■'.■J' ■J ,\^ xv s~i.^ ^os^^UieeuBeitifdBeL £>:_:•:.= ? PAET I. CHEMICAL PHYSICS. CHAPTER I. OF SOME PHYSICAL COi^DITIOXS OF MATTER. § I. Matter and Force. 37. Matter. — "Whatever occupies space and is revealed to our senses, is termed matter. Different kinds of it, as Tvood, "water, air, are called substances; and any limited portion of it is called a hody. The properties of matter are the characters by which it is knoTvn ; and these may be either general^ as those which belong to all matter, or specijic, those which serve to distinguish one body from another. 38. Bodies are of two kinds, simple and compound. Compound bodies are such as can be decomposed or separated into simpler parts or elements. Simple bodies, on the contrary, cannot be thus separated. Water is a compound, and can be resolved into two invisible gases, but neither of these can be again decomposed. Brass may be separated into copper and zinc, but no one has yet been able to obtain from these anything besides copper and zinc. 39. Persistence of Matter. — flatter is impenetrable. As it is created in space, it must occupy space ; two bodies cannot exist in the same place at the same time. Matter is thus persistent in space, and it is also persistent in time ; — it is indestructible. 37. "WTiat is said of matter and its properties ? 38. How are bodies divided ? Give examples. 39. What can you say of the indestructibility of matter? 40. Give ex- 28 CHEMICAL PHYSICS. There is no evidence that in the course of nature, or by any of the operations of art, matter is either called into existence or anni- hilated. It may be changed from state to state thousands of times without the smallest loss. A pound of ice converted into water or into steam continues to weigh exactly a pound. When fuel is burned, or water disappears by evaporation, or our own bodies are resolved into earth and air, it is only the migration of matter through the circle of natural transformations. Forms alone are destroyed — matter remains imperishable. 40. Changes of Matter. — The universe is everywhere in mo- tion. The atmosphere is agitated by winds ; the world of waters is in perpetual circulation ; plants and animals spring from the earth and air and return to them again ; all substances around us are undergoing slow transformations ; the stony records of the strata are but histories of past revolutions ; our ponderous earth shoots swiftly along its orbit, while the mighty sun, with all his attendant planets, is sweeping on forever through shoreless space. Nothing around or within us is absolutely at rest. 41. Force. — That which moves matter and produces change is called power, ov force. The causes of the foregoing changes are called the forces of nature. Thus the Force of Gravity draws a piece of iron to the earth ; Cohesive Force holds its particles to- gether ; Mechanical Force shapes It ; Heat Force melts it ; and Cliemical Force rusts or dissolves it. Matter and force are insep- arable ; we know nothing of force except through matter, and nothing of matter except by its forces. 42. Physical Changes. — Those various alterations of place, form, and quality which bodies undergo without destroying their distinctive jjroperties are termed physical changes. Thus iron may be cut into nails, rolled into sheets, drawn into wire, melted or magnetized, but through all these changes it still remains iron. Water changes its form, becoming a solid or vapor, but its peculiar composition as water remains unaltered. Gravity, cohesion, light, heat, electricity, and magnetism are the forces chiefly concerned in producing these changes, and are therefore called physical forces. That branch of science which treats of their efiects is termed Physics. amplcs of the chanpcs of matter. 41. What is force? Mention the eficcte of va- rious forces. 42. What arc physical properties? Physical changes ? 43. What KATUEE OF CHE^HCAL CHAXGES. 29 43. Chemical Changes. — K iron be rusted, burned, or dis- solved, it undergoes another and a deeper change ; its peculiar properties are destroyed, and the metal disappears. In common combustion air and fuel are both changed, and new substances are produced. These are examples of chemical changes, such as are going on constantly around us ; indeed, nature is a vast laboratory v^'here they are incessantly taking place upon a stupendous scale. Chemistry considers the composition of matter, the nature of its elementary parts, the properties of the compounds formed from them, and the forces by whicli its various combinations and de- compositions are produced. 44. Chemical Physics. — Physical forces and conditions have so powerful an influence over chemical action that some knowledge of them is indispensable to the chemical student. The progress of inquiry has, moreover, shown that the various forces are far more intimately related to each other than was formerly supposed, so that to understand them in the best manner they must be pre- sented together. Accordingly, under the title of Chemical Physics, we first treat of those physical agencies which are most intimately connected with the subject of Chemistry. § II. Gravity and Weighing. 45. One of the simplest facts of observation is that bodies are drawn down to the surface of the earth with power. The at- tractive force which produces this effect is called Gravity. It acts between masses of matter of every kind, and at all distances ; the earth, sun, moon, and all the heavenly bodies, thus influence each other. The various objects upon the earth's surface are not only powerfully attracted by the mass of our globe, but, in an infinitely lesser degree, they also attract it ; and it has been further demon- strated that they also attract each other. A pair of leaden balls two inches in diameter were attached to the ends of a rod which was suspended in the middle by a fine wire, Fig. 1. Two other balls of lead, a foot in diameter, were placed upon a revolving platform, and when the larger and smaller balls were brought near together, they were mutually attracted, as was shown by the motion of the is the peculiarity of chemical changes? WTi at does chemistry consider? 44. "WTiat has physics to do with chemistry ? 45. "What is the effect of gravity ? Its extent ? 30 CHKMTCAI, PIITSICS. Fig. L rod. The force exerted did not exceed the trrentr-imllioiith of the weight of the lesser ball, but was sufficient to slightly twist the wire, and give rise to a small oscilla- torv movement. The seemingly in- ert masses were thus proved to be alive with power. The force of gravity is propor- tional to the quantity of matter; that is, if the earth had twice its present mass its attraction would be doubled, and if but one-half its mass, its force would be only half as great. So with any body on the eartb, the force with which it is attracted in- creases or diminishes in exact pro- Matual attraction of leaden ba^s. portion to its quantity. 45. This force gives risa to Weight. — If a body, instead of being allowed to falL is supported, its tendency to descend is not destroyed. It is drawn downward with the same force, but as it is resisted, and at rest, the force takes the shape of pressure. This downward pressure of bodies is called their weight. The weight of a body is the force it exerts in consequence of its gravity, and. as tMs force depends upon the quantity of matter, it is clear that if the mass be doubled- the weight will be doubled : if the mass be halved, the weight will be halved. Weights are therefore nothing more than measures of the force of gravity in different objects. Thus we discover the close connections and depend- encies of all things. The same force which controls the mighty system of celestial orbs, measures quantities of matter in the daily transactions of business life. 47. Standard Weights.— The operation of iceigTiing consists in estimating the force with which any given body is attracted toward the eartli by comparing it with other masses of matter already weighed and marked according to some fixed standard, as Troy, Avoirdupois, or French weight. These standard scales are quite arbitrary, there being no natural starting-point, or unit. The grain weights were originally grains of wheat. The scales estab- Describe the experiment. To -what is this force proportional t 46. What is the caose of prcwure I What i« weight ? 47. What are standarda of we:ght> How IMPORTANCE OF WEIGHING IN CHEillSTKT. 31 Fig. 2. lished in tliis country are capriciously arranged, while tlie FrencK employ a decimal scale, which is far more convenient, and is grad- ually coming into use among men of science. 43. Weighing Instruments. — The instruments employed in fa- miliar weighing are steel-yards, spriogs, and scales, or balances. The chemical balance, Fig. 2, used for analysis, consists of an in- flexible bar, delicately poised at a point exactly midway between its extremities, from which the scale-pans are suspended. Its beam rests upon a fine edge of hardened steel, which is supported by a flat plate of polished agate. This beam oscillates toward the earth just as the rod in the pre- ceding experiment oscillated tow- ard the larger balls. Such a balance is as indispensable to the laboratory of the chemist as the telescope is to the observatory of the astronomer. The foundations of the science are numerical laws, which could never have been arrived at except by its rneans. B^_ o Prof. LiEBiG says, 'The great ^^' - -. ,. ^. , . ,, The Chemical Balance. distinction between the manner of proceeding in chemistry and natural philosophy is that one tceighs, while the other measures. The natural philosopher has applied his measures to nature for many centuries ; but only for fifty years have we attempted to advance our natural philosophy by weighing. For all great discoveries chemistry is indebted to the balance, that incomparable instrument which gives perma- nence to every observation, dispels all ambiguity, establishes truth, detects error, and guides in the true path of inductive inquiry.' §111. Corrvparative Weight — Specific Gravity. 49. "Weight, as thus far noticed, involves only the simple idea of gravity, and is termed absolute weight ; it has no reference to does the French differ from other weights? 48. What is the construction of the chemical balance? How does chemistry differ from natural philosophy ? What does LiEBiG say of the balance ? 49. How is bulk related to weight ? What cases 32 CHEMICAL PHYSICS. bulk or volume ; yet bodies difter very much in their density, or the quantity of matter which they contain in a given bulk. Thus, a pound of cork exactly counterpoises a pound of lead, though the former occupies forty times as much space as the latter. So 100 cubic inches Pounds. Grains. Of Hydrogen weigh . . . 2.14 " Air "... 81 " Water, " ... 3.604 "Iron "... 28.11^ "Platinum " . . 75.68 Platinum, the heaviest body we know, is thus nearly a quarter of a million times heavier than an equal bulk of hydrogen, the lightest of known substances. 50. We now proceed to connect bulk with weight, to find, not the absolute gravity of a substance, but its weight compared with another body of equal size, that is, its relative, or sjjecijic gravity. Any solid substance when immersed in water displaces a volume exactly equal to its own bulk, and, at the same time, loses a portion of its own weight just equal to that of the volume of water dis- placed. Water, found everywhere upon the globe, and easily puri- fied by distillation, is thus taken as the unit of comparison for solids and liquids. But variations of temperature alter the bulk of bodies, therefore sp. gr. is taken at the standard of G0°. 51. Specific gravity of Solids. — Fill a vessel vrith water, Fig. 3. Fig. 3, and drop in it a piece of sulphur which has been weighed. A quantity of water will then escape into the dish be- low, equal in bulk to the sulphur. Weigh the escaped water in the lesser vessel. If the suljDhur weighed two ounces, the water will weigh an ounce. That is, the sulphur weighs twice as much as an equal volume of water ; its specific gravity is, therefore, 2. The best plan, however, is to The Boiid displaces its bulk suspend the solid to the scale-pan of a bal- of water, aucc by a fine thread, or hair, and then are given of the range of weiglitB? What are the relations of platinum and hy- drogen! 50. What is ppccilic gravity ? "What is the principle upon which it de- pendB? 51. What is Bliown by Fig. 3? How is the specific gravity of Bolide ob- HOW SPECIFIC GRAVITY IS OBTAINED. 33 Fig. 4. counterpoise it, or get its weight in the air. Immerse the sus- pended body in a vessel of distilled water, Fig. 4, and as it weighs less, remove weights enough from the opposite scale-pan to restore the lost equipoise. Isow divide the original weight in air by the loss in water, and the quotient is the specific grav- ity of the substance. For in- stance, a piece of lead weighs in air, 820 grains, and loses in water 71 grains. The weight in air divided by the loss in water, gives 11.5 as the specific EfMnM gravity of the lead. Weighing a substance in water. 52. Specific gravity of Liquids and Gases. — Procure a small bottle and make a fine mark with a file and ink upon its neck. Counterpoise it in the balance. Fill to the mark with distilled water at 60° and weigh it. Empty and fill again with the liquid, the specific gravity of which is required. Its weight, divided bv that of the water, gives the desired result. Suppose the bottle holds a thousand grains of pure water ; it will be found to hold 1,845 grains of sulphuric acid, which therefore has a sp. gr. of 1.845. For 1000 : 1.000 : : 1845 : 1.845. It will hold 13,500 grs. of mercury, the sp. gr of which is hence 13.5 ; or Fig. &. 1,030 grs. of milk, sp. gr, 1.03. In practice it is usual to employ a bottle. Fig. 5, holding exactly 100 or 1,000 grains of distilled water at 60"^, which shows the result at once without calculation. The specific gravity of gases is obtained in a similar manner. A fiask or globe suspended from the arm of a balance is weighed when empty, and again when filled with air. This gives the weight of V^_ air, which is taken as unity. Other gases are then Sp. Gr. Bottle, substituted for the air, and their comparative weights ascertained. Gases are subject to variations of density, not only by alterations of temperature, but by changes of atmospheric pressure; these tained? 52. How is the specific gravity of liquidB obtained ? of gases? 53. Ho\T 2* 34 CHEMICAIi PHYSICS. -weights are therefore taken at the standard barometric pressure of 30 inches. 53. Specific gravity of Soil. — The specific gravity of soil, or any other substance in powder, is obtained as follows : Counter- poise a thousand-grain bottle and weigh iuto it 150 grs. of soil to be tested. Fill with water and weigh again ; water and soil give, say 1,096 grs., 150 of them are soil and 946 water; consequently 54 grs. of water have been displaced by 150 grs. of soil. The cal- culation is then easy, 54 : 1.000 : : 150 : 2.777 sp. gr. of the soil. In practice a precaution is to be observed. The soil contains air among its particles, which would vitiate the result. To obviate this, fill the bottle but half full of water at first, and shake it well with the soil ; the air escapes, and the bottle may then be filled with water. 54. Hydrometer. — Take a tumbler, or a light slender-necked bottle, loaded with some shot, and float it in pure rain-water ; it will sink to a certain depth, which raay be accurately marked upon the glass. If now placed in brine or milk, the mark will stand above the surface ; the vessel not sinking so deeply as before, be- FiG. 6. cause the liquids are heavier. Place it in alcohol, and the mark will disappear below the surface ; it sinks deeper than at first, because the liquid is lighter than water. Instruments arranged on this principle, and called Hydrometers or Areometers, are used to measure the density of liquids. They usually consist of a glass stem, Fig. 6, terminating in a bulb below, loaded with shot or mercury, and floating in a narrow glass ves'sel, containing the liquid to be tested. Scales are fixed within the stem, zero being the point at which the instru- ment sinks in distilled water at 60°. In lighter liquids it sinks deeper, and the scale ascends from zero. In heavier liquids it floats higher, and the Hj-drometer. sqsXq is reversed. These scales are arbitrary and diiferent in the various instruments. Tables accompany them, so that we see at a glance the sp. gr. which corresponds to any number upon the scale. Instruments of this kind are much used by manufacturers and dealers, to determine the density or strength of liquors, syrups, oils, lyes, &c. can wc get the epccific gravitj' of eoil ? 54. Describe the liydroraeter. \^hy IMPOETANCE OF SPECIFIC GRAVITY. 35 55. Specific gravity is among the most important of the phys- ical properties of bodies. It affords an important means of identi- fying them. The mineral iron pyrites, for example, is in color almost exactly like gold, and is frequently mistaken for it. But they are at once distinguished by the difference in specific gravity, an equal bulk of gold being nearly four times heavier than pyrites. So if gold is debased by alloying it with a cheaper metal, the specific gravity promptly detects the fraud. The proportion of alcohol in spirituous mixtures, the richness of milk, the strength of various solutions employed in the arts, and the identity and pu- rity of many substances are determined with more or less accuracy by finding this property. § ly. pfinute Constitution of IfatterJ' 56. From the force which acts between masses at all distances, we now pass to the study of another class of forces which only come into play when bodies are in contact. They seem to pertain to the interior structure of substances, and hence before treating of them, it becomes important to inquire what that inner mechan- ism is, or how matter is constituted. 57. Porosity of matter. — If we place a little water upon chalk or cloth, it disappears ; in a certain sense it penetrates them, but it does not enter the solid particles ; it only passes into vacant places termed pores. Not only loosely composed substances, as soil and flesh, but wood, rocks, stones, and even dense metals have the same porous texture. A pressure of a single atmosphere is sufficient to drive the liquid metal mercury through the pores of wood. Water gradually works its way through beds of rocks in the earth, and stones taken from the bottom of the sea at considerable depths, are found penetrated by it to their very centre. Mercury passes through lead, and water has been also forced through the pores of gold. So, that though matter is essentially impenetrable, it is also universally porous. 58. Interior movements of bodies. — If a closed India-rubber bag filled with air be squeezed, it will be compressed into less must its scales "be differently placed? 55. What are the uses of specific gravity? 67. How extensive is the property of porosity ? 58, Describe the illustrations of 36 CHEMICAL PHYSICS. Expansion of a gas. Fig. 8. Fio. 7. If alcohol and water be commingled, the mixture occupies a smaller space than did the separate liquids ; their particles have therefore approached closer to each other. If iron, or the densest of all metals, plati- num, be hammered, it will be driven into less compass, the metallic particles being forced into closer relation. A glass bulb with an open tube is partially filled with water, and inverted in a vessel of the same liquid, so that the upper space will enclose air. Fig. 7. If, now, heat be applied to the bulb, the air is expanded and the water pressed down. If the buJb be filled with water up to a point marked upon the neck with ink. Fig. 8, and the water heated, it will ex- pand and rise above the mark. Or if a copper ball, which just slips through a ring, be heated, it is en- larged so that it rests upon the ring, and will not pass through it. Fig. 9. But if we remove the lamps and wait awhile, the heat gradually escapes ; the air shrinks to its former compass ; the water falls again to the ink-mark, and the ball drops through the ring. 59. These expansions and contractions, exhibited by matter in its three-fold state, are the result of movements among the constituent particles, which first recede from each other, and then come together again. I^ot do these movements of the particles • occur at random ; they are strictly regular. A definite increase of pressure upon sub- stances occasions a corresponding approach of their particles ; as heat is steadily applied, dilation steadily follows, and if they are sub- jected to cold, contraction occurs, the dis- tance between the particles diminishing with every degree of descending temperature. 60. Atoms and their Interspaces.— From these facts, it is concluded that matter con- sists of exceedingly minute particles which Expansion of a liquid. Expansion of a Holid. tlio interior movements of bodies. 69. What is said of the reeularily of theeo movemcnte? 60. How Is matter supposed to be constituted? "What are atoms? COXSTITUTION OF MATTEE. 37 are never in absolute contact, but are surrounded bj unoccupied spaces, in which they are held by the action of internal forces. These ultimate, separated, material points, are called atomSy the word signifying an indimsible particle. Of their shape nothing is known. The intervals between them, it is supposed, are far greater than their diameters ; indeed the grouping of the celestial orbs is often taken to represent the distribution of atoms in a solid sub- stance. Sir John Herschel asks why the atoms of a solid may not be imagined to be as thinly distributed through the space it occu- pies, as the stars that compose the nebula ; and compares a ray of light penetrating glass to a bird threading the mazes of a forest. 61. For the sake of precision, it is convenient to restrict the term particles to those minute portions of bodies which are appre- ciable by the senses, or the microscope, while the word atoms des- ignates those infinitely smaller parts of matter of which we have no experience, being purely hypothetical creations. The term molecule is frequently used as the equivalent of atom, but it more properly signifies a cluster, or group of atoms, though still far more minute than sensible particles. The words j)ores and inter- stices are generally used as eciuivalent, but it would be well to confine the former term to those openings among particles which admit the passage of liquids, and limit the latter to those far smaller vacancies among ultimate atoms which are traversed by heat, light, and electricity. 62.. Divisibility of matter. — The division of matter may be carried to an amazing extent. Gold may be drawn out as a coating upon silver wire until the 492-thousand-miIlionth part of an ounce is still visible, with its proper metallic color and lustre. It has been estimated that in a drop of the blood of the musk-deer, such as would remain suspended upon the point of a fine needle, there are one hundred and twenty millions of globules. But these exam- ples of the divisibility of matter bring us only to the threshold of a world of wonders. Microscopic researches have introduced us to a realm of life peopled with animate beings, which are born, grow, reproduce their kind, and die ; and yet so minute, that many millions of them heaped together would not exceed in size a grain of sand. Ehrenberg estimates that there were forty-one thousand How are they believed to be related to their interepaces ? 61. Wliat are particles ? How do atoms differ from particles ? How is the term molecule used ? How are the terms pores and interstices used ? 62." What illustrations are given of the di 38 CHEMICAL PHYSICS. millions of their fossil shells in a single cubic inch of slate ; and yet these tiny beings are supposed to be endowed with organs of digestion, circulation, respiration, and locomotion — these to be made up of complex organized parts — these of chemical elements, and these again of ultimate atoms ! 63. The three states of matter. — Under the influence of various molecular forces, bodies assume the three-fold state of solids, liquids, and gases. In solids,- the atoms are so rigidly held together by attraction that the body retains its figure. In the liquid state, attraction is so feeble that the particles slide over one another, and the body takes the flowing condition ; and in the gaseous or aeri- form state, the repulsive forces predominate, driving the particles asunder. Most substances are capable of being changed from one of these states to another, and some of them, as water and sulphur, take on all three conditions. The term vapor is applied to those gases which readily relapse into the solid or liquid form, as steam, vapor of iodine, &c. T\"e will now notice some of those forms of force which are exerted between bodies only when in contact, and which arc known as molecular attractions. § y. Molecular Attractions. 64. Cohesion. — Though the atoms of a solid are separated, yet it does not crumble to pieces. They are held together by a force which reaches across their interstices and binds them in a fixed re- lation. This iorcQ is ihQ attraction of cohesion. It exists only be- tween particles of the same kind, and gives to bodies solidity and form. The hardness, elasticity, brittleness; malleability, and duc- tility of solids are the result of various unknown modifications of cohesive force. There is also a mlitual attraction among the par- ticles of liquids. In a drop of liquid, cohesion attracts the particles into a rounded figure, against the influence of their weight, which worJd spread them out ; pendant drops still further exemplify the same force. 65. Adhesion. — Adhesion is the force which unites dissimilar bodies and is exerted between substances of all kinds. The stick- ing of chalk to a blackboard, of metallic amalgams to the backs of vieibility of matter? 63. What are the three etates of matter? What ib the con- dition of their atoms? 64. What holds the atoms of a Boiiri together? What properties of eolids arc due to cobcBion ? What is said of the cohesion of liquids f MOLECULAR ATTEACTIONS. 39 Fig. 11. looking-glasses, of glue to wood, and of mortar to bricks and stones, are familiar examples of adhesive force. 66. Adhesion of liquids to solids. — If a glass rod be dipped in water, the liquid will rise round it above its level in the vessel, Fig. 10, and when withdrawn, it will be wet. fig. lo. But if the same rod be dipped in mercury, there is an apparent repulsion, Fig. 11, and the rod when withdrawn is dnj. If a rod of gold be dipped in the mercury it is wetted, or covered with a mercurial film. The wetting in this case shows an attraction between the liquid and the solid, and that it is sufficiently ^^^ s^^"' ^'^'^ "' '^'^*"^^- strong to produce adhesion. But there may be attraction without wetting ; glass is not wet by mercury, and still they are attracted, as may be easily seen. Suspend a flat, circu- lar plate of glass to the arm of a balance, coun- terpoise it, and lower the plate. Fig. 12, over a cup of mercury. No matter how near the glass approaches, while there is no contact, there is no attraction. But as soon as they are made to touch, a slight adhesion occurs, — sufficient to lift a portion of the mercury above its level in the vessel, the amount of which may be exactly measured by the number of weights required to be placed in the opposite scale- pan to separate them. 67. Conditions of Wet- ting. — If the adhesive force of any solid for any liquid ex- ceeds half the cohesive force of the liquid particles for each other, the solid will be wet. Thus, the adhesion of gold for mercury, and of water for Attraction of glass and mercury. wood exceeds half the cohesive force of the mercurial and watery particles for each other, consequently water wets wood, and mer- cury wets gold. But if the adhesion of the solid be less than half The glass rod iu mer- cury. Fig. 12. 65. What is adhesion ? 66. What is the effect if a glass rod be dipped into water ? Into mercury? What, if a rod of gold be dipped into mercury? What does the ■wetting show? How may adhesion be shown to exist when there is no wetting I 40 CHEMICAL PHYSICS. Fig. 13. CaiJillary tubes. Fig. 14, the cohesion of the liquid, wetting does not follow contact, as is exemplified by glass and mercury. 68. Capillary Attraction.— If glass rods with small apertures, open at both ends, Fig. 13, be dipped in water, the liquid immediately rises through the orifices to a height which increases in proportion to the smallness of the openings. The same thing may also be beautifully exhibited by placing two plates of glass, Fig. 14, upon their edges in a dish of colored water, one end being joined, and the other slightly separated. The influ- ence of the gradually approaching sides of the glass in attracting the liquid upward is seen in the course of the curve. From the circumstance that this effect is best produced by tubes with very fine apertures, the attraction that causes these phenomena is called Capil- lary, (from capillus, a hair.) 69. Reversed Capillarity. — If now a glass tube be dipped in tuqt- (lUid bcUwcn plates. i • t ^ i ^ cury, we have agam a disturbance of liquid equilibrium, but the effect is reversed. The interior column of mercury is depressed below the outside level, and its Fia 15. surface exhibits a convex shape, as seen in Fig. 15. The same thing occurs if the tube be greas- ed and plunged in water, and in all cases where the liquid cannot wet the solid. The common belief that depression in this case (as in that of the glass and mercury) is caused by repulsion, is quite erroneou.s. We have proved (29) that, instead of repulsion, there is a strong attraction between glass and mercury. The reversed cq)- illary action simply results from the preponder- ance of the cohesive over the adhesive force. In every body of fluid, each particle is kept in place by the mutual action of all the surrounding particles. But if a column of fluid be separated from Convex l*quid sur- face. 67. "WTi^n •wjll wetting occur, and when not ? 63. Dcseribe Fieures 13 and 14. What name has been given to this effect, and why ? 69. Explain Fig. 15. What ia MOLECULAE ATTEACTIOXS. 41 Fig. 16. the surrounding mass by interposing the walls of a tube, the sides of which exert no equivalent adhesive force, the cohesion of the mass below draws down the upper and outer particles, and pro- duces a roundness or convexity at the top. 70. Osmose. — Tie a piece of moistened bladder tightly over the end of a tube, place it in a vessel of water, and then fill it with alcohol up to the level of the outer liquid. The fluid in the tube will shortly begin to ascend, and may rise to a considerable height. Fig. 16. The external water passes through the membrane and mixes with the alcohol, while, at the same time, a feeble current of alcohol flows the other way and commingles with the water. "When differ- ent liquids are separated by a membrane in this manner, the one is transmitted fastest . osmose of liquids, which wets the barrier most perfectly. Dutrochet, who first drew attention to this matter, named the inflowing current endos- rrwse, and the outflowing one exosmose ; but these terms are lately less employed, and the phenomena are now known simply as osmose, from a Greek word signifying impulsion. The principle involvedis a modification of capillary attraction. The pores of the bladder are short capillary tubes, into which water finds its way because it can wet the walls of the pore. Osmose is thus a result of the force of adhesion (66). 71. Conditions of continuous Flow. — A capillary tube, however fine it may be, will not cause the liquid within it to over- flow; but if the liquid be removed from the top of the tube by evaporation or otherwise, the capillary force continues to supply it, and thus maintains the current. This may be seen in the wick of a lamp, when the oil is burned away and continu- ously supplied. If a small bladder be tied tightly to a tube, which is open at both ends and bent, as seen in Fig. 17, the Fig. 1- Osmose prodnc'ng a con- tiuuouo flow. the cause of this? 70. Describe Fig. 16. What is osmose? Upon what does it probably depend ? 71. How may osmose be made to produce a continuous flow ? 42 ' CHEMICAL PHYSICS. bladder and part of the tube being filled with alcohol and sub- merged in water, osmose •will set in and the liquid rise and over- flow drop by drop into the cup, the motion continuing till the liquids are uniformly commingled. These principles probably afford an explanation of the flow of sap in plants, and the circula- tion of blood and nutritious juices in animals. 72. Adhesion of gases to solids. — If iron filings are gently dusted over the surface of water, they float, though iron is eight times heavier than water. This is because of the adhesion and condensation of a layer of air upon their surface, which prevents the water from wetting them. The condensed air around the par- ticles forms a capillary cavity, and thus displaces a large volume of the liquid in comparison with that of the solid. Insects walk upon water and skim over its surface, because the air adhering to their feet forms capillary cavities, and prevents them from becom- ing wetted. 73. Osmose of gases. — The adhesion of gases to solids gives rise to currents, which pass through porous bodies with consider- FiG. 18. ^^^^ power and velocity. Close the end of a glass tube with wet plaster. After it is dry, if the tube be filled with hydrogen, and its open end intro- duced into a vessel of water, the liquid rises rap- idly. The hydrogen escapes outward through the porous plaster, while at the same time air enters the tube from without. But nearly four volumes, of hydrogen escape for one of air which enters, and these are called the diffusion-Tolumcs of hydro- gen and air. The diffusion volume of gases de- pends upon their density. If a thin sheet of In- dia-rubber be tied tightly over the mouth of a glass jar, and the vessel be then placed in an atmosphere Osmose of gases, ^f carbonic acid, movement slowly takes place ; a little of the internal air escaping outward, while so large a quantity of carbonic acid is transmitted inward as to distend the membrane into a dome-shaped cap, (Fig. 19.) If the situation of the gases be reversed, an opposite movement takes place, and the elastic sheet is deeply depressed, as the figure indicates. This principle is What natural phoiiorncna probably depend upon osmose t 72. "Wliat exampleB arc given of the adhesion of gases and solids? 73. AVhat does Fig. IS ehowf What is mc.nnl by diffusion-volumes? What is said of the osmotic action of in- di.i-rubber sheets? Of the lung membranes ? 74. How do gases behave when ex- MOLECULAR ATTEACTIONS. 43 Fig. 19. brought into play in atmospheric respiration. There is air on one side of the lung-membrane and blood on the other ; oxygen is transmitted through the barrier from the air to the blood, and carbonic acid from the blood to the air. 74. Diffusion of gases.— The vapor of water will rise and fill a confined vessel of air just as if the space were a vacuum, ex- cept that it will take a little longer time. When gases are exposed to each other, they will intermix or difi'use uniformly, even in opposition to gravity. If two jars be connected by a narrow tube, (Fig. 20,) and the lower filled with carbonic acid, while the upper one is filled with hydro- gen, difiusion takes place through the nar- row passage. The light hydrogen descends, and the carbonic Passage of gases through membranes. acid, though twenty times heavier, rises, and they become equally mingled in both jars. Our atmosphere owes its stability to this principle ; its constituents being perfectly intermingled. The baneful products of respiration, combustion, and decay, instead of accumulating, are incessantly dissolved away and dispersed in the atmospheric ocean. 75. Adhesion of gases to liquids. — "When a liquid is poured from one vessel to another, the gases of the air adhere to the descending stream, are carried downward, and a portion of them re- main combined with it. The force to be over- come by this adhesion is the elasticity of the gases, or the mutual repulsion of their particles. Press- ure and cold lower the elastic force, and therefore favor absorption. As the temperature rises, adhe- sion is diminished, and hence the readiest means ^^^^ of driving out a gas from solution is by boiling. Diffusion of gases. 76. Diffusion of Liquids.— Adhesion takes place between the particles of dissimilar liquids, causing their intimate mixture : thus a drop of ink will spread through a pint of water incorporating itself completely with the mass. This subject has been recently posed to each other ? Describe Fig. 20. How does this affect the atmosphere ? 75. What is the effect ofadhesion among liquids? 76. Describe liquid diffusion. 44 CHEMICAL PHYSICS. investigated by Prof. Graham. With suitable precautions to pre- Fio. 21. vent mechanical mixture, he placed small jars filled with liquids to be tested in larger ones containing distilled water as in fig. 21, and determined the amount of the inner solution that diffused into the water in a given time. Substances were found to differ greatly in diffusibility : chlorohydric acid is the most diffusible substance known. The equal diffusion of several solutions took place in the following times : Chlorohydric acid, 1; common salt, 2.33; sugar, 7; albumen, 49 ; caramel, 98. Substances thus tested are called dlf- fusates. §YI. Solution. 77. "Whenever the force of adhesion of the particles of a liquid for a solid exceeds the whole cohesive force of the latter, the solid is not only moistened, but its cohesion is overcome and solution occurs ; that is, the solid disappears — mixing uniformly with the liquid, which remains transparent. In this case the solid is said to have been dissolved by it, and the liquid employed is called the solvent. A liquid which dissolves one substance, may refuse to dissolve another, while substances insoluble in one liquid, are dis- solved in others ; and thus the hardest metals and minerals may be made to vanish and assume the transparent liquid form. 70. Whatever weakens cohesion favors solution. Thus, by powdering a substance, cohesion is partially destroyed and the sur- face increased ; solution is consequently promoted. Heat, in most ca=es, contributes powerfully to solution, its effect being, as is sup- posed, to weaken cohesion, by increasing the distance between the particles of the solid ; yet there are marked exceptions. Water just above the freezing point dissolves twice as much lime 'as at the boiling point, while the solubility of common salt seems hard- ly affected by temperature. Some substances increase in solubility regularly as the temperature increases; in many cases the solubil- ity increases faster than the temperature, and in others it rises with the increasing heat to a certain point, and then declines, while the temperature continues to ascend. 77. What ia Bolution ? Upon what docs It depend ? ^Vbat is a solvent? 78. What SOLUTION. 45 79. Saturation. — A liquid is said to be saturated when it has taken up as large a quantity of a solid as it can dissolve ; in which case the force of cohesion between the particles of the solid is equalled by the adhesion of the solid and liquid to each other. The solvent power of liquids varies much. Water is the great solvent, and so general and important is its use, that in speaking simply of the solubility of a body, it is always understood. 80. Precipitation. — If the adhesive force of the solid and liquid can be overcome, cohesion takes place between the dissolved par- ticles, which again unite as a' solid. This change is called jt?r^c?^2- tation, and the solid formed, a precipitate. Precipitation may be effected in three ways : First, by removing the solvent, as in evaporation. Second, by modifying the solvent. For example, camphor dissolves in alcohol, but if water be add- ed, it unites with the alcohol and so changes it that it can no longer hold the camphor in solu- tion, which is precipitated as a white cloud, and afterward falls to the bottom of the vessel. Third, by adding a substance which combines with the dissolved body, forming an insoluble compound. Fig. 22. Fig. Fig. 24. Paper filters. Fig Thus, if oxalic acid be added to lime water, it combines with the lime, precipitating it by the formation of an insoluble oxa- late of lime. This property is an important one in chemical opera- tions, as it enables us to separate the various constituents of a compound and de- tect the presence of a body when in solution with other substances. 81. Filtration. — The process of separating precipitates by straining or passing the fluid through any porous substance, is called filtration. The chemist uses unsized paper for this purpose, which permits the liquid to ooze slowly through, leaving the solid substance behind. The filter paper cut and folded as in Fig. 22 takes the shape of Fig. 23, which adapts it to the glass funnel. is the relation of cohesion to solution ? Of heat ? 79. In what does saturation consist ? 80. "What is precipitation ? How may it bo effected ? How is it impor- Filter stand. 46 CHEMICAL PHYSICS. To prevent the adhesion of the paper to the sides of the glass, and thus facilitate the passage of the fluid, the filter is often plaited, Fig. 24. The funnel supporting the filter usually rests upon the stand, Fig. 25. 82. Modes of Solution. — "Where there are mixed materials of variable solubility, with sufficient looseness of texture to permit a fluid to percolate through, one substance may be separated from the rest by being washed, or dissolved out. This is called lixhia- tion, a term first applied to the extraction of ley from ashes (leaching). The soluble principles of plants are extracted by infu- sion, which consists in pouring upon the substance a hot liquid. Decoction consists in boiling for a considerable time the materials to be separated. Digestion is the slow and gentle action of a sol- vent with warmth ; and maceration the act of softening the sub- stances by steeping. § YII. Crystallization, 1. -PRODUCTION OF CRYSTALS. 83. Crystalloid and Colloid states. — W^hen the particles of many substances are loosened either by solution, melting, or other- FiG 26 "^ise, 80 as to be permitted freely to move, they tend J. to arrange themselves in regular geometrical forms, /f\\ termed crystals, of which Fig. 26 may be taken as an . 48.00 Na. 23.00 t.rrjium, E. Strontium, Sr. 43.80 Fluorine, F. in.oo Sulphur, S. 16.00 Gliicinuniy Gl. 4.70 1 Tantalum, Ta. 68.80 Gold (Aurum), Au. 193.44 1 Tellurium, Te, 64.50 Hydrogen, H. 1.00 1 Terbium, Tb. Iodine, I. 127.00 Thallium, Tl. Iridium, Ir. 98.60 \ Thorinum, Th. 59.50 Iron (Ferrum), Fe. 28.00 ! Tin (Staunum) Sn. 59.00 Lmithanum, La. 46.00 1 Titanium, Ti. 25.00 Lead (Plumbum), Pb. 103.60 1 Tungsten ("Wol- W. 92.00 Lithium, L. 7.00 1 fram). Magnesium, M?. 12.16 Uranium, U. 60.00 Mans^aneso, mS. 27.48 Vanadium, V. 68.50 Mercury (Hydrargj-- ng. 100.00 Yttrium, Y. rum), 1 Zinc, Zn. 32.60 Molybdenum, m. 48.00 1 Zirconium, ■ Zr. 22.40 Nickel, Ki. 29.50 \ * Indium. 112. Analysis and Synthesis.— The separation of compound bodies into simpler ones is called analysis. A compound may con- sist of compounds, and the first analysis may give only its nearest or proximate parts, while the second shows its ultimate constitu- ents, or elements. Thus flour may be decomposed into gluten, starch, oil, and water {proximate analysis) ; but these substances may again be resolved into their final elements {ultimate analy- sis). Qualitative analysis determines of what elements a com- pound consists; quantitative analysis ascertains their pj'ojwrtions. Syntliesis consists in combining the elements into compounds ; it is therefore the reverse of analysis. * A rourth now metal lately discovered by Spectrum Analysis. natural objects be comparod to a language ? 112. "What is analysis ? Proxi- mate analysis? Ultimate? Qualitative? Quantitative? "What is synthcsi.s ? CHEMICAL ATTRACTIOir. 57 113. Affinity.— The force brought into play in carrying on these changes is not manifested alike between all kinds of bodies ; some exert it only in a feeble degree, and others powerfully. It seems to manifest a kind of preference or election, which induced the alchemists long ago to name it affinity. The term, however, is unfortunate, as it properly signifies resemblance or relationship, whereas in chemistry it is only the name of the force which pro- duces chemical union. 114. Conditions of its exercise. — Like adhesion, this force acts only between unlike bodies. If the earth consisted of but one kind of matter, mercury, for instance, there might be gravitation and cohesion, but affinity would be impossible. It might be physically changed by freezing, melting, or vaporizing, yet it would remain mercury still. But if sulphur were added, it would combine with the metal, forming a new substance, a com- pound^ and thus chemistry, which implies a plurality of elements, would come into existence. 115. However intimate the mixture of substances may be, their separate properties remain unchanged unless chemical action takes place. In the manufacture of gunpowder, its elements, char- coal, sulphur, and nitre, are separately reduced to a state of fine powder, then thoroughly mixed, moistened, and ground for hours with stones, and afterward intensely pressed and pulverized. But close as is the combination, it is only mechanical; water will wash out the nitre, and bi-sulphide of carbon dissolve the sulphur, leaving the charcoal. The particles are not brought within each other's attractions, and affinity still slumbers. But a spark of fire awakens it, the elements rush into combination and disappear, leaving in their stead a huge volume of gaseous matter. 116. Changes "wrought by Affinity. — Newness of properties, either in color, odor, form, density, or some other quality, is a con- sequence of all chemical union. It may convert two solids into a liquid, two liquids into a solid, or even two gases into a solid. Thus, when black charcoal and yellow sulphur combine, the com- pound formed is colorless as water, and highly volatile. Sulphur and quicksilver unite to form the bright-red vermilion. Nitrogen 113. What is meant by affinity? Why is this iiBe of the terra unfortunate? 114. Ho-w docs the force of affinity differ from that of gravitation and cohesion? 115. How is the difference between combination and mixture illustrated ? 116. What is said of the eflect of affinity in changing the properties of bodies ? 3* 68 CHEMICAL PHYSICS. and oxygen are neutral and tasteless, separate or mixed ; yet one of their compounds, laughing gas, is sweet, producing delirium when breathed ; and another, nitric acid, is an intensely sour, cor- rosive poison : they are both invisible, yet they form a cherry -red gas. Carbon and hydrogen are odorless, yet they combine to pro- duce our choicest perfumes. Mild and scentless hydrogen and ni« trogen form the pungent ammonia ; while suffocating and poison- ous chlorine, united with a brilliant metal, gives rise to common salt. The last-mentioned compound strikingly illustrates the enor- mous power of affinity in producing condensation. Thus 24 parts, by measure, of common salt contain 25.8 parts, or more than its own bulk, of the metal sodium, besides 30 parts by measure of liquid chlorine. No known mechanical force could have pro- duced this condensation, and yet affinity readily effects it ; — the product, rock salt, being more transparent than glass. 117. There is, however, a gradntion in these effects. Sub- stances resembling each other are feebly attracted together, and only lose their properties partially ; and the wider the difference, the stronger is the affinity, and the more complete the transforma- tion. If the elements are very similar, the compound will show its parentage ; if quite unlike, all traces of its derivation will be lost. Thus, iron and mercury form a compound whose metalhc aspect immediately betrays its origin; but who, on looking at gypsum, would suppose it consisted of caustic lime and corrosive sulphuric acid. 118. Affinities Unequal. — The chemical force which binds to- gether the constituents of a compound is definite, and, under like circumstances, remains always the same ; but it varies in intensity among different substances. Thus, carbonic acid will combine with soda, forming .carbonate of soda. But if acetic acid be brought into contact with this compound, it will drive off the car- bonic acid and take its place, forming acetate of soda. Again, the affinity of chlorohydric acid for the soda is superior to that of the acetic acid ; it will therefore expel it and form a new substance. Tables have been constructed, representing the order of affinities among different substances, but so many causes disturb the play of this force that they are of but little value. lUnBtrationB. 117. When win this change be grreatcet? When least? Exam- plea. 118. What iB said of the variability of affinity ? What will be the cftcct if ncetlc acid bo added to carbonate of soda? Hydroclilorlc acid to acetate of soda? CHEinCAL ATTRACTIOX. 59 119. Displacement. — Chemical compounds are formed in two wajs. First, where the affinitj is powerful, the substances com- bine directly when brought together. But by far the more fre- quent method, both in the laboratory and in nature, is where, in a body already formed, one of its ingredients is replaced by another substance, and a new compound results. The changes mentioned in the preceding paragraph are a series of displacements of this kind. This method of chemical action by substitution is very im- portant, and will be again referred to. 120. Commancement of chemical action. — "When some sub- stances are brought into contact, chemical union instantly occurs; but in most cases another force, heat, for example, is necessary to commence the action. Thus, a heap of charcoal may remain ex- posed to the air for years unchanged ; but, if heat be applied, it will arouse a chemical action between the charcoal and the oxygen of the air, which will continue till the entire mass is consumed. Phosphide of hydrogen, on the contrary, bursts into flame the moment it is exposed to the air. 121. Influence ofCohssion. — Cohesion obstructs the working of affinity. In very rare cases, as phosphorus and iodine, solids may directly combine ; but, as a general principle, cohesion must be entirely overcome, either by melting or dissolving one or both the ingredients, before chemical action can take place. Solution is, therefore, one of the grand processes of the laboratory, and sol- vents have been found for all substances. 122. The nascent state. — The moment in which substances arc liberated from union with each other is called the nascent (grow- ing) state, and, at this time, they often enter into combinations which could not be formed under other circumstances. I^itrogen and hydrogen gases, if mingled, do not unite ; but when set free at the same time, by the decomposition of vegetable matter, they readily combine to form ammonia. The chemical union of two substances is often effected by the bare presence of a third body, which re- mains unchanged during the process. This is termed catalysis^ or contact action, and its causes are not understood. 119. How does direct combination differ from combination by displacement ? 120. Hq-w do substances differ in cbemical energy ? What force promotes it ? Examples. 121. What effect has cohesion upon the play of affinity? Excep- tions. "What is said of solution ? 122. What is the nascent state I Its relation 60 CHEJaCAL rUTSICS. §11. Lav:s of Chemical Combination. 123. The Mathematics of Chemistry.— When instrnments of ■n-eigbing bad attained a sufficient degree of perfection, it was found that, however often matter might change its fonn, nothing was either gained or lost— that its quantity remained the same. But other results of the highest importance also followed. It was discovered, tbat the force of affinity, as well as that of gravitation, conforms to exact numerical laws; that there is a mathematical order in the domain of chemistry as absolute as that which reigns in the realm of astronomy. As the forces which govern the heav- enly bodies cause them to complete their revolutions with infinite regularity and precision, so the chemical force which binds to- gether the constituents of a compound, produces its results always in the same definite and unalterable proportions. This is the foundation principle of the science. 'When the composition of a sample of water, common salt, or lime, is once accurately deter- mined, the knowledge applies to all water, common salt, and lime ; and so of every other substance. Pure water consists of 8 parts, by weight, of oxygen, combined with 1 part, by weight, of hydro- gen ; and we can produce it by the union of its elements in these proportions, and no other. So potash invariably consists of 39 parts potassium and 8 oxygen ; and common salt, of 35 chlorine to 23 sodium. Certain numbers, ascertained by experiment, and called combining nurrtbers^ express the proportions in which ele- ments invariably unite to form all chemical compounds. 124. How marvellous is this order! The stones and soil be- neath our feet, and the ponderous mountains, are not mere con- fused masses of matter ; they are pervaded through their inner- most constitution by the harmony of numbers. The elements of the wood we burn are associated in fixed mathematical ratios. In the violence of combustion, the bond that held them together is destroyed ; they break away and rush into new combinations, but they cannot escape the law of numerical destiny. The burning to affinity? Give an example. What is meant by catalyeis ? 123. "What ira- important discoveries followed the introduction of the balance into chemis- try ? What is said to be the foundation of the science ? Examples. What if the proportion of the elements in water? In potash? Common salt? What are combining numbers ? 124. What is said of the constitution of aTl LAWS OP COMBINATION. 61 candle gradually wastes away before us, dissolves in air, and passes beyond tbe reacb of sight ; but in that invisible region, forces are playing among its unseen particles with the same exactitude and harmony as among those which rule the constellations. And so is it with all chemical mutations. In the gradual growth of living structures, in the digestion of food, and in the slow decay of organic matter, no less than in its quick combustion, the trans- position of elements takes place in rigorous accordance with the laws of quantitative proportion. jT 125. The Chemical Chart.— To represent these foundation facts of chemistry to the most impressible of the senses — the eye — and give the student the same advantage in the study of this science that is derived from maps in Geography and Astronomy, the author has prepared a Chemical Chart, which presents the laws of combination, in a great number of cases, in the simplest and clearest manner. The left column enumerates 15 of the most im- portant elementary substances, and represents each by a square colored diagram. Single squares represent elements, but when joined together, as shown by the converging lines, they indicate compounds. As a separate color is thus assigned to each element of a compound body, its exact composition is exhibited at a glance. The areas of the diagrams correspond to the combining numbers^ land thus represent relative quantities to the eye. The hydrogeo square being smallest, the oxygen square is 8 times larger, the carbon square 6, and the chlorine 35 times larger. Diagrams of the same color have always the same size. Thus oxygen, wher- ever found, is seen obeying the law of its fixed proportions ; its square is always of the same size, and so with all the other ele- ments.* 126. Equivalents. — If we take equal quantities of two ele- ments, we do not find that they possess equal powers of attraction. * Chlorine, Carbon, Sulrhur, and Phosphorns are represented npon the Chart by their natural color8. Fluorine, from its supposed resemblance to oxygen in properties, has an analogous tint ; Nitrogen is of the color of the air (sky blue), of ■which it is the chief ingredient. Oxygen, as the sustniner of combustion, and the agent which changes the blood from a purple to a florid tint, is represented of » crimson color. The bases of the alkalies have various shades of blue, corresponA- ing to the strength of the alkalies which they form. (The alkalies restore the blue vescetable colors discharged by acids.) Aluminum, the basis of clay, is of a clay color. Silicon, which is said somewhat to resemble carbon, is of a dark color. Iron forms green-colored salts, and manganese those of a rose color. natural objects ? 125. Why was the chemical chart devised ? Describe it. 126. On what is the idea of chemical equivalents based ? "Wliat example is given f 62 CHEMICAL PHYSICS. There is as much chemical energy or neutralizing power in one grain of hydrogen as in 8 grains of oxygen ; and 35 grains of chlo- rine neutralize 8 grains of oxygen only equally weU with 1 grain of hydrogen. Therefore. 1 gr. of hydrogen, 8 grs. of oxygen, and 35 grs. of chlorine, are of equal value chemically — in other words, they are equivalents. When two bodies combine with a third, as they are each equivalents of the third body, so are they also equivalents of each other, and unite together in exactly the same proportions. For example, 1 part of hydrogen combines with 8 of oxygen, and 35 of chlorine combine with 8 of oxygen, but 35 of chlorine is the very quantity which combines wjth 1 of hydro- gen. Thus the proportion in which any two bodies combine with each other is that in which they combine with every other. 127. Combining or equivalent numbers. — To each chemical Bubstance, therefore, is attached its fixed number, and these num- bers are so mutually related, that no one can be changed without a corresponding alteration of the whole series. "We may employ any scale, so the relative values are maintained. "We adopt the hydrogen scale, which is, perhaps, the best for general teaching. As hydrogen combines in the smallest proportion of any element, it is assumed as 1, oxygen will then be 8, nitrogen 14, &c. As oxygen, however, has the largest range of affinity, it is more con- venient, in laboratory work, to assume it as 100, in which case hydrogen becomes 12.5, and the other numbers are changed ac- cordingly. 128. Multiple proportions.— "When combinations occur in more proportions than one, the larger quantities are multiples of the smaller hy a whole number. The compounds of nitrogen and oxygen furnish a beautiful illustration of this law. The propor- tion of nitrogen is the same in all : 14 parts of nitrogen to 8 of oxygen form a compound with one set of properties ; twice 8 of oxygen gives another compound with dififerent properties ; thrice 8 produces still a different substance ; 32 parts, another ; and 40, or five times 8, yet another. (See Chemical Chart.) ''1*T29. The law of equivalents applies to compounds as well ^ to elements. The equivalent of a compound body is the sum of the equivalents of its elements. Thus the equivalent of lime is 28, 127. In fixing combining numbers, why is the hydrogen scale generally adopt- ed? What are the advantages of the oxygen scale? 128. What is meant by multiplo proportions ? Example. 129. How does the law of equivalents affect LAWS OF COMBrtiTATION. 63 as it is a compound of calcium 20, and oxygen 8 (20 + 8=28) ; for carbonic acid 22; carbon 6, oxygen 16 (6+16=22) ; and of mar- ble or chalk, it is 50; lime 28, carbonic acid 22 (28+22=50). A knowledge of the combining numbers is of the first impor- tance in all departments of practical chemistry, whether in the laboratory, or in the manufactory, to determine the quantities in which materials shall be employed. The combining numbers of the substances upon the Chart should be committed to memory. ^ 130. Combination by Volume.— In dealing with gas, it is more convenient to measure than to weigh it; and as it combines hj equivalents in weight, it becomes important to know what amount of volume they occupy. When we take equivalent quanti- ties of the gases, we find that the spaces they fill do not bear the same relation to each other as the equivalent weights, nor are the spaces all alike, yet a very simple relation does subsist between them, which is shown as follows : The equivalent number being 8 for oxygen, 8 grains of it are placed in a vessel which will ex- actly contain them. The gas is then removed, and 32 grains of solid phosphorus introduced, that number being the equivalent of this element. The phosphorus is then vaporized by heat, and the vapor exactly fills the vessel. The equivalent weights of oxy- gen and phosphorus are unequal ; but when brought into the same condition of vapor, they fill equal spaces, and have, therefore, equivalent volumes, which are expressed thus : oxygen = Qj, phosphorus = | \. 131. If, noAv, we take an equivalent of hydrogen, or 1 grain, we find that the vessel will hold but half of it ; its volume is therefore | | i , being double that of the oxygen or phosphorus. Consequently, if we wished to unite oxygen and hydrogen in equivalent weights, so as to form water, we would take one meas- ure of the former, and two of the latter. Sometimes gases are condensed by combination. Two measures of hydrogen and one of oxygen produce but two of watery vapor. Thus oxygen = Q, hydrogen = j I | , steam = f I !• In measuring by volume, oxygen has hitherto been taken as the unit, but Geehaedt makes hydrogen the unit. His views will be better understood afterj [ stu dying the nomenclature. compound bodies? How are their equivalents determined? Example. "Wliy is a knowledge of combining numbers important ? 130. How is the combining proportion of gases estimated? How are combining volumes ascertained? 64 CRTTMTCAL PHYSICS. § III. The Atomic Theory. 1 32. The laws of chemical combination which have been ex- plained are independent of all speculation, being the result of facts established bv mtiltiplied observations and experiments, and may be verified at any time by accurately analyzing a few chemi- cal compounds. But this was unsatisfactory — an 'explanation was demanded — a reason was required for the remarkable behavior of chemical force in thus rigidly limiting the proportions of combin- ing quantities. To solve this problem. Dr. Daltox offered the Atomic Ttieory, which has already been referred to in its physical aspects. 133. What it Teaches.— This theory assumes, firtt^ that all matter is composed of indivisible, unchangeable atoms; second, that atoms of the same element have the same weight, but that in different elements they have different weights; third, that the combining numbers represent these relative weights ; and. fourth, that all chemical compounds are formed by the imion of different atoms. 134. This doctrine, if accepted, offers an explanation of the laws of combining proportions. Thus, if water be composed of an oxygen atom weighing 8, and a hydrogen atom weighing 1, then its com- position must be definite and invariable, and every specimen of it, whether it be a grain or a ton, must give, upon analysis, % of one gas and I of the other. Also, if the atoms of each element possess invariable weight, they must, in all their combinations, exhibit equal and reciprocal values. And again, as an atom is the least quantity that can enter into combination, the compound can only be increased by the addition of whole atoms, so that the combining number expressing the large quantity must be an exact multiple of the single atomic number. The Chemical Chart offers a beauti- ful illustration of the atomic theory. 135. Whether matter be infinitely divisible or not, is an old con- troversy, not yet settled. It would seem that it is so, as we cannot imagine a particle so minute that we may not conceive it to be again divided. But putting aside speculation as to what may he, the chemist assumes that in the present order of nature there are 131. How U it jn the ca«? of water? 132. How have the laws of combination been detf-rmined? Why wa.s the atomic theorj- proposed ? 133. What is it« first ftB- eamption f Ita second ? Third f Fourth ♦ 131 What is eaid of thla theorj- if re THE ATOMIC THEORY. 65 ultimate indivisible atoms. The atomic theory has been objected to as not in accordance with all the facts of chemistry ; yet as a convenient hypothesis to facilitate study and inquiry, it has been, and is still of incalculable value. We subjoin two cases of its most recent application. 136. Isomerism.— Until lately, it was the prevailing opinion that chemical properties depend solely upon chemical composition, and hence that similar composition necessitates similar proper- ties. For a long time, if two substances of different properties were found, upon analysis, to have one composition, it was held that the experimenter must have erred. But so constant and in- creasing were such results as at length to establish the fact that bodies of the same composition may still have different proper- ties. Bodies thus constituted are said to be isomeric, from isos, equal, and meros, measure, and are called isomerides. For ex- ample, the fragrant oil of roses and the chief illuminating con- stituent of common street gas are isomeric ; a compound atom of each consists of four atoms of carbon and four of hydrogen. To explain this we are compelled to assume that the constituent atoms of a compound may have different arrangements. The same atoms which if grouped in one way give rise to one substance, if re- grouped in another give rise to a different substance. 137. If bodies have the same absolute composition, as in the above example, they are said to be metameric compounds, and the groupings of their constituent atoms may be represented by the structure of such words as ate, eat, tea, &c. But sometimes sub- stances have only the same proportional composition ; they are then said to he polymeric compounds. Thus aldehyde consists of carbon, four; oxygen, four; and hydrogen, two; while acetic ether consists of just double these elements ; yet the per cent, pro- portion of both these compounds is the same. The relations of such bodies resemble those of the words Fa, Papa; Tar, Tartar. 138. Allotropism. — Something analagous to this is manifested by the elements themselves. Within the last few years it has been found that the elements may change their properties and cepted ? 135. "WTiat does the chemist assume concerning atoms ? How is the atomic theory estimated ? 136. What views have heen held concerning the prop- erties and composition of bodies ? "WTiat has been recently discovered ? "VThat ia isomerism? Example! Explanation? 137. What is metamerism ? Polymerisra? 138. What is said of the different states of the same elements ? Example. What 66 CHEMICAL PHYSICS. pass from state to state. We have a striking instance of this in carbon, which in one condition gives us the brilliant, transparent, and almost incombustible diamond ; in another, the black, opaque, easily inflammable charcoal ; ^vhile in another we have the metal- like graphite. This curious phenomenon is called aUotropism, a word which means simply diiferent states. It was at first sup- posed that but few of the elements were allotropic, but it is now found that nearly all of them take on this doubleness of condition, while some have several phases. The explanation of these effects is that the atoms constituting the element are differently arranged in the different cases. § lY. The Nomenclature — Chemical Language. 139. The chemical nomenclature is a system of naming in which the structure of the terms employed expresses the composi- tion of the substances to which they are applied. The beautiful order of chemical composition is well fitted for such a device, and hence this nomenclature is the most perfect to be found in any of the sciences. It was devised by a committee of the French Acade- my in 1787, as it was found that chemical compounds were multi- plying so rapidly that no memory could retain their arbitrary names. "With the progress of the science the principles of the nomenclature have been changed and extended. 140. Naming the elements. — In the case of elements long known, the old established names were retained, but where a new one was discovered, a name was given expressive of some leading quality by which it was distinguished. Thus chlorine takes its name from its greenish color ; iodine from its purple vapor ; phos- phorus (bearer of light) from its being luminous in the dark. The lately discovered metals are distinguished by the common termi- nation iim^ as platinum, thalium. Among non-metallic elements, analogy of properties is indicated by similarity of termination, as chlorine, bromine, fluorine ; or carbon, boron, silicon. 141. Naming of binary compounds. — The union of two ele- ments forms a Unary compound {Ms. twice), three elements form term is applied to It f 139. What is the phemical nomenclature ? Wli at is paid of it? When and by whom -wae it devised? For what reason ? What has changed Itf 140. What rule has heen observed in naming the elements? How are the metals distinguiehed I How is analogy of properties indicated in other elements f THE NOMENCLATUEE. 67 a ternary^ and four a quaternary componnd. "Where the com- pound contains but one atom of each, both elements are designat- ed in the name. Thus a compound of oxygen and lead is called oxide of lead. "When binary compounds are decomposed by the electrical battery, one element passes to the positive pole, and is termed the electro-negatvoe element ; the other goes to the nega- tive pole, and is called the electro-positive element. In forming a name, the electro-negative ingredient is placed first, and marks the genus, while the electro-positive comes last, and indicates the spe- cies. The first, or electro-negative element, is distinguished by the termination ide ; thus oxygen forms oxides; chlorine, chlo- rides; iodine, iodides; fluorine, fluorides; carbon, carbides; sul- phur, sulphides ; phosphorus, phosphides. The suflix uret was formerly applied in these cases, as sulphuret of lead, carburet of iron, but it is now less used. 142. Acids. — Acids form an extensive and important group of binary compounds. They are generally soluble in water, sour to the taste, and change vegetable blue colors to red. Litmus^ a blue vegetable extract, is commonly used as a test of acidity. When not weakened by dilution with water, they decompose and destroy vegetable and animal substances, and likewise corrode and dissolve the metals. Acetic, sulphuric, and nitric acids are fa- miliar examples of this class. Acids are also distinguished by their powerful attraction for another class of bodies called lases. This is, indeed, their genuine test, for certain insoluble substances, as silica, neither taste sour nor affect blue paper, yet, when melted, they manifest acid properties, combining strongly with bases. The principle acids are of two kinds, called oxacids and Tiydracids. The former are so named because oxygen is their leading ingre- dient ; whereas, in the latter, it is hydrogen. 143. Naming the acids.— Oxacids are named from the element with which the oxygen unites. Thus sulphur with oxygen gives sulphuric acid; carbon with oxygen gives carbonic acid. The varying proportions of oxygen are distinguished by terminations and prefixes. Thus, ic indicates the stronger, ous a weaker, and 141. How is the number of elements in a compound denoted ? When there ie but one atom of each element in a binary compound, how is it named ? Which comes first? What termination has it? Examples. 142. What are acids? What is litmus? What is the distinguishing test of acidity? How are the principal acids divided ? 143. How are oxacids named ? How are the different proportions of 68 CHEMICAL PHYSICS. the prefix hjpo, -whicli signifies uri/ler, a still weaker acid. Thus, nitric acid contains more oxygen than nitrous acid, and this more than hrponitrous acid. The prefix hyper means more, as hvper- chloric acid, or more commonly perchloric acid, which contains more oxvgen than chloric acid. In naming the hydracids, both elements are mentioned ; as hydrogen and chlorine form hydro- chloric, or, according to the principle just laid down, chlorohydric acid : iodine and hydrogen iodohydric acid. 144. Bases. — All bodies which combine with acids and neu- tralize them are called hase^. This class includes alkalies, alkaline earths, and many other substances wholly unlike them in char- acter. Alkalies, in their leading properties, are the reverse of acids. They have an acrid, nauseous taste, and restore the vegetable blue colors turned red by acids. Like acids, however, they are power- fully solvent and corrosive. Potash, soda, and ammonia are ex- amples. Alkaline earths, as lime and magnesia, possess these qual- ities in a lower degree. 145. Naming the Bases. — Most of the bases are formed by the union of oxygen with metals, as oxide of iron, oxide of potassium. "When oxygen combines with the same element in different pro- portions, forming several oxides, the degree of oxidation is indi- cated by the use of prefixes. Thus, proto means one equivalent, or the lowest proportion of oxygen ; deuto^ two ; and trito^ three. Per denotes the highest degree of oxidation, and is often ap- plied to the deutoxide and tritoxide. Bin-oxii^Q. is equivalent to deutoxide, and f€r-oxide to tritoxide, while «e^<^?/i-oxides are those in which the oxygen is in the fjroportion of one and a half to one of the element with which it is combined. Some oxides of in- ferior basic properties are termed «w&-oxides. 146. Salts. — The combination of an acid and a base forms a salt. The properties of both constituents are neutralized, and the result- ant compound has entirely new qualities. The neutralization may be perfect or partial ; if perfect, a neutral salt is the result. If, however, there is not sufficient base completely to saturate the acid, an acid salt, or super-salt, is formed ; while, if the base is in ex- cess, a hasic salt, or sub-salt, results. The term salt is not limited oxygen denoted ? How are the hydracida named? 144. What are bascf? ? VThat are included in the class? What are alkaliea? Alkaline eailhe? 145. How is the proi)ortion of oxygen in a base expressed? 146. What are salts? Neutral Baits! Acid? Basic? What is said of the saline taste ? 147. How are the salts THE NOMENCLATUEE. 69 to bodies having a saline taste. Manj tasteless substances, such as glass, marble, and various minerals and rocks, being composed of acids and bases, are properly salts. The constitution of salts will be noticed hereafter. 147. Naming the Salts. — Salts are named from both thek ele- ments, as phosphate of lime from phosphoric acid and lime. But as several acids of the same general name may combine with one base, the salts formed are distinguished by turning the ic of the acid into ate of the salt ; and o us of the acid into ite of the salt. Thus, nitric acid forms nitrates, phosphoric acid, phosphates, &c., while nitrous acid produces mtrites, and hyposulphurous acid, hyposulphi^^. The basic element of a salt is indicated by its usual prefixes ; thus, protosul^hate of iron is sulphate of the protoxide of iron. Salts of the protoxide are called protosalts, and salts of the peroxide, ^ersalts. Illustrated exercises in the nomenclature of acids, bases, and salts, will be found upon the Chemical Chart. 148. Symbols. — To facilitate chemical labor, Beezelits intro- duced a system of symbols, by which, not only the names of sub- stances, but their composition and changes are expressed by abbre- viations. The symbols of the elements are the first letters of their names, as, for carbon C, for oxygen O, for hydrogen H, and for nitro- gen IvT. But, as several substances may have the same initial letter, we either employ, to distinguish them, the first letter of their Latin names, or add a second small letter. Thus, as C stands for carbon, CI is taken for chlorine ; and as P represents phosphorus, we use, for potassium, K, from Icalium, the Latin for potash. A symbolic letter denotes, not merely an element, but one propor- tion, or atom, of that element. Thus, H stands for one equiva- lent of hydrogen, and for one equivalent of oxygen. If more proportions than one are to be expressed, a small figure is added : thus, O2 stands for two proportions of oxygen, H3 for three of hydrogen. In the table of elementary bodies (111) the symbol and combining number are given opposite each name. ^49. Formulae. — To express composition we place together the/ symbols of the elements of which the compound is formed ; thus HO is the symbol for water, CO- for carbonic acid. Here the named ? What does ate signify ? He ? Examples. How is the basic element indi- cated? 148. What are symbols ? How are the symbols for the elements obtained? What doeg the symbol denote? How is more than one equivalent expressed? 70 CHEMICAL PHYSICS. electro-positive element is placed first. A collection of symbols expressing composition or changes is called a formula. In ex- pressing changes the sign -f signifies addition to or mixture Avith, while the sign = signifies equivalency with or conversion into. The substances which act upon each other to produce chemical changes are called reagents, and the changes themselves reactions. The results of reaction are expressed by means of chemical €q2ia- tions, in which the substances before the change are placed at the left, and the products of the change at the right. The reactioii between nitrate of baryta and sulphate of potash is thus expressed ^ Sulph. of potash. Mt. of baryta. Sulph. of baryta. Mt. of potash. KO, SO^ + BaO, no's = BaO, SO3 + KO, NO^ As nothing is either gained or destroyed in the operation, the quantities on each side are equal, as may be tested by forming an equation of the equivalent numbers. 150. A bare statement of the elements of a compound, with no indication of the way in which they are combined, is called an em- pirical formula (28). National formulae express the views of the chemist as to the manner in which the elements are grouped. Thus the empirical formula for nitrate of potash would be KNOe. But as it is formed by the combination of nitric acid and potash, it is rationally written as if it consisted of them ; thus K0,N05, the comma serving, as it were, to dissect the compound, and show how it is constituted. Sometimes the plus sign is used to indicate feeble attraction. Thus crystallized carbonate of soda is NaO, CO2 + IOHO, the ten equivalents of water being more loosely asso- ciated with the salt than the ingredients of the salt are with each other. To denote more than one equivalent of a compound, its formula is inclosed in a bracket with the number prefixed. Thus, three equivalents of nitrate of potash would be written 8(KO,N05). The figure prefixed multiplies only the symbols in the brackets, as in the following formula for crystallized alum, which contains 3 equivalents of sulphuric acid : Ala O3 3(S03)-f KO, 803-}-24IIO. 149. What are formu]a9 1 How are the symbols arranged? What does + signify ? What 18 meant by the sign = ? What are reagents and reactions 7 How arc the resultB of reaction represented? 160. What are empirical formijlsB? Rational for- mulje? Give an illuHtration. What does the plus sign sometimes denote? IIow Is more than one equivalent of a compound expressed ? If brackets are omitted ? THE NOMEN-CLATUKE. 71 V^^ If brackets are omitted, the figures multiply all between them and the next comma or plus sign. ^- "^Sl. Later vievsrs of Gerhardt and Laurent. — Certain ideas X advanced by these chemists have been latterly growing in favor. Hydrogen, being the lightest substance known, is taken as the standard for the specific gravity of gases. It is found that the bulk or volume of a grain of hydrogen is the same as that of 14 grs. of nitrogen, 35.5 grs. of chlorine, and 80 grs. of bromine. Now these numbers are precisely the atomic weights of the bodies, so that the same numbers express both atomic weight and specific gravity. But the same bulk of oxygen weighs 16 grs., which is just twice its atomic number. And when the vapor volumes of carbon and sulphur are determined, it is found that to fill the same space takes 12 grs. of carbon and 32 of sulphur ; these again being just twice their atomic weights. To obtain uni- formity therefore, as well as for other reasons which cannot be here stated, the atomic numbers of oxygen, carbon, and sul- phur are doubled. In this way the same numbers are made to express three facts, viz. : atomic weight, specific gravity, and combining volume. j/^\b1. On this view the symbols represent eqiiol wlumes of their^ elements. Hence the formula for chlorohydric acid, HCl, implies a combination of one volume of hydi'ogen with one of chlorine fTTIcll . "Water is a combination of two volumes of hydrogen with one of oxygen, thus [^o], and is written H2O ; while ammonia, HsN", im- plies a union of three volumes of hydrogen with one of nitrogen It will be noticed in the case of water that the doubling of oxygen is the consequence of halving the hydrogen ; if we take equal 'col- umes^ their weights are as 16 to 1 ; but as there are two volumes of hydrogen, the composition of water becomes H2O, the oxygen being 16. There are other reasons for considering the composition of wate'IC ELECTRICITY. Ley-.ien jar. comes charged. Then, on connecting the inner and onter coats by a conductor, discharge takes place, with a brilliant spark, and equilibrium is restored. The jar serves to accumulate Fig. 59. electricity, and a connected series of such jars forms the Ley den Battery. 173. Two kinds of electricity. — K a ball made of pith of elder be suspended bj a silken thread and brought near an escited glass tube, it will be first at- tracted to it, and then repelled from it. If another suspended pith ball be brought near a stick of excit- ed sealing wax, it will act in the same manner. Both balls are excited and both repelled. If the difi*erentl j excited balls are now brought near each other, ther are attracted together, whereas if both had. been excited bj the glass alone or bv the wax alone, ther would have repelled each other. There are thus two kinds of electricitv ; that from glass is called xitj'eoiis, and that from wax resinous. Each is self-repulsive, but bodies excited both ways attract each other ; or, as it is com- monly expressed, lilie electricities repel., and unlilce attract — the same principle that we have just seen in magnetism. 174. Electroscope. — The property of self-repulsion is employed to test the presence and intensity of electrical excitement. A simple electroscope is formed by suspending two pith balls by linen threads, as in Fig. 60. If touched by an excited body, they are repelled. Fig. 61, and the degree of divergence is a rough measure of the force awakened. 175. On the same principle, slips of gold leaf attached to a conducting rod in a glass jar. Fig. 62, form a very delicate electrom- eter. Such is the sensibility of the instru- ment that a slight flap of a silk handkerchief on the plate at top renders the leaves divergent. "We thus become aware how trifling are the causes that disturb the electric equilibrium of the objects around us. Xot the smallest change in place or condition can Fig. 60. Fig. 61. A Unexcitcd pith balls. 172. "Wliat is the electrical machine ? Describe the Leyden jar. How is it charged and discharged 1 "SVhat is a Leyden battery ? 173. Ho-w may it be shown that there are two kinds of electricity ? What are they called I How do they affect each other ? 174. Explain the electroscope, Fig. 60. 175. "WTiat does Fig. 62 represent f 80 CHEiTICAL PHYSICS. Fig. Ci occur %vitliout interfering ^vitli this rnvsterions agency, although the balance is so quickly ad- justed that we are not aware of the disturb- ance. ' In cutting a slice of meat, there may 15ass between the steel knife and silver fork enough electricity to move the needle of a tel- egraph.' (C.Y.Walkee.) V 176. Electric Tension. — The electrical ex- citement of a body may rise so high as to over- come the resistance which confines it and es- cape, rending a passage through the air, when Gold-leaf electroscope. ^H excitement disappears. A body electrically excited is said to be charged ; the restoration of equilibrium is called discharge, and is seen in the electric spark and the flash of lightning. The degree of excitement or intensity of the charge is called elec- trical tension, and may be compared to the pressure of steam, or the bending of a bow or spring ; its discharge to their release. 177. This analogy of the spring may. be carried much farther. It is a principle of nature that forces develop themselves in a double or op- posite way. We see this in mechanics in the elasticity of a spiral spring, Fig. 63. When unstretched it manifests no force. IsoT can it be stretched from one end alone. If hooked to the pin P, and the weight "W is attached, it will seem to be stretched by one end only. But this is a mistake; for by substitut- ing the weight V for the pin P, the strain upon the spring is the same ; as the arrow indicates, the forces are double, equal, and opposite. 178. The same principle is observed in electricity. It is a double force manifesting itself by actions and reactions which are equal and opposite. One kind of electricity cannot be produced unless it is accompanied by the other. Whenever vitreous elec- tricity is developed, a corresponding amount of resinous electricity Give infitanecs of its sensibility. "VMiat does this show us ? 176. Explain wliat ia meant by electric tciisioD. To what may it be compared? 177. In what manner »ro forces developed? IIo'.v may this bo Bhownl 178. How is it in electricity I Duality and polarity of me- chanical forces. FRAJmXINIC ELECTRICITT. 81 intariably accompanies it. It may not be at first perceptible, but will be recognized upon careful examination. Electricity is thus, like magnetism, u, polar force. 179. Electrical hypothesis. — Electricity has generally been re- garded as a sabtile material fluid p'Srvading all matter. Some hold that the two electricities are two fluids which are mutually at- tractive, though each is self-repellant. ^EA^'E:LIX simplifled the matter by regarding electricity as analogous to heat, and, as all the effects of heat and cold were explained by the excess or deficiency of a single fluid, caloric, he proposed to explain electrical effects by variations in quantity of a single electric fluid. He maintained that bodies vitreously electrified have an excess of it above their natural share, which excess he called the positive state, while bodies resinously electrified are deficient in the fluid, or in a negative, condition. The positive electrical state he distinguished by the plus sign (-{-), and the negative by the minus sign (— ). 'When both are used together, they signify neutralization, or no excitement. 180. The Franklinic terms and symbols are still used, but we must guard against their misguiding influence. Positive electri- city is no more positive, real, or powerful than negative, acd the terms might be reversed so far as the character of the electricities is concerned. Nor is the idea of a fluid at all adequate to explain the facts. Prof. Millee remarks: 'The supposition of an electric fluid is grad- ually being abandoned. The supposi- tion of a gravitative fluid might with nearly as much propriety be insisted on to explain the phenomena of gravi- tation, or a cohesive fluid to account for those of cohesion.' ^^ Electrical Induction. — Electri- cal bodies, like magnetic, act at a dis- tance to disturb the equilibrium of neighboring bodies. If an excited glass rod be brought near an electroscope, though there be no contact, the leaves will diverge, Fig. 64, and upon examination it will be found that the Induced electricity. 179. How has electricity been generally regarded ? What was Franklin's explana- tion? What do the eigns plus and minus signify ? ISO. In the use of these terms what are we to guard against ? How is the conception of electricity as a fluid now 4* 82 CHEMICAL PHYSICS. cap is negatively electrified, and the leaves positively. The approach of the excited tube decomposes their natural elec- tricity, the negative element being attracted, and the positive repelled. This action of an excited body, without discharge, through a medium upon distant bodies, is known as electrical induction. 182. Induction is a kind of preparation for discharge. "When electricity is about to move, or discharge to occur, the whole course through whicli it will pass is, as it were, felt out hefore- liand ; at first and infallibly the line of least resistance is found and pursued. If two conductors are before it, it takes the easiest course at the outset. Fig. 65. 183. Fig. 65 represents fragments of gold leaves j^ casually laid upon paper, and producing with the [§ paper a series of bad and good, conductors. A dis- y /> charge finds its path across the interrupted circuit jg— J from P to N, burning up the leaves and parts of Q-' leaves, as shown by the shaded track. These re- markable results are necessary consequences of the principle of induction. The charged body induces attractions in all directions, and the discharge will Sof course be determined through that range of ma- ^^ terials which from their nature and position are most excited ; which present the strongest attractions, and, i \\ of course, the least obstruction. I 184. Theory of Induction. — As there are all de- ™ grees of conduction and insulation. Dr. Faeaday r tbofthedis- -^^^^^ ^^^ '^^^ must look upon conduction and in- ~ charge. duction as only different degrees of the same mode of movement ; in all cases, it is an effect communicated from atoms to atoms. If, when a body is electrified, its particles discharge in- stantaneously into each other, conduction is the consequence. If the particles do not readily discharge, but hinder the course of the electricity, they are immediately forced into positions of con- straint : they become polarized^ and as each particle induces a state of polar tension in its neighbor, the effect is transferred to a regarded f What is it lhoiic:ht to be ? 181. What is the effect of an excited glass tube brought near an electroscope? What is induction said to be? 182. When electricity is about to move, what course does it take ? 18.3. Explain Fig. 65. Why is this? 184. Describe Faraday's theory of induction. Explain Fig. 66. On VOLTAIC ELECTEICITY. 83 distance. In Fig. 6Q, P represents a positively charged ^la. 66. - body, and a I) c d intermediate particles of air. These are thrown into opposite states or polarized, as is rep- resented hj Jhe white and black sides of the spheres, and thus the effect is propagated to the body IST, whichCC) Q cc is electrically excited. V/e have said that insulators ^ Q © & arrest electricity, but on this view they only stop move- ment by conduction ; they transmit it by induction through the polarization of their particles. As the polar particles are in active relations of force to those around, it is obvious the effects may be propagated in various directions. Hence the polarization may occur in curved lines, and induction take place round corners and behind obstacles. 185. Sources of electricity.— These are various. Besides or- dinary friction, the rubbing of water particles against the aperture when steam escapes is a powerful source of electricity. When- ever bodies are pressed together and separated, they exhibit traces of opposite electrical excitement. Many crystals are made elec- tric by mere compression ; Iceland spar pressed between the fingers becomes excited. If tourmaline be yig. 67. slowly heated, it becomes power- fully excited, as is represented in Fig. 67 (No. 1). When the heat is no longer added, the excitement dis- appears, but, as it cools, the electri- cal conditions are reversed (No. 2). tourmaline electrified by beat. That the particles are polarized through the whole length is shown by the fact that if the crystal be broken^ as the tempera- ture falls each piece is electrified (No. 3). Fracture, crushing, and combustion, all produce electricity. Carbon in burning is neg- ative, while the carbonic acid formed is positive. § lY. Yoltaic Electricity — Electro-Dynamics. 186. We have now to consider electricity in a state of motion and active force. This important branch of the science was dis- covered about 1790, by Galvani, while working with some dis- sected frogs, and in his honor is frequently called Galvanism ; but this view what is insiilation ? 1S5. "VYhat other sources of electricity are men- tioned? "What does Fig. 67 represent? 186. What is electro-dynamics? "Who 84 CHEMICAL PHTSICS. its most illustrious cultivator was Yolta, whose name is insepara- Llj connected wirli its foundation and progress, and from whom it is also called Voltaic electricity. Both these celebrated men were Italians. 187. Sulzer's experiment. — It was noticed by Sulzee, about a hundred years ago, that, if a silver coin be placed upon the tongue, and a piece of zinc beneath, a peculiar tingling sensation or taste vf ill be perceived when the ends of the metals are made to touch ; or, if the silver be pressed between the upper lip and the teeth, a flash of light will be observed when the metallic contact is made. This is an effect of voltaic electricity. 188. We have just stated that electrical disturbance may arise from simple contact of different substances. Yolta supposed that these effects were due to the same cause. But it is now generally considered that when electricity arises by metallic contact, it is owing to chemical change. Yoltaic electricity is produced when two unlike solids, usually metals, are immersed in a liquid which dissolves only one of them. It is a general law that no chemical action occurs unaccompanied by electrical disturbance, although the quantity is often so minute as to escape detection. Fig. G3. 189. The Voltaic Circuit. — A strip of zinc and one of copper are placed in a vessel containing water, to which has been added a little sulphuric acid. If not permitted to touch each other, as in Fig. 68, there is no effect. But if brought into contact, as seen in Fig. G9, several results ensue. The acid in the water grows weaker ; the zinc strip is cor- roded, wastes away, and bubbles of gas are seen to escape from the surface of the copper. If the metals are separated, the action ceases ; and, if this is done in the dark, a minute spark will be seen. Electricity seems to flow round and round in the direction of the ar- rows, like an invisible stream. The com- bination through which it passes is termed a voltaic circuity and the circulating force an a tie voltaic circiiit. electric,or electromotive current. If the plates discovered it? Why is it called voltaic electricity? 187. What ^vas Sclzer's experiment ? 183. When is voltaic electricity produced ? "What is said of chemical VOLTAIC ELECTEICITY. 85 be connected by means of a wire, wMcb may be a few inches or many miles in length, a current passes through the whole distance. If a non-conductor be substituted for the wire, the action instantly ceases. 190. The source of the electricity is the decomposition of the water, its oxygen combining with the zinc to form oxide of zinc, while hydrogen gas is set free. But the oxide of zinc is insoluble, and would form an impervious coating upon the plate, and quickly stop the process. This is prevented by the sulphuric acid which unites with the oxide, forming sulphate of zinc, and thus the plate is kept clean and the action maintained till the metal is consumed, or the acid all neutralized. 191. Amalgamation. — A slip of pure zinc introduced into the acid is but slightly, if at all, acted upon. But commercial zinc is contaminated with lead and other metals, the effect being to create minute currents between them and the adjacent particles of zinc, thus corroding the plate and wasting the electric force. To pre- vent tliis, the clean zinc surface is rubbed over with a little mer- cury, which forms an amalgam with it, increasing the energy of the zinc, and enabling it to be kept in acid without corrosion. 192. Blectrodas. — To the plates are usually soldered wires with terminals of platinum to withstjmd the action of corrosive liquids. The ends of these wires are known as the poles of the circuit, from an idea that they exerted an attractive and repellant action, like the poles of a magnet. But Faeaday has proved that there is no attraction or repulsion in the case, and suggested the better term electrodes, which means simply a door or way for the ekctricity. 193. Positive and negative parts of the circuit. — The terms positive and negative have a double application to different parts of the circuit, which often cofifuses the student. The copper pole is positive (which may be easily remembered by associating the four p's of the three words), and the zinc pole negative. But these terms are reversed when applied to the plates — zinc being now positive and copper negative. Whatever be the metals used, action? 189. Describe the voltaic circuit ? Its effects? 190. What is the source of the electricity ? "What is the office of the sulphuric acid ? 191. "What difficulty arises in the use of common zinc? How remedied ? 192. "WTiat are the poles of' the circuit? Why is 'electrodes' the better term? 193. How are the terms positive and iic^rative appl'-cd ? Where docs the positive electricity originate, and what is 86 CHE3IICAL PUYSICS. Fis. TO. -* iSi^ Polarity, bat no current. the positive plate, or the one chemically acted upon, originates positive electricity, which passes over to the negatively atiected plate, and is by that delicered at the positive electrode. 194. Polarities of the circuiL— The electric current originates in chemical changes, and requires a compound liquid capable of de- composition by one of the metals. To bring the chemical force into play, the voltaic circuit must be arranged so as to form a continuous chain of polarities. The theory of the action may be illustrated by representing the atoms of .the liquid to the eye. A plate of zinc with one end in chlo- rohydric acid assumes a state of electrical tension, and induces the same state in the atoms of hydrogen and chlorine which compose the acid, Fig. TO. The positive zinc at- tracts the adjacent atom of negative chlorine, but not with sufficient force to take it from the positive hydrogen. ]S'or is the matter helped by completing the circuit with another zinc plate, as shown in the figure. At two points, above and below, like electricities repel each other; the tensions are balanced, and there is no motion. ■«^**^95. But if now the second zinc plate be replaced by one of copper, the conditions are altogether changed; the polar- ities are unlocked, the liquid is decomposed, and there is an active circuit, as illustrated in Fig. 71. The copper imparts an additional amount of positive electricity to the zinc, the ten- sion of which is thus heightened, and receives a portion of ne- gative electricity in return. A powerful polar influence is thus communicated to the liquid. The incraftsed attraction of the zinc causes it to decompose the adjoin- ing atom of acid, combining with the negative chlorine ; while the atom of hydrogen, powerfully po- larized by induction, acts in the same way, decomposing the next Fig. 71. Conditions of circulation. Its course t 194. In what does the electric carrent oViginate ? What docs it re- quire ? What is the effect of one zinc plate in the acid ? Of two ? 195. What is the effect of rep'acing the zinc by a copper plate ! Draw Figures 70 and 71 upon VOLTAIC ELECTEICITY. 87 * atom of acid, uniting with its chlorine, and forming a new com- pound atom. This is repeated through the series, and the last at^m i€ hydrogen, having its positive electricity neutralized by the strongly negative copper, is set free. 106. Currents. — Here again we are in danger of being misled by terms which involve material views of force. The word ' current ' is to be used in a sense entirely figurative. In dealing with sub- tile, invisible forces, it is easiest to view thsm through the medium of analogy and apply terms borrowed from sensible objects. The effects of electricity resemble those of a stream, and from ap- propriating the terms we gradually acquire the idea of an unseen but real fluid flowing in currents through substances, or from one to another. But all we know in the matter is progressive effects^ and all we are entitled to assume is the progress of force. The movement of electricity is more analogous to that of sound, where pure impulse and not matter is borne forward. (319) If the ivory ball at one extremity of a closely sus- Fig. 72. pended series, Fig. 72, be raised and let fall, the one at the other end will be struck off", the intervening balls re- maining in their places, yet trans- mitting the impulse; there is only a Elastic balls, progress of force. "While the term current in electricity is con- venient and perhaps indispensable, we mean by it the same as if we should speak of a current of sound, or, in the case of the ball, a current of motion. 197. Two Opposite Currents. — We have seen that elec- tricity, like magnetism, is a polar force, displaying itself in a twofold way. When produced in the voltaic circuit, it separates into two equal and opposite powers — two currents which, when they meet, instead of doubling, neutralize each other. The electricity thus produced has been likened to a double-headed arrow rapidly elongating itself in opposite direc- tions. At first they move from each other, but turning through equal semicircles, they meet, each arrow-head destroying the other. the blackboard, and explain them. 193. In Avhat danger are we from Tising the word current? What do we really know in the matter? To what is the move- ment of electricity analogous ? To what else is it compared ? 197. In what respect have we seen electricity to be like magnetism ? To what are the movements of the current likened? What is meant when the direction of the current is spoken of? 88 CHEMICAL PHYSICS. The two currents. Fig. 73. Xhre two opposite electricities or polarities con- stantly meet and neutralize each other, and are constantly renewed. To avoid confusion, when the direction of the current is spoken of, the positive alone is indicated. In Fig. 73 the dark arrows show the direction of the positive current, the dotted arrows that of the nega- tive. 198. The Voltaic Pile.— The power of the circuit mav he increased by repeating its elements. The pile dis- covered by VoLTA and named after him was the first contrivance for augmenting the force of the electric current. It is made by preparing small plates or discs of metal, usually copper and zinc, and placing between them pieces of flannel moistened with an acid or saline solution. Such a pile is represented in Fig. 74. The Fig. 74. cloth is placed between the metals, and the ordei- begun is preserved. Commencing at the bottom there is copper (c), flannel (f), zinc (z), and upon that ^ copper, flannel, zinc, and so on to fifty or a hundred / ^^5^ sets, as may be desired, 74. The lower or copper f T'^^y p end is positive, and the other negative ; a current ' therefore moves in the direction of the arrows. This form of instrument gives a strong effect at first, but rapidly declines in power. 199. TheGalvanio Battery.— To augment the electrical effect, and at the same time secure steadi- ness of action and convenience of management, the compound circuits are arranged in other forms known as roltaic or gaUanic latteries. A series of cups or cells, containing an acidulated liquid, are arranged, in each of which there is a plate of copper and another of zinc; the copper plate of one cup being con- nected by a copper wire with the zinc plate of the preceding cup, Fig. 75. "We have already noticed the tendency Voltaic pile. Fig. Voltaic battery. 200. Smee's Battery.- 193. How may. the force of the circuit be increased ? "What is the voltaic pile ? Explain Fig. 74. 199. What objects arc secured by the galvanic battery ? How is it m.-idc ? 200. What hindrance is ovcrcomo by Smee's battery ? How is it done T VOLTAIC ELECTKICITY. Smee's cell. Fig. 77. of gases to condense upon solid substances. In the battery a film of hydrogen forms in this way upon the smooth copper and pla- tinum, which is a serious hindrance to the action. If, however, the surface be roughened, it passes off with ease. Smee removed this difficulty by using a silver negative plate, and coating it with platinum black. To form the single cell, two plates of amalgamated zinc are clamped against a piece of wood with a silver plate between them, Fig. 76. They are then suspended in a glass vessel, the piece of wood resting upon the top. The liquid used is sulphuric acid diluted with ten or fifteen times its weight of water. A binding screw attached to the silver plate connects the positive wire, and an- other from the zinc plate the negative. A series of these cells properly joined, or a series of connected plates immersed in a suitable trough, constitutes Smee's hattery. 201. Daniell's Battery.— Prof. Daniell made an important improvement in the bat- tery by using two different fluids separated by a porous partition. Fig. 77 exhibits a section of Daniell's cell ; a is an outer cylinder of copper filled with &, an acid solution of blue vitriol, which is kept saturated by crystals resting upon the perforated shelf/; c is a tube of porous ware, or unoiled leather, filled with d, 1 part of sulphuric acid to 7 water, and into this is plunged a rod of amalgamated zinc e. To the copper and zinc are attached binding screws for wire connections. 202. The blue vitriol consists of sulphuric acid and oxide of copper. When the action commences a double set of changes takes place in the liquid. Oxide of zinc is formed in the inner vessel, and the polarizing action taking place through the porous wetted body e, the sulphate of copper is decomposed in the outer vessel. The sulphuric acid set free is gradually transferred to the inner vessel, while the hydrogen, instead of being set free, com- bines with the oxygen of the oxide of copper, precipitating metal- How is a single cell constructed? What liquid is used? How are the wires at- tached? 201. In what did Prof. Daniell's improvement consist? Describe his aell. 202. Explain its mode of action. What ia said of it? 203. How does Danieirs cell. 90 CHEMICAL PHYSICS. Fig. 73. Grove's cell. lie copper upon the surface of the outer cylinder. This was the first constant battery, and is capable of maintaining a uniform strength for many hours. 203. Grove's Battery is also an arrangement for two fluids, like Daxiell's, its metals being amalgamated zinc and platinum, and its liquids nitric and sulphuric acids. Fig. 78 is a vertical section ; a is a jar of earthenware, c the outer liquid of dilute sulphuric acid ; 5 is a cylinder of amalgamated zinc con- nected with the negative electrode, and having a slit on one side to allow the free passage of the liquid. It is therefore exposed on both sides to the outer liquid c of dilute sulphuric acid ; d is a cup of unglazed earthenware filled with strong nitric acid e; / is a thin slip of platinum suspend- ed in the porous cup, and connected with the positive electrode. 204. In Grove's lattery the oxygen combines with the zinc, as in the other cases, but the hydrogen decomposes the nitric acid, unites with a portion of its oxygen, forming water and producing deutoxide of ni- ^^°- ''^- trogen, which rises into the air, and, reuniting with oxygen, forms nitrous acid fumes. The escape of these corrosive vapors is n disagreeable feature of this combination. Figure 79 represents a series of cells in working connec- tion. Geove's battery pro- duces very powerful and brilliant effects, and is much used in telegraphy. It is less con- stant than Daniell's, but according to Prof. Jacobi, when the pla- tinum and copper surfaces are equal, that of Geove is 17 times more powerful. 205. Eunsen's Carbon Battery is similar to Geove's, but re- places the expensive platinum by cheap carbon cylinders made by Groves battery. Grove's battery differ from the precedintj? 204. Explain its actirm. What is said of it ? 205. What ia Bdnsen's battery ? Of what does the Mayxooth battery VOLTAIC ELECTEICITT. 91 pulverizing gas-carbon (526), mixing it with flour, and baking it into hard pieces. Dr. Callan's Maynooth IjaUery consists of a water-tight cast-iron cell, containing a porous cell, in which is a plate of amalgamated zinc. Mixtures of strong sulphuric and nitric acids are used, and the effects are claimed to be more in- tense even than those of Geove's batterj. Schonbein's hattery re- sembles the one just described, except that the outer cell is formed of passive iron, which makes an excellent combination with zinc (704). 205. Resistance to the current. — As in machinery all the force applied is not available for work, some of it being absorbed by fric- tion, so all the electrical force generated in the battery cannot be made available for effect, a portion of it being destroyed by resist- ance of the materials of the circuit itself. The conductors are to a certain extent also obstructors. The resistance is, first, that of the liquid of the battery, which depends upon its conducting quality, and the distance between the plates. The larger the plates and the closer together, the less the resistance. Second, the wires offer a resistance dependent upon their length, narrowness, and material. 207. Quantity and Intensity. — These terras describe two con- trasted states of electrical manifestation, the meaning of which may be illustrated by reference to heat. Thus the heat in the human body is considerable in quantity, but low in intensity, while that of an ignited match is very small in quantity, but high in intensity. Of course there can be no electricity that does not possess to a certain degree both qualities, but one or the other is always in great excess. 208. In the battery the quantity of electricity depends upon the size of the plates ; the intensity upon the number of them. If we increase the size of a pair of zinc and cop- per plates, we increase the quantity of the electricity they produce, but not its in-' Fig. 80. Accumulating intensity. consist 1 ScHONEEis's? 206, In what respect does the battery repemhle ma- chinery? Where is the resistance, and on what does it depend? 207. What ia meant by quantity and intensity in electricity ? Do they exist together ? 208. Upon what does the quantity of electricity in the battery depend? The intensity? 92 CHEinCAL PHYSICS. t^nsitv ; "while, if vre redace the size, Tre reduce the quantitr, the intensity remaining the same. On the contrary, if vre multiply the number of pairs of equal size, the intensity is auraiented at an equal rate while the quantity is unchanged. The electricity de- veloped by a single pair is exceedingly feeble; the second cell adds no more to it, but intensifies its power. In Fig. 80 the arrows illustrate the accumulating intensity. 209. Frictional and current electricity. — It has been demon- strated that frictional and current electricity are one ; all the effects of the former being produced by the latter. But these modes of action are marvellously different. "We may view a spark as a fraction of a current ; and a rapid succession of sparks as an imper- fect approach toward a current. But the duration of a spark is infin- itely small compared with the time necessary to accumulate the elec- tricity which produces it. A six-inch electric spark is estimated to pass in the three thousand millionth part of a second (Walkee), but no frictional machine can supply abeguming to three thousand million such sparks in a second. The machine of the London Polytechnic Institute, with an 8T-inch plate driven by steam at 80 revolutions per minute, and a friction of 90 square feet of glass per second, gave the six-inch sparks no faster than they cotild be counted. The quantity is thus small, and the intensity high. But in the voltaic circuit, charge is as instantaneous as discharge ; the stream is unbroken ; the quantity is enormous, but the intensity low. 210. A flash of lightning in a drop of water. — Dr. Faeadat demonstrated that the electric current which is required to decom- pose a single grain of water is also sufficient to keep a platinum wire the ^roth part of an inch in diameter red hot for 3| minutes. But to produce the same eft'ect for the same time by frictional electricity would require 6,500.000 discharges from a Leyden jar 8 inches high and 7^ inches in diameter. It would, therefore, require this amount of static electricity to decompose a single grain of water. Dr. Faeaday further showed that this would suflice to charge an insulated conducting pane, such as a thunder-cloud, How may we v.iry either? What does Fig. 80 represent ? 209. In -what re9X)ect8 are current and frictional electricity alike? How does the duration of a sijark compare with the time required to accumulate it ? AVhat instance ie given ? How la it in the voltaic circuit ? 210. How much voltaic electricity is required to decoropoee a drop of water? How much frictional electricity is this equal to? EFFECTS OF VOLTAIC ELECTRICITY. 93 Fig. 81. thirty-five acres in area, the instantaneous discharge of which would constitute a powerful flash of lightning. 211. Voltaic electricity will travel through a conductor thousands of miles rather than penetrate a harrier of air a small fraction of an inch in thickness, while static electricity will leap through miles of intervening atmosphere. For sustained effects, as in chemical decompositions and telegraphy, w^here vast quantities of electricity are required, the hattery is employed, its current being raised to the requisite tension by multiplying the cells. § Y. EffccU of Yoliaic Electricity. 212. Decomposition of water. If the ends of the platinum wires connected with a battery are placed near each other in a vessel of water containing a little sulphuric acid to aid conduction, bubbles of gas will be seen to rise from the terminals and escape at the surface. A couple of glass tubes filled with water, and invert- ed in the vessel over the poles, serve to collect the rising gases. Fig. 81, which upon examination prove to be pure hydrogen and pure oxygen, the bulk of the former being twice that of the latter. The water becomes part of the circuit, and is decom- posed by a polarization of the line of compound particles between the electrodes in the same manner as occurs in the battery itself (195) ; only in this case, as the oxygen does not combine with the platinum, it is set free like the hydrogen. 213. Electrolysis. — This operation is termed electrolysis (ana- lyziug by electricity), and any substance that is capable of this de- composition is called an electrolyte. Solids are not electrolytes. Liquids, and certain liquids only can be electrolyzed. A good electrolyte should be a good conductor, and yield upon separation a conductor and a non-conductor. The binary compounds are resolved into their elements by the current, and the salts into acids and bases. Sulphate of soda yields sulphuric acid at the -|- pole, where it may be made to redden vegetable blue, while soda Electrolysis of water. 211. How do they differ in power to penetrate the air ? For what is the battery used ? 212. How is the decomposition of water effected by the current? Explain Fig. 81. 213. What is electrolysis ? "What bodies are good electrolytes? Exam- 94 CHEMICAL PHYSICS. appears at the — pole, and will there turn vegetable reds to blue By reversing the direction of the current, these beautiful effects are also reversed. 214. When compounds are electrolyzed their elements are found in opposite electrical states. Some, as oxygen, chlorine, sul- phur, appear at the positive electrode, and are called electro-nega- tive bodies ; while others, as hydrogen and the metals, appear at the negative electrode, and are called electro-positive. Of the 64 ■elements, 24 are usually ranked as electro-negative, and 40 as electro-positive. Oxygen heads the first list, or is the most power- ful electro-negative body, while the newly discovered caesium heads the other, being the strongest electro-positive substance. The elements may be arranged in such an order that each will be electro-negative to all which follow it, and electro-positive to all which precede it. 215. As the electric current thus originates in chemical changes and produces them, and as the atoms seem to be in opposite elec- trical states, it is obvious that electrical force is very closely allied to chemical power. The electro-chemical theory teaches that they are identical ; that electrical attraction causes chemical combina- tion, and that every chemical decomposition is due to the play of electrical forces. 216. Electrotype is the name given to the pro- cess of depositing metals from their solutions by electricity. The deposited metal assumes with ex- actness the form of any body npon which it is made to settle, so that when removed it forms a perfect counterpart of the object, copying and reversing all its markings and irregularities. To copy a medal it is first made perfectly clean, and the back and edges protected by a coating of varnish or wax. The battery used may be of various forms ; Daxiell's I cell. Fig. 82, answers the purpose. Into a glass tumbler, S, is introduced a lamp chimney, A P, with a piece of bladder tied over the lower end. This is filled with dilute acid, while the tumbler contains a strocg solu- Fio. 82. Electrotyping. pleB. 214. How is the division of the elementB into electro-negative and electro- positive effected? How are they proportioned to each other? IIow may the clomenta bo arranged? 215. What Is the electrochemical theory ? 216. What ia EFFECTS OF VOLTAIC ELECIEICITY. 95 tion of sulphate of copper. The medals m m are immersed in the sulphate of copper, and connected by wires to the zinc rod Z. Thus arranged, the sulphate of copper is gradually decomposed, and the metal evenlj deposited. The copper coating is then de- tached, and forms a perfect reverse or mould of the object. The Tvhole process is then repeated Tvith the mould, producing an exact copy of the original medal. 217. In electro-gilding and electro-plating the object is to impart a new and permanent metallic surface. In this way num- berless articles placed in solutions of silver and gold are coated Vvith these metals, from the thinnest gilt to the thickest plating. '^l 8. Heating efiects of the current. — A cur- rent passing through a conductor raises its tem- perature in proportion to the electricity arrest- ed. This depends first upon the quantity in motion, and second upon the resistance oflTered by the conductor. A wire which is but little heated by a current, if considerably reduced in diameter, becomes instantly white hot. The arrested electricity appears as heat. Two char- coal points brought into contact in the circuit, and then slightly separated, emit a light of daz- zling splendor, Fig. 83. 219. The electric Kght. — The brilliancy and purity of the electric light from charcoal points and the absence of contaminating products make it highly desira- ble as a source of illumination. But there is a mechanical diflBculty in the way of its use. Particles of carbon are constantly transfer- red from the positive to the negative poles ; one is shortened and the other lengthened, and that unequally, so that it is trouble- some to maintain them at the precise distance. 220. Blasting. — By passing a fine platinum wire through a charge of gunpowder, it is instantaneously exploded by the cur- rent. The same wire may pass through several charges and ignite them simultaneously. In excavating for an English railway, nine tons of gunpowder were buried in three masses in the Dover Clins, Electric li^ht. the electrotype? Describe the process. 217, What is the object in electro- gildicg and plating? 218. When electricity is arrested by a conductor, what becomes of it ? Upon what does the anaonnt of heat depend ? 219. "Wliat are the advantages and disadvantages of electric light? 220. How is the electric 90 CnEMICAI. PHYSICS. from 50 to 70 feet from the surface, and ignited by a distant bat- tery. The exi)losion detached 600,000 tons of the chalky cliffs. Powder is fired in the same way for blasting rocks under water. Fig. 84 Current and needle. § YI. Electro-Magnetism. 221. In 1820, Prof. Oeested, of Copenhagen, discovered that if a magnetic needle be brought near a wire along which an elec- tric current is passing, the needle will be influenced and caused to move. The degree of the motion will depend upon the strength of the current, and its direction upon the relative position of the needle and wire. If the wire be above and parallel to the needle, the pole next the negative electrode will move westward ; if beneath the needle, jt will move eastward. If the wire is on the east side, this pole will be elevated ; if on the west, it will be depressed. In all cases it tends to place itself at right angles, or trans- verse, to the wire. If the wire be bent, so as to pass above and below the needle, Fig. 84, the effect is increased ; and if it be coiled round many times in the same manner, it becomes still more powerful. The motion of a needle thus freely suspended becomes the visible test of an electric current. 222. The Asiatic Needle. — But a needle keeps its place in the magnetic meridian with considerable force, so that a very faint current will not move it. If two needles, however, are placed parallel, near each other, with reversed poles, their directive force is mutually neutralized. Two needles thus fixed upon an axis, Fig. 85, form the astatic (unstable) needle. If one is slightly stronger than the other, it still retains a feeble tendency to keep its north and south position. If now the wire of Fig. 85 were folded round both these needles, the same current would urge them in opposite -J directions, and there would be no motion ; but when the coil incloses only one of the needles, as the lower for example, the current impels current used in blasting ? 221. What -waa Prof. Okrstkd's diecovery ? Upon -what do the degree and direction of the motion depend? 222. What ia the aetatic Fig. 85. G < JV ^ 2f_ LI ^ Astatic needle. ELECTEO-MAGNETISM. 97 Fig. 86. ^^i^ MaEcnetizins a Bar. Fig. 8T. both needles in the same direction. If the needles be delicately suspended, it affords the means of detecting the faintest electrical current and forms the galvanometer. 223. Electro-Magnets.— K a bar of ^ steel be placed in a coil of wire, as in Fig. jlr= 86, and a current be sent through the coil, ii the bar becomes at once permanently ^ magnetic. If a bar of soft iron be intro- duced, it becomes magnetic, but only continues so as long as the current is maintained. A horse-shoe bar of soft iron, with a wire twisted spirally round it, as in Fig. 87, becomes a powerful magnet, capable of supporting a heavy weight, while the current is passing. 224. The Current a Magnet. — Electric currents , attract and repel each other like magnets. "When two wires are freely suspended near each other, if currents pass through them in the same direction, they attract each other ; if in opposite direction^, they repel each other. If a copper wire be coiled into a spiral. Fig. 88, and the extremity, «, hooks into a cup of mercury, while the other end dips into a second cup, the coil will be free to move in any horizontal direction. If now a current be transmitted through the coil, it arranges itself north and south^ just like the needle, and it will be at- tracted and repelled by another simi- lar coil in the same manner as two magnets. Hence Ampeee assumes that magnetic polarity is caused by electric influence,perpetually circulating round the particles of which the magnet is composed. Polarity of the Current. 225. Induced Currents.— If two conductors are placed near and parallel to each other, a current sent through one induces an op- posite current in the second. At the moment the circuit is form- ed and the primary current passes, a secondary current is produced in the opposite direction in the second wire. Electro-Magnet. sw jjmm ^s^^^i:^^ needle ? "Wliat is the galvanometer ? 223. -"What do Figures 86 and 87 repreaent ? 22^. How do electric currents affect each other ? Explain Fig. 88, What does 5 98 CHEMICAL PHYSICS. 226. Electro-magnetic Telegraph. — Tliia remarkable contri- vance consists of three parts : a battery for supplying the motive power, an insulated metallic line betu-ecn the points to be con- nected, and an apparatus for signalling, or registering messages. Two wires were at first thought necessary to complete the circuit, but it was early found that the earth might be made to replace one wire if the other was connected with the ground at both ends. The electrical impulse which traverses the wire circulates round a bar of soft iron, magnetizing and demagnetizing it as often as the connection with the battery is made and broken, and thus motion is communicated to the recording machine. 227. We must not forget that there is nothing like a current through the telegraph wires. We may be aided to understand ■what takes place by imagining a small tube, connecting two places, closely filled Avith a row of peas. As a pea is pushed in at one end, another falls out at the opposite end, although it is evident that nothing but motion has passed. But motion may pass although each pea keeps its position, if we suppose them all linked together by attractions upon their different sides. If the first pea were turned upon its centre^ it would turn in like manner the whole series. The peas may represent the atoms of the telegraphic circuit, and their motions the polarization of particles by which the effect is communicated. The wire of the circuit communicates its polarity to the bar of soft iron around which it is wound ; this be- comes magnetically polarized; and attracts the marking lever of the recording machine. § YII. Thenno- Electricity. 228. The Thermo-electric Pile.— As electricity produces heat, so heat in turn produces electricity. Thermn-eiectric A B, Fig, 89, is a bar of antimony, and B C a bar of bismuth soldered together at one extremity, and connected by the wire D at the other. When the place of junction is warmed an electric current is produced, which moves Amperb aseume? 225. Explain what is meant by induced currents. 226. Of ■what parts does Ibe eloctro-m.ngnctic telegraph coneiBt ? How is motion obtained? 227. Give the illustration of the peas. 228, Describe the thermo-electric pair, THERMO-ELECTEICITY. 99 Fig. 90. Fig. 91. in the direction of the arrows. If the junction B is chilled, the current moves in the opposite direction. Such a combination forms a thermo-electric pair. The eifect is increased if several of these are united, forming what is known as the thermo-electric pile. To secure a compact arrangement, thej are soldered together as in Fig. 90, and then combined as in Fig. 91, A representing one of the faces of the pile. "When both faces are equally heated, there is no current. If the face, A, is warmed, there is a current in one direction due to the a T difference of temperatures between the two faces. If the opposite face is warmed; or, what is the same thiug, if the face, A, is cooled, there is a reverse current. 229. In Fig. 92, A B represents the thermo-electric pile as Fig. 92. G Arrangement of the Bars. Tliermo-electric Pile as mounted for a mounted for lecture-room use. A shows one of the faces ; w w are wires connecting it with the galvanometer. The needle m n Fig. 89. Explain the conBtruction and action of the thermo-electric pile. "What does Fig. 90 represent? 229. Describe the pile as mounted for lecture-room 100 CHEMICAL PHTSICS. is suspended by a fibre S S of unspun silk, and protected from currents of air by the glass shade G. To one end of the needle is fixed a piece of red paper, and to the other a piece of blue. If the face of the pile is merely breathed upon, the warmth swings the needle round to 90°, or at right angles to the cur- rent, — the pieces of paper making the movement visible tlirough- out the room. This important instrument was invented by Nobili, and applied with remarkable success to researches in heat by Mel- LONi. It detects heat radiation from sources much lower than the human body, and announces the heat emitted from the bodies of insects. How wonderful, that the minutest quantity of heat we can detect, only appears after it has been first converted into electricity, then into magnetism, and then into mechanical motion ! 230. As the earth constantly turns upon its axis, the sun heats its mineral constituents unequally, which must give rise to east and west electrical currents, and, as the magnet tends to place itself across them, we see the reason for the direction of the needle. The earth's magnetism appears thus caused by the action of the sun. 231. Magneto-Electricity. — As electricity pro- duces magnetism, so magnetism may produce elec- tricity. If a bar of soft iron be introduced into a coil of wire, and a magnet be made to approach the bar, it is magnetized by induction, and at the same time a momentary current is produced in the surrounding wire. This is more simply shown by winding the armature of a horse-shoe magnet, Fig. 93, with a pjece of copper wire, one end of which is flattened and the other sharpened. When- ever the armature is removed or replaced, a spark is produced at C, indicating a current through the wire. 232. Induction Coils. — If one or two hundred feet of stout copper wire are wound into a close coil, and then twenty or thirty thousand feet of much finer wire (both well cov- ered with silk) be wound into a secondary coil around the first, a current sent through the inner wire and rapidly interrupted, in- duces very powerful currents in the outer coil, which give rise to Spark from Mag net. use. What is said of it? 230. How is the direction of the needle explained? To what is tlio earth's magnetism due? 231. How may electricity be pro- duced by magnetism? 232. What is the principle of RunMKORFF's coil? What I ANIMAL ELECTEICITY. 101 a stream of brilliant sparks. This is the principle of Euhmkoeff's coil^ one of the most energetic electrical machines yet devised, pro- ducing electricity in large quantity and of extraordinary intensity. 233. Tha Stratified Discharge. — If electricity be sent through an ordinary vacuum, the spark is changed to a diffused auroral glow. But vfhen the vacuum becomes more perfect, the light appears stratified^ or broken up into numerous rings or plates. Gassiot sealed platinum wire in glass tubes, and, by using an at- mosphere of carbonic acid which was first exhausted by the air pump, and the residue gradually absorbed by caustic potash, he produced a very perfect vacuum. "When the rarefaction is carried a step further than can be done with the air pump, on discharging ig. . a Ruhmkorff coil through it, nar- •+! .,„... i m "^L row bands transverse to the line of ^i||pilllllllllllllliilllB discharge are seen, as in Fig. 94. Increasing rarefaction widens the bands, and gives them a conical shape, as in Fig. 95, and, as the vacuum becomes more perfect, a series of luminous cylinders of an inch or more in depth appear, di- vided by narrow dark lines, Fig. 96, till at last, when the vacuum becomes perfect, discharge light and conduction cease. It seems thus proved that a vacuum, in- stead of being a good conductor, as was formerly supposed, is a perfect non-conductor, and that the presence of matter is indis- pensable to the manifestation of electrical force. Fig. 95. .? Fig. 96. Stratified Discharge. § YIII. Animal Electricity. 234. It was known to the ancients that certain fishes have a peculiar power of benumbing animals. It has been found that they possess electrical organs or batteries by which they can give powerful shocks, which produce all the effects of ordinary elec- tricity. Fig, 97 represents the torpedo with its electrical organs, is said of it ? 233. How does electricity appear in an ordinary vacuum ? When the vacuum is more perfect ? In the most perfect ? What does this prove I 102 CHEMICAL PHYSICS. FiQ, 97. Electrical Oreans of the Torpedo. riG> 98. a a, laid bare. They are situated on eacli side of the head, and are composed of five or six sided prisms, ex- tending vertically from the lower to the upper side of the fish. They are divided in horizontal partitions, so that the whole resembles a mass of honeycomb, the cells being filled with a dense fluid consisting of water, albumen, and a small portion of comm6n salt. These organs form a living lattery^ and are the source of electrical force, just as the muscles are of mechan- ical force. A dense mass of nerves links them with the brain, which has control of the discharges the same as of muscular movement. The seat of control is the electrical lobe ; if this be uninjured the animal may be skinned, its heart cut out, and the other portions of the brain extirpated, without loss of the faculty. 235. Galvani's well-known experiment with the frog was the starting-point of modern research in this branch of electricity. The legs of the frog are detached from the body, the skin removed, and the lumbar nerves exposed. They are then laid upon a glass plate with a small piece of zinc Z, Fig. 99, placed under the nerve, while the feet rest on a thin slip of silver. They are dead and powerless, but if now a wire, "W, be made to touch the pieces of metal, so as to form a connection between muscle and nerve, the legs instantly contract and kick away the silver. 236. Human Electricity. — As it is now admitted that no chemical change can occur with- out electrical excitement, and as the human body is a mass of rap- idly changing chemical materials, it must be a theatre of extensive electrical movements, though to Brain of Torpedo. C, Cerebrnm. O, Optic Lobe. R, Cerebellum. E, Elect. Lobe. Experiment with Legs of Frog. 234. Describe the electrict\l apparatus of the torpedo? What is its relation to the brain ? 235. "NVh.it is said of Galvani's experiment ? How is it performed f 236. What difficult problem is stated to be now demonstrated ? What has been proved by Matteccci ? By Dcbois-IIeymond t What was his experiment with the frogs f THERMAL EXPAISTSION-. 103 demonstrate this has been one of the most delicate and difficult prob- lems of science. The blood is an alkaline liquid, while the juice of flesh is acid, and the two liquids are only separated by the thin walls of the vessels. By the action of these fluids there must be in every mass of muscle myriads of electric currents. Matteucci has proved that currents of electricity are always circulating in the frames of all animals, and that a positive current is continually passing from the interior to the exterior of a muscle. The smallest shreds of muscular tissue have been proved by Dfbois-Reymond to manifest currents, the longi- tudinal section being always positive to the transverse sec- tion. By arranging a series of half thighs of frogs, alternately connecting the exterior and in- ^j^^^,^ ^^^^^^^ terior surfaces, Fig. 100, he ob- tained a current that decomposed iodide of potassium, deflected a magnetic needle 90°, and caused the gold leaves of an electroscope to diverge. CHAPTEE lY. HEAT. § I. Thermal Expansion — Thermometers. 237. This well-known force has an almost omnipotent con- trol over the states of matter ; it is an all-determining agency in nature, and is so essential to the numerous processes of the labor- atory that the chemist has been called the ' Philosopher by Fire.' The general science of heat is termed Thermotics^ from the Greek thermos^ hot, which gives us also the words thermal, tJmrmow.eter, ttc. 238. Expansion of Solids.— The general effect of heat upon matter is to expand it. The copper ball. Fig. 9, p. 36, when heated, enlarges and rests upon the ring ; when cooled, it shrinks and falls 237. What has the chemist been called, and why ? What is therraotics, and wlience Is the name derived ? 238. What is the general effect of heat upon matter ? What 104 CHEiriCAL PHTSICS. througli it. The copper, and all bodies of uniform atomic condi- tion, expand equally in all directions, while other substances, as crystals and wood, in which the atoms are differently arranged in different directions, expand unequally (267). "With a given amount of heat force, the same substance always •^^": '^^^' expands to the same degree ; but the same quantity of heat causes different substances to expand unequally. This may be shown by riveting together thin slips of different metals, for instance Expacsiou of Compound Bars. , , . . , , . t , i -n. brass and iron, mto a straight bar, Fig. 101. When dipped into hot water it is warmed, and the brass, expanding most, becomes longest ; the bar curves, the brass form- ing the convex side. If placed in ice water, the brass contracts most, and the bar curves in the opposite direction. Heat, which drives atoms asunder, is thus the antagonist force to cohesion : and a quantity of heat applied at a high temperature, produces more expansion than the same am-ount at a low one ; — the cohe- sion in the first case being partially overcome. 239. The expansion of solids, though small, takes place with tremendous force. The Bunker Hill monument has a slight daily motion as the sun expands its sides. The ponderous iron tubes of the Britannia bridge lengthen and shorten, and writhe and twist like a huge serpent, under the varying influence of solar heat. One of the tubes, 400 feet long, is depressed in the centre but a quarter of an inch by the heaviest train of cars, while the sun, expanding its upper side from morning to noon, elevates it in the centre two inches and a half! "Wheel tires and iron hoops are made smaller than the frames they are to surround, and put on while red hot, their contraction on being suddenly cooled binding together the parts with great firmness. Iron, when joined with less expansible materials, as bars laid in masonry, often works serious injury by its expansions and contractions. 240. Expansion of Liquids. — If the heat be sufficiently in- creased it overcomes cohesion, and the solid becomes a liquid. Liquids thus produced by heat, are also expanded by it, and to i» bodies expand equally in all directione, and what unequally? What does Fig. 101 roprcHcnt? What conclusions follow from this experiment ? 239. Wliat illustrations nrc given of the expauHivc force of heat ? Why are wheel tires made smaller than tho wheels thoy arc to surround ? How do iron bars work injury in masonry ? 240. What THERMAL EXPANSION. 105 rmicli greater degree than solids. While iron increases from freezing to boiling but ^fa, water expands 2V, and alcohol }, Hence the seasons materially aiFect the bulk of spiritous liquors * they measure five per cent, more in summer than in winter. By heating different liquids successively in a long-necked flask, Fig. 8, p. 86, their relative expansibilities- are shown. 241. Expansion of Gases.— But liquids cannot be indefinitely expanded ; a sufiicient repulsion of their atoms changes them into gases. As a general law gases expand much more than liquids, although certain liquids, as sulphurous and carbonic acids, are amongst the most expansible bodies known. As there are no varying cohesions to overcome, gases expand very nearly alike, increasing from the freezing to the boiling of water more than one third of their bulk. 242. Measurement of Heat.— As the effect of heat is expan- sion, the measurement of expansion becomes the measurement of the force. The common instruments for measuring heat are called thermometers. They measure not quantity of heat, but tempera- ture. Heat is the force producing the effect ; and temperature the intensity with which it acts. The thermometer gives the same report of a gill of water as of a gallon ; their temperatures are the same, though one contains a far larger amount of heat than the other. Liquids are better adapted for thermometers than either solids or gases ; as in solids the expansion is too slight to be easily perceptible, and gases are too sensitive to changes of atmospheric pressure to fit them for this purpose. 243. Mercurial Thermometer. — To make this instrument, a fine glass tube with a bulb upon the end is partly filled with mercury. The air is expelled from the rest of the tube by heating it till the mercury rises by expansion to the top, and at that moment the glass is hermetically sealed by melting the end of it with a blow- pipe. As it cools, the mercury falls in the tube, leaving a vacuum above. 244. Mercury has several important advantages as a thermo- metric fluid. It is readily obtained pure, and does not adhere to the tube ; it is sensitive to heat, expands with greater regularity is said of the expansion of liquids ? 241. How do liquids rank in expansibility ? Examples. Why do gases expand alike? 242. How is heat measured? "What are thermometers? "What do thermometers indicate? How are liquids beet adapted for thermometers? 243. How is the mercurial thermometer made? 5* 106 CHEMICAL PHYSICS. than most liquids, and has a range of 700 degrees between freez- ing and boiling. Temperatures below the freezing point of mer- cury are determined bj thermometers filled with alcohol tinged with some coloring matter, to make it visible. 245. The sealed tube is attached to a brass plate engraved with the thermometric scale, Fig. 102. It is then dipped into ice water, and a mark made op posite the top of the column of mercurv, called the freezing point. It is now introduced into boiling water, and the height to which the column rises is marked as the loiling point. These are natural standard points which serve as a basis for the division of the scale. In the Centigrade ther- moraeter the freezing point is called zero, and the ^Hijpir interval between that and the boiling point is ^ ~ marked off into 100 equal spaces called degrees. In Reaoiep/s scale the same space is divided into 80 degrees, and in both cases degrees below zero are distinguished from those above bj prefixing the minus signs (-). 246. The scale named after its inventor, Fahben- nEiT, and which has unfortunatelv come into general use in England and this country, is not so simple. He divided the space between freezing and boiling into 180 degrees ; but, instead of starting at the Common Th'.T- freezing point, he thought he would find the lowest possible cold, and make that zero. So with snow and ice he got the mercury down 32° below the freezing point, and commenced counting there. On this scale, therefore, freez- ing occurs at 32^, and boiling at 212°. The several scales are distinguished by their initial letters F., C, and R. The Centi- grade, affording decimal subdivisions, is the most simple and rational, and is gradually coming into use for scientific purposes. But as Faheexiieit's thermometer is generally employed and most familiar, it will be the one referred to in this book when no other is mentioned. 247. The Differential Thermometer consists of two thin glass 244. What advanta^os has mercury as a thermoraotric fiuid ? 245. ITow are they marked? "WTiat is the Centigrade pcale? Reacmer's? 246. Describe Fahrbxh bit's scale?. IIow did he get his zero? "WTial degrees arc used in this work! 247. Describe NATURE OF HEAT. 107 Differential Tlier- mometcr bulbs filled with air, and united bj a bent tube containing a col- ored liquid, Fig. 103. If heat be applied to Tia.im: one bulb, the air within it expands and presses (^) down the liquid, the degree of motion being shown bj the scale. This thermometer, as its name signifies, merely denotes the dif- ference in temperatures between the two bulbs, and has only been useful in scientific researches. 248. As mercury boils at 660°, temperatures above that degree are measured by the ex- pansion of solids. For Fig. 104. this purpose an instru- ment called the Pyrome- ter is employed. It con- sists of a bar of metal or clay. Fig. 104, one end of which is fixed, and the other joined to a lever which plays over a grad- uated scale, as the bar ex- pands or contracts. Pyrometar, V II. Nature of Heat. 249. Tiie Caloric Hypothesis. — Having noticed the general ef- fects of heat, we may now inquire into its nature. . The material hypothesis supposes it to be a kind of matter — a subtile fluid whose entrance into our bodies produces warmth, and its escape cold. This fluid — caloric^ is supposed to be stored up in the interstices of bodies, some holding more than others, according to their capaci- ties. It is assumed to have an attraction for matter and to com- bine with it, whilst its own particles are self-repulsive, and thus cause the atoms with which they unite to repel each other. This hypothesis, from its simplicity, has done service in times past, but such has been the recent and rapid growth of knowledge, that, instead of any longer guiding to truth, it only eclipses it. the differeutial thermometer? 248. Describe the pyrometer, 249, What is th« 108 CHEM2CAI. PHYSICS. 250. In judging of heat, we must not misinterpret its impres- Eions upon ourselves. If we plunge one hand in ice water and tlie other in Lot water, and then transfer bofh to water intermediatelj warm, it will seem hot to the one and cold to the oth^. Indeed, if we trusted our ordinaiy sensations, we ^ould helieTe m two opposite principles of heat and cold, a dockine which was long advocated nntil it was fonnd that these are merely lelafiTe, and tliat cold is but the absence of heat. Intense heat and intense cold produce the same sensadoBs; frozen mereory hBsteis the flesh like hot iron. Putting aside then our sensations, what k it that we know concerning the nature of heat ? 251. The Esseace of Heat is Motion. — TTith a few exceptions, which are perhaps no real exceptions (^So). the unirersal eflfect of heat upon all matter is to expand it. We say that bodies are heated and cooled, and that one warms another near iL Bat we strictly mean only that they expand and contract, and that a body in expanding contracts others, and in contracting expands th^n. Hence, divested of everything not belonging to it, we find the effect of heat to be simply a motion of erpatmon, in matter com- municable from body to body. Thns the e^ence of heat is irwtion. The motion of a m^ass implies the motion of its parts. K a body expands, it is becanse its atoms have receded &rthe^ from each other, that is, ha,ve mm>ed. Heat is therefore each a motion among the atoms of a body x& gires rise to expansion. This idea was clearly enunciated a hondred years ago by the jjhilosopher Locxe, who said, * Heat is a very brisk a^talion of the insensible parts of an object which produces in us that sensar tion from which we denominate the object hot, so that what in onr sensations is A^eaf, in the object is nothing but moUonJ 252. Universality of Motioii.— The later views of the forces compel the idea that the atoms of all matter are in a ^tate of ino^- sant movement As nothing aroand ns is at rest, the idea of the quiescence of atoms would seem to contradict the whole spirit and course of nature. The celestial bodies are in perpetual move- ment ; indeed each one has impre^ed upon it several motions. Our mat-enal byTX)thef ie of heat. ? How is it eetunated f 250. Hott may onr eeoataoos of hc^t mislead ne t Ho-w axe heat and eoid related ! 25L TTbal is tlw vnlvenal effect of heat ? When -we say that bodies are healed and coaled, -orhat do we «trjct]y mean t "Wliat is the esseDoe of heat ? What kind of motioa ? Give Locee's di f.- ii!t:o3 of heat. 252. What idea result* frota tbe later view of forr^- '' ^^ - s NATUKE OF HEAT. 109 ovm globe has a motion of rotation npon its axis, lasting a day — a motion of translation round the sun, continuing for a year. It has also one motion upon its axis accomplished in 19 years, and an- other which is only completed in 25,868 years ; it has also a fifth motion with the solar system through space, which may require millions of years for its completion. Thus the character of the solar system depends upon the motions of the planets, which we may look upon as its atoms. 253. It cannot be doubted that, at the other extreme of being among ultimate atoms, there is also an order of motions equally regular and systematic. Each atom, closely as it seems packed with its neighbors, is believed to be in a state of incessant vibra- tion, and all material bodies, however quiet and solid they appear, are supposed to be made up, nevertheless, of an infinity of these ' whirling parts ' which never touch each other and never rest. An atom may rotate upon its axis, oscillate, revolve through an orbit, or, like a planet, it may execute several of these motions at once. This idea has become the all-harmonizing principle of the forces. 254. As heat is a motion of atoms, intensity of the motion de- termines temperature. TVhen a body is heated, the vibration of its atoms is augmented ; the particles move through larger spaces ; are urged apart, and thus cause the body to expand in bulk. When the vibrations of the atoms of solids become sufficiently violent, they are loosened from the rigid grasp of cohesion, and, continuing to oscillate as before, they are now at liberty to slip or flow around and among each other. This is the liquid state, in which rigidity has disappeared, although a certain amount of lateral cohesion still remains (64). A further augmentation of heat increases the swing of vibration until the atoms are thrown quite beyond the sphere of cohesion, and fly asunder into the vaporous or gaseous state. ' The ideas of the best-informed philosophers are as yet uncertain regarding the exact nature of the motion of heat ; but the great point at present is to regard it as a motion of some Tcind, leaving its more precise character to be dealt with in future investigations.' probable concerning atoms ? "Utat is said of celestial motions ? 253. "What proba' bility does this create? What view is held concerning the motion of atoms 1 254. "What results from the intensity of atomic motion? "When a body is heated, ■what occurs within? "What results from the violent vibrations of the atoms of Bolids ? "What causes the change from the liquid to the vaporous state 1 "SVliat is 110 CHEMICAL PHYSICS. 255. The view just given is known as the dynamic hypothesis^ or the mechanical theory of heat. That branch of the science of therraotics which treats of the laws of heat as a motive power, is known as thermo-dynamics. A difficulty in acquiring the new view is, that the current language concerning heat implies the material hypothesis. It is so natural to regard heat as a tiling — to ascribe a substantive existence to that which is the subject of a name, that it will be necessary to guard against the misleading tendency of the ordinary terms. The pupil should strive to think of heat not as an abstract thing, but sunply as a contagious or communicable motion of atoms. It may be further observed that this hypothesis is far from being new. It has been maintained by the acutest scientific intellects, as those of Bacon, Boyle, Newton, Mongol- FiER, Seguin, Rumford, Davy, Leslie, and Young. But the late advances in the knowledge of force have brought it into a new prominence and caused its acceptance by the leading scientific minds of the age. {See note^ page 173.) / § III. Sources of Heat \ 256. The chief source of heat is the sun. As the stars are only remoter suns, we undoubtedly obtain from them a large amount of heat ; according to Pouillet, almost as much as from the sun itself. Combustion is a familiar source of heat which will be noticed here- after (579), and the vital heat of animals is due to the same cause (1257). Heat is also produced from the other forces — electricity, magnetism, and mechanical power. To consider the last-named source will aid us to clearer notions of the nature of heat and the true relations of the forces. 257. The Heat of Friction. — Nothing is more familiar than the fact that friction produces heat. "We warm our hands and ignite matches by rubbing them, whilst wood may be set on fire by the friction of one piece against another. The development of heat by friction may be strikingly shown by a simple mechanism. A hollow brass tube is mounted upright upon a table so as to revolve rapidly by turning a wheel. It is closed at the bottom, nearly filled with cold water, and tightly corked. The tube is then clasp- tho importnnt point in this connection ? 255. What is the view just pivcn called ? Wliat is thermo-dynamics? What difficulty is encountered here? AVhat should the student strive to do? Is this hypothesis new? Who liave formerly maintained It I How is it now regarded? 25C. What are the eourccs of heat? 257. What SOURCES OF HEAT. Ill ed in a groove formed by two pieces of oak, T, Fig. 105, joined by Fig 105. Machine for converting Mechanical Force into Heat. a hinge. Upon rapidly turning the wheel, the water is boiled, steam formed, and the cork exploded 20 feet into the air in two minutes and a half. Iron plates ground against each other by wa- ter have yielded a large and constant supply of heat for warming the air of a factory in winter. Heat is also produced by the fric- tion of fluids. Rennie inclosed 10 lbs. of water in a box, and, revolving it at the rate of 232 revokitions per minute, in a short time raised it to the boiHng point. Hence water running in sluices and the sea after long storms are sensibly warmed. 258. Compression al- so produces heat. A piece of cold wood or a cold leaden bullet squeezed forcibly in a hydraulic press are made warm^ Percussion is another source of heat. A cold bullet struck upon an anvil by a sledge ham- mer is heated. A lead- en ball lifted several feet and dropped repeat- edly, is warmed; and a cannon ball, when strik- ing an iron target or ship's side, is so intense- FiG. 106. Mercury 'vvarmed by pouring it. examples are given of the heat of friction ? Describe the experiment. 258. Give 112 CHEMICAL PHYSICS. ly heated as to produce a flash of light. The arrest of a liquid in motion is also a source of heat. If two glasses are swathed thickly round with listing, so that the warmth of the hand cannot affect them, and then cold mercury is poured from one to the other several times, Fig. 106, its temperature will be raised. 259. "What now is the source of heat in these cases ? The ca- loric hypothesis utterly fails to explain it. That theory maintains that the heat of friction exists in a latent state in the bodies rubbed : that different substances have different opacities for hid- ing and holding heat, and that friction diminishes this capacity, and thus brings it out, as squeezing brings the water out of a sponge. But this is grossly erroneous, as was proved by Davy. He rub- bed two pieces of ice together in a vacuum, and melted them by pure friction; but the water produced contained a far greater amount of heat than the ice, and the greater quantity could not by possibility be derived from the less. Besides, the amount of heat that various bodies naturally contain, as we shall soon see, is perfectly definite ; while, on the contrary, the heat produced by friction u inexhaustible^ and is utterly independent of the nature of the substance used. This was demonstrated by Count Rum- ford more than sixty years ago. 260. True Source of the Heat — The heat of friction depends not upon the properties of the bodies acting, but upon t?ie force spent in producing it. The great principle has been established that force like matter is indestructible. It may be changed from form to form, but can neither be created nor annihilated — the total amount in the universe remains forever the same. Hence when a moving body is stopped, its force is not destroyed, but sim- ply takes another form. TVhen the sludge hammer strikes the leaden buUet and comes to rest, the mechanical force is not anni- hilated, but is simply converted into heat, and if all the heat pro- duced could be collected, it would be exactly sufficient when re- converted into mechanical force to raise the hammer again to tho height from which it fell. So when two bodies are rubbed to- gether, their surface particles are brought into collision, mecha- nical force is destroyed, and heat ai)pear3 — the heat of friction. examples of compression and percussion. 259. How is this explained by the old hypothesis ? What ia the l>earing of Da^-y's experiment ? Why cannot the heal of friction proceed from the body itself ? 260. Upon what docs the heat of friction de- pend? What great principle ha« been arrived at respecting forces? WhenamoTing SOUECES OP HEAT. 113 261. We place a wheel upon a rough axle and set it to wMrl- iiag ; after a few turns it comes to rest, and the axle is found hot. The mechanical impulse has heen converted by friction into heat. Wq now lubricate the axle with some substance that reduces fric- tion, and set it to revolving again with the same impulse. It now turns a much longer time, and the temperature of the axle is but slightly raised. Yet precisely the same amount of heat is gene- rated in this as in the other case, though the friction is now against the air and the heat escapes without detection. 262. Take the familiar case of a railway train. Heat is gene- rated in the locomotive by combustion. A portion of it is wasted, and the remainder is spent in the expansion of water into steam, which through the machinery produces motion of the train. The object is to convert all the heat possible into mechanical motion, and so every rubbing surface is oiled, because each point of fric- tion is so much leakage and loss of motion by reconverting it into heat. But when the train approaches a station where it is desired to stop, what is to be done ? The moving force cannot be anni- hilated ; it must be transformed ; so the brakes are applied, the train slackens, smoke and sparks are produced, and the entire motion of the train is thus converted back again into heat. The rigorous relation of equivalency between heat and mechanical mo- tion will be considered hereafter (411). "We only call attention here to the fact that the checking and arrest of mechanical motion, however slight it may be, whether of air, water, or solid bodies, is a definite and universal source of heat ; and again that heat, whenever it disappears, invariably produces some form of motion or wotTc. 263. N"ow as heat produces mechanical motion, and mechanical motion heat, they must clearly have some common quality. While heat was regarded as material, it was impossible to see anything in common between them, for how could the fall of a body, for instance, be converted into imponderable matter ? On the con- body is stopped, what ■becomes of its force ? How is the case of the sledge hammer explained ? "When two bodies are rubbed together, what takes place ? 261. Explain the experiment with the wheel and axle. What becomes of the heat in the second case? 262. "What becomes of the heat in a moving locomotive? What is the effect of the rubbing surfaces ? What occurs when the train is stopped? What is the universal relation of mechanical force to heat ? 263. How have they a common quality? What is the difficulty here in the material view ? What does the me- chanical theory affirm ? When a moving mass is stopped by friction, what takes 114 CHEMICAL PHYSICS. trary, the dynamical theory affirms that as mechanical movement and heat are both modes of motion, they must be mutually and easily convertible. "When a moving mass is checked or stopped, its force is not annihilated, but the gross palpable motion is in- finitely subdivided and communicated to the atoms of the body, producing increased vibrations which appear as heat. And so ■when heat produces work, as in the steam engine, a certain amount of it is destroyed, the motion of the atoms of steam being converted into mechanical motion of the piston and machinery. § lY. Conduction and Convection of Heat. 264. How it is Conveyed. — The closely packed particles of bodies cannot vibrate without communicating their motion from one to another. Each atom takes up the motion of its neighbors and imparts it to others, and thus the effect is gradually propa- gated through bodies ; this is called conduction of heat. Bodies possess this power in very different degrees. If the particles vi- brate freely, they communicate their motion rapidly, and are said to be good conductors ; but if they are so trammelled that they cannot pass the motion freely, they are had conductors. j,j^ jQ^ 265. If several marbles are stuck by wax to a cop- per rod. Fig. 107, and heat be applied to one end, it gradually passes along the rod, the wax is melted, and the marbles drop off suc- sively. Generally the more dense a body is, the better it conducts ; therefore, solids are better conductors than liquids, and liquids than gases. As a class, metals are the best conductors, but they differ much among themselves in this respect. The imperfect conduction of liquids may be shown by filling a glass tube with water, inclining it over a lamp and applying the flame at the upper end, Non-conduction of Liquids. Fig. 108. The watcr will boil at the sur- TT ri Conduction of llcat. Fig. 108. place? 264. In -what way does heat movo through bodies? 206. Describe tho CONDUCTION AND CONVECTION OF HEAT. 115 face, while at the bottom there may still he ice for a considerable time. Dry air is one of the poorest conductors. Loose materials, as wool, cotton, sawdust, are bad conductors, chiefly owing to the air inclosed in their inner spaces. 266. Connection of Heat and Electricity. — The following table shows the relative conducting properties of several metals, the power declining as the numbers decrease : Conductibility. Names of Substances. For Heat. For Electricity. Silver 100 100 Copper 74 73 Gold 53 59 Iron 12 13 Platinum 8 10 German silver 6 6 Bismuth. 2 2 The conducting power of the metals for electricity is also given, and a remarkable correspondence is seen in the numbers. Those properties which make a metal a good conductor of heat render it also a good conductor of electricity, and those which obstruct the one obstruct also the other. The forces must also be closely con- nected in their modes of action. 267. Influence of Atomic Arrangement.— If the Fig. 109. atoms are disposed alike in all directions, conduc- /^^^^\ tion is uniform, but, if there is a polar arrangement y^^^^^v of atoms, conduction becomes unequal. This is ^^^^^^S^ seen in crystals. A slice of quartz cut across its ^^^^gy axis. Fig. 109, was perforated with a small hole E^uai Conduc- and covered with a layer of white wax. A wire ''""* was then inserted through the orifice and heated by an electric current. The wax melted in an exact circle, which showed equal conduction in all directions. A ^^^ i^o slice cut parallel with the axis, as in Fig. 110, treated in the ^mmm^^mmmmm^^) same way, gave an oblong out- line of the melted wax, showing ^<:^%^ym^/ -^y ' v;#^ that the heat travels with more facility along the crystalline axis ,1 ., rrn , -1 -. •/ Unequal Conduction. than across it. The metal bis- experiment with the marbles. How is the bad conduction of liquids shown ? 206. How does silver difier from bismuth in conducting power? What relation between the conduction of heat and electricity ? 267. "What condition of atoms 116 CHEMICAL PHYSICS. muth conducts both heat and electricity better along the planes of cleavage than across them. The same thing has been found in re- ference to wood ; it transmits heat better along the course of the fibres than across them. This principle economizes the warmth which the tree derives from the soil, by preventing its lateral es-' cape, and at the same time protects the tree from the injurious ef- fects of sudden changes of external temperature. This effect is also heightened by the non-conducting bark. 268. Conduction Influences Sensation. — The carpet feels warm- er to the naked feet than oil cloth, because the latter conducts away the heat faster from the skin, although both are at the same temperature. If the hand be placed upon silver at 120°, it will be burned, owing to the rapidity with which the motion of heat leaves the metal and enters the flesh. Water will not scald the hand if it be held quietly in it till it reaches 150°, while the contact of air at 250° or 300° may be endured. The principle of conduction ia of great importance, not only in nature, but in its application to the arts and requirements of daUy life. Nature protects the earth and crops from the excessive cold of winter by a layer of non- conducting snow; the birds she protects by feathery plumage, and quadrupeds by hair, wool, and fur. For winter clothing we select non-conducting textures ; but in summer, good conductors, as linen and cotton, to aid the escape of superfluous heat. 269. Convection. — Although liquids and gases are poor conductors, yet from the mo- bility of their particles they may be rapidly heated by a process of circulation or con- xection. If heat be applied to the bottom of a vessel containing water, the lower por- tion of the liquid is warmed, expands, becomes lighter, and ascends, its place being taken by the colder liquid at the sides — thus forming a set of currents which diffuse the heat through the whole mass. If a few particles of litmus Circulation of Heat, j^q dropped into a flask of boiling water, the central current, made visible by tiie blue tint it has acquired, may be seen rising to the surface of the liquid, where it bends over in influences conduction? What is shown by the experiments with quartz? What of wood ? How docs this aflcct trees ? 268. How does conduction influence sensa- tion? How is tlie principle employed in nature? In art? 269. How do liquids YlCr. 111. LATENT HEAT— INTERIOR WORK. Ill every direction, Fig. Ill, and travels down the side of the vessel. In this way, water is circulated through systems of pipes to warm houses. 270. Gases are heated in the same manner. The warm air in contact with a stove or other heated body becomes lighter, and ascends, while the colder and heavier air rushes in to supply its place. This, becoming heated, also ascends, and thus a system of currents is established which diffuses warmth through the apart- ment. This principle is applied in warming houses with hot air, and also in arrangements for artificial ventilation. In the ocean and the atmosphere the same exchanges are incessantly going on, in the former giving rise to vast currents which equalize its tem- perature,' and on land producing breezes, storms, trade winds, &c. § Y. Latent Heat — Interior Work, 271. Heat, by overcoming the cohesion of solids, detaches their atoms and changes them into liquids. That degree of heat which is required to liquefy a substance is called its melting point. From hundreds of degrees below zero up to thousands above, the various substances of nature melt at different temperatures, show- ing that each requires its particular amount of heat force to throw it into the liquid state. 272. Latent Heat. — Whenever a solid is changed to a liquid, a certain amount of thermal force disappears in the process. If we apply heat to a lump of ice at 32% it gradually melts, but the wa- ter produced is at the same temperature as the ice. What then has become of the heat ? In the language of the old hypothesis, the disappearing caloric is stored up in the water, where it stUl exists in a state of concealment as ' latent ' heat. But there is no evidence that it continues to exist as heat. According to the dyna- mic view, the heat does worh by overcoming the cohesion of the particles, and is consunied in forcing them into new relations. This theory maintains that force cannot disappear without pro- ducing some effect ; it teaches that what is called ' latent ' heat is simply that amount of thermal force which is consumed in pro- convey heat? Describe the experiment. 270. How are gases heated? 271. Ex- plain melting points. 272. According to the old view, what becomes of the heat when ice is melted ? What evidence is there that it still exists as heat? What 13 118 CHEMICAL PHYSICS. Fig. 112. ducing effects different from Jieat^ as fusion, evaporation, chemical changes, &c. 273. If we expose equal weights of different substances to the same source of heat, they do not all receive it with equal readiness or in equal amounts in the same length of time ; some will become much warmer than others. If a cake of wax, C D, Fig. 112, be placed upon the ring of a retort stand, and several metallic balls, having been immersed in a bath of hot oil, be placed upon it, they will sink through the waxiat differ- ent rates. The iron gets through first, and the copper follows. The tin baU just peers through the lower surface, and is stopped, while the lead and bismuth scarcely sink to half the depth of the Hot Metallic Balls. ^^^^^ Although the balls are all at the same temperature, yet they hold very unequal amounts of heat. "Water requires 30 times as much heat as mercury to raise an equal weight of it through the same number of degrees. Hence bodies are said to have different capacities for heat, and, as each substance seems to require a particular quantity for itself, that quantity is called its specljic heat. • 274. Calorimetry is the art of measuring the specific heat of bodies. This may be done in various ways : one is by observing the quantity of ice which equal weights of different substances melt in falling through equal degrees of temperature. The specific heat of water is found to be the highest of any known substance. Water being taken as 1, sulphur is 0.20, air 0.25, iron 0.11, copper 0.09, and lead, mercury, and gold, 0.03. 275. Twofold Action of Heat. — Thus when heat falls upon a body, a portion of it is manifested by the rising temperature, and is spent in producing increased vibrations of the atoms. But another portion is spent in forcing the particles of bodies into new posi- the dynamic view? nowdoeBitrcgardlatenthe.it? 273. Describe the experiment of the cake of wax. What does this prove! What is capacity for heat! Specific heat 7 274. What ia calorimetry ? 275. When heat falls upon a boiy, what hecomo* LATENT HEAT — ESTTEEIOK WOKK. 119 tions, and as different substances have different atomic constitu- tions, different amounts of heat are consumed in acting upon them — these amounts are their specific heats. 276. It has been weU suggested that the atoms drawn together by cohesion resemble a weight pressed to the earth by gravity. With a cord and pulley we can overcome the gravity and raise the weight ; and we can also cause it to oscillate as it rises. One portion of the force is expended in raising it from the ground, and anotlier in causing its vibrations. So with the atoms : at the same time that their vibrations are increased they are also forced into new arrangements. Heat consumed in this latter way is said to perform interior worTc. As the body cools, the constrained atoms gradually resume their former places, and the precise amount of heat is given out again. 277. Potential and Actual Energy. — TVhen a weight is drawn up by a cord, it may be perfectly at rest, but the new position makes it a store of force, which in its fall becomes maving force. "While suspended it was said to be in a state of possible ov potential energy; in falling, this is converted into actual energy. When it has fallen part of the distance, it is evident that a certain amount of potential energy is converted into actual energy; and, as it strikes the earth, all its potential energy is converted into actual energy, 'As potential energy disappears, actual energy comes into play; tJiroughout tTie universe, the sum of these two energies is constant.'' 278. This principle applies equally to atoms ; the weight and the earth may represent two mutually attracted particles. The atoms of wood and coal are in the raised condition oi potential energy ; oxygen may represent the earth ; they rush together in the fur- nace, and their potential energy is converted into the actual energy of heat. This again is spent in raising the atoms of water to the potential energy of steam. Again, the atoms of steam fall, and their potential energy is converted into the actual energy of the moving engine. 279. Tremendous Energy of Atomic Movements. — As our or- of it? 276. "What do atoms attracted together resemble? How are the twofold motions illustrated ? What is interior work ? 277. How does a weight suspended differ from one upon the ground? What is potential energy? Actual energy? Their relation ? 278. What is the condition of the atoms of wood and coal ? How do they produce the actual energy of heat ? What becomes of the heat ? 279. How are we too apt to regard interior work ? What is the most impressive lesson of 120 CHEMICAL PHYSICS. dinarv conceptions of force result from the large effects that strike the senses, we very naturally conclude that the interior work per- formed by heat among insensible atoms is but a trifling affair; but this is a grave mistake. The most impressive lesson of modem science is, that the material objects around us which appear so pas- sive are, nevertheless, filled with the most teemexdots ACTrmnEs. A pound of iron upon being heated from freezing to boiling expands -gljf of its length. The atoms are but slightly shifted, yet the heat necessary to move them would raise 8 tons one foot high ; or, in other words, the heat exerts a force upon the iron 16,000 times greater than that of gravity. 280. In melting 9 lbs. of ice, heat changes the position of the atoms, and confers upon them the potential energy of water. Ad- ditional heat drives the atoms farther asunder, and confers upon them the higher potential energy of steam. Still further heat (or an equivalent force) decomposes the steam, forming 1 lb. of hydrogen gas and 8 lbs. of oxygen gas, with a still higher state of potential energy. Xow, in returning to their former conditions, they give out an actual energy exactly equal to their potential energy. The clashing force of the atoms, as they revert to the successive states, has been represented by the fall of a weight down three great pre- cipices. The first fall — the collision of the two gases — is equal to the plunge of a ton weight down a precipice 22,320 feet high ; the second fall — the condensation of the steam — is equal to the descent of a ton down a precipice 2.900 feet high : and the third, the freezing of the water, is equal to the faU of a ton weight down a precipice 433 feet high. 281. Prof. TirsTJALL remarks, 'I have seen the wUd stone ava- lanches of the Alps, which smoke and thunder down the declivities with a vehemence almost sufficient to stun the observer. I have also seen snowflakes descending so softly as not to hurt the fra- gile spangles of which they were composed ; yet to produce from aqueous vapor a quantity of that tender material which a child could carry, demands an exertion of energy competent to gather up the shattered blocks of the largest stone avalanche I have ever seen, and pitch them to twice the height from which they fell.' modem pcience ? What are the comparative effects of heat and gravity upon a pound of iron? 280. What changes does heat -work in nine ponnda of water? What are the eteps of potential energy -which the atoms ascend ? To what ia their actual energy equal ? 28L What striking illostration doea Prof. Tvsdall giTC of the LIQUEFACTION FREEZING EBULLITION. 121 § YI. Liquefaction — Freezing — Ebullition. 282. The amount of force consumed in producing liquefaction is readily ascertained. If we take an ounce of ice at 32°, and one of water at 174°, and put them together, when the ice is melted, we shall have two ounces of water at 82°. The ounce of hot water has therefore parted with 142° of its heat in melthig the ice, which amount is the ' latent heat ' of the resulting water. Those who have attempted to melt snow for domestic purposes know by the delay in the result the great loss of heat involved. 283. "We here note the beneficial influence of thermal laws in the world's economy. If when ice is at 32°, the addition of one degree of heat would raise it to 33°, and thus throw it into the liquid form, all the accumulated snows of winter might be turned almost in an hour into floods of water, by which whole countries would be inundated. But so large an amount of heat is required to produce this change, that time must become an element of the process ; the snows are melted gradually in spring, and all evil consequences are prevented. 284. Freezing Mixtures. — Advantage is taken of the absorp- tion of heat in liquefaction to produce freezing mixtures, the most common example of which is salt and ice. In this case the salt melts the ice to unite with its water, which in turn dissolves the salt, so that both solids are changed to liquids. These changes require great heat, which is absorbed from surrounding bodies; the cold produced sinking the thermometer 40° below zero. Four ounces each of sal ammoniac and nitre finely powdered, and mixed with eight ounces of water, wiU reduce the temperature from 50° to 10°. A convenient method of freezing a little water is to drench powdered sulphate of soda (Glauber's salt) with muriatic acid ; it may sink the thermometer from 50° to zero. 285. Heat Liberated by Freezing.— If the change of a solid to a liquid consumes force, the reverse change must produce it ; the force therefore reappears as heat upon freezing. As the thawing of snow and ice in spring is delayed by the large amount of heat that is expended in the forming of water, so the freezing processes power of molecular forces? 282. How is the heat of liquefaction found ? 283. "What are the effects of this principle ? 284. How do snow and ice produce cold ? Men- tion another freezing mixture. 285. How is freezing a warming process ? Its 6 122 CHEMICAX PHYSICS. of autumn are delayed, "and the warm season prolonged, by the large quantities of heat that escape into the air, from the changing of water into ice. The same principle is made available to pre- vent the freezing of vegetables, fruits, &c., in cellars, during in- tensely cold weather. Vessels of water are introduced, which, in freezing, give out sufficient heat to raise the temperature of the room several degrees : freezing is thus made a means of warming. 285. Regelation. — Attention has lately been called to the fact that if pieces of moistened ice are brought into contact, they freeze together; lumps swimming in water — even warm water — may be made to cohere. This phenomenon is called regelation. The surface particles of the ice gain their liquid freedom, because they are confined only on one side, but when the surfaces are brought together, this liberty is instantly checked ; what was the surface becomes the centre, and cohesion takes place. Ice crushed to fragments can be refro^n in a few seconds under hydraulic pressure into a solid transparent mass, taking the shape of the mould in which it is pressed. It has long been a matter of inquiry by what property of ice those frozen rivers, the glaciers, slowly move along their tortuous beds, down the sides of mountains. It has been attributed to a viscous property by which the ice flows like thick tar; but regelation — the property of crushing and freezing under pressure — seems better adequate to explain the facts. 237. Ebullition. — Wlien water is gradually heated, minute bubbles are found at the bottom of the vessel, which rise a little way, arc crushed in, and disappear. These consist of vapor or steam, which is formed in the hottest part of the vessel, but as they rise through the colder water above, are cooled and con- densed. The singing sound of vessels upon the fire just before boiling is supposed to be caused by vibratory movements pro- duced in the liquid by the formation and collapse of these vapor bubbles. As the heating continues, these rise higher and higher until they reach the surface and escape into the air, producing that agitation of the liquid which is called boiling or ebullition. 238. The temperature at which this takes place is called the boiling point. Different liquids boil at difierent temperatures, but cfTect in nature? 286. "What is regelation? IIo-w are glacial motions explained ? 287. What ia the cause of boiling t 288. What is the boiling point ? What causes its LIQUEFACTION — FBEEZIXG — EBULLITION. 123 each liquid has a boiling point peculiar te itself. This varies with circumstances ; it is slightly influenced by the nature of the con- taining vessel. To glass and polished metallic surfaces liquids adhere with greater force than to rough surfaces ; and before vaporization can occur, this adhesion must be overcome. Sub- stances dissolved in a liquid also raise its boiling point on account of their adhesion. Under ordinary circumstances, water boils at 212°, but saturated with common salt its boiling point is 224". It has lately been shown that the amount of air dissolved in the water affects its boiling point, as it presses the watery particles asunder, and thus aids them to take on the gaseous state. Water purged of its air by long ebullition has been heated to 275° without boiling. "When it did boil the water was instantly changed into vapor with a loud explosion, the cohesion of its particles being suddenly overcome, like the snapping of a spring, by the repulsive power of the accumulated heat. The explosion of steamboat boilers, it is thought, may sometimes be owing to this cause. 289. But the most important circumstance that influences the boiling point is the pressure of the atmosphere. This resists the rising vapor, and as it fluctuates, the boiling point varies. At the level of the sea, atmospheric pressure is about 15 pounds upon every square inch of surface, and its variations make a difference of 4^ degrees in the boiling point. This pressure becomes lighter as we ascend into the atmosphere, and the temperature of the boiling point is corre- spondingly diminished, so that boiling water is less hot in high altitudes than in low ones. At the hospital of San Bernard on the Swiss Alps, which is 8,400 feet above the sea, water boils at 184°. 290. The Culinary Paradox affords a striking illustration of the boiling of water at a low tem- perature under diminished pressure. A flask half filled with boiling water is tightly corked and in- verted upon the ring of a filter stand, Fig. 113. The pressure of the confined steam will cause the boiling instantly to cease. If cold water be now poured upon the flask, the steam Culinary Paradox. variation ? "WTiat is the effect of removing air from -water ? Bure affect the boiling point ? How ascending a mountain \ 9. How does pres- 290. What is the 124 CHEMICAL PHYSICS. Fig. 114. Pulse Glass. Fio. 115. witliin will be condensed, the pressure relieved, and boiling will commence energetically. If again hot water be poured upon it, by renewing tlie steam and the pressure, the boiling ceases. The pulse glass is a tube connecting two bulbs, and half filled with ether, air being excluded. On grasping one of the bulbs, the heat of the hand so expands the ether, that its vapor forces the liquid into the other bulb with violent ebullition. Fig. 114. 291. The Spheroidal State.— Water adheres to most surfaces, but heat destroys this attraction, and, if drops of it fall upon a red- hot plate of metal, they gather into spheroids, roll about, and evaporate very slowly. Fig. 115 represents a mass of water in the spheroidal state. In this case the heat of the metal produces a layer of vapor which supports the drop, so that it does not touch the surface, but is driven about by a current of heated air. The temperature of the spheroid never reaches the boiling point of the liquid, as the vapor, being a non-con- ductor, does not transmit the heat from the metal, and besides, it is kept cool by evapora- tion from its surface. If the temperature of the plate be allowed to fall to a point at which the water wets its surface, it will be suddenly scattered in a kind of explosive ebullition. Fig. 116. 292. All volatile liquids act in this respect like water. Liquid sulphurous acid, when poured into a red-hot crucible, takes the sphe- roidal state, and, as its boiling point is 18° below the freezing point of water, we can actually freeze water by pouring it into sulphurous acid in a red-hot crucible. We can thus explain another remark- able fact. If damp with perspiration, or slightly moistened, the hand may for an instant be dipped in melted lead, or white-hot melted iron, without burning or discomfort. The thin film of Spheroid of Water. Fig. 110. Its Explosioa. culinary paradox ? The pulse glass ? 291. What is the spheroidal state ? How is the Fpheroid supported ? Why docs it not boil ? Why does it explode ? 292. How n\:iy water bo frozen in a red hot crucible? What facts docs this explain? VAPORIZATION. 125 moisture is thrown into the spheroidal condition, and presents an effectual barrier against the intense heat § YII. Yajporization. 293. The change of solids or liquids bj the force of heat to va- por is called 'caporization. Substances which are readily converted into vapor are said to be volatile, while those which are vaporized with difficulty are termed fixed or non-wlatile. The slow forma- tion of vapor from the surfaces of bodies is called evaporation. It goes on at all temperatures, even from the surface of ice and snow, but is rapidly increased as the temperature rises. 294. Heat of Vaporization. — A much larger amount of heat is spent in converting liquids into vapors than in changing solids to liquids, while the vapors are no hotter than the liquids from which they are formed. The heat has been consumed in producing the repulsive motion and the consequent enormous expansion of the gaseous body. If the liquid is exposed to the air, it is impossible to raise its temperature above its natural boiling point. All the heat added after boiling commences is carried away by the vapor. Water boiling violently is not a particle hotter than that which boils moderately. 295. The quantity of heat which disappears during evapora- tion is very large. "With the same intensity it takes 5^ times as long to evaporate a pound of water as it does to raise it from freezing to boiling ; it hence receives 5^ times as much heat. If therefore 180° were required to boil the pound of water, nearly 1,000° are necessary to change it to vapor, and being spent in producing the change of state, it of course disappears. This quan- tity is, therefore, the ' latent ' heat of steam. If the process be re- versed and the vapor be made to reassume the liquid form, the heat reappears. The condensation of a pound of steam will raise b\ pounds of water from the freezing to the boiling point. Steam is hence a valuable agent for transporting heat, as is done by steam pipes for warming buildings. 296. Its Cooling Effects. — ^As evaporation consumes heat, it is 293. What is vaporization ? Evaporation ? 294. What is said of the heat required ? How is it consumed ? Why does not boiling water grow hotter ? 295. How much heat is required to vaporize a pound of water ? What is the latent heat of steam ? If the eteam is condensed, what follows? 29G. Mention eome of the cooling effects 126 CHEMICAL PHYSICS. Fig. 117. a cooling process. "We experience this in the cold sensation of evaporating a few drops of ether from the hand. As the per- spiration evaporates from the skin, it becomes a powerful cool- ing agency and regulator of bodily temperature, while the vapor which escapes from the breath, by its absorption of heat, exerts a cooling effect within the body. It is interesting to observe how the great capacity of water for heat makes it so gratefully cooling as it enters the body, and how its still greater capacity for heat when passing into vapor enables it so constantly to bear away from us the germs of fever as it escapes from the system in the form of insensible or manifest perspiration. The pernicious effect of wearing wet clothing arises from the rapid evaporation of its moisture, which robs the body of large quantities of heat. Damp soils are cooler than dry ones, because evaporation dissipates the heat which falls upon them. The heat of torrid regions would be insufferable, were it not for the cooling effects of rapid evaporation. Wind hastens evaporation, as it carries away the air as soon as it is laden with moisture, replacing it with dri-er air. 297. Freezing by Evaporation. — Water may be frozen by its own evaporation, as may be seen in the experiment, Fig. 117. A vessel of water and another of sulphuric acid are placed under a bell jar from v>'hich the air is exhausted. The sulphuric acid absorbs the moisture of the water so rapidly that the lat- ter is soon frozen. 298. The Oryophonis or Frost Bearer is an instrument which strikingly illustrates this principle. It consists of a tube with a glass bulb at each extremity, one of which con- tains a little water. Air is expelled from the instrument by boiling the water, the aperture through which the steam escapes being seal- ed, while the remaining space is filled with vapor. The empty bulb is then placed in a freezing mixture, Fig. 118, and the vapor condenses, its place being Freezing Water. FiG. 118. The Crj'ophoruB. of evaporation, by evaporation 1 Wliy IB wet clolliing injurious? 297. How iu;iy water bo frozen 298. Explain the principle of the cryophorue. 299. How and by VAPORIZATION. 127 Fig. 119. supplied by vapor from the water bulb. Condensation and evapo- ration go on so rapidly tliat the water is soon frozen. 299. The greatest artificial cold has been produced by the rapid evaporation of highly volatile liquids. By the vaporization of car- bonic acid and ether in the vacuum of an air pump, Fakaday reach- ed 166" below zero, while, by mixing liquid protoxide of nitrogen with bisulphide of carbon in a vacuum, M. Natterer produced the lowest recorded temperature, 220° below zero. 300. Moisture in the Air.— The air always contains moisture, the amount of which varies vith the temperature. The power of the air to absorb moisture is called its capacity for ahsorption. When it contains as much as it is capable of holding at a given temperature, it is said to be saturated^ and any lowering of the temperature condenses it in the form of clouds, mist, fogs, dew, &c. The degree of temperature at which the mois- ture is condensed is called the deio point. If the temperature of the air has to fall but a few degrees before moisture is deposited, the dew point is said to be higli., and there is much moisture in the air ; while, if the temperature must fall far, the dew point is low, and the air contains less moisture. It is obvious, therefore, that, by finding these two points of temperature, one can easily obtain the amount of atmospheric humidity. 301. Kygromaters are instruments for measuring atmospheric moisture. The one most generally used is the icet l}ul'b hygrom- eter. Fig. 119, and consists of two thermom- eters, one of which shows the tempera- ture of the air. The bulb of the other is covered with muslin, which is kept con- stantly moist by a string leading from it to a reservoir of water below. Evaporation takes place from the moistened bulb at a rate which depends upon the dryness of the "^et Bulb Hygrometer. •whom have the lowest degrees of cold been found ? 300. Upon what does the amount of moisture in the air depend ? "What is the effect of lowering its tempera- ture ? What is the dew point ? Meaning of high and low dew points ? SOI. What are hygrometers? Explain the principle of the wet bulb hygrometer. S02. Of 128 CHEMICAL PHYSICS. air ; and by the coldness thus produced the mercury in the ther- mometer is correspondingly depressed. By comparing the differ- ence between the two thermometers at any time, and referring to a table, the quantity of moisture in the atmospliere is ascertained. Pje lOQ 302. Darnell's Hygrometer, Fig. 120, is a beautiful instrument for determining the dew point, constructed on the principle of the cryophorus. The long limb ends in a glass bulb & half filled with ether, into which dips a small thermometer. The bulb a on the short limb is empty and covered with muslin. The temperature of the air is shown by another thermometer, c, affixed to the stand of the instrument. "When an obseryatiun is to be made, a little ether is poured upon the muslin, and, as it evapo- r:ites, the temperature of the other bulb be- comes reduced. "When it is sufficiently cold Daniells Hygrometer. , , ,, . ^ jf j.\. - -j. ^^^ to condense the moisture of the air, it will be covered with dew. The thermometer in the tube & shows at what temperature this deposition takes place, and of course gives the dew point. This iustrument is more accurate than the former. The amount of moisture in the air of our artificially heated rooms is a matter of great importance to health, and the hygrometer is very valuable in enabling us to determine it. 303. Volume and Density of Vapor. — ^Equal bulks of difierent liquids generate unequal volumes of vapor. "Water yields a larger amount than any other liquid. "While a cubic inch of water gives 1,G94 inches of vapor, a cubic inch of alcohol yields 528, one of ether 298, and of oil of turpentine 193. But the less the volume of vapor, of course the greater its density. "While 'i(i.(S cubic inches of turpentine vapor weigh 68 grains, the same bulk of ether weighs 37, of alcohol 23, and of watery vapor but 9 grains. The density of vapor is increased, either by cold or pressure. The point fit which its temperature cannot be further lowered without re- turning to the liquid state, is called its maximum density. 304. Its i3Iastic Force. — All vapors are elastic, and have a Daxisll's bygrroraeter ? 303. How mach vapor is prodaced by a cubic inch of water? Of alcohol? Ether? Oil of turpentine? How do their densities com- paro? What is the maximum density of vapor ? 304. What is the elastic force of VAPOEIZATION. 128 Fig. 121. tendency to diffuse themselves through space, exerting more or less force against any obstacle that resists their expansion. This expansive force of vapors is called their elastic force or tension. In the barometer, a column of mercury 30 inches high is driven into the tube by the pressure of the air (563). It, therefore, re- quires a force of 15 lbs. per square inch to press the mercury all out of the tube. If a little water be introduced under the bottom of such a tube, it rises to the surface of the mercury, and in the vacuum above exhales into vapor with a suflScient force to press the mercury down below its former level. But the amount of this elastic force depends upon the temperature. At 36° below freezing, although the water is changed to ice, it still gives off a vapor of force sufficient to depress the mercury gV of an inch ; at 36° it sinks it | of an inch ; at 80°, 1 inch ; at 179°, 15 inches ; and at 212° the mercury is pressed entirely out of the tube, proving that the elastic force of the vapor at 212° or boiling point equals the atmospheric pressure. Different vapors have different degrees of elastic force. At 80° the vapor of alcohol depresses the column 2 inches, and that of ether 20 inches. 305. As the temperature rises above 212°, the elastic force increases, and the boiling point becomes higher and higher, as is proved by an apparatus called 'Marcet's Digester,' Fig. 121. This consists of a smaH globe of iron or brass, with three apertures, through one of which a thermometer is passed, air tight; through the second, a long glass tube, open at both ends, and reaching nearly to the bottom of the vessel ; while the third is furnished with a stopcock. To the tube is attached a scale divided into inches. Mercury is now poured in, sufficient to cover the end of the tube, and the globe is half filled with water, in which the thermometer bulb is immersed. Upon applying heat with the stopcocTc open^ the water boils at 212°, and the steam is driven out against the pressure of the at- mosphere. But if the stopcock be closed, the temperature begins to rise ; the steam being confined, its tension increases, and the vapor? How may it be ascertained ? 305. What are the parts'of Marcet's appa- ratus ? What takes place wheu heat is applied with the stopcock open ? "With it 6* Marcefs Digester. 130 CHEMICAL PHYSICS. mercury begins to be pressed up the tube. At 249.5" the mer- cury will have been driven up 80 inches, and the pressure is equal to an additional atmosphere ; at 356.6° it is equal to 10 atmospheres, and at 415.4° it is equal to 20. 306. Steam. — It is well known that the expansive force of heat, acting through the vapor of water, is the impelling power of the steam engine. In low-pressure engines, steam is used from below the pressure of the atmosphere up to 20 or 30 lbs. per square inch above it, while high-pressure engines employ steam of YO or 80 lbs. pressure to the inch. It has been noticed that gases expand equally by equal additions of heat, the proportion being about y^^ part of their volume with each degree of temperature. But with steam in contact with water and constantly generated, it is not the case. "With equal additions of heat, the expansion is more rapid at high temperatures than at low ones ; hence there is an econ- omy of force in using high-pressure steam. "With low pressure there is an economy of heat and fuel, but, as the steam, instead of being driven out, is condensed into water, the necessary apparatus renders the engine complicated and cumbrous. Steam separated from water expands uniformly like gases, and may part with its additional heat without being condensed. When it is thus sepa- rated, and receives an extra charge of heat, it is said to be super- heated. At high temperatures, it is used to carbonize wood and YiG,ni' disorganize animal matter, which it does, by reducing the flesh to a fluid mass, the bones being separated in a state of powder. It may be heated sufficiently hot to melt lead. 307. Distillation consists in vapor- izing a liquid by heat in one vessel, and condensing it by cold in another. Fig. 122. The object may be either to separate a liquid from non-volatile substances dissolved in it, as in distil- Distillation. -c 'l if r • Img water, to purity it from foreign ingredients, or to separate two liquids which evaporate at differ- ent temperatures, as alcohol and water. In the latter case, the clo.sed? 308 What steam prcPBurcs do difterent engines employ? How is lii?h- pressure steam economical? "What are the advantages and diearlvantagcs of low- pressure engines ? What is superheated steam f What is it used for ? 307. What VAPORIZATION. 131 heat is carried just high enough to vaporize the most volatile liquid. The product of the process is called the distillate. When solids are vaporized, the process is termed suhlimation^ and the condensed vapor a sublimate. 308. Condensation of Gases. — When a gas loses heat enough to change it to a liquid or solid state, it is said to be condensed. The distinction between gases and vapors was formerly supposed to be that the latter are condensible into liquids, while the former are not. But under the joint influence of pressure and extreme cold, many gases once considered permanent have been reduced to liquids, and some even to the solid state. Dr. Faeadat effected this by a very simple method. He placed the materials from which the gas was to be generated in one end ^^^' ^'^^' of a glass tube bent in the middle, which was then hermetically sealed. Fig.- 123. The ex- panding gas confined in so small a space ex- erted a tremendous pressure, the force of which . - . . ,. . , . , Condensation Tube. condensed a portion of it mto a liquid m the other end of the tube, which was immersed in a freezing mixture to facilitate the process. By this method, and at a temperature of — 166°, he succeeded in liquefying carbonic acid, chlorine, ammonia, and several other gases. More recently M. Batterer, of Vienna, applied a cold of - 220° and a pressure of 3,000 atmospheres; but some of the gases, as oxygen, hydrogen, nitrogen, carbonic oxide, refused to liquefy, even under this tremendous force. It is sup- posed, however, that, under the proper conditions of cold and pressure, all gases could be made to assume the liquid or the solid state. 309. Radiant Heat is a branch of thermotics usually treated in this connection ; but it is a mode of action so closely linked with light, that we shall obtain a clearer view of its nature by con- sidering them together. This will be especially proper, as a chief purpose in treating of the forces is to bring out the idea of their intimate connections and correlations. Is distillation? Its object? What is sublimation? 308. "What was the former distinction between vapors and gases % Does it still hold ? How did Dr. Faradat effect the condeneation of gases? How far has M. Natterer gone with these experiments. 309. Why is radiant heat deferred? 310. What is the common 132 CHE3IICAI, PHYSICS. CHAPTER Y. LIGHT-THE RADIANT FORCES. § I. Movements of Light. 310. In its common, restricted meaning, light is that agent which, acting on the eye, produces vision, and the general laws of its movement belong to optics. But science has shown that the solar raj, instead of being simple, is a sheaf of diverse forces which produce the most extensive and varied changes, physical and chemical, upon the surface of the earth. These effects, though of different kinds and differently named, are all due to one mode of action ; they have a common explanation, and hence require to be considered together. Light is called a radiant force, because it moves in raijs ; other forces, moving in the same manner, are also called radiants or radiation^ 311. Decrease of Intensity.— Eight moves in straight lines, and in all directions from the point of emission. As it radiates away, it diminishes in intensity as the square of the dis- tance from the point of emission ; that is, at a distance of two feet the light will be four times less intense than at one foot ; at three feet it has but one ninth the intensity, as shown in Fig. 124, i ^+~~"^ where the upper figures represent the distances, Decreasing Intensity, and the lower ones the corresponding intensities. It has been proved in various ways that this force moves through space with the velocity of 192,000 miles per second. 312. How Light is Received.— When it falls upon bodies, it is either thrown back from them (rejiected\ extinguished by them (absorbed), or passed through them {transmitted). Those which transmit it, as air and water, are termed transparent ; those which admit it only partially, as rough glass, or oiled paper, are called translucent, while those which refuse to transmit it are said to be opaque. We can see objects through a transparent substance, but notion of light? How is it regarded by Science? To what are the effects due ? What are radiant forces? 311. At what rate docs light diminish in intensity? What is its velocity ? 312. How do bodies receive light ? Wliat is transparency ? MOYEilEXTS OF LIGHT. 133 Fig. 125. Eeflection of Light. only light through a translucent one. The body traversed bj light is called a medium. No medium is perfectly transparent ; even the purest air absorbs a portion of the light in its passage through it. Nor are any substances absolutely opaque ; even gold in thin films transmits a greenish light. 313. Reflection. — When a ray of light strikes perpendicularly, or at right angles upon a polished surface, as at a &, Eig. 125, it is thrown back in ex- actly the same line; but if it fall ob- liquely, it is reflected obliquely, as is shown by the arrows. The angle of rebound is equal to the angle of striking, or, as it is commonly expressed, the angle of reflec- tion is equal to the angle of incidence. 314. Refraction.— When light passes from one medium to an- other of a difi"erent density, as from air to water, it is liable to be turned out of its straight direction. If its course be perpendicular, as a &, Fig. 126, it will not be divert- ed ; but if it fall obliquely, as at c tZ, it will be re- fracted^ and proceed to e. If the refracting me- dium have parallel surfaces, the ray on leaving it is again bent back to its original course, as is seen in the figure. For this reason, common window panes, which consist of plates of glass with parallel sur- faces, produce no distortion in the appearance of objects seen through them. If we partly immerse a stick in water, it will seem bent or broken at the point of entrance, owing to the rays from the immersed portion being refracted as they pass from the water to the air. The refracting power varies in different substances, generally increasing with their density. It, therefore, forms one of the distinguishing properties of bodies, and is fre- quently used as a test of chemical purity, as in detecting the adul- teration of essential oils, when other modes would prove insuffi- cient. 315. The Analysis of Light. — By the prism — a triangular piece of glass, or other transparent substance — the sheaf of rays is un- Translncency ? Opncity? A medium? 313. By -what law is light reflected? 314. What is refraction ? What causes the brokea appearance of an oar in water ? 315. How is light affected by the prism ! What is the spectrum ? What is th© 134 CHEMICAL PHYSICS. bound, and spread out before us. A beam of solar light pass- ing through such a prism, Fig. 127, is refracted by it, and pro- duces an oblong colored image called the solai' spectrum. It is usually considered to comprise the seven colors enumerated in the accompanying diagram. White light is, therefore, held to be a compound consisting of these colored lights, which are only separated by the prism. Each color has its own peculiar refrangibility, or degree of di- vergence from the original source, the red being least refracted, and the violet most. The separation of the colors in the spectrum is called dispenion^ and transparent substances differ much in this power. A hollow glass prism filled with oil of cassia gives a spec- trum (1), Fig. 128, more than twice the length of that produced by flint glass (2). Fig. 128. Decomposition of Light. ABO D E P o 11 ^pll 1 1 1 ^1 i i ! _ _J III^^^M ABCDEF G U 1. Spectrum fiom prism of oil of cassia. 2. From flint glass. The letters correspond to certain fine dark lines which cross the spec- trum and serve as its permanent landmarks. These lines are hence more separated in tlie highly dispersed spectrum (1) than in (2.) 316. The separate colors cannot be again decomposed ; hence they are called primary. Newton, who first decomposed the ray, assumed that there are seven ; Brewster holds to three primaries — red, yellpw, and blue, the remaining colors being compounded of these. IlERScnEL says any three colors of the spectrum may be taken as primary, and all the others compounded from them by the addition of white ; while Prof. Baden Powell remarks, ' The fact is, the number of primary rays is not really seven, but infinite.' fleparation of colors in the epectrum called ? "What is the effect of the oil-of-cassia priflm? 316. Why are the colors called primary? What was Newton's view of the conBtitution of the spectrum? Brewster's? IIerscuel's? Baden Towkll's? THE WAVE THEORY. 135 II. The Wave Theory. 317. The old hypothesis of light assumed it to consist of moving particles, or corpuscles, shot from the luminous source, which pass through transpar-int bodies, rebound from reflecting surfaces, and entering the eye, produce vision by striking against the optic nerve. But the luminous ray produces a variety of effects — heat and chem- ical force as well as light, with various kinds and gradations of each, and the foregoing explanation is profoundly insufficient to ac- count for all these complex and wonderful phenomena. Evidently there is but one principle of action among all the forces of the ray : the key to light and color must also unlock the mystery of the thermal and chemical radiations. We have this explanation in the ecai'e theory of light. 318. Motion of Sound — Sound is a radiation ; it proceeds rap- idly in straight lines in all directions from the point of emission ; is reflected and refracted according to the same laws which govern the other radiant forces, and may be passed through lenses and conveyed to focal points like light. But sound is proved to be a motion of waves or undulations transmitted through the air. Here then is a principle of nature employed to produce the kinds of ef- fect with which we are dealing. 319. Wave Motions. — "With these we are all familiar. If one extremity of a long cord, Fig. 129, be briskly moved up and down, wave-like motions pass rapidly from one end to the other. The parti- cles which compose the cord do not advance; they only move from side to side ; the undulatory motion alone flows on. If we toss a stone into still water, waves arise at the point of disturbance, and pursue each other in rapidly extending circles ; there is no current ; light objects are not drifted forward ; the water particles only rise and fall while the wave progresses. By wave length is Fig. 129. Undulation of a Cord. 317. What is the old hypothesis of light? What must a true theory of light explain ? 318. How does sound move ? In what way is it propagated ? 319. "What does the cord illustrate? What is it that goes forward ? Describe the motion of water waves. How do the water atoms move ? Tfhut is a wave length ? 320. How 136 CHEMICAL PHYSICS. here meant the distance from the crest of one wave to that of the next, or from depression to depression, as from a "^ ■ to &, Fig. 130, or from c to d. ^ ^^^^^ 320. Sound Waves.— So also a vibrating so- ^^^^^^^^ norous body, as a bell, throws the aerial particles Wave Len^'th ^^^^ agitation, and the undulations sent through the air breaking upon the nerves of hearing, the effect is transmitted to the brain as sound. A harp string, for ex- ample, is vibrated, and as it advances, it crowds together or con- denses the air particles before it ; as it retreats, the air particles behind it separate more widely, and a rarefaction occurs. Ad- vancing again, another condensation is produced; and again re- treating, there is another rarefaction. A condensation and a rare- faction constitute a sound wave — its length being the distance from the centre of one condensation to the centre of the next, or from the centi-e of one rarefaction to that of the next. These pulses are propagated through the air at the rate of 1,100 feet per second. 321. It is marvellous how slight an impulse throws a vast amount of matter into tremulous motion. We may easily hear the song of a little bird 500 feet above us ; but before that note could have travelled to our ears, it must have filled with wave pulsations a sphere of air 1,000 feet in diameter, or have thrown into agitation nearly 18 tons of atmospheric gases.* 322. The pitch of sound depends upon frequency of vibrations. The quicker a string vibrates, the more rapidly will the pulses fol- low each other ; the shorter will be the wave, and the higher the sound. Hence, the violinist, to produce a higher note, shortens the string by pressing his finger upon it. Shrill notes are caused by rapid vibrations, while the low notes result from those which are slower. The lowest note of a 7-octave piano is made by 32 vibrations per second; the highest by 7,680, while each mterme- * Gnnn nrc fired in the Alps to ptart avalanches by the concussion of the air, and it is said that great masses of snow are often poised with such perfect equi- librium that the sound of the voice alone is eufficieut to dislodge them. Spcalang of the chpmois hunters, Rogers says : ' From rock to rock, with giant hound, High on their iron poles they pass ; Mute, lest the air, convulsed with sound, Rend from above a frozen mass.* Is sound produced? How does a harp string affect the air? "What is a sound wave ? Its length ? Velocity ? 321. What is said of the power of a little bird to ttgitato the air f 322 Upon what docs pilch depend f IIow are sharp notes caused? THE WAVE THEOPvT. 137 diate note has its fixed number. Intensity or loudness of tone de- pends upon the intensity with which the air is struck by the vi- brating body, or the amplitude of the excur- sions of the vibrating particles. A string _ that swings from a to 5, Fig. 131, will pro- ,.""""'c""""^^ dnce a louder sound than if vibrating no ^>-""" """"--^,^ farther than c, though the pitch wiU be in g^^^^ of Vibration. both cases the same. 323. Ether. — I^ow the radiant forces are believed to be all propagated by undulatory motions ; but motions in what ? Sound has its medium — the air ; and the sound rays cannot cross a vac- uum, as there is nothing to convey them. But heat, light, and the chemical force dart through the most perfect vacuum we can pro- duce, and traverse in all directions the interstellar spaces. There must be something throughout these spaces to transmit the mo- tion. The wave theory of light assumes the existence of a univer- sal etlier — an infinitely rare and elastic medium which is diff'used through nature, pervading even the most solid bodies. It con- nects atom with atom and star with star. Through this universal medium — the dynamic bond of nature — waves are sent with a velo- city far exceeding those of sound. 324. It is objected to this idea of ether that it is a pure crea- tion of fancy, like caloric and phlogiston (579). It is urged that as we know the forces only as manifested in matter, and as S perfect vacuum has never been produced, it is better to assume that some form of actual matter is universal, and that the wave motions take place in that. But it is after all very much a ques- tion of terms. Both views assume a universal medium capable of transmitting undulatory motions ; one calls it material^ and the other ethereal. Ether is not held to be/(?rce, but only the medium for representing those motions by which force is transmitted. One ether suffices for all the forces, and thus by introducing the idea of unity in their modes of action, we are prepared to com- prehend their mutual relations. While the theory of ether may be objected to on some grounds, yet it is a vast advance on former What is said of the piano? What is intensity ? How illustrated ? 323. What is beliered of all the radiant forces ? Why is there prohahlj' a universal medium ? Describe the ether. Its uses. 324. What objection is made to ether? What has to be assumed at any rate ? What is ether held to be ? What is gained by the conception I What has an eminent authority remarked, and why ? 325. How is 138 CHEMICAL PHYSICS. ideas, and so combines and explains a multitude of facts whicli cannot be othervrise accoimted for, that an eminent authority has remarked, ' If it is not true, it deserves to be ! ' 325. Cause of Colors. — ^According to this \\evr, light is trans- mitted bj ethereal undulations just as sound is by those of the atmos2)here ; with only this difference, that while the air particles move backward and forward in the same direction as the advan- cing wave (normal vibratio7is), the ethereal particles move across the course of the wave {transverse vibrations). Thus the spec- trum is to the eye what the gamut is to the ear. As the pitch of sound depends upon the length of the air wave, so the color of light depends upon the length of the ethereal wave ; and as loud- ness of sound depends upon the extent of the swing of air parti- cles, so the brightness or intensity of color results from the extent of the excursions of the ethereal particles. 326. By several refined methods which cannot be detailed here, the lengths of the ethereal waves upon which colors depend have been rigorously established. The motions which produce red are slower, and the undulations longer than those which produce violet. It is found that 89,000 waves of red light would measure an inch, while 5T,500 waves of violet light would fill the same space. The other colors are intermediate, their num- ber of waves increasing gradually from red to violet. As light moves 192,000 miles per second, that length of ray streams into the eye each second. If this distance be reduced to inches, and the product be multiplied by 39,000, we shall have the number of waves which beat against the retina each second, when we look upon a red color. If the same product is multipled by 57,500, we get the number of pulses per second which strike the retina when looking upon a violet color. If a single second of time be divided into a million of equal parts, a wave of violet light trembles or pulsates in that incredibly short interval, 727,000,000 times ! If these results seem incredible, we should remember that we arc dealing with the resources of the Infinite. In treating of atoms we saw tlie minuteness of the scale upon which nature divides her spaces, and here we have her corresponding infinitesimal scale of time and force. the motion of light explained ? Differcnco between light and sound motions? To what is the Bpectriim compared? Upon what do color and brighliieee depend! 326. "What are the lengths of the red and violet waves t What is the velocity of THERMAL EADIATIONS. 139 327. It is necessary to distinguisli between vibrations and undulations ; the former take place among the atoms in all kinds of matter, the latter only in the transmitting medium. In the case of sound, the vibrations of a sonorous body produce undula- tions in the air, which, when falling upon other bodies, may set them also to vibrating. So the vibration of atoms in a flame, produces undulations in the ether ; these are transmitted to the nerve of vision, and, breaking against it, throw its atoms into the vibrations which produce sight. 328. The nerves of hearing can be acted upon only by a cer- tain range of air pulsations. There are air waves which fall upon the ear in regular recurrence, but exert no sensation ; they are either too slow or too fast. It is probable that the hearing organs of different animals have still different ranges of sensibility, per- ceiving sounds which are too high or too low for the human ear. Just so with the ethereal undulations ; the nerve of the eye is adapted to a certain range of pulsations, and waves too slow or too rapid do not awaken the sensation of light. 329. The colored spectrum, Fig. 127, embraces the range of ethereal undulations which produce luminous effects : below it are waves too slow to act upon the eye, while above it they are pitched too high. We shall soon refer to still more remarkable analogies between sound and light. But it is really no more ex- traordinary that myriads of ethereal waves beating incessantly upon the retina, should awaken the sensation of vision, than that a storm of air waves pouring upon the ear, perhaps from a hundred instruments at once, should give us the experience of music. Nature produces the most varied results by the simplest means ; conveying to us harmony and beauty— the anthem and the land- scape by the same method. § III. Thermal Radiations. 330. Heat is associated with light ; it moves with the same remarkable velocity ; is weakened by diffusicm at the same rate, and is reflected, absorbed, transmitted, and refracted by various light ? How many inches per second ? How many red -waves enter the eye each second? Of violet? 327. What is the distinction between vibrations and undulations ? 328. What is said of the range of audible sensation ? 329. Is the eye sensitive to all ethereal waves ? What is said of the unity of nature's metbods ? 140 CHEMICAL PHYSICS. Fio. 132. Eeflection of Dark Heat. Fig. 133. bodies in accordance with the same laws as light. When thus moving, it. is called radiant heat. 331. Luminous and Obscure Heat. — Radiant heat is of two kinds : that which accompanies light is called lumiiio us heat ; that which is emitted from dark bodies, as a stove below redness, is termed obscure heat. That dark radiations of heat obej the same laws of motion as light, may be proved by placing a warm iron ball, c. Fig. 132, opposite the thermo-electric pile p, the conical reflector be- ing turned away, so that no di- rect heat can reach it from the ball. A bright tin screen, m n, is then so placed that the angle made by the incident heat from the ball shall be the same as that reflected from the tin surface which strikes the pile. The moment the screen is placed in position, the needle of the galva- nometer starts, showing that reflection has taken place. 332. Thermal Spectrum.— "When a ray of light is decomposed by the prism, it is found that the heat is refracted like light, and is distributed through the colors, but the refrangibility is lower, and dark heat is therefore found below the red ray. The thermal spectrum was first traced by Sir John Herschel, and found to have the out- line represented in Fig. 133, its lower part being curiously discontinuous. 333. How Radiation takes place. — We can now explain thermal radiation in haiTnony with the later views of the nature of this force. As heat consists in the vibration of the particles of common matter, tliis motion is communicated to the ether in which they are im- mersed, and propagated through it exactly in the manner of light. The ethereal pulsations, striking against other substances, increase 330. What are the analogies of the motion of heat and light? What is radiant heat? 331. What is luminous heat? Obscure heat? What does Fig. 132 illus- trate f 332. What is the thermal Bpcctrum I 333. Uow ig the radiation of heat Thermal Spectrum. THERMAL KADIATIONS. 141 the vibration of their particles, and thus heat them. As a body cools, it loses atomic motion — the ether transmits this motion, and other bodies acquiring it are thereby warmed. 334. Exchanges of Heat. — All bodies, though at a hundred de- grees below zero, contain some heat ; that is, their atoms are all in vibration, though at varying rates. This motion muot be com- municated to the ether, so that all bodies radiate heat at all times, and are hence constantly exchanging it with each other. If a can- non ball at 1000° be placed beside another at 100°, it parts with its own motion rapidly to the other, as illustrated by the radiant Fig. 134. Fig. 185. ^ 1 Exchanges of Heat. lines. Fig. 134. But the ball at 100° also radiates its motion, though more slowly, thus returning a portion to the hotter ball ; and if a ball of ice were added, the same thing would take place, only in a feebler de- gree. If a body receives motion faster than it com- municates it, its tempera- ture rises ; if the reverse, it cools, and if the ex- changes are equal, there is equilibrium, or a uniform temperature. Hence, other things being equal, the rate of radiation depends upon temperature. 335. Infiuence of the Surface. — But thermal ra- diation is also influenced by surface. Eadiation from Leslie's Cube, In Fig. 185, o represents a explained? What is the part played by the ether! 334. Why must bodies con- Btantly exchange heat? What does Fig. 134 illustrate? What is i,he cause of equilibrium? 335. How do surfaces influence radiation? What are tbo best 142 CHEMICAL PHTSICS. cubical vessel of pewter vrith. one of its sides coated with a layer of gold, a second with silver, a third ^vith copper, and a fourth with varnish. The vessel is then filled with hot water, and placed at a little distance from the thermo-electric pile p. When the hot gold surface is turned to the pile, scarcely a trace of effect is observed, and so with the copper and silver; but when the varnished sur- face is brought round, a stream of heat strikes the pile, and the needle is driven round against its stops. The condition of the sur- face also influences radiation — rough, uneven surfaces being more active than bright polished ones ; hence, if the metal is covered with woollen or velvet, its radiant power is increased. Bright metallic vessels, therefore, retain the heat much longer than those which are tarnished. /^(f^336. Absorption. — Good radiators are good absorbers of heat ; that is, the surfaces which can easily communicate motion to the ether are equally capable of accepting it from the ether. On the contrary, a bad radiator, as a bright metallic surface, is a bad absorber, and therefore a good retlector. Hence, the thinnest metallic film upon a surface powerfully protects it from the action of radiant heat, 337. As bodies differ widely in their atomic condition, it is not to be expected that they will all act ahke upon the ether ; some will communicate more motion than others. This explains the dif- ierent radiating and absorbing action of bodies. Atoms vibrating singly cannot impress as much motion upon the ether as vibrating groups, or systems of atoms. The atoms of the elements — gold, silver, copper — vibrate singly, and disturb the ether but slightly ; while those of varnish, flannel, or velvet oscillate in masses, and transmit an increased amount of motion. 338. Influence of Color. — According to Melloxt, color exerts no influence upon the radiant power of surfaces ; white, black, and red radiating alike, so that as regards the loss of heat from this source, the color of our clothes is of no importance. On the con- trary, color powerfully influences the absorption of luminous heat. Dr. Franklin spread differently colored pieces of cloth upon the snow in the sunshine. The black sunk farthest, that is, melted most snow, and, of course, received most heat. The blue piece radiators f The purest t 336. How are radiation and absorption related? S37. What are we to expect from the atomic peculiarities of bodies' What kinds of atoms affect the ether least ? TMiat most t 338. ITow docs color affect radia- THERMAL RADIATIONS. 143 sunk to a less depth, the brown still less, and the white hardly at all. Hence by scattering soot over snow its melting may be hastened. Darkening a soil in color, is, therefore, equivalent to moving it farther south, and, for the same reason, black clothes absorb most solar heat. 339. De-TO-. — When the radiation of bodies is not compensated, their motion is gradually spent upon the ether, and their temper- ature sinks. Such is the case with objects exposed to the sky on clear nights. If good radiators, they rapidly lose heat, and, cool- ing below the temperature of the au-, at length begin to condense its moisture upon their surfaces : this is dew. The best radiators, as grass, leaves of trees, and porous soils, receive the most dew, while poor radiators, as smooth stones, and hard compact soils, remain almost dry. Clouds radiate back the heat received from the earth, so that cloudy nights are warm and dewless. If the tempera- ture sinks lower than 32°, the moisture is frozen, and becomes frost. 340. Transmission and Destruction of Waves. — An opaque body destroys the luminous waves which fall upon it, while a transparent one permits them to glide through between the atoms without interference. But there are bodies which destroy some of the waves and allow others to pass. If a piece of red glass be placed between the prism and the spectrum, it stops the blue rays and transmits only the red, that is, it cuts down the more minute waves, and gives passage only to the larger. If blue glass be used, there is a reverse effect, the red waves being extinguished, and the blue alone transmitted. Both glasses are transparent, yet if placed together in the path of the rays, they are as opaque as a plate of iron ; each destroying what the other transmits. If a solution of permanganate of potash be used in the same way, it destroys the central waves of the spectrum, leaving the colors of the extremi- ties with a jet-black space between. 341. Diathermancy. — This is also the case with the heat rays; they are of different kinds, like the colors of light, and are arrested and transmitted differently by different substances. Bodies which transmit heat freely are called diathermic ; those which arrest it, athermic. Eock salt (common salt in blocks) is the most perfect tion ? Absorption ? 339. How does dew depend upon radiation ? 340. "What is the effect of red glass upon the decomposed waves ? Of blue ? Of both ? Of Bolution of permanganate of potash? 341. What are diathermic bodies ? Athor- mic ? TThat are the properties of rock salt ? What has it been termed ? What is 144 CHEMICAL PHYSICS. Fig. 136. Glass interceptinc:, and Rock Salt transmitting Heat. Fig. 137. diathermic body, allowing all the heat rays — those from the sun and the hand to pass through with equal freedom. What glass is to light, a plate of rock salt is to heat, and it has hence been aptly termed ' the glass of heat.' This substance is therefore adapted to make prisms and lenses for the concentration and dispersion of dark heat. If a heated ball be placed between a plate of glass and one of rock salt, Tig. 136, and bits of phosphorus be laid upon stands beyond, though the salt be many times thicker than the glass, the dark heat passes freely through it, igniting the phosphorus, while it is quite arrested by the glass. In the same way a thin film of water will absorb the obscure heat, while liquid bisul- phide of carbon will transmit it. The relations of different substances to the radiants are repre- sented in the figures. The dotted arrows represent light ; the broken arrows, luminous heat, and the whole, or dark arrows, dark heat. If the plate of salt be smoked, it becomes opaque to light, but the heat still passes, while plates of trans- parent alum are opaque to obscure heat, and almost impervious to luminous heat. 342. Sifting the Rays.— We have said that the sunbeam is a bundle of heterogenous radia- tions, and that the ^ prism spreads them out into a spectrum, thermal at one end, chemical at the other, and luminous in the centre. The same thing holds true of all sources of heat, luminous and obscure — they emit rays of different quali- ties. When the mixed rays from any source aro passed through a plate, a certain portion of them is stopped, and another portion transmitted. But if the rays which have passed are made to Rock Salt. Fig. 138. Rock Salt Smoked. Fig. 139. it fitted for? What is sliown by Fig. 136? How ia rock salt related to the three radiations? Smoked salt? Glass? Alum? 342. When mixed rays pass through a Bubstance, what is the effect ? How are they treated by a second similar plate ? THERMAL EADIATIONS. 145 fall upon a second similar plate, a much larger proportion will bo transmitted than went through the first. The first plate sifted the raj, and the purified beam is better fitted to penetrate another similar plate. For example, a plate of alum stopped 91 per cent, of the heat rays, transmitting but 9 ; while a second alum plate transmitted 90 per cent, of the sifted rays, stopping but 10. 343. This principle explains the fact that glass readily trans- mits solar heat, while it stops the "heat from a red-hot cannon ball in large quantities. The rays of the sun in coming through the atmosphere are strained of the rays which would be stopped by glass, so that the altered beam passes our windows without loss. ^^44. Absorption of Heat by Gases.— Some new and highly in- teresting results have been lately arrived at by Prof. Tyndall on the relations of radiant heat to gases. The instrument he em- ployed consisted of a hollow tin cylinder, A B, Fig. 141, four feet Fig. 141. Tynd all's Apparatus for Gaseous Absorption. long and three inches in diameter. This is closed by caps contain- ing plates of the purest rock salt, which are screwed air tight upon its ends. The upper stopcock, 0, connects the cylinder with an air pump by which it may be exhausted, and through the lower stopcock, C, air or any other gas may; be admitted. The bent tube, U, contains fragments of pumice stone, moistened with caustic potash, to absorb carbonic acid from the entering air ; and How do the two alum plates behave toward heat rays ? 343, Why does solar heat pass through glass, while that from a hot ball is stopped ? 344. Of what parts does Tyndall's instrument for investigating the relations of heat to gases consist I 1 146 GHEiaCAI. PHYSICS. U' contains pieces moistened with salplmric acid, to absorb wa- tery Tapor. At one end of the cjlinder is placed the thermo- electric pile, with wires leading to the galvanometer, and at the other a cube, C, filled with hot water ; while a tin screen, T, cuts off and admits the rays. 345. Pure Air Diathezmic.. — ^If the cylinder be exhansted, and the screen wiihdrawn, heat enters, and traversing the vacnuin. foils upon the pile without any loss ; none of it is absorbed on the way. If now the cock C be tnmed, and puri&ed air be allowed i ; enter and fill the cylinder, there is no motion of the needle ; tLc sir arrests none of the heat. * Its atoms are apparenUj inc : n: - tent to shatter a ein^e calorific wave : it is a practical tsci . regards the rays of heaL' By a modification of the apparc: s : _r more delicate, and after thousands of experiments, Prof. Tt: : _ii found that dry air did exert a slight inflnence, deflecting the needle about one degree. Pure oxygen, hydrogen, and nitrogen beLive like air, being almost nentraL 34IS. ItifliiFinc e o£ Campaaxid Gases. — ^If now compound gases fire introduced into the cjlinder, a remarkable effect appearsL Olefiant gas, whidi is just as transparent as the air, arrests four fifths of the rays of heat. Pure, transparent ammonia is still more impenetrable, and arrests the heat as if the cylinder were filled with ink or pitch. The same effect is^ produced if only a small proportion of these gases is mingled with the air of the cylinder. To such an extent is this true that it has been affirmed that the ammonia escaping from a bottle of hartshorn by a single act of inhalation, will exert a more potent action on radiant heat than the whole body of oxygen and nitrogen in the apartment. Some bits of paper were moistened and placed in tubes, so that the entering air carried with it a feint trace of odor. The effect was marvellous : the aromatic vapor struck down the heat rays in crowds. The exhalation of bergamot arrested 44 times as much heat as the air; that of lemon, 65 times ; and of aniseed, 372 times. The absorbent power of the following gases b represented by the accompanying numbers : air, 1 : oxygen, 1 : nitroc^!;, 1 : hydrogen, 1 ; chlorine. 39; carbonic acid, 90; olefiac: j:.^>. . 7 1.195. Explain tbeir aseeL Sla. What Is the ^Kct xr WlwB filled -with pare air ! What did Tisdal: iortramentt MS. What is the effeet of defiant r dfectof a tn^eof ammosda? Of odant 31111 THEEMAL EADIATIONS. 147 347. The same explanation applies liere as in the former case (337). We saw that in solids, single atoms, or the atoms of ele- ments, communicated their motion to the ether in a very imperfect manner, while compound groups produced more powerful effects. The same general fact now appears under totally different circum- stances. The atoms are no longer embarrassed by cohesion ; their movements are perfectly free, yet here again the elements oxygen, hydrogen, and nitrogen can only act upon the ether in the feeblest degree, while those of the compound gases which move in massive groups, are thrown into powerful vibration by the ethereal waves, and react upon them with corresponding energy. Prof. Tyndall remarks that oxygen, hydrogen, and nitrogen swing in the ether with hardly any loss of moving force ; they bear the same relation to the compound gases that a smooth cylinder turning in water does to a paddle wheel. 348. Invisible rays thus become the means of sounding the atomic constitution of bodies. While heat passes through com- mon oxygen without being intercepted, ozone, which is but an- other form of oxygen, arrests a large proportion of it like com- pound gases; we therefore infer that its atoms are arranged in groups. Lampblack is an excellent radiator, and though an element, yet it is an allotropic condition of carbon, in which the atoms are probably grouped into complex molecules. 349. Absorption of Heat by Aqueous Vapor. — These views are not only interesting in themselves, but of the utmost import- ance in the economy of nature. Aqueous vapor is highly opaque to the dark radiations. Where the atmospheric gases arrest one ray of obscure heat, the small proportion of watery vapor contained in the air strikes down sixty or seventy rays. Luminous solar heat penetrates the air, and falling upon the earth, is changed into obscure heat, which cannot be radiated back into space. The watery vapor is thus the ' barb ' of the atmosphere which pre- vents the escape of the heat, and thus maintains the temperature of the earth. It follows that if aqueous vapor were withdrawn from the air, the terrestrial heat would so quickly radiate aw^ay, that the earth would soon become uninhabitable ; the invisible watery element of the air is, therefore, the blanket which keeps To what are tlie difierent atoms in the ether compared ? 348. What work do the invisible rays perform ? 349. What is the relation of aqueous vapor to obscure heat? What is the effect of the aqueous vapor of the air? What would be the 148 CHEMIC.O. PHYSICS. the world warm. In all those localities where the atmosphere is dry^ the nightly loss of radiant heat is great, so that even in the burning desert of Sahara there is nocturnal freezing. 350. The sun s rays fall with intense power upon the snowy summits of high mountains, but their ice never melts. Travellers testify that they have never suffered more from solar heat than when wading waist deep in the snows of Alpine mountains. But there is so little aqueous vapor in the higher atmospheric regions, that the heat escapes as fast as it is received, and thus high moun- tains are powerful condensers of the vapor which is brought by the air currents from below (574). ' Water in all iU forms is so active a radiator, that it must play a most important part in this moun- tainous condensation. As vapor it pours its heat into space, and promotes condensation ; as liquid it pours its heat into space, and promotes congelation ; as snow it pours its heat into space, and thus converts the surfaces upon which it falls, into more pow- erful condensers than they would otherwise be. Of the numerous wonderful properties of water, not the least important is this extraordinary power of discharging the motion of heat upon the interstellar ether ! ' — (Tyxdall.) § I Y. Interference of the Eadiants. 351. Interference of Waves — When two sets of waves upon water are made to flow together, two effects may take place. If the waves coincide, that is, if ^^' "■ ridge corresponds to ridge and furrow to furrow, their height will be increased; but if the ridge of one corresponds with the trough of another, they will neu- tralize each other and the water become still. This is called in- terference. If one of the systems lr.^.^^^::^^ of w'^^^T^ves. ^^ retarded a whole wave length, or any number of 'vchole wave lengths, there will still be no interference ; but if one be retard- effect of removing the aqueous vapor from the air ? 350. What is eaid of the heat upon high mountainB ? Why does not the enow melt ? What is the effect of the radiation of water In all its forms? 351. 'VS'Tiat is interference of water wav^s? INTEEFEEENCE OP THE RADIANTS. 149 ed half a wave length, one and a half, or two and a half, the hills will neutralize the hollows, and interference produce rest. These effects may be shown bj dropping two stones into still wa- ter near each other at the same moment. Two sets of concentric waves are formed. Fig. 142, and where their circles intersect each other and their crests coincide, the motion is heightened; but where crest coincides with depression, their motions are mutually destroyed. 352. Again, two stretched strings, or two tuning forks, may be so arranged, that, when simultaneously struck, they do not give forth a continuous sound ; but there is produced a series of sounds, alternating with a series of silences. For a moment the sound increases, then dies away and ceases, then again swells forth and declines, and so continues until the strings or the forks cease vibrating. During the pauses of silence, there is still rapid vibration, so it is certain that the sounds are extinguished by interference of their waves. 353. Interference of Light.— If a beam of colored light be ad- mitted into a dark room by two pinholes made near each other in a thin sheet of metal, and be made to fall upon a screen at a short distance, the rays intersect each other, and a series of dark bands alternating with bright h\ stripes will be formed upon the e\ screen by interference of the ray ^, from the two orifices. In Fig. 143, a /represent the two pin- ^f holes, and c d eh 2i portion of the screen, c g being a line joining the two surfaces at right angles, and midway between the pin- holes. The rays, « c, / c, pass through equal paths ; their waves coincide at c, and, heightening each other's effect, a bright band is produced at c ; a d^fd will differ by the length of one wave, a e^fe by the length of two waves, and a h, f h hj the length of three waves ; hence, there will be also bright bands at d, e, and 5. But the rays from the two orifices, meeting at 1, 2, 3, dif- fer in length successively by half a wave, a wave and a half, and Fig. 143. Interference of LiErht. How may these effects be shown ? 352. How is interference of sounds manifested ? 353. How may interference of light he produced ? Descrihe the experiment. 150 CHEMICAL PHYSICS. two waves and a half, and by thus interfering, extinguish each other and produce darkness. As the rays which meet at c are equal, it is obvious that all the other rays coming from a are lengthened, and all others coming from / are shortened. As this variation of length is gradual, there will be a gradual passage from the brightest light to complete darkness. This effect is ex- hibited by the shaded portion of the diagram. If the light from one aperture is intercepted, all the dark bands disappear. 354. The multiplicity of these remarkable phenomena is proof of the extent to which wave motion is employed in nature. Thus we have seen that motion added to motion produces rest ; that sound added to sound produces silence ; that light added to light produces darkness; and it has also been proved that heat added to heat produces cold, and chemical energy added to chemical energy produces inaction : in other words, there may be interference of the ttermal and chemical radiations just agj)f light and sound. § Y. Polarization of Light. ^ f-^nTtl jcRti Light Polarized by Reflection. 355. "When light is reflectet certain angles from the surface of glass, water, marble, polished wood, &c., a portion of it undergoes a re- markable change. Although taking place all around us constantly, we do not perceive it, but it may be de- tected in various ways. Two plates of glass are blackened on one side so as to have but a single reflecting sur- face, and then placed as shown in Fig. 144, rt, J, with their edges tow- ard the eye. A ray of common light falling upon a in the direction of the arrow is reflected, and, upon being thrown upon &, is again reflected. The ray is changed at cr, as the al- tered structure of the line shows, but the effect is not apparent. If now 354. What ia the extent of this principle? 365. What happens vfhcn light ia reflected at certain angles? JIow is this change detected ? What ie the effect of POLARIZATION OF LIGHT. 151 6, or the second plate, is turned a quarter round, its angle with the ray being preserved, reflection ceases, and the beam is extin- guished, Fig. 145. Turning it another quarter round. Fig. 146, the ray is again reflected; and still another quarter revolution, Fig. 147, brings it on the opposite side to Fig. 145, and again extinguishes it. The beam may be reflected from surface to sur- face any number of times in the same plane ; but it has lost the ability of being reflected in planes at right angles to that plane, while common light may be reflected in all directions. It thus appears that the ray has acquired different properties on different sides. From its analogy to magnetic polarity, this change is called polarization^ and the ray thus aflfected is said to be polarized. The angle at which the ray falls upon the polarizing surface is called the polarizing angle^ and diflers in different substances : for glass, it is 56° 45', while for water it is 53° 11'. 356. Polarizing by Transmission. — Light transmitted obliquely through a bundle of thin glass plates. Fig. 148, is polarized, and the same eflfect is also :prodliced by its passage through certain crys- tals. A stone, called the tourmaline^ is much used for polarizing purposes. A thin polished plate of it polarizes the light which passes through it, as in Fig. 149. If a second plate is placed parallel to the first. Fig. 150, the light passes through both ; but if the second plate is turned a quarter round. Fig. 151, the light is stopped. ' The rays of the meridian sun cannot pass through a pair of crossed tourmalines. Fig 149. Fig. 150. Fig. 148. Polarizntion by Thia Plates. The plate Fig, 151. Polarization by Tourmalines. polarizing the light is called a polarizer^ that which tests or detects it after it is changed, is termed the analyzer. turning the plate 6, fig. 144 ? How may the changed beam be reflected ? Wliat has the ray acquired ? "What is it called ? What is the polarizing angle ? 356. In what othei ways may light be polarized ? How do a pair of tourmalines affect the ray ? 152 CECEMICAL PHYSICS. 357. The wave theory affords a beautiful explanation of these phenomena. To recur to the illustration of the cord, it is obvious we can vibrate it up and down, horizontally, or in anv direction transverse to its length, Fig. 152. In common light the undulations take place in all these directions at once. It has been suggested that common light may be represented by a round rod ; polarized light by a flat one. Supposing the round rod to image to us the common ray, the Vibration in Different Planes. Fig. 153. Fig. 154. Fig. 155. Fig. 156. I]]ustrations of Planes of Vibration. radii. Fig. 153, will exhibit the system of transverse vibrations taking place in all planes. But the effect is just the same if we regard the vibrations as taking place in two planes only, at right angles to each other, as in Fig. 154. I^ow when common light is reflected in certain positions, which we have just noticed (355), one of its planes of vibration is destroyed, and the beam is polarized, its vibrations taking place all in one plane, Fig. 155. "We can now easily understand the action of the tourmaline upon light. A plate of this crystal suppresses one of the planes of vibration, and, therefore, trans- mits a polarized ray. This will pass through a second plate if it is held in such a manner that its structure coincides with the motion ; but if it is turned so as to cross the waves, the ray is obstructed. A card which readily slips through a grate when its plane coincides with the bars, will be .stopped if it is turned a quarter round, Fig. 156. Motion in a Single Plane. What IB the polarizer? The analyzer? 357. How do the undulations tak.e plnco m common liarht ? "What does figure 153 show? 154 1 What is the effect of the Ti. flection, Fig. 155 ? How does the tourmaline polarize light f How docs the figure POLARIZATION OF LIGHT. 153 Fig. 157. Polarized Rays. Fig. 158. 358. When a ray falls upon a transparent surface at a certain angle, its planes of vibration are resolved into tico^ one of which is reflected, and the other transmitted, Fig. 157 ; both are polarized, but one ray vibrates in one direction, and the other in another. 359. Double Refraction. — Some sub- stances possess the singular property of splitting the ray which passes through them, producing an effect which is known as double refraction^ Fig. 158. Iceland spar (a carbonate of lime) and many crystals possess this power ; print- ed words or a candle flame seen through them appearing double Fig. 159. The eflect is due to the molecular structure of the body. A cube of annealed glass, which usually gives only single refrac- tion, if unequally heated or subjected to pressure, divides the ray and manifests double refraction. The wave theory affirms that in double refraction the ray of common light has its two systems of undulations separated^ and that the re- sulting rays must, therefore, be polarized, and at right angles to each other. Such is the fact ; and if the beams be intercepted by a plate of tourma- line, one is stopped, and the other transmitted. 360. Circular Polarization. — Light affected in the manner de- scribed is said to be plane polarized. If the end of the cord, Fig. 152, be moved in a circle, circular waves will be formed, and so we have also circular polarization. The wave motion is similar to that which a strip of card would have if forced along two opposite grooves of a rifle barrel. Some substances rotate the ray in one direction, and some in another, while some rotate it more than others, but in each case the degree of rotation depends upon Double Refraction. Fig 159. Effect of Double Refraction. of the card and grate illustrate this? 358. How may, the ray be separated? S59. What 13 double refraction? How is it manifested? Upon what does it depend ? How does the wave theory explain it ? 360. How is circular polarization Illustrated? How do bodies differ in relation to this properU' ? How is the prop- 7* 154 CHEMICAL PHYSICS. the thickness of the medium. Solutions of sugar and most essen- tial oils turn the plane of j^olarization, and this property thus becomes a test of the nature of chemical substances, and of the strength of various solutions. Colored polarization is a branch of the subject having extreme interest, but it is too complex to bo considered here. 361. Uses of Polarized Light.— ISTot only is polarized light serviceable in the way just mentioned, but it has other applica- tions. The use of the tourmaline greatly diminishes the glare of reflected light, so that objects at the bottom of water, as rocks, shoals, or fish, may be more clearly seen ; and in the same way the pictures in a gallery may be better viewed.. It also affords a method of determining whether the light from celestial bodies is direct or reflected. In a scientific point of view polarized light has great interest as a means of revealing the inner constitution of various substances which is not detected by common light. § YI. Spectritm Analj/Qis. 362. Fraunhofer's Lines. — When the spectrum formed from a narrow line of solar light is viewed by a telescope, it is seen to be crossed by numerous dark lines of various breadths. They were discovered in 1802, by Dr. Wollaston, but excited little attention until they were rediscovered by Feauxhofer in 1815. He counted 590 from the red to the violet, and made a map of them, designating the most important by the letters of the alphabet (315). He further found that the lines did not vary in sunlight, examined at different times ; that the reflected light from the moon or from Venus gives the same distribution of them as the sun, while the spectra of the fixed stars differ from those of the sun and from each other. From these considerations Fkauxhofer drew the conclusion that the cause of the lines in the spectrum exists in the sun. 363. The Spectroscope is an instrument for observing the lines of the spectrum. Fig. 160 represents it in its simplest form. Rays of light from the sun or lamp a, enter a narrow vertical slit in the tube 7>, and passing through the prism c, are refracted and crtyused? 361. What is the advantaRO of looking at objects thro-.igh the toiir- malino? 362. What are FnAUNnoFEu's lines? What did Fraunhofer discover and Fig. 160. SPECTRUM ANALYSIS. 155 produce a spectrum. This is seen by looking into the spyglass d. Tlie more perfect instruments have a third tube situated at e. which contains a scale for accurately measuring , the spaces between the i"^ lines. To obtain a high ''^ dispersive power, hollow glass prisms filled with bisulphide of carbon are used, and several may be employed at once. When in use the whole is cov- ered, to exclude the in- terfering light.* 364. Spectra of the Eilements. — It is common- The Spectroscope. \j known that diflferent substances tinge the flame of burning bodies of various colors, as seen, for example, in the colored flames of fire- works ; but it has only lately been found that each element has, as it were, its ' mark,' or autograph of light. Each one, when burned under suitable circumstances, emits a light, which, when passed through the prism, produces a spectrum so peculiar that it may serve to identify the element from which it proceeds. The inves- tigation of the spectra of the elements was lately undertaken by KiEcnHOFF and Bunsen, of Germany, and the interesting results open to us a new method of chemical analysis. 365. How the Spectra are Produced. — To emit their peculiar light, bodies must be 'vaporized. An ordinary lamp or gas flame may produce the result, but it is most brilliant in the electric light. If a platinum wire be heated to whiteness, and its light passed through the prism, it gives a continuous spectrum ; but if it be con- * The Spectroscope of Fraunhofer was first used In this country by Dr. John W. Draper, of the University of New YOrk, more than twenty-five years ago. He modified it in 1842 in such a manner as to cast the fixed lines upon the sensitive surface of daguerreotype plates, and published a map of the results, showing four great groups of these lines beyond the limit of the violet ray, and probably doub- ling the nxmiber of lines up to that time known. About the same time Prof. Drapee published several papers on spectrum analysis, anticipating various thmgs which have been lately brought forward as new (399). conclude? 363. What is the Spectroscope? Describe it. 364 How do diflerent substances affect flames? What has been lately found? 365. In what condition -j. i. x j xi. j. the prism. If now it be turned, so that the ray/ is darTcencd^ and the wires C and Z are connected with the battery, the bar is made magnetic, it aff'ects the glass, and the ray instantly becomes visible. A chain of four polarities, electric, magnetic, luminous, and crystalline, is called into action in pro- ducing this remarkable eflect. If we add the organic polarity of the nerve of vision, we have a fifth link of the polar series. 396. Optical and Thermal Polarities. — It only remains now to state that heat is capable of being polarized like light to com- plete the mysterious chain of influences which shows that there is some common principle of action among these forces, and a deeper unity of cause than was formerly suspected. § II. Connection of the Radiant Forces. 397. The intimate connection of the radiant forces has been before referred to, but requires further illustration. Fig, 166 tallization t 394. Upon what does the power of the crystal to polarize light depend ? 895. What is the connection between magnctiem and light ? Describe the experi- ment, Fig. 165. What polarities arc here called into plaj* ? 396. What is said of I CONNECTION OF THE EADIANT FOKCES. 1G7 Tig. 166. represents the contents of a luminous beam a, spread out by the prism from & to c. The beating effects begin at 5, and extend through the space em- braced by the thermal bracket, varying in in- tensity and quality at chem- each point. The differ- Force, ences among the ther- mal rays so much re- semble those of color, Ther- ' mal { that Melloni designa- Force ted this phenomenon as the ' ideal coloration of heat.' The middle bracket of the diagram I>i^t"bution of tHe Forces of the Spectrum. gives us a scale of radiations which produces the world of colors, while the chemical bracket comprehends a wide range of chemical intensities which take effect upon different compounds in the dif- ferent spaces. The continuous lines indicate heat rays ; the broken lines, chemical rays ; and the dotted lines, luminous rays. 398. Identity of Heat and Light Motions.— It has been said that all these radiations obey precisely the same laws of movement ; but the analogies of heat with light are carried much farther than has yet been stated. Not only has the interference of heat been proved, but no change or manifestation can be impressed upon light that does not affect the associated heat in the same manner and degree. The heat ray undergoes double refraction by Iceland spar, and the two separated beams are polarized in planes at right angles to each other (359). The phenomenon of the. magnetic rotary polarization of Tieat has also been observed. These facts show beyond question that heat cannot be a material substance, but is a mode of motion of the same nature as light. 399. Dr. Draper's EJsiperiinent. — Still more conclusive on this point are the beautiful experiments of Prof. Deaper. He sub- jected various substances, under suitable circumstances for ob- servation, to the action of heat, and found the order of effects heat? What does this show? 397. "What does Fig. 166 represent? How does Melloxi regard the differences among the heat rays? What does the highest bracket in Fig. 166 include ? 398. In what additional respects does heat resemble light? 399. What is observed at the commencement of Draper's experiment? 168 CHEMICAL rUYSICS. strictly dependent upon the energy of the combustion, or source of heat. At the commencement of the action, as the body begins to be heated, the rays emitted are of the lowest refrangibihty, being but slightly refracted by a prism of rock salt. As the molecular action of combustion increases, the refrangibility and intensity of the heat rays increase. At about 1000'', the emitted rays become so energetic that they begin to act upon the eye, pro- ducing the sensation of a dull red light, and this effect takes place at the same thermometric degree with all solids. As the temper- ature ascends, the colors of the spectrum appear in the order of their refrangibility ; red, orange, yellow, green, blue, indigo, and violet. At 2130° all the colors are produced, and from their commixture the substance appears white hot ; actinic effects then appear in full intensity. As the body cools, the order of effects is reversed, and the colors disappear successively, from the violet to the red. 400. How Heat and Light Differ. — The foregoing experiment proves that all the diversified effects of the spectrum are due to one energy. Heat and light are not the same thing, but they have one cause. Heat rays differ from light rays simply as one color differs from another. It is well known that the selfsame force produces widely different effects according as it acts upon different media. The same electric current, if sent through a thin wire, pro- duces heat; if sent round a piece of iron, produces magnetism; and if through a conducting liquid, chemical decomjjosition. So, the same agent, acting upon different organs of the body, affects our consciousness differently ; — falling upon the nerves of feeling, it excites the sensation of heat ; and upon the nerves of seeing, the sensation of sight. 401. Fluorescence— Dark Rays changed to Light.— The con- version of one radiant force into another, and the influence of the body upon which it acts, are strikingly exemplified by a discovery of Prof. Stokes. He filled a glass tube with a solution of sulphate of quinine, and then moved it through the spectrum, entering at the red ray. No unusual effect was produced till it passed the extremity of the violet, and entered the region of the chemical rays, when ' a ghostly gleam of pale blue light shot across the As tho action becomes more interiBe, what follows ? What results when the hody cools ? 400. What does this experiment prove ? How docs heat differ from light ? How docs the electric current produce different effects ? How may the same agent produce different eensatioas? 401. Deecribo the experiment of Prof. Stokeb. § fiuo CONSERVATION OF FOKCE. 169 tube.' The dark cliemical force was changed to light by the quinine solution. Thus the same force acting upon one surface, produces one effect, and upon another, an opposite one. Various substances give rise to this result, as a decoction of horse chestnuts, glass stained with oxide of uranium, &c. They have the property of receiving rays of one refrangibility, and emitting them at a lower one ; and, as the colors of the spectrum are similarly low- ered in the scale of refrangibility by these substances, the phe- nomenon was first known as the degradation of light. The term* fluorescence is now applied to it, because it is very strongly manij ed by a body known asfluor spar. ^ ^^^ § III. Conservation of Force. 402. We have referred to tlio great truth that force, like mat- ter, is persistent and indestructible : its changes are but mutations from form to form ; an impulse of force can no more be created or destroyed than a particle of matter. This principle is known as the conservation of force ^ and is characterized by Dr. Faeaday as ' the highest law in physical science which our faculties permit us to perceive.' The phrase correlation of forces has been used to indicate their mutual convertibility, but both forms of expres- sion imply the same great principle. 403. History.— This is but another case, of which the history of science furnishes so many, where a great discovery belongs rather to an epoch than to an individual. In the growth of scien- tific thought, the time had come for the evolution of this prin- ciple, and accordingly several master minds seized upon it inde- pendently about the same time. Among these are Mayee and Helmholtz, of Germany, Colding, of Denmark, and Joule, Geoye, and Faraday, of England. These discoverers announced their results between 1840 and 1850; they became generally known during the next ten years, and are now established as comprehen- sive and guiding principles of science. 404. Origin of the Idea of Perpetual Motion. — To common What was the effect ? "What other substances manifest this property ? Hotv were the phenomena first known ? What are they termed now, and why ? 402. What is the conservation of force ? How is it characterized by Faraday ? What is the correlation of forces ? 403. What is said concerning its discovery ? To whom does It belong? What was done between 1840 and 1850? Between 1850 and I860? 8 170 CHEMICAL PnTSICS. observation, when a moving body comes to rest, its force is anni- hilated, and this has been generally believed. The notion that force might thus pass out of existence — from something to nothing naturally led to the corresponding idea that it might be creuted^ or come/>077i nothing. These loose conceptions of force gave rise to the fallacy of a perpetual motion — a machine that could go on forever., producing its OTvn power, vrith no external supply of force. 405. Persistence of I^Techanical Force, — This error was first detected in mechanics. It was found that machines do not create force, but only communicate, distribute, and apply that which is im- parted to them. In all cases, the force expended is exactly measured by the resistance overcome. In the case of water power, to lift a hammer of 100 pounds, 1 foot high, at least 100 pounds of water must fall through 1 foot ; or, what is the same thing, 2C0 pounds must fall through i a foot, or 50 pounds through 2 feet. If a hammer weighing 1,000 lbs. is employed, with the same driving force it wiU either be raised to only ~ the height, or tenfold the time will be required to raise it to the same height. Thus, in mechan- ics, a certain amount of power or change acting as cause produces an exactly equal amount of change as effect. 4.06. Convertibility of the Forces. — Xow what occurs here is but the consequence of a universal law which applies to all kinds of physical energy. The preceding pages have afforded numerous illustrations of the production of one force by another. Heat, we have seen, excites electricity, and through that magnet- ism, chemical action, and light. Or. if we start with magnetism, this may give rise to electricity, and this again to heat, chemical action, and light. So, chemical action produces heat, light, and electricity ; and it has been also found that a mere line of decom- jjodng particles manifests a direct magnetic influence. That elec- tricity sets the whole series in action is strikingly exemplified by electrifying tlie sulphuret of calcium, or some similar substance. At the instant of electrization, it becomes magnetic; is Jieated, and, if the electricity be sufficiently intense, it becomes luminous; that is, light is produced. It expands, therefore there is motion; and is decomposed — hence there is chemical action. 404. What is the origin of the idea of jxjrpetnal motion ? 405. What was found in regard to machines ? What is the relation between lifting a hammer and the d©3ceat of water ? 4C<;, What forces may be produced by heat ? What examples Fig. 167. CONSERVATION OF FORCE. iVl 407. ' Friction against Space.' — A new and remarkable illus- tration of the effect of resistance to motion in producing heat has been lately discovered. If a blade of copper or any conductor be moved backward and forward between the poles of an active and powerful electro- magnet, although it touches nothing, it will be resisted as if it were sawing through cheese, and become hot. A cop- per cylinder filled Magnetism resisting Motion. with alloy, and mounted between the poles, P P, Fig. 167, seems grasped by an invisible hand. If rapidly spun around by the string s s, attached to a wheel, it will grow hot, and, in three minutes, the alloy will be melted; indeed the copper cylinder may be made red hot. The heat produced is in precise proportion to the force expended in increasing the resistance. 408. Grove's Bxperiment. — In a very beautiful experiment, Mr. Geove produced the whole circle of forces by using light as the exciter. He inclosed a sensitive daguerreotype plate in a box having a glass front with a shutter over it. Between this glass and the plate was a gridirT)n of silver wire. The daguerreotype plate was connected with one extremity of a galvanometer coil, and the wire gridiron with a Bregitet's thermometer ; * this and the galvanometer being also connected, so as to form a complete circuit. "When the shutter was raised and a beam of light admit- ted, chemical action was produced in the plate ; electricity in the wires ; Tieat in Beeguet's helix ; magnetism in the coil, and motion in the galvanometer needles. 409. Forces Convertible in Definite Quantities. — These trans- mutations take place in definite quantities. It is well understood * Breguf.t's thermometer conBists of a vertical helix compounded of two rib- lioiis of diflerent metals. The slightest amount of heat, by causing unequal expan- e!on of the two metals (238), uncoils the spiral and produces motion, which is indicated hy a horizontal needle passing over a scale. are given of forces producing each other ? What ia the effect of electrifying the sulphuret of calcium? 407. What is the effect of sawing a piece of copper hack and forth between the poles of an electro-magnet? Describe the experiment, Fig. 167. 408. What is shown by Grove's experiment? 409. What is the 172 CHESUCAI* PHYSICS. that a certain amount of fuel is necessary to perform a given amount of work witli a steam engine. This means strictly that a definite quantity of the chemical action of combustion gives rise to a fixed quantity of heat, and this to a determinate quantity of mechanical eflfect. Dr. Faraday made the important discovery of the definite chemical effect of the voltaic current. He found that an equivalent of an element consumed in a battery gives rise to a definite quantity of electricity, which will produce exactly an equivalent of chemical decomposition. For example, the consumption of 32 grains of zinc in the battery, excites a current which will set free from combination 1 grain of hydrogen, 104 of lead, 103 of silver, 39 of potassium, and 31.6 of copper. These are the combining numbers of those elements, and establish a remarkable equivalency between chemical and electrical forces. 410. Atomic Heat- — The definite relation between combining numbers and specific heats is equally remarkable. For example, 28, 32, 103 are the atomic numbers of iron, copper, and lead ; but they also express the relations of these bodies to heat. They indicate the exact quantities of the metals which will be raised through equal temperature by equal sources of heat. It would take the same amount of burning alcohol to heat 23 lbs. of iron 100" that would be consimied in raising 32 lbs. of copper or 103 of lead through the same number of degrees. The correspondence is very close with the other metallic elements and with sulphur, while the atomic heat of several of the elements is douhU that of the bodies mentioned. 411. Units of Heat and Force, — To ascertain at what rate mechanical force produces heat, requires certain standards of com- parison, known as the units of heat and force. The English unit of heat is 1 lb. of water raised through 1 degree of Fahrenheit ; the unit of force is 1 avoirdupois pound falling through 1 foot of space ; or, as it is called, XhQ foot-pound. 100 lbs. of water raised through 10", would require 1,000 units of heat ; while 100 lbs. falling throngli 10 feet would produce 1,000 units of force. 412. The Mechanical Equivalent of Heat. — To Dr. Joule, of Manchester, England, is due the honor of having experimentally relation bei^reen fuel, heat, and work ? "WTjat did Faeadat find to be the rela- tioa bet-ween chemical action and electricity ? Examples. 4ia What is said of the relnliOQ between combining numbers and specific heats? Examples. 411. >Vhat are the units of heat and force? 412. Who determined the mechanical CONSERVATION OP FORCE. 1*73 demonstrated the mechanical equivalent of heat; — that is, how many units of force are equal to a unit of- heat. He agitated water, mercury, and oil successively, in suitable vessels, by means of paddles driven by falling weights, and determined the exact amount of force spent, and of heat produced. He also rubbed cast iron discs against each other, carefully measuring the force employed and the resulting heat. By varied and repeated experi- ments he found that the same expenditure of power produced the same absolute amount of heat, whatever materials were used; and that a pound weight falling through YT2 feet, or 772 lbs. fall- ing through 1 foot, and then arrested, produce sufficient heat to raise 1 lb. of water 1° ; so that the unit of heat is equal to 772 units of force. This is known as ' Joule's Law.' * 41 3. Further Links of the Dynamic Chain. — The law of equi- valence between mechanical energy and heat thus directly estab- lished is beautifully confirmed by introducing other links of force. An electric current, which, by resistance in passing through an im- perfect conductor, produces sufficient heat to raise 1 lb. of water 1 degree, sets free an amount of hydrogen which, when burned, raises exactly 1 lb. of water 1 degree. And again, the same amount of electricity will produce an attractive magnetic force by which a weight of 772 lbs. may be raised 1 foot high. 414. Significance of Joule's Law. — The establishment of the * It Is worth while here to note that the firft step in these erand views of the forces Avhich have been recently unfolded, was taken toward the close of the last century by an American, Benjamin Thompson, afterward known as Count RuMFORD. He went to Europe in the time of the revolution, and, devoting himself to scientific investigations, became the founder of the Royal Institution of Eng- land. He exploded the notion of caloric, demonstrated experimentally the con- version of mchanical force into heat, and arrived at quantitative results which, considering the roughness of his experiments, are remarkably near the establish- ed facts. He revolved a brass cannon against a steel borer by horse power for 2^ hours, and generated heat enough to raise 18f lbs. of water from 60° to 212°. He explicitly announced the view now held of the nature of heat, and wrote as fol- lows, the italics being his own : ' What is heat ? Is there any such thing as an igneous fluid ? Is there any thing that with propriety can be called caloric ? We have seen th.at a very considerable quantity of heat may be excited by the friction of two metallic surfaces, and given off in a constant stream or flux in all direc- tions without interruption or iiitermission, and without any signs of diminution or evhaitstion. In reasoning on this subject we must not forget that most remark- able circumstance, that the source of the heat generated by friction in these ex- periments appeared to be inexhaustible. It is hardly necessary to add that any thing which any insulated body or sj'stem of bodies can continue to furnish without ^wnitoiioTi, cannot possibly be a, material substance; and it appears to me to be extremely ditficult,if not quite impossible, to form any distinct idea of any thing capable of being excited and communicated in these experiments, except it be MOTION.' equivalent of heat? What is it? How was it ascertained? What is Joule's law? 413. How is the law of equivalence between mechanical energy and heat 1T4 CBEMICAI. FHYSICS. IHindple of coirelatMHi between, medunical force and heat eon- etitotes one of the most importanft erents in i^e progre^ of sci- aiee. It teaches ns that the movements we see arom^ as are not spontaneous, or ind^endeit oeeonences, hot links in the eternal chain of forces : that whoi bodies are put in motion, it is at the expense of some prefiooalj existii^ eaergy, and that when Ihey come to r^ their force is not destroyed, but lives on in other fcMmsL 'Every motion we see has its tiiermal Taloe ; and whoi it ceases, its eqairalent of heat is an inraziable result. Should the motion ci the hesTenlj bodies be arrested, it would pivduce » conflagration of the uninraiBe. 415. As the motions and masses of the planetary bodies are de&iite and determined, we can predict the exact consequence if those motions should cease. The earth is 8,000 miles in diameter, 5^ times heaTier than wat^, and mores throng its orbit at the rate of 68,000 miles an hour. Were its motion suddenly arrested it wcHdd genoate aheat equal to the combustion of 14 globes of an- thracite coal as lazge as the earth. Should it fall into the sun the diock would produce a heat equal to the combustion of 5,400 earOi- ^obes of solid coaL K the sun w^e a solid ma^ of anthracite his combustion would umintain the present heat but 5,000 years; whereas, if the planet, Ju|nta-, diould fall into ihe sun it wouM produce heat enou^ to itmifitain the solar auiadcm /or 35,000 fean (1196). 416. If a fragment of coal were taken to the. sun and burned it would give out a definite amount of heat, but if it should faSi from the earth to the sun it would produce 3,000 times more heat by its arrested motion. It has been suggested that meteoric matter £dling into the sun may be the adual cause of his heat. 417. Motion alone c uuve t U Me. — As two substances wh^i eombined chemically, produce heat, and remai» eomhinid, it may be asked, * How can the heat be regarded as converted chemical force, whfle that force is still in action?' This will be understood by referring to the case of gravity. Wh^i a lifted body fdls, it gives bade the force expended in lifting it, but gravity still attracts it to the earth with undiminished force. So with the chemical cmfinBedf 414. Wltat does tlua principle teach qb? Wbat wooSd nsolt if tlie ■MrvcBCfll of the beavcnly bodiea ohoald be amatcdt Ha. THiat if the earth's moCiaB were aaddcnly Mopped I Mentioo same fintlirr facts in thia i 41a. Whal ia said of a fncnent at eoall 417. Hov can the beat be < CONSERVATION OF FORCE. ITS atoms. They are detached, and then rush together again, giving back a force equal to that employed la separating them ; but they remain combined as the weight remains pressed to the ground. Neither gravity nor affinity are for an instant suspended; they are in constant action and are only resisted by antagonist forces : the amount of motion which results from this resistance measures the convertible force. Only force in action — which is known as living force, or vis viva — is convertible. 418. Relations of Matter and Force. — In the study of nature, questions of force are becoming more and more prominent. Tlie things to be explained are changes — active etfects— motions in ordinary matter, and the tendency is to regard matter, not as acted upon^ but as in itself inherently active. The chief use of atoms is to serve as points or vehicles of motion. Thus the study of matter resolves itself into the study of forces. Inert objects, as they appear to the eye of sense, are replaced by activities revealed to the eye of intellect. The conceptions of 'gross,' 'corrupt,' ' brute matter,' are passing avray with the prejudices of the past, and in place of a dead material world, we have a living organism of spiritual energies. 419. The principle of ihe correlation of forces is one of the most fruitful and far-reaching tbat science has established. Its introduction forms one of those intellectual epochs which change the standpoint of the philosopher, revealing old questions in new aspects, and bringing many new ones into view. It teaches with a new emphasis the great lesson of the unity of the universe, and the brotherhood of the agencies through which it is governed. And as the policy of the Divine Administration is one^ there can be no doubt that the principle applies not only to physical forces, but to all forces. Its operation has been traced, as we shall see, in the field of organization, and it opens a new and promising method of studying the various activities of human society. chemical force -while that force is etill in action ? 418. What are to be regarded in studying nature? State the chief use of atoms. What is said of force and mat- ter ? 419. Of the principle of the correlation of the forces ? PAET n. IXORGA^'IC CHEMISTRY, ORIGIN OF THE S C lEXCE — AL CHEM Y. 420. The Four Ancient Elements. — Thoughtful minds, as we have previously stated, never rest satisfied with appearances ; the J always seek for reasons and causes. This was the case in the most ancient times in regard to the ohjects of nature. They were held to he, not what they seemed, but formed of various commix- tures of four elements, fire, air, earth, and water, and for thou- sands of years the properties and changes of aU substances, animate and inanimate, were explained on this hypothesis. 421. This view was not without its philosophy. All bodies, it was said, must be either hot or cold, moist or dry. These are fundamental properties, and their various unions produce the four elements thus : Dt'yne-ss and WarmtTi and Moisture and Dryness and Warmth produce Moisture — Cold — Cold — Fiee; Air; "Water; Earth. These elements fire, air, earth, and water, may be transmuted into each other by exchange of properties. Thus, if cold is added to air it destroys the warmth and converts it into water : by the substitution of dryness for moisture, water is transformed into earth ; while, by reversing these changes, earth becomes water, and water, air. Thus, by the communication of properties, all things were supposed to be produced, the predominating element giving character to the body. prejudices are passinp a-way ? 420 How were the objects of nature regarded in ancient times ? 421. How were these elements produced ? How transmuted T ORIGIN OF THE SCIENCE — ALCHEMY. 177 422. The Foundation of Alchemy. — The leading fdea of the doctrine of the four elements was the instaMUty of the properties of matter. They were held to be like clothes which are put on and off at will — mere shifting and communicable things, the addi- tion or subtraction of which transformed one substance into another. Water was poured upon quick lime ; it disappeared and was transmuted ; that is, it lost the properties of water, and ac- quired those of stone. A small plant in a weighed portion of soil, by the addition of pure water only, grew into a vigorous shrub, increasing many pounds in weight, while the soil lost but a trifle. What more natural, therefore, than to suppose that water was ' transmuted ' into a living structure. This ancient and deeply established belief was the starting point of the labors of the al- chemists, who were the earliest chemists. 423. For centuries, philosophy had taught that the properties of matter are transferable ; ' then,' said the alchemists, 'let us trans- fer to lead and iron the properties of gold ! ' All bodies having a metallic lustre and appearance, they naturally regarded as metals ; such as preserved this lustre when exposed to fire, were called nolle, or perfect metals, while those which lost their lustre and malleability by heat were termed "base metals. The metals were, moreover, regarded as compounds consisting of opposite elements, one of which made them pure, and the other base, their rank being determined by the relative proportions of these elements. 424. Plausibility of the Idea. — iN'or were these views mere idle speculations ; they seemed strongly supported by facts. The alchemists saw that the lead ore — galena, had the metallic lustre and color of lead ; they, therefore, believed it to be a real metal. But, if heated, it gave off sulphur, while, at the same time, all its metallic properties — lustre, malleability, and fusibility — were heightened, and it became true lead, or a more perfect metal. What more reasonable than to suppose, that by the separation of a little more sulphur, it might be still further purified, and changed to silver ? And when, on further application of heat, a certain amount of silver was actually oltained from the lead, and from this silver a trace also of gold, it was not surprising that the 422. "What was the leading idea of this philosophy? "What common phenomena were interpreted as instances of transmutation ? What did the alchemists pro- pose? What bodies were called metals? How were they divided? What was their composition? 424. By what experiments and reasoning did they sustain the 8* 178 INOEGANIC CHEMISTEY. alchemist should honestly believe that he had created the three metals, and that by perfecting the operation, lie could convert all his galena into gold. 425. Again, the alchemists knew that the brilliant metal mer- cury volatilizes by heat and disappears in invisible vapor. Hence when a base metal lost its lustre in the fire, or rusted in the air, they supposed it was caused by the escape of the volatile mercury, which they regarded as the pure metallic principle. Thus, by diminishing their sulphur and increasing their mercury, the alchemists expected to finally perfect or ennoble all the base metals ; — that is, turn them into gold. The wondrous substance which should have the power of expelling the sulphur, fixing the mercury, and thus accomplishing transmutation, was universally believed in and sought for under the name of the Philosopher's Stone. 426. The alchemists, moreover, drew support for their belief from all imaginable sources. The metals were held to grow like plants, and the philosopher's stone was, therefore, the seed of gold. They said also, ' Does not fermentation transmute the sweet juices of plants into the invigorating and youth-giving water of life (aqua vitae, alcohol) ? Does not digestion transform food into blood ? ' In a decree of 1423, HE^'ET YL, of England, declared ' that the clergy should engage in the search for the philosopher's stone, for since they could change bread and Avine into the body and blood of Christ, they must also by the help of God succeed in transmuting the baser metals into gold.' 427. But the doctrine was carried much farther. If the metals might be thus transformed, what should limit the magical power of the transforming agent ! Other transmutations were equally possible, as that of weakness, pain, and disease into robust and perennial health, and thus the marvellous stone became also a universal medicine : or it might even change the decrepitude of old age back to the vigor and fire of youth, and thus become the elixir of life. 428. Motives of the Alchemists. — "Wo can now comprehend the power of the ruling motive that first drove men to investiga- tion. The love of knowledge and the desire to explore the secrets idea ? 425. What was the philosoplier's stone? 426. What other common changeB gave Bnpport to the belief? 427. What led to the search for a universal medicine and the elixir of life ? 428. Why was alchemy necessaiy ? 429. What instances are given ORIGIN OF THE SCIENCE — ALCHEMT. 179 of nature in quest of truth, were not sufficiently strong incentives in tliose days of darkness and ignorance. A mighty incitement was required that should rouse the most powerful passions of human nature, and this was providentially furnished by the belief in the philosopher's stone. Its possession would secure all the con- ditions of earthly happiness — boundless wealth, perpetual health, eternal youth ! — and for these ineffable prizes the alchemists labor- ed day and night, devising experiments, inventing processes, ran- sacking nature in a thousand directions, and putting her to every conceivable torture to wring out the wondrous secret. The ob- ject sought was not attained, but the foundations of chemistry were laid. Men working in the direction of an illusive purpose made many discoveries which they could not appreciate, but which were invaluable to the world. 429. Results of their Labors. — For example, a cobbler of Bo- logna, named Casoapjolo, who divided his time between shoe- mending and alchemy, discovered in one of his rambles a heavy stone now known as the sulphate of 'baryta. In experimenting with it he obtained, instead of gold, a most extraordinary sub- stance — ' a light magnet,' ' which absorbed the rays of the sun by day to emit them by night.' The cobbler was in ecstasy ; if the strange body could absorb the golden light of the sun, it might surely convert the base metals into gold — the sol of the alchemists. Thus was discovered the sulpliuret of barium, the first substance known to become phosphorescent by solar action. Again, an alchemist in Hamburg, named Brandt, long bafiled in the search for the philosopher's stone, reflecting one-day on the yellow color of urine, suspected that it might contain some gold-engendering principle. He began experimenting, and, after years of toil, at -length discovered, not gold, but phosphorus! In the same way, the alchemists sought for the alcaliest — the liquid that should dissolve all things; they failed, but discovered those powerful solvents — sulphuric, nitric, and muriatic acids, which have largely contributed to the arts of civilization. So the search for the elixir of life revealed many precious substances for the alleviation of suffering and the increase of human enjoyment. 430. Vitality of their Idea. — The power and persistence of the fundamental idea of the alchemists are surprising. It was only •where the search ended in discovery ? 430. "What is said of the persistence of this belief? 431. How must alchemy ho interpreted? What is its relation to chem- 180 IXOEGAXIC CUEMISTEY. near the close of the last century that the ancient belief in the transmutation of the elements was finally overthrown ; and we can now hardly conceive how deeply it was interwoven with universal thought. The great French chemist Lavoisier gave a course of public lectures with elaborate experiments to show that water could not be transmuted into earth ; whOe an Italian philos- opher went carefully into the proof that water from melted Al- pine snows was of the same nature as that from common springs and wells. 431. Alchemy, it is well known, was mixed up with magic, astrology, and various gross impostures, yet those who denounce it as utterly visionary and absurd, profoundly misread this chapter of man's mental history. Alchemy formed a natural stage in the growth of the human mind, and must be interpreted in connection with its period. It was the offspring of the old philosophy, but the parent of modern chemistry, and must always have a memor- able interest as the first experimental grapple of man with nature. CHAPTEE yn. THE ATMOSPHERIC ELEMENTS. (ORGAXOGEXS.) 432. Inorganic Chemistry is that branch of the science which treats of the properties of the chemical elements, and of the com- pounds they form, independent of the influence of life. 433. Classification of the Elements. — The simple bodies are divided into two classes, metals and metalloids^ or non-metallic elements. This general distinction is obvious and useful, but it corresponds to no clear line in nature, as the elements pass into each other gradually, two or three being ranked by some as metals, and by others as metalloids. 434. "We first consider these four remarkable elements, Oxy- gen, Hydrogen, Nitrogen, and Carbon, which have the leading Igtry? 432. What is inorganic cliemietry? 433. How are the simple bodice divided ? Why is this distinction faulty ? 434. What clemcntB do wo first con- OXYGEN. 181 share in the world's economy. Thej form the atmosphere, and are, therefore, termed the Atmospheric Group. Thej are, also, the chief constituents of the vegetable and animal world, and are hence called Organogeny — generators of organization. Is ext come Chlorine, Iodine, Bromine, and Fluorine, bodies which combine with metals forming saline compounds, of which common salt is a type, and hence called by Beezelius, Halogens., or salt formers. Sulphur, Phosphorus, Selenium, and Tellurium form a combus- tible group termed Pyrogens^ or fire producers. Lastly, Silicon ( and Boron are associated together as Hyalogens^ or glass former s. J §1. Oxygen. Symbol, 0. Equivalent^ 8. Specific Gravity, 1.1087. 435. 'We begin the study of chemical substances with that most remarkable and important element, oxygen gas. The word gas, which is applied to thin vaporous bodies like air, was first used in the seventeenth century, and is an interesting memorial of the state of mind out of which the science of chemistry grew. It had been observed that strange things occurred in certain mysterious places, as churchyards, caves, and the bottoms of mines and wells ; — there were lurid flames and sulphurous fumes, violent explosions, and sudden death. These were supposed to be the work of invisible spirits. In the operations of alchemy, ves- ;, sels would often explode with danger to those around, and this **also was attributed to the vexed and imprisoned spirits who thus avenged themselves upon their tormentors. ' The devout alche- mists, therefore, commenced their experiments with prayer, and stamped upon their vessels the mark of the holy cross ; — hence the name crucible.'' To these invisible agents, Yax Helmoxt first applied the term gas, from gaTist or geist, a ghost or spirit. The terms spirit of wine, spirit of nitre, &:c., are also significant of the superstitions of those early times. 436. Discovery of Oxygen. — This gas was discovered by Dr. PrjESTLEY, of England, in 1774, and rediscovered in the following year by the Swedish chemist, Scheele. Its discovery is also claimed by the French chemist, Lavoisiee. There was a beautiful eider? What are they called, and why? How are the remaining metalloids grouped ? 435. What is a gas ? Whence is the term derived ? Origin of the term crucible 1 436. When and by whom was oxygen discovered ? What is eaid of the 182 LN'Or.GAXIC CHEMISTRY. significance in the form of Peiestley's celebrated experiment. He submitted one of the compounds of mercury to the rays of the sun, concentrated by a burning-glass, when oxygen vras set free. It was fitting that the sun, who, by his chemical relation to oxygen, con- trols tlie destiny of the living world, should himself first summon this wonderful agent into the conscious presence of man. 437. Its Importance. — This has be.n justly pronounced the cap- ital discovery of the last century, rivalling in importance the great discovery of gravitation, by Newton, in the preceding century. It formed one of the great eras in the progress of human knowledge ; it put an end to old theories, laid the foundation of modern chemical science, and furnished the master key by which man has been enabled to open the mysteries of nature. But while the discovery of gravi- tation is unsurpassed in grandeur, that of oxygen is far more vitally linked with the course of earthly afi'airs. 438. Of its vast practical consequences, Prof. Liebig observes : ' Since the discovery of oxygen, the civilized world has under- gone a revolution in manners and customs. The knowledge of the composition of the atmosphere, of the solid crust of the earth, of water, and of their influence upon the life of plants and animals, was linked with that discovery. The successful pursuit of innumerable trades and manufactures, the profitable separation of metals from their ores, also stand in the closest connection therewith. It may well be said that the material prosperity of empires has increased manifold since the time oxygen became known, and the fortune of every individual has been augmented in proportion.' 439. Preparation. — Oxygen may be procured in many ways. To obtain a large supply, we may heat to redness black oxide of manganese in an iron bottle, fitted with a delivering tube through which the liberated gas escapes. A pound of this oxide usually yields about 1,400 cubic inches of impure gas. The chem- ical changes which take place may be thus expressed in symbols : — 3Mn02, give MnO, Mn^ O3+2O: that is, the peroxide of manganese is changed to two other com- pounds, and loses one third of its oxygen in the process. 440. By a New Process. — It has lately been found that by discovery ? How did Priestley make the discovery ? 438. "What doefl Prof. Liebig say of it ? 439. What is the common method of obtivining oxygen 1 Wbat OXTGEIT. 183 mixing nitrate of soda, NaO, NO5, with crude oxide of zinc, ZnO, in tlie proportion of 10 lbs, of the former to 20 lbs. of the latter, and heating them to redness in an iron retort, a large amount of oxygen is rapidly given off, diluted with about 40 per cent, of nitrogen. The mixed product contains about three times as much oxygen as the air, and may prove valuable for some heating and illuminating purposes, as its cost is said to be but one fifth that of oxygen by any other process. 441. From Chlorats of Potash. — It can be obtained still more pure, and very readily from ^^^ ^^^ chlorate of potash. Two or three hundred grains of the salt are placed in a glass retort, which 'is fitted tightly with a cork containing a glass tube, bent so as to dip under the shelf of the pneumatic trough, Fig. 168. The retort is heated, and the chlorate gives off more than a third of its weight of gas, an ounce furnishing nearly two gallons. This salt consists of chloric acid and potash, and in the change chloride of potassiimi is formed, the whole of the oxygen being disengaged — thus KO,C105=KCl+60. The decomposition of the chlorate is much facilitated by mixing with it one fourth its weight of oxide of copper, or black oxide of manganese thoroughly dried. These substances take no active part in the change, but seem to aid the decomposition by simple presence (catalysis). ^442. The Pneumatic Trough is a vessel by means of which gases are collected. It is usually filled with water, just under the surface of which there is a perforated shelf for the support of jars. Fig. 168. The jar, filled with water, and inverted, is lifted nearly out of the liquid, and slid upon the shelf; the water being supported above its level by atmospheric pressure (563). A con- Making Oxygen. is the chemical change? 440. Describe the new process? For what may it per- haps he used ? 441. How is it obtained from chlorate of potash ? Explain the re-action. How may the change he facilitated ? 442. Describe the pneumatic 184 INOEGANIC CHEXnSTPwT. vejing tube bends under the shelf, from "which the delivered gas rises into the jar, displacing the water. It may be then slid off, mouth downward, into a shallow vessel, containing a little water, and kept for use. In Fig. 168, the trough is represented as having glass sides which are very convenient for showing effects in the lecture room. The best form is ■^'°" ^^^' that of a cistern,. Fig. 169, so deep that jars may be conveniently in- verted in it, and with a large shelf for holding several of them. Gases may be transferred from one ves- sel to another by jjouring them upward^ as shown in Fig. 169. The vessel to be filled with gas is first filled with water, inverted, Pnenmatic TTouJh- ^^^ ^^^ ™^"*^ ^^^^^^ ^®^^^^' *^ ^^^® surface of the liquid. The mouth of the vessel containing the gas is then brought under the other by gentle inclination, and the gas rises in bubbles, displacing the water, and filling the second jar. 443. Physical Properties of Oxygen. — Oxygen is a transpa- rent, colorless, tasteless, inodorous gas, about -^ heavier than the atmosphere, and forming 23 per cent, of its weight. It refracts light the least of any known substance, and has never been con- densed into a liquid. It possesses weak magnetic properties, but loses them at a high temperature. The magnetic effect of atmo- spheric oxygen has been estimated as equal to a film of iron cov- ering the earth 2T0 of ^^ i^ch in thickness, and, as this property varies with the daily temperature, it is supposed that it may be concerned in the diurnal fluctuations of the needle. Oxygen is slightly soluble in water, 100 gallons of which absorb about 4| of the gas. 444. Its Chemical Properties.— Oxygen is perfectly neutral, possessing neither acid nor alkaline qualities ; but, though mild and bland and apparently the very type of passiveness, this substance is endowed with the most extraordinary power. Its attractions are the most intense and varied of all the elements. So remarkable is trough. How is it used ? What is the best form ? How ia pouring upward effected % 443. What are the phj'eical properties of oxygen ? Its magnetic effect in the atmosphere ? To what degree is it soluble ? 444. What are its chemical OXYGEN. 185 Fig. 170. its adaptive power that it combines mth every one of the simple bodies (except, perhaps, fluorine), giving rise to compounds of the most opposite and diverse properties. A glance at the chemical chart shows the wide range of its affinities. "With some elements it forms gases, with others liquids, and with others solids. Some it holds so slightlj that they are readily separated, and others it seizes with such power that the utmost skill of the chemist is tasked to force them asunder. Uniting with one set of bodies, it gives rise to neutral compounds, with another to corrosive acids, with another to burning alkalies. With some elements it forms nourishing food, with others deadly poisons ; mingled with an in- visible body like itself, it forms the air we breathe, and united with another twenty times lighter and rarer than itself, it pro- duces the water we drink. 445. The oxygen of the air (about one fifth of its weight), is equally diffused throughout it, and exists in a free or uncom- bined condition. All combustion in the open air is the result of the action of oxy- gen. It has a powerful affinity for the ele- ments of which fuel is composed, and unites with them with such violence as to give rise to the heat and light of our ordinary fires, as we shall see in Combustion (588.) 446. Combustion in Oxygen. — All sub- stances which burn in air, burn in pure oxy- gen with greatly increased brilliancy. If the flame of a taper. Fig. lYO, be extinguished, and a single spark remain upon the wick, on plunging it into ajar of pure oxygen, it will be re-lit and burn with extreme vividness ; and this may be repeated many times in the same vessel of gas. The combustion of a splinter of wood is brilliant, and a piece of bark charcoal glows and scintillates in the most beautiful manner. 447. Substances usually considered in- properties ? What extraordinary power does it possess ? A glance at the chart shows -what ? Give examples. 445. In what state does oxygen exist in the air ? "What is its office in combustion? 446. Describe the experiment, Fig. 170? Taper in Oxygen. Fig. 171. Combustion of Iron in Oxygen. 18G INORGANIC CHEMISTRY. Fig, 172. combustible also burn violently in oxygen. If a piece of fine iron wire (or, better still, a steel watcli spring) be coiled into a spiral and then tipped with sulphur, ignited and introduced into ajar of oxygen, it burns with dazzling brilliancy and splendid corrnsca- tions. Fig. 171. Occasionally globules of white-hot iron fuse into the glass even through an inch depth of water. 448. If a jar of oxygen be inverted over a stand upon which there is a little burning sulphur, a beautiful blue light is emitted, and the fumes produced circulate round in cu- rious rings. Fig. 172. If phosphorus be burned in the same manner, a blinding flood of light is produced, accompanied with great heat. In all these cases, the efifects are simply due to the union of oxygen with the burning body, and could we have weighed them before the experi- ment, and the products of combustion after- ward, they would have been found precisely equal. 449. Slow Oxidation.— The combustion of oxygen with the elements is called oxidation, and the products oxides. The cases of combus- tion we have been considering are examples of rapid oxidation, but oxygen frequently enters into slow combination at ordinary temperatures ^^^S^^ J and without perceptible heat, as in the rusting ^^^aaiTM^fiirrgsg^ of iron in the air. Heat, however, always ac- companies this slow combustion. An ounce of iron rusted in air, or burnt in oxygen, produces the same amount of heat, but in the former case it requires years for its development, and in the latter only as many minutes. Sometimes, under favorable circumstances, the oxidation becomes so rapid that the accumulated heat produces ignition, causing the phenomenon called spontaneous combustion. This is most liable to occur with porous substances which expose a large surface to the air. The tow or cotton used for wiping the lubricating oil Burning of Sulphur. Fig. 173. Phosphorus burn- ing in Oxygen. 447. What does Fig. 171 represent ? 448. What effects are seen -when sulphur and phosphorus are burned in oxygen? To what are they all duo? 449. What is oxidation ? What are oxides ? How docs blow difl'er from rapid combustion ? What is spontaneous combustion ? Where is it most likely to occur? 450. What OXYGEM. 187 from machinery, and then laid away in heaps, often ignites in this manner, especially if exposed to the sun. 450. Eremacausis. — The cause of decay in vegetable and ani- mal substances is the action of oxygen which breaks them up into simpler and more permanent compounds. This slow combustion is called by Liebig eremacausis. Oxidation is also the grand pro- cess by which the earth, air, and sea are purified from contamina- tions ; noxious vapors and pestilential effluvia being destroyed by a process of burning, more slow indeed, but as real as if it took place in a furnace. The ofi'ensive impurities which constantly flow into rivers, lakes, and oceans, as well as the decaying remains of the living tribes which inhabit them, are perpetually oxidized by the dissolved gas, and the water thus kept pure and sweet. For this reason waters that have become foul and putrid are purified and sweetened by exposure to the action of air. This eflfect, however, is largely dependent upon a condition of oxygen which has been but lately discovered (456). 451. Relation of Oxygen to Life. — Oxygen is the universal supporter of respiration, and, as this is the most important of the vital processes, it is hence the immediate supporter of life. From this circumstance it was first known as tital air. An animal con- fined in a given bulk of common air, having consumed its oxygen, dies. If immersed in pure oxygen, it lives much longer, but the efiect is too powerful — over-action, fever, and in a short time death, are the result. As the introduction of oxygen is the prime physiological event of animal life, the mechanism of all living beings is constructed with reference to this fact. The lungs of the higher races, the spiracula of insects, and the gills of fishes, are all adapted to the same purpose — the absorption of oxygen, either from the air or water. The animal organism is chiefly composed of combustible constituents, and we introduce this wonderful element incessantly, day and night, from birth to death, that it may perform its chemical work. The animal body is an oxidizin<: apparatus, in which the same changes occur that take place in t!)C flame, only in a lower degree, and a more regulated way. Every iB the cause of decay ? What is it called ? "What is said of oxygen as a purifier ? 451. Why was oxygen called vital air? When an animal is confined in a limited portion of air, what follows ? What if in pure oxygen ? How are all animals con- structed ? Of what are they composed ? What are they all incessantly doing ? For what purpose ? What is going on in the animal system ? Why is food taken ? 188 INORGANIC CHEMISTRY. organ, muscle, nerve, and membrane is wasted away, burnt to poisonous gases and aslies, and thrown from the system as dead and dangerous matter. If these constant losses are not repaired by the due supply of food, emaciation, decay, and finally death ensue. Starvation is thus unimpeded oxidation — slow burning to death. 452. Rate of Consumption of Oxygen. — Of the 15 lbs. of air over every square inch of the earth's surface, one fifth is oxygen. A man consumes by respiration about 2 lbs. each day ; that is, he withdraws daily all the oxygen from a column of air two thirds of an inch square, and reaching to the top of the atmosphere, or 45 miles high. In a year he removes all the oxygen over a space of 243 square inches, and in 70 years from an area 118 feet square. Six pounds of pure coal, in burning, consume 16 lbs. of oxygen; a steamship, therefore, which should burn 1,100 tons of coal in crossing the Atlantic, would consume nearly 3,000 tons of oxygen. Assuming the population of the globe 1,000,000,000, and that each individual in respiration requires but 1 lb. per day, assuming as much more for the processes of combustion ; and twice as much for the respiration of the animal kingdom, and then doubling this whole quantity for the universal and unceasing functions of decay (probably far too low an estimate), we have an aggregate of over 7,000,000 tons of oxygen withdrawn from the atmosphere each day. The oxygen in the atmosphere is computed to be about 1,178,158,000,000,000 tons, which, if separated from the air, and forming a layer of uniform density upon the earth, would be one mile deep. 45^. Oxygen in the World of Waters.— Enormous as this quantity seems, it is in reality but the bare starting point — the unit of that stupendous scale of prodigality, with which this element has been distributed in nature. Oxygen, condensed into 800 times less space, is the chief constituent of water, forming ^ of its weight. The ocean covers two thirds of the earth, and is estimated as averaging two miles in depth. Could the oxygen imprisoned in this liquid form be set free, it would be sufficient to WJiat is starvation? 452. How much oxygen docs a man consume in a day? From how much air is the oxygen removed in the siime time? In a year? In 70 years ? Wliat is the estimate concerning a steamship ? What is the wiioie amount of oxygen in tho atmospliere, and how much is consumed each day ? 453. Wliat proportion of water is oxygen? If this wero Bet free, what would it form? OXYGEN. 189 form an atmosphere around the globe, nearly a thousand miles deep, and of the same density as that now at the level of the sea! 454. Proportion in the SoKd Earth. — And these proportions are as nothing compared to the incalculable quantities of oxygen wrought into the solid fabric of the world. Of the three min- erals which form the chief mass of the earth's crust, silica, alumina, and lime, the first, and by far the most extensively dis- tributed, contains more than one half its weight of oxygen, and the other two almost one half It constitutes, also, three fourths of the weight of all animal bodies, and four fifths of that of the vegetable world. Thus, one half the ponderable matter of the earth, so far as man has explored it, is made up of a single chemical element, while the crowning wonder is, that when called up before us by the magic of chemistry, it is but an invisible gas, — no man has ever beheld it, — it seems the very type of spii'itual existence and invisible power ! 455. Office in Nature. — The part played by oxygen in the scheme of nature is imposing in the highest degree. In virtue of its boundless abundance, its diffusive nature, the vast range and strength of its attractions, and the unchangeableness of its com- binations, it would seem to have been appointed to the grand office of taking charge of all the other elements, and bringing them into an orderly and permanent system. The rocks and waters of the earth consist of materials given over to its custody. Saturated with it they are in a condition of the most perfect chemical stability. Enveloping our planet in its free condition, it manifests an irresistible passion to seize upon and possess all things. The deadly foe of life, it would destroy all organized beings, and pursuing them to the very tomb, decompose and dis- solve their structures, carrying back their elements to the quiescent mineral world. This element has, therefore, been personified as the genius of the air — an omnipresent, destructive spirit, which holds the globe in its consuming embrace ; which revels in con- flagration, and would reduce all things to ashes and rest. But the earth has not been left to the operation of its own forces. Celes- tial radiations are the antagonists of oxygen, and their agency in saving the world from its desolating influence, will be shown when we consider the subject of Physiological Chemistry (1194). 454. What proportion of the earth's crust is oxygen ? Of animal bodies ? Of vegetables? "What is said to he the croTvning ■v\'onder of all this? 455. What ia !■■ 190 INOEGANIC CHEMISTRY. Fig. 174. Making Ozone. §11. Ozone — AUotrojpic Oxygen, 456. How Produced.— "When electric sparks are passed through dry air, a peculiar odor is" perceived which has been called the ' electrical smelL' There was much doubt about the cause of it, until the investigations of Prof. Schoxbeix showed that it was an allotropic form of oxygen. From its peculiar odor, its discoverer named it ozone. Oxygen may be converted into ozone, not only by electricity, but in va- rious other ways. If a piece of phospho- rus be placed in a jar, and partially covered with water, its slow oxidation will soon produce ozone. Or, if we place a little ether in an open vessel, and then introduce into its vapor a moderately heated glass rod, Fig. 174, ozone promptly appears. If it be passed through a red-hot tube, it will be changed into com- mon oxygen, and even a temperature scarcely above that of boil- ing water robs it of all active power. 457. Properties and Test of Ozone. — Ozone seems to be oxygen greatly intensified in activity. It is armed with a new energy, and is capable of producing changes which, in its ordinary st^te, are impossible. It corrodes metals upon which before it could not act, for example, silver ; it quickly bleaches out colors, which are com- paratively permanent in the air ; it deodorizes tainted flesh, de- stroying its eflluvium instantly, and carries woody fibre in a short time through a course of decomposition, which, with common oxygen, would require years. This increased activity becomes the test of the allotropic condition. Ozone replaces iodine in its com- bination with the metals ; an effect oxygen cannot produce ; hence it decomposes iodide of potassium, setting free the iodine. Free iodine combines with starch, turning it blue; therefore, a test of ozone is made by soaking slips of paper in a mixture of starch and iodide of potassium. The slightest trace of ozono said of the oflSce of oxygen in nature ? 456. What id ozone ? How is it produced ? By what is it destroyed ? 457. What are tlic properties of ozone ? What is the tost of its presence? Give examples? What is its effect when breathed? OZONE — ALLOTEOPIC OXYGEN. 191 turns it immediately blue. Ozonized air irritates the respiratory organs, and a minute fraction of a grain kills a rabbit. 458. If some of the prepared paper be exposed for a few- minutes to the open air, it will often turn blue, which is supposed to be owing to the presence of ozone. The amount of ozone in the air is variable, and winds blowing from the sea are said to contain more of it than those which sweep over large tracts of land. Of its mode of production in nature nothing is known: it may be effected by electrical influence. It is probable that it is generated on a large scale in the atmosphere, and that it subserves a high purpose in the economy of the globe as a purifier of the air and hastener of decay. 459. Theory of Ozone. — There is much unanimity of opinion as to the explanation of ozone among those who have most ably investigated the subject, and the view has all the more interest as it is part of a general chemical doctrine which has lately become prominent. 460. It is well known that bodies wh*en in combination pre- sent characters very different from those which they exhibit in the free state. It seems, in fact, that few, if any elementary sub- stances are actually known to us in their uncombined condition, and that what we call the ' elements ' are, in reality, compounds of at least two atoms of the true element w^ith each other, the atoms being probably in different states. Thus hydrogen gas is TT) not simply H, l>^t >■ , or H2, or hydiide of hydrogen. Chlorme 01 \ gas is not CI, but (. , or chloride of chlorine ; while cyanogen is not Oi K, but p^„ > , or cyanide of cyanogen. According to this view the term atom applies to that smallest part of an element which can enter into combination, but which is not known in a separate form : while the word molecule is used to indicate the smallest quantity of any element which can exist in a separate state. For instance, E" is the atom, of nitrogen, ^ > its molecule. 458. Ho-w i3 it detected in the air? "What winds produce the greatest effect? How i3 it produced in nature? "What purpose does it subserve ? 459. What Is said of the theory of ozone ? 460. What is prohably the state of the so-called elements ? Give examples. "What then is meant by atom f "What by molecule ? 192 INOKGANIC CHEMISTRY. 461. Prof. Brodie maintains that when two particles enter into union with each otlier, it is because they are in different states — chemically positke and negative. Substances cannot com- bine with each other unless they are in this polar condition, and they retain it- in combination. Silver is not oxidized by common oxygen, because they do not become polar by contact. But if silver and oxygen are already combined with other elements, and, therefore, in opposite states, they may be made to unite with each other. Thus, in chloride of silver, the chlorine is chemically negative, and the silver chemically positive ; in oxide of potas- sium, the oxygen is chemically negative, and the potassium chem- ically positive. If these compounds are brought together, double decomposition results, and oxide of silver is formed thus : 01 Ag _ CI K K O Ag O. According to this view, ordinary free oxygen is a medium or neu- tral body, produced by atoms which are chemically positive and + — negative ; as O = O2, the molecule of free oxygen ; while ozone is polarized or decomposed oxygen. 462. Schonbein entertains similar views of the nature of ozone. He says there are two kinds or allotropic modifications of active oxygen, standing to each other in the relation of -H to — ; that is, there is a positively active and a negatively active oxygen — an ozone and antozone, which, on being brought together, neu- tralize each other into common or inactive oxygen, according to o o the equation 4-0 — = 0. / § III. Hydrogen, Sym. H. Equiv. 1. Sp. Gr. 0.0692. 463. Hydrogen was first described as an element by the Eng- lish chemist Cavendish in 1706. It is never found free in nature, but exists abundantly in combination, forming one ninth by weight of water and a considerable proportion, of all organized substances. 46L Wl1.1t does Prof. Bkodie give as the cause of chemical union ? Why will not silver unite with common oxygen? How is it in double decomposition? By thia view what is ozone? 402. What is Schonbein's view? 403. When and by whom was hydrogen discovered ? IIow is it found in nature ? What objection is made to its oamet 464. How is It generally obtained? In what ways? E.xplain Fig. 175. What HYDKOGEIi. 193 The word hydrogen signifies generator of uatei\ but it is strictly no more applicable to this element than to oxygen. 464. Preparation. — Hydrogen is generally obtained by the de- composition of water, which is effected in various ways. A cur- rent of electricity passed through water liberates both the oxygen and hydrogen, when they may be collected separately (212). Steam passed through a red-hot gun barrel is decomposed by the iron which combines with the oxygen, setting the hydrogen free. It is commonly prepared, however, by the action of dilute sul- phuric acid upon bits of zinc. The zinc is placed in a bottle and covered with water. A cork per- ■^^^- ■^'^* forated for the insertion of two tubes is then tightly fitted to the mouth of the bottle, Fig. 175. The tube for admitting the acid dips beneath the water ; the other delivers the gas, which is col- lected in jars in the same manner as oxygen. The water is decomposed by the zinc, which unites with its oxygen, forming oxide of zinc, while the hydrogen is set free and escapes. The sulphuric acid dissolves the oxide of zinc as fast Pi-eparingH^rogen. as it is formed, thus maintaining a clean metal- lic surface continually in contact with the water. The changes are represented by the following equation : Zn-l-HO + SOs = ZnO, SOa-hH. The portions first collected are not to be used, as, when mixed with air, hydrogen gas is always explosive, 455. Properties. — As thus prepared, hydrogen has a disagree- able odor arising from the impurities of the materials employed ; but pure hydrogen is a colorless, tasteless, inodorous gas, very slightly soluble in water and very inflammable. All attempts to liquefy it, either by pressure or cold, have failed. Dr. Faeaday found that it would escape through the joints of apparatus that were perfectly tight to other gases ; its atoms must therefore be comparatively much smaller. A stream of the gas directed against one side of a piece of gold leaf passes through so rapidly that it may be ignited on the other side. It is the lightest of all known substances, being 16 times lighter than oxygen and 14| times are the chemical changes ? Why are not the first portions used ? 465. What are the properties of pure hydrogen ? What is said of the smallnees of its atoms ? Of its 9 194 INOEGANIC CHEMISTRY. Fia. 176. lighter than air. This adapts it for inflating balloons, though coal gas (which contains hydrogen, and is very light) is generally used from its greater cheapness. Owing to its extreme rarity, a bell rung in hydrogen is scarcely audible ; and when it is inhaled, the voice becomes remarkably shrill. Though pure hydrogen is not poisonous, it will not support life, and an animal immersed in it soon dies from want of oxygen. 456. Combustion of Hydrogen. — There is a strong affinity be- tween oxygen and hydrogen. If these gases are mixed (2H to 10, by bulk), and then ignited, they combine with a violent explosion. Soap bubbles, if blown with this mixture from a bag, rise, and if fired with a candle, detonate like a pistol. The instantaneous con- densation of the gases produces a vacuum, and the sharp report is caused by the collision of the particles of air as they rush in to fill the void. 467. Burning bodies are commonly extinguished when plunged into hydrogen, although a jet of oxy- gen will burn in it. Oxygen and hydrogen burn quietly when brought cautiously into contact, emit- ting a feeble blue light. Three properties of hydro- gen may be shown by a very simple experiment — its Burning Hydro- levity, combustibility, and explosiveness. A jar is ^ ''■ filled with it, and though held mouth downward, it does not escape. If a lighted candle bo introduced, Fig. 176, it is extinguished, while the gases burn at the mouth of the jar. If the candle is withdrawn, it is relit by the flame at the mouth, while, if the jar is reversed, the hydrogen is mixed with a little air, and produces a slight explosion. 458. If hydrogen is generated in a jar and allowed to escape through a fine tube. Fig. 177, into the air, it burns, w^hen ignited, with a small, steady flame, giving out but little light, though producing intense heat. In all cases where hydrogen is burned with oxygen, water is the product. If a cold, dry glass is held over the ^^UiSIie^^^^ jet, it is quickly covered with a film of dew, which rapidly increases to drops of water. The gases unite to form steam, which then condenses into the liquid state. Fig. 177. use in balloons ? ITow is It related to sound ? To life ? 466. How is its affinity for oxygen shown ? What causes tbo explosion ? 467. What is taught by the exper- iment, Fig. 176? 468. What la the product when hydrogen is burned? How is HYDEOGEN. 195 Fig. i: Bingine Hj-dro- gen Flame. 469. Singing Flames. — A common experiment is to louver a glass tube over the gas jet, as represented in Fig. 1Y8, when a clear musical tone is produced. This is explained by supposing that the rapid current of air which rises through the tube interrupts the combustion, and, mingling with the hydrogen, produces a series of slight explosions in such rapid succession as to cause a continuous sound. The pitch of the sound varies vrith the size and length of the tube, and with the size of the jet ; and a series of tubes and jets may therefore be so grad- uated as to give the notes of the musical scale. A very pretty effect is produced by introducing the flame a short way into the tube, which may be held steadily in position by a clamp. No sound is emit- ted ; if now the experimenter pitches his voice to the proper note, the flame begins to sing in unison. A person twenty or thirty feet away, by thus speaking to it, causes the jet to start into song — a remarkable illustration of the effect of transmitted pulsations. 470. Combustion of Hydrogen by Condensation. — If a small quantity of the solution of the metal platinum be evaporated on a piece of writing paper, and the paper burned, the metal remains in a state of fine division known as spongy pla- tinum. K now a stream of hydrogen be directed upon a little ball of platinum sponge, it instantly becomes red hot, and remains so as long as the current lasts. The metal contains atmospheric oxygen condensed within its pores, and by con- densing the hydrogen also, their particles are brought within the range of affinity, and com- bination takes place with the production of heat. Dobeeeixee's lamp is a contrivance for employ- ing this principle. The outer glass vessel, «, Fig. 179, contains dilute sulphuric acid. The inner glass vessel, /, is without a bottom, and Dobereiser's Lamp, has suspended within it a piece of zinc. TThen the acid comes in contact with the zinc, hydrogen is immediately generated, and fills the vessel, /, pushing down the sulphuric acid so that it is no this shown? 469. How are mtisical tones produced? "What is the explanation? How is the effect of transmitted pulsations illustrated? 470. How may combus- FiG. 17 196 iiroisGAZEHr < :HK : Mf^fir g . On jet of gsB^ IS lit eseagws^ iiitrilQi» «pa& Hae jihrthniim at, i^ w] made red boL Ai tlie gu k«i«s tibe ireagel,/; tOae aod agna inn craitad; viidii liie zmc^ mere l^dragm K DcsAs and odiots lias'e eondd be comAeasteA into a fiqmi : mefiallie MttBiffeL Bat it ]i» 1k^ placed bf tibe attroi^eait anii-inet viih tibe ddoraos dcmwita are : and as in^ortant as vilh IftMise liaiee r^ud it as a neoiial cr In §r\r. Gin/^aund8€f (PrsiSaaade « 473. Of It need be said tfcai - bastorr upcz. : _;.: _ :^. .....--_/ .- — :^reBtlie ,) alL It is Ifte imsoet abwandant sob- 39 as if flie v^boie scbcme ofna- - ^Ttias. TtTTMng to solid ice» or -'iS cifarm inful%e tbe Toy : -tt:i fbe ocean^ cocdensed ■/j* sea^ it 43. I For vtai fa l{r- OXYGEN AXD HTDEOGEN WATER. 197 its circulation the grand processes of the world. Composing four fifths the weight of the vegetable kingdom and three fourths that of the animal, it is the first condition of all organization, and by innumerable transformations and decompositions, it is essential to the continuance of organic life. 474. isTor is it less indispensable in the laboratory of the chemist. It is the ready. Invaluable medium of a -p^^ jgo. thousand operations ; it is involved in nearly every chemical process ; in fact, the chemistry of water, theoretical and practical, might fitly be talcen to represent the present state of the science. 475. Composition. — "Water is a compound of 8 parts by weight of oxygen to 1 of hydrygen, or Decomposing Wa- by bulk 1 of oxygen to 2 of hydrogen. Its com- position may be proved in many ways, but one of the most simple is to throw a little metallic potas- sium upon its surface. The metal instantly decom- poses it, seizing upon the oxygen with such vio- lence as to produce vivid combustion, Fig. 180 ; the water seems set on fire. 476. But the composition of water may be shown in the most perfect manner by sending an electric current through a vessel of it. Fig. 181, as already __ described (212). The gases are set free in the ex- act proportions given above, and if mixed together and ignited, they combine with a loud and sharp Elect ro-Decom- explosion, the product .being pure water. The position, composition of water is thus demonstrated by both analysis and synthesis. An arrangement for exploding gases to determine the amount of their condensation is called a Eudiometer. 477. Water is not only decomposed as stated above, but also by sodium, iron, zinc, and many other metals ; in fact, they are classified according to their degrees of power in this respect. In numberless operations of chemistry, the elements of water are separated and reunited, and the same thing is going on perpetually in vegetable and animal organisms. drogen remarkable ? 472. How must we regard it as a neutral body ? 473. How are the properties of water related to the scheme of nature ? 474. How does the chemist regard it? 475. What is its composition 1 What simple experiment proves it ? 476. What does Fig. 181 represent ? What is an Eudiometer I 477. How 198 INORGANIC CHEillSTIiy. 478. General Properties. — Water, as is well known, is a trans- parent, tasteless, inodorous liquid. It is but very slightly con- densible ; according to Kegnatjlt, being compressed 1-47 millionth of its bulk for each atmosphere of pressure (563), and is perfectly elastic, as it regains its full dimensions when the pressure is removed. It evaporates at all temperatures ; boils at 212°, and freezes at 32°. At 60°, a cubic inch of pure water weighs 252.456 grains, which is 815 times the weight of an equal bulk of air. An imperial gallon weighs 70,000 grains, or just 10 lbs. The American standard gallon weighs 58,972 grains of pure dis- tilled water at the maximum density (484). In thin sheets, water is colorless, but when viewed in thick masses, it has a decided tint. Light passed through fifteen feet of pure distilled water, emerges of a bright and delicate blue-green, am^ by augmenting the thickness, the color is deepened. Natural waters are discol- ored by various impurities in different places. 479. Water Purified by Freezing. — During freezing, the sub- stances dissolved in water are expelled ; hence the ice of sea FiQ. 182. water (as is well known to sailors), when melted, be- comes fresh water. For the ^ V/^ same reason, water from ^^:^|^<^>>o melted ice contains no air, ^ ^, nor gas — fish cannot live in '"^^-^ it. Ice melted under spirits of turpentine, where no air can get access to it, produces water so cohesive, that it can ^c^^0'^o>^ ^^4^^^ (fViv^ ^® heated far beyond its boil- s >' kA> ^-Ory^ r f s\/ ? ^S/2 V^ ( yV^^ ^°^ point, when it bursts into ^-^ ^^^' \r ^^ explosive ebullition (288). Forms of Ice Flowers. (Tyndall.) ^qq^ Liquid Flowers in Ice. — When a ray from the sun or an electric lamp is made to pass through a block of pure ice, a portion of the heat is arrested, and must, of course, produce change. As it cannot warm the ice, it melts it. But the ice particles return to the liquid state in definite order, and, upon examining it with a magnifier, the ice is seen to be filled with beautiful flower-like figures, such as are shown in ore metala claasifled ? What is everywhere ocourring ? 478, What are the general OXYGEN AND HYDEOGEX — WATER. 199 Fig. 182. These consist of water, but as the liquid formed cannot quite fill the space of the melted ice (484), there occurs a little vacuum, which looks like a globule of burnished silver in the centre of the flower.* 481. Snow Crystals. — The aqueous vapor of the atmosphere, condensed by cold in winter, or at great heights in summer, assumes the most beautiful crystalline forms — those of snow flakes. Perfect snow flakes are six-sided stars, which shoot out an infinity of delicate needles, all diverging from each other at an angle of 60°. These frozen blossoms, as they have been aptly termed, are seen in an endless variety of most exquisite forms, a few of which are shown in Fig. 183. 482. The great specific heat of water (274) is a powerful agency in controlling climate. It is four times greater than that of air; that is, a pound of water in cooling one degree, would warm four pounds of air one degree. But as water is 770 times heavier than air, it is obvious that a cubic foot of water in cooling one degree, would warm four times 770 cubic feet of air, or 3,080 cubic feet one degree. Hence, the vast amount of heat stored up in oceans and lakes, being gradually imparted to the air during winter, modifies the severity of the cold, and explains the fact that island winters are less severe than those of continents or inland places. 483. Tlie very stability of nature seems to depend upon this quality of the earth's aqueous element. If the watery masses of * Prof. Tyndall, Trlio 'has-advan'^ed f lese ■beant'fnl researches, thus eloquently discour~es on this propertj' of ice : ' To many pei-sons here present, this block of ice nnayseem of no more interest acdheautj- thanahlockof glise , but, in theesdmation of science, it hears the same relation to'ghiss that an oratorio of Handel does to the cries of a market plnce. The ice is music, tl e glass is no'se ; the ice s order, the glass is confusion. In the glass, molecular forces constitute an inextricaMy entan- gled skein ; in the ice they are -woven to a symmetric web, the miracu'ous textures of which I will now try to reveal. — How shall I dissect this ce? In the soar beam, — or, failing that, in the beam of an electr'c lamp, we have an anatomist competent to perform this work. It shall pull the crystal edifice to j ieces, by accurat-iy reversng the order of its architecture. Silently and symmetrically tl e crystalliz'ng force builds up the atoms, s lently and symmetricnlly the electric beam will take theui down ! Probahly few here present were aware of the beauty latent in a block of common ice. And < nly think of lavsh ratnre operating thiTS throug'-ont the world 1 Every atom of so;id ice which shei ts the frozen lakes of the North has been fi^ed according to th s law. Nature ' lays her beam in muse,' and it is the funcfon of science to purify our organs, so as to enable us to hear the strain.' (Ttxdall's Lectures on Heat.) properties of water? 479. What is the effect of freezing Tipon water? What is said of water from melted ice ? 480. How are liquid flowers produced in ice ? 481. What are snow flakes ? Describe them. 482. How does the great specific heat 200 INORGANIC CHEillSTKY. 7S a It Forms of Snow Fiakes. (Glaisheb.) the globe, and that large proportion of it contained in our own bodies, lost and acquired heat as promptly as mercury, the varia- tions in temperature would be inconceivably more rapid than now ; the inconstant seas would freeze and thaw with the great- est facility, while the slightest changes of weather would send their fatal undulations through all living systems. But now the large amount of heat accumulated in bodies of water during sum- mer, is given out at a slow and measured rate ; the climate is tempered, and the transitions from heat to cold are gradual and moderated. 484. Unequal Expansion of Water.— Tliis liquid contracts as its temperature falls from the boiling point till it reaches 39°, when it remains stationary for a time. It then begins to expand, and in cooling through 7 degrees to the freezing point, it reaches the same volume it had at 48°. The point of greatest contraction is called the maximum density of water. This fact is of great importance in nature. If water continued to contract as it cooled, it would be denser and heavier at the freezing point, and, conse- quently, sink. Lakes and rivers would then begin to freeze at the of water affect climate? 483. "SVhat is said of the importance of this quality tn nature? 484. What is said of the uucqual expansion of water ? If water contin- OXYGEN AND HYDROGEN WATER. 201 bottom first, and, in the course of the winter, would become solid masses of ice ; while the length of time required to thaw them would greatly prolong the cold season. But as the surface stratum of water approaches the freezing point and freezes, it expands, and, becoming lighter, floats, and thus the coldest water and ice are kept at the surface, where, as they are almost perfect non- conductors of heat, they protect the mass of water below from the cold above. In freezing, water expands with such power as to burst the strongest vessels. Percolating through the minute crevices and fissures of rocks in summer, it freezes in winter, and expands with a force which breaks the solid stones, crumbling them into soil fit for the support of vegetable life. 485. The property of water by which these eflfects are pro- duced, has been regarded as exceptional, but this is not the case. Bismuth and other metals in the act of solidifying also expand. Nor is this effect, probably, any real exception to the law of expansion by heat. Another force is evidently brought into play which mashs the regular action of the heat. Clay contracts by heat, but it is due to the shrinkage from loss of water, which happens to be greater than the expansion produced by heat. So there can be little question that the play of crystalline forces interferes with the result. As liquids crystallize, on approaching solidification, there is a rearrangement of the molecules with enlarged interspaces and consequent expansion. 486. Atomic Constitution of Water. — There are various rea- sons for supposing that the composition of water, instead of being HO, is H2O2. Firsts the heat-absorbing power of aqueous vapor is high, like that of the complex- atom ed gases (346). Second^ when H and O combine to form water, there is so great a loss of mobility as to suggest that the atoms, instead of uniting in simple pairs, combine into higher and more sluggishly moving groups. Thirds the excessive amount of heat that results from their com- bination, suggests a great amount of atomic motion ; and, fourthly^ this idea is countenanced by the behavior of water in expanding by cold, as it approaches the freezing point, as just noticed. 487. Water of Combination. — Water unites with bodies with three degrees of intensity. In its closest union it forms com- ned to contract as it cooled, what would follow ? What instances are given of the force with which water expands in freezing ? 485. Is this propertj' of water excep- tional! What is the probable explanation? 486. What reasons are given for sup- 9* B^^ 202 rS'OEGAXIC CH£MISTEY. pounds known as hydrates, where the water is so intimately combined that a heat approaching to redness is required to sepa- rate it; slaked lime is such a hydrate. Secondly, it combines with crystalline bodies in definite proportions. This is termed the uater of crystallization, to distinguish it from the icater of hydra- tion. The formula for crystallized sulphate of magnesia, for example, represents both states of combined water : MgO, SO3, H0 + 6Aq. Thirdly, water combines in all proportions, in a still more loose, chemico-mechanical way, as a solvent. 488. Water is perfectly neutral, manifesting neither acid nor basic properties, and yet it is capable of playing the part of both. It combines powerfully with acids, and, acting the part of a base, is known as lasic water. Hydrated sulphuric acid, HO, SO3, is thus a sulphate of water, nor can the water be expelled from the combination, except by a more powerful base. It combines also with bases, potash for example, playing the part of an acid, and can only be displaced by a stronger acid. 439. Solvent Power of Water.— Its perfect neutrality enables it to take on the properties of other substances, and hence with equal facility it becomes sweet, sour, salt, asfringent, bitter, or poisonous, according as the bodies it dissolves possess these prop- erties. This solvent power is variable upon different substances, and at different temperatures. Thus, a pound of cold water will dissolve two pounds of sugar, while it will only take up two ounces of common salt, two and a half of alum, and eight grains of lime. Heat generally increases the solvent power of water ; thus boiling water wiU dissolve 17 times as much saltpetre as ice water. But there are exceptions to this rule ; ice water dissolves twice as much lime as boiling water. 490. The Water Atmosphere. — Water dissolves gases in the most diverse proportion, taking up 700 times its bulk of ammonia ; its own bulk of carbonic acid ; ■^-- its bulk of oxygen, and still less of nitrogen. There is, therefore, an atmosphere diffused through- out all natural waters, which is riclier in oxygen than common posing that the atomic constitution of water is H, O,? 4S7. What are hydrates f What ia meant by water of crj'stallization ? How else does water combine with bodiea? 488. What is baaic water? Examples. WTien does it play the part of an acid ? 489. How does the solrent power of water vary ? What ia the eflcct of heat OXYGEN AND HYDROGEN — WATEE. 203 air, and hence better adapted for supporting the life of aquatic animals. The gases absorbed by water give it a brisk, agree- able flavor, and if driven off by boiling, the liquid becomes insipid. 491. Different Kinds of Water, — As water dissolves a little of nearly every substance with which it comes in contact, it is never found perfectly pure in nature. Hence there are many varieties of natural water, as spring, river, rain, sea, and mineral water. Rain faUing in the country, away from habitations, and after a protracted wet season, is the purest water nature produces, as it is contaminated only with the natural gases of the atmo- sphere. In cities, as it falls through the air, it absorbs the various organic and gaseous impurities with which it comes in contact, and, flowing over the roofs of houses, carries down the deposited soot, dnst, &c. Water from melted snow is purer than rain water, as it descends through the air in a solid form, incapable of absorb- ing gases. 492. Mineral Impurities. — Rain water, which has filtered through the porous soil and strata of the earth, dissolves such portion of its soluble materials as it meets with, and carries theni down to the lower levels, so that they may ultimately collect in the sea. The amount of mineral water thus dissolved is remark- ably various. The water of the River Loka in Sweden, which flows over insoluble granite, contains only ~ of a grain of mineral matter in an imperial gallon. Common well-waters and spring and mineral waters contain ^rom 5 to 60 grains per gallon. Sea water contains 2,600 grains to the gallon; and that from some parts of the Dead Sea or the Great Salt Lake of Utah, as much as 20,000 grs. to the gallon — 400,000 times as much as the Loka water. 493. The mineral impurities of well and spring water are chiefly lime, magnesia, soda, and oxide of iron, combined with carbonic and sulphuric acids, which form carbonates, sulphates, and common salt. The most universal ingredients, however, are carbonate and sulphate of lime. Carbonate of lime, or limestone, upon it ? 490. Haw much ammonia does water dissolve ? How is it with other gases? "What is the effect of the dissolved gases upon the water? 491. "WTiy are there so many varieties of natural water ? How do different localities cause waters to differ? "What are the purest waters? 492. How does water obtain its mineral impurities? Crive instances of their variable quantity. 493. What are the chief 2 0-4 IXORGANIC CHEMISTRY. is not soluble in pure water, but dissolves in water containing free carbonic acid, -wbicli is present in most natural waters. 494. Sea Water. — Tbe solid constituents of sea water amount to about H per cent, of its weigbt, or nearly half an ounce to tbe ponnd. Its saltness is a necessary result of tbe circulation of matter. Rivers flow into tbe ocean witb tbeir saline constituents, wbile tbe water wbicb evaporates from tbe sea is nearly pure. Tbe ocean, tberefore, is tbe great depository of everytbing tbat water can dissolve and carry down from tbe surface of tbe conti- nents, and, as tbere is no cbannel for tbeir escape, tbey constantly accumulate. Tbe continuance of tbis process for numberless ages accounts for tbe present saline condition of tbe oceans. In tbe same way all lakes into wbicb rivers flow, and wbicb bave no outlet, are salt lakes. Tbe Dead Sea, for example, is situated at tbe bottom of an immense basin — several bundred feet lower tban tbe Mediterranean, and bas no outlet Tbe Jordan flows into it, bearing To grains of saline matter to tbe gallon, and tbere is no escape but by evaporation ; bence its excessive saltness. 495. Mineral Waters are usually tbose of springs wbicb con- •tain a considerable amount of various saline matters. Tbose abounding in salts of iron are called chalybeate, or ferruginous waters. If tbe waters are brisk and sparkling, carbonic acid gas is present, and tbey are termed carbonated, or acidulous waters. If the active ingredient be sulpbur, tbe spring is called sul- phurous. Tbe water of tbe celebrated Congress Spring, at Sara- toga, contains tbe following ingredients in a gallon : Chloride of Sodium, .... . 390,246 grains. Iodide of Sodinm, and Bromide of Polassium, . 6,000 " Carbonate of Soda, .... 9,213 " Carbonate of Magnesia, 100,941 " Carbonate of Lime, .... . 103,416 " Carbonate of Iron, ..... 1,000 «' Silex and Alumina, .... 1,036 « Total solid contents. 611,552 grains. 496. Hard Water. — TTatcr derives its quality of hardness from tbe presence of salts of lime, cbiefly tbe sulpbates ; a single grain of wbicb will convert 2,000 grains of soft into bard water. "Wben mineral ingredients of -well and spring water ? To what dooa carbonate of lime »we itB eolobility? 494. Explain the cause of the ealine condition of the ocean. OXYGEIT AND HYDKOGEN — WATE 205 common soap is put into hard water, instead of dissolving in it, as it does in soft water', it curdles, or is decomposed, and a new soap is formed wliicli contains lime instead of potash or soda. This new soap will not dissolve, and may often be seen on the surface in the form of a greasy scum. It adheres to whatever is washed in it, and gives to the touch the unpleasant sensation of hardness. To test this quahty of water, dissolve a little soap in alcohol, and place a few drops of it in the water to be examined. If it remains clear, the water is perfectly soft ; if it becomes turbid or opaque, the water is ranked as hard. Hard water is a less perfect solvent than soft water, and is, therefore, inferior to it for cuhnary purposes. 497. Organic Impurities of Water. — From the dust and insects of the air, drainage of residences, the decay of leaves and animals, and a multitude of other causes, water is liable to organic con- taminations. These may be either mechanically suspended, or dissolved in it. Water containing dissolved organic matter is highly dangerous to health, and should be carefully avoided. Solution of permanganate of potash is decomposed and decolor- ized by it, and, therefore, water which discharges the color from much of this reagent should be viewed with suspicion. 498. Organic impurities, if suspended mechanically in water, are noxious, but they are generally attended by a correction more or less efficient in the shape of animalculse, which feed upon them. These living inhabitants are never found in freshly fallen rain water, caught at a distance from houses, nor in spring or well water; but they more or less abound in cistern and reservoir, marsh, pond, and river waters. The Eiver Thames has been found to contain 23 different species of these organisms. They make a frightful appearance when exhibited by the oxy-hydrogen microscope, but they perform an invaluable service in consuming dead organic matter, and reducing it to its ultimate and innocent constituents — carbonic acid, water and ammonia. 499. Purification of Water. — The best method of purifying water is by distillation; to render it perfectly pure, it must be redistilled at a low temperature, in silver vessels. By filtration through sand, crushed charcoal, or other closely porous media, How is it with the Dead Sea ? 495. How are mineral waters classed ? 496. What is hard water ? Its action on soap ? Its test ? 497. Whence come its organic Impurities? Why should such water he avoided? How may we test iti 206 INOKGA^'lC CHEMISTRY. water mav be deprived of suspended impurities, and of all living beings. Boiling kills all animals and vegetables, expels gases, and precipitates carbonate of lime, which constitutes the fur or crust often seen lining tea kettles and boilers. Alum (two or three grains to the quart) cleanses muddy or turbid water. It is de- composed by carbonate of lime, and the alumina set free carries down the impurities mechanically ; but the sulphuric acid of the alum, combining with the lime, forms sulphate of lime, and makes the water harder than before. The alkalies, potash or soda, soften water by decomposing and precipitating the earthy salts. 500. Peroxide of Hydrogen, HO2, has been produced by the chemist, and called oxidated water. It is a transparent, sirupy liquid, with an astringent taste, a decided odor, and possesses active bleaching properties. It is very unstable in composition ; the mere contact of various substances causing it to decompose explosively. § Y. Nitrogen and its Compounds. X I T Pw O G E N . Syrn. K. Equiv. 14. Sp. gr. 0.971. 501. This gas was discovered by Rutheefobd in 1772. It is very extensively diffused in nature, forming about four fifths of the atmosphere, in which it plays the important part of diluting the oxygen, and adapting it to the conditions of life. It is an im- portant element of the vegetable kingdom, entering in consider- able quantity into many of its compounds. It is supplied to plants by ammonia and nitric acid, and exerts a very favorable influence upon the growth of vegetation. Our food is largely composed of nitrogen, and it forms 16 per cent, of the tissues of the animal body. It is an essential part of many powerful medicines, as quinine and morphia, and of some of the most dangerous poisons, as strychnine and prussic acid. Nitrogen is not found in any of the mineral formations of the earth's crust, except in some varieties of coal. 502. Preparation. — It is called nitrogen, generator of nitre, 498. What U Baid of animalcula in water? 499. Mention the various modes of cleansing water ? 500. "What are the composition and properties of peroxide of hydrogen ? 501. "WTiat are the proportion and oflaice of nitrogen in the atmo- NITKOGEN AND ITS COMPOUNDS. 20V Fig. 184. Fig. 185. because it exists in that substance, and may be produced from it. It is most commonly prepared by withdrawing oxygen from a por- tion of air. A small bit of phosphorus is placed in a little cup and floated on the water in a pneu- matic trough. It is then set on fire and a jar placed over it, as in Fig. 184. The phosphorus takes the oxygen, forming phosphoric acid, which fills the jar with ii white vapor ; but this is soon absorbed by the water, and nitrogen alone is left, the water rising to occupy the space of the van- Preparing Nitrogen, ished oxygen. One hundred volumes of water dissolve about two and a half volumes of nitrogen. 503. Properties. — IsTitrogen is a transparent gas without taste or color, and has never been condensed into a liquid. It is remark- able for chemical inertness, and can only be combined with other substances by indirect means. Owing to its weak afiinity for the other elements, it forms very unstable compounds, and on the slightest occasion escapes from them in its gaseous form. It sup- ports neither combustion nor respiration : a lighted taper in- troduced into it is immediately quenched, and animals placed in it quickly die, not from its poisonous action, but from lack of oxygen. Hence it was for- merly called azote^ or life de- stroyer. ^ 504. Nitrous Oxide, ]S"0. — Oxygen combines with nitro- gen to form a series of five compounds, remarkable as illustrating in a perfect manner the law of multiple combination. (See Chart.) The first in the series is protoxide of nitrogen, or nitrous oxide, called also, from its pecu- liar effects when respired, laughing gas, or exhilarating gas. It is prepared from nitrate of ammonia by moderately heating this salt in a flask. The gas escapes through a tube, and is collected in jars over water. Fig. 185. Four ounces of the salt produce one cubic sphere? How is It supplied to plants ? Where else is it found ? 502. Why is it called nitrogen? How is it prepared? 503. What are its properties ? Why are ite compounds unstable ? Why was it called azote ? 504. For what is the nitrogen Making Nitrous Oxide. 208 INOIIGANIC CHEMISTKY. foot of the gas. It should be allowed to stand for some time over water, to absorb any nitrous acid that may chance to be formed. The chemical change may be thus represented : HaNHO, NO5 = 4H0 + 2N0. One atom of nitrate of ammonia (or nitrate of oxide of ammonium), yields four atoms of water and two of protoxide of nitrogen. 505. Properties.— Nitrous oxide is a neutral, colorless, trans- parent gas, of a slightly sweetish taste, and very soluble in water — cold water absorbing about three fourths of its volume. Sp. gr. 1.527. It is an active supporter of combustion, relighting a glow- ing candle when plunged into it, and intensifying the combustion of phosphorus almost equally with pure oxygen. A pressure of 50 atmospheres at 45° condenses it into a clear liquid which boils at about 1126°, and may be frozen at about— 150°. 506. When breathed this gas produces a transient intoxication, attended sometimes with an irresistible propensity to laughter, and at others with a tendency to muscular exertion, individuals being variously affected according to temperament. The gas should be pure, and even then the experiment is not a safe one where there is an over-active circulation in the brain. These effects may undoubtedly be ascribed to an augmented oxidation, produced in the system by the gas. "When taken into the lungs, being far more soluble than oxygen, it is rapidly dissolved in the blood, and quickly diffused throughout the body. 507. Nitric Oxide NO2, {Deutoxide of Nitrogen), is formed by the action of nitric acid upon slips of copper in a similar way to the production of hydrogen, Fig. 175. A portion of the nitric acid is decomposed, giving up three atoms of its oxygen to the copper, IsTOq escaping. The oxide of copper thus produced unites with a portion of the nitric acid, forming nitrate of copper which gives a blue color to the solution. 3Cu + 4NO5 = 3CuO, NO5 + NOa. Nitric oxide is a colorless, irrespirable gp that has not been lique- fied, and which extinguishes most burning bodies. Brought in con- tact with air, it acquires oxygen and produces red fumes of NO4. and oxygen group of compounds remarkable? How is nitrous oxide prepared? Explain the chemical changes. 505. State its properties. 506. AVhat are its efl'ects when breathed ? How is this action accounted for ? 507. What is the com- position of nitric oxide ? How is it produced ? Give tho equation. What are its NITROGEN AND ITS COMPOUNDS. 209 508. Nitrous Acid, IsTOa, formerly Hyponitrous Acid. — ll\\\^ is a thin mobile liquid, producing an orange-red vapor, and form- ing a class of salts known as tlie nitrites. . Hyponiiric Acid (Pe- roxide of Nitrogen)^ NO4, is an orange-colored fluid with a cherry- red vapor. It boils at 82°, and solidifies at 8°. 509. Nitric Acid (Aqua Fortis), NO5, is a colorless liquid (sp. gr. 1.521) with an intensely sour taste. It smokes when exposed to the air, and is partially decomposed by the action of light, hy- ponitrio acid be- -eig.uq. ing formed, which gives it a yellow color. It unites with bases form- ing an extensive series of salts — the nitrates — which are all soluble in water; hence, ni- tric acid cannot be precipitated. It is obtained by decomposition of its salts. Equal weights of nitrate of potash and sulphuric acid are placed in a glass retort, which is supplied with a receiver B, kept cool by cold water flowing over it from the tube z, by means of a netting, Fig. 186. With the application of heat, the nitrate is decomposed, and the acid distils over into the receiver. The change is thus shown : (KO, N05) + 2(HO, SO3) = (KO, HO, 2S03) + (HO, NO5). That is, one atom of nitrate of potash and two of sulphuric acid furnish one atom of bi-sulphate of potash and one of hydrated ni- tric acid. 510. Nitric acid stains the skin, nails, and many other animal substances of a yellow color, and is therefore used to produce yel- low patterns upon woollen fabrics. It is also employed for etching on copper, for assaying or testing metals, and as a solvent for tin by dyers and calico printers. In consequence of its large propor- tion of oxygen, it corrodes the metals with great energy, and Preparing Nitric Acid. properties? 508. What is nitrous acid? Hyponitric acid? 509. What are the properties and compo.sition of nitric acid ? Why can it not be precipitated ? How is it obtained? Explain the reaction. 510. For what is it used? What of its 210 INORGANIC CHEMISTRY. hence is the most pow^ful of oxidizing agents. It ignites pow- dered charcoal and oil of turpentine, and oxidizes phosphorus so rapidly as to produce an explosion. 511. This acid is found in nature in combination with potash, soda, or lime in the soil of various localities ; with potash it con- stitutes the saltpetre of commerce. It occurs also in small quantity in rain water, especially after thunder storms, and is supposed by some to be produced by lightning, which com- bines the gaseous nitrogen and oxygen. Others suppose it to be produced hy the oxidation of ammonia which always exists in the air. 512. Ammonia, HsN {Ammonium, H4N*). This is the only known compound of nitrogen and hydrogen. They do not combine when mixed or heated, but only in the nascent state. Ammonia is therefore a constant product of the decomposition of organic substances which contain nitrogen. It is produced from the destructive distillation of horns and hoofs, which are rich in nitrogen, but the chief source of commercial ammonia is the liquor of the gas works. The gas is conveniently obtained by heating equal parts of newly slaked lime and dry powdered sal ammoniac Fig 187 ^^ ^ glass. The lime takes the chlorohydric acid, forming chloride of calcium, while gaseous ammonia is set free. The change may be thus shown : HslN", UCl + CaO = CaCl, HO + H3N. The gas may be collected in jars in the pneumatic trongl), but it must be over mercury, as water ab- sorbs it. It is, however, more convenient to pro- cure it by what is called the method of displacement. The gas generated in the lower vessel, Tig. 187, be- sLiii ii]!/' ^"o lighter than the air, accumulates in the upper Prodncii g Am portion of the inverted jar, displacing the air and ex- "''^""'- polling it downward. 513. Properties. — Ammonia is a colorless, irrespirable gas of a pungent, caustic taste, lighter than air (sp. gr. 0.59), and possesses strong alkaline properties, changing vegetable blues to green and yellows to brown. It neutralizes acids and forms definite salts. oxidizing power? 511. IIow is it found in nature ? 512. What is the composition of ammonia? When only is it formed ? What is its chief source < How may it be obtained ? How best oollccled ? 613. What are the properties of ammonia ? * See page 288. NITROGEN AND ITS COMPOUNDS. 211 Fig, 188. Testing Ammonia. Being a gas, it is called volatile alkali, to distinguish it from those which are fixed or solid. From the circumstance that it was derived from the horns of harts, it was called spirits of harts- liorn. Ammonia is recognized by its odor. If a rod dipped in chlorohydric acid be brought near a source of ammonia, a white cloud is produced by the union of the two in visible gases, Fig. 188. 514. Ammonia is used medicinally in various ways. It is administered internally as a stimulant, and applied externally as a counter irritant. Mixed with olive oil, it forms volatile liniment. It is the best antidote to prussic acid, but in large doses it is poisonous. It is of many uses to the chemist. 515. Solution of Ammonia. — Ammonia is rap- idly absorbed by water which will take up 700 times its volume of it, forming the aqua-ammonia of commerce. This is best prepared by evolving the gas from slaked lime and sal ammoniac, and passing it through a series of bottles. In making solutions of the absorbable gases several difficulties have to be guarded against. The action in the evolution flask is liable to various interruptions, while the water present in the apparatus rapidly absorbs the gas. This creates a partial vacuum, and the consequence is, that the water in the jar flows back into the flask, thus putting an end to the process ; also, if the gas is generated faster than it is ab- sorbed, there arises the danger of an explosion, unless there is a free outlet to the apparatus. These dangers are obviated by the arrangement known as Woulfe's Bottles, Fig. 189. 516. The flask in which the gas is generated is provided with a safety tube which serves both as a means of introducing a liquid and as a protection against the above mentioned accidents. "When the liquid is poured in, a Fig. 189. "Woclfe's Bottles. 614. What are some of its uses ? 515. Explain the process for forming aqua-ammo- nia? What trouble is to be guarded against ? 516. Bywhat means? 517. What 212 INORGANIC CHEMISTRY. portion of it is retained in the bend of the tube, acting there as a valve to prevent the access of air to the flask. Each bottle has an upright tube in the middle neck which acts as a safety tube, allowing the air in case of a vacuum to pass in, or the liquid to flow out, if the pressure of the gas becomes too great. The other tubes serve to connect the bottles with the flask and with each other. 517. Cold saturated aqua ammonia is lighter than water, boils at 130°, and freezes at — 40°. It is a colorless liquid with a pungent odor and strong alkaline taste. It is much used by chemists, and aflfords the best means of procuring ammonia, as the gas is readily expelled by heat. §yi. Carbon. 6 Sym, C. Equiv. f. Sp, Gr. (Diamond), 3.52. (Vapor)^ 0.829. 518. Carbon, from the Latin carlo, coal, is the name applied to the solid element of organic bodies with which we are familiar in the various forms of charcoal, mineral coal, lampblack, &c. It is on every account a most interesting element, and plays a very important part in the operations of nature. Carbon has three well marked allotropio forms — the diamond, graphite, and char- coal. 519. Properties of the Diamond. — The purest form of carbon is the diamond— 2l very extraordinary kind of matter. It is a crys- tal the most brilliant and precious of gems, and the hardest body known. Diamonds are found in the earth in various places, usually in the form of rounded pebbles covered with a brownish crust. Of their mode of production nothing whatever is known. The finest specimens are perfectly colorless and limpid, but they are also of various colors. The diamond has a very high re- fractive and dispersive power by which it flashes the most varied and vivid colors of light. It is a non-conductor of electricity, and resists the action of all known chemical substances. 520. Combustibility. — The diamond remains unchanged at a very high degree of heat ; but if made red-hot and carried into pure oxygen, it burns with a steady glow, like a little star, tho are the properties of aqua ammonia? 518. What is carbon ? What are its Ihreo allotropic forms t &19. What is tho diamond ? How is it formed ? Its properties ? CAEBON. 213 Fig. 190. prodnct being carbonic acid. From its high refractive power, re- sembling in this respect organic substances (315), Newtox pre- dicted that it would prove not only combustible, but of organic origin. This view seems to be supported by the fact that the crystal on being burned leaves a trace of ash in the form of a cel- lular net work. In the flame of the voltaic arc, the diamond be- comes white-hot, swells up, and is converted into a black coke- like mass. 521. Uses. — Being a powerful refractor of hght, the diamond has been sometimes employed for the lenses of microscopes, but it is chiefly used for cutting glass and drilling apertures through other gems. Diamond crystals are in the form of a regular octohedron, but their faces are often a little convex, as shown in the Fig. 190. Only the natural faces of the crystal can be used for cutting glass, and the curved edges are best. Angles obtained by cleavage pro- duce only a rough scratch, like quartz. Though the fissure made by the diamond in cutting glass is not more than the o^^ of an inch in depth, yet with a slight pressure on each side or a blow, it determines the course of the fracture through a very thick plate. 522. Diamond Cutting. — Diamonds are so hard ttat they can only be cut or wrought by means of diamond powder. This fine dust is mixed with olive oil and spread upon a plate which is made to revolve two or three thou- sand times in a minute. The gem is soldered to an arm and pressed against the revolving disc by means of weights. In this way the diamond is cut into three forms — the trilUant^ the rose, and the table, as shown by the ac- companying figures. The brilliant is cut vrith a plane or table at the top, surrounded with facets. It is also cut with facets below, which are made at such angles to those above that the most perfect reflection is produced. The brilliant, there- Diamond Crystal. Fig. 191. Brilliant. Fig. 192. Rose Diamond. Fig. 193. Table Diamond. 520. How may it be burned? "Why has it been regarded as of vegetable origin? 621. Its uses ? In cutting glass ? 522. How are diamonds cut ? Describe the bril- 2U INORGANIC CHEMISTEY. Fig. 194. fore, has the finest effect, but requires the Scacrifice of the largest portion of the gem. A brilliant cut diamond is esteemed equal in value to a rough one of twice the "weight, added to the cost of working it. The rose is cut into a hemispherical form with a pointed summit and 24 facets : it is flat beneath. Table diamonds are made from thinner specimens. 523. Value of Diamonds. — The w^eight and value of diamonds are reckoned by carats of four grains each. The average value of a perfectly cut diamond weighing one carat is $40. They increase in value, not in proportion to their weight, but to the square of their weight. The value of three dia- monds weighing 1, 2, and 3 carats is as 1, 4, and 9. This rate of valuation, how- ever, only applies to those of moderate size, as it would render the price of large diamonds so enormous as to place them beyond the reach of even the wealthiest. 524. Of the largest, or, first class dia- monds, there are but few ; perhaps less than a score altogether. These have been so coveted' by princes as to have figured quite prominently in oriental politics and diplomacy. Fig. 194 represents a diamond brought from India by a Mr. Pitt, and sold Fig. 195. Fig- ^96. The Pitt Diamond. Koh-i-noor, before cutting (side view). to the Regent of France for $500,000. and weighs 136 carats. After cutting {tipper face). It is of a light blue color, The dotted line shows its form before cut- liant. The rose. The table. 523. IIow are the ■weight and value of diamonds egtimated? 624, What does Fig: 194 represent? 195? What is its history? CARBON. 215 ting. One of the largest diamonds is the Koh-i-noor (mountain of light), which came from India, and, according to native legends, was found 4,000 years ago. It has been in the hands of various families, and its possession has cost many murders and wars. It now belongs to the British crown. Tig. 195 represents the gem in its original shape and size. It was only surface-cut in the rose form. In 1852 it was cut into a brilliant weighing 162^ carats, after one third of it was removed. Fig. 196 represents its size and upper face. It took thirty-eight days to cut it, by steam, the operator working twelve hours a day without cessation. 525. Graphite or Plumbago is another allotropic form of carbon. It is found in beds in the earth, and crystallizes in six- sided plates of a metallic lustre, resembling lead ; hence it is called hlack lead. Like the diamond, it resists the action of intense heat, and is useful to the chemist in making crucibles. It is friable, has an unctuous feel, and is used instead of oil, to relieve the friction of machinery. Being unaffected by the weather, it forms a valuable coating to protect iron-work from rust ; and, as it resists heat, it is fitted for stove polish. It is, however, often adulterated largely with lampblack, which may be detected by heating the suspected sample to redness, when the lampblack burns away. Its most important use is in the manufac- ture of pencils. The powder being subjected to enormous pres- sure coheres into blocks, and is then sawed into thin slices, and again into small bars, which are placed in grooved cedar sticks for use. Though apparently so soft, the particles of graphite are ex- tremely hard, and soon wear out the steel saws with which it is cut. 526. Graphite, unlike diamond, may be artificially produced. "When cast-iron, which has been melted in contact with an excess of carbon, is allowed to cool slowly, the carbon crystallizes out in the form of graphite. In the manufacture of coal gas, a layer of pure dense carbon, having a metallic lustre, is deposited upon the hottest parts of the retort. It is called gas carton^ and seems a modification of graphite, if, indeed, it be not itself an allotropic form of carbon. Beodie has produced a compound called graphic acid (O22H4O10), in which he considers the graphite as retaining its allotropic state, and he hence terms it grapJion^ with the symbol Gr. 625. What Is graphite ? Its properties and uses ? 526. How is it artificially pro- 21€ mS iaa fiitiMJini ag SEtaoBi SSi. ivtr daea it aitt b Be: CAUBON. 21V degree ; the spongy sort least. ' A cubic inch of charcoal,' says LiEBiG, 'must have, at the least computation, a surface of 100 square feet.' 531. The power of porous bodies to condense gases (72), in the case of carbon is of great importance. Charcoal absorbs noxious gases and offensive odors; and, when crushed, foul water filtered through it, and tainted meat packed in it, are restored to sweetness. The charcoal from bones (bone black) is superior to wood charcoal for purifying purposes. It is extensively used in sugar refineries to decolorize syrups. Vinegars, wines, &c., are bleached in the same way. 532. Charcoal not an Antiseptic. — Charcoal is a powerful de- odorizer, and disinfectant, but it is not an antiseptic, or preventer of change, as has been supposed. In fact, it is an accelerator of decomposition. It was formerly thought that charcoal acted by simply sponging up the deleterious gases, and retaining them in its pores ; but it has been lately shown that, by means of its con- densing power, it is a powerful agent of destructive change. The condensed oxygen seizes upon the other gases pfesent, and oxidizing them, forms new products. It thus changes ammonia to nitric acid, and sulphuretted hydrogen- to sulphuric acid. The body of a dead animal packed in charcoal, emits no odor, but instead of being preserved, its decomposition is much hastened. This property has been made medically available in the form of charcoal poultice, to corrode away sloughing and gangrenous flesh in ma- lignant wounds and sores. The dark, carbonaceous matter of soils is thus not only a magazine for storing gases, but a most potent agency of chemical change. 533. Dr. Stenhouse, who in 1855 first drew attention to the septic pow- ers of charcoal, has contrived ven- tilating arrangements in which the air of dwellings is filtered through it. He also invented a breath filter or respira- Give examples. How much surface has a cutic inch ? 531. How is this property utilized ? What kinds are test ? For what else is it used ? 532. "What is its rela- tion to decay ? How is this proved ? Its use in medicine and in soils ? 533. What 10 Fig. 197. Breath Filter. 218 INORGANIC CHEinSTKY. tor consisting of a hollow case of wire gauze fitted to tlie face, as shown in Fig. 197. It is filled with coarsely powdered charcoal, •which strains the air of its impurities before it enters the lungs. 534. Lampblack is a modification of charcoal. It is the soot deposited from the burning of pitchy and tarry combustibles. The smoke is conducted through long horizontal flues terminating in chambers hung with sacking, upon which the lampblack is de- posited. It is used for making printers' ink and black paint. In combustibility it stands at the opposite extreme from the diamond, and so great is the surface it exposes to oxygen, that it has been known to take fire spontaneously in the open air. 535. As in the diamond and graphite, the particles of the other varieties of carbon are extremely hard. Those of charcoal when rubbed between two plates of glass scratch it easily ; while pieces of anthracite coal have been used to cut glass like the diamond. The mineral coals found in the earth are forms of carbon, and will be noticed in Organic Chemistry. § YII. Compounds of Carhon and Oxygen. C A R B X I C ACID. {Carbonic Anhydride^ Fixed Air, Mephitic Air, Choice Damp of Miners.) Sym. COi. Equiv. 22. Sp. gr. 1,529. 536. All the forms of carbon when burned in the air unite with oxygen and form carbonic acid. This is a colorless gas with a slightly sour taste and about half as heavy again as air. It exists abundantly in the mineral crust of the globe, in the fixed or solid state, and was hence at first called fixed air. It exists also in a free condition in the atmosphere, where it is indispensable to the vegetable kingdom. It was first described by Dr. Black in 1757, and is remarkable as the first gas discovered. 537. Preparation. — Carbonic acid exists in limestone to the extent of 44 per cent, of its Jarfornnkin? weight, and is most conveniently obtained by the action of an acid upon powdered marble, are Dr. Bteshouse'8 inventions? 534. What is lampblack? How obtained ? Its propertios ? 535. A^Tiat i.^ said of the properties of carbon ? 536. What is carbonic COMPOUNDS OF CARBON AND OXYGEN. 219 or chalk. Any strong acid vrill answer the purpose, but chloro- hydric is the best. The powdered mineral is placed in a jar and covered with water. A little dilute acid is then poured down through the tube, Fig. 198 ; effervescence immediately takes place, and the gas escapes through the bent tube. It may be collected over water in the pneumatic trough, or, as it is heavier than the air, it will quickly displace it in an open vessel. The change is thus shown : CaO, CO2 + HCl = CaCl, HO + CO2. A cubic inch of marble will yield four gallons of the gas. 538. Test. — Carbonic acid combines with bases forming a class of salts known as the carbonates. Its test is solution of lime or clear lime water. "When exposed to carbonic acid, it turns milky from" the formation of insoluble carbonate of lime. Thus, if we expose a saucer of lime water to the air, in a short time its surface is covered with a thin film of carbonate of hme, proving that there is carbonic acid in the atmosphere. If we blow through a tube into a jar of lime water, it quickly becomes turbid from the same cause, thus showing that there is carbonic acid in the expired breath. 539. It Extinguishes Fire.— To prove this, and to show also that it is heavier than air, we have but to place a lighted taper in a jar, and pour in carbonic acid from an- ther vessel. Fig. 199 ; the invisible current pron:^)tly puts out the light. It has been proposed to employ this gas on a large scale to extinguish fires. Some pulverized chalk and a bottle of acid are placed in a suitably constructed vessel, and when wanted for use, the bottle is crushed and the gas set free in large quantities. Such is the construction of the ^ Fire Anni- Jiilator: This property of carbonic acid Yo^xx\u^ Carbonic AcTd. has been made available in extinguishing the accidental fires of coal mines. In one case an English mine had been on fire 30 years and burned a 9-foot seam of coal over an area of 26 acres, defying aU efforts to quench it. Eight million acid? AYhy -w^as it called fixed air? When and "by w'horn -was it discovered? 537. How do we obtain it? "What are the changes? 538. What are carbonates? What is its test ? How do we prove its presence in the air ? How in the breath ? 639. What is shown by Fig. 199? What is the fire annihilator? Where has tins 220 INORGANIC CHEMISTRY. cubic feet of the gas were poured into it for three "weeks day and night, and the fire was thus completely extinguished. 540. Poisoning by Carbonic Acid. — When respired, carbonic acid is fatal to life. If pure, it produces spasm of the glottis, closes the air passages, and thus kills suddenly by suffocation. When diluted with even ten times its bulk of air, and taken into the system, it acts as a narcotic poison, gradually producing stupor, insensibility, and death. This gas often accumulates at the bottom of wells, and in cellars, stilling those who may un- warily descend. To test its presence in such cases, it is common to lower a lighted candle into the suspected place, and if it is not extinguished, the air may be breathed safely for a short time. If the light goes out, it will be necessary before descending to let down dry-slaked lime, or pans of freshly burned charcoal to absorb the gas. 541. Sources of Carbonic Acid.— It is produced throughout nature on an immense scale. Oxygen of the air seizing upon the carbon of the organic world, whether in rapid burning, or slow decay, gives rise to this gas. The combustion of a bushel of char- coal produces 2,500 gallons of CO2. It is produced by fermenta- tion, and the slow decomposition of organic bodies, and also by the respiration of the entire animal world. Each adult man exhales about 140 gallons per day. It is also produced by decom- positions and oxidations in the earth, and comes up with the waters which rise to the surface. It escapes in vast quantities from volcanoes, both active and extinct. Rising to the surface, often more rapidly than it is diffused into the air, it accumulates in invisible pools and ponds. Through the celebrated Grotto del Cane, in Italy, a man may walk unharmed, but a dog with its nos- trils near the earth, is suffocated on entering. The poison valley of Java is a lake of carbonic acid, filled with the bleached bones of dead animals. 542. Effervescent Drinks.— The sparkling appearance and lively, pungent taste of various mineral waters are due to the car- bonic acid they contain. Water absorbs nearly its own volume of carbonic acid, but by means of a forcing-pump it may be made to receive a much larger proportion. ' Soda water ' is ordinarily property teen Buccesefully used ? 540. How does it act when breathed ? What precautions should be taken? 541, What are the sources of carbonic acid? M2 What is said of CO3 in mineral waters? In soda water? In fermented COMPOUNDS OF CARBON AND HTDEOGEN. 221 onlj water charged with carbonic acid. Being overcharged, when the pressure is withdrawn, the gas escapes with violent effer- vescence. The effect is the same whether the carbonic acid is forced into the water from without, or generated in a tight vessel, as is the case with fermented liq[uors ; the gas gradually formed is dissolved bj the water, and, escaping when the cork is with- drawn, produces the fuming and briskness of the liquor. 543. Its Liquid and Solid Forms. — Under a pressure of 36 atmospheres at 32°, carbonic acid shrinks into a colorless, limpid liquid lighter than water. When this pressure is removed, it does not suddenly resume its gaseous state, but evaporates with such rapidity, that one portion absorbs heat from another, and freezes it to a white solid, like dry snow. This solid carbonic acid wastes away but slowly, and may be handled, though if it rests long upon the flesh, it disorganizes it like red-hot iron. 544. Unlike other acids, the carbonic does not unite with water to form a definite hydrate. As a gas, a liquid, and a solid, it is anhydrous, and the later school of chemists designates it con- stantly as carhonic anhydride. 545. Carbonic Oxide, CO, is a colorless, almost inodorous gas, which burns with a pale, blue flame. It is produced by burning carbon with an imperfect supply of air, and its formation may be observed in an open coal fire. At the lower part of the grate, where the air is abundant, carbonic acid is formed. As it ascends into the hot mass above, it loses half of its oxygen, becoming car- bonic oxide. The liberated oxygen combining with the carbon of the fuel, also produces an equal quantity of the gas. As the car- bonic oxide thus formed, rises to the surface of the fire, it burns to carbonic acid with a lambent, blue flame. This gas may be ob- tained pure and in great quantities by heating one part of prussiate of potash with ten of sulphuric acid, in a capacious retort. Car- bonic oxide when respired, is still more deadly than carbonic acid. § YIII. Compounds of Carbon and Hydrogen. 546. These form an extensive and important group, but they belong chiefly to Organic Chemistry ; two only will be here men- tioned. These substances have long been regarded as only of drinks? 543. How ie solid carbonic acid obtained ? 544. Why is it called carbonic anhydride ? 545. "When is carbonic oxide formed ? Its properties when respired I 222 INOKGAJS^C CHEMISTRY. organic origin, but Berthelot has lately succeeded in producing them by the direct union of their elements. 547. Light Carburetted Hydrogen, CJI4. — {Marsh Gas, Fire Damp.) This is a colorless, inodorous, tasteless, inflammable gas, which burns with a yellow, luminous flame. If diluted with air, it is not injurious to life. It may be produced by heating in a glass flask, a mixture of two parts of Fig. 200. acetate of soda, three parts of caustic potash, and three of quicklime. It is called marsh gas, because it is a prod- uct of the decomposition of vegetal J matter contained in the mud of stag- nant pools. It may be collected by inverting a jar and funnel in the water, and stirring the mud beneath. Fig. 200, when the gas rises into the jar in bub- bles. It is often disengaged in large quantities in coal mines: mixed with Procuring Marsh Gas. ,^ • •, i ^ • i the air it becomes explosive, and con- stitutes the fatal fire damp. If the air is more than six times or less than fourteen times the bulk of the gas, the mixture explodes violently. Carbonic acid is produced by the combustion, so that those who are not killed by the burning or shock, are generally suffocated by the choke damp. 548. In some places, this gas rises from the earth in such quan- tities, as to be utilized for purposes of illumination ; as in the village of Fredonia, N. Y. In the deep wells sunk for brine and mineral oil, it often rises in such quantity as to be employed for driving the pumping engines, or for evaporating the liquids. 549. defiant Gas, C4H4 {Ethyline). — This gas may be pre- pared by mixing strong alcohol with five or six times its weight, of sulphuric acid in a retort, and applying heat. It is colorless, tasteless, nearly as heavy as air, with a marked odor, very inflam- mable, and burns with a bright and intensely luminous flame. "When mixed with air, it is explosive, and derives its name (oil- former) from the circumstance of its forming an oily compound with chlorine. It was liquefied by Faraday under great pressure. 648. Are the hydro-carhons always of organic origin ? 547. "What is light car- buretted hydrogen? How is it obtained? Why called marsh gas? "What is Are damp? 548. Other natural sources? 649. What are the composition and COMPOUNDS OF CAEBON AND HYDKOGEN. 223 It is decomposed by electric sparks, depositing half its carbon, and forming light carburetted hydrogen. 550. Illuminating Gas consists chiefly of the foregoing com- pounds of hydrogen and carbon. It is commonly produced from bituminous coal, by heating it in cast iron retorts, which are fixed in furnaces, and heated to redness by an external fire. Each re- tort receives a charge of 100 to 150 lbs. ©f coal every six hours, and in large gas works, several hundreds of them are kept at work day and night. At a moderate heat, tar and oil are pro- duced (957), but at a high temperature, gases are formed in large quantities. The principal products of this destructive distillation are a thick, black liquid, known as coal-tar^ steam, various corn- pounds of ammonia, sulphide of hydrogen, carbonic acid, light, carburetted hydrogen, defiant gas, and a solid, friable, carbona-^ ceous mass known as colce. 551. How Purified. — This heterogeneous mixture is whoUy unfit for illuminating purposes till purified. The liquid and gaseous products, as they are set free, flow out from the retort, through a tube into a receiver, called the Jiydraulic main., in which the tar and am- moniacal liquor are to a great extent sepa- rated from the gaseous products. But being hot, they stiU retain various matters in a vaporous state, which would be deposited, and clog the gas pipes ; these are still farther F'G 211. The GaBometer. separated by passing through the condenser., which consists of iron tubes surrounded by cold water. The gas is then passed through a mixture of lime and water (milk of lime), or through layers of properties of oleliant gas ? 550. What is illiimiDating gas ? How is it produced f "What other products result? 551. How is the gas purified? Describe the gas- 224 INORGA^slC CffEVnSTET. damp slaked lime, •which absorbs the carbonic acid and sulphide of hvdrogen. It is then sometimes freely washed with -vrater, which removes all its ammonia, when it is transmitted to a large storing vessel called the gasometer^ Fig. 201. This is an immense sheet iron cylinder, open at bottom, and closed at top, which floats in a cistern of water. Two pipes open into the interior, one to deliver the purified gas which fills and raises the gasome- ter, and the other, which is connected with service pipes, to con- vey it away for consumption. The gasometer is balanced by weights which are so graduated as to compress the gas sufficiently to force it through the pipes to the faithest points desired. 552. Composition- — This is variable, but it mainly consists of olefiant gas. light carburetted hydrogen, carbonic oxide, vapors of benzole and naphtha (958), with free nitrogen and hydrogen. Its value depends upon the proportion of olefiant gas, which is the chief light-producing compound. This is obtained first, and diminishes as the charge of coals is protracted, the poorer light- giving materials increasing. In one case, the gas first delivered contained 13 per cent, of olefiant gas. 82 of carburetted hydrogen, 3.2 of carbonic oxide, and 1.3 of nitrogen. After 10 hours, it yielded 20 parts carburetted hydrogen, 10 parts of carbonic oxide, 60 of hydrogen, and 10 of nitrogen. 553. Gas from other Sources. — Crude, refnse oil wliich is unfit for burning, is sometimes converted into gas by being made to trickle into a retort, containing firagments of coke, or bricks heated to redness. It contains no sulphur products, needs no purification, and is rich in olefiant gas. Resin, by being melted and treated in a similar way, yields a superior gas. An excellent gas is also produced from the distillation of wood ; but in point of economy, none of these sources can compete with coal. A pound of coal yields from three to four cubic feet of gas ; a pound of oil, 15 ; of tar, 12 ; and of resin, 10. 554. Extent of its Use. — Lluminating gas has come into use entirely within the present century. It was first employed in Lon- don, in 1802. and its use has extended until nearly 500.000 tons of coal are consumed in a year by the establishments of that city alone, cmeter. 552. Upon what does the value of the gas depend ? How do the propor- tions differ at different stages of the distillation? 553. "Wliat is eaid of gas from other BubstancesT Its economy? 554. When and -where -waa illaminating gii« first employed ? How much is now consumed there ? What thought is Boggested^ COMPOUNDS OP CAEBON AND NITKOGEN. 225 producing 5,000,000,000 cubic feet of gas, and yielding an amount of light which would be equal to that given by ten thousand mil- lion tallow candles, six to the pound. How wonderful that sun- beams absorbed by vegetation in the primordial ages of the earth, and buried in its depths as vegetable fossils through immeasurable eras of time, until system upon system of slowly formed rocks have been piled above, should come forth at last, at the disenchanting touch of science, and turn the night of civilized man into day ! § IX. Compounds of Carbon and Nitrogen, 555. Cyanogen — Symbol^ Cy. — Carbon and nitrogen do not unite directly ; but if animal matter, such as hides, horns, parings of hoofs, &c., be heated in a covered iron pot with carbonate of potash and iron filings, the carbon and nitrogen, as they are set free, combine to form a compound known as cyanogen, NO2. This substance was discovered by Gay Lussac in 1814, and is remark- able as being the first chemical compound known to play the part of an element. Cyanogen proved to be an electro-positive body which would combine directly with the metals, like chlorine. It was, therefore, called a compound radicle, and represented by the symbol, Cy. The doctrine of compound radicles has been since ex- tensively carried out (910). "When produced as above, cyanogen unites with potassium and iron, producing the salt ferro-cyanide of potassium, KoFeCya, HO, which forms the splen- did yellow crystals of commerce. The word Fig. 202. cyanogen signifies Hue producer, as it is a con- stituent of the pigment prussian blue. 556. Cyanogen is a transparent, colorless gas, poisonous if respired, and with a strong odor. It is very soluble in water, and hence must be collected in the pneumatic trough over mercury. It is reduced to a colorless, limpid liquid by a pressure of four atmospheres, and freezes into a transparent crystalline solid at 30". It may be best procured in small quantities by heating a little cyanide of mercury in a test tube. Fig. 202. The salt is decomposed, the gas escapes, Burning Cyanogen. 555. How may carbon and hydrogen be made to unite ? For what is cyanogen remarkable ? What doctrine has this led to ? Meaning of the word ? 556. "VVliat 10* 226 TSOBGA^SIC CHKVTSTET. and when ignited, bums with a beantifol blue flame edged with purple. Para/^yanogen is an insoluble isomeride of cvanogen. 557. Cyasohydiic Acid, HCt. {Hydrocyanic Acid^ Prv^ie Acid.) — This is a colorless, transparent liquid, and so xolatile that a drop on the end of a glass rod in the air solidifies bj its own evaporation. It mav be obtained br decomposing a salt of cyano- gen with strong acid, and then distilling it, the vapor having the odor of peach blossoms. It is one of the most insidiortS and deadly poisons, a few drops producing death in a few seconds. This acid is obtained hj distillation of the kernels of bitter almonds and various finits, and also from the leaves of the laurel, peach, &c. 558. Cyanogen forms several comi>ounds with oxygen, the best known of which are cyanic acid and fulminic acid. The lat- ter combines with metals, forming fulminates which are violently explosive. HydraUd cyanic acid is a volatile and highly corrosive fluid, which cannot be brought into contact with water without beiug instantly decomposed. Cyanuric acid is crystalline, soluble in water, and forms salts with metallic oxides. Cyamdidc is a white. i>orcelain-like substance, absolutely insoluble in water. Yet these bodies are all isomeric and may be converted into each other without loss or addition of constituents. CHAPTEPw Tin. THE ATM0 5PHEEE. § I. Its P?iyskal Properties. 659. This is the thin, gseeous medium which surrounds the globe. It is considered under a twofold aspect — in its mass, or as manifesting physical properties, and in its composition or chemical relations. The first belongs properly to Xatural Philosophy, but it will be useful to recall a few points which are of constant appli- are the propertieeof cyanogen? How is it obtained I &5'. What ie cyarjohydric acid? How obtained? lis propertiee? Where is it found? 558. What com- poarde doe» cyanogen form -snth oiygen ? What are fnlmiiiate§ ! Properties of bydrated cyanic acid? Cyanuric acid? Cyame^idel What ie eaid of these pub- I ? 559. Under -what arpecls may the air be oonndered? 500 What is tht THE ATMOSPHEEE — ITS CHEMICAL PROPERTIES. 227 cation. We have deferred the subject to this place, that the stu- dent may be familiar with the atmospheric constituents. 560. Weight of Air — It was first ^ „„, Fig. 203. discovered about 200 years ago that air, like all other forms of matter, has weight. If a light flask be exhausted, and then carefuUy counterpoised at the bal- ance, when the air is let in, it will be- come heavier and sink, Fig. 203. A cubic foot of air weighs 538 grains, or something more than an ounce, and a room 40 feet square and 18 feet high contains about a ton. 561. The Air Pump is an instrument for exhausting air from a tight vessel. In Fig. 204, P represents a piston which works air-tight in the cylinder c, and v v are valves of leather or silk which guard openings in the piston and the bottom of the cylinder. As the piston descends, v opens while v' shuts. The tube t connects the pump with the receiver F, which loses a portion of its air at each stroke. The receiver is a large glass vessel ground flat at the bottom so as to rest air-tight upon y.,\ , the pump plate. As its tf^^ name implies, it receives ^ objects for experiment. 562. Elasticity.— If a small tight india rubber ball containing air be placed within the re- ceiver and exhaustion take place, the air within will be dilated with force, and the ball will expand to several times its original size, as shown by the dotted "Weighing Air. Fig. 204. Fig. 205. P Expansion of Air. Air Pump, the ball returns to its original dimensions. At first the air with- out and within the ball press against each other equally^ but weight of the air ? 561. Explain Fig. 204 What is the receiver ? 562, Describe 228 INORGANIC CUEMISTRY. Fig. 20 n Ilecciver. Fig. 207. wlien the outside pressure is Avithdrawn, the air within, by its inherent elasticity, expands into a larger bulk. Air exists in the pores of bodies, and by taking off the pressure, it expands and escapes. This is shown in Fig. 206, which represents an egg in a glass of water under an exhausted receiver. 563. Atmospheric Pressure. — As the air has weight, it of course exerts pressure upon surround- ing objects. This pressure is in all directions, down- ward, sidewise, and upward. If a wine glass be filled with water, a card placed upon it, and then inverted, the upward pressure of the air supports the liquid in the glass, Fig. 207. This pressure is considerable. If the hand be placed over the open end of a glass and the air be exhausted, it will be held as if with a powerful weight. The weight, or pressure of the air at the level of the sea, is 15 lbs. on every square inch ; this is, therefore, called an atmosjyhere : 30 lbs. would be two atmospheres, and 1,500 lbs. a hundred atmospheres. 564. The weight of the air is not the same at all times. Winds and storms keep it in motion, condensing and rarefying it, and thus affecting its pressure. There are also tides in it as in the ocean — great at- mospheric waves, which sweep over the earth, and with these movements, the pressure con- stantly varies. 565. The Barometer. — Variations of pres- sure are measured by the 'barometer. To mako this instrument, a glass tube is taken, 83 or 34 inches long, closed at one end, and filled with quicksilver. It is then closed with the finger, as shown in Fig. 208, inverted, and its open end plunged into a vessel of quicksilver, o. The mer- cury then falls from Tc to n, leaving a vacuum, or place of no pressure in the upper end of the tube. The weight of the air pressing upon the mercury in the cup, supports the mercurial col- umn 30 inches high. But as the atmospheric Barometer. the experiment, Fig. 205. What property of the air is Lcro ebown? What ia CHEMICAL CONSTITUENTS OF THE AIR. 229 pressure varies, tlie column rises and falls along the scale of some 21 inches, attached to the tube. 566. Pressure upon the Human Body. — Upon the body of a medium sized man, having a surface of 2,000 square inches, the atmosphere exerts a crushing force of 31), 000 lbs., while the variation of an inch in the barometric column corresponds to a variation of 1,000 lbs. pressure upon the body. That we are not con- scious of this pressure is, because the air within us presses outward with equal force. By ascending a mountain till the mercurial column fell to 14 inches, and by descending in a diving bell till it rose to 45 inches, Humboldt exposed himself to a variation of 31 inches, or 31,000 lbs. of pressure upon his person. 567. Rarefaction in the Higher Regions. — As we rise from the surface of the earth, we leave a portion of the atmosphere below us, and the weight of that above, of course, decreases. Elasticity then comes into play ; under less pressure the air expands, and as we ascend, it grows more and more rare, the barometer falling in exact proportion. Fig. 209 is designed to represent a vertical section of the atmosphere, extend- ing upward about 45 miles. The left hand column of numbers shows the height in miles above the sea level ; the right column the corresponding height of the ba- rometer in inches. A, indicates the height of the high- est peak of the Himalaya Mountains. The small cir- cle marks the greatest height reached by a balloon (six miles), by Mr. Glmshee, in 1862 ; C, the sea level, and D, the deepest soundings yet obtained (by Capt. Denham, 8| miles). § IL Chemical Constituents of the Air. 568. The atmosphere is a mixture of several gases; nitrogen and oxygen constituting its bulk. There is a small proportion of carbonic acid and watery vapor, and variable traces of other substances. According to Dumas and Boussingault, its average composition by volume is 20.81 of oxygen, and 79.19 of nitrogen, in Fin. 209. ^0 MILES Bhown by Fig. 206 ? How is tlic pressure of the air shown ? How mucli is it ? 230 INOKGAIflC CHEMISTRY. 10,000 parts, or by \reight 23.01 of oxygen, and 76.99 of nitrogen. This was ascertained by passing a stream of air slowly over a weighed quantity of heated copper in a tube. The oxygen was absorbed by the copper, the gain in weight of the tube indicating its quantity. The nitrogen was received into an exhausted flask, which was weighed before and after the experiment. The propor- tions of tliese two gases in the atmosphere are nearly invariable. 669. If an artificial mixture of four parts nitrogen and one part oxygen be made, a candle will burn in it, and animals breathe in it as in ordinary air. The atmosphere is not a chemical com- pound, but a mechanical mixture ; its constituents being diffused throughout each other according to the great law of gaseous intermixture (74). 570. The proportion of watery vapor, in the atmosphere varies with the temperature. It usually ranges from the ^\ to the ooo of the bulk of the air. By passing known quantities of air through carefully weighed tubes of caustic potash, the carbonic acid is absorbed, and its proportion determined. It varies from 3 to 6 parts in 10,000 of air, and averages about one volume in 2,500. The quantity is variable within the limits above stated. It in- creases as we rise from the earth, and is less after a rain, which washes it down from the air ; it increases during the night, and diminishes after sunrise, is less over large bodies of water than over large tracts of land, and is more abundant in the air of towns, than in that of the country. Traces of nitric acid, ammo- nia, and carburetted hydrogen are also invariably present, and in the air of towns, sulphuretted hydrogen, and sulphurous acid-!. 571. Proportions of the Atmospheric Elements. — A very clear idea of these quantities may be gained by supposing the air throughout to be of a uniform density, and its elements separated into strata, in the order of their specific gravities. In such a case the air would extend to the height of about five miles (Geaham). it ? What is this called ? What of its variability ? 565. What is the brvrometer ? How is it made? What causes the height of the column to vary? 566. What is the pressure upon the body of a medium sized man ? To what variations did Humboldt expose himself? 567. What is Fig. 209 designed to represent? 568. What IB the composition of the air? How was it ascertained ? 569. What is the state of Its elements ? 670. What is the proportion of watery vapor ? How is the carbonic acid determined ? Where is it most abundant ? Of wh-at other sub- stances arc traces found ? 571. How may we get a clear idea of these quantitiee ? CHEATICAI. CONSTmjENTS OF THE AIB. 231 Its greatest quantity of watery vapor, if condensed, Tronld form a stratum of water about 5 inches deep ; tlie layer of carbonic acid would be about 13 feet deep ; that of oxygen about 1 mile, and that of nitrogen about 4 miles in depth. 572. Resulting Properties.— Each of the constituents of the air is essential to the present order of things. We have seen how imposing is the part played by oxygen, which is preeminently its active element. To duly restrain this activity, the oxygen is diluted and weakened by four times its bulk of the negative element, nitrogen. Their properties are thus perfectly adjusted to the requirements of the living world. Were the atmosphere wholly composed of nitrogen, life could never have been possible ; were it to consist wholly of oxygen, other conditions remaining as they are, the world would run through its career with fearful rapidity ; combustion once excited, would proceed with ungovern- able violence ; animals would live with hundred fold intensity, and perish in a few hours. 573. Offices of Watery Vapor.— These are numerous and im- portant in a high degree. Three fourths of the weight of plants and animals consist of water, and they are continually absorbing and exhaling it ; while the rate of this vital operation depends upon the degree of moisture in the air. Were it perfectly dry, evaporation from leaves would proceed faster than supply from the roots, and the plant would quickly wither and die. A man weighing 154 lbs. contains 116 lbs. of water; In absolutely dry air, he would quickly ex- hale this from skin and --^-it lungs, exhaust the tissues of their fluids, and shrivel to a mummy. 574. Its Precipita- tion. — When two cur- rents of air of different temperatures, saturated with moisture, meet and mingle, the re- sulting mean temperature falls below the point necessary to hold all the water in a state of vapor, therefore a portion of it must 572. If the proportion of oxygen were increased, what would follow? 573. Were Fig. 210 Formation of Clouds. 232 IXOBGA>T[C CTTKAnSTBT. felL A gentle precipitation produces clouds, a more rapid one, rain. Thus, southerly winds loaded \rith humidity, coming in contact with the colder air of northern latitudes, usually give rain. For the same reason, the contact of air in motion with the cold surface of the earth, causes precipitation. This accounts for the fact that a larger amount of rain falls near the ground, than in the higher regions of the atmosphere. So currents of warm air striking against the side of a mountain are cooled, and, as they rise, produce the clouds and excess of rain which are peculiar to mountainous regions. In Fig. 210, the arrows show the course of the air currents, and the effect when they strike a mountain. 675. When we remember that all the moisture which the atmosphere could hold, would make a sheet of water only 5 inches thick — no more^ perhaps, than is annually deposited as dew. we can only be amazed at the vastness of the effects which it pro- duces in nature. So rapid and constant is the evaporation, that many times this quantity is precipitated in the course of a year. The amount of rain deposited is greatest at the equator, and di- minishes tOTvard the poles. 576. The Carbonic Acid which is poured into the atmosphere in prodigious quantities and from innumerable sources, is as necessary to the vegetable world, as is oxygen to the animal world. It is absorbed by the leaves, and minute as is its pro- portion, if it were withdrawn, the vegetable world would quickly perish. 577. liiebig has shown that the air contains minute traces of ammonia, which are washed down, and may be detected in rain- water. Traces of nitric acid have also been frequently detected. This Substance is thought to be formed by electricity, every flash of lightning which darts across the sky combining a portion of the oxygen and nifrogen along the line of its course, and forming this acid. The saline particles of the ocean-waves, as they are dashed into ' foam and spray, are carried by the winds fiar inland. All these substances are brought down by the rains, and aid to quicken the growth of vegetation. The odorous the tb diy, vhat would follow! »74. What is the cause of c^oods and rain? \niy te there excess of rain near the groond, and on the moantain aidest ST5. What is eaid of the fall of nin ? S76. What is the office of carbcolc acid in tLe air I iTJ. Whence oome the anunonia and nitric acid of the atnuBphcict PHLOGISTON. 233 emanations of flowers, tlie miasms of marshes, and principles of contagion, though all producing eifects upon the hnman body, cannot he collected from the air, and not unfrequently elude the most delicate chemical tests. 578. The Atmosphere and the Living World. — The relations of the atmosphere to living beings, the stability of its composition, and the wonderful forces that are displayed within it, have been but lately unfolded by science, and are full of surpassing interest. The vegetable world is derived from the air ; it consists of con- densed gases that have been reduced from the atmosphere to the solid form by solar agency. On the other hand, animals, which derive all the material of their structure from plants, destroy these substances while living, by respiration, and when dead, by putre- faction, thus returning them again in the gaseous form to the air from whence they came. In respect to air, the oflBces of plants and animals antagonize. What the former derives from the air, the latter restores to it, thus maintaining its equilibrium and per- manence. We shall return to this subject again in Physiological Chemistry. CHAPTER IX. COMBUSTION AND ILLUMINATION. § I. Historic Notice — Phlogiston. 579. By the ancients fire was considered one of the four elements of nature — the most pure and perfect of them, which tended forever upward to its own place, the empyrean — the high- est heaven of pure fire and light. This doctrine held undisputed sway, so long as nature was not made a subject of experimental inquiry. But after a long period of laborious research on the part of the alchemists, a new order of facts was discovered, and a more definite theory of the cause and nature of fire was de- manded. Accordingly about the middle of the I7th century, the German chemist, Beccher, propounded a new hypothesis of com- What other Bubstances are mentioned ? 578. What is the relation of the atmo- sphere to living beings ? 579. What was the ancient theory concerning fire ? What 234 INORGANIC CHEMISTRY. • bustion, which was further illustrated hy his eminent conntrjman, Stahl, toward the close of the same century. This was the Phlogistic Hi/jwfJicsis. 580. How Combustion was Explained. — Tiiis doctrine as- sumed the existence of a rare ethereal principle called jMogiston^ which could not be isolated, hut existed in all bodies capable of burning. In the act of combustion phlogiston escaj^ed, and the burning was caused by its escape. The products of combustion, which were deprived of phlogiston, and all bodies incapable of burning, were said to be dephlogisticated. When Priestley had discovered oxygen, Avhich produced intense combustion, he be- lieved that it acted by powerfully attracting the phlogiston of combustible bodies, and hence named it dephlogisticated air. 581. Difficulties of the Idea. — The fact that tiie metals when burned were changed to rust or cinders, was explained on the supposition that they consisted of this rust, or calyx as it was called, and phlogiston ; when they were burned, phlogiston escaped, and the cinders were left. But at length it was observed that the calyxes were heavier than the metals from which they were produced ; how then could they have lost anything ? The hypothesis, however, was sufficiently elastic to cover this objec- tion : it was replied that phlogiston was a principle of lei:ity buoying up the substances with which it was associated, so that when it escaped, they became heavier. But the facts were no longer manageable by the h}-pothesis. 582. Its Abandonment. — The discovery of oxygen, and the introduction of the balance (48), by Lavoisier, of France, gave the death blow to phlogiston. Tlie general loosening of old ideas which marked the period of the French Revolution, was eminently favorable to scientific changes, and an improved system of chemistry was introduced, which was the more cor- dially welcomed that it was clothed in the simple and rational attire of a new and admirable language. In accordance with the dramatic spirit of the times, at a festival, ' Madame Lavoisier, robed as a priestess, committed to the flames on an altar, while a solemn requiem was chanted, the phlogistic system of chemistry.' The new doctrine of the chemistry of oxygen was, therefore, at first known as the French system. The effect of the led to ita overthrow ? 580. What was the phlogistic theory ? 681. How did it fail? COMBUSTIOX AXD HEAT. 235 new language was, in a great degree, to break connections with the past, and has, perhaps, led those who came after, to under- value the labors of the earlier chemists. 583. Phlogiston served an important purpose in its dav, and it scarcely becomes us to ridicule the doctrine, siace we of the pres- ent, with our better light, are by no means exempt from the charge of entertaining ideas quite as absurd. Sir David Beewster remarks : 'As to the generic idea of phlogiston, erroueous though it was and is, it is extant in science yet ; for it is impossible to see wherein caloric differs from it as a scientific conception, although elaborated with immensely greater precision, except that caloric is the matter of heat, while phlogiston is the matter oi Jire. Both phlogiston and caloric are substances, which have no existence whatever in the external world ; they have both been convenient, though fictitious repres6.ntatives of natural realities, and they have both been eminently useful in standing for certain phenomena in their several days, but the latter creation of the materializing tendency of unripe science, is not a whit better in essence than the former.' § II. Comhustion and Heat. 584. Combustion a Chemical Process. — Combustion in its pop- ular sense, is that form of chemical action which is accompanied by the disengagement of heat and light, and which usually takes place between the oxygen of the air, and certain organic bodies, as wood, coal, oil, &c. The chemist, however, gives to the term a wider meaning, which includes all degrees of oxidation; the violent burning of iron in oxygen, or its slow rusting in the air ; the rapid consumption of wood in the furnace, or its gradual decay ; the vital process of animal respiration, by which oxygen is changed to carbonic acid in the living body, and warmth pro- duced, are all alike, to him, cases of combustion. 585. It is an interesting circumstance that other cases of chemical action are brought about for the sake of the products formed, but in combustion the products are disregarded as worth- 5S2. What led to its abandonment ? "What is said of this change ? 583. To Tvhat is the theory of phlogiston compared ? 584. What is the common idea of combus- tion ? That of the chemist ? 585. How does it differ from other cases of chemical 236 IXORGANTC CHEMISTKY. less, and the operation valued solely on account of the forces which are its incidental result. 586. Bodies were formerly divided into comlustihles and sup- 2)ortcrs of combustion. Atmospheric oxygen was held to he a supporter of combustion, while hydrogen, carbon, and iron, which burn in it, were called combustibles. But, if the conditions of the experiment Fig. 177 be reversed — that is, if a jet of oxygen be ignited in an atmosphere of hydrogen — precisely the same effect will take place ; oxygen will then be the combustible, and hydrogen the supporter of combustion. The fact is, the action is mutual, and of the same kind on the part of both elements ; the distinction is therefore groundless. 587. The Process Self-supporting.— Every combustible sub- stance requires a certain elevation of temperature in order to ignite, and the maintenance of this temperature is essential to the continuance of the combustion. After a substance is once kindled, the heat given off by the rapid chemical action is usually more than suflBcient to maintain the combustion until the burning body is consumed. 588. Cause of the Heat. — It has been explained that chemical action produces heat by conversion of the motion of chemical atoms into heat vibrations. We have atoms separated and power- fully attracted, like lifted weights : they rush together, collision arrests motion, and their force is given out as heat. It is the clash or impact of the atoms of oxygen against the elements of burning bodies, which gives us the heat and light of combustion. By figur- ing to ourselves the atoms shot across the molecular spaces with intense force, and thus parting with their excess of motion, we have an explanation of the source of heat in combustion, which is in harmony with our latest knowledge of the nature of heat, and of its other modes of production, while in no other way is it pos- sible to explain its chemical origin. 589. Upon what the Amount of Heat depends. — In all ordi- nary cases of combustion, the amount of heat set free depends upon the quantity of oxygen brought into action, rather than on that of the body burned. Hence, the combustible which unites with the most oxygen while burning, will give off the most heat. action ? 5S6 "Wlmt old distinction is said to be erroneous ? 5S7. Why must combu8t:oa be first kindled? 5S8. What causes the heat and light of com- bustion t Deecribe the conception. 5S9. Upon what does the amount of heat COMBUSTION AND HEAT. 237 Thus, hydrogen in burning, takes up weight for weight three times as much oxygen as carbon does ; consequently, it gives off three times as much heat. 590. The complete burning of a combustible body requires the consumption of the same quantity of oxygen, whether the pro- cess goes on rapidly or slowly, and, in either case, the amount of heat set free is the same. Therefore, the intensity of the heat depends upon the rapidity of the combustion. Heat would be liberated from the burning of a pound of coal in ten minutes, six times as fast as if its combustion occupied an hour. This is the reason why the smith blows his fire, and why such powerful blowing apparatus is apphed to blast furnaces ; they diminish the time of the combustion, and correspondingly increase its vehe- mence. The powerful blast or draft also serves to expel from the fire the products of combustion which would impede it if suffered to accumulate. Yet excess of air is detrimental to the burning process, by conveying away heat, thus cooling the fuel, and checking the rate of combustion. 591. One pound of wood charcoal will raise from the freezing to the boiling point 73 lbs. of water ; 1 lb. of mineral coal will correspondingly heat 60 lbs. of water, and 1 lb. of dry wood will raise 35 lbs. of water through the same number of degrees. These are the highest results by careful experiments ; in practice we obtain a much lower effect, both on account of imperfect combus- tion, and from the fact that a large proportion of the heated air escapes through the chimney, before it has given off as great an amount of heat as it is capable of producing. The weight of air required to burn the fuel, is vastly greater than that of the fuel itself. It takes 11.45 lbs. of air to consume 1 lb. of charcoal, and as 1 lb. occupies nearly 13 cubic feet of space, the pound of char- coal will require about 150 cubic feet of air for its combustion. 592. Kindling Temperature. — TJie temperature at which oxy- gen goes into rapid combustion, differs with different bodies. Thus phosphorus ignites at 150°; sulphur at 480°, while the hy- drocarbons require a temperature of nearly 1000° to kindle them. The stability of the order of nature depends upon the gradation depend? Example. 590. Its intensity? How is this illustrated? How may excess of air be detrimental ? 591. Compare the heating effects of charcoal, min- eral coal, and wood. How much air is required to consume 1 lb. of charcoal ? 592. How do kindling temperatures vary ? How has the art of kindling fires pro- 2;J8 INORGANIC CHEMISTRY. of tho affinities between atmospheric oxygen, and the hydrogen and carbon of organic bodies. These are only brought into action at high temperatures. Did these bodies ignite at a much lo\Yer degree, like phosphorus, conflagrations, which are now compara- tively rare, would become universal. To ' make a fire,' requires an etibrt of reason, and, like the other arts, it has progressed wit the advance of thought. First, the friction of pieces of wot then flints, steel, and tinder ; and, lastly, with the progres/ of chemistry, phosphorized matches, the very perfection o^con- venience. § III. Flame and Illumination, 593. Nature of Flame.— Flame is produced by the combustion of gases, and is, hence, fire in motion. Substances yrhich burn with flame, are either gases already, or they containja gas which is set free by the heat of combustion. But flame do^ not neces- sarily produce light. In the burning of pure oxygdi and hydro- gen, there is intense flame, but so little light that it/can hardly be seen. If, into this non-luminous flame, we sift apittle charcoal dust, the particles of solid carbon are instantly hdated to incan- descence, and there is a bright flash of light. Thfe conditions of illumination are, therefore, first, an intense heati and, second, aj solid placed in the midst of it, which remains fixe|, and gives ou| the light. 594. The Compound Blowpipe.— These condiiflons are fulfillj most perfectly by means of the compound blownfipe of Dr. H|«e. The two gases are/collected in Jjtso- meters, or more^onvenientl^n in- -rubber baj^. Fig. 21 1/^ which connecy^f ^>7 fle:^we tubes jet, Eig: 212 ; the incr^lii«!0 by pressure on bass^,,j&»>9^ontrolled by stop- 'he gases are emitted to- gether and burned at the orifice, a. When ignited, they produce a blue flame which is hardly visible, but which has intense heating power, and produces tho most Fig. 211. Gas Bags for Blowpipe. gressodf 693. What is flame? What substances produce it In burning? What causes the light? What are the conditions of illumlnalion? 694. Describe the FLAME AND ILLUMINATION. 2S9 remarkable effects. Yery fine wire twisted together, or a steel watch-spring, burns with a shower . lof scintijji^tions. Substances which^ Fig. 212. Blowpipe Jet. do not fuse in the hottest blast fur- naces melt in this heat like wax, or dissipate in vapor. 595. The Lime Ball.— A little ball of lime, however, of the size of a pea, remains unalt( It glowg^p*tt*^'Dlinding brilliancj, hg what is known as the ' Drummond light,' the ' Lime light,' or the ' Calcium light.' It is employed as a substitute for the rays of the sun in the solar, or oxyhydrogen microscope, and is used in coast surveys for night signals. When reflected by a parabolic mirror in a pencil of parallel rays, it has been recognized in day- light at a distance of 108 miles. The hydrogen may be replaced without much disadvantage by ordinary coal gas. 596. In all ordinary illuminations the principle is the same as that of the lime light. The substances employed are hydrocar- bons : the union of oxygen and hydrogen gives rise to heat, and the carbon particles at the same time set free in the heated space and made luminous, are the source of the light. 597. How the Candle Bums.— The materials used for illu- mination, whether solids or liquids, are always converted into gas before burning. The candle first becomes a lamp, j^jq 213. and then a gas burner. When lit, the heat radiates downward, so as to melt the material of the candle and form a hollow cup filled with the liquid com- bustible. Fig. 213, and thus the candle becomes an oil burner. From this reservoir, the wick draws up the oil into the flame. Here, in the midst of a high heat, and cut off from the air, it undergoes an- other change exactly as if it were enclosed and heated in a gasmaker's retort ; it is converted into gas, and in this form finally burned. As the wick rises into the flame, it fills the interior as a sooty mass, and interferes with the combustion. To avoid this, wicks are sometimes plaited or twisted, so that Burning Candle. compound blowpipe. Its effects. 595 What is the Drummond light ? f;96. AVhat is the principle of ordinary illumination ? 697. Explain the process of burning a h3 240 INOKGANIC CHEMISTRY. The Flame IIollow. Fig. 215. in burning tbcy bend over to tbc side of tbe flame, and are con- sumed. r,G, 214. 593. Structure of the Flame. — As the wick remains thus imconsumed in the in- terior of tbe flame, it is obvious there can be no fire there. If we lower a piece of glass or a wire gauze over a candle or gas flame, as in Fig. 214, we shall see an interior dark space surrounded by a ring of fire. This in- ner sphere is filled with dark unburned hydrocarbon vapors, wliicb are enclosed by a shell of fire, or burning gas. If one end of a small glass tube be introduced into the candle flame, as in Fig. 215, these interior gases will be conveyed away, and may be lit at the other end. 599. Order of the Combustion. — There is an order of combustion in tbe flame, wbicb depends upon the order of affinities, and this is the hinging fact of illumination. In Fig. 216, a represents the nucleus of hydrocar- bon vapor. If now oxygen from without had the same affinity for both its elements, they would be consumed together, with but little luminous effect. But the oxygen decomposes the gaseous compound, and, seizing Fig. 216, "Upon the hydrogen first, surrounds a with the intensely A. heated space, h. At the same time the carbon particles are set free, and being heated white-hot, give out the mo- tion of light. The cone h is therefore the place of burn- ing hydrogen and the seat of illumination. The incan- descent carbon particles, as they pass outward, meet with oxygen at c, and are converted into carbonic acid in the outer cone. 600. To prove the constant presence of free carbon y- — H in the flame, it is only necessary to introduce into it any L^-vnI cold body, as a knife blade, or piece of porcelain, when it will be copiously deposited upon it as soot. Fig. 217 represents a cross section of the flame and the arrange- Gas from Flame. ghells of Flame. candlo. 698. What do Figs. 214 and 215 represent ? 599. What ia tho order of FLAME AND ILLUMINATION. 241 Fig. 217. Cross Section of the ' Flame. ment of its parts ; CH the unburned carbon and hydrogen, H the sphere of burning hydrogen across which the carbon particles float, and lastly the sphere of burning carbon. 601. By noting any common flame, it will be observed that it burns blue, and yields but little light at the base. This is because the oxygen at this point is so abun- dant as to burn simultaneously both hydro- gen and carbon. If we move a candle flama swiftly through the air, its light is dimin- ished for the same reason. The conical form of the flame is due to the currents of heated air ascending around it. 602. The amount of light produced depends upon the inten- sity of the heat, as was before stated (399). Dr. Deaper found that a body at 2,600^ emitted almost 40 times as much light as at 1,900°. 603. Effect of Coolmg the Flame.— If by any means the tem- perature of the flame falls below a certain limit it is immediately extinguished. The flame of a candle may be put out by lowering over it a coil of cold cop- per wire, Fig. 218. A piece of fine wire gauze held across the flame of a candle cools the combustible gases below the point of ignition, so that they rise through the meshes in the form of smoke. Fig. 219. The gauze may even become red hot and still not allow the FrG. 218. Copper Coil. Fig 219. flame to pass, so rapidly is the heat conducted away by the wire. Yet the cooled gases may be rekindled above, when the flame will go on burning as before, Fig. 220. 604. Safety Lamp. — On this principle the safety lamp is constructed. The explosions of carburetted hydrogen gas in coal mines from the unprotected lamps of the miners, caused immense destruction of life, and vari- Gauze stops the Flame. ous arrangements had been fruitlessly contrived to prevent these combustion ? 600. How may the presence of free carbon in the flame be proved ? Explain Fig. 217, 601. Why is there little light at the base ? To what Is the conical form due ? 602. Upon what does the amount of hght depend ? 603. Ex. plain Figs. 218 and 219. 604 What led to the invention of the safety lamp? 11 242 INOEGANIC CHEMISTRY. terrible accidents. Fig. Gas burns above. sire of diminishin Fig. 221. At length Sir Humphry Davy took hold of the subject. lie commenced a series of re- searches upon flame in August, 1815, and with such success as to produce the perfected lamp at the Royal Institution of London in the suc- ceeding November. With large liberality he presented it to the public, unrestricted by a patent : and it is interesting to remember that the researches on flame to which we are in- debted for the chief facts which have now been stated, were prompted by the noble de- human suffering. As is frequently the case in all departments of investigation, so here ; others besides Davy con- trived safety lamps upon the same principle, unknown to each other. 605. They consist simply of ordinary oil lamps enclosed in a cage of wire gauze which permits the light to pass out, but pre- vents all exit of flame. Fig. 221. The space within the gauze often becomes filled with flame, from the burning of the mixed gases which penetrate the net- w^ork ; but the isolation is so complete that the explo- sive mixture without is not fired. Fatal explosions still occasionally take jjlace, but they are due to care- lessness of the miners. An explosion occurred not long ago killing nearly a hundred people, and it was subsequently traced to the fact that a miner had broken a hole into the gauze of his lamp to hang it upon a nail ! 606. Influence of the Supply of Air. — As the in- tensity of light depends upon the rapid consumption of oxygen, there must be a free supply of air, and pro- vision for the ready escape of combustion products. The efiect of a lack of air upon the flame may be seen Safety Lamp, -[yj placing a glass cylinder over a burning candle so as to cut ofl:' the air ; the flame becomes dingy and feeble, Fig. 222. By slipping a couple of blocks under the cylinder. Fig. 223, the combustion becomes more energetic than it would be in the open at- mosphere, as by this means a rapid current of air is brought into con- Give its liistory. 605. Of what doea it consist? What is saM of the effects of cireicssnePB ? 60G. What experiments illustrate the Influence of supply of air? FLAME AND ILLUMINATION. 243 Air cut off. Fig. 223. Air supplied. tact witli the flame. If the cylinder be covered Fig. 222. at top, the flame is extinguished by the accumu- lation of the products of combustion. On the other hand too much air is injurious, as so large a proportion of oxygen mingles with the com- bustible gases that the carbon and hydrogen burn together. 607. Argand Burner. — This is an arrange- ment for increasing both the supply of air and the burning surface of the flame. In the candle flame and gas jet, combustion only takes place on the outside. The Argand burner has a circular wick by which a second current of air is admit- ted to the interior of the flame, thus burning with a double surface. This effect is increased by a glass chimney contracted so as to deflect the as- cending outer current of air strongly Tipoii the flame. See Fig. 224. 608. Blowpipe Flame.— The high heat of the blowpipe flame is also due to the introduction of air into the centre of its flame. This is accomplished by blowing through a tube, the form of which and manner of using are seen in Fig. 226. On applying the blast the flame is de- flected to the horizontal position, as shown more clearly in Fig. 225, and it now presents two distinct portions which have opposite chemical oflices ; a a represents the in- terior blue cone formed by the admixture of the oxygen with the unburned gases. The combustion is hero complete Argand Burner. ^^^ ^^^ ^^^^ ^^ Blowpi the flame most intense. From 5 to (J is the luminous cone, whkh consists of unburned gases at a high temperature. These have a Fig. 224. Fig. 225. 1^ Flame. 607. "WTiat is an argand Tjurner ? 608. How does the blowpipe illustrate the same thing? What is the reducing flame of the blowpipe? The oxidizing flame? 244 INORGANIC CHEMISTRY. Fig. 22G. powerful tendency to combine with oxygen and take it from the oxides of metals; it therefore forms a reducing flame. At the extreme point of the flame there is a reverse effect. There, oxy- gen at a high temperature is mechanically carried forward, and if driven against a metal rapidly oxidizes it ; this point is therefore known as the oxidiz- ing flame. 609. It is interesting to note that the elements which have been chosen to form combus- tible bodies universally are the only ones adapted to the pur- pose. Their products, carbonic acid and watery vapor, are transparent and therefore do not cloud and echpse the flame. They are also inodorous, tasteless, and, in small proportion, innocuous ; while the oxides of all other com- bustible substances capable of existing in a gaseous state are pungent and irritating. Using the Blo-wpipe. CHAPTER X. THE HALOGENS, OR SALT FORMERS, 610. The bodies that compose this group are Chlorine, Bromine, Iodine, and Fluorine. They are characterized by their indifference to each other and their strong affinity for the metals, uniting with them to form a class of compounds of which chloride of sodium, or common salt is the type. Hence their name Halogens^ or salt froducers. 609 What is said flf the products of combustion? 610. What are the halogens? Why are they so named ? 611. Wlicn and by viiom -was chlorine discovered ? Where is it found? 612. How is it obtained? How is the reaction expressed? CHLORINE AND ITS COMPO^sDS. 245 I. Chlorine aJnd its Compounds. Fig. 227. CHLORIXE. Sym. CI Eqidv. 35.5 Sp. Gr. 2.47. 611. CMorine \v-as discovered by Scheele in 1774, while noting the action of cUorohydric acid upon peroxide of manganese. It is never found free in nature, but exists abundantly in the mineral world, chiefly in combination with the metal sodium, as common salt. Animals and vegetables also contain it in this condition. 612. Preparation.— Scheele's method of obtaining chlorine by the action of chlorohydric acid on peroxide of manganese is still generally adopted. The manganese is placed in a flask provided with a safety tube for pour- ing in the acid, and a bent tube for conducting the gas to the receiver, Fig. 227. A little acid is first poured in and well shaken up with the manganese in order to wet every portion of it ; more acid is then added and a gentle heat ap- plied, when the gas is given off copiously. It may be collected over warm water or brine, and also by displacement, as seen in the figure. The greenish color of the gas from which it takes its name will indicate when the vessel is filled. The reaction may be thus expressed : MnO. + 2H01 = MnCl + 2H0 + CI. ^'^'"^ '^''°'"'""- Chlorine may also be prepared from common salt by the aid of sulphuric acid and oxide of manganese. 613. Properties.— Chlorine is one of the most energetic of the elements, surpassing even oxygen under some circumstances. Or- dinarily it is a yellowish-green gas, but by a pressure equal to four atmospheres it may be condensed to a transparent, yellow liquid which remains unfrozen at — 220°. The gas has a peculiar, suff'o- cating odor, and if inhaled, even when considerably diluted, pro- duces distressing irritation of the throat and lungs. When re- spired, however, in very minute quantities, it is not only harm- i 613. "What are the properties of chlorine ? What does Fig. 228 illustrate ? 614. !46 INORGANIC CHEMISTRY. Fig. 22S. less, but is said to be beneficial to those afiected ^itli pulmonary disease. Chlorine maintains combustion ; many bodies burn in it readily and some take fire in it spon- taneously, such as phosphorus, finely powdered antimony, and arsenic. Many organic compounds, rich in hydrogen, are decomposed by it so rapidly as often to burst into flame. A piece of paper saturated with oil of turpentine and plunged into a vessel filled with chlorine, Fig. 228, emits a dense, black smoke and usually ignites, from the rapid decomposition of the turpentine. Chlorohydric acid is formed and carbon deposited. 614. Cold water absorbs about two and a half times its own bulk of chlorine, the solution acquiring the color, taste, and smell of the gas. If this solution is cooled down to 36° F., a defi- nite crystalline hydrate of chlorine is formed, having the formula CI -f- lOHO. Liquid chlorine may be readily obtained from these crystals by hermetically sealing them in a curved tube. Fig. 229, and applying a gentle heat. This liberates the chlo- rine, which, pressing upon itself, assumes the condition of a liquid. It may be distinguished from the water present by its yellow color. Chlorine solution readily dissolves gold, and also acts in some cases as a powerful oxidizing agent (608). Light decomposes chlorine wa- ter, giving rise to chlorohydric acid and free oxygen ; hence it is necessary that it be kept in bottles protected by some opaque covering. 615. Bleaching Properties.— One of the most valuable quali- ties of chlorine is its bleaching power. A solution of it in water, or the moist gas, immediately discharges the colors of ordinary fabrics, indigo, common ink, &c. It is principally used in bleach- ing cotton cloth and rags of which paper is to be made. We have seen that oxygen is a powerful bleaching agent (457), and in chlorine bleaching it doubtless takes an important part. Not only does chlorine destroy the coloring matter by uniting with its hydrogen, but in moist bleaching it decomposes the water, setting Combustion in Chloriue. Fig. 229. Condensing Chiori;ie. How are chlorine crystals obtained? Liquid chlorine? Properties of chlorine CHLORINE AND ITS COMPOUNDS. 247 free oxygen which, in its nascent state, acts powerfully to oxidate and destroy the coloring particles. Dry chlorine will not bleach; it acts only through the agency of water. But it is so powerful that, if the bleaching solution is not quickly removed, it corrodes and weakens the fabric. It has no action upon carbon, and there- fore does not bleach printer's ink. Nitrate of silver added to a solution containing chlorine, or a soluble chloride gives a white precipitate of chloride of silver, AgCl, which on exposure to light changes first to violet, and then to black. It is the universal test for chlorine. 616. Allotropic Chlorine.— This element, like oxygen, has its active and passive condition. When hvdrogen and chlorine are produced and mingled in the darTc^ they do not unite ; if exposed to diffused daylight, they gradually combine, and if to direct sunlight, they combine explosively. Dr. Deaper found that chlorine gas which had been exposed to sunshine acquired the power of rapidly combining with hydrogen in the dark, and re- tained it for some time. When prepared in the dark, it is in a passive condition, but the effect of light so re-arranges its mole- cules as to exalt its activity and completely change its character. In its active state chlorine is highly electro-magnetic ; in its pas- sive state, it seems to become electro-positive, and capable of re- placing hydrogen in combination (922). The more refrangible rays are chiefly instrumental in producing this change. 617. Compounds of Chlorine.— Owing to the active character of chlorine, it forms compounds with nearly all the elements. It unites directly with many of the metals, producing chlorides, and also forms several important combinations with the non-metallic elements. The metallic chlorides will be noticed under the met- als; — we give here its more imp(^rtant non-metallic compounds. 618. Chlorohydric Acid. ECl {Eydroddoric Acid, Muriatic Acid). — The conditions under which these elements unite have just been noticed. The result is chlorohydric acid, a transparent, colorless gas, endowed with intensely acid properties. Two vol- umes of hydrogen combine with two of chlorine to form four volumes of the gas, no condensation taking place. •water? 615. How does chlorine act as a bleaching agent? 615. How does nitrate of silver act as a test for chlorine ? 617. What are the chlorides? 618. Howls hydrochloric acid formed ? 619. What is Fig. 230 ? 620. What are the properties 248 INORGANIC CHEMISTKY. Fig. 230. n:iiillliiiliiiiiiiiiiii|l!iiiHi!iiiiillllliiiiiliili Separating HCl. 619. Preparation. — For experimental purposes the gas may be readily obtained by heating a strong solution of chlorohydric acid in a glass flask furnished with a perforated cork through which a bent tube passes for conducting the gas to the receiver. Fig. 230 is a con- venient arrangement for this purpose. The gas must be collected by dis- placement, as it is greedily absorbed by water. 620. Properties. — Chlorohydric acid gas is unrespirable, very irri- tating to the eyes, and not a sup- porter of combustion. It is some- Avhat heavier than air, having a specific gravity of 1.24. Under a presure of 40 atmospheres, it condenses into a colorless liquid which has never beea frozen. When allowed to escape into the air, the gas combines with its moisture so rapidly as to produce white fumes. So great is its affinity for water that a lump of ice placed in ajar of the gas is liquefied, and the gas instantly absorbed. Free chlorohydric acid forms with ammonia dense white clouds of sal-ammoniac, as may be shown by bringing near each other two glasses, Fig. 231, one containing the acid and the other the alkali. 621. At a temperature of 40° F., water ab- sorbs about 480 times its bulk of chlorohydric acid gas, increasing in volume about one third, Gases pror]ucing a and forming a colorless fuming, intensely acid liquid, having a specific gravity of about 1.247, known as muriatic acid, spirit of salt, &c. This solution is one of the most important requisites of the laboratory, and is also used for many purposes in the arts. The gas may be generated on a small scale by the action of dilute sulphuric acid on common salt aided by a gentle heat. Good pi'oportions are two parts by weight of dilute acid to one part of salt. The gas is absorbed by cold water which is contained in a series of bottles connected with the generating flask, Fig. 232. The reaction consists in the de- ofHjClt E.'cplain Fig, 231. 621. What is muriatic acid? Describe its preparation. CHLORINE AND ITS COMPOUNDS. 249 Fig. 232. composition of the water of the sulphuric acid, its hydrogen taking the chlorine of the salt (which is composed of chlorine and sodium), and forming with it chlorohydric acid, while the oxygen unites with the sodium to form soda. The sulphuric acid combines with the soda, producing, if the acid is in ex- cess, a bisulphate, while the gas escapes, and is taken up by the water in the bottles. Ex- pressed in symbols we have Preparing Bolution of HCI. NaCl + 2 HO, SO3 = NaO, HO, 2SO3 + HCI. 622. The condensation of chlorohydric acid gas is attended with the liberation of a large amount of heat, which raises the temperature of the water, thus reducing its capacity for absorbing the gas. To obviate this, the bottles are surrounded by ice, or a mixture of ice and salt. In the manufacture of the acid on a large scale, the decompositions are carried on in iron cylinders. The acid is condensed in stoneware vessels arranged like Woulfe's bottles. 623. Chlorohydric acid gas occurs in large quantities as an inci- dental product in the manufacture of carbonate of soda from com- mon salt. Fntil within a few years, the gas was allowed to escape into the atmosphere, where it condensed, and fell as a corrosive rain, to the great detriment of the surrounding vegetation. It is now condensed in large towers, built for the purpose, and con- nected with the furnace in which the salt cake or sulphate of soda is manufactured. Pure chlorohydric acid is colorless, but the commercial article has a yellow tinge due to organic impurities, free chlorine, iron, (fee. 624. Nitro-Chlorohydric Acid. — A mixture of chlorohydric acid with nitric acid, constitutes the aqua regia^ or royal water of the alchemists, so named from the power it possesses of dissolving gold, the ' King of metals.' The mixture acts by setting chlorine free, which, at the moment of its liberation, attacks the metals. 622. What precaution is neceBsary? 623. Where is it now made in large quanti* 11* 250 IXOEGANIC CHEMISTRY. dissolving and combining with them. The proportions for the mixtures are two measures of chlorohydric to one of nitric acid. 625. Chlorine and Oxygen.— The affinity of oxygen for chlo- rine is so feeble that the two elements can only be induced to unite by indirect means. The combinations are numerous, but we can only notice a few of the most interesting. 626. Hypochlorous Acid, CIO, may be obtained by passing dry chlorine through a tube filled with red oxide of mercury. A portion of the chlorine takes the place of the oxygen, forming chloride of mercury, while another portion unites with the oxy- gen, at the moment of its liberation, forming hypochlorous acid. As a gas, its color is a shade darker than that of chlorine, and it has a similar pungent odor. It is a powerful oxidizing agent, and possesses remarkably strong bleaching power. 627. Bleaching Compounds.— When chlorine is passed through recently slaked lime (hydrate of lime), large quantities of the gas are absorbed, forming the hleaching powder of commerce. A few chemists regard this and the similar compounds of p^jiash and soda, as formed by the direct combination of chlorine with the base, having the formula in the case of lime CaO, CI. The ma- jority, however, maintain that they are compounds of hypochlo- rous acid with the base, which would make the symbol of the lime compound CaO, CIO. According to this view, the substances formerly known as chlorides of lime, potash, soda, &c., are hypo- chlorites of these bases. 628. Hypochlorite of Lime, CaO, CIO. — This is a white, spar- ingly soluble powder, used in great quantities for bleaching pur- poses. In the bleaching of cotton fabrics, the goods are first freed from all greasy impurities, and then digested in a solution of this powder. They are next dipped into very dilute sulphuric acid, where the chlorine is liberated, and exerts its bleaching power. This process requires to be repeated several times before the color is entirely discharged; after which the goods are thoroughly washed in water, in order to remove all trace of acid from the fibre of the cloth. 629. The change effected in modern days in the process of bleaching, is a striking example of the value of chemical skill as ties? 624. What is said of aquaregia? 625. Of the compounds of chlorine and oxygen ? 626. What is hypochlorous acid, and how is it obtained ? 627. Wliat are the thcoriefl of the composition of bleaching compounds ? 628. How is the bleach- CHLORINE AND ITS COMPOUNDS. 251 applied to the industrial arts. Formerly, cotton and linen fabrics were bleached by steeping them in alkaline liquors, then boiling them in water, and exposing them for a long time upon the grass, where they were frequently sprinkled, and this was followed by soaking them for weeks in sour milk. This was repeated again and again, the process being not only slow and tedious, but requiring a large amount of manual labor, and a great extent of grass land. The substitution of dilute sulphuric acid for the sour milk, in dissolving out the alkaline matter, greatly reduced the time in this part of the process, while the subsequent application of chlorine still further shortened the operation, so that in two days IS now accomplished what formerly took from four to eight months. 630. Chlorine is a disinfectant. It acts in the same way as in bleaching, by decomposing noxious efHuvia. The chlorides of lime, potash, and soda are the compounds best adapted to this purpose, as they gradually evolve the gas at ordinary tempera- tures. Chlorimetry is the name given to the process by which the pe^ntage of chlorine is determined in those compounds from which it may be obtained as a bleaching agent. The most accu- rate method, as devised by Gat-Lussao, consists in ascertaining the amount of arsenious acid which could be peroxidized by a known weight of the bleaching powder. 631. Chloric Acid, CIO5. — This, the most interesting compound ■ of chlorine and oxygen, has never been obtained in an uncom- bined form. It always retains one equivalent of water, OIO5IIO. If chlorine gas is passed througli a strong solution of caustic potash, it is rapidly absorbed, and a bleaching liquid formed, which, on thei application of heat, loses this property, and is con- verted into chloride of potassium and chlorate of potash. The chlorate of potash may be separated from the solution by crystal- lization, as it is less soluble than the chloride. Hydrofluo-silicic acid, added to a solution of these crystals, unites with the potash, carrying it down in an insoluble state, thus liberating the chloric acid, which may be obtained in a sirupy form, by evaporating the solution at a heat not exceeding 100°. A higher heat decom- poses the acid. "While in this state, it is very unstable, being de-. iiig eflfecleQ ? 629. How is the change in the mode of bleaching spoken of? 630. How does chlorine act as a disinfectant ? What compounds are best adapted for this, and why? What is chlorimetry? 631. How is chlofic acid obtained? 252 INOEGAXIC CHEMISTRY. composed bv the presence of anv combnstible matter, and eren bv diffused daylight. 632. Chlorates. — The chlorates are characterized by the ease Tvith which they yield their oxygen on the application of heat, by their powerful affinity for combustible substances, and by scintil- lating when thrown upon ignited coal. They are used as a source of oxygen, and in the manufacture of fireworks. 633. Chlorous Acid, Peroxide of Chlorine, and Perchloric Acid may be obtained by tlie decomposition of chloric acid. Sul- phuric acid, poured upon chlorate of potash, liberates cTdorous acid in the form of yellow vapors, which are very explosive. Peroxide of chlorine is also explosive. It resembles chlorous acid in appearance, and dissolves in about twenty times its bulk of water, forming a powerful bleaching solution. Perchloric acid is the most stable of the oxides of chlorine, and readily forms salts with various bases, which are all soluble, and decomposable by heat. § II. Bromine^ Iodine^ Fluorine. *• B R O il I X E . Sym. Br. Equir. 80. Sp. Gr. at 32", 3.187. 634. Bromine was discovered by Baixakd, a French chemist, in 1S26. in the 'mother liquor,' or hittem^lQ^ after the extrac- tion of the crystallizible salts from sea water. This is the prin- cipal source of the element, although it is found in the waters of various saline springs, and in a few minerals. Bromine is pre- pared by introducing into the mother liquor a current of chlorine, which sets it free. Ether is then added, which, on agitation, takes up the bromine, and rises to the surface as a deep red stratum. 635. Properties.— Bromine is the only element, except mercury, which exists as a liquid at ordinary temperatures. It is of a deep red color, and very volatile, with a disagreeable, irritating odor, from which its name is derived. It is a powerful poison, a drop on the beak of a bird producing instant death. It has bleaching 632 Describe the chlorates. 633. "^Vhat is said of chlorous acid ? Peroxide of chlorine ? Perchloric acid T 6G4. Where is bromine found f How is it prepared? 635. Properties of bromine t Uees t 636. What are the eonrces of iodine f Its BROMINE, IODINE, FLUORINE. 253 properties, and is soluble in water. It is used in photography, and, in minute quantities, as a medicine. Like chlorine, it forms an acid with hydrogen, and also unites with oxygen, giving rise to bromic acid, the only known compound of these two elements. IODINE. Syml. I. Equiv. 126.8. Sp. Gr, 4.94. 636. This useful substance was discovered by M. Cofetois, of Paris, in 1811. He first observed it in kelp, or the ashes of sea-weed, and it is still obtained from this source for commercial purposes. It exists in mineral springs, and has also been found in minute quantity in certain minerals. In its preparation the ashes are leached, and the solution evaporated, until the more readily crytallizable salts are removed. The mother liquor, which contains the iodine as iodide of sodium, is then distilled with sul- phuric acid and oxide of manganese, when the iodine comes over as vapor, and is deposited in the form of brilliant, bluish-black scales, resembling plumbago in appearance. 637. Properties.^ — Iodine is a non-conductor of electricity, and is sparingly soluble in water, though easily dissolved by ether or alcohol. When heated, it rises as a beautiful purple vapor ; hence its name, from iodes, violet-colored. In various forms, it is used extensively in medicine, but, taken in large doses, it acts as an irri- tant poison. The test for iodine is moistened starch, with which it forms a deep blue compound. If the iodine is in combination, it may be liberated by the addition of a little chlorine water, as it is necessary to the success of the test that it be in the free state. One part of iodine in a million of water may be detected by this means. 638. lodohydric Acid, HI, may be obtained in the form of a gas by heating iodine in hydrogen. It is a strong acid with a pungent odor, very soluble- in water, and readily decomposed by chlorine or bromine. Iodine combines with the metals, forming com- pounds remarkable for the beauty and variety of their colors. Its most important compound is formed by its union with potassium, which gives KI, or iodide of potassium. Like chlorine and preparation? 637. "What are its properties* What its uses? What is its test f 638. What are the properties of iodohydrio acid ? Other compounds of iodine ? 254 INORGANIC CHEMISTRY. bromine, it unites with oxygen, but the compounds possess no general interest. FLUORINE. Sym. F. Equiv. 19. Sp. Gr. 1.31. 639. Fluorine is only known in combination. It exists in various minerals, but most abundantly in fluorspar (fluoride of calcium), from which it is obtained as fluohydric acid by means of sulphuric acid. It is also found in minute quantity in the bones of animals and the enamel of the teeth, to which structures it is supposed to give hardness. Fluorine forms compounds with all the metals, and with many of the non-metallic elements, but it cannot be induced to unite with oxygen. 640. Fluohydric Acid, HF {Hydrofluoric Acid). — This may be obtained by decomposing fluorspar with sulphuric acid, the operation being usually aided by a gentle heat. Owing to the powerfully corrosive quality of this acid, it is prepared in leaden vessels. If required perfectly pure, platinum or silver vessels are used. The acid, as thus obtained, is a fuming, white liquid, which requires the greatest care in dealing with it, as, if allowed to come in contact with the skin, it produces a deep and exceedingly painful sore, very difficult to heal. It combines with water with avidity, producing a hissing noise. Many of the metals dissolve in it, fluorides being formed, and hydrogen liberated. Potassium decomposes it with an explosion. 641. The distinguishing characteristic of fluohydric acid is its corrosive action on glass. This may be shown by placing some powdered fluorspar, made into a paste with Fig. 233. sulphuric acid, in a leaden cup. Fig. 233, and covering it with a plate of glass, previously smeared on one side with beeswax, through which characters have been traced with a fine-pointed instrument. The waxed side is Acuoaof Fluorine. pl^^^d next the mixture, and a gentle heat applied to the cup.. After the lapse of half an hour, on removing the glass, and cleaning oflf the wax with the aid of a little oil of turpentine, the characters will be found eaten €39. What is said of fluorine ? 640. How is fluohydric acid prepared ? Wliat are its properties ? 641. Explain the process of etching upon glass. 642.' What is the SULPHUK AND ITS COMPOUNDS. 255 into the glass. The add has combined with the silica of the glass at the exposed points. This quality is taken advantage of to etch the labels on glass bottles that are to be used in laboratories and drug shops, where corrosive substances abound. CHAPTER XI. THE PYROGENS OK FIRE PRODUCERS. § I Sulphur and its Comj^ounds. 642. The elements of this group, Sulphur, Selenium, Tellu- rium, and Phosphorus, are closely allied to each other and marked by their strong attraction for oxygen. SULPHUR. Sym. S. Equiv. 16. Sp. Gr. 2. 643. Sulphur is a brittle yellow, solid, highly inflammable, burn- ing with a bright blue flame, and is insoluble in water or alcohol, but soluble in bisulphide of carbon. It is a non-conductor of electricity, and but a poor conductor of heat. 644. Sources. — Sulphur exists abundantly in nature, both free and in combination. It is found native in various volcanic districts, especially in the island of Sicily, where it is mined in immense quantity for the market. Many springs and small lakes, in which it is evolved in the combined gaseous state, often deposit it in considerable quantities. It exists in combination with various metals, forming sulphides, and, as a constituent of sulphuric acid, it is found in gypsum and other minerals. 645. Sulphur exists in plants, entering their roots in some soluble combination, and is present in a free state in the bodies of animals, chiefly in their muscular parts. It exists in eggs, and discolors the silver spoons with which they are eaten by forming the black sulphide of silver. The efficiency of many preparations for staining the hair black depends upon the lead they contain, which unites with the sulphur of the hair. distinctive property of this group? 643. What are the properties of sulphur? 644. What are its sources ? 645. Where else does it exist ? 648. How is it purified ? 256 INORGANIC CHEMISTRY. Fig. 234. 646. Sulplmr is volatile, and sublimes by heat. Advantage is taken of this property to separate it from the mineral impurities ■with which it is found associated. It undergoes a rough distilla- tion in earthen retorts. Iron pyrites contain^ 50 per cent, of sul- phur, whicli is separated either by roasting it in large heaps in the air, and collecting the melted sulphur in cavities, or by heat- ing the pyrites in tubes, and running off the sulphur into vessels of water. 647. Its Forms. — In commerce, sulphur exists in forms due to the different modes of its preparation : 1st, as Jlour of sulphur, a pale, yellow, gritty powder, obtained by sublimation ; 2d, as milh of sulphur, where it is procured in a very minute state of subdi- vision, by dissolving sulphur in a solution of an alkali, and pre- cipitating it with an acid ; 3d, roll sulpthur, or brimstone, obtained by running it into moulds in the melted state. 648. Its Allotropic States.— These are three. First, crystals which take the form of right, rhombic octa- hedrons. Fig. 234. They occur in nature, and may be produced by evaporating a solution of sulphur in bisulphide of carbon. These crys- tals have a sp. gr. of 2.05, and undergo no change in the air. The second form is that of oblique, prismatic crystals, which may be ob- tained by melting ordinary sulphur in a cruci- ble, and after it has cooled breaking the ves- sel, when the still fluid portion flows out, leaving a mass of crys- tals attached to the inner surface of the crucible, Fig. 235. These have a sp. gr. of 1.98, are not permanent in the air, and require a higher temperature to melt them than the former. 649. The third allotropic condition is ob- tained by the action of heat. Sulphur melts at 239° into a thin, pale, yellow liquid, in which solid sulphur sinks. If the heat is raised to 480°, it changes into a thick, tenacious, mo- Cry.,uiB by Fusion, j^gg^g^ colored body, which, if poured into cold water, becomes soft and elastic, like India rubber. In this state it Sulphur Crystals Fig. 235. How obtained from pyritos ? 647. "What is flour of sulphur ? What is milk of buI- pliur ? W})at IB roll fsulphur? 648. What is the firet allotropic form of sulphur? SULPHUR AND ITS COMPOUNDS. 251 is used to take impressions of medals, coins, &c. ; but it gradually resumes its former brittle condition. Sulphur is consumed largely in tlie manufacture of gunpowder, friction matches, sulphuric acid, and in medicine. It has an extensive range of affinity, ranking next to oxygen in this respect, and forming many important com- pounds. 650. Sulphurous Acid, SO2. — "When sulphur is ignited in the air, or in pure oxygen. Fig. 236, it burns with a beautiful blue flame, and forms sulphurous acid. This is a transparent, colorless gas, having a pun- gent suffocating odor familiarly known in the case of a burning match. It extinguishes com- bustion ; hence sulphur is often thrown into the fire to quench the burning soot of chimneys. It has a strong attraction for water. Allowed to escape into the air, it forms white fumes with its moisture, and a piece of ice thrust into the gas is Making^^^phuroua instantly liquefied. "Water at 60° takes up large quantities of this acid, the solution formed having the taste and smell of the gas. By cold or pressure it condenses into a liquid, and evaporates so fast that the cold generated will freeze water even in a red-hot crucible. 651. Sulphurous acid is used as a disinfectant, and in bleach- ing woollen and straw fabrics. The goods are moistened, and suspended in' large chambers, or, in a small way, they are put in inverted barrels, and exposed to the fumes of burning sulphur. The effect is produced, not by destroying the coloring matter, as in the case of chlorine, but by the union of the acid with the col- oring matter, which forms a white compound. If a red rose is held over burning sulphur, it is whitened, but the color is at once restored by weak sulphuric acid, which, being stronger, discharges sulphurous acid from combination. If woollens, after sulphur bleaching, are washed with a strong alkaline soap, the acid is neu- tralized by the alkali, the coloring matter liberated, and the yel- lowish color restored. 652. Sulphurous acid may be conveniently prepared by heat- ing strong sulphuric acid with copper turnings. One equivalent of the acid parts with one equivalent of its oxygen, thus liberat- The second ? 649. The third ? For what is it used ? 650. How is sulphurous acid formed ? "What are its properties ? 651. For what is it used ? How does it act in 258 INOKGAXIC CnF.MT.STRY. ing the sulphurous acid gas, while the oxide formed unites with another proportion of the acid, producing sulphate of copper. 653. Sulphuric Acid, S03HO. — This powerful acid is of great interest to chemists and manufacturers. It is found native in the craters of manv volcanoes, and in the water of mineral springs. It was formerly prepared bv distilling drv sulphate of iron (green vitriol) ; hence its old name, oil of titriol. Xow, however, it is usually obtained bv combining one equivalent of oxygen with sulphurous acid. SO2 is thus converted into SO3. 654. Sulphuric acid may be prepared on a small scale by an Fig. 237. Arraag.: . : Tr sparing Salphnric Acid. apparatus represented by Fig. 237. A large glass balloon, a. is connected by tubes with three flasks. Flask 5 supplies it with sulphurous acid; <•, with deutoxide of nitrogen; paunc Ac.d. factory the balloon is represented by large chambers lined with sheet lead, and the flasks by furnaces, Fi». 23S. In one furnace sulphur is heated, and pours into tlie chamber sulphurous acid, SO2. In another, nitre is heated in an iron pot with sulphuric acid. bleaching? What restores the color? 652. How may SO, be prepared? 653. What is sulphuric acid f What gave it its old Damef 654. Describe the process SULPHUR AND ITS COMPOUNDS. , 259 by whicll fumes of nitre acid, 'NOj^are produced and delivered into the chamber. The ISTOg is quickly deprived of an atom of oxy- gen by the sulphur, and becomes N0«. Steam and air are thrown into the chamber by another flue, and thus the conditions of action are secured. 655. The process depends upon the property possessed by the higher oxides of nitrogen of oxidizing sulphurous acid at the ex- pense of the oxygen of the atmosphere. The sulphurous acid is converted into the sulphuric, the oxygen being derived from the air, and the deutoxide of nitrogen being the carrier that transports it. A small quantity of IsTOa may thus form an endless quantity of SO3. These changes are represented in the following scheme. FROM AIR, 20 20 FROM THE \ N02_iN04 — >N0, HO S AS STEAM, HO \ FROM THE ^v. \ X \ FURNACE, S02v...,.^\J< ^^^ 2(S03H0) SO2ON ^ ^^-^ 2(S03HO) = 656. The large chambers of the manufactory are divided by leaden partitions with narrow openings, which serve to facilitate the intermixture of the gases as they pass on through the apart- ments. The bottom of the chamber is always kept covered with water to the depth of two or three inches, to absorb the acid as it falls. When the water has acquired a density of 1.5, by the absorption of acid, it is drawn off and boiled down in glass or platinum retorts, until it has a specific gravity of about 1.8. The acid thus obtained contains one equivalent of water to one of acid, SO3HO, and constitutes the ordinary sulphuric acid of commerce. 657. Properties. — Sulphuric acid has a thick, oily appearance, is without odor, and has at first a soapy feel, but it speedily cor- rodes the skin, causing an intense burning sensation. It is the most powerful of acids, and has an intense affinity for water. When a splinter of wood is dipped into it for a short time, it turns black, the acid taking away from it the elements of water, and leaving the carbon. In like manner, it decomposes and chars the of its preparation ? 655 Upon what does the action depend ? How is it effected ? 656. What further occurs in the manufactory ? 657. What are the properties of sulphuric acid. What is said of its affinity for moisture? What effects accom- 260 INORGANIC CHEillSTRY. skin and most other organic substances by removing their water. If a little concentrated acid is exposed to the open air in a shallow dish it will soon double its weight from the moisture absorbed. When sulphuric acid and water are mixed they shrink in bulk, and heat is produced. A mixture of four parts concentrated acid to one part water, Fig. 239, evolves sufficient heat to boil the ether in a test tube. The concentrated acid freezes at about —30°, and boils at 640°. Pure sulphuric acid is colorless, but slight traces of organic matter, as dust or straws, turn it of the dark shade usually seen in commerce. The commercial acid is cheap, but impure, containing traces of lead, arsenic, potash, and ohlorohydric and sulphurous acids. 658. Sulphuric acid is extensively used in the manufacture of carbonate of soda and chlorine, of citric, tartaric, acetic, nitric, and hydrochloric acids, of sulphate of soda, sulphate of magnesia, and various paints, also in dyeing, calico printing, gold and silver refining, and in purifying oil and tallow. Its chemical uses are innumerable. The test for sulphuric acid is chloride of barium, with which it forms a white insoluble salt. 1^ 659. Nordhausen Sulphuric Acid.— This is manufactured by the original process — the distillation of dried sulphate of iron in earthen retorts. It is a dihydrate, having one equivalent of water to two of acid, 2SO3 + HO, and is the strongest variety of sul- phuric acid. It derives its name from being manufactured in the town of Nordhausen, in Saxony. 660. Sulphuric Anhydride, SO3.— This may be obtained in the form of a white snowy solid, by distilling the Nordhausen acid, and collecting the fumes which pass over in a receiver surrounded by a freezing mixture. While in this condition, it exhibits no acid properties, and may be handled with impunity, if the hands are dry. But it fumes in the air, and rapidly absorbs moisture. When thrown into water it hisses like a hot iron, and the solu- tion thus formed possesses all the properties of the ordinary acid. 661. Hydrosulphuric Acid, HS {Sulphydric Acid, Sulphuretted Hydrogen^ Sulphide of Hydrogen). — This is a colorless, transparent gas, having the well-known odor of decayed eggs. It is feebly pany their union 1 What is said of the commercial acid ? 658 For ^vhat is it need? What ie its test? 659. Wliat is the Nordhanscn acid? 660. How is the anhydride oinained ? "What are its properties ? 661. Give the composition of eul- SULPHUK AND ITS COMPOUNDS. 261 acid, and burns with a pale blue flame, producing sulphurous acid and water. When breathed it is highly poisonous, and even when much diluted with air it has been proved fatal to many of the lower animals. By pressure the gas may be condensed to a color- less, limpid liquid, which freezes at —122°, the frozen portion sink- ing in the liquid. It readily dissolves in water, imparting to the solution its own taste and smell, as well as its slightly acid prop- erties. This gas is an abundant natural product from sulphur springs and the decay of organic matter containing sulphur, as albumen of eggs, flesh, &c. 662. Preparation. — It is usually obtained by decomposing pro- tosulphide of ii'on with dilute sulphuric acid, FeS + SO3, HO = FeO, SO3 + HS. Fig. 240. Fig. 24t) represents a convenient ar- rangement for its evolution. The sul- phide of iron should be broken into small lumps and placed in the flask. The cork and tubes may then be adjusted, and first water and then sulphuric acid poured in through the funnel tube. The gas is absorbed by the water of the sec- ond vessel. The solution must be kept in tightly secured bottles, as, if exposed to the air, it is gradually decomposed. Hydrosulphuric acid is one of the most important chemical reagents, and is used Preparing Sulphuretted Hydro- for precipitation of the metals. ^^"* 663. Bisulphide of Carbon, CS2 (Sp. Gr. of Liquid, 1.272 ; of Vapor, 2.644). — This is a very volatile, colorless liquid, boiling at 118.5°, has a sulpurous odor and pungent taste. It has never been frozen, and is used in thermometers which are to ineasure very intense degrees of cold. It is highly inflammable, burning with a blue flame, and yielding carbonic and sulphuric acids. It dissolves sulphur, phosphorus, and iodine, and is dissolved in ether, but not in water. It is produced by bringing vapor of sulphur into con- tact with red-hot charcoal, the compound vapor being condensed phuTctted hydrogen. "What are its properties? 662. How is It prepared? Ex- plain Fig. 240. For what is it used ? 663, What is bisulphide of carbon ? State 262 LNORGA^^c chemistry. in cold vessels. From its high dispersive power over light, it is used to fill hollow prisms of glass for spectroscopic observations. § II. Selenium and Tdluriura. SELENIUM. Sym. Se. Fquiv. 39.7. Sp. Gr. 4.8. 664. This is an element of rare occurrence. It has not been found free, but usually occurs in combination with iron, copper, or silver. It is a brown, brittle sohd, of metallic lustre and a glassy fracture. It presents a strong resemblance to sulphur, uniting with oxygen to form acids corresponding to the sul- phurous and sulphuric, and with hydrogen to form the selenide of hydrogen, a compound, if possible, more offensive than sulphide of hydrogen. TELLURIUM. Sym. Te. Equiv. 64.5. Sp. Gr. 6.6. 665. A rare substance, found sometimes native, but generally combined with metals. It has a metallic aspect resembling bis- muth, and was formerlly classed with the metals, but it is now placed with sulphur and selenium on account of its strong anal- ogy with these bodies. Its compounds with oxygen and hydro- gen resemble those of its associates. § III. Phosphorus and its Comjpounds. PHOSPHORUS. Sym. P. Equiv. 31. Sp. Gr. 1.83. 666. This interesting body is a soft, colorless, half-transparent, waxy solid, so extremely inflammable that it takes fire in the open air by the heat of the slightest friction, and burns with great violence, emitting a brilliant flame, and deuse, white fumes of phos- phoric acid. If quietly exposed to the air it undergoes slow oxi- dation, emitting white vapors of an odor like garlic. It must be it properties. Usob. 664. What is eelcnium? 665. What is tellurium ? 666. What are the properties of phosphorus? Why is it kept under water ? What are its PHOSPHOEus a:nd its compounds. 263 handled with caution, as the burns it produces are deep and diffi- cult to heal. From its inflammability it is kept under water. It is insoluble in water ; partially soluble in ether, but dissolves readily in bisulphide of carbon and various oils. 667. Source and Preparation. — Phosphorus combines with oxygen, forming phosphoric acid, and then unites with lime, produ- cing phosj)hate of lime. In this form phosphorus exists in bones, the phosphate of lime forming the mineral portion. The skeleton of a man contains from 1^ to 2 lbs. of phosphorus. To obtain it, the bones are first burned, and, the organic matter being con- sumed, they are reduced to powder and soaked in concentrated sulphuric acid. This decomposes the phosphate, removing two thirds of the lime. The remainder is then heated to a high tem- perature with charcoal in a close vessel. The carbon unites with the oxygen, liberating the phosphorus, which rises in vapor, and is condensed in water in the shape of yellow drops. These are melted under water and forced into tubes, thus forming the ordi- nary stick phosphorus. 668. Discovery. — Phosphorus was discovered by Beandt in 1669. The name signifies Vearer of ligli% and was given on ac- count of its property of being luminous in the dark. In all its characteristics, it was a very extraordinary body. ' If touched it took fire and burned furiously, exhahng a dense white cloud, which gathered like fleeces of snow, but, unlike snow, hiss- ing like a red-hot iron when touched with water or, if brought into contact with the body, blistering it like living fire.' We may imagine the mingled wonder and dread of the devout alchemists as they passed precious little bits of it around among the initiated under a name which hinted their dark suspicions — ' the Son of Satan.' 6^9, Phosphorescence. — If solutions of phosphorus in ether be spread upon the face in the dark, it causes a pallid glow, which soon passes away. The cause of this self-shining of phosphorus is probably its slow oxidation. Berzelius stated that it became luminous in nitrogen, hydrogen, or even in a vacuum, but Scheotter's more careful experiments show that to produce the eflTect a little oxygen must always be present. 670. Its Allotropic Forms. — Among the marked properties solvents? 667. What is its source ? How is it obtained ? 668. How was it at tirst regarded ? 669. How may phosphorcsceneo be exhibited ? To what is it due ? 264 INORGANIC CHEMISTRY. of this singular substance is the diversity of its allotropic con- ditions. It assumes six different forms. The Jirst is the common transparent state, or vitreous phosphorus. When this is exposed to light under water it changes to the second variety, which is white, opaque, and less fusible. The third is a symmetrical crystal of the regular system, formed by evaporating some of its solutions. ThO) fourth is a black, opaque variety, produced by sud- den cooling of the melted phosphorus ; Jifth^ a soft elastic sub- stance analogous to viscous sulphur, and formed by suddenly cooling phosphorus when near its boiling point ; and, sixth^ a red amorphous sort, which may be obtained by exposing vitreous phos- phorus to the rays of the sun between two plates of glass. 671. This red amorphous variety may also be produced by heat- ing common phosphorus in an atmosphere of carbonic acid, when it is obtained as a brick-red powder. As vitreous phosphorus may be called the active variety, this is the opposite or passive form. It is heavier than the former, red in color, does not shiue in the dark, nor melt at the heat of boiling water. It exhales no vapor or odor ; oxidizes but very slowly in the air, does not change oxygen into ozone, is chemically indifferent toward other elements, may be handled with impunity, or carried exposed in the pocket, and is not poisonous when administered in doses a hundred times greater than would be fatal in the common form (G. Wilson). At 500° it is reconverted into the active form and bursts into flame. ^^672. Uses — The chief use of phosphorus is in the manufacturTTl) of friction matches, and vast quantities are consumed in this way among all civilized nations. In making matches the blocks are sawn by machinery, and the ends first tipped with sulphur, and then with an emulsion of phosphorus in glue, with a little saltpetre, oxide of manganese, or chlorate of potash ; bodies all rich in ox- ygen. The manufacture is not only dangerous from the explosive nature of the materials used, but from the corrosive phosphoric vapors, which produce among the laborers the distressing disease known as caries of the lower jaw. An attempt has been made to avoid these evils by the use of passive phosphorus in this manu- facture, but as yet with only partial success. 673. OflSce in Nature. — The part played by phosphorus in the scheme of nature is of the highest interest. Existing, combined 670. How many are its allotropic forms? What aro they? 671. What are tho properties of passive phosphorus ? 672. For what is phosphorus used f Dcscribo PHOSPHORUS AND ITS COMPOUNDS. 265 Fig 241. "witli lime, in the primitive and volcanic rocks, by their gradual decay in the course of ages, it passes into the soil. The plants, with their thousand rootlets sucking up the soluble extract of soil, obtain compounds of phosphorus, "which rise "with the sap to the leaf. It is maintained by some that a portion of its compounds is here decomposed, the phosphorus being set free and thro"wn into the passive state by the chemical influence of the sunbeam ( 372 ). Ho"wever this may be, it is stored up in the seeds Trhich are des- tined to nourish man and the higher animals. One portion is em- ployed to build up the bony structure, "while another forms a large constituent of the nervous system and brain. What the precise office of phosphorus in the brain may be wq cannot say, but that it performs some high duty in the reactions of the mind "with its organ, is manifest from the fact that after prolonged brain-exercise there is a rise in the proportion of phosphoric products in the liquid excretion. 674. — Phosphoric Acid, "PO 5 {Phosphoric Anhydride). — When phosphorus is burned in dry oxygen, Fig. 241, the dense, "white vapors "which are formed condense upon the glass in snow-like flakes. This is ^;/i(?s- phoric ajihydride. It has a po"werfal attraction for moisture, absorbing it from the air, or, if brought into contact "with water, seizing it -with such vio- lence as to emit a hissing sound. Phosphoric acid is thus formed, "which always contains water in its composition. By evaporation, a vitreous-looking substance is produced, known as glacial phos- phoric acid. Its solution is very sour. 675. The intensity of the attraction of phosphorus for oxygen may be strikingly shown by directing a stream of the gas against a small piece of phosphorus at the bottom of a vessel of warm water, when a bril- liant combustion will be observed beneath the liquid Fig. 242. 676. Phosphoric acid is procurable from bones by the action of sulphuric acid, which displaces it by seiz- ing the lime, or by the direct oxidation of phosphorus Combustion of Phosplaoru». Fig. 242. Under "^ater. the process. "What is said of its dangers ? 673. Whence do plants obtain their phosphorus? 'Wliat are its oflB.ces in the animal Bj-stem? Its relations to mental action ? 674. What ia phosphoric anhydride ? Glacial phosphorus ? 675. How is 12 266 IXOEGAXIC CHEMISTKY. by nitric acid. It combines with water in three proportions, forming Monobasic or metaphosphoric acid, HO, PO5. Bi'.)asic or pyrophosphoric acid, 2H0, PO5. Tribasic or common phosphoric acid, 3H0, PO5. Tiiese three acids give rioe to three series of salts. 677. Phosphide of Hydrogen, PH3 {PkospTiurettedEydrogen). — This is a colorless gas, with a very offensive odor, is poisonous when inhaled, and produced in small quantities by the decay of animal matter. It may be prepared by heating small fragments of phos- phorus with a strong solution of caustic potash in a retort. The end of the retort tube dips beneath water, and as the gas passes out in bubbles, it rises to the surface and takes fire spontaneously. If some pieces of the phos- phide of calcium are thrown into a glass of water, the same thing takes place. Double de- composition with the water produces phosphu- retted hydrogen, which ignites at the surface and forms beautiful wreaths of vapor, Fig. 243. The other phosphides of hydrogen are of little interest. 678. Phosphorus combines with chlorine so TV th f Flame ^^^Grgetically as to take fire. It also forms nu- merous compounds with iodine, bromine, nitro- gen, and sulphur, but they are comparatively unimportant. CHAPTER XII. THE HYALOGENS OR GLASS FORMEES. § I. Silicon and its Compounds, SILICON. Sym. Si. Equiv. 14. 679. Silicon. — This element is never found free in nature, but exists very extensively in the mineral crust of the earth in its iritense attraction for water shown? 676. How is it obtained from "bones? Whence aribC the three scries of salte ? 677. What are the properties of phosphu- SILICOX AXD ITS COMPOUNDS. 267 combination with oxygen, forming silica. It has three allotropic states : first, amorphous silicon — a brown powder ; second, a variety resembling graphite ; and third, a crystalline form. It holds an equivocal place in classification, some ranking it with the metals. It is difficult to separate, and is of no importance except to the scientific chemist. 680.— Silica, Si02 {Silicic Acid, Silex, Sand). — This is a com- pound of silicon and oxygen, the proportions of which are unset- tled. Beezelius held that it is SiOs, analagous to sulphuric acid, and this view has been generally accepted. But later chemists consider it as 810-2, or analogous to carbonic acid. 681. — Silica is the most abundant of mineral substances. Its purest condition is that of quartz, in which it forms hexagonal crystals terminated by six-sided summits. Fig. 244. If j,. ^^ this mineral is heated to redness and quenched in water, it is reduced to a fine, white, tasteless, gritty powder, which is nearly pure silica. The chief constituents of aU sandstones is silica, and it occurs in large proportion in many other rocks ; these, by decomposition, yield the silicons principle or sand of soils. The common flint and many valuable stones, as amethyst, agate, chalce- dony, carnelian, jasper, opal, and sardonyx, consist of Quartz Crys- silica, variously colored by other substances. 682. Solubility. — In pure water, and in all acids, except the hydrofluoric, it is insoluble, but it is dissolved by alkaline solu- tions. Hence, all natural waters which contain alkaline carbonates hold also in solution a little silica. If wood be present in such waters, as it decays, the particles of silica are deposited in place of those that escape, and thus a copy of the wood in stone, or a petrifaction, is produced. 683. It is an Acid. — Though so insoluble and inert, silica is reaUy an acid, combining with bases, and forming silicates which are true salts. By the intense heat of the oxyhydrogen flame it is melted into a pure glass, and may be spun out into threads. But when mixed with alkalies it melts at a lower temperature, combin- ing with them to form ordinary glass. The most abundant min- retted hydrogen ? Ho-w is it obtained ? 678. Other compounds of phosphorus ? 679. "WTiere is silicon found ? "WTiat are its allotropic forms ? GSO. What is the composition of silica ? 681. "WTiat is the purest silica? What is said of its abun- dance? 682. Its solubility ? How are petrifactions formed? 683. What are e'li- 268 IXORGANIC CHEMISTRY. erals, mica, feldspar, hornblende, serpentine, &c., "whicli form the granitic, and many other rocks, are silicates of the alkalies and alkaline earths ; — like glass, they are also salts. 684. Silica of Soil.— At common temperatures carbonic acid is stronger than silicic ; hence, upon many of the silicates the air exerts a destructive agency. Its carbonic acid slowly unites with their bases, setting the silica free, thus forming one of the disinte- grating forces by which rocks are reduced to the condition of soil. At the moment of its liberation it is soluble in water. In this way, but still more powerfully by the action of alkalies, silica is dissolved by the water of soils, and, entering the roots of plants, performs an important office in giving stiffness and strength to the stalks of grains and grasses. 685. Soluble Glass.— If 8 or 10 parts of carbonate of soda or potash are mixed with 12 or 15 parts of sand and 1 of charcoal, on being heated they melt, and form a mass resembling ordinary glass ; but it entirely dissolves in hot water. This is known as solulle glass, and when applied to wood and other substances an- swers the protective purpose of a varnish or paint. 686. Its Colloidal Form. — If to a solution of soluble glass, chlorohydric acid be added, it neutralizes the alkali, and the silica separates as a transparent jelly — a fine example of the colloid state (83). It is a hydrate of silica, and is insoluble in water or acids. This gelatinous state may be continued by keeping it moist, but as soon as it is deprived of water it falls to a gritty powder. 687. Fluoride of Silicon, SiFg {Fluosilicic Acid). — This is a colorless gas produced when fluohydric acid is liberated in contact with silica. \Yhen passed into water the gas is decomposed, the silica becoming gelatinous, and the water a solution of hydrofluo- silicic acid, IIF, SiFo. 688. Silicates are salts of silica, and form a large class of nat- ural minerals. Most of them are fusible ; some, however, melt at only very high temperatures. They are all insoluble in water except the silicates of the alkalies. Those artificial silicates which are of interest in the arts will be noticed when speaking of their respective bases. cates? Give ex.imploB, 684. Wliat is the action of carbonic acid upon pilicatca? Wliat is the office of Bilica in plants ? 685. What is soluble glass ? 686. Describe Its colloidal form. Wbntisit? 087. What is fluoride of silicon ? 688. State th« gen:eeal peopeeties of the metals. 269 § n. Boron, Sym. B. Equiv, 10.9. 689. Boron is a rare substance always found in combination Tvitli oxygen, as boracic acid. It strongly resembles silicon, and, like it, is capable of assuming three allotropic states. 690. Boracio Acid, BO3. — This is found as a natural constitu- ent of several minerals, but the principal supply is derived from the lagoons of Tuscany. Here, the acid issues from the earth along with jets of steam, and is collected by throwing the jets into water. The acid is afterward separated from the water by evaporation in leaden pans so arranged that they are heated by the vapors as they escape from the earth. It is deposited in white, scaly crystals, which are purified by repeated crystallizations. These crystals have a glassy appearance, and are soapy to the touch. They dis- solve much more readily in boiling than in cold water, and form a solution having feebly acid properties. CHAPTER XIII. THE METALLIC ELEMEXTS. § I. General Properties of the Ifetals. 691. The metals form the largest division of the chemical ele- ments, and are distinguished by certain characteristics which they manifest in very different degrees. They have aU a peculiar shining appearance, called the metallic lustre. Most metals, however, may be obtained in conditions free from this lustre, while some bodies which are not metals, as iodine and plumbago, have also a metallic brightness. They vary in color ; several, as silver and platinum, are wbite, with tints peculiar to each ; others, as lead and tin, are bluish ; iron and arsenic are grayish ; calcium and barium a pale yellow ; gold a bright yellow, and copper red. 692. Hardness, Brittleness, Tenacity. — In hardness the metals exhibit wide differences ; steel scratches glass, while potassium is properties of the silicates. CS9. TVhat Is boron ? 690. How is boracic acid ob- t^ned ? 691. How are the metals distinguished ? What of their colors t 692. How 270 IXOEGAXIC CHEMISTRY. soft as wax. Some, as bismuth and antimony, are so brittle that thev maj be easily crushed in a mortar, while to pulverize gold or copper requires immense force. Their tenacity, which is deter- mined by the amount of weight which wires of equal diameter will support, is also various. If lead be taken as 1, copper is 17 and iron 26, Heat generally diminishes the tenacity of metals, but in the case of iron and gold it increases it up to 212''. 693. Malleability and Ductility. — Malleable metals are those which may be hammered into thin leaves. Gold heads the list, and has been reduced to a film the 2Fo?ooo of an inch in thickness. In ductility, or capability of being drawn into wire, platinum stands first. Wollastox produced wire from it but so-lwo of an inch in diameter. The foregoiug properties in each case vary with the texture of the metal. 694. Specific Gravity. — In this respect also there are great differences. TVhile platinum is 22 times heavier than water, lith- ium is but little more than half as heavy as that liquid. The lightest metals have the strongest afiinity for oxygen. 695. Fusibility.— The range of properties is here most remark- able. TrhUe mercury remains fluid at 39^, potassium and so- dium fuse below the boiling point of water ; silver and gold melt at a red heat, iron at a white heat (2,786^), and platinum only at the intense, but undertermined heat of the oxyhydrogen blow- pipe. 696. Volatility. — Mercury vaporizes at 602°, and several metals are so volatile that they may be distilled from their compounds. Lead is largely volatilized, and copper slightly so in the smelting furnaces, and even gold is dissipated in vapor in the focus of a powerful burning glass. Some of the metals emit odors ; arsenic gives the smell of garlic, while iron, tin, and copper by friction give forth distinctive odors. 697. Conduction of Heat and Electricity. — The metals are ex- cellent conductors of heat and electricity, but vary in this respect. "When separated from their compounds by electrolysis, they appear at the negative pole, and are hence electro-positive. It is remark- able that the vapors of the metals are non-conductors of electricity. 698. The metals occur in nature in three states. First, some do they vary in hardness, briltleneBf?, and tenacity? 693. In malleability and ductility? 694. Specific gravity? Relation to affinity? 695. How do they differ in fusibility? 696. In volatility? 697. What is their relation to heat and GENERAL PEOPEETIES OF TELE METALS. 271 of them, as gold, silver, platinum, and mercury, are often found un- corabined, and are said to occur in the native state. Second, many are found alloyed with each other, as gold and silver with mercury ; but usually they occur in combination with the metal- loids, for which they have a strong attraction. These compounds are known as metallic ores. 699. Distribution. — The soil and rocks beneath us, as has been stated, consist of metallic oxides, but the chief metals used in the arts are not so widely disseminated. They are found in various places and at various depths in the earth, in the form of seams, beds, or mineral veins. Fissures and openings among the older or fire-formed rocks often occur filled with ores, and are called lodes. The thickness and direction of veins are various, the most productive generally occurring near the junction of two dissimilar lands of rock. It is supposed they are ' accumulated there in consequence of slow voltaic actions which have been going on through uncounted ages, and which have been occasioned by ditFerences in chemical composition of the two contiguous rocks.' (MiLLEE.) The ores are procured by excavating shafts in the earth, cutting horizontal or inclined galleries, and by picking, w^edging, and blasting out the minerals. 700. Treatment of Ores. — This is first mechanical, then chem- ical ; the more valuable the ore, the more care does its manage- ment require, but the operations differ widely in different cases. The ores of lead and tin are dressed as follows : when brought to the surface, they are sorted, the purest lumps being set aside for the smelting furnace. The residue is then broken by hammers, and again sorted. The rougher portions are then crushed between revolving cylinders and the product passed through coarse sieves ; while the finer part is agitated in water by the hand process of jigging. The crushing is completed in the stamping mill, which consists of upright, wooden beams, shod with iron and lifted by steam or water power, which are allowed to fall upon the ore. The products are repeatedly washed, and the powdered ores settle in layers according to their specific gravities. 701. Roasting Ores — After ores have been prepared mechan- ically, they are subjected to chemical treatment, which is twofold electricity? 698. In -what three states are the metals found ? 699. How do they usually occur? How are the Yeins formed? How worked? 700. How are lead and tin ores dressed ? 701. "When are metals roasted ? Plow is it done ? "When is 272 INOEGAXIC CHEMISTET. Fig. 245. — roasting and reducing. If tljej contaiD volatile products, as Bulphur or arsenic, which may be removed by oxidation or heat, they are first roasted. This is done in an oven-shaped furnace, called a reverheratory^ Fig. 245. The fuel is placed at one end, and the heated gases and flame are rc- xerherated^ or thrown down from the arched roof of the furnace upon the ore, which is distributed over its bed. In this way ores are ox- idized. If they contain sulphur, it burns off and escapes as sulphurous acid, while arsenic is carried away as arsenious acid. Sometimes, as in the case of lead, the metal is at once procured by the operation of roasting. In other instances it is changed to the state of oxide, and then requires another process to set it free. 702. Reduction or Smelting of ores is the chemical process of deoxidation. It is effected by heating them to a high tempera- ture in contact with substances which ta,ko the oxygen from the metal by superior aflSnity. Carbon is the chief deoxidizing agent, and removes the oxygen in the form of carbonic oxide and carbonic acid. For the removal of various earthy impurities, sub- stances are employed termed fluxes, which, combining with them, melt and flow off as crude glass or slag. For laboratory opera- tions with the metals, small furnaces are indis- Laboratory Furnace, pen Sable, such as those represented in Fig. 246* Ileverberatory Furnacj. Fig. 246. § II. Theory and Constitution of Salts. 703. Salts result from the union of non-metallic elements with the metals ; they are therefore to be considered as compounds of the metals. It has been stated that salts are formed by the union another process required ? 702. What is Bmelting ? How efTected ? For -what is Mrbon used ? AVhat is the use of fluxes ? 703. llow are salts to bo considered ? THEORY AND CONSTITUTION OF SALTS. 2V3 of acids and bases, but a more complete account of their consitu- tion is now necessarj. 704. Two Kinds of Acids and Salts. — ^When oxygen was dis- covered it was found by Laycisiek to enter largely into the com- position of acids ; it was therefore believed to be the universal acidifying principle, and given a name which signifies acid-former. But it was afterward found that there are powerful acids, as the chiorohydric and iodohydric, which contain no oxygen at all^ their common principle being hydrogen. Hence two kinds of acids were recognized, oxacids and hydracids. 705. In like manner it was at first supposed that all salts were double compounds, acid united to base, as sulphuric acid to potash, KO, SO 3. But it was at length discovered that this composition represents but a part of the salt family, and if adopted would ex- clude common salt itself the very substance from which the term salt was derived. For, although common salt is produced by the addition of an acid and a base, chiorohydric acid to soda, yet there is not a simple union of the two binary compounds, but a double decomposition : the acid and the base are each split, and two com- pounds result ; thus I:^aO + HCl = iSraCl + HO. That is, when these substances are brought together, chloride of sodium and water are formed. Hence two kinds of salts are recognized, oxysalts and the haloid salts, or those which resemble common salt, from Jials^ salt. But it has been latterly maintained that there is only one type of acids and one of salts. Davy started the hypothesis that all acids are properly Jiydracids, and all salts binary. 706. The Later View of Acids — ^-It is well known to chemists that when the oxacids, sulphuric, nitric, and phosphoric, are deprived of water, they no longer possess true acid properties. Sulphuric an- hydride does not redden litmus, nor corrode the fingers ; but if water be added, it instantly becomes a powerful acid. iN'ow, as hy- drogen is present in all the hydracids, and as the oxygen compounds only become acid by the addition of water wMcJi contains hy- drogen^ it is assumed that not oxygen, but hydrogen is the universal acidifying principle ; and if there is but one acid-former, there is probably but one type of acids. The elements which combine with hydrogen to form acids are called radicles, as chlorine, iodine, &c. 704. What -R-as the early idea of oxj-gen ? TVTiat is now known ? 705. What was the first idea of salts ? "What was at length discovered? Constitution of common Bait, What is Dayt's hj-pothesis ? 706. Why has hydrogen heen regarded as tho 12* 274 INOEGAXIC CHEMISTET. 707. In speaking of cyanogen, it was ttated that there is a class of conajjound bodies of which that substance is a type, which play the part of simple elements, and are called compound, radicles. Cyanogen, NCo, combines directly with hydrogen (like the simple radicle chlorine), to form cyanohydric acid, HXCo. Xow it is assumed that the oxacids contain compound radicles in the same way ; and if this be admitted, the whole case is simplified. It is claimed that in sulphuric acid there is the radicle sulpbion SO4 ; in phosphoric acid, phospliion POc, and in nitric acid, nitration 'SO^ These radicles unite with hydrogen, and thus the oxacids are binary. Sulphuric acid is snlphionide of hydrogen. The change is simple. OLD TIEW OF ACIDS. XEW TIEW. Phosphoric acid, H0,P05. H.POe, analogous to H, Cy. Sulphuric acid, HO, SO3. H.SO„ " " H, CI. :N'itric acid, HO,^©^. H,NOe, " H,Br. Hence we arrive at the following definition : An acid is the hydrogen compound of a simpjU or compjound radicle uhich pos- sesses the pjower of neutralizing bases; its general formula being HE {hydrogen and radicle.) 708. Later View of Salts. — From this point of view the com- position of salts is also simplified ; one type of acids gives us also one type of salts. By replacing the hydrogen of chlorohydric acid, HCl, by sodium, we get common salt, XaCl. By replacing the hydrogen of cyanohydric acid by potassium, we get the salt cyanide of potassium, HXC2. And so by replacing the hydrogen of snlphionide of hydrogen by iron we get sulphionide of iron, FeS04, instead of the old sulphate, FeO,SOg. On this view we may define a salt to be the compjound formed by repAacing the hy- drogen of an acid by a metal ; and the general formula for a salt is MR (metal and radicle.) (For diagrams rendering this sub- ject easy of comprehension, see Author's Chemical Chart and Atlas.) 709. EBtimate of the Hypothesis. — Although the foregoing hypothesis is ingenious and useful, and is perhaps growing in favor with progressive chemists, yet upon close examination, it is acidifying principle? What are radicles? 707. Compound radicles? Explain the new view of acida. What is the definition of an acid by this view ? 708. Ac- cording to thie, how are ealts formed ? Give the definition of a salt. 709. "N^Tiat THEORY AND CONSTITUTION OF SALTS. 275 found liable to objection, and, as remarked bj Peof. Miller, cannot be considered as a correct representation of the composi- tion of a salt under all circumstances. A salt, when once formed, may be regarded as a whole ; it can no longer be looked upon as consisting of two distinct parts, but as a new substance maintained in its existing condition by the mutual action of all the elements which compose it. These different elements are not all united with each other in every direction with an equal amount of force. As a crystal cleaves in different directions as the force is differ- ently applied, so a salt may split up into different simpler sub- stances, according as the chemical force is applied one way or another. The probability therefore is, that neither the old nor the new view is absolutely correct, but that each may in turn well re- present the salt when subjected to the influence of different forces. 710. Sulpho-Salts — Sulphur is analogous to oxygen in chemical relations ; and as there are oxysalts, so there is also a class of sul- pho-salts, exactly corresponding to them in constitution. 711. Normal Salts. — The term normal salts has been applied to all those in which there is an atom of acid for each atom of oxygen in the lase. Carbonate of potash, KO, 00 2, is an example. Where the base consists of a sesquioxide containing three atoms of oxygen, it requires three atoms of acid to form a normal salt. Tor example, alumina, AI2, O3, requires three atoms of sulphuric acid to form a normal sulphate of alumina, AI2, O3, 3SO3. 712. If a solution of oxalic acid be added to that of potash in equivalent proportions, a neutral salt is formed. If this be re- dissolved, and another proportion of oxalic acid be added, it unites with the salt already formed, and an acid or super-salt is produced which reddens litmus and crystallizes in a different form from the first. Basic or sub-salts have an opposite structure — the base pre- dominating over the acid. It has been stated that water in combi- nation plays the part of both acid and base. With bases it unites as a feeble acid, and with acids as a feeble base. When one atom of water is combined with one of acid, it forms a monobasic acid ; if two of water, a Mhasic acid ; and if several, a polybasic acid. Hence, by replacing the water of polybasic acids by metallic bases, does Prof. Miller say of this theory? 710. What are sulpho-salts ? 71L What are Horraal salts ? 712. What Ib a neutral salt ? A supor-salt ? A sub-salt ? When 276 IXOPwGAXIC CHEinSTEY. vre get suh-salts or hasic salts. If different bases combine witb poly- basic acids, thej produce douUe salts. 713. In crystallizing from aqueous solutions salts combine with a definite proportion of water, wliich is contained in the crystal as uater of crystallization. Alum crystals contain nearly one half their weight of water. Certain crystals (Glauber's salts, for exam- ple), if exposed to the atmosphere, part with their combined water by evaporation, lose their brUliancy and crumble to a white pow- der ; this is called efflorescence. Other salts when rapidly crystal- lizing confine mechanically in their texture a portion of the mother liquor, causing them when expanded by heat to explode with a crackling noise, which is termed decrepitation. Others, when ex- posed to the air, absorb water and become semi-liquid, the process being called deliquescence. The salts that have been produced are already numbered by thousands, and there is no end to their multiplication. "We shall have space to notice but a few, and those briefly. CHAPTER XIY. METALS WHICH DECOMPOSE WATER AT OPvDIXAEY TEMPERATURES. 714. Authors vary in their classification of the metals, but they are usually arranged according to their affinity for oxygen. "We shall divide them into three groups : first, metals which decom- pose water at common temperatures ; second, metals which only decompose water at a red heat ; third, metals which cannot de- compose water at all. The first group comprises nine elements, as follows : — PoTASSirM, I Xhe first five metals of this group, when oxydated, produce alkalies, and are therefore called metals of the alkalies. The oxides of the remaining four are alkaline, though in a less degree, and have also an earthy appearance ; hence they are termed metals of the alkaline earths. C/ESIUM, ErniDiuM, Sodium, Lithium, Barium, Strontium, Calcium, Magnesium. Is an acid gald to be monobasic ? When bibaeic ? Wbon polybasic ? 713. What is water of crystallization? What ia effersescence ? Decrepitation? Deliqucs- METALS OF THE ALKALIES. 277 § I. Metals of the Alkalies. 1. POTASSIUM AND ITS COMPOUNDS, Potassium. Sijm. K {Kalium). Equixi.Z^. Sp. Gr. 0.855. 715. Potassium was discovered by Sir Humphrey Dayt in 1807, together with sodium, barium, strontium, and calcium. Before that time the alkalies and alkaline earths had been considered as simple bodies, and the discovery of their compound nature forms an interesting era in chemical science. Davy obtained this metal by subjecting moistened potash to the action of a powerful voltaic battery ; the positive pole gave off oxygen, and metallic globules of pure potassium appeared at the negative pole. 716. It is never found free in nature, but occurs abundantly in rocks and soils combined with oxygen, as potash. It is usually obtained by the action of charcoal upon carbonate of potash at a very high temperature. The carbonate is decomposed, the free carbon seizing the oxygen of the potash and escaping as carbonic oxide, while the metal distils over into suitable condensers, KO,C02+2C = K + 3CO. 717. Properties. — Potassium at common temperatures is a silver- white metal, and so soft that it maybe moulded like wax. It has a powerful affinity for oxygen. If thrown upon the surface of water, instant decomposition takes place ^._ Fig. 247, the potassium uniting with the oxygen to form potash. The liberated hy- drogen, together with a small quantity of volatilized metal, is ignited by the heat evolved during the decomposition, and comi^I^^^n^ssium. burns with a beautiful lilac flame as the globule floats about on the surface of the liquid. Potassium de- composes nearly all compounds containing oxygen, if brought in contact with them at high temperatures, and many even at ordi- nary temperatures. Hence, to preserve it pure, it is kept in naphtha, a liquid containing no oxygen. cence? 714. How are the metals classified? How is group first divided? 715. Wlien and by whom was potassium discovered ? By what means ? What was the effect of the discovery? 716. How does it occur in nature? How is it obtained ? 717. What are its properties ? Why is it kept in naphtha ? 278 INOKGAXIC CHEMISTRY. 718. Protoxide of Potassium, KO (Potash). — This, the most im- portant compouud of potassium, is always formed when the metal comes in contact with free oxygen. It has a powerful attraction for water, absorbing it with avidity when exposed to a moist at- mosphere, and forming a hydrate, or caustic potash^ KO, HO. This is generally procured by the action of caustic lime in a boiling so- lution of carbonated potash. The lime unites with the carbonic acid of the potash, forming insoluble carbonate of lime, which sub- sides. The clear liquid, containing the potash in solution, is then drawn off and concentrated by evaporation. If the heat be continued to a point little short of redness, the liquid flows without ebullition, and may then be run into moulds, where it solidifies on cooling, forming the small, grayish-white sticks of commerce. 719. Potash possesses all the properties of the alkalies in a pre- eminent degree. It saturates the most powerful acids, changes vegetable yellows to brown, restores the blues discharged by acids, and decomposes animal and vegetable substances, whether living or dead. It is used in medicine to cauterize and cleanse ulcers and foul sores; hence its name, caitstic potash. If a solution of potash be shaken in a bottle with any fixed oil, the two unite, forming a soap. This accounts for the soft greasy feel it has when touched by the fingers, as it decomposes the skin and forms a soap with its oily elements. When taken into the system, potash acts as a powerfully corrosive poison. Its active chemical character renders it an indispensable reagent in the laborator3^ 720. Iodide of Potassium, KI {Eydriodatc of Potash).— This may be formed by adding iodine" to a solution of potash, and gently warjning until the solution assumes a brown tint. It is a very soluble, white solid, which crystallizes in cubes, and is much used in medicine. 721. Carbonate of Potash, K0,C02. — Potash exists in plants in combination with various organic acids. When the plant is burned, these combinations are broken up ; the organic acids are decomposed into carbonic acid and water, and the liberated pot- ash unites with a portion of the carbonic acid formed by combus- 718. What is potaeh ? Hydrate of potash? How is caustic potash obtained? 719. What are its properties ? What is its action with oils ? Its uses in medicine ? In the laboratory? 720. Wiiat is iodida of potagBium ? Its uses? 721. How is -METALS OF THE ALKALIES. 279 tion, thus producing carbonate of potash. Tliis is a highly alka- line, deliquescent salt, and is used largely in the manufacture of soap and glass, in preparing caustic potash, &;c. It is also an im- portant reagent in the laboratory, and is a most valuable fertilizer. This salt rarely forms less than 20 per cent., and sometimes more than 50 per cent, of the weight of wood ashes. The ashes of dif- ferent plants, and even different parts of the same plant, yield it in varying amounts. "Wood ashes furnish the principal source of the carbonate of potash of commerce, from which it is obtained by leaching them and boiling the solution to dryness in iron pots. The residue is called 2Jotashes^ and these, when calcined, afford the impure carbonate known as 2yearlash. Potash, or pearlash, there- fore represents the readUy soluble portion of wood ashes, and con- sists chiefly of carbonate of potash with small amounts of carbon- ate of soda and common salt. 722. Bicarbonate of Potash, KO, 2CO2.— This is formed by passing carbonic acid through a strong solution of carbonate of potash, which combines with a second equivalent of the acid. It is employed as a source of potash in the formation of many of its other compounds, and is also used for making effervescing draughts by adding citric or tartaric acid to its solution, which, combin- ing with alkali, sets the gas free. 733. Kitrate of Potash, K0,N05 (Mtre, Saltpetre).— This salt occurs as a native product in the earth of various districts in the East Indies, and is separated therefrom by leaching the soil, and allowing the nitre to crystallize. It is artificially formed by heap- ing up organic matter with lime, ashes, and soil, and keeping the mass well moistened with urine for a period of two or three years, when the heap is lixiviated and the salt crystallized out. Besides these sources, nitre occurs in the sap of certain plants, such as the sunflower, tobacco plant, &c. 724. Xitre dissolves in about three times its weight of cold and one third its weight of boiling water. It is rich in oxygen, and when thrown upon burning charcoal is decomposed and defla- grates violently. Paper dipped in this solution, and dried, forms what is known as touch paper. When ignited, it burns slowly and carbonate of potash obtained? State the properties and uses of the salt ? How do its proportions vary in different ashes? What is pearlash? For what used? 722. What is bicarbonate of potash? Its uses? 723. How does nitrate of potash aceur? Explain its artificial formation. From what other sources ©btained? 280 rXOKGANIC CHEMISTRY. steadily until consumed ; hence its use in lighting trains of gun- powder, fireworks, &c. Nitre has a cooling, saline taste and strong antiseptic powers. Owing to the latter quality it is used extensively in packing meat, to which it imparts a ruddy color. It is chiefly consumed, however, in the manufacture of gunpowder; the large amount of oxygen it contains, and the feeble affinity by which it is held, adapting it for sudden and rapid combustion. 725. Gunpowder is an intimate mechanical mixture of about 1 part nitre, 1 part sulphur, and 3 parts charcoal. These propor- tions, however, vary somewhat in different countries, as well as in different sorts of powder. More charcoal adds to its power, but also causes it to attract moisture from the air, which of course in- jures its quality. For blasting rocks, where a sustained force, rather than an instantaneous one, is required, the powder contains more sulphur, and is even then often mixed with sawdust to re- tard the explosion. 726. Manufacture. — The nitre, sulphur, and charcoal, having been ground and sifted separately, are thoroughly mixed and then made into a thick paste with water. This is ground for some hours under edge stones, after which it is subjected to immense pressure between gunmetal plates, forming what is known as press-calce. These cakes are then submitted to the action of tbothed rollers, whereby the granulation of the powder is effected. The grains thus formed are sorted into different sizes by means of a series of sieves, and thoroughly dried at a steam heat. The last operation, that of polishing, is accomplished in revolving barrels, after which the powder is ready for market. The heavier tlie powder, the greater is its explosive power. Good powder should resist pressure between the fingers, giving no dust when rubbed, and have a slightly glossy aspect. The explosive power of gun- powder is due to a sudden formation of a large volume of nitrogen and carbonic acid gas ; one volume of the powder giving about 1,800 volumes of vapor. FireworlcB contain nitre as a chief in- gredient, mixed with charcoal, sulphur, ground gunpowder, and various coloring substances. 727. Chlorate of Potash, KO, CIOd.— This may be formed by 724. What is touch paper? For what ufied? What are the uses of nitre? 725. What la gunpowder ? How may its properties be varied ? 726. Describe its man- mfacturo t How mny good powder bo distinguished ? To what is tho cxploMvo SODIUM AND ITS COMPOUNDS. 281 passing clilorine gas througli a solution of carbonate of potash. Chlorate of potash is soluble in water, has a taste resembling that of nitre, melts at about 700°, and, if heated above that tempera- ture, parts with its oxygen. It is used in the manufacture of lucifer matches, in certain operations of calico printing, and as a source of oxygen. 2. SODIUM AND ITS COMPOUNDS. Sodium, Sym. JSTa. {Natrium). Uquiv. 23. Sp. Gr. 972. 728. Sodium closely resembles potassium in both appearance and properties. It is prepared in the same manner from its car- bonate, and like potassium, must be kept in naphtha to prevent its oxidation. When freshly cut it presents a silvery appearance, and if cast upon hot water bursts into a beautiful yellow flame, and is converted into oxide of sodium, or soda ; the same reaction taking place as in the case of potassium. Sodium is a very abundant metal, constituting more than two fifths of common salt, and exist- ing as a large ingredient of rocks and soils. 729. Oxide of Sodium, ISTaO (Soda). — This compound of so- dium strongly resembles the corresponding one of potassium, though its properties are somewhat less marked. For commercial purposes it is chiefly obtained from common salt. Soda, like pot- ash, attracts moisture from the air, forming a hydrate. It results from recent discoveries in spectrum analysis (346), that com- pounds of sodium are almost everywhere diffused. They are found in the atmosphere, and in particles of dust ; indeed it seems that we can hardly touch any substance without imparting to it a little soda salt from our hands. 730. Chloride of Sodium, NaOl (Common Salt).— This well known substance needs little description. It exists in great abundance both in solution and as a solid. Sea water contains in every gallon about 4 ounces of salt. Estimating the ocean at an average depth of two miles (Lyell), the salt it holds in solution would, if separated, form a solid stratum 140 feet thick. Saline springs in various 'idealities in this country yield enormous quan- tities of salt by the process of evaporation. The springs in the State power due? "What is the cofaiposition of fireworks? 727. Give the composition and properties of chlorate of potash. For what ia it used ? 728. What is sodium ? State its properties. 729. What is the composition of soda? Its Bources? 730. 282 INORGANIC CHEMISTKT. of New York alone furnish an annual supply of about 6,000,000 bushels. As a solid it occurs in extensive beds in various local- ities in Europe. The celebrated bed at Wielitzka, Poland, is said to be 500 miles long, 20 miles broad, and 1,200 feet thick, con- taining salt enough to supply the entire world for thousands of years. 731. Salt exists in small quantities in plants, and sometimes promotes their growth by being applied to the soil. It is also an ingredient of animal bodies, being contained in the blood. It forms an important constituent of the food of both man and beast, an adult consuming (as estimated by Peeeiea) about five ounces per week. _ 732. Common salt is readily sol- uble alike in hot or cold water, and usually crystallizes in cubes. A pe- culiar-shaped crystal, or aggregation of crystals, is often formed when the salt is allowed to crystallize from concentrated solutions. A small cube is first formed which sinks so as to bring its upper surface on a level, or a little below the surface of the water, Fig. 248. Other cubes form on this, and as the mass sinks, still others are deposited, each layer being attached to the upper and outer edge of the layer next below, until a form like that seen in Fig. 252 is obtained. 733. Salt is used for packing and preserving meat, as it prevents pu- trefaction, by absorbing water from the flesh (1127). It is also used as a source of sodium in the manufacture of caustic soda, and as a source of chlorine in the production of chlorohydric acid. It fuses at a red heat, and is hence used for glazing stoneware, earthenware, &c. Fig. 249. Fig. 250. Fig. 252 CryBtallization of Common Salt. "What is said of the natural occurrence and abundance of common salt ? 731. What of itB prcBcncc in plants and animals ? 732. Btatc its propertiee. Mode of crystal- SODIUM AND ITS COMPOUNDS. 283 734. Iodide and Bromide of Sodium, Kal, IsTaBr. — These com- pounds are formed in sea water, and are interesting only as being the commercial sources of iodine and bromine. 735. Carbonate of Soda, N'aO, CO2 + lOHO,— Soda is supposed to fill the place in marine plants that potash does in land plants, and its carbonate was formerly obtained by leaching their ashes. It is now manufactured almost entirely from common salt by -Le- BLAXc's process. This consists first in treating chloride of sodium with sulphuric acid, forming sulphate of soda, or salt caTce^ and chlorohydric acid. The next step in the process is the substitu- tion of carbonic acid for the sulphuric acid in combination with the soda. This is effected by heating the salt cake with finely ground coal and chalk in a reverberatory furnace constructed for the purpose. After the mass is thoroughly fused, it is raked out into wooden troughs and allowed to cool, forming hall soda, or blach ash. 736. In this operation the carbon unites with the oxygen of the sulphate of soda, thus forming carbonic oxide which escapes, leaving sulphide of sodium. An interchange now takes place be- tween the carbonate of lime and the sulphide of sodium, carbo- nate of soda and sulphide of calcium being the result. In sym- bols, NaO, SO3 + CaO, CO^ + 4C = FaO, CO^ + CaS + 4C0. The carbonate of soda, being the only constituent of the black ash that is readily soluble, is separated by leaching with warm water ; and lastly, the solution is evaporated to dryness, yielding the soda ash, or crude carbonate of commerce. Carbonate of soda is ex- tensively used in the manufacture of soap and glass, being both cheaper and purer than the ordinary potash. It is also used as a detergent, both in calico printing and in the laundry. 737. Bicarbonate of Soda, NaO, 2C0o, HO.— This is produced by passing carbonic acid through a solution of the carbonate. It forms the effervescing soda powders, and is used in bread making. 738. Sulphate of Soda, l^^aO,SO3 + 10HO {Glauber's salt).— This well-known salt may be formed by adding sulphuric acid to soda, and is chiefly procured in the manufacture of chlorohydric lization. 733. What are itg uses? 734. What is said of iodide and bromide of Bodium ? 735. How was carbonate of eoda formerly obtained ? How at present ? 736. Explain the changes. Uses of the salt. 737. What is bicarbonate ef soda ? 284 INORGANIC CHEMISTRY. acid. It has a bitter saline taste, and loses its -water of crystalliza- tion on exposure to the air. 739. Nitrate of Soda, ]SraO,N'05 {Soda- Saltpetre, Cubic mtre). — Procured native from parts of Brazil and Chili. Attempts have been made to substitute this salt for nitrate of potash in the man- ufacture of gunpowder, but its tendency to attract moisture from the air has rendered it impracticable. Nitric acid is obtained from it, and it has been somewhat used as a fertilizer. 740. Biborate of Soda, NaO, 2BO3 + IOHO {Borax).— Tins is obtained from the evaporation of the waters of several lakes in Thibet. It is procured artificially by heating boracic acid with car- bonate of soda, the carbonic acid being expelled, and the boracic acid taking its place. This salt has an alkaline taste and reaction, and possesses the property of dissolving many metallic oxides ; hence, its use as a flux in the welding of metals. It dissolves off the coating of oxide formed when they are heated, thus presenting a clean surface. 3. MANUFACTURE OF GLASS. 741. '^hen pure sand is heated with potash or soda, they fuse into a viscous, transparent mass before passing into the form of a liquid. 'While in this state they may be moulded into any desired shape, retaining their form and transparency when cold. "When the alkaline earths are heated with them, they are brought into the same condition. Thus we have a compound easily moulded at a certain stage of fusion, nncrystalline when cold, but transparent, hard, strong, insoluble and durable— that is, com- mon glass. 742. Materials of the Manufacture. — These are, first, silica, in the shape of pulverized quartz or sand. For the manufacture of the finest varieties of glass a pure white sand free from oxide of iron is employed. Second, there are the basic constituents of potash, soda, lime, magnesia, and oxide of lead, more or less pure, according to the quality of the glass required. Metallic oxides are employed as coloring agents. 733. What is sulphate of Boda? 739. Nitrate of soda ? 740. Give the composition of biborate of soda. lis uses. 741. When silica is heated with potash or soda, "u-bat results? "WTien with alkaline earths ? What are the properties of the com- pound? 742. What is the composition of glass ? 743. Describe the process. How SODIUM AND ITS COMPOUNDS. Fig. 253. 743. Process. — These materials are placed in pots or crucibles of refractory fire-clay, and several of tliem set in a large conical furnace. The fire is kept up day and night for months, the materials being added and withdrawn at pleasure. The plastic nature of the half-fused product adapts it for being easily worked into all desirable forms. The Rolling Melted Glass. Fig. 254. Fig. 255. workman dips an iron tube four or five feet in length into the waxy material, a portion of which ad- heres to it. To give it regular shape, he rolls it upon an even surface. Fig. 253 ; and to make it hollow, he blows through the tube. The glass may be pressed into various shapes between two moulds, one of which shuts into the other. Or it may be worked into globes and cylinders. If common window glass is to be made, the rounded mass upon the tube is blown into a pear shape, Fig. 254, which becomes elongated by swinging backward and forward, like a pendulum. By reheating, blowing and rolling, it is BiJwTng worked into the form of a cylinder, Fig. 255, which is cut ^^^^^• off at a and Z», and split along the line e. After again softening in the furnace, the cylinder is opened and spread out into a flat plate, as shown in Fig. 256. 744. Colored Glass. — The coloring of glass is effect- ed by fusing into the materials a small quantity of me- tallic oxide. Oxide of copper gives a green tinge; oxide of gold a ruby color ; oxide of uranium a yel- low ; oxide of cobalt a deep blue ; oxide of manganese a purple ; while a mixture of the oxides of cobalt and manganese produces a black glass. Enamel watch- dials and semi-opaque transparencies are glass rendered milk white by oxide of tin, or bone earth. 745. Varieties of Glass. — The silicates of lime, magnesia, iron, soda, and potash, in their impure form, produce the coarser kinds of glass of which green bottles are made. The sili- cates of soda and lime give the common window glass and French plate. Lime hardens glass, and adds to its lustre ; soda tends to are the variouB forma obtained ? 744. How are the different colors produced ? 745. Of what doeshottle glass consist? Window glass? What is the effect of lime? 286 INOEGA^nC CHEMISTEY. Fig. 256. give it a greenish tinge. Bohemian glass, the most beauaful va- riety, hard and highly infusible, is a sihcate of potash and lime. 746. Imitation of Precious Gems — Crystal glass, or Jiint glass, so called because pulverized flints were formerly used in making it, is a compound of the silicate of pot- ash and lead. The oxide of lead renders it very soft so as to be easily scratched, but Forming a Flat Sheet of Window Glass. ^^.g^^j^ reduces its transparency, brilliancy, and refractive power. Sometimes the proportion of oxide of lead rises as high as 53 per cent. Glass of this composition forms what is called paste, and, when suitably cut, is used to imitate the diamond. By the addition of a trace of oxide of iron the yellow of the topaz is imitated, and by oxide of cobalt the brilliant blue of the sapphire is pro- duced. 747. i^nealing Glass.— If glass is suddenly cooled after fusion, there seems an unequal strain upon its particles, and it is brittle and liable to crack on the slightest scratch or jar. This is shown by ' Prince Rupert's drops,' little pear-shaped bodies. Fig. 257, made by dropping globules of melted glass into water. The cooling of the outer particles while the inner ones are still fluid, prevents the latter from expanding as they cool, thus causing such an enormous strain upon the surface, that if the small end be nipped ofi", the whole mass flies to pieces with an explosion. To obviate this difiiculty, glass, after having received the desired form, is placed in large furnaces, which are maintained at a gradually decreasing heat for several days, until quite cool. This process is called annealing. Glass is cut by the diamond, and holes may bo bored through it with the end of a three-cornered file, if the point of friction be kept wet with spirits of turpentine. Fig. 257. Rupert's Drops. 746. What is flint glass ? What is the effect of lead upon it ? What is paste? 747. Why must glass bo annealed ? How is it done ? now is gl.aes cut and bored? 748. THE NEW METALS. 28V 4. CESIUM, RUBIDIUM, LITHIUM, AMMONIUM. CESIUM. Sym. Gs. Bquiv. 123.4. 748. The extraordinary circumstances under wlncli this metal and rubidium were discovered have been already stated (366). By evaporating a large quantity of the water containing caesium, BuNSEN obtained a small amount of it as a chloride, and after- ward as an amalgam, with mercury. Sucl^ is its affinity for oxygen, that even in the state of alloy it oxidizes in the air and decomposes cold water. It is the most electro-positive element known, surpassing potassium, which formerly ranked first in this respect. It forms extremely caustic hydrates and carbonates, while its bicarbonate occurs in permanent, glassy crystals. RUBIDIUM. Sym. M. Equiv. 85.36. 749. This new metal has analogous properties with the pre- ceding. It is silver-white in color, with a crystalline structure, and forms compounds similar to those of csesium. Geandeau has lately detected rubidium in the ashes of beets, tobacco, tea, and coffee. These metals are found associated with potassium, which they closely resemble, and are obtained in considerable quantity from the mineral Lepidolite. LITHIUM. Sym. L. Equiv. T. Sp. Gr. 0.5936. 750. This metal resembles potassium and sodium, though somewhat harder and considerably lighter, being the lightest metal known. Until recently, it was supposed to be very rare, but the late researches of Btjnsen' and Kieghoef show that it is quite abundant and widely distributed. By the spectrum analysis they have found it in sea-water, in the water of springs, in the ashes of plants, and in the human blood. What are the properties of csesium? 749. What of rubidium? Whence is it ohtained? 750. What are the properties of lithium ? Is it abundant? 751. Why- is ammonium believed to exist? What is its theory? 752. What are the 288 INOEGAlSriC chemistby. AMMONIUM. Sijm. H^K Equiv. 18. 751. Tliis is believed to be a compound radicle, Laving the nature of a metal, and forming oxides, salts, and even an amal- gam. Thus hydrated ammonia, n3N,H0, is regarded as an oxide of ammonium, H^iTjO. It has never been separated. But if an amalgam of potassium and mercury be placed in a solution of sal ammoniac (752), it swells up, assumes a pasty consistence, l)ut pre- serves its metallic lustre and the cliaracter of an amalgam. It is held that the potassium of the first amalgam has been replaced by am- monium, which has analogous metallic properties. The new amal- gam rapidly decomposes into mercury, ammonia, and hydrogen. 752. Chloride of Ammonium, £[4^, CI {Sal Ammoniac). — A solution of ammonia is neutralized by chlorohydric acid, crystals of chloride of ammonium being produced, which have a sharp taste, and dissolve in thrice their weight of cold water. Sal ammoniac is chiefly obtained by neutralizing the ammoniacal liquor of the gas works by chlorohydric acid. On evaporating the liquor the salt appears in the form of the tough, fibrous crystals of commerce. It is volatilized by heat. It is used in soldering to cleanse mo- tallic surfaces, the chlorohydric acid dissolving the coat of oxide. Mixed with lime, which decomposes it and expels the ammonia, it is used to fill smelling bottles, 753. Carbonate of Oxide of Ammonium {Carlonate of Ammo- nia). — There are several of these salts. Pure ammonia and car- bonic anhydride unite to form a neutral, anhydrous carbonate, n.-jl^T, COo, pungent, volatile and very soluble in water. The com- mon sal volatile, or smelling salts of the shops, is a sesquicarbonate 2H4NO,3CO,,. 754. Sulphate of Oxide of Ammonium, 114^0,503 110, is prepared in a large way by neutralizing the ammoniacal liquor of the gas works with sulphuric acid. It is a valuable fertilizer. Nitrate of oxide of ammonium H^XO, NO -j, IIO, is a soluble salt used as a source of nitrous oxide. There is a host of compounds of ammonia which are of interest only to the professed chemist. The ammoniacal salts are all soluble, and yield the ammoniacal odor by adding caustic lime or potash, or at a high heat. properties of chloride of ammonium ? Its uses ? 753. What carbonates are mentioned f 754 What other ealts of ammonia ? 755. What is barium I METALS OP THE ALKALINE EAETIIS. 289 § II. Metals of the Alkaline Earths. BAKIUM. Sym. Ba. Equiv. 68.6. 755. Barium occurs in large quantity in the mineral known as heavy spar (sulphate of baryta). It is a white, silver-like metal, and has a strong affinity for oxygen, tarnishing on exposure to the air. 756. Oside of Barium, BaO (Baryta)j\s a gray powder having a strong attraction for water, which it absorbs on exposure to the air, forming hydrate of baryta. The hydrate has an alkaline re- action, and unites with acids to form salts. 757. Chloride of Barium, Bad + 2H0.— This salt is readily soluble in water. It is interesting only as being the usual test for sulphuric acid, with which it gives a dense white, insoluble precipi- tate of sulphate of baryta. 758. Sulphate of Baryta, BaO, SO3 {Heavy Spar).— This, min- eral occurs in large quantities, and when ground is extensively consumed under the name of barytes in the adulteration of paints. Carbonate of baryta., BaO, CO2, is always formed when caustic baryta is exposed to the air. It occurs native in abundance, and is the chief source of the compounds of baryta. All the soluble salts of baryta act as powerful poisons when taken into the system. STRONTIUM. 8ym. Sr. Equiv. 43.8. 759. This metal resembles barium, in both appearance and properties. The nitrate of strontia is used considerably in the preparation of fire works, to the flames of which it imparts a beautiful crimson color. CALCIUM. Sijm. Ca. Equiv. 20. Sp. Gr. 1.57. 760. Calcium is a light yellow metal, somewhat harder than lead, very malleable, melts at a red heat, and oxidizes in the air. It exists in abundance in limestone, fluor spar, and gypsum. 756. Oxide of barium? 757. State the properties of chloride of barium ? Its use? 758. What is said of sulphate of baryta ? What of carbonate ? 759. Mention the uses of strontium ? 760. What is calcium ? "Where is it found ? 761. "What is the 13 200 INORGANIC CHEMISTRY. 761. Oside of Calcium, CaO {Lime). — Calcium forms but ono oxide, the well-known substance lime, wbicli exists in such vast quantities in combination with carbonic acid as limestone, and with sulphuric acid as gypsum. Lime is prepared by burning lime- stone in large masses in kilns. The carbonic acid is driven off into the air by the^ heat, and a white, stony substance remains, called quicTc lime, or caustic lime. One ton of good limestone yields 11 cwt. of lime. When this is exposed to the air it first rapidly imbibes moisture and crumbles to powder. This gradually absorbs carbonic acid, and becoming less and less caustic, regains the neu- tral condition of the carbonate. 762. Properties. — Lime exhibits the properties of a strong alkali, decomposing organic tissues and saturating the strongest acids. It is more soluble in cold than in hot water. Hence, when a cold saturated solution of lime-water is boiled, a portion of the lime is deposited, which accounts for the crust or far which lines the interior of tea-kettles in localities where the water is impreg- nated with lime. 763. Lime exists extensively in organized structures. The mineral portion of the skeleton of the higher animals consists of lime combined with phosphoric acid, and it is contained in the shells of the lower animals, chiefly united with carbonic acid. It also forms a large ingredient of plants. Lime is to be found in most fertile soils, and is much used in agriculture, as it promotes the decomposition of organic and inorganic matter, thus fitting it for assimilation by plants. 764. Hydrat3 of Lime.— When water is poured upon quick- lime it absorbs it (every 28 lbs. of lime taking nine pounds of water), swells to thrice its original bulk, crumbles to a fine white powder, and is converted into a hydrate of lime, OaO, HO. This process is called slaking^ and sufiicient heat is often produced by the chemical action to ignite wood. Lime water is a saturated, transparent solution of lime in water. Cream or milh of lime is a thick mixture of the hydrate with water, such as is used in white- washing. In tanneries the hides are immersed in milk of lime, conipoBition of lime ? How is it obtained ? What is the effect of exposure to tho air? 7G2. State the properties of lime. Explain the cause of the crust of tea- kettles. 163. Where is lime found in organic structures? What are its uses in agriculture? 764. How is the hydrate obtained? What is limo water? Milk of lime? ItflUBCd? 705. Of vh:it is the best mortar made ? What is the effect of METALS OF THE ALKALINE EAETHS. 291 which partially decomposes them, so that the hair may be easily removed. 765. Mortar and Cement. — Lime, mixed with sand, forms the mortar employed by builders to cement stones and bricks. To make the best mortar, the lime should be perfectly caustic and the sand sharp and coarse-grained. The nature of the changes by which the mortar becomes hardened is not satisfactorily explained. It is supposed to be owing in part to the lime absorbing carbonic acid from the air, and hardening into a carbonate of lime. In time the lime also partially combines with the silica of the sand? forming an exceedingly hard silicate of lime. Common mortar, when laid in water, not only refuses to harden, but its lime grad- ually becomes dissolved out and washed away. Hydraulic cement possesses the property of solidifying under water. This quality is owing to the presence of clay (silicate of alumina) in the lime of which it is composed. 766. Carbonate of Lime, CaO, COg. — Vast deposits of this salt are distributed all over the globe in the form of limestones, marbles, chalks, marls, coral-reefs, shells, &c. Numerous and ex- tensive as are these deposits, it is conjectured that they are all of animal origin. The densest limestone and the softest chalk are found to consist of the aggregated skeletons, or shells of myriads of tribes of the lower animals, which have existed in some former period of the world's history. The formation of coral reefs, which are sea-islands of carbonate of lime built up from the depths of the ocean by minute aquatic animals, is an example of similar deposits now in process of formation. 767. Carbonate of lime is decomposed by heat into carbonic acid and lime. It is soluble in water containing free carbonic acid ; hence the well and spring water of lime districts becomes impregnated with it, hard water being the result. When the hardness of water is due to this cause, it may be softened by the addition of lime water, which neutralizes the excess of carbonic aeid, the carbonate being precipitated. "Water containing car- bonate of lime in solution deposits a portion of it on free expo- sure to the air. Examples of this are often seen in caves. The water, as it trickles from fissures in the roof, deposits its carbonate time upon it? "What is hydraulic cement ? 766. What forms of carbonate of lime exist naturally? What is the origin of these deposits? What of coral-reefs? . 767. What is the effect of heat upon carbonate of lime ? How may hard water be 292 IXOEGAXIC CHEMISTET. Fig. 258. until pendent masses like those represented in Fig. 258 are formed. These are called sta- lactite^^ and where the water strikes on falling, other forms similar to those above grad- ually grow up from the floor, and are known as stalagmites. These often miite, thus form- ing a column. 768. Sulphate of lame, CaO, SO3 + 2H0 {Gypsum, Plaster, Alabaster). — This salt occnrs in many parts of the world, forming extensive rocky beds. In its pure, transparent form, it is known as sslenite, and in its compact and earthy_^ varieties as gypsum, jjlaster of Paris, and alabaster. TVhen powdered gypsum is heated to nearly 300°, it parts with its water of crystallization. If now it is made into a liquid paste with water, it again combines with it, and speedily hardens or sets, resuming its stony aspect. Owing to this property, it is used to take impressions of objects and make casts, by being run into hollow moulds. Colored and mixed with glue, it is used for the ornamental designs in architec- ture called stuccO'WorTc, Gypsum is used extensively as a fertilizer. Effects of lime in cares. MAGNESIUM. Sym. Mg. Equiv. 12. Sp. Gr. 1.7. 769. This is a white, brilliant, malleable metal, found abun- dantly in combination in many rocks and minerals, and occurs also in sea-water as a chloride. 770. Oxide of Magnesium, MgO (Magnesia). — Only one oxide of magnesium is known, and this is found by igniting the carbonate. It is a white, light powder, with feeble alkaline prop- erties, very sparingly soluble in water, but dissoh'ing readily iu acids. It is found in some minerals, in mineral waters, and in the Boflened? AVhatareBtalactitee? Ptabgmites? 76S. Givecompoi?ition of sulpliate of lime. How does it occur? What is eelenite? Use of gypsum for making casts 1 What are its other usesf 769. Describe magnesium. 770. State the ALUMINUM AND ITS COMPOrNDS. 293 ash of nearly all plants. In medicine it is used as a mild aperient and antacid. 771. Sulphate of Magnesia, MgO, SOg + VHO {Epsom Salts).— This is a common ingredient of mineral waters, and takes its name from the circumstance of its being contained in great quantities in the springs near Epsom, in England. The commercial supply is chiefly derived from sea-water, by precipitating the magnesia with lime, and then adding sulphuric acid. It may also be ob- tained from magnesian limestone. It is soluble in water, has a bitter, saline taste, and is used in medicine as a cathartic and an antidote to various poisons. It has also been used as a fertilizer. CHAPTEE XY. METALS WHICH DECOMPOSE WATER AT A RED HEAT. Aluminum, Glucinum, Thoeinum, Ytteium, Eebium, Teebium, Zirconium, Lanthanum, DiDTMIUM, Oeeium, Ieon, Manganese, Nickel, Cobalt, ZiNO, Cadmium, Tin. The first ten metals of this group are metals of the earths, but with the exception of alu- minum, they are very rare, and of no special interest. § 1. Aluminum and its Comj^ounds, ALUMINUM. Sym. Al. Equiv. 13.7. Sp. Gr. 2.5. 772. This important metal was discovered by the German chemist, Wohlee, in 1827. It is found in nature in immense quantities, being the metallic base of alumina which forms the argillaceous rocks, beds of clay, and a large proportion of granite. It is a shining, white metal, of a shade between silver and pla- properties of magnesia. Where is it found ? Its uses ? 771. What is sulphate of magnesia? What are its properties? Its tises? 772. Discovery of aluminum. 294 INORGANIC CHEMISTRY. tiniim, liarder than zinc, lighter than glass, and of remarkable strength and stiffness. It resists the oxidizing influence of moist air like silyer, melts at a still lower temperature than that metal, and, pound for pound, occupies four times its space. It is more sonorous than any other metal, giving forth a clear musical sound when struck. It is malleable and ductile like iron, exceeds it in tenacity, and combines with carbon, forming a cast metal which is not malleable. It resists the action of cold nitric and sulphuric acids, and, unlike silver, is not tarnished by sulphuretted hydrogen. It dissolves in chlorohydric acid, forming a chloride, and conducts electricity nearly as well as silver. Aluminum is obtained by de- composing chloride of aluminum by means of sodium, and as sodium is at present expensive, the manufacture of aluminum renders it a costly metal ($4 per lb.). It will undoubtedly be greatly cheap- ened, when it will become of invaluable service in the arts. Its alloys will be noticed in Chap. XYII. 773. Sesquioxide of Aluminum, AI2O3, {Alumina). — This, which is the only oxide of alumina, is an abundant natural product, being found in all soils and rocks. Crystallized and colored by oxide of chromium, it forms the ruby and sapphire, which rank next to the diamond in hardness and value. In a more massive form it is known as corundum. Alumina seems to possess the properties of both an acid and a base, uniting with either to form definite salts. It has a powerful attraction both for vegetable coloring matter and for the fibre of cloth ; hence, it is used by dyers to fix the colors upon their fabrics. It is then said to act as a mordant. Alumina is precipitated from organic solution by an alkali, and, if there is any vegetable or animal coloring matter present, this is also carried down with the alumina, forming what is termed a laTce. Carmine is a lake of cochineal. Alumina also absorbs and combines with oily matters ; hence, a certain kind of clay, called fullers' earthy is used to extract grease from wood, paper, &c. 774. Sidphate of Alumina and Potash, KO, SOg + AloOg, 380.., + 24HO {Alum). — Small quantities of this important salt are found native, but for commercial purposes it is prepared artificially by Where does it occur ? What are its properties ? How is it obtained ? Its price ? 773. Wiiat is alumina? Mention some of its varieties. Its properties. How is it used by dyers? How is carmine formed? What is fullers' earth? 774. Give the composition of alum. How is it formed ? 775. Itsproiierties? What ie burnt ALUMINUM A:ND ITS COMPOUXDS. 295 several different methods. In tliis country it is formed by treat- ing alumina or clay with sulphuric acid, and, after the lapse of a few months, adding potash, either in the form of sulphate or car- bonate. The whole is then leached, and the alum separated from the solution by crystallization. 775. Alum has a sweetish, styptic taste, and is soluble in 18 parts of cold water, or in its own weight of boiling water, the solu- tion having an acid reaction. "When heated, alum sjvells up into a light, puffy condition, at the same time giving off its water of crystallization, and leaving a white, anhydrous, infusible mass known as lurnt alum. 776. Alum is used largely for purifying and preserving skins, for mordants in dyeing and calico printing, for glazing paper, for hardening and whitening tallow, clarifying liquors, and in medi- cine as an astringent and caustic. Wood impregnated with it is almost incombustible. 777. Sulphate of soda or ammonia may replace the sulphate of potash in combination with the alumina, thus giving a soda or am- monia alum. In like manner the sesquioxides of iron, manganese, chromium, &c., being isomorphous with alumina, may replace it, forming an iron, manganese or chrome alum, all of which have the same crystalline form. 778. Silicate of Alumina, or Clay, is the result of the decom- position of feldspathic and silicious rocks, and is the basis of all kinds of pottery. Its adaptation for this purpose depends upon its plasticity when mixed with water, the readiness with which it may be moulded, and also upon its capability of solidifying when exposed to a high heat. After burning, the ware, though hard, is porous, and absorbs water with avidity, even allowing it to filter through. To prevent this, the ware is covered with a glassy coat- ing, or glazed. 779. Porcelain consists of a mixture of decomposed feldspar (called Tcaolirt), silica, and a small proportion of lime, the ingre- dients being carefully selected, and thoroughly ground and incor- porated, "^hen moulded into the proper form, the articles are dried and subjected to a high heat in a furnace, in which state the alum? 776. Usesofalum? 777. How does it illustrate isomorphism? 778. Give the composition and origin of clay. What quality adapts it for pottery. Why must the ware he glazed ? 779. What is porcelain '? Descrihe its manufiicture. How is it colored ? 780. How is common red pottery ware made ? Why is it ob- 296 IXOEGAinC CHEMISTRY. ware is called Mscuit. Thej are tben glazed by dipping them into a solution of powdered quartz and feldspar, which, when heated, fuses into the ware, giving it a vitreous coating which adds to its com- pactness and strength. The partial fusion of the materials gives porcelain the beautiful semi-transparency which distinguishes it from earthen ware. In coloring porcelain, the patterns are print- ed on paper which is applied to the biscuit while the color is still moist. "Whan the color is absorbed, the porcelain is subjected to another baking, which fixes the tint. In the finer kinds of porce- lain the colors are mixed with a fusible glaze, and applied with a hair pencil. 780. Common Red Pottery Ware owes its color to oxide of iron, and is glazed with a preparation of clay and oxide of lead. Vessels thus coated are objectionable for domestic use, as the lead glaze is sometimes dissolved by acids, producing poisonous effects. Bricks are unglazed. Stone uare is a coarse kind of porcelain glazed with salt. Fire bricks, muffies, and Hessian crucibles are made of a pure, infusible clay, containing a large amount of silica. The beautiful blue pigment ultramarine is a silicate of alumina, supposed to be colored with hyposulphite of soda and sulphide of sodium. § II. Iron and its Comj^ounds. IRON. Sym, Fe. {Ferrum.) Eqiiiv. 28. Sp. Gr. 7.8. 781. Were we to seek for that circumstance which might best illustrate the peculiarities of ancient and modern civilization, we should perhaps find it in the history of this metal. The ancients, imbued with a martial spirit and passion for conquest, made iron the symbol of war, and gave it the emblem of Mars. And if it were required also to symbolize the pacific tendencies of modern society, its triumphs of industry and victories of mind over matter, its artistic achievements and scientific discoveries, we should nat- urally employ the same metal iron. As gold nnd jewels have long been the type of barbaric and empty pomp, so iron may now be well regarded as the emblem of beneficent and intelligent industrv. jectionablo for domestic purposes? What is Btoneware? Firebrick? What ultramarine 1 781. "What is said of the relations of iron to civilization ? 782. Men- IR02^ AND ITS COMPOUNDS. 297 782. Uses of Iron.— Iron in some of its innumerable forms niinisters to the benefit of all. The implements of the miner, the farmer, the carpenter, the mason, the smith, the shipwright, are made of iron and with iron. Eoads of iron, travelled by iron steeds, which drag whole townships after them and outstrip the birds, have become our commonest highways. Ponderous iron ships are afloat upon the ocean, with massive iron engines to propel them ; iron anchors to stay them in storms ; iron needles to guide them, and springs of iron in chronometers by which they measure the time. Ink, pens, and printing presses by which knowledge is scattered over the world, are alike made of iron. It warms us in our apartments ; relieves our jolts in the carriage ; ministers to our ailments in the chalybeate waters or the medicinal dose ; it gives variety of color to rocks and soils of the earth, nourishment to vegetation, and vigor to the blood of man. Such are the powers of a substance which chemists extract from an otherwise worth- less stone. 783. Iron occurs in nature almost universally in a state of combination. The mineral masses which it forms with oxygen, carbon, sulphur, and the metals, and from which it is extracted, are called its ores. Of these there are no less than 19 varieties, 8 or 9 of which are worked for their iron alone, while several of the others yield substances of great value in the arts, such as sul- phur, arsenic, chronium, &c. 784. Ores of Iron. Magnetic iron ore, FeOjFeoOa (Loadstone). — This is a combination of the protoxide and sesquioxide, and is one of the richest ores of iron, containing 72 per cent, of the metal and 28 of oxygen. It is strongly magnetic, of a grayish color, and when rubbed gives a black powder. This ore is very widely dif- fused, and furnishes iron of the best quality. It affords the supe- rior iron obtained from Kussia, Germany, and Sweden. 785. Specular, or Red Iron Ore is a sesquioxide, FeoOg, very hard and sometimes presenting the appearance of polished steel. "When coarse, it is of a brown color, but its powder is always red, a quality which distinguishes it from the magnetic oxide. This oxide contains 63 per cent, of iron to 37 of oxygen. It exists in tion some of the uses of iron. 783. How does it occur ? What is said of its ores ? 784. What is the composition of magnetic ore ? What its quality ? Its properties ? 785. What is specular iron ore ? How distinguished from the magnetic ? When are red clays called ores? 786. What is red hematite? Brown hematite? 13* 298 INORGANIC CHEMISTET. all the red clays, -which, when they yield 25 per cent, of the metal, are termed ores. 786. Red Hematite, Fe O3, is another anhydrous sesquioxide, found in large quantities and considerably worked. Brown Hema- tite, or hydrated peroxide of iron, 2re2033I10, is very abundant throughout the world and particularly in the United States. It affords a yellow powder, and is not attracted by the magnet. It contains about 86 per cent, of peroxide of iron to 17 per cent, of water. 787. Carbonate of Iron {Spathic Iron, Steel Ore).— This con- tains 63 per cent, of oxide of iron, 34 per cent, of carbonic acid, and a small quantity of lime, magnesia, and manganese. A variety of steel is made directly from this ore. It is the source of the cheap German steel. 788. Clay Ironstone is another carbonate of iron, having a yellowish-brown color, and is one of the chief sources of the iron of commerce. It occurs among the coal measures mixed with clay, and contains about 37 per cent, of iron. There are several other ores worked for their iron to some extent, but those men- tioned are the most important. 789. Bisulphide of Iron, FeSs, is the pyrites of mineralogists, so named because it was used in firelocks to strike fire with steel before the introduction of gun flints. It occurs in large quantities and under several different forms. Yellow pyrites, when in the form of minute brilliant scales, is sometimes mistaken for gold {fooVs gold). It is tested at once by the sulphurous odor it emits when heated. This variety contains 47 per cent, of iron to 53 of sulphur. Pyrites is chiefly prized as a source of copperas, alum, Spanish brown, sulphur, and sulphuric acid. It is never worked for its iron. 790. Obtaining the Metal.— The process of separating iron from its ores is called reducing or reviving it, and the ores are said to be smelted. The operation is conducted in tall chimney-like structures, termed blast furnaces. They are constructed of stone, and lined with the most refractory fire brick, having the form seen in Fig. 259. The top or mouth of the furnace serves for charging it, and for the escape of smoke ; it is both door and 787. What is the composition of etcel ore? 788. Of clay iron Btone? What other ores are mentioned ? 789. What is bisulphide of iron ? What is fool'fl gold ? Uco of pyrites ? 780. IIow is the operation of Bmelting performed ? Dcecribe the blast IRON AND ITS COMPOUNDS. 299 cMmney. The tubes or tuyere pipes ^t the bottom serve to sup- ply the air, which is forced in by means of immense blowing cyl- inders driven by water or steam power. The amount of air thus forced through some large furnaces, exceeds 12,000 cubic feet per minute. Formerly the air was used at the ordinary temperature (cold dlasf)^ but within a few years an immense improvement has been effected by heating the air before it enters the furnace (hot Hast). 791. In some cases the materials are drawn up an inclined plane to the mouth of the shaft by the same engine that impels the blast mechan- ism. The furnace is supplied with ore, coal, and limestone broken into small fragments. When the heat is sufficiently intense the carbon of the fuel deoxidizes the iron, and carbonic acid is also expelled from the lime, leaving it caustic. Sand and clay, in greater or less quantities, now remain combined with the iron. The lime, acting as a flux, unites with these, forming the slag or scoria^ a crude semi-vitreous product. The melted iron, falling to the bottom of the furnace, accumulates and is drawn off by taking out a tap or plug. It is allowed to run into a bed of sand, containing straight channels and fur- rows running at right angles. The former are called by the workmen the sow^ and the latter the pigs; hence the term pig- iron. As the contents of the furnace are removed from below, crude ore is con- stantly supplied from above, and the opera- tion goes on day and night uninterruptedly for a course of years, or until the fabric demands repair. 792. The product of the smelting furnace is cast iron. This Smelting Furnace. Fig. 260. Texture of Cast Iron. furnace ? 791. What are the changes occurring in the furnace ? 792. What are the properties of cast iron ? To what due ? What is wrought iron ? 793. State the 300 INORGAinC CHEMISTKT. has a granular texture, Fig. 260, and is so brittle that it cannot bo forged, but maj be remelted and cast into moulds. It expands when first poured into the mould, so as to copy it perfectly, but subsequently contracts. The expansion is caused by the particles assuming a crystalline arrangement while consolidating ; the con- traction by the cooling of the metallic mass when solidified. These properties of brittleness and easy fusibility are due to the presence of a considerable quantity of carbon and other impurities, th^ removal of which converts it into wrought iron. ■ 793. Physical Properties of Iron. — Iron is of a grayish white color, and when polished has a perfect lustre. The various condi- tions under which it appears in the arts are due to the presence or absence of certain other substances, sucli as carbon, silicon, sul- phur, phosphorus, manganese, and arsenic. In the absence of these substances, iron is so malleable that books have been made of it with leaves as thin as paper, and so ductile that it may be drawn out into wires as thin as a hair. Its most useful quality, however, is its superior tenacity, or power of resisting strain ; no other metal being equal to it in this respect. Hence the value of iron in the manufacture of cannons and mortars, where the im- mense expansive force of gunpowder is to be resisted, and in the making of wire cables for suspension bridges. So great is its te- nacity that an iron wire 0.075 of an inch in diameter is capable of supporting a weight of 449 pounds. 794. Passive Iron. — In its ordinary condition iron oxidizes rapidly in the air, and dissolves in nitric acid. But under several circumstances it assumes different and peculiar chemical relations. If momentarily immersed in a strong mixture of nitric and sul- phuric acids it retains its metallic lustre, but has lost the power of either being oxidized in the air or of dissolving in nitric acid ; it has become passive^ or assumed an allotropic form. 795. Wrought Iron — The operation of separating carbon and other foreign substances from cast iron is usually conducted in reverberatory furnaces. In this process the fire is not mingled with the metal, as in the case of smelting, but the material is melted by causing the flame to impinge upon it on its way through the furnace, as shown in Fig. 201. A work- phy.-lcal properties of iron. 794. "What is passive iron? 795. How is wrnucrM iron obtained I 796. How may the quality be bUU improved? IIow is wrought IKON AND ITS COMPOUNDS. 301 Fig. 261. PuddliEg Furnace. man, with a long, oar-sliaped implement of iron, stirs (puddles) tlie melted mass until the carbon and other impurities of a like nature are burned awaj, and the metal becomes thick and pastj. This is called puddling. The pud- dler then rolls up from the mass a ball of about 75 lbs. weight, which he transfers to the tilting or trip hammer, where it is beaten bj heavy blows into a crude bar. By this operation the liquid impurities, consisting chiefly of silica and alu- mina, are squeezed out, as water is expelled from a compressed sponge. 796. The metal, still hot, is then passed between grooved cyl- inders, where it is rolled out into lar iron. The quality of metal is greatly improved when these bars are broken up, bound together, reheated to the welding point, and again passed through the roll- ing mill. This latter operation is often repeated several times, and is known as piling or fagoting. Wrought iron may be pro- duced directly from the magnetic ore. The process is conducted on what is termed a Catalan forge^ or lloomary^ a structure much resembling a blacksmith's forge, on a large scale. The operation consists in the reduction of the oxide by means of charcoal, aftei' which the iron obtained is put through the same course of ham' mering and rolling as if it came from the puddling furnace. 797. 'W'rouglit iron has a fibrous tex- ture, and rough, hackly fracture. Fig. 262. It is said to lose this tough, fibrous charac- ter by the effect of constant jarring, and to become crystalline. It usually contains a small quantity of carbon, which hardens the iron without affecting its other prop- erties, but if the amount exceeds ^ per cent., it renders the iron cold-short., that is. Fig. 262. brittle and liable to snap asunder when cold. The presence of sulphur, even in so small a proportion as Texture ofWrotight Iron, iron made from the ore ? 797. Wliat is the effect of carbon in wrought iron ? Of sulphur ? 798. "What is welding ? What precaution is necessary ? "WT^at metals 302 r!fOBGA2ac cheshstby. red heat, as it is liable to split when hammered; it is then said to be hoi-short. 793. Welding of Iron. — When wronght iron is heated to whiteness, it becomes soft, pasty, and adhesive, and two pieces in this condition may be incorporated, or hammered into one. This is called tcelding. Daring the heating a film of oxide is formed upon the surface of the metal, which would obstruct ih.% ready cohesion of the separate masses. To prevent this, the smith sprinkles a little sand upon the hot iron, which combines with the oxide, forming a fusible silicate of iron, which is easily forced out by pressure, leaving clean surfaces that unite without difficulty. This important quality is possessed only by iron, platinum, and sodium. All the other metals pass suddenly from, the solid to the liquid state at their respective melting points. 793. SteeL — This remarkable modification of iron is a com- pound of the metal with about one and a half per cent, of carbon. It is made by imbedding bars of the best wrought iron in pow- dered charcoal, in boxes or sand-furnaces, which exclude the air, and heating it intensely for a week or ten days. The chemical changes are obscure ; probably carbonic oxide penetrates the heated metal, is decomposed, surrenders part of its carbon and escapes as carbonic acid. The steel when withdrawn has a pecu- liar rough, blistered appearance, and is hence known as blistered steel. This method of making steel is called the process of cemen- tation. 800. In its properties steel combines the fusibility of cast iron with the malleability of bar iron. Its value for cutting instru- ments, springs, &c.. depends upon its quality of being tempered. When heated to redness and suddenly quenched in cold water, it becomes so hard as to scratch glass. If again heated and cooled slowly, it becomes as soft as ordinary iron, and between these two conditions any required degree of hardness can be obtained. As the metal declines in temperature, the thin film of oxide upon its surface constantly changes its color. The workmen are guided by these tints. Thus a straw color indicates the degree of hardness for razors ; a deep blue for sword blades, saws and watch springs. Steel receives a higher polish than iron and has less tendency to poseesa this property ! 799. "WTjat is steel ? How is it made ? "What is blistered •leel? 800. Ujvcn-wbai does i; 8 value for cutting itstnimentfi depend ? Howisttat lEON AND ITS COMPOUNDS. 303 rust. Nitric acid placed upon steel corrodes it, and leaves the car- bon as a dark gray stain ; hence it is often used for writing and ornamental shading upon this metal. 801. Oxides of Iron. — Iron has a strong affinity for oxygen, with which it forms four well marked compounds, viz. : the pro- toxide FeO ; the sesquioxide or peroxide FegOg ; the magnetic oxide, supposed to be a combination of the two preceding, and having the formula FeO, FcaOa, or Fe304, and ferric acid FeOg. The first three are the most abundant, existing in stones, rocks, and soils, and imparting to them their red and yellow colors. 802. The Protoxide is not found in the separate state, as it rapidly absorbs oxygen, and passes into the sesquioxide. It is the basis of all the green salts of iron, and in a state of combination is widely diffused, existing chiefly in those rocks having a greenish or dark tint. The iron in chalybeate waters usually rises to the surface as a protoxide, and theye absorbing oxygen from the air, the peroxide is formed, and sinks to the bottom as an insoluble, reddish sediment. 803. The Anhydrous Sesquioxide is known in commerce under the name of colcathar or rouge^ and is extensively employed in polishing glass, jewelry, &c. It is also used as a pigment. The hydrated sesquioxide, associated with alumina, forms the umbers and ochres so much used as pigments. 804. Magnetic Oxide.— The black scale, which forms on iron when heated, consists of magnetic oxide. This is also the result of the combustion of iron in oxygen gas. It is the only oxide pos- sessing magnetic properties. Ferric acid is a very unstable com- pound, and is of little account. 805. Protosulphate of Iron {Green Vitriol^ Copperas). — This salt, as its name indicates, is a compound of the protoxide of iron with sulphuric acid. It is largely manufactured at Stafford, Conn., from iron pyrites, which furnishes by oxidation both the acid and the base. It is used in dyeing, for making ink and Prussian blue, and in medicine. It often exists in soils to a pernicious extent, but is decomposed by lime ; gypsum being formed. determined ? What is the effect of nitric acid upon steel ? 801. What is the compo- sition of the oxides of iron ? 802. G-ive an account of the protoxide. 803. Of the anhy- drous sesquioxide. Of the hydrated. 804. "What is the magnetic oxide? 805. What 304 IXOKGAXIC CHEMISTRY. g III. Manganese^ Niclcel^ Zinc^ CobalU Cadmiiim^ Tin. MAXGAXESE. ^m, Mn. Equii\ 27.48. .S>. Gr. 8. 806. Manganese is a hard, brittle metal of a grayish-white color. It never occurs pure in nature, but its oxides are found combined with many ores of iron, a metal which it resembles iu many of its properties. Manganese is obtained by making its oxide into a paste with oil and lampblack, and heating it to white- ness in a covered crucible. It rapidly oxidizes when exposed to the air, and is best preserved in naphtha. 807. It forms no less than seven different compounds with oxygen. Its oxides are diffused in small quantities through most soils, and traces of them may be detected in the ashes of nearly aU plants. Protoxide of manganese is of a pale green color and is a powerful base, giving rise to rose-colored salts. The peroxide or hlach oxide, MnOo, is employed as a cheap method of procuring oxygen on a large scale, and for the manufacture of chlorine and steel. It is also used under the name of glassmaJcer's soap to de- stroy the green tinge given to glass by protoxide of iron and to oxidize carbonaceous impurities. K added to glass in large quan- tities, it gives it a purple color. NICKEL. S}jm. M. £quiv. 29.5. Sp. Gr. 8.8. 808. This is a brilliant white metal, somewhat malleable and ductile. At ordinary temperatures it is magnetic, but if heated above 630° it loses this property, acquiring it again, however, on cooling. It is used principally in the formation of alloys. Xickel forms oxides, but they are of little interest. COBALT. Si/m. Co. Bquir. 29.5. Sp. Gr. 8.9. 809. Cobalt generally occurs in combination with arsenic or nickel, though it is sometimes found native in meteoric masses. llie protosulphate ? 806. What is m.anganese ? How is it obtained 1 How kept ? 807. What is said of ita compounds with oxygen? "What of the protoxide ? Tha peroxide? Ita uses? 808. What are the properties of nickel? 809. VThat ig IRON AND ITS COMPOUNDS. 305 "When obtained pure it is a reddish-white, hard, brittle, strongly magnetic metal. It forms two oxides; the protoxide, OoO, and the sesquioxide, C02O3. The protoxide is a grayish powder, which, when fused with glass, imparts to it a beautiful blue color. Smalt is a glass, colored blue by oxide of cobalt and then reduced to an impalpable powder. It is used for coloring on glass, paper, &c. Zaffre^ used to impart a blue color to ordinary earthen ware, is an impure oxide of cobalt. 810. Chloride of Cobalt forms a pink solution which turns blue when dried. This solution is used as a sympathetic ink, the characters written with it being so pale as to be invisible till warmed, when they appear blue. On cooling they absorb moist- ure and again disappear. ZINC- ~^^\ Sym. Zn. Equiv. 32.5. Sp. Gr. 7. 811. Zinc is a brilliant, bluish- white metal, found abundantly in nature in combination with sulphur as zinc-blende^ and with oxygen and carbonic acid as calamine. It also exists in great quantities as a red oxide in IsTew Jersey. At common tempera- tures it is brittle, but when heated from 212° to 300° it may be rolled out into thin sheets, and retains its malleability when cold. At 400° it again becomes quite brittle ; at 770° it melts, and when exposed to air takes fire, burning with a whitish-green flame and forming oxide of zinc. Zinc soon tarnishes in a moist atmosphere, forming a thin film of oxide, which resists further change. This property renders it useful for a variety of purposes, such as for gas pipes, gutters, roofing, and for galvanizing iron, thus prevent- ing it from oxidation. .It is also used in the preparation of hy- drogen gas. 812. Oxide of Zinc, ZnO.— This is formed when zinc is burned with free access of air. It is a fine, white powder,^ and is the only oxide of zinc known. It is used largely as a paint. 813. Sulphate of Zinc, ZnO, SO3 {White Vitriol).— This may be prepared either by roasting the sulphide, or by the action of sulphuric acid on the pure metal. It strongly resembles the sul- cobalt? Mention its compounds. State their uses. 810. What is chloride of cohalt? 8U. What is zinc? How does it occur ? State its properties. Its uses. 812. What is oxide of ziuo ? For what used ? 813. How is sulphate of zinc oh' 306 rXOEGANIC CHEMISTRY. phate of magnesia, and is used in medicine and in certain opera- tions of calico printing. CADMIUM. Sijm. Cd. Equiv. 56. Sp. Gr. 8.G. 814. Cadmium is usually found associated with zinc. It is a white, volatile metal, somewhat malleable and ductile, and so soft as to leave a mark when rubbed upon paper. It forms an oxide, CdO, which may be obtained by burning the metal in air. Tix. Sym. Sn. {Stannum). Equiv. 59. Sp. Gr. 7.8. 815. Tin is a brilliant, silver- white metal, which occurs most abundantly in Cornwall, England. It has been found in this coun- try only at Jackson, IST. H., and in small quantities. It is softer than gold, slightly ductile and very malleable, common tin foil being often not more than pg^ of an inch in thickness. It melts at 442°. The peculiar crackhng sound given by tin when bent, is due to a disturbance of its crystalline structure. Owing to its weak affinity for oxygen it tarnishes but slightly on exposure to the air or moisture, and is therefore very valuable for domestic utensils. This property also renders it useful for coating other metals to prevent them from oxidizing. Sheet iron coated with tin, with which it forms an alloy, constitutes common tin ware. ~~"'^->,, 816. There are two well marked oxides of tin; the protoxide, SnO, and the binoxide, SnOo. The protoxide acts as a base, but j^ the binoxide, when combined with water, has distinct acid proper 1_^^ ties. Tin forms several very important alloys. 1 CHAPTEE XYI. METALS WHICH DO NOT DECOMPOSE WATER. ChROMIU:?!, COLUMBIinM, GitLD, Arsenic, Tantalum, Platinum, Antimony, Molybdenum, Palladium, Bismuth, Tungsten, Rii|»dium, Copper, Vanadium, Ruthenium, Lead, Uranium, 0smium, Thallium, Mercury, Iridium. Titanium, Silver, taincd? 814. What is cfidrnium? 815. What are the eourccB of tin ? Its proper- CHROMIUM, aese:n^ic. 307 § I. Chromium^ Arsenic. CHROMIUM. Sym. Cr. Equiv. 26.3. 8p. Gr. 6.8. 817. Chromium is an exceedingly hard, brittle, grayish- white metal, and derives its name {chroma^ color) from the beautiful color of many of its compounds. It is rarely met with, but is abundant in some localities. It usually occurs as a sesquioxide in combination with protoxide of iron, forming the mineral chrome iron-stone. It also occurs in union with oxygen and lead as chro- mate of lead. 818. Chromium has a strong attraction for oxygen, with which it forms several compounds. Among these the most im- portant is the sesquioxide CrgOg, and chromic acid CrOg, both of which resemble the corresponding compounds of iron. The sesquioxide is a feeble base, isomorphous with the sesquioxide of iron and with alumina ; it may therefore replace either of these in combination. The hydrated sesquioxide is of a pale green color, but by ignition loses its water, and becomes of a dark green. This oxide is used in coloring glass and porcelain, and is the coloring ingredient of green-stone, the emerald, &c. 819. Chromic Acid is interesting as being one of the constitu- ents of chromate of lead, the beautiful yellow pigment known as chrome yellow. The color of the ruby is due to the presence of this acid. In union with potash it forms the bichromate, a salt considerably used in the laboratory and in dyeing, calico print- ing, &c. ARSENIC. Sym. As. Equiv. T5. Sp. Gr. 5.8. 820. Arsenic is a crystalline, brittle metal, of a steel-gray color and bright metallic lustre. It is found alloyed with iron, nickel, cobalt, copper, tin, lead, &c. ; but the chief source of the arsenic of the shops is mispicJcel^ a double sulphide of arsenic and iron. The coarse, gray powder, sold under the name of fly poison, ties ? What is tin ware ? 816. What compounds of tin are mentioned ? 817. What is chromium? Why so named? 818. Wliat are the properties of chromium and its compounds ? 819. In Tvliat does the interest of chromic acid consist? 820. State the properties of arsenic. What are its sources ? What is fly poison ? EtFect of 308 rS'OEGAXIC cnzinsTEY. cobalt, (fcc, consists simplv of metallic arsenic. When arsenic is heated in a close vessel to 3j6', it volatilizes witbont fusion, giv- ing off a dense, colorless vapor, having the peculiar odor of garlic. If heated in the open air it takes fire, burning -with a blue flame, and uniting Trith oxvgen to form arsenious acid. 821. Arsenic and Oxygen.— There are but two of these com- pounds: arsenious acid, ASO3, 3.nd arsenic acid, ASO5. The first constitutes the common white arsenic of the shops, the well-known raWbane. It is soluble in about ten parts of hot water, the solution having a slightly sweetish taste and acid reaction. It also dis- solves readily in hot chlorohjdric acid, and in solutions of the alkalies. Combined with copper, it forms the beautiful pigment known as ScTieeJes green, which is used extensively in coloring paper hangings. Owing to its remarkable antiseptic power, it is used to preserve dried and stuffed specimens by collectors of ob- jects of natural history. Its most effectual antidotes are the moist hydrated oxide of iron and caustic magnesia. 822. Arsenic Acid is formed by oxidizing arsenious acid by means of nitric acid. It has strongly acid prop- erties, decomposing the carbonates with effer- vescence, and readily forming salts with the alka- lies. Sulphur forms no less than five compounds with arsenic, of which the most important are renlger or red orpiment, a bisulphide, and yel- low orpiment, or Mng's yellow, a tersulphide. 823. Arseniuretted Hydrogen, H3 As.— This gas may be formed by decomposing an alloy of 'nps. "*' arsenic and iron with dilute sulphuric acid, or 11 by introducing a solution of arsenic into a flask in which hydrogen is being evolved. It burns with a bluish-white flame, is highly poisonous and of a disgusting odor. 824. In Marsh's test hydrogen is gener- ated, and if arsenic be present arseniuretted hydrogen is formed. Fig. 263 shows the form ..:' an apparatus which answers very well for this purpose in a rough way. Bits of zinc and a little water are placed in the vessel, Fig. 2C3. a's Test. heat upon it? 821. "What are the composition and properties of ar-scnioas acid? What of Scheele's preen? 822. Of arsenic acid ? Of the compour.d-" of arsenic and sulphur ? 823. "What is arsenide of hydrogen ? 824. "What is Marbh's test for ANTIMONY, BISMUTH, COPPER, LEAD. 309 whicli is provided with a cork through which a tube is inserted. Sulphuric acid is now poured in through the funnel tube, and the evolution of hydrogen commences. After the air has been com- pletely expelled from the flask, the gas may be lighted at the jet. If the solution containing arsenic be now poured in through the funnel tube, the color of the flame immediately changes, and a cold, white surface, held so as to cut the flame in half, is stained with a black or brown spot by the deposition of metallic arsenic. Antimony produces a similar efi'ect, but a solution of hypochlorite of lime or soda dissolves the arsenical stain, leaving that made by antimony unchanged. This is a very delicate test, but great care should be taken that the sulphuric acid and zinc do not contain any previous traces of arsenic. §11. Antimony — Bismuth — Coj>per — Lead. ^ ANTIMONY. W < "-^ Sym. SI. {Stibium). Fquiv. 129. Sj>. Gr. 6.7. T 825. Antimony is a brilliant, brittle, bluish white crystalline metal, usually found in combination with sulphur, though it often occurs alloyed with other metals, and sometimes exists native. The principal source of the metal is the native sulphide, from which it is separated by heating with iron filings, or carbonate of potash. These combine with the sulphur, setting the metal free. 826. Oxides of Antimony.— The teroxide, SbOs, is the most important, as it furnishes the basis of the antimonial so much used in medicine. Antimonio acid, SbOg, readily combines with bases to form salts, and even unites with the teroxide, forming antimo- niate or antimony, or what is sometimes called antimonious acid. BISMUTH. Sym. Bi. Equiv. 2IO3. ^P- G'^- 9.8. 827. Bismuth is a hard, brittle, reddish white metal, found both native and in combination. At a high temperature it is slightly volfitile, and oxidizes rapidly. Its fusing point is 507°, but it forms alloys with other metals which melt below 212°. It forms two combinations with oxygen; the teroxide, BiOg, and bis- arsenic? 825. How is antimony found in nature? 826. What of its oxides? 827. What are the properties of bismuth ? What of its oxides ? 828. What 310 EsOEGAXIC CnKMTSTEY. mutliic acid, Bi05. The latter is interesting only to the chemist; but the former, in combination with nitric acid and water, forms pearl poicdcr, the popular cosmetic. COPPER. Sym. Cu. {Cuprmn). Equii. 31.7. Sp. Gr. 8.9. 828. This well-known metal needs little description. It is tough, malleable, of a red color, and often found native in masses of great magnitude. Its ores are numerous and wide-spread. Among the most common of these i§ the red oxide of copper, CuO, and copper pyrites, a double sulphide of copper and iron. Copper is stiffened by hammering, and softened by heating and suddenly cooling in water ; the reverse of the effect produced upon steel. In dry air it is hardly acted upon, but in a damp atmosjjhere it ac- quires a green crust of carbonate, familiarly known as verdigris. 829. Copper is an excellent conductor of heat and electricity, and is extensively used for telegraph wires. Being little affected by the air, it is better adapted for culinar}' and many other uten- sils than iron. Vegetable acids, however, dissolve it in the cold state ; hence sauces containing vinegar, and preserved fruits or jellies should not be allowed to remain in copper vessels, as the salts produced are poisonous. 830. Oxides of Copper. — Copper forms several oxides of which the protoxide or black oxide, CuO, is the most important, as it constitutes the basis of most of the salts of copper. It is used in organic analysis as a source of oxygen, and in the manufacture of glass and porcelain to impart a green color. 831. Sulphate of Copper, CuO, SO3 + 5HO (Blue Vitriol).— This is used largely in dyeing and calico printing, and as a source of many of the pigments containiug copper. 832. Nitrate of Copper, CuO, XO5 -fSHO, is formed by dis- solving copper in dilute nitric acid. It is a very corrosive, deli- quescent salt, of a deep blue color, is easily decomposed, and crystal- lizes in prisms. are the most common ore;? of copper ? How are its properties altered f Wtat i« TerdipriB? 829. For what ib copper well adapted? What precaution is given? 830. What is said of the oxides of copper ? S31. Of sulphate cf copper? 8S2. Of ANTIMONY, BISMUTH, COPPEK, LEAD. 311 LEAD. Sym. Ph. {Plumbum). Equiv. 103.6. 8p. Gr. 11.44. 833. This useful and common metal occurs under various mineral forms, of which the most valuable is galena^ a sul- phide. Lead is a soft, blue metal, easily scratched by the nail, and leaving a stain when rubbed upon paper. It is highly malleable, but not very ductile. In the air a film of oxide rapidly forms on its surface, which protects it from further corrosion. It melts at about 612°, and on solidifying contracts to such an extent as to render it unfit for castings. 834. If lead is exposed to the combined action of pure water and air, an oxide of lead is formed on the exposed surface, which is dissolved by the water with which it is in contact. This solution of oxide of lead absorbs carbonic acid, forming a carbonate of the oxide of lead, an insoluble but highly poisonous compound. The presence of chlorides or nitrates assists this corroding action, while it is re- tarded by the sulphates, phosphates, or carbonates. Bicarbonate of lime, a salt found in many spring waters, also prevents this cor- rosion by depositing a coating on the exposed surface. In the use, therefore, of lead water pipes, it should be carefully ascertained whether the water to be conveyed contains foreign matters, which will prevent its action upon the metal. 835. Oxides of Lead. — There are four oxides of lead, the most important of which are the 'protoxide and peroxide. The protox- ide of lead, P& (9, forms the basis of the ordinary salts of this metal, and is the well-known powder called litharge. As it easily fuses, and readily dissolves silica, it is much used in glass-making and in glazing earthenware. The peroxide of lead, Ph O21 called minium or red lead, is consumed largely in the manufacture of flint glass. 836. Carbonate of Lead, PbO,C02 {White Lead).—lMs, salt is found beautifally crystallized in nature, but it is largely manufac- tured as a paint. It is produced in several ways, but the follow- ing, which is known as the Dutch method, is considered the best. Thin sheets of lead, rolled up into loose scrolls, are placed in earthen pots with weak vinegar or acetic acid. Thousands of nitrate ? 833. What is galena ? Properties of lead ? 834. What is the action of crater upon lead ? How may the operation he assisted, or retarded ? In the use of lead pipes for water what should be determined ? 835. What is said of the oxides of lead ? What are the uses of litharge ? What of minium ? 836. What is car- 312 INOEGAXIC CHEMISTEY. these pots, fitted with lead covers and closely packed, are then buried in spent tan bark. The acetic acid corrodes the metal, forming a superficial coating of acetate of lead. The carbonic acid set free by the decomposing vegetable matter, displaces the acetic acid, combining with the lead, and forming the carbonate. The acetic acid thus released, attacks more metal, which is again car- bonized, and thus, with a small charge of vinegar, the operation is continued a long time, and a large quantity of lead changed. White lead is extensively adulterated with sulphate of baryta ; it may be detected by adding nitric acid, which dissolves the lead, leaving the baryta as an insoluble residue. 837. Thallium is a metal recently discovered by means of spectrum analysis, and is found in pyrites and in native sulphur. It is of a brilliant white, soft, malleable, has a specific gravity of 11.9, and resembles lead. It forms compounds with oxygen, chlorine, iodine, bromine, sulphur, and phosphorus — its oxides having a decidedly alkaline reaction. 838. Titanium, Columbium, Tantalum, Molybdenum, Tungs- ten, Vanadium, and Uranium, are very rare metals, and compara- tively unimportant. Titanium and uranium are somewhat used for coloring enamels and porcelain, and the salts of the latter possess considerable chemical interest. § III. The Nolle Metals— Mercury ^ Silver, Gold, Platinum, dec. MERCURY. Sym. Eg. {Eydrargyrum). Equiv. 100. Sp. Gr. 13.59. 839. Sulphide of mercury, or cinnabar, is the principal source of this metal, though it is sometimes found native and also combined with silver. It has a silver-white color, a brilliant lustre, and is a fluid at ordinary temperatures. It solidifies, when cooled to — 39°, and is then soft and malleable, but if reduced to a much lower temperature, it becomes brittle. It boils at about 662", and slowly volatilizes at all temperatures above 40°. Metallic mer- cury is used extensively in the manufacture of philosophical in- tonate of lead ? How i3 it produced ? How is it adulterated ? Explain the mode of its detection ? 837. What are the properties of thallium ? 838. Of titanium and uranium 1 809. In what state is mercury usually found ? "What are its proper- THE NOBLE METALS. 313 struments, thermometers, barometers, and as an alloy with tin for coating the backs of mirrors. It is also used largely in the ex- traction of gold and silver by the process of amalgamation. 840. Oxides of Mercury.— There are two oxides of mercmy. The first, the suboxide HgaO, is of little importance. The pro- toxide, HgO, commonly known as the red oxide^ or red "preci'pitate^ may be formed by heating metallic mercury up to 600°, with free access of air. A still higher heat decomposes it, liberating the oxygen, and reducing the mercury to the metallic state. This oxide forms the basis of most of the salts of mercury, and fur- nishes a ready source of oxygen gas. It is the compound from which oxygen was first obtained by Peiestlet, and by which Lavoisiee proved the composition of air. 841. Chlorides of Mercury. — Two chlorides corresponding to the above-named oxides are known. The subchloride HgoCl, familiarly known as calomel^ is prepared by. precipitating a solu- tion of subnitrate of mercury with common gait. It is a yellow- ish-white, tasteless, insoluble powder, used extensively in medicine. The chloride HgCl, or corrosive sublimate^ is formed by sublima- tion from a mixture of sulphate of the protoxide of mercury and common salt. Corrosive sublimate has a disagreeable, acrid, me- tallic taste, and is very poisonous. The proper antidote is white of Qg^^ which forms with it an insoluble, inert compound. 842. Sulphide of Mercury (cinnabar) occurs in large beds at Almaden, in Spain, and is also found in extensive deposits in California. It is produced in considerable quantity by artificial means, and sold as a pigment under the name of vermilu SILVER. Si/7n. Ag. (Argentum). Equivi 108. /S^?, Gr. 10.5, 843. Silver is found both native and in combination. When native, it occurs in fibrous, or crystalline masses ; and when com- bined with sulphur, it is usually associated with sulphides of lead, antimony, and copper. The principal mines of silver are those of Mexico and Peru. 844. Preparation. — Silver is obtained from the sulpliuret by ties? Its uses? 840. How many oxides of mercury are there ? What is the effect of heat upon the red oxide ? 84L "What is the composition of calomel ? Give its preparation. How Is corrosive sublimate formed? "What is the antidote? 842. What is vermilion? 843. What is the appearance of native silver? WiXh 14 ol4 IXOEGANIC CHEMISTRY. roasting the ore with common Bait, whicli converts it into a cUo- ride. It is then, togetlier with water, iron scraps and mercury, put into casks, which are reTolred on their axes. The iron re- moves the chlorine, and the mercnry ajpalgamates with the silver, from which it is afterward freed bj distillation. 845. Silver is separated from its comhination with lead bv melting the alloy and letting it slowly cool, when the lead solidi- fies in crystals, leaving the silver nearly pure. It is further re- fined by the process of cupellation ; a cupel being a shallow, porous vessel, made of bone ashes. When it is melted with access of air, the lead oxidizes ; the oxide, or litharge melts, and being absorbed by the cupel, leaves the silver pure, 846. Properties. — Silver is the whitest of the metals, with a bright, metallic lustre. It is very malleable, ductile and tena- cious. It may be extended into leaves not exceeding Yo\'r, « of an inch in thickness, and 1 grain may be drawn out into 400 feet of wire. Silver does not oxidize in the air at any temperature, but absorbs oxygen when melted, holding it mechanically and giving it off on solidifying. It is a good condnctor of heat and elec- tricity, and its polished surface is one of the best reflectors of light. Silver is chiefly consumed in coinage and in the manufac- ture of silver plate. Being too soft for these purposes when pure, it is usually alloyed with about -^ its weight of copper, which gives it the requisite hardness. 847. Ozides of Silver. — These can be formed only by indirect means. There are three of them, but the protoxide, AgO, is the only one which claims our attention. It may be made by dis- solving silver in nitric acid, forming nitrate of sUver, and then precipitating it with potash. It is a dark brown or black powder, which forms the basis of the most important salts of silver. It is decomposed below a red heat, oxygen being liberated, and the silver reduced to the metallic state. 843. Nitrate of Silver, AgO, NO 3. — This, the most interesting salt of silver, may be obtained by dissolving metallic silver in nitric acid ; colorless, anhydrous crystals being formed, which are reaxlily soluble in an equal weight of cold water. These crystals, •what is it asBociatcd in combinatjon ? 844. How is it oblalned from tLe eulplmret ? 645. How from Jts combin?.tion "with lead ? 646. WLat are the properties of eilvcr ? It« uses f Why is it alloyed ? 847. "What is said of the oxides of silver I 648. How U Dilrate of Hilver ohtained f For wliat used? How may the stain bo removed f THE NOBLE METALS. 315 when melted and cast into small sticks, form the lunar caustic of surgery. Nitrate of silver stains organic matter black under the action of light. Advantage is taken of this property in making indelible ink and hair dye. A solution of cyanide of potassium removes the stain thus produced. 849. ChloridG of Silver, AgCl, is occasionally found native in mines, and is called horn silver^ from its tough, horny texture. It may be prepared artificially by adding a solution of common salt to a solution of nitrate of silver, and appears as a white powder which darkens in color on exposure to the air. GOLD. Sym. Au. (Aurum). Equiv. 196.4. Sp, Gr. 19.34. 850. This is one of the most widely diffused of the metals and generally occurs in minute grains, though sometimes in masses weighing many pounds. In 1851 a lump weigh- ing 106 pounds was found in Australia, imbed- ded in a matrix of quartz. It sometimes occurs in crystalline form, as shown in Fig. 264. 851. Properties. — Gold is a beautiful yellow metal, with a brilliant lustre and high specific gravity. It is the most malleable of metals, is exceedingly ductile, and when pure is nearly as soft as lead. It fuses at 2016°, and does not oxidize in the air at any temperature. Gold is -,. 1 1 -u 1 . ., ^ 1 Crystal of Gold. dissolved by selenic acid, nascent cyanogen, and any solution that liberates chlorine ; but its usual solvent is aqua regia. Like silver, it is too soft for the purposes of coinage and jewelry when pure; the required hardness being imparted by alloying it with ^ of its weight of copper. This alloy forms the standard gold for coin in this country. 852. Carat is a term used to designate one of the parts or units of a certain number which is taken as the standard of pure gold. In the United States the number is 24, therefore pure gold is said to be 24 carats fine. If it contain 6 parts of alloy, it is 18 carats fine, and so on. Assaying is the determination of the amount of pure metal in an alloy, or specimen of bullion. 849. How is chloride of silver produced? 850. "What Is said of the occurrence of gold? 85L The properties of gold? 852. What ismeant by the term carat? "What 316 INORGANIC CHEMISTRY. 853. Preparation.— Gold is separated from all its ores except silver by amalgamation with mercury. It is obtained from silver by boiling it in nitric acid which dissolves out the silver, leaving the gold pure. In this operation, in order to prevent the silver from being mechanically protected from the action of the acid, it is necessary that there should be three times as much silver as gold. As the gold constitutes only one quarter of the mass, the process is known as quartation. 854. Gold forms compounds with oxygen, sulphur, chlorine, bromine, iodine, &c., but they are not of sufficient interest to re- quire mention. PLATINUM. Sym, PI. Equiv. 98.6. Sp. Gr. 21.5. 855. Platinum is a rare metal, always found native, and usual- ly associated with palladium, rhodium, and iridium. It also occurs alloyed with gold, copper, iron, and lead. Its chief sources are the mines of Mexico, Brazil, and the Ural Mountains. 856. Properties.— Platinum is of a grayish- white color, and closely resembles silver in appearance. When pure it scarcely yields in malleability to gold and silver ; is very ductile, and takes a good polish. But the qualities w^hich render it so useful, and in some cases indispensable to the chemist, are its extreme difficulty of fusion (being unaffected by any furnace heat), and the perfect manner with which it resists the action of almost all acids. It does not oxidize in the air at any temperature, and is not acted upon by simple acids. It is slowly dissolved by aqua regia. 857. We have already alluded to the power possessed by spongy platinum of condensing gases and causing the union of oxygen and hydrogen. Platinum hlach is a preparation of the metal in a still more minute state of subdivision, and has the property of effecting chemical changes more energetically than platinum sponge. It may be produced by electrolyzing a dilute solution of the metal. 858. With the exception of tlie bichloride, the compounds of jjlatinum are unimportant. The bichloride of platinum is useful to the chemist as furnishing an excellent test for potash, which it is assaying? 853. Explain the preparation of gold? 854. What other compounds of gold are mentioned ? 85^, IIow does platinum occur ? What are its chief eour- cee? 856. Its properties? Wi^y ZiliistraticHi of Is Fig. 26a Fi^. 267 Woody Fibres Gn-i COLLOID CONDITION OF MATTEE. 327 aspect. That the elements carry their allotropic conditions into combination seems to have been lately established by Beodie, who has succeeded in producing several compounds of carbon in which it evidently exists in the state of graphite (528). See Atlas. § III. Colloia'GmidUMU^J^^^ier — Dialysis. ^ 891.— The recent distinction of bodies into crystalloid or crys- tal-like, and colloid or jelly-like, has been stated; but the view is of such importance in connection with organic phenomena as to require further explanation. 892. Their Contrasted Properties.— It was said that the crys- talloids as water, acids, saline compounds, sugar, &c., tend to as- sume hard forms with angular outlines ; that they are easily soluble, and form solutions which are mobile, or without viscidity. Colloid bodies, on the contrary, as albumen, gum, glue, starch, &c., are soft, with rounded outlines, have little or no tendency to crystallize, are slowly soluble, and form viscid solutions. 893. Power of Diffusion. — In this respect there is a further important contrast of properties. This may be shown by pro- viding two jars and placing in one a little colored crystalloid, as bichromate of potash, and in the other a colored colloid, as cara- mel (burnt sugar). If each be covered several inches deep with another colloid, as starch jelly for example, after a few days it will be observed that the potash salt has diffused upward through the gelatinous mass, while the caramel has hardly discolored the jelly immediately above. This experiment illustrates a most important general principle, viz. : that crystalloids diffuse actively through colloids, and that colloids will not diffuse through each other. 894. Dialysis. — These facts open a new source of analysis. If a small hoop be prepared and one side of it be covered with strong paper (942), it forms a vessel like a sieve. Let this be floated upon pure water, and a mixture of crystalloids and colloids, as sugar and gum, be placed upon it. The paper is a colloid, and the crystal- lized sugar will diffuse rapidly through it into the water below, while hardly a trace of gum will pass. Any animal membrane, or a layer of gum, gelatine, or albumen, when used as a partition, acts tion of bodies is important in organic chemistry ? 892. Give some of their contraBted properties. 893. What are their powers of diffusion. "What does this experiment illustrate ? 894, Describe the experiment with the sieve. What is this mode of 328 OBGAI?^IC CHEMISTRY. in the same manner, transmitting crystalloids and arresting col" loids. Prof. Geaham calls this mode of separation dialysis. 895. A New Theory of Osmosis — These views afford a new- explanation of osmose (70). Graham maintains that it is not true capillary attraction which causes the flow of liquids through moist membranes, as formerly described, but that it is due to a combi- nation and decomposition taking place in the membrane. When a colloidal membrane is in contact with pure water upon one side, and a saline solution on the other, it combines with the water, but the saline solution, having a stronger attraction for the water than the membrane has, takes it away, and thus, by a con- stant hydration and dehydration of the intervening colloid, the motion of the currents is established. 896. Further Contrasts. — There are still other contrasts be- tween these two classes of bodies which throw light upon organic changes. The crystalloids are of a permanent nature, while the colloids are unstable. The former, from their hardness, are com- paratively unaffected by external agencies, while the latter, from their softness, are extremely susceptible to them. As might be supposed, the living body is formed of soft, impressible colloids, albumen, gelatin, fibrin, &c. As the colloids cannot diffuse into each orther, they are adapted for fixity of structure ; while, from their ready permeability by water containing crystalloid mate- rials, they give rise to the motion of fluids. 897. Mutability of Colloids. — Moreover, while the chemical equivalents of the crystalloids are generally low, those of the col- loids are always high. The crystalloids have a decided taste, and are chemically active, while the coUoids. from their high equiva- lents, and the massiveness of their complex atoms, are chemically inert, and insipid to the taste. But, physiologically, these relations are exactly reversed. The colloids are the seat and instruments of change ; they not only impel the circulations ; but, from their complexity and mutability, they are themselves capable of those rapid decompositions and transformations which are necessary for the manifestation of the vital actions. Having contributed for a while to the stability of the structure, they break up into the analyais called ? 895. What is Gkaham's new theory of osmose ? How are the oemolic currents established ? 896. State other contrasts between crystalloids and colloids. How do these properties affect the living body ? 897. ITow do crystal- loids and colloids differ chemically ? IIow physiologically ? 899. What does prox- OEGAIflC ANALYSIS. 329 simpler forms of crystalloids, and then rapidly diffuse away as waste products. 898. Speaking physiologically, the crystalloid has been termed the statical condition of matter, and the colloid the dynamical, Geaham remarks that the colloids possess energia^ and may be , looked upon as the primary source of the force appearing i n the / phenomena of vitality. ^■'^^^" ^ §IY. Organic Analysis. 1 899. Proximate Analysis determines the proportions of the 7 /proximate principles of organic bodies ; for example, the starch, / / sugar, gluten, ligneous fibre, and oily matter in the flour of wheat. The first step consists in thoroughly drying the substance to be analyzed by exposure to a heat of from 212° to 250° in an oven with double sides, inclosing water, brine, or oil, to maintain a steady temperature, which is indicated by a thermometer, Fig. 268. The proportions of water and solid matter are thus ascertained. The dried product is then exposed to the action of various substances in succession. "Water dissolves sugar lying ven. ^^^ gum, ether the fatty bodies, al- cohol various crystallizable organic principles, such as vegetable alkalies ; while diluted acids and alkalies are employed to effect other solutions ; they must always be used cautiously, however, as they tend to decompose organic matter. 900. Use of the Microscope. — In this kind of analysis the mi- croscope is of great use in determining the completeness of sep- aration, as it is often better fitted for the detection of organic par- ticles than any chemical tests that can be applied. For this reason the microscope has been made to do excellent service in the de- tection of adulterated mixtures of food. 901. The Mineral Elements of organized bodies are procured by taking a weighed portion of dry organic matter and carefully imate analysis determine? What is the first step? What the next process? 900. Is the miscroscope useful? 901. How are the mineral elements procured? 902. In what does ultimate organic analysis consist ? 903. Describe the apparatus 330 OEGAXIC CHEMISTRY. burning away the combustible part. The ash that remains is then submitted to the action of various solvents, and its several ingre- dients ascertained. 902. Forms in which Elements are obtained. — As the chief bulk of most organic substances consists of carbon, oxygen, hydro- gen, and nitrogen, ultimate organic analysis consists in determining the proportion of these elements. They may be obtained either separately or in a state of combination, but the latter method is most practicable. Nitrogen is generally produced in the form of ammonia ; hydrogen as Tvater, and carbon as carbonic acid. 903. The Apparatus of Analysis. — The analysis of a body con-. tainiug carbon, oxygen, and hydrogen is effected in the following manner : A sheet iron furnace in the form of a trough. A, Fig, 269, rests upon bricks, g g. A tube known as the comliistion Uihe, Fig. 269. Apparatus for Orgaum Analysis. half an inch in diameter and fifteen inches long, rests upon supr ports in the furnace. Tliis is closed at one end, and filled witli dry oxide of copper mixed with the substance to be analyzed. Oxide of copper is used because it readily imparts oxygen to combustibles in contact with it, but when heated alime, it bears a very high tem- perature without being decomposed. This tube is tightly connecti ed by a cork to the drying tube, which is filled with chloride of calcium, and accurately weighed ; f represents Liebig's potash bulbs which contain solution of caustic potash. These are also care- fully weighed and attached to the drying tube by air-tight con- nection. 904. The Process. — Tlie combustion tube is surrounded with charcoal and heated to redness. A portion of the oxygen of tho copper, seizing upon the hydrogen of the organic body, forms for organic analysis. 904. Describe the process. 905. How is the oxygen do- ORGAXIC ANALYSIS. 331 ■v\rater, whicli, passing off as vapor, is either condensed at f7, or absorbed by the chloride of calcium. Another portion of the oxvgen, combining with the carbon, forms carbonic acid, which, passing through the drjing tube, enters the bulbs, and is absorbed by the potash. When the combustion is complete, the potash tube is detached and weighed, the gain being in carbonic acid, three tenths of which is carbon. The chloride of calcium tube is also weighed ; its increase is water, one ninth of which is hydro- gen. As there is no other source for the carbon and hydrogen than the organic body, the quantity which it contained is thus determined. 905. Determining the Osy gen.— But the carbon and hydrogen together do not equal the weight of the original substance ; the de- ficiency is ash and oxygen. The proportion of ash being ascer- tained by incineration of another sample, the quantity of oxygen is the remaining deficiency, and is easily calculated. 905. Determining the Nitrogen. — If the compound to be ana- lyzed contain nitrogen, its quantity must be determined by a sep- arate process. When heated in a suitable apparatus with an ex- cess of hydrate of potash, the whole of the nitrogen escapes in the form of ammonia, which is easily collected, weighed, and the pro- portion of nitrogen determined. 907. Of course this is but the barest outline of the process, and is designed only to convey a general idea of the mode of pro- cedure. !N"umberless precautions and particulars of the most del- icate nature have to be observed, and only a'consummate skill of manipulation can produce trustworthy results. 903. Organic Equivalents. — The information furnished by bare analysis is but scanty; it does not give the combining propor- tions of a compound, or the number of its atoms. To obtain these, the unknown substance must be made to unite with some com- pound, the constitution of which is established. Various v^-ell- deterrained mineral substances are used — very frequently oxide of silver, which combines with many organic bodies. Its equivalent is Agios + 08=116. If it be desired to determine the combining number of acetic acid, a weighed portion of the oxide is made to unite with the acid, of which it takes an equivalent quantity. lermined ? 906. How the nitrogen ? 907. "What is necessary to obtain trustworthy results ? "WTiat does bare analysis fail to give ? 908. How are organic equivalents 332 ORGANIC CHEMISTRY. Suppose that the acetate of silver formed amounts to 48.73 grains. It is then barned. The acetic acid and the oxygen of the silver, are botli driven off, the loss being I7.2i grs., and there are 31.49 grs. of pure metallic silver left. Then Amount if silver. At. wt. of eilver. Amount of acid. At. wt. of acid. 31.49 : 108 : : 17.24 : 59 This product, 59, is, however, too high, as it includes the oxygen of the silver, which escapes with the acid. Deduct this, and we have 51 as the true atomic weight of acetic acid. 909. Calculating Formulse.— If now, by the process (904), we analyze the same quantity of acetic acid, we shall find that it contains 24 parts carbon, 3 hydrogen, and 24 oxygen. These quantities divided by the atomic numbers of the elements, give 4 equivalents of carbon, 3 of hydrogen, and 3 of oxygen, or C4H3O0J as the empirical fonnula of acetic acid. CTy^pP^ § ^* Tlieory of Compound Radicles.^' 910. Importance of Grouping — The recent advance in chem- istry compels us to the conclusion that the arrangement of atoms is of more significance than either their proportions or their kinds. Formerly organic compounds were classified according to their obvious properties, as acids, bases, &c. ; but at the present time the strict scientific jnethod is to distribute them into groups and series according to relationships of derivation and analogies of atomic arrangement. The doctrine is worked out in different ways by different authorities, and though chiefly of importance to the advanced chemist, it will be also interesting to the general student, as developing many curious facts and illustrating the direc- tion of progressive thought. 911. Compound Radicles have been referred to as combina- tions of elements, which play the part of simple bodies, so that we * " The German term radikal is commonly but inaccurately tranBlatcd radical, which is properly an adjective, the word radicle being the appropriate rendering." (Miller.) obtained ? How ib the combining number of acetic acid obtain(?d ? 909. ITow is tho formula determined ? 910. Wliat is paid of the arrangement of atoms ? How were organic compounds formerly classified ? What is the proeent strictly scientifio method ? 911. What are compound radicles ? Give the combinations of the simple HOMOLOGOUS SEEIES. S33 may trace them in their relations and changes as we do the ele- ments themselves. Potassium, for example, is an element; it com- bines with oxygen, forming oxide of potassium KO, and this again combines with water, forming EO, HO, or hydrated oxide of potas- sium. If, in place of water, nitric acid be used, we have nitrate of oxide of potassium, KO, NO 5, or with other acids, a large class of salts of oxide of potassium. Potassium is here regarded as the starting point, the root, or radicle^ of this series, and, being un- decomposable, it is called a simple radicle. 912. Example. — I^ow there are compounds or groups of ele- ments which behave in a similar way, and are hence called com- pound radicles. Ethyl, for example, is a radicle with the composition C4H5, and gives rise to a series of compounds, like potassium : thus, Ethyl, O4H5 Oxide of ethyl (wine ether), O4H5, Hydrated oxide of ethyl (common alcohol), C4H5, 0, HO. As potassium combines with sulphur, chlorine, iodine, &;c., to form a series of salts, so ethyl combines with the same elements to form a series of ethers, as follows : Oxide of potassium, KO Oxide of ethyl, C4 Hg O Sulphide of potassium, KS Sulphide of ethyl, C4 H5 S Chloride of potassium, KCl Chloride of ethyl C4 H5 CI Iodide of potassium, KI Iodide of ethyl, C4 H5 1 Bromide of potassium, KBr Bromide of ethyl, C4 H5 Br In the last column we have a series of ethers, in which S, 01, I and Br replace the O of common ether. Other compound radicles, as methyl (C2H3) and amyl (OioH,,), give rise in the same way to different series of ethers and alcohols. ■ 913. It was at first objected to this theory that the radicles were hypothetical bodies, which could not be separated or proved to exist. To this it is replied, that several of them have ieen sejo- arated^ while the view they afford greatly assists the comprehen- sion of organic changes. See Chemical Atlas and Chart. § YI. Homologous Series. 914. Homology is a term used to express an interesting rela- tion among organic substances, which has been made by Geehardt radicle potassium. 912. In -n-hat way do compound radicles act ? Example. 913. "What objection was made to this theory I How answered? 91i. What is Geb- 334 ORGANIC CHEMISTRY* tlie basis of classification in his system of chemistry. A series of compounds is called homologous when each member of it — that is, each compound — differs from the others in a regular manner, either by a uniform number, as OoHo, or its multiple; and when the properties of these different compounds are entirely analogous, yet differ in degree in proportion to the varying composition. 915. There is a class of compounds, for example, known as alcohols, which manifest a close analogy with each other, both in composition and in their modes of decomposition. In the sub- joined table the composition and homology of the most important of this group of bodies is represented. Homologous Series of Alco- Homologous Series of Vola- hols. tile Acids. Methylic alcohol, O^ H^ Oo Formic acid, O2 Ho O4 Common alcohol, O4 Hg O2 Acetic acid, O4 H4 O4 Propylic alcohol, Cq Hg 0, Propylic acid, Co H^ O4 Butylic alcohol, Og HjoOa Butyric acid, Cg Hg O4 Amylic alcohol, CjoHioOa Valerianic acid, , H , O4 Caproic alcohol, C , 2 H , 4 Oo Caproic acid, C,2 H12 O4 Caprylic alcohol, C , g H, 3 Oo Caprylic acid, C 1 g H , ^ O4 Laurylic alcohol, C04 Hog Oo Laurie acid, C24 H04 O4 Cetylic alcohol, O^o H34 O2 Ethalic acid, C32 H32 O4 Cerylic alcohol, O34 I-I56 O3 Cerotic acid, C54 H54 O4 Melissylic alcohol, O^o H^a O2 Melissic acid, Cgo H^o O4 Here it will be seen that the first six of the alcohols differ by the successive addition of CoOo, and the rest by its multiples, Formulae have been constructed to represent these compounds in which n n stands for 2, 4, 6, 40, or any even number of atoms of carbon and hydrogen, and by which the composition of the al-. cohols is indicated, thus CnHn+o Oo. 916. When any compound of a homologous series is decom- posed, it gives rise to compounds which are definitely related to it, but as they are differently constituted, they are termed hetero- logous compounds. The alcohols, when decomposed, give rise to a series of ethers, of aldehyds, and of acids ;— heterologous groups, but each forming a homologous series. The most complete of this series is that of the volatile acids, some of which are given in HARDT's basiB of classificalion ? What is a homologous series of compounds ? 915. Example. How do these compounds differ? How arc they represented in for- mula;? 916 "What arc heterologous compounds ? Example. "What is the most complete of this series, and from what derived ? "What is their difference and for- THEORY OF TYPES. 335 the table. They are derived from the alcohols by oxidation, and several of them occur in nature. They differ by an increment of C2 Ho, and have the following general formula, CnHn04 917. The extreme terms of this series are widely separated in properties ; formic acid being a pungent, corrosive, volatile liquid, which must be cooled to 82° to solidify it, while melissic acid is a solid fat which melts at 192°. But if we compare any compound of the series with the adjoining ones, the difference in properties will be found but slight. They increase in solidity, and their melting and boiling points rise gradually with each successive in- crease of the common difference. But a part of the series is given in the table; it rises uninterruptedly, step by step, from 2 to 38 equivalents of carbon and hydrogen, through nineteen links of the homologous chain ; above this there are gaps not yet filled. A few years ago only the first two members of the series were known. For illustrations of this and the following subject, see the Chemical Atlas. § YII. Theory of Types. 918. Convinced of the difficulty of representing the actual ar- rangement of the atoms of chemical compounds, many chemists maintain that we should represent in formulae only those relations and analogies among compounds which result from their modes of decomposition^ when subjected to the action of the same chemical reagents. To effect this, all substances are thrown into a few great classes of analogues, and some leading member of each divis- ion, having familiar and well-marked characteristics, is selected as the pattern or type of the class, from the formula of which that of all the others is derived. This view puts resemblance of chemi- cal properties out of the question ; hence the same type may com- prehend acids, bases, and neutral bodies. 919. Gerhaedt refers most of the bodies of organic chemistry to four principal types, as follows — the first column representing the types, and the second giving single examples of compounds arranged under them : mula ? 917. What is said of the extreme terms of this series ? How do the com- pounds dilTer successively? "What is further said of this series? 918. What do many chemists maintain in regard to formula? How is this result obtained? What is further said of this view? 919 What are Gerhakdt's four principal 336 OKGANIC CHEMISTRY. 1. The hydrog(fn type, g } or H, Mars^h^gas, hydride of Me- C.Hs ^ 2. The chloride or HI m,! i j • ^i CjH, ) Chiorohydiic acid type, CI \ Chlorohydric ether, ^^^^ ^ 3. The oxide or H)^ Alnnbnl C4H5 [ 0^ Water type, H f ^^ Alcohol, ^^^ ^ 4. The nitride or J? I at -n., , • ^'H^ ) >t Ammonia type, gp Ethylamine, h f" 920. Substitution and Replacement. — When the idea of a type is accepted, the changes that take place under it are regarded as replacements or substitutions. It is like preserving the general structure of an edifice, though constantly removing its individual bricks and stones and replacing them by others. Thus in the chloride type we can substitute for the -chlorine, iodine, bromine, or cyanogen, while the type remains unaltered. 921. Perhaps the most interesting case of substitution is where ammonia is converted into a complex organic base by replacing its hydrogen with various compound radicles. If bromide of ethyl be made to act upon ammonia, a new base ethylamine, C4H-j]Sr, appears. H This is a compound of the ammonia type, H }■ N, and may be repre- C4H3 ) sented thus, H >'S-^ that is, it is ammonia in which one atom H ) of hydrogen has been displaced by its equivalent of ethyl, C4H5. If this new compound be heated with bromide of ethyl, diethylamine C4H5) is obtained, O4H5 y'R- that is, another atom of hydrogen is re- H ) placed by an atom of ethyl. Again, the last atom of hydrogen may C Ji5 ) be replaced by the radicle, and triethylamine results, C4II5 >■ N. C4H5 ) Thus a new ammonia is formed, closely resembling in properties common ammonia. 922. Another remarkable instance of this substitution is that of chlorohydric ether, O4H5CI. Chlorine combines with this ether, forming a series of five new compounds, in which it displaces the hy- types ? 920. ITow are changes that take place under a type regarded ? What com- paiifion is made ? Example. 921. What remarkable case of eubetitution is given ? What is the composition of ethylamine ? Diethylamine? Triethylamine! 922, THEORY OF TYPES. 337 drogen, equivalent for equivalent, until the latter element is all re- moved, and the compound completely chlorinated. Neither the number of atoms in the compound, nor their arrangement are changed in this complete revolution of composition, while the boiling point and density steadily rise as the quantity of chlorine increases. 923. Coupling of Organic Compounds. — We have just seen that there is a class of substances produced by the union of two or more simple organic compounds, yet retaining the character of one and losing that of the other. Thus, ethyl unites with ammonia, its own characteristic properties disappearing, while those of am- monia continue. The terms coupling^ or conjugation of com- pounds, have been applied to this kind of union, while that con- stituent whose properties' disappear is called the copula. 924. The foregoing views are not sufficiently developed to serve as a basis of popular classification. "We shall adopt an ar- rangement less strictly scientific, but more convenient for the general student. The chief vegetable and animal products, and their most im- portant changes, will be noticed in the following order : — 1. The saccTiarine and amylaceous group. 2. The oleaginous group— fats and oils. 3. Acids, dases, and coloring principles. 4. nitrogenous compounds, their changes and products, 5. Animal products. 6. Chemistry of foods. 7. Ciwmistry of soils. CHAPTER XIX. THE SACCHARINE AND AMYLACEOUS GROUP. 925. This is an important class of organic bodies, composing the chief bulk of the vegetable kingdom, and entering largely into the diet of animals. They are distinguished by several chem- Give another case of this substitution. How is the compound affected by this revolution ? 923. "What is coupling of compounds ? 924. What is said of these vje"ws ? 925, What is the relation of the sapcharine and amylaceous group to the 15 838 OEGAXIC CHEMISTEY. ical peculiarities. Containing no nitrogen, thev are termed the Jion-nitrogenous group; being composed of three elements, carbon, hydrogen and oxygen, they are known as the tenutry group ; and, as they contain hydrogen and oxygen in tlie exact l)rop rtion to form water, they have been called hydrates of car- bon . We cannot say, however, that the hydrogen and oxygen exist in these compounds as water. Their mode of origin and mutual relations in the plant will be noticed in the chapter on vegetable growth. § I. The Sugars. 926. These sweet-tasted bodies are widely distributed through the vegetable kingdom, and lai'gely employed as food. There are several varieties of sugar, but we can notice only three: cane sugar, or sucrose; grape sugar, or glucose; and milk sugar, or lactose. 927. Cane Sugar, C,oH,iO,, {Sucrose.)— TYns, the most im- portant variety, has a specific gravity of 1.6, is soluble in one third its weight <;f cold water, forming a thick sirup, and is the sweetest of all the sugars. When evaporated from its solutions it readily crystallizes ; but when long boiled it acquires an atom of water, loses its property of crystallization, and acquires an acid reaction. If boiled for some hours, with a trace of acid added, it is changed to grape sugar, CisHioOis + 2 Aq. In its chemical relations sugar ranks with acids; it dissolves and combines with various bases, forming mccJiarates ; as 2PbO, C,2ll,<,0,o, saccharate of lead. Sucrose melts at about 320°, and by cooling forms the transparent, amber-colored solid known as harley sugar. If the melted sugar be heated to 420°, a brown, bitter mass results, known as caromel., w hich is much used by cooks and confectioners as a coloring agent. 928. Manufacture of Sugar. — Cane sugar is chiefly produced from the cane, beet root, sorghum, and the palm and maple trees; but by far the largest portion is from the sugar cane. The canes are crushed by passing them between grooved iron cylinders. The juice, when first expressed, is liable to rapid decomposition vesretable aud animal kingdoms? How are tliey named, and -why? 926. What are the sugars! Their varietiee? 927. Give the compoBilion of cane sugar. PiopertieB. How is it changed to glucose t What are saccharales? Caromel? 928, From what is cane eugar produced ? Give the mode of it* manufacture. ■^n THE SUGARS. 339 from the heat of the climate. This is prevented by the "addition of a small quantity of lime, which neutralizes acids and coagulates impurities. The juice is evaporated by boiling in large open ves- sels, and when reduced to a proper consistency, is transferred to coolers, where a portion of it crystallizes, forming raw, or brown sugar. On an average, a gallon of juice produces a pound of sugar. 929. Molasses. — The drainage of the raw sugar forms molas- ses. It contains a portion of the sugar that has been burnt and darkened in boiling, another part that has been changed to the nncrystallizable state, and still another of crystallized sugar. It has a strong, peculiar taste, and is acidulous. It is very absorbent of water ; indeed many kinds of raw sugar, from this cause, melt into sirup when exposed to the air. 930. Refining of Sugar. — Crude sugars are purified, or refined, by reducing them to a sirup and first filtering it through twilled cotton, to separate mechanical impurities. The same efiect is further promoted by the use of serum of blood. To decolorize the sirup it is again filtered through a bed of coarsely-powdered charcoal. It is then evaporated in vacuum pans — the air being exhausted, so that it will boil at a lower temperature — and finally re crystallized. 931. Grape Sugar, dsHioOj 2 -f- 2 Aq. ((9?wcose).— This variety of sugar is less soluble and less easily crystallized than sucrose. "We are familiar with it as the sweet grains of raisins, figs and other dried fruits, and it is also largely obtained by transformation of starch (951) ; hence it is cdlled starch sugar. Bernaed has shown that it is. normally produced in the livers of animals, and it appears as a morbid constituent of the urine in the disease called diadetes. The candied sugar of honey and sweetmeats consists of glucose. Fruit sugar was formerly supposed to be a distinct variety, but it proves to be rather a mixture of different kinds. 932. Milk Sugar, C 4H24O24 (Lactose), is obtained only from the milk of the mammalia, to which it gives its sweetish taste. It is obtained by evaporating clarified whey till it crystallizes. It is much less soluble, and, therefore, much less sweet than cane or grape sugar, and its crystals are hard and gritty. 929. How is molasses obtained ? What are its properties ? 930. How is sugar refined ? 931. How does grape sugar differ from sucrose ? From what is it ob- tained? What is frnit sugar? 932. What is milk sugar, and how ohtaincd? Fig. 270, Siarcli Grains of Poialoes. 340 OEGANIC CHEMISTEY. § II. Starch, 933. Starch, C.oHioOio iFecula, Amadiii). — This substance is found universally distributed in the Tege- table kingdom in grains, seeds, roots, and the pith and bark of plants. "When pure it is a snow-white glis- tening powder. Examined by the microscope, it is found to consist of exceedingly minute round, or oval grains, which vary in size Fig. 271. from -^ to yo.ioo o^ ^n inch in diameter. Potato granules are much larger than those of wheat or rice. Starch grains from different sources vary also in form and structure. Those of the potato are egg-shaped ; those of wheat are lens-shaped ; those of rice angular, while several kinds have a grooved aspect, and consist of concentric layers, like the coats of an onion. As each variety has some peculiarity by which it may be identified, the adulteration of wheat flour by potato, or other starches, a^ may thus -be detected. 934. Properties. — Starch is in- soluble in cold water, alcohol and ether, but swells up, and is con- verted into a paste in water containing 2 per cent, of alkali. If heated in water to 140° the grains swell and burst, producing a jelly-like mass (gelatinous starch, or amadin)^ which is used to impart a gloss to textile fabrics. The test of starch is iodine, which combines with it, forming a blue compound, 935. Sources and Varieties. — Starch is largely procured from potatoes, wlieat, and rice. Corn starch is obtained from Indian Properties 933. Give the composition of starch. Where is It found? Ita appearance? State the diffterences in starch grains. 934. What are the prop- erties of starch ? Its test ? 935. Give the sources and varieties of starch. Starch Grains of Plantain. Fig. 272. ^©^ ^^ ^ ^£63 I- s? Starch Grains of Rice. STAECH. 341 corn by chemical agency, being freed from the glutinous, oily, and ligneous elements of the seed, by the aid of alkaline solutions, and by grinding and bolting the corn in a wet condition. Sago is a brown- ish-white starch, obtained from the pith of the palm tree. Tapioca and arrow root are starches from the roots of West India and South American plants. 936. Transfonnations of Starch. — "When commercial starch is heated under pressure to 320°, it becomes soluble in cold water, and is changed into gum. It is sold under the name of British gum, and is successfully substituted for gum arable by calico printers in thickening their colors. If gelatinous starch is boiled for a few minutes wiih weak sulphuric acid, it changes from a viscid mass to a limpid fluid, and a substance is produced called dextrine, which resembles gum in properties. It is a transparent, brittle solid, isomeric with starch, soluble in water, incapable of fermentation, and produces right-handed rotation in a ray of polar- ized light ; hence its name. If the acid solution of dextrine is boiled for some hours, and the acid removed by neutralizing it with chalk and filtering, the liquid will be found to yield upon evapora- tion a mass of solid glucose exceeding in weight the starch from which it was produced. The starch has become grape sugar, C,oHi40i4, its increase in weight being due to the acquisition of the elements of water. The sulphuric acid suffers neither change nor loss, but seems to effect the transformation by its bare pres- ence. Unripe fruits contain starch, which by ripening is con- verted into sugar. 937. Gum, CisHuOn (Aralin). — These terms are applied to a class of substances which are often seen exuding in globular masses from the bark of trees, as the plum and cherry. Gum is translucent, tasteless, inodorous, and either dissolves in water, or swells up and forms with it a thick mucilage. It exists in small proportion in the cereal grains, but its chief source is tropical trees, from the bark of which it flows in such quantity as to be gathered for commercial purposes. Gum Arabic, the product of a species of acacia, is a hard, brittle substance, and is, perhaps, the best known of the gums. Its solution being very adhesive, is used as 936. "What is British gum, and how used? How is dextrine produced? Give its properties. How is it changed to grape sugar? What of unripe fruits? 937. What is gum or arabin ? Its sources and properties. What is gum arabic? 342 OEGAXIC CHEinSTET. a substitute for paste or glue. Mucilage or hassc^rin (C, oHiyO, o) is a kind of gum insoluble in -water, but which swells into a gela- tinous mass when moistened. It abounds in gum tragacanth, and also in quince seeds and linseed. 938. Vegetable Jelly, Pectin, or Pectic Acid, is a substance resembling starch and gum in its composition, which gives to the juices of fruits and roots the property of gelatinizing, ^hen boiled a long time it loses its gelatinous property, and becomes of a gummy nature. It is but slightly nutritive. § in. Woody FUjrc. 939. CeUulin, C,o H^o Oio-— This is the most abundant prod- uct of vegetation. Besides forming the chief bulk of all trees, it Fig. 2T3 Cells aud Air Passages of Vegetable Tissue, (Grat.) Fig. 274. exists in the straw and stalks of grain, in the membrane which envelops the kernel (bran), in the husk and skin of seeds, and in the rinds, cores, and stones of fruit. "Wood consists of slender fibres, or tubes closely packed together. Fig. 273. TVhen first formed these tubes are hoUow and serve to convey the sap, but in the heart wood of trees they become filled up and consoli- dated as shown in Fig. 274, the circulation of fluids taking place in the white external sap wood (alburnum). Upon the density with which the fibres are im- bedded together depends the property of hardness or soft- ness of wood. 940. Composition and Prop- -Woody fibre consists of two parts. Cellulin is the fibrous portion — the base of the woody tissue. It has been known as cd- Mncilage? 9C8. "What is eaid of pectin? 939. Give the composition of cellulin. "Where ia it found ♦ How is wood formed ? Uiwn what does its hardness de- pend t MO. Of what ia the fibrous portion of wood composed t State the prop- Tubes of Heart Wood. (Geat.) WOODY riBEE. 343 lulose, but it is better, as Miller suggests, to change it to cellulin, reserving the termination ose for the sugars. Cellulin, when pure, is white, tasteless, and insoluble in water, alcohol, or ether, but dissolves in a solution of oxide of copper in ammonia. It is nearly pure in cotton, linen, and elder pith. In the tissue of cell:. 11 a there is deposited a ligneous incrustation called lignin^ which is the thickening and hardening constituent of wood, and forms the principal part of its weight. It is difficult to separate and has not been obtained pure, nor has its composition been determined. It is deposited mixed with the coloring matter of the wood and with resinous substances, which increase its combustibility. 941. Transformations of Cellulin.— Cellulin is not colored blue by iodine, but when digested for a short time in sulphuric acid, it is changed and answers to the test of starch. It may be converted into sugar by the fdlowing process. Two parts of linen and cotton threads are soaked for 24 hours in three parts of sul- phuric acid, and the mixture is then largely diluted with water and boiled for a few hours. If the acid be then neutralized with chalk, a mass of glucose is obtained which, if the process is well conducted, may exceed in weight the woody fibre employed. 942. Paper is made chiefly from waste cotton and linen rags. They are bleached, boiled in alkali, and reduced to pulp by means of a beating engine. The pulp, formed into sheets and dried, is blotting paper. To convert it into writing paper, it is soaked in a preparation of glue and alum (sized), and then pressed between hot iron plates. To make vegetable parchment, thin, unsized paper is plunged for a few moments into a mixture of sulphuric acid and water, and then washed. In some unknown way the fibre is affected and the paper made five times stronger than before the process. 943. Gun Cottonj Osg H21 O^^O^i O30, Pyroxyline.—l^ tal>le casein t 1M4. What is eaid of the cinnpositioa of the albominoide ? PUTREFACTION AND DISINFECTION. 373 1046. These substances will be noticed in their physiological relations when we consider the subject of animal nutrition. The remarkable advance in organic chemistry of late years has brought them forward into new relations, and they have received many names. They are called protein compounds^ nitrogenous aliment- ary principles, and as one of the names of nitrogen is azote, they are termed azotized substances. As they form the materials from which the body is nourished and built up, Liebig- named them the plastic elements of nutrition ; they are also known 2.% jiesh-forming and Ijlood-producing compounds. §11. Putrefaction and Disinfection. 1047. A leading characteristic of the foregoing substances is, as we have stated, their instability. This is due, first, to the presence in large proportion of the fickle element nitrogen ; sec- ond, to the large number of elements combined together, and the resulting complexity of the attractions ; and third, to the great number of atoms associated, or the massiveness of the molecules. "When in a moist state, and exposed to atmospheric oxygen, the tottering equilibrium of the chemical fabric is overturned, and out of its ruins a new class of substances is produced. It is well known that flesh, blood, milk, dough, &c., all of which are rich in nitrogenous substances, will preserve their properties in the air only a short time, and pass into a state of decomposition, giv- ing forth offensive exhalations. This change is called putrefac- tion, and when once commenced, it rapidly spreads through the mass, communicating itself to all putrifiable substances with which it is brought in contact. 1048. Propagation of the Effects. — As a spark may kindle a conflagration that shall consume a city, so the minutest amount of putrescent matter is sufficient to affect an indefinite quantity of changeable substance. The remarkable communicability of these effects and their potency of action are painfully illustrated by phy- sicians, who sometimes wound themselves while dissecting. The small trace of decomposing matter from the dead body which clings to the dissecting knife is sufficient to establish a rapid de- 1045. Give the origin of protein. How is it considered by different chemists? 1046. By what names are the albuminoids known ? 1047. "What is a leading prop- erty of these substances? To what is it due ? What is putrefaction? 1048. What 374 ORGANIC CHEMISTRY. composition in tho living system, which, in many cases, quickly terminates in death. Another case in point is the communication of the virus of smallpox, which, when introduced into the blood, reproduces its peculiar putrefaction throughout the system. 1049. Products.— The chief products of putrefaction are hy- drogen, nitrogen, carbonic acid, ammonia, carburetted, sulphu- retted, and phosphuretted hydrogens, and acetic, nitric, and butyric acids. Other compounds also arise with the varying con- ditions. The gaseous combinations of sulplmr and phosphorus are the chief causes of the offensive odor of putrefying bodies. In addition to these well-determined products, putrefaction gives rise to anotlier class less tangible, but more baneful. The foul accumulations of neglected towns, and the decomposing organic matter of many swampy districts, give off invisible emanations known as miasms and malaria, which fill the air, and when in- haled, often occasion fatal fevers and epidemics. Of their compo- sition, nature, or mode of action, nearly nothing is known. 1050. Prevention of Putrefaction. — As the presence of moist- ure, a favoring temperature, and access of air are essential con- ditions of putrefaction, if any of them are withdrawn, the effect is prevented. It is well known that the most perishable organic substances, both vegetable and animal, may be indefinitely pre- served by drying. Cold checks decomposition, and it is entirely arrested by freezing. So, if the prime inciter of change, oxygen, is excluded, putrefaction cannot take place. This fact is illus- trated by the general practice of preserving all kinds of alimentary substances, meat, fruits and vegetables, in vessels which exclude the air. It is not enough, however, to remove the oxygen from the surface of the body ; that which is diffused within it must be expelled, which is done by boiling, or in some cases by a lower heat. 1051. Antiseptics are preventers of change — substances which act in various ways upon changeable bodies to preserve them. Common salt and saltpetre act by partial desiccation. They ab- stract water from the flesh, and hence concentrate the solution of of the action of putrescent bodies ? ExnmpleB. 1049. Mention the chief products of putrefaction. To what in the odor of piitrefylnt? bodies due ? What are other products of putrefaction? 1050. How is putrefaction prevented? How are or- ganic bodies preserved ? Examples. What is necessary to preservation ? 1051. What are antiseptics? Explain the action of salt and saltpetre. Of alcohol and PUTREFACTION AND DISINFECTION. 375 albumen witljin ; by surrounding the meat with salt water, and partially expelling the air, putrefaction is counteracted. Alcohol and sugar act in a similar way, removing a large portion of water from flesh and fruits, and surrounding them with unchangeable liquids and sirups, which prevent the access of oxygen. 1052. Other antiseptics act directly upon the albumen, coagu- lathig and fixing it in unchangeable compounds. The sap and juices of all plants contain more or less of dissolved albumen, which, by its putrefaction, becomes an active cause of the decay of wood. Eapid drying or ' seasoning ' renders the albumen inert, and the same object may be secured in less time by inject- ing the pores of the wood with any compound which coagulates the albumen. Wood is rendered indestructible by a process ap- plied by Dr. Ktan, which consists in steeping it in a solution of corrosive sublimate (kyanizing). Boucheeie cut into the trunks of living trees and introduced salts of iron, which were drawn up by the sap, and, impregnating the wood, increased its durability. Dried animal bodies are preserved from change by injecting in their veins corrosive sublimate, acetate of lead, chloride of zinc, and many other substances. These, like arsenic, are poisons. As life consists in change, and these arrest change, they destroy life, and thus conserve the structures in which it was manifested. 1053. Disinfectants. — A distinction is drawn between anti- septics and disinfectants — the former prevent putrefaction, the lat- ter arrest it; though some substances often act in both ways. Compounds rich in oxygen, and which, when mixed with putrefy- ing matter are decomposed, act as powerful disinfectants. The permanganates perform this office, rapidly destroying the odor of putrid matter, and oxidizing sulphuretted and phosphuretted hy- drogen. Nitric acid and several of the nitrates act powerfully in the same way. Fumes of nitrous acid and chlorine are efficient disinfectants. Chlorine is conveniently used in the form of chlo- ride of lime or soda ; the addition of a little sulphuric acid sets the gas free rapidly. In disinfecting rooms by fumigation with gases, it is to be remembered that they corrode all metallic surfaces. Vinegar, and especially wood vinegar, which contains a little creo- sote, is a valuable disinfectant. So also is sulphurous acid (fumes sugar. 1052. Of other antiseptics. Of seasoning. What is kyanizing ? Give BoncHERiE's experiment. How are animal bodies preserved, and why? 1053. What is a distinction between antiseptics and disinfectants ? Explain the action 376 OEGAXIC CHEIIISTRY. of burning sulphur) ; it destroys sulphuretted hydrogen by oxidiz- ing it, and it also acts by absorbing oxygen. The disinfecting power of charcoal has been elsewhere noticed. 1054. Natural Disinfectants. — We have seen that oxygen and ozone of the atmosphere and the carbonaceous element of the earth are natural disinfectants on a vast scale. "Water, although favor- ing decomposition, is an invaluable agent for removing and finally- destroying putrescent matters, and heat, although up to 140° a promoter of putrefaction, above that point, by becoming a dryer and disorganizer, destroys the sources and products of infection. §111. Fermentation. 1055. "When the ternary compounds, as sugar or starch, are exposed to the air, in a moist state, they exhibit but little tendency to change, and give rise to none of the effects of putrefaction. But if to a solution of sugar there be added a little putrefying flesh, blood, cheese, milk, flour paste, white of ^%%^ or any albuminous substance in a state of decomposition, their action is communicated to the sugar, which is broken up into new compounds. "When the putrefiable substances are considered with reference to the effects they produce npon the other class of bodies, they are called fer- inenU^ and the communication of that condition of change is known as fermentation. 1056. Mode of Action of Ferment. — When changing nitro- genous matter acts upon sugar to decompose it, there is no combi- nation between the elements of the two substances. All that is communicated, therefore, is an impulse of motion. The collision of oxygen shatters the nitrogenous group ; its motion is communi- cated to the atoms which compose the sugar, thus overturning their nicely balanced afiinities. But the sugar cannot, like albumi- nous compounds, take the infection and go on decomposing itself. It only acts as it is acted upon, and when the motion of the impel- ling body is exhausted, the action ceases. Two parts by weight of ferment only decompose a hundred parts of sugar. 1057. Vinous Fermentation. — When the sweet juice of fruits or plants is exposed to the air at the temperature of 70° or 80°, in of the latter ? Give examplce. 1054. "What are preat natural disinfccLante ? WTiat of water and heat ? 1055. How is ferraentation produced? "VSliat are ferments T 10.^6. State their mode of action. "When does jt cease ? WTiat proportion of fer- VOLATILE OR ESSENTIAL OILS. 353 ■weather. As it is less apt to become viscid than most other oils by exposure to the air, it is preferred for greasing delicate ma- chinery. In Southern Europe it is extensively used as a substitute for butter. 973. Palm Oil is expressed from the fruit of the palm tree, and is of an orange-yellow color. It contains 70 per cent, of olein and 30 per cent, of a peculiar fat resembling margarin, which is termed palmatin. It is largely employed in the manufacture of soap and candles. The oil of sweet almonds is mainly used in oint- ments, liniments, and soaps. Colza oil, or rape oil, is obtained from the seeds of a plant belonging to the cabbage family. It is extensively employed for illumination, and is also used for lubri- cating machinery. 974. Train Oil, or Whale Oil, is obtained from the fat of va- rious fishes, as the whale, dolphin, and the seal. It is of a yellow color, and not of a disagreeable odor unless the fish were putrid, or the oil expressed by a strong heat. It is used for illumination, to oil leather, in medicine, and in soap making. 975. Spermaceti is a solid fat which is found in the head of the sperm whale in connection with sperm oil. Pure spermaceti is a beautifully white, crystalline substance, somewhat unctuous to the touch, and resembles white wax in lustre and hardness. It is em- ployed for making candles, and in pharmacy as an ingredient in ointments. In this fat the ordinary base glycerin is replaced by another, termed ethal. 976. Butter is the oily portion of milk, and is a mixture of several fats, the principal of which are margarin and butyrolein. Beomeis found in 100 parts of butter 68 parts of margarin, and 80 of buty- rolein, the remainder being hutyrin, caproin, and caprylin, com- pounds of butyric, caproic, and caprylic acids, with glycerin. The characteristic odor and flavor of butter are owing to the presence of these latter substances. 977. Human Fat is soft, yellowish, and without odor. Its solid constituent is principally margarin, with a proportion of palmatin and olein. The bodies of persons that have been for years buried in churchyards are sometimes found to have been changed into a peculiar substance resembling fat, and termed adipocere. It is also Give its composition and uses. 973. From what is palm oil procured ? State its composition and uses. What of colza oil? 974. For what is whale oil used? 975. What of spermaceti? 976. Of what is butter composed? 977. What ia 354 ORGANIC CHEMISTRY. formed when the bodies of animals are exposed to running water till the muscular and membranous parts have been washed away. It has been shown that this substance is the original fat of the bodv, which has resisted decomposition, and is partly in the state of a fatty acid, and partly saturated by ammonia, with traces of lime and magnesia. § lY. Volatile or Essential Oils. 578. These differ in many particulars from the fixed oils. They readily volatilize, and are usually possessed of a strong odor and hot, pungent taste. They make only a transient stain upon paper, do not form soaps, and are all of vegetable origin. They dissolve in alcohol, ether, and acetic acids, and mix readily with the fixed oils. Their solution in alcohol is termed an essence, hence the name essential oils. 979. Preparation.— These oils are generally obtained by dis- tilling portions of the plant with water. The steam, as it passes over, carries Avith it the oil, although the boiling point of many of them is higher than that of water. The water and oil condense together, most of the oil floating upon the surface. A small pro- portion, however, is retained in solution by the distilled water which gives it the odor and taste of the essence. These solutions are termed ' perfumed waters,' as rose_jwai£j:, lavender water, &c. In some cases the oil is obtained by expression directly from the cells which contain it, as from fresh orange and lemon peel. In other cases, where the oil is so delicate as to be destroyed by dis- tillation, it is extracted by placing the plant or flower between layers of cotton, or of woollen cloth, saturated with some fixed oil. This gradually absorbs the volatile oil of the plant, and a fragrant essence is prepared by digesting the cotton in alcohol. The specific gravity of these oils varies from 0.847 to 1.17. 980. Compositioa of the Volatile Oils.— They generally con- tain two proximate principles, viz., Stearopten^ the solid constit- uent, and Elaopten^ which has a liquid consistence. In reference to their ultimate composition they are usually divided into three classes: 1st, those composed of carbon and hydrogen only; 2d, the composition of human fat ? What is adipoccrc ? 978. How do volatile differ from fixed oils? Why are they bo named? 979. How are they obtain- ed? What are perfumed watera? In what ways are essential oils prepared? 9S0. What is their composition. How are they divided ? 9S1. For what is the YOLATTLE OR ESSENTIAL OILS. 355 those composed of carbon, hydrogen, and oxygen ; and 3d, those which contain sulphur and nitrogen in addition to the last named. 981. The first class includes fifteen or twenty bodies that are remarkable for their Isomerism. Thus, the oils of turpentine, lemons, oranges, juniper, copaiba, citron, black pepper, and sev- eral others which have widely different properties, possess exactly the same composition — 100 parts of each containing 88.24 of car- bon and 11.76 of hydrogen. 982. Oil of Turpentine {Spirits of Turpentine) may be taken as a type of this class of substances. It is obtained by distilling with water the pitchy matter that exudes from the pine tree. The portion remaining after distillation is common rosin. Oil of tur- pentine is a colorless, limpid fluid, having a strong odor and dis- agreeable taste. It boils at 320°, and has a specific gravity of 0.86. It is highly inflammable and when purified is used for illuminating purposes, under the name of camphene. Burning fluid is rectified turpentine, or camphene dissolved in alcohol, which increases the proportion of hydrogen and renders it less smoky when burned. Turpentine is also used in varnishes as a solvent for resins and gums. Eydrochlorate of camphene or artificial camphor is obtained by passing a current of dry chlorohydric acid through oil of turpen- tine. It is a white, crystalline solid, closely resembling common camphor. 933. The second class, or those oils containing oxygen, in- cludes among others, common camphor, the oil of bitter almonds, and the oils of cummin, cinnamon, anise seed, peppermint, roses, lavender, &c. 984. Camphor is extracted by distilling the wood of the cam- phor tree (found in Japan and other parts of the East), with water, and collecting the vapors in a vessel containing rice straw. It condenses in the straw and is again sublhned, after which it is thrown into commerce ; but it requires subsequent purifications to fit it for use. Camphor is quite volatile and readily soluble in al- cohol, with which it forms a solution known as spirits of camplior. Taken in large doses it acts as a poison. 985. Black mustard seed, onions, horseradish, hops, &c., yield oils containing sulphur and belong to the third class. Many of first class remarkable? Examples. 9S2. What is oil of turpentine? Rosin? Burning fluid? Artificial camphor? 983. What does the second class include? 984. How is camphor obtained ? What is spirits of camphor ? 985. What is said 356 OEGAXIC CHEMISTRY. them are characterized by pungent, unpleasant odors, which are readily observable in the breath after eating substances containing them. § y. Resinous and Waxy Compounds. 986. Some plants produce in considerable quantities a sub- stance resembling beeswax, which has the same chemical constit- uents as the fats and oils. The glossy coating or varnish which is observed on the surface of leaves, fruit, and bark, rendering them impermeable to water, consists of tegetahle wax. 987. Beeswax, a secretion of the honey bee, is the most im- portant of these bodies. In its ordinary state it is yellow, but is bleached white by exposing it for some time in thin ribands to the joint action of air, light, and moisture. Wax is principally used in the manufacture of candles. 988. Resins are supposed to be formed by the oxidation of the essential oils. They are found in most plants, and exude from many of them in the form of a more or less viscid liquid, which consists of the resin united with a portion of essential oil. The pure resins are translucent, brittle solids, insoluble in water, but soluble in alcohol, ether, and volatile oils. They are bad con- ductors of electricity, are highly inflammable, and burn with a smoky flame. They are of various colors, but generally brown, green, or red. 939; Common Pine Resin — Colopfiony — Eosin. — This is the residue left after the distillation of crude turpentine, and constitutes from Yo to 90 per cent, of its weight. Common rosin consists of two isomeric acids, the syhic and pinic^ which unite with bases to form salts, and with alkalies to produce soaps. An oil termed syhic, or rosin oil, is obtained from this variety by distillation. Rosin has various uses, the most important of which are in tlio manufacture of a cheap varnish or coating applied to ships and in the manufacture of lamp black (534). It is also used in soldering and as a source of illuminating gas. 990. Lac is a resinous substance of much importance, found as an exudation on the branches of various trees in tropical coun- of the tliird claps? 9SC. Describe vegetable -wax. 9S7. What of beeswax? 988. What are resins, and where found? Their properties? 989. What is com- mon rosin, and of what does it consist? Mention the uses of rosin oil and of rosin ? 990. What is lac, and how formed ? What is stick lac ? Seed lac ? Uses? RESINOUS AND WAXY COMPOUNDS. 357 tries. The bark is punctured by an insect, thus opening a passage for the juice which, as it flows out, hardens over the insects. The twigs, when removed in this condition, constitute the stick lac of commerce. The resinous mass, when digested in a solution of carbonate of soda, yields a red coloring matter contained in the insects. This is largely used as a dye in the place of cochineal. The portion insoluble in the carbonate of soda is called seed lac, and this, when melted and purified, is shell lac. Lac is exten- sively consumed in the manufacture of varnishes and sealing wax, and also as a stiffening for hats. Guaiacum is a resin of a dark, greenish-brown color, and is the product of the lignum vitte tree. It is used medicinally. 991. Gum Resins are the solified milky exudations of plants. They consist of resin, essential oils, and a gummy substance pecu- liar to the plant. They are soluble in rectified alcohol, and form a class of valuable medicinal agents. Ammoniacum, assafatida^ aloe%^ myrrK gamloge^ &c,, belong to this class. 992. Balsams. — This name is given to the fluid compounds of resin and essential oil that exude from trees and shrubs. Among the most important are turpentine^ tals ajn copaiba ^ halsam tolu^ and gum hensoin. From the latter is obtained benzoic acid. 993. Amber is a fossil substance, sometimes occurring in beds of coal, but usually found on the shores of the Baltic Sea, where it is washed up by the waves during long storms. It is a mixture of several resinous substances, and often incloses insects in a state of beautiful preservation ; hence it is supposed to be a solidified resin. It is a yellowish, translucent body, somewhat heavier than water, and has the property of becoming electric by friction. Being quite hard and susceptible of a fine polish, it is used for making ornaments. 994. Varnishes are solutions of various resins in alcohol, the essential oils, or the drying oils, and are employed to give lustre and hardness to exposed surfaces. When alcohol is the solvent, the product is a sjnrit xarnish; when oil is used, an oil varnish. The resins principally used in the manufacture of varnish are mas- tic, sandarac, copal, lac, &c. 995. Elastic Gums — Caoutchouc or India Ruller. — This is What is guaiacum ? 991. Describe gum resins. Examples. 992. What of bal- sams ? 99a What is amber, and -where found? State its properties and wt.Q, 994. What of varnislies ? 995. What is caoutchouc, and how obtained? Give its 358 ORGANIC CHEMISTRY. the product of several tropical trees, from Trhich it exndes as a yellowish, milky liquid, in which the small caoutchouc globules are mechanically suspended. The juice is spread out in films, when it rapidly dries away, leaving the caoutchouc as a thin, elastic layer of a brownish-yellow color. Or, the juice is collected in vessels and poured in successive layers over moulds, on which it is dried by artificial heat. Pure caoutchouc is nearly white, the ordinary black color of the gum being due to the smoke which arises from the fire during the drying process. The solvents of caoutchouc are pure ether, chloroform, bisulphide of carbon, coal naphtha, and rectified oil of turpentine. It melts at about 250°, but on cooling does not return to its solid state. Caoutchouc contracts on being heated, thus forming one of the exceptions to the gen- eral law of expansion by heat (251). 996. Vulcanized India Rubber is formed by charging caout- chouc with two or three per cent, of sulphur. The operation in- creases its elasticity, and also its capacity for retaining it both at high and low temperatures. It moreover increases its insolubility, and fits it for a thousand applications in the arts for which ordinary caoutchouc would be unsuitable. The addition of magnesia and some bituminous matter to vulcanized rubber, gives it a high de- dree of hardness, and renders it susceptible Fio. 275. of a fine pohsh, but in a great measure de- stroys its elasticity. In this state it is largely used in the manufacture of combs, knife handles, and various ornamental ar- ticles. Caoutchouc, from the cohesiveness of its freshly cut edges, its elasticity, pliancy, and power of resisting most chem- ical agents, is of great use in the laboratory. Cohesion of Caoutchouc. ^^'' ^ P^^^^ ^f sheet rubber be wrapped over a glass rod, Fig. 275, on pressing together its freshly cut edges with a gentle heat, they will unite, forming a flexible tube which, on being tightly tied over two glass tubes, will serve to connect them together gas-tight. 997. Gutta Percha is a substance resembling caoutchouc, and properties. Its eolvents. To what is it an exception ? 996. How is vulcanized indir. rubber made ? "What is the chanc:e effected? How is it rendered still harder? For what used? WTiy is caoutchouc useful to the chemist? Describe Fig. 275. 997. What ia gutta percha, and how obtained f Give its properties. Its uses. 998. ACTION OP ALKALIES UPON OILS — SOAP. 359 obtained from plants in the same form of milky exudation. Under ordinary circumstances it is a tough, hard, unelastic body, insolu- ble in water or alcohol, but soluble in chloroform, bisulphide of carbon, turpentine, and most of the essential oils. Immersed in warm water, it becomes soft and plastic, and admits of being moulded in any desired form, retaining its shape on being cooled. In consequence of this property it is used in taking casts and impres- sions, copying the finest lines with fidelity. It is also readily welded while in this waxy condition. It is of a pale brown color, is an insulator of electricity, and becomes negatively electric by friction. § YI. Action of Alkalies ujpon Oils — Soajp. 998. Saponification. — It was stated that the oils and fats are saline bodies, consisting of fatty acids combined with a common base, glycerin. "When otber bases, as potash, soda or ammonia, are made to act upon the fatty substances, they expel the glycerin and take its place, uniting with the acids and forming soap. Soaps are therefore regular salts ; combinations of margaric, stearic and oleic acids with potash, soda, ammonia, or lime. The change by which they are produced is called saponification. 999. Process of Soap Making.— The alkalies generally used for soap making are potash and soda. They require to be in a caustic state, which is produced by dissolving them and passing the solution (lye) through newly slacked lime, which takes away the carbonic acid. In this caustic lye, the fats are boiled, their glycerin set free, and the soap formed in a state of solution in the water. To obtain it in a solid form the solution is boiled down till the soap ceases to be soluble and rises to the surface, when it is drawn off into moulds. Soda soap may be separated from the wa- ter in which it is dissolved by adding common salt, which forms a brine and at once coagulates the soap ; if potash lye is used, the addition of salt decomposes the potash soap, forming a soda soap, and chloride of potassium. 1000. Hard and Soft Soaps. — The consistence of soap depends chiefly upon its alkali. Hard soaps are made of soda, or a mix- ture of soda and potash, while in soft soaps potash alone is used, How is soap produced? "What is saponification? 999. Name the alkalies used. Describe soap making. How may soap be separated from the water ? 1000. Ho\V do hard and soft soaps differ? 1001. What is castile soap? Cocoa soap. 360 OEGAXIC CHEinSTEY. the latter alkali being deliquescent and consequently attracting water, which renders the soap liquid. The consistence of the oU. or fat also intiuences the quality of hardness. Those containing a large proportion of stearin and margarin, like tallow, form hard soaps, while those in which olein predominates, as the soft fats and oils, produce soft soap. The glycerin which is retained in soft soap also adds to its fluidity. 1001. Castile Soap is composed of olive oil and soda, its mottled appearaoce being due to the oxide of iron, with which it is colored. Soap made with cocoanut oil has the property of dis- solving in salt water, and is therefore used at sea. 1002. Properties. — Soap has a powerful affinity for water and may retain from 50 to 60 per cent, of it and still continue solid ; hence dealers generally keep it in damp places where it will ab- sorb moisture. It is soluble in fresh water, but with the excep- tion of cocoa soap, is insoluble in salt water. Soap dissolved in spirits of camphor, forms opedildoc. Volatile liniment is an am- moniacal soap. 1003. Mode in which Soap acts in Cleansing. — As water, having no affinity for oily substances, will not dissolve them, of course it cannot alone remove them from surfaces to which they may adhere. The oily matters which are constantly exuding from the glands of the skin, uniting with the outer dust, form a film over the body. The alkali of the soap acts upon the oil during ablution, partially saponifies it, and renders the unctuous compound freely miscible with water, so as to be easily removed. The cuti- cle or outer layer of the skin is chiefiy composed of albumen, which is soluble in the alkalies. The alkali of the soap, therefore, dissolves off a portion of the cuticle with the dirt ; every washing with soap thus removing the old face of the scarf-skin and leaving a new one in its place. The action of soap in cleansing textile fabrics is of a similar nature. Alkalies not only act upon greasy matter, but as is well known, dissolve all organic substances. In the case of soap, however, the solvent power of the alkali is in part neutralized, thus preserving both the texture and color of the fabric exposed to its action. The oily nature of the soap also in- creases the pliancy of the articles with which it is washed. 1002. What of 6onp in relation to water ? "What is opedildoc ? Volatile liniment ? 1003. How does soap act in cleansing? Explain its action upon the skin. Upon textile fabrica. 1004. "What of crashing fluids t Of camphene ? 1005. "Where and in VEGETABLE ACIDS. 361 1004. Solutions of the alkalies under the name of uasJiing Jluids are often used in cleansing textile fabrics. They act by precipitating whatever earthy salts the water may contain, there- by rendering it soft, and supplying an excess of alkali. Cam- phene, which has the property of dissolving oily substances without injuring the fabric, is sometimes employed as a detergent. CHAPTEE XXI Fig. 276. ORGAXIC ACIDS, BASES, AND COLGRIXG PRIXCIPLES. § I. Vegetable Acids, 1005. These substances are numerous in the vegetable king- dom, occurring abundantly in fruits, and often in the leaves, bark, and roots of plants. They exist in a free state, and combined with* bases, forming acid and neutral salts, both soluble and insoluble. They sometimes accumulate in the cells of plants in the form of crystals, of which Fig. 276 is an example from the cells of an onion. 1006. They usually consist of car- bon, hydrogen, and oxygen, the latter element being greatly in excess. Ox- alic acid, however, contains only carbon and oxygen, and in acetic acid the hydrogen and oxygen are in the proportion to form water. Some of these acids have been de- scribed in connection with groups to which they naturally belong, while the mode of their production is treated in Physiological Chemistry. We shall consider here a few others of the most im- portant. 1007. Tartai-ic Acid, O.H^Oio, 2H0.— This acid is found abimdantly in grapes, and is also present in the tamarind, the unripe berries of the mountain ash, and in small quantity in other plants. It exists in grape juice as bitartrate of potash (cream of Crystals in Cells. ■what state are organic aoids found ? Of what is Fig. 2TG an example ? 1006. What is said of their composition ? 1007. Where is tartaric acid found, and how ob- 16 362 ORGANIC CHEMISTRY. tartar), and is gradually deposited in the form of a hard crust on the sides of vessels in which wine is kept. From this bitartrate, it is obtained by the action of chalk and sulphuric acid. Its crys- tals, w hen pure, are colorless, transparent, permanent in the air, and dissolve readily in water or alcohol. It is extensively used by the calico printer and dyer for the removal of mordants. Mixed with bicarbonates of the alkalies, it forms the soda pow- ders of the effervescing draughts. 1008. Rochelle Salt is a tartrate of potash and soda, produced by saturating a solution of cream of tartar with soda. Tartar emetic, or tartrate of antimony and potash, long used medicinally, i* a violent emetic and cathartic poison. 1009. Citric Acid, Oi2H30ii,3HO, is found principally in fruits of the orange family (Aurantiac^), but is of frequent occur- rence in gooseberries, currants, and other acid fruits. It may be readily procured from the juice of the lemon by the aid of chalk and sulphuric acid. It has a pleasant acid taste, is very soluble in water, and is used in medioine, calico printing, and for effer- vescing draughts. 1010. Malic Acid, C3II4O3, 2H0, is the principal acid of un- ripe apples, hence its name from mains, apple. It is found abun- dantly in most acid fruits, and in the stalks of rhubarb, but is usually obtained from the unripe berries of the mountain ash. It is a colorless solid, dissolves readily in water and alcohol, and crystallizes with difficulty. The s dutions of all the acids named have an agreeable acid taste, but become mouldy if long kept, and gradually undergo decomposition. 1011. Oxalic Acid, OoO.,,HO. — This substance imparts the acid taste to common sorrel and the rhubarb plant, in which it exists as binoxalate of potash. In the barilla plant it is found as oxalate of soda, and in many lichens as oxalate of lime. It is commonly prepared by the oxidation of sugar or starch with nitric acid : 1 part of sugar is dissolved in 8 parts of nitric acid, and gently heated, when intense action ensues, with a copious disengagement of nitrous acid fumes. The crystals obtained are intensely sour and poisonous, and resemble Epsom salts, for which they are sometimes mistaken. In cases of poisoning with lainodf State it-> appearance and uses. 1008. "What is Rochelle salt? Tartar emetic? 10C9. Give the oripjin and properties of citric acid- 1010. Of malic. 1011. Give the composition of oxalic acid. "Where is it found, and how procured? VEGETABLE ACIDS. 363 it, chalk or magnesia, suspended in water, is tLe proper anti- dote. 1012. Oxalic acid is largely used in calico printing, and it is also employed as a delicate test for the presence of lime, with which it forms an insoluble salt. It removes ink and iron stains from linen by forming a soluble oxalate of iron, but the acid is so cor- rosive as to injure the fibre if not immediately removed by washing. 1013. Tannic Acid, O54 H22 O34. — There are several distinct compounds known under the name tannin^ which resemble each other in character and possess an acid reaction. They are found extensively diffused throughout the vegetable kingdom, and are all distinguished by an astringent taste. The bark and leaves of most forest trees, as well as of many fruit trees, contain a large quan- tity of tannin, and it is also found in various roots, shrubs, and seeds. Tannin is the astringent principle of tea and coffee. 1014. The most important of these compounds is that obtained from gall nuts — the gallotannic acid. It has an intensely astrin- gent taste, reddens litmus paper, and is very soluble in water. Tannic acid combines with the salts of the peroxide of iron, form- ing a blue-black precipitate used for coloring, and also in the man- ufacture of writing ink. The gradual darkening of pale watery ink is due to the oxidation of the iron it contains. Tannin forms insoluble compounds with starch, gelatin, and other organic bodies, the most remarkable being that with gelatin, which is the basis of leather. 1015. Gallic Acid is found associated with tannin in the gall nut, sumach, and other vegetable bodies, and is formed from tan- nic acid by exposing a solution of it for some time to the air. It crystallizes in silky needles, is freely soluble in boiling water, and does not precipitate gelatin. On applying a regulated sand heat, gallic acid is decomposed and pyrogalUc acid obtained. This acid is extensively used in photography. Both pyrogallic and gallic acids decompose the salts of silver, gold, and platinum; a property which is utilized in coloring human hair. The hair is first wet with a solution of gallic acid, and after drying, is moist- ened with an ammoniacal solution of a salt of silver. The salt is What of its crystals and the antidote ? 1012. What is said of its uses ? 1013. Where are the compounds of tannin found ? 1014. What is the most important ? Give its properties. Uses. To what is the darkening of ink due ? What compounds does tannin form? 1015. How is gallic acid obtained? Pyrogallic? For what 364 OSGAKIC CHEMISTET. decomposed and the liberated metal dyes the hair of a fine and permanent black or brown. 1016. There are many other vegetable acids yet imperfectly known, and many more the results of natural and artificial decom- position; bat they are not of sufficient importance to be here noticed. § IL The Organic Bases. 1017. The Vegetabls Alkaloids or Organic Bases are an im- portant natural group of substances, chiefiy formed in vegetables and giving to them their active properties. They are always found in the form of salts, and usually in combination with an organic acid- Nitrogen is an invariable element of the alkaloids, but some of them contain no oxygen. Those destitute of oxygen are oUy, volatile bodies obtained by distillation, and as they absorb oxygm rapidly from the air, they are produced in a current of hydrogen, or carbonic acid. Those which contain oxygen are prepared by dissolving the vegetable matter in dilute chlorohydric or sulphuric acid, which forms a soluble salt with the alkaloid. To the filtered solution a stronger base is added — such as lime, ammonia, or mag- nesia, which produces a copious precipitation of the alkaloid. 1018. Properties, — ^These bodies dissolve sparingly in water, but freely in boiling alcohol, are intensely bitter, and usually re- store the reddened color of litmus. They are the most powerful medicines and poisons known. Gallotannic acid precipitates most of the organic bases, forming insoluble compounds ; hence it is an excellent antidote to them when they have been taken in poison- ous doses. We shall notice only the more important alkaloids found in vegetable substances. 1019. Omnia, C4oH24N204 + 6Aq. — Quinine is extracted from pulverized Peruvian bark by acidolated water. It is a white, crystalline substance, which unites with acids, producing intensely bitter salts. The sulphate of quinine, which forms light, bulky crystals, is the salt employed in medicine. It dissolves sparingly in water, but freely in dilute sulphuric acid and alcohoL CincJio- nine is an analogous alkaloid'from the same source. »re they used f How do they color the hair t 1017. What is eaid of the orgnnic basest What of those destitute of ozj-gen? How are those contaioing oxygen prepared t 1018. Mention the properties of these bodies. What is the cSeci on them of gallotannic acidt 1019. Give the origin and properties of qutnix THE ORGANIC BASES. 365 1020. Nicotine, CioH^I^i, a volatile alkaloid, is the active principle of the tobacco plant. It is a colorless, inflammable, oily liquid, with a powerful and irritating odor of tobacco. It is contained in the smoke of the burning leaves and is exceedingly poisonous, a single drop being sufficient to kill a large dog. 1021. Morphia, C34lIi9N06+2Aq. — Morphine is the active principle of opium, which is the hardened, milky juice of the poppy. Opium is a very complex body, containing no less than seven organic bases and several other well-defined principles. Morphine (from Morpheus, in consequence of its sleep-inducing property) is a crystallizable, resin-like body, without odor, and possessing a bitter, disagreeable taste. It is a powerful narcotic and poison, largely used in medicine. 1022. Strychnia, Q^^^^^'EoO^.— Strychnine is chiefly ob- tained from the beans of the strychnos nux 'comica^ a small East Indian tree, but is found in several other plants belonging to that tribe. Cold water dissolves only -^^^-^ of its weight of strychnine, but it is soluble in essential oils and chloroform. Such is its in- tense bitterness that it imparts it perceptibly to T00,000 times its weight of water. It is a deadly poison, ^^ of a grain killing a dog in 30 seconds. It takes effect upon the nerve centres of the spinal axis, producing fearful convulsions. The terrible woor'ara poison, with which the South American natives poison their arrows, and which has been lately used as a remedy for tetanus^ is a variety of strychnine. So also is the poison of the upas tree of Java- Briicia is an alkaloid closely allied to strychnine and obtained from the same genus of plants. 1023. Common lettuce has slight narcotic properties, which are due to an alkaloid, lactucine. In the same way conicine is ex- tracted from the hemlock; aconitine, or aconite, from the monk's hood ; solanine from potato sprouts ; piperine from black pepper, and emetine from ipecacuanha. 1024. Caffeine or Theine, Oi6HioN'404-f-2 Aq.— The active principle of coffee, caffeine^ and of tea, theine, as also of the mate or Paraguay tea, are identical in composition. It is interesting to observe that the plants which have been selected to furnish 1020. "What of nicotine? 1021. Describe morphia. Its properties. 1022. Where is strychnia foimd ? State its properties. "What of the woorara and upas poisons ? What is brucia ? 1023. Mention some other vegetable alkaloids. 1024. Grive the composition of theiue. What is an interesting fact regarding this principle ? State 30G ORGAXIC CHEMISTRY. infusions for the daily beverage of three fourths of tlie human race should contain one and the same nitrogenized principle. TJieo- hro?nine, the active constituent of chocolate, is also nearly allied to caffeine. Coffee seldom contains more than one per cent, of the princii)le, -while tea furnishes three or four. Caffeine crystallizes in long, flexible, silky needles, has a slightly bitter taste, and dis- solves sparingly in cold water, but freely in hot water. 1025. Tea consists of four principal constituents. First, a yellow volatile oil, which produces its peculiar aromatic odor and flavor. It does not exist in the natural leaves, but is produced by the roasting process to which they are subjected. Tea yields but 1 per cent, of this oil. Second, theine. Third, tannic acid, which forms from 12 to 18 per cent, of its weight, and gives to tea its astringent properties. Fourth, tea leaves contain some 15 per cent, of an insoluble, glutinous substance, which is lost with the ' grounds.' 1026. The varieties of tea are numerous, depending upon soil, climate, time of picking the leaves, and the modes of their prepara- tion. Green tea is prepared from the young leaves, which are roasted and withered almost immediately after they have been gathered. They are then rolled in the hand, by which they ac- quire their twisted appearance, and quickly dried, sifted, and win- nowed; the whole operation being brief and simple. Black tea, on the contrary, upon being gathered, is exposed to the air for ten or twelve hours. It is then roasted, a large quantity of liquid ex- pressed from it, and after several alternate rollings, roastings, and exposures to the air, it is slowly dried over a charcoal fire. The dark color of black teas is mainly owing to the action of oxygen upon the juices during the long exposure of the leaves. 1027. Constituents of Cofifee. — Besides its caffeine, the coffee berries contain a considerable proportion of gluten, 5 per cent, of caffeic acid, and 14 or 15 per cent, of a fixed oil. An aromatic flavoring oil is developed during roasting, but according to Paten it does not exceed the y^ part of the weight of coffee. ^§111. Organic Coloring Princijples. U 1028. As a class, vegetable coloring matters do not possess many chemical characters in common, and are associated together it« proportion in tea and coffee. Its properties. 1025. Of wliat does tea consist ? 1026. What occasions the varieties of teat How is green tea prepared? Black tea I To what is ita dark color owing f 1027. What arc the constituents of coffee I ORGANIC COLOEnTG PRINCIPLES. 167 on account of their common applications in tlie arts. Some are acid, others neutral; some ternary, others quaternary. The most brilliant of vegetable colors, those of flowers, are fugitive, small in quantity, and difficult to separate. The coloring matters in the interior of plants, where they are not exposed to light, are less brilliant, but more durable. The coloring matters of plants are chiefly blue, yellow, and red ; no genuine black having been obtained from them. 1029. Dyeing. — The art of the dyer consists in impregnating textile fabrics with the various coloring matters in such a way that they will remain permanent, or fast^ under wear and wash- ing. Some coloring substances, as indigo for example, unite di- rectly "with the fibres, producing fixed or substantive colors. Others, those chiefly which are soluble in water, do not adhere ; they therefore require some intermediate substance which has an affinity for both the coloring matter and the fibre, and will bind them together in an insoluble compound. Such a substance is called a mordant^ from the latin mordeo^ to bite, because it w^as supposed to bite in the colors. Dyes which require a mordant are called adjective colors, and nearly all vegetable colors are of this kind. 1030. The principal mordants are salts of tin, iron, and alumi- FiG. 277. Fig. 278. Linen Fibres. "Woollen Fibres. na, which not only fasten the colors, but so change them t'-at one dye stuff gives different colors with different mordants. The tex- 1028. Wbat is said of the permanence of vegetable colors ? 1029. In what does dyeing consist? What are substantive colors ? Mordants? Adjective colors? 1030. What of the principal mordants ? 1031. Describe the process of calico 36 S OEGAXIC CHEinSTKT. tile 'fibres consist of hollow tubes, Figs. 277 and 278, wWgIi the mordant is supposed to enter, filling them like lungs, and thus facilitating the chemical action. 1031. Calico Printing.— In this operation the bleached and pre- pared goods are printed uitli the mordantshj patterns upon blocks or cylinders. As the cloth is subsequently passed through the dye, the coloring matter is fixed upon those parts where the mordant tvas applied. 'When the fabric is afterward washed, the color disappears from the other portions of the goods, and the printed figure appears. 1032. Blue Coloring Matters. — Indigo is obtained from the juices of a large number of East India and American plants, the prin- cipal of which belong to the genus indigoftra. This juice is color- less, but when exposed to the air it absorbs oxygen, and deposits a blue sediment which, in the form of a powder or cakes, is known as commercial indigo. It is nearly insoluble in all liquids except sul- phuric acid, with which it combines, forming sulpidndigotic acid. "VThen deoxidized, indigo becomes colorless and soluble in water, but on exposure to the air it again absorbs oxygen, and acquires insolubility and its deep blue color. Fabrics may therefore be steeped in a solution of colorless indigo, and on exposure to the air acquire a bright and permanent blue tint. If goods are boiled in sulphindigotic acid, a still brighter color {Saxon Uue) is produced. 1033. Litmus is obtained from several species of lichens, which are destitute of color. The product is at first purple, or red, but is changed to blue by the action of the ammonia used in its preparation. 1034. Red Coloring Matters.— Jladder.— The roots of the madder plant, ground to powder, furnish this valuable dye stuff. It is at first yellow, but reddens by exposure to air and ab- sorption of oxygen. In addition to red, madder furnishes purple, yellow, orange, and brown. Brazil tcood and sandal wood pro- duce red coloring matters, and the flowers of the red saffron yield so^icer. Carmine is contained in a species of Mexican cactus, and is obtained from the cochineal, an insect which feeds upon that jdant. It affords a brilliant red and purple dye. 1035. Yellow Coloring Matters.— Among the principal of printing. 1032. How is indigo obtained ? What is eulphir.digotic ac d I Explain the action of indigo upon fabrics. 1033. What of Ulmua ? 1034. What is madder ? Mention other red dyes. 1035. What aro the principal yellow dyes? 1036. "NVhat Fig. 279. Chlorophyll in Cells. ORGANIC COLORING PRINCIPLES. 369 these are quercitron^ from the bark of the black oak ; fustic^ from the wood of the West Indian mulberry, and weld^ from the reseda luteola. Annotto, used in dyeing nankeen, and also to color butter and cheese, is extracted from certain seeds grown in South America. Turmeric is obtained from the roots of an East Indian plant. 1036. Chlorophyll {Leaf -green) is the substance to which the vegetable world owes its uniform green color. It is of a resinous nature, soluble in alcohol and acids, but insoluble in water. Fig. 279 shows the grains of chlorophyll and needle-like crystals in the cells of a leaf. It exists only in minute quantity in plants, the leaves of a large tree, according to Beezelius, containing per- haps not more than 100 grains. This substance appears to be a direct product of the action of the sunbeam upon vegetation, as it is never seen except in those parts exposed to the light. Plants removed from a dark cellar into the sunlight turn rapidly of a green color, and every one may have remarked in spring how quickly, after a few days of cloudy weather, the unfolding vegetation is changed to a deep green by the rays of the sun. The change from green to red and yellow in the autumn leaves, is supposed to be OAving to the oxidation of their chlorophyll. 1037. Extractive Matter. — This term has been applied to nu- merous substances, chiefly vegetable, extracted by chemists, which have not yet been accurately examined. The number of known plants exceeds a hundred thousand, and each possesses peculiar principles in small quantity to which its flavor and medicinal properties are due. Of this vast number, but few comparatively have been studied by chemists, who designate whatever of this kind that is unknown as extractive matter. is chlorophyll ? Why is it thought to he a direct product of the Bunheam ? What of the change in autumn leaves? 1037. What does the term extractive matter 16* 370 ORGAinC CHEMISTRY. CHAPTEPw XXII. NITROGENOUS COMPOUNDS— THEIR CHANGES AND EFFECTS. § I. The Albuminous Compounds, 1038. The substances now to be noticed differ in very im- portant respects from those hitherto considered. They have more elements; they contain nitrogen in higher proportions, have a larger number of atoms, and are therefore more complex and prone to change. They do not crystallize, and are highly organ- ized. Though originating in the vegetable kingdom, they furnish the basis of the structures of all animal systems. The group comprises albumen, fibrin, casein, and their several modifications, and is hence called the albuminous or albuminoid group. 1039. Albumen. — We are most familiar with this body in the form of white of eggs, aglairy, insipidfluid, which coagulates by heat, producing a white solid; hence itsname, from a ?6m5, white. Albumen forms about 7 per cent, of the blood, and is found in variable pro- portions in all the secretions of the body. It also exists dissolved in the juices of plants, or dried in their seeds. When the water which has been used to wash starch from wheat flour or scraped potatoes, is allowed to stand until it becomes clear, and is then boiled, it assumes a turbid appearance, and deposits a flaky-white substance, which has the same character as white of e^^^ and is known as vegetable albumen. When dried it forms a brittle, yellow, gummy mass, which dissolves in cold water; but when coagulated it will not dissolve in water, either cold or hot. The change of coagula- tion does not alter its composition. The temperature at which it takes place varies; a strong solution of albumen in water becomes completely insoluble at 145°, and separates in flakes at 167°. The more it is diluted with water, the higher the temperature of coagulation. 1040. Chemical Properties. — Albumen consists of carbon, oxygen, hydrogen, and nitrogen — some 16 per cent, of the latter — and a small but definite proportion of sulphur and phosphorus. eignify? 1038 How do the nitrogenous compounds difTer from Ihoee hitherto considered ? "What does the albuminous group comprise ? 1039. What is the most familiar form of albumen ? Where is it found ? What is vegetable albu- men ? Ita properties f 1040. Give the composition of albumen. For what ie it an THE ALBUMES'OUS COMPOUNDS. 371 Its exact composition, however, is not determined. It is coagu- lated by many substances, as alcohol, strong acids, creosote, and corrosive sublimate ; therefore, in poisoning by these bodies, if the ■white of eggs be promptly swallowed, it seizes upon the noxious compounds and protects the stomach. Albumen, like water, seems capable of combining with both acids and bases. Alkalies render it soluble. White of egg and blood are both shghtly alkaline, from the presence of soda; the albumen being supposed to exist as al- luminate of soda. It forms also definite compounds with the acids. Vitellin is the albumen of the yolk of eggs. 1041. Fibrin is the name given to the substance which forms the basis or Jibre of muscular tissue. It occurs in bundles, as shown in Fig. 280, the parallel fibres having wrinkles or cross markings. If a piece of lean beef be long washed in clean ^;^^4iUAl3'Vvv\^^^^^^^^=:^-'^ water, its red color, which is due to blood, gradually disap- pears, and a mass of white, fi- brous tissue remains which is , • 7 ^7 . T •! Fibres of lean Meat, magninea. known as animal fihvin. Like albumen, it is capable of existing in two states : the soluble and the insoluble. In its soluble form it is a constituent of blood, forming in the healthy state abont 2 parts in 1000 parts of that liquid. The clotting of blood, when freshly drawn, is due to the coagulation of its fibrin, which solidifies into a network of fibres. Dilute solutions of potash and soda dissolve fibrin, as they do al- bumen. 1042. Gluten — Vegetable Fihrin. — "When wheat flour is made into a dough and then kneaded on a sieve or piece of muslin under a stream of water, its starch is washed away and there remains a gray, tough, elastic substance, almost resembling animal skin in appearance. When dried it has a glue-like aspect, and is there- fore called gluten. The crude gluten thus prepared, when freed from oil, albumen, &c., proves to be identical in composition with animal fibrin, and is hence named vegetable fibrin. Like muscle fibrin, it is soluble in very dilute chlorohydric acid. antidote ? Its chemical properties ? 1041. Describe animal fibrin. "What is its rela- tion to blood? 1042. How may gluten be procured? "Why is it called vegetable 372 OEGA2fIC CHEMISTKT. 1043. Casein is an essential constitnent of milk, existing in it to the extent of about 3 per cent., and forming its curd, or cheesy principle. Its soluble form in milk is due to a small portion of free alkali and when this is neutralized by an acid, the caeein is precipitated, or the milk curdl-cs. By neutralizing the acid, the casein is re-dissolved. The water in which flour has been washed contains a small portion of a substance, which is coagulated by acids: it resembles the curd of milk, and is called TcgctahU casein. It is found in large proportion in peas and beans. The Chinese make a cheese from peas which gradually acquires the smell and taste of milk cheese. 1044. Chemical Composition. — There is a remarkable identity in composition among the members of this group. The analysis of albumen from the hen's e^s, gives carbon 53.5, hydr<^«ai 7, nitrogen 15.5, oxygen 22, sulphur 1.6, phosphorus 0.4; and, with slight variations in the proportions of sulphur and phosphorus, this may represent the composition of the whole group. T.tcbig gives the following formula as the best approximation yet obtain- ed t^oward their composition : [c,i Albumen of blood, Albumen of flesh, } Cjw Hjc, Ocs ^S7 S, Fibrin of fiesh. Albumen of eggs, C^u H,e8 0^.^ ^-^ Sj Casein, C,«, H^^ 0>, "S^ S, Fibrin of blood. Case Haas 0« N«* Sj An important fact concerning these compound> i? iLui ihey are physiologically isomeric — are convertible into each other in the animril system. 1045. Protein. — When these albuminoids are dissolved in a solution of potash or soda by a gentle heat, if an acid be added, a grayish precipitate is formed, which is attended with the libera- tion of sulphur and phosphorus in the form of sulphuretted hy- drogen and phosphoric acid. Muldee calls this substance protein^ and he and many other chemists regard it as the radicle or base of the whole group. They hold it to contain neither sulphur nor phosphorus, and suppose the different albuminous bodies to be Tormed by combinations of protein with these elements and oxygen. LiEBiG and his adherents deny that any such radicle has ever been freed from sulphur, and reject the doctrine of protein altogether. fibrin I lOftS. Describe capein. Wbat oocasioiiB tlie curdling of mOk t Wh*! of Testable eaeeinf 1044. What is said of tbe eom p o w tion of tbe albiuiuDOidsf PUTKEF ACTION AND DISINFECTION. 3 '73 1046. These substances will be noticed in their physiological relations when we consider the subject of animal nutrition. The remarkable advance in organic chemistry of late years has brought them forward into new relations, and they have received many names. They are called lorotein compounds^ nitrogenous aliment- ary principles^ and as one of the names of nitrogen is azote^ they are termed azotized substances. As they form the materials from which the body is nourished and built up, LiEBia named them the plastic elements of nutrition; they are also known &^ Jiesli-forming and Mood-producing compounds. §11. Putrefaction and Disinfection. 1047. A leading characteristic of the foregoing substances is, as we have stated, their instability. This is due, first^ to the presence in large proportion of the fickle element nitrogen; sec- ond, to the large number of elements combined together, and the resulting complexity of the attractions ; and third, to the great number of atoms associated, or the massiveness of the molecules. When in a moist state, and exposed to atmospheric oxygen, the tottering equilibrium of the chemical fabric is overturned, and out of its ruins a new class of substances is produced. It is well known that flesh, blood, milk, dough, &c., all of which are rich in nitrogenous substances, will preserve their properties in the air only a short time, and pass into a state of decomposition, giv- ing forth offensive exhalations. This change is called putrefac- tion^ and when once commenced, it rapidly spreads through the mass, communicating itself to all putrifiable substances with which it is brought in contact. 1048. Propagation of the Effects. — As a spark may kindle a conflagration that shall consume a city, so the minutest amount of putrescent m^ter is sufficient to aff'ect an indefinite quantity of changeable substance. The remarkable communicability of these effects and their potency of action are painfully illustrated by phy- sicians, who sometimes wound themselves while dissecting. The small trace of decomposing matter from the dead body which clings to the dissecting knife is sufficient to establish a rapid de- 1045. Give the origin of protein. How is it considered by different chemists? 1046. By what names are the albuminoids known? 1047. "What is a leading prop- erty of these substances? To what is it due ? What is putrefaction ? 1048. What 374 ORGANIC CHEMISTRY. composition in the living system, which, in many cases, quickly terminates in death. Another case in point is the communication of the virus of smallpox, which, when introduced into the blood, reproduces its peculiar putrefaction throughout the system. 1049. Products. — The chief products of putrefaction are hy- drogen, nitrogen, carbonic acid, ammonia, carburetted, sulphu- retted, and phosphuretted hydrogens, and acetic, nitric, and butyric acids. Other compounds also arise with the varying con- ditions. The gaseous combinations of sulphur and phosphorus are the chief causes of the offensive odor of putrefying bodies. In addition to these well-determined products, putrefaction gives rise to another class less tangible, but more baneful. The foul accumulations of neglected towns, and the decomposing organic matter of many swampy districts, give off invisible emanations known as miasms and malaria^ which fill the air, and when in- haled, often occasion fatal fevers and epidemics. Of their compo- sition, nature, or mode of action, nearly nothing is known. 1050. Prevention of Putrefaction. — As the presence of moist- ure, a favoring temperature, and access of air are essential con- ditions of putrefaction, if any of them are withdrawn, the effect is prevented. It is well known that the most perishable organic substances, both vegetable and animal, may be indefinitely pre- served by drying. Cold checks decomposition, and it is entirely arrested by freezing. So, if the prime inciter of change, oxygen, is excluded, putrefaction cannot take place. This fact is illus- trated by the general practice of preserving aU kinds of alimentary substances, meat, fruits and vegetables, in vessels which exclude the air. It is not enough, however, to remove the oxygen from the surface of the body ; that which is diffused within it must be expelled, which is done by boiling, or in some cases by a lower heat. 1051. Antiseptics are preventers of change — substances which act in various ways upon changeable bodies to preserve them. Common salt and saltpetre act by partial desiccation. They ab- stract water from the flesh, and hence concentrate the solution of of the action of putreBcent bodice ? Examples. 1049. Mention the chief products of putrefaction. To what is the orlor of putrefying bodies due ? "What are other products of putrefaction? 1050. How is putrefaction prevented? How are or- ganic bodies preserved ? Examples. What is necessary to preservation ? 1051. What are antiseptics ? Explain the action of salt and saltpetre. Of alcohol and PUTREFACTION AND DISINFECTION. 375 albumen witliin ; bj surrounding the meat with, salt "vrater, and partially expelling the air, putrefaction is counteracted. Alcohol and sugar act in a similar way, removing a large portion of water from flesh and fruits, and surrounding them with nnchangeable liquids and sirups, which prevent the access of oxygen. 1052. Other antiseptics act directly upon the albnmen, coagu- lating and fixing^ it in nnchangeable compounds. The sap and juices of all plants contain more or less of dissolved albumen, which, by its putrefaction, becomes an active cause of the decay of wood. Eapid drying or 'seasoning' renders the albumen inert, and the same object may be secured in less time by inject- ing the pores of the wood with any compound which coagulates the albumen. Wood is rendered indestructible by a process ap- plied by Dr. Kyan, which consists in steeping it in a solution of corrosive sublimate {liyanizing). Boucheeie cut into the trunks of living trees and introduced salts of iron, which were drawn up by the sap, and, impregnating the wood, increased its durability. Dried animal bodies are preserved from change by injecting in their veins corrosive sublimate, acetate of lead, chloride of zinc, and many other substances. These, like arsenic, are poisons. As life consists in change, and these arrest change, they destroy life, and thus conserve the structures in which it was manifested. 1053. Disinfectants. — A distinction is drawn between anti- septics and disinfectants — the former prexent putrefaction, the lat- ter arrest it; though some substances often act in both ways. Compounds rich in oxygen, and which, when mixed with putrefy- ing matter are decomposed, act as powerful disinfectants. The permanganates perform this oflBce, rapidly destroying the odor of putrid matter, and oxidizing sulphuretted and phosphuretted hy- drogen. Nitric acid and several of the nitrates act powerfully in the same way. Fumes of nitrous acid and chlorine are efficient disinfectants. Chlorine is conveniently used in the form of chlo- ride of lime or soda ; the addition of a little sulphuric acid sets the gas free rapidly. In disinfecting rooms by fumigation with gases, it is to be remembered that they corrode all metallic surfaces. Vinegar, and especially wood vinegar, which contains a little creo- sote, is a valuable disinfectant. So also is sulphurous acid (fumes Bugar. 1052. Of other antiseptics. Of Beaeoning. What is kyanizing ? Give Bopcherie's experiment. How are animal bodies preserved, and why ? 1053. What is a distinction between antiseptics and disinfectants ? Explain the action 376 ORGANIC CHEMISTRY. of burning sulphnr) ; it destroys sulphuretted hydrogen by oxidiz- ing it, and it also acts by absorbing oxygen. The disinfecting power of charcoal has been elsewhere noticed. 1054. Natural Disinfectants. — We have seen that oxygen and ozone of the atmosphere and the carbonaceous element of the earth are natural disinfectants on a vast scale. Water, although favor- ing decomposition, is an invaluable agent for removing and finally destroying putrescent matters, and heat, although up to 140° a promoter of putrefaction, above that point, by becoming a dryer and disorganizer, destroys the sources and products of infection. § III. Fermentation, 1055. When the ternary compounds, as sugar or starch, are exposed to the air, in a moist state, they exhibit but little tendency to change, and give rise to none of the effects of putrefaction. But if to a solution of sugar there be added a little putrefying flesh, blood, cheese, milk, flour paste, white of ^%'g^ or any albuminous substance in a state of decomposition, their action is communicated to the sugar, which is broken up into new compounds. When the putrefiable substances are considered with reference to the effects they produce upon the other class of bodies, they are called fer- ments^ and the communication of that condition of change is known as fermentation. 1056. Mode of Action of Ferment. — When changing nitro- genous matter acts upon sugar to decompose it, there is no combi- nation between the elements of the two substances. All that is communicated, therefore, is an impulse of motion. The collision of oxygen shatters the nitrogenous group ; its motion is communi- cated to the atoms which compose the sugar, thus overturning their nicely balanced affinities. But the sugar cannot, like albumi- nous compounds, take the infection and go on decomposing itself. It only acts as it is acted upon, and when the motion of the impel- ling body is exhausted, the action ceases. Two parts by weight of ferment only decompose a hundred parts of sugar. 1057. Vinous Fermentation. — When the sweet juice of fruits or plants is exposed to the air at the temperature of 70° or 80°, in of the latter? Give examples. 1054. What are great nntwral disinfectants? What of water and heat ? 1055. How is fermentation produced? What are fermcnta? 105G. State their modo of action. When does it cease? What proportion of for- FEKMEl^rrATIOX. 3 '77 the course of a few hours a change commences ; small bubbles rise to the surface, the liquid becomes turbid, and begins to ferment, or, as is commonly said, to ^tcorJc.^ After a time the bubbles cease to rise and the liquid is no longer sweet, but has acquired a spiritous taste. If now it be distilled, an inflammable body is sep- arated, which is known as spirits of wine, or alcohol, a product of the decomposition of sugar. 1058. Yeast — During the process of fermentation, a grayish, frothy, bitter liquid is produced, known as yeast. When fresh, it is in constant motion, from the escaping gas, but o when dried it loses 70 per cent, of its % weight, and is converted into a honey- r;;;^^ looking solid. Yeast is a minute spe- ^r^ cies of plant. Under the microscope it ^ is seen to consist of numberless small rounded cells. Each little globule con- ^ , -„, ^ v. . , ^ Yeast Plant, ehowing how it Sists of an enveloping skin, or mem- Grows by Budding and by -, /. n . ,, i • . internal Granules. brane of albummous matter contammg a liquid. The yeast cells grow or expand from the minutest mi- croscopic points (granules), and also bud off from each other, as shown in Fig. 283. They are never formed except from the de- composition of albuminous substances, and their fermenting power is supposed to be due to the nitrogen they contain. "Whatever destroys the vitality of yeast, deprives it of the power of exciting fermentation ; hence when it is exposed to a temperature of 21 2°, its action is destroyed, and it is also checked by a cold of 10°. When yeast is dried and pulverized, or mixed with acids, alcohols, or alkalies, it also loses its power. 1059. In what manner the yeast plant acts in fermentation is not known. The most probable view is that of Pasteue, who maintains that the essential condition of fermentation is the con- version of albuminous matter into the membranes of the globules, and the assimilation and decomposition of the sugar in the process of their growth. 1060. Production of Alcohol. — When fruit sugar is acted upon by yeast, it is decomposed and gives rise to alcohol and carbonic mcnt is necessary ? 1057. Describe tbe vinous fermentation. 1058, What are the conditions of yeast ? Of what does it consist? 1059. State Pasteur's theory of yeast. 1060. What are the changes when sugars are acted on by yeast ? 1061. 378 0RGA2OC CHEMISTRY. Decomposition of Sugar. acid. Two atoms of alcohol and four of carbonic acid are produced, the breaking up into groups being shown by the accom- panying figures. 1061. Diastase. — Malt.— But the sugar itself may be a product of fermentation. "When seeds are exposed to air and moist- ure at a suitable temperature, germination commences. This consists in a series of changes, of which the first is an alteration of a portion of the nitrogenous matter and the production of an ill-understood compound called diastase. This is an active ferment, and taking eflTect upon the starch changes it to sugar and dextrine. When barley is treated in this way it swells and becomes sweet. Diastase is formed and the barley is termed malt. When the germ is about half an inch long the process is arrested by heat, but the dextrine is not destroyed. One part of malt does not contain more than -^^^ of diastase, but according to Persoz and Payen 1 part of diastase is sufticient to change 2000 of starch. Hence one part of malt can convert the starch of four or five parts of barley into sugar and dextrine. ,^']T^2^rewing Beer.— In this process the crushed oi- ^groumj malt is digested in water at 100° {malted)^ to extract all the solu- ble matter it contains. The liquid, which is termed sweet wort^ is then boiled to coagulate the excess of vegetable albumen. Hops are added to impart aroma and a bitter fiavor ; the cooled wort is then run into a fermenting vat, and yeast is added. In a few hours bubbles of gas begin to rise and the liquid becomes covered with a foam of yeast, which gradually hardens into a crust. This is called surface yeast — another portion falls to the bottom and is known as sediment yeast. The former requires a higher tempera- ture, and is apt to give rise to lactic acid and other acidulous prod- ucts. The globules of surface yeast are propagated chiefly by budding. Sediment yeast acts more slowly and at a lower tem- perature, generates no acid products, and propagates by granules. 1063. Though a portion of the yeast is spent in fermentation, Wlial iellic first cliangp in germination ? Wliat is the eflect of dir.Btaee ? Descrilo ra;i)t. What is tlie eflect of heat 7 Give the proportion of diastase. 10C2. De- ficribc the process of hrewing heer. How docs Hurfaci: differ from fiediment yea.sl f 1063. IIow is the procesa continued ? Kame the conetitucnts of beer. 1064. What FERMENTATION. 379 a much larger quantity is formed from tlie nitrogenous matter of the grain in solution. The fermentation is continued several days, but is checked before all the sugar is converted into alcohol, as it Tvould soon turn sour if the decomposition were complete. The liquid is now drawn off into casks, where it undergoes a second protracted fermentation (ripening)^ after which it is kept tightly closed from the air. It contains, in addition to the alcohol, a por- tion of saccharine, nitrogenous, and aromatic substances, together with various oils and mineral salts. 1064. Lager Beer is freed from all nitrogenized products by a slow and long-continued fermentation ; hence it may be preserved for years without further decomposition. Before consumption it lies stored in vaults for months, from which circumstance its name is derived {lagen^ to lay). The difference in color of malt liquors is owing to the various degrees of heat employed in malting. Ale is made from pale malt, while that used for porter is partially charred, giving it a brownish color and bitter flavor. 1065. Wines are obtained from the expressed juice of the grape and other fruits. The fresh grape juice, or must, is placed in vats in cellars, where the temperature is so low that the fer- mentation proceeds very slowly. Sometimes the wines are bot- tled before the fermentation is quite complete, and they continue to generate carbonic acid, which remains compressed within the liquid. If the carbonic acid is so abundant as to produce efferves- cence when uncorked, the wine is said to be ' sparHing ; ' if other- wise, it is termed ' still ' wine. The sweetness of wines is due to undecomposed grape sugar, the ferment being exhausted before all the sugar is changed. This excess of sugar preserves the wine from further decomposition, so that some of the sweet wines, such as Tokay and Muscadine, have been kept uninjured for a couple of centuries. "When the sugar is wholly decomposed the wines arc called ' dry,'' as Claret, Burgundy, Port, Sherry, &c. The acidity of wines is chiefly due to tartaric acid. Their flavor and aromatic qualities are owing to a volatile substance called (BnantJiic ether, which is developed during fermentation, and also to various other fragrant principles contained in the juice of the grape. Wines contain, in addition to the ingredients named, a proportion of is lager beer? What causes the diflference of color in malt liquors? Examples. 1065. How are wines made? How do sparkling wines differ from still wines? What is the effect of undecomposed sugar? To what is the acidity of wines 380 OKGAXIC CHEMISTRY. various albuminous, oilv, and coloring amount of acetic and other vegetable acid: 1066. matters, and a small Fig. 2S3. P'an of a Sl.U. Distilled liquors are obtained by subjecting various fermented mixtures to distilla- tion. The plan of a still is repre- sented in Fig. 283 ; a is a furnace, I a retort, containing the liquid to be separated ; and d the con- denser of cold water surrounding the icorm^ through which the condensed liquid passes. "When the fermented mixture is heated above the boiling point of alco- hol, 173°, that liquid rises with a portion of the water, passes over, and is condensed. It is then called spirits of loine, and when redistilled, rectified spirits of wine. The strongest commercial alcohol still contains some 10 per cent, of water, which can only be separated by adding chloride of calcium, or some other substance which has a powerful affinity for water. "When the water is entirely removed the alcohol is said to be ab- solute or anliydrous. 1067. Brandy is derived from the distillation of wine ; rum from that of fermented molasses, and arrack from the distillation of fer- mented milk. Whiskey is obtained from corn, rye, and potatoes, by first converting their starch into sugar, then into spirit, and distilling the product. Gin is produced from the distillation of the spirit of a mixture of barley and rye, and owes its peculiar flavor to juniper berries. 1068. Viscous Fermentation. — When certain saccharine juices, such as those of beets, carrots, or onions, are exposed to the air at a temperature from 86° to 104°, fermentation takes place, and the sugar disappears, but instead of carbonic acid and alcohol, lactic acid^ mannite^ and a mucilaginous, gummy substance are formed, which render the liquid viscid and ropy ; it is hence called the tiscous or lactic acid fermentation. Mannite is a substance of a weak saccharine taste, and is not changed to alcohol by fermenta- owintr? Their flavor, Ac ? Mention other ingredients of wines ? 1066 Deecribo Fi:?. 283. "What is ppirits of wine? Rectified Bpirits of wine ? Absolute alcohol t 1067. What is brandy ? Itum ? Arrack? Whiskey? Gin? 1068. DcBcribe tJio viscous ALCOHOL AND ITS DERIVATIVES. 381 tion. It is the chief ingredient of manna^ a kind of sugar which exudes from a species of ash tree in Southern Europe, and is used as a medicine. 1069. Lactic AcidjO^^H^OgjIIO, so called because it occurs in sour milk, is a colorless, sirupy, very acid liquid, which combines with bases, forming a class of salts, the lactates. § lY. Alcoliol and its Derivatives. ALCOHOL. 1070. Spirits of Wine— UtJiylic Alcohol, C4H6O2, sp. gr. of liquid at 33° 0.815; of vapor 1.613.— Alcohol is a colorless, mobile fluid, having a pleasant, fruity smell, and a burning taste. It is very volatile, about one fifth lighter than water, and has a strong attraction for that liquid, which causes it to absorb moisture from the air, thus rendering it valuable as an antiseptic. It is highly combustible, producing intense heat without smoke, and is there- fore well adapted to burn in lamps for chemical use. 1071. Alcohol has great value as a solvent, as it acts upon many substances which water does not dissolve, and is easily separated from them on account of its extreme volatility. It boils at 173°, and has never been frozen, although at — 166° it becomes viscid. In a concentrated form it is a potent poison, but when sufficiently diluted, it acts upon the animal system as a stimulant. Taken freely in this form it produces inebriation, and is the active principle of all intoxicating liquors. Alcohol, till of late, has been regarded as procurable only by organic decomposition — the de- struction of sugar — but it is now made artificially by the synthesis of its elements. 1072. Derivation of Acetic Acid. — If the vinous fermentation is not checked at the proper time, it passes on to a second stage, the acetous fermentation ; the liquid loses its spirit and quality, and becomes sour. Oxygen is absorbed, and the alcohol converted into vinegar or acetic acid, C4H303,I-I0. Pure diluted alcohol does not absorb oxygen when exposed to the atmosphere ; it is affected only by adding some matter in a state of change, or which fermentation. "What are mannite and manna sugar? 1069. "What is lactic acid? 1070. Give the composition of alcohol. Its properties. 1071. State some other properties of alcohol. 1072. What is the acetous fermentation ? Give the coid- 382 ORGANIC CHEMISTRY. Fig. 284. absorbs oxygen. The action proceeds slowly at first, but by de- grees a peculiar body, a kind of slimy vegetable mould, is formed, which is known as mother of vinegar^ and which acts something like a ferment to hasten the process. 1073. Aldehyd — The change from alcohol to acetic acid is not direct — an intermediate substance is formed, called aldehyd C4H4O2, so named from alcohol <^e7i?/-drogenated, or deprived of hydrogen. This substance may be produced by the gradual oxidation of alcohol, in various ways, or by transmitting a mixture of alcohol and air through a porcelain tube at a low red heat. Aldehyd" is a highly volatile, inflammable liquid, with a pungent, apple-like odor. 1074. When a few drops of alcohol are placed in a cup, its vapor will mingle with the air. If now a red hot coil of platinum wire be intro- duced into the cup, Fig. 284, the oxidation of the vapor commences (471), pungent odors of aldehyd are given off, and the wire is kept at a red heat by the continued oxidation. If the coil be sus- pended over the wick of an alcohol or ether lamp, Fig. 2S5, it will continue to glow for hours after the flame is extinguished, from the same cause. 1075. The Quick Vinegar Process. — As oxy- gen is the active agent in acetification, the rapid- ity of the process will obviously depend upon the abundance of its supply. If the air comes in con- tact with but a small portion of the liquid, months may be required to produce the change. In the quick vinegar process the liquid is made to trickle over beech shavings, which have been previously soaked in vinegar, and placed in a tall vessel. In Fig. 2i6 A A represents such a tub, near the top of which is a perforated shelf d ^ dC^o^ © o,^Q^ nute globules, which ^hen viewed by the ^'*^°*^^®cc^ ^^^&? microscope appear floating in a trans- S p "o ^-* p^ bules are lighter than water, and hence, O 6 jgj^^ '^ when the milk is allowed to stand undis- , cO^^>^-^ turbed, they slowly rise to the surface, o^^^'o^^s forming cream. Each little globule is Milk Globules. invested by a thin membrane of casein, which is ruptured by the agitation of churning, causing the butter to cohere in a separated mass. 1102. Spontaneous Curdling. — 'When milk is allowed to stand for a short time it sours and curdles ; that is, its casein changes from the dissolved to the solid state. This is brought about by a series of interesting changes, originating in the unceasing activity of atmospheric oxygen. Casein is insoluble in water. But in the milk it exists combined with soda, and this compound dissolves in water. Now when fresh milk is exposed to the air its oxygen seizes upon a portion of tbe casein and changes it to a ferment; this takes effect upon the milk sugar and converts it into lactic acid, which causes the sourness of the milk. TThen a sufficient quantity of the lactic acid is thus formed, it seizes upon the soda, takes it away from the casein, and forms lactate of soda. The casein, thus set free, shrinks in bulk and gathers into an insoluble, curdy mass. 1103. Artificial Curdling. — ^In making cheese the milk is curdled artificially, and in different countries various substances are employed for this purpose. Almost any acid will curdle milk, and vinegar, lemon juice, dilute muriatic acid, &c., are used to produce this effect. But the substance most generally employed for this purpose is rennet — the lining membrane of the stomach of a calf, salted and dried. The rennet is soaked in water, or whey, which, being added to milk at a temperature of 95°, coagulates it promptly. It was formerly supposed that the action of the gastric juice of the rennet produced the change, but the membrane acts with equal promptitude when washed thoroughly free from all croecope ? Hovr is cream formed ? Butter ? 1102. What is the cause of the curdling of milk? Explain the chemical changes. 1103. State the effect of aculs upon milk. What ia generally used to curdle milk ? To 'nhat is the chaugc ANIMAL SECRETIONS. 391 acid. The change is due to the decomposing animal matter of the rennet. This converts milk sugar to lactic acid, which neutralizes the soda, and precipitates the casein. Only a minute quantity of rennet is necessary; according to Beezelius, one part of the membrane heing sufficient to coagulate thirty thousand parts of milk. 1104. Cheese.— By the act of curdling, the milk is divided into two parts : first, the curd^ comprising all the casein, a large portion of oil, and a trace of sugar of milk, with some water ; and second, the lohey^ or fluid part, containing the bulk of water, the sugar of milk, and a small, variable proportion of oily matter. Of the saline matter in milk, the phosphates of lime and magnesia exist in the curd, while the remaining salts are found in the whey. The curd, separated from the whey and prepared in various ways, forms, when pressed, cheese. 1105. Renal Secretion (Uni'^''^ . — This liquid is separated from the arterial blood by the kid,' -; s, and contains the chief soluble waste products of the body. In fasting it is feebly acid, but during digestion it becomes slightly alkaline. "VYhen left undis- turbed for a time (which varies with the temperature), it putrefies, acquires a powerful alkaline reaction, and gives off ammonia. This excretion is the outlet of the nitrogenous products of the de- composed tissues, and of the saline constituents of the body. 1106. Urea, CsH^NsOo, is the chief product of the kidney excretion. It is a neutral body, crystallizes in slender prisms, and forms compounds with salts. It is not formed in the kidneys, but is separated by them from the blood. Uric^ or litliic acid^ CioH^I^^Oo, is a small constituent of human urine, but abounds in the excretion of birds and serpents. Urate of ammonia is the chief constituent of guano. It is this acid, principally, in combi- nation with soda, which accumulates around the joints in gout, and it is also a constituent of several of the stony concretions known as urinary calculi. Rippuric acid is another nitrogenous body found in urine. 1107. The openings from the surface of the body are lined with what are known as mucous membranes^ which are constantly owing? What proportion of rennet is necessary? 1104. Inlcwliat does curdling divide tl-e milk? Give the constituents of the curd. Of the whey. What is cheese? 1105. Whatis theoriginof urine ? Stnte its diftVrent conditions. Of what is it the outlet ? 1106. What of urea ? Where is uric acid found ? What is said of it in con- 392 ORGANIC CHEMISTRY. moistened by a viscid secretion called mucus. This is insoluble in water, and yields a glairy product called mucin. ^ '^- CHAPTER XXIY. CHEMISTRY OF FOOD. § I. Chemistry of Bread Mal'ing. 1108. Objects of Culinary Art. — Organized substances de- signed as human food — grains, roots, fruit and llesh — are many of them not adapted for this purpose in their natural condition, and to become digestible, require to be mechanically and chemically changed. This is effected chiefly by water and heat. These agencies soften some substances, dissolve others, and enable us to prepare palatable and nutritious dishes from the crude, tasteless,^ or noxious bodies furnished us by Nature. 1109. Preparing -the Dough for Bread.— This is usually done by first mixing suitable proportions of flour, water, yeast, and salt into a stiff batter, and exposing it for an hour or two to a gentle heat. The water hydrates the starch, dissolves the sugar and albu- men, and moistens the dry particles of the gluten, causing them to cement together all the ingredients into a cohering mass. The yeast now causes an active fermentation, converting the sugar of the flour into alcohol and carbonic acid. It also converts a por- tion of the starch into sugar. The carbonic acid is diffused throughout the mass in the form of minute bubbles, which, being caught by the tenacious gluten, cause the dough to swell and rise. When the fermentation is sufficient, the dough is kneaded into loaves for the oven. Leavened bread is made by substituting for yeast a ferment of sour flour paste (leaven). 1110. Changes of Bread in Baking.— When the prepared dough is exposed in an oven to a temperature of 350*, it loses from 10 to 16 per cent, of its weight by evaporation. But the ncction with gout and urinnry calculi? 1107. What of mucus ? 1108. AVhat chanpes must many organized bodies undergo to Gt tlicm for food i How are they effected ? 1109. How is bread dough prepared ? "What changes does the yeast produce ? Why does the bread rise ? "S^liat is leavened bread ! 1110. How does heat affect CHEMISTEY OF BREAD MAiaNG. 393 loaf increases in bulk to about twice its size. This is due to the expansion of the carbonic acid contained in its pores, the conver- sion of water into steam, and the vaporizing of alcohol, which is driven off' in the gaseous form. Attempts have been made in large bakeries to condense and save the alcohol, and a weak spirit was obtained, but it seems not to have repaid the trouble of its collection. The surface of the loaf is first dried and then dis- organized. The roasting converts the starch into gum, and pro- duces a peculiar, brown, soluble substance, known as assamar. If the heat is excessive, a thick carbonaceous crust is formed, which prevents the penetration of heat, and produces a raw interior. 1111. As the temperature within the loaf cannot rise above 212°, no changes go on there except such as are produced by the heat of the watery vapor. This is sufficient to stop the fermenta- tion, destroy the bitter principle of the yeast, and kill the yeast plant. In baking, about -j-V of the starch is converted into gum, the rest remaining chemically unchanged. The gluten, though not decomposed, loses its tough qualities, and unites closely with the starch paste. 1112. New and Stale Bread. — In newly baked bread the crust is dry and crisp, while the crumb is soft and moist, but after a short time this condition of things is quite reversed; the brown products of the roasting process attract moisture, and the crust grows daily softer, while the crumb becomes hard and dry. This appar- ent dryness, however, is not caused by loss of water, but by com- binations going on among the watery and solid atoms of the bread. That the moisture has only passed into a state of concealment may be shown by exposing a stale loaf in a closely covered tin vessel for half an hour to a heat of 130°, when it will again have the appearance of new bread. Well-baked wheaten bread contains on an average about 45 per cent, of water, so that the bread we eat is nearly one half water. 1113. Aerated Bread. — A new method has lately come into use In which carbonic acid is forced,under high pressur0,into the water the bread ? To what is its increase in bulk owing ? "What attempts are mentioned ? Describe the changes of the crust. 1111. To what are the changes within the loaf due ? In what do they consist ? 1112. What differences are mentioned between the crust and crumb ? To what is the drj'ness of the latter owing ? How is it proved ? What proportion of water does bread contain ? 1113. How is aerated bread made ? 17* 894 OEGANIC CHEMISTRY. employed for making the dough. The intermixture of the mate- rials, or Tcneading^ is effected by machinery under great pressure. As soon as the pressure is removed, the dough, rises from the ex- pansion of the compressed carbonic acid. 1114. Us9 of Chemical Substances. — Fermentation is often replaced by a quicker method of raising the dough, through the agency of chemicals. Bicarbonate of soda and chlorohydric acid are used, the soda being thoroughly incorporated with the flour, and the acid added to the water used for mixing. The acid com- bines with the alkali, forming common salt, and carbonic acid is set free, which distends the dough. To ensure neutralization, the ingredients should be pure, the proportions correct, and the mix- ture perfect. Soda powders consist of tartaric acid and bicar- bonate of soda. The soda combines with the acid, producing tar- trate of soda, and liberating carbonic acid. Cream of tartar is ex- tensively employed. "When sour milk is used, the carbonic acid is set free by lactic acid. 1115. Phosphated Bread. — The high price and pernicious adulteration of cream of tartar have created a demand for a sub- stitute. Prof. HoRSFORD claims to have found it in phosphoric acid, or acid phosphate of lime, which combines with the soda, setting free carbonic acid, and producing phosphate of soda and lime ; both normal constituents of the body. This preparation is now furnished as a yeast powder. 1116. Salts of Ammonia are sometimes employed for raising dough, but the gases formed are apt to communicate a disagree- able hartshorn flavor to the bread. All these chemical methods have one serious disadvantage — the gas is set free too suddenly to produce the best effect. The cautious use of chemicals, when pure, in bread making may be tolerated on grounds of convenience, but their employment by careless housekeepers in the commercial form is highly injudicious, as they are apt to be contaminated with injurious, and even poisonous impurities. 1117. Deterioration of Flour. — Flour tends to deteriorate by time. It is very hygroscopic, and the absorbed water gradually 1114. Bywhat is fermentation often replaced? What chemicals are mentioned ? Explain thoir action ? Wlint precautions are necessary ? What of soda powders? Sour milk? 1115. What is Prof Hobsford's substitute for cream of tartar? Describe its action. 1118. What of salts of ammonia? State the disadvantage of all these chemicals. What is eaid of the use of chemicals? 1117. Why docs flour CULINAEY CHANGES OF ALIMENTAEY SUBSTANCES. 395 Fig. 288. impairs the tenacity and fineness of the gluten. Oddlixg has shown that it is converted into a substance resembling diastase, which changes the starch of the flour into dextrine and sugar. Such flour of course makes a heavy, sodden bread ; flour, there- fore, should be preserved in a state of the utmost dryness. Liebig has ascertained that flour thus damaged may be greatly improved by lime water ; 100 parts of flour are mixed with 26 or 27 of lime water, and sufficient water added to form dough. The lime re- moves all acidity from the dough, somewhat augments the x^ro- portion of water absorbed, and restores the original qualities of the gluten. Common salt and alum cause dough to absorb more water than it would otherwise do. § II. Culinary Clmnges of Alimentary Substances. 1118. Effects of Boiling.— In boiling the food is surrounded by a powerful solvent, which more or less completely extracts cer- tain constituents of the food. Vegetable acids, sugar, gum, and vegetable albumen are all soluble in water, and by boiling are partially removed. The tougher parts are made ten- der, the hard parts softened, and the connec- tions of the fibres and tissues loosened, so as to be more readily masticated, more easily penetrated by the saliva and juices of the stomach, and therefore more promptly and perfectly digested. 1119. Breaking up of the Starch Grains.— The structure of starch grains has been described. They consist of layers or coats arranged concentrically around a point called the hilum. If one of these grains be strongly compressed between two plates of glass it breaks apart into several pieces, as seen in Fig. 288 ; but under the joint action of heat and water the membranes are torn asunder, or ex- foliated, by internal swelling, as represented by Fig. 289. deteriorate? "What has Oddlixg shown? How should flour be kept ? What ia LiEBiG's remedy? What change does the lime eflect? 1118. How does boiling change food? 1119. What is the structure of starch grains? What do figures Starch Grain Fractured- Starch Grains Ruptured by Boiling. 306 OKGAXIC CHEillSTEY. Fig. 290. 1120. Changes of Starch.— TVhen starcli is diluted with twelve or fifteen times its weight of water, and slowly heated, all the grains burst on approaching the boiling point, and swell to such a degree as to occupy nearly the whole volume of the liquid/form- ing a gelatinous paste. If a little of this be diffused through cold water, and examined with the microscope, it will be seen that the starch grains have greatly changed. They have increased to twenty or thirty times their original size ; the concentric hues are obliterated ; the membrane of the grain is ruptured, and its in- terior matter has escaped. "When starch is boiled in water for a considerable time it gradually changes, first into gum and then into sugar. A cold starch jelly left to stand, either closed or ex- posed to the air, undergoes the same change, but to effect it, months are required. 1121. How Potatoes are Changed by Cooking.— The potato is composed of three fourths water, and one fourth solid matter, which consists chiefly of starch. When examined by the microscope the tissue is found to consist of a mass of cells, each inclosing some 10 or 12 starch grains, loosely situated, as shown in Fig. 290, and surrounded by the potato juice, which contains albumen. If potatoes be of good quality they boil dry, or mealy, as it is termed; but their juice does not separate or boil out. It is absorbed by the starch grains, which form a com- pound with it and swell up, so as completely to fill and even burst the cells, as seen in Fig. 291. When the juice of the potatoes is only partially absorbed by the starch they are watery or uaxy. Potatoes when boiled in water do not form a jelly, like common starch, because the starch grains are protected, partly by the coats of the cells in which they are inclosed, and partly by the coagu- lated albumen. 1122. Quality of Water for Culinary Purposes.— Soft water, Potato Cells Before Boiling. illustrate? 1120. How is a eolntion of starch affected by heat ? What changes aro ficcii Avith the micropcopc? When starch is boiled for some time, what changes occur? What is the effect of exposing starch jolly to the air? 1121. Of what is the potato composed ? Wh:it docs Fig. 290 illustrate ? What becomes of thejuico ■nhcn potatoes boil mtalyl When are they watery 1 Why do not potatoes (oiin CULINAEY CHANGES OF ALIMENTARY SUBSTANCES. 3 9 7 Fig. 291. or tliat wliich is free from dissolved mineral matter, makes its way into organized tissues with much more readiness than hard water. Its higher solvent power better fits it also to act as a vehicle for conveying food into the living system. In culinary operations, where the object is to soften the texture of animal and vegetable matter, or to extract from it and present in a liquid form some of its valuable parts, as in making soups, broths, or infusions (as of tea and coffee), soft water is the best. But there are cases in which the solvent action of soft water is too great, as After Boiling. sometimes upon green vegetables, which it makes over tender, destroying the firmness that is essential to the preservation of their juices, which are dissolved and extracted, rendering the substance propor- tionately tasteless. In those cases therefore, where we do not desire to dissolve out the contents of a structure, but to preserve it firm and entire, hard water is better than soft. To prevent this over-dissolving action, soft water is often hardened by the addition of common salt, which also hinders the evaporation of the flavor- ing principles. 1123. Constituents of Flesh. — TVhen lean meat is chopped fine and soaked in cold water, there remains a solid residue consisting of the fibres, tissues, &c. It is white, tasteless, and inodorous. All the savory constituents of the flesh were contained in its juice, and were entirely removed by cold water. If the watery infusion thus produced be boiled, a clear, yellowish liquid is obtained which has the aromatic taste and other properties of soup made by boil- ing the flesh. When evaporated and dried, a sofr, brown mass, amounting to 12 or 15 per cent, of the weight of the original dry flesh, is left, having an intense flavor of roast meat. This extract, when dissolved in hot water, gives to it aU the properties of soup, retaining the peculiar taste of the flesh from which it was derived. 1124. Action of Heat upon the Constituents of Flesh.— The a jelly? 1122. "What is said of soft water as a Bolvent? "When should it be used ? When is its solvent power too great ? When is bard water to be preferred in cook- ing? What eflect has the addition of salt? 1123. What is the result when lean meat is chopped fine and soaked in cold water? State the effect of boiling this liquid uif usion ? What of this product when dried and evaporated t 1124. Describe 39S 0EGA^^c chemistry. effect of boOing upon fibrin is to render it hard and tough. Heat, as we have seen, changes liquid albumen to the solid condition, and renders it insoluble in water, either hot or cold. Fat is, of course, liquefied by the action of heat and, at a high temperature, is resolved into various acid and acrid bodies. 1125. The Cooking of Meat.— The first effect of applying a strong heat to fresh meat is to contract its fibres, press out a por- tion of the juice, and prevent the escape of more by partially closing the pores. In preparing meat for food, it is desirable that it should retLiin the ingredients of its juice; and this will depend much upon the method of culinary procedure. If the meat be in- troduced into the water uhen 'brisMy hoiling, the albumen at its surface, and to a certain depih inward, is immediately coagulated ; thus enclosing the mass in a crtist which prevents the juice from escaping, and also from being weakened and dissolved by the ex- ternal water penetrating within. The albumen coagulated within the meat also forms a protective sheath around the fibres, and thus prevents them from becoming shrivelled, tough, and hard by boiling. If, on the contrary, the meat be placed in cold water, and the temperature slowly raised to boiling, a portion of the savory and nutritive juices is dissolved out, and the meat becomes proportionally poorer for the loss, while, at the same time, the fibres grow hard and tough. TVliether the meat be surrounded by hot water, or exposed to heat in any other way, as soon as the water-proof coating is formed, the further changes are effected by internal vapor, or steam. In roasting or iahing^ therefore, the fire should at first be quite hot, as meat, when exposed to a slow heat, becomes dry and unsavory, from the constant escape of its juices through the open pores. 1126. Soups. — In the preparation of these, our object is the reverse of that just considered. We desire to take the nutritive and savory principles out of the meat, and obtain them in a liquid, or soluble form. To obtain the best liquid extract of meat in the form of soup, broth, or tea, the flesh is finely chopped and placed the action of heat upon the constituents of flesh. 1125. Mention its first effect. Wliat is desirable in cooking meat ? How does boiling WMter act upon meat I What is the reeiilt of placing meat in cold watei and slowly raistner its tem- perature? After the water-proof coating is formed, bovr are the further changes produced? Why, in roasting or baking meat, should the fire be at first quite hot ? 1126. What is the obJe«t In preparing soups f How ii this best effeeted f Why is CHEMISTET OF SOILS. 399 in cold icnter, wWcli is then sloT^lr heated and kept boiling for a few minutes, when it is strained and pressed. The meat sliould not be boiled long, as the effect is to coagulate and render insolu- ble the ingredients extracted by the cold water, and which should have remained dissolved in the soup. 1127. The Effect of Salt, when rubbed upon raw fresh meat, is to contract its fibres, thereby pressing out the juices, so that a brine is soon formed without the addition of any other liquid. This brine contains a large proportion of the albuminous con- stituents and mmeral salts of the meat, the removal of which impoverishes it and renders it incapable of complete or healthful nutrition. Salted meat is, therefore, dietetically much inferior to fresh meat. CHAPTEE XXV. CHEMISTRY OF SOILS. 1128. A few. years since a remarkable impulse was given to the subject of Agricultural Chemistry, chiefly through the labors of Prof. LiEBiG. The first effect of the movement was to create extravagant expectations in regard to what chem^try could ac- complish for agriculture. It was supposed that the farmer had only to obtain an analysis of his soil, and by comparing the re- sults with tables of the composition of crops, he could, by supply- ing the missing constituents, place his agriculture at once upon a simple, scientific, and successful basis. Experience quickly dissi- pated this fallacy, and then came a reaction, in which agricultural chemistry was denounced as misleading and worthless. The truth in this case lies between the extremes. While chemistry cannot be made a sole guide in agriculture, it can contribute important assistance, and is indispensable to the enlightened and most suc- cessful practice of the art. 1129. Prof. AxDEESox states that it is only in rare instances possible to connect together the chemical composition and prop- erties of the soU; that analysis is frequently incapable of dis- Jone boiling injurious? 1127. How does salt affect raw meat? Why are salted meats less nutritious than fresh? 1128. what is said of Liebig? "WTiat was the first effect of this impulse ? Its reaction ? Where does the truth lie ? 1129. Give 400 OEGAiaC CHEMISTRY. tinguishing between a fertile and a barren soil ; that it discloses only a ^:>a?'i of the conditions of fertility, and that with each ad- vancement in the accuracy of its processes the difficulties have in- creased, rather than diminished. Still, in the study of soils we cannot dispense with the aid that chemistry affords. 1130. Origin of Soils. — The mineral elements which compose the chief mass of soils are derived from the disintegration of rocks by air and moisture, heat and frost. Of course the composition of the rock determines that of the soil derived from it — an argilla- ceous rock producing a soil abounding in clay ; a calcareous rock in lime ; a silicious rock in sand. There is hence a relation be- tween soils and the rocks from which they are derived, but it is made so obscure by the transportation and admixture of materi- als, as to be discoverable only by the well-instructed geologist. 1131. In the crumbling down of rocks into soil, the decom- position is not complete. Besides a portion of liberated alkalies and alkaline earths, the sands and clays contain large amounts of potash, soda lime, and magnesia, locked up in combination, so as to be imperfectly or not at all available to growing vegetation. Yet the same forces, which disintegrated the rocks are still at work upon these constituents of soils, carrying forward the same decomposing changes, and gradually liberating the needed ele- ments of fertility. 1132. Variety of Soils — Soils are named from their pred(.m- inating element, as sandy^ argillaceous^ calcareous. Those con- taining excess of sand are light and porous; water escapes through them ; manures are wasted, and in drought plants lan- guish and die. On the other hand, an excess of clay makes a soil stiff, heavy, and retentive. A due admixture forms the loamy soil in which the evils of both extremes are corrected. It is suffi- ciently open to permit the free extension of the roots, and the ad- mission of air, while moisture and manures are retained. 1133. Physical Properties of Soils — The most important of these are specific gravity, tenacity, power of retaining moisture, of absorbing and retaining heat, and of absorbing moisture, carbonic acid, ammonia, and oxgyen from the air. These properties are most powerfully influenced by drainage, deep and subsoil plough- Trof. AxDERSOX's tpetimony. 1130 How do soils originate? "What is said of their composition? 1131. What do the sands and clays contain? How are they fertilized? 1132, Describe the varieties of soil. 1133. Mention their physical CHEMISTRY OF SOILS. 401 ing, mixture of soils, &c. But it is impossible to alter the physical character of soils without at the same time affecting their chemical properties. 1 1 34. Chemical Properties. — These relate to the composition, state of combination, and solubility of soil ingredients. The ele- ments, which most abound in soils, are not the most important. They contain the food of plants in but small proportions. If the soil is deficient in any of the constituents of plant food, or if they are locked up in inaccessible forms, plants will not grow, and the soil is said to be larren. If long cropping has removed any of the available constituents, it is brought to the same state, but is then said to be exhausted. 1135. Two Sources of Plant Food. — Plants live a double life. As will be explained in the following chapter, they have a twofold nutrition ; deriving mineral food from the soil, and organic from the air. How much comes from each source is an important question in practical agriculture, and has given rise to a lively con- troversy among agriculturists. The atmospheric elements, car- bonic acid, and ammonia may come also from the decomposi- tion of organic matter in the earth, and the question at once arises, in fertilizing a soil. Which class of constituents is most necessary ? 1136. Variation of the Mineral Elements. — "While the or- ganic constituents of plants are generally uniform, upon an exam- ination of their ashes it is found that different classes are marked by the prevalence of certain mineral elements. Some abound in potash, others in lime ; some in phosphates, and others in silica. Different parts of the same plant have also their predominating elements. "We have here one reason why all crops are not suited to the same soil, and why one crop may succeed where an- other fails. 1137. Liebeg's Mineral Theory. — Starting from these facts, LiEBiG maintains that the fertilization of soils is chiefly a question of the addition of such mineral substances, in a form suitable for absorption, as plants specially require. He holds that the organic ingredients are abundantly furnished by the air, but that the properties. How are they influenced ? 1134. What of their chemical properties? When are soils harren ? and when exhausted ? 1135. Explain the twofold life of plants. What question is in controversy ? 1136 State the variations in the min- eral elements. For what does this account? 1137. What is Liebig's mineraJ 402 ORGANIC CHEMISTRY. mineral constituents are not supplied in sufficient quantity, and in available condition to the roots. Other chemists, represented by La-WES and Gilbeet, of England, maintain the opposite view. They hold that the store of mineral substances in the soil is generally abundant for the wants of crops ; but that the atmospheric supply is not, and requires to be supplemented by ammoniacal manures, or those yielding nitrogen to the plant. 1138. The truth seems to be, that while plants if alloioed suffi- cient time can extract organic materials from the air, and attain a vigorous growth, yet if it be desired to rapidly increase their de- velopment, manures yielding ammonia and carbonic acid to their roots must be furnished. This policy, however, if long continued will exhaust the soluble inorganic constituents of the soil; hence in all permanent systems of agriculture, mineral fertilizers can no more be neglected than organic. 1139. Lime as a Fertilizer — Fertilizers are divided into min- eral and organic. Lime is one of the most important of the first class. It is used in the forms of marl and chalk, but most com- monly as slaked lime. It acts in various ways, but its least im- portant use is as plant food, for there are probably few soils which have not sufficient lime for this purpose. It acts mechanically to loosen tenacious soils, and chemically to decompose the silicates, liberating the alkalies, which are locked up in combination. It decomposes vegetable matters, converting their nitrogen into am- monia. It changes inert substances, so as gradually to render them useful to vegetation ; decomposes noxious compounds ; neu- tralizes baneful acids ; sweetens vegetation, and improves the qual- ity of nearly all crops. 1140. The compounds it forms in soils are generally insoluble ; its action is therefore slow, often requiring two or three years to produce its full effect. At first it may diminish crops, and does so invariably when applied in over doses. On light soOs, deficient in vegetable matter, it should be used sparingly. 1141. Gypsum is a valuable fertilizer for some crops, but the manner of its action is not known. Salts of potash, soda, .ind ammonia are excellent when they can bo afforded. Experience verifies what theory affirms — that ashes are most valuable. They theory? How ib it controverted ? 1138. What is eaid of organio and mineral fcr- tilizcrB? 1139. Into what arc fertihzers divided? Deeoribc the uses qf lime. What of it as plant food? 1140. Explain its action upon Boils. 1141. "What of CHEMISTRY OP SOILS. 403 restore to the soil the mineral matters which the crops remove, while the alkali they contain has the same beneficial effect as lime, with the superior advantage of acting immediately. Crushed bones form an exceedingly valuable manure, as their animal mat- ter yields nitrogen, and the mineral matter phosphate of lime. When bones are treated with sulphuric acid, a soluble phosphate is produced, which acts with more promptness than the neutral phosphate. . 1142. Farm Yard Manure. — With the exception of the small portion retained in the body, it is evident that the excretions of an animal represent the complete composition of its food, and if all restored again to the soil, would afford the restitution neces- sary to prevent exhaustion and maintain fertility. The solid ma- nure of animals consists of the indigestible and insaluble portions of their food. Liquid manure, on the contrary, represents the assimilated portion — that which was incorporated into the system, but was afterward decomposed and escaped from it in a soluble form. Liquid manure has, therefore, a far higher value as a fertilizer. 1143. Guano consists of the accumulated excretions of sea birds, deposited on rainless islands, and is sometimes found in masses a hundred feet deep. Its chief constituents are ammonia and phos- phate of lime, which amount in the best kinds to from I to ^ its weight. They occur in a soluble form, and its effect upon crops is therefore immediate and powerful. 1144. The golden rule of agriculture is to restore to the soil, 'in the shape of manure, exactly what it has lost in the crop. By failing to heed this principle millions of acres of the choicest land in this country have been utterly exhausted, and millions more are undergoing the same ruinous process. The skilful farmer econ- omizes every source of fertility. His manure heaps are sprinkled with gypsum, dilute sulphuric acid, or some other absorbent, to prevent the escape of ammonia ; liquid excretions are preserved in tanks, and no particle of it wasted ; compost heaps gather and utilize all forms of refuse, and while the accumulation of filth and noisome odors is prevented, the soil is enriched and culture made remunerative. Fertilizers are the farmer's motive power; with them he can do everything, without them nothing. gypsum salts gf potash, &c. Ashes ? Bones ? 1142. "Why is animal mantire so valuable? Give the comparison between solid and liquid manures. 1143, What of guauo? 1144. What is the golden rule of agriculture? How does the skillful PAET IV. PHYSIOLOGICAL CHEMISTRY. CHAPTER XXYI. VEGETABLE CHEiflSTRY. §1. Chemical and Vital Forces. 1145. Having noticed the properties of the chief organic com- pounds, we now pass to the chemistry of living beings, and the chemical relations of the organized kingdoms to each other and to the inorganic world. 1146. The Mystery of Life. — However viewed, the transcen- dent miracle of nature is Life. "W^hether considered as supporting the spiritual fabric of mind above, or as rooted in the inorganic world below, it is alike wonderful. Springing from ethereal airs and yet invincible ; constantly perishing, and yet abounding in earth, air, and sea ; forever conquered by death, yet evermore tri- umphant — 'strongest and weakest of the things God has made,' it is not surprising that it has been regarded as unlike all else in na- ture. It was but natural that the living system should be looked upon as the seat of a potent agency — the mysterious Vital Frinci- ple — which built up, maintained, and used the organic form, and subdued all surrounding forces. 1147. The Vital Force. — There has been a reluctance to con- sider the science of organized beings from a chemical point of view, as it was said the vital force here comes into play whicli overrides farmer manage ? 1145. What are we now to consider? 1147. Why ha*? there been a reluctance to conBider organized beinga from a chemical i)oint of view? Why is GERMINATION AND CELL GROWTH. 405 chemical laws and is itself inscrutable. But this idea is no longer admissible. In one sense all forces are mysterious ; yet they act with regularity, and whatever obeys law can be investigated. Though we cannot penetrate to the essential nature of any force, yet we may learn the manner of action and mutual connections of all forces. Vital force overcomes affinity, and so mechanical force overcomes gravity, but neither chemical force nor gravity is suspended. There are no unresisted forces in nature ; indeed, it is only by their constant resistance and overcoming that forces are called into exercise. 1148. Vital force is not denied, but in th§ present state of sci- ence it does not mean an independent principle, or force, like heat, or magnetism ; ' it is a collective term embracing all those causes upon which the vital phenomena depend' (Liebig). There are doubtless great obstacles in studying the changes of the living sys- tem, but as Prof. Millee remarks : ' The difficulty depends not so much upon the obscurity which enshrouds the nature of life — for the essential nature of all forces is equally inscrutable, but rather upon the extreme delicacy of the arrangements by which such changes are effected, and which are liable to injury from a multi- plicity of causes that have hitherto eluded scrutiny.' 1149. Having banished the superstition which blindly ascribed all things to an inscrutable vital force, and thus stopped inquiry at the outset, science has demonstrated that living beings are not aliens and exceptions in the universe, but parts of its wonderful plan ; that they are governed by its laws, and are to be studied by the same methods, and with the same success, as the other phenomena of nature. § II. Germination and Cell Growth. 1150. The Vegetable Embryo.— Every plant springs from a seed, and every perfect seed contains the rudiment of a new plant, called the germ or embryo. In some varieties it is so complete that the microscope reveals its structure— root, stem, and leaves. The minute plant lies imbedded within the seed, surrounded by a protecting mass, which consists chiefly of starch and gluten. this idea inadmissible? How do forces operate ? 1148. "What is understood by vital force ? From what arises the difficulty of studying the changes of the living sys- tem? 1149, What has science demonstrated? 1150. Describe the embryo. What 406 PHYSIOLOGICAIi CHEMISTRY. Fig. 292, shows the germ in Indian corn and its proportion to _ the surrounding matter of the seed, which Fig. 292. ° ' forms the principal bulk of ordinary cultivated grains. Wrapped in this envelope, the embryo remains at the disposal of external agents. In certain conditions it continues at rest and tor- pid; but when these conditions are changed, it suddenly awakens from its slumber, puts Germ of Indian Corn. „ ,, t ^ ' ^ xi • • forth a new power and begms to grow ; this is called germination. 1151. Chemistry of Germination.— The embryo during growth derives its nourishment from the surrounding body of the seed. To convey this nourishment requires a moving medium. This office is performed by water ; hence the first condition of germi- nation is exposure of the seed to moisture, the absorption of which causes it to swell and increase in bulk. But the nourishment can- not be transferred except in a soluble form, and the starch and gluten are insoluble in water. To remove this difficulty nature resorts to a beautiful process which necessitates the second con- dition of germination — the access of air. Oxygen is thus absorbed, and acting upon the gluten, changes a minute portion of it into diastase, which, taking effect upon the starch, transforms it first into dextrine, or gum, and then into sugar. A portion of sugar is oxidized into acetic and carbonic acids— the temperature rising — and the remainder is transferred to the embryo. This is now as- similated by the germ, but it has no power to organize the ele- ments which contribute to its nourishment. Heat also influences germination. Each kind of seed requires a certain temperature, although it varies in different species, from just above the freeziug point, to 100*' or 110°. Light impedes germination, the deoxi- dizing rays tending to Jix the carbon and thus check the formation of carbonic acid. 1152. Development of the Embryo. — Fed by its store of nu- triment, the embryo expands ; one part, the radicle, shoots down- ward to form a root, while the other, the plumula, or stem, ex- tends upward to the surface, as shown in Fig. 293. But when the stem appears above the ground, and expands its earliest leaves, does Fig. 292 show? When does germination take place? 1151. "Wliat nourishea the embryo during growth? Describe the first process of germination. The sec* end. Of what power is the germ destitute ? 1152. "What arc the radicle and plu- GEEMINATION AND CELL GROWTH. 407 tlie plant passes into another stage of existence, and a new order of phenomena is manifested. JSTo longer depending for nonr- FiG. 293. ishment upon ready made food furnished by the seed, it begins to exert a formative power — the true vegetable function — and produce from the min- eral elements of the earth and air such organized compounds as it may require. 1153. Minute Mechanism of Growth. — Vegeta- ble growth takes place through the action of certain bodies termed cells, which are very minute, closed bags or sacs, usually ranging in size from ^i to y^^ of an inch in diameter. When uncompressed, as in the pith of elder. Fig. 294, or the pulp of fruit. Fig. 295, they have a rounded form ; but when closely crowded by others, they become flat-sided, angular, and elongated, Fig. 296. 1154. Structure and Formation of Cells. — The cell consists of an outer membrane, or cell-wall, which incloses a lining sac, and within this is a dot or nucleus. In plants the outer membrane consists Embryo!^ of cellubse, and the inner one of nitrogenous matter. Fig. 294. Fig. 295. Cells of Elder Pith. Cells of Fruit Pulp. Cells of a Rootlet. This contains a viscid, albuminous liquid called protoplasm, in which float numerous small grains. At the rupture, or death of the parent cell, these grains are set free, and each one becomes the germ or nucleus of a new cell. At its surface a delicate mem- mula? How does the young plant now proceed? 1153. Describe the mechaoism of growth. 1154. Explain the structure of cells. Their formation. How do they 408 PHYSIOLOGICAL CHEillSTKY. brane appears, which gradually extends much beyond the original germ, giving rise to the cell cavity. Cells also multiply by division. The contents of the cell (1) become separated (2), and then a par- FiG '^i tition is formed across it (3) producing two cells ; the subdivision is thus carried on indefinitely, O, 2 p "-""^ 'I Cells also increase, as before noticed, by pro- V^ cess of budding and branching (1058). All the various tissues and structures of vegetables are built up of these cells, much as a wall is form- ed of bricks or stones ; with the difference that the living structure forms its own bricks. 1155. The CeU Wall.— Though the cell membrane is without the slightest trace of pores or openings, yet, like all organic membranes, it Grovi th of cali' ^^ permeable to fluids. The cell wall exhibits the remarkable property of retaining its liquid contents, whUe it permits the free transudation of other fluids. The passage of the fluids takes place by osmose. The termina- tions of the rootlets of plants consist of active cells which absorb water from the soil, and this, ascending through the fine woody tubes, passes through many millions of partitions before reaching the leaves. 1156. Cells are the little workshops of the organized world. By the free circulation of fluids, the raw materials are conveyed into them, and there transformed into organized matter. Different cells are specially adapted to produce different substances ; some forming starch, others oil, wax, acids, &c. § III. The Chemistnj of Yegetdble Growth, 1157. Architecture of the Tree. — In speaking of germination, we saw that the embryo is stamped with a polarity — a tendency to develop in opposite directions ; one part is to live in the earth, the other in the air. There is a deep significance in this architec- ture of the tree. Its stem, supported by widely-extended roots, rises high in the air ; it divides into branches, and subdividing into boughs and twigs, finally terminates in myriads of little, flat, green plates, called leaves, which are generally mounted upon caulliplyf 1165. How is the passage of fluids efl"ected? 1156. What is the office of the cells f 1157. How does the germ exhibit polarity ? What is said of the ar- THE CHEMISTRY OF VEGETABLE GnOWTH. 409 slender foot stalks. The idea evidently is to obtain the largest amount of surface which the material "will afford consistent "with the proper degree of strength. Furthermore, the atmosphere is ever in motion, so that by the swinging of the boughs, and the trembling of the leaves on their elastic foot stalks, the surface contact with the air is heightened to the utmost. 1158. Not without its purpose is all this admirable contrivance, and one might well anticipate that the economy of vegetation is in some way closely linked with the properties of the atmosphere- A microscopic examination of the leaf confirms this idea, by showing that its surface is covered by thousands of little open- ings (stomata), which are fitted either for the exhalation or inha- lation of gases. 1159. Food of the Plant. — "Water, containing dissolved a por- tion of the gases of the air — carbonic acid and ammonia — together with a minute proportion of earthy matter from the soil, is ab- sorbed by the mouths of the rootlets (spongioles), and enters the vegetable organism as crude sap. In this dissolved form the min- eral or inorganic world flows into the organic. The mineral solution, upon its entrance, mingles more or less with the or- ganized juices, so that unmixed, crude sap is never found in the plant. 1160. Nourishment from the Air. — Eising through the capil- lary tubes of the vegetable structure, the crude sap passes upward to the leaves. It there exhales its excess of water into the air, becomes condensed and digested ; new products are formed, and the sap is said to be eladorated. But the plant derives also a portion of its nourishment directly from the air, in the form of carbonic acid gas. Though the proportion of this gas in the at- mosphere is small, yet the vast leaf surface — each leaf being cov- ered by a film of moisture which is highly absorbent of carbonic acid — enables the foliage to withdraw it in considerable quantity from moving masses of air. 1 161. The largest portion of the nutriment of the plant is, how- ever, procured immediately from the soil. Carbonic acid, carbon- ate of ammonia, and nitric acid, are dissolved out of the atmos- phere by the falling rain, and penetrating the earth, enter the plants chitecture of the tree ? How ia the surface contact heightened ? 1158. Explain the design of this arrangement. 1159. How does the plant receive its food ? 1160. What becomes of the sap? How does the foliage absorb carbonic acid? 1161. 18 410 PHTSIOLOGICAi CHEMISTRT. br the roots. Shonld they be furnished to the roots bj decompo- sition of organic matters in the soil, these again may be traced back to the air, so that althoagh plants may be said to receive their food chie^y through the soil, they ddrire it from the air. The vegetable kingdom, and the atmosphere which surrounds it, consist of the same chemical elements. 1162. Chemical Changes in the Leaf. — The green leaves digest the crude sap ; they consist of living cells, which carry on acrive chemical changes, translating matter from the inorganic to the organic state. It was shown by Peiestlet, in the last century, that the foliage of plants in the scnshine gives off oxygen gas to the surrounding air. This may be seen by exposing a few fresh leaves to the sunshine in an inverted glass vessel, filled with water, Fig. 298 ; the air bubbles which arise and collect at top are oxygen. Carbonic acid thus enters the leaf, and oxygen is set free, the car- bon being retained- The leaves decompose the car- bonic acid, separating the carbon, which is Jixed in newly-formed organic compounds. This is probably Leaves ExTiai- the source of all the carbon in plants. ^° Oxygen. 1163. Water and ammonia are decomposed to furnish the hy- drogen and nitrogen of oi^anic substances ; the requisite oxygen being supplied by both carbonic acid and water. From these ele- ments the leaf constructs gum, dextrine, starch, albumen, cel- lalin, and many other products which are contained in the elab- orated sap, and conveyed to different points of the vegetable organism. 1164. Plants are thus universally instruments for separating oxygen — machines of deoxidati(m. It is through these operations, and by grouping the products thus formed, that the plant be- comes a constructor of organized bodies. 1165. Formation of Acids. — How the changes take place we do not actually know, but it is not difficult to see in what way they are probably performed- The atom of carbonic acid may be taken as the starting pouat. It consists of three elementary atoms, "WTiat 13 said of the roariahment of the plant immtdiattly from the soil? 1182. what waa proved by PatBSTLinr T How may it be ehown? Deacribe the chem- ical changes? 11631 Explain the farther processes of the leaf. 1164. How does the plaat coaatrpct organized bodies t 1165. How are acids enpposed to be THE CHEMISTRY OF VEGETABLE GROWTH. 411 one of carbon, and two of oxygen. ITopart of a vegetahle or animal structure contains for one atom of carbon more than two atoms of another element — most of them contain less. Organization there- fore begins by separating oxygen from carbonic acid. The vege- table acids are lowest in the organic scale, and arise from the first steps of deoxidation. For example, carbonic acid consists CO of COo, or COO, and dry oxalic acid of C^Oj,, or qqq- If, there- fore, from a group of two atoms of carbonic acid, but a single atom of oxygen be separated, the remainder represents oxalic acid. 1166. The process may now be carried a step higher, resulting in the formation of a more complex acid. If from a group of two atoms of oxalic acid two more atoms of oxygen are removed, and the hydrogen from the two atoms of water added, we have malic acid C4H2O4. To produce an atom of oxalic acid, but a single atom of oxygen is set free ; for an atom of malic acid, six are liberated. 1167. Production of Sugar, Starch, &c. — The products first formed are marked by an excess of oxygen, like carbonic acid, and have properties analogous to that acid. But as the process is car- ried farther, a higher and neutral class of bodies appears — the acids pass into sugar and its congeners. To produce an atom of sugar an atom of carbonic acid is taken, COO; half its oxygen is separated, making CO ; an atom of water is then decomposed, and its hydrogen made to replace the separated oxygen atom, thus COH. Twelve atoms of carbonic acid, and twelve of water, changed in this manner, give OigHigOia, or the glucose group without its combined water. 1168. It has been stated that this class of bodies, sugar, starch, cellulin, &c., are remarkable in having their oxygen and hydrogen in the exact proportion to form water, so that they may be regarded as hydrates of carbon. On this view we have but to suppose all the oxygen removed from the carbonic acid, and the resulting car- bon joined directly to water, to explain the synthesis of these sub- stances. It will be noticed that the deoxidizing process is carried much farther here than in the case of acids: to produce an atom of sugar, 0\2^\2^i2i 24 atoms of oxygen are set free. formed ? Example. 1166. How the more complex acids ? 1167. What is Baid of the products first formed ? What class now appears ? How are they produced ? 1168. Give the synthesis of the bodies. 1169. Pescribe the formation of fats and 412 PHYSIOLOGICAL CilEMISTBY. 1169. Production of Fats and Oils. — As these bodies con- tain an excess of hydrogen and a minimum of oxygen, being thus the reverse of acids, it is obvious that the deoxidizing pro- cess has been here carried much further. For the production of an atom of stearine, C114H1 ^qO 12, IM atoms of carbonic acid and 98 of -water must lose their oxygen, which would liberate no less than 3-26 atoms of this gas. In forming the pure hydrocarbons, the reduction of hydrogen and carbon is complete, all their oxygen being set free. 1170. Production of Nitrogenous Compounds, — The formar tion of these is perhaps less simijle. The large proportion of car- bon and hydrogen is of course obtained by deoxidation. But the complex albuminous group is probably buUt up by the couxAing of simpler compounds (923). It is supposed that all the higher or more complex organic compounds are thus formed ; and ' albu- men, casein, and the organic bases are regarded as coupled com- pounds, which they certainly are, although we do not yet know the copula belonging to them ' (Liebig). 1171. Changes of the Starch Group. — Physiologically, dex- trine, sugar, starch, and cellulin are one thing. Several of their modifications are strictly isomeric, and they are all convertible into each other by the addition or subtraction of an atom or two of water. In a chemical point of view they might all be formed in the leaf with equal ease ; but their diversities of physical character require their production in a certain order. Dextrine, gum, and sugar are probably first formed in the elaborated sap. These are soluble, and therefore easily transported from point to point of the vegetable organism. Cellulin is the fixed, insoluble member of the group, and, therefore, cannot be produced at first ; it is only formed where it is required to furnish tissue. Starch is a kind of intermediate product ; being insoluble, and taking the shape of minute grains, it is fitted to be temporarily deposited as a kind of nutritive stock, to be redissolved and transferred to other Ijlaces for use, wherever necessity requires. "We saw an example of tliis in the case of germination. Starch is the form in which the food for the future embryo is stored up in the seed, to be trans- formed into dextrine and sugar, and then again into the cellulin of the young germ. oils? "What ia said of the pure hydrocarbons I 1170. How are the nitrogenous compounds formed ? 1171. IIow are dextrine, sugar, etarch, and cellulin regarded chemically? Whrn .-in- dcxirin?, frimi, and sugar formed, and why? Cellulin t THE CHEMISTRY OF VEGETABLE GROWTH. 413 1172. Changes of the Albuminous Group. — In the living cell the nitrogenous protoplasm seems to be the active agent, or medium of vital changes. We saw its power of inducing transformation in the starch group, when treating of fermentation. It forms the lining of the cell, and the cellulin is deposited under its influ- ence to form the permanent wall or ceil fabric. When the cell is thus matured, its nitrogenous matter leaves it and is attracted on- ward into the newly growing parts. It is thus explained why so small a quantity of albuminous substance plays so all-important a part in the vegetable economy, and why such a mere trace of it is found in the woody structure of plants. The matured heart of trees yields but the faintest indication of nitrogen, while the sap- wood and young growing parts always contain a small proportion, which accounts for their tendency to rapid decay. These sub- stances are at length nearly all withdrawn from the fabric of the plant, and laid up in the fruit and seed. Being transferred to the animal system, their relations are changed, and they play the same part that the starch group did in the vegetable structure. 1173. Plants in Apartments. — As plants are purifiers of the air in a double sense, withdrawing its noxious carbonic acid and re- turning its life-giving oxygen, it might seem that they would be very efficacious for this purpose in inhabited rooms. They per- form this office in the day time, and are also useful in exhaling moisture into the air, which, in houses warmed by hot air, is often a most important service. But at night the regular vegetable function is suspended; carbonic acid is no longer withdrawn; oxygen is no longer set free, and the effect of the plant upon the air is due to leakage through the leaves of the gaseous contents of the sap. Carbonic acid wiU therefore be given off in very small amount at night, and just to that degree, vegetation is injurious in sleeping rooms. It is erroneous to speak of plants as respiring — exhaling oxygen by day, and carbonic acid by night. What of starch ? 1172. Describe the office of the protoplasm. What is said of the nitrogenous matter? Why does the sapwood and young growing parts decay rapidly ? What further changes do the nitrogenous bodies undergo ? 1172. Wliat office do plants perform in the daytime? What change occurs at night? To 414 PHYSIOLOGICAL CHEMISTRY. CHAPTER XXYII. DYNAMICS OF VEGETABLE GROWTH. § I. Tlie Forces of Organization. 1174. In the preceding paragraphs we have confined our at- tention to the material changes of vegetable growth ; we are now to regard it under the dynamic aspect, and take account of the forces brought into play. 1175. Hypothesis of Latent Vitality. — Before the establish- ment of physiological science upon its present inductive basis, when everything was quickly explained by the assumption of an all-powerful vital principle, it was held that the germ was 'poten- tially the tree ; that is, that all the vital energies of a vast vege- table organism which had been growing perhaps for hundreds of years, preexisted in the embryo in a dormant state, and that the growth consisted only in the waking up of this latent vitality. This absurd doctrine was long since replaced by the kindred notion that vital force exists in a dormant condition, not alone in the germ, but in all matter capable of becoming organized; that the germ, in attracting to itself the materials of growth and incorporating them into the living structure, only calls into activity their latent powers, and that the forces, heat, light, &c., are but vital stimulants which arouse the torpid energies of carbon, oxygen, hydrogen and nitrogen ; the growing cell appropriating the vital force thus set free. 1176. Later Views. — The progress of our knowledge of forces has swept away these assumptions, and shown that the same intel- ligible and beautiful principles which we have found in the inorganic world, extend also to the organized kingdom ; that the plant is no anomaly in nature, but a link in her vast chain of activities, and only to be understood in connection with the universal scheme. The career of the plant is a constant and admirable illustration of the great laws of the conservation and correlation of forces. It is now considered that, as the plant absorbs matter from the sur- rounding world, so it also absorbs force, and as it changes and assimilates that matter into organized and vital forms, so it also ■what extent are they injurious? 1174. How are wo now to consider vegetable growth ? 1175. "What was the old hypothcBis of latent \-itality ? By what was it replaced ? 117C. "What docs our knowledge of forces show? Of what ia the career THE FORCES OF OKGAXIZATIOX. 415 assimilates or converts surrounding forces into organized or vital force. Not that the plant deals with matter and force separately, for they are inseparable ; but in appropriating matter it appro- priates also the forces of which it is the medium. 1 1 77. Storing of Forces in Nature.— Conditions of matt/r rep- resent quantities of power. The solid state contains the least ; the force that melts it is stored up in the liquid; while the gaseous form represents a still higher condition of power. These forms of matter resemble springs coiled up to succe sive degrees of ten- sion: when relaxed tlieygive back their force. Ice is like the re- laxed spring ; water like the spring partially bent, and steam like the spring strained to a much higher tension. As the vapor re- laxes into water, it gives out the force of elasticity ; as it still further relaxes into ice, it gives out the l'»)rce of liquidity (2S0). 1178. Organic Bodies Reservoirs of Power. — Organic sub- stances, like bent springs, are stores of force, and represent the power expended in separating and grouping their atoms. Accord- ing to the extent of the organizing process, is the force stored away. In acids it is least ; in the starch group it is higher, and in the hydrogenated group highest. As the three states of m:itter con- stitute three reservoirs of power, the solid lowest, the liquid higher, and the aeriform highest, so organic bodies may be regard- ed as a fourth reservoir still higher. Organic substances may fall directly to the mineral state, as in open combustion, when their force is all given out at once in the intense form of heat and light ; or they may descend by the slow steps of decay, when the force is gradually released ; or again, they may be transferred to the animal system, and give out their power as animal force: but in all cases the force produced is precisely the same in amount. 1 1 79. Source of Germinal Force. — The economy of the plant is to store^ and not to expend. It is fixed; that is, it never con- sumes force by locomotion, and never draws upon its constantly accumulating stock, except in time of flowering. In germination we saw that the embryo is nourished by the stored material of the seed. But to effect the transformation and carry on new growth, force is required, and this is fiirnished by destruction of a portion of the plant an illustration ? Describe its mode of action. 1177. How are forces etored in nature? Give the comparison used. 1178. What is said of organic bodies in relation to force ? Examples. How may they be regarded ? In what ways may they lose their force, and what of its amount ? 1179. What is the func- 416 niYSIOLOGICAI. CIIEMISTKY. of the organized substance of the seed. The part destroyed gives up its force, to be reconsumed by the growing embryo, so that the plantlet at first draws upon its prepared stock of force, as well as of matter. 1180. Transferrence of Organic Force Xature furnishes many other illustrations of this principle, in which the forces're- leased in dissolution are immediately utilized in evolution. The yeast plant accompanies putrefaction : so the ' mould ' that appears upon damp, decomposing bodies, and the fungi that grow upon de- caying wood, are lower forms of growing vegetation. Thus or- ganization springs directly from disorganization. As the fall of one arm of a balance raises the other, so the descent of organized atoms to the mineral state gives out the force required to raise other atoms to the like condition. 1181. Influence of Elxtemal Forces. — When its store is con- sumed, the embryo opens its leaves to the air and light, and com- mences to form organic matter out of mineral substances. This requires a vast expenditure of power, for which there is no source but the forces of the external world. These are spent in produ- cing growth, and are stored up as vital force of the vegetable organism. According to the intensity with which these forces act, is the vigor of growth. In the tropics, where the temperature is high, vegetation is rank and luxuriant, and tribes of plants abound which can flourish only in torrid regions. Leaving the equator, and proceeding north or south, vegetation becomes less rich, and new varieties of i)lants appear with the declining temperature. Going still farther from the equator, as the forces diminish in in- tensity the vegetation becomes still more scattered and meagre, and toward the poles entirely disappears. The abundance of sub- stances which plants produce declines also in the same order. Tropical plants abound in various aromatic, medicinal, and coloring compounds, which are not yielded by those of higher latitudes. 1182. Again, in ascending mountains, the same remarkable phenomena are observed. Leaving tropical gardens at the base, we may, in a single day, ascend to the line of eternal snow, cross- tion of the plant ? From whence does it ohtain force ? IISO. Give examrles of the transferrence of force. What of organization? 11S7. Describe the action of the embryo. Where does it obtain ^^tal force? What determines the ^^gor of prrowth ? Howie this illastrated? What is said of the substances produced by plants? 1182. Give further example.^. What is thus proved ? 1183. Stale the re- THE FORCES OP ORGANIZATION. 4l7 ing belts of vegetation corresponding to those between the equator and the poles. Moreover, in extreme northern regions, where the sun shines uninterruptedly for three months and a half, th^ low- temperature and brevity of the season are compensated by the constant action of the solar forces, causing the vegetable world to spring into life as if by magic. That the quantity of force in action determines the quantity of organization, is thus proved on the most stupendous scale. 1183. The same fact is further illustrated in the growth of different varieties of plants. Boussingault found, as a result of numerous observations, that from germination to maturity the same annual plant receives very nearly the same amount of heat, whether grown in the temperate latitudes, or in the tropics. If the mean temperature is low, it will require more days to ripen than if it were high. 1184. Vast Force Exercised by the Leaf.~When we look upon the luxuriant foliage of the tree, we cannot fail to be im- pressed with its beauty, but we hardly suspect that those leaves which flutter so lightly in the breeze are engines for the exercise of enormous power. Yet such is the fact, for they decom'pose car- ionic acid. The atoms of a pound of carbon rush into union with those of oxygen — they fall down the chemical precipice with a force sufficient to raise a thousand weights each of a thousand pounds, one foot high. This expresses the strength of their at- traction for each other, and if they are to be separated, this amount of force must be again expended. So powerfully are the elements of carbonic acid held in combination, that the chemist can only separate them by the double action of a high heat and the most powerful affinity ; even then, only the carbon is set free, the oxygen remaining in a state of combination. But what no chemist has ever been able to accomplish, is effected by every green leaf and every humble blade of grass ; — they decompose carbonic acid at common temperatures^ retaining the carbon and setting the oxygen free. 1185. Motive Power of the Plant.— But the leaf cannot create the power it exerts. Though a chemical engine of wonder- ful efficiency, it is no more self-moving than the steam engine, or suit of BotTSSiNGATTLT's researches. 1184. "What proves that leaves are engines of vast power? Describe the force with which carhon unites with oxygen. Compare the power of the chemist and the leaf. 1185. Wliat cannot the leaf dof 18* 418 PHTSIOLOGICAIi CHEMISTRY. the water wheel. Its motive power is the sunbeam ; and as the steam engine moves at a rate proportional to the amount of steam supplied, and ceases to go at all if the steam is cut off, so the leaf performs its work at a rate proportioned to the intensity of the liglit which falls upon it, and ceases to act if it be withdrawn. 1186. In total darkness plants cannot grow, if there be but little light, they are white, watery, and sickly ; and even in the shade, as all have observed, they are feeble and dwarfed. The leaf can only decompose" carbonic acid in the day time. Plants, of course, grow at night ; cells multiply and transform materials constantly, but the initial act of organization upon which all else depends, the separation of carlon from oxygen^ only takes place under the influence of the light of the sun. 1187. The Organizing Region of the Spectrum.— To what por- tion of the complex ray is assigned the task of effecting the chemi- cal changes of the leaf is an interesting question. Heat, though largely absorbed in the organizing process, does not produce this effect. It was formerly attributed to the chemical, or actinic force, but the admirable researches of Dr. Dkapee proved that this view was erroneous. He placed some green leaves in tubes of carbonated water, and so arranged them in the several colors of the spectrum as to ascertain, from the amount of carbonic acid absorbed and of oxygen liberated, how the decomposing force is distributed. The result proved that the change takes place most actively in the yellow, orange, and green colors. At the ex- tremes of the spectrum, in the region of greatest heat and greatest chemical effect, the action was very feeble, or altogether wanting, while the amount of change corresponded to the intensity of the illumination. § II. Chemistry of the Sunbeam. 1188. In classical fable we are told that Prometheus stole a spark of celestial fire and warmed into life the earthly body he had formed. The mythologic dream was parallel with the truth of nature ; — the true Promethean spark is the Sunbeam^ which, by What Is said of Its motive power ? 1186. How is this proved ? IIow does the action of leaves during the night difTer from that under sunlight? II87. What qucbtion is stated? Describe Dr. Draper's experiment. What did It prove? CHEMISTRY OF THE SUNBEAM. 419 its wonderful alchemy transforms dead matter into organized and living forms. 1189. Extent of Solar Influence.— Not only life, but all the grand phenomena of force with which we are familiar upon this planet, have their origin in the sun. His radiations govern the movements of terrestrial atoms, and in these the movements of masses take their rise. Should that body cease to give out ema- nations, the earth would speedily lose its heat ; life would disap- pear, vapors condense, and liquids congeal. There would still be tidal influence, due to the attraction of the dark masses of the sun and moon, but, as the ocean would be solid, there could be only a slight movement in the atmosphere. There might also be volcanic force, due to the earth's central heat, although this too has been held as subject to astronomic agency. 1190. Effects of Solar Heat Alone. — Were the sun to radiate heat alone the earth would still remain dark, but the oceans would melt, and tides begin to lash the coasts. The atmosphere would be rarefied unequally as now ; storms would arise, and there would be the motive power of wind. Water would be converted into vapor, and condensed into invisible clouds and rain. Streams would channel their way to the sea, and falling in cataracts, would give rise to water power. The descending floods, bringing down the sediment, would gradually lower the continents and fill up the oceans, while the tides would gnaw away the shores; the distri- bution of land and water would be changed, and there would be all the extensive efifects of aqueous, geologic agency. 1191. Furthermore, the electrical conditions of matter would be disturbed; tropical tornadoes, and the milder storms of the temperate latitudes would be accompanied with thunder and lightning ; the unequal heating of the earth in its daily rotation would give rise to thermo-electric currents, and these would pro- duce magnetism. All these results would flow from solar radia- tions quickening the motions of earthly atoms, so that ice would change to water, and water to vapor. 1192. Effect of Increased Solar Action. — If we again suppose the energy of solar radiation so exalted that light is emitted with heat, the higher phenomena of organization become possible. 1188. What is the true Promethean spark? 1189. State the extent of solar ifl- fluence. What would follow if the sun should cease to emit rays ? 1190. What if it should radiate Ji^ut alo7ief 1191. Mention further results. 1192. What would b« 420 PUYSIOLCGICAL CHEMISTRY. "With the introduction of plant germs, the vegetable world would be called into being by the vitalizing cliemistry of the sun. The animal world, dependent upon the vegetable — consuming its mat- ter and its force — could then appear with all its multitudinous forms of power. The burning of wood and coal would also give steam power. Thus, in addition to all the forms of mechanical movement upon earth, its very energies and impulses of life origi- nate in the sun. 1193. The Organic Kingdom a Magazine of Force. — The vegetable world, born of the atmosphere, consists of condensed gases. The animal world, derived from the vegetable, is also but solidified air. So the food that we consume, the clothes that we wear, the houses in which we live, the fuel that warms us by the fireside — that transports us to distant places with lightning speed, and labors for us in a thousand ways, are all nothing but con- densed air. The sunbeam is the agent of condensation, and thus the organic world presents itself as a vast magazine of solar force. 1194. So the coal deposits — the carbonized remains of a vege- tation which flourished long before man appeared upon the globe, were condensed from an atmosphere richer in. carbonic acid, and perhaps by a more brilliant sun, and yet, this coal, having slum- bered in its ancient bed through uncounted eras of time, now comes forth to surrender its ethereal agents, light and heat, and return as carbonic acid to the air from whence it came. 1195. The Sunbeam the Antagonist of Oxygen. — "When treat- ing of oxygen it was stated that this element enshrouds the globe and tends to unite with and bring all things to rest, so that if the earth were left to the action of its own forces, life would quickly disappear, and leave the world a desert. But the earth's vegeta- tion is the beautiful instrumentality by which this action is arrest- ed. The leaves extract poisonous carbonic acid from the air, de- prive it of the elements it had seized, and return it again to the atmosphere, while the forces which impel these changes are the beams of the sun. These are the great antagonists of oxygen. Under its influence organized matter is rent into its elements and carried down to the mineral world ; under the influence of the solar rays it is again raised to the organized condition. If oxygen the effect if light accompanied heat I "What thus originate in the sunt 1193. How 18 the organic •world a magazine of force? IIM. What is said of coal? IIOS. "SVhat TTOuld be the influence of oxygen uncontrolled ? How ia ita nctioa ar CHEMISTRY OF THE SUNBEAM. 421 dilapidates thej renovate ; if that decomposes and breaks down, tliey construct and build up ; if that is seen in the falling leaf of autumn, they are proclaimed in the exuberant foliage and blossoms of spring. If oxygen is the mainspring of destruction, wasting, burning, consuming all things — the solar rajs constitute the mighty force of counteraction. They reunite the dissevered ele- ments, and substitute development for decay, calling forth a glory from desolation, and life and beauty from the very bosom of death. 1195. It is the Motive Power of the World.— Thus is the earth warmed, illumined, magnetized, and vivified by the sun. In the fall of the avalanche, the roar of the cataract, and the flow of rivers— in the crash of thunder, the glare of lightning, and the sweep of tornadoes— in the blaze of conflagration, and the shock of battle — in the beauty of flowers, of the rainbow, and the ever shifting clouds— in days and seasons, the silent growth of plants, and the elastic spring of animals — in the sail-impelled or steam- driven ship, and the flying train — ^in the heavy respiration of the laboring steam engine, and the rapid click of the telegraph ; in aU the myriad manifestations of earthly power, we behold the trans- muted strength of the all-energizing sun. 1196. Amount of Solar Radiation. — And yet the entire power displayed upon the globe is as nothing compared to the vastness of of its source. The earth arrests but the o.aoo-.^o o.oto of the whole amount of force that the sun emits. The total heat received by the earth would be sufficient to boil but 800 cubic miles of ice- cold water per hour, while the entire amount radiated by the sun would boil 700,000 million cubic miles of ice water in that length of time. The sun is 1,400,000 times larger than the earth, yet the force generated upon each square foot of his surface is equal to 7,000 horse power per hour. 1197. Stupendous as is this scale of power, it again sinks into insignificance, when we remember that our sun is itself a star — that it is but one of the countless millions of suns which fill the immeasurable spaces ; — each a fountain of energy of the same nature as that around which we revolve, and upon which we more imme- diately depend. Thus in the strictest sense the earth borrows its life from the stars. rested ? Describe the opposite action of oxygen and of the solar rays, 1195. How is the sun the motive power of the world? 1196. State the amount of solar radia- tion the earth receives. How does this compare with the entire amount radiated? 1197. What fact renders this amount of force comparatively insignificant ? State 422 PHYSIOLOGICAL CHEMISTRY. 1198. The Universe Culminates in Life. — If Astronomy has revealed to us a universe of unspeakable grandeur, Chemistry has linked the mighty mechanism to the course of terrestrial life. She teaches us not only that the leaves and flowers are distilled from the crystal medium in which they dwell, but that they are tissues woven in the loom of the universe — their warp the subtlest ethers of earth, their weft the radiations of the stars : not only that the leaf is the crucible of vitality, whose mysterious alchemy is interposed between ourselves and death, but that it is the won- drous mechanism appointed to receive and gather the life forces which God is perpetually pouring through His universe. 1199. — It is a fine suggestion of Humboldt that if we could imagine those movements of the stellar universe which take place in long periods to be compressed into a short space of time, and were we endowed vrith telescopic vision to behold them, we should then vividly realize that there is nowhere such a thing as rest. The stars which we term Jlxed would be seen all in motion; constella- tions drawing together ; clusters unfolding and condensing; nebulsB breaking up and universes melting away — motion in every part of the vault of heaven. Could we then be permitted to gaze into the living organism upon earth — plant, or animal — we should behold a kindred spectacle ; the constituent atoms in ceaseless movement — combining and separating — groups dissolving and rearranging, and all circulating in orderly and determined paths — movement in every point of the vital organism. Thus the motions of the ever- lasting suns, shot in radiant forms across the universe, reappear in the movements of organic beings. The unity of the scheme is un- broken — the harmonies of earthly life are but cadences of the ' music of the spheres.' the nature of celestial radiations. 1198. "What is said of Astronomy and Chem- istry? What does the latter teach us? 1199. Mention the suggestion of Hum- boldt. What should we see in the heavens ? What upon the earth, if we could gaze into Kha iiTing organism ? How is the unity of the scheme preserved ? 1200. CHANGES OP FOOD IN THE MOUTH 423 CHAPTEE XXYIII. ANIMAL DIGESTION. § I. Clicmges of Food in the Mouth. 1200. — Matter organized by the plant is consumed by the ani- mal to form its fabric and maintain its functions. It is to be con- verted into blood, the source upon which the whole system draws for whatever it requires ; but for this purpose food must be com- pletely transformed. No one element of diet contains all the necessary materials for the use of the adult ; various articles must therefore be mixed. Some of the elements of food are incapable of forming blood — these require to be separated. To effect these important changes in food is the great purpose of digestion^ which may be divided into three distinct and successive stages. 1201. Necessity of Saliva.— As in chemical analysis the first step consists in crushing to powder the materials to be acted upon, so, at the threshold of the digestive process, we find an admirable contrivance for crushing and reducing the food. It consists of a double system of teeth, so placed and shaped as to combine cut- ting, crushing and grinding, through vertical and side movements of the lower jaw, and made to work against each other by power- ful muscles. But no amount of mechanical action alone can liquefy solid aliment. To do this a solvent is required, and this office is performed by the saliva^ which is separated from the blood and poured into the mouth by three pairs of glands. 1202. Properties. — The salivary juice is a faintly blue, glairy liquid, readily frothing. In health it is always alkaline, from the presence of salts of soda, potash and lime, but its alkalinity in- creases during and after meals, while in prolonged fasting it be- comes almost neutral, and in some inflammatory diseases it is acid. It contains an organic principle named ptyalin, an albuminous sub- stance very prone to putrefaction. The tartar which collects upon the teeth is the residue left by evaporation of the water of the saliva, and consists of earthy salts cemented together by animal matter. What is said of food in connection with blood ? State the purpose of digestion. 1201. "What of the teeth ? What is the office of the saliva. 1202. Mention the prop- erties of the saliva. What is ptyalin ? Tartar ? 1203. Uses of saliva ? Give an 424 PHYSlOLOGICAIi CHEMISTRY. 1203. Uses. — Salira serves to lubricate the mouth and moisten the food, so that it may assume the pasty conditioa. It is indis- pensable to the sense of taste, as all food is tasteless ^hich the salira cannot dissolve. It also begins the operation of digestion. It converts starch into sugar, and sugar into lactic acid. If a little pure siarch be chewed for a short time, it "will become sweet; a portion of it has been changed to sugar. The importance of thoroughly masticating our food, especially the starchy kind, is thus apparent. Saliva exerts no digestive action upon the nitro- genous aliments. § II. Changes of Food in the Stomach. 1204. structure of the Stomach. — The masticated food is car- ried by the act of swallowing (deglutition) into the oisoi^liagus (gul- let), which conducts it downward into the stomach. This is a pouch- shaped enlargement of the digestive tnbe, with the form shown in Fig, 303. The capacity of the human stomach varies, but on an average, when moderately distended, it will hold about three pints. Its walls consist of three coats ; the outer is known as the serous membrane ; the middle consists of two layers of muscular bands, and the third is the mucous membrane^ which lines its in- ternal surface, and is of much greater extent than the outer coats. ^ „ , 1205. Mechanism of Secretion. — TVhen Fig. 301. , ,. . ^^^..^^_^ the Iming membrane of the stomach is mag- mSm wSS^-^ niSed about 70 diameters, the mucous mem- ^g^^^^ brane exhibits the honeycomb appearance SS^^^^B) seen in Fig. 301. Into these reticulated spaces ^^SSS^Bter there open little cup-shaped cavities called "^SS^MI^^P^ stomach follicUs^ which are about -^Is of an ''^r^ '^ inch in diameter. Fig. 302 represents the Inner Coat of Stomach, magnified secreting follicles from the stomach of a dog ; c a the mouths opemng upon the surface ; e f the closed tubes imbedded in the membrane below. The walls of these cavities are webbed over with a tissue of most delicate blood vessels, carrying streams of blood ; a network of veins surrounds their outlets upon the surface of the membrane, while nerves innumerable pervade the whole arrangement. 1206. The oflBcc of these follicles is to separate from the blood example of its digestive power. 1204. Describe the etomach. 1206. Explain the CHANGES OF FOOD IN THE STOMACH. 425 Stomach Follicles. the digestive fluid of tlie stomacli. This is done by cell growth. At the bottom of the cavities, in the little ^ ' Fig, 302. tubular roots, cells arise in immense numbers. Nourished by the blood, they multiply and swell until they are driven up in crowds to the surface, where they burst and deliver their contents into the stomach. 1207. The Gastric Juice is a limpid, col- orless, and always distinctly acid fluid, secre- ted by the cells of the stomach follicles. Its acidity is chiefly due to chlorohydric acid, though lactic acid is commonly present. It contains a nitrogenous body called pepsin^ or ferment substance, of which but little is known. Liebig does not consider it as a pe- culiar digestive agent, but as formed of mi- nute parts of the mucous membrane of the stomach, separated and in a state of decomposition. This substance, acted on by the oxy- gen swallowed in the frothy saliva, excites the digestive fermen- tation attributed to pepsin. The composition of the gastric juice varies in different kinds of animals, and seems adapted to different kinds of food. 1208. Its Action. — If coagulated white of egg be placed in water acidulated with chlorohydric acid, no solvent action takes place at common temperatures for a long time, though at 150° a slow dis- solving effect begins. But if a little pepsin be added to the liquid, the solution goes on actively. An ounce of water, mixed with twelve drops of chlorohydric acid and one grain of pepsin, will completely dissolve the white of an Qgg in two hours at the tem- perature of the stomach. It acts in the same manner on cheese, flesh, and the whole nitrogenous group, but has no solvent power on non-nitrogenous matter. Gastric juice, withdrawn from the stomach, produces the same effect, though by no means so rapidly as in the stomach. 1209. Peptones. — In digestion nitrogenous matters are not only dissolved, but remain dissolved. They seem to be modified in some peculiar way, and to this state the name peptone has been applied ; thus albumen produces an albumen peptone ; fibrin a mechanism of secretion. 1206. Its action. 1207. What is the gastric juice? How does Liebig regard pepsin ? 1208. Describe the action of the gastric juice. 1209. 426 PHYSIOLOGICAL CHEMISTET. fibria peptone, and casein a casein peptone — substances which continue dis-olved after the solvent is withdrawn. The presence of oily substances has been shown to be essential to the formation of these products, and therefore to stomach digestion. 1210. The quantity of gastric juice secreted is very large. The hourly destruction of fibrin throughout the system in average muscular action has been assumed as 62 grains, and it has been found that 20 parts of gastric juice dissolve one part of dry nitro- genous matter. To digest this quantity, some 60 or 70 ounces are required. It is, however, questionable whether the gastric juice is sufficient to dissolve all the nitrogenous matter required for the system. 1211. Motions of the Stomach. — The food, as it enters the stomach through the cardiac orifice. Fig. 303, is immediately sub- jected to a peculiar movement, by which it is thoroughly intermixed with the gastric fluid. This motion is produced by the alternate contraction and relaxation of the muscular bands, which produce a constant agitation or churning of the alimentary mass. These con- tractions cause the food to revolve round the interior of the stom- ach in from one to three minutes, but as chymification advances, the rapidity of the motion is increased. The combined efi'ect of the agitation and of the mingled solvent is to reduce the solid food to a unif >Tm. pulpy, semi-fluid mass called cl}yme, 1212. Limit of Stomach Digestion. — The opinion long enter- tained that the stomach is the exclusive seat of digestive changes, is now abandoned. We have seen that foods are divided into two great classes, based upon essential difi'erences of chemical compo- sition, viz. : the nitrogenous and the non-nitrogenous. This dis- tinction reappears in digestion. So difierent are these two kinds of aliment that they require totally different, nay opposite agents to dissolve them. Digestion commences in the mouth with an al- kaline liquid upon the non-nitrogenous portion of the food ; pro- ceeding to the stomach, it meets an acid ; the changes begun in the mouth are arrested; the alkaline saliva is neutralized, and action begins on the nitrogenous compounds. 1213. Absorption from the Stomach. — The liquefied food en- ters the circulating vessels by absorption, and passes into the What of peptones ? 1210. WTiat is said of the quantity of gastric juice secreted? 12U. Describe the motions of the stomach. What is cAr/me ? 1212. Is the stomach Ihe sole seat of digeation ? What of the nitrogenous and non-nitrogenous foods in THIRD STAGE OF DIGESTION. 4^7 blood. This is proved by the fact that when the outlet of the stomach is closed by tying it, water which has been swallowed disappears rapidly from the organ, and medicines act upon the system almost as promptly as under natural circumstances. In the same way portions of sugar, lactic acid, and digested nitrogenous substances, pass into the blood by absorption through the stom- ach veins. The remainder of the contents gradually oozes through the valvular opening that leads into the intestine. 1214. Why the Stomach does not Digest Itself. — To the ques- tion often asked, "Why the gastric secretion does not dissolve and digest the stomach itself, it has been triumphantly replied that the ' vital force ' of the living stomach prevents such a result. But Bernard and others have proved that the vital force offers no such resistance. On inserting the hind legs of a live frog into the stomach of a dog, through a fistulous opening, the flesh is almost as rapidly dissolved as though it did not belong to a living animal. The resisting power of the stomach is due to a sheath of mucus, and to the continuous formation of protecting cells, called epithe- lium^ during the process of digestion. § III. Third Stage of Digestion. 1215. Intestinal Digestion. — The partially digested food, dis- missed from the stomach, enters the duodenum^ or first portion of the intestinal tract, where the process is finished. The general scheme of the digestive tract is represented in Fig. 303. Into the duodenum two sihall tubes or ducts open ; one leading from the liver and pouring in Hle^ and the other from the pancreas yielding pancreatic juice, the first being much larger in quantity. 1216. The Bile is formed in the liver from the venous or dark blood, and is accumulated as gall or cystic Mle in a sac called the gall Madder. Human bile is a bitter, yellowish-green, ropy liquid, of a nauseating odor. Its viscidity is due to the presence of mucus from the gall bladder, which gives it a tendency to putre- faction. Bile contains a small proportion of nitrogen and a nota- ble amount of sulphur. In constitution it may be regarded as a species of soap — a combination of fatty acids with alkalies. relation to digestion ? 1213. IIow does food enter the blood ? State the proof. 1214. "Why does not the stomach digest itself? 1215. Describe intestinal 428 PHYSIOLOGICAL CirE:MISTRY. 1217. Ox bile consists of two resinous acids combined with soda ; the clwlic and cTioleic acids. Taurin is a highly sulphurized Fig. 303. Liver. Large intestices. Appendix of cacum. Stomacli. Spleen. Small intestine* Small intestines Digestive Tract in Man crystalline body, obtainable from bile by the action of acids. Cholesterine is a crystallizable, fatty constituent of bile, of which it forms only -pj ^oo P^^*- I^"^ i^ ^^ important as, from its insolu- bility, when once deposited, it cannot be reabsorbed. Hence, ac- cumulating in the gall bladder, it forms the chief ingredient of gall atones or liliary calculi. It is a constituent of blood and brains. 1218. The Pancreatic Fluid somewhat resembles the saliva. digeetion. 1216. What of the bile ? 1217. Of ox bile 7 Cholesterine? 1218. What THIRD STAGE OF DIGESITON. 429 It is alkaline, and rapidly changes starcli into sugar ; it serves therefore to complete the digestion of amylaceous substances. "When agitated with oil, it forms a very perfect emulsion, and un- doubtedly promotes the absorption of oily bodies. 1219. Besides the bile and pancreatic fluid, the walls of the intestine pour out an intestinal juice. By these three alkaline agents the digestion of the mouth is resumed. Starch is rapidly changed to sugar, and sugar to lactic acid. Although the secre- tions poured into the intestines are all alkaline, yet lactic acid is so rapidly produced that the intestinal mass quickly becomes acidulous. The conditions are thus furnished for the diges- tion of the nitrogenous substances that are not dissolved in the stomach. The changed food is here termed chyle. 1220. Intestinal Absorption. — Those substances which are dissolved in water in the intestines are taken up by the veins, while the oily and fatty matters, which are less perfectly dis- solved, are absorbed by a special arrangement of vessels called the lacteals ; these are extremely fine tubes, arising in the intes- tinal coats. The liquid which enters the lacteals is white, milk- like, and rich in oil. These vessels are gathered into knots or glands, so as to be greatly prolonged without consuming space. They finally gather into a tube called the thoracic duct, and pour their contents into a large vein near the left shoulder, and thu3 into the general circulation. 1221. The Blood. — The series of changes just described has for its object the preparation from the food of a nutritious fluid to supply materials of renovation and growth to all parts of the body. This fluid is the hlood and the apparatus of tubes (blood vessels) by which it is conveyed, is termed the circulatory system. 1222. In man and the higher animals, the blood is red, being of a bright scarlet when taken from the arteries, but of a deep purplish hue when drawn from the veins. It is unctuous to the touch, has a slightly resinous odor, a saline taste, and an alkaline reaction. When first removed from the body, the blood appears to the naked eye a uniform red liquid ; but when examined by the microscope it is seen to consist of two distinct parts — a clear and nearly colorless fluid called the plasma, and an immense number is the pancreatic fluid ? 1219. Explain the completion of digestion. 1220 How is intestinal absorption effected ? What of the lacteals, glands, &c. ? 1221. State the object of all these changes ? What is the circulatory system ? 1222. Describe the 430 PHYSIOLOGICAL CHEillSTEY. Fig. S04. lOeroeoopical Appearance of BioodDieca ¥iG.305^ of minute, rounded red particles floating In this liquid, whicli are known as hlood globules^ or blood cor- jju»cUs. These vary greatly in size and form in different animals. In man they are flat discs, -which have a diameter of about the 33^9 ^^ an inch, and are one fourth as thick. The corpuscles consist of a thick albuminous membrane call- ed globulin^ filled with a red color- ing matter, termed hematin^ in which iron is a large element 1223. Coagulation. After the blood has been removed from the body for a short time, it sponta- neously coagulates, separating into a dark red jelly, or dot {cras- samentum), and a pale colored slimy liquid (serum). Coagulation is caused by the change of soluble fibrin contained in blood to the insoluble state. The clot consists of fine fibrous threads, en- closing the red corpuscles, Fig. 305, It vras formerly supposed to be owing to the death of the blood, but the same effect is con- a&, fibres farmed in eoagnlated Wood; c, discs stantlvtakino^ place within entrapped in the meshes. (Magnified 280 times.) ., , . , ■,.■■% the Dody, as the hquid fibrin of the blood is deposited to produce solid flesh. As the fibrin coagulates it forms a fine network or jeUy throughout the liquid, which entangles and encloses the red corpuscles. It also contains a portion of the serum, which may be removed by pressure. The serum consists of water, albimaen, fatty matter, and various salts. 1224. Comi>osition- — This varies with age, sex, and the state of the individual. The chief constituents of the blood of man, according to Becqueeel and Eodiee, are as follows : blood. Of what does it consist? "What of the corpuscles? 1223. "What Is coag:ulationf How is it caused? 1224. What are the eonslitnents of blood? ANIMAIi NUTRITION. 431 Water, ...... 779.00 Fibrin, ..... 2.20 Fatty Matters, ..... 1.60 Albumen, ..... 69,40 Blood Corpuscles, .... 141.10 Extractive Matters, .... 6.80 1000.10 Salts, ..... 6.50 CHAPTEE XXIX. FINAL DESTINATION OF FOOD. §1. Animal Nutrition. 1225. In the present chapter we consider the final uses of food — the sequel of the course of chemical changes unfolded in the preceding pages. Plant products were divided at the outset into two groups, the nitrogenous and the non-nitrogenous. "We next found a twofold digestion conforming to this distinction, and we are now to find that this fundamental difference is observed in their ultimate uses. The nitrogenous class serves the purposes of nutrition^ the formation of structure ; the non-nitrogenous serve the purposes of respiration^ and are chiefly devoted to the produc- tion of animal heat. 1226. The Living Body a Furnace. — The living body is a reg- ulated furnace. Its constituents are combustible : a vital fire is sustained in the organism from birth to death, and the inhalation of oxygen is the draught by which it is supported. But this com- bustion must take place in such a manner that other important objects can be accomplished; while heat is to be constantly main- tained in ' the house we live in,' the structure must not be burned down in the process. 1227. Nitrogen is incombustible, and lowers the combustibility of all compounds into which it enters. Even hydrogen and phos- phorus lose their combustibility by union with nitrogen. The nitrogen of albuminous compounds, which gives them a low com- bustibility, adapts them to form the bodily structures which are to 1225. What are we now to consider? "Wliat of the distinction between the nitrogenous and non-nitrogenous bodies? 1226, How is the living body a fur- nace ? "What precaution is necessary ? 1227. How does nitrogen influence com- 432 PHYSIOLOGICAL CHEMISTRY. have a certain degree of permanence. What the iron is to the stove, the nitrogenous tissues are to the living body; they enclose and retain tiie non-nitrogenous as fuel. Both the fuel and the structure are essentially combustible; the stove 'burns out 'in time, and the bodily tissues waste continually ; but the difference between the two is sufficient for the great purposes of the animal economy. Liebig remarks : ' Without the powerful resistance which the nitrogenous constituents of the body oppose, beyond all other parts, to the action of the air, life could not subsist.' 1228. Office of Albumen.— When it was discovered that albu- minous substances are isomeric and convertible, and that they originate in the vegetable kingdom, the problem of animal nutri- tion was at once and greatly simplified. Albumen was found to be the universal starting point of animal nutrition— the liquid basis of tissue and bodily development. This is strikingly illus- trated by the process which takes place in the bird's egg during incubation. Under the influence of warmth, and by the action of oxygen, which enters through the porous shell — the same condi- tions as those which accompany respiration — all the tissues, mem- branes, and bones (by the aid of lime from the shell) are devel- oped. The foundation material from which they are all derived is albumen, and from this also originate the growth and constant reproduction of our own bodies during life. 1229. Nutrition of the Tissues. — The nutrition of the animal structures is, therefore, in a chemical point of view, a very simple process ; albumen is changed into fibrin, and fibrin to tissue. Al- bumen coagulates into a brittle mass, but fibrin, as we have seen, coagulates into tough, thread-like fibres, so that blood in which it is dissolved has been very properly called 'liquid flesh.' The re- lations of albumen, fibrin, and flesh have been aptly compared to those of raw cotton, the spun yarn, and the woven fabric. The conversion of albumen into fibrin, which commences in the lacteals and continues in the blood, is therefore a simple flesh-forming pro- cess. The product necessarily remains in a liquid state, that it may be distributed by the circulation into all parts of the system, while it gradually coagulates into muscular tissue. Cell growth is the instrumentality of change. buetibility? State the comparison. What is Liebig's remark? 1228. What is the office of albumen? Give the illustration, 1229, Define the nutrition •f animal tlssuea What comparison is used ? What of the fibrin formed, ANIlIAIi NUTRITION. 433 1230. Limit to the Nutritive Power.— There is no evidence that the living system has the power of converting one element into another. It may transmute compounds of similar constitution one into another, and it can destroy substances by a progressive series of changes, giving rise to new products at each descending step. But it can neither work upward, like the plant, nor com- bine for its own use materials that are present. The dissevered constituents of used-up tissues exist in the blood, but it is'entirely incapable of reconverting them into tissue. Nor has the body the power of transmuting the non-nitrogenous group into the nutritive, or of enabling the former to replace the latter in the exigences of the animal economy. It cannot make starch do the work of glu- ten. That nutrition consists essentially in the assimilation of al- buminous bodies, is now one of the best established principles of physiology. 1231. Yet the respiratory substances, though incapable of forming tissue, may yet essentially aid nutrition : such is the case with the fats. If the conversion of albumen into fibrin is incom- plete, the tissues are imperfectly nourished. The formation of tubercles m the lungs, which gives rise to 'consumption,' is due to this cause, as tubercular matter consists of half-formed cells and coagulated albumen deposited in the pulmonary tissue. The cause of this abortive nutrition is not the lack of sufficient nitro- genous matter to nourish tissue, but of some other principle. It has been recently maintained that it is due to a deficiency of the oily matter which is necessary for the formation of cells, and the growth of healthy structure. Cod liver oU and a free use of the fatty kinds of diet are recommended for such cases. 1232. Nitrogenous Diet.— iTone of the alimentary principles taken alone will support life ; a mixed diet is therefore required. But the proportion of the ingredients varies in different circum- stances. Severe exercise rapidly consumes the tissues, and neces- sitates a diet rich in nitrogenous principles. In childhood there is a double demand for these constituents, to supply the constant waste and promote growth. Milk, rich in nutrient matters, is the food furnished them by nature, and when replaced it should only and of cell groTrth ? 1230. State the power of the living system. Of what is it in- capable? In what does nutrition consist? 1231. What of the respiratory sub- stances? How does consumption illustrate their value? State the remedy pro- posed. 1232. What is said of the alimentarv princinles ? Of the food of children ? 19 PHTSIOIXMSlCAi CHEinsrET. hehj A generous, blood-producing diet sncli as milk, bread, meat, eggs. There is apt to occur in children a deficiency in phc^hate of lime from the rapid formation of bone, and as the articles just mentioned contaio an excess of phosphoric acid, lime water is olten a good addition to their food. 1233. Respiratory Poods.— The respiratorj principles taken into the system are either burned at once in the blood for the production of heat, or they accumulate as fsL The demand for them Taries with temperature, which depends upon season and climate. In summer, or in the tropical re^ons, where the tem- perature of the surrounding air lises nearly if not quite to blood heat (98°), there can be but slight necessity for generating heat within. Under those circumstance a diet of vegetables and fruita, with a low proportion of carbon and hydrogen, is selected by in- stinct. On the other hand, in winter or in the polar regions, where the temperature falls 100** or 150° below that of the body, a rich, heat-producing diet is required, and man instinctively seeks for fatty and oily foods. In northern regions blubber and oil are consumed in vast quantities. The greater density of the air in these cases also increases internal oxidation and the consequent heat 1234. Nntritive Value of Pood-— The first step in determin- ing this is to remove the water, which varies in amount from 10 to 98 per cent, in difierent kinds of food ; they are thus reduced to the same condition- Its nutritive value is then determined by a com- parison between the quantities of the two classes of ingredients. Bat the respiratory substances vary in heat-producing effect; 10 parts of fat equalling in this respect 24 of starch. By multiplying the fat by 2.4 it is reduced to its equivalent in starch. Thus the 9 pel" cent, of oil in Indian com is equal to adding 22 per cent, to its real Miount of starch- On the contrary, albuminous substances, whether in the form of albumen, gluten, or casein, have equal nu- tritive powers. Hence, by comparing the nitrogenous constituents of food with the respiratory, reduced to the expression for starch, we can determine the adaptation* of any article of diet to the two great functions of the living system. The following table from LiEBiG prcscDts the comparison : 12i3. Of the respiratory foodfi I How does Instmct lead n« to seiect food I 12M. Uovr ;: tie riUtnt:Te Tala« of foods determloedt Howls mOk adapted to tlie ANUIJlL i^ttrition. 435 ITutritive. Respiratory. Cow's milk contains, for 10 30 Human milk 10 40 Horse beans 10 22 Peas 10 23 Fat mutton 10 27 Fat pork 10 30 Beef » 10 17 Veal 10 1 Wheat flour 10 46 Oat meal 10 50 Rye flour 10 57 Barley 10 57 Potatoes (white) 10 86 Potatoes (blue) 10 115 Rice 10 123 Buckwheat 10 130 The above can be regarded only as an average an^ approximate statement. There is much variation in the proportions of the same class of substances, as we see in potatoes, and it must be still greater in different samples of the same kind of meat ; nor can anj such statement be relied upon as of itself a sufficient guide in the matter of diet. Still it is useful and rich in suggestions. Milk, for example, is the diet of a growing animal. It must furnish ni- trogenous material both for current waste and for increased devel- opment; hence it abounds in the curdy ingredient. But its prop- erties are admirably modified to suit special circumstances. Of all the young of the animal- world, none lead so quiet a life, or advance so slowly to maturity, as the human infant ; therefore hu- man milk is less rich in muscle-forming constituents than that of animals — the cow, for example, whose yoimg develop more quick- ly, and exert themselves much earlier. 1235. Metamorphosis of Tissue — Some substances have the power of influencing tissue changes without properly participating in them. Some increase metamorphosis ; others check it. Com- mon salt, for example, and an excess of water, act as hasteners of transformation, while alcohol and tea act as arresters of change. If we consume those substances which augment waste, it is said we require a fuller diet to compensate for the extra loss, or the body declines in weight with more rapidity than otherwise. But if we employ the arresters of metamorphosis, we save tissue, 3-oung ? 1235. How do diflferent substances influence physiological changes ? What is the effect of water and salt ? Tea and alcohol ? 1236. Why does the eys- 436 PHYSIOLOGICAL CIIEMISTEY. and can maintain our usual strength and weight on a more slender diet. The subject requires further elucidation.* § II. Respiration and Circulation. 1236. Destructive Force in the Systgm. — Separation of the body implies its waste ; nutrition presupposes destruction. Ali- ment is constantly supplied to the system, because it is constantly consumed. The tissue is the seat of a kind of polarity ; waste and supply in the healthy adult are equal and opposite forces. 1237. — As the body does not increase in weight, though mat- ter is constantly added to it, the destructive process going on within must be sufficiently active to use up and carry away the sanae amount of matter that is supplied through the channels of nutrition. The source of this perpetual waste and destruction is the act of respiration^ by which air is brought into contact with every portion of the animal fabric. 1238. Nature of Respiration — The relation of animals to the atmosphere is of the most direct and vital nature. All the pecu- liar processes which take place in the animal structure and which we call life^ are set in motion and kept in motion by atmos- pheric oxygen. Its effect is exerted upon the body through the medium of the respiratory organs. The action of oxygen is exactly of the same nature in all animals ; but the structure and arrange- ment of the respiratory mechanism differ according as they are destined to be acted upon by oxygen in the condition of a gas, or in a state of solution in water. Animals inhabiting the water have their breathing organs outside the body ; in air-breathing animals they are within. In marine animals they are termed hroncMa or gills, and are composed of feathery filaments, or tufts of blood vessels, situated externally, so as to be acted on by air contained in the water. The higher animals respire by lungs, which consist of membranous bags lodged within the body. They contain mil- lions of air cells, which are connected with the atmosphere by the * For a mnch more cxtendecl discussion of the physiological eflects of food, Iho ■tudent is referred to the author's " Household Science." ( tern require food ? What of its forces ? 1237. What is the extent of the destructive force ? Its source ? 1238. What ia the relation of oxygen to life ? Its medium ? How do the respiratory organs difl'er? Describe the gills. Lungs. 1239. How RESPIEATION AND CIKCULATION". 437 trachea and its brancliings, and are surrounded by a delicate mem- brane many times more extended than the surface of the body. 1239. The lungs completely fill the cavity of the chest, so that, by the alternate expansion and contraction of the surrounding walls and floor, they are correspondingly enlarged and diminished in size. The contractile pressure of the chest drives the air out (expiration), and when the muscles are relaxed, the external pres- sure of the atmosphere forces it back again {inspiration). Pulmonai-y Vein. Left Auricle. Left Ventricle. Aorta. Ideal view of the Circulation in Man. 1240. Circulation. — Air, entering the lungs, fills and distends the numberless little air cells. The enclosing membrane is over- spread "uith the finest network of capillary blood vessels. Pene- do the lungs act in breathing? 1240. Describe the process of circulation. What 438 PHYSIOLOGICAL CHEMISTPwY- trating the membrane, oxygen enters the blood, and, imparting to it a bright crimson color, rushes forward with it toward the heart. From the heart the blood passes througb the arteries to all por- tions of the bodj. These arteries divide and subdivide until they are reduced to the finest tubes, which are densely interlaced through all parts of the body. As they are distributed through the system, they are called systemic capillaries. In these vessels the oxygen is changed to carbonic acid, and the arterial blood to venous blood. Passing forward, it is gathered into the veins, re- turned to the heart, and then driven back to the lungs. Here the carbonic acid escapes through the membranes into the air cells ; it then diffuses into the bronchial passages and is expelled into the air. 1241. Fig. 306 is an ideal representation of the double circula- tion in man. The fine lines at the top represent the capillaries of the lungs; and at the bottom those of the^ general system. The double circulation is shown, and its relation to the heart. The vessels on the right side represent the arteries carrying blood charged with oxygen, and those on the left side the veins convey- ing carbonic acid. 1242. Oxidation throughout the System.— It was formerly supposed that oxygen combined with carbon and hydrogen directly in the lungs, but it has been proved that animals respiring pure hydrogen or nitrogen continue for some time to exhale carbonic acid. A frog was placed in a jar of hydrogen over mercury, and continued to expire carbonic acid for eight hours, thus showing that the changes do not take place immediately in the lungs, but throughout the system, and are due to oxygen previously absorbed. The physiological changes proceed so slaggishly in rep- tiles that they will live long in conditions of the atmo- sphere which, would bo quickly fatal to higher ani- mals. FiQ. 307. Capillar: vesselfl of the Liver. are the systemic capillaricB ? What are the further changes ? 1241». What docs Fie. 306 illustrate ' 1242. Where was oxidation formerly supposed to take pliic." ? What does the exi-criment with the frog prove ? What of reptiles ? 1243. Wli.it RESPIRATION AND CIRCULATION. 439 1243.— Iq the fine blood vessels distributed throughout the body, oxygen is constanily changed to carbonic acid, and arterial to ve- nous blood. The minuteness of these vessels is surprising. They are termed capillary, or hair-like, but they are far smaller than hairs. Fig. 807 shows the densely crowded blood vessels on the surface of a rabbit's liver, magnified eleven times. Through tliese won- drously fine tubes flows the vital stream, bring' ug the materials of nutrition, bearing away the products of waste, and itself inces- santly changing as it presses on. 1244. Conveyance of Oxygen. — In what manner the blood takes up the oxygen and transports it, is not so clearly seen. The absorbent power of its water is insufficient. Liebig's suggestion that the iron of the blood is the carrier, is unsatisfactory. The blood discs are the agents of transportation, and it is probable that they hold the oxygen in a peculiarly loose condition of union, sur- rendering it at all points to enter into other combinations. 1245. Gases Absorbed and Exhaled. — Abut 5 per cent, of the oxygen inhaled is absorbed by the blood. When oxygen combines with carbon, the bulk of the carbonic acid formed is exactly equal to that of the uniting oxygen. If, therefore, all the oxygen taken into the system were converted into carbonic acid, the a,mount of tiiis gas exhaled would just equal the oxygen in- haled. But this is not the case. The expired breath contains on an average about one seventh less than the absorbed oxygen. This deficiency combines with h"ydrogen, and appears in the breath as exhaled watery vapor. The bulk of the expired air is greater than that inhaled, owing to the presence of moisture and its high temperature. 1246. The average amount of air inspired and exhaled at each respiration is 30 cubic inches, and the average number of respira- tions 20 per minute, so that 500 cubic feet of air pass through the lungs in 24 hours. The amount of carbonic acid exlialed is variable, and is interestmg as the index of the rate of internal change. The more energetic the circulation, the larger the quantity of carbonic acid ; it is less during sleep than while awake, and less during fasting than after a full meal. 1247. How the expired carbonic acid may be measured is shown processps go on in the capillaries? Ho-w is their minuteness shown ? 1244. How is oxygen probably conveyed ? 1245. "What of the gases absorbed ? Of those exhaled ? 1246. How much air passes through the lungs in 24 hours ? What of the amount of 440 PHYSIOLOGICAL CHEMISTRY. in Fig. 808. A bird is placed in a bell glass, A, wbicb stands over mercury, i? is a vessel of Tvater Tvhich establishes a current of air through the apparatus as its water flows out. The tubes 1 and 2 contain pumice stone-moistened with potash, which absorbs all the carbonic acid from the entering air. The bulbs, C, contain lime wa- ter, and the foct that it remains clear proves that the air enters the bell glass free from carbonic acid. The air which the bird expires FiG. 308. Measuring the Carbonic Acid exhaled by a Bird. is drawn throngh the bulbs, i), containing lime water or potash, which had been carefully weighed. The carbonic acid exhaled by the bird is absorbed, and if the bulbs are again weighed after a given time, they indicate the amount of CO, exhaled by the bird. 1248. The Discovery of the Circulation was made upward of two hundred years ago by Dr. Haevet, but of its cause he had no true idea. This could not be known until the microscope was perfected, the capillary mechanism explained, and the sciences of chemistry and molecular physics developed. In the absence of real knowledge, the circulation of the blood has been ascribed to the drawing and driving actioij of the heart. 1249. Office of the Heart.— "While it is admitted that the im- carbonic acid exhaled. 1-247. How is it measured ? 124S. "Wl.at of Dr. Harvkt in relation to the circulation of the bloo J ? WTiat -was necesr^ary to explain its cause ! To wliat has it been ascribed ? 1249. To what degree does the heart move the RESPIRATION AND CIRCULATION. 441 pelling action of the heart moves the hlood through the large tubes, it is equally certain that it cannot drive it through the capillaries : the force which acts liere is the real cause of the cir- culation. There are animals destitute of a heart, but still with a definite chculation. Fishes have no heart on the arterial side be- tween the lungs (gills) and the systemic capillaries. The heart is introduced into the mechanism of the higher and rapidly acting animals as a regulator^ rather than a motor : it is the beating pen- dulum ; the falling weight is to be sought in the capillary system. 1250. Theory of the Circulation.— Dr. Deaper has given an explanation of the causes of the circulation of the blood on physical and chemical principles, and brought us nearer to a final solution of this interesting problem than any former investigator. We have seen how fluids rise in tubes by wetting their sides. When two liquids meet in a tube with unequal aflSnities for its walls, the one having the highest attraction will drive the other before it. The arterial blood is charged with oxygen which has a high aflin- ity for the walls of the capillary tissues. As the oxygen enters into combination with the materials it meets with, its aflBnity is satisfied, and arterial is changed to venous blood, which is driven forward by the constant pressure of the arterial current behind. The circulation is thus immediately due to respiration. Dr. Dra- per applies the same principle to the flow of sap in plants. Water of the soil, entering the rootlets and rising through the trunk and branches by osmose, passes into the leaf, and is there digested. The new gummy, or colloid product has less aflSnity for the walls of the tubes and tissue, and is constantly pushed forward by the freshly arriving sap. For illustrations of this view, see Draper's Human Physiology. 1251. Influence of Air. — From the foregoing considerations it will be seen that the influence of air is all controlling over the hu- man constitution ; it is the first condition of vital acti\dty — the immediate impelling power of life. Any one of its elements breathed alone would be fatal ; any other proportions would be dangerous, but mingled as they are, how bland, how balmy, how salutary they become ! It presses upon us with the weight of tons ; bathes the sensitive passages, distends the filmy mem- blood ? Where is the seat of chief action, and how proved ? What is the function of the heart? 1250. What is said of Dr. Draper's theory ? Explain it. How is it elsewhere applied ? 1251. What is said of the influence of air ? 1252. What is stated 19* 442 PHYSIOLOGICAL CHEMISTRY. branes of the air cells, and flashing through into the blood, is swept forward to the inmost depths of the system, corroding and con- suming in its progress the living parts ; and yet with such mar- vellous delicacy are all these things accomplished, that we re- main profoundly unconscious of them. Science has shown that there is a deep life-import in these never-ceasing rhythmic move- ments of inspiration and expiration, but it can add nothing to the simple grandeur of the primeval statement that the Creator ' breathed into his nostrils the breath of life, and man became a livins: soul.' § III. Production of Animal Heat. 1252. All Animals produce Heat. — If water containing animal- cules be gradually frozen under a microscope, the last drops seen to congeal are those which surround tlieir bodies. From this point upward, each class generates an amount of heat peculiar to itself. The temperature of the human body may be ascertained by placing the bulb of a delicate thermometer under the tongue, but to meas- ure more minute quantities of animal heat than this instrument can detect, the thermo-electric couple is employed. The action Fig. 309. Galvanometer for measuring Animal Heat. of the latter instrument has already been described. In Fig. 809 i^ represents an iron needle bent at the ends and soldered to cc, copper wires which are connected with a galvanometer G. As long as both points are at the same temperature the needle re- mains at rest ; but it moves when the heat of one exceeds that of the other. It was desired, for example, to compare the tempera- ture of a living and a dead insect. Each was fixed on a stick d d^ Fig. 310, planted in the earth of a flower pot a. The needles were of animal heat ? How Ih it mcapnred ? 1253. What is said of tho heat of the hu- PRODUCTION OF ANIMAL HEAT. 443 Fig. 310. then thrust into corresponding parts of the living and dead insect, when the motion of the galvanometer indicated the difference of their tem- peratures. 1253. Temperature in Man.— The heat of the human body varies but slightly from 98° the world over, though the external temperature changes daily and hourly, while the variation from latitudes and seasons is very great. The extremes of equatorial midsummer land arctic midwinter embrace a range of more than 200°, yet through all these thermal vicissitudes the body of a man in health deviates but little from the constant normal of 98°. 1254. — In view of these facts it has been maintained that the living body Meaeuring the lieat of insects, has some vital, mysterious, internal defence against the influence of external agents. But this is erroneous. It is a heated mass which has precisely the same relations to surrounding objects as any other heated mass. When they are hotter than itself, it receives heat ; when they are colder, it loses heat, and the rate of heating or cooling depends upon the difference between the tem- perature of the body and that of its surrounding medium. But in nearly all circumstances the temperature of the body is higher than the objects around it ; hence, it is almost constantly losing heat by radiation, conduction, and evaporation. 1255. Nervous Agency.— Animal heat has been ascribed to nervous agency, but such an idea is clearly disproved by what takes place in plants. There are two marked periods in the life of a plant in which it exercises the heat-evolving function, and becomes independent of surrounding temperature. This occurs in the germination of 'seeds and in flowering. A thermometer placed in a bunch of arum flowers rose to 121°, when the tem- perature of the air was but 60°. As plants have no nervous sys- tem, the effect in this case cannot be due to nervous action. The mnn body? 1-254. How has it been accounted for? "What are the facts in the case? 12.5.5. To -what else has animal heat been ascribed? "What disproves this view? How la' it related to the nervous system? 1256. To what is plant heat 444 rHYSIOLOGICAL CHEMISTRY. production of heat in the animal body is under the control of the nervous system probably in the same way that the fire that drives the steam engine is under the control of the fireman. 1256. Cause of the Plant Heat. — In both of the cases referred to there is an absorption of oxygen, which unites with the sugar of the flower and the oil of the seed, and a liberation of carbonic acid in exact proportion. That the heat is due chiefly to oxidation is proved by the fact, that when no oxygen is present, heat is not evolved ; whereas, if pure oxygen gas is employed, the liberation of heat is more rapid than nsual. 1257. Cause of Animal Heat. — The union of oxygen with car- bon and hydrogen is a source of heat under varied conditions. We can combine them in no way without producing heat. The animal body inhales oxygen and exhales carbonic acid ; there has therefore been a union, and that union must have produced heat- Here is a real cause, and one adequate to account for nineteen twentieths of the heat generated in the body. Muscular and ner- vous action produce heat, and this may probably explain the source of the deficiency. 1258. Effect of the Rate of Respiration. — The amount of heat generated in an animal is strictly connected with its rate of respi- ration, and the amount of oxygen it absorbs. In reptiles and fishes the structure of the respiratory organs is such that but a small proportion of oxygen is taken into the system. The quan- tity of heat produced is therefore small. Their temperature rises and falls with that of the surrounding medium, and is never but little above it ; hence they are called cold-llooded animals. Tlie respiratory mechanism of birds, on the contrary, is on a most per- fect plan ; it works rapidly, and their temperature is consequently maintained at a high rate, from 100° to 112°. Infants breathe more rapidly than adults, and their temperature is several degrees higher. 1259. Hibernation.— The most striking illustration of the in- fluence of respiration over bodily heat is seen in the case of those animals which pass the winter season in a state of profound sleep, or torpor (Jdhernation). In this condition the breathing becomes chiefly due? IT ow proved ? 1257. How do you acoonut for animal heat ? What of muscular and nervous action ? 1258. With -what is the heat connected ? "Why are reptiles and fishes ' cold-blooded ?' What of birds and infants? 1259. What docs hibernation illustrate ? Describe the state. Give some facts iu regard to hi- PRODUCTIOX OF ANIMAL POWER. 445 very slow, the imperfectly oxygenated blood flows sluggishly through the heart, and the heat of the animal falls, it may be, al- most to the freezing point. The marmot, in summer, is warm- blooded ; but as it passes into hibernation, the number of respira- tions falls from 500 to 14 in an hour, the pulse at the same time sinking from 150 to 15 per minute. An animal in hibernation has been placed in an atmosphere of pure carbonic acid and remained there four hours without injury, while if thus treated in its active condition, it would have perished instantly. 1260. Spontaneous Combustion. — There has long prevailed an opinion that the living body, under some circumstances, might take fire and be more or less completely consumed, and many cases of this kind are on record. Liebig, however, has demonstrated the impossibility of any such result, and affirms that no amount of fat, alcohol, or phosphorus which the living body could possibly contain, would render it combustible. Upon examination, the alleged instances of spontaneous combustion were found to be in' no case entitkd to credence. § lY. Production of Animal Poioer. 1261. The amount of thermal force generated annually in the body of an adult man is sufficient to raise from 25,000 to 30,000 lbs. of water from the freezing to the boiling point. All the acts of the body, every motion, utterance, breath, or thought consumes force. "We make about 9,000,000 separate motions of breathing in a year; thereby inhaling and expelling 700,000 gallons of air. At the same time the heart contracts and dilates 40,000,000 times — each time with an estimated force of 13 lbs., while thou- sands of tons of blood are annually driven through the heart and general system. Besides these involuntary acts, the organism gen- erates force for a thousand forms of voluntary, physical action. A healthy laborer is assumed to be able to exert a force equal to raising the weight of his body through 10,000 feet in a day. 1262. Rate of Physiological Change. — Corresponding to this activity is a high rate of internal change. The^iving body is like bernation, 1260. "What is said of spontaneous combustion 1 1261. How mncrh heat does a man annually produce ? How many motions of breathing ? What amount of air does he respire ? How many motions of the heart does be make? How much force can a laborer exert ? 1262. What amount of food does a man con- 446 PHYSIOLOGICAL CHEMISTRY. a waterfall ; while it appears an unvarying form it is yet composed of particles in a state of swift transition. A man consumes in a year 800 lbs. of solid food, the same amount of oxygen, and about 1,500 lbs. of water — or altogether a ton and a half of matter. Chossat ascertained the waste in various animals to be an average of 2V of their weight daily, and Schmidt determined it to be, in the case of the human being, ^'3 of the weight. JonxsTON says : ' an animal when fasting will lose from y\ to ^V of its whole weight in 24 hours'. The waste proceeds so rapidly that the whole human body is believed to be renewed in an average period of not more than 30 days — the man of eighty ye:irs has therefore shifted the substance of his corporeal being nearly a thousand times! 1263. Force Accompanies Change. — In the exercise of func- tional power, parts waste and are ever renewed. In all the deep- est recesses of the body, in every elastic muscle and 'conducting nerve, and even in the thinking brain, myriads of atoms are con- 'stantly dying and being replaced. As soon as we begin to live and act, we begin to die. The decomposition is in proportion to the activity. Muscles are rapidly changed, and are always more or less acid from the oxidized products in their substance. It has been fully proved by G. Von Liebig that muscles absorb oxygen and exhale carbonic acid as long as their contractility lasts. With the exercise of a muscle, blood is urged toward it ; if the current is stopped, it is paralyzed. So also with the nervous system ; brain power is dependent upon cerebral transformations. Indeed changes go forward more rapidly in the brain than in any other part, and, while cerebral exercise increases the brain ward flow, an arrest of the circulation, but for a moment, as in fainting, produces unconsciousness. 1264. Force the Result of Change. — It was formerly held that the body acts by virtue of an inherent 'vital property,' and that the changes which go on within it are coiisequences of its ac- tivity. This idea was but natural. As Mr. Hinton suggests, if man had first met with steam engines in nature he would have supposed them endowed with a peculiar ' active property,' which . ^ eume annually? How much oxygen ? Water? In what time does the material of the body chnnere? What is said of a man of eighty ? 1263. What is the effect of exercise? Wliat is the rato of decomposition? The condition of muscles? What has Liebig ])roved ? What is said of cerebral changes? 1264. Wliat was formerly held concerning the action of the body? How is this illustrated by the PEODUCnOX OF ANIMAIi POWER. 44*7 caused their movement, and when afterward the expansion and contraction of the steam was discovered, it would have heen looked upon as the result of the 'inherent activity,' and not as its cause. It was thus with the animal organism; it was studied backward, and effects taken for causes. But science has shown that molecular changes are the causes, and not the con- sequences of its activity, and that in this respect the living body is analogous to the steam engine and the galvanic battery. In the steam engine, power results from the oxidation of fuel ; in the voltaic battery, from the oxidation of zinc; in the living body, from the oxidation of food and tissue. 1265. The barbarian explains mechanism by supposing the machine to be alive. ' It died last night,' exclaimed the China- man in triumph, upon selling the first watch he had ever seen. It is only when we begin to discover the beautiful unity of Nature's plan that we reverse the primitive notion, and discover the living system to be a divinely constructed machine, adapted to the uni- versal economy of N'ature's forces. It is not strange that men were long in perceiving the mechanical relations of the livii;g sys- tem, as it is so unlike all other machines in the conditions of its action. It consumes itself and repairs itself. ' It is as if the wheels of the steam engine were made of coal, revolved by their own combustion', and*grew as fast as they were consumed. 1266. Analogies of the Living Body and the Steam Engine. — These have been traced, in several interesting particulars, as follows : THE STEAM ENCnSTE IN ACTION TAKES- THE ANIMAL BODY IN LIFE TAKES— 1. Fuel— Coal and wood— both com- 1. Food— Vegetables and flesh — bustible. both combustible. 2. Water (for evaporation). 2. Wateb (for circulation). 3. Air (for combustion). 3. Air (for respiration). AND PRODUCES— AND PRODUCES— 4. A steady boiling heat of 212° by 4. A steady animal heat of 0S° by quick combustion. slow combustion. 5. Smoke, loaded with carbonic acid 5. Expired breath, loaded with car- and watery vapor. bonic acid and watery vapor. 6. Incombustible ash. 6. Incombustible animal refuse. Bteam eugine ? To what is the living hody analoscus in respect to power ? 1265. How does the barbarian explain mechanism? When is the opposite view discov- ered? Why were not the mechanical relations of the body not earlier perceived? What is the mechauical peculiarity of the body ? 1266. Mention some points of 448 PHYSIOLOGICAL CHEMISTIIY. 7. Motive force of simple alternate 7. Motive force Of simple alternate push and pull in the piston, contraction and relaxation which, acting through wheels, in the muscles which, acting bands and levers, does work of through joints, tendons, and endless variety. levers, does work of endless variety. 8. A deficiency of fuel, water, or 8. A deficiency of food, drink, or air, first" disturbs and then air, first disturbs and tlicn stops the motion. stops the motion and the life. 1267. Source of Animal Power. — Like all other machines, the living body cannot create power ; it can only convert and use the stored force of food. The organic spring that was wound up in the plant is relaxed in the animal system, and gives out its force as animal power. And here, under the most complex con- ditions, we still trace the operation of the great law, that with definite material changes are associated determinate quantities of force. . Moreover, we see how the great dynamic scheme of nature is consummated in animal life. Its apparatus is designed for the expenditure of power. The strong, bony system is framed in parts to admit of free motion ; its hundreds of muscles are the instruments of action ; its circulatory system is the fountain of force,' and its nervous system binds all into a unit for effective effort. The energies of the universe are then gathered aiul poured through it for the accomplishment of the purposes to which it is destined. 1268. We have seen that the vegetable kingdom constitutes a fourth reservoir of stored force in the plan of nature (1176). Pro- fessor Dana holds that the animal is the fifth and highest form of ' magazined power.' From the immutable or slowly-changing granite we rise through more and more changeable forms of matter, solid, liquid, gaseous, organic, and reach the summit of the scale in the human brain. Dynamically, the rock and the brain are nature's opposite poles. The brain is formed of the most un- stable materials, consisting of four fifths water, through which is diffused the cerebral tissue, with a large proportion of uncoagu- lated albumen, phosphorized oils, and other changeable sub- stanties. So rapid are its transformations, that though but ^\ the weight of the body, it receives from \ to j\ of all the blood driven from the heart, to maintain its normal waste and repair. We are analogy l)etween the liviig body and the steam engine. 1267. What is the eourco of animal power? How is the animal body related to the universe? Explain (he action of its parts. 1268. How are animals placed in regard to power ? What are the opposite extremes of power ? Slate the composition of the brain. Its weight. CYCLES OF OEGANIC NATURE. ' 449 to conceive of the brain, therefore, less as a stable organ than as a torrent of change, mind being linked not properly with matter, but with matter in motion^ or in the highest physiological con- dition of power. CHAPTER XXX. CYCLES OF ORaANIC NATURE. 1269. That matter changes its form and is put by nature to a succession of uses has long been vaguely understood. Science has given precision to the idea and unfolded a mighty scheme of circu- lations and compensations by which the balance and harmony of terrestrial affairs is maintained. • 1270. Circulation of Water. — The equilibrium of the world of waters is preserved by a vast system of circulations ; whenever there is movement in one direction, there is counter movement in the opposite. From the surface of sea and land water is rising incessantly by evaporation into the air, but it all descends in the forms of rain, dew and snow, to be again elevated, and again to descend, perpetually. 1271. The rivers which flow into the sea correspond to rivers of vapor in the air moving in opposite directions. The water which is decomposed by the plant, and, ministering to its trans- mutations, is deposited in its structure or its products, is repro- duced by the animal, and by the processes of combustion and decay. Thus the waters are carried round in constant circles of distilla- tion and condensation, of decomposition and recomposition, and through this perpetual doing and undoing, the economy of the world and the order of life are maintained upon the planet. 1272. Circulation of Carbon. — In the form of carbonic acid this element is withdrawn from the air by plants, and as they slowly decay or rapidly burn, the carbon is again resolved into carbonic acid and restored to the atmosphere. If the vegetable matter is consumed by animals, a like result takes place through their respiration and decay. The same interchange goes on in the sea, for it mmst take place wherever there is life. There is a Its blood supply. How associated with mind? 1269. What has science unfolded ? 1270. How is water kept in circulation ? 1271. Describe its change^ 1272. How 450 PHYSIOLOGICAL CHEMISTRY. marine vegetation so near the surface of lakes and oceans that it may be acted on by light ; it absorbs carbonic acid from the water, decomposes it, and fixes its carbon. Aquatic animals consume it and give back carbonic acid by respiration to the watery medium. 1273. The time required for the complete revolution of these chemical wheels varies almost infinitely. We may consume fruit in which the formative processes are actively going on, and its sugar will be exhaled from the lungs as carbonic acid, and again absorbed by the leaves in perhaps an hour's time. On the other hand, the carbon of the coal beds, after slumbering in the earth for ages, is but to-day brought forth to be restored as carbonic acid to the air. 1274. Again, many tribes of marine animals form coverings of lime and carbonic acid which, accumulating in the course of time at the bottom of oceans, are converted into beds of shelly limestone. In the warmer parts of the ocean, little insects are also busy absorbing the same constituents from the water and building up coral reefs which are thousands of miles in extent. But is not the carbonic acid absorbed by the ocean, and thus, ap- propriated by its animals, chained down forever in the forming rocks? So it might well seem did we not know that the eternal law of nature is not fixity, but change. The balance that seems lost is still preserved, for carbonic acid, liberated in the depths of the earth from unknown sources and by processes we can but ob- scurely trace, is everywhere rising to the surface. By myriads of springs, by volcanoes, both active and extinct, in thousands of caves and hollows, in cellars and wells, and from all the soil over vast tracts of country, carbonic acid, in incredible volumes, is being continually set free and poured into the atmosphere. 1275. The marvellous perfection and delicacy of these adjust- ments become more striking when we consider how small an amount of carbon the air contains (570). Notwithstanding the prodigious quantities that are poured into and withdrawn from the air, this small and precise proportion remains unaltered from age to age. Two hundred million tons of coal are now annually con- sumed, producing six hundred million tons of carbonic acid. A century ago hardly a fraction of this amount was burned, yet the is carbon circulated upon land ? Upon the sea ? 1273. What of the time required for these changes ? 1274. How are beds of shelly limestone and coral reefs form- ed ? In -what way is the balance preserved ? 1275. What is said of the amount CYCLES OP ORGANIC NATURE. 451 enormous supply lias not sensibly disturbed the proportion of this gas in the atmosphere. 1276. Circulation of other Elements. — In the same manner oxygen and nitrogen are in perpetual movement. Oxygen enters the plant in a state of combination ; it is set free, is absorbed by the animal, combines with its carbon and hydrogen, is returned to the atmosphere, and reentering the plant, goes the rounds again and continually. Nitrogen, taken into the plant as ammonia, is converted into gluten, albumen, &c., and then, becoming the food of animals, is wrought into their structure. Decomposed and re- jected from the animal system, it is again ready to enter the plant. Thus, the antagonism of offices between plants and animals, which maintains the equilibrium of life, is complete. They may be con- trasted in their leading functions as follows : THE VEGETABLE THE ANIMAL Absorbs carbonic acid from the air. Returns carbonic acid to the air. SuppUes oxygen to the atmosphere. Withdraws oxygen from the atmos- phere. Decomposes carbonic acid, water, and Produces carbonic acid, water, and ammoniacal salts. ammoniacal sah-s. Produces the organic principles of Consumes the organic principles of food. food. Endows mineral matter with the prop- Deprives organic matter of the prop- erties of life. ertie? of life. Imparts to chemical atoms the prop- Deprives chemical atoms of the prop- erty of combustibility. erty of combustibility. Imparts to chemical atoms the power Imparts to chemical atoms the power of nourishing the animal. of nourishing the vegetable. Converts simple into complex com- Converts complex into simple com- pounds, pounds. Is an apparatus of deoxidation. Is an apparatns of oxidation. Is a mechanism of construction. Is a mechanism of reduction. Absorbs heat and electricity. Produces heat and electricity. 1277. And the ethereal atmosphere, so light, so mobile, so at- tenuated that it seems almost to connect the worlds of matter and of spirit, is the grand theatre of these mighty reactions. It is at once the fountain of life and the source of death. From its serene and inscrutable depths come the mysterious processions of living beings which crowd the earth, and it is the great sepulchre to which they all return ; it has received the disrupted and scattered elements of carbon in the air ? 1276. Describe the changes of ox3-gen. Of nitrogen. Men- tion some of the points of contrast between plants and animals. 1277. What ia 452 PHYSIOLOGICAL CUEMISTRY. of the dead of past generations, and is houjly gathering to itself the living of the present. 1278. Nature a Strict Economist.— Thus the beautiful and the unsightly, the noxious and the pure, the great and the small are all mingled together, and the same materials are perpetually going their rounds of service. The air we breathe and the water we drink to-day have been breathed and drunk a thousand times be- fore. ' Xo material is wasted, no force spent in vain. 1279. In nothing is the economy of nature more manifest than in the connection of the animal races. Matter and force are not suflered to run to waste by the death of animals which feed upon plants. There are flesh eaters of all grades, from man to the micro- scopic infusoria, some of which destroy and eat, while others con- sume only the decomposing dead. The putrefaction of animal car- casses would be oifensive and dangerous, and so numberless insect tribes are provided, the larvaa of which devour the decomposing mass, and are themserves eaten by larger animals. In the aquarium, which is a miniature organic world, plants feed animals and ani- mals feed plants ; but there must be flesh eaters, for if an animal is left to decay, the water becomes foul, and life is arrested. 1280. Death Essential to the Order of Nature.— Life and death are thus bound up indissolubly in the plan of nature. Each implies the other ; they are the opposite and equal arms of the or- ganic balance. The death of living parts begins with life, and is essential to life. ' The creation of a plant was the simultaneous institution of life and death — the establishment of an incoming and outgoing stream to be in constant flow as long as the king- doms of life should last. Vegetable and animal life and death are but parts of one idea involved in a single primal plan.' (Daxa.) 1281. The Course of Change Irresistible. — Nor is man able to arrest the onward course of natural changes, nor by any arts can he long withdraw the lifeless forms from the resistless cur- rents of circulation. In petty egotism he wraps the bodies of the dead in resinous swathings, and places them in massive mauso- leums, so that for hundreds, perhaps thousands of years, they may be kept from mingling with the restless elements ; but Time at the theatre of all these changes ? 1278. "What of nature as an economist ? 1279. Explain her economy in regard to animals. "Where ia it iiliistraled ? 12S0. "What are the mutual relation8X)f life and death ? 1281. "What is beyoud our power ? Ex- CYCLES OF ORGANIC NATUKE. 453 last, in his endless vicissitudes, enters the tomb, and restores the forgotten mould to the moving world from whence it came. 1282. Matter to be Kept Moving.— But though man caunot arrest the course of nature, he nevertheless has a control over its changes of the highest importance to himself and to society, and which involves very grave responsibilities. Air and water, the great media of circulation, when they have been used, are designed to pass on ; we have no right to them beyond their transient em- ployment. They are ours to-day, but to-morrow they belong to all. If we detain and suffer them to stagnate around us, they become the fruitful instruments of disease and death. The very qualities which make them serviceable render them also dangerous. They dissolve various ingredients, which are essential to life, or may become charged with noxious agents, which are fatal to it. Na- ture avenges herself by inflicting fearful penalties upon individuals and nations who tamper with and violate her laws. The great epidemics, the consuming fevers, the desolating plagues are divine admonitions to the wise that the ordinances of nature are not to be violated with impunity. 1283. Conclusion. — And thus our studies lead us to a new perception of that sublime lesson of science — the Unity of the Universe. The revolutions of the celestial orbs are paralleled by the ^ver-recurring cycles of matter upon earth ; while the energies in action obey in both cases the same beneficent but inexorable laws. It is the glory of Astronomy to have shown that the har- mony of our planetary system is maintained by the eternal war of hostile forces, which by their mutual counteraction keep the heavenly bodies in their circling paths. Chemistry has shown that this great principle is not limited to the field of celestial mechan- ism, but that it operates also upon earth, and governs the king- doms of terrestrial life. Here too there are conflict and counterac- tion—the omnipresent antagonism of warring forces resulting in the harmony and stability of the living world ; another illustration of that unity of design and harmony of action throughout the universe which proclaim the government of One Intimte Mixd. ample. 1282. How are air and water to be regarded ? What results from their de- tention? Examples. 1283. What great lesson are we taught by Science? What has Astronomy proved ? How has Chemistry extended this great principle ! PRONUNCIATION OF SOME TECHNICAL WORDS AND PROPER NAMES USeC IN THIS WORK. TECnj^ICAL WORDS- A9'-e-tate. A-9et'-ic. A-ge'-tous. A-con'-i-tinc (-tin). Al'-de-hyde {-hyd). Al-lo-trop'-ic. Al-lot'-ro-pism. Al-u'-mirnum. A-myl'-ic. An-ses-thet'-ics. Ar'-a-biu. "A-ther'-mic. A-toin'-ic. Bas-so'-rin. Bl-nox'-ide {-id). Bo-rag'-ic. Bro'-mine {-min). Brucia (Bru'-she-d). Bu-tyr'-ic. Caf-fe'-ine {-in). Caoutchouc {Ko-chooTc'). Cap'-il-la-ry, or Ca-pil'-la-ry. Cap'-ro-ic. Cholesterine {Ko-les' -ter-in). Chlorine {Klo'-rin). Co'-balt, or Cob'-alt. Col-loid'. Chry-oph'-o-rus. Di-al'-y-sis. Di-dym'-i-ura. Di-e-thy'-la-mine {-min). Er-e-ma-cau'-sis. E-lec-trol'-y-sis. E-thv'-la-mine {-min). Eth'-yle (-^0- Flu'-o-rine {-rin). Glu-9i'-nura. Guaiacum {Gwc-ak' -um). GlyQ'-er-in. Hel-i-och'-ro-my. Hip-pu'-ric. I'-o-dine {-din). In-ter'-sti-ces. I-som'-er-ism. I-so-mor'-phism. Lan'-tha-mum. Lith'-arge. Lith'-i-um. Mate {Mah'-ta). Mer-cap'-tan. Mor'-phine {-phin), Mol'-e-cule. Mo-lyb-de'-num. Nic'-o-tinc {-tiii). Ni-trog'-e-nous. O-lef'-i-ant. Par'-af-fin. Phe'-nyl. PEOIfUNCIATIOX, ETC. 455 Pho-cen'-ic. Pi'-nic, Pip'-er ine (-in). Plut'-i-uuui. Pro'-te-in. Ptyulin {Ty'-a-lin). Pyr'-o-gal'-lic. Pyr'o-geiis. Py-ri'-tes. Quinine {Kwe-nlne\ or Kwin'-in). Saccharine {Salc'-a-rin). Sa-li'-va. Sel'-e-nite. Se-le'-ni-um. Sta-lac'-tite. Sta-lag'-mite. Strychnine {Strik'-nin). Sui'-phur-ic, or Sul-phu'-ric. Tar-tar'-ic. Tet'-a-nus. The'-ine (-in). Tho-ri'-num. Tourmaline {Toor' -ma-lin). Tri-e-thv'-la-mine (-min). Vi-ter-lin. PEOPEE NAMES. Ampere (Ang-pare'). Bal-krd'. Bec'cher. Berthelot {Ber-tel-lo'). Bologna {Bo-lon -yah). Boucherie (Boosh-e-ree'). Bournon {Boor-nong'). Boussingault (Boos -ang-go). Breguet (Breg-wa). Bunsen {Boo7i-sen). Chevreul (Shev-reid'). Chossat {Shos-sah'). Courtois (Koor-twa). Descartes {Day-kart'). Dalton {DawV -ton). Dobereiner (Doe-hurr' -ein-air). Dubois - Eeymoud {Du - bwd - Ray- mond'). Dumas (Du-maW). Dutrochet (Bu-tro-sha). Ehrenberg (A' -ren-herg). Fraimhofer (Frown -ho-fer). Galvani (Gal-vah'-nee). Gerhardt ( Gair'-hart). Gay-Lussac (Gay-Loos-sac'). Graudeau (Gran-do). Hauy (A' -■wee). Humboldt (Hoom' -holt). Jacobi ( Ya-co'-bee), Joule (Jole). Kirchhofif (Keer' -sJioff). Laurent (Lo'-ront). Lavoisier (Lah-vwd-ze-a!). Leverrier (Le-ver-re-a). Leyden (Li'-den). Liebig (Lee' -big). Matteuci (Mat-tu -chee). Melloni (Mel-lo -nee). Mayer (My'-er). Mongolfier (Mon-gol-fe-a). Mulder (Mool'-der). Katterer (Xat' -tare-ur). Niepce (Ni-eps'). Oersted ( Urs'-ted). Reaumer (Ro'-mer). Regnault (Ray-no). Ruhmkorff (Roohm -korf). Scheele, or Sha'-la. Schonbein (Schen -bine). Seguin (Sa'-gan). Sulzer (Sool'-tser). i INDEX Absorption of heat by gases, 145. Acetous fermentation, 381. Acids, 67 ; theory of, 273 ; later view of, 273 ; bow formed, 410. Acids : acetic, 381. arsenic, 308. arsenious, 308. benzoic, 357. boracic, 269. butyric, 353. caproic, 353. caprj'lic, 353. carbolic, 348. carbonic, 218. chloric, 251. chlorohydric, 247. chlorous, 252. citric, 362. cyanic, 220. cyanohydric, 226. cyanuric, 226. fluohydric, 254. fluosilicic, 268. formic, 384. fulminic, 226. gallic, 363. gallolannic, 363, 334. hippuric, 391. hydrochloric, 247. hydrofluoric, 254. hydrosulphuric, 260. hypochlorous, 250. iodohydric, 253. lactic, 381. lithic, 391. malic, 362. inargaric, 350. meli^sic, 335. muriatic, 247. nitric, 209. nitrous, 209. ]iitro-chlorohydric, 249. oleic, 350. oxalic, 362. pectic, 342. perchloric, 252. phosphoric, 265. prussic, 226. pyrogallic, 363. 20 Acids : pyrolianeous, 345. silicic,''267. stearic, 350. sulphuric, 258. euiphindigotic, S6S. sulphurous, 257. tannic, 363. tartaric, 361. Acroleine, 350. Actinism, 159. Adhesion, 38 ; of liquids to solids, 39 ; of gases to liquids, 43 ; influence of on boiling point, 123. Adipocere, 353. Affinity, 57, 58. Air, 226 ; moisture in, 127 ; relation to ra- diant heat, 146 ; weight of, 227 ; rare- faction of, 229 ; constituents of, 229 ; properties of, 231 ; aqueous vapor of, 231 ; relations to life, 233 ; combustion in, 233 ; chemistry of, 2S5 ; intiuence of, 421. Air pump, 227. Albumen, 370; phj^siological effects of, 432. Albuminous compounds, 370. Alchemy, 176. Alcohol^ 381 ; artificial production of, 323 ; series, 334; raethylic, 345 ; abso- lute, 380 ; ethylic, S81 ; amylic, 384. Aldehyd, 382. Alkalies, 68 : metals of, 277. Alkaline earths, 276. Allotropism, 65, 326. Alloys, 317. Alum, 294. Alumina, 294. Aluminum, 293. Amalgamation, 85. Amalgams, 318. Amber, 357. Ammonia, 210. Ammojiium, 2S8 ; chloride of, 288. Amorphism, 49, Amylaceous group, 337. An.Tsthetics, 384. Analogy of the living body and steam engine, 447. Analysis, 56. Animal electricity, 101 ; products, 385 ; secretion, 389 ; digestion, 423 ; nutri- 458 IXDEX. tion, 431 ; body a furnace, 431 ; heat, production of, 442 ; cause of, 443 ; power, source of, 447 ; races, dep>end- ence of, 451 : ajjlagonism of plant and animal, 4o0. AntJmonial \riiic, 309. Antimony, 309. AiJiiseptic*, 217 ; 374. Aqua-ammonia, 211. Aqua-re^ a, 249. Aqueous Tapor, 230 ; relalion to radiant beat, 147. Arabic, 341. Architecture of the tree, 408. Argand burner, 243. Arsenic, 307 ; test of, 308. Arseniuretted Lydrogren, 308. AsLes, 279 ; as a fertilizer, 402. Asphaltum. 347. Assayix^, 315. AthermJc bodies, 143. Atmosphere, the, 226. Atanoepheric elements, 180. Atmospheric pressure, 228. Atomic rpaces, 37 ; theory, 64 ; heat, 172. Atoms, 36 ; moremems of, 109. Axis of crystals, 54. Azote, 207. B Balance, SL Balsams, 357. Barium, 269. Barometer, 225. Base?. 68 ; oraranic, 364. Battery, Smee'e galvaLic, 88 ; Daaiell-s, 89 ; Grove's. 90 : Bunsens carbon, 90 ; Mavnooth, 91 ; Schonbein's, 9L Beer," 378 ; lager, 379. Beeswax, 356. ^ Benzoin, 357. Benzole, 348. Berthelot's researches, 322. BDe, 427. Eiemuth, 309. B sulphide of carbon, 261. B tumen. 347. Bleachiiifr. 246, 250. Blood, 429 ; globules of, 430 ; coagula- tion of, 430 ; composition of, 431. Blo-svpipe, common, 243 ; oomponndj 238. Boling, 1-22, 123. Bones, 3S8 ; as a fertilizer, 403. Borax, 284. Boron. 269. Brain, 446. Braiidv, 380. Bra&B. 317. Bread making, 392 ; aerated, 393 ; phos- phated, 394. British gum, 341. Bromine, 252. Bronze, 318. Bruc«ia, 365 ; hurrsing fluid, 359. Bnusen's discoveries, 156. Butter, 353, C Cadmium, 300. Caesium, 156, 287. Caffeine, 3^. Calcium, 2b9. Calico prinfng, 36& Calomel, Sia~ Caloric. 107 ; Brewster on, 1S5. Calorimetrj-, 116. Camphene, 355. Camphor, 355 ; artiScial, 355. ^ Candle, burning of, 2S9. Caoutchouc, 357. Capillary attraction, 40. Carbon, 212: influence of in oi^anic eompouDds,325. Carbonate of lime, 29L Carbonate of soda, 2S3. Carbonic acid, test of. 219 ; poisoning by, 220 ; sources of; 220. Carbonic oxide, 221 ; expiration of, 439. Carbnretted hydrogen, 198 ; light, 222. Carmine, 368. Caromel, 338. Casein, 372. Catalvsis, 58. Ce]ls,'407. Cellulm, 342. Cements. 291. Charcoal, 216. Cheese, 39L Chemical attraction. 55. Chemical changes, 29. t^jemical Chart, 61. Chemical combii]ation,GO. Chemical physic?, 29. Chemistry of light, 158 ; of the etais. of Ti^etap 161 ; of the sunbeam, 418 ' Vie growth, 4(». Chlorate of potash, 1S3. Chloresterine, 29L CMoiide of mercury, 315. Chloride of sodium, 2SL Chl(H-ine, 243 ; a dianfectant, 2S1. Chloroform, S84. Cblorophylc, 369. C!joke damp. 218. Chromium, 307. Chyle, 429. Chyme, 426. Cinchonine, 364. Cinuabar. 31-1 Circuit, voltaic, 64. Circulation of blood, 436; com'se of, 437 ; discovery of, 440 ; Drapei»e theo- ry of, 441. CircuLition of matter over the globe, 448 ; of carlx)-), 449 ; of oxygen^ 445 ; of nitrogen, 445. Classification, 15. CleaTaee,53. Coal mineral, 346; distillation of, 348; oil, 348. Cobalt, 304. Cochineal, 358. Coffee, 365. Cohesion, 38. Coin, 318. Coke, 223. Collodion, 343. Colloid condition of matter, 46, S27. Colophony, 365. INDEX. 459 Coloring principles, 365. Color?, cause of, lo8. Combining numbers, 60. Combustioii, 233-244 ; epontaneous, 445. Common salt, 281. Compound radicles, 332. Conduction of heat, 114. Conncclion of polarities, 164. Connection of the radiant forces, 166. ConseiTation offeree, 169. Constitution of matter, 35. Cbnveclion, 116. Copper, 310. Corrosive sublimate, 313. Coupled compounds, 337. Cream of tartar, 361. Creosote, 345. Cryophorus, 126. Crystallization, 46 ; systems of, 52. Cryslals, forms of, 50 ; transformations of, 53 ; modes of production, 47. Culinary paradox, 123. Cupellation, 314. Cyanogen, 225. Cycles of organic matter, 448. Daguerreotype, 319. Daniell's battery, 89. Death in the order of nature, 451. Decay of wood, 345. Decrepitation, 276. Deliquescence, 276. Dew, 143. Dextrine, 341. Dialysis, 327. Diamagnetism, 76. Diamond, 213. Diathermancy, 143. Differential tliermometer, 107. Diffusion of liquids, 43 ; of gases, 43. Digestion in the stomach, 424; second stage of, 424 ; third stage of, 427. Dimorphism, 54. Disinfectants, 375. Distillation, 130; of wood, 344. Dobereiner's lamp, 195. Drummond light, 239. Dyeing, 367. Dyes from coal tar, 349. E Earth's motion, effect of arrest of, 174. EbuUition, 122. Economy of nature, 451. Efflorescence, 276. Elastic gum, 357. Electric light, 95. Electrical hypothesis, 81. Electrical induction, 81. Electricity, progress of, 72 ; Franklinic, 77 ; two kinds of, 79 ; a polar force, 80 ; sources of, 83 ; voltaic, 83 ; frictional and current, 92. Electrodes, 85. Electro-dynamics, 83. Electrolysis, 93. Electro-magnetism, 96. Electroscoiie, 79. Electrostatics, 77. Electrotype, 94. Elements, the four ancient, 176 ; the at- mospheric, ISO. Emery, 294. Empiricism, 19. Energy, potential an actual, 119. Epsom salts, 293. Equivalents, chemical, 62. Equivalents, determining, 331. Eremacausis, 187. Essential oils, 354. Ether, 383. Ethereal medium, 137. Ethers, fragrant, 385. Ethyl, 333. Eupion, 344. Evaporation, 125 ; of the body as a cool- ing agency, 126. Expansion, cause of, 109. Extractive matter, 369. Fats, 349. Fermentation, vinous, 376 ; viscous, 380 ; acetous, 381. Fibrin, 371. Filtration, 45. Fire, ancient idea of, 233. Fixed oils, 349. Flame, nature of, 238 ; structure of, 240 ; of the blowpipe, 243. Flesh, composition of, 385. Flesh juice, 386. Flowers in ice, 198. Fluorescence, 168. Fluorine, 254. Food, chemistry of, 392. Force, illustrations of, 28 ; physical, 28 ; ideas of progressive, 164 ; conservation of, 169 ; convertibility of, 170 ; persis- tence of, 170 : the result of change, 446. Forces of spectrum, 167. Formulce, 69 ; calculating, 332. Fraunhofer's lines, 154 ; cause of, 158. Freezing mixtures, 121. Friction a source of heat, 110. Furnace, reverberatory, 272. Fusel oil, 385. Galena, 177, 311. Galvanic batterj', 88. Gas, origin of the term, 181. Ga>es, influence of upon radiant heat, 146 ; condensation of, 131. Gnsometer, 223. Gastric iuice, 425. Gelatin, 386. Generalization, 15. Gerhardt's views, 71. Glass, manufacture of, 284. Glauber salts, 293. Glucose, 339. Glue, 387. 460 INDEX. Glulen, 371. Glycerin, 350. Gold, 315. Graphite, 215. Gravity, '29. Grove's battery, 00. Grove's experiment upon light, 171. G uano, 391 ; as a fertilizer, 4U3. Gum, 341. Gun cotton, 343. Gunpowder, 280. Gutta percha, 358. Gypsum, 292. H TTair, 388 ; coloring of, 363. Halogens, 244. Heat, influences solution, 44 ; expansion by, 104 ; nature of, 107 ; sources of, 110 ; sources of in friction, 112 ; con- nection with electricity, 115 ; radiant, 139 ; exchanges of, 141 ; absorption of by gases, 145 ; relation to light, 167, 168 ; atomic, 172 ; units of, 172 ; equivalent of, 172 ; animal, 444. Heat of combustion, cause of, 236. Heat rays, sifting of, 144. Heliochromy, 320. Hematite, 298. Homologous series, 333. Horny matter, 388. Humus, 345. Hyalogens, 266. Hydrogen, 192. Hydrometer, 34. Hygrometers, 127. Hypothesis, 15. I Ice, 120 ; of sea water, 198 ; flowers in, 198. Illuminating gns, 223. Illumination; 238. Imponderable matter, 72. India rubber, 357. Indigo, 368. Induction, 20; electric, 81; magnetic, 101. Interference of wave motions, 148 ; of light, 149. Iodide of potassium, 278. Iodine, 253. Iron, •.:96 ; properties of, 300 ; wrought, 300 ; oxides of, 303. Isinglass, 387. Isomcrinm, 05,326. Isomorphism, 54. Joule's law, 173. K Kakodyl, 38.5. Kirchhoff''8 discoveries, 156. Knowledge a growth, 15. Koh-i-nor, 214. Kyanizing, 375. Lac, 356. Lacteals, 429. Lactose, 339. Lamp, Dobereiner's, 195 ; safety, 241. Lampblack, 218. Latent heat, 117. Lead, 311. Leather, 388. Light, 132 ; reflection and refraction of, 133; absorption of, 143,157 ; interfer- ence of, 149 ; polarization of, 150 ; chemistry of, 158 ; relations to heat, 167, 168. Li gilt carbu retted hydrogen, 222. Lignin, 343 ; lignite, 346. Lime, 290. Lime light, 239. Liquefaction, 121. Litharge, 311. Lithium, 287. Litmus, 308. Living body a machine, 446. Lunge, 436. M Madder, 368. Magnesia, 292. Magnesium, 292. Magnetism, 73. Magnetism and light, 166. • Magneto-electricity, 100. Malt, 378. Manganese, 304. Manures, 402, 403. Marcet's digester, 129. Margarin, 351. Marsh gas, 202. Matches, 264. Matter and force, 27. Matter indestructible, 27 ; impressibility of, 163. Meat, 397 ; cooking of, 398 , salted, 399. Mercaptanp, 385. Mercury, 312. Metals, general properties of, 270 ; of the alkalies, 277. Metamorphosis of tissues, 435. Microscope, use of, 329. Milk, 389 , as food, 435. Minium, 311. Molasses, 339. Molecular attractions, 38. Moleculee, 37. Mordants, 367. Morphia, 365. Mortar and cement, 20;, Moser's images, 163. Mother liquor, 47 ; motLtf; of vinegar, 382. Motion, universality of, 108. Mucilage, 342. Mucous membrane, 424. MucuB, 391 ; mucin, 391. Mutual relations of the forcet, 164 Naphtha, 347. Nascent state, 59. N INDEX. 461 Nature of heat, 107. Necessity of the circulation of matter, 452. Nickel, 304. Nicotine, 365. Nitrate, of soda, 284 ; of silver, 314. Nitre, 279. Nitric acid, 209. Nitric o.\ide, 208. Nitrogen, 206. Nitrogenous compounds, 370, 431 ; diet, 433. Nitrous oxide, 207. N'omenclature, 66. Nordh.ausen sulphuric acid, 260. Nutritive power, limit to, 433 ; nutri- tion imperfect, 433 ; value of food, 434. O Observation, 14. Oil, physiological effects of, 433. Oils, 349 ; mineral, 347 ; fixed, 349 ; coal, 348 ; drying, 351 ; castor, 352 ; croton, 352 ; unctuous, 352 ; cod liver, 352 ; colza, 353 ; palm, 353 ; train, 353 ; vol- atile, 354; turpentine, 355 ; sylvic, 356- fusel, 385. Oleaginous group, 349. Oletiant gas, 222. Olein, 350. Opium, 365. Ores of iron, 297. Organic chemistry, 321. Organic compounds, artificial produc- tion of, 322 ; constitution of, 324 ; anal- ysis of, 329. Organogens, 181. Osmose, 41 ; of gases, 43 ; a new theory of, 328. Oxalic acid, 362. Oxygen, 181 ; magnetism of, 77 ; discov- ery of, 182 ; properties of, 183 ; com- bustion in, 185 ; relations to life, 187 ; rate of consumption, 188 ; proportion in nature, 189 ; theory of, 191 ; in bodily circulation, 439 , office of in circula- tion, 440. Ozone, 190. Pancreatic fluid, 428. Paper, 343. ParalBn, 345. Parchment, 387 ; vegetable, 343. Peat bogs, 346. Pectin, 342. Pepsin, 425. Peptones, 425, Peroxide of hydrogen, 205. Perpetual motion, 170. Petroleum, 347. Philosopher's stone, 178. Phlogiston, 233. Phosphorescence, 162, 263. Phosphorus, 262. Phosphuretted hydrogen, 266. Photography, 160, 318. Physiological change, rate of, 445. Physiological chemistry, 404. Pile voltaic, 88. Pitch, 344. Plants, 401 ; growth of, 405 ; in apart- ments, 413. Plaster of Paris, 292. Platinum, 316. Plumbago, 215. Pneumatic trough, 184. Poisons, 375 ; woorara,365. Polarity of particles, 75. Polaritjr, rise of the idea of, 164. Polarization of hght, 150. Porcelain, 295. Porosity of matter, 35. Potash, 278 ; carbonate of, 278 : nitrate of, 279. Potassium, 277. Pottery, 296. Precipitation, 45, Prevision a test of science, 12. Priestley, 181. Protein, 372. Putrefaction, 373. Pyrogens, 181. Pyrometer, 107. Q Quinia, 364 ; quinine, 364, R Radiant heat, 139. Radiants, 132. Radiation, 132. Radiators, good and bad, 142. Refraction, 133 , double, 153. Regulation, 122. Resins, 356 ; gum, 357. Respiration, 436 ; gasea absorbed and exhaled in, 439 ; influence of over ani- mal heat, 443. Respirator, 217. Respiratory foods, 434. Rochelle salt, 362. Rosin, 356. Rubidium, 156,287. Rmnford on heat, 173, S Safety lamp, 241. Sal ammoniac, 288. Saliva, properties of, 423. Saltpetre, 279. Salt rock, 144, 281 ; as asi antiseptic, 282, Salts, 68 ; theory of, 272 ; later view of, 274. Sap of plants, 409 ; circulation of, 441, Saponification, 359. Saturation, 45. Science, nature of, 18 ; why so recent, 19 ; claims of, 21. Science and art, 19. Sciences, succession of, 20. Selenium, 262. Selzer's experiment, 84. Shells, 389. Silicon, 266, 462 INDEX. of iron, 299. action of, SCO; Silver, S13 ; nitrate of, 314 ; chloride of, 315. Siniiiuer flame, 195. Smct's" battery, 88. emeliing of metals, 272 ; ISnow crystals, 199. Soap, 359 ; varieties of, 300. Soda, 281. Si)dium, 381. Soil, organic matter of, 346 ; origin of, 400. Solar influence, exteiit of, 419. Solar radiation, amount of, 421, Solar spectrum, 134. Soluble glass, 2GS. Solution, 44. Soups, 898. Spar, heavy, 289, Speciflc gravity, 31. Specific heat, 118. Spectroscope, 155. Spectrum, solar, 134 ; thermal, 140 ; chemical, 158 ; analysis, 154 ; organiz- ing region of, 418. Spermaceti, 353. Spheroidal state, 124. Stalactites, 292. Stalagmites, 292. Starch, 340. Steam, 130 ; superheated, 130. Stearin, 351. Steel, 302. Stomach, 424; follicles, 424; digestive limit of, 426 ; why the stomach does not digest itself, 427. Stratified discharge, 101. Strontium, 289. Strychnia, 365. Sublimation, 48. Substitution, 336. Sugar, 337 ; cane, 338 ; grape, 339 ; milk, 339 Sulphate of soda, 283 ; of ammonia, 288 ; of lime, 292. Sulphur, 255. Sulphuretted hydrogen, 260. Sulphuric acid, 258. Sulphurous acid, 257. Sunbeam the antagonist of oxygen, 420 ; motive power of the world, 421. Symbols, 69. Symmetry of forms, 51. Tnlbotypo, 320. Tannin, 363. Tar, 344. Tartar, 423 ; cream of, 3G1, Ten, 366. Tectl), 388 ; action of, 423. Telegraph, electro-magnetic, '. Tellurium, 262. Temperature, 105 ; in man, 442. Thallium, 156 , 312. Theory, 18 ; types, 335. Thermo-eleclricity, 98. Thermometer, 105 ; Fahrenheit, "i06. dilierential, 107 ; Breguet's, 171. Thermometric scales, 106. Thermometries, 103. Tin, 306. Tissues, nutrition of, 432. Topaz, 52. Tourmaline, 151. Turpentine, 355. Transmutation of metals, 178. Tyndall on ice, 199. Type metal, 318. U Universe, culmination of, 422. Urea, 391. Urine, 391. Vapor, elastic force of, 129. Vaporization, 125. Varnish, 357. Vegetable acids, 361. Vegetable alkaloids, 364, Verdigris, 310. Vinegar, 382. Vitelhn, 371. Volatile acids, series of, 334. Volatile oils, 354. Voltaic circuit, 84 ; polarities of, 86. Voltaic pile, 88. Volume, combination by, 63. W Washing fluids, 361. Water, 196 ; decomposition of, 93 ; com- position of, 197 ; imequal expansion of, 2U0 ; atomic constitution of, 201 ; Con- gress, 201 ; solvent power of, 202 ; min- eral, 203 ; impurities of, 205 , purifica- tion of, 205 ; circulation of, 448. Wave theory of light, 135. Waxy compounds, 356. "Weighing, 30. White lead, 311. Wine, 379 ; spirits of, 377. Wood spirit, 845. Woody fibre, 342. Woulfe's bottles, 211. Yenet, 377. Yellow coloring matters, 368. Zinc, 305. D. APPLET ON