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" <’ ■ " V , .' ^ vr'^^T'V.^ i' r> ^ .... , ... , -V. -. ' ", ■ ^r^• 1 ^.iV ^:^''fiKC^l^;^ v.;A H *. i^.- .-■ * ":'A / ' ■ v:^ .' ir- ^ ‘ ■ ' f'^^'-' '[^. y. ,.V A TEXT-BOOK ON CHEMISTEY. TOR THE USE OF SCHOOLS AND COLLEGES. BV JOHN WILLIAM DRAPER, M.D., Professor of Chemistry in the University of New York, Member of the American Philosophical Society, &c. With nearly Three Hundred Illustrations. ..v4 NEAV EDITION. NEW YORK: HARPER & BROTHERS, PUBLISHERS, 329 & 331 PEARL STREET, FRANKLIN SQUARE. 1854 . Entered, according to Act of Congress, in the year one thousand eight hundred and fifty-three^ by Harper & Brothers, in the Clerk’s Oifice of the District Court of the Southern District of New York. 3c> \2S-if BY THE SAME AUTHOR. 31 ^cxt-Book on I^'atural |})l)iloso|j|)g, FOR THE USE OF SCHOOLS AND COLLEGES. WITH NEARLY 400 ILLUSTRATIONS. l^MO, SHEEP, 75 CENTS. 701229 ■-k , '■*1 . ^ PREFACE. This text-book on Chemistry, intended for the use of colleges and schools, contains the outline of the course of Lectures which I give every year in this University. I do not, therefore, present to teachers an untried work. Its divisions and arrangement are the result of an experience of several years; an experience which has proved to me that there is required a text- book of small size, so that students can pass through it readily in the time usually devoted to Chemistry. Every instructor in this science must have observ- ed that the ordinary Treatises’^ or Elements” are by no means suited to his wants. When they are employed in the class-room, there are large portions which have to be omitted, and other portions too briefly explained. In fact, to study Chemistry suc- cessfully, the first thing which is wanted is a com- pendious book, which sets forth in plain language the great features of the science, without perplexing the beginner with too much detail. It will be understood, therefore, that this work, with little pretensions to originality, except where di- rectly specified, occupies a different field from that of the larger treatises. It is intended as a manual, ar- ranged in such divisions as practice has shown to be VI PREFACE. suitable for daily instruction. It is the exposition of what I have found to be a satisfactory method of teaching ; and of its success our annual examinations are the best testimonial. The unsuitableness of large text-books has led to many attempts to reduce their size by abstracts and compendiums ; but the difficulty can never be avoid- ed by that means ; the very structure of such works is faulty. We never want to use all that an author knows or can possibly say on the subject. It has been well remarked, that ‘‘the greatest service which can be rendered to our science is for some person who has had the management of large classes for several years to sit down and write a book, setting forth what he said and what he did every day in his Lectures. That is the thing we want.” While, therefore, this book is offered to instructors as a practical work, the object of which is to display the leading features of the science, I have endeavored to make it a representation of the present state of Chemistry. In this respect many of our most popu- lar works are defective. Among them I should not know where to turn for a simple exposition of the Wave theory of Light or of Ohm’s theory of Voltaic Currents ; yet the one is the most striking result of physical research, and the other is connected with the fundamental facts of Electro-chemistry. To the treatises of Hare, Kane, Grraham, Grregory, Fownes, Dumas, and Millon I must formally state my obligations. In Descriptive Chemistry I have followed them closely ; and in those cases Avhich are much more common than is generally supposed, where there are differences in the imputed properties of bod- PREFACE. Vll ies, I have consulted, wherever 1 could, either original memoirs or the annual reports of Berzelius. The number of wood -cuts, representing experi- mental arrangements, which have been introduced, will give to a beginner a clearer idea of the practical part of each Lecture, and, in our country colleges, may sometimes supply the place of defective or in- complete apparatus. To each Lecture is appended a set of questions. They enable a young student more quickly to apprehend the doctrines which are before him. University of New York, July 6, 1846. John William Draper. PREFACE TO THE NEW EDITION. The favor with which this hook has been received by the public, so many editions of it having been called for, has led me to give it a thorough revision, with a view of bringing it to the present condition of the science. The reader will find that extensive changes have been made in those parts which treat of the impon- derable principles, several of the Lectures having been entirely rewritten. I hope that the alterations and additions now pre- sented will secure for the work a continuance of that patronage which it has hitherto so extensively received. John W. Draper. University of New York, ) July 80, 1853 ) CONTENTS I.ecture I Page I. Constitution of Matter 1 II. Constitution of Matter {continued) " 6 III. Heat....... 11 IV. Expansion of Gases and Liquids 15 V. Expansion of Liquids and Solids T 21 VI. Expansion of Solids 25 VII. Capacity of Bodies for Heat 29 VIII. Capacity for Heat and Latent Heat 34 IX. Latent Heat {continued) 39 X. Vaporization 43 XL Ebullition 48 XII. Vaporization 52 XIII. Evaporation and Interstitial Radiation 58 XIV. Conduction 64 XV. Radiation 67 XVI. Theory of the Exchanges of Heat 72 XVII. Nature of Light 75 XVIII. Constitution of the Solar Spectrum 80 XIX. Wave Theory of Light *. . . 84 XX. Wave Theory of Light {continued) . * . . . 87 XXI. Wave Theory of Light {continued) 91 XXII. Production of Light 95 XXIII. Chemical Action of Light 99 XXIV. Chemical Action of Light {continued) 102 XXV. Electricity 105 XXVL Theory of Electrical Induction 109 XXVII. Laws of the Distribution of Electricity and General The- ories * 113 XXVIII. Faraday’s Theory of Electrical Polarization 117 XXIX. Voltaic Electricity 123 XXX. Effects of Voltaic Electricity 127 XXXI. The Electro-chemical Theory * 133 XXXII. Ohm’s Theory of the Voltaic Pile — Magnetism 138 XXXIII. Electro-dynamics — Thermo-electricity 145 XXXIV. The Chemical Nomenclature ...» 153 XXXV. The Symbols 156 XXXVI. The Laws, of Combination * 160 XXXVll. Constitution of Bodies — Crystallization 164 X CONTENTS. I.ecture XXXVIII. Chemical Affinity XXXIX. Pneumatic Chemistry — Oxygen Gas XL. Oxygen {continued) XLI. Hydrogen XLII. AVater XLIII. Nitrogen — Atmospheric Air XLIV. Atmospheric Air {continued) . . . '. XLV. Atmospheric Air {continued) XL VI. Compounds of Nitrogen and Oxygen XLVII. Compounds of Nitrogen and Oxygen XLVIII. Sulphur : XLIX. Compounds of Sulphur and Oxygen L. Sulphur and Phosphorus ...... LI. Compounds of Phosphorus and Oxygen — Chlorine LII. Chlorine {continued) LIII. Chlorine {continued) — Iodine LIV. Bromine — Fluorine — Carbon LV. Carbonic Acid LVI. Cyanogen — Boron— Silicon— Ammonium LVII. General Properties of the Metals LVIll. Potassium LIX. Sodium — Lithium— Barium LX. Strontium— Calcium — Magnesium — Aluminum LXI. Manganese — Iron LXII. Iron — Nickel — Cobalt — Zinc LXIII. Cadmium — Tin — Chromium — Titanium LXIV. Argenic LX V. Arsenic — Antimony — Tellurium — Uranium — Copper LX VI. Lead — ;Bismuth— Silver LXVII. Mercury— Gold— Platinum, &c V LXVIII. General Properties of Organic Bodies LXIX. The Non-nitrogenized .Bodies , . v , , LXX. Action of Agents on the Starch Group LXXI. The Metamorphosis of the Starch Group by Nitrogenized Ferments ^ LXXII. The Derivatives of Fermentative Processes LXXIII. The Derivative Bodies of 4lcph,ol LXXIV. Oxydation of AJcohol LXXV, Deriyatiyes .of Acetyle — the Kakodyle Group LXXVI. The Wood-Spirit Group.... LXXyiL .The Potato-Oil Group — the Benzyle Group LXXVIIL The Salicyle nnd Cinnamyle Groups. LXXIX. The Nitrogenized Principles— Ammonia — Cyanogen, .... LXXX. Bodies nUi.ed to .Cyanogen LXXXP Mellone-tJrea Page 173 178 183 187 192 197 203 208 213 216 221 225 228 232 236 240 245 249 253 260 264 268 274 281 285 291 295 299 304 309 314 318 322 326 329 334 337 341 345 348 352 356 361 364 CONTENTS. - Xi Lecture Page LXXXIf. The Vegetable Acids 368 LXXXIII. The Vegetable Alkalies 373 LXXXIV. The Coloring Principles 377 LXXXV. The Fatty Bodies 381 LXXXVI. The Resins, Balsams, and Bodies arising in destructive Distillation 385 LXXXVIL Animal Chemistry — Digestion and Nutrition 389 LXXXVIII. Origin and Deposit of the Fats and Neutral Nitrogenized Bodies 393 LXXXIX. The Transmission of Food through the System 397 XC. Nature of the Processes of Secretion 401 INTRODUCTION. CONSTITUTION AND GENERAL PROPERTIES OF MATTER. LECTURE I. Constitution of Matter. — Distinction between Chem istry and Natural Philosophy. — General Division oj Chemistry. — Active Forces and Ponderable Bodies . — Proof of the Atomic Constitution of Matter in the Casez of a Solid and a Gas. — Atoms are incojiceivably small — They are not in contact — They are unchangeable and indestructible. The physical sciences are divided into two classes, com- prehended respectively under the titles of Natural Phi- losophy and Chemistry. Natural Philosophy investigates the relations of masses to one another. The movements of tides in the sea under the conjoint influence of the sun and moon ; the descent of falling bodies to the earth ; the pressure of the atmosphere ; the various modes of rendering mechanical forces available, by the action of levers, pulleys, wedges, screws ; the phe- nomena of the planetary bodies, which move in elliptic orb- its around a central mass : these are all objects for the con- sideration of Natural Philosophy. Chemistry considers the relations of particles to each other ; it investigates the properties and qualities of differ- ent kinds of matter, their mutual influence, and the action of the imponderable principles upon them. It treats of the causes of those invisible movements which the molecules of bodies around us unceasingly undergo. It also includes many of the phenomena of living beings, explains the objects of respiration, digestion, and other such animal functions. Every change taking place in bodies is due to the oper- ation of some active force. It is one of the first principles in philosophy, that no movement or mutation can occur in Into what classes are the physical sciences divided ? Of what phenom- ena does natural philosophy treat ? What are the objects of chemistry ? K 2 CONSTITUTION OF MATTER, any thing spontaneously ; we must always refer it to a dis- turbing cause. Under the influence of heat, bodies increase in size ; under that of electricity, some are dissevered into their component elements ; under that of liglit, vegetables form from inorganic materials their organized structures. The science of chemistry resolves itself, therefore, into two divisions : the first, embracing the consideration of the act- ive forces of chemistry ; the second, the objects on which those forces operate. These active forces are Heat, Light, and Electricity. By the older chemists they are designated as imponderable sub- stances, from the circumstance that they do not affect the most sensitive balances. We can form no idea of the properties of bodies disen- gaged from the influence of these principles. Thus we find all material substances existing under one of three condi- tions, solid, or liquid, or gaseous ; and the majority can as- sume either of these conditions under the influence of heat. Water, for instance, at low temperatures, exists in the solid state as ice ; at higher temperatures, it assumes the liquid condition ; and at still higher, exhibits the gaseous form. We see, therefore, that it is the degree of heat to which it is exposed which determines its physical state. One of the first problems which the chemist has to solve is that of determining the true constitution of matter ; not of matter in the abstract, but as placed under the influence of these external powers. All the phenomena of chemistry prove that material sub- stances consist of indivisible and exceedingly minute por- tions, called Atoms, which are placed at certain distances from one another, those distances being variable, and de- termined by the agency of active forces. Thus, if we take a copper ball, a, Fig. 1, an inch in diameter, and pro- vide a ring, b, of such a size that the ball at common temperatures can read- ily pass through it, and having sus- pended the ball by means of a chain to a stand, d, expose What are the two leading divisions of chemistry ? What are the active forces of chemistry? Why are these called imponderable bodies? What are the three forms of substances ? What is it that determines these forms ? What is the constitution of matter? Describe the arrangement of the in- stviunf^nt, 1, and its use. Fig. 1. CONSTITUTION OF MATTER. 3 it to the flame of a spirit lamp, c, as it becomes warm it will be found to dilate^ so that, in the course of a few minutes, it can no longer pass readily through the ring, but if placed thereon, remains supported. While, under these circumstances, no visible change has taken place in the general properties of the ball, its weight remaining the same as before, its aspect is the same. We conclude, therefore, that its volume has increased because we have raised its temperature. But now, the lamp being removed, the ball, still resting on its ring, begins to cool. In the course of a few minutes it spontaneously drops through the ring. It has, therefore, become less than it was while hot, and, in point of fact, when its original temperature is reached, it has recovered its original size. From this simple but beautiful experiment, very import- ant conclusions may be drawn. The copper ball, in cooling, becomes less : a fact which at once suggests the idea that its constituent particles have approached each other. In its warm and dilated state, although it exhibited no ap- pearance of transparency, or of interstitial spaces, or pores through which light might pass, its particles were not touch- ing one another, for had they been in actual contact they could not have more closely approached one another, and contraction could not have taken place. As all bodies contract during the act of cooling, we infer that the particles of which they are composed are separated from each other by intervening spaces, and experiments such as, that we have been considering suggest two important observations: 1st. That all material substances are made up of small particles which do not touch each other ; and, 2d. That the intervening spaces may be varied at the pleasure of the experimenter. Let us consider a second illustration which will lead us to the same conclusion, selecting as the object of our experiment atmospheric air, a substance differing in all its physical and chemical relations from the copper ball. Let us take a tube of glass half an inch in diameter, and bent ^ Why, in this experiment, docs the ball finally drop through the ring? Could contraction take place if its particles were already in contact ? What two conclusions do these facts suggest? 4 CONSTITUTION OF MATTER. in the form exhibited in Fig. 2, a, c, d. The tube is closed at its upper end, a ; it is bent at c, and over its open extrem- ity, at d, a bag of India rubber ts tied, air tight. In the tube there has been previously inclosed a sufficient quantity of water to fill all the portion h, c, d, but the space from a to h is occupied by atmospheric air. It is to the volume of this atmospheric air that our attention is directed. If we compress the India rubber bag in our hand, the vol- ume of the air instantly becomes less, the diminution being greater in proportion as the pressure is greater. Now it is inconceivable that this phenomenon should ensue unless the aerial particles approached each other ; but such an ap- proach would be impossible if they were already in contact. Two particles could not occupy the same space at the same time. We conclude, therefore, that for atmospheric air, a gaseous body, as well as for copper, a solid, the same law holds good, and that both these forms of matter are constructed upon the same type ; that they are made up of particles set at distances from one another, and that we can change those distances at pleasure by resorting to changes of temperature or to mechanical forces. It is worthy of observation, that by proper means these interstitial spaces may be greatly increased or diminished, and in very many in- stances without any striking apparent change occurring in the substance under experiment. Thus, if we take a globe of glass two or three inches in diameter, a, Fig. 3, with a neck or tube, proceeding from it, and fill the globe full of water, with the exception of a small bubble of air which occupies its upper part, while the open extremity of the tube, b, dips beneath some Avater contained in a glass jar, c, then, covering the whole with an air-pump receiver, d, proceed to exhaust, we shall find that the little bubble, dilates as the machine is worked, and may be rendered a hundred-fold greater than at first. In this expanded condition, its par- ticles must have greatly receded from each other, and yet no remarkable physical change is to be observed. There Describe the instrument represented in Fig. 2. What is the use of this instrument ? With an increase of pressure, what happens to the included air? Can two particles occupy the same space at the same time ? What, then, is the deduction from this experiment ? What is the experiment given in Fig. 3 intended to illustrate ? Fig. 3. SIZE OF ATOMS. 5 are no dark or vacuous spaces ; but in this attenuated con- dition, it possesses the aspect which it had when at the common density. With these preliminary facts, we may now direct our at- tention, 1st, to the properties of atoms ; and, 2d, to the inter- stitial spaces which part them from each other. That the atoms of which bodies are composed are exceed- ingly small, we possess abundant proof By dissolving sub- stances in liquid media, and then greatly diluting the solu- tion, we can effect a subdivision to an incredible extent. A single drop of a solution of sulphate of indigo will commu- nicate a blue color to one thousand cubic inches of water, so that every drop of that diluted solution contains a portion of the coloring matter. In the same manner, by resorting to proper tests, we can show that a grain of copper, or silver, or gold, may be divided into many millions of smaller parts, each of which may be readily recognized. Nor is it alone by these chemical processes that such a minute subdivision may be effeeted : by the mechanical process of beating with a hammer, gold may be extended into leaves which are less than the 2 oo\) (r() inch thick, a dimension far less than the human eye, unassisted by microscopes, can discover, for the smallest spherical object visible to it is about 20^00 part of an inch in .diameter. By other processes, it has been estimated that this metal may be divided to such an extent, that a single grain will yield 80 millions of millions of vis- ible parts. The world of organization furnishes us with still more striking proofs. There exist animalcules of which it would require many millions to make up the bulk of a com- mon grain of sand, yet these are furnished with digestive and respiratory organs, with circulating juices, and with contrivances as elaborate as the mechanism of the highest orders of life. How minute, then, must the constituent par- ticles be ! All the results of chemistry prove that the ultimate atoms of bodies are unehangeable and imperishable. We can not effect their destruction, or impress them with new or unusual qualities, any more than we can call them into existence. Those familiar instances in which it appears that material To what extent can the constituent atoms be removed ? To what extent can sulphate of indigo be divided? Can similar results be obtained from metalline bodies ? What evidence have we on this point from mechanical processes ? What argument may be drawn from the construction of ani malcules ? Are the atoms of bodies either changeable or perishable ? 6 PROPERTIES OF ATOMS. substances are destroyed or dissipated, when properly under- stood, are only cases of transformation, or of the origin of new compounds. An atom once created can by no process be de- stroyed. When, therefore, coal disappears in the act of burn- ing, it is not, in reality, a destruction of the particles of which the coal consists, but these particles, uniting with one of the constituents of the air, give origin to a body of a dif- ferent form, an invisible and elastic substance, from which, however, the carbonaceous particles could be reobtained by resorting to proper methods. It is, moreover, obvious that the continuance and stability of the universe itself depend on the fact that by no natural process can material atoms be cither created or destroyed. LECTURE II. Constitution of Matter. — Of the Interstices hetween Atoms . — They are not casual, hut regulated . — Two Foi'ces are required to •produce this Result. — Cohesion and Heat. — Proof that these Forces act through very limited Spaces. — Analogy hetween the Structure of Mat- ter and the Structure of the Universe. Having, in the preceding lecture, established the atomic constitution of matter, let us now direct our attention to the intervening interstices. 4 . The distances that part the atoms of a given mass from one another are not casual or determined at random ; their magnitude is perfectly regulated. Thus, if we take a glass bulb, a. Fig. 4, with an open neck, h, and having filled the neck with water to a given mark, c, immerse its open extremity in a glass of water, d, it will be found that, so long as no extraneous cause intervenes, the water remains perfectly stationary at its original point, c ; but if, by the appli- cation of a spirit lamp, e, we raise the temperature of the How can the apparent destruction of bodies be explained ? Are the spaces between atoms regulated or at random ? What is the experiment, Fig. 4, designed to establish ? REGULARITY OF INTERSTITIAL SPACES. 7 air included in the bulb, it promptly dilates ; a dilatation which, however, does not proceed with irregularity, for the volume of the air steadily increases as the heat is steadily continued. Let the lamp now be removed, and as the tem- perature descends, the water comes back again to its orig- inal point, because the air recovers its original bulk. In the same manner, if we repeat the experiment illus- trated in Fig. 3^ we shall see that the bubble of air does not expand with irregularity as the pump is worked. It does not at one moment suddenly dilate, and then remain motion- less, but for each movement of the pump it increases corre- spondingly ; and as soon as the pressure is restored to the interior of the machine, it shrinks back to its original size. But these expansions and contractions are the result of movements among the constituent atoms, which at one time recede farther apart, and at another come closer together. It follows, therefore, from these considerations, that the dis- tances which separate the constituent atoms are not determ- ined by chance or at random, but their magnitude is strictly regulated. To produce these results two forces are required : 1st, a force of attraction, which continually tends to draw the atoms closer together ; 2d, a force of repulsion, which tends to remove them farther apart. The distance at which they are placed, at any particular moment, is determined by the balancing of these forces ; if the attractive force is made to increase in intensity, the particles approach ; if the repuls- ive, they recede. Names have been given to these forces, the attractive force being known under the name of cohesion ; caloric or heat appears to be the principle of repulsion. All attractive and repulsive forces diminish as the dis- tances through which they act increase. The attractive force of the earth, the force of gravitation, is of a certain in- tensity on the surface of our planet, but it diminishes as the distances become greater. The forces which connect to- gether the bodies of the solar system, and, indeed, one plan- etary system with another, act through great intervals of space.; thus the attractive force of the sun, operating through Can the same theory be proved by resorting to other disturbing processes ? How many forces are required to account for these facts ? What is their nature ? What is the relation between heat and repulsion ? Through what spaces can these forces operate ? S SIZE OF INTEHSTITIAL SPACES. many millions of miles, retains the earth in her orbit. But the attractive and repulsive forces which determine the po- sition of the constituent atoms of bodies are limited to a very minute space. If we take two leaden bullets, and having ' pared a small portion from the surface of each, so as to ex- pose a brilliant metallic spot, bring them within an inch of one another, they exert no perceptible attraction, and may be drawn apart with the utmost facility ; we may diminish the distance between them to the tenth, the hundredth, the thousandth part of an inch, and still the same observation I may be made ; we may even bring them in apparent con- : tact, and the attractive influence of the particles of the one upon those of the other is still undiscoverable ; but, on press- ing them together, we can finally bring them within the range of each other’s influence, and then they cohere to- gether as though they were a single mass, and require a considerable effort to separate them. The apparatus figured in the margin serves to illustrate the same result. Suspend a circu- lar piece of plate glass, a, Fig. 5, an inch in diameter, to one of the arms of a balance, b, c, counter- poising it on the opposite arm by ^ weights placed in the scale-pan, d. Beneath the plate of glass place a cup, e, containing some quicksilver, and it can be proved that so long as the glass is at a sens- ible distance from the surface of the quicksilver, no attrac- tion between them is exhibited ; for, were such the case, the arm of the balance should incline, and the glass descend. As long as the smallest perceptible space intervenes, no at- tractive action is developed ; but on bringing the two sur- faces in contact, they cohere ; and now it requires the addi- tion of a considerable weight in the scale-pan to draw them asunder. This result does not depend on the pressure of the air, for it equally takes place in a vacuum. From experiments of this kind, therefore, we gather that the spaces through which molecular attractions and repul- sions can act are very limited, and it follows of necessity that the interstices which separate the atoms of bodies are Fig.h. How can this be proved by leaden bullets ? Describe the apparatus, Fig. 5. What is its use ? What the fact which is proved by it ? Does the ex- periment depend on the pressure of the air ? CONSTITUTION OF MATTER. 9 exceedingly minute, for through those spaces the action of these forces extends. If the limiting distance through which molecular attraction and repulsion ean reach is, as there is reason to believe, from some of the experiments of Newton, less than the millionth of an inch, v/e are entitled to con- clude that the interstitial spaces are much smaller. To what, then, do these results finally point in regard to the constitution of matter, if, as we have seen, the constit- uent atoms themselves are inconceivably minute, and the spaces that separate them as small as we have reason to conclude ? We may look upon the universe as representing on a grand scale the constitution of matter on a minute one. The planetary bodies which compose the solar system, and which are held in their orbits by the attraction of a central mass, are separated from one another by enormous spaces, to which their own magnitudes bear but an insignificant proportion. About forty such bodies, great and small, com- pose the group or family to which our earth belongs. But as there are systems of opaque planetary bodies, so also there are systems of self-luminous suns, which compose to- gether colonies of stars. In the universe myriads of such systems exist, separated from one another by spaces so great that the mind can form no just idea of them. planet, such as Jupiter with its attendant satellites ; a self-lumin- ous star, like our sun with its surrounding bodies ; a group of shining stars, such as are scattered over our skies ; a col- lection of such groups as form the nebular masses ; these, in succession, furnish us with a series of illustrations on a scale continually increasing in dimensions of the constitution of matter, which is made up of isolated atoms placed at va- riable distances from each other, the size of these atoms bearing an insignificant proportion to the spaces intervening between them. The human mind is so constituted th^ it is unable to appreciate whatever is exceedingly great or exceedingly small. We can neither attach a precise idea to the magni- tudes and grander relations of the universe, nor to the atomic constitution of a grain of dust. Hereafter, when we come to speak of the phenomena of light, we shall see that by fol- lowing the same philosophical methods which have been What are the limiting distances through which molecular forces can act ? State the analogy between the constitution of the universe and the consti- tution of matter. A 2 10 CONSTI'TUflON OP MATTER, cultivated with such success iu astronomy, and which have furnished us with a general view of the constitution of the universe, we also can obtain a general view of the scale which has been used in the constitution of material bodies, a scale which brings before us new ideas of time and space. When we are told that in the millionth part of a second a wave of violet light pulsates or trembles seven hundred and twenty-seven millions of times, and that, if we divide a sin- gle inch into ten millions of equal parts, this violet wave is only one hundred and sixty-seven of such parts in length, we obtain a glimpse of the scale on which material bodies are composed, and must confess the inability of the human imagination to form a proper conception of such results, though we may feel a just pride in the intellectual power which has ascertained them. PART I. THE FORCES OF CHEMISTRY. LECTURE III. Heat. — Preliminary Ideas of the Nature of Heat, — In- fluence of Heat in the inorganic and organic Worlds, — Modes of Transference. — Illustrations of Expansion. — Heat determines the Magnitude and Form of Bod- ies — Affects our Measures of Time and Space — De- termines the Distribution of Animals and Plants. Writers on chemistry signify by the term Caloric the agent which excites in our bodies the sensation of heat. By some, however, heat and caloric are used synonymously. Those who look upon this force as if it were a material and imponderable substance, ascribe to the particles of caloric a self- repulsive power, and an attraction for the particles of ponderable bodies. So great is the control which caloric exercises over all kinds of chemical changes, that few experiments can be made in which transformations of substances take place without contemporaneous disturbances of temperature. In some, heat is evolved ; in others, cold is produced. To this agent, moreover, we so constantly resort for the promotion of molecular changes, that the chemist has been not inaptly designated the Philosopher by Fire. It is not alone in the inorganic world that the influences of caloric are traced. Life can not take place except with- in certain limits of temperature ; limits which are compre- hended between the freezing and the boiling points of water, that is, within one hundred and eighty degrees of our ther- mometer ; and, in point of fact, within a narrower range than that. It is, therefore, not alone in chemistry, but also What is caloric ? WTiat is heat ? On the hypothesis that caloric is an imponderable substance, what are its properties ? Why is it that the study of caloric is of such great importance in chemistry ? Within what limits of temperature can living things exist 12 HEAT PJIODUCES EXPANSION. in physiology, that the relations of this agent are of inter- est. When an ignited mass, as a red-hot hall, is placed in the middle of a room, common observation satisfies us that it rapidly loses its heat, its temperature descending until it becomes the same as that of surrounding walls and other bodies. This loss is due to several causes. A part of the heat is carried away by contact with the body which sup- ports the ball, a part by certain motions established in the surrounding air, and a part by radiation. This removal passes under the name oi transference ; and as soon as the temperature has declined to that of the adjacent bodies, an equilibrium is said to have been attained. There are two methods by which caloric can be transfer- red : 1st. By radiation ; 2d. By convection. Of the former we have two varieties — general radiation, and interstitial radiation. Under the influence of an increasing temperature sub- Fig, 6. stances expand. This takes place, whatever their form may be, whether solid, liquid, or gaseous. The experiment which is illustrated by Fig> 1 establishes this fact in the case of a copper ball ; and that the ^ same law holds good for liquids, may be proved by J taking a glass tufc, a, b, Fig. 6, open at the extrem- ^ ity, a, but having a bulb, c, blown upon it at the ^ other end. The bulb and a part of the tube, as high as b, is to be filled with any liquid substance, such as water, spirits of wine, or oil ; and the heat of a lamp, d, applied. As the liquid becomes warm, it dilates, , ^ as is shown by its rising in the tube, the dilatation increasing with the temperature. If novv^ the liquid be removed from the bulb, and the tube be inverted, as shown in Fig. 7, in a glass of water, we can prove the same fact for gaseous sub- stances, taking, as the type or representative of them, atmospheric air ; for, on simply grasping the bulb, c, . in the hand, the air which is in it dilates with the ' warmth, and bubbles pass in succession from the open end of the tube through the water in the glass, d. Through what causes does the temperature of a body descend ? What is meant by transference and by equilibrium ? In how many ways can caloric be transferred ? How many varieties of radiation are there ? By wliat means can it be proved that solids, liquids, and gases expand as their tern perature rises, and contract as it descends ? EFFECTS OP HEAT. 13 We conclude, therefore, that solids, liquids, and gases ex- pand as their temperature rises, and contract as their tem- perature falls. The magnitude of all objects around us is determined by their temperatures. A measure which is a yard? long in summer is less than a yard in winter ; a vessel which holds a gallon in winter will hold more than a gallon in summer. And as the degrees of heat vary not alone at different sea- sons of the year, but also during every hour of the day, it is clear that the dimensions of all objects must be undergoing continual changes. The appearance of stationary magni- tudes which such objects present is therefore altogether a deception. Heat thus determines the size of bodies ; it also determ- ines their form. As we have said, there are three forms of bodies, solid, liquid, and gaseous. A mass of ice, if ex- posed to a temperature of above 32°, melts into water ; and if that water be raised to 212°, it passes into the form of steam — a gaseous body. The assumption of the solid, the liquid, or the gaseous condition, depends on the existing temperature. In the same manner that it affects our measures of space, caloric affects our measures of time. Clocks and watches measure time by the vibrations of pendulums, or the oscil- lations of balance wheels, the uniformity of the action of which depends on the uniformity of their size. When the temperature rises, the rod of a pendulum lengthens, and its vibrations are made more slowly ; the clock to which it is attached loses time. When the temperature declines, the pendulum shortens ; it beats too quick, and the clock gains. Similar observations may be made in the case of watches. To obviate these difficulties many contrivances have been invented, such as the gridiron pendulum, the compensation balance wheel, &c. Advantage has also been taken of such ^ substances as expand but little for a given elevation of tem- perature ; and thus excellent clocks have been made, the pendulum rods of which were formed of a slip of marble. The natural, as well as the artificial measures of time, depend on the influence of heat. Our unit of time — the Is there any variation at different seasons in the length of measures or the capacity of vessels ? What is it that determines the form of bodies ? How can caloric affect our measures of time ? By what contrivances have this difficulty been avoided ? 14 CONNECTION OF TEMPERATURE AND TIME. day — is the period which elapses during one complete rota- tion of the earth on her axis. The length of this period is determined by the mean temperature of her mass. Should the mean temperature of the whole earth fall, her magni- tude must become less, or, what is the same thing, her di- ameter must shorten. It results from very simple mechan- ical principles, that a given mass, the dimensions of which are variable, rotating on its axis, will complete each rota- tion in a shorter space of time as its diameter becomes small er. Thus, when we tie a weight to the end of a thread, and, swinging it round in the air, permit the thread to wrap round one of the fingers, as the thread shortens by wrapping, the weight accomplishes its revolution in a less period. Now, transferring this illustration to the case before us, if the mean temperature of the earth had ever declined, she must have become less in size, and, therefore, turned round quicker, and the length of the day must have necessarily been less. But astronomical observations^ for a period of more than 2000 years back, prove conclusively that the length of the day has not changed by so small a quantity as the part of a second, and we therefore are warranted in inferring that the mean temperature of the globe has not perceptibly fallen. The distribution of heat on the surface of the earth de- termines, for the most part, the distribution of animals and plants ; to each climate its proper denizens are assigned. It is this which confines the lion to the torrid regions, and the white bear to the frigid zone. In the case of man, who has the power of accommodating his diet and his dress to external requirements, almost any part of the earth is hab- itable. Plants, like the inferior animals, have their locali- ties determined chiefly by the influence of heat. It is for this reason that even in tropical climates, if we ascend from the foot to the top of a very high mountain, we successively pass through zones occupied by trees and plants which, dif- fering strikingly from one another, have analogies with those which occupy respectively the torrid, the temperate, and the frigid zones, on the general surface of the earth. Do these disturbances affect the natural as well as the artificial measures of time ? How can it be proved that the mean temperature of the earth has not for many centuries changed ? What is it that chiefly determines the distribution of plants and animals ? EXPANSION OF GASES, 15 LECTURE IV. Expansion of Gases and Liquids. — Rudberg's Law . — Regularity of Gaseous Expansion. — Ascentional Pow^ er of expanded Gas. — Amount of Air contained in the same Volume at different Temperatures. — Gas Ther- mometers. — Expansion of Liquids. — The Mercury Thermometer. If we compare together the three forms of bodies, as re- spects their changes of volume under the influence of heat, we shall find that for a given rise of temperature, gases ex- pand the most, liquids intermediately, and solids least of all. To this rule but few exceptions are known ; liquid carbonic acid, however, expands about four times as much as any gaseous body. When heated from the freezing to the boiling point of water. 1000 cubic inches of iron become 1004 1000 “ “ water » 1045 1000 » “ air “ 1365 Recent experiments have proved that gases differ among themselves in expansibility, though the differences are not to any great extent. For the permanently elastic gases, atmospheric air may be taken as the type ; the experiments of Rudberg show that it expax.ds of its volume at 32° for every degree of Fahrenheit’s thermometer. As the same quantity of gas occupies very different volumes at different temperatures, it is necessary, in this and other such cases, to state some specific temperature at which the estimate of its volume is made ; the same gaseous mass occupies a much greater space at 75° than it does at 32°. In the instance before us, we consider the original volume to be that which the gas would have at 32°, and, as has been said, eveiy de- gree above that point will increase the volume by of the bulk it then possessed. Gases expand with uniformity as their temperature in- Of solids, liquids, and gases, which expand most by heat ? In what re- spect is liquid carbonic acid peculiar ? Is there any diiference among gases in their rates of expansion ? What is Rudberg’s estimate of the amount of expansion of air? Why are we required in these cases to adopt a specific temperature ? Do gases expand uniformly ? in EXPANSION OP GASES. creases. Ten degrees of heat produce the same relative ef- ' feet, whether applied at a low or at a high temperature ; this regularity probably arises from the want of cohesion which the gaseous particles exhibit; as we shall. presently see, it is not observed in the case of liquids and solids. The change in specific gravity of atmospheric air, when it Fig. 8. is warmed, is one of the causes of the rise of Montgolfier balloons. These, which were invented in France in the year 1782, consist of a bag or globe of light materi- als, such as paper or silk, with an aper- ture at the lower part, through which, by the aid of combustible material, as straw or shavings, the air in the interior may be rarefied. On a small scale, they may be made of thin tissue paper, pasted together so as to form a sphere of two or three feet in diam- eter, an aperture being cut in the lower portion six inches or more in width, and beneath it a piece of sponge, soaked in spirits of wine, suspended. This being set on fire, the flame rarefies the air in the interior of the balloon, which, though it might be at first flaccid, soon dilates, and the whole apparatus will now rise in the air, precisely on the same principle that a cork rises from the bottom of a vessel of water-. There is, however, another cause in operation in this case. The combustible material commonly employed gives rise (luring its burning to the disengagement of the vapor of wa- ter — -steam, which is much lighter than air. In the oper- ation of cupping, the glass receives for a moment the flame of a spirit lamp, and is then quickly applied to the surface of the skin ; the vapor of water quickly condensing, and the heated air contracting, a very good vacuum can be made. From the circumstance that the volume of air changes so readily with changes of temperature, contracting under the influence of cold, and dilating under that of heat, it is plain that in different climates on the earth’s surface a very different amount of atmospheric air is included under the same measure. A vessel which will hold precisely one ounce weight at the mean temperature of New York, will hold more than an ounce in the cold polar regions, and less than are Montgolfier balloons, and why do they rise? Why is it that ilio \vr‘i;>1it of nir in a given measure is different at different: places? GAS THERMOMETERS. 17 an ounce in the tropics. In the former situation the air is more dense, because it is in a contracted condition by reason of the low temperature, and therefore a greater weight is included under a given volume ; in the latter, the reverse is !the case. These facts are supposed to be connected with ' certain physiological results, as we shall hereafter see. The expansions of atmospheric air taking place with reg- ularity as the temperature rises, that substance is occasion- ally employed as a means of thermometric admeasurement. The air thermometer, called also Sanctorio’s thermometer, but which was invented by Galileo about 1603, consists of a tube of glass, a. Fig. 9, terminated at its upper ^ extremity by a bulb, b ; the other end of the tube ^ ^ being open, dips beneath the surface of some col- ^ oYcd water in a cup or reservoir, c, which serves also as a foot or support to the instrument. The bulb and part of the tube are full of air ; the re- mainder of the tube is occupied by the colored wa- ter, which, by its movements up and down, serves to : indicate changes in the volume of the included air. To the side of the tube a scale of divisions is affixed, and the tube is not arranged so tightly in the neck of the reservoir but that there is a free passage for “ the air in and out of that part of the instrument. On touch- ing the ball with the lingers, the air within it becomes warm, dilates, and depresses the liquid in the tube, or, on touching it with any cold body, it contracts, and the liquid rises. This form of thermometer is liable to a difficulty which renders it impossible to rely upon its indica- lo. tions, except under particular circumstances. It is affected by variations of atmospheric press- ure as well as by changes of heat. To prove that this is the case, place such a thermometer under the' receiver of an air pump, as shown in Fig. 10 ; on- producing the slightest degree of rarefaction, the liquid in the tube is instantly depressed, and on restoring the pressure of the air, it returns to its original position. Describe the thermometer of Sanctorio, By whom w-as it really invent^ ed ? How can the use of this instrument be illustrated ? By what dis- turbing cause IS Sanctorio’s thermometer affected? How may that bo proved ? v._ 18 EXPANSION OF LIOUIDS. The difFerential thermometer is a gas thermometer, so Fig, 11 . arranged as to he free from the foregoing difficulty. It consists of a glass tube, a h, Fig. 11, bent [] into the form represented in the b figure, with a bulb blown on each extremity. To the horizontal part a scale of divisions is affixed. The bulbs are full of atmospheric air, and in the tube there is a small column of colored liquid, which serves by its movements as an index. To under- stand the action of this instrument, it is only necessary tu consider what will take place when it is carried into a room the temperature of which is very high of very low. If the former, the air in both bulbs, becoming equally warm, will expand in both equally, and the column of fluid which acts as an index being pressed equally in opposite directions, does not move at all. If the latter, the air in both bulbs cool- ing equally, contracts equally, and again no movement en- sues. It is immaterial, therefore, whether we warm or cool both bulbs, the instrument is motionless. But if one of the bulbs, c, is made warmer than the other, d, movement at once ensues in the liquid column from c toward d. Move- ment of the index, therefore, takes place when the bulbs are at different temperatures, and hence the instrument is called a differential thermometer. It was formerly of considera- ble use in researches connected with radiant heat. Different liquids expand differently for the same thermo- metric disturbance. This is easily shown by an apparatus, as Fig. 12, in which we have three tubes, a, b, c, with bulbs on their ends, dipping into a trough, /, of tin plate. The tubes and bulbs should be all of the same size, and filled with the liquids to be tried to the same height. To each a scale is annexed. Let a be filled with quicksilver, h with water, and c with alcohol ; on pouring hot water into the trough, two phenomena are witnessed : Describe the differential thermometer. If this instrument be carried into a warm and then into a cold room, does its index move ? Wliy is it called differential thermometer? How can it be shown that different luiuids ex- pand differently ? Fig. 12. TUP. MERCURIAL THERMOMETER. 19 1st All the liquids expand ; 2d. They expand unequally when compared together, the mercury expanding least, the water intermediately, and the alcohol most. On being heated from the freezing to the boiling point ot water, Alcohol expands 1 part in 9 Oil “ 1 “ A Water “ 1 “ 22 TO Mercury “ 1 “ 55 50 Liquids which have arisen from the condensation of such gases as cyanogen, sulphurous acid, and especially carbonic acid, are among the most expansible bodies known, ihus liquid carbonic acid, warmed from 32° to 86°, expands four times as much as atmospheric air. In the case of several groups of liquids, as alcohol, sul- phuret of carbon, and wood spirit, it has been found that the rate of expansion is precisely the same if estimated at equal distances from their several boiling points. jr/^. 13 . Unlike gases, all liquids expand irregularly as their temperature rises, a given amount of heat pro- ducing a much greater effect at a high than at a low temperature. Ten degrees of heat, applied to a given liquid at 20 0"^, will produce a greater ex- pansion than if applied at 100^. The reason ap- pears to be, that as a liquid dilates its cohesive force becomes less, because its particles are being removed farther from each other , and, as the co- hesive force weakens, its antagonistic power, the heat, produces a greater effect. Advantage is taken of the properties of liquids in the making of thermometers. For these pur- poses, alcohol and mercury are the fluids selected. The mercurial thermometer consists of a fine cap- illary tube, Fig. 13, with a bulb blown on one end ; the bulb and part of the tube are to be fill- ed with quicksilver, and the air expelled from the rest of the tube by warming the bulb until the metal rises by expansion to the top of the tube, and at that moment hermetically sealing the glass by Of mercury, water, and alcohol, what is the order of expansion ? Do liquids, like gases, expand with regularity? What is the cause of ^if. ference ? For making thermometers, what liquids are selected , rlow is the mercurial thermometer made ? 20 THE MERCURIAL THERMOMETER. melting tlie end of it with a blow-pipe. As the thermom- eter cools, the quicksilver retreats from the top of the tube, and leaves a vacuum above it. It remains now to annex such a scale to the instrument as may make its indications comparable with other instru- ments. To effect this, the thermometer is plunged into a vessel containing melting ice or snow, and opposite the point at which the quicksilver stands is marked 32°. It is then transferred to another vessel in which water is rapidly boil- ing, and the point opposite which it then stands is marked 212°. The intervening space is divided into 180 equal parts ; these are degrees, and similar divisions are made on the scale for all points above 212° and below 32°. The zero point, or cipher of the scale, is therefore 32 degrees be- low the freezing point of water. It has been observed, that in the course of time the freez- ing point of some thermometers changes. This is due to the pressure of the air acting on the bulb, the thin glass of which yields to a certain extent, and the liquid consequent- ly rises in the tube. The same effect will often take place instantaneously by exposing a thermometer to a high tem- perature. It is therefore necessary to verify from time to time the graduations of these instruments. The zero point of the thermometric scale is not to be re- garded as indicating the total absence of heat. Observa- tions have been made in cold climates of degrees almost 80° below 0 ; and by the aid of liquefied protoxide of nitrogen, — 220° has been reached... The melting of ice and the boiling of water are the fixed thermometric points. They have been selected for the pur- pose of rendering thermometers comparable with each other. The numbers which are attached to these points are arbi- trary, and accordingly three different scales have been in- troduced in different countries. That which is commonly used in America and England is the Fahrenheit scale, which, as we h^ave just seen, makes the melting point of Ice 32°, and the boiling of water 212°. In France, the Centigrade scale is employed ; this has for the melting of ice 0°, and for the boiling of water 100°. In some parts of Europe, Is there a vacuum above the mercury in the tube ? How is the scale ad- justed ? What is the freezing and what the boiling point ? What is meant by the zero ? What are the fixed points ? Why are these fixed points em ployed ? What three scales have been introduced ? What is the Centi grade icale? THE MERCURIAL THERMOMETER. 21 Reaumur’s scale is used, the points of which are respective ly 0^ and 80°. Chemical authors always specify the ther mometer they use by a letter attached to the numbers ; thus, 212F., 100 0.,80 R., refer to the boiling of water on Fahrenheit’s, the Centigrade, and Reaumur’s scales. It is obvious that these degrees are readily convertible into each other by a simple arithmetical process. LECTURE V. Expansion of Liquids and Solids. — Importance of the Thermometer. — Alcohol Thermometer. — Point of Max- imum Density of Diquids. — Maximmn Density of Wa- ter connected with Duration of the Seasons. — Expan- sion of Solids. From the considerations advanced in Lecture III., we can perceive the importance of the thermometer. As all our measures of space and time are affected by variations of temperature, the thermometer, which measures those vari- ations, must necessarily be one of the fundamental instru- ments of physical science. If we state that a given object is a foot long, we must specify the temperature at which the measure was taken, for at a lower temperature it will be less than a foot, and at a higher it will be more. There are several peculiarities which quicksilver possesses that eminently fit it to be a thermometric fluid. 1st. It can always be obtained in a state of uniform purity. 2d. It ex- pands with greater regularity than most liquids, as its tem- perature rises, and when included in a bulb of glass, as in the common instrument, the irregularity of expansion of the glass almost exactly compensates the irregular expansion of the quicksilver, and hence the true temperature is very accurately marked. 3d. The range of temperature between the points of solidification and boiling is great, the former being — 39° Fahrenheit, and the latter at 662° Fahren- heit ; that is, about seven hundred degrees. 4th. It does not soil or moisten the tube in which it is contained, nor Wliat is Reaumur’s ? Can these be converted into cacli oi her ? Wliy is the thermometer such an important instrument ? What are the qualities which quicksilver possesses which fit it for these uses ? 22 MAXIMUM DENSITY OF WATER. does it adhere thereto, but moves up and down with facility. 5th. It is affected much more readily than water or spirits of wine by a given amount of heat, as we shall see when we come to speak of the capacity of bodies for caloric. When very low temperatures have to be measured, such as approach or are below the freezing point of quicksilver, we resort to thermometers filled with alcohol, tinged with some coloring matter to make its movements visible. This fluid requires a diminution of temperature of more than 180° below the zero of our scale before it solidifies, and hence is adapted to the measurement of low temperatures. If we take some water at 100° Fahrenheit, and, placing it in a vessel in which we can observe its volume, reduce its temperature, we shall find, agreeably to the general law heretofore given, that as it cools it contracts. As it success- ively passes through 80, 60, 50 degrees, it exhibits a con- tinuous diminution ; but as soon as it has fallen below 39°, although it may still be cooling, it begins to expand, and continues to do so until it reaches 32°, when it freezes. If we take some water at 32° and warm it, instead of expand- ing, it contracts, until it reaches 39° ; but from that point, any farther elevation of temperature causes it to obey the general law, and it expands. It is obvious, therefore, that if we take water at 39°, it is immaterial whether we warm it or cool it, it will expand. At that temperature, therefore, this liquid occupies the smallest bulk, and is at its greatest density, for neither by cooling nor warming can we reduce it to smaller dimensions. The particular thermometric point at which this takes place is designated the point of maximum density of wa- ter f and very exact experiments show that it is about 39|° Fahrenheit. There are many liquids which thus have points of max imum density, and which expand previous to assuming th( solid form. In the act of solidifying, water undergoes a ver^ great dilatation, amounting to about |-th of its volume ; thfj is the reason that ice floats upon it. Several melted metals exhibit the same phenomenon, and advantage is taken of Under what circumstances are alcohol thermometers used ? Does crater contract regularly when cooled from 10Q° to 32° ? Does it reguh .ly ex- pand when warmed from 32° ? At what thermometric point does tha' change take place ? What is the designation given to that point ? VV b ^ is that designation appropriate ? Are there other liquids which have ./oints of maximum density ? POINTS OF MAXIMUM DENSITY. 23 the fact in the arts. The alloy of which printers’ types arc formed, or stereotype plates cast, in the act of solidifying, expands, and hence forces itself into every part of a mould in which it may he poured, and copies it perfectly ; the same is the case with melted cast iron. But it is impopi- hle to obtain good castings with such a metal as lead, which contracts as it cools, and therefore tends to separate from the surface of the mould, or to leave vacant spaces in it. The fact that water possesses a point of maximum dens- ity is connected, to a great extent, with several remarkable natural phenomena ; the freezing of water on its surface is one of these results. If the water contracted as it cooled, the colder portions would descend, and rivers or ponds would commence to freeze at the bottom first, the solidification ad- vancing steadily upward. Such collections of this liquid would, during the course of a winter, become solid masses of ice, and they would greatly prolong that season of the year, from the length of time required to thaw them. But with things as they at present exist, the coldest water is the lightest ; it floats on the warm water below ; solidification takes place on the surface, and a veil or screen is soon form- ed which protects the liquid beneath. When the warm weather of spring comes on, the ice on the surface is in the most favorable position for melting, and thus the point of maximum density of water comes to be connected with the duration of the seasons. If salt is added to water, the point of maximum density descends, until, when the quantity is sufficiently great, it sinks below the freezing point. The observations just made apply therefore only to fresh, and not to salt water. We have already proved by the instrument represented in Fig. 1, that solid substances dilate ^ig. 14 . as their temperature rises. The same results may be made very apparent [\^c by the apparatus. Fig. 14. Upon a ^ strong basis or wooden board, a, b, let there be fastened two brass uprights, c with notches cut in them, so as to re- ceive the ends of the metallic bar, e. This bar should be very slightly shorter than the distance between the two up- What advantage is taken of this fact in the arts ? Why does water freeze first on its surface? How is it that these facts are connected with the duration of the seasons ? How does the instrument. Fig, 14, prove that a metallic bar expands when heated ? 24 EXPANSION OF SOLIDS. rights, that when it is placed resting in their grooves, if we take hold of it and move it, it will make a rattling sound as we push it backward and forward. If now wc pour hot water upon the bar, it dilates, as is proved on restoring it to its position between the uprights ; it will no longer rattle, for it occupies the whole distance between them, and per- haps there may even be a difficulty in forcing it into the grooves. For the determination of very small spaces, the sense of hearing may often be far more effectually employed than the sense of sight. The pyrometer, of which we have several varieties, is represented in Fig. 15. It may serve to illustrate the fact that solid substan- ces expand by heat. It consists essen- tially of a metallic bar, a a, resting at one end against an immovable prop, e, the other end bear- ing upon a lever, h. The extremity of this lever presses upon a second lever, c, which also serves as an index. Upon the index-lever a spring acts so as to oppose the lever 5, and the point of the index ranges over a graduated scale. If now lamps be applied to the bar, it expands, and the pressure taking effect on the lever, puts it in motion, the index traversing over the scale. On removing the lamp the bar contracts, and the spring, pressing the lever in the op- posite direction as soon as the bar is cold, brings the index back to its original point. Describe the pyrometer and the mode of using it. CONTRACTION AND DILATATION OF SOIilDS. ^25 LECTURE VI. Expansion of Solids. — Contraction of Solids . — They ex- pand irregidarly. — Different Solids expand* different- ly. — Points of Maximum Density. — Metallic Ther- mometers. — Nature of Thermometric Indications. It is a popular error, that when solid bodies have been heated, they do not return, on cooling, to their original size. Without resorting to any experimental proof, a few simple considerations will satisfy us on this point. If a bar of metal be exposed for a length of time in the open air, it will of course be subjected to continual changes of temper- ature ; whenever the sun shines on it it will expand, and during the cold night it will contract. If now, on cooling, it did not rigorously come back to its original size, but re- mained a little elongated, we should observe it increasing from day to day, and no matter how minute the difference might be, in the course of time it would become perceptible. Public edifices in cities are often surrounded by railings of cast iron, which are constantly exposed for years to varia- tions of heat and cold, but did any person ever observe them to grow or increase in size ? We conclude, therefore, that solid bodies, on coohng to their original temperature, regain their original bulk. By linear dilatation we mean increase in one dimension, as in length ; by cubic dilatation, increase in all dimensions, length, breadth, and thickness. Knowing the amount of linear dilatation of a given solid, we can easily ascertain its cubic dilatation, by multiplying the former by 3. This re- sult is near enough for practical purposes. Solids expand increasingly as their temperature rises, a phenomenon already observed in the case of liquids, and due to the same cause — a diminution of the cohesive force of the particles, because of their increased distance. Compared with one another, different solid substances ex- pand differently for the same disturbance of temperature. What decisi ve proof can ])c given that solids, on cooling to their original temperature, come back to their original size ? Wliat is linear dilatation? What is cubic dilatation ? How can the former bo converted into the lat- ter ? Does the same solid expand uniformly or increasingly os its temper- ature rises ? B 26 ^ COMPENSATION BAKSr This may be shown by having bars of difierent metals, but of precisely the same lengths, adjusted to the grooves of the instrument, Fig. 14. If a bar of brass and one of iron be compared, it will be found that the brass expands more than the iron, for it will entirely fill the distance between the uprights, while the iron rattles between them. This difference of expansion is also shown when two long common temperatures the compound bar is adjusted so as to be straight, but if hot water be poured upon it, it imme- diately curves, as represented at a c, the strip of brass be- ing on the outside of the curve ; if, on the other hand, it be ■ artificially cooled, the curvature is in the other direction, as at b dy the iron being on the outside of the curve. All this is obviously due to the fact that, for the same disturbance of temperature, the brass contracts and dilates much more than the iron. When the temperature is raised, the brass becomes the longer, and compels the compound bar to curve, it occupying the greater length of the curve. When the temperature falls, the brass becomes the shorter, and the bar curves in the opposite direction. By taking advantage of these metallic combinations, pen- dulums and balance-wheels for the accurate measurement of time have been constructed. The gridiron pendulum and the compensation balance are examples. The following table exhibits the expansion of various solid substances when heated from the freezing to the boiling point of water : Zinc (cast) . , . 1 in 323 Gold . . . . 1 in 682 Lead .... . 1 “ 351 Iron (wire) . 1 “ 812 Tin .... . 1 “ 516 Palladium . . . 1 “ 1000 Silver . . . . 1 “ 524 Platinum . . . 1 “ 1167 Copper . . . . 1 “ 581 Flint glass . 1 “ 1248 Brass .... . 1 “ 584 Black marble . . 1 “ 2883 Ice is much more expansible than the metals, surpassing. Fig. 16. slips of metal are soldered to- S gether face to face. If we fasten ‘a in this manner a slip of brass to a similar slip of iron, as in Fig. d 16, in which a a is the slip of iron and h b the slip of brass, at Do different solids expand alike ? Of brass and iron, which expands most ? Describe the construction of a compound bar, and the effect of warming and cooling it. What instruments are constructed on this property ? METALLIC THERMOMETERS. 27 in this respect zinc. Glass and platinum can be cemented together without parting as they cool, for their rates of ex- pansion are nearly alike. The process of cutting glass by means of a hot rod depends on unequal expansion. Though a solid substance is usually regarded as expand- ing equally in any direction, this is not always the case. In crystals, of which all the sides and angles are not alike, there may be a very different rate of expansion in different direc- tions, and it has even been observed that they may contract in one direction while they are expanding in another. The figure of a crystal of carbonate of lime is for these reasons different at the freezing and the boiling point of water. There are some metallic bodies which exhibit points of maximum density in the solid state. Rose’s fusible metal is an example. When heated from 32° to 111°, it ex- pands, but after that point it contracts, and continues to do so until it reaches 156°, at which temperature it is actually less than it is at 32°. From this point it again expands, and continues to do so until it melts, which takes place at about 201° Fahrenheit. Liquid thermometers have a limited range of indication. They can not be exposed to degrees of heat approaching the point of solidification, for then their movements become ir- regular ; neither can they be used for degrees near their boiling point, for if vapor should form, the instrument would be destroyed. But as there are many metals which require a very great degree of heat to melt them, it might be ex- pected that we should find among this class bodies well suited for thermometric purposes. The instrument given in Fig. 1 5 serves to illustrate such an apparatus, and also the difficulties encountered in its use. From the small extent to which metals expand, this form of instrument requires levers, or wheels, or some multiplying machinery connected with it, to make the changes more perceptible ; but such mechanical contrivances can not be employed without the introduction of certain causes of disturbance. Friction oc- curs on the centres of motion, the teeth of the wheels play on each other, and therefore the index, instead of moving with regularity and precision as the expanding bar presses, moves by starts often of several degrees at a time, then it What are the properties exhibited by Rose’s fusible metal ? Why can not liquid thermometers be used for very low and very high temperatures ? What difficulties occur in the use of this instrument ? 28 METALLIC THERMOMETERS. pauses, and once more starts again, the whole movement being incompatible with exactness. A compound strip of metal, as represented in Fig. 16, is free from many of these difficulties, and if of sufficient length, it will indicate temperatures with great delicacy. A modification of this instrument is known under the name of Breguet’s thermometer. It consists of a very slender strip of platinum, soldered to a similar piece of silver, and curved into a helix, or spiral, a h. Fig. 17. It is fastened at its upper extremity to a metallic support, c c, c and from its lower portion an index projects, which plays over a graduated circle. The expansion of silver is more than twice as great as that of platina ; when, therefore, the temperature of the thin spiral rises, curvature, with a corresponding motion of the index, takes-place ; and if the temperature falls, there is a movement in the opposite direction, as has been already explained. This Breguet’s thermometer is one of the most delicate instruments we have, for the mass of the spiral is so small compared with the mass of mercury in an ordinary thermometer, that every change in the surrounding temper- ature is followed with rapidity and precision. For many purposes in science and the arts, it is necessary to determine temperatures above a red heat. Danieli’s py- rometer is intended to meet these occasions. It consists of an arrangement by which the expansion of a bar of iron or platinum, while exposed to the heat to be measured, is reg- istered. The amount so registered is subsequently determ- ined upon a divided scale, and the temperature estimated therefrom. By the aid of such an instrument very high tem- peratures may be determined, and thus it has been shown that brass melts at 1869^ Fahrenheit, copper at 1996^, gold at 2200°, and cast iron at 2786°. The thermometer is commonly regarded as a measurer of heat. A little consideration will satisfy us that it is only so in a limited sense ; it does not indicate 1he quantity of Describe Bfeguet’s thermometer. AThy is this instrument so sensitive? Describe the principle of Daniell’s pyrometer. Give the melting points of some of the most important metals. Does the thermometer measure the heat to which it is exposed ? CAPACITY OF BODIES FOR HEAT. 29 heat present in the bodies to which it is exposed, for if im- mersed in a glass of water and a bucket of water drawn from the same well, it stands at the same point ; but of course there are very different quantities of caloric in the two cases. It is not, therefore, the quantity of heat, but the in- tensity, which it measures ; that is to say, not the quantity abstractly, but the quantity contained in a given space ; and in the mercury thermometer, that space is measured by the volume of the mercury in the instrument itself. It does not tell how much heat is absolutely present in the substances to which it is exposed ; and though it may stand at the same height in the same quantity of two different liquids, it does not follow that those liquids contain the same amount of caloric, as we are immediately to see. LECTURE VII. Capacity of Bodies fop.. Heat. — Methods of determining Capacities. — Warming. — Melting . — Cooling. — Mix ture. — Comparison betiveen the Thermometer and Cal- orimeter. — Definition of Specific Heat. Many years ago it was discovered by Boyle, that if two bottles of the same size and form were filled with different liquids, and placed before the fire so as to receive its heat equally, their temperature did not rise similarly ; thus, if one bottle was filled with water and the other with quick- silver, the temperature of the latter would rise much more rapidly than that of the former ; and, on making the exper- iment with a little care, it will be found that the same quan- tity of heat will raise the temperature of mercury twice as high as that of an equal volume of water. By extending these experiments to other substances, it has been fully proved that different bodies require different amounts of heat to warm them equally. What is it then, that it does actually measure ? What is meant by the intensity of heat? Describe Boyle’s experiment with water and quicksilver. To whtLt general result do such experiments lead ? State the different meth- ods by which capacities for heat may be determined. 30 THE CALORIMETER. Calorimetry. There are several different methods by which the capac- ity of bodies for heat may be determined, such as, 1st, by warming ; 2d, by melting ; 3d, by cooling ; 4th, by mixture. The first of these methods has already been illustrated by the experiment of Boyle. It consists essentially in exposing the same weight of the substances to be tried to a uniform source of heat, as, for example, a bath of hot water, and ex- amining how high their temperature has risen in a given space of time. Thus it will be found that it takes thirty times as long to warm water as to warm mercury, when equal weights are used, and hence we infer that the capac- ity of water for heat is thirty times that of quicksilver. The second process is involved in the action of the calo- rimeter, the operation of which may be easily understood from Fig. 18. Take a solid block of ice, a a, in. which a cavity of the form represented at b has been made, and provide a slab of ice, c c, which may close completely the mouth of the cav- ity. Suppose it were required to de- termine the relative capacities of water and quicksilver for heat. In a glass flask, d, place one ounce of water, and by immersing the flask in a bath of hot water, raise its tem- perature up to a given point, as, for example, 200^ ; then place the flask at this temperature in the cavity 5, and put on the cover, c c. The hot water in the flask begins to cool, and in descending to 32®, the point to which it will event- ually come, a certain portion of the surrounding ice is melt- ed, the water resulting therefrom collects in the bottom of the cavity, and when the cooling is complete, it may be pour- ed out and measured. In the next place, put in the flask one ounce of quicksil- ver, the temperature of which is raised as before to 200® by immersion in the hot-water bath ; deposit the flask in the ice cavity, and put on the cover. As the quicksilver cools, the ice melts, and when the collected water is meas- ured, it is found to be less than in the other ca§e, hi the Give an illustration of the first process. Show how the capacities of water and mercury may be ascertained by the second. What are the rela- tive capacities of equal weights of these bodies ? METHODS OP DETERMINING CAPACITIES. 31 proportion of 1 to 30. A given weight of water will there- fore melt 30 times as much ice as an equal weight of quick- silver, in cooling through the same number of degrees. * The calorimeter of Lavoisier, which is represented in Fig, 19, acts on the same prin- ciple as the block of ice. It con- sists of a set of tin vessels within each other ; in the central one, < 1 , the substance to be examined is placed, and between this and the next vessel, at b, the ice to be melted is introduced, broken into small fragments ; the water arising from the melting flowing off through a stop-cock, c, at the bottom into a measuring glass ; and in order to avoid any por- tion of the ice being melted by the warm external air, an- other layer of fragments of ice is placed on the outside at d, and the water arising from it is carried off by a lateral stop- cock, e. The third process, the method by cooling, known also as the method of Dulong and Petit, consists essentially in as- certaining the length of time required to cool through a given number of degrees. A substance which, like water, has a great capacity for caloric, and therefore contains a large amount of it, requires a greater length of time to cool ; but one like quicksilver, the capacity of which is small, having less heat to give forth, requires a corresponding short space of time. The method by cooling requires -several precau- tions ; among others, the bodies under investigation should be placed in vacuo. It gives very exact results. The method by mixture may be readily understood. If a pint of water at 50° be mixed with a pint of water at 100^, the temperature will be 75^, that is the mean. But if a pinL of mercury at 100^ be mixed with a pint of water at 40°, the temperature of the mixture will be 60° : so that the forty degrees lost by the mercury can only raise the tem- perature of the water twenty degrees. It appears, there- fore, that when equal volumes of these fluids are examined, the capacity of the water for heat is about twice as great Describe the calorimeter of Lavoisier, Describe the method of Dulong and Petit Describe the method by mixture. Fig. 19, 32 METHODS OF DETERMINING CAPACITIES. as that of mercury, and of course the result becomes still more striking when equal weights are used, being then, as we have seen, in the proportion of 1 to 30. The method of mixtures is not limited to the investiga- tion of liquid substances, but it may also be extended to sol- ids. Thus, if a pound of copper, heated to 300°, be plunged into a pound of water at 50°, the resulting temperature is 72° ; from which it appears that the capacity of water for heat is about ten times as great as that of copper. By resorting to these various methods, the capacities of a great number of substances have been determined, and in the treatises on chemistry, tables exhibiting such results are given. But it will have been noticed, from the foregoing instances, that it is not the absolute quantities of heat in bodies that we thus determine, but only relative quantities in substances compared together. Such tables require, therefore, one substance to be selected with which all the others may be compared, and for solids and liquids water has been chosen. Its capacity for heat is represented by 1*000, and with it they are compared. For gaseous bodies atmospheric air is chosen. Capacity of Bodies for Heat. Water .... . 1000 Cobalt . . . . . 106-96 Ice . 513 Zinc .... . . 95-55 Charcoal . . . . 414 Copper . . . . . 95-15 Sulphur . . . . 241 Arsenic . . . . . 81-40 Glass .... . 203 Silver . . . . . 57-01 Diamond . . . . 147 Gold. . . . . . 32-44 Iron .... . 113-79 Platinum . . . . 32-43 Nickel .... . 108-63 Mercury . . . . 33-32 From this it appears that the capacity of ice for heat is nearly half that of water, which stands at the head of all solid and liquid substances. .. In the form of steam the ca- pacity of water is less than in the liquid form, in the ratio of 847 to 1000 for equal weights. The calorific capacity of a substance therefore changes with its physical condition. The method which has been resorted to for determining the capacity of gases, is to pass them, when heated carefully to 212°, through a spiral tube immersed in water, the tem- perature of which is measured. Owing to experimental dif- Is this limited to liquid substances ? Do we thus determine the absolute quantities of heat in bodies ? What substance is used to compare solids and liquids ? What is the substance for gases ? black’s doctrine op capacities. 33 ficulties, the' results arrived at by different chemists exhibit considerable variation. By contrasting the nature of the results given by the cal- orimeter, Eig. 19, with the indications of a thermometer, we shall see more clearly what it is that the latter instru- ment in reality points out. The calorimeter measures quan- tities of heat, the thermometer intensities. As has been said, a thermometer placed in two vessels of different ca- pacities, filled with water from the same source, will stand at the same height in both, and indicate the same temper- ature. But it needs no experiment to assure us that, if these different quantities of water were placed successively in the interior of the calorimeter, they would melt different quan- tities of ice, the one melting more of the ice in proportion to its greater weight compared with the other. Dr. Black, who was one of the early investigators of these phenomena, introduced the term “ Capacity of Bodies for Heat,” implying the idea that this principle, entering their pores, could be taken up by different bodies in different amounts. Thus, if we have two pieces of sponge of the same size, one of which is of a very dense, and the other of a porous texture, and cause them to imbibe as much water as they can hold, the porous sponge will of course contain the greater quantity. These sponges may therefore be said to have different “ capacities for water and this is precisely the idea which is conveyed in Black’s doctrine of capacity. But, upon these principles, it would follow that the lighter a body is, that is, the greater the interstices between its atoms, the more caloric it should be able to contain. Oil, there- fore, which will float upon water, ought to have a greater capacity for heat than water ; but, in fact, it is the reverse, for its capacity, instead of being greater, is not one half. To avoid these difficulties, the term specific heat has been in- troduced by most writers, and the term capacity abandoned, a change which I think is to be regretted, especially when it is recollected that this objection does not contemplate the difference of the weight of atoms. The specific heat of bodies, or their capacity for caloric, increases with their temperature. Upon Black’s doctrine, How do the indications of the calorimeter compare with those of the ther- mometer ? On what analogy is Black’s doctrine of “ capacity” founded ? What is the objection to this doctrine? What is meant by specific heat? Does the capacity of bodies change with their temperature ? 34 VARIATIONS OP SPECIFIC HEAT. the cause of this is readily understood, for, in simple lan- guage, the pores become larger, and there is therefore room for more heat. Solid substances, when violently compressed, evolve a portion of their caloric : thus, a piece., of soft iron, when hammered, becomes red hot. The doctrine of Black here again ofters a ready explanation, for on the same prin- ciple that a sponge, when compressed, allows a certain por- tion -of its water to exude, so the metalline mass, when its particles are forced together, allows some of its caloric to escape. LECTURE VIIL Capacity for Heat and Latent Heat. — Variahility of Capacities under Compression and Dilatation . — The- ory of the Formation of Clouds . — The Fire Syringe . — Cold in the upper Regions of the Air. — Connection between Specific Heats and Atomic. Weights. — Latent Heat. — Caloric of Fluidity. When the volume of a gas increases, its capacity for heat increases, and a diminution of volume is attended with a diminution of capacity. Thus, if we place a Breguet’s thermometer under the receiver of an air pump, and exhaust rapidly, a sudden reduc- tion of temperature is indicated, arising from the fact that, as the rarefaction is effected, the ca- pacity increases, an increase which is satisfied at the expense of a portion of the sensible heat. Upon the same principle we can explain the sudden ap- pearance of a fog or cloud, when moist air is quickly rare- fied. It will be seen, when we speak of the nature of va- pors, that the quantity of vapor which can exist in a given space depends on the temperature ; thus, if a space sat- urated with vapor is cooled, a portion of the vapor assumes the liquid form. When, therefore, by the aid of an air- pump, we suddenly rarefy air saturated with moisture under Does the capacity of bodies change under compression? How is this ex- plained agreeably to Black’s doctrine ? When the volume of a gas changes, what are the changes in its specific heat ? What is the fact which the exper- iment of Fig. 20 proves ? What is the theory of the production of clouds ? Fig. 20. FORMATION OF A CLOUD. 3f a receiver, the capacity increases, cold is produced, and a part of the water takes on the form of drops. It Fig. 21 . is on this principle that the nephelescope acts : it consists of a receiver, a, Fig. 21, connected with a flask, Cy by an intervening stop-cock, b; the stop-cock being closed, the receiver is exhausted by the pump, and now, on suddenly opening the stop-cock, so that the air contained in the flask may rapidly expand into the receiver, a mist or cloud makes its appearance, due to the deposit of water in the form of minute drops. If the air at the time be very dry, it may be purposely ren- dered moist by being exposed to water. When atmospheric air is suddenly compressed, its capac- ity for heat diminishes ; this is well shown by an in- Fi^. 22 . strument such as is represented in Fig. 22, consisting ^ of a syringe, with a piston moving perfectly air tight in it. On the end of the piston there is an excavation, in which a piece of tinder may be fastened ; the pis- ton being rapidly forced into the syringe, the air is compressed, the capacity for heat becomes less, caloric is evolved, and the tinder set on fire. At one time these syringes were used as a means of obtaining fire. The variation in capacity of substances under variation of volume may be clearly understood and readily borne in mind by Black’s doctrine, as illustrated in the case of a moistened sponge. If a sponge which has imbibed as much water as it can hold be compressed, a portion of the water exudes, just as the air in the syringe allows a portion of iU heat to escape when pressure is made. On relaxing the force on the sponge, and allowing it to dilate, it will take up an increased quantity of water ; and air, when suddenly dilated, as we have seen, has its capacity for heat increased. From these facts, it appears that the heat of bodies exists under two different forms, as sensible and insensible heat. In the experiment with the syringe, just related, the heat that sets fire to the tinder existed previously to compression in the air ; it existed as insensible heat, but during the com- pression it put on the form of sensible heat. The same tran- Describe the nephelescope. What is the result of the action of this in- strument? When air is compressed, why does it emit heat? How can these changes be accounted for by Black’s doctrine ? What are the rela- tions betw’een sensible and insensible heat ? 36 SENSIBLE AND INSENSIBLE HEAT. sition is also recognised in the action of the nephelescope ; the heat, which was sensible before rarefaction, becomes in- sensible, and cold, or a depression of temperature is the result. The great degree of cold which reigns in the upper re- gions of the atmosphere is due, to a considerable extent, to the capacity of that dilated air for heat. On the same prin- ciple we can explain the formation of clouds from transpar- ent atmospheric air : a stratum of air, reposing on the sur- face of the sea, or the moist earth, becomes saturated with vapor ; by the warmth of the sun or other causes, it begins to rise in the atmosphere, and as it rises it expands, because the pressure upon it is continually becoming less. An in- creased capacity is the result of its dilatation, and, as is the case in the nephelescope, cold is produced, and a deposit of a part of the moisture takes place ; this moisture, appearing under the form of minute drops, is what we call a cloud. From the small capacity of quicksilver for heat,' we see one of the reasons that it is a suitable substance for forming thermometers ; it warms rapidly and cools rapidly, and there- fore follows variations of temperature much more promptly than water and most other liquids. There is a connection between the specific heat of sev- eral simple bodies and their atomic weights, pointing out the fact that elementary atoms have in many instances the same specific heat ; recently the same conclusion has been established in the case of certain oxides, carbonates, and sulphates. • Table of the Sjpecific Heats of Elementary Atoms. Iron .... . . 3-0928 Sulphur . . . . 3*2657 Zinc .... . . 3-0872 Mercury . . . . 3*7128 Copper . . . . . 3 0172 Silver .... . 6*1742 Lead .... . . 3-2581 Arsenic .... . 6-1326 Tin ... . . . 3-3121 Antimony . . . . 6-5615 Nickel . . . . . 3-2176 Gold . 6-4623 Cobalt . . . . . 3-1628 ’ Iodine .... . 6-8462 Platinum . . . . 3-2054 Bismuth . . . . 2-1917 From this table it appears that the first ten substances show a close approximation in their capacities for heat, if the quantities used be in proportion to the atomic weights, instead of equal weights ; that the next five have a double capacity ; and the last a capacity less by about one third. Describe the mode in which clouds form. Why does the capacity of quicksilver fit it for a thermometric liquid ? What is h-* relation of the specific heat of many elementary bodies ? LATENT HEAT. 37 Latent Heat. First Change of Form. Heat of Fluidity. When solid substances, which can resist a due tempera- ture without decomposition, are exposed to an increasing heat, a point is eventually reached at which they assume the liquid state. This point, known as the point of fusion or melting point, may be regarded as fixed for each sub- stance. For mercury it is 39*^ below the zero of the ther- mometer ; for iron, about 2800^ above. Table of the Melting Points of Bodies. Iron . . 2800 Sulphur .... . 232 Gold . . . . . . 2016 Wax . . . . ; . 142 Silver . . . . . . 1873 Phosphorus . . . . 108 Zinc . . . . . . 773 Tallow .... . 92 Lead . . . . . . 612 Olive Oil .... . 36 Tin . . 442 Ice . 32 Potassium . . . . 135 Mercury .... . —39 Some substances, perhaps all to a greater or less extent, pass through a condition intervening between the solid and liquid state, assuming a pasty consistency. The manufac- ture of glass depends on such a property ; it^is also striking- ly shown by various oils and wax. Indeed, different liquids may be said to present different degrees of liquidity : this is well seen when sulphuric acid, a dense, sluggishly-moving body, is compared with sulphuric ether, a substance of re- markable mobility. The liquidity of the liquid state seems generally to be increased by elevation of temperature. If we take a mass of ice, the temperature of which is at the zero point, and bring it into a warm room, examining the circumstances under which its temperature rises, they will be found as follows : the mass of ice, like any other solid body, warms with regularity until it reaches 32? ; then, for a considerable period of time, no farther elevation is per- ceptible, but it undergoes a molecular change, assuming the liquid condition ; when this is complete, the temperature again commences to rise. That we may have precise views of these facts, let us sup- pose that the mass of ice and the warm room into which it is carried have such relations to each other that the temper- ature of the former can rise from the zero point one degree per minute ; for thirty-two minutes the temperature of the Describe the change which ice undergoes when warming. CALORIC OF FLUIDITY. 38 ice will be found to increase, and at the end of that time, a thermometer, if applied, would stand at 32°. But now, al- though the heat is still entering the ice at the rate of a de- gree per minute, the process of warming ceases, and for 140 minutes no farther rise takes place ; the ice now commences to melt, and in 140 minutes the liquefaction is complete. The temperature then again rises, and continues to do so with regularity. . . . n We infer from results like the foregoing, that about 14U degrees of heat are absorbed by ice in passing into the con- dition of water ; and as this heat is not discoverable by the thermometer, it is designated as latent heat. A similar fact appears when any liquid, such as water, passes into the gaseous or vaporous condition. Thus, if some water be exposed to a fire which can raise its temperature at the rate of one degree per minute, that effect will con- tinue until 212° are reached ; at that point, no matter how much the heat be increased, the temperature remains sta^ tionary. The water undergoes a change of form, assuming the condition of a vapor, and the change is completed in about 1000 minutes. In this, as in the former instance, we infer that a large amount of heat has become latent, or undis- coverable by the thermometer, and that it is occupied m es- tablishing the elastie form which the water has assumed. The caloric which thus disappears when a solid assumes the liquid form, takes also the designation of caloric of fluid- ity, and that which disappears in the formation of a vapor, the caloric of elasticity. Table of the Caloric of Fluidity of Bodies. Water . . . . , . . 142° Zinc . . . . . . 4930 Sulphur . . . , . . 145'^ Tin. . . . . . . 500° Lead . . . . , . . 162'^ Bismuth . . . . . 550° Beeswax . . . . . . 175"^ By the method of mixtures the same results may be es- tablished ; thus, if a pound of water at 32° is mixed with a pound at 172°, the mixture will have the mean temper- ature, that is, 102° ; but if a pound of ice at 32° be mixed Is there any pause in the elevation of its temperature? How many de- crees of heat are absorbed during the liquefaction of ice ? What is latent heat ? How many degrees of heat are absorbed during the vaporization of water? What is the latent heat of steam? What is caloric of fluidity? What is caloric of elasticity ? How can the doctrine of latent heat be e» tablished by the method of mixtures ? HEAT EVOLVED IN SOLIDIFICATION. 39 with a pound of water at 172°, the mixture still remains at 32°, and the reason is clear, from the foregoing considera- tions, that ice, in passing into the liquid state, requires 140° of caloric of fluidity which are rendered latent. LECTURE IX. Latent Heat. — Heat evolved in Solidification . — Theory of freezing Mixtures. — Expansion during Solidifica- tion. — Fixity of the Melting Point. — Latent Heat con- nected with the Duration of the Seasons. — Nature of Vapors. — Caloric of Elasticity. When a liquid assumes the solid form, a considerable amount of heat is evolved. The cause is readily understood, from what we have seen taking place during the reverse process ; which has led us to the fact that the difference be- tween any given solid and the liquid which arises from it by melting is in the large amount of latent heat which is found in the latter, and which is occupied in giving it its form. A saturated solution of sulphate of soda may be cooled from its boiling point to common temperatures, in a vessel tightly corked, without solidification taking place ; but when the cork is withdrawn crys- tallization ensues, and heat is evolved. This may be proved by taking a bottle, a a, Fig. 23, filled with such a solution ; and having intro- duced the bulb of an air thermometer through the neck, h, by means of an air-tight cork, the mouth, c, of the bottle is to be carefully stopped. When the whole apparatus has reached the or- dinaiy temperature of the air, the stopper at c is withdrawn, and solidification at once takes place, or, if it should at first fail, the introduction of a crystal of sul- phate of soda will bring it on. At that moment it will be perceived that not only does the thermometer indicate a rise of temperature, but if the bottle be grasped, it will be found to be sensibly warm. Is heat absorbed or evolved when a liquid solidifies ? What is the cause of this ? How can it be illustrated with a solution of sulphate of soda ? Fig. 23 . 40 FREEZING MIXTURE. With care, water may he cooled to a point far below that of freezing without assuming the solid form. If, under these unusual circumstances, it be agitated, solidification of a part of the water ensues, and heat is evolved, the temperature rising to 32°. On these principles depends the action of freezing mix- tures, of which the following is an example : If we take eight parts of crystallized sulphate of soda, and mix it in a thin tumbler with five parts of hydrochloric acid, the sul- phate of soda, from being a solid, assumes the liquid form ; and taking, in order to effect that change, of form, caloric from surrounding bodies, it reduces their temperature. This may be shown by placing four parts of water in a thin glass test tube, and stirring it about in the mixture ; the water speedily freezes, even though the experiment may be made on a warm summer day. Table of Freezing Mixtures. Mixtures. Pts. Tliennometer Sinks. Deg. of Cold. Nitrate of Ammonia . Water 1 1 from -{-50° to-|-4° 46° Sulphate of Soda . . Hydrochloric Acid 8 5 from 50° to 0 50° Snow or pounded Ice Common Salt . . . 2 1 to 5° * Snow ...... Diluted Nitric Acid . 3 2 from 0° to —46° 46° All these mixtures depend essentially on the principle un- der consideration — that latent heat must be furnished to a substance passing from the solid to the liquid state. They consist of various solid substances, the liquefaction of which is brought about by the action of other bodies : thus, in the instance we have seen, the sulphate of soda is brought from the solid to the liquid state by hydrochloric acid, in which it dissolves, and heat is necessarily absorbed. Many substances, when solidifying, expand. This is the case with water, in which the amount of expansion is about |-th of the bulk. The force which is exerted under these circumstances is very great, and capable of tearing open the strpngest vessels. On a small scale, this may be easily Can water be cooled below 32° without freezing ? Give an example of a freezing mixture. What are the principles on which freezing mixtures act ? What is the amount of the expansion of water in the act of freezing ? SOLIDIFICATION OF WATER. 41 shown by filling a bottle full of water, and, having intro- duced the cork, fastening it tightly down with a piece of wire. On putting such a bottle into a freezing mixture, for example, snow moistened with nitric acid, congelation promptly takes place, and the bottle is burst. All processes of freezing are therefore processes of warm- ing, for the heat which has given the liquid form reappears when solidification takes place. The freezing point of water is usually spoken of as a fixed point, and is marked as such upon the scales of our ther- mometers ; but if water be cooled without allowing any movement or agitation of its parts, it may be brought as low as 15°. It is then in the same condition as the saturated solution of sulphate of soda just alluded to. The slightest motion is sufficient to solidify it. But, though water will retain its liquid form far below its freezing point, ice can not be brought above 32^ without melting. The melting of ice, and not the freezing of water, is therefore the fixed ther- mometric point. We have seen that the possession of a point of maximum density by water exerts a great effect upon the duration of the seasons ; a similar observation might be made as re- spects its latent heat. If ice, by the absorption of a single degree of heat, when it passes from 32°, could turn into water, the great deposits of winter would suddenly melt, and inundations be frequent ; or, if water, by losing a single de- gree of heat, turned into ice, freezing would go on with great rapidity. To the melting of ice, or the freezing of water, time is necessary ; the 140° of latent heat have to be dis- posed of ; this, therefore, serves to procrastinate the approach of winter, and causes the spring to come forward with more measured steps. In autumn the water has 140° degrees of heat to give out to surrounding bodies before it solidifies ; in spring it must receive the same amount before it will melt. This, therefore, serves as a check upon sudden changes in the seasons. Second Change of Form — Heat of Elasticity. Having thus discussed the leading facts observed in the How may the force with which this expansion takes place be illustrated? Is the freezing point of water a fixed thermometric point ? How low can \vater be cooled without freezing ? Is the melting of ice, or the freezing ot water, the fixed thermometric point ? What connection has the latent heat of water with the duration of the seasons ? 42 PROPERTIES OP VAPORS. change from the solid to the liquid condition, let us now turn our attention to the second change of form, the passage from the liquid to the gaseous state. Exposed to a rise of temperature, liquid substances boil at a particular point, which varies with their nature, as the following table shows. Table of Boiling Points, Ether 96^^ m. Nitric Arid . . • • 248° Sulphuret of Carbon 118^ Oil of Turpentine . 314° Ammonia .... 140° Phosphorus . . . . 554° Alcohol 173° Sulphuric Acid . . 620° Water 212° Mercury . . . , . 662° A technical distinction is made between a gas and a va- por ; by the latter we understand a gas which will readily take on the liquid form. Some of the leading peculiarities in the constitution of Fig. 24. vapors may be exhibited by the following experiment : Take a glass tube, a Fig- 24, with a bulb, b, blown on its upper ex- tremity ; pour water into the bulb, filling the tube to within an inch or two of the end ; this vacant ^space fill with sulphuric ether ; and now, closing the end of the tube with the finger, invert it in a glass of water, as is represented in the figure. The ether, being much light- er than water, at once rises to the upper part of the bulb, as is shown by the light space, the bulb being of course full of ether and water conjointly. On the application of a spirit lamp the ether vaporizes, and presses the water out of the bulb into the glass cup. Three important facts may now be established. 1st. Vapors occupy more space than the liquids from which they arise. 2d. They have not a misty or fog-like appearance, but are perfectly transparent. 3d. When their temperature is reduced, they collapse to the liquid state. That the first of these observations is true, is at once seen on comparing the quantity of ether with the volume of va- What is the distinction between a gas and a vapor? Describe the exper- iment represented in Fig. 24. VV^hat is the difference between a vapor and the liquid which forms it, as to volume ? Have vapors necessarily a cloudy appearance ? VAPORIZATION. 43 por which has risen from it ; the ether occupying but a small space at the top of the bulb, the vapor fills it entirely. We perceive, moreover, that ethereal vapor does not possess that cloudy appearance which is popularly attached to the term vapor, but that it is as transparent as atmospheric air. And, on removing the lamp, so that the temperature may fall, the liquid rushes up violently into the bulb, exhibiting the ready collapse of the ether vapor into the condition of a liquid. We have already proved that a large amount of heat be- comes latent, constituting the caloric of elasticity of vapors. The temperature of steam is 212^, as is that of the water from which it rises ; but it contains about 1000° of latent heat, which gives to it its new form. Difierent vapors pos- sess different quantities of latent heat ; thus, for ether, the number is 163° ; for alcohol, 376° ; and, as we have said, for water, 1000° ; or, according to the recent exact experiments of Brix, 972°. It is this great quantity of caloric which constitutes steam so efficient an agent for warming. The steam arising from one gallon of water will raise the tem- perature of five gallons and a quarter from the freezing to the boiling point ; its caloric of elasticity is nearly sufficient, were the steam a solid body, to make it visibly red hot in the daylight. In the warming of buildings by steam pipes, each square foot of their surface will heat 200 cubic feet of surrounding air to 75°, and will require about 170 cubic inches of boiler capacity for its proper supply. LECTURE X. Vaporization. — Vapors form at all Temperatures, — Form instantly in a Void. — Effects of removing Pressure . — Measure of Elastic Force of Vapors. — Cumulative Pressure. — Failure of Marriotte's Law. — Elasticity increases with Temperature. — Maximum Density of Vapors. Vaporization goes on at all temperatures. It is not nec- essary that the boiling point should be reached ; even ice On reduction of the temperature, what phenomena do they exhibit? How are these three facts proved ? What is the amount of caloric of elas- ticity of steam ? Mention it also in the case of ether and alcohol. 44 EFFECTS OF CHANGE OF PRESSURE. -will evaporate away. The thin films of this substance often F\g. 25. ’ seen incrusting windows may disappear without undergoing the intermediate process of fusion, and a mass of ice, freely exposed to the air on a dry, frosty day, loses weight. Steam, therefore, rises from water at all temperatures, but with more rapidity and a higher elastic force as the temperature is higher. In a vacuum vapors form instantaneously. If we take a barometer, a a. Fig. 25, and pass into the Torricellian vacuum which exists at its upper part a small quantity of sulphuric ether, even before it has reached the void space, vapor forms, and the mercury is instantly depressed. Under ordinary circumstances, when the instrument is standing at 30 inches, the column at once falls to 15 or 16, the space being now filled with the vapor of ether ; and if in succession other liquids are tried, the same general result is obtained — instantaneous vaporization ; but the amount of vapor set free is different in the different cases. Diminution of atmospheric pressure is, therefore, favorable to vaporization, and were the pressure of the air entirely re- 26. moved, there are many liquids which would as- sume a permanently aerial form. Take a glass tube. A, Fig. 26, closed at one end and open at the other, and, having filled it with water, in- vert it in a cup, B, and introduce into it a little sulphuric ether, which will rise to «, the top of the tube. The apparatus is ne:g: to be placed under an air-pump receiver, and exhaustion made : the ether enters into ebullition, and gives off vapor which is quite transparent. As long as the reduction of pressure con- tinues, the ether keeps the gaseous form, but on readmitting the air, it returns to the liquid state. By increase of press- ure, as well as by diminution of temperature, vapors may be reduced to the liquid condition. Though the law that vapors occupy more space than the liquids from which they come is of universal application, the increase of volume is by no means the same in all cases. How can it be proved that vaporization goes on at all temperatures ? What is the eflfect which ensues when a vaporizable liquid is passed into a Torri- cellian vacuum ? What substances exist commonly in the liquid state, in con- sequence of the pressure of the air ? What is the effect of an increased press- ure on vapors ? Do all liquids expand equally in assuming the vaporous state ? CUMULATIVE PRESSURES. 45 Under ordinary circumstances of pressure, a cubic inch of water at its boiling point produces nearly a cubic foot of steam, or 1696 cubic inched more accurately. The same quantity of alcohol produces 519 cubic inches, and of oil of turpentine 192 cubic inches. The elastic force exerted by vapors under certain limits can be measured by the apparatus given in Fig. 25. The theory of the process is very simple. The height at which the barometer stands is determined by the pressure of the air. In the experiment there described, as long as there is nothing to counterbalance that pressure, the mercury is forced up by it in the tube to a height of 30 inches ; but on introducing some ether, the vapor which forms, exerting an elastic force in the opposite direction, tends to push the mer- cury out of the tube. On the one hand, we have the press- ure of the air ; on the other, the elastic force of the ethereal vapor ; they press in opposite directions* and the resulting altitude at which the mercury stands expresses, and, indeed, measures the elastic force of the vapor. Thus, at a tem- perature of eighty degrees, water will depress the mercurial column about 1 inch, alcohol about 2 inches, and sulphuric ether about 20. These numbers, therefore, represent the elastic force of the vapors evolved. In close vessels, from which there is no escape, or where the escape is greatly retarded, a constantly Fig. 27. accumulated force is generated when the temperature is raised. Thus, if we place some water in a flask, a. Fig. 27, into which a tube, b b, is inserted air-tight by means of a cork, and bent in the form exhibited in the figure, and dipping nearly to the bottom of the flask, on the application of a spirit lamp, the vapor generated, having no passage of escape, accumulates in the upper part of the flask, and, exerting its elastic force, presses the liquid through the tube in a continuous stream. The mechanical force which thus arises, when every avenue of escape is stopped, is strikingly exhibited by the little glass bulbs called candle bombs ; these are small globules of glass, about as large as a pea, with a neck an inch long ; How can the elastic force of vapors be measured by the barometer ? What is the principle involved? When water is heated in a vessel from which the steam can not escape, what is the effect ? How may this be illustrated ? 46 RELATION OF VAPORS TO PRESSURE. into the interior a drop of water is introduced, and the term- Fig. 28. ination of the neck hermetically sealed by melting the glass. When one of these "" is stuck in the wick of a candle or lamp, as in Fig. 28, the heat vaporizes a por- tion of the water, and there being no passage through which the steam can escape, the bulb is burst to pieces with a loud explosion; a mechanical force which is wonderful when we consider the amount of water employed. It is a miniature representa- tion of what takes place on the large scale in the bursting of high-pressure steam-boilers. Marriotte’s law, the law which assigns the volume of a gas under variations of pressure, applies, under certain re- strictions, to the case of vapors. A permanently elastic gas, when the pressure is doubled, contracts to one half of its former volume ; if the pressure be tripled, to one third, and so on, but not so with vapors ; if, upon steam, as it rises from water at 212^, any increase of pressure be exerted, this vapor at once loses its elastic form, and instantly condenses into water. But vapors, like atmospheric air, if the pressure upon them is diminished, follow Marriotte’s law ; thus, if the pressure be reduced to one half, steam at once doubles its volume. For vapors, therefore, Marriotte’s law holds for diminutions of pressure, but in other instances, when the pressures are increased, it apparently fails, the vapors relaps- ing into the liquid form. That the elasticity of a vapor increases with its ternper- Fig. 2 ^. 21 -ture, may be readily proved by taking a tube one third of an inch in diameter and 20 inches long, closed at one end and open at the other, a a. Fig. 29, with a jar, b, an inch or more in diameter and 20 inches deep. Let the tube be filled with quicksilver, so as to leave a space of half an inch, into which ether may be poured ; invert the tube in the deep jar, also containing quicksilver ; the ether of course rises to the upper closed extremity. If now the tube be lift- ed in the jar as high as possible without admitting external air, a certain portion of the ether will va- What is Marriotte’s law ? Does it apply in the case of vapors under a diminution of pressure ? Does it apply under an increase ? What relation is there between elasticity and temperature ? MEASURE OF ELASTIC FORCE. 47 porize, and, depressing the quicksilver, its elastic force may be measured by the length of the resulting column. If now the end of the tube be grasped in the hand, or if it be slightly warmed by the application of a lamp, the mercurial column is at once depressed, proving that the elastic force of the vapor is increasing. As soon as the tube is warmed to the boiling point of the ether, the column of mercury is depressed exactly to the level on the outside of the tube. At this point, therefore, it balances, or is equal to the pressure of the air. Now let the tube be depressed in the jar ; it will be seen with what facility the vapor reassumes the liquid condition. As the tube descends, the vapor condenses, and the mercury keeps constantly at the same level. Under these circumstances, it follows that the vapor is at its maximum density. We can not increase that density by bringing pressure to bear upon it by depressing the tube, for the moment the attempt is made the vapor liquefies. The point of maximum density rises with the temperature of the vapor. The density of air at 212° being taken at 1000°, that of the vapor of water at its maximum density will be as follows : Table of the Maximum Density of Water-vajpor. Temperature. Density. Weight of 100 Cubic In, 32"^ 5-690 . •136 grains 10-293 •247 14-108 •338 100® 46-500 1-113 150® 170-293 4-076 212® 625-000 14-962 By exerting pressures to a sufficient degree on various gases, they have been converted into liquid bodies. Sulphur- ous acid, cyanogen, chlorine, carbonic acid, protoxide of ni- ♦ trogen, have yielded in this way. But hydrogen, oxygen, and nitrogen may be exposed to pressures of 50 atmospheres without liquefying. The condensation of carbonic acid is sometimes conducted on the large scale in strong vessels of wrought iron. If the resulting liquid is allowed to escape into the air, a portion is frozen by the evaporation of the rest. How can the increase of elastic force under these circumstances be shown ? At the boiling point of a liquid, what is the elastic force of its vapor equal to ? What is meant by the maximum density of a vapor ? How can it be shown that vapors thus in a Torricellian void are at the maximum density ? 48 BOILING. and a snowy, solid substance is the result. This, moisten- ed with sulphuric ether, will depress the thermometer tt —135° LECTURE XL Ebullition. — Theory of Boiling. — In Papin's Digester Water never Boils. — Instantaneous Condensation of Vapors. — Effect of Variations of Pressure. — Effect of Nature of the Vessel. — Boiling on Mountains. — Effect of Bed-hot Surfaces. By introducing different liquids into a tube, arranged as that represented in Fig. 29, we can prove that the observa- tion holds good in every case, that, as soon as the boiling point of a liquid is reached, the elastic force of the vapor rising from it is equal to the pressure of the air. We have said that at a temperature of 80°, the vapor of water will depress the mercurial column of a barometer about one inch ; but if the temperature be raised to 212°, the mercury is at once depressed to the level in the cistern ; at that temperature, therefore, the elastic force of the vapor is equal to the pressure of the air. Upon these principles, the phenomena of boiling or ebul- lition are easily explained. When the temperature of a li- quid is raised sufficiently high, vapor is rapidly generated from those portions of the mass which are hottest, and the violent motion characterized by the term “ boiling” is the result. This is due to the fact that the elastic force of the generated vapor at that point is equal to the atmospheric pressure, and the vapor bubbles expanding, can maintain themselves in the liquid without being crushed in ; they rise to the surface, and there burst. But, just before ebullitioif takes place, a singing sound is often heard, due to the par- tial formation of bubbles, which, so long as they are in the neighborhood of the hottest part, have elasticity enough to maintain their form ; but the moment they attempt to rise through the cooler portion of the liquid just above, their elas- ticity is diminished by their decline of temperature, and the atmospheric pressure crushing them in, they resume the li- At the boiling point of water, w^hat is the elastic force of its steam ? Ex- plain the phenomena of boiling. What is the cause of the singing sound ? BOILING. 49 quid condition ; for a few moments, therefore, while the va- por has riot gathered elastic force enough to maintain its condition perfectly, these bubbles are transiently formed and disappear, and the liquid is thrown into a vibratory move- ment which gives rise to the singing sound. Water, when heated in a vessel from which the steam can not escape, never boils. This takes place in the interior of Papin’s digester, which is a strong metallic vessel, in which water is inclosed, and the orifice through which it was in- troduced fastened up. As the steam can not escape, the water can not boil, no matter what the temperature may be. But the vapor which accumulates in the interior of the ves- sel exerts an enormous pressure. It is under the same con- ditions as were considered in the case of the candle bombs. Papin’s digester is used to effect the solution of bodies by water which are not acted on readily by that liquid at its common boiling point. As a vapor, rising from a vaporizing liquid, will bear no increase of pressure, so neither will it bear any reduction of temperature without instantaneously Fig. 30. condensing. This may be strikingly shown by an arrangement such as is represented in Fig. 3 0 . Into the mouth of a flask, a, let there be fitted a tube, 5, half an inch in diameter, and bent, as shown in the figure. Having intro- duced a little water into the flask, cause it to boil rapidly by the application of a spirit lamp : the steam which forms soon drives out the atmospheric air from the flask and the tube, and when this is entirely completed, and the vapor issuing abundantly from the mouth of the tube, plunge the end of the tube beneath some cold water, contained in the jar, c, and take away the lamp. As soon as this is done, the cold water, condensing the steam in the tube, rises to occupy its place, and presently passing over the bend, introduces itself with surprising violence into the interior of the flask, filling it entirely full, or, which more commonly takes .place, breaking it to pieces with the force of the shock. The low-pressure steam-engine depends on Why does water heated in a close vessel never boil ? Describe Papin’s digester. What is its use ? Can the steam of boiling water be cooled with- out condensation? Give an example of the rapidity of its condensation. 50 BOILING IN VACUO. this fact of the rapid condensibility of vapor, the high-press^ ure engine on its elastic force. Fig. 3L The principle involved in the action of the low-pressure engine, and more especially that form of it which was the invention of New- comen, is well illustrated by the instrument represented in Fig. 31. It consists of a glass tube, blown into a bulb at its lower extrem- ity. In the bulb some water is placed, and a piston slides, without leakage, in the tube. On holding the bulb in the flame of a spirit lamp, steam is generated, and the piston forced upward. On dipping it into a basin of cold water, the steam condenses, and the piston is depressed ; and this action may be repeated at pleasure. As the pressure of the atmosphere determ- ines the boiling point of a liquid, and as that pressure is variable, the boiling point is not fixed, but a variable point. There are many experiments which might be introduced Fig. 32 . as proofs of this fact. If a glass of warm water be placed beneath the receiver of an air pump, as in Fig. 32, when the rarefaction has reached a certain point, ebullition sets in, and the water continues to boil at a lower temperature as the exhaustion is more perfect. In a vacuum, water can be made to boil at 32®. On this principle, that the boiling point depends on the existing pressure, we give an explanation of a curious ex- periment, in which ebullition is apparently brought about Fig. 33. by the application of cold : Take a Florence flask, a, Fig. 33, and, having filled it half full of water, cause the water to boil violently, so as to expel all the atmospheric air ; intro- duce a cork which will fit the mouth of the flask air-tight a moment after it is moved from the lamp, and before any atmospheric air has been introduced. If the flask be now dipped into ajar, b, of cold water, its water begins to boil, On what property of vapor does the low-pressure steam-engine depend ? On what the high-pressure ? How may it be proved that the boiling-point depends on the pressure ? At what temperature will water boil in vacuo ? Explain the process by which warm water may be made to boil by the ap- plication of cold. LiaUlDS ON RED-HOT SURFACES. 51 and will continue to do so until its temperature is reduced quite low. The cause of this phenomenon is due to the fact that the cold water condenses the steam in the flask, and a partial vacuum is the result. In this partial vacuum the water boils, as in the experiment illustrated by Fig. 32 ; and the steam, as fast as it is generated, is condensed by the cold sides of the flask. Besides this variation of the boiling point under variation of pressure, the nature of the vessel in which the process is carried forward exerts a certain action ; thus, in a polished glass vessel, the boiling point is 214°, but in a rough metal vessel it is 212*^. If the glass has been carefully cleaned with hot sulphuric acid, water may be heated to 221° with- out ebullition ; and, on the contrary, if coated with a film of shell-lac, the boiling point will be 211°. Some travelers report, Aiat in certain mountainous regions meat can not be cooked by the ordinary process of boiling. As we ascend to elevated regions in the air, the atmospheric pressure becomes less, because the column of air above is shorter, and therefore there is less air to press. Under such circumstances, the boiling point of water of course descends, and may possibly become so low as to bring about the spe- cific change required in the cooking of meat. An ascent through 530 feet lowers the boiling point one degree. Upon this principle we can determine the altitude of accessible elevations, by determining the thermometric point at which water boils upon them. A peculiar thermometer, called the hypsometer, has been invented for this purpose. When a drop of water is placed on a red-hot polished sur- face of platinum, it does not, as might be expected, com- mence to boil rapidly, but remains perfectly quiescent, gath- ering itself up into a globule. If the platinum be now al lowed to cool, as soon as its temperature has reached a point at which it has ceased to be visibly hot, the drop of water is suddenly dissipated in a burst of steam. The ex planation given of this phenomenon is, that at the high temperature the drop is not fairly in contact with the red- hot surface, but a stratum of steam intervenes ; this, being How does the nature of the vessel affect the boiling point ? Why is it probable that meat can not be cooked on high mountains ? How high must we ascend to bring the boiling point to 211°? How may the altitude of mountains be determined by the thermometer ? What are the phenomena exhibited by water in contact with red-hot platinum ? What is the sup- posed explanation ? 52 THE BOILING POINT. a bad conductor, prevents ebullition from occurring, but as soon as the temperature declines, and this steam no longer props up the drop, an explosive ebullition ensues, because of the contact which has taken place. This condition is known as the spheroidal state of a liquid. Water enters upon it at temperatures between 288° and 340° of the hot surface, its own temperature being about 206°. It is said to be in consequence of this want of actual contact that the hand can be passed through red-hot and molten metal with- out being burned. I I ! LECTURE XII. Vaporization. — The Boiling Point rises with the Press- ure. — Relation hetioeen sensible and insensible Heat . — The Cryophorus. — Leslie's Process for freezing Water. — Variability of Moisture in the Air. — Hygrometers. — Method of the Dew Point. Under an increase of pressure, the boiling point rises, and the elastic force of the steam evolved becomes corre- spondingly greater. As we have seen, the elastic force of steam from water boiling at 212° is equal to the pressure of one atmosphere ; but if the pressure be doubled, the boil- ing point rises to 250° ; if quadrupled, to 294° ; and under a pressure of fifty atmospheres, it is more than. 500°. These results may be established by the aid of the boiler, represented in Fig. 34, a. It is a globular vessel of brass, and is about three inches in diameter. In its upper part are three perforations, into one of which the stop-oock, b, is screwed ; through the second a tube, c, is inserted, deep enough to reach nearly to the bottom of the boiler ; and through the third a thermometer, d, is introduced. Some quicksilver is poured in, sufficient to cover the end of the tube, c, half an inch or more deep, and upon it water is poured, the bulb of the thermometer being immersed in it. The stop- cock, h, being open, a spirit lamp is applied to bring the How is the boiling point affected by an increased pressure ? Describe the boiler. Fig. 34, and its_use. LATENT HEAT OF VAPORS. 53 water to its boiling point, and as the steam can freely pass out, this of course takes place at 212^. On closing the stop-cock, the steam can no longer escape, but, exert’ng its elastic force on the surface of the boiling liquid, presses the mercury up in the tube, c. The altitude of the mercu ;ial column measures the amount of this pressure, and the ther- mometer indicates the corresponding change in the boiling point : as soon as the pressure is equal to two atmospheres, the thermometer will be found to have risen to 250^. It is immaterial at what temperature vaporization is car- ried on, a very large amount of heat must always be ren- dered latent ; and, in point of fact, vapors generated at a low temperature contain more latent heat than those gen- erated at a high one. The relation which exists in the amount of heat rendered latent at different temperatures is very simple. The sum of the insensible and sensible heat is always the same; thus, water boiling at 212° absorbs 1000° of latent heat, the sum of the two quantities being of course 1212 ; but vapor rising from water at 32° contains of latent heat 1 180° ; here, again, the sum of the two quantities is 1212° ; and the same observation holds for intermediate temperatures. When vapors return to the liquid condition, the heat which has been latent in them reassumes the sensible form. They may thus be regarded as containing a great store of caloric, of the effects of which many natural phenomena furnish us with striking examples. Thus, there is a remarkable dif- ference between the climate of the eastern coast of America and the opposite European coasts in the same latitude, and this arises from the action of the Gulf Stream, a great stream of warm water, which, issuing from the Gulf of Mexico, and passing the Atlantic States, stretches across toward the Eu- ropean Continent. The vapors which arise from it give forth their latent heat to the air, and the southwest winds, which are therefore damp and warm, moderate the climates of those countries. I^he cryophorus, or frost bearer, an instrument invented by Dr. Wollaston, in which water may be frozen by the cold produced by its own evaporation, depends for its action on Do vapors generated at low or high temperatures contain most latent heat? What relation is there between the insensible and sensible heats of vapors at different temperatures ? When a vapor condenses, what becomes of its latent heat? What effect has the Gulf Stream on the climate of Europe? Explain the cause of it. 54 THE CRYOPHORUS. Fig. 35. the laws relating to latent heat. It is represented in Fig. 35, and consists of a bent tube, c, half an inch or more in diameter, with a bulb, a and b, at each of the extremities ; the upper bulb, b, is filled one third with water, and the rest of the space, with the tube, c, and the other bulb, a, is free from atmospheric air, and occupied by the vapor of wa- ter only. If now the bulb a be immersed in a freezing mixture of nitric acid and snow, although the tube, c, may be of considerable length, the wa- ter in the distant bulb, 5, presently freezes ; hence the name of the instrurhent, frost bearer, because cold ap- plied at one point produces a freezing effect at another, which is at a considerable distance. The action of the in- strument is simple : in the cold bulb, a, which is in contact with the freezing mixture, the vapor is condensed ; fresh quantities rise with rapidity from the water in the other bulb, to be in their turn condensed ; a continual condensa- tion, therefore, goes on in a, and a continual evaporation in 5, but the vapor thus formed in b must have caloric of elas- ticity ; it obtains it from the water from which it is rising, the temperature of which therefore descends until solidifica- tion takes place. Leslie’s process for freezing water in vacuo by its own evaporation is an example of the same kind. If some water in a watch-glass is placed in an exhausted receiver, with a large surface of sulphuric acid, as fast as vapor rises it is condensed by the acid ; a rapid evaporation of the water therefore takes place, the tem- perature falls, and congelation finally en- sues. In Fig. 36 this apparatus is repre- sented ; a is the watch-glass containing water, h a wide dish filled with sulphuric acid, and c a low bell jar in which the exhaustion is made. A drop of prussic acid held in the air on the tip of a rod solidifies, the portion that evaporates obtaining its latent heat from the portion left behind, and on the same principle liquid carbonic acid~“can also be solidified. The amount of watery vapor contained in the air is very variable. Many common facts prove this : the swelling of Fig. 36. Pescribe the cryophorus. What is the reason that cold applied to one bulb freezes water in the other? Describe Leslie’s process for freezing water in vaciio ? Why does a drop of prussic acid held in the air solidify ? HYGROMETERS. 55 wooden furniture takes place in consequence of damp weath- er ; and the opposite effect, or its shrinking, occurs during dry. Several instruments have been invented to determine what the amount is at any time ; they are called hygrom- eters. In one of these, the relative dampness or dryness of the atmosphere is determined by the stretching or contract- ing of a hair, which is very sensitive to such changes. A general idea of such an instrument may be obtained by con- sidering the metallic bar of the pyrometer. Fig. 15, to be re- placed by a hair, the movements of which would of course be communicated to the index ; in another a slip ef whale- bone is used instead of the hair. • Saussure’s hygrometer, which is constructed on these prin- ciples, has been very extensively used. It consists of a human hair eight or ten inches long, b c. Fig. 37, fastened at one extremity to a screw, a, and at the other passing over a pulley, c, being strained tight by a silk thread and weight, d. From the pulley there goes an index, which plays over the graduated scale, e e\ so that, as the pulley turns through the shortening or lengthening of the hair, the index moves. The instrument is graduated to correspond with others by first placing it under a bell jar, with a dish of sulphuric acid or other substance having an affinity for water, which, ab- sorbing all the moisture of the air of the bell, brings it to absolute dryness. The point at which the index then stands is marked 0. The hygrometer is next placed in a jar, the interior of which is moistened with water ; when the index has again become stationary, the point is marked 100°, and the intervening space divided into 100 equal parts. The hair should have its oily matter removed by soaking in sulphuric ether. This preparation renders it much more sensitive. There is a simple and ingenious instrument, the move- ments of which depend on these prin- 3 g ciples ; it is represented in Fig. 38 : a g, a thin slip of pine wood, a a, cut across the grain, a foot long and an inch wide, has inserted into its corners four needles, all pointing in one How can it be proved that the amount of moisture in the air is variable ? "What is the hygrometer ? Describe the hair hygrometer. Describe the in- strument, Fig. 38. 56 THE DEW POINT. direction backward ; if this instrument be set upon a floor or flat table, in the course of time it will crawl a consider- able distance. During dry weather the thin board contracts, and the two fore legs taking hold of the table, the hind ones are drawn up a little space ; when the weather turns damp, the board expands, and now the hind legs, pressing against the table, cause the fore ones to advance. Every change from dry to damp, or the reverse, produces, a walking motion in a continuous direction, and the distance passed over is a register of the sum total of these changes. But of all these hygrometric methods, the process known as “ the determination of the dew point” is by far the most philosophical. This method consists in cooling the air until it begins to deposit moisture. When there is much moisture in the air, it obviously requires but a slight diminution of temperature to cause a portion of the vapor to deposit as a Jew ; but when the air is dryer, the cooling must be carried to a greater extent. The precise thermometric point at which the moisture begins to deposit is called the dew point. Thus, if we take a thin metallic vessel containing water, and cool it gradually by the addition of a mixture of nitrate of potash and sal ammoni- ac, or any of the cooling mixtures, continually stir- ring with the bulb of a small thermometer, as soon as the temperature has reached a certain point a dew is deposited on the outside of the metallic ves- sel ; that temperature is the dew point for the time being. Knowing the tem- perature of the air, the dew point, and the baro- metric pressure, the abso- lute amount of vapor can be determined by a simple calculation. DanielFs hygrometer ^if- fords a ready and beautiful m ethod of determining the dew ^ What is meant by the “ dew point ?” What is tho process for ascertain- ing it ? Fi^. 39 . SPECIFIC GRAVITY OP VAPORS. 57 Fig. 40. point. It consists of a cryophorus, a c b, Fig. 39, the bulb b being made of black glass, and a covered over with mus- lin. The bulb b contains ether instead of water, and into it there dips a very delicate thermometer, cl. Usually, an- other thermometer is affixed to the stand of the instrument. When a little ether is poured on a, by its evaporation it cools that bulb, and ether distils over from b, which, of course, also becomes cold. After a time, the temperature of b sinks to the dew point, and that bulb becomes covered with a dew. The thermometer, dy then shows at what tem- perature this takes place, and of course gives the dew point. The PsYCHROMETER, or wet bulb hygrometer, consists of two mercurial thermometers which exactly correspond ; the bulb of one of them, A, Fig. 40, is covered with muslin, and kept constantly wet by water supplied by a thread from a reservoir, W. The bulb, B, of the other is left naked. Owing to the evaporation from the wet bulb, its temper- ature will be lower than the dry one, and this in proportion to the rate of evaporation or the dryness of the adjacent air. As soon as the air round the bulb is saturated with moisture, the point at which the mercury stands is the dew point. If both thermometers, the wet and the dry, coincide, the air contains moisture at its maximum density ; and the greater the difference be- tween them, the dryer the air. It is frequently necessary to remove moisture from air or gaseous substances. This may be done by conducting them through tubes containing bodies hav- ing a strong attraction for water, such as chloride of calcium, sulphu- ric or phosphoric acids. Such an arrangement is shown in Fig. 41, in which is the flask in which the gas is generated, b a bent tube con- necting with the drying tube, c, which is filled with fragments of chloride of calcium, or pieces of glass moistened with concentrated sulphuric acid. The gas escapes dry from the tube d. Fig. 41. Describe Daniell’s hygrometer and the mode of using it. Describe the process for drying gases. C 2 58 SPECIFIC GRAVITY OP VAPORS. LECTURE XIII. Evaporation and Interstitial Radiation. — Methods of Gay-Lussac and Lumas for ascertaining the Specific Gravity of Vapors. — Phenomena of Evaporation . — Control of Temperature^ — Effect of Dryness^ Stillness, Pressure, and Surface.— Evaporation a Cooling' Pro- cess. — Conduction of Solids. — Difference among differ- ent Metals. — -Rumford's Experiments. The specific gravity of vapors may be determined in sev- Fig. 42. eral ways. The following is the method of Gay- Lussac : A graduated j ar, a, is inverted in a basin of mercury, c, which rests upon a small furnace. A glass bulb is to be filled quite full with the li- quid under examination, and the quantity intro- duced is accurately weighed. The bulb is now slipped into the jar, a, and rises to its top. A cyl- inder, b, open at both ends, but the lower pressed down into the mercury, is next placed round a, and the interval hlled with clear oil. The fur- nace is now lighted ; the oil and the mercury be- come warm ; the bulb at last bursts, and, as its vapor depresses the mercury in the graduated j ar, its volume may be determined. Thus, know- ing the weight of the liquid, the volume of its vapor, and the temperature of the oil, we can easily calculate the vol- ume at 32°, and from that deduce the specific gravity. The method of Dumas consists in weighing a glass globe filled with the vapor to be tried. A portion of the sub- stance is to be introduced into the globe, the weight of which is first determined, and this is then held, as shown in the figure, in a bath of fusible metal placed over a small fur- nace. The heat of the melted metal vaporizes the sub- stance, drives out the air, and occupies the whole cavity in a state of purity. When no more vapor escapes from the end of the tube, it is sealed by the blow-pipe, and the tem- perature of the bath ascertained. The globe is now to be Describe Gay-Lussac’s method of determining the specific gravity of a vapor. Describe the method of Dumas. SPECIFIC GRAVITY OP VAPORS. 59 carefully weighed, when cold, a second time, and the point of the tube is then broken under quicksilver, which rises and fills it complete- ly, and this be- ing subsequent- ly emptied in- to a graduated j ar, the volume of the globe is ascertained. Knowing the volume of the globe, we know the weight of the air it con- tains, and this, subtracted from the first weight, is the weight of the glass when empty. Subtracting this again from the second weighing, gives us the weight of the vapor ; and as the air and the vapor occupied the same volume, their densities are as their weights. But, as their temperature was different, a farther calculation is required to bring them to the same standard. There are several conditions which exert a control over the rapidity of evaporation. The amount of vapor which can exist in a given space depends entirely on the tempera- ture. Thus the air included in a glass jar which is stand- ing over water contains, at 32^, a certain quantity of vapor ; but if the temperature rises to 60^, it contains more, and still more if it rises to 90^. Should the temperature de- scend, a part of the vapor is deposited as a mist. The quan- tity that remains in suspension is determined by the tem- perature alone. It is the application of this principle which constitutes the most beautiful part of Watt’s great invention, the low- pressure steam-engine. Taking advantage of the fact that the quantity of vapor which can exist in a given space is determined by the lowness of temperature of any portion of it, he arranged a vessel, maintained uniformly at a low tem- perature, in connection with the cylinder of the engine, and What is it that regulates the quantity of vapor in a given space ? On what principle does the steam-engine condenser depend ? 60 CAUSES CONTROLLING EVAPORATION thus reached the apparently paradoxical result of condensing the steam without cooling the cylinder. Among other causes exerting a control over evaporation in the air is the dry or damp state of that medium. As is well known, evaporation goes on V'lith rapidity when the weather is dry, and is greatly retarded when the weather is damp. So, too, a movement or current exerts a great ef- fect. When the wind is blowing, water will evaporate much more quickly than when the £iir is quite calm ; this obvious- ly depends on a constant renewal of surfaces, so that as fast as one portion of air becomes moist it is removed, and a dryer portion takes its place. Extent of surface operates in the same way ; the same quantity of water will evaporate much more rapidly if exposed in a plate than if exposed in a cup. Pressure also exerts a great control ; for, as we have seen, evaporation takes place instantaneously in a vacuum. While, therefore, there are several circumstances which can control the rate of evaporation, it is temperature alone which regulates the absolute and final amount. As we have just seen, a fixed quantity of vapor can exist in a cer- tain space at a given temperature ; and it matters not wheth- er that space is full of atmospheric air or is a vacuum, the absolute quantity will be precisely the same. At one time it was supposed that evaporation was due to a solvent power in the air — a kind of attraction between that medium and the water with which it is in contact ; but it is clear that such an opinion is wholly untenable, for the process goes forward with the greatest rapidity in a vacuum, when the air is totally removed. Although the evaporation of liquids, such as water, will take place at very low temperatures, there- is reason to be- lieve that the process has a limit ; thus, a minute quantity of vapor will rise from quicksilver at a temperature of 60°, but at 40° not a trace can be discovered. All processes of evaporation are cooling processes, because the vapor developed requires latent heat to give it the elas- tic form. For this reason, when any vaporizable liquid, as ether, is poured on the bulb of an air thermometer, or on the hand, cold is produced. "What effect have dryness or dampness over evaporation? What is the effect of a current ? What of extent of surface ? What of pressure ? What of temperature ? Does evaporation arise from a solvent power in the air ? Is there any limit to evaporation ? Why are processes of evaporation cool- ing processes ? CONDUCTION. 61 The pulse glass is an instrument which may serve as an illustration : it consists of a glass Fig. 44. tube, bent twice at right angles, and terminated by bulbs, as in Fig. 44. It is partially filled with spirit of wine, the rest be- ing occupied by the vapor of that substance. On grasping one of the bulbs in the hand, the warmth is sufficient to boil the liquid ; and as it distills over into the other bulb, an impression of cold is felt. Interstitial Uadiation or Conduction. We now come to the consideration of the mode by which heat is transmitted through bodies, or interstitial radiation, called by many writers conduction ; a term involving the idea that the particles of bodies are in actual contact, where- as it has been abundantly proved that they are separated from each other by interstices. The passage of the heat across these spaces is what is meant by interstitial radiation. From the currency which it has obtained, and the conve- nience of the expression, I shall continue to use the word conduction. , i rr Different solids conduct heat with different degrees ot la- cility. If we take a cylindrical mass of metal, and hold tightly against its surface a piece of white writing paper, the paper may be placed in the flame of a spirit lamp for a considerable time without scorching ; but if we take a cy- lindrical piece of wood of the same dimensions, and, wrap- pino^ the paper round it, expose it to the flame, it rapidly scorches. The metal, therefore, keeps the paper cool by carrying off its heat, but the wood, being a bad conductor, suffers the paper to burn. . ^ i By the aid of the apparatus of Ingenhouse, Fig. 45, the same fact may be proved in a more general 45. way. It consists of a trough of brass six inches or more long, three wide, and three • deep ; from the front of it project cylinders of metallic and other substances of the same length and diameter ; they may be of silver, copper, brass, iron, porcelain, wood, &c., in succession ; the Describe the pulse glass. What is interstitial V ^ auction ? How may it be proved that wood and metals conduct with differ- ent degrees of facility ? Describe the apparatus of Ingenhouse . 62 CONDUCTION OP HEAT. surface of each cylinder is smeared with bees’ wax. On pouring boiling water into the trough, the heat passes along these cylinders with a rapidity corresponding to their con- ducting power, and the wax correspondingly melts. On the silver bar the wax melts most rapidly, and on the wood most slowly ; on the others intermediately ; thus affording a clear proof that different solids conduct heat with different degrees of facility. Even among metallic substances great differences in this Fig. 46 . respect exist, as may be strikingly shown by the instrument. Fig. 46. Into a solid ball of copper, a, three wires of equal length and equal diameter are screwed — they may be , c copper, brass, and iron respectively : they are flattened at their farther extremities, h, c, di so as to afford a place on which pieces of phosphorus may be put. A lighted spirit lamp is now set beneath the central ball, the temperature of which soon rises, and the heat passes with different degrees of speed along the metals ; very soon the piece of phosphorus at the end of the copper takes fire ; then, some time after, follows that on the brass ; and last, that on the iron ; enabling us to prove to persons at a dis- tance the fact that these different metals conduct heat with different degrees of facility. Table of Conducting Power of Solids. Gold . . . . . . 1000 Tin . . . . . . 303*9 Silver . . . . . 973 Lead . . . . . . 179*6 Copper . . . . . 898 Marble . . . Iron . . . . . . 374*3 Porcelain . . . . 14*2 Zinc . . . . . . 363 Clay . . . . . . 11*4 If a piece of wire gauze be held over the flame of a can- dle or gas jet. Fig. 47, the flame fails to pass through ; but the gaseous matter of which the flame consists freely escapes through the meshes of the gauze, for it may be set on fire, as shown in the figure. Flame is gaseous matter, or solid matter in a state of excessive subdivision, temporarily sus- pended in gas, brought to a very high temperature. It can not. ‘therefore, pass through a piece of wire gauze, because What does it prove ? Are there differences in the conducting powers of metals ? How may that be proved ? Can the flame of a candle pass through a piece of wire gauze ? CONDUCTING POWER OF METALS. 63 the metallic threads, exerting a high con- ducting power, abstract its heat from the incandescent gas> and bring its temperature down to a point at which it ceases to be luminous. The safety-lamp of Davy is an application of this principle ; by it combus- tion is prevented from spreading through Fij. 48 . masses of explosive gas, by call- ing into action the conducting power of a metallic gauze, with which the lamp frame is sur- rounded, as in 48. The safety-tube of Hem- mings, used to prevent explosions in the ^ oxy hy- drogen blow-pipe, acts on the same principle. Count Rumford made several experiments to determine the conducting power of those vari- ous materials which are used for the purpose of clothing. He placed the bulb of a thermometer in the centre of a spherical glass globe of larger diameter, and filled the interspace with the sub- stances to be tried. Having immersed the ap- paratus in boiling water until it was at 212^, he transferred it to melting snow, and ascertained how long it took to fall a given number of degrees. Linen and cotton were found to be better conductors than wool and the various furs, and hence the reason that they are ferred as articles of summer clothing ; but he also found that much depended on the tightness with which the sub- stances were packed, for the conducting power apparently rose when they were closely compressed. These bodies act, therefore, as will hereafter be more distinctly seen, not so much by their own badly-conducting power, as by calling into action the non-conducting quality of atmospheric air. Crystalline bodies do not always conduct equally in every direction. If a plate cut from a rhombohedral ci^^stal be warmed from a point at its centre, the surface having been previously coated with wax, it will be found that the fusion of the wax takes place so as to present an ellipse, the longer axis of which is in the direction of the major crystalline axis. What is the reason of this ? What is the construction Davy’s safety-lamp ? On what method did Rumford proceed to determine the inducting power of clothing? . What was the effect compression Ho^' are these results connected with the non-conducting power ot 64 CONDUCTION OF LiaUIDS. LECTUEE XIV. Conduction. — Conduction of Liquids.— Tramference of Heat hy Circulation. — Conduction of Gases. — Con- ducting Power of Clothing. The conducting power of most liquids, such as water, is Fig. 49. very low ; a thin stratum is sufficient almost en- tirely to cut off the passage of heat. This may he j(M shown hy an apparatus such as Fig. 49, consisting of a jar, a, nearly filled with water, with an air thermometer included in such a manner that the hulb, h, is within a short distance of the surface, a depth of a quarter of an inch or less intervening. Y The tube of the thermometer may be passed through jk the lower mouth of the jar, c, water-tight by means of a cork, and the position at which the index-liquid stands having been marked, some ether is poured on the sur- face of the water, upon which it readily floats, and then set on fire. A very voluminous flame is the result, and a great deal of heat is evolved ; and, since the bulb of the thermom- eter is apparently separated from the burning ether by a thin film of water only, if the heat traversed that film the thermometer should rapidly move ; but the experiment proves it does not ; and we therefore conclude that water is a very bad conductor of caloric. While this conclusion is true, a little consideration will show that this experiment presents the facts in a very de- ceptive way ; and though, from its imposing character, it is generally relied on as a complete proof, yet, were water a much better conductor than what it actually is, the same results would be obtained. All flames, as we shall here- after see, are hollow ; they are merely incandescent on the surface. A great distance, in reality, intervenes between the thermometer bulb and the points of high temperature, and, in addition, the ether is rapidly evaporating away to feed the flame, and all evaporations are cooling processes. To a certain extent, all liquids conduct heat : thus, mer- How does the conducting power of liquids compare with that of solids ? How may water be proved to be a bad conductor? What deceptive cir- cumstances are there in this experiment ? Do liquids conduct heat at all ? CURRENT ACTION IN WATER. 65 cury is a very good conductor ; but in those liquids of which water is the type, the dissemination of heat is chiefly de- termined by the mobility of their particles, a process which passes under the name of convection or circulation. The apparatus. Fig. 50, illustrates the nature of this pro- cess : it consists of a wide tube into which water may be poured ; the lower portion, as high as a, being colored blue by the addition of some coloring substance, the intermediate portion, from a to b, being colorless, and the upper portion, from b to c, being tinged yellow. Now, by the application of a red-hot iron ring, dy of such a diameter that it can surround the jar, a space of an inch or more intervening all rounds the upper, yellow portion may be made even to boil : it shows no disposition to inter- mix with the portions beneath. But if the red-hot ring is lowered down so as to surround the blue portion, as it becomes warm it will be found to as- cend, first through the colorless stratum, and finally through that tinged yellow, on the top. When the lower portion of ' a liquid is warmed, currents are established, which, rising through the strata above, bring about a rapid dissemination of the heat. This may also be shown by taking a jar. Fig. 51, a, and filling it with water, rendered a little more dense pig, 51 . by some sulphate of soda, so as to bring its speci- fic gravity near that of some pieces of amber thrown into it. If a lamp now be applied to the bottom of the jar, currents are established in the water, rising up the center and descending down the sides of the liquid ; and in this manner, new portions' constantly presenting themselves on the surface exposed to the flame, the whole mass be- comes uniformly hot. The cause of this movement is due to the fact that when water is heated it expands. Those portions, therefore, which rest on the bottom of the vessel, and to which the heat is applied, as soon as they become warm, dilate, and, being What are the relations of mercury in this respect ? By what process does the dissemination of heat in a liquid take place ? Describe the experiment represented in I<\g. 50. Describe that represented by Fig. 51. What is the true cause of these circulatory movements ? 66 PROPAGATION OF HEAT IN LIOUIDS. Fig. 52. lighter than before, rise to the top of the liquid, while colder, and therefore heavier ones, occupy their place. If we take a jar of water. Fig. 52, and hav- ing introduced through apertures near the top and the bottom the thermometers a b, and into a brass trough, c, which surrounds the middle of the jar Avater-tight, pour boiling water, after a little time has elapsed we shall find that the upper ther- mometer has risen, but the lower one remains perfectly stationary. The cause is, that through all those portions which are above the place at which the heat is applied, that is, the middle of the vessel, currents are made to circulate, but in all those beneath no currents are established. When, therefore, heat is applied to the surface of water, it is not propagated downward ; when it is applied to the middle of a vessel containing that liquid, all the portions above become hot, but all those below remain cold ; and when it is applied to the bottom of the vessefi the whole mass soon becomes uniformly warm. In the vegetable world, advantage is taken of the non- conducting power of water in a very beautiful Avay. Soon after sunset, the leaves and other delicate parts of plants become covered with little drops of dew, which invest them on all sides. Under these circumstances, the process of con- vection, or the establishment of currents, is entirely cut off, for each of the drops is isolated, or has no communication with those around. The cold air does not so suddenly afiect these delicate organs as it would do were not this thin non- conducting film spread over them ; their action is, therefore, less liable to be deranged. Recent accurate experiments show that all liquids con- duct to a certain extent, though in many instances to a far less extent than what we see in the case of solid bodies. Among different liquids, difference in conducting power has also been discovered. If the conducting power of liquids is small, that of gas- eous bodies is still less perceptible. In these, as in liquids, the mobility of the particles is so great that heat is readily How can it be proved that the warm water floats on the surface of that which is cold ? What is the effect of applying heat to the top, to the mid- dle, and to the bottom of a vessel containing water? What advantage is taken in the vegetable world of the non-conducting power of water ? Do all liquids conduct heat ? Are there differences in iheir conducting power ? PROPAGATION OF HEAT IN GASES. 67 diffused through them. Thus, if we take ajar, Fig. 53, containing oxygen gas, and place a piece of burning sulphur in it on a stand, a, the vapor which rises from the sulphur moves in a current to the top of the jar, and then descends in beautiful wreaths of smoke down the sides, precisely representing the circulatory movements of liquids. The ventilation of buildings and mines, and the proper construction of furnaces and chimneys, depend upon these principles. By taking advantage of the non-conducting power of air, rooms may be kept warm with a small consumption of fuel, by furnishing them with double windows. A stratum of air, two or three inches thick, intervening between the win- dows, effectually cuts off the passage of heat. It is upon the same principle we explain Count Rumford’s experiments in relation to the conducting power of clothing ; he found 111 at when the same fibres are used, the apparent facility A\'ith which they transmit heat depends on the closeness with which they are packed : the non-conducting power of ail- is here evidently called into play, and the fibres act by }!reveriting the production of currents. In the case of sheep or other animals, which during the winter season are cov- ered with a thick coat of wool or fur, it is the non-conduct- ing power of the included air which is again brought into operation. LECTURE XV. Radiation. — Fr diminary Ideas on Fadiant Heat . — Analogies with Light. — Effect of Surfaces. — Felations between Radiation and Reflection . — The Florentine Ex- periment . — The Cold-ray Experiment. — Opacity of Glass to Heat. — Its increasing Transparency as the Temperature rises. — Properties of Rock Salt. But, though gases are bad conductors of heat, they free- By what process is heat diffused through gases? What is the use of double windows? Wliat connection has the non-conducting power of air with Count Rumford’s experiments ? In tjie economy of animals, what ad- vantage is taken of these principles ? 68 NATURE OF RADIANT HEAT. ly allow of its transmission by radiation. A person who stands at one side of a fire receives the heat of it, although no currents of warm air can reach him. In a vacuum, a piece of red-hot metal rapidly cools. The heat which, under these circumstances, escapes from bodies is entirely invisible to the eye ; it moves in straight lines, exhibiting many of the phenomena of the rays of light. Thus, if we interpose between a fire and a thermometer an opaque screen, the moment the rays of lighkare stopped the heat is simultaneously intercepted. The rays of heat, like the rays of light, are capable of being reflected by polished metallic surfaces. If a piece of planished tin be held before a fire in such a position as to reflect the light of it upon the face, the heat, also, is simi- larly reflected, and gives rise to a sensation of warmth. The analogy between light and heat is farther observed when rays of the latter fall upon bodies of a different phys- ical constitution from the metals. As glass is transparent to light, there are many bodies transparent to rays of heat, though, as we are presently to find, these bodies are not the same in both instances. And as there are substances, like lamp-black, which will absorb all the light which impinges on them, there are many which perfectly absorb heat : re- flection, transmission, and absorption are therefore common to both these agents. If we take two metallic vessels of the same size and shape, and having blackened one of them all over with the smoke of a candle, fill them both with hot water, and notice their rate of cooling, it will be seen that the blackened one cools Fi^. 54 . faster ; the same thing may be observed if, instead of blackening the vessel, it is covered with layers of var- nish. These results may be proved by the aid of Leslie’s canister, which consists of a cubical brass vessel, Fig. 54, set upon a verti- cal stem, upon which it can rotate j at a little distance is Do gases tjansmit radiant heat ? How may it be proved that radiant heat moves in straight lines ? Is it capable of reflection ? Are there any sub- stances transparent to radiant heat ? Are these the same bodies that are transparent to light ? Of two surfaces, one polished and the other blacken- ed, which radiates heat best ? VARIATION OF SURFACE RADIAIION. 69 placed the blackened bulb of a differential thermometer, d; a mirror, ili", receives the rays of the canister and reflects them on the thermometer. One of the vertical sides of the cube is left with a clear metallic surface, a second washed over with one coat of varnish, the third with two, and the fourth with three coats ; if these sides be presented in suc- cession to the thermometer, they will be found to radiate heat with very different degrees of speed, more heat escap- ing from them as the number of coats is increased. In the experiments of Melloni, it was found that the maximum was not attained until sixteen coats were applied. These results can only be explained on the principle that radiation does not take place from the surface of bodies merely, but from a certain depth in their interior. A highly-polished metal is a bad radiator, but on roughen- ing the surface, its quality is improved. As a general rule, good radiators are bad reflectors, and good reflectors are bad radiators. When rays of light, diverging from the focus of a concave parabolic mirror, impinge on the surface, they are reflected in parallel lines ; when parallel rays fall on such a surface, they are reflected to its focus. Thus, if from the point, a, Fig, 55, the focus of a parabolic concave, cf, rays diverge, they will be reflected in parallel lines, c d /i, e i, f k, and if at these points they be intercepted by the mirror, g k^ they will be reflected to its focus, b. Now, as the laws of reflection of radiant heat are the same as the laws of the reflection of light, it is plain that if we place any incandescent body, such as a red-hot cannon-ball, in the focus, a, the heat which radiates from it will finally be found at the other focus, b. This is beautifully illustrated by an experiment known under the name of the experiment with conjugate mirrors. In the focus, a. Fig. 55, of a parabolic mirror, c /*, place a red-hot cannon-ball, and in the focus, 5, of a second mirror, g /c, set opposite, but twenty or thirty feet off, place a piece When successive layers of varnish are put on a surface, what is their ef- fect ? When is the maximum reached ? What is the explanation of these results ? What is the general connection between radiation and reflection ? When rays diverge from the focus of a concave mirror, what is their path after reflection ? When parallel fays fall on a concave mirror, what is their path after reflection ? When a hot ball is placed in the focus of one of the mirrors, to what point does its heat epnverge ? Describe the Florentine ex- periment represented in Fig. 55. 70 OPACITY OF GLASS TO HEAT. of phosphorus, a screen intervening between. As soon as the arrangements are completed, remove the screen, and in Fig. 55. j a moment the phosphorus takes fire. That this effect is due to the reflecting action of the mirrors, as has been described, may be proved by removing the mirror, cf^ when it will be found that the phosphorus can not be lighted, even though the ball be brought within a very short distance of it. This striking experiment proves, first, that the rays of heat move in straight lines, like those of light ; and, second, that in the same manner they are subject to the ordinary laws of reflection. A variation of the foregoing experiment may be made by using a snowball instead of the cannon-shot, in which case a thermometer placed in the focus of the opposite mirror will exhibit a reduction of temperature. From this it was at one time supposed that there existed rays of cold precisely analogous to rays of heat, and that they observed the same law as respects the rectilinear nature of their movement, and were also subject to the law of reflection ; but, as we shall see when we come to speak of the Theory of the Ex- changes of Heat, a simple explanation of the whole result can be given, without implying the existence of a principle of cold analogous to the principle of heat. Let it be now supposed that in the focus of the mirror, g k, Fig. 55, the bulb of a delicate thermometer is placed, and in the focus of the other mirror, cf, a, metalline mass, a, What two facts does this experiment prove ? When a snowball is used instead of a hot shot, what is the result ? RADIANT HEAT OF DIFFERENT COLORS. 71 v.he temperature of which we can vary at pleasure. Be- tween the mirrors let there be interposed a screen of trans- parent plate glass ; and let us farther suppose that the tem- perature of a is 212°, or considerably below the point at which it is visibly red hot. Under these circumstances the thermometer exhibits no rise of temperature so long as the glass intervenes, but the moment it is removed the heat passes. A piece of transparent glass is therefore opaque to the rays of heat which come from a non-luminous source. Let us now suppose that the temperature of the metalline mass, a, continually rises. When it has reached a red heat, a certain proportion of the rays emitted by it begins to pass through the glass, as is shown by their effect upon the ther- mometer. When the mass is visibly red hot in the daylight, the rays go through the glass more readily, and when it has become white hot, or has reached the highest temperature we can give it, the glass transmits the rays with facility. These facts are of the utmost importance. They show that bodies transparent to light are not necessarily trans- parent to heat, and, therefore, that light and heat are sep- arate and independent agents. They farther show that, as respects glass, its transparency for heat differs with the tem- perature of the source from which the rays come. There is a certain well-known substance, rock salt, with which, if we could obtain plates large enough to intervene completely between the two mirrors, a different series of re- sults would be exhibited. Whatever might be the tempera- ture of the source, whether low or high, the rays would pass it with equal freedom. The warmth of the hand and the rays from melting iron would go through it alike. This substance, therefore, is permeable to all kinds of heat, as glass is permeable to all kinds of light. It constitutes the true glass for heat. The great conclusion which we draw from the experi- ments just described is, that there are different varieties of radiant heat. Some of them can pass through glass, and some can not. Hereafter we shall see that the intrin- Whal is the relation of glass to radiant heat of low intensity? What changes take place in the transmissive power of the glass as the temper- ature rises ? How are these facts connected with the physical independ- ence of light and heat ? What are the properties of rock salt ? Why is it the glass of heat? What general conclusion is drawn from the foregoing facts ? 72 THEORY OF EXCHANGES OF HEAT. sic differences in radiant heat are due to the same cause which gives different colors to light. LECTURE XVI. Theory of the Exchanges of Heat. — Physical Inde- pendence of Light and Heat . — Theory of Exchanges. — Explanation of the Cold Ray Experiment . — Well^ s Theory of the Deiv. — Cold on Mountain Tops. — Con- duction a Form of Radiation. — Temperature of the Sun. The earlier writers on chemistry supposed that if light and heat are not the same principle, they are mutually con- vertible ; that when the rays of light fall on any object and warm it, they do so because they become extinguished and changed into heat. But there are many facts which militate against this doc- trine. A vessel containing hot water radiates heat, and that heat is totally invisible in a dark room, nor can it be made to assume the luminous condition, even though concentrated by large concave mirrors. In addition, as we have already shown, the relation of transparency for these two agents is not the same. A piece of smoky quartz, or dark-colored mica, of such a degree of opacity as scarcely to admit a ray of light to pass, is freely traversed by radiant heat. Theory of the Exchanges of Heat. The theory of the exchanges of heat, comprehending an explanation of a great number of the phenomena we ordina- rily witness, depends upon the following principles : It as- sumes, 1st, that all bodies, no matter what their temperature may be, are constantly radiating heat at all times ; 2d. That the rate of radiation depends on the temperature, in- creasing as the temperature rises, and diminishing as it de- clines. What are the varieties of radiant heat due to ? What relation was for- merly supposed to exist between light and heat ? Can rays of heat exist without being visible? Can light exist unaccompanied by heat? What other evidence have we of the p%sical independence of these agents ? On what does the theory of the exchanges of heat depend ? THEORY OF EXCHANGES OF HEAT. 73 Thus the various objects around us are constantly emit- ting caloric, the warm bodies to the cold, and the cold ones to the warm. A mass of snow and a red-hot cannon-ball respectively give off heat, the ball emitting it in great quan- tities, and the snow in less. And even when adjacent bod- ies have reached the same thermometric point, they still con- tinue to exchange heat with one another. Upon these principles, we can readily account for the fact that bodies of different temperatures at first, finally come to an equilibrium. If an ignited cannon-shot be placed in the middle of a large room, it radiates its heat to the ceiling, the walls, the floor, and the various objects around ; they also radiate back again upon it ; but, from its elevated tem- perature, it emits its heat faster than they, and therefore gives out more than it receives. Its temperature constantly descends, and continues to do so until it receives just as much as it gives, which takes place when it has reached the same degree as the objects around ; for, other things being equal, bodies at the same temperature radiate with equal speed. The process must, however, stop as soon as that equality of temperature is attained ; for, if we suppose the shot to cool below that point, it would evidently begin to receive more heat from the objects around than it gave forth, and the excess accumulating in it, its temperature would at once rise. "When an equilibrium is obtained the process of radiation still continues, but the exchanges are equal. Two lighted candles placed together do not extinguish each other, or cease to exchange light with each other, nor do two bodies equally warm cease, for that reason, to exchange heat In a room, therefore, in which every thing has the same tem- perature, rays are continually exchanging, but each object maintains its own temperature, because it receives as much as it gives. If a red-hot ball and a thermometer bulb are placed near one another, the bulb receives more heat from the ball than it gives to it, and its temperature therefore rises ; but if a thermometer bulb and a snow-ball are placed in presence Do bodies at the same temperature still radiate ? Describe the process of cooling of an incandescent body. When does the descent of temperature cease ? When an equilibrium is obtained, what is the rate of exchanges ? Describe the action in the case of a red-hot ball and a thermometer bulb. D 74 THEORY OF THE DEW* of one another, the bulb, being the hotter body, gives mora than it receives, and its temperature therefore descends. This is the explanation of the experiment 'with the conju- gate mirrors. That experiment, as was observed, affords no proof that there are rays of cold : the effect is due to the fact that a mutual exchange is going forward between the two bodies, and the temperature of the hotter descends. The mirrors, of course, take no part in this phenomenon ; their office is merely to direct the path of the rays, as has been explained. Gn the principles of the radiation of heat is founded Wells’s theory of the dew. After the sun goes down of an evening, drops of water condense on the leaves, grass, stones, and other objects exposed to the air. It was once a question whether this dew descended in the form of a light shower, or ascended from the ground. There are also certain cir- cumstances apparently very mysterious attending its forma- tion : the dew rarely falls on a cloudy night ; it also appa- rently possesses a selecting power, depositing itself on some bodies in preference to others. The theory of Dr. Wells fur- nishes a beautiful explanation of these curious facts. During the day, the various bodies on the surface of the earth, re- ceiving the rays of the sun, become warm ; but at nightfall, when the sky is unclouded, they begin to cool ; for, the pro- cess of radiation continuing without any source of supply, their temperature must descend. While the sun shone they received as much heat from him as they gave forth to the ^%y, but when he sets the supply is cut off, and they there- 4>re cool ; and as there is always moisture in the air, their =«mperature descending, by-and-by the dew point is reach- tJd ; they become cold enough to condense water from the surrounding air, and this is the dew. And as different bod ies, according to the roughness or physical condition of theii surfaces, radiate with different degrees of speed, as Leslie’s canister proves, some of the objects exposed to the sky cool rapidly, and are covered with dew ; but with others the dew point is never reached : hence the apparent selecting power. When there is a canopy of clouds over the sky, dew can not form, for the cloud radiates to the earth as much as the Describe the action of a snow-ball and a thermometer bulb. How is this connected with the experiment with conjugate mirrors ? Unde’* what cir- cumstances does dew form? What is the theory of Wells? How aocs this explain the selecting power of bodies ? CONDUCTION. 75 earth radiates to it : the exchanges are equal, and the equi- librium is maintained ; but if the cloud disappears, the heat of the surface of the ground escapes away into the regions of space, and is lost ; hence cloudy nights are warm, and a clear is often a frosty night. For similar reasons, mountain tops are always colder than valleys. In a valley, the radiation is obstructed by the sides of the adjacent hills, but on the top of a mountain the free exposure to the sky permits of unchecked radiation. It has already been observed, that conduction is only a form of radiation. In its ordinary acceptation, the term con- duction implies passage from particle to particle, by reason of their being in contact ; but we have proved that the con- stitution of matter involves the existence of intorstices, and that heat can only pass from among these by radiating across the interstices ; hence the term interstitial radiation. An interesting conclusion may be drawn from the condi tions of the passage of radiant heat through glass. We have seen it is necessary that the heat should come from a source of very high temperature to pass this medium with facility. Now the heat of the sun passes with the greatest freedom, as is well known when we stand before a window through which the sun shines. In the focus of a convex lens of glass exposed in the sun’s rays, bodies may be readily set on fire. We infer, therefore, that the temperature of the sun is very high, a result which is corroborated by proofs drawn from other sciences. LECTURE XYII. Of Light. — Sources of Light. — The Sim. — Incande- scence. — Combustion. — Different Colors of Lights . — Shadoivs. — Conditions of the Intensity of Light . — Fhotometers^ Rumford's, Ritchie's^ and the Extinction of Shadows . — Velocity of Light. — Law of Reflection. — Refraction. — Burning Glasses. The phenomena of radiant heat lead us by imperceptible steps to the phenomena of light. In treating of the former, How does it explain the action of clouds ? Why is it colder on mount- ains than in valleys ? What is meant by interstitial radiation ? What con elusion may be drawn as respects the temperature of the sun ? 70 NATURE OF LIGHT. we have in many cases drawn illustrations from the latter ; and, indeed, there are facts in relation to caloric which it is absolutely impossible to understand until we comprehend the analogous facts in light. Light may be artificially produced by many different pro- cesses, such as the ignition of solids, combustion, and phos- phorescence. Any solid, if sufficiently heated, becomes lu- minous j combustible gases take fire at a certain temperature in the air ; and the diamond will emit a phosphorescent glow in a dark place, after it has been exposed to the day. It is, however, to the sun that we are chiefly indebted. The quantity of light furnished by him infinitely exceeds that of all other natural and artificial sources, and its brill- iancy is so great that the electric spark alone rivals it. When the temperature of solid substances is raised to 1000° Fahrenheit, they begin to be luminous in the day- light, or, as it is termed, are visibly red-hot. It requires a far higher temperature to render a gas incandescent. This may be shown by holding a piece of thin platina wire in the current of hot air which rises from the apex of the flame of a lamp ; the air is not visibly ignited, but the platina wire instantly becomes red-hot, showing the great difference in this respect between this metal and a gas. Different vapors and gases evolve different quantities of light when ignited. The flame of burning hydrogen is scarcely visible in the daylight j that of alcohol is but little brighter ; but, under the same circumstances, sulphuric ether emits much light. If we take a glass of the form Fig. 56, consisting of a bulb, a, and curved tube, b, and, hav- ing filled the bulb with ether, cause it to boil by the application of a lamp, c, the ether may be set on fire as it is forced out of the vessel by the pressure of its vapor. It burns in a beautiful arch of great brilliancy ; but if we substitute alcohol for ether, the light becomes quite insignificant. The light which is emitted by lamps and candles is, how- ever, in reality, due to the disengagement of solid matter. Mention some of the sources of light. At what temperature do solids be- come incandescent ? In the combustion of vapors and gases, is there any difference in the amount of light emitted ? How may this be illustrated ? To what cause are we to attribute the light emitted by lamps and candles ? ARTIFICIAL LIGHT. 77 The constituents of the gas which produces the flame are carbon and hydrogen chiefly ; of these, the latter is the more combustible, and is first burned ; for a moment, there- fore, the carbon exists in a solid form, in a state of extreme subdivision, and at a high temperature, but being in con- tact with the external air, it is immediately consumed. Artificial lights differ in color. If alcohol be mixed with common salt and set on fire, the flame is of a yellow tint ; if with boracic acid, it is green ; if with nitrate of strontian, it is red. It is upon these principles that the art of pyro- techny depends. From whatever source light may come, it exhibits the same physical properties. It moves in straight lines. When it impinges on polished metallic surfaces, it is reflected ; on dark surfaces, it is absorbed ; on transparent surfaces, as glass, it is transmitted. In the last case, it is frequently forced into a new path, as we shall presently see, and then the phenomenon takes the name of refraction, because the ray is broken from its primitive course. There are two different kinds of opacity, black and white ; charcoal is a black opaque substance, earthen-ware is opaque white. The shadows formed by opaque bodies arise from the in- terception of light in its rectilinear progress. They may be of two different kinds, the common and geometrical ; the former arises from a luminous surface, the latter from a lucid point ; the former consists of two portions, the umbra and 'penumbra ; in the latter, the passage from total darkness to light on the side of the shadow is abrupt, and without the intervention of any shade. The illuminating power of a light depends upon several conditions. As the distance increases it becomes less, the effect being inversely as the square of the distance ; that is, at two feet it gives only one fourth of what it would do at one, at three feet only one ninth. The absolute intensity of the light also determines the result ; thus, there are flames that are very brilliant, and others that are paler : the mag- nitude of the luminous surface is another of these conditions. The absorbent effect exerted on the passing rays by the air. How may artificial yellow, green, and red lights be made ? In what course does light move ? What is meant by the reflection, absorption, trans- mission, and refraction of light ? How many kinds of opacity are there ? What is the difference between common and geometrical shadows ? Whstt conditions determine the illuminating power of light ? 78 PHOTOMETRY. or medium traversed, another ; as is also the direct or oblique manner in which the rays are received on the illuminated surface. Of Photometers and the Measurement of Light. The methods resorted to for the measurement of the in- tensity of light are very inferior to those for heat. They are not absolute, but comparative measures. Three are in common use : they are known as E-umford’s method, Ritch- ie’s method, and the method of extinction of shadows. Eumford’s method depends on the principle that of two lights, the most brilliant will cast the deepest shadow. If, therefore, the lights to be compared are made to cast shad- ows of the same opaque body, side by side, upon a piece of paper, the eye can, without difficulty, determine which of the shadows is darkest, and the light which casts it being moved to a greater distance, or the other being brought nearer, when the two shadows are of precisely the same depth, the distances of the lights from the paper will indicate their relative illuminating power ; thus, if one is twice as far off as the other, its intensity is four times as great. Ritchie’s photometer depends on the equal illumination of surfaces. It con- sists of a box, a b, six or eight inches long, and one broad and deep. Fig. 57, in the middle of which a wedge of woodj/'e^, is placed, with its angle, e, up- ward. This wedge is covered with white paper, neatly doub- led to a sharp line at e. In the top of the box there is a conical tube, with an aperture, d, at its upper end, to which the eye is applied, and the whole may be raised to any suit- able height by means of the stand, c. On looking down through d, having previously placed the two lights, m n, the intensity of which we desire to determine, on opposite sides of the box, they illuminate the paper surfaces exposed to them, and the eye sees both those surfaces at once. By Describe Rumford’s and Ritchie’s photometric methods. mg. 57 . PHOTOMETRY. 79 changing the position of the lights, we eventually make them illuminate the surfaces equally, and then, measuring their distances from e, their illuminating powers are as the squares of those distances. In both this and the preceding method, a difficulty arises when the lights to be compared are of different tints. To some extent, this may be avoided by placing in Ritchie’s in- strument a colored glass at d. The third method, that of extinction of shadows, is much more exact, differences in the color of the lights even serv- ing to give greater accuracy. It depends on the following principle. If a light is made to throw the shadow of an opaque object upon a white screen, there is a certain distance at which, if a second light be brought, its rays, illuminating the screen, will totally obliterate all traces of the shadow. It has been found that eyes of average sensitiveness fail to distinguish the effect of a light when it is in presence of an- other sixty- four times as intense. The precise number varies with different eyes, but to the same eye it is always the same. If there be any doubt as to the perfect disappear- ance of the shadow, the receiving screen may be agitated or moved a little. This brings the shadow, to a certain ex- tent, into view again. Its place can then be traced, and on ceasing the motion the disappearance verified. When, therefore, we desire to measure the relative intens- ities of lights, we have only to determine at what distance they will extinguish a given shadow. Their intensities are as the squares of those distances. This is the method by which I determined the amount of light given off by ignit- ed solids at various temperatures, as will be hereafter men- tioned. Light does not move from point to point instantaneously, but at a rate which is measurable. From certain astro- nomical facts, it appears that the velocity is about 192,000 miles’ per second. When a ray falls upon a polished surface it suffers reflex- ion, and when it falls upon a transparent medium it under- goes refraction. It is in consequence of this that convex lenses converge the rays of the sun, and so produce a high temperature. In What difficulty is encountered in these methods? On what principle does the method by extinction of shadows depend ? Describe the process. At what rate does light move ? 80 newton’s discoveries. Fig . 58. this application they are called burning glasses, and, until the invention of the Voltaic pile and oxyhydrogen blowpipe, presented the most energetic means for elevation of temper- ature. If made of thin and pure glass, and of a diameter of from one to three feet, these lenses will effect the instan- taneous fusion of most earthy and metallic bodies. Even the most fixed metals volatil- ize at the focal point. LECTURE XYIII. The Constitution op Solar Light. — Newto7i"s Discov- eries . — The Solar Spectrum. — Order of the Intensity of Light. — Distribution of Heat . — The Chemical Ef- fects. — Distribution of Chemical Power. — Fixed Lines. Fig . 60. Sir Isaac Newton first succeeded in proving the compound nature of light by the aid of a very simple instrument, a glass prism. It consists of a piece of glass having three sides. Fig. 5^, a a, and is usually mounted on a brass stand, b, with a ball and socket joint, c, which allows us to place it in any required position. Let the shutters of a room be closed, and through an aperture in one of them, suitably situated, let a beam of the sun enter, Fig. 60, a. It pursues, of course, a straight path, following the dotted ^ line, a e. Now let the prism interpose in the position, b c, so as to intercept completely the ray. This goes no longer to e, but is bent out of its course, and moves in the direction d. Two striking facts are now to be re- What are burning glasses ? Describe the prism. State the effect which ensues when a ray passes through the prism. THE SOLAR SPECTRUM. 81 marked : first, the ray a is refracted or broken from its path ; and, second, instead of forming on the surface d, upon which it falls, a white spot, an elongated and beautifully-colored image is produced. These colors are seven in number : red, orange, yellow, green, blue, indigo, violet. The separation of these colors from one another is designated by the term Dispersion. Newton has shown that white light consists of these vari- ous-colored rays blended together ; and their separation in the case before us is due to the fact that the prism refracts them unequally. On examining the position of the colors, in their relation to the point e, to which they would all have gone had not the prism intervened, it is ascertained that the red is least disturbed or refracted from its original path, and the violet most ; for these reasons, we call the red the least refrangible ray, the violet the most refrangible, and the yel- low intermediately. That the mixture of these colored rays reproduces white light, may be proved by resorting to any optical contrivance which will reassemble them all in one point ; that point will be perfectly white. Let V r. Fig, 61, represent the spectrum which is given by a sunbeam after its passage through a prism, and e the point to which it would have gone had not the prism inter- vened ; the order of the colors commencing with that which is least disturbed from its path, or near- est to e, is as follows : Red, Orange, Yellow, Green, Blue, Indigo, Violet. These colors gradually blend into each other, so that their boundaries can not be traced ; and in- stead of a circular spot, which would have resulted had they gone forward to e, they are dilated out, so as to form an elongated figure with parallel sides ; at the two ex- tremities the light fades gradually away, so that we can not trace its limit with precision. What is meant by refraction ? What by dispersion ? What is Newton’s theory of the constitution of light ? Which is the least, and which the most refrangible ray ? Of what does white light consist ? What is the order of refrangibility of colors ? What is the figure of the spectrum ? D 2 Fig. 61. 82 DISTRIBUTION OP HEAT IN THE SPECTRUM. Besides this difference of color, the light differs in intrin= sic brilliancy in the different spaces. Thus, if we receive the spectrum on a piece of finely-printed paper, we can read the letters in each color at very different distances. In the yellow region the light is most brilliant, and there we can read farthest. From this point the light declines in brill- iancy to the two ends of the spectrum, its intensity in the colored spaces being in the following order : Yellow, Green, Orange, Red, Blue, Indigo, Violet. Sir W. Herschel discovered, while using large reflecting telescopes, that the calorific rays of the sun pass with differ- ent degrees of facility through colored glasses, and was led to examine the temperature of the colored spaces of the so- lar spectrum, to see whether the intensity of the heat follows the intensity of the light. It was reasonable to suppose that the yellow space, being the brightest, would be also the hot- test. He therefore placed delicate thermometers in the various colored spaces, and kept them in these spaces until they had risen as high as the ray could bring them. The thermometer v, Fig, 62, had risen the least, and in succession, z, y, o, r; that which was immersed in the red being the highest,. It thus appears that the distribution of heat in the colored spaces of the solar spectrum is not the same as the distribution of light ; that the yellow ray, though it is the most luminous, is far from being the hottest, and that the intensity of the heat stead- ily increases from the violet to the red extremity. But this is not all : he farther found, that if a thermom- eter be brought out of the red region in the position x, be- yond the limits of the spectrum, and where there is no light whatever, it stands higher than any of the others. From this a most important conclusion may be drawn, that the light and heat existing in the sunbeam are distinct and in- How may the illuminating power be determined ? What is the order of illuminating power? Describe the discovery of Sir W. Herschel. Is the distribution of heat in the spectrum the same as the distribution of light ? What fact indicates that the light and heat are separate and independent agents ? RAYS OP CHEMICAL ACTION. 83 dependent agents, and that such processes as we are con- sidering they may he perfectly separated from each other. It was discovered by some of the alchemists, centuries ago, that the chloride of silver, a substance of snowy white ness, turns black on exposure to the light. More recently, a great number of such bodies have been found — bodies which change, with greater or less rapidity, under the influx* ence of this agent. The iodide of silver, which forms the basis of the process known as the Daguerreotype, is such ; and a mixture of chlorine and hydrogen gases in equal vol- umes, though it may be kept unchanged for a great length of time in the dark, explodes violently on exposure to the sunshine. In the same manner, changes take place in a great variety of organic compounds ; the most delicate veg- etable hues are soon bleached, and, indeed, a ray of light can* scarcely fall on a surface of any kind without leaving traces of its action. If a piece of paper, spread over with chloride of silver, be placed in the solar spectrum, it soon begins to blacken. Buf it does not blacken with equal promptitude in each of the colored spaces ; the effect takes place most rapidly among the more refrangible colors, and especially in the violet re^ gion. As in the case of heat, the effect extends far beyond the limit of the spectrum, and where the eye can not discover a trace of light. We may be led, therefore, to conclude that there exists in the sunbeam an agent capable of producing chemical effects, which exerts no action on a thermometer, which can not be perceived by the eye, and which, therefore, is neither heat nor light. By placing mixtures of chlorine and hydrogen in small vials, and immersing them in the colored spaces, we can readily determine the place of max- imum action, and the distribution of the chemical in- fluence throughout the spectrum. In this, as in the former instance, the greatest effect is found among the more refrangible colors, and from that point diminishes toward each extremity of the spectrum. What changes does chloride of silver undergo in the sunshine ? When a mixture of chlorine and hydrogen is exposed to the sun, what occurs ? How does light change vegetable colors? Which ray darkens the chloride of Silver most ? What proof have we that another agent exists in the sun’s r:i\s l)esides light and heat? AVliat ray affects the mixture of chlorine and liwlroion most i)Owerfully ? Fig. 63. 84 FIXED LINES. When the aperture which admits a ray of light into the dark room, Fig. 60, is a narrow fissure or slit, not more than the one thirtieth of an inch in width, the spectrum which is formed by the action of a prism is crossed by great num- bers of black lines. These always are found in the same position, as respects the colored spaces, and, from the in- variabihty of that position, are much used as boundary marks. They are designated by the letters of the alphabet, and their relative magnitude, with their position, is given in Fig. 63, on the previous page. LECTUEE XIX. Wave Theory of Light. — Proofs of the Existence of the Ether. — Light consists of Waves in it . — The Ethereal Particles move hut little. — Distinction between Vibra- tion and Undulation. — FresneVs Theory of Transverse Vibrations . — Transverse and Normal Waves, — Brill- iancy of Light defends on Amplitude of Vibration. The cause of light is an undulatory movement taking place in the ethereal medium. That such a medium exists throughout all space, seems to be proved by a number of as- tronomical facts. It exerts a resisting agency on bodies moving in it. From its tenuity, we should scarcely expect that it would impress any disturbance on the great planetary masses ; but on light, gaseous cometary bodies, it produces a perceptible action. The comet of Encke, with a period of about 1200 days, is accelerated in each revolution by about two days ; and that of Biela, with a period of 2460 days, is accelerated by about one day. As there is no other ob- vious cause for these results, astronomers have very gener- ally looked upon them as corroborative proofs of the exist- ence of a resisting medium, that universal ether to which so many other facts point. In this elastic medium, undulatory movements can be propagated in the same manner as waves of sound in the air. It is to be clearly understood that the ether and light are distinct things ; the latter is merely the efiect of move- What are the fixed lines ? How are these lines designated, and what is their use ? What proofs have we of the existence of an ethereal medium ? What is the relation between the ether and light ? MECHANISM OF WAVES. 85 ments in the former. Atmospheric air is one thing, and the sound which traverses it another. The air is not made up of the notes of the gamut, nor is the ether composed of the seven colors of light. Across the ether, undulatory movements, resembling, in many respects, the waves of sound in the atmosphere, trav- erse with prodigious velocity. From the eclipses of Jupi- ter’s satellites, and other astronomical phenomena, it appears that the rate of the propagation of light, or the velocity with which these waves advance, is 192,000 miles in a second. We are not, however, to understand by this that the ethereal particles rush forward in a rectilinear course at that rate : those particles, far from advancing, remain stationary. If we take a long cord, a Fig. 64, and having fastened it by the extremity, 5, to g 4 a fixed obstacle, com- | mence agitating the end, ^ ^ \ a, up and down, the cord | will be thrown into wave- ^ like motions, passing rapidly from one end to the other. This may afford us a rude idea of the nature of the ethereal movements. The particles of which the cord is composed do not advance or retreat, though the undulations are rap- idly passing. So, too, if in the centre, c, of a surface of water. Fig. 65, we make a tapping motion with the Fig. 65 . finger, circular waves are propagated, which, expanding as they go, soon reach the sides of the vessel which holds the water. A light object placed on the sur- face is not violently drifted forward by the waves, but remains entirely motion- less. We see, therefore, that there is a wide distinction between the motion of a wave and the motions of the particles among which it is passing. They retain their places, but the wave flows rapidly forward. A distinction is to be made between the words vibration and undulation. In the case of the cord. Fig. 64, the vi- At what rate is light propagated ? Do the ethereal particles move forward at that rate ? How may the movements of ethereal waves be represented by a cord ? How may they be represented on the * surface of water? Do the vibrating particles move forward with the wave ? 86 THEORY OP TRANSVERSE VIBRATIONS. bration is represented by the movement exerted by the hand at the free extremity, a ; the undulation is the wave-like motion that passes along the cord. In the case of the wa- ter, Fig. 65, the vibration was represented by the tapping motion of the finger, the undulation by the resulting wave. We therefore see that these stand in the relaJ;ion of cause and effect : the vibration is the cause, and the undulation the effect. Throughout the ethereal medium, each particle vibrates and transmits the undulatory effect to the particles next beyond it. In the same way as a vibrating cord agitates the sur- rounding air, and makes waves of sound pass through it, so does an incandescent or shining particle, vibrating with pro- digious rapidity, impress a wave-like movement on the ether, and the movement eventually impinging on the eye is what we call light. To refer again to the simple illustration given in Fig. 64 : it is obvious that there are an infinite variety of directions in which we may vibrate that cord or throw it into undula- tions. We may move it up and down, or horizontally right and left, and also in an infinite number of intermediate di- rections, every one of which is transverse, or at right angles Fi^.ee. to the length of the cord, 3is a b bj c c, &c.. Fig. 66. This is the peculiarity of the movement of light. Its vibrations are trans- verse to the course of the ray ; and in this it differs from the movement of sound, in which the vibrations are normal, that is to say, executed in the direction of the resulting wave, and not at right angles to it. This great discovery of the transverse vibrations of light was made by M. Fresnel. It is the foundation of the whole theory of optics, and offers a simple but brilliant explana- tion of so many of the phenomena of light, that the undula- tory theory is by many writers designated the Theory of Transverse Vibrations. It may, however, be remarked, that though light consists What is the distinction between vibrations and undulations ? How does each ethereal particle propagate the wave to those beyond it ? Is there any analogy between sound and light ? In how many ways may a cord be vi- brated ? What is implied by the term theory of transverse vibrations ? COLORS DEPEND ON WAVE-LENGTH. 87 of rays originating in these transverse motions, it is not im- possible that there may be other phenomena which corre- spond to movements in other directions. To those move- ments our eyes are totally blind, and hence we can not speak of them as light. In the same way there may be motions in the air, due to transverse vibrations, but to them our ear is perfectly deaf. But it is not improbable that God has formed organs of vision and organs of hearing in the case of other animals upon a different type ; eyes that can perceive normal vibrations in the ether, and ears that can distinguish transverse sounds in the air. Lights differ from each other in two striking particulars — ^brilliancy and color. These are determined by certain affections or qualities in the waves. On the surface of water we may have a wave not an inch in altitude, or a wave, as the phrase is, “mountains high.” Under these circum- stances, waves are said to differ in amplitude ; and, trans- ferring this illustration to the case of light, a wave, the am- plitude of which is great, impresses us with a sense of in- tensity or brilliancy, but a wave, the amplitude of which is little, is less bright. The brilliancy of light depends on the magnitude of the excursions of the vibrating particles. LECTURE XX. Wave Theory of Light. — Colors of Light deiiend upon Wave Lengths. — Interference of Sounds. — Young's Theory of Interference of Light. — Condition of Inter- ference. — Explanation of Lights and Shades in Shad- ows. By the length of a wave upon water, we mean the dis- tance that intervenes from the crest of one wave to that of the next, ox a 5 from depression to depression. Thus, in Fig. 67, from a to b, or, what is the same, from c to cl, constitutes the wave length. In the ether the length of the waves determines the phe- Are other motions possible ? What is meant by the amplitude of waves ? On what does the brilliancy of light depend ? What is meiint by the length of a wave ? 88 TWO SOUNDS PRODUCE SILENCE. nomenon of color ; this may be rigorously proved, as we shall soon see, when we come to the methods by which phi- losophers have determined the absolute lengths of undula- tions. It has been found that the longer waves give rise to red light, the shorter ones to violet, and those of interme- diate magnitudes the other colors in the order of their re- frangibility. Two rays of light, no matter how brilliant they are sep- arately, may be brought under such relations to one another as to destroy each other’s effect and produce darkness. Light added to light may produce darkness. Two sounds may bear such a relation to each other that they shall produce silence ; and two waves, on the surface of water, may so in- terfere with one another that the water shall retain its hor- izontal position. Take two tuning forks of the same note, and fasten by a QQ little sealing wax on one prong of each a disc of card-board, half an inch in diameter, as seen Fig. 68, a. Make one of the forks a little heavier than the other, by putting on the end of it a drop of the wax. Then take a glass jar, b, about two inches in diameter and eight or ten long, and having made one of the forks vibrate, hold it over the mouth of the jar, as seen at d, its piece of card- , board being downward ; commence pouring water into the jar, and the sound will be greatly re-enforced. It is the column of air in the jar vibrating in unison with the fork, and we adjust its length by pouring in the water ; when ilie sound is loudest, we cease to pour in any more water, the jar is adjusted, and we can now prove that two sounds added together may produce silence. It matters not wliich fork is taken, whether it be the light or the loaded, on making it vibrate and holding it over the mouth of the resonant jar, we hear a uniform and clear sound, without any pause, stop, or cessation. But if we make both»vibrate over the jar together, a remarkable phe- nomenon arises, a series of sounds alternating with a series of silences ; for a moment the sound increases, then dies What is the connection between color and wave-length ? What is meant by the interference of lights or of sounds? Give an illustration of the in- terference of sounds. What is the character of the sound which the re- sonant jar emits ? LAWS OF INTERFERENCE. 89 away and ceases, then swells forth again, and again declines, and so it continues until the forks cease vibrating. The length of these pauses may be varied by putting more or less wax on the loaded fork ; and as we can see that even during the periods of silence both forks are rapidly vibrating, the experiment proves that two sounds taken together may produce silence. Under these circumstances, waves of sound are said to in- terfere with each other, and in like manner interference takes place among the waves of light. We can gather an idea of the mechanism by considering this case in waves upon water, in which, if two undulations encounter under such circumstances that the concavity of the one corresponds with the convexity of the other, they mutually destroy each other’s effect. If two systems of waves of the same length encounter each other after having come through paths oi equal length, they will not interfere. Nor will they interfere even though there be a difference in the length of these paths, pro- vided that diflerence be equal to one whole wave, or two, or three, &c. But if two systems of waves of equal length encounter each other after having come through paths of unequal length, they will interfere, and that interference will be com-, plete when the difference of the paths through which they have come is half a wave, or 1 J, 2 J, 3J, See. These cases are respectively shown at a and c cl, Fig- 69, at the point of encounter, x ; in the Fig. 69. first instance, the two sets of waves are ^ cc a in the same phase, that is, their con- cavities and convexities respectively h correspond, and there is no interfer- ^ ence ; but in the second case, at the point of encounter, x, the two systems ^ ^ are in opposite phases, the convexity of the one corresponding with the concavity of the other, and interference takes place. Upon these principles, we can account for the remarka- ble results of the following experiment : From a lucid point. Why are there pauses in it ? At the time of these pauses, are the forks vibrating ? When two waves upon water encounter each other, under what circumstances will they interfere ? When systems of waves of equal length encounter one another, when do they, and when do they not, interfere ? 90 INTERFERENCE OF LIGHT. s, Fig. 70, which may be formed by the rays of the sun Fisr. 70. converged by a double convex lens of short focus, or by passing a sunbeam ^ through a pinhole, let rays emanate, 0 and in them place the opaque obsta- e cle, a bj which we will suppose to be a cylindrical body, seen endwise in the figure ; at some distance beyond place . a screen of white paper, c to receive ^ the shadow. It might be supposed that this shadow should be of a magnitude included between % y, because the rays, s a, s b, which pass the sides of the obstacle, impinge on the paper at those points. It ° ' might farther be supposed, that within the space x y the shadow should be uniformly dusky or dark ; but, on examining it, such will not be found to be the case. The shadow will be found to consist of a se- ries of light and dark stripes, as represented in Fig. 71. In its middle, at e, Figs. 70 and 71, there is a white stripe ; this is succeeded on each side by a dark one ; this, again, by a bright one, and so on alternately. Upon the undulatory theory, all this is readily explained. Sounds easily double round a corner, and are heard though an obstacle intervenes. Waves upon water pass round to the back of an object on which they impinge, and the undu- lations of light in the same manner flow round at the back of the piece of wire, a by Fig. 7 0 ; and now it is plain that two series of waves which have passed from the sides of the obstacle to the middle of its shadow, that is, along the lines aCyb 6y have gone through paths of equal length, and, there- fore, when they encounter at the point e, they will not in- terfere, but exalt each other’s effect. But, leaving this central point, e, and passing \o fy it is plain that the systems of waves which have come through the paths a fy b f, have come through different distances, .for b fh longer than a f ; and if this difference be equal to the length of half a wave, they will, when they encounter at the point fy interfere and destroy each other, and a dark stripe results. Describe the experiment represented in Fig. 70. Is the resulting shadow uniformly dark ? At the central point of the shadow, is it dark or light ? Explain the cause of this central light space, and of the alternate dark and light ones on each side of it. LENGTH OF WAVES. 91 Beyond this, at the point gy the waves from each side of the obstacles, a g, b gy again have come through unequal paths ; but, if the difference is equal to the length of one whole wave, they will not interfere, and a white stripe re- sults. Reasoning in this manner, we can see that the interior of such a shadow consists of illuminated and dark spaces alternately : illuminated spaces, when the light has come through paths that are equal, or that differ from each other by 1, 2, 3, 4, . . &c., waves ; and dark, when the difference between them is equal to J, IJ, 2^y 3J, . . &c., waves. That it is the interference of the light coming from the opposite sides of the opaque object which is the cause of these phenomena, is proved by the circumstance that if we place an opaque screen on one side of the obstacle, so as to prevent the light passing, the fringes all disappear. LECTURE XXI. Wave Theory of Light. — Measurement of the Length of a Wave of Light. — Length differs for different Colors. — Measurement of the Period of Vibrations. — Nature of Polarized Light. — Plane y Circular y and Elliptical Polarized Light. — Reflection, Refraction, and Absorp- tion of Light. The experiment. Fig. 70, may enable us to determine the length of a wave of light. This may be readily done by measuring the distances af and b f or from the sides of the obstacle to the first bright stripe from the central one, for at that point the difference between those two lines, af and b f is equal to the length of one wave. We might em- ploy the second bright stripe ; the difference then would be equal to two waves. Farther, if, instead of using ordinary white light, radia- ting from the lucid point, s, we use colored lights, such as red, yellow, blue, &c., in succession, we shall find that the What is the length of the paths of the waves which go to the illuminated spaces, and of those which go to the dark ones ? How can it be proved that the waves from the opposite sides of the obstacle interfere ? How, by this arrangement, might we measure the length of a wave of light ? 92 FREaUENCY.OF WAVE- VIBRATION. wave length determined by the process just explained dif fers in each case ; that it is greatest in red, and smallest in violet light. By exact experiments made upon methods more complicated than the elementary one here given, it has been found that the different colored rays of light have waves of the following length : JVave Lengths of the Different Colors of Light. The English inch is supposed to be divided into ten mill- ions of equal parts and of those parts the wave lengths are : For red light . . . 256 “ orange . . . . . 240 “ yellow . . . . . 227 “ green . . . . . 211 For blue ..... 196 “ indigo 185 “ violet 174 In this manner, it is proved that the different colors of light arise in the ether from its being thrown into waves of different lengths. Knowing the rate at which light is propagated in a sec- ond, and the wave length for a particular color, we can readily tell the number of vibrations executed in a second, for they plainly are obtained by dividing 192,000 miles, the rate of propagation, by the wave length. From this it ap- pears, that if a single second of time be divided into one million of equal parts, a wave of red light trembles or pul- sates 458 millions of times in that inconceivably short in- terval, and a wave of violet light 727 millions of times. In speaking of the constitution of matter in Lectures I. and II., I had occasion to allude to the amazingly minute scale on which it is constructed. The remarkable facts we are now considering are a monument to the genius of New- ton and his successors, for they give us a just idea of the scale of space and time upon which Nature carries on her works among the molecules of matter. Common light, as has been said, originates in vibratory motions taking place in every direction transverse to the ray. With polarized light it is different ; to gather an idea of the nature of polarized light, we must refer once more to the cord. Fig. 66, which, as has been said, serves to imitate common light when its extremity is vibrated vertically, hor- When different colors of light are used, are the waves found to be of equal length ? What is the length of a wave of red and of violet light respective- ly ? How can we ascertain the number of vibrations in a second ? On the undulatory theory, in what direction do the ethereal particles vibrate in the case of common light ? What is the case in polarized light ? POLARIZATION OF LIGHT. 93 izontally, and in all intermediate positions in rapid succes- sion. But if we simply vibrate it up and down, or right and left, then it imitates polarized light ; polarized light is, there- fore, caused by vibrations transverse to the ray, but which are executed in one direction only. There is a certain gem, the tourmaline, which serves to exhibit the properties of polarized light. If we take a thin plate of this substance, c d, prop- Fig. 72. erly cut and polished, and allow M a ray of light, a b, Fig. 72, to ^ j|l fall upon it, that ray will be free- |j! ly transmitted through a second L| plate if it be held symmetrically to the first, as shown at e f ; but if we turn the second plate a quarter round, as seen at g h, then the light can not pass through. The rays of the meridian sun can not pass through a pair of crossed tourmalines. The cause of this is obvious : if we take Fig. 73. a thin lath or strip of pasteboard, c Fig. i d 73, and hold it before a ^ge, or grate, ab, c ' ^ it will readily slip through when its plane [ coincides with the bars ; but if we turn it a quarter round, as at e then of course it can not pass the bars. Now the plate of tourmaline. Fig. 72, c dy polarizes the light, a by which falls upon it , that is, the waves that pass through it are vibrating all in one plane. They pass, there- fore, readily through a second plate of the same kind, so long as it is held in such a way that its structure coincides with that motion, but if it be turned round so as to cross the waves, then they are unable to pass through it. There are many ways in which light can be polarized : by reflection, refraction, double refraction, &c. The result- ing motion impressed on the ether is the same in all cases. Light modified as just described is designated plane po- larized light ; but there are other varieties of polarization. If the end of the rope. Fig. 66, be moved in a circle, circular waves will be produced, imitating circularly polarized light ; and if it be moved in an ellipse, elliptical polarized light. Describe the optical properties of the tourmaline. Give an illustration of the phenomenon. What is the cause of the action of the second tourmaline plate? Mention some of the methods by which light may be polarized. What is circularly polarized light ? What is elliptically polarized light ? 94 LAWS OF REFLECTION AND REFRACTION. The undulatory theory of light gives a clear account of the ordinary phenomena of optics. The general law under Fig. 74. which light is reflected from polished surfaces is a direct consequence of it ; that law is : that the angle, deb, Fig. 74, made by the reflected ray, d c, with a perpendicular, c b, drawn to the point c, at which the light im- pinges, is equal to the angle, a c b, which the incident ray makes with the same perpendic- ular, or, as it is briefly expressed, “ the angles of incidence and reflection are equal to each other, and on opposite sides of the perpendicular.” By the aid of this law, we can show the action of reflect- ing surfaces of any kind, and discover the properties of plane and curved mirrors, whether they be concave or convex, spherical, elliptical, paraboloidal, or any other figures. From the undulatory theory, the law of the^ refraction of light also follows as a necessary consequence. It is : “ in every transparent substance, the sines of the angles of in- cidence and refraction are to each other in a constant ratio and by the aid of this law we can determine the action of media bounded by surfaces of any kind, plane or spherical, concave or convex. It explains the action of lenses, and the construction of refracting telescopes and microscopes. Sir Isaac Newton’s discovery, that white light arises from the mixture of the different colored rays in certain propor- tions, explains the cause of the colors which transparent media often exhibit ; thus, if glass be stained with the oxide of cobalt, it allows a blue light to pass it, and upon such principles the art of painting on glass depends ; different colors being communicated by different metallic oxides. The cause of this effect is readily discovered ; for, if we make the light which enters a dark room, as in Fig. 60, pass through such a piece of stained glass before it goes through the prism, and examine the resulting spectrum, we find that several rays are wanting in it ; that the glass has absorbed or detained some, and allowed others to traverse it. A piece of blue glass thus suffers most of the blue light to pass, but stops the green, the yellow, &c. But it is also to be observed, that the light which is transmitted by any of What is the general law of reflection ? What is the law of the refraction of light? WTiat is the cause of the colors of transparent media? Is the light transmitted through these colored media pure ? PRODUCTION OF LIGHT. 95 these colored media is not pure, it is contaminated with other tints ; the blue glass, for instance, does not stop all the rays except the blue ; it allows a large portion of the red to pass, and hence the light it transmits is more or less compound. LECTURE XXII. • Production of Light. — By Incandescence. — Point at which Bodies are Red Hot. — All Solids shine at the same Degree. — Colors Emitted. — Rate of Brilliancy. — Nature of Flames. — Phosphorescence. — Controlled by Temperature. A theoretical explanation of the chemical action of light must depend on the views entertained of the nature of that agent. In a series of memoirs, published in the Lon- don and Edinburgh Philosophical Magazine between the years 1847 and 1851, 1 have investigated the circumstances under which light arises by artificial processes, and shall here proceed to detail the chief results. There are three general processes by which light is ob- tained artificially: 1st. By the ignition of bodies; 2d. By their combustion or burning ; 3d. By phosphorescence. 1st. Of the Production of Light by Ignition. — All sohd substances shine when their temperature is raised to a cer- tain degree. The point at which this occurs has been vari- ously estimated. Sir Isaac Newton places it at 635° ; Davy, at 812° ; Wedge wood, at 947° ; Daniell, at 980°. By taking advantage of the improved means which the pres- ent state of science offers, I found that for platinum it is 977°, or, if Laplace’s coefficient of dilatation be used in the calculation, 1006°. By inclosing a number of different substances with a mass of platinum in a gun-barrel, the temperature of which was gradually raised, it was found, on looking down the barrel, that they all commenced to shine at the same moment, and this even though, as in the case of lead, the melted condi- tion had been assumed. I therefore infer that all solids and liquids begin to shine at the same degree of the thermometer. What is the temperature of ignition ? Do all substances shine at the same degree ? 96 LIGHT BY COMBUSTION. The color of the light which the ignited substance emits depends upon the degree of heat to which it is exposed. Making due allowance for the physiological imperfections of the eye, there can be no doubt that the first rays which appear are the red, and as the temperature is made grad- ually to go up, the yellow, orange, green, blue, indigo, and violet are emitted in succession. At 2130° all these colors are exhibited, and from their commixture the substance ap- pears white hot. It may therefore be inferred, that as the temperature of an incandescent body rises, it emits rays of light of an in- creasing refrangibility. By the aid of the method of extinction of shadows it was proved, that as the temperature of an ignited solid rises, the intensity of the light increases very rapidly. For example, platinum at 2600° emits almost forty times as much light as it does at 1900°, as the following table shows : Intensity of Light emitted hy Platinum at different Temjperatures. Temperature of the Platinum. Intensity of its Light. 980 ^ . . . 000 1900 . . . 0*34 2015 . . . 0-62 2130 . . . 1*73 2245 . . . 2-92 2360 . . . 4*40 2475 . . . 7-24 2590 . . . 12-34 From a parallel series of experiments, in which the heat radiated by the ignited platinum was measured, a striking analogy between the two agents appears. Thus, if the quantity of heat radiated by platinum at 980° be taken as unity, it will have increased at 1440° to 2*5 ; at 1900° to 7*8 ; at 2360° to 17*8 nearly. The rate of increase is, there- fore, very rapid, as in the preceding case. 2d. Of the Production of Light hy Combustion. — It has been long known that all common flames are incandescent shells, the interior of which is dark, and it has been sup- posed that there are certain flames which emit particular rays only, but an examination by the prism showed that in every flame every prismatic color is found. The red which What is the order in which the colored rays arc emitted ? At what rate does the brilliancy of the light increase ? Does the same hold good for the radiant heat ? What is the condition of the interior of a flame ? LIGHT BY COMBUSTION. 97 burning cyanogen, and the blue which burning sulphur emits, are compound colors. By burning solid carbon in oxygen gas, it appeared that there is a connection between the refrangibility of the light which a burning body yields and the intensity of the chem- ical action going on, and that the refrangibility always in- creases as the chemical action increases. From this it appears that flames, such as those of lamps and candles, consist of a series of concentric and differently colored shells, the most interior one being red, and having a temperature of 977°. Upon this, in succession, are placed orange, yellow, green, blue, indigo, and violet shells. The flame, looked at directly, appears to yield white light, be- cause of the commixture of these rays ; but, on being sub- mitted to the action of a prism, they are separated from each other, and their individual existence proved. If, therefore, we could isolate a horizontal section of such a flame, it would have the aspect of an iris or rainbow ring. Upon the principle that, the more energetic the chemical action, the higher the refrangibility of the light emitted, we may explain, without difficulty, the colors which different flames present. The red tints predominate in the flame of burning cyanogen, because in that gas there is an element wholly incombustible — the nitrogen. This, as it is set fre cuts off the free access of the air, and the burning goes on tardily — very much in the same manner as in an oil lamp to , which the air is imperfectly supplied. On the other hand, carbonic oxide burns blue, because of the small quantity of air required to carry it to its maximum of oxydation. The color of flames depends, therefore, on the completeness or in- completeness of the combustion ; this principle readily ac- counting for those cases in which means are used for retard- ing or promoting the rate of burning, as where an atmos- phere of oxygen is used, or air introduced into the interior of a flame by means of a blowpipe, the bright blue cone arising in this latter instance being a striking indication of the increased rapidity of combustion. There is, therefore, a direct connection between the ve- hemence with which chemical affinity is satisfied and the refrangibility of the resulting light. If, as there are many reasons for supposing, all chemical changes are attended by What is the structure of a flame ? Explain the cause of the colors of flames. Why is the blowpipe cone blue ? E 98 PHOSPHORESCENCE. vibratory movements of the particles of the bodiej engaged it might well be anticipated that these vibrations should in crease in frequency as the action becomes more violent. But it is to be remembered that an increased frequency of vibration is the same thing as an increased refrangibility. 3d. Of the Production of Light hy Phosphorescence . — All solid substances, except the metals, possess the property of shining after they have been exposed to the sun. In some, the effect lasts but for a moment ; in others, it is of longer duration and considerable splendor. Among the best phos- phor! may be mentioned the sulphuret of barium, the sul- phuret of calcium, certain varieties of fiuor spar, and of dia- mond. Phosphorescence has generally been regarded as unattended by the emission of heat. By suitable experimental arrangements, I ascertained that the best phosphori, when at their maximum of glow, do not increase in volume by so much as the part ; but that there is minute expansion can not be doubted, since, when means sufficiently delicate are resorted to, a feeble rise of temperature can be detected. The intensity of the light disengaged is to some extent deceptive ; for, by resorting to the method of the extinction of shadows, it was shown that a fine specimen of chlorophane, at its maximum of bright- ness, yielded a light three thousand times less intense than the flame of a very small oil lamp. The quantity of light a substance can receive when e^f- posed to the sun depends upon the temperature. The colder the phosphorus is, the more brightly will it subsequently shine. If kept hot during its exposure, it will not shine at all. If a diamond placed upon ice is submitted to the sun, and then brought into a dark room, the temperature of which is 60°, for a time there is a glow, but presently the light declines and dies out. Let the diamond now be put in water at 100° ; again it shines, and again its light dies away, tf it next be removed from that water and suffered to cool, and then be reimmersed, it will not shine again ; but if the water be heated to 200°, and the diamond be dropped into it, again it glows, and again its light dies away. There is, therefore, a correspondence between the light disengaged and the temperature applied. What is the connection between chemical affinity and refrangibility What substances exhibit phosphorescence ? Do phosphorescent bodies ex pand ? What is the actual intensity of the light of phosphori ? How is phos phorescence controlled by temperature ? CHEMICAL ACTION OF LIGHT. 99 The phenomena of phosphorescence may all be explained on the principles of the theory of undulations ; for from a shining body undulations are propagated in the ether, and these, impinging on a phosphorescent surface, throw its mole- cules into a vibratory movement. These, in their turn, im- press on the ether undulations ; but, by reason of the differ- ence of its density, compared with that of the molecules, they do not lose their motion at once, but it continues for a time gradually declining away, and ceasing when the vis viva of the molecules is exhausted. We may therefore abandon expressions derived from the material theory of light, such as the absorption and subse- quent emission of the luminous agent, and conclude that, whenever a radiation falls upon a surface of any kind, it throws the particles thereof into a state of vibration, as when a stretched string is made to vibrate in sympathy with a distant musical sound. This view includes at once all the facts of the radiation of heat and the theory of calorific ex- changes ; it also offers an explanation of the connection of the atomic weights of bodies and their specific heats. It sug- gests that all cases of the decomposition of compound mole- cules, under the influence of light, is owing to a want of consentaneousness in the vibrations of the impinging ray and those of the molecular group, which, unable to maintain it- self, is broken down, under the periodic impulses it is receiv- ing, into other groups, which can vibrate along with the ray LECTURE XXIII. Chemical Action op Light. — Action of Natural and Ar- tificial Lights. — Preliminary Absorption. — Change in the Ray. — Necessity of Absorption. — The Daguerreo- type. — Explanation of the Process. — Its Imperfections — Other Processes. When a solar spectrum falls upon paper covered over with chloride of silver, the chloride turns black in the more refrangible regions. The darkening effect of light was known to the alchemists. The bleaching action on vegeta- ble colors must have been observed from the earliest times, On what principles may phosphorescence be explained ? 100 CHEMICAL ACTION OF LIGHT. but it is only recently that the phenomenon has been more particularly investigated. From whatever source it may he derived, light exerts chemical action. The moonbeams are sufficiently intense to give copies of that satellite on sensitive surfaces, as I found in 1841. Lamplight and other artificial lights are often peculiarly energetic. These decomposing effects take place on those portions of the substance only on which the rays actually fall. There is no lateral spreading, nothing analo- gous to conduction. When a sensitive substance receives light for a short space of time, no change takes place, the rays are being actively absorbed ; but as soon as that preliminary absorption is over, they act in a manner which is* perfectly definite ; if, for in- stance, it be a decomposition they are bringing about, the amount of decomposing effect will be precisely proportional to the quantity of rays absorbed. When a beam from any shining source causes a decom- posing efiect, it is always itself disturbed ; the medium which is changing impresses a change on the ray. Thus, a mixture of chlorine and hydrogen unites under the influ- ence of a ray, but that portion of the ray which passes through the mixture has lost the quality of ever bringing about a like change again. •When a beam from any shining source falls on a change- able medium, a portion of it is absorbed for the purpose of effecting the change, and the residue is either reflected or transmitted, and is perfectly inert as respects the medium itself. No chemical effect can therefore be produced by such rays except they be absorbed. It is for this reason that wa- ter is never decomposed by the sunshine, nor oxygen and hydrogen made to unite ; for these substances are all trans- parent, and allow the rays to pass without any absorption, and absorption is absolutely necessary before chemical ac- tion can ensue. But with chlorine the case is very different. This sub- stance exerts a powerful absorbent action on light ; the ef- fect takes place on the more refrangible rays ; when mixed Give examples of the chemical action of light. Do artificial lights possess that property ? What is meant by preliminary absorption ? What change is impressed on the ray ? Does the ray undergo absorption ? Why can not water be decomposed in the sunshine ? PHOTOGENIC PORTRAITS. 101 with hydrogen and set in the light, it unites with a violent explosion. The process of the Daguerreotype is conducted as follows : A piece of silver plate is brought to a high polish by rub- bing it with powders, such as Tripoli and rotten-stone, every care being taken that the surface shall be absolutely pure and clean, a condition obtained in various ways by different artists, as by the aid of alcohol, dilute nitric acid, &c. This plate is next exposed in a box to the vapor which rises from iodine at common temperatures, until it has acquired a gold- en yellow tarnish ; it is next exposed, in the camera obscura, to the images of the objects it is designed to copy, for a suit- able space of time. On being removed from the instrument, nothing is visible upon it ; but on exposing it to the fumes of mercury, the images slowly evolve themselves. To prevent any farther change, the tarnished aspect of the plate is removed by washing the plate in a solution of hyposulphite of soda, and finishing the washing with wa- ter ; it can then be kept for any length of time. Several important improvements on the original process have been made : 1st, by exposing the plate, after it has been iodized, to the vapor of bromine, or chloride of iodine, which gives it a wonderful sensibility ; 2d, by gilding the plate, after the other operations are complete, by the aid of a mixture of hyposulphite of soda and chloride ol gold ; this acts like a varnish, fastening the picture, and giving it a more agreeable yellow tone. The art of taking portraits from the life, which has now become a branch of industry, was invented by me soon after the Daguerreotype was known in America ; at that time, this, which is by far the most valuable application of the chemical agencies of light, was looked upon in Europe as entirely beyond the powers of this process ; but subsequent- ly great improvements in it have been made. My memoir descriptive of the art may be seen in the London and Ed- inburgh Philosophical Magazine (September, 1840), and the facts are also specified in the Edinburgh Review (Jan- uary, 1843), in which the discovery is attributed to its proper source, the author of this book. Why do chlorine and hydrogen explode ? Describe the process of the Daguerreotype. Are the images visible at first? By what means are they brought out ? How is the picture preserved from farther change ? MeO'. tion some of the later improvements of the process. 102 CHEMICAL ACTION OF LIGHT. When a beam falls upon the surface of a Daguerreotype plate, it communicates to the iodide of silver a tendency to decomposition, but iodine is never set free because of the metallic silver behind. On exposing a surface disturbed in this manner to the vapors of mercury, entire decomposition of the iodide ensues, its silver unites with the mercury, form- ing a white amalgam, and the iodine corrodes the metallic silver behind. The utmost care must be taken in all Da- guerreotype processes to have no vapors of iodine, or bro- mine, or chlorine about the camera or other apparatus ; they possess the quality of effacing the effects of light, and the most common source of failure among Daguerreotype artists is due to neglecting this precaution. There are some important difficulties to which the Da- guerreotype is liable. For taking landscapes it is not avail- able. Green and red colors impress no change upon it. The order of colors and light and shadow is not, therefore, strictly observed. There are many other photogenic processes now known : several have been invented by Mr. Talbot ; among them may be mentioned the calotype. Sir J. Herschel, also, has discovered very beautiful ones, and these possess the great advantage over Daguerre’s, that they yield pictures upon paper. In minuteness of effect they can not, however, be compared to the Daguerreotype. LECTURE XXIV. The Chemical Action op Light. — Fixed Lines. — Phos- phorescence. — Decomposition of Carbonic Acid. — Spec- tral Impressions. — Effects of Amplitude, Frequency, and Direction. — Cause of Chemical Decompositions by Light. The fixed lines discovered in the luminous spectrum, as represented in Fig. 63, also occur in the impressions left upon sensitive surfaces on which the spectrum is received. In this process, is iodine set free from the plate ? With what does the iodine unite under the influence of the mercurial vapor? Why is not the Daguerreotype applicable to landscapes ? Mention other processes of pho- togenic drawing. Can the fixed lines be depicted on sensitive surfaces ? CHEMICAL ACTION OF LIGHT. 103 as was discovered by M. Becquerel and myself about the same time (1842). In this instance, however, they are far more numerous, and occur in groups of many hundreds be- yond the visible limits of the violet ray. It has already been mentioned that light causes the phos- phorescence of most bodies. Thus, if oyster-shells be cal- cined with sulphur and exposed to the sun, they shine for a considerable time after in the dark. Nor does it require that the time of exposure should be protracted ; the flash of an electric spark is sufficient But, what is very remark- able in this case, the rays which excite the phosphorescence can not pass through a piece of colorless glass ; to them it is quite opaque. The experiments of Mr. Wilson show that a great number of bodies not commonly supposed to be phos- phorescent are so in reality ; that for a few moments after they have been exposed to the sun, they emit a phosphores- cent light. Thus a sheet of writing paper, on which a key had been laid, having been exposed for a few moments to the sun, on being suddenly removed to a dark room, emitted a pale light, the shadow of the key being perfectly visible. Even the hand, after being dipped in the sunshine, emitted subsequently light enough to'be visible in a dark place. The various principles of which we have been speaking exert no ordinary control over the phenomena of the natural world. Thus it is to the influence of light that the vegeta- ble world, owes its existence ; for plants can only obtain carbon from the air while the sun is shining on them, and it is of that carbon that their solid structures are chiefly formed. It has been a question to which ray this eflect is due ; but in 1843 I prov-^ that it is the yellow light which is involved. Dr. Priestley discovered that the leaves of plants will effect the decomposition of carbonic acid gas un- der water ; and on immersing tubes filled with water hold- ing this gas in solution, and containing a few green leaves, I found that at the blue extremity of the spectrum no effect whatever took place, while decomposition went on rapidly in the yellow ray. As connected with the minute changes of surface which are effected when the different radiant principles fall upon foodies, as in the instance of the Daguerreotype, we may here allude to the formation of spectral impressions, which, What is Mr. Wilson’s experiment ? What ray effects the decomposition of carbonic acid ? What are spectral impressions ? 104 CHEMICAL ACTION OP LIGHT. though invisible, may be brought out by proper processes. One of these I described several years ago. Take a piece of polished metal, glass, or japanned tin, the temperature of which is low, and, having laid upon it a wafer, coin, or any other such object, breathe upon the surface ; allow the breath entirely to disappear ; then toss the object off the surface and examine it minutely ; no trace of any thing is visible, yet a spectral impression exists on that surface, which may be evoked by breathing upon it. A form resembling the object at once appears, and, what is very remarkable, it may be called forth many times in succession, and even at the end of many months. Other instances of the kind have subse- quently been described by M. Moser. On the Chemical Action of Light. In considering the action of a ray of light upon a decom- posable body, there artf three different points to be discussed, so far as the ray itself is concerned : 1st. To what extent, and in what manner, is the result affected by the intensity of the ray ; i.e.^ by the amplitude of the vibrating excur- sions ? 2d. How is it affected by Xhe frequency of the pul- satory impressions ? 3d. How by the direction in which the vibrations are made, as involved in the idea of polariza- tion? 1st. By means of burning lenses I found that it is not the intensity of a beam which determines its decomposing pow- er, and that we can not produce greater effects by concen- trated light than we can by the application of the simple sunbeam continued for an equivalent period of time. Nor can such optical contrivances effect the decomposition of sub- stances on which a feeble beam has no action. 2d. Rays of the highest refrangibility, and, therefore, of the most frequent vibrations, commonly have the greatest activity. On the number of impulses a ray can communi- cate in a given period of time, depends its power of destroy- ing the constitution of any group of atoms. And the phe- nomena of interference arising from the superposition of wave motions occur exactly as might have been predicted. 3d. The direction of wave motion as involved in the idea of polarization, whether plane or circular, seems to exert no effect. How far does the chemical action of a ray depend on amplitude ? How far on w ave-length or frequency ? How far on the polarized condition ? ELECTRICAL MACHINES. 105 The immediate cause of the decomposition of substances by the agency of light is, that the rays forcing the material particles on which they fall into a state of rapid vibration, in many compound molecules the constituent atoms can no longer exist together as the same group, because of the im- possibility of their being animated by conspiring motions, and dislocation, rearrangement, or decomposition is the result. LECTURE XXV. Electricity. — First Observations in Electricity. — De- scription of Electrical Machines . — The Spark a Test of Electrical Excitement. — Repulsion of Electrified Bodies. — Simple Means of Excitement. — Conductoi'S and Non-conductors. — Insulation. — Electric Effects take place through Glass. — Medicated Tubes. It was observed, six hundred years before Christ, that a piece of amber, when rubbed, acquired the quality of attract- ing light bodies. This fact remained without value for more than two thousand years, a striking memorial of the barren nature of the philosophy of those times. Within the last two hundred years it has given birth to an entire group of sciences, and established the existence of an imponderable principle, which, from the Greek word TjXsKTpov, signifying amber, has taken the name Electricity. The catalogue of substances in Fig. 75 . which electric development can be produced was greatly increased by Gilbert, who showed that glass, resin, wax, and many other bodies are equally effective as amber. To his successors we owe the electrical machine, an instrument which en- ables us readily to demonstrate the properties of electricity. Electrical machines are of dif- ferent kinds. They may, however, be divided into plate and cylinder What is the immediate cause of decomposition by the agency of light? What was the first observation made in electricity? From what does the agent derive its name ? What varieties of electrical machines have we ? E 2 106 ELECTRICAL MACHINES. machines. These instruments are respectively represented^ inFig.75 3indFig.76. In each of them there are three distinct portions. First, a piece of glass, the shape of •which differs in different ca- ses; in Fig. 75 it is a cir- cular plate, in Fig. 7 6 a cyl- inder; and from these the instruments take their name. Second, the rubbers, made of silk or leather, stuffed with hair : the office of these is to press lightly on the glass as it turns round, and produce friction. Third, a brass body, of a cylindrical or rounded shape, but with points on that por- tion of it which looks toward the glass. It is supported on glass props, and is termed the prime conductor. Some mech- anism, such as a winch, is required to turn the glass on its axis ; and when it is desired to bring the machine into activity, all the parts of it having been made thoroughly clean and dry by rubbing with a piece of warm silk or flannel, a little Mo- saic gold or amalgam of zinc being spread on the rubber, as soon as the winch is turned the instrument becomes excited. One of the most striking manifestations of electrical de- velopment is the spark ; this, which must have been often seen when the back of the domestic cat is rubbed on a frosty night, was discovered in the case of glass or sulphur by Otto Guericke, and by him referred to its proper source, electric excitement. On presenting a brass ball or the fin- ger to the prime conductor of the machine, the spark passes, attended with a slight report. It may be very beautifully Fie- 77- shown by pasting small pieces of tin- foil round a glass tube in a spiral a ^ c form, as shown in Fig. 77, a h c, distances of the twentieth of an inch intervening between each piece, and the ends of the tube terminated by balls. On presenting one of these balls to the prime conductor, and holding the other in the hand, as the spark passes, it has to leap over each interstice between the spangles of tin- foil, and exhibits a beautiful spiral line of light. What are the three essential parts of these machines ? What is the rub- ber ? What is the prime conductor ? How is the machine excited ? How may the electric spark be exhibited ? ELECTRICAL LIGHT AND REPULSION. 107 Fig. 79 . By pasting the tin-foil on a pane of glass in such a way as to direct the spark properly, words may be written in electric light, as shown in Fig. 78. As the electric spark can hard- ly be confounded with any other physical phenomenon whatever, its presence is always in- dubitable evidence of electric excitement. Thus we can prove that electricity may be transferred to the human body from the machine, by placing a man on a stool supported by glass pillars. Fig. 79. If he touches the prime conductor j with one hand, sparks may be drawn from any part of his clothing or body. To Otto Guericke, who was also the inventor of the air pump, we owe another of the most im- portant discoveries in electricity : that bodies qq which have touched an excited substance are subsequently repelled by it ; thus, if we rub a glass tube. Fig. 80, a, until it becomes electri- fied, and then present it to a feather, by sus- pended by a silk thread to a stand, c, the feather is at first attracted, and then immediately re- pelled. On this principle, that under certain circum- ' stances repulsion takes place, are founded different methods for ascertaining the existence of electric excite- F>g. 8i. ment, when too feeble to cause a spark. Thus two light balls of cork, Fig. 81, a b, suspended by linen threads so as to hang side by side, as soon as they are electrified, repel each other. It does not, however, require an electrical machine to demonstrate the principles of this agent. A piece of stout brown paper three inches wide, and a foot long, if held before the fire until it is quite dry and smokes, and then drawn between the knee and the sleeve, becomes highly excited, especially if the person wears wool- en clothing. It will yield sparks more than an inch long. Let a, Fig. 82, be the termination of the prime conduct- Why may it be used as a test for electric excitement ? Can electricity be transferred from the machine to the body? What discovery did Otto Guericke make in electricity? How may this property of repulsion be il-* bistrated ? By what simple means may electrical experiments be made ? * n b 108 CONDUCTORS AND NON-CONDUCTORS. Fig. 82 . or, and in a hole in it place the long h ^ brass rod h, terminated by the brass ball c. If the finger is approached to the ball, sparks freely pass, showing that along brass elec- tricity is conducted ; but if a glass rod of the same diameter and length, and terminated by a brass ball, be employed, I not a solitary spark can be obtained, proving that glass is a non-conductor of electricity. |i^ The important fact that substances may be divided into two classes, conductors and non-conductors, was first acci- dentally discovered by Dr. Grey, who found that all metals and moist bodies are conductors, and that glass, resins, wax, sulphur, atmospheric air, are non-conductors. In the treat- ises on chemistry, tables may be found exhibiting the rela- tions of bodies in this respect. The conducting power of the same substance differs with circumstances ; thus ice and glass are non-conductors, but water and melted glass are conductors. "We see, from these facts, the explanation of the structure of the prime conductor ; the electricity derived from the glass by friction passes easily along the brass portion, but can not escape into the earth, owing to the glass supports which re- fuse it a passage. When a body is thus placed upon glass, it is said to be electrically insulated, and the process is called insulation. Although electricity can not pass through glass. Sir Isaac Newton found that this substance is no impediment to the exertion of its influences. Thus, in Fig. 83, if a be the brass ball of the prime conductor, any light objects, such as bits of paper or fragments of cork, placed on a metal stand, b, beneath, will be attracted ; and though a pane of glass, c, be placed between a and h, still the same phenom- enon takes place. . . Soon after electricity became a subject of popular atten- tion, it was currently believed that, if medicines of various kinds were sealed up in glass tubes, and the tubes electri- cally excited, their peculiar virtues would be exhaled in such How may it be proved that brass is a conductor and glass a non-conduct- or? Mention some of the leading substances belonging to each of these classes. Explain the structure of the prime conductor. Can electric influ- ences pass through glass ? What was' formed v meant bv medicated tubes TWO SPECIES OP ELECTRICITY. 109 a manneir as to impress the operator with their specific ptsr- gative, emetic, or other powers. Like many of the popular delusions of our times, this imposture was supported by the most cogent evidence, and maladies cured publicly all over Europe. Like them, these “ medicated tubes’" have served to prove the worthlessness of human testimony when de- rived from the prejudiced and ignorant. It should be remarked that, in their action upon materiel bodies, electricity and caloric differ greatly. The former has no kind of influence in determining magnitude, whereas ths size of any object depends upon its temperature. LECTURE XXVI. Theory of Electrical Induction. — Two Species of Elec- tricity. — Their Names. — General Law of Attraction and Repulsion. — Theory of IndiLction. — Permanent Excitement by Induction . — Takes place through Glass. — Illustrative Experiments. A VERY celebrated French electrician, Dufay, having caused a light, downy feather to be repelled by -an excited glass tube, intended to amuse himself by chasing it round the room with a piece of excited sealing-wax. To his sur- prise, instead of being repelled, the feather was at once at- tracted. On examining the cause of this more minutely, he arrived at the conclusion that there are two species of elec- tricity, the one originating when glass is excited, and* the other from resin or wax. To these he gave the names of vitreous and resinous electricity, thus pointing out their ori- gin ; they are also called, for reasons which will be given hereafter, positive and negative electricities. He found that these different electricities possess the same general physical qualities ; they are self-repulsive, but the one is attractive of the other. This is readily proved by hanging a feather by a linen thread to the prime conductor of the machine, and, when it is excited, bringing near to it Does electricity affect the magnitude of bodies ? How was it first dis covered that there are two species of electricity ? What names have been given to these electricities ? What are their physical qualities t How may this self-repulsion and mutual attraction be proved ? 110 ELECTRICAL INDUCTION, an excited glass tube. The feather is already vitreously electrified, and the tube, being in the same condition, at once repels it ; but a stick of excited sealing-wax being res- inously electrified, that is to say, in the opposite condition to the feather, at once attracts it. Two cork balls, as in Fig. 81, suspended by conducting threads, always repel one another when both are excited either vitreously or resinous- ly ; but if one be vitreous and the other resinous, they attract. These various results may all be grouped under the fol- lowing general law, which includes the explanation of a great many electrical phenomena. Bodies electrified dis- similarly attract, and bodies electrified similarly repel ; or, more briefly, like electricities repel, and unlike ones attract. There are many ways in which electrical excitement can be developed : in the common machine it is by friction ; in the tourmaline, a crystallized gem, by heat ; and in other cases, by chemical action and by conduction. Electrical dis- turbance also very often arises from induction. By the term electrical induction we mean that a body which is already excited tends to disturb the condition of others in its neighborhood, inducing in them an electric con- dition. Thus, let a. Fig. 84, be the terminal ball of the prime conductor, and a few inches ofl' p. let there be placed a secondary conductor, d c, of brass supported ^ on a glass stand, and at each ex- tremity, d and c, of the conduct- or, let there be arranged a pair of cork balls suspended by linen threads, as shown in the figure. As soon as the ball, a, is electrified by turning the machine, and without any spark passing from it to the secondary con- ductor, the balls will begin to diverge, showing that the condition of that conductor is disturbed by the neighborhood of the excited ball, a. It will farther be found, on presenting an excited piece of sealing wax to the pairs of cork balls, that one set is at- tracted, and the other repelled. They are, therefore, in op- What is the general law of electric attractions and repulsions ^ In what ways may electric excitements be developed ? What is the meaning of elec- tric induction ? Give an illustration. In a secondary conductor disturbed by an electrified body, what are the conditions of its ends ? * & Fig. 84. h ELECTRICAL INDUCTION. Ill Fig. 85 . posite electrical states. The disturbing ball is vitreously electrified, and that end of the secondary conductor nearest it is resinous, the farther end being vitreous. If the disturb- ing ball, a, be no^v removed, the electric disturbance ceases, and the corks no longer diverge. These phenomena of electric induction are not dependent on the shape of bodies^ Let there be two flat circular plates, a 5, Fig. 85, supported on glass stands, and set a few inches apart, look* ing face to face. Let one of them, be elec- trified positively by contact with the prime conductor, as indicated by the sign + ; it im- mediately induces a change in the opposite plate, the nearest face of which becomes neg- ative — , and the more distant, positive. It is evident that this disturbance is a consequence of the law, that “ like elec- tricities repel, and unlike ones attract.’* In the plate 5, both species of electricity exist, and a being made positive, even though at a distance, exerts its attractive and repulsive agen- cies on the electric fluid of 5, the negative electricity of which it attracts, and draws near to it ; the positive it re- pels and drives to the farthest side ; so that the disturbed condition of the body 5 is a result of the fact, that a being electrified positively, will repel positive electricity and at- tract negative. Now let the plate h be touched by the finger, or a chan- nel of communication opened with the earth ; the positive electricity of a still exerting its repulsive agency on that of 5, will drive it into the ground, and h will now become neg- ative all over. Let h be once more insulated by breaking its communi- cation with the ground, and let a be removed ; it will now be found that h is permanently electrified, and in the oppo- site condition to a. -pig. 86. By manipulating in this manner, we can there- fore effect a permanent disturbance in the condi- tion of an insulated body, by bringing an excited \ one in its neighborhood. In these changes, the intervention of a piece of glass makes no difference. Let a circular plate of glass, a, Fig. 86, be set so as to intervene be- What is the cause of this disturbance ? How may we by induction perma- nently electrify a body ? Can electrical induction take place through glass ? 112 MISCELLANEOUS EXPERIMENTS. Fig, 87. tween the metallic plates, a and 5, and still all the phe- nomena occur as before. Electric induction, therefore, can take place through glass. On the principles of induction, and of electric attraction and repulsion, many very interesting experiments may be explained. The following may serve as examples : To the ball of the prime conductor, Fig, S7, let there be suspended a circular plate of brass, «, six inches in diameter, horizontally, and beneath ) it another plate, b, supported on a conducting foot, parallel and at a distance of three or four inches. On the lower plate, b, place slips of paper or of other light substance, cut into the figure of men or ani- mals. On setting the machine in motion, so as to electrify the upper plate, the objects move up and down wdth a dancing motion ; and the cause is obvious : the plate a being positive, repels by induction the positive electricity of the figures through the conducting stand into the earth, and thus, they being rendered negative, are attracted by the upper plate ; on touching it, they become electrified posi- tively like it, and then are repelled, and fall down to dis- Fig 88 charge their electricity into the ground, and this motion is continually repeated. Upon a horizontal brass bar, a b, Fig. 88, three bells are suspended, the outer ones at a and b by chains, the middle one at c by a silk thread. Between the bells, the metallic clappers, cl e, are sus- pended by silk, and from the center bell the chain y* extends to the table. On hanging the arrange- ment by the hook at g to the prime conductor, the bells Fig. 89 . ring, the clappers moving from the outer to the Central bell and back, alternately striking them. On a pivot, a. Fig. 89, suspend a bell jar having four pieces of tin- foil pasted on its sides, bed; con- nect the jar, by means of the insu- lated wire 3 /, with the prime con- ductor, so that the pieces of tin-foil Describe the experiment of the dancing figures, and explain the principles involved in it. Describe the experiment of the bells, and the cause of their ringing. Explain the arrangement and cause of movement of the rotating jar. 113 DISTRIBUTION OF ELECTRICITY. may receive sparks. On the opposite side arrange a con- ductor, X, in connection with the ground by a chain. On putting the machine into activity, the jar will commence rotating on its pivot. Take a cake of sealing wax or gum lac, eight or ten inches in diameter, and receive on its surface a few sparks from the prime conductor by bringing it near the ball. Then blow upon its surface from a small pair of bellows a mix- ture of flour of sulphur and red lead, which have been in- timately ground together in a mortar. This mixture is of an orange color, but the moment it impinges on the cake it is, as it were, decomposed ; the yellow sulphur settling on one portion, and the red lead on another, giving rise to very curious and fantastical figures. LECTURE XXVII. Laws of the Distribution of Electricity, and the Gen- eral Theories. — Distribution of Electricity. — On a Sphere. — Ellipsoid. — Action of Points. — Franklin's Discovery of the Identity of Electricity and Lightning. — Tlbe Leyden Jar . — The Discharging Rod . — The Electric Battery. When electricity is communicated to a conducting body, it does not distribute itself uniformly through the whole mass, but exclusively upon the surface ; thus, if to the spherical ball a, Fig. 90, supported on an in- Fig.^o. sulating foot, b, there be adjusted two hemispherical caps, c c, also on insu- lating handles, it may be proved that any electricity communicated to a dis- tributes itself entirely on its surface ; for if we place upon a the caps c c, and then remove them, it will be found that every trace of electricity has disappeared from a, and has accumulated on the caps, which, while they were upon the ball, formed its superficies. How may p©wder of sulphur and red lead mixed together be separated ? Does electricity distribute itself on the surface or m the interior of bodies t How may its superficial distribution be pioved ? 114 DISTRIBUTION OF ELECTRICITY. Fig. 92. Again, if we take a large brass ball, a, Fig. 91, supported on an insulating stand, and having on its upper portion an aperture, through which we may have access to its interior, it will be found, on ex- amination, that the most delicate electrometers can discover no electricity within the ball, the whole of it being on the external superficies. In the case of a spherical body, not only is the distribution entirely superficial, but it is also uni- form ; each portion of the sphere is electrified alike. But where, instead of a spherical, we have an ellipsoidal body, it is different ; thus, if we examine the condition of such a conductor, Fig. 92, the quantity of elec- tricity in its middle portion, as at a, will be the smallest, and it increases as we advance toward the ends, b and c ; and in different ellipsoids, as the length be- comes greater, so the amount of elec- tricity found on the extremities is great- er. When, therefore, a conductor of an oblong spheroidal shape is used, the in- tensity of electricity at the extremities of the two axes, a d and b c, Fig. 92, is exactly in the proportion of the length of those axes themselves ; and should the disproportion in length and breadth of the conducting body be very great, as in the case of a long wire or other pointed body, a very great concentration will take place upon the points. On this principle we explain the efiect of pointed bodies on con- ductors : if the prime conductor of the machine have a nee- dle or pin fixed upon it, the electricity escapes away into the air, visibly in a dark room ; and in the same way, if pointed bodies surround the electrical machine, it can not be highly excited, as they rapidly take the charge from its conductor. At a very early period electricians had observed the close similarity between the phenomena of the electric spark and those of lightning, but in the year 1752 Dr. Franklin proved that they were identical. He was waiting for the erection of the spire of a church in Philadelphia, on the extremity of which he intended to raise a pointed metal rod, with a In the interior of an electrified hollow ball, does any electricity exist ? On a spherical body, is the distribution uniform ? How is it on an ellipsoid? When the disproportion of the axes of the ellipsoid is great, what is the dis- tribution ? How may we explain the effect of pointed bodies ? THEORIES OF ELECTRICITY. 115 view of withdrawing the electricity from the clouds, when the accidental sight of a boy’s kite suggest d to him that ready means of obtaining access to the more elevated re- gions of the air. Accordingly, having stretched a silk hand- kerchief over a light wooden cross, and arranged it as a kite, he attached to it a hempen string terminating in a silk cord, and, taking advantage of a thunder storm, raised it in the air ; for a time no result was obtained, but the string be- coming wet by the rain, and thereby rendered a better con- ductor, he perceived the filaments which hung upon it re- pelling one another, and on presenting his knuckle to a key which had been tied to the end of the hempen string, re- ceived an electric spark. The identity of lightning and electricity was proved. Franklin soon made a useful application of his discovery ; he proposed to protect buildings from the effects of lightning by furnishing them with a metallic rod, pointed at its upper extremity, and projecting some feet above the highest part of the building, and continuously extending downward until it was deeply buried in the ground. This contrivance, the lightning rod, is now, as is well known, extensively applied. There are two theories respecting the nature of electric- ity : 1st, Franklin’s theory, which assumes that there is but one fluid ; 2d, the theory of two fluids, called also Dufay’s theory. Franklin’s theory is, that there exists throughout all space a subtle and exceedingly elastic fluid, called the electric fluid, the peculiarity of which is, that it is repulsive of its own particles, but attractive of the particles of other mat- ter ; that there is a specific quantity of this fluid which bodies arc disposed to assume when in a natural condition or state of equilibrium ; and that, if we communicate to them more than their natural quantity, they become posi- tively electrified ; or, if we take from a portion of that which is natural to them, they become negatively electrified. Dufay’s theory is, that there exists throughout all space a universal medium, called the electric fluid, of which the immediate properties are unknown, but which is composed of two species or varieties of electricity, the vitreous and Under what circumstances was the discovery of the identity of lightning and electricity made? What is the lightning rod ? What theories of elec- tricity have been introduced ? What is Franklin’s theory ? What is the theory of Dufay ? 116 THE LEYDEN JAR. resinous, called also the positive and negative ; that, as re-" spects itself, each of these electricities is repulsive, hut at- tractive of the other kind ; and that, when they coexist in equal quantities in a body, it is in a neutral state or condi- tion of equilibrium, but if the positive or negative electrici- ties are in excess, it is accordingly positively or negatively electrified. In some respects the theory of two electricities ha^ ad- vantages over that of one ; by it several phenomena can be explained which are difficult of explanation by the other. Among such may be mentioned the repulsion of negatively electrified bodies, and the distribution of negative electricity on the surface of conductors, which is the same as that of positive. On the principles of either of these theories, we can see how it is that we can never produce one kind of electricity without the other simultaneously appearing. In the com- mon electrical machine, if the revolving glass is positively electrified, the rubbers which produce the friction are nega- tive ; in the tourmaline, if one end of the crystal, when warmed, becomes positive, the other end is negative. The two varieties must be always co-ordinately generated. “ In 1745 the Leyden jar was discovered. This consists of Fig, 93. a glass jar, Fig. 93, coated on its inside with C a piece of tin-foil within an inch or two of its upper edge, and also on its outside to the same point ; through the cork which closes the mouth of the jar, a brass rod, terminated by a ball, BB||| I passes ; the rod reaches down to the inside BBII i coating and touches it. On holding this instru- -JHBII IL exterior coating, and presenting H|n| its ball to the prime conductor, a torrent of sparks passes into the jar : and when it is fully charged, if, still retaining one hand in contact with the out- side, we touch the ball, a bright spark passes, with a loud snapping noise, and the operator receives through his arms and breast what is called the electric shock. If we take the discharging rod, Fig. 94, consisting of two brass arms, a a, terminated by balls working on a joint, b, In what points does the latter appear to be more correct than the former ? Why are twth electricities always produced together ? Describe the struc- ture of the Leyden jar. How may it be used? Describe the discharging rod. ELECTRIC BATTERY. 117 and supported by an insulating handle, c, by bringing one of its balls in contact with the outside coating of a Ley- den jar, and its other ball with the ball of the jar, ^ ^ the discharge will take place as before, but the op- erator, protected by the glass handle, receives no V / shock. If between the outside coating of a jar and one of ^ the balls of the discharging rod a piece of card-board ft is made to intervene, and the spark passed, the card TTc will be found to be perforated, a burr being raised on 11 both sides of it, as though two threads had been drawn I j through the hole in opposite directions at the same ^ time ; and from this an argument in favor of the theory of two fluids has been drawn. When a great number of jars are connected together, so that all their inside coatings unite, and all their outside coatings are also in contact, they constitute what is termed an electric battery, as seen in Fig. 95. By this instrument many of the more violent effects of electricity may be illustrated, such as the splitting of pieces of wood, and the ignition and dispersion of metallic wires. LECTURE XXVIII. ELECTFaCAL INSTRUMENTS AND FaFvADAY’s ThEORY OF Electric Polarization. — Theory of the Leyden Jar. — Quadrant., Gold-leaf and Torsion Flectrometers . — Theory of Electric Folarization. — Specific Inductive Capacity. The office which is discharged by the metallic coatings of a Leyden jar is illustrated by the apparatus, Fig. 96. It consists of a conical glass jar, to the interior and exterior How is it used ? What is the effect when the discharge is passed through a piece of card-board? Describe the electric battery. ^What is the office of the coatings of the Leydeii jar 1 118 CONDENSING ACTION* of which movable coatings of thick tin plate are adapted, the interior one having a rod and ball projecting from it. This may be charged like any other Leyden vial, but on taking off its outside coating and removing its interior, they may be handled and brought in contact with each other, and no spark passes ; but on restoring them to their for- mer position, and applying the discharging rod, the jar is discharged. They therefore only serve to make a complete conducting communication be- tween all parts on the interior and all on the exterior of the jar. The condensing action of the Leyden vial, which enables it to hold so large a quantity of electricity, is due to induc- tion. When the inner coating is brought in contact with the prime conductor, it participates in its electrical condition. We may therefore suppose it to be positively electrified. The positive electricity of the interior, decomposing the elec- tric fluid of the outside coating, repels its positive electricity into the earth ; for to charge a Leyden vial the outside coating is placed in communication with the ground. It therefore appears that the inner coating is positive, the outer negative, and the whole jar, viewed together, is in the neu- tral condition. The interior coating continues, under these circumstances, to receive a farther charge from the prime conductor ; by induction through the glass, this again repels more of the same kind, the positive, into the ground, and the negative accumulates as before. In this manner an indef- inite quantity might be accumulated, were it not for the fact that, owing to the distance which intervenes between the two coatings, by reason of the thickness of the glass, the quantity of positive electricity in the interior is never pre- cisely neutralized by the quantity of negative on the exte- rior, for all inductive actions enfeeble as the distance in- creases. The action of the Leyden vial may be illustrated by the following experiments : within an inch of the ball, a, of the prime conductor, Fig. 97, bring a secondary conductor, 5, supported on an insulating stem, c, and on putting the How may this be proved ? To what cause is the condensing action of the Leyden jar due ? What is the action of the positive electricity depos- ited on the inner coating, on the electric fluid of the outer ? Why must the outer coating be in connection with the ground ^ Why is the charge of the jar limited ? Fig. 96. ACTION OF THE LEYDEN JAR. 119 electrical machine in activity, two or three sparks will pass from a to 6 , ^ ^ but after that no more. The cause ^ ^ of the refusal, on the part of the sec- ondary conductor, to receive any far- ther charge, is obviously due to the fact that the electricity which is al- ready communicated to it repels that upon the ball, a, and prevents the passage of any more. If now we take a Leyden jar h. Fig. 98, and, having in- sulated it on a stand, bring it within a short Fig. 98. distance of the ball, of the prime con- a ductor, it in the same manner will only re- ceive a few sparks. But if we place a conductor, c, which is connected with the ground, near to the outside coating, it will be found that for every spark that passes between a and b, one passes between the outside coating and c, and the sparks follow each other in rapid succession, until the jar becomes fully charged. From this, therefore, we gather, that while positive electricity is passing into the interior of the jar, it is escaping from the exterior, and that the reason the jar condenses is because its sides are in opposite condi- tions, the positive electricity of the interior being nearly neutralized by the negative electricity of the exterior. Electrometers are instruments for measuring the 99 intensity of electric excitement. The cork balls, which were represented in Fig. 81, are one of the most simple of these contrivances. The distance to which they will diverge is a rough measure of the intensity of the electric force. The quadrant elec- trometer depends essentially on the same principles. It consists of an upright stem of wood. Fig. 99, to which is affixed a semicircular piece of ivory, from the centre of which there hangs a light cork ball playing upon a pivot. When this instrument is placed on the prime conductor or other electrified body, the stem participates in the electricity, and, repelling the cork What is the reason that a secondary insulated conductor refuses to re- ceive more than two or three sparks? When the Leyden jar is insulated, can it be charged ? On bringing a conductor in connection with the ground, near the outer coating, what is the result ? Describe the cork ball elec- trv)meter. Describe the quadrant electrometer. 120 ELECTROMETERS. ball which hangs in contact with it, the amount of repulsion may be read off on the graduated semicircle ; but it is ob- vious that the number of degrees is not expressive of the true electrical intensity, and that no force, no matter what its intensity may be, can ever repel the ball beyond ninety degrees. The gold-leaf eiectrometer. Fig. 100, ^ consists of a glass cylinder, a, in which two gold leaves are suspended from a conduct- ing rod terminated by a ball or plate, h. On the glass opposite the leaves pieces of tin-foil are pasted, so that when the leaves diverge fully they may discharge their elec- ' tricity into the ground. This is a very del- rr. . — icate instrument for discovering the pres- ence of electricity, but the torsion electrometer of Coulomb is to be preferred when it is required to have exact measures of the quantity. \ ^ Coulomb’s electrometer consists of a glass cylinder, a, Fig. 101, upon the top of which there is fixed a tube, d, in the axis of which hangs a glass thread, h a, to the lower end of which a small bar of gum lac, c, with a gilt pith ball at each extremity, is fasten- ed. Through an aperture in the top of the glass cylinder, another gum lac rod, d, with gilt balls, may be introduced. This goes under the name of the carrier rod. If now the lower ball of the carrier rod be charged with the electricity to be meas- ured, and introduced into the interior of the cylinder, as seen in the figure, it will repel the movable ball. By taking hold of the button, h, to which the upper end of the glass thread, a, is attached, we may, by twisting the glass thread forcibly, bring the carrier ball and the movable ballj in contact. The number of degrees through which the thread requires to be twisted represents the amount of elec- tricity. To the button, h, an index and scale are attached, not shown in the figure. By this we can tell the numbei’ of degrees of twist or torsion which have been given to the Why does the quadrant electrometer give inaccurate indications ? De-J scribe the gold leaf electrometer. Describe Coulomb’s torsion electrometer! FARADAY S THEORY OF INDUCTION. 121 thread. These angles of torsion are exactly proportional to the quantities of electricity. One of the most delicate electroscopes is that of Bohnen, berger. It consists of a small Zamboni’s pile, a b, Fig. 102, supported horizontally beneath a glass shade, and from its extremi- ties, a b, curved wires pass, which terminate in parallel plates, 2 ^ One of these is therefore the positive, and the other the neg- ative pole of the pile. Between them there hangs a gold leaf, d g, which is in metallic communication with the plate 0 n by means of the rod c. If the leaf hangs equally be- tween the two plates, it is equally attracted by each, and remains motionless ; but, on communicating the lightest trace of electricity to the plate o 7i, the gold leaf instantly moves toward the plate which has the opposite polarity. Many of the fundamental phenomena oT electricity have been explained by Dr. Faraday upon the hypothesis that in- duction is an action of polarization, taking place in the con- tiguous molecules of non-conducting media, and propagated in curved lines. Whatever may be the form or constitution of bodies, an electric charge can not be given to them without at the same time giving a charge of the opposite kind, but of the same amount, to them or other bodies in their vicinity. This charge is not confined upon their surfaces by the press- ure of the atmosphere, but through the polarization of the aerial or solid particles of the surrounding dielectrics, pro- ducing in them a charge of the same amount, but of an op- posite kind. Thus, if a positively electrified ball be placed ill the centre of a hollow metallic sphere, the intervening space being filled with atmospheric air, the charge is not retained upon the ball by the pressure of the air, but be- cause each aerial particle assumes by induction a polarity of the opposite kind on the side nearest to the ball, and of the same kind on the side farthest off. This state of force is therefore communicated to the interior of the hollow sphere, which is electrified to the same amount, but of an opposite kind to the ball. Describe Bohnenberger’s electrometer. What is the basis of Faraday’s theory of induction? On this theory, are charges confined by pressure of the air? Describe ihe action of an electrified ball in the interior of a srdicrc. F Fig. 102. 122 INDUCTIVE CAPACITIES. That this polarization of the particles takes place, is shown by the position which small silk fibres or spangles of gold assume when placed in oil of turpentine through which in- duction is established. Each particle disturbs not merely that which is before it or behind it, but it is in an active re- lation with all surrounding it, and hence the polarity can be propagated in curved lines, and induction take place round corners and behind obstacles. On these principles, we can easily account for the distri- bution of electricity on spherical or ellipsoidal conductors, the repulsion of bodies similarly electrified, the condensing action of the Leyden vial, and many other similar phe- nomena. By a variety of experiments. Dr. Faraday has proved that inductile action takes place in curved lines, the directions of which can be varied by the approach of bodies. He has also shown that the particles of solids, as gum lac, glass, &c., assume this character of polarity. Non-conducting bodies, through which the action of induction takes place, are die- lectrics, and each of them has a specific induct- ive capacity. Thus, if three metallic plates, ah c, Fig. 103, be insulated parallel to each other, atmospheric air intervening between a and h, and a plate of gum lac between b and c, the inductive action of the gum lac will be found to exceed that of the air. The ^ following table gives some of these results : ^ Inductive capacity of air I’OO “ “ glass . . . : T76 “ “ lac 200 “ sulphur 2-24 All the gases have the same inductive capacity, whatever their density, elasticity, temperature, or hygro metric con- dition may be. The electrophorus is an instrument which depends for its action on induction, and is of frequent use in chemistry. It consists of a cake of gum lac or sealing wax, b, Fig. 104, on which is placed a flat metallic plate, a, with an insulating Does induction take place in straight or curved lines ? Can the particles of solid bodies be polarized ? What are dielectrics ? What is meant by the specific inductive capacity of dielectrics ? Of air, glass, and sulphur, what are the inductive capacities ? What is the case with gaseous bodies ? Despribe the electrophonis. THE ELECTROPHORUS. 12S^ handle, c. On exciting h with a piece of warm flannel, i' becomes negatively electric, and a being placed on it, and the finger brought near, a negative spark, driven from a by the re- pulsive influence of 5, is received. On lift- ing a by its insulating handle, a positive spark is obtained ; on putting it down on h, a negative one. And in this manner we may obtain an unlimited number of sparks ; positive ones when a is lifted, and negative ones when it is down. A little reflection will show that none of this electricity comes from the excited cake h, but is merely the effect of its inductive influence on the electric condition of the metallic plate a. The electrophorus may be used when the weather is too damp for the common machine to - work. LECTURE XXIX. Voltaic Electricity. — Of Electricity in Motion. — Sul’ zer's Experiment. — Galvani's Discovery . — Volta's The’ ory. — Water is a compound Body. — Description of a simple Voltaic Circle and its Properties. — Direction of the Current. — Different Kinds of Combinations . — Use of Sulphuric Acid. — Origin of the Electricity. During the last century, a German author of the name of Sulzer observed that, when two pieces of metal of difier- ent kinds, as silver and zinc, are placed one above and the other beneath the tongue, as often as their projecting ends are brought in contact, a remarkable metallic taste is per- ceived. To explain this result, he supposed that some kind of vibratory movement was excited in the nerves of the tongue. It is the first recorded phenomenon attributable to Voltaic electricity. In the year 1790, Galvani, an Italian anatomist, observed the contractions which ensue when a metallic communica- tion is made between the nerves and muscles of a dead frog ; he found that, if a single metal is employed as the line of What fact was first described in Voltaic electricity ? What was the fact discovered by Galvani ? 124 GALVANIC EXPERIMENTS. communication, contractions of the muscle take place when- Fig, 105 . ever the metal reaches from the nerve to the muscle ; hut that if two pieces of different kinds are used, the contrac- tions are much more energetic. Thus, if we take the skinned hind legs of a frog, Fig. 105, hanging together by a piece of the spine, around which tin- foil has been twisted, every time that we simultaneously touch the tin-foil and the mus- cle with a bent copper wire, or with a copper and zinc wire, C Z, conjointly, a convulsive contraction takes place. To explain this effect, Galvani supposed that the muscu- lar system of animals is constantly in a positively electrical state, while the nervous system is negative. In the same manner, therefore, that a discharge takes place in the case of a Leyden vial, when a line of communication is opened between the two coatings, the muscular contractions in this case are to be accounted for. For some time these phe- nomena went under the name of animal electricity ; they subsequently have received the designations of Galvanism and Voltaic electricity. But Volta, another Italian philosopher, was led to suppose that the cause of this remarkable result is not due to any peculiarity of the animal system, but to the contact of the pieces of metal employed. This led to the invention of the Voltaic pile, an instrument which has achieved a complete revolution in chemistry. It is interesting to remark what great results may, in the hands of a true philosopher, spring from the most insignifi- cant observations. The convulsive spasms of a frog’s leg have ended in showing that the entire crust of the earth is made up of metallic oxides, have revealed the mystery why the magnetic needle points to the north, and revolutionized the science of chemistry. What we have already said in the foregoing Lectures re- specting electricity refers chiefly to that agent in a motion- less or stagnant state, as the mode of its distribution on con- In what manner did he explain it? Under what names did these phe- nomena successively pass ? What was Volta’s supposition ? What is the difference between common and Voltaic electricity ? THE SIMPLE CIRCLE. 125 ductors, the action of the Leyden vial, &c. The phenome- na of Voltaic electricity are those which arise from electric- ity in a state of motion. From the great advances which these sciences have re- cently made, we are able to present the various topics in- volved in a much clearer way than by merely tracing them in a historical sketch. I shall not, therefore, pursue the order in which these facts were successively discovered, but present them in what now appears the simplest manner. It is to be admitted, though of that abundant proof will soon be given, that water is not a simple, but a compound body ; that it consists of two elements, oxygen and hydrogen gases. It is also to be understood that metallic zinc may be amalgamated or united with quicksilver, by putting it in contact with that fluid metal, under the surface of dilute sulphuric acid. Strips of zinc thus amalgamated exhibit a pure metallic brilliancy. If now we take a strip of amalgamated zinc, an inch wide and three or four inches long, and a piece of clean copper of similar size, 2: and c. Fig. 106, and placing them side by side in a glass, containing water slightly acidulated with sulphuric acid, we have one of the forms of a simple Voltaic circle. In this, it is to be observed, that so long as the me- tallic plates remain without touching each other, no remarkable phenomenon appears ; but if we take a metallic rod, d, and let it connect the top of the zinc and copper together, a series of new facts arises. First, from the surface of the copper, bubbles of gas are evolved ; they are minute, but so numerous as to make the water turbid ; if collected, they are found to be hydrogen gas. Secondly, the plate of zinc rapidly wastes away, as is easi- ly proved by weighing it from time to time ; and on exam- ining the liquid in the cup, we discover the cause of this waste, for that liquid contains oxide of zinc ; coupling this fact with the former, we infer that, so long as the metallic rod, d, is in its place, water is decomposed, its oxygen unit- ing with the zinc, its hydrogen escaping from the copper. On removing the rod, d, all these phenomena at once cease. Is water a simple or a compound body ? What is meant by amalgamated zinc? Describe a simple Voltaic circle. As long as the plates are not in contact, does any phenomenon take place ? On communicating by a metal- lic rod, what gas is evolved from the copper? What happens to the zinc? Why do wc infer that water is decomnosed ? 126 PHENOMENA OF A SIMPLE CIRCLE. Thirdiji, if, instead of a metallic rod, c?, a rod of glass, or other non.'-v^onductor of electricity, be employed, no decom- position tifcii.es place. This, therefore, indicates that the agent which is in operation is electricity. Fourthly, if for the line of communication, d, a piece of metal he employed, and we cautiously lift it from the zinc or copper plate, the moment the contact is broken, in a dark room, we see a minute electric spark. It has been already observed that the electric spark can not he confounded with any other natural phenomenon. Fifthly, if the line of communication he a very slender platinum wire, as long as it remains in its position, its tem- perature rises so high tnat it becomes red hot, and may he kept so for hours together. Now, recollecting that the igni- tion and fusion of metals take place when they are made to intervene between the coatings of a Leyden vial, and con- sidering all the facts which have just been set forth, we see that the following conclusion may be drawn : that in an active simple Voltaic circle water is decomposed, its oxygen going to the zinc and its hydrogen to the copper, and that a continuous current of electricity accompanies this decom- position, running from one metal to the other, through the connecting rod. The direction of this current may he determined by sev- eral processes ; it is as follows : the electricity, leaving the surface of the zinc, passes thrtugh the liquid to the copper, then moves through the connecting wire back again to the zinc, performing a complete circuit ; hence the term Voltaic circle. Simple Voltaic circles are of several kinds ; that which we have been considering consists of two different metals with one intervening liquid, but similar results can be ob- tained with one piece of metal and two different liquids. In the foregoing experiment we have used dilute sul- phuric acid : this acid discharges a subsidiary duty. Zinc, when it oxidizes, is covered with a coating impermeable to water and air ; it is this grayish oxide which protects the common sheet zinc of commerce from farther change. "When, therefore, a Voltaic pair gives rise to a current by If a glass rod is used instead of a metallic one, what is the result ? How can a spark be made visible ? Can a platinum wire be ignited ? From these facts, what conclusions may be drawn ? What is the course of the current ? What other kinds of Voltaic circles are there ? ELECTROMOTIVE SOURCE. 127 the oxydation of its zinc, that current would speedily stop were not the oxide removed as fast as it forms ; this is done by the sulphuric acid, which forms with it a sulphate of zinc, a substance very soluble in water, and the metal thus continually presents a clear surface to the water. As to the immediate cause which gives rise to the Voltaic current, there has been a difference of opinion among chem- ical authors. Volta believed that the mere contact of the metals was the electromotive source, and endeavored to prove, by direct experiment, that if a piece of copper and zinc are brought in contact and then separated, they become excited, the one positively and the other negatively ; upon these principles, he was led to the discovery of the Voltaic battery. But many facts have now indisputably shown that the origin of the current is to be sought in the chemical changes going on ; and in the instance we have had under consideration, it is due to the decomposition of water. That the electromotive action does not depend on the contact of the metals, seems to be proved by the fact that, by chang- ing the nature of the liquid intervening between them, we can change the current both in direction and force. LECTURE XXX. Effects of Voltaic Electricity. — Invention of the Vol- taic Pile. — CruickshanP s Trough. — Hare's Battery. — Smee's Simple and Compoujid Battery. — Grove's Battery . — Voltaic Effects, the Spark, Deflagration of Metals. — Ignition of Wires. — Arc of Flame. — Decom- position of Water. — Nature of the Gases evolved. It has been already observed that, in the discussions which arose respecting animal electricity, Volta attributed the action entirely to the metals employed, and, reasoning on this principle, he concluded that the effect ought to in- crease, if, instead of using a single pair of metals, a great number of alternations were employed. Accordingly, on What is the use of sulphuric acid in these combinations ? What was Volta’s opinion as to the electromotive source ? What is the view now taken ? What arguments may be adduced for its correctness ? How was Volta led to the invention of the pile ? 128 THE VOLTAIC TILE. taking thirty or forty silver coins and discs of zinc, and pieces of cloth moistened with acidulated water, of the same size, and arranging them in a pile or column, carefully observing Fig. 107. to place them in the same order, silver, cloth, zinc — silver, cloth, zinc, &c., he found his ex- pectation verified. On touching, with moist- ened hands, the end of the pile, a shock was at once received, and on making them communi- cate by a piece of wire, an electric spark passed. This instrument. Fig. 107, is the Voltaic pile. From the important uses to which the pile was soon de- voted, it became necessary to have it under a more conve- nient form. There are several inconveniences attending the original construction : it is liable to overset, is trouble- some to put in action, and requires to be taken to pieces and carefully cleaned every time it is used ; its maximum effect lasts but a short time, owing to the weight of the su- perincumbent column pressing out the moisture from the lower pieces of cloth ; and as soon as they become dry, all action ceases. These difficulties were avoided, to a great extent, in the trough battery, which soon replaced the former instrument. Fig. 108. It consists of a box or trough. Fig. 108, three or four inches square at the ends, and a foot or more long ; grooves are made in the sides and bottom of this box, and into them pieces of zinc and copper, soldered face to face, are fastened, water tight, by cement. These grooves are about half an inch apart, and into their inter- stices acidulated water is poured, care being taken that the metals are arranged in the same direction, so that if the se- ries begins with a copper plate, it ends with a zinc. The apparatus is obviously equivalent to Volta’s pile laid on its side, and the facility for charging it, and removing the acid when the experiments are over, is very great. From the extremities two flexible copper wires pass : they are called the polar wires, or electrodes of the battery. Describe the Voltaic pile. What are its effects ? What inconveniences are there in the original form ? Describe the trough battery. Describe some of the improvements in the battery. hare’s, danieli/s, and simee’s batteries. 129 Fig. 109. Some very convenient forms of Voltaic battery have been invented by Dr. Hare. In one of these, the liquid is poured off and on the plates by a quarter revolution of a handle ; in others, the trough is made movable, so that it lifts up when all the arrangements are ready, and the plates are immersed. In almost all the recently improved forms of Voltaic bat- tery, the zinc is amalgamated. This prevents what is term- ed local action — a waste in which much metal is consumed without adding to the power of the current, and Avhich like- wise deteriorates the acid liquid by the accumulation of sul- phate of zinc. When amalgamated, all the zinc consumed aids in the current. When it is required to have a current, the intensity of which remains constant for a length of time, Daniell’s battery is to be preferred. It consists of a copper cylinder, C, Fig. 109, in which a solution of sulphate of copper is poured ; within this is a second cylinder, P, of porous earthen- ware, filled with dilute sulphuric acid, A, into which an amalgamated zinc rod, Z, dips. From the copper and zinc, rods project, terminated by binding screws, with which the polar wires may be connected. Smee’s battery is also a very valuable com- bination : it consists of a plate of platinized sil- ver, or platinized platinum, S, Fig. 110, on each side of which are placed parallel plates of amalgamated zinc, Z ; these plates are held tightly against a piece Fig. no. of wood, 10 , by means of a clamp, b, to which, and also to the silver plate, bind- ing screws, for the purpose of fastening polar wires, are affixed. The whole is = suspended, by means of a cross-piece of wood, in ajar containing dilute sulphuric acid. Smee’s compound battery, represented !i||i in Fig. Ill, is nothing more than a series || of the foregoing simple circles. The figure shows one containing six cells; the posi- tion of the platinized silver and zinc plates Wliaf arc the forms introduced by Hare, Daniell, Since, and Gk sjiectively ? F 2 130 grove’s battery. of one of the pairs is seen at S and Z. It is to be charged with dilute sulphuric acid. Fig . 111. Probably the most powerful of all Voltaic combinations is the instrument invented by Mr. Grove. It consists of two Fig . 112. metals and two liquids, amalgamated zinc and platina, dilute sulphuric acid and strong nitric acid. Ajar, P, Fig. 112, three quarters of an inch in diameter, and made of porous or unglazed earthen- ware, is to be filled with strong nitric acid, N, and in it a slip of platina is placed ; this porous earthen- ware cup is then set in a glass cup, A, nearly three inches in diameter; in this is placed a plate of zinc, Z, one eighth of an inch thick, and of such a size, as respects its other dimensions, that it will readily pass between the porous cup, P, and the glass. In the glass, A is placed dilute sulphjuric acid. In this manner several cups are to be provided, the ar- rangement being, zinc in contact with dilute sulphuric acid, and platina in contact with strong nitric acid, with a porous cup intervening between. The workman also previously connects each zinc cylinder with the slip of platina, which is in the next cup, by soldering between them a strip of copper. Grove’s battery owes its force to the decomposition of water by zinc. But the hydrogen is not evolved from the surface of the platina, as it would be in a single circle ; it is here taken up by the nitric acid, which undergoes rapid deoxidation, and therefore, during the use of this battery, volumes of deutoxide of nitrogen are evolved. A battery of fifty cups gives rise to very striking effects ; but five or ten are quite sufficient to repeat all the following experiments. What are the chemical effects taking place in Grove’s battery ? DEFLAGRATION OF METALS. 131 Fig. 113. On separating the polar wires of such a battery from each other, a brilliant spark passes, and, if the separation be grad- ual, a flame constantly proceeds from one to the other ; the light of which, when the wires are of copper, is of a beauti- ful green color. If, on the surface of some quicksilver contained in a glass. Fig. 113, we lower a thin piece of steel, or iron wire, connected with one of the poles of the battery, the mercury being kept in contact with the other, the steel . takes fire and deflagrates beautifully, emit- ting bright sparks, and the mercury is rap- idly volatilized. When thin metal leaves are made to in- tervene between the polar wires, they are at once dissipated, the flames they emit being of diflerent colors in the case of different metals. If a piece of platinum wire is made the channel of com- munication from one pole to the other, if it does not fuse at once, it becomes incandescent, and remains so as long as the instrument is in activity. When the polar wires are terminated by pieces of well- burned charcoal, or that variety of carbon which is formed in the interior of gas retorts, the light which passes between them when they are removed from contact is one of the most brilliant that can be obtained by any artificial means. With powerful batteries, the pieces of charcoal may be sep- arated several inches apart without the light ceasing, and then it moves from one pole to the other in an arched form. Fig. 114, the convexity of the arc being upward. This form is due to the current of hot air which rises from the ignited space between the poles, and the light may be blown out by the mouth, just in the same manner that we blow out a candle. But, in a scientific point of view, by far the most interest- ing experiment to be made with the Yoltaic battery is the decomposition of water. Through the bottom of a glass vase or dish, at the point a b, Fig. 115, two platinum wires On separating the polar wires of a battery, what phenomenon arises ? How may iron wire be deflagrated? Wliat phenomenon is seen during the deflagration of metallic leaves ? When a thin platinum wire communicates between the poles, what is the result ? How is the arc of light formed, and what are its properties ? Describe the process for the decomposition o( water. 132 DECOMPOSITION OF WATER. Fiff. 115. are introduced, water-tight ; they pass into the vase, as a c, b parallel to each other, hut not touching. Over each of these wires a tube is to be inverted ; the tube e over c, andjT over the vase and the tubes being previously filled with water acidulated slightly, to improve its conducting power. Now let the wire a c be connected with the positive pole of the Voltaic battery, and h d with the negative ; bubbles of gas in a torrent arise from their extremities, and pass up- ward in the tubes, displacing the water. The quantity of gas thus collecting in the two tubes is unequal, and when- ever we stop the decomposition there will be found in f double the quantity which is in e. When a sufficient amount is collected, let the tube e, containing the smaller portion of gas, be cautiously removed, preventing any atmospheric air from getting into its interior, by closing it with the finger, and then, turning the tube upside down, let a stick of wood, with a spark of fire on its extremity, be immersed in the gas. In a moment the wood bursts into a flame, proving that this is oxygen gas. Then take the other tube, and allow to pass into it a quantity of atmospheric air equal to the volume of gas it already holds ; remove the finger and apply a light, and there is an explosion. But this is the property of hy- drogen gas. We therefore conclude that in this experiment water has been decomposed and resolved into its constituent ingredients, oxygen and hydrogen ; and, farther, that in Fig. 116 . water there is, by volume, twice as much H hydrogen as there is oxygen gas. The sep- aration of the two is perfect, so much so that the decomposition may be conducted in different vessels. Thus, let N and P be tubes, through the closed upper ends of v^hich platinum wires pass ; invert them in glasses of water, with a siphon of large ^ bore connecting them. On making N com- municate with the negative, and P with the positive pole, decomposition ensues, hydrogen gas accu- mulating in N, and oxygen in P. What is the relative proportion of the gases collected ? How can it be ■p-oved that the less quantity is oxygen and the larger hydrogen ? What is ne constitution of water by volume ? POL All DECOMPOSITION. 133 LECTUUE XXXI. The Electro-chemical Theory. — Theory of the Decom- 2 Wsition of Water. — Decomiiosition of Metallic and other Salts. — BecquereV s Illustration of the Formation of Minerals. — Davy's Discoveries. — Electro-chemical Theory. — Electrolytes. — Faraday's Theory of definiie Action . — The Electrotype. The prominent fact connected with the decomposition of water is the total separation of the constituent elements on the opposite polar wires or electrodes. From the positive wire oxygen alone escapes, and from the negative hydrogen ; there is no partial admixture, but the separation is perfect and complete. Though the polar wires may be separated from each other by a considerable distance, the same result is uniformly ob- tained, and it is to be remarked that the evolution of gas takes place on the wires alone ; no intervening bubbles make their appearance in the intermediate space. The principle on which this is effected may be easily understood, by supposing H H and O 0, Fig. 117, to represent atoms of hydrogen and oxygen o ' respectively ; each pair of them, therefore, ' represents a particle of water. Now, if we slide the upper row of atoms upon the r lower, as shown at h A, o o, it is obvious that a hydrogen atom will be set free at one extremity of the line, and an oxygen atom at the other, and that, as re- spects all the intermediate pairs of atoms, though they have changed their places, yet every particle of hydrogen is still associated with a particle of oxygen, constituting, therefore, a particle of water ; and it is at the extremes of the. line alone that the gases are set free. So in the polar decom- position by the pile, all the liquid intervening between the poles is affected, decompositions and recombinations suc- cessively taking place, the hydrogen atoms moving in one Do these polar decompositions effect a total separation of the bodies ? In the decomposition of water, do any gas bubbles appear in the intervening space ? liow is tliis explained ? How is it, if dtcoinpositions are going on in the intervening space, that the gases are not there seen ? O H I' i K 134 VOLTAIC DECOMPOSITIONS. direction, the oxygen in the other, finally to be set free on the surface of the polar wires. This capital discovery of the decomposition of water by Voltaic electricity was originally made by Nicholson and Carlyle. It is by far the most satisfactory method of dem- onstrating the constitution of that liquid. After it was made known, any lingering doubts which still remained on the minds of some chemists in relation to the composite nature of water were speedily removed. In the same manner that water is decomposed by the Voltaic battery, so, also, many metallic and other salts yield to its influence. Thus, if into ajar containing a solution of blue vitriol, the sulphate of copper, two metallic plates are introduced parallel to each other, and one of them brought in connection with the negative and the other with the positive pole of the battery, decomposition of the salt takes place ; the sulphate of copper being resolved into its constituents, sulphuric acid and the oxide of copper, and the latter reduced to the condition of metallic copper by hydro- gen simultaneously evolved with it; arising from the decom- position of a part of the water. In this manner the copper may be deposited, with a little care, under Ijie form of a tough metallic mass. If in a cubical glass vessel, Fig. 118, divided into two decomposition of the iodide takes place, its iodine being evolved at the positive wire, and giving with the starch a deep blue color, the blue iodide of starch, while the liquid in the other partition remains colorless. M. Becquerel obtained some very beautiful results by the aid of weak but long-continued electric currents, illustrating the probable mode of formation of mineral substances by such currents traversing the crust of the earth. If we take a glass tube bent into the form of a U, and close the bended Can metallic salts be in like manner decomposed ? Describe the polar decomposition of iodide of potassium. Can decompositions be produced by very feeble Voltaic currents ? Fig. 118. partitions by a diaphragm, ^ a, and both partitions filled with a solution of iodide of potassium, mixed with a M solution of starch, and the positive and negative wires of the battery introduced, BECaUERELS EXPERIMENTS. 135 Fig. 119. Fig. 120. part with a plug of plaster of Paris, putting in one of the branches a solution of car- bonate of soda, and in the other of sulphate of copper, immersing in one of the solutions a zinc plate, and in the other a copper, connected together by a piece of bent wire, the liquids communicate through the porous plug, and crystals of the double carbonate of copper and soda form on the plate im- mersed in the copper liquid. In the same manner, other compound salts and mineral bodies may be produced. Or if we take a jar, A, and fill it with a so- lution of nitrate of copper to a, and then with dilute nitric acid to B, and immerse in it a slip of copper, C D, presenting equal surfaces to the two liquids, an electric current is generated, the - copper is dissolved in the upper solution, and is deposited in crystals at D in the lower. As in this manuer water and various saline bodies undergo decomposition by the action of the pile, it occurred to Sir H. Davy that proba- bly other substances, at that time supposed to be simple, might also be decomposed. He accordingly subject- ed the alkaline and earthy bodies, then reputed to be ele- mentary, to the influence of a powerful battery, and found that his supposition was verified. On placing a fragment of caustic potash between the poles, it immediately melted ; from the positive, oxygen gas escaped in bubbles, and from the negative, small metallic globules, having the appear- ance of quicksilver, emerged ; these were characterized, however, by the singular qualities of an intense affinity for oxygen, so that they would take fire on being touched by water, or even ice, and were so light as to swim upon the surface of that liquid. The result of Davy’s experiments proved that the alka- line substances and all the earths are oxidized bodies, and in most instances oxides of metals. On these principles, Davy established a division of ele- mentary bodies into electro- positive and electro-negative Describe some of the arrangements of M. Becquerel for illustrating the probable mode of formation of minerals. What were the discoveries of Davy respecting the alkaline and earthy bodies ? ]36 ELECTRO-CHEMICAL THEORY. substances. The former are those which, during a polar decomposition, go to the negative pole, and the latter those that go to the positive. The electro-chemical theory as- sumes that all bodies have a natural appetency for the as- sumption of the positive or negative states respectively, and that all the phenomena of chemical combination are mere- ly cases of the operation of the common law of electrical attraction ; for between particles in opposite states attrac- tion ought to take place, and when in a compound body, such as water, which consists of particles of negative oxy- gen and positive hydrogen, the poles of an active Voltaic battery are immersed, they will effect its decomposition, the negative oxygen going to the positive pole, and the positive hydrogen to the negative pole. Davy’s theory thus not only accounts for the decomposing agencies of the battery, but also for all common cases of chemical combination, referring both to the fundamental law of electric attraction. With all its simplicity, it would be very easy to show, however, that it is founded on a groundless assumption, and can not account for a great num- ber of well-known facts. The Voltaic pile can not decompose all bodies indiscrim- inately. An electrolyte — for so a decomposable substance is termed — must always be a fluid body. It also appears that all electrolytes must have a binary constitution, or con- tain one atom of each of their two constituent ingredients. Mr. Faraday discovered that the action of an electric cur- rent in effecting the decomposition of various bodies is per- fectly definite : thus, if we make the same current pass through a series of vessels containing water, iodide of po- tassium, melted chloride of lead, they will all be decom- posed, but in very different quantities. If of the w^ater there be decomposed 9 parts,' there will be 165 of iodide of potas- sium, and 139 of chloride of lead ; but these numbers rep- resent what will be hereafter given as the atomic weights of the bodies in question. A current which can set free one grain of hydrogen will evolve 108 of silver, 104 of lead, 39 of potassium, 31-6 of copper, &c., these being the atomic weights of those substances respectively. What is meant by the electro-chemical theory ? Does this theory also account for chemical combination ? To what bodies is the decomposing in- fluence of the Voltaic battery limited ? Gan substances other than binary compounds be thus decomposed? Explain Faraday’s law of the definite action of a Voltaic cunent. THE ELECTROTYPE. 137 A very beautiful application of electro-chemical decom- position has of late been introduced into the arts. It passes under the name of the electrotype. It consists in the pre- cipitation of metallic copper, gold, silver, platina, &c., on different surfaces, by the aid of a Voltaic current. Thus, suppose it were required to obtain a perfect copy in copper of one of the faces of a medal ; let Fig. 121 . a glass trough, N O^Fig. 121, be filled with a solution of the sul- phate of copper, and to the nega- tive wire, Z, of a Smee’s Voltaic battery, let the medal N be at- tached, all those portions, except the face designed to be copied, be- ing varnished over, or covered with wax, to protect them from contact with the liquid. To the positive wire, S, let there be attached a mass of copper, C. As soon as the battery is in action, decomposition of the sulphate takes place, metallic copper is precipitated on the face of the medal, copying it with surprising accuracy. This copper is, of course, withdrawn from the sulphate in the so- lution ; but while this is going on, sulphuric acid and oxy- gen are being evolved on the mass of copper, C. They therefore unite with it ; and thus, as fast as copper is pre- cipitated on N by oxydation, new quantities are obtained from C, and the liquid keeps up its strength unimpaired. In the course of a day the medal may be removed. It will be found incrusted with a tough, red coat of Fig. 122 . copper, which may be readily split off from it. It is a perfect copy of the surface on which the deposition took place, and, in turn, it may be used as a mould for obtaining a great number of casts. Gilding, silver-plat- ing, and platinizing are now performed on the same principles, the electrotype being one of the most beautiful contributions which science has of late given to the arts. An instrument, the Voltameter, has been invented by Mr. Faraday for measuring quan- tities of Voltaic electricity. It is represent- ed in Fig. 122. It consists of a glass j:»r, Describe the electrotype. 138 DIFFERENT VOLTAIC BATTERIES. filled to the height d with water, and through its cover, c, a graduated tube, passes. In the lower part of the tube at g, two pieces of platina-foil, which form the term- inations of the polar wires of the battery, the current of which is to be measured, are introduced, the connection with those wires being made by the aid of the mercury cups, e f. The tube, a, having been filled with water, as soon as the current passes decomposition takes place, the gases collect- ing in the graduated tube, and measuring the amount of the current. LECTURE XXXII. Ohm’s Theory of the Voltaic Pile. — Magnetism and Electro-magnetism. — Volta's Pile. — Hare's Calorim- otor. — Zamboni's Pile. — Ohm's Theory. — Electro-mo- live Force. — Resistance. — General law for the Force of the Current. — Laws and Phenomena of Magnetism . — Electro-magnetism, Oersted' s Discoveries in . — The Gal- vanometer. — Electric Rotations. — Tangential Force. — Electro-magnets. With a given amount of metallic surface we can produce Voltaic batteries having different qualities. Thus, if we take a square foot of copper and a square foot of zinc, and place between them a piece of wet cloth, we shall have a battery which can not give shocks, nor effect the decompo- sition of water, but which will cause a fine metallic wire to become white hot, or even to fuse. If, again, we take a square foot of copper and a square foot of zinc, and cut each into 144 plates, an inch square, and arrange them with sim- ilar pieces of cloth as a Voltaic pile, the instrument will give shocks, and decompose water rapidly. From the same quan- tity of metal two different species of battery may be made ; one consisting of a few plates of large surface, or one of a great number of alternations of smaller plates. Of these varieties of battery, the calorimotor of Dr. Hare is an example of the first. It consists of a series of zinc plates, all connected together, and one of copper, also simi- larly connected, constituting therefore, in reality, a single pair Describe the Voltameter. What are the two principal forms of battery? What does the calorimotor illustrate ? OHM S THEORY OF VOLTAIC CURRENTS. 139 of very large surface. The great amount of heat evolved by this apparatus is its peculiarity. The electric pile of Zamboni is an example of the other kind. It consists of a series often or twenty thousand discs of gilt paper, alternating with similar pieces of very thin zinc foil. These are arranged in a tube, and kept in contact by the pressure of screws at each end. In Fig. 123, the pile is laid on a pair of gold leaf electroscopes, both of which diverge, the one be- ing positive and the other negative, the central parts of the pile being neutral. This instrument exhibits no calorific effects ; its phe- nomena are those of elec- tricity of high tension. These, and, indeed, many of the phenomena of the electric current, are clearly accounted for by the aid of Ohm’s theory of the Voltaic pile, of which the following is an exposition : 1st. By ELECTRO-MOTIVE FORCE we Understand the causes which give rise to the electric current ; this, as we have ex- plained in the simple circle, is the oxydation of the zinc. 2d. By RESISTANCE we mean the obstacles which the cur- rent has to encounter in the bodies through which it passes. When we affect the electric current in any portion of its path, either by varying thp electro-motive force, or changing the resistances, we simultaneously affect it throughout the whole circuit ; so that, in a given space of time, the same quantity of electricity passes through each transverse section of the circuit. In any Voltaic circle, simple or compound, the force of the current is directly proportional to the sum of all the electro- motive forces which are in activity, and inversely propor- tional to the sum of all the resistances ; that is to say, the force of any Voltaic current is equal to the sum of all the What does Zamboni’s pile illustrate ? What is the effect produced by a battery of large plates 1 What by one of many alternations 1 What is meant by electro-motive force ? In a simple circle, what is its origin ? What is meant by resistance ? On affecting one part of a current, is the rest affect- ed ? What conclusion is draw^n from that fact ? What is the force of the current equaf to ? Fig. 123. 140 ohm’s theory. electro-motive forces, divided by the sum of all the resist- ances. The resistance to conduction of a metal wire is directly as its length, and inversely as its section ; that is to say, the longer the wire is, the greater its resistance, and the thicker it is, the less its resistance. If we augment or diminish, in the same proportion, the electro-motive forces and the resistances of a Voltaic circuit, the force of the current will remain the same ; if we in- crease the electro-motive force, the force of the current in- creases ; if we increase the resistance, the force of the cur- rent diminishes. If, in two Voltaic circles of equal force, the same resist- ance is introduced, the forces of the currents may he enfee- bled in very different proportions ; for the newly-introduced resistance may, in one of the circles, bear a very great pro- portion to the resistances already existing, and, in the other, a very insignificant proportion. The following, therefore, is the general law which de- termines the force of a Voltaic circuit. 1st. The electro-motive force varies with the number of the elements, the nature of the metals, and of the liquids which constitute each element ; but it does not in any man- ner depend on the dimensions of their parts. 2d. The resistance of each element of a Voltaic circuit is directly proportional to the distance between the plates, as occupied by the liquid, the resistance of the liquid itself, and the length of the polar wire connecting the ends of the cir- cuit ; and inversely proportional to the surface of the plates in contact with the liquid, and to the section of the connect- ing wire. 3d. The force of the current is equal to the electro-mo- tive force divided by the resistance. From the circumstance that lightning has been repeatedly known to render implements of steel magnetic, and from a general analogy which exists between the phenomena of magnetism and those of electricity, it was long ago believed that these phenomena were due to one common cause ; but In a wire, w'hat is the law of resistance ? How does the force of the cur- rent change with changes in the electro-motive force and the resistance? When a new resistance is introduced into two circles, does it follow that both will be affected alike ? Give the general law which determines the force of the Voltaic current. MAGNETISM. 141 it was not until 1819 that their true relationship v/as first established by (Ersted. The phenomena of the magnet itself were discovered more than 2000 years ago. The natural magnet, or loadstone, which is an iron ore, possesses the quality of attracting pieces of iron or steel, but upon almost all other substances it is Avithout action. To hardened steel it communicates its own properties in a permanent manner ; but soft iron is only tran- siently magnetic, and as soon as it is removed from the in- fluence of the magnet it loses its power. Bars of steel which have been magnetized can communicate their activity to other bars ; they are, therefore, of constant use in physical investigations, and are of two forms, straight bars and horse- shoe magnets. If a magnetic bar have iron fil- ings sifted over it, they collect, as represented in Fig. 124, chiefly at the two extremities, cl d, few of them being found in the middle. If a piece of card-board is laid over a magnet, and the fil- ings dusted on it, they arrange themselves in curves, called magnet- ic curves ; there being in this, as in the for- mer instance, centers of action, P P, toward the extremities of the bars, around which the curves are arranged. The appear- ance is shoAvn in Fig. 125. A light magnetic bar, S N, c so arranged that it can be ^ j] poised on a pivot, C, with freedom of motion, is a mag- I netic needle. It was discov- I ered by the Chinese that such j a needle, Fig. 126, possesses polarity, or points north and What are the properties of a magnet? What is the difference of its action on iron and steel ? What are the forms of artificial magnets ? How may the existence of poles be sho\Mi by iron filings ? Describe a magnetic nee- dle. . What is meant by its polarity ? Fisr. 124 . 142 ELECTRO-MAGNETISM, south, a fact of the utmost importance in navigation. When to a needle the poles of a bar are approached, it exhibits at- tractive and repulsive movements. The law under which these take place is, “ Like poles repel, and unlike ones at- tract two north or two south poles repel, hut a north and a south attract. Either pole of a magnet is attracted by a piece of unmagnetized soft iron. The intensity of magnetic action is inversely proportional to the square of the distances. The north and south polarities can not be isolated from one another. If we take a long magnet, JST S, Fig. 127, and break it in two, we shall not insulate the north polarity in one half and the south in the 2sr' IQ- Fig. 127. S 1 ^ s' "N" S' 1 ^ -_i other, but each of the broken magnets will be perfect in it- self, having two poles — one fragment being N' S', and the other N" S". Of Electro-Magnetism. If a magnetic needle be brought into the neighborhood Fig. 128. of a wire along which an electric cur- A rent is passing, the needle is at once disturbed from its position, and tends to set itself at right angles to the wire. Thus, if there be an electric current moving in the direction A B in a wire, and directly over the wire, and par- allel to it, there be a suspended nee- dle, as soon as the current passes the needle is deflected from its position, and if the current is sufficiently pow- erful, comes at right angles to the wire. The direction in which the transverse movement takes place de- pends on the relative position of the needle and the wire : thus, 1st, if the wire be above the needle and parallel to it, that pole next the negative end of the battery moves westward ; 2d, if the wire be beneath the needle, it will move eastward ; 3d, if the wire be on What is the law of magnetic attractions and repulsions ? How does the intensity of magnetic action vary ? What is the direction in which the nee- dle mpves in the four positions round the wire ? ELECTRO-MAGNETISM. 143 the east side of the needle, the pole is elevated ; 4th, if on the west, it is depressed : in all these various positions, the tendency being to bring the needle at right angles, or trans- verse to the wire. It follows, from these facts, that if a magnetic lacts, tnat ii a magnetic ^ needle be placed in the \ interior of a rectangle of Fis^. 129 . wire. Fig. 129, through which a current is made to flow, all the portions of the wire conspire to move the needle in the same direction. The effect, therefore, becomes much greater than in the case of a single continuous wire. On the same principle, if, instead of a single turn, the wire is repeatedly coiled upon it- Fig. 130 . self, as at a d d a, Fig. 130, so as to make a great many turns, the effect upon the included needle, n s, is greatly increased, and when the needle is made nearly astatic, that is to say, its tendency to point north nearly destroyed by arranging it Fig. 131 . upon an axis with another needle sim- ilar to it in all respects, but with its poles reversed, as N S, S S, Fig. 131, the directive tendency of the one nee- dle neutralizing the other, but both tending to turn in the same direction by the current in the coil of wire, in- asmuch as one is within the coil and the other above it, the arrangement forms a most delicate means of dis- covering and measuring an electric current. It is called a galvanometer. As action and reaction are always equal and contrary, it is obvious that if a conducting wire be movable and the magnet stationary, the latter can be made to impress motions on the former. What is the effect on a needle in the interior of a rectangle ? What is the principle of the galvanometer? On the same j rinci];! can ihc wire be made to move ? 144 ELECTRO-MAGNETIC ROTATION. Fig. 133. Conducting wires can be made to revolve round the poles of a magnet, or the pole of a magnet round a conducting wire ; thus, in a glass cup, Fig. 132, let a magnet, n, be fixed verti- cally, and the cup filled with mercury ; by means of a loop, a, let a conducting wire, b, be suspended, having perfect freedom of motion. If an electric current is made to pass down this wire through the mercury, and escape by the path d, the wire rotates round the pole n as long as the current passes. From this and similar experi- ments, it therefore appears that the force exerted between a conducting wire and a magnet is not a direct attractive or repulsive power, but one continually tending to turn the movable body round the stationary one, deflecting it continual- ly, and acting in a tangential direction. Hence it is sometimes spoken of as a tan- gential force. If round a bar of soft iron a conduct- ing wire, covered over with silk, be spi- rally twisted, as in Fig. 133, whenever an electric current is passed, the iron be- comes intensely magnetic, and loses its mag- netism as soon as the current stops. A bar an inch in diameter, bent so as to represent a horseshoe, Fig. 134, with a wire covered with silk for the purpose of separating its successive strands from each other, may be made to give rise to very striking results. Professor Henry, by a modification of the con- ducting wire, succeeded in imparting so in- tense a degree of magnetism to a piece of soft iron that it could support more than a ton weight. If under one of these electro- magnets a dishful of small iron nails be held, the moment the current passes, the nails are all attracted, and, while they are held by Fig. 134. Describe a method of showing the rotation of a wire round the pole of a magnet. What is the nature of the force exerted between a conducting wire and a magnet? Describe the construction and properties of a straight electro-magnet. Describe the horseshoe clefctro-magnet. MAGNETIC AND DIAMAGNETIC BODIES. 145 its poles, may be moulded, as it were, by the hand in vari- ous shapes, but as soon as the current stops they fall off. It is upon this principle of producing temporary magnet- ism by an electric current that Morse’s electric telegraph depends. When different substances are suspended between the polar terminations of one of these horseshoe electro-magnets — in the magnetic field, as it is termed — it is found that some arrange themselves from pole to pole, and others trans- versely to that position ; the former are called magnetic and the latter diamagnetic bodies : Magnetic Bodies. Iron, Nickel, Cobalt, Platinum, Palladium, Titanium, Bottle glass, Crown glass, &c., &c. Diamagnetic Bodies, Bismuth, Antimony, Zinc, Tin, Rock crystal, Wood, Beef, Bread, &c., &c. Hot air is more diamagnetic than cold air ; a flame, there- fore, spreads itself transversely in the magnetic field. In an atmosphere of coal gas, oxygen presents the aspect of a strongly magnetic body. LECTURE XXXIII. Electro - dynamics — Thermo - electricity, &c. — Am- ferds Discovery. — Properties of a Helix. — Nature of the Magnet. — Faraday's Discovery of Magnetic Elec- tricity. — Magnetic Machines. — Faradian Currents . — Thermo-electricity. — Production of Heat and Cold by Electric Currents . — Thermo-electric Pairs. — Peculi- arity of these Currents. — Electro-motive Power of Heat. — Melloni's Pile and Thermometer. — Improvements in Thermo-electric Pairs. — Animal Electricity . — Steam Electricity. Soon after the relation between electrieity and magnet- i.sm was established, M. Ampere discovered that there are reactions between electric currents themselves. What are magnetic and diamagnetic bodies X G 146 PROPERTIES OF A HELIX. Fig. 136. Two electric currents flowing in the same direction at- tract each other, but two electric currents flowing in oppo- Fig. 135. site directions repel ; or, more briefly, ‘ ‘ Like currents attract, and unlike ones repel.” If a conducting wire be bent in the form of a helix, its terminations returning to- ward its middle, as shown in Fig. 135, it exhibits all the properties of an ordinary magnetized bar ; for, as soon as the current passes, it points north and south, and is attracted and repelled by the poles of a magnet lust as though it were a magnet itself. A very neat arrangement for illus- trating these results is seen in Fig. 136. A small simple circle, consisting of a zinc and cop- per plate, connected together by means of a wire bent so as to form a flat coil, is floated by means of a cork in acidulated water. The current runs round the coil in the direction of the arrows, and the arrangement, obeying the mag- netic influence of the earth, turns, with its plane pointing north and south, just as a magnet would do if introduced into the interior of the coil, in the position shown in the figure by the dark line. Ampere infers, from the analogy of these instruments, that the magnet owes its qualities to electric currents cir- culating in it in a transverse direction. The directive ac- tion of the magnetic needle or the electric helix depends on the reaction of electric currents circulating in the earth, due to the unequal heating of its surface by the rays of the sun. "We have seen that an electric current can develop mag- netism in a bar of iron or steel ; in the former, transient, in the latter, permanent magnetism. Thus, if the iron bar, n s. Fig. 137, be placed in the axis of a helix of copper wire, along which a current is flowing, the current develops What is the law of reaction between electric currents ? Describe the phenomena of the electro-dynamic helix, Fig. 135. Describe those of the flat coil. What is Ampere’s theory of the nature of the magnet ? MAGNETO-ELECTRIC CURRENTS. 147 magnetism in the bar. It was discovered by Faraday that the converse also holds good, and that a magnet can give rise to an electric cur- rent. Thus, in Fig. 137, let the terminations a b oi the helix c be brought in contact, and having placed a soft iron bar, n s, within it, let the bar be made magnetic by the approach of a strong magnet. As n s assumes the magnetic condition, it generates a current, which runs through the helix c ; and if at this moment the wires a h are drawn apart, a bright spark, sometimes called the magnetic spark, passes. It does not come, however, from the magnet itself, but is due to the electric current estab- lished in the helix by the disturbing action of the magnet. If between the terminations a 6 a slender wire is placed, it may be made red-hot, or water may be decomposed, or any of the phenomena of a Voltaic battery may be exhibited by the aid of this magneto-electric current. On this principle are constructed the magneto-electric machines, of which different foims have of late been so generally introduced for the purpose of the medicinal application of electricity. They all depend essentially on the principle, that if we coil round a piece of soft iron a conducting wire, as often as the iron is magnetized a wave of electricity flows through the wire. If two conducting wires be placed parallel and near to each other, when an electric current is passed through one of them a wave of electricity flows in the opposite direction through the other ; and on the first current stopping, another wave, coinciding with it, passes through the second wire. These momentary currents are all called, from Fi^.idS. the name of their discoverer, Faradian currents. If we take a bar of antimony, a, Fig. 138, and one of bismuth, 5, and having soldered them end to end at c, pass a feeble current through them in a direction from the antimony to the bismuth, the temperature of the com- pound bar rises ; but if the current passes in the opposite direction, cold is produced. By Can a magnetized bar be made to develop electric currents ? What are the properties of these currents ? What is the principle of the magneto- electric machine ? What is meant by Faradian currents ? What is their direction ? IIow may heat and cold be produced by a current in a com- pound bar ^ 148 THERMO-ELECTRIC CURRENTS. fixing thermometers into the substance of the bars, these facts may be readily verified, and in the latter case, when water is placed in a depression made for it in the bar, and the reduction of temperature slightly aided, it can be frozen by the electric current. The same compound bar of bismuth and antimony, hav- ing its extremities connected together by a wire, whenever heat is applied to the junction, an electric current sets from the bismuth to the antimony, and when cold is applied, from the antimony to the bismuth. These important facts were discovered by Seebeck in 1822, and the currents have been designated by him thermo-electric currents. For the production of these thermo-electric effects, two metals are not necessarily required. One end of a thick metallic wire being made red hot and brought in contact with the other, a current instantly passes from the hot to the colder portion, and continues to flow in diminishing quantities until the two ends have reached the same tem- perature. Or if a metallic ring be made red hot in any limited portion of its circumference, so long as the heat passes with freedom to the right hand and to the left, elec- tric development does not appear ; but if we touch with a cold rod the hot portion, abstracting thereby a portion of its heat, a current in an instant runs round it. It is not alone in metals that these thermo-electric cur- rents can be induced ; other solids, and even liquids, may originate them. Among metals associated together, the relation often exhibits singular changes. Copper and iron form a very active couple until their temperature approaches 800° F. ; the current then stops, and on continuing the heat, another current is developed, passing in the opposite way. The same takes place with a pair of silver and zinc, at a temperature of 248° F. Thermo-electric currents generated in metallic bars, ex- periencing little resistance to conduction, have therefore very little tension ; the thinnest stratum of water is a per- fect non-conductor to them. In any thermo-electric couple, the quantity of electricity evolved depends upon the temperature ; but, as I have What are thermo-electric currents ? Can they be generated by one metal only? Can they originate in other solids besides metals, and in liquids? What is the action of a pair of copper and iron, and silver and zinc? Why have they so little tension ? THE THERMO-ELECTRIC MULTIPLIER. 149 shown in a memoir on the electro-motive power of heat, in- serted in the Philosophical Magazine for June, 1840, it is not directly proportional to it, except through limited ranges of temperature ; we can not, therefore, make use of these currents for the determination of temperatures with accu- racy, on the hypothesis of the proportionality of the quanti; ties of electricity to the quantities of heat. By joining a system of bars alternately together, we may reduplicate the effects of a single pair. As might have been predicted on the theory of Ohm, and as I have shown in the memoir just quoted experimentally, where the con- ducting resistance remains the same, the quantity that passes the circuit is directly proportional to the number of pairs. It is upon this principle that, several years ago, M. Mellon! constructed his thermo-electric multiplier. Fig, 139. Fig, 139. Thirty or forty pairs of minute bars of bismuth and anti- mony, F F, with their alternate ends soldered together, are arranged in a small space, so that their ends expose an area not exceeding the section of the bulb of a common ther- mometer, the current that passes from this pile being so conducted, by means of wires, C C, as to deflect a magnetic needle. To the thermo-electric pile a galvanometer is there- fore attached, as seen in Fig. 140, which represents the whole instrument in section and perspective. A B C is the coil of the multiplier, its terminal wires ending in the con- necting cups, F F'. The coil rests on a plate, D E, which can be made to revolve by means of a wheel and screw con- nected with the button G. An astatic combination of nee- dles is supported by the frame Q; M N, by a single silk thread, V L. To protect the instrument from currents of air, it is covered with a glass cylinder, F L, strengthened by brass rings, P S, Y Z ; K T is the basis on which the cylinder rests. The angle of deflection of the needle is Is the quantity of electricity evolved proportional to ihe temperature? What is the principle of the ihermo-electrio multiplier of Melloni ? How is it constructed ? 150 THERMO-ELECTRIC PAIRS. Fig. 140. Fig. 141, >vvv 1 c b a A/ h' m u taken as the measure of the temperature. Of all thermom- eters, this is by far the most sensitive. I have introduced certain improvements in the construc- tion of the thermo-elec- tric element. Let a, Fig. 141 , be a bar of an- timony, and 5 a bar of bismuth. Let them be soldered along c cl, and at cl let the temperature be raised ; a current is immediately excited, but this does not pass round the bars a 5, inasmuch as it finds a shorter and readier channel through the metals between c and d, as indicated by the arrows. Nor will the whole current pass round the bars until the temperature of the soldered surface has become uniform. An improve- ment on this construction is, therefore, such as is represent- ed at a' y , v/hich consists of the former arrangement cut out along the dotted lines ; here the whole current, as soon In what manner may the simple thermo-electric pair be improved ? ANIMAL ELECTRICITY. 151 as it exists, is forced to pass along the bars. One of the best forms of a thermo-electric pair is given at 5'', where a" is a semi-cylindrical bar of antimony and 5" of bismuth, united by the opposite corners of a lozenge-shaped piece of copper, c. The heat is to fall on c, which becomes hot and cold with promptitude, and determines a current. Besides the various sources of electricity to which I have referred, there are certain animals which possess the power of controlling the equilibrium of the electric fluid in their neighborhood at will, being accommodated for this purpose with a specific nervous apparatus. The torpedo, a fish living in the Mediterranean, and the gymnotus electricus, which is found in some of the fresh water streams of South America, have this property. The shock of the torpedo passes through conducting bodies, but not through non-con- ductors. A gymnotus which was exhibited in London was found to deflect a magnetic needle powerfully by its dis- charge. A steel wire was magnetized by it, and iodide of potassium decomposed. In an interrupted metallic circuit a spark was seen, and the induced spark was also obtained by a coil. The current passed from the anterior to the pos- terior parts of the animal. Mr. Faraday, the author of these experiments, calculates that the quality of electricity passing at each discharge of the fish was equal to that of a Leyden battery containing 3500 square inches charged to its highest degree, and this could be repeated two or three times with scarce a sensible interval of time. As the electricity which these animals discharge depends on their nervous action, the production of it is attended with a corresponding nervous exhaustion. It is, therefore, not improbable that the converse of these actions holds good, and hereafter it will be found that electricity reacts on the nervous fluid. It has been shown by Matteucci that in all living ani- mals there is a current of positive electricity from the in- terior to the exterior of every muscle, and by arranging a series of muscles in such a way as to form a pile, magnetic effects and chemical decomposition may be produced. In concluding this subject, I may mention a source of What is animal electricity? By what animals is it exhibited? What effects have been produced by the electricity of the gymnotus ? What is the computed quantity of the electricity in each discharge ? Why is this electric development attended with a nervous exhaustion? What is the direction of the muscular current ? 152 ELECTRICITY PRODUCED BY STEAM. electricity which of late has excited much attention. When high-pressure steam is allowed to escape from a boiler through a narrow jet, a powerful excitement is produced, and sparks many feet in length may he obtained. The effect appears to be due to the friction of minute drops of water against the tube through which the steam is escaping. What is the cause of electricity produced by steam ? PART II. LECTURE XXXIV. The Nomenclature. — The French Nomenclature . — Ta hie of Elementary Bodies. — Nomenclature for Com pou7id Bodies, Adds, Bases, and Salts. Until after the discovery of oxygen gas, the nomencla- ture of chemistry was very loose and complicated. The trivial names which were bestowed on various bodies had frequently little connection with their properties ; sometimes they were derived from the name of the discoverer, or some- times from the place of his residence. Glauber salt takes its designation from the chemist who first brought it into notice, and Epsom salt from a village in England, in which it was at one time made. It is obvious that such a system of nomenclature, as soon as the number of compound bodies increased, would not only become unmanageable, but, by reason of the impossibility of carrying in the memory such a mass of unconnected terms, offer a very serious impediment to the progress of the science. Lavoisier and his associates, about the close of the last cen- tury, constructed a new nomenclature, with a view of avoid- ing these difficulties. Its principles, with some modifica- tions, are now universally received. The following is a brief exposition of it : Natural bodies may he divided into two classes, simple and compound ; the former are also called elementary. By simple or elementary bodies we mean those which have not as yet been decomposed. Among simple substances, those which have been known for a long time retain the names by which they are popu- larly distinguished ; thus, gold, iron, copper, &c. ; and when What was the nature of the nomenclature used by the older chemists? When was the system now in use invented ? What is meant by simple or elementary bodies ? What is the rule for the old simple bodies ? G 2 154 NOMENCLATURE FOR SIMPLE BODIES. new bodies belonging to this class are discovered, they are to receive a name descriptive of one of their leading prop* erties ; thus, chlorine takes its name from its greenish color, and iodine from its purple vapor. It is to be regretted that this rule has often bee:i overlooked. Some doubt exists as to the exact number of the ele- mentary bodies. It may be estimated at 62, including three metals recently discovered, the titles of which have not yet been completely established. Of the list of elementary bodies, the metals form by far the larger portion, there being 49 of them ; the remaining 13 are commonly spoken of as non-metallic substances. By some authors these are called metalloids, in contra-distinction to the metals, an epithet which, however, is very objectionable. Table of elementary or simple Substances, with their Sym- bols and Atomic Weights. Non-metallic Elements. Symbols. At. wts. Metallic Elements. Symbols. At. wts. Oxygen . . 0. 8-013 Erbium .... E. — Hydrogen . H. 1-000 Terbium . . . Tr. — : — Nitrogen . N. 14-19 Manganese ‘ . . Mn. 27-72 Sulphur . . S. 16-12 Iron Fe. 27-18 Phosphorus P. 32-00 Cobalt .... Co. 29-57 Carbon . . c. 6*04 Nickel .... Ni. 29-62 Chlorine Cl. 35-47 Zinc Zn. 3231 Bromine Br. 78-39 Cadmium . . . Cd. 55-83 Iodine . . I. 126-57 Lead Pb. 103-73 Fluorine F. 18-74 Tin Sn. 58-92 Boron . . B. 10-91 Bismuth ... Bi. 71-07 Silicon . . Si. 22-22 Copper .... Cu. 31-71 Selenium . Se. 39*63 Uranium ... U. 217-20 Mercury . . . Hg. 202-87 Metallic Elements. Silver .... Ag. 108-31 Potassium . K. 39-26 Palladium . . . Pd. 53-36 Sodium . . Na. 23-31 Rhodium . . . R. 52-20 Lithium . . L. 6-44 Iridium .... Ir. 98-84 Barium . . Ba. 68-66 Platinum . . . Pt. 98-84 Strontium . Sr. 43-85 Gold Au. 199-2 Calcium Ca. 20-52 Osmium . . . Os. 99-72 Magnesium Mg. 12-89 Titanium . . . Ti. 24-33 Aluminum . Al. 13-72 Tantalum . . . Ta. 184-90 Glucinura . G. 26 54 Tellurium . . . Te. 64-25 Yttrium . . Y. 32-25 Tungsten . . . W. 99-70 Zirconium . Z. 33-67 Molybdenum . . Mo. 47-96 Thorium . Th. 59-83 Vanadium . . . V. 68-66 Cerium . . Ce. 46-05 Chromium . . . Cr. 28-19 Lanthanum La. — Antimony . . . Sb. 64-62 Didymium . D. — Arsenic .... As. 37-67 What is the rule for the simple bodies newly discovered ? What is the number of the elementary bodies ? Of these, to what class do the greater part belong 1 What are the symbols for the elementary bodies ? What are their atomic weights ? NOMENCLATURE FOR COMPOUNDS. 155 To this table the names of four metals, recently discov- ered and hut little known, might be added. They are Ni- obium (Nb.), Norium (No.), Pelopium (Pe.), and Ruthe- rium (Ru.). Compound bodies may, for the most part, he divided into three groups : acids, bases, and salts. By an acid we mean a body having a sour taste, reddening vegetable blue colors, and neutralizing alkalies ; by a base, a body which restores to blue the color reddened by an acid, and possessing the quality of neutralizing the properties of an acid ; by a salt, the body arising from the union of an acid and a base These definitions, however, are to be received with consid erable limitation. The nomenclature for acid substances is best seen from an example. Thus sulphur and oxygen unite to form an acid : it is called sulphuric acid ; the termination in ic being expressive of that fact. But very frequently two substances will form more than one acid, by uniting in different pro- portions ; in this ease the termination in ou^ is used ; thus we have sulphurous acid, so called because it contains less oxygen than sulphuric. The prefix “ hypo” is also used, as in hyposulphurous and hyposulphuric acids : it indicates acids containing les^ oxygen than sulphurous and sulphuric acids. The prefix “ hyper” is used in the same way ; thus, hyperchloric acid, an acid containing more oxygen than chloric acid. "With respect to bases, the generic termination is in ide. If oxygen and lead unite, we have oxide of lead, and in the same manner we have chlorides, bromides, iodides, and fluor- ides. And if these elements form compounds in more pro- portions than one, we indicate their proportion by the Greek numerals, protos, deuteros, tritos : thus we have protoxides, deutoxides, tritoxides ; the protoxide of lead contains one atom of oxygen and one of lead, the deutochloride of mer- cury two atoms of chlorine and one of mercury, &c. In the same manner, the prefixes sub, sesqui, and per are used ; thus, a suboxide contains the lowest proportion of oxygen, a peroxide the highest proportion, and a sesquioxide inter- Into what groups may compound bodies be divided ? What is the defi- nition of an acid ? What is a base ? What is a salt ? What do the term- inations ic and ous indicate t What is the meaning of the prefixes hypo and hyper ? What does the termination ide signify ? What the prefixes protos^ deuteros, and tritos, sub, sesqui, and per ? 156 METHOD OP SYMBOLS, venes between a protoxide and a deutoxide, its oxygen being in the proportion of one atom and a half. By an alloy, we mean the substance arising from the union of two metals ; thus copper and zinc unite to form brass, which is an alloy. If one of the metals is mercury, the compound is called an amalgam. And when sulphur, phosphorus, carbon, and selenium unite with metals, or with each other, the termination uret is used ; thus we have sul- phurets, phosphurets, carburets, &c. With respect to the nomenclature for salts, the termina- tions ate and ite are used to indicate acids in and cuts re- spectively. The sulphate of potash contains sulphuric acid, .and the sulphite of potash sulphurous acid. And as we have already seen that different oxides arise by the union of oxygen in different proportions, and these bodies frequent- ly give rise to different series of salts, the operation of the nomenclature may be readily traced : thus, the protosul- phate of iron is the sulphate of the protoxide of iron, but the persulphate of iron is a sulphate of the peroxide, and the deutosulphate of platinum a sulphate of the deutoxide of platinum. When the relative quantity of the acid and base varies, Latin numerals are employed ; thus the bisul- phate of potash contains two atoms of sulphuric acid and one of potash. Salts are said to be neutral if neither their acid nor base be in excess. If the acid predominates, it is an acid, or super-salt > if the base, it is a basic, or sub-salt. LECTURE XXXV. The Symbols — Failure of the Nomenclature in the Case of Com'plex Compounds. — Failure in Difference of Grouping. — Symbols for elementary Bodies. — Expres- sions for several Atoms . — Use of the Plus Sign. — Ex- pressions for Grouping. So long as the constitution of compound bodies is sim- ple, there is no difficulty in applying the nomenclature, or What is an alloy and an amalgam ? When is the termination uret em- ployed? What do the terminations ate and ite indicate ? What is the no- menclature for the salts ? What is a neutral salt ? What is an acid, or 8uper-s£^lt ? What is a basic, or sub salt ? IMPERFECTIONS OP THE NOMENCLATURE. 157 in recognizing from the name of the compound the nature and proportions, of its constituents. Thus, protoxide of hy- drogen clearly indicates a body in which one atom of oxy- gen is united with one of hydrogen, bisulphate of potash a body composed of two atoms of sulphuric acid and one of potash, and even in more complicated cases, such as the sulphato-tri carbon ate of lead, &c., the same principle will serve as a guide. But when compound bodies consist of a great number of atoms, the nomenclature ceases to be of any service. Thus, starch is composed of twelve atoms of carbon, ten of hydrogen, and ten of oxygen. Fibrin is composed of forty-eight atoms of carbon, thirty-six of hydrogen, four- teen of oxygen, six of nitrogen, with minute but essential quantities of sulphur and phosphorus. On the principles of the nomenclature, it would be difficult to give to the first a technical name, and in the case of the latter impos- sible. The peculiarity of organic compounds is, that they con- tain but few of the elementary bodies, being chiefly made up of carbon, hydrogen, oxygen, and nitrogen ; but these, as in the case of fibrin, unite in a very complicated way, very often hundreds of atoms being involved. The nomen- clature is therefore inapplicable to organic chemistry. There is also another very serious difficulty in its way. It has been discovered that compounds may consist of the same elements, united in precisely the same proportions, so that when they are analyzed they yield precisely the same results, and yet they may, in reality, be very differ- ent substances. Identity in composition is no proof of the sameness of bodies. Thus we may have the same ele- ments uniting together in the same proportion, and yielding a solid, a liquid, or a gas indifferently. This result may de- pend on several causes, as will be presently explained ; -but among these causes I may here specify what is termed by chemists “ Grouping.” Thus, suppose four elementary bod- ies, A B C D, unite together, there is obviously a series of compounds which may arise by permuting or grouping them differently, as in the following example : Under what circumstances does the nomenclature apply, and when does it fail ? What is the peculiarity of organic compounds ? Why is the nomenclature inapplicable to organic chemistry ? Is identity of composi- tion any proof of the identity of bodies? What is meant by grouping? 158 METHOD OF SYMBOLS. (1) A + B+C + D. (2) AC +BD. (3) A D "4" C B. &c. &c. The method of symbols, which is designed to meet these difficulties, and is, in reality, an appendix and improvement upon the nomenclature, was originally introduced by Ber- zelius ; but the form which is now most commonly adopted is that of Liebig and Poggendorffi The advantages which have been found to accrue from it are so great, that it is now introduced into every part of chemistry, so that it is impossible to read a modern work on this science without having previously mastered the symbols. The student should not be discouraged at the mathemat- ical appearance of chemical formula?. He will find, by a little attention, that they are founded upon the simplest principles, and involve merely the arithmetical operations of addition and multiplication. The following is a brief exposition of their nature : For the symbol of an elementary substance we take the first letter of its Latin name, as is shown in the table given in the last lecture. Those symbols should be committed to memory. But as it happens that several substances some- times have the same initial letter, to distinguish between them we add a second small letter. Thus, carbon has for its symbol C. ; chlorine. Cl. ; copper (cuprum), Cu. ; cad- mium, Cd., &c. It may be observed that in the case of recent Latin names the German synonym is always used ; thus, potassium is called kalium in Germany, and has for its symbol K. ; sodium is called natrium, and has for its symbol Na.y &c. But a symbolic letter standing alone not merely repre- sents a substance ; it farther represents one atom of it ; thus, C means one atom of carbon, and O one atom of oxygen. If we wish to indicate that more than one atom is pres- ent, we affix an appropriate figure, as in the following ex- amples • ^12 . . Ojo- Thus, nitric acid is composed of one atom of nitrogen united to five of oxygen, and we write it NO^. Give an example of grouping. What are the symbols for elementary bod- ies ? When two bodies begin with the same letter, how are the symbols arranged ? What does a single symbol standing alone represent ? How are more atoms than one represented ? METHOD OP SYMBOLS. 159 When a compound, formed of several compounds, is to be represented, we make use of an intervening comma ; thus, strong oil of vitriol is composed of one atom of sulphur and three of oxygen, united with one atom of water, which is composed of one atom of oxygen and one of hydrogen, and. we write it SO^, HO. If we desire to indicate that compounds are united with a feeble affinity, we make use of the sign + ; thus, the composition of sulphuric acid may be written SO^, or K 218 NITKIC ACm, NITRIC ACID. NOs = 54 255. Nitric acid, the most important of the compounds xxf oxy- gen and nitrogen, and one of the most important of the acid bodies, was first discovered during the ninth century. The discovery of this and some of the other powerful acids form one of the epochs in chemistry. The science can scarcely be said to have existed until that time, the Egyptians, Greeks, and Romans having no knowledge of these bodies, nor, in- deed, of any more powerful than vinegar. The constitution of nitric acid was determined by Mr. Cavendish, who formed it synthetically by passing electric sparks through atmospheric air in contact with a solution of pota:sh. The nitrate of potash was obtained. Nitric acid also occurs to a small extent in rain water, especially after thunder storms, and by some supposed to originate upon the same principles as in Cavendish’s experi- ments ; but probably it is due to the oxydation of ammonia, which always exists in the air. The chief supply is derived indirectly from the decay of vegetable or animal matter, in the presence of oxygen gas, and in contact with basic bod- ies. Collections of such refuse pass under the name of ni- tre beds, and, in France and Germany, furnish the saltpetre which is used for the manufacture of gunpowder. In the East Indies, nitrate of potash is obtained by lixiviation from the soil in which earthy nitrates naturally occur. From South America the nitrate of soda is exported ; it is found as an efEorescence on soils in which common salt prob- ably exists. In most of these cases the nitric acid arises from the oxy- dation of ammonia produced during putrefactive ferment- ation. iViTg + Og . iVDs + 3HO. The formula shows the probable nature of the action ; one atom of ammonia, under the influence of eight of oxygen, will yield one of nitric acid and three of water. The nitric acid of commerce is made by distilling equal weights of sulphuric acid and nitrate of potash. The pro- cess may be conducted in a small way in a glass retort. A, Fig. 220 ; and it is found advantageous to use the quantity When was nitric acid discovered ? How was its composition determined by Cavendish? What is the source of the nitric acid in rain water? From what sources is nitrate of potash produced ? How may nitric acid arise from the oxydation of ammonia ? How may nitric acid be made ? NITRIC ACID. 219 Fig, 220. of sulphuric acid here stated, because a soluble bisulphate of potash is formed, which may be easily removed without breaking the retort. Half as much sulphuric acid would effect the decomposition, but it would require a higher tem- perature, and the neutral sulphate which forms could with difficulty be removed. The change Avhich takes place is thus exhibited : (/fO, NO,) + 2( JJO, 80^) (ifO, HO, 280,) + {HO,NO,^,) that is, one atom of nitrate of potash and two of sulphuric acid furnish one atom of bisulphate of potash, and one of hydrated nitric acid distills over into the receiver, B, which is kept cool by a stream of Avater flowing from i into a A^es- sel, c c, the Avaste water passing through led. A net is wrapped over the receiver to distribute the water evenly. In this process nitrate of soda may be advantageously sub- stituted for nitrate of potash. Hydrated nitric acid thus produced is a colorless liquid, which boils at 248° F., though this point changes with the amount of water in the acid. It freezes at — 40° ; is de- composed into oxygen and nitrogen by being passed through a red-hot glass tube. It turns yellow in the sunshine, oav- ing to a portion being decomposed and nitrous acid set free, which dissolves in the residue, and gives it an orange tint. The nitric acid of the shops (aqua fortis) commonly possess- es this color, from which it may be freed by boiling in a glass vessel. It stains the skin and other organic matters What are its properties? When passed through a red-hot tube, what happens to it ? Why is commercial nitric acid often yellow ? What is the action of this acid on the skin and on metallic bodies ? 220 PROPERTIES OF NITRIC ACID. yellow, and hence is used in the arts of dyeing. Its action on many metalline and other combustible bodies is exceed- Fi^. 221 . ingly violent, owing to the great amount of oxygen it contains. Poured upon some pieces of copper in a wine-glass, over which a bell jar may be inverted {Fig. 221), an effervescence takes place, and the red fumes of nitrous acid abundantly form. Though it is one of the most powerful oxydizing agents we possess, it often happens that, in a state of great concentration, it will scarcely act on a metal, but the addition of a little water causes the action to set in. Nitric acid (iV'Og) was, until recently, regarded as a hy- pothetical or imaginary body, the nearest approach to it being the strongest aqua fort is ; this has a specific gravity of 1*521, and consists of one atom of hypothetical nitric acid and one of water. Its formula, therefore, is KO^ + HO. Its molecular constitution probably is NO,+H. It is, as we shall find hereafter, a hydrogen acid. But M. Deville has shown that the anhydrous acid may be pre- pared by the action of chlorine or dry nitrate of silver. It presents the form of colorless crystals, which melt at about 85®, the boiling point being 113®, and gradually decomposes at ordinary temperatures. Nitric acid of commerce can be purified by distillation, rejecting the first portions which come over, as they contain chlorine, and leaving a portion in the retort containing sul- phuric acid and fixed impurities. If twelve parts are dis- tilled, the first three may be cast aside, and one left in the retort ; the intermediate eight are pure. "When it is in a solution, nitric acid may be detected by the addition of sulphuric acid, and a drop or two of proto- sulphate of iron ; a' brownish color is produced where the two liquids meet. When in a concentrated state, the evo- lution of red fumes, by the action of copper, detects it. It also gives a blood-red color with morphia. The nitrates deflagrate when ignited with combustible matter; a result which may be well shown by grinding together a few ounces of nitrate of potash and common sugar, and setting What is the nearest approach to hypothetical nitric acid ? Why can not it be isolated T How may it be purified ? How may it be detected ? SULPHUR. 221 fire to the mixture. Owing to the solubility of all its com- pounds, nitric acid can not he precipitated. LECTURE XLYIIL Sulphur. — Natural and Artificial Forms. — Frcparation of Flowers. — Properties of Sulphur. — Its Vapor . — Oxygen Compounds of Sulphur. — Sulphurous Acid . — Preparation. — Properties. — Bleaching E ffects. — Con- densation to the Liquid State. — Its Compounds. SULPHUR. fclG-12. Much of the sulphur in commerce is derived from vol- canic countries, in which it occurs often in a pure and crys- tallized state. It is one of the most common elementary substances, being found abundantly united with various metals, such as iron, copper, lead. In combination with lime, baryta, &c., it occurs as sulphuric acid, and is also an ingredient of many animal and vegetable products. Sulphur is met with under three different forms : roll sulphur, flowers of sulphur, and lac sulphuris. Roll sulphur is an impure variety, which receives its form from being cast into ’cylindrical moulds ; the flowers of sulphur are formed from the impure brimstone by sublimation ; lac sul- phuris differs from the foregoing in being of a white color. It is prepared by precipitation from the persulphuret of po- tassium by hydrochloric acid. The preparation of flowers of sulphur is conducted in an apparatus, such as Fig. 222. A is a room, or chamber, of Why can not nitric acid be detected by precipitation ? Under what forms does sulphur naturally occur ? What are its artificial forms ? How are the flowers of sulphur made ? 222 PROPERTIES 0P SULPHUR. 2000 feet capacity ; c is a pan containing sulphur, which is melted by the furnace, os; the vapor passes along i cl 5, and, entering the chamber, is there condensed. The re- sulting flowers are removed through the door p. If an ex- plosion occurs, when the process commences, it lifts the valve e, and the gases escape through the chimney, t. M ikZ" is a shed under which the apparatus is constructed. As the iron pan becomes exhausted, new quantities of brim- stone can be introduced through the door n. Sulphur commonly exists as a solid of a yellow color, and of a specific gravity of 1*99, having neither taste nor smell. It melts at 226° F. into a pale yellow-colored liquid ; but, what is very curious, if the heat be raised to about 450° F., it changes to the color of molasses, and be- comes so thick and tenacious that the capsule in which the fusion is carried on may be turned upside down without the sulphur flowing out. At 600° F. it boils, and, as the heat approaches that point, it again becomes fluid ; and, as it cools, runs through the same changes again in a reverse or- der. If suddenly quenched in cold water at the low tem- perature, before it thickens, it solidifies into ordinary sul- phur ; but if heated for a time to near 600°, and then quenched, it becomes, on cooling, elastic, like India-rubber, and may be drawn into long threads ; and in this state is sometimes used for taking casts of coins, for by keeping a few days it slowly returns to the condition of ordinary sul- phur. When rubbed on a piece of flannel it becomes highly elec- tric, assuming the negative state, and at one time was used in the making of electrical machines, before the powers of glass were discovered. A roll of it held in the warm hand emits a crackling sound, the crystals of which it is com- posed separating from one another. It is a bad conductor of heat and electricity, crystallizes under two different sys- tems, and is, therefore, a dimorphous body, one of its forms being an acute rhombic octahedron, and the other an oblique rhombic prism. When heated to about 300° F. in the open air, it takes fire, and burns with a blue flame, emitting a suffocating odor, fumes of sulphurous acid gas. It is wholly What are the properties of sulphur? What changes may be observed in it when melting ? What electrical condition does it assume by friction ? What are its conducting powers ? Why is it called a dimorphous body? At what temperature does it take fire, and what is the product of its com^ bustion? SULPHUROUS ACID. 223 insoluble in water ; its proper solvent is the bisulphuret of carbon. The vapor of sulphur is of a deep yellow color, and has the high specifie gravity of 6 '648. In it metallic bodies will burn precisely as they do Fig. m in oxygen gas. Dr. Hare has shown that if a gun barrel be heated red hot at the breech, and a piece of sulphur dropped into it, the muzzle being closed with a cork, an ignited jet of sulphur vapor issues from the touch-hole, in which, if a bunch of iron wire be held, it takes fire and burns brilliantly. Sulphur has a very extensive range of affinities, uniting with most metallic substances in several different propor- tions, with hydrogen and also with oxygen. With the lat- ter substance it furnishes the following compounds : SO^ . . SO3 . . their designations are, respectively, Sulphurous acid. Sulphuric acid. Hyposulphurous acid. Hyposulphuric acid. Sulphureted hyposulphuric acid (acid ofXianglois). Bisulphureted hyposulphuric acid (acid of Fordos and Gelis). SULPHUROUS ACID. = 32 146. This acid may be formed by burning sulphur Fig. 224 . in oxygen gas or in atmospheric air ; in the lat- ter instance the resulting gas is, of course, con- taminated with nitrogen. The process may be conducted under a bell jar, the burning sulphur being placed on a capsule or stand. But a much better process is to effect the par- tial deoxydation of sulphuric acid by heating oil of vitriol with mercury, which deprives it of one atom of oxygen, forming an oxide of mercury, which unites with one atom of the excess of sulphuric acid pres- ent to form a sulphate. For many of the ordinary purposes to which sulphurous acid is applied, it may be procured by the action of fragments of charcoal heated with sulphuric What is the specific gravity of its vapor? Does it support combustion? What are the oxygen compounds of sulphur ? How may sulphurous acid be made ? What is the principle of the process when sulphuric acid acts on mercury or charcoal ? 224 SULPHUROUS ACID. acid. In this case, however, carbonic acid is also evolved. When a solution in water is required, the gas may be pass- ed directly into that liquid, but if it be necessary to retain it in a gaseous state, it must be received in jars at the mer- curial trough, or collected by the method of displacement. It is, under the ordinary circumstances, a transparent and Fig. 225. colorless gas, having an unpleas- ant taste, and the smell charac- teristic of burning sulphur. It is wholly irrespirable, and prompt- ly extinguishes a lighted taper. Its specific gi'avity is 2*222, and, therefore, if a stream of it which has been cooled by flowing from the generating flask a. Fig. 225, through a bent tube, h, immersed in a jar of cold water, be conducted to the bottom of another jar, c, the gas, as it col- lects, displaces the atmospheric air, floating it out of the ves- sel. This process is of very general application in the col- lection of gases which are absorbable by water, and is known under the name of the method by displacement. In a jar of sulphurous acid thus collected, if a lighted taper be immersed, it is at once extin- guished. If the jar be inverted over water, the gas is speedily dissolved, that liquid taking up about thirty-seven times its volume of the gas. If vegetable colors are submitted to its influence, 1 they are bleached, but the color is not destroyed as in bleaching by chlorine, since it can be re- stored by the action of a stronger acid. Sulphurous acid is among the gases one that most readily takes the liquid form. If there be connected with the flask from which this gas is being evolved a bent tube passing through iced water in a jar, and the gas, after traversing* this tube, be conducted into a bottle placed in a freezing mixture of snow and dilute nitric acid, it condenses into a colorless fluid of the specific gravity 1*45, which boils at 14^ F. This fluid is sometimes used to produce intense cold by its evaporation. What are the products in each case ? Vv^hy must the gas be collected over mercury ? What are it? properties ? What is the method by displace- ment? To what extent is this acid soluble in water? Are its bleaching effects permanent ? How may it be condensed ? Fig. 226. SULPHURIC ACID. 225 With bases, this acid forms a complete series of salts, the sulphites, which are readily decomposed by the stronger acids, and are occasionally employed as deoxydizing agents, from the circumstance that metallic oxides may be reduced by them, their sulphurous passing into the condition of sul- phuric acid. LECTURE XLIX. Compounds of Sulphur and Oxygen. — Sulphuric Add, — The Anhydrous Acid. — Its Affinity for Water . — German Oil of Vitriol. — Its Constitution and Uses . — Common Sulphuric Acid. — Preparation on the large Scale. — Its Chemical Relations. — Purification. — De- tection. — Other Sulphuric Acids. SULPHURIC ACID. ^03 = 40159. This compound is not alone the most important of the acids of sulphur, but also the most important of all acids. By the aid of it, nitric, hydrochloric, and many other strong acids are made for commercial purposes. In the production of carbonate of soda and chloride of lime, immense quanti- ties of it are consumed. Of sulphuric acid we have several varieties, differing from each other in the amount of water they contain. 1st. There is anhydrous sulphuric acid, the formula for which has al- ready been given as containing one atom of sulphur and three of oxygen. This substance may be prepared by sub- mitting the fuming oil of vitriol of Xordhausen to a tem- perature of about 290° Fahr., when there distills over a white substance of a crystalline aspect. It fumes in the air, melts at 77° Fahr., is converted into vapor at 160°, has an intense affinity for water, in which, if it be placed, it hisses like a red-hot iron. It is to be particularly remarked, how- ever, that the acid powers of this substance are very feebly marked ; it shows little tendency to unite with other bodies, and when such combinations are effected, the resulting sub- stances are different from the true sulphates. What are the properties of this liquid ? For what purposes are the sul- phites employed? What are the properties of anhydrous sulphuric acid, and now is it prepared ? K 2 OIL OF VITRIOL. 2(1. German, or Nordhausen oil of vitriol, HO, 80^ + SO3. This substance is prepared by taking green vitriol, and, by exposure to heat, driving off its water of crystallization (six atoms), and also a portion of its saline water. If the dried, powder be placed in a stone- ware retort and exposed to a high temperature, there distills over a dark oily liquid ; hence the term oil of vitriol : this is the substance in ques- tion. Its formula shows that it is composed of two atoms of anhydrous acid united to one of water. A considerable quantity of it is used in the arts for dissolving indigo. 3d. Common sulphuric acid, HO, 80^. This is the substance which passes in commerce as com- mon oil of vitriol. It is made on the large scale by burning sulphur with nitrate of potash or soda, and conducting the sulphurous and nitrous acids which result into large cham- bers lined with lead, in which steam is thrown, the bottom of the chamber being covered with water. The sulphurous acid takes oxygen from the nitrous acid, reducing it to the condition of deutoxide ; but this being done in the presence of atmospheric air, which fills the chamber, the deutoxide instantly reassumes the condition of nitrous acid. The deutoxide, therefore, continually transfers oxygen from the atmospheric air to the sulphurous acid, and brings it to the condition of sulphuric acid. After a time, the water at the bottom of the chamber be- comes charged with sulphuric acid ; it is then concentrated by drawing off the excess of water in platina or glass boilers, and finally assumes the specific gravity 1*845. It is a dense oily liquid, freezes at — 15°, and boils at 620°. The attraction of common sulphuric acid for water is very Fig. 227 . ii^tense. If a tube, containing some ether, be stirred in a glass {Fig. 227) in which sulphuric acid and water are being mixed, the temperature rises so high that in a few moments the ether boils. On the same principle, it will remove from most gases which are passed over it any water they may con- tain ; and, as we have seen in Lecture XII., water may be frozen by taking advantage of the rapidity with "What is the process for preparing the German oil of vitriol ? What is its appearance? For what purpose is it used? What is the process for pre- paring commercial sulphuric acid? What are its properties ? What illus- trations may be given of its intense affinity for water ? ACIDS OP SULPHUR. 227 which sulphuric acid will absorb its vapor. Organic sub- stances may also be charred by the action of this acid ; for example, woody fibre is a compound of carbon with the ele- ments of water, and when acted upon by sulphuric acid, the carbon is set free, the acid taking from it a portion of its water. Sulphuric acid of commerce is never pure ; it contains sulphate of lead, derived in the process of its manufacture, and also, sometimes, arsenic, selenium, and nitrous acid. From the first it may be purified by dilution with water, in which sulphate of lead is insoluble ; but when required en- tirely pure, it must be distilled, the first portions being re- jected. The presence of sulphuric acid may be detected by any of the soluble salts of barium, such as the chloride of barium, or the nitrate of baryta, the white sulphate of baryta pre- cipitating insoluble in water and acids. To black woolen clothing this acid communicates a red- dish stain, removable by being touched with ammonia. Besides the compounds just described, we have other def- inite hydrates of sulphuric acid, thus : (4) SO^ + 2HO. (6) SO^ + 3HO, The fourth of these has a specific gravity of T78, and crystallizes at 39° Fahrenheit in large and beautiful crys- tals. The fifth has a specific gravity of 1632. HYPOSULPHUROUS ACID, S^O^ = 4S'266, has not yet been isolated ; one of its salts, the hyposulphite of soda, is extensively used in the Daguerreotype process for removing the sensitive coating on the plates. HYPOSULPHURIC ACID, is a sirupy liquid of a very acid taste, and is not applied to any use. Besides these, we have two other acids of sulphur : Sulphureted hyposulphuric acid, = 88* *475, discovered by Langlois. Bisulphureted hyposulphuric acid, = 104*595, discovered by Fordos and Gelis. Chemists are now very generally agreed that all these By what substances is it usually rendered impure ? How may it be pu- rified? How may it be detected? How may sulphuric acid stains on *jlothing be removed ? What other hydrates of this body are there ? What are the uses of hyposulphurous acid ? What other sulphur acids are there I 228 SULPHURETED HYDROGEN. compounds are to be regarded as hydrogen acids — a strik- ing departure from the Lavoisierian doctrines. They have been led to this view by the consideration that no well- marked acid exists in which hydrogen is not found ; that all these sulphur acids possess the same neutralizing power, though the quantity of oxygen they contain is so different. They regard them all as being formed by the union of one :;tom of hydrogen with a series of different compound radi- cals, as the following table shows : Sulphurous acid H-\- SO3 Sulphuric acid iT-f- O. Hyposulphurous acid S03-\- S. Hyposulphuric acid O3. Acid of Langlois iZ-j- iSOa >S03 -f- Acid of Fordos and Gelis . . . Af-{- “f" ^2- Chlorosulphuric acid JZ’-j- ^S'03 -j- C/. Nitrosulphuric acid jfZ" iS O3 -f- NO^. lodosulphuric acid /f-f- /; and, extending these views to the constitution of other acids generally, an acid is defined to be “a compound of hydro- gen with a simple or compound radical, in which the hy- drogen may be replaced by any other metal.’* LECTUEE L. Sulphur and Phosphorus. — Sulphureted Hydrogen . — Mode of Preparing it. — Its Odor, Acid Relations, and other Properties. — Extensively used as a Test. — Occurs in Nature. — Relations to the Animal System. — Bisul phureted Hydrogen. — Selenium. — Phosphorus. — Pre- pared from Bones. — Shines in the Dark. — Action of Light. — Comhustihility. — Compounds with Oxygeyi. SULPHURETED HYDROGEN. HS = 17T2. mg. 228. This gas may be eagily prepared by the ac- tion of hot hydrochloric acid on the native sul-' phuret of antimony pulverized, and may be collected over a saturated solution of salt or warm water. The action of the materials' being S\S^ -f ^[HCl) Sb^Cl^ + S{HS ) ; that is, one atom of the sesquisulphuret of an- What is the nature of the views now held in relation to the acids of sul- )hur, and acids generally ? Describe the process for preparing sulphureted lydrogen? SULPHURETED HYDROGEN. 229 tlmony and three of hydrochloric acid yield one of the ses- quichloride of antimony and three of sulphureted hydrogen. Sulphureted hydrogen is a colorless and transparent gas, having the odor of rotten eggs. It is absorbed by water readily, that liquid taking up two or three times its volume. Its specific gravity is 1*177. It is combustible, and 229 . may readily be burned from a jet placed in the flask in A which it is being evolved, the products of its combus- y tion being sulphurous acid and water ; but if the air 1 in which it is burned be limited in quantity, water alone is produced and sulphur deposited. Its solu- ! tion in water decomposes gradually by contact with the air, the hydrogen undergoing oxydation, and the K sulphur being set free. It has the properties of a weak acid, reddening litmus feebly, and yields with metallic bases wa- ter and sulphurets : MO + HS,.. HO + MS. many of these sulphurets being insoluble and highly col- ored : antimony gives an orange precipitate ; arsenic and cadmium, yellow; lead, brown; and manganese, flesh-col- ored. On this principle, the presence of sulphureted hydro- gen may be always detected : the carbonate of lead, for ex- ample, is blackened; and hence, white paint exposed in places in which sulphureted hydrogen is being evolved turns dark, and metallic silver tarnishes, and finally becomes black. By a pressure of about seventeen atmospheres the gas may be liquefied. The action of sulphureted hydrogen on metallic bodies may be illustrated in a very interesting manner by writing on a sheet of paper with a solution of acetate of lead, the letters being invisible until exposed to a stream of this gas, when they turn black. Its action in producing precipitates may be shown by conducting a stream of it through a solu- tion of tartar emetic, arsenious acid, or acetate of lead. Sulphureted hydrogen is sometimes naturally dissolved in spring water, constituting the mineral waters of various places, as the Virginia Springs. It is also said to be con- tained in the brackish water of the mouths of large rivers, due, perhaps, to the action of the organic matter they con- What are its distinctive properties ? What are the results of its com- bustion ? What is the nature of the precipitates it gives with metallic ox- ides ? How may this action be illustrated ? Is this gas soluble in water ? What is the probable cause of its occurrence at the mouths of large rivers ? 230 SELENIUM. — PHOSPHORtrS. tain upon the sulphates existing in the sea. It has been thought by some authors that the existence of this gas in the air of those places is connected with the fevers which there prevaiL Sulphureted hydrogen is exceedingly pois- onous when respired. There is another compound of sulphur and hydrogen, the constitution of which is not precisely known, though it is usually described as bisulphureted hydrogen, and its formula is therefore HS 2 . In its properties it is said to have sev- eral analogies with the deutoxide of hydrogen. SELENIUM. ^e = 39-6. This element was discovered by Berzelius in certain vari- eties of pyrites. It is a rare substance, analogous, in many respects, to sulphur. It burns in the air, forming an oxide which exhales the odor of decaying horseradish. PHOSPHORUS. P = 32. A remarkable substance, first discovered by Brandt, and how extensively procured from burned bones, in which it oc- curs as a phosphate of lime. It is found, also, in other ani- mal products, being an essential ingredient in fibrin and al- bumen, and also in the brain and nervous matter. To procure it, burned bones are reduced to powder, and digested with dilute sulphuric acid ; the liquid is strained, mixed with powdered char- coal, and, when dry, introduced into a stone-ware retort, a, Fig. 230, to the neck of which a bent copper tube, b, is at- tached, the mouth of which dips beneath water. The re- tort being now exposed in a furnace to a white heat, half the phosphoric acid in the mix- ture is deoxydized by the char- coal, carbonic oxide gas escap- ing, and phosphorus distilling over. Phosphorus is commonly transparent and colorless. When What other compound of sulphur and hydrogen is there ? What is sele- nium? From what source is phosphorus derived ? PROPERtIfiS OB' PHOSPHORUS. 231 exposed to the light it turns of a deep red, and this takes place in a vacuum, or in gases which have no action on the phosphorus. In lustre and general appearance it has a waxy aspect. Exposed to the air it smokes, and in a dark place shines — a property from which its name is derived. During this slow oxydation it exhales an odor much resem- bling that experienced when an electrical machine is in high activity. At 32° it is brittle, at 1 13° it melts, at 572° it boils, distilling over unchanged, if oxygen be absent. But in the air it takes fire and burns at about 120°, with evo- lution of fiakes of anhydrous phosphoric acid. Its specific gravity is 1 11 . From the intense affinity which phosphorus has for oxy- gen, it requires to be kept under the surface of water. It is met with in commerce in the form of small sticks, a form given to it by melting it in glass tubes under warm water, and pushing the resulting cylinders out as soon as they have set. If kept in an opaque bottle it is white, but it slowly turns more or less red on exposure to the daylight. From the facility with which it takes fire, it is necessary to handle it very carefully, and to avoid keeping it in con- tact with the warm hand too long. A few particles of dry phosphorus placed between two pieces of brown paper and rubbed with a hard body, take fire and burn furiously as soon as the papers are separated. It is upon this principle that it will readily inflame by the heat of friction, that its useful application in the manufacture of friction matches depends. In chlorine, or the vapor of bromine and iodine, it takes fire spontaneously. The red variety of phosphorus is commonly regarded as an allotropic modification, or phosphorus in the passive state. Its melting point is much higher than that of the ordinary phosphorus, being higher than 480°. It does not shine in the dark. Its specific gravity is 1'964. It shows no disposition to unite with sulphur, and does not oxydize in the air. There are several compounds of phosphorus and oxygen, as follows : What remarkable property does this body possess ? Why is phosphorus to be kept under the surface of water ? What is the action of light upon it ? What useful application is made of its ready combustibility ? What are the properties of the red variety of phosphorus ? How many compounds of phosphorus and oxygen are there ? 239 PHOSPHORUS AND OXYGEN. F^O ..FO.. FO^ . . FO,. These are respectively Oxide of phosphorus. I Phosphorous acid. Hypophosphorous acid. | Phosphoric acid. LECTURE LI. Compounds op Phosphorus and Oxygen. — Oxide of Fhosphorus. — Freparation of. — Hypophosphorous and Fhosphorous Acids. — Fhosphoric Acid . — Three States of Hydration. — Froperties of these three Acids . — Their Salts. — Fhosphureted Hydrogen. — Spontaneously In- flammable and No7i-inflammable Varieties. — Chlorine. — Freparation of — Its Relation to Combustion and Respiration. OXIDE OF PHOSPHORUS. P^O. This oxide may he formed by causing a stream of oxygen gas, from the tube, a. Fig. 231, to be directed upon phosphorus under hot water in a glass, b. A brilliant combustion under the water is the result, with the production of phosphoric acid and of a red powder, which is the substance in question. HYPOPHOSPHOROUS ACID, PO, is very little known ; it is formed when phosphorus is boiled in alkaline solutions. PHOSPHOROUS ACID, P03, is formed during the slow combustion of phosphorus in the air ; it may also be produced by acting on the sesquichlo- ride of phosphorus with water. The solution of this acid is sometimes used as a deoxydizing agent. PHOSPHORIC ACID, PO 5 . Anhydrous phosphoric acid is formed when phosphorus burns in dry air or oxygen gas {Fig. 232). It condenses in How is oxide of phosphorus made ? What is its appearance ? How are hypophosphorous and phosphorous acids produced ? Under what circum- stances is anhydrous phosphoric acid produced ? Fig. 231. ACIDS OF PHOSPHORUS. 233 •white flakes of a snowy appearance, and pos- sesses an intense affinity for water, in which, if placed, it hisses like a red-hot iron. It can scarcely be said to possess acid proper- ties. Until it has united with water, those properties are very feebly developed. With water, phosphoric acid unites in three proportions, producing Fig. 232. Monobasic phosphoric acid . . PO^-\~ ifO, or if-j-POg. Bibasic “ “ . . PO5-I-2PO, or 2P-|- PO7. Tribasic “ “ . . PO5 3if0, or POg. These acids also have the names of metaphosphoric, pyro- phosphoric, and common phosphoric acids respectively. Either of them may exist in solution with water. Metaphosphoric, or the monobasic phosphoric acid, may be obtained by dissolving phosphorus in dilute nitric acid, evaporating, and exposing the residue to a red heat. It may also be obtained by dissolving the anhydrous acid in water, evaporating and igniting it. In both these cases a transparent body, like ice or glass, is produced ; hence called glacial phosphoric acid. It contains one atom of water, which can not be removed from it by heat. Monobasic phosphoric acid is characterized by giving a white granular precipitate with nitrate of silver ; it also coagulates albumen, producing white curds. If kept in a solution of water, or boiled with it, it passes into the tribasic state. Pyrophosphoric, or bibasic phosphoric acid, may be ob- tained by heating the common phosphoric acid to 417° F. for some time. In solution it neither precipitates silver nor coagulates albumen, but its salts yield, with silver, a ffaky white precipitate. Like the former, this turns into the tri- basic acid by boiling with water. Common, or the tribasic phosphoric acid, may be obtained from bone earth by the action of the oil of vitriol, which yields a precipitate of sulphate of lime ; or, more easily, by boiling a solution of the anhydrous phosphoric acid. In so- lution it neither precipitates silver nor coagulates albumen, but its salts yield a Canary-yellow precipitate with the ni- How many compounds does it yield with water ? How is metaphosphor- ic acid made ? What is g^lacial phosphoric acid? What are the properties , characteristic of monobasic, bibasic, and tribasic phosphoric acids respect- ively ? 234 PHOSPHURETED HYDROGEN. Irate of silver. By exposure to a low heat it becomes bi- basic, and to a red heat, monobasic. These hydrogen acids of phosphorus give rise to a very extensive and complex class of salts, according to the ex- tent to which their hydrogen is replaced by metallic bodies. Thus the monobasic phosphoric acid can yield only one series of salts, in which all its hydrogen is replaced by a metal ; but the bibasic can yield two different series, accord- ing as the metal replaces one or both atoms of base ; and the tribasic can yield three different series, according as one or two, or all three of its hydrogen atoms are replaced. , PHOSPHURETED HYDROGEN, PH^ = 34*4, may be made by boiling phosphorus in a strong solution of lime or potash in a retort, Fig. 233, the neck of which dips beneath the surface of water, a few drops of ether being previously put into the retort. As the bubbles of gas break on the water, they take fire, burning with a bright yellow light, and there ascends through the air a ring of gray smoke, which dilates as it rises, and exhibits a curious rota- tory movement of its parts. This gas, also, may be made by bringing the phosphuret of calcium in contact with water. Phosphureted hydrogen is a colorless gas, exhaling a pe- culiar odor, like garlic, and, when burning, produces phos- phoric acid and water. It exists under two forms ; 1st. Spontaneously inflammable ; 2d. Kot spontaneously inflam- mable. It is said that the first may be changed into the second by small quantities of the vapor of ether, oil of tur- pentine, &c., and the second into the first by the addition of a minute quantity of nitrous acid. How many series of salts can each class yield ? Describe the preparation of phosphureted hydrogen ? What are the properties of phosphureted hy- drogen ? How may its two forms be ponverted into each other ? PREPARATION OF CHLORINE. 235 CHLORINE. C/== 35-47. Chlorine is found abundantly in nature in union with so- dium, forming common salt, a substance which, for the most part, gives to the sea water its salinity, and constitutes the deposits of rock salt. It is, therefore, an abundant sub- stance. Chlorine is best made by the action of hydrochloric acid on peroxide of manganese : MnO^ + 2HCl.,. = . .,MnCl+2HO+ Cl; that is, one atom of peroxide of manganese and two of hy- drochloric acid yield one atom of the chloride of manga- nese, two of water, and one of chlorine. Half the chlorine is, therefore, given off as chlorine gas, and the other half remains as chloride of manganese. Chlorine gas being very soluble in cold water, and act- ing with great energy on mercury, it can neither be collected at the water nor mercu- rial trough ; but, having a specific gravity of 2*470, we are able to collect it by the niethod of displacement, as shown in Fig. 234. It may, however, also be collected over warm water or a saturated solution of common salt. When chlorine is required in a state of dryness, it may be obtained by an apparatus like that represented in Fig. 235. a is the retort containing the hydrochloric acid and man- Fig. 234. ganese. It is connected with a small receiver, h, which re- tains part of the water which the gas may bring over ; this. In what substances does chlorine chiefly occur ? How may it be formed ? What are its properties ? How is it procured in a state of drj'ness ? 236 PROPERTIES OF CHLORINE, again, is connected with a chloride of calcium tube, c, which effects the perfect drying of the gas. Chlorine is a gas of a pale yellowish green color. It may be liquefied by a pressure of four atmospheres. A taper immersed in it burns for a few minutes with a dull red flame, emitting volumes of smoke, due to the fact that the Fig. 236. liydrogen of the flame continues to burn or unite with the chlorine, forming hydrochloric acid ; but the carbon, having little aflinity for chlorine, is set free in an uncombined state, as lampblack. Pow- dered antimony, or thin brass leaf, plunged in this gas, becomes incandescent, and burns, producing a chloride. A piece of phosphorus immersed in it takes fire at common temperatures, and burns with a pale flame. The smell of chlorine is dis- agreeable, and its effect, even in a diluted state, suffocating. It irritates the air passages of the lungs, producing hiccough and an unpleasant expectoration. LECTURE LII. Chlorine, continued. — Bleaching Properties.- — Combus- tion of Hydrocarbons. — Disinfecting Qualities. — Com- pounds with Oxygen. — Properties of Hypochlorous^ Chlorous^ and Chloric Acids . — Quadrochloride of Ni- trogen. — Hydrochloric Acid. — Preparation in the Gas- eous and Liquid States. The most valuable property of chlorine is its power of discharging vegetable colors, on which is founded its appli- Fi 237 bleaching and calico printing. ■ This property may be illustrated in many ways. By pouring a solution of litmus or indigo through a fun- j\| nel, a. Fig. 237, into a flask, b, containing chlorine # decoloration takes place instantly, or, if the i hi color is not completely discharged, it will be found, in a short time, to disappear. The same takes place when a solution of chlorine in water is used. What are its relations in the combustion of a taper, and how does it act on certain metals and phosphorus ? What is its effects on the animal sys- tem ? Of the properties of chlorine, which is the most valuable ? How may it be illustrated ? PROPERTIES OF CHLORINE. 237 The peculiarities of chlorine in supporting com- 238. bustion are remarkable, when compared with those of oxygen gas. A piece of paper, Fig. 238, dipped in oil of turpentine, takes fire in a moment at com- mon temperatures when placed in ajar of chlorine, and, as we have seen, phosphorus and several of the metals undergo spontaneous ignition in the same manner. These phenomena depend on the intense affinity which chlorine has for electro-positive bod- ies, but it is very remarkable that it seems to have little dis- position to unite with carbon. As in the burning of a taper, so in this experiment with turpentine, it is the hydrogen which burns, and the carbon is evolved in clouds of smoke. Chlorine is also used by physicians for the purpose of destroying miasmata, and the effluvia of sick rooms or oth- er places. It is necessary, from its irrespirable qualities, to disengage it slowly and with caution where patients are present. The chlorides of soda and lime are commonly used. Free chlorine maybe detected by its smell, its bleaching action on indigo solution, and giving a white, curdy precip- itate with the nitrate of silver. Its solution in water is readily made by introducing a small quantity of water into a bottle full of chlorine, agitating it, and opening the mouth of the bottle from time to time under water ; the gas being gradually absorbed, the bottle becomes full of water, which, of course, contains its own volume of chlorine. This solu- tion decomposes in the sunshine, evolving oxygen gas, the water being decomposed. "With oxygen chlorine unites in several proportions, producing CIO . . CIO^ . . CZO 5 . . CIO,. They are designated Hypochlorous acid. I Chloric acid. Chlorous acid. | Perchloric acid. HYPOCHLOROUS ACID. = 43-483. Hypochlorous acid may be obtained by agitating the red oxide of mercury, suspended in water, with chlorine. If a strong solution of it be placed in an inverted tube, and^ What is the cause of the clouds of smoke deposited when carburets of hydrogen bum in chlorine gas ? For what purpose is chlorine used by phy- sicians? How may chlorine be detected? How may a solution of it be made ? What compounds of chlorine and oxygen are known ? How is hy- pochlorous acid made, and what are its properties ? 238 ACIDS OF CHLORINE. pieces of diy nitrate of lime be added, the gas is disengaged, and rises to the top of the tube. It is of a deeper color than chlorine, bleaches powerfully, and, by a slight eleva- tion of temperature, explodes, evolving two volumes of chlo- rine and one of oxygen gas. The bleaching compounds are compounds of chlorides and hypochlorides. They are easily decomposed by acids. Thus, when chloride of lime is to be used for disinfecting pur- poses, it is merely required to expose it with water to the carbonic acid of the air, or to add a little of it, from time to time, to a vessel containing dilute sulphuric acid. CHLOROUS ACID, 0/0^= 67 522, may be made by cautiously acting on small quantities of chlorate of potash with sulphuric acid. It is a yellow gas, which explodes furiously from very slight causes, the warmth of the hand being often sufficient to give rise to a violent action. It contains two volumes of chlorine and four of ox- ygen, condensed into four volumes. It may be convenient- ly made by operating on a few grains of the chlorate in a Fig. 239 . test tube. If into a glass, a. Fig. 239, contain- ing water, a small quantity of chlorate of pot- ash is placed, and upon it a few fragments of phosphorus, and sulphuric acid be poured through a funnel, so as to act on the chlorate, chlorous acid is set free ; it communicates a golden yel- low color to the water, and as each bubble pass- es by the phosphorus it sets it on fire, furnishing a beauti- ful instance of combustion under water. CHLORIC ACID, 0/05 = 75*535, may be made by decomposing the chlorate of baryta by sul- phuric acid, and evaporating the solution. It is a yellow, viscid acid : a piece of paper dipped in it is set on fire. It does not bleach. It forms salts, one of which, the chlorate of potash, is of considerable importance, and is used for the preparation of oxygen. A few grains of the chlorate of potash, ground in a mortar with a pinch of flowers of sul- phur, explodes incessantly during the trituration. PERCHLORIC ACID. 0/0^ = 91*561. The perchlorate of potash forms along with the chloride What are the properties of chloric acid ? How may the combustion of phosphorus under water be produced by it ? How is chloric acid made ? HYDROCHLORIC ACID. 239 of potassium when one third of its oxygen is expelled from chlorate of potash; the two salts may be separated* from each other by boiling in water, the perchlorate crystallizing on cooling. From this perchloric acid may be obtained by distil- lation with an equal weight of oil of vitriol, mixed with half as much water. It may be obtained in the form of a white crystalline mass, very deliquescent, and its solution is some- times used as a test for potash, with which it gives a sparing- ly soluble salt. The solution fumes in the air, has a specific gravity of 1*65, and does not possess bleaching properties. CHLORINE AND NITROGEN. These substances unite, forming an oily liquid, when a warm solution of sal ammoniac is exposed to chlorine gas. The resulting body is regarded as a quadrichloride of nitro- gen (JVCIJ. By its violent explosions, several eminent chemists have been seriously injured. The mere contact of oily matter produces a detonation. CHLORINE AND HYDROGEN. HYDROCHLORIC ACID. = 36*47. This acid, called also muriatic acid, is easily prepared by placing in a flask six parts of common salt and ten parts by weight of oil of vitriol, mixed with four of water, the mixture being sufiered to cool before it is introduced. On heating the mixture, hydrochloric acid is evolved, which passes along a bent tube into a bottle containing six parts (by weight) of water. The end of the tube dips but a very short distance beneath the surface of this water, so that if the liquid should rise it may be received into a ball blown upon the tube, and the extremity of the tube becoming uncov- ered, atmospheric air may pass into the interior of the flask. At the close of the process, the liquid in the bottle, which should be constantly surrounded by ice water in a small tank, more than doubles its volume, and is a pure solution of hydrochloric acid. The action is Na Cl + 2{HO, 80^)... = .. . HCl + (iVaO, HO, 2SO,) ; that is, one atom of chloride of sodium and two of sulphuric acid yield one atom of hydrochloric acid and one of the bi- sulphate of soda. How is perchloric acid prepared, and for what purpose is it used ? What made ? chloride of nitrogen ? How is hydrochloric acid 240 HYDROCHLORIC ACID. From the liquid thus produced, or from the commercial muriatic acid, by heating in a flask, pure hydrochloric acid gas may be obtained ; it may also be less advantageously procured by the direct action of strong oil of vitriol on com- mon salt, the reaction in this case being NaCl -+• HO, SO^ . IICl + NaO, SO^, Pure hydrochloric acid is a transparent, colorless gas, possessing powerful acid qualities, very absorbable by wa- ter, which liquid takes up several hundred times its own volume of the gas ; it fumes in moist air, and has a pungent odor. If a dry Florence flask {Fig. 240) be filled with it by the process of displacement, and the mouth of it opened un- der the surface of cold water, the water rushes up into the flask, absorbing the gas with great violence. The specific gravity of hydrochloric acid is 1-284. It contains equal volumes of its constituents, united without condensation. LECTURE LIII. Chlorine, co’^^mv'ED.— Production of Hydrochloric Acid ly Light. — Action of Hydrochloric Acid on Metallic Protoxides . — Muriatic Acid Solution. — Detection of Hydrochloric Acid. — Nitro-muriaiic Iodine. — Sources of. — Preparations and Properties . — Tests for Iodine. — Its Action on Starch. — Hy dr iodic Acid . — " Oxygen Compounds of Iodine. Pure hydrochloric acid gas is also obtained when a mix- ture of chlorine and hydrogen, in equal proportions, is ex- posed to the light. In the dark these gases appear to have no disposition to unite, but if they be placed in a flask cov- ered over with a wire screen, and a beam of the sunlight reflected upon them from a looking-glass, a violent explosion ensues, and hydrochloric acid is formed. I have found that, in this remarkable experiment, the How may the gas be procured ? What are the properties of hydrochloric acid gas 1 How may its affinity for water be proved ? What is its con- stitution ? What is the action of sunlight on a mixture of chlorine and hy- drogen ? Fig. 240. PROPERTIES OP HYDROCHLORIC ACID. 241 action is chiefly duo to the chlorine, which, from being in a passive, assumes an active state by exposure to rays of an indigo color. It may be thrown into the same condition in many other ways ; lor example, by the contact of spongy platina. Moreover, when chlorine by itself has been ex- posed to the sun, it gains the quality of uniting more easily with hydrogen than chlorine which has been made and kept in the dark. When hydrochloric acid is brought in contact with me- tallic oxides, decomposition of both ensues, and metallic chlo- rides are formed, thus : MO -f HCl MCI 4- HO; or, M2O3 + 2>{HCl) .M^Cl^ + 3HO; that is, one atom of a metallic protoxide with one atom of hydrochloric acid yields one atom of a protochloride of the metal and one of water. But, in the case of a sesquioxide, one atom of it with three of hydrochloric acid yield one atom of the metallic sesquichloride and three of water. The constitution of hydrochloric acidj and its ac- tion on metallic oxides, may be strikingly illustrated by taking a flask, b {Fig. 241), filled with it, in a perfectly dry state, and allowing the peroxide of mercury, in fine powder, to fall through it. The bi- chloride of mercury, corrosive sublimate, instantly forms, and drops of water make their appearance on the sides of the flask. It is under the form of a solution in water, as liquid mu- riatic acid, or spirit of salt, that hydrochloric acid is chiefly used. The mode of obtaining it has been described in the last Lecture. This liquid, when concentrated, has a speci- fic gravity of 1’21, and contains 42 per cent, of acid. It smokes in the air, and reddens blue litmus powerfully. The commercial acid is usually .of a ^^ellow color ; it contains chloride of iron, derived from the iron vessels from which it is distilled. It also often contains sulphuric acid, chlorine, sulphurous acid, tin, or arsenic, and is, therefore, best pre- pared by the process described, which yields it in perfect pufity. Hydrochloric acid may be detected by yielding, when in To which of these bodies is this action due ? What is the action of hy- drochloric acid on metallic oxides ? What arc the products of the action of hydrochloric acid on peroxide of mercury ? What arc thp properties of liquid muriatic acid ? What are its impurities ? L 242 NITRO-MURIATIC ACID. Fig. 242. ^ state with ammonia, dense white clouds of sal ammoniac. If two glasses, one filled with this acid, and the other with ammonia, be brought near each other, a white cloud forms between them. A glass rod, a {Fig. 243), dipped in am- monia, may be used for the same pur- Fig. 243. pose. With nitrate of silver, hydro- chloric acid yields a white chloride of silver, which turns black in the light, being the same precipitate given under the same circumstances by free chlorine. From this latter substance it may be distinguished by litmus water, which is bleached by chlorine, and reddened by hydrochloric acid. Nitro-muriatic acid, or aqua regia, is formed by adding to hydrochloric acid one half or a third of its volume of ni- tric acid. The nitric acid, furnishing oxygen to the hydro- chloric acid, forms water, and chlorine, with nitrous acid, is set free in the solution. Aqua regia is used as a solvent for platina and gold, a result which may be illustrated by placing a sheet of gold leaf in the mixture. IODINE. J=126'57. • Iodine chiefly occurs in the products of the sea, being found in sea- weed ^ sponge, &c. ; and also in certain brine springs, and in some ores of silver and zinc. It may be obtained by lixiviating the ashes of sea-weeds, and evaporating the solution until no more crystals are de- posited. The residual liquor is then acted upon by sulphuric acid, and subsequently heated with peroxide of manganese, in a leaden retort, ah c {Fig. 244, page 243), the iodine distills over into the receivers, d. It is a solid substance, of a deep blue or black appear- ance, with a semi-metallic lustre, communicates to the skin a fugitive yellow stain, and exhales an odor like that of sea beaches. It crystallizes in rhomboidal plates, is brittle, and has a specific gravity of 4-948. At 225^ it melts, and boils at 347^, exhaling, even at moderate temperatures, a splendid purple vapor, from which its name is derived. The specific gravity of this vapor is 8*707 ; it is, therefore, one of the heaviest gaseous bodies known. - How may hydrochloric acid be detected? What is the preparation and property of nitro-muriatic acid? From what source is iodine procured? What is the method of its preparation? What is its appearance? What is the color of its vapor ? From what circumstance is its name derived ? IODINE. 243 Fig. 245. Fig. 246. Iodine supports combustion much in the same manner as chlorine. A jar, a {Fig. 245), con- taining a few grains of it, placed in a small sand bath, b, and warmed by a spirit lamp, c, may be easily filled with its dense vapor, the atmos- pheric air floating out before it. In this vapor, if a lighted taper is plunged, it exhibits a retard- ed combustion ; but a piece of phosphorus, intro- duced on a spoon, takes fire and burns. In the same manner, if a quantity of iodine be placed in a small capsule, and upon it a fragment of dry phos- phorus {Fig. 246), spontaneous ignition en- sues, Avith the evolution of phosphoric acid, and the vapor of iodine, iodide of phosphorus, remaining in the capsule. In Avater, iodine is but slightly soluble, that liquid taking up weight, and assuming a brown color. Al- cohol dissolves it freely, forming tincture of iodine. In solutions of the iodides, iodine may be dissolved. With many substances iodine gives characteristic reac- tions. The iodide of potassium, with the acetate of lead, yields a golden yellow precipitate ; with the bichloride of What are its relations as resDects combustion 1 Is it soluble in water and alcohol ? ^ 244 IIYDIUOCIC ACID. mercury, a fine scarlet-colored biniodide. This substance ; possesses the singular quality that, if dried and sublimed in a tube, it yields crystals of a brilliant yellow aspect, which become red on being simply touched with a hard body. With a solution of starch, free iodine yields a deep blue color, the solution becoming colorless if heated, but the blue color returning on cooling, provided the temperature has not been carried to the boiling point. If a potato be cut in two, and a little tincture of iodine poured on the surface, innumera- ble blue specks make their appearance, each corresponding to the position of a granule of starch. Starch and free iodine will, therefore, mutually detect the presence of each other. HYDRIODIC ACID. 7/1= 127*57. Hydriodic acid gas may be obtained by dissolving in a so- lution of iodide of potassium as much iodine as it will hold, adding small pieces of phosphorus, and warming the mix- ture. A colorless transparent gas is evolved, which fumes in the air, and may be collected over mercury. Its specific gravity is 4*384. It has the general relations of hydro- chloric acid, and, like it, is very soluble in water. Fig. 247. A solution of hydriodic acid in water may be made by passing a stream of sulphureted hydro- gen from a flask, a {Fig. 247), through water, bi in which iodine is suspended. The acid forms, and sulphur is deposited : 1+ HS...=z HI. With nitrate of silver this acid yields a pale yellow pre- cipitate, the iodide of silver. This is the substance which forms the basis of the remarkable compound used in the Daguerreotype. In that case it is formed by holding a plate of pure polished silver in the vapor of iodine ; the plate tarnishes and turns yellow, and, if set in the sunshine, turns promptly of a deep olive black. Iodine yields two oxygen acids, iodic {10^ and periodic acid (/O 7 ). With nitrogen, also, it gives character- ized, like the analogous compound of chlorine, by the facility with which it explodes. How may it be detected ? In what manner is hydriodic acid made ? What is the simplest method of obtaining a solution of it ? What is the precipitate it yields with nitrate of silver? What are the oxygen com- pounds of iodine ? BROMINE. 245 LECTURE LIV. Bromine. — Fluorine. — Bromine. — Sources of. — Proper^ ties. — Compounds of. — Fluorine. — Hydrofluoric Acid. — Its Properties and Action on Glass . — Carbon. — Al- lotropic Forms of. — Preparation of some of those Forms. — Diamond. — Oxygen Compounds of Carbon. — Car- bonic Oxide. BROMINE. Br = 78-39. Bromine occurs in sea water, and also, to a more consid- erable extent, in certain brine springs both in America and Europe. From these it may be obtained by evaporating the water until the salt solution is concentrated, and after the chloride of sodium has crystallized from the liquor, pass- ing through it a current of chlorine gas, the solution turning yellow as the bromine is set free. It is next agitated with sulphuric ether, which carries to the surface all the bro- mine. This is then acted on by potash, which gives a mix- ture of bromate of potash and bromide of potassium. On ignition, oxygen is expelled, and the whole converted into the latter salt, from which the bromine may be distilled by the aid of peroxide of manganese and sulphuric acid. It is a liquid of a deep blood-red appearance, solidifying at — 40° F., and boiling at 113° F. Its specific gravity is 2-99. It exhales an orange vapor, and is commonly kept beneath the surface of water. Its smell is very disagree- able, a circumstance from which its name is derived. Like chlorine, it bleaches, and in all its relations possesses a gen- eral resemblance to that substance. A lighted taper burns for a short time in its vapor with a greenish flame. Phos- phorus burns spontaneously in it. Bromine yields a hydrogen acid {HBr), hydrobromic acid, and with oxygen, bromic acid [BrO^. In their general properties these bodies resemble the corresponding com- pounds of chlorine. The bromide of silver is much more sensitive to light than either the chloride or iodide. FLUORINE, E= 18-74, is found in combination with calcium, as the fluoride of cal- From what source is bromine obtained ? What are the properties of bro mine, and to what bodies has it a close analogy ? 246 CARBON. cium, or fluor spar. It occurs also in the topaz and other minerals. In the enamel of teeth and in bones it has been detected, especially in fossil bones, which sometimes contain as much as ten per cent, of fluoride of calcium. The special properties of fluorine are as yet unknown, for it has not been isolated. Various attempts have been made at different times, but without satisfactory results. It pos- sesses an intense affinity for electro-positive bodies, and gives rise to a series of compounds resembling those of chlorine, iodine, &c. It does not unite with oxygen. HYDROFLUORIC ACID. HF=1974. This energetic acid may be obtained by decomposing fluo- ride of calcium by sulphuric acid in a vessel of platina or lead, the vapors being conducted into a metallic receiver kept at a low temperature. The action is CaF+HO, SO ^.. . = . . . CaO, SO^ + HF. It is a smoking liquid, which acts powerfully on the skin, boils at a temperature of a little above 60 ^ F., and possesses the remarkable quality of corroding glass. If a piece of glass be coated over with a thin film of bees’ wax, and letters or other marks made through the wax to the glass with a pointed implement, on setting it over a vessel of lead or tin in which, from a mixture of fluor spar and sulphuric acid, hydrofluoric acid is escaping in vapor, the glass is deeply etched on all those parts which have been uncovered, as is seen when the wax is removed. Liquid hydrofluoric acid may be employed for the same purpose, but the letters are not so visible as when the vapor is used. CARBON. 0 = 604. This, which is one of the most interesting and important of the elementary bodies, occurs under many different natu- ral forms. It is an essential ingredient in the structure of all animal and vegetable beings ; it is found in various states in the air, the sea, and the crust of the earth. The striking peculiarity of carbon, which at once arrests our attention, is the different allotropic conditions under which it is presented. This substance may be said to yield in itself a whole group of elementary bodies. Among these Are the special properties of fluorine known ? How is hydrofluoric acid made ? What remarkable quality does it possess ? From what sources may carbon bo procured T What is its most striking property ? FORMS OF CARBON. 247 might he enumerated, (1.) Diamond, which crystallizes in octahedrons, is transparent, incombustible, except in oxygen gas, and the hardest body known ; hence its use in cutting glass. (2.) Gas-carbon, which, unlike diamond, is a good conductor of electricity, and is opaque. (3.) The various forms of charcoal, anthracite coal, and coke. (4.) Plumba- go, which has a metallic lustre, is opaque, and so soft and unctuous that it is used to relieve the friction of machinery. (5.) Lampblack, a powerful absorbent of light and heat, and possessing such strong affinity for oxygen that it can take fire spontaneously in the air. Other forms of carbon might be cited ; these, however, are enough to establish the fact that this single body fur- nishes varieties which differ more strikingly from each other than many different metallic bodies. Charcoal is made by the ignition of wood in close ves- sels, the volatile materials being dissipated and the carbon left. The nature of the process may be illus- J Ij trated by taking a slip of wood, d, Fig. 248, and plac- jM ing its burning extremity in a test tube, a. This re- tards the access of the surrounding air, and, as the combustion proceeds, a cylinder of charcoal is left. Tig. 249 . Lampblack, is formed on a similar principle. In the iron pot, a, Fig. 249, some pitch or tar is made to boil, a small quantity of air being ad- mitted through apertures in the brickwork. Imperfect combustion takes place, the hydrogen alone burning, the carbon being carried as a dense cloud of smoke into the chamber ^ c by the draft. In this there is a hood, or cone, of coarse cloth, which may be raised or lowered by a pulley. The sides of the chamber are covered with leather, and on these the lampblack collects. Diamond is the purest form of carbon. Its specific grav- ity is 3*5 : it exhibits a high refractive and dispersive action upon light. Charcoal possesses, in consequence of its por- ous structure, the quality of absorbing many times its own Mention some of its allotropic forms. How are charcoal and lampblack made ? What are the properties of diamond ? 248 CARBONrC OXIBE. volume of different gases. Ivory black, which is made by the ignition of bones in close vessels, has the valuable qual- ity of removing organic coloring matters from their solu- tions : a property which may be shown by filtering a solu- tion of indigo through it. In all its forms, carbon seems to be infusible, but when burned in air or an excess of oxygen, they all give rise to carbonic acid gas. It combines direct- ly with several of the metals, yielding carburets. With oxygen it gives two compounds, CO designated respectively as carbonic oxide and carbonic acid. CARBONIC OXIDE, CO = 14 053, is produced when carbon is burned in a limited supply of 'oxygen, or when carbonic acid is passed over red-hot iron or over red-hot carbon. In these cases the actions are : CO 2 + C ...rzr...2(CO). CO 2 + Fe... = ...CO + FeO. In the first the carbonic acid unites with one atom of carbon, and yields two of carbonic oxide ; in the second, it loses one atom of oxygen to the iron and yields one of Ei^. 250 . carbonic oxide. It may also be pre- pared by heating oxalic acid with oil of vitriol in a flask, a. Fig. 250, the decomposition giving equal volumes of carbonic acid and carbonic oxide, as is explained under oxalic acid. The acid may be separated by passing the mix- ture through a bottle, 5, containing potash water, and the Fig. 25 i. oxide collected over water. But the best process for procuring it is to heat one part of prussiate of potash with ten of oil of vitriol in a retort : the carbonic oxide comes over in a state of purity. As obtained by any of these processes, it is a colorless gas, which may be kept over water, in which it is only sparingly soluble. It is without odor, and is irre- spirable. A j et of it burns in the air with What are the properties of ivory black? What are the oxygen com- pounds of carbon ? What is the action of carbon and of metallic iron on carbonic acid at a red heat ? How is carbonic oxide produced from oxalic acid ? From what other substance may it be procured ? CARBONIC ACID. 249 a beautiful blue flame, combining with oxygen and yielding carbonic acid. Its specific gravity is O’ 97 22 : it has never been liquefied. It is the combustion of this gas which pro- duces the blue flame often seen in a coal fire. Carbonic oxide is a compound radical, giving origin to a series of bodies. LECTURE LV. Carbonic Acid. — Methods of Preparation hy Decomposi- tion and Combustion, — General Properties, and Rela- tion to Combustion and Respiration. — Its Solution in Water. — Exists in the Breath. — Its Liquid and Solid Forms. — Light Carbureted Hydrogen. — Marsh Gas. — Natural and Artificial Production. — Olefiant Gas. — Action ivith Chlorine. CARBONIC ACID. C02 = 23-066. Carbonic acid is commonly prepared by the action of dilute hydrochloric acid on chalk, or any carbonate of lime, the action being CaO, CO., + HCl CaCl, HO + CO,\ that is one atom of carbonate of lime and one 252. of hydrochloric acid yield one atom of chloride of calcium and one of water, and one atom of carbonic acid gas is set free. The process may be conducted in a flask, as in the figure, the gas being evolved so rapidly that it may be collected over water, though that liquid ab- sorbs it very freely. Carbonic acid is abundantly formed in many processes. It is the result of the complete combustion of carbonaceous bodies, is evolved during the respiration of animals, and in alcoholic fermentation. It is the fixed air of the older chemists. It is a colorless and transparent gas at common temper- atures, with a faint smell and slightly acid taste. It is ir- What are the properties of carbonic acid gas 1 How is this gas made ? Under what circumstances is carbonic acid formed during combustion ? In what other processes does it appear? L 2 250 CARBONIC ACID. respirable, and acts in a diluted state as a narcotic poison ; even air, containing one tenth of its volume of this gas, pro- duces a marked effect. Its specific gravity is 1-527, and it may, therefore, be collected by displacement {Fig. 253). For the same reason, it collects in the bottom of wells and pits, and often suffocates workmen who de- scend into such places. It does not support combustion ; a lighted taper lowered into a jar partly filled with it is extinguished the moment it reaches the gas. It may be poured from one vessel to an- other ; and if a jar of it is poured upon the flame of a can- dle, the light is at once extinguished. Its density and other qualities may be well illustrated when it is formed by the action of fuming nitric acid on carbonate of ammonia, a smoky cloud marking its position and movements. Carbonic acid reddens litmus water, but the blue color Fig. 254. restored on boiling, the acid being Fig. 255. n driven off by the heat. It is soluble I: in water, which, under increased Ij pressure, takes up several times its II volume of it, constituting the soda II water of the shops. Its solubility may be established by agitating it with water in Hope’s eudiometer. Fig. 254, or by passing it through Nooth’s soda-water machine. Fig. 255. A common test for the presence of car- bonic acid in wells is to lower a lighted candle, and if its flame be extinguished, it is inferred that the gas is present ; but it does not follow that a man may safely descend into such places though a candle will continue to burn. If, through a tube, the breath be made to pass into lime- water, a deposit of carbonate of lime renders the water milky ; or, if the breath be conducted through litmus water, the color changes to red ; the air thus expired from the lungs contains three or four per cent, of carbonic acid. Under a pessure of thirty-six atmospheres, carbonic acid condenses into a liquid characterized by the extraordinary What are the properties of carbonic acid ? What are its relations to com- bustion? What is its specific gravity? What is soda water? How may- carbonic acid be detected ? How can its existence in the breath be proved ? Fig. 2.53. CARBON AND HYDROGEN. 251 quality that it is four times more expansible by heat than even atmospheric air. This liquid, when allowed to escape through a jet, evaporates so rapidly, and produces so much cold, that a portion of it instantly solidifies. Solid carbonic acid is a substance not unlike snow; mixed with alcohol or ether, it produces a degree of cold equal to — 180° Fahr. Although carbonic acid has the name of an acid, it pos- sesses the properties indicated by that term in a feeble de- gree. The gas contains its own volume of oxygen. The common test for its presence is lime-water, which is render- ed turbid by it. CARBON AND HYDROGEN. These substances unite, producing many compounds, some of which are solid, some liquid, and others gaseous. They are, of course, all combustible bodies, and the description of nearly all of them belongs to organic chemistry. LIGHT CARBURETED HYDROGEN, CH2 = 8 04, occurs abundantly in coal mines, and forms with their at- mospheric air explosive mixtures ; it is also found during the putrefaction of vegetable matter under water ; on stirring the mud of ponds, bubbles of this gas escape ; hence the name marsh gas. It may be obtained artificially by heat- ing acetate of potash with hydrate of baryta. (7TO) + + {BaC. ^O) , {KO, CO,) + {BaO, CO,) + 2Cir,; that is, one atom of acetate of potash with one of hydrate of baryta yield one of carbonate of potash, one of carbonate of baryta, and two of light carbureted hydrogen gas, the acetic acid being decomposed, by the aid of water, into car- bonic acid and marsh gas. It is a colorless gas, burns with a yellow flame, producing water and carbonic acid. Its specific gravity is 0*555, forms explosive mixtures with air, and is the fire-damp of coal mines. The choke-damp, which exists in mines after an explosion, is carbonic acid gas, orig- inating from the combustion. This gas is decomposed by chlorine in the light, but not in darkness. What are the properties of liquid and solid carbonic acid t What is the test for it ? How may light carbureted hydrogen be made ? Where is it found naturally ? Of what does the explosive gas of coal mines consist ? 252 OLEFIANT GAS. OLEFIANT GAS. Olefiant gas may be made by heating one part of alcohol Fig. 256. with four of sulphuric acid in a flask, a, Fig. 256. The vapor of ether which comes over with it may be removed by causing the gas to pass through a small bottle, 5, containing sulphuric acid, be- fore being collected at the trough. It ' may also be obtained by an apparatus such as Fig. 257, in which b is the flask containing alcohol Fig. 258. and sulphuric acid, and a an interposed globe to receive the ether, oil of wine, and water, which distill over. Olefiant gas is transparent and color- less ; burns with a beautiful flame {Fig. 258) ; forms an explosive mixture with oxygen, giving rise by its combustion to carbonic acid and water. If mixed with an equal volume of chlorine, the gases [ condense into an oily liquid, from which olefiant gas has received its name. With twice its volume of chlorine, if it be set on fire, hydrochloric acid is formed, and carbon is deposited as a dense black smoke. Olefiant gas also exists as one of the chief ingredients in the gas employed for illuminating cities. ; How is olefiant gas prepared ? What are the products of combustion of olefiant gas ? What is the action of chlorine on it ? From what has it de- xived its name ? CYANOGEN* 253 LECTURE LVL Cyanogen. — Modes of Preparation. — Liquefaction. — An Electro-negative Compound Radical. — Bisulphuret of Carbon. — Boron. — Boracic Acid . — Terfluoride of Bo- ron. — Silicon. — Silicic Acid. — Fluoride of Silicon. — Compounds of Hydrogen and Nitrogen. — Amidogen. — Ammonia. — Ammonium . — Theory of Berzelius. CYANOGEN, Cy..OR BICARBURET OF NITROGEN. C^N=26.23. Carbon unites with nitrogen, forming a bicarburet, when these substances are in the nascent state and in presence of a base. It may be obtained very easily by exposing the cyanide of mercury to heat, or by heating a mixture of six parts of ferrocyanide of potassium and nine of corrosive sub- limate. It is a colorless gas, having a peculiar odor. It burns with a beautiful purple flame, dissolves readily in water, and still more so in alcohol, condenses into a liquid by a pressure of 3’ 6 atmospheres at 45° Fahrenheit, as may be shown by heating with a lamp cyanide of mercury in a bent tube, as seen in Fig. 259 ; the tube being Fig. 259. closed at both ends, liquid cyanogen accu- mulates at the cool extremity. Though a compound body, it has all the properties and characters of a powerful electro-negative ele- ment. A farther description of it and its compounds will be given under organic chemistry. BISULPHURET OF CARBON, = 38-28, may be made by passing the vapor of sulphur over char- coal ignited in a tube, and receiving the product in a cold bottle ; the apparatus is represented in Fig. 260. Into the top of a large iron bottle, two tubes, h c, one straight and the other bent, are inserted ; the bottle having been filled with charcoal, pieces of brimstone are dropped in through the tube h as soon as the bottle is red hot. The sulphur and carbon unite. The product passes along the tubes cf cooled How is cyanogen made ? How may it be condensed into a liquid ? How is bisulphuret of carbon formed ? BORON. — -BORACIC ACID. S54 by a stream of water from the cock, d, the water being con- ducted by a string, h, into a basin, x. The vapor passes into the bottle, ?^, which is partially filled with ice, and the incondensable gases pass out through m. It is a transpa- rent liquid of a very disagreeable odor, has the quality of dissolving sulphur and phosphorus, boils at 108® Fahren- heit, and is therefore very volatile. BORON, 5 = 10*9, was discovered by Davy as the basis of boracic acid, from which it may be set free by potassium at a red heat. It is an olive-colored solid, which burns when ignited in oxy- gen gas or atmospheric air, and produces boracic acid. BORACIC ACID. 503 = 34*939. Boracic acid exists in the waters of the volcanic springs of Tuscany. It is also brought from India combined with soda, and may be artificially procured by dissolving one part of bo- rax in four of hot water, and adding half apart of sulphuric acid. On cooling, the boracic acid is deposited in small crys- Fig, ^61, talline scales, which may be purified - by recrystallization. Boracic acid melts at a red heat _ into a transparent glass. Its crystals, raised to 212® Fahrenheit, lose half , their water. It Volatilizes readily when boiled in water, is soluble in ::r^) c i rorn ir, boron derived? How is boracio acid prepared? SILICON.*— SILICIC ACID. 5255 alcohol, the solution burning with a green flame. The ex- periment may be made in a glass instrument like Fig. 261, a b c. It is a very feeble acid, and even turns yellow tur- meric brown, like an alkali. TERFLUORIDE OF BORON, BF^ = 66*94, i is formed when a mixture of fluor spar, boracic acid, and oil of vitriol is heated in a flask. It is decomposed by water, by which it is rapidly absorbed. In damp air it forms white fumes. SILICON. ,Si== 22-18. This element may be prepared by igniting the silico-fluo- ride of potassium with potassium, act- Fig. 262. ing upon the resulting substance with water, which removes the fluoride of potassium, and leaves the silicon as a nut-brown powder. It exhibits two allotropic states. Prepared as first described, it takes fire and burns when heated in atmos- pheric air ; but if previously ignited in close vessels, it shrinks in volume, and, passing into its other state, becomes incombustible in ox- ygen gas. SILICIC ACID. ,St03 = 46-219. Silicic acid is one of the most abundant bodies in nature, existing under the innumerable forms of the quartz miner- als, sands, and sandstones. Rock crystal and flint are pure silicic acid. It may be obtained in a more convenient form by fusing white sand with four parts of carbonate of potash, dissolv- ing the resulting silicate in water, and decomposing the so- lution with hydrochloric acid. The silicic acid separates as a gelatinous hydrate, slightly soluble in water, which, when washed and dried, yields a white powder absolutely insolu- ble in water. There is reason to believe that the silicon exists in its different allotropic states in these two forms of silicic acid. Silica is a gritty substance, sufficiently hard to scratch glass. Its specific gravity is 2-66. It combines with the What is the color it communicates to flame ? How may silicon be pre- pared ? In what respect does it differ after ignition ? What is the constitu- tion of silicic acid, and how may it be prepared ? What are its properties ? 256 FL.UORIDE OF SILICON. alkalies in excess to form glass. It requires a higli temper- ature for fusion. Hydrofluoric acid is the only acid which dissolves it. FLUORIDE OF SILICON, SiFs = 7S‘22, may he obtained, as just stated, by dissolving silica in hy- Fis^. 263 . drofluoric acid, or by heating a mixture of fluor spar and sa’nd with sulphuric acid. It is col- orless ; fumes in the air ; its spe- cific gravity is 3*66. Trans- mitted from the flask which generates it, a, Figure 263, through water, it is decompos- ed, hydrated silica being de- j posited. To prevent the tube which delivers the gas being stopped up by the silica, some quicksilver, e, may be put in the vessel, d, and the tube dip- ped into it, so that the bubbles of gas may not come in contact with the water until they have reached the surface of the metal ; the sulphuric acid may be introduced through the funnel, L In the water, hydrofluosilicic acid forms, which is sometimes used as a test for potash. Nitrogen and .Hydrogen yield three compounds : they are designated respectively by the names Amidogen. Ammonia. Ammonium. AMIDOGEN. iViY2 = 1619. Amidogen is a hypothetical compound radical, the exist- ence of which, in several compounds, is inferred. On heat- ing potassium in ammoniacal gas, one third of the hydrogen is set free, and an olive substance remains, the amidide of potassium. This, in contact with water, yields potash and ammonia. K, NH^ + HO... = ...KO + NH^. When, the fluoride of silicon is passed through water, what are the pra- ducts? How many compounds of nitrogen and hydrogen are admitted? What is amidogen ? AMMONIA. 257 Amidogen is an electro-negative compound radical like cy- anogen. AMMONIA. iYiJa = 17-19. This substance, called also 'volatile alkali^ from its prop- erties, is an abundant product of the putrefaction of animal matters, and may be obtained by the destructive distillation of horn ; hence the term, spirit of hartshorn : it also exists in the air, and is a common product of many chemical re- actions. It may be obtained by heating in a flask, a, Fig. 264, equal quantities of slacked lime and muriate of ammonia, and, as its specific gravity is only 0*590, it may be collected, as in the cut, in a flask or jar, b, with the mouth downward, by displacing the heavier air. The action is (NH. X HCl) + (CaO, HO) CaCl + 2HO + NH^. It is a transparent and colorless gas, of excessive pun- gency, and having all the qualities of a strong alkali. It turns turmeric paper brown, is absorbed with wonderful ra- pidity by water, which, at 32° F., takes up 780 times its vol- ume of the gas, a result which may be illustrated by invert- ing a flask full of it in some cold water, when the water rushes up with sufficient violence to destroy the flask very frequently. Ammonia neutralizes the strongest acids, as may be shown by dropping it into litmus water which has been reddened by sulphuric or nitric acid. It is composed of three volumes of hydrogen mg. 265 . with one of nitrogen, condensed into two vol- umes. It may be recognized by its remarkable odor, and by the formation of white clouds when a rod, a, Fig. 265, dipped in muriatic acid, is approached to it. It condenses into a liquid at 60° under a pressure of 6*5 atmospheres. Its solution in water, known as aqua ammoniac, is pre- pared by passing the gas evolved from slacked lime and sal ammoniac through Wolfe’s bottles, as is represented in From what substances may ammonia be procured ? What is the specific gravity ? .What class of bodies does it closely resemble ? How may its affinity for water be illustrated ? How does it act on reddened litmus water ? What is its constitution ? How may it be detected ? By what process is aqua ammonias made ? 258 AMMONIUM. Fig. 266 ; the water will take it up until its specific gravity is lowered to O' 872 ; it then contains 32 J per cent of gas. This solution, somewhat diluted, is much used by chemists for neutralizing and precipitating. It also afibrds the best means of obtaining ammonia, merely requiring to be warm- ed in a flask, when the gas readily comes off. AMMONIUM, Am = iVH4= 18-19, is a hypothetical body, and believed to be of a metallic na- ture ; its symbol is, therefore. Am. It maybe combined with mercury by decomposing a solution of an ammoniacal salt by a Voltaic current, the negative pole being in contact with a globule of that metal, or by putting an amalgam of potas- sium and mercury in water of ammonia. Under these cir- cumstances, the mercury swells, and eventually becomes of a soft consistency like butter, preserving its metallic aspect completely. All attempts to separate the ammonium from this amalgam have failed. It decomposes into NH^ and H, It is now generally agreed by chemists that ammonium is the basis of the salts of ammonia. Thus, sal ammoniac, called also the muriate of ammonia, is NH^ + HCl; but this is evidently the same as iVAT^ + Cl^ that is, the chlo- ride of ammonium. In all cases where ammonia forms neutral salts with the so-called oxygen acids, it requires an atom of water, but this water evidently gives it the con- stitution, not of iViJg + HO, but NH^ + 'tfi® water, What is the nature of ammonium ? In what state may it be obtained ? How can it be shown that it is the base of the ammonia salts ? AMMONIUM. 259 therefore, makes it oxide of ammonium, which will unite with sulphuric, or nitric, or any other acid, precisely after the manner of any other metallic oxide. Moreover, the compounds of ammonia with this atom of water are iso- morphous with the compounds of the oxide of potassium. From these facts, therefore, we see that when sulphuric acid unites with ammonia, the atom of water which the acid contains gives to the salt the constitution iVS;, O + iSOg, or NH^ + or Am + the latter formula being analogous to Am + Cl, the chlo- ride of ammonium or sal ammoniac. This view of the na- ture of the ammonia compounds is known under the name of the ammonium theory of Berzelius. Of the compounds of ammonium with other bodies, the protosulphuret, S, may be mentioned under the name of hydrosulphuret of ammonia. It is much used as a test. There are also other sulphurets. What is meant by the ammonium theory of Berzelius ? THE METALS. LECTURE LVII. General Properties of the Metals. — Definition of a MetaL — Color, Specific Gravity, Hardness, Tenacity, and other Properties. — Relations to Heat. — Compounds with other Bodies. — Division into Groups . — The Ox- ides and their Reduction . — The Sulphurets and their Reduction. . Of the elementary bodies, by far the larger portion are metallic. By a metal we mean a body which possesses that peculiar manner of reflecting light which is known under the designation of metallic lustre. It is also a good con- ductor of electricity and heat. Of these there are at least forty-two, and probably forty-five, three having been recent- ly discovered. Most of the metals are of a white color, hut they differ from each other by slight shades, some having a faint blue and others a pinkish tint. There are three which are strik- ingly colored : gold, which is yellow, and copper and tita- nium, which are red. In specific gravity they differ ex- ceedingly ; potassium is so light as to float upon water, and iridium is twenty-one times as heavy as that liquid. Many of the metals are malleable, that is, can be extend- ed into thin sheets under the blow of a hammer ; others are so brittle that they may be reduced to powder in a mortar ; some of them are ductile, and may be drawn into fine wires, the order for malleability not being the same as that for ductility. Thus, iron may be drawn into fine wire, but can not be beaten out into such thin sheets as many other met- als. Of all metals gold is the most malleable, and platina has been drawn into the finest wires. In hardness the metals differ much. Potassium is so soft What is the definition of a metal ? How many metals are there ? What is their color commonly? Which three are the colored metals? Of the metals, which is the lightest, the heaviest, the most malleable, the softest, the hardest, the most fusible, and the most volatile ? PROPERTIES OF THE METALS. 261 that it may be moulded by the fingers, but iridium is among the hardest bodies known. In tenacity or strength the same differences are seen : of all metals iron is the most tenacidus. The same metal differs very much in this respect at differ- ent temperatures. In their relations to heat, well-marked distinctions also may be traced. Mercury at all ordinary temperatures is in a melted condition ; but platina can only be fused before the oxyhydrogen blow-pipe. As respects volatility, mercury, cadmium, potassium, sodium, zinc, arsenic, and tellurium may be distilled or sublimed at a red-heat. The metals unite with electro-negative bodies and with each other. In decomposition by the Voltaic battery, they pass to the negative pole, and are therefore described as electro-positive bodies. Their compounds with oxygen, chlorine, &c., pass under the names of oxides, chlorides, &c. ; their compounds with each other under the name of alloys, or, if mercury be present, of amalgams. They also unite with sulphur, phosphorus, and carbon. Chemical writers usually divide the metals into groups founded upon their relations with oxygen gas. The follow- ing simple division is the one I adopt : 1st. Metals which de- compose water at common temperatures ; 2d. Metals which can not decompose water at common temperatures, but do it at a red heat ; 3d. Metals which can not decompose water at all. 1st Group. Cerium. Titanium. Potassium. Manganese. Arsenic. Sodium. Iron. Antimony. Lithium. Nickel. Tellurium. Barium. Cobalt. Uranium. Strontium. Zinc. Copper. Calcium. Cadmium. Lead. Magnesium. Tin. Bismuth. Silver. 2d Group. •3d Group. Mercury. Aluminum. Chromium. Gold. Glucinum. Vanadium. Palladium. Thorium. Tungsten. Platinum Yttrium. Molybdenum. Rhodium. Zirconium. Osmium. Iridium. Lanthanum. Columbium. The older chemists divided the metals into four classes : 1st. Alkaline, such as potassium. 2d. Earthy, such as mag- nesium. 3d. Imperfect, as zinc. 4th. Noble, as gold. With what other substances do they unite ? Into what groups may they be divided ? What is the division formerly in use ? 262 METALLIC OXIDES. THE METALLIC OXIDES. Metallic substances unite with oxygen with different de- grees of intensity, and in very different proportions, many of them giving rise to a complete series of oxides, and pro- ducing, 1st. Basic oxides. 2d. Neutral or indifferent oxides. 3d. Metallic acids. 1st. The basic oxides are commonly protoxides or sesqui- oxides, which form neutral salts with hydrogen acids, with the production of water. To form such salts, for every atom of oxygen in the base there is required one atom of acid. A basic protoxide, therefore, requires one atom of acid, a ses- quioxide three, and a deutoxide two, to form a neutral salt. 2d. The neutral, or indifferent, oxides contain more oxy- gen than the base, and, when heated with acids, give off that oxygen, a basic oxide resulting. 3d. The metallic acids always contain more oxygen ; they may be sesquioxides, deutoxides, teroxides, or quadroxides, and are commonly formed by deflagrating the metal with nitrate of potash. REDUCTION OF THE METALLIC OXIDES. Some of the oxides, such as those of mercury, silver, and gold, may be reduced by heat alone ; but the greater num- ber require the conjoint action of carbon, which, at a high temperature, decomposes them with evolution of carbonic oxide. Among powerful reducing agents may be mention- ed the formiates and the cyanide of potassium, the former acting through the affinity of carbonic oxide for oxygen, and the latter through the affinity of carbon and potassium con- jointly. The deoxydation of metals may also be accom- plished by reducing agents, such as phosphorous and sul- phurous acids, or by the action of other metals; iron, for in- stance, will precipitate metallic copper from its solutions. Fig. 267. ^ilT A lifc The Voltaic current affords a powerful means of efiecting the reduction of met- als in philosophical investigations ; by its aid the alkaline metals were originally obtained. The electrotype, already de- scribed, is an example of its action ; even solutions of metallic salts are readily de- composed by it. Thus, if a glass jar, T, What substances do metals yield with oxygen ? How are metallic acids commonly made ? By what processes may metallic oxides be reduced ? METALUC SULPHURETS. 263 Fig. 267, be divided into halves, and a paper diaphragm be introduced between them, the halves being tightly press- ed together by the ring B B, if the jar be filled with any metallic solution, such as the sulphate of soda, and the pos- itive and negative wires of the battery dipped in the oppo- site compartments, after a time the metallic oxide will be found in one of them and the acid in the other, a total de- composition having taken place. THE METALLIC SULPHURETS. Many of these, such as the sulphurets of iron, lead, and copper, are found abundantly in nature ; or they may be made artificially by heating the metal with sulphur, or by deoxydizing metallic sulphates by charcoal or hydrogen gas, which converts them into sulphurets ; or by the action of sulphureted hydrogen on their oxides, which yields a metal- lic sulphuret and water. From their solutions under these circumstances, iron, manganese, zinc, cobalt, and nickel can not be precipitated, though they may by hydrosulphuret of ammonia. The sulphurets of a metal are usually equal in number and similar in constitution to its oxides ; and as oxygen compounds unite with each other to produce oxygen salts, the sulphurets, in like manner, also unite with each other to produce sulphur salts. REDUCTION OF THE SULPHURETS. The metallic sulphurets may often be reduced by melt- ing them with another metal having a more powerful affin- ity for sulphur ; thus, iron filings will decompose sulphuret of antimony, sulphuret of iron forming, and antimony being set free. On the large scale, however, a different process is resorted to ; the sulphuret, by roasting, is converted into a sulphate, much of the sulphur being expelled during the process as sulphurous or sulphuric acid. The resulting sul- phate is then acted upon by lime and carbon at a high tem- perature ; the lime decomposes the sulphate, setting free the metallic oxide, which is at once reduced by the carbon, the sulphate of lime turning simultaneously into the sulphuret of calcium, which floats on the surface of the metal as a slag. By what processes may metallic sulphurets be obtained ? What metals can not be precipitated by sulphureted hydrogen? What relation exists between the sulphurets and oxides? How are the sulphurets reduced? What is the process on a large scale ? 204 POTASSIUM. The metals also unite with chlorine, iodine, bromine, carbon, phosphorus, &c., and some with hydrogen and ni- trogen. These compounds will be described in their proper places. LECTURE LVIII. Potassium. — Discovery of, and Properties. — Relations to Oxygen and Water. — Its Oxides. — Caustic Potash . — , Tests for Potash. — Haloid Compounds of Potassium. — Salts of the Protoxide^ the Carbonate, Nitrate, Chlo- rate, (^C. POTASSIUM. ic = 39'15. Potassium was first obtained by Sir H. Davy, who de- composed its hydrated oxide (potash) by a Voltaic current. From the positive pole oxygen gas escaped in bubbles, and metallic potassium in globules appeared at the negative. It was subsequently discovered that the same substance could be decomposed by iron, and also by carbon at a high temperature ; and the latter of these substances is now ex- clusively resorted to for the preparation of potassium. The carbonate of potash is ignited with charcoal in an iron bot- tle, and the potassium received into a vessel containing naphtha. The productiveness of the operation is greatly interfered with by the circumstance that the carbonic oxide which is evolved, as it cools below a red heat, unites with much of the potassium, producing a gray substance, which chokes the tubes and diminishes the yield of the metal. Potassium is a bluish white metal, which, at 32° F., is brittle, melts at 150° F., and boils at a red heat, yielding a green vapor. Its specific gravity is *865 ; it is, there- Fi^. 268 . fore, much lighter than water, on the surface of which it floats. At 70° F. it may be mould- ed by the fingers, being soft and pasty. It possesses an intense affinity for oxygen, and hence requires to be preserved in bottles containing naphtha. A piece of it thrown From what was potassium first obtained? What process is now in use for its preparation ? What circumstance interferes with the productiveness ofthis process ? What are the properties of potassium ? OXIDES OF POTASSIUM. 265 upon water takes fire, and burns with a beautiful pink flame. In the air it speedily tarnishes, and, oven when brought in contact with ice, it decomposes it with the evolution of flame. In these cases the combustion arises from the hy- drogen uniting with the oxygen of the air and reproducing water ; the potassium simultaneously burns. POTASSIUM AND OXYGEN. There are two oxides of potassium, a protoxide and a per- oxide, KO.,. KO^. The affinity of potassium for oxygen is so great that it takes that substance from almost all other bodies, and hence is used as a powerful deoxydizing agent. Protoxide of Potassium. KO = 47 T 6 3 . This substance can only be formed by the action of po- tassium on dry air or oxygen. It possesses a great affinity for water, and is converted by it into the hydrated oxide of potassium, commonly called caustic potash. Hydrated Oxide of Potassium. KO, HO = 56*176. This substance is best procured by boiling two parts of pure carbonate of potash with twenty of water, and having previously slacked one part of quicklime with hot water, the cream which it forms is to be added by degrees, and the whole boiled. The process should be conducted in an iron vessel to which a lid can be adapted, so as to exclude the air during cooling ; the resulting carbonate of lime settles perfectly, and the hydrate may be obtained by evaporating the solution rapidly in a silver vessel, pouring out the melt- ed residue on a silver plate, or casting it into the form of small cylinders. The decomposition which takes place in the foregoing process is simple, KO, CO.,, + CaO, HO...= ... CaO, CO, + KO, HO; that is, the lime takes carbonic acid from the carbonate of potash, and the oxide of potassium unites with water. The solution may be known to be free from carbonic acid by not effervescing when mixed with stronger acids. The hydrate of potash is a white solid, having a power- How many oxides does it form? How is the hydrated oxide, or caustic potash, obtained ? What is the nature of the decomposition ? Of what prop- erties is the hydrate of potash possessed, and what are its uses ? M 266 OXIDES OF POTASSIUM. ful affinity for water, and abstracting it rapidly from the air. Taken between the fingers, it commnnieates to the skin a soft feel, and, if a concentrated solntion be used, soon effects a disorganization ; hence it is used by surgeons in the form of small sticks as an escharotie. It possesses pre- eminently the alkaline qualities, and, indeed, may be takeni as the type of that class of bodies, neutralizes the most pow- erful acids perfectly, and communicates to turmeric paper, or turmeric solution, a brown tint. It turns the infusion of red cabbage green, and, possessing an intense affinity for car- bonic acid, is used in organic analysis to absorb that gas. Potash in combination occurs in all fertile soils, and is essential to the growth of land plants, from the ashes of which its carbonate is abundantly procured. This may be shown by filtering water through the ashes of wood, when the clear liquid will be found to answer to all the tests in- dicating the presence of potash. It occurs also abundantly in feldspar, and hence is found in clays. The want of fer- tility in soils appears occasionally to be due to the absence of this body. The bichloride of platinum gives, with a solution of pot- ash, a yellow precipitate of the chloride of platinum dnd potassium. When the amount of potash is small, it is well to add alcohol at first, in v/hich the double chloride is in- soluble. Ammonia yields a similar precipitate; but this may be avoided by exposing the substance, in the first in- stance, to a red heat before testing. Perchloric acid, with alcohol, yields a white precipitate. Tartaric acid, if added in excess, and the mixture stirred with a glass rod, bearing gently on the sides of the vessel, gives white streaks of the bitartrate of potash 'wherever the rod has passed over the glass. Of other compounds of potassium, the following may be mentioned : Peroxide of potassium, KO^. Chloride of potassium, KCl. Iodide of potassium, KI. Bromide of potassium, KBr. Protosulphuret af potassium, KS. PcBtasulphuret of potassium, KS^ It also combines with hydrogen in two proportions, pro- ducing a solid and a gas, the latter of which takes fire spontaneously in the air. How may the existence of potash in the ashes of plants be proved** What are the tests for the presenee of the substance? Name some of its other compounds. SALTS OF POTASH. 267 Of these compounds, the most important are the peroxide of potassium, which is formed by passing oxygen over red- hot potash ; it is decomposed by water, evolving oxygen and producing potash ; the chloride of potassium, which is analogous to common salt ; the iodide, much of which is consumed in medicine, under the name of hydriodate of potash. It may be prepared by dissolving iodine in a so- lution of potash till the liquid begins to appear brown, then evaporating to dryness, and igniting the residue : oxygen is evolved, and iodide of potassium remains ; it may be then dissolved in water, and crystallized. It is white, crystal- lizes in cubes, and is very soluble in water and hot alcohol. Its solution will dissolve large quantities of iodine. The pentasulphuret is the chief ingredient of liver of sulphur, which is formed by fusing sulphur with carbonate of potash at a low temperature. SALTS OF THE PROTOXIDE OF POTASSIUM. Carbonate of Potash is obtained by lixiviating the ashes of plants. In an impure state it forms the potashes and pearlashes of commerce. It may be obtained pure by ig- niting the bitartrate with half its weight of the nitrate of potash. It has an alkaline taste, its solution feels greasy to the fingers, it is very soluble in water, and deliquescent. Bicarbonate of Potash ^ formed by transmitting a stream of carbonic acid through a solution of the former salt. It crystallizes in eight-sided prisms with dihedral summits. Sulphate of Potash, formed by neutralizing the follow- ing salt. Crystallizes in anhydrous, oblique, four-sided prisms, soluble in about ten times its weight of water. Sulphate of Potash and Water, sometimes designated as the bisulphate of potash ; it is the residue of the produc- tion of nitric acid. It is soluble in water, and has an acid reaction. It crystallizes in rhombohedrons. Nitrate of Potash is extracted on the large scale from certain soils in which organic matter is decaying in contact with potash. It crystallizes in six-sided prisms, fuses at a heat beneath redness, with evolution of oxygen gas. It is soluble in about three times its weight of water, at common temperatures. This salt enters as an essential ingredient in gunpowder, which is composed of about one atom of nitrate What are the properties of the iodide ? From what is the carbonate ob- tained ? What is the origin and use of the nitrate ? 268 SALTS OF POTASH. SODIUM. of potash, one of sulphur, and three of carbon. The sulphur of this mixture accelerates the combustion, while the oxy- gen of the nitre forms carbonic acid with the charcoal. The products, therefore, of the perfect combustion of gunpowder are carbonic acid, nitrogen, and the sulphuret of potassium. It commonly happens, however, that sulphate of potash is formed. The proportions of the ingredients of gunpowder are varied for different uses. The powder used for mining, for example, contains more sulphur than that used for fire- arms. Chlorate of Potash . — When a stream of chlorine is pass- ed into a solution of potash, the chloride of potassium and the chlorate of potash result ; the latter is deposited in flat, scaly crystals. The chlorate of potash contains no water ; it dissolves in about fifteen times its weight of that fluid ; melts at a red heat, with evolution of pure oxygen ; deflagrates with com- bustible bodies, sometimes with much violence. LECTUHE LIX. Sodium. — Preparation of. — Relation to Oxygen and Wa- ter. — Color communicated to Flame. — Its Oxides . — The Hydrated Oxide. — Tests for Sodium. — Haloid Compounds. — Common Salt. — Salts of the Protoxides ^ Carbonates^ Sulphates, Nitrates, Sfc. — Lithium. — Ba- rium. — Its Oxides. — Haloid Compounds. — Salts of the Protoxide. SODIUM. Na = 23'3. Sodium may be obtained by the same process as potas- sium, but is best procured by igniting the calcined acetate of soda with powdered charcoal in an iron bottle ; and, as the sodium does not act upon carbonic oxide, the operation is much more productive than in the case of the other met- al. Like potassium, it is to be kept in bottles under the surface of naphtha. In color, sodium resembles silver ; its spe.cifie gravity is 0*9348; it therefore floats upon water. It melts at 194° How is the chlorate of potash made ? How is sodium obtained, and what are its uses ? What are its properties compared with potassium ? OXIDES OF SODIUM. 2H9 F., and is more volatile than potassium. Thrown upon water, it decomposes it with a hissing sound, and with the evolution of hydrogen, but no flame appears. If, however, the water is hot, then a beautiful yellow flame, character- istic of sodium and its compounds, is the result. SODIUM AND OXYGEN. With oxygen sodium forms three compounds : the suhox- ide, protoxide, and peroxide. Trotoxide of Sodium. iVhO = 31-313. This, like the corresponding potassium compound, is pro- duced by oxydizing sodium in dry air. It is a white pow- der, which attracts moisture from the air and forms the hy- drated oxide of sodium, commonly called caustic soda. Hydrated Oxide of Sodium ^ NaO + HO = 40-323, or caustic soda, may he made by the same process as that given for caustic potash, by using carbonate of soda, and, when the resulting carbonate of lime has settled, evaporat- ing the liquid. The best proportions are one part of quick- lime to five of carbonate of soda in crystals. Caustic soda resembles caustic potash in most of its prop- erties. It is deliquescent, has a strong affinity for carbonic acid, and acts upon animal tissues as an escharotic. Its salts are generally more soluble than the potash salts, and on this are founded the methods recommended for distin- guishing the latter compounds from it. Moreover, the soda compounds communicate to the flame of alcohol, or to the blow-pipe, a yellow color : the same tint which is charac- teristically seen when sodium is placed in hot water. Chloride of Sodium. NaCl — 58-77, The chloride of sodium, common salt, is obtained abund- antly from the waters of the sea, to which it gives their sa- linity. It is also found as rock salt, deposited extensively in certain geological formations. Common salt is the general type of that extensive class of compounds which have derived the name of salt bodies from it. It crystallizes in cubes, and, when in mass, is often perfectly transparent, and permits the passage of heat of What compounds with oxygen does it give ? How is caustic soda ob- tained ? What are its properties and uses ? What color do the sodium compounds give to flarpe ? What is the constitution of common salt ? From what sources is it derived ? What are its properties ? 270 SALTS OP SODA. every temperature through it freely. It melts into a liquid at a red heat, crystallizes in cubes, and is not more soluble in hot than cold water. It is extensively used in the prep- aration of hydrochloric acid and chlorine ; immense quan- tities, also, are annually consumed in the preparation of car- bonate of soda, which is made by first acting on the com- mon salt with oil of vitriol, so as to turn it into sulphate of soda, and igniting this with charcoal and carbonate of lime: an impure carbonate of soda is the result, known under the name of black ash, or British barilla. Common salt is extens- ively used for the curing of meat. It is also an essential article of food, being decomposed in the animal system, and furnish- ing hydrochloric acid to the gastric juice and soda to the bile. The compounds of sodium with bromine, iodine, sulphur, &c., are not of interest. SALTS OF THE PROTOXIDE OF SODIUM. Carbonate of Soda is sometimes obtained by lixiviating the ashes of sea- weeds. Large quantities are also procured from the decomposition of sulphate of soda by saw-dust and lime at a high temperature, the carbonaceous matter de- composing the sulphuric acid and generating carbonic acid, which unites with the soda, while the liberated sulphur is partly dissipated and partly unites with the calcium. From the resulting mass carbonate of soda is obtained by lixivia- tion. The crystals, as found in commerce, contain general- ly ten ounces of water ; there are two other varieties, the one containing eight atoms, and the other one atom of water. Large quantities of the carbonate of soda are also sold in an uncrystallized state, under the name of salts of soda. The figure of the crystals of this salt is a rhombic octahedron. They effloresce on exposure to the air. They are soluble in five times their weight of cold and in less than their own weight of boiling water. Bicarbonate of Soda, or the double carbonate of soda and water, is formed by transmitting a stream of carbonic acid through a solution of the carbonate, and is in the form of a white powder. It is less soluble in water than the former. There is a sesquicarbonate, which passes in Com- merce under the name of trona. How is barilla obtained from common salt ? Why is it essential as an article of food ? From what source is the carbonate of soda obtained ? l3e- gcribe the preparation of it from the sulphate. SALTS OF SODA. 271 Sulphate of Soda is the Glauber’s salt of the shops ; oc- curs as a natural product, and also as the result of the prep- aration of hydrochloric acid. It is in prismatic crystals of a bitter taste, efflorescing in the air, and becoming anhy- drous. Water dissolves more than half its weight of this salt at 91^° F., but above that degree it is less soluble* When a solution of three parts of this salt in two parts of water is corked up in a flask while boiling, it may be cooled without crystallization taking place ; but if the cork is with- drawn, crystallization commences at once, or if it does not, the introduction of any solid matter produces it, and the temperature of the solution at once rises. Nitrate of Soda is found abundantly in different parts of America in the soil ; it crystallizes in rhomboids, dissolves in twice its weight of cold water, and, from its deliques- cence, can not be used in the manufacture of gunpowder. Phosphate of Soda {tribasic) is formed by neutralizing phosphoric acid with carbonate of soda ; two of the hydro- gen atoms are replaced ; it crystallizes in oblique rhombic prisms, dissolves in three times its weight of cold water, is of an alkaline taste, and gives a lemon-yellow precipitate with nitrate of silver. By the addition of soda to it a sub- phosphate is formed, in which all three of the hydrogen atoms of the acid are replaced ; but by the addition of phos- phoric acid to the ordinary phosphate, till it ceases to give any precipitate with chloride of barium, the biphosphate of soda results, a salt very soluble in water. Its crystals are rhombic prisms. In it only one of the hydrogen atoms is replaced. Microcosmic Salt, or the phosphate of soda, ammonia, and water, is made by dissolving seven parts of phosphate of soda in two parts of water, and adding one part of sal ammoniac. At a low heat it parts with its water of crys- tallization, and the temperature rising, it loses its ammonia and saline water, becoming monobasic phosphate of soda. It is nauch used in blow-pipe experiments. Pyrophosphate of Soda (bibasic) is procured by heating the phosphate. It gives a white precipitate with nitrate of silver. What ig the cemmefcial name ef the sulphate of soda ? Wliat pecu- liarity is there in the crystallization of its solution ? Why can not the nitrate be used for gunpowder? What is the difference between the phos- phate, the pyrophosphate, and the metaphosphate of soda ? What is micro • cosmic salt ? 272 LITHIUM. BARIUM. Metaphosjphate of Soda (monobasic) is formed by heat- ing microcosmic salt to redness. It is soluble in water, melts at a red heat, and gives, with dilute solutions of the earthy and metallic salts, viscid precipitates, t Biborate of Soda, the borax of the shops. It is import- ed in a crude state from the East Indies, and manufactured from the natural boracic acid of Italy by the addition of carbonate of soda. It crystallizes in octahedrons, or in ob- lique prisms, the former containing five, the latter ten atoms of water, all of which is lost by exposure to a red heat, the salt then fusing into a glass. It is of great use in blow- pipe experiments. LITHIUM. i = 6-42. This rare metal occurs in certain minerals, such as spodu- mene, lepidolite, &c. It is a white metal, communicating to flame a red color. It yields a protoxide, the carbonate of which is of sparing solubility in water, thus forming the link of connection between the potash and soda carbonates, which are very soluble, and the carbonates of the alkaline earths, as baryta and strontia, which are insoluble. This brings us to the metals of the alkaline earths, which form a division of our first group ; Ihe first of these is BARIUM. Ra = 68*7. The existence of barium was first proved by Davy, who isolated it by electrifying mercury in contact with the hy drate of baryta ; an amalgam formed, from which the mer cury was subsequently distilled, leaving the barium as a metal of a gray color like cast iron, heavier than sulphuric acid, in which it sinks, obtaining oxygen rapidly from the air, and giving rise to the production of the protoxide of barium, baryta. Protoxide of Barium, Ba O = 7 6 • 7 1 3 , may be obtained by igniting the nitrate of baryta, the de- composition being BaO, .,.Ba0 + N0^+0; that is, one atom of nitrate of barytes yields one of protox- From what source is borax derived, and what are its uses ? In what minerals does lithium occur ? What is the relation of its carbonate to those of the preceding and subsequent metals ? How was barium first obtained f What is the process for obtaining the protoxide, and also its hydrate ? OXIDES OF BARIUM. 273 ide of barium, and one of nitrous acid and one of oxygen gas are expelled. This protoxide is a white colored body, possessing a strong affinity for water, with which it exhibits the phenomenon of slacking, as is the case to a less extent with lime, heat being evolved. It has an acid taste, is soluble in water, and absorbs carbonic acid from the air. Its specific gravity is about 4-000. Its soluble salts are poisonous. Hydrate of Baryta, BaO, HO = 85*726, is formed by slacking the protoxide, and is a wffiite powder, very soluble in hot, but less so in cold water, yielding, there- fore, crystals when a hot solution cools : these contain nine atoms of water of crystallization. The cold solution is used as a test for carbonic and sulphuric acids, with which it forms insoluble white precipitates. This solution is most easily obtained by calcining the na- tive sulphate with pulverized charcoal, which converts it into the sulphuret of barium. To a boiling solution of this body oxide of copper is added till the liquid ceases to black- en a solution of acetate of lead. On being filtered, the so- lution of hydrate of barytes is obtained. Peroxide of Barium, BaO^ = 84-7, IS made by igniting chlorate of potash with barytes, or by passing oxygen over barytes in a red-hot tube. It is used in the preparation of peroxide of hydrogen. Of the other compounds of barium, the chloride is much used as a test for sulphuric acid ; it may be made by de- composing carbonate of baryta by hydrochloric acid. The sulphuret of barium is made by igniting the sulphate of baryta, heavy spar, with charcoal, which deoxydizes both the sulphuric acid and the baryta. It dissolves in hot wa- ter, and from this solution a solution of caustic baryta may be obtained by boiling with the oxides of lead or copper, and separating the sulphurets of those metals by filtration. By acting upon it with hydrochloric or nitric acid, the chloride or nitrate of baryta may be prepared. SALTS OF THE PROTOXIDE OF BARIUM. Carbonate of Baryta is found native, as the mineral What acids is a solution of baryta used to detect ? How is the perox- ide made ? What is its use ? For what purpose is the chloride of barium employed ? M2 274 STRONTIUM. Witherite, and may be prepared by precipitating a soluble salt of baryta with an alkaline carbonate. It is soluble in 4300 times its weight of cold water, and 2300 of boiling water. Sulphate of Baryta, found native abundantly as heavy spar, and from it most of the compounds of barium are prepared. It is called heavy spar, its density being 4*47. It crystallizes generally in tabular plates, and is wholly in- soluble in water. LECTURE LX. Strontium. — Uses in Pyrotechny . — Salts of Protoxide . — Calcium. — Protoxide of — Sources in Nature . — Tests for. — Haloid Ccnnpounds, Chloride, Fluoride, Sulphur- ets, SfC. — Salts of the Protoxide, Carbonate, Sidphate, Phosphate, CMoride. — Magnesium. — Protoxide. — Salts of Protoxide, Carbonate, Sulphate, Double Phos- phate. — Aluminum. — Sesquioxide. — Uses in the Arts. — Tests. — Salts of the Sesquioxide, Double Sulphate, Alum. — Manufacture of Porcelain and Glass. — Other Metals. STRONTIUM. Sr = 43*8. ^ This metal may be obtained by the same processes which have been used for obtaining barium, with which it has a considerable analogy. Its natural compounds are the sul- phate and carbonate, from which its other preparations may be obtained. Strontium yields a protoxide, which is the basis of a se- ries of salts, differing from baryta salts in not being poison- ous. The chloride and nitrate are used in pyrotechny for the purpose of communicating to flame a brilliant crimson color. The red fire of theatres contains the latter salt, and the former, if dissolved in alcohol, communicates to its flame the characteristic test of the strontium compounds. How may the sulphate of barytes be converted into the sulphuret of barium? What are the properties of the carbonate and sulphate of baryta? In what respect does strontium differ from barium ? What is the color it communicates to flame ? CALCIUM. 275 SALTS OF THE PROTOXIDE OF STRONTIUM. Carbonate of Stroniia is the strontianite of mineralo- gists. Sulphate of Strontia is the celestine of mineralogists. It is not so heavy as sulphate of baryta, and is said to be soluble in about 4000 times its weight of boiling water. Nitrate of Strontia forms an ingredient of the red fire used in theatres ; it crystallizes in octahedrons, and is solu- ble in five times its weight of cold water, and half its weight of boiling water. CALCIUM. Ca = 20*5. Calcium has never been obtained in quantities sufficient to permit a full examination of its properties. It oxydizes with rapidity, yielding a protoxide, known also as quicklime or lime. Lime occurs as a carbonate in the various limestones, marbles, chalks, &c., which form in many countries exten- sive mountain ranges. Its other salts are very abundant. From the carbonate, pure or quicklime may be obtained by exposure to a bright red heat. If the limestone contains silica, it may, however, be overburnt, a silicate of lime forming, which prevents the product from slacking. It possesses a strong affinity for water, and unites therewith with a great elevation of temperature, as exhibited in the process of slacking. Exposed to a high temperature, it phosphoresces splendidly. The hydrate which forms when lime is slacked is white ; it is soluble to a small extent in water ; and it is remarkable that cold water dissolves much more than hot. Lime-water is colorless, of a partial- ly caustic taste, neutralizes acids perfectly, restoring to red- dened litmus its blue color. It is used as a test for carbon- ic acid, with which it gives the white carbonate of lime. Milk of lime is nothing but lime-water in which hydrate of lime is mechanically suspended. The hardening of lime mortars depends chiefly on the absorption of carbonic acid. Hydraulic lime possesses the quality of setting under water. It contains oxide of iron, alumina, and silica. Lime is best detected by oxalate of ammonia, with which What are the mineralogical names of the carbonate and sulphate of stron tia? What is lime ? Under what forms does it occur in nature ? From the carbonate, how may lime be produced ? What, is the action of water »n it ? What are the properties of lime-w'ater? What is milk of lime t 276 COMPOUNDS OF CALCIUM. it gives a white precipitate of oxalate of lime, provided the solution be not acid. Among other compounds of calcium may be mentioned Chloride of Calcium, CaCl = 55*97, foi*med by dissolving carbonate of lime in hydrochloric acid, evaporating the solution to a sirup, and, on cooling, the chloride crystallizes. It is exceedingly deliquescent. Chlo- ride of calcium, dried without crystallizatign, is used in or- ganic analysis for collecting water, and, generally, in other chemical operations for drying gases. Fluoride of Calcium, CaF = 39*24, called, also, fluor spar, and frequently found as a mineral associated with lead. Crystallizes in cubes, octahedrons, &c., of various colors. It is found in fossil, and, to a small- er extent, in recent bones. It is used for various ornament- al purposes, and is the source from which the compounds of fluorine are derived. Sulphur et of Calcium, CaS = 36*62, obtained by igniting the sulphate of lime with charcoal, and constitutes Canton’s phosphorus, commonly made by igniting oyster shells with sulphur ; possesses the curious quality of shining in the dark, after a brief exposure to the sun or to the rays of an electric spark. SALTS OF THE PROTOXIDE OF CALCIUM. Carbonate of Lime is abundantly found in nature, form- ing whole ranges of mountains, the limestones, marbles, &c., of mineralogists. It occurs pure in the form of Iceland spar, in rhomboidal crystals, possessed of double refraction. It is dimorphous, assuming the form of six-sided prisms, as in the mineral called Arragonite. It is anhydrous, insolu- ble in water, but in water charged with carbonic acid it is soluble, and is deposited from such a liquid on boiling, or by the difiusion of carbonic acid into the air. The carbon- iq acid is expelled from this salt by a red heat, and the ac- tion of the more powerful acids. Carbonate of lime may be obtained in union with water, by boiling hydrate of lime with a solution of sugar. For what purposes is the chloride of calcium used? Under what forms does fluoride of calcium occur ? What singular quality does the sulphuret of calcium possess ? What are the dimorphous forms of carbonate of lime f Under what circumstances is it soluble in water ? MAGNESIUM. 277 Sulphate of Lime — Gypsum — occurs native, both in crystals, the primary form being a rhombic prism, and also in extensive crystalline masses. It contains two atoms of water ; there is a variety, however, passing under the name of anhydrite, which contains no water. On calcining the hydrous sulphate of lime at a low red heat, it becomes plas- ter of Paris, and has the property of setting into a hard mass when made into a paste with water. The sulphate of lime is soluble in 500 parts of boiling water, and often occurs in the water of springs, to which it communicates hardness. Phosphate of Lime — Bone-earth Phosphate — is one of the tribasic phosphates ; it is precipitated when earth of bones is dissolved in muriatic acid, and the solution neu- tralized by ammonia. Chloride of Lime — Bleaching Powder — is made by ex- posing hydrate of lime to chlorine. It is a white powder, exhaling a faint odor of chlorine, and is used extensively as a bleaching agent. MAGNESIUM. i»f^==12-7. Magnesium may be procured by igniting a mixture of chloride of magnesium and sodium in a porcelain crucible ; the chloride of sodium forms, and magnesium is set free. The chloride may be dissolved by water. It is a white, malleable metal, which melts at a red heat, and, with excess of air, oxydizes, forming Protoxide of Magnesium. MgO = 20'713. This substance, called, also, calcined magnesia, or sim- ply magnesia, may be made by heating the carbonate to low redness ; the carbonic acid is driven off, and the mag- nesia remains as a white powder, insoluble in water, but neutralizing acids completely, and forming with them a complete series of salts. Magnesia occurs very abundantly in nature, often asso- ciated as a carbonate with carbonate of lime, as in dolo- mitic limestone. It also occurs in fertile soils, and is essen- tial to the growth of certain plants. It is well distinguished from all the foregoing alkaline earths by the relation of its sulphate. The^ sulphates of Under what forms does sulphate of lime occur, and for what purpose is it used ? In what does the phosphate of lime occur ? What is bleaching pow- der ? How is magnesium obtained ? What are the properties of it ? Under what names does the protoxide pass ? What is dolomitic limestone ? m SALTS OP MAGNESIUM* baryta, strontia, and lime form a series of salts, the solu- bility of which, in water, is constantly increasing ; to these the corresponding magnesia salt may be added ; it is very soluble. Magnesia is precipitated from its sulphate by the caustic alkalies, and by the carbonates of potash and soda as a car- bonate, but not by the carbonate of ammonia in the cold. It may be detected by adding carbonate of ammonia and phosphate of soda in succession, when the phosphate of magnesia and ammonia is precipitated. Heated before the blow-pipe, after having been moistened with nitrate of co- oalt, magnesia becomes of a pinkish color. SALTS OF THE PROTOXIDE OF MAGNESIUM. Carbonate of Magnesia is found native, and may be prepared by boiling the sulphate with an alkaline carbon- ate, diffusing the precipitate in water, and passing a stream of carbonic acid through it ; by spontaneous evaporation, the carbonate of magnesia is deposited in crystals. The carbonate of magnesia, the magnesia alba of the shops, is prepared by precipitating the sulphate of magnesia with the carbonate of potash ; it occurs in light white cubical cakes, or in powder, and is not a true carbonate, for it does not contain a full equivalent of carbonic acid. It is said to be a compound of one atom of hydrate of magnesia with three atoms of hydrated carbonate of magnesia. It is very slightly soluble in water. Sulphate of Magnesia — Epsom Salts of commerce — is produced by the action of dilute sulphuric acid on magne- sian limestone. Its crystals are small four-sided prisms, soluble in an equal weight of cold and three fourths their weight of boiling water, the solution having a bitter taste. A low heat expels six out of the seven equivalents of the combined water. Phosphate of Magnesia and Ammonia^ one of the va- rieties of urinary calculus, may be formed artificially when a tribasic phosphate, a salt of ammonia, and a salt of mag- nesia are mixed together. Magnesium is the last of the alkaline earthy metals. Its history completes that of our first group of metallic bodies. How may magnesia be detected ? How is its carbonate prepared ? Of what is Epsom salt compose^ ? In what form is the phosphate of magnesi* and ammonia sometimes found ? ALUMINUM. 279 At the head of the second group we find aluminum, the first of the earthy metals. ALUMINUM. AI=137. Obtained, by Wholer, by the action of sodium on the chlo* ride of aluminum, being the same process as that given for the preceding metal. It is a gray powder, which melts beneath a red heat ; takes fire when heated in air, producing Sesquioxide of Aluminum. = 51*539. This oxide, called, also, alumina and clay, occurs nat* urally under certain forms, which are highly prized, as the ruby and sapphire. In a more impure condition it yields the various common clays, which also contain silica or me- tallic oxides, or other extraneous bodies. Alumina may be prepared from the sulphate of alumina and potassa, common alum, by precipitating the sulphuric acid by chloride of barium. The sulphate of baryta goes down, and there is left in the solution chloride of potassium and chloride of aluminum. When the mass is dried, water is decomposed ; hydrochloric acid is then expelled, and alumina, mixed with the chloride of potassium, remains be- hind ; the latter is to be dissolved away by water, leaving the alumina as a white substance, which, with water, forms a plastic mass, capable of being moulded, and retaining its shape when baked. After ignition, it adheres to the tongue, and during the act of drying it contracts considerably in volume, a property which formerly gave rise to the inven- tion of Wedgewood’s pyrometer. The presence of alumina gives to the clays those proper- ties which fit them for the purpose of the potter and brick- maker. Alumina is also used as a mordant to fix the colors of certain dyes upon cloth. Alumina is precipitated from its solutions by fixed alka- lies, which yield a white hydrate of alumina, soluble in an excess of the precipitant. It is also thrown down by alka- line carbonates ; and, when these precipitations are made in a solution tinged with coloring matter, the alumina car- ries it down with it. Such colored precipitates pass under How is aluminum prepared? What is the constitution of its oxide? Under what natural forms does it occur? How may alumina be prepared? What principle is involved in Wedgewood’s pyrometer? What is meant by a mordant ? How may the presence of alumina be recognized ? 280 PORCELAIN. EARTHEN-WARE. GLASS. the name of lakes ; and it is this property of attaching such colors to itself, enabling it to cause their firm adhesion to cloth fibre, which is the principle of its application as a mordant. Among the purposes to which alumina is applied may he mentioned the manufacture of Porcelain, and the dificrent kinds of earthen- ware. The former substance, first made by the Chinese, is very compact and translucent. It con- sists essentially of clay mixed with a fusible body, which binds all its parts together, and is covered with a glaze, which does not terminate abruptly on the surface, but per- vades the substance of the mass. In this respect it differs from common earthen-ware. Feldspar, or the silicate of lime, are bodies suitable for communicating this glassy structure. . In the manufacture of porcelain, great care is taken to select clay free from iron. It is mixed with powdered quartz and feldspar, and the requisite shape given it either by the potter’s wheel, or by pressing it into moulds. It is then dried in the air, and more perfectly in a furnace, and, when ignited, forms biscuit. This is dipped in the glaze, sus- pended in water, and becomes covered over with a uniform coat of it. It now remains to dry it once more, and fuse the glaze upon it. Earthen-ware consists of a white clay mixed with sil- ica. It is glazed with a fusible material containing oxide of lead, and colored of different tints by metallic oxides ; for example, blue by cobalt. Connected with the manufacture of pottery may also be mentioned the manufacture of Glass, of which there are several varieties, some consisting of silica, potash or soda, and lime, others containing a large quantity of oxide of lead If silica be heated with carbonate of potash and lime, or oxide of lead, carbonic acid is expelled, and glass forms. The mass is kept in a fused condition till it is free from air bubbles, and is then cooled until it becomes plastic, so that it may be blown or moulded. Articles of glass, after they are manufactured, require to be annealed or slowly cooled down. This allows their parts to assume a regular structure, and prevents excessive brittle- ness. What are lakes ? What substances are used in the preparation of por celain and earthen-ware ? How is glass made ? Why must it be annealed SALTS OF ALUMINUM. 281 Soluble glass is formed when silica is heated with twice its weight of carbonate of soda or potash. It derives its name from the fact that it is for the most part soluble in water. SALTS OF THE SESQUIOXIDE OF ALUMINUM. Sulphate of Alumina is made by dissolving alumina in dilute sulphuric acid. It enters into the composition of the alums. Sulphate of Mumina and Potash — Mum. — This im- portant salt is prepared from alum slate. It crystallizes in octahedrons, has an astringent taste, reddens litmus paper. It dissolves in about eighteen times its weight of cold, and less than its own weight of boiling water. It contains twenty-four atoms of water, and, when exposed to heat, foams up, melting in its own water, which, being evapora- ted away, leaves a white porous mass, commonly called burnt alum. In the same way that the sulphate of potash unites with the sulphate of alumina, so also do the sulphates of am- monia and of soda, forming respectively the ammoniacal and soda alums. The alumina in the common alum may be replaced, also, by the sesquioxides of iron, manganese, or chromium, giving iron, manganese, and chrome alums. The following metals, Glucinum, Thorium, Yttrium, Zir- conium, Lanthanium, and Cerium, are very rare bodies, and, being of little interest, may be passed over without farther notice. LECTURE LXI. Manganese. — Its Seven Oxides. — The Peroxide and its Applications. — Mineral Chameleon. — Acids of Manga- nese. — Salts of the Protoxide. — Iron. — Its Natural Forms. — Reduction on the Great Scale. — Cast Iron . — Wrought Iron. — Steel. — Passive Iron. MANGANESE. Mn=z 2T7. Manganese may be procured by igniting its oxides with What are the properties of the sulphate of alumina and potash ? How may manganese be obtained ? What are its properties ? How many qx ides does it furnish ? How may manganese be detected ? 282 MANGANESE. a mixture of lampblack and oil in a powerful furnace, the reduction being somewhat difficult. It is a white metal, specific gravity 8 0 13, requiring a white heat for its fusion, and oxydizing readily in the air. It is remarkable for the number of oxygen compounds which it yields ; they are MnO . . . Mn^O ^ . . . MnO^ . . . MnO^ . . . Mn^O ^ . . . Mn^O^ . . . designated respectively. Protoxide of manganese. Sesquioxide of manganese. Peroxide of manganese. Manganic acid. Permanganic acid. Red oxide of manganese. Varvicite. Of these, the protoxide may be made by passing hydrogen gas over red-hot peroxide of manganese. It is of a green color, is a basic body, and forms a series of salts, of which the sulphate is used in dyeing. It is isomorphous with mag- nesia and zinc. Hydrosulphuret of ammonia yields with it a flesh-colored precipitate, ferrocyanide of potassium a white, and the chloride of soda a dark brown hydrated peroxide. The sesquioxide is made by igniting the peroxide, as will be presently explained. The red oxide and varvicite occur as minerals ; but of the whole series the peroxide is by far the most valuable. Peroxide of Manganese, Mn Og = 43-726, is found abundantly as a mineral, and passes in commerce under the name of black oxide of manganese, a name indi- cating its color. It is insoluble in water, and, when exposed to a red heat, gives off one fourth of its oxygen, forming the sesquioxide, as stated above, the action being 2(ilf^02) Mn^O^ + O. On this fact is founded one of the processes for obtaining oxygen gas. Heated with hydrochloric acid, it yields chlo- rine, as has been explained. It was formerly called glass- makers’ soap, from the circumstance that it removes, when added to melted glass, the stain of protoxide of iron, by turn- ing it into peroxide, and causes the glass to become color- less ; but if too great a proportion of peroxide of manganese is used, the glass assumes an amethystine color. Peroxide of manganese, when ignited with caustic potash in a platina crucible, yields a substance known as Mineral, What is the constitution of the peroxide ? What color does it give t® glass ? COMPOUNDS OP MANGANESE. 283 Chameleon i which is of a green color. Water dissolves from it the Manganate of Potash, which is of a beautiful grass green, the solution speedily passing through a variety of shades of purples, blues, and reds. As yet, manganic acid is a hypothetical compound, and has not been insulated. When mineral chameleon is dissolved in hot water, a red solution is obtained of the Permanganate of Potash ; from the permanganate of baryta a crimson solution of Perman- ganic Acid may be procured by the aid of sulphuric acid ; but permanganic acid can not be obtained in the solid form. Among other compounds of manganese, the following may be named : Protochloride of manganese MnCl r= 63*15. Perchloride “ “ Mn^Clj = 303" 19. Perfluoride “ “ Mn^Fl-j = 186*46. The protochloride may be made by acting on the peroxide with muriatic acid, evaporating to dryness, and fusing at a red heat. On digesting with water, the protochloride dis- solves, and any impurity of iron is left in the state of oxide. Then, by crystallizing, the chloride can be obtained in pink crystals. The perchloride is produced when permanganate of potash, common salt, and sulphuric acid are heated. It is a dark greenish and volatile liquid. The perfluoride is obtained by distilling sulphuric acid, permanganate of pot- ash, and fluor spar ; it is a greenish yellow gas. SALTS OF THE PROTOXIDE OF MANGANESE. Protosulphate of Manganese, formed by dissolving prot- oxide of manganese in sulphuric acid. The figure of its crystals depends on the temperature at which they were formed. They have a rose-colored tint. It is insoluble in alcohol, very soluble in water, and is used by the dyers to produce a fine brown color. There is but one sulphuret of manganese. It is obtained as a hydrate when manganese is precipitated by hydrosul- phuret of ammonia {MnS, HO). It is of a flesh-red color IRON. Fe = 28*00. Iron sometimes occurs in a native state and as meteoric iron, also as oxide, carbonate, sulphuret, &c. It is one of How is mineral chameleon made ? What are its properties ? Can man- ganic acid be isolated ? How may the chhirides of manganese be formed ? What are the properties of the fluoride ? What is the formation and use of the protosulphate of manganese ? 284 IRO^’ the most abundant of the metals. Much of what is found in commerce is derived from clay iron-stone, which is an impure carbonate containing silica, alumina, magnesia, and other foreign substances. The native peroxide of iron, red haematite ; the hydrated peroxide, brown haematite ; the black oxide, or magnetic iron ore, furnish some of the finer varieties of the metal. From clay iron-stone metallic iron is procured by the ac- tion of carbonaceous matter and lime at a high temperature. The ore, having been roasted, is thrown into the furnace with coal and lime. If the iron is in the ore as a silicate, the lime decomposes it at those high temperatures, forming a slag of silicate of lime, and the oxide of iron set free is instantly reduced by the carbonaceous matter ; the metal sinking down, protected by the slag, is let off by opening a hole in the bottom of the furnace. The substance thus produced is not pure iron ; it contains carbon and other impurities, and passes under the name of cast or pig iron. It is purified by melting and sudden cool-, ing, which converts it mto fine metal; this fine metal is then melted under exposure to air, which burns off the car- bon as carbonic oxide, and the mass, from being perfectly fluid, becomes coherent. It is now subjected to violent me- chanical action, such as hammering or rolling ; this forces out or burns off the impurities, increases its tenacity, and it becomes the wrought iron of commerce. Cast Iron melts readily at a bright red heat, and ex- pands in solidifying ; on this depends its valuable applica- tion for making castings. Kept under the surface of salt water for a length of time, cast iron becomes converted into a body somewhat like plumbago, due, probably, to the re- moval of the iron as a chloride ; the carbon which is left behind is sometimes observed, as it dries, to become hot : a phenomenon to be accounted for by its porous state. These facts have been frequently verified in the case of cannon which have lain for years at the bottom of the sea. There are two forms of cast iron, white and gray ; the former con- tains about five per cent, of carbon, the latter three or four. Pure Iron may be obtained by decomposing precipitated peroxide of iron by hydrogen gas, and melting the result. What are the forms under which iron chiefly occurs? How is it obtain ed from clay iron-stone ? What is cast iron ? By what processes is it con verted into wrought iron? What are the properties of cast iron? Whal changes does it undergo under water ? How may pure iron be obtained 1 IRON. 285 The metal has a bluish color, is more ductile than mallea- ble, and is the most tenacious of all bodies. It becomes very soft at a red heat, and possesses the welding proper- ty ; on this depends the art of forging it. Its specific grav- ity is 7*7. It is one of the few magnetic bodies, and, when soft, its magnetism is so transient that it may gain and lose that quality a thousand times in a minute. The melting point of iron is very high. In the mode of preparing it from cast iron it does not undergo the process of fusion, but its particles are simply welded together. The fibrous struc- ture which wrought iron possesses is the chief cause of its great tenacity ; a wire ^th of an inch in diameter will bear a weight of 60 pounds. Steel, which is a valuable preparation of iron, is made by. placing alternate strata of iron bars and charcoal pow- der in a close box and keeping them red hot. The process is known by the name of cementation. The iron gains about 1'5 per cent, of carbon. Steel is much more fusible than iron, and becomes excessively hard and brittle by being brought to a red heat and then suddenly quenched in cold water. When allowed to cool slowly, it is quite soft, and various degrees of elasticity and hardness may be given to it by the process of tempering. By placing a piece of platina in nitric acid of a specific gravity of 194, and then bringing an iron wdre in contact with it and withdrawing the platina, the iron assumes a passive or allotropic state. It now exhibits no tendency to unite with oxygen, can not precipitate copper from its solu- tions, and simulates the properties of platina and gold. LECTURE LXII. Iron. — Oxides of . — Three Oxides and Ferric Acid . — Tests for Iron. — Salts of the Protoxide and Peroxide. — The Sidphurets. — Nickel. — Its Peduction from the Oxalate. — Cobalt. — Smalt. — Zaffre . — S^jmpathetic Ink. — Zinc. — Distillation of. — Salts of the Protoxide. IRON AND OXYGEN. Iron burns with rapidity in oxygen gas, as may be proved \vnat are its properties? What is steel? How is it made, and what are its properties ? How may iron be rendered passive ? 286 OXIDES OF IRON. Fi^. 269 . igniting a piece of it in wire coiled into a spiral form in a jar of that gas {Fig. 269), when it will be found to take fire and burn beautifully. In at- mospheric air, under favorable circumstances, the combustibility of this metal may be proved. Thus, fine iron filings, sprinkled in the flame of a spirit lamp, burn with scintillations ; exposed to air and moisture, it slowly rusts. Iron yields four oxides : Protoxide .... FeO — 36'013. Black oxide . . . 7^6304 = 116'052. Peroxide .... Fe^O^ = 80 039. Ferric acid .... . FeO^ = 52'039. Frotoxide of Iron. jPeO = 36*013. This oxide has not yet been insulated, but it exists, united with acids, in an extensive series of salts, from which it is thrown down as a hydrate by alkalies, and is then of a white color, which darkens as it passes into the state of peroxide. Ferrocyanide of potassium gives a white precipitate, and the ferridcyanide a deep blue. Hydrosul- phuret of ammonia gives a black sulphuret of iron. Sul- phureted hydrogen and gallic acid give no precipitate. Black Oxide of Iron. jP^gO^ =116*052. This oxide, known also as the magnet or loadstone, is found as a mineral. It is a compound of the protoxide and peroxide. The scales of iron found in blacksmiths’ forges mainly consist of it. It may also be produced by decom- posing the vapor of water by metallic iron in a red-hot tube. Peroxide of Iron, FefO.^ = 80*039, is found in nature as oligist iron, or as a hydrate. , It may be produced artificially as a hydrate by precipitation from a solution of persulphate of iron by a caustic or carbonated alkali, or in a pure state by igniting green vitriol ; there is then left a red powder, known as rouge, used for polishing metals. This oxide is not magnetic; it is the basis of a series of salts which yield, with alkalies, a brown hydrated peroxide ; with ferrocyanide of potassium, Prussian blue ; How may the rapid oxydation of iron be illustrated ? How many, oxides does this metal yield ? What are the reactions which the protoxide fur- nishes with tests ? Under what natural forms does the black oxide occur? How may it be formed artificially ? What are the natural forms of the per- oxide ? How may it be prepared ? For what purposes is it used ? What is its action with reagents ? OXIDES OF IRON. 287 with sulphocyanide of potassium, a blood-red solution ; with wannin and gallic acid, a black. This last is of considerable interest, constituting the basis of ordinary ink. The presence of iron can always be determined by pass- ing it into the condition of peroxide, and applying the fore- going tests. Ferric Acid, JPeOg = 52*039, is prepared by heating peroxide of iron with four parts of nitrate of potash. The result is treated with cold water, which yields a red solution of the ferrate of potash. This slowly decomposes in the cold, and very rapidly when the solution is warm. The ferrate of baryta precipitates when the potash solution is acted on by a soluble salt of baryta. It is a permanent body, of a crimson color. Among other compounds of iron, the following may be named : Protochloride of iron . . . . . . FeCl = 63*47 Perchloride “ . . . = 162*35 Protiodide “ . . . = 153*57 Protosulphuret “ . . . . . . FeS = 44*12 Sesquisulphuret “ . . . = 104*36 Bisulphuret “ . . . . . . FeS^ = 60*24 Of these, the protochloride is formed by passing hydrochlo- ric acid over red-hot iron. It is white, but forms a green so- lution in water. The perchloride, in solution, by dissolving peroxide of iron in hydrochloric acid. The protiodide, by boiling an excess of iron filings with iodine, and evapora- ting; it forms, on cooling, a dark gray mass. Its solution absorbs oxygen from the air. The protosulphuret of iron, which is much used for forming sulphureted hydrogen, may be made by heating a mass of iron to a white heat, and ap- plying to it roll sulphur, and receiving the melted globules in a bucket of water. It may also be procured by igniting iron filings with sulphur. The bisulphuret occurs abun- dantly as a mineral of a golden yellow color, crystallized in cubes or allied forms, and known as Iron Pyrites. It fre- quently assumes the form of various organic remains, being one of the common petrifying agents, but in this state differs essentially from the cubic pyrites, both in color and oxydiz- ability, these fossil remains rapidly decaying under exposure What is common ink? How may the presence of iron be detected? What are the properties of ferric acid? Of the other compounds, mention some of interest. What is iron pyrites ? What is the difference of its forms ? 288 SALTS OF IRON. NICKEL. to the air, but the other form being unacted on. Besides these, there is a sulphuret of iron which is magnetic. SALTS OF THE PROTOXIDE OF IRON. Carbonate of Iron may be obtained from the sulphate by an alkaline carbonate, falling as a whitish precipitate. It turns brown, however, from the absorption of oxygen. It occurs as a mineral in spathic iron, and dissolves in water containing carbonic acid, forming chalybeate waters. Protosuljphate of Iron — Copperas — Green Vitriol — is prepared largely by the oxydation of iron pyrites, and crys- tallizes in oblique prisms of a grass-green color. It has a styptic taste, dissolves in twice its weight of cold, and three fourths its weight of boiling water. It contains five atoms of water. At a low red heat it becomes anhydrous. In this state it is used for the manufacture of the Nordhausen sulphuric acid. SALTS OF THE PEROXIDE OF IRON. Persulphate of Iron may be formed by adding to a so- lution of the protosulphate of iron half an equivalent of sul- phuric acid, and peroxydizing by nitric acid. With water it forms a red solution. NICKEL. iVi = 29-5. Nickel may be obtained by igniting its oxalate in a cov- ered crucible, carbonic acid escaping, and the metal being reduced. NiO + C2O3 ... = ... iW + 2(002) ; one atom of the oxalate of nickel yielding one of the metal and two of carbonic acid gas. Nickel is a white metal, requiring a high temperature for fusion. It is magnetic, and has a specific gravity of 8*5. It is commonly associated with iron in meteorites, and enters into the composition of German silver ; unites with oxygen, forming a protoxide and sesquioxide, the former yield- ing salts of a green color ; the latter is an indifferent body. SALTS OF THE PROTOXIDE OF NICKEL. Sulphate of Nickel crystallizes from its solutions with six atoms of water in slender green prisms, which, when ex- How is carbonate of iron formed ? What is the process for preparing the sulphate ? How is the persulphate obtained ? By what process is nickel obtained ? What are its properties ? Under what remarkable circumstan ces does it occur with iron ? COBALT. ZINC. 289 posed to the sun, change into an aggregate of octahedrons, becoming opaque. Nickel is chiefly used in the preparation of German sil- ver, an alloy of copper, zinc, and nickel. It is of a white color, takes a good polish, and is malleable. COBALT, Co = 20-5, is generally associated with iron and nickel, and Aviih tliei > occurs in meteoric iron. Like the preceding metal, it iini}’ be obtained by igniting its oxalate in a covered crucible, carbonic acid being disengaged and metallic cobalt left. It is a pinkish white metal, requiring a high temperature for fusion. Its specific gravity is 7 *8. It is magnetic, as re- cent experiments have proved. It forms a protoxide and a sesquioxide, the former being the basis of a class of salts which are chiefly of a pink or blue color. Smalt is a sili- cate of cobalt, and Zaffre an impure oxide ; the former is used to communicate to paper a faint blue tinge, and the blue color which the oxide gives to glass is taken advantage of in coloring the common varieties of earthen-ware. Co- balt is easily detected upon this principle. The chloride of cobalt may be made by dissolving the oxide or the metal in hydrochloric acid. It is a pink solu- tion, which turns blue when dried. It forms a beautiful sympathetic ink^ for letters written with it, especially on paper which has a pinkish tinge, are entirely invisible"^ but become of a bright blue color when the paper is warmed, the letters again fading as they become cool and moist. ZINC. Zn = 32-3. Zinc is a very abundant metal, immense quan- tities of it occurring in the state of New Jersey and in various other places. From zinc blende, which is a sulphuret, converted by roasting into an oxide, or from the carbonate brought into the same state by ignition, the metal may be obtained by the process of distillation by descent. The oxide, mixed with charcoal, is introduced into a crucible which has an iron tube passing through a hole in its bottom, as seen in Fig. 270, and the What change does the sulphate of nickel undergo in the sunlight ? How is cobalt procured ? Is it magnetic like nickel ? What is smalt ? What is zaffre ? What arc the uses of cobalt ? What property does the chloride possess ? By what process is zinc obtained ? N 290 zoro. lid being luted on, tbe temperature is raised to a white heat, and the zinc, distilling over, may be condensed in water. Zine is a bluish- white metal, which melts at about 770® F., and, if exposed at a bright red heat to the air, takes fire and burns with a brilliant pale green flame. Its spe- cific gravity is about 7*00. At common temperatures it is brittle, but it may be rolled into thin sheets at about 300^ F., and then retains its malleability when cold. During its combustion there arises from it a great quantity of flocculent oxide, which formerly went under the name of nihil cdhum, or philosopher’s wool. Among the compounds of zinc may be mentioned Protoxide of zi;BC ZnO = 40*313. Chloride « ...... Sulphuret ** ZnS =48*4. Of these, the oxide is formed, as has been said, during the combustion of zinc. It is also precipitated as a white hydrate from its soluble salts by potash or soda, soluble in excess of the precipitant. The chloride may be made by the action of hydrochloric acid on metallic zinc. It is used in the arts for soldering under the name of butter of zinc. The sulphuret occurs as a mineral under the name of zinc blende. SALTS OF THE PROTOXIDE OF ZINC. Sulphate of Zinc — White Vitriol . — This salt is formed in the process for procuring hydrogen gas by the action of dilute sulphuric acid on zinc. It crystallizes in colorless prisms with six atoms of water, and is soluble in two and a half parts of cold water. It has a styptic taste, and red- dens vegetables blues. There are three different subsul- phates of this oxide. Silicate of Zinc, the electric calamine of mineralogists; remarkable for becoming electric when heated. Is there any connection between tbe ductility of zinc and its temperature? During combustion, what arises from it ? How may it be detected ? How is white vitriol prepared ? What is electric calamine ? CADMIUM. TIN. 291 LECTURE LXIII. Cadmium. — Sources of. — Its Volatility. — Tin. — Block and Grain. — Its Properties. — Protoxide and Stannic Acid. — Chlorides of Tin. — Mosaic Gold. — Its Uses . — Chromium. — Chromiron. — Green Oxide and its Uses. — Chromic Acid. — Salts of the Sesquioxide. — Salts of Chromic Acid. — Other Metals. — Titanium. CADMIUM. Cd=zbhQ. Cadmium usually occurs associated with zinc as a carbon- ate. In the preparation of that metal by distillation, as has been described., the cadmium first comes over. From any impurity of zinc it may he separated by precipitation from an acid solution by sulphureted hydrogen, which throws the cadmium down as a yellow powder, but does not act on the zinc. The sulphuret of cadmium is then dissolved in nitric acid, the oxide precipitated by potash, and, when dry, re- duced by charcoal. The compounds of cadmium are not important. The metal itself is very volatile. TIN. Sn = 5T9. Tin occurs as an oxide in England, Mexico, Germany, and the East Indies. It may he reduced by the action of char- coal at a high temperature. It is found in commerce under two forms, block tin and grain tin. If a bar of tin is heated, the purer parts, being the more fusible, ooze out of it, con- stituting grain tin, and the mass which is left behind is block tin. Tin is a white metal like silver. It oxydizes in the air superficially, the action ceasing as soon as a thin crust is formed. At a red heat it oxydizes rapidly, forming putty powder, used for polishing metals. It is very malleable, and may be rolled into thin foil. When bent backward and forward it emits a crackling sound. It is very soft ; its specific gravity 7*2. It melts at 442^, and burns when raised to a high temperature in the air. Some of its com- pounds are Under what circumstances does cadmium occur? What are the native forms of tin ? What are block and grain tin ? What are the properties of tin ? When a bar of tin is bent backward and forward, what phenomenon arises ? 292 COMPOUNDS OF TIN. Protoxide of tin SnO — 65*913. Sesquioxide = 129*839. Peroxide SnO^ = 73*926. Protochloride SnCl = 93*37. Perchloride SnCl^i = 128*74. Protosulphuret SnS = 7^' Persulphuret SnS 2 = 90*1. The protoxide may be made by precipitation from the protochloride by carbonate of potash. It is to be washed with warm water, and its water finally driven off in a cur- rent of carbonic acid gas at a red heat. It is of a black color, is easily set on fire in atmospheric air, passing into the condition of peroxide. Its salts reduce the noble metals to the metallic state, when added to their solutions, and yield with the chloride of gold the Purple of Cassius. The per- oxide, called also stannic acid, from exhibiting weak acid properties, may be made by the action of nitric acid on tin. It is a hydrate in the form of a white powder, insoluble in acids and wate*r ; but if obtained by precipitation from per- chloride of tin, it is soluble both in acids and alkalies. Melted with glass, it forms a white enamel. The protochloride may be made by dissolving tin in warm hydrochloric acid. The solution, when concentrated, depos- its crystals of the hydrated potochloride. These are decom- posed when heated. The anhydrous protochloride may be had by passing hydrochloric acid gas over metallic tin at a red heat. The perchloride is procured by distilling eight parts of tin with twenty-four of corrosive sublimate. It is a smoking fluid, and was formerly called the Fuming Li- quor of Libavius. A solution of this substance, much used in dyeing, is made by dissolving tin in nitro-muriatic acid, or by warming a solution of the protochloride with a little nitric acid. ..Of the sulphurets, the first may be formed by pouring melted tin on sulphur, and igniting the powdered result with more sulphur in a crucible. It is a bluish gray com- pound. The persulphuret is obtained when two parts of peroxide of tin, two of sulphur, and one of sal ammoniac are ignited in a retort. It is a body of a golden yellow col- or, formerly called Aurum Musivum, or Mosaic gold, in small scales of a greasy feel, and is used for exciting elec- How is the protoxide made, and how do its salts act on those of the noble metals ? How is stannic acid prepared ? What does it yield with glass ? What is the fuming liquor of Libavius ? How is mosaic gold made, and what is its use ? CHROMIUM. 293 trical machines, being much more energetic than the com- mon amalgam, though less durable in its power. Tin furnishes several valuable metallic combinations : Tin Plate is sheet iron superficially alloyed with it. The soft solders are alloys of lead and tin. Pewter is an alloy with antimony. CHROMIUM. Cr = 28. Chromium occurs abundantly near Baltimore as the chro- mate of iron {Chrome Iron)^ more rarely as the red chro- mate of lead. The metal may be obtained by the action of charcoal on the oxide at a high temperature, and is of a yellowish- white color. It takes its name from its tendency to produce highly colored compounds. It is very infusible, and has a specific gravity of about 6 00. Its compounds, to be here described, are Sesquioxide of chromium .... Cr^O^ = 80'039. Chromic acid CrO^ z=z 52 039. Sesquichloride of chromium . . . Cr^Cl^ = 162 26. The sesquioxide may be prepared by heating the chro- mate of mercury to redness in a crucible. The mercury is driven off, and the chromic acid partially deoxydized, leav- ing a beautiful grass-green powder, the sesquioxide. It may also be obtained by heating the bichromate of potash red hot, and washing the residue in water ; also as a hy- drate, by boiling a solution of bichromate of potash with muriatic acid, and adding alcohol ; the mixture becomes of a green color, and ammonia precipitates the hydrated ses- quioxide. It is a weak base, yielding a class of salts of a blue or green color. In the state of hydrate it is soluble in acids ; but, on making it red hot, it suddenly becomes incandescent, passes into another allotropic state, and is now insoluble. This sesquioxide is isomorphous with the ses- quioxides of iron and alumina. In its two allotropic states it yields corresponding classes of salts, one of which is green, and the other reddish green. It is used for communicating a green color to porcelain. Chromic Acid may be made by adding one volume of a saturated solution of bichromate of potash to one and a half of oil of vitriol. On cooling, red crystals of chromic acid are deposited. It is isomorphous with sulphuric acid, pro- What alloys does tin furnish ? Under what forms does chromium occuy in nature ? How is its sesquioxide prepared, and what is its use ? How is chromic acid made ? 294 COMPOUNDS OP CHROMIUM. duces with bases yellow and red salts, is a powerful oxy- dizing agent, is decomposed by a red heat into the sesquiox ide, destroys the color of indigo and other dyes, and may be detected by producing with the salts of lead, chrome yellow, and by its ready passage, under the influence of deoxydiz ing agents, into the sesquioxide. The sesquichloride is procured when chlorine is passed over a mixture of the sesquioxide and charcoal in a red- hot tube. It is a lilac-colored body, which forms a green solution in water. There is also an oxychloride, which may be distilled as a deep-red liquid from a mixture of chromate of potash, common salt, and oil of vitriol. The fluoride, which is a red gas, is obtained by distilling in a silver re- tort a mixture of chromate of lead, fluor spar, and oil of vitriol. It is decomposed by the moisture of the air, form- ing chromic and hydrofluoric acids. SALTS OF THE SESQUIOXIDE OF CHROMIUM. Sulphate of Chromium and Potash — Chrome Alum, — When the oxide of chromium is dissolved in sulphuric acid, and mixed with the sulphate of potash and a little free sulphuric acid, crystals of chrome alum are deposited in red or blue octahedrons. The sulphate of chromium alone does not crystallize. Chrome Iron, a compound of the sesquioxide of chro- mium and the protoxide of iron, is found native, crystal- lized in octahedrons, and also massive. It furnishes most of the compounds of chromium. SALTS OF CHROMIC ACID. Chromate of Potash may be made by igniting chrome iron with one fifth its weight of nitrate of potash. It crys- tallizes in small, lemon-yellow prisms, and is very soluble in hot water. The crystals are anhydrous. Bichromate of Potash may be prepared from the former by adding an equivalent of acetic acid : it crystallizes in prisms of a ruby red. Large quantities are consumed by dyers. Chromate of Bead-^ Chrome Yellow, obtained by pre- Does chromic acid possess bleaching powers? How are the chloride and fluoride obtained ? What is the form of the latter body ? What ia chrome alum ? What is the constitution of the two chromates of potash ? What is chrome yellow ? ARSENIC. 295 cipitation. from either of the foregoing salts by a soluble salt of lead. It is used as a paint. Dichromate of Lead is formed by adding chromate of lead to melted nitrate of potash, and dissolving out the chromate of potash and excess of nitre by water. It is of a beautiful red color. The following metals, Vanadium, Tungsten, Molybde- num, Osmium, and Columbium, are not applied to any pur- poses in the arts, or are so rare as not to be of general in- terest. Titanium might be included in the same observa- tion ; it is, however, deserving of remark, as being a red metal like copper, and titanie acid, one of its oxygen com- pounds, is used in the coloring of artificial teeth. LECTURE LXIV. Arsenic. — Preparation of the Metal, — Properties of Ar- senious Acid , — Two Varieties of it, — Two methods of detecting it. — Process in Cases of Poisoning. — Sul- phureted Hydrogen Test, — Marshs Test . — The Cop- per Test, — Difficulties arising from Antimony. ARSENIC. As=iZl'l, Arsenic is obtained by sublimation in a current of air of the arseniuret of cobalt and iron, the vapor condensing as a white oxide. This being mixed with powdered char- coal or black flux, and heated, the metallic arsenic mg. 271 , sublimes. The process may be conducted in a tall vial imbedded in a crucible filled with sand, two thirds of the vial projecting above the heated sand. On this cooler portion the metal condenses. It is also sometimes found in a native state. Arsenic is a metallic body, of an aspect darker than cast iron ; it is very brittle, its specific gravity is 5*88, and, when slowly sublimed, it crystallizes in rhombohedrons. At 356° P. it sublimes without undergoing fusion, its melting point being much higher than that of sublimation. Its va- por has a smell of garlic, as may be readily recognized by What is the color of titanium ? From what substances, and in what manner, is arsenious acid prepared ? How is the metal obtained from it T What are its properties ? Why can not it be melted ? What is the odoi of its vapor ? 296 COMPOUNDS OF ARSENIC. throwing a little arsenious acid on a red-hot coal. Arsenic prepared by black flux tarnishes, it is said, from containing a little potassium. Among its compounds, the following may be mentioned : Arsenious acid Arsenic acid Protosulphuret of arsenic . Sesquisulphuret of arsenic Arseniureted hydrogen . . . As^O^— 99*439. . 115*465. . AsS = 53*8. As^S^ =z 123*7. AsH z= 38*7. A-Tseuious Acid is formed when arsenic is sublimed in atmospheric air. It is a white substance, which, when the process is conducted slowly, crystallizes in octahedrons. Similar octahedral crystals may be obtained by heating ar- senious acid itself in a tube to 380° F. When the opera- tion has been recently performed and a large mass sublimed, it IS a glassy, transparent body, which in the course of time slowly becomes milk-white. The specific gravity of arse- nious acid is 3-7. It is nearly tasteless, of sparing solubility m water, the two varieties differing in this respect. By 100 parts of water, 11*5 of the opaque, but only 9*7 of the transparent, are dissolved. This substance passes cur- rently under the name of arsenic. It ought not to be for- gotten that the arsenic of chemical writers and that of commerce are very different bodies : the one is black and the other white ; the one is a metal and the other its oxide. Arsenious acid may be detected by several methods : 1st. W^ith ammonia sulphate of copper, it gives an em- erald green precipitate ; the arsenite of copper, or Scheele’s green. 2d. With the ammonia nitrate of silver, a canary yellow precipitate ; the arsenite of silver. 3d. With sulphureted hydrogen, a solution, previously acidulated with, acetic or muriatic acid, yields a yellow pre- cipitate, the sesquisulphuret of arsenic, orpiment This when dried and ignited with black flux (a mixture' of char- coal and carbonate of potash, obtained by igniting cream of tartar in a covered crucible), yields a sublimate of metallic arsenic. From the metal, how may arsenious acid be procured ? What change does the glassy variety underp in time ? Of these varieties, which is molt water? What is the difference between the arsenic of chemists and the arsenic of commerce ? What is the action of ammonia sulphate of cppp on arspious acid ? What of the ammonia nitrate of silver'' What of sulphureted hydrogen ? TESTS FOR ARSENIC. 297 4th. With the materials for generating hydrogen gas ; that is, sulphuric acid, zinc, and water, placed in a bottle ; if arsenious acid be present, arseniureted hydrogen is disen- gaged. When set on fire, it burns with a pale blue flame, emitting a white smoke ; and if a piece of cold glass be held in the flame, there is deposited upon it a black spot of arsenic, surrounded by a white border of arsenious acid. This stain is volatilized on heating the glass. Or if the ar- seniureted hydrogen be conducted through a tube of Bohe- mian glass, made red hot at one point by a spirit lamp, it is decomposed, and metallic arsenic deposited on the cooler portions beyond the ignited space. 5th. If a solution containing arsenious acid be acidulated with hydrochloric acid, and boiled with slips of copper, the metallic arsenic is deposited upon the copper as an iron gray crust. In cases of poisoning by this substance, it is unsatisfac- tory to apply, in the first instance, color-giving tests, such as the first, second, and third, as the liquor obtained from the stomach is itself highly colored and turbid. It is, there- fore, desirable to examine that organ and its contents minute- ly, endeavoring to discover any white granules, or specks, which may be supposed to be arsenious acid, and if such are found, to examine them separately. The contents of the stomach, the larger pieces having been divided, are to be boiled in water, and strained through a linen cloth. A current of chlorine gas passed through this liquid coagulates and separates much of the animal matter ; or, what is more convenient, if the solution be first acidulated with nitric acid, and then nitrate of silver be added, much of the animal matter may be removed. By the addition of a solution of common salt, the excess of the silver salt may be precipitated, and the liquor being filtered, is then fit for the third or fourth of the foregoing tests. In the application of sulphureted hydrogen, the liquoi having been clarified as just stated, the gas is passed through it until it smells strongly. It is then to be boiled for a short time, to expel the excess of gas, and filtered. The yellow precipitate of sesquisulphuret of arsenic, or orpiment, which What is the process for detecting it by arseniureted hydrogen ? What is that by copper ? In cases of poisoning, why can not color tests be ap- plied ? How is the liquid obtained from the stomach to be clarified ? De- scribe the test by sulphureted hydrogen. N 2 298 marsh’s test. Fig. 272. is collected, is to be thoroughly dried, and introduced, with twice its bulk of black flux, into the bulb, a, of a tube, such. as Fig. 272, made of hard glass. On the temperature being raised by a lamp, metallic arsenic sublimes, forming an iron black ring round the part b. By cutting off the bulb of the tube and heating the black crust gradu- ally, it slowly sublimes toward the colder part, producing a white deposit of arsenious acid in octahedral crystals. In the application of Marsh's test, the liquor, having been cleared either by chlorine or by nitrate of silver, as above described, is to be introduced into a bottle containing dilute Fig. 273. sulphuric acid and zinc, a tube, bent as represented in Fig. 273, a, passing later- ally from the cork ; arseniureted hydrogen now passes off, and may be set on Are as it escapes from the end of the tube, and ex- amined by holding in the flame a piece of cold glass, b. If no spot be produced, then the tube, which for this reason should be made of a hard glass not contain- ing lead, is to be ignited by a spirit lamp at the point c, and the gas will deposit its arsenic a little beyond that point. In this manner, the tube being kept red hot for hours, the smallest quantity of arsenic may be discovered. If the liquor, notwithstanding the care taken to clear it, froths when the hydrogen is disengaged, so as to interfere with the results by choking the tube, the gas is best collect- ed under a jar at the pneumatic trough, and may be subse- quently examined. The fifth test, by copper, may be sometimes advanta- geously applied to collect the arsenic from solutions ; the crust upon the copper may be subsequently examined, ei- ther by sublimation or otherwise. It is to be remembered that antimony will yield results closely resembling those of arsenic by Marsh’s test ; but on heating the glass plate on which the stain has been depos- ited, if it be arsenic, it will totally volatilize away ; but if antimony, though the flame of a blow-pipe be thrown upon Describe Marsh’s test. How may a small quantity of metal be separated from a large quantity of liquid by this test ? When the liquid froths, what course is to be pursued ? When may the test of copper be advantageously applied ? What metal closely resembles arsenic in these respects ? ARSENIC. 299 it, it will not disappear, but only gives rise to a yellow ox- ide, which turns white on cooling. In medico-legal investigations, it should also be remem- bered that, as sulphuric acid and zinc of commerce some- times contain arsenic, it is absolutely necessary that the spe- cimens about to be used be critically examined themselves by being tried alone before the suspected solution is added. LECTURE LXV. Arsenic. — Antiseptic Quality of Arsenious Add. — An- tidote for Poisoning. — Arsenic Acid. — Isomorphous with Phosphoric Add. — Realgar and Orpiment. — Ar^ seniureted Hydrogen. — Antimony. — Reduction of . — Oxides, Chlorides, and Sulphurets of. — Antimoniuret- ed Hydrogen. — Detection of Antimony. — Tellurium. — Uranium. — Copper.— of. — TJ&e of Oxide. — Detection of. — Salts of Protoxide. Arsenious Acid possesses a remarkable antiseptic qual- ity, and hence often preserves the. .bodies of persons who have been poisoned by 4t Advantage is also taken of this fact by the collectors of objects of natural history in pre- serving their specimens. The antidote for poisoning by arsenic is the hydrated ses- quioxide of iron. It may be made by adding carbonate of soda to the muriate of iron. It should be given in the moist state, mixed with water. After being once dried, it loses much of its power. It produces an inert basic arsen- ite of the peroxide of iron. Arsenic Acid is found in nature in union with various bases. It may be made by acting on arsenious acid with nitric acid, with the addition of a little hydrochloric acid, and evaporating till the nitric acid is expelled. The result- ing acid contains three atoms of water, and is isomorphous with tribasic phosphoric acid. The arseniates yield, with nitrate of silver, a dark-red precipitate of the tribasic arse- Why is it necessary to examine the sulphuric acid and zinc employed in these experiments ? Does arsenious acid possess an antiseptic quality T What is the antidote for this poison ? How is it prepared ? How is arse- nic acid prepared ? What fact arises from the isomorphism of arsenic and phosphoric acids ? 300 ANTIMONY. niate of silver. The monobasic and bibasic forms of the acid are not known. It should not be forgotten in medico-legal inquiries respecting arsenic, that the arseniate of lime may naturally replace phosphate of lime in bone earth, and this acid substitute the phosphoric in other parts of the system. The protosulphuret of arsenic may be obtained by melt- ing arsenious acid with sulphur. It occurs as a mineral Realgar, and is a red-colored substance. The sesquisulphuret is deposited when a stream of sul- phureted hydrogen is passed through a solution of arsenious acid. It is a yellow body, and is used in dyeing ; it is also known under the name of Orpiment. Arseniureted Hydrogen is prepared by acting on an al- loy of zinc and arsenic with dilute sulphuric acid. It is a colorless gas, burns with a blue flame, exhales an odor like garlic. Its specific gravity is 2*695. It is decomposed by chlorine, iodine, and the arsenic is separated by heat and by the rays of the sun. ANTIMONY. Sb = 64*6. This metal occurs commonly as a sesquisulphuret in na- ture, from which it may be obtained by heating with iron filings, a sulphuret of iron forming, and metallic antimony subsiding to the bottom of the crucible. It may also be obtained by fusing the sulphuret with black flux, which, produces a sulphuret of potassium and metallic antimony. Antimony is a blue-white metal, of a very crystalline structure, and so brittle that it may be pulverized. It melts at 810^ F. Its specific gravity is 6*7. It possesses, at high temperatures, an intense affinity for oxygen ; a frag- ment of it the size of a pea being ignited on a piece of char- coal before the blow-pipe, and then suddenly thrown on the table, takes fire, breaking into a multitude of globules, and filling the air with fumes of the white sesquioxide. Anti- mony yields the following compounds : Sesquioxide of antimony Sh^O^ = 153*239. Antimonious acid = 161*252. Antimonic acid . Sb^O^ = 169'265. Sesquichloride of antimony .... Sb^Cl^ = 235*46. Perchloride “ Sb^Cl^ =306*3. Sesquisulphuret “ . . . . . Sb^S^ =177*5. Persulphuret “ Sb^S^ =209*7. Oxysulphuret - “ .... . 2Sb^S^-\- Sb^Os — 5Q^’2. What is realgar ? What is orpirnent ? How may arseniureted hydrogen be made ? From what source is antimony obtained ? What is the process for its prenaration ? What are its properties ? COMPOtJNDS OP ANTIMONY. 301 The Sesquioxide of Antimony may be made by adding to an acid boiling solution of chloride of antimony carbon- ate of soda. It is a gray powder, and is the base of a class of salts, among which tartar emetic may be mentioned. These salts give an orange-colored precipitate with sulphur- eted hydrogen. Antimoniom Acid is produced by heating the oxide of antimony, or antimonic acid. It is a white powder, and unites with bases, forming antimonites. Antimonic Acid may be prepared by acting on metallic antimony with nitric acid. Sesquichlorlde of Antimony is made by dissolving one part of sulphuret of antimony in five ^ hydrochloric acid, and distilling. As soon as the matter which passes over becomes solid, the receiver is to be changed, and, contin- uing the heat, the sesquichloride is collected. It was for- merly known as butter of antimony. The perchloride may be made by burning antimony in chlorine gas. The oxy- chloride is produced when the sesquichloride is placed in contact with water. It was formerly known as powder of algaroth. The sesquisulphuret occurs abundantly as a mineral, as has been said. It is also formed by the action of sulphuret- ed hydrogen on the salts of the oxide of antimony. In this case it is of an orange color, in the former it has a metallic aspect. The persuljpliuret is procured when the sesquisul- phuret and sulphur are boiled in a solution of potash, the liquor filtered, and an acid added, a yellow precipitate going down. It was known formerly as the Golden Sulphuret of Antimony. The oxysulphuret occurs native as the red ore of antimony, and may also be made by boiling the ses- quisulphuret with a solution of potash. On cooling, precip- itation of it takes place. It is stated, however, by Berze- lius, that this is not a true compound, but merely a mechan- ical mixture of the oxide and sulphuret in irregular pro- portions. This precipitate is also known under the name of Kermes Mineral. From the liquor, after the kermes is separated, an acid throws down the golden sulphuret of an- timony. What color is the precipitate yielded by the salts of the sesquioxide and sulphureted hydrogen ? How is antimonious acid prepared ? What is the butter of antimony ? What is the powder of algaroth ? What is the aspect of the native sesquisulphuret ? What is the golden sulphuret ? What is kermes mineral ? S02 imANIUM.— COPPER. Antimoniureted Hydrogen . — ^When hydrogen is evolved from a solution containing tartar emetic (tartrate of anti- mony and potash), this substance is produced. It is a gas, having a superficial resemblance to arseniureted hydrogen, and when used as in Marsh’s apparatus, gives a stain on glass resembling that of arsenic. From arsenic it may be distinguished by not being volatile. The soluble salts of antimony may be distinguished by giving an orange precipitate with sulphureted hydrogen, sol- uble in sulphuret of ammonium, but again precipitated by an acid. Antimony furnishes some valuable alloys : printer’s type metal, for example, j§ an alloy of this substance with lead. It expands in the act of solidifying, and therefore takes ac- curate impressions of the interior of a mould. TELLURIUM. Te = 64*2.. Tellurium is a rare metal, of a white color, very fusible and volatile, having several analogies with selenium, and uniting with hydrogen to form tellureted hydrogen, which, with water, yields a claret- colored solution. URANIUM, U=:217, is likewise a very rare metal, of the nature of which there are considerable doubts, it being supposed t^at what was formerly regarded as the metal is in reality its protoxide. It may be remarked, if these observations are incorrect, that uranium has the highest equivalent of any of the element- ary bodies. It is used to a small extent to give black and yellow colors to porcelain. COPPER. Ctt=31-6. Copper is often found native, and in certain parts of the United States in masses of very great magnitude. It also occurs as a carbonate and sulphuret. In the latter com- bination, it is found with the sulphuret of iron, as yellow copper ore. This being roasted, the sulphuret of iron changes into oxide, the copper sulphuret remaining un- changed. The mass is then heated with sand, which yields a silicate of iron, the sulphuret of copper separating. How is antimoniureted hydrogen made ? How may the salts of antimony be distinguished ? What are the properties of tellurium t What is remark- able as respects the alleged atomic weight of uranium ? Under what forms does copper naturally occur ? What is the process for its reduction ? SALTS OP COPPER. 303 This process is repeated until all the iron is parted ; and now the sulphuret of copper begins to change into the oxide, which is finally decomposed by carbon at a high temperature. Copper is a red metal, requiring a high temperature for fusion. Its specific gravity is 8*617. It has great tenac- ity, and is ductile and malleable. A polished plate of it, heated, exhibits rainbow colors, and is finally coated with the black oxide. It is one of the best conductors of heat and electricity. Among its compounds, the following may be mentioned : Protoxide of copper CuO = 39*613. Suboxide “ Cu^O = 71*213. Chloride “ CuCl =66*02. Dichloride “ Cu^Cl = 98*62, Disulphuret “ Cu^S = 79*32. Protoxide of Copper may be made either by igniting metallic copper in contact with air, or by calcining the ni- trate. It is a black substance, not decomposable by heat, but yielding oxygen with facility to carbon and hydrogen, and hence extensively used in organic analysis. It is a base, yielding salts of a blue or green color. The suboxide, call- ed, also, red oxide, occurs native as ruby copper. It is a feeble base. The disulphuret also occurs native, as copper pyrites. Copper is easily detected. Caustic potash gives, with its protosalt, a pale blue hydrate, which turns black on boil- ing. Ammonia, in excess, yields a beautiful purple solu- tion ; ferrocyanide of potassium, a chocolate-brown precipi- tate ; sulphureted hydrogen, a black ; and metallic iron, as the blade of a knife, precipitates metallic copper. SALT8 OF THE PROTOXIDE OF COPPER. Carbonate of Copper. — The neutral carbonate of copper is not known ; but there are several varieties of dicarbori^^ ates. One, which passes under the name of Mineral Green^ is formed by precipitating with an alkaline carbonate. It occurs naturally in the form of Malachite. Blue coppei ore is ^another dicarbonate ; the paint called Green Verdi- ter has a similar composition. Sulphate of Copper — Blue Vitriol — is prepared for com- merce by the oxydation of the sulphuret of copper. It crys- What are its properties ? Which of its oxides is used in organic anal* ysis ? How may copper be detected ? Under what forms do the carbon- ates of copper occur? 304 LEAD. tallizes in rhomboids of blue color, with four atoms of wa- ter. It is soluble in four times its weight of cold, and twice its weight of hot water. It is an escharotic, an astringent, and has an acid reaction. With ammonia it forms a com- pound of a splendid blue color, which may be obtained in crystals ; with potash, also, it forms a double salt. There are also subsulphates of copper. Nitrate of Copper, formed by the action of nitric acid on metallic copper. It crystallizes in prisms or in plates. It acts with very great energy on metallic tin. There is a subnitrate of copper. Ars,enite of Copper — Scheele's Green — produced by add- ing solution of arsenious acid to the solution of ammonia sulphate of copper. Copper yields several valuable alloys. Brass is an alloy of copper and zinc ; gun metal, bell metal, and speculum metal, of copper and tin. The gold and silver of currency contain portions of this metal ; it communicates to them the requisite degree of hardness. LECTURE LXYI. Lead. — 'Reduction of Galena. — Relations of Lead to Water . — The Oxides of Lead. — Detection of Lead . — Bismuth. — Silver. — Amalgamation. — Crystallization. — Cupellation, — Properties of Silver. — Salts of Silver. LEAD. P6“ 103-6. Lead occurs under various mineral forms, but the most valuable one is galena, a sulphuret. From this it is read- ily obtained. The galena, by roasting in a reverberatory furnace, becomes partly converted into sulphate of lead ; the contents of the furnace are then mixed, the temperature raised, and the sulphate and sulphuret produce sulphurous acid and metallic lead, the action being PbO, So^ + PbS. .. = ... 2SO^ + P^2. ' Lead is a soft metal, of a bluish-white color. Its speci- What are the method of preparation and properties of the sulphate ? What is Scheele’s green ? What are brass, gun metal, and bell metal ? Why is silver and gold coinage alloyed ? Under what form does lead chiefly oc- cur ? How is galena reduced ? COMPOUNDS OF LEAD. 305 fic gravity is 11*381. It melts at 612° F., and on the surface of the molten mass an oxide (dross) rapidly forms. At common temperatures it soon tarnishes. In the act of solidifying it contracts, and hence is not fit for castings. It possesses, at common temperatures, the welding property ; two bullets will cohere if fresh-cut surfaces upon them are brought in contact. Under the conjoint influence of air and water lead is corroded, a white crust of carbonate form- ing. But when there are contained in the water small quantities of salts, such as sulphates, these form with the lead insoluble bodies, which, coating its surface over, pro- tect it from farther destruction. For this reason, lead pipe can be used for distributing water in cities without danger. Lead is one of the least tenacious of the metals. The tar- trate of lead calcined in a tube yields one of the best pyro- phori. On bringing it into the air at common temperatures, it spontaneously ignites. Of the compounds of lead, the following are some of the more important : Protoxide of lead Sesquioxide “ Peroxide “ Red oxide “ Chloride “ Iodide “ Sulphuret “ PhO =111-613. P 62 O 3 = 231-239. P 6 O 2 =119-626. P63 04 = 342-852. PbCl = 139-62. Phi = 229-9. PbS =119-7. The protoxide is made by heating lead in the air ; it is a yellow body, which fuses at a bright red heat. In the first state it is called massicot ; in the latter, litharge. It yields a class of salts, being a base. It is slightly soluble in water. The peroxide is made from red lead by digest- ing it with nitric acid, which dissolves out the protoxide, and leaves the substance as a puce colored powder. The red oxide, or red lead, is rnade by calcining lead in a cur- rent of air at 600° or 700° F. It is used in the manufac- ture of flint glass. The chloride is made by the action of hot hydrochloric acid on protoxide of lead : on cooling, it is deposited in crystals. The iodide is formed when any solu- ble iodide is added to protosalt of lead ; it is a beautiful yellow precipitate, soluble in boiling water, forming a color- less solution, which, on cooling, deposits golden crystals. Why can not lead be used for castings ? What is the action of pure wa- ter, and water containing salts, upon it ? What is massicot ? How is it prepared ? What is litharge ? How is the peroxide prepared ? How is minium made ? 306 SALTS OF LEAD.— BISMUTH. The sulphuret is galena ; it crystallizes in cubes, and has a high metallic lustre. Lead is easily detected by sulphureted hydrogen, which throws it from its solutions as a deep brown or black pre- cipitate, and by the iodide of potassium or chromate of pot- ash, which gives with it a yellow precipitate. Sulphuric acid yields with its salts a white insoluble sulphate of lead. SALTS OF THE PROTOXIDE OF LEAD. Carbonate of Lead — White Lead — Ceruse . — This salt forms as a white precipitate when an alkaline carbonate is added to a solution of a salt of lead. Large quantities of it are consumed in the arts as white paint. For commerce it is procured by mixing litharge with water containing a small proportion of acetate of lead \ carbonic acid gas is then sent over it, and the carbonate rapidly forms. It is also made by exposing metallic lead in plates to the action of the vapor of vinegar, air, and moisture, the metal becom- ing oxydized and carbonated. Nitrate of Lead may be formed by dissolving litharge in dilute nitric acid ; it crystallizes in opaque white octa- hedrons, which dissolve in seven or eight times their weight of cold water. They contain no water of crystallization, and are decomposed at a red heat, as stated in the descrip- tion of nitrous acid. By the action of ammonia, three oth- er nitrates of lead may be obtained. ^ Among the alloys of lead are the soft solders. Two parts of lead and one of tin constitute plumber’s solder ; one of lead and two of tin, fine solder. BISMUTH. J5i = 71*07. Bismuth is found both native and as a sulphuret. It is of a reddish color, melts at 497°, and may be obtained in beautiful cubic crystals by cooling a quantity of it until solidification commences, then breaking the surface crust and pouring out the fluid portion. When bismuth is dissolved in nitric acid, and the solution poured into water, the white subnitrate is deposited, once used as a cosmetic ; when this is washed, and subsequently heated, the protoxide is left. There is also a peroxide. How may lead be detected ? Mention some of the methods by which white lead may be made. What change does the nitrate undergo at a red; heat? Of what are the common solders composed? What are the propsq erties of bismuth ? " SILVER. CRYSTALLIZATIOTf. CUPELLATION. 307 Fusible metal is an alloy of eight parts of bismuth, five of lead, and three of tin ; it melts below the boiling point of water, and may be obtained in crystals. SILVER. A^ = 108-31. Silver is found native, and as a sulphuret and a chlo* ride, occurring, also, with a variety of other metals, and in small proportion with galena. When disseminated as a metal through ores, it may be collected from them by amal- gamation with quicksilver, and, on distilling, the quicksil- ver is driven off. When it is obtained from the sulphuret, that ore is roast- ed with common salt, which changes it into a chloride. This, with the impurities with which it may be associated, is put into barrels, which revolve on an axis, along with water, pieces of iron, and metallic mercury ; the iron re- duces the chloride to the metallic state, and the silver amalgamates with the mercury. This is washed from the impurities, strained through a bag to separate the excess of mercury, and the residue is driven ofi^ by distillation. . The extraction of silver, when it occurs in small quantity with lead, has been recently much improved by the intro- duction of the process of crystallization. It depends upon the fact that an alloy of lead and silver is more fusible than lead. A large quantity of argentiferous lead is melted and allowed to cool. As the setting goes on, the first portions which solidify are pure lead ; they may be removed by iron colanders, and by continuing the process there is finally left a portion containing all the silver. This is exposed to a red heat, and a stream of air directed over it ; oxydation of the lead takes place, and the litharge is removed by the blast, the process being finally completed by cupellation. A cupel is a shallow dish made of bone ashes, and is very porous. In this, if an alloy of lead and silver be heated with access of air, the lead oxydizes, and, melting into a glass, soaks into the cupel, or may be driven from the sur- face by a blast of air directed from a bellows. At the same time, any copper or other base, metal oxydizes and is re- moved along with the lead. The completion of the process is indicated by the silver assuming a certain brilliancy, or flashing, as the workmen term it. "What is fusible metal ? Under what forms does silver commonly occur? How is it reduced from the sulphuret ? What is the process of amalgama- tion ? What is the process of crystallization ? What of cupellation f 308 COMPOUNDS OF SILVER. Silver is a white metal capable of receiving a brilliant polish. It is malleable and ductile, an excellent conductor of heat and electricity. Its specific gravity is 10'5. It melts at 1873° F., and, when melted, absorbs a large quan- tity of oxygen, giving it out again as soon as it solidifies, and assuming a frosted or porous appearance. The pres- ence of a minute quantity of copper prevents this efiect. Silver is so soft that, for making plate or coins, it requires to be alloyed with a portion of copper ; from this it may be purified by dissolving it in nitric acid, and precipitating the silver as chloride by a solution of common salt. Silver shows little disposition to unite with oxygen, though it tar- nishes readily % the action of sulphureted hydrogen. It yields three oxides, but of its compounds the following are the most important : Protoxide of silver .... AgO = 116*323. Chloride ... , AgCl = U3'78. Iodide “ .... Agl =234-48. Sulphuret “ .... AgS = 124*43. The protoxide may be made by t^ie action of caustic pot- 2 |jSh on a solution of nitrate of silver, or by boiling recently- prepared chloride in potash. It is a dark powder, which may be reduced by heat alone. The chloride is sometimes found native, as horn-silver, and may be made by precipita- tion from the nitrate by hydrochloric acid, or a soluble chlo- ride. Like the iodide, it turns dark on exposure to the in- digo rays, and hence is used in photogenic drawing. The sulphuret is produced whenever sulphureted hydrogen acts on oxide of silver, or even metallic silver ; it is a black com- pound. Silver is easily detected by precipitation as a chloride : a curdy, white precipitate, insoluble in water, but soluble in ammonia. It turns dark on exposure to the sun. SALTS OF THE PROTOXIDE OF SILVER. Nitrate of Silver — Lunar Caustic — procured by dis- solving silver in nitric acid, diluted with twice its weight of water. It crystallizes in tables which are not deliques- cent and contain no water of crystallization. It enters into fusion at 426° F., but at higher temperatures undergoes de- What are the properties of silver? Why does it frequently require to be alloyed with copper ? What remarkable relation does it possess to ox- ygen ? How may the protoxide be prepared ? What changes do the chlo- ride and iodide exhibit under the influence of light ? How may silver be detected ? How is lunar caustic made ? MERCURY. 309 composition. It is frequently cast into small sticks and used by surgeons as a cautery. It is soluble in its own weight of cold and half its weight of hot water, and, when in con- tact with organic matter, turns black in the rays of the sun. Ammoniuret of Silver — Bertlwllet' s Fulminating Sil- ver — is formed by digesting precipitated oxide of silver in ammonia. It explodes with the utmost violence under the feeblest friction, with the evolution of nitrogen and the va- por of water. LECTURE LXYII. Mercury. — Process o f Reduction . — The Liquid State of — Its Oxides. — Calomel and Corrosive Suhlimole . — Detection of Mercury. — Its Salts. — Amalgams. — Gold. — Chloride of. — Purple of Cassius. — Palladium. — Platinum. — Its Catalytic Effects. — Platinum Black. — Iridium. — Rhodium. MERCURY. Hg — 202. Mercury may be obtained from the bisulphuret (cinna- bar) by distillation with iron filings. It is also, to a certain extent, found native. The striking characteristic of mercury is its liquid condi- tion. Its melting point is the lowest of that of any of the metals, being — 39° F. Its specific gravity at 47° F. is 13-545. It boils at 662° F. Kept at that temperature in the air for a length of time, it produces red oxide, but at common temperatures it is not acted on by the air. It may be freed from impurities for the purposes of the laboratory by being kept in contact with dilute nitric acid. It gives the following compounds of interest : Protoxide of mercury Peroxide “ Protochloride “ Bichloride “ Protosulphuret “ Bisulphuret “ . HgO — 210 013. . HgO., =218-020. . HgCl =237-42. . HgCl^ = 272-84. . HgS =218-1. . HgS^ = 234-2. The protoxide may be made by triturating calomel with potash water in a mortar. It is a black powder, which is Under what forms does mercury commonly occur ? What is the most striking property of this metal ? How may it be purified ? What are the properties of the protoxide of mercury ? COMPOUNDS OP MERCURY •sio decomposed by light or any of the reducing agents. The peroxide may be formed, as stated above, by the action of air on hot mercury, but more easily by dissolving mercury in nitric acid, and evaporating and heating the salt until no more fumes of nitrous acid are evolved. It is a red pow- der, and when warmed becomes almost black, the color re- turning as the temperature descends. Like the former, it is a base, and yields a class of salts. The Protochloride, or Calomel, may be made by adding hydrochloric acid to the protonitrate of mercury, or by sub- liming a mixture of bichloride of mercury and mercury. It is a white powder, insoluble in water, and darkens slowly by exposure to sunshine. The bichloride (or Corrosive Sub- limate) is formed when mercury burns in chlorine gas, but more economically by sublimation from a mixture of per- sulphate of mercury and common salt. It is a heavy, white crystalline body, soluble in water, has a metallic taste, and is poisonous. The antidote for it is albumen (the white of an egg). Of the sulphurets of mercury, the protosulphuret is black, and the bisulphuret commonly red ; in this case it passes in commerce under the name of vermilion, and is used as a paint. It can be obtained, however, quite black, a pecu- liarity already observed in the case of the peroxide, and still more strikingly in the biniodide, which may be sublimed in beautiful yellow crystals, which become of a splendid scarlet color by merely being touched. Mercury may be detected by being precipitated from its soluble combinations by metallic copper as a metal. Its salts, either alone or with carbonate of soda, heated in a tube, yield metallic mercury, which volatilizes. SALTS OF THE OXIDES OF MERCURY. Nitrates of the Oxides of Mercury. — When cold dilute nitric acid acts on mercury, it gives rise to neutral or basic protosalts, as the acid or mercury is in excess ; if the acid be hot, a pernitrate forms ; these salts are decomposed by an excess of water, giving rise to basic compounds. The neutral pernitrate exists in solution only. What are the properties of the peroxide of mercury ? What is calomel ? What is corrosive sublimate ? What is the antidote to it ? For what purpose is the bisulphuret employed ? What change occurs to the yellow biniodide when 4t is touched ? How may mercury be detected ? How are the proto- nitrate and the persulphate prepared ? GOLD. 311 Persulphate of Mercury is formed by boiling sulphuric acid and mercury, and evaporating to dryness. It occurs in the form of a white granular mass, and is decomposed by water, giving a yellow precipitate, a subsulphate called Turpeth Mineral. The alloys of mercury are called amalgams ; the amal- gam of tin is used for silvering looking-glasses, and that of zinc for exciting electrical machines. GOLD. 199-2. Gold is found native, and may be obtained by washing or by amalgamation with mercury. It may be purified from silver by quartation ; that is, fusing it with three times its weight of silver, and then acting on the mass with nitric acid. The gold is left as a dark powder. From all other metals gold is distinguished by its yellow color. Its specific gravity is 19*3. It melts at 2016° F. It is the most malleable of all the metals, as is proved by gold-leaf, which may be obtained jo"^oo thick- ness ; is not acted upon by the air or oxygen. Objects of art covered with it have retained their brilliancy for thou- sands of years. No acid alone dissolves it ; but it is solu- ble in aqua regia, and also by chlorine. It can, however, be made to yield two oxides, a protox- ide and a teroxide ; and two chlorides having the same constitution ; the terchloride is formed by the action of ni- tro-muriatic acid (aqua regia) on gold. When evaporated, it yields red, deliquescent crystals. Deoxydizing agents, such as protosulphate of iron, reduce it to the metallic state ; this is probably due to their decomposing water and present- ing hydrogen to the chloride. Hydrogen gas decomposes the terchloride, and, by heating it, it first changes into the protochloride and then into metallic gold. With a solution of tin it forms the Purple of Cassius. This and the ac- tion of protosulphate of iron serve as a test for it. PALLADIUM. Pd = 53-3. Palladium is found associated with platinum, and is best obtained from the cyanide of palladium by ignition. It is a white metal, requiring a high temperature for fusion ; Under what forms does gold occur ? What is quartation ? What are the properties of this metal ? How many oxides does it yield ? How is the terchloride prepared ? What is the purple of Cassius ? With what metal is palladium generally associated ? What are its properties ? 312 PLATINUM. specific gravity 11*5. It does not tarnish in the air, is dis- solved by nitric acid and aqua regia, is one of the wielding metals, and, when heated, acquires a purple oxydation like watch spring. It is used to some extent by dentists. Its compounds are not of importance. PLATINUM. = 98-84. Platinum is found native, but always associated with other metals. It is obtained by first forming a chloride of platinum and ammonium ; this, when ignited, leaves pure spongy platinum, which being exposed to powerful pressure, and then alternately made white hot and hammered, be- comes a solid mass. Platinum is a white metal. Its specific gravity is very high, being 21*5. It can not be melted in a furnace, but fuses before the oxyhydrogen blow-pipe. It is a welding metal, and on this fact its preparation depends. ' It is very malleable and ductile, is not acted upon by oxygen, air, or any acid alone, but dissolves in aqua regia. It possesses the extraordinary property of causing hydrogen and oxygen to unite at common temperatures, an elfect which takes place with remarkable energy when the metal is in a spongy state. A jet of hydrogen falling upon spongy platina in the air makes it red hot, and presently after the gas takes fire. It also brings about the rapid transformation of alcohol into acetic acid, and various other chemical changes. Fi^. 274 . If a quantity of ether be poured into a glass jar. Fig. 274, and a coil of pla- tinum wire, recently ignited, be intro- duced, the metal continues to glow so long as any ether is present. Platinum is invaluable to the chem- ist. It furnishes a variety of imple- ments of great value, and is met with under the forms of crucibles, tubes, wire, foil, &c. Platinum Black is prepared by slow- ly heating to 212° a solution of chloride of platinum, to which an excess of carbonate of soda and What superficial effect takes place when it is heated in the air ? How is platinum obtained Trom its ores ? What is the specific gravity of this metal ? By what acid may it be dissolved ? What remarkable relations does it possess to hydrogen gas ? Under its influence, what is alcohol transmuted into ? What is platinum black ? IRIDIUM. RHODIUM. 313 some sugar have been added. It is a dark powder, and possesses the property of determining a variety of chemical changes with much more energy than platinum in mass. Platinum can be caused to yield two oxides, which are not of any importance ; and two analogous chlorides, of which the bichloride, which is the common platinum salt, is made by dissolving the metal in nitro-muriatic acid, and evaporating to a sirup. It is soluble in water and alcohol, and is used for detecting the salts of potash. IRIDIUM. Jr = 98-84. Iridium is associated with platinum. It is said to have been found of specific gravity 26*00. Dr. Hare has obtain- ed it 21*8; it is, therefore, the heaviest of the metals. Its name is derived from the different colors (iris) of its com- pounds. RHODIUM. R = 52-2. Like the former metal, rhodium is associated with the platina ores. It is a hard white metal ; its specific grav- ity is 11*00, and is sometimes used to form tips to metallic pens. Wliat are the properties of iridium ? What are those of rhodium ? 0 PART IV. ORGANIC CHEMISTRY. LECTURE LXYIIL Peculiarities of Organic Bodies . — Their constituent El- ements . — Prone to Decomposition. — Carbon always present. — Compound Radicals . — Doctrine of Substi- tution . — Types. — Action of Heat . — Eremacausis . — Propagation of Decay. — Action of Acids and Alkalies. The theory of molecular arrangement, which has been al- ready given, forms the foundation of organic chemistry. It asserts that the characters of compound bodies do not alone depend on the nature of their constituent elements, nor even on the relative amount of those elements ; but that varia- tion of physical forms may result from atoms of the same name and of the same number arranging themselves in sub- ordinate groups, which groups then unite with each other. The leading ultimate elements of organized bodies are carbon, hydrogen, nitrogen, and oxygen. Almost all organic bodies arise from variations in the number and grouping of identical elements. Now a partial consideration of the conditions under which the theory of molecular arrangement acts, exhibits to us a most striking difference in the nature of the compounds formed upon its principles and the compounds heretofore de- scribed as examples of inorganic chemistry. In the one, peculiarity of grouping is the grand feature ; in the other, the character of the combining elements. Urea differs from the cyanate of ammonia in the arrangement of its constitu- ents only ; but the leading mark of distinction between sul- phuric and phosphoric acids is, that the one contains sul- phur and the other phosphorus. The number of substances which, besides the four men- On what do the characters of compound bodies depend ? Of what four reading elementary bodies are organic substances chiefly composed ? In what striking respect do the.se substances differ from inorganic ones ? CHARACTERS OF ORGANIC BODIES. 315 tioned above, enter into the composition of organic bodies is very limited. Among such may be mentioned potash, soda, lime, magnesia, oxide of iron, chlorine, fluorine, sulphur, phos-- phorus, and silica. Some of those bodies, such as alumina, which appear to take the lead in inorganic productions, arc here scarcely seen. While the laws of inorganic chemistry appear to be fully in operation as respects the bodies on the study of which we are now entering, there are some peculiarities which deserve to be pointed out. The remarkable instability, or proneness to decomposition, which so many of them exhibit, generally tends to the production of secondary compounds of a much more stable nature. At a red heat all organized bodies are decomposed ; and as the elements of which thej consist are endowed with the most energetic affinities, any extensive elevation of temperature tends to impress upon them a change. ‘With but few exceptions, the attempts which have hitherto been made to produce them artificial* ly have been abortive ; but this is, probably, rather due tc our want of knowledge than any intrinsic impossibility in efi’ecting such combinations. With the exception of a few bodies, such as ammonia, which, in point of fact, belong rather to inorganic chemistry, all organized bodies contain carbon. Of late, by indirect processes, chemists have succeeded in obtaining pseudo-or- ganized compounds, into the constitution of which such bod- ies as platinum and arsenic enter. In inorganic chemistry we see a constant disposition to the binary form of union : a disposition wffiich is well rep- resented by the electro-chemical theory. Thus, potassium unites with oxygen, two bodies together, to form potash ; and this, again, with sulphuric acid, two bodies together, to form sulphate of potash. In very many instances, the same thing can be traced in organic chemistry; only here, instead of having such bodies as chlorine or iodine, potassium or so- dium to deal with, we find compound bodies which dis- charge analogous functions. These bodies go under the name of compound radicals. They may be divided into dis- tinct groups, some discharging the duty of electro-negative, What other elements are found among organic bodies ? In their decom- position, what do they generally produce ? Can any of them withstand a red heat ? Can they be formed oy artificial means ? What is meant by compound ridicals? 1 310 COMPOUND RADICALS. some of electro-positive, and some of indifferent bodies, several cases they have been insulated, but in others t remain as yet as ideal or hypothetical bodies. Table of Compound Radicals. Amidogen. Iridiocyanogen. Acetyle. Oxalyle. Sulphocyanogen. Kakodyle. Cyanogen. Mellone. M ethyle. Ferrocyanogen. Uryle. Formyle, Ferridcyanogen. Benzyle. Cetyle. Cobaltocyanogen. Salicyle. Amyle. Chromocyanogen. Platinocyanogen. Cinnamyle. Ethyle. Glyceryle. The qualities of bodies depending as much on the mode of arrangement of their constituent particles as on the chem- ; ical nature of those particles, it has been found convenient to arrange them in groups, according to their type of struc- ture ; thus, for instance, in the former department of chem- i istry, such bodies as hydrochloric, hydriodic, hydro bromic j acids may be arranged together as belonging to one type ; and from the first of these all the rest may be conceived as arising, by substituting an atom of iodine, bromine, fluorine, &o;, for the atom of chlorine which it contains. I The bodies which can thus be substituted for each other j appear to have certain relationships ; for the substitution of i| a given substance can not take place indiscriminately by all other bodies. As a general rule, in inorganic combinations, j electro-negative bodies can only be substituted by electro- i negative, and electro-positive by electro-positive. But many j of the most prominent cases in organic chemistry are pre- j cisely the reverse. In them, for example, we find chlorine, j a powerful electro-negative, taking the place of hydrogen, an equally powerful electro-positive body, and, in the com- pound, discharging all its functions. For these reasons, it has been supposed that the electro-chemical theory fails to furnish any explanation ; but I have proved that chlorine, f like many other bodies, can assume different allotropic j states ; at one time being an active electro-negative body, j and at another quite passive. Moreover, it ought not to be 1 forgotten that hydrogen, in relation to carbon, is as much an | electro-negative body as chlorine itself. A chemical type is, therefore, a system, or group of atoms "Wliat compound radicals are known? Under what circumstances can bodies be substituted for each other? Is there any difference in this re- spect betw^een inorganic and organic bodies ? "WTiat is a chemical type ? DESTRUCTION OF ORGANIC COMPOUNDS. .'U? of a certain number, arranged in a certain relationship with each other. From this each atom may be displaced, and one of another kind substituted in its stead ; and this may be carried forward until not one of the original atoms is left, the new group officiating in all respects like its ])rcde- cessor. But should one of the atoms be displaced, and no new one substituted for it, then, the remaining atoms chang- ing their position, the type is broken up and a new one is the result. Organic compounds, being for the most part composed of carbon, hydrogen, nitrogen, and oxygen, exhibit a con- stant tendency to break up into subordinate groups, and eventually to give rise to the production of the simpler bi- nary bodies, carbonic acid, water, and ammonia. The car- bon constantly inclines to unite with oxygen to form carbonic acid, the hydrogen, in the same manner, to form water, or, with the nitrogen, to produce ammonia ; and these tenden- cies may be satisfied in a variety of ways. Elevations of temperature in the open air at once give rise to carbonic acid, water, and free nitrogen ; or if in close vessels out of the contact of air, to an extensive series of compounds, dif- fering in each case with the substance exposed, and of a less complex constitution. Even in the air, at common temperatures, a slow action often goes on, as in the decay of wood or the souring of wine ; hence called eremacausis (slow combustiow). When a combustible substance is ignited in the air at one point, the burning presently spreads throughout the whole mass ; and»in the slow combustion, eremacausis, the same takes place. A substance undergoing such a change, if placed in contact with another capable of undergoing it, propagates its effect throughout the whole mass. For this reason, the decay of yeast, a ferment, impresses a metamor- phosis on sugar, compelling it to give off carbonic acid gas ; and putrefaction of fresh meat is easily brought on by the contact of putrid animal matter. Nitric, sulphuric, and other strong acids impress striking changes when heated with organic matters; thus, when the former acts on starch, oxalic acid is formed ; when sulphuric Under what circumstances do new types result? What are the binary bodies eventually produced ? What is the result of elevation of tempera- ture in the open air? What in close vessels? What is meant by erema- causis? In what respect does eremacausis resemble common combustion? What is the effect of strong acids and alkalies on organic bodies ? 318 THE NON-NITROGENIZED BODIES. acid acts on oxalic, it totally destroys it, resolving it into carbonic acid, carbonic oxide, and water. In the same man- ner, also, basic bodies produce striking changes, generally giving rise to the production of acids, and the evolution of hydrogen and ammonia. In the present state of organic chemistry, it is impossible to present a perfect system of arrangement, as in inorganic chemistry, or one approaching to the finish of that depart- ment. The course, therefore, which I shall now take is rec- ommended rather for its usefulness in facilitating study than for the propriety of its classification. The Non-nitrogenized Bodies. — The Starch Group , — Starch. — Action of Iodine . — Various Forms of Starch. — Production of Dextrine. — Action of Diastase. — Leio~ come . — Cane Sugar . — Glucose. — Distinction betiveen Cane and Grape Sugar. — Milk Sugar. — Gum. — Dig' nine. The non-nitrogenized bodies, which we shall first consid- er, are characterized by the peculiarity that they form a group, each member containing twelve atoms of carbon, united with hydrogen and oxygen in the proportions to form water. They are, for the most part, indifferent bodies. Starch — Fecula (C'^g^io^io) — found abundantly in the vegetable kingdom, and may be obtained from potatoes by rasping and washing the mass upon a sieve, the starch being carried off by the water. It may also be obtained from flour by making it into a paste with water and then washing it. The starch separates, and gluten is left behind. How many carbon atoms does each member of the amyle group contain? In what proportion are their oxygen and hydrogen? Mention some of the chief bodies of this group. Frpm what sources, and in what manner, is gtaroh obtained ? LECTURE LXIX. The Starch Group. Starch Cane sugar (crystallized) .... Grape sugar Milk sugar . Gum . . . Lignine . . VARIETIES OF STARCH. 31 $> It is a white substance, commonly met with in irregular prismatic masses, which shape it assumes while drying. It is insoluble in cold water, and also in alcohol, and consists of granules of difierent sizes, as it is derived from difi'erent plants, those of the potato being about the two hundred and fiftieth of an inch in diameter. When starch is heated in water, the covering membrane of each granule bursts open, and the interior matter dis- solves out. If the proportion of starch be considerable, the whole forms a jelly-like mass, which may be dried in a yel- lowish body, having the same constitution as starch itself. Gelatinous starch passes under the name of Amidine. With free iodine, starch strikes a deep blue color. When water containing this compound is heated to 212° F., the color totally disappears, and is not restored on cooling ; but if the source of heat be removed as soon as the color disap- pears, and before the temperature reaches 212° F., the color returns. Starch and iodine constitute an exceedingly deli- cate test for each other. In commerce, starch is found under various modifications, such as ArroW'TOot, Tapioca, Cassava, Sago. It forms an important article of respiratory food. Inuline, which is de- rived from the dahlia and other plants, is a substance ap- proaching starch in many respects. When starch is boiled in water with a small quantity of sulphuric acid, it changes into Dextrine, a substance of the same composition ; the acid being subsequently removed by carbonate of lime and filtration, that body is procured on evaporation as a gummy mass. But if the ebullition be continued for a longer time, the dextrine disappears, and grape sugar comes in its stead. Starch may also be con- verted into grape sugar by the action of a peculiar ferment, Diastase, which is contained in an infusion of malt. Ge- latinous starch may, in the course of a few minutes, at 160° F., be converted into dextrine by this substance, and soon after into sugar. In either of these cases the presence of atmospheric air is not required ; the final action being that the starch simply assumes three atoms of water, and be- comes converted into grape sugar. What is the size of its granules ? What is the effect of hot water on it? What is a amidine ? What is the action of iodine on starch ? Mention Borae other varieties of starch. How is it converted into dextrine ? How into grape sugar ? What is diastase ? What is its action on starch ? 320 CANE SUGAR. GRAPE SUGAR. When baked at a temperature of about 400° F «tarch becomes soluble in water, and passes in commerce under tlie name ot hritisli Gum, or Leiocome. Cane Sugar + 2HO) is found abundantly in the juices oi many plants, and is chiefly extracted for coxa- mercial purposes from the sugar-cane, which, being crushed between rollers, yields a juice, which is mixed with lime and boiled ; a coagulum having been removed from it, it IS rapidly evaporated, at as low a temperature as possible, and then crystallized. In this state, after a brownish sir- up, molasses, has drained from it, it passes in commerce un- der the name of Muscovado, or brown sugar. This is pu- rifled by boiling in water with albumen, which, coagula- ting separates many of the impurities ; the solution is then decolorized by animal charcoal, evaporated, solidified in co- nical vessels, and, being washed with a little clean sirup IS thrown into commerce as loaf-sugar. Sugar is also ob- tained from the sap of the maple-tree, and from beet-root hrom a strong solution sugar crystallizes in rhombic prisms, which are colorless ; they pass under the name of au gar Candy. It is soluble in one third its weight of cold water and in any quantity of hot. It has a sweet and proverbially characteristic taste. When heated, it melts and gives rise to a yellowish, transparent body, called Bar- ley b>ugar. _ But if kept at a temperature of 630*^ F. it turns of a reddish-brown color, constituting Caramel. Sutr- ar unites with various bodies, such as lime and oxide of lead, and with common salt yields a crystallized product. i3y caserne it is transformed into lactic acid Grape Sugar-F-mit Sugar- Glucose-Starch Sugar ^“^«^^(^i 2 ^i 40 u)-is the substance just de- • n arising lom the transmutation of starch under the influence of acids. It occurs naturally in many vege- table juices and in honey. j n Compared with cane sugar, it is much less soluble in water, and less disposed to crystallize. It requires IJ parts of water for so ution. It may be distinguished by its action with caustic alkalies and sulphuric acid, the former turn- mg It brown, and the latter dis solving it without blacken- ^ How is Bri'jsh gum formed ? From what sources, and by what means IS cane sugar derived? ^What are its Drooerties ? Rw means, amel formed ? What is the difference Sn cane a^d gra‘ Bv what test may they be distinguished ? ^ ^ MILK SUGAR, — GUM.— LIGNINE. 321 ing, while cane sugar is little acted on in the former in* stance, and blackened in the latter. The two varieties may also be distinguished by being mixed with a solution of sulphate of copper, to which, if caustic potash be added, blue liquids are obtained, and these being heated, the grape sugar throws down a green precipitate, which turns deep red, the solution being left colorless : the cane sugar alters very slowly, a red precipitate gradually forming, aud the liquid remaining blue. Grape sugar, like cane sugar, gives with common salt a crystallized compound. When heated to 212 ^ F. it loses two atoms of water, and becomes Cy^ Milk Sugar — Lactine (^^12-^^12^12) — obtained by evaporating whey to a sirup, and the crystals which then form are to be purified by animal charcoal. It is spar- ingly soluble, requiring five or six times its weight of wa- ter. The crystals are gritty between the teeth. It is through the alcoholic fermentation of this body that the Tartars procure intoxicating milk. Besides the foregoing, there are several subordinate vari eties of sugar, among which may be cited Ergot sugar ; Eucalyptus sugar ; and others, as liquorice sugar, mushroom sugar, or man- nite, &c. Gum. — Gum Arabic is obtained from several species of the mimosa or acacia, from the bark of which it exudes ; is obtained in white or yellowish tears, of a vitreous aspect. It dissolves in cold water, forming mucilage, from which it may be precipitated pure, as Arabine, by alcohol. Bassorine is the principle of Gum Tragacanth ; it does not dissolve in water, but merely forms a jelly like mass. With this substance should be classed Pectine, the jelly obtained from currants and other fruits. This substance furnishes Pectic acid by the action of bases. Lignine. — This substance, with Cellulose and other bod- ies, forms the woody fibre or ligneous tissue of plants. It occurs in a state of purity in the fibres of fine linen and cotton, and, as is well known, is of perfect whiteness, insol- uble in water and alcohol, and tasteless. Strong and cold What are the properties of milk sugar? Mention some other varieties of sugar ? From what source is gum derived ? What are arabine, basso- rine, and pectine ? How may lignine be prepared ? When pure, what is its color, and what is its relation to water ? O 2 I 322 ACTION OF SULPHURIC ACID ON SUGAR. sulphuric acid converts it into a dextrine, as may be shown by adding to that substance pieces oflinen, taking care that the temperature does not rise so as to blacken the mixture, which is to be w'ell stirred, and suffered to stand. for a time. On dissolving it then in water, and neutralizing by the ad- dition of chalk, dextrine is obtained ; or if, before neutral- izing, the solution is well boiled, grape sugar is produced. LECTURE LXX. j Action of Agents on the Starch Group. — Action of Sulphuric Acid on Sugar. — Glucic Acid j)roduced by ■ Lime. — Melassic Acid. — Action of Nitric Acid. — Pro- duction of Oxalic Acid. — Constitution of Oxalic Acid. — Its Salts. — Oxamide. — Saccharic Acid. — Rhodizon- ic and Croconic Acids. — Mucic Acid. — Xyloidine. — j Its Properties. | In the preceding Lecture we have already explained the | change of starch into sugar, and of ligriine into dextrine, un- der the influence of sulphuric acid ; and in the vegetable I world there can be no doubt that these and other similar modifications arise from the action of many causes. On in- j specting the constitution of the group, it will be seen that, in theory, this is to be done by the addition or abstraction of water. When melted grape sugar is mixed with strong sulphuric j acid, and the diluted solution neutralized with carbonate of baryta, the sulphosaccharate of baryta is found in the solu- tion. The Sulphosaccharic acid is a sweetish liquid, read- j ily decomposing into sugar and sulphuric acid. jj When, in the process of converting cane sugar into grape ! sugar by boiling with sulphuric acid, the action is long con- | tinued, a dark-colored substance is formed, consisting of two ^ different bodies, JJlmine and TJlmic Acid, or, as they are ' termed by Liebig, Sacchulmine and Sacchulmic Acid. The I latter is converted into the former by continual boiling in , water. ! When a solution of grape sugar containing lime is kept How may lignine be converted into dextrine and crape si:g-r ? In this change, what is the action impressed on the lignine ? How is sulphosac- charic acid made ? What are sacchulmine and sacchulmic acid ? OXALIC ACID. 323 for some time, the alkaline reaction of the lime finally dis appears through the formation of Glucic Acid, the consti- tution of which is CqH^O^. It is soluble, deliquescent, of a sour taste, and yielding, for the most part, soluble salts. If grape sugar be boiled with potash water until it becomes black, a dark substance may be precipitated by an acid. This is Melasinic Acid, its constitution being Cy^H^O^. These are some of the less important results of the action of acid and alkaline bodies on the starch group ; there are others of far more interest. Oxalic Acid (CgOg, HO -f- 2Aq ). — Oxalic acid is form- ed by the action of nitric acid on starch or sugar, or any other of the starch group, except gum and sugar of milk. One part of sugar is to be mixed with five of nitric acid, di- luted with twice its weight of water, and the acid finally distilled off until the residue will deposit crystals on cooling. These, being collected, are to be purified by redissolving and crystallizing. They are oblique rhombic prisms, more soluble in hot than cold water, of an intensely acid taste, and poisonous to the animal economy, chalk or magnesia being the antidote. Oxalic acid also occurs naturally in several plants, in union with potash or lime. As the foregoing formula shows, the crystals of oxalic acid contain one equivalent of saline water and two of water of crystallization. The latter may be removed by exposure to a low heat, the crystals then becoming a white powder, and subliming without difficulty. Any attempt to remove the saline water and isolate the oxalic acid (as C^O^) leads to its decomposition. Thus, when the acid is heated with oil of vitriol, total decomposition results; equal volumes of car- bonic oxide and carbonic acid are set free ; for the consti- tution of oxalic acid is such, that we may regard it as com- posed of an atom of each of these bodies : C203... = ...C02+ CO; and upon this is founded one of the methods of preparing car- bonic oxide gas. The gaseous mixture which results from the action of the oil of vitriol is passed, as in Fig. 250, through a bottle containing potash water, which absorbs the carbonic acid, and the carbonic oxide may be collected at the water trough. What is the constitution of glucic acid ? What is the action of potash on grape sugar? Describe the preparation of oxalic acid. What is the anti- dote to it? What i.s the action of oil of vitriol on oxalic acid ? 324 SALTS OF OXALIC ACID. The production of oxalic acid from sugar by nitric acid is due to the replacement of hydrogen by an equivalent quan- tity of oxygen. . . +- ^18 . . + IZgOg ; that is, one atom of dry sugar with eighteen of oxygen yields six atoms of oxalic acid and nine of water. Salts of Oxalic Acid. There are three potash salts : 1st. Neutral Oxalate of Potash, made by neutralizing oxalic acid with carbonate of potash ; crystallizes in rhombic prisms, soluble in three times its weight of water. ^ 2d. Binoxaldte of Potash, made by dividing a solution of oxalic acid into two parts ; neutralize one with carbonate of potash, and then add the other. It crystallizes in rhombic prisms, has a sour taste, and dissolves in forty parts of water. It occurs naturally in several plants, as the Oxalis Acetosella. 3d. Quadroxa^ late of Potash. Divide a solution of oxalic acid into four ]>arts ; neutralize one, and add the rest. It crystallizes in octahedrons ; is less soluble than either of the foregoing. These salts are sometimes used for the removal of ink stains from linen. Oxalate of Ammonia, prepared by neutralizing a hot so- lution of oxalic acid with carbonate of ammonia. It crys- tallizes in rhombic prisms, which are efflorescent. Its so- lution is used, as has been already stated, as a test and pre- cipitant of lime. When exposed to heat in a retort, is is, for the most part, decomposed into water, ammonia, carbonic acid, cyanogen, and other compounds ; but a substance of the name of Oxamide also sublimes, the constitution of which is C^H^NO^...^...NH^-^2{CO), that is, containing the constituents of one atom of amidogen and two of carbonic oxide. This remarkable substance, when boiled with potash, yields, through the decomposition of water, oxalate of potash and ammoniacal gas. Oxalate of Lime occurs naturally, forming the skeleton of many lichens, and is obtained, as has just been said, by precipitating a lime salt. It is soluble in nitric acid, and. How is oxalic acid produced from sugar ? How many oxalates of pot- ash are there? How are they prepared? For what purpose are the^ Balts sometimes used? Under what circumstaiices does oxamide forrn? What is its constitution ? GUN COTTON. 325 Ignited in a covered crucible, is converted into carbonate of lime. Saccharic Acid "I" 5iJO ) — Oxalhydric Acid — made by the action of dilute nitric acid on sugar. It is a pentabasic acid. Hhodizo^ic Acid +-3J/0), obtained by the action of potassium on carbonic oxide at a red heat. When boiled, it changes into Croconic Acid^ a yellow body having the constitution + HO. Mucic Acid -}- %HO), obtained by the action of dilute nitric acid on gum or sugar of milk, as in the prep- aration of oxalic acid by ether members of the starch group. It requires sixty times its wei^it of water for solution. De- composed by heat, it yields pyromucic acid. Xyloidine ^^ 5 )^ made by the action of nitric acid, sp. gr. 1*5, on the starch, which is converted into a gelatinous body, and yields this substance as a white pre- cipitate when acted on by water. Its origin is apparent from a comparison of its formula with that of starch. Xy- loidine is insoluble in boiling water, but by the continued action of nitric acid changes into oxalic acid. 100 parts of starch yield 128 of xyloidine. Gun Cotton. — Pyroxyline. A remarkable compound, proposed as a substitute for gunpowder by Schonbein, whose process for preparing it has not yet been divulged. It may be made by the action of monohydrated nitric acid on cotton, paper, or sawdust ; and still more conveniently by a mixture of nitric and sulphuric acids on those sub- stances. The cheapest and best process for its preparation is that discovered by Professor Ellet, of South Carolina College It consists in soaking carded cotton for a few minutes in a mixture of pulverized nitrate of potash and oil of vitriol, washing the result in hot water to free the cotton from the potash salt, and finishing the washing by a weak solution of ammonia. Gun cotton appears white, like ordinary cot- ton, the fibre being little changed ; it is somewhat harsh to the touch ; when perfectly dry, it explodes when heated to about 300° F., or by the blow of a hammer. It is esti- Hovv is saccharic acid made ? How is the rhodizonate of potash formed ? What is its composition? How is it changed into croconic acid? Under what circumstances does mucic acid form ? Decomposed by heat, what does mucic acid yield ? How is xyloidine prepared, and what are its properties? 326 FERMENTATION. mated as having about three times the mechanical force of gunpowder. 100 parts of cotton yield about 165 of gun cotton. It contains twice as much nitric acid as xyloidine. LECTURE LXXI. On the Metamorphosis of the Starch Group by Nitro- GENI2ED Ferments. — Action of Leaven. — Bread. — Fer- mentation of Sugar. — Fermentation of Grajpe Juice . — Primary Action on the JSerment. — Activity of Fer- ments due to Nitrogen. — Effects of Temperature. — Pro- duction of Butyric Acid. — Ferments of different Prop- erties. — Production of Wine and intoxicating Liquids. In the preceding Lecture we have traced the action of the more powerful inorganic agents on the amyles, and seen how a variety of bodies of different characters arise, some of which, as oxalic acid, are of very considerable importance But there is another system of changes which can be im- pressed on this group of bodies, far more curious in its na- ture, and leading to far more important results. When flour, made into a paste with water, is brought in contact with Leaven, that is to say, a similar dough, under- going an incipient putrefactive fermentation, at a temper- ature of 60^ or 70° F., bubbles of gas are disengaged, the paste swells up, and, when baked, forms leavened bread. This ancient process, which is now in use all over the world, depends on the action of the changing leaven being propa- gated to the sugar which the flour contains. The sugar is resolved into alcohol and carbonic acid gas, the former of which may be obtained by distilling the dough ; and the bubbles of the latter, entrapped in the yielding mass, gives to the bread the lightness for which it is prized. But this process may be better traced by observing the phenomena of alcoholic fermentation in the case of pure sug- ar. If we take a solution of sugar in water, it may be kept for a length of time without undergoing any change ; but if nitrogenized matters, such as blood, albumen, leaven, in a state of putrescent decay, are mixed with it, then, at a What is the action of leaven on flour? What is the action of decaying nitrogenized matter on a solution of sugar ? ACTION OF FERMENTS* 327 temperature of 70° F., the sugar rapidly disappears, car* boiiic acid is given off, and alcohol is Ibund in the solution. The change is obvious. ^ . 2( C,H,0,) + 4(CO,) ; that is, one atom of dry grape sugar yields two of alcohol and four of carbonic acid. The final action, therefore, of the ferment is to split the sugar atom into carbonic acid and al- cohol. Of all ferments. Yeast, for these purposes, is the most pow- erful ; it is a substance w’hich arises during the fermenta- tion of beer. It is probable that, in the various sugars, the first action is to bring them into the condition of grape sug- ar, and then the metamorphosis ensues. By an analogous transformation of the sugar contained in fruits, the dillerent wines and other intoxicating liquids are formed ; thus, if we take the expressed juice of grapes which has not been exposed to the contact of air, it may be kept for a length of time without change ; but if a single bubble of oxygen is admitted to it, fermentation at once sets in, the grape sugar disappears, and alcohol comes in its stead, car- bonic acid gas being disengaged, and the nitrogenized sub- stance, yeast, deposited. If a solution of pure sugar be add- ed, it is involved in the change, and portion after portion will disappear; but, finally, the yeast itself is exhausted, and then any excess of sugar remains unacted upon. It is obvious that the primary action is an oxydation of the ferment, and the moment its particles are set in motion, the motion is propagated to the adjacent body, the particles of which submit in succession ; and therefore the ferment- ation is not a sudden action, but one requiring time. More- over, it is plain that the action is limited ; a given quantity of yeast will transmute only a definite quantity of sugar. The ferments, or bodies which possess this singular quality, are nitrogenized bodies ; and, inasmuch as non-nitrogenized bodies never spontaneously ferment while oxydizing, it is to the nitrogen that we are to impute the qualities in question. Temperature has a remarkable control over ferment ac- tion. The juice of carrots or beets, fermenting at 50° Into what bodies does the sugar atom split ? What is the action of yeast on sugar? Describe the action of yeast on grape juice. What is the pri- mary action in these cases ? Is the action of the ferment definite ? To what element in the yeast is the action due ? WTat is the effect of tem- perature on fermentation ? 328 ACTION OF FERMENTS. Fahr., will yield alcohol, carhonic acid, and yeast ; hut the same juices, lermeiituig at 120° Fain*., produce lactic acid, gum, and maiinite. Under these circumstances, therefore, alcohol is the product of lermentation at low, and lactic acid at high teraperature&^! But when milk ferments at 50° Fahr., lactic acid is the chief product, while at 80° Fahr. the casein acts like a yeast ferment, the milk sugar becoming transformed into grape sugar, and then resolving itself into alcohol and car- bonic acid. In this instance the action is the reverse of the former, lactic acid being the product of a low, and alcohol of a high temperature. A very remarkable decomposition takes place when casein ferment acts on sugar at 80° Fahr. in presence of carbon- ate of lime. Under these circumstances, carbonic acid gas and hydrogen are evolved, and Butyric Acid appears. On comparing the constitution of butyric acid with alcohol, it will be seen that the latter contains the elements of the for- mer, with an excess of hydrogen ; so that, duriiig this fer- mentation, the alcohol atom is divided. All ferments possess certain properties in common, but each has its specific powers ; and the products which are evolved difier in diflerent cases. Most commonly the ac- tivity of. these bodies is excited by an incipient oxydation, the result of wdiich would be to bring the ferment itself to a simpler constitution. In this respect, therefore, the first stage of fermentation is a combustion at common tempera- tures, or an eremacausis of the ferment itself ; but this ac- tion is speedily propagated to the surrounding mass, which becomes involved in the change. Whatever, therefore, pre- vents the incipient oxydation of the ferment, puts a stop to the whole process. By raising their temperature to 212°, and then cutting off the access of air, substances which would otherwise undergo a very rapid change may be kept for any length of time without alteration. On this princi- ple, meats, milk, and other viands may be preserved. We have now pointed out the peculiarities of ferment ac- tion, showing that two successive stages may be traced in the process ; the first arising in the oxydation of the fer- Describe the causes of tbe fermentation of vegetable juices and of milk ? Under what circumstances does butyric acid form? What is the change ■which the ferment itself undergoes ? What is the effect of cutting off the access of air ? What are the two stages of ferment action ? PREPARATION OF WINES. meiit, by which its molecules are decomposed ; and the second, which consists in the propagation of this movement to the surrounding particles, upon which changes are im- pressed, the nature of which differs with the temperature and the specilic action of the ferment itself. Wine is made from the expressed juice of grapes, which, containing a nitrogenized body, albumen, when exposed to the air undergoes spontaneous fermentation ; the course of the action being, 1st. The oxydation of the vegetable albu- men ; 2d. The propagation of its action to the grape sugar. If the sugar is in excess, the wine remains sweet ; il‘ the albumen is in excess, the wfne is dry. The wine, as soon as the first action is over, is removed into casks. During these changes, the bitartrate of potash, which exists natur- ally in grape juice, and which, though sparingly soluble in water, is much less so in alcohol, is deposited. It goes un- der the name o^Argol. Most other fruit juices contain free acid, such as malic or citric ; and hence good wine can not be made from them, because, if all the sugar is removed, they possess a sharp taste ; and if, as is commonly the case, a portion is, left to correct the acidity, it is liable to run into a second fermentation. . Inferior liquids, such as cider, perry, &c., are made from other vegetable juices, as those of apples, pears, &c. Beer, porter, and ale are made from an infusion of malt, which is barley, a portion of the starch of which is transposed into sugar by partial germination. The principles of the fer- mentation are, in all these instances, the same. LEOTUIIE LXXII. On the Derivatives of Fermentative Processes. — Alcohol. — Its Propei'ties. — Exists in Wines, — Lactic Acid. — Production and Properties. — Sulphuric Ether. — Its Distillation . — The Ethyle Series . — Chloride . — Bromide. — Nitrate, cj-c . — (Enanthic Ether. ALCOHOL {Hydrated Oxide of Ethyle) By \he distillation of wine, or aiiy other fermented sac- What is the process for the making of winp ? When is the wine sweet and when dry ? What is argol ? Why are other fruit juices less propei for making wine than grape juice ? How is alcohol procured ? 330 LACTIC ACID. charine juice, spirits of wine may be obtained. As first pre- pared, it contains a large quantity of water, which comes over with it. This product being rectified, and the first por- tion preserved, yields a spirit containing twelve to fifteen per cent, of water. By putting this into a retort with half its weight of quicklime, keeping the mixture a few days, and then distilling at a low temperature, absolute or anhy- drous alcohol is obtained. Anhydrous alcohol is a colorless liquid, of a burning taste and pleasant odor. Its specific gravity, at 60° F., is 0*795. It boils at 173° F., and at a still lower point if slightly diluted with water, though the boiling point rises if the water be in greater proportion. It has not been yet frozen. The spe- cific gravity, also, varies with the amount of water present ; and hence the purity of spirits of wine may be determined by ascertaining its density. Alcohol is very inflammable, burns with a pale blue flame, with the production of car- bonic acid gas and water. It is much used in chemical in- vestigations as furnishing a lamp flame free from smoke, and as possessing an extensive range of solvent powers, act- ing upon resins, oils, and other bodies, which arq not acted upon by water. The strong wines, such as port and sherry, contain from*, nineteen to twenty-five per cent, of alcohol ; the light win& from twelve per cent, upward ; and beer, porter, &c., from five to ten per cent. Lactic Acid Fermentation . — We have already seen that vegetable juices as well as milk will, under certain cir- cumstances of temperature, yield, during fermentation, lac- tic acid instead of alcohol. This acid may therefore be made by dissolving a quantity of sugar of milk in milk, put- ting it in a warm place, and allowing it to turn sour spon- taneously. A part of the casein of the milk here acts as the ferment, and as lactic acid is set free, it coagulates the rest and mak-es it insoluble. By the addition of carbonate of soda, to neutralize the acid, this is prevented, and the ferment, resuming its activity, produces more lactic acid. When, by this process, all the sugar is exhausted, the liquid is boiled, filtered, evaporated to dryness, and the lactate of How may it be obtained anhydrous ? What are its properties ? How may the strength of spirits of wine be determined ? For what purposes is it used in chemistry ? How much alcohol per cent, is contained in port, iherry, beer, and ale ? LACTIC ACID. LTMKK. 331 soda dissolved out by hot alcohol. From this alcoholic so- luUon the acid may be obtained by precipitating the soda by sulphuric acid. Lactic Acid {C is obtained as a sirupy so- lution by concentrating in a vacuum over oil of vitriol. It is colorless, has a specific gravity of 1 -215, is very sour, and soluble in water and alcohol. It yields a complete series of salts, most of which are soluble. Among these salts, the most interesting are those of lime and of zinc. Ether — S'ldphuric Lther — Oxide of Ethyle — Ether is prepared by distilling equal weights of alcohol and oil of vitriol, receiving the resulting vapor in a Liebig’s condenser, a d h c, as in Fig, 275, the condenser being cool- ed by water from the reservoir, z, flowing into the funnel, 6*, the waste passing into the vessel, 5, and the ether distilling into the bottle, e. The process is to be stopped as soon as the mixture begins to blacken. The first product may be rectified by redistillation from caustic potash. Ether is a colorless and limpid liquid, of a peculiar odor and hot taste. It boils at 96"^ F., and has not yet been frozen. Its specific gravity, at 60^ F., is ’720. It volatil- izes with rapidity, and therefore produces cold. It is com- Vrhat is the process for obtaining lactic acid ? V/hat is its constitution? What are its properties ? How is ether made ? What are the properties of ether ? COMPOUNDS OF ETHYLE. Sd2 bnstible, and burns with the evolution of much more light than alcohol. The specific gravity of its vapor is 2 586. ■VYith oxygen or atmospheric air it forms an explosive mix- ture, and, kept in contact with air, it becomes acid from the plod action ot acetic acid. It dissolves in alcohol in ail pro- portions, but ten parts of Avater are required to dissolve one of it ; it also dissolves many fatty substances, and hence is of considerable use in organic chemistry. Ether is regarded as the oxide of an ideal compound rad- ical, ethyle, Avhich gives rise to a series of other bodies. T/ie Ethyle Group. Ethyle, C^Ef^ :r:z: Oxide of ethyle = Ae, O. Hydrated oxide = Ae, O 4- HO. Chloride of ethyle . . . . = Ae, Cl. Bromide “ ....=:= Ae, B. Nitrate “ ....=. Ae, 04- NO.. Hyponitnte “ . . . . == Ae, O 4- NO.. &c. The oxide of ethyle, as has just been stated, is ether it- self The hydrated oxide is alcohol. Chloride of ^ Ethyle — Hydrochloric Ether — may be made by saturating rectified spirits of Avine with dry hydro- chloric acid gas, and distilling the result at a low temper- ature, conducting the A^apor through a bottle of Avarm wa- ter, and then condensing in a receiA^er surrounded by a freezing mixture. It is a colorless, volatile liquid, of a pe- cuhar aromatic smell; the specific gravity is *874. It boils at 52^, and is not decomposed by nitrate of silA^’er. Bromide of Etlujle {Hydrobromic Ether) and Iodide of Ethyle {Hydriodic Ether) are not of any importance ; and the same remark may be made as respects the suhohu- ret and the cya7iide. Niti'ate of Ethyle — Nitric Ether — may be made on the small scale by distilling equal weights of alcohol and nitric acid with a small quantity of nitrate of urea. The latter substance is used to prevent the nitric acid deoxydizing, and giving rise to the production of hyponitrite instead of nitrate of ethyle. Nitrate of ethyle is insoluble in water has a density of boils at 185°, and has a sweet taste. Its vapor explodes when heated. Is ether soluble in water? What elass of bodies does it dissolve ’ Of what substance is it an oxide ? What is the true name of hydrochloric ether, and how is it prepared ? How is the nitrate of ethyle ? COMPOUNDS OF ETHYLE. 333 Hyjoonitrite of Ethyle — Nitwits Ether {AeO, NO ^). — This ether may be made by passing the hyponitrous acid, disengaged from one part of starch and ten of nitric acid, through alcohol, diluted with half its weight of water and kept cold. It is a yellowish, aromatic liquid, having the odor of apples. It boils at 62° F. Its density is *967. The sweet spirits of nitre is a solution of this ether with al- dehyde and other substances in alcohol. Carbonate of Ethyle — Carbonic Ether [AeO, CO ^. — made by the action of potassium on oxalic ether, and distil- lation of the product with water. It floats on the surface of the distilled liquid, is an aromatic liquid, and boils at 259®. Oxalate of Ethyle — Oxalic Ether — prepared by distil- ling four parts of binoxalate of potash, five of sulphuric acid, and four of alcohol into a warm receiver. The product is washed with water to separate any alcohol *or acid, and re- distilled. It is an oily liquid, of an aromatic odor ; it boils at 353° F., and is slightly heavier than water. With an ex- cess of ammonia it yields Oxamide and alcohol. With a smaller proportion of ammonia and alcohol it yields Oxa- methane, CqH^NO^. Acetate of Ethyle — Acetic Ether {AeO, and Formiate of Ethyle — Formic Ether l^AeO, C^NO ^ — are procured in a similar manner with the foregoing, substi- tuting in one case acetate of potash, and in the other for- miate of soda. CEnanthic Ether {AeO, is prepared from an oily liquid which passes over during the distillation of cer- tain wines. It has a powerful vinous odor, is a colorless liquid, specific gravity '862 ; it boils at 410° F., dissolves readily in alcohol, and gives their peculiar aroma to the wines in which it is found. From it oenanthic acid may be obtained by the successive action of potash and sulphuric acid. It is an oily body, becoming a soft solid at 55® F. How is nitrous ether prepared, and what are its properties ? How are carbonic ether, acetic ether, and formic ether made ? From what source is cenanthic ether derived ? What is its relation to various bodies ? 334 SULPHOVINIC AND PHOSPHOVINIC ACIDS. LECTURE LXXIII. Derivative Bodies of Alcohol. — Sulphovinic and Phos- phovinic Acids. — Products of Sulphovinic Acid at dif f event Boiling Points . — The continuous Ether Process. — The continuous Olefiant Gas Process. — Dutch Li- quid. — Successive Substitutions of Chlorine in it . — Heavy and Light Oil of Wine. — Sulphate of Carhyle and its derivative Acids. Sulphovinic Acid — Bisulphate ofEthyle .2S O 3 + HO). — A mixture of sulphuric acid with an equal weight of alcohol is to be heated to the boiling point, and then allowed to cool. It is then to be diluted with water and neutralized with carbonate of baryta ; the sulphate of baryta subsides. The solution is then filtered, evapora- ted, and, when cold, the sulphovinate of baryta crystallizes. From this the sulphovinic acid may be obtained by precip- itating the baryta with dilute sulphuric acid, and evapor- ating the resulting solution in vacuo. It is a sirupy liquid, of a sour taste, giving rise to a series of soluble salts, which decompose at the boiling point, as will be presently seen. Phosphovinic Acid {C^H^O, PO 5 + 2HO) is made on the same principles as the foregoing, phosphoric acid being substituted for sulphuric, and decomposing the resulting ba- ryta salt in the same way. It is a sirupy liquid, of a sour taste, and dissolves in water, alcohol, and ether very readily. It is decomposed by heat. If sulphovinic acid be diluted so as to bring its boiling point below 260° F., it is resolved at that temperature chief- ly into sulphuric acid and alcohol, which distills over. If the boiling point is from 260^^ F. to 310° F., the distil- lation results chiefly in the production of hdyrated sulphuric acid and ether. If, by the addition of sulphuric acid, the boiling point is carried above 320° F., the action is more complex, but the chief product which passes over is olefiant gas. How is sulphovinic acid made ? What is its compositipn ? What is the composition and mode of preparation of phosphovinic acid ? Wliat is the result of the exposure of sulphovinic acid at different boiling points ? CONTINUOUS ETHER PROCESS. 335 The ordinary method of preparing ether is, therefore, ob- viously very disadvantageous, because it is only within a particular range of temperature that that body is evolved. At first the low temperature yields alcohol, and as the heat rises, the mixture begins to blacken, and olefiant gas to bo evolved. To obviate these difficulties, a very beautiful process, the continuous process, has been introduced. It consists in taking a mixture of eight parts by weigh t%f sulphuric acid and five of alcohol, specific gravity *834, the boiling point of which is about 300^ F. This is brought to that temper- ature, and alcohol of the same density is allowed slowly to flow into the mixture, the boiling point being steadily kept as near 300° F. as possible, and the mixture maintained in a state of violent ebullition. Water and ether distill over together, and may be passed through a Liebig’s condenser ; they collect in the receiver in separate strata, or, if thiy does not take place at first, the addition of a little water in the receiver insures it. In this manner a very large quantity of alcohol may be converted into ether and water by the action of a limited amount of sulphuric acid ; and in a similar manner, by ad- justing the boiling point so as to be between 320° and 330° F., olefiant gas may be continuously obtained. All, therefore, that is required, is to CQnvey the alcoholic vapor through a mixture of oil of vitriol with half its* weight of water, which has the required boiling point. In this pro- cess the acid does not blacken, and it is therefore much more advantageous than that described for the preparation of olefiant gas in Lecture LV. Cloride of Olefiant Gas — Dutch Liquid — is prepared by mixing equal volumes of chlorine and olefiant gas in a large glass globe. It is a colorless and fragrant liquid, soluble in alcohol and ether, but less so in water. It boils at 180° F., and when acted on by a solution of caus- tic potash in alcohol, it yields chloride of potassium and a substance which, on being cooled by a freezing mixture, condenses into a liquid. This liquid, brought in contact with chlorine, absorbs that substance, and yields a new compound, C^H^Cl, which may again be decomposed Describe the continuous process for the preparation of ether. Describe the continuous process for preparing olefiant gas. How is Dutch liquid pre pared ? 836 SUBSTITUTIONS IN DUTCH LiaUID. |jy an alcoholic solution of potash into chloride of potassium and a new volatile body, There is an iodide and a bromide of olefiant gas, which possess a constitutiqn analogous to the chloride. When chlorine gas is made to act upon Dutch liquid, three different substances may he successively formed by the gradual abstraction of hydrogen, and its equivalent substi- tution by chloriim. These substances are as follow : Dutch liquid ( 1 .) CiH^Ch. ( 2 .) v3.) Ck. The first and second of these products are volatile liquids, the third is the perchloride of carbon, in which it appears that all the four atoms of hydrogen in the Dutch liquid have been removed, and their places occupied by four atoms of chlorine. This perchlo7'ide of carbon is a white crystalline body, soluble in alcohol and ether. Its melting point is 320° F. By passing its vapor through a red-hot porcelain tube, it is decomposed, yielding and free chlorine, and this again gives rise to subchloride of carbon^ by being passed through an ignited porcelain tube at a white heat. The former of these bodies is a colorless liquid, and the latter a silky solid. Heavy Oil cf Wine 2SO^ may be procured by the destructive distillation of sulphovinate of lime, or by distilling two and a half parts^ of oil of vitriol and one of spirit of wine. It is a colorless liquid, heavier than water, and having an odor of peppermint. Boiled with water, it yields sulphovinic acid, and Light or Siveet Oil of Wine, a substance which, after standing a few days, deposits white ‘inodorous crystals of Ltherine, The residue, which still remains liquid, is Etherole, C^H^. It is a yellowish liquid, lighter tlian water, and soluble in alcohol and ether. Sulphate of Carbyle djSOg) arises when the va- por of anhydrous sulphuric acid is absorbed by pure alcohol, it is a white crystalline body. When dissolved in alcohol and water added, the solution neutralized by carbonate of baryta, filtered, concentrated, and then mixed with alcohol, What is the nature of the series of bodies arising from the action of chlo- rine on Dutch liquid?' Under what circumstances does the heavy oil of wiiie form ? How is sweet oil of wine prepared ? What are etherine and etherole ? When the vapor of anhydrous sulphuric acid is passed into pure alcohol, what is the result ? OXYDATION OF ALCOHOL. 337 the Ethionate of Baryta precipitates. This, when decom- posed by dilute sulphuric acid, yields Hydrated Ethionic Acid, the constitution of which is diSOgd- 2HO. Ethionic acid yields a series of salts, many of which can be obtained in crystals. On being boiled, solution of ethionic acid yields sulphuric acid and Isethionic, the peculiarity of which is, that it is isomeric with sulphovinic acid, both con* taining 280^ + HO. LECTURE LXXIV. OxYDATioN OF Alcohol. — TheAcetyle Group. — Aldehyde. — lU Preparation and Properties. — Aldehydic Add. — Davy's Flameless Lamp. — Acetal produced by Pla- tinum Black. — Acetic Acid, Production of. — Nature of the Change from Alcohol to Acetic Acid. — 8alts of Acetic Acid. It has been already stated (Lecture LXXIL), that when alcohol is burned in contact with oxygen gas or atmospheric air, the sole products of the combustion are carbonic acid gas and water. But when the oxydation is partial, the hy- drogen is removed by preference, and a new series of bodies is the result, designated as The Acetyle Series. Acetyle, = Ac. Oxide of acetyle . . . =AcO. Hydrated oxide of acetyle (aldehyde) . . = AcO -j- HO. Acetylous acid (aldehydic acid) .... Acetic acid = AcOa -{- HO. Acetyle is an ideal body, dilTering from ethyle by con- taining only three atoms of hydrogen instead of five. Its oxide, also, has not yet been insulated. Hydrated Oxide of Acetyle — Aldehyde — may be obtain- ed by distilling two parts of the compound of aldehyde and ammonia, dissolved in two parts of water, with a mixture of three of oil of vitriol and four of water, and redistilling the product from chloride of calcium at a low temperature. It is a colorless liquid, of a suffocating odor. Its density is 790, its boiling point 72^ F. It is soluble in water and How are ethionic and isethionic acids prepared? What is acetyle T How is aldehyde prepared ? What are its properties ? P 338 ALDEHYDE. ACETAL. alcohol. It slowly oxydizes in the air, and more rapidly under the influence of the black powder of platinum, pro- ducing acetic acid. Heated with caustic potash, it yields aldehyde resin, a brown body of a resinous aspect. Alde- hyde has received its name from the circumstance that it contains the elements of alcohol minus two atoms of hydro- gen {Alcohol Dehydrogenatus). When pure aldehyde is kept for a length of time at 32^ F. in a close vessel, it yields JEllcddchydc^ a substance iso- meric with itself, but possessing different properties,^ the specific gravity of its vapor, for example, being three times that of the vapor of aldehyde. From it there is also pro- duced, at common temperatures, a second isomeric body, Metaldehydc. ^ _ -j Aldehydic Acid may be obtained by digesting oxide of silver with aldehyde, and precipitating the metal with sul- phureted hydrogen. It contains one atom of oxygen less than acetic acid, and is one of the products of the slow combustion of ether in Davy’s flameless lamp, which may be made by putting a small quantity of ether in a jar {Fig, 276), and suspending in the vapor, as it mixes with atmospheric air, a coil of platina wire which has receiitly been ignited. The wire remains incandes- cent as long as any ether is present. The same result is obtained by putting a spiral of platina wire, or a ball of spongy platina, over the wick of a spirit lamp, the lamp being lighted for a snort time, and then blown out ; the platinum continues incandes- cent, evolving a peculiarly acrid vapor. Acetal containing the elements of ether and aldehyde, is produced by the oxydation of vapor of alcohol by black powder of platinum, the alcohol being placed in a jar, with moistened platinum black in a capsule above it. In the course of several days the alcohol will be found to have become sour ; it is then to be neutralized with chalk and distilled. Chloride of calcium separates an oily liquid Fig, 276. From what is the name of aldehyde derived? Under what circumstan- ces do elaldehydc and metaldehyde form ? What is Davy s tameless .amp Mention some of its products. What is the constitution of acctai . rhay it be prepared by platinum black ? ACETIC ACID. 339 from the distilled product. This, on being distilled at a temperature of 200° F., yields acetal. It is a colorless and aromatic liquid, lighter than water, and boiling at 203° F. It yields, under the influence of an alcoholic solution of caustic potash, by absorbing oxygen from the air, resin of aldehyde. Acetic Acid — Pyroligneous Acid — Vinegar + HO). — When dilute alcohol is dropped on platina black, oxydation takes place, and the vapors of acetic acid are formed. On the large scale it is also Fig. 277 . formed by allowing a mixture of alcohol, water, and a small quantity of yeast, Fig. 277, to flow over wood shavings which have been steeped in vinegar con- tained in a barrel through which atmos- pheric air is allowed to circulate by the apertures c, c, c. The temperature rises, and the acetification goes on with rapidity, the product being collected in the receiver, d. Vinegar, also, is formed by the spontaneous souring of wines or beer containing ferment, and kept in a cask to which atmospheric air has access. During the destructive distillation of dry wood, acetic acid (hence called pyrolig- neous acid) in an impure state is found among the products. The strongest acetic acid may be made by distilling pow- dered anhydrous acetate of soda with three times its weight of oil of vitriol. The product is then re-distilled, and ex- posed to a low temperature, when crystals of hydrated acetic acid form ; the fluid portion is poured off, and the crystals suffered to melt. It is a colorless liquid, which crystallizes below 60° F. ; has a very pungent odor, and, placed on the skin, blisters it ; boils at 248° F., the vapor being inflam- mable. It dissolves in water, alcohol, and ether ; and in a less pure state, as vinegar, its taste, odor, and applications are well known. If its constitution be compared with that of alcohol, . Alcohol Acetic acid it is seen to differ from that substance in the circumstance that two hydrogen atoms have been removed from the al- Mention some of the different methods by which acetic acid may be made. Why is it sometimes called pyroligneous acid ? What change does alcohol undergo in passing into acetic acid ? 340 SALTS OF ACETIC ACID. cohol, and their places taken by two oxygen atoms. Hence the various processes for its production are easily explained. Acetic acid gives rise to several important salts. Acetate of Potash (7fO, C^TTgOg) is obtained by neutral- izing acetic acid with carbonate of potash, evaporating to dryness, and fusing. This salt is very deliquescent, and has an alkaline reaction. Acetate of Soda is made on the large scale by saturating the impure pyroligneous acid formed in the destructive dis- tillation of wood, with lime, and then decomposing the ace- tate of lime with sulphate of soda. The sulphate of lime precipitates, the solution being crystallized, and the crystals subsequently purified by draining, fusing, solution, and re- crystallization. The crystals effloresce in the air, and are soluble in water and alcohol. Acetate of Ammonia — Spirit of Minder er its. — The so- lution is made by saturating acetic acid with carbonate of ammonia, and the solid by distilling acetate of lime and hy- drochlorate of ammonia ; the acetate of ammonia passes over, and chloride of calcium is left. Acetate of Alumina is made by the decomposition of a solution of alum by acetate of lead. It is much used by dyers as a mordant. Acetates of Lead. — 1st. Neutral Acetate {Sugar of Lead) may be made by dissolving litharge in acetic acid. It occurs in colorless prismatic crystals, and also in crystal- line masses. It has a sweetish, astringent taste, from which its commercial name is derived. It is soluble in about its own weight of cold water. The crystals effloresce in the air. 2d. Subacetates of Lead — Sesquibasic Acetate — is formed by partially decomposing the neutral acetate by heat. Its solution is known as Goulard's Water. Two other sub- acetates may be made by the action of ammonia on the neu- tral salt. Their solutions have an alkaline reaction, absorb carbonic acid from the air, and give rise to a precipitate of the basic carbonate. Acetates of Copper. — 1st. Neutral Acetate — Distilled Verdigris — made by dissolving verdigris in hot acetic acid. On cooling, it yields green crystals, soluble both in water Mention some of the more important salts of acetic acid? How is the ucetate of soda made ? What is the spirit of Mindererus ? For what pur- pose is acetate of alumina used ? What varieties of acetate of lead are there, illd how are they formed ? What are the varieties of acet.ite of copper ? DERIVATIVES OF ACETYLE. 341 and alcohol. It is used as a paint. 2d. Bibasic Acetates of Copper — Yerdigris — may be made by the action of vin- egar and air conjointly on metallic copper. Verdigris is a mixture of several acetates, one of which may be obtained by digesting it in warm water ; a second arises on boiling this ; the insoluble residue of the verdigris contains a third. LECTURE LXXV. Derivatives of Acetyle. — The Kakodyle Group. — Clilor acetic Acid. — Acetone. — Chloral and Heavy Mu- riatic Ether. — Substitutions of Chlorine i?i Eight Mu- riatic Ether. — Sulphur-alcohol. — Its Relations to Mer- cury. — Xanthic Acid . — The Kakodyle Group. — Oxide. — Chloride. — Kakodijlic Acid. Chloracetic Acid {C^HO^Cl^. — This remarkable body is formed when a small quantity of crystallized acetic acid is exposed to the sunshine in a jar-full of chlorine gas. The crystals which form on the inside of the vessel are to be dissolved in water, and the solution evaporated in vacuo with capsules containing caustic potash and oil of vitriol. A little oxalic acid is first deposited, and then the chlora- cetic acid crystallizes as a colorless and deliquescent body, with a powerfully acid taste, and capable of corroding the skin. It melts at 115^ F., and boils at 390°. By com- paring its constitution with that of acetic acid, it will be seen that in its formation three atoms of chlorine have been substituted for three of hydrogen. It yields an extensive series of salts. Acetone — Pyroacetic Spirit {C^H^O) — may be made by passing acetic acid vapor through a red-hot iron tube, or by the distillation of dry acetate of lead. It is a limpid, color- less, and volatile liquid, boiling at 132°, burns with a bright flame, and is soluble in water and alcohol. Nordhausen oil of vitriol, distilled with acetone, abstracts from it one atom )f water, yielding an oily body, the constitution of which is C^H^ ; it is lighter than water, and has an odor of garlic. Sir R. Kane considers acetone to be the hydrated oxide How is chloracetic acid made ? What is the relationship between acetic and chloracet ic acid ? What is the mode of preparing pyroacetic spirit ? 342 CHLORAL, of an ideal radical, Mesityle, and has been able to produce the oxide and chloride ofmesityle. Zeise also dis- covered a compound consisting of the oxide of mesityle and bichloride of platinum. Chloral { C — When dry chlorine is passed into anhydrous alcohol, and the action finished by the aid of heat, hydrochloric acid is produced ; and on its ceasing to appear, if the product be agitated with three times its volume of oil of vitriol, and the mixture warmed, an oily liquid floats on the acid : this is chloral. It may be puri- fied by successive distillation from oil of vitriol and quick- lime. It is an oily, colorless liquid, which causes a flow of tears, leaves a transient greasy stain upon paper, has a den- sity of 1*502, boils at 201°, is soluble in water and alcohol ; it yields no precipitate with nitrate of silver. When kept for a length of time in a sealed tube, it spontaneously be- comes a white, solid, insoluble chloral. In this condition it is little soluble in water, and reverts to its other state by being warmed. If chlorine acts on alcohol containing water, heavy Mu~ riatic Ether is formed. It is a colorless and volatile liquid. The action of chlorine upon common ether, and also on the compound ethers, is very interesting. It consists in the gradual removal of hydrogen, chlorine being substituted for it. This, in many instances in which the aid of the sun- light is resorted to, terminates in the entire removal of the hydrogen. In the compound ethers it is the basic hydrogen which is removed, while that of the acid escapes, as in the case of chlorureted acetic and chlorureted formic ethers. When the vapor of light hydrochloric ether is acted upon by chlorine gas, a complete series of compounds may be ob- tained, the hydrogen eventually disappearing : Hydrochloric ether C^H^Cl ; Monochlorureted hydrochloric ether . . ; Bichlorureted “ “ . . TricHorureted “ “ . . C^lf^Cl^; Quadrichlorureted ‘‘ “ . . C^H Cl^; Perchloride of carbon CIq ; furnishing, therefore, a very striking instance of the doctrine of substitution. Mercaptan — Sulphii7''alcohol{^C — is prepared by saturating a solution of caustic potash, specific gravity 1*3, What is mesityle ? What is chloral ? Under what circumstances does insoluble chloral form ? Describe the successive action of chlorine upon ether. How is mercaptan prepared ? XANTHIC ACID. KAKODYLE, 343 with sulphureted hydrogen, and distilling it with an equa. volume of sulphovinate of lime of the same density. It passes over with water, on the surface of which it floats as a colorless liquid, specific gravity *842, soluble in alcohol. It boils at 97°, smells like onions, and burns with a blue flame. Mercaptan corresponds to alcohol in which all the oxygen has been replaced by sulphur ; but in its action on metallic oxides it answers to the hydruret of a compound rad- ical, Thus, with peroxide of mercury, it forms a mercaptide with the production of water ; and this may be decomposed by sulphureted hydrogen, sulphuret of mercury subsiding, and mercaptan being reproduced. Mercaptan derives its name from its strong affinity for mercury [Mer- curium C'aptans). Xanthic Acid {CqH^S^O-{-HO ). — Hydrate of potash is to be dissolved in twelve parts of alcohol, specific gravity *800, and bisulphuret of carbon dropped into the solution until it ceases to have an alkaline reaction. On cooling to zero, the xanthate of potash crystallizes: it is to be dried in vacuo. It is soluble in water and alcohol, but not in ether ; and from it xanthic acid may be procured by the ac- tion of dilute hydrochloric acid. Xanthic acid is an oily liquid, heavier than water, which first reddens and then bleaches litmus paper. At 75° it is decomposed into alco- hol and bisulphuret of carbon. It is also decomposed by the action of the air. Kakodyle {C^HqAs =z Kd) is a compound radical, which gives rise to an extensive group of bodies, in which it acts the part of a metal. The Kakodyle Group. Kakodyle, C^H^As Kd. Oxide of kakodyle = KdO. Chloride “ = KdCl. Iodide “ = Kdl. Sulphuret = KdS. &c. &c. Kakodyle may be obtained by decomposing the chloride of kakodyle with metallic zinc in an apparatus filled with carbonic acid gas, and may be purified by redistillation from zinc, similar precautions being taken to exclude atmospheric air. It is a colorless liquid, of a powerful odor, taking fire What remarkable qualities does mercaptan possess ? From what is its name derived? What is the process for preparing xanthic acid? What is ks action on litmus paper ? What is kakodyle ? How may it be isolated . 344 KAKODYLE. on the contact of air, oxygen gas, or chlorine ; boils at 338°, crystallizes at 21°, and is decomposed by a red heat into olefiant gas, light carbureted hydrogen, and arsenic. Oxide of Kahodyle — Alkarsine — Cadeds Fuming Liq~ uor — is prepared by the distillation of acetate of potash and arsenious acid, receiving the products in an ice-cold vessel, the temperature being finally carried to a red heat. The oxide comes over in an impure state, sinking to the bottom of the other products. It is t6 be decanted, washed with water, boiled, and then distilled in a vesseLfull of hydrogen from hydrate of potash. It is a colorless liquid, specific gravity 1*462, boils at 300°, and solidifies at 9°; is spar- ingly soluble in water, but more so in alcohol ; is excessive- ly poisonous, possessing a concentrated smell like garlic. Heated in the air, it burns, producing carbonic acid, water, and arsenious acid. Chloride of Kakodyle may be procured by the action of a dilute solution of corrosive sublimate on a dilute alcoholic solution of oxide of kakodyle ; a white precipitate falls, which, distilled with strong hydrochloric acid, yields cor- rosive sublimate, water, and the chloride of kakodyle passes over. When purified by chloride of calcium, and distilled in an atmosphere of carbonic acid, it is a colorless liquid, of a dreadful odor, heavier than water, and insoluble therein, but soluble in alcohol. It is very poisonous. It boils at about 212°, the vapor taking fire in the air. Kakodylic Acid — Alcargen {Kd . O3) — may be made by the action of oxide of mercury upon oxide of kakodyle un- der the surface of water, at a low temperature. Kakodylic acid forms crystals which deliquesce in the air, are soluble in water and alcohol, but not in ether. It is not acted Upon by oxydizing agents, such as nitric acid, but is reduced to oxide of kakodyle by several deoxydizing bodies. It is not' poisonous. Kakodyle furnishes a complete series of bodies : the iodide, sulphuret, cyanide, and a substance isomeric with the oxide, which has the name of parakakodylic oxide. What are alkarsine and Cadet’s fuming liquor ? How is it prepared, and what are its properties ? What is the process for preparing the chloride of kakodyle ? What are its properties ? What is the constitution of alcargen ? COMPOUNDS OP METHYLE. 345 LECTURE LXXVI. The Wood-Spirit Group. — Methyle. — Its Oxide and Hy drated Oxide. — Salts of Methyle. — Formic Acid, nat ural and artificial Production of. — Derivatives of Wooa Spirit. — Substitutions of Chlorine in Oxide of Methyle. — Substitutions in Chloride of Methyle. In the destructive distillation of wood in the preparation of pyroligneous acid, there passes over a body to which the name of wood spirit has been given. This is the hydrated oxide, or alcohol of an ideal compound radical, passing un- der the name of methyle. The Methyle Group. Methyle, = Me. Oxide of methyle . . . . = MeO. Hydrated oxide = MeO HO. Chloride = MeCl. &c. &c. Oxide of Methyle — Methylic Ether — Wood Ether {C^ H^O). — This substance is made from the hydrated oxide on the same principle that ether is obtained from alcohol : one part of wood spirit and four of oil of vitriol being heat- ed in a flask, the vapor is passed through a small quantity of caustic potash solution, and received at the mercurial trough. It is a permanently elastic gas, colorless, and has a specific gravity of 1*617, burns with a pale flame, is very soluble in water, which takes up thirty-three times its vol- ume of it, and yields it unchanged when heated. Hydrated Oxide of Methyle — Wood Spirit — Pyroxijlic Spirit — may be separated from crude wood vinegar hy dis- tillation. It passes over with the first portions along with a little acid, which, being neutralized with hydrate of lime, the wood spirit may he separated from the oil which floats on its surface, and redistilled. The product thus obtained may he rectified in the same manner as common alcohol, and rendered anhydrous hy quicklime. It is then a color- less liquid, of a hot taste and peculiar smell. It boils at Under what circumstances is wood spirit produced ? What is its ideal compound radical? How is the oxide of methyle prepared, and what is its form ? What is the constitution of pyroxylic spirit ? What are its proper- ties ? 346 COMPOUNDS OP METHYLS. 152°, and has a specific gravity of *798 at 68°. It is sol- uble in water, dissolves resins and oils, and may be burned like spirit of wine. It then exhales a peculiar odor. Chloride of Methyle [MeCl) may be made from the re- action of sulphuric acid upon common salt and wood spirit. It is a colorless gas, which may be collected over water ; has a density of 1*731. It has a peculiar odor, is inflam- mable, and may be decomposed by passing through a red- hot tube. Sul'phate of Oxide of Methyle {MeO, SO^) may be pre- pared by distilling one part of wood spirit with eight or ten of oil of vitriol ; the product is to be washed with water, and redistilled from caustic baryta. It is an oily, neutral liquid, smelling like garlic ; specific gravity 1*324. It boils at 370°. It is not soluble in water, but is decomposed by that liquid, especially at the boiling temperature, into sul- phomet hylic acid and hydrated oxide of methyle. It is to be observed, that in the series of wine alcohol there is no compound corresponding to this. Nitrate of Oxide of Methyle [MeO, NO^) is obtained by the action of a mixture of wood spirit and oil of vitriol upon nitrate of potash. It is a colorless liquid, heavier than water ; boils at 150° ; burns with a yellow flame. Its va- por explodes when heated. In a solution of caustic potash, it decomposes into nitrate of potash and wood spirit. Oxalate of Oxide of Methyle {MeO, C^O^ is made by distilling oxalic acid, wood spirit, and oil of vitriol. The liquid which is collected is allowed to evaporate ; it yields crystals of the oxalate. When pure, it is colorless ; melts at 124°, and boils at 322°. It is decomposed by hot water into oxalic acid and wood spirit, by solution of ammonia into oxamide and wood spirit. Sulphomethylic Acid {MeO, 2SO^ + HO), the com- pound corresponding to sulphovinic acid, and prepared in the same way, by substituting wood spirit for alcohol. It is thus procured as a sirup or in small crystals, soluble in water and alcohol. It is an instable body, and possesses many analogies with sulphovinic acid. Formic Acid{C 2 HO^ + HO). — This acid, in the wood- For what purposes may pyroxylic spirit be used ? ‘ How is the chloride of methyle prepared? In the wine series, is there any compound analogous to sulphate of oxide of methyle ? How is the nitrate obtained, and what are its properties ? Describe the preparation of the oxalate and of sulpho methylic acid. What is the constitution of formic acid ? FORMIC ACID. — CHLOROFORM. 347 spirit series, is the analogue of acetic acid in the alcohol se ries. It may be procured on principles similar to those in- volved in the preparation of acetic acid, as by the gradual oxydation of the vapor of wood spirit in the air under the influence of black platinum. In a dilute state it may be prepared by distilling one part of sugar, three of peroxide of manganese, and two of water, with three parts of sul- phuric acid, diluted with an equal weight of water. The liquid which distills is to be neutralized by carbonate of soda, purified by animal charcoal, and redistilled along with sulphuric acid. It occurs naturally in the bodies of red ants, and hence has obtained the name of formic acid. From the distillation of those animals it was originally procured. Anhydrous formic acid obviously contains the elements of two atoms of carbonic oxide and one of water. It yields two hydrates, respectively containing one and two atoms of water. The first, for which the formula has al- ready been given, is procured by the action of sulphureted hydrogen on formiate of lead. It is a colorless liquid, of a strong odor ; boils at 212°, and crystallizes below 32°. It is inflammable, and has a specific gravity of 1’235. It blis- ters the skin. Formic acid yields a complete series of salts. Chloroform {C^HCl^) is made by distilling wood spirit with a solution of chloride of lime. It is a colorless liquid , specific gravity 1*48 ; boils at 141°. It burns with a green flame, and is decomposed by an alcoholic solution of potash into chloride of potassium and formiate of potash. The re- lationship between formic acid and chloroform is obvious : it consists in the substitution of three atoms of chlorine for three of oxygen.' There are also two analogous compounds: Formomethylal is prepared by distilling wood spirit, oxide of manganese, and dilute sulphuric acid. On saturating the product with potash, formomethylal separates as a colorless oily liquid: specific gravity *855; boils at 107°, and soluble in water. Methyle-mercajptan . — Formed as the common mercap- tan, by substituting sulphomethylate of potash for sulphovi- nate of lime. It is analogous to common mercaptan. How is it procured? From what circumstance is its name deprived? What are its properties ? How is chloroform obtained ? What is the pro- Bromoform . . Iodoform . . . cpss for preparing formomethylal ? 348 THE POTATO-OIL GROUP. When chlorine is made to act on the oxide of methyle at common temperatures, it removes one of the hydrogen atoms ; and by continuing the action, a second may be taken away, and the process of substitution, as shown in the fol- lowing series, may be carried so far as to end in the removal of oxygen and the production of chloride of carbon. Oxide of methyle C^H^O. 1st substitution Cl. 2d “ C^H O, C/g. 3d “ O, Cl^. 4th “ (chloride of carbon) . Cl^. Other methylic compounds furnish similar series, thus : Chloride of methyle 1st substitution 2d “ (chloroform) Cl^. 3d “ (chloride of carbon) . . Cl^. LECTURE LXXYIL The Potato-Oil Group. — Fusel Oil. — Chloride of Amyle. —Sidphmnylic Acid. — Amilen. — Relations of Yaleria- nic Acid. The Benzyle Group.- — Oil of Bitter Almonds. — Benzoic Acid. — ^id])hohenzoic Acid. — Chloride of Benzyle . — Benzamide. In the distillation of brandy from potatoes, a volatile oil passes over. It is regarded as the hydrated oxide of an ideal compound radical, which passes under the name of Amyle, having the constitution The Potato-Oil Group. Amyle, Cio^^n —Ayl. Amyle ether =AylO. Amyle alcohol (potato oil) AylO-\-HO. Chloride of amyle . AylCl. &c. &c. Amilen CiqHio. Valerianic acid Of these, amyle and its oxide, amyle-ether, are ideal. Hydrated Oxide of Amyle — Amyle Alcohol — Potato Oil — Fusel Oil {C ^qH^^O + HO) . — This substance passes Describe the series of substitutions of chlorine on the oxide of methyle. Describe the analogous substitutions with chloride of methyle ? What is »,he imaginary radical of the potato-oil group? What are the nature and re- lations of fusel oil ? COMPOUNDS OF AMYLE. 349 over toward the end of the first distillation of potato spirit, and communicates to it a milky aspect. 'On standing, it floats on the surface, and may be purified by washing with water, drying with chloride of calcium, and redistillation. It is a fluid oil of a suffocating odor, which acts powerfully on the animal system. Its specific gravity is *818 ; it boils at 269'^. Chloride of Amyle {AylCl) is made by distilling equal weights of potato oil and perchloride of phosphorus, w^ash- ing with potash water, and redistilling from chloride of cal- cium. It as an aromatic liquid, boils at 215°, and burns with a green flame. Under the influence of sunshine, eight of its hydrogen atoms may be removed, eight chlorine atoms being substituted for them, yielding forming chlorureted chloride of amyle. The Iodide and Bromide of Amyle are compounds anal- ogous to the chloride. Acetate of Oxide of Amyle is obtained by distilling ace- tate of potash, potato oil, and sulphuric acid. It is a color- less liquid, which boils at 257°. Sulphamilic Acid {AylO, 2SO^H+ O) is generated when sulphuric acid is made to act on an equal weight of potato oil. From this, by the successive action of carbonate of baryta and sulphuric acid, it may be procured by oper- ating on the same principles as for sulphovinic acid, to which, both in constitution and properties, it is the analogue. It is a sirupy or crystalline body, and is decomposed by ebul- lition into potato oil and sulphuric acid. Amilen is obtained by the action of anhydrous phosphoric acid on potato oil \ it is an oily liquid, which boils at 320°. In constitution and position, it therefore occupies, in the amyle series, the same situation that olefiant gas does for the wine-alcohol series, and, indeed, is isomeric with that body. Valerianic Acid bears the same relation to the amyle group which acetic acid does to the wine-alcohol group, or formic acid to the wood-spirit group. It is form- ed when warm potato oil is dropped on platinum black in contact with the air. It occurs naturally in the root of the Valeriana OJ)icinalis, but is best made by heating potato What are the properties of the chloride of amyle? To what substance is sulphamilic acid analogous? What relation is there between amilen and olefiant gas ? What is the relation between acetic and valerianic acids ? From what natural source may the latter be derived ? 350 THE BENZYLE GROUP. oil in a flask, with a mixture of quicklime and hydrate of potash, for several hours at a temperature of 400°. The white residue is immersed in cold water, and distilled with a slight excess of sulphuric acid, so as to drive off hydrated valerianic acid and water. It is a colorless oil of an acid taste, combustible, and boiling at 347°. When acted, upon by chlorine in the dark, and the action aided by heat, it gives rise to Chlorovalerisic Acid + HO), in which there has been a removal of three hydrogen atoms and a substitution of three of chlorine. Under the influence of the sunshine, by the same process, another hydrogen atom is removed, and Chlorovalerosic Acid forms, its constitution being C^qH^CI^O^ + HO. Of this series, benzyle, the radical, is an ideal body. It is a radical which discharges the functions of a metallic body, giving rise to oxides, chlorides, iodides, &c., as the table shows. Hydruret of Benzyle — Oil of Bitter Almonds {BzH) — is obtained by the distillation of bitter almonds, from which the fixed oil has been expressed, with water, and arises from the action of the water upon Amygdaline contained in the seed. It may be purified by distillation from protochloride of iron with hydrate of lime in excess, and is a colorless liquid of an agreeable odor, slightly heavier than water, and also slightly soluble therein, but very soluble in alcohol and ether. It boils at 356°. In the air it passes into benzoic acid by absorbing oxygen. Oxide of Benzyle — Benzoic Acid {BzO + HO.) — This acid is obtained by sublimation from gum benzoin, that sub- stance being placed in a shallow vessel, over the top of which a cover of filtering paper is pasted, and this covered by a taller cylinder of stouter paper. On heating, the va- pors pass through the filtering paper, and, condensing in feathery crystals in the space above, fall down upon the pa- How is valerianic acid made artificially ? What is the successive action of chlorine upon it ? What is the radical of the benzyle series ? What is oil of bitter almonds? From what substance does it arise? What is ben zoic acid? By what nrocc'^scs ma3’ it be prepared^ The Benzyle Group. Benzyle, 6^14-^5^2 Hydruret of benzyle Oxide of benzyle (benzoic acid) . . Chloride =zBz. &c. DERIVATIVES OF 6ENZYLE. 351 per and are retained by it. A better method is to boil a fixture of the gum with hydrate of hme, ^ the solution, add hydrochloric acid, and the benzoic acid crystallizes in thin plates on cooling. It may be subse- quently sublimed. When pure it has no odor. It melts at 212°, and boils at 462°. Its vapor excites coughing it is much more soluble in hot than m cold water. It terms a series of salts, and is sometimes used for the separation ot iron from other metals. ti-^\ Sulphobenzoic Add SO^ 4- 2ff ), a i acid, formed by the action of anhydrous sulphuric acid upon benzoic acid, the mass being dissolved in water and neu- tralized by carbonate of baryta. On filtering, and adding hydrochloric acid to the hot solution, on cooling the sulpho- bLzoate of baryta crystallizes, which may be decomposed by dilute sulphuric acid. It is a white crystalline mass. Chlorideof Benzyle (.BzCZ).— When chlorine gas is pass- ed through oil of bitter almonds, hydrochloric acid is formed, and, after expelling the excess of chlorine by heat, chloride of benzyle remains. It is a colorless liquid, of a disagree- able odor, heavier than water, combustible, and decomposed bv boiling water into benzoic and hydrochloric acids. Benzamide {C,,H,NO^) is foimed by the action of chlo- ride of benzyle on dry ammonia, the hydrochlorate ot atn monia being removed from the resulting white mass by cold water From a solution in boiling water, the benzamide crystallizes. It melts at 239°. It corresponds in its chem- ical relations to oxamide. , , „ Hydrobenzamide made by e ac lo pure oil of bitter almonds on solution of ammonia, the pro- duct being washed with ether, and from its alcoholic solu- tion this substance crystallizes ; but when impure almond oil is employed, three other compounds may be obtained . they are benzhydramide, azo benzoyle, and nitrobenzoyle. ■ What is the process for preparing ^“fohobenzoic acid? ^ ride of benzyle made ? How are benzamide and hydrobenzamide lormea . 352 DERIVATIVES OF BENZYLE. LECTURE LXXVIII. The Salicyle and Cinnamyle Groups. — ^enzoine^ Sen- zone, Benzine. — Hippuric Acid. — The Salicyle Group. — Artificial Formation of Oil of Spircea,— Compounds of Salicyle. — Melanie Acid. — The Cinna- myle Group. — Compounds of Cinnamyle. Benzoine a body isomeric with bitter al- mond oil. It is tbund in the residue after purifying that oil from hydrocyanic acid by distillation from lime and ox- ide of iron, and may be obtained by dissolving- out those bodies by hydrochloric acid. It crystallizes from an alco- holic solution, on cooling, in colorless crystals, which melt at 248°. It dissolves in an alcoholic solution of caustic potash, which, by boiling until the violet color has disap- peped, furnishes benzilate of potash, a salt from which ben- zihc acid may be obtained by hydrochloric acid. The con- stitution of Benzilic Acid is -f HO, Benzone {C ^^H^O) is obtained by the distillation of dry benzoate of lirne at a high temperature, carbonate of lime remaining behind. The decomposition is interesting, the benzoic acid atom being divided, and yielding benzone and carbonic acid. C,,H,0, C,,H,0 + CO,. Benzine ( C^giTg) arises when crystallized benzoic acid IS distilled from hydrate of lime at a red heat. It is an oily liquid, and, after being separated from the water which cornes over with it, is to be rectified. It boils at 187°, so- lidifies at 32°, and is lighter than water. In its formation tie liydiated benzoic acid is resolved into benzine and car- bonic acid. C^^H^ + 2(CO,). Sulpliohe7tzide{C^^H,SO^) is formed by taking the sub- stance which arises from the union of benzine with anhy- drous sulphuric acid, and acting upon it with an excess of benzoine bear to oil of bitter almonds ? What is the ■ distillation of dry benzoate of lime ? What is the nature of ;he decomposition? What is the result of the distillation of crystallized lenzoic acid and hydrate of lime ? What is the result of the actfon of an- ydrous sulphuric acid and benzine ? Tiin SAI.ICYLE GROUP. 353 water. The sulphohenzide, which is insoluble in that liq uid, may be obtained in crystals from its ethereal solution. It melts at 212° F. From the acid liquid from which it has been separated hyposulphobenzic acid may be obtained. Its constitution is Nitrobenzide produced by the action of fuming nitric acid on benzine, with the aid of heat. It is an oily liquid, of a sweet taste, heavier than water, and boiling at 415°. From it Azohenzide may be obtained by distillation with an alcoholic solution of caus- tic potash, in the form of red crystals. Chlorhenzinei^CYiddi^Cl^ is formed by the union of ben- zine and chlorine in the sun-rays. When distilled, the solid yields hydrochloric acid and a liquid, Chlorbenzide Hippuric Acid ( C^qH^NO^ + HO) is found in the urine of graminivorous animals, and occurs in the urine of per- sons who have taken benzoic acid. It may be prepared by evaporating the fresh urine of the cow, and acidulating the concentrated liquor with hydrochloric acid ; crystals of hippuric acid are deposited, which may be decolorized by bleaching liquor and hydrochloric acid. It crystallizes in square prisms, sparingly soluble in cold water, of a bitter taste and acid reaction. By a high temperature or the ac- tion of sulphuric acid, it yields benzoic acid. THE SALICYLE GROUP. There is contained in the bark of the willow and other trees a bitter crystalline principle, Salicine This substance may be extracted by boiling the bitter bark in water, and digesting the concentrated solution with ox- ide of lead to decolorize it, removing any dissolved lead by sulphureted hydrogen, and evaporating until the salicine crystallizes. It forms white needles of a bitter taste, much more soluble in hot than cold water. Distilled with bi- chromate of potash and sulphuric acid, it yields hydrosali- cylic acid, or the artificial oil of meadow sweet, a substance containing Salicyle^ the ideal compound radical of a series of bodies. What is the action of nitric acid on benzine ? What substance results from the union of benzine and chlorine ? From what sources may hippu ric acid be obtained ? Under what circumstances does benzoic acid pro- duce it? From what is salicine obtained? What is the constitution ot salicyle? How may the oil of meadow sweet be made artificially? 354 COMPOUNDS OP SALICYLD^ The Salicyle Group. Salicyle si Hydrosalicylic acid SIH. Iodide of salicyle = SlI.' Chloride ~ siCl. Hydrosalicylic Acid— Oil of Sjdrcea Ulmaria, or Mead- 010 Sweet H) — is prepared by distilling one part of salicine, one of bichromate of pot ash, two and a half of sulphuric acid, and twenty of water ; the salicine being dissolved in one portion of the water, and the acid mixed with the rest. The yellow oil which comes over is rectified from chloride of calcium. It may also be obtained by distill- ing the flowers of meadow sweet with water. It is trans- parent, but turns red in the air. It is slightly soluble in water, and very soluble in alcohol. Its specific gravity is 1 173 , it boils at 385*^ F. It contains the same elements as benzoic acid. Salicylic Acid ^ + O) is obtained by the action of hydrate of potash on the foregoing body by the assistance of heat. After the disengagement of hydrogen is over, the mass is dissolved in water, and salicylic acid separates in crystals on the addition of hydrochloric acid. It is more soluble in hot than cold water, and is charred by hot oil of vitriol. Chloride of Salicyle {C^^H^O^Cl) is made by the action of chlorine on hydrosalicylic acid. Its crystals are insol- uble in water, but soluble in solutions of fixed alkalies, from which it separates on the addition of an acid, resisting de- composition even when boiled in caustic potash. It unites with caustic potash. bromide and Iodide of Salicyle also exist, but are not of interest. CJdorommide — Ammoniacal gas is absorbed by the chloride of salicyle, producing a yellow body, which crystallizes from a boiling ethereal solution. It is insoluble in water. When acted upon by hot acids, it yields a salt of ammonia and chloride of salicyle ; an alkali forms with it ammonia and chloride of salicyle. There is an analogous bromosamide. Salicyluret of Potassium (ESI) is formed by the action What is the constitution of salicylic acid ? What is the action of am- ^oTuced of salicyle ? Under what circumstances is melahic acid CINNAMYLE. 355 of oil of meadow sweet on a solution of caustic potash. It forms in yellow crystals from its alcoholic solution, and has an alkaline reaction. Melanie Acid is produced when the crystals of salicyluret of potassium are exposed in a moist state to the air. They first turn green and then black, and alcohol extracts from them melanic acid. CINNAMYLE. The essential oil of cinnamon is supposed to he the hy- druret of an ideal compound radical, cinnamyle, analogous to henzoyle, and yielding a series. The Cinnamyle Group. Cinnamyle, CisHrOg = Ci. Hydruret of cinnamyle (oil of cinnamon) . . . . = CiH. Oxide “ (cinnamic acid) . . . . = CiO. Chloride “ = CiCl. &c. &c. Hydruret of Cinnamyle — Oil of Cinnamon {C^^H^O^ + H) — is obtained by infusing cinnamon in a solution of salt, and then distilling the whole. It is heavier than wa- ter, and may be separated from that liquid by contact with chloride of calcium. Cinnamic Acid [C^qH^O^-\- O) is formed when oil of cinnamon is exposed to oxygen gas, the oil becoming a white crystalline mass, hydrated cinnamic acid. It may also be obtained by boiling hard Tolu balsam with hydrate of lime. The cinnamate of lime crystallizes as the solution cools, benzoate of lime remaining in solution. The crystals are decolorized by animal charcoal, and then decomposed by hy- drochloric acid ; from the hot solution cinnamic acid crys- tallizes. It melts at 248^, and boils at 5^0°. It is solu- ble in boiling water and in alcohol ; is decomposed by hot nitric acid, and yields benzoic acid, with oil of vitriol and bichromate of potash. Chlorodnnose {C^^H^Cl^O^ arises from oil of cinnamon by the substitution of four atoms of chlorine for four of hy- drogen, and is made by the action of chlorine on oil of cin- namon by the aid of heat. It crystallizes from its alcoholic solution in colorless needles. What is the essential oil of cinnamon ? What is the constitution of cin- namyle ? How may cinnamic acid be prepared ? What is the constitution of chlorocinnose, and how is it prepared ? 350 COMPOUNDS OP AMMONIA. LECTURE LXXIX. The Nitrogenized Principles. — Ammonia and its Salts. — Cyanogen. — Preparation and Properties of Prussic Acid.— Amy g(Mine and Synaptase.— The Cyanides. —Oxygen Acids of Cyanogen. Ammonia. — I have already described in Lecture LVI., the compounds of-hydrogen and nitrogen, under the names of sLniidogen., ammonia, and ammonium, and have also shown the relation there is between the salts of potash and soda and those of the oxide of ammonium. This compound met- al is a hypothetical body ; its existence may, however, he illustrated by passing a Yoltaic current through a globule of mercury in contact with moist chloride of ammonium, or by putting an amalgam of mercury and potassium in a strong solution of that salt. The mercury rapidly increases in volume, retaining its metallic aspect, becomes of the con sistency of butter, with a very trivial increase of weight j the resulting substance is the A/nwioniacal A.'nicblgaTYi, All attempts to insulate ammonium from it have failed. The most impoitant salts of ammonia are the folio wino* \ Chloride of Ammonium — ^al Ammoniac — Muriate of Ammonia — formerly brought from Egypt, but is now made from the ammoniacal liquors resulting from the de- structive distillation of animal matters, coal, &c. It is sol- uble in watery crystallizes in cubes or octahedrons, and sub- limes below a red heat unchanged. It is decomposed by lime and potash, and is formed when the vapors of ammo- nia mingle with those of muriatic acid. titrate of Ammonia is formed by neutralizing nitric acid with ammonia. It is deliquescent, and therefore very soluble in water. It melts at 240°, and at a higher tem- perature decomposes into steam and protoxide of nitrogen as is explained in Lecture XLVI. ’ Carbonates of Ammonia.— The neutral carbonate only exists in combination. With the carbonate of water it What is ammonium ? How is the ammoniacal amal gan. prepared ? From what sources is sal ammoniac derived ? For what purpose is nitrate of am monia employed ■* a x- i THE CYANOGEN GROUP. 357 unites, forming Bicarbonate of Ammonia^ which may he prepared by washing the commercial Sesquicarbonate with water or alcohol, which leaves it undissolved. The carbon- ate of ammonia of commerce is prepared by sublimation from a mixture of sal ammoniac and chalk. Its constitu- tion is not uniform, though it is commonly regarded as a sesquicarbonate. Suljohate of Ammonia may be made by neutralizing sulphuric acid with carbonate of ammonia. It is soluble in twice its weight of cold water, and crystallizes in six-sided prisms. Hydroml])}iuret of Am^nonia is made by passing sul- phureted hydrogen into water of ammonia until no more is absorbed. Though colorless at first, it absorbs oxygen, and, sulphur being liberated, it turns yellow. It is of consider- able use as a metallic test. Cyanogen. — Bicarburet of Nitrogen — The mode of preparing this remarkable body, and also its lead- ing properties, have been described in Lecture LYI. It is of great interest in organic chemistry, as being the first dis- tinctly established compound radical, and the best repre- sentative of the electro-negative class of those bodies. We may call to mind that it is easily made by the de- composition of cyanide of mercury at a low red heat, is a gaseous body, soluble in water, and, therefore, must be col- lected over mercury. It is combustible, and burns with a purple flame. Baracyanogen (CgiV). — When the cyanide of mercury is decomposed in the process for preparing cyanogen, a brownish substance is set free, which is paracyanogen. It is insoluble in water and alcohol, and is only remarkable in being isomeric with cyanogen. Hydrocyanic Acid — Prussic Acid — Cyanide of Hydro- What is the carbonate of ammonia of commerce ? How is hydrosulphuret of ammonia made, and what is its use ? What is the constitution of cya- nogen ? What interesting fact is connected with its discovery ? What are its properties? What is paracyanogen? The Cyanogen Group. Cyanogen, C^N . Hydrocyanic acid Cyanic acid . . Fulminic acid . Cyanuric acid . = CyH. 358 hydrocyanic acid. gm (C 2 iV+ .ff).— Hydrocyanic acid may be obtained in a state of purity by passing dry sulphureted hydrogen gas over dry cyanide of mercury in a tube, and conducting the vapor, which is evolved when the tube is warmed, into a vial iminersed in a freezing mixture. The result of the de- composition IS sulphuret of mercury and hydrocyanic acid. In a state of aqueous solution, it is best obtained by the ac- tion of dilute sulphuric acid on the ferrocyanide of potas- sium in a retort, and receiving the vapor in a Liebig’s con- denser. Having aseertained the strength of the product, it may then be diluted to the proper point. This examina- tion may be conducted by precipitating a known weight of the acid with nitrate of silver in excess, collecting the cya- nide of silver on a weighed filter, washing, drying, and re- Weighing, which gives the weight of the cyanide. This, nearly weight of the pure hydrocyanic acid, Anhydrous hydrocyanic acid is a colorless and very vol- atile liquid, which exhales a strong odor of peach blooms • has a density of -705 ; boils at 79°. It mixes with wate^ and alcohol in any proportion. A drop of it held in the air on a glass rod becomes solidified by the rapid evaporation Irom Its surface. In the sunlight it decomposes rapidly producing a dark-colored substance ; and the same change goes on, though much more slowly, in the dark. It is one ot the most insidious and terrible poisons, a few drops pro- Queing death in a few seconds ; and even its vapor, largely diluted with air, brings on very unpleasant symptoms. Un- der the action of strong acids it is decomposed into ammo- nia and formic acid, the change being very simple ■ C^N, H+2,HO = NH^ -f- cIhO^. Under such circumstances, hydrochloric acid yields mu- ria,te of ammonia and hydrated formic acid. Hydrocyanic acid may, to a certain extent, be preserved from spontane- mberal'^ld^^ presence of a minute quantity of any Prussic acid may be detected by its smell, and by yield- ing a precipitate of Prussian blue when acted upon in so- lution successively by sulphate of iron, potash, and an ex- How may hydrocyanic acid be made ? By what nrocess ran llitZZTi actiofofst?o®ng chLngeTHowmayTbeTteLl? spontaneouf AMYGDALINE. 359 cess of hydrochloric acid. The liquid in which the poison is suspected to exist should be acidulated with sulphuric acid and distilled, and the hydrocyanic acidr will be found in the first portions which come over. Amygdaline ( — A crystallizable substance found in bitter almonds, the kernels of peaches, &c. ; is of considerable interest in connection with hydrocyanic acid, inasmuch as these organic bodies yield, when distilled with water, that substance. The change consists in the action of water upon amygdaline by the aid of an azotized ferment called Sijnaptase or Emuhine, which constitutes the larger portion of the pulp of almonds; the bitter almond oil at the same time makes its appearance. Amygdaline may be ab- stracted from the paste of bitter almonds, from which the fixed oil has been expressed, by the aid of boiling alcohol, which being subsequently distilled off, the sugar which is contained in the sirupy residue is destroyed by fermentation with yeast. The liquid being evaporated again to a sirup, is mixed with alcohol, which precipitates the amygdaline as a 'white crystalline powder, purified by being redissolved in alcohol and left to cool. It is soluble in hot and cold water, but sparingly soluble in cold alcohol. A weak so- lution of it in water, under the influence of a small quan- tity of the emulsion of sweet almonds, yields at once oil of bitter almonds and hydrocyanic acid. When amygda- line is boiled with an alkali, it yields Amygdalinic Add, which forms a salt with the alkali, and ammonia is evolved. Cyanide of Potassium {KCy) may be formed by the direct union of cyanogen and potassium, or by the ignition of the ferrocyanide of potassium in a close vessel. For common purposes in the arts it may be formed in a state somewhat impure by mixing eight parts of ferrocyanide of potassium, rendered anhydrous by heat, with three of car- bonate of potash, also dry, and fusing the mixture in a cru- cible, stirring it until the fluid part of the mass is colorless. The sediment is allowed to settle, and the clear liquid poured off ; it is the substance in question. Cyanide of potassium is very soluble in water, yields colorless octahe- dral crystals, which deliquesce in the air ; it melts without What is amygdaline ? What is the action of synaptase and water upon it ? How may it be obtained? By what processes may the cyanide of po* tassinm be made ? 860 COMPOUNDS OF CYANOGEN. change at a red heat, and exhales the odor of prussic acid. It is very poisonous. Cyanide of Mercury may he made by dissolving red ox- ide of mercury in hydrocyanic acid, or by the action of a solution of ferrocyanide of potassium on sulphate of mercu- ry, the cyanide crystallizing from the filtered hot solution. It forms fine prismatic crystals, more soluble in hot than cold water. It is poisonous ; and, when decomposed at a low red heat, yields cyanogen gas. Cyanic Add {CyO -{- HO) is procured by heating in a retort cyanuric acid deprived of its water of crystallization ; a colorless liquid comes over into the receiver, which is the hydrated cyanic acid ; it has a strong odor like acetic acid, and produces blisters on the skin. It is decomposed by the contact with water into bicarbonate of ammonia. C^NO, HO + 2HO C^O^ + iVZZg, and is a very instable body, spontaneously changing in a short time into Cyamelide, a body of the same constitution, but a white opaque solid, insoluble in water and alcohol, and decomposed by hot oil of vitriol into carbonate of am- monia. Ftdminic Acid ( Cy^O^ + 2HO) has not yet been insu- lated, but some of its salts, presently to be described, are characterized by the violence with which they detonate under very trivial disturbances. It is a bibasic acid. Cyanuric Acid {Cy^O^ + 2 HO) may be made by heat- ing urea, which disengages ammonia ; the residue is dis- solved in hot sulphuric acid, and nitric acid added until the liquid becomes colorless : on mixing it with water, and allowing it to cool, the cyanuric acid separates. Its crys- tals are efflorescent ; it is sparingly soluble in water, and is a tribasic acid ; and, as has been already stated, at a red heat it may be distilled, and yields cyanic acid without any other product. How may the cyanide of mercury be prepared ? Exposed to heat, what does it yield ? What are the constitution and properties of cyanic acid ? What of fulminic acid ? What of cyanuric acid ? DERIVATIVES OF CYANOGEN. 36] LECTURE LXXX. Bodies allied to Cyanogen. — Salts of the Oxycyanogen Acids. — F ERROC yanogen. — Ferrocyanides of Hydro- gen and Potassium. — Prussian Blue and Basic Blue. — Ferridcyanogen. — SuLPHocYANOGEN. — Compounds tvith Hydrogen and Potassium. — Melam^ Melamine, (^C. Cyanate of Potash (/fO, CyO) maybe prepared by ox- ydizing cyanide of potassium by oxide of lead in an earthen crucible ; the result boiled with alcohol yields, on cooling, crystals of cyanate of potash, in thin transparent plates, which undergo no change in dry air, but with moisture be- come converted into bicarbonate of potash and ammonia. Cyanate of Ammonia — Urea ( C^H^N^O,^. — The vapor of hydrated cyanic acid, mixed with ammoniacal gas, yields cyanate of ammonia. The solution in water, when heated, gives off ammonia, and the cyanate changes into Urea, from which caustic alkalies can not disengage ammonia. Urea may also be made from the action of sulphate of am- monia or cyanate of potash. Fulminate of Silver {2AgO, is made by dis- solving silver in warm nitric acid and adding alcohol. It separates from the hot liquid in white grains, which, being washed in water, are dried in small portions on filtering paper. It detonates with wonderful violence when either struck or rubbed. It is sparingly soluble in hot water, and crystallizes from that solution on cooling. It yields, by di- gestion with water and metals, salts, as those of zinc and copper. Fulminate of Mercury {2HgO, is prepared in the same manner as the foregoing, and, like it, is very ex- plosive. It is used for making percussion caps. Chloride of Cyanogen (CyCV) is prepared by the action of chlorine on moist cyanide of mercury in the dark. It is a colorless gas, soluble in water, congeals at 0®, and boils How is the cyanate of potash made ? How may urea be formed artifi- cially ? What is the process for preparing fulminating silver, and what are its properties? For what purpose is fulminate of mercury used? What results from the action of chlorine on cyanide of mercury in the dark ? a 3>o3 COMPOUNDS OF FERROCYANOGEN. at 11° ; condenses into a liquid under the pressure of four atmospheres. When kept in this condition, in sealed tubes, for a length of time, it assumes the solid state, which form may also be given to it by acting on anhydrous hydrocyanic acid by chlorine in the sun’s rays ; hydrochloric acid is formed, and the solid cyanide crystallizes. It exhales a pe- culiar odor, melts at 284°, and is soluble in alcohol and ether FERROCYANOGEN. Ferrocyanogen ( CqN^Fc = Cfy) is an ideal compound radical. Hydroferrocyanic Acid {Cfy^ 2II) may be obtained by decomposing the insoluble ferrocyanide of lead by sulphu- reted hydrogen while suspended in water. The solution be- ing filtered, is to be evaporated with sulphuric acid in vacuo until the acid is left solid. It may also be prepared by agitating its aqueous solution with ether, or by adding hy- drochloric acid to a strong solution of ferrocyanide of potas- sium, and then mixing it with ether, which precipitates the acid. It is soluble in water, to which it gives a powerful acid reaction. It decomposes alkaline carbonates with ef- fervescence, and does not dissolve oxide of mercury in the cold. In these respects, therefore, it strikingly differs from hydrocyanic acid. Ferrocyanide of Potassium — Prussiate of Potash — {2K, Cfy -f 3ZfO). — This salt is made on the large scale by igniting potash, iron filings, and animal matters in an iron vessel ; the mass is then acted upon by hot water, which dissolves out a large quantity of cyanide of potassium, which is converted into the ferrocyanide by the iron, and the fil- tered solution, on cooling, yields it in lemon-colored crystals, soluble in four parts of cold water. It is not poisonous. At a red heat it decomposes, and yields cyanide of potassium. It is a very valuable reagent ; with copper it yields a choc- olate precipitate ; with protoxide of iron, a white ; and with peroxide of iron, Prussian blue. Common Prussian Blue (f>Cfy + 4jPe) is prepared by precipitating a persalt of iron by solution of ferrocyanide of * potassium ; when dry, it is of a deep blue, with a lustre of coppery-red. It is insoluble in water, is decomposed by al- What is ferrocyanogen ? How is hydroferrocyanic acid obtained ? How Is the prussiate of potash prepared ? Is it poisonous ? What color does it give with protoxide and peroxide of iron ? What is common Pmssian blue ? What is its composition ^ COMPOUNDS OF FERRIDCYANOGEN. 363 kaline solutions, which yield alkaline ferrocyanides, and pre- cipitate oxide of iron. It is soluble in solution of oxalic acid, and then constitutes the basis of blue writing inks, which are used for steel pens. It is also much employed as a paint. Basic Prussian Blue (^Cfy, 4jPe + FeO^ is formed when the white precipitate, yielded by a protosalt of iron with ferrocyanide of potassium, is exposed to the air. As its formula shows, it is common Prussian blue, with perox- ide of iron. It differs from Prussian blue in the remarka- ble peculiarity that it is soluble in pure water. FERRIDCYANOGEN. Ferridcyanogen ^ hypothetical compound radical, which yields some compounds of interest. Ferridcyanide of Potassium (3 A-f- Cfdy) may be made by passing chlorine through a dilute solution of ferrocyanide of potassium until it ceases to yield a precipitate wdth a per- salt of iron. The liquid being concentrated, yields, on cool- ing, deep-red crystals, the solution of which is of a greenish color. It gives no precipitate with peroxide of iron, but with the protosalts a bright blue, lighter than Prussian blue, and known as TurnhulVs Blue. Cobaltocya7iogeny a hypothetical radical, yielding com- pounds analogous to the preceding bodies. Sulphocyanogen {Csy), a compound radical, not yet insulated with certainty. Its formula shows that it is a bisulphuret of cyanogen. Hydrosulphocyanic Acid (GsyH) may be obtained by decomposing sulphocyanide of lead by sulphureted hydrogen in water. The solution is decomposed by ebullition. It has the odor of acetic acid. It yields with peroxide of iron a blood-red color. Sulphocijanide of Potassium {KCsy) may be made by heating powdered ferrocyanide of potassium with half its weight of sulphur and one third of carbonate of potash, and keeping it melted for a short time. The mass is then boil- ed with water, which dissolves out the sulphocyanide, and the solution being concentrated, yields prismatic crystals of For what purposes is it used ? In w'hat respect does basic Prussian blue differ from it? What is the constitution of ferridcyanogen? What is Turnbull’s blue ? What are cobaltocyanogen and sulphocyanogen? What color does hydrosulphocyanic acid yield with peroxide of iron ? By what process is sulphocyanide of potassium made ? 861 MELLON E. the salt. It is soluble in water and alcohol, and deliques- ces in the air. It melts at a red heat. Its solution with peroxide of iron yields a blood-red color. Melam produced when sulphocyanide of ammonium is distilled at a high temperature, or by heating dry sulphocyanide of potassium with twice its weight of sal ammoniac. It is insoluble in water, but dissolves in strong sulphuric acid. When heated, it yields mellone and ammonia. Melamine ( CqMqWq) is produced when melam is dissolv- ed in a hot solution of potash. It separates on cooling. It is a basic body, uniting with acids. Ammeline remains in the solution after the melamine has crystallized. It may be precipitated with acetic acid. Ammelide is prepared by dissolving am- meline in sulphuric acid, and precipitating with alcohol. LECTUUE LXXXI. Mellone — U re a. — Mellone, Preparation of. — Mello- nides of Hydrogen and Potassium. — Natural and ar- tificial Formation of Urea . — Uric Acid.— Its Proper- ties. — Derivatives of Uric Acid. — Parabanic, Oooalu- ric, and Thionuric Acids. — Alloxantine. — Purpurate of Ammonia. — X.anthic and Cystic Oxides. Mellone — Me). — If sulphocyanide of potassium be acted upon by chlorine or nitric acid, a yellow powder is deposited ; this, when heated, gives off bisulphuret of carbon and sulphur, and there is left a yellowish powder, which is mellone. The relation of its constitution with cyanogen is obvious. It resists a moderate heat without change. Hydromellonic Acid {MeH) — By adding hydrochloric acid to a hot solution of mellonide of potassium, this acid separates as a white powder on cooling. It is partially sol- uble in hot water, and possesses strong acid powers. What results from the distillation of the sulphocyanide of ammonium? What are melamine, ammeline, and ammelide ? How is mellone pre- pared? What is the acti«*u of hydrochloric acid on the mellone of potas- sium ? UREA. URIC ACID. 365 Mellonide of Potassium (KMe) maybe prepared by melt- ing ferrocyanide of potassium with half its weight of sul- phur, and adding, when the fusion is complete, five per cent, of dry carbonate of potash. The resulting mass is acted on by water, and the solution being filtered, is evaporated, until, on cooling, it forms a mass of crystals, from which the sul- phocyanide may be removed by alcohol, and the mellonide left. It is soluble in water, and yields, by double decom- position with the salts of baryta, lime, &c., mellonides of these bodies, for the most part sparingly soluble. Urea may be obtained from urine by add- ing to it, when concentrated, a strong solution of oxalic acid. The precipitated oxalate of urea is to be boiled with pow- dered, chalk, and the filtered solution concentrated until the urea crystallizes on cooling. It may also be made artifi- cially by adding to a strong solution of cyanate of potash an equal weight of dry sulphate of ammonia ; the solution is evaporated to dryness in a water bath, and the urea dis- solved out by alcohol. It crystallizes in prisms, very solu- ble in water, but permanent in the air. At a high temper- ature it gives off ammonia and cyanate of ammonia, cya- nuric acid remaining. Urea contains the elements of cya- nate of oxide of ammonium, has neither an acid nor alkaline reaction, is decomposed by hot alkaline solutions, with evo- lution of ammonia, and, by uniting with two atoms of wa- ter, yields carbonate of ammonia, a result which takes place during the putrefaction of urine, the change being brought on by a nitrogenized ferment — the mucus of the bladder. Urea unites with acids, and forms, with nitric and oxalic acids, characteristic salts. Uric Acid — Lithic Acid — may be obtain- ed from the solid urine of serpents, which, being boiled in solution of caustic potash and filtered, yields uric acid, by the addition of hydrochloric acid, as a white, inodorous, and sparingly soluble powder ; soluble without change in sul- phuric acid, from which it is precipitated by water. Uric acid also exists in human urine, and appears to be always a product of the action of the animal economy. Of its salts, the urate of soda is interesting ; it is the chief ingredient of gouty concretions in the joints, called chalk-stones. The How may urea be made artificially? What are its properties? To what substance does it give rise in fermentation? Under what circumstan- ces does uric acid occur? What are chalk-stones ? 366 PAEABANIC ACID. urate of ammonia occurs as a urinary calculus, and is often deposited from urine as a reddish cloud or powder. Allantoin is prepared by boiling uric acid with peroxide of lead ; the filtered solution, being concen- trated, deposits prismatic crystals of allantoin on cooling. It is soluble in 160 parts of cold water. By a solution of caustic alkali it is decomposed into ammonia and oxalic acid, assuming, during this change, the elements of three atoms of water. Alloxan is made by the action of concen- trated nitric acid on uric acid in the cold. The uric acid is to be added in small portions successively, until about one third the weight of the nitric acid has been used. An effervescence takes place, and there is left a white mass, from which the excess of acid is to be drained. The sub- stance is then to be dissolved in hot water and crystallized. Its solution has an acid reaction and a bitter taste, and stains the skin purple, and, with a protosalt of iron and an alkali, yields a characteristic blue compound. Alloxanic Acid {C^HNO^ + HO) may be prepared by decomposing the alloxanate of baryta by dilute sulphuric acid. The alloxanate itself is obtained by the addition of barytic water to a warm solution of alloxan. It is a strong acid, decomposing carbonates, and even water, by the aid of zinc. Mesoxalic Acid (<^ 30 ^ + 2HO). — Mesoxalic acid may be obtained by boiling a solution of alloxan with acetate of lead, the resulting mesoxalate of lead being decomposed by sulphureted hydrogen. It is a strong acid, resists a boiling heat, and is bibasic. Mykomelinic Acid is prepared by boiling a solution of alloxan with an excess of ammonia, and then precipitating by an excess of dilute sulphuric acid. It is a light yellow powder. Parahanic Acid + 2 HO) is formed by the ac- tion of strong nitric acid on alloxan, or uric acid, by the aid of heat. The crystals form on cooling, and may be dried by draining, and then recrystallized. It is soluble in water, reddens litmus, and forms beautiful prismatic crystals. Under what form does urate of ammonia occur? How may allantoin be prepared? What is the action of C9ld nitric acid on uric acid? How is alloxanic acid prepared? What substance results from boiling alloxan with acetate of lead? How is mykomelinic acid prepared? What substance results from the action of hot nitric acid on uric acid ? ALLOXANMINE. 367 Oocaluric Acid + HO) may be made by de- composing a hot solution of the oxalurate of ammonia by dilute sulphuric acid, and cooling rapidly. The ammonia salt is itself procured by boiling a solution of the parabanate of ammonia, when it crystallizes, on cooling, in small nee- dles. Oxaluric acid is a white crystalline powder ; it con- tains the elements of one atom of parabanic acid and three of water, and its solution, by boiling, yields oxalic acid and oxalate of urea. Thionuric Acid{CQH^N2S20^2 + 2HO), a bibasic acid prepared by decomposing tWnurate of lead with sulphu- reted hydrogen. It contains the elements of one atom of alloxan, one of ammonia, and two of sulphurous acid. Uramile {CqH^N^O^. — When an excess of a saturated solution of sulphurous acid in water is mixed with a cold solution of alloxan, and an excess of carbonate of ammonia with caustic ammonia added, and the whole boiled, the thionurate of ammonia is deposited on cooling. From this the lead salt, used in the preparation of the foregoing acid, may be obtained by acetate of lead. The thionurate of am- monia, with a little hydrochloric acid, being boiled in a fiask, there separates a white body, which is uramile. It differs from thionuric acid in not containing the elements of two atoms of sulphuric acid. If the thionurate of ammo- nia is mixed with dilute sulphuric acid and evaporated in a water bath, Uramilic Acid is deposited ; it is Alloxantine is made when sulphureted hydrogen gas is passed through a cold solution of alloxan. The product is filtered, washed, and boiled in water, which deposits the alloxantine, on cooling, in transparent rhombic prisms, which turn red on exposure to ammonia. This sub- stance is alloxan, with one atom of hydrogen. A hot solu- tion of it is decomposed when a stream of sulphureted hy- drogen is passed through it, and Dialuric Acid forms. Murexide — Furpurate of Ammonia — may be made by the action of dilute nitric acid on uric acid, and then adding ammonia, or by boiling equal Aveights of uramile and red oxide of mercury with eighty times their weight of water, rendered alkaline by ammonia. The liq- What is the relation between oxaluric and parabanic acid ? How is uramile prepared? How is alloxantine prepared? What is the action of dilute nitric acid and ammonia on uric acid? What is the color of the crj*# tals of murexide ? 368 THE VEGETABLE ACIDS. uid turns of a deep purple color, and, when filtered, depos^ its, on-^cooling, crystals of murexide in square prisms, which, by reflected light, are of a green metallic lustre, and, by transmitted light, of a purple. It is sparingly soluble in cold water, but much more so in hot, and is one of the most splendid compounds known. Murexan — Purpuric Acid. — Murexide is to be dissolv- ed in a solution of caustic potash, and dilute sulphuric acid added. It forms a yellow powder, and, dissolved in am- monia, gives rise to the foregoing body. Xanthic Oxide occurs as a urinary calculus of a brown color and waxy aspect. The calculus may be dissolved in dilute potash, and xanthic oxide precipitates as a white powder by carbonic acid. It is a waxy body. Cystic Oxide {CqH^NS^O^ occurs also as a urinary cal- culus. LECTURE LXXXII. The Vegetable Acids. — Tartaric Acid, Preparation of. — Salts of Tartaric Acid.— Acids allied to Tartaric. — Citric and its allied Acids. — Malic and its allied Acids . — Tannic Acid . — Gallic Acid. — Acids allied to them. Of the vegetable acids several will be described with their associated alkalies. The following are those of which I shall treat in this Lecture : Tartaric . . Paratartaric Pyrotartaric Tartralic Tartrelic Citric . . Aconitic . . Malic . . Maleic . . Fumaric . . Tannic . . Gallic . . Ellagic . . Pyrogallic . Metagallic . . Cs £T^Oxo-}-2HO. . Og H^Oiq 2 HO. . C, I HO. 2Ca H^O^o^^sHO. . Cs -H4O10 -f- HO. . Oi^H^Oii — 3HO. . C^H O3 -- HO. . Ca -\-2HO. . H^Oe +2iFO. . C^H Os -h HO. . CisHsO^ + 3 HO. , Ct HOs -\-2H0. . A AO 4 ■ A H^Oz . A AOa How may murexan be prepared? Under what circumstar ces do xanthic oxide and cystic oxide occur ? SALTS OP TARTARIC ACID. 889 Besides acids such as these, which constitute a very nu- merous group, there is another class, which pass under tha name of Coupled Acids, the peculiarity of which is, that they consist of an acid affixed or coupled to another body, which, without affiecting the neutralizing power of the acid, accompanies it in all its combinations. Thus, hyposulphuric acid couples with naphthaline to form hyposulphonaphtha- lic acid, which neutralizes just as much of any base as hy- posulphuric acid could do, the naphthaline not changing its powers. Tartaric Acid ( — A bibasic acid which occurs, as has been already stated, in the juice of grapes and other fruits as bitartrate of potash. It may be obtained by dissolving cream of tartar in boiling water and adding pow- dered chalk, a tartrate of lime precipitating. The rest of the tartaric acid may be obtained from the solution by the addition of chloride of calcium, which yields another portion of tartrate of lime, which may be decomposed by digesting with an equivalent proportion of dilute sulphuric acid. The concentrated and filtered solution yields crystals acid to the taste, inodorous, and soluble both in water and alcohol ; the solution decomposes by keeping. Tartaric acid yields sev- eral valuable salts. Tartrate of Potash — Soluble Tartar {2KO, — may be made by adding carbonate of potash to cream of tartar. It is very soluble. Bitartrate of Potash — Cream of Tartar {KO^ HO, CgJT^Ojo)- — This is the salt which is deposited from the juice of the grape during fermentation, as Argol. It may be purified from the coloring matter it contains by solution in hot water, and the action of animal charcoal. In cold water it is very sparingly soluble. It yields black flux when ignited in a close vessel, the black flux being carbon- ate of potash enveloped in carbonaceous matter. Tartrate of Potash and Soda — Pochelle Salt — Salt of Seignette {KO, NaO, C^HJ^^q-\-\QHO) — may be pro- cured by neutralizing a solution of the foregoing salt with carbonate of soda. On evaporation and cooling it separ- ates in large prismatic crystals. Tartrate of Antimony and Potash — Tartar Emetic What are coupled acids? From what source is tartaric acid derived? What is soluble tartar? From what source is cream of tartar derived? What is Rochelle salt ? a 2 370 SALTS OT TARTAHIC ACID. {KOSb^O^, C^H^O^^+2HO).—Th\s valuable medicinal agent is made by boiling oxide of antimony with a solution of cream of tartar ; on cooling, the crystals are deposited. They are much more soluble in hot than in cold water, and dissolve without decomposition. Racemic Acid — Paratartaric Acid. — This remarkable acid, which has the same constitution as tartaric acid, and resembles it very closely, is found in the grapes of certain parts of Germany and France. Racemic acid, however, differs from tartaric in yielding a precipitate with a neutral salt of lime. Pyrotartaric Acid is obtained by the destructive distillation of tartaric acid, coming over with a variety of other products. The action of heat on tartaric acid is remarkable. When exposed to a temperature of 400° F., it melts, throws off water, and yields in succession three different acids, tartra- lic, tartrelic, and anhydrous tartaric acid, the constitution of which, compared with tartaric acid, is as follows: Tartaric acid -j- 2 HO. Tartralic “ 2C8JT4O10 + 3 i? 0 . Tartrelic “ Cgi^iOio-i- HO. Anhydrous tartaric C^H^^Oiq. All these, by the continued contact of water, pass back into the condition of tartaric acid. Citric Acid (C' 12 ^ 5^11 + ^dlO), a tribasic acid, occur- ring abundantly in the juice of lemons and other sour fruits, and separated therefrom by the aid of chalk and sulphuric acid. It is clarified by digestion with animal charcoal, and yields prismatic crystals of a pleasant taste, and soluble both in hot and cold water. The crystals are of two different forms, according to the conditions of their formation ; those which separate in the cold by spontaneous evaporation con- tain five atoms of water, three of which are basic ; but those which are deposited from a hot solution contain only four. The citrates form a very numerous family of salts, for, as the acid is tribasic, we may have them with three atoms of metallic oxide, or two of oxide and one of water, or one of oxide and two of water, besides subsalts. Aconitic Acid — Equisetic Acid {C^HO^ + HO) — is ■How is tartar emetic prepared? What is the relation between racemic and tartaric acids ? Describe the action of heat on tartaric acid. From what source is citric acid obtained ? How many classes of salts does citric acid yield? What substano© results from the fusion of citric acid? MALie ACID. TANNIC ACID. 371 formed by fusing citric acid, and the resulting brown prod- uct is dissolved in water, the change being ^C,HO,) + 5{HO), that is, one atom of hydrated citric acid yields three of aco- nitic acid and five of water. Acoiiitic acid is remarkable from occurring naturally in the Aconitmn Napellus and Equisetum Fluviatile. Malic Acid (CgJZ^Og + 2HO), a bibasic acid, occurring in the juice of apples and other fruits. It may also be pre- pared from the stalks of rhubarb, in which it occurs with oxalate of potash. It is a colorless solid, soluble in water, the solution changing by keeping. When heated in a re- tort, it melts, and then boils, emitting a volatile acid, the Maleic Acid, CqH^Oq + 2 HO, which condenses with the water in the receiver ; at the same time there forms in the retort crystalline scales of Fumaric Acid, CJHO^ + HO which may be separated from the unchanged malic acid by solution in cold water. It is to be observed that maleic fumaric, and aconitic acids are isomeric bodies. Tannic Acid {C-^qH^O^ + ZHO). — An astringent prin ciple found in the bark of the oak, nut-galls, and ^ig, 278 . other vegetable productions. It may be separ- ated by placing in a vessel, b, Fig. 278, pow- dered galls. On pouring on them sulphuric ether, a liquid drops through the funnel tube, c, into the bottle, a, spontaneously separating into two portions ; the lower, which is a solu- tion of tannic acid in water, is to be decanted and evaporated in the presence of sulphuric acid in vacuo. It yields tannic acid, or tannin, in the form of an uncrystallized mass. This acid is soluble in water, but much less so in ether, has an astringent taste and reddens lit- mus paper. With the persalts of iron i*t yields a characteristic and valuable precipitate of a black color, the basis of common writing ink. It forms insoluble com- pounds with starch, gelatine, and other organic bodies, that with gelatine being of considerable interest. It is the basis of leather. From the characteristic precipitate it gives Prom what sources is malic acid derived? What two acids are yielded by it under the action of heat? What is the relation between maleic, fu- marie, and aconitic acids ? How is tannic acid made ? What color does •t yield with persalts of iron ? What is the basis of leather? 872 GALLIC ACID. with that metal, it is used as a test for iron, which must, however, he in the state of peroxide, as the protosalts are unacted upon. The gradual darkening of pale writing inks is due to the gradual oxydation of the iron they contain. Catechin — There is a body extracted by hot water from catechu, called catechin. It crystallizes in nee- dles, and does not form an insoluble compound with gela- tine, and gives a green color with persalts of iron. By the •action of caustic potash in excess, it yields a black and in- soluble substance. Japonic Acid. By the action of carbon- ate of potash, it yields Kuhinic Acid. Gallic Acid {Cr^HO^ + 2UO) may be formed by ex- posing a solution of tannic acid to the air, or by making powdered galls into a paste with water, and keeping it ex- posed in a warm place to the air for some weeks. The mass is then pressed and boiled with water. On cooling, the solution precipitates a quantity of gallic acid, which may be purified by recrystallization. Like tannic acid, this sub- stance yields no precipitate with a protosalt of iron, but a deep blue-black with a persalt. It does not, however, pre- cipitate gelatine. Its crystals are soluble in one hundred parts of cold and three parts of boiling water. The solu- tion has an astringent taste. Tannic acid passes into gallic acid by oxydation, carbonic acid and water being evolved. Cjs/isOiz + 0 ,...^... + 2HO) + 2{HO) + 4(C'02); that is, one atom of tannic acid and eight of oxygen yield two of gallic acid, two of water, and four of carbonic acid. Ellagic Acid or gallic acid minus one atom of water, may be extracted after the removal of gallic acid by an alkali, and precipitated as a gray powder by hydrochloric acid. Fyrogallic Acid (Cg-fZgOg) sublimes when gallic acid is heated in a retort to *420°. It is in the form of white crys- tals, which are soluble in water. It strikes a black color with the protosalts of iron. Metagallic Acid is formed when gallic acid is suddenly heated in a retort to 500^. It is a black mass, insoluble in water, but soluble in alkalies, from which it is precipitated as a black powder by acids. From what cause do pale writing inks darken ? What is catechin ? How inay gallic acid be prepared ? How is ellagic acid procured ? What is the action of heat on gallic acid ? VEGETABLE ALKALIES. 373 LECTURE LXXXIIL The Vegetable Alkalies. — General Properties of Vege^ table Alkalies. — Morphia. — Its Preparation and Prop- erties. — Other Alkalies of Opium. — Meconic Acid . — . Alkalies of Bark, Quina, Cinchona, Spc. — Kinic Acid — Strychnia and Brucia . — Table of Alkcdoids. — Arti- ficial Alkaloids. The vegetable alkalies constitute an extensive class of bodies, which are, for the most part, the active medicinal agents of the plants in which they occur. They are gener- ally sparingly soluble in water, but more soluble in boiling alcohol, of a bitter taste, and characterized by containing nitrogen. In their natural state they are united with an acid, and, possessing basic properties in a very marked man- ner, neutralize acids completely. This quality seems to de- pend on the nitrogen they contain, and has no reference to their oxygen, for the quantity of this latter element which may be present seems to have no relation to their neutral- izing power, and, indeed, in some of them it is not present at all. In many respects they are analogous to ammonia, their salts, unlike those of some of the compound radicals, such as ethyle, &c., undergoing decomposition in the same manner as the salts of ammonia. Thus the chloride of ethyle does not decompose the nitrate of silver, but the an- alogous compounds of ammonia and vegetable alkalies do ; and these bodies may therefore be separated from the nat- ural combinations in which they occur precisely as we should separate lime, or potash, or magnesia in their salts. Most of the vegetable alkalies are poisonous bodies, and, in- deed, among them we meet with some of the most terrific poisons known. There are several recently-discovered ar- tificial substances, such as Aniline, and those containing arsenic and platinum, which ought to be classed with these basic bodies. Of the numerous vegetable alkalies, those which I shall now describe are the most important. What are the vegetable alkalies ? What element do they all contain \ In what condition are they commonly found ? What are their relations to acid bodies ? What are their general properties ? Have any of them beei made artificially ? S74 MORPHIA.— NARCOTINfi. Morphia {C^^H^qNOq + 2HO). — -This substance is the active principle of -opium, and was the first discovered of these alkalies. It was insulated by Sertuerner in 1803. It may be prepared by mixing a concentrated infusion of opium with a solution of chloride of calcium in excess ; the mix- ture, when warmed, deposits a precipitate of meconate and sulphate of lime, and the hydrochlorate of morphia remains in solution. From this it may be crystallized by evapora- tion, and a dark liquor, containing narcotine and coloring matter, separated by pressure in a piece of flannel. The impure hydrochlorate may be re-dissolved and re-crystal- lized, and, by repeating the operation, or resorting to ani- mal charcoal, it may be obtained quite white. The salt may now be dissolved in hot water and acted on by an ex cess of ammonia, which throws down pure morphia as a white precipitate. It may be obtained in crystals by solu- tion in alcohol. Morphia is almost insoluble in water ; it neutralizes acids, and forms crystallizable salts. Its solution is bitter. It dissolves readily in dilute acids, and yields a deep orange- red color when acted on by strong nitric acid. The most common of its salts are the hydrochlorate, the sulphate, and the acetate. Narcotine is associated with morphia in opium. It may be obtained by digesting the insoluble por- tion witli dilute acetic acid ; the precipitate produced by ammonia is to be dissolved in alcohol, and purified by an- imal charcoal. It yields prismatic crystals, insoluble in wa- ter, and is a weak base. By the action of peroxide of man- ganese and sulphuric acid, and by bichloride of platinum, it yields an extensive series of bodies, some of which are acids and others bases. Codeine — The hydrochlorate of morphia, prepared as above described, contains this base ; and when the precipitation with ammonia is made, it remains in solu- tion. When pufe, it crystallizes in octahedrons, and is a powerful base. Along with this body, in opium, there oc- casionally occur other substances of less importance, as The- baine, P seudomorphine, Narceine, and Meconine. Meconic Acid 3iTO). — A tribasic acid, asso- From what is morphia obtained? When was it discovered? Give a process for its preparation. How is narcotine prepared ? What are its properties ? What other alkaline bodies are obtained from opium ? CimNA. — CINCHONA. 375 ciated with morphia in opium. It may be obtained from the meconale of lime, which precipitates in the preparation of morphia by mixing it with warm dilute hydrochloric acid, and repeating the operation until all the lime is re- moved. When purified from coloring matter, it crystallizes in scales, which are soluble in water and alcohol. When heated, it loses six atoms of w'ater of crystallization ; and if its solution be boiled, or the dry acid heated in a retort, Comenic Acid, 2HO, a bibasic acid forms with the disengagement of water and carbonic acid. Meconic acid yields, with the persalts of iron, a blood-red solution. It forms several series of salts, like all tribasic acids. Comenic acid, when heated, yields carbonic acid and a new body, Pyromeconic Acid, with a small quantity of an- other substance, parameconic acid. Pyromeconic acid is composed of HO. Quina — Quinine — This, which is one of the most valuable of the vegetable alkalies, is obtained from Cinchona Bark, The decoction of the ground bark in di- lute hydrochloric acid is to be boiled in an excess of milk of lime, and the precipitate acted upon by boiling alcohol; on evaporation Cinchona is deposited in crystals, but the quina remains in solution. It may be precipitated by the addition of water, and obtained in crystals from the spon- taneous evaporation of its solution in absolute alcohol. Q,uina neutralizes acids perfectly, giving rise to salts, of which the hydrochlorate, phosphate, sulphate, &c., are em- ployed in medicine. It is sparingly soluble in water, but very soluble in alcohol or acids. The basic sulphate of qui- na, a common preparation, is sparingly soluble in water, but the neutral sulphate is much more so. For this reason, sulphate of quina is often dissolved in dilute sulphuric acid. Cinchona ((712^12-^^)- — This alkali is obtained, as just stated, in the preparation of quina, with which it is asso- ciated in bark, and is found in large quantity both in the gray and red bark. It crystallizes in prisms, is sparingly soluble in water. Its salts, like those of the foregoing, are very bitter. Tw'o other analogous bodies exist in different species of bark. They are Chinoidine and Aricine. How is meconic acid procured ? What is the action of heat upon it ? What color does meconic acid yield with persalts of iron ? When come- nic acid is heated, what acids does it yield f From what source is quina derived ? How is cinchona prepared ? What other alkalies exist in bark ? 376 STRYCHNIA. BRUCIA. Kinic Acid HO) is associated with the foregoing bodies in bark. It is obtained by decomposing the kinate of lime, obtained in the manufacture of sulphate of quina by oxalic acid, filtering the solution from oxalate of lime, and the kinic acid crystallizes on evaporation. It is very soluble in water. Strychnia occurs in Nux Vomica, St. Ig- natius's Bean, in the poison ZTpas Tieute, and other vege- table products. It may be extracted from nux vomica seeds by boiling them in dilute sulphuric acid, and then acting with lime and alcohol as described in the case of quina. Strychnia requires 7000 parts of water for solution, and communicates to it an intensely bitter taste. It is one of the most violent poisons known. Its alkaline powers are well defined, and it produces a complete series of salts. It is soluble in hot alcohol, but not in ether. The antidote for an over-dose of it is an infusion of tea. Brucia {C is associated with strychnia, and, being very soluble in cold alcohol, is readily separated from it. It is also more soluble in hot water, and possesses the poisonous character of strychnia. These substances are found in union with Igasuric Acid. The following table gives the names of other vegetable alkalies, and bodies analogous to them : Aconitine. Daturine. Picrotoxine. Antearine. Delphinine. Piperine. Asparagine. Elaterine. Phloridzine. Atropine. Emetine. Populine. Caffeine — Theine. Gentianine. Salicine. Chelidonine. Hesperidine. Solanine. Chinoidine. Hyosciamine. Stramonine. Colchicine. Meconine. Thebaine. Conine. Narceine. Theobromine. Curarine. Nareotine. Veratrine. Daphnine. Of some of these bodies, as nicotine and conine, it may be remarked that they are volatile oily liquids, which can form crystallizable salts and acids. They both contain ni- trogen, and are interesting in their relations to the three fol- lowing bodies, which may be formed artificially. With what acids are these bodies associated? From what sources is strychnia procured ? What are the properties of strychnia ? What is the best antidote to its poisonous effects ? With what other alkali is it asso- ciated ? Mention some other vegetable alkalies ? What analogous substan- ces have been formed artificially ? COLORING BODIES. 377 Aniline — This substance is formed by tbe action of potash on isatine, and is also one of the ingredi- ents of the oil of coal tar. It is an oily liquid, boils at 358^, and yields crystalline salts with acids. Leukol — Formed with the foregoing in oil of coal tar, from which it may be separated by distillation. It is also an oily liquid, and can yield crystallizable salts. Quinoline i^G — Formed by distilling quinine or strychnine with caustic potash. An oily liquid, very bitter, strongly alkaline, and yielding crystallizable salts. Besides these bodies there are other artificial bases of an analogous nature, but which differ in the remarkable par- ticular of containing platinum and arsenic; such, for exam- ple, as the platina bases of Reiset and Gros, or the arsenico- platinum radical kakoplatyle. The formation of these or- ganic bases leads us to hope that the vegetable alkalies themselves will hereafter be artificially formed. LECTURE LXXXIV. The Coloring Bodies. — General Properties of Coloring Principles. — Madder. — Hcematoxyline. — Carihamine, — Yelloio Colors. — Chlorophyll. — Indigo . — Sulphin- digotic Acid. — Deoxydized Indigo. — Action of Heat and Reagents on Indigo. — Litmus. — Carmine. ^ The coloring principles derived from the organic kingdom may be conveniently divided into two classes : the non-nitro- genized and the nitrogenized. They may also be readily classed into groups, as blue, red, yellow, green. For the most part, they are derived from vegetable productions. For some coloring matters, tbe fibres of those tissues com- monly employed for clothing have a sufficient affinity as to hold the color so that it can not be removed by mere wash- ing, and is permanently dyed. But in other instances this is not the case ; the artist then has to avail himself of the qualities possessed by intermediate bodies, such as alumina and the oxide of tin, which at once possess the double qual- ity of an affinity for the coloring matter and an affinity What may be remarked as respects the salts of Reiset and Gros ? Hov? may coloring principles be classified ? S78 NON-NITROGENIZED COLORS. for the cloth fibre. The attraction of these bodies for col- oring matter may be illustrated by precipitating alumina in a solution tinged by litmus ; the solution becomes perfectly clear, its color going down with the precipitate, and form- ing with it a lake. NON-NITROGENIZED COLORING MATTERS. The ^lue non-nitrogenized coloring matters are chiefly found in flowers and fruits. They are reddened by acids, and turned green by alkalies. The Hed non-nitrogenizing coloring matters are of some importance ; among them may be mentioned Madder Red^ the sublimed crystals of which are known as Alizarine Madder also furnishes a purple and a yellow color. Hcematoxyline is the coloring matter of log- wood ; it is soluble in water and alcohol, and furnishes, with iron salts, the black dye for hats. The same principle is yielded by Brazil-wood and cam- wood. Carthamine is a very beautiful red, obtained from safflower ; it is used for making pink saucers. The Yelloiv coloring matters. Among these may be mentioned Quercitrine HO), derived from the Qiiercus Tinctoria ; Gamboge, the dried juice of the Gar- cinia Gamhogia ; Turmeric, used as a test for alkalies, which turn it brown, from the Curcuma Longa; and Anatto, from the seeds of the Bixa Orellana. The Green coloring matters. Chlorophyll, the constitu- tion of which is not known. It is the green coloring mat- ter of leaves. It is insoluble in water, but soluble in al- cohol and ether, and is a fatty substance. It is also found, under very interesting circumstances, in the animal system as the coloring matter of bile. NITROGENIZED COLORING MATTERS. The nitrogenized coloring matters, among which are some of the most valuable dyes that we possess, may also be di- vided according to their tint. Indigo is derived from the juice of several species of In- digofer a, and is formed from a colorless or yellow compound From what source are the blue non-nitrogenized colors obtained % What js alizarine ? What are haematoxyline and carthamine ? From what sources are quercitrine, gamboge, turmeric, and anatto derived? Whait is chlorp- phyll ? From what soqroe is indigo derived? INDIGO. 379 which is dissolved out from the leaves of these plants when they are allowed to ferment with water. A deep blue pre- cipitate (indigo) forms. It appears, therefore, to be a pro- duct of oxydation. It comes in commerce in small masses, which, when rubbed, exhibit a coppery aspect, is insoluble in water, alcohol, dilute acids, and alkalies, and may be sublimed, yielding a purple vapor, which condenses into ciystals of pure indigo. It dissolves in about fifteen parts of strong sulphuric acid, but still better in Nordhausen oil of vitriol, yielding a mass which is soluble in water. It is Sulphindigotic Acid. By contact with deoxydizing agents, blue indigo becomes colorless, as may be shown by digest- ing powdered indigo,, green vitriol, hydrate of lime, and water together. In this state, as in its natural condition, it is soluble in water, and white indigo may be precipitated by hydrochloric acid. On exposure to the air, deoxydized indigo absorbs oxygen rapidly, and becomes blue and in- soluble. When indigo is submitted to destructive distillation, it yields an oily liquid. Aniline, possessed of powerfully basic properties, and described in the last Lecture. The relation which exists between blue and white indi- go is seen from their formulas. Blue indigo Cx^H^NO^. White indigo Ci^H^NOz- By several chemists indigo is regarded as containing a radical, Anyle, = the symbol for which is An. On this view', blue indigo is the anhydrous deutoxide of anyle, AnO^, and white indigo the hydrated protoxide, AnO, HO. Under the action of heat and of reagents, indigo yields an extensive class of bodies, to which much attention has been given. In this place I can do little more than enu- merate some of them. With dilute nitric acid it yields Anilic or Indigotic Acid. With strong nitric acid it yields Picric or Carbazotic Acid, a substance of a yellow color, bitter taste, and forming explosive salts. Heated with bi- chromate of potash, sulphuric acid, and water, it yields /m- tine, which crystallizes in red prismatic crystals, and con- tains the elements of blue indigo, with two additional atoms of oxygen. This body, under the influence of an alkaline How is sulphindigotic acid made ? What is deoxydized indigo ? How is aniline made ? What is the relation between IdIuc and white indigo What is anyle ? What are indigotic acid, carbazotic acid, and isatine? 380 LITMUS.— CARMINE. solution, unites with one atom of water, and changes into Imtinic Acid. Under the influence ot chlorine, isatine yields Chlcrrisatine, by an atom of chlorine substitutii»g one of its hydrogen atoms, and Bichlor isatine ^ by the substitu- tion of two chlorine atoms for two hydrogen ones ; and these, again, as in the case of isatine itself, acted upon by alkaline solutions, yield each an acid. Caustic alkalies, acting on indigo, yield Crysanilic and Anthranilic Acids. Litmus is derived from the Rocella Tinctoria, Lecanora Tartarea, &c. These lichens yield to ether a crystalline substance, to which the name Lecanorine is given. It does not contain nitrogen. It is in white crystals, soluble in hot alcohol and ether. This substance, heated with baryta or alkalies, yields Orcine, by losing two atoms of carbonic acid. Orcine crystallizes in prisms, which have a yellowish tint and a sweet taste. Mixed with ammonia, and exposed to the air, oxygen is absorbed, and the liquid assumes a deep purple tint. From this acetic acid precipitates a deep-red powder, Orceine^ which contains nitrogen, and is supposed to*be the basis of the dye-stuff of litmus. With alkalies it gives a blue color. Litmus is extensively used in chemistry as a test for acids and alkalies. Carmine is the coloring matter of the cochineal insect. Coccus Cacti. The coloring matter may be obtained from the insect by water or ammonia. The carmine of commerce is a lake containing alumina. Aloes is the inspissated juice of certain species of Adoe^ used as a purgative medicine. When heated with nitric acid, and water added, a yellow precipitate is thrown down, which, when purified, is Chrysammic Acid. It yields yel- low crystals of a bitter taste, and furnishes a solution of a purple color. Its salts are crystallizable, by transmitted light of a red color, with a green metallic reflection like murexide. The liquid from which this acid was precipi- tated contains picric acid. What is the effect of alkaline solutions on isatine ? What is the effect of chlorine upon it? From what sources is litmus derived ? What are or- cine and orceine? From what source is carmine derived? How is chiys- ammic acid prepared ? THE FATTY BODIES. 381 LECTURE LXXXV. The Fatty Bodies. — Properties of the Saponifiable Fats. — Distinction between Fixed and Volatile Oils. — Prep- aration of Soaps. — Stearine and Stearic Acid. — Mar- garine and Margaric Acid. — Oleine and Oleic Acid.^ Margarone. — Production of Glycerine. — Natural Oils, as Palm Oil, Cocoa Tallow, and Nutmeg Butter . — Spermaceti. — Cholesterine . — Three Classes of Volatile Oils . — The Camphors. This class of substances is characterized by several well- marked peculiarities, and may be conveniently divided into two natural groups, oils and fats. They belong both to the vegetable and animal systems. In the former they usually abound in the seeds or fruits ; in the latter they are depos- ited in the cellular structure of the adipose tissue. The natural fats are usually mixtures of two or more ingredi- ents, which differ from one another in consistency. In most instances they are stearine and margarine, along with a liq- uid oleine. These oils can not be distilled without under- going decomposition ; exposed to the air, they gradually ab- sorb oxygen and evolve carbonic acid. Many of them, in which this change takes place with rapidity, turn into res- inous bodies ; and hence their application, in the art of painting, as drying oils. When acted upon by alkalies, the fixed oils and fats give rise to soaps, and hence are spoken of as Saponifiable. Oily bodies may be divided into fixed and volatile. The fixed oils decompose when heated ; the volatile ones distill. A simple test, therefore, is sufficient to distinguish them. When a few drops of an oily substance are put on paper, if it be a volatile oil it soon evaporates, and leaves the pa- per without a stain; if fixed, the paper remains greasy. The fixed oils have but little odor, the volatile oils common- ly a characteristic one. They are all insoluble in water ; Into what natural groups may the fatty bodies be divided ? What are the natural fats ? What change do the drying oils undergo ? How may the fixed oils be distinguished from the volatile 1 What is the difference of their properties 1 382 SAPONIFICATION. many of them are soluble in alcohol ; but in ether they are freely dissolved. By exposure to a low temperature the constituent prin- ciples of a mixed oil may often be separated from each other, the more solid substances separating as the temper- ature descends. When olive oil is thus treated, an expo- sure of 40° F. causes a deposit Margarine : the fluid por- tion which is left is Oleine. Animal fats exposed to press- ure between folds of blotting paper communicate to it oleine, atid the solid residue which is left behind is a mixture of margarine and Stearine. When the fixed fats are boiled with alkaline solutions. Soaps are formed ; these substances, which are of extensive use in domestic economy and the arts from their detergent qualities, are freely soluble in wa- ter. In the process of making them, the fats undergo a change ; they form true acids, stearine yielding stearic ifcid, margarine margaric acid, and oleine oleic acid, which may be set free by decomposing the soap with an acid. 'With them there is also formed a sweet substance. Glycerine^ which appears to be the same, whatever fat may have been originally employed. Of the varieties of soap met with in commerce, Soft Soap is made from potash, combined with whale or seal oil ; Hard White Soap from tallow and caustic soda ; Hard Yellow Soap from soda, tallow, palm oil, and resin. In the preparation of white soap the alka- line solution is made to boil, and tallow added in small por- tions until no more can be saponified ; the solution now con- tains soap and free glycerine ; the former is separated by the addition of common salt, in a solution of which it is insoluble. It floats on the top of the liquid. It is then run into moulds, and cut into bars for commerce. In this process the man- ufacturer does not add so much salt as to separate all the water. Commercial soap still contains from 40 to 50 per cent. Stearine may be obtained from purified mutton fat by suffering a warm ethereal solution to cool. The stearine crystallizes, and margarine and oleine are left in solution. A repetition of the process purifies it. It is a white body, insoluble in water and in cold alcohol. It melts at 130°. When saponified, it yields glycerine and stearic acid. What is the effect of a reduction of temperature on mixed oils ? Into what may olive oil be thus decomposed ? What are soaps ? How may the different varieties be formed ? How is stearine prepared, and what are its properties ? STEARIC AND MAUGARIC ACIDS. 383 Stearic Acid {Cq^Hq^Oq) may be crystallized from a hot alcoholic solution, is insoluble in water, and without taste or smell. It is soluble both in alcohol and ether, melts at 158°, and may be volatilized without change. Margarine. — This substance remains with oleine in the ethereal solution arising in the preparation of stearine, and may be obtained from it by evaporation and pressing the soft mass in paper. Margarine is found more abundantly in human than in other kinds of fat. Margaric Acid {OqqHqqOq) is prepared by saponifying margarine with potash and decomposing with hydrochloric acid. It is also formed with other products by the distilla- tion of stearic acid. It crystallizes in white needles, its melting point being 140*^. Oleine. — When almond or rape oil is dissolved in ether and the solution exposed to a low temperature, the marga- rine crystallizes, and oleine may be obtained by evaporating the ether. It remains liquid at a temperature of 0°. From it Oleic Acid may be obtained by saponifica- tion and decomposition with muriatic acid, as in the fore- going instances. Its melting point is about 20°. It gives rise to a class of salts. Margarone — When a mixture of margaric acid and lime is distilled, this substance is formed, and car- bonic acid separates. It is a white solid, like spermaceti, and melts at 170°. Glycerine (OgHgOg). — This substance arises when any fatty matter is saponified with potash, the soap being de- composed with tartaric acid, and dissolving the glycerine out by alcohol. It is a colorless liquid, specific gravity 1’26 ; it is soluble in water and alcohol, but not in ether. It may be cooled to a very low point without assuming the solid form. When mixed with sulphuric acid, the two bodies unite directly, and Sulpho glyceric Acid is the result : an acid having many analogies with sulphovinic. Palm Oil is brought from Africa, and much of it used in the manufacture of yellow soap. It is of a reddish-yellow color, and contains, besides oleine, a solid fat, Palmitine. It is insoluble in water, slightly soluble in hot alcohol, but What is the process for preparing stearic acid ? How are margarine and margaric acid obtained ? What are the properties of oleine ? How is oleic acid made ? What is margarone ? Under what circumstances does glvcw- line form ? What are palm oil and palmitine ? 384 FATTY BODIES. very soluble in ether. Its melting point is 118®. By sa- ponification and decomposition with an acid, it yields Pal- mitic Acid, the melting point of which is 140°. It is a bibasic acid. Cocoa Tallow. — A solid fat obtained from the cocoa-nut, and used in the manufacture of candles. Its oleine and Btearine may be separated by pressure, or by boiling alco- hol, from which the stearine crystallizes on cooling. Among other fatty substances and allied bodies may be mentioned Nutmeg Butter, which yields, among other pro- ducts, Myristicine, and by saponification, Myristic Acid. Elaidine, which arises from the action of nitrous acid on oleine ; it furnishes, by the common process, Elaidic Acid. Suberic Acid, which arises from the action of nitric acid on cork. Succinic Acid, by the destructive distillation of am- ber, or by the continued action of nitric on stearic acid Sehacic Acid, by the destructive distillation of oleic acid. Butyrine, Caproine, and Caprine, which are contained in butter. These yield, by saponification and decomposi- tion, Butyric, Caproic, and Capric Acids. Butyric acid can be made, as we have seen, artificially by fermentation. Bees' Wax is a mixture of two bodies : CeHne, which may be dissolved by boiling alcohol, and Myricine, which is in- soluble therein. Spermaceti, which is obtained from cer- tain species of whales, yields, under the process for glyce- rine, a substance, EtJial, and this, under the action of hot potash, gives Ethalic Acid, with evolution of hydrogen gas. Cholesterine is obtained from biliary calculi * it also occurs in the substance of the brain. The Volatile Oils. — These, for the most part, are found in plants, or are derived from them by simple processes. Many of them are extensively used in the arts in the man- ufacture of varnishes, and others in the preparation of per- fumery. Their solutions in alcohol form Essences, and in water Medicated Waters. They are commonly obtained by the distillation of those parts of the plants in which they occur, with water, and consist of two substances, a solid por- tion, Stearopten, or camphor, and a true oil. They may be divided into groups according to their constitution. What is palmitic acid ? Mention some other bodies belonging to the same class. From what are suberic, succinic, and sebacic acids derived? What bodies are contained in butter, and what acids do they yield ? What two substances are found in bees’ wax? From what are spermaceti and cholesterine derived ? . VOLATILE OILS. 385 Volatile Oils containing Carbon and Hydrogen. Turpentine. Bergamotte. Citron. Cubebs, C'opaiva. &c. Storax. Volatile Oils containing Carbon^ Hydrogen^ and Oxygen. Cajeput. Lavender. Rosemary. Peppermint. Pennyroyal. Valerian. Spearmint, &c. Volatile Oils containing Sulphur. Black mustard. j Onions. Horseradish. | Asafoetida. The stearoptens (camphors) of the volatile oils are best lepresented by common camphor, which is extracted from the Laurus and Dryabalonops Camjphora by distilling with water. It is a white, tough, semitransparent mass, lighter than water, of a well-marked odor, melts at 3d0^, and soon after sublimes rapidly unchanged. Artificial Camjplior is made by passing dry muriatic acid gas into oil of turpentine. It is a muriate of oil of turpentine. The true camphors originate in several different ways ; some- times by the oxydation of the oils from which they are de- rived ; sometimes they are hydrates of those oils ; and some times they are isomeric with them. LECTURE LXXXVI. The Resins, Balsams, and Bodies arising in Destruct- ive Distillation. — Colojphomj, Gum Lac, Amber, Sfc. — India-rubber. — Balsams. — Products of the Destruct- ive Distillation of Wood. — Paraffine, Eupione, Crea- sote, and allied Bodies . — The Destructive Distillation of Coal. — Naphthaline, Paranapthaline, Kyanol, Car- bolic Acid. — Products of slow Decay . — Ulmine and Ul- mic Acid. — Crenic and Apocrenic Acid . — The Varie- ties of Coal and other subsidiary Bodies. The resins are bodies in many respects analogous to the camphors, but are distinguished from them by the circum- stance that they are not volatile without decomposition. In many instances they act as acids ; they all contain oxygen. Into what groups may the volatile oils be divided? What are the cam- phors ? What is common and artificial camphor ? Wliat are the resins? R 386 RESINS. BALSAMS. Colophony is a mixed resin, obtained by the distillation of turpentine with water, the oil of turpentine passing over It iS a mixture of two resins, Pinic and Sylvie Acids^ which may be separated by cold alcohol, in which sylvic acid is insoluble. Guin Lac^ which is one of the resins, occurs under three forms : shell lac, stick lac, and seed lac. It is used in the preparation of lacquers, and is the chief ingredient in seal- ing-wax. Among other resins may be mentioned Copaly MaUic, Dragon's Blood, Gamboge, Sandarac, and Dam- mar a Resin. Amber is a substance belonging to this class. It is form- ed in beds of bituminous wood, and often incloses insects in a state of beautiful preservation. Its specific gravity is about 1'07. By distillation it yields succinic acid. Caoutchouc — Indian-rubher, or Gkim-elastic — is the pro- duct of the Jatropa Elastica, the Heevea Caoutchouc, and several other tropical trees. The milky juice which they yield is dried on moulds of various forms ; it turns of a black color by being smoked. From its imperviousness to water, this substance has of late been introduced for a great va- riety of purposes. It is combustible, burns with a bright flame, is softened by boiling water, and still more so by ether. In ether, as also in naphtha and coal oil, it may be dissolved. Bags of it, soaked in ether until they become gelatinous, may be distended, by blowing into them, to a very great size, and thus become useful for a variety of purposes. Very few chemical agents act upon India-rubber : it is extensively used for connecting the parts of chemical apparatus. Balsams are compounds of resins with volatile oils ; some of them also contain benzoic or cinnamic acids. Some, as benzoin, are solid ; and others, as the Balsams of Tolu and Peru, are viscid fluids. THE PRODUCTS OF THE DESTRUCTIVE DISTILLATION Ol* WOOD, &c. When wood is submitted to distillation in close vessels, a black, inflammable liquid called Tar is formed ; it contains What substances may be obtained from colophony ? What is gum lac ? What acid does amber yield by distillation ? Prom what sources is India- rubber derived ? What is the cause of its black color ? How may it be softened, and in what dissolved ? What are the balsams ? What are tar and pitch ? DESTRUCTIVE DISTILLATION. 387 a great many remarkable bodies, among which the following may be mentioned. The solid black residue which is left after the distillation or inspissation of tar constitutes Pitch. Paraffine {C .H) is obtained by distilling tar, several oils coming over : it is from the heaviest that this substance is extracted. It is a solid substance, lighter than water, of a fatty appearance; it melts at 111° F., and distills un- changed. Few chemical agents act upon it : it remains un- changed by the alkalies, acids, &c., but is soluble in turpen- tine and naphtha. From its chemical indifference it has ob- tained its name {Parum Affinis). Eupione occurs abundantly in animal tar, from which it may be prepared by distillation, and subsequently purified by rectification from sulphuric acid. From paraf- fine it may be separated by exposure to cold, or, being more volatile, by distillation. It is a colorless liquid, specific grav- ity *074 ; it boils at 339° F. It is insoluble in water, but very soluble in alcohol. Creasote is extracted from the heavy oil of tar by a com- plicated process. It is an oily, colorless liquid, of a burning taste, exhaling a powerful odor of wood smoke. It is slight- ly heavier than water, boils at 400° F., is combustible. One hundred parts of water dissolve about of this substance, and obtain its peculiar odor. It has the remarkable prop- erty of coagulating albumen and preserving flesh from pu- trefactive changes. From this latter circumstance its name is derived. Among allied substances may be mentioned Picamar^ an oily liquid of a bitter taste, which boils at 518° F., and com- bines with bases to form crystalline compounds. Kapno- mar, a colorless liquid, having an odor of rum ; boils at 360° F., and forms, with oil of vitriol, a purple solution. Cedri^ ret, which forms red cry&tals, giving, with creasote, a purple solution, and with sulphuric acid a blue. Pittakal, a dark blue solid, which yields blue precipitates with metallic salts. It contains nitrogen. When coal tar is submitted to distillation, like wood tar, it yields a volatile oil, which, by being submitted to rectifi- cation, becomes Coal Oil, or Artificial Naphtha. From it What properties distinguish paraffine ? What are the properties of eu- pione? What remarkable properties does creasote possess? From what IS its name derived? From what sources are picamar, kapnomar, cedriret, and pittakal obtained ? 388 NAPHTHALINE. a variety of substances may be extracted ; they either pre- exist in the oil, or are formed by the operation. Naphthaline ( is obtained by rectifying coal gas tar; it forms colorless or crystalline plates, melting at 136® F., and boiling at 413° F. It exhales a peculiar odor, is very combustible, insoluble in water, but soluble in ether and alcohol; the specific gravity of its vapor is 4*528. It dissolves in sulphuric acid, and the solution, on being diluted with water and saturated with carbonate of baryta, yields two salts, one containing Sulphonaphthalic Acid^ and the other an acid less known. Paranaphthaline is associated with naphtha- line, but differs from it by being insoluble in alcohol, by which liquid they may therefore be separated. - Kyanol an oily liquid, which, though volatile, has a boiling point of 358® F. It is heavier than water, with which it may be combined, and is soluble in alcohol and ether. It possesses basic properties, and yields several well-defined salts. • Carbolic Acid — Hydrate of Phenyle — is found in that portion of oil of tar which boils between 300® F. and 400° F. This, being agitated with potash, and the result decomposed by an acid, yields carbolic acid, which may be purified by rectification from caustic potash. It is an oily liquid, but may be obtained in long, needle-shaped crystals. A splinter of pine- wood first dipped in it and then in strong nitric acid becomes of a blue color, which then passes into a brown. In many particulars this substance resembles creasote so closely, that a supposition has been entertained that they are in reality the same body. When woody matter is gradually decomposed by contact with air and moisture, JJlmine and TJlmic Acid are pro- duced. They arise from a partial oxydation, attended by the production of carbonic acid and water, the action being orginally occasioned by azotized matter in the wood; cor- rosive sublimate, or any other body which possesses the qual- ity of checking ferment action, may therefore be resorted to to prevent the dry-rot of wood. When the access of air is Tor the most part cut off, the brown bodies, ulmine and What are the properties of naphthaline ? What substance closely re- sembles it? What are the properties of kyanol? What substance does carbolic acid closely resemble ? Under what circumstances are ulmine and ulmic acid produced ? What bodies may be employed to prevent dry-rot. BODIES PRODUCED BY DECAY. 389 ulmic acid, no longer appear alone, but with them many other substances, of the family of the hydrocarbons, arise. Besides these, as in the formation of vegetable soil and turf, azotized acids, such as the Crenic and Ajpocrenic, appear. These originate in the decay of the nitrogenized constitu- ents of the wood, an action which probably precedes its general disorganization. They are often found in mineral springs, in combination with oxide of iron, forming ochery stains. Crenic acid, by exposure to the air, changes into Ajpocrenic Acid, a substance much less soluble in water. There is abundant proof that all the varieties of coal have originated from woody fibre. For the production of these, it seems requisite that the wood should be immersed in water at a moderately high temperature, and without free contact of air. The ulmine bodies form from the decay of wood at the surface of the earth ; the coal bodies under a heavy pressure. Of these we have many varieties, differ- ing much in constitution : Lignite, which is of a brown color, and in which the structure of the wood is more or less perfectly preserved ; the various forms of Bituminous Coal, as cannel coal, Newcastle coal, &c. ; Anthracite, which contains but little hydrogen. With these more valuable natural products are frequent- ly found small quantities of others of less importance, as Ozocherit, or fossil wax ; Idrialine, which is isomeric with oil of turpentine ; Petroleum, or Naphtha, which in many Eastern countries is collected in wells. It arises, probably, from the decomposition of coal by the action of the natural heat of the earth. LECTUBE LXXXVII. Animal Chemistry.^ — Equilibrium of the System. — Caus- es of Diminution and Increase. — Relation of Oxygen to the Food. — Digestion, the Nature of it. — Description of the Process. — Artificial Digestion . — Two great Va- rieties of Food. — Nutrition in the Carnivora and Gra- minivora. — Routes of the Passage of Nutritious Mat- ter into the System. In the preceding Lectures I have given the descriptive From what bodies do crenic and apocrenic acids arise 7 What ig th^ source of the diiferent varieties of coal ? What is lignite 7 390 ANIMAL CHEMISTRY. history of many of the more important organic compounds, and chiefly those belonging to, or derived from, the vegeta- ble kingdom. It remains now to mention another class which seems to bear a closer relation to animal beings. The appearance and destruction of these compounds lead by ready steps to a consideration of the physiological func- tions of the animal mechanism. There are certain causes which tend constantly to change the weight of an adult, healthy individual; causes of in- crease and causes of diminution. Among the former may be mentioned food, drinks, and atmospheric air ; among the latter, urine, faeces, transpired and expired matters. And these, in the course of a year, amount to many hundred pounds; yet the resulting action of the mechanism is such that, at the end of that time, the weight remains un- changed. This fact, the constancy of adult weight, can, therefore, only be explained by an examination of the action of the matters introduced into the interior of the system on each other, or an examination of the matters rendered. What- ever is fit for food, when burned in the open air, with free access of oxygen, must yield carbonic acid, water, and am- monia ; and these, in point of fact, are the results of the ac- tion of the animal mechanism. Oxygen gas, introduced by the respiratory process through the lungs, effects eventually the destruction of the hydrocarbons and nitrogenized bodies which have been introduced through the stomach ; and car- bonic acid, ammonia, and the vapor of water, or substances in a transition state, which tend eventually to assume those forms, are the result. An elevated temperature must, as a consequence, be obtained. Before the introduction of chemical principles into the science of physiology, it was a favorite idea that the animal system possessed the peculiarity of resisting the influence of external agents. This is an error. There is no essen- tial difference between the physical effects taking place in the body during life and after death, nor is there any prin- ciple of resistance to external agents possessed by living structures. The only distinction is, that during life the ef- fete materials pass off by appointed routes — -the kidneys, the What causes are in operation tending to change the weight of an adult animal? Mention some of the causes of increase and some of diminution. What is the chemical nature of the food ? PROCESS OP DIGESTION 391 lungs, or the skin ; and after death, these passages being closed, they accumulate in the interior of the body. The matters returned by an animal to the external world are all found to be oxydized bodies, or such as arise from processes of oxydation. The result is, therefore, forced upon us that the primitive action of the mechanism is the oxy- dation of the food in the system by air which has been in- troduced through the lungs. The process of digestion appears to be exclusively for the object of effecting the minute subdivision of the food. By the action of the teeth or other organs of mastication, it is first roughly divided and simultaneously mixed with saliva. It is then passed into the stomach, and in that organ mixes with the gastric juice, a viscid and slightly acid body. This mixture is perfected by certain movements which the food now undergoes, and under the conjoint action of the saliva and the gastric juice it is totally broken up into a gray, semifluid, homogeneous mass, sometimes acid and sometimes insipid, of the consistency of cream or gruel, called Chyme. This gradually passes out through the pyloric orifice of the stomach, and enters the intestine. It has been a question whether artificial digestion could be performed, but it now appears to be universally admit- ted that an acidulated water, containing animal matter in a state of change, has the power of impressing analogous changes on organized substances submitted to its action, just as the gastric juice, containing hydrochloric or acetic acid, with animal matter undergoing metamorphosis, de- rived from the saliva or the coats of the stomach, possess- es the power of dissolving fibrin or coagulated albumen. Soon after its entrance into the intestine the chyme is mingled with bile and pancreatic juice, the former coming from the liver, the latter from the pancreas. The effect appears to be a division of the chyme into three parts : 1 st. A creamy fluid ; 2d. A whey-like fluid ; 3d. A red sedi- ment : the two former, commingled, constitute what is des- ignated the Chyle. What gas is introduced through the lungs ? How do these act on each other? Do animal structures possess any power of resisting the influence of external agents ? Why do we conclude that the oxydation of the food is the principal effect going on in the system? What is the object of di- gestion ? How is chyme prepared ? Can digestion be conducted artifi- cially? With what fluids does the chyme mingle? What is their action on it ? What is chyle ? 392 PRODUCTION OF CHYLE. It has been already remarked that the aim of the digest- ive process appears to be the subdivision of the food. It ia for this that the teeth comminute it ; and the gastric juice, excited to activity by the oxygen introduced with the saliva, breaks down by its ferment action all albuminous and fib- rinous matters, and prepares the food, in this condition of extreme subdivision, for its passage into the blood-vessels. Before we can trace the changes which then occur, it is proper, however, to remark that, as respects the food itself, it may be distinguished into two varieties : 1st. The food of nutrition, or the nitrogenized food ; 2d. The food of res- piration, or the non-nitrogenized food. The nutritive processes of carnivorous animals are very simple ; they live on the graminivora, and find, in the car- cases they consume, the fats, the fibrin, and other such bodies which are necessary for their own economy ; these, therefore, simply require to be brought into a state of solu- tion, or of extreme subdivision, and then are absorbed into the blood-vessels. In these cases the fats constitute the food of respiration, and the nitrogenized bodies that of nu- trition. But the graminivora find in the vegetable matters they use the same essential principles ; their fibrin, albumen, and fats are directly obtained from plants, in which they naturally occur. In the digestive process of the two great classes of animals, there is not therefore, in reality, any dif- ference ; both find in their food the elements they require. There is reason for believing that the two classes of food are introduced into the system by different routes — ^the fatty or respiratory food passing through the lacteals, and the ni- trogenized bodies being taken up by the veins. What two great varieties of food are there ? Describe the nutritive pro- cesses of the carnivora. What is their respiratory food ? Describe the nutritive processes of the graminivora. By what routes are the two v ’*’*»- ties of food introduced into the system ? ORIGIN OF FAT. 393 LECTURE LXXXVIII. Origin and Deposits of the Fats and Neutral Nitro- GENizED Bodies. — Artificial Formation of Fat. — It may be made in the Animal System, or directly ah- sorbed from the Food. — Proofs of the latter . — Varieties of Fat arising in partial Oxydation. — Changes in Fat as it passes through the Systems of the Graminivora and Carnivora. — Its final Destruction. — Origin and Deposit of the Neutral Nitrogenized Bodies. — Proper- ties of Fibrin, Albumen, Casein, Protein, Gelatin, SfC. Two opinions have been entertained respecting the origin of the fat which occurs in the adipose tissues of animals. 1st. It has been supposed to be produced by processes taking effect in the system ; or, 2d. Simply collected from the food. In many various processes fatty bodies arise. Thus, when flesh meat is left in a stream of water, a mass of ad- ipocere is eventually found. During the action of nitric acid on fibrin, and in the preparation of oxalic acid from starch, oily bodies are apparently produced. There is every reason to believe, however, that these are rather insulated than formed, or that they pre-exist in the bodies from which they are apparently derived. But recent experiments, as in the preparation of butyric acid from sugar, have decisively demonstrated that the fatty bodies can be artificially formed from the non-nitrogenized by processes such as those of fermentation, and, consequently, we have every reason to suppose that the animal system can form fats from the food, although none might occur there naturally. But, though the power of forming oily from amylaceous bodies may be possessed by the animal mechanism, there can be no doubt that in many instances it is not resorted to, and that fats contained in the food are at once absorbed into the system. Often this absorption takes place with so slight What opinions have been held respecting the origin of fat ? In what pro- cesses is it apparently produced ? What reason is there to believe that it can be formed from the starch bodies ? What reason is there for believing that many fats are directly absorbed into the system ? R 2 394 ABSORPTION OP FAT. a change impressed upon the oil, that without difficulty we can detect its presence by its odor or its taste. Thus the milk of cows which are fed on linseed cake tastes strongly of that substance ; and at those seasons of the year when such animals feed on young shoots or leaves containing odoriferous oils, the taste is at once detected in the milk. The deposition of fat upon an animal, and the production of butter in its milk, bear a certain relation to the amount of oleaginous matters found in its food. For this reason, Indian corn, which contains from eight to twelve per cent, of oil, furnishes one of the most available articles for feed- ing and fattening cattle. It is now, however, admitted, that where foods without fat are used, the system possesses the power of effecting their production ; thus bees will pro- duce wax though fed upon pure sugar, and animals will grow fat though fed on potatoes alone. A great number of the fatty bodies may be derived from inargaric acid by processes of partial oxydation. With a limited supply of oxygen gas, ethalic and myristic first make their appearance ; and the supply being still continued, there follow cocinic, 1 auric, &c., the process being as shown in the following table : These partial oxydations being perfected, there result at last carbonic acid gas and water, the same bodies which appear when a fat is directly burned in the open atmospheric air. The fats which occur in plants pass into the systems of graminivorous animals, and there undergo changes, a series of partial oxydations occurring. It is only a part which is completely destroyed so as to produce carbonic acid and wa- ter, and this part is the element of respiration. The res- idue accumulates in the cells of the adipose tissues, and, de- voured by the carnivorous tribes, is destined to undergo in them those successive changes which bring it back to the Is there any relation between the production of butter and the quantity of oil in the food ? Can bees form wax from sugar? By what process can the fatty bodies be derived from each other ? In what do these partial ox- ydations terminate at last ? What change occurs to vegetable fats in pass- ing through the systems of the grarninivora? What is the object of the en- tire combustion of a portion of it ? By what means is the residue at last brought to the same state ? Margaric. Ethalic. Myristic. Cocinic. Laurie. CEnanthytio. Caproic. Valerianic. Butyric. Capric. FIBRIN, ALBUMEN. 395 condition of carbonic acid and water, and restore it to the atmosphere from which it was originally derived by plants. The amylaceous bodies and fats, or the non-nitrogenized bodies, are, therefore, the food of respiration ; their office is to neutralize the oxygen introduced by the lungs, and, by the production of carbonic acid gas and water, keep up the temperature of the animal system. I have already described the fatty bodies, and given the history of their general properties. It is unnecessary to re- peat here what has been already said. When the expressed juices of plants, such as beets, tur- nips, &c., are allowed to stand, t|iere is deposited, after a short time, a coagulum or clot, which does not appear to differ in any respect from animal Fibrin. If this be re- moved, and the temperature of the juice raised to 212° F., it becomes turbid again, from the deposit of a second body. Albumen, On separating this and slowly evaporating, a film forms on the surface, identical with Casein. These three bodies contain nitrogen, and may, therefore, be looked upon as the representatives of the neutral nitrogenized class. Fibrin{C^QH^^O-^^NQ . + {S.F ) ). — This substance may be obtained by beating fresh-drawn blood with twigs, and washing with water and ether the clot which adheres there- to. As thus prepared, fibrin is a white, elastic body, insol- uble in water, alcohol, or ether, but soluble in hydrochloric acid, with which it yields a blue solution. It possesses the power of decomposing rapidly the deutoxide of hydrogen. When dried it shrinks very much in volume, but, for the most part, recovers its bulk when again moistened. Fibrin derived from arterial and venous blood is not altogether the same ; the latter may be dissolved in a warm solution of nitrate of potash, but the former can not. In the formula annexed to this body, the symbols within the brackets mere- ly mean small and indeterminate quantities of sulphur and phosphorus. Albumen occurs abundantly in the serum of blood and in the white of eggs, from which it may be obtained by neu- tralizing in a solution of it the associated soda with acetic acid, and on dilution with cold water it falls as a white pre- cipitate, soluble in water containing a minute quantity of What bodies constitute the food of respiration ? What is the composir tion of fibrin? From what sources may it be derived ? What are its prop erties? What are the sources and properties of albumen ? 396 PROTEIN AND ITS DERIVATIVES. alkali. Exposed to a sufficient heat, common albumen co- agulates and becomes a white body, wholly insoluble in wa- ter. The strong acids also unite directly with it, and form insoluble compounds ; acetic and the tribasic phosphoric acid are exceptions. With metallic salts, as corrosive sub- limate, it gives insoluble precipitates ; hence its use as an antidote for that poison. Its constitution is identical with that of fibrin, except that it appears to contain twice as much sulphur. Casein is found abundantly in milk. It is insoluble in water, but, like albumen, is readily dissolved if free alkali is present. It may be obtained by coagulating milk with sulphuric acid, and dissolving the curd, after it has been well washed with water, in a solution of carbonate of soda. By standing it separates into two portions, oily and watery. From the latter the casein is re-precipitated by sulphuric acid, and the process repeated. The casein is finally washed with ether to remove any trace of fat. It is a white sub- stance, soluble in an alkaline water, the solution not being coagulated by boiling, but a skin forms on the surface as evaporation goes on. It can, however, be coagulated by cer- tain anim?tl membranes, as by the interior coat of the stom- ach of a calf. It contains five or six per cent, of bone earth. The foregoing bodies are sometimes spoken of as the Protein group, from the circumstance, as is shown in their formula, that they all contain a body which passes under the designation of protein. It may be ex- tracted from them by dissolving either of them in an alka- line solution, and precipitating by an acid. It is a taste- less, white, insoluble body, soluble in acetic acid and in al- kalies. It yields a binoxide and tritoxide, which may be produced by boiling fibrin in water in contact with air. These substances are the chief constituents of the huffy coat of inflammatory blood. Gelatin [C ^ is prepared by dissolving isin- glass in warm water. It forms, on cooling, a soft jelly, which contracts as it dries. Solution of gelatin is precip- itated by corrosive sublimate, tannic acid, or infusion of galls ; with the latter bodies it yields a precipitate which is the basis of leather. Glue is an impure gelatin. What are the sources and properties of casein ? What is protein ? What relation has it to the foregoing bodies ? WTiat oxides does it give ? How is gelatin obtained ? What precipitate does it give with infusion of galls ? ENTRANCE OF FOOD INTO THE SYSTEM. 397 On examining the constitution of some of the leading tissues of the animal system, it is plain that they hear a re- markable relation to protein, as is shown in the following table : Protein, . . . . = Pr. Arterial membrane = Pr 4- HO. Chondrin (rib cartilage) . . . = Pr4- PO -j- O. Hair, h^ns = Pr-f- NH^-^O^. Gelatinous tissues =z2Pr -j- SNH^ HO These different bodies are therefore derived from the pro- tein group by processes of partial oxydation, for in their con- stitution they correspond to oxides, hydrated oxides, &c. The nitrogenized bodies introduced into the system pass through the same changes as the non-nitrogenized : partial oxydations giving rise to various tissue forms, and ending in perfect oxydation, with a production of water, ammonia, and carbonic acid. Whether we regard the respiratory or the nutritive food, we see that the result is the same. Introduced through the blood-vessels into the system, it is brought under the destructive influence of oxygen arriving through the lungs, and, as I have already explained, the amount of oxygen is so adjusted to the amount of these classes of food combined, that in an adult and healthy individual the weight does not change, even after the lapse of a considerable period of time. LECTURE LXXXIX. Of the Introduction of Respiratory and Nutritious Food into the Blood, and its Transmission through the System. — Absorption by the Lacteals and Veins . — Cause of the Circulation of the Blood. — Constitution and Properties of the Blood. — Plasma and Disks. — The Offices of each. — The Coagidation of Blood. — Analysis of Blood. The ordinary principles of capillary attraction are amply sufficient to account for the absorption of nutritious matter from the intestinal cavity, both by the lacteal vessels and What relation does protein bear to other tissues ? What changes do the nitrogenized bodies pass through ? What physical principle is involved in the absorbent action of the lacteals and veins ? 398 CIRCULATION OP THE BLOOD. the veins By this it is eventually brought into the gen» eral current of the circulation, and distributed to every part of the system. With respect to the forces involved in the circulation of the blood, most physiologists have regarded the hydraulic action of the heart as amply sufficient to account for all the phenomena. It is now on all hands conceded that this or- gan discharges a very subsidiary duty. The whole vege- table creation, in which circulatory movements of liquids are actively carried on without any such central mechanism of impulsion ; the numberless existing acardiac beings be- longing to the animal world ; the accomplishment of the systematic circulation of fishes without a heart ; and the oc- currence in the highest tribes, as in man, of special circu- lations which are isolated from the greater one, have all served to demonstrate that we must look to other principles for the cause of these remarkable movements. The cause of the circulation of the blood is to be found in the chemical relations of that liquid to the tissues with which it is brought in contact. On the principles of capil- lary attraction, a liquid will readily flow through a porous body for which it has a chemical affinity, but it will refuse to flow through it if it has no affinity for it. On this prin- ciple we can easily explain why the arterial blood presses the venous before it in the systemic circulation, and why the reverse ensues in the pulmonary. This explanation of the circulation of the blood, which I offered some years ago, is now admitted by many of the leading physiological writ- ers to be true. The systemic circulation takes place because arterial blood has a high affinity for the tissues, and venous blood little or none. The pulmonary circulation takes place be- cause venous blood has a high affinity for atmospheric oxy- gen, which it finds on the air cells of the lungs, and arte- rial blood little or none. On the same principle we may explain the rise of sap in trees, the circulatory movements in the different animal tribes, and the minor circulations of the human system. The most striking peculiarity of the blood is the incessant What reasons are there for supposing that the action of the heart is not the only cause of the circulation ? What explanation may be given of the circulation in the capillaries ? What is the Cause of the systemic circula- tion ? What of the pulmonary ? CIRCULATION OF THE BLOOD, 399 change which it undergoes. It is constantly being destroy- ed, and as constantly being reproduced. It consists of two portions, the Plasma, a clear fluid, of a yellowish tinge, which contains fibrin, albumen, and fat ; and in this there float disk-like bodies of different shapes and magnitudes in different animals. In man they are about xoVo^^ inch in diameter, consist of a sac of Globulin, a body of the protein family, and in the interior they contain a red sub- stance, Hcematin, which gives them their peculiar color. On one portion of them there is a nucleus or speck, consist- ing of coagulated fibrin. When the disks are old and about to be destroyed, their interior is filled with Hcemajphein, a yellow substance, corresponding to the coloring matter of the urine. Besides these, there are lymph, chyle, and oil globules in the blood. A continuous metamorphosis goes on during the circula- tion of the blood ; the plasma serves for the purposes of nu- trition, the disks for the production of heat. They absorb oxygen in the air cells of the lungs, and transmit it to all parts of the system ; and as they grow old and disappear, new ones are formed from the plasma. Although fibrin is know^n to exist in plants, I doubt very much whether it is directly absorbed as Fibrin into the system. Besides the direct proof which we have from the analysis of these bodies, we know that fibrin and albumen so closely resemble each other in constitution that they are mutually convertible into each other. During the hatch- ing of an egg from its albumen the flesh (fibrin) of the young chicken is formed, a phenomenon accompanying the absorption of oxygen from the air. In the human system, abundant observation has proved that there is a direct con- nection between the quantity of oxygen introduced through the lungs and the amount of fibrin in the blood. When the respiratory process is unduly active, the disks oxydize with rapidity, and the amount of fibrin increases ; but when the reverse takes place, there is a restraint on the change of the disks, and the amount of fibrin declines. The coagulation of the blood is a phenomenon which has excited much attention, physiologists generally looking upon Of what parts is the blood composed? What are the properties of the plasma ? Of what are the disks composed ? What are globulin, haematin, and haemaphein ? What are the functions of the plasma and disks respect- ively ? What reasons are there for supposing that fibrin may be made in the system from albumen or casein ? 400 COAGULATION OF THE BLOOD. it either as wholly inexplicable, or what, in reality, amounts to the same thing, as due to the death of the blood. What connection there is between its life and fluidity, is not so very apparent. A little reflection will, I am persuaded, deprive this phenomenon of much of its fictitious importance, since it is plain that the coagulation .of the blood, or, in other words, the separation of fibrin from it takes place in the body as well as out of it, for from this coagulated fibrin the muscular tissues are formed, and from it their waste is repaired. By passing through two capillary circulations, the systemic and the pulmonary, the rapidity of the process is very much interfered with ; but still, it eventually takes place. I here insert one of Lecanu’s analyses of the blood ; it may serve to give an idea of the constitution of that liquid. It must not be forgotten, however, that such analyses, be- yond mere general results, are of little value ; the composi- tion of the blood varies incessantly in the same individual. For instance, the mere accident of his being thirsty, or hav- ing recently drank abundantly of water, will make an entire change in the analysis of. the blood. Water 780-145. Fibrin . 2-100. Coloring matter 133 000. Albumen 65-090. Crystalline fatty matter 2-430. Oily matter . 1-310. Extractive matter 1-790. Salts and loss 149-35. 1000-000. The following represents the constitution of hsematosin : Carbon 66-49. Hydrogen 530. Nitrogen 10-50. Oxygen 11 0.5. Iron 6'66. 100 - 00 . Does the coagulation of the blood take place during life ? Of what are the muscular tissues composed ? What circumstances tend to change the constitution of the blood ? PROCESSES OF SECRETION. 401 LECTURE XC. Nature of the Processes of Secretion. — Origin of Secretions. — Phenomena of Respiration. — Arterializa- tion. — Production of Animal Heat. — Removal of effete Mattel's. — Constitution of Milk . — Uses of that Secre- tion. — Mucus. — Pus. — Bile. — Urine. — Calculi. — Bones. — Nervous Matter. During the starvation of an animal all its various secre- tions are still formed ; a consideration which proves that the production of urine, bile, and other such bodies is, in re- ality, connected with the destructive processes going on in the animal system. These processes of decay originate in the action of oxygen admitted by the process of respiration. The lungs, which constitute the organ by which air is introduced, are originally developed as diverticula from the oesophagus, and finally become an immense congeries of cells emptying into the trachea. In respiration they are perfectly passive, the air being introduced and expelled al- ternately by muscular contraction. It is commonly esti- mated that, on an average, about 17 inspirations are made each minute, and at each inspiration about 17 cubic inches of air are introduced. The blood presents itself on the air cells of a deep blue color, and is then known as venous blood. Through the thin wall of the cell it obtains oxygen from the air, and gives out carbonic acid. It is the coloring matter of the disks which discharges this function, and during the act of change its tint alters to a bright crimson. It is said now to be arterialized, or to constitute arterial blood. The mag- nitude of the scale on which this operation is carried for- ward may be appreciated from the circumstance that in a man of average size, in a single day, about seven tons of blood have been exposed to 226 cubic feet of atmospheric air. The oxygen thus introduced acts directly either on the tis- How is it known that the secretions arise from destructive processes ? What is the structure of the lungs ? How many inspirations does a man make, on an average, in a minute I How many cubic inches of air are in- troduced at each inspiration ? What is meant by the arterialization of tho blood? What action does. the oxygen introduced exert? 402 NUTRITION OP MILK. • sues themselves, as it is distributed by the systemic circula- tion, or on the elements of respiration they contain. In the latter case, carbonic acid gas and water are the result ; in the former, carbonic acid, water, and ammonia. But these changes can not take place without an elevation of temper- ature. Carbon and hydrogen can neither burn in the air nor in the animal system without evolving heat. The high temperature which an animal can maintain is therefore di- rectly proportional to the quantity of oxygen it consumes. The tissues being thus acted upon, give rise, during their metamorphoses, to new products, which require to be re- moved from the system ; these, passing under the name of secretions, are discharged by glands or other special organs. Thus the carbonic acid, for the most part, escapes from the lungs ; the ammonia through the kidneys ; the water through both those organs and the skin. Liebig has at- tempted to show that if the elements of urine be added to the elements of bile, they will represent the elements in the blood ; and there can be no doubt that the sulphates and phosphates found in the urine arise directly from the sul- phur and phosphorus previously existing in the muscular fibre and nervous matter. As an illustration of the principles here given in relation to the functions of nutrition and secretion, the constitution and properties of milk may be cited. The following is an analysis of it : Water 873.00. Butter ..... ‘ 30 00. Casein 48*20. Milk sugar 43*90. Phosphate of lime 2*31. “ “ magnesia *42. “ “ iron . *07. Chloride of potassium 1*44. “ “ sodium *24. Soda in combination with casein . . . *42. 1000 * 000 . Of the substances here mentioned, all are undoubtedly obtained directly from the food. In the herbage on which a graminivorous, milk-giving animal feeds, every one of In what does animal heat arise ? Through what channels are the lead- ing secretions, water, anunonia, and carbonic acid, discharged ? What sup- posed relation is there between the constituent of the urine and bile con- jointly and those of the blood? From what do the sulphates and phos- phates of the urine arise ? What are the chief constituents of milk ? From what source are they derived ? CHYLE. MUCUS. PUS. BILE. 403 these constituents occurs. I have already shown that the butter, or fat, and the casein are thus directly derived, and the evidence is equally complete that all the salts of phos- phoric acid and chlorine arise from the same source. A young animal, which, in the first periods of its life, is nourished exclusively on milk, finds in that milk all the various compounds it requires for its own existence and growth. The respiratory food is there — it is the butter and milk sugar ; the nitrogenized food is there — it is the casein ; and we have already seen that albumen and casein are both convertible into fibrin ; the casein, thus, in the mother’s milk, becomes converted into flesh in the young animal. To insure the growth of its bones, phosphate of lime (bone earth) is present ; there is also chlorine to form the hydro- chloric acid of its gastric juice, and soda, which is an essen- tial ingredient in its bile. It remains now to add a brief description of the proper- ties of the remaining leading animal substances, among which may be mentioned : Chyle is usually of a white or reddish- white tint. It re- sembles blood in constitution and power of coagulating. It contains much fat, which gives to it a cream-like aspect. Mucus exudes from the surface of mucous membranes. It is of a white or yellow color, of a viscid constitution, and insoluble in water. It dissolves in a solution of potash, and is precipitated by an alkali. Pus, a secretion from injured surfaces, resembling mucus in many respects, but distinguished by not being soluble in potash solution, but converted by it into a gelatinous body, which can be pulled out in threads. Bile, a yellow liquid, secreted by the liver from the por- tal blood ; it turns green in the air, has a bitter taste and an alkaline reaction, due to the presence of soda. Its color- ing matter is chlorophyl. It is regarded as a choleate of soda, the constitution of choleic acid bieng ^ 16 ^ 66 ^ 2 ^ 22 ' Of the correctness of this formula there is considerable doubt, since it has been recently affirmed that Tauriiie, which is a derivative body, contains a large amount of sul- phur. What becomes of the butter, milk sugar, casein, phosphate of lime, chlo- rine, and soda in the body of the young animal ? What is chyle ? What is mucus ? How may pus be distinguished from mucus ? What are the chief properties of bjle ? From what is it formed? What does taurine contain ? 404 URINE. NERVOUS MATTER. Urine, a yellow-colored fluid, secreted by the kidneys ; has an acid reaction; its specific gravity from 1*005 to 1*030 ; putrefies at a moderate temperature, its urea pass- ing into the condition of carbonate of ammonia. The chief constituents of urine are urea, uric acid, the sulphates and phosphates of potash, Soda, lime, ammonia, and a yellow coloring matter, with mucus of the bladder. The constitution of the urine changes in disease. In Dia- betes it contains grape sugar, as may be shown by the test of sulphate of copper, already mentioned. Diabetic urine may even be fermented with yeast, and alcohol distilled from it. Urinary Calculi are stony concretions often formed in the bladder of man and many animals ; they are of differ- ent kinds : 1st. Uric acid. 2d. Urate of ammonia. 3d. Phosphate of lime, magnesia, and ammonia. 4th. Oxalate of lime, or mulberry calculus. 5th. Cystic and xanthic oxides. Bones consist of two parts, an animal and an earthy matter. The latter is the phosphate of lime (bone earth). Nervous Matter consists of an albuminous substance with several fatty principles, distinguished by the remark- able fact that they contain phosphorus. In addition, it contains cholesterine. It would not agree with the object of these Lectures were I here to offer any detailed remarks on the functions of the brain and the nervous system. Of the action of the lungs, the liver, the kidneys, or other such organs, we are beginning to have a very distinct idea ; but it is altogether different with the functions of the cerebro-spinal axis ; there every thing is in mystery and darkness ; yet it is in what may be hereafter discovered in relation to the action of this system that our chief hopes of the advance of animal chem- istry and physiology depend. WTiat are the chief constituents of urine ? How may sugar be detected in diabetic urine ? What varieties of urinary calculi are there ? Of what are bones composed ? What are the chief constituents of nervous matter ? INDEX. A. Absolute alcohol, 329. Acetal, 338. Acetification, 339. Acetone, 341. Acetyle compounds, 337. Acid, acetic, 339. aconitic, or equisetic, 371. aldehydic, 338. alloxanic, 366. amygdalinic, 359. anilic, or indigotic, 379. anthranilic, 380. antimonic, 301. antimonious, 391. apocrenic, 389. arsenic, 299. arsenious, 296. tests for, 296. benzoic, 350. boracic, 254. butyric, 328. capric and caproic, 384. carbolic, 388. carbonic, 249. liquefaction of, 250. chloracetic, 341. chloric, 238. chlorous, 238. chlorovalerisic, 350. chromic, 293. chrysammic, 380. chrysanilic, 380. cinnamic, 355. citric, 370. comenic, 375. crenic, 389. croconic, 325. cyanic, 360. cyanuric, 360. dialuric, 36?. elaidic, 384. ellagic, 372. ethalic, 384. ethionic, 337. ferric, 287. formic, 346. fulminic, 360. fumaric, 371. gallic, 372. Acid, glucic, 323. hippuric, 353. hydriodic, 244. hydrochloric, 239. hydrocyanic, 357, hydroferrocyanic, 362. hydrofluoric, 246. hydroflu os ilicic, 256. hydrosalicylic, 354. hydrosulphocyanic, 36i hydrosulphuric, 228. hyperchloric, 238. hyperchlorous, 238. hypermanganic, 283. hyponitrous, 216. hyposulphuric, 227. hyposulphurous, 227* igasuric, 376. isatinic, 380. isethionic, 337. japonic, 372. kinic, 376. lactic, 330. lithic, 365. maleic, 371. malic, 371. manganic, 282. margaric, 383. meconic, 374. melanic, 355. melasinic, 323. mesoxalic, 366. metagallic, 372. metaphosphoric, 233. mucic, 325. muriatic, 239. mykomelinic, 366. myristic, 384. nitric, 218. nitromuriatic, 242. nitrous, 216. cenanthic, 333. oleic, 383. oxalic, 323. oxalhydric, 325. oxaluric, 367. palmitic, 384. parabanic, 366. pectic, 321. phosphoric, 232.* 406 INDEX. Acid, phosphorous, 232. phosphovinic, 334. picric, or carbazotic, 379. pinic, sylvic and pimaric, 386. purpuric, 368. pyrogallic, 372. pyroligneous, 339. pyromeconic, 375. pyrophosphoric, 233. pyrotartaric, 370. racemic, 370. rhodizonic, 325. rubinic, 372. saccharic, 325. sacchulmic, 322. salicylic, 354. sebacic, 384. silicic, 255. stearic, 383. suberic, 384. succinic, 384. sulphamilic, 349. sulphindigolic, 379. sulphobenzoic, 351. sulphoglyceric, 383. sulphomethylic, 346. sulphonaphthalic, 388. sulphosaccharic, 322. sulphovinic, 334. sulphuric, 225. sulphurous, 223. tannic, 371. tartaric, 369. thionuric, 367. ulmic, 322, 388. uramilic, 367. uric, 365. valerianic, 349. xanthic, 343. Acids, coupled, 369. Aconitine, 376. Affinity, cKemical, 173. Albumen, 395. vegetable, 395. Alcargen, 344. Alcohol, 329. Aldehyde, 337. Alizarine, 378. Alkarsin, 344. Allantoin, 366. Alloxan, 366. Alloxantine, 367. Alumina, 279. sulphates, 281. Aluminum, 279. Alums, 281. Amalgamation process, 307. Amalgams, 311. Amidine, 319. Amidogen, 256. Amilen, 349. Ammeline and ammelide, 364. Ammonia, carbonate, 356. nitrate, 356. preparation and properties of, 257, 356. sulphate, 357. * Ammoniacal amalgam, 258, 356. Ammonium, 258. chloride, 356. sulplurets, 259. Amygdaline, 359. Amyle compounds, 348. Anatto, 378. Aniline, 373, 377, 379. Animal chemistry, 389. Anthracite, 247. Antearine, 376. Antimony, 300. chloride, 301. oxide, 301. , sulphurets, 301. Aqua regia, 242. Arabine, 321. Argol, 329. Aricine, 375. Arrow-root, 319. Arsenic, 295. sulphurets, 300. Arterialization, 401. Arterial membrane, 397. Atmosphere, composition of, 200. physical constitution of, 199. Atmospheric pressure, 201. Atomic weights, 154. Atoms, 5. Atropine, 376. Aurum musivum, 292. Azote, 198. B. Balloons, 16. ^ Balsams, 386. Barium, 272. chloride, 273. oxides, 272. sulphuret, 273. Barley sugar, 320. Barometer, 208. Baryta, 273. carbonate, 273. sulphate, 274. Bassorine, 321. Batteries, voltaic, l!57. Bell metal, 304. Benzamide, 351. Benzine, 352. Benzoine, 352. Benzone, 352. INDEX. 407 Benzyle compounds, 350. Bile, 403. Biscuit ware, 280. Bismuth, 306. nitrates, 306. oxides, 306. Bleaching powder, 277. Blood, composition of, 400. Boiling points of fluids, 50. Bone earth, 277. Bones, composition of, 404. Boron, 254. Brain, composition of, 404. Brass, 304. British gum, 320. Bromine, preparation and properties of, 245. Brucia, 376. Buffy coat, 396. Butyrine, 384. C. Cadmium, 291. compounds of, 291. Caffeine, 376. Calamine, electric, 290. Calcium, 275. chloride, 276. fluoride, 276. sulphurets of, 276. Calculi, urinary, 404. Calomel, 310. Calorimeter, 31. Camphor, 385. artificial, 385. Caoutchouc, 386. Capacity for heat, 29. Caramel, 320. Carbon, 246. chlorides of, 336. its compounds with oxygen, 248. sulphuret of, 253. Carbonic oxide, preparation and prop- erties of, 248. Carbyle, sulphate of, 336. Carmine, 380. Carthamine, 378. Casein, 395, 396. vegetable, 395. Cassava, 319. Cast iron, 284. Catechin and catechu, 372. Cedriret, 387. Cellulose, 321. Cerine, 384. Cerium, 281. Chameleon, mineral, 282, 283. Charcoal, properties of, 247. Chinoidine, 376. Chloral, 342. Chloric acid, 238. Chlorine, 235. compounds with oxygen, 237. preparation and propertied of, 235. Chlorisatine, 380. Chlorocinnose, 355. Chloroform, 347. Chlorophyll, 378. Chlorosamide, 354. Chlorureted acetic ether, 342. formic ether, 342. Chlorous acid, 238. Cholesterine, 384. Chondrin, 397. Chrome yellow, 294. Chromic acid, salts of, 294. oxide, salts of, 294. Chromium, 293. oxide, 293. Chyle, 391, 403. Chyme, 391. Cinchona, 375. Cinnabar, 310. Cinnamyle compounds, 355. Circulation of blood, 398. Clays, composition of, 279. Clay iron stone, 284. Coagulation, 399. Coal, 389. oil, 388. Cobalt, 289. characters of salts of, 289. chloride, 289. oxalate, 289. oxides, 289. Cobaltocyanogen, 363. Cocoa tallow, 384. Codeine, 374. Cohesion, 7. Colchicine, 376. Cold rays, 74. Colophony, 386. Coloring principles, 377. Colors, 88. Columbium, 295. Combination, by volumes, 163. laws of, 160. Combining numbers, 160. table of, 154. Combustion, 183. Compound radicals, 316. Condensation of vapors, 49. Conicine, or conia, 376. Copper, 302. alloys of, 304. arsenite, 304. carbonates, 303. 408 INDEX. Copper, nitrate, 304. oxides, 303. sulphate, 303. Corrosive sublimate, 310. Creasote, 387. Cryophorus, 53. Crystallization; crystallography, 165. Cupellation, 307. Curarine, 376. Cyamelide, 360. Cyanides, metallic, 359, 360. Cyanogen, 253, 357. chlorides of, 361. Cystic oxide, 368. D. Daguerreotype, 101. Dammara resin, 386. Daphnine, 376. Daturine, 376. Decomposition of water, 131. Delphinine, 376. Deutoxide of nitrogen, 215. Dew, 74^ Dew-point, 56. Dextrine, 319. Diamond, 247. Diastase, 319. Differential thermometer, 18. Diffusion of gases, 211. Digestion, 392. Dimorphism, 169. Dispersion, 81. Dragon’s blood, 386. Dross, 305. Dutch liquid, 335. E. Earthen-ware, manufacture of, 280. Ebullition, 48. Elaidine, 384. Elaldehyde, 338. Elaterine, 376. Electricity, action of, on the magnet, 141. animal, 151. conduction of, 107. of steam, 152. statical, 105. voltaic, 123. Electro-chemistry, 133. Electrolysis, 134. Electrometers, 119. ^ Electrotype, 137. Electrophorus, 122. Emetine, 376. Emulsine, 359. Enamel, 292. Equivalent numbers, 154. Equivalent numbers, table of, 154. Eremacausis, 317. Essences, 384. Ethal, 384. Ether, 331. continuous process for, 335. Ethers, compound, 332. Ether, heavy muriatic, 342. Etherole and etherine, 336. Ethyle group, 332. Eudiometer, Ure’s, 199. Eupione, 387. Evaporation, 60. at low temperatures, 60. Expansion of solids, 23. fluids, 18. gases, 15. F. Faraday’s theory of polarization, 121. Fatty bodies, 38b. Fermentation, alcoholic, 326. - lactic, 328, 330. Ferridcyanogen compounds, 363. Ferrocyanogen compounds, 362. Fibrin, 395. vegetable, 395. Fixed air, 249. Flame, structure of, 186. Fluoride of boron, 255. Fluorine, 245. Formomethylal, 347. Freezing of water by evaporation, 54. Freezing mixtures, 40. Fusel oil, 348. Fusible metal, 307. G. Galvanism, 124. Galvanometer, 143. Gambogo, 378. Gay-Lussac’s law, 213. Gelatin, 396. Gentianine, 376. Geoffrey’s tables, 176. Glass, manufacture of, 280. soluble, 281. Globulin, 399. Glucinum, 281. Glucose, 320. Glycerine, 382, 383. Gold, 311. compounds of, 311. Goniometers, 168. Goulard’s water, 340. Graphite, 247. Gravity, specific, of gases, determin- ation of, 164. Green, Scheele’s, 304. Grove’s battery, 130. INDEX. 409 Gum, British, 320. Arabic — tragacanth, 321. Gun cotton, 325. Gunpowder, 267, 268. Gypsum, 277. H. Haemaphein, 399. Haematin, 399. Haematite, 284. Haematoxyline, 378. Hair, 397. Hare’s batteries, 129, 138. blow-pipe, 191. Heat, animal, 402. capacity for, 29. conduction of, 61. exchanges of, 72. latent, 39. radiation, ^reflection, absorp- tion, and transmission of, 67. varieties of, 71. Hesperidine, 376. Horn, 397. Hydrobenzamide, 351. Hydrogen, antimoniureted, 302. arseniureted, 300. light carbureted, 251. peroxide of, 197. persulphuret of, 230. phosphureted, 234. preparation and proper- ties of, 187. sulphureted, 228. Hygrometer, Daniell’s, 56. Hygrometiy, 55. Hyoscyamine, 376. Hyponitrous acid, 216. Hyposulphurous acid, 227. I. Ideal coloration, 102. Iclrialine, 389. Indigo, 378. Induction, 110. Interference, 88. Interstices, 6. Inuline, 319. Iodine, preparation and properties of, 242. Iridium, 313. Iron, 283. , carbonate, 288. cast, varieties of, 284. characters of salts of, 286. chlorides, 287. manufacture, 284. oxides of, 286. passive, 285. sulphates, 288. s Iron, sulphurets, 288. Isatine, 379. Isomerism, 171. Isomorphism, 170. K. Kakodyle and its compounds, 343. Kapnomar, 387. Kermes mineral, 301. Kyanol, 388. L. Lac, 386. Lactine, 321. Lampblack, 247. Lamps, safety, 63. Lantnanium, 281. Latent heat, 39. Laughing gas, 214. Laws of combination, 160. Lead, 304. action of water on, 305. alloys of, 306. carbonate, 306. characters of salts of, 306. chloride, 305. iodide, 305. nitrate, 306. oxides, 305. Leaven, 326. Lecanorine, 380. Leiocome, 320. Leukol, 377. Leyden jar, 116. Light, cause of, 75. chemical action of, 83. reflection, refraction, and po- larization of, 92-94. wave theory, 76, 83. Lignine, 321. Lignite, 389. Lime, 275. carbonate, 276. chloride, 276. phosphate, 277. salts, characters of, 276. sulphate, 277. Liquor of Libavius, 292. Lithium, 272. Litmus, 380. xM. Madder, 378. Magnesia, 277. carbonate, 278. characters of salts of, 278. phosphate, 278. sulphate, 278. Magnesium, preparation and proper- ties of, 277. 410 INDEX. Magnetism, 141. Magnets, artificial, 146. Magneto-electricity, 147. Malachite,N303. Manganese, characters of salts of, 282. chloride, 283. oxides of, 282. preparation and proper- ties of, 282. sulphate, 283, Margarine, 382, 383. Margarone, 383. Marriotte, law of, 46, 212. Marsh’s test for arsenic, 298. Maximum density, 22. Meconine, 374, 376. Medicated waters, 384. Melam and melamine, 364. Mellone, 364. Mercaptan, 342. Mercury, 309. characters of salts of, 310. chlorides, 310. iodides, 310. nitrates, 310. oxides of, 309. sulphates, 310. sulphurets, 310. Mesityle, 342. Metaldehyde, 338. Metal, fusible, 307. Metals, general properties of, 260. classification of, 261. Methyle compounds, 345. Microcosmic salt, 272. Milk, composition of, 402. Mindererus spirit, 340. Mineral chameleon, 282, 283. Molybdenum, 295. Mordants, 280. Morphia, 374. Mosaic gold, 292. Mucilage, 321. Mucus, 403. Multipliers, 143. Murexan, 368. Murexide, 367. Muscovado sugar, 320. Myricine, 384. N. Naphtha, 388, 389. Naphthaline, 388. Narceine, 374. Narcotine, 374. Nervous substance, 404. Nickel, 288. sulphate, 288. Nihil album, 290. Nitric acid, 218. Nitrobenzide, 353. Nitrogen, chloride of, 239. its compounds with oxy- gen, 198. preparations and proper- ties of, 197, Nitrous acid, 216. oxide, 214. Nomenclature, 153. Nutmeg butter, 384. Nutrition, function of, 397. O. OEnanthic ether, 333. Ohm’s theory, 139. Oils and fats, 381. Oil of bitter almonds, 350. cajeput, 385. cinnamon, 355. copaiva, 385. horseradish, 385. lavender, 385. lemons, 385. mustard, 385. peppermint, 385. rosemary, 385. spiraea, 354. storax, 385. turpentine, 385. vitriol, preparation of, 225. wine, heavy, 336. Oils, palm and cocoa, 383, 384. volatile, 384. Oleine, 382, 383. Olefiant gas, 252. Orcine, orceine, 380. Organic bodies, classification of, 318. decomposition of, by heat, 315. general characters of, 314. chemistry, 314. Orpiment, 300. Osmium, 295. Oxalates, 324. Oxamethane, 333. Oxamide, 24, 333. Oxygen, preparation and properties of, 179. Ozocherit, 389. P. Palladium, 311. Palmitine, 383. Palm oil, 383. Papin’s digester, 49. Paracyanogen, 357. Paraffine, 387. Paranaphthaliiie, 388. INDEX. 411 Paschal’s experiment, 209. Pectine, 321. Perchloric acid, 238. Petroleum, 389. Pewter, 293. Phloridzine, 376. Phosphorescence, 83, 103. Phosphoric acid, 232. Phosphorus, compounds with oxy- gen, 231. preparation and prop- erties of, 230. Phosphureted hydrogen, 234. Photography, 101. Picamar, 387. Picrotoxine, 376. Pile, voltaic, 128. Piperine, 376. Pitch, 387. Pit-coal, 389. Pittakal, 387. Plasma, 399. Platinum, 312. black, 312. chlorides, 313. oxides, 313. power of determining un- ion of gases, 312. salts, combustible, 377. spongy, 312. Plumbago, or graphite, 247. Polarization of light, 92. Populine, 376. Porcelain, manufacture of, 280. Potassium, chloride of, 267. iodide of, 267. peroxide of, 265. preparation and proper- ties of, 264. sulphurets of, 267. Potash, 265. bicarbonate, 267. bisulphate, 267. carbonate, 267. chlorate, 268. hydrate of, 265. nitrate, 267. salts, test for, 266. sulphate, 267. Potato oil and its compounds, 348. Prism, 80. Protein, 396. Prussian blue, 362. Pseudomorphine, 374. Purple of Cassius, 292, 311. Pus, 403. Putty powder, S9S. Pyroacetic spirit, 341. Pyrometer, 24. Daniell’s, 28. Pyroxylic spirit, 345. Q. Quercitron bark, 378. Quicksilver, 309. Quina, 375. Quinoline, 377. R. Radiation, 67. Rays of the sun, chemical, 100. Realgar, 300. Reflection, law of, 94. Refraction, law of, 80, 94. Resins, 385. Respiration, 185. Rhodium, 313. S. Sacchulmine, 322. Safety jet, Plemming’s, 63. Safety lamp, 63. Sago, 319. Salicine, 353, 376. Salicyle compounds, 354. Seheele’s green, 304. Secretion, 401. Selenium, 230. Silicon, 255. Silver, 307. ammoniuret, 309. characters of salts of, 308. chloride, 308. German, 289. iodide, 308. nitrate, 308. oxides, 308. sulphuret, 308. Smalt, 289. Soaps ; saponification, 382. Soda, biborate, 272. bicarbonate, 270. carbonate, 370. hydrate of, 271. nitrate, 271. phosphates of, 271. sulphate, 271. Soda water, 250. Sodium, chloride, 269. preparation and properties of, 268. Solanine, 376. Solder, 293. Specific gravity, 164. heat, 29. Spectres, 103. Spectrum, solar, 81-83. Speculum metal, 304. Spermaceti, 384. Spiraea ulmaria, oil of, 354. Starch, 318. 412 INDEX. Steam, elastic force of, 53. engine, 49, 59. Stearine, 382. Stearopten, 384. Steel, 285. Stone-ware, manufacture of, 280. Strontia, 274. nitrate, 275. sulphate, 275. Strontium, 274. chloride, 274. Strychnia, 376. Sublimate, corrosive, 310. Substitution, 317. Sugar, cane, 320. eucalyptus, 321. from ergot of rye, 321, grape, 321. of diabetes insipidus, 320. of milk, 321. Sulphobenzide, 352. Sulphocyanogen compounds, 363. Sulphur compounds with oxygen, 223. occurrence in nature, 221. properties of, 222. Sulphureted hydrogen, 228, Sulphuric acid, 225. Sulphurous acid, 223. Symbols, 156. table of, 154. Synaptase, 359. Systems, crystallographical, 165. T. Tapioca, 319. Tar, varieties of, 387. Tartar, cream of, 369. Taurine, 403. Tellurium, 302. Thebaine, 374. Theine, 376. Theobromine, 376. Thermo-electricity, 148. Thermometer, Breguet’s, 34. construction of, 19. differential, 18. Sanctorio’s, 17. scales, 20. Thorium, 281. Tin, 291. chlorides, 292. oxides, 292. sulphurets, 292. Tinned plate, 293. Titanium, 295, Transverse vibrations, 86. Tungsten, 295. Turmeric, 378. Turpeth mineral, 311. Type metal, 302. Types, chemical, 316. U. Ulmine, 322, 388. Undulatory theory, 84. Uramile, 367. Uranium, 302. Urea, 361, 365. Urinary calculi, 404. Urine, composition of, 404, V. Vanadium, 295. Vapor, elastic force of, 52. Vapors, density of, 58. nature of, 42. Vaporization at low temperatures, laws of, 43. Vegeto-alkalies, 373. Veratria, 376. Verdigris, 340, 341. Vermilion, 310. Vinegar, 339. Vitriol, blue, 303. green, 288. oil of, 226. white, 290. Voltameter, 137. Volumes, combination by, 163. W. Water, composition of, 134, 192. of crystallization, 196. Waves, length of, 91. Wax, 384. Wines, 329. Wire gauze, 62. Wood-spirit and its compounds, 345. ether, 345. Woody fibre, 321. X. Xanthic acid, 343. oxide, 368. Xyloidine, 325. Y. Yeast, 327. Yttrium, 281. Z. Zaffre, 289. 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