ; the liquid contains ammonia, alloxantin, alloxan, and urea, posed. The instant the murexid is brought into contact with hydrosulphu- ric acid it is decomposed into alloxantin, dialuric acid, and murexan, with the separation of sulphur. An equivalent of alloxan, alloxan- tin, murexan, and urea, together with 2 eq. ammonia, contain the elements of 2 eq. murexid and 11 eq. water. 1911. Murexan. C 6 N 2 H 4 0 5 ; eq.=109.02. The purpuric acid Murexan. discovered by Prout as the product of the decomposition of murexid. Prepared by dissolving murexid in caustic potassa by the aid of heat, which is applied till the blue colour disappears, when dilute sulphu- ric acid is added in excess. 1912. It falls in crystalline scales of a silky lustre ; is insoluble in water and dilute acids, but is taken up by ammonia and the fixed alkalies in the cold without neutralizing them. It is dissolved by concentrated sulphuric acid, from which it is again precipitated un- changed by water. If a solution of murexan in ammonia he exposed to the air, it acquires a purple-red colour, and deposits the brilliant crystals of murexid ; with an excess of ammonia the solution again becomes colourless, and is then found to contain oxalurate of ammo- Uric Oxide, or Xanthic oxide. 1913. Two eq. murexan, 1 eq. ammonia, and 3 eq. oxygen, con- Theory, tain the elements of 1 eq. murexid and 3 eq. water ; 1 eq. murexan, 3 eq. oxygen, and 1 eq. ammonia, are the constituents of 1 eq. oxa- lurate of ammonia. 1914. Uric Oxide, or Xanthic Oxide. C 5 N 2 H 2 0 2 . A rare consti- tuent of urinary calculi ; first discovered by Marcet. 1915. Urinary calculi, which contain this ingredient, are dissolved in caustic potassa and the solution saturated with carbonic acid, when the uric oxide is precipitated. 1916. A white precipitate ; when dried, it forms a pale yellow Properties hard mass, which acquires a waxy lustre by friction : it is dissolved by the pure and carbonated alkalies ; in small quantity by hot water, hydrochloric and oxalic acids. It is soluble in concentrated sulphu- ric acid with a yellow colour ; no precipitation is caused by the ad- dition of water to the solution. It is dissolved in nitric acid without effervescence ; on evaporating to dryness, a lemon-yellow residue is left, which is not reddened by ammonia, is partially soluble in water, but perfectly and easily in potassa ; the solution has a light reddish- yellow colour, and leaves on evaporation a red residue. 1917. Exposed to the destructive distillation, it evolves an odour of urine, hydrocyanic acid, and carbonate of ammonia, but no urea. The calculi, which contain uric oxide, have a light brown, or bright brown surface ; the fracture is scaly, of a strong lustre, and also of a brown or deep flesh colour ; by friction the lustre becomes resinous. 1918. Cystic Oxide. Discovered by Wollaston ; a rare consti- tuent of urinary calculi ; an organic base. 1919. The calculus is dissolved in aqueous ammonia, and the filtered solution evaporated in the air, when the cystic oxide crystal- lizes. 1920. In the calculus it exists as a yellowish-white confused crys- 55 Destructive distillation. Cystic Ox- ide. 434 Vegetable Alkalies. chap- vn. talline mass of a brilliant lustre : crystallizes from its solution in potassa, on the addition of acetic acid, in hexagonal plates ; from ammonia, in white transparent scales. It is decomposed by heat, with the evolution of sulphurous and ammoniacal products of an of- fensive odour. It is readily dissolved by mineral acids, with which it forms crystalline compounds. Salt of. 1921. It forms with hydrochloric acid an anhydrous salt which is composed of 1 eq. of the base and acid. The salt with nitric acid i3 formed of 1 eq. of acid, 1 eq. of base, and 2 eq. water, the half of which is separated by a temperature of 105°. It is soluble in the pure and carbonated alkalies ; but if the solution be heated it is de- composed at first with the evolution of ammonia, but as the evapora- tion proceeds, a very combustible gas, which burns with a blue flame, and smells like sulphuret of carbon, is given off. The occurrence of the cystic oxide is so rare, that it is impossible to institute any inves- tigation of this remarkable substance. According to the analysis of Thaulow, its formula is C 6 NH 6 0 4 S 2 . L. 823. CHAPTER VII. Section I. Vegetable Alkalies * Vegetable 1922. These alkaline bodies have been discovered since the year alkalies. 1817, and their number is daily increasing. The most important only can be comprised in this chapter. Almost all plants, which are remarkable for their poisonous or medicinal properties, when sub- jected to a chemical examination, have been found to contain an alkaline principle. Precipita- 1923. It has been found that all the vegetable alkalies are preci- ted by tan- pitted by tanniu, or infusion of nutgalls. These precipitates are usually white powders, bitannates of the alkali, insoluble in cold water, and easily decomposed by an alkaline or earthy base. Henry has proposed infusion of nutgalls as an excellent reagent for obtain- ing these alkalies. His process is as follows : Digest the plant containing the alkali in warm water, acidulated with sulphu- ric acid. Neutralize the clear liquor bv potassa, and add a concentrated infusion of nutgalls as long as a precipitate falls. Separate the precipitate, wash it with cold water, and mix intimately with a slight excess of slaked lime. Dry the mixture over the vapour-bath till it is reduced to powder. Digest this powder in alcohol or ether. Filter, distil off the alcohol or ether. Set the residue aside for some days. The alkali will be deposited in crystals. t How dis- 1924. These bodies have been distinguished by names terminating tinguished. j n ^ that they m ight resemble potassa, soda, and ammonia, and the name of the neutral principles with which they are associated in vegetables has been made to terminate in ine or in. They are all compounds of carbon, hydrogen, nitrogen, and oxygen. * The materials for this chapter have been principally derived from Thomson’s Chem of Org. Bodies, to which the student must be referred for the description of many ot the less important substances, t Jour, de Pharm. xxi. 213. Quinia. 435 1925. Cinchonia. C 2 oH 12 NOl£*, — 158.0, was detected by Pel Sect, i. letier and Caventou in 1820, in the gray Peruvian bark, which is cinchonia. considered as the bark of the cinchona nitida or the cinchona conda - minea , and is not much esteemed for its medical properties. But there is reason to suspect that the cinchona lancifolia of Loxa, the most celebrated of all the varieties contains the same principle. It i _ obtained from the pale bark by digesting it in dilute hydro- chloric acid, precipitation by an alkali or earth, solution in alcohol and crystallization.! 1926. It crystallizes in prismatic needles, and requires 2500 times CrystaUme its weight of water for solution. It is very soluble in alcohol ; has s ?q™bflity. a bitter taste, is not altered by exposure to the air. Its alkaline pro- perties are well marked. 1927. The salts of cinchonia have a bitter taste ; are precipitated Characters by oxalates, tartrates and gallates, and by the infusion of gallnuts. of its salts ‘ It combines with acids forming neutral salts and disalts, or salts com- posed of two atoms base united to 1 atom acid. T. 1928. Quinia. C 20 Hi 2 NO 2 == 162.0. In, 1820 Pelletier and Caven- Quinia. tou pointed out the alkaline character of this substance, and showed it might be obtained in a separate state. | Since that period sul- phate of quinia has come into general use as a medicine, and has almost superseded the use of bark. 1929. Quinia may be extracted from the yellow bark usually considered as the cinchona cordifolia. The bark is boiled in water acidulated with sulphuric acid: the solution of Process, sulphate of quinia thus formed is decomposed by lime ; sulphate of lime is formed, and the quinia mixes mechanically with it, as it is precipitated. Alcohol dissolves the quinia and leaves the sulphate of lime. The alcohol being evapo- rated, the quinia is procured by itself; neutralized by dilute sulphuric acid, and boiled with animal charcoal to destroy the colouring matter, a solution is pro- cured, which gives crystals of the sulphate on evaporation. 1930. As sulphate of quinia is prepared on a large scale, it is more convenient to obtain quinia from that salt. Nothing more is su i p hate. necessary than to dissolve the sulphate in water, and to mix the so- lution with a dilute solution of ammonia. The quinia falls in white flocks, which become a little coloured during drying. 1931. It crystallizes with difficulty from hot alcohol in fine nee- Characters, dies and then is in the state of a hydrate. Exposed to heat, it softens and falls down as a white powder ; at 302°, or a few degrees higher, it melts and loses the whole of its water (T ). Suddenly cooled,- it becomes yellow and brittle ; slowly cooled, it assumes a fibrous texture, and becomes opaque. By friction it becomes nega- tively electric. * The atomic composition is given, as stated by Thomson. t The following process was adopted by Pelletier and Caventou for the extraction of Pelletier and cinchonia. Two kilogrammes (4 2-5 lbs. avoirdupois) of gray bark in powder were di- Caventou*# gested in 6 kil. (13 1-5 lbs.) of alcohol. This treatment was repeated four times. The proCess ' alcoholic tinctures were all united, and the alcohol was distilled off after the addition of two litres (122 cubic inches) of water. The residual liquor was filtered, and it left on the filter a reddish matter apparently resinous, which was washed with water con- taining a little potassa till the liquid passed without colour. The matter remaining on the filter, after being well washed with distilled water is greenish white, very fu- sible, soluble in alcohol, and capable of crystallizing. It was cinchonia with foreign matter. It was purified by the action of hydrochloric acid, magnesia, and repeated boiling in alcohol which dissolved the cinchonia. $ Ann. de Chim. et Phys. xv. 345. 436 Vegetable Jllkalies. Chap, vii. 1932. When freed from water and placed in that liquid, quinia swells and absorbs it. Its taste is intensely bitter. It is soluble in 200 times its weight of boiling water ; very soluble in alcohol and in ether. distirf tS 1933. The salts of quinia are distinguished by a strong bitter taste ; guished. those in crystals have a pearly lustre ; most of them are soluble in water, and several in alcohol and in ether. These solutions are pre- cipitated by oxalic, tartaric, and gallic acids, and also by infusion of nutgalls. Sulphate of 1934. Sulphate of Quinia. The powerfully febrifuge properties quinia. 0 f this salt have introduced it into general use as a medicine, and it has become an important article of manufacture, especially in France.* * * § The process usually followed is the following of M. Henri, junior, with some slight modifications-! Adultera- 1935. Sulphate of quinia, from its commercial value, is frequently non detect- adulterated. The substances commonly employed for the purpose are water, sugar, gum, starch, ammoniacal salts, and earthy salts, such as sulphate of lime and magnesia, or acetate of lime. Pure sulphate of quinia, when deprived of its water of crystallization by a heat of 212°, should lose only from 8 to 10 per cent, of water. Su- gar may be detected by dissolving the suspected salt in water, and adding precisely so much carbonate of potassa as will precipitate the quinia. The taste of the sugar, no longer obscured by the intense bitter of the quinia, will generally be perceived ; and it may be se- parated from the sulphate of potassa, by evaporating gently to dry- ness, and dissolving the sugar by boiling alcohol. Gum and starch are left when the impure sulphate of quinia is digested in strong alcohol. Ammoniacal salts are discovered by the strong odour of ammonia, which may be observed when the sulphate is put into a warm solution of potassa. Earthy salts may be detected by burning a portion of the sulphate.! Disulphate. 1936. Disulphate of Quinia effloresces; is soluble in 740 times its weight of water at 55°, and in 30 times its weight of boiling water. It dissolves in 80 times its weight of alcohol of sp. gr. 0.85. It crystallizes in tufts composed of fine needles of a pearly lustre. It fuses and then resembles liquid wax: at a higher temperature it as- sumes a fine red colour, and burns without leaving any residue. From Liebig’s analysis, as quoted by Thomson, it is composed of 85 quinia, 10 sulphuric acid, and 4.17 water. 1937. Neutral sulphate of quinia may be formed by adding a little sulphuric acid to the solution of the disulphate. § 1 938. Salicin , CjHsC^^AS.O, although notalkaline is analogous to Composi- tion. Neutral sulphate. * The annual produce in Paris exceeds 1200,00 ounces per annum. T. + For details of which, see T. Orff. Bodies, 233, and Ure’s Diet. Arts and Manuf. 1064. t Several of the preceding directions are taken from a paper on the subject by Phil- lips. Phil. Mag. and Ann. ni. 111 . (Turner.) According to Thomson, margaric acid and boracic acid are employed ; the former may be separated by weak hydrochloric acid which dissolves sulphate of quinia but leaves the margaric acid 3 the boracic acid is discovered by incinerating a portion of the suspected salt. § Hydro ferrocyanate of Quinia has been found a more powerful febrifuge than the sulphate, but is liable to decomposition. For the method of preparing this, and the other salts of quinia, see T. Orff. Bodies , 236. Narcotina . 437 the alkalies from cinchona. It is obtained from the bark of the willow sect, i. {salix helix), and exists in several species, also in the bark of the Salicin, poplar ( populus tremula). It is white, very bitter, soluble in water and alcohol. With concentrated sulphuric acid it becomes of a beautiful red colour ; this holds with solutions containing only of their weight of it ; and the presence of salicin in any bark may thus be ascertained. It has been employed as a substitute for Use ' quinia. 1939. Veratria , C 34 H22NQ 6 ,=288, the alkaline principleof veratrum Veratria. album , white hellebore, and colchicum autumnale , meadow saffron, has the aspect of resin, is white and fusible at about 240°. Alco- hol and ether dissolve it. It has no smell, but when drawn into the Characters, nostrils, even in minute quantity, it produces violent and long-con- tinued sneezing. Its taste is excessively acrid, it occasions frightful vomiting, and a few grains are fatal. ^ 1940. Strychnia exists in the seeds or fruits of several species of strychnia. strychnos , particularly in the nux vomica. It was found also in the poisonous matter called upas. It is intensely bitter, and requires ri 2500 times its weight of boiling, and 6667 times its weight of cold 13raC erS ' water for solution. It is highly poisonous ; occasioning violent con- tractions of the muscles, and tetanus ; the best antidote is infusion of nutgalls, or warm tea. In very small doses it has been employed in paralysis, and it is said sometimes with success. 1941. Brucia resembles the foregoing, and has been found to ac- company it in the different vegetable bodies which contain it.f 1942. Narcotina. C 40 H 2 ,jNO 12 , = 370.24. Discovered by Desrone Narcotina. in 1803. t It is obtained from opium. Digest opium in water, filter and evaporate to the consistence of an extract. Process. Ether digested on this extract dissolves the narcotina together with some other substances. Distil off the ether, and dissolve the residual matter in hot water or boiling alcohol, digest the solution with animal charcoal. Decant the clear liquid and precipitate the narcotina by ammonia. If not white, the narcotina may be dissolved in hydrochloric acid, and the solution be again treated with animal charcoal, thrown down by ammonia, washed and dried. 1943. Narcotina is white, and is deposited from boiling ether or Characters * alcohol in needle-form crystals of a pearly lustre. It does not re- store the blue colour of litmus paper reddened by acids ; but as it combines with and neutralizes acids must be considered as an alkali. ^ cl j onof - 1944. Its taste is not bitter. In contact with hyponitrous acid it hyponi- assumes a carmine-red colour and gives out red vapours. In about trous acid, half a minute the action increases, the narcotina catches fire and burns with a large white flame. There remains a blackish spongy matter consisting partly of charcoal and partly of bitter principle of Welter, or carbazotic acid.§ ’ It is insoluble in cold water, very little soluble in boiling water, but readily soluble in ether and in fixed oils. 1945. The salts of narcotina may be obtained by dissolving it in ^ned° b " dilute acids and concentration. 1946. It may be introduced into the stomach without producing any deleterious or even sensible effect. Orfila administered it to the * Delphinia exists in the delphinium, staphysagria, or stavesacre. + Enietia or Emetina is obtained from the various roots sold under the name of ipe- Emetia. cacuanha. These are the roots of the cephoelis ematica, callicocca ipecacuanha , and viola emetica. T. 263. t Ann. de Chim. xlv. 257. §Jour. de Pharm. xxii. 382. 438 Chap VII. Morphia. Action of nitric acid and heat. Process. Action on animals. Detection of morphia, Vegetable Alkalies. amount of several drachms a day, without perceiving any action whatever. It was speedily fatal however to dogs. 1947. Morphia — Morphina. C^H^NOs, - 284. This is one of the most important of the vegetable alkalies, and the principle on which the narcotic properties of opium depend ; insoluble in cold water; boiling water dissolves about of its weight of it; dis- solved by boiling alcohol, crystallizing in six and four-sided prisms, tasteless when pure. Extremely bitter when rendered soluble by alcohol or an acid. 1948. Nitric acid changes its colour to orange-red, which gradu- ally passes into yellow. By heat the transparent crystals lose per cent, of water and become opaque and white. If the heat is increased the morphia melts, and forms a yellow liquid, which be- comes white and crystalline on cooling: by continuing the heat, it gives out a resinous odour, and burns with a red flame. 1949. Morphia is obtained by various processes ;* the following is recommended by Thomson : Macerate opium in twice its weight of water for 24 hours, agitating the mix- ture occasionally to promote solution. Decant and pour over the undissolved E ortion a new quantity of distilled water, equal to the portion first employed. Lepeut this process four times, or till everything soluble in cold water be taken up. If the opium be of good quality, about three fourths of it will be dissolved and the remaining fourth remains in a solid state. Filter the solutions thus ob- tained, and evaporate the whole to dryness in a low heat to prevent any portion of the residue from being decomposed or injured. Pour distilled water upon this dry residue. The whole will dissolve except a brilliant crystalline matter, which is narcotina. Heat the solution to the temperature of 212° and add to it ammonia in slight excess. Boil the mixture for ten minutes, to drive off this ex- cess, and then allow the liquid to cool. The morphia precipitates in crystals, pretty pure ; but a portion of it swims on the surface, mixed with impurity If the morphia thus obtained be digested in sulphuric ether, a portion of narcotina is dissolved, and the morphia is rendered more pure. It may be rendered quite pure by dissolving it in boiling alcohol, digesting the solution with ivory black, filtering and crystallizing This process should be repeated three or four times, in order to free the morphia from all impurity. An easier mode of purifying it is to dissolve it in sulphuric acid, taking care to avoid an excess of acid. By evaporation the? sulphate of morphia is obtained in crystals. Let this salt be de- composed by digesting it with magnesia The sulphate of magnesia is washed off, and the morphia, which is mixed with the excess of magnesia employed, is to be dissolved in boiling alcohol, and crystallized. Opium yields at an average about of its weight of pure mor- phia. 1950. When pure, owing to its insolubility, it is almost inert ; for Orfila gave twelve grains of it to a dog without its being fol- lowed by any sensible effect. In a state of solution, on the contrary, it acts on the animal system with great energy, Sertuerner having noticed alarming symptoms from so small a quantity as half a grain. From this it appears to follow that the effects of an over-dose of a salt of morphia may be prevented or diminished by giving a dilute solution of ammonia, or an alkaline carbonate, so as to precipitate the vegetable alkali. 1951. Many experiments have been made to discover a ready mode of detecting morphia, and distinguishing it from other bodies. When this alkaline substance, or any of its salts, is placed in contact * For which see B. ii. 532 ; Edin. Med. and Surg. Jour. Nos. 107 and 111; Amer. Jour. xiii. 27. 439 Acetate of Morphia. with a neutral solution of a neutral salt of peroxide of iron, it strikes a s e ct> i. blue colour. The addition of a slight excess of acid causes this co- lour to disappear immediately. The addition of too much water causes the blue colour to pass into red. 1952. When opium is administered as a poison, its presence is rendered obvious by the peculiar odour of that drug, as well as by the red tint given to persalts of iron by the meconic acid of the opium ; but when death is occasioned by a salt of morphia, it becomes neces- sary to eliminate the morphia, a practical process of considerable de- licacy. The method suggested by Lassaigne for detecting acetate Lassaigne’s of morphia, may be applied to its saline combinations in general.'* rnethod. The suspected solution is evaporated by a temperature of 212°, and the residue treated with alcohol, by which the salt of morphia, together with osmazome and some salts, is dissolved. The alcohol is next evaporated, and water added to separate fatty matter. The aqueous solution is then set aside for spontaneous evaporation, during which the salt of morphia is generally deposited in crystals. From an aqueous solution of the salt, ammonia throws down a crystalline precipi- tate, which may be recognised as morphia by the combination of the following characters : — By the figure of its crystals; its bitter taste ; solubility in alcohol ; alkalinity ; by the orange-red tint developed by nitric acid ; and by the peculiar action of iodic acid. The last character is particularly valuable in distinguishing morphia from other vegetable alkalies : the latter combine with iodic acid and form iodates ; but morphia decomposes iodic acid, and sets iodine free, which may then be delected by starch. A grain of morphia in 7000 grains of water may be discovered by this test.f T. 1953. Hydrochlorate of Morphia. This salt is much employed in Hydro-^ Edinburgh as a medicine.! It crystallizes in needles, and dissolves c in from 15 to 20 times its weight of cold, and in less than its weight of boiling water. 1954. Acetate of Morphia is less convenient in medical practice Acetate, than the foregoing salt, being variable in constitution. It is apt to lose a portien of its acid, even when kept in crystals ; and during * Ann. de Chim .. et de Pfiys. xxv. 102. t Serullas. Robinet, in Jour, de Pharm. x iii.24. For Hare’s method of detecting minute quantities of opium, see Amer. Jour. xii. 290. tThe method of preparing it now in general use was suggested by Robertson, and Gregory'* pro- improved by Gregory and Robiquet, Edin. Med. and Surg. Jour. Nos. 107 and 111, chlorate o f ydro ' and Jour, de Pharm. xix. 156. The aqueous solution of opium is concentrated in a morphia, vessel of tinned iron, to the consistence of a thin syrup, when a slight excess of chloride of calcium, neutral, and quite free from iron, is added. The mixture is boiled fora few minutes, and then poured into an evaporating basin. Resinous flocks, meconate of lime, and colouring matter precipitate. But this last matter does not separate well unless the liquid has been sufficiently concentrated. After this deposit has subsided, the clear liquid is evaporated on the sand-bath. During the evaporation a new depo- sition takes place, which must be separated before the liquid be allowed to crystallize. The concentrated liquid is now to be allowed to cool, under constant agitation. The crystals of hydrochlorate of morphia are deposited in abundance. They are to be put into a stout cloth, and subjected to pressure, which squeezes out a black liquid, con- taining various impurities. The crystals are now to be dissolved in water, at 70°, filtered through cloth, mixed with a little chloride of calcium, crystallized and com- pressed as before. These crystals are again dissolved in water, the liquid is satu- rated with chalk and animal charcoal being added, the whole is digested for 24 hours at 194°. It is then filtered and concentrated. The crystals are deposited rapidly, and when freed from the mother water they are white and neutral. The salt thus ob- tained iw dried at a temperature of 150°. It usually amounts to about one tenth of the weight of opium employed, and consists of hydrochlorate of morphia and a little hydrochlorate of codeina; from which it might probably be freed by digesting in ether. T. Org. Bodies, 271. 440 Vegetable Alkalies. Chap . VII. Codeia. Narceia. Thebaia. Meconia. Characters. Brucia. Conia. Parillia. the evaporation crystals of morphia are sometimes deposited. It is readily formed by dissolving morphia in acetic acid.* * * § 1955. Codeia was discovered in 1832, by Robiquet, in the hydro- chlorate of morphia made by Gregory’s process. (1953 n.) Ammonia added to a solution of this substance in water precipitates the mor- phia, leaving the codeia in solution, which can be separated by crystallization. It has an alkaline reaction, fuses when heated to 300°, does not render nitric acid red, and is more soluble in water than morphia. 1956. In doses of from 4 to 6 grains it produces an excitement similar to intoxication, which is followed by depression, nausea, and vomiting. 1957. Narceia} is another alkali discovered by Pelletier in the watery infusion of opium. It is white and crystalline, melting at about 200°. Its salts are blue when dissolved in a particular quan- tity of water, the colour changing to violet and red as it is increased. 1959. Thebaia is the name of an alkaline principle found in opium, which is considered the same as the paramorphine of Pelletier. It is white, crystalline, soluble in ether, and fuses at 266°. 1959. Meconia. C^HsC)*. This is another constituent of opium, but is not possessed of alkaline properties, and contains no nitrogen. It is found in minute quantity, opium yielding but about of its weight of meconia. It is white, has no odour, and when first put into the mouth has no taste, but soon imparts an impression of acri- dity. It is soluble in water, alcohol and ether. It fuses at 194°. It resembles fat in appearance.! 1960. Brucia or Brucina resembles strychnia (1940), and may be procured from the nux vomica in small quantity, and also from the Brucia ant i-dy sent erica.*} Like morphia, it strikes a deep red tint with nitric acid, and strychnia, which produces this effect, is consi- dered as containing a small portion of brucia. It acts upon animats like strychnia, but is a less active poison. It is intensely bitter. 1961. Conia is the active principle of conium maculatum , or hem- lock, and next to hydrocyanic acid, the most virulent poison known. || 1962. Parillia or Parillina exists in the root of smilax sasaparilla, common sasaparilla of commerce. It is white, of a peculiar odour, * The basis of Battley’s sedative liquor is supposed to be acetate of morphia- t Probably from vaQxrj, torpor. t From 40 lbs. of opium Couerbe obtained 50 ounces of morphia, l£ “ codeia, I “ thebaia, 1 “ meconia, § “ narceia. Colour produced by agitating the preceding substances with sulphuric acid mixed with a little nitric acid : Morphia gives a brownish colour. Codeia “ green “ Thebaia “ yellow rose “ Meconia “ turmeric yellow and then a red Narceia “ chocolate “ (Reid.) § False angustura, the seeds of which were brought from Abyssinia by the traveller Bruce. || See Christison in Trans. Edin. Boy. Soc. xiii. Alcohol . 441 a sharp bitter taste, and nauseous. When swallowed to the extent Sect, xt. of 13 grains, it occasions nausea, vomiting, diminishes the rapidity of the pulse, and acts as a sudorific. 1963. Nicotina exists in the leaves and seeds of tobacco. At Nicotina. common temperatures it is a liquid of the consistence of honey, of an acrid taste and a brown colour. It is a virulent poison. Its salts are distinguished by their taste of tobacco and their acrid causticity* Section II. Intermediate Bodies . 1964. In this class, which is merely temporary, Thomson has placed all the vegetable principles which seem capable of entering into definite compounds with other bodies, and which have not as yet been proved by satisfactory experiments to be either acid or alkaline. Alcohol and its Compounds. 1965. Alcohol , C 4 H 5 0+H0, eq. 46.00, is the intoxicating ingre- Alcohol, dient of all spirituous and vinous liquors. It does not exist ready formed in plants, but is a product of the vinous fermentation. 1966. Common alcohol or spirit of wine is prepared by distilling Spirit of whiskey or some ardent spirit, and the rectified spirit of wine is wme - procured by a second distillation. The former has a sp. gr. of about 0.867, and the latter of 0.835 or 0.84. In this state it contains a quantity of water, from which it may be freed by the action of substances which have a strong affinity for that liquid. Thus, when carbonate of potassa heated to 300° is mixed with spirit of wine, p ur jfi e d. the alkali unites with the water, forming a dense solution, which, on standing, separates from the alcohol, so that the latter may be removed by decantation. To the alcohol, thus deprived of nart of its water, fresh portions of the dry carbo- nate are successively added, until it falls through the spirit without being moist- ened. Other substances, which have a powerful attraction for water, may be substituted for carbonate of potassa. Gay-Lussac recommends the use of pure Jime and baryta ;+ and dry alumina may also be employed. A very convenient process is to mix the alcohol with chloride of calcium in powder, or with quicklime, and draw off the stronger portions by distillation. Another process, which has been recommended for depriving alcohol of water, is to put it into the bladder of an ox, and suspend it over a sand-bath. The strongest alcohol which can be procured by any of these pro- cesses has a sp. gr. of 0.796 at 60° F. This is called absolute alco- hol, to denote its entire freedom from water. *The following table exhibits the quantity of this substance yielded by 1000 parts of various kinds of tobacco : Cuba . „ . . * 8.64 Maryland .... 5.28 Virginia ..... 10.00 He de Vilain . . . . 11.20 Lot . . . . 6.48 North . . . 11.28 Lot-et Garonn . . . .8 20 For smoking .... 3.86 T. Organic Bodies, 286, Several other principles analogous to the foregoing, have been obtained from vari- | ous plants, on which their activity depends. These have been particularly described i together with the processes for obtaining them in Thomson’s late volume, t An. de Ch. lxxxvi. t Jour de Soi. xviii. 442 Chap VII. Absolute ■lcohol. Soemer- ing’s ex- periments. Christi- son’s ex- periments. Properties. Effect of cold. Organic Chemistry — Intermediate Bodies. 1967. An elegant and easy process for procuring absolute alcohol, has been proposed by Graham.* A large shallow basin is covered to a small depth with quicklime in coarse powder, and a smaller one containing three or four ounces of commercial alcohol is supported just above it. The whole is placed upon the plate of an air-pump, covered by a low receiver, and the air withdrawn until the alcohol evinces signs of ebullition. Little alcohol evaporates, as its vapour is not condensed by lime, but all the water evaporates and its vapour is absorbed by the lime. Common alcohol is in this way entirely deprived of water in the course of about five days. The tempera- ture should be preserved as uniform as possible during the process. Sulphuric acid cannot be substituted for quicklime, since both va- pours are absorbed by this liquid. 1968. According to Soemering when spirit of wine is enclosed in a bladder, and exposed for some time to the air, it is converted into alcohol, the water only escaping through the coats of the bladder.t But the recent experiments of Christison do not confirm this, who found that spirit, whatever its strength, became weaker when thus exposed. They however confirm the results obtained by Graham, and absolute alcohol of the density of .796 was obtained in two months by exposing rectified spirit in an open cup enclosed in a con- fined space with quicklimeT 1969. Alcohol, obtained by slow and careful distillation, is a lim- pid, colourless liquid, of an agreeable smell, and a strong pungent flavour. Its specific gravity varies with its purity ; the purest ob- tained by rectification over chloride of calcium being .791 ; as it usually occurs it is .820 at 60°. If rendered as pure as possible by simple distillation, it can scarcely be obtained of a lower specific gra- vity than .825, at 60°. Absolute alcohol boils at 168^-° F.§ 1970. Hutton is said to have succeeded in freezing alcohol, but the fact is doubtful, as the means by which he effected its congela- tion were never disclosed. Walker exposed it to a temperature of — 91 but no congelation took place. Even when diluted with an equal weight of water, it requires a cold of 6° below 0 to congeal it. When of a specific gravity of .810, it boils at the temperature of 173.5°, the barometrical pressure being 30 inches. In the vacuum of an air-pump it boils at common temperatures. 1971. Alcohol may be mixed in all proportions, with water, and the specific gravity of the mixture is greater than the mean of the two liquids, in consequence of a di- minution of bulk that occurs on mixture, as may be shown by the following experiment : Fig. 190 represents a tube with two bulbs, communicating with each other, the upper one being supplied with a well ground glass stopper. Fill the tube and lower bulb with water, pour alcohol slowly into the upper bulb, and when full put in the stopper. The vessel will now be completely filled, the alcohol lying upon the wa- ter; if it be inverted, the alcohol and water will slowly mix and the Fig. 190- § * Edin. Phil. TVans. 1S28. t Quart. Jour. viii. 331, and Henderson’s Hist, of Wines, Lond. 1824. t Edin. Phil. Jour. July, 1839. § Ure. Alcohol. 443 . condensation that ensues will be indicated by the empty space in the tube. A Sect. 11. considerable rise of temperature takes place in this experiment in consequence of the condensation. 1972. The strength of such spirituous liquors as consist of little Strength else than water and alcohol, is of course ascertained by their specific tained. gravity ; and for the purpose of levying duties upon them, this is as- certained by the hydrometer.* But the only correct mode of ascer- taining the specific gravity of liquids, is by weighing them in a deli- cate balance against an equal volume of pure water, of a similar temperature.! Proof spirit contains equal weights of alcohol and water ; sp. gr. 0.917. 1873. There are other methods of judging of the strength of spi- rituous liquors, which, though useful, are not accurate, such as the taste, the size and appearance of the bubbles when shaken, the sink- ing or floating of olive oil in it, and the appearances exhibited when burned ; if it burns away perfectly to dryness, and inflames gunpow- der or a piece of cotton immersed in it, it is considered as alcohol: the different spirituous liquors leave variable proportions of water when thus burned in a graduated vessel. 1974. Alcohol is extremely inflammable, and burns with a pale c'ombus- blue flame, scarcely visible in bright daylight. It occasions no fuli- tion of al- ginous deposition upon substances held over it, and the products of coho1 - its combustion are carbonic acid and water, the weight of the water considerably exceeding that of the alcohol consumed. Ac- cording to Saussure, jun., 100 parts of alcohol afford, when burned, 136 parts of water, the production of which may be shown by sub- stituting the flame of alcohol for that of hydrogen, in the apparatus described in Chapter iii., under the article Water (403), and if the tube at its extremity be turned down into a glass jar, it will be found that a current of carbonic acid pisses out of it, which may be rendered evident by lime water. There are some substances which communicate colour to the flame of alcohol ; from boracic acid it acquires a greenish-yellow tint ; nitre and the soluble salts of baryta cause it to burn yellow, and those of strontia give it a beautiful rose colour ; cu- Fig. 191 . preous salts impart a fine green tinge. 1975. Alcohol dissolves pure soda and potassa, but it does not act upon their carbonates : consequently, if the * The hydrometer of Bate, constructed for the Commissioners of Great Britain, has a scale of 4 inches in length divided into 100 parts and 9 weights, giving a range of 900 divisions, and expresses specific gravities at the temperature of 62° F. To render this instrument so accurate as to in- volve no error of appreciable amount, the weights are constructed so that each successive weight has an increase of bulk over the preceding weight equal to that part of the stem occupied by the scale, and an increase of weight sufficient to take the whole of the scale, and no more, down to the J k. liquid. Fig. 191 represents this instrument and two of its nine ballast / \ weights. It comprehends all specific gravities between 820 and 1000 and indicates true sp- gr. with almost perfect accuracy at 62° F. Ure’s Did. \ J Arts and Manuf. 23. \ / In France the alcoometre of Gay-Lussac is employed, for which see Ibid. j I In the United States the hydrometer of Dicas is used. j l t In the Phil. Trans, for 1794, Gilpin has given a copious and valua- ble series of tables of the specific gravity of mixtures of alcohol and water, f q and of the condensation that ensues, with several other particulars. Other \ J tables by Tralles and Gay-Lussac, will be found in Ure’s Did. Arts and \ I Manuf. 18—24. v \ Use as a solvent. Bale’s hydrom.- eter. 444 Organic Chemistry — Intermediate Bodies. Alcohates. Chap, vii. latter be mixed with alcohol containing water, the liquor separates into two portions, the upper being alcohol deprived to a considera- ble extent, of water, and the lower the aqueous solution of the carbonate. The alcoholic solution of caustic potassa was known in old pharmacy under the name of Van Helmont’s Tincture of Tar - tartar*” °* tar ' ^ ts llse * n Purifying- potassa has already been stated (845). 1976. The greater number of sulphates are insoluble in this men- struum, but it dissolves many of the hydrochlorates and nitrates. It also dissolves the greater number of the acids. It absorbs many gaseous bodies. It dissolves the vegetable acids, the volatile oils, the resins, tan, and extractive matter, and many of the soaps ; the greater number of the fixed oils are taken up by it in small quanti- ties only, but some dissolve largely.* 1977. Graham has shown that alcohol may in many instances be combined with saline bodies, performing as it were the part of water of crystallization. Such combinations may be termed alco- hates. They are obtained by dissolving the substances by heat in absolute alcohol, and are deposited as the solution cools, mor* or less regularly crystallized. They appear to be definite compounds, and in some of them the alcohol is retained by an attraction so powerful, as not to be evolved at a temperature of 400° or 500°. t 1978. When the vapour of alcohol is passed through a red-hot copper tube, it is decomposed, a portion of charcoal is deposited, and a large quantity of carburetted hydrogen gas is evolved. 1979. Alcohol exists ready formed in wine and spirituous liquors, and may be collected without heat. Brandet procured it from wine by precipitating the acid and extractive colouring matters by suba- cetate of lead, and then depriving the alcohol of water by dry carbo- nate of potassa : the pure alcohol may then be measured in a graduated tube. Gay-Lussac obtained alcohol from wine by distil- ling it in vacuo at the temperature of 60° F. He also succeeded in separating the alcohol by the method of Brande ; but he suggests the employment of litharge in fine powder, instead of subacetate of lead, for precipitating the colouring matter.^ 1980. The preceding researches of Brande led him to examine the quantity of alcohol contained in spirituous and fermented liquors. According to his experiments, brandy, rum, gin, and whiskey, con- tain from 51 to 54 percent, of alcohol, of specific gravity 0.825. The stronger wines, such as Lissa, Raisin wine, Marsala, Port, Madeira, Sherry, Tenerifle, Constantia, Malaga, Bucellas, Calcavella, and Vi- donia, contain from between 18 or 19 to 25 per cent, of alcohol. In Claret, Sauteme, Burgundy, Hock, Champagne, Hermitage, and Gooseberry wine, the quantity is from 12 to 17 per cent. In cider, perry, ale, and porter, the quantity varies from 4 to near 10 per cent. In all spirits, such as brandy or whiskey, the alcohol is sim- ply combined with water; whereas in wine it is in combination with Decom- position. Alcohol in Brande’s results. * It may be remarked that many errors exist in the published estimates of the solu- bility of substances in alcohol, arising from the existence of water either in the solvent or substance dissolved. t Graham has examined the alcoholic combinations of chloride of calcium, nitrate of magnesia, Ate. see Quart. Jour., N. S., Dec. 1828. t Phil. Trans. 181 1 and 1813. § Mem. d'Arcueil, vol. iii. Alcohol. 445 mucilaginous, saccharine, and other vegetable principles, a condition Sect, u. which tends to diminish the action of the alcohol upon the system.* 1981. From recent experiments Christison is of opinion that the christi- alcoholic strength of many wines has been overrated. The follow- son’s recent ing table shows some of his results; the first column gives the per- Cents' centage of absolute alcohol of sp. gr. 793.9, by weight, and the second the per-centage of proof-spirit- sp. gr. 920 by volume. Alcohol p. c. P. By Wgh. Sp. p . c. By Vol. Port — weakest .... 14.97 30.56 mean of 7 wines - 16.20 33.91 strongest - - £ 17.10 37.27 white port - 14 97 31.31 Sherry — weakest - 13.98 30.84 mean of 13 wines, excluding those very long kept in casks - 15.37 33.59 strongest - - 16.17 35.12 mean of 9 wines very long in cask in the East Indies - 14.72 32.30 Madre da Xeres - 16.90 37.06 Madeira \ a11 lon S in cask in X stron g est 14.09 30.80 Madeira £ the tast Indies $ wea kest - 16.90 36.81 Teneriffe, long in cask at Calcutta - 13.84 30.21 Cercial - 15.45 33.65 Dry Lisbon - - 16.14 34.71 Claret, a first growth of 1811 7.72 16.95 Chateau-Latour, first growth 1825 - 7.78 17. 6 Ordinary Claret, a superior “ vin ordinaire” 8.99 18.96 Malmsey - - - 12.86 28.37 Rudesheimer, superior quality 8.40 18.44 Do. inferior . 6.90 15.19 Giles’ Edin. Ale before bottling 5.70 12.60 Same ale 2 years in bottle - 6.06 13.40 Superior London Porter 4 months bottled - 5.36 1 1.91 t 1982. The composition of alcohol in the state of vapour is thus Composi- stated by Thomson : tion of al- cohol va- 1 vol. olefiant gas . . . . 0.9722 sp. gr. pour ac- 1 “ vapour of water 0.6250 “ cording to Thomson, 1.5972 “ condensed into 1 vol. ; so that its sp. gr. is 1.5972 when in the state of vapour. 1983. Olefiant gas is a compound, 2 vols. carbon vapour, and 2 vols. hydrogen gas united together, and condensed into 1 volume. So that a vol. of it is equivalent to 2 atoms of carbon, and 2 atoms hydrogen. 1984. Liebig has given another view of the composition of alcohol, Liebig’s founded upon the experiments lately made to determine the compo- sition of ether. According to him, ether contains no water, but is composed of C 4 H 5 -f-0, or it is an oxide of (C 4 H 5 ). Alcohol is a hy- drate of ether, or it consists of (C 4 H 5 0)-(-H0. This view recom- mends itself by its simplicity, and by the facility which it presents to us in explaining the nature of the numerous compounds formed by means of alcohol! * For Brande’s table of proportion of alcohol in wines, see his Chem. ii. 565. t Edin. Philos. Jour. July, 1839. t Thomson, Org. Bodies , 300. 446 Chap, VII. Aldehyde. Obtained. By spongy platinum. Properties. A solvent. Action on oxide of silver. Liebig’s analysis. Organic Chemistry — Intermediate Bodies. 1185. Aldehyde .* This remarkable substance was first noticed by Dobereiner, but has been particularly examined by Liebig, t 19S6. It is a colourless liquid, having a peculiar ethereal smell and is obtained by passing the vapour of ether through a large glass tube heated to redness. The products being introduced into sulphu- ric ether, the aldehyde is retained in combination. Dry ammoniacal gas is then passed into the solution,- which forms a crystalline compound with the aldehyde, termed ammonia aldehyde. From this compound it is procured by adding an equal weight of water, and then diluted sul- phuric acid to unite with the ammonia, heating it afterwards in a retort.! The product of distillation is hydrated aldehyde, which is separated from the water by distilling it from chloride of calcium. 1987. Aldehyde may also be formed by the action of spongy pla- tinum with air and alcohol, or by distillation from 4 parts of water and 4 of alcohol, mixed with 6 of peroxide of manganese, and 6 of aqueous sulphuric acid. 198S. It is very volatile, of sp. gr. 0.790, and boiling at 7l£°. Its vapour when inhaled produces a kind of cramp in the stomach. It combines with water in all proportions, with evolution of heat. It takes fire readily, burning with a pale flame and much light. Kept in a vessel full of air it absorbs oxygen, and is converted into very concentrated acetic acid ; this is promoted by spongy platinum. 1989. Aldehyde dissolves sulphur, phosphorus, and iodine ; ab- sorbs chlorine and bromine with production of hydrochloric and hy- drobromic acids. § 1990. When heated with water and oxide of silver, at first mode- rately and then raised to the boiling temperature, in a glass tube, the silver is revived and covers the glass with a brilliant coating. The oxide of silver is also reduced when a few drops of ammonia are ad- ded to aqueous aldehyde and it is heated with the oxide, affording an easy method of ascertaining the presence of the smallest quantity of aldehyde in any liquid. 1991. When kept in vessels to which air has access, oxygen is absorbed, and prismatic crystals are formed, which fuse at 212°, and at a higher temperature sublime. They are hard, inflammable, and soluble in alcohol and ether. 1992. Liebig analysed aldehyde by heating it with oxide of cop- per ; the result was as follows : Carbon - - 53 67 or 4 atoms =3.0 or per cent. 54.55 Hydrogen - 8.97 or 4 “ = 0.5 or “ 9.09 Oxygen - - 37.36 or 2 “ = 2. or “ 36.36 100.00 5.5 100.00 * From alcohol dehydratus. t Ann. de. Chim. Ct Phys. lix. 296, and Ann. de Pharm. xiv. 133. t For minute details, see T. Organic Bodies , 301. § Liebig is of opiuion that in these reactions the aldehyde is changed into chloral and bromal. Acetal 447 The density of its vapour he found 1.532.* Sect, n. 1993. Aldehyde resin is produced when potassa is dissolved in Aldehyde alcohol, and most speedily when the access of air is permitted. It resitl - is to the presence of this substance that the alcoholic solution of po- tassa owes its reddish-brown colour. It is produced also when a solution of potassa in alcohol and acetal is exposed to the air. This is a useful character to enable us to distinguish acetal from acetic ether and other ethereal liquids. All the liquids containing' alde- hyde assume a reddish-brown colour when heated with potassa ; and when diluted with water the resin of aldehyde separates in brown flocks. f 1994. Acetal was obtained by Dobereiner by the following pro- Acetal, cess : Place alcohol of sp. gr. 0.8631 upon a saucer and in the saucer a support, the Process, top of which is raised a few lines above the alcohol ; upon the support place a number of watch-glasses having a quantity of spongy platinum in each. Cover the whole with a bell glass, open above, standing in the saucer so that the va= pours which condense may fall back into the alcohol. The apparatus is left in a place not too cool till the alcohol acquires a very acid taste. The whole is then distilled over carbonate of lime. To the product of this distillation add chloride of calcium in powder, which causes the separation of an ethereal liquor, to which Liebig has given the name of acetal. 1995. Acetal is colourless, and of sp. gr. 0.823 ; it boils at 203° ; Properties, burns with a bright flame, and by the action of spongy platinum is converted into acetic acid. It may be considered as C 4 H 4 -f- * If we consider the vapour as composed of 4 vols- carbon vapour, 4 vols. hydrogen gas, and i vol. oxygen gas, condensed into 2 vols, we have 4 vols. carbon vapour =1.6666 4 “ hydrogen gas =0.2777 1 vol. oxygen =1.1111 2)2-9555 1.4777 = sp. gr. of aldehyde vapour. The vapour then is composed of 4 vols. carbon, 4 vols. hydro- gen and 1 vol. oxygen condensed into 2 vols. It is easy to see how, by means of oxygen, aldehyde is converted with such facility into acetic acid, Acetic acid - - - C 4 H 3 O 3 Aldehyde - - C4H4O2 If, therefore, the oxygen combine with one of the atoms of hydrogen, and convert it into water, while another atom of oxygen replaces the hydrogen, it is obvious that al- dehyde will become acetic acid. Liebig is of opinion that there exists an unknown basis composed of C4 H 3 , to which he has given the name of alde-hyden. The oxide of this basis is C4 H 3 O, and when this oxide is combined with an atom of wa- ter, it constitutes aldehyde, the true formula for which is C4 H 3 0+ HO. Acetic acid is C 4 H 3 O 3 + HO. It is obvious also that aldehyde and alcohol differ from each other merely by the aldehyde containing 2 atoms less hydrogen than alcohol. Alcohol is - - C 4 H6 62 Aldehyde is - - C 4 H 4 O 2 . (Thomson, 304.) f Aldehydic Acid is prepared from aldehyde and oxide of silver, and is composed of Aldeh . C 4 H 4 .O 3 . It differs from acetic acid merely iu containing an additional atom of hy- e y lc aci ‘ drogen. Bromide and Iodide of Aldehyden have been discovered, for which see T. 3^7. t For some other compounds see T. Org\ Bodies, 310. Thomson has given the name of deutocarbohy drogen to olefiant gas, and shown its relation to aldehyden as follows : Aldehyden . . C 4 H 3 Chloride of . . . C 4 H 3 -j- Cl Bromide of “ . . C 4 H 3 + Br 448 Chap. VII. Chloral. Properties, Insoluble chloral. Ethal. Ether. Sulphuric ether. Process. Chloroform. Bromoform. Organic Chemistry — Intermediate Bodies. 1996. Chloral* was discovered by Liebig. It is obtained by passing a current of dry chlorine gas through absolute alcohol. A prodigious quantity of chlorine is necessary and a great deal of hy- drochloric acid is formed.! 1997. It is liquid, colourless, tasteless, of a penetrating odour, and of an oily appearance. It combines with water, sulphur, bromine and iodine ; is decomposed when heated with different earths and metals, metallic chlorides being formed.! 1998. Liebig has given the name of insoluble chloral to the sub- stance formed when chloral is left to the action of concentrated sul- phuric acid at common temperatures. During the conversion of alcohol into chloral, the alcohol loses 5 atoms of hydrogen and gains 3 atoms of chlorine. For every atom of alcohol converted into chlo- ral 10 vols. of hydrochloric acid are formed, and 3 vols of chlorine enter into chemical combination with it. T. 1999. Ethnic C 16 H 17 0, eq. = 121. This substance has been de- scribed by Thomson in this place from its analogy to alcohol and sulphuric ether. It was obtained by Chevreul from spermaceti or cetine. With sulphuric acid it forms sulphocetic acid. 2000. Ether. This name has been given to the light, volatile, inflammable, and fragrant liquids, obtained by distilling in a glass retort a mixture of alcohol and any strong acid. The different kinds of ether have been distinguished by the name of the acid employed in the process. That which is best known is sulphuric ether. 192 To prepare sulphuric ether, equal weights of sulphuric acid and alcohol 0 are exposed to heat in a plain glass retort, pouring in the alcohol first and then the acid by a long glass funnel (Fig. 192;, and adjusting the retort in a sand-bath already heated to the temperature of 200°, in the manner shown in Fig. 193. The acid and the alcohol should be well mixed by shaking them toge- ther in the retort, when the temperature rises considera- bly, and the receiver should be tubulated to convey away the atmospheric arr, and any other gaseous products that may be formed towards the Fig. 193. Iodide of aldehyden Olefiant gas Chloride of deutocarbohydroeen Bromide of “ Iodide of “ Aldehyde Aldehydic acid • Acetic acid C 4 Hs + I C 4 H3 + H C 4 Ha Cl + HC1 C 4 Ha Br + HBr C Hs I + H I C 4 H 3 O -I- HO C 4 Ha Oa + HO C 4 H 3 0 3 + HO Chloroform is obtained by distilling a mixture of alcohol and aqueous solution of bleaching powder, as a limpid fluid of sp. gr. 1.430. It is a compound of 1 atom bi- carhuret of hydrogen with 3 atoms of chlorine. Bromoform is analogous to the last and is obtained when a mixtu-e of bromide of lime and alcohol, or acetone, is distilled. It is an oily looking liquid, heavier than sulphuric acid, and its composition is the same as that of chloroform. * From chlorine and alcohol. + If we employ an avoirdupois pound of alcohol, we shall require 66.453 cubic inches, or almost 38£ cubic feet of chlorine gas, or 48 cubic feet of hydrochloric acid gas. T. t It differs from chloroform by containing two atoms more of carbon and two atoms of oxygen. § From first syllables of ether and alcohol. Ether. 449 close of the operation. The neck of the receiver should fit closely to the neck Sect. I. of the retort, and the joint he rendered tight by tying it round with a piece of linen or cotton cloth spread over with paste made of flour. The bent tube fixed to the tubulure of the receiver should be made to pass into a second receiver, or to dip into a bottle in the manner represented, which is kept cold by placing it in ajar or basin with water or ice ; the tube must not fit tightly to the neck of the bottle, but allow any gas that may come over to be freely disengaged. The first receiver should be tied round with apiece of linen or cotton cloth, that it may be more easily kept cold ; ice or snow should always be used when it can be pro- cured. 2001. The distillation is generally continued till a quantity of liquid has come over equal to one half the alcohol employed. More ether is said to be obtained when it is kept constantly boiling than at a lower temperature, though this has been disputed ; the retort should not be filled more than half full, and great attention must be paid to the heat applied during the whole of the operation, as the mixture is apt to boil over when urged with too strong a fire. 2002. The ether that condenses in the receiver is never obtained pure at first, being always mixed with a little alcohol that distils Purified< over unaltered, and some sulphurous acid. To remove these, it is mixed with potassa, taking five or six grains for every ounce of alco- hol employed, and distilled again from a retort with a very gentle heat till five or six sevenths shall have passed over ; the potassa re- tains the sulphurous acid, along with some water and alcohol. To separate the alcohol completely, it maybe shaken with about three fourths of its bulk of water, which combines with all the alcohol and a little ether. It is then distilled by a very gentle heat, and may be rendered still stronger by distillation from chloride of lime. It should be kept in bottles with well-ground glass stopples. On a small scale, an ounce or two of alcohol with as much sulphuric acid by weight, will be sufficient to show the process, con- densing the product in a common flask.* 2003. Ether is a colourless liquid, of a hot pungent taste and fra- properties, grant odour. It is highly exhilarating, and produces a degree of intoxication when its vapour is inhaled by the nostrils. Its sp. gr. varies with its purity. Lowitz is said to have procured it as light as .632 ; Brande states that he never obtained it lower than *The London Pharmacop. directs the distillation of ether with potassa, for its pu- rification from sulphurous acid; and Phillips has given the following d Sections for gg 1 s 1 8 lhps pr0 ‘ procuring ether for pharmaceutical purposes, which answer extremely well. “ Mix with 16 ounces of sulphuric acid, an equal weight of rectified spirit, and distil about 10 fluid ounces, add 8 ounces of spirit !o the residuum in the retort, and distil about 9 fluid ounces ; or continue the operation until the contents pf the retort begin to rise or the product becomes considerably sulphurous ; mix the two products, and if the mixture consists of a light and heavy fluid, separate them ; add potassa to the lighter, as long as it appears to be dissolved ; separate the ether from the solution of potassa, and distil about nine tenths of it, to be preserved as ether sulphuricus, the specific gravity of which ought to be at most .750.” In the preparation of ether on a large scale considerable risk is incurred by fire, recourse has therefore been had to steam as the source of the requited heat. In the apparatus employed at Apothecaries’ Hall (Lond.) the still is of cast iron, lined with lead ; the steam is conducted through the mixture of acid and alcohol by a contorted leaden pipe at the bottom of the still, and is supplied by a boiler calculated to resist the pressure of 190 lbs. on the square inch ; in this way the mixture is very rapidly raised to its boiling point, and a larger relative quantity of ether is obtained. The boiler is placed in a distant apartment. The condensing apparatus and refrigeratory are of the usual construction, but abundantly supplied with cold water. Brande’s Pharmacy, 456. 57 450 Chap. VII. Volatile. Exp. Boiling point Exp. Exp. Explodes witn oxy- gen, Exp. And with chlorine. Organic Chemistry — Intermediate Bodies. .700 ; as ordinarily prepared, its sp. gr. varies between .730 and .760, and as met with in commerce, it must be considered as a mix- ture of pure ether and alcohol.* * * § 2004. It is extremely volatile, and when poured from one vessel into another, a considerable portion evaporates; during its evapora- tion from surfaces, it produces intense cold, as may be felt by pour- ing it upon the hand ; and seen, by dropping it upon the bulb of a thermometer, which sinks to many degrees below the freezing point. The sp. gr. of the vapour of ether compared with atmospheric air, is, according to Gay-Lussac, as 2.586 to l.OOO.t Two ounce mea- sures of ether converted into gas at the temperature of 72.50 fill the space of a cubic foot. The change may be exhibited by placing a large bell glass filled with hot water on the shelf of the pneumatic trough and passing the ether from a phial up into it. The vapour will fill the jar, and may be fired with suitable precautions. 2005. At mean pressure, sulphuric ether, when of a sp. gr. of .730, boils at 98°, and under the exhausted receiver of an air-pump, at all temperatures above — 20° ; hence, were it not for atmospheric pressure, ether would only be known in the state of vapour. In consequence of the cold produced during the vaporization of sulphuric ether, the phenomena of boiling and freezing may be exhi- bited in the same vessel. For this purpose procure a very thin flask which fits loosely into a wine-glass, as shown in Fig. 194. Pour a small quantity of ether into the flask, and of water into the glass, and place the whole under the receiver of an air-pump ; du- ring exhaustion, the ether will boil, and a crust of ice will gradually form upon the exterior of the flask.t 2006. Ether is highly inflammable, and in con- sequence of its volatility it is often kindled by the mere approach of a burning body; a circumstance which renders it highly dangerous to decant, or open vessels of ether near a candle. § Fig. 194. The inflammability of ethereal vapour may be shown by passing a small quan- tity into a receiver, furnished with a brass stop-cock and pipe, and inverted over water at a temperature of 100°. The receiver becomes filled with the vapour, which ma)i be propelled and inflamed; it burns with a bright bluish-white flame. 2007. When ether is admitted to any gaseous body it increases its bulk. Oxygen thus expanded, produces a highly inflammable mixture ; if the quantity of oxygen be large and of ether small, the mixture is highly explosive, and produces water and carbonic acid. Into a strong two ounce phial, filled with oxygen gas, and wrapped round with a cloth, let fall a drop of ether. On applying the flame of a candle, a violent detonation will ensue. 2008. The vapour of ether also explodes with chlorine, as is shown by the following experiment. * For table of sp. gr. see Henry’s Chem. ii. 333. + 2.5S22, T. and L. t After using ether, air should be drawn through the pump many times to get rid of the ether, as it injures the valves. § In spirit warehouses or druggists’ laboratories where ether is distilled the safety lamp (Fig. 174) may be advantageously used. Chloride of Ethal. 451 Fill a bottle of the capacity of three or four pints, with chlorine gas, taking care Sect. I. to expel the water as completely as possible. Then throw into it about a drachm ^ or a drachm and a half of good ether, covering its mouth immediately with a piece of light wood or paper. In a few seconds white vapour will be seen moving circularly in the bottle, and this will soon be followed by an explosion, accom- panied with flame. At the same time a considerable quantity of carbon will be deposited. When a small quantity of ether is poured into a large jar of warm chlorine, it occasionally happens that a considerable explosion ensues. 2009. Ether freezes at — 46°. When exposed to light in a vessel partially filled, and which is frequently opened, it gradually absorbs oxygen, and a portion of acetic acid is generated. 2010. Ether dissolves the resins, several of the fixed oils, and Dissolves nearly all the volatile oils ; it also dissolves a portion of sulphur, and resins, &c. of phosphorus; the latter solution is beautifully luminous when poured upon warm water in a dark room. The fixed alkalies are not soluble in ether, but it combines with ammonia. It dissolves the oxides of gold and platinum, and these solutions on have been employed for coating steel with those metals, with a view gold and to ornament and as a defence from rust.^ platinum. 2011. When a coil of platinum wire is heated to redness, and then suspended above the surface of ether contained in an open ves- sel (Fig. 53), the wire instantly begins to glow, and continues in that state until all the ether is consumed. During this slow com- bustion, pungent acrid fumes are emitted, which, if* received in a separate vessel, condense into a colourless liquid possessed of acid properties, owing to the formation of acetic acid. 2012. It has been already stated (1567) that sulphuric ether con- Base of sists of C4H5O, and that it possesses the characters of a base, being ether - capable of neutralizing acids, oxygen, chlorine, bromine, iodine, and fluorine. These new compounds are at present very inaccurately termed ethers. The base of ether is C 4 H 5 to which Liebig- has given the name of ethyl . t Common ether is an oxide of ethyl, t 2013. In preparing ether the ebullition is continued till white va- Sweet oil pours appear, and the smell of sulphurous acid is perceived, and by ol wme - continuing the heat a yellowish liquid comes over which has been called the sioeet oil of wineX 2014. Chloride of Ethyl— Hydrochloric Ether. C 4 H 5 C1. This chloride of compound is generated by the action of hydrochloric acid on alcohol, ethyl, and maybe prepared by several processes: — by distilling alcohol previously saturated with hydrochloric acid gas, or mixed with an *If to a saturated solution of gold or platinum, in nitro-hydrochloric acid, there be Ufe of ethereal added about three parts by measure of good sulphuric ether, it soon takes up the me- sotu tals, leaving the acid nearly colourless below the ethereal solution, which is to be c \ carefully decanted off; into this the polished steel is for an instant plunged, and im- mediately afterwards washed in water, or in a weak alkaline solution. Though the coaling of platinum is the least beautiful, Stodardt, who has made many expe- riments upon this subject, considers it as the best protection from rust. Polished brass may be coated by the same process. These surfaces of gold and platinum, though very thin, are often a useful protection ; with gold the experiment is particu- larly beautiful, and well illustrates the astonishing divisibility of the metal. The ethereal solution of gold is not permanent, but, after a time, deposits the metal in the form of a film, in which crystals of gold are often perceptible. t From recent experiments LOwig concludes that by the action of potassium on chloride of ethyl, chloride and ethylide of potassium are formed, and that by the ac- tion of water upon the latter, the ethyle is set tree. Lond. and Edin. Phil. Mag. } July, 1839. t See T. Inorg. Cfiem. ii. 307, and B. ii. 692. 452 Chap. VI T. Properties. Sulphuret of ethyl. Process. Mercaptan. Other ethers. Hydrocyanic ether. Sulphohydric, Chloric ether. Organic Chemistry — Intermediate Bodies. equal volume of strong hydrochloric acid ; by heating a mixture of 5 parts of alcohol, 5 of strong sulphuric acid, and 12 of fused sea- salt in fine powder; or by distilling alcohol with the chlorides of tin, bismuth, antimony, or arsenic. The products are transmitted through tepid water, by which free alcohol and acid are absorbed, and the pure hydrochloric ether is then received in a vessel sur- rounded by ice or a freezing mixture. 2015. Hydrochloric ether is a colourless liquid, of a penetrating, somewhat alliaceous, ethereal odour, and a strong rather sweet taste. It is so volatile that it boils at about 54°. When inflamed, as it issues from a small aperture, it burns with an emerald-green flame without smoke, yielding abundant vapours of hydrochloric acid. 2016. Sulphuret of Ethyl , or Mercaptan. C 4 H 5 S-|-HS. This new substance was discovered by Zeise and named mercaptan , on account of its energetic action on the red oxide of mercury.* Althionate of baryta, lime, or potassa, was heated with a strong solution of protosulphuret of barium. There distilled over along with the water an ethereal liquid, while the althionate was changed into sulphate. 2017. The ethereal liquid was lighter than water, colourless, of a penetrating odour, resembling that of garlic. Its taste was sweet ; it inflamed readily, giving out the odour of sulphurous acid. When distilled it was divided into two distinct liquids. To the first the name of thialic ether was given, and to the second mercaptan. 2018. Mercaptan acts with force upon potassium, hydrogen gas being evolved and the metal converted into a colourless salt, very soluble in water and in alcohol. These solutions give a yellow pre- cipitate, with acetate and nitrate of mercury.! There are six bodies to which the term ether has been applied, but which are not considered such by Thomson, by whom they have been constituted a distinct class, having for their base not C 4 H S but C 4 H 4 (the tetartO’Carbo-hydrogen of Thomson), they are 1 Light oil of wine . . C 4 Hi 2 Chloric ether • • . . C 4 H 4 +Cl 2 t 3 Bromic “ . . . . C 4 Hi + Bnj 4 Iodic " . . . Ci Hi -f- I 2 5 Acetal “ . . Ci H 4 + H£0 C Sulphocyanic The third set of bodies classed among the ethers, consists of che- mical compounds of sulphuric ether and an acid. Of these Thomson enumerates twenty, for which see Org. Bodies , 329. * Ann. de Chim. et de Phys. lvi. 87. t Cyanodidc of Ethyl — Hydrocyanic Ether , C 4 Ho(C 2 N), was discovered by Pelouze, and is obtained by heating a mixture of equal parts of cyanodide of potassium and althionate of baryta. Sulphohydric Ether, CiHs(HS) ? was formed by Lowig by the action of oxalic ether and sulphuret of potassium. It has no action on red oxide of mercury, and by this character is distinguished from mercaptan. See T* Org. Bodies , 328. t Chloric Ether is the name which has been applied to a liquid obtained by distilling a gallon from a mixture of three pounds of chloride of lime and two gallons of alcohol, sp. gr. 0 844, and rectifying the product. This was discovered by Guthrie in the United States and Souberain in France. See Guthrie’s account in Amer. Jour. xxi. As this liquid does not contain chloric acid, Bache has proposed for it the name of chlorine ether. It is extremely volatile, of a sweetish taste, boiling at 166°, and having the sp. gr. of 1.486. VVhen diluted with water it is employed as a diffusible stimulant. Oxalic Ether . 453 2019. Nitric ether. Nitrous ether ; G 4 H 5 O+NO 3 . Various sect. 1. processes are given for obtaining this liquid it is produced by the Thomson’s action of equal weights of nitric acid and alcohol, the acid being 3d set. added in small successive quantities to the alcohol, and the mixture Nitric cooled after each addition, to prevent the violent action that would e otherwise ensue. It collects on the surface of the mixture and is cautiously withdrawn. 1. Fig. (195) represents an arrangement proposed by Torrey — a a Woulfe’s bottle, b a receiver, e e glass fun- nels ground to the necks, and glass rods ground to the funnels, the acid being in one funnel, and the alcohol in the other ; by means of the glass rods the admis- sion of either is regulated at pleasure. 2. Introduce into a sufficiently capacious retort equal weights of alcohol, (specific gravity 820) and of nitric acid of commerce (specific gravity 1 30) and connect it with five Woulfe’s bottles, the first of which is empty and the remaining four half filled with a satu- rated solution of salt in water. Apply a gentle heat to the retort, till the liquor begins to effervesce; then withdraw the fire, and the gaseous matter passing through the bottles, which should be kept cold by ice, deposits the ether upon the saline solution, from which it is to be decanted, shaken with chalk, and re- distilled at a very gentle heat.t 2020. In all experiments with nitric acid and alcohol, great care Caution, must be taken not to mix a large quantity of acid with the alcohol at once, as the gaseous products that are immediately produced are apt to throw out the whole of the mixture with explosive violence.! Nitrogen, protoxide and binoxide of nitrogen, and carbonic acid gases are disengaged. 2021 . The nitrous agrees with sulphuric ether in its leading pro- perties; but it is still more yolatile. When recently distilled from quicklime by a gentle heat, it is quite neutral ; but it soon becomes acid by keeping. It is decomposed by potassa, and, on evaporation, crystals Qf the nitrite or hyponitrite of that alkali are deposited (Mem. d’Arcueil, i.) It is soluble in 48 parts of water, and in all proportions in alcohol ; this last solution is the spiritus cetheris nitrici , Sweet or sweet spirit of nitre of the Pharmacopoeia.^ s P ir ^ °f 2022. Oxalic ether. C 4 H 5 0 -f-C 203 . Is obtained from 1 part of™* * * § ^ alcohol, 1 binoxalate of potassa, and 2 parts of sulphuric acid. It ether, is purified by boiling with pounded litharge. It is an oleaginous liquid, boiling at 263°. When a current of dry ammoniacal gas is passed over it a substance is obtained which has been called by Du- mas || oxamethane .IF * Thomson’s Inorg . Chem. 318- t See description of an apparatus for this process by Hare, in Am. Jour. vol. ii. p. 326 and xxxiii. 241. t Though a small quantity of acid may be added to a large quantity of alcohol without much action, a small quantity of alcohol cannot be added to a large quantity of acid without violent action. § Two lb. of nitrate of potassa and a lb. and a half of sulphuric acid are mixed in a Proceai for glass retort, 9 and a half lbs. of alcohol are gradually poured in ; it is digested with a gentle heat for two hours, the heat is then raised and a gallon distilled off; to this I pint of diluted alcohol and an ounce of carbonate of potassa are added and a gallon distilled off. U.S. P- |j Ann. de. Chim. et de Phys. liv. 241, and Ann. de Pharm. ix. 129. IT Etheroxalate of Potassa. It was shown by Leibig that oxalic ether has the pro- Prepara- tion. 454 Chap. VII. iEnanthic ether. Properties. Thomson’s 4th set. Pyroxylic spirit. Properties. Action of platinum sponge. Action of sulphuric acid. Etheroxalate of pola*sa. Used as a sol- vent, &o. Organic Chemistry — Intermediate Bodies. 2023. (Enantkic ether. C 4 H 5 0 -j-C 1 4 H 1 30 2 . It is to this remarka- ble ether that the peculiar odour of wines is owing.* * When large quantities of wine are distilled we obtain, at the end of the process a small quantity of an oily liquid. The same liquid is obtained when the lees of wine are distilled ; 2024. It has a strong taste, is usually colourless, and is a mix- ture of cenanthic ether with an excess of cenanthic acid. The ether is separated by distillation. It is very liquid, has a strong odour of wine and produces intoxication when inspired. t 2025. The fourth set of bodies, which have by some been classed among ethers , are certain acidulous salts, consisting of 1 atom of ether united to 2 atoms of an acid. They are 1 Heavy oil of wine 2 Althionic acid 3 Phosphovinic acid 4 Oxalovinic acid - 5 Tartrovinic acid - 6 Racemovinic acid 7 Camphovinic acid 2026. Pyroxylic spirit. C 4 H 5 (Hft0l)+S0 3 C 4 H 5 Q+2(S0 3 )+HO C 4 H 5 0+2(P0 2 4) C 4 H 5 0+2(C 2 0 3 )+H0 C 4 H 5 0+2(C 4 H 2 0 5 )+HO C 4 H 5 0+2(C 4 H ,0 5 )+H0 C 4 H 5 O+atC.cHfiO 5 )+HO C.»H 3 0-|-H0=32. This name has been given to the volatile liquid which is formed when wood is subjected to heat, and which is found in the aqueous liquid which comes over. This is decanted off to separate it from the tar, and when again dis- tilled the pyroxylic spirit is in the first tenth part of the product. It is rectified over quicklime. 2027. Pyroxylic spirit is colourless, and has a peculiar odour, alcoholic and aromatic mixed with that of acetic ether. It boils at 150°, its sp. gr. is .798 not differing much from alcohol. t 202S. When its vapour is mixed with air in contact with plati- num sponge, heat is evolved and formic acid produced. If allowed to fall drop by drop on the spongy platinum, it burns and carbonic acid is produced. Its vapour explodes with dry chlorine. Distilled with chloride of calcium it gives rise to chloroform. 2029. When a mixture of 1 part of pyroxylic spirit and 4 parts of concentrated sulphuric acid is distilled, a gas comes over, which possesses the constitution of alcohol vapour. The very same thing takes place in this distillation as when we heat a mixture of alcohol and sulphuric acid. One half the water is abstracted relative to the perty of combining with bases like an acid, and this salt is obtained when oxalic ether is dissolved in absolute alcohol and as much hydrate of potassa is added as is just sufficient to neutralize half the oxalic acid. Lehrbuch der chim. 2 Aufl. i. 644. * Ann. dc Chim. et de Phys. lxiii. 113. + For the other ethers of this division see T. Org. Bodies , 333. t Pyroxylic spirit is extensively used by hat makers, for the purpose of dissolving shell lac and mastic to stiffen hats and render them water proof. According to Scan- lan a fluid of higher sp. gr. and lower boiling point is oblained by distillation by sa- turating the purified acid with slacked lime, and subsequent distillation as longas the product is of less sp. gr. than water. This product is rectified in a still, consisting of a boiler and rectifier of copper of peculiar construction placed in a bath of w r ater, and kept at such a temperature as will condense water, but retain the more volatile pro- ducts in the slate of vapour till they pass the last part of the apparatus where they are cooled. See Rep. Brit. Assoc. 1835, 40. Colouring Matters . 455 other ingredient, the carbohydrogen.* * * § ** When alcohol is used olefiant Sect, r, gasf is converted into ether ; but when pyroxylic spirit is used, the compound is C 2 H 3 0, or it contains an atom of olefiant gas less than ether.l 2030. When pyroxylic spirit is made to act on the hydracids, a Action on set of compounds is formed very analogous to the ethers which the hydracids. same acids form with alcohol. Dumas and Peligot consider them as compounds of the hydracid and a base which they term methy- lene. § CHAPTER VIII. Section I. Colouring Matters. 2031. A great number of vegetable principles are comprised under the term colouring matter, and are extensively employed in the processes of dyeing and calioo-printing.H 2032. Some of these are used as chemical re-agents and for test- ing the presence of acids and alkalies. The infusion of red cabbage has been already described (56 n.) ; the colouring matter of violets may be used for the same purpose. 2033. Litmus is the blue colouring matter prepared from the lichen rocella which grows in the Canary islands, and the leconora tartarea Litmus * which is collected in Norway. From the latter is also prepared cudbear?* the colour being developed by the aid of ammonia. The colouring matter of the leconora has been termed erythrin , and that of archil orcin. 2034. Litmus is more easily affected by acids than the colouring Effect of . matter of cabbage, but is not turned to a green by alkalies. If pre- ac id s and viously reddened by acids, it may be used for detecting alkalies, the alkalies, original blue tint being restored. ft * Carbo-hydrogen is the name applied by Thomson to the gas evolved when pyroxy- lic spirit is treated with aqua regia, it is composed of 1 vol. of carbon vapour and 1 vol. of hydrogen gas. t Deutocarbohydrogen of T. t This is the same thing in both cases as abstracting one half of the water which the spirit contained. But in reality Alcohol is . . . . C< H 5 O + H O While this gas is . . , C 2 H 2 H O T. 350. § For details see T. Orff. Bodies , 350. || Acetone. C 3 H 3 O. This name is given to what was termed pyro-aceiic spirit, and Acetone which is obtained by heating several acetates. It is a transparent, volatile and in- ce on ®‘ flammable liquid, entering into combination with water, alcohol, ether and some vola- tile oils. Mesite is a product of the distillation of wood named from ysairrjs a mediator. 5T For a more particular description of the various colouring matters, and of the pro- cesses followed for their extraction and fixation, constituting the art of dyeing, the student must be referred to Thomson’s Orffanic Chemistry , 367. Ure’s Diet, of Arts and Manyf. Berthollet on Dyeing , and Thomson on Calico-printing in Records of General Science, Vols. i. ii. iii. ** First called Cuthhert from Dr.Cuthbert Gordon who first made it. tt To prepare test papers, rub some good litmus with hot water in a mortar, pour . the mixture into an evaporating basin, and add pure water until the proportion is about u7t P papef« n ° half a pint for each ounce of litmus. Cover it up and keep warm for an hour, then 456 Colouring Matters. Chap, vni. 2035. Turmeric is the root of the curcuma longa, a plant grow- Turmeric. ing in the East Indies. It is yellow and its colouring matter has been called cur cumin ; it is imparted to boiling alcohol and sepa- rated by ether from which it is obtained by distillation. It is changed to brown by alkalies and some neutral salts. 2036. Many colouring giatters have a great attraction for metallic oxides, combining with tham when they are separated from solutions in which both the colouring matter and the oxides have been pre- viously dissolved ; thus when potassa is added to a solution contain- ing hydrochlorate of tin and litmus, the potassa unites with the hy- drochloric acid, litmus and oxide of tin falling down in combination. Lakes. The precipitates thus obtained are called lakes. 2037. On this property are founded many of the processes in Dyeing. dyeing and calico-printing. The art of the dyer consists in giving a uniform and permanent colour to cloth. This is sometimes effect- ed merely by immersing the cloth in the coloured solution ; where- as in other instances the affinity between the colour and the fibre of the cloth is so slight, that it only receives a stain which is re- moved by washing with water. In this case some third substance is requisite, which has an affinity both for the cloth and colouring matter, and which, by combining at the same time with each, may cause the dye to be permanent. A substance of this kind was for- Mordants. merly called a mordant ; but the term basis , introduced by Henry is now more generally employed. The most important bases, and indeed the only ones in common use, are alumina, oxide of iron, and oxide of tin. The two former are exhibited in combination either with the sulphuric or acetic acid, and the latter most commonly as the chloride. Substantive 2038. Substantive colouring matters include those which have so colours, strong an attraction for cloth, that they can attach themselves to it permanently, and without the action of any other substance, as indigo. Adjective. Those which require a mordant are termed adjective colouring matters. Bleaching. 2039. Colouring matters are bleached by chlorine, which is usually employed in union with lime (901) ; sulphurous and some other acids are also used to remove colour. Red dyes, 2040. For red dyes , Brazil wood, lac, archil, madder and cochi- neal, are the principal colouring matters in common use. The cochi- neal, is procured from an insect, which is believed to derive its colouring matter from a particular vegetable principle upon which it feeds. decant the clear liquor, and poor fresh hot water uprn the residue. Cover up and keep- warm as before, evaporate. These operations are to be repeated until all the colour is removed. The first solution is to be kept apart from the second and third, which may be mixed and reduced by evaporation until a piece of filtering paper dipped in ana dried is of a blue colour. Paper is then to he dipped into the solution ; it should he bibulous and not sized. The solution should be poured into a dish and the paper be drawn through it piece by piece, be drained, and dried where no acid fumes or those of burning charcoal can have access to it. As soon as dry the paper should be placed in a well closed tin box. The tint ought to be a pure blue, and can be judged of by applying a drop of very weak acid which should produce a vivid red. Turmeric pa- per is prepared in a similar manner. See Faraday’s Chem. Manip. 272. 457 Indigo — Cerulin . 2041. Yellow dyes are procured principally from saffron, hiccory, Sect. J - quercitron bark, turmeric, fustic and annatto. Yellow, 2042. Black dyes are made with the same materials as writing Black, ink, logwood and madder are also employed with oxide of iron. 2043. Blue dyes are commonly prepared with Prussian blue or Blue, indigo. Three different colouring principles have been detected in indigo, indigo blue , indigo red and indigo brown . It is obtained from an American and Asiatic plant the Indigofcra, and the Ne- rium tinctorium ; an inferior sort is prepared from the Isatis tinctoria or wood, a native of Europe. 2044. Indigo C 16 H 5 N0 2 as it occurs in commerce, is far from being Indigo, pure, more than half its weight consisting of matter destitute of a blue colour and incapable of being used as a dye stuff. Part of these impurities may be dissolved by water, part by alcohol, and part by dilute acids and by alkaline leys. 2045. The best way of obtaining pure indigo, is from the calico-printers’ Obtained vat, in which the indigo has been deprived of its blue colour by sulphate of iron pure, and is held in solution by means of lime water. The colour of this solution is yel- low. If a quantity of it be put into an open vessel it absorbs oxygen from the atmosphere and the indigo precipitates of a blue colour. If the precipitate be digested in hydro-chloric acid, washed and dried, it is pure indigo. 2046. Indigo sublimes in long flat needles at about 550°, its va- Sublimed pour is transparent and reddish violet. It melts and is decomposed indigo- at nearly the same temperature. The sp. gr. of sublimed indigo is 1.35. 2047. It is insoluble in water, but soluble in sulphuric acid, the Solubility, indigo being changed into what has been termed cerulin.* It is de- &c - composed by nitric acid, with the formation of indigotic and carba- zotic acids. 2048. When treated with something capable of abstracting oxy- Action of gen, it assumes a white or yellowish-white colour, and becomes solu- substance^ ble in the different bases. This white substance has been called by Liebig indigo gen, it does not alter by exposure to dry air, but when indigogen. placed under water assumes a deep-blue colour and acquires a cop- pery tint when dried. It dissolves in alkalies, but does not neu- tralize them. It is soluble in alcohol, but insoluble in acids and water. Fill one leg of a syphon with a solution of indigogen in lime water, and the Exp. other leg with hydrochloric acid, the indigogen will separate in white flocks. Substitute nitric acid for hydrochloric, the precipitate will become blue and gra- dually disappear. Make a solution of indigogen in lime water, pass oxygen gas into it, it will be E X p. absorbed and indigo be reproduced and precipitated. 2049. Cerulin is precipitated from the solution in sulphuric acid cerulin. by any salt of potassa formin g ceruleo-sulyhate of potassa, of so deep a blue colour that when moist it appears black. Water in a wine glass containing °f its weight of it is distinctly blue.t 2050. According to Crum if the action of sulphuric acid on indi- ph e ni c in go be stopped at a certain point a new substance is formed possess- * Saxon blue • + According to Berzelius when indigo is dissolved in sulphuric acid, two new acids are formed hypo-sulpho-indigotic and sulpho -indigotic. 58 458 Chap fX. Uses of in- digo. Different tints produ- ced. Anotta. Saffron. Chlor- ophyllite. Chromule. Oils, their characters, Zunthin. Carthamin. Organic Chemistry — Oleaginous Substances. in g rather singular properties. It is formed at the instant indigo changes from yellow to blue; Crum has called this phenicin* * * § 2051. Indigo is used for dyeing woollen, silk, linen and cotton blue. To enable it to combine with the cloth, it must be in a state of solution and this state is induced in two ways. I. The indigo is deprived of its oxygen, and reduced to the state of indigogen ; this combines with alkalies and forms a compound soluble in water. 2. The indigo is dissolved in sulphuric acid, as in dyeing Saxon blue.! T - 2052. By combining red, yellow, blue or black colouring matters, all other tints may be produced, and by varying the strength of the colouring matter, or the strength of the mordant, different shades of the same colour may be had.t 2053. Anotta or Rocou is a name given to the pulp of the seeds of the bixa orellena a South American shrub. It dissolves in small quantity in water, better in alcohol, and the solution is orange yel- low. It is often adulterated with powder of bricks, &c. ; the fraud is detected by exposing anotta, previously dried at 212°, to a red heat till it is quite burnt. If the anotta be pure the residual matter will not exceed 13 per cent. ; all over that is adulteration. § 2054. Saffron consists of the dried stigmas of the crocus sativus. The colouring matter is termed polychroite on account of the nume- rous colours which it is capable of assuming. It is obtained from the watery infusion of saffron by evaporation, digestion of the resi- duum in alcohol and evaporation. 2055. Chlorophyllite&v Chr'omulite is the term applied to the green colouring matter of vegetables ; in the autumn it is reddened by the production of acid. 2056. Chromule is the name given to the various coloured prin- ciples obtained from the leaves and flowers of plants. CHAPTER IX. Section I. Oleaginous Substances. 2057. Oils are characterized by a peculiar unctuous feel, by in- flammability and by insolubility in water. They have been divided into fixed and volatile oils, the former being comparatively fixed in the fire and giving a permanent greasy stain to paper, while the lat- ter, owing to their volatility produce a stain which disappears by gentle heat. * Ann. Philos. 2 d series, v. 95. Berzelius calls it the purple of indigo. TraiUde Chim. vi. 98. t For details see T. Org. Bodies , 381. t Zanthin is obtained from madder and is yellow ; the other coloupng principle of this root is alizarin and is red. Carthamin is the red colouring matter of safflower. From this rouge is prepared, the carthamin being ground with talc. Hoematin is the colouring matter of logwood 5 Brezilin of Brazil wood ; Santalin of Red sanders. § Jour, de Pharm. xxii. 101 . H*matin. Fixed Oils . 459 2058. There seems little reason to doubt that the fixed oils con- Sect, i. stitute, in reality, salts, or rather each oil is a mixture of two or more salts, if the term salt can be applied to the compounds of the oily acids with glycerin, which acts the part of a base. T, 427. 2059. The fixed oils are usually contained in the seeds of plants, Fixed, as for example in the almond, linseed, rape-seed, and poppy-seed ; but olive oil is extracted from the pulp which surrounds the stone. Obtained, They are procured by bruising the seed, and subjecting the pulpy matter to pressure in hempen bags, a gentle heat being generally employed at the same time to render the oil more limpid. 2060. Fixed oils are nearly inodorous, have little taste, and are Properties, lighter than water, their density in general varying from 0.9 to 0.96. Some, such as cocoa-nut and palm-oil, are fixed at 50° or 60 ; but most of them are fluid at common temperatures, and they all be- come limpid in becoming warm. They are commonly of a yellow colour, but may be rendered nearly or quite colourless by the action of animal charcoal. At or near 600° they begin to boil, but suffer partial decomposition at the same time, an inflammable vapour being disengaged even below 500°. When heated to redness in close vessels, a large quantity of the combustible compounds of car- bon and hydrogen is formed, together with the other products of the destructive distillation of vegetable substances ; and in the open air they burn with a clear white light, and formation of water and carbonic acid. They may hence be employed for the purposes of artificial illumination, as well in lamps, as for the manufacture of gas. 2061. By exposure to the air they absorb oxygen, become rancid Effect of and sometimes assume a waxy consistence. Some few, such as lin- air - seed, and nut-oil, and the oils of the poppy and hemp-seed become covered with a pellicle, and when thinly spread upon a surface, in- stead of remaining greasy, become hard and resinous ; these are termed drying oils, and their drying quality is much improved by Dryingoils. boiling them upon a small quantity of litharge.* 2062. The absorption of oxygen by fixed, and especially by dry- Spontane- ing oils, is under some circumstances so abundant and rapid, and °us com- accompanied with so much heat, that- light porous combustible mate- ustl0a ‘ rials, such as lampblack, hemp, or cotton-wool, may be kindled by it. Substances of this kind, moistened with linseed-oil, have been known to take fire during the space of 24 hours, a circumstance which has repeatedly been the cause of extensive fires in warehouses and in cotton manufactories. 2063. Nitric acid acts with great energy on the fixed oils. In a Actinn 0 f small proportion, its chief effect is to render them thicker. Red and nitric acid, smoking nitric acid, when suddenly mixed with a fixed oil, especially with the addition of a little sulphuric acid, occasions a violent com- * The drying oils, and especially nut-oil, form the basis of printer's ink, the history Printers » ink . of which will he found in Lewis’s Phil. Commerce of the Arts. The oil is heated and set fire to, and after having been suffered to burn for half an hour is extinguished, and boiled till it acquires a due consistency 3 in this state it is called Varnish,, and is viscid, tenacious, and easily miscible with fresh oil, or with oil of turpentine, by which it is properly thinned, and afterwards mixed with rosin, soap, and lamp-black. See also Ure’s Diet. Arts and Manuf. 1031. 460 Organic Chemistry — Oleaginous Substances. Cha P- IX - bustion. Chlorine gas, passed through them, thickens them, and ren- ders them tenacious like wax. Effect °f 2064. Fixed oils are converted into a peculiar kind of acids* and & c a 1GS ’ glycerin when heated with the fixed alkalies and water. The acids uniting with the alkali constitute soap, the glycerin remains in solu- tion. The acids are the margaric, stearic and oleic. Stearine 2065. The researches of Chevreul on the nature of oils and fats and Oleine, have shown that these bodies are compounds of at least two other compounds, one of which is solid at common temperatures, while the other is fluid. To the former he applied the name of stearine, from areaQ suet, and to the latter elaine or oleine , from elaiov oil. Oleine is the fluid principle of oils, and gives fluidity to those oils in which it predominates. It requires a cold of 20° for congelation, and is prepared from oils by exposing them to a cold of about 25°, and pressing the congealed mass between folds of bibulous paper ; when the oleine is absorbed, and may be separated by pressing the paper under water. Oleine is well adapted for lubricating the wheels of watches or other delicate machinery, since it does not thicken or become rancid by exposure to the air.t Croton oil. 2066. Croton oil, is obtained from the seeds of the croton tiglium , a tree growing in the East Indies. It is yellow, of an acrid taste, soluble in alcohol and ether. Its purgative qualities are owing to a portion of crotonic acid dissolved in the oil. A single drop generally acts as a purgative. Olive oil. 2067. Olive oil is expressed from the pericarpium of the fruit of the olea europea, or common olive. Its sp. gr. at 77° is .9109, it congeals at 36° depositing little spheres of stearin. Action of 2068. By the action of hyponitrous acid on olive oil a solid is hyponitrous formed which has been called elaidin ; it is saponified by potassa or soda, glycerin being evolved and a fatty acid which combines with the alkali and forms soap. The acid has been called the elaidic acid. Palm oil. 2069. Palm oil is one of the solid oils and is extracted from the cocos butyracece ; it is yellow and has the consistence of lard. It is said to be composed of stearine 31, elaine 69. It is used in the manufacture of yellow soap. Cocoa oil. 2070. Cocoa nut oil is white and hard, and contains both elaine and stearin. It is used as a substitute for tallow. The stearin is used as a substitute for wax in the manufacture of candles. Wax. 2071. Wax differs from the solid vegetable oils in its consistence and in the way in which it combines with alkalies ; but it resem- bles them so much that an accurate line of separation cannot be drawn. Beeswax. 2072. Bee's wax, though an animal production, agrees so closely with wax from plants, that it would be improper to separate them. It is an exudation from the rings in the abdomen of bees. * See Oily Acids. t The watchmakers purify olive oil, by plaeing it in a phial along with a plate of lead ; after being corked it is exposed in a window to the direct rays of the sun. A cheesy matter separates, the oil loses its colour and becomes limpid. The clear oil is poured off and kept for use. Volatile Oils . 461 2073. Yellow wax is purified by fusion in water and casting into Sect, n. thin ribbons which are exposed to light and moisture by which it is Purified, bleached. When pure it has no taste or smell, unbleached wax fuses at 142°, if bleached, at 155° ; the sp. gr. of the former is about .9600, of the latter .8203. It is insoluble in water, but soluble in boiling alcohol. 2074. Bee’s wax has been stated to contain two distinct kinds of Cerin and wax, called cerin and myricin M Cerin is soluble in fixed and vola- m Y ricln - tile oils, insoluble in water, cold alcohol and ether, and of the con- sistence of wax. It unites with caustic alkalies and forms a soap. It fuses at 143£°. 2075. Myricin fuses at 149°, at common temperatures is insoluble in alcohol. It cannot be converted into soap by caustic potassa. According to .Hess 100 parts of wax are composed of Hydrogen, - 12.95 Carbon ------ 79.77 Oxygen ------ 7.33* 3076. Myrtle wax is obtained from the myrica cerifera , a shrub M t j e that is common in the United States. The wax is separated from W ax. the berries by means of hot water.! 2077. Galactin , or cow-tree wax exists in the milk of the cow tree Galactoderdron utile , a large tree resembling the fig, which grows in South America. Section II. Volatile Oils. 2078. The volatile oils may be divided into three sets ; 1. Those volatile that contain only carbon and hydrogen ; they are lighter than water, oils, and seem to have the property of combining in definite proportions with acids. Hence they are probably bases or analogous to bases. 2. Those that contain carbon, hydrogen and oxygen. They are pro- bably as heavy, or heavier than water, and seem to have the pro- perty of combining in definite proportions with bases, and are, there- fore, analogous to acids. 3. Vesicating oils. They contain sulphur, and probably also nitrogen. 2079. These oils are generally obtained by distilling the plants which afford them with water in common stills ; the water and oil pass over together, and are collected in the Italian recipient shown in Fig. 196, in which the water ha- ving reached the level a b , runs off by the pipe c, and the oil being generally lighter than water, floats upon its surface in the space d. The whole contents of the recipient are then poured into a funnel, the tube of which is closed with the finger, and when the oil has collected upon the surface, the water is suffered to run from it, and the oil transferred into a bottle. The distilled water being saturated with the oil, should be retained for a repetition of the distillation. The produce of oil is sometimes increased, by adding salt to the water in the still, so as to elevate its boiling point a few degrees. * According to late experiments of Hess bee’s wax when pure, is always of the same constitution, but by oxidation is converted into an acid. t According to Ettling’s analysis, cerin, myricin and cerain are isomeric bodies, and composed of C 18 H 19 O. t See Dana's analysis, Amec. Jour. 1. 294. Fig. 196. How ob- tained. 462 Chap IX. Properties. Adultera- tion. Exp. Oil of tur- pentine. Action of hydrochlo- ric acid. Boiling point. Organic Chemistry — Oleaginous Substances. Some of the volatile oils are obtained by expression, such as those of lemon , orange , and bergamot , which are contained in distinct ve- sicles in the rind of those fruits. 2080. The volatile oils vary considerably in specific gravity, as will be seen by referring to the Tables. The volatile oils have a penetrating odour and taste, and are gene- rally of a yellowish colour ; they are for the most part very soluble in alcohol, and very sparingly soluble in water ; these solutions con- stitute perfumed essences and distilled waters. The latter are princi- pally employed in pharmacy, and the former as perfumes. When pure they pass into vapour at a temperature somewhat below that of 212°, when distilled with water, they pass over at its boiling point. They are inflammable, and water and carbonic acid are the results of their perfect combustion. As many.of these oils bear a very high price, they are not unfrequently adulterated with alcohol and fixed oils. The former addition is rendered evident by the action of water ; the latter by the greasy spot which they leave on paper, and which does not evaporate when gently heated. 2081. Nitric and sulphuric acids rapidly decompose the volatile oils. A mixture of four parts of nitric, and one of sulphuric acid, poured into a small quantity of oil of turpentine, produces instant inflammation. 2082. The relative quantity of essential oils, furnished from dif- ferent materials, is liable to much variation ; the products of 1 cwt. of the different vegetable substances are given below.* 2083. Oil of turpentine is obtained from turpentine, a viscid, transparent, semifluid substance, which exudes from various species of the genus pinus. Common turpentine of the shops flows by inci- sion from the pinus abies and pinus sylvestris. To obtain the vola- tile oil, called oil of turpentine, the turpentine is mixed with water and distilled. The oil comes over with the water, and the residue is common rosin. • 2084. Oil of turpentine absorbs a large quantity of hydrochloric acid, and forms a crystallizable substance resembling camphor. From the analysis of artificial camphor it is probable that pure oil of turpentine is C 20 H 16 . 20S5. Oil of turpentine begins to boil at 313° ; if the ebullition is continued the temperature rises to 350°, or even higher, showing the presence of more than one volatile oil. The sp. gr. of its vapour at 313° is 4.83 air = 1. * Juniper berries (common) Ounces. 4 to 5 Dilto (fine Italian) . . 7 to 8 Aniseed (common) . 32 to 36 Ditto (finest) . . 36 to 38 Caraways . from tbs. 3 oz. lbs. oz. 12 to 4 12 Dill seed from 2 to 2 6 Cloves from 18 to 20 Pimento from 2 to 3 4 Fennel-seed . 2 Leaves of the Juniperus Sabina 14 Resins ... 463 2086. It takes fire in chlorine, giving out much smoke. It dis- Sect.n._ solves iodine.^ 20S7. Camphors. The term camphor has been applied by apo- Camphors, thecaries to various solid bodies, which occasionally appear in vola- tile oils. They are distinguished by their great volatility, a strong and peculiar smell, by melting when heated, and burning brilliantly when held to a lighted candle. 2088. Common Camphor. C^HgOi. In its ordinary state it is Common white, semi-transparent, and concrete. Its specific gravity .9887. It cam ph° r - fuses at about 300°, in close vessels. It dissolves in the fixed and volatile oils and in alcohol. It is scarcely acted upon by the alka- lies ; some of the acids dissolve, others decompose it. The camphor of commerce is obtained from the Laurus Camphora , and comes chiefly from Japan. It is originally separated by distil- lation, and subsequently purified in a subliming vessel somewhat of the shape of a turnip, from which the cakes of camphor derive their form. When slowly sublimed it crystallizes in octohedrons or in six- sided pyramids. 2089. The analysis of camphor by Dumas gave carbon 78.02, hy- Composi- drogen 10.39, oxygen 11.59. tion. 2090. Camphrone was discovered in 1835 by Fremy, bypassing Camph- fragments of camphor into a porcelain tube, heated to redness, and rone * containing lime. It is a slightly coloured liquid, having the odour of camphor. It boils at 167°. 2091. Dumas distinguishes by the name camphogene , what he Campho- considers as the basis of camphor. It is a volatile oil composed of 10 gene ’ atoms carbon and 8 atoms hydrogen. It may be extracted pure from artificial camphor. Camphor consists of an integrant particle of camphogene and an atom of oxygen. t 2092. Resins. Resins are the inspissated juices of plants, and Resins, commonly occur either pure or in combination with an essential oil. They are solid at common temperatures, brittle, inodorous, and insi- pid. They are non-conductors of electricity’', and when rubbed be- come negatively electric. They are generally of a yellow colour, and semi-transparent. 2093. Resins are fused by the application of heat, and by a still higher temperature are decomposed. In close vessels they yield em- pyreumatic oil, and a large quantity of carburetted hydrogen, a small residue of charcoal remaining. In the open air they burn with a yellow flame and much smoke, being resolved into carbonic acid and water. 2094. Resins are dissolved by alcohol, ether, and the essential Solvents of. oils, and the alcoholic and ethereal solutions are precipitated by wa- ter, a fluid in which they are quite insoluble. Their best solvent is pure potassa and soda, and they are also soluble in the alkaline * The volatile oils are very numerous ; many of them have been described by Thom- son, but there are many not yet described. Raybaut of Paris has given a table of no fewer than 207 volatile oils prepared by himself, with the names of the plants from which they were obtained, and the quantity from a given weight of the plant, in the Jour . de Pharm. xx. 444. See T. Organic Bodies, 459. t For description of camphors from oil of peppermint and other essential oils, see T. Org. Bodies , 493. 464 Chap. IX Uses. Tar and pitch. Balsams. Venice tur- pentine. Copaiva. Properties. Organic Chemistry — Balsams . carbonates by the aid of heat. The product is in each case a soapy compound, which is decomposed by an acid. Concentrated sulphuric acid dissolves resins ; but the acid and the resin mutually decompose each other, with disengagement of sulphu- rous acid, and deposition of charcoal. Nitric acid acts upon them with violence. 2095. The uses of resin are various. Melted with wax and oil, resins constitute ointments and plasters. Combined with oil or alcohol, they form different kinds of oil and spirit varnish. Sealing wax is composed of lac, Venice turpentine, and common resin. The composition is coloured black by means of lampblack, or red by cin- nabar or red lead. Lampblack is the soot of imperfectly burned resin. Of the different resins the most important are common rosin, copal, lac, sandarach, mastich, elemi, and dragon’s blood. 2096. When turpentine is extracted from the wood of the fir-tree by heat, partial decomposition ensues, and a dark substance, consist- ing of resin, empyreumatic oil, and acetic acid is the product. This constitutes tar ; and when inspissated by boiling, it forms pitch. Common resin fuses at 276°, is completely liquid at 306°, and at about 316°, bubbles of gaseous matter escape, giving rise to the ap- pearance of ebullition. By distillation it yields empyreumatic oils : in the first part of the process a limpid oil passes over, which rises in vapour at 300°, and boils at 360° ; but subsequently the product be- comes less and less limpid, till towards the close it is very thick. This matter becomes limpid when heat is applied, and boils at about 500° F. At a red heat resin is entirely decomposed, yielding a large quantity of combustible gas, which has been employed for the pur- pose of artificial illumination. * 2097. Balsams. These are semi-fluid resins containing a volatile oil, which may, in general, be separated by distillation, leaving the solid resin. In this division Thomson includes turpentine in which the oil is united with two resins, which Unverdoben has distin- guished by the names pinic and silvic acids , and Berzelius by the terms resin alpha and resin beta. The oil varies from 5 to 25 per cent., as do the resins also. 2098. Venice turpentine is extracted from the pinus larix , or com- mon larch. It is limpid, of a light yellow colour, and of the consis- tence of honey. It contains from IS to 25 per cent, of oil of turpen- tine, what remains after distillation is colophan or common rosin. It dissolves in alcohol. t 2099. Copaiva is obtained from the copaifera officinalis and coria- cea; it exudes from incisions made in the trunk of the tree. It is transparent, yellow, of an agreeable smell and pungent taste. Its sp. gr. is 0.950. It yields a volatile oil by distillation. 2100. It is insoluble in water, but imparts to it its peculiar taste * In the arrangement of the apparatus for this purpose, the rosin liquefied by heat is allowed to pass into the retort containing coal or colce. It has not been found econo- mical in England. See Ure’s Diet. Arts and Manuf. 1076. t Slrasburg turpentine is extracted from the pinus picea. Canada balsam is obtained from the pinus canadensis and balsamea and the tur- pentine of Cyprus and Chio from the pistacea lerebinthus. Copal. 465 and smell. It dissolves in all proportions in absolute alcohol ; alco- Sect, n. hoi of sp. gr. 0.848 dissolves only the 9th or 10th of its weight. It dissolves in ether and fixed and volatile oils.* * * § It combines with sa- lifiable bases. It has a remarkable affinity for magnesia, 1 part of magnesia dissolving in 30 of balsam into a transparent liquid. 3101. It is sometimes adulterated with fixed oils ; which can be Adultera- detected by alcohol dissolving the balsam but leaving the oil. Cas- detect ' tor oil is however soluble in alcohol, but it may be detected by agi- tation with ammonia, sp. gr. .965, in a glass tube ; the solution is transparent if the balsam be pure, but milky if it contains castor oil. 2102. Balsam of Peru is obtained from the myroxylon peruiferum B a ] samo f of South America. Two varieties occur in commerce, one obtained p eru by incisions in the tree, having a slight tint of yellow; the other by boiling the branches and bark of the tree in water. According to the analysis of Stoltze balsam of Peru is composed of Volatile oil . . . . 69. Resin very soluble in alcohol . ,20.7 Do. little . . . 2.4 Benzoic acid .... 6.4 Extractive matter . . . 0.6 Moisture .... 0.9 — 100 . The oil is much less volatile than the other volatile oils, and can- not be separated by distillation.! 2103. The principal solid resins are, rosin or colophan, mastich,! Solid re- sandarach, eletni, guaiacum, § storax, dragon’s blood, II benzoin, and sins - anime. 2104. Copal is the most important of this class, it flows from the Co P a b rkus copalinum and eloeocarpus copaliferus ; the first a native tree of America, the second of the East Indies. It is white with a tint of brown, sometimes opaque, at others nearly transparent. It differs from other resins in not being soluble in alcohol nor in oil of turpen- tine without peculiar management. Its sp. gr. varies from 1.045 to 1.069. 2105. Its solution is much employed as a varnish, in the forma- uses, tion of which several processes are followed. IF The following me- thod is recommended by Lenormand : * Stoltze in Berlin Juhrb. xxvii. 2, 179. + Balsam of Tolu is obtained from the tulifera balsamum, it is reddish brown, be- comes brittle by exposure to the air, and has a fragrant odour, It dissolves in ether, alcohol, and the volatile oils. For other balsams see T. Org. Bodies , 520. t From late investigation of resins it appears that inastich consists of two resins ; the one soluble and acid, the other insoluble and not acid. Johnson, in Phil. Trans. April 1839. § Guaiacum is rendered blue by various animal and vegetable substances ; it becomes Adulltriti#n 0 f blue when rubbed with the gluten of wheat, or the farina. It is often adulterated with guaiacum 1 . common rosin. To discover this fraud, dissolve the guaiacum in caustic potassa ; if pure the solution is limpid, but muddy if rosin be present, as long as there is excess of alkali. || Lump Dragon’s blood is the natural and pure resin, w'hile the strained and red va- rieties, being manufactured articles, are more or less decomposed : it contains alcohol and ether with considerable tenacity, but they may be expelled by long exposure to a temperature not higher than 200°. Johnson, Phil. Trans. April 1839. H Nicholson’s Jour. ix. 157; T. Org. Bodies , 544; Neil in Trans. Soc. of Arts, xlix. Ample details for making a great variety of varnishes are given in Ure’s Diet. Arts and Manuf. 1264. 59 466 Chap. IX. Solution of copal. Lac. Solvents. Amber. Succinic acid. Gum re- sins. Foetid gum resins. Organic Chemistry — Gum Resins. Drop upon the pieces of copal pure essential oil of rosemary. Those pieces that are softened by the oil are fit for the purpose, the others are not. Reduce them to a fine powder ; put this powder into a glass vessel not thicker than a finger breadth ; pour oil of rosemary over it, and stir it about with a glass rod. In a short time the whole is converted into a thick liquid. Pour alcohol on this liquid by little at a time, incorporating it, by gently agitating the vessel, till it is of the requisite thinness for use.* 2106. Lac is an important resin deposited in different trees in the East Indies, viz. ficus indica , /. religiosa , and rhamnus jujuba. It flows out in the state of a milky liquid, in consequence of the punc- ture of a small insect, the coccus ficus , on the branches of these trees, made by the insect in order to deposit its ova. The various kinds of lac distinguished in commerce, are stick-lac , which is the substance in its natural state, investing the small twigs of the tree ; seed-lac , which is the same broken off; and which, when melted, is called shell-lac. These substances have been examined by Hatchett. Their component parts are exhibited below. t 2107. Water dissolves the colouring matter of lac, and alcohol the resin which constitutes the chief ingredient of lac. A solution of borax in water dissolves lac; the best proportions are 20 grs. of bo- rax, 100 grs. of lac, and 4 ounces of water. This solution mixed with lampblack, constitutes Indian ink. Lac contains a peculiar body called laccin. 2108. Amber is a substance which, in some of its properties, re- sembles resin ; it is however, very sparingly soluble in alcohol, and difficultly soluble in the alkalies. When submitted to distillation, it furnishes an acid sublimate, which has received the name of succinic acid. It is found in beds of wood coal. Section III. Gum Resins. 2109. The term gum resin is applied to a number of concrete ve- getable juices which contain various proportions of resin, gum, and other vegetable principles. They are opaque, solid, brittle, or some- times with a fatty appearance. They are less combustible than the resins; they do not melt like resins but are softened by heat, and swell. They burn with flame. They are partially soluble in water and alcohol. The aqueous solution is milky, the alcoholic transpa- rent, but becomes milky on dilution. Their best solvent is dilute alcohol. 21 10. Those gum resins which have a fetid or alliaceous odour, are ammoniac, galbanum, assafcetida, opoponax, and sagapenum. The stimulating gum resinst are olibanum, myrrh, euphorbium, and bdellium ; the first is the frankincense of the ancients. * Jour, de Chim. iii. 218. t Restns Colouring matter Wax Gluten Foreign bodies . Loss Stick- Lac. Seed-Lac. Shell-Lac. 63 88.5 90.9 .10 2.5 0.5 6 4.5 4.0 56 2.0 2.8 6.5 ■ - — 4.0 2.5 1.8 -- ■ 100 100 100 Phil. Trane. 1894 t Of Thomson. Neutral Vegetable Principles. 4b 2111. The cathartic gum resins are aloes, scammonv. and gam- Sect.iv. boge. The sedative gum resins are opium, lactucarium* * * § and upas. 2112. Of the sedative gum resins opium is the most important ; Opium, it is the milky juice of the papaver somniferum, inspissated into a dark coloured solid by exposure to the atmosphere. Its best sol- vent is common spirits. Its principal constituents have been al- ready described. It differs much in its qualities. Section IV. Neutral Vegetable Principles . 2113. Neutral vegetable principles are those bodies which neither Neutral possess the properties of acids nor bases, and which so far as is principles, known, do not combine in definite proportions with other substances. They have been arranged by Thomson in thirteen divisions. 2114. Amides , or Amidets. The term amide signifies an anhy- Division drous ammoniacal salt deprived (if an expression apparently contra- Ami ‘ dictory may be allowed) of an atom of water. (1562) 2115. Oxamide . C 2 0 2 +NH 2 = 44. (T.) This was discovered by Oxamide, Dumas in 1830.1 When oxalate of ammonia is heated in a glass obtained retort, it loses in the first place its water of crystallization, and the crystals become opaque. The salt then melts and boils, but only in those parts which receive immediately the impression of the heat. Those portions which melt undergo decomposition and disappear rapidly. $ When the distillation is at an end some trace of charcoal merely remains in the retort ; all the rest has been volatilized. In the receiver is found water impregnated with carbonate of ammonia. This water holds in suspension a flocky matter of a dirty white co- lour. § The white flocks and deposit on the beak of the retort con- stitute the substance called oxamide. To purify it, it is washed out upon a filter and thoroughly edulcorated with cold water. Being nearly insoluble, it remains on the filter. 2116. The gases disengaged during the distillation change their Gases nature as it proceeds; they are ammonia, then carbonic acid and evo Te oxide, and cyanogen ; water and carbonate of ammonia are also formed. II 2117. Oxamide is obtained in crystallized plates, or as a granular Properties, powder. When pounded and well washed it is a dirty-white pow- der, resembling uric acid, without taste or smell, or any action on vegetable colours. It is volatile, and crystallizes when cautiously heated in an open tube. It is not sensibly soluble in cold water ; but dissolves in boiling water. 2118. Heated in sulphuric acid it dissolves, and gas is given out Ac ^ on in abundance, consisting of equal vols. of carbonic acid and carbonic of S. oxide. At the same time a quantity of ammonia is formed, which * Lactucarium is obtained from the juice of the Lactuca sativa or common garden jettuce. t Ann. de Chim. et de Phys. xliv. 129. t But the mass in general retains its appearance, and a careful examination is neces- sary to be able to perceive the thin layer of the salt which is in a state of fusion. § The neck of the retort exhibits usually crystals of carbonate of ammonia, and a thick layer of the same white matter. 4 H Liebig has shown that when caustic ammonia is added to oxalic ether, alcohol is evolved, and a copious deposit of oxamide is produced. This is by far the most eco- nomical method of preparing oxamide. See Ann. de Pharm. ix. 129. T. 591. 468 Organic Chemistry — Neutral Vegetable Principles. and of po- tassa. Analysis. Ether oxa amide. Chap, ix. combines with the acid. Boiled in a concentrated solution of po- tassa it gives out ammonia in abundance, with the formation of oxalic acid which combines with the potassa. 2119. According to the analysis of Dumas* its constituents appear to be C2O2-I-H2N = 44.0. If we add HO (an atom of water), the oxamide becomes C2O3-I-H3N, or oxalate of ammonia.! t . 592. 2120. Fit her oxamide is obtained when a current of dry ammonia- cal gas is passed over a given quantity of pure oxalic ether. Sitcci- namide is formed when the same gas is made to act upon anhydrous succinic acid. Benzamide is obtained when the gas is absorbed by pure chloride of benzoul. Sulphamide is formed when dry ammo- niacal gas is combined with anhydrous sulphuric acid. 2121. This division comprises benzoyl and its compounds.! 2122. The base of benzoic acid has been termed by Liebig and Wohler benzoyl, and was obtained by Laurent by passing a current of chlorine gas through benzoin kept in fusion while the gas was passing; hydrochloric acid was formed and benzoyl disengaged. It was purified by solution in alcohol and crystallization. 2123. The volatile oil of bitter almonds is a hydret of benzoyl, and this oil has the property of absorbing oxygen and of being con- verted into benzoic acid. The change may be thus explained: Division 2d. Benzoyl. : The oil is Benzoic acid CuHg O2 ChH 5 0 3 Explana- tion. Properties. Analysis. So that the oil contains 1 atom more of hydrogen, and l atom less of oxygen, than the acid ; 2 atoms of oxygen are absorbed, the one unites with 1 atom of hydrogen and forms water, while the other combines with (C u H 5 0 2 ) and converts it into benzoic acid. C, 4 H 5 02 must be the base of benzoic acid, and the oil must be this base com- bined with an atom of hydrogen, or a hydret of benzoly. t, 2124. Benzoyl is slightly yellow, without taste or smell ; insoluble in water, very soluble in alcohol and ether, crystallizing in six-sided prisms. Its lustre is vitreous. It may be volatilized without decom- position ; becomes solid at about 196° ; burns on platinum with a red flame, t. 603. The analysis afforded Carbon . 14 atoms per cent. 80. Hydrogen . 5 “ “ “ 4.76 Oxygen 2 “ “ “ 15.24 100 . Com- 2125. The compounds of benzoyl and their composition are the pounds of r 11 r * r Benzoyl. following : Benzoyl ... C14H5 O 2 Hydret of “ or oil of bitter almonds C14H5 Oa H Benzoin ----- C 14 H 5 O 2 + H Benzoic acid - ChHs O 2 + O Chloride “ » »> - - C14H5 O 2 4 - Cl Bromide u * - - C14H5 Oa -f Br Iodide “ - - - C 14 H 5 O 2 -I-I Sulphuret w ... CmHg O 2 -f- 3 Cyanide “ - - - Ci 4 Hs O 2 + C 2 N * Ann. de. Chim. et de Phys. xliv. 129, and Jour, de Pharm. xvii. 177. 1 NH 2 +C 2 O 2 , «q- 44.39. L. 762. t Bentule. Tand L. Sugar . 469 Benzone* * * § ChH 5 C) Sect. IV. Benzinet C 6 H 3 . Now, 2(C 6 H 3 )4-2(C0 2 )=Ci 4 H 5 0 2 4-0 2 Benzamide C 14 H 5 0 2 -|-H 2 ^ Benzimide C 14 H 5 0 2 4"HiN^ ? Nitrobenzidei 2(C 6 H g^-j-NO^ Sulphobenzide 2(C 6 H 3 )-|-S0 3 Azotobenzide§ 2(C 6 H 3 )-j-N 2126. Spiroil and its compounds. Spiroil is the supposed base of Division the volatile oil extracted from the flowers of the spiraea ulmaria. It 3d * is a compound of C 12 H 5 0 4 with an atom of hydrogen. It has not been obtained in a separate state, but it has been combined with ox- ygen, chlorine, bromine, iodine and hydrogen, and shown to form definite compounds with each. 2127. Sugar. C 12 H 10 O 10 = 162.24. The term sugar has been Division applied to various substances characterized by a sweet taste. 4th ‘ 2128. Sugar may be extracted from the juice of a number of ve- Sugars, getables, and is contained in all those having a sweet taste ; that which is commonly employed is the produce of the arundo uon 0 ’ saccharifera , or sugar-cane, a plant which thrives in hot climates. Its juice is expressed and evaporated with the addition of a small quantity of lime, until it acquires a thick consistency ; it is then transferred into wooden coolers, where a portion concretes into a crystalline mass, which is drained and exported under the name of muscovado , or raw sugar. The remaining liquid portion is molasses , Molasses or treacle. A gallon of juice yields on an average about a pound of raw sugar. 2129. The juice, which flows spontaneously from incisions made Varieties of in the American maple-tree, affords a quantity of sugar sufficient su ° ar ‘ to render it a process worth following. The juice of the carrot, the melon, II and still more remarkably of the beet ( beta vulgaris , L.) yields a considerable proportion of sugar. To obtain it from the lat- ter vegetable, the roots, softened in water, are to be sliced, and the juice expressed. It is then to be boiled down, with the addition of a Beet sugar, little lime, till about two thirds remain, and afterwards strained. These boilings and strainings are repeated alternately, till the liquid attains the. consistence of syrup, when it is left to cool. The su- gar thus extracted, retains somewhat of the taste of the root ; but it may be purified by the operation used for the refining of West India sugar, and it then loses its peculiar flavour. The quantity obtained varies considerably ; but in general it may be stated at between four and five pounds from 100 lbs of the root, besides a proportion ot un- crystallizable syrup. In Germany the expense has been calculated at about three pence per pound. H * This term was applied from the analogy between benzone and acetone, the name given by Dumas and Liebig to the liquid formerly called pyroacetic spirit. + The benzine of Mitscherlich is the same with the bicarburet of hydrogen of Fa- raday. t Formed when nitric acid is made to act upon his benzin. § A substance obtained by distilling a mixture of nitrobenzide and lime. For de- tails respecting these compounds, see Thomson’s Org. Bodies , 604. || Quart. Jour. N. S. 1 . 239. IT See Chaptal On the manufacture of Sugar in France, Phil. Mag. xlvii. 331. For details respecting the manufacture and refining of sugar, see Ure’s Did . Arts and Manuf. 1191. 470 Organic Chemistry — Sugar. Chap. IX. Action of sulphuric acid, Of nitric acid, Of acids in general. Absorbs ammonia. Solvents. Effect of heat. Product of its distilla- tion. Liquid su- gar. Sugar of grapes. 2130. ' Sugar is altered by the action of the strong acids. Con- centrated sulphuric acid poured upon sugar blackens it, and causes it to deposit a charry matter when we dilute the acid with water. When long boiled with this acid it is converted into sugar of grapes, or that species of sugar into which starch is converted by the same process. 2131. By nitric acid it is converted into oxalhydric and oxalic acids : 480 grs. of sugar, treated with 6 ounces of nitric acid, diluted with its own weight of water, and cautiously heated, separating the crystals as they are formed, yielded 280 grs. of oxalic acid. So that 100 parts of sugar yield by this treatment 58 parts of oxalic acid.* Hydrochloric acid acts upon sugar like the sulphuric. When chlo- rine is passed through a solution of sugar, it transforms it into oxal- hydric acid, while the chlorine is converted into hydrochloric acid. 2132. Malagutti and Bouchardtt have lately ascertained that acids, in general, even when very dilute, act upon sugar in the same man- ner when assisted by heat. They first convert it into uncrystallizable sugar, then into sugar of grapes, then into uncrystallizable sugar, then into ulmic acid ; and finally, if atmospheric air be present, into ulmic and formic acids. 2133. Sugar combines with the acidifiable bases. When intro- duced into ammonia, over mercury, it absorbs the gas, diminishes in bulk, becomes coherent, compact, and soft, so that it can be cut with a knife, and gives out an ammoniacal smell. 2134. Sugar is soluble in alcohol, but not in so large a proportion as in water. When the solution is set aside it deposits crystals. It unites with oils, and renders them miscible with water. A moderate quantity of it retards the coagulation of milk ; but a large quantity promotes it. 2135. When heated sugar melts, swells, becomes brownish black, and exhales a peculiar smell known in French by the name caromeh At a red heat it bursts into flame. See Appendix. 2136. When distilled in a retort sugar yields water, pyromucic acid, empyreumatic oil, and a bulky charcoal. When a solution of sugar is used carbonic acid and carburetted hydrogen are obtained. It is therefore decomposed by heat.t 2137. Liquid sugar exists in a variety of fruits and vegetable juices. It is distinguished by being uncrystallizable. It may be obtained from the stalks of the zea mays , or Indian corn and constitues a con- siderable portion of the molasses of common sugar. 2138. Sugar of grapes. C 12 H l2 0 I2 . Verjuice, or the liquid ob- tained from unripe grapes, contains tartar, sulphate of potassa, sul- phate of lime, much citric acid, a little malic acid, extractive, and water, but neither guin nor sugar. As the grapes advance to matu- rity, the citric acid disappears, and gum and sugar appear in its place. The ripe grape juice yields from a third to a fifth of solid matter. * Cruickshanks, Rollo on Diabetes , 460. + Jour, de Pharm. xxi. 440, and 627. t For the result of Prout’s analysis of sugar, see Phil. Trans. 1827. Fremy obtained an oily looking matter lrom 1 part sugar and 8 parts lime, which yielded acetone CqH^O and metacetone C5H5O. Two atoms of sugar may be re- solved into 3 atoms metacetone. 6 atoms carbonic acid and 7 atoms water ; and 1 atom of sugar into 3 atoms of acetone, 3 atoms of carbonic acid and 2 atoms water (T. 636). Starch and gum distilled with lime afford the same products. 471 Amylaceous Substances. The sugar may be extracted with the aid of potassa and heat. It is Sect. iv. less sweet than that from sugar cane. 2139. Starch may be converted into a sugar possessing the pro- Conversion perties of sugar of grapes, by mixing it with about 4 times its weight starch of water, and about part of its weight of sulphuric acid, boiling in 0 sugar " for 36 hours, supplying water as it evaporates, saturating the acid with lime, separating the sulphate of lime and concentrating. 2140. Honey is also a variety of sugar containing a crystallizable and an uncrystallizable portion ; the predominance of one or other of which gives to it its peculiar character ; they may be partially sepa- rated by mixing the honey with alcohol, and pressing it in a linen bag; the liquid sugar being the most soluble, passes through, leaving a granular mass, which forms crystals when its solution in boiling alcohol is set aside. Honey also frequently contains wax, and a little acid matter. 2141. Manna is an exudation from the Fraxinus ornus, a species Manna of ash, growing in Sicily and Calabria. It exists in the leaves of celery and several other plants. To obtain pure manna, dissolve the manna of the shops in boiling alcohol and allow it to cool ; the manna crystallizes. It has a sweet and somewhat nauseous taste, and is used in medicine as a mild aperient. The sweetness of manna is owing, not to sugar, but to a distinct principle called mannite. Its solution in water does not appear susceptible of vinous fermentation. 2142. Liquorice sugar is the inspissated juice of the glycyrrhiza Lj quor j ce glabra a native of Spain. It combines with bases and with salts, sugar. It precipitates the greater number of metallic solutions. 2143. Glycerin. C G H70 5 =83. (T.) This substance was called Glycerin, by Scheele sweet principle of oils. To obtain it an oil may be digested with an alkaline ley till converted into p r0 cess. soap. The soap being separated, the alkaline liquid is saturated with sulphuric acid, and any excess of acid removed by carbonate of baryta. Filter and evapo- rate to the consistence of a syrup : dissolve the syrup in alcohol and filter ; evap- orate the alcoholic solution ; the glycerin remains. 2144. It is a colourless syrup, uncrystallizable, of a sweet taste Properties, and without smell. From the analysis of Liebig and Pelouze 1 atom of glycerin is combined in stearin with 2 atoms of stearic acid. 2145. Amylaceous substances. When wheat flour is formed into a Division paste with water, and then held under a small stream of water, 5th ‘ kneading continually till the water runs off colourless, the flour is o U ? y S ub-* divided into two constituents gluten and starch. The starch is re- stances, moved by the water and subsides on standing. 2146. The common process for obtaining the starch of wheat consists in p rocess f or steeping the grain in water till it becomes soft; it is then put into coarse linen obtaining bags, which are pressed in vats of water; a milky juice exudes, and the starch s t arc h. falls to the bottom of the vat. The supernatant liquor .undergoes a slight fer- . mentation, and a portion of alcohol and a little vinegar is formed, which dis- solves some impurities in the deposited starch ; it is then collected, washed, and dried in a moderate heat, during which it splits into the columnar fragments which we meet with in commerce, and which are generally rendered slightly blue by a little smalt. 2147. Starch or Fecula , may be separated from a variety of sub- stances ; and many roots. By diffusing the powdered grain or the rasped root in cold water, the grosser parts may be separated by 472 Organic Chemistry — Amylin. Chap IX. Arrowroot. Sago. Properties of starch. Insoluble iu alcohol, &c. Composi- tion of starch. Amidin. Amylin. Analysis. a strainer and the liquor which passes deposits the starch, which is to be washed in cold water and dried in a gentle heat. 2148. Arrow root consists entirely of very pure starch. It is ex- tracted from the potato, and the roots of the jatropha manihot afford the variety known as cassava and tapioca. Sago , another variety, is extracted from the pith of a species of palm the sagus raphia which grows in the East India Islands.* Salop comes from Persia and is supposed to be the prepared roots of different species of orchis. Of rice, starch constitutes, according to Braconnot, from 83 to 85 per cent. 2149. Pure starch is a white substance, insoluble in cold water, but readily soluble at a temperature between 160° and 180°. Its solution is gelatinous, becomes mouldy and sour by exposure to air, and by careful evaporation yields a substance resembling gum in appearance, which is a compound of starch and water. Starch is insoluble in alcohol and in ether ; its most characteristic property is that of forming a blue compound with iodine. 2150. Starch consists essentially of two distinct substances. 1. The liquid portion which fills each little vesicle composing it, and this liquid consists of water holding in solution a peculiar substance which is called amidin. t 2. The vesicular portion of the grain, insoluble in water, and called amylin.\ According to Guerin — Vary, potato starch is composed of Exterior tegumentary amylin, - 2.12 Amidin 38.13 Amylin 59.75 100 § 2151. Amidin or the soluble part of starch has neither taste nor smell. Cold water dissolves it, but it is more soluble in boiling water: it is insoluble in alcohol and ether. Its aqueous solution soon becomes acid. Digested in nitric acid it forms oxalhydric acid, and then oxalic acid. 100 parts of amidin and 250 of sulphuric acid at the temperature of 150° furnish 95.8 parts of anhydrous sugar. 2152. Amylin is insoluble in water, it does not dissolve in boiling water, nor in alcohol or ether; but it swells in water and becomes white. When 100 parts are digested with 800 of nitric acid, 25.46 parts of anhydrous oxalic acid are formed. When digested in sul- phuric acid and water it is converted into sugar: 100 parts of amy- lin give 110.57 of hydrous sugar. From pure amylin Prout obtained Carbon 43.31 Hydrogen ------ 6.49 Oxygen 50.20 100 Numbers which lead to the conclusion that it is composed of 12 atoms carbon, 10 hydrogen and 10 oxygen. (T.) It is probable that the dextrine of Biot and Person consists chiefly of amidin. T. 656. * See an account of its preparation in Forest’s Voyage, p. 3f. t Vary in Ann. de Chim.et de Phys. Ivi. 231. t From the Greek word apvl or starch. § Jour, de Pharm , xxii. 210. Xyloidin. 473 2153. Hordein may be obtained from barley*meal made into a Sect. iv. paste with water and washed by a current of water dropping on it. Hordein. The starch and hordein are washed away. By boiling in acidulous water, the starch is taken up, and the hordein remains unaltered. It amounts to from 54 to 56 per cent, of the meal. 2154. It is a yellow powder, resembling sawdust ; insoluble in Properties, water and alcohol, does not yield ammonia ; but yields oxalic and acetic acids. During the malting of barley, the hordein is converted into starch. 2155. Lichenin is the name given to what was once called the Lichenin. starch of the cetraria islandica or Iceland moss, which when good yields about 44^- per cent. In cool water it swells up but does not dissolve. It is coloured blue by iodine, and is precipitated by alco- hol. It appears to be isomeric with amidin. According to Herber- ger it is poisonous.* 2156. Inulin is obtained from the roots of the inula helenium , Inulin. colchicum autumnale, and more abundantly from the dahlia 'purpurea. It is a fine, white, tasteles powder. It is precipitated from its aque- ous infusion by infusion of nut-galls. 2157. Lignin or woody fibre constitutes the fibrous structure of lignin, vegetable substances, and is the most abundant principle in plants. The different kinds of wood contain about 96 per cent, of lignin. It is prepared by digesting the sawings of any kind of wood succes- sively in alcohol, water, and dilute hydrochloric acid, until all the substances soluble in these menstrua are removed. 2158. Lignin has neither taste nor odour, undergoes no change by Propertie s. keeping, and is insoluble in alcohol, water, and the dilute acids. By digestion in a concentrated solution of pure potassa, it is converted according to Braconnot into a substance similar to ultnin. Mixed with strong sulphuric acid it suffers decomposition, and is changed into a matter resembling gum ; and on boiling the liquid for some time the mucilage disappears, and a saccharine principle like the sugar of grapes is generated. Braconnot finds that several other substances which cpnsist chiefly of woody fibre, such as straw, bark, or linen, yield sugar by a similar treatment.! 2159. Xyloidin is a substance obtained by the action of con- Xyloidin. centrated nitric acid on starch, lignin and some other substances. When the acid of density 1.5 is added to starch, a solution is ob- tained, which if treated immediately with water, deposits the xyloidin. Xyloidin is a compound of nitric acid and starch, an atom of water in common starch being replaced by an atom of nitric acid.! It is very combustible. § 2160. The exudations from various trees and plants which have Division been called gums, may be arranged under three genera, viz. arabin , bassorin and cerasin. 2161. The term Arabin was applied by Chevreul to gum arabic, Arabin. * Jour, de Pharm. xvii. 229. + Ann de Chim . et de Phys. xii. For other principles of this division see T. Org, Bodies. t Pelouze. § See Jour, of the Frank . Instit. xxiv. 119. 60 474 Chap. IX. Properties. Uses. Action of sulphuric acia. Bassorin. Cerasin. Division 7th. Glutinous substances. Properties. Albumen. Organic Chemistry — Albumen. which consists almost entirely of arabin. Gum arabic comes from the Levant but its use has been in a great measure superseded in G. Britain by gum Senegal. It is in small rounded drops or tears, sp. gr. is 1.355. It is composed of Arabin - - - - 79.4 Ashes . - l . . . . 3.0 Water 17.6 100 2162. Arabin is colourless, tasteless, inodorous, and transpa- rent, friable when dry, tough when moist. It softens at a tempera- ture between 282° and 392° and may be drawn out into threads. It is insoluble in alcohol. With water it forms mucilage. It is viscid and glutinous, and is used by calico-printers to thicken their colours and mordants to prevent their spreading on the cloth. It may be kept for years without much change, but finally becomes acid. 2163. Boiled with sulphuric acid it is converted into sugar, but which differs from starch sugar in not fermenting with yeast. With nitric acid it yields mucic and oxalic acids. Its atomic composition is the same as that of sugar in crystals. 2164. The principal varieties of gum consisting altogether or chiefly of arabin, are gum arabic, gum Senegal and mucilage of lintseed. 2165. Bassorin was first noticed by Vauquelin in a gum from Bass ora. When this gum is treated with water, the bassorin re- mains in a gelatinous form. It has since been found in gum traga- canth and cherry-tree gum. It is solid, colourless, insipid and ino- dorous ; insoluble in water, but swells up and becomes a jelly. It is insoluble in alcohol. By the action of nitric acid mucic and oxalic acids are formed. With sulphuric acid it forms a crystalliza- ble sugar. 2166. Cerasin is the name given to a substance in cherry-tree gum which remains undissolved when that gum is treated with cold water. It is isomeric with arabin. It is solid, insipid and inodo- rous; insoluble in alcohol, swells in cold water, but does not dis- solve. When boiled in water it is converted into arabin.* 2167. Gluten may be obtained from wheat-flour, by forming it into a paste and washing it under a small stream of water. The starch is thus washed away, and a tough elastic substance remains, which is gluten. Its colour is gray, and, when dried, it becomes brown and brittle. It is nearly insoluble in water and in ether. When allowed to putrefy it exhales an offensive odour, and when submitted to de- structive distillation, it furnishes ammonia, a circumstance in which it resembles animal products. Most of the acids and the alkalies dissolve it. Gluten has been resolved by modern chemists into four distinct principles, viz. albumen , emulsin , mucin , and glutin. 2168. Albumen. When fresh gluten is digested in hot alcohol till every thing soluble is takeu up, a bulky substance of a grayish * Calendulin is obtained from the flower of the calendula officinalis, or Marygold. Saponin was discovered in the root of the saponaria officinalis . Caoutchouc . 475 colour remains, which constitutes what has been called vegetable s«ct. iv. albumen. It is soluble in water ; but coagulates when heated. It is insoluble in alcohol and ether. When dry it is opaque. It is pre- cipitated from acid solutions, by carbonate of ammonia. 2169. Emulsin is the name given to a peculiar substance which Emulsin exists in almonds, and which has the property of decomposing mu m * amygdalin, and of forming hydrocyanic acid and volatile oil of bit- ter almonds. 2170. Mucin is obtained when alcohol is boiled upon the gluten Mucin of wheat. It dries into transparent grains, burns like animal mat- ter; is more soluble in water than gluten, and constitutes about 4 per cent, of the gluten of wheat flour. 100 parts of hot water dis- solve 4 parts of mucin, and the solution soon putrefies. 2171. The aqueous solution of mucin is precipitated by infusion of nutgalls, slightly by alcohol. When made into a paste with starch and kept for 10 hours at 145° it converts the starch into sugar and dextrine. 2172. Glutin may be obtained by boiling alcohol upon the gluten Glutin ob- of wheat and freeing the solution from mucin by repeated precipita- tained. tions. On evaporating the alcohol the glutin is left as a yellowish translucent matter. 2173. Glutin is almost insoluble in water, but soluble in alcohol, Characters, ether, dilute acids and caustic alkaline leys. It is precipitated by infusion of nutgalls.* 2174. Caoutchouc, elastic gum or Indian rubber, is the concrete juice of the Hcevea caoutchouc and Iatropa elastica , natives of South ^ ision America, and of the Ficus Indica and Artocarpus integrifolia , Caout- which grow in the East Indies. It is a soft yielding solid, of a chouc. whitish colour when not blackened by smoke, possesses considera- ble tenacity, and is particularly remarkable for its elasticity.! It is inflammable, and burns with a bright flame. It is insoluble in water and alcohol ; but it dissolves, though with some difficulty, in pure ether. It is very sparingly dissolved by the alkalies, but its elasti- city is destroyed by their action. By the sulphuric and nitric acids it is decomposed, the former causing deposition of charcoal, and the latter formation of oxalic acid. 2175. Caoutchouc is soluble in the essential oils, spirits of turpen- tine, ether, naphtha, cajeput oil, and in the volatile liquid obtained by distilling caoutchouc ; and from all these solvents, except the essential oils, it is left on evaporation without loss of its elasticity. * Zein is the name given by Gorham (Jour, of Scien. xi. 205.) to the gluten of zea zein. mats or Indian corn. According to Gorham it contains no nitrogen and yields no ammonia when distilled ; but Bizio affirms that he obtained ammonia from it. Viscin is obtained from bird-lime 3 which is prepared from the middle bark of the vi.cin, holly boiled in water and deposited in pits till it becomes viscous. Pollenin is a peculiar substance found in the pollen of the pinus abies , lycopodium p 0 iienin. clavatum, &c. Legumin is contained in the cotyledons of the seeds of papilionaceous plants. L#gumin. Amygdalin exists in the bitter almond. Amygdalin. Glairin is the name applied to a substance observed in the sulphureous waters of Giairin. some springs. It gelatinizes by concentration. Decomposed it yields ammonia. It is probably of vegetable origin. t For some curious experiments on the connection between the temperature of caoutchouc and its elasticity see T. Org. Bodies , 696, and Manchester Memoirs , ii. 2d series. 476 Organic Chemistry — Caoutchouc. Chap. IX. Preparation of caou- tchouc. Effect of heat. Use*. Before actually dissolving, the caoutchouc swells up remarkably, and acquires a soft gelatinous aspect and consistency ; in this state it is used for rendering cloth and leather impervious to water, and, as suggested by Mitchell, may be cut with a wet knife into thin sheets or bottles, and be extended to a great size.* In preparing caoutchouc for the action of spirits of turpentine, ammonia is now used with advantage. The caoutchouc is cut into shreds, covered with caustic ammonia, and left in this state several months ; it becomes soft, swells, but is still elastic. It is then treat- ed with spirits of turpentine, and by agitation converted into an emulsion ; in a short time it swims on the surface, and may be removed. A much smaller quantity of turpentine is required when the caoutchouc has been thus softened. 2176. When caoutchouc is cautiously heated, it fuses without de- composition ; but at a higher temperature it is resolved into a volatile liquid of a brown colour, which amounts to -^ths of the original caoutchouc. When carefully rectified, a very volatile liquid of sp. gr. 0.64 is obtained, which is very combustible and burns with a bright flame, mingles with alcohol, and dissolves copal and other resins. It is very useful as a solvent for caoutchouc and for the pre- paration of varnishes. 2177. Caoutchoucjin thin sheets is exceeding useful in the labo- ratory, for joining glass tubes, &c. so as to make an air tight joint and at the same time preserve flexibility. 2178. The milky juice carried from South America was found by Faraday to be composed of Water, 56.37 Caoutchouc 31.70 Albumen 1 .90 1 Wax, a trace - An azotic body 7.13 Gummy body 2.90 100 His analysis of caoutchouc gave Carbon, 87.2 Hydrogen, 12.8 Thomson thinks it composed of an equal number of atoms of carbon and hydrogen. Products of 2179. By distillation at a low temperature and exposing the pro- distillation. d ucts t0 a freezing mixture, several different liquids have been obtained from caoutchouc.t These are Eupion§ a limpid liquid that boils at 124°; Caoutchene an oily substance ; Heevene which remains * Soak the common bags in sulphuric ether, sp. gr. 0.763, at a temperature not less than 50° Fahr. for a period of time not less than one week, (the longer the better.) Empty the bag, wipe it dry, put into it some dry powder, such as starch, insert a lube into the neck, and fasten it by a broad soft band slightly applied, and then commence by mouth or bellows the inflation. If the bag be unequal in thickness, restrain by the hand the bulging of the thinner parts, until the thicker have been made to give way a little. When the bag has become by such means nearly uniform, inflate a little more, shake up the included starch, and let the bag collapse. Repeatthe inflations until the bag is sufficiently distended. t From recent experiments Ure infers that albumen is not a necessary constituent of the juice. See his new experiments in Philos. Mag. July 1839. t Bouchardt, Jour, de Pharm . xxiii. 454. § From the Greek ev well and nuov fatty. Paraffin— Eupion, 477 after the volatile oils are distilled off ; it is an acid liquid boiling at Sect. iv. 600° and burning like the volatile oils ; and carburet of hy- drogen. 2180. Extractive. Most plants yield to water a substance differing j) ivis - on from any proximate principles of vegetables, which constitutes apart 9th. of what is called an extract in pharmacy, and which has been express- Extractive, ed by the term extractive. It is always mixed with other princi- ples and there is no proof that it is identical in different plants. Berzelius distinguishes it by the name of apotheme (deposite). 2181. Many vegetable substances have an intensely bitter taste, Div — on and on that account are employed in medicine, by brewers, &c. ioth. There appears to be a great variety of bitter principles, many of Bitter prim which have received distinct names derived from the name of the ciples ' vegetable, as quassite from Quassia, gentianite from gentian, eolo- cynthite from colocynth, &c. 2182. Products of the destructive distillation of vegetable sub - Division stances. Some of these are found in matters existing on the earth ; p^' uctg of but it is probable that they have been formed originally by the destructive destructive distillation of vegetables or trees, in some great processes distillation, of nature. 2183. Naphtha. This liquid exudes from the earth in Persia and Naphtha, some other countries ; and is obtained by distilling petroleum and asphaltum, and by rectifying coal tar. Naphtha is limpid, and colour- less, like water ; it has a bituminous odour, a sp. gr. of 0.817 and D ' . burns with much flame and smoke. Pr0petUeS - 2184. It is insoluble in water, but soluble in alcohol. It softens caoutchouc which swells in it to more than 30 times its original bulk and becomes gelatinous and transparent : by long boiling a solution is effected. 2185. Petroleum is less limpid than naphtha, and unctuous to the p etro i e um. touch. Asphaltum is a solid, brittle bitumen of a black colour, and Asphaltum. vitreous lustre. It is soluble in about 5 times its weight of naphtha, and the solution forms a good varnish. It is found on the surface and on the banks of the Dead Sea, and in large quantities in Barba- does and Trinidad. 2186. Among the products of the destructive distillation of vege- Tar from table and animal substances is a black inflammable liquid called tar. coal. A large quantity is formed during the distillation of wood and the preparation of coal gas. This tar has been found to contain several new principles paraffin , eupion , creosote , picamar , capnomor and pittacdl. 2187. Paraffin is obtained most abundantly from the tar of the Paraffin, beech tree. It is a transparent and crystalline substance, of a white colour, and destitute of taste and smell. It melts at 110° into a colourless oil : at a higher temperature it boils and may be distilled. Its sp. gr. is 0.870. 2188. It has very little tendency to combine with other bodies ; hence its name paraffin ( parum affinis.) Ether is its best solvent. 2189. Eupion is obtained by distilling the tar which is procured by Eupion, decomposing animal matter in the dry way. It may also be obtained from vegetable and coal tar ; or much purer from rapeseed oil. The 478 Chap. IX. Properties. Creosote. Properties. Solubility, &c. Coagulates albumen. Arapalin. Organic Chemistry — Creosote. oil is distilled in an iron retort with a moderate fire, so that the oil may not pass over.* 2190. It is a colourless liquid, which does not become solid though cooled down to — 4°. It is tasteless but smells like blossoms. It boils at 116£°. Its sp. gr. is 0.655. Absolute alcohol dissolves it. Naphthaline, camphor, tallow, and many other substances dissolve in eupion ; caoutchouc swells enormously in it, and on boiling is dis- solved. 2191. Creosote was discovered by Reichenbach in 1832. It exists in impure pyroligneous acid, but is best prepared from those portions of the oil distilled from wood-tar which are heavier than water. The oil is first freed from adhering acetic acid by carbonate of po- tassa, and, after separation from the acetate, is distilled. A little phosphoric acid is mixed with the product to neutralize ammonia, and another distillation resorted to. It is next mixed with a strong solution of potassa, which combines with creosote, allows any eupi- on which may be present to collect on its surface, and by digestion decomposes other organic matter : the alkaline solution is then neutralized by sulphuric acid, and the oil which separates is collect- ed and distilled. For the complete purification of the creosote, this treatment with potassa, followed by neutralization and distillation, requires to be frequently repeated. 2192. Creosote is a colourless transparent liquid of an oily con- sistence, which retains its fluidity at — 17°, has a sp. gr. of 1.037 at 68°, boils at 397°, is a non-conductor of electricity, and refracts light powerfully. It has a burning taste followed by sweetness, and its odour is like that of wood-smoke or rather of smoked meat. It is highly antiseptic to meat : the antiseptic virtue of tar, smoke, and crude pyroligneous acid seems owing to the presence of creosote. Its name, from xpsds Jlesh, and oru>£w I save , was suggested by this property. 2193. Creosote requires about 80 parts of water for solution, and is soluble in every proportion in alcohol, ether, sulphuret of carbon, eupion, and naphtha. It has neither an acid nor alkaline reaction with test paper, but combines both with acids and alkalies. With potassa, soda, lime, and baryta it forms compounds soluble in water; but the creosote is separated even by feeble acids. Of the acids, it unites most readily with the acetic, dissolving in every proportion : by strong nitric and sulphuric acid it is decomposed. Creosote unites also with chlorine, iodine, bromine, sulphur, and phosphorus. 2194. Creosote acts powerfully in coagulating albumen, this effect being produced by a solution of one drop in a large quantity of water. It acts with energy on living beings. Insects and fish thrown into the aqueous solution of creosote are killed, and plants die when watered with it. It appears useful in medicine ; it is said to be very efficacious as a topical application in tooth ache, ulcers, and cutaneous diseases; and it probably admits of many other applications. Creosote is a compound of carbon, hydrogen, and oxygen ; the ratio of its elements is C,;H 3 £0.t T. * For details of the process see T. Org. Bodies , 726. iAmpelin was prepared by Laurent from the oil of bituminous slate, which boils at 392° and 536.° (Ann. de Chim. et de Phy. xiv. 326.) It is an oily looking liquid soluble in water. Naphthaline , . 2195. Picamar. This substance is the bitter principle of tar, whence it derives its name (in pice amarum.) It is present in the heaviest portions of the rectified oil of tar, and when these are treat- ed by potassa, a crystalline compound of the alkali and picamar is formed : this compound, when purified by repeated solution in water and crystallization, is decomposed by phosphoric acid, and the picamar separated by distillation. 2196. Picamar is an oily colourless liquid, of a peculiar odour and very bitter taste. Its sp. gr. is 1.100, and it boils at 545°, being con- siderably less volatile than creosote. It is insoluble in eupion and sparingly soluble in water ; but it dissolves without limit in alcohol and ether. It has no action on test paper ; but it unites with potassa as above mentioned, and strong sulphuric acid dissolves it without decomposition. From its permanence in the air, its fixity when heated, and its oily nature, it is well adapted for greasing machinery and protecting it from rust. 2197. Pittacal. When the heavy oil of tar is digested with a so- lution of baryta, a fine blue colour appears, which is due to pittacal, from TUTTa pitch , and xallog ornament . It is a solid of a beautiful blue colour, which admits of being fixed as a dye. It is very perma- nent, contains nitrogen as one of its elements, and appears to belong to the same class of bodies as indigo. 2198. Capnomor. This substance occurs along with creosote, pi- camar, and pittacal in the heavy oil of tar. On digesting that oil with solution of potassa, the three latter principles are dissolved, and the capnomor collects on the surface, combined with a little eupion. The capnomor is then dissolved by sulphuric acid, in which eupion is insoluble ; and from the solution, on being neutralized with carbo- nate of potassa, capnomor separates, and is purified by distillation. Its name is derived from xanvog smoke , and polga part, because it is one of the ingredients of smoke. 2199. Capnomor is a colourless transparent liquid, of a pungent taste and rather pleasant odour, has a sp. gr. of 0.975, and refracts light almost as powerfully as creosote. It boils at 365°. It is inso- luble in water and solution of potassa, and is soluble in alcohol, ether, and eupion. It has the property of dissolving caoutchouc, espe- cially when heated, and is the only ingredient of tar which does so : its presence in coal naphtha is the cause of the solvent action of that liquid on caoutchouc. The composition of capnomor has not been ascertained, though doubtless carbon and hydrogen are its principal ingredients, t. 5 . From its being decomposed by nitric acid Thomson is inclined to suspect that it contains oxygen. 2200. Cedriret has been still more recently obtained by Reichen- bach from the rectified oil of the tar of beech wood. It strikes a red colour with persulphate of iron, and all substances that easily part with oxygen ; even the oxygen of the air renders the liquid red. It forms red crystals which lie upon the filter, entangled in each other like a net, hence the name from cedrium an old name for the sour water of tar burners , and rete a net. 2201 . Naphthaline. C 10 H 4 = 64 eq. This substance was discovered in 1819 in one of the condensing vessels erected in London for the 479 Sect. IV. Picamar. Properties. Pittacal. Capnomor. Properties. Cedriret. Naphtha- line. r 480 Chap. IX. Obtained. Properties. Action of chlorine. Nitronaph- thaiese. In oil and coal gases. Coal gas obtained. NAphlhAlic acid. Organic Chemistry — Coal Gas. distillation of coal tar.* It was named from its connexion with coal naphtha. 2202. When coal is heated in iron retorts, for the preparation of coal gas, much brown semi-fluid matter is obtained called coal tar. It is from this tar that coal naphtha and naphthaline are procured. To obtain the latter the tar is distilled. The first fourth that comes over is partly naphtha, with water holding ammo- nia and naphthaline in solution. The next fourth part is a dense oil mixed with naphthaline, the latter increases in quantity as the distillation proceeds. From the last portions distilled the naphthaline crystallizes and may be freed from the oil by pressure between folds of blotting paper and then subliming at a gentle heat.t 2203. Naphthaline is white and of a pearly lustre. Its smell is aromatic, its taste pungent. It evaporates spontaneously. It melts at 174° and boils at 4 10°. I With sulphuric acid it forms sulpho- naphthalic acid. 2204. Chlorine and bromine act with violence on naphthaline, heat is disengaged and hydrochloric and hydrobromic acids are formed. It is composed of 10 atoms carbon and 4 hydrogen = 65.2. 2205. When nitric acid and naphthaline are left in contact at com- mon temperatures no action takes place. But if the acid is boiled, red vapours are emitted and an oily layer collects on the surface, which affords two products : one solid, which is nitronaphthalese, the other a liquid separable by bibulous paper. Another substance obtained from coal tar is paranaphthaline , so named by Dumas from its composition being the same as that of naphthaline.^ 2206. In the coal and oil gases prepared for ordinary combustion, small portions of several of the foregoing substances are believed to be present, communicating their peculiar properties and improving the brilliancy of the light. The distillation of coal is conducted in oblong cast-iron cylinders, or retorts, which arc ranged in furnaces to keep them at a red heat, and all the volatile products are conveyed by a common tube into a condensing vessel , kept cold by immersiou in water ; and in which the water, tar, ammoniacal, and other con- densable vapours, are retained ; the gaseous products consist principally of carbu- retted hydrogen, hydrosulphuric acid gas, carbonic oxide and acid ; these are passed through a mixture of quicklime and water in vessels called purifiers , by which the hydrosulphuric acid and carbonic gases are absorbed, and the carburet- ted hydrogen and hydrogen gases, transmitted sufficiently pure for use in to gaso- emters , whence the pipes issue for the supply of streets, houses, &c. The coke remaining in the retorts is of a very good quality. || * Ann. Philos, xv. 74, vi. N. S. 135, and Phil. 7 Vans. 1821, 209. t Reichenbach has endeavoured to prove that naphthaline does not exist ready formed in coal-tar, but that it is formed when the oil existing in this tar is exposed to a high temperature, but this was not confirmed by the experiments of Laurent, for which see T. Org. Bodies, 738. t413£°, Dumas. 5 Naphthalic Acid. C 10 H 2 O 4 . This acid has great resemblance to benzoic ; it is white, when pure, and crystallizes in long feathery crystals. It melts at 212 ° and may he volatilized without decomposition. Its fumes readily take fire. It has no smell, and a weak taste. While ary it does not affect litmus paper, but reddens it if moistened. It combines with bases and forms naphthalates. The greater number of these when heated elongate to a great extent under the form of a black glass, at- tended with the disengagement of a peculiar crystallizable matter. This acid belongs to the volatile acids of Thomson (Org. Bodies, 27) to whose de- scription the reader is referred for details and for an account of its compounds. || For a full account of the process, see Ure’s Diet. Arts and Afanuf. 545. Animal Charcoal 481 2207. The best kind of coal for distillation is that which contains Sect, iv, most bitumen and least sulphur ; 112 pounds of good coal are capa- ble of yielding from 450 to 500 cubic feet of gas of such quality, that half a cubic foot per hour is equivalent to a mould candle of six to the pound, burning the same space of time. H. The sp. gr. of the gas varies, the mean as given by Ure is 0.529 and that of oil gas 0.96.* 2208. The apparatus for the conversion of oil into gas consists of Oil S as - a furnace with a contorted iron tube containing fragments of bricks or coke, passing through it, into which, when red-hot, the oil is suffered to drop ; it is decomposed, and converted almost entirely into charcoal, which is deposited in the tube, and into a mixture of carburetted hy- drogen, and hydrogen gases, of which one volume may be regarded as equivalent to two of coal-gas, for the production of light.! The commonest whale oil, quite unfit for burning in the usual way, affords abundance of excellent gas, requiring no other purifica- tion than passing through a refrigerator to free it from a quantity of empyreumatic vapour. A gallon of whale-oil affords about 100 cubi- cal feet of gas. 2209. Lamp-black is prepared from the refuse of resin collected in , the distillation of oil of turpentine. It is a fine black powder, ex- black, ceedingly light. The soot which collects in chimneys where coal or wood is burnt differs from lamp-black. When boiled with water a matter is deposited of the appearance of pitch; alcohol and ether re- move a portion of an exceedingly acrid and bitter taste, which Bra- connot has called asbolin, from ckjGoXt] soot ; it is fluid and not volatile. 2210. Animal charcoal, though derived from the animal kingdom, Animal is supposed to owe its most important properties to the charcoal charcoal, which it contains. It is known as ivory black and is prepared from * The illuminating power of different gases burned in the same circumstances, is m um i na ting proportional, generally speaking, to their sp. gr. as this is to the quantity of carbon power of can- they contain. A mould tallow candie of 6 in the pound, burning for an hour, is equi- dle ® andlam P*- valent to half a cubic foot of ordinary coal gas, aud to four tenths of a foot of good gas. The flame of the best Argand lamp of Carcel, in which a steady supply of oil is main- tained by pump-work, consuming 649 grains in an hour, and equal to 9-38 such candles, is equivalent to 3.75 cubic feet of coal gas per hour. A common Argand lamp, equal to 4 candles, consumes 463 grains per hour, and is represented by 1.6 cubic feet of gas. Ure. t The cut (Fig. 197) represents an apparatus contrived by me, and which is very convenient for obtaining oil gas, in sufficient quantity for the exhibition of its properties ; a is a vessel of cast iron about 1 6 inches in depth, and 5 in diameter at its upper part ; having a cast iron cover, with two openings, to the smallest of which, a copper pipe leading from a funnel-shaped oil vessel b, is secured by brazing; into the larger opening a gun-barrel c is screwed which enters a small copper condensing vessel d fur- nished with a cock for drawing on any oil, or condensable va- pours that may pass over. From the upper part of the condenser a copper or lead pipe issues, whic;h conveys the gas to the gaso- meter. When oil gas is to be obtained, the vessel b is filled with oil, and the pieces of bricks are put into the retort a, the cover is then secured by a rod of iron passing through the ears ee, and the joint is made tight by a mixture of about 2 parts of sal ammoniac, l of sulphur and 30 of cast iron filings or borings, made into a paste with water.* This retort may be placed in any convenient furnace, and when heated to redness the cocky is turned so as to allow the oil to pass drop by drop. W. * This cement should be allowed to become hard before the apparatus is mead. 61 Oil gas appara- tus. 482 Of the Parts of Plants . Chap. IX, Uses. Sup of plants. Changes of, Peculiar juices. Gum resin. Air in plants. Bark. Neutral com- pound* con- taiaiog aitro- C*d. the bones of animals which are heated in close vessels, so as to drive off all the volatile matter. The earth of bones remains mixed with charcoal. Being reduced to powder it is fit for use. 2211. It is a much more powerful discolourizing principle than ve- getable charcoal. It is much employed in refining sugar. When used to remove the colour of liquids, it acts much better if the liquid be slightly acid or neutral, and at a boiling temperature. It appears to act chemically upon the colouring matter.* Section V. Of the Parts of Plants. 2212. It is the general opinion that plants receive a considerable part of their nourishment by the root ; that it enters them in a liquid state, and passes up in proper vessels towards the leaves. This liquid is distinguished by the name of sap. In nearly all vegetables it is as liquid as water. It always contains an acid, sometimes free, but more commonly combined with lime and potassa. Various ve- getable principles are also present; of these sugar is the most remarkable, and mucilage. Sometimes albumen and gluten, and tannin can be detected. When left to itself, sap soon effervesces and becomes sour ; or even vinous, when the proportion of sugar is con- siderable. X j, 2213. In its passage to the leaves the sap is altered by a process similar to that of digestion in animals, and formed into all the liquid substances required for the purposes of the plant. These liquids flow from the leaves towards the root in appropriate vessels, and have received the name of the peculiar juices of vegetables. They j* differ in different plants. They always contain much more vegeta- ble matter than the sap. Sometimes they exude spontaneously and may always be procured by incisions through the bark. 2214. The milky juices concrete into a solid matter which has been called gum resin. Several of the gum resins are employed in medicine ; the most important of which is the juice of the poppy af- fording opium. 2215. In many plants the stem is hollow and filled with air ; in some, as the onion, it is contained in the leaves ; it is lodged in the r: pod of the pea, and in the leaves of some species of fuci. In some a plants the proportion of oxygen in this air is greater than in common air,t and others contain more nitrogen ; but generally so far as expe- riments have been made it is common air unaltered. 2216. The bark is composed of three distinct portions ; the outer- most or epidermis, the parenchyma, and that next the wood the cor- tical layers. The latter consist of several thin membranes, composed of fibres forming a kind of net-work. * See Bussy’s experiments, T. Org. Bodies, 756, and Jour, de Pharrn. v iii. 257. There are several substances obtained from plants by processes similar to those employed for obtaining the vegetable alkalies, which have been arranged together by Thomson. They are caffein from coffee, piperin from pepper, daphnin from daphne alpina and mezerium, jalappin from jalap, sinapin from mustard, hesperidin from the unripe orange and lemon, populin and plumbagin. For details see T. *>rg. Bod. 757. t Priestley, iii. 279. Wood* * * § — Cotton. 483 2217. The substance known as cordis the epidermis of the quercus Sec t, v. tuber, which contains a peculiar principle called suberin. Three Cork. [different kinds of cinchona bark were early distinguished, the pale, red and yellow. The first is the bark of the cinchona lancifolia , the Isecond of the c. oblongifolia, and the last of the c. cordifolia .* 2218. The roots of a great variety of plants are employed in me- Roots, ilicineand the arts. The substances found in them are various ; and indeed, as the peculiar juices of the roots are always included in ! such examinations, it is clear that almost all the vegetable principles ] will be found in them. t. 2219. Bulbs are composed of concentric coats like the onion, or Bulbs, i are imbricated. Several of them are used as nutritive articles of food, and some constitute active medicines. Squill, the bulbous root of the scilla maritima , owes its peculiar Squill, properties to a species of bitter principle which has been called scilitin. Potatoes are the bulbs of the solanum tuberosum, an American Potatoes, plant, said to grow wild in Peru and Chili. According to Einhof potatoes afford Starch Fibrous matter Albumen Mucilage 15t 7 1.4 4 27.4 They afforded also a mixture of tartaric and phosphoric acids. When potatoes are exposed to the action of frost, they acquire a Action of sweet taste, followed by an acid taste, owing to the rapid evolution of frost upon, acetic acid, and the root soon putrefies. The sugar is formed at the expense of the mucilage. Potatoes differ from wheat and barley by containing no gluten. 2220. Woods. The mere woody fibres of all plants are probably Woods, nearly the same, and the differences are owing to the various propor- tions of liquids and empty spaces with which the woody fibres are intermixed.! The vegetable fibres in herbaceous plants correspond to the wood of trees. In some it is flexible and tough, as in hemp, nettles, &c.§ 2221. Cotton is a soft down which envelopes the seeds of various Cotton, species of gossypium. It has q. strong affinity for some of the earths, especially alumina ; hence this substance is used to fix colours on cotton ; the cloth is steeped in a solution of alum or acetate of alu- mina, and afterwards dyed. Several of the metallic oxides also combine with it readily, of which oxide of iron is one of the most re- markable. Oxide of tin also combines with it and is used as a mor- dant. 2222. Cotton combines readily with tannin and forms a yellow or brown compound. Hence infusion of galls, and of other astringent substances is often used as a mordant for cotton. * The bark from which quinia is extracted in France, is called quinquina calisaya ; but the species of cinchona to which it belongs does not seem yet accurately known. T, t For table of the quantity of starch from different kinds of potatoes, see T. Org » Bodies, 841. t For a table of the results of the analysis of various woods see T. Org. Bodies , 849, § Perhaps the fibres ought to be considered rather as the libtr or inner bark. 484 Chap. IX Quantity of oxygen required lor combustion of woods. Senna. Night- shade. Hemlock. Flowers. / Colouring matter. Of the Part$ of P huts. 2223. The quantity of oxygen required for burning 100 parts of various kinds of wood has been made the subject of experiments which are important, as this oxygen is proportionable to the quan- tity of heat evolved by each. 100 parts of Tilia Europea, lime require Ulmus suberosa, elm “ Pinus abies,^r M “ larix, larch u Acer campe6tris,Tnfl^Ze “ Pinus picea, pitch-pine “ Juglans regia, walnut “ Quercus robur, oak M Betula alba, birch “ 140.523 139.408 138.377 , 138.082 136.960 136.886 135.690 133 472 133.229* 2224. Leaves. Senna. According to Lagrange the leaves of the Cassia senna are characterized by containing a peculiar extractive principle, cathartina , which, by long boiling, passes into a resinous substance, in consequence of absorbing oxygen ; they also contain a resin which resists the action of water, and is soluble in alcohol; the whole of the soluble matter amounts to about one third the weight of the senna.t 2225. Nightshade. The leaves of the Atropa Belladonna con- tain, according to Vauquelin, 1. Vegetable albumen, or gluten. 2. A bittor narcotic princi{He. 3. Nitrate, muriate, sulphate, binoxalate, and acetate of potassa. Brandes announced the existence of a new vegetable alkali in this plant, which he calls atropia. It forms brilliant acicular crystals, tasteless, and difficultly soluble tn water and alcohol. 2226. Hemlock , conium maculatum. This plant was formerly called cicuta ; it contains a peculiar principle conicina , and its juice in chemical composition has a striking similarity to that of the cab- bage. 2227. Flowers. The colouring matter of most flowers is extremely fugitive, and is generally much changed by mere exsiccation. They usually communicate their colour to water; the infusion of blue flowers is generally reddened by acids, and changed to green or yel- low by alkalies ; that of yellow flowers is made paler by acids, and alkalies render it brown ; the red infusion of many flowers is exalted in tint by acids, and changed to purple, and in some instances, to green, by alkalies. It is probable that one and the same principle gives colour to seve- ral of the blue and red flowers, but that the presence of acid in the latter produces the red ; the petals of the red rose, triturated with a little carbonate of lime and water, give a blue liquor ; alkalies render it green, and acids restore the red. 2228. A colouring matter analogous to that of the violet, exists in the petals of red clover, in the red tips of those of the common daisy, of the blue hyacinth, the holly-hock, lavender, in the inner leaves of the artichoke, and in numerous other flowers ; reddened by an acid, it colours the skin of several plums, and the petals of the scarlet ge- * Ann. de Pharm. xvii. 144. t In the Lond. Med. Repot, rol. xv. ^69, the effect* of the various re agents on in» fusion of senna are detailed by Batlay. • 485 Seeds-— Coffee ranium and pomegranate. Some flowers which are red, become s «ct. v- blue by merely bruising them ; this is also the case with the colour- ing matter of red cabbage leaves, and of the rind of the long radish. Smithson has suggested that the reddening acid is in these cases the carbonic, which escapes on the rupture of the vessels which inclose it. 2229. The petals of the common corn-poppy , rubbed upon paper, give a purple stain, little altered by ammonia, or carbonate of soda, but made green by caustic potassa. The infusion of poppy-petals in very dilute hydrochloric acid, is florid red ; chalk added, renders it of the colour of port wine ; carbonate of soda in excess gives the same colour, but excess of potassa changes it to green and yellow. The expressed juice of the black mulberry possesses nearly the same pro- perties.^ 2230. Seeds. Starch is an essential component of the greater Se«ds. number of seeds, and it is generally united in them with a variable portion of gluten, and often of fixed and of volatile oil. Davy examined a number of seeds with a view to determine their relative nutritive powers: for the results of his experiments see Ag- ricultural Chemistry, 4to. 131. 2231. Almonds, the seeds of the amygdalus communis, consist of Almonds, an albuminous substance and oil ; the latter may be obtained by ex- pression, five pounds yielding about one pound of cold drawn oil, and about a pound and a half when aided by heat. The bitter almond affords by pressure an oil analogous to that from the former ; but if the expressed cake be distilled with water, a portion of volatile oil eminently poisonous, and smelling strongly of the almond, is ob- tained ; this oil is used as a flavouring material by confectioners, and by the manufacturers of noyeau.f 2232. Colocynth. The pulp of the fruit of the cucumis colocynthis Colocynth. or bitter cucumber is much used in medicine under the name colo- quintida. It contains a peculiar bitter principle colocynthin. 2233. Elaterium is deposited from an infusion of the fruit of the Elaterium. momordica elaterium or wild cucumber. The active principle has been obtained by Paris and Faraday and named elatin.X 2234. Coffee, the seed of the Coffea Arabica has been examined Coffee, both in its raw and roasted state. Hermann has given the following comparative analysis of coffee from the Levant and from Martinique, § the results of which differ much from those of Cadet: Resin Levant. 74 . Martinique . 68 Extractive 320 - - 310 Gum 130 - - 144 Fibrous matter « - 1335 - - 1386 Loss - - - * - 61 - 12 1920 1920 When coffee is roasted it undergoes a peculiar change of compo- * Smithson, Phil. Trans. 1818, 110. tin the Phil. Trans, for 1811, Brodie has detailed a variety of experiments illus- trative of its action as a poison. I Paris’ Pharmacol. 4th edit. Sf8. % C roll’s Annales , 486 ('hap IX. Mustard. Lupuliu. Citisin. Fruits con- tain acid, And sugar. Colouring matter. Sap green. Colouring Matter of Fruits . sition attended by the formation of tannin, and a volatile, fragrant, and aromatic principle ; but in this state it has not been examined with any precision. It is developed also by roasting barley, beans and various vegetables, which are on that account occasionally employed as substitutes for coffee. Robiquet discovered in coffee the principle called caffein. 2235. Mustard. The seed of the sinapis nigra derives its acri- mony from volatile oil ; it also contains a tasteless fixed oil, albumen, gum, and traces of sulphur and earthy salts. 2236. Lupulin was discovered by Ives* and Payen and Cheva- lier, about the same time, in the leaves of the Humulus lupulus or common hop. It is extremely bitter, of a yellow colour, and has an aromatic odour. It is the principle on which the characteristic pro- perties of the hop depend. 2237. Citisin was discovered by Payen and Chevalier in the seeds of the Cj/tisus Laburnum. Its colour is yellow, and it has a disagreeable taste ; it is soluble in water, alcohol and ether. It is easily decomposed by heat, and the strong acids produce the same effect. 2238. Fruits. The acid matter contained in fruits is either the tartaric, oxalic, citric, or malic; or a mixture of two or more of them ; but the nature and proportion of the acid varies at different periods of their growth ; gluten and starch are found in some fruits, and a gelatinizing substance, which has sometimes been regarded as identical with animal jelly, but which is probably a compound of gum and one or more vegetable acids. 2239. Most of our common fruits also contain sugar, and it exists in all those the juice of which is susceptible of vinous fermentation. In some fruits the quantity of sugar is increased by mashing and exposure to air; this is remarkably the case with some of the rough- flavoured apples used for cider, the pulp of which becomes brown, and at the same time sweet by a few hours* exposure. 2240. The colouring matter of fruits seems in most cases to bear a strong resemblance to that of flowers. The red juice of the mulberry was found to exhibit the same characters as the colouring principle of the wild poppy ; carbonated alkalies render it blue, but caustic potassa changes it to green and yellow : the juice of red currants, cherries, elder-berries, and privet-berries, and the skin of the buckthorn berry, appear to contain a similar colouring prin- ciple. 2241. The unripe berries of the buckthorn furnish a juice, which, when inspissated, is known under the name of sap green. It is soluble in water, and rendered yellow by carbonate of soda and caustic potassa ; the acids redden it, and carbonate of lime restores it to green, which is therefore probably the proper colour of the substance. t * Amer. Jour. ii> t Smithson, Phil. Trans. 181 S, p. 116. Fermentation* 487 Section VI. Phenomena and Products of Fermentation. Sect. VI. Malt. Beer. 2242. The term fermentation is employed to signify the sponta- t ^ menta * neous changes, which certain vegetable solutions undergo, placed under certain circumstances, and which terminate either in the pro- Vinousan(i duction of an intoxicating liquor, or of vinegar ; the former termi- acetous, nation constituting vinous , the latter acetous fermentation. The principal substance concerned in vinous fermentation is su- gar ; and no vegetable juice can be made to undergo the process, which does not contain it in a very sensible quantity. In the pro- duction of beer, the sugar is derived from the malt ; in that of wine, frpm the juice of the grape. 2243. Malt is barley which has been made to germinate to a cer- tain extent, after which the process is stopped by heat. The barley is steeped in cold water, and is then made into a heap or couch, upon the maltfloor ; here it absorbs oxygen and evolves carbonic acid ; its temperature augments, and then it is occasionally turned to prevent its becoming too warm. In this process the radicle lengthens, and the plume called by the maltsters the acrospire , elongates ; and when it has nearly reached the opposite extremity of the seed, its further growth is arrested by drying at a temperature slowly elevated to 150° or more. The malt is then cleansed of the rootlets. 2244. In the manufacture of beer , the malt is ground and infused in the masli- tun , in rather more than its bulk of water, of the temperature of 160° or 180°. Here the mixture is stirred for a few hours; the liquor is then run off, and more water added, until the malt is exhausted. These infusions are called wort , and its principal contents are saccharine matter , starch , mucilage , and a small quanti- Wort, ty of gluten. The strength of the wort is adjusted by its specific gravity, which is usually found by an instrument, not quite correctly called a saccharometer , since it is influenced by all the contents of the wort, and not by the sugar only.* The wort is next boiled with hops, amounting upon the average, to 20 dh e weight of the malt, their use being to cover the sweetness of the liquor by their aromatic bitter, and to diminish its tendency to acidify. The liquor is then thrown into large, but very shallow, vessels, or coolers, where it is cooled to about 50°, as quickly as possible ; it is then suffered to run into the fermenting vat , having been mixed with a proper quantity of yeast. (See Addenda ) 2245. In the fermenting vessel, the different sub- stances held in solution in the liquor begin to act upon each other ; an intestine motion ensues, the temperature of the liquor increases, carbonic acid escapes in large quan- tities ; at length this evolution of gas ceases, the liquor becomes quiet and clear, and it has now lost much of its sweetness, has diminished in specific gravity, acquired a new flavour, and become intoxicating.! * It is a brass instrument, of the shape shovvn in fig. 198, so adjust- ed in weight as to sink to the point marked 0°, in distilled water, at the temperature of 70°, and when immersed in a liquor of ihe same tem- perature, and of the specific gravity of 1. 100, it is buoyed up to the mark 100, just above the bulb. The intermediate space is divided i^o 100 equal parts, and consequently will indicate intermediate degrees of sp. gr. This is the most useful form of the instrument, though not that in common use. The specific gravity of the wort for ale is usually about 1.090 to 1.100 and for table beer from 1.020 to 1-030. t The distillers prepare a liquor, called wash , for the express purpose of producing from it ardent spirits; instead of brewing this from pure malt, they chiefly employ raw grain, mixed with a small quantity only of malted grain ; the water employed in the mash-tun is of a lower Fig. 198. 50 100 488 Product t of Distillation . c hap tx - 2246. Wine is principally procured from the juice of the grape, Wine. and some other saccharine and mucilaginous juices of fruits. This sweet juice is termed must. The principal substances held in solu- tion in grape juice are sugar, gum, gluten, and tartrate of potassa. It easily ferments spontaneously at temperatures between 60° and 80°, and the phenomena it gives rise to closely resemble those of the wort with yeast. After the operation, its sp. gr. is much diminished, its flavour changed, and it has acquired intoxicating powers. Vinous 2247. As the fermentation of must takes place without adding any fermenta- ferment, it is obvious that the requisite substance is present in the juice, tion. This was separated by Fabroni and found to be analogous to the gluten of plants; and gluten being substituted for it, the fermentation suc- ceeded. He has shown that the saccharine part of must resides in the cells of grapes, while the glutinous matter, or ferment, is lodged on the membranes that separate the cells. It is only after the juice is squeezed out that these two substances are mixed. All other juices that undergo spontaneous fermentation have been shown by Thenard and Seguin to contain a similar substance. Air necea- 2248. Gay Lussac has shown that the juice of fruits will not fer- sar y- merit, if completely excluded from the air. But if a little oxygen gas be let up to it, this gas is absorbed and fermentation goes on, the carbonic acid evolved being 100 times as great as that of the oxygen absorbed.* 2249. It seems probable that the tartaric acid is partly decomposed and a portion of malic acid formed during the process, which is analogous to combustion, being attended by the evolution of caloric and the formation of carbonic acid. Exp. 2250. If a mixture of 1 part sugar, 4 or 5 of water, and u little yeast, be placed in a due temperature, it also soon begins to ferment, and gives rise to the same products as wort or grape- juice ; and the results may easily be examined by suffering the process to go on in the apparatus fig. 199, con- sisting of a mat rice containing the fermenting mixture, with a bent tube issuing from it, and passing into an inverted jar standing in water. Fie. 199. Products of 2251. When any of the above-mentioned fermented liquors are distillation, distilled, they afford a spirituous liquor ; that from wine is termed brandy; from the fermented juice of the sugar-cane we obtain rum ; and from wash, malt spirit ; and these spirituous liquors, by re-distillation, furnish spirit of wine, ardent spirit, or alcohol . t Odourof 2252. The peculiar odour of wine is owing to the presence of a wines small quantity of a substance analogous in properties to a volatile temperature than that requisite iu brewing, and the mashing longer continued ; by which it would appear lhat*a part of the starch of the barley is rendered into a kind of saccharine matter. The wort is afterwards fermented with yeast. * Ann. de Chim. xvi. 245. t For the proportions of alcohol furnished by different fermented liquors see p. 445. The experiments of Brunde {Phil. Trans. 1811 — 13) show that it is a real educt. See also Henderson’s Table in Brewster’s Jour. i. 166. 489 Acetification. oil. It amounts, at an average, to about 4-77 P art °f wine. Sect, vi. It may be obtained by distilling the lees of wine. It has been called jEnanthic c znanthic ether. ^ ether. 2253. Acetous fermentation. When any of the vinous liquors are Amenta exposed to the free .access of atmospheric air at a temperature of t i 0IK 80° or 85° they undergo a second fermentation, terminating in the production of a sour liquid, called vinegar. Vinegar is usually ob- vinegar, tained from malt liquor or cider, while wine is employed as its source in those countries where the grape is abundantly cultivated. 2254. The colour of vinegar varies according to the materials Properties, from which it has been obtained; that manufactured in England is generally artificially coloured with burnt sugar : its taste and smell are agreeably acid. Its specific gravity is liable to much variation ; it seldom exceeds 1.0250. When exposed to the air it becomes mouldy and putrid, chiefly in consequence of the mucilage which it con- tains, and from which it may be in some measure purified by careful distillation. 2255. Neither pure alcohol, nor alcohol diluted with water, is sus- ^ ceptible of this change. The weaker the wine or the beer the more un dergo the readily it is converted into vinegar, yet strong wines yield a better change, vinegar, so that alcohol contributes to the formation of the acetic acid. Wine entirely deprived of glutinous matter does not undergo the acetous fermentation, until some mucilaginous matter is restored to it. 2256. Wine which is completely deprived of all access to atmos* >s pheric air never becomes sour. In order to understand what takes formation place during the conversion of alcohol into acetic acid, we have on ^y ”^ cetic to attend to the constitution of these two bodies. Alcohol is C 4 H 5 0 aci -j-HO while acetic acid is C 4 H 3 0 3 -j-H0. In the first place 2 atoms of oxygen are absorbed from the atmosphere for every integrant part of alcohol present. These combine with two atoms of hydro- gen and form water, leaving the alcohol in the state of C 4 H 3 0-|-H0, this is aldehyde. The aldehyde has a strong affinity for oxygen and absorbs 2 atoms of it from the atmosphere, and is converted into C 4 H 3 0 3 -|-H0 or acetic acid. Thus during the conversion of alcohol into acetic acid, every atom of alcohol absorbs 4 atoms of oxygen from the atmosphere Here unless the air be renewed the process ceases to go on. Even when the process is properly conducted about Y^th of the whole acetic acid formed is lost. But when the air is not supplied to enable the aldehyde to absorb oxygen as fast as it is formed, a great deal is volatilized, and the consequent loss of acetic acid may be very great.! 2257. When the acetous fermentation is over the whole of the Ma ] ic ac jd malic acid of the wine has disappeared as well as the alcohol. We and alcohol must conclude that they have been both converted into acetic acid. dlsa PP ears - Part of the glutinous matter undergoes the same change, part is de- posited in the state of flakes, and part remains in solution, disposing the vinegar to decomposition. * Ann. de Chim. et de Phys. lxiii. 113. t This shows the necessity on the part of manufacturers of perpetually renewing the air of their chambers. 62 490 Chap. X. Sugar es- sential. Panary fermenta- tion. Putrefac- tion. Offensive products . Proximate principles. Nitrogen. Ammonia. Organic Chemistry — Animal Substances. 2258. Sugar appears to be the essential constituent in liquors to be converted into vinegar and the quantity of vinegar formed is pro- portional to the sugar. ^ T. 1032 . 2259. Panary fermentation. The change which dough undergoes, attended with the disengagement of carbonic acid gas, has been called the panary fermentation. The adhesive gluten of the flour enables it to be distended by the carbonic acid gas, and the mass rises. The mean heat of a baker’s oven is 448°, this stops the fermentation, and the detained gas is expanded, giving to the loaf its vesicular structure. Carbonate of ammonia is sometimes em- ployed to render the bread porous. 2260. Putrefaction. Vegetable substances are decomposed spon- taneously if moist, provided the air has access to them and the tem- perature be not much under 45°, nor so high as to drive off the moisture. Plants do not putrefy in vacuo, or at least very slowly. If placed in bottles, well closed, and exposed to the temperature of boiling water a partial vacuum is formed within and they may be kept fresh for a considerable length of time.t 2261. When vegetables contain nitrogen the gases given off du- ring putrefaction are peculiarly offensive ; this is the case with the cruciform plants, and wdien sulphur and phosphorus, it is much more so. When these substances putrefy on the surface of the ground, they leave humus or vegetable soil, which consists chiefly of the extractive matter called by Berzelius apotheme. CHAPTER X. ANIMAL SUBSTANCES. Section I. Ultimate Principles of Animal Matter, and Products of its Destructive Distillation. 2262. The proximate principles of the animal creation consist, like those of vegetables, of a few elementary substances, which by com- bination in various proportions, give rise to their numerous varieties. Carbon, hydrogen, oxygen, and nitrogen, are the principal ultimate elements of animal matter ; and phosphorus and sulphur are also often contained in it. The presence of nitrogen constitutes the most striking peculiarity of animal, compared with vegetable bodies ; but as some vegetables contain nitrogen, so there are also certain animal principles, into the composition of which it does not enter. 2263. The presence of nitrogen stamps a peculiarity upon the products obtained by the destructive distillation of animal matter, and which are characterized by the presence of ammonia, formed by the union of the hydrogen with the nitrogen. It is sometimes so abun- * Seven water, one sugar, and some yeast ferment in a proper temperature and form an excellent vinegar. Ann. de Ckim. lxii. 248. For a full account of the processes see Ure’s Diet. A. and M. 1. t On this is founded the method of preserving vegetables, fruits, &c. See Ure’s Diet. A. and M. 1045. Putrefaction. antly generated as to be the leading product ; thus, when horn, oofs, or bones, are distilled per se, a quantity of solid carbonate of mmonia, and of the same substance combined with ernpyreumatic il, and dissolved in water, are obtained ; hence the pharmaceutical reparations called spirit and salt of hartshorn , and Dippel’s animal il. Occasionally the acetic, benzoic, and some other acids are >rmed by the operation of beat on animal bodies, and these are >und united to the ammonia; cyanogen and hydrocyanic acid also equently occur. 2264. If the gas evolved during the decomposition of animal bo- ies be examined, it is generally inflammable, and consists of carbu- ;tted hydrogen, often with a little sulphuretted and phosphuretted ydrogen ; carbonic oxide, carbonic acid, and nitrogen are also some- mes detected in it. The coal remaining in the retort is commonly very difficult of iti- neration, a circumstance depending upon the common salt and hosphate of lime, which it usually contains, forming a glaze upon s surface which defends the carbon from the action of the air. .nimal charcoal is also found to be more effectual in destroying co- •ur and smell, than that obtained from vegetables. 2265. By the term putrefaction we mean the changes which dead aimal matter undergoes, and by which it is slowly resolved into new roducts. These changes require a due temperature, and the pre- mce of moisture ; for below the freezing point of water, or when srfectly dry, it undergoes no alteration. During putrefaction the parts become soft and flabby, they change i colour, exhale a nauseous and disgusting odour, diminish consi- srably in weight, and afford several new products, some of which scape in a gaseous form, others run off in a liquid state, and others re contained in the fatty, or earthy residuum. The presence of air, though not necessary to putrefaction, materi- ily accelerates it, and those gases which contain no oxygen, are 3ry efficient in checking or altogether preventing the process. Car- Dnic acid also remarkably retards putrefaction ; and if boiled meat 3 carefully confined in vessels containing that gas, it remains for a ery long time unchanged, as seen in Appert’s method of preserving teal.* * This method is now successfully practised in England, upon the great commercial ale, for keeping beef, salmon, soups, &c. perfectly fresh and sweet for exportation, he process is as follows ; Let the substance to be preserved be first parboiled, or ra- er, somewhat more, the bones of the meal being previously removed. Put the meat to a tin cylinder, fill up the vessel with seasoned rich soup, and then solder on the 1, pierced with a small hole. When this has been done, let the tin vessel thus pre- ired be placed in brine and heated to the boiling point, to complete the cooking of the eat. The hole of the lid is now to be closed by soldering, whilst the air is rarefied, he vessel is then allowed to cool, and from the diminution of volume, in consequence ‘the reduction of temperature, both ends of the cylinder are pressed inwards and be- >me concave. The tin cases, thus hermetically sealed, are exposed in a test-chamber, r at least a month, to a temperature above what they are ever likely to encounter ; om 90° to 110° F If the process has failed, putrefaction takes place, and gas is solved, which will cause the ends of the case to bulge, so as to render them convex, stead of concave. But the contents of those cases which stand the test will infalli- y keep perfectly sweet and good in any climate, and for any number of years. If ere be any taint about the meat when put up, it inevitably ferments, and is de- cted in the proving process. For a variety of details and methods of preserving animal and vegetable substances se Ure’s Did. Arts and Manuf. 1046. 491 Sect. I. Carburet- ted hydro- gen. Putrefac- tion. Antisep- tics. Method of pre- serving meats, &c. 492 Chap. X. Effect of the effluvia. Fumiga- tion. Adipocere. Fibrin. Properties. Action of acids. Albumen. Organic Chemistry — Animal Substances. There are several substances which, by forming new combinations with animal matter, retard or prevent putrefaction, such as chlorine and many of the saline and metallic compounds ; sugar, alcohol, vo- latile oils, acetic acid, and many other vegetable substances also stand in the list of anti-putrefactives, though their mode of operating is by no means understood. 2266. The effluvia which arise from putrescent substances, and more especially those generated in certain putrid disorders, have a tendency to create peculiar diseases, or to give the living body a ten- dency to produce poisons analogous to themselves. An atmosphere thus tainted by infectious matter, may be rendered harmless by fumi- gation with the volatile acids, more especially the nitrous and the hydrochloric ; chlorine is also very effectual: the vapour of vinegar, though sometimes useful in covering a bad smell, is not to be relied on. It appears evident that the acid and chlorine act chemically upon the pernicious matter, and resolve it into innocuous principles. 2267. When muscular flesh is immersed in a stream of running water, it is partially converted into a substance having many of the properties of fat combined with a portion of ammonia. The same changes have been observed where large masses of putrefying ani- mal matter have been heaped together, or where water has had occa- sional access to it. Nitrate of ammonia is also sometimes formed under the same circumstances. Section II. Fibrin, tyc. 2268. Fibrin is the principal part of muscular fibre, and is found also in the blood of animals. It is solid, tasteless, inodorous ; has a whitish appearance : some elasticity, and is rendered hard and brittle by drying. Soluble in strong acetic acid, swelling at first, and forming a concentrated jelly. 2269. It is decomposed by strong and by diluted nitric acid, pure ni- trogen being evolved from it when the acid is diluted ; a yellow pow- der, called yellow acid , is formed during the reaction of the nitric acid. Berzelius has affirmed that it is a compound of nitric acid and fibrin after it has been affected by the acid. With sulphuric acid, a solution is procured, containing a peculiar white matter called leu- cine ; the sulphuric acid is separated from it by chalk, the solution of the leucine being then filtered and evaporated. Diluted hydrochlo- ric acid has little action on fibrin, and by the strong acid it is de- composed. Fibrine is also dissolved by concentrated solutions of potassa, soda, and ammonia, being at the same time decomposed. It is insoluble in water ; alcohol converts it into a fatty matter. 2270. It is procured from muscular fibre by macerating it in water, or by stirring newly drawn blood with a stick, when it collects in con- siderable quantity upon it. The analysis of fibrin affords carbon 53, hydrogen 7, nitrogen 19, oxygen 19. 2271. Albumen , 50 carb., 7 hyd., 15 nit., 26 oxy., is found abun- dantly in the solid form, and in solution in water, constituting in the latter case liquid albumen. Bone, Muscle , fyc. 493 2272. Solid albumen is found in the cellular membrane, and in Sect, in. a great number of other animal solids. Liquid albumen forms the Solid Albu- white of the egg, and almost the whole of the serum of the blood. men It is a thick fluid, distinctly alkaline from the presence of soda, com- bines with cold water, and is coagulated at 160° by heat ; it is also coagulated by alcohol, by sulphuric, nitric, hydrochloric, metaphos- Properties, phoric, and many other acids ; by ferrocyanate of potassa after the addition of acetic acid ; by bichloride of mercury, hydrochlorates of tin and iron,mcetate of lead, and by the infusion of galls. Phospho- ric and pyrophosphoric acids do not precipitate it. The coagulated albumen generally carries along with it a portion of the precipitating agent. 2273. With bichloride of mercury, a precipitate of chloride of mer- cury and albumen is formed ; or of the oxide of mercury, according to more recent investigation. Bichloride of mercury detects albumen Coagulated in 2000 parts of water. ^ An excess of albumen dissolves those pre- g^^cif 0 cipitates which are compounds of albumen and an oxide. It is also instantly coagulated by Voltaic electricity ; and if two platinum wires connected with a small battery be immersed into diluted albumen, a very rapid coagulation will take place at the negative pole, and scarcely any effect at the positive pole. 2274. Albumen coagulated by heat, or by drying successive layers in the open air, resembles nbrine much, and can scarcely be distin- guished from it by the action of tests. Berzelius states that it has no action on binoxide of nitrogen, but that fibrine produces a disengage- ment of oxygen. 2275. Gelatine , 47 carb., 7 hyd., 16 nit., 27 oxy., is not found, Gelatine, like the preceding substances, in any animal fluids. It is obtained prin- cipally from skin, bones, membranes, ligaments, and tendons. Isin- glass is a purer variety, which is prepared from the sounds of the sturgeon and other fish. It is solid, soluble in water, hot or cold ; not coagulated by heat or acids ; forms a solution which gelatinizes when cold, even when 100 parts of water are used with only 1 of gelatine. Tannin precipitates it copiously; the compound is called tanno-gela- tine, and is of the same nature with leather, which is usually pre- pared by the action of tannin (derived from oak-bark) with the skins of animals. Glue consists of impure gelatine. Gelatine is insoluble in water ; converted into a peculiar saccharine matter by sulphuric acid ; not precipitated by bichloride of mercury or subacetate of lead. 2276. Osmazome is found associated with muscular fibre and Osmazome. other animal matters; it is particularly distinguished by its solubi- lity in water and alcohol at any temperature, and by not forming a gelatinous solid when its solution is evaporated. Osmazome is re- garded as the matter which gives to broth its peculiar flavour. Section III. Bone, Muscle, fyc. 2277. Bones contain about 33 per cent, of animal matter, and 67 Bones of earthy substances. The animal matter is composed principally of c gelatine and marrow or fatty matter. The following are the compo- * Bostock, in Nicholson’s Jour xiv. 494 Chap X. Analysis bones. Effect of heat. Horns, &c. Hair. Brain. Blood. Organic Chemistry — Jlnimal Substances. nent parts of the earthy matter in 100 parts of bones, omitting fractions : — Phosphate of lime, about . . . .51 parts. Carbonate of lime, . . . . . 11 “ Fluoride of calcium, . . . 2 “ Phosphate of magnesia, . . 1 “ Soda, chloride of sodium, and water in smaller proportion. Silica and alumina, with Oxides of iron and manganese, have also been detected. 2278. Exposed to heat in the open air, the animal matter is con- sumed, and the earthy substances alone left. Exposed to heat with- out access of air, ammonia, inflammable gases, oily matter, water, and other substances, are evolved, much of the carbon of the decom- posed animal matter remaining with the earthy substances of the bone. In this condition it is termed ivory black , which is much em- ployed as a decolourizing agent, charcoal from animal substances (2210) being very powerful in this respect. If the charcoal be re- quired perfectly free from earthy matter, hydrochloric acid may be employed to dissolve it ; and when it has been removed by solution, the remaining charcoal should be well washed, and heated to red- ness, before it is used to destroy animal or vegetable colouring matter. 2279. If bones be kept for some time in diluted hydrochloric acid, all earthy matter is removed, and the animal matter which remains retains the original form of the bone. 2280. Teeth are composed of the same materials as bones, but contain less animal matter. 2281. Horns , hoofs , nails , tendons , the cuticle , and the true skin , are composed principally of gelatine ; horns contain also coagulated albumen, and a portion of earthy matter. 2282. The muscles are composed principally of fibrine, with albu- men, gelatine, osmazome, fatty, and saline matter. 2253. Hair , wool , and feathers , are considered to contain a pecu- liar animal matter. Silica, sulphur, iron, manganese, and other substances, more particularly salts of lime, have also been detected in them. 2254. In brain and the matter of the nerves, 80 per cent, of water are found. Albumen, fatty matter, and osmazome, constitute the other principal ingredients. A variable proportion of phosphorus has also been detected, along with minute quantities of salts and sulphur. Section IV. Blood , Respiration i Animal Heat. 2285. The blood is a fluid slightly saline, unctuous, and has a pe- culiar odour. Sp. gr. 105, and temperature above 97° when newly drawn, or while circulating in the bloodvessels ; it appears to be ho- mogeneous, but by the microscope it is found to consist of a fluid almost without colour, in which numerous red particles are sus- pended. 2286. When removed from the bloodvessels, a halitus or vapour arises from the surface, composed of water and a little animal mat- ter, and after a few minutes the whole mass gradually assumes a Blood. 495 solid consistence. Shortly afterwards a few drops of yellowish fluid Sect. iv. gather on the top, and, finally, the blood spontaneously separates into two parts, the clot or crassamentum, which is thick and solid, and the serum or fluid portion. From 2 to 3 parts of crassamentum are usually procured, with 1 of serum. 2287. The conversion of the fluid mass into the solid form is Coagula- called the coagulation of the blood, and it commences within two or'JjjjJJJ** three minutes after its removal from the bloodvessels ; the clot or bl0 ° * coagulum, however, often continues to contract slightly for two or three days ; it then assumes the form of a cup, and floats amidst the serum. The cause of the coagulation is not known ; it has been attributed to a vital action, the blood being considered to have the property of vitality as well as the living solids. It indeed contains organized solids floating in a transparent medium. 2288. The coagulation is accelerated by exposing the blood to a Accelera- temperature of 120°, or drawing it from a small orifice into a shallow led > vessel. 2289. It coagulates quickly if the air be rapidly exhausted from the vessel in which it is received ; and it has been observed to coa- gulate speedily in proportion to the depression of the vital energies, as, for instance, in hoemorrhage. Hence the blood last removed ge- nerally coagulates first. Alum, and the sulphates of zinc and copper, promote this change. The tint of coagulum is much affected by the colour of the vessel in which the blood is received. 2290. Saturated solutions of hydrochlorate of soda, hydrochlorate Prevented, of ammonia, nitrate of potassa, and potassa, death arising from vio- lent mental emotions, or preceded by severe exercise, prevent the process of coagulation. Low temperatures produce a similar effect, or retard it much ; thus, blood which coagulates in five minutes at 60°, requires fully an hour at 40°. 2291. It has been stated that the blood does not coagulate in cases of death induced by lightning, but this has lately been contradicted. In animals killed by a powerful galvanic battery the blood has been found coagulated. 2292. Besides a particular exhalation from the blood, heat is evolved during coagulation. Carbonic acid gas was supposed to be disengaged; but it is not now considered that any of this gas is evolved. 2293. The blood according to M. Le Canu, consists of the follow- Composi- ing substances in 1000 parts : tion/ Water, ....... 785.590 Fibrin, ....... 3.565 Albumen, - - - . . . 69.415 Colouring matter, ...... 119.626 Crystalline fatty matter, termed Seroline, (Cholesterine ?) - 4.300 Oily matter, 2.270 Extractive soluble both in alcohol and water, - - 1.920 Albumen combined with soda, .... 2.010 Chlorides of sodium and potassium, with phosphates, sulphates, carbonates, of potassa and soda, .... 7.304 Carbonates of lime and magnesia ; phosphates of lime, magne- sia, and iron ; peroxide of iron, .... 1.414 Loss, - - - 2.586* * According to Gmelin and Tiedeman blood does not contain free carbonic acid. See their Researches on Blood in Rec. of Gen . Sci. 1. 56. 496 Chap. X. Peculiar volatile matter. Effect of bleedings. Crassa* mentum. Colouring matter. Action of chlorine. Obtained. Organic Chemistry — Animal Substances. 2294. Small portions of alumina, silica, and manganese, have been found in the blood, and even a minute trace of copper, by Sarzeau and O’Shaughnessy. 2295. Baruel maintains that the blood contains, in addition to the preceding principles, a volatile matter peculiar in each species, which is disengaged when the blood is mixed with strong sulphu- ric acid. 2296. The proportion of the different substances in blood varies at different periods of life, in different individuals, and in disease. The proportion also of the serum to the clot varies much from the shape of the vessel in which the fluid is received. The fatty mat- ter has been regarded as Cholesterine. 2297. From experiments made on the changes produced in the composition of the blood by repeated bleedings, it appears that the albumen and salts decrease at each bleeding ; the diminution is, however, very variable, and even after the fourth time does not amount to one and a half per cent. In the globules the same dimi- nution takes place, but to such a degree that they are at least re- duced to less than one-half their original quantity. 2298. The proportion of solid matter of the serum, and solid matter of the clot, is variously estimated, but Prevost and Dumas give the following relative quantities, in 1000 parts of human blood Water, 784 Solid matter of crassamentum, - - 129 -serum, 87 2299. In the Crassamentum the principal solids are the fibrine and colouring matter of the blood, mixed with albumen derived from the serum. By washing in a cloth with water, all the colouring matter may be removed, the fibrine being left. The fibrine is found not only in the red globules, but also in solution in the serum, as it cir- culates in the living system. 2300. Colouring matter of the blood. Regarded formerly as de- pending essentially upon iron for its tint, which is attributed now to a peculiar animal matter resembling albumen, and called Hemato- sine. It differs from albumen in its colour, and is black when pure; it has a reddish colour when reduced to powder. It is more easily coagulated by heat than albumen, and is not precipitated by the ace- tate or subacetate of lead. It contains carbon, oxygen, hydrogen, and nitrogen, with a minute quantity of iron. It acts with other agents in the same manner as albumen. 2301. When chlorine is transmitted through a solution of the colouring matter, a white flocculent matter is precipitated, and a transparent fluid is obtained, in which the iron may be detected by all the usual tests. Iron cannot be detected by the usual reagents, when dissolved in a solution containing organic matter. 2302. It is obtained by diluting a solution of colouring matter in albumen with 10 parts of water, and heating the liquid, when the colouring matter is separated by coagulation at the temperature of 149°, while albumen remains in solution till heated to 160°. It is also precipitated by several metallic oxides. A solution of the colouring matter in excess may be procured by stirring the clot in Endosmose — Ex osmose . 497 water, having drained it previously on bibulous paper, after cutting Sect. IV. it in thin slices. The solution of colouring matter in albumen is procured by stirring newly drawn blood, so as to remove the fibrme. 2303. Erithrogen (from bqvOqos, ruber) is a term applied by Bizio Erithrogen. to a peculiar animal principle obtained by him in a diseased gall- bladder, and which he considered as the base of the colouring mat- ter of the blood. It is turned red by nitrogen. 2304. The serum constitutes the fluid portion of the blood ; it is gerum of a pale yellow colour, with a slight tinge of green, and sometimes presents a milky appearance. Sp. gr. 1.030. It contains free alka- li (soda.) 2305. It is coagulated by heat, acids, alcohol, and by galvanism. Effect of On cutting and pressing the coagulum when produced by heat, a small heat, &c. quantity of colourless limpid fluid exudes, called the serosity , con- taining a considerable portion of the saline matter of the blood, and also a portion of animal matter. 2306. According to Marcet, 1000 parts of the serum consist of — Analysis Water, ----- 900. Albumen, ----- 86.8 Hydrochlorate of potassa and soda, - 6.6 Muco-extractive matter, 4. Carbonate of soda, - - - - 1.65 Sulphate of potassa, - - - 0 35 Earthy phosphates, - - - - 0.60* 2307. Respiration consists in the inspiration and expiration of air, R eS pi ra „ during which the air received into the lungs meets with the blood, tion. when it changes from the dark purple colour of venous blood to the bright and brilliant red colour which it presents in the arteries. No difficulty is now entertained with respect to the air penetrating through the thin membrane of the cells of the lungs, as numerous experiments, particularly those of Mitchellt and Faust, have shewn that air can pass through membranous matter, and affect chemi- cally the contents within. 2308. The experiments on the diffusion of gases illustrate the Exp. passage of air through apertures impervious to water ; while the movements that take place in different fluids separated by a mem- branous partition, also clearly prove the facility with which an inter- change of principles can ensue with great force where it was not previously suspected. Dutrochet, who made many interesting ex- periments on this subject, found that a bladder filled with a sirupy fluid and placed in water, soon absorbed so much of the water that it burst, a portion of the viscid fluid also escaping through the pores. Endosmose Endosmose is the term applied to this peculiar action as it is observ- and exos- ed in liquids, and exosmose to the passage of a portion of fluid from & the interior to the other portion of liquid with which it may be sur- rounded ; this exosmic movement always accompanies the endosmic action. The extensive surface on which the fluid is spread in the * A valuable paper on Blood and Chyle by Muller will be found in Rec. of Gen . Sci. i. 424. iAmer. Jour. Med. Sci. Philad. 63 498 Chup. X. Effect of air, &c. Arteriali- zation. Oxygen re- moved, And carbo- nic acid formed, Its quanti- ty. Animal heat. Organic Chemistry — Animal Substances . cells of the lungs, must be peculiarly favourable for the absorption of oxygen from the air by the blood, and the evolution of carbonic acid. 2309. Blood agitated with air or oxygen becomes of a florid red in the same manner as in the lungs ; but with nitrogen and with car- bonic acid the colour is darkened. The quantity of air affected ap- pears to correspond with the amount of colouring matter in the blood. The presence of saline matter, as in the serum of the blood, is essential to the change of colour ; it does not take place without it, however freely the air or oxygen may be supplied, as Stevens proved. The experiments of Gregory and Irvine have shewn that oxygen is necessary to induce the red tint in the globules diffused through serum, or any similarly diluted solution of saline matter,, though the change may be produced in a strong saline solution without any oxygen. Arterialization is the term applied to the changes that are produced in the fluid derived from the food, as it is converted into blood. 2310. During respiration, the quantity of oxygen in the air is diminished, and in man it is replaced by an equal bulk of carbonic acid gas ; in other animals, the quantity of this gas given out is occasionally observed to be greater, and sometimes less than the oxygen consumed. Every minute, it has been calculated byAllen and Pepys, 26 cub. inches of carbonic acid are produced, an estimate considered rather high by many chemists ; the air given out from the lungs contains, according to other estimates, 3.6 per cent, of carbonic acid ; according to them, from 6 to 8 per cent, of this gas. 2311. The quantity of carbonic acid according to Coathupe is but 6.4 per cent. According to his recent experiments 460.800 cubic inches, or 266.66 cubic feet of air pass through the lungs of a healthy adult in 24 hours, of which 10.666 cubic feet will be converted into carbonic acid gas =23S6.27 grs. or 5.45 ounces avoirdupois of car- bon. This gives 99.6 grains of carbon per hour, produced by the respiration of one adult or 124.328 pounds annually.* 2312. The experiments of Thomson, Prout, and Fyfe, shew that the quantity of carbonic acid evolved at different temperatures varies much under different circumstances, and even at different periods of the day. 2313. By a forced expiration, about 200 cub. inches of air may, on an average, be expelled from the lungs. 2314. The nitrogen of the air is little affected, apparently, by res- piration ; occasionally its quantity appears to be increased, and sometimes it is diminished, the effect varying with the seasons and other circumstances. 2315. Animal heat. The discovery of carbonic acid in the air dis- engaged from the lungs during respiration, was made by Black. He considered respiration analogous to combustion, and that the car- bonic acid is formed in the lungs. Crawford, adopting his views, believed that the capacity of the blood for caloric is increased at the moment the carbonic acid is produced, and hence the reason why no burning heat is perceived in the lungs; but the capacity of the * See Coathupe’s experiments in Lond. and Edin. Philos. Mag. June, 1639. 499 Blood— Buffy Coat . blood, he supposed, is diminished as it passes from arterial to venous Sect, iv. blood in the extreme capillaries, when the heat that had originally Theories? been produced (though not rendered sensible in the lungs) is evolved, diffusing an equal degree of warmth over the whole body. His ex- periments, however, as to the relative capacities of oxygen, carbonic acid, venous, and arterial blood, on which the theory rests, have not been supported by other chemists. 2316. Ellis considered that carbon is separated from the blood as an excreted product, and then acts on the air inspired. 2317. Hassenfratz and Le Grange proposed another view of the manner in which the carbonic acid is produced, and it is most gene- rally received at present. They considered that the oxygen of the air is absorbed by the blood, and a corresponding quantity of car- bonic acid evolved, produced during the course of the circulation by the oxygen which had been previously absorbed. Carbonic acid gas has been detected in venous blood, being evolved when it is trans- ferred directly from the living body into an atmosphere of hydrogen gas. 2318. The skin affects the air much in the same manner as the lungs, carbonic acid being produced and oxygen consumed. 2319. In some animals, respiration is carried on entirely by the skin, and a considerable quantity of carbonic acid evolved. 2320. The production of animal heat was considered by Black to Black’s depend upon the formation of carbonic acid by the oxygen of the theory, air combining with the carbon of the blood. Numerous experiments have now proved, that the greater the heat produced in the body, the greater the consumption of oxygen in the lungs ; it is also sup- posed that this operation is not the only source of animal heat, but that it may be developed in part by other operations going on at the same time. 2321. By disease, blood is much altered in its properties. In Effect of cases of cholera it is very much affected; its colour becomes dark, disease, sometimes it acquires the consistence of tar, and is less readily affected by the oxygen of the air. It loses much water, and most of its saline matter, the proportion of albumen and colouring mat- ter being increased. Its density is greater, and it does not co- agulate. 2322. Blood occasionally presents a white appearance, owing to the presence of fatty matter in considerable quantity, which is de- tected by ether dissolving it, and giving a solution, from which it may be procured by evaporation. 2323. In cases of inflammatory action, the crassamentum is cov- Buffy coat, ered with a coat of pure fibrin, usually called the buffy coat. This arises from the blood being so altered in its qualities, that the fibrin it contains in solution coagulates more slowly than the rest of the blood, and part of it is deposited above the red clot. The red glo- bules of the blood, are considered heavier than pure fibrin, con- sisting of a small portion of colourless fibrin in the centre, which is surrounded by the colouring matter of the blood. When the blood is removed from the body, and the colouring matter escapes from the globule, the fibrin from the centre adheres firmly to- gether. 500 Chap. X. Effects of disease on blood. Saliva. Pancreatic juice, Gastric juice, Its action on food. Bile. Organic Chemistry — Animal Substances. 2324. The blood is affected to a great extent in a number of other diseases, though this may not in general be so easily recognised as in the preceding cases, chemical analysis being required to point out the change. Occasionally, however, the change is sufficiently evident, as in jaundice, when the blood acquires a greenish-yellow tint in consequence of the absorption of bile. The black vomit observed in yellow fever is regarded as a compound of blood and hydrochloric acid. Urea is frequently observed in the blood, more especially in those cases when the secretion of urine is suppressed. Section V. Salivary , and Gastric Juices , Bile. 2325. The Saliva contains a small quantity of solids in solution, scarcely amounting to 1 per cent. The solid matter is composed of a peculiar animal matter and saline substances, among which free soda and sulphocyanate of potassa have been detected. It varies, however, in its composition, and has been frequently observed acid, neutral, and alkaline. 2326. Pancreatic juice. Regarded formerly as being of the same nature with saliva, though now considered very different, containing a little albumen, curdy matter, osmazome, a free acid (acetic?), but no sulphocyanic acid is present. 2327. Gastric juice. This fluid is secreted in its proper form only from the stimulus of food, when hydrochloric acid may be distinctly traced in it, to which the great solving powers which it possesses are attributed; acetic acid is also associated with it. The hydrochloric acid is probably derived from common salt, and to the soda produced, as the hydrochloric acid is removed, the alkaline reaction of the blood may perhaps be attributed. The stomach itself is supposed to be defended from the action of the corrosive acid by assuming a pe- culiar electric condition. In cases of sudden death, the stomach is often found corroded in consequence of the action of the acid on its fibres. Gastric juice acts powerfully in coagulating milk. 232S. The gastric juice acting on the food produces a pulpy mass, termed chyme, from which, in the intestines, a milky fluid, the chyle is absorbed ; this contains the nutritious matter derived from the food, and is conveyed to the heart, and thence to the lungs, where it acts with the air, and is converted into arterial blood. 2329. Bile is a greenish-yellow coloured fluid, generally rather viscid, having a sweetish bitter taste and nauseous odour. Heavier than water, alkaline ; coagulated by acids. Thenard regards the bile of the ox as a compound of about 7 parts of water and 1 of animal and saline matter, composed of — Picromel. Hydrochlorate of soda. Resin. Hydrochlorate of potassa. Yellow matter. Sulphate of soda. Soda. Phosphate of lime. Phosphate of soda. Magnesia and oxide of iron. The saline matter constitutes a small proportion of the ingredients. Cholesterine, an odoriferous animal matter, and another peculiar animal matter, osmazome, gluten, cholic acid, and some fatty sub- See experiments of Tiedemann and Gmelin in Ann. de Chim. lix. 348. Caseous Matter-— Chyle. 501 stances, have also been found in bile; In human bile, similar ingre- Sect, vi. dients have been detected. 2330. Picromel. Solid, crystalline, soluble in alcohol and water ; picromel. taste sweet. Prepared from bile by precipitating sulphuric acid and some other substances by acetate of le£d, then adding subacetate of lead, the oxide falling down with the picromel and resin. By hydro- sulphuric acid acting on the precipitate suspended in water, sulphuret of lead is formed, being left undissolved along with the resin ; the picromel remains in solution. 2331. Cholic Acid is solid, crystalline, reddens litmus, and has a Cholic sweet taste. Biliary Calculi are composed principally of choleste- acid * rine, and the colouring matter of the bile. Sometimes they contain no cholesterine. 2332. Cholesterine is white, crystalline, with a pearly lustre. Choleste- Melts at 278° ; does not form a soap with potassa. Insoluble in rine - water; dissolved abundantly by boiling alcohol; sparingly soluble in cold alcohol. By the action of nitric acid, cholesteric acid is produced. Section VI. Milk and Chyle. 2333. Milk contains the following substances, of which the first, Milk, water, constitutes nearly 929 parts in 1000 : — Water. Hydrochlorate of potassa. Butter. Acetate of potassa. Caseous matter. Phosphate of potassa. Sugar of milk. Phosphate of lime. Lactic acid. Traces of iron. 2334. Cream contains rather more than 3 per cent, of caseous mat- Cream, ter, and 4 of butter, the rest being whey. 2335. Whey consists principally of water, with small portions of Whey, animal matter, and a large quantity of a peculiar saccharine matter, called sugar of milk, which may be procured by evaporation. 2336. Butyrine is the name given to oily matters which constitute Butyrine. butter. 2337. Caseous Matter is the curdy substance obtained from milk Caseous coagulated by rennet, the infusion made by the action of water upon matter ‘ a portion of the stomach of the calf, which is powerful in coagulating milk. It always contains in this condition some foreign matter asso- ciated with it, being soluble in water when pure, and forming a mu- cilaginous solution. Sulphuric, nitric, hydrochloric, and other acids ; alcohol, the infusion of galls, and a variety of other substances, coa- gulate milk by combining with the caseous matter. 2338. Caseous matter is maintained by some chemists to contain two distinct principles, caseic acid , and caseous oxide of aposepi - dine. Others again regard it as approaching very nearly to coagu- lated albumen in its leading characters. 2339. Chyle is the milky looking fluid taken up from the chyme. Chyle. It approaches in its characters to blood, but has only a slight pink tint, and contains less solid matter. It forms a less firm crassamen- tum during coagulation, and from its serum a flocculent precipitate is obtained by heat, termed byProut incipient albumen. The chyle of two dogs analyzed by him contained from 89 to 94 of water, 502 Organic Chemistry — Animal Substances. Chap, x. the rest being fibrin, incipient albumen, albumen with a slight pink tint, and minute quantities of sugar, and oily and saline matters. Stearine. Section VII. Oleaginous and Fatty Substances. 2340. These resemble jnuch in all their leading characters the fixed oils of vegetables. Stearine is found in most of them asso- ciated with variable proportions of oleine. Berard prepared a sub- stance very similar to fat, by passing through a red-hot tube a mix- ture of carbonic acid, carburetted hydrogen, and hydrogen. Dobe- reiner succeeded in producing an analogous compound with coal gas and watery vapour. 2341. Stearine is obtained with facility in brilliant crystals when deposited from a hot ethereal solution. It is very soluble in hot ether, sparingly soluble in cold ether. It is also soluble in boiling alcohol. Melts at 129°. Prepared by boiling mutton suet in ether, after melting it to separate any membranous matter, and removing the adhering solution from the crystals by bibulous paper ; this pro- cess is repeated with the crystals several times. Similar processes may be adopted in preparing stearine from other fatty matters. 2342. When boiled with a solution of potassa or soda, it is resolved into stearic acid and glycerine. The stearic acid may be separated by neutralizing the alkali with sulphuric acid (1690). 2343. Margarone is the name given to another fatty matter very similar to stearine, but more soluble in ether, and melting at 117°. It is procured by allowing the matter separated from the stearine (1693) to evaporate and crystallize spontaneously. 2344. Olein is obtained by pressing lard in bibulous paper, to which it adheres. It is similar to that procured from vegetable sub- stances.* 2345. Ambergris is considered to be a concretion produced in the Ambergris, stomach of the spermaceti whale. It is found floating on the sea coast of India and Africa. It consists principally of a peculiar fatty matter, called ambreine, which resembles cholesterine.t 2346. j Dippers Oil is the name given to a thin limpid oil, the pro- duct of the destructive distillation of animal substances. 2347. Fat , Hogs’-lard and Suet, are compounds of stearine and oleine in various proportions; they melt at various temperatures be- tween 59° and 102°. The stearine and oleine differ often in the fat obtained from different animals. 2348. Hircine is procured from the fat of the goat and sheep. 2349. Spermaceti is prepared from the fatty matter found in the head of the spermaceti whale. Solid, white, crystalline, insoluble in water, soluble in ether and alcohol. Melts at a temperature below 212°. It is usually mixed with a little fluid oil, and is termed eetine when purified by solution in boiling alcohol and crystallization. Ethal is a solid fatty mutter which remains after the separation of margaric and oleic acids ; boiling eetine with potassa or soda, so as to produce soap. Margarone. Olein. Dippel’s oil. Fat, hogs- lard, and suet. Hircine. Sperma- ceti. * Adipodre. See 2267. t Cholesterine . See Bile. Lactic Acid. 503 2350. Spermaceti Oil is the fluid expressed from the fatty matter Sect, vm. from which the spermaceti is obtained. 2351. Train oil is procured by heating blubber to 212°. Its often- Train oil. sive odour arises from decomposed animal matters which are mixed with it. Section VIII. Mucus , Pus , fyc. 2352. Mucus. The existence of a distinct principle to which this Mucus, name has been applied is doubtful. The mucus described by Bos- tock is soluble in hot and cold water, and does not gelatinize. Tan- nin and bichloride of mercury do not precipitate it. The mucus of the nose is rendered transparent by water, but not dissolved. It is dissolved by nitric acid, dilute sulphurie acid, and potassa. 2353. Pus varies much in its qualities, according to the nature of Pus. the source from which it is produced. Healthy pus is a bland, thick fluid, apparently homogeneous, but composed of a thin transparent fluid, with opaque globules floating in it. Sp. gr. 1.030. Neutral, but becomes acid by the action of the air. Soluble in sulphuric, nitric, and hydrochloric acids, and in alkalies. Ammonia produces a gelatinous mass with it. 2354. The following are the principal tests which have been pro posed for distinguishing pus from mucus : — Tests. Mixed with an equal weight of water, and then with an equal weight of a saturated solution of carbonate of potassa, Diffused through water. Dissolved in potassa, and water added, Dissolved in sulphuric acid, and water added. Mucus. does not gelatinize. from a catarrh, it floats, not affected. • remains suspended in the water. Pus. produces a jelly. Tests of mucus and pus. precipitated. precipitated. precipitated. 2355. Fluid of Serous Surfaces. Composed principally of water, Fluid 0 f se- with small portions of albumen, mucus, and saline matter. The rous sur- lymph which lubricates the cellular membrane is considered of ana- fac€s * logous composition. Small portions of lactic acid are also found in it. 2356. Lactic acid has been found in most animal fluids, and in a Lactic acid, number of vegetables ; it was first obtained from sour milk, from which its name is derived. Its concentrated solution is sirupy, very acid, and can displace acetic acid from its combinations. It is pre- pared by evaporating solutions containing it to a sirupy consistence, extracting the lactic acid by alcohol. By combination with oxide of zinc, separating it afterwards by baryta, and ultimately removing the baryta by sulphuric acid, it is obtained in a pure form.* * Formic Acid has been already described ( 1610 ). 504 Organic Chemistry — Animal Substances. Chap. X. Urea. Uric or li- thic acid prepared . Purpuric acid. Cyanuric acid. Urine. Analysis- Decom- posed. Section IX. Urea — Uric Acid. 2357. Urea has been already described (1742). According to Cass and Henry it does not exist in urine uncombined, but united with different acids in different beings ; in man combined with hip- puric acid, in serpents and birds with lithic acid, or at least with the peculiar acid, which, according to Liebig, is its radical.* 2358. Uric or Lithic Acid may be prepared from calculi of uric acid, or from the uri 9 acid deposited from acidulated urine, by dissol- ving it in a solution of potassa, and adding an acid to precipitate it from the urate of potassa. t 2359. Purpuric Acid is white when pure, and is particularly dis- tinguished by the brilliant coloured purple compounds which it forms with several of the salifiable bases. Formed in combination with ammonia by the action of nitric and uric acids. The ammonia may be displaced by potassa, and the purpuric acid precipitated by adding sulphuric acid to combine with the potassa. The erythric acid of Brugnatelli, and the sediment often deposited from urine in fevers, and called at one time rosacic acid, are considered by Prout to be composed of purpurate of ammonia. 2360. Cyanuric Acid, called also Pyrouric Acid , is formed when uric acid is heated, or by the action of chlorine on different compounds containing cyanogen and water. Urea also may be made to produce this acid (1761). 2361. A peculiar colouring matter, not containing any purpuric acid, has also been discovered in the urine. 2362. Urine is a transparent limpid fluid, of an amber colour ; sp. gT. 1.02244 when recently discharged it has an acid reaction, but after a short time it acquires decided alkaline properties. The following are the component parts of urine, according to Berzelius, in 1000 parts : — • Water, - 933.00 Urea, 30.10 Uric acid, ..... 1.00 Free lactic acid, and lactate of ammonia with ani- mal matter, - - - - - 17.14 Mucus of the bladder, - 0.32 Sulphate of potassa, .... 3.71 “ soda, .... 3.16 Phosphate of soda, .... 2.94 Phosphate of ammonia, - - - 165 llydrochlorate of soda .... 4.45 “ ammonia, .... 1.50 Earthy matters with a trace of fluate of lime, - 1.00 Siliceous earth, ... 0.03 Sulphur, phosphorus, and albumen, are also found, but in very small quantities. In children, and also in graminivorous animals, a considerable amount of benzoic acid may be detected. Its sp. gr. varies very much, both in health and disease. 2363. Urine is quickly decomposed spontaneously ; and as the *Jour. dc Pkarm. March, 1S39, and Edin. Philos. Mag. Aug., 1839. t See Thomson in Rec. of Gen. Sci. ii. 3. 1 1.0138, Thomson. Urinary Calculi. urea is resolved into carbonate of ammonia, phosphate of lime and Sect, ix. phosphate of ammonia and magnesia are deposited. 2364. From disease the urine is often much changed in its quali- ties ; the following are the principal alterations. 2365. The urine often becomes so loaded with different materials, Deposition that much is deposited in the solid form before it is discharged, ofCalculi, giving rise to the production of urinary sand or calculi, according to the cohesion of the precipitated matter. 2366. Uric Acid Calculi are of a brownish-yellow colour, and ge- nerally consist of different layers of acid. They are decomposed by Unc acid ' heat, soluble in potassa, produce purpurate of ammonia by nitric acid. In most calculi, small portions of uric acid may be detected. An excess of uric acid, or the decomposition of urate of ammonia by other acids, are considered the principal causes of the deposition of uric acid. 2367. Urate of Ammonia Calculi have a clay colour ; evolve am- Urate of monia when heated with potassa. With the other agents mentioned ammonia, in the preceding paragraph, the same phenomena are produced as with uric acid calculi. 2368. Oxalate of Lime Calculi are rough and tuberculated on the Oxalate of surface. Healed to dull redness they produce carbonate of limeH ime > Heated to whiteness nothing is left but quicklime. With sulphuric acid, sulphate of lime is formed, and then the oxalic acid may be se- parated in solution by water. 2369. Phosphate of Lime Calculi. Not decomposed by heat ; phosphate insoluble in potassa; soluble in diluted nitric or hydrochloric acid; of lime, give no ammonia when heated with potassa ; not dissolved by cold acetic acid. 2370. Phosphate of Ammonia and Magnesia Calculi evolve am- phosphate monia w T hen heated alone, or with potassa. Not dissipated by heat, a ™™°* though the ammonia is expelled. Soluble in diluted nitric and hy- Magnesia, drochloric acids ; soluble also in cold acetic acid. 2371. The Fusible Calculus is a mixture of phosphate of lime Fusible, with phosphate of ammonia and magnesia. It is melted by heat. Cold acetic acid dissolves the phosphate of ammonia and magnesia, but does not affect the phosphate of lime. 2372. The Carbonate of Lime Calculus is distinguished in the Carbonate same manner as common carbonate of lime. A portion of animal of lime, matter is generally blended with it. A calculus composed of oxalate and carbonate of lime has lately been noticed. Both these varieties, however, are extremely rare. 2373. The Alternating Calculus consists of alternate layers of Alterna _ some of the preceding calculi. Siliceous Gravel has occasionally ting, been noticed in some urinary complaints. It is not affected by heat, is insoluble in acids, fuses with alkalies added in excess, and pro- duces silicated potassa. 2374. Cystic Oxide Calculi contain a peculiar animal matter, cys- Cystic ox- tic oxide, which is soluble in acids, alkalies, alkaline carbonates, and ide > lime-water. Xanthic Oxide Calculi consist of another peculiar ani- mal matter. With nitric acid it produces a lemon-yellow coloured compound. . 2375. Fibrinous Calculi are composed of fibrin. The last three ^2][- ous 64 506 Organic Chemistry — Mdenda. Addenda. Production of Sugar, Albumen, &c. Urea de- tected. varieties of calculi are extremely rare, and are decomposed by heat, in the same manner as other animal substances. 2376. The uric acid and the phosphate of ammonia and magnesia calculi, are those most frequently observed. 2377. Sugar is found in considerable quantity in the urine of in- dividuals affected with diabetes ; 6 per cent, of sugar may often be procured from it. Kane obtained a still larger quantity. Albumen is often found in large quantity in the urine of individuals affected with some varieties of dropsy, coagulating when exposed to heat like the serum of the blood. In some cases it has coagulated even within the bladder. 2378. Urea is sometimes found in excess in urine. Prout states, that, when this is the case, nitric acid added in an equal bulk to a few drops of urine in a watch-glass, produces a crystalline precipi- tate of nitrated urea in half an hour. Healthy urine produces it more slowly. It is not absent in diabetic urine, as was at one time supposed. 2379. In some diseases of the liver, the urine becomes tinged with bile, and has a deeper yellowish tint than usual. Hydrochloric acid produces a green tint in urine charged with bile. r. 179 . ADDENDA, . . Radiation of Caloric . The late experiments of Melloni have af- of^aloric. f° r ded results which do not confirm the deductions of Leslie (215) in regard to the influence of the state of surfaces upon radiation. A square vessel was made out of a block of marble, the sides of which were of uniform thickness, and the external surfaces were differently prepared. The first was smooth and brilliant ; the second was equally smoth, but unpolished, and tarnished ; the third was streaked in one direction ; and the fourth in two, crossed at right angles. The vessel was then filled with hot water, and projected the same quantity of radiating caloric from each of the four sides. Experi- ments with metallic surfaces were attended with a much more abun- dant emission of caloric from streaked surfaces than from polished ; this is attributed by Melloni to a change of hardness or density, in consequence of the mechanical compression. A surface of cast silver had nearly one third more radiating power than one of the same me- tal forged, and the radiating power of the latter was increased four fifths by roughening with emery, while that of the former was dimin- ished nearly one fifth. ^ Influence of Influence of Colour on Absorption of Odours. Some important ob- colour on seryations have been made by Starkt on the influence of colour on of Odours* t ^ le absorption and disengagement of odorous matters. He found that white bodies are the least absorbent, and dark the most so ; and has made several important applications of the results of his experi- * Edin. Philos. Jour. xxvi. 299. + Phil. Trans. 1833. Addenda . 507 ments in respect to clothing, white-washing, the retention of noxious Addenda. effluvia by different coloured bodies, and the consequent communica- tion of disease. Compound Blow-pipe. The notice of Hemming’s safety tube was Compound inserted (128) after the apparatus had been subjected to severe blow-pipe, trials, the results of which fully warranted its recommendation as a valuable addition to the compound blow-pipe. Since then an explo- sion of the mixed gases has occurred in a strong copper globe to which the safety tube was attached. The tube being uninjured and still arresting explosion as perfectly as before, the cause of the occur- rence cannot be attributed to its imperfection ; while it furnishes ad- ditional caution not to mix the gases prior to their combustion. The student should also bear in mind that explosion may occur, even when the gases are contained in separate vessels, from unequal pressure ; an accident which Dr Torrey informs me he has experi- enced, the jet becoming clogged at the outlet, and a portion of the gas under the greatest pressure being forced into the vessel containing that under less pressure. This, however, can never occur when the double concentric jet (Fig. 129), as contrived by me, is used, the two orifices of the conical extremity being in the same plane — in the jet where the two orifices open into one common outlet, (as in Fig. 128 e,) the accident may occur. ^ Photographic Drawing . Paper may be prepared with a solution p^otogra- of bichromate of potassa, instead of the silver salt (1247), which phic draw- acquires a deep orange tint on exposure to the sun. The paper should in S- be well soaked in the saturated solution of the salt, dried rapidly at a brisk fire, excluding it from day-light. Paper thus prepared is sufficiently sensitive for taking copies of prints, dried plants, &c. The portion covered by the object retains the original bright yellow tint, and the object is represented yellow upon an orange ground. To fix the drawing, it is to be carefully immersed in water, by which the portions of the salt that have not been acted upon by the light are dissolved out, while those which have been exposed to it are fixed in the paper. The object then appears white upon an orange ground. A pleasing variety may be made by using sulphate of indigo with the bichromate of potassa, the colour of the object and of the paper being then of different shades of green. t A method of fixing images of objects upon metal has been recently £) aguer ,. e > s made known by Daguerre. A plate of silvered copper, well cleaned method, with dilute nitric acid, is exposed to the vapour of iodine, and an ex- tremely thin coating of iodide of silver is formed. Several precau- tions are required to render the coating uniform, the chief of which is the use of a rim of metal round the plate. The prepared plate is placed in a camera obscura and allowed to remain from eight to ten minutes. It is subsequently exposed, at an angle of 48°, to the va- pour of mercury, and when it has been heated to 167° F. the images appear. The plate is then exposed to the action of hyposulphite of soda and finally washed in a large quantity of distilled water.! * See an account of this explosion in Amer. Jour, xxxvii, 104. t Ponton in Trans. Soc. Arts, Scotland , May, 1839. tSee Jour. Franklin Inst. xxiv. 207. 608 Addenda . Addenda. Detection of Iodine and Bro- mine. Oxide of Phospho- rus. Detection of Iodine and Bromine. Schweitzer has very recently described a method of ascertaining the proportion of iodine and bro- mine in water, by which he obtained from 100,000 grs. of the water of the Congress spring of Saratoga 0.12164 gr. of iodide of silver, representing in 1000 grs. of the water 0.00067 gr. of iodine. Schweitzer recommends an ammoniacal solution of chloride of silver, prepared by mixing one part of a saturated solution of recently pre- cipitated chloride of silver in ammonia with one of liquid ammonia (sp. gr. 0.935) and two parts water. If to a concentrated solution of chloride of sodium containing one thirtieth part of a bromide, a few drops of this solution be added, the solution of chloride of sodium will remain clear, but if the most minute particle of an iodide be present, it will be rendered turbid. For the method of examination for bromine, and of analysing sea-water, see Bond, and Edin. Phil. Mag. July, 1839. The quantity of iodine in sea-water is very minute, 174 pounds Troy not containing one grain. The following is a comparative analysis of sea-water : Water Chloride of sodium “ potassium “ magnesium Bromide of magnesium Sulphate of magnesia - “ lime - Carbonate of lime On. Grs. 964.74372 . . 959.26 - 27.05948 . 27.22 0 7' . . 0.01 - 3 CG658 . 6.14 0.02929 . . — - 2.29578 . * 7.02 1.40662 . . 0.15 - 0.03301 J Carbonate of lime and magnesia. i 0.20 1000.00000 1000.00 Very beneficial results in scrofulous diseases are stated by Schweitzer to have followed from the internal and external use of the waters of several saline springs in Germany, concentrated by evaporation. Oxide of Phosphorus. M. Botger has found that sulphuret of carbon is the best solvent of phosphorus, dissolving 20 parts at mean temperature, while the oxide of phosphorus is not acted upon by it. To separate the oxide he directs to put the impure oxide, obtained by combustion, into a large bottle, pour sulphuret of carbon upon it with an equal measure of absolute alcohol ; cork the bottle, and shake it well for about a minute, then allow the oxide to subside, and pour ofF the phosphorized liquor ; repeat this operation with a fresh portion of the sulphuret and alcohol, and then put the oxide of phosphorus on a filter, and wash it first with alcohol, and then with water; after this dry it by exposure to the air, or, what is better, under a receiver • with sulphuric acid. The product resists combustion at a high temperature ; with chlo- rate of potassa it produces a strongly detonating powder, violent explosion taking place even during mixture without much pressure. According to Pelouze, the oxide obtained by combustion and purified by distillation, is P 3 -f-0, while that procured by the decomposition of the chloride (565 note) consists of P 4 -|“0.t * By Schweitzer. t By Laurens. t Jour, de Pharm. Feb., 1839, and Lond. and Edin. Phil. Mag. July, 1839. Addenda. 509 Detection of Nitric Acid. Richemont has proposed a method of Addenda, much delicacy of detecting nitric acid, depending on the fact that a Detection mixture of a concentrated solution of protosulphate of iron and sul- of nitric phuric acid becomes rose-red by the addition of deutoxide of nitro- acicl * gen, or purple, if the latter is present in larger proportion ; the quantity of the deutoxide required is so small, that an exceedingly minute portion may be detected by it. A small quantity of sulphuric acid is added to the solution to be examined, the latter being equal to three fourths of the bulk of the former. When the mixture has cooled, drop in a concentrated solution of protosulphate of iron, which, if any nitric acid is present, decomposes it, causing the evo- lution of nitric oxide, which produces the rose-red or purple tint. This mode of operating detects one part of nitric acid in 24.000 of water.^ Detection of Nitrogen. Mix the gas under examination with Detection from 3 to 6 times its volume of a mixture of oxygen and hydrogen of nitro S en * (in equal vols.), and detonate the whole in a eudiometer by the elec- tric spark. Mix the fluid that bedews the eudiometer after the explosion with sulphuric acid, to which a few drops of protosulphate of iron in solution have been added, the fluid will assume the rose- red tint if the minutest portion of nitrogen is present. It is of course necessary to avoid any source of fallacy arising from the pre- sence of atmospheric air in the oxygen and hydrogen employed.! Indelible Ink. A solution of the gluten of wheat in pyroligneous Traill’s in- aoid, has been recommended by Traill, as an indelible ink. He dj. delible mk. rects the gluten to be separated from the starch as completely as pos- sible, and when recent to be dissolved in the acid with the aid of heat. This forms a saponaceous fluid which is to be tempered with water until the acid has the usual strength of vinegar. Each ounce of the fluid is then to be ground with from 8 to 10 grains of the best lamp-black, and 1J gr. of indigo.! Salts of Baryta and Strontia. According to Smith these salts Salts of are distinguished, by the action of chromate of potassa and acetic baryta and acid. It is only necessary to add to a solution of the salt, a solution strontia * of chromate of potassa, which, if baryta be present, will produce a light yellow precipitate insoluble in acetic acid. This reagent will also serve to distinguish baryta from lime.§ Ethyle. When small pieces of potassium are placed in a glass Ethyle. tube 3 to 5 lines wide, containing chloride of ethyle, a powerful ac- tion ensues, and the metal becomes covered with a white crust, which should be broken up so as to cause a fresh metallic surface to be exposed to the action of the fluid. The mixture soon begins to boil, and chloride of ethyle distils over. A tube bent at right angles should be fixed in the mouth of the large one to connect it with a receiver kept cool by a freezing mixture. If sufficient chloride of ethyle is present, all the potassium is converted into the white crust, which is dissolved by water with the disengagement of hydrogen k, * Lond. and Edin. Phil. Mag. xiii. 393. t Richemont, Ibid, t Edin. Philos. Jour. xxv. 213- § J. L. Smith, in Amer. Jour, xxxvi. 183. See also a method by Rose, in Lond. and Edin. Phil. Mag. Jan., 1839. 510 Mdtnda. Addenda. Disastase. Dextrine. gas. On agitating the watery solution with ether and decanting the ethereal solution, a volatile oily fluid is obtained by evaporating in vacuo at a low temperature. This fluid burns vividly, has a peculiar odour, and very acrid taste. The white powder consists of C 4 H 5 . From these experiments Lo wig concludes, that by the action of potassium on chloride of ethyle, chloride and ethylide of potassium are formed, the latter combination being decomposed by the action of water, setting free the ethyle, either pure or as a hydrate.* Diastase , is the name given lo a substance extracted from malted barley, and which may be applied to important purposes in domestic economy. It is obtained by macerating the ground malt in cold water for some time. It is then pressed and the liquid filtered, and heated to 158°. The coagulated portion is separated and the liquid being again filtered is mixed with a sufficient quantity of al- cohol to throw down the diastase, the diastase is again dissolved in water and thrown down by alcohol, and this is to be repeated several times. Diastase is solid, white, insoluble in water, but soluble in dilute alcohol. Its solution separates amidin from all starchy substances containing it, hence its name.t It exists in the seeds of malted barley, oats and wheat. One part is sufficient to render soluble the interior portion of two thousand parts of starch, and to convert it into sugar. To prepare it upon a large scale, 850 lbs. of water are heated to 86°, 10 parts of ground malt are then added and the heat raised to 140° ; 220 lbs. of flour are then added and the whole well mixed. When the temperature has risen to 158° we should endeavour to keep it steady at that point, or at least not to allow it to cool below 150°, nor to rise above 167°. In twenty minutes the liquid becomes more transparent, and from being viscid and thready at first, it becomes almost as fluid as water. When this happens the temperature should be suddenly raised to 212°. The whole is then left at rest, the clear portion drawn ofF, filtered and evaporated by means of steam at 230°, the scum being removed. When sufficiently concen- trated, it is poured into a receiver of tin plate or wood, and on cool- ing it coagulates into an opaque jelly. While hot, if it be mixed with yeast and kneaded into the dough ; it serves well for the preparation of bread. If spread out in thin layers and dried in the air, or by a stove, we obtain dextrine , which being reduced to powder, may be introduced into all kinds of pastries, chocolate, bread, &c.t Dextrine dissolved in diluted alcohol has been lately recommended as a temporary varnish for oil paintings, preventing the imbibition of colours, even when employed a few days after the finishing of the picture. Applied with a soft brush, it gives a clearness like a light varnish, which can be removed by a moist sponge, when, after a few months, common varnish may be applied with its ordinary effect. The same solution serves as a perfect varnish for water colours, and f * Poggendorff, Ann. 45, p. 347, and Lond. and Edin. Phil . Mag. July, 1839. t From duaTtjfH, to separate. t T. Org. Bod. 666. Addenda. 511 for fixing pencil and crayon drawings. The solution of dextrine, in Addenda. about an equal portion of warm water, furnishes a paste which re- mains liquid and possesses great energy. It may be advantageously used as a substitute for the greater number of common pastes.* Nature of Ferment , or Yeast. The following results have been given by M. Cagnard-Latour.f Yeast is a mass of small globular bodies capable of self-reproduction, and of course oxygenized, and yeast, not an inert or purely chemical substance. These bodies appear to belong to the vegetable kingdon, and are generated in two different modes. They appear to act upon a solution of sugar as if they were alive, whence it may be inferred, that it is in all probability by some effect of their vegetation that they disengage carbonic acid from this solution and thus convert it into a spirituous liquor. In a valuable memoir by T. A. Quevenne,! the author arrives at the following conclusions : — 1st. Yeast is a substance which con- stantly presents the appearance of little globules of nearly uniform figures. 2d. These globules appear to be always of the same nature, whatever their origin. 3d. It is the insoluble constituent part of these globules which is apt to produce fermentation, and not the ex- tractive matters which accompany it. 4th. The globules of yeast can effect the decomposition of sugar not only at a temperature from 10° to 30° or 40° Cent. (50° to 86° or 104° F.), but even at the heat of boiling water ; but, with this difference, that at a temperature in- ferior to 50° they transform the sugar into alcohol and carbonic acid, while above 50° (= 122° F.), alcohol appears not to be formed ; the only gas obtained in either case is carbonic acid. 5th. Yeast, du- ring the alcoholization of sugar, undergoes a thorough modification. It loses all its nitrogen, which goes to form ammonia, by which means its fermentative power is completely exhausted. 6th. The globular aspect of yeast, and its principal chemical properties, are sufficient to induce us to regard it as an organic substance of new formation ; and hence fermentation ought not to be considered merely as a decomposition, but simply as a modification which gives birth at one and the same time to products both organic and inorganic. 7th. The circumstances under which fermentation takes place, and the phenomena which accompany it, and the influence which a great number of bodies have over the progress of the operation, are of a nature to induce the belief that it is actually owing to a sort of vege- tation, but this proposition requires additional proofs Respiration of Plants. Edwards and Colin have instituted expe- Reg irat - on riments upon the respiration of plants from which they have drawn o/pfaSs. 0 the following results : — 1st, that water is decomposed ; 2d, that the oxygen of the decomposed portion, unites with the carbon of the seed, and forms carbonic acid gas ; 3d, that this carbonic acid disengages itself from the seed, in whole or in part ; and 4th, the other portion of the decomposed water, the hydrogen, is absorbed by the seed, in whole or in part. They also infer frdm their experiments that re- spiration is not, as it has been hitherto considered, solely a function of excretion.il * Jour. Franklin Inst. xxiv. 114. t Comptes rendus de Vlnstit., 1837, 906. t Jour, de Pharm. Juilliet, 1888. § See Jour. Franklin Instil, xxiii. 119. || Ann. des. Sci. Nat. Dec,, 1838, and Edin. Philos. Jour. July, 1839. 512 Addenda. Addenda. New com- pound of Dicyanide with binox- ide of mer- cury. Preserva- tion of po- tassium. Emulsin. New compound of Bicyanide with Binoxide of Mercury. When dilute hydrocyanic acid is digested on red oxide of mercury, in ex- cess, a white nearly insoluble compound is formed, which may be separated from any soluble bicyanide which may be present in the supernatant liquid by collecting it on a filter. Boiling water dis- solves the new compound, and leaves the excess of oxide of mercury. On cooling, the salt is, in a great measure, deposited on the sides and bottom of the vessel in minute, pure, white, transparent, prismatic needles. This salt is anhydrous, its solution has an alkaline reac- tion, and it consists of equal atoms of the two mercurial compounds, or it is (HyCy 2 -f-Hy0 2 ). When heated in a tube, it decomposes with a slight detonation, giving off carbonic acid, nitrogen, cya- nogen, and metallic mercury, leaving a black residue (para-cyano- gen.) Neutralized by nitric acid, it gives a beautiful salt in long, delicate, quadrangular prisms, which are represented by HyCy 2 -[- (Hy0 2 +iN0 5 ), and are very soluble in water. It gives also with acetic acid, a crystalline compound, in which the quantity of acid appears to exist in a still smaller proportion. With acid nitrate of silver, it gives Wohler’s salt (HgCy 2 -f-AgN-{-4H), nitrate of mercu- ry remaining in solution. With neutral nitrate of silver and vari- ous other salts, it gives crystalline compounds.* Preservation of Potassium. Dr Gale has stated that the oil of copaiva contains oxygen, which renders it liable to convert potassium into potassa, forming with it a peculiar species of soap; from ex- periments made upon several specimens of the balsam, the oil ob- tained from them afforded similar results, and he is of opinion that no substance hitherto used will supply the place of naphtha.! Emulsin. The following process has been employed for obtain- ing emulsin , by Thomson and Richardson. Sweet almonds were triturated in a mortar and small portions of water gradually added until a milky fluid was obtained. This fluid was mixed with four times its vol. of ether and frequently agitated so as to effect an in- timate mixture. A clear fluid gradually separated at the bottom of the stoppered bottle in which the experiment was made, which in the course of three weeks was drawn off by means of a syphon. The fluid was filtered, and to one half of the clear solution a large quan- tity of alcohol was added ; a copious precipitation of white flocks ensued ; these were emulsin. Washed with alcohol, and dried over sulphuric acid in the vacuum of an air pump, it was obtained in the state of a white powder, without taste or smell, soluble in water, in- soluble in alcohol and ether. Its analysis gave the relation of the carbon and nitrogen as 6CO a : IN or 3C: IN. When boiled with baryta, ammonia was disengaged, and from the experiments it was inferred to be an amide, and the salt formed with baryta to be a com- pound of baryta and emulsic acid. The authors are inclined to infer that fibrin, gelatin, casein, &c: are all amides.! * Johnston in Eighth Report of British Association, 69. + Amcr. Jour. xxi. 64. t Eighth Report of British Assoc. 48. APPENDIX. Chemical Formula. Various changes have been made in chemical formulge. Thus Berzelius now uses HO, KO, FeS, instead of H+O, K+O, Fe+S, for water, potassa, and sulphuret of iron. The formula for apophyllite is now 8 Ca Si + KS* + 16 aq ; the 8 denoting 8 eq. of CaSi, or silicate of lime, which are united with 1 eq. of bisilicate of potassa, and 16 of water. The system of Liebig and Poggendorff is based upon the following principles. Numbers are placed below and to the right of the symbols which affect those to which they are at- tached. Numbers are placed before the symbols which affect all that follow as far as the next full stop or sign of addition. A figure placed before a parenthesis applies to all con- tained within it. The same compound may therefore be written in different ways. Thus the constitution of a crystal of alum is represented by KS T A ISs + 24H, or KO, SO;? -1- AI 2 O 3 , 3S0 3 -f 24 aq. To distinguish water in different states of combination Liebig and Poggendorff propose to express water of crystallization by aq. When the water is more powerfully retained and the compounds are more permanent, or in the state of hydrates , the water is denoted by an h attached to the symbol of the substance containing it. Thus A being the symbol of acetic acid, Ah is the symbol of the hydrate; M s O,M|, + 4 aq. denotes the malate of magnesia and 5 eq. of water, but distinguishes 4 of these as water of crystallization, while the fifth is united with the malic acid and forms with it a hydrate. The symbol HO is used in doubtful cases, and when changes effected by chemical action are explained. L. and T. 240. Wollastons Synoptic Scale of Chemical Equivalents* The scale consists of a moveable slider with a series of numbers upon it, from 10 to 320, on each side of which and on the fixed part of the scale, are set down the names of various chemical substances. The scale is founded on the constancy of composition in chemical compounds (106) ; the equivalent power of the quantities that enter into combination (108); and the proper- ties of a logometric scale of numbers. The numbers are so arranged, that at equal intervals they bear the same proportion to each other. The student will easily observe and understand this, by measuring a few dis- tances upon the scale with a pair of compasses, or even a piece of paper. If his paper extend from 10 to'20, it will also extend from 20 to 40, or from 55 to 110,orfrom 160 to 320. Whatever number is at the upper edge of the paper will be doubled at the lower. If any other distance be taken, the same effect will be observed. If, for instance, the paper ex- tends from 10 to 14, then any other two numbers found at its upper and lower edge will be in the same proportion as these two numbers 10 and 14. Thus make the upper number 100, and the lower number will be 140. Now supposing that the paper were cut of such a width that, one of its edges being ap- plied upon the scale to the number representing the equivalent of one body, the other should coincide with the number of the equivalent of a second body ; then upon moving the paper, wherever it was placed over the numbers, those at its upper and lower edges would still represent the corresponding proportional quantities of the two bodies as accu- rately as at first, because the numbers at equal distances on the scale are proportional to each other. Thus suppose the upper edge were made to coincide with 40 and the lower * The paper, by its author, describing the scale is inserted in the Philosophical Transactions for 1814. 65 514 Appendix. with 78, then the upper edge might be called sulphuric acid, and the lower baryta ; and this width once ascertained, the paper wherever applied upon the scale, would shew at its lower edge the quantity of baryta necessary to combine with the quantity of sulphuric acid indicated by its upper edge It is evidently of no consequence whether the paper be moved up and down over the the scale, or the line of numbers be moved higher and lower, to bring its different parts to the edges of the paper. And supposing the piece of paper just described to be pasted upon the side of the scale, then by moving the latter any of the numbers might be made to coincide with the upper oi lower edge at pleasure, and consequently the quantity of sul- phuric acid necessary to combine with any quantity of baryta, and vice versa, ascertained by mere adjustment and inspection of the scale Or if, instead of referring to the separate piece of paper, marks were to be made on the side of the scale at 40 and 78, and named sulphuric acid and baryta, the same object would be attained, and the same method of in- quiry rendered available. Other substances are to be put down upon the scale exactly in the same manner. Thus the scale being adjusted until the number 40 coincides with the sulphuric acid already marked, then sulphate of baryta is to be written at 118, and thus its place is ascertained; nitrate of baryta at 1312 ; soda at 32 ; sulphate of soda at 72; and a similar process is to be adopted with every substance, the number of which has been ascertained by experiment. The instrument, which in this state merely represents the actual numbers supplied by ex- periment, will faithfully preserve the proportions thus set down, whatever the variation of the position of the slider may be. it is therefore competent to change all the numerical expressions to any degree required, the knowledge of one only being sufficient first by ad- justment, and then by inspection to lead to the rest, A few illustrations of the powers and uses of this scale will be sufficient to make the student perfect master of its nature and applications. Suppose that in analysing a mineral water, the sulphates in a pint of it have been decomposed by the addition of muriate of baryta, and the resulting sulphate of baryta w ashed, dried, and weighed : from its quantity may be deduced the oxact quantity of sulphuric acid previously existing in the mineral water. Thus, if the sulphate of baryta amount to 43.4 grains, the slider is to be moved until that number is opposite to sulphate of baryta, and then at sulphuric acid will be found the quantity required, namely 14.7 grains. In the same manner the scale will give infor- mation of the quantity of any substance contained in a given weight of any of its com- pounds; these having previously been deduced from experiment, and accurately set down cn the table in the manner just explained If it be desired to know how much of one substance must be used in an experiment to act upon another, it is evident that the equivalent must be taken, and this may be learned from the scale. Suppose that a pound of sulphate of baryta has been mixed with charcoal, and well heated, to convert it into a sulphurct, and that by the addition of nitric acid it is to be converted into nitrate of baryta The quantity of acid which will probably be re- quired may be learned by bringing 100 to sulphate of barvta, and then by looking for the number opposite nitric acid : it will be found to be 40. But this represents the quantity of dry acid : casting the eye therefore lower down, upon liquid nitric acid of a specific gravity of 1.50, it will be found that 01 lbs. or a little more, is the equivalent for 10U lbs. and conse- quently tint 61 hundredth parts, or somewhat above six-tenths of a pound of such acid, will bo sufficient for the pound of sulphate of baryta operated with. If a certain weight of carbonate of barvta be r quired in that moist and finely divided state, in which it is obtained by precipitation, and in which it cannot be weighed, the accu- racy of tho quantity may be insured by taking the equivalent of dry muriate, or nitrate of baryta, precipitating it by an excess of carbonate of potassa, and then washing off the the salts which remain in solution. Suppose 100 grains of the carbonate were required; by bringing that number to carbonate of baryta, it will be found that the quantity of dry muriate necessary will be 105.8 parts, and the quantity of nitrate 133.4 ; and if the quantity of carbonate of potassa necessary for this purpose be also required, it will be found oppo- site the name of that substance on the scale, to be a little less than 70 parts, so that 5 or 10 parts more will ensure a satisfactory excess. The second paragraph of Wollaston’s description of this scale may be transcribed, as a further illustration of the powers of the instrument. “ If, for instance, the salt under ex- amination be the common blue vitriol, or crystallized sulphate of copper, the first obvious questions are — (1) How much sulphuric acid does it contain? (2) How much oxide of copper? (3) How much water? He [the analytic chemist] may not be satified with these first steps in the analysis, but may desire to know further the quantities (4J of sulphur, (5) of copper, (6) of oxygen, (7) of hydrogen. As means of gaining this information, he naturally considers the quantity of various reagents that may be employed for discovering the quantity of sulphuric acid (8), how much baryta, (9) carbonate of baryta, or (10) nitrate Appendix. 515 of baryta, would be requisite for this purpose ? (11) How much lead is to be used in the form of (12) nitrate of lead; and when the precipitate of (13) sulphate of baryta, or (14) sulphate of lead are obtained, it will be necessary that he should also know the proportion which either of them contains of dry sulphuric acid. He may also endeavour to ascertain the same point by means of (15) the quantity of pure potassa, or (16) of carbonate of potassa requisite for the precipitation of the copper. He might also use (17) zinc, or (18) iron for the same purpose, and he may wish to know the quantities of (19) sulphate of zinc, or (20) sulphate of iron, that will then remain in the solution.” All these questions and points are answered by moving the slider until the number ex- pressing the quantity operated with coincides with sulphate of copper crystallized. 5, Water. Let it for instance be 100 : this being brought opposite crystallized sulphate of cop- per, the information relative to all the above points, except the sixth and seventh, is sup- plied by mere inspection. The sixth may be supplied by substracting (5) the quantity of copper from (2) the quantity of oxide of copper, or by halving the quantity at 2 oxygen, or taking the third of that at 3 oxygen. The seventh relates to the quantity of hydro- gen in the 5 water present in the salt; this quantity of hydrogen does not come with- in the line of numbers, but may easily be obtained by doubling the quantity of water, or doubling the quantity of the salt used, which will then bring Id hydrogen into the scale, and the half of this is to be taken as the quantity in 5 water, or in 100 grains of the salt. Putting therefore 200 to sulphate ©f copper, 10 hydrogen, is indicated as 17 parts nearly, when of course the half of this, or 8<# parts is the quantity in 100 grains of the crystallised salt of copper. Whenever it thus happens that the number known or the number sought for is out of the scale, then some convenient multiplier of the numbers may be used. The most con- venient method is to use the tens or the hundreds as units, or what is the same thing, to consider for the time that decimal points are inserted between the units and the tens, or between the tens and the hundreds of all the numbers on the scale. Thus if it were required to ascertain how much magnesia and sulphuric acid were contained in a pound of crystallized sulphate of magnesia, no 1 exists upon the scale, and of course no fractions or small parts of 1 ; but imagine decimal points between the tens and the hundreds, then 10 upon the scale becomes one-tenth, 22 twentytwo hundredths, 100 one, 220 two and two-tenths and so on. Bringing therefore 100 to crystallized sulphate of magnesia, it represents the 1 pound, and by inspection it will be found that it contains 16 hundredths of a pound of magnesia, and 3*2^ hundredths of a pound of sulphuric acid. As another illustration; suppose that the quantity of magnesia in 50 lbs. of crystallized Epsom salt were required ; upon bringing 50 opposite the name of the sail, the quantity of magnesia will be found smaller than any quantity expressed upon the scale : but all that is necessary to obtain the answer is, to double the quantity of the salt, and then to halve the quantity of magnesia indicated ; in which way it will be found that the 50 lbs. contain about 8 lbs. of the oxide. These Synoptic scales are generally constructed of paper or wood. It is almost impos- sible that they should be accurate, because of the extension and contraction of the paper, and the facility with which it yields to mechanical impressions, and may be stretched when in a moistened state. These scales should never be considered as accurate when they first come from the instrument-maker. They may be examined by a pair of compasses or a a piece of paper, as before described (p. 513), to ascertain how nearly, equal intervals on the scale of numbers, accord with equal proportions between the numbers at the extremi- ties of those intervals and thus the degree of error in them, and the part where it exists to the greatest extent may be observed : but it will be useless to do so, with the view of finding one so accurate as to dispense with calculation in exact analytical experiments. Those scales, which are laid down directly upon wood, though not liable to the same sources of error as the paper scales, are still seldom, if ever, so accurate as to compete with calculation. The errors just referred to, relate to the accuracy of the scale of numbers, and its pro- portional value in every part. Others relate to the imperfect and inaccurate results of the experiments, by which the numbers representing the equivalent or combining quantities of bodies are obtained. If an inaccurate result be mistaken for a correct one, and the pro- portional number of a body be entered erroneously upon the scale, it is evident that all estimations of substances including that body, which are given by the scale, must involve this original inaccuracy. Whenever therefore a more accurate determination of the num- ber of a body is obtained than was before possessed, its place on the scale should be cor- rected; and as the equivalent numbers of substances, previously undetermined, are satis- factorily ascertained, the substances themselves should be put upon the scale in their proper situations, as before described. In consequence of the unavoidable errors in the scale of numbers, which, however small, still interfere in the investigation of complicated cases, and the determination of 516 Appendix. accurate conclusions, the instrument should only be used in those instances where accu- racy within a certain degree is sufficient for the purpose. All nicer results should be obtained by calculation from a table of equivalents : if, for instance, the quantity of sul- phuric acid in 64.7 grains of sulphate of baryta were required to two or three places of decimals, it would be better to take the equivalent numbers of sulphate of baryta and sulphuric acid from such a table, and to say, as the first number is to the second, so is 64.7 to the quantity of sulphuric acid it contains, than to work with the scale. The present determination of the sulphate of baryta is 1 18, and that of sulphuric acid 40, hydrogen being 1 or unity, and as 1 18 is to 40, so is 64.7 to 21 932 very nearly. It will be impossi- ble to ascertain this last number accurately on an ordinary scale, or to observe how far it differs from 22. There are numerous tables of equivalents published in different chemical works. Whichever may be adopted should be examined from time to time, and the numbers affix- ed to bodies on it corrected, whenever they are more accurately determined. It has been shewn by Gay-Lussac and others that all gases and all volatile substances when in the state of vapour, combine or act chemically in volumes, which have very simple relations to each other. These volumes once ascertained, may be considered in the rela- tion of equivalents, and their proportions aie so simple, as to be remembered without the least difficulty : it is therefore highly advantageous in all tables of chemical equivalents, to place small diagrams by the sides of the substances and their numbers, which may represent the volumes of the equivalents when brought into the state of gas or vapour. For it re- quires no great power of discernment to perceive that, if bodies combine in definite weights, and also in simple ratios of volumes, these volumes 60 combining must contain the weights previously found to be definite : for whether two substances which combine to form a third, are observed by weight or volume, still they combine only in one pro- portion. So arranged, the table will have an appearance of the following kind : Hydrogen 1 • □ Oxygen ♦ 8 a Chlorine - 36 . • □ Iodine - 125 • □ Water - 9 • □ Muriatic acid - - 37 - CD Hydriodic acid, - 126 • m Ammonia - 17 - m and will be found very useful when referred to for gaseous or vaporous substances. The proportions of these volume? are much more easily remembered than the proportions of their equivalent numbers ; which, added to the facility with which the bulk of gases or vapours are ascertained, may often properly induce the chemist to dispense with the deter- mination of weights, and work with volumes only.* * Faraday’s Chemical Manipulation. Appendix, 517 TABLE I. The following are the results obtained by a commission appointed by the Parisian Academy of Sciences to examine the elastic force of vapour They were obtained by experiment up to a pressure of 25 atmospheres, and at higher pressures by calculation . Elasticity of the vap. taking amospheric £ press, as unity. Temperature accord- ing to Fahr. Elasticity of the vap. taking atmospheric press, as unity. Temperature accord- ing to Fahr. ] 212° 13 380.66° H 233.96 14 386.94 2 250.52 15 392.86 2 h 263.84 16 398.48 3 275.18 17 403.82 3 ft 285.08 18 408.92 4 203 72 19 413.78 4 ft -300.28 20 418.46 5 3U7.5 21 422.96 5 * 314 24 22 427.28 6 320 36 23 431.42 64 326.26 24 435.56 7 331.70 25 439.34 336.86 30 457.16 8 341.78 35 472.73 9 350.78 40 486.59 10 358.88 45 491.14 11 366.85 50 510.60 12 374.00 * Braude’s Jour. N. S. viii ; 191. 518 Appendix. TABLE II. Table of the Elastic Force of Aqueous Vapour at different Temperatures , expressed in Inches of Mercury. TEMP. Fah . Force of Vapour. TEMP . Fah . Force of Vapour. TEMP. Fah . Force of Vapour. Dalton. Ure. Dalton. Ure Dalton . Ure. 3*2 c 0.200 0.200 79° 0.971 126° 3.89 33 0.207 80 1.00 1.010 127 4.00 34 0.214 81 1.04 128 4.11 35 0.221 82 1.07 129 4.22 36 0.229 83 1.10 130 4.34 4.366 37 0.237 84 1.14 131 4.47 38 0.245 85 1.17 1.170 132 4.60 39 0.254 86 1.21 133 4.73 40 0.2 t >3 0.250 87 1.24 134 4.86 41 0.273 88 1.28 1&5 5.00 5.070 42 0.283 89 1.32 136 5.14 43 0.294 90 1.36 1.360 137 5.29 44 0.305 91 1.40 138 5.44 45 0.316 92 1.44 139 5.59 46 0.328 93 1.48 140 5.74 5.770 47 0.339 ; 94 1.53 141 5.90 48 0.351 95 1.58 1.640 142 6.05 49 0.363 | 96 1.63 143 6.21 50 0.375 . 0.360 97 1.68 144 6.37 51 0.388 ; 98 1.74 145 6.53 6.600 52 0.401 i 99 1.80 146 6.70 53 0.415 : 100 1.86 1.860 147 6.87 54 0.429 I 101 1.92 148 7.05 55 0.443 0.416 102 1.98 149 7.23 56 0.458 ! 103 2.04 150 7.42 7.530 57 0.474 104 2.11 151 7.61 58 0.4! H ) 105 2.18 2.100 1 53 7.81 59 0.507 106 2.25 153 8.01 60 0.524 0.516 107 2.32 154 8.20 61 0.542 108 2.39 155 8.40 8.500 62 0.5< JO 109 2.46 156 8.60 63 0.578 110 2.53 2.456 157 8.81 64 0.5 H 7 111 2.60 158 9.02 65 0.616 0.630 112 2.68 159 9.24 66 0.(535 113 2.76 160 9.46 9.600 67 0.655 114 2.84 161 9.68 68 0.676 115 2.92 2.820 162 9.91 69 0.698 116 3.00 163 10.15 70 0.721 0.726 117 3.08 164 10.41 71 0.745 118 aie 165 10.68 10.800 72 0.770 119 3.25 166 10.96 73 0.796 120 3.&3 2.300 1.17 11.25 74 0.823 121 3.42 168 11.54 75 0.851 0.860 122 3.50 169 11.83 76 0.880 123 3.59 170 12.13 12.050 77 0.910 124 3.69 171 12.43 78 0.940 125 3.79 3.830 172 12.73 Appendix. 519 TABLE II. — Continued. TEMP. Fah. Force of Vapour. 1 TEMP. Fah. Force of Vapour, j I TEMP. Fail. Foree of Vapour. Dalton. Fre. Dal ion. Ure. Dalton. lire. 173° 13.02 224° 37.53 j i 275° 83.13 93.480 174 13.32 225 38.20 39.1101 276 1 84.35 175 13.62 13.550 226 38.89 40.100 277 85.47 97.800 176 13.92 227 39.59 ! 278 | 86.50 | 177 14.22 228 40.30 1 I 279 ! 87.63 j 101.600 178 14.52 229 i 41.02 | 280 88.75 101.900 179 14.83 230 ! 41.75 i 43.100 281 89.87 | 104.400 180 15.15 15.160 231 42.49 | j 282 t 90.99 181 15.50 232 43.24 | 283 92.11 107.700 182 15.86 2&3 44.00 j | 284 93.23 183 16.23 234 44.78 | 46.800i j 285 94.35 S 112.200 184 16.61 235 | 45.58 ! 47.220 1 286 95.48 1 185 17.00 16.900 236 46.39 i J 287 96.64 114.800 186 17.40 237 47.20 1 ! 288 97.80 1 1 187 17.80 238 48.02 1 50.3001 289 | 98.96 118.200 188 18.20 239 | 48.84 1 290 100.12 1 120.150 j 189 18.60 240 49.67 | 51.700i ! 291 ; 101.28 j 190 19.00 19.000 241 50.50 | ! j 292 102.45 123.100 191 19.42 242 51.34 53.600 293 103.63 i 192 19.86 j 243 52.18 I 294 j 104.80 i 126.700 | 193 20.32 244 53.03 1 295 105.97 I 129.000 194 20.77 245 j 53.88 | 56.340 ! 296 107.14 195 2] .22 21.100 246 54.68 1 ! 297 108.31 j 133.900 196 21.68 ; 247 55.54 1 298 109.48 : 137.400 | 197 22.13 248 i 56.42 ' 60.400 299 i 110.64 198 22.69 249 ! 57.31 300 | 111.81 | 139.700 199 23.16 250 58.21 ! 61.900 301 112.98 200 23.64 23.600 251 59.12 ; 63.500 [ 302 ' 114.15 144.300 201 ! 24.12 252 60.05 i 303 * 115,32 ! 147.700 i 202 24.61 253 61.00 304 | 116.50 203 25.10 254 61.92 66.700 305 117.68 1 150.560 ; 204 25.61 255 62.85 1 67.25 ! 1 306 118.86 ; 154.400 I 205 26.13 25.900 256 63.76 307 120.03 206 26.66 257 64.82 69.800 308 i 121.20 | 157.700 207 27.20 258 65.78 ! 309 I 122.37 208 27.74 259 i 66.75 310 1 123.53 161.300 209 28.29 260 i 67.73 72.300 ! 311 124.69 164.800 210 28.84 28.880 261 i 68.72 | 312 ' 125.85 | 167.000 211 29.41 262 | 69.72 75.900 313 | 127.00 212 30.00 | 30.000 263 1 70.73 314 128.15 1 213 30.60 264 ! 71.74 ; 77.900 i 315 ! 129.29 * 214 31.21 265 | 72.76 78.040 ! 316 1 130.43 215 31.83 266 | 73.77 317 1 131.57 216 32.46 33.400 267 ! 74.79 j 81.900 318 | 132.72 217 33.09 j 268 1 75.80 319 1 133.86 218 33.72 269 j 76.82 84.900 320 ; 135.00 219 34.35 1 270 i 77.85 - 86.300 321 I 136.14 220 34.99 1 35.540 , 271 i 78.89 88.000 322 137.28 221 35.63 36.700 II 272 79.94 1 323 138.42 222 36.25 ! || 273 ! 80.98 91.200 | 324 : 139.56 I 223 36.88 il 274 1 82.01 ! 325 140.70 520 Appendix. TABLE III. Dr Ure's Table, showing the Elastic Force of the Vapours of Alcohol and Ettver at different Temperatures , expressed in Inches of Mercury. Ether. Alcohol sp . gr. 0 813. Alcohol sp . gr. 0.813. Temp. Force of Vapour. Temp. Force o: Vapour. Temp. Force of Vapour. 34 ° 6.20 32 ° 0.40 193.3 46.60 44 8.10 40 0.56 196.3 50.10 54 10.30 45 0.70 200 53.00 (34 10.00 50 0.86 206 60.10 74 16.10 55 1.00 210 65.00 84 20.00 60 1.23 214 69.30 94 24.70 65 1.49 216 72.20 104 30.00 70 1.76 220 78.50 105 30.00 75 2.10 225 87.50 110 32.54 80 2.45 230 94.10 115 35.90 85 2.93 232 97.10 120 39.47 90 3.40 2-36 103.60 125 43.24 95 3.90 238 106.90 130 47.14 100 4.50 240 111.24 135 51.90 105 5.20 244 118.20 140 56 . JX ) no 6.00 247 122.10 145 62.10 115 7.10 248 126.10 150 67.60 120 8.10 249.7 131.40 155 73.60 125 9.25 250 132.30 160 80.30 130 10.60 252 138.60 165 86.40 135 12.15 254.3 143.70 170 92.80 140 13.90 258.6 151.60 175 99.10 145 15.95 260 155.20 180 108.30 150 18.00 262 161.40 185 116.10 155 20.30 264 166.10 190 124.80 160 22.60 195 13 - 3.70 165 25.40 200 142.80 170 28.30 205 151.30 173 30.00 210 166.00 178.3 33.50 180 34.73 182.3 36.40 185.3 39 .< K ) 190 43.20 Appendix. 521 TABLE IV. Dr Ore’s Table of the Quantity of Oil of Vitriol , of sp. gr. 1.8485, and of Anhydrous Acid , in 100 Parts of dilute Sulphuric Acid , at different Densities. Liquid. Sp. Gr. Dry. Liquid. Sp. Gr. Dry. Liquid. Sp. Gr. Dry. 100 1.8485 81.54 66 1.5503 53.82 32 1.2334 26.09 99 1.8475 80.72 65 1.5390 53.00 31 L2260 25.28 98 1.8460 79.90 64 1.5280 52.18 30 1.2184 24.46 97 1.8439 79.09 63 1.5170 51.37 29 1.2108 23.65 96 1.8410 78.28 62 1.5066 50.55 28 1.2032 22.83 95 1.8376 77.46 61 1.4960 49.74 27 1.1956 22.01 94 1.8336 76.65 60 1.4860 48.92 26 1.1876 21.20 93 1.8290 75.83 59 1.4760 48.11 25 1.1792 20.38 92 1.8233 75.02 58 1.4660 47.29 24 1.1706 19.57 91 1.8179 74.20 57 1.4560 46.48 23 1.1626 18.75 90 1.8115 73.39 56 1.4460 45.66 22 1.1549 17.94 89 1.8043 72.57 55 1.4360 44.85 21 1.1480 17.12 88 1.7962 71.75 54 1.4265 44.03 20 1.1410 16.31 87 1.7870 70.94 53 1.4170 43.22 19 1.1330 15.49 86 1.7774 70.12 52 1.4073 42.40 18 1.1246 14.68 85 1.7673 69.31 51 1,3977 41.58 17 1.1165 13.86 84 1.7570 68.49 50 1,3884 40.77 16 1.1090 13.05 83 1.7465 67.68 49 1.3788 39.95 15 1.1019 12.23 82 1.7360 66.86 48 1.3697 39.14 14 1.0953 11.41 81 1.7245 66.05 47 1.3612 38,32 13 1.0887 10.60 80 1.7120 65.23 46 1.3530 37.51 12 1.0809 9.78 79 1.6993 64.42 45 1.3440 36.69 11 1.0743 8.97 78 1.6870 63.60 44 1.3345 35.88 10 1.0682 8.15 77 1.6750 62.78 43 1.3255 35.06 9 1.0614 7.34 76 1.6630 61.97 42 1.3165 34.25 8 1.0544 6.52 75 1.6520 61.15 41 1.3080 33.43 7 1.0477 5.71 74 1.6415 60.34 40 1.2999 32.61 6 1.0405 4.89 73 1.6321 59.52 39 1.2913 31.80 5 1.0336 4.08 ' 72 1.6204 58.71 38 1.2826 30.98 4 1.0268 3.26 71 1.6090 57.89 37 1.2740 30.17 3 1.0206 2.446 I 70 1.5975 57.08 36 1.2654 29.35 2 1.0140 1.63 1 69 1.5868 56.26 35 1.2572 28.54 1 1.0074 0.8154 • 68 1.5760 55.45 34 1.2490 27.72 1 67 1.5648 54.63 33 1.2409 26.91 66 522 Appendix. TABLE V. Table of Muriatic ( Hydrochloric ) Acid , hy Dr Ure. Acid of 120 in 1<)0. Specific Gravity Chlorine. Muriatic Cjab. Acid of 1^0 ill loo. 100 1.2000 39.675 40.777 66 99 1.1982 39.278 40.369 65 98 1.1964 38.882 39.961 64 97 1.1946 38.485 39.554 63 96 1.1928 38.089 39.146 62 95 1.1910 37.692 38.738 ! 61 94 1.1893 37.296,38.330 60 93 1.1875 36.900 37.923 1 59 92 1.1857 36.503 37.516) 1 58 91 1.1846 36.107 37.108, 57 90 1.1822 35.707 36.700 56 89 1.180235.310 36.292 55 ! 88 1.1782(34.913 35.884 54 ! 87 1.176234.517 35.476 53 86 1.174134.121 35.068 52 ! 85 1,1721:33.724 34.660 51 | 84 1.1701 • T 3.328 34.252 50 83 1.1681 32.931 33.845 49 82 1.166132.535 33.437) 48 81 1.164132.136 33.029 47 1 80 1.162031.746 32.621 46 | 79 1.159931.343 32.213 45 78 1.157830.946 31.805 44 77 1.155730.550 31.398 43 1 76 1.153630.153 30.990, 42 75 1.1515 29.757 30.582 41 ! 74 1.149429.361 30.174 . 40 | 73 1.147328.964 29.767 39 | 72 1.145228.567 29.359! 1 38 | 71 1.1431 28.171 28.95] 1 37 70 1.141027.772 28.544 36 69 1.138927.376 28.136 35 68 1.136926.979 1 27.728 1 34 67 1.1349(26.583 1 27.321 1| 33 Specific Gravuy. Muriatic Lius. 1328 26.186 26.913 1308)25.78920.505 1287 25.392 p 26.098 I I . 1 267 J 24.996 i 25.690 I I. 1247,24.599125.282 1.122624.20224.874 1.120623,80524.466 1.1J8523.408J24.058 1.1164 23.012l23.050 1.114322.61523.242 I. 112322.21822.834 I I. 1 102 2 1 .822 22. 426 j 1.1082 21.425*22.019, 11.1061 21.02821.611 I. 104120.6:1221.203 II. 102020.23520.796 1.1000 19.837 20.388 1.0980 19.440 19.980 I. 096019.04419.572 II. 0939 18.647 19.165 1.091918.25018.757 .0899 17.854 .0879 17.45? .085917.060 ,0838 16.664 ,0818 16.267 .0798 15.870 18.349 17.941 17.534 17.126 16.718 16.310 0758 15.077 15.494 0738 14.680 15.087 0718 14.284 14.679 0697 13.887 14.271 0677 13.490 13.863 0657 13.094 13.456 Ac|d i f 120 in 1 U 0. Specific G, ayity. Chlorine. Muriatic, Gas. 32 1.0637 12.697 13.049 31 1.0617 12.300 12.641 30 1.0597 11.903 12.233 29 1.0577 11.506 11.825 28 1.0557 11.109 11.418 27 1.0537 10.712 11.010 26 1.0517 10.316 10.602 25 1.0497 9.919 10.194 ! 24 1.0477 9.522 9.786 23 1.0457 9.126 9.379 22 1.0437 8.729 8.971 21 1.0417 8.332 8.563 20 1.0397 7.935 8.155 19 1.0377 7.538 7.747 18 1.0357 7.141 7.340 17 1.0337 6.745 6.932 16 1.0318 6.348 6.524 15 1.0298 5.951 6.116 14 1.0279 5.554 5.709 13 1.0259 5.158 5.301 12 1.0239 4.762 4.893 11 1.0220 4.365 4.486 10 1.0200 3.968 4.078 9 1.0180 3.571 3.670 8 1.0160 3.174 3.262 7 1 1.0140 2.778 2.854 6 1 1.0120 2.381 2.447 5 1.0100 1.984 2.039 4 1.0080 1.588 1.631 3 1.0060 1.191 1.224 9 1.0040 0.795 0.816 1 ; 1.0020 0.397 0.408 * Dictionary of Arts and Manufactures, 873. Appendix. 523 TABLE VI. Dr Ure's Table of the Quantity of Real or Anhydrous Nitric Acid in 100 Parts of liquid Acid , at different Densities . Sp Gr. Real Acid in 100 parts of the li- quid. Sp. Gr. Real Acid in 100 parts of the li- quid. Sp Gr. Real Acid in 100 parts of the li- quid. 1.5000 79.700 1.3783 52.602 1.1895 26.301 1.4980 78.903 1.3732 51.805 1.1833 25.504 1.4960 78.106 1.3681 51.068 1.1770 24.707 1.4940 77.309 1.3630 50.211 1.1709 23.910 1.4910 76.512 1.3579 49.414 1.1648 23.113 1.4880 75.715 1.3529 48.617 1.1587 22.316 1.4850 74.918 1.3477 47.820 1.1526 21.519 1.4820 74.] 21 1.3427 47.023 1.1465 20.722 1.4790 73.324 1.3376 46.226 1.1403 19.925 1.4760 72.527 1.3323 45.429 1.1345 19.128 1.4730 71.730 1.3270 44.632 1.1286 18.331 1.4700 70.933 1.3216 43.835 1.1227 17.534 1.4670 70.136 1.3163 43.038 1.1168 16.737 1.4640 69.339 1.3110 42.241 1.1109 15.940 1.4600 68.542 1.3056 41.444 1.1051 15.143 1.4570 67.745 1.3001 40.647 1.0993 14.346 1.4530 66.948 1.2947 39.850 1.0935 13.549 1.4500 66.155 1.2887 39.053 1.0878 12.752 1.4460 65.354 1.2826 38.256 1.0821 11.955 1.4424 64.557 1.2765 37.459 1.0764 11.158 1.4385 63.760 1.2705 36.662 1.0708 10.361 1.4346 62.963 1.2644 35.865 1.0651 9.564 1.4306 62.166 1.2583 35.068 1.0595 8.767 1.4269 61.369 1.2523 34.271 1.0540 7.970 1.4228 60.572 1.2462 33.474 1.0485 7.173 1.4189 59.775 1.2402 32.677 1.0430 6.376 1.4147 58.978 1.2341 31.880 1.0375 5.579 1.4107 58.181 1.2277 31.083 1.0320 4.782 1.4065 57.384 1.2212 30.286 1.0267 3.985 1.4023 56.587 1.2148 29.489 1.0212 3,188 1.3978 55.790 1.2084 28.692 1.0159 2.391 1.3945 54.993 1.2019 27.895 1.0106 1.594 1.3882 1.3833 54.196 53.399 1.1958 27.098 1.0053 0.797 ^24 Apptndiz. TABLE VII. I able of Lowitz , showing the Quantity of Absolute Alcohol in Spirits of different Specific Gravities. 100 Parts Specific Gravity. 100 Parts. Specific Gravity. 100 Parts. Sp. Gravity. Alcohol. Water At 68°. At 60'. Alcohol Water At 64°. At Alcuhol. Water At 63°. At 60°. 100 0 0.791 0796 66 34 0.877 0.881 32 68 0.952 0.955 99 1 0.794 0.798 65 35 0.880 0.883 31 69 0.954 0.957 98 2 0.797 0801 64 36 0.882 0.886 30 70 0.956 0.958 97 3 0.800 0.804 63 37 0.885 0.889 29 71 0.957 0.960 96 4 0.803 0.807 62 38 0.887 0.891 28 72 0.959 0.962 95 5 0.805 0 809 61 39 0.889 0.893 27 73 0.961 0.963 94 6 0.808 0812 60 40 0.892 0.896 26 74 0.963 0.9G5 93 7 0.811 0815 59 41 0.894 0.898 25 75 0.965 0.967 92 8 0.313 0817 58 42 0.896 0.900 24 76 0.966 0. ♦ 8 91 9 0.816 0820 57 43 0.899 0.902 23 77 0.968 0.970 90 10 0.818 0822 56 44 0 901 0.904 22 78 0.970 0.972 89 11 0.821 0.825 55 45 0.903 0 906 21 79 0.971 0973 88 12 0.823 0-827 54 46 0.905 0.908 20 80 0.973 0.974 87 13 0 826 i 0-830 53 47 0.907 0.910 19 81 0.974 0.975 86 14 0.828 ! 0-832 52 48 0.909 0.912 18 82 0.976 0.977 85 15 0.831 0-835 51 49 0.912 0.915 17 83 0.977 0.978 84 16 0 834 0-838 50 50 0.914 0.917 i 16 84 0.978 0.979 83 17 0.836 0840 49 51 0.917 0.920 15 85 0.980 0.981 82 18 0.839 0.843 ! 48 52 0.919 0.922 14 86 0.981 0.982 81 19 0.842 0.846 , 47 53 0.921 0.924 13 87 0.983 0.984 80 20 0.844 0.848 ; 46 54 0.923 0.926 12 88 0.985 0.986 79 21 0.847 0.851 45 55 0.925 0.928 11 89 0.996 0.987 78 22 0.849 0.853 i 44 56 0.927 0.930 10 90 0.987 0.988 77 23 0.851 ! 0.855 43 57 0.930 0.933 9 91 0.988 0.989 76 24 0 853 0.857 42 58 0.932 0.935 8 92 0.979 0.990 75 25 0.856 I 0.860 41 59 0.934 0.937 7 I 93 0.991 0.991 74 26 0.859 0.863 40 60 0.936 0.939 6 ! 94 0.992 0.992 73 27 0.861 0.865 39 61 0.938 0.941 5 | 95 0.994 72 28 0.863 0 867 39 62 0.940 0.943 4 96 0.995 71 29 0.866 0.870 ' 37 63 0.942 0.945 3 ' 97 0.997 70 30 0.868 1 0.872 36 64 0.944 0.947 o ' 98 0.998 69 31 0.870 1 0.874 ! 35 65 0.946 0.949 1 99 0.999 68 32 0.872 0.875 ) 34 66 0.948 0.951 0 100 1.000 67 33 0.875 0.879 1 S3 67 0.950 0.953 | Appendix. Specific Gravity of E ssential and other Oils. Oil of Anise-seed, 0.9958 “ “ Bergamot, . 0.685 * 4 “ Cajeput, 0.048 “ “ Caraway, .... . 0.975 “ M Cassia, .... 1.071 “ u Cinnamon, 1.035 “ 44 Cloves, .... 1.061 44 “ Fennel, .... . 0.997 Oil of Juniper, ... 0.911 44 44 Lavender, . . . 0.898 44 “ Lemons, 0.8517 44 44 Nutmegs, . . 0.948 44 “ Peppermint, 0.899 44 “ of Roses, (Ottar of Roses) . 0.832 44 44 Rosemary, 0.85 Oils of Fermented Liquors. Oil of Grain Spirits, .... . . . . 0.635 44 44 Potato Spirits, .... . 0.821 Tables of Weights and Measures , of the Correspondence between Fahren- heit's, Reaumur's, and the Centigrade Thermometers, and of Freezing Mixtures. WEIGHTS AND MEASURES. WEIGHTS. The standard according to which the present system of weights is regulated, is the Troy brass pound.* It contains 5760 grains. Imperial Standard Troy Weight 24 grains = 1 pennyweight. 20 pennyweights = 1 ounce. 12 ounces = or, n 1 pound. Grains. Pennyweights. Ounces. Pound . 24 = 1 = l 21X itItt 480 = 20 — 1 tV 5760 = 240 = 12 * For important remarks on weights and measures and on the standard weights of the United States, see HassieFs Reports to Congress, \ $37— $. 526 Appendix. Avoirdupois Weight. The pound avoirdupois contains 7000 grains, each of which is equal to a Troy grain, being thus heavier than the Troy pound by 1240 grains. 1 drachm — 27.34375 grains. 16 drachms = 1 ounce — 437.5 16 ounces = 1 pound — 7000 28 pounds = 1 quarter = J 96000 4 quarters = 1 cwt. or 112 lbs. = 784000 20 cvvts. = 1 ton or, = 15680000 Pound. Ounces. Drachms. 1 = 16 = 256 = 7000 grains. Tff = I = 16 = 437.5 i TF = 1 = 27.34375 Apothecaries ’ Weight. The pound in Apothecaries' Weight is equal to the Troy pound, containing 5760 grains, but is differently subdivided. 1 pound ||j = 12 ounces = 5760 grains. 1 ounce 3 — S diachms — 480 1 drachm 3 — 3 scruples 60 1 scruple 3 = 20 grains = 20 or. Pound. Ounces. Drachms. Scruples. Grains. 1 = 12 — 96 = 288 = 5760 1 = 8 = 24 = 480 1 = 3 = 60 1 = 20 The following tables show the correspondence between the Troy , Avoirdupois, an d Apothecaries’ Weights. Troy Weight. Avoirdupois. Apothecaries’ 9 1 pound 1 ounce 1 pennyweight 13 oz. 2 dr. 17.8125 grs. 1 1 15 1562 0 0 24. 1 pound. 1 ounce. 1 scruple 4 grs. Avoirdupois. Troy Weight. Apothecaries’. 1 pound = 1 Jb 2 oz. 11 dwt. 10 gr. = 1 lb 2 § 4 3 2 9 1 ounce = 0 0 18 5.5 = 0 0 7 0 17.5 grs. 1 drachm = 0 0 1 3.34 = 0 0 0 1 7.34 Apothecaries’. 1 pound 1 ounce 1 drachm 1 scruple Troy Weight. 1 pound 1 ounce 2 dwt. 12 gr. 0 20 Avoirdupois. = 13 oz. 2 dr. 17.8125 grains. = 1 1 15.1562 = 0 2 5.3 125 = 0 0 20 . French Decimal If eight. — Gramme = 15.4063 Troy Grains. Milligramme Centigramme Decigramme Gramme 0.0154 grain? 0.1.540 1.5406 15.4063 Appendix* 527 MEASURES. The Imperial Standard Gallon contains ten pounds Avoirdupois weight of distilled water, weighed in air at 62° Fahr. and 30° Barotn., or 12 lb. 1 ounce 16 pennyweights and 16 grains Troy, = 70,000 grains weight of distilled water. A cubic inch of distilled water weighs 252.458 grains, and the imperial gallon contains 277 274 cubic inches. Imperial Measure. Quarter Bushel Peck Gallon 1 Quart 8 Bushels. 4 Pecks. 2 Gallons. 4 Quarts. 2 Pints. Distilled Water. Grains. Avoird. lb. Cub. hich. Pint. Quart. Galls. Pecks. Bush. Qv. 8750 = 1.25 = 34 .659 = 1 17500 = 2.5 = 69.318 2 = 1 70000 = 10 = 277.274 = 8 = 4=1 140000 = 20 = 554.548 = 16 = 8 = 2 = 1 560000 =80 = 2218.192 = 64 = 32 = 8 = 4 = 1 4480000 = 640 = 17745.536 = 512 = 256 = 64 = 32 = 8 = 1 Apothecaries ’ Measure (London Pharmacopoeia). The gallon of the former wine measure, and of the present Apothecaries’ measure, con- tains 58333.31 grains weight of distilled water, or 231 cubic inches, the ratio to the impe- rial gallon being nearly as 5 to 6, or as 0 8331 to 1. 1 Gallon ~ 1 Pint 0 1 Ounce f § 1 Drachm f 5 8 Pints. 16 Ounces. 8 Drachms. 60 Drops, or Minims. Gallon. Pints. Ounces. Drachms. Minims. Gr. of Dist. Water •. Cub Inch. 1 == 8 = 128 = 1024 = 61440 = 58333.31 = 231 1 = 16 = 128 .== 7680 = . 7291.66 = 28.8 1 -= 8 = 4S0 — 455,72 = 1.8 1 = 60 = 56.96 = 0.2 French Decimal Measure of Capacity, Litre — 61.02525 15406.312 grains of distilled ivater. British cubic inches . or Millilitre Centilitre Decilitre Litre 0.06102 cubic inches. 0.61025 6.10252 61.02525 Table showing the Weight in Grains of various Measures (Apothecaries) of liferent Fluids. 'Specific Gravity. Weight in Grains of 1 fuit. 1 Ounce. 1 Drachm. | 1 Minim . Distilled Water Sulphuric Ether Alcohol - Solution of Ammonia ... Muriatic acid - Nitric acid Sulphuric acid 1.000 0.720 0.796 0.925 1.118 1.480 1.848 7291 66 524 >.99 5801.16 6744.78 8152.07 10791.65 13474.98 455.72 328.12 362.76 421.54 509.50 674.47 842.18 56.96 41.01 45.34 ! 52.69 63 68 84.30 105.27 0.947 0 683 0.749 0.878 1.061 1405 1.754 628 Appendix. Fig'-r. G=P %\ A-/ V Apparatus for obtaining Potassium. Fig. 1, an iron pot made of the best malleable iron, about 12 inches long, and 5 or 6 in diameter ; the iron at least three eighths of an inch thick. A lid is fitted accurately to it, and this is secured by an iron rod passing through two holes in the upper part of the pot. A gun-barrel passes from the cover to the re- ceiver. The receiver consists of two pieces. It is made of tinned cop- Fig. 2. per. The piece (Fig. 2) is a thin parallelopiped, 10 inches long, 5 or 6 broad, and thick. It is shut at the top and open at the bottom. It is divided by l£) a diaphragm, a , to within one third of the bottom. On one side is a small hole into which the end of the gun-barrel enters, and to which it is luted air-tight, or, what is better, fitted by grinding. Opposite to it is another opening, fitted with a cork through which an iron wire passes air-tight. It passes also through a cork fitted into the hole in the diaphragm. The use of this wire is to keep the gun-barrel from being filled up during the process. Fig. 3 is the other part of the receiver, open above, and shut below. Fig. 2 fits it exactly. A few inches of naphtha are put into Fig. 3, and Fig. 2 is placed in it; being well luted with fat lute or putty to exclude air. A bent glass tube proceeds from 2 at 6, Fig. 4, well luted, which plunges into a vessel filled with naphtha; to allow the escape of the gases. Fig. 4 shows the arrange- ment of the iron pot, recei- ver, and furnace. The iron pot should be luted before it is used, as it is apt to be melted ; this is best done by binding it round with iron wire, covering it with a stiff cla}" lute mixed with about one fifteenth part of iron filings and charcoal, and a little thread cut into pieces about an inch in length. This is bound round again with wire, and the whole rubbed over with lute. It should be allowed to dry a day or two before using, and the cracks should be filled up. The iron pot is placed, as represented, above a piece of fire-brick, and fixed to it with fine clay. The body of the furnace may be about 18 inches long, 15 broad, and 18 deep ; the walls from 5 to 10 inches thick, and the flue 6 inches square (inside). The upper part of the furnace is covered by a flat cast-iron plate about three fourths of an inch thick, and with an opening in the centre through which fuel is introduced, a moveable cover of th§ same metal being fitted to it by an iron bolt passing through a hole bored in it and in the plate ; it allows us also to see very conveniently the state of the apparatus within the furnace Another opening is made on a level with the branders, to allow the fire to be withdrawn whenever it may be necessary ; it is constructed in such a manner as to al- low it to be easily closed up with a brick and a little mortar, which may be removed again with the same facility. A door is also placed below to regulate the admission of the air, and a damper in the vent to diminish the draught if this should be necessary. The aper ture in the side of the furnace for the gun-barrel must not be forgotten. After everything has been properly adjusted, the fire may be put on. A little water comes away when the apparatus becomes red-hot ; soon after, carbonic oxide gas is evolved ; and when it is at white heat, a very dense vapour is disengaged, which burns with a brilliant flame. The receiver intended to condense the potassium may then be fixed to the extremity of the gun barrel without the furnace. The receiver is that recom- mended by Berzelius, which should be kept cold by ice. When the gas begins to be disengaged slowly, this arises in general from the tube being so obstructed as to prevent it from passing out readily ; the plug is then taken out, and the obstructing matter removed as completely as possible, but if the gas does not appear then to increase in quantity, it will be better to withdraw the fire and allow the apparatus to cool. Too mueh caution cannot be taken in endeavouring to clear the tube either during the distillation or after the apparatus has been allowed to cool, for the tube being frequently obstructed while the materials are at a high temperature and still producing gas, it is obvi- Appendix. 529 ous that a large quantity must be accumulated in a short time, and the moment the impe- diment to its free passage is removed, it often expands with explosive violence, and gives rise occasionally to serious accidents* The mixture of charcoal and potassa is prepared most easily by exposing six or seven pounds of cream of tartar (cr ude tartar may be used) tq a red heat, in large earthen or iron crucibles, till no more gas is disengaged, reducing it to powder in a mortar, when cold. This is transferred immediately to an iron pot, that it may be prevented from attracting water from the air. Brunner states that when the tartar is mixed with one twelfth of its weight of charcoal a larger quantity of potassium is obtained. This additional quantity of charcoal is useful also in preventing the fusion of the carbonate of potassa at the high tem- perature to which it is afterwards exposed. A powerful lamp (Fig. 5), where a large flame is required, may be formed by filling a ring of tin of an inch or more in diameter, and an inch in length, with wick yarn, and placing it in a shallow tin vessel, in the centre of which is a tube or cavity into which the ring fils loosely. The tube is soldered at the top to the body of the lamp, but a small space is left at the bottom to permit the passage of the alcohol with which the lamp is filled. The lamp is filled by pouring the alcohol upon the wick. The upper edge of the ring rises a little above the top of the lamp, as seen in the section Fig. (i. The power of different metals of conducting heat may be shown Fi". 7. by the apparatus, Fig. 7. See paragraph 203. Fig. 8 represents a convenient funnel for conveying gases into vessels the funnel be- ing prolonged by a tube at right angles, and inverted' in a basin of water, a small piece may be removed from the edge to admit the pipe from a retort. Fig. 9. Advantage will sometimes be gained by cement- ing a thin piece of wood to a cork made tapering, through both which tubes may be passed and secured, as in Fig. 9, for intro- ducing into bottles and flasks. Barium , Strontium , and Calcium . Dr Hare has recently obtained, by an im- proved process, all three of these metals. Saturated solutions of the chlorides were substituted for moistened oxides, and exposed to a powerful Voltaic circuit, in con- tact with mercury as a cathode ; the resulting amalgams were distilled by means of vessels of iron. The avidity of the metals for oxygen was such, that, to see their bright metallic surfaces, it was necessary for the eye to follow closely the movements of the file or bur- nisher. They were brittle, and much harder than potassium or sodium. See Jhncr. Jour. Oct., 1839. * On one occasion when the apparatus was not touched till 36 hours after the fire had been withdrawn, on tapping the gun -barrel to remove it more easily, the whole of the glass tube was broken to pieces so excessively small that no trace of it could be found; a peculiar detonating compound indeed is lormed within the tube, small quantities of which were found in almost every part of the room, and exploded with very little friction, Keid. 530 Appendix. Absorption of Gases by Charcoal. Saussure found that charcoal prepared from box-wood absorbs during the space of 24 36 hours, of Ammoniacal gas, ..... 90 times its vol. Hydrochloric acid, . . . . .85 Sulphurous ...... 65 Sulphuretted hydrogen, . . . . .81 (Henry.) Nitrous Oxide, ..... 40 Carbonic acid . . . . . .35 Olefiant gas, ...... 35 Carbonic oxide, ...... 9.42 Oxygen, . . . . . . 9.25 Nitrogen, ....... 7.5 Hydrogen, . . . . . . 1.75 GENERAL INDEX ABB ABB RE VIA TION of symbols , 35 Acetates , 377 Acetal, 447—452 Acetate of alumina, 380 ammonia, 378 copper, 379 iron, 378 lead, 379 lime, 378 mercury, 379 morphia, 439 potassa, 378 tin, 378 zinc, 378 Acetic acid, 376 procured, 376 by platinum, 377 (n*) from wood, 376 glacial, 377 properties of, 376 theory of its formation, 489 Acetification, 489 Acetone, 455 (n) Acetous acid, 376 fermentation, 489 Acidity, oxygen not essential to, 122 Acids, containing nitrogen, 391 oxygen, action of, 122 fixed, 382 produced by chlorine, 122 hydrogen, 122 from metals, 225 termipology of, 103 metals oxidized by, 122 oily, 390 transfer of, by galvanism, 97 vegetable, 369 Acid, acetic, 376 — 489 acetous, 376 aldehydic, 447 (n) ACI Acid, aloxanic, 426 althionic, 394 — 454 antimonic, 287 antimonious, 286 apocrenic, 394 arsenic, 275 arsenious. 272 azuhnic, 391 benzoic, 381 boracic, 175 bromic, 204 carbonic, 153 quantity produced by respiration, 498 camphovinic, 454 carbazotic, 392 chloric, 192 chloriodic, 201 (n) chlorocarbonic, 195 (n) chloronitrous, 195 (n) cholic, 501 chromic, 279 cinnamomic, 382 (n) citric, 383 columbic, 285 crenic, 394 croconic, 373 cyanic, 398 cyanilic, 422 cyanuric, 403 erythric, see Alloxan , 425 esculic, 3S2 (n) ethionic, 395 fluoboric, 207 fluosilicic, 208 formo-benzpilic, 395 composition of, 396 formic, 373 fuluninic, 401 * (n) signifies note. ALB ACI 532 Acid, gallic, 3S7 hydro-bromic, 203 hydriodio, 198 hydro-chloric, 184 hydro-cyanic, 405 hydrous, 406 hydro -ferrid cyanic, 417 hydro-ferrocyanic, 412 hydro-fluoric, 205 hydro-oleic, 391 hydro-selenie, 217 hydro-sulphuric, 214 hydro-telluric, 293 (n) hypo-chlorous, 189 hypo-nitrous, 145 hydro-sulphocyanic, 420 hypo-phosphorous, 172 hypo-sulpho-indigotic, 395 — 457 (n) hypo-sulphuric, 168 hypo-sulphurous, 168 indigoticJ 392 iodic, 200 kinic, 388 lactic, 380 — 503 lithic, 504 malic, 382 margaric, 391 meconic, 386 mellitic, 375 mesoxalic, 427 metaphosphoric, 174 molybdic, 282 monoxylic muriatic, 184, 188 mykomelinic, 427 naphthalic, 381 (n) 480 (o) nitric, 147 process for, 148 (n) nitro-hydrochloric, 188 nitro-sulpluiric, 329, 337 (n) nitrous, 146 oleic, 391 osmic, 319 oxalic, 369 oxalovinic, 454 oxaluric, 428 oxymuriatic, see Chlorine parabanic, 428 pectic, 393 perchloric, 193 periodic, 201 (n) permanganic, 254 phosphoric, 173 glacial, 175 phosphorous, 173 phosphbvinic, 395 (n) — 454 pinic, 464 prussic, 405 purpuric, 433 — 504 pyrogailic, 387 pyroligneous, 376 pyrophosphoric, 174 racemovinic, 454 rhodizonic, 373 selenic, 180 Acid, selenious, 180 silicic, 177 silici-fluoric, 208 silico-hydrofluoric, 361 sorbic, see Malic, 382 stearic, 390, 391 suberic, 381 (n) succinic, 375 — 466 sulpho-cetic, 448 sulpho -oleic, 391 sulpho-indigotic, 395 — 457 (n) sulpho-naphthalic, 395 sulphur, 355 sulphuric, 165 sulphurous, 163 silvic, 464 tannic, 388 tartaric, 383 tartrovinic, 454 telluric, 294 (n) tellurous, 293 thionuric, 429 titanic, 292 transfer of, by galvanism, 97 tungstic, 283 uramilic, 430 uric, 423—504 vanadic, 281 Action, chemical, 14 Adipocere, 492 Aeriform bodies, see Gases conducting power of, 65 expansion of, 41 matter, its power of sustaining indue tion, 82 Affinity, chemical, 13 results of, 13 of aggregation, 2 elective, 11 inferred, 17 single, 17 tables of, 18 influenced, 19 measured. 23 Agitation, its effect, 17 Air , effect of respiration on, 498 atmospheric, 136 analysis of, 138 an electrode, 99 composition of, 137, 139 uniformity of, 139 compression of evolves heat, 50 Dalton’s theory, 140 Graham’s experiments, 140 necessary to fermentation, 488 properties of, 136 pump, 137 purity estimated, 137 thermometer, 46 Alabaster, 325 Albumen , antidote to corrosive sublimate, 30 animal, 492 liquid, 493 solid, 493 vegetable, 474 AMM 533 ANT Alchoates, 444 Alcohol , 441 absolute, 442 Alcohol , action of platinum on, 377 (n) composition of, 445 of sulphur, 220 strength of ascertained, 443 uses, 443 in wine, table of, 445 Aldehyde, 446 its composition, 447 (n) resin, 447 Algaroth, powder of, 286 Alkali, volatile, 208 Alkalies , 104, 22S metallic bases of, 229 vegetable, 232—434 Alkaligenous metals, 228 Alkaline earths, 228 Alkalimeter , 158 Allanile, 289 Allantoin, 425 Alloys, <2,21 characters of, 224 formed, 224 (h) qualities of the metals altered in, 228 Alloxan, 425 Alloxanic acid, 426 Alloxantin, 430 Almonds, 485 bitter, oil of, 468 Althionic acid, 394 — 454 Alum, 330 impurities in, 247 (n) chrome, 331 iron, 331 magnanese, 331 Alumina, 247 acetate of, 380 in blood, 496 obtained, 247 purified, 247 (n) properties of, 247 quantity of water taken up by, 248 [n] recognized, 248 sulphates of, 326 Aluminium, 247 sesquichloride of, 248 process for, 248 sesquioxide of, 247 Alizarin, 458 (n) Amalgams, 307 Amber, 466 acid of, 375 Ambergris, 502 Amides , theory of, 364 signification of the term, 467 Amidet, 364 Amidin, 472 Ammelid, 398 Ammelin, 397 Ammonia, 208 preparation of, 208 acetate of, 378 Ammonia, anomalous cyanate of, 399 bicarbonate of, 350 action of chlorine on, 210 action on oxalic ether, 467 (n) analysis of, 210 benzoate of, 382 basic cyanate of, 399 carbonate of, 349 carbo-sulphuret of, 357 chlorides with, 359 cleaning gold by, 296 (n) cyanates of, 399 liydrochlorate of, 353 native, 354 hydrocyanate of, 409 hydrofluate of, 354 bydrosulphate of, 354 inflamed with oxygen, 209 metallization of, 307 muriate of, 353 nitrate of, 335 oxalate of, 371 phosphate of, and magnesia, 344 purpurate of, see Murexid, 431 sub-carbonate of, 350 sulphate of, 323 urate of, 505 water of, 210 Ammonia-aldehyde, 446 Ammoniac Sal, 353 Ammoniacal salts recognized, 353 Ammonia and magnesia, phosphate of, 344 Ammonium, 209 bicarbonate of oxide of, 350 cyanuret of, 409 ferrocyanuret of, 413 nitrate of oxide of, 335 sesquicarbonate of oxide of, 350 sulphate of oxide of, 323 Amygdalin, 475 (n) Amylaceous substances, 471 Amylin , 472 Analysis, defined, 36 proximate, 37 of light, 74 Anhydrite, 325 Animal carbon, 152 — 481 heat, 498 theories of, 499 substances, 490 contain nitrogen, 490 — — proximate principles of, 490 putrefaction of, 491 • effect of heat upon, 491 Animals, effect of narcotina upon, 437 Annealing, 178 Animal heat, 494 Anions, defined, 98 Anotta , 458 Anode, defined, 98 Antimonial powder, 286 Antimonic acid, 287 Antimonio-sulphurets, 358 Antimonious acid, 286 ATO 534 BER Antimony , 285 alloys of, 288 butter of, 287 chlorides of, 287 detected, 286 distinguished from arsenic, 275 glass of, 287 golden sulphuret of, 288 ignited, detonates with vapour, 25 salts of, 286 sulphurets of, 287 tartarized, 286 Antiseptics, 491 Ants, acid from, 373 ApperCs method of preserving meat,&c.491 Apocrenic acid, 394 Apparatus, chemical, 106, 115 for freezing, 53 (n) Nooth’s, 154 (n) for liquefying carbonic acid, see In- dex to apparatus Aqua Ammonia, 210 fort is, 151 regia, 188, 354 Arabin, 473 Arbor Diana, 310 Saturni, 299 Argot, 384 Arrow-root, 472 Arseniatec, 345 Arsenic, 271 acid, 275 obtained, 271 alloys of, 277 chlorides of, 275 detected, 273 properties of, 272 oxide of, 272 persulphuret of, 357 sesquichloride of, 275 solution of, Fowler’s, 345 tests of, 273 Arsenio-sulphurets, 357 Arsenious acid, 272 action of galvanism on, 275 [n] solubility, 272 solution made, 272 [n] Arsenites, 345 Arseniuretted hydrogen, 276 Arterialization, 493 Asbolin, 481 Asphaltum, 477 Assay, see Gold and Silver. Atmospheric air, 136 composition of, 139 contains carbonic acid, 140 Dalton’s theory of, 140 weight of, 137 Atomic theory, 30 weights, 30 Atoms, defined 2, 29 elementary, 2 figure of, 31 Atoms, organic, 362 use of the term, 30 Atropa belladonna, 484 alkali of, ‘484 Attraction, 2 contiguous, 2 chemical, 3 heterogeneous, 13 results of, 13 Auro-chloridrs, 358 Auric acid, 313 A arum musivum 268 Azote, 135 oxide of, 141 Azotic gas, 135 Azulmic acid, 391 BACHE’S apparatus, 66 (n) Baldxoin’s phosphorus, 77 (n) Balloons, 124 Balsams, 464 Balsam of Canada, 464 (n) of Peru, 465 of Tolu, 465 (n) Barilla, 348 purity of ascertained, 349 (n) Barium, 237 chloride of, 239 peroxide, use of, 131 pfotosulphuret of. 239 hydrosulphurel, 356 peroxide, 239 properties, 237 protoxide, 238 Bark, 482 Baryta, 233 carbonate, 350 chlorate of, 340 hydrate, 233 properties, 233 pure obtained, 324 sulphate, 323 sulpho-naphthalate, 395 (n) test of sulphuric acid, 168 of carbonic acid, 238 Bases, 104 Basic water, 5 cyanate of ammonia, 399 Basis in dyeing, 456 Bassorin, 474 Battery, voltaic, 91 Battery's sedative liquor, 440 (n) B ’ar-berry, acid from, 3S8 Beer, 487 Bees-xoax, 460 Beet-sugar, 469 Benzamide, 364 — 468 Benzoate of ammonia, 382 Benzoic acid, 381 sublimation of, 382 Benzoyl , theory of, 365 compounds of, 468 properties of. 468 Benzule, 381 (n) BertholetVs views, 23 CAL BOR 535 Berzelius, his symbols, 35 theory of combustion, 121 Bicarbonate of potassa, 348 soda, 349 oxide of ammonium, 350 Bicar buret of nitrogen, 219 Bi-chloride of mercury, 304 Bi-chromate of potassa, 346 Bi-cyanuret of mercury , 411 Bile, 500 Biliary calculi, 501 Biniodide of mercury , 305 Binoxalate of potassa, 371 Binoxide of hydrogen, 134 nitrogen, 143 Bisulphate of potassa, 322 Bismuth, properties of, 290 chloride, 291 magistery, 291 oxide, 291 sesquioxide, 291 Bi-sulphuret of carbon, 220 apparatus for, 221 (n) Bitartrate of potassa, 384 Bitter almonds, oil of, hydret of benzoyle, 468 Bittern, 203 Black dyes, 457 flux, 271 (n) lead, 261 Black, Dr, his theory of animal heat, 499 Bleaching, 182 powder, 243 assay of, 243 (n) Bladders for gases, 107 Bleeding , effect of, 496 Blood, 494 buffy coat of, 499 coagulation of, 495 accelerated, 495 colouring matter of, 496 composition of, 495 absorbs oxygen, 119, 498 effect of chlorine on, 496 oxygen, 498 of diseases on, 499 peculiar principle in, 496 serum of, 497 Blow-pipe compound, 127, 128 Brooke’s, 128 Blue-dyes, 457 Bodies, state of influenced by heat, 37 Boiling point, 55 influenced by pressure 55 of mercury, 55 of water, 301 Bologna phosphorus, 323 Bone, 493 composition of, 494 effect of heat on, 494 phosphate of lime, 344 (n) Boracic acid, obtained, 175 native, 175 properties, 176 with fluorine, 207 Borates, 346 Borax, 347 Borofiuorides, 361 Boron, 175 terchioride, 195 (n) Boyle’s fuming liquor, 354 Braude’s experiments on wines, &c>, 444 Brandy, 488 Brain, 494 Brass, 297 Brazil wood, 458 (n) Bromine, 202 and hydrogen, 203 action on combustibles, 203 on metals, 226 detected, 202 obtained, 202 properties, 203 Bromic acid, 204 ether, 452 Bromides, 205 (n) Bromoform, 448 (n) Bronze, 2$~l Brooke’s blow-pipe, 128 Brucia, 437 Buckthorn berries, 486 Buffy coat of the blood, 499 Bulbs, 483 Butter, 501 Butyrine, 501 Brunswick green, 359 CABBAGE, infusion of, 14 (n) Cadmium, 264 oxide, 265 (n) properties, 264 sulphuret, 265 (n) Caffein, 486 Calamine, 263 Calcination, 225 Calcium, 240 bromide, 244 (n) chloride, 243 fluoride, 205 phosphuret, 244 process for, 218 (n) 244 (ra) protoxide, 241 Calculi, biliary, 501 urinary, 505 varieties of, 505 Calico-printing , 456 Calomel, 303 process for, 303 (n) Caloric, absorption of, 69 during evaporation, 61 liquefaction, 51 solution, 52 capacity for, 48 apparatus for illustrating, 48 cause of vapour, 54 combined, 50 conducting power of bodies for, 63 of liquids and gases, 64, 65 conductors of, 63 confined air a bad conductor of, 64 CAR 536 CER Caloric, definitions of, 37 Hare’s apparatus, 64 Rumford’s experiments, 63, 65 evolved by increase of density, 50--53 • during separation of salts, 54 the condensation of vapour, 61 by mechanical pressure, 50 expands bodies, 38 expansion of air by, 41 liquids, 39 mercury, 40 solids, 38 • water, 41 general observations on, 37 influences the state of bodies, 50 influenced by surface, 66 Bache’s apparatus for illustrat- ing, 66 (n) latent, 50 of steam, 58 made sensible, 53 apparatus for illustrating, 56 Melloni’s experiments, 70 nature of, 71 peculiar effect of, 42 polarization of, 70 radiation of, 506 ■ theories of, 70 reflection of, 67 Pictet’s experiments, 68 radiant, 65 sensible made latent, 57 sources of, 71 specific, 48 of gases, 49 Stark’s experiments, 67 Calorimeter , 48 Calorimutor, Hare’s, 89 Camphogene, 463 Camphors, 463 common, 463 Camphrone, 463 Camphovinic acid, 454 Canada balsam, 464 [n) Canton's phosphorus, 77 (n) Caoutchouc, 475 Caoutchene, 476 (n) Capacity for caloric, 48 Capnomor, 479 Carbazotic acid, 392 obtained, 392 salts of, 392 Carbon, 151 bisulphuret of, 220 • process for, 220 (n) a sulphur-acid, 221 bromide of, 205 (n) combustion of, 151 dichloride, 195 (n) and hydrogen, 211 liydroguret of, 214 and iron, 227 and nitrogen, 219 perchloride of, 194 periodide of, 202 (u) Carbon, proto-chloride of, 194 (n) and sulphur, 220 quantity produced by respiration, 498 varieties of, 152 Carbonates, characters of, 347 Car bo -sulphur et of hydrosulphate of ammo- nia, 357 Carbonates, double, 353 Carbonate of ammonia, 349 baryta, 350 copper, 352 iron, 352 lime, 350 magnesia, 351 potassa, 347 protoxide of iron, 352 of lead, 352 soda, 348 strontia, 350 Carbonic acid, 153 absorbed by water, 155 • quantity, 133 [n] • by lime, 351 apparatus for solidifying. See Plate /. composition of, 153 effects on vegetation, 157 expelled by heat, 351 fatal to life, 155 generated in combustion, 156 liquefied and frozen, 157 Mitchell’s experiments, 157 [n] procured, 153 properties of, 154 a product of respiration, 156 , 498 quantity produced by respiration, 498 specific gravity of, 154 tests of, 156 water impregnated with, 154 Carbonic Oxide, 154 explodes with oxygen, 160 processes for, 159 properties of, 160 Carbo-sulphuret of potassium, 356 hydrosulphale of ammonia, 357 Carburet, 103 of iron, 261 Carburettcd hydrogen, light, 211 action of chlorine on, 212 combustion of, 212 procured, 211 properties of, 212 from animal bodies, 491 Carthamin, 458 (n) Caromel, 470 Cassava, 472 Caseous matter, 501 Cassius, purple of, 314 Cast iron, 261 % Cations, what, 98 Cathartina, 484 Cathode, what, 98 Caustic, lunar, 337 Cedriret, 479 Cerasin, 474 Cerin, 461 CHL 537 COA Cerium, 289 oxides, 289 Ceruleo-sulphate of potassa, 457 Cerulin, 457 Ceruse, See White lead Chain of cups, galvanic, 90 Chameleon mineral, 254 Charcoal, 152 absorbing power, 152 — 530 animal, 481 conducts galvanism, 95 properties, 152 spontaneous combustion of, 153 See Carbon . Chemical action, 15 promoted, 16 influenced, 16 — 22 effects of, 15 results of, 14 attraction, 13 how exerted, 13 modified, 19 illustrated, 14, 16, 17 energies of bodies influenced by light, 74 equivalent, 25 Chemical symbols, 33 — 513 table of, 34 formulae, 33 nomenclature, 102 Chemistry , defined, 1 foundations of, 1 organic, 362 inorganic, 118 ChevreuVs researches on oils, &c. 460 Chio turpentine , 464 [n] Chloral, 448 Chlorates, characters of, 339 Chlorate of baryta, 340 potassa, 339 soda, 349 (n) Chloric acid, 192 ether, 452 [n] Chlorides, 184, 225 with ammonia, 359 of gold, 314 auro, 358 oxy, 359 platino, 358 hydrargo, 358 rhodio, 359 of iodine, 201 [n] metallic, 226 with phosphuretted hydrogen, 360 various, 195 [n] Chloride of nitrogen, 193 bromine, 204 [n] ethyl, 451 potassium, 233 zinc, 263 Chlorine, 180 absorbed by water, 181 action on ammonia, 210 metals, 183 • carburetted-hydrogen, 212 antidote to, 182 [n] 68 Chlorine, action on olefiant gas, 214 condensed, 184 effect of light on, 185 detected, 184 explosion of, 184, apparatus for, PI. II. with ether, 450 hydrate of, 182 nature of, 195 obtained, 181 peroxide of, 191 supports combustion, 182 unaltered by heat, 183 uses, 184 weight, 182 with cyanogen, 41 hydrogen, 184 metals, 225 nitrogen, 193 oxygen, 189 phosphorus, 183 mercury, 183 • tin, 183 Chloriodic Acid, 201 [n] Chlorites, 341 Chloroform, 448 [n] Chloro carbonic Acid , 195 [n] Chloro -nitrous Gas, 195 [n] Chlorophyllite, 458 Chlorous Acid, 191 process for, 192 Choak damp, 156 Cholera, effect of on the blood, 499 Cholesterine, 501 Cholic acid, 501 Christison’s experiments on alcohol, 442 table of strength of wines, 445 Chromates, characters of, 345 Chromate of iron, 277 — 346 acid from, 279 lead, 346 potassa, 346 zinc, 346 [n] Chrome alums, 331 Chromic acid, 279 Chromium, 277 chlorides, 280 oxides, 278 perfluoride, 280 Chromule, 458 Chromulite, 458 Chyle, 501 Cinchona, varieties of, 483 acid in, 388 Cinchonia, 435 Cinnabar, 306 factitious, 306 manufacture of, 306 [n] native, 307 Cinnamomic acid, 382 [n] Circles, voltaic, 85 Citisin, 486 Citric acid, process for, 383 from currants, 383 Clothing substances , conducting power of, 63 Coagulation of blood, 495 CYA COO 538 Coaly gas from, 212 — 480 distillation of, 480 mines, fire damp of, 212 Coating of vessels , 105 [n] Cobalt , obtained, 268 alloys, 270 chloride, 269 oxide, 269 properties, 269 Cobaltate of ammonia, 269 [n] Cocoa-nut oil, 460 Codeia, 440 Coffee, analysis of, 485 Cohesion, 2 diminished, 19 Coke , 153 Colchicum autumnale, 437 Colcothar, 327 Cold, artificial produced, 51, 60 by rarefaction of air, 50 by carbonic acid, 158 [n] by ether, 450 tables of mixtures for, 51 Colocynthin, 485 Colocynth, 485 Colophan, 464 Colouring matters, 455 Colouring matter of flowers, 484 of fruits, 486 of blood, 496 Colours, adjective, 456 Colour, its influence on absorption of calor- ic, 69 of odours, 506 Colours, theories of, 74 destroyed by chlorine, 182 removed by carbon, 152 substantive, 456 Columbic acid , 285 Columbium, 281- acid of, 285 oxide of, 285 obtained, 284 same as tantalum, 284 Combination, laws of, 24 accounted for, 24 Combining proportion, 25 Combustion, 121 Berzelius’ theory 121 Lavoisiers’ theory, 121 in oxygen gas, 120 increases the weight of bodie«, 121 of alcohol, 443 Compounds of many proportions, 24 Compound voltaic circles, 91 radicals, 367 Compound blow pipe. 507 Conductors of caloric, 63,529 Congelation , artificial, 60 Conicina, 484 Conium maculatum, 484 Constitutional water, 5 Contiguous attraction , 2 Contraction from heat, 42 Cooling , rate of, varied by surface, 66 Copaiva, 464 adulteration of detected, 465 Copal, 465 solution of, 465 Copper, acetate of, 379 alloys of, 297 cleaning of, 296 [n) chlorides, 296 combination with ammonia, 328 di-carbonate, 352 effect of galvanism on, 95 • heat on, 294 ores of, 294 oxychloride, 359 plates, preservation of, 298 (n] properties, 294 scales, 328 [n] sulphate of oxides of, 328 sulphurets, 296 whitened by arsenic, 275 (n) Copperas, 326 Cork, 483 Corn poppy, petals of, 485 Corrosive sublimate, 304 antidote to, 305 Cortical layers, 482 Crassamentum,4% Cotton , 483 Crawford' s experiments, 53 Crosse's experiments, 98 Croton oil, 460 Cream, 501 Cream of tartar, 384 Crenic acid, 394 Creosote, 478 Croconic acid. 373 Crocus of antimony, 287 Crude tartar, 384 Cryophorus, 61 (n) Crystallization, agency of cohesion, 20 conditions for, 3 connexion of with chemistry, 13 influence of light upon, 7 laws of, 9 promoted, 6 systems of, 10 theories of, 7 water of, 5 Crystallized tin, 265 [n] Crystals, axes of, 9 large forms of obtained, 6 from fusion. 4 Cupellation, 308 [n] Cuticle, 494 Currants, acid from, 383 Cyanates of ammonia, 399 anomalous. 399 basic, 399 Cyanic acid, 398 properties of. 399 Cyanodide of Ethyle, 452 (n) Cyanogen, 219 analysis of, 220 compounds of, 396 obtained, 219 EMU DOB 539 Cyanogen, properties, 220 and hydrogen, 405 and iron, compounds of, 412 iodine, 419 oxygen, 398 Cyanurates, 404 Cyanurets, double, of metals, 412 Cyanurets of ammonium, 409 ■ potassium, 409 iron, 410 palladium, 411 silver, 411 Cyanuric acid, 403 radical of, 398 Cystic oxide, 433 DALTON, his theory of atoms, 29 ofelements, 31 (n) of the atmosphere, 140 Daguerre, his invention, 507 Daniel's experiments, 8 Decomposition, 18 by electro-magnetism, 102 — galvanism, 96 Decrepitation, 6 Deflagration, 225 Deflagrator, Hare’s, 91 Deliquescence, 5 Davy, his galvanic experiments, 96 — list of voltaic circles, 87 [n] — protector, 87 — safety lamp, 78 — theory of galvanism, 101 — theory of chlorine, 185 Delphinia, 437 (n) De Luc's columns, 92 . Density, maximum of water, 43 Deoxidation, 122 Deoxidizing rays, 75 substances, their action on indigo, 457 Dextrine, 510 Dephlogisticated air , 118 nitrous air, 141 Detonating powders, 340,402 Deutocarbohydrogen , 474 [n] its relation to aldehyden, 447 (n) Dew, 62 point, 63 Diagrams, 19 Diamond, pure carbon, 151 combustion of, 151 Dichloride of carbon, 195 [n] sulphur. 195 [n] Differential thermometers, 46 Diffusion of gases, Mitchell’s exp’ts on, 497 Diffusiveness of gases, 140 Dilatation of air , 41 Dippel's oil, 491,502 Diseased blood, 499 Disinfecting liquid, 349 [n] Distillation, 132 destructive, 368 of vegetables, 477 Distilled water , 162 Dobereiner's lamp, 125 Double elective affinity, 17 carbonates, 353 fluorides, 361 iodides, 360 sulphates, 330 Dragon's blood, 465 Drummond's light, 76 Ductile metals, 223 Dumas' process for carbonie ©xide, 159 Dutch gold, 297 Dutrochet, experiments of, 49’([ , Dyeing, 456 Dyes, black, 457 blue, 457 red, 456 with indigo, 458 EARTHS, alkaline, 228 bases of, 228, 237 Ebullition , 56 Efflorescence, 5 effects of, 21 Effluvia of putrescent substances, 492 Elaine, 460 Elastic gum, see Caoutchouc, 475 Elaterium, 485 Elasticity , effects of, 21 increased by heat, 21 influences results, 22 Elatin, 485 Elective affinity, 17 Electricity, 79 and galvanism, identity of, 85 action on ammonia, 209 on albumen, 493 by induction, 81 Faraday’s theory of, 81 nature of, 94 quantity and intensity, 94 sources of, 84 theories of, 79, 81 voltaic, 85 Electrical battery, 84 Electro-chemical equivalents 100, decomposition, 101 Faraday’s theory of, 101 Electrodes, 98 Electrolytes, only excite, 99 Electrolytic action, 99 Electrolyze, 98 Electromagnetism, 102 Electrometer , 80 Volta's, 100 (n) Electrophorus, 84 Electro-positive bodies, 101 negative, 101 Erithrogen, 497 Ethylide of potassium , 510 Elements, chemical, 37 Emetic tartar, 385 Emmet's process for formic acid, 374 Emetina, 437 [n] Emulsin, 475 Eliquation , 309 [n] 300 Enamel , 178 (n) FRU FEC 540 Endosmose , 497 Epsom salts, 325 Equivalents, chemical, 25 of compounds, 25 determined, 28 electro-chemical, 100 uses of, 28 Erythrin, 455 Erythrogen, 497 Ethal, 448 Ethyle, 509 . Ethyl, 451 chloride of, 451 cyanodide of, 452 (n) sulphuret of, 452 Ether, 448 sulphuric, 448 purification of, 449 Philip’s process for, 449 (n) production of cold by, 57 explodes with oxygen and with chlo- rine, 450 action on oxides, 451 base of, 451 hydrochloric, 451 nitric, 453 oxalic, 453 cenanthic, 454 thialic, 452 hydrocyanic, 452 (n) sulphohydric, 452 (n) chloric, 452 (n) iodic, 452 sulphocyanic, 452 Ethers, theory of, 365 Etheroxalate of potassa, 453 (n) Ethionic acid, 395 Ether oxamide, 468 Ethiop's mineral, 307 Euchlorine, 189 Eudiometry, 137 Gay Lussac’s method, 145 (n) Eudiometer , 137 Doebereiner’s, 139 Priestley’s, 139 Ure’s, 138 (n) Volta’s, 138 Eupion, 476 — 477 Evaporation, 4, 57 Exosmose, 497 Expansion, 38 of air, rate of, 42 (n) Extractive, 477 Extractum Saturni, 379 FARADAY, his experiments, 93 electrical investigations, 81 induclometer, 82 new terms, 98 theory, 81, 82, 101 volta-electrometer, 100 (n) Fat, 502 Feathers, 494 Fecula , 471 Fermentation, 487 acetous, 487 — 489 panary, 490 vinous, 487 Fermented liquors, strength of, 444 Ferro-cyanogen, compounds of, 412 Ferro-cyanurets, 413 decomposed by heat, 413 with two basic metals, 416 Ferrocyanuret of ammonium, 413 mercury, 415 potassium, 413 potassium and iron, 416 Fibrin, 492 Finery cinder, 256 Firedamp of mines, 212 Fireworks without smell, &c. 125 Fixed acids, 382 oils, 459 effect of air on, 459 spontaneous combustion of 459 Flame, what, 213 light and heat of, 77 tinged by selenium, 179 red and green, 336 (n) Flour, wheat, 471 Flowers of sulphur, 162 colouring matter of, 484 Fluidity, caloric of, 50 Fluoboric acid, 207 obtained, 207 properties, 207 Fluids, imperfect conductors, 65 Fluoric acid, see Hydro-fluoric, 205 Fluosilicic acid, 208 singular appearance, 208 Fluorides, double, 361 Fluoride of calcium, 205 Fluorine, 205 action on metals, 226 Fluor spar, 205 Flux, black, 271 (n) white, 333 (n Fly powder, 272 Forbes's experiments, 70 spark from magnet, 102 Formic acid, 373 Formo-benzoilic acid, 395 Forms of crystals, 9 Formulce, chemical, 33, 513 abbreviated, 35 Fowler's solution, 345 Freezing mixtures, 51 apparatus for, 53 (n) in vacuo, 60 Leslie’s method, 60 of mercury, 53 by carbonic acid, 157 bv ether, 450 Freezing and boiling, of water and ether, 450 * Frost, 62 bearer, 61 Friction, light from, 77 Fruits, 486 GAS 541 GOL Fruits , acids of, 486 contain sugar, 486 colouring matter of, 486 Fulminating gold, 313 platinum, 318 powder, 334 silver, 310 mercury, 402 Fuming liquor, 267 Furnaces, 111 Fusibility of metals, 223 Fusion, watery of crystals, 6. GAL AC TIN, 461 Galena, 298 Gallic acid obtained, 387 properties, 387 use, 388 precipitates by, 387 Galls, 387 Galvanic arrangements, 85 battery, 89 Hare’s, 89 pile, 90 trough, 90 Galvanism, see Voltaic electricity, 85 excitement of, 85 and electricity, identity of, 94 decomposes water, 96, 131 theories of, 92 Gases, equivalent weights of, 32 expansion of by heat, 42 condensible by pressure, 118 apparatus for experiments on, 107 method of weighing, 116 transferring, 113 quantities of absorbed by water, 133 00 purity ascertained, 138 from gun-powder, 335 give out their latent heat by compres- sion, 50 ratios of combining vols. 33 calculated, 33 specific heat of, 49 specific gravities of, 32 tendency to become thoroughly mix- ed, 127 general law of their union by vols. 31 diffusion of, Mitchell’s exp’ts, 497 tend to mix together, 127 liquefaction of, 117 solidification of, 157 as bottles, 107 bags, 107 holder, 109 Gas, what, 105 ammoniacal, 208 arsen in retted hydrogen, 276 azotic, or nitrogen, 134 binoxide of nitrogen, 143 light carburetted hydrogen, 211 carbonic acid, 153 carbonic oxide, 159 Gas, carburetted hydrogen, 211 coal, 480 chlorine, 180 chloronitrous, 195 (n) cyanogen, 219 fluoboric acid, 207 hydriodic acid, 198 hydrochloric acid, 184 hydrogen, 122 hydrosulphuric acid, 214 — — properties of, 215 action on metals, 215 * salts of, 215 hydro-zincic, 327 (n) hydrotelluric acid, 293 (n) nitric oxide, 143 nitrogen, 134 nitrous acid, 146 nitrous oxide, 141 ■ purity ascertained, 142 oil, 481 olefiant, 213 oxygen, 118 oxymuriatic acid. See Chlorine gas phosgene, 195 (n) phosphuretted hydrogen, 217 protoxide of nitrogen, 141 seleniuretted hydrogen 217 sulphuretted , 214 sulphurous acid, 163 Gas lights, 481 Gay Lussac's theory, 31 apparatus for hydrogen, 123 method of analysis of gases, 145 (n Gasometer, 108 mercurial, 110 (n) Gelatine, properties of, 493 test of, 493 Glaser's polychrest salt, 334 Glair in, 475 (n) Glass, 178 action of hydrofluoric acid on, 206 annealing, 178 of antimony, 287 of borax, 347 pastes, 178 [n] etching on, 206 method of colouring, 17S [n] varieties of, 178 vessels, acted upon, 178 Glauber's salt. See Sulphate of soda. Glauberite, 330 Glucina, method of obtaining, 249 distinguished, 249 properties, 249 Glucinium, 248 sesquioxide of, 249 Glue, 493 Gluten, 471 — 474 Glutin, 475 Glycerin, 471 Gold, malleability of, 312 alloys of, 315 chlorides of, 314 fulminating, 313 INS HEA 542 Gold, oxides of, 313 pure, 312 — 314 percyanuret of, 412 precipitants of, 314 revival of, 314 solution in ether, 314 — 451 standard of U. S., 315 (n) separated, 312 — 329 [n] cleaned, 296 (n) assay of, 316 powder, 316 effect of galvanism on, 95 mosaic, 268 — 297 (n) Dutch, 297 fineness of, 316 colour destroyed, 315 ductility destroyed, 315 analysis of alloys of, 315 Gooseberries, acid from, 393 Goniometers , 8 Graduated vessels, 107 Graham's experiments, 140 on alcohol, 442 Graphite, 261 Gravel, urinary, 505 Green fire, 336 (n) Gregory’s process for hydro-chlorate of morphia, 439 (n) Gravitation, 2 Gravity, influence of, 23 specific, effect of chemical union on, 16 of gases, 32, 114, 116 of solids, 115 of powders, 115 of liquids, 116 water, standard of, 114 Gum resins, 466 — 482 fetid, 466 cathartic, 467 sedative, 467 Gums, 473 Gunpowder, composition of, 334 Gypsum, 325 HJEMA TITE, red, 257 Hcemaiin, 45S (n) Half equivalents, 26 Hare's apparatus, 64 blow pipe, 127 calorimotor, 89 reservoir for hydrogen, 123 Hair, 494 Haloid salts, 105, 358 Hassenfratz, his theory of animal heat, 499 Haiiy's theory, 7 Heat. See Caloric, 37 animal, 498 Black’s theory of, 499 of flame, 77 guarded against, 69 nature of, 71 latent, 50 and cold, sensations of, 37 operation of on animal bodies, 491 polarized, 70 Heat, influences affinity, 22 radiant, 65 sources of, 71 specific, 48 transfer of prevented, 64 theories of, 70 Henry’s apparatus, 58 (n) HeSvene, 476 Hellot’s ink, 270 (n) Hemlock, 484 Heterogeneous attraction, 13 Hircine, 502 Hog's lard, 502 Homberg’s phosphorus, 242 pyrophorus, 330 Honey, 471 stone, 375 Hoofs, 494 Hops, 486 Hordein, 473 Horn silver, 310 Horns, 494 Humus, 490 Hydrate, what, 133 of hypophosphorous ucid, 172 Hydriodates, 199 Hydriodic acid, 198 properties, 199 decomposed, 199 test of, 200 use, 200 Hydrobromic acid, 203 process for, 204 properties, 204 Hydro carburet, 211 Hydrochlorate of ammonia, 353 native, 354 Hydrochloric acid, 184 process for, 185, 187 (n) absorbed by water, 186 apparatus for, 187 (n) composition, 189 liquid, 187 recognized, 189 theory of, 185 Hydrocyanate of ammonia, 409 Hydrocyanic acid, 405 with metallic oxides, 409 Hydroferrocyanic acid, 412 and metallic oxides, 413 Hydrofluoric acid, 205 action on glass, 206 on metals, 207 Hydrofluate of ammonia, 354 Hydrofluates, 207 Hydrofluorides, 361 Hydrometers, 443 INDIAN CORN, sugar of, 470 Indigo, 457 Indigogen, 457 Intermediate bodies, 441 Ink, indelible, 338, new, 509 printers’, 459 (n) Insoluble cyanurets, 409 543 LIM KIN Insoluble, chloral, 448 Inulin, 473 Iodic ether , 452 Iodine, nature of, 198 detection of, 198 — 508 in sea water, 508 oxide of, 200 and chlorine 201 and nitrogen, 201 and oxygen, 200 and phosphorus, 198 sources of, 196 test of, 198 lodurets, 198 Iodous acid, 200 Iridium. 320 Iron , 256 alum, 331 action of water on, 256 of nitric acid, 257 (n) of sulphuric acid, 257 acetate of, 378 bisulphuret of, 260 black oxide, 258 carbonate of protoxide, 352 carburets of, 261 cast, 261 combustion of in oxygen, 120 with carbon, 227, 261 chlorides, 258 chromate of, 277 acid from, 27 and cyanogen constitution of the com- pounds of, 412 cyanuret of, 410 fluorides of, 259 (n) gray, 261 oxychlorides of, 359 phosphurets of, 260 (n) properties, 256 protiodide of, 259 protochloride of, 258 protoxide of, 257 sesquiferrocyanuret of, 415 process for, 415 sesquioxide of, 257 sesquichloride of, 258 sesqu iodide of, 259 (n) sulphate of protoxide, 326 test of, 389 varieties of, 261 Isinglass, 493 Isomeric bodies, 36 Isomorphism, 12 advantages of, 12 JELLY obtained by pectic acid, 393 Jackson, his lamp. See Frontispiece. KELP, 348 Kermes, 288 King's yellow, 277 Kinic acid, 388 LABARRAQUE’S liquid , 349 (n) Lac, 466 varieties of, their composition, 466 (n) solvent for, 454 (n) Laccin, 466 Lactates, 380 Lactic acid, 380 — 503 Lactucarium, 467 (n) Lakes, 456 Lamp, safety, 78, 213 aphlogistic, 78 Jackson’s, 120 (n) black, 481 Lapis lazuli, colouring matter of, 236 (n) Latanium, 320 Latent heat, 50 made sensible, 53 Lavoisier' s theory, 121 Laws of combination, 24 advantage of, 27 Lead, acetate of, 379 action of water on, 298 alloys of, 300 carbonate of protoxide, 352 poisonous, 299 (n) chloride of, 300 detected, 299 oxides of, 298 oxychlorides of, 359 peroxide of, 300 properties of, 298 purified, 298 salts of, poisonous, 299 (n) solvent of, 298 subacetate of, 379 sugar of, 379 Leather, 389 Legumin, 475 (n) Leslie's method of freezing, 60 experiments on radiation, 66 photometer, 75 Leucine, 492 Leyden jar, 83 Libavius, fuming liquid of, 267 Lichenin, 473 Liebig's compound radicals, 367 Light, 71 analysis of, 74 chemical effects of, 75 magnetical, 75 double refraction of, 73 Drummond’s, 76 of flame, 77 influence on vegetation, 76 from percussion, &c., 77 polarization of, 73 reflection of, 72 refraction of, 72 Lignin, 473 Lime, acetate of, 878 bone phosphate of, 344 (n) carbonate of, 350 chloride of, 243 fluate of, 205 hydrate of, 241 MER MAN 544 Lime , hydrochlorate, 242 light of, 76 milk of, 241 nitrate, 336 oil of, 242 oxalate of, 372 phosphates of, 344 phosphuret, 244 properties of, 241 solubility of, 241 sulphate of, 325 test of, 242 water, 241 Liquefaction, 51 of gases, 117 • chlorine, 184 carbonic acid, 157 apparatus for, Plate I. Liquids, expansion of by heat, 39 evolve heat, 53 manner in which they conduct heat, 64 specific gravity of, 116 Liquorice, sugar, 471 Lithia, discovery of, 237 distinguished, 237 obtained, 237 Lithic acid, 504 Lithium, 237 chloride of, 237 (n) fluoride of, 237 (n) Litmus, 455 Lixivium, what, 197 [n] Logometric scale, 513 Loco foco matches, 171 [n] Lunar caustic , 309, 337 Lupulin, 486 MAGISTERY of bismuth , 291 Magnesium, 245 chlorides of, 246 hydrate, 246 [n] protoxide of, 245 Magnesia, 246 calcined, 246 (n) carbonate of, 246 (n) sulphate of, 325 . adulteration of, 326 (n) Magnesite , 351 Magnet, * Electro, 102 spark from, 102 decomposition by, 102 Magnetism, Electro, 102 Magnetizing rays, 75 Maize, formic acid from, 374 Malachite, 352 Malic acid, 382 Malt, 487 Manganate of potassa, 254 Manganese, 251 acids of with potassa, give different colours with water, 254 in' blood, 496 alum, 331 perchloride, 255 Manganese, perfluoride, 255 peroxide, 252 uses of, 253 protochloride of, 255 (n) protosulphuret of, 256 (n) salts of, 252 red oxide of, 253 composition, 253 Manganic acid, 254 Manipulation with tubes, 113 Manna, 471 Mannite, 471 Maple sugar, 469 Marble, 153 MarceVs apparatus for boiling, 56 (n) for freezing, 57 (n) Margaric acid, 391 Margarine, 390 — 502 Marsh's method of detecting arsenic, 274 Massicot, 298 Mastic, 465 solvent for, 454 (n) Matches for instantaneous light, 171 (n) Matter, quantity of, 22 Measure of affinity, 23 Meat, preservation of, process for, 491 (n) Mechanical division , advantage of, 16 Meconates, 387 Meconia, 440 Melam, 397 converted into cyanuric acid, 397 Melamin, 396 combinations of, 397 Mellite, 375 Mellitic acid, 375 Mellon, 220 (n ) 396 Melloni's experiments, 70, 74 Mercaptan, 452 Mercurial trough , Newman’s, 110 (n) — 163 (n) Mercury, acetate of, 379 adulteration of, 301 action of chlorine on, 303 oxygen, 225 alloys of, 307 bichloride of, 304 process for, 304 (n) bicyanuret of, 411 chlorides of, 303 congelation of, 301 apparatus for, 53 (n) by carbonic acid, 158 (n) detected, 305 expansion of, 40 ferrocyanuret of, 415 fulminating, 402 iodides of, 305 oxides of, 302 pernitrate of peroxide of, 302 action of water on, 303 protacetate of, 379 protochloride of, 303 prussiate of purified, 301 (n) MOL 545 NIT Mercury, specific gravity increased by con- gelation, 301 sulphates of oxides of, 329 sulphurets of, 306 with potassium, 307 Mesite, 455 Mesoxalic acid, 427 Metals, acids from, 225 action of acids on, 228 bromine, 226 carbon, 227 chlorine, 225 fluorine, 226 hydrogen, 227 iodine, 226 phosphorus, 227 sulphur, 226 sulphuretted hydrogen, 215 alloys of, 224, 227 amalgams, 224, 228 classification of, 228 conduct heat, 222 decomposing water at a red heat, 229, 251 double cynnurets of, 412 enumeration of, 222 fusibility of, 223 fused and ignited by galvanism, 95 malleable, 222 (table m) not essential in Voltaic circles, 8S oxidation of, 225 qualities altered, 224, 228 salifiable bases from, 225 seleniurets of, 227 specific gravities of, 222 speculum metal, 297 (n) sulphurets of, 226 tenacity of, 223 Metallic alloys , 227 chlorides, 226 phosphurets, 227 seleniurets, 227 sulphurets, 226 Metaphosphoric acid, 174 peculiarity of, 175 Metaphosphates, 342 Meteoric stones contain nickel, 256 Microcosmic salt, 343 Milk, 501 Minder erus' s spirit, 378 Mineral chameleon , 254 green, 352 yellow, 359 Mineral waters, separation of salts from, 21 (n) Minium , 299 Mitchell's process for phosphuret of calcium, 218 [n] experiments on passage of air, 497 Mitscherlich' s discovery, 12 Mixture, frigor-ific, 51 Molasses, 469 Molybdenum, hydrate of, 282 ore of, 282 obtained, 232 Molybdenum, oxides of, 282 properties, 282 sulphurets, 283 Molybdic acid, 282 Molybdo- sulphurets, 357 Mordant, what, 456 Morphia, 438 acetate of, 439 detection of, 438 hydro-chlorate of, 439 process for, 439 [n] Morrichini, his experiments, 75 Mosaic gold, 268, 297 [n] Mucin, 475 Mucus, 503 Multiples, law of combination in simple, 25 Murexan , 433 Murexid, 431 Muriates. See Hydrochlorates, 353 Muriatic acid. See Hydrochloric, 184 impurities of, 188 prepared, 187 Muscles, 494 Muscovado sugar, 469 Must, 488 Mustard, 486 Mykomelinic acid, 427 Myricin, 461 Myrtle wax, 461 NAILS, 494 Narceia, 440 Narcotina, 437 Naphtha, 477 Naphthalic acid, 480 (n) Naphthaline, 479 Nascent state, what, 21 Nature of chlorine, 195 Neutral compounds, 25 vegetable principles, 467 Neutralization, 14 Newman's trough, 110 (n) Nickel, 270 chloride of, 271 (n) detected, 270 (n) properties, 270 protoxide, 271 Nicotin, 441 Nightshade, 484 Nitrates, characters of, 332 of baryta, 335 copper, 336 lime, 336 oxide of ammonium, 335 oxides of mercury, 336 potassa, 333 protoxide of copper, 336 Nitrate of silver, 337 of soda, 335 of strontift, 336 Nitre, 333 decomposed, 333 Nitric acid, 147 action on animal matter, 149 69 OIL 546 OXI Nitric acid, action on fixed oils, 459 iron, 257 (n) lead, 300 metasl, 150 phosphorus, 150, 174 sugar, 470 volatile oils, 462 boiling point of. 149 decomposed, 150 detected, 509 effect of light on, 149 oxide of, 1-13 properties of, 149 proportion of real acid in 100 parts, 523. prepared, 147, 148 (n) purified, 148 Nitric ether, 453 Nitrites, 339 Nitrogen, 134 in animal substances, 490 analysis of, 143 detected, 509 process for, 134 and oxygen, 135 — carbon, 219 binoxide of, 143 properties, 144 use of, 145 chloride of, 193 phosphuret of, 220 (n) protoxide of, 141 quantity absorbed by water, 133 (n) quadrochloride of, 193 sulphuret of, 221 (n) supposed base, 135 teriodide of, 201 Nitronaphthalese, 480 Nitrous ether , 453 Nitrous air, dephlogisticated, 141 acid, 146 properties, 147 gas, 143 Nitro -hydro chloric acid, 189 sulphuric acid, 329, 337 Nitrous oxide, 141 analysis of, 143 absorbed by water, 133 (n) Nitrous turpeth, 337 Nobilli's experiments, 70 Nomenclature, 102 Noyeau. 485 Nux vomica, 437 OERSTED'S discoveries, 102 (Enanthic ether, 454 Octohedral system, 10 Oil gas, 481 apparatus, 481 (n) cocoa nut, 460 croton, 460 olive, 460 palm, 460 of tartar, 348 Oil, of turpentine, 462 Oil, of wine, 452 almonds, 485 Oils, action of acids on fixed, 459 action of nitric acid on, 459 action of alkalies on,- 460 combustion of, 469 drying, 459 soap from, 390 spermaceti, 503 train, 503 volatile, 461 watchmaker’s 460 (n) sweet principle of, 471 Oily acids, 390 Oleaginous substances, 458 — ■ 502 Olefiant gas, 213 action of chlorine on, 214 properties of, 214 quantity absorbed by water, 133 (n) Oleic acid, 391 Olein, 391, 502 Oleine, 460 Olive oil, 460 Opium, 467 alkali of, 438 detected, 438 process for, 438 acid in, 386 substances in, 440 (n) Organic chemistry, 362 principles, 362 classes of, 363 matter in water, 132 (n) Organic and Inorganic compounds , distinction between, 362 Orpiment, 277 Osmazome, 493 Osmic acid, 319 Osmium, 319 oxide of, 319 Oxalate of ammonia, 371 lime, 372 calculi, 369, 505 potassa, 371 Oxalic acid, 369 composition of, 371 decomposed, 371 distinguished, 370 from tannic acid, 389 properties of, 3/0 theory of its production, 370 poisonous, 370 in vegetables, 369 Oxalovinic acid, 454 Oxalurate of ammonia, 428 Oxaluric acid, 428 Oxamide, 467 analysis of, 468 obtained, 467 properties of, 467 action of sulphuric acid on, 467 Oxide, carbonic, 159 quantity absorbed by water, 133 (n) . by charcoal, 530 cystic, 433 PAR 547 PHO Oxide , nitric, 143 nitrous absorbed by water, 133 (n) by charcoal, 530 of phosphorus, 171 — process for, 172 (n) 508 of selenium, 179 uric, 433 xanthic, 433 Oxides, nomenclature of, 103 reduction of, 225 sesqui, 102 Oxy- chlorides, 359 of copper, 359 lead, 359 iron, 359 Oxygen, absorbed by the blood, 119 by combustible bodies, 121 by tannic acid, 389 action of on blood, 498 compounds of combustible bodies with, 122 of chlorine with, 189 derivation of, 103 diminished in combustion, 120 by respiration, 498 explosion with ether, 450 loss of compensated, 141 not the sole principle of acidity, 122 produces oxides and acids, 122 union with hydrogen forms water,129 nitrogen, 141 chlorine, 189 gas, 118 its effect on indigo, 457 properties, 119 procured, 118 combustion of carbon in, 120 of phosphorus, 120 quantity absorbed by water, 133 (n) — by charcoal, 530 required for combustion of woods, 484 supports life, 119 Oxyhydrogen, blow pipe, 128, 507 Oxyiodides , 360 Oxymuriatic acid. See Chlorine. Oxy muriates. See Chlorates. Oxy salts, 320 PALLADIO- CHLORIDES, 358 Palladium, 319 cyanuret of, 411 oxides of, 319 Palm oil , 460 Panary fermentation, 490 Pancreatic juice, 500 Paper, test, 455, 370 Parahanic add, 428 Paracyanogeu, 220 (n) Paraffin, 477 Paranaphthaline, 480 Parillia, 440 Parts of plants, 482 Particles of bodies, 2 integrant, 13 Pectic acid, 393 obtained, 393 Pectin, 393 Pearlash, 347 sources of, 348 . _ quantity of alkali in, ascertained, 158 Pearl-white, 291 powder, 291 (n) Pelletier and Caventou s process for Cm- chonia, 435 (n) Perchlorates, 341 Perchloric acid, 193 Perchloride of carbon, 194 of manganese, 255 of phosphorus, 195 (n) Percussion, light from, 77 Percyanuret of gold, 412 Perfluoride of manganese, 255 Perfumed essences, 462 Periodic acid, 201 (n) Periodide of carbon, 202 (n) Permanganic acid, 254 Peroxide of hydrogen, 134 Persulphuret, of arsenic, 277 hydrogen, 216 Petroleum , 477 Peru, balsam of, 465 Pewter, 268, 288, 300 Phlogiston, 121, 122 Phosphates, characters of, 342 detected, 342 Pitch, 464 Plating of copper, 312 Portfire, 335 (n) Phenicin, 457 Phosphorescence, 78 Phosphori, solar, 76 Phosphoric acid, 173 distinguished, 174 glacial, 175 prepared, 174 matches, 171 (n) test of, 174 union with bases, 174 Phosphorous acid, 173 Phosphorus, 169 action on metals, 227 of nitric acid on, 174 Baldwin’s, 77 (n) Bolognian, 323 bromides of, 205 (n) Canton’s, 77 (n) characters of, 169 combustion in oxygen, 120. 170 ■ slow, 170 . under water, 340 effect of light on, 171 equivalent of, 171 inflames in rarefied air, 1 /0 oxide of, 171 Verrier’s process, 172 (n) Botger’s 508 solution in ether, 171 union with chlorine, 183 hydrogen, 217 POT 548 PRO Phosphorus, union with iodine, 198 oxygen, 171 use in eudiometry, 139 Phosphovinic acid. 395 (n) — '454 Phosphuret of calcium, 218 (n) of nitrogen, 2-0 (n) Phosphurets , metallic, 227 Phosphuretted hydrogen , 217 prepared, 217 chlorides with, 360 combustion in oxygen, 219 effect of light on, 219 salts of, 355 Photogenic drawing, 311 (n) 507 Picamar, 479 Picromel, 501 Pinchbeck , 297 Pictet's experiments , 68 Pistol , electrical, 125 Pittacal, 479 Plants, parts of, 482 respiration of, 511 juices of, 482 Platina-mohr, 377 (n) P latino -chlorides, 358 biniodide of potassium, 360 of hydrogen, 360 Platinum, 316 action on hydrogen and oxygen gases, 316 on alcohol, 377 (n) on carbonic oxide, 160 chlorides of, 317 conducts caloric slowly, 316 ethereal solution of, 451 fulminating, 318 iodide of, 318 oxides of, 317 properties of, 316 spongy, 316 sulphurets of, 318 test's of, 318 Plesiomorphism, 13 Pneumato- chemical trough, 108 mercurial, 110, 163 (n) Polarization of heat, 70 of light, 73 Poles, voltaic, 98 Pollenin, 475 (n) Polychroite, 458 Poppy, 485 Potash, caustic, 232 Potassa, 232 acetate of, 378 action on organic compounds, 368 bicarbonate of, 348 binoxalate of, 371 bisulphate of, 322 bitartrate of, 384 carbonate of, 347 chlorate of, 339 distinguished, 232 affords oxygen, 119 action on inflammables, 339 of sulphuric acid on, 340 Potassa , chromates of, 346 croconate of, 372 fusa, 232 etheroxalate of, 453 [n] iodate of, 341 manganate of, 254 nitrate of, 333 preparation of, 232 properties of, 232 proto-hydrate of, 232 pure, prepared, 232 [n] purified, 232 quadroxalate of, 372 bistearate of, 390 sulphate of, 322 bisulphate, 322 sulpho-indigotate of 395 tartrates of, 385 Potassium, 229 apparatus for, 528 boro-fluoride of, 361 bromide, of 233 [n] carbo-sulphuret of, 356 carburet of, 233 [n] chloride of. 233 compounds of, 231 cyanuret of, 409 ■ process for, 410 decomposes water, 231 ferrocyanuret of, 413 fluoride of, 233 [n] and hydrogen, 233 hydro-sulpiiuret of, 356 iodide of, 233 phosphurets of, 234 [n] platino-biniodide of, 360 processes for, 230 properties, 230 seleniurets of, 234 [n] sulphurets ol, 234, 234 [n] and iron, ferrocyanuret of, 416 tersulphuret of, 234 Potatoes, 483 Powder, fulminating, 334 gun, 334 with chlorate of potassa, 340 (n) Precipitate, red, 302 process for, 302 (n) Precipitates, apparatus for drying, 59 Precipitation, 18 Preservation of animal substances, 491 Pressure, influences the boiling point, 56 crystallization, 6 chemical action, 23 Prevost's theory, 71 Priestley's method of analysis, 139 Primitive forms, 8 Printers' ink , 459 (n) types, 288 Prismatic colours,! A systems, II Proof spirit, 443 Proportion, what, 25 Proportions in which bodies combine, 23 compounds of many, 24 REF 549 SAP Proportions, laws of, 24 limited, 24 in volumes, 331 Protector, Davy’s 87 Proto-chloride of manganese , 255 (n) Protoxide of nitrogen, 141, decomposed, 143 process for, 142 properties, 142 Prussian blue, 415 constitution of, 416 Prussiate of mercury, 219 potassa, 410 Puddling of iron, 261 Pulse glass, 56 Pulvis antimonialis, 286 Purification of alcohol, 441 Purple of Cassius, 266 Purpurate of ammonia, see Murexid, 431 Purpuric acid, 433 — 504 Pus, 503 Putrefaction, 490 effluvia from, its effects, 492 Pyr acids, theory of, 366 Pyrites, iron, 260 copper, 294 Pyroligneous acid, 37 6 Pyrometer, 38 Daniel’s,38 Pyrophorus, Homberg’s, 330 Pyrophosphoric acid, 174 Pyrophosphates, 345 Pyroxylic spirit, 454 uses of, 454 [n] Pyrrhine, 132 [n] QTJADROXALATE of potassa, 372 Quadro chloride of nitrogen, 193 analysis of. 194 Quantity of matter, its influence, 22 Quevenne, his observations on yeast, 511 Quinia , 435 adulteration of, 436 disulphate of, 436 hydro-ferrocyanate of, 436 [n] process for, 435 sulphate of, 436 RACEMOVINIC ACID, 454 Radiant heat, 65 Radiation in vacuo, 66 theories of, 70 Radicals, compound, 367 Radical vinegar, 376 Ratios, combining, 26 Rays , luminous, 74 calorific, 70 chemical, 75 Red fire, 336, [n] dyes, 456 Refiner's verditer, 352 [n] Reflection of heat, 67 cold, 68 Refraction, double, 73 of light, 72 of inflammables, 72 Regulus of antimony, 285 Rennet, 501 Resin, alpha, 464 beta, 464 Resins, 463 gum, 466 solvents ©f, 463 dissolved by ether, 451 solid, 465 Respiration, 494—497 consumption of oxygen by, 498 carbon produced by, 498 Rhodio- chlorides, 359 Rhodium, 319 Rhodizonic acid, 373 Rhombohedral system, 12 Rocou, 458 Rochelle salt, 385 Romd de Lisle's theory, 7 Roots, 483 Rosin, 462 — 464 I Rouge, 458 [n] Rum, 488 Rumford's experiments, 65 SACCHAROMETER, 487 Safety lamp, 213 principle of the, 213 Saffron, 458 Sago, 472 Sal ammoniac, 353 native, 354 Salicin, 436 Saliva, 500 Salop, 472 Salt, common, chloride of sodium, 236 Glauber’s, 322 of lemons, 371 of hartshorn, 491 Salts , ammoniacal, 353 atomic composition of, 104 characters of, 105 composition illustration by, 25 double, 104, 321 haloid, 105, 358 microcosm ic, 343 neutral, 104 orders of, 104 oxy, 320 of phosphuretted hydrogen, 355 saturated solution of obtained, 4 (n) solution of, produces cold, 52 super, 104 sulphur, 105,355 Santalin, 458 (n) Sap green, 486 SIL 550 SPE Saratoga waters, iodine in, 508 Saturation, 3, 14 Saturn, sail of, 379 -Sauer kraut, acid in, 380 Saxon blue, 457 Scale of equivalents , 513 Scheele’s green, 345 Sealing wax, 464 Sclerotium giganteum, 393 Sclerotin, 393 Sea salt , hydrochloric acid from, 185 theory of, 186 Secondary action, 98 Seebeck's experiments, 74 Seeds, 485 Seignette's salt, 385 Selenic acid. 180 Selenious acid , 180 Selenites, 180 Selenium. 178 bisulphuret of, 221 (n) equivalent of, 179 sources of, 178 oxide of, 179 tinges flame, 179 Seleniuret of phosphorus, 221 (n) Seleniurets, metallic, 227 Seleniuretted hydrogen, 217 Seltzer water, 349 (n) Senna, 484 Sensible heat. 53 Serous fluids, 503 Sesquiferrocyanuret of iron, 415 Serum, 497 solid matter in, 496 analysis of, 497 Signal lights, 335 (n) Silica, 177 in blood, 496 obtained, 177 properties, 177 U9es, 178 Silicic acid, 177 Silico-fluorides, 361 Silicon, 176 obtained, 176 oxide of, 177 properties, 176 terchloride of, 195 (n) Silver, alloys of, 311 assay of, 308 (n) chloride of, 310 cupellation ol, 308 (n) cyanates of, 401 detonating, 310 effect of galvanism on, 95 eliquation of, 309, (n) fulminating, 310 glance, 311 horn, 310 ores of, 307 oxide of, 309 properties of, 308 Silver, purification of, 307 solvent of, 309, 337 (n) standard, 312 sulphate of oxide of, 329 sulphuret of, 311 tarnish of, 308 tree, 310 triphosphate of oxide of, 344 Silvering for dials, 312 Simple bodies 37 Skin, 494 affects the air, 499 Smalt, 270 Smells removed by charcoal, 152 . chlorine, 184 Soap, 460 Soda alum, 331 Soda, bi-borate of, '347 a new one, 347 (n) bi-carbonate of, 349 carbonate of, 348 distinguished, 235 liquid. disinfecting, 349 (n) nitrate, 335 powders, 385 (n) preparation of, see Potassa properties of, 235 sesquicarbonate of, 349 sulphate of, 322 tartrate of, and potassa, 385 triphosphate of, 343 water, 349 (n) Sodium, 234 bromide of, 236 (n) chloride of, 236 fluoride of, 236 [n] iodide of, 236 [n] oxides of, 235 properties of, 234 proto-sulpluiret of, 236 protoxide of, 235 sesquioxide of, 235 Scemering’s experiments on alcohol, 442 Solar phosphori, 77 Solders, 300 Solids- expansion of. 38 Solubility, tried, 4 [n] Solution, defined, 3 objects of, 3 produces cold, 51 saturated, 4 [n] Soot, 4S1 Somerville’s experiments, 75 Sorbic acid, see Malic acid. Sorrel, salt of, see Oxalic acid • Specific gravity, 114 changed, 16 caloric, 48 of gases, calculated, 33 heat, 48 Speculum metal, 297 Spectrum, solar, 74 Speiss, 270 SUL 551 SUL Spelter , 263 Spermaceti , 502 oil, 503 Spiroil. 469 Spirit of wine , 488 Spiritus cetheris nitrici , 453 Spongy platinum, action of on gases, 139 carbonic oxide, 161 Squill, 483 Stannates, 267 Stark's experiments, 67, 70 Starch, obtained* 471 test, prepared, 200 [n] converted into sugar, 471 in seeds, 485 State of bodies, 50 Steam apparatus, 56, 59 latent beat of, 58 uses of. 59 Stearic acid , 390 Stearine, 502 Steel, 227, 262 alloyed, 263 coated with gold, &c. 451 [n] tempering of, 262 Stodartd's exp’ts on coating steel, 451 (n) Strasburg turpentine, 464 (n) Stream tin, 265 (n) Strontium, 239 chloride of, 240 iodide of, 240 (n)J obtained, 240 peroxide of, 240 (n) protoxide, 239 Strontia, carbonate of, 350 salts of, 240 sulphate, 324 Strontianite,, 350 Strychnine , 437 Street spirit of nitre , 453 Sublimate , corrosive, 304 Sublimation of benzoic acid, 381 — 382 Sub -acetate of lead, 379 Sub carbonate af ammonia, 350 Substantive, colours, 456 Substitutions , theory of, 366 Succinamide, 468 Succinates 376 Succinic acid, 375 in amber, 466 Suet, 502 Sugar , 469 from beets, 469 acid from, 374 action of acids on, 470 of grapes, 470 of starch, 471 liquid, 470 of lead, 379 Sulphamide, 468 Sulphates, characters of, 321 classification of, 322 (n) decomposition of, 227 double, 330 of potassa and alumina, 330 Sulphate, of alumina, 326 of ammonia, 323 of baryta, 323 of cobalt, 328 copper, 328 iron, 326 lime, 325 lithia, 323 magnesia, 325 mercury, 329 nickel, 328 oxide of ammonium, 323 potassa, 322 quihia, 436 silver, 329 soda 322, strontia, 324 zinc, 327 Sulphite of baryta, 332 lime, 332 Sulphites. 165 332 Sulpho-cetic acid 448 Sulpho -cyanic acid, 420 Sulpho hydric ether, 452 (n) Sulpho -naphthalic acid, 480 Sulphur, 161 acids, 355 alcohol of, 220 combination of carbon with, 22& ■ metals with. 226 combustion of, 162 contains hydrogen, 162 crystallized, 161 equivalent of, 162 flowers of, 162 vapour of, 162 salts, 355 Sulphur et of Ethyl, 452 Sulphurets, action of heat on, 226 of antimony, 287 arsenic, 276 iron, 259 nitrogen, 221 (n) phosphorus, 221 platinum, 318 silver, 311 tin, 267 vanadium, 281 Sulphuretted hydrogen. See Hydrosulphx$~ ric acid gas. Sulphuric acid, 165 action on iron, 257 on oxamide, 467 analysis of, 167 boiling point, 167 ether, 448 manufacture of, 165 — illustrated, 166 theory, 166 of Nordhausen, 165 purified, 166 strength of ascertained, 167 test of, 168 uses, 168 THE 552 URI Sulphurous acid. 163 analysis of, 164 bleuclies, 164 convertible into sulphuric acid, 164 liquefied, 165 Surface , influence of on radiation, 66, 506 Sweet oil of wine, 451 Sylvius, salt of, 378 Symbols, chemical, 33 Berzelius’s, 35 table of, 34 Sympathetic ink, 270 (n) Synthesis, 36 Systems of crystallization , 10 TABLES of affinity, 18 equivalent weights and specific gravity of gases, 32 freezing mixtures, 51 symbols, 34 Tannic acid, 388 artificial, 390 distinguished, 389 varieties of, 389 Tannin, 388 Tanno- gelatine, 389 Tantalum, same as Columbium, 284 Tapioca, 472 Tar, 464 Tartar, cream of, 384 emetic, 385 Tartaric acid, 383 properties, 384 a test, 384 Tartrate, of antimony and potassa, 385 iron and potassa. 385 potassa, 384 potassa and copper. 335 and soda, 385 7'artrovinic acid, 454 Tellurium, 293 action of nitric acid on, 293 Tellurous acid, 293 Temperature, 43 ascertained, 44 changed by chemical union, 16 by solution, 52 influences athnity, 21 of the globe equalized, 61 of steam, 58 Tempering. 262 Tendons , 494 Terchloride of gold, 314 Teriodide of nitrogen, 201 Tests, liquid, 14 Test papers, made, 455 (n) Tetarto-carbo-hydrogen, 452 (n) Texture, effect, of, 63 Thebaia, 440 Theory of volumes, 31 Thermometer, 44 differential, 46 reduction to mean height of the, 42[n] Thermometer, self registering, 47 Seix’s, 47, new viii Thermometers, correspondence between, 45 Thialic ether, 452 Thionuric acid, 429 Third body, efiect of a, 17 Thorium, 250 Thorina, 250 properties of, 250 Tin, 265 acetate of, 378 alloys of, 268 chlorides of, 267 crystallized, 265 [n] filings, 265 [n] foil., 265 [n] oxides of, 266 permuriate of, 267 properties, 265 salts of, 268 sulphurets of, 267 Tincal, 317 Titanium, 291 metallic, 292 oxides of, 292 Titanic acid, 292 Titano -fluorides, 361 Tolu, balsam of, 465 (n) Torpedoes, 310 Torrey's apparatus for nitric ether, 453 Train oil, 503 ! Triphosphates , 343 of lime, 344 magnesia, 344 oxide of silver, 344 soda, 343 Tube apparatus, 117 'Tungsten, 283 chlorides of, 284 oxides of, 283 Tungstates, 284 Tungstic acid, 283 'Tungsto- sulphurets, 358 Turmeric, 456 Turpentine , oil of, 462 Slrasburg, 464 [n] Venice, 464 Turpeth mineral, 329 Tutenag , 297 UNIT, chemical, 29 Union of sub stances, in certain proportions, 23 Uramil, 429 Uramilic acid, 430 Uranium, 289 oxides of, 289 Urea, 399—504 compounds of, 400 t/re’s drying apparatus, 59 (n) Urets, what, 103 Uric oxide, 433 acid, 504 Urine, 504 WOL VOL 553 Urine , phosphate of ammonia and magnesia in, 344 urea from, 400 component parts of, 504 VAN ABIC ACID , 281 Vanadium, 280 oxides of, 281 sulpliurets of, 281 Vaporization, 54 Vapours, dilatation of, 51 table of elastic force of, 520 aqueous, 517,518 Varnishes, 464 Varvacite, 253 (n) Vegetable acids, 369 alkali, 232 bodies, 362 principles, 362 form definite compounds, 363 classes of, 363 soil, 490 Vegetables, alkalies in, 434 distinguished, 434 decompose water, 134 growth &c., affected by light, 76 decomposition of, 490 of carbonic acid by, 157 products of destructive distillation of, 477 principles in, 362 neutral, 467 Venice turpentine, 464 Ventilation, 41 Ver atria, 437 Verdigris, 379 composition of, 379 (n) Verditer, 352 Verjuice, 470 Vermilion, 306 Vernier’s process, for oxide of phosphorus, 172 (n) Vinegar, 376 — 489 distilled, 376 Vinous fermentation, 487 Viscin, 475 (n) Vision, 71 Vitriol, blue, See Copper, sulphate of, 328 green. See Iron, sulphate of, 326 white, See Zinc, sulphate of, 327 oil of, table of, 521 Volatile oils, 461 obtained, 461 action of acids upon, 462 quantity afforded by various seeds, &c, 462 (n) Volta’s eudiometer, 138 pile, 90 crown of cups, 90 theory, 85, 92 evidence against, 93 Voltaic electricity, 85, 88 circles, 85, 88 — without metals, 88 chemical effects of, 96 Davy’s experiments, 96 effect on metals, 95 70 Voltaic electricity, Faraday’s experiments, 93 magnetic effects of, 102 new terms, 98 WASH, 487 (n) Water, action of on lead, 298 analysis of, 131 by galvanism, 96 by vegetables, 132 apparatus for showing 1 the composi- tion of, 131 — « decomposition of, 96, 131 basic, 5 composition of, 129 illustrated, 130 compressible, 133 constitutional, 5 * removed, 5 contains air, 133 of crystallization, 5 decomposed by galvanism, 96, 131 by potassium, 231 distilled, 132 expands by cold, 43 frozen by ether, 450 by rapid evaporation, 60 gilding, 316 hard, 325 of ammonia, 210 process for, 211 (n) maximum density of, 43 not essential in voltaic circles, 87 properties of, 132 quantity of gas absorbed by, 133 (n) quantity of denoted, 5 Seltzer, 349 (n ) a slow conductor, 65 soda, 349 (n) standard weight and^measure of,132(n) Waters, distilled, 462 Wax, 460 bees, 460 cow tree, 461 myrtle, 461 sealing, 464 Weight, 2 atomic, 30 of gases, 32 Weights and measures, 525 Weiss his systems of crystals, 10 Wells’ experiments, 62 Welther’s tube, 187 (n) Wenzel’s law, 27 Wheat four, 471 JVhey, 501 White oxide of bismuth, 291 flux, 333 (n) lead, 299 pearl, 291 vitriol, 327 Wilson’s phosphorus, 77 (n) Wine, 488 heavy oil of, 454 light oil of, 452 sweet oil of, 451 odour of, to what owing, 488 Wire gauze, effect of, 78 YTT 554 ZIR Wollaston's cryophorus, 61 (n) scale, 29, 513 theory of crystals, 8 theory of galvanism, 92 thermometer, 56 Woods , quantity of oxygen required for combustion, 484 Wood, affords oxalic acid, 370 (n) pyroxylic spirit, 454 Woody fibres, 483 Wool , 494 XANTHIC OXIDE, 433 Xyloidin , 473 YELLOW DYES, 457 Yellow, King’s, 277 acid, 492 Yttria, 249 Yttrium, 219 properties of, 249 salts of, 249 ZAFFRE, 270 Zanthin, 458 (n) Zeine, 475 (n) Zinc, acetate of, 378 amalgamated, 87 [nj blende, 264 chloride of, 263 circle, 86 combustion of in oxygen gas, 120 flowers of, 263 for hydrogen gas, 263 [n] properties, 263 protoxide of, 263 sulphate of protoxide, 327 uses of, 264 Zirconia, 251 properties of, 251 Zirconium, 250 properties, 251 sesquioxide of, 251 INDEX TO THE FIGURES OF APPARATUS, &c. Fig. JACKSON’S oxyalcohol lamp, 1, 2 Front. Air Pump, 5, 6 do. De Luc’s columns, 7 do. Dish for freezing water, 8 do. Clarke’s electro-mag. machine, 9, 10 do. New thermometer, 11 do. Adams’ apparatus for solidifying carbonic acid gas, 1,2 PI. I. Do. for washing precipitates, 1, 2 P1.1I. Galin’s cylinder holder, 3,4, 5 do. Condensing apparatus, 6 do. Cooper’s mercurial receiver, 7 do. Seffstroem’s support, 8 do. Hare’s app’ts for hyd. and chlorine, 9 do. Haiiy’s primitive forms,? 1 to 6 Page 8 Daniell’s method of developing crystalline structure, 7 8 Simple and compound forms, 8 to 13 9 Weiss’s system of crystalliza- tion, 14 to 20 11 Apparatus for hydrochlorate of ammonia, 21 15 Pyrometer, 22 38 Apparatus for illustrating the expansion of liquids, 23 39 Do. do. do- 24 to 25 40 Do. do. of air, 26 41 Do. change of specific gravity in liquids by heat, 27 41 Do. ascent of heated air, 28 41 Thermometers, 29 to 34 46 Apparatus for illustrating ca- pacity of bodies for heat, 35 48 Do. evolution of heat by con- densation of air, 36 50 Do. for freezing mercury, 37 53 Pulse glass, or manometer, 38 56 Apparatus for illustrating the effect of diminished pressure on the boiling point, 39 56 Marcet’s apparatus for increas- ed pressure, &c. 40 56 Fig. Page Marcet’s ap’ts for freezing mercury, 41 57 Henry’s do, for boiling, &c. 42 58 Wollaston’s steam tube, 43 59 Leslie’s method offreezing wa- ter in vacuo, 44 60 Cryophorus, 45 61 Marcet’s modification 46 61 Hare’s apparatus for exhibit- ing the conduction of water, 47 64 Rumford’s do. do. do. 48 65 Davy’s do. do, the ra- diation of heat in vacuo, 49 66 Bache’s do. absorption, &c. of beat, 50 66 Pictet’s do. illustrating the radiation ofheat, 51 68 Diagram illustrating the re- fraction of light, 52 72 Ignition of platinum wire, 53 78 A phlogistic lamp, 54 78 Electrometer, 55 80 Series of electrical conductors, 56 81 Electrophorus, 57 84 Voltaic circles, 58, 59 86 Simple circle, 60 88 Circular arrangemeut, 61, 62 89 Hare’s calorimotor, 63 89 Method of forming copper and zinc plates, 64, 65 89 Crown of cups, 66 90 Voltaic pile, 67 90 ■ trough, 6C, 69, 70 90 Wollaston’s Plates, 71 91 Hare’s deflagrator, 72 to 74 91 Figure’s illustrating Faraday’s experiments, 75 to 78 93 Arrangements for decomposing water by galvanism, 79 to 81 96 Davy’s cups, 82 97 Arrangement for transfer of acid and alkali, 83 97 Faraday’s voltameter 84 100 Gas bottles, 85 to 87 106 556 »> < 1 Fig. Page Flexible tube. 88 106 Iron gas bottles, 89, 90 107 Apparatus for manipulating with gases, 91 to 9o 107 Pneumatic troughs. 96, 97 108 Graduated tube, 98 108 Gas funnel. 99 108 Gasometer, 100 108 Gas holder, 101 109 of Pepys, 102 109 of Hope, 103—4 no Newmann’s mercurial trough, , 105 no Detonating tube, 106 in Furnaces, 107—110 in Apparatus for submitting _ to electricity, 111 Pepy’s transferring tube, 112 Transferring of gases from tubes 113 Hydrostatic balance, 114 Leslie’s apparatus for taking specific gravity of powders, 115 Jars for combust’n in ox. gas, 116 — 1 IS Gay Lussac’s hyd. gas ap’ts, 119 Hare’s hyd. gas reservoir, self- regulating, 120 Bladder and pipe for hyd. gas, 121 Arrangement for extinguishing dame in hyd. gas, 122 Dobereiner’s lamp, 123 Electrical pistol, 121 Small calorimotor for explod- ing gases, 125 Tube for exploding gases, 126 Arrangement for do. by electricity, 127 Hare’s compound blow pipe, 123 Concentric jet for do. 129 Brooke’s blow pipe, 130 Apparatus for the formation of water, 131 to 133 Do. for decomposition of do. by iron, 134 Do. do. do. do. by galvanism, 135 Distillation, 136 App’ts for obtaining nitrogen, 137, 138 Ure’s eudiometer, 130 Apparatus for decomposition of protoxide of nitrogen, 140 Do. for distillation of nitric acid, 141, 142 Do. for action of nitric acid and phosphorus, 143 Do. for carbonic acid gas, 144, 145 Nooth’s apparatus, 146 Apparatus for exhibiting the escape of carbonic acid, 147 Do. for ascertaining loss of do. 148 Alkalimeter, 149 Apparatus for sulphurous acid, 150 Reid’s mercurial trough, 151 112 113 114 115 116 120 123 123 124 124 125 125 125 126 126 127 127 12S 130 131 131 132 131 13S 143 14S 150 154 151 155 158 159 163 163 Apparatus for illustrating the formation of sulphuric acid. Do. for phosphorus, Do. for combustion of phos- phorus in oxygen gas, 154, Do. for oxidation of phosphorus, Do. for chlorine gas, Do. for combustion in do. 158, Davy’s do. do. of charcoal in do.* Woulfe’s apparatus. Apparatus for hvpochlorous acid gas, (Euchlorine) 162, Glass syringe for taking up chlo- ride of nitrogen, Apparatus for iodine, Do. for passing gases into liquids. Do. for hydrofluoric acid. Do. fur ammoniacal gas, Do. for decomposing do. Do. for exhibiting the action of chlorine and ammonia, Do. for obtaining aqua ammonia. Do. for do. do. do. Method of illustrating the effect of wire gauze, Davy's safety-lamp, 174, Apparatus for phosphuretted hyd. Do. for bisulphuret of carbon, Ure’s instrument for testing chloride of lime. Marsh’s apparatus for detecting arsenic, 179, Berzelius’s tube for reduction Matras for red precipitate, Cupel mould, Muffle, Cupelling furnace, Apparatus for illustrating the formation of sal ammoniac, Do. for hydrosulphate of ammonia, Sublimation of benzoic acid, Apparatus for hydrocyanic acid. Do. for condensation of alcohol and water, Hydrometer, Apparatus for sulphuric ether, 192, Do. for freezing with ether, Torrey’s apparatus for nitric ether, Italian recipient for distillation of oils, Apparatus for oil gas, Saccharometer, Apparatus for fermentation. Apparatus for potassium, Alcohol lamps, &c. , * This also answers for decomposing by* drosulphuric acid gas by galvanism. Fig. Page 152 166 153 169 ,155 170 156 174 157 181 159 183 160 183 161 187 163 190 164 194 165 197 166 200 167 206 168 208 169 210 170 210 171 210 172 211 173 213 175 213 176 218 177 221 178 243 180 274 181 274 182 302 1S3 308 184 308 185 309 186 354 187 355 188 382 189 405 190 442 191 443 ,193 448 194 450 ,195 453 196 461 197 481 198 487 199 488 528 529