CORNELL UNIVERSITY LIBRARY GIFT OF Theron Cole least CORNELL UNIVERSITY LIBRARY wu A MANUAL or CHEMISTRY, ON THE BASIS OF TURNERS ELEMENTS OF CHEMISTRY; CONTAINING, IN A CONDENSED FORM, ALL THE MOST IMPORTANT FACTS AND PRINCIPLES OF THE SCIENCE. DESIGNED AS A TEXT-BOOK FOR COLLEGES AND OTHER SEMINARIES OF LEARNING. Sixth Bevised Grition. REWRITTEN AND RESTEREOTYPED, WITH MANY NEW ILLUSTRATIONS, BY JOHN JOHNSTON, LL. D., . PROFESSOR OF NATURAL SCIENCE IN THE WESLEYAN UNIVERSITY, ' PHILADELPHIA: <* HARLES DESILVER, No. 714 CHESNUT STREET. KEEN & LEE, 148 LAKE STREET, CHICAGO. a olin ay Jae 1357 Entered, according to Act of Congress, in the year 1856, by CHARLES DESILVER, in the Clerk’s Office of the District Court of the United States for the Eastern District of Pennsylvania, STEREOTYPED BY J. FAGAN. TO 4 PARKER CLEAVELAND, LL.D. PROFESSOR OF CHEMISTRY, MINERALOGY, AND NATURAL PHILOSOPHY, IN BOWDOIN COLLEGE, BRUNSWICK, ME.; DISTINGUISHED NO LESS FOR HIS PERSONAL VIRTUES THAN AS THE AUTHOR OF THE FIRST AMERICAN WORK ON MINERALOGY AND GEOLOGY; The following Pages ave Wespectlully Xnscridev, IN TOKEN OF THE DEEP SENSE OF OBLIGATION ENTERTAINED BY HIS FRIEND AND FORMER PUPIL, JOHN JOHNSTON. (iii) PREFACE TO TBE PRESENT, OR SIXTH REVISED EDITION. By the original contract between the publishers and compiler of this work, provision was made for a periodical revision, in order that new and important discoveries might be introduced without delay, and the work be made to conform as much as possible to the rapidly advancing science. These revisions have been carefully attended: to, and considerable alterations in the plates from time. to time have been required; the whole of the part on Organic Chemistry, in the last preceding revision, having been rewritten and restereotyped. But the progress of the science is, and has been, still onward;—new and important facts have rapidly been made known, and new views, throwing more or less light on points heretofore considered obscure and doubtful, have been proposed; so that in the present revision an entire recast of the work has been found necessary. Encouraged by the favor heretofore shown the work, the publisher has cheerfully incurred the expense of stereotyping it anew, including the preparation of many new illustrations; and the results of our joint labors are here presented to the public in a book substantially new, though retaining the former title. The changes which have been made are too great and important to be discussed here ; —for a knowledge of them ad (v) vi PREFACE. the intelligent reader is referred to the pages of the work itself; they are such only as the new aspects of the science seemed imperatively to demand. The principles which have been followed in its preparation are indicated in the extracts from the advertisements to former editions, which will be found further on. Many of the new cuts have been derived from the profusely illustrated work of Reg- nault; others are original, or have been obtained from miscellaneous sources. The Grouping of the Elements adopted is nearly the same as that of Gmelin;—it is not free from objection, but is considered the best yet proposed on this difficult point. In preparing the remarks introductory to the part on Organic. Chemistry, important aid has been derived from Dr. W. Gibbs’ “ Report on the Recent Progress of Organic Chemistry,” prepared for the American Asso- ciation for the Advancement of Science, and printed in the Proceedings of their ninth Meeting, at Providence, R. 1, August, 1855. Many thanks are due to teachers and other kind friends, for judicious suggestions and encouraging words during the preparation of the work; and it is now offered to the public in the confident expectation that it will be found not less adapted for use in the school or lecture-room than preceding editions. MippLeTowN, Or., July, 1856. EXTRACT FROM THE ADVERTISEMENT TO THE FIAST EDITION, (1840.) Tae preparation of the following pages was undertaken by the advice of the late lamented President of the Wesleyan University, with the primary design of providing a suitable Text-book on Chemistry, for the use of the annual classes in that institution. There are indeed already before the public many excellent works on this branch of science, the great merits of which the subscriber is happy to acknow- ledge; but ho long since became convinced, from his experience in teaching, of the need of a work of a little different character, for the special use of students in our higher seminaries of learning, as w text-book. The object of a great majority of students, even of those who pursue a collegiate course, is, not to make themselves familiar with minute details of facts or processes of mani- pulation, but to understand the great principles of the science, and the leading facts which serve for its foundation. To facilitate the accomplishment of this purpose is the object of the present work. In preparing it, the excel- lent “ Elements of Chemistry” of the late Dr. Turner has been adopted as the basis, and all of that work incorporated in it which was suited to our purpose. His arrangement has been uniformly followed, with a few unimportant excep- tionz, which it is not necessary here to particularize. This arrangement, on the whole, is considered the best that has ever been proposed. The part of Dr. Turner’s work omitted is taken up chiefly with details of facts and discussions of opinions and theories, which indeed is important in a work designed for the general student, but which would be out of place in a book prepared expressly to be used as a text-book. Its place, however, has been in part supplied by matter compiled from various other sources, so that the work is thought to be sufficiently large for the ordinary use of students, as the study of this science is usually pursued in this country. It has constantly been an object, while the work should be true to the science, and present in true proportion all its important features, to make it at the same time as practical as possible; to lead the student to apply the principles he learns to the solu- tion of natural phenomena, or processes he may witness in the arts. EXTRACT FROM THE ADVERTISEMENT TO THE SECOND EDITION. In the present edition the work has been carefully revised, and indeed re- compiled from the seventh edition of Turner’s, and many additions made to adapt it to the advancing state of the science. * # * * The extracts from other authors are always introduced in their own lan- guage, except in cases where it was necessary to make some little change to incorporate the extract the better with the passage with which it comes in connection. In a few instances tho names of authors are introduced in the text. To avoid the necessity of constantly introducing quotation marks and references, a list of the authors which have been used will be given. To facilitate the acquisition of the science, the text is divided into paragraphs, and numbered; and references to important facts and principles introducéd as frequently as they seemed necessary. As in many institutions so much time cannot be devoted to this science as would be requisite for a thorough study of the whole work, the less important parts have been printed in smaller type, which may be omitted on the first reading. The intelligent student, however, it is hoped, will not be satisfied without a perusal, at his hours of leisure, of the whole work. (vii) LIST OF WORKS MADE USE OF, MORE OR LESS, IN THE PREPARATION OF THIS WORK. Elements of Chemistry, by the late Edward Turner, M.D., F.R.S., &c., edited by J. Liebig, M.D., Ph.D. F.R.S., &c., and Wm. Gregory, M.D., F.R.8.E. 7 Flements of Chemistry, &c., by Robert Kane, M.D., M.R. LA, &. Dublin. Chemistry of Organic Bodies, by Thomson. Do. Inorganic Bodies. Two vols. Ure’s Dictionary of Chemistry. Two vols. 2.8 ‘ Encyclopedia Metropolitana. Articles, Electro-magnetism, Electricity, Galvanism, Heat, Light, and Chemistry. Library of Useful Knowledge. Articles, Electricity, Galvanism, Magnetism, Electro- magnetism, Chemistry, &. ‘Thomson’s Outlines of the Sciences of Heat and Electricity. Traité de Chimie Appliquée aux Arts, par M. Dumas. Six tomes. Traité de Chimie, par J. J. Berzelius; traduit par Me. Esslinger. Huit tomes. Abrégé Elémentaire de Chimie, par J. L. Lassaigne. Deux tomes, i‘: Organic Chemistry in its applications to Agriculture and Physiology, by Liebig, edited yy Webster. ‘s Animal Chemistry, or Organic Chemistry in its applications to Physiology and Pathology, yy Liebig. Lectures on Agricultural Chemistry and Geology, by J. F. W. Johnston. Elements of do. do. Thomson’s “ First Principles.” Two vols. Prof, Silliman’s Chemistry. Two vols. Prof. Hare’s Compendium of Chemistry. Faraday’s Chemical Manipulation, edited by Dr. J. K. Mitchell. Thomson’s History of Chemistry. Two vols. A Treatise on Chemistry by Michael Donovan, Esq.; Lardner’s Cabinet Cyclopedia. Prof. John W. Webster’s Manual of Chemistry, on the basis of Prof. Brande’s. United States’ Dispensatory, by Drs. Wood and Bache. American Journal of Science and the Arts, conducted by Prof. Silliman. Henry’s Elements of Chemistry. Three vols. Cleaveland’s Mineralogy and Geology. Dana’s Mineralogy. Shepherd’s Mineralogy. Three vols. Griffin’s Chemical Recreations. Journal of the Franklin Institute. Parke’s Chemical Catechism. Chaptal’s Chemistry applied to Agriculture. Elements of Chemistry, by M. Lavoisier, translated from the French by R. Kerr, F.R. 8. Watson’s Chemical Essays. Five vols. Noad’s Chemical Manipulation and Analysis, Do. Lectures on Electricity. Knapp’s Chemical Technology. Vols. I., IT. Gibbs’ Report on the Recent Progress of Organic Chemistry. Gmelin’s (L.) Havd-book of Chemistry, translated by Henry Watts. Vols. I. to IX. Traité de Chimie Elémentaire, Theorique et Pratique, par L. J. Thenard. Cinq tomes, Cours de Chimie Elémentaire, par A. Bouchardat. Deux tomes. 3 Legons sur la Philosophie Chimie, professées an Collége de France. par M. Dumas. Théorie des Proportions Chimiques, et Table Synoptique des Poids Antomiques, ete. par J. J. Berzelius. oe Traité de Mineralogie, par M. L’Abbé Haiiy. Quatre tomes. Eléments de Physique, etc., par M. Pouillet. do. Lehrbuch der Chimie, von E. Mitscherlich, Berlin, 1844, See aie oa zon Professor Dr. F. F. Runge. ours de Chimie Gener: par J. Pelouze et E. Fremy. i > Atlas de 46 Planches. ° y. Trois tomes, accompagné d’un Gerhardt (Ch.), Traité Chimie Organique. Regnault, Cours Elémentaire de Chimie. The same, translated into English by Dr. T. F. Betton, M.D. Besides the above, reference has often been made to various other works, as Le Dicti naire des Sciences Naturelles, Annales de Chimie et de Physique, t! ious] aaa Philosophical Transactions, ‘ke. yeique, the various Encyclopedias, (viii) CONTENTS. PARTI. THE IMPONDERABLE AGENTS. PAGE TN TRODUCLION Sscessiseivsscesves sciences sennsccusnviscessarsvaversecsseessiVerceseces 1B Nature ahd Sources of Heat.......s10:.sssssesce socesevescecscsssscscescesessece 17 Expansion of Bodies by Heat..... BUVeU SAN Set sanissvoes wee 18 Thermometers...... evs saieseisnsjesees oases seeresoes senses even’ 22 Distribution of Heat... seeeee secescea ae seese's 29 Relation of Heat to Chances # in the State of Boilies. “6 eveseee 86 Specific Heat.—Capacity of Bodies for Heat... ssssssssecsossees deveesees 58 Il. LIGHT.” Nature and Sources of Light...... esse ssessseseoee 60 Distribution of Light.....0....cee00es ses wee 65 Decomposition of Light......ssscceccessescseesses tenes eoeeee sesscrrseetoesnseeees 68 * ‘UI, ELECTRICITY. Nature of Electricity.—Electrical Theories..........+:csccecsssecsssces eesees Distribution of aac soioa Siesiedaapaveaedsn acy wesilsscivcdees Sources of Electricity ........0.sssccese cosssouce cccescecs soseeeseece saessenes soseee Galvaniom .....cc0: sseseseee aves Effects of Galvanic Electricity... wee _ Electro-magnetism......++ dneaesnne bi sessssesacenaass ooseesene resesnenese PART II. GENERAL CHEMISTRY. The Elements.—Chemical Affinity...... sso Laws of Combination.—Atomic Theory..... Nomenclature of Chemistry.—Symbols..... = CONTENTS. PART III. SPECIAL CHEMISTRY—INORGANIC. PAGE vee 172 + 178 «» 174 CEASSIFICATION OF ELEMENTS.. sendiwecsean: METALLOIDS, OR Nowasenannce Fipiasiey Group I, — Oxygen...... 0. Hydrogen.... Nitrogen ..... Group II. —Chlorine...... Todine.......0 Tellurium... Grovr IV. — Phosphorus. Gaur V. — Carbon sisccsece csscccces onsen eeee seeee Seuaesenee aveassess sasisvesecss . 257 Silicon........ Boron.essce coscee soveceass THE METALS o0.cesseeseceeseee cvscen eee GENERAL PROPERTIES ...0+ Group I. — Potassium.....cae cessscccecccces secs cee on soa dis'es) esinesize sie aeeees 298 Sodium.... Grovp [TI]. —Aluminum,......cssssececseccceesee covase Glucinum.... Zirconium ... Thorium.... Yttrium ... Erbium.... Terbium... wie Cerium...... cé 98 Lanthawtrn., Didymium ......000 OONTENTS. xi Cobalt ..... Nickel......... Group V. — Antimony.... Bismuth...... Molybdenum... Tungsten... Titanium..... Columbium .. Tantalum ......scccescsseee Group VI.—Mercuwry...... saaeae was egdandiacasss sues tae, Silver... soe 000 ceecccses soocecessescees sccees PART IV. SPECIAL CHEMISTRY—ORGANIC. GENERAL PROPERTIES OF ORGANIO Bopizs.. Srarcu, Sugar, Gum, LIGNINE.......00 aaaess 405 Starch, or Fecula....se wsesee es - 405 Sugars... 408 GUIS ...... cccesnccccerceseeeccecee ove wanSsbineessebeeeeoiess 411 Woody Fibre, Lignine, Calictioserscs.c aive'sbdcetiocenssinsesedasuecelsse 412 Atconots AND SupstaNcEs DERIVED FROM re sassacee 418 Wine Alcohol... sa wdishiauaiauevlessneeicuaseedessieesvsezes 418 Methylic Alechol, ¢ or x Wood Spirit... os seeseeee 428 Armylic Alcohol.....ssscccocescersesese eves seas seeweauaaeaeeeeees 4380 Sulphur Alcohols, or Mercaptans.......0cesesesscevesseeecversecsereress 40a xii CONTENTS. ETHERS.—COUPLED, OR VINIC ACIDS...cccececrecestecseeceeseesesceeesesseees 433 Ethers of Wine Alcohol........... I. Simple Ethers...... If. Compound Ethers... 438 Ethers of Methylic Alcohol. 440 I. Simple Ethers......... savoee 440 II. Compound Ethers. « 442 Ethers of Amylic Alcohol... 443 VouaTILy, oR EsseNnrviAL OMs...... . 444 Carbohydrogen Volatile Oils.. 446 Oxygenated Volatile Oils.... - 448 452 Sulphuretted Volatile Oils... Camphorsseo seers cee cecseecneece sueeees sescceceneee 403 Coumarxrine....ccersecesrereoes es Fixep Oms anp ce acledctesewe 455 Glycerine.......: tse 456 Stearine and Stontio ‘Add... . 457 Margarine and Margaric Acid . 458 Oleine and Oleic Acid......... w. 458 Other Proximate nai of the Fats.. seve 459 Soaps and Plasters.........sssssseeeseeeescees sreveve 462 RESINOUS SUBSTANCES ..sssisesesceens vee 463 VEGETABLE ACIDS NOT INCLUDED IN- 1 Baroenine GROUPS... - 465 ORGANIC ALKALIES, OR ALKALOIDS .osccsses socsseeestsceeees sees . 469 ALKALOIDS OF THE ETHERS, OR CONJUGATED AMMONIAS... » 471 ORGANIO COLORING-MATTERS «. cess sescae cee cecees voceeee tseoees THE AMIDES AND NITRILES ...+0.scecce ces ccesessce svcees sncsees tences soveee sseeee 478 CYANOGEN AND ITs COMPOUNDS.. 480 Compounds of Cyanogen amd Oxygen... ie « 481 Compounds of Cyanogen and Hydrogen.. «. 484 Sulphocyanates or Sutphocyanides..........000 ~ 485 Compounds of Cyanogen and the Metals.... . 486 Double Cyanides.—Polycyanides........... «~ 487 ALBUMINOUS, OR PROTEINE CoMPOUNDS... . 490 CuemicaL PHENOMENA OF VEGETATION... . 494 COMPOSITION OF THE ANIMAL TISSUES......scceescsscsesce sosesscce sesceessces 498 Tue Bioop.—PHENOMENA OF RESPIRATION AND DIGESTION. ............ 500 TUG BOO vssvcveseci saute scos css oeedad esvasesas'avsssessececceessves - 501 Phenomena of Digestion...:.. «. 508 Phenomena of Respiration... Sau aW esse Ab odes ecdxcuueeiove 506 SevezaL ANIMAL SECRETIONS AND Exenenions NOT BEFORE Noticep 510 APPENDIX.—TABLES OF WEIGHTS AND MEASURES... ccccscssccssssseses DID MANUAL OF CHEMISTRY. PAR PART I, THE IMPONDERABLE AGENTS. INTRODUCTION, 1, WE recognize as matter or substance whatever possesses the four properties of extension, impenetrability, inertia, and gravity, or weight. By the first of these properties every body occupies a portion of space; by the second, it refuses to allow another body to occupy this space at the same time with itself; by the third, it is incapable, of itself, of changing its state, whether of rest or motion; and by the fourth, if unsupported, it falls to the earth. Whatever does not possess all these properties is not recognized as matter. 2. Natural science embraces the whole range of material things: their properties, the changes they are capable of undergoing, and the laws of their changes. 8. As has been suggested by Gmelin, all the changes of which any portion of matter is capable may be referred to the three causes or forces of Repulsion, Attraction, and Vitality. 4, Repulsion is manifest in the property of matter denominated impenetrability, and in the expansion of bodies, especially by the influence of heat, as will be shown hereafter. Quzstions.—1. What is matter or substance? Define what is meant by the four properties mentioned.— 2. What does Natural Science em- brace ?—3. To what three causes may all changes of matter be referred ? —4. In what is repulsion manifest ? 2 (18) 14 INTRODUCTION. 5. Attraction manifests itself in a variety of forms: 1. As Gravitation, or that force which acts at all distances, however great, and between the largest masses. 2. Cohesion, or that force which, acting only at distances immeasurably small, unites the parts of the same mass. 8. Electrical and Magnetic Attraction. 4. Chemical Attraction or Affinity, which acts only at insensible distances, and between the ultimate particles of bodies, and pro- duces homogeneous compounds. 6. Vitality is that peculiar force or power, possessed both by animals and plants, by which the simple affinities of the various substances contained in their bodies are so modified and controlled in their action, as to produce the complex, and almost innumerable organic compounds, such as sugar, woody-fibre, albumen, &c. Changes produced by all the varieties of attraction above mentioned, except the fourth, or last, pertain properly to Physics or Natural Philoso- phy; while those produced by Affinity, either alone, or as it is controlled by vitality in the bodies of plants and animals, belong to Chemistry. The changes produced by the action of affinity consist in the combina- tion of dissimilar substances into a homogeneous mass, or, occasionally, the separation of dissimilar substances from a homogeneous mass. We may, therefore, define Chemistry as the science which treats of the com. bination of dissimilar substances into homogeneous compounds, and of the separation of dissimilar bodies from homogeneous compounds. 7. Molecules or Atonrs,—All bodies, it is believed, are made. up of infinite numbers of indefinitely small particles—too small to be detected by the eye, even when aided by the most powerful microscopes — which are called molecules or atoms (from a, priva- tive, and temno, I cut), indicating their supposed indivisibility. Our knowledge of them is obtained indirectly, as we shall see hereafter; but it is believed that all the molecules of the same substance are precisely alike in weight, size, and form, as well as other properties. 8. Simple and Compound Bodies——From what has been said above, the distinction between simple and compound bodies is obvious. Simple substances are such as are believed to be com- Questions.—5. What are the different varieties of attraction? Define the several varieties. 6. What is vitality? What changes pertain to Natural Philosophy or Physics? What to Chemistry? The changes pro- duced by the action of affinity consist in what?—7. Of what are all bodies composed? Do we have any direct knowledge of these atoms ?— 8. What are simple bodies ? : INTRODUCTION. 15 posed of only one kind of particles, as carbon, sulphur, copper, and gold ; compound substances are composed of two or more kinds of particles, which are held in union more or less intimate by their affinity. The separation of the elements of a compound is called its decomposition. The composition of a body may be determined in two ways, analyti- cally or synthetically. By analysis, the elements of a compound are separated from one another, as when water is resolved by the agency of galvanism into oxygen and hydrogen; by synthesis they ar¢ made to combine, as when oxygen and hydrogen unite by the electric spark, and generate a portion of water. Each of these kinds of proof is satis- factory; but when they are conjoined—when we first resolve a particle of water into its elements, and then reproduce it by causing them to unite—the evidence is in the highest degree conclusive. 9. Matter is Indestructible; that is, it cannot be made to cease to exist. This statement seems at first view contrary to fact. Water and other volatile substances are dissipated by heat; and coals and wood are consumed in the fire, and disappear. But in these and other similar phenomena, not a particle of matter is annihilated: the apparent destruction is owing merely to a change of form or of composition. “The power of the chemist is, therefore, limited to the production of these changes. 10. Different Forms of Matter.—Matter exists in three forms or states: the solid, liquid, and gaseous. Besides these, there are the three imponderable agents, Heat, Light, and Electricity, which, if they are ever proved to be material, will constitute a fourth form of matter. It is believed that the particles of a substance, even the most solid, are never in actual contact, but are held in close proximity by the two opposite forces of attraction and repulsion; and that the particular state, whether solid, liquid, or gaseous, in which a body is seen, depends upon the relative intensity, for the time, of these forces. If the force of attraction altogether prepondcrates in a body, it is solid, and the particles, in general, are held firmly in their QuEstions.— What are compound bodies? Give an illustration. In what two modes may the composition of « body be determined? Ex- plain analysis and synthesis. —9. Can matter be destroyed? To what is the power of the chemist limited ?—10. What different forms of matte: are there? What is said of the imponderable agents? Are the parti- cles of matter ever in contact? Upon what will the state of matter i1 any particular case depend? Are not the particles of solids in contact! What reasons are given for this opinion ? 16 INTRODUCTIEN. places, and are incapable of motion among themselves. But the particles are not in actual contact, for, by cooling, or by great pressure, the dimensions of any body may be contracted, and, therefore, its particles brought nearer to each other. This will appear more fully hereafter. In liquids, there is a degree of cohesion among the particles which, however, are capable of perfectly free motion among them selves. -That there is a degree of cohesion existing between the particles is shown by the drop, which is composed of particles held together by a slight force; but this slight force does not interfere with the freedom of their movements. Gases are distinguished by their tendency to expand, or enlarge their volume, when external pressure is removed. In them cohe- sion is entirely wanting. The term fluid is applied to both liquids and gases. Some substances are found naturally existing in one of these states, and some in another; and many can be made to pass from one state or form to another, simply by varying their temperature, or the pressure to which they are exposed. Thus, water at a moderate temperature is liquid, but in the cold weather of winter it freezes, that is, becomes solid; and if it be heated sufficiently, it is changed into steam, or becomes gaseous. The metal, platinum, is found always in the solid state, though it may be melted by very great heat; but carbon is known onlyas a solid. Several substances, found naturally in the gaseous state, may be changed to liquids by great pressure, or by extreme cold; and, by a still greater cold, some of them may be frozen. Others, as atmo- spheric air, have hitherto resisted all attempts to reduce them to the liquid or solid form. Heat, light, and electricity are said to be imponderable, because they possess no appreciable weight; but they certainly exhibit some of the ordinary properties of matter. They may be accumulated in bodies, are capable of being attracted and repelled, and often produce various che- mical and mechanical effects. But because they possess no weight, so far as we can determine, many choose to consider them, not as matter, but only properties of matter. Questions.——Is there any cohesion among the particles of liquids ? How is this shown? How are gases distinguished? How is the word fiuid used? What is said of the natural state of substances? What are the imponderables? Why are they so called? I. HEAT. NATURE AND SOURCES OF HEAT. 11. The word Heat is used indiscriminately to indicate the sen- sation we experience by placing the hand in contact with a heated body, or the cause of the sensation. To indicate the latter, the word caloric has sometimes been used. The discussion of this subject properly pertains to Physics, or Natural Philosophy, (6,) but the agency of heat is so intimately connected with nearly all chemical changes, that a treatise upon Chemistry would be im- perfect without u previous development of some of its more important laws and phenomena. 12. Nature of Heat.— Heat cannot be obtained separate from matter; it is invisible, and, so far as we are able to determine, entirely destitute of weight. It is not, therefore, (10,) believed to be material; but in describing its effects, and its relations to matter in general, we speak of it as an exceedingly subtile fluid, the particles of which constantly repel each other, but are attracted by other substances —as capable of being transmitted through space, and the interior of bodies, and of being accumulated in quantities in them. It is present in all bodies, and cannot be wholly separated from them. For if a substance, however cold, be transferred into an atmosphere which is still colder, a thermo. meter placed in the body will indicate the escape of heat. Heat appears to be attracted by all bodies, but is self-repellent, as is shown by the fact that two bodies easily movable, when heated in a vacuum, repel each other. 13. Sources of Heat.—The chief sources of heat are: the Sun, Combustion, and other chemical changes, Friction, Electricity, and Vital Action. The Sun is the great source of heat to our system. The inten- sity of the solar heat appears to be directly in proportion to the number of rays that can be collected upon a given surface ; and at one time philosophers were able to produce a greater hat by “ Questions. —11, How is the word Heat used? Caloric? Is the agency of heat connected with chemical changes?—12. Can heat be obtained separate from matter? Do we speak of heat as being material? Is heat present in all bodies? Is it attracted by matter?—13. What sources of heat are mentioned? How may the sun’s rays be concentrated 30 as to produce a great heat? 2* (17) 45 NATURE AND SOURCES OF HEAT. collecting the sun’s rays by means of the convex lens or concav mirror, than by any other mode. But although the sun’s_rays are not made use of in the arts wher great heat is required, yet their momentous importance to all the inha- bitants of the earth cannot be over-estimated. Without them all the water upon the face of the globe would soon be congealed, and animal and vege- table life cease to exist. Combustion is the great source of artificial heat, as the sun is the source of natural heat. Besides wood, nature has provided immense deposits of combustible material, in the form of mineral coal, in the bosom of the earth. These are found in almost every country, and seem to be provided by the Creator as an unfailing resource for man, when, from the increase of the species, or from his own negligence or extravagance, the supply from the vegetable world should fail or become deficient. Friction is a well-known source of heat. By the friction of the parts of heavy machinery, especially when not well oiled, heat has often been evolved.sufficient to ignite wood ; and the same effect is said to have been produced in ships by the rapid descent of the cable. Some tribes of the aborigines of this country were accus- tomed to kindle their fires by rubbing smartly one piece of wood against another. In the boring of cannon, heat enough has been evolved to raise the temperature of a considerable quantity of water so as to boil. The heating effects of electricity will be considered hereafter. The influence of vztal action in developing heat is seen in all warm-blooded animals, which are maintained at a temperature often much above that of the air and other surrounding bodies, though heat must constantly be escaping from them. EXPANSION OF BODIES BY HEAT.—THERMOMETERS. 14, All bodies, with a very few exceptions, expand when their temperature is increased, and contract when it is reduced. How this effect is produced we really do not know, but appearances in- dicate that the particles of heat entering among the particles of the body, partially overcome their cohesion, and cause them to sepa- Questions.—What is the great source of artificial heat? What is said of friction as a source of heat? —14. Are all bodies expanded by heat? Ilow are bodies affected by a reduction of their temperature? NATURE AND SOURCES OF HEAT. 19 rate farther from each other. On the other hand, when the particles of heat are withdrawn, the molecules of the body are allowed to approximate each other more closely. A substance is therefore less dense when heated, than when cold. 15. Expansion of Solids.—The expansion of solids by ‘heat is not very considerable, but may easily be made very sensible. Leta bar of brass be accurately fitted into a gauge, when cold, and then let it be slightly heated ;, it will be found to have increased so much in length as not to fit the gauge. If the gauge be also made of brass, and the experiment performed in the warm weather of summer, the same result will be produced by cooling the gauge in ice-water, because of its contraction by the cold. This Expansion of Solids. experiment indicates a change only in length, but a corresponding change is at the same time produced, both in breadth and thick- ness, as may be demonstrated in various modes, which the ingenious student will readily devise. 16. Different Solids, when equally heated, do not expand equally; every substance possesses an expansibility peculiar to itself. But a body expanded by heat, and again cooled to the same temperature it had at first, suffers no change in its dimensions. Nor does the same substance expand equally at all temperatures with an equal increase of heat; in general, the expansibility increases with the temperatute. Thus, a body heated ten degrees at a high tempera- ture, expands more than when the same amount of heat is added ata low temperature. 5 The different expansibility, of the two metals, copper and plati- num, may be shown by soldering together a thin slip of each, and applying a moderate heat to the ZS compound bar. Both plates will be equally heated, but the cop- per being the most expansible, ; the bar will be curved, the cop- Different Expansion of two Metals. Qurstions.—15. How may the expansion of a solid by heat be shown? 16. Do all bodies expand equally when equally heated? Does the same substance at different temperatures expand equally for equal increases of temperature? How may the different expansibilities of two metals, as copper and platinum, be shown? 20 NATURE AND SOURCES OF HEAT. ‘ per being on the convex side. See figure, in which the copper is supposed to be on the lower, and the platinum on the upper side. Other metals, used in pairs in a similar manner, would show the same result, but with many of them the effect would be less decided. An instrumeat like the following, at the same time that it shows the different expansibilities of two metals, serves as an : excellent thermometer for many practical pur- poses. A and B are pieces of iron wire -2,ths of an inch in diameter, and a foot long; ‘and C a piece of brass wire of the same size and length. At the bottom they are all fastened together by brazing or otherwise; at the top, a piece of brass is fixed to the two pieces of iron, and through it, near the centre, is a hole in which the brass wire, C, plays freely. Now, . by immersing the thin wires in: boiling water, hot oil, or melted lead, they are all expanded ; but the brass expanding. more than the iron, its upper end is pushed upward against the lever, D, which in turn acts upon E, producing considerable motion at its extremity, where may be placed a graduated scale, as 8. Such an instrument will be sensibly effected by even Different Expansion of Metals. moderate changes of temperature. The following table shows the expansion in length of rods of several substances, when transferred from the freezing to the boiling point of water : Substances. Hapa ig At bi Substances. ae . ae Flint Glass...... ceeee ToEB Copper........0..00. she Woods cesses csasaaes yae9 Brassos-ccc seen yess s ska Platinum...........- Wit ZING assists oils eel does ako Gold iiigariavee teaver ste TAD i535: dye cacs's 2 yraiooes « ats SiUlV6B vaccace end aie's + sts Bismuth............ aly TROti sn okdacnncindedes ahs DG Ad wai ose ayeraigns ieee sit Steel........... seeee ght Antimony........... oh Quustions.—Describe the instrument represented by the second figure of this paragraph. What is the design of the instrument? What are some of the most expansible of the metals, as indicated in the table? “NATURE AND SOURCES OF HEAT. 21 17. Practical Applications.—This property of bodies, and particularly of the metals, has been applied to various useful purposes in the arts. The iron band or tire of a carriage-wheel is made a little smaller than the circumference of -the wheel, but, being expanded, is sufficiently enlarged to be slipped on; and the immediate application of water prevents it from burning the wood, and brings the iron to its original dimensions, causing it to grasp the wheel with great firmness. Other examples are of frequent, occurrence in the arts. The expansions and contractions of bodies by change of temperature also occasion some inconveniences. The accurate movement of clocks depends upon the length of their pendulums, which being sensibly affected by changes of temperature, they are made to go faster in cold, and slower in warm weather. Brittle substances, when unequally heated, are often broken by the unequal expansions and contractions to which they are liable. The danger is greater if the substance is a bad conductor of heat, as is the case with glass, and particularly if it is thick. Hence, glass vessels that are to be used about the fire, or with hot water, should be made as thin as is consistent with the requisite strength. . Metallic or other instruments used for measuring length or capacity vary with change of temperature—a circumstance that sometimes ocea- sions serious difficulty where very great accuracy of measurement is required. It has been found by very accurate examination, that the Bunker Hill Monument, which is built of granite, is daily made to change its poSition slightly, by the heat of the sun, which expands the sides upon which the rays fall. # 18, Expansion of Liquids—In solids, the expansive force of heat is opposed by the cohesion of their ‘ particles, and is therefore less effective than in. liquids, in which there is only a very slight cohesion of the particles. A liquid, therefore, will expand on being heated, much more than a solid. The expansion of » liquid may be shown in the following manner. Take a glass flask (called a mattrass or bolt-head), of the form represented in the figure, and partly fill it with some liquid, as water, and tie a thread around the stem, as on A, to indicate the height of the water in it; and then apply for a few minutes the heat of a i = spirit-lamp. Both the glass and the water will Expansion of Liquids, . Questions.—17. What is said of the dire of wheels? How are brittlu substances affected by sudden changes of temperature? What is said of the Bunker Hill Monument? 18. What is said of the expansion of liquids by heat? How may the expansion of a liquid be shown? 22 THERMOMETERS. be expanded; but the water will expand more than the glass, and will then rise in the stem, as shown in B. But all liquids when equally heated do not expand alike,—every one possesses an expansibility peculiar to itself. Thus, it has been found by making the experiment, that 1000 parts of water, at the freezing point, : when heated so as to boil, are expanded to 1046 parts; but 1000 parts of mercury, heated in like manner, expand only to 1008 parts. Ether is more expansible than alcohol, and alcohol more expansible than water. Liquids, as well as solids (16), are expanded more at high than at low temperatures, by a given addition of heat. 19, Expansion of Gases.—All gases expand equally when equally heated, and the expansion is proportional to the increase of temperature. When 1000 parts of any gas are heated from 82° to 212° of Fahrenheit’s thermometer (an instrument soon to be described), they expand to 1365 parts, or 44 part of the volume at 32° for each degree. In the case of gases that are capable of becoming liquid by pressure, this law does not hold strictly true when they are ui” about to assume the liquid form. « to pensioty To show the expansion of air by heat, let a glass flask, filled * with air, be placed as in the figure, with its mouth immersed in water; then warm it slightly, by grasping the bulb in the hands, or breathing upon it, when the air will escape in bubbles, in consequence of its expansion by the heat. On cooling, the air within contracts, and the water rises in the stem to supply the place of the air which was expelled. THERMOMETERS. 20. Thermometers are instruments for ascertaining and mea- suring changes of the ‘temperature of bodies, of which there are several kinds. The name is derived from the two Greck words, thermos, heat, and metron, a measure. The first instrument of the kind, so far as we know, was con- structed but little more than two hundred and fifty years ago, by Sanctorio, an Italian philosopher. Sanctorio’s thermometer was made in the following manner. A glass tube of small diameter, having a bulb blown at one end, was Questions.—Do all liquids expand equally when equally heated? How much do 1000 parts of water expand when heated from thé freezing to the boiling point? 19. Do gases expand by heat? What is the amount of their expansion for each degree of heat? How may the expansion of air by heat be shown? 20. What are thermometers ? THERMOMETERS. 23 partly filled with a colored liquid, and the stem passed through a cork, and inverted in a vessel containing the same kind of liquid, and having a wide bottom, as in the figure, so as to stand upright firmly. Through the cork a small perforation was made, so as to allow the air to pass freely, and to the stem a graduated scale was attached, to mark the rising and falling of the liquid in it. Now, in an instrument of this kind, it is plain that when the bulb is heated, the air within will be expanded, as before explained, and the liquid in the stem will fall; and a motion of the liquid in the opposite direction will take place when the bulb is cooled. The rise and fall of the liquid will also be proportional to the change of temperature in the bulb. Air Thermo- This thermometer will very well answer some specific ™*** purposes, but as it will be affected by changes of atmospheric pressure as well as by changes of temperature, it cannot be applied to general use. . The differential thermometer may be con- sidered as a modification of the preceding. It consists of a glass tube, bent twice at right angles, with a bulb at each end, and is supported on a stand, as shown in the figure. In the tube is contained a portion of colored oil of vitriol, or other liquid; but both bulbs are left filled with air, and to one of the arms is attached a graduated scale. When both bulbs are equally heated or cooled, this instrument indicates no change : but if one is heated or cooled more than the other, a motion is at once occasioned in the liquid in the stem, the direction of which will be readily understood from the explanations already given. This thermometer therefore indicates the difference of temperature at any time existing between the bulbs, and hence its name. It is exceedingly delicate, and is especially adapted for some particular purposes. Differential Thermomter. Questions. —Describe Sanctorio’s air thermometer. What objection is there to its use? Describe the differential thermometer. 24 THERMOMETERS. 21, The Common Thermometer.—The thermometer in com- ‘mon use consists simply of a glass tube of an exceedingly small bore, with a bulb blown at one extremity, and filled with mercury to about one-third the height of the stem. The air being expelled, the tube is hermetically* sealed, and the freezing point ascertained by hold- ing it a short time in water containing ice, and the boiling point by holding it in the same manner in boiling water. Both points are marked on the stem bya file. It is necessary that these two points should be accurately determined, in order that the indica- tions of different instruments may be compared with each other. By the term freezing point here, is meant the temperature at which water freezes or ice melts, which, with certain exceptions, is always the game, as will be fully explained hereafter; so, also, pure water always boils at the same temperature, provided attention is paid to certain cir- cumstances to be discussed further on in the work. This temperature is called its boiling point. It will be unnecessary here to give a minute description of the method of making thermometers, as, at the present day, they can be everywhere obtained at a very moderate price. ‘‘ Besides, the construction, though simple in theory, is difficult in practice. It requires great tact and dex- terity to produce one of very moderate goodness; and without steadily watching the process as performed by another, or previously possessing much practical knowledge in glass-blowing, &c., it would be a vain attempt.”—Faraday’s Chemical Manipulation, p. 144. The graduation of the scale of the thermometer is a matter of great importance; and it would be fortunate for us if we had but one, instead of three or more, as isthe fact. We have seen that in all thermometers there are two fixed points; and the question now before us is, into how many parts or degrees, shall the space between them be divided? Unfor- tunately, this question has been answered differently by different artists, and in a manner entirely arbitrary. Fahrenheit, a German artist, whose thermometer is generally used in this country and in England, divided it into 180 parts or degrees, and placed the zero, or the beginning of the scale, 32 degrees below the freezing point; 80 that the temperature of melting ice or freezing water is 32 degrees, and that of boiling water (32 + 180 =) 212 degrees. Celsius of Sweden proposed to divide the space into 100 parts, and placed the zero at the freezing point. His thermometer is called the centigrade thermometer, and is used in France and Sweden, and some other parts of Europe. * A glass tube is sealed hermetically by melting the end by means of the blow-pipe, and thus perfectly closing it. For this purpose the end is usually drawn out into a fine point. Qusstions.—21. Describe the common thermometer. What are the freezing and boiling points? How are these determined? Describe the scale adopted in Fahrenheit’s thermometer. Where is the zero or begin- ning of this scale? Describe the scale of the centigrade thermometer. THERMOMETERS. 25 Reaumur divided it into only 80 parts, placing the zero, or beginning of the scale, like Celsius, at the freezing point; of course the boiling point is at 80. Below zero of each of the scales, and above the boiling point, degrees are marked, of precisely equal magnitude with those of the other part of the scale. Temperatures below zero are usually indicated by placing a horizontal line before the figures representing the degrees. Thus, --12° means 12 degrees below zero on the scale used. The numbers 180, 100, and 80, which severally represent the number of degrees on the above scales, are to each other as 9,5, and 4. Recol- lecting, therefore, that the zero of Fahrenheit is 32 degrees below that of the other scales, the expert arithmetician will find no difficulty in reducing the degrees of one scale to those of another. Thus, to convert the degree of temperature indicated by Fahrenheit’s seale into its centigrade equivalent, we multiply the degrees above or below 82° by 5, and divide by 9. Suppose the temperature by Faren- heit’s thermometer is 140°, what is the corresponding degree in the centigrade? Hz. 140— 32108, and 108 X 5—540, and 540 ~ 9—60. On Fahrenheit’s scale, therefore, 140° are equivalent to 60° of the centi- grade. thermometer. — Let us suppose again that the temperature by the centigrade thermo- meter is 60°; it is required to find the corresponding degree by Fahren- heit’s instrument. Hz. 60 9-540, and 540+ 5=—108. To this (108) we must now add 82, because the beginning of Fahren- heit’s scale is 32° below that of the centi- grade. Thus 108°-+ 82°= 140°. In this work, and in most works in the English language, if nothing is said to the contrary, it is always to be understood that temperatures are expressed in degrees of Fahrenheit’s scale; but, to avoid confusion, we often place F.,C., or R., after the figures expressing the degrees, to indicate what thermometer has been used. The relation between the three scales above described is indicated in the accom- panying figure. Though mercury is chiefly used in filling thermometers, yet other liquids are also sometimes employed. At very low tem- ~- pigeront Thermometers. peratures mercury is frozen, so that it ceases to answer the purpose designed; in such cases, therefore, alcohol thermometers alone can be used. 22. The Register Thermometer, while it answers the same pur- pose as another thermometer, at the same time indicates or registers & i Qurstions.—Describe the scale of Reaumur’s thermometer, How are the degrees determined below the freezing point and above the boiling point? How may we convert temperatures as indicated by Fubrenheit’s seale into its centigrade equivalent? How may we convert centigrade into Farenheit degrees? Is mercury always used in constructing ther- mometers ? 3 26 THERMOMETERS. the extremes of temperature that may occur during the absence of the observer. It consists of two thermometers, with the stems bent near the bulb, and placed in a horizontal position, attached to the same frame, as shown in the following figure : Register Thermometer. The one usually placed uppermost is a mercurial thermometer, having in the tube a small piece of iron or steel wire, which is pushed forward by the mercury as it expands, but does not recede with it when it contracts. The point at which the iron is left, of course shows the maximum temperature attained.. The other thermometer is filled with colored alcohol, and contains in the liquid in the stem a similar piece of iron, inclosed in glass to pre. Breguet’s Thermometer. j Sol es (_— Yi pu vent oxidation, around which the alco- hol flows while that in the bulb is ex- panding, so as not to be moved, but which is drawn along with it by capil- lary attraction, when it contracts so as to be kept at its surface. It is there- fore left at the lowest point to which the spirit has contracted, and of course shows the minimum temperature. Both pieces of iron or steel, which thus serve as indices, may be brought to any posi- tion in their respective tubes by means of a magnet applied on the outside. 23, Breguet’s Thermometer is made eieety of solids. It consists of a very thin strip of platinum, soldered to a Qurstions.—22. Describe the register thermometer. Breguet’s thermo- meter. THERMOMETERS. 27 similar strip of silver, and coiled in a spiral, as shown in the figure (page 26). The upper end of the coil is then attached to a firm support, and to the other extremity is fixed a pointer or index, which is made to revolve by any change of temperature, by reason of the unequal expansions and contractions of the two metals. Beneath the pointer is placed a circle which may be gra- duated to any scale desired. It is a very delicate instrument. A modification of this instrument is used in the United States’ Coast Survey, for determining the temperature of the water in deep soundings, at sea, The Pyrometer (from pur, fire, and metron, a measure,) is an instrument for measuring temperatures too high to admit of the use of the thermo- meter. The only one now in use is Daniel’s pyrometer, which is not of sufficient importance to require description here. By it the melting point of cast iron’ has been shown to be about 2786° F., that of gold to be about 2016° F., copper 1996°, silver 1860°, and zinc 718°, 24; Exceptions to the general Law of Expansion.—There is a remarkable exception to the general law (14) concerning the expansion of bodies by heat, as above stated. Water is most dense at the temperature of about 40°, and expands, whether it is heated above this point or cooled below it. To show this, fill an ounce vial with water at a tempera- ture of 65° or 70°, and adapt to it a cork, through which passes a glass tube of small bore. Then insert the cork and tube, and fill the latter with water one or two inches above the neck of the vial, and expose the whole to the cold atmosphere of winter, or immerse the vial in a freez- ing mixture of snow and salt ; the contraction of the water in the vial will very soon be “made evident by the fall of that in the tube; but the falling will shortly cease, and an upward motion commence, indicating an expansion of the water in the vial, although its temperature must be i all the time falling. The volume of the water has there- f fore first been diminished by reduction of its heat, and water Expansion again expanded; and by making use of the thermometer, when Freezing. it isfound that the change takes place at about 39° or 40°, A large thermometer tube, nearly filled with water, may be used for the same purpose. 25. The most important effects result from this remarkable property of water. If the density of water continued to increase until it arrived at the freezing point, as is the case with mercury im Qurstions.—What is the design of the Pyrometer? 24. What exceptions are there to the general law of expansion of bodies by heat? Describe the method of showing the expansion of water by reduction of temperature. 28 THERMOMETERS. and other liquids, ice would be heavier than water, and as soon as , formed would subside to the bottom in successive flakes, until the whole of the water, however deep, would become solid. The effects of such an arrangement can be easily conceived. Countries which, in the present state of things, are the delightful abodes of innumerable animated beings, would be rendered uninhabitable, and must inevitably become dreary and desolate wastes. But, since water expands previously to its freezing, as well as during this change, ice is lighter than water, and floats upon its ees protecting the water, to some extent, from the further influence of frost. The cause of the expansion of water at the moment of freezing is attri- buted to a new and peculiar arrangement of its particles. Ice is in reality crystallized water, and during its formation the particles arrange them- selves 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, and still better by receiving particles of snow as they fall upon a piece of black cloth. They will often be found to be small but beautiful crystals or collections of crystals, presenting a great variety of forms. Some of the more com- mon forms are shown in the figure. Snow Crystals. Quxstions.—25. What is said of the importance of this remarkable pro-~ perty of water? What is suggested as the cause of this expansion of water in rreezing ? DISTRIBUTION OF HEAT. 29 26. The view just taken of the cause of the expansion of water when freezing is sustained by the facts observed in the formation of anchor ice, or ground ice, as it is often called. This ice is found in certain circumstances at the bottom of bodies of water, and not at the fop, as with. ordinary ice. It has little tenacity, and may be supposed to consist of the primary crystals of water. Separately, they are believed to possess a higher specific gravity than water, bit, when aggregated according to the law stated above, at angles of 60° and 120° to form common ice, on account of the insterstices necessarily left among them, the volume is so increased as to diminish the specific gravity to the point we usually witness.— Manuscript Noles of Professor Cleaveland’s Lectures in Bowdoin College, 1832. , DISTRIBUTION OF HEAT. Heat constantly tends to diffuse itself, and its distribution is effected by Conduction, Convection, Radiation, Reflection, and Transmission. 27. Conduction of Heat.—Heat is said to be conducted, when it is transmitted from particle to particle through a body, as when one end of a metallic bar is held in the fire until the whole becomes heated. : ? : - The passage of the heat in such cases is evidently progressive, as may be shown in the following manner. Take a small bar of copper, 18 or 20 inches in ome i length, and cement to it several small bullets, or mar- bles, about two inches from each other, by means of wax, .ag shown in the figure, and then apply the heat of a lamp to one end. As the « heat progresses along the Conduction of Ileat, bar, it will melt the wax, and the balls will drop off in succession, ea) Quustrons.—26. What is said of anchor ice in this connection? What are some of the modes by which heat tends to diffuse itself? 27. When is heat said to be conducted? How may the conduction of heat along a bar of coppes be shown ? 1 30 DISTRIBUTION OF HEAT. the one nearest the lamp falling first, and the one farthest from it last. “ Substances differ greatly in their power of conducting heat; a rod of glass, or a piece of charcoal, an inch long, may be heated to redness at one extremity, and yet be held in the fingers by the other extremity; but it cannot be done with a similar piece of metal, because, on account of its better conducting power, the whole very soon becomes too much heated. The apparent temperature of a body, as determined by the hand, will often depend upon its conducting power. Thus, if on a cold morning of winter, the hand is placed upon a piece of metal, and then upon a piece of woollen cloth, the former will feel much colder than the latter, because the metal in equal times conveys away from the hand more heat than the cloth. 28. Substances are divided into two classes in reference to their ability to conduct heat, called conductors and non-conductors. There are, however, no absolute non-condactors; heat: penetrates the substance of all bodies; the only difference in them, in this > respect, is in the rapidity with which & the process takes place. Gold is usu- ally considered the best conducting substance known; and very porous solids, the. interstices of which are filled with air, as cotton, or sheep’s wool, and fur, are the poorest con- ductors. A convenient method to determine the relative conducting power of dif- ferent substances, is, to have them made into cylinders of equal diame- ter, and set in a thin piece of wood at sufficient distances from each other, both extremities of each piece projecting a little from the wood. If the board be held in Conduction of Heat. Questions.—Do substances differ from each other in their power to con- duct heat? Why will some substances feel colder than others, when it is known that all must be at the same temperature? 28. Into what two classes are substances divided in reference to their conducting powers? What is usually considered as the best conductor known? What method for determining the relative conducting power of several substances is pointed out? DISTRIBUTION OF HEAT, 31 a horizontal position, a small piece of phosphorus may be placed upon the upper extremity of each of the substances experimented upon, and the lower ends exposed to the same temperature by plunging them in heated oil or sand: and the times that elapse before the ignition of the phosphorus upon the several substances, will indicate with some accuracy their relative conducting powers. The following table exhibits the relative conducting power of several metals and other substances: ¥ Gold...... «. 1000 804 Silver... w. 978 18¢ Copper..... 898 28 Platinum.. 381 12 Tron...... we 874 11 LNG wiresssvsaceeves a dubiintin giosuea te 363 In the arts, advantage is taken of the imperfect conducting powers of bodies, to prevent the passage of heat in any direction, particularly in confining it. Hence furnaces are generally lined with “ fire-brick,” or a thick coating of clay and sand. Wooden handles are fitted to metallic vessels, or a stratum of wood or ivory is interposed between the hot vessel and the metal handle. Ice-houses are constructed with double walis, which have their interstices filled with fine charcoal, saw-dust, or some other non-conducting substance, to prevent the influx of heat from without. The design of clothing is to retain the heat produced by the system; and hence the warmest clothing will be that which possesses the least conducting power. In winter, the poorest conductors are selected, and in summer the best, as it is then desirable that the superfluous heat may be permitted at once to escape. If, in summer, the temperature of the atmosphere should rise considerably above that of the system, it would be found advantageous to use the same clothing as in cold weather. Snow, in consequence of its imperfect conducting power, serves as clothing to the earth, and prevents its surface from being cooled down as low as it would otherwise be. Inquids of all kinds, except mercury, are poor conductors of heat. This may be shown by ce- menting a thermometer tube in a glass funnel, yoy hae inverting it, and filling it with water, so as to Ether burnson the cover the bulb about a quarter of an inch, or — *™*/#ee of Water. even less, as shown in the figure. Then pour upon the surface QuEstions.—What is the use of “ fire-brick” in coal-stoves? How are ice-houses constructed? What is the design of clothing? What is said of the benefits of snow in winter? How is the poor conducting power of liquids shown by the burning of ether? 32 DISTRIBUTION OF HEAT. of the water a little sulphuric ether, and inflame it; the ether will burn brilliantly, but without affecting the thermometer for some time, although the flame is so very near the bulb. S In like manner, heated oil, poured ; upon the surface of water in a tum- bler, can scarcely be made to affect a small thermometer placed at the bottom. If a tube ten or twelve inches long be nearly filled with water and placed in an inclined position, so that the heat of a spirit-lamp can be applied near the centre, the water in the upper part of the tube may be made to boil, while the lower portion will remain per- feetly cold. If, before applying the heat, a piece of ice be con- fined to the bottom, it will remain unmelted while the water above is boiling. Mercury, though liquid, is a very good conductor of heat. Gases are even poorer conductors than liquids; and it is for this reason that very hot or very cold air can be endured in contact with a person, though exposure to a liquid of the same temperature would produce intense pain, or perhaps even worse effects. Double windows and double doors, with air between them, are sometimes used to insure the greater warmth of dwellings. 29. Convection of Heat.—Though fluids are poor conductors of heat, yet, if the heat be applied to the bottom of the vessel con- taining them, in consequence of the mobility of their particles, it is rapidly diffused through the whole mass. The heated portions are expanded, and becoming, in consequence, specifically lighter than the rest, they rise through the centre of the vessel, the colder portions around the sides at the same time descending to take their place. Thus an upward and a downward current will be at the same time established, which will continue until the whole is heated to the boiling point. This mode of distribution is called the convection of heat. y Nae, Water boils in vessel with Ice. Questions.—How is the poor conducting power of liquids shown by the boiling of water in a vessel containing ice? 29. How is the heat dis- tributed through a liquid when it is applied to the bottom of the vessel containing it? What name is given to this mode of the distribution of heat? DISTRIBUTION OF HEAT. 33 These currents may readily be shown by filling o flask with water containing some insoluble powder, as pulverized gum copal, and APES the heat of a small lamp, as represented in the figure. When large quantities of water are slowly heated, the upper portions will frequently be found quite warm, while that in the lower part of the vessel will remain comparatively cold; and this though the fire is applied beneath, Hence it is not unfrequent, in bathing establish- ments, to draw both warm and cold water from the same reservoir. Similar currents are produced in gases when heated; and it is on this account that the heated air, with the smoke and other gases from a fire, ascend in a chim- ney, or the pipe from a stove. 30. Radiation of Heat.—A hot body suspended in the air emits heat in all directions in right lines, like Currents formed in vessel of Water radii drawn from the centre to the caches surface of a sphere. This mode of distribution 2 is termed the radiation of heat. The radiation of heat from hot bodies is singularly influenced by the nature and condition of their surfaces, which is perhaps the most important circumstance connected with the subject. It is probable that every sub. stance in nature has a radiating power peculiar to itself, but, in any case, very much will depend upon the nature of the surface of the body. By many experiments, it has been proved that bodies with bright polished surfaces retain their heat much longer than when their surfaces are rough and unpolished. Adding even a thin coat of whiting or lampblack to a bright tin vessel greatly increases the radiating power of its surface, so that boiling water or other hot liquid contained in it will be cooled more rapidly in consequence. The same effect will be produced by scratching its surface with coarse sand-paper. Some important practical considerations will naturally suggest themselves in connection with this subject. Whenever it is desired that the heat of a fluid or other substance should be retained, vessels with bright and polished - metallic surfaces should be used, but the reverse if the heat is to be distri- buted. Thus tea and coffee pots are usually made of some bright metal, while stoves and stove-pipes, for the diffusion of heat, are made with dark and rough surfaces. Pipes to convey steam from the, boilers in steam- engines to the cylinders, and pipes to convey heated air from furnaces to the different apartments of a building, should be bright, or else they should be protected by some non-conducting covering. QuEstions.—30. When is heat said to be radiated? How is the radia- tion of heat affected by the nature of the surface of the heated body? What surfaces radiate best? What practical considerations suggest themselves in view of these principles ? 34 DISTRIBUTION OF HEAT. 81. Reflection of Heat.—That heat may be reflected, 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 per- mits the observer to see in it the reflection of the fire; as soon as it is brought to this inclination, a distinct impression of heat will be produced 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 2 Pp to the spot where its heating power is exerted, L ' ‘RB. the angles which these lines form with a line s perpendicular to the reflecting plane are called the angles of incidence and reflection, and are invariably equal to each other. Thus, let AB (see figure) be the reflecting EE eT surface, and R a ray of heat, which strikes A D ‘'B this surface at D, in the direetion RD; it Reflection of Heat. will be thrown off or reflected in the direction eee DI. Ifaperpendicular PD be erected at the point D, the angle RDP will be the angle of incidence, and IDP the angle of reflection. These principles, which have just been developed concerning heat, apply as well to the invisible rays emitted from a moderately heated substance, as to those accompanied by light from an incandescent body, or the rays of the sun. é 82. The Absorption of Heat by bodies sustains an intimate relation both to its radiation and reflection. Bright and polished surfaces, it is well known, are the best reflectors; and these are just the ones, we have seen (30), which radiate least. And rough, unpolished surfaces, which radiate heat best, are found to be the best absorbers. Surfaces may therefore be divided into two classes, those which afford an easy passage to heat, and those which do not. The former will be good radiators and absorbers, and the latter good reflectors and retainers. The color of a body influences considerably its absorbing, but not its radiating power; surfaces that are black, other things being equal, absorb-. ing heat more readily than those of a lighter coldr. Questions.—81. How may the reflection of heat be shown? Define the angles of incidence and reflection. Do these principles apply to rays of heat unaccompanied by light? 32. What surfaces are the best absorbers of heat? Into what two classes may surfaces be divided in reference to their power to transmit heat? DISTRIBUTION OF HEAT. 35 Both the radiation and the reflection of heat are well shown by placing a heated cannon-ball in the focus of a concave reflector, having another similar refléctor facing it at a distance, in the focus of which is placed one Parabolic Reflectors. of the bulbs of a differential thermometer, The rays from the ball C are reflected in parallel lines from the reflector A (see figure), and are again concentrated on the thermometer D, by reflection from the second o@hcave mirror B. : If a piece of phosphorus be substituted for the thermometer at D, it may cften be inflamed, even when the reflectors are ten or twenty feet distant from each other. ; . If a lump of ice is made use of, instead of the heated ball, the thermo- meter in the focus of the other reflector will fall; in which case the bulb of the thermometer is the radiating body, and its heat is received by the ice. 33, Transmission of Heat—When a ray of heat is thrown upon a body, it must either be reflected, absorbed, or transmitted by the body. We have already seen the conditions upon which reflection and absorption depend, and it remains only to consider the circum- stances of transmission. In general, transparent substances afford the most ready transmission of heat, but there is a great difference among them in this respect. Even atmospheric air transmits heat but imper- fectly. This is shown conclusively by an experi- ment of Davy. He contrived to heat a platinum wire by means of galvanism, within a receiver con- I taining two concave reflectors, with a thermometer eae aoe in the focus of one of them, the heated wire being See er aie oe in the focus of the other. Now, when the air was exhausted to ,},th part of its ordinary density, the thermometer, it was Questions.—Explain the effect of parabolic reflectors in reflecting heat. How is a lump of ive to be used instead of a heated ball? 83. When a ray of heat falls upon a body, in what three ways may it be disposed off How does the presence of the air affect the transmission of heat? 36 RELATION OF HEAT found, would be raised, by means of the ignited wire, three times as high as when the air in the receiver was at its natural pressure. Bodies that transmit heat freely are said to be diathermanous (from the two Greek words, dia, through, and thermos, heat), as those which afford a free passage to light are said to be transparent. By experiments made with a very delicate piece of apparatus, called the thermo-mulliplier, it has been shown that the most diathermanous sub- stance known is rock-salt, in pure transparent crystals. Of different specimens of glass, some are much more diathermanous than others, though all are equally transparent ; and some colored glasses, and other bodies only partially transparent, afford w ready passage to heat, or are highly diathermanous. It appears, also, that the ray of heat, like a ray of light, is really com- pound, or composed of rays of heat of different kinds, some of which have a greater penetrating power as regards most diathermanous media, than ‘others. In this respect heat from an oil-lamp will differ from that of a spirit-lamp, though both are equally intense; and the heat of both will differ from that of heated metal. The rays of heat from the sun possess this penetrating power, as I have called it, in a greater degree than any kind of artificial heat. Thus, a pane of window-glass, held between the face and a coal-fire, is found at once to intercept most of the heat; but no such effect is produced by holding it before the face when exposed to the direct solar ray. ; The rays of heat, like those of light, may be refracted; and some of them being more refrangible than others, like the different colors of light, they may be separated from each other by means of the prism. The ray of heat, like a ray of light, may also be polarized, and in a similar manner. See Decomposition and Polarization of Light. RELATION OF HEAT TO CHANGES IN THE STATE OF BODIES. 34. Relation of the Three Forms of Matter to each other.— We have seen above (10), that, omitting the imponderable agents, which are not known to be material, every substance must be in one of the three forms, or states, solid, liquid, or gaseous; and that the particular form a body assumes will depend upon the relative intensity of the cohesive and repulsive forces existing among its particles. If the repulsive force be comparatively feeble, the particles will adhere so firmly together, that they cannot move freely upon one another, thus Questions.—What are diathermanous bodies? Will heat from all sources be transmitted alike? What is said of the rays of the sun in this connection? May the rays of heat be refracted? Polarized? 34, Upon what will the particular form or state of a body depend? : TO CHANGES IN BODIES. 37 constituting a solid. If cohesion is so far counteracted by repulsion that the particles move on each other freely, a liquid is formed; and, should the cohesive attraction be entirely overcome, so that the particles not only move freely on each other, but would, unless restrained by external pres- sure, separate or expand to an indefinite extent, an aeriform substance will be produced. Now, the property of repulsion is manifestly owing to heat; and as it is easy, within certain limits, to increase or diminish the quantity of this principle in any substance, it follows that the forms of bodies may be made to vary at pleasure: that is, by heat sufficiently intense, we have reason to believe, every solid, provided decomposition does not take place, may be converted into a liquid, and every liquid into vapor. The converse ought also to be true; and, accordingly, several of the gases have been condensed into liquids by means of cold, or cold and pressure combined, and the liquids have been solidified. ‘The temperature at which liquefaction takes place is called the melting point, or point o fusion; and that at which liquids solidify, their freezing point, or point of congelation. Both these points are different for different substances, but usually the same, under similar circumstances, in the same body. 35, Liquefaction.—By the liquefaction of a substance, we mean its reduction from either the solid or gaseous to the liquid state; but generally it is the former change which is intended. Tf, when the temperature of the air is at zero, as is often the case in some parts of our country, a quantity of ice be brought into a room, and placed near a fire, it will be gradually heated, like any other solid, as a thermometer placed in it will indicate, until the temperature reaches 32°; but it will stand at this point until the whole is melted. The thermometer will then begin again to rise, as it did before. Now, it is plain that it must have been receiving heat as rapidly while the thermometer was stationary, as before and afterwards; but the heat thus communicated did not affect the thermometer, because it was all absorbed by the ice, and was expended in changing the ice into water. It has there- fore become insensible to the thermometer, and is properly called latent heat; and if it was known to be material, we might per- haps, with some propriety, consider water as a compound of ice and heat. The quantity of heat which is thus lost or becomes insensible, during the melting of a mass of ice, is sufficient to raise the tem- Questions.—To what is the property of repulsion owing? What is the melting point of a body? The freezing point? 85. What is meant by the liquefaction of a body? Is heat always required to produce lique- faction? Why cannot ice be heated above 32°? 4 88 RELATION OF HEAT perature of an equal weight of water about 140°, as may be shown in the following manner: Let a pound of water at 32° be mixcd with a pound of water at 172°, and the temperature of the mixture will be intermediate between them, or 102°. But if a pound of water at 172° be added to a pound of ice at 32°, the ice will quickly dissolve, and on placing a thermometer in the mixture, it will be found to stand, not at 102°, but at 32°. In this experiment, the pound of hot water which was originally at 172°, actually loses 140° of heat, all of which enters into the ice, and causes its lique- faction, without affecting its temperature. 36. Heat of Fluidity—The heat thus required for the lique- faction of solids is often called their heat of fluidity; and the quantity necessary for the purpose is not the same in any two substances. While the heat of fluidity of water is, as we have just seen, 140°, that of spermaceti is 145°, that of lead 162°, that of tin 500°, and that of bismuth 550°. That is, to melt any given weight of one of these substances, an amount of heat is required that would heat the same weight of the substance the number of degrees indicated, provided no change of state should take place during the process. The melting point of nearly all substances is the same as their freezing point; but this point varies greatly in different substances. Thus, solid mercury melts (and liquid mercury freezes) at —39°; ice at 82°; sperma- ceti at 132°; sulphur at 226°; tin at 442°; lead at 612°; zine at 778°; silver at 1873°, and gold at 2016°. 87. Freezing Mixtures are made of various salts and liquids, which have such an affinity for each other, that rapid liquefaction is produced, without the direct application of heat. But as this agent is always required when this change takes place, it must be absorbed from surrounding objects, which therefore lose their heat, or become cold. A good mixture of this kind is made of snow, or finely broken ice, and common salt, both of which, when mixed together, become rapidly liquid; and the process is attended with great cold, so that a thermometer immersed in it will fall to zero, Questions.—What is the quantity of heat absorbed by ice when it is melted? How is this shown? 86. What is the heat of jluidity of a sub- stance? Will it be the same in all substances? What are the melting points of the several substances mentioned? 37. What are Sreezing mixtures 2 TO CHANGES IN BODIES. 39 or below. Of course, if a vessel of water be immersed in it, the water will in a short time be frozen. Saltpetre, dissolved in cold spring water, will often reduce the tem- perature to 32°, or lower, so that water may be frozen by it; but the greatest cold is produced in this mode by mixtures of certain of the salts and acids. Thus, powdered sulphate of soda three parts, and diluted nitric acid two parts, mixed at 50°, will sink the temperature to —8°; and phosphate of soda nine parts, and the same diluted acid four parts, will produce a cold of —12°. The greatest cold that can be produced in this way is found to be about —100°, but by other means still lower tem- peratures have been obtained. But it is not possible, in the present state of our knowledge, entirely to deprive a body of heat. Since solids, on becoming liquid, absorb heat, as we have seen, it necessarily follows, that when liquids become solid, heat must be given out. The freezing point of water is usually said to be 32°; but if it be contained in a close vessel, and cooled very slowly without agitation, its temperature may be reduced, without freezing, to 20°, or lower. Slight agitation will now case it to freeze sud- denly, and the temperature will rise at once to 82°, the ordinary freezing point. The portion that has frozen, therefore, has given out sufficient heat to raise the temperature of the whole mass some 12°. Saturated solutions of several of the salts, made at elevated temperatures, upon being slowly cooled, exhibit the same phenomenon. A beautiful experiment may be performed by making a satu- rated solution of Glauber’s salt in warm water, and setting it aside in a closely corked-vial till it cools. If now the cork be removed, or the vessel violently agitated, the salt will immediately crystallize, and a thermometer placed in it will rise several degrees. 38. Provision of Nature—We cannot but notice here the beautiful and unexpected manner by which nature, to some extent at least, checks the cold of winter, which might otherwise be destructive. The cold atmosphere causes large quantities of water to congeal, but at the same time heat is given out, which prevents so great a reduction of temperature as might, but for this circumstance, be experienced. Questions.—What is the greatest cold that can be produced by freezing mixtures? Is heat given out when liquids become solid? May water have its temperature reduced below the ordinary freezing point? What is the effect on the thermometer when freezing at length is produced? Describe the experiment with Glauber’s salt. 38. How is the excessive cold of winter to some extent checked? 40 RELATION OF HEAT The peculiar mode provided by the Creator to check the heat of summer, which might otherwise become excessive, will be noticed hereafter. 39. Vaporization.—By the term vaporization is meant the conversion of solids or liquids into gases. Aeriform bodies are often divided into vapors and gases, accord- ing to the relative force with which they resist condensation; but the distinction is of little consequence. Heat is always required to convert a solid or liquid into a gas; usually, it is communicated directly; as when water is made to boil over a fire, but if not applied directly, it will always be absorbed from surrounding bodies. * In most cases, when heat is applied to solids, they first melt, or become liquid, and afterwards, by a continuance of the heat, are converted into vapor; but some, as metallic arsenic, and certain salts, pass at once, when heated, from the solid to the gaseous state. Gases occupy considerably more space than the liquids from which they are formed. Water, when converted into steam, expands about 1700 times, so that a cubic inch of water forms nearly a cubic foot of steam; but most liquids expand much less than this. Alcobol, for instance, is expanded, when converted into vapor, only 659 times its original volume, and sulphuric ether 443 times. Volatile substances are such as are readily converted into vapor by heat or at ordinary temperatures, while those that are incapable of this change are often called fixed substances. Two or more gases, whatever may be their density, when brought in contact, readily intermix with each other, and become equally diffused through the vessel that may contain them. This is seen in the atmosphere, which is composed of gases differing in density, but they remain uniformly diffused. If we fill two bottles with gases of different densities, as hydrogen and carbonic acid, and connect them by a narrow tube, as shown in the figure on p. 41, the lower containing the most dense gas, in a short time the two Questions.—What is meant by vaporization? Is heat always required when a vapor is formed? Do gases occupy more space than the solids or liquids from which they are formed? How many times does water expand when it takes the form of steam? Alcohol? Ether? TO CHANGES IN BODIES. 41 gases will diffuse themselves equally through the whole space. The mixture of the gases will even take place through thin membranes, whether animal or vegetable; the least dense of the gases passing the most rapidly. A good method to show this is to fill an ox bladder with carbonic acid, or even atmospheric air, and suspend it with the neck tied firmly in a large vessel filled with hydrogen. A transfer of the gases through the substance of the bladder will take place, but the hydrogen entering more rapidly than the denser gas escapes, the bladder will after a time be burst. 40. Ebullition—Boiling Point—When a liquid in an open vessel is exposed to any source of heat, the temperature gradually rises, like that of any other sub- stance in similar circumstances, until a certain point Diffusion of is attained, when a violent motion commences in it, “** called ebullition or boiling; and no heat can then cause any further increase of temperature. If the heat be continued, the quantity of liquid gradually diminishes, or, as we familiarly say, is boiled away, until the whole is gone. The commotion in the liquid is occasioned by portions of it at the bottom, where the heat is applied, being converted into vapor, and rising in bubbles to the surface. Ordinarily it will be found that water boils at 212°, which is therefore called its boiling point; but the temperature at which other liquids boil is not necessarily the same, every liquid having a boiling point peculiar to itself. Thus, the boiling point of alco- hol is only 173°, and that of sulphuric ether 96°, while that of sulphuric acid is 620°, and that of mercury 662°. 41. Boiling Point dependent upon Circumstances.—But the boiling point of a liquid is not to be considered as perfectly con- stant; it depends upon several circumstances, the most important of which is the pressure of the atmosphere upon the surface of the liquid. By heating a small vessel of water to about 200°, and placing it under-the receiver of an air-pump, it begins to boil when the air is very moderately exhausted. So, on ascending a mountain, by Questions.—What is said of the diffusion of gases of different densi- ties? Describe the experiment with the ox bladder. 40. What is ebulli- tion or boiling? What is the effect of continuing the heat? What is the boiling point of water? Is this point in other liquids the same? 41. What are the circumstances which affect the boiling point of aliquid? Describe the ee with the air-pump. 49 RELATION OF HEAT which a part of the atmospheric pressure is avoided, the boiling point falls in proportion to the ascent. At the hospital of St. Bernard, situated upon a point on the Alps, about 8400 feet above the sea, water boils at 196°; and on the top of Mount Blanc it was observed by Sausure to boil at 184°. This is just as we should expect, for the expansion of the vapor has to take place directly against the pressure of the atmosphere on the surface of the liquid; and the degree of heat necessary to produce the expansion will be to some extent proportional to the expansive forcé required. The pressure of the atmospbere at the surface of the sea is usually about 15 pounds to each square inch, but it is subject to some variation ;' and the boiling point of any liquid will of course vary at the same time with the atmospheric pressure. In a perfect vacuum, water boils at 72°, and sulphuric ether at —46°, or about 140° lower than in the open air. As might be expected, sulphuric ether may easily be made to boil under an exhausted re- ceiver, without heat, even in the coldest weather. For this purpose let a little good ether, in a wine- glass, be placed under an air-pump receiver, as represented in the figure; upon working the pump, it will boil violently. The experiment will usually succeed best if some small pieces of metal are dropped into the ether, before placing it under the receiver. While the boiling is in progress considerable reduction of tem- perature takes place, and water contained in a small vial placed in the ether will be frozen. 42. Other circumstances affecting the boiling point are, the: nature of the containing vessel, and the presence of soluble sub- stances in the liquid. Thus water boils in metallic vessels at 212°, but in a clear glass vessel one or two degrees more are Boiling of Ether. Quzstions.—What is said of the boiling point upon high mountains? What is the boiling point of water in 1 vacuum? Describe the experi- ment with ether under the exhausted receiver of the air-pump? While the ether boils how is the thermometer in it affected? 42. What other circumstances are mentioned as affecting the boiling point? TO CHANGES IN BODIES, 43 ‘ required; so any substance, as a salt, held in solution in the water, causes a rise of the boiling point. Water saturated with common salt boils at 224°; saturated with saltpetre at 238°, and with chloride of calcium at 264°. : 43, Effect of increased Pressure.—If water or other liquids boil at a lower temperature by diminishing the pressure upon the surface, so a higher temperature is re- quired for this purpose when the pres- lad sure is increased, as in a steam boiler. : Water cannot be heated above 212° in : | the open air, because any additional heat ow is expended in converting a portion of it into steam, which at once makes its escape into the air; but if it be confined in a strong vessel, it may be heated to any ee temperature even to redness. The rise of the boiling point under LU increasing’ pressure is well illustrated and c proved by WMarcet’s steam apparatus, Ure which is represented in the accompany- ing figure. A is a hollow brass globe, He supported on a stand, and in it is con- @ tained a little mercury, and a small quan- tity of water. Through an air-tight collar, a graduated glass tube, C, is inserted, so as to reach very nearly to the bottom, both ends of it being open. B is a ther- mometer, having its bulb in the water or mercury. Now, by applying a lamp the water is heated, and when the tempera- ture has risen to 212°, the steam will begin to issue freely through the faucet, F; but, by closing the faucet, the escape of the steam will be prevented, and the temperature will rise; the mercury at the same time by the pres- sure of the steam within, being forced up the tube C0. And the Marcet’s Apparatus. _ Questions.—43. Why cannot water be heated above 212° in the open air? What, if the steam be confined? Describe Marcet’s steam apparatus. 44 RELATION OF HEAT height to which it may rise will always show the exact amount of the pressure. By this means it has been determined that, at a heat of 250°, the tension of steam, thus confined in a boiler, is equal to two atmospheres, or 80 pounds to the square inch; at 275° its tension is equal to three atmospheres; and four atmospheres, or 60 pounds to the square inch, at 294°. The expansive force of steam’ confined in this manner is the propelling power in the steam engine. (See author’s Nat. Philo- sophy, p. 178.) ; 44, Evaporation.— But it is not only when a liquid is heated, and made to boil, that it is changed into vapor; this change, in most, and probably in all liquids, and many solids, is ever taking place, whatever may be their temperature, when they are con- tained in open vessels. This slow formation of vapor is termed evaporation. It is seen in the drying of clothes, when wet with water or alcohol, and in the gradual diminution of a quantity of either of these liquids, when left in an open vessel. Hven in the forms of ice and snow water gradually evaporates. Evaporation is much more rapid in some liquids than in others; and it is always found that those which have the lowest boiling point evaporate with the greatest rapidity. Thus, alcohol, 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 evapora- tion, are extent of surface, and the state of the airas to temperature, dryness, stillness, and density. The same quantity of liquid, exposed in a shallow vessel, will evaporate more rapidly than in one of a different form, because of the large amount of surface in contact with the air; so, also, currents in the air increase evaporation by removing the vapor as fast as it is formed. Increased pressure of the atmosphere diminishes evaporation. Questions.—What is the tension of steam at 250°? 44. Do water and other liquids take the form of vapor without ebullition? Do all liquids evaporate with the same facility? What are the chief circumstances which influence evaporation? TO CHANGES IN BODIES. 45 45. Heat is absorbed by the Formation of Vapor.—During the slow evaporation of water, or other liquids, as well as when they are evaporated by boiling, a large amount of heat is absorbed, and becomes latent in the vapor produced. It is on this account that ether, alcohol, or even water, though at the same temperature as the air, always feels cold when a little is dropped upon the hand. The natural heat of the hand is absorbed and carried off in the vapor that is formed. The evaporation of good sulphuric ether may easily be made to freeze water, even in the warmest weather. For this purpose let a very small glass vial, covered with muslin, be filled with water, and suspended by the neck from some convenient support; then drop slowly upon the muslin good sulphuric ether, from the mouth of a vial, or by means of a dropping tube. In a few minutes, ice will begin to form; and if the operation be continued, the whole of the water will be frozen, perhaps breaking the vial containing it. Porous earthen vessels are often used in hotels and other places, in warm weather, to contain water for drinking. A portion of the water gradually exudes through the vessels, and eva- porates from the surface, by which that within is kept several degrees colder than the tem- perature of the atmosphere. Such vessels are said to be much used in Spain, where they are called alcarrazas, People crossing the deserts . of Arabia in caravans, are said sometimes toload == s camels with earthenware bottles filled with water, Freezing of Water by Evapo- which is kept cool by wrapping the jars with ration of Ether. linen cloths, and keeping them moist with water. 46. The freezing of water by its own evaporation under the receiver of an air-pump, is a common experiment. A shallow dish containing strong oil of vitriol is first placed upon the plate of the machine, and over it, supported by a tripod of wire, is placed a small capsule filled with water. The receiver being now put in its place, covering the whole, by working the pump the Questions.—45, Is heat absorbed during the slow evaporation of a liquid? Describe the mode of freezing of water by the evaporation of ether. 46. Describe the experiment with water and sulphuric acid under the receiver of the air-pump. 46 RELATION OF HEAT Freezing Water under Ex- hausted Receiver with Oil of Vitriol. air is exhausted, rapid evaporation from the surface of the water commences, which is continued because of the absorption of the vapor by the acid beneath, until the water is frozen. Without the acid, or other substance to produce the same effect, the receiver would soon be filled with vapor, and no further evaporation take place; the vapor of water, at ordinary temperatures, not having sufficient tension to lift the valves of the pump, as it is worked. Indeed, a small drop of water may be frozen under the receiver of an air-pump by its own evaporation, without the use of any substance to absorb the vapor. Let a single drop Freezing Water by its own Evaporation. of water, on a piece of charred cork, hol- lowed a little on its upper surface, be placed under the air-pump receiver, and by working the pump a few seconds, it will be frozen by the rapid evaporation which takes place from its surface. The burnt cork capsule is preferable to one of glass or metal, since, as the water does not adhere to its surface, not so much heat is received from it. 47. Latent Heat of Vapors.—lIt is not easy to determine with precision the amount of latent heat in vapors, or the relative quantity of heat absorbed as they are formed. The results obtained by different experimenters, therefore, are not uniform. It is believed that water, in taking the form of vapor, absorbs nearly 1000° of heat, or heat enough to raise the temperature of an equal weight of water 1000°, if it could be confined. The amount of heat in different vapors varies Qursrions.— What purpose does the acid serve? Explain the method of freezing a drop of water upon s piece of burnt cork under an exhausted receiver. 47. What is the amount of latent heat in steam? TO CHANGES IN BODIES. 47 with their nature; in no two vapors is it the same. Thus, while the latent heat of watery vapor is, as we have seen, about 1000°, that of vapor of alcohol is only 373°, that of vapor of ether 163°, vapor of oil of turpentine 138°, and of sulphide of carbon 144°. The heat which is absorbed when water or other liquid is con- verted into vapor, will, as a matter of course, be given out again when this-vapor is condensed into the liquid form. On this prin- ciple, steam is often used for warming buildings, being conveyed in pipes through the different apartments. As it passes along the pipes, it is condensed, giving out its heat; and the water that is formed runs back again into the boiler. 48. Distillation—The process of distillation consists simply in evaporating a substance, and again condensing the vapor, by causing it to come in contact with a cold surface. This is usually accomplished by having a tube of considerable length, leading from the top of a close boiler, and passing in the form of a spiral through a vessel which is kept filled with cold water. In the laboratory, the apparatus figured below answers well for distilling small quantities of any liquid. A retort, R, con- tains the liquid to be distilled, and the vapor is received into a flask, F, the mouth of which is slipped on the neck of the retort, but the joint not made perfectly air-tight. The flask should be kept cold: by being immersed in cold water, or by having a small stream’ of water constantly falling upon it from a vessel above. For larger operations, a Lei- % big’s condenser is indispensable. It consists of a glass flask, for a 7 boiler, which may be heated in o small furnace, as represented in the figure on page 48, or by means of a spirit-lamp, and a metallic case, a, in which is inserted, through perforated corks, a glass tube, dd, designed Questions.—Describe the mode of warming buildings by the use of steam, 48. In what does the process of distillation consist? 48 RELATION OF HEAT to be kept constantly surrounded with cold water.- From the vessel, i, a stream of cold water enters the funnel, c, and, as it is heated, escapes at the highest part by the tube, A, and is collected in a basin, 6. The glass tube, dd, is connected at one end, by means of a smaller tube, with the boiler, and at the other end, with the receiving-vessel, e, in which is col- af | | _ (Sa iy | ae ui i H " Distillation. lected the distilled liquid condensed in passing through the tube, dd. The crooked funnel in the boiler serves to introduce the liquid to be distilled. By the process of distillation volatile substances, whether liquid or solid, may be separated from those that are fixed, or even from such as are less volatile than themselves Water is distilled to purify it from salts or other substances it may contain in solution or suspension; and alcohol, by distillation, is separated from water, which is less volatile than itself, as well as from fixed substances. The application of this process to solids is usually termed their sub- Umation. 49. Boiling produced by Cold. We have seen above (41) the effects of diminishing or removing the atmospheric pressure in promoting ebullition, and we are now prepared to understand another ingenious method of accomplishing this object. Let a flask, with a cork well fitted to its mouth, be partly filled with water, and made to boil briskly by means of a spirit-lamp; then suddenly insert the cork and remove the lamp: the water will \ Questions.—Describe Leibig’s condenser. How is it that substances may be separated from one another by distillation? 49. Describe the experiment of boiling water by the application of cold. TO CHANGES IN BODIES. 49 continue to boil, and by immersing it in cold water, as shown in the figure, the boiling will become violent. The same effect will be pro- duced by inverting ‘the flask and applying snow or even cold water to the bottom. But if the flask be held again a moment over the lamp, the boiling will instantly cease. The reason of this is, because the upper part of the flask, when the cork is inserted, is filled with steam, which is condensed by the appli- cation of cold to the outside, and a vacuum produced. The warm water within then boils, as in a vacuum produced by any other means; but if heat be applied, steam will be again formed, and fill the upper part of the flask, and, by its pressure upon the surface of the water, prevent further boiling. If the flask is firmly corked, so as to exclude the air perfectly, when it has become cold the water within, as the flask is handled, will fall from side to side, almost like masses of ice, and producing a similar sound to the ear. This is because there being no air within to break up the water as it is thrown in any direction, it falls in a mass and strikes against the sides of the glass with much the same effect as a solid. A small toy of this kind, made of glass tube, and hermetically sealed, is called a water- hammer. 50. The Cryophorus.— The cryophorus, or Srost-bearer (from the two Greek words, cruos, frost, and phero, I bear), is an instrument for freezing water by its own evaporation, which beautifully illustrates some of the foregoing principles. It consists of a tube, half an inch or more in diameter, with a bulb blown at each end, one of them having a small aper- ture, A, by which a small quantity of water is introduced, sufficient only partly to fill one of the bulbs. This water is first all collected in the lower bulb, and the heat of a lamp 4 ———— applied, so as to cause it to boil briskly; and Cryophorus. while the interior is filled with steam, the aperture at A is quickly Boiling by Col Questions.—What will be the effect of holding the flask over a lamp? What is the effect if, when cold, the flask is shaken? 60. Deseribe the eryophorus. 50 RELATION OF HEAT sealed hermetically, and the lamp removed. When it has become cold, the water is passed to the upper bulb, as represented in the figure (p. 49), and the instrument supported on a stand, with the lower bulb in a beaker glass. All the interior is now filled with vapor of water, except a part of the upper bulb, but no evapora- tion of the water can take place, because of the presence of this vapor. But by removing the vapor, which is accomplished by sur- rounding the lower bulb with a freezing mixture of salt and snow, to condense it rapidly, evaporation of the water is produced, attended with cold sufficient to freeze the most of it, even in the warmest weather. 4 The pulse-giass, as it is called, is a very similar instrument, and is made in the same manner, except that ether is used in it, instead of water. By grasping one of the bulbs J firmly in the hand, the vapor, by its pateaee" - expansion, will immediately force all the liquid into the other; and the moment it has all passed through the stem, an appearance of vio- lent ebullition is produced, attended by a distinct sensation of cold in the hand which grasps the bulb. This is occasioned by the rapid evaporation of the film of liquid lining the inside of the bulb. 51, Effect of Perspiration upon the Animal System.—The effect of evaporation in withdrawing heat is admirably illustrated by the process of perspiration. The natural temperature of the human body is about 98°, but when we take active exercise, or are exposed to a great degree of heat, there is a tendency to a rise of tempera- ture above that which is conducive to health; and the most injurious effects would ensue, if they were not prevented by the rapid evaporation which takes place from all parts of the surface of the system. Examples of the power of the human body to sustain great and apparently even dangerous elevations of temperature, are on record: It is well known that individuals have voluntarily exposed them- Qurstions.—Describe the pulse-glass. 51. What is the effect of perspira- tion upon the animal system? Will the human body sustain high tem- peratures for a time without injury? TO CHANGES IN BODIES. 51 selves for several minutes,in ovens, to temperatures even a hun- dred degrees above that of boiling water, without suffering any injury. The very rapid perspiration that takes place in such cir- cumstances, prevents the destructive elevation of temperature in the system which would otherwise take place. 52. Temperature of the Seasons Modified.—The heat of sum- mer is always greatly modified by the evaporation which take place from the surface of the earth, and the stalks and leaves of plants and trees. When a stalk of Indian corn (zea maize), or other plant, is cut down in midsummer, or a branch removed from a tree, the leaves soon begin to wither, because of the eva- poration of the moisture in them. But the evaporation is no more rapid from them after being cut than before, but now the supply of water from the earth, received by the roots, ceases, and the withering we notice is a necessary consequence. We see therefore that vegetation in warm weather is sending forth into the atmosphere immense quantities of water by evaporation, besides that which rises from the surface of the earth itself; and as a result, the temperature of the atmosphere is more or less cooled. In other words, the heat is thus prevented from becoming as excessive as it would be but for this arrangement. We have seen above (88) that heat given out by the freezing of water in winter, prevents the low reduction of temperature that would otherwise be experienced; and we cannot here less admire the wonderful provision of Providence, by which, on the other hand, the excessive heat of summer is, to some extent, limited. 58. Liquids upon very Hot Surfaces.—Liquids, as water,~thrown upon metallic surfaces, heated nearly to redness, instead of adhering to the surface and rapidly evaporating, will sometimes be seen to roll around in globules, apparently without touching, until at length they gradually disappear. This is occasioned by an atmosphere of vapor that is formed around the globules of liquid, by its rapid formation preventing the tem- perature from rising as high as the boiling point, and also by its elasti- city preventing the liquid from coming in contact with the metallic plate. Alcohol dropped upon the surface of heated oil of vitriol, exhibits a like phenomenon. This has been called the spheroidal state of liquids. Questions.—52. How is the heat of summer modified? Why does plant-stalk, separated from its root, so rapidly wilt in warm weather Is water constantly evaporating from the leaves and stalks of plants? 53. Describe the action of a drop of water upon a very hot surface. 52 RELATION OF HEAT 54, Dew.—Dew is a deposit of moisture from the atmosphere upon a cold surface in contact with it. If, in the summer, a ves- sel is left but a few minutes filled with ice-water, or even cold spring-water, dew soon collects upon it, and after a time, the water thus condensed trickles down the surface in drops. A surface upon which dew is seen to form will always be found colder than the surrounding air; and the particular temperature at which it begins to form is called the dew-point. When the air is very dry, ‘this point will always be considerably below the temperature of the air; but when there is much moisture present this will not be the case. In fair weather, during the summer season, there is usually seen, in the morning, a copious deposit of dew upon the leaves of plants, and upon other substances exposed to the open air. This is occasioned by the radiation of heat from bodies at the surface of the earth, which takes place rapidly during the night, cooling them down considerably below’ the temperature of the air. Substances, therefore, which radiate slowly (380), as polished metallic surfaces, seldom have any dew upon them, while good radiating surfaces near them will be abundantly covered with it. In cloudy weather (without rain), there is generally little dew, because the heat radiated from the earth is reflected back by the clouds; and by suspending even a small handkerchief by the four corners, a few inches from the earth, the deposition of dew on substances under it is, for the same reason, prevented. In some warm countries, water is said to be frozen during the night by the rapid radiation which takes place from its surface. The water for this purpose is poured into shallow pans, so situated as to receive as little heat as possible from the earth. 55. Hygrometers.—Hygrometers are instruments for determin- ing the relative quantity of watery vapor present at any time in the atmosphere. Daniel’s hygrometer (represented in the figure on p. 58) is much in use. It consists of a tube, A, with a bulb at each end, and is formed in the same manner as the cryophorus Quzstions.—54. What is dew? Under what circumstances is it de- posited? How do the leaves of plants and other bodies at the earth’s surface become colder than the air? Why is there usually little dew in cloudy weather? 55. What are hygrometers? TO CHANGES IN BODIES. 53 (50), except that it contains ether instead of water. The tube is supported by a stand; and the lower bulb, which is usually made of colored glass, is about half filled with the ether, having in it the bulb of a very deli- cate thermometer, with its stem extending upward in the tube. The other bulb is empty, or contains only the vapor of ether, and is covered with muslin. To the stand B is attached a small thermometer, to indi- cate the temperature of the air. By pour- ing a little ether upon the muslin, the bulb is cooled, and the vapor of ether within condensed, and a rapid evaporation of the : B ether in the bulb produced, as in the cryo- pene phorus. This occasions a cooling of the colored bulb, and a deposition of dew upon its surface, the small thermometer within showing the exact temperature at which the process commences, which is taken as the dew-point. Properly, however, it is the difference between the temperature thus obtained, and the tem- perature of the air, which shows the real state of the air as to moisture. A decided objection to the use of this instrument is found in the fact, that it is extremely difficult to determine accurately the moment when the formation of dew upon the bulb actually commences. Its indications, therefore, cannot always be fully relied on. The wet-bulb thermometer is now mostly used to determine the hygrometric state of the atmosphere. Two thermometers are attached to the same support, as shown in the figure on p. 54, one of them having a piece of muslin wrapped around its bulb, which is kept wet by a string leading to it from a small fountain of water, attached also to the support between the thermometers. Now, as the evaporation from the muslin necessarily reduces the temperature, this thermometer will always stand a little lower than the other, the bulb of which is dry; and, moreover, as the PD H He t iB Ht H U Le! Hel Questions. — Describe Daniel’s hygrometer. Describe the wet-buld thermometer. 5* 54 RELATION OF HEAT rapidity of the evaporation from the muslin will depend upon the dryness of the air, the difference between the readings of the thermometers will indicate its true hygrometrie condition. 56. Watery vapor exists in three different states : 1. As transparent, invisible steam, as it rises from boiling water, and before it comes in contact with the air; 2. As it appears partially condensed, after escaping into the air; and 3. As it exists in the atmosphere at all temperatures, but invisible to the eye. That steam, before coming in contact with the atmosphere, is perfectly transparent and invisible, is shown by partly filling a glass vessel - with water and causing it to boil rapidly. The Wet-bulb mer™ steam within, above the water, cannot be seen until it escapes into the air, and becomes partially condensed, as stated above. Clouds are collections of watery vapor, in this partially con- densed state, in the upper regions of the atmosphere, and differ from fog only in their more elevated position. é The moisture that constitutes clouds, when fully condensed, falls in rain upon the earth, or is solidified and falls in beautiful crystals (25), as snow. If the drops of rain are frozen after they are formed, hail is produced. If in warm weather a quantity of air be forced into a large glass receiver, so as to produce a pressure of at least two atmospheres, 8 slight mistiness will usually be seen within, occasioned by a partial con- densation of the watery vapor forced in with the air. If the process is several times repeated, drops of water may be obtained, forming a kind of artificial rain. In the manner stated above, all the water upon the surface of the earth is subjected to a constant natural distillation; pure water, in the form of vapor, rises in the air from the leaves of plants, from the earth, and from the surface of the ocean, rivers, and lakes, to be again diffused, in rain and snow, over the earth, producing everywhere vigor and life, both in the vegetable and animal world. 57. Liquefaction and Congelation of Gases.—By great pres- sure, or by pressure and a low reduction of temperature, many of Quesrions.—56. In what three states does watery vapor exist? What are clouds? Whatis rain? 57. How may many of the gases be reduced to the liquid state ? a aDY g e reduce TO CHANGES IN BODIES. 55 the gases may be reduced to the liquid state, and the liquids thus formed solidified or frozen. Indeed, all gases may be considered as the vapors of extremely volatile liquids. Some of them, how- ever, have never yet been reduced to the liquid state. The usual method to liquefy a gas, is to put the materials from which it is to be formed into a strong glass tube, bent in the middle, as represented in the figure, and hermetically sealing it. As the gas is evolved the pressure of course increases, but at length a point is attained, depending upon the temperature and the nature of the gas, when it begins to condense as a liquid, the quantity of which is in- creased by the further evolution of gas from the materials, without any increase of pressure, if the temperature is kept uniform. The bent tube is particularly adapted for the liquefaction of cyanogen gas. To form this gas, dry cyanide of mercury is used, a portion of it being placed in the closed end of the tube, and the other end hermetically sealed. Moderate heat is then applied to the end containing the cyanide, the other end being cooled by a freezing mixture of snow and salt. As the cyanide is decomposed by the heat, the cyanogen first takes the gaseous form, but is subse- quently condensed by the pressure and cold, and collects in the empty end of the tube. Of the different gases, some require a much greater pressure than others to condense them to the liquid state. At 0° sulphurous acid gas becomes liquid under the ordinary. atmospheric pressure, but at 32° it requires a pressure of 2 atmospheres to produce the effect. Carbonic acid gas at 0° has a tension of 23 atmospheres, and at 32° a tension of 36 atmospheres; at higher temperatures the tension is still more increased. The liquids formed from the gases, in the manner described, may be frozen by the great cold produced by their own evapora- tion, or by exposing them in tubes to intense cold. In the former ease, the solids formed will appear like snow, and in the latter, like tlear, transparent ice. Liquefaction of Gases. Quest1ons.—What is the usual method to liquefy a gas? Do all gases require a like pressure to reduce them to the liquid state? 56 RELATION OF HEAT 58. For preparing small quantities of solid carbonic acid, the following apparatus answers well, and is much less expensive than such’as are usually purchased of the manufacturers of philoso- phical instruments. . The generator, A, is made of a common mercury flask, having the aper. ture at the neck a little enlarged, so as to be about an inch and a quarter in diameter. A plug of cast-steel, B, is then made of a bar two inches at Sid L A. least in diameter, and turned with a Ha ——— rt na wide and smooth shoulder so as to fit il accurately upon a collar of block-tin, Ti IK when screwed into its place, as repre- <= sented in the figure. The valves, | which are the most difficult part to construct, on account of the great pressure that is to be overcome, are inserted in the plugs, a second one of which, precisely like the preceding, is made to screw into the receiver, C. Into the upper end of each plug, a hole [a an inch in diameter is bored about one ra tf tf inch deep, and terminates in a conical saat TTL point ; from which an aperture, a tenth il of an inch in diameter, is bored quite Solidifying Carbonic Acid. through the plug. EH is composed of two parts, so constructed that when screwed firmly into the cast-steel plug, and the part H which terminates in a conical point screwed down, all escape of the gas from the generator is effectually prevented. When the part H is screwed upward, the escape of the gas around E is prevented by the firm pressure of the shoulder of E upon the washer I, and a shoulder upon the lower part H, which presses against the bottom of E, and produces the same effect with regard to the escape of the gas around the thread of the screw H. : Instead of the valve described above, the following answers better for the generator, as the passage at the bottom of the plug is not liable, as in the other construction, to be closed by the sulphate of soda which is formed. The part H extends quite through the plug, having at the lower extremity @ nut, P, attached firmly by a screw and soldered. Now when the screw H is turned upward, the thread on which extends from I downward about an inch, the nut P perfectly closes the passage below, but by turning the screw down, the passage through the plug is opened at P, and closed at I, allowing the gas to escape laterally, as in the other construction. The receiver, C, is made of common boiler iron, and ; should be about two inches internal diameter, and of the same height as the generator, which will make it of the capacity of Questions.—58. Describe the a acid. pparatus for preparing solid carbonic TO CHANGES IN BODIES. 57° about a pint. The tube L should screw into the plug connected with the receiver, having its other extremity terminate in a conical point to fit into a cavity prepared for it in the other plug. By means of the stirrup- screws M and N, and the block of wood QO, the receiver may then be firmly screwed in its place; and when both the valves are open, there will be a free passage between it and the gencrator, but no communica- tion of either with the open air. To make use of this apparatus, the generator and receiver are separated, and the plug B being removed, 23 pounds of bicarbonate of soda, made into a paste with the same weight of water, sre introduced into A, and 214 ounces of strong sulphuric acid are poured into several copper ves- sels, made a little shorter than the length internally of the generator, and of such a diameter that they will just pass the aperture. These being nearly filled with acid are dropped into the generator, which, after the plug B is inserted, is allowed to lie on one side for fifteen’ or twenty minutes, and several times rolled over, to mix the acid with the soda. The receiver is‘then attached to it as seen in the figure, by means of the stirrup-screws M and N; and, if kept sufficiently cool by means of ice, the liquid carbonic acid formed in A will shortly be distilled over into C, the passage between them being of course previously opened. _ ‘The valves are now to be closed, and the receiver, which contains the liquid carbonic acid, separated from the generator. A small tin cup (not represented in the figure) is them to be attached to the tube L, to receive the jet of acid from the receiver. It is essential that the liguid acid should escape into this cup, which is effected by having a small tube pass from the steel plug nearly to the bottom of the receiver, or by inverting the receiver before opening the valve. : The apparatus should be well tested, at least three times, before run- ning any risk by venturing to handle it while charged. This is best done by means of a hydraulic press; but the same object may be accomplished very effectually by standing the apparatus when charged in a tub of water heated to about 150°, so that when the apparatus and water have attained the same temperature, it shall not be lower than 130°. Ifa more severe test is desired, the water may be made still warmer. In constructing an apparatus, care should always be taken to make the receiver of not more than one-fifth the capacity of the generator. The quantity of materials used should also be just sufficient very nearly to fill the generator. * In using this apparatus, when the liquid is received in the cup, it hisses and boils with the greatest violence; and the cold produced by the evaporation of a part of it is so great as to freeze the rest, which is retained in the cup as a fine white snow. By rolling this in balls, and wrapping it in cotton, it may be kept some time; but in the open air it evaporates rapidly, and intense cold is produced, equal, it is said, to —148°, By moistening the solid with ether, and placing it in an exhausted receiver, it is claimed that a temperature as low as 175° or 180° below zero has been produced. The solid does not mix with water when immersed in it; .a ball of it thrown upon the surface of water floats about lightly, and at Quzstions.—How is the freezing of the liquid accomplished? At what temperature is the solid formed? 58 SPECIFIC HEAT. length a portion of water in contact with it is frozen by the iutense cold. With sulphuric ether or chloroform it mixes readily, and the pasty mass rapidly evaporates, producing intense cold. Mercury which congeals at about —40° is readily frozen by being kept a short time in contact with the solid, surrounded by some cotton, or by immersing it in a mixture of the solid and ether or chloroform. SPECIFIO HEAT.—CAPACITY OF BODIES FOR HEAT. 59. When a body is exposed to any source of heat, its tem- perature rises, and the substance of heat is supposed to accumu- late in it; but the same quantity of heat, imparted to different bodies, will not raise their temperature alike. Thus, if a pound of water and a pound of mercury, in similar vessels, and at the same temperature, be exposed to the same source of heat, the temperature of the mercury will rise about 30°, while that of the water rises only 1°. It appears, therefore, that it requires 30 times as much heat to raise the temperature of water any given amount, as it does to produce the same effect. upon mercury. This idea is expressed by saying that the specific heats of these substances are as 30 to 1; or we say (as some. prefer) that the capacity for heat of water is to that of mercury as 30 to 1. If, instead of comparing equal weights of the two substances, we take equal volumes—as a pint of each—and expose them to the same uniform source of heat, we shall find that while the water gains 1° of heat, the mercury will gain 2°, or a little more. To express this relation we use the term relative heat; and we say therefore that water has more than twice the relative heat of mercury. : Other methods of determining the specific heat of bodies have been devised, one or two examples of which will be given. If a Questions.—What is said of the solution of the solid in chloroform and ether? How may mercury be frozen by use of the solid acid? 59. Will the same quantity of heat imparted to different bodies heat them alike? If like quantities of water and mercury are exposed to the same source of heat will they in the same time be heated alike? SPECIFIC HEAT. 59 pound of olive-oil and a pound of water be heated to some given temperature, say 80°, and then placed in a cold room, and the number of minutes noted which is required for each to cool an equal number of degrees, say to 50°, it will be found that the oil will cool in less than half the time required by the water; but as both substances must be supposed to lose equal quantities of heat in equal times, it follows that the water must have contained more than twice as much as the oil; or the capacity of water for heat is more than twice that of this oil. If a piece of copper, of a pound weight, be heated to 800°, by holding it a few minutes in mercury at this temperature, and then immersed in a pound of water at 50°, the copper will give out heat to the water until the temperature of both will be at 72°. Now, the copper has lost 228° of heat, and the water has acquired 22°, The specific heat of water, therefore, is to that of copper as , 228 to 22. It is usual to make water the standard in comparing the specific heats of bodies, considering its specific heat as 1-000; we shall then have the specific heat of mercury 1:99°—-033, and that of copper 232,—= 096. No two substances have the same specific heat, but every sub- stance has a specific heat -peculiar to itself, and which is to be considered as one of its own peculiar properties. The following table exhibits the specific heats of several well- known substances :— , Diamond sce sessoene Mercury.......eses - Graphite... seeeee 0-202 | Oil of Turpentine. Charcoal ....sseccecccereeeee 0-201 | Ether..........0. sssssssse eee The specific heat of a body depends to some extent upon its tempera- ture, being greater as the temperature is higher. Change of density in a body. is usually attended by a correspond- ing change in its specific heat, which is increased as the density is Quesrions.—What is the ratio of their capacities for heat, or their specific heats? What is taken as the standard for the specific heat of bodies ? 60 NATURE AND SOURCES OF LIGHT. diminished, and diminished as the density is increased. This is seen in solids, as when a piece of iron is heated by hammering, which increases its density and causes a portion of its latent heat to be given out, thus raising its temperature ; but is best illus- trated by the gases, the densities of which are more easily made to vary at pleasure. Thus, if we suddenly compress a portion of a gas, its temperature is sensibly raised; but, on the other hand, if we diminish its density, it becomes colder by the absorp- tion of heat occasioned by its increased capacity for heat. A delicate thermometer placed under the receiver of an air-pump falls as the air is exhausted. 2 60. The Fire Syringe is an instrument by which dry tinder or spunk may be ignited by the heat. pro- duced by the sudden compression of a portion of at- mospherie air. It consists of a hollow cylinder, closed at one end, and a solid piston fitting it accurately, and having in its under side a cavity to receive the substance to be ignited. To use it, the tinder or spunk is put in the place fitted for it, and the piston is then plunged forcibly into the cylinder; on removing it, the combustible substance will gene- rally be found ignited. If the cylinder is of glass, a flash of light will often be seen when the air is Fire Syringe. compressed. Ii. LIGHT. NATURE AND SOURCES OF LIGHT. 61. Nature of Light.— Although innumerable observations and experiments have been made upon light, yet it must be admitted that some doubt and obscurity still remain concerning its real nature. But, in the absence of positive knowledge, two theories of light have been proposed, by each of which nearly all Quxstions.—How does change of density in a body affect its specific heat? 60. Describe the fire syringe. 61. Do we underst th real nature of light ? - eae: NATURE AND SOUROES OF LIGHT. 61 the phenomena attending it may be satisfactorily explained ; and it ig admitted that each is also attended with its peculiar difficulties. These are called the Newtonian, or corpuscular, and the undulatory theories. 62. The Newtonian theory supposes light to be material, and to consist of inconceivably minute particles, which, however, are too subtile to exhibit the common properties of matter. These particles, emanating from luminous bodies, such as the sun, the fixed stars, and incandescent substances, and traveling with im- mense velocity, excite the sensation of light, it is supposed, by passing Bodily through the substance of the eye, and striking against the expanded nerve of vision, the retina. The whole language of optics is founded on this theory. 63. The undulatory theory, or theory of Huygens, which is now generally adopted, denies to light a separate material exist- ence, and ascribes its effects to the vibrations or undulations of a subtile ethereal medium, supposed to be universally present in nature, the pulses of which, in some way excited by luminous objects, pass through space and transparent bodies, and give rise to vision by impressing the retina, in the same way as pulsations of air impress the nerve of hearing, to produce the sensation of sound.—(See Natural Philosophy, p. 188.) 64, Light is not a homogeneous substance, as might be sup- posed, but the white light of the sun is made up of rays of several different colors, as will be shown when we come to speak of its decomposition, or analysis. So, also, it is capable of producing several distinct classes of effects, which have been attributed to the action of distinct agents; as the colorijic rays, or the rays which produce the phenomena of color, the heating tays, and the chemi- cal rays, or those which are capable of producing chemical changes. Thus it is possible, by causing the solar ray to pass through certain substances, to separate the heat entirely from it; or its illuminating power may be destroyed, and a distinct, invisible ray of heat be obtained. So, also, chemical effects may be produced by rays which seem to be destitute of any heating or illuminating power. Qursti10ons.—62. Describe the Newtonian, or corpuscular theory of light. 63. Describe the wndulatory theory. 64. What colored rays are contained in the white light of the sun? What other rays? 6 62 NATURE AND SOURCES OF LIGHT. 65. Sources of Light—The sun is the great source of light to the earth, and all things upon its surface. As rays of heat always accompany the light of the sun, it is natural to suppose that the sun is an intensely heated mass, which is constantly throwing off both light and heat in every direction, like a red-hot cannon-ball suspended in the air; but this cannot be proved. At the present day, it is generally believed that the body of the sun is a dark, opaque substance, surrounded by luminous clouds, unlike any- thing, perhaps, with which we are acquainted upon the earth, but which are the real source of the sun’s rays. These clouds are supposed to be of great thickness; but occasionally they break away in places, showing the body of the sun beneath them, which constitute the spots often seen upon his surface. The great distance of the sun from the earth—95,000,000 of miles—very probably will ever prevent us from knowing more with certainty of his real nature. Artificial light is produced by various modes, but chiefly by combustion, by the burning of a lamp or candle, or a mass of charcoal; but it may also be produced by galvanism,—in a man- ner to be hereafter explained,—by decaying animal and vegetable substances, called phosphori, and by every means which produce great heat. All bodies begin to emit light when heat is accumulated within them in great quantity; and the appearance of glowing or shining, which they then assume, is called incandescence. The tempera- ture at which solids in general begin to shine in the dark, is between 600° and 700°; but they do not appear luminous in broad daylight till they are heated to about 1000°. The color of incandescent bodies varies with the intensity of the heat. The first degree of luminousness is an obscure red. As the heat aug- ments, the redness becomes more and more vivid, till at last it acquires a full red glow. If the temperature still increase, the character of the glow changes, and by degrees it becomes white, shining with increasing brilliancy as the heat augments. Liquids and gases become incandescent when strongly heated; but a very ; Qurstions.—65. What is the great source of light to the earth? How is artificial light produced? At what temperature do bodies begin to emit light? NATURE AND SOURCES OF LIGHT. 63 high temperature is required to render a gas luminous, more than is sufficient for heating a solid body even to whiteness. The dif- ferent kinds of flame, as that of a wood-fire, candles, and gas-lights, are instances of incandescent gaseous matter. ‘Artificial lights differ greatly in color, some being of a brilliant white, and others being red, blue, yellow, or green. The chemical agency of artificial light is in general analogous to that from the sun; but in. most cases it is too feeble to produce very decided effects. 66. Many substances have the power of emitting a feeble light, unat- tended by sensible heat, and are called phosphori (from two Greek words, phos, light, and phero, I bear). Certain living animals also possess the same property, as the glow-worm, and the common fire-fly. This pro- perty of bodies is termed their phosphorescence. Some phosphori, as that prepdred by mixing sulphur and oyster-shells, and exposing the mixture for a time to a strong heat, the diamond, fluor- spar, &c., shine only after having been heated, or exposed for a few moments to a strong light; while others, as moist, decaying wood, and decaying fish, shine without such preparation, even at ordinary tem- peratures. Light sometimes appears during the process of crystallization. This is exemplified by a tepid solution of sulphate of potassa in the act of crystallizing ; and it has been likewise witnessed under similar circum- stances in a solution of fluoride of sodium and nitrate of strontia. An- other instance of the kind is afforded by the sublimation of benzoic acid. Allied to this phenomenon is the phosphorescence which attends the sud- den contraction of porous substances. Thus, on decomposing by heat the hydrates of zirconia, peroxide of iron, and green oxide of chromium, the dissipation of the water is followed by a sudden increase of density suited to the changed state of the oxide, and a vivid glow appears at the same instant. The essential conditions are that a substance should he naturally denser after decomposition than it was previously, and that the transition from one mechanical state to the other should be abrupt. 67. Photometers are instruments for measuring the comparative intensities of different lights, of which several kinds have been proposed; but it does not enter into our present purpass to describe or discuss their comparative merits. To determine the comparative intensities of two lights, as that from different candles or lamps, the following method, originally proposed by Count Rumford, is perhaps as reliable as any; and has the advantage of requiring little and very cheap apparatus. Let L be a lamp, and C a‘candle, the lights of which we desire tc Qurstions.—Do artificial lights differ in their colors? 66. What are phosphori? 67. What are photometers ? 64 NATURE AND SOURCES OF LIGHT. compare. Provide a screen, S, of white paper, which is to be put in a frame and properly supported by a stand, as shown in the figure, and also a small cylinder, C, of wood or some opaque sub- stance. Then place this cylinder in an upright position in front of the screen, in such a position that its shadow from both of the lights shall be thrown side by side upon the screen, but not over- lapping each other, and removing the lights to different distances, until the shadows appear of perfectly equal intensities. The com- parative intensities of the two lights will then be as the squares of the distances of the lights from the screen. In the present case, L/ will be the shadow from the light of the lamp, and (’ that from the light of the candle; and the intensity of the lamp light will be to that of the candle light as LLis to €C’*. If LL’ Photometer. is 50 inches and CO’ 45 inches, then will the light of the lamp be to that of the candle as 2500 is to 2025, or as 1-284 is to 1. This method is founded upon the fact to be illustrated in the next paragraph, that the intensity of the light from any luminous body, at different distances, will be inversely as the squares of those distances. The experiment must, of course, be conducted in a dark room. ; Quest10Ns.—Describe the method of determining the comparative intensities of two lights by a comparison of the shadows they produce. DISTRIBUTION OF LIGHT. 65 DISTRIBUTION OF LIGHT. 68. Light is distributed, or diffused abroad, by several modes ; as by radiation, reflection, refraction, &e. Light emanates from every point in the surface of a luminous body, and is equally distributed on all sides, if not intercepted, diverging like radii drawn from the centre to the surface of a sphere. Thus, if a single luminous point were placed in the centre of a hollow sphere, every point of its concavity would be illuminated, and equal areas would receive equal quantities of light. ach ray, when not interrupted in its course, and while it remains in the same medium, moves in a straight line, as is obvious by the appearance of shadows cast by the side of a house, or of a sun-beam admitted through a small aperture into a dark room. Owing to these modes of distribution, it follows that the quantity of light which falls upon a given surface decreases as the square of its distance from the luminous object increases—the same law which regulates the heating power of a hot body. , 69. The passage of light is progressive, time being required for its motion from one place to another. It comes to the earth from the sun in about 8} minutes,—a distance of 95,000,000 miles,— which shows its rate of progress to be about 195,000 miles a second. Owing to this prodigious velocity; the light caused by the firing of a cannon or a sky-rocket is seen by different specta- tors at the same instant, whatever may be their respective dis- tances from the rocket, the time required for light to travel 100 or 1000 miles being inappreciable to our senses. 70. Reflection of Light.—Light is reflected in the same man- ner as heat (31), obeying precisely the same laws. This always takes place when it passes from one medium into another of dif- ferent nature or density, whether the media be solid, liquid, or gaseous. Different media, however, differ much in their power of reflection. Bright metallic surfaces, as polished silver or clean mercury, Qurst10oNns.—68. How is light distributed? Does light emanate from every point of an object? What is said of the course of a ray when not interrupted? 69. Is the passage of light from point to point instanta- neous ? oe is its velocity? 70. When is light said to be reflected? 66 DISTRIBUTION OF LIGHT. ' reflect nearly all the rays which fall upon them; while those which are dull and rough reflect but a few. The reflection of light, like that of heat, takes place at the surface of bodies, and appears to be influenced rather by the condition of the surface than by the internal nature or structure of the reflecting body. Let AB be the reflecting surface, EC the ray incident at C, and C D the reflected ray, and let PC be perpen- dicular to AB. ECP will then be es ms - the angle of incidence, and PCD the ot es angle of reflection, both of which will be equal. It is not necessary that the reflecting surface should be a plane, as might be supposed ;—it may be either concave, as ab, or convex, as A’ B’, and the same results would follow. Light has precisely the same characters after being reflected: as before, but is less intense, because of the absorption of a part of the rays. 71, Refraction of Light—When a ray of light passes through the same medium, as glass or water, or when it passes perpen- dicularly from one transparent medium to another, it moves in perfectly straight lines; but when it passes obliquely from one medium to another of different density, it is thrown more or less out of its first direction, and is said to be refracted. ze Thus, a ray of light, R, passing through ‘ the air, when it comes in contact with a piece of polished glass at A, does not move === on in a straight line to R’, but is bent downward or refracted, and emerges from the glass at B, where it is again refracted in the opposite direction, and takes the same course, though not precisely the same path, as it had at first. Refraction always takes place when a ray of light passes obliquely from one medium to another of different density, but not always to the same amount; this will depend upon the refracting power of Takia of tae Refraction of Light. Quzstions.—Describe the angles of incidence and reflection. 71. When is light said to be refracted ? DISTRIBUTION OF LIGHT. 67 the two media, and also upon the obliquity of the ray to the sur- faces of the media in contact. When the ray passes from a rare to a dense medium, it is always refracted or bent towards a line perpendicular to the surface at the poiut of contact, and from this line when it passes in the opposite direction, from a dense to a rare medium. To understand the relative positions of the incident and th refracted ray, in the case of any two media, the following law needs to be well studied. Let AB in the gre be the surface of some transparent medium more dense than air, as water, and let IC be a ray of light incident upon it at C; it will not pass on in a straight line, but on entering the water will be bent downward, to E; IC is then called the incident ray, and CE the refracted ray. ‘Let PP’ be a line perpendicular to the surface at C, then angle ICP will be the angle of incidence, and HCP’ the angle of refraction. If now from C as a centre we draw the circle AP BP’, and also the lines Ia and Ec both at right angles to P P’, then will Ia be the sine of the angle of incidence and Hc the sine of the angle of refraction. And for the same two media these lines will always have the same ratio to each other, whatever may be the angle of incidence. Thus, if a second ray, 7C be incident at C, it will emerge at e¢; and the sines of the angles of incidence and refraction, that is, the lines 75 and ed will have to each other the same ratio as the lines Ia@ and Ec; and the same will be true for the same media, whatever may be the angle of the inci- dent ray. The quotient obtained by dividing the sine of the angle of inci- dence by that of the angle of refraction is called the index of refraction for the media used; for the same media it is always Index of Refraction. Quzstions.—What is the course of the ray in passing from a rare to a dense medium? When from a dense to a rare medium? Describe the angles of incidence and of refraction. Describe the index of refraction. 68 DECOMPOSITION OF LIGHT. | the same, but varies with different media. Usually the air is taken as one of the media, so that the index of refraction for any substance is the quotient thus obtained in the case of a ray of light in passing from air into that substance. The index of refraction for water is thus found to be 1:33, for common flint glass 1-56, for oil of cassia 1:64, for phosphorus 2-22, and for the diamond 2:43. (For the Polarization of Light, see the author's “ Natural Philosophy.’”’) DECOMPOSITION OF LIGHT. 72. The Solar Spectrum.—The white light of the sun is not a homogeneous substance, but is capable of being separated into several rays of entirely different colors. This was first effected by Newton, by passing it through a triangular piece of clear, solid glass, called a prism. In the figure following, let S be a ray of light from the sun, 4 admitted into a darkened ; room through the window- shutter, DE; it will pass downward to the floor, at a little distance from the wall, producing a circular spot of clear white light, W. Then let the prism A BC be held in the ray, and at once the Decomposition af Tigh spot at W will disappear, and, in its stead, an elongated and beautifully colored image of the sun will be seen upon a screen hung up in front of the window, or on the wall at the opposite side of the room, if no screen be used. The several colors will appear in the order indicated, the violet being uppermost and the red lowest. _Questions.—What is the index of refraction for water? Flint-glass? Diamond? 72. How may light be decomposed? Describe the exverie ‘nent with the prism. ; ¢ DECOMPOSITION OF LIGHT. 69 Tt will be seen that the light, in passing the prism, has been twice refracted, or bent upward, first as it entered the glass, and again as it issued from it; and that the separation of the several colors has been in consequence of their different refrangibilities. The violet being most refrangible, is found uppermost in the picture, and the red is lowest, because least refrangible. The other colors occupy intermediate positions, depending upon their respective refrangibilities. The colored image thus produced is called the solar spectrum , and, according to Newton, it is composed of the seven colors named in the figure, which are therefore called primary colors. 78. More recent investigations by Brewster render it probable that there are in the spectrum really only three colors, red, yellow, and Glue, and that the other shades are produced by mixtures of these in different proportions; a mixture of the blue and the yel- low, for instance, producing the green, and a like mixture of the _ red and yellow producing the orange. Indeed, it is believed that each of these three colors extends over the whole spectrum, but each is much more intense at one part of the spectrum than else- where, the blue being most intense near the top, and the red near the bottom, with the most intense portion of the yellow between them. The solar spectrum, therefore, as produced by the prism, may be considered as composed of three simple spectra super- imposed upon each other. The distribution of the rays in each of these simple spectra is represented by the shading of the annexed figures, in which B represents the blue, Y the yellow, and R the red, each color being supposed to be separated from the others. If the three spectra be thrown one upon another on the same screen, the ordinary solar spectrum : will be produced. Colors of Spectrum, 74, Heating and Chemical Rays.—It has been stated above that light is capable of producing several distinct classes of B x T Questions.—What are Newton’s primary colors? Why are these sepa- rated by the prism? 78. What colors only are contained in the spectrum, according to Brewster? How are the othercolors produced? 74. In what part of the spectrum are the greatest heating effects produced? 70 DECOMPOSITION OF LIGHT. effects, as those of color, those of heat, and besides these, others which may strictly be called chemical effects. Now, these several effects are not produced in every part of the spectrum with equal facility ; the greatest illuminating power is found to be in the yel- low, while the greatest heat is in the red, or a little below it, and the greatest chemical effects are produced in the extreme violet. The chemical effects of light are various and important; a mix- ture of chlorine and hydrogen gases may be kept together in the dark for any length of time, without combining, but unite with an explosion when placed in the direct sunlight. On the other hand, many compound substances are decomposed by light, as certain preparations of gold and silver. Ifa piece of white paper ‘be coated over with a thin film of white chloride of silver, care- fully prepared in the dark, and then placed in the solar spectrum, the part in the violet ray will soon become black, while that in the red will scarcely be affected. Between these extremes there will be produced various shades of gray and purple. It appears, therefore, that the sun’s light is made up of three kinds of rays, viz., the colorific rays, or rays of light proper, the heating rays, and the chemical rays, the last of which are most, and the heating rays least, refrangible. The light of the sun produces most important effects in the vegetable world; many plants will not grow in the dark, and others growing in the shade have their nature entirely changed. But a discussion of these topics does not belong to our present subject. 75, Photography.—By this name we designate the various modes of producing pictures by the action of light. If a piece of white paper is moistened with a dilute solution of common salt, and then one side of it washed with a solution of nitrate of silver, the surface becomes coated with chloride of silver, which readily turns black or dark chestnut by exposure to the direct rays of the sun. If, now, before exposing paper thus prepared to the light, any small flat object, as a flower, or piece of lace, be placed upon it, an image of the object will remain upon the paper, and may be Quzstions.—In what part of the spectrum are the greatest chemical effects produced? Does the light of the’sun produce any important effects upon vegetable bodies? 75. Whatis photography? What method is mentioned for preparing a photographic paper ? DECOMPOSITION OF LIGHT. 71 yetidered permanent by soaking it immediately in a saturated solution of common salt, or of iodide of potassium. The unaltered chloride of silver in the paper is by this soaking dissolved out, while the part that has become colored resists the action of the solvent and therefore remains in the paper. Talbot's Calotype Process, invented by a gentleman of this name, is conducted as follows: A sheet of writing paper of a firm texture is brushed over on one side. with a solution of 50 grains of nitrate of silver in an ounce of water, and then dried in a dark room, and subsequently soaked two or three minutes in a solution of iodide of potassium, containing about an ounce of the iodide to a pint of distilled water. It is then to be again. soaked for some minutes~in water, and thoroughly dried, and preserved for use. When required for use, the paper is to be washed on the side previously iodized by gallo-nitrate of silver, prepared for the occasion in the following manner: Dissolve 100 grains of nitrate of silver in 2 ounces of distilled water, and add to it an equal volume of strong acetic’ acid, and then mix with it several volumes of saturated solution of gallic acid in cold distilled water. This last preparation should be made only in small quantity for the particular occasion, as it spoils by keeping. The last washing should be made in the dark, or with only a feeble candle light ; and the paper dried carefully, excluding the light of day, to the action of which it is exceedingly sensitive. Paper prepared in this way may be used in the manner first described, or in the camera obscura, for the taking of portraits. If the picture at first is not sufficiently distinct, it may be improved by washing it again in the gallo-nitrate of silver. Finally, it is to be rendered permanent by washing it with solution of bromide of potassium, or of common salt. The picture thus formed is what is called a negative picture— that is, the light and shade are reversed, as compared with an ordinary engraving; but a positive one may be formed from the first by using it as an object for forming a.second picture upon another sheet of the same prepared paper. For this purpose it is Quustions.—Describe Talbot’s Calotype process. What are negative and what posifive pictures? 72 DECOMPOSITION OF LIGHT. placed with its face downward upon the prepared paper, and then exposed to the direct rays of the sun, as directed above (75). The new picture is to be rendered permanent in the same manner as before. Numerous other preparations are in use for producing pictures upon paper, but none of them equal in sensitiveness the one just described. Though the materials to be used are different, as well as the processes, yet the essential principles are the same in all. The light produces a chemical change in the parts of the picture exposed to its influence, and the picture is fized by soaking the paper in a solution capable of dis- solving out the sensitive substance contained in the parts which have not undergone this change, in consequence of being in the shade. Paper prepared for the taking of pictures is called photogenic paper, and generally cannot be long kept, even in the dark. 76. The Daguerreotype process, so called from the name of the inventor, is applied only to plates of silver, which are usually spread upon plates of copper. The silver surface is first very thoroughly cleaned by washing with dilute nitric acid, and rub. bing with leather or cotton and some polishing substance, as very fine colcothar. It is then to be subjected for a few minutes to the action of vapor of iodine, by placing it ina box which has some crystals of iodine spread upon the bottom; by this means, an exceedingly thin coating of iodide of silver is formed upon the surface of a straw-yellow color, which is very sensitive to the action of light. It is then placed in a camera obscura, and the image of any object in front is made to fall upon it fora few moments, by which such a chemical change is produced in the thin coating of iodide of silver, that subsequent exposure to the vapor of mercury, at about 165° F., brings out a beautiful picture of the object. By close inspection, it will be found that in the parts of the picture where the most light has fallen such a change has been produced that the mercury is capable of acting upon it, but in other parts the bright surface of the silver remains un- affected; and further, the action of the mercury upon the silver plate will be in proportion to the intensity of the light upon the different parts. : Instead of pure iodine, the bromide or chloride of iodine may be used for preparing the plates; but the last compound is said to ‘be, on the whole, much the best. Quzsrions.—How are pictures prepared in this way fixed or rendered permanent? 76. Describe the Daguerreotype process. DECOMPOSITION OF LIGHY®. 73 The picture, when taken from the mercurial process, is rendered permanent by removing the coating of iodide of silver, which is readily done by merely pouring over it-a warm solution of hypo- sulphite of soda or of common salt. It is further improved, and the shades rendered deeper, by heating upon it a solution of chloride of gold and hyposulphite : of soda. The Daguerreotype process is very simple, but to insure suc- cess, close attention must be paid to various minute particulars, which cannot here be discussed. "1. Thermography is a name which has been given to certain modes, dependent, it is believed, upon heat, by which one body is. made to depict itself more or less minutely upon another, either in contact with it or in its vicinity. Thus, if we write with some soft substance upon glass, and then breathe upon it, the writing becomes visible. So if we allow a piece of coin to lie for a time on a plate of metal or glass, and then breathe upon it, an image of the coin will be produced. If while the piece of coin lies upon the metallic plate it is gently heated by a spirit-lamp, and when cold exposed to the vapor of mercury, a very distinct image of the coin will be formed. In some cases, we are told, this effect will be produced when the coin has not touched the plate, but only remained for a time near it. 7 : 78. Double Refraction of light takes place when a ray is passed through certain transparent crystals, and some organized sub- stances, so that objects seen through them in particular directions appear double ; and the rays emerging from them are found to have undergone a further change, by which they have acquired peculiar properties on different sides, and are said to be polarized. Light is also polarized by other means, as by reflection at particular angles from most non-metallic substances, and by refraction. For a very full discussion of the subject, see Natural Philosophy, page 259. Rays of heat may be polarized in the same manner and by the same means as those of light. Questions.—77. What is thermography? 78. When is light said to be doubly refracted ? 7 74 NATURE OF ELEOTRICITY. III. ELECTRICITY. « NATURE OF ELECTRICITY.—ELECTRICAL THEORIES. 79. Nature of Electricity.—As in the cases of heat and light, we know nothing of the real nature of electricity, all our know- ledge on the subject being limited to its effects. Like heat and light, it is imponderable; no accumulation of it in any substance adds to the weight of that substance, even when tried by the most delicate balances; but many of its effects are so like those of a mechanical ‘agent, that it is usually considered a separate material substance. When certain substances, such as amber, glass, sealing-wax, and sulphur, are rubbed with dry silk or cloth, they are found to have acquired a property, not observable in their ordinary state, of causing contiguous light bodies to move towards them ; or, if the substances so rubbed be light and freely suspended, they will move towards contiguous bodies. After a while this curious phe- nomenon ceases; but it may be renewed an indefinite number of times by friction. This property was first noticed in amber; and therefore the principle thus developed was called electricity (from the Greek, electron, amber). When a substance, by friction or other means, has acquired the property just stated, it is said to be electrified, or to be electrically excited ; and its motion towards other bodies, or of other bodies towards it, is ascribed to a force called electric attraction. But its influence, on examination, will be found to be not merely attractive ; on the contrary, light substances, after touching the electrified body, will be disposed to recede from it just as actively as they approached it before contact. This is termed electric repulsion. 80. Theories of Electricity —In the absence of positive know- ledge in regard to the nature of this agent, two theories have been proposed, to account for and connect together the established facts. _ Questions.—79. Do we understand the real nature of electricity? Is it imponderable? What is the derivation of the term electricity 2 When is a substance said to be excited or electrified 2 ; ELECTRICAL THEORIES. 75 Dufay’s theory (from the name of its proposer) supposes that every substance, in its natural state, contains in itself two highly subtile and elastic fluids, in such a state of combination that their presence is entirely disguised; but that the various phenomena of electrical excitement are produced by one or the other of them, accumulated in a body in excess. The particles of each finid are - supposed to have a strong attraction for those of the opposite kind, and for other matter, but are highly repulsive of each other. These fluids are supposed to be separated by the various modes of producing electrical excitement, to be hereafter described ; and one of them being collected in excess in a body, as just stated, produces the phenomena witnessed. In most cases, when glass or any other vitreous substance is rubbed, the electricity which is collected is the reverse of that obtained when seéaling-wax is subjected to friction; and hence the former is called vitreous, and the latter resinous electricity. Franklin’s theory of electricity supposes that all bodies, in their natural state, contain in their substance a certain quantity, called their natural share, of a single, subtile, elastic fluid, which pro- duces no sensible effects; but that the phenomena of electrical excitement are produced when the body is made to contain either less or more than its natural share. It supposes that the particles of this fluid repel each other strongly, but are attracted by all other matter. When a body contains more than its natural share, it is said to be positively electrified; and negatively electrified, when it contains less. Glass and other vitreous substances, when rubbed, are supposed to take more than their natural share of the fluid, or become positive; while resinous substances, in the same circumstances, lose a portion of their natural electricity, or become negative. These states are often indicated by the algebraic signs + and —. The terms vitreous and positive, of the two theories, are there- synonymous, as are also the terms resinous and negative. Hither of these theories is found to answer well in explaining most of the phenomena of electricity, but that of Dufay is gene- 7 : oe Quzstions. — 80. Describe Dufay’s theory of electricity. Describe F snklin’s theory. What terms were proposed by him? What terms of t) two theories are synonymous ? 76 DISTRIBUTION OF ELECTRICITY. rally preferred ; though the terms positive and negative, of Frank- lin’s theory, are almost universally used. From the above it will readily be seen, that when two bodies are either positively or negatively electrified, they repel each other, but attract each other when one is positive and the other negative. 81, Electrometers.—Electrometers are instruments for indi- cating the presence of electricity, or its intensity. A pith-ball, sus- pended by a dry silk thread from any convenient support, answers the purpose quite well; but the following, called the gold-leaf electrometer, is a more sensitive instrument. It consists of two slips of gold-leaf, suspended in a cylindrical glass vessel, from a metallic plate at the top. If the bottom is also made of metal, its sepsi- tiveness will be increased. When an excited body is brought near the metallic plate, the leaves at once diverge, in consequence of their being broughv into the same state, whether positive or negative, by the inductive influence of the excited body, in a manner to be hereafter explained. Electrometer. DISTRIBUTION OF ELECTRICITY. 82. Conduction of Electricity.—Some substances allow the electric fluids to pass over them freely, and are therefore called conductors ; while others, that do not possess this property, or only imperfectly, are called non-conductors. If electricity be im- parted to one end of a conductor, such as a copper wire, the other extremity of which touches the ground, or is held by a person standing on the ground, the electricity will pass along its whole length and escape in an instant, though the wire were several miles long; whereas excited glass and resin, which are non-con- ductors, may be freely handled without losing any electricity except at the parts actually touched. Questions. — Which of these theories is now generally preferred? When do bodies attract and when repel each other? 81. What are electrometers? Describe the gold-leaf electrometer. 82. What is said of the conduction of electricity? What are conductors and non-conductors ? DISTRIBUTION OF ELECTRICITY. 77 To the class of conductors belong the metals, charcoal, plum- bago, water, and aqueous sdlutions, and substances generally which are moist, or contain water in its liquid state,-such as animals and plants, and the surface of the earth. These, how- ever, differ in their conducting power. Of the metals, silver and copper are found to be the best conductors; and after these follow gold, zinc, platinum, iron, tin, lead, antimony, and bismuth. Aqueous solutions of acids and salts conduct much better than pure water. To the list of non-conductors belong glass, resins, sulphur, diamond, dried wood, precious stones, earth, and most rocks when quite dry, silk, hair, and wool. Air and gases in general are non-conductors if dry, but act as conductors when saturated with moisture. It is not, however, to be understood that any very definite line can be drawn between the two classes of conductors and non-conductors; but there seems to be a very regular gradation from the most perfect con- ductor to the most imperfect, or most perfect non-conductor. This _ division of substances is, however, found very convenient, though in some instances individuals might differ with regard to the class to which a particular substance should be assigned. 83. Insulation—When a conductor is supported upon a non- conducting substance, it is said to be insulated, and electricity may be retained upon it for a time; but even then it will be gradually diffused and disappear. ‘This is occasioned in part by the conducting power of the air, which is considerable, except when it is very dry. In damp weather, many electrical experi- ments cannot well be performed, because of the rapid diffusion of the fluid through the air, and the deposition of moisture upes the surfaces of insulators. When two substances are rubbed together, both elonteicitten are always developed, one of them going to one of the substances, and the other to the other substance; and both electricities may be retained, if the two substances rubbed together are insulated. Quesrions.—What substances are classed with conductors, and what with non-conductors? Can any definite line be drawn between the con- ductors and non-conductors? 88. When is a body said to be insulated? Why do electrical experiments often fail in damp weather? Are both electricities always developed by friction? T* 78 DISTRIBUTION OF ELECTRICITY. 84, Induction of Electricity. An electrified body always exerts a peculiar influence on the natural electricity of other bodies in its vicinity, called induction, the nature of which will be seen from the following explanation: Let A be a positively excited glass tube, held near one end of an insulated conductor, B, supposed to be in its natural state; the natural electricity in B will instantly be dis- turbed, and, on examination, it will be found that the end next the excited glass is negatively electrified, and the other end positively, as shown by the algebraic signs. If, instead of the glass tube, some other substance, negatively electrified, had been used, the elec- tricities of the two ends of the conductor B would have been reversed. In every case, the part of the conductor next to the excited body will be in the opposite state of excitement, while the other end will be in the same state as the excited body. In the experiment nothing but air is supposed to be between tke excited body A, and the conductor B, but the inductive influence is exerted through all non-conductors. Thus, if a clean and dry pane of glass be held between A and B, the result will be the same. Let A and B, in the next figure, be two metallic discs, supported upon pillars of glass, their edges being towards the eye, and let a spark of positive electricity be communicated to one of them, as A ;—it will immediately act by induction upon the natural electricity of B, causing the side next to A to be negative and the other to be positive. The effect is pre- cisely the same as in the preceding | -©=| experiment, but the form of the con- Induction of Electricity, ductors different. If now we touch the Induction of Electricity. Questions.—84. What is meant by induction? Explain the experi- ment described in this paragraph. Explain the experiment described in connection with the next figure. DISTRIBUTION OF ELECTRICITY. 79 back of B with the finger, the positive fluid escapes, and the whole dise becomes negative. The action of the positive body, A, has taken place through the stratum of intervening air; and any other non-conductor may be substituted for it. If, for instance, a plate of glass be interposed, the two plates may then be brought much nearer together, and the same results will follow. Instead of the metallic discs, we may simply. apply a metallic coating to the two sides of a pane of glass; which, if the coating do not reach within one or two inches of the edge, serves as a sufficient insulator. 85. The Leyden Jar.—The Leyden jar receives its name from the city of Leyden, in Holland, where it was invented. It is essentially the same thing as just described, except that a glass jar is substituted in the place of the pane. It consists of a glass jar, coated both inside and outside with tin-foil, except a part around the top, as shown in the figure. Through a varnished wooden cover, A, a wire, having ‘a knob at top, is passed, and a chain, B, extends to the inside coating. Now, when either positive or negative electricity is communicated to the knob at the top, it is im- mediately diffused over the whole inside coating; and by its inductive influence, the outside coat- ing takes on the opposite kind. When in this state,—the two coatings being oppositely elec- trified,—the jar is said to be charged; and a discharge takes place when a communication is established between the knob and the outside coating, the equilibrium being restored with a bright flash of light and a sharp report. As the human system is a good conductor, this discharge may take place through it, by grasping the outside coating with one hand, and touching the knob at the top with the other; or several persons may form a line by grasp- ing hands, the one at one extreme touching the outside coating, while the one at the other extreme touches the knob. ALI will feel the shock, as it is called, at the same instant. While the jar is receiving the charge, it must not be insulated, that is, the outside must communicate with the earth. As the Leyden Jar. Quzstions.—85. Why is the Leyden jar so called? Describe its con. struction and use. How is the shock produced in the system? 80 DISTRIBUTION OF ELECTRICITY. positive fluid collects on the inside, the outside becomes negative by the expulsion of the positive fluid naturally in it, and the accumulation of the negative fluid in its stead, drawn from the earth. But if the outside is insulated these transfers to and from it cannot take place, and therefore the jar cannot become charged. 86. Free Electricity resides in the Surface of Bodies.—It has been demonstrated that the electricity of an excited body resides entirely upon its surface. Let A be a sphere of metal, suspended by a silk thread, and excited by receiving a spark of electricity ; and let BB be two covers of paper, gilt outside and inside, and held by glass handles. Let them now be applied to the excited globe, and then instantly removed; it will be found that the electricity has been entirely removed from the ball to the covers. Resides upon the Surface. The free electricity therefore was entirely accumulated upon the surface of the ball. 87. Distribution over Surface.—The fluid will be distributed over the surface of an excited conductor, in a mode dependent upon its form;—if it be a perfect sphere, the fluid will be dis- tributed equally over every part, but if it be more or less élongated, as in the prolate spheroid, the fluid accumulates in the ends, where the intensity is greatly increased if the spheroid happens to be very considerably LM Distributionon Elipsoid, elongated. Qusstions.—While receiving the charge must the jar be insulated? Why? 86. In what part of anexcited conductor does the electricity reside? 87. In what manner is electricity diffused over the surface of a sphere? How is it diffused over the prolate spheroid? SOURCES OF ELECTRICITY. 81 If the extremity of the conductor is carried out to a point, the fluid at once escapes from it, and all excitement disappears, even though it remains insulated. In the same manner, a sharp point projecting from a conductor receives the fluid silently upon it, and the body becomes excited. The effect of points in discharging or receiving either of the fluids is therefore apparent; and the circum- stance must always be particularly regarded in the construction of electrical apparatus. : The escape of positive electricity from a point in a dark room is always attended by the appearance of a faint blue light in the form of a brush, as represented in A, but the escape of the negative fluid, in the same circumstances, presents the appearance of a star, as shown in B. It is to be noticed, that in such experiments the espape of either fluid is to be considered as precisely —Pleciricty Be equivalent to the entrance of the other. SOURCES OF ELECTRICITY. 88, As we have seen above, electricity is believed to be con- tained in all bodies; which are therefore properly its sources; but the earth, as being by far the largest mass to which we have access, is its chief source. We propose, however, under this head, to speak of the different modes of exciting or collecting it, which are friction, change of temperature, and chemical action. 89. Friction.—It is believed that electricity is always developed when one substance is rubbed against another, one of the fluids passing to one of the substances, and the other to the other sub- stance, as before stated; but, in most cases, neither of the fluids is retained, because the rubbing substances are not insulated. If Quzstions.—What is the effect if one part of an insulated conductor is extended out to a point? What is said of the influence of points in receiving the fluid? 88. What is the great source of electricity? What are the different modes of exciting electricity? 89. Is electricity always developed when one substance is rubbed against another? How may both be collected and retained ? 52 SOURCES.OF ELECTRICITY. both be insulated, both the positive and negative fluids may be retained (83). 90. The electrical machine is an instrument for developing electricity by friction more abundantly than it can be done by the simple means heretofore pointed out, though most of the great principles of the science, as we have seen, may be demon- strated without it. The figure in the margin represents the cylinder machine in its usual form. A isa cylinder of glass, firmly sup- ported, and capable of being turned on its axis by a handle; and R is a conductor, supported on a pillar, having the rubber attached to it, with a flap of silk, S, extend- ing nearly over the cylinder. C is made ; of sheet-brass, and is called the prime con- Electrical Machine. ductor, because it receives the electricity from the cylinder as it is turned, by means of several pointed wires (87), extending inwards towards the cylinder. It is supported upon a pillar of glass. Now, when the cylinder is turned, electricity is abundantly developed by the friction of the rubber against its surface, and is received by the prime conductor, in which it accumulates. The use of the flap of silk, 8, is to prevent the fluid from escaping in the air, as the cylinder is turned. From the principles heretofore discussed, the learner will readily perceive that it is the positive electricity that will be accumulated in the prime conductor; but the negative (83) will also at the same time accumulate in the rubber, if it be insulated. But no considerable quantity of electricity can usually be collected, unless the rubber communicates with the earth, or, which is the same thing, with the floor of the room. An elegant plate electrical machine is represented in the next figure (p. 88). AB is a firm base of wood, mounted on castors, so as to allow the machine to be moved around easily upon the floor; CCC the prime conductor, supported upon pillars of glass; PP two circular plates of . Questions.—90. Describe the electrical machine. Describe the large plate machine. SOURCES OF ELECTRICITY. 83 glass upon the same axis, and turned by the handle H; RRRR the rubbers, of which there are eight, and F IF flaps of silk to prevent the MUMFORD So. Electrical Machine. escape of the fluid before reaching the point from the prime conductor. This machine, when put in proper order, developes electricity rapidly, and is decidedly preferable to the cylinder machine. When used, the machine should be dry and warm, and per- fectly clean and free from dust. Its action is also greatly increased by spreading the surface of the rubber, where it presses against the cylinder, with a soft amalgam of zinc, tin, and mercury, or with the yellow sulphide of tin, called aurum mustvum, the latter, on the whole, being preferable. Quzst10n.—What is the substance spread over the rubber? ~ 84 SOURCES OF ELECTRICITY. To prepare the amalgam, melt in wu crucible three parts of zinc and oue of tin, and, after removing it from the fire, add four or five perts of wereury. Stir the mass with a stick a few seconds, and pour it out upon a clear marble slab, or plate of metal, and allow it to remain several hours before breaking it up. When wanted for use, grind it as fine as possible in a mortar, and mix it with sufficient tallow to cause it to adhere well to the rubber. If the aurum musivum is used, it is to be mixed with tallow and spread upon the rubber in the same manner. When the machine operates properly, if the knuckle be pre- sented near the prime conductor, a vivid spark passes between them, and a slight stinging sensation is felt; the same thing also takes place on presenting the knuckle to the rubber, provided it be insulated. In the first case the effect is produced by accu- mulated positive electricity; in the second, by the negative. 91. The Electrophorus (from electron and phero, I bear) is an instrument for readily obtaining small quantities of electricity. It consists of a plate of resin, A, about 12 inches in diameter, contained in a shallow dish of metal, and a metallic disc, D, a little smaller than the plate of resin, provided with a glass handle, for removing it from the resin at plea- sure. To operate well, the surface of the resin should be perfectly smooth. To charge the electrcphorus, the dise is removed, and the surface of the resin rubbed briskly witha piece of warm, dry flannel, or struck several times with a dry silk handkerchief, folded up for the purpose, by which a negative electricity is excited. If, now, the disc of metal be restored by means of its insulating handle, its lower surface will become posi- tive by induction (84), and its upper surface negative. By touching the upper surface of the disc, when in this position, with the finger, the negative electricity will be discharged ; and if it be then removed carefully by its handle, it will be found highly charged with positive electricity, so that a considerable spark may be obtained from it. As the cake of resin has lost nothing of its electricity by the operation, the process may be repeated any number of times, with the same result. Electrophorus. - Questions.—How may a spark be obtained from th ine* 91. Describe the electrophorus. asia SOURCES OF ELECTRICITY. &5 The Hydro-Electric Machine is an instrument for exciting elec- tricity by means of high-pressure steam. The excitement is attri- buted to the friction of the steam, carrying with it drops of water, against the pipes from which it issues. 92. Atmospheric Electricity—The general phenomena of thunder and lightning are well known. They are occasioned, as Franklin first demonstrated, about a century ago, by immense accumulations of electricity in the clouds, between which and objects upon the earth violent discharges are frequently taking place. The discharge is believed to differ in nothing from the discharge of a spark from the conductor of an electrical machine, except what necessarily results from the quantity and intensity of the fluid accumulated. Inghtning-rods, which are so common at the present day, are rods of metal erected upon buildings, extending a distance above them at the top, and at the bottom connecting with the moist earth. Being made of metal, which is a good conducting material, any discharge that may happen upon the building will be con- veyed by them without danger to the ground. Often several of them are attached to the same building, at dif- ferent points, but they should always be connected together, and also make two connections, at least, with the moist earth. Any attempts to insulate the rod from the building are, to say the least, useless. Buildings with tin or copper roofs, and metallic water-conductors extending downward, require special electrical conductors only for the chimneys or other -projecting parts, and also from the water-conductors to the moist earth below. Electricity excited by friction is frequently called statical elec- tricity, to distinguish it from dynamic electricity, which will be hereafter described, under the head of Galvanism. 93. Thermo -Electricity.— If a crystal of tourmaline, the extremities of which are dissimilar, is slightly heated in the flame of a spirit-lamp, one end will be found, on examination by a delicate electrometer, to be positive, and the other negative ; QuEstions.—What is the hydro-electric machine? 92. What is said of lightning and thunder? Who first explained their cause? What are lightning-rods? What is said of buildings with methllic roofs? 93. How may crystals sometimes be electrically excited ? 86 SOURCES OF ELEOTRICITY. but the excitement is very feeble. Crystals of some other sub- stances may be excited in the same manner, But the more common method of exciting electricity by change of temperature, is to heat slightly the ends of two or more small rods of different metals at their junction, as repre- sented in the figure. Let A be a small rod of | antimony, and B another of bismuth, soldered together at one end; and then let the heat of a spirit-lamp be applied, for a moment, ‘at the point fs where they are soldered; while the bars are warm- »=—=s/" ing, the bismuth will be negative, and the antimony positive. The bismuth is called the positive, and the antimony the negative metal, because, while heating, the positive fluid appears to originate in the former, and flow to the latter; but an electrometer will show the different states of the metals, as above indicated. Other metals—and even non-metallic substances—may be used, with similar results. German silver and brass answer very well, the former corresponding in its action with the antimony, and the latter with the bismuth. The effect will be considerably increased, if several pairs of the metals, arranged as above, are associated together, as shown in the accompanying figure, the alternate rods, A, being of German silver, and the intermediate ones, B, of brass. When the metals are gently heated at the points of junction at one ex- tremity of the bars, and kept cool at the other, the terminal bars become excited, and a constant current flows over any conducting sub- stance, as a copper wire, connecting the extremities of the series. If the upper ends of the rods be heated, the direction of the cur- rent over the wire will be as shown by the arrow. If the lower ends be heated, or the upper ends cooled, its direction will be reversed. Thermo-Electricity. Thermo-Electricity. Quzstrons.—Describe the mode with two metals. How may the effect be increased ? SOURCES OF ELECTRICITY, 87 To render the instrument more compact, the metallic bars may be placed side by side, with only a slip of silk between them, the ends being bent a little, so as to admit of being soldered as before. Such an instrument constitutes the thermo-electric pile, which is figured in the margin, P and N being the positive and negative poles. The existence and direction of these cur- rents are best shown by a delicate galvanometer, an instrument to be hereafter described. By reversing the experiment, and passing a current of electricity through the series of bars, they will be heated or cooled, according to the direction in which the current is made to pass. 94, Chemical Action.—Chemical action, as the solution of a metal in an acid, and the combustion of charcoal in an ordinary fire, it is believed, is always attended by the development of elec- tricity.. In the combustion of charcoal, the gas arising from the coal is positive, while the coal itself, if insulated, is negative; and when a metal is dissolved in an acid, a current of positive electricity always passes from the metal to the liquid, and any conducting substance, as a plate of copper, contained in it. Let Z be a zinc plate immersed in water, acidulated with a little sulphuric acid, con- tained in a glass vessel, and C a plate of copper, also immersed in the same liquid; the zinc will be gradually corroded, and a current of positive electricity pass from it through the liquid to the copper; and if the plates are connected by a wire, the current will pass over it in the direction indicated by the arrows. But, although we have, in these and other cases of chemical action, such decided and even powerful developments of electricity, it is admitted, that in very many cases where chemical action really takes place, no indications of electricity have as yet been observed. The action of one salt upon another, of one metal upon another, or Thermo-Electric Pile. Simple Circuit. Quxstions.—Describe the thermo-eleciric pile. 94, Is chemical action always attended by the development of electricity? Describe the simple galvanic circle. Are indications of electrical excitement always observed during chemical action? 88 GALVANISM. of a simple element, as oxygen or sulphur, upon a metal, may be mentioned, as instances in which no electrical excitement is actually known to take place. The electricity of chemical action, sometimes called dynamical electricity (92), properly constitutes the subdivision of the general “subject of electricity called GALVANISM; and under this title it will be discussed more at length, as it is this branch of the general subject which more especially concerns the student of chemistry. GALVANISM. 95. The science of Galvanism owes its name and origin to the experiments on animal irritability made by Galvani, professor of anatomy at Bologna, Italy, in the year 1790. In the course of some of his investigations, he discovered the fact that muscular contractions are excited in the leg of a frog recently killed, when two metals, such as zine and silver, one of which touches the crural nerve, and the other the muscles to which it is distributed, are brought into contact with one another. The experiment with the legs of a recently killed frog is easily repeated, in the following manner :— After killing the frog, immediately separate the hind-legs, with a small portion of the spine, and remove the skin; then bind around the part of the spine removed with the legs a piece of tin-foil, F, and, holding it up with the left hand, apply a piece of silver coin, or a rod of silver, S, bent, if neces- sary, so that it shall touch the tin-foil and the flesh of one of the legs at the same time. At each con- tact of the metals, the muscles of the leg will be violently contracted, and jerking of the legs pro- Bpcedceit duced. ; The experiment succeeds best when the Frog. whole is kept wet with clean water. The irrita- Querstions.—By what name is the electricity of chemical action gene- «. rally known? 95. What was the discovery of Galvani? Describe the experiment with the legs of the frog. GALVANISM. 89 bility of the muscles will gradually subside, but sometimes it will continue more than an hour after the death of the animal. The large legs of some insects, especially those of the grasshopper, may be used for the same purpose. It - is necessary only to remove witha sharp A penknife a portion of the skin from each B side of the thick part of one of the leap- ing legs, so as to expose the flesh; then by laying the under side of the leg upon a small piece of moistened zinc, Z, and Z bringing a piece of copper, C, in contact Experiment with Grasshopper. with the flesh exposed on the upper side, no motions will be observed until the copper also touches the zinc, when quick movements or jerks of the lower part of the leg, A B, will be seen, each time the contact is made. 96. Simple Galvanic Circles—A, simple galvanic circle is formed of three substances, two of which are usually metals, and the third a liquid, as a dilute acid.. The arrangement de- scribed in paragraph 94 constitutes such a circle. The zinc is acted upon by the acid, and the electrical disturbance takes place over all that part of its surface covered with the liquid; and a current of positive electricity flows to the liquid. If, now, a plate of copper, or other metal not capable of being acted upon by the liquid, be introduced, it will become positive by receiving elec- tricity from the liquid; and, by connecting the two plates by wires, @ constant current is established over these wires, as shown by the arrows. It matters not, so far as galvanic action is con- cerned, at what part the plates touch each other. A current is formed, whether contact betwéen the plates is made below, where covered with liquid, above, where uncovered, or along the whole length of the plates, provided both plates are immersed in the same vessel or diluted acid. But in every case a circuit must be formed, around which the electricity may traverse, ‘either in a single current, or in many partial currents, into which it may divide itself, as will be the case when the metals are in contact along their whole surfaces. ‘This last result it is desirable to avoid; and therefore the metals are always to be kept separate below. the liquid, and above it also, except at the part where the Questions.—Describe the experiment with the leg of a grasshopper. 96. What constitutes a simple galvanic circle? When is the electricity excited? What is the use of the plate of copper? In what direction does the positive current flow? Must the circuit always be complete ? 8 * 930 GALVANISM. current is desired to pass. Usually, a wire is connected with each plate, which may be brought in contact or separated at pleasure. When they are in contact, the circuit is said to be closed ; when they are separated, it is said to be broken, or open. 97. As the electricity is developed entirely by the chemical action between the zinc plate and the acid, it is only upon the surface of the zine covered by the acid that the electric disturbance takes place; and, other things being equal, the quantity of elec- tricity set in motion will be propor- tional to the extent of zinc surface thus exposed to the acid. And in every case, in order to establish the current, the circuit must be made complete. Thus, if we take two cups of dilute acid, immersing in one a copper, C, and in the other a zinc, Z, plate, and connect the two by a wire, as shown in the figure, though some chemical action will take place, no current will be established, for the reason that no circuit has been formed. Chemical action does indeed take place in the cup containing the zinc plate, and its electricity no doubt is disturbed ; but, still no current can be esta-- blished. For this it is necessary, further, to add the conducting wire AB, as shown in the next figure; the direction of the current will then be as shown by the arrows, It is to be understood that here, as elsewhere, in using this lan- guage, we have reference to the positive fluid; but in reality there is just as much reason to believe there is also at the same time a Circuit not Formed. Circuit Complete. Quusrions.—When is the circuit said to be closed? When open? 97. To what will the quantity of fluid put in motion be proportional ? Explain the necessity of completing the circuit, as illustrated by the figures in this paragraph. GALVANISM. 91 negative current established in the opposite direction. In every case, the direction of the positive current will be /rom the metal acted upon to the liquid, and that of the negative, of course, the {reverse. The direction of the positive current, therefore, in the 2 apparatus last figured, is from the zinc cell to the copper cell, over Z the wire connecting the cells, and from the copper to the zine over the wire connecting the plates, as shown in both cases by the arrows. To break the circuit it matters not which of these wires is inter rupted; both are equally necessary to complete the circuit. 98. A simple galvanic 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, even a plate of metal, with two portions of the same liquid, may be made to constitute the-simple circuit, provided only the conditions are such that one side of the metal shall be acted upon by the liquid more readily than the other. This will be effected, if one portion of the liquid is warmer or stronger than the other, or if one sur- face of the metal is rough and the other polished. We have above represented the positive current as passing from the zinc, through the liquid, to the copper, and in the opposite direction over the wires connecting the plates above the liquid; this will always’ take place when a, diluted acid is used, which attacks the zinc more violently than it does the copper; but if a solution of ammonia be substituted for the acid, the copper will be most acted upon, and the current will move in the opposite direction. It is not necessary that copper and zinc alone should always be used in these experiments; other metals may be adopted, with equal, and, in some cases, with ‘even more decisive results. Nor is it required that the liquid should always contain an acid; other substances, as solutions of the salts, are often very efficacious in exciting this subtile fluid. The conditions required are, that the metals and liquid used should be such that chemical action will take place more readily between one of them and the liquid than between the other and the liquid; and that metal is always found positive (below the surface of the liquid) which is most acted upon by it. Other things being equal, the galvanic action will be more intense, the greater the difference between the the two metals Quzstions.—Is there a current of the negative fluid? What is its direction as compared with that of the positive? 98. How may a simple circle be formed of a single metal and two liquids? Will the positive current always pass from the zinc to the copper? Why is the direction reversed when aqua ammonia is used? May other metals besides copper and zinc be used? What are the conditions required? 92 . GALVANISM. used, as regards their tendency to be acted on by the particular menstruum in which they are immersed. Besides the above arrangement, there are several modifications of the simple galvanic circle, each possessing its own peculiar advantages, which will be described hereafter. 99. Compound Galvanic Circles—Galvanic Batteries—The compound galvanic circle, or galvanic battery, consists of a num- ber of simple circles, so arranged in a series, that the copper of each simple circle is connected with the zinc of the one adjacent. One extreme of the series, it will be evident, will be copper, and the other zinc; they are often called the poles of the battery, the former being positive and the latter negative. The voltaic pile (from the name of its inventor) deserves here to be noticed, as the earliest and simplest instru- ment of this kind, though by no means the most efficient. It is formed of pieces of copper, c, zine, 2, and cloth, the latter being moistened with a solu- tion of salt or acidulated water. Commencing with either of the metals, upon this is placed a piece of cloth, and then a piece of the other metal; the three, of course, constituting a simple galvanic circle. Upon this circle other simple circles are then formed in the same manner, care being taken to place the metals throughout the series in the same order. The series may be extended indefinitely ; but, usually, from fifty to one hundred pairs of metallic plates will be found as many as can be employed advantageously. When in action, the extreme zine plate, which is represented as uppermost in the figure, will be negative, and the extreme copper plate positive; and if they be connected by wires, the current will flow in the direction of the arrows, both through the series, and over the wires. The extremes of the series are called its poles, or electrodes (from electron, and odos, a way). Voltaic Pile. QuEstTions.—99, What constitutes the galvanic batter : 1 or co: circle? What constitutes the poles of the arrangement e Deserve dhe voliaic pile. How many pairs of plates are n ? or electrodes ? e ceded? What are the poles, GALVANIS5M. 93 The voltaic pile is now rarely employed, because we possess other modes of forming galvanic combinations which are far more powerful and convenient. Cruickshank’s battery, one of the earliest invented, consists of a trough of baked wood, about thirty LTPPPIIEET. SU mill) A i inches long, in which are placed, Cruickshank’s Battery. lit ia - li ee il ill iia il at equal distances, fifty pairs of zinc and copper plates, pre- viously soldered together, and so arranged that the same metal shall always be on the same side. ach 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 con- structed is always ready for use, and is brought into action by filling the cells left between the pairs of plates with some conve- nient solution, which serves the same purpose as the moistened cloth in the pile of Volta. An excellent compound circle, or battery, is formed by com- bining a number of cups like that ‘ represented in paragraph 94. ach cup contains a zine, Z, and copper plate, C, the zine of one cup being con- nected with the copper of the next, through the whole series, leaving the two extreme plates free; and the cups are filled with diluted acid, or a solution of salt. The two free plates, constituting the extremities of the series, will be the poles, or electrodes; and when they are connected by wires, the current will be established in the direction of the arrows. By studying closely this arrangement, it will be seen that the actual quantity of electricity flowing over the wires connecting the electrodes, is no more than when a single cup only, with a single ‘pair of plates, is used, The same electrical disturbance takes place in each cup, over the whole surface of the zinc plate which is covered with the liquid, the part of this plate above the liquid oo Compound Circuit. Quesrioxs. —Describe the trough battery. What is said of the quantity of electricity flowing in the compound circle, or battery? How does this appear? 94 GALVANISM. becoming negative, and the liquid becoming equally positive; the copper plate then serves as a conductor to take up this positive electricity, and convey it to the negative zinc of the next cup, by which it will be exactly neutralized. However extensive the series may be, this will take place with every alternate zine and copper plate except the extreme ones; so that the quantity pass ing over the wires connecting the electrodes, will be only that of the single pair of plates constituting the extremes of the series. 100. But although the quantity of electricity developed at the electrodes of the compound circle is no more than we should obtain by using a single pair of plates, yet it will be found to have acquired a very important property, called intensity. By this term is meant its power to overcome resistances which may impede the passage of the current. The current from a single pair of plates, however large they may be, will always be exceed- ingly feeble, .and will not flow unless the wires connected with them are in actual contact; .but, if the polar wires of the com- pound circle are once brought in contact, they may be separated at a little distance, and the current will continue to pass between them, with a brilliant flame. The reason is, because the current fromthe compound circle possesses sufficient intensity to overcome the resistance of the thin stratum of air between the wires, which is not the case with the current of the simple circle. So, if the polar wires of the simple circle are grasped, one in each hand, by the operator, not the least sensation is felt, because there is not sufficient intensity to impel the current through the system, which is comparatively a poor conductor; but if the same is done with the polar wires of the compound circle, especially if the series be extensive, the moment the circuit is formed, a pow- erful shock is experienced, similar to that received from the Ley- den jar. This is owing to the increased intensity of the current from the compound circle, enabling it to overcome the resistance which is interposed. . Questions.—100. What benefit then is derived from increasing the series? What is meant by intensity? -Why will not any sensation be produced in the system by a single cell? GALVANISM. 95 101. From the above facts.we deduce this important practical principle: that, to produce a current of quantity, a single pair only of large plates is wanted; but to give intensity, a number of simple circles must be combined, in the manner deseribed. Compared with frictional or statical electricity, that of the most powerful galvanic battery has always ouly a feeble intensity, but the quantity is often immense. The energy of any battery, whether composed of one or many simple circles, will depend very much upon the nature of the liquid used. A solution of common salt, sulphate of soda, nitrate of potassa, alum, or other salt, will answer the purpose, but acids are better. Generally, one of the stronger acids is used, diluted with 15 or 20 times its weight of water. For ordinary purposes, 2 mixture of equal parts of nitric and sulphuric acids, diluted with 20 times their weight of water, will be found to answer well. 102. Nature of the Chemical Action in the Battery—The development of electricity by the usual galvanic arrangements is attributed chiefly, if not entirely, to the decomposition of water in contact with the zinc plates. Water is a compound of oxygen and hydrogen, and is incapable of acting upon zinc, unless some acid be also present. But when a piece of this metal, in its usual impure state, is immersed in diluted acid, the water is decom- posed, its oxygen combining with the zinc, forming, oxide of zine, while the hydrogen rises in bubbles and escapes in the air, and at the same time the oxide of zinc is taken up by the acid. If, now, a plate of copper is placed in the diluted acid at a little distance from the zinc, and the two connected by a wire, constituting a simpie galvanic circle (97), the bubbles of hydrogen will not rise around the zine as before, but around the copper; showing that the gas has in some way been transmitted through the liquid between the plates, though not the least appearance of any motion can be observed by the eye. If the connecting wire is removed, the evolution of hydrogen at the copper plate at once ceases with the cessation of the electrical current, but continues to rise slowly QuEstions.—101. What is said of the intensity of the excitement pro- duced by the galvanic battery, as compared with that of statical electricity ? What acids are recommended for use in the battery? 102. What is said of the chemical action that takes place when a piece of zinc is immersed in w dilute acid? What is the occasion of the bubbles upon the zinc? When a copper plate is connected with the zinc where do the bubbles of hydrogen make their appearance? 96 GALVANISM. around the zinc. This latter effect, however, is occasioned by the impurity of the zinc. Thus it would seem that the development of the current is occasioned entirely by the decomposition of the water, and the formation of oxide of zinc. When the battery is in active operation, though the hydrogen is rapidly evolved at the copper plates, yet the whole surfaces of these plates will be all the time covered with a film of this gas, which interferes with its conducting power, and prevents the fre passage of the current; at the same time, as a matter of course, diminishing very considerably the energy of the battery. Te remedy this difficulty, several new forms of the battery have recently been invented, which act with great energy, and will here be briefly described. 103. Daniel’s Constant Battery.—This excellent instrument consists of a cylindrical vessel of copper, C, in which is placed another smaller one, L, made of unoiled leather, or unglazcd porcelain, through which water will gradually percolate; and in the latter is contained a rod of zinc, Z, about an inch in diameter. To charge it, the inner porous ves- sel, which coutains the rod of zinc, is filled with diluted sulphuric acid (acid 1 part, and water 8 parts), and the space around the inner vessel with a saturated solution of blue vitriol, acidulated with Danie’s en, SUlphuric acid. To the side of the copper vessel, and also to the zinc rod, wires are soldered, with binding screws for holding the polar wires; the one connected with the copper being positive, and the other negative, as shown by the algebraic signs. = Usually, the zine rod is amalgamated with mercury, which is done by rubbing the surface with mercury, while covered with some weak acid. This renders the chemical action over the whole surface more uniform, and the action of the battery more constant ; but the same thing may be accomplished with less trouble, by using the zinc in its ordinary state, and substituting, in the porous QueEstions.—103. Describe Daniel’s battery. How is the zinc omal- gamated? GALVANIB8M. 97 cell, a saturated solution of sulphate of soda (Glauber’s salt), instead of the diluted acid. The above arrangement, it is plain, constitutes a simple galvanic circle; and its action is particularly energetic and constant, in consequence of the accumulation of hydrogen gas upon the copper plate (102) being completely avoided. This will appear from the following explanation. In this instrument, as in the more common one first described, the electricity is developed at the surface of the zinc, by the decom- position of the water; the oxygen combining with the zinc, and the hydrogen passing through. the porous vessel into the vitriol solution, and thence to the sides of the copper vessel, which con- stitutes the copper plate of the series (98). Here the hydrogen does not make its appearance in bubbles upon the surface of the copper, as in the common arrangement, but enters into a new combination with the oxygen of the oxide of copper deposited from the vitriol solution. Blue vitriol is a compound of sulphuric acid and oxide of copper; and while the battery is in operation, it is all the time decomposing, its acid passing into the porous cup, to act upon the zine, while the oxide of copper is itself also decomposed, its oxygen combining with the hydrogen at the sur- face of the outer vessel, which receives a new coating of metallic copper. Any number of these arrangements may be united, by connecting the zine of one with the copper of the next, as heretofore described (99); and a battery so constructed has this great advantage, that no action takes place when the circuit is not closed. It is also very constant in its action, affording a uniform current for seve- ral hours in succession. The figure in the margin repre- sents a battery of this kind, of six series. When a battery of this kind is to be used some time, a quantity of un- dissolved blue vitriol should be kept in the upper part of the copper cell, either upon a shelf provided for the : purpose, or in a muslin bag, to keep the solution constantly saturated Qursrions.—How is the hydrogen disposed of in this arrangement? Why is it called a constant battery? How are the separate ceéllg to be united to form the compound arrangement? 9 98 GALVANISM. 104. Grove’s Cell —This battery, invented by Professor Grove, of London, is remarkable, not only for the constancy of its action, but also for its great intensity. : The construction of this battery is shown in the accompanying figure. A glass or porcelain cup, of a proper size, is used, and in it is placed a hollow cylinder of zinc, Z, (usually having a slit in one side, to allow a free passage to the liquid), and inside of this, a small cylindrical cup, C, of porous or unglazed porcelain. The glass cup is then filled with diluted sulphuric acid (of the same strength as is used in Daniel’s battery), and the porous cup with strong aquafortis (nitric acid). Lastly, a thin slip of platinum, P, is suspended in the aquafortis, and supported by a piece of wood attached to the side of the glass cup, through which a wire passes, and is bent in the form represented in the figure. A projection upward from the zinc supports a binding screw, shown on the right, and another is soldered to the wire to which the platinum is attached, shown at the left. These, of course, serve as the positive and negative poles of the circle; and to them the polar wires may be attached, when required. The zine should be well amalgamated, as heretofore described. The action of this battery is essentially the same as that of Daniel’s, except that the hydrogen from the decomposition of the water, passing into the porous cell, is expended in decomposing the nitric acid, which, when the instrument is in action, gives off copious nitrous fumes. To understand this, it is necessary to recollect that nitric acid is a compound of nitrogen and oxygen; and the hydrogen entering the porous cell takes away a part of its oxygen, forming. water; and the binoxide of nitrogen which is liberated rises, and uniting with more oxygen from the air, forms. the nitrous fumes. Grove’s Cell. * A battery of twelve series of Grove’s arrangement is represented in the following figure. The cups are contained in a box of wood, for the sake of convenience in handling, and between the cups are partitions to Quesrions.—104. Describe Grove’s cel]. What in this case becomes of the hydrogen? GALVANISM. 99 hold them more steadily. The hollow cylinders of zinc, when made for this purpose, are cast with arms rising from one side, and then project- A NI Ne Pee nei es! AN f a Pipes! : Ale fe i ing a distance horizontally ; and to the end the platinum plate is firmly soldered, so as to hang directly in the nitric acid cup of the next adjacent series, The whole, it will be observed, forms a connected series; and the terminal zinc at one extremity, and the platinum at the other, with each of which @ binding screw is connected, constitute the negative and positive poles. The terminal platinum plate i is supported in its place by a wire passing through a piece of wood attached to the side of the box or the cup, as represented in the figure. When a greater power is required than is afforded by a battery of this size, it is found more con- venient to connect two or more batteries together than to have a larger number united in one series. The batteries are connected by extending a wire from the positive pole of one to the negative of the next; they then in reality become a single series. This is the kind of battery generally used in working the magnetia telegraph, as it excels all others in the constancy and intensity of its action. 105. Smee’s Cell.—This very efficient arrange- ment is. represented in the figure in the mar- gin. Two plates of zine, well amalgamated, are firmly held together against a piece of wood, W, by means of a brass clamp and screw; and between them is a plate of silver, 8, the surface of which has been coated over with metallic platinum, in a state of fine powder, called plati- num black. The zinc and silver plates are then suspended in a glass vessel, the piece of wood resting upon the top. A binding screw, con- stituting the + pole, is connected by a wire Smee's Cell. Grove’s Battery. Questions.—What is said of the character of batteries of this kind? 105. Describe Smee’s arrangement. 100 GALVANISM. (which is insulated from the brass clamp through which it passes) with the silver plate, and another, constituting the — pole, is soldered to the clamp which holds the zine plates in their places. The liquid used in the glass cup is sulphuric acid, diluted with 10 or 15 times its weight of water. The peculiar advantage possessed by this form of the battery depends upon the rapid evolution of hydrogen from the platinized silver plate. We have seen above (102) that the accumulation of this gas upon the smooth surface of the copper plate, in the old arrangement, considerably retards the passage of the electric cur- rent, by preventing the liquid in a measure from coming in contact with the plate; but this is avoided, in Smee’s arrangement, by the roughened surface of the silver plate, produced by the platinum deposit. Compound eircles or batteries are readily formed by combining the simple series of Daniel with each other, or those of Smee with each other ; but the proper mode of doing it will be easily understood without further illustrations. For many purposes, they answer well; but neither of them possesses the energy of that of Grove above described. As batteries are sometimes constructed, and as, they are usually repre- sented in books, the direction of the current appears to be the reverse of that in the simple circuit, but this is in consequence of there being a superfluous plate at each extremity which serves only as a conductor. In the figures in this book, however, these superfluous plates are not represented, and the remarks in the text are made with reference to instruments of this construction. 106. Bunsen’s arrangement is constructed on the same principle as Grove’s, except that hollow cylinders of carbon surrounding the zinc, are substituted instead of the platinum plates. The carbon cylinders are made of carbon from gas-retorts, by grinding it to a powder, and ie kneading it with flour dough, and afterwards baking it in a strong eat. 107. Ohm’s Formula.—The effective force of a battery of any construction will depend upon a number of conditions, or circumstances, which are well expressed in a formula devised by Prof. Ohm, and therefore generally known by his name. : To estimate the effective force of any galvanic arrangement, two things are to be considered, viz: 1. The electromotive force, or absolute tension of the electric fluid, and 2. The resistance to be overcome. As there must always be some resistance to the passage Quzsrion.—What is the peculiar advantage of Smee’s arrangement ? 106. Describe Bunsen’s arrangement. 107. What is the design of Ohm’s formula? To estimate the effective force of a battery what two things must be considered ? GALVANISM. 101 of the fluid, the effective force must always be less than the full electromotive power, if such resistance did not exist. The resist- ance will be occasioned chiefly by the wires connecting the poles, but something is due also to the liquid between the plates. In the case of a single cell, let the absolute tension be repre- sented by ¢, and let r be the resistance of the wire, and 7’ the resistance of the liquid between the plates, and A the effective force; then will A = — That is, the effective power of the cell will be directly proportional to the absolute tension of the electric fluid, which will in general depend upon the activity of the chemical action taking place, and inversely as the sum of the resistances of the liquid between the plates, and that of the con- ducting wire. To apply the same law in the case of a compound series or nt r+ used to represent the whole number of cells. We see, therefore, that the effective power will be directly proportional to the elec- tromotive force of each cell, multiplied by the number of cells, and inversely as the resistance, which is made up of the resistance of the wire connecting the poles, and the resistance of the fluid of the cells. The resistance r will be proportional to the length of the wire and inversely as the area of its section. The resistance 7’ will be proportional to the thickness of the stratum of liquid, and inversely as its conducting power. 108, Animal Electriecity.—Several animals, as the gymnotus electricus, which is found in the fresh waters of some parts of South America, the si/urus electricus, found in some African rivers, and the torpedo, a species of which has been taken, though rarely, upon the sea-coast of Massachusetts, possess the power of giving strong shocks of electricity, by means of peculiar galvanic arrangements with which nature has provided them. . The electrical apparatus of these animals is plainly connected with the nervous system, and is perfectly under the animal’s con- battery, we have the following formula: A = ———, in which x is Quzstions.—Vhat resistance will there always be to the passage of the current? To what is the effective force of a battery proportional ? 108, What animals are mentioned as possessing the power of giving shocks of electricity? Is their electrical apparatus under control of the will? Q* 102 EFFECTS OF GALVANIC ELECTRICITY. trol. It is made use of as a defence against enemies, and in paralyzing other small fishes, which are immediately seized for food. The shock given by some of these animals is very powerful. EFFECTS OF GALVANIC ELECTRICITY. 109. Galvanic electricity, as we have seen, differs essentially from ordinary, or statical electricity, in several important particu- lars, as its feeble intensity, its immense quantity, and its flowing in a continuous current; and, as we should expect, there is a cor- responding difference in the effects which these two kinds of electricity are capable of producing. In consequence of the feeble intensity of the- most powerful galvanic battery, it is quite incapable of producing many of the more brilliant effects of the common electrical machine, but others are produced not less important. In fact, in the galvanic battery the ordinary signs of electrical excitement are almost wholly want- ing, plainly for the reason that these indications depend chiefly upon intensity. Thus, when the circuit of a powerful battery is broken, that is, when the poles or electrodes are disconnected, both of them give signs of electrical excitement, if examined by the ordinary tests; one of them being positive, and the other negative, 2s before explained; but the indications are exceedingly feeble. A Leyden vial may also be charged by establishing a communi- cation between one of its surfaces and one of the electrodes, while the other surface is connected with the other electrode ; but the charge will always be slight. Either of thé electrodes will give a spark to a conductor pre- sented to it, but it is shown best by bringing the two polar wires in close proximity; and on establishing the communication be- tween the electrodes by the hands, previously moistened, a powerful shock is felt, precisely like that produced by the Qusstions.—109. In what respect does galvanic differ from statical electricity? In the charged galvanic battery, are the ordinary signs of electrical excitement apparent? May the Leyden vial be charged by an active battery? How maya spark be obtained from one of the elec- trodes? How is the shock produced? EFFECTS OF G@ALVANIC ELECTRICITY. 103 discharge of the Leyden jar. But the shock is felt only at the moment the current is established ; if afterwards the hands be held firmly in their places a peculiar feeling of numbness in the muscles in the line of the current succeeds, and continues until the current is again broken. 110. Heating Effects—Deflagration—When the communica- tion between the electrodes of an active battery is established by various substances capable of conducting the current, they often become intensely heated, and sometimes even consumed or dissi- pated in vapor by the heat. Thus a small wire interposed in the circuit will become red-hot in an instant, and gold and silver leaf, ‘in the same circumstances, will take fire and burn with brilliant scintillations. ' This heating effect of the galvanic current may be produced at a distance from the battery, and gun-powder or gun-cotton and other combustibles ignited. Let W be two copper wires, coated with tarred twine, so as to insulate them perfectly, having their ex- tremities connected by a very small platinum wire soldered to them, as shown through the glass cup C. Let the cup be now filled with gunpow- der or gun-cotton, and the other ends of the wires 2 brought in contact with the GS era nora eetes pees poles of the battery 5 3 immediately on the passage of the current, the platinum wire will be heated, and the powder exploded. The wires, if well coated, may be extended under water, and a sub- marine magazine exploded... This method has been used for exploding the powder in the blasting of rocks. i A mixture of oxygen and hydrogen may be inflamed in the same manner; for this purpose the mixed gases are contained in a_pistol, into which the wires are inserted, as shown in the figure on’p. 104. Quesrions.— Does the shock continue while the current flows? 110. How may the heating effects of the current be shown? How may gunpowder be inflamed? Describe the method of exploding « mixture of oxygen and hydrogen. 104 EFFECTS OF GALVANIC ELECTRICITY. Pistol. When pieces of well-burnt charcoal are attached to the polar wires, on bringing them near each other, a most brilliant are of flame appears between them, and:the points appear to be vividly ignited, as if heated by any other means. But the heating effect does not depend upon the combustion of the coal, since it is equally as great when the charcoal points are excluded from the air. To produce the effect, the points must first be brought into contact, but they may afterwards be separated-some distance, and the arc of flame will continue. At the same time a por- tion of the carbon point in connection with the positive pole disappears, and the other point is elongated as if a by matter transferred from the other side. If the char- ti coal connected with the positive pole be hollowed out so Metal Vola 28 to receive pieces of metal, as silver, gold, or platinum, talized. -when the current passes the metals will not only be fused, but appear to be even volatilized, and pass off in fumes. 111. Chemical Effects, Decomposition—The chemical effects of the galvanic current are seen chiefly in the decomposition of compound substances, and in the operations of electro-metallurgy, soon to be explained. Thus, when two gold or platinum wires Quustions.—Describe the experiment with the charcoal points. How may the metals, as gold and platinum, be even volatilized? 111. In what are the chemical effects of galvanism chiefly seen ? EFFECTS OF GALVANIC ELECTRICITY. 105 are connected with the opposite ends of a battery, and their free extremities are plunged into the same cup of water, but without touching each other, hydrogen gas is disengaged at the negative, and oxygen at the positive wire, these being, as we have seen (102), the elements of water. If the wires are brought into actual contact in the water the current is conducted directly through without acting upon the water, and if any other metal except gold or platinum is used for the posi- tive pole, it will be rapidly attacked by the liberated oxygen. By using one or the other of the two pieces of apparatus figured in the margin, the oxygen and hydrogen may be collected separately or together, as i Decomposition of Water. may be desired. The first piece consists of an open el with a shelf and support for two tubes, N and P, which are closed at the top, and binding screws marked + and — which connect with wires passing un- derneath the edge of the ‘glass, and terminating in the mouths of the tubes. After filling the tubes and inserting them in their places,—the vessel being previously nearly filled with water, the current from the battery is made to pass through in the ordinary way. Very soon the gases will be seen to collect in the tubes; and as water contains by nt Decomposition of Water. volume twice as much hydrogen as oxygen, the tube N con- QuEst10ns.—How may water be decomposed by the current? Describe the apparatus for decomposing water and collecting the gases formed in separate tubes. Describe that for collecting the gases together. 106 EFFECTS OF GALVANIC ELECTRICITY. taining it will be found to fill proportionably faster than the other. When the two wires terminate in the same tube, the two gases will be collected together; and by passing afterwards a spark of common electricity through the mixture they will be again united, with an explosion. In decomposing water, it is well always to add a few drops of oil of vitriol, to increase its conducting power. If other compound bodies, such as some acids and solutions of salts, are exposed to the action of galvanisni, they are also decom. posed, one of their elements appearing at one electrode, and the other at the other. An exact uniformity in the circumstances attending the decomposition is also remarked. Thus, in decom- posing water or other compounds, the same kind of body is always -disengaged at the same side of the battery. The metals, inflam- mable substances: in general, the alkalies, earths, and the oxides of the common metals, are found at the negative electrode; while oxygen, chlorine, and the acids, go over to the positive electrode. 112. Those substances which appear at the positive side have been called electro-negative bodies, while those that are separated at the negative wire are called electro-positive bodies. The decomposition of a salt, which must be in solution, may be shown in the following manner :—Let two wine-glasses be filled with a solution of sulphate of soda, (which is a compound of sulphuric acid and soda,) and let some fibres of moistened cotton be extended between them, as shown in the figure. If the current is then transmitted through the cups, the salt will soon be decomposed, and the cup in connection with the positive electrode will be found to contain weak sulphuric acid, and that in con- nection with the negative electrode a solution of soda. If, now, a little red cabbage-water be poured into each, the acid liquid will become red, and the soda solution green. Decomposition of Galt. Quxstions.—May other compounds also be decomposed? In de- composing a compound, will the same element always appear at the same electrode? 112. What are electro-negative and electro-positive substances ? EFFECTS OF GALVANIC ELECTRICITY. 107 A compound to be decomposed by the current must be in the liquid state, and must of course be a conductor; but all com- pounds answering these conditions are not by this means capable of direct decomposition. Yet compounds, not directly decom- posable by the current, are often decomposed indirectly by the hydrogen derived from the decomposition of water that is present. Thus, sulphuric acid is not directly decomposed by the current, but hydrogen separated from the water present, making its appear- ance at the negative pole, unites. with the oxygen of the acid, and causes the evolution of fumes of sulphuric acid. Following the suggestions of Faraday, the term electrolysis (from electron, and luo, I unloose) is now very generally used to express this electro-chemical decomposition; and the term electrolyte to indicate a compound capable of being thus decom- posed. The positive pole or electrode is also called the anode, and the negative pole the cathode (from ana, upward, kata, downward, and odos, a way). But instead of the terms anode and cathode, most writers prefer to say positive or negative electrode, as the case may be. The elements of a compound capable of separation by this mode, are termed zons (from the Greek participle ton, going); the anion being the element which appears at the anode, and tha cation the element which goes to the cathode. It will at once be seen that the anions are electro-negatives, and the cations electro- positives. It is not to be inferred from the above remarks, that every sub- stance will always make its appearance at the same electrode, whatever may be the other substance from which it .is separated by the electrolytic action. Oxygen does indeed always appear at the positive electrode, and potassium at the negative; but in the electrolyses of the compounds of other substances, that element will appear at the positive electrode which is most clectro-negative, and that at the negative which is most positive. 118, The following table exhibits the electrical relations of several of the more important elements. It is to be understood that each sub- Quzstions.—Are all compounds directly decomposable by the current? Define the terms, electrolyte, anode and cathode. What are ions ?—what anions and cations? Will every substance always make its appearance at the same electrode, whatever may be the other from which it is sepa- rated? What is the law in this respect? 108 EFFECTS OF GALVANIC ELECTRICITY. stance in the first column is electro-negative as compared with each one below it, but in the second column each substance is negative as com. pared with all above it: Oxygen. Potassium. Fluorine. Sodium. Chlorine. Calcium. Todine. Carbon. Sulphur. Hydrogen. Nitrogen. Zine. Phosphorus. Iron. Arsenic. Bismuth. Antimony. Tin. Gold. Lead. Mercury. Copper. Silver. | Silver. 114. We have seen that the decomposition of a compound takes place only when the current is made to pass through it—then one of the ingredients is collected at one electrode, and the other at the other electrode; thus in the electrolysis of water, the oxygen is collected at the positive and the hydrogen at the negative elec- trode. But howis it that these effects are produced? and at what precise point or points? Are both gases liberated at each elec- trode, but one only, hydrogen (the electro-positive element), col- lecting at the negative electrode, and the other, oxygen (the electro-negative element), collecting at the positive pole? This would require that opposite currents of oxygen and hydrogen should be passing by each other in the liquid between the poles while the battery is in operation, of which we have no evidence. Or, does the decomposition take place along the whole line be- tween the poles traversed by the current? Other similar inquiries may be made, which cannot be answered positively, but the fol- lowing is believed to be a correct representation of the phenomena witnessed, so far as we are able to determine. Water is a com- pound of hydrogen, which we will represent by H, and oxygen, which we will indicate by O;—and the compound by 2. A tier or row of particles between the poles we may then represent thus: H, H, H, H, H, H — +000000 Questions.—114. When only does the decomposition of a compound take place? Describe the manner in which the decomposition of water is supposed to be effected by the passage of the electric current. EFFECTS OF GALVANIO ELECTRICITY. 109 the sign + indicating the position of the positive pole, and — that of the negative. Instantly as the current begins to pass, oxygen from the decom- position of thé water appears on the positive side, and hydrogen from the same decomposition at the negative side, a state of things which may be répresented ‘as follows: ,H, H, H, H, H, H Pe +000000 We have now one less particle of water than before, and one of the elements of the decomposed particle is found at oné electrode, and the other at the other electrode. To produce this effect, it is only necessary that, by the action of the current, all the particles of hydrogen should be removed one place to ‘the right, or all the particles of oxygen one place to the left. That is, the electrolysis of every particle of water in the track of the current has taken place, but the immediate reunion of all the particles has followéd, except the extreme particle of oxygen, on the one hand, and the extreme hydrogen on the other. The oxygen and hydrogen thus liberated, at once make their escape; and the continued action of the current produces a like effect on other particles of water until the action ceases, or all the water is decomposed. , 115. The quantity of electricity required to effect the decomposition of any compound is probably always the same, as would be shown if we had means to measure it accurately; and the relative quantities of several electrolites decomposed by a given quantity of electricity will be represented by the combining numbers of these compounds. We shall hereafter have occasion to allude to this point again, in connection with the subject of combining proportions or equivalents. N16, Electro-Metallurgy is the name applied to the deposition of the metals from their compounds by the chemical agency of the galvanic current. We have seen above (103), in describing Daniel’s battery, that during its action there is a constant depo- sition of metallic copper upon the negative plate. Now, if, for the copper plate in this arrangement, a medal, or coin, or other conducting body be substituted, the deposition of the copper upon it will take place in the same manner, and all its minute pecu- Questions.—115. Is the quantity of electricity required to effect the same decomposition always the same? 116. What is elcctro-metallurgy ? 10 I10 EFFECTS OF GALVANIO ELECTRICITY. liarities will be copied. An apparatus of this kind, called the electrotype, is figured below. ‘ A glass vessel is partly filled with a saturated solution of blue vitriol, and in this is placed a porous vessel, containing dilute sulphuric acid, and a rod of zinc, Z, having a binding screw at! top. The medal or coin to be copied is then suspended in the vitriol solution by means of a wire inserted in the binding screw. The surface of the medal on which the copper is to be de- posited should be perfectly clean, and the other surface should be protected by a coating of wax or varnish. In the figure, two medals, M, M, are supposed to be connected at the same time with the zine. A better method than the above is to use a regular Smee’s battery, and to have the blue vitriol solution in a separate ves- sel, as in the annexed figure. Then let the article to be copied, A, be connected with the zinc of the battery, and a plate of copper, ©, with the silver, both being suspended, at a little distance from each other, in the vitriol solution. By the action of the battery, the piece of copper will be gra- dually dissolved, and a corresponding deposit of metallic copper made upon the medal. Electrotype. Electrotype. In -the battery here used, one of the zinc plates is supposed to be removed, presenting clearly to view the plate of silver. 117, Other metals besides copper may be deposited in this manner. but a battery of several cells is in most cases required. The most im- portant application that has been made of this discovery is in depositing silver and gold in thin lamin: upon other metals, called plating or gild- ing. For this purpose a Daniel’s or Smee’s battery of about four cells answers well, and a fifth, which is called the depositing cell. This is Quzstion.—Describe the apparatus called the electrotype, - ELECTRO-MAGNETISM. 111 filled with a solution of cyanide of potassium, and used in the same manner as just described for obtaining a deposit of copper, except that silver or gold must be used instead of the copper, C, according as one or the other of these metals is to be precipitated. ELECTRO-MAGNETISM. 118, Natural Magnet, or Loadstone.—Among the ores of iron, pieces are often found which possess the property of attracting and retaining pieces of iron or steel with more or less force, and are called magnets or loadstone. Hach magnet always has two points iu which the attractive force appears to be concentrated, which are called the poles. They are always readily found by rolling the magnet in iron filings, which will be pollectod: more at these points than in other places. Gene- sp Maun, .Tally they are nearly opposite to each other. (See figure.) If a magnet is broken into several pieces, each always retains the same magnetic properties as the whole mass, but in less degree. Sometimes a magnet has more than two poles. 119. If a magnet be suspended horizontally by a thread, or placed upon a piece of cork floating in a vessel of water, one of the poles will turn towards the north, and is hence called the north pole, and the other towards the south, and is called the south pole. If two magnets thus suspended are brought near each other, it will be found that like poles repel each other, but unlike poles attract. \These attractions and repulsions extend to some dis- tance, and are not affected by the interposition of other bodies, not capable of becoming magnetic. This may easily be shown by interposing a pane of glass, or plate of copper, or a thin piece Questions.—118. What is the natural magnet, or loadstone? What are the poles? What is the effect if the magnet be broken in several pieces? 119. What is the north pole? What the south pole? When two magnets freely suspended are brought near each other, what is observed of like, and what of unlike poles? 112 ELECTRO-MAGNETISM. of wood between the two magnets, when it will be seen that the action of the magnets upon each other is the same as before, and does not even suffer diminution by the interposed substance, except as the distance between them is increased. 120. Magnets and Diamagnets—It has of late been very satisfactorily determined that all substances may be divided into two classes,—the magnetic and the diamagnetic. To the first class belong all substances which, like iron, nickel and cobalt, are attracted by either pole of a magnet when presented near them; and when shaped into bars and free to move (as when suspended by a thread in the centre) in the vicinity of a magnet, they arrange themselves in the direction of a line uniting its : 2 poles. Two bar magnets best illus. trate this property; when in the Magnets. vicinity of each other, and free to move, they take the position indicated in the figure. The substances already named are the only ones that possess: this property in any considerable degree ; but others have recently been added to the list, as manganese, chromium, titanium, palla- dium, platinum, oxygen gas, &c., in which the magnetic property is manifested only when a powerful magnet is used. Diamagnetic substances are such as are repelled by either pole of a magnet, and when made into the form of bars and free to move, in the vicinity of the poles of a Ni magnet, arrange themselves at right angles to a line uniting its poles. This relative position of the magnet and diamagnetic bar is shown in the a¢companying figure. This diamagnetic property is manifested more powerfully by bismuth than by any other substance, but phosphorus, antimony, zine, tin, sodium, mercury, copper, gold, glass, ether, alcohol, and many other bodies, are similarly affected. The experiment can only be shown by using very powerful magnets. DIAMAGNET Magnet and Diamagnet. QuEstIon.—120. Into what two classes may all substances he divided? How do magnetic substances arrange themselves when brought into the vicinity of a magnet? How do diamagnetic substances ? ELEOCTRO-MAGNETISM. 113 121. Magnetic Induction——When either pole of a magnet is brought in contact with a piece of soft iron, or only very near it, the iron itself becomes magnetic, and remains so until the magnet. is removed. The figure following represents several pieces of iron, placed in different positions near the poles of a magnet; on examination, they will all be found to have the magnetic property, their poles. being developed as indicated by the letters N and 8. Magnetic Induction. This influence of a magnet upon pieces of iron, which extends to a distance around its poles, is called its inductive influence. This influence is exerted by a powerful magnet to a considerable distance from either pole, or even through other bodies (119) which are not themselves capable of becoming magnetic. A piece of iron or other substance which is attracted by either pole of a magnet, is evidently first rendered magnetic by induction, and then the attraction follows as a necessary consequence. But the first piece, as a nail, being rendered magnetic by induction, will act in like manner upon a second, and this upon a third, and so on; so that several pieces may be lifted one after another, as represented in the figure. But it will be found, when the connection with the first magnet is broken, the pieces of iron instantly lose their magnetism, and fall asunder. 122. Pieces of hardened steel will also be affected in ae sw . . NEU a similar manner, but much less readily, and, unlike Induction. Questions. —121. What is the effect when either pole of a magnet is brought near a piece of soft iron? What is meant by magnetic induc- tion? Why is a piece of soft iron attracted by a magnet? . «& 10* ; 114 ELECTRO-MAGNETISM. iron, they retain the magnetism that has been induced. ‘They therefore become permanently magnetic, and for nearly every _purpose are superior to the natural magnet, and may be denomi- pated artificial magnets. The same magnet may be used suc- cessively to magnetize any number of steel bars, without losing any of its virtue; from which it follows that the magnet commu- nicates nothing to them, but only by its influence developes some hidden principle already there. Artificial magnets are frequently made in the form of the horse-shoe, and are called horse-shoe _ magnets. To the poles a short piece of soft iron is usually accurately fitted, called the armature or keeper. 123. The Magnetic Needle—Dipping Needle.—A slender bar of magnetized steel, suspended upon a pivot, so as to revolve freely, constitutes the magnetic needle. Sometimes it is attached to a circular card, and suspended upon a pivot, as in the mariner’s compass. 124. If a steel bar be suspended by its centre of gravity, and afterwards carefully magnetized, it will be found not only to place itself in the magnetic meridian, but to assume a position inclined to"the horizon. In northern latitudes, the north pole will be depressed and the south pole elevated, while in southern latitudes the south pole will be depressed. The angle of inclination is generally nearly the same in the same place, and is called the dip of the needle ; and a needle nicely balanced and adjusted for showing the dip is called a dipping needle. The dip of _the needle is subject to considerable variation, but at the present time it is, at Baltimore, about 71° 30’; at Philadelphia, 72° 15’; at New York, 73°; at Middletown, Conn., 73° 80’; and at Boston, 74° 24. The magnetic needle does not always point to the true north and south, but deviates more or less from this position at different times and places. This is called its variation. At Philadelphia, in 1840, the variation was 8° 52’ W., and at Middletown, Conn., about 6° 40’, 125. Terrestrial Magnetism.—The earth may be considered as a great natural magnet, which, by its action on the needle, in the same manner as any other Magnet, causes it to place itself in QuEstions.—122, May magnetism be induced in pieces of tempered steel? What are artificial magnets? 123. What constitutes the magnetic needle? 124, What is a dipping needle? 125. What may the carth be considered ? . ELECTRO-MAGNETISM. 115 the position of north and south. Indeed, it is by the inductive influence of the earth that magnetism is developed in bodies upon its surface. This is shown in bars of iron or steel that have stood long in a vertical position, which are always found to be magnetic. Tongs and pokers, from-their being usually kept in-an upright position, are almost always found to be magnetic. As it has been agreed to call that pole of the needle which points northward, the north pole, it is evident that the pole of the earth situated north must be a south pole; that is, it must possess southern polarity. So, also, the south pole of the earth must possess northern polarity. 126. Relation between the Electric Current and Magnetism. —TIt has been long known that a discharge of lightning will often affect seriously the magnetic needle, sometimes reversing its poles ; but it was not until 1819 that Cirsted made his famous discovery, which has served as the basis of the beautiful science of Electro- Magnetism. He first observed that when the wire, connecting the electrodes of an active galvanic battery, is brought near a magnetic needle, it is made to deviate from its ordinary position, and assume a new one, depending upon the direction of the current and the position of the wire in regard to the needle. Thus, the needle being in its natural position,—Ist, if the connecting wire be above the needle and parallel to it, the pole next the negative electrode will move westward; 2d, if the wire be beneath the needle, it will move east- ward; 3d, if the wire is on the west side, this pole will be depressed; and, 4th, if it be on the east side, it will be elevated. The figure in the margin indicates the motion that will be pro- st duced in the first of the above cases. Current and Needle. If the wire be placed under the needle, and the current made Questions. —Why do tongs and pokers become magnetic by standing in a vertical position? What is said of the north and south poles of the earth? 126. What was the fact first observed by Cirsted as regeids the wire conducting a galvanic current and a magnet? 116 ELECTRO-MAGNETISM. to pass from north to south, the motion of the needle will be the game as indicated in the figure. It follows, therefore, if the wire be bent around the needle, in the form of a rectangle, so as to ==. convey the current in one direction ——=7}=—_ } above the needle, and back again, in —_—= the opposite direction beneath it, both parts will conspire to produce the same effect, and the motion of the needle will be much increased. Stich an arrangement is represented in the annexed figure. In all these cases, the tendency of the needle is to settle directly across the wire, or at right angles to the direction of the current, while the influence of the earth is exerted to bring it in its first position, parallel with the wire, supposing the experi- ment to be commenced with the needle in its natural position. The position it will ultimately take will therefore be intermediate between these two. Current and Needle. 127. To avoid the directive influence of the earth upon the needle, the astatic (from the Greek astatos, unstable) needle has been contrived. It consists of two needles, of nearly equal strength, fixed to the same axis, with their poles reversed in reference to each other, and | suspended by a thread, as shown’ in the : } . figure. One of the needles being a little >, ___—Ss-—: more highly magnetized than the other, or “nf 5\ a little larger, they will have a slight ten- dency to settle in the meridian. If, now, a wire is bent several times around the lower needle, each turn or coil being coated with some insulating sub- stance, when the current is passed around it, its influence on both needles will be to turn them in the same direction; and the Astatic Needle. Qurstions.—What is the effect if the wire is bent ar : ound pass several times around the needle? What is the meal plenty of the needle? 127. What is the astati 2 ibe i ence : ic needle? Describe its con- ELECTRO-MAGNETISBM. 117 arrangement becomes a most delicate in- strument for indicating the passage of the feeblest currents. Such an instru- ment is called a galvanometer, or gal- vanoscope. To protect it from currents of air, the whole is usually enclosed in a glass case; and beneath the upper needle, and above the coil of wire, a graduated circle is placed, to indicate exactly the comparative deflections of the needle. Such an instrument, in connection with a thermo-electric pile (93), becomes a most delicate thermometer, which is casblo of indzating a change of tem- (NINE perature of only a very small fraction of a degree. 128. Tangential Force —By a careful inspection of the motions produced in the needle by the currént in the several positions of the wire, as described in paragraph 126, it will be evident that the real tendency of each pole is to revolve around the connecting. wire in a circle, the plane of which is perpendicular to the wire ;— around the north pole in one direction and around the south pole in the other. The force which causes this motion is exerted in lines which are tangents to the circumference of these circles, and is therefore called a tangential force. The motion of the needle actually produced will of course depend upon the mode in which it is supported, as well as the position of the wire in reference to it. It is to be remarked, too, that the pole is a mere point situated near the extremity of the needle ;—between this point and the wire the force is exerted. This point,—the magnetic pole,—cannot exist independent of the needle itself, which must therefore always move with it; and therefore in order to determine the real motion in any particular Astatic Needle. Quzstions.—Describe the galvanometer, or galvanoscope. 128. What is the real tendency of each pole of a magnet when brought near the wire? What is the force called which produces this motion? Upon what will the motion actually produced depend? 118 ELECTRO-MAGNETIS8M. case we are to consider the two circumstances,—First, the motion the pole tends to make, and Secondly, the motion of which the needle is susceptible. Upon these two conditions plainly will depend the actual motion that will result. 129. In order easily to remember the particular motion a pole will tend to make in any given case, take the following example. Let us suppose the conducting wire to be placed in a vertical 5) position, and the current of posi- I! tive electricity to be descending through it, the tendency of a north pole in the vicinity of the wire yi, will be to move around it in a hori- zontal circle, in the direction indi- a — cated by the arrows in the figure, <] ! or in the direction of the hands N of a watch with the dial upward. Seer The tendency of the south pole would be to revolve in the opposite direction. If the direction of the electrical current is reversed, and it is made to pass up- ward, both poles would tend to revolve in the opposite direction from that described above. Whatever may be the position of the conducting wire with reference to the needle, the motions produced will always be in accordance with these statements; and reference being had to this particular position of the conducting wire and the needle, we can always determine by inspection in what direction the needle will move, whatever may be the position of the wire in regard to it. We have here been speaking only of motions produced in the needle by the conducting wire; but it is plain that if the pole of a magnetic needle tends to revolve around a fixed conducting wire, a free wire will have a tendency to révolve around the pole of a fixed needle. The fact is, the influence is mutwal, and both the wire and the pole tend to revolve, as we will proceed to show. Questions.—To determine the real motion that will be produced in a given case, what two things are to be considered? 129. When the cur- rent is descending perpendicularly, what will be the tendency of the north pole of a needle in the vicinity of the wire? ~ ELECTRO-MAGNETISM. 119 130. Both the revolution of a pole around a fixed wire, and the revolution of a wire around a fixed pole, may be shown by the apparatus, a section of which ig seen in the cut in the margin. A and B are two glass vessels, filled nearly to the top with mercury. A wire, supported by a pillar be- tween the vessels, has one end bent down so as to dip into the mer- cury in A; and the other end is bent into a hook, on which a short piece of wire is suspended, so that its lower end shall also dip into the mercury in the vessel B. Conducting wires pass through the bottoms of both vessels, with binding screws, C and D, to connect them with the poles of the battery; and to that in A, a small magnet is attached by a thread, so that one of its poles may be a little above the surface of the mercury; and in the vessel B another small magnet is firmly fixed, with one pole a little above the mercury. When the current is passed through this apparatus, as indicated by the arrows, the upper pole of the magnet in A will revolve slowly around the conducting wire, and the free con- ducting wire suspended in B will revolve around the fixed pole near it. : Both Pole and Connecting Wire revolve. 131. Further Experiments illustrating the Relation of the Magnet and a Galvanic Current.—Experiments to illustrate the relation of a current and the magnet may be multiplied almost indefinitely. De la Rive’s Ring is a very beautiful contrivance to show the influence of a magnetic pole upon a conducting wire capable of motion. A copper wire is bent into a circle about an inch in Questions.—130. Describe the apparatus figured in paragraph 130. What is the point illustrated? 120 ELECTRO-MAGNETISM. diameter, and the two ends passed through a piece. of wood or cork, and soldered, one to a slip of zinc, Z, and the other to a slip of copper, C. If, now, it be placed in a bowl of water containing a little acid, a current of electricity will cir- = culate along the wire, in the direction SS of the arrows; and if a bar magnet See be brought near it, it will be attracted or repelled, according as one pole or the other of the magnet is presented to it. As represented in the figure, if the north pole of the magnet is presented to it, it will be attracted; the south pole will first repel it, but in a little time it will turn around, and will then be attracted. We may, therefore, properly regard it as a flat magnet, having its two poles in the centre of the circle, the one on one side, and the other on the other; the south pole being in that surface on which, when held before you, the positive cur- rent flows in the direction of the hands of a watch. The apparatus will be more powerful if the conducting wire, covered with silk, to prevent lateral communication, be formed into several circles of the same diameter, on the principle of the multiplier. 182. But what are the forces that have produced these special movements? Giving our attention for the present only to the part of the current upward on one side of the ring and downward on the other, we have seen (129) that the downward current tends to revolve around the north pole of a needle in the direction of the hands-of a watch, and the upward current in the opposite direction ; let these facts be kept in mind while the eye rests upon the figure, and it is plain that the.effect must be to cause the Ting to approach the pole, or apparent attraction ensues. If, now, the magnet be suddenly removed, and the south pole presented, in accordance with the same laws, the ring recedes, turns around, and again approaches the pole! \ Questions.—181. Describe De la Rive’s Ring, and the mode of using it. What may we regard it? 182. Give the reasons for these movements. : ELECTRO-MAGNETI8M. 121 183. The galvanoscope is represented by the next figure N and S are the north and south poles of a permanent horse-shoe magnet, supported upon a stand; and between them, in-a small glass tube, is a strip of gold leaf, connected at top and bottom with binding screws, as shown in the figure. Now when the current is passed through the gold leaf, it is made to curve to one side or the other, according as the motion of the current is upward or downward. As the poles are situated in the figure, if the direction of the current is downward, the curving or convexity of the gold leaf will be upward from the plane of the paper; but if the current is upward the strip-of gold leaf will be convex in the opposite direction, or backward from the plane of the aper. eae é Pap Galvanoscope. 134. The Revolving Spur Wheel, figured. in the mare is made to revolve by the a ‘ action of a magnet upon the galvanic current. A wheel W made of sheet brass, is supported in such a manner that its rays touch in a globule of mercury in the base beneath, from which a concealed wire extends to the binding screw A, the other binding screw B being connected, in like manner, with the ~ Revolving Wheel. - wire R which supports the wheel. NS is a magnet placed so Questions.—133. Describe the galvanoscope. 184. Describe the re- volving spur wheel, and give the reasons for the movement produced. 11 122 ELECTRO-MAGNETISM. that its poles shall be as nearly as possible one on each side of the ray of the wheel which for the time is in contact with the mercury. When the poles of the galvanic battery are connected with the binding screws, a ray of the wheel being in contact with the globule of mercury, the current passes through it, and the wheel is made to revolve on its axis. A permanent magnet may be used, or an electro-magnet, as represented in the figure (p. 121). 135. Relation of Current to the Earth’s Magnetism.—The ring described in paragraph 131 is acted upon by the earth’s magnetism precisely in the same manner as by the magnet, only that the influence-is less in degree. In order that it may be made to move by the magnetism of the earth, it is only necessary that it should be enlarged sufficiently, and a powerful current passed through it. The following modification of it answers a good purpose. ——— Let A and B be two a — id metallic pillars, insulated from each other, provided each with a horizontal arm terminating in a small cup filled with mercury, and connected at the bottom with binding screws. Let a ring R of copper wire, 8 or 10 inches in diameter, be suspended by the ends of the wire from the cups enc cucesppaeeti of mercury, and the poles of the battery connected with the binding screws ;—the current will pass around the circle of wire, which, by the influence of the earth’s magnetism, will be made to move until at length it will take a position with its plane at right angles to the meridian. Supposing the direction of the current to be as indicated by the arrows, and recollecting that the Qusstions.—135. Does the earth’s magnetism act upon a current in the same manner as a magnet? Describe the movemeuts produced in the ring here figured when conveying the current by virtue of the earth’s magnetism. : Be a ELECTRO-MAGNETISM. 123 north pole of the earth really possesses southern (125) polarity, let the intelligent student determine which side of the circle of wire will settle to the east and which to the west! It may afford some aid to reflect that the action on the circle of wire will be the same as if it were square, as shown in the margin, in which it appears there are four parts conveying the current, _ ee two on which its motion is horizontal in oppo- site directions and on the same side of the point of support. The influence of these is | lost and may not therefore be further con- | sidered. On the other two parts the motion of the current is in opposite directions,— — being on one upward and on the other down- Upward and Downward ward—and on opposite sides of the point of Caneel support. Now the tendency of the part conveying the upward current will be to revolve round the north pole of the earth in one direction, and of the part conveying the downward current to revolve around this pole in the opposite direction; considering then the mode in which the wire is suspended, it is plain that the tendency of the circle of wire will be to settle with its plane due east and west, or at right angles to the meridian. If, then, before passing the current, the plane of the circle of wire is placed in the meridian when the current is made to pass it will turn on its points of support until it takes a position at right angles to the meridian. In every case, the side of the circle conveying the downward current will move towards the east, and the other side of course towards the west. The same movement will be produced if the wire conveying the current is bent several times around, as represented in the first figure on the next page, and supported by its two ends resting in cups of mercury, with which the two poles of the battery are to be connected by binding screws not represented in the figure. The influence of each coil conspires to produce the same effect, and therefore the motions described will be more readily produced. Querstions.—Explain the reasons for the motions which are produced. by the earth’s magnetism, as illustrated by the preceding figure, and also the two figures on the next page. 124 ELECTRO-MAGNETISM. But it is not necessary that the dif- ferent coils of the wire should lie in the same plane, the result being the same if it is wound in the form of a helix, Influence of Earth’s Magnetism. as represented in the next figure; the helix then truly repre- senting a bar magnet, as will be found by holding either pole of a magnet near either end. : By examining the direction of the current in this helix, con- sidering it as a bar magnet, it will be found that is the south pole in which (when it is held up before the eye) the current is moving in the direction of the hands of a watch. It is searcely necessary to remark that, in the other pole, the direction of the current is the reverse of this. 186, Induction of Magnetism by a Current.—Magnetism is -induced in a bar of soft iron by the simple passage of a current near it, in a direction at _ Tight angles to the bar. Thus, if WI be the eonducting wire, and NS a small piece of iron lying under the wire, while the current is pass- ing, magnetic polarity will be induced in the Induction of Magnetism iron, N being a north pole, and 8 a south by a Ciurrent. pole, when the current passes from W to I; but if the current pass from I to W, the poles will be reversed. But, if thé wire is made to pass around the iron many times, the effect will be greatly increased. This is accomplished by Quzstions.—When the south pole of the helix is held up before the face, in what direction is the current found to be moving? 136. How is magnetism induced in a picce of iron by the galvanic current? ELECTRO-MAGNETISM. 125 placing the iron in a helix of wire, as shown in the figure. The current. being then made to p Ww pass in the direction of the arrows, the iron becomes strongly magnetic, with its poles as shown by the letters Nand 8. The cups P and N serve to connect it with the battery. When the current is broken, the iron ceases at once to be magnetic; but if a piece of hardened steel be substituted for the iron, it retains*its magnetism permanently. A magnet formed in this manner, by the passage of a current of electricity around it, is very properly termed ang electro-magnet. Magnets of this kind have some- times been made of sufficient strength to sustaina = weight of 2000 or even 8000 pounds. For this pur- pose, a bar of iron of considerable size is bent in the form of a horse-shoe, and the conducting wire made to pass many times around it, as represented in the figure. An armature of soft iron (122) is attached © ' to the poles, as with the common magnet, from which ™ tube the end containing the crystals must be Preparation of Liquid Chlorine. kept ‘cold by means of ice. The aqueous solution, if prepared in the dark and kept constantly from the action of light, undergoes no.change (173), but if once exposed for a few moments only to the sun’s rays, decomposition of the water commences, hydrochloric acid is formed, and oxygen set free. The proper test of chlorine, either free or in combination, is solution of nitrate of silver; silver and chlorine always forming a dense white pre- cipitate, quite insoluble in water, but readily soluble in aqua ammoniz. S Compounds of Chlorine and Oxygen 231, The compounds of chlorine and oxygen are five in number, as follows, viz. :—C10,C10,,C10,,C10,, and C10, all of which are acids; but as the affinities of these substances for each other are very feeble, their compounds are all decomposed by slight causes. 232, Hypochlorous Acid —Cl0O; eq., (35-4 + 8 =) 43-4.—This is a gaseous substance, of a yellowish-green color, like that of chlorine, but a shade deeper. It exists in combination with lime in the common bleaching-powder. 238. Chlorous Acid—ClO,; eq., (35-4 -+ 24 —) 59-4—Is prepared by the action of oil of vitriol upon chlorate of potash. 234, Hypochloric Acid—C10,; eq., (35-4 + 32 =) 67-4.—This com- pound is also gaseous, and of a deep yellowish color. It is formed by the action of sulphuric acid upon chlorate of potash. If a few grains Quzstions.—How is the aqueous solution of chlorine prepared ? May the compound of chlorine and water be crystalized? 280. How may these crystals be used to form liquid chlorine? Can.the aqueous solu- tion be long preserved without decomposition? What test for chlorine is mentioned? 231. What compounds of chlorine and oxygen are there? What is the number of equivalents of oxygen in each of these ? COMPOUNDS OF CHLORINE AND HYDROGEN. 211 of chlorate of potash are placed in a wine-glass, and a little sulphuria acid poured in, the glass will be soon filled with the gas, which will be recognised by its color. If now a rag, wet with oil of turpentine, be pre- sented to it, on the end of a wire or a stick, it will be inflamed, and the gas at the same time exploded. 235. Chloric Acid—Cl0,; eq., (85-4 + 40 =) 75:-4.—Chloric acid is obtained by passing a current of chlorine through a strong solution of potash, with which it combines as it is formed, pro- ducing chlorate of potash. At the same time with the chlorate of potash there is also produced much chloride of potassium; the reaction takes place between 6 equivalents of chlorine and 6 equiva- lents of potash, according to the following equation :— 6KO + 6C1=5KCl + KO,CIO,. The chlorate being only slightly soluble in water, some separates in erystals by a little evaporation of the water, while the chloride remains in solution. To obtain the acid in a separate state, chlorate of baryta is first produced and then decomposed carefully by sulphuric acid. The BaO,SO, which forms is separated by filtration, and the chloric acid obtained as a syrupy liquid. It is decomposed at a tem- perature of 104°. Perchloric Acid possesses no characters that render it of any special interest. Compounds of Chlorine and Hydrogen. 236. Hydrochloric Acid—HCl; eq., (85:4 + 1=) 36-4.— This is the only known compound of chlorine and hydrogen; and, in solution in water, has long -been used in the arts, under the names of muriatic acid, and spirit of salt. It is formed by the action of diluted sulphuric acid upon common salt. The sulphuric acid should be diluted with about an equal weight of Quzstions.—235. How is chlorate of potassa formed? How is chloric acid procured from this salt? 236. What is the only compound of chlorine and hydrogen that is known? How is hydrochloric acid prepared ? 212 COMPOUNDS OF CHLORINE AND HYDROGEN. water, and be allowed to cool before being used. The changes which take place are as follows :— NaCl + SO,,HO = NaO,SO, + HCl. From this it appears that the water of the oil of vitriol is essential to the process; it is decomposed, yielding its oxygen to the sodium to form soda, which combines with the acid, and its hydrogen to the chlorine to form the hydrochloric acid. Abundant fumes of the gaseous acid will be given off, which should in no case be allowed to diffuse themselves in a room where there are articles of delicate apparatus made of metal, as they will be sure to be corroded after a little time, if pot immediately. It is also formed by the direct union of its elements. When equal measures of chlorine and hydrogen are mixed together, and an electric spark is passed through the mixture, instantaneous combination takes place, heat and light are emitted, and hydro- chloric acid is generated. A similar effect is produced by flame, by a red-hot body, and by spongy platinum. Light also causes them to unite. A mixture of the two gases may be preserved, without change, in a dark place; but if exposed to the diffused light of day, gradual combination ensues, which is completed in the course of twenty-four hours. The direct solar ray, like flame and the electric spark, produces an explosion by a, sudden inflam. mation of the whole mixture; but to insure the success of the experiment, the gases should be very pure, and the chlorine recently prepared over warm water. The glass vial containing the mixed gases, after being filled, should be instantly covered with a black cloth, which can be suddenly removed by a stick, or wire, after it is placed in the sun’s rays. Hydrochloric acid is, of course, a chloride of hydrogen. When pure it is a colorless gas, of which 100 cubic inches weigh 39-38 grains, giving it a density of 1-25. By strong pressure it may Quzstions.—Explain the equation. Is the presence of water essential] to the formation of hydrochloric acid? May it be formed by the direct union of its elements? What several means are mentioned by which the gases may be made to combine? What are some of the properties of hydrochloric acid? COMPOUNDS OF CHLORINE AND HYDROGEN. 213. be compressed into a liquid. It is quite irrespirable, and in- capable of supporting combustion. Water absorbs it with avidity, taking up, under favorable circumstances, no less than 480 times its own volume. During the absorption it increases considerably in volume, and the saturated solution has a density of 1:21, and contains about forty-two per cent. of the acid. In preparing the liquid hydrochloric acid, a Woulfe’s apparatus (225) is used, only a very little water being contained in the first bottle, in which most of the impurities mixed with the gaseous acid will be* deposited.. In the open air, copious fumes of the gas constantly arise from the liquid, which produce a cloud of smoke if any ammonia be present in the air. Thus, let a little aqua ammoniz be poured into a glass vessel, A, with a large mouth, and then invert over it a tumbler, the inside of which has been thoroughly moistened with common hydrochloric acid. The two gases, coming in con- tact, unite, and fill both glasses with a dense, white Hiydeoeblioete ale smoke, which is solid hydrochlorate of ammonia (159), in a finely divided state. The same thing is shown when a glass rod moistened with hydrochloric acid is brought near an open vessel containing aqua ammoniz. Gaseous hydrochloric acid is composed of equal volumes of chlorine and hydrogen united without condensation. One volume of chlorine weighs 2-440 One 7 hydrogen “ 069 Forming two vols. hydrochforie acid 2.509 . The. weight of 1 vol., or the theoretical density of the gas, is therefore 2509 — 1-254, 2 287. Aqua regia, so called because of its ability to dissolve gold and platinum, is a mixture of two parts of hydrochloric to one of nitric acid. Leta single leaf of gold be placed in a wine- Questions.—What is said of the absorption of hydrochloric acid by water? What is said of the fumes produced by the gas with ammonia? What is said of the volumes of chlorine and hydrogen which unite to form this acid? 237. Whatis agua regia? Why is it so called? 214 COMPOUNDS OF CHLORINE AND NITROGEN. glass contaming a little hydrochloric acid, aud another leaf in a separate glass with some nitric acid; the gold will remain undis- solved in both glasses for any length of time; but, on mixing the contents of the glasses, the whole of the gold will be speedily dis- solved. The real solvent in this case is the chlorine, which is liberated by the action of the acids upon each other. The reaction is shown by the following equation. Thus, NO, + 2HCl = NO; + 2HO + CL. This decomposition, however, proceeds only so far as’ to saturate the liquid with chlorine, but if heat is applied to expel the chlorine, ora metal placed in the liquid with which it will unite, new quan- tities of the acid are decomposed. Nitrohydrochloric acid, there- fore, is a source of chlorine in a very concentrated state, and is capable of dissolving several substances which are not attached by any single acid. Hydrochloric acid may readily be distinguished by its odor and volatility, and by its giving, with a solution of nitrate of silver (230), a precipitate of the white chloride of silver, which is blackened by exposure to the light. Liquid hydrochloric acid is extensively used for various pur- poses in the arts, and is one of the most important chemical agents of the laboratory. Compounds of Chlorine and Nitrogen. 238. Terchloride of Nitrogen.—NCl,; eq., (14 + 106-2 =) 120-2.—There is known only a single compound of these ele- ments, the terchloride of nitrogen. It is prepared by pass- ing a current of chlorine through a solution of the hydrochlorate, or other salt of ammonia, and takes the form of a dense yellow liquid, which is seen in small globules at the bottom of the solu- tion. The reaction is expressed in the following equation :— NH,,HCl + 6Cl=4HCl + NCI, Qurstions.—What compound of gold is formed? How may hydro- chloric acid be known? 288, What compound of chlorine and nitrogen is there? What is said of it? Explain the equation. IODINE, 215 The liquid has a density of 1-65, and may be distilled under a pressure Jess than one atmosphere, but at 212° it explodes with the utmost violence. So also it detonates violently by the mere contact with phosphorus, many of the oils, &c., and never should be handled but with the greatest care. IODINE. Symbol, 1; Equivalent, 127; Density, 4-95 239. History.—TIodine from (diodes, violet color) was discovered in the ashes of sea-plants, from which it is still prepared, by M. Courtois of Paris, in the year 1812. It is found also in certain ores of silver and zinc, in sea-water, and in the water of certain mineral springs. 240. Preparation.—As stated above, the iodine of commerce is obtained from the ashes of sea-plants, especially the /ucus Preparation of Iodine. palmatus. The ley obtained by lixiviating the ashes is first evaporated, to separate a portion of the carbonate of soda and Qurstions.—239. When was iodine discovered? In what is it found? 240. What is the mode of preparing iodine from the ashes of sea-plants ? 216 IODINE. other saline compounds it contains, which are less soluble than the iodine compounds—chiefly the iodides of sodium and magne- sium—and are therefore first to crystalize out from the solution ; the residue is then mixed with peroxide of manganese and sul- phuric acid, and a gentle heat applied, when the iodine distils over, as a beautiful violet-colored vapor, into a receiver prepared for the purpose, where it is condensed. A simple apparatus like that represented in the figure on the preceding page answers well for the distillation. A good method to show the evolution of iodine, is to heat in a glass globe, over a lamp or ignited charcoal, a small quantity of sulphuric acid, and throw suddenly into it 25 or 30 grains of iodide of potassium. A large quantity of iodine will instantly be set free, and its vapor fill the globe. 241. Properties.—Iodine, at ordinary temperatures, is a soft, friable, nearly black solid. Usually it is in small shining orys- tals, which have a metallic lustre, and a density of 4:95. Heated a little above 212°, it, melts, and is then converted into a beau- tiful violet-colored vapor, which has a density of 8-70 (air being 1), and 100 cubie inches weigh 270-1 grains. Iodine is a non- conductor of electricity and heat, and is allied to oxygen and chlorine in many of its properties. Its odor resembles that of chlorine, but is less offensive. It is sparingly soluble in water, requiring about 7000 times its own weight of this liquid for com- plete solution; but alcohol and ether dissolve it freely, forming a deep brown solution. A few of the crystals pressed upon the skin produce a deep stain, which however soon disappears. Starch affords a delicate test of iodine, forming with it a beau- tiful blue. The starch should be prepared by dissolving it in hot water, and allowing it to cool before using. Leta little hot water be poured upon ashes obtained by burning a piece of sponge, and, after filtering, add a drop or two of solution of starch; then pour in a few drops of sulphuric or nitric acid, and stir it gently, and almost always the blue color will be observed, indicating the presence of iodine. Qurstions.—241. Describe the properties of iodine. What ig saic of its solubility in water? In alcohol and ether? What test of itdine is mentioned? How may iodine be detected in sponge ? COMPOUNDS OF JODINE AND OXYGEN, HYDROGEN, ETc. 217 Todine has not been much used in the arts, but is largely em- ployed in medicine. In the Daguerreotype process (76), it is essential ; and recently it is said to have been employed in dyeing. Compounds of Iodine and Oxygen, Hydrogen, ce. 242. Iodine and oxygen combine in three proportions, pro- ducing iodous IO,, iodic IO,, and periodic 10,, acids; neither of which however possesses any special interest. 248, Hydriodic Acid, HI, (iodide of hydrogen,) is a gaseous substance, of a specific gravity 4:39, and in many of its properties strongly resembles the corresponding chloride of hydrogen (hydro- chloric acid). It is absorbed by water, and then forms the liquid hydriodic acid. It is best prepared by placing in a glass tube alternate layers of iodine, powdered glass (to prevent too rapid action) and posphorus, slightly mois- tened. with water. Iodide of phos- phorus is first formed, which is decomposed by the water, producing phosphorous acid and hydriodie acid, the last of which being gaseous makes its escape, and may be collected in a dry bottle by displacement of the air, or it may be condensed in water. Preparation of Hydriodic Acid. 244, Teriodide of Nitrogen—NI,.—From the weak affinity that exists between iodine and nitrogen, these substances cannot be made to unite directly. But when iodine is put into a solution of ammonia, the alkali is decomposed; its elements unite with different portions of iodine, and thus cause the formation of hydriodic acid and teriodide of nitrogen. The latter subsides in the form of a dark powder, which is characterized, like chloride of nitrogen, by its explosive property. It often detonates spontaneously as soon as it is dry, and even when moist, by the slightest causes. Heat and light are emitted during the explosion, and iodine and nitrogen are set free, the former of which may be seen at the instant in the form .of vapor. Questions.—What use is made of iodine? 242. What compounds of iodine and oxygen are mentioned? 243. Describe hydriodic acid How is it formed? 244. Describe teriodide of nitrogen. 218 BROMINE. . Chlorine combines with iodine when made to pass over it in a dry glass tube, or when passed through water in which crystals of iodine are diffused. The two substances form several different compounds, but they are not at present well understood. One of these, probably the proto- chloride, IC], has been used in the Daguerreotype process. BROMINE. Symbol, Br; Equivalent, 80; Density, 2-97. 245, History.—Bromine was discovered in 1826, in sea-water ; and received its name, bromine (from bromos, offensive odor), in consequence of its exceedingly disagreeable smell. Recently it has been obtained in large quantities from the waters of some of the salt-springs in Pennsylvania and Virginia. 246. Preparation.—The usual mode of preparing bromine is a little complex. First, the brine from the spring is evaporated, and the common salt removed by crystalization, then the mother- liquor, or bitéern, as the. uncrystalizable residue is called, is treated with a current of chlorine to decompose the bromides of magne- sium, sodium, &c., and sulphuric ether afterwards added, by which the bromine that has been separated from its compounds by the chlorine is taken up, and rises to the surface as a solution of bromine in ether. Another method is to mix with the solution sulphuric acid and peroxide of manganese, as in the preparation of iodine; and then distilling with a gentle heat. The same apparatus (240) may be used as in the preparation of iodine, but the receiver must be kept cool by a current of cold water. 247. Properties.—Bromine is a liquid of a blackish-red color, and specific gravity 2°97. At a temperature a little below zero it is frozen, and boils at about 117°, forming a vapor of a beau- tiful blood-red color, and specific gravity 5-39, air being 1. It Questions.—What is said of the compounds of chloride and nitrogen ? 245. When was bromine discovered? From what is the name derived ? 246, From what is it obtained? What is the mode of preparing it? 247. Describe its properties. : COMPOUNDS OF BROMINE, WITH OXYGEN, ETC. 219 stains the skin yellow, like iodine, but less intensely. Vapor of bromine ignites phosphorus spontaneously, and a lighted candle burns in it a short time. Bromine, in many of its properties is closely allied to chlorine and iodine. Taken into the system it is highly poisonous, and its vapor possesses considerable bleaching power. With starch it forms a yellow color. Like chlorine, it forms a compound with water, which crys- talizes when exposed to the cold of a freezing mixture of salt and snow. The compound is Br,10HO. Bromine is sometimes used in medicine, and much more extensively in photography, especially in the Daguerreotype process. Compounds of Bromine, with Oxygen, Hydrogen, &c. 248, Bromic Acid, BrO,, is the only well determined com- pound of bromine and oxygen. It is a liquid, and may be pro- cured of the consistency of syrup. It is very corrosive, and sour to the taste, and by a temperature of 212° is decomposed. 249 Hydrobromic Acid, HBr, is a colorless gas of a density 2-73. To prepare it, a tube of the form of the letter W is pro- vided, and the part at the left " filled with pieces of phosphorus mixed with pounded glass, and the whole moistened with water. Into the end at the right some bromine is then poured, and a cork firmly inserted; and into Preparation of Hydrobromic Acid. the other end a smaller tube is fixed, by means of a perforated cork, to convey away the hydro- bromic acid as it is formed. The whole being ready, a gentle heat is applied to the part-containing the bromine; and the vapor as it is formed, attacking the phosphorus, first produces bromide’ Querstions.—What other elements does bromine resemble? Does it combine with water? What use is made of it? 248. Describe bromic acid.. 249. Describe hydrobromic acid, and the mode of preparing it. 220 FLUORINE. of phosphorus, which is at once decomposed by the water, forming phosphorous and hydrobromic acids, the latter of which, being gaseous, passes off, and may be collected over mercury. The gas is rapidly absorbed by water, like hydrochloric acid, and the concentrated solution gives off fames in the air. In most of its properties it closely resembles hydrochloric acid. By intense cold and pressure the gas may be condensed to the liquid form. 250. Hydrobromic acid is composed of equal volumes of vapor of bro- mine and hydrogen combined without condensation. Thus, 1 vol. vapor of bromine weighs 5-390 a ee hydrogen ‘“ 069 2 vols. hydrobromic acid, 5-459 One volume of the acid therefore weighs 2-729. FLUORINE. Symbol, F; Equivalent, 19; Density, 1-29. 261. History and Properties.—Fluorine has long been known to exist, but it has not, until recently, been obtained in a separate state. It is found in nature in considerable abundance in the mineral called fluor spar, which is a compound of this substance with calcium, the metallic base of lime. It is a brownish-colored gas, of specific gravity about 1:29 (probably), and bleaches like chlorine. Such is its affinity for other substances that it attacks them with violence, even gold and platinum; and can be prepared and kept only in vessels made of fluor spar, which, being already saturated with the substance, is not acted on by it. QueEstTions.—What is said of the absorption of hydrobromi i water? 250. Considered as gaseous, what - its éetnpacition? "Gh Ole the history and properties of fluorine. What is said of its affinity for other substances? Of what only can vessels be made to contain it? Why is not this substance acted on by it? ; COMPOUNDS OF FLUORINE. 221 Compounds of Fluorine. Fluorine seems to be incapable of uniting with oxygen, but combines with hydrogen, forming the acid compound HF. 252. Hydrofluoric Acid—HF; eq., (19 +1 =) 20.—This acid is formed by subjecting powdered fluor spar, moistened with strong sulphuric acid, to a very gentle heat in a leaden vessel. The acid distils over as a pungent, corrosive, vapor, but may be condensed in a leaden receiver, that is kept surrounded with ice. The reactions are as follows :— CaF + SO,,HO = Ca0,S0, + HF. As thus formed, the acid has a density of 1-07, and manifests a strong affinity for water, with which it combines with great energy. It attacks glass powerfully, combining with its silica, and may therefore be used to etch it. This is done by spreading a thin coat of bees’-wax or varnish upon the glass, and tracing the design upon it, taking care to cut quite through the wax. The liquid acid is now poured over the coated surface, or it is exposed a few minutes to the acid vapor, and the wax afterwards removed.; the design will then be found beautifully traced upon the glass. This acid attacks anima] substances powerfully, and, therefore, should always be handled with great care. Fluorine unites also with chlorine, iodine, bromine, and some others of.the elements, but the compounds are not important. Quzstions.—Does fluorine combine with oxygen? 252. Describe the mode of preparing hydrofluoric acid. Describe its properties. How may it be used for etching upon glass? What is said of its action upon ani- mal substances? Does fluorine combine with chlorine, iodine, &. ? 19* 222 SULPHUR, Group IIL SuLPHUR Elements in many of their properties closely resembling SELENIUM feat other, and forming similar acid compounds with Teriurium ) oxygen and hydrogen. SULPHUR. Symbol, 8; Equivalent, 16; Density, 1-99. 253, History and Preparation—Sulphur, called also rim- stone, bas been known from the remotest antiquity. It occurs, as a mineral production, in many parts of the world, particularly in volcanic regiens, as in the neighborhood of Naples, in some of the Sandwich Islands, and in the island of Sicily. In combination with several of the metals, as iron, lead, copper, &c., it is still more abundant, and is found in almost every place. From one of its compounds with iron, called iron pyrites, it is procured in large quantities, for the purposes of commerce. It is found, also, in many organic bodies, as in eggs, in the hair, horns, and hoofs of animals, and in the seeds of black mustard. The island of Sicily furnishes a large part of all sulphur of commerce; the native sulphur here occurs in immense beds mixed more or less with gypsum, lime, and other earthy matter. This sulphurous earth is first heated in pots so as to melt the sulphur, which is dipped out with ladles, the earthy matter settling to the bottom. The sulphurous earth remaining as sediment is then heated in earthen pots, which are arranged in double rows, and entirely inclosed in mason-work, except at the top, where is an opening by which they are charged and emptied. At the sides, in the open air, pots are arranged to receive the sublimed sulphur, which, taking the liquid form, passes finally into buckets situated as shown in the figure on next page. Quzstions.—What elements constitute group 3d of the metalloids? 253. Give the history of sulphur. With what is it found combined? In what organic bodies is it contained? Describe the mode of separating it from the earthy matter with which it is mixed. 7 SULPHUR. 223 Separation of Sulphur. The figure represents a section of the mason-work with two of ae included pots, and also the external receivers with which they re connected, and the buckets. 254. Properties.—Sulphur is a brittle solid, of a greenish- ellow color, emits a peculiar odor when rubbed, and has little ite. It is a non-conductor of electricity, and is excited nega- vely by friction. It fuses at 226°, and becomes nearly as liquid 3 water; but if the heat be raised as high as 430°, it becomes ) tenacious that the vessel containing it may be inverted without pilling it, and is then of a dark molasses color. When heated > at least 428°, and then poured into water, it becomes a ductile iass, which may be used for taking the impressions of seals. fter some time, it changes into its ordinary state. Fused sulphur has a tendency to erystalize iu cooling. A crys- line arrangement is perceptible in the centre of common roll ulphar; and, by good management, regular tystals may be obtained. For this purpose, sveral pounds of sulphur should be melted in a earthen crucible; and, when partially cooled, 1e outer solid crust should be pierced, and the rucible quickly inverted, so that the inner and 3 yet fluid parts may gradually flow out. On Sulphur Crystalized. reaking the solid mass, when quite cold, a confused arrangement f prismatic crystals will be found in the interior. Sulphur is dimorphous (184); that is, it is capable of crys- izing in two distinct primary forms, the oblique rhombic QuzEstions.—254. Describe the properties of sulphur. How may it be ystalized? Why is it said to be dimorphous? 224 SULPHUR. prism, and the rhombic octahedron, the first belonging to the monoclinic, and the second to the trimetric system. Sulphur i is very volatile, and begins to rise in vapor even before it is completely fused. At about 750°, it boils, and the vapor, if in a close vessel, will be condensed on any cold surface, forming the flowers of silat: The density of its vapor is about 6-65. When vapor of sulphur is brought in contact with vapor of alco- hol, they unite; but solid sulphur is quite insoluble in alcohol, or water, but dissolves in boiling oil of turpentine, and in sulphide of carbon. By melting the flowers of sulphur and pouring it into moulds, the roll-sulphur of commerce is formed. In this form it is very brittle, and will sometimes break by the heat of the hand. It is the only substance known that always becomes negatively excited ky friction, whatever may be the nature of the substance used as the rubber. 7 The vapor of sulphur combines readily with iron and other metals, attended with all the phe- nomena of combustion. Let the breech of a gun-barrel be heated to redness, and a lump of sulphur dropped into it, and then let the muzzle be instantly closed by a cork; a jet of vapor of sulphur will issue violently from the touch-hole, which will be inflamed as it enters the air; and a bunch of small iron wire, held in it, will burn freely, forming sulphide of iron, which will fall in drops. The sulphur of commerce generally hag an acid reaction, pro- bably in consequence of a slight oxidation that is gradually taking place. Organic substances in contact with sulphur are always more or less acted upon by the acid or acids thus produced. Tron Wire and Vapor of Sulphur. Quzstions.—What is the boiling point of sulphur? What are the flowers of sulphur? Is it soluble in water or alcohol? How is roll- sulphur formed? What is said of its electrical state when rubbed? How may iron wire be made to burn in vapor of sulphur? Why does the sul-. phur of commerce usually have an acid reaction? COMPOUNDS OF SULPHUR AND OXYGEN. 225 Uses of Sulphur.—Sulphur is used extensively in the arts, and in medicine. It is employed in the manufacture of guapowder, sulphuric acid, the different kinds of matches, vermillion, &., and for taking impressions of seals. In medicine, it is used in cuta neous diseases, and as a cathartic and alterative Compounds of Sulphur and Oxygen. 255. Sulphur and oxygen form as many as seven different com- pounds, viz. :— . Hyposulphurous acid.......... Wels sess napaecae anes 8,0.: 1 2. Trisulpho-hyposulphuric acid..............0..008 8,05. 8. Bisulpho-hyposulphuric acid..........ccseesees 8,0,. 4, Monosulpho-hyposulphuric acid.............seceee 8;0;. 5. Sulphurous acid.........cccccceeeseveceseeeenenees .. SO,. 6. Hyposulphuric acid..........ccscessseceseeseseeees 8,0,. 7. Sulphuric acid............ceeesees iad vinetewiaree nels SO. Of these, the fifth and last are by far the most important; and only these will be here described. 256. Sulphurous Acid —SO,; eq., (16 + 16 =) 32. —This substance is gaseous at ordinary temperatures, and is the sole product of the combustion of sulphur in the open air, or in dry oxygen gas. It is more conveniently prepared, however, by heat- ing strong sulphuric acid in contact with mercury or pieces of copper. One equivalent of the sulphuric acid gives up one equivalent of its oxygen to unite with the metal, and the oxide thus formed is immediately dissolved by a second atom of the sulphuric acid, while the sulphurous acid passes off asa gas. Thus, Hg + 280, = Hg0,S0O, + SO,. Another very easy method is to heat in a retort a mixture of 6 parts of powdered peroxide of manganese and 1 part of sulphur. Questions.—What use is made of sulphur in the arts? 255. How many compounds of sulphur and oxygen are mentioned? 256. Describe sulphurous acid, and the mode of preparing it. 226 COMPOUNDS OF SULPHUR AND OXYUEN. By this mode, the peroxide gives up one-half of its oxygen, which unites with sulphur to form the sulphurous acid, and protoxide 5 of manganese remains in the retort. An arrangement like that figured in the mar- gin, answers well for its preparation, by either mode. As the gas forms it is made to pass through a little water, to condense any vapor of sulphuric acid that may have come over, and it may then be collected over mercury. Sulphurous acid is a dense, colorless gas, 100 cubic inches of which weigh 68-55 grains, giving it a specific gravity of 2-24. It is distinguished from all other gases by its suffocating odor, which every one has recognized in burning sulphur. It is absorbed largely by water, and may be condensed into the liquid form by moderate pressure, or by a cold of zero. A little of the liquid may be obtained very’ easily, by putting a small quantity of d mercury and sulphuric acid in Preparation of Sulphusone Acid in Liquid g bent tube, as represented in the figure, sealing it hermeti- cally, and supplying heat to the extremity, a, which contains the materials, while the other, 6, is kept cool by means of ice, or.the evaporation of ether. The liquid will be soon found to collect in the cool part of the tube. Care should be taken not to heat the tube too much, lest it should burst. . A better method to procure the liquid is to prepare a tube, (as in the figure on next page,) by closing one end, and drawing out a part in the middle to a capillary bore, and then inserting it in a freezing mixture of snow and salt. If, now, a current of the gas, first dried by passing” through a chloride of calcium tube, be made Qurstions.—What is said of the odor of sulphurous acid? How may it be obtained in the liquid form ? COMPOUNDS OF SULPHUR AND OXYGEN. 227 to enter the open end of the tube, it will be con- densed and collected in the lower part. When this part is nearly filled, still keeping in the freezing mix- ture, the upper part’ may be separated and the lower part hermetically sealed, and the liquid preserved for any length of time. Or a tube like that cane in the figure on the right , margin may be used. The bulb at the centre part is to be sur- , rounded with a freezing mixture eeu in a suitable vessel, as B glass Preparation of Liquid Sul- phurous Acid. tumbler; and when a sufficient phurous Acid. quantity of the ftuid has accumulated, the two ends of the tube may be hermetically sealed before it is removed from its place in the freezing mixture. Under the ordinary atmospheric pressure it becomes liquid at about 14°, but at a temperature of 59° it requires a pressure of about 2 atmospheres. The liquid has a density of 1-42. When allowed to escape in the open air it eva- porates rapidly, producing a cold of —60° to —76°, according to. the temperature of the air and other circumstances. By severe cold it may be frozen, and with water it forms a compound (SO,9HO) which may be solidified. 257, Sulphurous acid is composed of 1 volume of oxygen and } of a volume of vapor of sulphur, condensed into 1 volume. If we burn a small quantity of sulphur in a glass globe over mercury, the sulphur is converted into sulphurous acid, but after cooling the volume of gases is found to be unchanged. The acid therefore occupies the same space as the oxygen entering into its composition Therefore if we subtract the weight of the volume of oxygen from that of a volume of sulphurous acid, there should remain 3 of avolume of vapor of sulphur. This we find to be the case very nearly. Thus, 1 vol. sulphurous acid weighs 2-247 1 “ oxygen (subtract) “ 1-106 —— a 4 ¢ vapor of sent 1-141 Quzstions.—Describe the two modes mentioned for collecting sul: phurous acid in glass tubes. At what temperature does it become liquid? What is the density of liquid sulphurous acid? What is said of the cold produced by its evaporation? 257. What is the composition, of one’ volume of sulphurous acid ? 228 COMPOUNDS OF SULPHUR AND OXYGEN. We have heretofore (254) taken the volume of sulphur vapor to be 6-654; one-sixth of which is 1:109. The discrepancy in the results is occasioned by the great difficulty in obtaining accurately the real weight of the volume of sulphur vapor. 258. Sulphurous acid is much used for bleaching, especially articles of straw; which, in a moist state, are suspended in an atmosphere charged with the gas. For this purpose, the gas is formed by burning sulphur in the air, in some enclosure, as a box or empty cask, in which the articles to be bleached are suspended. 259. Sulphuric Acid—SO,; eq., (16 + 24 =) 40.—This acid is always seen as a dense liquid, not unlike oil in appearance ; and, having been formerly obtained altogether by the distillation of green vitriol (sulphate of iron), it received the name, ot? of vitriol, by which it is now often known. It is prepared at the present time, at Nordhausen, Germany, by the same mode. Green vitriol is thoroughly dried by heat, and then distilled, at a high temperature, by which it is decomposed, and the acid passes over and condenses as a brown oil-like liquid, which still contains one eq. of water for every two eq. of the acid. Its cumposition, there- fore is 280,,HO. Its density is 1:9, or nearly twice that of water. When this liquid is again distilled, at a moderate heat, a dry, silky solid is obtained, which is the pure compound, SOx; but it possesses no acid properties until water is added, which changes it to common sulphuric acid. This solid has a strong affinity for water, and hisses like a hot iron when thrown into it. 260. The common method of preparing the oil of vitriol of com- merce is, to burn a mixture of sulphur and nitrate of potash, or soda, in a furnace so contrived that the current of air which supports the combustion conducts the gaseous products into a large leaden chamber, the bottom of which is covered to the depth of several inches with water. Numerous complicated changes take place in the leaden chamber, during the combustion of the sulphur, by which the oxygen from the air is transferred Questions,—258. What use is made of sulphurous acid ? i sulphuric acid. How is the Nordhausen acid prepared ? ek solid acid be obtained from it? What is the composition and densit of the Nordhausen acid? 260. What is the mode of preparing the eon. mon oil of vitriol of commerce ? COMPOUNDS OF SULPHUR AND OXYGEN. 229 to the sulphurous acid formed by the combustion of the sulphur, converting it into sulphuric acid. In the first place, as the mixture burns, sulphurous acid is formed (256), and binoxide of nitrogen;—the latter by the decomposition of the nitric acid of the salt;—and the two gases with a current of air are carried together into the leaden cham- ber, the binoxide of nitrogen, NO,, at the same time absorbing oxygen, and being thus converted (218) into nitrous acid (NQ,). Secondly, these two gases, in the absence of water, are capable of combining to form a crystaline solid, the composition of which is NO,,2SO,, and which, on coming in contact with water, is at once decomposed into binoxide of nitrogen and sulphuric acid. Thus, NO,2S0, = 280, + NO. Or, more properly, NO,,280,, 2HO = 2(S0,,HO) + NO;. Thirdly, if at the same time as the mixed gases from the com- bustion of the sulphur enter the chamber, steam be also forced in, the ‘crystals just alluded to are not formed, but all the reac- tions described take place in the order mentioned, the hydrated sulphuric acid, as it forms, falling like rain to the bottom of the chamber. The binoxide of nitrogen, being set free, combines again with atmospheric oxygen present, forming nitrous acid, NO,, as before, and this, with the sulphurous acid, by the reaction of water, again producing sulphuric acid, and so on indefinitely. These are the essential reactions that take place in the process, but they are often, perhaps always, accompanied by others, which however tend to the same result, viz., the conversion of the sul- phurous acid, formed from the burning sulphur, into sulphuric acid. Questions. — Describe the reactions which take place. Firstly? Secondly? Thirdly? Do other reactions tending to the same result usually accompany the above? 20 230 COMPOUNDS OF SULPHUR AND OXYGEN. Firstly, a portion of the nitrous acid, NO,, in the leaden cham- ber, when but little moisture is present, is converted into mono- hydrated nitric acid, and hyponitrous acid, NO,. Thus, 2NO, + HO = NO,,HO + NO,. If a large quantity of moisture is present, the nitrous acid is con- verted into hydrated nitric acid and binoxide of nitrogen. Thus, 6NO, + nHO = 4NO,,nHO + 2NO,. Any nitrous acid, NO,, that may have been formed, as indi- cated in the second equation above, when the supply of moisture is increased, undergoes a similar: change, producing nitric acid and binoxide of nitrogen. Secondly, sulphurous acid, SO,, by the reaction of hydrated nitric acid, is converted into hydrated sulphuric acid, while the nitric acid, NO,, by the loss of oxygen is changed to nitrous acid, NO, Thus, : SO, + NO; + »HO = 8O,,nHO + NO,. We have, then, as the result, sulphuric and nitrous acids, the former of which mixes with the water at the bottom of the cham- ber, while the latter, remaining in the gaseous state, is ready again to go through the same reaction as before, being thus made a vehicle for conveying oxygen from the atmosphere to the sul- phurous acid. In some manufactories, no nitrate of potash is used, but the sulphur is burned alone, and nitric acid, in proper vessels, is placed in the leaden chambers in such a situation that it shall be evaporated by the heated sulphurous acid and other gases enter- ing from the furnace; reactions similar to those above take place with the same results. The figure following will serve to illustrate the process. CC is a section of the chamber lined inside with sheet lead, and sup- ported at the ends by mason-work. At A is the furnace for Questions.—Describe the other reactions tending to the same result which accompany those already mentioned. COMPOUNDS OF SULPHUR AND OXYGEN 231 Manufacture of Sulphuric Acid. burning the mixture of sulphur and nitric salt, the fumes of which are carried directly into the chamber, now filled only with air, and at B a steam boiler from which steam in one or more jets is constantly entering the chamber, for the purposes described above. A valve at the the top allows the escape of the spent gases. 261, Fora class experiment, the apparatus figured below answers well to illustrate the mode of manufacturing this acid. A large Illustrates the reparation of Oil of Vitriol. —- balloon glass, A, is provided, containing a small quantity of water, a two-necked flask, B, partly filled with ‘small pieces of Qurstions.—Describe the first figure on this page. 261. Describe the apparatus figured in connection with this paragraph. What is illustrated by it? 2382 COMPOUNDS OF SULPHUR AND OXYGEN. copper, and a second flask, C, containing mercury and strong oi) of vitriol. These two flasks, B and C, are connected with the balloon, A, by means of tubes inserted in perforated corks, as shown in the figure; and a lamp then applied to B, from which sulphurous acid fumes will soon be made to pass over to the bal- loon, A. Into the flask, B, some nitric acid, a little diluted with water is now poured by the long-necked funnel, which, acting upon the copper (217), will soon supply binoxide of nitrogen to mix with the other gases contained in A. The red fumes of nitrous acid will at once appear in A, and all the changes take place described above, resulting in the production of a small quantity of oil of vitriol. Through the cork in the mouth of thv balloon glass, A, two glass tubes bent at right angles are inserted, by which the air within may be changed, by blowing into one of them by the mouth. In the manufacture of this acid on a large scale, the acid, as it comes from the Jeaden chambers, always has an excess of water, its density varying from 1-35 to 1:50. It is then heated in leaden pans until its density becomes about 1-75, and, finally, in platinum retorts, by which all excess of water is expelled, and its density is brought to 1:84. Its boiling point is then 617°, and its freezing point —30°. A Oil of vitriol, we thus see, always contains water; the most con- centrated, that of Nordhausen, as stated above, containing one atom to every two atoms of the acid; or, expressed by symbols, its composition is 280,,HO. As prepared by the ordinary mode, it contains one atom of acid to one of water, or its composition is SO,,HO. If to about 49 parts of common oil of vitriol we add 9 parts of water, we have an acid the specific gravity of which will be about 1-78, and its composition SO;,2HO. It will then freeze at about the same temperature as water, but on the applica- tion of heat the solid does not melt until the temperature rises to 45°. A fourth compound of water and sulphuric acid is SO,,3HO, which has a specific gravity of 1-63. It boils at about 888°. QueEstions.—What is the density of the acid as it is drawn from the. leaden chambers? How is a portion of the water expelled? What is the proportion of water in the Nordhausen acid? In common oil of vitriol? Are there other definite compounds of this acid and water? COMPOUNDS OF SULPHUR AND OXYGEN. 233 Common oil of vitriol is the monohydrated acid, SO,,HO. Exposed to the open air it rapidly absorbs moisture, and increases in volume, so that a small vessel partly filled with it, if left open, is often found running over after a few days. Place a few drops of it in a watch glass in the pan of a small balance, and exactly counterpoise it by weights placed in the other pan; in a very few moments the effect of the absorption of moisture will be seen. It may therefore be used to separate moisture from gases which are not acted on by it, by passing the gas through tubes containing pieces of pumice stone moistened with the acid. Sulphuric acid is, perhaps, the most important of all the acids, as by its aid nearly all the others are produced. Its acid pro- perties are very decided ; aided by heat, it decom- poses animal and vegetable substances, causing a deposition of charcoal, and formation of water, which it absorbs. Its affinity for water is very great, and the combination of the two substances is attended with the production of considerable & heat. If a mixture of four parts of the acid and Mixture of SEO produces one of water is stirred ‘with a test-tube containing Heat. sulphuric ether, the heat generated will be sufficient to cause the ether to boil. Free sulphuric acid is occasionally found in the water of springs, as at Byron, Genesee County, New York; but such cases are rare. Uses,—Sulphurie acid is applied in the arts, and in the labora- tory, to very many important uses; as, in the preparation of the other acids, the extraction of soda from common salt, the manu- facture of alum, sulphate of iron, chlorine, &c. It is also used as a solvent for indigo, and in the various manufactures of the metals. Test.—Chemists possess an unerring test of the presence of sulphuric acid. Ifa solution of chloride of barium is added to a Questions.—How may the absorption of water from the atmosphere by oil of vitriol be shown? What is said of the affinity of this acid for water? What is the effect when it is mixed with water? What use is made of it? What test of its soluble salts is mentioned ? é 20 * 234 COMPOUNDS OF SULPHUR AND HYDROGEN. liquid containing free sulphuric acid, or any sulphate in solution, it causes a white precipitate, sulphate of baryta, which is charac- terized by its insolubility in acids and alkalies. : ® Compounds of Sulphur and Hydrogen. t 262. There is only one well-determined compound of sulphur and hydrogen, the protosulphide, or hydrosulphuric acid, HS; though by a particular process a second compound is obtained, as a heavy, yellowish liquid, which is supposed to be a bisulphide, HS,. The former only will be here described. 263. Hydrosulphuric Acid—HS; eq., (16+1=) 17.—This substance, often called sulphuretted hydrogen, is gaseous, and may easily be prepared by the action of diluted sulphuric acid upon powdered protosulphide of iron, formed by intensely heating a bar of iron, and then rubbing it with a roll of sulphur, or by heating intensely common iron pyrites (native bisulphide of iron) for some time in a covered crucible. One mode of preparing hydrogen, it will be recollected (197, 204), is by the action of dilute oil of vitriol upon metallic iron ; but if instead of iron we use sulphide of iron, a particle of sulphur being liberated at the same time as the particle of hydrogen, the two combine, and gaseous sulphide of hydrogen is evolved. The reactions are as follows :— FeS + SO,,HO = Fe0,80, + HS. An apparatus like that represented in the figure on the next page is convenient for the purpose. The sulphide of iron is first introduced, and after the cork with the tubes is inserted, the acid is added by means of-the long-necked funnel. The gas may also be prepared by the action of hydrochloric acid upon native sulphide of antimony finely pulverized, aided Quxstions.—262. What only well-determined compound of and hydrogen is mentioned? 263. How is it Brepared? ned phide of iron prepared for the purpose? Describe the reactions that take place. COMPOUNDS OF SULPHUR AND HYDROGEN. 235 by a gentle heat. The reactions then are as expressed in the following equation :— SbS + HCl = SbCl + HS. Hydrosulphurie acid is a colorless gas, of a most offensive odor, similar to that of putrefying eggs; 100 cubic inches of it weigh 86-93 grains, giving it a density of 1-191. At the ordinary summer temperature, it takes the liquid form under a pressure of about 15 atmo- spheres: and by a cold of —122° is frozen. A jet of it burns readily in the open air, forming water and sulphurous acid. Cold water absorbs 2 or 3 times its own volume of the gas, and acquires its peculiar odor and taste; but the gas.is all given off again when the water is boiled. Water impregnated with the gas, if kept for a time, becomes milky from the decomposition of the gas, and the separation of the sulphur contained in it. Sulphur-springs, which occur in many places in New York, Virginia, and other States, are springs, the waters of which are naturally impregnated with hydrosulphuric acid. They may always be recognised by the offensive odor, which extends to a distance around them, and by their blackening pieces of silver coin, by the formation of sulphide of silver. Water, possessing all the properties of that of the most noted sulphur- springs, may be prepared artificially, by passing a current of this gas, for a few minutes, through cold water. Let a little diluted sulphuric acid be poured upon some powdered sulphide of iron, in a small bottle, and then insert a cork with a bent tube, as shown in the figure, the other " Hydrosulphurie, Acid. Preparation of Sulphur Water. Quzstions.—What are some of the properties of hydrosulphuric acid ? What is said of its absorption by water? What are sulphur springs? How may sulphur water be prepared artificially ? 236 COMPOUNDS OF SULPHUR AND HYDROGEN. end of which shall dip in a vial of cold water. After the gas has bubbled through it a few minutes, it will be found fully impregnated. This gas blackens many colorless metallic salts, by the forma- tion of metallic sulphides. An amusing experiment may be performed in the following manner: Let a picture be traced on white paper with a solution of sugar of lead, which is perfectly colorless, and the picture, at a little distance, will be invisible. Let the back of the paper be now moistened by means of-a wet sponge; and, after tacking it to the wall, let a current of this gas be directed against it, and all the parts traced by the lead solution will in- stantly become dark brown, or black, by the formation of sulphide of lead on the paper. Picture. 264, The composition of this gas is easily determined by heating some tin-foil in a measured quan- tity of the gas. Let the tube be of the form represented in the figure, and let the tin-foil be placed in the upper part by means of a wire after the gas, carefully measured, has been introduced; and then having the open end of the tube im- mersed in mercury, heat the tin-foil by means of a spirit- lamp. All the sulphur will be immediately absorbed by the metal, and there will remain only the hydrogen, which will however occupy the same space as before. Now, Analysis of HS. One volume of hydrosulphuric acid gas weighs 1-191 One e hydrogen (subtract) -069 There remains for the sulphur, 1-122 This is very nearly (162) the weight of one-sixth of a volume of vapor of Questions.—What is said of the action of sulphur water upon many colorless metallic salts? 264. How may the composition of hydrosul- phuric acid be determined? COMPOUNDS OF SULPHUR AND CHLORINE. 237 sulphur; so the composition of hydrosulphuric acid must be one volume of hydrogen and one-sixth of.a volume of sulphur vapor, condensed to one volume. Compounds of Sulphur and Chlorine. 265, There are, it is believed, several compounds of these two elements, but two only (or perhaps, three) have been obtained in a separate state, the dichloride, S,Cl, and the chloride, SCI. 266. Dichloride of Sulphur—S,Cl; eq., (2 x 16 + 35-4=) 67-4.—The formation of this compound requires an apparatus which is somewhat complex. To prepare the chlorine, a flask, A, containing some peroxide of manganese, is provided, a tubulated retort, D, containing a quantity of sulphur, and a three-necked bottle, B, for the purpose of washing the chlorine. These are connected together by tubes, as shown in the figure, and some hydrochloric acid poured into A by means of the crooked tube, fg a Dichloride of Sulphur. the design of which is to prevent any escape of the gas, as would be the case if the liquid was poured directly in. Hverything Quzstions.—265. What is said of the compounds of sulphur and chlorine? 266. How is dichloride of sulphur formed? 238 COMPOUNDS OF SULPHUR AND CHLORINE. being ready, heat is applied to the sulphur in D, so as to melt it, and also a gentle heat to A, to cause a slow evolution of chlorine. This gas, after being washed in B, is dried by passing through a chloride of calcium tube T, and finally comes in contact with the vapor of sulphur in D, where the compound in question (S,Cl) is formed, and passes as a vapor into the receiver, H. This being kept cool by a stream of cold water from the vessel F, the dichloride is condensed, and any atmospheric air or other gaseous matter passes off by the waste-tube inserted in HE. The liquid thus obtained must be separated from a little sulphur it contains by a second distillation. Dichloride of sulphur is a reddish-yellow liquid, having a dis- agreeable, and very peculiar odor, which boils at about 280°. Its specific gravity is 1:69, and that of its vapor 4°668, It is imme- diately decomposed by contact with water. Dichloride of sulphur, considered in the gaseous state, is composed -of one volume of chlorine, and one-third of a volume of sulphur vapor, condensed into one volume. Thus, One volume of chlorine weighs 2-440 One-third vol. sulphur vapor weighs oesa 2-218 One vol. dichloride (or its density), 4-658 The density thus obtained, called the theoretical density, it will be seen, differs but slightly from that given above, obtained by direct experiment. 267. Chloride of Sulphur—SCl; eq., (16 + 35-4 =) 51-4.— This compound is prepared by passing a current of chlorine through a quantity of the preceding, until it is entirely saturated, and then distilling at a temperature of 147°.+ It is a deep red fluid, having a density of 1-62. The density of its vapor is 3-549. Considered in the gaseous state, it is composed of one volume of chlorine and one-sixth of a volume of sul- phur vapor, condensed te one volume. One volume of chlorine weighs 2-440 One-sixth of a vol. sulphur vapor weighs 1-109 One volume of chloride, 3-549 The compounds of sulphur with nitrogen, iodine and bromine, being of little interest, are not here described. _ Questions.—Describe the properties of dichloride of sulphur. 267. How is chloride of sulphur formed? Describe its properties. SELENIUM. 239 SELENIUM. Symbol, Se; Equivalent, 39:5; Density, 4:32. 268. History, etc.—Sclenium was discovered, in 1817, by Berzelius, and received its name from selene, the moon. It is usually found associated with sulphur, in some of its compounds with other substances, especially sulphide of iron (iron pyrites). It is found also in combination with copper, lead, mercury, silver, and other metals. From any of these it is prepared by several different processes. Selenium, at ordinary temperatures, is a solid of a deep brown color, the shade varying a little, according as it is seen in a powder or in a solid mass. When melted and suddenly cooled, it has a vitreous conchoidal fracture, and becomes negatively electrical by friction in very dry air. When heated to 212°, it becomes partially fluid, and perfectly so at a temperature a little higher than this. Heated to 700°, it sublimes like sulphur, which it closely resembles in many of its properties. At a temperature of 212°, ora little higher, especially if it has been heated con- siderably above this and again cooled down, it is viscid, and may be worked like softened sealing-wax, and drawn out into small threads. When heated in the open air, it readily takes fire and burns, exhaling a strong odor not unlike that of decaying horse-radish,—a character by which it may always be distinguished. Compounds of Selenium and Oxygen. 269. Selenium forms with oxygen three compounds, SeO, SeO,, and SeQ,. The. latter two are acids, and in many of their properties quite similar to sulphurous and sulphuric aside, to which they correspond in composition. Questions.—268. In what is selenium found? Describe its pros pertics.' 269. What compounds does it form with oxygen ? 240 OOMPOUNDS OF SELENIUM AND OXYGEN.—TELLURIUM. 270. Selenous Acid—SeO,; eq., (89°5 + 2 x 8=) 55-5.—To prepare this acid, a retort contain- ing a mixture of chlorate of potash and peroxide of manganese is connected, as represented in the figure, with a tube bent downward 80 as to receive a quantity of selenium at the lowest part. Heat is then applied to the chlorate by which oxygen gas is evolved, and also to the selenium in the tube. As the selenium becomes heated, it burns slowly, with a blue flame, and the selenous acid is collected in the upper part of the tube in the form of white acicular crystals, which are very soluble in water. Preparat ion of eOg. Q71. Selenic Acid—SeO,; eq., (89-5 + 3 x 8 =) 63-5.—Selenic acid is prepared by burning selenium with nitrate of potash, when seleniate. of potash is formed, from which the acid may be obtained in the liquid form. Its chief interest is found in its close resemblance to the corres- ponding sulphur acid, SO3, and in the fact that it is capable of dissolving gold. : With hydrogen selenium forms a compound, hydroselenic acid, HSe, which is gaseous, and irritating to the eyes, nose and lungs. It is ab- sorbed by water, like hydrosulphuric acid, and the solution, like that of hydrosulphuric acid, is decomposed by contact with the air. The compounds of selenium with sulphur, chlorine and bromine are not of sufficient interest to require attention in this work. TELLURIUM. ‘Symbol, Te; Equivalent, 64-5; Density, 6-2. 272, History, ete.—Tellurium is a rare substance, which has sometimes been found native, but is usually combined with the metals, as gold, silver, bismuth and lead. It is generally pre- pared from the telluride of bismuth, which is found in Schemintz in Hungary. Quzstions.—270. Describe the mode of preparing selenous acid. 271. Describe selenic acid. What compound does selenium form with hydrogen? 272. Describe tellurium. COMPOUNDS OF TELLURIUM WITH OXYGEN, ETO. 241 Tellurium, in some of its physical properties, closely resembles the metals with which it is often associated; but in its chemical properties it is more nearly allied to the non-metallic elements, especially sulphur and selenium. When pure, it has a clear white color, and bright metallic lustre ; and in its general appearance is not unlike antimony. It melts at a dull red heat, and, by slow and careful cooling, may be obtained in crystals, the primary form of which is the rhombo- hedron. Ata very high temperature it becomes gaseous. Compounds of Tellurium with Oxygen, Etc. 273. Tellurium forms with oxygen two acid compounds, viz., tellurous acid, TeO,, and telluric acid, TeQs, which, as will at once be seen, are similar in composition to the corresponding compounds of sulphur and selenium. With hydrogen, also, like the two elements just named, it forms a. single gaseous compound, hydrotelluric acid, HTe, the smell of which is even more offensive than that of hydrosulphuric acid. Tellurium combines with chlorine, iodine, bromine, sulphur, sele- nium, etc. Group IV. Two elements which are solid at ordinary tempera- oo BUS | tures, and similar in many other properties. Many of their compounds are isomorphous. PHOSPHORUS. Symbol, P; Equivalent, 32; Density, 1-8 to 2. 274. History—Phosphorus was discovered by an alchemist of Hamburg, in 1669; and received its present name (from phos, light, and pherein, to carry) from the circumstance that, at ordinary temperatures, it always appears luminous in the dark. Quzstions.—273. What is said of the compounds of tellurium witb oxygen? 274, Give the history of phosphorus. , 21 242 PHOSPHORUS. It is not found in nature in a separate state; but in combination with oxygen and lime, it is very generally diffused, being con- tained in all fertile soils, without exception, and in many vegetable and animal substances. 275. Preparation.—Phosphorus, at the present time, is pre- pared entirely from bones, which are first heated in the open air until they become white, so as to destroy all the animal matter they contain. More than half their weight remains, which is chiefly phosphate of lime. This is then ground to a fine powder, and digested, for one or two days, with dilute sulphuric acid, in the ratio of 8 parts of the bone ashes to 2 parts of acid and 15 or 20 parts of water. The action of the sulphuric acid upon the phosphate of lime, is to take away a part of its lime; forming with it sulphate of lime; and as the whole of the phosphoric acid of the original phos- phate is then in combination with only a part of its lime, it is plain that this must now be a super-phosphate of lime. This latter is soluble in water, while the sulphate of lime which has been formed is insoluble; more- water is therefore added, and a clear liquid obtained, which is evi- dently solution of super-phosphate TT ne of lime. This liquid is now eva- Sa porated until it begins to be quite y) thick, when it is mixed intimately J with charcoal, in fine powder, and thoroughly dried. It is next in- troduced into an earthern retort, a, which is placed in a proper furnace, as represented in the figure; and to the neck of the retort, a wide copper tube, B, is attached, which connects with a vessel of water. The heat is then gradually raised, when the phosphorus distils over, and is condensed in the water. Much combustible gaseous matter, also, Preparation of Phosphorus. Quzstion.—275. Describe the mode of preparing phosphorus. PHOSPHORUS. 248 comes over and escapes by the second tube, inserted in the water-vessel. The affinity of charcoal for oxygen at low temperatures is not very considerable, but when highly heated it is intense, and sufficient to abstract the oxygen from the phosphoric acid of the acid phosphate of lime, causing the liberation of the phosphorus. This, taking the gaseous state, distils over and is condensed to the liquid form, and finally solidified. The phosphorus thus procured is still impure, and is to be melted in hot water, and pressed through porous leather. 276. Properties.—Pure phosphorus is of a light flesh-color, and nearly transparent. At common temperatures, it is a soft solid, of specific gravity about 2, and may easily be cut with a knife. At 108° it fuses, and at 554° is converted into vapor, which has a density of 4-326. It is soluble, by the aid of heat, in naphtha, in fixed and volatile oils, and in some other liquids. By the fusion and slow cooling of a considerable quantity, it may be erystalized, and also from its solution in bisulphide of carbon. The crystals belong to the monometrie system. It is usually seen in long, slender sticks, of a waxy lustre, which are made by melting the phosphorus under water and pouring it into glass tubes. Phosphorus may be distilled without difficulty. For a cal operation, fit a green glass retort to a tube bent, as represented in the figure, and having its extremity drawn out to a fine point, but not closed. Sepa- rate the retort and tube, and put in the first a small quantity of phosphorus, and in the latter a little water; and again con- nect them firmly together. If now the retort is carefully heated, the phosphorus will gradually distil over and collect in the water in the lowest part of the tube. Distillation of Phosphorus, Quzsri1oxs.—What is the effect produced by the charcoal? 276. De- scribe phosphorus. In what is it soluble? In what form is it usually seen ? 244 PHOSPHORUS.: Phosphorus is exceedingly inflammable. Exposed to the air, at common temperatures, it undergoes slow combustion, emits a white vapor of a peculiar alliaceous odor, appears distinctly luminous in the dark, and is gradually consumed. On this account, phosphorus should always be kept under water. In the open air, even the heat of the hand, aided by the slightest friction, is sufficient to inflame it; and it should therefore always be handled with the greatest caution. It burns in the air with a brilliant, yellowish-white light and. intense heat; but in oxygen gas, its combustion is particularly splendid. A good method for performing the experiment is to place a piece of phosphorus in a small cup on a stand, a few inches high, in a basin of water, and, having ignited the phospkorus by touching it with a piece of heated wire, : == dexterously to place over it a large bell-glass, Combustion of Phos- previously filled with oxygen. By careful phorus in Air or Oxygen. tanagement, but little of the oxygen will be lost. It may also be made to burn under warm water, by forcing a current of oxygen upon it by means of a gas-bottle, or a flexible tube, leading from a gasometer. A red suboxide is formed which readily takes fire in the open air. The red crust which forms upon the surface of pieces of phosphorus exposed to the action Caatiacs Pees -of light, is believed to be a peculiar isomeric, or aula toy ae cn under 2ilotropic (178) condition of this substance. It Water v8 may be obtained by keeping a quantity of phos- : phorus for several hours, at a temperature of 450° to 480°, in a gas which does not act upon it, as nitrogen or hydrogen. This red or amorphous phosphorus differs essentially from ordinary phosphorus. Its melting point is about 482°, and it is non-luminous in the air at ordinary temperatures. Heated to 500°, it changes to ordinary phosphorus. Quzstions.—How is phosphorus affected in the open air? How is it usually preserved? May it be distilled? What is said of its com- bustion in oxygen gas? How may it be made to burn under water.?. COMPOUNDS OF FHOSPHORUS AND OXYGEN. 245 277. Uses.—Phosphorus is now used in large quantities in the manufacture of friction-matches, which ignite by slight friction. For this purpose it is made into a paste, with gum or glue, by which it is made to adhere to small pieces of wood or paper pre- viously dipped in melted sulphur, and is also protected from the action of the air. The paste is sometimes mixed with nitrate or chlorate of potash, or oxide or nitrate of lead, but this is not necessary. Occasionally, fine emory or powdered glass is mixed in the paste, to increase the friction.. Phosphorus is of great service in the laboratory, and has been sometimes used in medicine. Compounds of Phosphorus and Oxygen. 278. There are four compounds of phosphorus and oxygen, the atomic constitution of which appears to be P,O,PO,PO, and PO,. The last three are acids; but only one of these, the last, will be specially described. 279, Dinoxide of Phosphorus—-P,0.—This compound is prepared by the combustion of phosphorus under hot water, as in paragraph 276. Atmo- spheric air may be substituted for the oxygen. The oxide appears as flocculi of a brick-red color. It absorbs oxygen from the air, and mixed with phosphorus it renders it more combustible. . 280. Hypophosphorous Acid— PO.— May be obtained as a syrupy liquid, but cannot be erystalized. It cannot be obtained separate from - water. 281. Phosphorous Acid—PO;.— Phospho- rous acid may be prepared by the action of the air upon sticks of phosphorus, at ‘ordinary temperatures. For this purpose, place a few sticks of phosphorus in a funnel under a bell-glass, as represented in the figure, The glass is supported a little above the table, to allow the air to enter. Reg- nault advises to put the sticks of phosphorus in small glass tubes, having capillary aper- tures for the acid to pass through as it is SSS Preparation of POs. QuzEsTIoNs.—277. What use is made of phosphorus? How are friction- matches made? 278. What compounds of phosphorus and oxygen are there? 279. How may dinoxide of phosphorus be prepared? 281. How may eee acid be prepared ? 2 246 COMPOUNDS OF PHOSPHORUS AND OXYGEN. formed, but they are not essential. Too large quantities of phosphorus should not be used at once. 282. Phosphoric Acid—PO,; eq., (82 + 40 =) 72.— This acid is formed by burning phosphorus in air or in oxygen gas, as in the experiment given above (276). To prepare it perfectly anbydrous, the receiver should be placed over mercury, and the oxygen or air supplied should be perfectly dry. The acid appears as a dense white vapor, which is gradually precipitated, and may be collected. In the open air it at once absorbs moisture. If the white flakes are collected and ignited, the mass, after cooling, is semi-transparent, and is called glacial phosphoric acid. This acid may also be formed from calcined bones. To prepare the common acid, a very good mode is to digest phosphorus in nitric acid, with the aid of heat. One part of phosphorus, with 13 parts of the acid, of specific gravity 1-20, is placed in a glass retort which connects with a receiver’ that is kept cold by a stream of cold water, as shown in the figure, and heat applied. Red fumes of nitrous acid are given off, and the phosphorus rapidly consumed. The liquid collected in the receiver is now to be poured back into the retort, and heated until the water and any remaining nitric acid are expelled. On cooling it will become solid, and present the same appearance as ‘glacial phosphoric acid just described. The acid-thus obtained contains 1 eq. of water for each eq. of the acid, and is called mono- hydrated acid. The anhydrous phosphoric acid has a very strong affinity for water, and when thrown into it, unites with it with great energy, often producing slight explosions, in consequence of the heat pro- ——S Preparation of POs. QueEstions.—282, What is the composition of phosphoric acid? How is it prepared? How by the use of nitric acid? What is said of its compounds with water ? COMPOUNDS OF PHOSPHORUS AND HYDROGEN. 247 duced. With water it forms three different compounds, as fol- lows, the first two of which have been called, respectively, meta- phosphoric, and pyrophosphoric acids. Monohydrated, or metaphosphoric acid, PO,,HO. Bihydrated, or pyrophosphoric acid, PO,,2HO. Trihydrated, or common phosphoric acid, PO,,3HO. These three acids, or rather compounds of acid and water, can- not be distinguished from each other by external appearance, but dissolved in water they manifest chemical characteristics which render them quite distinct; they also form salts, which, though much alike in their general properties, are nevertheless easily dis- tinguished from each other by the proper tests. Compounds of Phosphorus and Hydrogen. There are several compounds of phosphorus and hydrogen, but one only will claim attention from us, the common phosphuretted hydrogen, PH;. The others are P,H, and PH,. 283. Phosphide of Hydrogen—PH,; eq., (32 + 3 =) 85.— This gaseous substance, called also phosphuretted hydrogen, is - best prepared by heating some sticks of phosphorus in a strong solution of caustic pot- ash, in a small glass retort, which, at the beginning of the opera- tion, should be quite filled with the mate- rials. If, then, the mouth of the retort is == made to dip slightly in a basin of water, each bubble of the gas, as it breaks into the air, will burst into a flame, PHs spontaneously combustible. Quzstions.—283. What phosphide of hydrogen is mentioned? How is it prepared ? 248 COMPOUNDS OF PHOSPHORUS AND HYDROGEN. with the formation of beautiful wreaths-of smoke of phosphorio acid, as shown in the figure. In the presence of potash phosphorus has the property of decomposing water, especially if the temperature be raised ; the oxygen and the hydrogen both combining with separate portions of the phosphorus, producing the teroxide of phosphorus (phos- phorous acid) and the terphosphide of hydrogen. Thus, 2P + 3HO + KO = KO,PO, + PH. Instead of potash, milk of lime may be used with the same result. Still another method of procuring it is to decompose phosphide of calcium by water, or dilute hydrochloric acid; but when this acid is used, the gas which is given off is not spon- taneously inflammable. It seems to be very well determined that the spontaneous combustion of this gas, in certain cases, is owing to the presence of the vapor of another phosphide of hydrogen con- taining proportionably more, phosphorus, which =» way be separated by passing the gas through a PH® epontane- tube surrounded by a freezing mixture. ae combusti' = Other combustible gases, as hydrogen, are made to inflame spontaneously by receiving a portion of the vapor of this inflammable phosphide. To prepare phosphide of calcium, select a tube of green glass, half an inch in diameter and a foot long; seal one end hermetically, and bend it a little, as represented in the figure. In the sealed end put some pieces of phosphorus, and then, holding the straight part in a horizontal position, introduce some lumps of well burned lime. The part containing the lime is next to be heated to redness by means of burning charcoal, when heat is also to be applied to the phosphorus sufficient to volatilize it; and the vapor coming in contact with the heated lime, at once unites with it to form the phosphide of calcium. This should be preserved in bottles with close stoppers; but even then it gradually undergoes decomposition. Terphosphide of hydrogen is a colorless gas, with a very disagreeable Preparation of Phosphide of Calcium. Quzstions.—Describe some of the properties of phosphide of hydrogen. To what is its spontaneous combustion owing? ‘ OTHER COMPOUNDS OF PHOSPHORUS. 249 odor,* and is irrespirable; 100 cubic inches of it weigh 36-75 grains, giving it a specific gravity of 1-18. 1 vol. of phosphorus vapor weighs 4-826 6 vols. of hydrogen weigh (069 x 6) -414 Forming 4 vols. of the terphosphide, 4:740 One volume therefore weighs. or the density of the gas is, 1:185 a Other Compounds of Phosphorus. Phosphide of Nitrogeh, N,P, is a white solid, which is infusible even at a red heat. ; 284. Chlorides of Phosphorus.—There are two chlorides of phosphorus, PCl,, and PCl,, corresponding in composition to phosphorous and phos- phorie acids. ~ The Terchloride of Phosphorus is formed in the same manner, and by using the same apparatus, as chloride of sulphur (266). The chlorine Preparation of PCI8. is formed in the flask A, and after being washed in water and dried in the chlorine of calcium tube, is brought in contact with the vapor of pkos- * Those who have observed the odor of this gas, and that of the liquid emitted by the American skunk (Mephitis Americana) when disturbed, cannot but have noticed the resemblance between them; which seems to render it probable that the fluid emitted by the skunk contains, in solution, a portion of the gas, or some other nearly-related, com- pounds of the same substances. This is rendered still more probable from the fact, that the fluid, when emitted by the animal in the dark, is distinctly phosphorescent.—Sce Godman’s Natural History, vol. 1, 289: “Philadelphia Edition, 1829. Question.—284. What chlorides of phosphorus are mentioned ? 250 ABSENIC. phorus in the retort, D, where the chloride is formed, and afterwards con- densed in the receiver E, which is kept cool by a stream of cold water It is a colorless liquid, of a density of 1-45, which boils at about 172°. 285. Perchloride of Phosphorus is formed by saturating the preceding with chlorine. It is a solid, having its point of fusion, and also its boil- ing point, at about 298°. : Bromine and sulphur combine readily with phosphorus, but the compounds are not important. : Iodide of Phosphorus is formed by bringing the two sub- stances together in a vessel where as little air may have admission as possible. It forms a dark-colored mass. These two substances afford one of the few instances in which reaction takes place between two solids. Let a few crystals of iodine be dropped into a wine-glass, upon a small piece of phosphorus, and immediately place over it a bell-glass. . By the heat produced, the phosphorus will be inflamed and a portion of the iodine. sublimed ; and the white cloud of phosphoric acid (152), mingling with the dense iodine vapor, presents to the eye a very pleasing appearance. Prep. of Iodide of Phosphorus. ARSENIC. Symbol, As; Equivalent,-75; Density, 5-88. 286. History and Preparation.—Arsenic has very generally been classed with the metals, chiefly on account of its metallic lustre, and comparatively high specific gravity; but, in its chemical properties, it is much more closely allied to the metal- loids, with which it is here classed. . Arsenic sometimes occurs native, but usually it is found in com- bination with the metals, and especially with iron and cobalt. The substance itself, or some of its compounds, seems to have been known from the earliest times. Tt may readily be prepared by heating the mineral called mis- pickel, which is a natural compound of arsenic, sulphur and iron, in close vessels, by which the arsenic is expelled and the sulphide Quzstions.—285. How is iodide of phosphorus prepared? What is said of the action of iodine and phosphorus upon each other? 286. Why bas arsenic often been classed with the metals? Why is it here classed with the metalloids? With what is it usually found combined? . COMPOUNDS OF ARSENIC AND OXYGEN. 251 of iron remains. By again heating it with black-flux, the arsenic is obtained nearly pure. If the pulverized mineral is well mixed with black-flux at the beginning, and no air admitted into the apparatus, a single operation will afford it in great purity. Let a common Hessian crucible be half filled with the mixture, and then place another crucible, a size smaller, in an inverted position above it, as shown in the figure, carefully luting them at their junction. A moderate heat should then be applied to the lower crucible and very gradually raised. -The arsenic will be sublimed from the mixture and condensed in small crystals in the inverted crucible, which should have a 1 very small aperture in the bottom, to allow the air to See escape as the heat is raised. : 287. Properties—Arsenic is a brittle substance, of a dark color, and feeble metallic lustre. Heated to about 356°, it is sublimed, without first melting, as is the case with most solids. Its vapor has a strong garlic odor, by which its presence may ‘be recognised, and a density of 10-37. Heated in the open air, it readily takes fire and burns with a livid flame. _ Arsenic is often sold under the very improper names of cobalt and jly-powder. Compounds of Arsenic and Oxygen. aad: 288. Two compounds only of arsenic and oxygen are known, both of which are acids, and in composition correspond to phos- phorous.and phosphoric acids. 289, Arsenious Acid—AsQ,; eq., (75 + 3 x 8=) 99.—This compound is the arsenic, or rats’ bane, of commerce, well known as a destructive poison. It is always produced when arsenic or its ores are heated in the open air. It is usually sold in a state Qurstions.—How may arsenic be separated from its compounds? 287. Describe arsenic. What is said of its odor? 288. What com- pounds of arsenic and oxygen are known? 289. By what names is arsenious acid often known. 252 - COMPOUNDS OF ARSENIC AND HYDROGEN. of fine white powder; but when first sublimed, it is in the form of brittle masses, more or less transparent, colorless, of a vitreous lustre, and conchoidal fracture. This glass, which may also be obtained by fusion, gradually becomes opaque without undergoing any apparent change of constitution, but becomes more soluble in water than before. Its specific gravity is 8-7. At 380° it is volatilized, yielding vapors which do not possess the odor of garlic, and which condense unchanged on cold surfaces. If thrown on burning charcoal, the garlic odor is perceived, because of the reduction of the oxide by. the carbon. Destructive as this substance is to the animal system, in minute doses it is sometimes used in medical practice; and in some countries, as in parts of Austria and Hungary, it is habitually used much in the same manner as narcotics, and even administered to horses. The effect is said to be to give a roundness and fulness of form, and clearness and freshness to the complexion. -Horses accustomed to receive it in their food, have a fat and plump appearance, and bright and glossy skins. It also improves their breathing. This substance is so frequently used to destroy life, that its detection in suspicious cases becomes an important object; but we reserve our remarks on this point until some others of the many compounds of arsenic have been described. 290, Arsenic Acid—AsO,; eq., (75 -+ 8 x 5 =) 115.—This acid may be formed by dissolving arsenious acid, just described, in nitric acid mixed with a little of the hydrochloric, and evaporating to dryness. It is a powerful acid, much resembling phosphoric acid (247); with which it is isomorphous. Its salts are also isomorphous with the salts of phosphoric acid. Compounds of Arsenic and Hydrogen. 291. Two compounds of these elements are known, one of which is solid, and the other gaseous. Of the former, little is known, with cer- tainty, and we therefore do not further allude to it. 292. Arsenido of Hydrogen, Arseniuretted Hydrogen— AsH,; eq., (75 + 3 =) 78.—This gas is evolved when arsenide of tin or zinc is treated with strong hydrochloric acid, or when sulphuric or hydrochloric acid is made to act upon zine or iron in the presence of any soluble com- pound of arsenic. To prepare it, pour upon some pieces of zinc diluted sulphuric acid with a few drops of solution of arsenious acid; the gas, which burns with a feeble blue flame, will be at once rapidly evolved. : Questions.—Describe arsenious acid. For what purpose is it often used? 290, To what other acid is arsenic acid analogous? 292. How is arsenide of hydrogen prepared ? COMEOUNDS OF ARSENIC WITH SULPHUR, ETC. 258 When thus prepared, the reactions are as indicated in the following formula, the zinc being oxydized at the expense of the oxygen both of the water and the arsenious acid. Thus, 6Zn + 8HO + AsO, + 680, = 6 (Zn0,S0;) + AsH,. The gas has a peculiar nauseating odor, and is exceedingly poisonous, Its density is 2-69, and by a cold of —22° it is converted into a liquid under the ordinary’ atmospheric pressure. By chlorine it is instantly decomposed, chloride of arsenic and hydrochloric acid being. formed. By solution of blue vitriol it is rapidly absorbed, and atsenide of copper precipitated. The equivalent of this gas, AsH;, answers to 4 vols., which is thus constituted : : 1 vol. of arsenic vapor weighs 10-370 6 * hydrogen 7 ‘414 4 vols. arsenide of hydrogen, 10-784 Weight of one vol., or the calculated density of the gas, 2-696. We shalt have occasion to speak of this compound again in connection with the detection of arsenic. Compounds of Arsenic with Sulphur and Other Elements. 293, Sulphides of Arsenic.—The bisulphide of arsenic, AS,, is found native, and called realgar by mineralogists. It may also be formed by art. Itis Of a dull red color. The tersulphide, AsS,, is the orpiment or king’s yellow of commerce. It is formed artificially by passing a cur- rent of hydrosulphuric acid through an arsenic solution containing a little free acid. It is also found as a natural production, and-is of bright yellow color, and is sometimes called sulpharsenious acid. A third compound of these elements, the pentasulphide of arsenic, AsS,, called also sulpharsenic acid, is formed by mixing solutions of hydrosulphuric and arsenic acids. It forms slowly, and some days are often required before the whole is precipitated. The compounds of arsenic with chlorine, iodine, phosphorus, &c., will be found described in larger works. : ae : uC Questions.—Describe the reactions which take place in the prepara- tion of arsenide of hydrogen. What are some of the properties of this gas? 293, What is realgar? What is orpiment? 22 254 DETECTION OF ARSENIC. Detection of Arsenic. 294. Poisoning by arsenious acid is at the present day, unfor- tunately, very common; and it therefore becomes a matter of special importance to be able with certainty to detect the instru- ment of death. 295, There are as. many as ten or twelve different tests for arsenic, but we shall confine our remarks to some of the most important. A single test should never be relied on, but several different ones should always be applied to separate por- tions of the suspected substance. I, Marsh’s Test—Put into a two or four ounce vial some pieces of clean zinc, and pour on them a small quantity of dilute oil of vitriol (oil of vitriol 1 part, and water 8 parts), and insert a cork with a small tube, as shown in the figure. Very soon hydrogen gas will begin to be evolved, as in the prepara- tion of hydrogen. After a little time the jet of hydrogen may be inflamed; and if all the materials used were pure, a piece of glass or porcelain held in the flame will receive no stain, but only a deposition of moisture from the com- bustion of the hydrogen. . The cork and tube being now removed, introduce some of the suspected substance, or water in which the suspected substance has been digested, with the aid of heat if neces- Marsh’s Test. Sary, and immediately replace the cork and tube. In a little time the jet of gas may be relighted; and if any appre- ciable quantity of arsenious acid is present, a piece of clean glass or porcelain held in the flame will at once receive a black stain upon its surface, caused by a deposition of arsenic. If the quantity of arsenious acid present is large, the flame will be of a pale color, and the blackening of the glass held in the flame will be instantaneous; but if the quantity be small, the blackening effect will be produced only after a little time. The deposition of arsenic here is from the arsenide of hydrogen, which is formed in the manner heretofore (292) explained. The cold substance held in the flame causes the deposition of the arsenic while the hydrogen is consumed. This is perhaps the most delicate test of arsenic known, but in using it some precautions must always be observed to avoid mistake. In some cases, where organic substances are present, spots similar to those pro- duced by arsenic may be formed, that may be mistaken for arsenic by Questions.—295. What is said of the number of tests for arsenic? Describe Marsh’s test. From what is the arsenic deposited? What is said of the delicacy of this test ? : v DETECTION OF ARSENIC. _ 255 the inexperienced ; and antimony will form spots very much like those of arsenic. Means must therefore be adopted to test the material form- ’ ing the dark spot upon the porcelain. For this purpose, it will generally be sufficient to hold the spot a few minutes in the flame of a spirit-lamp ; if the deposite be arsenic it will be volatilized, and disappear, but if pro- duced by antimony or other substances, it will remain. So also arsenic spots, exposed a few minutes, at a moderately elevated temperature, to vapor of iodine, become yellow, and then subsequently disappear by exposure to the air. II. Reinch’s Test—In a portion of the suspected liquid, made acid by hydrochloric acid, place a piece of metallic copper, previously filed per- fectly bright, and heat the whole nearly to the boiling point. If any appreciable quantity of grsenious acid be present, the arsenic will be deposited upon it as a gray crust of a metallic lustre. = III. Test by Hydrosulphuric Acid—Through a portion of the sus- pected substance, supposed to be in the liquid form, acidulated with muriatic acid, pass a current of hydrosul- phurie acid gas for half an hour, and then boil it a few moments; if arsenic be pre- sent, a yellow -precipitate—orpiment (293) —will be formed. The mode of passing the current of gas through the liquid will be seen by the accompanying figure. The materials for producing the gas are put into w flask, and a tube, bent twice at right angles, is inserted through a cork, so as to be air-tight; the other end is then immersed in the liquid, contained in a glass vessel, so as to reach near the bottom, and the gas, as it escapes, bubbles through the liquid. The mode is the same as before described (263). The precipitate (orpiment) thus formed, is entirely soluble in aqua ammoniz, and in solutions of the alkalies, * IV. Test by Ammonia-Nitrate of Silver.—Nitrate of silver forms with arsenious acid solutions a precipitate of arsenide of silver, which is of a peculiar canary yellow color, and is soluble in nitric acid. To ensure the formation of this precipitate, the arsenious solution should be slightly alkaline, and therefore the ammonia-nitrate of silver is used in preference to the simple nitrate. This is prepared by pouring into the nitrate of silver solution aqua ammonia, until the precipitate at first’ thrown down is nearly all dissolved. A precipitate very similar in its appearance to the above would be produced by phosphoric acid in the suspected liquid; so that the pre- cipitate formed by use of this test should always be further examined, before any reliance is placed upon it. V. Test by Ammonia-Sulphate of Copper—Solution of sulphate of cop- per produces in neutral or alkaline solutions of arsenious compounds a beautiful green precipitate, sometimes called Scheele’s green. In making Quzsrioxs,—Describe Reinch’s test. Describe the test with hydro- sulphuric acid. Describe the test with ammonia-nitrate of silver. Describe the mode of testing with ammonia-sulphate of copper. What will be the calor of the precipitate? : 256 DETECTION OF ARSENIC. the experiment, it is best to use the ammonia-sulphate of copper, which is prepared by pouring into @ solution of blue vitriol, aqua ammonia, until the precipitate at first formed is nearly all redissolved, as in the corresponding preparation of ammonia-nitrate of silver. But this test also may form with other substances a precipitate similar in appearance to the above, so that further examination should always be made. VI. Flandin and Danger’s Test.—Dry the suspected substance (sup- posed to be organic, as sugar or starch,) and treat it with one-fourth of its weight of the strongest oil of vitriol, and apply heat until it is quite dry ;—the whole will now be reduced to a black, friable mass, which can easily be pulverized, and is then to be boiled with strong nitric mixed with a little hydrochloric acid. By this process the arsenic, in whatever form it may be, is converted into arsenic acid, which after the whole has been again evaporated to dryness, to expel any remaining nitric acid, and redissolved in pure water, may be examined by the appropriate tests, not for arsenious but for arsenic acid. For this latter purpose, the ammonia-nitrate of silver may be used, which gives with arsenic acid a brick-red precipitate. Or, the arsenic acid being obtained in solution, may be precipitated as arseniate of lime by lime-water, and from this precipitate pure arsenic with its metallic lustre maY be obtained by the process next to be described. VII. Reduction of the Arsenic—When arsenic is present in any appre- ciable quantity, it may always be obtained in a separate state, so as to be recognised by its peculiar metallic lustre and garlic odor; and no chemist in any particular case will positively swear to its presence unless he is able thus to procure it! For this purpose, provide a tube of hard glass, a quarter of an inch in diameter and three or four inches long, with one end. hermetically sealed; and fill it to the depth of half an inch with a mixture of the suspected substance, charcoal, and carbonate of soda, the whole being previously well dried at a moderate heat, and ground together to a fines powder. After wiping the inside of the tube with a little cotton attached to a wire, to remove any dust or remaining moisture, a strong heat is applied to the end of the tube containing the mixture, by which the arsenic will be separated, to be again condensed upon the sides of the tube a little above the heated part. The bright metallic lustre will at once be recognised, and by breaking the tube and heating the part coated, as in the figure, the peculiar garlic odor will be perceived. Other Test of Arsenic. tests may also be applied to it if desired. This last test may be applied to any of the precipitates obtained by the previous tests. Qurstions.—Describe Flandin and Danger’s test. Describe the mode of testing by reduction of the arsenic. How does the arsenic show itself? May the last mode be applied to the precipitates obtained by the other modes? CARBON. 257 296, In these directions we are supposed, os a general thing, to be operating with pure arsenical solutions, but in cases of actual poisoning it will usually be otherwise ; and it often becomes an important object to be able to separate the organic matter contained in the suspected sub- stance. Sometimes the substance will be soluble, as sugar, which will not interferé badly with the operation; and at others it will be of such a character that it can be removed by passing through it a current of chlorine, or it may be that it can be removed only by heating it with strong oil of vitriol, as heretofore (VI.) described. In any particular ease, the mode of proceeding to be pursued must be adapted to its peculiar circumstances. Group V. a Combustible bodies, and incapable of béing volatilized even Boron at the highest temperatures. ~- CARBON. Symbol, C; Equivalent, 6; Density (erystalized), 3°52. 297. History.—Carbon, though rarely met with in nature per- fectly pure and uncombined, is one of the most important of the _ elements, forming, as it does, an essential ingredient of nearly all vegetable and animal bodies. It is found in a variety of forms; and when uncrystalized and uncombined, its color is always black. : 298. Preparation and Properties—Carbon presents itself to us in a variety of forms, as the diamond, graphite or plumbago, mineral coal, charcoal, gas coal, and perhaps we may add lamp- black, though the latter very probably differs from charcoal only in being in a state of fine division. QuestIons,—296. In these directions what are we supposed to operate with? Will this usually be the case in practice? Will it often be neces- sary to separate organic matters from the suspected substance? What elements constitute the fifth group? How are they characterized? 297. Give the history of carbon, 298. What are some of the varieties of carbon ? 22* 258 CARBON. The diamond is pure crystalized carbon, and is the hardest substance known in nature. The crystals are of the form of the regular octahedron, but the faces are frequently a ZS, little convex, as shown in the figure. Such crys- tals, properly set, are used for cutting glass, a pur- QZ pose for which they are admirably adapted. Heated intensely in the flame of the compound blowpipe, . the diamond is entirely consumed, forming carbonic acid, just as if the same weight of pure charcoal had been con- sumed. Diamonds are generally very small, the largest ever found weighing less than six ounces. A single diamond has been sold for more than half a million of dollars. It is generally found in the same situations as gold and platinum. A few crys- tals of little value have been discovered in the vicinity of the gold mines in some of the Southern States. It is a powerful refractor of light, and seems to have the faculty of absorbing light, and giving it out again after a time. A diamond held in the sun’s rays a few seconds, and then removed at once to a dark room, phosphoresces very distinctly for a few seconds. : Graphite, or plumbago, called also, very improperly, Black lead, is a variety of carbon, containing usually a little iron. It is often found crystalized in thin scales, of a hexagonal form. It is not unfrequently formed as an artificial production in iron fur- naces, and is sometimes quite free from iron. It is used for the manufacture of pencils, and in the con- struction of crucibles that are to be exposed to a very intense heat. For this purpose, it is ground to a fine powder, and mixed thoroughly with fire-clay. These crucibles are used chiefly for melting metals. Mineral coal is of two kinds; the bituminous, and the non- bituminous, or anthracite. Bituminous coal is distinguished by its softening, like wax, when heated, and giving off much gas, which burns with flame. ~ Diamond. Questions.—What is the diamond? What is said of its hardness? What use is made of it? What is the effect of the intense heat of the compound blowpipe upon it? What is said of the size of diamonds ? What is said of the absorption of light by the diamond? What is graphite or plumbago? What use is made of it? What two kinds of mineral coal are there? How is bituminous coal distinguished ? CARBON. 259 It is also much lighter than anthracite, and more easily ignited. Some of the different varieties of bituminous coal are caking, splint, cherry,-and cannel coal. Jet, also, which is used in jewelry, is a bituminous coal; and in the same family may be included wood or Bovey coal, sometimes called lignite. Anthracite, or stone-coal, differs from the above varieties, in containing no bituminous matter; and, therefore, it yields no inflammable gas by heat. Its sole combustible ingredient is carbon; and, consequently, it burns without flame. It is found in different countries, but nowhere in such profuse abundance as in the eastern part of the State of Pennsylvania, which supplies most of the northern and eastern parts of the United States with fuel. All the varieties of mineral coal are believed to have been formed from vegetable substances, which, in the changes the earth’s surface has undergone, have become buried beneath it. When bituminous coal is subjected to a high temperature in close vessels, or with only a limited supply of atmospheric air, the volatile or bituminous manner is expelled, and the remaining porous carbon is called coke. It is used for many important purposes in the arts, = Charcoal is prepared by exposing vegetable matter, and espe- cially wood, to a high temperature in close vessels, or in such circumstances as to avoid the presence of atmospheric air. By the heat a large quantity of water, acetic acid, tar, and other matters, is expelled, and the carbon, with any mineral matter which has been absorbed from the soil, remains. The latter con- stitutes the ashes which remain after the combustion of the coal in the open air. : The usual method of preparing charcoal for ordinary purposes, is to ignite large heaps of wood, which are covered with earth so as to admit only a limited supply of atmospheric air; and the result is to char or convert into coal a large part of the wood, by the heat occasioned by the combustion of the other part. Questions.—What is said of anthracite or stone-coal? Where is it found in this country? What is coke? How is charcoal prepared ? What constitutes the ashes? 260 CARBON. The figure, diminished from Knapp’s Technology, represents a section of a coal-pit ready to be ignited. The stake at the centre serves as a support for beginning the heap; and by one side of which space is left to kindle the fire, by dropping in pieces of very dry wood and burning coals. Charcoal is a black, hard, brittle substance, perfectly insoluble in every liquid, but attacked and oxidized by strong nitrig acid. It is a good conductor of electricity, but a non-conductor of heat ; is little acted upon by air and moisture, and is perfectly infusible in the most intense heat that can be applied to it. Heated in the open air, it takes fire and burns freely, especially if in large masses, leaving only a small residue of ashes. 299. Charcoal possesses the property of absorbing a large quantity of air, or other gases, at common temperatures, and of yielding the greater part of them again when it is heated. Recently-burned charcoal absorbs air and moisture so rapidly, for a few days, as materially to increase its weight. Both are absorbed and retained with such force, that a red heat is required to expel them. This absorption of air may be readily shown in the fol- lowing manner :—Let a piece of charcoal, of moderate size, be heated to redness for a few minutes, and then quenched under Qurstions.—Describe chareoal. 299. What is said of the absorption of gases by charcoal? How may the absorption of air be shown? CARBON. 261 mercury, and placed under a receiver, over -the mercurial cistern. The mercury will shortly begin ’ to rise, in consequence of the absorption of the air within; and the process will continue for several hours. p Charcoal, likewise, absorbs the odoriferous and 22 coloring particles of most animal and vegetable substances. When colored infusions of this kind are digested with a proper quantity of charcoal, a solution is obtained which is nearly, if not quite, colorless. Tainted flesh may be deprived of its odor by this means, and foul water be purified by filtration through charcoal. The sub- stance commonly employed to decolorize fluids is animal charcoal reduced to a fine powder. It loses the property of absorbing coloring matters by use, but partially recovers it by being heated to redness. At very high temperatures charcoal has a higher affinity for oxygen than any other substance, and is therefore often heated with oxides of the metals to deoxidize them, or deprive them of their oxygen. : Charcoal absorbs Gases. - Lampblack is minutely divided carbon, prepared by burning rosin or tar in a confined portion of air, so that the hydrogen only of: the material is consumed, and the carbon remiains as an exceedingly fine powder. It is used as @ pigment, and for other purposes. Gas coal is a deposite of nearly pure carbon upon the inside of the large retorts used in the manufacture of illuminating gas, It is very hard and black, and a good conductor of electricity. Uses.—Carbon is used as fuel; in forming gunpowder; asa pigment; in the formation of steel; as a polishing-powder; and in medicine as an antiseptic, &e., &c. : QuestT10ns.—What is said of the affinity of charcoal for oxygen at high ar lia What is lampblack? What use is made of it? What is gas coal? 262 COMPOUNDS OF CARBON AND OXYGEN. Compounds of Carbon and Oxygen. 300. Carbon combines with oxygen in two proportions, form- ing carbonic oxide, CO, and carbonic acid, CO,. - 801. Carbonic Oxide, Protoxide of Carbon—CO; eq.; (6-4 8=) 14.— This is a gaseous substance, and is best prepared by heating a mixture of equal parts of dry powdered chalk and iron-filings in a gun-barrel. The chalk, which is carbonate of lime, when heated, gives off its carbonic acid (the compound next to be described) in contact with the heated iron, by which one-half of its oxygen is instantly absorbed, and the carbonic oxide thus produced passes on, and may be collected over water. Thus, Ca0,CO, -+ Fe = CaO + FeO + CO. Another method of preparing it, is to heat gently a mixture of oxalic acid and five or six times its weight of oil of vitriol, by which both car- bonic oxide and carbonic acid are produced in equal volumes; but the ~~" preparation of CO. latter may readily be separated by passing it through a solution of caustic potash or milk of lime, in the three-necked bottle, and collected over water. The changes which take place are as follows, viz:— C,03,8HO + $05,HO = S0,,4HO + CO, + CO. The density of the gas is about 0-97; 100 cubic inches weighing 30-20 grains. It is highly combustible, and burns with a beautiful blue flame. Questions.—300.—What compounds of carbon and oxygen are there? 301. Describe the mode first mentioned for preparing carbonic oxide. The second mode. Is carbonic oxide combustible? What is the color of the flame? COMPOUNDS OF CARBON AND OXYGEN. 263 It will not support respiration or’ combustion; and a lighted candle being immersed in it, as heretofore described in connection with hydrogen (198), is in- stantly extinguished. It is this gas which gives the blue flame seen about the fire of the blacksmith, and in anthracite stoves, when the door is suddenly opened soon after the fire has been kindled, and'in furnaces for the reduction of the metals from their ores. Carbonic oxide is believed to be composed of 1 vol. of carbon vapor and 1 vol. of oxygen combined with- out condensation. Thus, 1 vol. of carbon vapor weighs -836 1 vol. of oxygen’ se 1-106 2 vols. of carbonic oxide “ 1-942 1 vol. of the oxide therefore “ ‘971 CO is Combustible. 302. Carbonic Acid—CO,; eq., (6 + 16 =) 22. — Carbonic acid is remarkable as being the first gaseous substance recognised, after atmospheric air, which must always have been known. It was first described by Dr. Black, in ea and called, by him, jixed air, because. he found it ued i in common limestone and magnesia; from which it may be expelled by heat, or by the action of any strong acid. It may be collected over water, but a por- tion will be absorbed. A gas-bottle, of the form shown in the figure, is con- venient for preparing it. Some frag- ments of marble, and water, are placed in the bottle, and the cover put on, and then strong hydrochloric acid is poured into the long-necked funnel. As thus prepared, carbonic acid is a colorless, inodorous gas, of specific gravity 1:52; 100 cubic inches weighing 47-14 ‘grains. Preparation of C02, It is considered 4 compound of 1 vol. of carbon vapor and 2 vols. of oxygen condensed to 2 vols. Thus, QueEstions.—302. When was carbonic acid discovered ? ? What was it first_ called? How may it be prepared? What is its specific gravity ? What is it composed of? 264 COMPOUNDS OF CARBON AND OXYGEN. * 1 vol. of carbon vapor weighs -836 2 vols. of oxygen «(1-106 x 2) 2-212 2 vols. of carbonic acid <“ 3-048 The weight of 1 vol. thereforeis , 1-524 Or we may consider it a compound of 2 vols. of carbonic oxide and 1 vol. of oxygen, condensed to 2 vols., as follows: 2 vols. of carbonic oxide weigh (-971 x 2) 1-942 1 vol. of oxygen se 1-106 Giving for the weight of 2 vols. of CO,, 3-048 And for the weight of 1 vol., as before, 1-524 Carbonic acid is so much heavier than atmospheric air, that it may be poured from one vessel to another without difficulty. Let a bottle, with a wide mouth, be filled with the gas, and then plunge into it a piece of lighted paper, or other substance, so that some smoke may be mixed with it and render its motions visible. Then hold the bottle in the hand, as if pouring a liquid from it (as represented in the figure), and the motion of the gas, as it is emptied from it, will be made’ apparent to the eye. Another instructive experiment of the same character may be “ performed as follows: Provide “a glass jar with a large mouth, and place at the bottom a lighted taper, as shown in the figure. Then having filled another jar of about equal capacity with carbonic acid gas, carefully re- move the cover and gradually pour the contents into the first- Candle Extinguished. mentioned jar;—the flame of the taper will first be considerably disturbed by the motion ocea- sioned by the descending gas, and will finally be extinguished. CO? poured from a Vial. Quustions.—How may the high specific gravity of carbonic acid be shown by pouring it from a vessel? How may the flame of a candle bo extinguished by it? , COMPOUNDS OF CARBON AND OXYGEN. 265 By a pressure of 36 atmospheres, at 32°, it is converted into a beautiful transparent liquid, which may be frozen by intense cold, in the manner already explained. 303. It is capable of supporting neither combustion nor respira- tion;—a burning candle plunged into it is instantly extinguished ; and a living animal, thrown into a vessel containing it, even though considerably diluted with air, soon dies. Carbonic acid is always produced by ordinary combustion; and lives have often been lost by persons placing an open dish of burning charcoal in their bed-rooms before retiring to rest. The oxygen of the air in the room is taken up by the carbon, and the gas in question takes its place, producing the effects described. It is produced, also, by the decay of animal and vegetable substances, and sometimes is found collected in caves and wells, and is called choke-damp. Though this gas does not support com- bustion, as the experiment is ordinarily made, yet potassium, sodium, and some other of the metals may be made to burn in it. For this purpose, fill a flask with dry carbonic acid gas, and drop into it a small piece of potassium, and apply the heat of a lamp at the point where the metal lies, by means of a blowpipe. When it has become very hot the metal takes fire and burns brilliantly, the carbon of the carbonic acid decomposed being deposited upon it as a black powder. 304, Soda-fountains are formed by compressing a large quantity of this gas in water, contained in a strong vessel adapted to the purpose. When the tube leading from the fountain is opened, the water is forced out by the pressure, and effervesces violently by the escape of the gas. Soda-powders, &c., often used to pro- duce an agreeable drink, in the absence of a soda-fountain, consist of bicarbonate of soda and tartaric acid, which, when mingled QuzstIons.—May carbonic acid be compressed to the liquid form? 303. Is it always produced in ordinary combustion? How may potas- sium be made to burn in it? What becomes of the carbon of the carbonic acid? 304. How are soda-fountains formed ? 23 266 COMPOUNDS OF CARBON AND HYDROGEN. together in solution, produce, by chemical action, tartrate of soda, the carbonic acid passing off into the air with effervescence. So, also, the effervescence which takes place on opening a bottle of beer, cider, or champagne wine, is owing to the escape of this gas, which has been produced by the fermentation of the liquid. All kinds of spring and well-water contain it in small quantity, and become insipid to the taste by boiling, in consequence of the gas having been expelled. It is also always present in the atmo- sphere, and in some cases accumulates in considerable quantities, as at the Grotto del Cane, in Italy, through which a man may pass without danger, but a dog on entering it is instantly suffo- cated. ‘The carbonic acid here constantly issues from the earth, and accumulates at the bottom, while the air above remains com- paratively pure. 305. Lime-water is an excellent test for carbonic acid; and a vessel of it being al- lowed to stand a few hours, becomes coated with a pellicle of carbonate of lime, by ab- sorbing this gas from the air. So lime-water becomes milky by blowing into it with a tube from the lungs, for ‘the same reason. A por- tion of the lime is changed into carbonate of lime, which is insoluble, and gives the water its Lime-water. milkiness. Compounds of Carbon and Hydrogen. 806. Carbon and hydrogen combine in a number of different proportions, producing compounds, several of which are of special interest, because of their isomeric character; but we shall here describe only two, both of which are gaseous, viz., light carbu- retted hydrogen, C,H,, and olefiant gas, C,H,, Questions.—What is said of the Grotto del Cane in Italy? 3805. How is lime-water affected by blowing through it with the mouth? Give the reason for the milkiness produced? 3806. What is said of the com- pounds of carbon and hydrogen ? : COMPOUNDS OF CARBON AND HYDROGEN. 267 807. Light Carburetted Hydrogen—C,H,; eq., (12 + 4=) 16.—This gas, called also Jire-damp, marsh gas, alae es and dicarburet of hydrogen, is formed by the slow decomposition of wood, and woody substances, under water, especially in warm weather; and may be obtained by stirring the mud and other matters at the bot- tom of stagnant pools (see figure), : and collecting the bubbles of gas in Collecting Marsh eet a receiver, as they rise. It some- times accumulates in large quantities in coal mines, where it is formed by the action of water upon the coal. It is best prepared by heating in a flask, made of hard glass, a mixture of 2 parts of acetate of soda, 3 parts of caustic potash, and 8 of quick-lime. The composition of the acetic acid is ©,H,0,, which, it will be perceived, is precisely equal to 2 eq. of carbonic acid, and 1 of the hydrocarburet in question. Thus, C,H,0,=2C0, + C,H, The use of the lime is to protect the gas from the action of the potash. Light carburetted hydrogen is a colorless, transparent gas, 100 cubic inches of which weigh 17-37 grains, giving it a specific gravity of 0-56. One volume contains 2 vols. of hydrogen, } of a vol. of carbon vapor. Thus, 2 vols. of hydrogen weigh (-069 x 2) -138 4 vol. vapor of carbon (82° _ 418 1 vol. of the hydrocarburet, 556 A burning candle is extinguished by it, but it is, itself, highly combustible, and burns with a feeble, yéllow flame. Mixed with twice its own volume of oxygen, or seven or eight times its volume Qurstions.—307. In what situations is light carburetted hydrogen b naturally formed? How may it be collected? How may it: be prepared artificially ? 268 COMPOUNDS OF CARBON AND HYDROGEN. of air, it explodes violently by the eleetric spark, or on the ap- proach of flame. 308. Olefiant Gas, or Heavy Carburetted Hydrogen—C,H, ; eq., (24 + 4=) 28.—This gas was first described in 1796, by some Dutch chemists, who gave it the name, olefiant gas, because of its forming with chlorine a peculiar oil-like liquid. It is color- less and tasteless, and but slightly absorbed by water; 100 cubic inches weigh 30-41 grains, so that its density is 0-98. Its volume contains 2 vols. of hydrogen, and 1 vol. of vapor of carbon, as follows: 2 vols. of hydrogen weigh (-069 x 2) -188 1 vol. of vapor of carbon, 886 Giving for 1 vol. of olefiant gas, ‘974 Olefiant gas is prepared by mixing, in a capacious retort, one part of alcohol with four of concentrated sulphuric acid, and heating the mixture, as soon as it is made, by means of a lamp or ignited charcoal. The acid soon acis upon the alcohol, effer- vescence ensues, and olefiant gas passes over, mixed with other substances, chiefly sulphurous acid, from which it may be purified by washing it with solution of lime or caustic potassa in several of Woulf’s bottles, as shown in the figure. | As might be expected, olefiant gas does not. support com- bustion ; but a jet of it burns in the air, or in oxygen gas, with a Questions.—Does light carburetted hydrogen form explosive mixtures with oxygen or atmospheric air? 308. By whom was olefiant gas dis- covered? Why was it so called? Describe it. How is it prepared ? What is said of the light produced by its combustion ? COMPOUNDS OF CARBON AND HYDROGEN. 269 brilliant white light. Mixed with oxygen, or air, in proper pro- portions, it explodes violently, like the preceding compound. 309. Illuminating Gas is usually a mixture of olefiant and light carburetted hydrogen gases, and is formed by distilling, in large cast-iron retorts, rosin, tar, or other resinous or oily sub- stances, or bituminous coal. Besides the gases mentioned, there are also formed other hydro-carbons, but in less quantity. Tllumi- nating gas is used in immense quantities in large cities, for lighting the streets, and for fixed lights in stores and other buildings. Illuminating gas.is now chiefly prepared from bituminous coal, and as it passes from the retorts is mixed with tar, carbonic acid, sulphuretted hydrogen, salts of ammonia, and other matters, from which it must be freed before being admitted to the burners. For this purpose, it is washed by passing it through water, and then further purified by passing through vats containing recently- slaked lime. If this gas is made to pass through a heated tube it is decom- posed, and a part of its carbon is deposited as a coating upon the inside of the tube. In this way large deposits of pure carbon are often formed in the retorts of gas-works. It has been de- scribed above (299) as gas carbon. 810. The History .of gas manufacture, for illuminating purposes, pos- sesses much interest, as showing the great benefit conferred by science on the arts, and domestic and public economy. In 1680, Mr. Clayton, of Yorkshire, England, observed that a brilliant light was produced by igniting the gas which issued from a close vessel containing bituminous coal when heated, but it was a century after this before any direct experiments were made with it, with reference to its use in the arts. In 1785, the preparation of gas for illumination, from the destructive distil- lation of wood, was suggested; but, in 1792, some buildings were actually illuminated with gas, in Cornwall, England; and the same thing was repeated in 1798, at a foundry in Birmingham. In 1805, some of the cotton-mills in Manchester were first lighted with gas, by means of permanent fixtures, prepared for the purpose; and this date may be assumed as the beginning of the use of gas-lights for practical purposes. In a half century, therefore, has this manufacture attained its present importance; and the time is not distant when the quantity annually con- sumed.in every civilized country will be greatly increased. Questions.—809. What is illuminating gas? How is it usually pre- ared? What is the substance now generally used for producing it? 310. What is said of the history of the use of illuminating gas for prac- tical purposes ? 23 * 270 NATURE OF FLAME.—THE SAFETY LAMP. s Nature of Flame.—The Safety Lamp. 311. What we term the combustion of a substance is occasioned by its entering into combination with some other substance, usually the oxygen of the atmosphere, and then taking another form as a compound (198). Of the two substances thus required to produce combustion, one is called the combustible substance, and the other the supporter of the combustion; but the action is really mutual between them, and neither can burn without the other. The supporter of ordinary combustion, oxygen, is always gaseous, but the combustible may be either solid, liquid, or gaseous. Flame is gaseous matter in a state of combustion, and is made incandescent by the intense heat of the combustion. Two gases are needed to produce it, one of which must be combustible, and the other, of course, a supporter of combustion. The action is mutual between them ;—neither will burn alone ;—and a jet of either will burn in the other. : In the common lamp or candle, the combustible gases are sup- plied from the oil, or tallow, which is gradually raised, by the capillary action of the wick, into the flame, where it is decom- posed by the heat. As these gases, thus produced, escape from * the wick, and come in contact with the oxygen of the atmosphere, the two combine, producing the phenomena of light and heat, with which all are familiar. A careful inspection of the flame of a lamp or candle, as it burns quietly, will show, that it is composed of three parts, viz :—Ist, a central part, a, surrounding the wick, and extending a little above it, of gaseous matter that has emerged from the wick, and is making its way outward to the atmosphere, which it has not yet reached, and therefore has not yet become ignited; 2d, the bright part of the flame, 6, which, in the form of a conical shell, incloses the part a, and Hil ~— consists of gaseous matter in a state of rapid combustion, | Gannc’ the combustible particles, as they reach the air, uniting f | Quzstions.—311. What is ordinarily termed combustion? Must there be two substances to produce combustion? What are they called? What is flame? In the common lamp or candle, how are the combustible aes supplied? Of what several parts is the flame of acandle composed? What is the dark interior part? NATURE OF FLAME.—THE SAFETY LAMP. 271 with its oxygen, with the evolution of much light and heat; and, 3d, the part, cc, outside of the part last mentioned, composed chiefly of heated air, and mixed with a small portion of com- bustible matter in a state of ignition. That the dark, interior portion, a, is composed of combustible gas, may be shown by inserting, in the centre of the flame, one end of a small glass tube, as shown in the figure, and conveying away a portion, and igniting it as it escapes at the other end. So, when . the flame of a candle is suddenly extin- guished, the heat in the wick continues, for a short time, sufficient to decompose j| the tallow, and the combustible gases g,5 from centre of Flame. continue to rise in the form of smoke ; : and may often be again relighted by applying the flame of another candle to the ascending smoke, several inches above the wick. In the flame of a jet of gas, precisely the same phenomena, in every particular, will be observed3;—the dark central cone of unconsumed gas, surrounded by the brilliant hollow cone of flame, and this enveloped in still another less brilliant cone. In the latter case, the gas is previously formed and consumed as it issues into the air, but in the case of the candle or lamp, it is formed in the wick, and instantly consumed as it escapes. 812. That there is really no combustion in the dark central part of the flame, appears from the fact that the wick remains there uncon- sumed, and is even protected by the gas existing > there from being attacked by the oxygen of Effect of Braided the air. In burning ordinary tallow candles, a the wick occasionally becomes too long, and requires to be snuffed ; but the wicks of the best spermaceti and wax candles, being plaited, QuESTIONS.—_How may the real character of this gas be shown? Will the same phenomena be shown in the flame of 2 jet of gas? 812. Why does not the wick of a candle burn off quite down to the tallow? 272° NATURE OF FLAME.—-THE SAFETY LAMP. the end curls outward when heated by the flame, and coming in contact ‘with the oxygen of the air, is gradually consumed as the candle burns away. The necessity of snuffing is therefore avoided. The plaited or braided wick, while the candle is burning, will always bend toward that side in which (\ the direction of the separate strands is upward J and inward, and of course from the other side iu which the direction is upward and outward. Generally the simple braiding of the wick is sufficient, but sometimes a cord or bobbin is braided in with one of the strands, as repre- sented in one of the figures in the margin; and sometimes, also, a cord is bound to the braided wick, by a thread wound spirally around ‘it. The intensity of the light from any flame, other things being equal, will depend upon the intensity of the combustion, and this will depend in turn upon the regular and abundant supply of the combustible and the supporter. When the wick of a candle becomes too long, or that of a lamp is too high, only the hydrogen of the gases formed from the decomposed oil is consumed, the carbon escapes in a finely divided state, as a dense, black smoke. This is because of the too rapid supply of the combustible, and the usual remedy is to diminish the length of the wick by snuf- fing or otherwise, but the same thing would be accomplished by increasing the supply of the supporter, oxygen. This last pur- pose is effected by the use of a glass chimney, by which a current of air is supplied more rapidly to the flame. By the Argand burner (so named from the inventor), a cur- rent of air is also supplied to the centre of the flame, the wick being in the form of a hollow cylinder, as shown in the figure on next page. Both through the centre of the flame and around ZZ = ye LLL Braided. Wicks. Qurst1ons.—How are the wicks sometimes made to bend outward in the air, so that the end is consumed? Upon what will the intensity of the light from a flame depend? What occasions the disagreeable smoke sometimes produced by a lamp? How is the defect usually remedied? What is the benefit of a chimney to a lamp? Why are hollow wicks often used ? , NATURE OF FLAME.—THE SAFETY LAMP. 273 the outside strong currents of air are csta- blished, as shown by the arrows. The effect, is to produce a perfect combustion of all the oil or other combustible material supplied to the flame. , It is found that the intensity of light produced by a flame depends very much upon the amount of carbon consumed. The flame of pure hydrogen is very feeble, as is also that.of the vapor of aleohol and ether ;—and these latter-contain compara- tively little carbon. But add to alcohol ai one-fourth of its volume of camphene, 5 i ait which is rich in carbon, and a brilliant ini i flame is produced. This mixture con~ pamp with Hollow’ stitutes the common burning fluid. Glass Chimney. 313. The blowpipe (193) is, as we have seen, simply a con- trivance to supply air to the flame from the lungs. The instrument is usually applied to one side of the flame, and as the current of air is forced through it, it is bent towards the opposite side. By means of this ‘ instrument a very intense heat may be produced, sufficient for many im- portant purposes. Much will depend ‘ju any particular case upon the mode of using the flame; and the inexperienced student, before commencing, will consult works that treat at length of this subject. Use of Blowpipe. 314. Safety-Lamp.—The safety-lamp is the invention of Sir H. Davy, to avoid the danger of explosions from mixtures of the above gases with air, which often occur in coal mines, when unprotected lamps are made use of. It consists simply of a com- Quzsti0ns.—What is the composition of burning fluid? 318. Describe the mouth blowpipe. May a very intense heat be produced by it? 314. For what special purpose was the safely-lamp invented? 274 NATURE, OF FLAME.—THE SAFETY LAMP. mon Jamp, the flame of which is surrounded by wire gauze, through which, it is found, flame will not ordinarily pass. This lamp, as it is usually constructed, is represented in the figure on the left. Its action in arresting flame is easily under- stood when the nature of flame is considered. We have seen that this is simply gaseous matter in a state of combustion, and therefore is intensely heated ;—now if by any means we can diminish the heat of this gaseous matter, so that it shall fall below the point of ignition, the combustion, and consequently the flame, must cease. And this effect is produced by the wire gauze. To show the effect, let a piece of such gauze, b, be held in the flame of a candle, a; the flame appears to be cut off by the gauze, and the gases pass through unconsumed, as shown at d, and, by dexterous management, may be relighted.. The occurrence of combustible gases in coal mines is occasioned by the action of water upon the coal; and they often collect in large quantities in places not properly ventilated, forming mix- tures with the air, ready to explode with excessive violence on the first approach of the unprotected candle of the miner. Before the invention of the safety-lamp, such accidents were of frequent occurrence ; and coal miners lived and worked in perpetual fear! All this is avoided by the use of the safety-lamp ;—and, in view of what has been said above, the mode in which it operates to afford the desired protection is easily understood. When this Safety-Lamp. Effect of Wire Gauze. Questions.—Describe the safety-lamp. What is flame? Will ordi- nary flame pass through wire gauze? What is the reason given for this fact? How may this be shown by a lighted candle and a piece of wire gauze? How are inflammable gases formed in coal mines? What is the effect when these gases, mixed with atmospheric air, come in contact with tho flame of a lamp? What is the effect when the safety-lamp is used ? COMPOUNDS OF CARBON AND NITROGEN. 275 lamp is carried into an atmosphere containing a considerable pro- portion of fire-damp, this latter immediately takes fire, and burns freely within the gauze, but the flame is not communicated to that without. At first, the flame of the lamp seems to be simply en- larged, but soon it leaves the wick entirely, and the whole space immediately inside the gauze seems filled with flame. When this takes place, the miner is obliged to retire, lest, by the intense heat, the wire of the gauze should be melted or oxydized, and the flame communicated to the mixed gases, without. The same effect might also be produced by stroug currents of air, which sometimes occur, forcing the concentrated flame against a particular part of the gauze, and causing it to break, or heating it so as to allow the passage of flame through it. The mode in which the safety-lamp wperates may be shown quite well, by pouring a little sulphuric ether into a common glass receiver, which should be inverted and agitated a little, so that it may be filled with a mixture of air and vapor of ether, and then letting the lighted lamp down into it. The mixture of air and vapor of ether entering through the gauze, burns brilliantly within’ the gauze, but the flame is not com- municated to that without. It should be remarked, that wire gauze serves as a protection against explosive mixtures of atmospheric air and the carburetted hydrogen only; a mixture of atmospheric air or oxygen with pure hydrogen may be ex- ploded through a very narrow tube of great length. Compounds of Carbon and Nitrogen. 315, There are several compounds of these two substances, but we shall notice only one, the bicarbonide of nitrogen, CN, or cyanogen (from kuanos, blue, and gennao, to produce, because it is an ingredient of Prussian blue). ‘é 816. Bicarbonide of Nitrogen, or Cyanogen—C,N, or Cy; eq., (12 + 14 =) 26.—This is a gaseous substance, and is readily formed by heating bicyanide of mercury (to be hereafter described) in a glass retort by a QueEstions.—Will it answer for the miner to remain with his lamp in the explosive mixture? Describe the experiment for showing the opera- tion of the safety-lamp. Will wire gauze in this manner prevent the explosion of mixtures of hydrogen and oxygen? 315. What is said of the compounds of -carbon and nitrogen? From what does cyanogen derive its name? 316. How is bicarbonide of nitrogen, or cyanogen prepared ? 276 COMPOUND OF CARBON AND SULPHUR. spiritdamp. It is colorless, has a very pungent odor, and is easily com- pressed into a liquid; and by the cold produced by a mixture of solid carbonic acid and sulphuric ether, this liquid may be frozen. Of the pure gas, 100 cubic inches weigh 56-47 grains, giving it a density of 1-82. Cyanogen is composed of 1 vol. of vapor of carbon and 1 vol. of nitrogen, as follows, viz. : 1 vol. vapor of carbon weighs 0-836 1 “ nitrogen “0-972 Weight of 1 vol. of: cyanogen, 1-808 Cyanogen, though u compound, is remarkable for combining with the elementary bodies in the same manner as an element, forming a class of compounds which are called cyanides. Further remarks concerning it will be deferred to Organic Chemistry. Compound of Carbon and Sulphur. 817. These elements combine in only one proportion, forming the following compound: 318. Bisulphide of Carbon—CS,; eq., (6 + 32 =) 38.—This compound, called also sulpho-carbonic acid, is formed by heating to redness pieces of charcoal in a porcelain tube or retort, and then causing vapor of sulphur to come in contact with it. The figure on next page represents a good arrangement for the pur- pose, everf when a considerable quantity is to be prepared. The retort, R, of stone ware, is first filled with pieces of well-burned charcoal, and the tube T inserted nearly to the bottom, and luted well around the neck, to prevent any escape of gaseous matter. It is then to be placed in a suitable furnace, and con- nected with a Liebig’s condenser, C, and this with a receiving vial, V, partly filled with water. A small tube of glass inserted into the cork allows the air to escape as the vial is filled. Questions.—Describe bicarbonide of nitrogen or cyanogen. For what is it remarkable? 317. H6w many compounds of carbon and sulphur are known? 818. Describe the mode of preparing bisulphide of carbon, or sulpho-carbonic acid. COMPOUND OF CARBON AND SULPHUR. 277 — (= Preparation of CS2. When everything is ready, a fire is kindled in the furnace, and when the retort becomes well heated, pieces of sulphur are occa- sionally dropped into the tube T, and a cork immediately inserted. The sulphur being sublimed by the heat comes in contact with the heated charcoal, with which it combines, producing the com- pound in question. This now passing into the condenser, takes the liquid form, and is collected in the receiver, V. It will be observed that this process is a case of combustion (193), the carbon being the combustible, and the vapor of sul- phur the supporter; and the compound formed, CS,, is analogous to carbonic acid, CO,, which is formed when carbon is burned in‘ oxygen. And as carbonic acid combines with oxybases, to form salts, the composition of which is RO,CO,, so sulphide of carbon combines with sulphur bases, to form compounds of the analogous form, RS,CS,. The letter R is here used indefinitely, for any element whatever. ‘ Bisulphide of carbon is a colorless liquid, which boils at about 112°, and has a density of 1:27. It does dot mix with water, but dissolves readily in alcohol or ether. Its odor is excessively fetid and nauseous. Both sulphur and phosphorus are dis- solved in it, and may be obtained in crystals by the gradual Questions.—What is said of the relationeof bisulphide of carbon to carbonic acid? May this be considered as a case of combustion? Which of the substances is to be considered as the combustible body, and which the supporter? What are some of the properties of bisulphide of carbon? 278 SILICON. evaporation of the solution. By its evaporation in the open air a very considerable cold is produced, but under-the receiver of the air-pump its evaporation is so rapid as to occasion a cold of —76°. It burns freely in the open air, producing carbonic and sulphurous acids, and with oxygen its vapor forms an explosive mixture. SILICON. Symbol, Si; Equivalent, 21-3; Density, ?. $19. History.—Silicon was first obtained by Berzelius, in 1824. It was then considered a metal, and named stlicium, but is now generally ranked with the non-metallic elements. It is never found in its separate state in nature, although it is really very abundant in every place in silicic acid (silica), and the various siliceous compounds which constitute the rocks and soils. Next to oxygen it is the most abundant element found upon the earth. 820. Preparation.—To prepare silicon a somewhat complex g substance is selected, the double fluoride of silicon and potassium, which is a white powder like starch. When this compound is heated in a. glass tube with nearly its own weight i of potassium, by means of a spirit-lamp, és the fluorine combines with the potassium, nee and the silicon is separated from the mass . by washing with water, which dissolves the fluoride of potassium and leaves the silicon very pure. The reactions which take place are represented by the following equation : Preparation of Silicon. 3KF,28iF,; + 6K = 9KF + 28i. Questions.—319. Has silicon sometimes been ranked with the metals? Is it abundant in nature? 3820. How may it be prepared? COMPOUND OF SILICON AND OXYGEN. 279 321. Properties.—Silicon, as thus obtained, is a powder of a dark, nut-brown color, without metallic lustre, and is a non-con- ductor of heat and electricity. It stains the fingers, and adheres to everything that comes in contact with it; and when heated in the atmosphere or oxygen gas, it takes fire and burns, with the formation of silicic acid. In close vessels, silicon, like charcoal and boron, is capable of enduring a very high temperature without fusion, but is ren- dered harder and more compact. It is now incombustible, even when highly heated in the air or in oxygen gas, and is unaffected by the blowpipe, even in contact with chlorate of potassa. Compound of Silicon and Oxygen. 322, There is known only asingle compound of these elements, the teroxide, SiOs. 323. Silicic Acid, or Silica—SiO,; eq., (21:3 + 24) 45:3. —This is one of the most abundant compounds in nature, and is found quite pure in quartz, flint, caleedony, agate, &c.; and, in combination with other substances, in the material of all soils, and nearly all rocks. Alone, silica is nearly infusible, but may be melted in the intense heat of a compound blow-pipe. It is not acted upon by any acid except the hydrofluoric (252), but, at high temperatures, euters into combination with the alkalies and earths. It is very hard, and has a harsh feeling to the fingers, even in fine powder. In quartz crystals, which are usually six-sided prisms, terminated by six-sided pyramids, it is familiar to every one. By heating silica in fine powder, with four times its weight of carbonate of potash, in a platinum crucible, the carbonic acid is displaced, and silicate of potash formed; which, being treated Questi0ns.—321. Describe the properties of silicon. 322. What com- pound only of silicon and oxygen is there? 823. What is said of the abundance of silicic acid, or silica? What is said of its fusibility?. Is it acted upon by any of the acids? What is the usual form of its crystals? What is the effect when silica in fine powder is heated with carbonate of potash? 280 OTHER COMPOUNDS OF SILICON. with diluted hydrochloric acid, yields a gelatinous precipitate of hydrated silica. This is soluble in water, and constitutes soluble glass, or liquor of flints;—terms sometimes used. It is some- times found in the waters of hot springs, as the Geysers of Ice- land; and, in fact, in very small quantities, in most natural waters. In this state it is taken up by the rootlets of plants, and is found in their ashes after incineration. It is especially abun- dant in the grasses and the straw of the cereal grains, and in the stalks of rushes and reeds. In the gelatinous state, silica has occasionally been found in the cavities of minerals, when they have been broken. Exposed to the air, and especially if heated, the water evaporates, and dry, harsh, insoluble silica only remains. All the different varieties of glass ‘are silicates of different bases, or mixtures of these silicates. This subject will be treated of more at length hereafter. It is in its power thus to combine with the bases, so as perfectly to neutralise them, that this compound, oxide of silicon, or silica, evinces its claims to be considered as an acid. Other Compounds of Silicon. $24. Terchloride of Silicon—SiCl,; eq., (21-3 + 106-2 —) 127-5.—This compound is formed by heating silicon in dry chlorine, or by passing a current of the latter over a mixture of silica and carbon when heated in a porcelain tube. It is a colorless, volatile liquid, which boils at about 188°, and has a density of about 1-52. By contact with water it is de- composed, producing silica and hydrochloric acid. 825. Terfluoride of Silicon—SiF,; eq., (21-3 -+ 57 =) 78:8, — This fluoride, called also, fluo-silicie acid, is obtained by gently heating a mix- ture of equal parts of dry and finely-powdered glass and fluor-spar, made into a paste with strong oil of vitriol. The oxygen of the silica and the fluorine of the fluor-spar here exchange places, while the sulphuric acid combines with the lime that is formed, thus, neglecting. the water of the sulphuric acid, 8CaF + Si, + 880, = 3(Ca0,80,) ++ SiFy. Questions.—Is silica found in nature? Is it taken up by the roots. of plants? Of what are all the different kinds of glass composed? 824. How is the terchloride of silicon formed? Describe its properties. 825. Describe the terfluoride of silicon. x BORON. 281 Terfluoride of silicon is a colorless gas, with a pungent, acid odor, and in the open air forms dense white fumes by combining with the moisture it contains. Its density is 3-57. . By contact with water it is at once decomposed, gelatinous silica is deposited, and the water is found to contain a peculiar compound, called hydrofluosilicie acid, the composition of which is 3HF, 2SiF. The experiment is best performed by putting the materials in a dry retort, A, connected with » receiver, R, partly filled with water, and placed so that it can be gently shaken occasionally, in order that the film of silica forming upon the surface may be broken up, and a fresh surface of water exposed. When hydrofluosilicic acid is saturated with a base, as potassa, the hydrogen is replaced by an equivalent quantity of the metal of the base. Thus, 3HF, 2SiF,; + 3KO = 8KF,28iF, + 3HO. The compound 3KF,2SiF, is the double fluoride of silicon and potas- sium (320) used in the preparation of silicon. Silicon is capable also of forming compounds with sulphur and bromine, _BORON. Symbol, B; Equivalent, 10-9; Density, 2. 326. History—Boron, in a separate state, was first obtained by Davy, in 1807. It is found in nature only in combination, and in comparatively small quantities. Though it occurs in Questions.—How is terfluoride of silicon affected by contact with water? What is the composition of hydrofluosilic acid? 326. When and by whom was boron discovered? Is it found naturally in a separate state? 24 * 282 BORON. several minerals, as datholite and boracite, it is obtained chiefly from the waters of certain hot springs, especially in Tuscany and the Lipari Islands, where it occurs in solution, ds boracic acid. 327. Preparation—To prepare boron, first make a saturated solytion of borax in boiling water, and, while hot, pour in sul- phuric or hydrochloric acid until the ‘solution tastes distinctly sour. As it cools the boracic acid will separate in white, shining scales, which are to be thoroughly washed and dried by fusion in a platinum cru- cible. We thus obtain boracic acid, which is then’ to be mixed with potassium (or sodium), and heated in a glass tube, as in the preparation of silicon. A part of the boracic acid yields its oxygen to the potassium, and the potassa so formed enters into combination with the rest of the boracic acid to form borate of potassa. By treating the mass with cold water the latter compound is dissolved, and the boron is seen floating in the liquid as a fine powder of a brownish color, and may be collected on a filter. Before filtering, some sal am- monia should be dissolved in the mixture, which has the effect to prevent the escape of the finely-powdered boron through the filter. The mode in which the sal ammonia operates to produce this effect is not understood. Preperstion of Boron. 328. Properties.-—Boron is a dark olive-green powder, without taste or smell, and incapable of fusion in the strongest heat. It is insoluble in water or alcohol. Heated in the open air to about 600°, it takes fire and burns brilliantly, forming boracic acid. It is a non-conductor of electricity and heat. Questions.—827. How is boron prepared? Describe the reactions which occur. 828. Describe boron. How is it affected when heated ? OTHER COMPOUNDS OF BORON. 283 Compound of Boron and Oxygen. 329, Boracic Acid—BO,; eq., (10-9 + 24 =) 34:9. — This acid may be obtained from the common borax of commerce, as just described in the preparation of boron; it is also produced by the combustion of boron in the air. Boracie acid is slightly soluble in water and in alcohol; and when the latter solution is inflamed it communicates to the flame ‘a beautiful green tinge, which is characteristic of this substance. To make the experiment, fill a common dropping tube, of the form AB in the figure, with the solution; and, inserting , a cork firmly in A, apply the heat of a lamp to the bulb, and inflame the jet of liquid as it issues from the capillary orifice, B. The flame will be of a beautiful green. The color of the flame may also be shown very well simply by moistening one end of a pine stick in the solution, and in- flaming it, Green Flame produced by BOs. Other Compounds of Boron. 380. Terchloride of Boron—BCl,; eq., (10-9 + 106-2=) 117-1.—This compound is formed by preparing an intimate mixture of boracic acid and carbon, and causing a current of dry chlorine to pass over it ina porcelain tube, kept at a red heat. It is a colorless gas, of a density of 4-03 ;—in the open air it forms dense white fumes with the moisture con- tained therein, and in contact with liquid water it is instantly decom- posed, forming hydrochloric and boracic acids. $31, Terfluoride of Boron—BF,; eq., oe -L 57 =) 67-9.—Terfluoride of boron, or fluoboracic acid, is a colorless gas, of specific gravity 2-37. It is prepared by heating in w gun-barrel a mixture of 2 parts of pul- Qusstions.—829. How is boracic acid procured from borax? Describe this acid. ‘ What color does it give to the flame of alcohol when dissolved in it? How may it be shown? 880. How is the terchloride of boron formed? 331. How is the terfluoride of boron formed ? 284 THE METALS.— GENERAL PROPERTIES. verized fluor spar (fluoride of calcium), and 1 part of fused boracic acid. It has a strong affinity for water, which dissolves 700 or 800 times its own volume of the gas, and acquires a sour taste and a strong acid reaction, and chars wood like oil of vitriol when brought in contact with it. Boron combines also with sulphur, forming a tersulphide, BS,. THE METALS. General Properties. 332. Characteristic Properties. —The metals are generally good conductors of electricity and heat, and possess a peculiar lustre called the metallic lustre, which can scarcely be imitated by other substances. When their compounds are decomposed by the galvanic battery, they always make their appearance at the negative electrode (112), and are therefore, without exception, to be considered as electro-positive. But these properties are much more distinct in some metals than in others. Most of the metals are also characterized by their great density, as gold and platinum; but two at least, potassium and sodium, are lighter than water. All of them except mercury are solid at ordinary temperatures. The ancients were acquainted with only seven metals, viz.: gold, silver, iron, copper, mercury, lead, and tin; but there are now known, with certainty, forty-seven; and the discovery of several others has been announced, though perhaps not fully proved. 333. Sources of the Metals——Though several of the metals are found in animal and vegetable substances, they seem to form no necessary part of any organic compounds. Most of them, as iron, lead, and zine, are found in the earth in combination with other non-metallic elements, as oxygen, sulphur, or arsenic, and are said to be mineralized, and the compound is called an ore ; but a few, as platinum, gold, and sometimes copper, silver, bis- Quustions.—332. What are some of the characteristic properties of the metals? How many metals were known to the ancients? Are all the metals solid at ordinary temperatures? 3833. Do any of the metals form any part of organic compounds? What constitutes a motallic ore? THE METALS.—-GENERAL PROPERTIES. 286 muth, &c., occur in the metallic state, and are said to be found native. Some are found in the form of salts, especially as sili- cates, carbonates, and sulphates. The metals occur sometimes in beds, which are more or less parallel with the earthy strata containing them, but more fre- quently in veins or lodes, which traverse the strata in every direction. The veins are more abundant in the older than in the newer rocks; and their appearance indicates that they are fissures which have been produced in the strata subsequent to their” deposition, and then filled by filtration of the metallie matter from above, or by injections from below. Besides the metallic compounds, or ores, these veins always contain other minerals; as quartz, carbonate of lime, heavy spar, and fluor spar, which con- stitute the gangue, or vein-stone. 334. Relations to Light.—The relations of the metals to light are in some respects peculiar and interesting. Their peculiar lustre, called the metallic lustre, has already been alluded to; this lustre entirely disappears when they are reduced to a fine powder, but reappears when the substance is rubbed with a burnisher. All the metals except gold are perfectly opake, even when reduced to the thinnest laminz possible. Gold in the form of leaf transmits a feeble green light. The best method to observe this light is to place an un- broken leaf upon a piece of white plate glass, and press it gently with a bunch of cotton to make it adhere. It may then be preserved for any length of time. The color of most of the metals, seen in mass, is grayish-white, as platinum, iron, lead, and potassium, but seen in powder the color is a deep gray. By burnishing the particles, the original grayish-white is restored. Gold in mass has a beautiful yellow color, and in powder a deep purple, almost black. Copper and titanium. are red. 335. Malleability and Ductility—Some metals possess the property of malleability, that is, admit of being beaten into thin Questions.—When is a metal said to be found native? 3834. What is said of the lustre of the metals? Is this lustre seen in a metal when it is reduced to powder? Are most of the metals opake even when reduced to thin lamine? What is the color of most of the metals? What is said of their color when in fine powder? What metal is yellow? What metals are red? 3835. What malleable metals are mentioned? 286 THE METALS.— GENERAL PROPERTIES. plates or leaves by hammering. The malleable metals are gold, silver, copper, tin, platinum, palladium, cadmium, lead, zine, iron, nickel, potassium, sodium, aluminum, and frozen mercury. The other metals are either malleable in a very small degree only, or, like antimony and bismuth, are actually brittle. Gold surpasses all the other metals in malleability; one grain of it may be extended so as to cover about 52 square inches of surface, and the film will have a thickness of only sga/ggpth of an inch. Nearly all malleable metals may be drawn out into wires, a property which is expressed by the term ductility. The only metals which are remarkable in this respect are gold, silver, platinum, iron and copper. The process of wire-drawing consists in drawing the metal through round holes made in plates of steel for the purpose. The steel plate is made with a number of holes, of different diameters, through which the rod of metal is made to pass successively, its diameter at each operation being a little reduced and:its length increased. A machine for this purpose is represented by the accompanying figure. AB is the plate of steel through which the wire is dtawn,—it is held “Wire Drawing. firmly in its place by a support, D. A rod from the rolling mill, in the form of a coil, or a coil of wire, is placed upon the reel, F G, which turns Qurstions.—What metals are mentioned as being brittle? What is said of the malleability of gold? Are the malleable metals also ductile? Describe the process of wire-drawing? THE METALS.— GENERAL PROPERTIES. 287 easily upon its axis; and the end of the wire, drawn out a little with the hammer, is passed through the plate and attached to the drum, C, which is turned by machinery, and by its motion winds the wire around itself, at the same time, of course, withdrawing it from the reel. To form small wire it is in this way passed many times through the plate; and, to prevent its becoming hard and brittle, it is several times annealed during the process. The passage of the wire through the plate is facili- tated by dipping the coils occasionally in « moderately strong solution of sulphate of copper, by which it receives a thin coating of metallic copper. r 336. The malleability and ductility of any substance would seem to depend very nearly upon the same properties, but it is found in the case of. metals that they are not. precisely the same. In the following table, in the first column, several of the metals are arranged in the order of their malleability, beginning with the most malleable; in the second column, the same metals aro arranged in: the order of their ductility.. The table is from Regnault. Malleability. Ductility. 1. Gold. 1. Gold. 2. Silver. 2. Silver. 8. Copper. a 8. Platinum. 4, Tin. 4. Iron. 5. Platinum. 5. Nickel. 6. Lead. 6. Copper. 7. Zine. 7. Zine. 8. Iron. 8. Tin. 9. Nickel. 9. Lead, Both the malleability and ductility of several of the metals vary with the temperature. Thus iron, though partially malle- able and ductile at the ordinary temperature of the atmosphere, is much more so at a red heat; and zinc is very malleable from 212° to 350°, but loses this property if cooled down to 32°, or heated to 600°. At the latter temperature it is decidedly brittle. When a metal has been hammered or rolled, or drawn out into wire, its hardness as well as density is increased ; and it becomes less malleabf®. This property, however, is restored by annealing it, which consists in heating it to redness and then cooling it Quzstrows.—836, Do the malleability and ductility of a substance depend upon the same properties? Are the malleability and ductility of some of the metals affected by their temperature? What is said of iron and zinc in this connection? What is meant by the annealing ofa metal? Why is this often necessary in working many of the metals? 2838 THE METALS.— GENERAL PROPERTIES. slowly. But the tenacity is often very much diminished by the process, sometimes even more than one-half. $37. The tenacity of a metal is determined by ascertaining the greatest weight a wire made of it, of a given diameter, will sus- tain. The determination is made by attaching one end of the wire to a firm support, and to the other end fixing a pan to receive the weights. Wires 0-787 of a line in diameter (= to about ;%,th of an inch), made of the several metals mentioned below, were loaded gradually until they broke with the weights placed opposite to their names in the following table. These. numbers therefore indicate their relative tenacities. Pounds. Pounds. Tron Wire -..c-sceessseee sees soveee 549 | Gold .icrceccccercseccccessccceseevees LOL Copper.... 802 | Zinc.. 7 Platinum. Silver........ . 274 | Tin... ea ‘soned Saas ieee MOT MEAs ccmane sauces AUS When a metallic wire is tested in this manner its length is increased with the weight, but if the load has not been too great it contracts again to the same length as at first, on the removal of the load. If the load be increased beyond a certain point, a permanent elongation is produced; and usually no great further increase is needed to break the wire. 338. The specific gravity of the metals, like many of their other properties, are very dissimilar. The specific gravities of some of the more important of them are contained in the following Table of the Specific Gravity of Metals at 60°, compared with Water as Unity. Platinwm......... secseeeeceeeeeees 20-98 | Cobalt...... 006 saonueante haus mneey 8-53 Gold...eccorees ... 19-02 | Nickel... « 8-27 Tungsten. - 17-65 | Manganese. « 8-01 Mercury.. + 13-56 | Iron... oe 78 Palladium.. 11-05 | Tin... 7-29 Lead......... we 11-35 | Zine......... .. 6°86 Silver..... »» 10-47 | Antimony..... » 6:70 Bismuth..... ww. 9°82 | Chromium. . 5:09 Uranium. .- 9°00 | Titanium...... «= 5:03 Copper...... +. 8-09 | Aluminum. . 8-07 Cadmium..... «. 8-60 | Sodium....... eee 0-97 Molybdenum.....ssceese cesses ves 8-06 | Potassium........... sR esees 0-86, 1 : Questions.—337. How is the tenacity of a metal determined? What metal of those mentioned has the greatest tenacity? Whatis the second? 838. What is said of the specific gravity of the metals? What metal is mentioned as having the greatest specific gravity? What is the second? ‘ THE METALS.— GENERAL PROPERTIES. 289 _ 839. Crystaline Characters.—Many of the metals have a dis- tinctly crystaline texture. Iron, for example, is fibrous; and zinc, bismuth, and antimony aro lamellated. Metals are some- times obtained also in crystals—and most of them, in erystaliziog, assume the figure of the cube, the regular octahedron, or some form allied to it. Gold, silver, and copper occur naturally in crystals, while others erystalize when they pass gradually from the liquid to the solid condition. Crystals are most readily pro- cured from those metals which fuse at a low temperature ; and bismuth, from conducting heat less perfectly than other metals, and, therefore, cooling more slowly, is best fitted for the purpose. Several of the metals form small but very beautiful crystals, as they are slowly separated from their solutions by the galvanic current. If in a solution of sulphate of copper we place two plates of copper, and connect them with the two electrodes of a galvanic battery in feeble action, after some time the plate on the negative side will become covered with small crystals of metallic copper, while the other plate will be gradually dissolved. Tt is believed that some of the metals, in certain peculiar circum- oo may assume ® erystalline structure, even when in the solid 340. Alloys ——Many of the metals are capable of combining with each other, forming compounds called alloys, which will be described in their proper places. They possess all the charac- teristic physical properties of the pure metals, and many of them are of great service in the arts. Generally, alloys are more fusible and more oxidable than their constituents separately. Their malleability and ductility usually are much less, and their hardness greater, than those of the metals of which they are composed. Compounds of mercury with other metals are called amalgams. 341. Metallurgy.—The reduction of the metals from their ores, and the methods adopted in working them in the arts, con- Quzstions.—339. Do any of the metals possess a crystaline te 3 What metals are mentioned as being camieiiines found a erystals ae scribe the mode of obtaining crystals of copper by the galvanic process ? 340. What are alloys? Do alloys possess the usual physical properties of the metals? What is said of their fusibility? What of their malle- ability ae ductility? What are amalgams? 341. What is metallurgy? > : “= 290 THE METALS.— GENERAL PROPERTIES. stitutes a distinct branch of chemical science, called by this name. Most of the metals have an extensive range of affinity ; many of them form compounds with nearly all the non-metallic clements, and all without exception combine with oxygen. As many of the metallic ores are oxides, the reduction of this class of compounds becomes particularly important. It is effected in several different modes, as, 1. By mere heat. By this method the oxides of gold, silver, mercury, and platinum may be decomposed. 2. By the united agency of heat and combustible matter. Thus, by transmitting a current of hydrogen gas over the oxides of copper or iron heated to redness in a tube of porcelain, water is generated, and the metals are obtained in a pure form. Car- bonaceous matters are likewise used for the purpose with great success. Potassa and soda, for example, may be decomposed by exposing them to a white heat, after being intimately mixed with charcoal in fine powder. A similar process is employed in metallurgy for extracting metals from their ores, the inflammable materials being wood, chareoal, coke, or coal. In the more deli- cate operations of the laboratory, charcoal and black fluz* are employed. 3. By the galvanic battery. This is a still more powerful agent than the preceding; since some oxides, such as baryta and strontia, which resist the united influences of heat and char. coal, are reduced by the agency of galvanism. 4. By the action of deoxdizing agents on metallic solutions. Phosphorous acid, for example, when added to a liquid containing oxide of mercury, deprives the oxide of its oxygen, metallic mcr- cury subsides, and phosphoric acid is generated. In like manner one metal may be precipitated by another, provided the affinity of the latter for oxygen exceeds that of the former. Thus, when mercury is added to a solution of nitrate of oxide of silver, metallic silver is thrown down, and oxide of mercury is dissolved * Black flux is prepared by deflagrating nitre with twice its weight of cream of tartar When equal weights are used, it constitutes white flux, Questions.—What is said of the affinity of the metals? What are most of the metallic ores? What are some of the different means by which these ores may be reduced? SALINE COMPOUNDS, OR SALTS. 991 by the nitric acid. On placing metallic copper in the liquid, pure mercury subsides, and a nitrate.of the oxide of copper is formed ; and from this solution metallic copper may be precipitated by means of iron. To reduce the other compounds of the metals, other modes are adopted, which cannot here be particularly doscribed. ~ The relations of the various metalloids to the metals will be descrihed as each of these latter elements shall come in review before us, so far as demanded by the special object of the work. 842. Classification of the Metals.— The metals have been _ variously classified by different writers; but the following arrange- ment into six groups will probably answer our purpose as well as any we can adopt. 1. Metals, the protoxides of which are alkalies. 2. Metals, the protoxides of which are alkaline earths. 8. Metals, the protoxides or sesquioxides of which are earths. 4. Metals which; at a red heat, decompose the vapor of water, but are not acted upon by liquid water. 5. Metals-which are incapable of decomposing water, and whose oxides are not reduced by the mere action of heat. 6. Metals whose oxides are reduced by a red heat. ° Saline Compounds, or Salts. 343, A salt is a compound of two other binary compounds, which sustain to each other the relation of acid and base; the former being electro-negative in reference to the latter, which is electro-positive. Thus, sulphate of soda, NaO,SO,, is a com- pound of sulphuric acid (teroxide of sulphur) and soda, which is the protoxide of sodium; the former being electro-negative in reference to the latter, which is electro-positive. ; The acids take their name from the fact that when soluble their taste is very generally sour,—but this may not always be Questions.—342. What are the metals included in the first group? . ee In the third? Inthe fourth? In the fifth? In the sixth ? : at is a salt? Iustrate by an e le. H the acids generally characterized ? a ee vi 292 SALINE COMPOUNDS, OR SALTS. the case; they are mostly combinations of two metalloids, as the sulphuric, nitric, and hydrochloric acids, but sometimes they are formed of a metal and metalloid, as the manganic and chromic acids, and the sulphides of tin and antimony, which are capable of acting as acids. Most of them have the property of changing the blue solution of litmus to red. The bases, or electro-positive binary compounds, are always formed by the combination of a metal with a metalloid, as the protoxide of potassium (potassa), the protosulphide of potassium, and the protoxides of iron, copper, and silver. 344, Oxysalts,— A large majority of all known acids and bases are oxides, called oxacids and oxybases; and the salts formed by their union are therefore called oxysalts. They are therefore double oxides. The metallic oxides, in regard to-their disposition to combine with each other as acids and bases, and with the oxides of the metalloids, to form salts (as suggested by Regnault), may be divided into several very distinct classes, as, 1. Basie oxides, which combine readily with salts and form definite, erystalizable salts. Most of them are protoxides, as potassa, KO, soda, NaO, protoxide of silver, AgO, and the protoxide of iron, FeO. A few are sesquioxides or suboxides. 2. Acid oxides, which, as the name implies, possess acid properties ;— they combine with bases to form salts, and very generally change the blue solution of litmus to red. Most of ‘them are bi- or teroxides, ag plumbic acid, PBO, (binoxide of lead), chromic acid, CrOs, and man- ganic acid, MnQ,. Occasionally they are still higher oxides, as per- manganic acid, Mn,0,. 8. Neutral oxides, which may combine with either acids or bases, as alumina, Al,O,, and the sesquioxide of antimony, Sb,0,; or with neither, ag the binoxides of silver, potassium, barium, and ‘strontium, Some of these, by the action of acids, especially if heated, are decomposed. 4. Saline oxides, which result from the combination of a basic metallic oxide with a higher oxide of the same metal, as the magnetic oxide of iron, Fe,0,, which is really a compound of the protoxide, acting as a base, with the sesquioxide, acting as an acid; and its proper formula is therefore FeO,Fe,03. The oxides of manganese, Mn,O,, and of chromium, Cr,0,, furnish other examples. Qurstions.—Are most of the acids formed by combinations of the metalloids? Do some of the metals form acid compounds? How do the acids generally affect the blue solution of litmus? Of what are the bases mostly composed? 344. What is said of a majority of all the known acids and bases? What four classes of metallic oxides are mentioned? SALINE COMPOUNDS, OR SALTS. 2938 345. Sulphur Salts—Two sulphides often combine, forming double sulphides, analogous to the double oxides. They possess, in many respects, similar characters to the double oxides or oxy- salts, and are called sulphur salts. Some of the principal sulphur bases are the protosulphides of potassium, sodium, lithium, barium, strontium, calcium, and mag- nesium; and some of the more important sulphur acids are the sulphides of arsenic, antimony, carbon, tin, gold, and hydrogen. The sulphur salts generally are so constituted that if the sul- phur they contain were replaced by an equivalent quautity of oxygen, oxysalts would be produced. Thus, the carbosulphide of potassium, KS,CS,, when the sulphur is replaced by oxygen, becomes carbonate of potassa, KO,CO,; and, in like manner, the double sulphide of potassium and arsenic, KS,As8,, by a similar substitution, becomes arseniate of potash, KO, AsO,. 346, Chlorosalts—The chlorosalts are double chlorides, one of the simple chlorides acting as a chlorobase, and the other as a chloroacid, as the double chloride of gold and potassium, KCLAuCl,, called also aurochlorate of chloride of potassium, and platinochlorate of chloride of sodium, NaCl,PtCl,.- In the same manner two iodides (an iodobase and an iodoacid) bro- mides, or fluorides, may unite to form in each case a series of salts analogous to the preceding, but not much is known of them. - It is to be observed that these combinations take place only between members of the same series, as oxides with oxides, sulphides with sul- phides, &.; it is evidently possible that members of different series may unite, as an oxide with a chloride, a chloride with a sulphide, &c.; but it is a question not fully settled whether such compounds are ever really formed. 347. Haloid Salts.—Besides the compounds recognised by the above remarks as salts, the binary compounds of chlorine, iodine, bromine, and fluorine with many of the metals, have been classed .with the salts by Berzelius and other eminent chemists, because of their resemblance, in many of their properties, to the salts, Quzstions.—845. What are sulphur salis? What is said of the con- stitution of the sulphur salts? Give an example. 246. What are chloro- salis? May the iodides, bromides, &c¢., form similar series of salts? Are these combinations always between members of the same series? 347. What are haloid salts, so called? Are these compounds salts, accord- ing to the definition of a salt adopted above ? : 25 * 294 SALINE COMPOUNDS, OR SALTS. 4 properly so called. To distinguish them from the salts proper, they have been called haloid salts. But we prefer to limit the definition of a salt, as given above, although in so doing we of course exclude common salt, chloride of sodium, from the class, The elements, chlorine, iodine, &c., which, by combining with metals, form the so called haloid salts, combine also with hydrogen, forming acid compounds called hydracids (168), as the hydrochloric, hydriodic, &c. Now when powerful hydrous acids are-brought in contact with the haloid salts, important reactions take place, dependent upon the water of the acid. Thus, by the action of oil of vitriol upon chloride of potas- sium, we obtain sulphate of potassa and hydrochloric acid, as shown in the following equation: HCl + 80,,HO = KO,SO, + HCl. Here the water of the acid is decomposed, yielding its oxygen to the potassium to form potassa, and its hydrogen to the chlorine to form hydro- chloric acid. So, on the other hand, the action of a hydracid on an oxybase results in the production of a haloid salt and water. Thus, KO + HCl = KCl + HO. 348. Neutralization of Acid and Base—When an acid and base combine to form a salt, the peculiar and characteristic pro- perties of each, in a great measure, disappear, the new compound formed not being characterized by the properties of either of its ingredients, but possessing others entirely distinct. Thus, an acid is generally sour to the taste, and changes vegetable blues to red, but the salts it may form with bases possess neither of these properties ; so, also, the alkalies are caustic to the flesh and taste, and combine with oils to form soaps, but the salts which they form with the acids are entirely destitute of these properties. Most of the other peculiar properties of both acids and bases, when the two combine, are affected in the same manner, and they are therefore said to be eutralized. 849. Salts are often spoken of as divided into the three classes of neutral salts, super or acid salts, and sub or basic salts; but the distinction Questions.—What is said of the elements chlorine, iodine, &c., which form the so-called haloid salts by combining with the metals?” What reactions take place when powerful hydrous acids act upon these salts? Give an illustration. 348, When an acid and base combine do the pecu- liar properties of each disappear? Give some further illustration, 849. What three classes of salts are mentioned ? SALINE COMPOUNDS, OR SALTS. 295 cannot always be made with accuracy. In general, a neutral salt is formed by the union of a single equivalent of the acid and base, while an acid salt contains two or more equivalents of acid to one of base; and a sub or basic salt contains two or more equivalents of base to one of acid. But this is to be understood as liable to many exceptions. Frequently ‘salts denominated neutral contain as many equivalents of acid as there are equivalents of oxygen in the base. Thus, the neutral sulphate of soda is NaO,SOg, and sulphate of the protoxide of iron Fe0,S0O,, but the sulphate of the peroxide of iron is Fe,0,,3S803. Some few acids have the property of combining with bases in such a manner that one equivalent of acid will hold in union with it one, two, three (or even more) equivalents of base, and yet these several salts are considered as neutral; such acids are called polybasic acids. Phosphoric acid (282) furnishes an instance of the kind. 350. Solubility and Crystalization of the Salts.—Nearly all the salts are solid at ordinary temperatures, and very many of them ate susceptible of crystalization. Very generally they are more soluble in warm than in cold water, and often their solubility increases in proportion as the temperature of the water is ele- vated. The following table’ shows the quantity of nitrate of potash soluble in 100 parts of water at several different tem- peratures : Temperatures. Parts soluble in 100 parts water. 82° 13-3 64° 29:0 113° 74-6 DUT? wats iambic seeansacbaniminnnenwine wee In some gases, the solubility rapidly increases as the tempera- ture is raised, up to a certain point, and then diminishes. Sul- phate of soda (Glauber’s salt) furnishes an instance of this kind. Of this salt 100 parts of water, at 32°, take up 12 parts; at 77°, 99 parts; at 91°, 322 parts;—but above this temperature the solubility diminishes, so that at the boiling point only about 212 parts will be held in solution. Questions.—What in general isa neutral salt? What is a super or acid salt? What is a sub or basic salt? Do salts denominated neutral often contain as many equivalents of acid as there are equivalents of oxygen in the base? Give an example. What are polybasic acids? 850. Are the salts usually solid at ordinary temperatures? Are they more soluble in warm or cold water? What is said of the solubility of nitrate of potash in water at different temperatures? How is the solubility of sulphate of soda in water affected, as the temperature of the water is raised? 296 SALINE COMPOUNDS, OR SALTS. Crystals of soluble salts may generally be obtained by making a saturated solution at an elevated’ temperature and allowing it to cool slowly. Thus, a saturated solution of alum at 100° or 150°, on cooling deposits beautiful octahedral crystals; and if a tree or basket made of copper wire is placed in the solution when warm, the crystals will attach themselves to it in various posi- tions, presenting a very beautiful appearance. 351. Salts soluble in water,—and even some that are insoluble —often retain in their crystals a portion of water, which is called water of crystalization. Thus sulphate of soda in crystals con- tains 10 equivalents of water, and its proper formula is NaO,SO, +10HO. This is the case however only when the crystalization takes place at a temperature below 92° or 93°; when it crys- talizes at a higher temperature the crystals are anhydrous. The same salt will often combine with very different quantities of water when deposited from its solution at different temperatures. Sulphate of protoxide of manganese, erystalized from an aqueous solution, at 43°, has the formula, MnO,SO; + 7HO; when crys- talized between 43° and 68° its formula is MnO,SO, + 6HO; and again when crystalized between 68° and 86°, its formula is Mn0,S0, + 4HO. . When a salt of the kind last mentioned is heated in the open air, it gives up its water in successive portions, as the tempera- ture is raised. Sometimes the last equivalent of water is held by a much stronger force than the rest, and can be driven off only by a red heat, and then an entire change in the nature of the salt takes place. The water in such a case is called constitutional water. 352. Sometimes a salt in a dry atmosphere loses a part or all of its water of crystalization, and falls to powder; it is then said to effloresce. Again, some salts absorb moisture from the air, and are then said to deliguesce. Common pearlash (carbonate of pot- Querstions.—How may crystals of salts soluble in water often be ob- tained? 3851. What is water of crystalization? Give an illustration. Will the quantity of water of crystalization often depend upon the tem- perature of the solutions from which the crystals are deposited? What will be the effect when a salt of this kind is heated? 352. When is a salt said to effloresce? When to deliquesce? SALINE COMPOUNDS, OR SALTS. 297 ash) is an instance of a deliquescent salt. Left in the open air for a time, it will absorb sufficient water to effect its solution. 353. Water holding a salt in solution invariably has a higher boiling point than pure water. The following table shows the boiling points of saturated solutions of several of the salts. Salts, ee Boiling Point. Chlorate of potash..........sse0 GED: aasscassaesscswetncsesavectes 220° Common Salt......... » 41:0... een fn DOU? Nitrate of potash. . 885-0 .... a eens 241° Nitrate of Lime......ssesssseeees O20! aerscedacsestavessiesesseesd see 304° But the steam from such boiling solutions, as it escapes into the open air (omitting any regard to variations of atmospheric pres- sure), will always be of the same temperature of 212°. When a hydracid, as the hydrochloric, HCI, acts upon a metal, as zine, the acid is decomposed, and a chloride of the metal formed, the hydrogen being set free; thus, Zn + HCl = ZnCl + H. So when liquid hydrochloric acid is poured upon potash, the reactions are ; ' KO + HClLHO—KCl + HO + H. ‘In both these cases, therefore, as will be seen by an examination of the formule, the particle of hydrogen of the hydracid has simply been displaced, and a particle of metal substituted. . Now all the oxyacids, or nearly all,—at least in their active state,— contain water, as the sulphuric acid, SO,,HO, and nitric acid, NO,HO. They may indeed be obtained free from water, as SO,, and NO,, but they are then solid and quite inert, possessing none of the active properties of the liquid acids, which, however, they immediately assume on the addition of water. The reaction between zinc and oil of vitriol is Zn + SO;,HO = Zn0,80, + H. Quzstrons.—358. What is said of the boiling point of water holding a salt in solution? What is said of the temperature of the steam formed? When a hydracid acts upon a metal what are the reactions that take place? What when hydrochloric acid acts upon potash? In these cases ig the hydrogen simply.replaced by the metal? Is the result the same when the hydrated oxyacids act upon the metals? Explain by reference to the action of sulphuric acid upon zinc. 298 SPECIAL DESCRIPTION OF THE METALS.—POTASSIUM. Now as hydrated sulphuric acid only, S0,HO, is capable of acting upon this metal, and not the dry acid SO,, may we not in this case also, in like manner, consider the metal as simply replacing the hydrogen ? If this view be adopted, as it has been by some eminent chemists, then it is required that the formule of the hydrated acids, the sulphuric, nitric, &., should be changed accordingly, sulphuric acid being not SO,,HO, but SO,,H, or, as generally written, H,SO,. So also nitric acid is to be considered, not NO,,HO, but H,NO,, and so of other acids. We shall not discuss the subject further, but simply give the formule for several well known salts, according to the old and generally received view, and also according to the new view. Salts. Common Theory. New Theory. Sulphate of Soda.........06 Sulphate of Zinc... oe Nitrate of potash.........00. Chlorate of potash Separate Description of the Metals. 354, The classification of the metals adopted in this work has already been indicated (842). Group I. Powasercir Metals, the protoxides of which are alkalies.—The protoxides Senet of these metallic elements are very: soluble in water, and Lireroi possess in an eminent degree the peculiar properties denomi- nated alkaline properties. POTASSIUM. Symbol, K (Kalium); Equivalent, 39-2; Density, 0-865. 355. History.—Potassium was first obtained by Sir H. Davy in 1807, from potash, which is the protoxide of the metal. He Qurstions.—If this view be adopted, how should the formula for com- mon sulphuric acid, or oil of vitriol, be written? How that for nitric acid? .854. What metals are included in the first group? How are they characterized? 355. By whom was potassium discovered? POTASSIUM. 299. procured it by subjecting a piece of caustic potash, slightly moistened, to the action of a powerful galvanic current, when oxygen made its appearance at the positive, and the metal potas- sium at the negative, electrode. Previous to this time, potash and the other alkalies and earths had been considered as simple substances. Potassium, in combination with oxygen and other bodies, is very generally diffused in the rocks and soils of every place, but is never found in nature in a separate state. It is contained in most vegetable and many animal substances. 856. Preparation—This metal is best prepared by heating intensely dry carbonate of potash mixed intimately with half its weight of fine charcoal-powder and iron filings. The potash, being an oxide of potassium, at a high temperature yields its oxygen to the charcoal and. iron, and itself distils over into a receiver prepared for the purpose. The following apparatus answers well for the operation. A com- mon mercury bottle, A, covered with an infusible lute, and well dried, is three- fourths ‘filled with cream of tartar that has been previously charred and mixed with one-fourth or one-fifth of its weight of pulverized char- coal, and placed in a proper furnace, with a piece of gun-barrel, B, about a foot in length, extending outward and conuect- ‘ing with ar eceiver, C. s Preparation of Potassium. Quxstions.—How did Sir H. Davy procure potassium? How were potash and the other alkalies considered previous to this time? Is pot- ash very generally diffused in nature? 3856. How is potassium now usually prepared? What is the effect produced by the charcoal? De- scribe the apparatus figured in the margin, and the mode of using it, * 800 POTASSIUM. A fire of hard coal is then kindled in the furnace (represented in section in figure), which should have a good draft, by con- necting with a chimney, GF, of sufficient height, in order to produce the greatest heat possible; and the metallic potassium, as it is liberated in the gaseous state, escapes through the iron tube, B, and is condensed and collected in the bottom of the receiver, C. In this receiver some naphtha is placed, to protect it from the atmosphere. Charred cream of tartar is used because it furnishes an inti- mate mixture of carbon and carbonate of potassa, but instead of it dry carbonate of potash (pearlash) may be mixed intimately with half its weight of pulverized charcoal. The receiver, C (seen in section), is best made 0 of sheet copper, in two parts, M and N, the upper part, N, being without a bottom, and fitting accu- rately into the lower part, M. The upper part, N, is also divided into two parts by a vertical partition, as shown in figure; it is also provided with two tubulures, o and p, directly opposite each other, the one, o, to receive the end of the gun-barrel, B (in the first of the accompanying figures), and the other, p (corresponding to KH in the first figure), to allow the insertion of an iron wire to remove the obstructions that will occasionally collect in the gun-barrel leading from the iron bottle. A small opening is also made for this purpose in the partition " of the receiver, N. During the operation much ineondensible gaseous matter passes over and escapes by a tube of glass (shown in the first figure) provided for the purpose; and as it is necessary that the receiver should be kept cold, a small stream of cold water is made to fall upon it constantly, which is prevented from entering the lower part, M, by a rim of metal passing round it, as shown in the figures. The tubulure, p, is to be kept closed by a cork, except as it is necessary to remove it for a moment to insert the iron =e when obstructions occur in the gun-barrel. The potassium, after the action has ceased, will be found in irregular masses in the naphtha at the bottom of the receiver ; Prep. of Potassium. Qurstion.—Where will the potassium he found? BINARY COMPOUNDS OF POTASSIUM. 801 but it will not be pure. It is now collected in a bag of cloth, through which it is squeezed by compressing the bag with pincers while held in a cup of warm naphtha. If necessary, it may be further distilled in a small iron retort. 357. Properties.—Potassium is a solid, in color and lustre much resembling lead. At 150° it melts, and at a dull red heat may be distilled. in vessels void of gases capable of combining with it. It is the lightest metal known, having a density of only 0-865, and floats upon the surface of.water. At ordinary tem- peratures it is soft like wax, but at 32° it becomes quite hard. But its most characteristic property is its affinity for oxygen ;— when thrown upon the surface of water it absorbs the oxygen so rapidly as to be inflamed, and burns with a beautiful rose-colored flame. In the open air, the freshly-cut’ surface absorbs oxygen so rapidly as to be tarnished instantly; and heated even in carbonic acid (303), it takes fire and burns — combustion of by absorbing the oxygen. In consequence of its 7 eee affinity for oxygen it can be preserved only in , tubes hermetically sealed, or under some liquid that does not contain oxygen, as naphtha, which is fouad to answer the pur- pose well. Binary Conipounds of Potassium. 358. Protoxide of Potassium—KO ; eq., (89-2 +.8 =) 47-2. —This is potash, or potassa, and is always formed when the metal is exposed in the open air, or oxygen gas, or acted on by water.’ In the latter case, the potash formed is immediately dis- solved by the water, as will be found by applying the usual tests. Pure potash is a white, inodorous substance, with a pungent, caustic taste, and very soluble in water. It absorbs carbonic acid Quzstions.—857. Describe some of the properties of potassium. What is said of its affinity for oxygen? What is the effect when a small piece of it is, thrown upon water? How is it preserved? Why is naphtha selected for this purpose? 358. What is the common name for protoxide of potassium? Describe potassa? Does it usually contain water? 26 802 BINARY COMPOUNDS OF POTASSIUM. and water rapidly from the air, and should therefore be kept in close bottles. When prepared by the slow oxydation of potassium in dry air or oxygen gas it is anhydrous, but when formed by the oxydation of the metal in water, or from any of its salts, it is always in the state of a hydrate. ; Potash forms with water two compounds, the monohydrate, KO,HO, and the pentahydrate, KO,5HO; the former of which is the caustic potash of commerce. To prepare it, pearlash (car- bonate of potash) is dissolved in ten times its own weight of water, and half its weight of recently-slaked lime mingled with it, in successive portions, and the whole boiled briskly for half an hour. It is then allowed to settle, and the clear liquid is drawn off. The lime, in this process, decomposes the carbonate of potassa, and forms insoluble carbonate of lime, which settles to the bottom; and the clear liquid contains nearly pure potassa. This may be pre- served for use in well-closed bottles, or it may be evaporated to dryness in a vessel of such a.form as not to allow any con- siderable accession of air. To insure per- Be fect purity, it must be again dissolved in A ee absolute alcohol, and the solution filtered and evaporated as before. The hydrate is soluble in alcohol, which is not the case with sul- phate of potash, usually present in pearlash, or carbonate, portions of which may have escaped decomposition by the lime. 359. To prevent the absorption of car- bonic acid from the air while filtering, an apparatus like that figured in the margin is used. It consists of two vessels, A and D, of equal capacity, and connected with each other. The throat of the upper vessel or weeny - a Filtering Apparatus. + Quzstions.— What hydrates of potash are mentioned? How is pure caustic potash prepared from the carbonate? Why should it be dissolved in alcohol and filtered? 859. Describe the mode of filtering the alcoholic solution. BINARY COMPOUNDS OF POTASSIUM. 303 funnel, A, is obstructed by a piece of coarse linen loosely rolled up, and not pressed down into the pipe through which the solution is filtered. The pipe, c, extending from e to }, serves for the air to pass from the lower vessel to the upper; and the operation goes quietly on, free from contact with the atmosphere, except the little contained within the apparatus at the beginning of the process. Solution of potassa is highly caustic, and its taste intensely acrid. It possesses alkaline properties in an eminent degree, converting the vegetable blue colors to green, and neutralizing the strongest acids. It absorbs carbonic acid gas rapidly, and is consequently employed for withdrawing that substance from gase- ous mixtures. Potassa is employed as a reagent in detecting the presence of bodies, and in separating them from each other. The solid hydrate, owing to its strong affinity for water, is used for depriving gases of hygrometric moisture. Caustic potash attacks all animal substances with avidity, and neutralizes all acids. With the fats and oils it combines readily, forming the well-known compound called soap, of which we shall have occasion to speak again hereafter. This property is charac- teristic of all the alkalies. : The pentahydrate possesses no special interest. 360, Peroxide of Potassium, KO,, as is shown by the formula, is a teroxide. It is of a dull yellow color, and is formed by burn- ing potassium in an excess of dry oxygen gas. Thrown into water, it gives up two-thirds of its oxygen, and solution of caustic potash is formed. 361. Chloride of Potassium, KCl, is readily obtained by neu- tralizing carbonate of potash, KO, CO,, by hydrochloric acid. The reactions which take place have already (347) been explained. Like common salt (chloride of sodium), it crystalizes in cubes, which are anhydrous. i Iodide of Potassium, KI, is formed by heating potassium in contact with iodine; or, by digesting iodine in a hot solu- Questions.—What is said of the action of potash upon animal sub- stances? What does it form with the fats and oils? 860. What is peroxide of potassium? 3861. What is chloride of potassium? How is * jodide of potassium formed ? 304 . SALTS OF POTASH. tion of caustic potash, and exposing the mass, when dry, to a red heat, and subsequently crystalizing from solution in water or alcohol. It is a white solid, very soluble in water, usually seen erystalized in cubes, and is often sold under the name of Aydrio- date of potash. Solution of iodide of potassium has the property of dissolving iodine, and becomes of a brown color; it also dissolves other iodides, as the iodides of mercury. Todide of potassium is much used in medicine, and in certain photographic processes. Bromide, KBr, and fluoride, KF, of potassium, like the chloride and iodide, crystalize in cubes. 362, Sulphides of Potassium.—There aro at least five sulphides of potas- sium, KS, KS,, KS,, KS,, and KS,, which, as shown by their formule, contain, respectively, 1, 2, 8, 4, and 5 equivalents of sulphur in combina- tion with 1 equivalent of the metal. The most important of these is the pentasulphide, KS,, which is easily prepared by heating gently a mixture of carbonate of potash and sul- phur, or by boiling a solution of caustic potash with an excess of sulphur. It is a yellowish-brown solid, very soluble in water, and is used in medicine, especially. in cutaneous diseases, under the name of hepar sulphuris, or liver of sulphur. The tersulphide is also used in the same manner. Salts of Potash. 363. Carbonate of Potash, KO,CO,.—Carbonate of potash, or pearlash, is prepared for the purposes of commerce by leaching the ashes of forest trees, and evaporating the lye thus obtained to dryness, and then: heating the dry mass to redness for a time in open vessels, to burn out the combustible matter which is con- tained in it. As thus procured, it is a white spongy mass, very caustic to the taste, and absorbs moisture rapidly from the air, so that it must be kept in close vessels. It is very soluble in water, but insoluble in alcohol, and is easily fused at a red heat. That found in commerce is very impure, being mixed with silica and other substances. It is manufactured in large quantities in the. United States, in the Canadas, and in Russia. Qurstions.—What use is made of iodide of potassium? 362. What is said of the sulphides of potassium? 863, Whatis pearlash? How is it prepared? Describe it. What countries furnish it in large quantities? - SALTS OF POTASH. 805 If pure carbonate of potash is required, as is often the case in the laboratory, the tartrate (cream of tartar) or oxylate is heated to redness in the open air, treating the charred mass thus formed with warm water, and filtering. The solution may then be eva- ‘porated to dryness, if the dry salt is desired. By slowly evaporating a solution of carbonate of potash the salt may be crystalized, though not without difficulty. The article sold as potash is the same as pearlash, except that it is not subjected to the last process of calcination. It is a dark- colored mass, and contains much caustic potash, as well as car- bonate, and is. used extensively for the manufacture of soap. Pearlash is employed in the manufacture of glass and paints, and for various other purposes. 364. Bicarbonate of Potash, KO,2CO,.—This salt is pre- pared by subjecting pearlash in solution, for some time, to an atmosphere of carbonic acid, which is absorbed in large quantity. Though less caustic to the taste than pearlash, it is still highly alka- line. It is less soluble also than pearlash, and less deliquescent. It may be obtained in crystals with less difficulty than the car- -bonate, and the crystals contain a single equivalent of water. Their formula may therefore be written KO,CO, + HO,CO,, that is, the salt may be considered as a double carbonate of potash and water. This salt is extensively used under the name of saleratus. 365. Nitrate of Potash, KO,NO,.—This salt, the saltpetre, ‘or nitre, of commerce, is formed, in this country, by decomposing the nitrate of lime, which abounds in the caverns of some of the Western States, by carbonate of potash, and filtering and eva- porating the solution thus obtained. In some parts of Europe it is prepared in nitre-beds, which are made by heaping together old mortar, refuse animal matter, wood-ashes, &., in which it gradually forms by the action of the atmosphere. The mass is QuEstions.—How may pure carbonate of potash be prepared? What is the article known in commerce as potash? 364. How is bicarbonate of potash prepared? May it be obtained in crystals? By what name ig it familiarly known? 3865. By what names is nitrate of potash known in commerce? How is it prepared in this country? How in some parts of Europe? : 26 * 306 SALTS OF POTASH. lixiviated with hot water; and the solution by evaporation yields crude nitre. Nitrate of potash is usually seen in long six-sided prisms. It is a colorless salt, of a cooling saline taste, and is very soluble in water. Its density is about 1:93. Heated to redness, it first melts and is then decomposed, giving off, at first, pure oxygen, and afterwards, if the heat is increased, nitrogen and nitric oxide. Thrown on burning charcoal it is decomposed, producing violent deflagration, by which it may always be distinguished from sul- phate of soda, for which it has sometimes been mistaken. It is a powerful antiseptic, and is used with common salt in the preserva- tion of meat and other substances. . But the chief use of nitre in the arts is in the manufacture of gunpowder, which is composed of nitre six parts, and charcoal and sulphur each one part, the whole being moistened and thoroughly ground together, and subsequently pressed and granu- lated. When fired, the nitre, by its decomposition, furnishes oxygen, which combines the carbon, forming carbonic acid, the sulphur at the same time uniting with the potassa. The action of gunpowder depends upon its generating, when decomposed, a large quantity of gaseous matter at a high temperature. The gases are chiefly nitrogen and carbonic acid, which, at the moment of explosion, occupy more than 1000 times the volume of the powder from which they are formed. The formation of the gases is not instantaneous, but occupies a certain time, and the ball is forced from the gun with a velocity due to the ultimate effect of the whole. When made for particular purposes, the proportion of the ingre- dients is sometimes considerably varied. We may, in fact, con- sider gunpowder as of three kinds, which may be called sporting powder, war powder, and blasting powder; the former of which is required to detonate more rapidly and violently than either of the others. The composition of the three kinds is usually about as follows :— Querstions.—Describe nitrate of potash? How does heat affect it? What is the effect when it is thrown upon burning charcoal? What uses are made of it? What is the composition of gunpowder? What are the chemical reactions that take place when it is fired? Upon what doos the action of gunpowder depend? What different kinds are mentioned? SALTS OF POTASH. 307 For sporting powder.........Nitre.........76'9 parts, Sulphur..... 96 * Carbon......13°5 «¢ 100-0 « For war powder.......0+ esses Nitre cocoon 70°O parts, Sulphur.....12:5 « Carbon.......12°5 «€ For blasting powder.........Nitre.........62-0 parts, Sulphur.....20-0 « Carbon.......18-0 « 100-0 « Theoretically, it would seem that the best proportion would be 1 equivalent of nitre, 1 equivalent of sulphur, and 3 equivalents of carbon. Thus, KO,NO, + 8S + 8C = KS +N + 800,. The proportion by weight of the several ingredients would then be as follows :— In 100 parts. -Nitre, 1 equivalent.........101-2.........74°85 Sulphur, 1 « socorvece 16'O..000000011°84 Carbon, 8 “ cccerevee 18-O.ceeee00 18°81 100-00 This is very nearly the same proportion as that given for war powder above; but the reactions which take place in the combustion of the powder not being necessarily the same precisely as indicated in the above formula, nor, indeed, in any two cases with the same powder, consider- able variation in the proportion of the ingredients may be allowed. For the best powder, the materials should be freed from all impurities before using them. 366. The comparative force of different specimens of gunpowder, or the initial velocity a given quantity of it will communicate to a ball of a given weight, is determined by several modes, only one of which, called the ballistic pendulum (see figure on next page), will be described, and that very briefly. It is composed of two parts, the bullistic pendulum, P, and the pendulum-gun, G, the former of which, P, consists of a conical box, containing a mass of lead, suspended by an iron rod, in the manner of a QueEstions.—What is the difference in the composition of the three kinds of gunpowder? Is the composition of gunpowder exactly the same as would seem to be required by the chemical formula? 866. How is the comparative force exerted by different kinds of gunpowder, when fired, determined? Describe the ballistic pendulum. 3808 SALTS OF POTASH. pendulum, from some very firm support. G is a common gun-bar- rel supported in an frame, which is also suspended in the man- ner of a pendulum, the gun-barrel, when hanging freely, being made to point to the mass of lead. Atmn and op are graduated arcs, each having at- tached to it a slider, which is carried along with the movement of the rod to the furthest point to which it oscil- lates, but does not re- turn with it. The gun-barrel is now charged with the proper quantity of the powder to be tested, and the ball placed init, and fired; and the ball being projected into the mass of lead causes it to move to the left (as the appa- ratus is represented in the figure) to a certain distance, which will be exactly shown by the slide upon the graduated arc, mn. At the same time the gun-barrel will recoil to the right, as will be shown by the slide upon op. The initial velocity of the ball may now be calculated from the distance either slide has traversed, by means of the proper mathe- matical formule. To insure accuracy, attention must be paid to several particulars in the adjustment of the apparatus, which are not here alluded to. Ballistic Pendulum. 367. Sulphate of Potash, KO,SO,—This salt is easily pre- pared artificially by neutralizing carbonate of potassa with sul- phuric acid; and it is procured abundantly by neutralizing with carbonate of potassa the residue of the operation for preparing nitric acid (221). Its taste is saline and bitter. It generally erystalizes in six-sided prisms, hounded by pyramids with six sides, but its primary form is the right rhombic prism. The erystals contain no water of crystalization, and suffer no change by exposure to the air. They decrepitate when heated, and enter ‘into fusion at a red heat. They require 16 times their weight of water at 60°, and 5 of boiling water for solution. : Quzstions.—367. How may sulphate of potash be prepared arti- ficially? What are some of its properties? SALTS OF POTASH. 309 368, Bisulphate of Potassa, KO,2SO,, is easily formed by ex- posing the neutral sulphate with half its weight of strong sulphuric acid to a heat just below redness, in a platinum crucible, until acid fumes cease to escape. It has a strong sour taste, and reddens litmus paper, and in crystals may be considered a double sulphate of potassa and water, KO,SO,+HO,SO;. It is much more soluble than the neutral sulphate, requiring for solution. only twice its weight of water at 60°, and less than an equal weight at 212°. It is resolved by heat into sulphuric acid and the neutral sulphate. 369. Chlorate of Potash, KO,C10,.—This salt is formed, to- gether with chloride of potassium, by passing a current of chlorine through a strong solution of pearlash. The reactions are as -follows :-— 6KO,CO, + 6Cl = 5KCl + KO,CIO, + 6CO0,. ‘The carbonic acid escapes during the process, and the chloride of potassium being very soluble remains in solution, while the chlorate crystalizes in shining white scales. The chlorine, before entering the potash solution, should be made to pass through a three-necked bottle containing a little Preparation of KO,C10s. water, to separate any sulphuric acid which may pass over with it. The proper arrangement is represented in the figure. Qusstions.—868. How is bisulphate of potash formed? 869. How is chlorate of potash formed? Describe the reactions that take place. 310 a SODIUM. Its taste is not unlike that of nitre, but it is much less soluble than that salt. Heated moderately, it melts, and at a red heat is decomposed, giving up the whole of its oxygen. Thrown on burning charcoal, it deflagrates like nitre, but more energetically. A few of the crystals, wrapped in tin-foil, with a piece of phos- phorus, or a little sulphur, explode violently by a blow from the hammer. It was formerly used in the manufacture of Lucifer matches, and has been substituted for nitre in gunpowder; which, however, when thus prepared, is liable to explode from causes so slight that its manufacture is dangerous. The silicates of potash will be described hereafter. 870, Sulphur-Salts of Potassium.—Protosulphide of potassium, as the electro-positive element, combines with many other electro-negative sulz phides, forming true salts (845), but we shall here describe only the following two :— Hydrosulphate of Potassium, or, more properly, the hydrosulphate of sulphide of potassium, KS, HS, is prepared by passing a current of hydro- sulphuric acid ae through a solution of potash. When the solution is concentrated the salt may be obtained in crystals. Carbosulphate of potassium, KS,CS,, may also be crystalized. It is prepared by pouring bisulphide of carbon into’an alcoholic solution of protosulphide of potassium. SODIUM. Symbol, Na (Natron); Equivalent, 23; Density, 0-972. 371. History and Preparation—Sodium was discovered in 1807, by Davy, a few days after the discovery of potassium. The first portions of it were obtained by means of galvanism; -but it may. be procured in much larger quantity by chemical pro- cesses, precisely similar to those just described for obtaining potassium. Its preparation is less difficult than that of potassium. Qurstions.—Describe the properties of chlorate of potash. What is the effect when it is thrown on burning charcoal? What use has been made of it? Why may it not be used in the formation of gunpowder? 870. How is hydrosulphate of potassium formed? What is its com- position? What is the composition of carbosulphate of potassium? 371. How is sodium prepared? BINARY COMPOUNDS OF SODIUM. 311 372. Properties.—Sodium has a strong metallic lustre, and in color is very analogous to silver. It is so soft at common tem- peratures, that it may be formed into leaves by the pressure of the fingers. Sodium soon tarnishes on exposure to the air, though less rapidly than potassium. Like that metal it is instantly oxydized by water, hydrogen gas in temporary union with a little sodium being disengaged. When thrown on cold water, it swims on its surface and is rapidly oxydized, though in general without in- flaming; but with hot water it scintillates, or even takes fire, and burns with a beautiful yellow flame, which readily distinguishes it from potassium. By throwing two pieces, one of sodium and another of potas- sium, af the same time, into a vessel of water, both will usually be inflamed; and the characteristic colors of their flames will be seen together. Sodium is preserved under naphtha in the same manner as potassium. Binary Compounds of Sodium. $73. Protoxide of Sodium—Na0O; eq., (23 + 8 =) 31.—This compound, usually called soda, is formed by the oxydation of sodium, as potassa is from potassium. With water it forms a solid hydrate, which is easily fusible, and very soluble both in water and alcohol. It is a powerful alkali, and very similar in all its properties to potassa. Hydrate,of soda is prepared from the carbonate in the game manner as the hydrate of potash. The hydrate is known as caustic soda ;—it contains a single equivalent of water, and ita formula is therefore NaO, HO. Peroxide of Sodium, NaO,, is formed by burning sodium in dry air or oxygen gas. Qurstrons.—872. Describe the properties of sodium. What is the effect when it is thrown upon water? How is it preserved? 873. What is soda? Describe its properties. By what name is the hydrate of soda knuwn? What is peroxide of sodium? ‘ 312 BINARY COMPOUNDS OF.SODIUM. 374. Chloride of Sodium—NaCl; eq:, (23+35-4 =) 58-4.— This is the common salt of commerce. It may be formed by burning sodium in chlorine, but is obtained in great abundance as a solid deposit, called rock salt, in various parts of the world, as in England, Poland, and at Abingdon in Virginia; and in solution in the waters of brine springs, which abound in New York, Pennsylvania, Virginia, Kentucky, Ohio, and other States, as well as in other countries. Sea-water contains about 2-7 per cent. of this substance, while the water of the great salt lake in Utah Territory contains about 20 per cent. Around this latter body of water are plains, many miles in extent, which, in the dry season, are covered with incrustations of very pure salt to the depth of more than half an inch.. In the rainy season it is more or less dissolved. Rock salt is sometimes mined of sufficient purity for use, and requires only to be pulverized ; but more frequently it is mixed with clay and oxide of iron, and must then be dissolved, and the pure liquid drawn off.and evaporated. In warm countries, as on the coast of Portugal, in the south of France, and the West India Islands, this substance is obtained by the spontaneous evaporation of sea-water, which is allowed, on the rise of the tide, to flow into shallow basins, being passed from one to another, as it becomes more concentrated; and finally, the evaporation is finished by means of artificial heat. In cold countries, as on the borders of the White Sea, the pro- cess is commenced in a very different manner. :—the sea-water is exposed to the cold atmosphere, by which a large part of the water is separated in the form of ice, and the remaining liquid portion is drawn off and evaporated. Pure chloride of sodium has an agreeably saline taste. It fuses at a red heat, and becomes a transparent brittle mass on cooling. Tt deliquesces slightly in a moist atmosphere, but undergoes no change when the air is dry. In pure alcohol it is insoluble. It Quzstions.—374. What is the common name for chloride of sodium? , Where is it found in the solid state? What are brine springs? What is the proportion of it contained in sea-water? In the water of the great galt lake in Utah Territory? How is this substance procured in certain warm countries? How in certain cold countries? Describe some of the properties of common salt? BINARY COMPOUNDS OF SODIUM. 313 requires twice and a half its weight of water-at 60° for solution, and its solubility is not increased by heat. It crystallizes in cubes, which are anhydrous, and have a density of about 2:18 — when its solution is slowly evaporated in the open air hopper-shaped crystals, as figured in the margin, are of common occurrence. Their formation may be explained as fol- lows :—first a small cubical crystal forms at the surface of the solution, which tends to sink and depress the surface, as shown in the figure A. Soon Hopper-form Crystals. Oryst. Common Salt. - other small crystals form and attach themselves to the first one at its four upper horizontal edges, by which it is a little more de- pressed, as represented in the figure B; a further additions in the,same manner Zs causes a further depression, as seen in O, and so on. Cryst. Common Salt. A saturated solution of common salt does not freeze even at 0°, but hydrated crystals are formed which have the formula, NaCl +- 4HO. It fuses at a red heat, and may even.be sublimed without change. The uses of this substance are well known. Besides the ordi- nary purposes to which it is applied, in preserving meat from putrefaction, and in seasoning food, it is used extensively in the arts, in glazing pottery-ware, in the manufacture of bleaching- salt, carbonate of soda, hydrochloric acid, ‘&e. “The name, salt (Lat., sal), was originally given to this sub- stance alone, but was subsequently extended to an immense class of compounds which have been known as salts. By our present Questions.—Describe the mode in which hopper-formed crystals are sometimes produced. What are the uses of this substance? Does it belong to the family of salis, according to the definition of the word which we have adopted ? 27 814 SALTS OF SODA. technical arrangement (347), it is entirely excluded from the class. Sodium forms“definite compounds with zodine, bromine, fluorine, sulphur, &., but they are not described in this work. Salts of Soda. 375. Sulphate of Soda, NaO,SO;.—Sulphate of soda, or Glau- ber’s salt, is sometimes found native in dry situations, but more frequently in solution in the waters of mineral springs. It is also obtained in the manufacture of hydrochloric acid (236). It was first made known by Glauber, from whom it received its name, althotgh he himself called it sal-mirabile. It hag a cooling, saline, and somewhat bitter taste; and is very soluble in water at a temperature 91° or 92°, but less so in water that is very cold or very hot (350). The crystals of this salt usually contain more than half their weight of water of crystalization, which escapes when they are exposed to the open air, and they crumble into a white powder. Their proper formula is NaO,SO,+10HO. The water therefore constitutes nearly 56 per cent., as will be found by making the calculation. Sulphate of soda is used in medicine as a cathartic, and for the preparation of the carbonates of soda. Bisulphate of Soda may be obtained in crystals which have the formula, Na0,2S0, + 3HO. Deprived of its water of crystalization, it may be used in preparing anhydrous SO, (259). ~ $76. Hyposulphite of Soda, Na0,S,0,.—This salt, which is much used in the daguerreotype process, for removing the sensitive coating from the silver plate, after being taken from the mercurial vapor bath, is prepared by first passing a current of sulphurous acid gas through a solution of car- bonatg of soda, to form sulphite of soda, and then dissolving sulphur in a, concentrated hot solution of the sulphite. ‘ It may be obtained in crystals, which, according to some, contain 5, and according to others, 10 equivalents of water. It is also called dithionate of soda. QueEstions.—375. What is Glauber’s salt? What are some of its pro- perties? What is said of its water of crystalization? What use is made of it? 876, What use is made of hyposulphite of soda? Se SALTS OF SODA. 815 377. Carbonate of Soda, NaO,CO,.—-The carbonate of-soda of commerce was formerly obtained by lixiviating the ashes of sea-weeds, in the same manner as the carbonate of potassa is obtained from the ashes of land-plants. But it is now manu- factured altogether from common salt, which is first converted into sulphate of soda by sulphuric acid, and then the sulphate, mixed with charcoal and carbonate of lira is heated intensely in a wind-furnace. The materials, which consist of about 2 parts of the anhydrous sulphate, 2 parts of chalk (carbonate of lime), and 1 of charcoal, are well ground together, and in- troduced upon the hearth, H H, of a reverbatory furnace, similar to that represented in section in thefigure; and by continued action of the heat, carbonate’ of soda, NaO,CO,, oxysulphide of calcium, CaS,CaO, and carbonic oxide, CO, are formed :—the latter compound being gaseous, of course passes off. The oxysulphide of calcium being insoluble in water, it is now only necessary to digest the black mass which comes from the“furnace in warm water, and filter, and a solution of carbonate of soda is obtained. This is now evaporated to dryness. It may be obtained in erystals, which always contain much water of crystalization, and effloresce in dry air. It is the sal soda of commerce. The mixture as taken from the furnace is the soda ash, or British barilla of commerce, and has been sometimes used as a manure. , Ss Sa = Preparation of fee of Soda. Ee SR Carbonate of soda is extensively used in the manufacture of glass and hard soap, and for other purposes. Sesquicarbonate of Soda, 2Na0,3CO,, called trona, is found in the waters of certain lakes in Egypt, in Hungary, and in this country in springs among the Rocky Mountains. Questions.—377. From what was carbonate of soda formerly obtained? How is it now manufactured? Describe the process. 316 SALTS OF. SODA. 378. Bicarbonate of Soda, NaO,2CO,.—This salt is formed by exposing the carbonate in solution to an atmosphere of carbonic acid, in the same manner as the bicarbonate of potash. Like the cor- responding salt of potash, it always contains one atom of water, and may be considered a double carbonate of soda and water, according to the formula, NaO0,CO,+HO,CO,. It is often used by bakers as a substitute for sal-zeratus. 879. Biborate of Soda, NaO,2BO.—This salt occurs in solu- tion in the waters of certain lakes in Thibet and the East Indies, from which it is obtainéd by evaporation, and was formerly im- ported into this country and England under the name of tincal. When refined, by solution and recrystalization, it is sold as borax, a substance well known for its extensive use in the arts in various metallurgic operations. At present, most of the borax of com- merce is obtained from Tuscany, where it is prepared by adding carbonate of soda to the native boracie acid (326) of the hut springs which abound in an extensive volcanic district of thut country. To obtain it pure, several recrystalizations are required. Ordinary borax crystalizes in right rhombie prisms, which con- tain 10 equivalents of water; but when crystalized from a hot solution the crystals are octahedrons, and contain only 5 atoms of water. When borax is heated, it first loses its water of crystalization, which causes it to froth up very much; and at a red heat fuses into a clear transparent liquid, which on cooling has the appear- ance of glass. At high temperatures, it dissolves most of the metallic oxides, and becomes colored. Borax is used as a flux in metallurgic operations, in the pre- paration of certain kinds of glass, and in medicine. 380. Nitrate of Soda, NaO,NO,, resembles nitrate of potassa in many of its properties, but cannot be substituted for it in the manufacture of gunpowder, because of its tendency to absorb QueEstions.—378. What is bicarbonate of soda? What use is made of it? 879. Where is biborate of soda obtained? What is it often called? Where is most of the borax of commerce obtained at the pre- sent time? What use is made 6f it? 380. For what is nitrate of soda used? SALTS OF SODA. 317 a moisture from the atmosphere. It is used instead of nitrate of potash in the preparation of nitric acid, and sometimes as a manure. * 381. Phosphates of Soda.—Phosphorie acid forms with soda (and the bases) three series of salts, viz., tribasic or ordinary phosphates, bibasic or pyrophosphates, and monobasic or meta- phosphates, corresponding to the three states (282) of the acid. I. Tribasic Phosphate of Soda.—Of this there are three va- rieties, viz.: 1. The salt, 3NaOQ,PO;. 2. The salt, (2NaO + HO) PO,. 3. The salt, (NaO0+2HO) PO;. The three varieties are tribasic, but the base. of the first consists of 3 eq. of soda; the base of the second of 2 eq. of soda and 1 eq. of water; the base of the third of 1 eq. of soda and 2 eq. of water. The water serving as base in such salts is called basic water. The first two varieties usually crystalize with 24 eq. of water, and the third with 2 eq. of water. If heated, they readily give up their water of crystalization, but a red heat is required to expel the basic water. All of them in solution give a yellow precipitate, 3AgO,PO,, with solution of nitrate of silver. Il. Bibasic Phosphate of Soda—Pyrophosphate of Soda.— This compound furnishes two varieties, viz., 1. The salt, 2NaO,PO,; 2. The salt, (NaO+ HO) PO;. Both varieties are bibasic, but the base of the first consists of 2 eq. of soda, and that of the second of 1 eq. of soda and 1 eq. of water. Bibasic phosphate of soda crystalizes with 10 eq. of water ; —the solution of both varieties gives, with nitrate of silver, a white precipitate, 2Ag0,PO,. TIL. Monobaste Phosphate of Soda—Metaphosphate of Soda —Na0,PO;.—This phosphate in solution gives a white precipitate with solution of nitrate of silver, AgO,PO,; but its composition, it will be observed, differs from that procured from the bibasic phosphate. Solution of this phosphate also has the property of Quxstions.—381. What is said of the salts formed with soda by phos- phoric acid? What varieties of tribasic phosphate of soda are there? How may they be tested when in solution? What varieties of bibasic phosphate of soda are there? What is said of the precipitate they give with nitrate of silver? What is metaphosphate of soda? - 27* 818 LITHIUM. coagulating the whites of eggs, an effect .not produced by the other phosphates. For the methods of preparing these varieties and sub-varieties of phosphate of soda, the inquiring student will consult larger works on this science, especially the excellent one of Regnault ; the object of the present work not permitting so much minute detail. With other bases phosphoric acid probably forms similar series of salts, but the subject has not been fully investigaged. 382. Characteristics of Potash and Soda Salts—All the salts of potash and soda that are soluble are distinguished from other metallic salts, except the salts of lithia, which are very rare, by giving no precipitate with solutions of the alkaline carbonates. It is therefore sufficient, practically, to be able to distinguish between these two classes of salts; for which the following tests will suffice. : With tartaric acid potassa forms a sparingly soluble salt, which, if the solution is moderately concentrated, appears as a white precipitate; but with soda no precipitate is formed, as the corresponding salt of soda is very soluble. ‘ With potash a strong solution of chloride of platinum forms a yellow precipitate, the double chloride of potassium and platinum, which be- comes more copious by the addition of alcohol; but in the same circum- stances no precipitate is formed by the salts of soda, because of the solubility of the double chloride of platinum and sodium. LITHIUM. Symbol, L; Equivalent, 6-4; Density, —? 883. History, Etc.— Lithium is a very rare substance, and is found only in a few minerals, as spodumeme, and the variety of mica called lepidolite. It is obtained from these in combination with oxygen as the protoxide, lithia. From this the metal may be procured with some diffi- culty by means of galyanism. It is a white metal, like sodium. The protoxide, lithia, is a powerful alkali, like potash or soda, but is less soluble The name’is from the Greek, lithos, a stone, in allusion to sthe source from which it is obtained. 2 . The salts of lithia, heated before the blowpipe, give a red tinge to the flame. QueEstrons.—382. How are the soluble salts of potash and soda dis- tinguished from other salts? Describe the mode of distinguishing a soluble salt of potash from one of soda by means of tartaric acid. B means of solution of chloride of platinum. 888. What is said of lithium? From what is the name derived? AMMONIUM. 819 Ammonium. (Not Isolable.) 384, History, Ete.—This name is given to a supposed com- pound of nitrogen and hydrogen, NH,, which has never yet been obtained in a separate state, but is believed by many to enter into the composition of most of the ammoniacal compounds, and to possess in some respects the characters of a metal. Its symbol is written NH,, or Am. When strong aqua ammonie (225), in contact with a little mercury, which is connected with the negative electrode of the galvanic battery, is subjected to the action of a strong electrical current, oxygen is liberated at the positive electrode and the mer- cury increases very much in volume,: and becomes less fluid, having the consistency of butter or soft lard, but still retains perfectly its metallic lustre. This has very much the character of an amalgam; and we may suppose that under the influence of the current, ammonium, NH, (equal to NH, + H) has been formed from the ammonia and the hydrogen of the water, and at once united with the mercury, the oxygen escaping at the other electrode. The same compound may also be obtained simply by com- bining a little potassium or sodium with 50 or 100 times its weight of mercury, and pouring on it a strong solution of sal ammoniac, NH;,HCl. In this case the reaction seems to be KHg + NH,,HCl = KCl+NH,Heg. This compound, called ammoniacal amalgam, when removed from the solution in which it was formed, rapidly undergoes spontaneous decomposition, yielding ammonia and hydrogen in the proportion of 2 volumes of the former and 1 volume of the latter. After a little time the mercury alone is found entirely unchanged. Qurstions.—384. What is the compound to which the name ammo- nium is given? Has it been obtained in a separate state? What is the mode of preparing ammoniacal amalgam by the use of the galvanic bat- tery? Explain the reactions by which we may suppose the new sub- stance to be produced. Describe the mode of producing it by the use of gal ammoniac in solution. What are the reactions that appear to take place? What is the effect when the amalgam is removed from the solu- tion? What are obtained when it decomposes ? 820 BINARY COMPOUNDS OF AMMONIUM. If this amalgam is subjected to a temperature of 32°, it crys- talizes in cubes, and its decomposition is retarded. Although this compound, NH,, which has received the name of ammonium, has not been obtained in a separate state, its existence in combination with other bodies would seem to be established; and also its peculiar metallic character. It is capable of replacing potassium and sodium in combination, and is there- fore isomorphous with them. Ammonia, NH;,, has heretofore (224) been described. It has been called volatile alkali, because of its reactions with other substances, and especially with the acids, being the same as those of the other alkalies, the protoxides of potassium, sodium, and lithium. We introduce the subject again for the purpose of describing some of its more important compounds, which we shall do according to this ammonium theory, as it is called; because it affords us, in the present state of our knowledge, the most simple and lucid view of this important class of bodies that can be presented. But, at the same time, it should always be kept in mind that the existence of ammonium, NH, even in com- bination with other substances, is not to be considered as fully determined. Binary Compounds of Ammonium. 885. Protoxide of Ammonium, NH,O, or AmO.—As is the case with ammonium, the existence of this compound is hypo- thetical. But all the ammonia salts of oxygen acids, contain an atom of water in their composition, which appears to be essential to their existence. This atom of water, combined with the am- monia, NH,, forms the compound in question, protoxide of ammo- nium, NH,0, which unites with the acid to form the salt. Thus, the composition of nitrate of ammonia, as formerly supposed, is _. NH,,NO,,HO, which evidently is the same as NH,O,NO,, except as to the mode of the arrangement of the particles. Questions.—How is this amalgam affected by a cold of 832°? What is said of the relation of ammonium to potassium and sodium? Why has. ammonia been called volatile alkali? 885. What is said of protoxide of ammonium? SALTS OF AMMONIA. 821 As ammonium is isomorphous with potassium and sodium, so this compound is isomorphous with potash and soda, which it is capable of replacing in many of their compounds. 386. Chloride of Ammonium, NH,Cl.—This is the compound often called sal-ammoniac, and hydrochlorate of ammonia. If it be considered as a proper hydrochlorate of ammonia, its formula of course will be NH,,HCI. It may be obtained by neutralizing carbonate of ammonia by‘ hydrochloric acid ; but for use in the arts it is procured from the liquor obtained in the distillation of bones, in preparing animal charcoal, and also from that which condenses in the manufacture of coal-gas. The latter affords it in large quantities. Sal-ammoniac isa white solid, very tough, and difficult to pulverize, and has a density of about 1-45. It has a pungent, saline taste, and is very soluble in water; and sublimes without fusion at a temperature below redness. Triturated with recently- slaked lime, it yields ammonia, which is easily recognised by its pungent odor. It is used for various purposes in the arts and in medicine. Salts of Ammonia. 387. Carbonates of Ammonia.—There are several carbonates of ammonia. The one best known is the sal-volatile of the shops, which is a sesquicarbonate. It is a semi-transparent solid, which is very soluble in water, and has the pungent odor of ammonia. Its composition, on the “ammonium theory,” is 2NH,0,3CO,; but considered without reference to this theory, its formula is usually written 2NH;,38C0,+2HO. By long exposure to the air it is converted into a bicarbonate, NH,O0,2CO, + HO. Besides these, there is also a neutral carbonate of ammonia. Sulphate of Ammonia, NH,0,S0,.—Sulphate of ammonia is a soluble salt, isomorphous with sulphate of potassa. It is some- Questions.—Is ammonium isomorphous with potassium and sodium ? 386. What is sal-ammoniac? How is it obtained? Describe its pro- perties. 3887. What carbonates of ammonia are mentioned? Describe sulphate of ammonia, ~ : 322 SILICATES OF POTASH AND SODA—GLASS. times found in the lava of volcanos, and may be formed artificially by saturating aqua ammonia or solution of carbonate of ammonia with sulphuric acid. It is sometimes used as a manure. Nitrate of Ammonia, NH;,NO, + HO, or, as it is now con- sidered, nitrate of oxide of ammonium, NH,0,NO,, is prepared by neutralizing nitric acid with ammonia, or its carbonate. It is a white salt, very soluble in water, and destitute of any ammo- niacal odor. It is used in preparing nitrous oxide (215). 388, Phosphate of Soda and Ammonia, (Na0,NH,0,HO)PO,.—This is the compound called microcosmie salt, and much used as a flux in blow- pipe operations. Its crystals contain 8 eq. of water of crystalization, which is given up at a very moderate heat; and, at a high temperature, both the basic water.and ammonia are expelled, and the very fusible metaphosphate of soda only remains. It is prepared by dissolving in 2 parts of hot water 6 or 7 parts of phos- phate of soda, and then adding 1 part of sal-ammoniac. On cooling, the salt in question crystalizes, while chloride of sodium remains in solution. 389, Hydrosulphate of Sulphide of Ammo- nium, NH,8,HS.—This compound, it will be observed, is a sulphur salt (845), being com- posed of two sulphides, sulphides of ammo- nium and hydrogen. It is prepared by pass- ing a current of hydrosulphuric acid through aqua ammonia, which is to be kept cool during the operation. The apparatus repre- sented in the figure will answer for the purpose. : It is much used in the bones as a test Preparation of NH‘8,HS. for several of the metals, Silicates of Potash and Soda— Glass. 390. Silica, or, more properly, silicic acid, combines at, high temperatures with the alkalies and earths apparently i in indefinite proportion, producing compounds which at very high temperatures are more or less liquid, but at a lower heat have a pasty con- sistency, and when cold are hard, uncrystaline, and more or less Quustions.—388. What use is made of phosphate of soda and am- monia? How is it prepared? 889. How is hydrosulphate of sulphide of ammonium prepared? To what class of salts does it belong? 3890. How is silica made to combine with the alkalies and earths? What is said of the compoun 1s produced? ° SILICATES OF POTASH AND SODA — GLASS. 823 transparent. All these compounds are known under the name of glass. : There are several kinds of glass, all of which are double sili- cates of potassa and soda; or one of these with silicate of lime, lead, magnesia, baryta, alumina or iron, but the proportions are variable. Silicic acid has no action upon the bases at ordinary tempera- tures, but it readily combines with them in a state of fusion, or with their carbonates; in the latter case of course expelling the carbonic acid. 391. When silica is fused with 2 or 3 times its own weight of carbonated potash or soda, a compound is formed which is soluble in hot water, and has been called soluble glass, or liquor silicum. The solution, when applied to wood and other com- bustible substances, soon dries and forms a transparent coating which protects them from the air and renders them less combustible when exposed to great heat. If the proportions are reversed, and 2 parts of silica and 1 part of carbonate of potash or soda are used, a proper glass is formed, which is quite insoluble in water, and nearly all acids. The proportions of the ingredients in the different varieties of glass are exceedingly variable, but common window, or crown glass, is always a mixture of silicate of potash or soda and lime. Crystal, or flint glass, is a silicate of potash or soda and oxide of lead; it is softer than other kinds, and more fusible and dense, and therefore better adapted for optical purposes. When a thread of it is heated in the flame of a lamp, it is blackened by the reduction of the oxide of lead.’ 392. Bohemian glass, which is very infusible, contains “only silicate of potash and Hme. It is much used in the manufacture of chemical apparatus. The finest kinds of glass are made only of the purest materials ; but impure materials, containing alumina and the oxides of iron and manganese, answer for such glass as that of which green bottles are made. QuESsTIONS. —What is glass? 891. How is soluble glass formed? Of what is crystal glass composed? 392. What is said of Bohemian glass? _ 824 SILICATES OF POTASH AND SODA — GLASS. Though, as above stated, glass is considered insoluble in water and the acids, except such as contain fluorine (252), yet certain varieties of it are sometimes attacked by acids, solutions of the alkalies, or of their car- bonates, and even by pure water, especially at a boiling temperature. Glass that has been a long time buried in the earth, is sometimes found with a pearly incrustation upon its surface, in consequence of the separa- oe of its alkalies; and is sometimes quite soft, so as to be cut with a ife. All these different varieties of glass have a density varying from 2:4 to 3-7, but glass may be made of a density as high as 5-4, Enamel, used for various purposes, and especially for watch and clock faces, is made of silica and potash, or soda and oxide of lead, and rendered opake by oxide of tin. Colored glass is made by adding to any of the varieties metallic oxides, as those of cobalt, copper, manganese, antimony, gold, &. A white opake glass, in imitation of porcelain, is made by adding to the glass when in fusion arsenious acid. 393. Manufacture of Glass.— The materials for glass are first to be fused together, at a high temperature, and in such a manner that no impurities from the ) smoke of the fire or other source shall be mixed ) with it. This is done by using pots made of fire- clay, and entirely enclosed within the walls or the furnace, except the projecting mouth. The figure in the margin represents the section of one, with its opening or mouth towards the left hand. Usually several are placed in a circle in the same furnace, and heated by the same fire. The principal instrument used is an iron tube or pipe, four or five feet in length ;—one end of this being dipped into the melted glass, which has now the consistency of soft wax, a portion adheres to it, and is removed from the pot. As its shape is irregular, it is first rolled on an iron plate, called a marver (see figure), to give it a cylin- Melting Glass. Glass Operations--Marver Questions.—Is glass entirely insoluble in water and the acids? Of what is enamel made? How is colored glass formed? 3893. Describe briefly the mode of manufacturing window glass. SILICATES OF POTASH AND SODA —~ GLASS. 325 drical form, and is then blown into a pear-shape (as seen in figure A), by forcing air through the pipe from the lungs. As the glass is still soft, to prevent it from inclining in one direction or another, as it would inevitably if held still for a moment, it is kept constantly whirling, by rolling the pipe in the hands. If held in the position A, the hollow mass will gra- dually become elongated, and if inverted and held in the position B, the upper part sinks, and it takes the form here seen ;—of course, in any particular case, the workman will be guided in the mode of handling by a regard to the form which he wishes to give it. As rapid cooling is constantly taking place, the glass has to be re-heated frequently, which is done by holding it in a heated furnace provided for the purpose. For common window glass, the mass in the form of B, being re-heated to soften it, is held by the rod with the alasa down- ward, and swung backward and forward in the manner of a pen- dulom, until it is sufficiently elongated, and has the form C ;— Glass Blowing. Prevaration of Window Glass. by this time it has partially cooled, and by holding the extreme point a little time in the furnace it is softened so that a blast of air from the lungs is forced through it, and an assistant with shears accurately removes the lower part, giving it the form D. The cylindrical part is now to be separated from the rod by a section around the upper part, as shown in HK, and subsequently a longitudinal fracture is made in the hollow cylinder thus obtained 326 SILICATES OF POTASH AND SODA — GLASS. through its whole length; and it now only remains to open the cylinder thus prepared in order to reduce it to a perfect plane. This is done by softening it in a proper furnace and piercing the part gently with an iron rod, as represented in the figure. Preparation of Window Glass. 394. The variety of window glass called crown glass is pre- pared in a different mode. The melted mass taken from the melting-pot is first blown into the form of a globe, and then an iron rod attached to it on the side opposite that to which the tube adheres, and the tube separated by applying a little cold water. This, of course, leaves an opening, which becomes enlarged by softening in the heating furnace, and giving it a rapid rotary motion by means of the iron rod.held in the hand. By heating it several times in this way, the rapid rotary motion being con- tinued, the globe is at length opened out, and becomes a circular disc, which, after the proper annealing, is cut into panes by a diamond. 395, Many articles now made of glass, are blown in metallic moulds prepared for the purpose, or are pressed between two moulds, one of which shuts into the other, so as to give the proper shape. This is called pressed glass. Plate glass, used for mirrors and for large windows, is poured, when in a state of fusion, upon a plane surface, and a roller passed rapidly over it, to reduce it to the proper thickness. The surfaces are then ground down to a perfect plane by means of * Questions.—394. How is crown glass manufactured? 895. Describe the mode of forming articles of pressed glass. Describe the mode of forming plates for mirrors. SILICATES OF POTASH AND SODA ——GLASS. 327 friction with sand and fine emery, and then finely polished by friction with colecothar, or red oxide of iron. Small articles of glass may readily be made of glass tube before a blowpipe, which is blown by a bellows worked by the foot. The best fuel to be used is hurning fluid, consisting of four parts of strong alcohol and one part of camphene; but oil or tallow will answer. A very little experience will enable one to bend even quite large glass tubes, and to perform many other operations of great importance in the laboratory. All articles made of glass, if suddenly cooled, are exceedingly brittle, and liable to fracture from the slightest causes, even trifling changes of temperature: They are therefore annealed by placing them in a furnace prepared for the purpose, and, after becoming quite hot, are allowed to cool very slowly. By this means such a change is produced in the molecular arrangement of the particles, that this tendency to fracture is much diminished. Articles of glass that have not been annealed, sometimes break in a singular manner ;—a tumbler half filled with liquid, and grasped by the hand, will break quite around at the surface of the water by the slight heat of the hand; or a thick glass tube several inches in length will split through its whole length simply by being wet, especially if merely touched by a hard substance, as a piece of wire. Occasionally, after being handled and laid aside, they break spontaneously. 396, The Bologna, or philosopher's vial, is made in the form of an ordinary vial, but with thicker sides and a very thick bottom, and is not annealed. A smart blow may be given to it by a piece of lead or of wood, or a leaden shot dropped into it, without producing any effect; but by dropping into it a small angular piece of flint, it almost invariably falls to pieces. Sometimes even coarse sand will produce this effect. In this, and in the following case, the result is due to the want of annealing. Prince Rupert's drops are simply drops or tears of glass, which are made by allowing the glass when melted to drop from the end of a rod into water, by which they are sud- denly cooled. They are perfectly solid, but when the small end is broken off, the whole mass falls to powder, with wu yf slight explosion. Vie Quzstions.—Why are all articles made of glass annealed before using? What is likely to be the effect if the process is omitted? 396. Describe the Bologna vial. What are Prince Rupert’s drops? 328 BINARY COMPOUNDS OF BARIUM. Grovr II. Barium Metals, the protozxides of which are alkaline earths.—These Srronrium | latter are called baryta, strontia, lime, and magnesia. They Catcrum possess the same: properties which characterize the alka- Maanesivum J lies, but in less degree. . BARIUM. Symbol, Ba; Equivalent, 68-5; Density, —? 397. History, Ete—This metal is procured by passing vapor of potassium over baryta (oxide of barium) at a red heat, or by passing the galvanic current through hydrate of baryta in contact with mercury, the latter forming the negative electrode of the battery. The amalgam thus obtained is carefully heated in a glass tube through which a current of dry hydrogen is constantly passing, and the mercury expelled. The barium will be left in small globules. It has the color and lustre of silver, and melts at a red heat, but is not easily volatilized. In the air it is rapidly oxydized, and when heated burns with a red flame. It is also rapidly oxydized when thrown into water. Its name is from the Greek barus, heavy; its compounds generally possessing this characteristic property. Binary Compounds of Barium. 398. Protoxide of Barium, BaO; eq., (68-5 + 8=) 74-5.— This compound has been known many years as barytes or baryta. It may be obtained by decomposing nitrate of baryta by heat, which is best done by using an earthern retort in a furnace (as represented in the figure on next page), and applying the heat as long as gaseous matter is evolved. Quzsrions.—What metals are included in the second group? What do their protoxides form? Do these earths possess alkaline properties? 897. How is barium procured? How is the metal affected in the air? From what circumstance or property is the name derived? 398. How may the alkaline earth, baryta, be obtained? 7 SALTS OF BARYTA. 3829 Baryta is a gray powder, which slakes like lime when water is poured upon it, and becomes very hot. It dissolves readily in water, but is less soluble than potash or soda—a pro- perty by which the alkaline earths are distinguished from the alkalies. It is very caustic to the taste, and affects vegetable colors in the same manner as the alkalies. Peroxide of Barium, BaO,.—This oxide may be formed by passing a cur- rent of dry oxygen gas over baryta, at a low red heat; or by simply heating baryta in an atmosphere of oxygen. It is used only for the pur- pose of preparing peroxide of hydrogen (206). Preparation of Baryta. Chloride of Barium, BaCl; eq., (68-5 + 354 =) 103-9.— This compound is formed by dissolving the native carbonate of baryta in diluted hydrochloric acid, and by other modes. It crystalizes in white scales, which contain two atoms of water. It is very soluble in water, and is much used as a test for sul- phuric acid, with which baryta forms an insoluble sulphate. Salts of Baryta. 399. Carbonate of Baryta, BaO,CO,, is found native, and called witherite by mineralogists. From it all the other salts of baryta may be prepared. _ Sulphate of Baryta, BaO,SO,.—Sulphate of baryta is found abundantly in various places, often in beautiful crystals. It has a density of about 4:4, and is insoluble in water. When pow- Questions.—Describe the properties of baryta. Describe the mode of preparing peroxide of barium. How is chloride of barium formed? For what purpose is it used? 399. Is carbonate of baryta found native? What is said of, the occurrence of native sulphate of baryta? 28 * 330 BINARY COMPOUNDS OF 8TRONTIUM. dered and mixed with charcoal, and heated intensely, it is con- verted into sulphide of barium, from which the other salts of baryta may be prepared, as from the native carbonate. By mineralogists, it is called heavy spar, because of its great weight. Ground to a fine powder, it is used as a substitute for white lead, either alone or mixed with white lead. All the soluble com- pounds of baryta are poisonous. Nitrate of Baryta, BaO,NO,.— This salt of baryta is prepared by digesting the native carbonate, or the sulphide, obtained as just de- scribed, in nitric acid. Its only use is in certain chemical analyses, and in procuring the earth baryta. STRONTIUM. Symbol, Sr; Equivalent, 44; Density, —? 400. History, Etc.— Strontium is obtained from its oxide, strontia, in the same manner as barium; and in its appearance it is said very much to resemble that metal. Like barium, also, it decomposes water with the evolution of hydrogen, and oxydizes rapidly in the open air. It receives its name from Strontian, a village in Scotland, near which it was first obtained. Binary Compounds of Strontium. 401. Protoxide of Strontium, SrO; eq., (44 + 8=) 52.— This compound, which is the earth strontia, is formed by the oxydation of strontium. It is prepared also by heating the nitrate of strontia to redness, by which the acid is expelled. It much resembles baryta, seeming to sustain much the same rela- tion to it that soda sustains to potash. Questions.—How is sulphate of baryta affected when heated with charcoal? What is it called by mineralogists? For what purpose is it used? Howis nitrate of baryta formed? 400. Give the history, &c., of strontium? From what is the name derived? 401. How is the alka- line earth, strontia, procured? What is said of its relation to baryta? BINABY COMPOUNDS OF OALCIUM. 831 Salts of Strontia. 402, Carbonate of Strontia, Sr0,CO,, is found native ;—it is the stron- tianite of mineralogists. Sulphate of Strontia, Sr0,SO,, is also found native, and is called celestine. Treated in the same manner as described for sulphate of baryta (309), the other salts of strontia may be prepared from it. Nitrate of Strontia, Sr0,NO,, is prepared by dissolving the native car- bonate in diluted nitric acid, or from the sulphide, as described under sulphate of baryta. It is much employed in fire-works, to give a beau- tiful red color to the flame. To show this red fire, mix intimately 40 ‘parts of this salt, 13 of sulphur, 5 of chlorate of potash, and 4 of sul- phide of antimony, and burn the mixture upon a dry brick, or marble slab, in a dark room. The nitrate contains water, and should be well dried before mixing with the other ingredients. All the compounds of: strontia communicate a red tint to flame in which they are heated. CALCIUM. Symbol, Ca; Equivalent, 20; Density, —? 403, History, Ete —Calcium is the metallic base of lime, from -which it has been obtained, but only in very small quantity. The process is precisely the same as that given above for obtaining barium from baryta. It is said to be of a brilliant white color, and rapidly oxydizes in the air. Little is known of its other properties. Binary Compounds of Calcium. 404. Protoxide of Calcium—Lime, CaO; eq., (2048 =) 28. .— This compound, commonly known by the name of lime and quicklime, is obtained by exposing carbonate of lime to a strong Questions.—_402, What is the mineralogical name for carbonate of strontia? Sulphate of strontia? How is nitrate of strontia prepared? What useismade ofit? 403. Give the history, &c., of calcium. 404. What is the common name for protoxide of calcium? How is it prepared from the native carbonate? 333 BINARY COMPOUNDS OF CALCIUM. 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; -but to obtain lime for ordinary Pune common limestone is ‘tied, The calcination of the carbonate, to procure lime for common purposes, is effected in kilns, or pits, which are usually constructed of stone, upon a hill-side, so that the limestone may be conveniently introduced at the top, and the lime, after calcination, re- moved from the opening at the bot- tom. Wood is very generally used for the fuel, but bituminous coal may be substituted for it, the pieces of limestone being placed so that the flames pass through it. When the Lime Kiln. calcination is finished, of which the experienced eye can easily judge, the fire is extinguished, and the lime, when cold, removed. The calcination of a large kiln usually require five or six days. Sometimes the calcination is carried on in perpetual kilns, as they are called. The limestone is then introduced in successive layers, with layers of coal between them; and the fire, once kin- dled, is continned for an indefinite time, layer after layer of the coal being consumed, and the lime, after calcination, being removed from below. As the mass settles down in the kiln, new layers of limestone and coal are introduced at the top. Lime is a brittle, white, earthy solid, the specific gravity of which is about 2:3. It phosphoresces powerfully when heated to full redness, and hence its use in the Drummond light (201). It is one of the most infusible bodies known; fusing with difficulty even by the heat of the oxyhydrogen blowpipe. Exposed to the air, it gradually absorbs carbonic acid, and crumbles to powder. It has also a powerful affinity for water, Questions.—Ilow is the calcination usually effected? Describe the mode of calcining lime by the use of coal for fuel. Describe the pro- perties of lime. SALTS OF LIME. 333 which is absorbed instantly on being poured upon it; and the combination is attended with great increase of temperature, and formation of a white bulky hydrate. The proccss of slaking lime consists in forming this hydrate, and the hydrate itself is called slaked lime. It differs from the hydrates of strontia and baryta, in parting with its water at a red heat. Recently-slaked lime dissolves sparingly in water, and has this singular property, that it is more soluble in cold than in hot water. The solution has a caustic, acrid taste, and acts upon vegetable colors like the alka- ° lies. Exposed to the air, it absorbs carbonic acid; and if agi- tated, becomes milky, from the formation of insoluble carbonate of lime. Mortar, for building, is prepared by mixing sand with recently- slaked lime. It becomes very hard by exposure to the air, in consequence of the absorption of carbonic acid by the lime. Combination seems also to take place, to some extent, between the silica of the sand and the lime. When the limestone from which the lime is made contains a considerable portion of silica, alumina, &c., it constitutes hydraulic cement, or water-lime. Mortar prepared from this, has the property of becoming hard under water, which is not the case with that prepared from pure lime. 405. Chloride of Calcium, CaCl.—This compound is formed by dis- solving carbonate of lime in hydrochloric acid. It is much used in the operations of the laboratory, especially for removing moisture from gases, which it effects readily in consequence of its great affinity for water. It is often called muriate of lime. Fluoride of Calcium, CaF, is the fluor spar, or Derbyshire spar of mine- ralogists. It is of great use to the chemist as affording the chief source of the element fluorine. "Salts of Lime. 406. Carbonate of Lime, CaO,CO,.—This is one of the most abundant mineral productions known ; it is found in every country Qvestions.—In what consists the slaking of ime? Is lime soluble in water? Howis mortar prepared? What is hydraulic cement, or water- lime? 405. How is chloride of calcium prepared? What use is made of it? 406. What varieties of carbonate of lime are mentioned? 334 SALTS OF LIME. as limestone, chalk, Iceland spar, marble, &. It is decomposed by heat, and furnishes the quicklime used in preparing mortar. The beautiful stalactites, frequently scen suspended from the roofs of caverns, are formed of this compound. Though insoluble in pure water, it is slightly soluble in water containing an excess of carbonic acid. Water permeating the soil above the caverns, first becomes charged with carbonic acid, and afterwards takes up a little carbonate of lime, which is again deposited as the water, drop after drop, hangs suspended for a time from the roof. This is occasioned partly from the evaporation of the water, and partly by the escape of the carbonic acid, when the water becomes exposed to the free air of the cavern. Asa portion of the water falls to the bottom of the cavern, corresponding deposits of car- bonate of lime, called stalagmites, are formed upon the floor, and gradually build themselves upward. Sometimes a stalactite from the roof is formed downward until it reaches the corresponding stalagmite from below, when the two, becoming connected, form Stalactites. a column or pillar, as shown at the left in the figure, which is from Knapp’s Chemical Technology. 407. Sulphate of Lime, CaO,SO, + 2HO.—This compound is well known as gypsum, and plaster of Paris. Pure, crystalized Questions.—How are stalactites in caverns formed? What are tho corresponding deposits on the floor of the cavern called? 407. What varieties of sulphate of lime are mentioned? SALTS OF LIME. 835 specimens are sometimes called selenite, and compact varieties, alabaster. Common gypsum contains considerable water, which may be expelled by heat; but there is a variety destitute of water, called anhydrite by mineralogists. When powdered gypsum, the water of which has been expelled by a moderate heat, is again made into a paste with water, it soon becomes hard, or “sets,” -as the workmen say ;—a property which adapts it admirably for many purposes in the arts. In stereotyping, a coat of this paste is spread carefully over a page of type, set in the ordinary manner, which, soon becoming hard, is removed, and a cast in common type- metal taken from it. This, after certain preparations, and the emendation of any broken letters that may be found, constitutes a stereotype plate, used in printing. In a very similar manner it is used for preparing busts of living per- sons. The process is conducted as follows: The individual is prepared by removing the clothing from his neck and shoulders, coating the heir with paste, and applying a little oil or soap to the part which ~ is to be covered by the plaster. He then places himself on his back on wu table, his head being supported about an inch above the table by a small block of wood, and surrounded on three sides by a box prepared for the purpose, as represented in the figure. The operator, having his calcined plaster properly mixed with water, pours a portion of it into the box, so that it may fill up the space under the head; and continues to mix small portions at a time, and és add it to the mass, until the whole cies telat teas head and face are inclosed, except a small opening at the nostrils. The whole soon becomes hard, attended by a considerable elevation of tem- perature, but not so much as to be uncomfortable to the subject of the operation. 7 In order to remove this plaster inclosure, the operator has taken the precaution, before applying the plaster, to draw around the head two pieces of thread or twine, one so that it shall come just below the ears, as the person lies upon the table, and the other just above them, bring- ing the ends of both around under the chin; and just as the plaster is about to set, taking one of these threads by the two ends, he pulls it out laterally so as to divide the mass into two parts, as if cut with a knife. Quest10ns.—What is the effect when powdered gypsum is exposed to a moderate heat? What now is the effect when it is mixed with water? Describe the mode of forming plaster busts of living persons: 336 SALTS OF LIME. When the second thread has been drawn out in this way, the plaster inclosure of the face and head will of course be diyided into three parts, the upper part covering the face, and beneath this a ring covering the ears, and below this the third part covering the back of the head and neck.- The part covering the face is now to be carefully removed, which may be done without difficulty; but the second piece which incloses the ears, will have to be divided below the chin and at the top of the head, and removed in two pieces. This being done, the subject of the opera- tion is again at liberty to remove himself from the table, leaving the remaining piece in its place. : The four pieces being brought together, each in its proper place, it is evident that the operator has a perfect model or mould of the head and all the features of the face, from which the bust is to be prepared; buta further description of this part of the process will not be needed. If a part of the breast is to be included with the bust, the arrangements must of course be made accordingly, in preparing the mould. The opera- tion requires some labor, but is less disagreeable to the subject than might be supposed before making the trial. Sulphate of lime is extensively used as a manure in many countries, with excellent effect. It is slightly soluble in water, and is often found in well and spring water, and gives it the property called hardness. Phosphates of Lime.—There are several of these salts. One variety is found native, and is called apatite; it is an essential ingredient of all fertile soils, and is contained in all varieties of grain used for bread. It also constitutes the chief part of the solid matter of the bones of animals. 408. Hypochlorite of Lime, Ca0,C10.—This is the well-known chloride of lime, bleaching-powder, or bleaching-salt of commerce. It is formed by passing a current of chlorine through recently- slaked lime. It is a white powder, and emits a faint odor of chlorine. Great use is made of it in bleaching (229). For this purpose it is dissolved in water, and the articles to be bleached soaked in the solution, and then dipped in very dilute acid. The chlorine which is thus liberated produces the bleaching effect. The process is usually several times repeated. It is also used as a disinfecting agent, the chlorine, as it is gradually liberated, having the property of destroying deleterious gases present in the atmosphere. The commercial value of bleaching-salt depends entirely upon the quantity of chlorine it is capable of evolving when used, and is usually \ determined by the quantity of indigo a given weight of it will bleach. Questions.—What is said of the phosphates of lime?, 408. What is hypochlorite of lime? What use is made of it? BINARY COMPOUNDS OF MAGNESIUM. 337 Tests of Lime.—The proper test for lime is oxalic acid, which forms with it, in solution, an insoluble white precipitate. Oxalate of ammonia is generally used. A salt of lime dissolved in alcohol gives to the flame a red color, very similar to that communicated by strontia (402), but of a slightly different tint. MAGNESIUM. Symbol, Mg; Equivalent, 12; Density, 1:87 409. History, Etce.—Magnesium is obtained from its chloride by passing vapor of sodium or potassium over it when heated to redness in a glass tube; the alkaline chloride formed, and any undecomposed chloride of magnesium which may remain, are washed out with cold water, and the metallic magnesium subsides. It is a white metal, of considerable brilliancy, and quite malle- able. Heated in the open air, it readily takes fire, and burns with a brilliant flame, producing the protoxide of the metal. It is rapidly oxydized by boiling, but not by cold water. Binary Compounds of Magnesium. 410. Protoxide of Magnesium—Magnesia, Mg0.—Magnesia is best obtained by heating the carbonate to redness, by which the carbonic acid is expelled. It may also be prepared by decom- posing nitrate of magnesia by heat. It is a soft, white powder, and is usually sold under the name of calcined magnesia. It. is very slightly soluble in water, requiring for this purpose 5000 -or 6000 times its own weight of water. Hydrate of magnesia, . MgO,HO, is found native at Hoboken, New Jersey, and other places. Magnesia is very infusible, and communicates this pro- perty to minerals in which it predominates, as tale and soapstone. Magnesia is extensively used in medicine as an antiacid. In Qurstions.—What tests of lime are mentioned? 409. How is magne- sium obtained? Whatis said of the metal? 410. Describe the protoxide of magnesium. What use is made of magnesia? ae 29 838 SALTS OF MAGNESIA. the state of hydrate it is said to be a good remedy in cases of poisoning with arsenic. Chloride of Magnesium, MgC1.—Chloride of magnesium, which, ag we have just seen, is made use of to obtain the metal, is best procured by dissolving magnesia in hydrochloric acid, and adding to the solution an excess of sal-ammoniac; and, after expelling the water, heating the residue in a platinum crucible, by which means the sal-ammoniac used will be driven off. Without the sal-ammoniac, the chloride of magne- sium would be decomposed by the heat required to expel the water. Salts of Magnesia. 411, Carbonate of Magnesia, Mg0,CO,.—Carbonate of mag- nesia is found native, in the magnesite of mineralogists, and may also be formed from the native sulphate by precipitation with an alkaline carbonate. It is nearly insoluble in pure water, but dis- solves in water impregnated with carbonic acid, forming the liquid magnesia of the shops. When obtained by precipitation with an alkaline carbonate, it always contains a portion of hydrate of mag- nesia, and is usually seen in beautiful square blocks, which are remarkable for their lightness. It is extensively used in the practice of medicine. Sulphate of Magnesia, MgO,SO,.—This is the well-known Epsom salt, used in medicine. It is not unfrequently found in the waters of mineral springs, as at Epsom, in England, and may readily be formed by dissolving magnesia, or its carbonate, in sulphuric acid, and by the action of this acid upon the mineral called dolomite, which is a double carbonate of magnesia and lime. Its erystals contain 7 eq. of water of crystalization. It is very soluble, and has a bitter, saline taste. It may readily | be distinguished from sulphate of soda by the form of its crystals, or by pouring into a solution of it some caustic potassa, which will cause a white precipitate. In sulphate of soda, no precipitate will be formed. -QuEstions.—Describe the mode of preparing chloride of magnesium. 411. Describe the carbonate of magnesia. What is the common name of sulphate of magnesia? Where.is it sometimes found? How may it be distinguished from sulphate of soda? ALUMINUM. 339 Silicates of Magnesia, of which there are several, abound in nature, especially in the talcose and serpentine rocks. There is no specific test of magnesia, but it is distinguished from other substances by different tests; and from most of its soluble salts phosphate of soda, with ammonia, separates a white precipitate, which is a double phosphate of magnesia and ammonia. Grovr ITI. ALUMINUM Eablet Metals, the protoxides or sesquioxides of which are earths.— toa The oxides of these metals, which constitute the earths, are ae called alumina, glucina, zirconia, thorina, yttria, &e. They cea. are distinguished from both the alkalies and alkaline earths ee by being quite insoluble in water, and, of course, destitute ee of any alkaline reaction. They, however, combine readily atin with, and neutralize the most powerful acids. Dipymium ALUMINUM. Symbol, Al; Equivalent, 13-7; Density, 3-7. 412. History, Ete—-The metal aluminum is obtained by de composing chloride of aluminum by the action of sodium or potassium, in the same manner’as magnesium is prepared from its chloride. It is found, after the process, in small globules, which may be brought into a single mass by melting it in a close crucible, or under dry chloride of sodium. Instead of chloride of aluminum, the mineral called cryolite, which is a double fluoride of aluminum and sodium, may be used in its preparation. Aluminum is very malleable, and has the brilliant lustre and white color of silver. It is not oxydized in the atmosphere at ordinary temperatures, but burns brilliantly when heated to red- ness. Cold water does not affect it. A small piece that had been rolled was. found to have a density of 3:7, as given above. The name of this metal, aluminum, is derived from alum; a double sul- phate of alumina and potassa, from which the earth is very readily obtained. Quzstions.—What metals belong to Group III.? How are they cha- racterized? 412. How is metallic aluminum prepared? What native mineral may be used for the purpose, instead of the chloride? Describe the metal. 340 BINARY COMPOUNDS OF ALUMINUM. Binary Compounds of Aluminum. 413, Sesquioxide of Aluminum, AJ,0,,—This is the earth’ alumina, and is one of the most abundant of nature’s: pro- ductions. Like silica, it is found in every soil, and in almost all rocks upon the face of the earth. Crystalized, it forms the raby and the sapphire, two of the most valuable gems. Emery, also, so much used in the arts, is chiefly composed of this earth. It forms a large part of clay, and gives to it its tenacious character, fitting it for the use of the potter. Pure alumina is a white powder, without taste or smell. It is easily prepared by pouring solution of caustic potash into a solu- tion of’alum, and washing and heating the soft-mass that is precipitated. It contracts much in drying, and the dried mass adheres tenaciously to the tongue when applied to it. Alumina, though usually serving as a base in the compounds which it forms, occasionally becomes the electro-negative ele- ment, and serves the part of an acid. Thus, it combines with potassa to form aluminate of potassa, and with baryta in like manner. The mineral called spinelle is a native aluminate of magnesia. This earth is remarkable for its tendency to unite with organie substances. Ifa cotton cloth is immersed in a solution of acetate of alumina, the earth will deposit itself completely on the fibres of the cotton and leave the acetic acid free. On this principle depend some of the most important processes in calico-printing. When heated with nitrate of cobalt, it forms a beautiful blue com- pound. : Native hydrate cf alumina is occasionally found, as gibbsite and diaspore. Chloride of Aluminum, Al,Cl,.—This compound is interesting as fur- nishing the means of obtaining the metal aluminum. For this purpose it must be anhydrous, and is obtained by passing a current of dry chlorine through a mixture of alumina and charcoal, heated to redness, in a porcelain tube. Questiovs.—413. What is said of the abundance of alumina? What gems are mentioned as composed of this earth? Describe alumina. Does it, in combination, act as a base or an acid? What is said of its tendency to unite with organic substances? How is chloride of aluminum formed ? SALTS OF ALUMINA. 841 Salts of Alumina. 414, Sulphate of Alumina, AJ,0,,350,.— This salt, though containing 8 eq. of acid, is considered a neutral (349) sulphate. It is obtained by treating the purest clays with sulphuric acid, raoderately diluted. “It is very soluble in water, and may be obtained in small crystals, which contain 18 eq. of water. It is used in dyeing. 415, Sulphate of Alumina and Potash, Al,0,,3SO, + KO,SO,. —This double salt is the well-known alum of commerce. It is usually formed from a mineral substance called alum-slate, which isan argillaceous, slaty rock, containing iron pyrites. It is some- times found naturally formed as an efflorescénce upon the surface of the rock. Alum is usually seen crystalized in octahedrons, which always contain 24 eq. of water; it is very soluble in boiling water, and has a sweetish, astringent taste. When the crystals are heated, they melt and froth up very much, in consequence of the large quantity of water they contain. Alum is much used in medicine and in the arts, especially in dyeing and calico-printing. The alumen ustum, or burnt alum, used in medicine as a caustic, is alum that has been deprived of its water of crystalization by heat. Common or potash alum is the type of a whoie family of alums ; as soda alum, ammonia alum, iron alum, chromium alum, &c. Soda and ammonia alums are produced by causing these sub- stances to replace the potash in common alum; and iron and chromium alums, by replacing the alumina by the sesquioxides of iron and chromium. ‘These alums are all exceedingly alike in their various properties, and all contain, when crystalized, 24 atoms of water. The relation of these different alums (183) to each other in composition will best be seen by comparing their formule. Questions.—414, How is sulphate of alumina formed? 415. What is the composition of alum? From what is it usually formed? What use is made of it? What are some of the different alums that are known? 29 * 342 SALTS OF ALUMINA. 1, Potash, or common alum...... KO,803 + Al,0,,350, -+- 24HO. T. 2 2. Soda alum......seccsrsccseee srecee NaO,8O, + Al,05,8S03 + 24H0. 8. Ammonia alum......... ... NH,0,80, + Al,03,880, + 24HO0 4, Ferio-potassa alum... - KO,80,, + Fe,05,380, + 24H0. IL. 4 5. Ferio-soda alum..........0+.... NaO,S0, + Fe,03,880, + 24HO. 6. Ferio-ammonia alum.... - NH,0,80, + Fe,0,,880, + 24HO. III, 7. Manganeso-potash alum....... KO,SO; + Mn,0,,380, -++ 24HO. IV. 8. Chromio-potash alum.......... KO,80, + Cr.03,380, + 24H0. Both the manganeso and chromo series have a soda and an ammonia alum, the same as the other series. Cubic alum, so called because its crystals usually are cubes, is formed by pouring solution of carbonate of potassa into a saturated solution of common alum at about 122°, constantly stirring the mix- ture forsome time. Its composition is KO,SO,+ Al,0,2SO + 9HO. 416. Silicates of Alumina.—Several double silicates of alumina and other bases are found native, some of which are of great im- portance in the arts. eldspar is a double silicate of alumina and potash, while albite, or Cleavelandite, is a double silicate of alumina and soda. Spodumeme and petalite are the same as the latter, except that they contain less soda, and a small portion of lithia. Sometimes feldspar undergoes a natural decomposition, losing its potash and part of its silica, and is then called kaolin. This substance, which is essentially silicate of alumina, more or less pure, is the basis of all the varieties of porcelain or China-ware. The articles are made of this of the proper form, and, when dry, are exposed to a high temperature in a furnace, by which they become very compact, but do not fuse. They are then dipped in the glaze, which consists chiefly of feldspar, ground to a fine pow- der, and suspended in water, coating of which adheres over the surface; and when the articles are dried and again subjected to the heat of the furnace, it fuses and forms a glassy envelope, which incorporates itself with the body previously formed, and increases its compactness and strength. The glaze also renders Questions.—Of those alums mentioned in the table, what is the dif- ference in composition between the first and second? The first and third? The first andfourth? First and seventh? Seventh and eighth? 416. What native silicates of alumina are mentioned? What is kaolin? What use is made of it? Describe the mode of manufacturing articles of porcelain. SALTS OF ALUMINA. 343 them impervious to liquids, and even to the gases. For the finer kinds of porcelain, the kaolin, which constitutes the body, is mixed with some substance, as alkali or lime, by which it is ren- dered partially fusible, and the glaze therefore becomes more perfectly incorporated with it, so as to render articles made of it slightly translucent. The colors are applied after the first burning, and before the glaze, and are composed entirely of metallic oxides. 417, All the different kinds of clay are composed essentially of alumina and silica, both of which are very infusible, except when mixed with the alkalies or lime, or certain metallic oxides, especially the oxides of iron. Common clay always contains car- bonate of lime and oxide of iron, and is therefore quite fusible. Fire clay, so called because of its infusibility, contains no lime ; when free from metallic oxides it is called pipe clay, and articles made of it are uncolored when removed from the fire. Stone-ware is made of an infusible clay; and when the articles are sufficiently heated in the furnace, common salt is thrown upon them, the soda of which, combining with the materials of the clay, forms a fusible compound that constitutes the glaze. With- out this the articles would be porous, and water and other liquids would percolate through them. Red carthen-ware is made of the most common kinds of clay, which contain lime and iron, and is so fusible that only a mode- rate heat is needed in baking articles made of it. The articles, after being shaped upon the potters’ wheel, are thoroughly dried, and then coated over with litharge (oxide of lead), in fine powder, which, by the heat of the furnace afterwards applied, fuses and spreads over the surface so as to form a fine glaze. Such vessels, however, should never be used with acids, which would attack the oxide of lead and produce poisonous compounds. Bricks are usually made of the same kind of clay as that just described. No glaze is required for them. The best bricks are now pressed when partially dry, to render them more solid, and Quzstions.—417. Of what are all the different kinds of clay com- posed? What is fire clay? How is the glaze applied to articles of stone- ware? Describe red earthen-ware. How are bricks made? 344 GLUCINUM, ZIRCONIUM, AND THORIUM. to give them a smoother surface. The red color is occasioned by the oxide of iron in the clay, or the sand mixed with it, which, by the heat in burning, becomes peroxidized. 418. Glucinum, G; Eq., 4-7.—This metal receives its name from the circumstance that the salts of its oxide, glucina, are sweet (Greek, glukus, sweet,) to the taste. It is obtained from its chloride in the same manner as magnesium and aluminum. ; Glucina is an oxide of the metal, but whether it is a protoxide, GO, or a sesquioxide, G,0,, has not been determined. It is obtained chiefly from the mineral species called beryl, and therefore the metal has by some been called beryllum. If we consider it as a sesquioxide, the equiva- lent of the metal will be 6-96, instead of the number given above. 419, Zirconium, Zr; EY., 34.—Zirconium, in combination with oxygen, is found in the mineral species zircon, which is a silicate of zirconia. It is present also, in small quantity, in some few other minerals. The earth zirconia is believed to be a sesquioxide of the metal, Zr,Og. 420. Thorium, Th; Eq., 59-6.—Thorium is found only in a few very rare minerals, as thorite, pyrochlore, and monasite. The earth thorina is a protoxide, ThO. Yttrium, Erbium, and Terbiam are found associated in a very few rare minerals, especially in gadolinite, a mineral species obtained chiefly from Sweden. Cerium, Lanthanum, and Didymium occur together in several mineral species, cerite, allanite, orthite, &c., but are obtained only in small quantity. Of these six metals last mentioned, little is really known ;—except yttrium and cerium, they have but recently been discovered. Grove IV. MANGANESE Iron ZINC CuromMium Metals which decompose vapor of water at a red heat, but CaDMIUM are not acted upon by liquid water. TIN : CoBALT NICKEL 421, The metals of this group are not as well characterized as those of some of the other groups. All that we have named as included in it do indeed, at a red heat, decompose the vapor of - Questions.—What occasions the red color of bricks? 418. Describe glucinum, and the mode of preparing it. 419. In what is zirconium found? 420. What other metals are mentioned as belonging to this group? Name the metals of Group IV. How are they charactorized ? 421. Are the metals of this group as well characterized as those of some other groups? MANGANESE. 845 water, but some of them also act slightly upon liquid water. This is the case more particularly with the first named, man- ganese ; but some of the others, as iron and zine, are oxydized by water, at ordinary temperatures, especially if atmospheric air be also present. ~ MANG A NESE. Symbol, Mn; Equivalent, 28; Density, 8:3. 422. History.—Manganese was first obtained by Gahn, from the substance then called magnesia nigra, which has since been found to be an oxide of this metal. It received its present name to distinguish it from magnesium, which has already been der scribed. Itis never found in nature in its metallic state, but its compounds are very generally diffused, and traces of it occur in both animal and vegetable substances. 423. Preparation — Metallic manganese, in consequence of its great affinity for oxygen, is not obtained without considerable diffi- culty. To procure it, the black oxide, in fine powder, is mixed into a paste with oil and lampblack, and exposed, in a close cru- cible, to the highest heat of a powerful furnace. The oxide should first be heated alone in a covered crucible, to reduce it to the form of protoxide, and this 4 then mixed with the lampblack and oil, as directed above. The last heating, which should be con- tinued two hours, is best performed in a ‘porcelain crucible, well closed by a cover, and then luted in a common Hessian crucible, as shown in the figure, which represents a section through the Preparation of centres of both crucibles. A little powdered Manganese. borax mixed with the materials facilitates the collection of the metallic globules into a mass. The metal will be found in a button at the bottom of the crucible. QuzstTions.—422, Give ah history of manganese. 38238. How is the metal prepared ? - 346 BINARY COMPOUNDS OF MANGANESE. ’ 424. Properties.— Manganese is a hard, brittle. metal, of a grayish-white color, and granular texture. It is exceedingly infusible, requiring the highest -heat of a wind-furnace for fusion. It soon tarnishes on exposure to the air, and absorbs oxygen with rapidity when heated to redness in open vessels. In water at ordinary temperatures it is slowly oxydized, and the action becomes more decided as the heat is raised. . The metal is best preserved in pieces of glass tube, hermetically .ealed. : Binary Compounds of Manganese. 425. Oxides of Manganese——There are six oxides of man- ganese, viz. : The protoxide, MnO, which is a powerful base. The sesquioxide, Mn,O;, which is a weak base. The red oxide, Mn,0,,=MnO + Mn,0,, a saline oxide (844 : 4). The binoxide, MnO,, called also peroxide and black oxide. Manganic acid, MnQ,, and Permanganic acid, Mn,O,. 426. Protoxide of Manganese, MnO.—This compound, though existing frequently in combination, is obtained in a separate state with some difficulty, in consequence of its strong tendency to absorb oxygen from the air. The following is the best method of procuring it. A glass tube with a bulb, A, near the middle, is provided, and the bulb partly filled ee SS SSS = Preparation of MnO. with powdered carbonate of manganese. A larger tube, B, is filled loosely with dry chloride of calcium, or pieces of pumice stone impreg- nated with strong oil of vitriol, and connected with the first tube, as Quzsrions.—424. What are the properties of manganese? 425. How many compounds of manganese and oxygen are there? 426. Describe the mode of preparing the protoxide by means of hydrogen gas. BINARY COMPOUNDS OF MANGANESE. 847 shown in the figure. The two-necked bottle, C, contains pieces of zinc and water. ‘When the whole is arranged as represented, some oil of vitriol is poured into the bottle, C, and the whole interior of the apparatus is soon filled with hydrogen gas, which is deprived of its moisture by passing the tube, B, so that dry hydrogen only surrounds the manganese compound. A spirit-lamp is now placed under A, the heat of which decomposes the carbonate of manganese, leaving the protoxide as a fine powder; and the absorption of oxygen is prevented by the hydrogen. After a proper time the tube, A, may be removed, and the extreme point closed hermetically by the lamp; the tube on the other side of the bulb may also be drawn out and closed in the same manner, which is accom- plished the more readily if, after intro- ducing the manganese compound, the \ERD tube has been a little reduced, as Preparation of MnO. shown in the accompanying figure. Prepared in this way, the protoxide is a powder of a delicate green color; and thus inclosed from the air, may of course be preserved for . any length of time. 427. Peroxide of Manganese, MnO,.—This is the common, or black oxide, of this metal. It is found in considerable abun- dance in the State of Vermont, and in other places in this country, and in Europe. Heated alone, it is reduced to the sesquioxide, Mn,0;, but when heated with sulphuric acid it is reduced to the protoxide, with which the acid combines. ‘This last operation may be performed in glass vessels. Heated with hydrochloric acid, chloride of manganese is formed, and chlorine evolved. It is much employed in the arts, in the manufacture of glass, and bleaching-salt, and for other purposes. When crystalized, it is called by mineralogists pyrolusite. The sesquioxide very much resembles the peroxide in appearance, and is dften fraudulently sold for it. 428. Manganic Acid, Mn0. —This compound has never | been obtained in a separate state, but only in combination with bases. Ié is interesting as the first metallic acid we are called to consider in the progress of our cotirse. It is formed, in combination with potash, by heating equal weights of peroxide of manganese and nitrate of potash to dull redness in an open crucible. The compound, manganaite of potash, is of a dark-green color, and has long been known by the name of chameleon mineral. Dis- solved in cold water, it forms u beautiful green solution, which by con- tinued dilution changes to blue, purple, and, finally, to a brilliant red. Questions.—427. Is the black, or peroxide, found native? What use is made of it? 428. Describe the mode of preparing manganate of potash, What is it called? ‘ 348 SALTS OF MANGANESE.—IRON. Hence its name. Tho changes are much more rapid when hot water is used. 429. Permanganic Acid, Mv,0,.—This acid, in combination with potash, is formed when solution of the manganate of potash is made with hot water, as above described, by the absorption of oxygen from the air. It is to the formation of this compound that the red color is owing, which is finally obtained by solution of chameleon mineral. From this red solution purple crystals of permanganate of potash may be obtained; but when an attempt is made to separate either this or the preceding acid from the bases with which they are united, they are decomposed. Chloride of Manganese is formed by digesting the black oxide in hydro- chloric acid. There are two known, the protochloride, MnCl, and sesqui- chloride, Mn,Cl,. Salts of Manganese. There are several salts of manganese, but the only one of im- portance in the arts is the following : 430. Sulphate of Manganese, MnO,SO,.—This salt is formed by digesting the peroxide in strong sulphuric acid by the aid of heat, and filtering when it has become cold. The crystals of the salt are of a rose-red color, and are very soluble in water. They always contain some water of crystalization, the quantity depend- ing upon the temperature of the solution in which they are formed. ‘ Carbonate of Manganese, MnO,CO,, is found native in the mineral called diallogite. IRON. Symbol, Fe (Ferrum); Equivalent, 28; Density, 7-7 to 7-9. 431, History.—Iron, the most abundant and most useful of all the metals, has been known from the remotest antiquity. The ores of the metal, as well as the metal itself, and some of its manufactures, are mentioned in the writings of Moses, and it is well known the ancient Greeks and Romans were acquainted with it. : Iron has been found native in small quantities in different Qurstions.—429. How is permanganate of potash formed? 430. De- scribe the sulphate of manganese. 431. Has iron been long known? Has it been found native? IRON. 3849 countries, but recently a real mine of very pure iron seems to have been discovered in the territory of Liberia, on the western coast of Africa. The occurrence of iron of meteoric origin, associated with nickel, and sometimes with cobalt and other metals, is not uncommon. One mass, at least, of this kind was actually seen to fall from the atmosphere, which was subsequently examined ; but many others have been found in such situations as to leave no doubt that they originated in the same manner. As no such compound has ever been found in proper iron-mines, it is believed that these bodies must have their origin in some region foreign to the earth. Common meteorites, which have often been seen to fall from the atmosphere, are of a different composition, containing usually no metallic iron, but various compounds of iron, manganese, sulphur, &e. There are many ores of iron, but the most important are the hydrated peroxide,'‘called by mineralogists brown hematite ; the peroxide (specular iron, or red hematite), and the black or mag- netic oxide, which is a compound of the two preceding. The last is the natural magnet, or loadstone. English iron is obtained chiefly from the clay-iron stone, which is an impure carbonate of iron, found abundantly in connection with the coal-measures ; but in this country the metal is extracted almost entirely from the ores previously mentioned. 432. Preparation.—The preparation of perfectly pure iron is a matter of considerable difficulty; but the ordinary method of reducing it from its ores, is, to heat them intensely, after having been reduced to smal] fragments, with charcoal or coke, and lime or siliceous sand, as the nature of the particular ore may require. The oxygen of the oxide of iron is absorbed by the heated carbon and carried off as carbonic acid, while the flux —for so the lime or sand is called when used for this purpose — unites with the earthy part of the ore and forms a fusible compound, that remains QueEsrions.—What is said of meteoric iron? What metals are usually found in combination with meteoric iron? What are some of the most important ores of iron? 432. Describe the ordinary modes of reducing the ores of iron. Why are fluxes used in the operation? 350 IRON. : upon the surface; the melted iron, by its superior weight, falling to the bottom. The nature of the flux used must depend, in any particular case, upon the character of the ore that is used. Most iron ores occur ip the granite rocks, and therefore the gangue (that is, the earthy matter of the ore,) is mostly silica, which of itself is very infusible (823), but forms a fysible mass when mixed with lime. Limestone, in fragments, is therefore intro- duced with the ore, which is first by the heat changed to caustic lime, by expulsion of the carbonic acid; and the lime then unites with the silica, producing the fusible silicate of lime, which, at the high temperature, flows freely, and allows the reduced particles of iron to unite in a mass. Occasionally, an iron ore occurs in a limestone region; and then, the lime alone being also infusible, a flux of silica (sand) is required. When a sufficient quantity of melted iron bas accumulated in the furnace, it is drawn off by an aperture at the bottom, which is opened for the purpose. After the iron has been removed, the slag, formed by the union of the flux with the earthy matter of the ore, is also drawn off. The accompanying figure represents a section of a blast-furnace, which is used for the reduction of iron ores. It is usually built of stone, thirty or forty feet high, and lined inside with fire-brick. The charcoal, or coke, and the ore, in proper proportion, with the necessary flux, are thrown in at top; and AA are pipes leading from a powerful bellows, worked by water or steam- power, for supplying the blast of air. This air thus forced in, will, of course, be of the same temperature as the external atmo- sphere, and constitute the cold blast; but sometimes the hot blast is used, in which case the tubes are so arranged over the top of the furnace-that they are kept hot by the blaze from the burning. mass, and the air, passing through them, becomes heated, and enters the fire at a temperature of 400° or 600°. When once put in operation, a furnace is usually kept in full employment for many months, until repairs are needed; the fucl, Blast-Furnace. Questions.—What is used for flux when the ore is dug from siliceous rocks? Describe the blast-furnace used for reducing ores of iron. How is the air sometimes heated before being forced into the furnace? Isa furnace, when once heated, kept long in operation ? IRON. "351 with a proper proportion of ore and flux, being regularly supplied at the top. The iron obtained by this process is the cast or pig-iron of com- merce, and contains a considerable quantity of carbon and other substances, by which it is rendered much more fusible than pure iron, but is at the same time harder and more brittle. It receives it name from the fact that it may be cast, or melted, and poured into moulds, so as to form articles of any desired figure ’ For this purpose, a pattern of the desired article is formed of wood, and moulded in sand; and the melted metal is poured into the cavity thus produced. The iron is usually melted Pouring Cast-iron. in a cGpola furnace, and drawn off in vessels lined with clay (see figure), from which it is conveniently poured. ; To convert cast into malleable iron, it is exposed, in a melted state, to a current of air, which pisyee over its surface, or is forced through it. The process is usually conducted in a reverberatory fur- nace, a section of which is shown in the figure in the margin. G is the grate upon which the fire is kindled, and HH the hearth which contains the melted metal. As the blaze from the fuel passes to the chimney, C, it comes in contact with the melted iron, and the carbon it contains—and per- haps other impurities—is gradually burnt out, and the iron becomes malleable. This process is called puddling. But it is not absolutely essential that cast-iron should be fused in order to be changed into the malleable state. When small LEE > = LZ ee A Quzstions.—What is the kind of iron obtained by the process de- scribed? Why is it called cast-iron? How is it fashioned into articles of any desired form? How is cast-iron converted into malleable iron? May small articles made of cast-iron be converted into malleable iron without being fused? Describe the process. 352 IRON. articles made of cast-iron are heated for a time in contact with powdered oxide of iron in close vessels, they are converted into malleable iron, and still retain their form perfectly. The carbon is gradually extracted by the oxygen of the oxide of iron used. 433. Properties—We have already, under the last head, in part described the properties of iron. It is a hard metal, of a peculiar gray color, and strong metallic lustre, which is sus- ceptible of being considerably heightened by polishing. Heated to redness, it becomes very soft and pliable, and is easily worked under the hammer, which gives it a decidedly fibrous structure. When malleable iron is strongly heated, it does not at once change to the liquid state, like most of the other metals, but becomes soft and pasty at the surface; so that two pieces in this state, upon being hammered or firmly pressed together, unite in one piece, or are welded together. Iron is, perhaps, all things considered, the most useful metal known, and it is owing in a great measure to this property, in which it is peculiar; only a few other metals possessing it, in an inferior degree. Iron has a strong affinity for oxygen, and exposed to the air and moisture, it rusts,,or oxydizes. Heated intensely in the blacksmith’s forge, or in the flame of the compound blowpipe, it burns with brilliancy. The same effect is produced by igniting a wire in a receiver of oxygen gas (192), or dropping iron-filings into the flame of a spirit-lamp. It has the property also of be- coming magnetic, under the influence of another magnet (121), or of the galvanic current (136). But pure iron loses its mag- netism when the influence of the current is removed. Some of the compounds of iron, especially steel and the black oxide, how- ever, retain their magnetism permanently. The iron of commerce is never pure, but contains in combination more or less carbon, and other substances. Perfectly pure iron can be obtained only by heating one of the oxides, Qurstions.—483. Describe the properties of iron. How is malleable iron affected when heated to redness? Describe the process of welding. Are there other metals capable of being welded? What is said of the affinity of iron for oxygen? How is it affected when exposed to air and moisture? How may iron be made to burn? How may pure iron bo procured? . IRON. 353 or the protochloride, in an atmosphere of hydrogen. For this purpose, the same apparatus may be used as figured in paragraph 426 for forming protoxide of manganese. The oxide or chloride being heated by a lamp, is decomposed by the current of dry hydrogen, and the iron remains as a grayish-black powder, which may take fire spontaneously if the air be admitted, but may be preserved any length of time by seal- ing the tube hermetically. By reducing the iron in a porcelain crucible, at a very high temperature, it may be obtained in a solid mass, with a metallic lustre. : 434, Steel is a carbonide of iron. It is formed by heating bars of malleable iron in close vessels in contact with charcoal, by which process a small quantity of carbon is absorbed and incorporated with the iron. This process is called cementation ; and, although the proportion of carbon absorbed by the iron is small, yet very important changes are produced in its properties. It becomes more fusible, and may now be melted like cast-iron, and at the same time has become harder, and is capable of being tempered, that is, of being made hard or soft, at pleasure. This is done by first heating the article to redness, and then cooling it suddenly by plunging it into cold water, or oil, by which it is made very hard and brittle, and subsequently heating it mode- rately, and allowing it to cool slowly. By the last heating, a partial annealing (336) is effected, and, if the operation has been well conducted, a proper degree of hardness is produced. ~ Bars of steel, from the cementation process, always present a blistered surface, occasioned by the liberation of gaseous mat- ter—probably carbonic oxide—within their substance; but when the metal has been melted and: cast in moulds, it has a per- fectly uniform texture, and is called cast-steel. The melting of blistered steel, to form cast-stcel, requires a very high temperature, and is performed -in w furnace, a vertical sectior of which is represented by the first figure on next page. A is a small rectangular chamber, containing the crucible and fuel, and connects with the chim- ney, C, by a horizontal flue, B. The top of this chamber is covered with a lid, EF, which may be removed, at pleasure, to allow the introduction of the fuel and the crucibles, and the current of air is regulated by a damper, R. The crucibles are made of the most refractory clays, and of the form represented in the second figure. When the steel is perfectly Quzstions.—434, What is steel? How isit formed? In what does it differ from iron in its properties? ow are bars of blistered steel con- verted into cast-steel? How are articles made of steel tempered? What is meant by this? 30 * 854 IRON. fused, the crucible is withdrawn, and the melted metal poured into iron ingot oulds prepared for the purpose. : Melting Furnace. Binary Compounds of Iron. 435. Oxides of Iron.—There are four oxides of iron, as follows, viz :— The protoxide, FeO, which is a powerful base. The sesquioxide, Fe,O,, which is a feeble base, isomorphous with alumina, Al,O;. It is often called the peromide. The oxide, Fe,O,, called also black or magnetic oxide, which is considered a compound of the proto and sesquiowides j—thus, FeO + Fe,0;=Fe,0,. It belongs to the class of “saline oxides” (344 : 4). Ferric acid, FeOs. The red, or sesquioxide of iron, is obtained by heating green vitriol (sulphate of the protoxide of iron) to redness in the oper air, and is used as a polishing-powder, under the name of rouge Qurstions.—435. Describe the oxides of iron. How is the red or ses- quioxide obtained ? IRON. 855 or colcothar. Earth or clay highly impregnated with it forms the red ochre used by painters. The black oxide constitutes the scale that always forms upon the surface of iron when heated to redness in the open air. Large accumulations of it are often seen by the side of the smith’s anvil. This oxide, found native, con- stitutes the native magnet, or loadstone, as stated above. It is found crystalized in beautiful octahedrons, and in masses, and is one of the best ores of the metal. Ferrie acid, FeO,, in combination with potash, as ferrate of potash, is formed by heating a mixture of iron-filings and nitrate of potash in an iron crucible; and the salt may be separated from the mass by treating it with cold water. It cannot be obtained in a separate state. 486. Chlorides of Iron.—There are two chlorides of iron, the proto- ‘ehloride, FeCl, and the sesguichloride, Fe,Cl,; the first may be obtained by dissolving iron in hydrochloric acid, and the second by treating the sesquioxide in the same manner. They possess no particular interest. 437. Sulphides of Iron—The protosulphide, FeS, of iron is readily formed by heating a mixture of iron-filings and sulphur, or by pressing a bar of iron heated to whiteness into a mass of sulphur. The sulphur and iron combine with great energy, and the liquid sulphide collects in a mass at the bottom, forming, on cooling, a hard, brittle solid. It is used in preparing hydrosul- phuric acid (263). Bisulphide of tron, FeS,, is the tron pyrites of mineralogists. It is of a beautiful yellow color, resembling gold, for which it has often been mistaken. ,It is usually ecrystalized in cubes. It is used in the manufacture of green vitriol and sulphuric acid, and sometimes for extracting its sulphur. Though the sulphides of iron are very abundant in nature, they cannot be used for the extraction of the metal, because of the great expense it requires, and the iron obtained is of an inferior quality. * t 438. Carbonides of Iron.—Both cast-iron and stcel, as we have seen, are considered as carbonides of iron, but the ingredients do QueEstions.—What is the red ochre of painters? What is the natural magnet, or loadstone? 436. Describe the chlorides of iron. 487. Describe the sulphides of iron. How may the protosulphide be formed? For what is the bisulphide sometimes mistaken? 4388. What is said of tho carbonides of iron? 356 SALTS OF IRON. not seem to be united exactly in definite proportions. Cast-iron usually contains from 2 to 5 per cent. of carbon, while steel seldom contains as much as 2 per cent. Graphite, called also plumbago, and black lead, has been considered as a carbonide of iron, but probably it is only a particular form of carbon, usually containing a portion of iron as an accidental impurity. It is found abundantly in nature, and is used in the manufacture of pencils and crucibles, and as a polishing-powder for stoves and other articles made of iron. Protiodide of iron, Fel, is formed by digesting iron-filings or wire in water containing iodine, and evaporating the solution obtained. It is used in medicine. Salts of Iron. 439. Carbonate of Iron, FeO,CO,, occurs native and is called spathic tron, or steel ore, by mineralogists. An impure variety is called clay-iron stone. It may also be obtained by adding solution of carbonate of soda to solution of green vitriol. Car- bonate of iron, though insoluble in pure water, is dissolved by water charged with carbonic acid, and is thus contained in the water of chalybeate springs. 440. Sulphate of iron, FeO,SO;.—This salt is the green vitriol or copperas of commerce, so extensively used in the arts, In crys- tals it contains 7 eq. of water, and its formula of course is FeO,SO, +7HO. The crystals belong to the monoclinic system. It is a sulphate of the protoxide, and is prepared on a large scale at Strafford, Vermont, and other places, from iron pyrites, which is first roasted slightly, and then exposed in heaps to the atmo- sphere, from which oxygen is absorbed, converting the sulphur into sulphuric acid, and the iron into oxide of iron; the two together then “uniting to form the salt in question. For use in the laboratory, it is readily formed by the action of dilute oil of vitriol upon metallic iron. It often forms upon specimens of Questions.—What is graphite? 489. Is carbonate of iron found na- tive? What is it called by mineralogists? 440. What is the green vitriol or copperas of commerce? How is it manufactured in Vermont? What use is made of it? CHROMIUM. 357 iron ores contained in cabinets, by the action of the atmosphere, and is seen as a yellowish-white powder. It is used in coloring black, and in the manufacture of writing- ink, and for other purposes. When this salt is heated it first parts with its water, and at a full red heat, with its sulphuric acid, a portion of which is de- composed into sulphurous acid and oxygen, but the rest passes off unchanged. By the oxygen of the decomposed acid, the | iron is peroxydized, orig the colcothar of commence, befora® mentioned. 441, Nitrate of Iron, FeO,NO,.—Nitric acid acts readily upon iron, and at the same time with the nitrate of iron there is formed also nitrate of ammonia, the ammonia being produced by the union of a portion of the nitrogen of the acid with the hydrogen of the water. The nitric acid should be considerably diluted. 442, Tests of Iron—The usual test for iron is solution of yel- low prussiate of potash, which forms with it a beautiful blue. For an experiment, let a small quantity of common hydrochloric acid be largely diluted with water, and then pour into it a few drops of solution of this prussiate, which will instantly give a fine sky- blue color if iron be present in the acid, as is almost certain to be the case. The iron is derived from the utensils made use of in the manufacture of the acid. With tincture of nutgalls, the soluble salts of iron form at first a dark-blue precipitate, which finally becomes black. CHROMIUM. Symbol, Cr; Equivalent, 26-7; Density, 6 443. History, Ete.—-Chromium was discovered in 1797. It is found in considerable abundance in Massachfsetts, Penn- sylvania, and other States, in the mineral called chrome iron, and also in combination with oxide of lead. Its name comes from the Greek chroma, color, in allusion to the splendid color Quesrions.—441. How is nitrate of iron formed? 442. What tests of iron are mentioned? 443, What is said of chromium? From what ig the name derived ? 358 SALTS OF CHROMIC ACID. of many of its compounds. It is prepared by heating its oxides mixed with charcoal, but not without difficulty. The metal has a white color, and distinct metallic lustre. It is very brittle, and with difficulty fusible. Metallic chromium is not used in the arts, but several of its compounds are important. Binary Compounds of Chromium. 444, Oxides of Chromium.—Oxygen forms several compounds with chromium, which, in composition and many of their pro- perties, are analogous to the oxides of iron and. manganese} so that these three metals form a kind of natural family, in the same manner as potassium, sodium, and lithium. Only two of these oxides, the sesquioxide, Cr,O,, and the teroxide, or chromic acid, CrO,, are of sufficient importance to claim attention here. The former of these, Cr.03, in combination with protoxide of iron, form- ing the compound, Fe0,Crg05, constitutes the native chromic iron, which is the most abundant ore of the metal. It may be prepared by various modes, but the following is perhaps the best, as it leaves the oxide ina proper state for use in the arts. Heat ina crucible an intimate mixture - of 4 parts of bichromate of potash and 1 part of starch, and wash the mass thoroughly with hot water, to separate the carbonate of potash that has been formed. The residue, after being dried, is again heated, and the pure sesquioxide remains. Sesquioxide of chromium is not decomposed by heat, and when fused with fluxes, it imparts to them a green color. It is used in staining glass and porcelain. It replaces alumina (415) in the chromic alums. Chromic acid CrO,, is prepared by decomposing a saturated solution of bichromate of potash with 14 times its volume of oil of vitriol; bisul- phate of potash is formed, and the chromic acid separates in brilliant red crystals, which are very soluble in water, and deliquescent in the air. It is a powerful oxydizing agent, and strong alcohol thrown upon tke dry crystals is very soon inflamed. With bases it forms important salts, The chlorides and sulphides of chromium are not important. Salts of Chromic Acid. 445, The Chromates of Potash are formed by heating a mix- ture of native chrome iron in powder with nitre, digesting the Quxstions.—444, What is said of the oxides of chromium? How may the sesquioxide be formed? How is chromic acid prepared? What is said of the action of alcohol upon it? 445. How is bichromate of potash formed ? i ZINC. 359 mass obtained in hot water, and saturating the solution with dilute sulphuric acid. After a little time the clear red liquid is poured off, and evaporated, when crystals of bichromate of potash, KO, 2CrO,, are separated, from the excess of sulphuric acid present, and the sulphates of iron and alumina. The neutral chromate of potash, KO,CrQ,, is now easily pro- cured by neutralizing a solution of the bichromate with carbonate of potash, and crystalizing. The bichromate, which is of a deep red color, is much used in dyeing, and in calico-printing, and for many purposes in the chemical laboratory. 446. Chromate of Lead, PbO,CrO;.— This is the beautiful chrome yellow, used as a paint. It is formed by mixing solutions of one of the chromates of potash and acetate or nitrate of lead. The beauty of the color will depend somewhat on the strength of the solutions used, and other circumstances. Chrome green is formed by mixing the chromate of lead with Prussian blue, in a particular stage of the process of manufacture. ZINC. Symbol, Zn; Equivalent, 32:5; Density, 7. 447, History.—This metal has been known several centuries, but was not, for many years, much used. Its chief ores are calamine, which is a native carbonate, and d/ende, which is a sulphide; but several others are known. ‘These ores are found in considerable abundance in New Jersey, and other parts of this country. . 448. Preparation.—The ores of zinc are reduced by first roasting them in the open air, and then distilling them with charcoal in close crucibles, from which a tube descends directly Questions.—How is the neutral chromate of potash formed? 446. De- scribe the mode of preparing chromate of lead. By what name is it familiarly known? What use is made of it? How is chrome green pre- pared? 447. Has zinc been long known? What ores of it are men- tioned? 448. Describe the mode of reducing the metal from its ores, 360 ZINC. through the bottom. The metal is volatilized by the heat, and descends through the tube, from which it is received into a vessel of water. The necessity of excluding the air perfectly, arises from the fact that vapor of zinc, on coming in contact with the oxygen of the air, is at once oxydized; and the object of having the tube which conveys away the volatilized metal pass directly downward, is, to preserve its temperature so high that it shall not be- come clogged by the condensed metal. The figure in the margin represents the section of a crucible used for this purpose, with its charge of ore and charcoal, and,tube made of fire-clay passing downward through the bottom. The cover is carefully luted on, and it is supported a little above the grate of the furnace by a fire-brick. The zinc, as it is separated from the ore, taking the gaseous state, passes downward through the tube into a basin of water placed below to receive it. The part of the tube below the bottom of the crucible, not being surrounded by the fire, remains comparatively cold; and the metal, before it reaches the water, is condensed to the liquid state, and falls in drops into the water. Commercial zinc usually contains iron, lead, and other impurities, from most of which it may be separated by distillation in this manner. Crucible for reducing Zine 449. Properties—Zine has a bluish-white color and a strong metallic lustre. In masses, it always has a highly crystaline structure, and in commerce it is called spelter. When cold it is quite brittle; but heated to about 300°, it becomes malleable, and may be rolled into thin sheets. Heated to 773°, it melts; at a little higher temperature, in the open air, it takes fire and burns with a brilliant white flame, producing the protoxide, which assumes an exceedingly delicdte gossamer appearance, and has been called nihil album, philosophers’ wool, and by other names. Zinc is much used in the arts, in the preparation of brass, in the construction of galvanic batteries, and, rolled in thin sheets, as a substitute for sheet-iron and tin-plate. Recently it has been \ QueEstions.—Why is it necessary to exclude the air? form of crucible used in reducing these ores. 449. Describe the pro- perties of zinc. What is its melting point? What is produced when it is highly heated in the open air? What use is mada of zinc? Describe the SALTS OF ZINO. 861 considerably used as a coating for sheet-iron, in the same manner as tin, to protect it from oxydation. The iron thus prepared is known in the arts as galvanized iron. Binary Compounds of Zinc. 450. Protoxide of Zinc, ZnO.—This is the only oxide of zine known. It is of a yellowish-white color, and may be prepared, as above described, by heating zinc in the open air, or by precipi- tating it from solution of white vitriol (sulphate of zinc) by car- bonate of ammonia. It is much used in painting as a substitute for white lead; and is manufactured on a large scale directly from the ores of zine, in France, and in New Jersey. 451. Chloride of Zinc, ZnCl—Chloride of zine is formed by dissolving commercial zine in hydrochloric acid, or by burning zinc in chlorine gas. By evaporation it may be obtained as a white solid, but is very deliquescent in the air. Mixed with sal-ammoniae, it serves an excellent purpose in tinning articles of copper, brass, and other metals. Sulphide of Zine, ZnS.—This compound of zine is found native, and constitutes, as has been stated, one of its ores. It may be prepared arti- ficially by heating the metal with sulphur. Salts of Zinc. There are several salts of zinc, but the most important is the following :— . . 452. Sulphate of Zinc, ZnO,SO,.—Sulphate of zinc is a white salt, which, in commerce, is called 2zohite vitriol. It is very soluble in water; and is sometimes used in medicine as a power- ful emetic. The ordinary salt contains 7 atoms of water of crystalization, and its formula is Zn0,SO, + 7HO; but by using the proper means, it may be crystalized with 5, 2, or even 1 atom of water. _Quzstions.—450. What is the only oxide of zinc that isknown? What use is made of it? 451. How is chloride of zinc formed? To what use is it applied? 452..What is sulphate of zinc called in commerce ? 31 362 CADMIUM.—TIN. Oxide of zinc is precipitated from its soluble salts by the caustic alka- lies, but the precipitate is again dissolved by an excess of the alkali. Carbonate of zine is found native, and called calamine. CADMIUM. Symbol, Cd; Equivalent, 56; Density, 8-6. 453. History, Ete —Cadmium is a very volatile metal, usually found associated with zinc. In appearance it can scarcely be distin- guished by the eye from tin, but is rather harder. It melts at 442°, —the melting point of tin,—and sublimes at a temperature but little above the boiling point of mercury. Its properties indicate that it would be a useful metal in the arts, but it has hitherto been found only in small quantities. Protoxide of Cadmium, CaO, is the only compound of these two elements that is known. The protosulphide, CdS, is found native, as the grenockite of mineralogists. TIN. Symbol, Sn (Stannum); Equivalent, 58; Density, 7:3. 454. History.— Tin has been known from the most remote antiquity, and was in common use in the time of Moses. It is supposed the ancients obtained it chiefly from Cornwall, England, the mines of which still yield a large part of the tin of commerce. It is found also in India, Germany, Chili, and Mexico; but has not yet been discovered in the United States, except a few small crystals of the oxide in Chesterfield, Massachusetts, and at Mid- dletown, Connecticut, and a small vein of the same ore in tho town of Jackson, New Hampshire. The chief ores are the oxide and sulphide. 455. Preparation and Properties. — Most of the tin of com- merce is obtained from the oxide, which is reduced by the action Questions.—453, What is said of cadmium? What is its melting point? 454. Has tin been long known? Where was it obtained in ancient times? What countries now produce tin? Is it found in the United States? What are the chief ores of tin? 455. Mention some of its more important properties, : ‘ BINARY COMPOUNDS OF TIN. 363 of charcoal at a high temperature. It is a brilliant white metal, like-silver, but is less hard than the latter It is very malleable, and is rolled into very thin leaves, called tin-foil. It is inelastic, and when a rod of it is bent, a peculiar crackling noise, called the cry of tin, is produced, occasioned by its erystaline structure. It melts at 442°, and at a red heat is rapidly oxydized; at a white heat it burns with flame. Tin is not readily acted on by the atmosphere or by moisture, but is dissolved slowly by hydrochloric acid, forming chloride of tin, and by hot sulphuric acid, forming sulphate of the protoxide; by dilute nitric acid it is converted into the binoxide, which is insoluble in the acids. Uses.—Tin is used for many purposes in the arts, both alone and combined with other metals, as in Britannia metal, which is an alloy of tin and antimony, with a small proportion of copper. It is also used extensively to coat sheets of copper and iron, to prevent the oxydizing influence of the air and moisture, and other agents. Thin sheets of iron, coated over with tin, constitute the well-known and highly useful ¢in-plate. Binary Compounds of Tin. 456. Oxides of Tin.—There are two well-defined oxides of tin, the protoxide, SnO, and the peroxide, SnO,; but the latter alone possesses sufficient importance to require a description. Peroxide of Tin is formed by exposing the metal to the action of nitric acid a little diluted. It may also be precipitated from a solution of the perchloride of tin (soon to be described) by an alkali. As obtained by the mode last mentioned, it is soluble in acids, but not as procured by the other mode. Itis of a yellowish-gray color, and from the circumstance that it is capable of combining with bases in the manner of an acid, it ‘has been called stannic acid. It is much used as a polishing-powder, underthe name of putty of tin. Melted with ingredients for forming glass, it produces a white enamel. - ° 457. Chlorides of Tin.—Protochloride of Tin, SnCl, is formed by dis- solving tlie metal in boiling hydrochloric acid. By evaporating the solution it may be obtained in crystals, which contain 2 eq. of water. It is used as a mordant in dyeing, and as a powerful deoxydizing agent in the laboratory. The perchloride, SnCl,, is formed by distilling a mix- ture of 1 part of tin-filings and 3 parts of corrosive sublimate, or by cau- Questions.—To what use is tin applied? What is the tin-plate of com- merce? 456. What oxides of tin are known? What is the substanco called putty of tin? To what use is it applied? 457. What chlorides of tin are there? 364 COBALT.— BINARY COMPOUNDS OF COBALT. tiously dissolving the metal in nitro-bydrochloric acid. It is much used as a mordant in dyeing, and as a disinfecting agent. There are two sulphides of tin ;—the persulphide, SnS,, sometimes called aurum musivum, or mosaic gold, has a yellow color, and metallic lustre, and is used as a paint, and also instead of the zinc amalgam (90) for exciting electrical machines. There are no important salts of tin. COBALT. Symbol, Co; Equivalent, 29:5; Density, 8°5. 458, History, Etc.—Cobalt is almost always found associated with nickel, the metal next to be deseribed ;—as found in mines both are usually in combination with arsenic. The pure metal is obtained with some difficulty. The best mode is to heat oxa- late of cobalt in a small crucible, on which a cover is closely luted. It is of a reddish-white color, and is hard and brittle, and difficult to fuse. It is capable of becoming magnetic. Cobalt is comparatively a rare metal. In combination with arsenic, it -is found at Chatham, in Connecticut, in the minerals called smaltine and chloanthite. a Binary and Other Compounds of Cobalt. 459. Oxides of Cobalt.—There are two oxides of cobalt, the protozide, CoO, and the sesqguioxide, CogO3, the former of which, mixed with some impurities, is sold in commerce as a gray powder, under the name of zaffre. Fused with silica and potash, it forms smait, which is used for coloring glass, porcelain, &., blue. The sesgui or peroxide is unimportant. 460. Chloride of Cobalt, CoCl, is formed by dissolving zaffre in hydro- chloric acid. The solution has a pink color, and yields by evaporation small crystals of the same tint. Writing made with a diluted solution of it is nearly invisible, but becomes of a beautiful but pale blue color when the paper is warmed by the fire, and again disappears as the paper cools. It has been called Hellot’s Sympathetic Ink. The addition of a salt of nickel gives the writing a green color. The salts of cobalt possess no especial interest. The subcarbonate is a fine powder of a very delicate pink tint. i . Questions.—What sulphides of tin are there? 458. With what other metal is cobalt usually found associated? Where is this metal found? 459. What oxides of cobalt are there? 460. How is chloride of cobalt formed? Describe the mode of using Hellot’s Sympathetic Ink. NICKEL.—ANTIMONY. 865 NICKEL. Symbol, Ni; Equivalent, 29-6; Density, 8-8. 461. History, Ete—Nickel and cobalt, as before intimated, are in nature almost inseparable companions. Arsenical nickel and cobalt are found at Chatham, in Connecticut, and also in Missouri, and in various places in Europe; but mines of these metals are not common. Nickel is generally, if not always, com- bined with meteoric iron (431), of the mass of which it sometimes constitutes as much as ten per cent. ‘Pure nickel has a grayish-white color, and strong metallic. lustre. It is quite hard, but malleable, and is nearly as difficult to melt as iron. Like iron and cobalt, it is capable of becoming magnetic. It is not readily acted upon by the air or by moisture. It is much used in the arts to form the alloy called German silver, which is composed of copper 10 parts, zinc 6, and nickel 4. None of the compounds of nickel possess sufficient interest to require description here. * Group V. ANTIMONY BisMuTH Leap CoprEr Metals which are incapable of decomposing water, and VANADIUM whose oxides are not reduced by the mere action of heat. MoLYBDENUM All of them, except lead and copper, are brittle; and TUNGSTEN all, except antimony, bismuth, lead, and copper, are TITANIUM fusible only at very high temperatures. URANIUM CoLuMBIUM PELOPIUM ‘ ANTIMONY. Symbol, Sb (Stibium) ; Equivalent, 129; Density, 6-7. 462. History.— Antimony is remarkable as having been the first metal discovered after the seven metals (332) known to the Quzstions.—461. What is said of the metal nickel? In what.is it almost always found? Describe the metal. For what isit used? How are the metals of Group V. characterized? Name the metals of this group. Ate For what is antimony remarkable? 866 BINARY COMPOUNDS OF ANTIMONY. ancients. It has been found in the metallic state, but is prepared chiefly from the sulphide, which is not of unfrequent occurrence. 463. Preparation.—The metal, called also regulus of antimony, is obtained by heating the sulphide with iron-filings, or carbonate of potash. When iron-filings are used, the sulphur is simply transferred from the antimony to the iron, and, of course, sul- phide of iron is formed; but the metal thus obtained always contains a portion of iron, and is otherwise impure. By the other process, the sulphur is converted into sulphuric acid, which combines with the potash, forming sulphate of potash; and the metallic antimony, being thus set free, falls to the bottom of the crucible. 464, Properties.—Antimony is a very brittle metal, of a white color, and brilliant lustre. It always has a highly crystaline structure, and melts at a temperature a little below redness; and may be slowly distilled in a current of hydrogen gas. A small fragment, heated on a piece of charcoal, before the blowpipe, takes fire; and when thrown upon the floor breaks into numerous globules, which continue to burn as they are scattered, leaving a train to mark their path, and filling the air with fumes of the oxide. 465. Alloys of Antimony.—Antimony, being very brittle, is not adapted for use alone in the arts, but with other metals it forms several very useful alloys. One of these, called Britannia metal, is composed, of tin 88 or 90 parts, and antimony 12 to 10 parts. Sometimes a small proportion of copper is added, not exceeding 3 or 4 per cent. of the whole. Its alloy with lead will be described hereafter. Binary Compounds of Antimony. 466. Oxides of Antimony.— Antimony forms with oxygen two com- pounds which are well-defined, viz., oxide of antimony, SbO,, and anti- monic acid, SbO,; but these are capable of combining with each other so as to form one or two other intermediate compounds. Questions.—463. How is antimony obtained from the native sulphide? Describe the two processes. 464. Describe the metal. How is it affected when intensely heated in the air? 465. What alloys of antimony are used in the arts? 466. What oxides of antimony are mentioned ? BISMUTH. 367 467, Chlorides of Antimony.— There are two chlorides of antimony, SbCl,, and SbCl;, corresponding in composition, it will be seen, with the oxides. : The terchloride, SbClg, is sometimes called butier of antimony. It is soluble in a small quantity of water, but if the solution be diluted, a white powder is precipitated, called powder of algoroth. It is an oxy- chloride, SbCls,2Sb0, + HO. 468. Sulphides of Antimony.—Two sulphides of antimony are known, corresponding in composition with the oxides and chlorides, and having the formula SbS,, and SbS,. The first of these is the native sulphide ;— when this is roasted in the air, oxygen is abSorbed, and -oxysulphide of antimony, SbS, + SbO,, is formed, often called glass of antimony, or liver of antimony. When the native sulphide is boiled in a solution of potassa or soda, a liquid is obtained, from which, on cooling, an orange-red matter is de- posited, called Kermes mineral. On subsequently neutralizing the cold solution with an acid, the golden sulphide of the pharmacopeeia is ob- tained. These compounds now possess little interest, but formerly were much used in medicine. The salts of antimony are unimportant, except tartar emetic, used in medicine, which will be described hereafter. BISMUTH. Symbol, Bi; Equivalent, 213; Density, 9-8. 469. History, Etc.—Metallic bismuth is found in small quan- tities in Monroe, Connecticut, and other places, but is chiefly obtained from the native sulphide. In mass, it much resembles antimony in its erystaline structure, but has less lustre, and is of a reddish color. It is brittle when cold, but may be ham- mered when moderately heated. It melts at about 477°, and sublimes at a high temperature. By melting a considerable quantity in a large crucible, placing it in a situation to cool very slowly, and pouring off all that remains liquid, as soon as it begins to solidify at the surface, crystals of considerable size may be obtained. The metal is unchanged in the atmosphere, but tarnishes slightly by moisture. Heated in the open air it burns with a bluish flame. It is too brittle for use by itself in the arts, but with some other metals Qurstions.—467. What is said of the chlorides of antimony? 468. What sulphides of antimony are known? 469. Is bismuth found native? De- scribe the metal. May it be obtained in crystals? What is said of ite use in the arts? 368 LEAD. it forms important alloys. It may be substituted, in whole or in part, for antimony in Britannia metal (465). : In some of their chemical properties, antimony arid bismuth are analo- gous to phosphorus and arsenic, and also to nitrogen. Binary and other Compounds of Bismuth. There are several oxides, chlorides, &c.; but they possess no special interest. 470. Nitrate of Bismuth, BiO0,NO,;.—This salt is formed by dissolving the metal in nitric acid. It is soluble in water; but if the solution is largely diluted, the salt is decomposed, and subnitrate of bismuth precipi- tated. This last salt is used in medicine, and also as a cosmetic. LEAD. Symbol, Pb (Plumbum); Equivalent, 103-7; Density, 11-44. 471. History —Lead is one of the seven metals known to the ancients. Its most important and most abundant ore, from which all the lead of commerce is extracted, is the sulphide, the galena of mineralogists ; but it is found in many other forms, as carbonate, sulphate, phosphate, &c. It is very abundant in different parts of this country. 472, Preparation—The metal is reduced from the native sul- phide by first roasting it in the open air, and subsequently heating it with lime in a charcoal fire. The ore usually contains a little silver, which remains in combination with the lead. The metal is also easily reduced by heating the native sulphide, in fine powder, with iron nails, in a close crucible. The sulphur of the ore, in this case, passes directly to the iron, forming sul- phide of iron. 473, Properties.— Lead is a bluish-gray metal, and when recently cut has a strong metallic lustre; but the surface soon tarnishes on exposure to the air. It is soft and malleable, but Qurstions.—470. Describe the nitrate of bismuth. 471. What is the most common ore of lead?, What other ores are mentioned? 472, How is the metal reduced from the native sulphide? What is the second mode mentioned? 478. Describe the properties of lead. BINARY COMPOUNDS OF LEAD. 369 not very tenacious. Heated to about 635° it melts, and at very high temperatures is slightly volatilized. Exposed to the air and moisture, it is gradually corroded; and a crust, the white car- bonate, is formed upon its surface. The peculiar properties of lead fit it for use in the arts for many purposes; but one of its most important uses is in con- structing pipes for conveying water. But when the water is to be used for drinking, care should always be taken to have the tubes kept constantly filled with water, as the introduction of air tends to form the highly poisonous carbonate; and even then the water should not be used until it has been proved by experiment that the particular water to be discharged by the tube is not capable of acting upon the lead. Lead is gradually acted on by boiling sulphuric acid; but its only proper solvent among mineral acids is the nitric, which forms with it a soluble salt. 474, Alloys of Lead.—Lead forms with other metals many useful alloys. Two parts of tin and one of lead, fused together, form soft solder, which is much used in cementing together the different pieces of articles made of tin-plate, Britannia metal, &c. A coarser kind, which requires a higher temperature to melt it, is composed of. lead 8 parts and tin 1 part. Pewter is an allay of lead and antimony, and sometimes a little copper. Type- metal is an alloy of 3 parts of lead to 1 of antimony. Tin, lead, and bismuth, form a very fusible alloy; when made of 8 parts of bismuth, 5 of lead, and 8 of tin, it will melt in boiling water. Binary Compounds. of Lead. 475, Protoxide of Lead, PbO.—Protoxide of lead is formed by heating lead, in the open air, a little above its melting point; oxygen is gradually absorbed, and a yellow powder formed, which was formerly used as a paint, and called massicot. As usually manufactured, it is in the form of reddish-yellow scales, occa- Qurstions.—What is said of the use of lead for water-pipes? What is the only mineral acid that dissolves lead? 474. What alloys of lead are mentioned? What is pewter? Type-metal? What alloy of lead melts in boiling water? 475. How is protoxide of lead formed? 370 % SALTS OF LEAD. sioned by its having been partially fused. It is much used in painting as a dryer, and is called litharge. It fuses readily at high temperatures, and enters into combination with several of the earths and alkalies, producing a transparent glass, which renders it an excellent substance for glazing some kinds of earthenware. With powerful bases it is capable of combining as an acid. 476. Peroxide of Lead, PbO,.— This oxide is obtained by digesting red lead (the compound next to be described) in nitric acid, which dissolves out the protoxide, leaving the peroxide quite pure, in the form of powder. It is also called plumbic acid. 477. Red Oxide of Lead, Pb,O,.—This compound is the red lead, or minium, of commerce, much used in the arts as a paint, and as one of the ingredients in the manufacture of flint glass. It is formed by heating metallic lead to a temperature of 500° or 600°, in the open air, so as to oxydize it without fusing the oxide, and continuing the heat for some time. Heated to redness, it gives up a portion of its oxygen and is reduced to the protoxide. Minium is a compound of the proto and peroxides (2PbO,PbO,), and is therefore a plumbate of the protoxide of lead. 478. Sulphide of Lead, PbS.—This compound has already been men- tioned as constituting the only important ore of lead, called galena. It is also formed by passing a current of sulphuretted hydrogen through a solution of any salt of lead. As it occurs native, its color very much resembles that of metallic lead, and its structure is always crystaline. Salts of Lead. 479. Carbonate of Lead, PbO,CO,.—This is the white lead of commerce, so extensively used in painting. It is formed by several different modes, and is also found as a natural production.. Nearly all the white lead of commerce, at the present time, is adulterated by mizing sulphate of baryta (899) with it in fine powder. By treating the mixture with nitric acid, the carbonate Questions.—What use is made of the protoxide of lead? What is said of its fusibility? 476. Describe the mode of preparing the peroxide. 477. What is the red lead or minium of commerce? What use is made of it? 478. Describe sulphide of lead. 479. What is the white lead used by painters? With what is it usually adulterated? How may the fraud be detected? 3 COPPER. 871 of lead will be dissolved, and the baryta left as a white powder. Taken into the system, “white lead acts as a violent pale pro- ducing the disease called painters’ cholic. 480. Sulphate of Lead, PbO,SO,.—Sulphate of lead is found native, and called anglesite by mineralogists, It is also formed when solution of any sulphate, as sulphate of soda, is mixed with solution of any salt of lead. It is sometimes used in painting as a substitute for white lead. Nitrate of Lead, PbO,NO,,—Nitrate of lead is easily formed by dis- solving metallic lead, or its protoxide, or carbonate, in nitric acid. Zinc, iron, and tin precipitate lead from all its soluble salts in its metallic state. Make a solution of 1 part of nitrate or acetate of lead in 24 parts of distilled water, acidulated with acetic acid, and suspend in it, near the top, « piece of clean zinc; the precipitation of the lead will immediately commence, and in the course of 24 or 48 hours, the metal will appear in the form of large thin leaves, called sometimes arbor Saturni. 481. Test of Lead—llydrosulphuric acid precipitates‘lead as a dark- colored sulphide from all its soluble salts, and even blackens those that are insoluble, as the carbonate, when suspended as a fine powder in water. COPPER. Symbol, Cu (Cuprum); Equivalent, 31-7; Density, 8-9. 482, History.—Copper has been known from the earliest ages, and is often found in the earth in its metallic state. Masses of immense size of nearly pure metal have been found in the region of Lake Superior. One, 40 feet long, was estimated to weigh 200 tons. It is also found as a carbonate, sulphide, and oxide, as well as in other combinations. The ores of copper are very generally diffused, some of them being found in almost every country. 483. Preparation.—Metallic copper is obtained from the oxides and the native carbonates, simply by heating these ores with char- coal; but the sulphide, especially when mixed with iron, is T Qurstions.—480. What is said of the sulphate of lead? Describe the -mode of forming the arbor Saturni. 481. What test of lead when in’ solution is mentioned? 482. Has copper been long known? What is said of masses that have been found native? What ores of copper are mentioned? 483. How may the metal be reduced from its oxides and carbonates ? 372 BINARY COMPOUNDS OF COPPER. reduced with more difficulty, and the process is too complicated to be given here in detail. 484. Properties.—Copper is distinguished by-its peculiar red color. It is very ductile and malleable, but less tenacious than iron. To fuse it a bright red heat is required, but its melting point.is much below that of cast-iron. It forms crystals belong- ing to the monometric system. It is less liable to be corroded by air and moisture than iron, but is gradually acted on by the joint agency of these elements, and becomes coated with a green crust, which is carbonate of copper. Heated to redness in the air, it becomes oxydized, and nitric acid readily dissolves it. It is used extensively in the arts, both alone and in combination with other metals. 485. Alloys of Copper.—Copper forms with other metals many very useful alloys. Three parts of copper with one of zinc con- stitutes brass; and by a variation of the proportions, the alloys called tombac, Dutch gold, and pinchbeck, are produced. Bronze is an alloy of copper and about 10 per cent. of its weight of tin; and bell-metal, an alloy of 4 parts of copper with 1 of tin; while speculum metal, used for the mirrors of reflecting telescopes, con- tains about 2 parts of this metal to 1 of tin. Equal parts of copper and zine form hard solder, which is used in soldering articles of brass. Binary Compounds of Copper. 486. Oxides of Copper.—Red oxide of copper, Cu,0, is a sub- oxide; it is found native. The black or protoxide, CuO, is also found native, and is produced when copper is heated to redness in the open air. It is also easily procured by heating to redness the sulphate or nitrate of copper. There are two other oxides. Chlorides of Copper.—Of these there are two, the subchloride, Cu,(, and the protochloride, CuCl, but they possess no special interest. Suiphides of Copper.—There are two sulphides of copper, corresponding in composition to the chlorides, viz., the subsulphide, Cu,S, and the proto- sulphide, CuS. Copper pyrites, vitreous copper, and variegated copper are’ native sulphides of copper, or copper and iron, Quzstions.—484. How,is copper readily distinguished from the other metals? Describe its properties. 485. What alloys of copper are used in the arts? 486. What oxides of copper are there? What chlorides? What sulphides ? ‘ SALTS OF GOPPER. 878 Salts of Copper. 487. Sulphate of Copper, CuO,S0,, or, in crystals, Cu0,SO, + 5HO.—This is the blue vitriol of commerce; and is formed by dissolving the protoxide in sulphuric acid. It is very soluble in water, and is extensively used in the arts. Its color,is a fine blue, 488. Nitrate of Copper, Cu0,NO,, or, in crystals, Cu0,NO, + 3HO, is easily formed by dissolving metallic copper in dilute nitric acid. It does not crystalize readily; and is deliquescent in the air, and exceedingly corrosive. 489. Carbonates of. Copper——There are several carbonates of copper, a3 azurite and green malachite, which are found native, and are made use of as ores of copper. They also contain water. G'reen verditer, or mineral green, is a hydrated subcarbonate, obtained by precipitating a solution of blué vitriol with carbonate of potash or soda. — Silicates of Copper, more or less hydrated, are found native in the mineral species called dioptase and chrysocolla. 490. Arsenite of Copper, or Scheele’s green, is prepared by first dissolving arsenious acid and pearlash together in warm water, and then pouring into it gradually warm solution of sulphate of copper. It is of a beau- tiful green color, and is much used in painting. In commerce, it is called Paris green. Test of Copper.— Ammonia produces a deep blue color in diluted solutions of any of the salts of copper, by which they may always be distinguished. — 491. Vanadium, V; Eq., 68-6.—This is a metal of rare occurrence, being found only in some iron ores in Sweden, some lead ores in Scot- land and Mexico, and recently in some copper ores from Lake Superior. Molybdenum, Mo; Eq., 46,—Molybdenum is found as a sulphide in the mineral species called molybdenite; and also in other combinations. It is a white metal, and has a density of 8-6. Tungsten, W, (Wolfram); Eq., 95.—This metal is found in several mineral species, especially the species called wolfram, which is a tunr- state of iron and manganese. It forms several oxides, chlorides, sul- phides, &c. Titanium, Ti; Eq., 25.—Titanium is found in several mineral species, as rutile, anatase, and brookite. It is of a red color, and resembles cop-~ Quzstions.—487. What is the commercial name for sulphate of cop- per? 488. How is nitrate of copper formed? 489. What is said of the carbonates of copper? 490. What use is made of arsenite of copper? What test of copper is mentioned? 491. What other metals are men- tioned as belonging to this group? 32 374 MERCURY. per. Its density is about 5-8. The native oxide is used in coloring mineral teeth, so as to imitate the color of natural teeth. Uranium, U; Eq., 60.—Uranium occurs in several species as pitch- blende, uranite, &. Many binary compounds of it are known, as well as some of its salts. Columbium, Cb, is the name given to a metal found in the mineral species called columbite, which is obtained at Middletown and Haddam, in the State of Connecticut. Taritalum, Ta, is a metal very similar to the preceding, which is ob- tained from the European mineral, tantalite. Little is really known of these two metals last mentioned. The existence of the two metals named pelopium and norium (Table, p. 145), is doubtful. Group VI. Mercury SILVER 7 Goup Noble metals, whose oxides are reduced by a red heat.—No PLATINUM one of them, except osmium, is capable of decomposing Osmium water under any circumstances. Ierrom The oxides of iridium and ruthenium, and some of those PALLADIUM of osmium, are not perfectly reduced by heat, without the Ruopium presence of carbon, or some deoxydizing agent. RvurHenium MERCURY. Symbol, Hg (Hydrargyrum); Equivalent, 100; Density, 13-6. 492. History and Preparation.—Mercury, or quicksilver, is one of the seven metals of the ancients. It is sometimes found in its metallic state; but most of the mercury of commerce is reduced from the native sulphide, called cinnabar. It is not very generally diffused, there being but few mines that afford it in any considerable quantity. Most of the mercury used in this country comes from Spain; but it is obtained also in Germany, Siberia, in Southern Asia, and in California. The metal is extracted from the native ‘sulphide either by roasting it alone, so as to oxydize the sulphur and sublime the mercury; or by heating it with lime. Quzstiows.—What use is made of the native oxide of titanium? How are the metals of Group VI. characterized? Name the metals of this group. 492, Was mercury known to the ancients? By what other namo is it known? From what ore is it obtained? What is the mode of ex- tracting the metal from the native sulphide ? MERCURY. 875 Besides the native compound above mentioned, there are other ores of the metal, but they are found only in small quantities. 493. Properties. — Mercury is distinguished from all other metals by being liquid at ordinary temperatures. It is white as silver, and has a brilliant lustre. Cooled to —40°, it freezes or becomes solid, and is then very malleable, and nearly the color of lead; at 662°, it boils and forms a colorless vapor, the density ‘of which (air being 1) is 6-976. At lower temperatures, even as low as 70°, it gives off vapor, as is shown by the whitening of pieces of gold-leaf suspended above it in a close glass bottle, and by its action upon the iodized silver plates in the Daguerreotype process. The best method to obtain solid mercury is by means of solidi- fied carbonic acid (58). A portion of the solid acid is made in the form of a ball, with a cavity in the upper side to receive the mercury, and the whole enveloped in cotton to protect it from the atmosphere. In a few minutes the mercury will be solid, and may be preserved in this condition for several hours with a very small quantity of the solid acid. The metal is also readily frozen by a mixture of the solid acid and ether. By slow cooling, mercury forms crystals belonging to the monometric system. 494, Mercury is usually imported into this country in strong iron bottles, and generally is very pure, and serves for every purpose without purification. In this state it is scarcely oxydized by the atmosphere, but as it is capable of dissolving other metals, as tin, lead, silver, and gold, by use in the laboratory it often becomes contaminated with them, and thus is more liable to become oxydized, as will be shown by a pellicle of oxide floating upon its surface. In this state, a portion will adhere to the fingers, or other substance, when dipped in it; and it does not roll in perfect globules over the surface of other bodies, like pure mercury. To purify mercury, several processes are resorted to ;—-one method is to pour it into a bottle with some sulphuric acid, or dilute nitric acid, which oxydizes and dissolves the foreign metals. It should stand in the bottle several days, and be frequently shaken to expose all the metal to the action of the acid. At the proper time, the mercury is to be removed and washed with water. Quzstions.—493. Describe the properties of mercury. Give its freez- ing and boiling points. Does it evaporate at temperatures below its boiling point? How may it be solidified? 494. What other metals will mercury dissolve? How may it be known when other metals are held in solution in it? Describe the method of purifying mercury. 376 MEROURY. Another method is to distil the mercury, by which it is separated perfectly from silver, gold, and tin, bat not from arsenic, zinc, or cad- mium, which are also volatile. To distil mercury, a cast-iron vessel is used of the form represented in the figure. When using it, the cover should be well luted on, and the tube kept cold by a constant stream of cold water. To obtain mercury of sufficient pany for use in thermometers and arometers, and especially the latter, it will generally be found necessary to subject it to both of these modes of purification in succession, the distillation being first in order. Distilling Mercury. 495. The only acids that act on mercury are the sulphuric and nitric acids. The former has no action whatever in the cold; but on the application of heat, the mercury is oxydized at the expense of the acid, pure sulphurous acid gas is disengaged, and a sulphate of mercury is generated. Nitric acid acts energetically upon mercury, both with and without the aid of heat, oxydizing and dissolving it with evolution of binoxide of nitrogen. 496. Uses.—Mercury is made use of for many important pur- poses, in medicine, in the laboratory, and in the arts. In the construction of thermometers and barometers it is absolutely essential, and for the mercurial bath, to enable the chemist to collect and transfer gases that are absorbed by water. In union with various other substances it constitutes the bases of many important medicines. Several of these preparations will be described in their proper places. 497. Amalgams.— This term is exclusively applied to the alloys of mercury with the other metals. Quicksilver unites with potassium and sodium when agitated in a glass tube with that metal, forming a solid amalgam. When the amalgam is put into water, the alkaline metal is gradually Questions.—What will be necessary, in order to obtain mercury of sufficient purity for thermometers and barometers? 495. What acids only act upon mercury? Explain the action of sulphuric acid. Of nitric acid. 496. To what uses is mercury applied? 497. To what is the name amalgam given? BINARY COMPOUNDS OF MEROURY. 377 oxydized, hydrogen gas is disengaged, and the mercury resumes its liquid form. A solid amalgam of tin constitutes the silvering of looking. glasses; and an amalgam made of J part of lead, 1 of tin, 2 of bismuth, and 4 of mercury, is used for silvering the inside of hollow glass globes. This amalgam is solid at common tem- peratures; but it is fused by a slight degree of heat. The amalgam of zinc and tin (90) is used for promoting the action of the electrical machine. Binary Compounds of Mercury. 498. There are two oxides of mercury, the gray oxide, which is considered a suboxide, Hg,0, and the protoxide, HgO, which is of a red color. The suboxide, Hg,0, is readily prepared by mixing calomel briskly in a mortar with pure potassa in excess, so as to effect its decomposition as rapidly as possible, and then washing the precipitate formed in cold water, and drying sponta- neously in a dark place. This oxide is a black powder, and is insoluble in water, but unites with the acids as a weak base. The protoxide, HgO, is the red precipitate used in medicine. It is formed either by heating mercury nearly to its boiling point in a vessel to which the air has access, or by cautiously heating the nitrate so as to expel the nitric acid. The latter mode is the one usually adopted. It is usually seen in very small, shining, erystaline scales, which have a brick-red color. Heated to red- ness, it is decomposed, yielding mercury in the gaseous state, and oxygen. Red oxide of mercury is slightly soluble in water, and gives it an alkaline reaction. 499. Subchloride of Mercury, Hg,Cl; eq., (200 + 35-4 =) 235-4.—This compound, the well-known calomel used in medi- cine, is easily prepared by pouring a solution of nitrate of the suboxide of mercury into a dilute solution of common salt, when Questions.—What is it that forms the silvering of mirrors? 498, What oxides of mercury are there? How is the suboxide prepared? How is the protoxide prepared? What is it called? How is it affected when heated? Is it soluble in water? 499. What is calomel? Describe the mode of preparing it. To what use is it applied? 32 * 378 BINARY COMPOUNDS OF MERCURY. the calomel is precipitated as a white powder, which is. insoluble in water and the acids when cold. It is sometimes found native, and is called horn-quicksilver, or native calomel. Its density is about 7. Calomel is sublimed without change by a moderate heat, and may be obtained in small crystals. Jt is usually seen as a white powder, with a slight yellowish tinge; and may always be known by instantly turning black as ink, when touched with a drop of aqua ammonia, or solution of any caustic alkali. This compound of mercury has long been extensively used in medicine, and the estimation in which it has been held may, perhaps, be inferred from the names by which it has been known at different times, and in different countries. The following are some of them :—Aercurius dulcis, draco mitigatus, sublimatum dulce, aquila alba, aguila mitigata, manna metal- lorum, panchymogogum minerale, panchymogogum quercetanus ! Calomel vapor has a density of nearly 8-2, and is composed of 1 vol. of mercury vapor, 4 of a vol. of chlorine condensed to 1 vol. ‘Thus, 1 vol. of mercury vapor weighs 6-976 4 ‘“ chlorine * «1.220 1 vol. subchloride vapor weighs 8-196 500. Chloride of Mercury, HgCl; eq., (1004-35:4 =) 135-4. —Chloride of mercury—the corrosive sublimate of the pharma- copweia—is obtained either by acting on mercury by nitrohydro- chloric acid, or by sublimation from a mixture of sulphate of the protoxide of mercury, and common salt. The latter is the mode usually adopted in practice. Both the sulphate and the salt should be perfectly dry and well mixed ;—the reactions will then be as follows : Hg0,SO, + NaCl = NaO,SO, + HgCl. The sublimation may be effected in a retort of hard glass over a charcoal fire; and the operation should be conducted in such a situation that all the fumes escaping may be immediately con- veyed away by a strong draft of air. QueEstions.—May calomel be sublimed? How many volumes of its constituents does one volume of it contain? 500. How is chloride of mercury prepared? By what name is it known in pharmacy? Desvribe the reactions when sulphate of mercury and common salt are used in its preparation. BINARY COMPOUNDS OF MERCURY. 379 As corrosive sublimate is usually seen, it is colorless, semi- transparent, and has a crystaline structure. It has an acrid, burning taste, and leaves a nauseous metallic flavor on the tongue. It has a density of 6-5, fuses at 509°, and boils at 563°. It is soluble in 16 times its weight of water, and in alcohol and ether. When its solution in water is agitated with ether, the latter abstracts the bichloride, and rises with it to the surface of the former; and it may thus be separated from many other substances when contained with them in solution. Its aqueous solution is gradually decomposed by light, calomel being deposited. Applied externally, it is highly corrosive to the flesh; and taken internally is a most deadly poison. Albumen precipitates it as an inert compound, and is therefore indicated as a proper remedy in cases of poisoning with it. 501, The kyanizing (from the name of the inventor, Mr. Kyan,) of tim- ber consists in soaking it for a time in a solution of this substance, which protects it from the attacks of worms and insects; and also, by combining with thé albumen contained in it, preserves it from decay. The method given above for the preparation of calomel, though very easy, is not the one usually adopted in practice; a better result is obtained by mixing 100 parts (1 eq.) of mercury.and 135-4 parts (1 eq.) of corrosive sublimate, and subliming with a moderate heat, the whole being converted into calomel. Thus, lig + HgCl= Hg,ClL. 502. Iodides of Mercury.—There are two iodides of mercury, corre- sponding in composition with the oxides and chlorides. The protiodide is precipitated as a beautiful red powder by mixing together solutions of iodide of potassium and chloride of mereury. The’ powder, after washing and drying, may be sublimed by a moderate heat, but it then becomes yellow. After cooling, the color gradually changes to red; and the change is instantaneous if it is rubbed in a mortar. Its vapor has the highest density of any known gaseous substance, being 15-69. It appears to be composed of equal volumes of mercury vapor and iodine vapor, condensed to one volume. 1 vol. iodine vapor weighs 8-716 1 “ mercury “ “6976 ey 1 vol. vapor of HgI weighs 15-692 Quzstions.—Describe chloride of mercury. Is it poisonous? How is a solution of it affected by albumen? 601. In what does the kyanizing of timber consist? Describe the mode of preparing calomel (or sub- chloride) by using the chloride and metallic mercury. 502. What iodides of mercury are there? Describe the protiodide, and the mode of pre- paring it. What is said of the density of its vapor? Of what is a volume of the vapor composed? 380 SALTS OF MERCURY. 503. Suiphides of Mercury.— There are two sulphides of mercury, which are exactly analogous in composition to the preceding compounds, The protosulphide, HgS, as we have seen, constitutes the chief ore of mercury, being found native, as cinnabar. It may also be prepared by art in several ways, and then forms the brilliant red pigment called vermillion. In vapor the density of this substance is about 5-4; and 1 volume of it contains 2 of a volume of mercury vapor, and 4 of a volume of sulphur vapor, as shown below: | 2 vol. mercury vapor weighs (6-976 X2==) 4651 $vol. sulphur“ Ke (44 =) 0-789 1 vol. vapor of HgS weighs 5-390 As21+1—$41= 7, it is evident that the union of these two sub- stances is accompanied by an expansion ;—it is the only instance of the kind yet known. The other binary compounds of mercury possess no special interest. Solts of Mercury. 504. Nitrates of Mercury.—Nitric acid acts violently upon mercury, and forms with its oxides several salts, differing from each other accord- ing as the temperature may be more or less elevated, or the acid more or less diluted. Cold, dilute nitric acid acts slowly upon mercury, and forms with it a salt of the suboxide, which crystalizes with two atoms of water, and has for its formula Hg,0,NO,+-2HO; but if the acid is hot, and of the usual strength, a salt of the protoxide is formed, which, when erys- talized, has the formula, 2Hg0,NO, + 2HO. Still other nitrates of this metal may be formed, but these are the most important. 505. Sulphates of Mercury.— Sulphuric acid acts but slightly upon mercury when cold; but if heated, a sulphate of either the suboxide or protoxide is formed, according to the temperature. If 5 parts of sul- phuric acid are boiled upon 4 parts of mercury, sulphate of the protoxide, Hg0,S80,, is formed—the compound used (500) in the manufacture of cor- rosive sublimate. Boiling water decomposes this sulphate, forming a yellow basic salt, 83Hg0,SQx, called turpeth mineral. 506, Chlorosalts of Mercury. — Protochloride of mereury combine- readily with other metallic chlorides, forming numerous crystalizable salts, which by some have been called Hydrargo-chlorides. Compounds Questrons.—503. What is said of the sulphides of mercury? What is vermillion? Of what is one volume of vapor of HgS composed? What is said of the union of these two substances? 504. What is said of the nitrates of mercury? 505. What is said of the action of sulphuric acid upon mercury? 506. Does chloride of mercury combine with other metallic chlorides? What are the compounds called? SILVER. 381 of this character, with the chlorides of potassium, sodium, lithium, am~- monium, barium, &c., are made simply by mixing their solutions. The double chloride of mercury and ammonium was formerly used in medical practice, under the name of salt of alembroth. SILVER. Symbol, -Ag (Argentum); Equivalent; 108; Density, 10-5. 50%. History.—This metal was known to the ancients. It frequently occurs native in silver mines, both massive and in octahedral or cubic crystals. It is also found in combination with gold, tellurium, antimony, copper, arsenic, and sulphur. In the state of sulphide, it so frequently accompanies galena, the chief ore of lead, that the lead of commerce is rarely quite free from traces of silver. Most of the silver mines, which afford the metal at the present day, are in South America and Mexico; but in smaller quantities it is obtained in several countries of Kurope, and other parts of the world. . Nearly all the silver obtained from the mines at the present time is found native, or is extracted from the sulphide ; but there are many other mineral species which contain the metal. 508, Preparation— When metallic silver is contained in small particles, disseminated through the ore, it is extracted by tritu- rating the ore in fine powder with mercury, which dissolves the silver, and separates it at once from the mass, as'an amalgam. The amalgam is then subjected to pressure in leather bags, by which a portion of the mercury is separated, and the remainder is expelled by heat. This is called the process of amalgamation. Other ores of silver require to be treated differently, but the numerous processes adopted cannot be here described. Silver is purified from small quantities of other metals present, except gold, by the process of eupellation, which has been prac- tised from a very remote age. The process depends upon the Questions.—What is sali of alembroth? 6507. Has silver been long known? With what other metals is it found associated? From what. ores is most of the silver of commerce extracted? 608. Describe the mode of extracting silver from its ores by the amalgamating process. 382 SILVER. fact that the metals (except gold) which are usually in combina. tion with silver, as copper, lead, tin, &., are more oxidable than silver, and therefore when the alloy is kept for a time at a high temperature in the open air, these metals are oxydized, and the silver left perfectly pure. In large refineries, the oxide, as it is formed, is blown off by a bellows, so as to expose constantly a fresh. surface to the air; but in small opera- tions, as in the testing of coin or plate, the cupel proper is used, which is made of bone- earth, of the form of a small cup, as represented in the figure. This has the peculiar property absorbing the mixed oxides as they are formed, and thus the f necessity of using the bellows is avoided. For small operations, cupels are made about an inch in diameter, and half an inch deep. A vertical ae Cupe. Section is shown in the annexed figure. Cupel. 509. We will suppose the object is to test some coin or plate, which contains with the silver some copper, and perhaps a little tin or lead. A small piece of the alloy is accurately weighed, and placed in the cupel with 10 or 20 times its weight of pure lead, and subjected to a strong heat, in such a manner that the air shall have constant access to it. When it becomes suffi- ciently heated, oxydation of the lead and other metals com- mences, and the mixed oxides being absorbed as they are formed, after a little time the silver is left perfectly pure. The cupel with the silver is then removed, and when cold the button of silver is detached and again carefully weighed. The heating is usually conducted in a muffle, placed in a proper furnace, so as to exclude dust and smoke, but allow the access of air. The muffle (sce figure) acai is in fact a small oven, made of fire-clay; and is placed in the furnace so as to be entirely surrounded by the burning fuel, as shown in the figure on next page, which repre- sents a vertical section of the furnace through its centre, with the muffle in its place. M is the muffle, with several cupels in it; A, B and C openings, which may be closed at pleasure by means of fire-brick doors, A, B, C, prepared for the purpose. To insure perfect success in the Quzstions.—509. Describe the process of cupellation. Of what is the cupel formed? What purpose does it serve? Describe the mufile. ' SILVER. 383 operation, attention is required to various particulars, which cannot be here given in detail. Alloys of gold, subjected to the same process, are purified from all other metals except silver and platinum. 510. Another mode of testing alloys of silver, called the wet method, is’ to dissolve the silver alloy in nitric acid, and precipitate the silver by a standard solution of common salt, previously pre- pared with accuracy. This solution is made of such a strength, that 1000 parts of it, by measure, will precipitate exactly 1000 parts by weight of pure silver ; and the proportion of silver in the alloy will of course be determined by the number of parts of the solution required to pre- cipitate it. This is the mode practised at the United States mints, to determine the fineness of coin. . This method cannot be used when the 7 alloy contains a metal, as mercury, whose oY A Yee chloride is insoluble. Section of Furnace and Muffle. 511. Properties.—Silver is a soft, white metal, and is very malleable and ductile. It has a brilliant lustre, and is susceptible of receiving a very fine polish. It is not acted upon by the atmosphere or by moisture, but is readily blackened by sulphur. Articles of silver often become tarnished, merely by the sulphurous gases which are diffused from the fires in houses in which mineral coal is used for fuel. Its melting point is about 1873°, and if kept some time in fusion it absorbs oxygen in large quantity, which is given off again when the metal cools. Silver is attacked by sulphuric acid only by the aid of heat, but is freely dissolved by nitric acid, even when cold. Silver is used in every country for many important purposes— for coin, and for manufacture into various articles of utility or ornament; but to render it more stiff and hard it is always alloyed with a portion of copper. Questions.—510. Describe the wet method of testing alloys of silver. 511. Describe the properties of silver. What acids act upon it? For what purposes is silver used ? eek aati 384 BINARY COMPOUNDS OF SILVER. The standard of purity for silver coin varies in different countries; but the coin of the United States contains 900 parts of pure silver and 100 parts of copper ;—that is, one-tenth part of the weight of the coin is copper, except the three-cent piece, of which $ths are silver and ith copper. ie the present time, the largest silver coin issued from the United States Mint is the half-dollar, which is required to weigh 192 grains; the weight of the smaller coins being in the same proportion, except that of the three-cent piece, which is 12% grains. The quantity of pure silver in the half-dollar is, according to the above, 172-8 grs.+=192—19-2, This gives as the value of pure silver $1,38.8 per ounce. The value of coin is always estimated in proportion to the amount of pure metal it contains, no attention being paid to the alloy. It is remarkable that the addition of copper scarcely produces any change in the brilliant white color of silver, provided it does not exceed about one- eighth of the latter metal. : Silver combines with other metals, forming alloys, which, however, possess no particular interest. Binary Compounds of Silver. 512, Oxides of Silver.—Silver forms with oxygen three compounds, 2 suboxide, Ag.O, protoxide, AgO, and binoxide, AgO,'; but only the protoxide is important. This is thrown down as a dark-colored powder, when solu- tion of caustic potash is poured into a solution of nitrate of silver. Heated to redness it gives up all its oxygen, and pure silver is obtained. It forms the base of all the oxysalts of silver ;—is slightly soluble in water, but very soluble in aqua ammonie. By digesting this oxide for a time in concentrated aqua ammoniz, a black compound is formed, which is highly explosive, sometimes called Sfulminating silver. Its composition has not been satisfactorily determined. The most probable opinion is, that it is a nitride of silver, NAg,. formed by the reaction: 8AgO + NH, = NAg, + 3HO. 518. Chloride of Silver, AgCl; eq., (108 4- 85-4—) 143-4.—This com- pound is occasionally found as natural production, and called horn silver, and is easily formed artificially, by pouring solution of common salt into a solution of nitrate of silver. Formed by this mode, it is a beautiful white powder, which, however, soon becomes purple in dif- fused light, or black if exposed to the direct light of the sun, or if warmed before a fire. It is insoluble in water, but soluble in ammonia and hyposulphurous acid. ~ Quzsrions.—What proportion of the silver coin of this: country is sil- ver? What is the alloy? What is the largest silver coin now issued from the United States Mint? What does this give as the value per ounce of pure silver? In estimating the value of coin, is any allowance made for the value of the alloy used? 512. What oxides of silver are there? Whiclf of these constitutes the base of the salts of silver? 518. Describe the chloride of silver. How is it prepared artificially ? SALTS OF SILVER. 385 Nascent hydrogen reduces it to the metallic state by absorbing the chlorine to form hydrochloric acid. To effect the reduction, the chloride is covered with water acidulated with sulphuric acid, and pieces of zine introduced, and the whole occasionally stirred. The metallic silver is obtained in fine grains. Iodide of Silver, AgI, is found as a natural production, and may also be formed by precipitation from solution of nitrate of silver by iodide of potassium. , Sulphide of Silver, AgS.—This compound is found in nature, alone, and in combination with other metallie sulphides, particularly sulphide of lead, in the ore called argentiferous galena. Sulphide of silver may also be formed artificially by several processes. Salts of Silver. 614, Nitrate of Silver, AgO,NO,;.— This is the only salt of silver of any practical importance, and is well known by the name of lunar caustic. It is usually sold in small sticks, which are wrapped in paper, but may also be obtained in beautiful white, tubular crystals. The sticks usually contain a portion of nitre, which has been melted with it when cast in the moulds. Nitrate of silver is formed by dissolving silver in nitric acid, diluted with twice its weight of distilled water. It is soluble in one-half its weight of boiling water, and its own weight of cold water. It is the basis of indelible ink, as it is called; but writing done with it, and stains made by it, may be removed by solution of cyanide of potassium. Nitrate of silver is very caustic to the flesh, and is used in medicine as a cautery. From its solu- tion, metallic copper precipitates the silver as a fine powder; by mercury, the silver is thrown down in an arborescent form, which has been called the arbor Diane. : Sulphate of Silver, AgO,SO;, may be formed by boiling sul- phuric acid upon metallic silver. It is a colorless salt, slightly soluble in boiling water. Questions. — Describe the mode of reducing the chloride by means of zine and oil of vitriol. What other binary compounds of silver are mentioned? 514. What is lunar caustic? Describe its properties. What use is made of it? 33 386 GOLD. GOLD. Symbol, Au (Aurum); Equivalent, 198; Density, 19-26. 515, History. — Gold appears to have been known to the earliest races of men, and to have been esteemed by them as much as by the moderns. With the exception of the rare mineral telluride of gold, it has hitherto been found only in the metallic state, either pure, or in combination with other metals. It is sometimes found in quartose rocks, but more frequently in alluvial depositions, especially among sand in the beds of rivers, having been washed by water out of disintegrated rocks in which it originally existed. Though usually found in irregular rounded lumps and grains, it is sometimes obtained in crystals of the monometric system as Crystals of Gold. represented by the accompanying figures, taken from the American “Journal of Science. Gold is obtained at the present day in large quantities in California, Australia, and some parts of the Ural Mountains, and less abundantly in Hungary, and other countries of Europe. In small quantities, it occurs in Georgia, North Carolina, and Virginia. 516. Preparation.—As gold exists in its ores in the metallic state, it is generally separated from them by the process of amal- Questions.—515. Give the history of gold. In what situations is it found? Is it occasionally found in crystals? 516. Describe the mode of separating silver from gold, called guurtation. GOLD. 387 gamation, similar to that already described for obtaining silver, by which means it is separated from all other metals except silver. To remove this, so much silver must be added to it that the gold shall constitute but a fourth of the whole, and the mass boiled in nitric acid, which then readily acts upon it, dissolving out all the silver, and leaving the gold in a state of purity. This process has been called quartation, from the circumstance that the pro- portion of gold, in order that the nitric acid shall dissolve out all the silver, must not exceed a guarter of the whole mass. Other metals, except silver, may also be separated from it by cupel- lation (508). To prepare absolutely pure gold, a piece of coin may be dis- solved in aqua regia, and precipitated with solution of sulphate of protoxide of iron. The reactions are as follows : AuCl, + 6Fe0,SO, = Au + Fe,Cly + 2(Fe,0,,380,). The gold thus obtained is in a minutely divided state, and is of a purplish brown color. It is to be collected on a filter, and washed with very dilute hydrochloric acid, and fused with a little borax and saltpetre. - 617, Properties.—Gold is readily distinguished from all other metals by its brilliant yellow color, and by its great malleability and ductility. It is capable of being beaten out into leaves so thin that light may be transmitted through them, which then appears of a greenish yellow color. It is not acted upon by air or moisture, though exposed to their influence for ages; nor is it oxydized by being kept in a state of fusion for any length of time. When intensely heated by the galvanic current, or by means of the compound blowpipe, it burns with a greenish blue flame, and is . dissipated in the form of a purple powder, which is supposed to be an oxide. Selenic acid, aided by heat, dissolves it, and a mixture of selenic and hydrochloric acids, without heat; but its proper solvent is aqua regia, which is a mixture of 1 part of nitric and 2 parts of hydroéhloric acid. It fuses at about 2016°. Quesrions.—Why does the process for separating silver from gold here described receive the name quartation? How may absolutely pure gold* be prepared? 517. How is gold distinguished from the other metals? Describe some of its properties. What is the only proper solvent of gold ?, 388- BINARY COMPOUNDS OF GOLD. 518. Gold and silver, from the estfmation in which they have been held, have been long known as the ‘precious metals;” and it is usual to esti- mate their purity in carats, A carat is to be understood as J,th part of the mass; and a piece of gold or silver is 14, 18, or 20 carats fine, when so many 24ths of the whole are fine metal, the rest being alloy. But in the Mint of the United States, their fineness is estimated in thou- sandths: thus, gold or silver is said to be of the fineness 654, 789, 921, or 994 thousandths, when so many thousandths of the whole mass con- sist of pure metal, the rest being alloy. The alloy of silver is always copper, but the alloy of gold may be either copper or silver, or a mixture of the two. Pure gold is so soft that some alloy is always needed to give it the proper stiffness, and to prevent too rapid wearing. In the gold coins of this country, one-tenth part is alloy, which is a mixture’of silver and copper. The gold eagle of the United States weighs 258 grains, of which 25-8 grains are alloy. The value of standard gold is therefore estimated at $18.604 per ounce, and that of pure gold at $20.671 per ounce. ‘ Native gold is almost always alloyed with silver, but the proportion of this metal is very variable. Gilding consists in coating over the surfaces of bodies with a thin film of gold. Articles made of metal were formerly gilded by applying to their surface, properly cleaned and smeared with nitrate of mercury, amalgam of gold, and then. expelling the mercury by heat; but this mode has been entirely superseded by the electrotype process, heretofore (116) described. In both cases the surface of gold requires to be burnished. Articles made of non-metallic substances are gilded by a coating of gold leaf. ‘Binary Compounds of Gold. 519. Oxides of Gold.—There are two, and perhaps three, oxides of gold; but the teroade, AuOg, alone possesses any special importance. It is of a yellow color when first formed, hut becomes black when all the water is expelled. It ix used in coloring glass and porcelain purple. In some cases it secms to act the part of a feeble acid, and has been called auric acid. 520. Chlorides of Gold.—There are two chlorides of gold; the derchloride, AuCls, the one usually seen, is formed when gold is dissolved in aqua regia. By evaporating the solution carefully, the chloride may be obtained as a solid, which is very soluble in water, alcohol, and ether. Solution of chloride of gold is very easily decomposed by green vitriol, and by organic Quusrions.—518. Why have gold and silver been called the precious metals? How has the fineness of these metals, or rather alloys of them, usually been estimated? What is meant when an article of gold or silver is said to be 18 carats fine? How is the fineness of these metals esti- mated at the United States Mint? What is the alloy used for the gold coins of this country? What is the weight of the United States eagle? What does this give as the value per ounce of standard gold? Of pure gold? How is gilding performed? 519. What oxides of gold are there? -620. What chlorides? ty, PLATINUM. 389 ’ substances. Protochloride of tin forms with it a beautiful purple powder, called purple of Cassius. Aqua ammonia precipitates, from solutions of terchloride of gold, a fulminating compound called fulminating gold, of uncertain composition. Salis of Gold. 521. The oxides of gold do not unite as bases with the acids, but the teroxide, as an acid, combines with bases, forming some unimportant salts, which are called aurates. Chlordsalts of Gold—Terchloride of gold combines with many other metallic chlorides, like the chloride of mercury, forming a series of chloro- salts, sometimes called auro-chlorides. PLATINUM. Symbol, Pt; Equivalent, 99; Density, 21-5. 522. History.— Platinum was first recognised as a distinct metal in 1741, but was not described until 1749. It has hitherto been obtained chiefly from Brazil, Peru, and some other parts of South America, and from the Ural Mountains. It occurs only in the me- tallic state, associated with other metals, as gold, silver, lead, palladium, osmium, iridium, and rhodium. 523. Preparation.— To prepare pure platinum, the native grains, or com- mercial platinum, are dissolved in boiling aqua regia, and, after standing for a time, the clear solution is poured off, and the platinum precipitated by solution of sal- ammoniac, as a double chloride of plati- num and ammonium. By heating this precipitate, both the chlorine and am- monia are ‘expelled, and the metallic Platinum in Aqua Regia. Quzstions.—How is purple of Cassius formed? 521. Whut is said of the chlorosalts of gold? 622. Give the history of platinum. What is the state in which it occurs? 523. Describe the mode of preparing pure platinum. 890 PLATINUM. platinum remains as platinum sponge, which, when treated with hot water, appears as a dark gray mud. : This is now pressed in a hollow cylinder, by which means the particles of metal are made to adhere, ‘bo that the dise thus obtained may be carefully heated, and hammered on an anvil. The metallic grains now become firmly welded together, and the mass may be worked in any desired form. 524. Properties.—Platinum is a white metal, much resembling silver, but of a darker color, and of inferior lustre. When pure, it is very malleable and ductile. It is the most dense: substance known to man (except, perhaps, iridium), but is quite soft; and pieces of it, when heated, may be welded like iron, though not so easily. No single acid attacks it, but it is soluble in heated aqua regia. By heated nitre, or potassa, or soda, it is oxydized. It cannot be melted by the most intense heat of the hottest fur- nace; but may be fused by the compound blowpipe. When a large surface of the metal is exposed to a mixture of oxygen and hydrogen, it has the singular property of causing them to com- bine, either silently or by an explosion. It acts in this way more readily when used in the spongy form (200, 523), as precipitated from its solution by sal-ammoniac. Platinum black, in which the metal is in a still more finely divided state, acts energetically in the same manner, causing the rapid union of various gases besides oxygen and hydrogen, when submitted to its influence. This form of platinum is prepared by electrolizing a dilute solution of chloride of the metal, or by boiling a solution of the chloride mixed with carbonate of soda and sugar. If a.coil of platinum wire, recently ignited, be sus- pended in a deep glass, containing a little ether at the bottom, it will instantly become incandescent, and glow : . with a red heat, until the ether is entirely dissipated lati- : y perce sine tue The same effect may be produced by placing a coil of Quzstions.—How are the particles of finely divided metal made to unite so as to form a solid mass? 524. Describe the properties of plati- nun. By what alone is it dissolved? How is it affected by heated nitre or potash? How is a mixture of oxygen and hydrogen affected when expused to a large surface of this metal? What is said of platinum black in this connection? Describe the experiment with a coil of platinum wire and ether. BINARY COMPOUNDS OF PLATINUM. 391 small platinum wire over the wick of a spirit-lamp, and after lighting it, suddenly extinguishing the flame. The wire will continue at a. red heat until all the alcohol is consumed, Such a lamp (called a flameless lamp) is represented 1n the accompanying figure. 525, Uses.—Platinum is of great importance in the laboratory, and is much used in the arts, especially for retorts for condensing (261) sul- phuric acid. Its present value in the marketis jnace Lani: about half that of gold. It was formerly issued as coin by the Russian government, but the practice has been discontinued. : Binary Compounds of Platinum. 526. Oxides of Platinum.—Platinum forms with oxygen two compounds, the protoxide, PtO, and the peroxide, PtO,, both of which are feeble bases, and unite with some of the acids to form salts. : Chlorides of Platinum.—Two chlorides of platinum are known, analo- gous in composition to the oxides. The bichloride, PtCl,, is the most important of all the compounds of this metal, and is obtained by treating the metal with boiling aqua regia, and carefully evaporating, to expel the excess of acid. It is much used in the laboratory. Sulphide of Platinum, PtS, may be formed by heating platinum-filings in vapor of sulphur. 527. Salts of Platinum.—The salts of platinum, at least the oxysalts, are not important. Oxalate of the protoxide, and sulphate and nitrate of the binoxide, are known. Chlorosalts of Plattnum.—The bichloride of platinum combines with other metallic chlorides, forming a series of chlorosalts, called also platino-chlorides. 628. Osmium, Os; Eq., 99-5.—This rare metal is in combination with platinum and iridium ;—with the former in the so called native platinum grains, and with the latter in the mineral species called iridosmine. Itis of a grayish color, and metallic lustre; is slightly malleable, and has a density of about 10. It combines readily with oxygen when heated, and ia attacked by nitric acid, which converts it into osmic acid. . ‘ Small grains of the native iridosmine are used for the tips of gold pens, because of their hardness and capability to resist the corrosive action of the ink. ; Qursrions.— Describe the flameless lamp. 525. To what uses is platinum applied? 6526. What oxides of platinum are known? What chlorides? How may sulphide of platinum be formed? 627, Are there any important salts of platinum? 528. What is said of osmium? What use is made of the native grains of osmium and iridium? 392 BINARY COMPOUNDS OF PLATINUM. There are known no less than five oxides of osmium, viz., 0s0, 0s,0,, OsO,, Os0,, and Os0,; of which the last two possess acid properties, and are called the osmious and osmic acids. Two chlorides only of osmium are known, a protochloride and a bichloride. 529. Iridium, Ir; Eq., 99.—Iridium, as stated above, is found chiefly in combination with osmium. It has not been obtained in a malleable state, but only as a hard compact mass; and its density cannot therefore be well determined, but by some it is believed to exceed that of platinum. It is not attacked by nitric acid, nor even by aqua regia when pure, but at a red heat enters into combination with chlorine, with which it forms two compounds, the protochloride, IrCl, and the bichloride, IrCl,. 530. Palladium, Pd; Eq., 53-3.—This metal, often contained in plati- num ores, is obtained chiefly from a native compound of this metal with gold, found in some parts of South America. It is nearly as white as silver, and scarcely less fusible than platinum. It is malleable and-ductile, and receives a fine polish under the burnisher. Its density is 11-8. Palladium is used for the construction of the beams for delicate balances, and also for the graduated scales of astronomical instruments. 531. Rhodium, Rh; Eq., 52-2.—Rhodium, which receives its name from the rose-color of some of its compounds, is contained in small quantities in most platinum ores, and is sometimes found in combination with gold. It is of a gray color, and even more infusible than platinum. It is attacked by aqua regia only when alloyed with platinum, or some other metal, Its density is 10-6. Ruthenium, Ru, is the name given to a metal recently discovered in some platinum ores. In its general properties it resembles iridium. QuestTions.—What oxides of osmium are known? 529. In what is iridium found? 580. Describe palladium. What use is made of it? 581. Describe rhodium. What is said of ruthenium? PART IV. SPECIAL CHEMISTRY—ORGANIO. GENERAL PROPERTIES OF ORGANIC BODIES. 532. Introduction—In the preceding part of this work, we have traced the chemical history of all the elementary substances at present known, and that of many of their most important com- pounds, as they are produced by the.action of their affinities, uncontrolled except by the agencies of heat, light, and electricity; but we have now to discuss altogether another class of compounds, called organic, because produced almost exclusively by the organs of plants and animals, or derived from substances so produced. Organic Chemistry, therefore, is that branch of the general science of Chemistry which tréats of the history, properties, and transformations of animal and vegetable substances. ‘These are always compound, and differ from inorganic or mineral compounds chiefly in their origin, and in the circum- ‘stance that most of them are of a more complex composition. 533. Organic and Organized Bodies.—There is, however, a certain class of organic bodies,—called organized bodies,—whose essential physical properties are altogether peculiar. These are always insoluble, and incapable of crystalization, and exhibit an organized structure, often visible to the naked eye, and always apparent under the microscope: To this class belong all the proper tissues of the animal and vegetable systems, constituting the organs by which all their various functions are performed. Sugar, gum, alcohol, and urea are organic substances, the two Questions.—532. What has been treated of in the preceding parts of this work? What are now to be treated of? Define Organic Chem- istry. How do organic bodies differ from inorganic? 633. What are organized bodies? What is said of sugar, gum, &c. ? (393) 394 GENERAL PROPERTIES former being found ready formed in plants and sometimes in animals, and thé two latter, being derived usually from sub- stances so produced, but they are not organized. On the other hand, the ‘cellular tissue of wood, the pith of an elder tree, and the skin of an animal, are organized; and their pecu- liar structure is apparent to the eye, at least when aided by the microscope. The figure in the margin, from Regnault’s Chem- istry, represents a cross section of the pith of the elder, as seen under the microscope. This ex- hibits a peculiar regularity of structure, which, however, is not common ;—the structure of two different organized bodies seldom ne presents any striking similarity. Of the next two figures, the first repre- sents a microscopic view of a longi- Vase es ep Gin So ono at ad pe ee i Ae Bene Nae “l rg Cor sae Pith of Elder. Stalk of Asparagus. Cross Section of Same. tudinal section of a stalk of asparagus, and the second a cross section of the same. 534, Vitality—In the production of organic bodies, the simple affinities of the particles of which they are composed are over- Questions.—What is said of the various tissues of the system? How may the organized structure always be seen? What is represented by the figure in the matgin? What by the next two figures? 534. By what are the affinities of matter controlled in the production of organic compounds ? OF ORGANIC BODIES. 895 ruled or controlled by another power or force, called the vitae power, vitality, or the principle of life. Its influence is abso- lutely essential for the production of most organic compounds, which, it is believed, can never be formed by the simple opera- tion of the ordinary affinities of the elements of these compounds. And it follows, as a necessary consequence, that after death, that is, when this principle has ceased its influence, and the simple affinities of the elements of an organic compound are left uncon- trolled, they will show a disposition to break up, and re-arrange themselves in a new order. In this way the old compound is destroyed, and perhaps several new ones formed ; or the simple elements may be entirely set free. This is what is termed the spontaneous decay, or putrefaction of a substance. Often this process is affected by the presence of the atmosphere, and is always much influenced by the temperature, and other circum- stances. Although many organic compounds are found, as such, in the bodies of plants and animals, by far the greater number are produced by the actions of the various reagents, as the acids, alkalies, and salts, either cold or aided by heat, upon these compounds. Thus, sugar and starch occur abundantly in plants, but from them, by the action of reagents, a long list of other compounds are produced, which are never found in the plants themselves. Alcohol, the almost innumerable ethers, and many acids, are of this kind. Some compounds, as acetic and oxalic acid, are found ready formed in organic bodies, and may also be produced by the action of reagents upon other organic substances. But it is not to be understood that all organic substances are equally liable to decay; some of them, as sugar, wood, and gum, of vegetable origin, and gelatine, of animal origin, if kept dry, may be preserved apparently for any length of time. The chief elements of organic bodies are carbon, hydrogen, oxygen, and nitrogen, which are combined in different’modes, afid in different proportions; but besides these some organic substances also contain sul- phur, phosphorus, chlorine, calcium, potassium, sodium, magnesium, iron, silicon, &c. Some few organic compounds have been formed artificially, that is, without the aid of the vital principle ; but not any organized body. Questions.—Is the influence of this principle of vitality essential to the production of organic compounds? Why, after death, do most organic substances spontaneously decay? Are most organic compounds found ready formed in the bodies of plants and animals? What is said of alcohol and the ethers? May some organic bodies be preserved for a long period? What are the chief elements of organic bodies? 396 GENERAL PROPERTIES 535. Molecular Structure of Compounds.—It is well known that two compounds, exactly the same in composition (172), often differ very considerably in their properties. This difference is believed to be occasioned by differences in the mode of arrange- ment of the particles in the compounds, or, in other words, in their molecular structure. In general, while we understand well the elements of many compounds, we really know little of the mode in which these elements are grouped together in any particular case. We know, for instance, that the equivalent of sulphuric acid, SQ,, contains 1 atom of sulphur and 8 atoms of oxygen, but we cannot say whether these are grouped as $430, 80+ 20, or SO,+0, for these three modes are all alike possible. Here it would seem that there can be only three modes of combination, but in more complex compounds the number of possiblo modes may be greatly increased. i This supposed difference in the mode of combination or grouping of the atoms of a compound, may be represented to the eye by means of a dia- gram. Thus, let us suppose that we have a compound of two simple a | a | Modes of Grouping. substances, and that in the atom of the compound there are 8 atoms of each of the elements ;—representing the particles of one kind of mat- ter by the dark squares, and the other by the light ones, the four figures show as many independent modes of grouping. Now, as every inde- pendent mode of grouping of the particles may produce a new substance, it is plain that we may thus have four substances, all having the same ultimate composition, yet possessing properties altogother different. _ 536, Compound Radicals — Nomenclature.—Compound radi- cals are chemical compounds which are capable of performing the functions of simple substances; they combine with elementary bodies and with other compounds in the same manner as simple Questions.—535. May substances having the same composition differ in their properties? How is this difference believed to be occasioned? What is said of sulphuric acid in this connection? How is the supposed difference in the mode of grouping among the atoms of a compound illus- trated by the figure? 536. What are compound radicals ?. OF ORGANIC BODIES. 897 substances, and may often be substituted for these in the com- pounds of which they form a. part. One of the best known of these compound radicals.is cyanogen, C,N (316), which, as is shown by the formula, is a bicarbonide of nitrogen. This group of atoms, it is well determined, is capable of combining with the metals and other substances in the same manner as oxygen, chlorine, sulphur, &c., producing compounds similar to the oxides, chlorides, &c., which are called cyanides. United with oxygen it forms cyanic acid, with hydrogen it forms hydrocyanie acid, &e. So through a long series of other com- pounds, this group of atoms is found everywhere performing the functions of a simple substance. Other compound radicals which have been determined are methyle, C,H, ; ethyle, CyH,; butyryle, CgH,; valyle, CgHy; amyle, C,H, &c. Still other compounds of the same character, but having a more com- plex composition, are benzyle, C,,H;0.; cacodyle, C,HgAs; slanmethyle, C,H,Sn; zinemethyle, CgH,Zn; stibmethyle, (CgH3),8b, &. 537, That these groups of atoms, and many others, do enter, as such, into composition with the simple substances, and with each other, and are capable of being transferred by single or double decomposition from one compound to another, are facts too well established to be contro- verted. All those mentioned above, except perhaps benzyle, have also been obtained in a separate state; and many that have not been thus obtained may, with great probability, be assumed as having a real - existence. a Considering the existence of these groups denominated compound radicals as fully established, it will be seen at once that it furnishes a ready mode of classifying organic compounds, and also for forming for them a systematic nomenclature. Thus, if we take ethyle, C,H, as the basis or starting point of a series, we have for its binary compounds the oxide, chloride, iodide, sulphide, &c.; and for salts of its oxide, the hyponitrite, nitrate, acetate, &c., as follows, viz. : Binary Compounds. 1. Ethyle...........0 C,H,. . 2. Oxide of ethyle, C,H,0, common sulphuric ether. - 8. Chloride “ ©,H,Cl, hydrochloric “ 4. Iodide “C,H; I, hydriodic ee 5. Sulphide “ C,H,S, hydrosulphuric ‘ Salts of Oxide of Ethyle. 1. Nitrite of oxide of ethyle, C,H;,0,NO,, hyponitrous ether. 2. Nitrate Ss “ C,H,0,NO,, nitric “ 3. Acetate « « C,H,0,C,H,0,, acetic €e Quzstions.—~What compound radicals are mentioned? 537. Have many of ad groups have been obtained in a separate state? 398 GENERAL PROPERTIES The foregoing are given as examples only; —this series might be extended much further, and many other series might be introduced, as the methyle series, which would include the compounds of methyle, C,H, analogous to the above, the acetyle series, the cacodyle series, &c. A nomenclature of organic compounds constructed on this principle has been adopted by able and judicious chemists; but as there is no proof that such a nomenclature truly represents the real molecular structure of these compounds, we do not make use of it in this work. 538. A slight examination only is needed to show that most organic compounds may be arranged in series in a variety of ways, each new mode requiring or supposing a new molecular arrangement, Thus in the compounds represented in the table above, if we commence with ole- fiant gas, or ethylene, C,H,, instead of ethyle, C,H,, then we may con- sider the latter, C,H,—C,H,,H, as the hydride of ethylene, and ether, C,H,0 —C,H,,HO, as hydrate of ethylene, hydrochloric ether, C,H,Cl= C,H,,HCl, as hydrochlorate of ethylene, &c. 539, The real mode in which the_particles of organic compounds are arranged (88) at least in most cases, has not yet been satisfactorily determined; and it is therefore impossible, in the present state of our knowledge, to fix upon a proper systematic nomenclature. The same may also be said of the formule used to represent these compounds. A distinction is often made between empirical and rational formule, the former representing the composition as determined by ordinary analysis, without any attempt to indicate the arrangement of the particles; the latter, on the other hand, representing not only the composition of the compound, but also its molecular structure. Thus, the composition of acetic acid, as determined by analysis, is C,H,0,; but when this acid combines with a base it always parts with one equivalent of water (or its elements), so that its salts, the acetates, have the general formula, RO,C,H,03;. This would seem to indicate that the formula for the acid should be written C,H,0,,HO. But certain considerations have led us to the belief that in anhydrous acetic acid, C,H,0,, 1 equivalent of the oxygen is held in a different state from the rest, and therefore its formula should be C,H30,,0. Adopting these views, then, while it is admitted that the empirical formula, C,H,0,, represents correctly the elements of acetic acid, its rational formula will be, C,H,0,.0 + HO. In other words, it is a compound having for its primary radical, acetyle, C,H, and for its secondary radical, C,H3;0,~—(Dr. Gibbs’ Report, p. 43.) : 540. In the following pages, a systematic nomenclature, according to ‘any particular theory, is not attempted;—-the names of compounds, adopted are those in general use, with a few unimportant modifications. Quzstions.—Why is not the nomenclature of the compound radical theory made use of in this work? 6538. May most of the organic com- pounds be arranged in series in a variety of ways? Give the illustration in the text. 539. Has the real molecular structure of organic compounds been determined? What are empirical, and what rational formule? Give the illustration by reference to acetic acid. 540. What is said of the nomenclature used in the remaining part of this work ? OF ORGANIC BODIES. 399 In many cases, compounds are named from some one of the natural’ pro- ductions in which they are found, as malic acid from malum, an apple; citric acid, from citron, a lemon; valerianie’ acid, found in the root of the plant called valeriana officinalis ; cinchonia, obtained from the bark of the cinchonia condaminea, &c. The formule, in general, are to be considered only as empirical; frequently, two formule are given for the same com- pound, with the sign — between them. In such cases, the first is always the empirical formula, while the second indicates something further, as it regards the supposed constitution of the compound, or the mode of its reactions with other substances. The formula for cane sugar, for in- stance, is written C,.H,,0,;—C,pH,0,-+ 2HO, by which it is indicated that 2 equivalents of water (or the elements of water) sustain a relation to the compound different from that of the other atoms of these eleménts, Laws of Combination and Transformation. 541. We have seen (536), that in organic compounds certain groups of atoms, called compound radicals, frequently are found to perform the functions of simple substances. Many of these groups are already known, and many more will probably be here- after discovered. If all the groups capable of acting in this man- ner, with their properties and relations, were known, it is very probable that the transformations of organic bodies would not differ essentially from those of inorganic matter, except as they are affected by this circumstance. In other words, all cases of chemical action would be reduced to instances of direct union, or of single or double elective affinity. - When potassium is burned in oxygen gas, direct union takes place between the two elements, and potassa (oxide of potassium) is formed— K-+O=KO. But when potassium is thrown into water, we have a case of single elective affinity, as shown by the equation representing the reaction;—thus, K+ HO—KO-+H. We may say in this case, either that the oxygen is transferred from the hydrogen to the potassium, or that the potassium has replaced the hydrogen of the water. When solutions of nitrate of baryta and sulphate of soda are mixed together, we have an instance of what is called double elective affinity; and by a double transfer of elements we have formed the two new compounds, sul- phate of baryta and nitrate of soda. Thus, BaO,NO, + Na0,S0,— Ba0,S0, 4+. NaO,NO,. Questions.—How are compounds often named? Are the formule given to be considered as empirical or rational? 641. What is said of the transformations of organic compounds as compared with those of inorganic matter? What illustrations are given from inorganic chemistry ? 400 GENERAL PROPERTIES 642, So in organic chemistry, most if not all reactions will be similar to one or another of the above cases. When olefiant gas, C,H, (808), which is properly an organic product, and chlorine, Cl, are brought together, they combine to form an oil-like liquid, C,H,Cl, But often when two compounds have in this way combined, the new and more com- plex compound that is formed may, by a slight change of circumstances, or even spontaneously, break up into compounds of less complex consti- tution. We have a case of this kind in sulpho-vinic acid, which is formed by the union of alcohol, C,H,0, with sulphuric acid. Thus, (H_09-} 2(S0,,HO) =C,H,02,2(S05HO) = C,H,0,HO, 2(S0,HO). This last substance, called monohydrated sulpho-vinic acid, when heated, breaks up, not into alcohol and monohydrated sulphuric acid, but into ether, C,H,O, and 280,,3HO. But most of the transformations in organic bodies may be considered as instances of double decomposition, or double elective affinity. The action of chlorine upon acetic acid is properly of this kind, as is shown by the following equation. Thus, C,H,0, + 6C1=C,HCI,0, + 8HCL Acetic Acid. Chloracetic Acid. It is, indeed, true that chlorine, one of the substances used, is not a com- pound, but we are to consider that the action is the same as if each of the three atoms of hydrogen were successively replaced, giving for the first atep in the process the reaction, C,H,O, + 2C1—C,H,C10, + HCl. One atom of the chlorine is transferred to the acetic acid, which at the same time gives up 1 atom of its hydrogen to combine with the second atom of chlorine, to form hydrochloric acid. This reaction three times repeated results as given above, in the replacement of 3 atoms of hydrogen by as many atoms of chlorine. 543. Substitution or Metalepsy—We have seen above that by the action of chlorine upon acetic acid, C,H,O,, the latter loses 3 atoms of hydrogen, and takes in their place 3 atoms of chlorine ; in other words, 3 atoms of chlorine are substituted in the acid for an equal number of atoms of hydrogen. The new compound, C,HCI,0,, is called chloracetic acid, and in most of its properties closely resembles acetic acid, from which it has been formed. Transformations of this kind are of very frequent occurrence; Quzstions.—542. What is the effect when olefiant gas and chlorine are brought together? When two substances combine so as to form a more complex compound, will they sometimes break up in such a manner as to form compounds different from those which at first united? Give the illustration by reference to alcohol and sulphuric acid. What is said of acetic acid and chlorine in this connection? 548. What is the change produced in acetic acid by the action of chlorine? OF ORGANIC BODIES. 401 and the exchange or substitution may take place between atoms or groups of atoms (compound radicals) which are similar to each other in their chemical relations. Hydrogen seems to be more frequently replaced than any other element; and there may be substituted for it chlorine, iodine, bromine, or a metal, or even a compound radical, as methyle, ethyle, &c. Instances of the latter kind are seen in ethylamine, diethylamine, &c., in which one or more atoms of hydrogen in ammonia are replaced by ethyle. Thus, ammonia —NHHH, ethylamine — NHHO,H,, diethylamine — NH(C,H;) (C,H,) = NH(C,H;),, &e. As hydrogen, chlorine, iodine, &c., form a natural family, one of which may replace another in the compounds they form; so nitrogen, phos- phorus, arsenic, antimony, and bismuth form another family, the indi- viduals of which sustain a similar relation to each other. Arsenide of hydrogen, AsH, (292), corresponds to ammonia in which the nitrogen is replaced by arsenic; and the compound, Sb(C,H,)s, may be regarded as ammonia in which the nitrogen is replaced by antimony, and the hydrogen by ethyle. Still another natural family is formed by oxygen, sulphur, selenium, and tellurium. Alcohol, C,H,O,, by a substitution of sulphur for its oxygen, forms mercaptan, or sulphur alcohol, C,H,S,. 544, Conjugated or Coupled Compounds.—Many of the com- pounds produced by transformations in accordance with the above principles, are frequently called conjugated or coupled compounds. They may be radicals only, or acids, or bases. As the name implies, they are supposed to be formed by the union of other compounds; and usually the characteristic properties of one or the other of the coupling compounds will be more or less pre- served in the new or coupled compound. ‘Thus, ethalamine, NHHC,H,, is a coupled or conjugated ammonia ;—it is a sub- stance formed on the type of ammonia, and possessing nearly the same properties, ethyle, C,H;, being the couplet. So the com- pounds, (C,H;)sSb, C,H;,Zn, C,H,Bi, &e., are called conjugate metals. : 545. Homologous Bodies.— Homologous bodies are bodies which may be arranged in series, all the members of which are similar in their general properties and chemical relations, Questions.—Between what may substitutions take place? What other elements or compound radicals may be substituted for hydrogen? What elements constitute a natural family with nitrogen, capable of replacing each other? 6544. What are conjugated or coupled compounds? What examples are given? 545. What are homologous bodies? 34* 402 GENERAL PROPERTIES and are composed of the same elements, but differ from each other in composition by the addition or subtraction of the ele- ments, C,H,, or some multiple of this expression. Of this kind are the alcohols, all of which, though they differ greatly in some of their properties, still have many points of resemblance. The composition of all that are known will be seen by the following table : Names. Formulz. b . Methylic alcohol (wood spirit)........+10+es000 CgH,O, Common, or Wine alcohol.......sesseseeseereresee CHO. . Propylice alcohol......-. t tpenceaes seerescareccseseee OgHaOo. Butyrie ‘ o» CgH 0p. Amylic 6¢ (fusel Oil)... sceseeseceneeseee Cig Og. Caprylic 6 saeeevesevceconsceeee cveeeeaceseeen Cig H g0p. . Ethal (ethalic-alcohol)....... +» CyeH3,0, . Cerotine (cerotic alcohol)... ss sserenseeee + CegH sg: . Melissine (melissic alcohol)....sesceererssesee CggHeg0o- CONIA TP Or Each of these compounds, denominated alcohols, it will be seen, con- tains 2 atoms of oxygen;—the first, or methylic alcohol, contains C,H,; the second, C,Hg—C,H, + C,H,; the third, C,H,, and so on for the others, by the addition in each case of C,H,, or some multiple of this expression. In the cases requiring a multiple of O,H,, it would seem that one or more intermediate compounds are wanting. These may here- after be supplied ;—as, for instance, between amyljc and caprylic alcohol the compound, C,,Hj,0,, is not yet known, but when a compound having this constitution shall be discovered, it is safe to predict that it will have the general properties of this class of bodies. We have, therefore, as a general expressive for the alcohols, the- formula, CynHo(n + 1)0o- we Besides the above series of alcohols, many other series are known, among which are the following, taken from Gibbs’ Report: Hydrogens. Acetenes. Formic Acids, Oleic Acids. H C,H, . CHO, C,H,0, CoH, C,H, C,H,0, CH,0, CH CH, CHO, C4 pH,0, fs TH, OH, C,H,0, C,9H 1,0, Fon, i ConHen + 1 ConHon CanHonO4 ConHo(n-+ 1)04 546. The compound, C,H,, which in all these series sustains so im- portant a relation, has been called the homologizing body. But it is Questions.—In what do homologous bedies of the same series differ from each other in composition? What series of substances of this kind is mentioned? What is said of the composition of the alcohols? Give the general formula for the alcohols. 546, What is the compound, C,H,, here called? OF ORGANIC BODIES. 403 probable, .that in other series other compounds, or perhaps a certain number of atoms of an element, may serve as the homologizing body. Thus, the ethyle and phenyle compounds differ from each other by Cy, which may be considered as the homologizing body connecting the cor- respondirig compounds of the two classes, so as to form two terms of a homologous series. . 547. Homologous bodies of the same series are in general similarly affected by the action of a reagent; and the resulting compounds will be homologous. This is implied in the definition of those bodies given above. The alcohols, Cg,Ho(n+-4)0,, for instance, by the action of oxydizing reagents yield corresponding homologous acids, Cy,H—,0,;— and intermediate between the alcohol and acid, in several cases, another compound is known, called an aldehyde a alcohol dehydrogenatus), and having the composition, Ca,Hn0,. ther compounds of this series, we may confidently anticipate, will hereafter be discovered. The following table contains the formule of the alcohols, their cor- responding aldehydes (when known), and acids:. Alcohols, ‘ Aldehydes. Acids, 1. Methylic... CgH,O. «10.2.0 ~ seensaeee OpH,0y. 2. Wi CH Og wee eeee "C,H,0. —sssveeee CHO, 3. CyH Og vreveevee CgHgQg — avevereee CgH Oy: 4. C,H 0. CyHyOg — seveeeeee CHO, 5. CipHl gg veeerevoe- OygHgQg sevsreeee Crp Oy 6. Caprylic ... CigH gO, «recvees ones Cy gH gy. 7. Ethalic..... CggHs,0 -- CypHa0g oveeerere CagH 904. 8. Cerotic..... Cg HO, + — neeesees O54H 5404. 9. Melissic.... CggHggQz »-seereee ————svverveee Ogg Hg 04 Besides the acids in the above list, several others are known of the same series, some of which will hereafter be mentioned; but the cor- responding alcohols and aldehydes have not been discovered. 548, In every homologous series as yet known, containing oxygen, the number of atoms of this element is constant; and the same appears to be true of nitrogen, as will hereafter be shown. In the alcohol series, Cz,H(n-+-4)0,, it is evident the smallest value we can give to n is 1, and the formula then becomes C,H,0,, which represents methylic alcohol, but what the extreme upper limit may be we are ignorant, If in the general formula for the alcohols we make n= 0, the formula becomes H,0,—2HO, which represents 2 atoms of water. Water is therefore said to be the type of the series. In like Qurstions.—May there be other homologizing bodies? 547. What is said of the effect of reagents upon homologous bodies of the same series? Into what are the alcohols converted by oxydizing reagents? What inter-: mediate product is obtained in some cases? What are contained in the table in this paragraph? 548. What is said of the oxygen and nitrogen in the homologous series now known? Why is water said to be the type of the series of alcohols? 404 GENERAL PROPERTIES OF ORGANIC BODIES. manner the general formula for the oleic acids, Cy,H(,—,)0, when n == 1, becomes 0,0, == 2C0,; the type of the series is therefore car- bonic acid, CO,. 549, Although all the compounds of any homologous series are essen- tially similar in their leading properties, yet we may often observe a gradual transition as we pass from one to another of the same series. The carbo-hydrogens (Hydrogens and Acelenes, p. 402,) having the smallest number of atoms are gaseous at ordinary temperatures, but as we ascend in the series, that is, as the number of atoms in the com- pound is increased, they become less and less volatile, until the higher members of the series, at the ordinary temperature, are liquid, or even solid. Methylic‘alcohol, the first in the alcohol series, boils at 152°, and the others have each a higher boiling point in proportion as the number of atoms is increased. The last three are solid at ordinary temperatures. In general, in any series, the boiling point becomes higher as the whole number of atoms in the compound is greater. 550. Analysis of Organic Substances.—The analysis of a compound has for its object to determine its composition; and in organic chemistry may be either proximute or ultimate. By the proximate analysis of a substance we separate and determine its proximate principles, or, in other words, the several organic compounds which may be contained in it, as sugar, gum, albumen, &c.; but by its ultimate analysis we determine its ultimate elements, as carbon, hydrogen, nitrogen, &c. The methods of separating the proximate principles will be described as we progress, but for general modes of analyses the intelligent student will consult works treating specially of Analytical Chemistry. 551. Proximate principles are the proper organic compounds, which cannot be separated into other kinds without evidently changing their nature; they are usually characterized by one or more of the following properties, viz. : 1. Capability of combining in definite proportions with other elementary substances, or well determined compounds. 2. Capability of crystalizing, when obtained in the solid state, or having a definite mélting point. 8. Having a definite boiling point, and being capable of distillation, or sublimation, without decomposition, or a change of properties. These compounds are seldom found uncombined in organized bodies, and their separation, or the proximate analysis of the substances con- taining them, becomes an important object to the chemist, and is often attended with no little difficulty. S Questions.—549. Do we observe a gradual transition in the properties of the members of a homologous series as we pass from one to another? Give an instance to illustrate. 6550. Define what is meant by the proxi- mate and what by the ultimate analyses of an organic compound. What is w proximate principle? 551. What are the characteristics by one or more of which an organic compound will usually be distinguished ? STARCH. 405 STARCH, SUGAR, GUM, LIGNINE. 552, These four organic bodies constitute a natural family, possessing this remarkable peculiarity, that each member is composed of twelve atoms of carbon, united with a certain num- ber of atoms of water, or rather with the elements of water, oxygen and hydrogen. In general, they are nutritious sub- stances, and do not possess any very active chemical affinities. STARCH, OR FECULA, CH, Ov. 558, Sources.—Starch, or fecula, is obtained from a variety of vegetable substances, as the different grains; and from many roots, as the potato; and also sometimes from the stems of plants. It is contained in the cavities of the vegetable tissues, in the form of small, white grains, which always have a rounded outline, but vary considerably in size and form, as obtained from different sub- stances. Hach grain is inclosed in a delicate envelope that is not readily acted upon by cold water, but is ruptured by the expansion of the inclosed substance, when the water is heated nearly to the boiling point. . To show the appearance of the starch globules, in their cells in the vegetable tissue, cut a very thin slice of a potato, and examine it carefully by means of the Section of Potato. compound microscope ;—their appearance will be much as repre- sented in the above figure. If the slice before examination is -moistened with a very dilute alcoholic solution of iodine, the starch globules will be colored blue, while the other parts remain uncolored. The next figure shows the arrange- © Kaley ment of the starch globules in a grain starch Giobules in a Grain of Rye . QuzstTions.— 552. Of what are starch, sugar, m, &c., composed? 553. From what is starch obtained ? How is buh ae inclosed How may the grains of starch be shown in the potato? 406 STARCH. of rye. A, the outer seed-coat, which constitutes the bran after grinding ; B, the gluten (to be described hereafter); and C, the grains of starch. The grains of starch from different sources vary greatly i in size, and present different outlines. Of the following figures, A repre- sents starch grains of the potato, B those of wheat, and © those of peas. B Cc of 0® Qo Oye “sez Oy pe Starch Grams of the Potato. Ditto of Wheat. Ditto of Peas. 554, Preparation and Properties—Starch is easily obtained from potatoes by met ve tubers, and then inclosing the pulp in a piece of cloth, and washing it freely ‘with cold water, at the same time pressing the mass between the hands. From wheat or rye flour it is easily procured by placing the flour upon a piece of muslin, and working it with the hand while a small stream of water is poured upon it. The starch is washed through with the water, while the gluten remains as a tenacious mass upon the muslin. After a few hours the starch, will all subside. Separating Starch from Wheat Flour. QUESTIONS. —What is said of the appearance of starch globules from different sources? 554. How may starch be obtained from the potato? How from wheat or rye flour? STARCH. 407 Starch is an insipid white solid, quite insoluble in cold, but slightly soluble in boiling water. In the latter case, the granules are broken, and the broken envelopes floating in the solution give it the consistence of a jelly. ‘In this state it is used for stiffening ‘linen. Though quite insipid to the taste, it forms a large part of many articles of food, as the different grains, rice, the potato, and other esculent roots. It also performs important functions in nearly all vegetables during their growth. The substances known as arrow-root, tapioca, and sago are different varieties of starch. Iodine forms with starch a beautiful blue compound, which is quite insoluble in water; it therefore serves as an excellent test for it. 555, When starch is kept for some time at a temperature between 300° and 400°, it undergoes a peculiar change, and becomes soluble in cold water, and is called British gum, or leiocome. A substance very similar to the above, but called dextrine, is produced by gently heating starch in water acidulated with sulphuric acid, or con- taining infusion of malt. It has the same composition as starch, but is very soluble in cold water, and is not colored by iodine. If the mixture is boiled for some time, grape-sugar is formed, of which more will be said hereafter. Diastase is a substance produced in small quantity in the process of malting grain, and is found in the potato soon after germination com- mences, in the parts near the young germs. It is noted for its specific action upon starch, converting it first into dextrine, in the same manner as diluted sulphuric acid, and afterwards into grape-sugar. Diastase is known to contain nitrogen, but its composition, further than this, has not been well determined. 556. The operation of malting consists in exposing grain (usually bar- ley) to the proper degree of heat and moisture, with the free accession of atmospheric air, to produce incipient germination, and then suddenly checking it by elevating the temperature. This is done by first soaking the grain in water until it is fully swelled, and then placing it in heaps upon a floor until it begins to germinate, when the further progress of the vegetable process is arrested by quickly drying it at a moderately-elevated temperature. During the incipient germination, a portion of diastase is produced, by which, in the subsequent processes to which the grain is subjected, much of the starch of the grain is converted into dextrine and grape-sugar; and the grain (now called malt) becomes fitted for the uso to'which it is applied. It is chiefly used in the manufacture of beer. Qurstions.—What is said of the properties of starch? What varieties of it are mentioned? 655, What test of starch is mentioned? How is starch affected by a heat of 800° or 400°? What is dextrine? What diastase? 556. What is malt? What use is made of malt? 408 SUGARS. SUGARS. 557. There are several varieties of sugar, but the most important are cane and grape-sugar,—names suggested by the sources from which they are respectively obtained. All the varieties of sugar possess a sweet taste, are soluble in water, and are susceptible of undergoing a peculiar change, called the vinous fermentation, by which aleohol is produced. 558. Cane-Sugar, C,,.H,,0,,.—Most of the sugar of commerce is obtained from the sugar-cane (arundo saccharifera), repre- sented in the figure ;—-scale, one inch to four feet. But it is procured also in this country in large quantities from the sap of the sugar-maple (acer saccharinum). Many plants contain it in their juices, as the common beet and other roots, and the stalks of Indian corn. Their juices, after being expressed from the plant, are evaporated until a dense syrup is obtained, from which a large portion of the sugar erystalizes on cooling ; and the remaining liquid portion is ‘then drained off, and constitutes treacle, or molasses. Pure sugar is-a white, inodorous sub- stance, of a very agreeable, sweet taste, which it imparts to its solutions. By slow evaporation, in a very warm room, it is obtained in large rhomboidal crys- tals, which are sold as rock-candy. It . is very soluble in water, but is dissolved Sugarcane: only in small quantity in alcohol. Its density is 1-6. It melts at about 356°, and on cooling forms a transparent, vitreous mass, called barley-sugar, which, however, = ae Qussrions.—557. How are the sugars characterized? 558. From what is cane-sugar obtained? Give some of the properties of sugar? What is barley-sugar ? SUGARS. 409 after a time, becomes white and opaque, and is then found to be a mass of small crystals. Its composition remains without change. By heating cane-sugar to 420° or 425°, a change of composition is effected; it then gives up 2 atoms of water, and a brown substance oe formed, called caramel, which has the composition, CigH,Op- E 559. Grape-Sugar—Glucose, C,.H,,0, = CeH iO + 2HO.— This substance, which much resembles the preceding, has for its composition, when crystalized, C,,H,O,; but by a boiling heat, two equivalents of water are expelled. It is more generally diffused in nature than cane-sugar, being found in the grape and most other sweet fruits. It constitutes also the solid part of honey. It may be obtained from grapes by expressing the juice, and neu- tralizing the free acid with chalk, and then clarifying and crys- talizing in the same manner as with cane-sugar. Grape-sugar is less soluble in water, and forms a less tenacious syrup, and is less sweet than cane-sugar. One ounce of water will dissolve three ounces of cane-sugar, but only about two-thirds of an ounce of grape-sugar; and it is estimated that one ounce of the former has an equal sweetening capacity with two and a half ounces of the latter. Grape-sugar does not crystalize as readily as cane-sugar, and is soluble in oil of vitriol, while cane- sugar is blackened by it. A dilute solution of sulphate of copper, containing a little potassa, or tartrate of potassa, is at once rendered colorless by grape-sugar, at the ordinary temperature, but this effect is produced by cane-sugar only by boiling. This serves as an unfailing test to distinguish the two varieties of sugar. The color of the copper solution is destroyed by the precipita- tion of suboxide of copper, Cn,0. 560. Grape-sugar may be prepared from several substances which have a similar composition, as starch, gum, and woody- fibre or lignine, and is occcasionally found in the animal system, as in the disease called diabetes. It then makes its appearance in the urine. It is sometimes called starch, sugar, diabetic sugar, and glucose. The latter name is more properly applied to the Quesrions.—What is caramel? 559. Describe grape-su i ‘ F What : . gar. What is said of its solubility in water and its sweetness, as compared with cane- sugar? How may the two kinds be distinguished from each other? ae ee the mode of preparing grape-sugar, or glucose, from starch. 35 410 SUGARS. sugar preparea from starch, &e., but the identity of this substance with the sugar of grapes is generally admitted. To prepare grape-sugar from starch, 1 part of sulphuric acid is mixed with 200 parts of water, and heat applied until the mixture begins to boil; 50 parts of starch are then added, and the boiling continued until the liquid becomes perfectly clear. Powdered chalk is then introduced, a little at a time, in order to neutralize the acid; and by a few hours standing the sulphate of lime formed will be precipitated, leaving the liquid clear, which is now solution of glucose. By evaporation of the water it may be obtained in crystals. Wood, the composition of which, as we shall hereafter see, is nearly the same as that of starch, also yields grape-sugar, or glucose, by boiling with sulphuric acid. The process is essentially the same as the above, except that a large proportional quantity of the acid is used. In both of these processes the acid remains unchanged, but by its pre- sence, in some unexplained mode, it occasions the starch and the cellulose of the wood to unite with an additional quantity of water—or the elements of water—thus converting it into sugar. Thus, Starch (or cellulose), C,H i019 -+ 4HO = C,H 01, From clean linen, or cotton rags, more than their own weight of sugar may be formed. Grape-sugar, prepared in this way, is used to adulterate cane-sugar, and in the manufacture of beer and alcohol. Sugar of sour fruits, as currants, cherries, plums, &c., possesses the composition, C,,H,,0,9, and readily ferments, producing aloohol, but is uncrystalizable. 561, Milk Sugar, Lactine, C2,H,,0.,— C.,H,,0,,-+- 5HO.—This sweet principle is obtained by evaporating the whey of milk, purifying with animal charcoal, and crystalizing. It is less soluble in water than either of the other varieties of sugar, and less sweet to the taste. Under cer- tain circumstances, it is capable of undergoing the alcoholic fermentation, like the other varieties of sugar; and in some countries, it is well known that an intoxicating drink is made from camels’ milk. But when in solution it is allowed to stand in the open air, at ordinary temperatures, lactic fermentation takes place, and lactic acid, CgH,Og— CgH;0;,HO, is formed. This change takes place in the ordinary souring of milk. By the action of dilute acids at 212°, lactine is converted into grape-sugar. 562. Mannite, CgH,0,, though not analogous to sugar in composition, is similar to it in some of its properties. It is found in many plants, but chiefly in a substance, called manna, obtained from certain species of the ash, , Quzstions.—Describe the mode of preparing grape-sugar from wood. Does the acid remain unchanged in the operation? What is said of the sugar of sour fruits? 561. What is milk-sugar, or lactine? May it undergo the alcoholic fermentation? 562. Describe mannite. - GUMS.—WOODY FIBRE. 411 @uMms, C,H, Ov. 563. We designate by the name of gum a variety of vegetable substances, which are very soluble in water, but insoluble in alcohol, and unerystalizable. Their composition is the same as that’ of starch, but they differ from this substance in several of their properties. The gums generally exude from the bark of trees, as the cherry and peach trees, and are found on the outside in trans- parent masses, which are more or less globular in form. A gum is a colorless, transparent, insipid, inodorous solid, and when perfectly dry is very brittle, and has a vitreous fracture, When put into water, it first softens and swells up considerably, and then dissolves, forming a mucilage which is often used as a substitute for paste, for which it answers well. Its solubility is increased both by acids and alkalies. Gum Arabic, gum Sene- gal, and gum tragacanth are the most common varieties of this substance. Solutions of gum Arabic, and probably also those of the other gums, yield sugar by boiling with sulphuric acid;—boiled with nitric acid, nucie acid is formed. 564, Pectine is a substance closely resembling gum, which is found in many fruits and in certain roots; it is the substance contained in cur- rants, cherries, apples, &c., which they yield on being boiled, and espe- cially when boiled with sugar. It is a kind of vegetable mucus, and found in smali quantity in many vegetables, By the action of an alkali, er almost any base, it is converted into an acid, called pectic acid. WOODY FIBRE, LIGNINE, CELLULOSE. 565. Wood from a growing tree is of a very complex compo- sition. By examination with the microscope, it is found to possess a highly organized structure (533), consisting of vascular tissue, having its cells filled with a variety of substances, as starch, solution of sugay and mineral salts, albuminous com- Qussrions.—563. Describe the gums. From what are they obtained? What are some of the varieties of gum? How are the gums affected by sulphuric acid? By nitric acid? 564. Describe pectine. 565. What is said of the composition of growing trees? 412 WOODY FIBRE. pounds, oils, and resins, depending upon the natural family and species to which the tree belongs. The first figure in the margin repre- sents a transverse section of the stem of atree. A is the outer bark, which is usually rough, and has lost its vitality, and serves only as a covering to the parts withio: 3B is the inner fibrous bark, in which the sap-vessels are found, serving the purpose of the veins of animals. Inside of this is the wood, consisting of the part (, which is usually whiter than the rest, and is therefore called the alburnum, or sap-wood; and the heart-wood, D, which is more solid and durable than the sap-wood, and of a darker color. Both the alburnum and the heart-wood are composed of concentric 7 layers, an addition of a layer being made to the alburnum each year, im- mediately beneath the bark. The next figure represents a transverse section, magnified, of a piece of pine, showing the two kinds of wood—A, the albur- num; B, the heart-wood. The inner rings of the alburnum are gradually converted into firm heart-wood, and seem then no longer to partake of the vitality of the tree. In annual plants, the woody part corresponds to the alburnum of trees. Section of Stem. Section of Pine. 566, Cellulose, C,,H,,0,).—The vascular tissne of which we have spoken is composed chicfly of cellulose, the composition of which, it will be observed, is the same as that of starch, though it differs essen- tially from this substance in some of its properties. Cellulose constitutes the basis of wood, and is obtained by digesting saw-dust, paper, or linen or cotton rags, successively in aleohol, ether, diluted acid, diluted alkaline solutions, and water, so as to remove every- thing which is soluble in these menstrua. It is found in very different states; as indigestible and hard, in wood, and in the shells of nuts; as tender and easily digestible, in the esculent Questions.—What is represented by the first figure on this page? What by the second? 566. In what is cellulose found? What is said of its composition ? WOODY FIBRE. 413 roots, and in the pulp of fruits, as the apple, pear, &c.; as light and porous, in the pith of the elder, and in cork; and as soft and flexible, in the fibres of cotton, flax and hemp. 567. Lignine, Woody Fibre—The vascular tissue of plants, when first formed, is composed of nearly pure cellulose, but after- wards the cells become lined with a hard incrusting substance, which, in trees and shrubs, for years increases in thickness and solidity. This is called lignine, or sometimes woody fibre, though the latter term is more properly applied to wood as found in the tree, and composed of both cellulose and lignine. Lignine is found more abundant in the heart-wood than in the alburoum. The composition of lignine is believed to be essentially the same as that of cellulose, but it has not been fully determined. | We have seen above (560), that wood treated by sulphuric acid is con- verted into grape-sugar, but it is only the cellulose that is capable of this change; lignine is not affected by sulphuric acid, or only charred. The mutual relations of starch, sugar, and woody fibre, are singular and important. ‘heir composition, we have seen, is nearly the same; and they are convertible into each other by easy processes; indeed, we are able to recognise this conversion as really taking place, in certain cases, in the natural process of vegetation, as shown in the malting of grain. The same change takes place in the ripening of many fruits, as the-apple and pear, which are acid until they approach maturity, when they become more or less sweet. The sap of the maple and other trees contain sugar, which subsequently becomes changed into woody fibre, and thus contributes to the enlargement of the tree. Changes produced upon Woody Fibre by Acids. 568. Wood, plunged into strong sulphuric acid, especially if a little warm, is instantly charred, as if held near a hot fire. This is occasioned, it is believed, by the strong affinity of the acid for water, the elements of which, oxygen and hydrogen, are abstracted by it from the wood, leaving the black carbon. If the sulphuric acid be diluted, or if added in small quantities, so as entirely to avoid any rise of temperature, the effect is to form sugar, as we have already seen. Questions.—567. In what is lignine or woody fibre found? What is said of the mutual relations of starch, sugar, and woody fibre? Are they capable of conversion one into another? 568. What is the effect ot strong sulphuric acid upon wood? What if the acid is diluted ? 35 * 414 WOODY FIBRE. 569. Gun Cotton — Pyroxyline—This substance, which is noted for its explosive property, is formed by the action of very strong nitric acid, or better, by a mixture of the most concen- trated nitric and sulphuric acids, upon cotton, flax, paper, or fine saw-dust. ; To prepare it, make a mixture of equal parts (by volume) of the strongest nitric and sulphuric acids, and then press into it as mach cotton as can be moistened with it; and, after standing five or ten minutes, press out as much of the acid as possible, and wash thoroughly with a large supply of pure water, and dry carefully without artificial heat. It will be found that two ounces of each of the mixed acids will be sufficient for 75 or 100 grains of cotton. When thus prepared, the cotton appears much as before the process, but has u harsh feeling, and the fibres are less tenacious than in the original cotton. It also gains considerably in weight during the process, so that from 100 grains of cotton as much as 175 grains of .gun-cotton will often be obtained. It takes fire very readily, often at a temperature even below 212°, especially if the heat is suddenly applied; and burns. with an immense volume of flame. Placed on a plate of metal, and very gradually heated, it may sometimes be completely decomposed, without igniting, leaving behind a residue of carbon. When properly prepared, it explodes with great violence, and is entirely consumed. Its power to propel balls is much greater than that of the best gunpowder, which is still further increased by soaking it in a solution of chlorate of potash before drying. The composition of pyroxyline is is uncertain; but it is known that, by the action of the acids, oxygen and hydrogen (in the form of water) are separated from the cotton, and, at the same time, nitric acid com- bines with it. The most probable opinion is that 2 equivalents of cellulose combine with 5 equivalents of nitric acid, giving up at the time 3 equiva- lents of water. Thus, CoqH 0 oy + 5NOg = CoqH 70 47,5NO, ++ 3HO. Gun-cotton, though insoluble in water or alcohol, is usually found quite soluble in sulphuric ether containing a little alcohol. But this is not always the case; and it is believed there are at least two different com- pounds formed in the process, one of them being soluble in alcoholic ether, and the other insolzble. The insoluble variety appears also to explode with more violence than the other. The gelatinous ethereal solution of gun-cotton is used in surgery, as a substitute for sticking-plaster, or court-plaster, under the names of col- lodion and liquid cuticle. Xyloidine is an explosive compound similar to pyroxyline, produced by the action of strong nitric acid upon starch. Questions.—569. Describe the process of preparing gun-cotton. Give its properties. What is the most probable opinion concerning the com- position of pyroxyline, or gun-cotton? In what is it soluble? What is xyloidine ? WOODY FIBRE 415 Changes of Woody Fibre, by Air and Moisture. 570. When lignine is kept perfectly dry, or constantly im- mersed in water, it may be preserved for any length of time; but exposed to air and moisture, it undergoes a slow decay, called eremacausis (from erema, slow, and kausis, combustion), by the absorption of oxygen, and the evolution of water, or its elements, and carbonic acid. The chemical changes which in this case occur, are very nearly the sme as in combustion, except that they take place more slowly. Io both cases, the constituents of the wood, with the addition of oxygen from the air, are converted into carbonic acid and water; in both cases, also, the hydrogen is oxydized more rapidly than the carbon, as is shown by the black color during combustion, aud the dark brown during the slow decay of vegetable matter. The flame which appears during the combustion of wood and other vegetable substances, is occasioned by the burning of the gaseous hydro-carbons, evolved as the first effects of the application of heat. 571, Humus, Geine.—Every fertile soil contains more or less organic matter in a state of decay, to which its fertility is, in a great measure, owing, and which has received various names, as humus, geine, ulmine, vegetable mould, humic, geic, and ulmic acids, &c. This decaying matter, which we will call vegetable mould, is ever changing, as the carbon and hydrogen are oxydized and separated; and from this and the carbonic acid, water, and ammonia, formed from them in the soil, the plants derive their chief nourishment, by means of their roots, which are extended in every direction. 572. Peat.—Peat consists of partially decayed vegetable matter, which is found in beds, in moist places, in every country, and is usually mixed with more or less matter of mineral origin. It is formed from vegetable matter when slowly decaying under water, and of course free from the influence of the oxygen of the air. Water is decomposed, yielding its oxygen to one portion of carbon, to pane carbonic acid, while another portion of carbon unites with the hydrogen, forming light carburetted hydrogen (307), which often issues from the soil in large quantities, as the fire-damp of coal mines; but most of the carbon remains behind as peat. Recently formed peat is also usually found interlaced with the Quzstions.—570. May wood be preserved if kept perfectly dry? What is the effect when exposed to air and moisture? What is said of the chemical changes which take place in eremacausis? 671. What is contained in every fertile soil? 672. Describe the formation of peat. 416 WOODY FIBRE. fibrous roots of growing plants, and retains, more or tess distinctly, the forms of many of the piants of which it has been composed; but old peat is more homogeneous, and may be cut into the form of bricks, like moist clay. In many countries it is used extensively for fuel, being first thoroughly dried. 573. Coal.—A sufficient description of the different kinds of mineral coal has already (298) been given. Immense deposits of this mineral are found in many countries, which have no doubt been formed from vegetable matter, at a comparatively early period in the world’s history. They are usually not very distant beneath the surface; and are con- tained between rocky strata of great extent. Occasionally these strata are covered with many feet of rock and earth ;—everything indicating that vast changes have taken place in the earth’s surface since their formation. That all the varieties of mineral coal have been produced from the matter of plants, which in former periods grew up and flourished pre- cisely as plants now do, is universally believed by men of science. The evidence is found in the position of the coal, which always occurs in the form of beds interstratified above and below with solid rock formed at the same time with itself ;—in the vegetable impressions which abound in the rocky strata of every coal formation;—and in the organized structure often exhibited by the coal itself. We may suppose that, by the decay of the vegetable matter, peat was first produced, which was subsequently converted into proper coal, in a manner not fully understood. Mines of coal are limited to the temperate zone, none of it being found in very warm or very cold climates. : 574. Petroleum.—Petroleum, or rock-oil, is an odoriferous, oily liquid, which, in many countries, exudes from the rocks and ground, being formed, in all probability, from vegetable matter at the same time with . peat and coal. It is often found upon the surface of lakes and springs, as at Seneca Lake in New York, where it is called Seneca oil. By distil- lation, petroleum yields a, yellowish liquid, lighter than water, called naphtha, or oil of naphtha ; which is probably » mixture of several com- pounds that have not yet been separated. It is the liquid used to pre- serve the alkaline metals. of siphons Loadstone .....ssesssseceeee evel ll, 849 Capeddien oe teee ekacas 478 Lunar caustic ....... 885 Lymph ........ 510 orf eevee tere oeceecceesensenene M Madder .....c00sseceevvsscenesaccess ATT Magic Circle ...escesssseeeeeesesvees 125 INDEX. MAGNESIUM o0.. Magnesite .... Magnet....cccee serseceass electro..... Magnetic induction needle .... terrestrial .....000 «ss Magneto-electric machine....... Malachite....0.scsscsnesssscses ones Malamide...... 2.00. MANGANESE 00000 ses cee ners Manna .....00 oe Mannite..... Marble ......+ Marcet’s apparatus... Margarine ... cer « Margarone cacser cece cseseescs veces Massicot...... Satsudseinoseeieotentess | Mastic... sssossccereoee sssvavieceeas Melam ........ Melamine ......000 eoveeee Melissine.......s0ssereeee Mellon.......0 Mercaptans 2.0... seevessereseeees ove Mercaptides .......006 MERCURY ..... Metalepsy ......ssesesee Metallurgy, electro... Metamylene.......... Methylal........ Methylamine .. SUQAT Of cevecconeeececceeonenee Mineral, chameleon...... ...... pitch... Minium........ Molasses ... Molybdenite ... MOLYBDENUM vescsscecssecseesececse PAGE 387 338 111 125 . 113 - 114 126 114 132 373 479 vee B45, vee 410 .. 410 497 384 438 458 458 © 369 464 486 . 486 + 462 . 486 432 432 » 374 - 427 sees 423 wee 400 + 109 vere 448 - 430 472 » 510 410 347 + 878 « 416 . 370 408 378 878 + Nicotine.. INDEX. Monasitec.cccseesosceesssetrersse ees Mordants... Morphia, Morphine. Mortar .....c0e0ssesooes Mosaic gold... Muscles ..... Myricine... Myvosine ... Myrtle Wax ...cssscssscessseses ove N Naphtha......... Naphthalene . Naphthaline .. Narcotine........ Nascent state ... Natron .......0005 NICKEL...... NIC ssesccssa vevesececvssaensocrees Fer Nitriles...... guises eakeasipawesnk bang NITROGEN Nomenclature .......cceceseescoveee Nutgalls.....scceessceere seaesewanis Nutrition .......c0sccscceses cooseeeee Oo Ohm’s formula.. Oil of aniseed........0 | pitter almonds......ccsceeee CINNAMON, gor cpurdpug anererens cumin .... CLOVES instar Menace CLOMI.......00 voveoecese roveee garlic ..... juniper... TeMo......000 eeeeee mustard, black. PCPPCL oeoeee seve spirea ulmaria.. turpentine....... PAGE 844 476 469 833 864 498 461 452 461 416 417 417 470 seee 205 see 819 wee 865 - 470 305 480 194 15T 468 508 - 100 452 448 451 452 452 447 453 447 447 452 447 452 452 525 PAGE Oil of winter green...... seve 451 Oil, castor.. tecsseeee 460 fusel.... 430 Oleine ......cceesecssesecresesce severe 4506 Opium ..ssccecessevccsencessersseeeers 469 Orcine .......00 00 477 893 253 3844 .. 891 440 174 Organic bodies ......ssss00 cesses eee Orpiment ......000cereessersececes cee 892 460 - 505 Palmatine. Pancreatic juice .. Paracyanogen ..... Paraffine...... Paramylene.. Pendulum, ballistic ......ssessesee Pepsine ..rrecece sorseveer severe socves Phenol... .sseee oes PHOSPHORUS.... Photography... Photometers.... Picrotoxine...... Pinchbeck.... Piperine....... Pitchblende..... Plasters ...+00 008+ Plaster of Paris PLATINUM. sovees see Plumbago..... Polymerism ..eccccssecsssssseeseere 157 526 PAGE Porcelain oo... seeseeee 842 Potassa, Potash. POTASSIUM weeesee Potato oil...... Propione..... Prussian blue. Wneeeccececece Pulse glass ........ Purple of Cassius... , Purpurine ......4 Pyroacetic wilt Pyrochlore .......+ weevee 279 wa 478 ww. 8381 sees B74 Quinia, Quinine...... 0.0006. sesaee 470 R Quartz ..... ences seceeenenceees 54 251 Bain ...cccceseee eee Rats-bane .. Realgar ..... Red Jead...... precipitate ........... ze Prussiate of potash... Register thermometer ... Repulsion.......ssse cere ReSin..sssseer covers ceceen ove Respiration of animals........... 506 plants....0.cee 495 RHODIUM ..s.cseee ce seseeececsscer O92 Rocelinine.... eres ATT Rochelle salt... seco 467 Rock candy .. see 408 Rock oil... coeee 466 RoSin we sscececee coeeseeee sressssveene 4683 Rotation of Crops...ececeveseseeree 497 ooee seevee 877 sevaee 488 25 eee INDEX. Rupert’s drops .. RUTHENIUM ...... Riutile ....csececve ces ccs ccesscccecs vee 8 Safetiy lamp... eseccccsscecccenceces Sago ... see ceeeee Saleeratus........ Sal-ammoniac... mirabile..... BOD. scersicsecssecasecs hepsteadeees volatile ..... see cocceenenes oneeee Glauber’s.... microcosmic. rock.... Saliva.......secses sosssees Sandarac...cssssvecsssserceesevece eae Sapphire... 0000 Scheele’s green. Sealing-wax.....sse0 Selenite ....... SELENIUM.. Seneca oil. Shells sai cccessssisssvcesoenesess say SillCa sscsicwecece sense S1z1con... Silurus electricts........ssccees vee SILVER ..... Smalt.... whee eewvesece o neeo cence costae a er eens seeccceosece PAGE 340 421 . 827 392 378 270 407 805 » 821 314 315 321 312 338 314 322 812 450 504 464 340 3878 464 835 239 416 - 500 279 « 278 101 381 364 . 864 462 . 811 315 265 310 869 372 INDEX. Solar spectrum ....ecececoessoeee ove Soluble glass.... ooecen, Spathic irom ......cssscsees soneenene Specific gravity of atoms.. Specular iron ......s0 essesssnenenee Speculum metal... Spelter ......... cee Spermaceti ......... Spheroidal state of liquids...... Spinelle ...cccececsscooscs voscessesces Spirit of hartshorn.........sece eee Mindererus.. turpentine ......seccccnee SALE osccisseesssessasessans, wine Spirit-lamp ....,..16eccser eee Spodumeme ...... 1014 sseveeeee B18, Springs, sulphur .. eocccecce Stalactites...... +00. Stalagmites... 3s ae Stanethyle......10. cecsssees coseesese Starch sssess sosess'ensecesccisscaessaes Steam..... Stearine......csevcccssccvces cee ceeeer Stearoptens ......ssccces reese ceceee Steel ......scserecesee Stereotype plates... Stibethyle ...... 0.008 Stibium ..........00 vee. Strichnia, Strichnine.... Strontia....c.recceescesce reece Strontium qa ecesaveustervesreee Styrax..cccecccces cccven cscs rovcesees Styrole .....00. Substitution ........ Sugar, barley... CADE... MILK. ecseeecoeee of lead........ Of sour fruits... seceee PAGE 63 280. 356 |: 2» 151 349 872 360 | 460 | 51 840 202 | 426 | 446 211 420 421 342 | 235 834 + 884 474 405 43 456 446 853 335 474 365 471 330 330 451 « 461 400 408 ve 408 «- 409 « 409 - 410. 425 410 527 ; PAGE Sulphoform.....sceccssssesraseee 442 SULPHUR... seesseseenee ' springs... SBYMbO]S...000 seesees ‘Synaptase .. Sympathetic ink....... cersecenseee 461 wee 114 ee 468 + 874 . B74 - 407 sersvere 463 eevee 417 serene ore, 466 : Tantalite...... ‘TANTALUM.. |; Tapi0ca sesees sereeseeee PAT sisvcssswenaced chases coal... Tartar’ seossssiieseeseazs CTEAM Of seecer sennes vepecsens, 467 CMCC raners senecs scerennesae 467 | Telegraph, electro-magnetic..... 183 TELLURIUM wecsesees seseesecarenevege, 240 TERBIUMsspoepeseenessecenepeescases GFL Thermography ......0008 Thermometers..... THOYING o...00 ceeeene Tincal ....... TITANIUM... Tombac..... Tonka bean Torpedo..... Treacle ... Tronaice seve TProostite ssc averer TUNGSTEN .++ esse Turmeric root.. Turnbull’s blue.. Turpentine, spirits of...... 528 PAGE Turpentine, Oil Of.....essceeesssees 446 Turpeth, mineral.......seseseereee 880 TUrnsol......s0e csecesees soneesserceee 477 Type metal ......sccossercerseceerers O09 U Ulmine ...... 2.00. sstissbevenceossesss 415 TY aniter...cccccescoscevsesesessssees O74 URANIUM sisscassssccssses svcesvcssees 874 .482, 512 Ui ....c0scceveece ceseorececveceeees B12 v Valeronitrile ......scssceceecereesees 480 VANADIUM woeseesees avietacveraes BIS Vanilla ..ccocsce sescseceecccocsessceee 454 Vaporization.. veoree 40 Verdigris ... iscieeisissseesss 420 Verditer, green...ceccerceaecceees O77 Vermillion...... s+. Vial, Bologna...... Vinegar ......06 oa sb avevaevecsseuaas 5 Vinous fermentation.. Viscous wo Vital air sesces cre tssees tuvscaeren sdces Volatile alkali........scceessesesoees 202 Voltaic pile .....cccssescesessereenne 92 THE coves 471, INDEX. PAGE Ww Water .. ...s00 ccsesenee sesseocesses ces constitutional...... of crystalization ..... Time ...00s eveccacee ceveccees vee Wax, De@8?-..sceccrsse ceccssescees Bee 185 296 .159, 296 331 Whiskey, ..+00cceeercesesescsees seers White lead......scccsecccsceceeeesees Wo0d ....00e ae Swe Aciseeesens coceseess Wood naphtha.......ss.ccscerces ace spirit....... svarseee 428 VINOZOL ecesers ssvcenrenceess 424 x Kanthine ........ cssccsseecveeceevees 477 Kyloidine .......00 seeessveeeees Y Yeast wrccsseroveececesscseee cersevees 418 Yellow prussiate of potash...... 487 CLYOME eeveesesesceserereree BOD King’S...cecseere ove A YTTRIUM esessseee sovsseeee seeseseoees Zaffre..... ZING essoeeees Zincethyle.. Zircon ....0 ZIRCONIUM aia ZixCODID...606 sence sevecevssessecsees O44 END. eee Bispc ert: are ee