ARMY MEDICAL LIBRARY WASHINGTON Foiraded 1836 tofmr Section. Number ..J...J..Q..JL^.J... Fobm 113o, W. D.. 8. G. O. >ro 3—10543 (ReviMd Juno 13, 1936) THE PRINCIPLES OF CHEMISTRY,^'' ILLUSTRATED BY ' f SIMPLE EXPERIMENTS. De. JULIUS ADOLPH STOCKHARDT. »• * PROPESSOK IN THE ROYAL ACADEMY OP AGRICULTURE AT THARAND, AND ROYAL INSPECTOR OP MEDICINE IN SAXONY. TRANSLATED FROM THE THIRD GERMAN EDITION, « C. H. PEIRCE, M. D. LIBRARY , f^EON GENERAL'S rrICE i J.'X. 15. iyu2 CAMBRIDGE: in 'iLtFfl PUBLISHED BY JOHN BAfr^LETT. BOSTON: PHILIPS, SAMPSON, & CO. PHILADELPHIA: THOMAS, COWPERTHWAIT, & CO. 1850. Entered according to Act of Congress, in the year 1850, by John Baetlett, in the Clerk's Office of the District Court of the District of Massachusetts. i%56 CAMBRIDGE: STEREOTYPED AND PRINTED BY METCALF AND COMPANY, PRINTERS TO THE UNIVERSITY. PREFACE. The following work has been translated, at the rec- ommendation of Professor Horsford, as a good intro- duction to the study of chemistry. Such alterations only have been made in the text, as were required to adapt it to use in this country. Other changes might have been desirable, such as sub- stituting the hydrogen for the oxygen scale of equiva- lent weights, the Fahrenheit instead of the Centigrade thermometrical scale,* the adoption in every instance of a scientific instead of a popular nomenclature, &c.; but, after due deliberation, it was concluded not to depart from the original, except when absolutely ne- cessary to do so. Where alterations in modes of ex- pression, &c, have been made, the meaning of the author has been carefully retained. In some few instances, the scientific nomenclature usually adopted in our chemical books has been de- parted from; but this could not well be avoided with- out somewhat marring the character of the original * It is highly probable that the Centigrade thermometer will in a few years be generally adopted in this country for scientific purposes. IV PREFACE. work. The changes, however, that have been intro- duced, will in no way confuse the more advanced student, even if they do not assist the learner. There has been in many cases great difficulty in rightly translating terms used in the arts and man- ufactures, for the obvious reason that there must be many peculiar technical terms in use in Germany, where arts and manufactures, such as porcelain-mak- ing, metallurgy, brewing, wine-making, &c, are so extensively cultivated. An important part of the labor of translating has been performed by a friend, whose familiar knowledge of the German language has been to me of much value and assistance. I am also under great obligations to the Rev. Dr. Francis, for his kindness in looking over the pages as they issued from the press, and for many valuable suggestions. C H. P. INTRODUCTION. The rapid progress of experimental science during the last twenty-five years is to be ascribed, in great measure, to the fact that pupils, as well as instructors, have become experimenters. This is especially true with respect to chemistry. For every contemporary of Davy, engaged in experimental researches in this de- partment, there are probably, at present, scores of per- sons occupied in the same field. The fruits of this la- bor are to be seen in the improved condition of manu- factures ; in the more substantial scientific basis upon which many processes, formerly altogether empirical, are now securely fixed; in the progress of agriculture, and the arts generally; and, to some extent, in the progress of medicine. The course of instruction to which this greatly in- creased experimental investigation is chiefly to be at- tributed, namely, the practical or experimental course, bears the same relation to the study of text-books on chemistry that anatomical dissections do to the perusal a* vi INTRODUCTION. of essays on operative surgery, or the solutions of problems in celestial mechanics to lectures on the ar- chitecture of the heavens. It is, beyond question, the most efficient method to secure a sound and available knowledge of the science, either elementary or more comprehensive. Works designed to teach chemistry by experiment are already in use, both here and abroad, but most of them take for granted the possession of expensive ap- paratus, and a laboratory; scarcely any are designed to bring the practical study of the science within the means of the more elementary schools; — and none are to be found suited to the winter-evening firesides all over the country, where the younger and the more advanced of both sexes would delight in chemical ex- periments, did not the apparently necessary expense of apparatus forbid them. It is to meet the latter two wants, as well as those of a general text-book, that the work of Professor Stock- hardt, edited by my late assistant, Dr. Peirce, is em- inently suited. The apparatus necessary for many of the most in- structive and interesting chemical experiments would cost but a few dimes, and as many dollars would fur- nish the requisites for all, or nearly all, the most impor- tant experiments, if performed in the simple manner laid down in this book. A few tubes and flasks a spirit-lamp, some corks, india-rubber and reagent bot- tles, almost complete the list. In consequence of the INTRODUCTION. VU extensive adoption of this as an introductory work in the schools of Germany, sets of apparatus to accom- pany it are advertised by manufacturers. The qualifications of this work, as a text-book for schools, are such as to leave little, if any thing, to be desired. The classification is exceedingly convenient. The elucidation of principles, and the explanation of chemical phenomena, are admirably clear and concise. The summary, or retrospect, at the close of each chap- ter, presenting at a glance the essential parts of what has gone before, could scarcely have been more happily conceived or expressed for the wants of a pupil or an instructor. The book is also well adapted to the wants of teach- ers who desire to give occasional experimental lectures at a moderate expense, — and of those, who design to commence the study of chemistry, either with or with- out the aid of an instructor. E. N. HORSFORD, Eumford Professor in the University at Cambridge. \ CONTENTS. PART I. INORGANIC CHEMISTRY. SECTION Chemical Action,..........1 Weighing and Measuring......... 8 Specific Gravity (Areometer, &c),.......11 The Ancient Division of the Elements,.....18 Water and Heat,..........21 Expansion by Heat, and Thermometer. Expansion of Liquids,.........22 Thermometer,..........24 Expansion of Solids,.........27 Expansion by Cold,.........28 Melting of Solids,..........30 Latent Heat,..........32 Boiling and Evaporation. Boiling of Water,..........34 Steam,...........35 Aqueous Vapor, . •.........37 Distillation,......• . . . . 41 Diffusion of Heat. Conduction of Heat,.........42 Radiation of Heat,.........43 Formation of Dew,.........44 Solution and Crystallization. Solution,............ 45 Crystallization,..........50 Composition of Water,.........55 X CONTENTS. Non-Metallic Elements, or Metalloids- First Group: Organogens. Oxygen (oxides, acids, bases, salts, neutralization, &c), ... 56 Hydrogen (spongy platinum, explosive gas, formation of water, chem- ical symbols and formulas),........82 Air (barometer, safety-tube, Spritz-bottle, influence of the air on boil- ing, current of air, gases, vapors, composition of air), ... 90 Nitrogen or Azote,.........101 Carbon (charcoal, soot, coke, graphite, diamond, carbonic acid, car- bonic oxide gas),..........103 Combustion (conditions of combustion; rapid and slow, complete and incomplete combustion, flame, &c.),.....Ill Retrospect of the Organogens. Second Group: Pyrogens. Brimstone, Sulphur (amorphous and dimorphous bodies, flowers of sulphur, precipitated sulphur, sulphuret of iron), . . . . 123 Sulphuretted Hydrogen,........132 Selenium,............ 137 Phosphorus,...........j3g Phosphuretted Hydrogen (predisposing affinity, water-bath, &c), . 145 Retrospect of the Pyrogens. Third Group: Halogens. Chlorine (nascent state, degrees of oxidation, of sulphuration, of chlorination, &c),....... ^n Iodine>............155 Bromine, Fluorine,...... . efi Cyanogen,...........15? Retrospect of the Halogens. Fomh Group i Hyalogcns. Boron and Silicon, .... Retrospect of the Metalloids. Acids. First Group : Oxygen Acids. Nitric Acid (acids, bases, neutralization, &c), Nitrous Acid, Nitric Oxide, Nitrous Oxide 161 CONTENTS. x} Carbonic Acid (diffusion, mineral water, &c),.....164 Sulphuric Acid (anhydrous, Nordhausen, common, &c.), . . 168 Sulphurous Acid,..........174 Phosphoric Acid,......... J76 Phosphorous Acid, Oxide of Phosphorus,.....177 Chloric Acid, Hypochlorous Acid, &c.,.....178 Cyanic Acid, Fulminic Acid,........17g Boracid Acid (glass, blow-pipe, volatilization of fixed snbstances, &c), 180 Silicic Acid,...........183 Retrospect of the Oxygen Acids. Second Group: Hydrogen Acids. Hydrochloric Acid or Muriatic Acid (haloid salts, &c.), . . .185 Aqua Regia, or Nitro-muriatic Acid,.....188 Hydrobromic and Hydriodic Acids,.......189 Hydrofluoric Acid (etching on glass),......190 Hydrocyanic or Prussic Acid.........191 Retrospect of the Hydrogen Acids. Retrospect of the Combinations of the Metalloids with Oxygen and Hydrogen. Third Group: Organic Acids. Tartaric Acid (tartar, formation of organic acids, &c), . . .194 Oxalic Acid,...........196 Acetic Acid,...........198 Retrospect of the Vegetable Acids. Radicals,............199 Capacity of Neutralization,........200 Light Metals. First Group: Alkali Metdk. Potassium (carbonate of potassa, lye, nitre, gunpowder, chlorate of potassa, matches, tartar, liver of sulphur, &c.), .... 201 Sodium (common salt, Glauber salts, carbonate of soda, borax, solder- ing, glass, &c), ...........215 Ammonia (dry distillation, chloride of ammonium, carbonate of am- monia, &c.),...........227 Lithium,...........236 Retrospect of the Alkalies. xu CONTENTS. Second Group: Metals of the Alkaline Earths. Calcium (chalk, quicklime, burning of Ume, mortar, gypsum, chloride of lime, &c),.......... Barium and Strontium (heavy spar, &c),.....248 Magnesium (Epsom salt, white magnesia, &c), • • • .249 Retrospect of the Alkaline Earths. Third Group: Metals of the Earths. Aluminum (clay and loam, Artesian wells, arable soil, earthen-ware, alum, &c),...........252 Glucinum, Yttrium, Zirconium, &c.,......266 Retrospect of the Earths. Retrospect of the Light Metals. Laws of Chemical Combination (classification of chemical combina- tions, chemical proportions, equivalents, atoms, amorphism, dimor- phism, isomorphism, atomic weights).......267 Heavy Metals. First Group of the Heavy Metals. Iron (oxide of iron, and ores, cast-iron, wrought-iron, steel, salts of iron, green vitriol, &c, Prussian blue, prussiate of potassa, sulphu- ret of iron, &c),..........275 Manganese (black oxide of manganese, salts of manganese, &c.), . 297 Cobalt and Nickel (smalt, German silver, &c.), .... 303 Zinc (granulated zinc, white vitriol, distillation of zinc, &c.), . 309 Cadmium,............315 Tin (tinning, salts of tin, mosaic gold, &c.)......316 Uranium,............328 Retrospect of the First Group of Heavy Metals. Second Group of the Heavy Metals. Lead (litharge, sugar orlead, white-lead, lead-tree, sulphuret of lead, &c),............329 Bismuth (fusible metal, oxide of bismuth, &c), . . 344 Copper (oxide of copper, colors of copper, reduction of metals, salts of copper, blue vitriol, verdigris, sulphuret of copper, alloys of copper, brass, &c),...... „ .„ Mercury (oxide of mercury, salts of mercury, cinnabar, amalgams, &c.)j 365 Silver (alloys, lunar caustic, &c), .... ' „7q Gold (alloys, solution of gold, &c.), . ' <3 CONTENTS. XV Caoutchouc (gum elastic, gutta percha), .... 584 Retrospect of the Fats, Volatile Oils, and Resins. XII. Extractive Matter (extracts, crystallizable and uncrystallizable extractive matter, &c),.......585 XIII. Coloring Matter, or Pigments.......590 XIV. Organic Bases or Alkaloids (morphine, quinine, &c.), . . 596 Retrospect of the Extractive and Coloring Substances, and of the Vegetable Bases. XV. Organic Acids (racemic acid, citric acid, malic acid, tannic acid, &c.),..........598 XVI. Inorganic Constituents of Plants (ashes), arable soil, . . 607 XVH. Nourishment and Growth of Plants,.....613 Uncultivated Plants, Food of Plants, .... 614 Cultivated Plants,........615 Retrospect of Vegetable Matter in General. Animal Matter. Animal Life. Constituents of the Animal Body, &c., . . .619 I. Tlie Egg (white of eggs, yolk of eggs, egg-shells), . . 622 II. The Milk (butter, caseine, milk-sugar, &c.), .... 625 Digestion,..........635 III. The Blood (fibrine, blood corpuscles, albumen, &c.), . . 636 Respiration and Means of Nourishment, .... 639 IV. The Flesh (juice of flesh, muscular tissue, boiling of meat, prep- aration of broth and soup, salting of meat), . . . 640 V. The Bile,..........645 VI. The Skin (gelatine, glue, leather, horny substance, &c.), . . 646 Vn. The Bones (bone-earth, animal coal, bone-dust, &c), . . 654 VIH. Tlie Solid Excrements and Urine (urea, uric acid, guano, &c.), . 659 Retrospect of Animal Matter in General. PART FIRST. INORGANIC CHEMISTRY. (mineral chemistry.) 1 INORGANIC CHEMISTRY. CHEMICAL ACTION. 1. Every one knows that iron, heated to redness, changes into scales or cinders, and that, exposed to moist air or earth, it is converted into rust; that the expressed juice of the grape gradually turns to wine, and this, again, to vinegar; that wood in a stove, or oil in a lamp, disappears in burning; and that animal and vegetable substances in time putrefy, disintegrate, and finally disappear. Iron cinders and rust are iron altered in constitution; iron is hard, tenacious, of a grayish-white color, and brilliant; by heating to redness it becomes black, dull, and brittle; on exposure to moisture it is converted into a powder of a yellowish-brown color. Wine is altered must, in which nothing of the sweet taste peculiar to the grape-juice can be perceived ; but it has acquired a spirituous flavor, together with a heating and intoxicat- ing power, which was not in the must. Vinegar is v*u<^ altered wine; it has an acid smell and taste, and has ^~/^. lost its spirituous flavor, as well as its exhilarating -virv*^ 4 CHEMICAL ACTION. properties, its tendency being rather cooling and seda- tive. Search must be made in the air for the oil and wood which have disappeared during combustion; both these substances are converted into vapor or gas, and warmth and light are thereupon evolved with the phenomenon of fire. Of a similar nature are the changes which animal and vegetable substances under- go, if kept for a sufficient length of time; they are gradually converted, as they putrefy or decay, into vari- ous kinds of gas, some of which emit a very disagree- able odor. Such processes, by which the weight, form, solidity, color, taste, smell, and action of the substances become changed, so that new bodies with quite different prop- erties are formed from the old, are called chemical pro- cesses, or chemical action. 2. Wherever we look upon our earth, chemical action is seen taking place, on the land, in the air, or in the depths of the sea. The hard basalt, the glass-like lava, become gradually soft, their dark color passes into lighter, they crumble to smaller and smaller pieces, and are finally changed to earth. A potato placed in the earth grows soft, loses its mealy taste, becomes sweet, and finally decays. The bud, that sends forth a sickly pale shoot in a dark cellar, when exposed to the light and air grows up a vigorous, firm, and green plant, which, %nbibing its nourishment from the moist air and soil, forms from their elements new bodies, not to be found previously in the water or the air. A delicate network of cells and tubes pervades the whole plant imparting to it firmness; these we call vegetable tissues or woody fibre. We find in the sap, which passes up and down through these cells, albumen and other vis- cous substances; in the leaves and in the stalks a CHEMICAL ACTION. 5 j,,vy.J? green coloring matter, — chlorophylJr; and in the ripe/\/\(ly ^' tubers, a mealy substance, — starch. None of these sub- <^u*^, (pt> stances are injurious to health; but if the potatoes r* o V>&vff grow in the dark and without soil, for instance, in the cellar, there is produced in their long pale shoots a very poisonous body, solanine. /tr^-v^w.^t^^^-^^/^^i , The potato forms one of our most important articles l-ntt, faAw of food. The starch contained in it is not soluble in water, but when received into the stomach quickly undergoes such a change that it can be dissolved or di- gested, and then introduced as a liquid into the blood. The blood comes in contact in the lungs with the in- haled air; the blood changes its color, the air changes its constitution, and the heat which we feel in our bodies is developed. We must conclude, from these changes, that chemical action is going on in our own bodies. 3. As long as a plant or an animal lives, the chemical processes are under the guardianship of a higher mys- terious power, which is called the vital force, and by which they are constrained to furnish the materials for the structure of the animal or vegetable bodies. The vital force is, as it were, the architect who plans the building, and sees that the requisite materials are pro- cured by the chemical processes, and worked up accord- ing to his will. Hereupon arise innumerable new bod- ies, which cannot be artificially imitated, as, for exam- ple, wood, sugar, starch, fat, gelatine, flesh, &c.» They are called organic compounds, or animal and vegetable substances, in opposition to inorganic or mineral bodies, which may be artificially imitated by putting together their constituent parts. When life in an animal or veg- etable ceases, the chemical powers obtain the mastery, and these, as if they were the grave-diggers of nature, fulfil the old motto, — "Earth to earth, and dust to 6 CHEMICAL ACTION. dust." The leaves of the potato plant become yellow, and then brown; they fall off, and are gradually con- verted into a dark powdery substance, —humus. In the course of time even this disappears, with the excep- tion of a little ashes, which cannot take flight with the rest. What here it takes years to bring to pass, happens in minutes if we throw the dry leaves into the fire. The chemical action is in both cases quite similar,— the only difference consists in the time in which it occurs; it goes on rapidly, as combustion, under a strong heat, and slowly, as a process of decay, at a moderate tempera- ture. But what appears to us annihilation is only change. The substances which have been, not an- nihilated, but only rendered invisible by combustion or decay, we find again under another form, with exactly the same weight, in the air; from the air, they are again drawn down to the earth by the chemical processes going on in living plants. 4. We see from this how the inscrutable power of the Almighty appointed the chemical processes for his servants, in order, by their agency, to produce the eternal vicissitude which we daily observe around us in all nature, and to call forth evermore, in uninterrupted succession, new life from death; thus it must be self- evident how improving and instructive for every think- ing man is that science which explains to him this vicissitude, and opens to him a clearer insight into the wonders of creation. This deeper insight will not only lead the mind of man to higher improvement and perfection, but must also fill it with greater admiration and profounder rev- erence for Him, who revealed to us in these wonders his unsearchable omnipotence and wisdom. In another point of view, the interest in chemical CHEMICAL ACTION. 7 knowledge will be most powerfully excited by the use- ful application which can be made of it in every-day life. Chemistry teaches the apothecary how to com- pound and prepare his medicines; it teaches the physi- cian how to cure maladies by means of these medi- cines ; it not only shows the miner the metals con- cealed in rocks, but aids him also in smelting and working them. Chemistry, in connection with physics, has been the principal lever by which so many arts and trades have been brought to such a degree of per- fection within the last few decades, and by its means we ^ have been supplied with the numberless convenienceso £ /C . 037/ -3*3 >' Larger Measures. Meter. Decameter = lf-rf9* o\ Millimeter = 100s *i £/e« SPECIFIC GRAVITY. 15 The system of weights was derived from the measure of length, in the following manner. A cubical box was taken, measuring exactly one centimeter in each direction, and this was filled with water at its greatest density (at the temperature -f-4° C.); the weight of this quantity of water was called a gramme. This is taken as the unit of the decimal weights, and is multi- plied or divided by ten. Smaller Weights. Larger Weights. Gramme. Gramme. Decigramme = ^ gramme. Decagramme = 10 gr. Centigramme = j£5 " Hectogramme = 100 " Milligramme = ^ " Kilogramme = 1,000 " Myriagramme =10,000 " One gramme is equal to 15.44579grs. Troy. One kilogramme is equal to 21b. 3oz. 4.17dwt. Av. It is well enough known that the body whose weight is to be ascertained must be put into one scale, and in the other weights sufficient to restore the index to its original perpendicular position. The-weight of a body thus determined is, in scientific language, called its ab- solute weight. Thus, a piece of sugar weighing two ounces has an absolute weight of two ounces; or, if a vessel be filled with two pounds and one ounce of water, this water has an absolute weight of two pounds and one ounce. SPECIFIC GRAVITY. *** v-ifo>, ?*■ {frjiM 11. Ice floats in water, iron sinks in it, because the former is lighter, the latter heavier, than water. But if we put a piece of ice in spirit it sinks, or if we put a piece of iron upon quicksilver or mercury it floats; conse- quently, ice is heavier than spirit, iron lighter than quick- 16 SPECIFIC GRAVITY. silver. It also follows that spirit is lighter than water, since it can support less weight, and quicksilver heavier than water, as it can bear a greater weight. The terms heavier and lighter, in this sense, correspond to what in scientific language is called specifically heavier or specif- ically lighter, and equal bulks are always to be under- stood in speaking of the comparative weights of bodies. The expression, ice is lighter than iron, means, therefore, that, taking equal bulks of each, the former weighs less than the latter; and when we say that quicksilver is heavier than water, we mean that in equal volumes, as a pint, for instance, the quicksilver has a greater weight than the water. But in absolute weight, no regard is paid to the volume of substances. In order to ascertain how many times heavier quick- silver is than water, or iron than ice, it is only ne- cessary to weigh equal volumes or portions of each, and to compare their weights. If, for example, we take five vessels, each of which would contain exactly 100 grains of water, and fill them respectively with spirit, ice, water, iron, and quicksilver, the following differences of weight will be found: the vessel filled with spirit would weigh 80 grains; with ice, 90 grains; with water, 100 grains; with iron, 750 grains; with quicksilver, 1,350 grains. To facilitate the comparison of the numbers which denote how much greater the specific gravity of one body is than that of another, water has been fixed upon as the standard or unit. Therefore, in the above case the question is, How much lighter than water are spirit and ice, and how much heavier are iron and quick- silver ? or, in other words, How many times is 100 con- tained in 80, 90, 750, and 1,350 ? The other numbers, then, are to be divided by 100, the weight of water and there is found for SPECIFIC GRAVITY. 17 Spirit, -j5^-, or, in decimals, 0.80; it is therefore -£- lighter than water. Ice, ■&$, or, in decimals, 0.90; it is therefore -jV lighter than water. Iron, -f^, or, in decimals, 7.50; it is therefore 7-j times heavier than water. Quicksilver, xot, or, in decimals, 13.50; it is therefore 13£ times heavier than water. These numbers represent the specific weights (sp. gr.). Thus, according to calculation, spirit having a specific gravity of 0.80, 80 parts of it would occupy the same space as 100 parts of water; therefore it is only four fifths as heavy as water, or, what is the same thing, one fifth lighter than water. The specific gravity of quick- silver being 13.5, that is, 13£ parts of quicksilver do not take up more space than one part of water; since it is 13^ times heavier than water. 12. Determination of Specific Gravity. — Experiment. — To determine the specific gravity of a fluid, a vial is weighed, filled with water, and then again weighed. This gives the weight of the water. Now pour out the water, and refill the vial either with spirit, syrup, lye, beer, or some other liquid, and ascertain by the balance the weight of each. Then divide the weight of each of these fluids by the weight of the water, and the quotient indicates the specific weight. It is very convenient to use a vial made to contain exactly 1,000 grains of water, as then, without any calculation, the number of grains which such a vial contains of any liquid expresses its specific weight. 13. Experiment. — Weigh a flask filled with water; then place a half-ounce weight on the pan which holds the weights, and by the side of the flask nails enough to adjust the beam. Remove both nails and 2* Fig. 3. 18 SPECIFIC GRAVITY. flask from the pan, and put the nails into the flask A bulk of water wUl be displaced equal to that of he naffs to determine its amount, replace the flask, after it has been thoroughly wiped on the outside, upon the pan, and remove weights from the other pan until the equi- poise is restored. The weights taken away (about 32 grains) form the divisor, and the half-ounce or 240 grains, the dividend; the quotient -3-2- = 7.5, » the specific gravity of iron, of which the nails were made 14. Experiment— If we have to determme the specific grav- ity of a piece of iron, or of any other body which cannot be put into a flask, it must be fastened by a piece of fine thread to the pan of a com- mon balance, (Fig. 3, b,) the cords of this pan having been previously shortened. Weigh the body first in air, and then in water, immers- ing it an inch deep. As it sinks, the opposite pan falls; consequently iron must be lighter in the water than in air. If the iron in the air weighed half an ounce, then, in order to restore the equilibrium, it will be necessary, as in the former experiment, to remove from the pan a 32 grains, equal to the weight of the bulk of water displaced by the iron. The loss of weight is the same, whether the water be removed from the vessel or mere- ly displaced within it. This forms the divisor, and 240, SPECIFIC GRAVITY. 19 the weight of the iron in the air, the dividend, giving the quotient \-2- = 7.5. 15. Every substance becomes lighter in water in pro- portion to the amount of water displaced; this is a law of nature. If it displaces less water than its weight in the air, it sinks; if more, it floats. Even very heavy bodies can be made to float by increasing their volume; ships are constructed of iron, although it is eight times heavier than water; a tumbler floats upon water, and yet the specific gravity of glass is from three to four times greater than that of water. A thick piece of iron, weighing half an ounce, loses in water nearly one eighth of its weight; but if it is hammered out into a plate or a vessel of such a size that it occupies eight times as much space as before, it then loses its whole weight in water, and will float, sinking just to the brim. If made twice as large, it will displace one ounce of water, — consequently twice its own weight; it will then sink to the middle, and can be loaded with half an ounce weight before sinking entirely. 16. Areometer, or Hydrometer. — The same body will sink to a greater or less depth in different liquids, — deeper in the lighter ones, and not so deep in those which are denser. This has suggested a very conven- ient instrument for determining the spe- l(l0 F's " cific gravity of liquids, the hydrometer { j2q, or areometer. This instrument consists of a hollow glass tube, made as repre- sented in Fig. 4. The interior is hol- low, and blown out into a bulb at the lower end, to cause it to float; the under part is loaded with quicksilver or shot, to give it a vertical position. The main tube serves to denote the depth to 20 SPECIFIC GRAVITY. which it sinks in any liquid, by means of a scale of degrees, with which it is furnished. There are vari- ous instruments of this kind, especially adapted for determining the density of spirits, brandy, oil, lye, syrup, &c. If a hydrometer for weighing spirits is put into water, it sinks only to the lowest point on the scale 0° (Fig. 4, a); but in the strongest alcohol, which is much lighter than water, it sinks to the highest point, 100°. A scale for testing lye (Fig. 4, b) must, on the contrary, have the 0° point at the top of the scale, to which it would sink in pure water; for lye being heavier than water, the instrument would be more or less buoyed up in it, according to its strength. In hydrometers for lighter liquids, the degrees proceed from the bottom to the top, in those for heavier liquids from the top down-. wards. In most of these scales the degrees are arbi- trary ; and in order to convert them into the correspond- ing specific numbers, tables, constructed for the pur- pose, must be referred to. 17. Experiment. — Pour brandy into a cylindrical jar, and observe the degree which it marks on the hydrometer; then put it in a warm place, and, when lukewarm, again note the degree, which will be higher than before, as the heat has expanded the liquid, made it lighter, and consequently apparently stronger than it really is. (§ 22.) The specific gravity of all bodies, when warmed, is less than when cold. On this account, in determining the density of bodies, regard should be paid to their temperature, and it has been agreed to consider 15° C. (§ 24) as the mean temperature. In the more accurate hydrometers, the mercury serving as the counterpoise has been ingeniously con- trived also to indicate the degree of heat of the liquid, by connecting with it a graduated tube. The small THE ANCIENT ELEMENTS. 21 Fig. s. scale, a, (Fig. 5,) denotes the temperature, the long scale, b, the density. The small scale is frequently so constructed, that the degrees cor- respond to those on the long scale, and in order to guard against error it is only necessary to add the degrees below the mean temperature to the density, or to subtract from the density those above. Gold is nineteen times, and silver ten times, heavier than water; gold alloyed with silver / \ must, therefore, have a less specific weight than pure gold. The specific weight of brass is only = 8. Alcohol and ether are lighter in propor- tion to their purity and strength, while lye, syrup, the acids, &c, increase in density according to their purity. Hence it is evident how important it is, in many cases, to know the specific gravity of a body in order to judge of its quality. THE ANCIENT DIVISION OF THE ELE- MENTS. 18. Matter and Forces. — As we discern in ourselves the visible body, and its ruler, the invisible spirit, so we recognize in external nature bodies which we can handle and weigh, and forces or powers ruling these bodies and having no weight. 19. Aggregation. — The innumerable natural bodies which we meet with on the earth may be divided into three great classes; they are either solid, Uqidd, or aeri- form, and each of these states in which bodies exist is called its state of aggregation. 22 THE ANCIENT ELEMENTS. Cohesion.-To divide a piece of ice into smaller fragments, a greater force is requisite than to separate water into minute portions; whence we infer that the particles of the solid ice adhere more strongly than those of the fluid water. A certain attracting power is regarded as the cause of this difference; it acts on the very smallest particles of matter, and is called cohesion or homogeneous attraction. In solid bodies, cohesion is stro^er than in liquids, and in aeriform bodies hard- ly a trace of it can be perceived. The Ancient Elements, so called. — Of solid bodies, the most widely diffused is earth; of liquids, water; and of the aeriform bodies, air. From this the ancient phi- losophers concluded that all solid matter was formed of earth, all liquids of water, and aeriform bodies of air; on this account they called them elements, or pri- mary matter. They cannot now be regarded as such in a chemical point of view, since they have been decom- posed into still more simple bodies; but they may be viewed as physical elements, that is, as types of the three aggregate states of bodies. 20. We have no absolute knowledge of the forces of nature, they having as it were a spiritual existence. We are nevertheless as firmly convinced of their reality as we are of the reality of our own spirit, for we know them by their phenomena and effects. A piece of iron, on being thrown into the air, falls to the ground, which is ascribed to the power of gravitation; if exposed to a moist atmosphere, it rusts, that is, it unites with the oxygen of the air. This is the result of chemical force; and the force of electricity can free the iron again from this union. By the force of magnetism, a piece of iron, when balanced on a pivot, takes a direction from north to south; by the force of heat it can be WATER AND HEAT. 23 melted, &c, &c. From this it appears that there are various forces, but it is not improbable that they have one common origin, in the same way that all the differ- ent powers of the mind, will, imagination, judgment, &c, are all referred to one single spirit. Fire, the fourth of the old elements, may be regarded as the symbol of these forces. This also has lost its place among the chemical elements, since it is merely a phenomenon of chemical processes affording light and heat. Of these old elements, fire (heat), water, and air play an important part in most chemical experiments; heat being influential in promoting chemical changes, and water being the most usual solvent of solid and aeriform bodies. The air deserves consideration in all cases, for almost all chemical experiments are per- formed in it, and it may exert injurious or beneficial effects upon them. These three so-called chemical ele- ments will therefore first be more particularly con- sidered. WATER AND HEAT. 21. Water covers about three quarters of the sur- face of the globe; it exists sometimes solid, as at the poles, and sometimes fluid, as in warmer regions. In the form of rivers it intersects the land in all directions; while it rises in vapor into the air, and, forming clouds, returns in rain to the earth. Thus we find it in nature in its three aggregate forms, and it is obvious that these external differences have been effect- ed by the agency of heat. Hence water is peculiarly 24 WATER AND HEAT. well adapted to serve as a study of the most impor- tant effects of heat. EXPANSION BY HEAT, AND THERMOMETER. 22. Expansion of Liquids. — Experiment.— Take the tare of a flask, —that is, place it on one of the pans of a balance and equipoise it by weights put into the opposite pan; — then fill it with water, ana ascertain the weight of the latter. Warm the flask on a tripod over a simple spirit-lamp, moving it round gently at first, that the flask may heat gradually. The water will soon rise, and part of it run over. When it begins to boil, remove the lamp and let the vessel cool, and the water will then sink deeper than it stood before. How much has been displaced is found by its loss in weight; it will amount to about ~ of the first weight. The burning spirit, or alcohol, heats the bottom of the glass vessel, which in turn communicates heat to the water. The heat expands the water, consequently it occupies a greater space than before, and part of it must run over. Hence it follows that warm water must be fighter than cold water. If a pitcher filled with two pounds of ice-cold water be afterwards filled with boiling water, it will weigh about an ounce and a half less. As it cools, it contracts again to its former density. The same occurs with all other liquids, and indeed also with solids and gases: hence, it may be stated as a natural law, that all bodies expand by heat, and con- EXPANSION BY HEAT, AND THERMOMETER. 25 tract on cooling. But the amount of expansion is very different in different bodies at the same temperature; alcohol, for example, expands two and a half times more, mercury two and a half times less, than water. When fluids are to be bought and sold by measure, an advantageous application may be made of this prin- ciple. If a hundred measures of brandy or alcohol are purchased in hot, and sold in cold weather, there will be a loss of four or five measures; therefore we should gain by buying in winter and selling in summer. 23. Experiment. — In order to observe more accurate- ly the expansion of water by heat, adapt to a flask a cork, rendered so soft by gentle pounding that it may be exactly fitted to the opening by mere pressure; perforate the cork with a round file, and make the hole just large enough to admit a glass tube. Fill the flask with water, so that, when the cork is firmly pushed in, the water shall stand at about a, (Fig. 7,) and heat it as in the former experiment. The water, which in the former experi- ment was displaced from the flask, in this case rises in the tube, and the higher in proportion to the smallness of its bore. By this means very slight changes of space are rendered visible, and these de- viations may be applied to the measurement of heat. This is done by particular instruments called ther- mometers. 24. Thermometer. — Water might be employed for measuring heat, by marking the boiling and freezing points, and graduating the intervening space; but mercury is far better adapted to the purpose, as it boils and freezes at greater extremes of temperature, 3 26 WATER AND HEAT. and more rapidly denotes the variations of heat and cold. i „ i „ The vessel containing the mercury may also be regarded as consisting of a flask and tube, but which, instead of being joined by a cork, are composed of one entire piece. Having introduced into it a sufficient quantity of mercury, and sealed the open end by fusion, it is immersed in melting snow, and the point to which the quicksilver falls is marked freezing point; that to which it rises in boiling water, boiling point. The space between these two points can now be divid- ed into degrees, to form the scale. The degrees below the freezing point are of the same dimensions as those above. There are several scales in use, though it is to be regretted that more than one has been adopted. The most common are the three following:—Reaumers (R.), divided into eighty degrees; the centigrade of Celsius (C), into one hundred; and Fahrenheit's (F.), into one hundred and eighty degrees. The difference between these can be easily seen in the annexed figure. According to R. water freezes at 0° and boils at 80°; according to C. it freezes at 0°, and boils at 100°; ac- cording to F. it freezes at +32°, and boils at 212 \ Fahrenheit, a philosophical- instrument maker, commenced counting, very strangely, not at the freezing point, but at 32° below it. His scale is still in common use in England, and the high numbers found in English reckonings are thus accounted for. In GermanVj Reaumers thermometer is used R. Fig. 8. C. F. 1oK.c/.n8CL_____n L____n«>o-----n'2'2 + U,?—+ V—+ F2 $? o........o-.....+i 12 Jm:.j- m.....i L° EXPANSION BY HEAT, AND THERMOMETER. 27 except for scientific purposes, when the Centigrade, in common use in France, is employed, and it has been adopted in this work. In order to compare these ther- mometers with each other, it need only be remembered that 4° R. are as large as 5° C. or 9° F. In reduc- ing Fahrenheit to Reaumer or Centigrade, if the de- gree be above the freezing point, 32° must first be sub- tracted, which process must be reversed in order to re- duce the degrees of the other scales to those of Fahren- heit. To the degrees above 0°, the sign -f- is prefixed, to those below, the sign —. A cylindrical thermometer, graduated to 300° C, Fig. 9. like that in the annexed figure, is best suited for chemical experiments, as it can be easily adapted to a perforated cork, and then fitted to a flask, in which liquids are to be heated to a certain tem- perature. The degrees above the boiling point are to be divided off at distances equal to those below. 25. Quicksilver freezes at —40° C. In the northern regions of the earth a degree of cold of —50° C. has been observed, and by artificial means the temperature can be lowered to —100° C. When great degrees of cold are to be measured, alco- hol is used in the construction of this instrument, as it does not congeal at —100° C. 26. Quicksilver boils at 360° C, therefore its use must be limited to temperatures below this point. The high temperatures attending ignition are measured by the expansion of platinum bars, a metal which does not melt even in the hottest furnace. Such an instru- ment is called a pyrometer. By means of lenses, and by chemical action, a degree of heat of more than 2000° C. may be produced. 28 WATER AND HEAT. 27. Expansion of Solids.— If an iron vessel, when cold, is just large enough to pass through the door of an oven, it cannot be removed from it when heated. The iron bands or tires of carriage wheels are applied while red-hot to the frame, and on cooling they contract and bind the wood-work together with great force. A metal- lic disk, which, when red-hot, fits exactly into a circular box, will, on cooling, become loose, and shake in it. The tire and the disk both become smaller on cool- ing. These examples show that solids also are ex- panded by heat, and contracted by cold, and explain many of the phenomena of common life. Clocks go faster in winter, and slower in summer, because the pendulums elongate in summer, and consequently vi- brate slower, while in winter they become shorter, and vibrate more rapidly. A piano gives a higher tone in a cold than in a warm room, on account of the contrac- tion of the strings; a nail driven into the wall becomes loose after a time, because the iron expands in summer and contracts in winter more than the stone or the wood, and thus the opening is gradually enlarged. For this reason, in the construction of railroads the rails must not be laid too close together; in the ar- rangement of steam-pipes, these must not be too firmly inclosed; in roofing; the zinc plates, instead of being nailed together, must overlap each other, that they may neither tear nor warp on alternate contraction and ex- pansion. Brittle bodies, as glass and porcelain, expand or con- tract so rapidly, by sudden heating or cooling, that they break. Experiment. —Wind round a vial two bands of paper, a and b, Fig. 10, and secure them firmly with thread* pass a cord round the vial, between these folds of EXPANSION BY HEAT, AND THERMOMETER. 29 paper, and move the vial quickly to and fro on the cord until the latter breaks. Then immediately pour cold water upon the place, and the glass will break as even- ly as if cut. The sharp edges can be removed with a file. In this manner, common vials, and Cologne, and even larger, bottles, may be converted into vessels adapted to chem- ical and other purposes. It is well known that heat is produced by the friction of two bodies upon each other; that by sliding quickly down a line or a pole by the hands, these will be burnt, and that rapid motion will ignite the axles of a carriage, unless they are well greased. Thus, in the above ex- periment, the friction produced great heat in the glass, the string emitted a burnt odor and broke, and great expansion of the glass was produced. When the outer surface was suddenly cooled by the cold water, the expanded particles at once contracted, and more rapidly in the external particles than in those of the inner surface, causing the fracture of the glass; and the more easily the greater its thickness. If the tempera- ture had been slowly reduced, it would not have broken. Thus, it is obvious, (a,) that glass and porcelain ves- sels intended for sustaining high temperatures, such as flasks, alembics, retorts, capsules, &c, should be thin, particularly at the bottom; and (b) that, when used, they should always be gradually heated and cooled. The above method of heating glass by a cord fur- nishes the apothecary with a simple expedient for re- moving stoppers which are too firmly fixed in the bot- tles to be taken out by turning or tapping them. 3* Fig. 11. 30 WATER AND HEAT. Wind a cord round the neck of the bottle, and move it quickly until sufficient heat has been produced to loos- en the stopper. No two solids expand alike; the metals expand the most, and all solids less than fluids. The expansion of gaseous bodies will be considered under the head of air. (§ 97.) 28. Expansion by Cold. — A remarkable exception to this law, of expansion by heat, and contraction by cold, occurs in the case of water. Experiment. —A large flask is arranged as directed in experiment 23, inserting also a cylindrical thermometer, a, through a hole made in the cork. The flask is filled with water to the top of the tube b, and placed in a vessel filled with snow. A strip of paper may be pasted on this tube, upon which the level of the water may be marked as the thermometer falls. The water as it cools will sink in the tube until the mercury stands at 4° C.; yet on cooling still more it does not fall any farther, as we should expect it would, but, on the contrary, it begins to rise again, and continues to do so till it reaches the freezing point. At 0° C. it stands at the same point as when its temperature was at 8° C. Water is accordingly the densest at -f 4° C.; all other liquids continue to increase in density as they cool. 29. However unimportant this exception may appear at first, our admiration must be the greater when we reflect upon its consequences. WTere it not for this our country would have the climate of Greenland! MELTING OF SOLIDS. 31 The freezing of our waters, as the winter sets in, is principally owing to the coldness of the atmosphere. Consequently, the upper part of the water is colder and heavier, and sinks to the bottom; the warmer water ascends, becomes cold, and also sinks. If the water continually became denser, to its freezing point, this circulation would continue till the whole mass of water to its* greatest depth reached 0° C, and a few cold days would suffice to convert all our ponds, lakes, and rivers into ice. This does not happen, because the cir- culation ceases when its temperature has fallen to 4° C.; when the water, though yet colder, becomes light- er, and floats on the surface. Thus, freezing can only take place at the surface, and the ice be but gradually formed. At a small depth below the ice, the water always retains the temperature of 4° C. MELTING OF SOLIDS. 30. The expansion of bodies is the first general effect of heat; but in solid bodies another effect is ob- served; they change their aggregate state, they be- come liquid, they melt. Many of them become soft be- fore melting, so that they can be kneaded; for instance, butter, glass, and iron; in this condition, glass can be bent and moulded like wax, and iron can be forged. ExperVhient. — Hold a piece of a small glass tube in the upper part of the flame of a spirit-lamp, revolving it slowly between the fingers ; when red-hot, it will be so soft that it can be bent into any shape desired. Thus are easily formed any of the numerous bent tubes required in chemical experiments. For softening larger tubes, a lamp with a double blast must be used, as this gives a much stronger heat than the simple lamp. To 32 WATER AND HEAT. break a glass tube, a scratch is made upon it with a three-cornered file, at the place to be broken, and then it can be parted by gently pulling with both hands. Most solid bodies become suddenly fluid, as ice, lead, &c. 31. Experiment. — Place one vessel containing snow or ice, and another containing a piece of tallow, on a warm stove, testing from time to time the melting sub- stances with a thermometer; the temperature will re- main stationary in the first vessel at 0° C, in the other at about 38° C, so long as any ice or tallow remains un- melted, but when the melting is complete it will com- mence rising. The degree of heat at which a body melts is called its melting point. Every substance has its own melting point, sometimes above and sometimes below the freezing point; for example, lead melts at above 300° C, silver at above 1000° C.; solid quicksilver at —40° C. If these two vessels containing water and melted tallow are placed in the cold, it will be observed that the tallow soon hardens at about -f-35° C, but the water not until the mercury has fallen to 0° C. Thus the congelation of fluids takes place at about that temperature at which they pass from the solid to the fluid state. Many substances, coal for instance, have never yet been melted, and others have never been frozen, as, for instance, alcohol; but it is very probable that, when some method of producing the greatest degrees of cold and heat is discovered, we shall succeed in rendering all solid bodies liquid, and all liquids solid. 32. Latent Heat — Experiment — Put two vessels of equal size on the hearth of a warm oven, one of them containing a pound of snow at 0°, and the other a pound of water at 0°; when the snow is melted re- MELTING OF SOLIDS. 33 move them both. By the touch merely it will be per- ceived that the snow-water is still cold, while the water in the other vessel has become warm; and the thermom- eter will indicate that in the former the temperature is at 0° C, in the latter at 75° C. Both vessels have received equal degrees of heat, and when put into the oven were of the same temperature; the question then suggests itself, What has become of the 75° of heat imparted to the vessel filled with snow? The reply is, This heat has been absorbed by the snow, thus convert- ing it into a fluid, — melting it. Experiment — Put one pound of snow at 0° C. into the vessel containing the water heated at 75° C, and then test with the thermometer; as soon as all the snow has disappeared, the quicksilver will fall to the freezing point. Consequently the snow has taken from the hot water 75° C. of heat, and has thus become liquid. 33. Experiment — This heat has by no means been annihilated in the water, but is concealed there (latent), and continues thus hidden as long as the water exists in a fluid state. But it will again become free, or sensible to the touch, when the water assumes a solid form. This may be rendered obvious by sprinkling £ of an ounce of water upon 1-^ ounce of quicklime ; the lime swells, becomes very hot, and finally crumbles into a fine powder. If this is weighed when cold, it will be found to have increased in weight by half an ounce; thus two ounces of slaked lime have been produced from an ounce and a half of quick lime; the quarter of an ounce of water missing has passed off as steam. The water alone could have effected this increase of weight by combining chemically with the lime; and it can exist there only in a solid state, as the slaked lime is an entirely dry pulverulent substance. This great devel- 34 WATER AND HEAT. opment of heat can be explained thus: partly because the water, in becoming solid, gives up the heat which it had absorbed in passing to the fluid state, and partly because of the chemical combination between the two bodies taking place with great energy. A disappear- ance of heat always ensues when solid bodies become fluid; but an evolution of heat, on the contrary, when liquid bodies became solid; and thus is explained very simply, for example, why the air remains cool when the snow and ice are melting in the spring, and why the weather moderates on the fall of snow. That heat which is felt by us, and which is indicat- ed by the thermometer, is called free heat; it has but a feeble affinity for bodies, and easily leaves them on cooling. That imperceptible heat on which the fluidity of liquid bodies depends, and which on freezing escapes or becomes free, is called latent heat. Hence a fluid may be regarded as a combination of a solid with la- tent heat. BOILING AND EVAPORATION. 34. Boiling of Water. — Water, as is well known, boils when heated to a certain temperature. Experiment. — Water, to which some sawdust has been added, is heated in a test-tube over a spirit- lamp. The tube is held by the upper part, and rotated for some minutes between the fingers, that the flame may have equal access to all the lower parts of the tube. If the water be carefully observed, it will be seen that the sawdust ascends on the upper BOILING AND EVAPORATION. 35 surface of the liquid, and descends in the lower strata; the warm water, becoming lighter, rises upwards, while the colder, consequently heavier, water sinks; the water circulates. In consequence of this circulation, the heat- ing of fluids takes place more rapidly when the heat is applied beneath. Test-tubes are cylindrical glass vessels with rounded bottoms. To prevent their breaking on the application of heat, the bot- tom must be thin, and blown of a uniform shape. A sim- ple wooden rack, as in the annexed figure, serves as a convenient stand for them. Experiment. — Repeat the former experi- Fig. 14. ment, using instead of the tube a flask, (■-'^^n and omit the sawdust, so that the water \ 9°* j may remain clear; in a short time many little bubbles will appear on the walls of the flask, which will gradually increase in size, and rise towards the surface. These bubbles consist of air, which is expanded by heat and expelled from the water. All spring-water contains some air in solution, and to this is chiefly due its refreshing taste, which is not found in boiled water or in that which has been standing for some time. Afterwards, when the water has be- come quite hot, larger bubbles appear on the hotter part of the flask, which, also ascending, be- come smaller and entirely disappear before reaching the surface of the water; they consist of aeriform water (steam), which condenses as it comes in contact with 36 WATER AND HEAT. the cooler liquid above. The collapsing of the particles of water at the places where these steam-bubbles dis- appear occasions that peculiar noise which precedes boiling, and which is commonly called the singing of the water. When the whole mass of water is heated to 100° C, these bubbles no longer condense, but rise to the surface, where, surrounded by a thin film of water, they remain quiescent for a few seconds, and then, their watery mantle again sinking, they finally burst. This is the boiling of water. It boils at 100° C.; other liquids boil more readily,— alcohol, for instance, at 80° C.; others again more difficultly, — mercury, for in- stance, at 360° C. 35. Steam. — The space above the boiling water in the interior of the flask appears vacant, but it is in fact filled with aeriform water, which has displaced the air that was in it. This aeriform water is called steam. It is almost 1700 times lighter than water, because a quantity of water yields nearly 1700 measures of steam at 100° C. Within the flask the steam is trans- parent and invisible, but in the open air it ascends in the form of white clouds, which greatly increase if cold air is blown into the flask by means of a glass tube. On cooling, the transparency of the vapor is dis- turbed, on account of the formation of drops of water, so small and light as to float in the air. Clouds also consist of this partly condensed vapor. As the con- densation increases, the drops become so large and heavy, that they descend as rain. A thermometer im- mersed in boiling water indicates 100° C.; if placed in the steam immediately above, it shows the same; and this temperature will not rise higher, however lon<* the boiling be continued, or however strongly the flame of the lamp be urged. This is similar to what occurs in BOILING AND EVAPORATION. 37 the melting of snow; heat disappears, and its disap- pearance proceeds from the same cause in both cases; steam requires heat for its existence as such, and is so intimately combined with it that the excess is no longer perceptible, — it is latent. If water may be regarded as a combination of ice with latent heat, so steam may be considered as a combination of ice with still more latent heat; which latter becomes free again on the conversion of steam into water. 36. Experiment. — Adapt the shorter limb of a bent glass tube, by means of a perforated cork, to the neck of a flask, and pass the longer limb to the bottom of a beaker-glass or common tumbler. Pour into each of these two vessels two ounces and a half of ice-cold water, and grad- ually heat the glass upon a tri- pod until it boils. Note the time re- quired for this operation. Con- tinue the process until the water in the beaker-glass begins to bubble, and note also the time, which will be found the same as that required for heating the water in the flask. The steam formed in the flask has no other outlet than through the tube into the water, where it condenses, until the contents of the second glass reach the temperature of 100° C, and boil. Both of the vessels must now be weighed; and it will be found that the flask weighs half an ounce less 4 38 WATER AND HEAT. and the beaker-glass half an ounce more than before; consequently, half an ounce has passed from the for- mer as steam, and has been condensed again in the latter; and yet this half-ounce of steam, which it- self was not hotter than 100° C, could heat to the boiling point two ounces and a half of ice-cold water. What is the source of these 500 additional degrees of heat? They were latent in the steam, and, on its being condensed, were set free. These were caused by the heat of the spirit-lamp, as must be obvious from the above-noted amount of time consumed. Assuming that the time required to boil the water in the first flask- was ten minutes, and also ten minutes for boiling the water in the second vessel, it follows, that the same amount of heat which was required for heating two ounces and a half of water was only sufficient to evap- orate half an ounce of water; the whole heat given out in the last ten minutes from the spirit-lamp must con- sequently have been converted into latent heat. If half an ounce of boiling water received during the evapora- tion the amount of 500° of heat, then the steam evolved must have given off just as much heat when it again assumed a liquid state; consequently, it must be able to raise the temperature of two ounces and a half of water at 0D C. to that of 100° C. The property of steam to absorb a large quantity of heat, and to part with it again during condensation, peculiarly adapts it for the heating of other bodies, the burning of them being thus guarded against, as the heat of steam in open vessels can never exceed 100° C. Apothecaries avail themselves of steam in the prepara- tion of infusions, decoctions, and extracts; it serves for many of the processes of cookery, and for the distilla- tion of spirits; it is employed in dyeing and bleaching BOILING AND EVAPORATION. 39 establishments, and is often resorted to for heating apartments, buildings, laundries, &c. AERIFORM. LIQUID. A !» SOLID. The increase and decrease of heat produced by change of the aggregate state of bodies will be made clear by the annexed diagram. As the steam ascends in the direction of the arrows (by liquefaction and evaporation) heat becomes latent, and as it descends (condensation of vapor and congelation of fluids) heat is liberated. 37. Aqueous Vapor. — Water exposed in a vessel to the open air disappears in summer more rapidly than in winter; the heat of the air renders it aeriform,—it evap- orates. The same happens as in evaporation over the fire, only in the former case evaporation takes place without any visible motion of the water, owing to its becoming aeriform, not throughout the whole mass at once, but upon the surface only. Vapor rises in an in- visible form in the air. Warm air, indeed, receives more of it than cold, but a fixed quantity of it only for each temperature. Thus one hundred measures of air at 0° C. absorb two thirds of a measure of vapor;at 10° C, one measure and a quarter; at 20° C, two and an eighth measures, &c. If the air has not yet absorbed all the vapor which it can, it eagerly takes up more, as, for example, when one hundred measures of air at 20° C. 40 WATER AND HEAT. contain only one or one and a half measures of vapor; it is then called dry air, and wet articles are soon dried in it by rapid evaporation. But if it be already saturat- ed with vapor it is called moist, air; and damp articles cannot be dried in it, or at least but slowly. If yet more vapor be added to this saturated atmosphere, or if it be cooled, then the excess separates in visible particles, called mist or fog when they lie upon the surface of the earth, and clouds when they float in the higher regions of the atmosphere. The white smoke which in winter is seen rising from the chimneys, the visibleness of the breath in frosty weather, and the smoking of rivers in winter and after a storm, are phenomena of the same kind. 38. If the cooling of the air is occasioned by a cold solid body, the vapor is then condensed in small drops of water, as may be observed on the outside of a cold glass when brought into a warm room, and the deposit of moisture on the inside of our window-panes, when cooled by the external cold air. The temperature at which this occurs is called the dew-point, signifying the temperature at which the air is saturated with vapor. Experiment — Fill a tumbler one quarter full with cool water, place in it a thermometer, and at short intervals gradually add ice or cold water, until moisture begins to deposit on the outside of the glass. Then observe the degree indicated by the thermometer, which is the dew-point. If much cold water must be added before the glass clouds over, that is, if the dew-point is much lower than the temperature of the air, fair weather may be expected; while, on the contrary, if the difference be- tween the dew-point and the temperature of the air be BOILING AND EVAPORATION. 41 but slight, rain may soon be expected, as then the air requires but a slight addition of moisture or increase of cold to become saturated. Instruments by means of which the amount of moisture in the air is ascertained tty&re called hi/grometers. Many substances readily im- *-*.bibe moisture from the air, and become damp; such bodies, for instance, as catgut, carbonate of potassa, sul- phuric acid, fresh barley-sugar, &c, are called hygro- scopic. 39. Evaporation may be accelerated, not only by heat, but also by a current of air, because by this means the air above the surface of the fluid, which is charged with vapor, is removed and replaced by a drier, and, as it were, more thirsty air, which takes up the vapor more rapidly and abundantly than the former. For this rea- son, the earth dries rapidly after rain, when followed by a high wind, and hence it is necessary in kilns, laundries, drying-rooms, &c, to arrange them in such a manner that the air, when saturated with moisture, may be constantly replaced by dry air. 40. That heat disappears during slow as well as rapid evaporation (§ 36) may be readily illustrated by the fol- lowing experiment. Experiment. — Fill a tube half full of water, and fasten securely round the bulb of it a piece of cloth; saturate the cloth with cold water, and then twirl the tube rapidly between the hands; presently the water in the tube will become sensibly colder, and the degree of cold may be accurately determined by the thermometer. Moisten the cloth with ether, a very volatile liquid, and twirl it again in the same manner as before; by which means its contents, even in summer, may be convert- 4* 42 WATER AND HEAT. ed into ice. Water evaporates slowly, ether rapid- ly; and both require heat for their conversion into vapor, and in the above experiment they obtain this heat from the water in the bulb, which is of course the reason of the water becoming cold. On this principle one feels cool on just leaving the bath, when invested in damp garments, or when the floor of a hot apart- ment is sprinkled with water. It explains, also, how man is enabled to support the scorching ^n of the hottest climates, and even to endure a heat of 100 C, without his blood exceeding the temperature of from 38° to 40° C.; it is owing to the more copious per- spiration, which, by evaporation, renders all the heat above 40° C. latent. If we blow on hot soup, it is also the increased evaporation which cools it more rapidly; but if we blow on the cold hands in winter, they be- come moist and warm, because the latent heat con- tained in the vapor of the breath is set free, as the vapor is condensed into water. 41. Distillation. — If evaporation be carried on in a close vessel, the water may be collected as it forms. Experiment — A small glass retort is half filled with water, and heat- ed ; the steam, as it forms, passes through the neck of the retort in- to a glass receiv- er, contained in a vessel filled with cold water, and is there condensed. That the refrigeration may take place more rapidly, the receiver is covered with coarse blotting-paper, which is frequently moistened by cold DIFFUSION OF HEAT. 43 water. This operation is called distillation (from dis- tillare, to drop), and the pure water obtained is said to be distilled. It is purer than spring-water, for this rea- son, that the non-volatile, earthy, and saline portions contained in all spring-water do not ascend with the vapor, but remain in the retort. By this means very volatile bodies also can easily be separated from less volatile ones; as brandy from the less volatile water. Copper stills are usually employed for distillation on a large scale, and for condensers vats are constructed, holding serpentine pipes, or worms, which present a greater condensing surface than if the pipe had passed directly through the vat. The cold water with which the vats must be filled is very soon warmed by the heat liberated in the condensation of the steam, and must occasionally be renewed by leading off the hot water from above, and letting in a fresh supply of cold water beneath. DIFFUSION OF HEAT. 42. Conduction of Heat. — Experiment— A test-tube, nearly filled with water, is held over a spirit-lamp, in such a manner as to direct the flame against the upper layers of the water; the water will boil at the top, but remain cool below. If mercury is treated in a similar way, its lower layers will gradually become heated. The particles of mercury will communicate the heat to each other, but not so the particles of water. Sub- stances through which, as in mercury, heat rapidly passes, are called conductors; but bodies which comport 44 WATER AND HEAT. like water are called non-conductors of heat. In the former class are included particularly the metals, and in the latter, stone, glass, wood, snow water, and especial- ly cloth, fur, linen, straw, paper, ashes, &c. The conductors are readily heated, and soon become cold again, as is well known to be the case with iron stoves A piece of iron feels hotter in the sun and colder in the shade than a piece of wood at the same temperature. The explanation of this delusion of the sense of touch is, that the warm iron conducts the heat more rapidly to the hand, while the cold iron withdraws it more rapidly than the wood is capable of doing. The non-conductors of heat are slowly heated, and also slowly cooled; for this reason, stoves constructed of brick (the Russian stove) and those made of Dutch tiles, a preparation of clay, retain their heat longer than iron stoves. Non-conductors are frequently employed both for preventing the quick heating and the quick cooling of bodies. Vessels of glass and porcelain are placed on sand (a sand-bath) or ashes, to heat them - gradually, and thus guard against their breaking. If a " hot liquid is to be poured into them, it must be done by small portions at a time, twirling the vessels round for some minutes before adding more. On removing a vessel from the fire, the precaution should be taken never to place it while hot on metal or stone, but always on some non-conductor, such as straw (straw rings), wood, paper, cloth, ut no fine solid particles, can pass; these remain on the fato Writing-paper cannot be used for filtration, as its pores are filled up by glue or starch. 48. Experimelt-Your a part of the obtained solu- tion into a saucer, and pass strips of fine blotting or of letter paper one or more times through it, until they have acquired a distinct blue color. Preserve these strips, after being dried, in a box >» they are called blue litmus or test-paper; they are reddened by vinegar, lemon-juice, and all acid fluids, and serve to test a liquid, to ascertain whether it is kcid (has an acid reaction). / Experiment — Mix cautiously another portion of the solution with lemon^ce, until the blue color appears distinctly red; this also serves tpxolor paper. The red test-paper is used for the purpose of recognizing a class of substances opposed to acids, that is, alkaline or basic bodies; these restore the original blue color of the paper, as can be seen by bringing it into contact with lime-water or moistened ashes. 49. Experiment. — Add gradually, with constant agi- tation, to one ounce of cold water, powdered saltpe- tre, as long as it continues to be dissolved, perhaps about a quarter of an ounce; if more is added than is necessary, it will remain undissolved at the bottom of the vessel. This solution is said to be saturated in the cold. If this mixture be boiled, and saltpetre again be added, then about two ounces more will be required to saturate the water. A thermometer held in this boiling saturated solution will indicate about 108° C, while simple boiling water indicates only 100° C. All saline solutions boil and freeze with more difficulty than water. All bodies soluble in water behave in a similar man- SOLUTION AND CRYSTALLIZATION. 51 ner; that is, they are soluble in it only in fixed quanti- ties, and in most cases hot' water dissolves more of them than cold. 50. Experiment — If the solution obtained in the last experiment be poured into a porcelain dish, previously heated, and be suffered to remain quiet until cold, then the two ounces of saltpetre which were last added separate again, not as powder, but as regularly formed prisms. These prisms are six-sided, and are surmount- ed by two faces similar to a roof; they are called crys- tals of saltpetre. (Fig. 23.) All crystals are character- ized by having planes, edges, and angles, constructed, as it were, of simple triangular, quadrangular, or poly- angular pieces, artificially polished; this symmetry is Fig. 23. found even in the interior of them, as can easi- ™ly be seen by holding a piece of transparent crystal towards the light, and turning it slowly round; or breaking it, when the fragments will often exhibit the same regular form which characterized the whole crystal. Thus in in- animate nature a mysterious power exists, similar to that which compels the bees to construct their six- cornered cells, and the potato to produce its five-angled corolla and five stamens, and by which the smallest particles of bodies, called atoms, are forced to arrange themselves in a fixed order, assuming a regular shape. But this can only be accomplished by a body in its fluid or aeriform state, since a free'motion of the atoms is essential. Time also is required for this operation; hence crystals are always more regular the more slowly they are formed. Many of the splendid crystals which have been dug from the depths of the earth were, per- haps, thousands of years in forming. 51. Experiment. — Evaporate the mother-liquor of 52 WATER AND HEAT. the former experiment, at a gentle heat, until scales are formed on the surface, then remove it from the fire, and let the liquid cool, stirring constantly with a wooden stick. In this way, instead of crystals, a powder of saltpetre will be obtained. The mother-liquor, just alluded to, may be regarded as a cold saturated solution, containing about a quarter of an ounce of saltpetre. If by evaporation only so much water is left as is sufficient when hot to keep in solution but a quarter of an ounce of saltpetre, then crystals begin to appear in the form of a film on the colder parts, indicating the saturation of the liquid. If this again is allowed to cool quietly, a second crop of crystals would be obtained; but by continual stirring they are broken at the moment of their formation, — by slow movement into a coarse, and by rapid movement into a fine powder. This may be called interrupted crystallization. Sugar presents a similar example; the same syrup, when cooled quietly, yields rock-candy; if stirred, it yields common loaf-sugar. 52. Experiment. — Put into boiling water as much common salt as will dissolve, and let the solution cool; no crystals will form, because salt is as soluble in cold as in hot water. Now evaporate one half of the solu- tion over a spirit-lamp, and set aside the other half in a warm place; in the first case, mere irregular grains of salt will be obtained, but in the latter case, after some days, regular cubes of salt will be deposited. 53. Experiment — Dissolve a spoonful of salt and one of saltpetre in lukewarm water, and put the solution in a warm place, that the water may gradually evaporate; the two salts, which are intimately united in the solu- tion, will upon crystallization separate completely from each other. The saltpetre separates into lon<* prisms. SOLUTION AND CRYSTALLIZATION. 53 containing no trace of the common salt, and the latter separates into cubes, entirely free from saltpetre. Thus the particles of salt and saltpetre did not attract each other; but upon crystallizing out of the solution, the homogeneous salts assumed separately a regular form, precisely as if one only of these two substances had been dissolved. 54. In our" climate, water takes a solid form during the winter only, and it is well known that, as snow or ice, it often forms the most regular crystals. But it also exists in a solid form in many bodies where we should not expect to find it; one pound of iron-rust, for example, contains nearly three ounces, and one pound of slaked lime four ounces, of water, and yet both are apparently dry. This water is said to be chemically combined. It also unites with other solid bodies, for which it has an affinity. Such combinations of solids with water are called hydrates. It is also frequently present in salts, as can be shown in a simple manner in the case of the well-known Glauber salts.^^^.t^(X - «[j ^L&^L^. Experiment — Place half an ounce of crystallized Glauber salts in a warm place, when it will soon lose its transparency, and finally crumble into a white powder, weighing hardly a quarter of an ounce. That which has been lost was water, and it is evident that it was this water which gave to the salt its crystalline form and transparency, these both vanishing with the escape of the water. For this reason the water, on which depends the crystalline form of many salts, is called the water of crystallization. Saltpetre and com- mon sajtj treated like Glauber salts, lose nothing in -zX**^-*^* weight, neither do they become opaque nor pulverulent; ^L^-c<^ l they contain no chemically combined water. 5* 54 WATER AND HEAT. Fig. 24. COMPOSITION OF WATER. 55 Besides that electricity, which we admire on a erand scale in the majestic phenomena of lightning, frwhich we generate on a small scale by rubbing li'us bodies'together, a second kind of electricity is also recognized, which is called galvanic force, or gal- vanism. This has attained great importance in chem- istrv as by means of it the chemist is enabled to de- compose almost all chemical combinations, even into their component parts or chemical elements. By gal- vanic force water can easily be decomposed into its ele- mentary parts. This sort of electricity may be gener- ated in various ways; it is developed in every chemical combination or decomposition, indeed quite frequently when heterogeneous substances, whether solid, liquid, or aeriform, are brought into contact The oldest and most common gal- vanic apparatus is the voltaic pile, in which electricity is excited by the contact of two different metals, commonly zinc and copper. A cop- per plate placed upon one of zinc is called a pair of plates; many such pairs are laid, one above the other, each pair being separated by a piece of cloth moistened with salt water. The relative position of the met- als in each pair must be observed throughout the whole series, so that, if the pile commences with a zinc plate, it shall terminate with a cop- per one. These two extremities are COMPOSITION OF WATER. 55 called the poles. Zinc is called the -f- pole, and copper the — pole; they are provided with metallic wires, that the electric or galvanic stream which is excited in the pile may be conveyed to any place desired. When the two ends of the wires are brought very near to each other, sparks are seen to dart from one to the other; this is a token of the galvanic current, manifesting itself in the same manner as the current of the electrical ma- chine. To decompose water by means of this pile, the two wires, being previously tipped with platinum, are con- ducted into a vessel of water, and two test-tubes, filled with water, are inverted, one over the end of each wire; there are evolved from the ends of both wires small bubbles of air, which ascend into the test-tubes, gradually displacing the water from them. From the -f- or zinc wire, only half as much gas is generated as from the other; consequently the tube connected with the zinc will only be half emptied by the time the water from the other is entirely expelled, and a glowing shaving introduced into it will burst into a brilliant flame ; it is called oxygen gas (O). The gas evolved from the — or copper end, on the contrary, ex- tinguishes this shaving; but the gas will burn spon- taneously if kindled by the flame of a lamp, held over it; — it is called hydrogen gas (H). These are the component parts of water; it consists of one measure (volume) of oxygen, and of two measures of hydrogen. From one measure of water, when decomposed into its elements, several thousand measures of these two gases may be obtained. 56 METALLOIDS. NON-METALLIC ELEMENTS, OR METAL- LOIDS. FIRST GROUP: ORGANOGENS. OXYGEN (O). At. Wt.= 100. - Sp. Gr. = 1.1. 56 Oxygen mav be obtained in great quantities from water, by means of the galvanic battery; but in a more simple manner as follows. Experiment — Introduce into a somewhat tall, but not too thin, test- Fg26- tube, 109 grains of red oxide of mercury. One end of a bent glass tube is adapted to it by means of a per- forated cork, and the other end is conducted into a vessel filled with water. Either suspend the tube by means of a piece of cord or wire, or support it by a retort-holder. vJtj&&>>, ju- A retort-holder is a wooden stand provided with a mov- api^M. able vice, by which glass vessels can be held in the most convenient manner, as shown in the annexed figure. Then heat the test-tube until all the oxide of mercury has disappeared. The red powder becomes black as the heat increases, and bubbles of air escape, which are collected in a glass bottle held over the end OXYGEN. 57 of the tube, this bottle having been previously filled with water and then inverted into the bowl, after clos- ing the mouth of it with the finger or a glass plate. No water will escape until bubbles of air from the tube are passed into it, which, on account of their greater levity, ascend and displace the water. When the water is displaced, remove the bottle and close it with a cork, replacing it with another bottle, likewise previously filled with water, and repeat this process until the evolution of gas ceases. The first bubbles that pass over consist of atmospheric air contained in the test- tube, but the oxygen gas quickly succeeds. This is one of the component parts of the red oxide of mercury, and can easily be recognized by the vivid combustion in it of a glowing shaving. At the same time there is formed on the upper part of the test-tube a brilliant metallic mirror, which consists of mercury, the second element of the red oxide. When the latter has entire- ly disappeared, immediately withdraw the tube from the water, let the test-tube cool, and unite the mercury adhering to its walls into a single globule, by means of a feather. It will amount in weight to 101 grains ; this, subtracted from the original weight, 109 grains, leaves 8 grains, the amount of the oxygen. The red powder consists of a brilliant heavy metal and of a gas, two entirely dissimilar bodies. If these are chem- ically combined together by proper means, they will unite again to a red oxide, a body in which the pecu- liar properties of mercury as well as of oxygen are en- tirely lost. 57. This experiment shows, also, how the force of heat alone can destroy a chemical combination, or in other words the affinity of two bodies for each other. This can be explained as follows. Chemical affinity 58 METALLOIDS. acts only at imperceptible distances, consequently only when bodies are in closest contact; heat counteracts this power, for it exerts an expansive action, and conse- quently separates the constituent particles from each other. In the cold, or at ordinary temperatures, the single particles of the quicksilver (Q) and oxygen (O) are so closely united, that chemical a F's2' 6 force is sufficient to hold them to- (q) (q) gether (a, Fig. 27); but at an increased ^\ temperature they are so far separat- ed (b), that the influence of chem- ical attraction is overcome. This occurs so much the more readily in this instance, as both the quicksilver and oxygen, having, when heated, a strong tendency to become aeriform, help likewise to counteract the chem- ical force. 58. The bottles containing the oxygen appear to be empty, for oxygen is as colorless and invisible as com- mon air, and is without odor or taste. In German it is called Sauerstoffluft, signifying sour gas. Experiment. — Introduce a glowing shaving into a bottle of oxygen; it will kindle and burn for some time with great brilliancy and a very dazzling flame, and then be extinguished. The same takes place when a piece of lighted tinder is affixed to a wire and sus- pended in the oxygen; the tinder burns with a lively flame, while, as is well known, it merely smoulders away in the open air. Oxygen possesses, at a high temperature, a strong affinity for the component parts of wood and tinder; that is, it combines with them with great energy, and consequently with the development of heat and light. When the combination has ended, and the oxygen is consumed, the combustion ceases. The product of the combustion, that is, the combina- OXYGEN. 59 tion of the wood with the oxygen, is also aeriform; but burning substances are extinguished in the newly formed gas. If the bottle be rapidly whirled round, the gas formed by the combustion will escape, and atmos- pheric air will supply its place. Air contains free oxy- gen ; and a kindled shaving will burn in it for some time, but far slower and less briskly than in pure oxy- gen ; because common air contains only one fifth part of oxygen. Accordingly, a combustion in oxygen pro- ceeds five times more rapidly and violently than in at- mospheric air. 59. Experiment. — To prepare a larger quantity of oxygen, take one hundred grains of chlorate of potassa, and heat it in the same manner as described in the former experiment; the salt will soon melt, and after- wards boil. As soon as the boiling commences, the flame must be diminished, to prevent the mass from foaming over. When the liquid thickens, if some of the substance should be found adherent to the colder parts of the test-tube, approach it with the flame of the lamp, until it is again melted down. As soon as the gas ceases to be generated, draw the tube immediately from the water. 60. For collecting gases in larger quantities, the fol- lowing contrivance may be resorted to. Make a shelf out of slate or a piece of lead, some inches broad, and so long that it will rest about half way up the sloping walls of the vessel in which it is to be placed; bore a small hole through the centre of the shelf with some appropriate instrument. When wanted for use, pour into the vessel as much water as will be sufficient to cover the shelf 60 METALLOIDS. an inch deep, and then invert the vessel intended for ! the reception of the gas, with its mouth exactly over i the opening, placing the extremity of the glass tube, | from which the gas proceeds, directly beneath, so that the gas may enter it as through a funnel. This con- trivance is called a pneumatic trough. In order to col- lect and preserve larger quantities of gas, and to ex- periment with them more conveniently, special contriv- ances, called gasometers, are used in chemical labora- S tories. 9s Oy ~k>£<3i-<, 61. Chlorate of potassa contains for every one hun- dred grains about forty grains of oxygen chemically combined; by the application of heat, these become free and escape. Red oxide of mercury contains only eight per cent, of oxygen; therefore the former will yield five times more oxygen than the latter. If vials of twelve ounces' capacity are selected for receiving the gas, we shall be able to fill five of them, and shall have in each about eight grains, or nearly twenty cubic inches, of oxygen. Chlorate of potassa may, under some circumstances, as when strongly rubbed, or treated with sulphuric acid, occasion very dangerous explosions; but no dan- ger is to be apprehended from the application of it, when made as above directed. 62. Experiment. — Add warm water to the salt re- maining in the test-tube after the expulsion of the oxy- gen, and place the tube in a warm place until the salt is dissolved; evaporate the solution gradually, over a stove, when small cubic crystals (chloride of potas- sium) will be deposited. The chlorate of potassa crys- tallizes in thin tables or plates, the heated mass*in cubes; this difference in the form of the crystals alone indicates that, by the heating of the former,' an entirely OXYGEN. 61 new salt is formed, and one, indeed, which no longer contains oxygen. The following diagram will illus- trate this more clearly. Chlorate of potassa consists of Chloric ^Oxygen______________—.Oxygen Acid < Chlorine__ (escapes as gas.) and $ Oxygen Potassa (p0tasSium Chloride of potassium (remains in the tube.) Experiments with Oxygen. 63. Experiment a. — Fasten a piece of charcoal to a wire, and kindle it in the flame of a lamp, and then in- troduce it into a bottle of oxygen; it will burn very vividly, and with a flame. If a piece of moistened blue litmus-paper (§ 48) be introduced into the bottle, after the combustion, it will be reddened; consequently an acid gas has been formed from the charcoal and the oxygen; it is called carbonic acid. Close the flask, shake it a few times, and place it aside. 64. Experiment b. — If some pieces of sulphur are fastened to a longer wire, kindled and sus- pended in a second bottle, they will burn with a beautiful blue flame. The gas formed from this union of sulphur and oxygen has a very irritating odor; it like- wise turns litmus-paper red, and conse- quently it is of an acid nature. It is called sulphurous acid. This bottle is also closed and preserved for future use. 65. Experiment c. — Take a small piece of phos- phorus, which, on account of its inflammability, must be cut off under water from the stick, and place it, after having been well dried between blotting-paper, 6 Fig. 29. 62 METALLOIDS. Fig. 30. in a scooped-out piece of chalk. Fasten the latter to a wire, and introduce it into a third flask of oxygen. Affix the wire to a transverse piece of wood, so that the chalk may hang a little below the centre of the bottle. If the phosphorus be now touched with a hot wire, it will kindle and burn with a dazzling brilliancy, filling the bottle with a thick white smoke. This smoke consists of a chemical combination of oxygen and phosphorus; it reddens the blue test-paper, consequently is also an acid; it is called phosphoric acid. If the bottle be allowed to stand for a time, the smoke will sink to the bottom, and dissolve in the water previously put there, which thus acquires an acid taste. 66. In the same way as the tasteless coal and sul- phur and the phosphorus acquire, by combination with oxygen, acid properties, so many other simple bodies are converted by oxygen into acids ; this is the reason why it has received the name oxygen, derived from two Greek words, one of which signifies acid, and the other to generate. Thence the words oxidate and oxide, so frequently occurring in chemistry. Oxidate signifies to unite with oxygen, to burn; oxide is the product of the combination, and signifies a burnt substance, that is, a substance combined with oxygen. The acids just alluded to may also be called acid oxides. 67. Experiment d. — Fix securely to a wire a piece of sodium, and let it remain for some hours in a bottle filled with oxy- gen ; it becomes converted into a white mass, which easily dissolves in water. The solution obtained has an alkaline taste, similar to lime-water; the color of blue Fig. 31. OXYGEN. 63 test-paper is not changed by it, but it turns red test- paper blue; this is a combination which may be re- garded as the opposite of acids; it is called oxide of sodium. Let this also be kept for future use. The metal sodium has such an extraordinary affinity for oxygen, that it quickly attracts it from the air. Therefore, to preserve it unchanged, it must be kept in some liquid containing no oxygen; as, for instance, in naphtha or petroleum. 68. Experiment e. — A piece of fine iron wire is so wound round a slate or common lead pen- cil, that, on the withdrawal of the latter, the wire may have a spiral form. Fasten the upper part of this wire, as in experiment c, to a cross-piece of wood, and place on the lower end of it a small portion of tinder. When this is kindled, introduce the wire into the oxygen; the burning tinder heats the iron to redness, which then burns brilliantly, throw- ing out sparks. The iron, when red-hot, combines with the oxygen. The burnt or oxidized iron (iron scales) melts, and falls to the bottom in globules, which are so hot that they are liable to melt into the glass, though it be partly filled with water. This heat, as in the preceding case, is the result of chemical combination taking place. Oxide of iron is insoluble in water, and for this reason it affects the color neither of the blue nor of the red test-paper; if it were soluble, it would, like oxide of sodium, convert the red into blue paper. 69. Such combinations of oxygen as are not acid, but agree in their properties with the oxide of sodium or of iron, are called bases or bake oxides. Most of the combinations of the metals with oxygen belong to the bases. 64 METALLOIDS. 20 " iron, 1 " hydrogen, 70. By the foregoing experiments on oxidation, the question recurs, — How much carbon, sulphur, &c, have the eight grains of oxygen contained in each bottle consumed or taken up ? The reply is,— They have taken up different quantities. They have united as follows: — 8 grs. of oxygen with 3 grs. of carbon, forming 11 grs. of carbonic acid. 8 « u « 8 " sulphur, "16 " sulphurous acid. 6£ " phosphorus," 14i " phosphoric acid. 23 " sodium, " 31 " oxide of sodium. 28 " black oxide of iron. 9 " oxide of hydrogen (water). Carbonic acid may be prepared in different ways, but it is always so constituted as to contain eight grains of oxygen united with three grains of carbon, and this same regularity exists in all the above compounds, as indeed in all chemical combinations. It is a law of nature; chemical combinations always take place accord- ing to certain fixed proportions by measure^ or weight. This doctrine is called Stochiometry (from o-Toixetov, ele- ment, and fikrpov, measure). 71. Experiment.— The liquid in the vessel c red- dened blue test-paper, and had a sour taste; the liquid in the vessel d, on the contrary, turned the red paper blue, and had an alkaline taste. Add the latter slowly, and at last only by drops, to the former, testing the mixture frequently with a strip of blue and of red test paper; there will be a point when the color of these two papers will no longer be changed. The acid and alkaline tastes have likewise disappeared, and the mix- ture has acquired a slightly saline taste; it is neutral. The phosphoric acid has chemically combined with the oxide of sodium, forming a new body having no similarity to either of the substances of which it was OXYGEN. 65 composed. To obtain a better knowledge of it, let the liquid remain in a warm place until the water has evaporated, when small crystals will be deposited. Such a combination, consisting of an acid and a base, is called a salt. This salt, phosphate of soda, is called soluble, because it assumes a liquid form upon the ad- dition of water. 72. Experiment. — Pour into the bottle which con- atined the carbonic acid gas (experiment 63), some « lime-water (§ 46), and agitate it; the liquid will be- come milky, and after standing, a white powder will subside. The lime in the lime-water is a base, as well as the oxide of sodium; the lime combines with car- bonic acid, they mutually neutralizing each other ; but the salt which is formed (carbonate of lime or artificial chalk) is insoluble in water, and hence separates from it. That the carbonic acid here disappears, and is con- densed into a solid body, is indicated by the suction exerted upon the finger with which the mouth of the bottle was closed during the shaking, and the rushing in of air after its removal. 73. Experiment. — Quite the same thing occurs, when lime-water is poured into the bottle of experi- ment 64; the irritating odor of the sulphurous acid contained in it vanishes, owing to its combining with the lime. The salt formed (sulphite of lime) is diffi- cultly soluble in water. 74. Experiment. — Pour gradually into the bottle of experiment 68, one dram of common sulphuric acid. It heats on uniting with the water; and, after repose and frequent agitation, the red oxide of iron which col- lects on the sides of the vessel, as well as the black oxide of iron at the bottom, will dissolve. In this case, also, a salt is formed, since the base (oxide of 6* 66 METALLOIDS. iron) has united chemically with the acid; the yellow- ish liquid holds the iron salt in solution. 75. Degrees of Oxidation. — Oxygen is a universal food for all elements ; it is consumed by them, and, as already stated, in fixed quantities. But the appetite of an element for oxygen often varies according to the circumstances under which the latter is presented to it; for example, it is greater under the influence of heat than of cold, greater where there is an excess than where there is a deficiency of oxygen. Hence many elements frequently consume greater quantities of it at a high than at a low temperature, and when the sup- ply is copious than when it is deficient; and this ex- cess or diminution of consumption is likewise pre- scribed by fixed laws. The different proportions in which substances unite with oxygen are called its de- grees of oxidation. 76. When sulphur is burnt in oxygen gas or in the air, it combines with oxygen, forming sulphurous acid; but it can be made to unite with one half as much more oxygen, and then sulphuric acid is formed. When phosphorus is rapidly burnt, it forms with oxygen phosphoric acid; but if it be exposed to the air without the application of heat, or be burnt with im- fl #3 perfect access of air, then phosphorous acid is princi- pally formed, which contains two fifths less oxygen than phosphoric acid. Accordingly, by the terms sulphuric and phosphoric acids, are to be understood combinations with more oxygen; by the terms sulphurows and phosphorous acids, combinations with less oxygen. If an element yields more than two acids with oxygen, then new names are formed by prefixing to the acids the terms per or hypo; for instance, perchloric acid, hyposulphuric and hyposulphurous acids, &c. OXYGEN. 67 77. Besides the red oxide or peroxide of quicksilver (§56) there is yet another combination of quicksilver with oxygen, which is black, and contains only half as much oxygen as the former; it is called the protoxide of quicksilver. Iron also forms two combinations with oxygen; one of a reddish-brown color (sesquioxide of iron), and the other of a black color, containing one third less oxygen (protoxide of iron). Accordingly a peroxide or a sesquioxide is the combination of a metal with a greater quantity of oxygen, and a protoxide is a combination with a less quantity of oxygen. Many metals have the power of uniting in more than these two proportions with oxygen; in this case, the combi- nation with a less quantity of oxygen than in the pro- toxide is called suboxide, but that with more oxygen than in the per- or sesqui-oxide, is called hyperoxide. Neither the lower nor the higher oxides act as bases, that is, they will not unite directly with acids to form salts; but, nevertheless, this may happen when the sub- oxide receives so much oxygen, or the hyperoxide parts with so much, as to form, in either case, per- or sesqui- oxides or protoxides. Some metals in their highest state of oxidation possess no longer basic properties, but, on the contrary, acid properties (metallic acids). 78. If we compare the different quantities of oxygen which one and the same body can take up, they will always be found in very simple proportions; for in- stance : — In sulphurous and sulphuric acids, as 2 to 3. " phosphorous and phosphoric acids, " 3 to 5. " protoxide and peroxide of mercury, " 1 to 2. " protoxide and sesquioxide of iron, " 2 to 3. A similar regularity exists in all other chemical com- binations. 68 METALLOIDS. 79. The hyperoxides easily give up a part of their ox- ygen, either when heated alone or with certain acids; hence they can be made use of for obtaining oxygen. An oxide of frequent occurrence in nature is the hy- peroxide of manganese, used for coloring potters' ware brown. It is a combination of the metal manganese with oxygen. Oxygen is usually obtained from this when wanted in large quantities, as it can be put in an iron vessel and heated to a bright redness. If the manganese is heated alone, one third of the oxygen contained in it is obtained, and red oxide of man- ganese remains behind; but if heated with the addi- tion of sulphuric acid, one half of its oxygen is ob- tained, and the remainder is protoxide of manganese, which combines with the sulphuric acid, forming a salt. 80. Oxygen is absolutely necessary to all living crea- tures. All the air which we breathe must contain free oxygen; if this is wanting, suffocation is induced. The chemists who discovered it seventy years ago, and first prepared it pure, gave to it, for this reason, the name of vital air. In later times it was designated Zjt*''flVfi?<3ji/ empyreal air, because it was found that every combus- 1T'(/P/s(olJ-< tion, however familiar to us, was a process of oxida- tion, in which the oxygen of the air combined with the particles of the burning material. The symbol for ox- ygen is O, the first letter of oxygen. It has been agreed to express simple bodies by the first letters of their Latin names. HYDROGEN (H). j O At. Wt. = 12^5. — Sp. Gr. = 0.068. 81. Experiment. — Boil some water for fifteen min- utes, that all the air contained in it may be expelled * let HYDROGEN. 69 it cool, and fill a bowl and a test-tube with it; close the latter with the finger, and invert it under the water in the bowl. Now secure to a wire a piece of sodium, of the size of a lentil, and thrust it quickly under the opening of the test-tube; the metal frees itself from the wire, and, as it is lighter than water, it ascends into the tube, floating there with a circuitous motion; a gas is evolved from the water, which in a few moments be- comes displaced by the gas from the tube. This kind of gas is the second element of water, and is called hydrogen. The experiment in § 67 demonstrates that sodium has a very great affinity for oxygen, and this affinity is so strong, that the sodium removes from the water its oxygen, whereby the hydrogen is liberated. Close the tube again with the finger, remove the tube from the vessel, and hold a burning taper over it, when the gas will burn with a flame. Hydrogen is a com- bustible gas. If the interior of the moist tube be tested with a strip of red test-paper, this assumes a blue color. The same base, oxide of sodium, has been formed as when the sodium was exposed to oxygen or to the air. It is dissolved by the water. 82. What sodium accomplishes at ordinary tern- Fig. 34. peratures, iron cannot do until it is heated to redness. 70 METALLOIDS. Pass water in the form of steam, obtained by boiling the water in the retort, a (Fig. 34), through a red-hot iron pipe containing a spiral wire; for instance, a gun- barrel. At this high temperature the iron in the pipe unites with the oxygen in the water, forming black ox- ide of iron, and the hydrogen is set free. This is the method by which the celebrated French chemist, Lavoi- sier, sixty years ago, proved that water is not a simple body, but consists of two gases, oxygen and hydrogen. 83. The decomposition of water by iron is more ea- sily effected through the presence of an ally, which sup- ports the iron in its endeavour to extricate the oxygen from the water. Such an all/ is sulphuric acid. Experiment — Put a quarter of an ounce of wrought- iron filings into a flask, and pour over them two and a half ounces of wa- ter. No action takes place, but if half an ounce of common sulphuric acid be gradually added, at the same time keeping the flask in constant motion, ebullition and heating of the liquid will immediately ensue. The ebullition is caused by the evolution of a species of gas, hydrogen. Insert into the opening of the flask a perforated cork, to which is fitted a bent glass tube. Allow the first por- tions of the gas to escape, then collect it, as the oxygen was collected, in a flask filled with water over the pneumatic trough. There is one indispensable caution to be observed in experimenting with hydrogen, which is, not to admit the gas into the receiver until all the atmospheric air t'.c- isting in the flask has been expelled, as otherwise an ex- plosion might take place. HYDROGEN. 71 Fig. 36. 84. Experiment. — If sulphuric acid is poured into water, considerable heat is evolved ; but this heat is much stronger when the water is poured into the sulphu- ric acid. The mixture is best made in the following manner. Pour two and a half ounces of water into a sufficiently large stone jar, which is placed in a bowl filled with water; now weigh in a flask half an ounce of^ommon sulphuric acid, pour this *2 (tf&yuC'j in a small stream into the water, stirring the water con- tinuously with a glass or porcelain rod, and let the jar remain in the bowl until it is entirely cold. This mix- ture is called diluted sulphuric acid; the strong acid, on the contrary, is called concentrated sulphuric acid. 85. Experiments with Hydrogen. Experiment a. — Inflame hydrogen con- tained in a flask, and immediately pour in some water. The water does not extin- guish the flame, but rather increases it, since it rapidly forces the gas out of the flask. The gas does not burn in the in- terior of the vessel, but only on the out- side, where it is surrounded by atmos- pheric air. Experiment b. — Hold an empty tumbler over a flask of hydrogen for some minutes, then quickly invert the former, and apply to it a lighted taper, when a flame will burst forth from the tumbler with a whizzing noise. The gas has ascended from the flask into the tumbler, and is consequently lighter than common air. In this experiment the lower vessel must not be immediately exposed to the lighted taper, because, if all the hydrogen 72 METALLOIDS. is not displaced, an explosion might ensue that would break the flask; but if the taper be applied after ten minutes have elapsed, the flask will be found no longer to contain any combustible gas, this having entirely es- caped. Hydrogen is the lightest of all gases; 14i measures of it weigh only as much as one measure of atmospheric air. On account of its levity, it is used for filling bal- loons. Experiment c. — If, instead of the glass tube, a piece of pipe-stem be adapted to the cork of the flask from which hydrogen was evolved, and the gas then lighted, it will burn like a taper. To kindle the gas, instead of a match or a taper, very finely divided platinum may be employed. This can be prepared in a few minutes by dropping a solution of platinum on blotting-paper, at- Fi gg taching it to a wire, and igniting it over a spirit-lamp, till nothing but a gray coherent ash remains. The platinum is thus re- duced to an extremely minute state of sub- division, and in this state it exhibits the remarkable property of igniting in hydro- gen and inflaming it. It is called spongy platinum, and is employed as tinder in the well-known Dobereiners inflammable lamp. The apparatus here represented consists of a syphon, b (Fig. 39), fitted perfectly air-tight at c into the lower vessel, v; the lower part of the syphon is encompassed by a cylinder of zinc. If diluted sulphuric acid is now poured in, hydrogen is evolved, the pressure of which forces back the liquid into the vessel b, until the piece of zinc is no longer in contact with the liquid. Upon opening the stop-cock, r, the gas issues from the fine jet, t, and is directed against the spongy platinum. As the HYDROGEN. 73 Fig. 39. gas escapes, the sulphuric acid de- scends again into the lower vessel, and generates fresh hydrogen upon reaching the zinc. Spongy platinum possesses, in a high degree, the pow- er of absorbing oxygen and condens- ing it within its pores; if hydrogen be then presented to it, these two gases will be brought into such in- timate contact, by the powerful force of attraction, that they will chem- ically combine to form water, and the heat thus liberated is sufficient to ignite the pla- tinum tinder, and to inflame the gas, which subse- quently issues from the jet. Many aeriform bodies, which do not freely unite with each other, can be forced to combine by means of spongy platinum. 86. Explosive Gas. — The extraordinary degree of heat developed by the chemical union of oxygen and hydrogen may be shown by the following experiments. Insert into the opening of a large pig's bladder, which has been softened by soaking in water, the broken-off neck of a flask, and bind it firmly round with a string. Then select two perforated corks, fitting this neck. One cork is connected with a bent glass tube, conducting the oxygen from the apparatus in which it is evolved (§ 59) into the bladder, which soon becomes filled with it. When this operation is finished, replace the first cork by the second, having a glass tube adapted to it only a few inches long and drawn out to a point at its outer end, and provided with a wax stopple pressed upon the opening. A glass tube may be formed into a point by heating it in the flame of a spirit-lamp, constantly turn- ing it round at the same time, till it becomes so soft 7 74 METALLOIDS. Fig.4o. at the desired place, as to be easily drawn out. Break it at the slender part, and hold it in the flame for some moments, until the sharp edges are rounded off by incipient melting. It would be more convenient, though somewhat more expen- sive, to substitute for the above contrivance a jet provided with a small brass stop-cock. The bladder thus arranged and filled with oxygen is now placed on blocks, at such a height that the point of the glass tube shall be on a level with the hydrogen flame, produced as explained in a former experiment. Press upon the bladder with the hand, and the oxygen will escape, blowing into the hydrogen flame, which then takes a horizontal direction. This flame has but little brilliancy, less than the hydrogen flame alone, not- withstanding which it affords the (greatest heat yet known.) Hold in it a platinum wire, a metal which has never yet been melted in the hottest furnace, and it will melt like wax; hold in it a piece of chalk scraped to a fine point, and it will emit light (sidereal light) of the most dazzling splendor. A watch-spring or a fine iron wire burns in it, throwing out sparks as in oxygen. (§68.) But what is the cause of this powerful heat? It is the result of the energetic chem- ical combination of two substances with each other. Every chemical combination or decomposition is attended with liberation of heat. Exact experiments have shown that two measures of Fis. 41. HYDROGEN. 75 hydrogen unite with one measure of oxygen, conse- quently in just the same quantities as obtained in the decomposition of water by galvanism. (§ 55.) The re- f x suit of the combination is water. But two measures oi^f^y^^f^^ hydrogen and one of oxygen do not yield three meas- tik\ &t*4ut.~i urcs of vapor; they afford two measures only. Thus-^ ^ the two gases condense one third by chemical union, q-t ,*^*y /. t If both the hydrogen and oxygen were suddenly mixed <«—^, fc together and then ignited, the whole mass would com-^?^///„ bine together at once, producing a most violent report,*? and bursting the vessel to pieces) Such a gaseous mix-' ture is called, for this reason, explosive gas. No dan- ger is to be apprehended from the apparatus described, as the explosive gas is formed at the point where the oxygen meets the hydrogen flame, and only in small quantities at once. This apparatus is an oxy-hydrogen blowpipe on a small scale. Hence explosive gas may be regard- ed as chemically decomposed water, and water as chem- ically combined explosive gas, or as burnt hydrogen. Fig. 42. 87. Experiment. — That water is really formed during the combustion of oxygen and hydrogen, or when they chemically unite, can easily be shown by inverting a flask over the hydrogen flame; the glass soon becomes clouded over, because the water, which at this heat is generated in the form of steam, condenses in small globules on the cold sides of the glass. By this method one full meas- ure of water has been obtained from one thousand measures of oxygen and two thousand measures of hydrogen. By the decomposition of water (analysis), and by combining together its elements (synthesis), it is proved to consist, in volume, of one measure of 76 METALLOIDS. oxygen and two measures of hydrogen, yielding two measures of vapor; in iveight, of eight parts of oxygen and one part of hydrogen, yielding nine parts in weight of water. The great difference between the numbers of the measures and those of the weight depends on the fact, that one measure of hydrogen weighs sixteen times less than one of oxygen. On account of the property pos- sessed by hydrogen when combined with oxygen of forming water, the name Hydrogen (generating water) has been given to it; its chemical symbol is according- lyH. 88. The chemical symbols, which, as previously stated, are derived from the initials of the Latin names of the elements, present not only a very convenient and simple mode of designating the elements, but they represent also their atomic weights, which are given at the head of the different sections. Consequently O signifies not merely oxygen, but 100 parts in weight of it (pounds, ounces, grains, &c.); H, not only hydrogen, but also 12^ proportions in weight of it. When two elements are in combination, this is designated by uniting together their symbols; H O, for instance, is the formula for water, and this indicates, not only that water consists of hydrogen and oxygen, but also that it is composed of 12£ parts in weight of hydrogen (1 At. H) and 100 parts of oxygen (1 At. O); or what is the same thing, of 1 part of H and 8 parts of O in weight. In more complex combinations, the different members are sepa- rated from each other by a comma, or the sign -f, as will be seen in the following sections. The smaller num- bers in the formula placed below the letter modify only the symbol immediately preceding, but the larger num- bers prefixed to the sign modify all the symbols as far HYDROGEN. 77 as the next comma or -J- sign. EL, signifies accordingly two atoms of hydrogen, H,, three atoms, &c.; but 2HO indicates two atoms of hydrogen and two atoms of oxygen, &c. It is earnestly recommended to every be- ginner in chemistry to familiarize himself with this com- prehensive language of symbols. 89. The change which iron underwent, when, by the aid of sulphuric acid, it decomposed water and liberat- ed the hydrogen, remains now to be considered. Experiment. — Pour the contents of the flask of ex- periment 83 into a porcelain dish, heat them to boiling, and filter them. A black residue will remain on the filter, which consists of carbon that was contained in the iron; the iron itself has been dissolved, and has passed through the filter; it is no longer iron as such, but has been converted into a salt of iron, which, on the cooling of the solution, is deposited in green, trans- parent crystals. The formation of it is explained in the following diagram: — Water = oxygen and hydrogen Iron_________/ = oxide of iron *fy tv.iAS.y Sulphuric acid__________/ = salt of iron. This salt is accordingly called sulphate of iron, com- monly known as green vitriol. Iron and sulphuric acid cannot combine directly with each other, for it is a rule in inorganic chemistry, with but few exceptions, that simple bodies unite only with simple bodies, and com- pound only with compound bodies; however, this com- bination can take place when the iron is oxidized, and thus converted into a compound body. The water contains the oxygen requisite for this purpose, but the iron has not power enough to extricate it without the assistance of the sulphuric acid, which, having a strong 7* 78 METALLOIDS. affinity for a base, cooperates with it and enables it to overpower the water, and a base is formed (protoxide W of iron) which immediately unites with the sulphuric acid. The liberated hydrogen escapes as gas. This sort of affinity is called disposing affinity. Zinc is frequently used instead of iron in the prep- aration of hydrogen. AIR. 90. The earth is surrounded by air, as by a mantle; «t ptej/trvUit is called the atmosphere, and is supposed to extend tfcf>i«.f*> ■<■ about forty-five miles above the solid earth. Theairpos- ^ Um , sesses no color, and is transparent; hence it is invisible, and its particles are so easily displaced that it cannot be grasped by the hand. But it is rendered obvious that the air is material, and fills every space commonly called empty, by wrapping moist- ened paper round a funnel, so that it may fit exactly into the mouth of a flask; if the fun- nel be now filled with water, the fluid will not run into the flask, as the air contained in the latter will not let it enter ; but if the fun- nel be raised a little, the air escapes, and the water immediately rushes into the flask. We learn also by the balance that a flask con- taining atmospheric air weighs more than it does when the air has been exhausted from it. But air is so light $VK'V,w,U.\)[YdX 800 measures of it weigh only as much as one measure of water, yet the atmosphere presses with great weight on the earth and upon every thing there- on. But this pressure is only noticed when the air is removed from a place, thus leaving it without counter- pressure. AIR. 79 91. Pressure of the Atmosphere. — Experiment — Wrap some tow round one end of a stick, and grease it with tallow, thus forming a plug, which must be fitted tightly into a strong test-tube. Boil some water in the test-tube, and when the air has been expelled by the steam, causing a vacuum, insert the plug; as the water cools, the plug will be pressed down upon the surface of the water; by heating, it is again forced up by the steam thus generated, and by immersing in cold water it is again forced down. Fig. 44. jn consequence of the cooling and condensation of the steam a vacu- um is formed, and therefore the counter-pressure against the weight of the exterior air is removed; the pressure of the latter, accordingly, forces down the plug. On this principle, the piston is forced up /Ja^^o/ -f< and down in the cylinder of rnany.^ ^?. steam-engines. 92. This pressure often causes the rising and falling of liquids in tubes. Experiment—If water is boiled as was directed at §36, 80 METALLOIDS. 3- by means of steam, and during the boiling the lamp is removed, then the pressure of the air acting on the surface of the water in the bSaker-glass will very soon force the water contained in it through the tube back into the flask, which in a short time becomes quite filled with water. The counter-pressure of the steam must naturally decrease as it cools and condenses. As long as the lamp is under the flask, the pressure of the steam is stronger than that of the air, and the steam, being continually generated, forces the air previously contained in the flask into the water of the beaker-glass. This reflux of liquids is particularly to be feared, when such kinds of gases are con- ducted into water as are absorbed by it read- ily, and in large quantities. This is pre- vented by passing through the cork a second , glass tube open at both ends, and letting it reach nearly to the bottom of the flask, by which tube air can penetrate into the flask as the pres- sure of steam diminishes. This contrivance is called a safety-tube. 93. Barometer. — It has been proved by exact calcu- lation that the atmosphere presses upon the earth with a force equal to that of a layer of quicksilver 30 inch- es deep, or a layer of water 13^- times deeper (34 feet), water being 13 } times light- er than quicksilver. The instrument by which the amount of atmospheric pressure can be determined is called the barometer. Fig. 47. Water 34 feet kig-fi -J^jSer 30 inches ^ |ggj||llt Surface of the earth. AIR. 81 Fill a glass tube, 32 inches in length, one end of which is closed, with quicksilver; close it with the finger, and invert it into a vessel of quicksilver; on removing the finger, the mercury will not run out, but will fall some Fig 48. inches, perhaps to s (Fig. 48). The height pi of the quicksilver, from a b to s, amounts to about 30 inches. The quicksilver does J ' not fall lower, on account of the external : pressure of the atmosphere, which is ex- erted on the quicksilver at a b, and not S at s, since this end is closed. The col- \ umn of quicksilver in the tube may be s regarded as the counterpoise to the at- mospheric pressure, and it is hence con- j eluded that the latter exerts just as much S pressure upon the earth as a column of » quicksilver 30 inches high. If the tube be opened at the top, the pressure of the air on both extremities being then made equal, the quicksilver will flow from the tube. The space above the quicksilver, at s, is a vacuum, and is Fig. 49. called the Torricellian vacuum, from the name of the inventor. In common barom- eters the tube is curved at the bottom, and provided with a bulb. This bulb is open at the top, and supplies the place of the vessel filled with quicksilver in the preceding fig- ure. Here also the pressure is only exerted at one extremity, for the atmosphere can only press on the mercury contained in the bulb. The height from o (Fig. 49) to the top of the quicksilver amounts to about 30 inches. If weights be placed on one pan of a balance, the 82 METALLOIDS. opposite one will rise, but on their removal it will sink. The same thing happens with the barometer. Any in- crease in the weight or density of the air presses the quicksilver up, and the barometer rises; but any di- minution of weight will make it fall. The height of the quicksilver may be read off by affixing to the upper part of the tube a scale divided into inches and tenths of an inch. The mean state of the barometer is at 30 inches, and 31 is called a very high, and 29 a very low, state of the barometer. In this part of the coun- try, as a general rule, the north and west winds cause the barometer to rise, and the south and east winds cause it to fall. The former winds, blowing chiefly from the land, are cooler, and at the same time drier, than the latter, which pass over the ocean, there be- coming saturated with moisture; the former likewise come from colder into warmer, while the latter, on the contrary, proceed from warmer into colder regions; by which the capacity of saturation for vapor is increased in one case and diminished in the other. Hence it is very natural that, when north and west winds prevail, it should rain less frequently than during south and east winds; and that the former winds are dry, while the latter are damp. This is perhaps the principal reason why barometers are regarded as weather prophets. Why water does not flow from a jar inverted over the pneumatic trough, why it continues to flow through a s/phon after the air has been exhausted, why liquids will not run into a vessel when the air is confined, or why water will only rise to the height of 34 feet in a suction pump, are questions that scarcely require fur- ther explanation. 94. If the pressure or tension of a confined quantity of air be increased, by compressing it either directly or AIR. 83 by the addition of more air, it can be forced to stream out from a small opening with great rapidity, as is shown on a small scale in the common bellows, and on a larger scale in the blacksmith's bellows. Should there be water before this opening, the air will press it out in a jet or stream. Experiment. — Take a piece of a fine glass tube, drawn out to a point, and adapt it, by means of a perforated cork, to a bottle. Fill the bottle half full of water, and blow into it through the point of the tube; when the blow- ing ceases, the air will escape in a stream. But if the bottle be in- verted as soon as the air is blown in, then the water will be spurted out by the compressed air above. Such an apparatus (the Spritz or washing-bottle) is frequently em- ployed for washing residues or precipitates remain- ing on filters, in order to free them from soluble mat- ter. There is a similar contrivance connected with the common fire-engine, called the wind-hose, and employed for throwing an uninterrupted stream of water. 95. The pressure of the atmosphere exerts great in- fluence on the boiling of water, and of other liquids. If water is brought to boiling when the quicksilver in the barometer is very low (in foul weather), brisk ebullition will take place at about 99° C.; when the quicksilver is is very high (in clear weather) boiling will not occur under 101° C. Experiment — Heat a flask half filled with water till the water boils briskly; then remove it from the 84 METALLOIDS. Fig 5, fire and quickly cork it; the boil- ing immediately ceases, but will commence again if cold water be poured over the upper part of the flask. In this manner it can be made to bubble or boil, even though it be only lukewarm. There is no air in the flask, it having been expelled by the steam, and it could not reenter it, on the cooling and condensation of the steam, on account of its having been closed. Consequently there is no pressure of an- on the water, and it will boil even at a temperature of 20° C. The boiling ceased on account of the pressure of the steam upon the water; but the steam being con- densed by the cold water, the pressure was so much diminished, that a portion of water again became aeri- form with a boiling motion. In many manufactories, an appropriate apparatus has been contrived for boiling and evaporating in a vacuum, as, for instance, in sugar- houses. The air is densest at the level of the sea, and thinner in proportion to its distance from the earth, as there is less air above it. Hence the mercury will stand lower, and water boil more easily, on the top of a mountain Tr"^ff£/'than in the valley below. (On the top of Mont Blanc '■rf<\[%*^ quicksilver rises only to the height of 16 inches in the t~t!Sr< '2* barometer' and water boils at 84° C. Hence the barom- i'rVlT-i^ eter and the bouing point of water may be employed ✓r^<>/ **> for calculating the heights of mountains. / \,S?%'? 96' AS Water boils more easily under diminished ,^ ^ a. /£t(Pressure, so it boils tcith more difficulty when the pres- r, ,*. t< sure is increased. An increase of pressure can be pro- U~<~ ; 'duced, not only by the air, but by the steam of the U sure is increased. An increase of pressure can be '- ; 'duced, not only by the air, but by the steam of the .. £ ter itself, if new steam be constantly generated, while the escape of that already formed is prevented. This is best done by heating water confined in a strong and firmly closed vessel. For this purpose a Papin's Di- gester may be used, in which water may be heated to the temperature of 200° C, and indeed still higher, whilst in open vessels it cannot be heated above 100° C. If the amount of steam in it is twice as much as in an uncovered vessel, the pressure is said to amount to two atmospheres; if there is 3, 4, 5, 10, 20 times the quan- tity, there is said to be a pressure of 3, 4, 5, 10, 20 at- mospheres. Vessels of this kind are often employed to effect a complete penetration of the water into solid and hard substances. Thus, for example, water at 100° C. dissolves the gelatinous matter only on the surface of the bones, whilst water at a temperature ranging from t 110° to 120° entirely penetrates the bones, and extracts the gelatine also from the interior of them. 97. Air and Heat. — Heat expands the air in quite the same way as it does solid and liquid bodies, but to a much greater extent. Experiment. — Dip a glass tube, provided with a bulb, into water, and heat the bulb gently; a part of the air is expelled, and escapes in bubbles through the water; consequently, there is not room enough in the bulb for the heated air; but it requires a larger space than it did in its cold condi- tion. It follows from this, also, that the warm air is lighter than cold. If the lamp be removed, the air remaining in the bulb will contract on cooling, and water will 8 86 METALLOIDS. be pressed up into the bulb, replacing the air which has been expelled. 98. Current of Air. — A great many phenomena of daily occurrence may be explained by the difference in levity between warm and cold air. When a fire is kindled in a stove for the heating of an apartment, the air immediately in contact with the stove is first heated, becomes lighter, and ascends; colder air rushes in to supply its place, and this is likewise heated and as- cends; consequently, a constant circulation of air is kept up. By a similar circulation, the whole atmos- phere of the earth is kept in continual motion. At the equator the strongly heated air ascends and moves in the upper regions of the atmosphere towards the poles, while in the lower regions the current of cold air flows from the arctic zone towards the equator, in order here to re- store again the equilibrium, disturbed every moment by the ascent of the warm air. These regular currents of air, the direction of which is somewhat diverted by the revolution of the earth on its axis, are called trade-winds. In every heated apart- ment, a difference between the heat of the air near the ceiling and that near the floor is very perceptible. If a door or window in such a room be opened, a current of air is produced, the direction of which may easily be perceived by holding a lighted candle in the opening; the flame, when held above, at c (Fig. 53), is blown from vtMJto/wv, AIR. 87 the room; when placed below, at a, it is blown into it; consequently, the light warm air above rushes out of the room, and is replaced by heavier and colder air from be- low. A draught of air is also noticed in passing from the sunshine into the shade; where the sun shines, the warmer air ascends, and the colder air from the shade supplies its place. For the same reason, a current of air is produced wherever a fire is burning, in every stove, and round every lamp. The air-balloons, first constructed by Montgolfier, strikingly show how buoyant air may be rendered by heat; these are caused to ascend merely by fill- ing them with air, kept continually hot by a fire be- neath. 99. Gases. — Formerly, atmospheric air only was known, but chemistry has shown that there are various kinds of air, light and heavy, poisonous and innocent; some which are combustible, others not so, but which will support combustion, and others which extinguish it. It has also been shown that some sorts of air are conceal- ed or chemically bound in many solid and liquid bodies, in which, from their external appearance, the presence of gases would never have been suspected; as, for in- stance, oxygen in oxide of mercury, and oxygen and hydrogen in water. These kinds of air are commonly called gases. The aeriform state is their natural con- dition, and they only assume the solid or liquid state on compulsion. Their densities, like solids and liquids (§ 23), are likewise expressed in numbers; but it must be remembered that in this case atmospheric air, and not water, is assumed as unity. Vapor. — Many other bodies become aeriform on being heated, some quite easily, as alcohol and water; others with more difficulty, as sulphur and mercury; 88 METALLOIDS. but on being cooled they lose their gaseous form, and assume again the liquid or solid state. Such species of air are called vapor or steam; they become gaseous only upon compulsion, their natural state is liquid or solid. Composition of Air. 100. The last question concerning air is, What are its component parts ? for that it is not a simple sub- stance, not an element, has already been stated. Experiment. — Fasten a piece of tinder to a wire, drop some alcohol upon it, and hold the wire in a vessel con- taining water, so that the tinder may be some inches above the water. Then kindle the Jj^J^ spirit, and immediately place an empty flask over it, so that the mouth of it may dip into the water; the flame will soon cease burning, and some of the water will rise into the flask, in proportion to the amount of air disappearing during the combus- tion. The consumed air was oxygen, which united with the constituents of the alcohol. Close the flask tightly with the finger, shake it briskly, and again open it below the water, when a little more water will enter. The air which is in the flask is called nitrogen; it is sometimes called azote (a privative, and fafj, life), from its inability to support respiration. It forms the chief element of at- mospheric air; this consisting of four measures of nitrogen, and only one of oxygen. - NITROGEN. 89 NITROGEN OR AZOTE (N). At. Wt. = 175. — Sp. Gr. = 0.97. 101. Nitrogen gas, the preparation of which has just been given, is erroneously called azote, as we are con- tinually breathing it without perceiving any injurious effects from it; it stops respiration only when it con- tains no oxygen, and because it contains none. The human body is so constructed, that it will not thrive on substances intended as nourishment if they are present- ed to it in their purest form. Strong alcohol acts as a poison, but when diluted with four or five times its quantity of water, as in wine, it is invigorating. Even the respiration of oxygen would soon destroy life, were it not diluted with four times its measure of nitrogen, as in atmospheric air. Nitrogen has neither color, smell, nor taste, and in a chemical point of view it must be regarded as a very inert or indifferent body, since it does not combine di- rectly with any other substance. If we would combine it with another body, we must adopt a circuitous meth- od. It is very widely diffused in nature, particularly in the organic kingdom, for we find it in all plants and animals. It is also contained in saltpetre or nitre, whence its name nitrogen (generator of nitre); its sym- bol is N. 102. Besides oxygen and nitrogen, air contains vapor and carbonic acid. The presence of the former is ren- dered obvious by the fall of rain, snow, dew, &c.; and that of carbonic acid can easily be determined by letting lime-water remain exposed to the air, as in § 46, or by shaking it in a flask containing air. Lime has an affinity for carbonic acid, and forms with it an insoluble salt (carbonate of lime, or chalk). This occasions a 8* 90 METALLOIDS. cloudiness in the liquid; it is the affirmative answer to the question put by the Ume-water to the air. If you ask, What is the source of this carbonic acid ? the re- ly is, It is formed wherever substances are burning, •wherever men and animals are breathing, and wherever decay and putrefaction are taking place. In 100 measures of atmospheric air are contained, — 79 measures of nitrogen, or N. 21 " " oxygen, " O. i _ i « " carbonic acid, " C O* 30 IS ' and variable quantities of water, " H O. In crowded rooms, and other confined places, the air becomes deteriorated; that is, poorer in oxygen and richer in carbonic acid. That the air also contains other foreign ingredients is p not strange, since it is the constant receptacle of vol- atile substances and dust. The air coming from the Spice Islands, even at the distance of eight or ten miles, is impregnated with the odor of cinnamon and cloves. The dust contained in the air can be discerned in the sun-beam, &c. These ingredients are usually so small, that they can be determined neither by weight nor by measure. COAL AND FIRE. CARBON (C). e\ 6h) i 1. RETROSPECT OF THE ORGANOGENS. 113 carbon in the second ring imparts to the flame its illuminating power, just as the glowing wire rendered the alcohol flame luminous. If a cold knife be intro- duced into the flame, a portion of the carbon wiU be so much cooled that it cannot burn, and will be deposited upon the knife in the form of soot. If a wire be held through the flame, the glowing part at the hot margins will remain clear, while soot will be deposited upon that part of it which is in the interior of the flame. The brightness of a flame always depends, as the foregoing experiments show, upon the presence of a solid body, usually soot, which glows in the flame ; if it be only heated to redness, the flame will give out a smoky red fight, but, on the contrary, a brilUant light when heated to a white glow. The four simple substances now treated of form the chief elements of plants and animals, and are hence called Organogens (generators of organic bodies). RETROSPECT OF THE ORGANOGENS (OXYGEN, HYDRO- GEN, NITROGEN, AND CARBON). 1. As we distinguish on a small scale, within our- selves, body and spirit, so we distinguish also on a great scale, in nature, matter (body) and forces (spirit). 2. All matter is ponderable. Absolute weight de- termines the actual weight of a body in the air; spe- cific weight the relative weights of substances of equal bulks. 3. Bodies occur in three aggregate states; they are either solid, liquid, or aeriform. 4. The earth may be regarded as the representative 10* 114 METALLOIDS. of solid bodies; water, of liquid; air, of aeriform bodies; and fire, as the type of the natural forces. 5. The single particles of bodies are held together by a power caUed cohesion. It is strongest in solid, and weakest in aeriform substances. 6. This force is weakened by heat, strengthened by cooling; bodies are expanded by heat, and the single particles are removed from each other; by cooling, on the contrary, they are again contracted into a smaller space. 7. Heat also changes the aggregate state of bodies; it renders solid bodies liquid (melting), and Uquid bod- ies aeriform (evaporation, boiling). 8. On cooling, gaseous bodies become fluid (distil- lation, rain), fluids become solid (hardening, freezing). 9. On the melting and evaporation of soUd and fluid bodies, heat becomes combined or latent (production of cold); on the freezing of fluid and the condensation of gaseous substances, heat becomes free (production of heat). 10. All bodies contain, accordingly, latent heat, and the fluids always less than the gaseous. 11. Solid bodies also become fluid by solution in a liquid. If they separate again from such solutions in a regular form, they are said to be crystallized. Movable- ness and time are necessary for crystallization. 12. Gaseous bodies which on cooling easily become liquid, are called vapors; those which are converted into liquids with difficulty, or not at aU, are called gases. 13. Cohesion of bodies can also be destroyed by cut- ting, breaking, &c.; hereby their form only is changed, their original constitution remaining the same. These are exterior or mechanical changes. RETROSPECT OF THE ORGANOGENS. 115 14. But changes also occur by which bodies are so entirely altered in their constitution and properties, that they can no longer be recognized as the original bodies, but must be regarded as new bodies. These are inte- rior or chemical changes. 15. A power, more or less inherent in all bodies, is regarded as the cause of the chemical changes ; it is called affinity, or elective affinity. In inanimate or inor- ganic bodies this power rules unrestrained, but in Uving or organic bodies it is regulated by the vital power of vegetables and animals. 16. Affinity acts only at insensible distances; when matter is in the closest contact. 17. Affinity is stronger between bodies in proportion to their greater dissimilarity, and so much the weaker the more they are alike. 18. Chemical changes may be produced in two ways; either by the combination of simple bodies into com- pound ones (synthesis), or by the separation of the com- pound bodies into their constituent parts (analysis). 19. By analysis bodies are finally obtained which can be no further decomposed; these are called simple bodies or chemical elements. About sixty of them only are as yet known. One element cannot be converted into another. 20. Almost every chemical compound may be decom- posed by electricity or galvanism. 21. By heat, the affinity of bodies for each other is sometimes strengthened, sometimes weakened; heat as- sists both in combining and in decomposing bodies. 22. All chemical combinations take place according to fixed measure and ircight. This conformity to law also prevails where substances combine together in sev- eral proportions (degrees of oxidation, &c). 116 METALLOIDS. 23. Heat is evolved during almost all chemical changes, and not unfrequently gives rise to the phe- nomenon of fire (combustion). 24. What is ordinarily called combustion is a combi- nation of carbon or hydrogen with the oxygen of the air, — an oxidation. 25. To oxidize signifies to combine a body with ox- ygen. The body combined with oxygen is generally called an oxide. 26. There are two different sorts of oxidation, acid and basic; the metalloids form with oxygen, by prefer- ence, acids ; the metals, by preference, bases. 27. Acids and bases have a very great affinity for each other; when they combine together, the acid prop- erties of the former and the basic properties of the lat- ter disappear (neutralization). The newly formed body is called a salt. 28. The chemical elements are designated by the in- itial letters of their Latin names (chemical symbols); from the latter chemical formulas are constructed, which represent the constitution of the compound bodies. SECOND GROUP OF METALLOIDS: PYROGENS. *X< fa^l, £**~'S*tiH*4. BRIMSTONE, SULPHUR (S). At. Wt. = 200. — Sp. Gr. = 2.0. 123. Sulphur, an article very familiarly known, which, on account of its easy combustibility, is em- ployed in the manufacture of matches, &c, has nei- ther taste nor smell. It has no taste, since it is not soluble in water. When we throw some flowers of sulphur into cold or hot water, it is not dissolved. We sulphur. 117 perceive taste only in such bodies as can be dissolved in water, since they alone will dissolve in the saliva; for example, there is taste in salt and sugar, but none in insoluble substances, as stones, charcoal, starch, &c. Sulphur has no smell, as it does not volatilize at the ordinary temperature. We can only perceive smell in a body when volatile, consequently gaseous or vaporous particles, are given off from it, and come in contact with the lining membrane of the nose. 124. Experiment. — Sulphur is fusible. Heat two ounces of flowers of sulphur in a small stone-ware crucible, over a spirit-lamp; it is converted, at a temper- ature a little above that of boiling water, into a thin, brownish fluid. If you pour some of it into cold water, you obtain again soUd sulphur. If this, after being previously dried, is returned to the crucible, it will sink in the fluid mass, showing that solid is heavier than melted sulphur. Almost all other bodies behave in the same manner; ice, which floats on water, being an ex- ception. 125. Experiment — Sulphur may be crystallized. Let the crucible containing: the melted sulphur Fig. 76. . & r r stand till a crust has formed over the surface; \ \ break this quickly, and pour out the portion remaining fluid. Upon afterwards breaking the crucible, the cavity of the sulphur will be found lined with fine crystals, in the form of lengthened pillars (Fig. 75), which are called oblique rhombic prisms. This is the second method of forming crystals, and differs from the mode of obtaining those of saltpetre and salt (§§ 50, 52), inasmuch as in the one case the \ body was rendered liquid by solution, in the other by heat. ^ 118 METALLOIDS. If the sulphur is allowed to cool quietly, without de- canting the Uquid portion, this also will become solid, and such a dense mass of crystals will be formed, that there will be no vacant space between them. This mass, on being fractured, presents a glistening appearance, owing to the reflection of light from the surfaces of the minute crystals. Such a body is said to be crystalline, or to have a crystalline structure. 126. In different parts of the world, particularly in volcanic countries, large beds of sulphur (native sul- phur) are not unfrequently found, and, in these beds, fissures and cavities studded with the most beautiful crystals, which required, perhaps, centuries for their for- mation. These native crystals have a very different form from those artificially prepared. They occur in pointed four-sided pyramids, applied base to base (Fig. 76); such a form is called an acute octahedron, because contained under eight acute triangles. Thus sulphur, like car- bon in diamond and graphite, assumes two different forms ; it is dimorphous. 127. Experiment. — Sulphur may be made to assume a still different state. Heat a test-tube, support- ed by means of a wire twisted round it, and filled with powdered sulphur, over a spirit-lamp; on fusing, the sul- phur runs together, so that it only half fills the tube. The sulphur first be- comes thin, Uke water, but on further heating it becomes brown, and so thick and viscid that the tube may be inverted without the sulphur flowing out. Thrown into water while in this condition, it forms a transparent, soft, elastic mass, sulphur. 119 which, after a few days, is reconverted into solid sul- phur This sulphur, resembling melted glass, is said to be amorphous, a term applied to all other bod- ies, having no regular form; such as gum, pitch, g 12& ^Experiment — If the sulphur in the test-tube be heated still more strong- Fig. 78. ly, at a temperature, per- haps, four times above that of boiling-water, it begins to boil, and is thereby converted into a reddish-brown vapor, sul- phur fumes; thus sulphur is volatile, and may, like water, assume all the three states of aggregation (solid, fluid, and aeriform). Sulphur is twice as heavy as water, and the fumes six and a half times heavier than common air. Within the tube, the, fumes of sulphur are transparent, and have a reddish-brown color ; but after escaping, on the contrary, they appear as a yellowish smoke, being condensed by the cold air into a dust of solid sulphur. If these fumes be conducted into a glass jar, immersed in cold water, the sulphur condenses in it in the form of a soft yellow powder, known in commerce by the name of flowers of sulphur. In the preparation of sulphur on an extensive scale, the operation is conducted in large chambers. The process by which a volatile substance is evaporated and condensed again into a solid is called sublimation. In distillation, the vapor is con- densed into liquid (the distillate), in subUmation, into a solid (the sublimate). If, in this experiment, the receiver were not kept cool, 120 METALLOIDS. it would gradually become so hot that the sulphur would pass over as a fluid, and on this principle native sulphur is purified on a large scale. The earthy im- purities, not being volatile, remain behind while the sulphur is distilled over, and again condensed. The melted sulphur is commonly poured into moistened wooden moulds, and is then caUed roll-sulphur. 129. Experiment. — Fill a test-tube half full of soap- boiler's lye; add to it as much flowers of sulphur as can be taken up on the point of a knife, and boil the mixture for some time; a part of the sulphur wiU be dissolved, imparting to the liquid a yeUowish-brown color. The clear liquid is now decanted, diluted with water, and vinegar added to it; it will immediately assume a milky appearance, owing to the separation of the sulphur in the form of an exceedingly fine powder, which is so light that a considerable time must elapse before it will subside. Collect the powder on a filter, wash it with water, and dry it at a gentle heat. It is called milk of sulphur, or precipitated sulphur, and is sulphur in its finest state of subdivision, caused by the separation of each of its particles by the water. Precipitated sulphur has a pale yellowish tint,. but on being melted it be- comes distinctly yellow, owing to the union of the single particles into a larger mass. This method is frequently employed in chemistry to convert solid substances into the finest powder. Such substances thus reduced to a fine powder are not unfrequently amorphous. The solution of sulphur in lye is more complex than that of sugar or of salt in water; as several other pecu- liar combinations of sulphur with the component parts of water are formed at the same time. One of them, sulphuretted hydrogen (H S), is gaseous, and occasions the offensive smell which is emitted on the addition of SULPHUR. 121 vinegar to the solution of sulphur. The vinegar unites with the constituent of the lye, which then loses its power of holding the sulphur in solution. 130. Experiment. — If sulphur be heated in a vessel with free access of air, for example, in an iron spoon, or be touched by some red-hot body, it burns with a blue flame; that is, it unites with the oxygen of the air, under the phenomenon of fire, and forms with the oxygen, as has been previously shown (§ 64), an ir- ritating gas, sulphurous acid (S O*). If another atom of oxygen be added to this, there is then formed the common and very important acid, called sulphuric acid (S 03). This property which belongs to sulphur, of igniting and continuing to burn at a very moderate heat, is the , reason of its being so commonly used for all kindling purposes. By means of it, other bodies of more difficult combustion may be heated to the temperature at which they can continue to burn (matches, gunpowder, fire- works, &c). The kindling of a simple coal-fire well illustrates how, by gradual transition from easily inflam- mable materials to those of more difficult ignition, the latter are finally brought to that degree of heat at which they will ignite and continue to burn. Thus, sparks of iron, thrown out by the striking of the steel, ignite the fine coal of the tinder; this kindles the matches, by means of which, first straw, then wood, and finally coal itself, are brought to the temperature requisite for burn- ing. The following is the scale in the order of com- bustion : — tinder, sulphur, straw, wood, pit-coal. 131. Sulphur is the strongest chemical body, next to oxygen, and has, like it, a powerful affinity for all other ^ elements. Experiment — Boil some sulphur in a test-tube, and 11 122 METALLOIDS. Fig. 79. expose a very thin copper plate to the brownish vapor; the copper will glow vividly for some moments, lose its red color and flexibility, become gray and brittle, and weigh one quarter more than before. The newly-formed gray crystalline body is called sulphuret of copper. Both elements have intimate- ly combined, and in fixed proportions. The properties of the sulphur, as well as of the copper, have entirely disappeared. The great heat produced is a consequence of the chemical combi- nation, since, in accordance with a law of nature, heat is evolved wherever bodies chemically combine with one another, but in most cases the heat does not amount to actual glowing or combustion. In a similar manner almost all other metals may be converted into sulphur metals. We find many of these, however, already formed in the earth, and min- ''■*^ jf* ^ ers ca^ them glance, blende, or pyrites. The pyrites i/~~^' having the lustre of brass, and found in almost aU pit- , Ttsuf1 r^coal, is sulphuret of iron; red cinnabar is sulphuret ?H-'/'//(^V of mercury, &c. The sulphuret of copper, artificially '4-h^e * rj, prepared as above, occurs also as an ore, and is then called copper pyrites. Experiment. — Mix three fourths of an ounce of iron- filings, half an ounce of flowers of sulphur, and one fourth of an ounce of water, in a smaU vessel, and put it in a warm place; the mass becomes heated, the wa- ter evaporates, and in half an hour a black powder will be obtained, in which no particles of iron or of sulphur wiU be perceived; a chemical compound, sulphuret of iron, is formed. If the two substances be mixed togethei without water, no combination will take place, unless SULPHURETTED HYDROGEN. 123 they be heated to redness; the water effects the combi- nation, by bringing the particles of sulphur and iron into such close contact that they can attract each other. It is, as it were, the bridge by which one body passes over to the other. Sulphur has also another resemblance to oxygen, that of combining with other bodies in greater or less quan- tities, according to circumstances. The quantities here also are always fixed and unchangeable for every in- dividual combination (stochiometry). In the simple gray sulphuret of iron, 100 ounces of iron are always united with 57 £- ounces of sulphur; in the yellow iron pyrites 100 ounces of iron always unite with 115 ounces of sulphur (degrees of sulphuration); if more sulphur is present, it remains uncombined. The degrees t of oxidation are distinguished by the terms protoxides, sesquioxides, and peroxides ; in the combinations of sul- phur, when the sulphur predominates, they are called sesquisulphurets and persulphurets; and when the sul- phur is not in excess, they are called protosulphurets; and in the latter term, when there is a deficiency of sulphur, the syllable sub is substituted for proto. The chemical symbol for sulphur is = S. Proto- sulphuret of iron is expressed by the symbol Fe S; per- sulphuret of iron, by Fe S*. Fe, the first two letters of the Latin word ferrum, is the symbol for iron. SULPHURETTED HYDROGEN, OR HYDROSULPHURIC ACID (H S). 132. Experiment. — Put half an ounce of protosulphu- ret of iron (Fe S) and half an ounce of diluted sulphuric \ acid (§84) into a two-ounce flask, and quickly stop the flask with a cork, to which a bent glass tube is adapted. 124 METALLOIDS. Volatile. Introduce the longer limb of the tube into a bottle filled with cold water. The atmos- pheric air contained in the flask and tube first passes over, followed by a very offensive gas, which dis- solves in the water, to which it like- wise imparts its fetid odor of rotten eggs. This gas is called sulphuretted hydrogen. The decomposition in this case is similar to that effected in the preparation of hydrogen from iron (§ 84). Water is decomposed, its oxygen unites with the iron, forming, protoxide of iron, and this unites with the sulphuric acid, forming green vitriol; but the hydrogen of the water escapes, and takes with it as a companion the sulphur contained in the sulphuret of iron. The light, gaseous hydrogen possesses in a great degree the power of rendering other bodies aeriform on uniting with them, even those which are not volatile or have but a slight tendency to become so; just as an eloquent speaker can communicate his enthusiasm to a heavy and indifferent audience. Even carbon, which has never been Uquefied, is converted into a light gas when com- bined with hydrogen, as in illuminating gas. When the disengagement of the gas ceases, add some diluted sulphuric acid that the gas may again be gener- ated. The water is known to be saturated with the gas, when, on shaking the bottle, the finger by which the opening is closed is no longer sucked in, or, more cor- rectly speaking, pressed in; one measure of water con- tains two and a half measures of gas in a saturated SULPHURETTED HYDROGEN. 125 solution. It is put up in smaU well-stoppered bottles, which are labelled Hydrosulphuric Acid. If air be ad- mitted, the solution becomes turbid, owing to the oxy- gen of the air uniting with gQUj the hydrogen of the sulphu- retted hydrogen, forming Fluid, water, and the consequent liberation of the sulphur as a fine powder. If, during the evolution of the gas, the bottle of wa- ter be removed, the gas issuing from the tube can be ignited by a match ; it burns with a blue flame, and its nauseous odor is no longer perceptible, but is re- placed by the well-known odor of burning sulphur. Gas- Both constituents unite with the oxygen of the air, the Vapor sulphur forming sulphur- ous acid, and the hydrogen water. The inhalation of sulphuretted hydrogen is detrimental to health; hence precautions should be taken to avoid it. When experimenting with it, it is best to do so where there is a free circulation of air. A cloth moistened with a little alcohol, and held before the mouth, is like- wise a good protection. Sulphuretted hydrogen turns blue litmus-paper red; it also combines with many bases, and hence it is an acid. It has also been called Hydrothionic Acid, from two Greek words, signifying water and sulphur. Thus, oxygen is not essential to the acidity of a compound, since hydrogen also possesses this acidifying principle ; but the latter produces acids with but few elements, whilst oxygen does with numerous elements. 11* 126 METALLOIDS. 133. Experiments with Sulphuretted-Hydrogen Water. Experiment a. — Drop some sulphuretted-hydrogen water upon a bright silver or copper coin, and upon a piece of lead and iron; the first three metals tar- nish quickly, and finally become black; they com- bine with the sulphur, forming a dark sulphur metal, whilst the hydrogen escapes; the iron, on the contrary, undergoes no change. Pb is the symbol for lead, plumbum. Experiment b. — Put into one test-tube a small portion of litharge, into another some ignited iron-rust, and pour upon them liquid , hydrosulphuric acid; the yellow Utharge, oxide of lead, becomes immedi- ately black, an exchange of elements takes place, the hydrosulphuric acid gives its sulphur to the lead of the litharge, and receives in return the oxygen of the latter. Accordingly, sulphuret of lead and water are formed, and the offensive odor disappears. In the vessel containing the iron-rust neither the color nor the smell is affected, — a proof that no chemical change has taken place. Experiment c. — Repeat the same experiment with a small crystal of sugar of lead instead of the litharge, and some green vitriol instead of the iron-rust, together with a few drops of vinegar, these salts having been pre- viously dissolved in a large quantity of water; the re- sult will be the same as in the former experiment. Su- gar of lead is the acetate of the oxide of lead; the salt I | SULPHURETTED HYDROGEN. 127 of lead is converted into sulphuret of lead, which sub- sides sooner or later as a black precipitate. When this solution is extremely diluted, it is only colored brown. The acetic acid and acetic acid, and acetic acid. is set free, and remains in solution. Experiment d. — If some lime-water or soda be added to the vitriol solution, which in the former experiment remained unaffected by the addition of sulphuretted hydrogen, it will imme- diately assume a deep nso u e. Diack co]or# The added Fluid. base effects, what other- wise would not have oc- Siuwey curred, a combination of the sulphur with the iron, and for this reason, that the new base itself unites with the sulphuric acid of the green vitriol. The sulphuric acid has so great an affin- ity for the protoxide of iron, that it will not part with it unless in the presence of a stronger base, which the lime and soda have proved themselves to be. Lime is oxide of calcium, and is represented by the symbol Ca O. From these experiments the following rules are de- rived : — a.) Sulphur in its moist state, and when dissolved in water, has a very great affinity for metals, and converts metals, metallic oxides, and salts into sulphur metals. b.) Most of the metallic sulphurets are insoluble in water; hence sulphuretted hydrogen is peculiarly adapt- ed for precipitating metals from their solution, so that they can be separated and collected by filtration. If 128 METALLOIDS. sulphuretted hydrogen be passed through a solution of acetate of copper, sulphuret of copper will be precipi- tated, and can be separated by filtration from the acid. All the sulphurets do not possess a black color; sulphu- ret of antimony has an orange-red color, sulphuret of arsenic a yellow, and sulphuret of zinc a white color. On this is partly based the application of sulphuretted hydrogen as a re-agent, that is, as a means of detecting many metals. Wine containing lead is blackened by hydrosulphuric acid, which for this reason is called Hahnemann's wine-test. c.) Many metals are precipitated from their solutions by the addition merely of sulphuretted hydrogen, as sulphurets; for example, copper, silver, gold, lead, mer- cury, tin, antimony, and arsenic (these are called elec- tro-negative bodies); and others are not precipitated until a stronger base is added; for example, iron, zinc, manganese, cobalt, and nickel (these are called electro- positive). Sulphuretted hydrogen may accordingly be used to separate one class of metals from another; it is therefore an important means of separation in analyt- ical chemistry. 134. Hydrosulphuric acid has, as already mentioned, the formula H S, which indicates that it is composed of one atom of hydrogen and one of sulphur, and the simi- larity of this formula to that of water, H O, is apparent. 135. It is well known, that during the decomposition of animal substances, blood, flesh, hair, urine, excrements, white and yolk of eggs, &c, a putrid odor is evolved; this is owing to sulphuretted hydrogen, which is formed from the small quantity of sulphur contained in many animal substances, and from the hydrogen of the water, and is diffused in a gaseous form in the air. It will no longer appear strange that copper vessels, if exposed to SELENIUM.--PHOSPHORUS. 129 such an atmosphere, will tarnish, become brown, and indeed, finally, black. 136. Sulphur is also met with in vegetable substances, particularly in the leguminous plants, — peas, beans, lentils, &c, — and in some acrid plants, such as mustard and horseradish. If these be heaped together in a pile when moist, they will, on decaying, likewise evolve sul- phuretted hydrogen. 137. Finally, it remains to be stated that this gas oc- curs also in some mineral waters, as may be recognized by the smell and taste. Many of these springs, for in- stance, the celebrated springs of Aix-la-Chapelle, are re- sorted to by invalids, and are called sulphur springs. A rotten wooden pump or log would convert an other- wise potable water, if it should contain gypsum, into a^^A^ nauseous sulphuretted water; by purifying the well and <& ''-^ * ■ introducing a new log, the water may be rendered com- pletely odorless and good. SELENIUM (Se). Selenium is an element which has a great resem- blance to sulphur. It is of rare occurrence, and is con- tained in the red matter deposited from certain varieties of sulphuric acid, especially after the acid has been di- luted with water. _ PHOSPHORUS (P).(p<.o0'4>*if; d>U)J?£?* At. Wt. = 400. — Sp. Gr. = 1.75. (/ 138. Great care is required in experimenting with , phosphorus, that it does not take fire at an unseason- able moment, as it continues burning with the greatest violence, and might occasion dangerous wounds. It may catch fire even when lying upon blotting paper, par- 130 METALLOIDS. ticularly in summer-time, or by the heat of the finger. Hence it must be kept, and also cut, under water. On being taken from the water it should be held by a pair of forceps, or be stuck on the point of a knife. Pru- dence also would dictate to experiment with small quan- tities only at a time, and to have a vessel of water in readiness, in which it may be quenched in case it should catch fire. 139. Phosphorus is, in its properties, closely allied to sulphur, but it has an incomparably more irritable tem- perament. Sulphur may be regarded as the phlegmatic brother of phosphorus. Phosphorus, Uke sulphur, melts, boils, evaporates, and burns, but far more easily and rapidly. In winter it is brittle, in summer flexible as wax. When pure and freshly prepared it is colorless, . transparent, and amorphous, but after a time it becomes yellow, and coated over with a hydrated white crust. Phosphorus is insoluble in water, but soluble in ether, alcohol, sulphuret of carbon, and oils. 140. Experiments with Phosphorus. Experiment a. — Put into a small flask, first a quarter , of an ounce of ether, then a piece of phosphorus, of the size of a pea. Cork the flask and let it stand some days, frequently shaking it. Decant the liquid; it con- tains in solution about one grain of phosphorus, and will serve for the following experiments. Experiment b. — Pour some drops of this solution upon the hand, and rub them quickly together; the ether will evaporate in a few moments, but the phos- phorus will remain upon the hands in a state of mi- nutest division. The more finely it is divided, so much « the more easily does it combine with the oxygen of the air. During this combination it diffuses a white smoke and a strong light (it phosphoresces), causing the hands PHOSPHORUS. 131 to shine in the dark; hence its name, phosphorus, from us, light, and Qipttv, to carry. On rubbing the hands this light becomes more vivid, as a fresh surface of phos- phorus is thus continually presented to the oxygen of the air. The heat thus evolved is too feeble to occasion ignition. This oxidation, taking place at a low temper- ature, is called slow combustion. The hands, during the phosphorescence, have an alliaceous smell, and impart at the same time a sour taste to the tongue, as the com- bination of the oxygen with the phosphorus is an acid; it is called phosphorous acid, and consists of one atom of phosphorus and three atoms of oxygen. When a larger quantity of acid is required, put a stick of phosphorus into a flask, and let it remain in the cellar until the phos- phorus is converted into a colorless acid Uquid. A por- tion of the phosphorous acid thus prepared takes up yet more oxygen and becomes phosphoric acid; accordingly, the liquid thus obtained is a mixture of these two acids. Experiment c. — Moisten a lump of sugar with the solution of phosphorus, and throw it into hot water. The heat of the latter volatiUzes the ether and the phos- phorus, both of which rise to the surface of the water and there inflame spontaneously on coming in contact with the oxygen of the air. The combustion in this case is brisk and complete. The phosphorus takes up a larger quantity of oxygen, one atom of it uniting with five of oxygen; there is formed a scentless phosphoric acid, which is always generated when phosphorus is completely burnt, that is, with a flame, as has already been explained. Experiment d. — Pour some of the ethereal solution of phosphorus upon fine blotting-paper; the latter ig- nites spontaneously after the ether has evaporated. The more minutely the phosphorus is divided, so much the more readily it begins to burn. 132 METALLOIDS. Experiment e. — Put a piece of phosphorus of the size of a pea on blotting-paper, and sprinkle over it some soot or pulverized charcoal; it melts after a while, and spontaneously inflames. The finely pulverized charcoal causes this combustion, owing to its porosity. It eagerly absorbs oxygen from the air, imparts it again to the phosphorus, and, being also a non-conductor, the cooling of it is prevented. 141. Phosphorus is also easily ignited by friction, and is, for this reason, employed in the manufacture of fric- tion-matches. The combustible mass consists of phos- phorus intimately kneaded with mucilage or glue. But as the mass, becoming hard on drying, would pre- vent the admission of air to the phosphorus, there must be added some substance rich in oxygen, as black ox- ide of manganese, nitre, or red-lead, from which the phosphorus can abstract the oxygen necessary for its ignition. A temperature of 65 - 70° C. is requisite for kindling matches (§ 113); in this case the temperature is caused by friction. The coating of the match is thus broken and kindled, and the continued burning is now maintained by the oxygen of the air. 142. Experiment. — Put a piece of phosphorus, of the size of a pea, into a wine-glass, and pour hot water upon it, until the glass is half filled; the phosphorus melts, but does not ignite, as ac- cess of air is prevented by the water. But if air be carefully blown by the mouth through a long glass tube upon the bottom of the wine-glass, a combustion will ensue which is visible, espe- PHOSPHORUS. 133 cially in the dark. The phosphorus enters at once into oxidation, but with the formation of a low- er compound; it swims as a red-hot powder in the liquid, and is caUed oxide of phosphorus, containing for every two atoms of phosphorus only one atom of oxygen. 143. Experiment — We obtain the same combina- tion by gently heating a piece of phosphorus of the size of a pea, placed in the middle of a glass tube, about twelve inches long. When ignition commences, remove the lamp. While the tube is held hori- zontally, the combustion is feeble and imperfect, be- cause the heavy smoke, consisting of phosphoric and phosphorous acids, passing off slowly, allows the ad- p 63 mission of only a smaU quantity of air. Some red ox- ide of phosphorus is also deposited on the upper part of the tube. But the combustion becomes at once more vivid by inclining the tube, and when the tube is held perpendicularly it is complete, as then the draught of air is most powerful. In this way phos- phorus may be oxidized to either degree required; it must be slowly burnt to form phosphorous acid, imper- . fectly to form oxide of phosphorus, and completely to M. " form phosphoric_acid_ The experiment is also well P 0^- adapted for illustrating the principle of draughts in chimneys, &c. (§ 111). 111. Phosphorus was formerly obtained from urine, and is now universally prepared from bones. Bones consist of gelatine, lime, and phosphoric acid (P Os). The gelatine is removed by calcining the bones. It is burnt. 12 134 METALLOIDS. The lime is removed by sulphuric acid. Sulphate of Ume is formed. ' The oxgyen (03) is expelled by igniting Phosphoric the bones with charcoal (carbonic acid acid. 1 gas is disengaged). Phosphorus (P) remains behind. As phosphorus is volatile and highly inflammable, the phosphoric acid and charcoal are heated in a close vessel, commonly in an earthen retort, the beak of which dips under water contained in the basin, where the vapor of phosphorus is to be condensed. This process is accordingly one of distillation. The carbonic oxide, together with some phosphuretted hydrogen and car- buretted hydrogen gas, escape through the water. Charcoal, at a glowing heat, has the power of ab- stracting oxygen from almost all acids and bases, as in this case from phosphorus, or, chemically speaking, to deoxidate or reduce them; thus carbonic oxide (CO), which escapes, is formed from carbon and oxygen. Almost all metals are obtained from native metallic oxides or ores, by heating them with charcoal. PHOSPHURETTED HYDROGEN (PH3). 145. Experiment. Put into an ounce flask a quar- ter of an ounce of slaked lime, and a piece of phosphorus the size of a pea, fill it up to the neck with water, and place it in a small vessel con- taining a strong PHOSPHURETTED HYDROGEN. 135 Bolution of salt, prepared by adding half an ounce of salt to one ounce and a half of water. Fit to the flask a bent glass tube, one end of which is made to dip into a basin of water; heat the salt water to boiling, and a gas wiU be evolved, which, as it issues from the tube and comes in contact with the air, inflames spon- taneously. This gas is called phosphuretted hydrogen, and consists of several combinations of phosphorus and hydrogen, chiefly of P H3. If you collect it in a small jar filled with water, it immediately ignites upon the admission of air. Both the phosphorus and the hy- drogen combine with the oxygen of the air, and there results phosphoric acid (P Os) and water (HO). The first rises as a white smoke, and the gas, as it issues in separate bubbles from the water, takes the form of a wreath. Phosphuretted hydrogen, when unburnt, emits the smell of garlic. 146. In the preparation of sulphuretted hydrogen (§ 132), the iron deprived the water of its oxygen, and the sulphur took the liberated hydrogen. What these two substances together accomplished, phosphorus can effect alone; it abstracts from the water both its oxy- gen and hydrogen, and it divides itself between the elements of the water. Phosphorus forms with oxy- gen two acids, phosphoric and hypophosphorous acids, which remain behind; but it forms with hydrogen a volatile gaseous combination, which escapes. Phos- phorus, however, can only effect this in the presence of a strong base, for instance, lime, with which the acids composed of phosphorus and oxygen combine. Thus, lime does not directly aid in the decomposition of water, but it encourages the phosphorus to exert more power and activity. The lime would gladly have combined with acids, but there are none present; they may, how- 136 METALLOIDS. ever, be formed, if the phosphorus abstracts the oxygen from the water. This does take place, and we can say the lime urges on the phosphorus, — disposes it to de- compose the water, in order, as it were, to satisfy its own eagerness to unite with an acid. Thus is defined the name which this kind of affinity has received; it is called disposing affinity. This term expresses an affin- ity, an eager desire to combine with a body not yet existing, but which body may be formed from the ele- ments present, and which is in reality formed in conse- quence of this desire. 147. If we now reflect upon the processes of prepar- ing hydrogen (§ 84) and sulphuretted hydrogen (§ 132), we shaU see that in both of these instances a disposing affinity is also exerted. But the impelling body, in these instances, is an acid, — the powerful sulphuric acid. This acid has a strong desire to unite with a base, and it urges the iron to convert itself into a base, which is readily accomplished when the iron com- bines with the oxygen of the water. The other ele- ment of the water is thereby set free, and escapes as a gas, in the first case alone, in the second accompanied by sulphur, which the iron releases at the moment when it combines with the oxygen, for which it has a preference. 148. It may, perhaps, be asked why the sulphuric acid did not immediately combine with the metallic iron, or the lime with the phosphorus; this could not take place, as simple substances, with but few exceptions, combine only with simple ones, and compound only with compound substances. Hence the compound, sulphuric acid, cannot combine with the simple element, iron, but can combine with the compound, protoxide of iron. Neither can the compound, lime, enter into combination RETROSPECT OF THE PYROGENS. 137 with simple phosphorus; but it will do so immediately, when phosphorus, by combining with oxygen, becomes a compound body. 149. In the last experiment, the flask was placed in salt water, in order to guard against the ignition of the phosphorus, in case the flask should accidentally break. Salt water, at the strength specified, will not boil under 109° C.; consequently the boffing in the flask is more active than if it had been placed in pure water, the temperature of which, under ordinary pressure, can only be raised to 100° C. The apparatus for heating substances by means of hot water or saUne solutions, is called a water or saline bath. By such contrivances extracts are evaporated, and substances dried, which, at a stronger heat, would easily burn, or be otherwise de- composed. Phosphorus and sulphur are especiaUy characterized by their great inflammability; hence they may be called pyrogens, or fire-generators. RETROSPECT OF THE PYROGENS (SULPHUR AND PHOSPHORUS). 1. Simple bodies combine only with simple bodies, compound only with compound bodies. 2. In order that two bodies may act chemicaUy on each other, one of them must, as a general rule, be liquid or gaseous. 3. When a body is suddenly precipitated from its liquid or gaseous state, as a solid, it is then obtained as a fine dust (milk of sulphur and flowers of sulphur). 4. All finely divided and porous bodies eagerly ab- 12* 138 METALLOIDS. sorb gases, and condense them within their pores; in many cases this is done so powerfully as to force the gases into chemical combination (spongy platinum, charcoal). 5. An incomplete combustion or oxidation takes place when the supply of air is deficient; a slow combustion, when substances combine with oxygen at the common temperatures; but a complete and rapid combustion, when the union takes place at a high temperature, and with an abundant and constant supply of air. In the two former cases, lower degrees of oxidation are formed, and in the latter, higher degrees of oxidation. 6. In chemical reactions the right of the strongest prevails; a stronger chemical substance can expel a weaker from its combination, and replace it. This is called decomposition by simple elective affinity. 7. Decomposition by double affinity takes place when two combinations mutually exchange elements. 8. If a single or double elective affinity is caused by the presence of a third body, commonly a strong acid or a strong base, it is called disposing affinity. 9. Deoxidate, the opposite of oxidate, is a term ap- plied to the depriving compounds of their oxygen. 10. In order to detect a chemical substance, and to separate it from others, the solution of it is mixed with reagents, that is, with such bodies as form with it an insoluble compound (precipitate), or change its color, smell, &c.; such changes are caUed reactions. 11. Taste is perceived only in soluble bodies, odor only in volatile ones. :* CHLORINE. THIRD GROUP OF METALLOIDS 139 HALOGENS. O-XS it V- Fig. 84. CHLORINE (CI). X_A\a>fJOj>',y^i^rL. At. Wt. = 443. — Sp. Gr. == 2.5. 150. Experiment. — Pour one ounce and a half of 5 j muriatic acid upon a quarter of an ounce of finely «j n powdered black oxide of manganese, and heat it grad- 5? ually in a flask, to which is adapted a bent glass tube; a yellowish-green gas is disengaged, which is coUected by a process already described. This gas is called chlorine (from xXoopefr, green), be- cause it has a greenish color. Fill with it several six-ounce bottles of white glass, and cork them up. Fill, likewise, a bottle with two thirds of chlorine and one third of water, and shake it up; suction is exerted upon a finger which closes the mouth of it,— a proof that a vacuum has been occasioned. If the finger be removed, the air rushes in at once. This vacuum was caused by the chlorine having been dissolved in the water, which may be in- ferred also from the disappearance of the yellow color in the vacant space of the bottle. One measure of water dissolves two measures of chlorine. This solu- tion is caUed chlorine water. Muriatic acid, which is usually prepared from com- ,',x J^c mon salt, is a combination of chlorine and hydrogen, ^v and belongs to the class of hydrogen acids; if it be de- 140 METALLOIDS. prived of the hydrogen, the chlorine is set free. This is done in the following manner. When muriatic acid ; is added to hyperoxide of manganese (Mn 02), the ^ oxygen of the manganese takes from the muriatic acid £ its hydrogen, and water is formed, but simultaneous- * ly also hyperchloride of manganese (Mn Cl2), from the | liberated manganese and chlorine. The hyperchloride / of manganese, however, loses at a very gentle heat half of its chlorine, just as the oxy- Fiuid. gen escaped from the hyper- oxide of manganese at a glow- Fluid. mS neatj only it loses it far more readily. From hyper- chloride of manganese, there is accordingly formed pro- tochloride of manganese and free chlorine, the latter of which escapes as a yellowish gas. Mn CLj is resolved into Mn CI and CI. 1 If the oxygen of the manganese is previously expelled by heat, and then conducted into muriatic acid, it no v longer possesses the power of withdrawing from the acid its hydrogen, and consequently no chlorine will be evolved. Oxygen has this power only at the very moment when it is separating from its combination with another body, that is, in its nascent state. When actually liberated, it has far less inclination to aban- don its freedom. This peculiarity appertains to other elements, and it is often taken advantage of to force into combination such bodies as have but slight affin- ity for other bodies, and which combination could not have been effected in a direct way. Chlorine is not only obtained from manganese, but ^ from all bodies which part easily with their oxygen, ^ as, for instance, chlorate of potassa, red lead, &c, by « heating them with muriatic acid. * CHLORINE. 141 151. Muriatic acid derives its chlorine from common salt, more than half of which consists of chlorine; con- sequently, this gas may be also obtained from salt by mixing three quarters of an ounce of it with half an ounce of black oxide of manganese, two ounces of sul- phuric acid, and one ounce of water, and heating them; by adding sulphuric acid to the salt, muriatic acid is formed, and set free, and this is decomposed by man- ganese, in the way already mentioned. Chlorine acts as a poison on being inhaled; hence, care must be taken not to inhale it while operating with it. For greater security pour some drops of alcohol and- ammonia upon a cloth and wave it frequently in the air; the chlorine contained in the air will then be so altered, that it will lose its injurious properties. 152. Experiments with Chlorine. Experiment a. — In order to recognize the odor of chlorine, smeU cautiously chlorine water (but not the gas); the chlorine water may be tasted also without danger. The smell of chlorine is pecuUarly pungent and suffocating, and it has a harsh, styptic taste. Experiment b. — If a flask containing chlorine gas be exposed to the air, no diminution of chlorine will be per- ceptible ; but if the flask be inverted it will contain in a short time only atmospheric air. Chlorine is two and a half times heavier than common air, and its specific gravity is 2.5. Experiment c.— Introduce a piece of Utmus-paper into chlorine gas, and it becomes white; pour chlorine water upon red wine, or ink, and both the liquids will lose their color. Chlorine bleaches and destroys all colors derived from the animal or vegetable kingdom. In consequence of this property, chlorine has become a most important agent in bleaching; and linen, cotton, paper, and other 142 METALLOIDS. materials, may now be rendered perfectly white by it in a few hours; while, by the old method of laying them on the grass in the sun, weeks, and even months, were required for effecting it. This method of bleaching is caUed quick bleaching, the other is called grass- bleaching. The modern method is very excellent, and does not in the least injure the strength of the fabric, provided all the chlorine be completely removed again after the bleaching is finished, which is not so easily done as many bleachers suppose. If this precaution is not observed, or if the chlorine water is too strong or in excess, then indeed, after the color is destroyed, the fibres of the yarn or fabric itself will be attacked. The fault is not to be attributed to the chlorine, but rather to the injudicious application of it. A salt has lately been introduced into commerce, under the name of antichlorine, bymeans of which, if any chlorine should happen to remain in the bleached materials, they will not be in the slightest degree injured by it. As the health of the laborers is endangered by the use of chlo- Cef^6/^rme gas or chlorine water, chloride of lime is now - C<* C 11 substituted, a salt in which chlorine is chemically com- bined, but from which it may be easily disengaged on mere exposure to the air. Experiment d. — Apply chlorine water to decaying and nauseous substances (water from flower-pots, ma- nure, rotten eggs, &c.); the bad odor will at once en- tirely vanish. Thus it not only decomposes colors, but also the volatile combinations formed during decay, and which occasion disagreeable odors. It acts in a similar manner also upon morbific matter (malaria, miasm), which, being diffused in the air or attached to clothes and beds, may communicate disease. Chlorine is there- f fore a powerful disinfecting agent, and is used for puri- CHLORINE. 143 fying all morbid matter and infected atmospheres, and for arresting the decay of organic substances. Musty casks may also be purified by washing them first with chlorine water, and then with some milk of lime. Mouldy cellars, in which milk or beer cannot be kept without turning sour, are again rendered serviceable for a long time by fumigating them with chlorine gas, or by washing them with chlorine water, or a solution of chloride of lime. Experiment e. — Fill a small flask with chlorine wa- ter, and invert it in a vessel filled with water; if this is put away in a dark place, it remains unchanged; but if it is exposed to the sun, a colorless gas will collect in the upper part of the flask, in which a glowing taper will inflame ; this gas is oxygen. After some days the water will entirely lose its chlorine odor, and wiU have acquired a sour taste, and instead of bleaching blue litmus-paper, it wiU redden it. Three elements only were present, the constituents of water and chlorine; thus it is obvious, that the chlorine must have united with the hydrogen of the water to form muriatic acid, the oxygen being set free. Chlorine had here the choice between hydrogen and oxygen ; it chose the for- Remains in . . solution, mer; it has, consequent- Escapes as ly, a greater affinity for hydrogen than for oxygen. This affords another ex- ample of simple elective affinity. The chlorine water should therefore be protected from the light, and this can be most conveniently done by pasting black paper round the vessel containing it. The bleaching and disinfecting power of chlorine is now easily explained by its strong affinity for hydrogen. 144 METALLOIDS. All animal and vegetable substances contain hydrogen, which is taken from them by chlorine. But if a sin- gle chemical pillar falls, the whole chemical structure tumbles with it. By the abstraction of the hydrogen, the coloring matter becomes colorless, the odorous prin- ciples scentless, the morbific matter innoxious, insoluble substances are very frequently rendered soluble, &c. Experiment f. — Dissolve in a test-tube a small quan- tity of green vitriol (sulphate of Fig. 85. iron), in cold water, and add to the solution a few drops of sul- phuric acid; then, some chlorine water; the solution will immediately assume a yeUow color. In this case, also, the water is decomposed; the hydrogen passes to the chlorine, but the oxygen is not liberated, since it here meets with a body which already contains oxygen, but which is capable of receiving stiff more, namely, protox- ide of iron. This becomes more highly oxidized, and the yellow liquid now contains sulphate of sesquioxide of iron. Consequently we have in chlorine water a powerful oxidizing agent, by means of which we can easily convert protoxide salts into salts of the sesqui- oxide or peroxide. Experiment g. — Put into chlorine water some pure gold-leaf; it will soon disappear, as the simple element chlorine combines with the simple element gold. The combination is called chloride of gold; it is soluble in CHLORINE. 145 water. Chlorine has a very great tendency to combine with the metals. These combinations comport them- selves like salts; they are called chlorine metals, and most of them are soluble in water. Experiment h. — Pour into a vessel filled with chlo- rine gas a Uttle metafile antimony, in fine powder; it will fall in a glowing state to the bottom, as though it were a shower of fire. The fire is caused by the violent combination of the chlorine with the antimony. The white smoke which fills the flask is the new combina- tion formed, viz. chloride of antimony. If a fine brass wire, on which a piece of tinsel has been fastened, be introduced into chlorine gas, the wire will burn with a vivid combustion, and with the emission of sparks. Here combustion means the same as a combination with chlorine. Brass consists of zinc and copper; ac- cordingly, chlorides of zinc and copper are formed. Both dissolve in water, and the chloride of copper im- parts to the solution a green tinge. Experiment i. — Place in this solution a polished knife-blade; in a short time it wiU be covered with a coating of the red metal, copper. The iron possesses a still greater affinity for chlorine than copper does, and, as in chemical reactions the right of the strongest prevails, so the iron seizes the chlorine, and the copper is deposit- ed in the metallic state. This method is frequently em- ployed for precipitating a metal from its solution. Pol- ished steel is, accordingly, a reagent for copper, and by means of it we can ascertain, very simply and accurate- ly, whether copper is present in pickled cucumbers, or preserved fruit, which may have been carelessly prepared in copper vessels. 153. Experiment — If a piece of sodium of the size of a pea is thrown into a cup containing chlorine water, 13 146 METALLOIDS. it will move rapidly round, just as in common water, with a hissing noise, and finaUy disappear ; but if a suf- ficient quantity of the chlorine was present, the liquid will not afterwards give a basic reaction, as in the ex- periment in §67; neither will it have an alkaline, but a saline taste. If allowed to evaporate gradually over a warm stove, small cubic crystals remain behind, the constituents of which are chlorine and sodium. Thus, from these two elements a salt has been formed, famil- iarly known as common salt. 154. Chlorine, Uke oxygen and sulphur, unites in several proportions with other substances. Thus, there are different chlorides, as well as different oxides and sulphides. The combinations containing smaller quantities of chlorine are called protochlo- rides; those containing larger quantities are called perchlorides. IODINE Q).JLt£>A~1fJ'/ /m*^*4^-^ At. Wt. = 1586. —Sp. Gr. = 5. 155. Iodine is a solid body, somewhat resembling plumbago; it smells a Uttle like chlorine, has a pungent taste, and stains the skin brown. Experiment — Put 24 grains of iodine into a flask, and pour over them half an ounce of strong alcohol; if the iodine is pure it will entirely dissolve. This dark brown solution is caUed tincture of iodine. Water dis- solves only a trace of iodine, but yet is rendered yellow by it. Experiment. — Put a little iodine upon a knife, and hold it over the flame of a lamp ; the iodine melts, and is afterwards converted into a violet-colored gas,— io- t dine fumes. As the iodine fumes are nearly nine times BROMINE. 147 heavier than common air, they sink in it. Iodine owes its name to the color of its fumes, the Greek word lo>ins meaning violet-colored. The fumes appear more beautiful when the iodine is heated in a small flask. After cooling, the walls of the flask become Uned with small brilliant crystals of solid iodine, affording an ex- ample that regular crystals may also be formed when bodies pass from the aeriform into the soUd state. Experiment. — Boil one grain of starch in a test-tube with one drachm of water, and add to the thin paste thus obtained a few drops of tincture of iodine; the iodine combines with the starch; the combination is of a deep blue color. The blue color disappears on boiUng, but returns again on cooling. If one drop of the starch paste is mixed with one quart of water, even at this ex- treme dilution, the iodine tincture wiU impart to it a violet tinge. Consequently, it is an exceedingly sen- sitive reagent for detecting starch, and starch, on the other hand, for detecting iodine. If a Uttle iodine tinc- ture is dropped upon flour, potatoes, &c, the presence of starch in these substances will at once be indicated. BROMLNE (Br). At. Wt. = 1000. —Sp. Gr. = 3. 156. Bromine is a deep brownish-red, heavy, and very volatile Uquid. Its name is derived from the Greek word Pp&fios, signifying a strong odor. Bromine, at common temperatures, emits yeUowish-red fumes, which have a suffocating and offensive odor, similar to that of chlorine. It produces a yellow color with starch. Iodine and bromine have, in their relations to other bodies, the greatest similarity to chlorine. Like chlorine, they possess a strong affinity for hydrogen, and form 148 METALLOIDS. with it acids; they also combine with the metals form- ing protoiodides and periodides, protobromides and perbromides, which comport like salts. If a polished silver plate be held over the fumes of iodine and bro- mine, it is colored, first yellow, then violet, and then blue, owing to these vapors combining with the silver. This film of iodide and bromide of silver is decomposed al- most instantaneously in the light, slowly in the shade, and not at all in the dark. On this property is founded the Daguerreotype process. Iodine and bromine are also used in medicine for dispelUng tumors and goitres, and in the treatment of scrofula, &c. Both of these two substances are faithful companions of chlorine ; wherever common salt occurs, whether in the earth, the sea, or mineral springs, small quantities of them are present, not in a free state, however, but combined with metals. The different sea-weeds attract these combinations from the sea-water, and from these sea-weeds iodine and bromine are extracted. Both of these bodies have poisonous properties. FLUORINE (Fl). j^b*, fr ■£/*"• At. Wt. = 235. Fluorine is likewise an element having similar prop- erties to chlorine, but it is hardly known in its isolated state. The mineral known as fluor-spar, crystallizing in cubes, consists of fluorine and calcium. CYANOGEN (C2N or Cy). At. Wt. = 325. — Sp. Gr. = 1.8. 157. Prussian-blue, universally used as a pigment, con- sists of iron, carbon, and nitrogen. But both the two lat- CYANOGEN. 149 ter substances are so closely combined with each other, that they may be regarded as one. The most striking thing in this combination is, that, although a com- pound, it combines with the elements exactly in the same manner as though it were itself an element For this reason, under the name cyanogen, it is here included among the elements. It forms an exception to the pre- viously mentioned rule, that simple bodies can only combine with simple, and compound only with com- pound bodies. Cyanogen comports towards other bodies in a manner similar to that of chlorine, iodine, bromine, and fluorine; it is gaseous, and, like these, forms with hydrogen an acid, the poisonous prussic /V acid, and, like them, also unites with metals, forming protocyanides and percyanides. The cyanogen com- pounds have Ukewise the character of salts. The com- bination of cyanogen with iron, as already stated, is of a beautiful blue color, and hence the name cyanogen, from the Greek word K&avos, blue. The five metalloids, chlorine, iodine, bromine, flu- orine, and cyanogen, are characterized as follows: — 1. They have a far greater affinity for hydrogen than for oxygen. They combine with the latter only on compulsion (oxygen acids). 2. Their combinations with hydrogen are acids (hy- drogen acids). 3. Their combinations with the metals are salts. These salts are called haloid salts, to distinguish them from the common or oxygen salts, which consist of an acid and a base. On account of this latter peculiarity, these elements have been called halogens, or salt producers. 13* 150 METALLOIDS. RETROSPECT OF THE HALOGENS (CHLORINE, IODINE, BROMINE, FLUORINE, AND CYANOGEN). 1. Crystals may be formed,— 1st, from a solution, either by cooUng (saltpetre), or by evaporation (com- mon salt); 2d, from a molten fluid, by congelation (sulphur); and 3d, from vapor, when it becomes solid immediately on cooling (snow, iodine). 2. The crystallized or regularly formed bodies are the reverse of the amorphous bodies, in which no defi- nite form is to be perceived (vitreous and pulverulent bodies). Many bodies can assume two, or even several, different forms, and are called dimorphous or polymor- phous bodies (coal, sulphur). 3. Water can dissolve, not only solid, but gaseous bodies; for instance, chlorine, sulphuretted hydrogen, &c, and the more of them the colder it is. 4. Not only heat, but light also, may effect or de- stroy chemical combinations. 5. A body has a greater inclination to combine with another body at the very moment when it is separated from a combination (nascent state). 6. There are, also, by way of exception, compound bodies, which, just as if they were chemical elements, can combine with simple bodies (cyanogen). <\jaA6f, FOURTH GROUP OF METALLOIDS: HYALOGENS. &v,A^^' L<- BORON (B), .^l.,',^ , At. Wt = 136, and SILICON m.- (St). At. Wt. = 277. 158. Both of these substances occur, in nature, only in combination with oxygen; boron but seldom, as in RETROSPECT OF THE METALLOIDS. 151 boracic acid or borax; and silicon very abundantly, as in sand, quartz, and almost all other stones. The word silicon is derived from the Latin silex, flint; hence its symbol, Si. Boracic and silicic acids form, with many bases, amorphous salts (glass, slag, glazing); for this reason, boron and siUcon may be called hyalo- gens or glass producers. RETROSPECT OF THE NON-METALLIC BODIES, OR METALLOIDS. 1. The thirteen substances now treated of may be called the non-metallic bodies, or metalloids, because they do not possess a metallic appearance. 2. Heat and electricity pass through them very slow- * ly; they are bad conductors of heat and electricity. The metals, on the contrary, which give rapid transit to those forces, are good conductors. 3. On decomposition by galvanism, the metalloids always separate at the positive pole (the zinc side), and the metals at the negative pole. As the positive pole only attracts bodies endowed with the opposite or neg- ative electricity, and the negative pole only those en- dowed with positive electricity, so the metalloids are called electro-negative bodies and the metals electro- positive bodies. 4. Almost all the metalloids combine with hydro- gen, but, as a general rule, the metals do not. Some of the hydrogen combinations have acid properties (hydro- gen acids). 5. In the same manner, the metalloids combine with oxygen, forming acid-oxides or oxygen acids. The metals also combine with oxygen, but forming mostly oxides or bases. 152 ACIDS. 6. The following are the states of aggregation of the metaUoids at the ordinary temperature: — 7 metalloids, solid: C, S, P, Se, I, B, Si. 1 " fluid: Br. 5 « gaseous: O, H, N, CI, (Cy). 7. They form four famiUes or groups, founded on their resemblance to each other. 1st group, Organogens, animal and plant producers: 0, H, N, C. 2d *» Pyrogens, fire producers: S, P, Se. 3d " Halogens, salt producers: CI, I, Br, F, (Cy). 4th " Hyalogens, glass producers : B, Si. ACIDS. FIRST GROUP: OXYGEN ACIDS, OR COMBINATIONS OF THE METALLOIDS WITH OXYGEN. NITROGEN AND OXYGEN. 1.) Nitric acid, or aquafortis (H O, N Os). 159. Experiment. — Introduce into a small retort hal -fotttU'f an ounce of powdered saltpetre and half an ounce ol *-€t_:,&dy- common sulphuric acid, and let the retort stand erec ' vsy for some time, ir Fig-*' order that much as possibli of the sulphuiii acid remainini in the neck ma; flow down int the retort. The imbed the latte NITROGEN AND OXYGEN. 153 in sand contained in an iron vessel, adapt to the beak of it a receiver, wrap round the joint some strips of mois- tened blotting-paper, and heat gently. In a short time a yeUowish fuming fluid passes over into the receiver, which is placed in a vessel filled with water, and must frequently be sprinkled with cold water; this fluid is heavier than water, and is called nitric acid. Saltpetre is a salt, consisting of nitric acid and a base. The base is caUed oxide of potassium, or more briefly potassa, and has for its symbol K O. Sul- phuric acid is a stronger acid than nitric acid; that is, it has a greater affinity than the latter for potassa; it therefore expels the nitric acid, which, by the appli- cation of heat, is converted into vapor, but is condensed again in the receiver as a fluid. A quarter of an ounce of sulphuric acid would in- Voiatiie. deed have been sufficient to expel all the nitric acid, volatile. ^ut the process is con- ducted much more easily when double the quantity is employed. This explains why the safine residuum left in the retort has still a very acid taste; it is called ftisulphate of potassa. If only one half of the sulphuric acid had been employed, neutral sulphate of potassa would have remained be- hind. Nitric acid has the same constituents as common air, but in different proportions. The air contains for every four measures of nitrogen one measure of oxygen; nitric acid, on the contrary, contains ten times more of the latter element; consequently, for every four measures of nitrogen, ten measures of oxygen; or, what is the same thing, for every two measures of N (1 atom), five meas- ures of O (5 atoms). These two gases are only me- 154 ACIDS. chanicaUy mixed together in the air, but in the nitr acid, on the contrary, they are chemically combine* This is a striking example how wonderfully the proj erties of bodies change, when they chemically combiii with each other. When mechanicaUy mixed togethe the constituents of nitric acid form a life-sustainin gas, while, when chemically combined, they form on j&#aj*-<^Aj; 0f the most corrosive fluids. a^^ /£ jt might, perhaps, be supposed that nitric acid coul 4^*ti/' be formed more directly and simply from the air; bi this cannot be done, because the inert nitrogen will nc voluntarily combine with oxygen; this combinatio can only be effected by a circuitous method, which wi be described hereafter. The strongest nitric acid contains in every pound tw and a quarter ounces of water, or in each atom of aci one atom of water, without which latter it cannot exist if this is withdrawn from it, it is resolved into oxyge and a lower oxygen-compound of nitrogen. Man other bodies, especiaUy organic bodies, behave in a sin ilar manner. This water has been called water of cot stitution, denoting thereby that it is indispensably neces sary to the constitution—to the existence—of the boc ies referred to. The water of crystalUzation is neces sary only to the continuance of the form and shape ( the crystals. The crude nitric acid of commerce, whic is commonly prepared in large iron cylinders, contain perhaps, from 10 to 12 ounces of water in the pounc consequently it is three or four times weaker than tl above. 160. Experiments with Nitric Acid. Experiment a. — A drop of nitric acid is sufficient 1 acidify several spoonfuls of water, and even at a great dilution it wiU redden blue litmus-paper; nitric acid accordingly distinctly characterized as an acid. NITROGEN AND OXYGEN. 155 Experiment 6. — The weU-known volatile alkali, more correctly called ammonia, may serve as the antithesis to the acids. It has an alkaline taste, has no action on blue test-paper, but turns red test-paper blue ; it has the character of a base. Its exceedingly pungent odor is also characteristic. Experiment c — Add carefuUy, and by drops, some nitric acid to half an ounce of ammonia, until the color of red or blue test-paper remains unchanged by it. When this point is attained, you will no longer perceive either the acid or the alkaline taste or smen. The taste has become saline, the smeU has vanished. This process, as already mentioned, is called neutralization. Upon evaporating the solution a white salt remains be- ' hind, nitrate of ammonia. By appropriate means, the nitric acid, as weU as the ammonia, may be again liber- ated from this salt. It is characteristic of all acids, that they combine with bases, forming entirely new bodies, called salts, and thus lose their acid properties. Experiment d. — If lead be heated for a long time in the air it abstracts oxygen from it, and becomes con- verted into a reddish-yellow powder, called oxide of lead, or, popularly, litharge. Take up a small portion of this litharge on the point of a knife, put it into a test-tube, and add some nitric acid. The greater part will be dis- solved by gentle heating. Filter the solution while warm, and put it in a cold place ; a salt will be depos- ited from it in white brilliant crystals of nitrate of oxide of lead. This shows that oxide of lead is also a base, as it combines with acids forming salts. This salt is soluble in pure water. Nitric acid dissolves most of the metalUc oxides, and forms with them salts, all of which are soluble in 156 ACIDS- water. For this reason, nitric acid is often used f cleaning metals, for instance, copper and brass instr ments, which, during the process of annealing, soldi ing, &c, have become covered with a coating of oxid Experiment e. — Pour over some shot common niti acid, slightly diluted with water; a solution is also ( fected in this instance, but it is accompanied by tl evolution of a yellowish-red vapor of a suffocatir smell. This vapor is caUed nitrous acid, and contain as its name implies, less oxygen than nitric acid. Tl missing oxygen has united with the lead, and has co verted it into an oxide. Part of the nitric acid is d composed, while another part of it combines with tl oxide, and forms the same salt, as in the former expei ment. This likewise crystallizes from its solution, if is evaporated until a film forms on its surface. In this case nitric acid exerts, as we see, a doub action; it first oxidizes the lead, and then combim with the oxide formed. The lead is apparently di solved, but it is obvious that this is quite a differe kind of solution from that of common salt or sugar water. The salt and sugar are unchanged in the sol tion, while the lead is not contained in the Uquid as metal, but as a salt, a nitrate. The same thing occu with all other metals which are soluble in nitric acii as, for example, with silver, mercury, copper, iron, & Gold is not dissolved by it; hence it may be separati from silver by means of nitric acid. Experiment f. — The metaUoids, as well as the m< als, are oxidized by nitric acid; charcoal, on beii boiled in it, becomes carbonic acid ; sulphur, sulphui acid; phosphorus, phosphoric acid; &c. In all the cases yellowish-red fumes of nitrous acid are evolved. Experiment g. — Organic substances also, for exai NITROGEN AND OXYGEN. 157 pic, wool, feathers, wood, indigo, &c, are oxidized and decomposed by heating with nitric acid. This sort of decomposition may be regarded as combustion in the moist way. If organic substances are aUowed to re- main for a short time only in contact with this acid, they will assume a yeUow color, owing to the evolution of nitrous acid. In this manner wood may be stained, and silk may be died yeUow; the hands and clothes arc also stained yellow by nitric acid. Cotton ex- periences a most remarkable change if soaked for a short time in the strongest nitric acid; it wiU then de- t/onate and explode, like gunpowder, only far more vi- olently. (See Gun-cotton, in the second part of this work, under the head of Vegetable Fibre.) Strong nitric acid is partially decomposed, and colored yellow, by the , rays of the sun. Nitric acid, as the preceding experiments show, is very easily decomposed, and with the liberation of oxy- gen, which, in the nascent state, has the greatest desire to combine again with other bodies. Nitric acid is, owing to this property, one of the most important means of oxidation. Experiment h. — The nitric acid salts, also, are easily decomposed. Having powdered some of the nitrate of lead, obtained in experiment d or e, throw it upon a red- hot coal; decomposition will ensue, with the emission of sparks, and beads of metafile lead will remain be- hind. The nitric acid will hereby be completely re- solved into nitrogen and oxygen; the latter, as well as the oxygen of the oxide of lead, combines with the coal, forming carbonic acid, which, together with the nitrogen that has become gaseous, quickly escapes and occasions the emission of sparks. This sudden evolution of gases from a soUd body is caUed detonation. 14 158 ACIDS. 2.) Nitrous Acid (N 03). 161. This acid is always produced as a disagreeab secondary product from nitric acid, when this, as in tl previous experiment, is employed for dissolving or o: idizing metals or other substances. At the commo temperature it forms reddish-yellow suffocating fume which at a very low temperature may be condensed inl a blue liquid. As the inhalation of these vapors is ii jurious to the lungs, experiments performed with thi acid should always be done where there is a free circi lation of air. Fuming Nitric Acid. — Nitric acid wiU dissolve larg quantities of nitrous acid fumes, and is thereby cor verted into a reddish-yeUow liquid, which in open ves sels gives off the same colored fumes. It is then call& fuming nitric acid (N 03 -f- N Os). On dilution wit water it becomes, first green, then blue, and finall colorless, while the nitrous acid escapes. 3.) Nitric Oxide (N 02). 162. Experiment. — Pour over a cent, placed in wide-mouthed bottle, a little water, and then add b degrees some nitric acid, until a brisk effervescence en sues. This effervescence is caused by the evolution of i gas, which must be collected in a jar of white glas over the pneumatic trough. It is caUed nitric oxide, am consists of two measures (1 at.) of nitrogen and tw measures (2 at.) of oxy gen. Close the mouth c the jar under water; i seems to be empty, for th nitric oxide is colorless but if the jar be opene( and air be carefully blow in, then the jar become NITROGEN AND OXYGEN. 159 filled from above with yellowish-red vapors. The ni- tric oxide takes thereby from the air one atom of oxy- gen, and is converted into nitrous acid, and N Oz be- comes N 03. On account of this property, it has an important application in the preparation of common sulphuric acid (§ 172). It is here formed from nitric acid, because the copper withdraws from it three atoms of oxygen, and becomes an oxide, which combines with undecomposed nitric acid, forming nitrate of the oxide of copper. This salt is obtained in blue crystals by cvaporating the solution of the cent. 163. 4.) Nitrous Oxide (N O) is a combination of two measures (1 at.) of nitrogen with one measure (1 at.) of oxygen; it is a colorless gas, which, when inhaled, has an intoxicating effect, and is therefore , called also exhilarating gas. This gas may be regarded as atmospheric air, containing double its usual amount of oxygen. By the following table it will be seen that both the volumes and the weights of the constituents of the four compounds just treated of are in regular proportion: — In Weight. In Volume. oz. oz. 175 N. with 500 0, or 2 vols. (1 at.) N. with 5 vols, (at.) 0, to N Os. 175— « 300— " 2 " (1 at.) — " 3 " " — " N03! 175— " 200— " 2 " (1 at.) — " 2 " " — " NO2. 175— « 100— " 2 " (1 at.) — " 1 « " — « NO. By one measure or atom of oxygen (O) is here meant 100 ounces, grains, &c, in weight. On the other hand, by two measures or one atom of nitrogen (N) is meant a quantity in weight of 175 ounces, grains, &c. 160 ACIDS. CARBON AND OXYGEN. 1.) Carbonic Acid, ox fixed air (C Oa) 164. It has already been shown, when treating of carbon, that coal and all our combustible substances form, during brisk combustion, carbonic acid (§115), and that this gas may be detected by lime-water, which is thereby rendered turbid, owing to the formation of an insoluble salt, carbonate of lime. Chalk, limestone, and marble are also carbonates of Ume, and from them carbonic acid may be prepared in large quantities. Experiment. — Pour into an eight-ounce flask half an ounce of nitric acid and half an ounce of water, and then add some pieces of chalk or limestone. Adapt to the flask a bent glass tube, and conduct the gas, which escapes with effervescence, into a jar placed over the pneu- matic trough, and collect it, as was directed under oxy- gen. The stronger nitric acid expels the feebler carbonic acid, while it combines with volatile, the base-lime (CaO). The nitrate of lime formed (Ca 0, votk N 03) is a soluble salt; therefore there remains in the flask a clear liquid, from which, by evaporation, the nitric acid salt may be obtained in a solid form. Experiment. — Repeat the experiment, but instead of nitric acid take half an ounce of sulphuric acid (S 03), carefully diluted with two ounces of water (§ 84); you will obtain carbonic acid and sulphate of Ume. The CciQ. CO.T H 0 NO- CARBON AND OXYGEN. 161 Volatile. liquid in this case does not become clear, since the sul- phate of Ume (Ca O, S 03) is a salt difficult to dissolve; it is the same substance with that commonly caUed gypsum, or plaster of Paris. Having finished the experiment, collect and dry the gypsum, and preserve it for future experiments. The last two experiments are obvious examples of simple elective affinity. Experiment—Add some sulphuric acid to the ni- tric acid solution of the first experiment; the clear liquid will become thick and tur- bid, gypsum being likewise formed, because sulphuric acid, which is stronger than the nitric acid, expels the latter, and combines with the lime. 165. Experiments with Carbonic Acid. Experiment a. — If moistened blue test-paper is ex- posed to carbonic acid it is reddened, but on being left in the air for some time the blue color is restored; car- bonic acid is a volatile acid. Experiment b. — A burning taper is ex- tinguished when held in carbonic acid, and it is fatal to men and animals if they inhale it. Carbonic acid gas can neither support combustion nor life. Experiment c. — Invert a jar filled with car- bonic acid over one containing only atmos- pheric air; if after some moments you intro- duce into each of these jars a burning taper, that in the upper vessel will continue to burn, while that in the lower one wiU be ex- 14* Fig. 90. 162 ACIDS. tinguished. Carbonic acid is heavier than common air; it has sunk into the lower jar, while the atmospheric air has ascended into the upper one. If a flask, filled with carbonic acid, be held with its mouth obliquely over the flame of a lamp, so that the gas can flow out, the light wiU be extinguished. Experiment d. — Repeat the experiment of the two jars, filfing, instead of the upper one, the lower one with carbonic acid. If, after some hours, you add lime-water to both of the jars, and shake them, you wiU obtain in both of them a precipitate of carbonate of lime, — a proof that the carbonic acid has partly ascended into the upper jar. Both gases have intimately united to- gether, or the carbonic acid, though heavier, has ascend- ed, and the common air, though lighter, has diffused itself towards the bottom. This voluntary mixing of the different kinds of gases together is caUed diffusion of gases. This diffusion of gaseous bodies, since it maintains a constant equafity and balance of the con- stituents of the atmosphere, is of great importance in the economy of nature, and accounts for the fact that the constitution of the air is everywhere nearly uni- form, although in one place free oxygen is withdrawn from it, and in another place carbonic acid is added ^v PHOSPHORUS AND OXYGEN. 179 more economical previously to convert the copper into an oxide by heating it in the air, and then dissolving it in sulphuric acid. Silver and mercury comport them- selves also like copper. When they are to be dissolved in sulphuric acid, concentrated acid must be used. When larger quantities of sulphurous acid are re- quired, it is usually pre- pared by heating sulphuric acid with charcoal. The coal likewise abstracts one atom of oxygen from the sulphuric acid, and be- comes converted into carbonic oxide, which escapes in company with the sulphurous acid. Volatile. Volatile. The following proportions, in weight, of sulphur and oxygen, always exist in the two combinations just con- sidered : — 200 oz. of sulphur and 300 oz. of oxygen, or 1 at. S and 3 at. O, form S 03. 200 « u « 200 " " " 1 " S and 2 " O, " S 02. Sulphur forms with oxygen several other acid com- binations, as hyposulphuric acid, trithionic acid, hypo- sulphurous acid, tetrathionic and pentathionic acids; but these, as less important, wiU not be treated of here. PHOSPHORUS AND OXYGEN. 1.) Phosphoric Acid (P Os). 176. When phosphorus burns with a flame in oxy- gen, or in the air, a white acid vapor, called phosphoric acid (§65), is formed; 400 grains of phosphorus are thereby always combined with 500 grains of oxygen, or 1 atom of phosphorus with 5 atoms of oxygen; this 180 ACIDS. acid, consequently, has the formula P 05. If phos- phorus is burned under a dry bell-glass, this vapor will .1, > be deposited as a white powder (anhydrous phosphoric yj[^ytl ' acid), which diUquesces in the air, but dissolves in wa- \^pj? 0{f' ter, for phosphoric acid is hygroscopic, and easily solu- jLn a t;(j'/f^j, growth of plants, will be treated of hereafter. li4i>xc*,L. 2.) Phosphorous Acid (P03). */u?jl^x/ *v 177. This acid, which contains for one atom of phos- ) 179. Cyanogen, although composed of two elements (carbon and nitrogen), comports itself, nevertheless, ex- actly like a simple body, and, moreover, like a salt-former, and can form several acids with oxygen. Two of these are of great interest in a scientific point of view, because they have quite the same constitution, but entirely dif- ferent properties. They consist of equal atoms of cyanogen and oxygen. One of them is called fulminic acid (Cy2 OA, and is united with the oxide of*mercury in fulminating mercury, and with the oxide of silver in the fulminate of silver. The weU-known percussion-caps afford a familiar example of the violence with which these salts explode, on being rubbed or struck by some hard body. One of these caps contains only one third of a grain of fulminate of mercury. The fulminic acid separates, on exploding, into two gases, nitrogen and carbonic oxide, which suddenly occupy a space several/* thousand times greater than before. The second acid 184 ACIDS. is called cyanic acid (CyO); it likewise decomposes very readily, but without explosion or danger. Bodies which contain just the same constituents, and in exactly the same quantity, but at the same time are quite dissimilar in their properties, are called isomeric (from foos, equal, and /Upos, part), or similarly constituted bodies. BORON AND OXYGEN. Boracic Acid, B03. 180. Experiment — Dissolve in a porcelain dish half W-fr "/<^{fh ounce of bpjax in an ounce and a half of boiling 4£7. water, and add muriatic acid_ by drops to the solution, until the liquid gives a strong acid reaction; on grad- uaUy cooUng, the boracic acid will separate in scaly , plates, which are purified by being again dissolved and recrystallized. Boracic acid is combined in borax with a base, soda; the stronger muriatic acid seizes upon this soda, and forms with it muriate of soda (or chloride of sodium and water), which remains dissolved, while the less soluble boracic acid separates from the liquid in crys- tals. There are some places in Italy where hot vapors containing boracic acid issue from the earth; large quan- tities of this acid are now obtained from these vapors, by conducting them into basins of water, where they condense with the boracic acid. Experiment. — Take a piece of small platinum wire, about two and a half inches long, and bend one end of it into a hook; moisten this part with the tongue and dip it into boracic acid, so that a small portion of it may BORON AND OXYGEN. 185 remain adhering to the platinum. Now direct with the lips a stream of air through the blow-pipe into the flame of a spirit-lamp, and approach the boracic acid to the point of the horizontal flame; it wiU first melt and sweU in its water of crystaUization into a spongy mass, but by contin- uous blowing will be converted into a transparent glass bead. Boracic acid does not volatilize on ignition. If you moisten the glass bead, and apply to it, either powdered chalk, Utharge, or iron-rust, and again heat it to melting, these substances will unite most intimately with the boracic acid, and be dissolved by it, and likewise vitrified. Most of the combinations of boracic acids with bases become vitreous on heating; that is, they melt together, forming sometimes a white, and some- times a colored glass. 181. The blow-pipe is an excellent instrument, on a small scale, for volatiUzing, heating to redness, melting, oxidizing, or reducing substances. A double combus- tion takes place in the blow-pipe flame, in the interior by means of the air which is blown into it, and exter- nally by means of the atmospheric air. By this means, two cones of light are formed, a smaUer interior cone of a blue color, and a larger exterior cone, of a yellowish appearance; the former is caUed the reducing flame, the latter the oxidizing flame. If you wish to take oxygen from a body, — for instance, from an oxide, — hold it at the point of the blue flame, where it meets with soot or carbon, which combines with the oxygen of the oxide, forming carbonic acid. But if, on the other hand, a 16* 186 ACIDS. body is to be oxidized, then it is held at the point of the outer flame, where the oxygen of the air can have free access to it. In order to acquire a practical knowl- edge of the blow-pipe, first attempt to convert a piece of lead, placed upon charcoal, into an oxide, by exposing it to the outer flame; and afterwards to restore this oxide to its original metallic state, by exposing it to the inner flame, in order to reduce it. The habit must, moreover, be acquired, of breathing through the nose while blowing, and to do this the cheeks must be kept constantly distended. When this habit- is acquired, the chest is no longer strained by blowing, and a long uninterrupted stream of air may be kept up. 182. Experiment. — If you mix some boracic acid in a mortar with alcohol, and kindle the latter, it will burn with a green flame. In this way boracic acid may easi- ly be detected. Some of the acid, though not volatilized by heat, as shown in a previous experiment, escapes with the alcohol. Other bodies also exhibit a similar incon- sistency ; when heated by themselves, they are complete- ly non-volatile, but they volatilize, and frequently at very low temperatures, when they find themselves in company with another body which is very volatile. Thus, in the present instance, the alcohol is the occasion of the vola- tilization of the boracic acid. Hot steam will also ren- der large quantities of non-volatile silicic acid volatile, and carry it off with itself. Common salt is constantly taken up by the vapors which rise from the ocean into the air; it is again precipitated with the rain, and in this manner is diffused over the whole earth. Boracic, Uke phosphoric acid, is, in the moist condi- tion, a very weak acid, but at a glowing heat it is one of the strongest acids. SILICON AND OXYGEN. 187 SILICON AND OXYGEN. Silicic Acid, or Silica (Si 03). 183. That which is commonly caUed flint is caUed in chemistry silicic acid. We find it tolera- bly pure in quartz and flint, and in rock crys- tal often beautifully crystallized in six-sided prisms, or six-sided pyramids, and so transpar- ent, that ornamental stones, the so-called Bo- hemian diamonds, are made from it. The red corriGlian, the violet amethyst, the green chrys- c^dizvufzoj). oprase, the variegated agate and jasper, the^fj*t>,?a&&c), opal and chalcedony, — these well-known pre- uiU&A^U* cious stones consist, likewise, of silica; their colors are chiefly owing to the presence of metaUic oxides. Com- mon sand is rendered, by hydrated oxide of iron, yeUow or brown colored silica. In its natural state, silica is so hard as to give sparks with steel, and is quite insoluble in water and acids, except hydrofluoric acid. It may, perhaps, seem astonishing to some, that such bodies as our common sand, or flint, should be included among the acids. The reason is, that silica, just like other acids, combines with bases, and forms salts. Experiment. — Boil in a porcelain vessel one drachm of finely ground sand and two drachms of caustic alkali, with one ounce of water, for some hours, sup- plying the water, occasionally, as it evaporates; then let the mixture stand in a closed vessel, for the impu- rities to settle. Part of the sand dissolves in the alkali, and forms with it a thickish opalescent mass. If you add muriatic acid to this solution, a thick gelatinous precipitate of silicic acid will be formed. If, on the contrary, you previously dilute the Uquid with from ten to twelve times its quantity of water, and then remove 188 ACIDS. the potassa by muriatic acid, the liquid wiU remain clear, and the silicic acid remain dissolved in the water. But this solubiUty is destroyed as soon as the liquid is evaporated to dryness, and the silicic acid is then thrown down as a white powder, which is completely insoluble in water. Thus, as is obvious, sificic acid exists also in two quite dissimilar isomeric modifica- tions, one insoluble, as occurring in siliceous stones and rocks; and another soluble, as found in plants and water. Almost aU our springs, as weU as our plants, con- tain small quantities of siUcic acid. If we evaporate spring-water, we find silica in the insoluble residuum; and if we burn a plant, we obtain it in the ashes. Grasses, and the different sorts of grain, are particularly rich in silica, and for this reason they have been called siliceous plants. SiUca is to these plants what bones are to men, — the substance to which the stalk owes its firmness and stiffness. If the soil is deficient in soluble siUca, these properties wiU be wanting to the stalk, and it wiU bend over. The horse-tail plant (Equisei £i^,^^^jtum) contains so much siUca that it may be used for ^t(_, polishing wood. Silicic acid is found even in the animal kingdom, particularly in the class of Infusoriae, which are only visible under the microscope; the shells of many Infusoria? are formed of silicic acid. The combination of silicic acid with bases may be effected more completely by fusion. Most of the sili- cates thus obtained are amorphous, and are said to be vitreous. Silicic acid has in this respect the greatest resemblance to boracic acid, and it also resembles it in being an extremely feeble acid in its moist state; but when heated, on account of its non-volatifity, it sur- passes all other acids in strength. In its isolated state, RETROSPECT OF THE OXYGEN ACIDS. 189 silicic acid can be melted only by the heat of the oxy- hydrogen blow-pipe. RETROSPECT OF THE OXYGEN ACLDS. 1. Most of the combinations of the metalloids, or non-metallic elements, with oxygen, are acids (acid oxides). 2. Most of the combinations of the metals with oxy- gen are bases (basic oxides). 3. The acids redden blue test-paper, the bases color the red paper blue (when they are soluble). 4. The acids have an acid taste, and the bases an alkaline taste (when they are soluble). 5. When acids and bases combine together, the acid as well as basic properties are destroyed (neutraliza- tion), and new compounds are formed, salts; these have a brackish taste if soluble in water, but are taste- less if insoluble in water. 6. The principal characteristic of the acids is, that they combine with bases, forming salts; therefore we class all bodies which do this among the acids, even if they do not possess an acid taste or reaction. The same rule applies conversely to the bases. 7. Most of the acids, in the state in which they are commonly obtained and employed, are chemicaUy com- bined with a fixed quantity of water (hydrates). Many acids cannot exist without water (water of constitu- tion). By adding more water, we obtain the diluted acid. 8. One and the same element often forms several acids, with unequal, but always fixed, quantities of oxygen. 9. The acids have an unequal affinity for bases; 190 ACIDS. some have a greater affinity, for example, sulphuric acid; others a less, as carbonic acid; the former is called a strong, the latter a feeble acid. Feeble acids may be expelled from their combinations by the stronger ones. 10. The non-volatile acids are, when heated (in their dry condition), mostly stronger, but at ordinary tem- peratures (in the moist condition) weaker, than the vol- atile acids. The strength of the affinity consequently varies according to the temperature. 11. The acids just considered are called in a narrow sense oxygen acids, because they contain oxygen, and owe to it their acid properties. 12. The combinations of oxygen acids with bases are caUed oxy-salts. SECOND GROUP: HYDRACLDS, OR COMBINATIONS OF THE HALOGENS WITH HYDROGEN. 184. As oxygen combines with the metalloids, form- ing acids, so also hydrogen can convert some of them into acids. The five halogens — chlorine, bromine, io- dine, fluorine, and cyanogen — are acidified by hydrogen. Oxygen, as has been shown, is able to form several acids with one and the same metalloid; for instance, with sulphur it forms sulphuric and sulphurous acids; with nitrogen, nitric and nitrous acids, &c.; but hydro- gen produces, with each of the above-named halogens, only a single acid or combination. CHLORINE AND HYDROGEN, MURIATIC ACLD (H CI). 185. Experiment — Put into a porcelain capsule a < grain or two of common salt, and drench it with sul- CHLORINE AND HYDROGEN. 191 phuric acid; there escapes, with effervescence, a gas, which has a pungent odor, an acid taste, and reddens moistened blue test-paper; this gas is muriatic acid, or hydrochloric acid. If you pour some ammonia upon a shaving, and wave the latter to and fro over the cap- sule, a thick white smoke is formed; and the acid odor of the muriatic acid, and also the pungent fumes of the ammonia, vanish. The acid fumes are neu- tralized by the volatile base contained in the ammonia ; there is formed an odorless salt (chloride of ammonium), and in such a minute state of subdivision, that it floats in the air. We can, in this way, easily determine whether the air contains muriatic acid, or, by reversing the experiment, whether it contains ammonia, and also deprive these gases of their suffocating and injurious properties, and remove them from the air. Experiment. — Mix carefully in a flask a quarter of an ounce of water with three quarters of an ounce of Fig. 100. sulphuric acid, and after the mixture has become cold, add to it half an ounce of common salt. Adapt to the neck of the flask a cork provided with a glass tube, the long limb of which passes into a phial, containing 192 ACIDS. one ounce of water. If you heat the flask in a sand- bath, the muriatic acid escapes, but more quietly than iu the former experiment, because the sulphuric acid has been somewhat diluted. The tube must but just dip into the water ; for should it reach to the bottom of the phial, the whole liquid might suddenly flow back into the flask, if the heat should chance to slacken, as it might, for instance, from the flickering of the spirit-lamp by an accidental current of air. The muriatic acid is so eagerly absorbed by the water, that, when the evolution of the gas diminishes, a vacuum is formed in the tube and flask; the exterior air then presses more strongly upon the water and forces it up (§ 92). When a gase- ous body condenses into a liquid, it no longer requires the latent heat by which it became gas or vapor, and therefore this heat is set free. From this it follows that A the water in which the muriatic acid condenses or dis- solves must soon become warm. But warm water can receive much less gas than cold; accordingly, in order to obtain a concentrated solution of muriatic acid, we must place the phial in a basin of cold water. When the liquid in the receiver has sufficiently increased, one of the blocks must be withdrawn from beneath, so as to keep the end of the tube near the surface of the liquid. The solution thus obtained has an intensely acid taste and reaction; it is called hydrochloric acid, but is commonly known under the name of muriatk acid. One measure of water absorbs more than four hundred measures of muriatic acid gas; the strong mu- riatic acid thus obtained fumes in the air, because a part of the gas escapes. If you heat it to boiling, then half of it escapes, and an acid only half as strong remains behind; but this is always somewhat heavier than water. CHLORINE AND HYDROGEN. 193 The muriatic acid of commerce is commonly yellow, and contaminated with sulphurous acid, sulphuric acid, chlorine, iron, and sometimes even with arsenic. Muri- atic acid is likewise manufactured from common salt and sulphuric acid; but, instead of glass vessels, large iron cylinders are employed, capable of containing some quintals of common salt. The gas is conducted into several bottles or jars, connected with each other, and which are filled with water. When the water in the first vessel becomes saturated with hydrochloric acid, the gas passes over into the second, then into the third vessel, and so on, saturating each successively. This is a very convenient method of conducting gas- es through liquids. Such vessels, which are commonly pro- vided with two or three necks, are call- ed Woulfe's bottles. The upright tube in the middle neck serves as a safety tube, that is, it pre- vents the liquid from being forced back; if a vacuum is formed in one of the bottles, the air enters through this tube. Common salt consists of chlorine and sodium; if water is added to it, the chlorine will abstract from it hydrogen, and the sodium oxygen, and muriate of soda is formed. This is de- foiatiie. composed by the more powerful sulphuric acid, Non- which combines with the olalile. base, and expels the hy- drochloric acid. The sulphate of soda (Glauber salts) 17 194 ACIDS. remains behind as a white salt, and is used in the man- ufacture of the important article, carbonate of soda. The constituents of muriatic acid gas are equal atoms of chlorine and hydrogen, and it is represented by the symbol H CI. If you fiU a jar half with chlorine and half with hy- drogen, and put it in a dark place, no union ensues; but it takes place instantaneously when the jar is ex- posed to the direct rays of the sun. The union is ac- companied by a violent detonation, which often breaks the glass, so that it is not advisable to perform this ex- periment. But it proves that Ught also compels some substances to combine chemically with each other. 186. Experiments with Muriatic Acid. Experiment a. — Put some iron nails in a phial, and pour upon them some muriatic acid; brisk effervescence will ensue. When this has continued some minutes, hold a burning taper over the mouth of the phial; the gas which escapes inflames; it is hydrogen. The mu- riatic acid is decomposed, and its second constituent, chlorine, combines with the iron. The iron disappears, and it dissolves; that is, it combines with the chlorine, forming a soluble compound. When the effervescence has ceased, heat the phial by placing it in hot water, and afterwards pour its contents on a filter of white blotting-paper. Put the liquid which passes through (the filtrate) in a cool place; a salt is deposited from it in greenish crystals, called protochloride of iron (Fe CI), that is, iron united with chlorine. Many other metals may also be dissolved, like iron, in muriatic acid, and converted into salts. Experiment b. — Pour some muriatic acid upon iron- rust that has been put into a test-tube; it dissolves, but without evolution of gas. In this case, the hydro- CHLORINE AND HYDROGEN. 195 gen of the muriatic acid meets with a body with which it can combine, namely, the oxygen of the oxide of iron; and it does combine with it, forming water. The yel- lowish-brown solution, which it is difficult to crystallize, yields, upon evaporation, a brown mass caUed sesquichlo- ride of iron (Fe2 Cl3). This salt contains one half more chlorine than the former. Muriatic acid is very often used for dissolving metalUc oxides. Experiment c. — Dissolve some crystals of the proto- chloride of iron, obtained according to experiment a, in a little water, and then add some chlorine water; the greenish color is converted into a yellow color, and the solution yields, on evaporation, brown sesquichloride of iron. The chlorine combines with the protochloride of iron, and makes it sesquichloride of iron. Experiment d. — Dissolve some carbonate of soda in water; the solution turns red test-paper blue ; it has a basic reaction. Drop carefully into the solution some muriatic acid, until neither the red nor the blue paper is affected by it. Thus muriatic acid, just like an oxygen acid, has the power of neutralizing bases. If you put the liquid in a warm place, a salt wiU be deposited in small cubes; you readily perceive, both by the shape of the crystals and by the taste, that it is common salt. Here also the oxygen of the base has combined with the hydrogen of the muriatic acid, forming water, but the chlorine with the sodium, forming common salt. The carbonic acid of the carbonate of soda escapes with effervescence. Experiment e. — If you drop into a test-tube some muriatic acid, and then a few drops of a solution of ni- trate of silver (lunar caustic), a white cloudiness is formed, which does not happen in pure water. This cloudiness proceeds from the chloride of silver, which is 196 ACIDS. insoluble in water. Nitrate of silver is the most accu- rate test for muriatic acid and its salts. If muriatic acid is diluted with from 800 to 900 parts of water, and is poured upon land, it exhibits a fertiliz- ing power, Uke that of sulphuric acid (§ 173). 187. Haloid Salts. — Like chlorine, the other salt pro- ducers, or halogens, also combine with metals forming salts; these salts are called haloid salts. As has been shown, they may be prepared, — 1.) By uniting a halogen with a metal (§ 156). 2.) By uniting a halogen with a metalUc oxide (§ 152). 3.) By the solution of a metal in a hydrogen acid (§ 186). 4.) By the solution of a metalUc oxide in a hydrogen acid (§ 186). If the two last-mentioned instances be attentively ■> considered, it may, perhaps, appear surprising why it was not assumed that muriatic acid combined with the base without further decomposition, just as it was as- sumed with regard to sulphuric acid, and the other oxy- gen acids. This cannot generally happen, because many of the haloid salts, when they are quite dry, con- tain neither oxygen nor hydrogen. Completely dried common salt, for example, contains no hydrochloric acid, but chlorine, — no oxide of sodium, but sodium, — as has been ascertained by the most accurate experiments. But if the haloid salts contain water, or are dissolved in water, then they may certainly be regarded as consist- ing of a base and a hydrogen acid, for it amounts to the same thing, whether the hydrogen exists in the water or in the hydrogen acid, the oxygen in the water or in the metallic oxide. A solution of salt may accordingly be regarded as chloride of sodium and water, or as muriate of soda. (Na CI -f- II O is the same as Na O, H CI.) AQUA REGIA. 197 Formerly the combinations of chlorine with the met- als were universaUy called muriates. The names, muri- ate of lime, muriate of baryta, muriate of oxide of iron, &c, have therefore the same signification as chloride of calcium, chloride of barium, chloride of iron, &c. When chlorine combines with a metal in several proportions, the combination with less chlorine is called protochlo- ride, that with more chlorine, sesquichloride, and that with still more chlorine, perchloride (§ 154). If water is contained in them, or if they are dissolved in it, the protochlorides may be regarded also as protomuriates, and the perchlorides as permuriates; for example,— Protochloride of iron and water is the same as proto- muriate of oxide of iron. (Fe CI + H O = Fe O, H CI.) Sesquichloride of iron and water, the same as the muriate of the sesquioxide of iron. (Fea Cl3-f 3 H O = Fe2 03 + 3 H CI.) AQUA REGIA, OR NITRO-MURIATIC ACLD (2 H CI + N 05). /WW/ ^ 188. Experiment — Put into a flask one drachm of nitric acid, and into another two drachms of pure muriatic acid, and add to each some genuine gold-leaf; it will not be dissolved. But if both Uquids are mixed together, the gold very soon disappears, because it is dis- solved. Gold is deemed the king of metals, hence the name aqua regia. On evaporating this solution, a yel- low salt remains behind, which consists of gold and chlorine. As the muriatic acid did not voluntarily give up its chlorine to the gold, it is highly probable that it was compelled to do so by the nitric acid. This process may be easily explained, if we refer to the preparation of chlorine from muriatic acid and hyperoxide of manganese. 17* 198 ACIDS. The nitric acid acts upon the muriatic acid just like the manganese; it contains, like the latter, much oxygen, and parts with it very readily. This happens also in the present case, and the liberated oxygen abstracts from the muriatic acid its hydrogen, to form water. Consequently the chlorine is set free, which, being a simple and strong chemical body, immediately unites with the gold, which is likewise a simple body. The nitric acid loses there- by two atoms of its oxy- gen, and is converted into nitrous acid, which es- capes in yellowish fumes. Aqua regia is employed for dissolving gold and plati- num, neither of which metals is attacked by other acids. BROMINE, IODINE, AND ELUORLNE, + HYDROGEN. 189. Hydrobromic and Hydriodic Acids. — Both of these acids closely resemble muriatic acids. Their com- binations with metals are called protobromides, perbro- mides, protoiodides, and periodides, &c, of the metals. They occur in nature accompanying common salt, con- sequently in sea-water and marine plants, in salt springs, &c, but only in minute quantities. 190. Hydrofluoric Acid. — Experiment — Rub to a powder a piece of fluor-spar, of the size of a hazle-nut, and put it into a small bowl, which has been pre- viously rubbed with oiled paper; then pour sulphuric acid upon it till a thin paste is formed. Cover t the bowl with a piece of window- Fig. 102. CYANOGEN AND HYDROGEN. 199 glass, which has received a coating of wax, and from some parts of which the wax has been removed by scratching with a needle, or other pointed instrument. After the lapse of some hours, remove the wax by melt- ing it, and then rubbing it off with oil of turpentine; those parts of the glass left bare will be found to be corroded. Fluor-spar consists of fluorine and calcium, and is de- composed by sulphuric acid, in the same manner as common salt was; hydrofluoric acid is formed and escapes in vapor. This acid has the property of dis- solving silica; therefore it withdraws the latter from the glass, where it is not protected by the wax, and the glass consequently becomes rough and opaque. In this manner drawings are often etched on glass. By con- ducting the fumes into water, liquid hydrofluoric acid is obtained, which may likewise be employed for etching on glass. Lead or platinum vessels must be used in the preparation of it, on account of its property of corroding glass and porcelain. We also find fluoride of calcium, in smaU quantities, in the bones and teeth of the Mammalia. CYANOGEN AND HYDROGEN, HYDROCYANIC ACID (H Cy). 191. The great similarity which Cyanogen, composed of carbon and nitrogen, has to the halogens, is also manifested by its combining with hydrogen, forming an acid. This combination is the notorious prussic or hydrocyanic acid, a few drops of which are sufficient to kill instantaneously a smaU animal. As muriatic acid is obtained from chlorides by sulphuric acid, so prussic acid is also obtained from the cyanides by means of sulphuric acid, and it is also gaseous, like muriatic acid. To obtain it in a liquid form, the gas is 200 ACIDS. conducted into water, or alcohol, by which it is ab- sorbed. It is colorless, like water, and it is easily recog nized by its peculiarly oppressive odor, which is very similar to that of bitter almonds. Such a dangerous ar- ticle should only be prepared by experienced workmen. Prussic acid is found also in small quantities in some seeds, particularly in bitter almonds, and in the kernels of stone fruits, as plums, apricots, &c. Prussic acid combines with bases, forming water and metallic cyanides (protocyanides and percyanides). The most familiar of these are the yellow ferrocyanide of potassium (prussiate of potassa), and the blue ferrocy- anide of iron (prussian blue). RETROSPECT OF THE HYDROGEN ACLDS. \ 1. The haloids or halogens — chlorine, bromine, io- dine, fluorine, and cyanogen — form acids, not only ^ with oxygen, but also with hydrogen. •y' 2. The halogens have a greater preference for hydro- S~r gen than for oxygen ; hence, when left to their own free ^ will, they always combine with the former. ^ 3. Hydrogen unites with the halogens only in one ^' proportion; consequently, each of them forms only one single hydrogen acid. 4. All the hydrogen acids have the same constitution; they always consist of equal atoms of a halogen and hydrogen. 5. The hydrogen acids combine with metals, forming chlorides, bromides, &c, whilst their hydrogen escapes. 6. The combinations of the halogens with the metals possess exactly the properties of salts ; for this reason they are called haloid salts. t 7. The hydrogen acids combine with the bases, form- ing haloid salts and water. RETROSPECT. 201 8. If water is present in the haloid salts, they may be regarded as combinations of the hydrogen acids with bases, or as hydrogen acid salts, just as the oxygen salts are regarded as combinations of oxygen acids with bases. 9. Many metals may combine with the halogens in sev- eral, generally in two, proportions. When the halogen ' "* is in excess, they are called perchlorides, perbromides, &c.; but when deficient, they are caUed protochlorides, \fi protobromides, &c. The former correspond with the "xT peroxide salts, the latter with the protoxide salts. &i RETROSPECT OF THE COMBINATIONS OF THE METAL- ^ LOIDS WITH OXYGEN AND HYDROGEN. / 192. The combinations which hydrogen forms with s the halogens have been here grouped together, because they have the greatest similarity to each other. These J. combinations possess the distinctive character of strong acids. The other metalloids can also combine with hydrogen, but they do not form acids with it, sulphur alone being an exception, the combination of which with hydrogen certainly comports^ itself like an acid, though |u>^/ttf, /&&, only as a very feeble one (§ 132). The contrary oc- curs with nitrogen; this forms with hydrogen a base, ammonia. The combinations of the other metalloids with hydrogen, some of which have already been treat- ed of under the separate metaUoids, exhibit neither basic nor acid properties; they are, on this account, called neutral or indifferent bodies. Oxygen and hydrogen constitute the indifferent body, water; carbon and hy- ^ drogen, the indifferent illuminating and marsh gas; phosphorus and hydrogen form phosphuretted hydro- gen, also an indifferent body. 202 ACIDS. The combinations which oxygen forms with the non- metalUc elements, or metalloids, are, indeed, mostly acids, but we find among them some which possess an indiffer- ent character; namely, nitrous and nitric oxides (NO and N 02), the oxide of phosphorus, and carbonic oxide gas (C O). As is obvious, the combinations with the least quantity of oxygen are those in which the acid properties are wanting; these acid properties are developed on the increase of the oxygen, and most strongly in those com- binations which contain the greatest quantity of oxygen. Since the combinations which the metalloids form, on the one side with oxygen, and on the other with hy- drogen, are among the most important and most inter- esting chemical bodies, the annexed scheme will pre- sent nearly a correct idea of the strength of the affini- Fig. 103. Affinity for Oxygen. Metalloids. Affinity for Hydrogen. }. \o SiUcon. ■ o Boron. Carbon. ■ n'. . D o O Phosphorus. □; la Sulphur. D fp Selenium. u '■O- Nitrogen. □ &$■: Cyanogen. n- Iodine. 151 o Bromine. In c Chlorine. D Fluorine. D TARTARIC ACID. 203 ties which each of the metalloids possesses for these two elements. The size of the circles represents the affinity for oxygen, that of the squares the affinity for hydrogen. From this it is apparent that the partiality of the met- alloids for hydrogen increases in proportion as it dimin- ishes for oxygen, and the reverse. THIRD GROUP: ORGANIC ACIDS. 193. The oxygen and hydrogen acids are commonly caUed inorganic or mineral acids, because they are prin- cipally found in the mineral kingdom, or prepared artifi- ciaUy from minerals and earths. But there are, besides, many other acids, found either already existing in ani- mals and plants (formic acid, citric acid), or which maji-.A« ^-Us«. ^ be artificially produced from organic substances (lactic ■=-«-^ * ^^ acid, acetic acid). Such acids are called organic, or~ ^>*~*"~<"> vegetable and animal acids. They have the greatest similarity to the inorganic acids in their properties and combinations, but not in their constitution. Three of them only will be treated of at present as examples of this class of acids, one a volatile, and the other two non-volatile acids; the others wiU be considered in the second and third parts of this work. TARTARIC ACID (H 0, T). 194. Tartaric acid has very much the appearance of a salt; it crystallizes in colorless oblique prisms, which are permanent in the air and have a very acid taste. Experiment. — Place a small crystal of tartaric acid upon a piece of platinum foil, and heat it over the flame of a spirit-lamp; it will first melt, then become brown, and finally black, and emit at the same time a pecuUar 204 ACIDS. empyreumatic odor. If, during the Fig. 104. process of charring, you hold over the acid a dry, cold glass vessel, it will become lined with globules of water ; consequently the acid contains oxygen and hydrogen. The dark residue resembles coal, but it is more certainly deter- mined as such by its burning completely at a higher heat. Accordingly, tartaric acid has, when heated, the greatest similarity to burning wood. In fact, it consists of the same elements, namely, carbon, hydrogen, and oxygen, but in different proportions. All vegetable acids consist of C, H, and O, and are charred and con- sumed on being heated. By these two characteristics the organic acids are essentiaUy distinguished from the inorganic, which consist only of two elements, and which are neither charred nor consumed in the fire. Experiment. — Pour a Uttle warm water over some tar- taric acid; it wiU dissolve therein, for it is readily soluble in water. If you dilute the solution with more water, and put it aside in a moderately warm place, sUmy flakes will be deposited, and the acid taste wiU graduaUy be lost,—it putrefies. In a similar manner, aU organic acids, when they are diluted with water, decompose after a time. Experiment — Mix graduaUy a solution of tartaric acid with ammonia; there wiU be a period when the acid properties of the tartaric acid and the basic ones of the ammonia will have disappeared. Accordingly, tartaric acid, just like other acids, can neutralize bases, and form with them salts. The tartrate of ammonia obtained is easily soluble. Experiment. — Neutralize a solution of carbonate of f potassa with a solution of tartaric acid; the carbonic TARTARIC ACID. 205 acid escapes; the Uquid, however, remains clear, because the neutral tartrate of potassa (KO, T) formed is an easily soluble salt. But by adding yet more tartaric acid, the Uquid becomes turbid, and deposits a quantity of smaU, transparent crystals, which are difficultly solu- ble in water, have an acid taste, and contain twice as much acid as the neutral salt, besides, also, some wa- ter of crystaUization. These crystals are caUed acid tartrate of potassa, or bitartrate of potassa (K O, 2 T •f HO); commonly, tartar, or when they are pulverized, cream of tartar. The salts of potassa may accordingly be used as a test for tartaric acid. Tartaric acid is generaUy prepared from tartar or argol, which is obtained in large quantities from the wine countries, where it is deposited from wines in their / fermenting casks, as a white or reddish crust. The po- tassa might be very easily removed from this salt by means of sulphuric acid; but then two soluble sub- stances would be obtained, which could not well be separated from each other. For this reason, the potassa is first replaced by another base, namely, by Ume, which forms with sulphuric acid an insoluble, or at least very difficultly soluble compound. By boiUng tartar with water, and adding chalk to it, then tartrate of lime is obtained, as a white insoluble powder; if this, after being sufficiently washed, is put by for some time with water and sulphuric acid in a warm place (digested), the lat- ter unites with the Ume, and forms gypsum, whilst the tartaric acid, being set free, dissolves in the water, and crystallizes from the solution after evaporation. The chemist is often obUged to resort to such circui- tous means in order to separate two bodies from each other, both of which are equally soluble in water or in some other liquid. 18 206 ACIDS. Experiment—If you heat the crystalline powder of tartar, obtained in the former experiment, on platinum foil, it will, like the tartaric acid, become black, and is consumed, emitting an empyreumatic odor; but there will, however, finaUy remain a white powder, which has an alkaline taste, a basic reaction, and which, on the addition of an acid, wiU effervesce like carbonate of potassa. The acid burns up, but not the alkali; on the combustion of the acid, carbonic acid is formed, which combines with the potassa; consequently, carbonate of potassa is formed. All salts of the alkalies, or alkaline earths, with an organic acid, are in the same way de- composed by heat, and converted into carbonates. 195. We can decompose sulphuric acid into sulphur and oxygen; and from sulphur and oxygen we can again reproduce sulphuric acid. Not so, however, with >, tartaric acid; we may succeed in demolishing it, but it is beyond our power to reproduce it again. We can- not artificially produce the organic acids from their ele- ments. We are stiU ignorant how they are formed in plants and animals. AU that is known on this point concerning the vegetable acids is, that they are formed from carbonic acid and water, the two chief sources of the nourishment of vegetables. But by what power, and in what manner, these two bodies are forced to combine in the grape-vine to form tartaric acid, in the fruit of the lemon-tree to form citric acid, in apples to form malic acid, &c, we are entirely ignorant. We here stand, as it were, on the boundary line of our knowledge; whether it will be permitted to us at some future period to advance beyond this limit, further inves- tigations must show. In the mean time we must as- sume that the unknown power which causes the shoots, leaves, and blossoms to put forth from the seeds,—we OXALIC ACID. 207 call it vital power, — is also able to produce chemical combinations and decompositions more powerful and manifold than it is possible for the chemist to accom- pfish in his retofts and crucibles. In this sense we re- gard the organic acids, as in general all organic sub- stances, as the chemical productions of the vital activity of plants and animals. The organic acids are briefly designated by a horizon- tal line placed above their initials. The Latin name for tartar is tartarus ; the symbol for tartaric acid is T. 196. Fig. 105. OXALIC ACID (H 0, O, or H 0, C2O3). OI ^ * '•£ **** **^ *£ ---- ^ 4^~ Experiment — Heat with free access of air, in a porcelain dish, one fourth of an ounce of sug- ar, mixed with one and a half ounces of con- centrated nitric acid, and one ounce of water. In a short time a strong evolution of yeUow- ish-red fumes (N 03) will commence. Con- tinue boiUng until these vapors cease, and then put the Uquid in a cool place; colorless crystals (right rhombic prisms) will be sepa- rated, which must be purified by recrystalli- zation. They have an intensely strong acid reaction, and are poisonous; they are called oxalic acid. This acid, Uke most acids, contains water chemicaUy combined, without which it cannot exist. Experiment. — Pour into a test-tube twenty grains of oxalic acid, and one drachm of fuming oil of vitriol, and carefully heat the mixture; a gas will be evolved. Let this pass through lime-water contained in another test- tube. One half of the escaping gas is absorbed by the lime-water, which thereby becomes turbid; this is car- bonic acid (C 02). The other half escapes through the 208 ACIDS. open tube, and burns, when kindled, with a bluish flame; this is carbonic oxide gas (CO). When the evolution of the gas ceases, there wiU be found in the first test-tube common sulphuric acid; consequently, the fuming oil of vitriol has received water, namely, the chemically combined water contained in the oxaUc acid. The oxalic acid, when it loses its water, is resolved into the two gases just mentioned; it may, accordingly, be regarded as a combination of 1 atom C 02, and 1 atom C O, or C2 03. On comparing this constitution with that of sugar, it will be seen that the sugar contains still more carbon than the oxalic acid, besides some hydrogen; conse- quently a portion of its carbon, and aU its hydro- gen, must have been withdrawn. This was done by the oxygen of the nitric acid, which oxygen, uniting with the carbon, formed carbonic acid, and with the hydrogen, formed water. This process may be regard- ed as a combustion (oxidation) in the moist way. Sug- ar has exactly the same constituents as wood. If a wood-shaving be ignited, at first the hydrogen princi- paUy burns, because it is very readily combustible; at last principaUy the carbon, because this burns with more difficulty (§ 120). The same succession of phe- nomena also takes place on the boiling of sugar with nitric acid; the hydrogen is at first principaUy oxidized, and afterwards the carbon; but the latter only partially, on account of the insufficient supply of nitric acid, just as wood is only partially consumed when there is a de- ficiency in the supply of the air. The partly consumed wood (charcoal) burns completely if we heat it still' longer in the air ; it is converted into carbonic acid by OXALIC ACID. 209 the oxygen of the air. Partly burnt sugar (oxalic acid) consumes completely when we boil it with still more nitric acid; it is converted into carbonic acid by the oxygen of the nitric acid. 197. Experiments with Oxalic Acid. Experiment a. — Place some crystals of oxaUc acid upon a piece of platinum foil, and hold them in the flame of a spirit-lamp. They melt, inflame, and burn without becoming black or leaving any residue. The product of the combustion is carbonic acid; C2 03 and O (from the air) are converted into 2 C 02. Experiment b. — Neutralize a hot concentrated solu- tion of oxalic acid with a hot concentrated solution of carbonate of potassa; neutral oxalate of potassa (KO, C2 03), an easily soluble salt, is formed. If you now add as much more oxalic acid, hard crystals wUl be depos- ited on cooling, which have an acid reaction ; they are called acid oxalate, or bin oxalate of potassa. One atom of potassa can thus combine with two atoms of acid. As has been previously stated, salts with two atoms of acid are caUed acid salts. The binoxalate of potassa is likewise formed in the substance of many plants during their growth, and it is found abundantly in the leaves of the wood-sorrel (OxaUs), from which it may be ob- tained. The acid salt is far less soluble than the neutral. Experiment c. — Heat some binoxalate of potassa upon platinum foil; like the tartar, it will be converted into carbonate of potassa, but without being charred or blackened. The oxalic acid is thereby converted, as above, into carbonic acid and carbonic oxide, and a portion of the former combines with the potassa. Experiment d. — Agitate a little gypsum with water V and let the Uquid settle ; the decanted water contains a small quantity (S£D) of gypsum in solution. If a solution 18* 210 ACIDS. of oxalic acid is poured upon this solution of gypsum, you will soon obtain a precipitate of oxalate of Ume; consequently oxaUc acid has a greater affinity for Fluid. Ume than sulphuric acid has, since it is able to Solid. ' displace the latter acid. The decomposition takes place more rapidly and perfectly when the oxaUc acid has been previously neutralized by ammonia (NH3), because another body is thus presented to the sulphuric acid, for which the latter has a greater affinity than for the water; it be- comes thereby more ready, as it were, to release the lime. Oxalic acid is the best test for Ume and Ume salts. Experiment e. — Add some spoonfuls of water to a r. 6; SOj f piece of green vitriol of the size of a pea, and moisten f tf- O, with the solution a piece of white blotting-paper; when this has imbibed the liquid, spread over it some ammo- nia. The ammonia withdraws the sulphuric acid from the green vitriol, and protoxide of iron must conse- quently be separated in and upon the paper, to which it imparts a greenish tinge. On drying, the protoxide of iron becomes converted into sesquioxide of iron, and the green color is at the same time changed to yellow. In a similar manner, cotton, and other fab- rics, are often dyed brown or yellow. Mix some oxafic acid with water into a thin paste, and dot the yeUow paper with it in several places ; the color will soon dis- appear from those spots, and you obtain a white pattern ' on a yeUow ground. Oxalic acid easily dissolves ses- CaO,S03—^HO SO3 H6c,Op^-ctto,c2oa l3—^HONHj SOJ HQNH^.QOh^ c«o c2o3 * ACETIC ACID. 211 quioxide of iron, and both are removed by washing. Upon this is founded the important use of this acid in calico printing, as likewise its appUcation for the re- moval of ink-spots from Unen or paper. One of the principal constituents of ink is oxide of iron, which be- ing dissolved by oxalic acid, the black color of the ink disappears also. This explains why oxaUc acid, or an oxalate containing a free acid, causes the white spots on fabrics dyed yeUow by peroxide of iron, and also why it removes ink-spots from garments, paper, &c. ACETIC ACLD (HO, A). £ j4^ 03 198. Vinegar is likewise a vegetable acid. It is often formed spontaneously, producing mischievous conse- quences. It is formed when sweet or spirituous Uquors, thin syrups, the juice of fruit, wine, beer, &c, remain exposed to the air. The sugar is converted by degrees into alcohol, which becomes vinegar when access to the oxygen of the air is not prevented. But the method by which this takes place wiU not be considered until sug- ar and alcohol are treated of. We shall now merely describe the method of preparing acetic acid from crude vinegar. Our common vinegar contains in every pound only from half an ounce to two ounces of acetic acid; the rest is water. If you boil vinegar, the acid smell of the fumes indicates that the acid contained in it is volatile; therefore it cannot, like other acids, be made stronger by evaporation; but this may be done in the foUowing manner. Experiment — Add to one pound of colorless vinegar V from one to one and a half ounces of litharge (oxide of lead), and let the mixture stand in a vessel for some 212 ACIDS. hours, in a warm place, stirring it frequently. The liquid will become clear on standing, and then if you evaporate it down to two and a half or three ounces, and let it cool, prismatic crystals of acetate of oxide of lead will be deposited. This salt is commonly caUed sugar of lead from its sweetish taste. The acetic acid is held so firmly by the oxide of lead, that it can no longer escape with the steam during evaporation, or at least only in trifling quantities. Other bases may be substi- tuted for the oxide of lead. Experiment. — Place upon a piece of charcoal some sugar of lead, and heat before the blow-pipe ; the salt first melts in its water of crystallization, then it becomes brown, and is finally charred; the acetic acid is thus decomposed, like tartaric acid on the heating of the salts of tartaric acid. After being completely burnt, globules of metaUic lead remain upon the coal. The litharge is ^ also decomposed; the glowing coal abstracts from it its oxygen, and forms with it carbonic oxide gas, which escapes; consequently metalUc lead must remain behind (reduction or deoxidation). Experiment. — Mix cautiously half an ounce of sul- Fig. 106. ACETIC ACID. 213 phuric acid with half an ounce of water, and when cold pour the mixture into a flask containing one ounce of pul- verized sugar of lead. Now connect a glass tube and receiver with the flask, and distil the mixture at a mod- erate heat, on a sand-bath, until about three fourths of an ounce of the fluid has passed over. This presents an example of simple elective affinity; the strong sul- phuric acid unites with the oxide of lead, and forms with it a white, insoluble compound, which remains in the flask, while the acetic acid, rendered volatile by the heat, is converted into steam, which is condensed in the cold receiver into liquid acetic acid. The acid thus obtained is colorless, and has an ex- ceedingly sour taste and smeU. The strongest acetic acid (hydrated acetic acid) crystallizes on cooUng; a somewhat diluted acetic acid is called concentrated vinegar. Experiment — Add to strong acetic acid some drops of oil of cinnamon and cloves; if the acid was suffi- ciently strong they will dissolve. This mixture is called aromatic spirit of vinegar. Experiment. — Pour some acetic acid upon a piece of lean meat, and it will gradually become soft and gelatinous. Common vinegar has also the same effect, but in a less degree; it is indeed weU known, that meat impregnated with vinegar becomes very tender and di- gestible (soluble) when boiled or roasted. Acetic acid cannot exist without the presence of wa- ter ; seven ounces of the strongest acid contain one ounce of water chemically combined. The Latin word for vinegar is acetum; the symbol for acetic acid is, ac- cordingly, H O, A. To detect the salts of acetic acid, heat them in a test- tube with concentrated sulphuric acid; when fumes having a very acid smeU will be evolved. 214 ACIDS. RETROSPECT OF THE VEGETABLE ACIDS. 1. Almost aU vegetable acids consist of carbon, hy- ie^^^t- ^ drogen, and oxygen (oxalic acid being an exception.) ^a^- £>*y 2. They are generated during the growth of plants, ■/" €-0 /7I in which they are found either free or combined with bases. 3. We cannot artificially prepare them from their elements, like the inorganic acids. 4. Some vegetable acids may indeed be also artifi- ciaUy imitated, but as a general rule this is effected by the metamorphosis of other vegetable substances. 5. AU vegetable acids are charred by heat, and are at last completely consumed (inorganic acids are not). 6. Most vegetable acids cannot exist without the presence of water; this water plays therein the part of a base. 7. Vegetable acids comport themselves towards bases like the inorganic acids ; they form with them salts. 8. The vegetable salts are likewise decomposed by heat; the acid is charred and consumed, while the base remains behind, usually combined with carbonic acid. RADICALS. —CAPACITY OF NEUTRALIZATION. 199. The word radical signifies root or base, and is often employed in chemistry to denote that substance which is regarded as the fundamental element or base of a chemical compound. The metaUoids unite with oxygen, and some of them also with hydrogen, forming acids, and they are consequently regarded as the bases of the acids, and may be caUed the acid radicals. Sul- phur is accordingly the radical of sulphuric acid; car- ' bon, of carbonic acid; and chlorine, of chloric and RADICALS. 215 muriatic acids, &c. With regard to the vegetable acids, which are composed of three elements, carbon, hydrogen, and oxygen, if the oxygen be assumed as the acidifying principle, then the carbon and hydrogen are regarded as the acid radicals; or if hydrogen be con- sidered this principle, then carbon and oxygen would be the radicals. In either case the radical consists of two elements; and for this reason the vegetable acids are said to be acids with a compound radical, in contra- distinction to the mineral acids, which are regarded as acids with a simple radical, because they have only one element for their base. According to this classification, the hydrocyanic and fulminic acids must be classed among the acids with compound radicals, since the rad- ical cyanogen is composed of carbon and nitrogen. This theory is also applied to bases and salts. The metals combine with oxygen, forming bases, and are accordingly the fundamental elements of the bases, — basic radicals. Iron, for example, is the radical of the oxide of iron, and calcium the radical of lime. The oxide or the base is regarded as the fundamental ele- ment of the salts ; it has received the name salt radical. Protoxide of iron is accordingly the radical of green vit- riol, lime that of chalk, &c. 200. It has already been demonstrated, by several ex- periments, that the acids are neutralized or saturated by bases, and also that every acid on neutraUzation combines with a definite quantity only of a base. It now remains to consider how large this quantity may be for every acid. It has been ascertained, by accurate experiments, that 100 ounces of sulphuric acid require for neutral- ization exactly 118 ounces of potassa, or 70 ounces of Ume, or 90 ounces of protoxide of iron, or 278 ounces 216 ACIDS. of Utharge. Further researches have led also to the surprising discovery, that these so unequal quantities of the different bases contain precisely the same amount of oxygen, namely, 20 ounces. Sulphuric Acid Oxygen. 100 oz. are neutralized by 118 oz. of potassa ; these contain 20 oz. 100 " " " " 70 " " lime; " " 20 " 100" " " " 90" " protoxide of iron j" " 20" 100 " " " " 278 " " oxide of lead; " " 20 " It follows as a law for sulphuric acid, that 100 ounces of it require always for neutralization a quantity of some base in which are contained 20 ounces of oxy- gen. Thus the number 20 has been caUed the capacity of neutralization of sulphuric acid. The action of bases upon aU the other acids has been examined in the same manner, and the capacity of neutraUzation of the latter determined. That of nitric ^ acid, for example, is 14^; that of carbonic acid, 36j; that is, every quantity of any base containing exactly 14f ounces of oxygen is able to saturate or neutralize 100 ounces of nitric acid; every quantity of a base con- taining 36^- ounces of oxygen is able to saturate or neutralize 100 ounces of carbonic acid. Instead of comparing, as has been done here, the acids with the oxygen of the base, the oxygen of the acid is also sometimes compared with the oxygen of the base. This may be done very easily, if we only know in the first place how much oxygen is contained in 100 ounces of an acid. Oxygen Oxygen. 100 oz. of sulphuric acid contains 60 oz., and require in the base 20 oz. 100 " « nitric acid " 73| " " " " " 14|"' 100 " " carbonic acid " 72$ " " " " " 36$" And hence may be deduced the following simple pro-'' portion for the combination of the acids with the bases, that is, for the salts. POTASSIUM. 217 The oxygen of the acid bears the proportion to the oxygen of the bases: — In aU neutral sulphates, as 60 to 20, or as 3 to 1. « « nitrates, " 73| " 14|, " " 5 " 1. « « carbonates, « 72j " 36|, " " 2 " 1. Water acts also as a base when chemicaUy com- bined with an acid. In common sulphuric acid (HO, S 03), for example, the oxygen of the acid bears a pro- portion to the oxygen of the water as 3 to 1; in the strongest nitric acid (H O, N Os), as 5 to 1, &c. LIGHT METALS. FIRST GROUP: ALKALI-METALS. POTASSIUM (K). J^A ffi <&r fo-S At. Wt. = 489. — Sp. Gr. = 0.8. 201. Potash, or Carbonate of Potassa (K O, C 02). Experiment — Fit into a funnel a filter of blotting- paper, and place upon it a handful of wood- Fig. ic7. ashes, and graduaUy pour hot water over them; the liquid filtered through has an al- kaline taste, and turns red test-paper blue. If you evaporate it to dryness in a porcelain dish, a gray mass finaUy remains behind, which becomes white after being heated to redness in a porcelain crucible; it is called crude potash. In those countries where wood is abundant, — in America, Russia, ^&c., — it is prepared in a similar manner on a large scale, and is an article of great demand in commerce. 19 218 ALKALIES. There are to be found in ashes all the substances which the plants received from the soil during their growth ; they are not volatile, and therefore remain be- hind while the characteristic parts of the wood or plant are consumed. The soluble portion of the ashes is taken up by the water (potash and other soluble salts); those which are insoluble (siUca, insoluble salts, and unburnt pieces of coal) remain behind on the filter. Experiment. — Pour half an ounce of cold water upon half an ounce of commercial potash, stir it frequently, and let it stand for one night. Separate the Uquid by filtration from the sediment, which consists principally of silica; evaporate it down to one half, and again leave it in repose for one night, when most of the for- eign salts wiU be deposited in crystals. Again filter the liquid and evaporate to dryness, continuaUy stirring with a glass rod, and you will obtain a white granulated mass, purified potash. Potash is very easily soluble; therefore it is the first of the ingredients which is taken up by water, and the last which is separated from it; but the other admix- tures are much less so, and they remain partly undis- solved, and partly separate in crystals from the liquid, before the potash shows even the slightest tendency to crystallize. There are thus two methods by which substances of different degrees of solubifity may be separated from each other. 202. Experiments with Potash. Experiment a. — Put one portion of potash in a ves- sel, and let it stand in a dry apartment, and put an- other portion in a cellar; the former becomes moist, the latter deliquesces. Both attract water from the air, but that in the dry atmosphere of the room less than tliatf in the damp air of the cellar. Potash is a very hygro- scopic salt. ^plP f<% *"^~ * f, POTASSIUM. 225 a lively reddish flame. After the combustion is finished, the potassium has apparently vanished; but it is in fact in solution in the water, being, however, no longer po- tassium, but potassa, as we may easily ascertain by red test-paper, the color of which wiU be changed by the water to blue. Consequently it has, during the com- bustion, combined with oxygen; this oxygen it took from the water, and so much heat was thereby evolved that the second constituent of the water, hydrogen, was inflamed. If a piece of potassium is divided with a knife, it pre- sents a glistening surface like silver; but it immediately tarnishes on exposure to the moist air, and soon be- comes converted into a white body, hydrate of potassa. In this case it takes the oxygen from the air. Salts of Potassa. Salts are produced, as has been before stated, when a base combines with an oxygen acid or a hydrogen acid (oxygen salts and haloid salts). As there are hundreds of acids, so also hundreds of potassa salts may be prepared. But those only will here be considered which are of especial importance in science, the arts, or the common uses of life. 206. Sulphate of Potassa (KO, S03). Dissolve half an ounce of potash in two ounces of „. , , warm water, and neutralize with diluted Fig. ill. ' sulphuric acid; evaporate the filtered Uquid till a film appears on the surface, then let it remain quiet for one day. The hard crystals obtained (six-sided double prisms) are sulphate of potassa; they are sparingly soluble in water, and have a somewhat bitter taste. This salt forms a constituent of the well-known alum. K 0^0% +AI\*oS£()6 + 1 J\ H 226 ALKALIES. Acid Sulphate, or Bisulphate of Potassa (KO, 2 S03 -|- HO) is obtained as a secondary product in the preparation of nitric acid from saltpetre (§ 159). It contains one atom of base and two atoms of acid, and has a very acid taste. But the second atom of acid is more feebly combined than the first, and may be ex- pelled by the application of strong heat. 207. Saltpetre, Nitre, or Nitrate of Potassa (K O, N Os). Dissolve half an ounce of carbonate of po- tassa in one ounce of hot water, and neutral- ize with nitric acid; afterwards boil and filter the liquid, and set it aside to cool; prismatic crystals of nitre wiU be deposited from it, which have a cooUng taste, and undergo no alteration in the air. Experiments with Nitre. Experiment a. — Heat some nitre in a test-tube; it melts; if you pour it by drops upon a cold stone, you will obtain globules of nitre. Upon the application of a stronger heat, oxygen will escape, and afterwards nitrogen; consequently, the nitric acid is thereby re- solved into its two elements. Experiment b. — If you throw a little nitre on a glow- ing coal, it wiU sparkle briskly ; it deflagrates. In this case, also, the nitric acid is decomposed, and its sud- den conversion into two gases is the cause of the spark- ling. The oxygen, becoming free, finds in the coal a body with which it can combine; the escaping gases are, accordingly, carbonic acid and nitrogen. A portion of the carbonic acid formed combines with the potassa, which remains behind. From K O, N 05, and 2\ C are formed K O, C O.,, and l!2 C Oa. The hard saline mass, congealed from its molten state, remaining on the coal, has a basic reaction, and effervesces with acids; it is POTASSIUM. 227 carbonate of potassa, or potash. In order to render sub- stances more inflammable, they are often drenched with a solution of nitre; as, for example, tinder, &c. Experiment c. — Mix thoroughly in a mortar six drachms of powdered nitre, one drachm of charcoal- powder, and one drachm of sulphur; this is pulver- ized gunpowder. Take a little on the point of a knife, put it on a stone, and ignite it with a match ; a brisk deflagration will ensue. Knead the rest of the powder, with some drops of water, into a paste, and squeeze it through a leaden colander. The thread-like mass thus obtained is, when partly dry, divided by gen- tly rubbing with the fingers into small grains; this is gunpowder. Experiment d. — Place some gunpowder upon an iron plate, and ignite it; oiatiie. ^he explosion follows even more quickly than with the pulverized gunpow- biatiie. jg^ because the granulat- Not ed gunpowder is less com- pact than the pulverized. In this, as in the former deflagration, there are also evolved from the coal and the nitric acid, as in experiment b, carbonic acid and nitrogen, two gases which instantly occupy a space several thousand times greater than before. Sulphur not only effects an easier ignition of the gunpowder, but it causes also a stronger evolution of gas; since it combines with the potassium of the nitre, forming sul- phuret of potassium, whereby three atoms of free car- bonic acid are evolved, while in experiment b (without sulphur) only an atom and a half of this gas has been set free. If the deflagration of the gunpowder takes place in 228 ALKALIES. a confined space, as in a gun-barrel, the explosive vio- lence with which the two gases are suddenly expanded is strong enough either to project the ball or to burst the gun. The sulphuret of potassium remaining on the iron gun-barrel soon becomes moist in the air, and then emits the odor of sulphuretted hydrogen (§ 133); at the same time, the iron is blackened by the formation of sulphuret of iron upon the surface. Experiment e. — Mix twenty grains of iron filings with ten grains of nitre, and heat the mixture in an iron spoon, the handle of which has been fixed into a cork; a brisk ignition of the mix- ture wiU ensue; the iron will be oxidized by the oxygen of the nitric acid, while the nitrogen escapes. The po- tassa remaining behind may be dissolved by water. Nitre is on this account weU adapted for converting metals into metaUic oxides. /. — If nitre be heated with sulphuric acid, the nitric acid escapes (§ 159). g. — Animal substances are preserved from putrefying by nitre ; it is therefore used in the packing of meat. The manufacture of nitre is conducted in a very pe- culiar manner. Animal substances, for instance, pieces of flesh, hides, hair, &c, are mixed with Ume and earth, and then moistened with water or urine, and suffered to putrefy slowly. Animal substances are rich in nitro- gen, which, during putrefaction, is set free in the form of ammonia (NH8) ; this, after a time, unites with the oxygen of the air, forming nitric acid (and water), which acid is immediately neutralized by the Ume. If animal POTASSIUM. 229 substances decay without the presence of lime, or some other strong base, no nitric acid, but only ammonia, will.be produced; consequently, it is the strong base which disposed the nitrogen to combine with the oxygen (§ 146). After the completion of the putrefaction, add water to extract the soluble matter, and a solution of nitrate of lime is obtained, which is converted by car- bonate of potassa into soluble nitrate of potassa, and insoluble carbonate of lime. Nitre-beds, so called, are prepared in this way. We also obtain nitre from the East Indies, where it is spontaneously generated in many limestones containing potassa. 208. Chlorate of Potassa (K O, CI Os). This salt, as its formula indicates, may be regarded as a brother of nitre; but its disposition, compared with , that of the latter, is far more intractable and violent, since chloric acid is much more easily decomposed than nitric acid. Experiments with Chlorate of Potassa. Experiment a. — Chlorate of potassa is, by merely heating, very easily resolved into oxygen and chloride of potassium; therefore it is used in the preparation of oxygen, as was described in § 59. Experiment b. — When thrown on glowing coals, it deflagrates stiff more briskly than nitre; the oxygen, as it is liberated, occasions a very energetic combustion of the coal. This salt cannot be employed in the prep- aration of gunpowder, as the rapidity with which it explodes would be too much for the guns; yet, on this very account, it is extremely serviceable in fire-works, especially for producing variegated fires. The greatest caution must be observed in pulverizing and mixing it, as it may explode by merely rubbing or pounding it. When it is to be ground fine, it should always be previous- 20 230 ALKALIES. ly moistened with some drops of water; the mixing of it with other substances must always be done with the hand. Experiment c. — Introduce some crystals of chlorate of potassa into a beaker-glass, and add a smaU quan- tity of alcohol, and afterwards a few drops of sulphuric acid ; the sulphuric acid expels the chloric acid, which is immediately decomposed, and there is so great an evolution of heat as to inflame the alcohol. Experiment d. — Mix some chlorate of potassa be- tween the fingers with about half as much flowers of sulphur, and throw the mixture into sulphuric acid, contained in a beaker-glass; a brisk crackling and an ignition of the sulphur take place. This experiment is daily performed, though in a somewhat different way, in every German household, although not exactly with . the view of studying chemistry. Every one performs it who ignites a match by means of the match-flask. The red mass on the end of the match consists of chlo- rate of potassa and sulphur, which has been colored red by cinnabar; and the flask contains asbestos, moistened AtfftiCfTOj, with sulphuric acid. The asbestos serves to prevent ■l.Aavv, rfl'LV-*ne t°° deep immersion of the match. VAJjM' ^i 4*0 e. — Chlorate of potassa, like nitre, oxidizes the metals yjM^c^p^ • on being heated with them. /. — If you heat chlorate of potassa with muriatic acid, chlorine escapes. This does not proceed, however, from the chlorate of potassa, but from the muriatic acid, which is deprived of its hydrogen by the oxygen of the chloric acid, in the same manner as it was by the oxy- gen of the manganese, or of the nitric acid. Chlorate of potassa is prepared by passing chlorine into a hot solution of potassa; the process is illustrat-' ed by the annexed diagram: two salts are formed POTASSIUM. 231 simultaneously, chloride of potassium and chlorate of potassa; the first is easi- sparingiy ly, the latter more spar- soluble. . , 1 1 1 • ingly soluble in water; they may therefore be Easily . j r u soiubie. separated from each other by crystallization. Silicate of Potassa is the principal constituent of most rocks and of glass (§ 204). 209. Chloride of Potassium, or Muriate of Potassa (KC1). Dissolve half an ounce of carbonate of potassa in water, and neutralize with muriatic acid; upon concentrating the solution, cubic crystals will be obtained, having a taste similar to common salt. They consist of potassium and chlorine, and if dissolved in water, they may be regarded as muriate of potassa, K CI -f- H O, being the same as K O, H CI. 210. Iodide of Potassium, or Hydriodate of Potassa, (K I). This salt likewise crystallizes in cubes, is easily sol- uble in water, and is employed in medicine as a valu- able remedy. Experiment. — To prove that iodine is really con- tained in this white salt, heat a small portion of it in a test-tube with a little manganese and some drops of sulphuric acid, when violet fumes will be evolved. If common salt is treated in the same manner, chlorine, as is known, wiU be given off. The chemical action is the same in both cases. 211. Tartar, or Bitartrate, of Potassa (KO, 2T-f- *>HO). Common sorrel, the branches of grape-vines, unripe 232 ALKALIES. grapes, &c, have an acid taste; they contain an acid salt, tartar (§ 195). These plants absorb the alkali from the soil, but by some unknown process they prepare the tartaric acid by means of their own organization. Ripe grapes also contain tartaric acid, but the sour taste is concealed in them by the sweet taste of sugar, and we do not per- ceive it until the sugar is converted by fermentation into alcohol; that is, until the must is converted into wine. A great part of the tartar is deposited in the wine-casks as a hard, gray, or red crust (crude tartar). When this is purified from coloring matter by recrys- tallization, we obtain a white tartar (purified tartar). The powder of it is weU known under the name of cream of tartar. Tartar is very sparingly soluble in water. That it burns on heating, forming carbonate of potassa, has been already shown under tartaric acid. Pure carbonate of potassa is commonly prepared from tartar. Neutral Tartrate of Potassa (KO, T). To prepare this salt, dissolve half an ounce of pure carbonate of potassa in two and a half ounces of water, then add one ounce of purified tartar, and let the mix- ture stand for a day in a warm place, frequently stirring it. The filtered Uquid, after sufficient evaporation, yields prismatic crystals, or, when evaporated to dry- ness, a white powder. This salt is very easily soluble, but is also very easily decomposed by other acids, even by very feeble ones. On mixing a solution of it with vinegar, a white powder, cream of tartar, is precipitated. The second atom of the base is very easily abstracted' by other acids, and thus the sparingly soluble acid salt, tartar, is again formed. POTASSIUM. 233 As in the above experiment the second atom of the acid in the tartar was neutraUzed by potassa, so we can also neutralize it by other bases. We obtain «in this manner double salts, several of which are used as val- uable medicines. Tartrate of potassa + tartrate of water = cream of tartar. " " " -f " " soda = Rochelle salts. " " " -f- " " ammonia = ammoniated tartar. " " " -f- " " peroxide of iron = tartarized iron. " " " + " " oxide of antimony = tartar emetic. 212. Salt of Sorrel, Acid Oxalate, or Binoxalate of Potassa (K O, 2 C2 03 + 2 H O). The leaves of the wood-sorrel have a sour taste, and contain also an acid salt, the base of which is likewise potassa; the acid, however, is not tartaric, but oxaUc acid. In those places where the sorrel grows abun- dantly the juice is expressed, and the salt is obtained, ' by evaporation and crystallization, in white, sparingly soluble crystals. It has already been noticed (§ 197). It is in common use for removing ink-spots from linen. 213. Liver of Sulphur, or Ter sulphuret of Potassium (3KS3-f-KO, S03). Experiment—Put a mixture of one drachm of sulphur and two drachms of dry carbonate of potassa into an iron ladle ; cover it with a strip of sheet-iron, and heat it until the effervescence has ceased and the mass flows quietly. The fused mass has the color of liver, and on this account has received the name liver of sulphur; pour it upon a stone, and if it should inflame, cover it with a vessel to extinguish it. On exposure for some time to the air it becomes greenish and moist, and evolves an odor like that of rotten eggs. The simple sul- phur cannot combine directly with the compound car- 4 bonate of potassa, but it can do so if the latter surrenders its carbonic acid and its oxygen. This does take place. 20* 234 ALKALIES. The carbonic acid escapes with effervescence, while the oxygen combines with one quarter of the sulphur, form- ing sulphuric acid, which unites with a portion of the undecomposed potassa, forming sulphate of potassa; accordingly, the liver of sulphur is a mixture of tersul- phuret of potassium and sulphate of potassa. Experiment — Pour water into a test-tube contain- ing some liver of sulphur; you obtain a yeUowish- green solution. If to this you add diluted sulphuric acid, a strong evolution Volatile. Soluble. of sulphuretted hydrogen takes place, and the Uquid becomes milky from the precipitation of two thirds of the sulphur (milk of sulphur). A decomposi- inaoiubie. tion of water hereby takes "* place; the oxygen of the water converts the potassium into potassa, which unites with the sulphuric acid, but the hydrogen escapes, with one third of the sulphur, as sulphuretted hydrogen. The same thing is effected, though far more slowly, by the carbonic acid of the air, and thus is explained why the liver of sulphur (as weU as the residue left on the combustion of gunpowder) emits a smell like that of rotten eggs when it is left exposed to the air. The liver of sulphur is chiefly used for preparing sul- phur baths. A similar preparation is obtained in the moist way, as has been described (§ 129). Besides this combination of potassium with sulphur, there are several others, containing either more or less sulphur. The simplest compound of sulphur and potas- sium (KS) is obtained by heating together sulphate oi/ potassa and charcoal, which latter abstracts the oxygen POTASSIUM. 235 both from the potassa and from the sulphuric acid, forming with it carbonic oxide, which escapes. In the same manner all sulphates are converted into sulphurets by heating them with charcoal. 214. Potassa Salts as Manure. — The salts of potassa exercise a very beneficial influence upon the fertility of the soil, and are particularly adapted for those plants, in the ashes of which, when burnt, the potassa salts are found; namely, for the grape-vine, potatoes, turnips, &c. Such plants may be called potassa plants. It is now known that plants do not flourish even in the richest soil, unless they find in it certain bases (potassa, Ume, &c), and also certain acids (silicic, phosphoric, sul- phuric, &c). In order to ascertain what acids and bases, or, in other words, what salts, are required for the cultivation of a certain plant, it is merely necessary to burn this plant and examine the ashes. The sub- stances which are found, though their amount is gener- ally but very small, must be regarded as indispensable to the nourishment of this plant. If the soil is destitute of potassa, neither turnips nor grape-vines will flourish in it; if destitute of lime, it will produce neither clover nor peas. By the addition of potassa salts we can restore to such a soil its fertility for the potassa plants, and by the addition of lime we again render it produc- tive for the lime plants. On this is founded the appli- cation of the so-called mineral manure (lime, gypsum, wood-ashes, salt, &c.) to our fields. Common manure also, and soap-suds, operate partly in the same way, since they are rich in phosphoric acid, as well as in al- kaline and in lime salts. If turnips are cultivated sea- son after season upon the same field, the potassa will finally become exhausted, and turnips will no longer grow there; the same thing happens when peas are 236 ALKALIES. planted year after year upon the same land, as they will at last exhaust all the soluble lime from the soil. But turnips will flourish in this latter field, because it still contains potassa, and peas in the former field, where lime is still present. Thus is explained, in a very simple manner, the advantage of the rotation of crops, which has been universaUy introduced into agriculture. SODIUM (Na). At. Wt. = 290. —Sp. Gr. = 0.9. Common Salt, Chloride of Sodium, or Muriate of Soda (Na CI). 215. Experiment. — Dissolve one ounce of salt in two and three fourths ounces of cold water; the water will dissolve no more, even if added. Repeat the experi- -> ment, using hot instead of cold water; the result is precisely the same. Common salt has the remarkable property of being equally soluble in hot and in cold water. A larger quantity of almost aU other salts is dissolved by hot than by cold water. Put one of these solutions in a warm place; by the gradual evaporation, regular transparent crystals of common salt are formed. Boil down the other solution, quickly stirring it aU the while; it yields a granular, opaque, saline powder (disturbed crystallization). Salt is pre- pared as last described on a large scale, and hence the granular state of common salt. Experiment. — If you expose a solution of salt in an open place during the extreme cold of winter, transpar- ent prismatic crystals will be formed, which contain more than one third of water. When placed on the sodium. 237 hand they quickly become opaque and deliquesce into a syrupy mass, in which numerous small cubic crys- tals may be perceived. This experiment shows very clearly, — 1.) How one and the same body may assume differ- ent forms at different temperatures; at common tem- peratures salt crystallizes in anhydrous cubes, but under the influence of cold in hydrated prisms. 2.) How great an influence temperature exerts upon the affinities of bodies for each other. At a temper- ature above the freezing point, salt has no affinity for water; we obtain anhydrous cubes ; below the freezing point it has an affinity for water, and we obtain prisms which consist of a chemical combination of salt and water. 3.) How easily chemical bonds of affinity may be destroyed again; the heat of the hand even is sufficient to destroy the affinity of salt for water. Experiment — Heat some common salt on a plati- num foil; it will snap briskly, and part of it wiU be thrown off from the foil; that which remains melts when the foil becomes red-hot. The snapping proceeds from a trace of water (water of decrepitation), which has remained in the interstices of the crystals ; on being heated it expands and bursts the crystals asunder. Salt has been previously twice artificially prepared; namely, once from sodium and chlorine (§ 153), and again from soda and muriatic acid (§ 186); its constit- uents are accordingly already known. It has the formula Na CI. If water is present, it may be regarded also as muriate of soda, for Na CI -f- H O is equal to Na O, II CI. 216. The earth and sea abound in common salt; it may therefore be easily procured in large quantities. 238 ALKALIES. In many places it is found in the interior of the earth, in immense beds, from which it is broken up and dug out. This salt looks Uke a transparent stone, and so is called rock-salt. In those places where the rock-salt is mixed with stones and earth, a hole is bored in the middle of the bed, and water is let into it. The water is pumped out again as soon as it has be- come saturated with the salt, and is again expeUed by evaporation. In some places springs are found contain- ing salt in solution, the so-caUed natural salt springs. These are always occasioned by the water permeating the earth over a bed of rock-salt, and appearing as a spring at some lower level. As the natural springs commonly contain much more water than is necessary for the solution of the salt, a cheaper method than that of fire, namely, a current of air, is first employed for the evaporation of it. The salt water is pumped up to the top of a lofty scaffold- ing fiUed up with fagots (graduation-house), and from which it is made to faU by drops through the fagots. It diffuses itself over the branches, and thus presents a very large surface to the air passing through, whereby a very rapid evaporation is effected. AU natural salt waters contain gypsum in solution; this is first deposit- ed, since it is difficultly soluble, and encases the branch- es with a hard crust. When the greater portion of the water is evaporated, the concentrated brine is finally boiled down with constant stirring in large pans, and the granular salt, which separates, is raked out and dried. During the evaporation, a solid incrustation is deposited at the bottom of the pans, consisting principally of Glauber salts and gypsum, and from which Glauber salts are extracted. Finally, a somewhat thick liquid ' remains, the so-called mother-water, from which no SODIUM. 239 more salt can be extracted; it contains the easily soluble foreign salts present in the brine, namely, chlo- rides of calcium and magnesium, and bromide of mag- nesium, and is used for baths and for the preparation of bromine. In hot countries, salt is also prepared from sea-water, which is evaporated in shallow tanks by the heat of the sun. It is caUed bay-salt, and has a bitterish taste, ow- ing to the presence of salts of magnesia. A pound of sea-water contains from one half to five eighths of an ounce of common salt. 217. Small quantities of common salt are found in al- most every spring of water, in every soil, in every plant. Is this universal diffusion of salt to be regarded as acci- dental? By no means. This is one of the spiritual advantages to be derived from the study of the natural sciences, that they lead us to distinguish, in the wonder- ful arrangements of nature, not the sport of chance, but the forming hand of an Eternal Wisdom. We find common salt everywhere in nature, because it is indis- pensable to the life of animals and plants. Without salt, no complete digestion of food could take place, and therefore we justly regard it as a universal condi- ment. Animals find it in the meat and plants by which they are nourished; plants receive it from the soil and rain, and it is well known that we can promote the fertility of our fields by the application of a coarse kind of salt. Salt is also used for preserving animal and vegetable substances, it having the power of preventing chemical decompositions, or, in common language, putrefaction or decay. Meat and fish are salted down, and wood * for the purpose of building is rendered more durable by being impregnated with salt. 240 ALKALIES. 218. Glauber Salts, or Sulphate of Soda (Na O, S 03 + 10 HO). As most of the potassa salts, potassa, and potassium are prepared from carbonate of potassa, so most of the soda salts, soda, and sodium are prepared from com- mon salt. In the latter case, however, an in- *f; ' direct process must often be resorted to, since ]j_|l| chlorine is not so easily removed from sodium ! as carbonic acid is from potassa. The chloride of sodium must first be converted into sulphate \ of soda. We are already acquainted with this L. I. salt, it having remained in the retort after the ^—^ preparation of muriatic acid (§ 185), where common salt was heated with sulphuric acid. It was formerly taken as a popular medicine, under the name of Glauber salts, so called from its discoverer, the phy- sician, Glauber. We find it also in many mineral waters, for instance, in the Carlsbad and Pullna waters, and in the incrustation of the salt-pans, as was men- tioned under common salt. It is readily soluble, crys- tallizes in four or six sided prisms, and has a nauseous bitter taste. Experiment — Place half an ounce of transparent crystaUized Glauber salts in a warm place; they soon become covered with an opaque white coating, and final- ly crumble into powder; they effloresce. The powder obtained weighs hardly a quarter of an ounce. That which was lost was water. Glauber salts contain more than half their weight of water of crystaUization. It is thus obvious that it is this chemically combined water which imparts to the salt its form and transparency, both of which are lost when the water is evaporated by the heat; but they reappear when the pulverulent an- hydrous salt is dissolved in boiling water, and the solu- SODIUM. 241 tion aUowed to cool. Carbonate of potassa is a deli- quescent salt, common salt is a permanent salt in the air, while Glauber salts are efflorescent. Salts which efflo- resce must be kept in a cool place, well corked up. Experiment — If a crystal of Glauber salts is heated on charcoal before the blow-pipe, it soon melts, because it dissolves in its water of crystalUzation (watery fu- sion) ; it becomes dry as soon as the water is expelled; but finally it melts for the second time when heated to redness (igneous fusion). Those salts which contain no water of crystaUization undergo only the latter kind of fusion. Experiment — Heat in a smaU flask half an ounce of water to 33° C, and keep it at this temperature, gradually add- ing crystaUized Glauber salts, as long as they are dissolved, amounting to about an ounce and a half. If a stronger heat be now appUed to the saturated solution, a salt will separate (anhydrous crystals); if you let it cool, a salt wiU Ukewise sep- arate (hydrated crystals); — fur- nishing another example of the great influence exerted by tem- perature on the affinity of water for other substances. Glauber salts have the pecuUar property of being most soluble in water, not at the boiUng point, but at a lower temperature. Experiment. — If you dissolve crystallized Glauber salts in water, cold is produced; but if, on the contrary, you dissolve anhydrous Glauber salts in water, then heat is produced. You wUl observe exactly the same phe- 21 242 ALKALIES. nomena if you perform this experiment witn carbonate of soda, taking first the crystallized and then the cal- cined carbonate of soda. Whence the source of this heat ? It comes from the water, because a part of the water combines with the anhydrous Glauber salts, or the anhydrous carbonate of soda, as water of crystalli- zation. Consequently, it is a phenomenon very similar to that which takes place in the slaking of Ume (§ 33). 219. Sulphuret of Sodium (Na S). Experiment. — Mix a small portion of anhydrous Glauber salts with a little charcoal powder, and heat the mixture on charcoal before the blow-pipe; they will melt with brisk effer- vescence into a brown mass, which dissolves in water, forming a yellowish Uquid. The coal, when heated to redness, abstracts the oxygen both from the soda and from the sul- phuric acid, and forms with it carbonic oxide gas, which escapes with effervescence; sodium and sulphur remain be- hind, combined with each other. That is, the coal de- oxidizes the sulphate of soda, or reduces it to sulphuret of sodium. \ If you drop muriatic or diluted sulphuric acid into Volatile. sodium. 243 Volatile. the solution, the dis- agreeable smeU of sulphuretted hydrogen wiU be given off, just as in the case of liver of sulphur (§ 215). If you now let the liquid evapo- rate on a glass plate, you obtain, in the former case, small cubes of common salt, and in the latter, a pul- verulent incrustation of Glauber salts. 220. Carbonate of Soda (Na O, C 02 + 10 H O). Experiment — Prepare some more sulphuret of sodi- um in the manner just described, rub it in a mortar with the adhering particles of charcoal and with about its own weight of chalk, and ignite it again before the blow-pipe. Boil the baked saline mass in water, and then filter the liquid. A gray powder remains behind, which, when drenched with muriatic acid, evolves sulphuretted hydrogen ; it is sulphuret of cal- cium. The liquid, after being evaporated on a shaUow glass dish, leaves behind a white powder, which has an alkafine reaction and effervesces with muriatic acid, but yet without emitting any disagreeable odor; it is carbonate of soda. The TOhibie!y sulphur has thus passed to the calcium of the chalk, while the oxygen and the carbonic acid of the chalk have passed to the sodium. By these processes it will be seen that, as in the daily affairs of life, so also in chemistry, we can often obtain indi- rectly that which could not be gained directly. So- dium has a stronger affinity for chlorine than for oxy- gen ; therefore we cannot prepare soda directly from CVOCO,—^NaO.COl Easily soluble. 244 ALKALIES. common salt; but by means of sulphuric acid we can easily convert the haloid salt into an oxy-salt, — into sulphate of soda. The strong sulphuric acid cannot be directly expelled from this; we therefore first decompose it into oxygen and sulphur, and afterwards remove the sulphur by another metal, calcium, which forms with sulphur an insoluble compound. Soda is thus obtained, yet not in a free state, but as carbonate of soda; car- bonic acid, however, is so feeble an acid, that it may easily be expelled by another acid, or by caustic lime. As carbonate of soda possesses almost the same properties as carbonate of potassa, and may be advan- tageously employed instead of the latter in washing and bleaching, and also in the manufacture of glass and soap, it is now manufactured on a large scale in chemical works. There are, in Germany, laboratories where from ten to twelve thousand quintals of soda are annually made. The process pursued is essentiaUy the same as that already described, except that the two operations, described as separate above, are unit- ed into one; the chalk or Umestone is added, in the first place, to the Glau- ber salts and charcoal, and the whole mass is heated. This is done in a large oven-shaped fur- nace, represented in the figure, a is the grate, b the ash-pit, p the chim- ney, d d the hearth for receiving the mixture, i the aperture for throwing in the mixture, and g an open- Fig 120. sodium. 245 ing for stirring it and scooping it out. They are called flame-furnaces, because the heating is effected, not by the fuel itself, but by the flame passing over the bridge c; they possess this important advantage, that the ashes of the pit-coal or peat do not become mixed with the substance to be heated. In many countries an impure soda is also obtained from the ashes of marine plants (kelp). Carbonate of soda consists of equal atoms of soda and carbonic acid. It occurs in commerce, either crys- tallized, — it then contains more than half its weight of water of crystallization (10 atoms) and effloresces very very readily, — or calcined, consequently anhydrous. The latter, accordingly, when it occurs pure, is of more than twice the strength of the crystalUzed. Carbonate of soda is easily soluble in water. Many mineral wa- * ters —for example, the Carlsbad springs—contain great quantities of it in solution; Carlsbad salt, obtained by evaporating the waters of the spring, is a mixture of carbonate and sulphate of soda. Bicarbonate of Soda (NaO, 2C02 + HO) is more sparingly soluble than the former salt, and is frequently used in effervescing powders, because it evolves on being mixed with acids as much again car- bonic acid as the simple carbonate. Effervescing pow- ders are prepared by triturating together equal portions of tartaric acid and bicarbonate of soda. If you put this mixture into water, tartrate of soda is formed, and carbonic acid escapes. When heated, this salt com- ports itself like the bicarbonate of potassa. s 221. Soda, or Oxide of Sodium (Na O). If you take from the carbonate of soda its carbonic 21* 246 ALKALIES. acid, soda will remain behind. This is done by boiling a solution of soda with quicklime, in the same manner as was described under potassa (§203). The liquid thus obtained is called caustic soda lye, and yields, after evaporation, caustic soda. This contains, like caustic potassa, yet one atom of water, which it does not part with even when heated to redness; hence it has been more correctly caUed hydrate of soda (Na O, HO). The hydrate of soda has a corrosive action, forms soap with fat, and hard glass when melted with sand; it is a very strong base, Uke caustic potassa, for which it is often substituted in preference in the arts. 222. Sodium (Na). On abstracting oxygen from the soda metalUc sodium is obtained. This metal is prepared Uke potassium, which it greatly resembles, though it does not act so violently upon other bodies, for instance, upon water. Put upon cold water, it oxidizes without flame, but put upon hot water, the escaping hydrogen ignites, and burns with a yellow flame. We have now passed from the most widely diffused common salt to the element sodium, treating each one in that succession which it is necessary to pursue in the actual preparation of these substances. The foUowing summary statement may serve to fix them on the mem- ory : — From common salt, or chloride of sodium, sul- phate of soda is prepared; from this, sulphuret of so- dium ; from this, carbonate of soda; then soda; and finally sodium. A few other salts of soda will now be considered. 223. Phosphate of Soda. Experiment — Neutralize half an ounce of carbonate sodium. 247 of soda, dissolved in water, with phosphoric acid pre- pared from bones; filter the liquid from the phosphate of lime which separates, and evaporate the filtrate until a film forms on the surface; on cooling, transparent crystals will be deposited, which contain more than half their weight of water of crystaUization. They easily effloresce, and yield a yellow precipitate, with a solution of nitrate of silver. Experiment — Let some of the crystals of the phos- phate of soda effloresce in a warm place, and afterwards heat them to redness in a porcelain crucible. When the mass is cold, dissolve it in water, and evaporate the solution; you obtain a salt which contains far less water of crystallization than the >■ former one; it no longer effloresces, and yields with nitrate of silver a white precipitate ; it has received the name of pyrophosphate of soda. This example shows how the affinity of a salt for water may be weakened by being heated to redness, and how the properties of a salt may be changed, according to the amount of water with which it is chemically united. 224. Nitrate of Soda (NaO, N05). Experiment — Dissolve half an ounce of carbonate of soda in a little hot water, and neutral- ize it with nitric acid; then evaporate the solution till a pellicle begins to form, when crystals wiU separate, having the form of an oblique rhombic prism; they are nitrate of soda. They deflagrate on charcoal like ^ nitrate of potassa, only somewhat less violently, and have the greatest similarity to it in other respects. 248 ALKALIES. Large districts of this salt are found in America, whence whole ship-loads of it are exported, under the name of Chili saltpetre; and it is substituted for the more costly nitre in the manufacture of nitric acid and some of its salts. But it does not answer for making gunpowder, as the powder thus prepared becomes moist, and deto- nates too slowly. 225. Biborate of Soda (Borax) (Na 0,2 B 03 + 10 H O). The hard, colorless crystals commonly called borax, and generaUy covered with an efflorescent powder, con- sist of soda and boracic acid. Boracic acid, in the moist condition, is a feeble acid; therefore, like carbonic acid, it cannot entirely conceal the basic properties of soda; and borax has an alkaUne taste, and colors red test-paper blue. Borax contains half its weight of wa- ter of crystallization. Experiment. — Heat some powdered borax upon a platinum wire before the blow-pipe; it wiU puff up and swell in its water of crystallization, and be converted into a porous spongy mass; on being further heated, it fuses to a transparent bead. Moisten this bead with the tongue, apply it to litharge so that some of the lat- ter may adhere to it, and again hold it in the exterior flame of the blow-pipe; the litharge is dissolved; the bead remains colorless and transparent. If you now substitute for the litharge other metallic oxides, you will likewise observe that the oxides will dissolve, but that at the same time the bead will be colored by them; namely, yellowish-red, by sesquioxide of iron and oxide of anti- mony ; green, by the oxides of copper and chromium; blue, by oxide of cobalt; violet, by a small portion of oxide of manganese; and brownish-black, by an excessf of manganese. The metalUc oxides comport themselves SODIUM. 249 also in the same manner, when they are fused into common glass or earthen ware. They are for this rea- son called vitrifiable pigments (borates or siUcates of metalUc oxides). On account of this property which borax has of dis- solving metallic oxides, it is used in chemistry as a blow-pipe test for the detection of metallic oxides, and in the trades for soldering, or joining one metal with another. Hold by the forceps a piece of copper, on which is placed a piece of tin and iron wire, over the flame of a spirit-lamp; the tin will indeed melt, but it will not adhere either to the copper or the iron. Repeat the ex- periment, having previously smeared the copper and the wire with a paste made of borax-powder and water; the result is now quite different, for the melting tin unites with both metals, and the wire, when cold, is found to be firmly soldered upon the copper. The explanation of this different result is simply as fol- lows. Metals only adhere to metals when they have clean, pofished surfaces; the clean surface is lost on heating the metals, because a layer of oxide is formed upon them by the oxygen of the air; but the bright sur- face is restored again by the borax, which, when it melts, dissolves the oxide formed. Borax occurs native (tincal) in many of the lakes of Asia; but it is now prepared also from boracic acid, which is obtained from some hot springs in Italy, and Ms neutralized by soda. 250 ALKALIES. 226. Glass (Silicic Acid combined with Bases). As boracic acid forms with soda, when heated, a vit- reous compound, so silicic acid, which is very analogous to boracic acid, forms likewise a vitreous combination with soda, and also with other bases, as with potassa, lime, oxide of lead, oxide of iron, &c. Glass, glazing, enamel, &c, are varieties of this combination. Experiment. — Melt some carbonate of potassa or soda upon a platinum wire before the blow-pipe, and then add a Uttle finely pulverized sand; upon placing it again in the blow-pipe flame, effervescence will ensue, and afterwards a clear bead wiU be formed. If the proportion of sand used be small, the glass formed (basic silicate of potassa or soda) will dissolve in water on long-continued boffing; it is then called soluble glass (§ 204). If more sand is taken, a glass (acid silicate of potassa or soda) is obtained which it is very difficult to dissolve in water. To make a glass which shall be entirely insoluble, not only in water but also in acids, beside the potassa and soda, some other earth or metallic base — for instance, lime or litharge — must be added. Common glass is thus manufactured in glass- houses. The materials which are chiefly employed in the manufacture of glass are, — a) quartz, flint, or sand; b) carbonate of potassa or wood-ashes; c) carbonate of soda or Glauber salts; d) Ume or chalk; e) litharge or minium. These substances, after being pulverized, are mixed together, thrown into earthen pots, and heated in a furnace until the mass is one uniform fluid. In this state it may be moulded like wax, cut and bent, pressed into moulds, and blown, and may accordingly* be manufactured into aU possible shapes and forms; on SODIUM. 251 cooling, it becomes hard and brittle. In order to di- minish in a measure the brittleness, the glass must be cooled very slowly (annealed). Glass vessels that are rapidly cooled often crack when they are carried from a warm into a cold room; this defect may, to a certain degree, be corrected, by gradually heating the vessels in water tiU it boils, and then aUowing it to cool very slowly. For coloring and painting glass the vitrifiable pig- ments, as noticed in § 225, are employed. The milk- white color which we observe in the opaque glass of the lamp-screens, and in the enamel of the dial-plate of watches, is produced by finely ground bone-earth or oxide of tin, neither of which substances is dissolved by the vitreous mass, but only mixes with it mechanically, and renders it opaque, as chalk does water. Glass is ground by sand and emery, polished by sesquioxide of iron and tripoli, etched by hydrofluoric acid, and very easily perforated by the point of a three-cornered file, which should be frequently moistened with oil of tur- pentine. The two principal kinds of glass are, — a) Crown or Bohemian glass, consisting of potassa (soda), lime, and silica. b) Flint or crystal glass, consisting of potassa, oxide of lead, and silica. Common bottle-glass contains the same ingredients as crown glass, with the addition of sesquioxide of iron, which imparts to it a brownish-yellow color, or of protoxide of iron, which gives it a green tinge. This iron is contained in the impure materials (yeUow sand and wood-ashes) used in the preparation of the ordinary sorts of glass. 252 ALKALIES. SYSTEMATIC ARRANGEMENT OF THE COMPOUNDS OF POTASSIUM AND SODIUM. Metals: Potassium. Sodium. Oxides: Oxide of potassium, or caus- Oxide of sodium, or caustic tic potassa. soda. Sulphurets: Sulphuret of potassium, or Liver of sulphur. Sulphuret of sodium. Haloid Salts: Chloride of potassium. Chloride of sodium. Iodide of potassium. Iodide of sodium. Oxy-salts; Carbonate of potassa. Carbonate of soda. Bicarbonate of potassa. Bicarbonate of soda. Chlorate of potassa. Nitrate of potassa, or salt- Nitrate of soda, or Chili salt- petre. petre. Sulphate of potassa. Sulphate of soda, or Glauber salts. Bisulphate of potassa. Bisulphate of soda. Sulphite of soda. Phosphate of soda. Silicate of potassa, or glass. Silicate of soda, or glass. Basic silicate of potassa, or Biborate of soda, or borax. soluble glass. Tartrate of potassa. Bitartrate of potassa, or tartar. Double salts of tartar. Binoxalate of potassa, or salt of sorrel. Acetate of potassa, &c. , AMMONIA (NH3). At. Wt. = 213. — Sp. Gr. [as gas] = 0.6. 227. Experiment — 1.) Mix intimately together forty grains of fine iron filings, and two grains of hydrate of potassa (caustic potassa), and heat them in a test-tube, to which is adapted a bent glass tube (Fig. 26). As soon as the atmospheric air is expelled, receive the gas as it is evolved in a separate flask; it may be inflamed AMMONIA. 253 Volatile. Soluble. Insoluble. Volatile. Soluble. Insoluble. by a lighted taper; it is hydrogen. It comes from the water of the hydrate of potassa, the oxygen of which combines with the iron. The potassa serves to hold fast the water, un- til a red heat is pro- duced : water, by itself, could have been heated only to 100° C. Experiment — 2.) Heat forty grains of iron filings and two grains of nitre in the same manner as before. You obtain a gas in which a Ughted taper is extin- guished; it is nitrogen. The same occurs in the case of nitric acid as with the water; the Iron abstracts from it oxygen ; and its second constituent, nitrogen, is thereby set free, and escapes. Experiment. — 3.) Unite the two former experiments into one, that is, heat eighty grains of iron filings at the same time with two grains of po- tassa and two grains of nitre, in an open test-tube: neither hy- drogen nor nitrogen is evolved, but a combination of both in a gaseous form, having a pungent odor resembling that of ammonia. A strip of moistened red test-paper held over the test- tube is turned blue; consequently, this new kind of gas alkaline character; we caff it ammonia. 22 Volatile. Non- volatile. possesses an 254 ALKALIES. Ammonia is, as we see, a chemical combination of hy- drogen and nitrogen. But these two bodies unite with each other only at the moment of being liberated from another combination (nascent state). If they do not come together till afterwards, when they have already become gaseous, no union takes place. , In ammonia, one atom of nitrogen is always com- bined with three atoms of hydrogen; therefore its formu- la is N H3. From three measures of hydrogen and one measure of nitrogen are formed, not four measures, but only two measures, of ammoniacal gas; accordingly, the ammoniacal gas occupies only half the space previ- ously occupied by its constituents, and a condensation of one half is produced by chemical combination. In the formation of water from its constituents, this con- densation amounted to two thirds (§ 87). 228. Ammonia by dry Distillation. — Ammonia is also produced when animal substances are heated with ex- clusion of air. These substances always contain nitro- gen and hydrogen, which, at the moment of being set free by heat, combine with each other, forming am- monia. Experiment — Reduce to a coarse powder one ounce Fig. 124. AMMONIA. 255 of bones, and heat them in a flask as long as any vola- tile matter continues to escape. The flask must be previously connected, by a bent glass tube, with a bottle containing a little water, which bottle must be kept cool in a basin of water. Adapt to the cork of the receiving bottle another, glass tube open at both ends, through which those gases may escape which are not absorbed by the water. These smell very disagreeably, but the odor vanishes when they are inflamed. The gases burn with a luminous flame, like pit-coal gas, which they much resemble in their constitution. A brownish-black tarry matter is deposited in the bottle, which is known under the name of oil of hartshorn, or DippeU's &ri\-%t7vr%>J mal oil. After the completion of the dry distillation,^ frC* it is separated from the watery solution by filtering through paper previously moistened with water. The filtrate still contains some of this oil in solution, and has thereby a brown color and an agreeable odor. But at the same time we perceive also a pungent smell of am- monia, which latter is also detected by means of red test-paper, the color of which is changed to blue. Add some lime-water to this ammoniacal solution; it becomes turbid, and emits a more powerful odor of ammonia. The turbidness is owing to the precipita- tion of carbonate of lime, the ammonia not being free in the liquid, but combined with carbonic acid. Car- bonic acid is generated during every combustion or charring of organic substances; it here finds a base in the ammonia, and consequently combines with it. In the carbonate of potassa and carbonate of soda, we have already seen that the basic properties of the po- tassa and of the soda are not entirely concealed by the carbonic acid, — that the base, as it were, still glimmers through. Ammonia also comports itself quite in the 256 ALKALIES. same manner; although chemically combined with carbonic acid, it still emits a pungent odor, and affords an alkaline or basic reaction. Formerly this pungent brown liquid was used as a popular sudorific, and was called spirit of hartshorn, because it was prepared from harts' horns, instead of from bones. For the same rea- son, the impure dry carbonate of ammonia prepared from it received the name, still in use, of salt of hartshorn. It is only with difficulty that this pungent oil can be separated from the carbonate of ammonia ; this separa- tion is most easily effected by converting the carbonate of ammonia into chloride of ammonium. Sal Ammoniac, or Chloride of Ammonium (N H3, H CI). 229. Experiment. — Neutralize the ammoniacal liquid Cf obtained in the last experiment with muriatic acid; boil it with some animal charcoal, and filter it. After fil- tration, the liquid has less color than before, because a great part of the coloring matter has been absorbed by the coal (§ 105); after sufficient evaporation it yields brown crystals, which are finally rendered entirely col- orless by repeated solution and boiling with coal. This salt was formerly prepared in the district of Ammonia, in Africa, from camel's dung; hence its name, sal am- moniac. The ammonia in this, as in its other salts, is so completely neutraUzed by the acids, that you can no longer recognize it by the smeU. Experiments with Sal Ammoniac. Experiment a. — If some sal ammoniac is heated upon a platinum foil, over the flame of a spirit-lamp, it volatilizes in white fumes. All ammoniacal salts are volatilized by heat. If the vapor of sal ammoniac is condensed in a cold vessel, you obtain it as a solid, AMMONIA. 257 transparent mass, which is pulverized with difficulty. The sal ammoniac of commerce generally occurs in this form; it is then caUed sublimed sal ammoniac. Experiment b. — Throw some powdered sal ammo- niac into water in which a thermometer is immersed; the powder readily dissolves, and the mercury falls considerably. In this manner, artificial cold may be produced. Experiment c. — If sal ammoniac is triturated with slaked lime or potassa, it evolves a strong ammoniacal odor, because the potassa or the lime abstracts from it the muriatic acid. This mixture is sometimes used for fining smefiing-bottles. Experiment d. — Put a piece of tin, the size of a pea, Fig 125. upon a bright cent, and hold it, by means of a pair of forceps, in the flame of a spirit-lamp ; when the tin is melted, rub it upon the cent with a rag; it will not adhere to it. Now re- peat the experiment, but strew at the same time some powdered sal ammoniac upon the copper surface ; the tin is now equally diffused by the rubbing. On this is founded the important ap- plication of sal ammoniac in tinning and soldering. The muriatic acid of the ammonia combines with the oxide of copper formed by heating, and thereby a bright surface of copper is produced, to which the fused tin will firmly adhere; hence we perceive, also, during the process of tinning, a smeU of free ammonia. Ammonia and the ammoniacal salts are commonly prepared from »al ammoniac. 22' 258 ALKALIES. Ammonia, or Water of Ammonia (N H3 -f- Aq). 230. Experiment — Pour an ounce and a half of water upon a quarter of an ounce of sal ammoniac and three drams of slaked lime, contained in a flask, ar- ranged as described in Fig. 106, and then apply a mod- erate heat; the Ume abstracts from the sal ammoniac, as has already been seen, its muriatic acid, and the am- moniacal gas escapes. As soon as it is released it as- cends, since it is nearly one half Ughter than common air; it turns red litmus-paper blue, and forms thick white fumes of sal ammoniac when a paper moistened with muriatic acid is held in it. If the longer Umb of the tube is now passed nearly to the bottom of a phial containing one ounce of water, the gas is dis- solved, and you obtain a solution of ammonia (water of ammonia). One measure of water can absorb more than 600 measures of ammoniacal gas. Since much latent heat must therefore be liberated, the receiving vessel should be placed in cold water. A second tube, open at both ends, may be adapted to the cork of the flask to prevent the water being forced back from the phial in case the heat should accidentaUy be dimin- ished. The tube must reach to the bottom of the flask, for otherwise the gas would escape through it. The solution of ammonia is lighter than water, and so much the lighter in proportion to the amount of am- moniacal gas it contains; for this reason, its strength may be very accurately determined by its specific gravity. Its most important properties have already been mentioned. On account of its corrosive properties it is also caUed caustic ammonia. AMMONIA. 259 231. Hydrosulphuret of Ammonia, or Sulphuret of Am- monium (NHj, HS). Experiment. — Pass a stream of sulphuretted hydro- gen gas, evolved as described in § 132, into a solution of ammonia, as long as the solution continues to receive the gas. This solution must be kept in well-closed glass bottles, because it is decomposed on exposure to the air, and becomes yellow. It is one of the most important chemical reagents, as wiU be shown here- after. 232. Carbonate of Ammonia (2 NH3, 3 C02 + 2 H O). The crude carbonate of ammonia has al- ?J^' m_ ready been treated of; the pure is prepared P [ from sal ammoniac and chalk, by sublima- tion. Experiment. — Introduce a mixture of half ^^^ an ounce of chalk and a quarter of an ounce T~T of sal ammoniac into a four-ounce flask, | having a thin bottom; place it in a sand- bath, and heat it over a spirit-lamp. As soon as pungent vapors are perceived, invert v^s^ a somewhat larger flask over the former, and the fumes will soon condense into a white saUne mass. By double elective affinity there are formed volatile carbonate of ammonia, which sublimes, and chloride of calcium, which remains behind, since it is not volatile. Carbonate of ammonia (or, more correctly, sesqui- carbonate of ammonia) is a white substance having a pungent ammoniacal odor, which gradually attracts more carbonic acid from the air, and becomes bicarbo- v nate of ammonia. This salt is frequently used by bakers, instead of yeast, for raising gingerbread, spice- 260 ALKALIES. cakes, &c.; it escapes in the heat as a gas from the dough, and renders it Ught and porous. Other ammoniacal salts may easily be prepared from the carbonate of ammonia, by expelling the carbonic acid by means of a stronger one; for instance, by sul- phuric, nitric, or acetic acid, &c. 233. Ammonia from putrefying Substances. — One other source of ammonia yet remains to be noticed. It occurs wherever organic substances are undergoing putrefaction and decay. Carbonate of ammonia is evolved from all vegetable and animal substances which contain nitrogen, when they putrefy or decay; hence the pungent odor of stables and manure-heaps. If you put a bowl containing muriatic acid or diluted sulphuric acid in such places, the odor vanishes, and the muriatic acid is gradually converted into muriate of ammonia, and the sulphuric acid into sulphate of am- monia. Thus we possess in the acids a simple and cheap means of purifying the air in such places. Putrid urine contains so much carbonate of ammonia, that it is used instead of soap-water for washing wool, and indeed even for the preparation of muriate of ammonia itself. 234. When we reflect upon the action of the ani- mal substances already treated of, we cannot but be surprised to find how very much the nitrogen contained in them varies in its affinity for other elements. The nitrogen of organic substances combines, — With hydrogen, at common temperatures, forming ammonia (decay). With oxygen, at common temperatures, and in the presence of a strong base, forming nitric acid in nitre- beds. With hydrogen, on the application of heat and with- out access of air, forming ammonia (dry distiUation). AMMONIA. 261 With carbon, on the application of heat, without ac- cess of air, and in the presence of a strong anhydrous base, forming cyanogen. With hydrogen, on the application of heat, without access of air, and in the presence of a hydrated base, forming ammonia. But it escapes uncombined, on the application of heat, with free access of air (complete combustion). 235. The Salts of Ammonia afford an excellent ma- nure for soils. They are the principal ingredients in many kinds of manure; and therefore we should en- deavour to prevent the escape of ammonia from manure- heaps, by sprinkling them from time to time with di- luted sulphuric acid, or by strewing gypsum over them, whereby sulphate of ammonia is formed, which does p not volatiUze at common temperatures. When bones decay, carbonate of ammonia is likewise produced from the gelatine, and to this is to be ascribed the second beneficial influence which pulverized bones exercise upon the growth of our cultivated plants (§ 176). Those plants which grow wild can receive only so much ammonia as they find in the air; but by manur- ing we give a much larger quantity of it to cultivated plants; and thus is in part explained the far greater fertility of manured arable land in comparison with that which is not manured. Ammonia affords another example of the circulation in the great economy of nature, similar to that present- ed in the instances of carbonic acid and water, the two other principal sources of nourishment for the vegetable world ; and we cannot but be astonished at the simple v manner in which the Creator has connected life and death with each other. During the processes of putre- faction and decay, the dead animals and plants are con- 262 ALKALIES. verted into carbonic acid, water, and ammonia; and from these three products of decay are reproduced all the innumerable plants which cover the surface of our earth. Fig. 127. Dead animals and plants. Living plants. 236. The great resemblance of ammonia to potassa and soda has long since given rise to the conjecture, that a metal might also be concealed in it, as well as in the potassa and soda. If a body—for instance, cyanogen— which comported itself exactly like a chemical element, like chlorine, could be generated from nitrogen and car- bon, so also it was possible that a body might be formed from nitrogen and hydrogen which should comport itself like a metal, like potassium. Chemists have not yet succeeded in separating such a metal from ammonia or its salts; nevertheless, the opinion is maintained by many of them, that such a metal does reaUy exist, and consists of one atom of nitrogen and four atoms of hy- drogen (NH4). They have called it ammonium] and, according to this view, regard hydrated ammonia (NH3 -f- HO) as oxide of ammonium (NH, O), mu- riate of ammonia (NH3 -f- H CI), as chloride of ammo- nium (NH, CI), &c, which amounts to the same thing, since the constitution of these two bodies is not changed, whether the hydrogen is considered as belonging to the water or to the muriatic acid, or as combined with the ammonia. A compound of one atom of nitrogen and two atoms of hydrogen (NH2) has been caUed amide. RETROSPECT OF THE ALKALIES. 263 LITHIUM. A very rare base, lithia or oxide of lithium, occurs in several minerals and mineral waters ; it possesses prop- erties analogous to those of potassa. Many salts of lithia impart a beautiful crimson color to the blow-pipe flame, and to the flame of burning alcohol. RETROSPECT OF THE ALKALIES (POTASSA, SODA, AND AMMONIA). 1. Of all bodies, potassium and sodium have the greatest affinity for oxygen; they float upon water, and decompose it with great violence. 2. Their oxides are the most powerful bases. The ox- g ide of potassium is commonly called potassa, or caustic ka^cOsK potassa; the oxide of sodium, soda, or caustic soda; and &"<&,& J* ammonia may also be regarded as caustic ammonia. 3. These three oxides are commonly called alkalies, also caustic alkalies. Formerly potassa was called vegetable alkaU; soda, mineral alkaU; and ammonia, volatile alkaU. 4. The alkalies are easily soluble in water, have an alkaline taste, and exert a strong caustic action on animal and vegetable substances. 5. The alkalies have a very great affinity for car- bonic acid. They absorb it eagerly from the air, and become converted into alkaUne carbonates. 6. Carbonic acid cannot be expelled from the alka- line carbonates by heating, but it escapes immediately, with effervescence, on the addition of other acids. v 7. The alkaline carbonates, carbonate of potassa, of soda, and of ammonia, are easily soluble in water, and have likewise an alkaline taste and a basic reaction. 264 ALKALINE EARTHS. 8. Potassa and soda, with sand, yield melted glass; and with fat, a soap, which is soluble in water. 9. Most of the salts which the alkalies form with acids are soluble in water. Most of the potassa salts are permanent in the air, some deliquescent; most of the soda salts contain water of crystalUzation, and effloresce in a dry atmosphere. 10. Potassa and soda salts are not volatile in the heat, but the salts of ammonia are so. 11. A weaker base wiU often remove the acid from a stronger base, when it forms with this acid an insol- uble compound. SECOND GROUP: THE ALKALINE EARTHS. £*X^, j»4^f^.£^^CAJLCI\JM (Ca). At. Wt. = 250. — Sp. Gr. ? Chalk, or Carbonate of Lime (CaO, C02). 237. It is already known that chalk consists of car- bonate of lime; it was used, indeed, in several of the earlier experiments for the preparation of carbonic acid. We find just the same constituents also in common limestone, in marble, oyster-sheUs, &c. There are whole ridges of mountains consisting of limestone, and extensive districts having a lime or calcareous soil; Fig. 128. carbonate of lime is one of the principal _____ constituents of our earth. We also find r~^~^~jm it in transparent crystalline forms, rhom- / 'fir bohedrons, and six-sided prisms, and then call it calcareous spar. The great differ- ence which these stones present in their exterior ap-^ pearance cannot be wondered at, for we see a similar variety of form in our common sugar; we have it crys- CALCIUM. 265 taUized in candy, granular-crystaUine in loaf-sugar, amor- phous in bonbons, and pulverulent in pounded sugar. All limestones effervesce when treated with an acid, and may thus generaUy be distinguished from other stones. If you smear a piece of limestone in single spots with fat or some varnish-paint, and then pour upon it an acid (a weak solution of nitric acid is the best), the lime dissolves in those places only which are unprotected by the fat or paint, the greasy spots ac- cordingly remaining raised. If a stone thus prepared is passed over with printing-ink, this will adhere only to the elevated places, and may be transferred from them to paper. This is the method used for engraving on stone, and the limestones used in this kind of engrav- ing are caUed lithographic stones. Experiment — Blow air into lime-water, through a glass tube; a precipitate of carbonate of lime is formed (see Fig. 81); •ontinue the blowing, and the precipi- tate will, for the most part, dissolve again. The car- bonic acid first precipitates the lime, then it dissolves it again. Carbonate of lime is quite insoluble in water, but is soluble in water impregnated with car- bonic acid. Let half of the liquid remain exposed to the air, it will gradually become turbid, and carbonate of lime will be deposited; boil the other half in a test- tube, bubbles of carbonic acid will escape, and carbo- nate of lime will be rapidly precipitated. What here happens on a small scale frequently occurs in nature on a large scale. The water, as it trickles through the earth in those places where the decay of organic mat- ter is going on, finds carbonic acid ; therefore almost all spring-water contains carbonic acid. The carbonic acid water so formed finds in almost all earths and stones carbonate of lime, some of which it dissolves; therefore 23 266 ALKALINE EARTHS. A. W*)* almost all spring-water contains carbonate of Ume (hard water). When this water flows along in brooks, the car- bonic acid escapes again, and the carbonate of lime is deposited as sediment; this water, free from lime, is now called soft water. The same thing happens when water U, ^^»*containing lime, as it percolates through the earth or fis- sures in rocks, meets with hollows and caverns; here the carbonate of lime frequently deposits itself in soUd mass- a. 11 k t'/es, called stalactites. The walls of cellars and bridges *. ■% *-/tfiJs are sometimeS found covered with an incrustation of sta- y J lactites. The calcareous tufa deposited from the Carls- f^^\/;t' bad waters also consists principally of carbonate of Ume. If you boil hard water, carbonate of lime is also precipitated; this happens especially when large quan- tities of it are evaporated, as in steam-boilers. Peas and beans, boiled in hard water, become incrusted with a thin coating of lime, which prevents the water from penetrating, so that they do not become soft; for such purposes, the water should previously be boiled, or ex- posed for some time to the air. Caustic Lime, or Quicklime (Oxide of Calcium, CaO). 238. Experiment. — Put a piece of chalk upon coal, and heat it strongly before the blow-pipe for several minutes; it wiU then become much lighter than before, lose its marking properties, and will no longer effervesce with acids; it has by the heating lost its carbonic acid, and is now called burnt lime. If a portion of it is placed on moistened red Utmus-paper, it causes blue spots; consequently it has a basic reaction, which chalk has not. For burning large masses of chalk or limestone, kilns , of the annexed form are constructed, a is the fire-door, with the grate, upon which pit-coal or turf is burnt; b, the CALCIUM. 267 Fig. 129. opening ior the draught of air; c and d, the ash-pit. In this, as in the flame-furnace, the flame only enters the kiln, which is filled with Umestone; conse- quently the Ume cannot be rendered impure by the ashes of the fuel. A kiln is usuaUy provided with several such furnaces, e and/are the dis- charge outlets for extracting the lime, when it is weU cal- cined, fresh carbonate of lime being introduced at the top as the burnt lime is removed. Such furnaces may be kept going for years without interruption. Quicklime has two strong affinities, namely, for wa- ' ter and for carbonic acid. On exposure to the air it first attracts water, and thereby crumbles into powder, — it is slaked; afterwards it absorbs also carbonic acid, when it again effervesces with acids. The rapid slaking of lime by drenching with water, and the con- sequent evolution of heat, have been previously treated of (§ 33). Three pounds of Ume combine with one pound of water, forming a fine powder of hydrate of lime (CaO-f-HO), or slaked Ume. When mixed with water into a paste, it is mortar; if more water is added, it becomes milk of lime; and when mixed with 600 times its quantity of water, a clear solution, lime- water, is obtained. Like Glauber salts, it is much more soluble in cold than in hot water, the latter dis- solving only half as much as the former. On account of the great affinity of burnt lime for water, it may be V employed for drying damp places, and for preparing an- hydrous or absolute alcohol from the common alcohol. 268 ALKALINE EARTHS. Examples of the avidity with which quicldime com- bines with carbonic acid have already been given, under combustion, and in the preparation of caustic potassa and of caustic soda. Hence it is very useful for purifying air which contains much carbonic acid; for instance, the air in old cellars, weUs, mines, or in ceUars in which fermenting Uquors, as wine, beer, brandy, &c, are kept. Milk of Ume is also commonly used for abstracting from crude iUuminating gas its carbonic acid, as well as the admixture of sulphuretted hydrogen. It is Ukewise in general use for white- washing ; it becomes quickly white and dry, and then it is no longer hydrate of Ume, but chalk. 239. Lime as Mortar. — Glue is used for joining to- gether pieces of wood; and mortar, a mixture of lime and sand, for cementing together stones. This is the most important application of lime. A mixture of lime and sand, on exposure to the air, gradually forms into a hard and stony mass. This consoUdation is to be as- cribed to three causes; — 1st, the water evaporates, and the hydrate of lime remains behind as a cohesive mass; 2d, the Ume attracts carbonic acid from the air, and there is formed a mixture of hydrate of lime and carbonate of lime, which possesses greater firmness than either body separately; 3d, on the surface of the sand a chemical combination is graduaUy formed of the silicic acid with the lime, both becoming, as it were, incorpo- rated together. This explains the remarkable hardness of the mortar in old buildings. When our structures of the present day shall have stood for centuries, the mortar about them wiU certainly possess the same de- gree of firmness, provided good quartz sand has been £U,4<,&t* employed in its preparation, and not the argillaceous *7* / A/k^ sand so often used. Sand also diminishes the shrink- CALCIUM. 269 ing or contraction of the mortar, and prevents its crack- ing as it becomes dry. Old mortar accordingly con- sists of hydrate of Ume, carbonate of Ume, silicate of lime, and silica (sand). If you burn a Umestone in which clay is contained, or an intimate mixture of chalk with one fifth of clay, you will obtain a burnt Ume, which, when mixed with water and sand, yields a mortar that hardens quickly, like plaster of Paris, and becomes as hard as stone un- der water; it is caUed hydraulic cement, and is weU a^i/A' adapted for building piers of bridges, or other structures **^' under water. Clay is silicate of alumina; therefore hydraulic cement is an intimate mixture of quicklime (>- C? with siUcate of alumina. 240. Further Experiments with Lime. t Experiment — Wrap a piece of quicklime in paper or in a Unen rag, and set it aside for some weeks ; the paper and the Unen wiU become, after a time, so rotten as to be easily torn; the Ume, to use a common ex- pression, has eaten them. Thus quicklime, Uke potassa or soda, exerts a corrosive action upon organic sub- stances, and for this reason it is also frequently caUed caustic lime. If you rub between the fingers Ume made into a paste with water, you readily perceive by the feeling its caustic action upon the skin. In tanneries the hides are immersed in milk of lime, in order to loosen them, so that the hair may easily be rubbed off; and in agriculture, Ume is mixed with weeds, such as couch-grass, &c, to accelerate their de- composition. It is, however, altogether wrong to mix lime with manure that is already in a state of decay V and putrefaction, because it contains ammoniacal salts, the ammonia of which would be set free bv the lime, 23* 270 ALKALINE EARTHS. and escape; the manure would thus lose much of its efficacy. Many plants, as peas, clover, tobacco, flourish only in a soil containing lime. If you burn such plants, you always obtain, let them grow wherever they wiU, ashes which contain more than half their weight of lime salts; we call such plants lime plants, and must conclude from these two facts, that Ume is as indispensable for the Ufe of many plants, as common salt is for that of animals. Thus agriculturalists possess in Ume an excellent ma- nure for those fields where Ume is deficient. Experiment. — Dissolve a little soap in hot water, and add Ume-water to it; the solution becomes turbid, and afterwards white flakes are deposited, which feel sticky when rubbed between the fingers. The same thing is observed on washing with soap and lime-water; the soap neither lathers nor cleanses. Therefore, water containing Ume, the so-called hard water, cannot be used for washing. The viscous mass which separates is Ume soap, a combination of the fatty substances con- tained in the soap with Ume. Potassa and soda soap are soluble in water, Ume soap is insoluble. Caustic Ume is a combination of oxygen with a metal, which has received the name calcium (Ca); it may therefore be called, also, oxide of calcium (CaO). Lime is, next to the alkalies, one of the strongest bases. Gypsum, or Sulphate of Lime (Ca O, S 03 -f- 2 H O). 241. Experiment — Expose to a moderate heat in an iron vessel the gypsum obtained in .former experiments (§§ 164, 176), stirring it during the heating, which must be continued till vapors cease to escape from it; it will afterwards weigh one fifth less than before, and is caUed ? calcined gypsum. The loss of weight is owing to the CALCIUM. 271 water of crystaUization which was driven off by the heat. A temperature of 120° C. is sufficient to effect this. Experiment. — Wind round the brim of a dollar-piece -LvPtL-v. a strip of paper, firmly securing the ^v^-**^ loose end of it by seafing-wax. A box is thus made, the bottom of which is formed by the doUar. Now mix two even spoonfuls of calcined gypsum and a spoonful of water into a paste, stir it round quickly, and pour the paste into the box; after a few minutes it will become so hard, that both the paper and the coin can be removed. A reversed impression of the coin will appear on the un- der side of the gypsum. After this is perfectly dry, smear the impression with a strong solution of soap, mixed with a few drops of oil, and upon pouring over it * some of the gypsum paste, a true stamp of the coin will be obtained. The rapid hardening may be thus ex- plained; the anhydrous burnt gypsum again chemically combines with as much water as it has lost during the ignition. If the gypsum had been heated above 160° C, it would not have hardened; it having then lost its affin- ity for water. In a similar manner, figures of plaster of Paris are made in hollow moulds. Gypsum is used in architecture for making on waUs and ceiUngs various ornamental figures and designs, called stucco-work. ^\.+i- cUUxS- * Gypsum is a mineral of very frequent occurrence ixr>tie^-' **" nature, and in some locafities, as at Jena, it forms entire ^'-u*. . ranges of hills. When crystalHzed in tables it is termed selenite, and the white, compact, granular variety is called alabaster. It is also frequently contained in Bpring-water. v Gypsum is very sparingly soluble in water, half an ounce of the latter dissolving only half a grain of gypsum. 272 ALKALINE EARTHS. To detect gypsum in a liquid, add to one portion a solution of chloride of barium, whereby the presence of sulphuric acid is indicated; and to another portion, a solution of oxaUc acid, by which the presence of Ume is shown. OxaUc acid is the most certain test for lime salts (§ 197). That gypsum, as weU as quicldime, is a valuable manure for many plants, especially for the leguminous plants, is weU known to farmers, who frequently spread it over their clover-fields. The plants hereby not only absorb the lime, but also the sulphur of the sulphuric acid. Gypsum has also a beneficial effect on the growth of plants, as it absorbs the carbonate of ammo- nia contained in the air and in rain-water, and fixes it in the soil, these two salts being converted respectively into sulphate of ammonia and carbonate of lime. When gypsum is heated to redness with charcoal, sulphuret of calcium is obtained, which, Uke the Uver of sulphur, evolves sulphuretted hydrogen, when drenched with diluted acid. 242. Phosphate of lime constitutes, as already men- tioned, the principal ingredient of bones; it occurs in the mineral kingdom as apatite and phosphorite. 243. Nitrate of lime (Ca O, N 05) is always formed when azotized substances and lime remain for some time together in contact (§ 207). This salt is very often generated in the plaster of walls, in those build- ings where urinous liquids or ammoniacal fumes are present, as in stables. The Ume loses hereby its adhe- siveness, and crumbles, especially when the rain washes out the easily soluble nitrate of lime. This process is commonly called the crumbling away of the walls.* -------------------------------------------------v * " The injury thus done to a building by the formation of soluble ni- trates has received (in Germany) a special name, Saltpetrefrass (produc- tion of soluble nitrate of lime)." — Liebifs Ag. Chem. CALCIUM. 273 Chloride of Lime, or Hypochlorite of Lime (Ca O, CI O -f Ca CI). 244. Experiment — Mix half an ounce of slaked lime with six ounces of water, and conduct into this milk of lime, with frequent agitation, as much chlorine as wiU evolve from two ounces of muriatic acid and half an ounce of black oxide of manganese. The liquid, clari-//* tied by standing, may be regarded as a solution of chloride of lime, and must be kept protected from the air and light. It would seem at first as if the chlorine united directly with the lime, but this is not possible, since, as a general rule, simple bodies cannot combine with compound bodies. The process is as follows. Half of the Ume releases its oxygen, and is converted into calcium, which, being a simple body, combines with chlorine; the oxygen, Uberated from the lime, com- bines with the rest of the chlorine, forming hypochlo- rous acid (CIO), which, Bleaches, being a compound body, can now unite with the other half of the Ume. Thus are formed a haloid bleach1 sa^' chloride of calcium, and an oxygen salt, hy- pochlorite of lime. The latter is the essential agent, the bleaching power, in the chloride of Ume; chloride of calcium is to be regarded only as an unnecessary make-weight. Accordingly the name of chloride of lime is incorrect, but, like many other terms of general acceptation, it would be inconvenient not to retain it. It must not be forgotten, however, that chloride of lime is a very different body from chloride of calcium. By the old process, bleaching required weeks, and even months; now, by means of chloride of Ume, cotton 274 ALKALINE EARTHS. and linen are bleached in as many days. For this rea- son, vast quantities of chloride of lime are manufactured in chemical laboratories, and are consumed in bleacher- ies and calico print-works. The preparation of it on a large scale is conducted upon the same principle as that just described, except that, instead of milk of lime, slaked Ume is used, which is spread upon hurdles in chambers, and which, like nulk of Ume, absorbs the chlorine. Chloride of Ume, thus prepared, is a gran- ular powder, which absorbs moisture from the air, and emits the odor of chlorine. Upon adding water to it, the same liquid is obtained as that prepared above. 245. Experiments with Chlorine. Experiment a. — Immerse a piece of cotton, printed with various colors, into a solution of chloride of lime; if there are vegetable colors among those with which the cotton is printed, they wiU bleach, though but slowly. Experiment b. — Proceed in the same manner, add- ing, however, to the solution some drops of diluted muriatic or sulphuric acid; the bleaching wfil then take place instantaneously, attended with the evolution of a strong smell of chlorine. The acids expel the feeble, hypochlorous acid, and this is resolved into oxygen and chlorine. If you let the material remain for some time in the solution of the chloride of Ume, the vegetable fibres wiU also be decomposed (eaten) by the chlo- rine, and will lose their firmness. Experiment c. — Drop some tincture of indigo into a portion of the solution; the indigo is immediately de- composed, and its blue color changed to yellow. Con- tinue to add the indigo till the blue color remains un- affected, and note the quantity of indigo used; in this calcium. 275 manner the strength of the different sorts of chloride of lime may be determined, for the more hypochlorous acid there is contained in the chloride of Ume, so much the more indigo it is able to deprive of its color. Experiment d. — Chloride of Ume, as weU as free chlorine, destroys the noxious effluvia evolved during the decay or putrefaction of organic substances. The im- pure air of stables is destroyed by strewing about chlo- ride of lime, and damp cellars are purified by washing the floors and walls with a solution of it, &c. In all these decompositions, the chlorine always combines with the hydrogen of the coloring and odor- ous matter. If chlorine is conducted into a solution of carbonate of soda, instead of into milk of lime, we obtain hypo- chlorite of soda, likewise a bleaching Uquid, known as Labarraque'ls disinfecting liquor. Chloride of Calcium, or Muriate of Lime (Ca CI, or CaO,HCl). 246. Experiment. — Mix muriatic acid with half its quantity of water, and add to it pieces of chalk until effervescence ceases; then evaporate the filtered solution to the consistency of a syrup. We obtain from this, on cooling, large prismatic crystals of chloride of calci- um, which must be quickly dried by pressure between folds of blotting-paper, and kept carefully excluded from the air, as they are exceedingly deliquescent. In the winter season, this salt may be employed for freezing mercury. For this purpose let it remain one night in a cold place, then grind it up in a cold mortar, and mix it with snow; if some mercury, contained in a glass tube, is now introduced into the mixture, it will become solid, and a spirit-of-wine thermometer wnl indicate a 276 ALKALINE EARTHS. temperature of —40° C. The snow and the chlo- ride of calcium melt; from two solid bodies is thus formed a liquid, and during this transition a great quantity of free heat must necessarily become latent Crystals of chloride of calcium contain half their weight of water of crystallization ; on being heated, the water passes off, and we obtain fused chloride of calcium, one of the most hygroscopic salts, which may be em- ployed for preparing absolute from common alcohol, and for drying certain gases. For this latter purpose, fill a capacious glass life .*—-'*■ •^fa*^fe»gj^b-- tU^6 W^ ^ra£" A adapt to each I end of the tube, by means of perforated corks, two small glass tubes, through which the gas may be transmitted; during its passage, all the moisture will be abstracted from it by the chloride of calcium. In the preparation of ammo- nia (§ 230), chloride of calcium is obtained as a secon- dary product. It has already been mentioned (§ 244), that it forms a constituent (though a useless one) of chloride of lime. 247. Fluoride of Calcium (Ca Fl), commonly called fluor-spar, is a mineral of frequent occurrence in nature, and is often found in cubic crystals of great beauty. It is easily fused by heat (hence its name), and it yields, when treated with sulphuric acid, hydrofluoric acid (§190). BARIUM AND STRONTIUM. 277 BARIUM AND STRONTIUM (Ba and Sr). My& *"■ At. Wt. = 855. —At. Wt. = 548. 248. These two metals have so great a similarity to calcium in their properties and combinations, that they may be regarded as brethren. Their oxides are termed baryta (Ba O) and strontia (Sr O), and when water is added to them they evolve heat, as is the case with lime, and afford a basic reaction. The carbonates of baryta and strontia are, like chalk, insoluble in water, and at a strong heat lose their carbonic acid, yet not so readily as chalk. The salts of lime, as has been seen, are very easily prepared by merely adding acids to marble or chalk ; but the salts of baryta and strontia are not so easily obtained, because baryta and strontia are rarely found in nature combined with carbonic, but most frequently with sulphuric acid; consequently, with an acid which is stronger than all others. It is therefore necessary, as in the preparation of soda, to adopt a circuitous method; it must first be reduced to a sulphuret by heating with charcoal; this sulphuret may be afterwards decomposed by acids. Chloride of barium, or muriate of baryta (Ba CI), is the most common soluble salt of baryta. It crystaUizes in transparent tables, and is used in medicine. The chemist also makes use of it as the surest test for sul- phuric acid and the sulphates (§ 171). Nitrate of baryta serves also for the same purpose. Sulphate of Baryta (Ba O, S 03). Experiment. — Dissolve some Glauber salts in water, and add a solution of chloride of barium, as long as any precipitate is produced; chloride of sodium and 24 278 ALKALINE EARTHS. sulphate of baryta are Soluble, formed by double elec- tive affinity ; the latter is insoluble, quite insoluble in water, and also in acids, and is therefore thrown down as a heavy white powder. The ponderous mineral, known as heavy spar, which is frequently found in beautiful tabular crystals, associat- ed particularly with metalUc ores, is the native sul- phate of baryta. Baryta and the baryta salts are pre- pared from it. This mineral, when ground to powder, is frequently used for the adulteration of white lead. The most remarkable characteristic of the strontia salts is that of communicating a crimson tint to the flame of burning substances. Nitrate of strontia, like the other nitrates, deflagrates upon burning charcoal, and is used for producing a crimson flame in fireworks, prepared from potassa, sulphur, and charcoal. Qdoride of strontium, or muriate of strontia, is soluble in alcohol, and imparts to its flame a crimson color. MAGNESIUM (Mg). At. "Wt. = 158. —Sp. Gr. = 1.7. Epsom Salt, or Sulphate of Magnesia (MgO, S03-f-7HO). 249. Envelop in a fold of strong paper a fragment of serpentine mineral; crush it with a hammer, then pulverize it in an iron mortar, and mix half an ounce of it in a porcelain basin with some common sulphuric acid to the consistency of a paste, and set it aside for some days in a warm place. Then stir in carefully an ounce and a half of water, let the mixture stand again for some days, and finaUy decant the warm clear liquid. NaO, SO*--^-BaO S03 MAGNESIUM. 279 It will have a green tint, owing to the presence of some protoxide of iron. When boding, add gradually nitric acid to it, until the liquid has assumed a yellow color; the protoxide will be thereby converted into sesqui- oxide of iron. If evaporated until a pellicle is formed, crystals will be deposited, which must be dissolved again in boiling water, and recrystallized. Sulphate of sesquioxide of iron, which can be crystallized only with difficulty, will remain in the mother liquor. The crys- tals have a bitter taste. Their constituents are sul- phuric acid and a base, caUed magnesia (Mg O). The taste of aU the soluble salts of magnesia is bitter. This base is combined in the serpentine with siUcic acid, which the stronger sulphuric acid displaces and com- bines with, forming a soluble salt, whffe the silica re- mains behind undissolved. We find silicate of magne- sia also in other minerals; for instance, in meerschaum,^. J-ta- soap-stone, talc, asbestos, hornblende, and in several****' •'~v** varieties resembfing mica, &c. AU these minerals have a sUppery or greasy feeling, and are mostly in- cluded under the general head of talc. Magnesia is sometimes called also talc earth. Epsom salt is one of the most common purgatives, and is much employed in medicine. We usually ob- tain it in commerce, not in perfect crystals, but in the form of smaU acicular crystals, owing to the evaporation a&x&cc having been carried on after the formation of the pel- -n-e<^ Ucle, and to the stirring of the mass while cooling. Qs^fs/ <* Consequently a disturbed crystallization has taken place. In many places, for instance, at Saidschutz in Bohemia, there are springs holding Epsom salt in so- lution, and they are often resorted to by invalids. If their waters are evaporated, this salt is Ukewise ob- tained from them. 280 ALKALINE EARTHS. Fig. 132. Carbonate of Magnesia. 250. Experiment — Dissolve half an ounce of Ep- som salt in four ounces of cold water, and add a solution of carbonate of soda as long as a precipitate continues to fall. The precipitate is carbonate of magnesia, but sulphate of soda remains in the solution; thus the Epsom salt and carbonate of soda have exchanged their acids. The milky Uquid is now heated to boiUng, filtered, and the precipitate washed and dried; it is very fight and white, and is known as the magnesia alba of the apothecaries' shops. During the ebulUtion, some carbonic acid escapes. Carbonate of magnesia is also found in many kinds of marble and Umestone, caUed dolomite. Magnesia (Oxide of Magnesia) (Mg O). If you heat carbonate of magnesia to redness, it loses, like chalk, its carbonic acid, and at the same time the water with which it was chemically combined; the magnesia remains behind as a light powder, commonly caUed calcined magnesia (oxide of magnesia). It is nearly insoluble in water, and consists of a metal, mag- nesium, and of oxygen. Chloride of Magnesium, or Muriate of Magnesia (MgCl, or MgO, II CI). 251. Experiment. — Add to carbonate of magnesia' some dUuted muriatic acid; the carbonic acid escapes, RETROSPECT. 281 but the chloride of magnesium is dissolved in the liquid. This salt is always found associated with com- mon salt, and as it is very soluble and hygroscopic, it remains in the mother liquor on the evaporation of salt-springs. Therefore Epsom salt may also be ob- tained from the mother liquor, by converting chloride of magnesium into sulphate of magnesia. The bitter taste of sea-water is owing to this salt. Experiment. — Put into a glass of water a few drops of the above solution, or a Uttle Epsom salt, and then add to it a solution of phosphate of soda ana some ammonia; the liquid first becomes turbid, and finally a crystalline precipitate is deposited (phosphate of mag- nesia and ammonia). In this way the presence of magnesia may be most certainly detected. f RETROSPECT OF THE ALKALINE EARTHS (LIME, BARYTA, STRONTIA, AND MAGNESIA). 1. The metals of the alkaline earths have, Uke the alkali-metals, a very great affinity for oxygen; the preparation of them is exceedingly difficult. 2. Their oxides are called alkaline earths;—earths, because they are sparingly soluble; alkafine, because they have a basic reaction. (The alkaUes are easily soluble.) 3. The alkaline earths are, next to the alkalies, the strongest bases. 4. The alkaline earths have a caustic action, but far less than the alkalies; hence the terms caustic lime and caustic baryta. 5. They likewise eagerly absorb carbonic acid from the air. 6. The carbonates of the alkaUne earths are quite 24* 282 METALS OF THE EARTHS. insoluble in water (the carbonates of the alkaUes are easily soluble). 7. The carbonates of the alkaline earths lose their carbonic acid by exposure to a powerful heat (the alkalies do not). 8. The alkaline earths form with fats insoluble soap (the alkaUes soluble soap). THIRD GROUP: METALS OF THE EARTHS. ALUMINUM (Al). AtWt. = 171. — Sp. Gr. f. rfcifc. ef*~«*, stsu«^r*is',~&&fu.1 Clay and .Loam.JLun**^,**^**** 252. The peculiar action of clay on being mixed with water is familiar to every one, forming with it a compact, ductile mass, which may be kneaded into any shape; it is plastic or flexible. If a mixture of lime and sand is treated in the same manner, it wiU not co- here, but remain friable. Common clay contains more sand than plastic clay, and, owing to the presence of ul , covf**; iron ochre, has a yellow or brown color. There is 'XffoO stiU a coarser variety of clay, mixed with stiff more ^ ' sand, commonly called ld~am. Experiment. — HoUow out a piece of clay, and pour some water into the Fig. 133. HHl^l^— - - «/*=^!ll§ilif cavity thus formed; the - - ~-^^^^^^m ^^^r JlP water will not percolate [__ Ipt^?;^^—3 ^^^^Jjjjjj through the clay, as it would through sand or lime. When beds of clay exist beneath the soil, the rain is unable to penetrate far down in those places; and consequently bogs and marshes are formed. These ALUMINUM. 283 may be drained by boring holes through the clay-beds, down to a looser layer of earth, through which the water can flow off. There are found in many places in the interior of the earth alternate beds of clay and siUca, or sand, one Fig. 134. above the other. If these strata ascend on each side, / forming hills, the rain-water, as it runs down, must col- lect between the layers of clay, and rise in them as in a tube, since it cannot find a vent in any direction. If, in such a geological formation, a low situation be se- lected for boring through the upper strata of clay, the water will be forced out above the surface of the soil, and a natural fountain will be the consequence, from which the water will be forced still higher on boring through the second layer of clay. These fountains are called Artesian wells, from the province of Artois, in ^C, **-- France, where the nature of the soil is peculiarly adapt- ed to such works. Experiment — Put on a paper filter half an ounce of dry pulverized clay, and on another half an ounce of sand ; pour water over each, and weigh them as soon as the filtration has ceased; the clay will weigh three \ eighths of an ounce, and the sand only one eighth of an ounce more than before. If the sand had been very 284 METALS OF THE EARTHS. coarse, its increase of weight would have been stiU less. Clay is, indeed, insoluble in water, but, like a sponge, it can imbibe and retain a large quantity of it; it has a very great capacity of retaining water. In consequence of this property, it also parts with water again much more slowly than sand does, as may be easily seen if you put both filters in a warm place to dry. These two species of earths exhibit, when dry, a stiU greater difference: the clay forms solid, hard lumps, the sand remains a loose, granular powder. 253. Experiment — If you digest some clay in an infusion of logwood (§ 174), the clay acquires, after standing some hours, a violet color, and the Uquid be- comes much more transparent. The clay has the power of absorbing coloring matter, and rendering it in- soluble. Potters' clay, or pipe-clay, comports itself in the same manner towards unctuous substances, and fience it is much used for extracting grease-spots from wood, paper, &c, by spreading it over their surface, and letting it remain one or more days in contact with them. A soft variety of clay is employed in cotton-factories, under the name of fuller's earth, for removing again the grease applied to the wool in spin- ning. 254. Experiment. — Expose half an ounce of thor- oughly dried clay to the air for some wTeeks, when it will be found to have gained in weight. This increase of weight can only proceed from the substances which it has absorbed from the air; these are water, carbonic acid, and ammonia. Of the presence of the ammonia you may easily be convinced by the smell, or if you triturate a piece of clay taken from an old wall, in the vicinity of barns especially, with some lime and a few drops of water. Clay, when freshly dug, diffuses no ALUMINUM. 285 odor of ammonia, or only a very sUght odor, on being treated in the same manner. Thus is explained, also, the pecuUar smeU which you perceive in all argillaceous stones when you breathe upon them, and by which you can readily determine whether clay is contained in an earth or stone. As water, carbonic acid, and ammonia are the most important means of nourishment for plants, it is very obvious that clay must enhance the fertility of the soil, because it attracts those substances from the air. That clay is especially efficacious which has remained for years in contact with the air, since in consequence of slow weathering, soluble salts of lime; and potassa (nitre, &c.) have formed in it. For this reason, bricks, or clay fragments of old budd- ings, are valued by the experienced farmer as excellent manure. Clay, when gently burnt, also experiences a similar change (§ 258). Constituents of Arable Land. <&*, Jljb a<^>, a*. 255. Clay, or loam, and sand form the principal ingre- dients of our arable land; therefore, the knowledge of their properties is of great importance to the agricul- turalist, since it enables him to form a judgment as to the different action of soils in wet or dry, in cold or hot weather, &c. A soil whoUy composed either of sand or of clay is totally unproductive ; but a mixture of them affords a fertile soil. A clayey ox fat soil is too compact and heavy, not allowing the roots, of the smaller plants particularly, sufficient room to spread; it is likewise so dense that it wiU not allow of a free circulation of air. By showers of short duration it becomes baked; that is, a crust forms on the surface, \vhich prevents the water from penetrating into the soil; but after long continued rains it becomes muddy, 286 METALS OF THE EARTHS. and then it aUows the water to evaporate but slowly, and remains for a long time wet and cold. A sandy or lean soil suffers from the opposite disadvantages; it has too little consistency and is too porous, and there- fore does not hold firmly the roots of the plants ; it is easily raised up and blown away by the wind ; it per- mits the rain to penetrate too deeply, and afterwards to evaporate again too rapidly. These properties consti- tute what is called the physical or external condition of the soil. It is now evident, that the physical condition of a clayey soil may be ameliorated by the addition of sand, and that of a sandy soil by the addition of clay, loam, or marl. W —L> * 256. Estimation of Arable Soil. — Experiment. — To ascertain the relative amount of clay and sand in a soil, triturate half an ounce of it in a mortar with some water into a uniform paste. Dilute it with more water, and pour the turbid Uquid into a tall glass, rinsing out with water what remains in the mortar. On stand- ing, the earthy particles wiU settle to the bot- tom, according to their different specific grav- ities, first the coarse, then the fine sand, and finally the clay or loam ; and an approxima- tive conclusion of the comparative quantity of each may be arrived at by observing the dif- ferent heights of the layers of sand and clay. This estimation may be rendered more ac- curate by again disturbing the sediment, and, after a short time, decanting it into another vessel, using the precaution, however, not to decant the sand, which, on account of its greater weight, sinks first to the t ottom. The residue is again stirred up with water, and t le lat- ter decanted, and these processes continued ui.til all the clay is washed out from the sand. While ( ecant- ALUMINUM. 287 Fig. 136. ing, hold a rod against the rim of the glass, so that the liquid may not be lost by flowing down on the outer surface of the vessel, or else besmear the rim with tallow, which wiU likewise prevent the adhesion of the liquid to the glass. The sand is dried and weighed, and the loss in the original half-ounce is to be calculated as clay. This operation, by which light bodies are mechan- ically separated from heavier ones, is called elutriation. 'dUXj; It is frequently employed to separate finely crushed ores from the admixture of the lighter particles of stone and earth. f The third very important ingredient of arable soil is lime (§ 237), which may be estimated in the following manner. Experiment.—Put into a capacious flask half an ounce of weU-dried earth; pour over it three ounces of water, and then add gradually half an ounce of muriatic acid, and let it remain for some hours in a warm place. When the effervescence has ceased, pour the liquid upon a filter, and wash the flask and filter with some ounces of warm water. Add ammonia to the yellow- ish filtrate tiU it has a decided smell of it; the brown flaky precipitate which is hereby separated consists of hydrated oxide of iron, which you must remove by a second filtration. The clear solution obtained is then boiled in a flask, and a concentrated solution of carbo- nate of ammonia or carbonate of potassa is added, as \>ng as any precipitate forms. This is carbonate of lime, which you must collect on a filter, wash, dry, 288 METALS OF THE EARTHS. Fig. 137. and weigh. A more simple method is *=?l to pour the contents of the flask into a graduated glass cylinder, and determine by measure the lime which soon settles at the bottom. You previously determine the weight of a degree of lime, once for all, by dissolving 4, 6, 8, 10, &c, grains of chalk in diluted muriatic acid, precipitating them by carbonate of ammonia, and then marking the space occupied by the pre- cipitate in the graduated cyUnder. If you have more Uquid than the cyUnder holds, you may either evaporate the liquid, or perform the experiment with half the quantity. This method, however, will not give very accurate results when the soil contains not only Ume, but also alumina, since this is partiaUy precipitated at the same time with the carbonate of Ume. These two simple tests, the mechanical and the chemical, deserve to be more frequently employed by the farmer than they actually are; indeed, by means of them, and without any costly apparatus or much ex- pense of time, he can make himself sufficiently ac- quainted with the most important constituents of his different soils. Earthen- Ware. 257. The plastic property of clay, together with that of hardening by heat, renders it peculiarly adapted for the manufacture of earthen-ware. The clay, having been more or less purified by elutriation and kneading, is either fashioned by the hand upon the potter's lathe, or formed by pressure in moulds into articles of various shapes ; these are first dried in the air, and then baked ALUMINUM. 289 in furnaces, until they have become hard like stone. The clay contracts in drying, but stiU more in baking; consequently, earthen-ware is smaller after being baked than before. On account of this property, small cylin- ders of clay were formerly used for measuring high temperatures (WedgewoooVs pyrometer). Though earthen-ware acquires by baking great hardness and solidity, yet it stiU remains so porous as to imbibe water, and also to let it sweat through. This fault is remedied by covering the ware with a vitreous coating, the so-called glazing, which is composed of the same materials as glass (§ 226). The most important kinds of pottery are, — a.) Bricks and flower-pots, made of loam or coarse clay, mostly unglazed. The brownish-red color of the bricks is owing to the presence of oxide of iron. f b.) Earthen-ware, made of common clay, and coated with a glazing of litharge and clay. c.) Stone-ware (fine earthen-ware), made of very white clay, and likewise covered with a glazing of li- tharge and clay. d.) Delft-ware, stone-ware covered with a glazing, which is rendered opaque and of a milky whiteness (enamel) by oxide of tin (white Dutch tiles, &c). e.) Porcelain is made of the finest clay (porcelain clay or kaolin), with felspar, and baked till fusion com- mences ; the glazing consists of potassa-glass, without litharge. /.) English stone-ware (ordinary porcelain) is made of gray clay, not strongly baked ; the glazing is prepared from common salt, which is thrown into a hot pottery furnace, and consists of soda-glass without litharge \milk-pans, beer-flagons, &c). Only the vitrifiable pigments (metallic oxides) can 25 290 METALS OF THE EARTHS. be employed for staining and ornamenting the different kinds of pottery. Composition of Clay. 258. Experiment. — Dry thoroughly a piece of white clay, and expose it for some hours to a powerful heat, which is most easily done on the hearth of a heated oven; then rub two ounces of it to a powder in a por- celain bowl with one ounce of sulphuric acid; pour upon the mixture one ounce of water, and let it remain some weeks in a warm place. Frequently stir the mass during this time with a glass rod. Finally, dilute it with six ounces of boiling water, and strain it through Unen. The residue on the latter consists principally of silicic acid, but a base caUed alumina (Al2 03) is found dissolved in the liquid. Clay is, accordingly, an insoluble salt, silicate of alumina. Before the clay is heated, the siUcic acid holds on so firmly to the base that the sulphuric acid is not able to expel it; but it can do this after the clay has been moderately heated. All clay (and loam) contains, besides silicate of alumina, variable quantities of silicates of potassa, soda, Ume, &c, which are likewise rendered dissolvable by burning the clay. To these alkalies, as well as to the greater porosity of the heated clay, it is to be attributed that a heavy clayey soil, which is impervious to the air, is converted merely by burning into very fertile arable land, and that badly (slightly) burnt bricks yield a very efficient material for manure. Sulphate of Alumina (AL, 03, 3 S03 -f- 18 HO). 259. Experiment. — Evaporate the liquid obtained in the former experiment till only one and a half or two ALUMINUM. 291 ounces of it remain, and then put it in a cool place; it will crystaUize in thin silky plates of a pearly lustre, which are very deliquescent; it is sulphate of alumina. Pour off the liquor remaining behind, which always contains free sulphuric acid, and again dissolve the crystals in a little water. In factories the solution is frequently evaporated to dryness, and a solid mass is thereby obtained, which is employed in caUco-printing and dyeing. Alumina, or Oxide of Aluminum (Al2 03). 260. Experiment. — Add a solution of carbonate of soda to half of the above solution of sulphate of alumi- na, until the Uquid reacts basically; a brisk efferves- cence ensues, and Volatile, a gelatinous pre- cipitate is formed, soluble. which, after repeat- ed washings with insoluble, water, will dry in a warm place into a white powder. This powder is a combination of alu- mina with water, hydrate of alumina (ALj 03, 3 H O). It is insoluble in water, and cannot combine, like the bases previously considered, with carbonic acid ; hence the carbonic acid gas, set free from the carbonate of soda, escapes with effervescence. Alumina differs from clay in not being rendered plastic by water, and from lime, baryta, strontia, and magnesia in not giving an alkaline reaction. The constituents of alumina are aluminum and oxy- ^gen, consisting of one atom of aluminum and one and a half of oxygen. Such bases are called sesquibases to distinguish them from the simple bases, hitherto consid- 292 METALS OF THE EARTHS. ered, as K O, Na O, Ca O, &c. The numbers of these sesquibases are doubled, in order to avoid the inconven- ience of using fractions; thus 1: 1| :: 2:3, = Alj 03. Experiment — Heat in a test-tube some alumina with potassa; it dissolves in it completely, since it enters into combination with the potassa. We caU alumina a base, because it combines with acids ; we may also re- gard it as an acid, for it combines also with bases. We shall hereafter find among the metalUc oxides other such irresolute, double-faced characters, which play the part of a base towards strong acids, and of an acid to- wards strong bases. Striving to be both, they are in reality neither, and therefore salts with an alumina base always have an acid reaction, and those with an alumina acid a basic reaction, but both of them are very easily decomposed. Alumina is a body of extremely difficult fusibility; we can only melt small quantities of it before the oxy- hydrogen blow-pipe. The melted alumina has the ap- pearance of glass, and a hardness which is only sur- passed by that of the diamond (artificial rubies). In this form we find alumina also in nature; the ruby, the most costly red precious stone, and the sapphire, the most costly blue stone, consist of crystallized alumina. Emery has also the same constitution, and is employed, on account of its hardness, for poUshing metals and glass. Alum (Sulphate of Alumina and Potassa). (KO, S03 + AL, Oa, 3 S 03 + 24 H O.) 261. Experiment. — Saturate two ounces of boiling water with sulphate of potassa, and add to it a solution of sulphate of alumina, obtained at § 259. Stir the mix-' ture tiU it is cold, and decant the clear liquor from the ALUMINUM. 293 white sediment. The sediment is alum in a state of powder. If dissolved in boiling water and slowly cooled, you obtain from it crystallized alum in beauti- ful, transparent, four-sided double pyramids (octahe- drons). Thus alum is a combination of two different salts, — it is a double salt. The two salts, sulphate of potassa and sulphate of alumina, have united chemi- cally together, for a new body with new properties is formed from them; they have united chemically with each other, for definite quantities of both salts have entered into combination, namely, half an ounce of sulphate of potassa, and an ounce of sulphate of alumina; or, more accurately, 1 at. K O, S 03, and 1 at. AL2 03, 3 S 03. Alum is diffi- cultly soluble in cold water, easily so in hot water, has an acid reaction, and, like all the salts of alumina, has an astringent taste. 262. Experiments with Alum. Experiment a. — Heat a small crystal of alum before the blow-pipe; it foams and melts, forming a white porous mass (burnt alum), the foaming is owing to the evaporation of the water of crystallization, which con- stitutes nearly one half of the weight of the alum. Experiment b. — Hydrate of alumina is precipitated by carbonate of soda from alum, in the same manner as from sulphate of alumina. Experiment c. — Boil half an ounce of Brazil-wood ' for fifteen minutes, in six ounces of water; decant the decoction, and dissolve in it half an ounce of alum; it 25' 294 METALS OF THE EARTHS. thereby acquires a more briUiant red color. Now add to it a solution of carbonate of potassa or of soda, as long as any precipitate is produced; this precipitate is of a fine red color, and, when dried, constitutes the Brazil-wood lake of commerce. In a sinular manner colored precipitates (lakes) are obtained from other veg- etable coloring-substances. This example serves to show the powerful attraction which alumina has for coloring matter. Almost aU colors of the animal and vegetable kingdom may be precipitated by alumina from their solutions, which accounts for the great im- portance of the alumina salts in dyeing and calico- printing. For this purpose the acetate of alumina is very frequently substituted for alum, because the feeble acetic acid more readily leaves the alumina than the strong sulphuric acid does. It is obtained by mixing together a solution of acetate of lead and sulphate of alumina (or alum), whereby, by double elective affinity, soluble acetate of alumina (alum mordant) and insoluble sulphate of lead are formed. Experiment d. — Moisten a piece of alum (or clay or alumina) with a drop of a solution of nitrate of cobalt, and heat it before the blow-pipe; the nitric acid is driven off, but the oxide of cobalt which remains be- hind imparts a beautiful blue color to the compound of alumina. This fact is frequently taken advantage of as very accurate means of detecting alumina. By a simffar process, a valuable and very beautiful blue pigment is prepared, called smalts. Another splendid blue pigment, ultramarine, has been made within a few years, by heating to redness a mix- ture of alumina, sulphuret of sodium, and a trace of iron. This pigment must be carefully kept from con- tact with acids, as they would evolve from it sulphu- retted hydrogen, and destroy the color. ALUMINUM. 295 263. Alum is not prepared on a large scale directly from clay and sulphuric acid, but from rocks contain- ing alumina and also sulphur (pyrites); for instance, aluminous slates or shales. If these rocks are allowed to remain for some time exposed to the air (weather- ing), or are moderately heated (roasted), there is formed from the sulphur sulphuric acid, which now combines with the alumina. 264. Alum affords a fine example for elucidating the principle of so-caUed isomorphism. For instance, we are able to replace the potassa in the alum by an- other simple atomic base, namely, soda or ammonia, or to replace the alumina by another sesquibase, name- ly, sesquioxide of chromium, or sesquioxide of iron, without thereby changing the octahedral crystalline form. We thus obtain the foUowing kinds of alum: — Potassa alum, consisting of sulphate of alumina + sulphate of potassa. Soda alum, " " " -f " " soda. Ammonia alum, " " " -f- " " ammonia. Chrome alum, " sulphate of chrome -f- " " potassa 7^p 6^/ (soda or ammonia). -tXt oxySen are white, insoluble, and earthy, like aluminum, #r* ' and are caUed Glucina, Yttria, Zirconia, &c. RETROSPECT. 297 RETROSPECT OF THE EARTHS ("ALUMINA, &c.). 1. The earths are combinations of the metals of the earths-with oxygen. 2. They are entirely insoluble in water. 3. They do not combine with carbonic acid. 4. The most important of these earths is alumina, which, combined with silica (clay, loam), forms a prin- cipal ingredient of arable land, and of many kinds of rocks. 5. Alumina is a much weaker base than the alkaUes and alkaUne earths. 6. Weak bases, as if they were acids, combine with strong bases. 7. Many bodies may, in chemical combinations, re- place another body, atom for atom, without a change of the crystalUne form taking place (isomorphous sub- stances). 8. Neutral salts are salts in which, for every atom of oxygen which the base contains, there is an atom of acid. 9. Many neutral salts may combine with one or sev- eral atoms of acids; such combinations are called acid salts. 10. There" are also combinations of neutral salts with one or more atoms of bases; they are termed basic salts. 11. When two different salts unite chemically with each other, they are called double salts. RETROSPECT OF THE (LIGHT) METALS HITHERTO CONSIDERED. 1. The metals of the alkalies, of the alkaline earths, and of the earths, are caUed light metals, because they are specifically lighter than the other metals. 298 CHEMICAL PROPORTIONS. 2. They never occur in nature as pure metals, neither as pure oxides (with the exception of alumina), but al- ways as salts, and constitute, together with siUca, the principal portion of our earth. 3. Of all bodies, they have the greatest affinity for oxygen, and form with it oxides, which (with the excep- tion of the earths) dissolve in water. 4. The oxides of the metals of the alkaUes, and of the alkaline earths, are the strongest bases (alkaUes, alkaline earths). 5. On account of their great affinity for oxygen, the preparation of the light metals is very difficult, since the combination between the metal and oxygen can only be destroyed in the strongest charcoal-fire, or by the galvanic current. Only potassium, sodium, and aluminum are as yet accurately known. 6. Until the year 1807 the alkaUes and earths were regarded as simple bodies; but at that time the English chemist, Davy, succeeded in resolving them into metals and oxygen, by means of the galvanic current. 7. Most of the light metals are able to decompose water, even at ordinary temperatures, and without the aid of an acid; that is, to withdraw from it the oxy- gen, and consequently liberate the hydrogen. LAWS OF CHEMICAL COMBINATION. Before proceeding to the consideration of the other metals, it will be well to revert to the laws of chemical combination, often mentioned in the foregoing pages, and to reduce them to a methodical system. 267. Classification of Chemical Combinations. — As in- numerable words may be formed from the twenty-six CHEMICAL PROPORTIONS. 299 letters of our alphabet, so Ukewise innumerable com- pounds may be prepared from the sixty-two chemical elements. These may be classed into three great di- visions. Combinations of the first order are formed when elements unite with elements; to this belong, for instance, acids and bases. When these are com- bined together, we obtain combinations of the second order, for instance, salts. From the union of the salts with salts are produced combinations of the third order, for instance, double salts. We find something quite analogous to this in the construction of our language. From letters we form syllables, from syllables single words, and from single words compound words. 268. Wlien bodies combine chemically with each other, it is always in certain fixed and invariable proportions. Water, in whatever condition it may exist, whether in springs or in the sea, as ice or vapor, is uniformly com- posed of 12^ ounces of hydrogen and 100 ounces of oxygen. When artificially prepared by burning hydro- gen in oxygen gas, exactly the above proportion of each gas is required, that is, 12^ grains, ounces, or pounds of hydrogen are required for every 100 grains, ounces, or pounds of oxygen. If 13 ounces of hydrogen are taken, half an ounce of hydrogen remains behind; or if 101 ounces of oxygen are taken, then an ounce of oxygen remains behind. Quicklime, whether prepared from marble or limestone, from chalk or oyster-shells, invari- ably contains 250 ounces of calcium and 100 ounces of oxygen; and sulphuric acid, whether manufactured by the Nordhausen method, from green vitriol, or accord- ing to the English method, by the combustion of sul- phur, always contains 200 ounces of sulphur to 300 ounces of oxygen. 269. It has also been ascertained, by the most reli- able investigations, how many parts by weight of the 300 CHEMICAL PROPORTIONS. other elements combine with 100 parts by weight of oxygen. Since these quantities, as will hereafter ap- pear, are of great importance in chemistry, the num- bers representing those of the most common elements are given, as follows: — 100 ounces of oxygen, = O, combine with 124 ounces of hydrogen, orH. 489 ounces < »f potassium, orK. 175 n nitrogen, " N. 290 (C sodium, " Na. 75 u carbon, " C 225 l( ammonium, "NH*. 200 :< sulphur, " s. 250 tc calcium, " Ca. 400 ii phosphorus, " p. 855 tc barium, " Ba. 443 it chlorine, " CI. 158 IC magnesium, "Mg. 1000 a bromine, " Br. 171 11 aluminum, " Al. 1586 II iodine, " I. 350 IC iron, " Fe. 325 ii cyanogen, " Cy. 345 u manganese, " Mn. 136 !( boron, " B. 368 (( cobalt, " Co. 277 ({ silicon, " Si. 369 II nickel, " Ni. 407 !< zinc, " Zn. 1350 11 silver, "Ag. 735 tl tin, " Sn. 1232 (( platinum, " Pt. 1294 « lead, " Pb. 2458 [( gold, " Au. 1330 II bismuth, " Bi. 328 11 chromium, " Cr. 396 " copper, " Cu. 937 i; arsenic, " As. 1250 (( mercury, " Hg- 1613 (i antimony, " Sb. These numbers are called combining proportionals, because they express the proportion in which an ele- ment chemically combines with 100 parts of oxygen. If ,we now wish to ascertain the composition of po- tassa, or of oxide of mercury, we have only to refer to the table, and we find, that in potassa 489 ounces or parts of potassium combine with 100 ounces or parts of oxygen, and that in the oxide of mercury, 1250 ounces of mercury combine with 100 ounces of oxygen. Accordingly, the elements with the smaller propor- tional numbers must be regarded as more powerful than those with larger proportional numbers. Potassium, for instance, is 2\ times stronger than mercury, since 489 ounces of it unite with the same quantity of oxygen that 1250 ounces of mercury do. 5* CHEMICAL PROPORTIONS. 301 270. Equivalents. — Further experiments have led to the surprising discovery, that these numbers not only indicate in what proportion the elements combine with oxygen, but also in what quantities they combine with each other. These quantities are the same as those of the proportional numbers. 12^ ounces of hydrogen combine exactly with 100 ounces of oxygen, forming water; with 200 ounces of sulphur, forming sulphu- retted hydrogen; with 443 ounces of chlorine, forming ,-•' muriatic acid. The same quantity of sulphur which, with 300 ounces of oxygen, formed sulphuric acid, yields, with 489 ounces of potassium, sulphuret of po- «/ tassium, with 350 ounces of iron, sulphuret of iron, * and with 1250 ounces of mercury, sulphuret of mer- cury (cinnabar). If the iron is heated with cinnabar, yf the sulphur passes to the stronger iron, and the mer- cury is set free. 350 ounces of iron are thus just suffi- ' , cient to decompose 1450 * ounces of cinnabar, and con- sequently to liberate 1250 ounces of mercury. If more iron is employed, a portion of it remains uncombined; if more cinnabar, a part of it remains undecomposed. •V When in a chemical combination one element replaces an- other, it always happens in the quantities specified by the combining proportionals. For 100 doUars can be bought 6 ounces of gold, or 12 ounces of platinum, or 100 ounces of silver, or 1,500 ounces of mercury; consequently, 6 ounces of gold have the same mercantile value as 12 ounces of platinum, or 100 ounces of silver, &c. The same prin- ciple holds good in chemistry. 350 ounces of iron, 489 ounces of potassium, or 1250 ounces of mercury, com- bine with 100 ounces of oxygen; accordingly, 350 * Cinnabar is composed of mercury 1250 + sulphur 200 = 1450. 26 302 CHEMICAL PROPORTIONS. ounces of iron have the same chemical value as 489 ounces of potassium, or 1250 ounces of mercury. This is the reason why these numbers are likewise termed equivalents (from cequus, equal, and valor, value). Thus, by one equivalent of oxygen is to be understood 100 parts of it by weight; by one equivalent of iron, 350 parts by weight; and by one equivalent of mercury, 1250 parts by weight, &c. 271. The same law of equivalent proportion applies also to the chemical combinations of the second and third order, to which the process of a neutralization of a base by an acid, and the capacity of saturation of acids, re- ferred (§ 200). When the basic properties of a base, and also the acid properties of an acid, have disappeared, then these two bodies have united with each other in precisely those quantities which are determined by the natural law. The amount of this quantity for each body may easily be ascertained by adding together the equivalent numbers of their component parts. Chalk is carbonate of lime (Ca O, C 02). Lime consists of Carbonic Acid consists of 1 eq. of calcium = 250 1 eq. of carbon = 75 and 1 eq. of oxygen = 100 and 2 eq. of oxygen = 200 Combining number of Ca 0 = 350 Combining number of C O2 = 275 That is, in chalk 350 ounces of lime are always com- bined with 275 ounces of carbonic acid, and exactly the same proportion must be used in the artificial prepara- tion of chalk from its constituents. The combining proportion, or equivalent number, of chalk is accord- ingly = 625. If we wish to convert chalk by common sulphuric acid into gypsum (Ca O, S 03) we must first seek for the proportional number of the acid. We commonly find in it one equivalent of anhydrous sulphuric acid, united with one equivalent of water. CHEMICAL PROPORTIONS. / 303 The constituents of The constituents of Bulphuric acid are water are 1 eq. sulphur = 200 I eq. hydrogen = 12j and 3 eq. oxygen = 300 1 eq. oxygen =100 Eq. of S 03 is thus = 500 Eq. of HO is thus = 112J Consequently, the combining proportion of common sulphuric acid is 612y. This quantity just suffices to convert the above obtained 625 ounces of chalk into sulphate of lime. The carbonic acid which thereby escapes amounts to 275 ounces. Gypsum combines always with two equivalents of water of crystalUzation; its constituents are, conse- quently, — 1 eq. of Ca O = 350 1 eq. of S 03 = 500 and 2 eq. of H O = 225 Equivalent number of cryst. gypsum = 1075 = CaO, SO3 + 2HO. ' If you heat it, the water is expelled, and there re- mains for calcined or anhydrous gypsum the equiva- lent 850. It is evident that water enters into chemical combinations with the acids, bases, or salts, not as being essential to their constitution, but only as form- ing a portion of them. Previously to the discovery of this law, hardly fifty years ago, it could only be ascertained by laborious trials how much of one body was required to combine with another, or to replace another; it is now only necessary to refer to the table of the proportional or equivalent numbers to ascertain beforehand the quan- tity to be employed. 272. Multiple Proportions. —-Many elements have the capacity of combining with three, four, five, or even more proportions of oxygen, sulphur, chlorine, &c, thus producing the different oxides, sulphides, chlorides, &c, described in section 154. This would 304 CHEMICAL PROPORTIONS. at first seem to be inconsistent with the law that bodies always combine with each other in fixed proportions; but on more mature consideration of the subject, it will be obvious that no inconsistency exists, and that these greater or less quantities are not promiscuously com- pounded, but that they are Ukewise combined in fixed and invariable proportions. If we ascend a hill, it is at our own option to take many or few, long or short steps, since the inclina- tion is not interrupted by perpendicular acclivities; but on mounting a flight of stairs or a ladder, a deter- minate and regular number of steps only can be taken. In like manner, bodies which combine in several propor- tions with another body do so in different, but yet in in- variable quantities, and such combinations always take place in ratios of 1^, 2, 2y, 3, or 3^, but never in ratios of 1\, or If, or ly, &c. The ascent takes place, as it were, only by whole or half steps; thus, for instance,— „„ „ , f 100 oz. of oxvgen, carbonic oxide =CO. 75 oz. of carbon i ,„„ „ "„,... ^. r> „ ., •< 150 " " oxalic acid = C2O3. torm,witn yQQ „ u carbonic add =C02. f 100 oz. of oxygen, nitrous oxide = N O. 75 oz. of nitro- J 200 " " nitric oxide = N O2. gen form, with | 300 " " nitrous acid = N 03. [500 " " nitric acid =N05. '100 oz. of oxygen, protoxide of manganese, = Mn O. 150 " " sesquioxide of manganese = Mn2 O3. 200 " " hyperoxide of manganese = Mn Oj. 300 " " manganic acid = Mn 03- 350 " " permanganic acid = Mn2 O7. In the combinations of carbon, the ratio of the oxygen is as . . . . 1: 1|: 2 In the combinations of nitrogen, the ratio of the oxygen is as . . . 1:2:3:5 And in the combinations of manganese, the ratio of the oxygen is as . 1: 1$ : 2:3: 3$ 375 oz. manga- nese form, with CHEMICAL PROPORTIONS. 305 It is obvious that these numbers stand in a very simple ratio to each other, and that the larger numbers are a multiple of the smaller number; this is expressed by calUng it the law of multiple proportions. 273. Gaseous bodies always combine with each other in certain volumes. The volume of the gases is very often less, after combination, than the sum of their volumes in their separate state. Examples. From 1 vol. of chlorine and 1 vol. of hydrogen are formed 2 vols, of hydrochloric acid gas. From 2 vols, of hydrogen and 1 vol. of oxygen are formed 2 vols, of aqueous vapor. From 3 vols, of hydrogen and 1 vol. of nitrogen are formed 2 vols, of ammoniacal gas. ' From 6 vols, of hydrogen and 1 vol. of sulphur are formed 6 vols, of sulphuretted hydrogen gas. Thus the same constancy characterizes the combi- nations by volumes as those by weight, and they are marked by a still greater simplicity. And if it were possible to convert all bodies into gases, probably a similar simple proportion by measure or volume would be observed in aU chemical combinations. 274. Atoms. — After having proved by a vast number of facts, the result of the most laborious investigations, that chemical combinations always take place accord- ing to fixed volumes and weights, the cause of this wonderful immutabifity is sought for. A thinking man, when he knows that a thing happens, and how it happens, wiU always inquire, Wliy is it thus, and not otherwise ? This question could not be solved by any ^ effort of experiment and observation ; but reflection has enabled us to arrive at an idea by which we can ex- 26* 306 CHEMICAL PROPORTIONS. plain ro ourselves this regularity and unchangeable- ness. This idea has received the name of the atomic theory. It is as follows: — 1.) Every substance is composed of small particles, which lie in contact with each other, and are called atoms; between these atoms there are interstices or pores. In light bodies the atoms are more remote from each other, and the interstices are larger, than in heavy bodies. When substances are subjected to cold or pressure, the atoms approximate more closely, and the bodies become denser and specificaUy heavier, while, if heated, the atoms separate from each other, the pores become larger, and the bodies consequently more ex- ■ panded and specifically lighter. The atoms are farthest distant from each other in gases and vapors; in steam, for instance, they are 1700 times more remote than in the Uquid water, since the former occupies 1700 times more space than the latter. 2.) Simple bodies have simple atoms, compound bodies compound atoms. For example, — Carbon: Oxygen: Calcium: Carbonic oxide: Carbonic acid : I.ime: 3.) These small particles, of which the mass of a body consists, cannot be further divided into yet smaUer par- CHEMICAL PROPORTIONS. 307 tides. Thus is explained the name afomus (that which ^ />* cannot be divided). / rf>^' * * 4.) They are so small that they can neither be seen nor counted, even by means of the most powerful mag- nifying-glass ; and they have, therefore, only an imagi- nary existence. 5.) When a solid body separates slowly from a fluid, its atoms have time to arrange themselves beside each other in a definite manner, and we obtain regular crys- tals ; but on becoming suddenly solid, an irregular dis- position of the atoms takes place, and the body appears amorphous (vitreous or pulverulent). 6.) The position of the atoms towards each other may be varied. As four baUs may be put in the fol- # lowing positions, — 'oocd 88^080800 so atoms also may Ue beside each other, arranged sometimes in one and sometimes in another manner. Thus is explained why one and the same substance may often appear in different forms of crystallization, or with a different structure, consequently in two dif- ferent states (dimorphous). Sulphur, at ordinary tem- peratures, crystalfizes from its solutions in octahedrons; but when fused, it crystallizes on cooUng in oblique prisms (§§ 125, 126). A newly forged iron axle has a fibrous texture, but after being used for some time its texture becomes granular. 7.) The atoms of different bodies have also probably a different size. A regular square may be constructed of four peas; but if we replace one of the peas 308 CHEMICAL PROPORTIONS. by a bean a mustard-seed then in both cases the regular form is disturbed; it re- mains, however, unchanged, when a baU of lead of the same size as the pea is substituted for it, though the square wiU now present a different appear- ance. This is an illustration of what occurs with the atoms. We have seen, in the case of the alums, that the potassa may be replaced by soda or ammonia, or the alumina by sesquioxide of chromium or sesquioxide of iron, without changing the form of the crystals. We therefore conclude, that potassa, soda, and ammonia have equally large atoms; they are isomorphous (of the same shape); the same applies also to alumina, and to sesquioxide of chromium and of iron. If we see, on the contrary, that a change takes place in the form of the crystals when we replace one body by another, we thence infer that there is an unequal size of the atoms in these bodies. 8.) The isomeric state of bodies is explained very simply by the atomic theory. The most manifold and regular grouping may be produced on a chess-board by transposition of the white and black squares; for in- stance, — S m •* CHEMICAL PROPORTIONS. 309 Each figure is composed of eight white and eight black squares, but though the absolute number is the same, the grouping is different. In a, one and one, in b, two and two, in c and d, four and four, squares are so joined together as to present a different appearance. If we imagine these squares to be atoms, we obtain an idea of isomeric bodies, and it is thus rendered clear how there may be bodies of the same constitution and form, yet presenting an entirely different appearance, and possessing different properties. Those exceedingly dissimilar bodies, caoutchouc (gum elastic), petroleum, and ffluminating gas, afford a striking example of ex- ternal difference and interior conformity. They have the same constituents (carbon and hydrogen) both in quafity and quantity. 9.) The atoms of the different bodies must finally possess also weight, and, indeed, very different degrees of it. If a piece of chalk, containing perhaps a milHon of atoms, has a fixed weight, so also must the smallest particle of it possess weight, however slight it may be ; for a body having weight can never be formed of a body having no weight. Chalk always contains 350 ounces of lime, and 275 ounces of carbonic acid. If a large piece of chalk has this constitution, so a smaller piece, even the minutest particle, must unite in the same proportions. If we suppose chalk to be composed of one atom of lime, and one atom of carbonic acid, we ascribe to the atom of Ume a weight of 350, and to the atom of carbonic acid a weight of 275. In 350 ounces of lime are always contained 250 ounces of calcium and 100 ounces of oxygen ; this combination, also, is to be regarded as consisting of equal atoms; accordingly, one atom of calcium weighs 250, and one atom of oxy- gen 100. FinaUy, in 275 ounces of carbonic acid are 310 HEAVY METALS. always contained 75 ounces of carbon united with 200 ounces of oxygen; wherefore 75 is to be regarded as the weight of an atom of carbon, and 200 as that of two atoms of oxygen. The numbers are exactly the same as those given in the Ust of proportional or equivalent numbers. Thus these numbers in an atomic point of view may be re- garded as the relative weight of the atoms; hence the third and simplest name for them, atomic weights. HEAVY METALS. FIRST GROUP OF THE HEAVY METALS. IRON, FERRUM (Fe). At. Wt. = 350. — Sp. Gr. = 7. 275. If gold is called the king of metals, iron must be deemed by far the most important and useful sub- ject in the metallic realm. Iron was formerly regarded as the symbol of war, and received the name of Mars, and the symbol <£ ; but who does not know that it has now attained also a great, an indescribably great impor- tance in the peaceable occupations of men ? It is not only converted into swords and cannons, but into ploughshares and chisels, and into a thousand other implements and machines, from the simple coffee-mill to the wonderful steam-engine. It is the ladder upon which the arts and trades have mounted to such an extraordinary height. It is the bridge upon which we now glide over mountains and vaUeys with the rapidity almost of magic. IRON. 311 Pure gold is found on the surface of the earth, and it is only necessary to free it from earthy admixtures to obtain it in a pure metallic state. Not so with iron. The ore in which this lies imbedded must be procured from the earth by skilful operations, and its oxygen ex- pelled by ingenious methods, and by exposure to the hottest fire, in order to convert it into metallic iron; the latter must again be fused and refined by different operations before it can be forged and welded. Gold is presented to men by nature as a gift, but iron must be struggled for by the most laborious toil, by exertion both of the bodily and rrrental powers. Thus iron has become a blessing to those countries whose inhabitants are occupied with the mining and working of it; for, as history teaches, in those countries are found the bless- ings attendant on labor, health, contentment, prosper- ity, and intellectual culture, in a far greater degree than in those countries where gold abounds and industry is neglected. In another respect, also, iron, of aU the heavy metals, appears to be the most important to mankind. It is the only metal which is not injurious to the health, the only metal which forms a never-failing constituent of the body, especially of the blood; the only metal, finally, which is found everywhere on the earth, in all stones and soils, and in almost every plant. Although we are ignorant wherein consists the influence which it exer- cises upon the life of animals and plants, yet its uni- versal diffusion must lead us to conclude that it has pleased the Highest Wisdom to invest iron with an importance for organic life similar to that possessed ^ by common salt, lime, phosphoric acid, and some other substances. 312 HEAVY METALS. Experiments with Iron (Iron Ore). 276. For these experiments fine iron filings are em- ployed, such as are kept in apothecaries' shops. Experiment a. — Place 17 J grains of iron fifings upon a piece of charcoal, and heat it for some minutes in the flame of the blow-pipe, directed upon one spot; it be- comes red-hot, and the heat spreads throughout the whole mass, as is apparent from the iridescent tints, which precede the red heat. The iron on cool- -ing acquires a darker, al- most a black color, and bakes into a coherent mass weighing about 18| grains. Thus, 17| grains have combined with l1 grains of oxy- gen. If you multiply these numbers by 20, you obtain 350 grains of iron (1 atom), and 25 grains of oxygen (\ atom), or four atoms of iron to one atom of oxygen. This body may be termed suboxide of iron. In the protoxide of iron, one atom of iron (350) always combines with one atom of oxygen (100); consequently the suboxide may be regarded as a mixture of one atom of protoxide of iron and three atoms of metallic iron. Experiment b. — Subject again the above mass to a red heat, for a longer period, in the blow-pipe flame. It continues to increase in weight untU it has finally gained from six to seven grains. It now forms the same combination as was produced by the burning of iron in oxygen, and in the forging and welding of iron, A IRON. 313 namely, the well-known iron cinders. It is a mix- ture of protoxide and sesquioxide of iron. The pro- toxide (Fe O) cannot be prepared in a pure state by this method, as sesquioxide is always simultaneously formed; but from the color of the suboxide and of the black oxide, it may be inferred that it has a black color. We perceive this color, also, in all those rocks which contain protoxide of iron, generally in combination with sificic acid. Almost all black and green stones, for instance, basalt, clay-slate, greenstone, serpentine, &c, owe their color to protoxide of iron. An iron ore, which has-the same constitution and the same black color as iron cinders, occurs abundantly in many places. It is called magnetic oxide of iron, and is not only attractable by the magnet, but is itself likewise magnetic. A small magnet may be prepared by placing a piece of magnetic iron ore (loadstone) between two rods of iron, when the magnetic force passes from the stone into the iron. The celebrated Swedish iron is mostly obtained from this variety of iron ore. Experiment, c. — Iron cinders, when exposed for a long time to the exterior or oxidizing blow-pipe flame, become covered with a red pulverulent .coating; they take yet more oxygen from the air, and become sesqui- oxide of iron (Fe2 03). Experiment d. — The sesquioxide of iron may be pre- pared more easily in the following manner. Place a crystal of green vitriol upon charcoal, and heat it until it has become of a brownish-red color. The water and sulphuric acid escape, and the protoxide of iron (Fe O) remaining behind absorbs one half as much again oxygen, and becomes converted into sesquioxide of iron (Pe? 03). The red color of the latter is more clearly brought out by rubbing it on paper with the 27 314 HEAVY METALS. nail. In the same manner, sesquioxide of iron remains behind when green vitriol is heated in the preparation r of oil of vitriol; this forms an article of commerce under \J^- the name of caput mortuum, English or polishing rouge, and is a favorite and cheap pigment for varnish, and is also used in the polishing of glass and metals. Sesquioxide of iron occurs native in many places of the earth, sometimes crystalUzed, as in iron-glance; sometimes compact, as in r?d iron-stone; or radiated, ^A^*^as in red heniatite; or earthy, as in red ochre. It is often also mixed with clay, and is then called clay iron- stone. The coloring matter of red stones or earths is owing to the presence of sesquioxide of iron. Many of the above-named bodies form immense beds in the in- terior of the earth, and are used as valuable ores (spec- ular iron) for the manufacture of iron. Experiment e. — Introduce some iron filings into a tumbler, and fiff it with spring-water; the iron will gradually lose its lustre, and assume a black color; it is converted into magnetic oxide of iron. Repeat this experiment with water that has been boiled; in this, the iron will retain its metallic lustre. The cause of this difference is owing to the air and carbonic acid, which are present in aU spring-water, and slowly ox- idize the iron. These gases are expeUed by boiling, therefore no oxidation takes place in water that has been boiled. Experiment f. — If you now pour off the water, so that the iron comes in contact also with the air, rust begins to form upon it. The iron absorbs so much ox- ygen that it becomes a sesquioxide ; it also absorbs a definite quantity of water (3 atoms), which may be re- garded as the cause of the yellow color of rust. Rust is therefore hydrated sesquioxide of iron (Fe2 03, 3 H O). IRON. 315 If you keep the iron moist, and stir it round several times every day, it will, after a time, be completely con- verted into rust. This combination frequently occurs also in nature, and is used as an excellent iron ore, under the name of brown iron ore. When mixed with clay it is called yellow clay iron-stone, yellow ochre, &c. The yellow or brown color which we see in so many stones when they are exposed to the air, the yellow or brown color of the soil, loam, or sand, always proceeds from the hy- drated sesquioxide of iron. The weathering of black varieties of stone to a brown stratum, and finally to a yellow arable sod, wffl now no longer appear strange; the black protoxide of iron contained in them is grad- ually oxidized into a yellow hydra d sesquioxide of iron. Experiment g. — Put a small quantity of the mag- netic oxide of iron obtained at b, or some iron filings, into a phial; fill the latter with artificial Seltzer-water, and let it stand, well stopped up, for one day. The white flakes which deposit on the bottom of the phial are carbonate of the protoxide of iron, formed from the protoxide of iron of the iron cinders, and from the carbonic acid of the Seltzer-water. The chemically combined water in this case communicates a white color to the black protoxide of iron. The clear liquid also contains some of the carbonate of iron in solution, as is evident from the inky taste peculiar to solutions of iron. It is then to be poured into a tumbler, and left for some time exposed to the air. In proportion as the free carbonic acid escapes, the surface is covered with a delicate white peUicle, the color of which gradually changes to yellow, then to red and violet; finally, the peUicle assumes a yellowish-brown color, and faUs as 316 HEAVY METALS. rust to the bottom. Protoxide of iron attracts oxygen tolvjuqwith great avidity, and is converted into magnetic oxide Hc^^£f iron, and finally into hydrated sesquioxide of iron. The salts of protoxide of iron act also in the same man- ner ; this is the reason of their becoming yellow by long keeping, or by exposure to the air. A very thin peUicle of magnetic oxide of iron gives a yeUow reflection; a thicker pellicle, a red or brown, and a still thicker one, a violet and blue reflection; this explains the iridescent changes of color presenting such a beautiful appearance on the surface of standing waters. In those places where spring-waters flow over stones containing iron, natural solutions of carbonate of iron (chalybeate waters) frequently occur, which are likewise decom- posed by the air. This decomposition of the carbonate of iron is the source of the brown mud which is de- posited in large quantities from some waters. By the accumulation of this mud, large beds of hydrated ses- quioxide of iron are formed, known under the name of bog-iron ore, and from which iron is worked. This ore usually contains also some phosphoric acid. The carbonate of protoxide of iron is found in many countries in the form of a light gray massive stone, and in such large quantities that iron is obtained from it. The famous Styrian steel is principally prepared from this ore, which is caUed spathic iron ore, or spherosid- erite. Mixed with clay, it very frequently occurs asso- ciated with pit-coal, and it is from this ore that most of the English iron is obtained. 277. In attending to the combinations which iron yields with oxygen, we have also become acquainted with the most important iron ores from which iron isr prepared on a large scale. They are the following: — Fe O -j- Fe2 Os, or magnetic iron ore. IRON. 317 Fe O, C 02, or spathic iron (clay iron-stone, sphe- (X. 4fr* rosiderite). l4^ Fe., 0„ or specular iron (red hematite, iron-glance, &c). Fe^ 03 -f- 3 H O, or brown iron ore (yeUow iron-stone, yeUow ochre, &c). Cast-Iron, Bar-Iron, and Steel. 278. Working of Iron. — In order to extract metallic iron from the ores just mentioned, they must be de- prived of their oxygen. This is generaUy done by ex- posing them with charcoal to a red heat. As a general rule, a mixture of several kinds of ore is used for smelt- ing, because experience has taught that this process is then conducted more easily and more completely than when only one kind of iron ore is employed. The ores, containing carbonic acid, water, or sulphur, must pre- > viously be heated in appropriate furnaces to expel these volatile gases (roasting of the ores). It must also be borne in mind that the iron ores are never pure, but always contain foreign ingredients (gcmgues)] for in-£t. ^ stance, silica, clay, lime, manganese, phosphorus, &c./iz-c*^, Silica especially forms a principal ingredient in iron ores. This does not melt even when exposed to the hottest furnace-fire; and yet it must be melted, that • the iron may flow from the ores, and be obtained as a coherent mass. This is effected by the addition of a base, commonly lime, with which the silicic acid wnl combine. A lime-glass is formed, and if loam or clay be present also an alumina-glass, both of which, when combined, melt more readily than each separately, and flow off as slag. The substance which forms this fusible compound is termed the flux; and the combi- nation of the prepared ore and the flux is called the mixture. Alternate layers of this mixture, and of wood- 27* 318 HEAVY METALS. charcoal or of coke are now thrown into a large furnace, caUed the blast-furnace, constructed as shown in the annexed figure. Fig. 140. The portion a of the blast-furnace is called the shaft; b is the boshes, c is the crucible part, and e is the hearth. The mouth of the furnace serves both for charging the materials, and for the escape of the smoke; it is thus both a door and a chimney. In the upper portion of the shaft the mixture is heated to redness (it is roast- ed) ; during this process the carbonic acid of the lime- stone also escapes. Farther down, the charcoal ab- stracts from the iron ore its oxygen, and escapes with it as carbonic oxide, which at the opening is entirely IRON. 319 consumed, on access of air, into carbonic acid, and oc- casions the bright flame which issues from the top. In the boshes, where the greatest heat is evolved, the reduced iron melts and falls in drops upon the hearth, together with the siUca, Ume, and clay; these form a slag, which floats on the molten iron, and is drawn off at t. The melted iron is suffered to flow off from time to time, by a smaU opening made in the side-wall of the hearth. After having heated to a hundred degrees or more the air necessary for burning the charcoal or coke, it is forced at d, by means of large bellows, or other wind apparatus, into the furnace, in which a heat of perhaps 1200° or 1400° C. may be produced. In pro- portion as the melted iron and the slags are removed from beneath, fresh charges of ore, Ume, and charcoal are introduced at the top, and in this manner the > smelting often continues uninterruptedly for five or six years, according as the furnace holds out. Iron Ore, Flux, Fuel, Iron + Carbon, Oxygen -f-Carbon, Silica (clay). Lime (clay). Product, Carburetted Iron (cast-iron). Carbonic Oxide and Carbonic Acid. Silicate of Lime and > y. Silicate of Alumina $ «*' The slag from the blast furnaces has generally a green or blue color, owing to the protoxides of iron and of manganese there dissolved in it. They are fre- quently formed into square blocks, and used for build- ing-stones. 279. Castor Crude Iron.—The metal obtained by the above process is by no means pure iron, but a chemical mixture of iron and carbon. A hundred- weight of iron takes up, at the hottest white heat, from * about four to five pounds of carbon, and Ukewise some siUcon from the silicic acid, some aluminum from the 320 HEAVY METALS. clay, and sometimes also a trace of sulphur, phos- phorus, arsenic, &c, when these were contained in the iron ore. Cast-iron, thus obtained, is characterized by the following properties. a.) It is fusible at a glowing white heat (wrought- iron and pure iron are not); therefore it is especially adapted for those iron articles which are made by cast- ing. For remelting iron on a small scale, graphite crucibles are made use of, but on a large scale shaft- furnaces (Schachtbfen), or the so-called cupola-furnaces. b.) Cast-iron is brittle, and can neither be forged nor welded (bar-iron and steel may be bent, forged, and welded). The application of cast-iron must, therefore, be limited to the manufacture of such articles as are not exposed to being bent, or to strong concussions. Very recently, however, a method has been discovered for imparting to cast-iron a certain degree of flexibility, ^ and even of maUeabiUty, by exposing it for several days with iron scales or spathic iron to a red heat. The term malleable cast-iron (fonte malleable) has been given to this kind of iron. There are two kinds of cast-iron in commerce, known as gray and white iron. The gray iron is almost black, has a granular texture, and admits of being filed, bored, &c.; the white iron, on the contrary, is of a silvery whiteness, possesses a lamellar-crystaUine texture, and is so hard as not to be acted upon by steel instruments. Crude white iron, by remelting and very slow cooling, is changed to gray; on the other hand, the gray is changed to white iron by being heated and suddenly cooled. Gray iron is best adapted for castings; white iron is the most suitable for the manufacture of bar iron and steel. t 280. Malleable or Bar Iron. — Cast-iron, by being IRON. 321 deprived of its carbon, is converted into malleable iron, and acquires the following very important properties. a.) Bar-iron possesses great ductility and tenacity, and may be hammered or roUed into sheets, and drawn out into fine wire, which is not the case with cast-iron. b.) At a less degree of heat than that of fusion, it becomes soft, like wax or glass, so that two glowing pieces may be welded into one. Upon this property rests its capacity of being welded, which is possessed by no other known metal, except platinum. AU the other metals become fluid instantaneously, as is the case with ice, without undergoing previous softening. c.) Wrought-iron is sufficiently soft to be worked by steel instruments, and it does not become harder, if, when heated to redness, it is suddenly quenched in water (steel is thereby rendered brittle). d.) Wrought-iron is distinguished, moreover, from cast-iron by its fibrous texture, composed, as it were, of threads incorporated together; while cast-iron has the appearance of being a baked granular mass. But it is a very striking fact that fibrous wrought-iron, by re- peated jolts or blows, becomes gradually granular and brittle, as, for example, in the axletrees of carriages. Thus, also, in solid bodies, their particles or atoms can change their position with regard to each other, which was formerly supposed to be possible only with liquid bodies. By thoroughly heating and reworking, the former strength and flexibility, as well as the fibrous texture, is restored to the iron. Wrought-iron is not entirely freed from carbon; it contains, however, only from a quarter to a half pound ^of it for each hundred-weight. Iron entirely free from carbon is softer and more tenacious than bar-iron; thus we see that it is the chemical combination of the car- 322 HEAVY METALS. bon with the iron, as in cast-iron, which destroys these two properties of softness and tenacity. 281. Refinery of Iron. — 1. Finery Process.— The method which is employed for separating carbon from the cast-iron is very simple. The carbon is burnt out by heating the iron to fusion, and constantly stirring it while exposed to a current of air, the oxygen of which combines with the carbon, forming carbonic oxide gas. During the operation, a considerable portion of the iron (one quarter) is converted by oxidation into iron cin- ders, which fuse with the sand, that either adheres to the cast-iron, or is purposely strewed upon the hearth, and form with it a heavy black slag of sificate of magnetic oxide of iron. The iron mass becomes graduaUy more tenacious, since the iron melts so much the more diffi- cultly the less carbon it contains; and finally, in the form of a loosely coherent mass (the bloom) is placed under a loaded hammer, by a few blows of which the remaining slag is pressed out, and the iron particles are formed into a compact mass. The latter is afterwards usuaUy hammered or rolled into bars or bands. This method of converting brittle cast-iron into ductile and maUeable iron is called the finery process. The object of the refinery is, as has just been shown, to separate the carbon from the iron. The annexed scheme serves to render the process more inteUigible. Cast Iron, Air, Sand, Iron |, Iron i, Oxygen, Silica, Carbon. Oxygen. Products, Wrought Iron, Slag, Carbonic Oxide. 2. Puddling Process. — For the refining or decarbon- izing of larger quantities of iron, the reverberatory fur- naces are used, similar to those employed in the prep- aration of soda (§ 220). As in these furnaces the fuel IRON. 323 Fig 141- does not come in contact with the iron itself, a cheaper fuel than char- coal may be made use of, for instance, pit-coal or turf, the ashes of which, if mixed with the iron, would certainly spoil it. These are call- ed puddling furnaces, be- cause the iron must be kept constantly stirred (puddled). 282. Steel. — Steel holds a middle place between cast and wrought iron, both as to the quantity of carbon it contains, and other properties. a.) If quenched when heated to redness, it is ren- dered hard and brittle (Uke cast-iron); if cooled some- what more slowly, it is rendered elastic, and if cooled very slowly, it is soft, ductile, and malleable (Uke bar- iron). b.) It is less fusible than cast-iron, and more so than bar-iron. c.) It contains, in every hundred-weight, from two to two and a half pounds of carbon. To these properties steel owes its importance as a material for thousands of articles, especiaUy for cut- ting instruments, since it may be made soft ox hard, elastic or brittle, at pleasure. The article manufactured is usually first heated to redness, then suddenly cooled by quenching it in water, and afterwards tempered in ^rder to diminish its hardness and brittleness. Experiment. — Hold a steel knitting-needle in the flame of a spirit-lamp till it is red-hot, and then quickly 324 HEAVY METALS. plunge it in cold water; it thereby becomes so brittle as to break on any attempt to bend it. Again hold the needle in the fire, and observe the changes of color which it passes through; it will first become yellow, then orange, crimson, violet, blue, and finally dark-gray. The cause of this change of color is the same as that of the ferruginous water (§ 276), namely, a film of oxide forms upon the steel; at first the film is thin, and has a yellow appearance, but graduaUy it becomes thicker and also darker, as the heat increases. The final result — the dark gray coating — is iron scales. On the standing of the ferruginous water in the air, the oxida- tion advanced (§276) a step further; in that case, the final result was a brown substance, — hydrated sesqui- oxide of iron. A definite degree of hardness and elas- ticity of the steel corresponds to each of these tints, the needle when covered with the yeUow film being the hardest and most brittle, and when presenting a blue aspect being in its softest and most elastic condition. The workmen in steel impart to their articles various degrees of hardness and elasticity by tempering; files and razors are made very hard and brittle, — saws, watch-springs, &c, soft and elastic. 283. Steel may be prepared in various ways: — 1.) By partly refining cast-iron, so that only one half of the carbon is burnt out (crude steel); or 2.) By the process of cementation, which consists in filling an iron box with bar-iron and powdered char- coal, and then maintaining the whole for several days at a red heat. The carbon graduaUy penetrates into the iron, thus converting it into steel (blistered steel). Both these kinds of steel must be rendered uniform^ either by repeated hammering (tilting) of it when heat- ed to redness (tilted steel), or by remelting (cast steel). IRON. 325 Steel may be ornamented by corroding its poUshed sur- face with acids, whereby a variety of light and dark colored shades and impressions will be produced {damaskeening). From the constituents of bar and cast iron it may be inferred that steel can be made by an intimate combi- nation in equal proportions of those two substances. In this manner, indeed, the exterior surface of wrought- iron articles — as, for instance, of agricultural imple- ments, chains, &c. — can easily be converted into steel, by being heated in melted cast-iron. This object may be attained more easily by strewing ferrocyanide of po- tassium over the hot iron (§ 292). Iron, nickel, and cobalt are the only metals which are attracted by the magnet Magnetism immediately vanishes from bar-iron when it is removed from the magnet; while steel, on the contrary, retains its mag- netic power, and does not lose it until heated to red- ness (steel magnet). The magnetic oxide of iron is likewise attracted by the magnet, owing to the protox- ide contained in it, but the sesquioxide of iron is not so attracted. Salts of Iron. 284. The protoxide and sesquioxide of iron form salts with acids; we have, accordingly, two series of iron salts: — a) the salts of protoxide of iron are gen- erally green, and consist of one atom of protoxide of iron, and one atom of acid; b) the salts of sesquioxide of iron are usually of a yellowish-brown color, and con- sist of one atom of oxide and an atom and a half of acid (or 2 : 3). Iron and Acids. It has already been mentioned (§173) that many 28 326 HEAVY METALS. metals dissolve only in diluted acids, others only in concentrated acids, and that the former take the oxy- gen requisite for their oxidation from the water, while the latter take it from the acids. Iron, together with manganese, zinc, cobalt, nickel, and tin, belongs to the first-named class of metals, which are called water-de- composing or electro-positive metals. The mere circum- stance, that in the presence of an acid they are able to abstract oxygen from the water, leads to the supposi- tion that they are more powerful chemical bodies than those metals which cannot do this. This supposition is in reality confirmed ; the electro-positive metals evince a far greater affinity for oxygen, sulphur, chlorine, &c, and their oxides a much greater affinity for the acids, than is exhibited by the other metals and their oxides. It may be weU in this place to remind the student that a solution of a metal does not contain a metal as such,^ but always a metaUic salt in solution (§ 160). 285. Green Vitriol, or Sulphate of Protoxide of Iron (FeO, S03-J-6 HO). This salt, which is always formed when iron is dis- solved in diluted sulphuric acid, is often caUed green vitriol, on account of its pale-green color. By slowly evaporating the solution, the salt may easily be ob- tained in oblique rhomboidal prisms; these crystals contain nearly one half their weight of water of crys- taUization. Experiment. — Dissolve 100 grains. of blue vitriol (§ 175) in an ounce of water, and introduce into the solution a piece of polished iron, which has been previ- ously weighed ; the blue color wiU gradually change to green, while the iron is covered with a red coating of copper. The stronger iron takes from the copper its iron. 327 oxygen and sulphuric acid, and combines with both of them; 32 grains of me- talUc copper are de- Soluble. . ! i -i c n na posited, whue full 28 grains of iron have been insoluble, dissolved. But 32 is to 28 nearly as 396 (the atomic weight of copper) is to 350 (the atomic weight of iron); accordingly, one atom of copper is re- placed by one atom of iron. This process is called the reduction of a metal by the moist way. The supernatant liquor contains in solution no longer any copper, but only green vitriol, which may be crystaUized by evap- oration. Thus is explained the inappropriate name of copperas, very commonly applied to sulphate of iron. > Experiments with Green. Vitriol. Experiment a. — Let a solution of green vitriol stand for some time in the air; it will gradually assume a yel- lowish color, and a brownish-yeUow substance, hydrat- ed sesquioxide of iron, is deposited. AU the other salts of protoxide of iron do the same ; namely, they attract oxygen from the air, and are gradually converted into salts or sesquioxide of iron. But the acid present is not sufficient to dissolve all the oxide, as this has a greater capacity for saturation, that is, requires more acid for its solution than the protoxide of iron does; therefore, a portion of the oxide formed faUs to the bot- tom. For the same reason, a sesquioxide or peroxide al- ways separates from the protoxide salts of the other met- als, when they are converted into higher oxide salts. A ^ clear solution may be obtained, by adding a sufficient quantity of acid to dissolve the precipitated oxide. Experiment b. — Boil half an ounce of green vitriol 328 HEAVY METALS. with an ounce and a half of water and one dram of sulphuric acid, in a porcelain bowl, and add a few drops of nitric acid to the solution, until the color of it is changed to yellow ; it now contains sulphate of sesqui- oxide of iron in solution, which must be kept for use. The same effect, namely, the conversion of the protox- ide into sesquioxide of iron, is thus quickly produced by the oxygen of the nitric acid, which in the former experiment was only slowly caused by the action of the air. Three atoms of oxygen are withdrawn from the nitric acid, and, accordingly, nitric oxide is produced (§ 162), which has the property of imparting to a solu- tion of green vitriol a dark color. On boiUng, the nitric oxide escapes, and is converted in the air into nitrous acid, forming the yeUow fumes that are given off dur- ing the oxidation. Experiment c. — Prepare (1.) a diluted solution of green vitriol, (2.) a mixture of one part of a solution of sulphate of sesquioxide of iron and four parts of water (see former experiment), and (3.) a mixture of the first and second; and then add ammonia to each of the three liquids, until they emit a distinct ammoniacal odor. There is formed in the 1. Solution of protoxide of iron, a greenish white pre- cipitate of hydrated protoxide of iron ; 2. Solution of magnetic oxide of iron, a black precip- itate of hydrated magnetic oxide of iron ; 3. Solution of sesquioxide of iron, a yellowish brown precipitate of hydrated sesquioxide of iron. Ammonia is a stronger base than either protoxide or sesquioxide of iron; for this reason, it abstracts from them their sulphuric acid, and the oxides will be precip-, itated, since almost all the metalUc oxides are insoluble in water. If the metalUc oxides, at the moment of their IRON. 329 separation from a IFcO S03-—^=-HONH3,S03 Soluble. VFes,03,3HO Soluble. Insoluble. combination, meet with water, they readily com- bine with it, form- ing hydrates. This is the reason why the metallic oxides, insoluble, which are obtained in the moist way, frequently have a very different color from those prepared in the dry way (by heating to redness). If you heat the hydrate, the water is expelled, and the oxides appear now in their character- > istic color. This change of color is weU illustrated in the case of common bricks, which, before being burnt, have a yellow color, owing to the presence of hydrated sesquioxide of iron; when burnt, they are red, because the hydrated water is expelled by the heat, and thereby anhydrous sesquioxide of iron is formed, which pos- sesses a red color. If the above precipitates are filtered, a striking change is soon perceptible in the protoxide of iron, its color changing first to a dark green, then to black (magnetic oxide of iron), and finaUy to brown (hydrated sesquioxide of iron), according to the amount of oxygen absorbed. As already stated, one of the most important properties of protoxide of iron is", that it combines eagerly with still more oxygen, a property which, as we have seen, it communicates also to the salts in which it is contained. ^ The black precipitate of magnetic oxide of iron com- ports itself in the same manner. But if you boil it pre- 28* 330 HEAVY METALS. viously to filtration, it will retain its black color on dry- ing. In this state it is used as a medicine, under the name of black oxide of iron. Experiment d. — If you pour alcohol upon some bruised nutgalls, the liquor, after a few days, wiU have a brownish-yeUow color, and a very astringent taste. This liquid — called tincture of galls — contains in so- lution, besides several other ingredients, two organic acids, tannic acid, or tannin, and gallic acid. Add some of this tincture to a solution of green vitriol, and some of it likewise to a mixture of water and sulphate of sesquioxide of iron; in the former, a light-colored pre- cipitate wffl be formed, which assumes at first a violet, and finaUy a black color; but in the second Uquid a black color is immediately produced; and, on standing, a black precipitate will be deposited. This black precip- itate consists principally of tannate and gallate of sesqui- -\ oxide of iron. By adding to this gum or sugar, com- mon ink is prepared, the mucilaginous or saccharine liquid thus obtained holding the gaUate and tannate of iron in suspension. The combination of tannin and gaUic acid with protoxide of iron is not black, but it becomes so on exposure to the air, since the protoxide is thus converted into sesquioxide. This explains the pale color of fresh ink, and its becoming dark on the paper. If you dip a linen rag first in tincture of galls, and then in a solution of iron, the black precipitate is formed in the fibre itself, and thus adheres so firmly to it that it' cannot be washed out again. This is the general method used for dyeing cloth, leather, hair, &c, either black or gray, and for this reason the iron salts, especially green vitriol, have a very extensive applica- tion in dyeing and calico-printing. r 286. Nitrate of sesquioxide of iron (Fe2 03,3 N06) is IRON. 331 obtained by adding iron filings to diluted aquafortis, as long as they continue to dissolve in it. Nitric acid fur- nishes an abundant supply of oxygen to the iron, and this takes up as much oxygen as it can bind, and is converted into a sesquioxide. This solution is of a brown color, and is used in dyeing. If some aquafortis is dropped upon cast-iron, steel, or bar-iron, black spots are produced, because the iron, but not the carbon, is dissolved. These spots are darker in cast-iron, and lighter in bar-iron. Hence, to ascertain how much car- bon is contained in a sample of iron, you have only to dissolve a weighed quantity of it in diluted nitric acid, and to weigh the charcoal remaining behind. 287. Acetate of sesquioxide of iron may be prepared directly, by dissolving freshly precipitated and stiU moist hydrated sesquioxide of iron in acetic acid. When > mixed with alcohol and ether, it forms Klaprothh ethe- real tincture of acetate of iron, which is sometimes used as a medicine. When the shoemaker pours beer upon iron nails to prepare the iron-black with which he black- ens his leather, he obtains acetate of sesquioxide of iron; for on exposure to the air the beer is changed into vin- egar, and the iron to sesquioxide. Leather is a combi- nation of the skin with tannin ; when the latter meets with the sesquioxide of iron, black tannate of iron (ink) is formed. An iron mordant is now frequently pre- pared for dyeing purposes, by dissolving iron-rust in wood-vinegar (pyroUgnite of iron). 288. Phosphate of protoxide of iron is prepared by mixing a solution of green vitriol with a solution of phosphate of soda; the white precipitate produced be- comes gradually blue by attracting oxygen from the air ^ (phosphate of the magnetic oxide of iron, blue iron- earth). Phosphate of sesquioxide of iron is white, and occurs in the ashes of many plants. 332 HEAVY METALS. Iron and Chlorine. 289. Protochloride of Iron (Fe CI), a green salt, is formed by dissolving Volatile, iron in muriatic acid; sesquichloride of iron Non- (Fea Cl3), a brown salt. volatile. 1 j. 1 . by dissolving sesquiox- ide of iron or hydrated sesquioxide of iron in muriatic acid, or by the addition of chlorine water to protochlo- ride of iron (§ 186). Protochloride of iron is also called muriate of protoxide of iron, and sesquichloride of iron is often called muriate of sesquioxide of iron. Iron and Cyanogen. As chlorine combines with iron, so also cyanogen can form combinations with iron. Two of them, Prus- sian blue and yellow prussiate of potassa, have acquired very great importance in the arts. 290. Prussian Blue, or Ferrocyanide of Iron (3FeCy + 2Fe2Cy3). If magnetic oxide of iron is agitated with prussic acid, the black precipitate becomes blue; this insoluble compound is termed Paris blue; or, when it is mixed with white substances, — for instance, alumina, clay, starch, &c, — Prussian or mineral blue. Its constitution may be more readily imprinted on the memory by re- garding it as prussiate of black oxide of iron. It con- sists, in fact, of protocyanide and sesquicyanide of iron, since a haloid salt and water are always formed when a hydrogen acid combines with a metallic oxide (§ 187). Both modes of consideration harmonize well with eachf other, for prussiate of protoxide of iron is the same as cyanide of iron -f- water, A IRON. 333 Fe O -f H Cy = Fe Cy -f HO; and prussiate of sesquioxide of iron is the same as sesquicyanide of iron -f- water, Fe2 03 + 3 HCy = Fe2 Cy3 -f- 3 H O. Prussian blue, on account of its splendid color, is not only an important article for staining wood, paper, &c, but it is also one of the principal pigments for dyeing cloth, cotton, silk, &c. The color thus prepared is called, in dyeing establishments, potassa blue, to distin- guish it from indigo blue. Prussian blue, although it contains prussic acid or cyanogen, is not poisonous. Similar inconsistencies frequently occur in chemical combinations. Sometimes a poisonous combination is formed from innocuous bodies; and sometimes a harm- less compound from poisonous constituents. Accord- ingly, a correct inference cannot always be drawn as to the medical effects of a compound merely from its con- stituents. Experiment. — Mix thoroughly together one dram of Paris blue (pure Prussian blue) and a quarter of a dram of oxalic acid, with some water; the color insoluble in water is rendered soluble by the oxalic acid, and a blue liquid is obtained, which, if thickened with gum Arabic, may be used as a blue ink. Experiment. — If you heat some Prussian blue upon charcoal before the blow-pipe, an empyreumatic odor is produced; the cyanogen is consumed (C2 N is con- verted by the oxygen of the air into 2CO, and N), and you finaUy obtain only a brownish-red residue of ses- quioxide of iron. Most of the cyanogen compounds are decomposed in a similar manner by being heated to redness. 334 HEAVY METALS. 291. Ferrocyanide of Potassium, or Prussiate of Potassa (2 K Cy, Fe Cy + 3 H O). Experiment — Heat to boiling an ounce of finely pulverized Prussian blue with three ounces of water, and as it boils add gradually caustic potassa, until the blue color of the mixture disappears. You obtain a turbid, brownish-yellow liquid, which you render clear by filtration. What remains upon the filter is hydrat- ed sesquioxide of iron, which is separated by the stronger potassa from the Prussian blue. Tabular crystals are deposited, on cooling, from the clear yeUowish liquid; they are commonly called yellow prussiate of potassa, but in chemical language fer- rocyanide of potassium. This double salt is formed as foUows: — Prussian blue: iron with more cyanogen + iron with less cyanogen, Potassa: oxygen and potassium, Water: water, .„ , , , . ., C cyanide of potassium-J-pro- Products: hydrated sesquioxide of iron, < _. ., » . J ^ ( tocyanide of iron. (Insoluble.) (Soluble.) The potassium of the potassa, as we see, replaces the iron in the sesquicyanide of iron, forming cyanide of po- tassium, which forms a double salt with the remaining undecomposed protocyanide of iron. The oxygen of the potassa passes to the liberated iron, and converts it into sesquioxide of iron. Accordingly, we have in the yellow salt potassium and iron both combined with cyanogen. As water is present, the cyanide of potas- sium may be regarded also as prussiate of potassa, and the protocyanide of iron as the prussiate of protoxide of iron, and the whole salt as a combination of potassa and protoxide of iron with prussic acid. Such being iron. 335 the case, the prussic acid may be expelled from it by a stronger acid; this, in fact, does take place, for prussic acid is prepared from this salt by adding to it sulphuric or phosphoric acid and some water, and then distilling the mixture. If blood and potassa lye are boiled together and evaporated to dryness, and the remaining mass is heated to redness, a yellow solution of ferrocyanide of potassium is obtained by the lixiviation of it with water. This salt, prussiate of potassa, must not be confounded with cyanide of potassium, a combination consisting of potassium and cyanogen alone, without iron, and which is a white salt and a most deadly poison. The ferrocyanide of potassium (the use of which term instead of prussiate of potassa will prevent the liability of mis- taking one compound for the other) is not poisonous. Ferrocyanide of potassium is prepared on a large scale in a manner similar to that above described. Blood, horn, leather, or other animal substances, are charred; this is best done by dry distillation, in order to obtain ammonia as a secondary product (§ 228); the charcoal thus obtained is then mixed with carbonate of potassa and iron, and the mixture fused at a red heat in a reverberatory furnace. In animal charcoal there is still contained nitrogen. This nitrogen, when heated to redness with a strong base, unites with carbon, forming cyanogen. The cyanogen then enters into combination with the potassium of the carbonate of potassa, which is reduced by means of the coal, forming cyanide of potassium. By dissolving the fused mass in water, a portion of the salt gives up its cyanogen to the iron, whereby ferrocyanide of potassium (and caustic po- tassa) is formed, which, after sufficient evaporation, crystallizes from the solution. 336 HEAVY METALS. 292. Experiments with Ferrocyanide of Potassium. Experiment a. — By mixing a solution of ferrocy- anide of potassium with sulphate of sesquioxide of iron a deep blue precipitate v( Prussian blue is produced; for from Ferrocyanide of potassium: protocyanide of iron -f- cyanide of potassium, and Sulphate of sesquioxide of iron: ------ iron, oxygen, and sulphuric add, - . C protocyanide of iron + sesquicyanide of iron are lormea £ (insoluble), and sulphate of potassa (soluble). Experiment b. — Mix a solution of ferrocyanide of potassium with a solution of green vitriol; a fight blue precipitate is formed (prussiate of protoxide of iron and potassa, or ferrocyanide of iron and potassium). Set aside one half of the solution, frequently stirring it; the light color of the precipitate graduaUy changes to a darker blue. This change takes place more rapidly by > adding to the other portion a few drops of nitric acid, and heating the mixture. In both cases oxidation takes place, whereby a portion of the protoxide is con- verted into the oxide, so that prussiate of the magnetic oxide of iron or ferrocyanide of iron is formed. Both of the methods here given are employed in the preparation of Prussian blue on a large scale. In dyeing, the cloth is first steeped in a solution of iron, and then passed through a slightly acidified solution of ferrocyanide of potassium. Experiment c. — Add a solution of ferrocyanide of potassium to a very diluted solution of blue vitriol; you obtain a purple red precipitate of ferrocyanide of copper. The copper gives up its oxygen and sulphuric acid to the potassium of the ferrocyanide of potassium, and sulphate of potassa remains dissolved in the liquid. This is the most accurate test for detecting the presence IRON. 337 of copper in a liquid. Most of the basic elements, like copper in this instance, form double compounds with protocyanide of iron. Experiment d. — Sprinkle some ferrocyanide of po- tassium upon a piece of red-hot sheet-iron, and quench it quickly in cold water; the iron becomes so hard as to resist the action of the file, a coating of steel having been formed on its surface by the carbon of the cyano- gen. This simple process is especially adapted for im- parting to agricultural implements a greater degree of hardness and durabffity. 293. Red prussiate of potassa, or ferricyanide of po- tassium, is distinguished from the yellow prussiate by containing sesquicyanide instead of protocyanide of iron. When added to salts of the protoxide of iron it . forms a deep blue precipitate (but no precipitate is pro- duced by it in the salts of the sesquioxide of iron) ; therefore, it is not only used for producing a blue color, but also as a reagent to distinguish the salts of the sesquioxide from those of the protoxide of iron. Iron and Sulphur. 294. Experiment — Protosulphuret of Iron (Fe S). — On adding some sulphuretted hydrogen water to a slightly acidified solution of green vitriol, no precipitate is produced; but if sulphuret of ammonium is added, a deep black precipitate is formed; this precipitate is sulphuret of iron. 295. Experiment — Sesquisulphuret of Iron. — Twen- ty grains of sulphur and thirty grains of iron filings are thoroughly mixed and heated before the blow-pipe «( flame directed upon one part of the mass; this part at- tains a red heat, which rapidly pervades the whole mass. The yellowish-brown substance obtained is 29 338 HEAVY METALS. sesquisulphuret of iron. Another method of preparing this substance, and of applying it to the evolution of sulphuretted hydrogen, has been described (§ 131). This combination also occurs native (magnetic py- rites).* Experiment. — If you moisten protosulphuret of iron with water, and let it remain exposed to the air for some weeks, small green crystals wiU be found dissem- inated throughout the mass, both the iron and the sul- phur having graduaUy attracted oxygen from the air. Fe S is thus converted into Fe O, S 03. 296. Bisulphuret of Iron (Fe S2).— Iron containing twice as much sulphur as the protosulphuret occurs native in many ores, and frequently in hard coal, and is caUed iron pyrites or bisulphuret of iron. It has quite the appearance of brass, and usuaUy oc- curs in cubic crystals. If heated in a re- tort, half of the sulphur distils over, and is coUected, and a black sulphuret of iron remains behind; accordingly sulphur may be prepared from it. Green vitriol is pre- pared from this residue, by piUng the latter in heaps, and leaving it for several months exposed to the air. The green vitriol thus formed is freed from earthy im- purities by Uxiviation and evaporation. The salts of iron may be detected by their behaviour before the blow-pipe, by ammonia, tincture of gab's, sulphuret of ammonium, and ferrocyanide of potas- sium. * The composition of magnetic pyrites generally corresponds to the fonnula Fe7 Ss = 5 Fe S + Fe2 S3. — Cours Elementaire de Chimie par Regnault. MANGANESE. 339 Systematic Synopsis of the Compounds of Iron. Iron. Carburetted Iron. a.) Wrought-iron (iron -f- £ per cent, of carbon). 6.) Cast-iron (iron -f- 5 per cent, of carbon). c.) Steel, a mixture of both. Sulphurets of Iron. a.) Sulphuret of iron, black. b.) Bisulphuret of iron, yellow. c.) Sesquisulphuret of iron, brownish-yellow, a mixture of both. Oxides of Iron. a.) Protoxide of iron, black. Hydrated protoxide of iron, white. b) Sesquioxide of iron, reddish-brown. Hydrated sesquioxide of iron, yellowish-brown. c.) Magnetic oxide of iron, black. d) Ferric acid (lately discovered). Salts of Iron. a.) Salts of the Oxide. Salts of the Protoxide. Salts of the Sesquioxide. (Green.) (Brown.) Sulphate of the protoxide of iron. Sulphate of the sesquioxide of iron. Nitrate " " " Nitrate " " " Carbonate " " " Acetate " " " Acetate " " " Phosphate " " " Phosphate " " 6). Haloid salts. Protochloride of iron. Sesquichloride of iron. Ferrocyanide of potassium (yellow). Ferricy an ide of potassium (red). Ferrocyanide of copper (red). Ferrocyanide of iron (blue). MANGANESE (Mn). At. Wt. = 345 — Sp. Gr. = 8. 297. Black Oxide or Hyperoxide of Manganese (Mn 02). Several experiments have already been performed with this mineral, which is chiefly obtained from the Harz Mountains and from Thuringia; we use it espe- 340 HEAVY METALS. ciaUy for the preparation of oxygen and chlorine. It is one of the few combinations of oxygen termed hyper- oxides or superoxides ; so called because they contain an excess of oxygen, which they give out when heated to redness, or when heated with sulphuric acid. 100 ounces of black oxide of manganese, which contain 36 ounces of oxygen (2 atoms), yield at a moderate heat 9 ounces (^ atom), at an intense red heat 12 ounces (f atom), on heating with sulphuric acid 18 ounces (1 atom), of oxygen. Therefore hyperoxide of man- ganese is excellently adapted for combining other bodies with oxygen, as was shown in the preparation of chlo- rine, when the oxygen of the hyperoxide of manganese oxidized the hydrogen of the muriatic acid, forming water, and thereby Uberated the chlorine of the muriatic acid. Glass-makers often add hyperoxide of manganese to A the fused glass, to render the color of the black or dark- green bottle-glass yellow or orange, a shade which is generally preferred. In this case, also, an oxidation is effected by the hyperoxide of manganese. The dark color of the glass is owing to the protoxide of iron; this obtains oxygen from the hyperoxide of manganese, and becomes sesquioxide of iron, which colors the fused glass brown or yellow. If added in small proportions to white glass, it gives it a violet color, and in this way artificial amethysts are made. Experiment. — Mix into a thin paste with water one fourth of a dram of finely pulverized hyperoxide of man- ganese, one dram of Utharge, one of clay, and spread it over a tile. Put the latter between two glowing coals, or direct upon one part of it a strong blow-pipe flame; the mass melts, and forms on cooling a brilliant t* black coating, or, if less manganese be used, a brown MANGANESE. 341 coating. This is the method by which potters prepare their black or brown glaze. 298. Manganese (Mn). — By intensely heating the hyperoxide of manganese with charcoal, all its oxygen may be expelled, and a grayish-white brittle mass (Mn) is obtained, much more difficult of fusion than even iron. Other Combinations of Manganese. 299. Experiment. — Mix in a porcelain crucible a quar- ter of an ounce of hyperoxide of man- ganese with one eighth of an ounce -gg^jS^--- of sulphuric acid, and expose the /^^jFg*% mixture to a gentle heat for fifteen I £?^l1 I minutes, and then to a strong heat \\ \j^ I f°r an hour. After cooUng, boil the t JJ^ gBy^ \^ black mass in water, and evaporate the solution to dryness, constantly stirring it when nearly dry; the reddish-white powder is sulphate of protoxide of manganese (Mn O, SOs -f- 4 H O). Half of the oxygen escaped during the heat- ing, and protoxide of manganese (Mn O) remained be- hind, which, being a salt-base, combined with the sul- phuric acid. Muriate of protoxide of manganese, or protochloride of manganese (Mn CI), was formed dur- ing the preparation of chlorine (§ 150), and remained in the flask, having obtained a yellow color owing to the presence of chloride of iron. Most of the salts of the protoxide of manganese have a reddish color. 300. Dissolve a portion of the sulphate of protoxide of manganese, and use the solution for the three foUow- ing experiments. Experiment a.— On exposure to the air, the solution acquires a dark-brown color, and after a time deposits 29* 342 HEAVY METALS. a powder of the same color, just as occurred in the solution of the sulphate of protoxide of iron. The protoxide of manganese attracts oxygen from the air, and is converted into hydrated sesquioxide of manga- nese, from which a part separates, sufficient acid not being present to retain aU the sesquioxide in solution. Experiment b. — If some ammonia or potassa is added to another portion of the solution, the stronger bases wffl overpower the sulphuric acid, and, hydrated pro- toxide of manganese (MnO-j-HO) wiU separate as a white precipitate. On filtering and drying, it wiU be- come converted into dark-brown hydrate of sesquioxide of manganese (Mn2 03 -f- 3 HO), precisely as occurred with the hydrated sesquioxide of iron. If a piece of linen, immersed in the solution, is dried, and then passed through a solution of potassa, the precipitate wiU adhere firmly to the fibres of the cloth, and will ac- "V quire, on exposure to the air, a fine dark-brown color, called by dyers manganese-brown. Experiment c. — Add some sulphuretted hydrogen to a third portion of the solution; no change takes place until some ammonia is added, when a flesh-colored pre- cipitate is produced, consisting of manganese and sul- phur (Mn S). In this manner, the presence of manga- nese in a solution may be ascertained, for manganese is the only metal which, on combining with sulphur, yields a metalUc sulphuret of a pink color. This ex- periment also affords another example of double elec- tive affinity causing a decomposition which could not be effected by simple elective affinity. 301. Acids of Manganese. — Manganese is character- ized by combining with still more oxygen than is already contained in the hyperoxide. Experiment. — Mix intimately together in a mortar MANGANESE. 343 one dram of hyperoxide of manganese and one dram of caustic potassa; put the mixture in a porcelain crucible, and heat it strongly for half an hour. When cold, add some water to the black mass; you will obtain a green solution, which becomes clear by set- tling in a test-tube. This green color is owing to the formation of a salt, which is called manganate of potassa, or chameleon mineral. By the ignition with potassa, the hyperoxide of manganese is disposed to receive an additional atom of oxygen from the air, and Mn 0, is converted into Mn 03, which latter compound comports itself as an acid; that is, it combines with the base present, forming a salt (KO, Mn 03). Experiment — Pour half of the green solution into a wine-glass, dilute it with water, and leave it in repose; the green color soon begins to change, passing through > bottle-green and violet to a crimson-red, a brown pow- der (hyperoxide of manganese) being at the same time deposited. This apparently voluntary change is occa- sioned by the carbonic acid of the air, which combines with a portion of the potassa and expels the manganic acid. The manganic acid (Mn 03), however, on being deprived of its base, immediately separates into two parts, one of which contains less oxygen (hyperoxide of manganese, Mn 02), and the other more oxygen (per- manganic acid, Mn2 07) ; 3 Mn 03 is converted into Mn Os and Mn2 07. The red color belongs to the per- manganic acid, which remains in solution, combined with a portion of the potassa. Experiment. — Add some drops of sulphuric acid to another portion of the green solution, when the change of color from green to red, that is, the conversion of ^ manganate into permanganate of potassa, wiU take place instantaneously. 344 HEAVY METALS. The most remarkable characteristic of these acids is the facility with which they surrender that portion of their oxygen which stamps them as acids. Even a piece of wood, paper, or any other organic substance, thrown into the green or red solutions, decomposes them and removes their color, and for this reason they should never be filtered through paper. From its sin- gular changes of color, manganate of potassa has re- ceived the name of chameleon mineral. 302. Manganese forms with oxygen alone a great variety of combinations. 100 lbs. of oxygen 1 at.0 150 lbs. of oxygen 1J at. 0 200 lbs. of oxygen 2 at. O 300 lbs. of oxygen 3 at. O 350 lbs. of oxygen 3i at O It is, moreover, hereby rendered very obvious, that it is the quantity of the oxygen which makes one and the same element sometimes a base, sometimes an acid. Some idea may be formed of the great army of salts which manganese alone, in virtue of this double char- acter, can caU into the field, when we reflect that it not only combines with all the acids, forming protoxides and sesquioxides, but also with all the bases, forming manganates and permanganates. 345 lbs. of manganese form with or 1 at. Mn 345 lbs. of manganese or 1 at. Mn 345 lbs. of manganese or 1 at. Mn 345 lbs. of manganese or 1 at. Mn 345 lbs. of manganese , form with or 1 at. Mn " " form with form with form with Protoxide of man- ganese, = Mn 0. Sesquioxide of man- ganese, = Mn2 O3. Hyperoxide of man- ganese, = Mn 02. Manganic acid, = Mn03. Permanganic acid, = Mn2 O7. J^tcU.^^ - The zinc condenses mostly in the tube, and falls down in drops, as metal, into a vessel containing water. This CADMIUM.--TIN. 353 is again to be melted and cast into sheets. The zinc of commerce always contains an admixture of small quantities of iron and lead. If the amount of lead is more than one and a half per cent, then the zinc re- mains brittle, even when heated, and cannot be rolled out into sheets. CADMIUM (Cd). At. Wt. = 697.—Sp. Gr. = 8.6. 315. Cadmium is a rare metal, and may be regarded as the twin brother of zinc, in the ores of which it is found in smaU quantities. It is chiefly distinguished from zinc by its malleability when cold, and by being precipitated from its solution by sulphuretted hydrogen as yellow sulphuret of cadmium. As already mentioned, this reagent gives no precipitate with the salts of zinc, but the latter is thrown down by sulphuret of ammo- nium, as white sulphuret of zinc. TIN, STANNUM (Sn). At. Wt. = 756. — Sp. Gr. = 7.2. 316. Tin is one of the few metals which were known in the most ancient times. It becomes fluid at a very moderate heat, at 230° G, and in many countries its ores are found in the sand with which the surface of the soil is covered; therefore it was easily obtained and easily smelted. Formerly it was fetched principally from the British Islands, which were, therefore, called also Tin Islands, and even at the present time they, together with Malacca in the East Indies, furnish the purest tin. The properties which especially characterize tin, and render it a very valuable metal, are its beautiful lustre, and its great softness and flexibiUty, — its slight 30* 354 HEAVY METALS. affinity for oxygen, in consequence of which it long retains its brightness in the air and in water, — its easy fusibifity, which renders it peculiarly weU adapted for casting, and for coating other metals (tinning). It has, indeed, lost much of its earUer importance as a mate- rial for making many vessels of domestic use, such as dishes, cans, &c, since such articles are now hand- somely and cheaply manufactured from glass and por- celain. But it is now applied in the arts and trades in a variety of ways not formerly in use. In the older works on chemistry, it is caUed Jupiter, and has the symbol 21. 317. Experiments with Tin. Experiment — Heat a piece of tin upon charcoal be- fore the blow-pipe ; it will soon become covered with a powder, of a yeUow color when hot, but white when cold; this is peroxide of tin, a combination of one atom of tin with two atoms of oxygen (Sn 02). Peroxide of tin thus obtained is not soluble in any acid, and cannot be fused by the strongest heat. It is so delicate a pow- der, that it is often used for poUshing glass and metals. Tin also occurs native as an insoluble oxide, either crystallized (crystals of tin ore), or scattered through va- rious kinds of rocks (tin-stone of Saxony and Bohemia), or, finally, as an ingredient of the sand or debris of low grounds in many countries (wood-tin in England). Ox- ide of tin is the only ore from which tin is largely extract- ed ; its most common admixtures are iron and arsenic. Experiment. — Place two grains of tin and eight grains of lead on charcoal, and heat them before the blow-pipe; they melt and combine most intimately with each other; an alloy of tin and lead is obtained. If this is heated to redness, the oxidation proceeds so tin. 355 rapidly, that the mass takes on a Uvely motion, and con- tinues to glow even when it is removed from the fire. In this manner the potter prepares the porcelain-like glaze for earth- en baking-pans, and for Delft ware. Add some powdered bo- rax to this mixture of oxides of lead and tin, and form with it a bead upon platinum wire; the bead is not transparent, but, ow- ing to the presence of the infusi- ble peroxide of tin, is opaque, and looks like porcelain (enamel). 318. Alloys of tin and lead are generally used by workers in metal, under the name of solder, for join- ing metals together (soft soldering). Solder is to the tinman what glue is to the carpenter. An alloy of two parts of tin and one part of lead is the most easily fusible, and is called fine solder. Another alloy, used in the soldering of coarser articles, such as gutters, is composed of two parts of lead and one part of tin, and is caUed coarse solder; it is so thick that it does not spread of itself, but must be applied by smearing. For soldering those metaUic articles which are to be subject- ed to a stronger heat, brass, or some other alloy of diffi- cult fusibility, is made use of (hard solder or brazing). Some lead is added even to the tin of which the tin- man makes his articles, because pure tin is somewhat brittle, and does not adapt itself well to the moulds. The quantity of lead which can be added to tin is in many countries regulated by law (| to \). Such an alloy is called proof tin, to distinguish it from refined or grain thij which is tin in its greatest purity. If an acid, such as is used in cookery, be poured on proof tin, 356 HEAVY METALS. the tin only is dissolved; tin has, accordingly, the power of protecting lead from the attacks of acids. Tin and Muriatic Acid. 319. The most important solvent of tin is muriatic acid; the two most important salts of tin, protochloride and perchloride of tin, are prepared by means of it. Protochloride of Tin. —Experiment — Place in two porcelain bowls or earthen pots some tinfoff, and then add some muriatic acid to one of the portions. After some hours pour this acid upon the tin of the second vessel, and then again into the first vessel, re- peating the process so that the metal may come in contact for some days alternately with the air and the muriatic acid. Protoxide of tin is formed by the oxy- gen of the air; it is dissolved by the acid. We thus obtain a solution of the muriate of protoxide of tin, or v protochloride of tin, from which, on evaporation and cooling, colorless rhomboidal prisms are deposited. In commerce this salt is called salt of tin. It possesses, in common with the salts of protoxide of iron, the prop- erty of attracting with great avidity still more oxygen from the air, and changing into a peroxide salt. Thus is explained why the salt of tin, which has been for some time exposed to the air, no longer presents a clear, but a milky, solution. To obtain a clear solution, muriatic acid must be added, which combines with the precipitated peroxide of tin. 320. Protoxide of Tin (Sn O). — Experiment. — Pom- some ammonia upon a solution of salt of tin; the white precipitate which is formed is hydrated protoxide of tin. By boiling the solution, the combination of the protoxide and water is destroyed, and an anhydrous'' protoxide of tin is formed, which has a dark-green col- TIN. 357 or, and must be quickly washed with boiled water and dried, as it likewise attracts more oxygen from the air. If you heat the dried protoxide before the blow-pipe, it burns with great briskness, like tinder, forming per- oxide of tin. 321. Per chloride of Tin (Sn Cl2). — Experiment.— Add chlorine water to a solution of salt of tin, until the odor of chlorine is no longer destroyed. Sn CI is thereby converted into Sn Cl2, or perchloride of tin. This combination can also be obtained by boiUng a solution of salt of tin in a mixture of muriatic acid and nitric acid, or by dissolving tin in aqua regia. The dyers call this liquid permuriate of tin, tin mordant, or red spirits. By the addition of ammonia peroxide of tin is obtained, which is distinguished from that formed at § 317 by its dissolving very easily in acids. Protoxide and peroxide of tin dissolve also in potassa lye, and comport themselves, like alumina (§ 260), as acids towards strong bases. 322. Experiment. — If a few drops of a solution of gold are added to a very diluted solution of protochlo- ride of tin, a purple-red precipitate is formed (but not in a solution of perchloride of tin), which is called purple of Cassias, or gold purple, and is one of the most im- portant vitrifiable pigments, because it produces, when fused into glass or porcelain, the most superb purple- red color. Solution of gold is a good test for the salts of the protoxide of tin. 323. Experiment — Mix a decoction of Brazil-wood with protochloride or perchloride of tin; the yellowish- red color of the liquid is converted into a beautiful crim- ■v son-red. Similar advantageous changes of color are also effected by these salts in other coloring matters, and on this account they are very frequently used as so-caUed mordants in dyeing and calico-printing. 358 HEAVY METALS. Tin and Nitric Acid. 324. Experiment. — Heat some grains of tin with nitric acid in a test-tube ; the tin is converted, under a brisk evolution of yellow fumes, into a white powder, peroxide of tin. The nitric acid will perhaps copvert the tin into an oxide, but it cannot combine with the oxide produced. The peroxide of tin thus obtained combines indeed with other acids, but not so completely as that obtained according to § 321; that prepared by heating does not at all unite with them, as has been already stated (§317). Peroxide of tin accordingly oc- curs in three isomeric states; namely, the insoluble, the very easffy soluble, and the difficultly soluble, in acids. Tin and Sulphur. 325. Experiment. — Sulphuretted hydrogen water * produces, in a solution of protochloride of tin, a reddish- brown precipitate of protosulphuret of tin (Sn S), and in a solution of perchloride of tin a yeUow precipitate of bisulphuret of tin (Sn S2). It is obvious, that in the first case one atom of chlorine is replaced by one atom of sulphur, and in the latter case two atoms of chlorine by two atoms of sulphur. Protosulphuret of Tin (Sn S). — Experiment — Both these metalUc sulphurets may be prepared in the dry way. Envelop 12 grains of flowers of sulphur in a piece of tinfoil, weighing 24 grains, then roll up the package so that it may be introduced into a test-tube, and heat it; half of the sulphur burns up, but the other half, under a lively glowing, combines with the tin, forming a brownish-black mass of a metalUc lustre^ (Sn S). If you sprinkle the glass, while stiff hot, with water, it is rendered friable, and can easily be separated tin. 359 from the fused protosulphuret of tin. The weight of the latter amounts to nearly thirty grains. Bisulphuret of Tin (Sn S2). — Experiment — Pulver- ize the thirty grains of protosulphuret of tin thus obtained, and mix the powder intimately with six grains of sul- phur and twelve grains of sal ammoniac; put the mixture into a thin-bottomed glass flask of an ounce capacity, and heat it for an hour and a half in a sand-bath. You obtain bisulphuret of tin, but in this case as a mass having a golden lustre, and to which the name aurum musivum or mosaic gold has been given. It may be used for giving a gold-like coating to wood, gypsum, clay, &c. (bronzing). The sal ammoniac is found again as a subUmate in the upper portion of the flask; it promotes the formation of the beautiful gold color, without itself undergoing or producing any chemical change. 326. Preparation of Tin. — Tin is prepared in smelt- ing-houses, in a very simple manner, from tin-stone (peroxide of tin). The finely stamped ore is first roasted, by which process the arsenic is volatilized and the iron oxidized. Then it is washed or elutriated with water, whereby the lighter particles of stone (the gangue), and to a great extent also the oxide of iron, are washed away. FinaUy, it is fused with charcoal in a blowing-furnace, and carbonic oxide gas and metalUc tin are obtained, the latter of which flows off below. The \Saxony tin is usually cast in thin sheets, and the Eng- lish tin in slender bars. Most of the tin of commerce contains traces of arsenic and other metals. A bar of 360 HEAVY METALS. tin emits a grating sound on being bent, and by repeat- ing the operation several times in succession, it becomes very hot; the reason is, that the tin, on hardening, assumes a crystalUne texture, and these crystalline par- ticles are displaced by the bending, and rub against each other. These crystals may be very beautifully pro- duced upon tinned-iron sheets. Experiment — Heat a piece of tin plate (tinned-iron plate) upon a tripod, over a spirit- lamp, tiU the tin is melted; then quench it with water, that the tin may harden quickly. The surface of the plate has a dull gray aspect, for it is covered with a film of oxide ; but the most beautiful crys- taUine figures wUl very soon appear upon it by rubbing it alternately with baUs of paper, one of which is mois- ^ tened with diluted aqua regia, and the other with po- tassa lye. Both these liquids dissolve the coating of oxide, and lay bare the pure metalUc tin surface (moiri metallique). 327. Tinning. — Experiment. — The method of coat- ing copper or brass with tin has already been described (§ 229). This may be done also in the moist way, by heating to their boiUng point finely divided tinfoil, or tin scrapings, in a pot with cream of tartar and water, and then boiling for half an hour in this Uquid some brightly polished copper or brass articles; as, for in- stance, cents or brass nails. The free acid of the cream of tartar effects a solution of some of the tin, and on longer boiUng this tin wiU again separate as a metal upon the more electro-positive copper or brass, as in § 284. In this manner pins are tinned, or whitened. Experiment. — Let some vinegar stand over night in RETROSPECT. 361 a vessel of tin plate, and then test it with a solution of gold; the purplish color which forms indicates that even the weak vinegar can dissolve tin. Tin is not in- deed so poisonous as lead or copper, but yet it is in- jurious to health; therefore, acid food and drinks should not be aUowed to stand for any length of time in tin or in tinned vessels. Spurious silver-leaf is made of an alloy of tin and zinc, which is hammered out into extremely thin leaves. URANIUM (TJ). cv/> o-**^ s£u a^i-*^. At. Wt. = 750. —Sp. Gr. = ? 328. Uranium is one of the rarer metals, and occurs in combination with oxygen in a black mineral called pitch-blende, found in Saxony. From it is prepared ' the uranate of ammonia, a beautiful yellow powder, known in commerce under the name of oxide of ura- nium. At a white heat it is reduced to black protoxide, and yields a very permanent black pigment for painting on porcelain. The yellowish-green (may-green) glass, now so popular, likewise owes its color to the oxide of uranium. The following metals, Cerium, Lanthanium, and Di- '• *-£-*-* dymium, are mentioned here only by name, as chemical*. A «»^< rarities. /^-«<*»«. ^>*-« , '. RETROSPECT OF THE FIRST GROUP OF HEAVY METALS. 1. The metals hitherto considered possess the prop- erty of decomposing water, when they are heated to redness, or with the presence of an acid (water-decom- 31 362 HEAVY METALS. posing metals); therefore diluted acids are employed for dissolving them. 2. At their lowest degrees of oxidation, they are strong bases. 3. None of these metals are found pure in nature; they most frequently occur as oxides, consequently combined with oxygen. 4. The specific gravity of these metals is from 6.6 to 8.8. 5. Iron, manganese, zinc, cobalt, and nickel are not precipitated as sulphurets from their acid solutions by sulphuretted hydrogen, but only by sulphuret of ammo- nium (aU the other heavy metals are converted by either of the solutions into sulphurets). This fact is made available in analytical chemistry, as an important means of separating the above-named (electro-positive) from the other (electro-negative) metals. SECOND GROUP OF HEAVY METALS. LEAD, PLUMBUM (Pb). At. Wt. = 1294. —Sp. Gr. = 11.5. 329. Next to iron, lead is the most widely diffused and the cheapest metal; it is, at the same time, also very useful, not merely because we cast shot and types from it, and construct sulphuric-acid chambers of it, but also on account of the many useful combinations which it forms with oxygen and the acids. This metal appears as an enemy to human health, not, however, openly, but under the mask of friendship; for it conceals its noxious effects behind a sweet taste^ which is peculiar to most of its combinations. These effects, moreover, do not manifest themselves immedi- LEAD. 363 ately when the lead enters the system ; it is often only after the lapse of years that they appear (lead colic). It is, for this reason, classed among the slow poisons. Perhaps, also, this was the reason why it was formerly compared with the god of time, and received the name of Saturn and the sign \. The external properties of lead, its lustre, its easy fusibility, its softness and pli- ability, its high specific gravity, &c, are well known; therefore we shall proceed at once to the consideration of its internal or chemical character. Experiments with Lead. 330. Experiment. — Pour into one glass distilled wa- ter, into another spring-water, and place in each a piece of lead; the distilled water soon becomes turbid, and reacts basically, but not so the spring-water. Pure water readily attacks lead, and converts it into hy- drated oxide of lead; in spring-water, on the contrary, there is formed in time, by the sulphates almost always present in it, some insoluble sulphate of lead, which forms a firm coating upon the metallic lead. This ex- plains the harmlessness of leaden pumps, which, in many countries, are quite generaUy used instead of wooden pumps. 331. Experiment. — If lead is heated before the blow- pipe in the exterior flame, it melts at about 320° G, and is thereby coated with a gray film ; indeed, it is finaUy entirely converted into a gray powder. This may be regarded either as suboxide of lead, or as a mixture of oxide of lead with metallic lead. By continued blow- ing, this gray color is changed to yellow; the yellow v body is protoxide of lead (Pb O). At a stronger heat the oxide melts, and solidifies on cooling into a reddish- yellow mass, composed of briUiant scales, the weU- 364 HEAVY METALS. known litharge. By directing upon it the inner blow- pipe flame, metallic lead will again be obtained. This easy reducibleness, which is pecuUar to almost all salts of lead, together with the incrustation of yellow oxide, deposited upon the charcoal, is a certain test for the pres- ence of lead. Oxide of lead contains, for every 100 pounds of lead, 8 pounds of oxygen, or one atom of lead (1294) and one atom of oxygen (100); lead, consequently, is one of those chemically feeble bodies which have a very high atomic weight, since 1294 pounds of it is able to accompUsh only as much as 350 pounds of iron, or 407 pounds of zinc. Protoxide of lead in the form of litharge has a very great application in the arts and trades. How lead-glass (flint-glass), lead-glaze, and sugar of lead are prepared from it, has already been de- scribed; the manufacturing chemist likewise prepares from it red lead, white lead, and other lead colors, and lead salts; the apothecary compounds insoluble soap (lead plaster), by boiling it with olive-oil; the cabinet- maker makes a varnish that dries rapidly, by boiling it with linseed oil, &c. The English litharge is esteemed the purest; that of Saxony and Goslar always contains small quantities of oxides of copper and iron, perhaps also a little sffver. The preparation of it on a large scale will be described under silver. By melting li- tharge in a Hessian crucible, a brownish-yellow trans- parent glass is obtained on cooling'; this consists of oxide of lead combined with some silicic acid. The siUcic acid came from the crucible. 332. Red Oxide of Lead. — Experiment. — Heat in a ladle one dram of litharge and a quarter pf a dram o£f chlorate of potassa; the yellowish mixture smoulders to a red powder, which must be well washed with LEAD. 365 water. The same thing happens on heating the li- tharge for a day, but not to the melting point, and at the same time frequently stirring it. In both cases the litharge receives one third more of oxygen ; in the for- mer case from the chloric acid, in the second case from the air; and is thereby converted into Pb304; this compound is called red oxide of lead, or minium, and is much used as a scarlet pigment. 333. Peroxide of Lead (Pb O,). — Experiment. — If you heat some red lead gently in nitric acid for a few minutes, it is resolved into an oxide, which dis- solves, and into hyperoxide (Pb 02), which remains un- dissolved as a dark-brown powder. Lead is one of the few metals which combine with oxygen, forming hyper- oxides. Lead and Acids. 334. The best solvent of lead is nitric acid. Sul- phuric, phosphoric, and muriatic acids cannot dissolve lead, because they form with it insoluble, or very diffi- cultly soluble salts. As protoxide of lead is easily made, the most advantageous method of preparing the salts of lead is by dissolving the protoxide in acids, be- cause that portion of the acid is thereby saved which would otherwise have been required for the conversion of the lead into the oxide of lead. Nitrate of Lead (Pb O, N03) has already been pre- pared in two ways (§ 160). 335. Sulphate of Lead (Pb O, S 03) (§ 173).—This salt is easily formed by simple or double elective affinity, when sulphuric acid or sulphate of soda is added to a solution of lead. p]ven in a solution of lead more xhan a thousand times diluted, a white turbidness is produced, since the sulphate of lead is an entirely in- 31* 366 HEAVY METALS. soluble salt; we have, accordingly, in sulphuric acid, a very delicate test for salts of lead. This salt is ob- tained in great quantities in print-works, as a secon- dary product in the preparation of the acetate of alu- mina (alum mordant) from sugar of lead and alum (§ 262). 336. Chloride of Lead (Pb, CI). — Experiment.— Heat to boiling one dram of litharge, with half an ounce of muriatic acid and half an ounce of water, and decant the clear liquid from the sediment into a glass vessel; you obtain, on cooling, lustrous white acicular crystals of chloride of lead (horn-lead). This salt is but very sparingly soluble in water. Experiment. — If two grains of litharge and fifteen grains of sal ammoniac are fused together in an iron spoon, there is obtained a combination of a small quantity of chloride of lead, with a large proportion of oxide of lead, in the form of a briUiant, yellow, lami- nated mass, which when triturated yields a handsome yellow powder. This powder is used by painters under the name of Cassel or mineral yellow. 337. Acetate of Oxide of Lead (PbO, A +3 HO), „. ,„, combined with one seventh of its weight of Fig. 151. _ ° /~^ water of crystallization, forms the most im- ■""tn portant soluble salt of lead, sugar of lead | (§ 198), which commonly crystaUizes in four- i sided prisms. On exposure to the air, some [ of its acetic acid is driven oft' by the carbonic ^1/ acid of the air, and the salt then yields with water a turbid solution, but which may be rendered transparent by adding to it a few drops of acetic acid. Basic Acetate of Oxide of Lead is prepared by digesting a solution of sugar of lead with oxide of lead, whereby part of the oxide of lead is dissolved. LEAD. 367 This combination is kept in the apothecaries' shops in a liquid form, under the name of solution of subacetate of lead, or Goulards extract. When mixed with spring- water it forms the so-called lead-water, which has a milky appearance, because some carbonate of lead is formed and separated by the carbonic acid of the water. 338. Tartrate of Oxide of Lead. — Experiment.— Mix a solution of two grains and a half of sugar of lead with a solution of one grain of tartaric acid; the white precipitate formed is collected on a filter, washed, and dried; it is insoluble tartrate of lead. Experiment. — FiU a small phial one third full of dry tartrate of lead, and heat it in a sand-bath over a spirit-lamp, as long as fumes continue to escape. These have an empyreumatic odor, and burn with a blue flame, because they contain much car- bonic oxide gas, which is gener- ated by the carbonization of the tartaric acid. But the tartaric acid contains so much carbon, that a portion of it remains behind, intimately mixed with the metallic lead. The black substance obtained is a pyrophorus, which inflames spontaneously when poured out upon a stone, because, on account of its great po- rosity, it imbibes oxygen eagerly from the air. The yel- low powder produced by the ignition is oxide of lead. If the phial is closed while it is yet hot, this py- rophorus will retain its inflammability for several days. Hydrate of Oxide of Lead. — Experiment. — By add- ing ammonia to a solution of sugar of lead as long as a precipitate forms, hydrate of oxide of lead is obtained 368 HEAVY METALS. as a white powder. It is converted by heating into yeUow anhydrous oxide of lead. 339. Carbonate of the Oxide of Lead (Pb O, C O,). Add to a solution of sugar of lead a solution of car- bonate of soda, as long as a precipitate is formed; the precipitate is carbonate of oxide of lead. The pigment known under the name of white lead is likewise car- bonate of lead, but mixed with variable quantities of hydrated oxide of lead (basic carbonate of lead). This is prepared on a large scale in different ways. a. According to the English method, litharge is mixed with vinegar to form a paste; this is then spread upon a stone slab, and exposed to the fumes of burning coke, the carbonic acid of which combines with the oxide of lead. The acetic acid acts in this case the part of a mediator. Like the nitric oxide in the sulphuric-acid chambers, it dissolves the oxide of lead, and then tenders it to the carbonic acid ; when it has given up the first portion, it dissolves a second, &c. It is obvi- ous that in this way a smaU quantity of acetic acid (or else of sugar of lead) is sufficient to aid in converting gradually a large quantity of litharge into white lead. b. By the oldest, the Dutch method, a large number of jars, in which some vinegar has been poured, are arranged in a building upon a layer of stable-manure or tan, and rolls of sheet-lead are then suspended in the jars above the vinegar, and the whole covered with another layer of stable-manure. After the lapse of several months, the rolls of lead are found to be mostly, if not entirely, converted into white lead. The manure is decaying straw, the spent tan is decaying wood; de- cay is a slow combustion, or, what is the same thing/ a slow conversion of organic substances into carbonic LEAD. 369 acid and water. In every combustion or decay, heat is liberated; this in the present case is sufficient to evapo- rate gradually the vinegar. Accordingly, oxygen, aque- ous vapor, fumes of vinegar, and carbonic acid, are present in the air of the white-lead chambers. If you suppose that these substances combine with the lead in the succession just mentioned, the following order of changes will take place : — 1. oxide of lead ; 2. hydrat- ed oxide of lead; 3. acetate of oxide of lead; 4. basic carbonate of oxide of lead. Thus there is formed first oxide of lead, which, just as in the former process, is converted into carbonate of oxide of lead, through the mediation of acetic acid. The finest kind of white lead is that of Krems, called on the continent of Europe white of Kremnitz. c. By the French method, the white lead is prepared in the moist way by conducting carbonic acid into a solution of basic acetate of lead (Goulard's extract). As was seen above (§ 337), a solution of sugar of lead can dissolve still another atom of oxide of lead; this is precipitated by the carbonic acid as white lead, whereby neutral acetate of lead is once more formed in the liquid, which is again digested with litharge, and afterwards treated with carbonic acid. In this way one pound of sugar of lead may be made gradually to dissolve, and again precipitate as white lead many pounds of litharge. The white lead obtained by this method has indeed a dazzling white color, but it does not possess so much body as that prepared in the English or Dutch manner. The cheaper sorts are ob- tained by mixing white lead with powdered sulphate of * baryta; the latter remains behind when white lead is dissolved in diluted nitric acid. On heating white lead, the carbonic acid and water are expeUed, and the yel- low residue is oxide of lead. 370 HEAVY METALS. 340. Lead- Tree. — Experiment. — Dissolve half an ounce of sugar of lead in six ounces of water, clarify the liquid by adding some drops of acetic acid, pour it into a phial, and then sus- pend in the latter a zinc rod, by attaching it to the cork; the zinc is soon covered with a gray coating, from which brilliant metallic spangles will gradually shoot forth, finally filling up the interior of the phial. They consist of pure lead (the lead-tree). After twenty-four hours, no trace of lead can be found in the solution ; it has been replaced by the acetate of zinc; the stronger zinc has abstracted from the weaker lead all its oxygen and acetic acid. By this experi- ment, not only the difference in the strength of affinity of these two metals is clearly shown, but it beautifully illustrates also the stochiometrical law of chemical combination and decomposition ; for it is only neces- sary to weigh the lead formed, and the piece of zinc before and after the experiment, to ascertain that the weight of the precipitated lead is to the loss of zinc as 1294 to 407. An atom of lead has thus been replaced by an atom of zinc. Lead and Sulphur. 341. Sulphuret of Lead (Pb S). — Experiment. — Add some sulphuretted hydrogen to a solution of sugar of lead; the deep black precipitate is sulphuret of lead (§ 133). One grain of sugar of lead dissolved in two pounds of water shows itself in this manner by a brown color; so that we have in sulphuretted hydrogen an exceedingly sensitive test for salts of lead. f In this combination, namely, as sulphuret of lead, we most frequently find lead in nature, and from it alone LEAD. 371 metallic lead is obtained on a large scale. This ore is called galena, and is easily recognized by its grayish- black color, its shining metalUc lustre, its cubic form, and its great specific gravity. 342. Preparation of Lead. — Sulphur is so firmly combined with the metals in the sulphurets, that it is impossible to expel it as easily as oxygen, for instance, by heating it with coal. Therefore a circuitous method must be adopted; namely, first to convert the metallic sulphuret into an oxide (roasting), and then to expel the oxygen (reduction). To effect this, the galena is heated continuously with access of air, whereby both the lead and the sulphur are combined with oxygen. The lead is converted into oxide of lead, which remains behind, and the sulphur into sulphurous acid, which escapes; some sulphate of lead is also formed at the ' same time. The roasted galena consists, therefore, essentially of oxide of lead (together with some sul- phate of lead); this has now only to be heated with coal in a flame or blast-furnace, in order to separate the metallic lead (lead-works). A second mode of freeing the lead from sulphur consists in heating the galena with a metal which has a greater affinity for sulphur, and replaces the lead. Such a metal is iron. Iron and sulphuret of lead are mutually converted into lead and sulphuret of iron. The iron acts here just in the same way that the zinc did in the formation of the lead-tree ; one atom of iron replaces one atom of lead, therefore 350 pounds of iron can separate or throw down 1294 pounds of metalUc lead. %_ ^" Lead Shot. — Lead may be granulated by pour- ing it through a broom into water, as described under zinc. The same principle is applied in the manufac- 372 HEAVY METALS. ture of shot, only that an iron cullender is used instead of a broom, and the drops of lead are let fall from such a height, that they solidify before reaching the water. For making the largest-sized shot, a tower at least 150 feet high is required. A small quantity of arsenic is usually added to the lead, to render the drops perfectly globular. As lead and arsenic are both inimical to health, shot should never be used for washing out bottles. BISMUTH, BISMUTHUM (Bi). At. Wt. = 1330. — Sp. Gr. = 9.8. 344. Bismuth is a metal chiefly found in Saxony; it frequently accompanies the cobalt ores, and, as al- ready mentioned, in the smelting of this ore for smalt, it separates as cobalt-speiss, nickel also being generally present. The metal is procured from this, and also from the native ore, by a very simple process. It oc- curs both in the ores and in the speiss in a pure state, when it melts at a temperature which need be only two and a half times higher than that of boiling water; consequently, it is only necessary to heat the ores mod- erately upon an inclined plate, when the bismuth melts and flows off below, while the other metals or ores, to- gether with the gangue, remain behind unmelted. This method of working the metal is called eliquation. Bis- muth is brittle, has a crystalline laminated texture, and a reddish-white color. Experiments with Bismuth. 345. Experiment — Heat a piece of bismuth upon charcoal before the blow-pipe; it melts with the ejec- tion of sparks, and volatilizes at a higher temperature BISMUTH. 373 with brisk ebullition. A portion of the fumes condense on the charcoal, coating it with a yellow powder; this is oxide of bismuth (Bi^ 03). If you throw the glowing metallic bead into a small paper box, it divides into small globules, which, while still glowing, will skip about for some moments. An odor like that of garlic, which is frequently emitted during the ignition, proceeds from arsenic, small quantities of which occur in almost all commercial bismuth. 346. Experiment.—Melt together in a ladle two drams of bismuth, one dram of lead, and one dram of tin; the alloy formed has the very remarkable property of be- coming completely liquid when thrown into boiUng water. Bismuth melts at 250° G, lead at 320° G, tin at 230° C, and yet the mixture of these three metals melts below 100° G By increasing the quantity of lead, aUoys may be prepared which readily become liquid at any temperature desired above 100° G They are sometimes employed as safety-plates in steam-boilers. The heat of the steam increases with the tension of the steam in the boiler; therefore the alloy, to be used, has only to be so selected that, in case of a too great in- crease of steam, the plate may be melted by the heat of the steam before an explosion of the boiler itself can take place. As these alloys, in their melted state, do not bum the wood, they are also very well adapted for making metallic copies of engraved wooden moulds, for calico-printing, and block-impressions. This aUoy is called Rose's metal, after the inventor. 347. Experiment. — Bismuth is most easily dissolved by nitric acid. Dissolve some bismuth at a moderate nhoat in this acid, and pour the solution into a large quan- tity of water; it becomes very turbid, and after stand- ing quietly, a white precipitate subsides, which contains 32 374 HEAVY METALS. only one fourth as much nitric acid as the salt which crystallizes out from the bismuth solution when you let it cool. This powder is subnitrate Acid salt. Soluble. 0f oxide of bismuth, and is used as a medicine. A small proportion of oxide of bismuth, with a large proportion of nitric acid, remains Basic salt, insoluble. dissolved in the liquid. The an- nexed diagram denotes the decom- position hereby taking place, which is of more general interest, as showing that the affinities of bodies for each other may be changed by greater or less dUution with water. The salts of bismuth may be recognized by this be- haviour with water. By adding sulphuretted hydrogen to the solution remaining from the former experiment, you obtain a brownish-black precipitate of sulphuret of bismuth. COPPER, CUPRUM (Cu). At. Wt. = 396. —Sp. Gr. = 8.8. 348. In ancient times copper was chiefly obtained from the island of Cyprus, where its ores were found in great abundance ; this explains the name, cuprum. It being afterwards deemed expedient to give mythologi- cal names to the metals, copper received the name of Venus, the protecting goddess of Cyprus, and the sign the poisoned rats may not vomit the poison into them. Arsenious acid, Uke chloride of mercury, prevents the decay of organic substances; therefore the skins of animals intended for shipping are'rubbed with arsenic upon the flesh side. Arsenious acid readily gives up its oxygen in the heat to other bodies; for this reason it is added by glass-makers to melted glass, to convert its black or green color into yellow. It acts like black oxide of manganese (§ 297) ; namely, it oxidizes the protoxide into sesquioxide of iron. A solution of white arsenic and mercury in nitric acid is used by hat-makers to remove the shining smooth coating from the fur of bares. 413. Reduction of Write Arsenic. Experiment. — Draw out a glass tube into a point, ARSENIC. 421 Fie. 162. introduce into it a very Uttle arsenious acid, and f^ put upon it a splinter of charcoal; then heat the tube to redness in the flame of a spirit-lamp, first at the place where the coal lies, and after- wards at the pointed extremity of the tube; the glass becomes coated on the inside above the coal with a black metallic mirror, because the m oxygen is withdrawn from the vapors of the II arsenious acid while they pass over the glow- ID ing coal. This is one of the surest methods of detecting small quantities of arsenic. 414. Combinations of Wliite Arsenic with Bases. Experiment — If ten grains of arsenious acid and twenty grains of carbonate of potassa are heated with half an ounce of water, the arsenic very readily dis- f solves, and a solution of arsenite of potassa is obtained. a.) Add gradually to one half of this liquid a solution of fifteen grains of blue vitriol in half an ounce of hot water; a yellowish-green precipitate soon subsides, which, on drying, passes over into a dark-green. This arsenite of oxide of copper occurs in commerce under the name of Scheele's green. b.) The other half of the solution is likwise mixed in a flask with a solution of fifteen grains of blue vitriol in half an ounce of water, and then acetic acid (concen- trated vinegar) is added as long as effervescence con- tinues ; the whole is then boiled for five minutes, after which the flask is put in a basin of hot water, that the cooling may take place very slowly. We obtain in this way, after twenty-four hours' repose, a double com- y pound of arsenite and acetate of copper, which, on ac- count of its splendid green color, is extensively used as a pigment Of its numerous names, those most known 36 422 HEAVY METALS. are Schweinfurth green, vert de mitis, and Vienna green. This color is as poisonous as white arsenic; hence ex- treme caution in the use of it cannot be too strenu- ously urged; it may even prove dangerous as a green paint for rooms, since, under some circumstances, vola- tile combinations of arsenic are formed from it, and unite with the air. 415. Arsenic Acid (As 05). — If arsenious acid is boiled with nitric acid, it takes from the latter lg' ' two additional atoms of oxygen, and becomes (^y\ arsenic acid. The same acid is obtained, com- ! bined with potassa, by fusing together arseni- j ous acid and nitre. The biarseniate of potassa ! thus produced, which crystaffizes in beautiful kj/ four-sided prisms, has hitherto been consumed in immense quantities in calico-printing, not so much to produce colors as to prevent their formation "* on certain points of the texture. 416. Sulphuret of Arsenic. — Experiment — Dissolve some grains of arsenious acid in boiling water, and add to the solution sulphuretted hydrogen; a precipitate of yellow sulphuret of arsenic (As S3) is formed, three at- oms of sulphur replacing three atoms of oxygen. In this way arsenic may easily be detected in Uquids, and separated from them; the salts of cadmium and oxide of tin are the only ones, except arsenic, which give a yel- low precipitate with sulphuretted hydrogen.* Sulphuret of arsenic is redissolved by sulphuret of ammonium. Sulphuret of arsenic also occurs native, and is called orpiment, or king's yellow, and was formerly used as a yellow pigment, but it is earnestly advised never to employ this color in the painting of rooms, as f * The salts of antimony are precipitated of an orange-yellow color by sulphuretted hydrogen. * ARSENIC. 423 it evolves upon lime walls an exceedingly poisonous gas (arseniuretted hydrogen). A sort of yellow arsenic, having the color of yellow wax or porcelain, is also pre- pared in arsenical works by the sublimation of white arsenic with a Uttle sulphur; this consists principaUy of arsenious acid, and contains but a smaU quantity of sulphuret of arsenic. A combination of arsenic with one atom less of sul- phur (As S2), which is sometimes transparent like ruby- red colored glass, and sometimes opaque like brownish- red porcelain, has received the name Realgar, or red sul- phuret of arsenic. Preparation of Arsenic. — Arsenic is most frequently found combined with sulphur and iron, as arsenical py- rites. Most of the white arsenic is prepared from this ore by roasting it in a reverberatory furnace, and, as already mentioned, condensing in poison towers the fumes containing arsenious acid. The iron and sulphur are oxidized at the same time with the arsenic; but the oxidized iron remains behind, and the oxidized sulphur (S 02) escapes with the smoke into the air. 417. Arseniuretted Hydrogen Gas (As H3).— Exper- iment — Introduce into a small flask diluted sulphuric acid and some pieces of zinc, and let the hydrogen which is evolved escape through a tube drawn out to a point, and after some time ignite it (§ 85); you ob- tain in this manner a hydrogen- lamp. If you hold a glazed porcelain capsule for some min- utes in the flame, you will per- ceive upon it only a circle of 424 HEAVY METALS. ■* small drops of water, which form during the combustion of the hydrogen, and condense on the cold portion. If you now dip a piece of wood into Schweinfurth green, so that only a little of it shall remain adhering to the wood, and introduce it into the flask, the flame, after the gas has been rekindled, will present a bluish-white appearance, and will deposit on the porcelain held in it a black or brown smooth spot (mirror); this mirror is metalUc arsenic. Like sulphur and phosphorus, arse- nic also wiU combine with hydrogen, forming a kind of gas, which, in company with the free hydrogen, es- capes and burns. The flame is cooled by a cold body below the temperature which arsenic requires for burn- ing ; hence the latter condenses on the porcelain, just in the same way as carbon or soot is deposited on it when held in the flame of a candle. The carbon sepa- rates as a light, pulverulent body, arsenic as a coherent mirror. This incredibly sensitive test is called, after its inventor, Marsh's arsenical test. It follows from the previous remarks, that care should be taken not to in- hale the escaping gas, particularly the unburnt gas; but here more than ordinary caution is necessary, as arseni- uretted hydrogen is a most poisonous gas, and one to which some chemists have already fallen a sacrifice. 418. Antimoniuretted Hydrogen. — Experiment. — Re- peat the same experiment, substituting tartar emetic for Schweinfurth green; black spots are in this case also deposited on the porcelain, but they are darker, and often have a sooty appearance; they consist of metallic antimony. To distinguish spots of antimony with cer- tainty from spots of arsenic, drop upon them a solution of chloride of lime; the spots of antimony remain un- f changed, while the arsenical mirrors dissolve immedi- ately. RETROSPECT. 425 r. Antimony and arsenic are the only metals which combine with hydrogen; they comport themselves in this respect like the metalloids; they may be regarded as the link, the bridge, which joins the territory of the non-metaffic bodies or metaUoids with the metals. RETROSPECT OF THE THIRD GROUP OF THE HEAVY METALS. 1. The metals chromium, antimony, and arsenic, together with the previously-mentioned rarer metals, cannot decompose water ; therefore concentrated acids must be employed for their solution. 2. Their lower degrees of oxidation comport them- selves sometimes like bases, and sometimes like acids, but the higher only as acids. 3. These metals occur most frequently in nature / combined with sulphur. 4. Antimony and arsenic are precipitated from their solutions as sulphurets by sulphuretted hydrogen, but are redissolved by sulphuret of ammonium. Chromi- um is not converted into a sulphuret by sulphuretted hydrogen. 5. Antimony and arsenic can, like the metalloids, unite with hydrogen, forming gaseous compounds. RETROSPECT OF ALL THE METALS. Metals. 1. All metals have a peculiar lustre, are opaque, and the best conductors of heat and electricity. 2. Most of the metals will crystallize on cooling ^ slowly (most commonly in cubes). 3. All the metals are fusible, but at very different de- grees of heat; many of them, also, may be volatilized. 36* 426 HEAVY METALS. 4. All metals can combine with oxygen, sulphur, and chlorine. '. 5. They Ukewise combine with each other when they are fused together (alloys). Metallic Oxides. 6. Most of the metals form basic oxides with oxy- gen. Almost aU the metalUc oxides are insoluble in water. 7. Many metals possess one known degree only of oxidation, but most of them have two, some, indeed, three, four, and even five degrees of oxidation. The highest comport themselves as acids. 8. MetaUic oxides may be prepared from the metals :— a.) By exposure to the moist air. b.) By heating with access of air. c.) By decomposition of water at the ordinary > temperature. d.) By decomposition of water at a red heat. e.) By decomposition of water with the aid of an acid, and precipitation by a strong base. /.) By treating with concentrated acids, and pre- cipitation by a strong base. g.) By heating with nitre or chlorate of potassa. 9. The metalUc oxides may be deoxidized or re- duced to metals: — a.) By mere heating (noble metals). b.) By heating with charcoal. c.) By heating in hydrogen gas. d.) By a more electro-positive metal (having a greater affinity for oxygen). e.) By the galvanic current. ^ RETROSPECT. 427 Metallic Sulphurets. 10. The sulphurets of the fight metals are soluble in water, those of the heavy metals are, on the contrary, insoluble. 11. A metal has commonly as many degrees of sul- phuration as of oxidation. 12. The metaUic sulphurets may be prepared, — a.) Directly by rubbing or melting together sul- phur and a metal, or by heating the metal in the fumes of sulphur. b.) By adding sulphuretted hydrogen or sulphuret of ammonium to a metallic oxide or salt. c.) By heating metaUic sulphates with charcoal. 13. Sulphur may be expeUed from the metallic sul- phurets, — a.) By heating them with access of air (roasting). b.) By a more electro-positive metal. c.) By heating in steam. d.) By heating with strong acids. Metallic Chlorides. 14. Most of the metalUc chlorides may be crystal- lized, and are soluble in water. 15. As a general rule, a metal combines in as many proportions with chlorine as it has degrees of oxida- tion. 16. Metallic chlorides are prepared, — a.) By bringing the metals or metalUc oxides into contact with chlorine. b.) By dissolving metals in muriatic acid. c.) By dissolving metals in aqua-regia. d.) By double elective affinity, on mixing metallic chlorides with oxygen salts. 428 HEAVY METALS. 17. Chlorine may be separated from the metals, — a.) By mere heating (the noble metals only). b.) By heating in hydrogen gas. c.) By a more electro-positive metal. d.) By a stronger acid, for instance, sulphuric acid. The Oxygen Salts. 18. Every acid usually forms a salt with every me- tallic base; hence, there is an infinite number of salts. 19. Suboxides must receive oxygen and hyperoxides part with it before they can combine with acids. 20. Most of the salts may be crystallized, sometimes with and sometimes without water of crystallization. 21. The salts behave very differently towards water; some dissolve in it very easily, others with difficulty, and others not at all. 22. Salts may be prepared, — a.) By exposing metals to the air. b.) By dissolving them or their oxides in acids. c.) By decomposition of the metallic sulphurets with acids; also by a spontaneous weathering of the metallic sulphurets. d.) By mutual decomposition by means of predis- posing simple or double elective affinity. 23. Many of the salts, by mere heating, lose their acids, which either escape (carbonic acid), or burn up (organic acids). 24. The salts, like the oxides, may be reduced to met- als. If this is effected by ignition with charcoal, it is necessary to superadd a strong base (carbonate of soda, lime), which attracts the acid from the salt. Occurrence of Metals in Nature. t 25. The metals principaUy occur native in five forms, RETROSPECT. 429 viz.:—1. uncombined, or massive', 2. combined with sulphur, as pyrites, glance, and blende; 3. with arsenic, as arsenical metals; 4. with oxygen, as oxides ; 5. with oxygen united with acids, as salts. Of the best known metals, the foUowing occur the most frequently: — 1. Pure. 2. As Sulphurets. 3. As Arsenical Metals. Gold, Lead, Cobalt, Platinum, Antimony, Nickel, Silver, Copper, Silver, Bismuth, Silver, Iron. Mercury, Mercury, Arsenic. Arsenic, Iron, Zinc. 4. As Oxides. 5. As Salts. Manganese, Potassium and Sodium, Tin, Barium and Strontium, Iron, Calcium and Magnesium, Chromium, Aluminium, Zinc, Zinc \ and Iron, Uranium, Lead and Copper. Copper. Classification of the more common Chemical Elements. It is very difficult so to classify the chemical ele- ments, — so to bring them, as it were, into rank and file, — as to present at the same time a correct idea of their external and internal properties, and of their affin- ities for each other. In the following scheme, the two elements which are the most dissimilar, the most op- posed,— namely, the most electro-negative (most acid), 430 HEAVY METALS. oxygen, and the most electro-positive (most basic), potas- sium, — form the two final members of the series; then the former is succeeded by those bodies which comport themselves like oxygen in their properties and combina- tions, while potassium is followed by those similar to itself. At the junction of the two series, the undecided elements are found, — those comporting themselves < sometimes negatively and sometimes positively. If it is a law in chemistry, that bodies combine together so much the more eagerly the more dissimilar they are to each other, while bodies similar in their properties show at most only a very slight incUnation to combine, then this scheme may present to us at the same time a prob- able idea of the affinities of the elements for each other. Those bodies most remote from each other in the series have a great desire to combine, while those the nearest to each other have but little or no desire to unite. Thus, ^ oxygen most readily, desires to unite with the potas- sium, next with the sodium, next with the calcium, barium, and so on; it comports itself most indifferently towards fluorine. Potassium, on the other hand, shows the greatest affinity for oxygen, then for the salt-form- ers, sulphur, &c.; but the least affinity for its neigh- bours and kindred, sodium, barium, &c. Let it be dis- tinctly understood, however, that this scale of affinity is a very fluctuating one, and is subject in many cases to essential modifications. t RETROSPECT. 431 Oxygen Fluorine •3 Chlorine 5" 1 Bromine ? o Iodine g" a Sulphur | 0' Selenium " l-t Phosphorus f I: Nitrogen © Carbon c t Boron ! Silicon Arsenic Antimony ^ + Potassium a Sodium 2* Barium and Strontium 9 ro a -" Calcium and Magnesium o* Aluminium g Chromium 3" On? w Manganese r fron Zinc ~- Nickel and Cobalt '§ » Lead and Bismuth 0 | Copper o en g Mercury f => Silver .£ Tin "omc Platinum and Gold Hydrogen. ± V PART SECOND. ORGANIC CHEMISTRY. (vegetable and animal chemistry.) 37 r ORGANIC CHEMISTRY. VEGETABLE MATTER. ' 419. An inscrutable wisdom has given to the seed the power of germinating in the moist air, and of growing up into a plant, which puts forth leaves, flow- ers, and fruit, and then perishes and disappears. Ger- mination, growth, flowering, seed-bearing, and decay are the principal stages of existence through which the plants have to pass. When they have produced seeds, that is, new bodies capable of life, they have fulfilled their destiny, and their course then tends downwards to decay. Whether they live only one short sum- mer, or survive hundreds of years, the general principle remains essentially the same. The Divine agency which effects these changes, and calls forth the phenomena of life in the vegetable world, is, in its essence, wholly unknown to us. A particular V name, vital power, has indeed been given to it, but from this we derive no clearer conception or understanding of it. Its operations are conducted in such a mysterious manner, that it is not probable that the vague specula- 436 vegetable matter. tions of the inquiring mind on this point will ever lead to bright or clear ideas here below. We feel, indeed, the rushing of the vital current in the joy which penetrates us when in the spring this force causes the buds to ex- pand, and covers the earth with showers of blossoms, as weU as in the melancholy which seizes upon us when in the autumn the withering of the leaves announces to us its departure; but whence this force comes, and whither it goes, and how it calls forth, as it were by magic, the wonders of the vegetable world, we are in- deed absolutely ignorant. That only which it produces, and from which it was produced, are comprehensible to our senses. 420. There are two ways open to the inquirer, by which he may gain a partial insight into the mysterious workshop of vegetable Ufe : — 1st, that of observation, which, by the aid of the microscope especially, has led "*»' to a very accurate knowledge of the structure of plants, and of the changes which their separate parts (organs) undergo during their growth; 2d, that of chemical ex- periment, by which the constituents of plants, their food, and some of the transformations of matter occurring during the growth of the vegetables, have been discov- ered. The knowledge acquired in these two ways of the inward and outward changes which plants undergo during their existence, is called vegetable physiology. 421. There are generated in plants during their growth many substances having a perfect individuality of their own, which in many cases we can distinguish from each other by their taste. Grapes, carrots, and many other fruits and roots, have a sweet taste; they contain sugar. The branches and leaves of the grape- f vine have a sour taste; they contain an acid salt. Those of the wormwood have a bitter taste ; they contain a pe- vegetable matter. 437 culiar bitter principle. The latter emit also a strong odor, which proceeds from a volatile oil. In the seeds of the different species of grain, and in the tubers of the potato, we find a mealy substance, starch; in the seeds of the rape and of the flax-plant a viscous juice, fat oil. From the cherry and plum trees exudes a mucilaginous sub- stance, which is soluble in water; from the firs and pines a similar substance, but which is insoluble in water; the former we call gum, the latter pitch. The magnificent colors of flowers proceed from a coloring matter; the noxious effects of poisonous plants from vegetable bases, &c. These substances are called by the general name of proximate constituents of plants. Many of them are to be found in almost every plant, while others occur only in particular species of plants. We cannot imitate by art the workings of nature in / living plants, as we were able to do most perfectly in inorganic chemistry. The chemist, by chemical anal- ysis, has, indeed, determined with the utmost accu- racy of what elements the proximate constituents of plants are composed, and in what proportions by weight; but he has never yet succeeded in reconstruct- ing these constituents from their elements. 422. Unripe grapes taste sour, ripe ones sweet; therefore we conclude that during the ripening the acid of the grapes has been converted into sugar. Common barley tastes mealy; if suffered to germinate it ac- quires a sweet taste, because during germination a por- tion of its starch is converted into sugar. Similar changes occur in every Uving plant; indeed, they fre- quently take place when the vital power has become ^ extinct in the plant. Potatoes, for instance, become sweet by allowing them to freeze; aU the starch of the germinated barley is converted into sugar by adding 37* 438 VEGETABLE MATTER. water to it, and letting it remain for some hours in a warm place. That which is thus produced by the vital activity of the plants, or by cold or heat, namely, the transformation of one vegetable substance into another, we are also able to effect by various other means. Art in this respect can indeed do more than nature, since it produces combinations — for instance, alcohol, pyrohg- neous acid, and many other compounds — which we never find ready made in the living plants. The num- ber of these combinations may be increased almost in- numerably by the aid of inorganic bodies, such as strong acids and bases, chlorine, &c.; — letting these operate upon vegetable substances, which are thereby changed in an infinitely varied manner, and transformed into new bodies. Thousands of such new combinations have been discovered within the last twenty years; our posterity will probably count them by milfions. > 423. If you ask what are the elements of which the proximate constituents of plants are composed, the answer is, the four foUowing are the principal ones, — carbon, hydrogen, oxygen, and nitrogen, — which are therefore caUed organogens. Many of the vegetable tissues contain all the four elements (CHON), and are called azotized compounds; but others, and by far the largest proportion, contain only the first three ele- ments (C H O), and are called non-azotized compounds. From these few elements, with the addition of small quantities of sulphur, phosphorus, and some inorganic salts, the Creative Power is able to produce the count- less multitude of plants which cover the surface of our earth. 424. If it is obvious, from this simple constitution, f that the great variety of vegetable matter does not de- pend upon the number of the constituent parts, we VEGETABLE MATTER. 439 must presume that this variety is owing to the different ways in which these four elements are joined together and combined with each other. And such is indeed the fact. It has already been mentioned (§ 274), that in the isomeric compounds, that is, in such as possess the same composition, but not the same properties, a differ- ent arrangement of the atoms is to be supposed; in the same manner as in a chess-board, where the white ¥:=! = % and black squares may be grouped together, either 2 and 2, or 3 and 3, or 4 and 4, &c. This variety in the grouping of the atoms, which happens only as an exception among inorganic substances, occurs as a gen- oral rule among organic compounds; and it has here so / much the larger scope, because always three or four, and sometimes even more elements, are present, which enter into combination with each other, while, in the department of inorganic chemistry, commonly only two elements unite with each other; and likewise be- cause it is a law in organic chemistry, that the atoms of the elements do not unite singly, as with minerals, but always in groups; namely, 2, 3, 4, 6, 8, 10, or more atoms of one element, with any number of atoms of the other elements. Organic substances have, therefore, an incomparably more complicated constitution than the inorganic com- pounds, as the following examples show. From the weU-known amber, a pecu- liar acid, succinic acid, is obtained, which consists of four atoms of carbon, two atoms of hydrogen, and three atoms of oxygen, and has accordingly the formula C< H< 03 (see Fig. 165). 440 VEGETABLE MATTER. Fig. 167. Fie. 166. If one atom of oxygen is added to ©@@© tnis' we have tne constitution of malic ®'g) acid = C4 H204 (see Fig 166). @®®0 If one more atom of oxygen is added, that of tartaric acid = C4 Ha Os (see Fig. 167). ®0®® Fig 163. \nd by adding yet another atom ©®©@®® of oxygen, that of formic acid = glfS C4 H2 06 (see Fig. 168). But, on the other hand, if one atom of hydrogen is added to the succinic acid, which was the starting-point, the consti- tution of acetic acid is obtained = C4 H3 O3, &c. (see Fig. 169). If we are not yet able to produce all the transforma- tions as they are here given, yet the possibility of suc- ceeding at some future time cannot be doubted. Sugar, starch, and wood have precisely the same constitution, namely, C6 Hs Os; they are isomeric. If we imagine these three elements grouped together in different ways, as, for instance, in starch: in wood: in sugar: Fig. 170. ®®®@ @®®® Co)® Fig. 171. VEGETABLE MATTER. 441 then we can form an idea how one and the same quan- tity of the same elements may combine, forming such very different bodies; and it would not now excite any great astonishment, if, on further investigation, hun- dreds of different substances of the same constitution should be discovered, since, by mere transposition of the above sixteen atoms, more than a hundred different arrangements or groupings may be produced. 425. The instability of organized substances, which has already been referred to, is now simply explained by these complex proportions of the atoms. They are like complicated machinery. In the spinning-wheel we have one wheel, one spindle, and one band; but in a spinning-machine, hundreds of wheels, spindles, and bands, all connected together into one whole. Now, as in complicated machinery a wheel is more likely to / come off, a spindle to bend, a wire to break, thereby causing a greater disturbance throughout the whole of the machine than can possibly happen in the simple spinning-wheel, so also complex organic bodies are much more liable to disorganizations and changes than the more simple inorganic bodies. For if in the former only one of the many atoms leaves, or even changes, its place, or if another atom, whether of the same or of a different element, is added to it, the body at once ceases to be that which it was, and becomes a new peculiar compound. The famiUar terms combustion, ignition, singeing, charring, rotting, decaying, fermenting, curd- ling, growing musty and sour, bleaching, fading, &c, are all chemical metamorphoses of the kind referred to, and it is well known that these metamorphoses are peculiar to animal and vegetable substances. The sources from which the vegetable world derives its four fundamental substances (carbon, hydrogen, 442 VEGETABLE MATTER. oxygen, and nitrogen), and the form in which it re- ceives them, will be treated of more fully at the close of this part. I. VEGETABLE TISSUE. 426. Germination of the Seeds. — The vital force slumbers in the seed; it is called into activity by moist- ure and heat. Experiment — Pour water over some beans, and let them remain in a moderately warm place, till the embryos burst forth, and the swollen seeds divide into two parts. If we now examine them closely, we shaU perceive at the extremity of each seed, where the germ appears, two delicate white leaflets; from these, as the plant continues to grow, the stem and leaves are developed, while the other ex- tremity of the germ forms into a root. The solid mass of which these young organs consist is called vegetable tissue; it consists of variously-formed cavities, which are filled with a colorless liquid, the sap. If the bean- plant is exposed to the action of light, a green coloring matter (chlorophyll) is produced in the sap; but this substance is not formed in the roots, since they are screened from the light by the surface of the earth. The two lobes of the bean (cotyledons) gradually dis- appear as the development of the plant advances; they serve as its first nourishment. The embryo of most plants is furnished with a pair of cotyledons (di- cotyledonous). (7 VEGETABLE TISSUE. 443 Experiment. — Barley, when caused to germinate in the same manner, puts forth only a single embryo, Fig. 174. from which first the leaves and then the stalk are developed. All our grasses and bulbous plants germinate in this manner (monocotyledonous). If you pour off the water from the barley when the seeds are swelled and thoroughly steeped, and then put it in a cool place, piled up in heaps, you can, by occasion- ally turning it, so retard and regulate the growth that the radicles only wiU sprout forth. If you now arrest further vegetation by quickly drying the grain in a warm oven, the brewers' malt is obtained. The root- lets may be easily rubbed off after drying; they yield an excellent manure, and consist principally of vege- ' table tissue rich in potassa and other salts, which salts, during the process of germination, have passed from the grain into the radicle. 427. Vegetable Tissue. — All the cells and vessels of plants are composed of vegetable tissue. This sub- stance is to plants what bones, flesh, and skin are to the animal body; it forms the solid mass of all vege- table organs, and consequently imparts to plants their shape and firmness ; it forms the ducts or veins of the plants, through which the sap circulates. We find it very finely ramified, tender, soft, and easily digestible in the young leaves, flowers, and stems, and in the so- called pulp of fruit and roots, as apples, plums, carrots, &c.; hard and indigestible in straw, wood (woody tissue), and in the husks of grain (bran); hardened like \ stone in the stones of plumbs, cherries, and peaches, and in the sheUs of nuts; Ught, poroue, and elastic in the pith of the elder, and in cork; lengthened and pUant in hemp, flax, and cotton. 444 VEGETABLE MATTER. 428. The transverse section of the stem of a tree illustrates the influence which age exerts upon the vegetable tissue, and how this tissue va- ries in one and the same tree. Inside the bark (a) lies the inner fibrous bark (b), which consists of lengthened tubes, and is peculiarly adapted to supply the place of veins in the tree. Here the sap principally circulates, and therefore a tree will die when the inner bark is girdled, whilst (as seen in many hollow trees) the tree will Uve on if only the inner and outer bark remain, though the wood itself is entirely rotten and gone. From the inner bark towards the exterior is deposited every year a new layer of bark, and towards the centre a new layer of wood (annual circles). The Ught and whiter wood, lying next the inner bark, is caUed the sap-wood (c); but this, by the annuaUy increasing compressure, becomes denser and more soUd, and then it is caUed heart-wood (d). The latter is usually darker, and is frequently impregnated with coloring matter (red-wood). The an- nexed figure will give an idea of the artistical internal structure, which is manifest even in appar- ently simple dense wood, as viewed under a strong magni- fying-glass. It represents the transverse section of a pine bough, the portion marked a rep- resenting young ligneous cells, those marked b the matured ceUs. Fig. 176. VEGETABLE TISSUE. 445 Most plants contain in the inner and outer bark a styptic-tasting substance, soluble in water, and which is known by the name of tannin, or tannic acid. 429. Linen is the inner bark of the flax-plant. Dur- ing the process of retting, the outer bark, by the long- continued influence of moisture and air, passes over into decay, and then, after rapid drying, may be rubbed off by bending it backwards and forwards (breaking); but the filaments of the inner bark, which do not so readily decay, remain behind, and after being parted into their finest fibrils, and arranged parallel by the so- called heckling, form the well-known flax. The tow, which falls off during this process, consists of tangled fibres of the inner bark. Flax has a gray color, because it contains a gray coloring matter, which is not soluble in water and lye, t though it becomes soluble in lye by exposing the flax, the thread spun, or the linen woven from it, during a long time, to the action of Ught, water, and air. This is done in the bleaching-yard by spreading it on the grass (grass bleaching). The coloring matter, hereby altered and rendered soluble, is removed from time to time by boiUng with lye. Bleaching may be accomplished more rapidly by the application of chlorine, which, on account of its very strong affinity for hydrogen, attracts hydrogen from all organic substances, whereby they be- come colorless and soluble (chlorine bleaching). The question here oocurs, Why is it that in these two bleach- ing processes the coloring matter alone, and not the vegetable tissue at the same time, is decomposed ? The reason is, because the coloring matter consists of t four elements (C H O N), but the vegetable tissue of only three elements (CHO); according to §425, the more complicated substance, consisting of four ele- 446 VEGETABLE MATTER. ments, is more readily and rapidly decomposed than the less complicated substance, consisting of three el- ements. If, when the Unen has become white, the bleaching were still continued by either of these meth- ods, the vegetable tissue would then be decomposed and become rotten; a case which often occurs when linen, cotton, or paper is treated too long, or with too strong a solution of chlorine. 430. Bast. — Soak the bark of the Hnden-tree in water tiU the outer bark is decomposed, and has be- come brittle; when it is dry the inner fibrous part of the bark can be peeled from it, and it then forms the linden bast, used for tying up plants. The outer cover- ing of the trees, which is commonly, but erroneously, called bark, consists by no means of the proper bark alone, but of two essentially different parts, which have grown very closely together; the external layer is the proper bark (epidermis), the inner is the bast (liber). 431. Cotton consists of deficate hollow hairs, which form in the cotton-plant in considerable quantities around the seeds. As it exists in nature it is beauti- fuUy white (except the Nankin cotton, which is yel- low), and consequently requires no bleaching. When, however, cotton thread or cotton fabrics are bleached, it is merely in order to remove the oily, sweaty, and mealy substances (weaver's glue, &c.) which have be- come attached to them during spinning and weaving. This is now usually effected by boiling with soda-lye or milk of Ume, or immersing them in a weak solution of chloride of Ume. The lime which remains adhering is then removed by exceedingly diluted acids (acid bath), and the acid, in its turn, by rinsing in water. It is well known how important the above-mentioned sorts of pliant vegetable tissue are, on account of their VEGETABLE TISSUE. 447 application for making thread, twine, and fabrics of every variety; we clothe ourselves in woody fibre, we write and print upon it, we build our houses of it, &c. 432. Vegetable Tissue and Water. — Experiment — Pour some lukewarm water over sawdust, and let it stand for a day; then squeeze out the liquid through a cloth and boil it; a slight turbidness will appear, and on longer standing a loose sediment will be deposited. Water does not dissolve the woody fibre, though it does the sap contained in it; in this sap, as in that of all other plants, there is always found a substance in solu- tion, which is very analogous to the white of eggs, and which, like it, coagulates in boiUng; it is caUed vege- table albumen. There are also contained in the Uquid, separated from the albumen, various other substances in solution (mucus, gum, tannin, &c), which are not > precipitated by boiling. If the sawdust, after it has been dried, is treated with alcohol, this will also dis- solve some substances (pitch, &c.); and so also will ether, lye, and other liquids. Therefore, in the prepa- ration of perfectly pure woody tissue, it must be treated with various solvents in order to remove all the constit- uents of the sap. CHANGES OF VEGETABLE TISSUE. a.) Changes of Vegetable Tissue by Acids. 433. Wood, when dipped in sulphuric acid, is charred; when in nitric acid, it is dyed yellow, and by longer im- mersion it is entirely decomposed, as has already been observed (§§ 160, 173). Sulphuric acid attracts from \ the woody fibre hydrogen and oxygen, which combine to form water, and then unite with the sulphuric acid; nitric acid yields oxygen to it, and consequently oxidizes 448 VEGETABLE MATTER. it. By very long continued treatment, aU the carbon of the wood may finally be oxidized into carbonic acid, and all the hydrogen into water. Chlorine decomposes the vegetable tissue by abstracting hydrogen (§429). Diluted sulphuric acid operates very differently from the concentrated acid; if paper, Unen, &c, are boiled for several hours with the former, the vegetable tissue is converted, first into gum, and finally into sugar. Explosive Vegetable Tissue, or Gun-Cotton (Pyroxy- lin).— By exposing vegetable tissue (cotton, hemp, linen, sawdust, &c.) for a short time to the action of highly concentrated nitric acid, it acquires the re- markable property, Uke that of gunpowder, of igniting and exploding with great violence when touched by a lighted match. Experiment — Mix half an ounce of the strongest nitric acid (sp. gr. = 1.5) with one ounce of strong > sulphuric acid; pour the mixture into a porcelain mor- tar, or a cup, and press into it with the pestle as much cotton (wick-yarn, cotton-cloth, printing-paper, &c.) as can be moistened by the acid. When the cotton has soaked for five minutes, it is to be taken out with a glass rod, put into a vessel containing water, and washed repeatedly with fresh quantities of water, un- til it no longer reddens blue test-paper. The cotton is then squeezed out with the hand, spread upon a sheet of paper, and dried in an airy place. It is dan- gerous to dry it upon a stove, as it easily takes fire. If the gun-cotton thus prepared is struck smartly with a hammer upon an iron anvil, it detonates violently; when touched with a hot wire or a lighted match, it burns instantaneously, without leaving any residue; f when fire-arms are loaded with it, it acts like gun- powder, but its explosive power is three or four times VEGETABLE TISSUE. 449 greater than that of the latter. Gun-cotton being, there- fore, an exceedingly dangerous substance, the great- est caution is indispensable in conducting experiments with it, and only very small quantities should be used at once. The chemical changes which cotton undergoes by immersing it in the above acid mixture consist chiefly in this, that it gives up a portion of its hydrogen and oxygen (as water), and receives instead nitric acid (consequently, nitrogen with much oxygen). Gun- cotton contains, therefore, much more oxygen than the common cotton, and likewise nitrogen, in chemical combination ; the former causes the rapid combustion, while the latter, together with the gases formed by the combustion, causes the rapid explosion. The sulphuric acid cooperates only indirectly, by attracting and retain- > ing the water contained in the nitric acid, and that which separates from the cotton. b.) Changes of the Vegetable Tissue by Alkalies. 434. The effect of alkalies on vegetable tissues may readily be seen by wrapping a piece of quickfime in paper, and letting it remain there for some weeks, when the paper will become quite rotten. The farmer and the gardener, being weU acquainted with this action, are accustomed to mix in lime or ashes with couch- grass and other weeds, to accelerate the rotting and decay. c.) Changes of the Vegetable Tissue by Heat, with free Access of Air. ^ 435. That wood, &c, when heated with access of air, is consumed, that is, is decomposed into carbon and water, has already been fully treated of in the former 38* 450 VEGETABLE MATTER. part of this work. All vegetable substances are con- sumed in the same way, by means of the oxygen of the air. If inorganic substances (salts and earths) are present, they, since they are not volatile, remain be- hind as ashes. Vegetable, and Ukewise animal substances, can be consumed, not only by the oxygen of the air, but also by the oxy^fen of other bodies ; as, for example, by that of oxide of copper, of chromate and chlorate of potassa, or directly by pure oxygen itself. If the water formed during the combustion is absorbed by chloride of cal- cium, and the carbonic acid by a solution of potassa, then, by the increased weight of the chloride of calcium and the potassa, the quantity of the water and of the carbonic acid may be ascertained, and from these the weight of the hydrogen and carbon which the con- sumed body contained may be calculated. That which >. is wanting in the weight of the original body under examination is the amount of oxygen which it con- tained. In this manner the three elements comprised in an organic body, carbon, hydrogen, and oxygen, may be very accurately determined; such an exami- nation is therefore caUed an elementary analysis. If, in addition to the three above-named elements, an organic body contains nitrogen also, it escapes uncombined during the combustion in the form of gas, and can be collected and estimated by a special method of analysis. But on heating such bodies with bases having a strong affinity for water, — for instance, with hydrate of po- tassa or soda and Ume, — then (with but few excep- tions) the nitrogen contained in them escapes in com- bination with hydrogen, as ammonia, from which the contents of nitrogen can be accurately calculated. VEGETABLE TISSUE. 451 d.) Changes of the Vegetable Tissue by Heat, the Access of Air being prevented. 436. Imperfect Combustion of Wood. — When wood is heated with insufficient access of air, as is the case, for instance, in most of our stoves, a portion of the car- bon remains un burnt, and is deposited as soot from the gases which form the flame. Moreover, during the pro- cess, a portion of the burning carbon takes up only half as much oxygen as when there is an abundant supply of air, and there is formed, not only carbonic acid, but also carbonic oxide gas (fumes of charcoal). But, besides these compounds, other singular sub- stances are formed, as is indicated by the peculiar smeU of the smoke, and by the lustrous acid and resinous soot deposited upon the lower parts of chimneys. The products of the decomposition of vegetable tissue may be more clearly recognized if you heat the wood with entire exclusion of air. Experiment. — Subject wood, as was described in Fig. 177. § 119, to dry distillation; you obtain a great variety of products easily to be distinguished by characteristic 452 VEGETABLE MATTER. properties; — 1. charcoal, which, since it is not volatile, remains behind; 2. illuminating gas, a mixture of car- buretted hydrogen, carbonic acid, and carbonic oxide gases ; 3. wood-vinegar, a watery acid Uquid; 4. wood- tar, a thick, brown, resinous liquid. The two former substances have been already described, so that only the two latter remain to be more fully considered. 437. Pyroligneous Acid, or Wood- Vinegar. — One pound of dry beech-wood yields nearly half a pound of pyroligneous acid. In its crude state it has a brownish- black color, owing to the tar which it contains in solu- tion, and a smoky odor, together with a very acid, dis- agreeable, smoky flavor. On account of its containing acetic acid, and its cheapness, it is now much used in the preparation of acetates, particularly such as are em- ployed in caUco-printing and dyeing; for instance, acetate of iron, of lead, of soda, 6cc. Experiment — Pour some wood-vinegar upon a piece of lean meat, and let it soak for a few hours; it can then be dried and packed without passing into putre- faction, as in a few hours it has experienced the same change, and acquires the same degree of firmness, usually produced by being suspended for months in the smoke (rapid smoking). 438. Wood-vinegar owes its antiseptic properties to a peculiar substance, which has received the name of creosote (flesh-preservative); one pound of pyroligneous acid contains about a quarter of an ounce of it in solu- tion. Pure creosote is a colorless Uquid, gradually be- coming brown by age, and of an oily consistency; it has a strong smell of smoke, a very burning taste, and disorganizes the tender skin of the tongue or the mouth, f and, taken internally, is a powerful poison. Creosote is now frequently applied as a remedy for the toothache, VEGETABLE TISSUE. 453 when it is usually mixed with oil of cloves ; but it must also be diluted with alcohol, in which it readily dis- solves, as its action would otherwise be too corrosive. One dram of water will dissolve one drop of creosote; this solution (creosote-water, or aqua Binelli), which acts upon flesh in the same manner as the pyroligneous acid, is employed as a sedative. The smoke which is formed in our stoves by the incomplete combustion of wood, or of pit-coal, always contains fumes of creosote, to which is owing its peculiar smeU, and its property of causing lachrymation. Every thing which prevents complete combustion, such as a deficient draught of air, or moist fuel, must, accordingly, favor the forma- tion of creosote, and render the smoke more irritating. Flesh is most effectually cured by this smoke, which is expressly generated for this purpose by burning green > fagots, or obstructing the draught of air. 439. When pyroligneous acid is very slowly distilled, a spirituous, volatile liquid, very similar to brandy, first passes over, which is called crude pyroxilic spirit. The chief component of this fluid is a substance which, in its properties and changes, has great similarity to alco- hol, or spirits of wine, though its constitution is differ- ent. On account of this similarity, it is called py- roxiUc spirit (hydrated oxide of me thy le). 440. Wood-tar is of a resinous nature, that is, in- soluble in water, though soluble in alcohol; it is more- over very rich in carbon, as is in some degree indicated by its black color. On distfflation, it separates into a volatile oil (oil of tar), and into a non-volatile black pitch (§576). This separation takes place, also, but tmore slowly, when wood is smeared with tar; the piteh, hardening in the pores of the wood, then pre- vents the penetration of the water, and hereby, as by 454 VEGETABLE MATTER. the creosote also contained in the tar, the decomposi- tion of the wood by putrefaction is arrested (tarring and calking of ships, &c). The dry distillation of wood shows in a very strik- ing manner with what extraordinary readiness organic substances may be decomposed and transformed into very remarkable new bodies. The wood has only to be heated in order to be resolved into an acid and a spirituous body, — into oily and resinous substances,— into illuminating gas and carbon. And these are not aU the products of the decomposition of wood. Be- sides the substances here mentioned, a dozen others, at least, have been discovered, which are generated simul- taneously with them, and each of which may be con- verted by heating, by treating with acids, bases, chlo- rine, &c, into numerous other bodies. Here a great field opens for chemical investigation, a field which has \ indeed no bounds, and which must be so much the more extended, since all vegetable matter, heated with exclusion of air, becomes charred and decomposed into products of combustion, but which are different in different bodies, as is obvious in the dry distillation of tobacco in tobacco-pipes, of pit-coal, brown coal, &c. 441. Imperfect Combustion of Pit-Coal.— Pit-coal and brown coal are formed from the vegetables of a for- mer era, which were washed together in heaps during some revolution of the earth, and deeply buried be- neath mud and soil. When pit-coal is heated with ex- clusion of air, we obtain, in the same manner as from wood, — 1. carbon (coke); 2. a combustible gas (illu- minating gas); 3. an aqueous, empyreumatic liquid (tar-water); and 4. a resinous, black, viscid liquid (pity coal tar). The aqueous empyreumatic liquid obtained from pit- VEGETABLE TISSUE. 455 coal contains only a trace of vinegar, but in larger quantities a basic body, ammonia, combined with car- bonic acid; it may therefore be employed as a manure, or for the preparation of sal ammoniac. The pit-coal tar, which is now very generally em- ployed for smearing over wood, iron, and the roofs of buildings, to protect them from moisture, may also, like wood-tar, be separated by distillation into a vol- atile substance (oil of coal-tar), and into a pitchy, non- volatile substance (artificial asphaltum); but the pe- culiar substances (kyanole, pyrrol, leucol, carbolic acid, rosolic acid, brunolic acid, naphtaline, &c.) contained in the latter are quite different from those of the former. Of these substances, naphtaline, a white, camphor-like body, has been examined most closely; but the names only of some of the new combinations resulting from y these researches will here be mentioned, to show, alas! with what a flood of new and strange names this sin- gle substance has inundated chemistry. The follow- ing compounds are formed by the action of nitric acid upon naphtaline: nitronapht-alase, -aleise, -alise, -ale, -esic acid, -isic acid, phtalic acid, phtalamide, &c.; by treating with chlorine: chloronaphta-lase, -lese, -Use, -lose, &c. 442. A decomposition similar to that which pit-coal undergoes during dry distillation must also be pro- duced, perhaps, in many places in the interior of the earth, by volcanic heat, for we know that in many countries substances either issue from the earth, or are imbedded in it, which have a very great similarity to the products of the distillation of pit-coal, as is shown lui the following arrangement. 456 VEGETABLE MATTER. Occurring Native in the Earth. a.) Inflammable gases (sacred fire of the Bra- mins), issuing here and there from the crevices of rocks. b.) Naphtha, oozing out of the earth in Persia. c.) Mineral tar, found in many places in Persia and France. d.) Natural aspftaltum (pitch of Judea), found in the Dead Sea, and other Asiatic seas. e.) Ammonia, issuing in a watery vapor, associ- ated with boracic acid, from the earth near Tuscany. /.) Anthracite (C), like pit-coal, occurring in immense beds in the earth. e.) Changes of the Vegetable Tissue by Air and Water. (Decay and Putrefaction.) ■Qju?t of the air, it imbibes moisture, and becomes gradually brown and rotten, — it passes into decay. The chem- ical process which thus takes place very much resem- bles those changes which wood undergoes in combus- tion, except that it takes place far more slowly; what is effected by combustion in minutes is effected by decay only in the course of years. By combustion, the con- stituents of the wood and the oxygen of the air are converted into carbonic acid and water; the same prod- ucts are also formed on the decay of wood. In com- bustion, the hydrogen is oxidized more rapidly than the carbon; the same happens also in decay. This ex- plains why wood, on combustion, as well as on decay, assumes a darker—first a brown, and then a black— color. When proportionably more hydrogen passes^ off than carbon, the residue must necessarily, as the decomposition continually progresses, be richer in ear- Artificially produced from Pit-Coal. a.) Illuminating gas. b.) Oil of coal-tar. c.) Oil of coal-tar. d.) Artificial asphaltum (pitch of pit-coal). e.) Ammoniacal empyreu- matic liquid. f) Coke(C). VEGETABLE TISSUE. 457 bon, and consequently, as a general rule, also of a dark- er color. 444. Humus. — The brown or black substance into which vegetable matter is converted by decay has re- ceived the name humus. As wood, which is only par- tially consumed, can be consumed stiU further, so also humus is gradually further decomposed, and in most cases, after complete combustion or decay, there is final- ly left only a small quantity of non-volatile salts and earths, — the ashes, — which the wood has absorbed from the earth during its growth. If these two processes of decay are supposed to be going on in two distinct peri- ods, then there are formed, — in combustion, in decay, ,. ( water (much), ( water (much). from the wood in ) carbonic ^ from the wood in J carbonic add> > wood in I jeriod, ) , the 1st period, ( half.bumt wood. the 1st period, ( humus . from the half- ( ,.. , . „ burnt wood in the \ W&ter .(bttle)' from the humUS \ water ' 2d period ' carkonic ac"* i iQ the 2d period, } carbonic acid; there remain, ashes. there remain, ashes. Humus is identical with decaying Organic Matter.— In this acceptation it has for many years been known and valued in agriculture. Vegetable mould (humus) is the term applied to the upper black or brown layer of earth, which has been formed in forests by the decay of the leaves which faU off; the dark, fat, arable soil, con- taining much •partially decomposed organic matter, is said to be rich in humus, while the dry, light soil, in which it is wanting, is said to be poor in humus. The farmer knows that, contrary to what happens in his 1 woodlands, the humus diminishes in his fields, and so much the more rapidly as the crops are more abundant; he knows that fields rich in humus are, as a general 39 458 VEGETABLE MATTER. rule, more fertile than those which are poor in humus. Therefore he seeks to restore to his land the humus consumed in vegetation by ploughing in straw and animal excrements (manuring), or fresh plants (green manuring), or by the alternation of plants which leave behind many roots in the soil (fallow plants) with such as are only feebly rooted (grain). On an acre of land which was cultivated with clover, several thou- sand pounds of roots remained behind in the soil; upon one cultivated with wheat or grain, only from one fifth to one sixth as much; it is therefore appar- ent, that in the former case from five to six times more humus must be generated by the decay of the roots than in the latter. The increase of fertility which the farmer thus aims at is, however, by no means to be as- cribed to the humus alone, since the inorganic constit- uents (salts and earths) which are present in manure *> and in the soil have a principal share in it (§ 611). If we consider the formation of humus, we shall at once perceive that various substances are included un- der this term ; for its constitution alters every day, since a little of its carbon and hydrogen is every day oxid- ized and separated. We may easily conceive, that very old humus may contain as much again carbon as that which is recent, or even more. The ideas concerning humus became still more vague when chemists first thought of designating by this name other brown and black colored substances, the products of the evapora- tion of vegetable juices or decoctions, or which were formed from wood, starch, sugar, &c, by boiUng the latter with acids or alkalies. The term humus thus be- came, as it were, a foundling-hospital, into which were f brought all the substances formed from vegetable or an- imal matter, provided they were black or brown, and VEGETABLE TISSUE. 459 were insoluble, or nearly insoluble, in water. The humus generated by decay, as we find it in ara- ble soil, is now thought to be a mixture of several distinct brown substances, namely, of ulmine, hu- mine, ulmic acid, humic acid, geic acid, crenic and apocrenic acids, which are produced consecutively, according to the above series, from vegetable mat- ter. The two latter acids are soluble in water, and are partly the cause of the yeUow or brownish color which we perceive in the water of marshes or bogs; the other three acids are only soluble in water when alkaUes are added; finaUy, the first two substances, ul- mine and humine, can neither be made soluble by wa- ter nor by alkalies. Accordingly, by the general term humus we must understand a mass of brown decaying matter, partly soluble, partly insoluble, partly acid, t partly neutral, which, with the uninterrupted presence of air, water, and heat, may be still further decomposed, and thereby carbonic acid and water evolved. Car- bonic acid and water are indispensable to the nour- ishment of plants; hence, in a soil rich in humus, the plants will grow more vigorously, because they find there, and can absorb by their rootlets, more of these two nutritive substances than they could in a soil poor in humus. Humus exerts, moreover, a bene- ficial influence upon vegetation, because it loosens the soil by the development of carbonic acid, because it possesses the power of attracting water from the air, and of retaining it for a long time, and because, by means of the acids contained in it, it is able to abstract from the air, and also from manure, the third means of nutri- V ment for plants, ammonia. 445. Putrefaction. — The decomposition of vegetable tissue takes place in a somewhat different manner 460 VEGETABLE MATTER. when the air is entirely or partially excluded, — for instance, when the decomposition takes place under water, as we observe in ponds, marshes, and rivers. Experiment —Thrust a pole into the mud of a pond, and catch the bubbles which rise, in a bottle fiUed with water, and held inverted over them; when all the water is displaced from the bottle, close it up while under the water. Introduce a little wa- ter into the bottle, and afterwards a small piece of caustic potassa or quicklime, close it immedi- ately, shake it a few minutes, and then remove the stop- per under the water; a part of the water wiU press into the bottle, because the bases have absorbed a portion of the gas. The gas absorbed was carbonic acid. If you now apply a burning match to the mouth of the bottle, and expel the remainder of the gas by pouring in wa- ter, it will ignite and burn with a blue flame. This is called marsh gas (light carburetted hydrogen gas); it consists of carbon and hydrogen, like the common illuminating gas, but it contains, com- pared with this, a smaller quantity of carbon, and there- fore burns without giving a bright Ught. These two gases, carbonic acid and marsh gas, originated in the wood, leaves, branches, roots, &c, of the vegetables which sunk to the bottom of the water, and were there decomposed. VEGETABLE TISSUE. 461 When oxygen is wanting, the hydrogen of the vege- table tissue combines with a portion of the carbon while, if there is an abundant supply of oxygen, the hydrogen unites with the latter. Here, too, a substance similar to humus, and richer in carbon, remains behind; in ponds, as a black mud, in marshes, as peat This kind of decomposition is called putrefaction; it is some- what analogous to the change which wood undergoes on incomplete combustion (charring, dry distillation), as is shown by the following arrangement: — In charring, a.) illuminating In putrefaction, the vegetable tis- sue is convert-« ed into 6.) carbonic acid, c.) partially con- sumed sub- stances (tar, coke, &c). the vegetable tis- sue is convert- ed into ' a.) marsh gas, b.) carbonic acid, c.) partially rot- ted substan- ces (mud, peat). 446. Peat is formed from marsh plants, which slowly rot under water; every year a new vegetation arises, which, on perishing, sinks to the bottom, and thus, in the course of time, a morass is formed. The young peat consists of a brown, fibrous network, in which the separate parts of the plant may be clearly distin- guished ; but after a time it decomposes into a black, slimy mass, which may be cut into pieces of the shape of bricks. The old, black turf only smoulders away on burning, a proof that the hydrogen of the plants from which it was formed has mostly disappeared during putrefaction. 447. As above stated, carbonic acid was continually generated in the formation of peat; a portion of this carbonic acid remains in solution in the water, and this explains why the water which percolates through 39* 462 VEGETABLE MATTER. beds of peat into the earth, and reappears as springs in deeper places, often contains so much carbonic acid that it can be used as mineral water (acidulous springs). If the water during its course meets with rocks containing protoxide of iron, Ume, magnesia, &c, it may, by means of its carbonic acid, dissolve small quantities of them (§§ 237, 276). In this man- ner many of the mineral waters occurring in nature originate, as, for instance, the celebrated Marienbader springs, &c. 448. Besides peat, we find two other vegetable sub- stances in the earth, which are likewise used as fuel, on account of their richness in carbon, — brown coal and pit-coal. Both are the remains of a vegetation which covered the earth before it was inhabited by man. It is highly probable that they were formed from the vege- tables and trees of a primeval age, when, by inundation, or some other violent revolution which the crust of the earth underwent, they were buried under immense beds of sand and clay, and were there decomposed by a pro- cess similar to that of putrefaction, while the sand hardened into sandstone, and the clay into slaty clay or shale. In those places where the layers of earth were not sufficiently strong to prevent the escape of the carbonic acid and of the marsh gas, we often find, as, for instance, in many species of brown coal, the form of the wood so well preserved, that the annual rings may be distinguished in it (bituminous wood) ; but in other places the wood is transformed into a brown mass, which has a strong resemblance to humus, or peat (brown coal). But if the pressure of the superin- cumbent mass of earth was so strong as to prevent the f escape of the gases formed during the decomposition of the imprisoned plants, they must necessarily have re- VEGETABLE TISSUE. 463 mained behind with the coal. This, together with the compressure of the weight of a layer of earth or stone a thousand, perhaps several thousand, feet thick, ac- counts for the dense, compact, stone-like nature of many kinds of coal, especially of pit-coal, and also for their property of burning with a flame. Those gases which were condensed in the coal we obtain again, as illuminating gas and carbonic acid, when we heat the coal in a retort. It is generally known that moist vegetable matter, as grass, hay, manure, &c, becomes hot, and is converted into a black, carbonaceous rich mass, when piled to- gether in compact heaps. This smouldering sort of carbonization, taking place here on a smaU scale, must occur also on a large scale, when, by some revolution of the earth, masses of plants are washed together in 4 heaps, and covered over with mud ; and this smoulder- ing must be so much the more complete the greater is the pressure under which the decomposition takes place, and the longer the time occupied in effecting it. Pit-coal is usually found at greater depths in the earth, and between older layers of rocks (in the tran- sition rocks), than the brown coal, which mostly oc- curs nearer the surface of the earth, between more recent layers of rocks (in the tertiary rocks) ; we therefore conclude that the formation of pit-coal com- menced at an earlier period, and that of brown coal not till a later period. The extraordinary differences occurring in this process of decomposition, according to the variety of plants, and the cooperation of more or less water, heat, air, pressure, &c, are very evident V in the extraordinary variety of the products formed. Many of the pit and brown coals burn with a vivid flame, others with a feeble one, and some without 464 VEGETABLE MATTER. any; many melt in the heat, others crumble to a sandy powder; many yield but one per cent, of ashes, while others yield from 25 to 30 per cent., &c. 449. White Rotten Wood. — Experiment. — Put, dur- ing the summer, some sawdust, moistened with water, in a closed vessel, and let it stand for some months; the wood will graduaUy lose its firmness, and be con- verted into a white, friable substance. A splinter of wood wiU not continue to burn in the air of the vessel, since the air no longer contains free oxygen, but car- bonic acid. The water, too, has disappeared: it has chemically combined with the woody tissue. A similar transformation frequently occurs in the interior of the trunks of trees, where the air cannot have free access; the well-known white rotten wood is formed in this way. When the air has free access, a brown substance (humus, ulmine) is produced, such as occurs in hoUow > elms, willows, Undens, and other trees. The decomposition to which wood is exposed by de- cay and putrefaction may be retarded and checked, — 1. By rapid drying, whereby the water of the sap is removed. 2. By steeping in water or steam, by which process the sap is dissolved and removed. 3. By smearing with bodies which prevent the pene- tration of the water; for instance, with varnish, tar, pitch, &c. 4. By impregnating with saline solutions, which act antisepticaUy; for instance, with corrosive sublimate (kyanizing), salts of Ume, iron, &c. f STARCH. 465 'Jfit.a&n&Il. STARCH, OR FECULA. 450. A mealy substance, which is known under the name of starch, or fecula, is deposited in most vege- tables, particularly at the period of ripening, from the juices with which the cells of the Fig. iso. plants are filled. It appears to the naked eye like particles of meal, but under a power- ful microscope it is found to consist of small, generally regular grains or glob- ules. Their position in the plant is shown in the annexed figure, which represents a section of some of the cells of a potato. j If a fresh plant is bruised and macerated in water, and the liquid then squeezed out, a large portion of the starch will pass with the juice from the vegetable tissue, and will settle, after standing quietly awhile, as a mealy mass. Potatoes, grain, and leguminous plants are very rich in starch. 451. Potatoes. — Experiment. — Rasp some potatoes on a grater, knead the pulp thus obtained with water, and squeeze it in a linen cloth; the fibrous particles of the cells remain behind, but the juice, together with a large portion of the starch, runs through. If you let the turbid liquid remain quiet for some hours, it becomes clear, because the heavier starch settles at the bottom. Now decant the liquid, wash the starch several times with fresh water, allowing it to settle each time, and V then dry it in a moderately warm place. Experiment. — Heat in a flask the clear Uquid de- canted from the starch; it becomes turbid when the 466 VEGETABLE MATTER. heat approaches the boiling point, and, after boiling for a few moments, deposits a flaky, grayish-white sub- stance, which is to be collected on a filter. It is the same substance already referred to (§ 432), vegetable al- bumen, characterized by its property of dissolving in cold and warm water, but of coagulating in boiUng water. It contains nitrogen, which the starch does not Experiment. — Put some of the coagulated albumen upon a piece of platinum foil, and heat it over a lamp; it wiU burn and emit a very disagreeable empyreumatic odor. When starch is treated in the same manner, it also gives oft' an empyreumatic, but far less unpleasant smeU. All azotized substances comport themselves in this respect Uke albumen; aU non-azotized substances, like starch; therefore, when a piece of wooUen cloth is singed, it diffuses a far more disagreeable odor than a piece of cotton or linen, because nitrogen is contained ^» in the wool, but not in the cotton or linen. A freshly-cut potato has a white color, which, how- ever, on longer exposure to the air, passes over to brown; a similar change takes place in the Uquid pressed out from the grated potatoes; at first it is color- less, but graduaUy becomes darker. The substance, not yet accurately studied, which effects this change of color, is designated by the general term coloring matter; it is soluble in water, as is evident from the last-men- tioned property. Experiment. — Mix twenty drops of sulphuric acid with three ounces of water, and pour this acid water upon a potato cut in thin slices ; after standing twenty- four hours, the slices are to be taken out, and washed with water till they have no longer an acid taste, and f then dried. During this process the potatoes lose their juices, and also their albumen and coloring matter, and STARCH. 467 after drying form a solid, mealy, white, and tasteless substance, which swells up and becomes soft when boil- ing water is poured upon it. Potatoes dried without this treatment become gray and horn-like, and acquire an unpleasant smell. 452. Peas. — Experiment — Pour a handful of peas into a capacious vessel containing water, and let it stand for some days in a warm room; a great part of the water is absorbed by the peas, causing them to swell up, and finally to become so soft that they can easily be mashed between the fingers. When in this state bruise them in a mortar, and add sufficient wa- ter to form with them a thin paste, which may be squeezed out by means of a linen cloth. Here, also, we obtain, as from potatoes, — 1. a fibrous substance, which remains on the cloth; 2. starch, which is deposited, > after standing, from the turbid Uquid ; 3. vegetable albu- men, when the decanted liquid is heated to boiUng. Experiment. — When you have separated, by boiling and filtering, the vegetable albumen from the above- mentioned liquid, add to the latter a few drops of some kind of acid ; a flaky white body will once more be de- posited ; this is called vegetable caseine (cheesy matter), on account of its great similarity to the cheese con- tained in milk (animal caseine) in its constitution and also in its properties. Vegetable caseine, Uke vegetable albumen, contains nitrogen; but it is distinguished from the latter by this, namely, that it is not coagulated by boiling, though it is by acids. It occurs in the juice of many plants, but it is most abundant in the seeds of leguminous plants; potatoes, likewise, contain small V quantities of it. 453. Wheat Flour. — Experiment — Moisten a hand- ful of wheat flour with sufficient water to form a stiff 468 VEGETABLE MATTER. paste when triturated in a mortar; inclose it in a piece of thick linen, and knead it frequently, adding water as long as the liquid which runs through continues to have a milky appearance. After standing some time, a white powder will settle from the turbid water: this is wheat starch. Starch is one of the principal constituents of flour, as indeed of all sorts of meal; the second constituent re- mains behind in the cloth, mixed with vegetable fibre, and is a viscous, tough, gray substance, which has re- ceived the name gluten (vegetable fibrine). The gluten only sweUs up in water, without being completely dis- solved ; in its constitution it corresponds exactly with albumen, and, Uke this, contains nitrogen. When the water decanted from the starch is boiled, it becomes turbid, and when partially evaporated yields a flocculent precipitate ; thus wheat meal contains also v some vegetable albumen. 454. If the results of these experiments are grouped together, we shall find that there are always present in potatoes and peas, and also in wheat flour, the two non-azotized substances vegetable tissue and starch, and also one or several of the azotized compounds veg- etable albumen, caseine, and gluten. Non-Azotized Substances. In potatoes : vegetable tissue, starch ; In peas : vegetable tissue, starch; In wheat: vegetable tissue, starch. Azotized Substances. In potatoes : vegetable albumen (caseine); In peas : vegetable albumen, caseine (much); In wheat : vegetable albumen, gluten (much). The three substances above named, containing nitro- STARCH. 469 gen and sulphur, have the general name of albuminous compounds ; hitherto they have been called proteinaceous compounds. Small quantities of one or more of them occur in the sap of every plant. 455. Potato starch exhibits, under the microscope, the form of egg-shaped grains, consisting of many scales over- lapping each other; it glistens in the sun, is hard to the touch, and has al- ways more of a pulverulent than of a concrete character. In the starch of peas many of the grains are concave in the direction of their length, while others seem to be formed by the growing together of sev- eral globules. Wlieat starch consists of dull, flat- tened, lenticular grains, which, when C\ /) o'tf) m°ist) readily adhere to each other, on 0 -T""'/-^ which account the wheat starch of rS*°f\ ° commerce always comes in loose lumps. C-J ^oW o When ground, it is known under the name of hair-powder, SfC. Arrowroot is a starchy meal used in medicine, which is prepared in the East and West Indies from the roots of some marsh plants. 456. Experiment — If some starch is placed in a ladle, and gently heated with constant agitation till dried up, hard, horny granules are obtained, which swell when boiling water is poured on them, and be- come gelatinous and translucent; these granules are * called sago. The genuine sago comes from India, where it is prepared from starch, which is extracted from the pith of many of the palm-trees. 40 470 VEGETABLE MATTER. We find the starch granules swollen by water, also, in boiled potatoes. One pound of crude potatoes con- tains about three quarters of a pound of watery juice, and from two ounces to two and a half of starch; at the heat of boiling water or steam, this juice is ab- sorbed by the starch, so that the swoUen grains fill up the cells, which thereby acquire a round shape. The annexed figure represents the magnified reticulated ceUs caused by the coagulated albumen of the juice, which fills up the interstices between the single granules. All our baked food contains starch as its principal ingredient, and owes to it its friable and light character. 457. Experiment. — Heat in a vessel half a dram of starch, with an ounce or an ounce and a half of water, constantly stirring it till it boils; the mixture first be- v comes sfimy, and finally as thick as a jeUy. The grains of starch absorb water, and swell up, so that the single membranes break open. This swollen starch is well known for its adhesive properties, and is variously em- ployed as a means of thickening printing colors. When linen and other woven fabrics are passed through a thin paste of starch, they acquire, after drying, a degree of stiffness, and by ironing or strong rubbing and press- ing a bright gloss (dressing). The swelling of many of our most common articles of food, such as rice, groats, barley, beans, peas, lentils, &c, when boiled with water, is now readily explained by their containing a large quantity of starch. Experiment. — If you let some starch paste remain for a length of time in a warm place, it gradually be-/ comes thin and sour ; it thus passes into a peculiar acid, which has received the name of lactic acid The same STARCH. 471 acid is produced when milk becomes sour, and it im- parts to curdled milk and to buttermilk their well- known sour taste. Experiment — Dilute some starch paste with a large proportion of water, and add to it a few drops of tinc- ture of iodine (§ 155) ; an intensely deep blue liquid (iodide of starch) is produced. The same color may be perceived by dropping some tincture of iodine upon meal, potatoes, carrots, &c. We have in iodine an ex- tremely delicate test for starch. There is a peculiar species of starch called inuline, which occurs in the roots of the elecampane and the dandelion, and in the bulbs of the dahlia ; this is colored yellow by the tincture of iodine. Another variety of starch, which is colored brown by the tincture of iodine, is found particularly in Iceland t moss, and is caUed lichenine. Change of Starch into Gum and Sugar. 458. Starch Gum. — Experiment. — If starch is heat- ed in a ladle over a gentle alcohol flame, and during the heating (roasting) is constantly stirred to prevent its burning and baking on the bottom of the ladle, it ac- quires after a while a yellow, and finally a brownish- yellow color, and then possesses the new property of dissolving, both in cold and in hot water, into a muci- laginous liquid. (Common starch is entirely insoluble in cold water, and only swells up in hot water.) Starch thus transformed is called roasted starch, starch gum, or le'iocome. It is well adapted for the thickening of colors and mordants in calico-printing, and therefore is now \ often made on an extensive scale, usually by roasting starch in large coffee-roasters. Experiment — Mix thoroughly, in a smaU dish, half 472 VEGETABLE MATTER. an ounce of starch with one dram of water and four drops of nitric acid; let the mixture dry in the air, and then place it on the hearth of a heated oven, which is just hot enough to hiss feebly when touched with the moistened finger. After some hours, all the nitric acid will be expelled, and the starch will dissolve almost.en- tirely in cold water, and completely in hot water. Starch-gum thus made is white, or has only a slight yeUowish tinge. Experiment. — Make a paste of potato starch by boiling starch with water, and, while yet hot, add to it, in a saucer, some drops of sulphuric acid, with constant stirring. That this acid effects a change is evident, for the viscid mass very soon becomes a thin Uquid. Now place the saucer on a jar, in which some water is simmering (steam-bath), and let it remain over the hot steam (the contents of \< the saucer not being heated quite to the boiling point), until the liquid has become semi-transparent. When this is the case, add prepared chalk by small portions at a time to the liquid, until it ceases to give an acid reaction, and after having filtered it from the gypsum, leave it to evapo- rate in a warm place. The dry residue has an amor- phous, vitreous appearance, an insipid taste, and dis- solves in water, forming a transparent viscid fluid; it is not soluble in alcohol. Vegetable substances with such properties are usually called gums; the gum ob- tained from starch has received the special name of dextrine. 459. Starch-Sugar. — Experiment. — Repeat the for- mer experiment, with the following deviation. Bring r to brisk boiling two ounces and a half of water, to which twenty drops of sulphuric acid have been add- STARCH. 473 ed, and then add one ounce of starch mixed with a little water, forming a paste, but only in small quan- tities at once, that the boiUng may not be interrupted. When aU the starch is stirred in, let the mixture boil for some minutes, then neutralize the acid by chalk, and evaporate the filtered liquid to the consistency of a thick sirup. It possesses a very sweet taste, and con- sists of a solution of sugar in water. The starch-sirup thus made, as weU as the white, solid starch-sugar, easily prepared from it, are now both articles of com- merce. Starch, as shown by these experiments, is converted by sulphuric acid, on moderate heating, into gum; on stronger heating, into sugar. In the latter case, also, dextrine is first formed, but this soon passes over into sugar. Accordingly, sulphuric acid exerts two different j actions. By the first action, the starch becomes, gum (dextrine). By the second action, the dextrine becomes sugar. It has not yet been explained how this effect is produced. Starch, starch-gum, and starch-sugar have each the same constitution (isomeric), so that their difference undoubtedly depends upon a different ar- rangement of the atoms of carbon, hydrogen, and oxy- gen contained in them, and it is undoubtedly the sul- phuric acid which effects this change in the position of the atoms. No portion of the sulphuric acid has been decomposed, neither has any of it combined with the organic substance; for we find again, in the gypsum formed, exactly the same quantity of sulphuric acid that had been originaUy employed. Accordingly, in this case it exerts an action quite different from the usual action ; it is an action like that of spongy platinum, which can excite a chemical activity in another substance, without 40* 474 VEGETABLE MATTER. itself undergoing any change. This peculiar mode of action of sulphuric acid and of platinum is often desig- / nated by the name of " action of presence " (contact), or n A -■ action by catalysis (power of conversion). t if/ 460. Malt and Diastase. — Experiment — Pour two js /£ ounces of lukewarm water upon a quarter of an ounce ^ a of coarsely pulverized barley-malt; let the mixture re- main some hours near a fire or stove, or in the sun, and then strain it through a linen cloth; there is found in the filtrate a substance not yet weU known, called \, i (^'diastase, by means of which the starch may be con- c L r verted into gum and sugar in the same way as by sul- phuric acid. Experiment. — Rub a quarter part of the diastase with some hot starch paste, made of a quarter of an ounce of potato starch and two ounces of water; heat the mixture moderately (but not above 65° C), until \ the paste is formed into a thin, transparent liquid. Now boil this liquid for some time at a stronger heat, strain through a cloth, and let it evaporate in a warm place. The mass remaining behind is like that ob- AtA. tained at § 458, and consists of dextrine* or starch-gum. X A^-^4.Experimenl. — Treat the other three quarters of the diastase in the same way, but prolong the heating for several hours, which may be most conveniently done on the hearth of a stove or fireplace, applying to the liquid a heat not above 70° or 75° C. Here also dex- trine is the first product formed; but this is soon con- verted on further boiling into starch-sugar, as may easily be perceived by its taste. By evaporation, sirup of starch is obtained, as in § 459. 461. The remarkable change which malt communi- / cates to starch is to be ascribed to the diastase con- tained in the malt. This substance obviously acts in a STARCH. 475 very similar manner to sulphuric acid, but its mode of action is as yet likewise unknown. At 100° C, conse- quently, on boiling the liquid, the effect of the malt (diastase) is destroyed. The process of forming sugar by means of the diastase of malt is of great impor- tance to the brewer and brandy-distiller, as in the manufacture of beer from barley or wheat, or brandy from rye and potatoes, the starch of these substances must always be previously converted into sugar, before fermentation and the consequent formation of alcohol can take place. In both cases it is the diastase of the malt, indispensable in brewing and in the distillation of brandy, which effects this change in the so-called mashing process. 462. The taste of malt is sweet and mucilaginous, because the conversion of the starch into dextrine and > 6Ugar commences during germination, the further prog- ress of which is arrested in this case by drying. If the germinated barley is aUowed to continue growing, as it does in the open fields, all the starch gradually vanishes from the grain, and passes, in the form of dex- trine and sugar, into the juice of the young plant, as is obvious from the sweet taste of the latter, and from its mucilaginous feeUng when rubbed between the fingers. A similar metamorphosis is also clearly to be per- ceived in the potatoes. The quantity of starch con- tained in one hundred pounds of the same kind of po- tatoes has been found to be, in August, 10 pounds ; in September, 14; in October, 15; in November, 16; in December, 17; in January, 17; in February, 16; in v March, 15; in April, 13; in May, 10. Accordingly, the quantity of starch in potatoes increases during the autumn, remains stationary during the winter, and in 476 VEGETABLE MATTER. the spring, after the germinating principle is excited, it diminishes. It is a well-known fact, that on germina- tion potatoes become soft, mucilaginous, and afterwards sweet; the dextrine forming from the starch renders them mucilaginous, and the sugar forming from the dextrine renders them sweet. This process of trans- formation advances still further in the earth, the pota- toes becoming constantly softer and more watery, and when the starch is completely consumed in the growth of the young plant, the process of decay commences, and its products, carbonic acid, water, and ammo- nia, may be regarded as food for the somewhat older plant. 463. Unripe apples and pears are colored blue by tincture of iodine; consequently they contain starch. When completely ripe, they cease to give this reaction; therefore starch has disappeared on ripening, as ap- v pears by the taste of the fruits; they are sweet, and we must therefore presume that here also a transfor- mation of the starch into dextrine and sugar has taken place. It appears, also, that frost is capable of exert- ing a similar influence upon these vegetable substances, which are rich in starch ; it is well enough known, that frozen potatoes, apples, medlars, 6cc. have a sweet taste after being thawed. III. GUM AND VEGETABLE MUCUS. 464. It has already been explained, when speaking of dextrine, what kind of vegetable matter is caUed gum, / and likewise that it is an intermediate substance be- tween starch and sugar. Dextrine is one of the most GUM AND VEGETABLE MUCUS. 477 widely diffused substances in the vegetable kingdom, since we find it in greater or less quantities in the juice of every plant. But there exist in many plants certain sorts of gum, and sometimes in such abundance, that they exude from the bark as a viscid Uquid, and harden upon it in transparent globular masses, such as we see on our peach and cherry trees. The name resin, by which these dried vegetable juices are frequently designated, is erroneous, because by resins are meant those vege- table juices which do not dissolve nor soften in water, but are soluble in alcohol. The action of gum is dif- ferent ; this is insoluble in alcohol, but is softened and dissolved by water. 465. Gum Arabic. — The best known of these pecu- liar sorts of gum is gum Arabic, which exudes spon- * taneously from several species of acacia in Africa. The finer sorts of it are white, the more common kinds have a yellow or brown color. When weU dried, it is so hard and brittle that it may be reduced to a powder by pounding. Experiment. — Pour two drams of cold water on one dram of gum Arabic, and occasionally stir the mixture ; the gum wiU, after a few days, entirely dissolve in the water, forming a viscid transparent mucilage,. which may be diluted at pleasure with more water. This mucilage has great adhesiveness, for which reason it is often used, instead of paste or glue, for joining together paper, &c, or for converting a pulverulent substance into a coherent mass (crayons, pastilles, &c.); it has,/J,^^ moreover, a thick consistency, and hence is variously&f^CA v employed in calico-printing as a thickening material iox^ex^te colors and mordants, and in finishing and dressing operations. A variety of gum obtained from the shores 478 VEGETABLE MATTER. of the Senegal, whence it has been called gum Senegal, is peculiarly well adapted for the latter purpose, as it yields a thicker mucilage than the common gum Arabic. Experiment. — Pour some drops of mucilage of gum Arabic into alcohol; they wiU not mix with each other, as the gum is insoluble in alcohol. If the mucilage is previously mixed with water, forming a thin clear liquid, and is then added to the alcohol, a turbidness ensues, and afterwards a flaky precipitate will subside; accord- ingly, alcohol may be used for removing gum from those liquids which contain gum. In a chemical sense, only those sorts of gum are designated by the name of gum which dissolve com- pletely in cold water, and thus form a clear, transparent Uquid. y^uejL^ ^6*v«466. Gum tragacanth is also a vegetable exudation, 'A. /ttf/zikwell known as a stiffening material, and as forming l/0j <*~ with water an adhesive paste; it exudes from the tra- ff a £<^-gacantha, a shrub which grows in Greece and Turkey, r ^i'0 and it occurs in commerce in the form of white, tortuous filaments, or bands. Experiment. — Let a piece of tragacanth remain for some days in cold water; it will soften and sweU into a stiff, viscid jelly; a single dram of it is sufficient to convert one pound of water into a thick mucilage. The tragacanth does not dissolve, but, like starch, onl\r swells up; if the mucilage is boiled, the mass be- comes more uniform, but a complete solution is not effected. This kind of gum has been caUed vegetable mucus (bassorine), to distinguish it from the former; it occurs / also in many other plants, as, for instance, in the leaves of the maUows and the coltsfoot, in the roots of the SCGAR. 479 althea and salep, in flax and quince seeds, and in car- rageen, &c. This mucilage abounds in the cores of the quince, for it surrounds the seeds as a whitish, transpar- ent substance ; it must obviously be very plentiful, since one dram of quince-cores is sufficient to convert half a pound of water into a thick mucilage. 467. Experiment. — If you pour a large quantity of water upon some of the gum of cherry or plum trees, part of the gum will be dissolved after some time, but a part will remain undissolved as a turgid mass (vegetable mucus, cerasine). These two vegetable ex- i*c\<* udations must accordingly be regarded as mixtures of gum and vegetable mucus. 468. Pectine. — The juices of many fruits and roots, for instance, currants, gooseberries, cherries, apples, carrots, &c, contain a peculiar kind of mucus, which v communicates to the juice the property, especially when previously boiled with sugar, of hardening into a gelat- inous mass after cooling. This mucus, to which the stiffening of the juice is to be ascribed, has received the special name of pectine (vegetable jeUy). yr » ktc J c v y >y IV. SUGAR (SACCHARUM). 469. Sugar of Starch.— The manner of converting starch into sugar has already been described under the head of Starch. This sugar may be prepared in two ways; either by boiUng with diluted sulphuric acid (sirup of starch), or by digesting the starch with malt or diastase (malt sirup). Both of these sirups may be re- garded as concentrated solutions of sugar in water. If a very concentrated sirup of starch is allowed to remain 480 VEGETABLE MATTER. standing for some time, a granular sediment separates from it, while a part of the solution of sugar remains fluid and ropy. The soUd sugar thus obtained, which consists of fine granules, is caUed starch-sugar, and the liquid portion, which, even on being evaporated to dry- ness, always again attracts moisture and deUquesces, is caUed liquid sugar. Honey bears a strong resemblance to starch-sugar. If it is kept for some time after being melted, the mass, at first homogeneous, likewise separates into two parts, into a granular solid residue, and into a sirupy liquid. The former consists of starch-sugar, the latter of liquid sugar. This species of sugar (starch-sugar) is formed also in many vegetables, and is especially abundant in fruits; as, for example, in plums, cherries, pears, figs, grapes, &c. The white coating of prunes and the white, sweet grains in raisins consist of it. On account of this origin, sugar of starch is also caUed grape-sugar. If you taste a dried granule of sugar from a raisin, and then a little common sugar, you will at once per- ceive that the former is much less sweet than the latter; one ounce of common sugar has the same sweetening capacity as two ounces and a half of grape-sugar. The solubiUty of these two varieties of sugar in water is likewise very different, grape-sugar dissolving in it much less readily and more slowly than common sugar. While one ounce of cold water can dissolve three ounces of common sugar, it is able to take up only two thirds of an ounce of grape-sugar; the solution of sugar (sirup) prepared from the former is, accordingly, of a much stronger and more tenacious consistency f than that prepared from grape-sugar. 470. Cane-Sugar. — Our common sugar is different SUGAR. 481 from those kinds of sugar just described; it is either prepared in the tropical regions, from the juice of the sugar-cane (cane-sugar), or in France and Germany, from the juice of the beet (beet-sugar). The operations whereby this sugar is obtained on a large scale are the foUowing: — 1. Expressing the juice from the sugar-cane or the rasped pulp of the beet, either by strongly squeezing, or by hydrostatic pressure. 2. Boiling down the juice with the addition of lime, by which several foreign substances are precipitated, until it acquires the consistency of a thick sirup; on cooling, the crude sugar is deposited from it, in brown- ish-yeUow crystaUine grains (raw sugar, or Muscovado sugar). The Uquid sugar which does not crystaUize is aUowed to drain off, and forms the well-known brown * sirup (molasses). 3. Refining the raw sugar, that is, the removal of the brown sirup stiU adhering to it. This is done,— a), by redissolving the raw sugar in a Uttle water; b), by fil- tering the brown solution through coarsely-ground ani- mal charcoal, which retains the coloring matter; c), by evaporating the clarified solution in vacuum pans. The concentrated sirup is then allowed to cool in moulds of a conical shape, stirring it frequently to dis- turb the crystalUzation; a soUd mass, consisting of smaU fragmentary crystals, the common loaf-sugar, is obtained, from which the remaining liquid sugar is re- moved by letting a concentrated solution of crystal- lizable sugar gradually percolate through (liquoring). The thoroughly purified and glistening white sugar is * caUed refined loaf-sugar; that which is not so com- pletely clarified, and has a yellowish tinge, is the com- mon loaf-sugar. 41 482 VEGETABLE MATTER. Experiment — Dissolve half an ounce of sugar in a quarter of an ounce of hot water; the viscous solution is called white sirup. If this solution is put in a cup, and set aside in a warm place, and evaporated slowly, the sugar will separate from it, crystaUizing in obUque six-sided prisms. In a similar manner white candy is prepared on a large scale from refined sugar, brown candy from raw sugar. As the crystals deposit more readily on substances having a rough than on those having a smooth surface, fine threads or pieces of wood are stretched across the vessels containing the sirup, and they soon be- come coated with crystals. 471. Cane-sugar, as already stated, has a much sweeter taste than grape-sugar; therefore, when used as a sweetening agent, it possesses a far greater value v than the latter. The white sugar now occurring in the market in Germany is frequently found to be composed partly or entirely of starch-sugar. Experiment. — Put into a test-tube a piece of cane- sugar, and into another some granules of grape-sugar taken from a raisin, and pour over them strong sul- phuric acid; the cane-sugar becomes black by gentle heating (it is charred), but not so the starch-sugar. An opposite reaction takes place when the two sorts of sugar are heated with a solution of potassa; the grape- sugar, but not the cane-sugar, assumes a dark color. Experiment—These two sorts of sugar may be more accurately distinguished from each other by the copper test. First add to the solutions of sugar some drops of a solution of blue vitriol, then some drops of a ' solution of potassa, and place both vessels in hot water; the liquid containing the grape-sugar assumes SUGAR. 483 in a few minutes a reddish-yeUow color, while that containing the cane-sugar remains blue. The grape- sugar is able to abstract from the oxide of copper half of its oxygen, whereby reddish-yellow suboxide of cop- per is formed (§ 354); cane-sugar is also able to effect this change, but not till after boiUng, or after standing several days. The sugar is converted by the oxygen taken up into an entirely new substance, caUed formic acid. Grape-sugar may be distinctly recognized by this test, even in an extremely diluted solution. 472. Liquid Sugar. — By this very indefinite name are commonly designated all those kinds of sugar which do not yield on evaporation a soUd crystalline or granular, but a vitreous amorphous mass, which on exposure to the air again attracts water, and deUques- ces. This kind of sugar is commonly called sirup and / molasses. 473. Sugar of milk is that particular kind of sugar which occurs in milk, and imparts to it its agreeable sweetish taste. It is obtained in hard, white, crystal- line masses, by evaporating the sweet whey. Sugar of milk is much less sweet to the taste than grape-sugar, and requires six parts of cold water for its solution. It is well known that milk becomes sour by standing for some days; this is owing to the sugar of milk being gradually converted into a pecuUar acid, called lactic acid. 474. Mannite is a substance resembling sugar, consti- tuting the principal part of manna (the concrete sweet juice of some species of the ash, growing principaUy in Italy). 484 VEGETABLE MATTER. CHANGES OF SUGAK. 475. a.) Change by Heat. — Experiment — Boil in a dish half an ounce of sugar with one dram of water, until the viscous solution begins to assume a yellowish tinge; then pour it upon a plate previously smeared with a Uttle oUve-oil. The transparent brittle mass is melted sugar in an amorphous state (barley-sugar or bonbons). The sugar is first dissolved by water; on boiling, the water is again evaporated, and the sugar passes graduaUy from the dissolved to the melted state. The yeUowish color indicates that aU the water has passed off, and that the sugar is on the point of becom- ing burnt. If the transparent sugar is kept for some weeks, it becomes opaque and crystaUine, when it can easily be ' broken up and finely comminuted. There is a scientific \ interest in this, as it clearly affords another illustration (§ 280) of the fact, that, even in a solid state, the small- est particles of sugar (its atoms) can change their sit- uation with respect to each other. Experiment — Repeat the former experiment, but without stopping the heating on the appearance of the yellow color; the sugar wiU grow darker, until it finally attains a brownish-black color, and will exhale at the same time a pecuUar empyreumatic odor. On cooUng, it is obtained as a hard, almost black mass, which soon deliquesces in the air, forming a dark sirup, and is called burnt sugar or caramel. A couple of drops of it impart to a large vessel filled with water the appear- ance of Jamaica rum. On account of its strong color- ing properties, burnt sugar is much used for imparting ' to liquors — vinegar, alcohol, &c. — a yellow or brown color. SUGAR. 485 Experiment. — When exposed to a still stronger heat, the sugar becomes charred, and finally burns up like wood, as may easily be seen by holding a piece of it on a platinum foil over an alcohol flame. The flame indicates also that inflammable gases are evolved. Pure sugar leaves no residue. If it con- tains Ume, white ashes remain behind upon the foil, which do not volatilize even at the strong- est heat. 476. b.) Change by Acids. — Experiment. — If you add a few drops of lemon-juice, or a little tartaric acid, to a thick, boiling solution of sugar, it immediately be- comes a thin liquid, which does not crystaUize on evap- oration ; thus is explained why the sweet juices of fruits, in which organic acids are always present, do not yield, on being boiled down, a solid sugar, but only a thick sirup. If you treat the solution of sugar as directed in the copper test (§ 471), you will find that it now con- tains grape-sugar; cane-sugar is therefore converted by boiling with organic acids into grape-sugar. This met- amorphosis is produced also in various other ways, as by mere prolonged boiUng of the solutions of sugar, by boiling them with diluted sulphuric acid, by fermenta- tion, &c. If sugar is boiled for a long time with diluted sulphuric acid, it finally passes into a brown substance, resembling humus. When boiled with nitric or other acids, which yield oxygen, it oxidizes first into sac- charic acid, then into oxaUc acid, and finally into car- bonic acid and water. Sugar, as though it were an acid, can combine in fixed proportions with oxide of lead, Ume, and many other bases ; but it thereby loses its sweet taste. 41* 486 VEGETABLE MATTER. RETROSPECT OF THE VEGETABLE MATTER HITHERTO CONSIDERED (VEGETABLE TISSUE, STARCH, GUM, MUCUS, AND SUGAR). 1. Organic substances are such chemical combinations as are formed in animals and vegetables during Ufe. 2. But we also designate by this term those chemical combinations which are formed from animal and vege- table matter, whether they are transformed with or without artificial assistance (products). 3. Organic matter undergoes decomposition with re- markable facility. We observe such changes, — a.) In living animals and plants (germination, ripen- ing, &c, — respiration, digestion, &c). b.) In dead animals and vegetables (fermentation, putrefaction, decay, &c). c.) In the decay of animal and vegetable matter (charring, burning, &c). d.) In the treatment of organic substances with acids, bases, &c. 4. In aU these changes, the form only of the organic body disappears; the elements of which they consist are unchangeable; they vanish from our sight only be- cause they assume an aeriform shape. 5. We have not yet succeeded (with a few unim- portant exceptions) in preparing and imitating the or- ganic combinations by putting together their constit- uent parts; we are only able to decompose them, and to convert the elements into new bodies. 6. The four organogens, oxygen, hydrogen, carbon, and nitrogen, are the principal constituents (the ele- mentary constituents) of all that lives and has ever lived. A few inorganic substances only are added to them, as sulphur, phosphorus, potassium, calcium, &c. RETROSPECT. 487 7. These four organogens have the power of com- bining in an unlimited manner with each other, and, indeed, not only with each other, but also with many inorganic substances; the number of the organic com- binations is therefore almost infinite. 8. Thus, since the difference of organic matter can- not, as in inorganic substances, consist in the number of the constituents, so the cause of this difference must be sought for in the varied juxtaposition or grouping of these constituents (compound radicals). 9. Vegetable tissue, starch, gum, mucus, and sugar are among the most widely diffused of the groups of atoms (or proximate constituents) occurring in the vegetable kingdom. They are present in all plants. 10. They have neither acid nor basic properties, and are therefore called indifferent vegetable bodies. 11. There is a very great similarity in their consti- tution ; namely, they consist of only three elements, carbon, hydrogen, and oxygen (they are non-azotized); and, moreover, they contain oxygen and hydrogen al- ways in the same proportions as in water, namely, in equal atoms. 12. These four proximate constituents of the vege- table kingdom form a principal ingredient of all our veg- etable food; they perform, accordingly, a very impor- tant part in the process of animal Ufe. 488 VEGETABLE MATTER. V. ALBUMINOUS SUBSTANCES (Azotized and Sulphurized Substances). ALBUMEN, CASELNE, AND GLUTEN. 477. Under the head of Vegetable Tissue, when speaking of the preparation of starch, it has already been shown what is to be understood by vegetable al- bumen, caseine, and gluten, and that all plants contain in their juice one or more of these azotized substances. Vegetable albumen is soluble in water, but is rendered insoluble by boiling (it coagulates). It is found partic- ularly abundant in culinary plants and in oily seeds, as in almonds, rape-seed, flax-seed, poppy seeds, &c. Vegetable caseine is likewise soluble in water, yet it does not coagulate by heat, though it does by adding an acid to a solution of it. The leguminous plants, ^ such as peas, beans, lentils, &c, are very rich in it. Gluten (vegetable fibrine) is insoluble in water, and forms an essential part of wheat. Experiment — Add to one dram of bruised peas half a dram of caustic potassa and one ounce of water, and boil the mixture till a drop of the liquid causes a brown spot on lead-paper (paper which has been moistened with a solution of sugar of lead). The dark color pro- duced on the lead-paper is owing to the formation of sulphuret of lead; it indicates that sulphur from the peas has been rendered soluble by the potassa. By now adding a few drops of sulphuric or muriatic acid to the liquid, the presence of the sulphur also makes itself known by the smell, since sulphuretted hydrogen gas is evolved (§ 213). Vegetable albumen and gluten, when f thus treated, give rise to the same phenomena. The tarnishing of silver spoons on remaining for some time ALBUMEN. 489 in boiled peas, &c, is now simply explained, as sul- phuret of silver has been formed on the surface. Veg- etable albumen (likewise animal albumen) contains, besides sulphur, a smaU quantity of phosphorus. It has hitherto been assumed, that a common funda- mental body (an organic radical) was contained in the albuminous substances, which was called proteine; but more recent investigations have shown that such an or- ganic element does not exist. 478. It has been ascertained by careful experiments, that the chief proximate constituents of animal matter have the same constitution as the albuminous substan- ces of the vegetable kingdom, and this has led to the conclusion, that the component parts of the bodies of those animals whose food consists entirely of vegeta- bles are derived from these albuminous substances. This conclusion is most fully confirmed by the consti- tution of the blood, the component parts of which are albuminous matter (albumen and animal fibrine). Now, as the blood is the medium of nourishment, the blood being first formed from the food, and afterwards all the other parts of the animal body from the blood, so we may fairly infer that from the albumen, caseine, and gluten which we receive in the form of bread, peas, &c, the albuminous substances of the blood are formed, and from these the other parts of the body. For this reason, articles of food are esteemed nutritive in propor- tion to the amount of nitrogen they contain. CHANGE OF ALBUMINOUS SUBSTANCES BY DECAY AND PUTREFACTION. 479. Formation of Ammonia. — Experiment. — Put some gluten, some coarse meal, or some peas, into a 490 vegetable matter. flask, pour in some water, and connect the flask by means of a glass tube with a second flask, filled about an inch deep with water, and let them remain in a moderately warm place. Insert, also, between the cork and the neck of the first flask, a strip of lead-paper, in such a manner that part of it shall hang down into the flask. The following changes will be observed to take place, more rapidly at a warm, more slowly at a cold temperature: — a.) Bubbles of gas escape from the glass tube into the second flask; they consist of carbonic acid (and some hydrogen), as may be seen by the turbidness which follows on the addition of Ume-water. b.) The lead-paper is colored dark, a sign of sulphuret- ted hydrogen being generated. c.) A pungent smell of ammonia is evolved from the liquid standing over the gluten, when it is heated with lime or potassa; consequently ammonia has also been formed. If we compare this process of decomposition with that which takes place on the putrefaction of non-azo- tized substances (§445), we shaU observe the foUowing principal difference in the result: — On the putrefaction of albuminous substances, their nitrogen and sulphur (and phosphorus) combine with hydrogen, forming ammonia and sulphuretted hydrogen (and phosphuretted hydro- gen). These aeriform substances are the chief cause of the very disagreeable odor which is given off during the decay or putrefaction of azotized substances, — for in- stance, animal substances. During the progress of this decomposition, there is formed also, as in ligneous fibre, a brown substance resembling humus. However disgusting may be the products of putrefac- tion and decay, they nevertheless contain within them- ALBUMEN. 491 selves the germ of the most beautiful compounds ; the most beautiful plants arise from such products of de- cay. Indeed, the most nauseous-smelling decaying azotized substances are the most powerful means of rendering our fields and gardens fertile (the best ma- nures). 480. Formation of Nitre. — Experiment. — Mix some flax-seed meal with wood-ashes, sand, and lime, and let this mixture remain exposed to the air for several months in the summer season, frequently moistening it with water, and stirring it. If the mixture is then treated with hot water, and the solution evaporated, prismatic crystals will be formed from the latter on cooUng, which will detonate smartly when thrown upon glowing coals; they consist of nitre (§ 207). Here, also, ammonia is in the first place formed ' from the nitrogen of the vegetable albumen, present in great abundance in the flax-seed meal; but it is induced by the predisposing influence of the strong base to un- dergo still further putrefaction, that is, to attract oxygen from the air, whereby water is formed from its hydro- gen, and nitric acid from its nitrogen, the latter of which combines with the potassa and lime. From ammonia = N H3 and oxygen = Os Q3__ are formed nitric acid and water = N05-(-3H0. In a similar manner nitre is often generated in arable land, whence it passes into the juice of plants; thus it is known that beets and tobacco growing upon very strongly manured soil, and also those rank plants grow- ing on manure-heaps, such as henbane, thorn-apples, Cv'c, are frequently so rich in nitre, that when dried they emit sparks, if burnt on charcoal. 481. The extraordinary facility with which albumi- 492 VEGETABLE MATTER. nous substances undergo decomposition, when they are exposed to the air in the moist state, is explained very simply by the fact that they contain five, indeed, six ele- ments, and always several atoms of each, as component parts (§§ 425, 429). If during their decomposition they come in contact with non-azotized substances, these al- so are induced to enter into decomposition, — they are, as it were, infected. There follows in this connection that important change which sugar experiences when it is brought in contact with albuminous substances in a state of decomposition. This metamorphosis, known under the name of spirituous fermentation, wffl be more particularly considered in the foUowing pages. RETROSPECT OF THE ALBUMINOUS SUBSTANCES (AL- BUMEN, CASEINE, GLUTEN). 1. The albuminous substances are characterized by containing, not only carbon, oxygen, and hydrogen, but also nitrogen and sulphur. 2. On account of this complex nature, they are decom- posed with the greatest ease (fermentation, putrefaction, decay). 3. If while they are decomposing they come in con- tact with other organic substances, they cause these also to enter into fermentation, decay, putrefaction, &c. 4. All vegetables contain, though not always in great quantity, one of these substances; from this universal diffusion, we infer that it has an important office to dis- charge ; 5. Which office consists undoubtedly in this, that by means of it the growth and nourishment of plants may be brought about. CONVERSION OF SUGAR INTO ALCOHOL. 493 VI. CONVERSION OF SUGAR INTO ALCO- HOL (Alcoholic Fermentation). 482. Experiment — Half an ounce of honey is dis- solved in four ounces of water, and some of the gluten or caseine from experiment § 479, in a state of decom- position, is added to it; the liquid is then put in a moderately warm place (18° to 24° C), when it soon enters into fermentation, with the evolution of a large quantity of gas. If you perform the experiment in a flask furnished with a bent glass tube, one end of which is passed under a second flask, filled with water, which is invert- ed over the pneumatic trough, the gas may easi- ly be collected; it consists of carbonic acid. If the liquid still retains a sweet taste after the evolution of the gas has ceased, then add an- other portion of the gluten to it, whereby the fermenta- tion is again renewed. FinaUy, all the saccharine taste will have disappeared, and the liquid wiU have ac- quired a spirituous flavor. The fermented liquor is called metheglin; instead of sugar it contains alcohol, and this is the reason of its intoxicating effect. A por- tion of the gluten is found at the bottom of the vessel, converted into a brownish residue. All albuminous matter in a state of decomposition, as, for instance, old cheese, putrefying flesh, blood, &c., acts like putrefying gluten; but the substance which possesses this fermenting power in the highest degree is the altered gluten of barley, obtained in great quan- 42 494 VEGETABLE MATTER. tity as a secondary product in the brewing of beer (sur- face yeast, or brewer's yeast). All substances which are able to excite fermentation in solutions of sugar are designated by the term ferment. Surface yeast (§ 488) is accordingly the most powerful ferment. Experiment — Repeat the former experiment, adding, instead of the gluten, a teaspoonful of yeast to the honey-water; the process of fermentation wiU now pro- ceed much more rapidly and regularly. 483. The change which the sugar experiences during this process may be rendered very inteUigible by com- paring together the formulas of sugar, alcohol, and car- bonic acid. 1 atom of honey or grape-sugar consists of C6 06 Hg; from this are formed 1 atom of alcohol = C4 02 H6, and 2 atoms of carbonic acid = C2 04 = 2C 02. Alcohol and carbonic acid, added together, yield again the constituents of sugar. Thus sugar is resolved by fermentation into alcohol and carbonic acid. Fig. 1S9. ®@®@@® ®@ ®@®@ ®®®®@® ®®Q® @® Grape sugar. Alcohol. Carbonic acid. Both substances did not previously exist in the sugar, but they are new products of a pecuUar decomposition of the sugar, — peculiar for this reason, that they are exclusively made up of the elements of the sugar, without any thing being either subtracted from it or added to it. The ferment works also in the same pe- ? culiar manner; it induces a decomposition of the sugar, yet without combining with the sugar, taking any CONVERSION OF SUGAR INTO ALCOHOL. 495 thing from it, or giving any thing to it; its mode of operation is analogous to that of sulphuric acid, when the latter converts starch into sugar (§ 459). The ac- tion of the ferment, however, differs from that of sul- phuric acid just alluded to, since the ferment itself does not remain unchanged, but is also decomposed during the fermentation. Accordingly, two sorts of changes are going on by the side of each other in the fermenting liquids ; — 1.) that of the azotized ferment; 2.) that of the non-azotized sugar. The ferment always commen- ces the change, which is continued in the sugar, as if the latter were infected. The process is very similar to what occurs in the case of a fresh apple, which be- gins to rot on coming in contact with one already in the act of rotting. Experiment. — Instead of honey, take a solution of , white sugar, and add some yeast to it; in this case the fermentation will not take place so soon, since the cane- sugar must pass into grape-sugar before its decom- position into alcohol and carbonic acid can commence. This transition takes place simply by the addition of one atom of water; for if one atom of water is added to the cane-sugar, = C6IL 05, there is formed C6 Hg Oe, or grape-sugar. WLNE. ' tn^y^^^ 484. AU sweet vegetable juices pass spontaneously into fermentation without the necessity of adding to them a ferment, because they always contain sugar and one of the albuminous substances, as albumen, caseine, 1 or gluten. Experiment. — Submit freshly expressed beet-juice to a temperature of about 20° or 25° C.; the juice will 496 VEGETABLE MATTER. soon effervesce, deposit a sediment, and be converted into a spirituous Uquid (beet-wine). In the same manner currant and gooseberry wines are prepared from currants and gooseberries, cider from apples, the so-called cherry-water by fermenting and afterwards distilling the cherry-juice, rum by ferment- ing and afterwards distiUing the juice of the sugar- cane, &c. The most common of all the fermentations of this kind is the fermentation of the grape-juice, wine being the result. In order to prepare clear wine, the grapes are pressed, the juice (must) is poured into vats and al- lowed to remain in them in the ceUar, where, as the temperature is tolerably low, the fermentation proceeds so slowly that it is not completed until after some months. The young wine is racked off from the lees, and poured into fresh vats ; it still contains a small quantity of sugar and albuminous matter, which are both gradually converted, the former into alcohol and carbonic acid, the latter into lees (after fermentation). In the manufacture of red wine, the purple grapes are bruised, and then fermented, together with their skins and stalks ; a red coloring matter is extracted from the skins, and tannin from the stalks and seeds, the tannin imparting to this species of wine its favorite astringent taste. Sparkling wine (Champagne) is made by letting the fermentation proceed in corked-up bottles, whereby the carbonic acid formed is retained in the wine. 485. The grapes growing in northern countries, for instance, in Germany, contain proportionably more albuminous matter and tartar than sugar, which ac- counts for the difference in the smell and taste of wine. The taste of the German wines is not sweet, because the albuminous substances present are more than suffi- CONVERSION OF SUGAR INTO ALCOHOL. 497 cient to decompose all the sugar; the odor (the flower or the bouquet) is peculiarly pleasant, because, the tartar being abundant, there is generated during the fermen- tation a volatile substance (aenanthic ether), which pos- ©t-i/v f ^~ sesses a very agreeable odor. a^i/dof; (i&«, It is different with the grapes of the more southern countries, as Greece, Spain, Portugal, &c. Here, in consequence of the higher temperature, the grapes are richer in sugar, but poorer in tartar and albuminous matter. In this case the latter substance is not suffi- cient to effect the decomposition of all the sugar during the fermentation, so that a part of the sugar remains undecomposed, and gives to the wine a sweet taste. Neither is any cenanthic ether generated, since the due quantity of tartar is wanting; consequently these wines possess no bouquet. 486. Experiment. — If some wine is put into a retort, and subjected to distillation at a moderate heat, at first the more volatile alcohol, together with the cenanthic ether, will pass over. A very agreeable smelling spirit is thus obtained, known in commerce under the name of Cognac, or French brandy. In the wine countries, the /•". <7n., y-^A lees remaining after the wine is racked off are general- D, £sLa ^A> ly used for this purpose, since, in the swollen, pap-like -^fe flis-dCl state into which they settle in the vats, they retain me- chanicaUy a large quantity of wine. 42* 498 VEGETABLE MATTER. BEER. 487. Next to wine, beer and brandy are the most im- portant fermented liquors. The manufacture of them differs essentially from that of wine in this respect; that materials are employed which contain no sugar already formed, but instead of it starch, such as barley, wheat, rye, potatoes, &c. Starch cannot, like sugar, be resolved directly into alcohol and carbonic acid; and, when employed in the manufacture of alcohol, it must previously be converted into sugar. This, in the pres- ent case, is always effected by the diastase of the bar- ley-malt in the so-caUed niashing process of the brewers and brandy-distillers (§ 461). Experiment — Pour a mixture of an ounce and a half of cold water and two ounces of boiling water upon half an ounce of bruised malt, and set it aside for some hours in a warm place, where it will reach a tem- perature of about 65° or 75° C.; a sweet liquid is thus obtained, composed, not only of dextrine and sugar, but containing also the gluten, thereby rendered soluble, which was present in the malt. The brewer calls this liquid the wort Strain it with pressure through a cloth, and boil the liquid for some time, until it becomes clear and transparent; then let it cool to 30° C, and add to it a teaspoonful of yeast; it will soon begin to fer- ment, and after some days wiU clarify again; the clear, fermented liquor is beer. This is the mode of making the Berlin white or pale beer, which is not bitter. If during the boiUng some hops (female flowers of the hop- vine) are added to the wort, an aromatic bitter substance l is dissolved from them (liwulin), which not only imparts to the beer a pleasant and bitter taste, but also a great- er body. i,c, . U ^ ^ f CONVERSION OF SUGAR INTO ALCOHOL. 499 488. What is particularly remarkable in the above fermentation (superficial fermentation) is the great quan- tity of yeast that separates. It proceeds from the glu- ten of the barley, which is dissolved during the maiming process, but in the course of the fermentation is again precipitated as insoluble yeast. This is called surface yeast, it being raised to the surface in consequence of the great evolution of carbonic acid, and when the vats are full, it is caused to pass out through the bunghole; it is the best ferment, and the quantity ob- tained in the last experiment is sufficient to bring to complete fermentation the wort of a whole pound of malt. Its power of exciting fermentation is destroyed when it is rendered quite dry, or when it is boiled, or very finely triturated; and likewise by mixing antisep- tic substances with it, as, for instance, alco- Ftg. 191. noj? pyroligneous acid, sulphurous acid, vola- tile oils, &c. This yeast, when examined through the microscope, has exactly the form of simple vegetable cells (a); and their increase in the wort takes place in the same manner as in the most simple plants, new cells or buds developing themselves on each globule of the old yeast. These globules are hollow, filled with an azotized liquid, to which is to be ascribed the power of the yeast to excite fermentation. New beer holds, also, some sugar and gluten in solu- tion; therefore, Uke wine, it undergoes, when kept, a second slight fermentation (after-fermentation). If this is allowed to take place in weU-stopped bottles, so that the carbonic acid cannot escape, a foaming beer (bottled beer) is obtained, in the same way as in the manufac- ture of sparkling Champagne. But all the gluten is not separated, even by the sec- 500 VEGETABLE MATTER. ond fermentation, and hence the upper fermenting (light) beer undergoes a stiU further change on being exposed to the air; it is the alcohol, however, which is now altered by the albuminous matter undergoing de- composition; it passes into vinegar, and the beer be- comes acid. 489. Experiment — Repeat the former experiment, but cool the wort below 10° C. before adding the yeast, and then let the liquid remain in a cool place; a very gradual fermentation takes place, which will not be concluded for several weeks, perhaps even months. During this process, the carbonic acid is evolved in very small bubbles, and the yeast settles at the bottom of the vessel (sediment ferment, bottom yeast). The beer thus prepared contains scarcely a trace of gluten or yeast, and therefore can be kept for years without be- coming sour; it is, moreover, richer in carbonic acid than that obtained by the superficial fermentation pro- cess, because at the lower temperature, and by the more gradual elimination of carbonic acid gas, it was able to retain more of it. The stronger kinds of beer (Bavarian beer, strong beer, &c.) are made in this way. The thick bottom yeast, separating during this process, acts in- deed as an exciter of fermentation upon the sugar, but far more slowly and gently than the frothy surface yeast. 490. The peculiarities of the two methods of fermen- tation may be elucidated as foUows : — Surface Fermentation Bottom Fermentation a.) takes place at a higher temper- at a lower temperature (5- ature (12 - 20° C); 10° C). b.) takes place rapidly (in three or slowly (in six or eight weeks). four days); c.) in this case imperfect separation in this case thorough separation of of the yeast by flowing over; the yeast by settling. d.) surface yeast is finely divided bottom yeast is compact and heavy. and frothy; CONVERSION OF SUGAR INTO ALCOHOL. 501 e.) surface yeast is a strong exciter bottom yeast a feeble exciter of fer- of fermentation; mentation. f) surface fermented beer soon be- bottom fermented beer does not. comes sour; g.) surface fermented beer contains bottom fermented beer more. but little carbonic acid; , It) serves for the manufacture of serves for the manufacture of strong weak beer; beer. ' i.) by lowering the temperature the by raising the temperature the y surface fermentation may be bottom fermentation may be converted into bottom fermen- converted into surface fermen- tation, tation. 1 Experiment — Subject a weighed or measured quan- ^tityof beer to distillation (§486); a weak alcohol, to- '' -gether with carbonic acid, will first pass over, and finally ;» only a watery Uquid. Pour the yet fluid residue into a ^', cup, and set it in a warm place ; it dries up, forming a ' dry amorphous mass (extract of beer), which consists ^principally of dextrine, sugar, and the bitter principle of ' hops. By determining the strength and the quantity of the alcohol, and the weight of the extract obtained, we - have the two most important factors for estimating the j nature and purity of the beer. BRANDY. 491. The preparation of brandy is similar to that of " beer, inasmuch as substances containing starch are like- wise employed in the preparation of it, and as the starch must first be converted into sugar before the fermenta- tion can proceed. This is done, as in the case of beer, by the mashing process, that is, by the operation of the diastase of the malt upon the starch. To this end either boiled and mashed potatoes or rye are mixed ■ with bruised barley-malt and hot water, so as to form a paste, which is to be kept at a temperature of 70° C, until a complete formation of sugar is effected; then 502 VEGETABLE MATTER. brewers' yeast (surface ferment) is added to the sweet mash or wort previously cooled off, whereby fermenta- tion is induced. When this fermentation is concluded, put the mass into a copper boiler, and distil the vola- tile alcohol from the non-volatile parts (husks, gluten, fibrous matter, &c). The residue is used as a nourishing food for the fattening of cattle. Formerly simple stills were used for this distillation, and a thin spirit (brandy or low wines) was obtained, which consisted of about one third of alcohol and two thirds of water; but now a more complicated apparatus is universaUy employed, by means of which a brandy of double the strength is ob- tained (rectified spirit). The principle upon which this apparatus depends wffl be explained in the foUowing experiment. 492. Rectification or Strengthening of Brandy. — Ex- periment. — Pour three ounces of common brandy in- to a capacious flask, and carefully distil half of it into a vessel, which is cooled by means of very cold water, or what is still better, by ice. If the brandy Fig 192. contained thirty per cent, of spirit, then the ounce and a half of alcohol, first passing over, wiU contain at CONVERSION OF SUGAR INTO ALCOHOL. 503 least fifty per cent. Alcohol is more volatile than water, therefore it first passes over, in company with a smaller quantity of the latter, while the larger quantity of the water, together with the fusel oil which might haVe been contained in the brandy, remains behind in the flask (phlegm). 493. Experiment — If you connect with the flask and the receiver an intermediate vessel, a wide-mouthed vial, for instance, which is easily done by means of Fig. 193. two glass tubes bent at right angles, and a cork perfo- rated with two holes, and then repeat the above ex- periment of distillation, the alcohol vapors passing over will first condense in the middle vessel. But as this vessel is not cooled down, the liquid condensed in it will finally also boil, and the vapors thus formed will pass over into the receiver surrounded with cold water, and will there be condensed for the second time. In this manner a double distillation (rectification) is effect- ed. The flask contains boiling brandy (at 30° Tral- les*); the intermediate vessel, boiling rectified alcohol • The alcoholometer of Tralles floats to a figure on the stem, which indi- cates the percentage of alcohol, by volume, in the liquor in which it is placed. 504 VEGETABLE MATTER. (at about 50° Tralles). After the termination of the experiment, the first vessel will contain phlegm; the second, weak spirit; and the third, very strong highly rectified spirit (of 70 to 80° Tralles). If you adapt to the corks of the first two vesselt a couple of thermometers, which shall dip into the liquid, you will find that the Uquid in the flask boiled at the commencement of the experiment at 85° C, and at the end of the experiment at from 95 to 100° C, wThile that contained in the second vessel commenced boiling at 80° C, and ended with boiling at from 85° to 90° C. It is obvious from this that a strong spirit boils at a much lower temperature than that at which weaker spirits boil. The strongest alcohol (absolute) boils at 78° C, consequently at twenty-two degrees lower than water. 494. Experiment. — Connect with a flask a tolerably x large glass tube, which is so bent that its middle part may have a slight inclination upwards, as is shown in the annexed figure; from b, this tube is wound round Fig. 195. with moistened wick-yarn, the end of which hangs down at a. At a, bind a strip of cloth (several timea CONVERSION OF SUGAR INTO ALCOHOL. 505 folded together and smeared with some drops of olive- oil) round the tube, so that the water from the wick may not run down upon the flask. Now distil as be- fore three ounces of brandy, but during the distillation continually drop cold water upon the wick-yarn, at b, in order to cool the vapor of brandy as it passes over. Catch the water running down the outside of the tube in a vessel placed below the end of the wick-yarn. If the distillation is arrested when about one ounce of brandy has passed over, we shall have a stronger spirit in the receiver than was obtained in the experi- ment in § 492, because, by the partial cooUng of the vapor of the brandy, the principal part of the less vol- atile aqueous steam was condensed, and therefore a vapor richer in alcohol passed into the receiver, while the water condensed in the tube flowed back into the > flask. * This principle of partial refrigeration has been most successfully applied to the distillation of brandy on a large scale. The best-known apparatus used for this purpose is called the dephleg- mator, and is so contrived that the hot vapors rising from the still must pass through several copper channels before reaching the refrigerator; these channels have a division-wall in the cen- tre, and are kept cold exter- nally by a constant current of water. We obtain in this way a spirit of from 70° to 80° Tralles, while a simple still X yields only a weak spirit of 30° Tralles. 495. Alcohol is rendered not only stronger, but purer, by the above-mentioned rectification. Besides alcohol, 43 Fig. 196. 506 VEGETABLE MATTER. there is formed from grain and potatoes, during fer- mentation, an oily, disagreeably smelling liquid, the so- called fusel oil, and also some vinegar. Both are less volatile than alcohol, and therefore, during the above rectification, are for the most part condensed with the water, which flows back. The phlegm is accordingly a mixture of water with alcohol, fusel oil, and vinegar. The alcohol may be thoroughly purified from the fusel oil by letting it stand for some time in contact with freshly burnt charcoal, and then filtering it off; the fusel oil remains behind in the pores of the charcoal (§ 105). 496. In the same way that brandy is made in Ger- many from grain and potatoes, a spirituous liquor caUed arrack is prepared in the East Indies from rice, by mashing, fermenting, and distilling, and mixing with it the seeds of the palm-tree, thus imparting to it a peculiar flavor, and an odor resembling that of rum. 497. All fermented liquors contain alcohol, and owe to this their intoxicating power. The quantity of it contained in our ordinary spirituous Uquors is shown in the following table: — Pure Alcohol. In 100 measures of common beer are contained l£ — 2 measures. '• 0- FU«fC strong beer, 3 — 5 porter or ale, 6 — 8 wine, 10 — 15 Madeira wine, 18 — 24 French brandy, 40 — 45 liqueur, rum or arrack, 45 50 — 50 — 60 rectified spirit, 60 — 70 alcohol, 70 — 75 highly rectified alcohol, 86 — 90 SPIRIT OF WINE, OR ALCOHOL. 498. Anhydrous Alcohol. — Alcohol has as yet only CONVERSION OF SUGAR INTO ALCOHOL. 507 been obtained by the fermentation of sugar. In the preceding chapters we have already shown how alcohol is formed, how it is rendered stronger, and how it is purified. This is done by incomplete distillation, or • by incomplete condensation, since the alcohol is more difficult to volatilize than water, and its vapor more , difficult to condense than steam. But aU the water \ cannot be separated in this way from the alcohol, as the alcohol retains one tenth part of the water so firmly that it can neither be withdrawn from it by distillation nor by cooling. In order to procure it absolutely an- hydrous, a body must be presented to it which has a greater affinity for water, and fixes it so firmly, that it cannot evaporate with the alcohol at the boiling point of the latter. Such a body is quicklime. Experiment — Put into a flask one ounce of quick- ' lime that has been broken into small pieces, and pour upon it one ounce of very strong alcohol; connect a receiver with the flask, as in the experiment in § 49:2, and let the mixture remain in repose for one day. The lime gradually combines with the water of the alcohol (it slakes), and the latter is procured anhydrous by dis- tilling it off at a moderate heat. The best method of distilling in this case is over the water-bath (Fig. 83). Anhydrous alcohol is also called absolute alcohol. In this experiment, the vessels used must be previously rinsed out, not with water, but with strong alcohol, because the moisture adhering to the vessel would again impart water to the anhydrous alcohol. 499. Properties of Alcohol. — Alcohol has a burning taste, and a penetrating, agreeable odor. Strong alco- hol, especially absolute alcohol, acts as a poison when swallowed; but when diluted, it is, as is well known, stimulating and intoxicating. 508 VEGETABLE MATTER. Strong alcohol has never been frozen, even at a cold of —100° C.; it is therefore excellently adapted for the making of thermometers by which great de- grees of cold are to be measured. For this reason it is likewise serviceable in the illuminating-gas apparatus, for preventing in winter the freezing of the water which settles in the gas-pipes, and the consequent obstruction of the pipes. The illuminating gas, on leaving the gas- ometers, is first made to pass through alcohol before it is conducted farther, whereby the steam is not only withdrawn from the gas, but so much vapor of alcohol is also added to it, that the Uquid now condensing in the pipes does not freeze at the temperature of our winters. If common alcohol is placed in an open vessel, the al- cohol evaporates more rapidly than the water contained in it. Strong alcohol may also attract water from the air. Thus is explained why aU spirituous Uquids must, when in unclosed vessels, lose strength, and be- come richer in water. The young chemist is frequently reminded of this fact in the case of the spirit-lamp; it wiU not burn when it has remained exposed to the air for some time unprotected. Why not? The spirit has passed away through the wick, the phlegm remaining behind. The boiling and evaporation of alcohol have already been treated of at §§ 493 and 494, and the combustion of it in § 121. Alcohol contains so little carbon, that no soot is separated during its combustion ; hence, also, the alcohol flame emits but a feeble light. The strength best adapted for spirit used in burning is that from 75° to 80° TraUes; if it is weaker, aU the water will not evaporate during the combustion, and phlegm remains r behind. 500. Alcohol may be mixed with water in every pro- CONVERSION OF SUGAR INTO ALCOHOL. 509 portion, and it becomes specifically heavier the more water it contains ; therefore, its specific gravity is a very simple, and at the same time a sure, test for the greater or less strength of alcohol. This is most conveniently ascertained by the areometer (alcoholometer). Abso- lute alcohol has a specific gravity of 0.792; that is, a vessel capable of containing just 1,000 grains of water is entirely filled by 792 grains of absolute alcohol; it is accordingly about one fifth fighter than water. In this alcohol, the alcoholometer sinks to the topmost point of the scale, to 100°, while in pure water it sinks to the lowest degree only of the scale, which is marked 0° (§ 16). The scales most in use are those of Tralles and Richter, which deviate very widely from each oth- er, since Tralles made the mixtures of alcohol and water from which he determined the degrees by meas- / ure or volume, while Richter made them by weight. The former, for instance, called that alcohol which consisted of one measure of alcohol and one measure of water, fifty degrees; but the lat- ter gave this number to a mixture consisting of one pound of alcohol and one pound of water. There must, of course, be more alco- hol in the latter than in the former mixture, because one pound of alcohol occupies a greater volume than one pound of water; and thus is explained why one and the same alco- hol shows more degrees on Tralles's alcohol- ometer, and consequently appears stronger than by Richter's. If you mix 50 measures of alcohol and 50 measures * of water, you do not obtain 100 measures, but only about 97 ; thus a condensation t akes place, as in the mix- ing of sulphuric acid with water (§ 173). This explains 43* Fig. 197. 510 VEGETABLE MATTER. the heating which always takes place when water and alcohol are mixed together. The knowledge of this fact is of economical importance for those merchants who now frequently prepare brandy by diluting strong spirit with water, since this liquid is commonly sold by measure. 501. Alcohol, like water, is a solvent for many sub- stances, and, indeed, it not only dissolves many sub- stances which are also soluble in water, such as tannin, sugar, &c, but many others, which are insoluble or near- ly insoluble in water, such as resins, volatile oils, &c. Experiment. — Pour into a flask, containing one dram of bruised gall-nuts, an ounce of water, and into anoth- er flask, containing the same quantity of gall-nuts, an ounce of alcohol; fasten over both flasks a piece of moistened bladder, in which some holes have been pierced with a needle, and set them aside for some days in a warm place. We obtain in both cases dark-col- ored, very astringent-tasting liquids (infusions and tinc- tures), which are to be clarified by filtration. They both hold in solution a peculiar principle of gall-nuts, called tannin or tannic acid. The watery infusion will decom- pose after a time, with the formation of vegetable mould; but not so the spirituous tincture, because al- cohol has the power of preventing the commencement of putrefaction. Experiment. — Prepare in the way just described an infusion from one dram of powdered cinnamon and water. A slightly colored liquid is obtained, and this, if evaporated on a warm stove, leaves behind an almost tasteless gum, which easily dissolves again in water. Now pour some alcohol upon the cinnamon r that remains, and let them digest for several days; we shall obtain a dark-brown, fiery, spicy, and astringent- CONVERSION OF ALCOHOL INTO ETHER. 511 tasted liquid (tincture of cinnamon). If some of this tincture is evaporated to dryness, a brown, glistening mass (resin) remains behind, which may be redissolved in alcohol, but not in water. Besides several other sub- stances, the water has accordingly dissolved principally gum, the alcohol principally resin (and volatile oil) from the cinnamon. These examples are sufficient to show in how many ways alcohol may be employed as a means of solution and preservation. The principal solutions effected by it are,— a.) The tinctures of pharmacy, alcoholic extracts of medicinal plants, roots, barks, &c. b.) The lac varnishes, solutions of resin in alcohol. c.) The so-called perfumed waters, eau de Cologne, so- lutions of volatile oils in alcohol, &c. d.) The liqueurs and cordials, solutions of volatile oils (oil of cumin, oil of peppermint, &c.) sweetened with sugar, or of bitter and aromatic substances (sweet-flag, cloves, orange-peel, &c), in alcohol. Two of the various changes which alcohol may un- dergo are specially important, namely, its conversion into ether and vinegar. VII. CONVERSION OF ALCOHOL INTO ETHER. *i , ^^ 502. Elayle, or Olefiant Gas. — Experiment. — Mix very gradually, and with constant stirring, two ounces x of common sulphuric acid with half an ounce of strong alcohol (§ 84); the heating which ensues on the union of these two fluids is still greater than that which takes 512 VEGETABLE MATTER. place on mixing together sulphuric acid and water. When the mixture is cold, pour it into a flask, and heat it in a sand-bath (see Fig. 84), at first cautiously, that it may not rise over, and afterwards somewhat more strongly; a kind of gas is evolved, which is to be col- lected, as has been described, in flasks immersed in cold water. Inflame the gas contained in one of the flasks, and immediately pour in water; it burns with a highly luminous flame; it is illuminating gas (C4H4), which is formed from the alcohol. The alcohol is resolved into illuminating gas and There is formed from alcohol, illuminating gas and 2 water. There are likewise formed at the same time sulphur- ous and carbonic acids, the former of which may easily be recognized by the smell; they are generated by the carbon of a portion of the alcohol decomposing a por- tion of sulphuric acid, and abstracting from the latter its oxygen. In order to purify the illuminating gas from these two volatile acids, it has only to be conducted through milk of lime before it is collected. The illuminating gas thus obtained has received the name of elayle, or olefiant gas, because it condenses with the chlorine, forming an ethereal liquid, which, like oil, is insoluble in water. - • 503. Sulphuric Ether. — Experiment.— Mix one ounce of strong alcohol with one ounce of common sulphu- ric acid, but now without cooUng the vessel by cold CONVERSION OF ALCOHOL INTO ETHER. 513 water, because by the heating of the mixture the desired chemical change is promoted. That such a change has really taken place is known by the peculiar smell, differ- ent from that of alcohol, and by the altered (brownish) color of the liquid. The change which a portion of the alcohol has hereby experienced is as foUows : — Fig. 200. ®®©®foxo) ®&&®@ There is formed from alcohol, ether (oxide of ethyle), and I water. While in the former experiment, by an excess of sul- phuric acid, two atoms of oxygen and two atoms of hy- drogen were separated from the alcohol, in the latter case the alcohol loses only half as much of these two elements, namely, one atom of each, which two com- bine to form water. From the alcohol (C4 He 02) there is formed a new body (C4 Hg O) which has re- ceived the name oxide of ethyle (Ae O), because it isjLlJyjPy able, like a base, to combine with acids. In the pres- 7/ 'hv,^ ent case the oxide of ethyle meets with free sulphuric acid, with which it combines, forming bisulphate of oxide of ethyle (Ae O, 2 S 03 -f 4 H O). This com- pound, which is contained in the elixir acidum Halleri and in the mistura sulphurico-acida,r is more simply designated by the name of sulphuric ether. 504. Ether. — H the liquid of the preceding experi- ment, consisting of sulphuric ether, is heated, it resolves itself into oxide of ethyle (ether), water, and sulphuric acid. Experiment. — Put the mixture prepared from alcohol and sulphuric acid into a flask connected with a glass * Preparations occurring in some European pharmacopoeias. 514 VEGETABLE MATTER. tube and a receiver (see Fig. 106), close the opening remaining between the neck of the receiver and the glass tube by binding round it a piece of moistened bladder, in which some fine holes are pierced, and heat the flask carefully in a sand-bath till the contents of it assume a bubbling motion. Maintain the boiling of the liquid till about half, or at most three quarters, of an ounce of the Uquid is distilled over. In this experi- ment the liquor, as it is distilled, must be subjected to a powerful refrigeration, because it is extremely vola- tile ; it is therefore advisable to perform the experiment in winter, and to surround the receiver with snow. Care must also be taken not to bring any burning sub- stance too near the vapors or the liquid which pass over, as they are both exceedingly inflammable. The distilled, colorless Uquid possesses a penetrating, pleas- ant smell; it is called crude ether. In order to purify it, shake it up in a smaU vessel with half an ounce of water, and one dram of potassa lye; close the vial, and let it remain standing for an hour with the bottom upwards. Crude ether contains a mixture of water, alcohol, and frequently also, when the distillation is continued too long, some sulphurous acid; these substances combine with the water and the potassa added, and form with them the heavier liquid layer, which settles at the bottom of the vial. The very thin and mobile liquid floating above is ether, which separates, because it comports itself towards wa- ter in the same manner as oil does, and is dissolved by it only in very small quantity. If you now loosen the stopper of the inverted vial, the aqueous liquid will run out, while the ether remains behind. If the latter is re- quired entirely pure, it must be again distilled or rectified. The most profitable way of preparing ether on a CONVERSION OF ALCOHOL INTO ETHER. 515 large scale is the following. Nine pounds of sulphuric acid and five pounds of alcohol are mixed together, and heated to the boiUng point. While the mixture is still boiling, just so much alcohol is allowed gradually to drop in, as there is ether distilled over. One single pound of sulphuric acid is then sufficient gradually to convert into ether thirty pounds of alcohol, at nine- ty per cent., or an unlimited quantity of absolute al- cohol. 505. Explanation of the Formation of Ether. — Alco- hol is distinguished from ether merely by this, that it contains one atom of hydrogen and one atom of oxy- gen, consequently one atom of water, more than the latter. Accordingly, the production of ether may thus be explained in the simplest manner: sulphuric acid, on account of its strong affinity for water, abstracts from the alcohol one atom of water, and thus the alcohol is converted into ether. But the process is somewhat more complex, because there is an intermediate station — the bisulphate of oxide of ethyle — on the way between the alcohol and the ether. This complex compound, having the character of a salt, acts very differently according as it is heated in a concentrat- ed or in a diluted condition. When diluted with six, or, at most, with eight atoms of water, this compound boils at from 130° to 140° C, and is thereby resolved into ether, water, and hydrated sulphuric acid; the two former volatilize without combining chemically with each other, and the latter remains behind. When the bisulphate of the oxide of ethyle is diluted with from nine to ten atoms of water, it boils even at a Atl30Otol40O. Ether. Water. Hydrated sul- phuric acid. 516 VEGETABLE MATTER. lower temperature than 130° C, and is thereby re- solved into alcohol and hydrated sulphuric acid. Alcohol. Here, too, ether and water are first separated, but both, when in a nascent state, plfurifacid"1' combine chemically with each other, forming alco- hol. This is the reason why, in the last-mentioned method of preparing ether, the sulphuric acid becomes ineffectual after it has transformed thirty times its own weight of alcohol at ninety per cent, into ether; it has then become so diluted by the water which it has ab- stracted from the hydrated alcohol, that nearly nine atoms of water have combined with two atoms of sul- phuric acid. It has already been shown, in the first part .of this work, by several experiments, how other bodies also, at different temperatures, evince sometimes a stronger, sometimes a weaker affinity for water, or, indeed, none at all for it. 506. Experiments with Ether. a.) Pour some drops of ether upon the hand; it will evaporate in a few moments, imparting to the hand a perceptible feeling of coldness (§ 40). Ether is so very volatile that it boils when in summer it is put in the sun (at 35° C.); therefore it must always be kept in tightly closed bottles, and in cool places. b.) Dip one piece of wood into ether, another into alcohol, and hold both to the flame of a candle; the ether burns with far greater briskness, and also with a much more luminous and a somewhat fuliginous flame. Its stronger illuminating power is simply ex- plained by its containing a larger amount of carbon. Aeo — % sog 8-9 HO- CONVERSION OF ALCOHOL INTO ETHER. 517 The process in burning is the same as with alcohol; the ether being also converted into carbonic acid and water. c.) If you pour some drops of ether into a tumbler, and after some minutes, when the ether is converted in- to vapor, apply to it a burning taper, a sudden ignition ensues, accompanied by an explosive noise. The va- por of ether forms, like hydrogen or marsh gas, when mixed with atmospheric air, a kind of explosive gas, and several violent explosions have been occasioned by carrying lighted candles or lamps into those places where, owing to the breaking of a bottle filled with ether, its vapor has become diffused in the air. d.) Ether may be mixed with alcohol in any propor- tion whatever. When mixed with three parts of alco- hol, it is much used as a stimulating and restorative ' medicine, under the name of Hoffmann's anodyne liquor. e.) Put a piece of tallow, or a few drops of olive oil, into a test-tube with some ether; both will entirely dis- solve in it. But they are not soluble in alcohol or water. Therefore ether may. be advantageously employed for dissolving and separating such substances as wall dis- solve in it, but not in other liquids. Besides fat, many of the resins, and the so-called gum elastic (caoutchouc), are soluble in ether. Ether is also very generally called sulphuric ether; but this appeUation is incorrect, since pure ether neither contains sulphuric acid, nor has any sulphur in its com- position. 507. Combinations of Ether with Acids. It has already been stated, that ether, though it does not give a basic reaction, yet comports itself as a base, that is, combines with acids. These combinations, how- 44 518 VEGETABLE MATTER. ever, cannot be directly produced by the mixture of ether with acids. Ether combines with acids at the moment of formation only, or when it is liberated from some other combination; but after it has once been set free, it no longer shows any inclination to combine with acids. These combinations may be called salts of ether, or salts of oxide of ethyle, just as the terms salts of potassa and salts of potassium are used, but they are generally spoken of as kinds of ether. Most of them are liquid, and have a volatile, cooUng taste. They are com- monly prepared by distilling the different acids with alco- hol, and often in the presence of sulphuric acid. Those only which are best known will be here aUuded to. Acetate of Oxide of Ethyle, or Acetic Ether (AeO, A), is a very volatile liquid, having an agreeable odor, and is employed in medicine. Nitrite of Oxide of Ethyle, or Nitrous Ether (Ae O, N 03), has an agreeable odor, like that of fruit, and is contained, diluted with alcohol, in the spir. nitr. ath. (sweet spirits of nitre) of the apothecaries, which is known as a medicine. Chloride of Ethyle, or Muriatic Ether (Ae CI), forms a constituent of the spirit of muriatic ether. QZnanthate of Oxide of Ethyle, or (EnantJiic Ether (Ae O, Oe), is contained in wine, and is the cause of the so-called bouquet of certain sorts of wine. Butyrate of Oxide of Ethyle, or Butyric Ether, now occurs in commerce under the name of rum-ether, or essence of rum, and is used for imparting to alcohol an odor similar to that of rum. 508. Organic Radicals. Formerly organic substances were considered as im- mediate combinations of carbon, hydrogen, oxygen, CONVERSION OF ALCOHOL INTO ETHER. 519 nitrogen, &c.; accordingly they were divided into ter- nary compounds (having three elements), quaternary (having four elements), &c. But in modern times the hypothesis has been adopted, that a simple manner of combination may exist in organic substances analo- gous to that of the inorganic compounds ; namely, that a simple group of atoms, as of carbon and hydrogen, may comport itself in the same way as an element or a radical; the group C2 N (cyanogen), for instance, com- ports itself as such. This supposition has already been most beautifully confirmed in many cases, and since alcohol and ether, and their metamorphoses, are pecu- liarly adapted for illustrating this new mode of consid- ering the subject, we will cite them as examples. In these combinations we consider a group of four atoms of carbon and five atoms of hydrogen (C4H3) as the elementary substance, as the radical, and call it ethyle (Ae). Accordingly, we now regard ether (C4 H5 O) as oxide of ethyle (Ae -J- O); alcohol (C4 H6 Oa) as hydrat- ed oxide of ethyle (AeO-j-HO); sulphuric ether as bisulphate of oxide of ethyle (Ae 0,2 S 03-f-4 H O); acetic ether as acetate of oxide of ethyle (Ae O, A); mu- riatic ether as chloride of ethyle (Ae CI), &c. It will be readily perceived from this grouping, that the organic compounds show a surprising resemblance to the inorganic, and may be very well compared with them; the ethyle series, for instance, with the potas- sium series, in the following manner: — Potassium corresponds to ethyle, Potassa " " oxide of ethyle (ether), Hydrate of potassa " " hydrated oxideof ethyle (alcohol), Bisulphate of potassa " " bisulphate of oxide of ethyle, Acetate of potassa " " acetate of oxide of ethyle (acetic ether), Chloride of potassium " " chloride of ethyle, &c. 520 VEGETABLE MATTER. The radicals of this kind, among which may be reck- oned, also, cyanogen and ammonium, are termed com- pound or organic radicals. Ether belongs to the divis- ion of radicals forming bases. VIII. CONVERSION OF ALCOHOL INTO VINEGAR. 509. Experiment — Mix in a glass vessel half an ounce of brandy with three ounces of spring-water, and put in the Uquid a slice of leavened rye bread, or black bread (Schwartzbrod), which has been previously soaked in strong vinegar, or instead of it a little leaven; cover the vessel with a piece of perforated pasteboard, and put it in a place where the temperature is between 30° and 40° C.; the spirituous liquor wiU, after some weeks, be converted into vinegar. This conversion does not take place in a closed vessel, as the oxygen of the air is indispensable to the process; a great quan- tity of oxygen is consumed, since the formation of vine- gar consists in an oxidation of the alcohol by the oxygen of the air. Neither is any vinegar formed if you do not add the bread or the leaven. As the solution of sugar does not of itself pass over into alcohol, neither does the alcohol of itself pass over into vinegar. But as an easily resolvable body (ferment, ^yeast, &c.) disposes sugar to enter into decomposition simultaneously with itself, so also acid bodies, that may be easily decom- posed, such as black bread, leaven, vinegar, &c, are able to bring the alcohol into that state in which it ab- sorbs oxygen. The mode of action of these substances, which are called vinegar ferments, resembles that of the CONVERSION OF ALCOHOL INTO VINEGAR. 521 nitric oxide in the sulphur-chambers ; they are, like the latter, the transferrers, that is, they attract the oxygen from the air, and give it up again to the diluted alcohol. In the same manner with pure diluted alcohol, all other alcoholic liquids, as beer, wine, cider, &c, may, by receiving oxygen, be converted into vinegar, and it is well known that vinegar is frequently prepared from them. If, as is ordinarily the case, they contain gluten or lees in solution, then these substances replace the vinegar ferment, and the acidification ensues sponta- neously, when the liquid is exposed in loosely covered vessels to a temperature of from 30° to 40° C. This acidification most readily occurs immediately after a spirituous fermentation, which has taken place at too high a temperature ; for this reason, in the hot months of summer, the brewers and brandy-distillers find diffi- > culty in keeping their fermenting wort and mash from turning sour, which can only be prevented by rapid refrigeration. Liquids, also, containing starch and sugar, may pass over into vinegar, but only after these have been pre- viously converted by fermentation into alcohol. This explains why the farmer obtains vinegar, when, having poured water upon the peels and refuse of fruit, he sets them aside near the stove; why boiled food, preserved fruits, &c, become acid after a time. The spirituous fermentation, which first takes place, is always fol- lowed by an effervescence or fermentation in these cases, because the carbonic acid, formed from the sugar at the same time with the alcohol, escapes. From this is derived the term vinegar fermentation, by which, in 1 earlier times, the process of the formation of vinegar was designated, this effervescence being regarded as an essential phenomenon in the generation of vinegar. 44* 522 VEGETABLE MATTER. But it is now known that no evolution of gas takes place during the conversion of alcohol into vinegar. 510. Experiment. — Fill two tumblers loosely with the stalks of grapes, and fill one entirely and the other only half fuU with wine, beer, or a mixture consist- ing of one part of brandy, one part of beer, and six parts of water. Put both vessels in a warm place, and once or twice every day pour the mixture from one vessel into the other, so that each may be alternately full and only half full of the Uquid. The alcohol con- tained in the brandy will, in this manner, be much more rapidly oxidized into vinegar, because the liquid adhering to the grape-stalks is, in this state of fine di- vision, surrounded by air, and thus has a far better op- portunity of attracting oxygen from the latter. The effervescence taking place at the commencement was owing to the sugar contained in the beer and the grape-stalks, and which was first converted into alco- hol and carbonic acid. The alcohol thus formed was likewise afterwards changed into vinegar, and this is the reason why the vinegar thus produced is more acid, that is, richer in acetic acid, than that obtained by the former experiment. 511. Quick Method of making Vinegar. — The tran- sition of alcohol into acetic acid takes place yet more rapidly by subdividing the alcohol still further, or by exposing a still greater surface of the liquid to the air than in the way just described. This is effected in the following manner. A tub four or five yards high is filled with shavings of beech-wood, and is furnished with a perforated shelf, which is placed somewhat below the upper f opening. Through each of the small holes a straw or a piece of packthread is passed, prevented from falling CONVERSION OF ALCOHOL INTO VINEGAR. 523 through by a knot at the upper end. By this means an extreme division of the alcohol is effected, as when it is poured in at the top, it only trickles slowly down through the holes by means of the straw or packthread, and then diffuses itself over the shavings, forming a very thin liquid layer, which presents to the air a sur- face many thousand times more extensive than was produced by any former method. Several large holes are bored round the lower part of the tub, and likewise in the perforated shelf; glass tubes are fitted into the holes made in the latter, in such a manner that the liquid, when poured into the top, may not run off through them. A free circulation of air is here- by produced, the cooler air enters by the openings in the tub, gives up its oxygen to the alcohol diffused over the shavings, and in consequence of this oxida- tion, or slow combustion, so much heat is evolved in the interior of the tub, that the temperature rises to 40° C. The air, hereby becoming warmer, and con- sequently lighter, passes out of the tub through the glass tubes in the shelf, and from an eighth to a fourth poorer in oxygen than when it entered. Strong vinegar is used as a ferment in this process, the tub and shav- \ ings having previously been moistened with it, and a certain quantity being also added to the mixture of brandy which is to be converted into vinegar. In 524 VEGETABLE MATTER. such a tub (vinegar-generator), heated brandy, beer, wine, &c. may be converted into vinegar in a few hours, by being passed through the cask three or four times ; hence this is caUed the quick method of making vinegar. 512. Explanation of the Process of forming Vinegar. — In order to convert alcohol into vinegar, four atoms of oxygen must enter into combination with one atom of alcohol. From one atom of alcohol and four at- oms of oxygen, = C4IL 02 -j- 4 O, are formed one atom of acetic acid and three atoms of water, = C4 H, 03 -f- 3 H O. The alcohol is accordingly oxidized into acetic acid and water. This process may be regarded as a slow and imper- fect combustion, and we shaU here also find confirmed what was stated of the combustion of wood in the air (§ 120), and of the combustion of sugar by nitric acid (§ 196); namely, that the easily combustible and easily oxidized hydrogen combines with the oxygen before the difficultly combustible carbon does. Here, as is ob- vious, none of the carbon of the alcohol is consumed, but one half of its hydrogen is consumed or oxidized by the oxygen of the air, one atom of oxygen, moreover, being taken from the air. Aldehyde. — We have thus far considered only the starting point (alcohol) and the extreme point (acetic acid) of the process of the formation of vinegar; but half way between these two there is a peculiar com- pound, which may be regarded as half-converted alco- hol, or half-made vinegar. It is formed from the alco- hol wmen two atoms of oxygen enter into combination with it, thereby converting two atoms of its hydrogen f into water. The name aldehyde (that is, al- alcohol, de- from which, hyd- hydrogen is taken) has been given to it. CONVERSION OF ALCOHOL INTO VINEGAR. 525 From alcohol, = C4 H6 02 and 2 O, is formed aldehyde, = Ct H4 Oa and 2 H O. This compound is always produced in the first period of the formation of vinegar, and occasions the peculiar suffocating smeU often perceived in vinegar-chambers. Aldehyde very greedily attracts two more atoms of ox- ygen from the air, and is thereby converted into hy- drated acetic acid (H O, C4 H3 03). This occurs in the second period of the formation of vinegar, when an acid odor prevails in the vinegar-chambers. Aldehyde may be very easily produced, and it may be readily recognized by its characteristic odor, when, as was directed in § 114, a glowing platinum wire is held in alcohol vapor, or yet more easily, by pressing down «n alcohol flame by a wire net. In both cases it is formed because the temperature is not high enough to effect a » complete combustion of the alcohol vapor. A portion of the latter then takes up only two atoms of oxygen from the air, and there is produced aldehyde vapor, and, together with this, some acetic acid and other gas- eous products. After this statement of the process of the formation of vinegar, it will no longer appear strange that alde- hyde and acetic acid are formed in all cases when alco- hol unites with bodies which are rich in oxygen, and which readily part with it, as, for instance, chromic acid, nitric acid, black oxide of manganese, sulphuric acid, &c. It may now also be easily explained how vinegar is produced from wood by dry distillation. Wood con- sists of C6 H5 05; acetic acid of C4 H3 03, or, if multi- X plied by 11, of C6 H4i Oh. Consequently, it is only necessary to abstract a little hydrogen and oxygen from the wood, in order to transfer it into acetic acid. 526 VEGETABLE MATTER. 513. Acetyle.— Aldehyde and acetic acid may, like ether and alcohol, be regarded as combinations of an organic radical. This radical is called acetyle (Ac), and it is assumed to be composed of four atoms of carbon and three atoms of hydrogen (C4 H3). Accordingly, aldehyde (C4 H4 02) is the same as hydrated oxide of acetyle (Ac -f- O -f- H O) ; acetic acid (C4 H3 03) is the same as oxide of acetyle (Ac -f- 3 O). Acetyle belongs to the class of radicals forming acids. 514. Properties of Vinegar. — Vinegar is an acetic acid diluted with much water, and frequently mixed also with foreign substances, which it obtains from the mtlt, fruit, wine, &c, from which it is prepared. The esteemed yellow or brownish color is often imparted to it artificially by burnt sugar, or extract of chicory. The vinegar which occurs in commerce under the name of wood-spirit contains in every hundred measures from eight to twelve measures of acetic acid, wine-vinegar from six to eight, and com- mon table vinegar only from two to five; the rest is water. In order to ascertain the strength of vinegar, we adopt a course similar to that used in testing carbonate of potassa (§ 202); that is, we examine how much of some base (ammonia is the best) a fixed quantity of it is able to neu- tralize. Glass cylindrical jars, constructed for this pur- pose, and divided into degrees, are called acetometers. If vinegar is allowed to remain for some time exposed to the air, it begins to decompose (to putrefy), and so much the more readily the weaker it is. This is indi- cated sometimes by a white film (mould), sometimes by Fig. 202. CONVERSION OF ALCOHOL INTO VINEGAR. 527 the separation of gelatinous matter (vinegar mother), sometimes by the generation of infusoria, which can often be distinguished by the naked eye when a glass of vinegar is held towards the sun (vinegar eels). Fur- ther decomposition may be arrested for a time by boil- ing the vinegar. Vinegar is somewhat less volatile than water. When it is distilled, first a weaker, and finally a stronger, col- orless vinegar passes over (distilled vinegar), and the foreign non-volatile mixtures remain behind. When vinegar is exposed to the cold, the water con- tained in it is frozen before the acetic acid is; hence, weak vinegar may be made stronger by partial freezing. Wine, when exposed to the cold, acts in the same manner. To impart to vinegar a more pungent or more acid taste, such substances as Spanish pepper, pellitory root, and indeed sulphuric acid, are sometimes added to it. The latter adulteration may readily be detected in the following manner. Experiment. — Fill a jar half full of water, and place upon it a cup containing the vinegar to be tested, together with some grape- sugar; then let the jar remain on a hot stove till the vinegar has evaporated. If the residuum is of a black color, then the vinegar contains sulphuric acid. When heated over hot water, the vinegar only is volatilized, while the sulphuric acid, if any is present, remains be- hind, and finally, when all the aqueous particles have vanished, attains such a strength, that it decomposes the sugar and chars it. 528 VEGETABLE MATTER. CONVERSION OF SUGAR INTO LACTIC AND BUTYRIC ACIDS. 515. If an open vessel, containing some expressed juice of the beet, is put in a warm place, where it will be heated to between 30° and 40° C, the beet-juice will enter into fermentation, in the same manner as in § 482 ; but when the fermentation is finished, notwith- standing that aU the sugar has disappeared, we do not find any alcohol in the fermented liquid, but a peculiar acid (lactic acid), and a mucilaginous gummy sub- stance. This process of decomposition has been called mucilaginous fermentation; it very remarkably illus- trates the extremely different kinds of decomposition of one and the same organic substance, according to the temperature at which the decomposition takes place. At a temperature of from 10° to 20° C, the beet-juice entered into spirituous fermentation, and its sugar was resolved into carbonic acid and alcohol; at a higher temperature it likewise fermented, but in this case the sugar is converted into carbonic acid, lactic acid, gum, and some other products. The sugar contained in many vegetable substances likewise undergoes a similar change, when these are mixed with salt, and kept for some time in a compressed state. The acid taste which we perceive in pickled cabbage, beans, gherkins, &c, is owing principally to lactic acid, which is formed in these substances in a way not yet thoroughly investigated. But beside this acid, we frequently find in the above- mentioned pickles another, called butyric acid, which imparts to them their peculiar odor. This acid, it seems, may also be produced by the metamorphosis of vegetable mucus, for it is always generated when FERMENTATION OF BREAD. 529 vegetable mucilaginous substances — for instance, al- tha?a-root, quince-cores, linseed, &c. — are allowed to remain for some time in water. FORMATION OF ALCOHOL, ACETIC ACID, AND LACTIC ACID, ON THE BAKING OF BREAD. 516. Meal. — The seeds of the various kinds of grain which we use in the preparation of meal and bread contain, as principal constituents, starch and gluten, and also a Uttle sugar. On grinding the grain, the husks and the parts contiguous to them, which are rich in oily matter (nitrogen and phosphate of lime), separate, constituting the bran, and there is left from the inner whiter mass, called the albuminous substance, the meal. The gluten is tougher, and more difficult to grind, than t the starch ; this explains why the finer white meal, ob- tained by repeated sifting (bolting), is richer in starch, while the coarser and darker meal is richer in gluten. The nutritive property of meal is to be ascribed to the azotized gluten; unbolted meal, and bread made of it, are accordingly more nutritive than white meal and white bread, but at the same time less digestible (soluble). Experiment. — Mix some flour with lukewarm water to a thick paste, cover it with a board, and let it remain for eight or ten days in a warm place. The paste is gradually altered, and two distinct periods may be ob- served during the change. In the first place, on the second or fourth day bubbles of air are evolved from it, having an acid, unpleasant smell, and the dough now possesses the capacity of converting sugar into lactic 1 acid, as may be readily perceived by adding a Uttle of it to some sugared water, and letting it stand in a warm place. -After six or eight days the dough acquires a 45 530 VEGETABLE MATTER. pleasant smell, and it now acts, when added to a solu- tion of sugar, like yeast; that is, it effects a decompo- sition of the sugar into alcohol and carbonic acid. If the dough is allowed to stand yet longer, it again ac- quires an acid taste, but which now proceeds from the acetic acid into which the alcohol previously generated gradually passes over (leaven). In this state it also excites a spirituous fermentation in sugared water; but this spirituous fermentation immediately passes over into the acid, into vinegar formation. It is obvious, from what has previously been stated, that the different actions of the flour, when in a state of decomposition, upon the sugar, depend upon the albuminous matter, the gluten, contained in the flour; consequently, we might call the slightly altered gluten a lactic acid fer- ment, that which is more altered an alcohol ferment, and that which is still further altered a vinegar ferment. 517. Bread. — What thus takes place slowly pro- ceeds rapidly in the making of bread, since a ferment is purposely added to the flour, which has been stirred up with water. In the making of white bread, the surface yeast of beer is used as a ferment; this, as is known, is the most powerful alcohol ferment. The sugar contained in the meal is thereby resolved into alcohol and carbonic acid, which struggle to escape, whereby the tough mass of dough is disintegrated, and rendered light and porous (rising of the dough). These substances, together with about half the water employed, volatilize by the rapid heating in an oven, having a temperature of from 160° to 180° C, and the cellular partitions of the baked bread attain such a solidity, that they retain their form and place even after cooling. But if the heat of the oven is not sufficient, or the dough is too Vatery, FERMENTATION OF BREAD. 531 then the partitions harden too slowly, and, on the escape of the carbonic acid, collapse, or run into each other (slack baking). This happens most frequently with dark bread, since, in consequence of its amount of gluten, it retains the water more obstinately, and ac- cordingly dries and hardens more slowly, than white bread, in which the starch is more abundant. Leaven is commonly used as a ferment in the prep- aration of black bread. There is formed, during the process, besides alcohol and carbonic acid, a little acetic and lactic acids (perhaps also some butyric acid), which communicate to the bread an acid taste. From three pounds of flour we obtain about four pounds of bread; consequently, a quarter of the bread consists of fixed water. The light, porous bread dissolves easily in the stomach; we say that it is easily digestible, and that / the compact heavy bread is difficultly digestible. 518. It is known (§ 458) that starch is converted, by roasting, into gum (dextrine); a part of the starch un- dergoes, also, this change in the oven, particularly on the surface of the baked bread, which receives the strongest heat from the roof of the oven. If the crust of the hot bread is rubbed over with water, and the bread is then replaced for a few minutes in the oven, some of the dextrine is dissolved, and forms, after the evaporation, the lustrous coating which we see on loaves of bread, and rolls. 519. Carbonic acid, as applied to the rising of bread, may be more or less advantageously generated in other ways than by the fermentation of sugar; indeed, quite other substances may be used for the purpose, such ' as those which become aeriform on the application of heat. Experiment — Mix intimately together two grains of 532 VEGETABLE MATTER. finely pulverized bicarbonate of soda, and a dram and a half of flour, and knead the mixture into a dough with one dram of water, to which four drops of common muriatic acid have previously been added. Let the dough remain for some time in a warm place, and then bake it on the hot flue of a stove, or in a spoon over an alcohol lamp. A porous mass of bread is obtained, because the carbonic acid of the soda salt is expelled by the muriatic acid, and raises the dough while it is yet soft. The common salt which is formed remains behind in the bread, and imparts to it a saline taste. This method has been introduced in many places for making bread, cake, &c. on a large scale. Experiment — Rub a dram and a half of flour with some grains of carbonate of ammonia, and then knead it with a dram of lukewarm water into a dough, and treat it as in the last experiment. In this case, also, the mass will become light and porous after the rising and baking, because the carbonate of ammonia (salt of hartshorn) is rendered aeriform by the heat, and during its escape the particles of the dough are forced asunder. In this way the bakers usually prepare their light and spongy cakes, as, for instance, spice-cakes, &c. Alco- hol and rum, which are sometimes kneaded with dough to promote the rising, act in a similar way. RETROSPECT OF THE CHANGES OF SUGAR AND ALCOHOL. 1. Sugar is converted, — a.) By the loss of oxygen and hydrogen, into water and brown substances rich in carbon. b.) By the addition of oxygen, into saccharic acid, oxalic acid, and water, and finally into carbonic acid and water. RETROSPECT. 533 c.) By contact with azotized substances at a low tem- perature, into (rich in hydrogen) alcohol and (rich in oxygen) carbonic acid (spirituous fermentation). d.) By contact with azotized bodies at a somewhat higher temperature, into lactic acid, mannite, and many other substances (mucilaginous fermentation). 2. By the changes mentioned under c and d, the azotized body is also simultaneously transformed into new combinations (yeast, ammoniacal salts, &c). 3. The conversion of the sugar into alcohol and car- bonic acid, and that of the azotized body into yeast, take place at a low temperature slowly (bottom fermen- tation), at a higher temperature rapidly (surface fermen- tation). 4. Hitherto alcohol has been prepared only by this method, namely, by the fermentation of sugar. 5. Starch is indeed used for the manufacture of alco- hol, but it must always be previously converted into sugar. 6. Alcohol is converted, — a.) By the loss of all its oxygen and some hydrogen, into elayle (olefiant gas) and water. b.) By the loss of some oxygen and hydrogen, into oxide of ethyle (ether) and water; this oxide of ethyle can combine as a base with acids (compound ethers). c.) By the addition of oxygen, into aldehyde and wa- ter, and by still more oxygen, into acetic and other acids. If we follow the process of oxidation, as it proceeds, we shall observe the following order of changes: —s)w**x Q J^J 4 From alcohol and oxygen are formed aldeto dVand water; C^ n^ G^ " aldehyde and oxygen '' " ^r/efPacW; .- C« H j <% " acetic acid and oxygen " " formic acid and water; " formic acid and oxygen " " oxalic acid and water ;£"*_ C,j f tt " oxalic acid and oxygen " " carbonic acid. ^ * 45* : 534 VEGETABLE MATTER. 7. The last products of this process of oxidation are consequently those into which the alcohol passes when it burns up, namely, carbonic acid and water. 8. Sugar belongs to the organic compounds rich in carbon, alcohol to those rich in hydrogen, acetic and the other acids to those rich in oxygen. IX. FATS AND FAT OILS. 520. Experiment — Break open an almond, and squeeze the white meat together by means of the finger- nail ; small drops of fluid will be expressed, which are slippery to the touch, and render blotting-paper greasy and transparent. This liquid is called oil of almonds. If the almonds are first pounded, and then subjected in a cloth to strong pressure, we shaU obtain more than one fourth of their weight in oil of almonds. A great many plants contain a similar oily juice, especially in their seeds, and from many of the latter oils are ob- tained by pounding and expressing. The term fat oils has been given to this kind of oils, because they are unctuous to the touch, and thick flowing. They occur, but less abundantly, in almost all plants, even in those where we should not expect to find any ; for instance, in different grains, grasses, &c. 521. Experiment. — Boil some fat pork cut up into small pieces for some time in a little water, and while the soft mass is yet hot, strain it through a linen cloth; a fat oil will float on the surface, but it is fluid only at a temperature of about 30° C.; below this tem- perature it congeals into a solid, yet soft, white sub- stance. This is also lubricating to the touch, and pro- FATS AND FAT OILS. 535 duces greasy spots on paper. Such kinds of fat, which, at the common temperature, have a soft unctuous con- sistency, are called lard, or, improperly, fat; and the cellular membrane and skin remaining in the cloth, and saturated with fat, are called scraps. 522. The suet of mutton, when treated in the same way, yields a fat which, when hot, is also fluid, Uke oil, but which, when cooled only to about 36° C, congeals, and then forms tallow, a still harder substance than lard. By boiling and roasting, we can melt out fat from all animal substances, especiaUy from those of the domestic animals, in which we are able to produce a great quantity of fat by keeping them confined, and giving them a plentiful supply of food. The fats ob- tained by boiling with water are white, as thereby they do not become heated above 100° C.; while those ob- / tained by roasting have a yellow or brown color (brown butter, gravies of roast meat, &c), because in this case a portion of the fat becomes burnt by being subjected to a stronger heat, — to a heat, perhaps, even above 300° C. In a strict sense, animal fats belong to the last division of this work, but they agree in their properties so exactly with the vegetable fats, that the subject will be rendered more intelligible by consider- ing them together under the same head. The fats of vegetables are mostly liquid (fat oils), those of the carnivorous Mammalia and of birds are soft (lard), and those of the ruminating Mammalia hard (tallow). { PROPERTIES OF FATS. 523. Experiment. — Rub a little fat upon paper, and place it upon a hot stove ; the grease-spot will not dis- 536 VEGETABLE MATTER. appear, however long the paper may be heated, since the fats are not volatile. Fats not only spread with great ease on paper, but also on all other porous substances; as, for instance, on wood, leather, &c. Since the fats remain soft for a long time in the interior of these substances, we possess in them means for rendering flexible substances supple, and of maintaining them in this state. For this reason, leather harnesses and shoes are greased from time to time; and for the same reason, also, the leather-dresser impregnates his lamb-skins with fish oil in the fulling- mill, to give them greater softness and pliabiUty when they are worked up into gloves, &c. That clay and loam have a great power of absorbing fat is obvious, as these substances are able to draw out again the grease that has been soaked into wood or paper. Thin substances acquire a greater transparency when their pores are fiUed with fat instead of air; common paper is rendered in this way so transparent, that it may be used for tracing and for transparencies. 524. The fats float upon water; they have accordingly a less specific weight than water. On account of this property, they may be used for excluding air from other bodies. A solution of green vitriol speedily attracts oxygen from the air, and deposits brown hydrated ses- quioxide of iron (§ 285); but it remains unchanged when it is covered with an oily film. Freshly expressed lemon- juice soon moulds in the air; it does not mould under a covering of oil. Preserved fruits keep much longer when melted butter is poured over them. Fats are insoluble in water; hence they may be used for protecting other bodies from being penetrated by water. By greasing with tallow or fat, we render our shoe-leather impervious to moisture ; by oiling, we pre- FATS AND FAT OILS. 537 vent the rusting of iron in the damp air; and by a coating of linseed oil, or Unseed-oil varnish, we guard against the penetration of dampness into wood, sails, cordage, and their consequent rapid moulding and rot- ting. Lumber and timber saturated with oil remain, as has been shown by late experiments, unchanged in the moist earth, while common wood is frequently de- stroyed by putrefaction, in the course even of a few years. 525. Emulsion. — Experiment. — Shake some oil and water briskly together in a test-tube; the oil separates into small drops, and renders the water milky; but on quietly standing, it soon rises again to the surface. It is kept in suspension in the water much longer when some mucilaginous substances, such as gum or albu- men, are contained in the water; as may be seen by trit- urating some oil with albumen, yolk of eggs, or a thick solution of gum Arabic, and afterwards gradually add- ing water. The milky fluid thus obtained is called an emulsion (oleaginous emulsion), and the oil in it will not separate from the water till after some days. Experiment. — A second mode of preparing emul- sions consists in bruising seed rich in oils, such as al- monds, or rape-seed, in a mortar, and gradually adding water. In all these seeds mucilaginous and albumi- nous substances are present, which are dissolved by water, and effect a fine division of the oil. We have a natural emulsion in the milk of milch ani- mals. Cow's milk is turbid, because the butter floats about in it in small globules, invisible to the naked eye ; these globules of fat are kept suspended in the water because a body similar to albumen—the caseine — is dissolved in the milk. On longer standing, the caseine becomes insoluble (it coagulates), and the Ughter butter collects, as cream, upon the surface of the milk. 538 VEGETABLE MATTER. 526. Drying Oils and Unctuous Oils. — Experiment. — Rub upon a copper coin a drop of linseed oil, upon another a drop of olive oil, and let them both remain for several days in a warm place; the Unseed oil will dry up into a resinous solid mass, while the olive oil will remain greasy. All oils absorb oxygen from the air, and become thereby thicker, and also acquire a disagreeable smell and taste (rancid); but there is an essential difference between them, as many oils become perfectly hard and dry, while others, on the contrary, remain soft and sticky. Accordingly, oils are divided into two classes, into drying and unctuous oils. The former may also be called varnish oils, as they are par- ticularly adapted for varnishing. The latter are called unctuous oils, because, when it is desired to prevent, by means of grease, the friction and heating of solid bodies, these oils remain soft and unctuous much longer than the drying oils. 527. By the absorption and condensation of oxygen taking place on the drying of oils, heat must be liberat- ed, as in every condensation of an aeriform body to a liquid condition. Under some circumstances, as when freshly oiled or varnished substances, such as wool, linen, &c, are closely heaped together in large masses, this heat rises to such a degree, that spontaneous com- bustion occurs; therefore it is not prudent to lay such articles too closely upon each other, before they have become thoroughly dry. CHANGES OF FAT BY HEAT. 528. Experiment. — Heat some linseed oil over an alcohol flame, and test the temperature of it occasion- ally by a thermometer. At first the heat rapidly rises to FATS AND FAT OILS. 539 Fig. 204. 100° C, and remains for some time at that temperature, dur- ing which time the oil boils moderately; this behaviour is occasioned by all crude oil containing watery particles, which evaporate at 100° C. As soon as these have vol- atilized, the temperature is suddenly elevated even above 300° C, when the oil begins to boil for the second time, but emitting now a white smoke having a very disagreeable odor. This vapor consists of decom- posed oil, principally of illuminating gas, and burns, when kindled, with a brisk flame; fats are accordingly combustible, but only at a temperature sufficiently high to effect their chemical decomposition. Illuminating gas is frequently prepared on a large scale from oils, by causing them to drop upon a red-hot iron vessel, from which the gas generated (oil gas) is conducted by a pipe into a receiver (gasometer). 529. Every lamp, every candle, is an illuminating- gas apparatus on a small scale. But in this case the combustion takes place only with the aid of an easily combustible body, the wick. When a fresh candle is lighted, the cotton of the wick first inflames, and the heat thus produced is sufficient to melt the tallow in contact with the wick. The melted tallow now ascends by capil- lary attraction (§ 106), through channels formed by the fibres of the cotton lying be- side each other, and in these channels it becomes heated by the flame to a temperature of above Fig. 200. 540 VEGETABLE MATTER. 300° C, and consequently is decomposed into illumi- nating gas. Whale oil, rapeseed oil, oil of colza, olive oil, taUow, and wax are most frequently used as illuminating materials. 530. Experiment. — Let some drops of water fall from a shaving, that has been dipped in water, into some oil burning in a spoon; the oil spatters about, because the heavier water sinks in it and is suddenly converted into vapor, which ejects the oil. Burning fat, such as varnish, lard, &c, should therefore never be quenched with water; but the quenching may be done easily and without danger, if the vessel is covered with a board or a piece of sheet-iron, ,thus excluding the air, which is requisite for continued combustion. 531. As in wood (§120), so also in fats, the hydro- gen burns more briskly than the carbon, and this is the reason why the partly burnt oil remaining after the extinction is richer in carbon, and has a darker color. An empyreumatic oil of this kind is kept by the Euro- pean apothecaries, under the name of oil of bricks, or philosophic oil. On yet further heating, the Unseed oil becomes continually blacker, and at the same time thicker, so that it finaUy acquires a viscid consistency, (factitious birdlime), and when mixed with soot forms the basis of the important printing-ink. COMPOSITION OF FATS. 532. The similarity in the combustion of fats and wood indicates that they have a similar constitution. Indeed, both bodies possess the same constituents, name- ly, carbon, hydrogen, and oxygen; the difference depends only upon the quantity; the fats contain, namely, more hydrogen and less oxygen than wood. They accord- FATS AND FAT OILS. 541 ingly belong to one and the same category with alcohol and ether, — to that of the organic bodies which are rich in water. 533. Stearine and Oleine. — We cannot, however, regard fats, like woody fibre or alcohol, as homogene- ous bodies, but as mixtures of several more simple kinds of fat, into which the fats, without being chemically decomposed, may be separated. Experiment. — If, during the winter, you place a ves- sel containing lamp oil in the cold, part of it wiU con- geal into a solid mass, like tallow, while the other part remains fluid ; the oil is accordingly separated by the cold into two fats, one solid and one fluid. The solid fat has received the name of stearine, the fluid that of oleine. By repeated cooling, the greater part of the stearine may be separated from the oil. The stearine obtained is pressed between blotting- paper as long as the paper absorbs any Uquid oil (oleine). Experiment—Twist a wire round a wide-mouthed vial, in such a manner as to form two handles, by means of which the vial may be suspended in a jar, which is then half filled with water, and heated upon a tripod. Put into the vial one dram of tallow and enough strong al- cohol — absolute alcohol is the best — to fill it three quarters full. When the contents of the vial boil, remove the lamp, and leave the vial in the water-bath, till the melted tallow has again settled at the bottom, and then pour the hot su- pernatant alcohol into a beaker-glass. Repeat the boiling three or four times, with fresh alcohol. Let the alcohol stand for some hours in cold water, covered 46 542 VEGETABLE MATTER. over; afterwards filter the liquid from the granular powder that has separated, wash the powder several times with cold alcohol, and dry it in an airy place. This mass, which, when dry, is laminated and slightly lustrous, is the stearine of mutton-taUow; the oleine must be sought for in the filtered alcohol. It remains behind, in the form of a somewhat thick oil, when the alcohol is aUowed to evaporate in a cup in a warm place. As is obvious from these experiments, stearine and oleine form the approximate constituents of fat, and this is the reason why some fats are hard, some soft, and others Uquid; the solid stearine predominates in the former, the fluid oleine in the latter. Pure stearine be- gins to melt at 60° C, pure oleine begins to solidify only at a very low temperature. One pound of mut- ton contains about three quarters of a pound of stea- rine ; one pound of oUve oil barely a quarter of a pound. The following are among the most important fats :— A. VEGETABLE FATS. a. Drying Oils (Varnish Oils). 534. Linseed Oil. — The weU-known Unseed yields, on being subjected to pressure, a yellow oil, equal to one fifth of its own weight, which is gradually bleached by long exposure to the sunlight. It is most frequently used in oil varnishes. Experiment. — Add to an ounce of linseed oil a quar- ter of a dram of litharge, and half a dram of acetate of lead ; put the mixture in a warm place, and frequently ' shake it. The liquid, clarified by settling, now dries much quicker than it would have done before ; it is the FATS AND FAT OILS. 543 common linseed-oil varnish, which, mixed with colors, is generally used for imparting a gloss to wood, metal, &c. The so-called oil-cloth is cotton cloth smeared with colored varnish; oil-silk is varnished silk. This varnish is commonly prepared, on a large scale, by heat- ing one hundred pounds of linseed oil with one pound of litharge, and maintaining the mixture for an hour at a temperature of 100° C. A stronger heat renders the varnish darker and thicker, and, besides, might easily cause it to boil over and take fire. The slimy, dingy white sediment which remains after both processes is a combination of mucilaginous substances with oxide of lead. All oils contain, in the unpurified state, mu- cilaginous (gummy and albuminous) substances, which retard the drying; these are rendered insoluble by oxide of lead. Varnish is, accordingly, Unseed oil free from mucilage. By kneading together linseed-oil varnish and chalk, we obtain a plastic dough, common putty. Hemp oil, from hemp-seed, of a yellowish-green color, is also used in the preparation of varnish, and likewise for burning, and for the manufacture of green soap. Poppy oil, from poppy-seeds, serves as a table oil, and for the preparation of a very clear varnish. Castor oil, from the seeds of the castor-oil plant, is a purgative medicine. Oil is also obtained from pumpkin-seeds, walnuts, sunflower-seeds, &c. b. Unctuous Oils (remaining viscous). 535. Oil for burning is expressed from rapeseed. In order that it may burn without depositing soot on the wick, it must be refined, that is, purified from 544 VEGETABLE MATTER. its slimy parts. This is done, not by oxide of lead, but by sulphuric acid. Experiment. — Mix one ounce of crude rape oil with eight drops of common sulphuric acid, and shake it frequently; in half an hour add half an ounce of water, again shake the mixture briskly, and set it aside for some days, when the oil floating on the surface will be freed from slime (refined). The slimy parts, charred by the sulphuric acid, and rendered insoluble, are found settled in the water at the bottom of the vessel. The sulphuric acid yet adhering to the oil is removed by re- peated washing with water. Sulphuric acid chars, as is known, aU organic substances (§ 173), some (for instance mucilage) easily, others (for instance oil) with difficulty; if just enough sulphuric acid, therefore, is added to the oil to char the mucilage, then the muci- lage only is destroyed, and the oil remains undecom- posed. A larger quantity of sulphuric acid would also attack the off. Olive oil is pressed out from the pulp of olives, the fruit of the olive-tree. The finest cold-pressed Prov- ence oil is of a bright yeUow color, the hot-pressed common oUve oil is greenish; these two sorts are, as is well known, universally used as a table condiment, and for greasing machinery. There is a thicker, darker kind, of an inferior quality, which is used in France and Italy for the manufacture of the so-called Naples or Marseilles soap. Oil of almonds is obtained by subjecting sweet almonds to pressure. Bitter almonds also yield by cold pressure a good oil of almonds, while by hot pres- sure an oil is obtained containing prussic acid. Oils are obtained also from hazle-nuts, beech-nuts, plum and cherry stones, apple-seeds, &c. FATS AND FAT OILS. 545 Cocoa-nut oil, from the meat of the cocoa-nut, is, at average temperatures, as soft as hog's lard; it has a white color and a somewhat disagreeable smell. Palm oil, a yellow fat, similar to butter, likewise pro- ceeds from the fruit of a species of palm-tree. Its yellow coloring matter is removed when heated to 130° C. (bleaching by heat). Cocoa-nut oil and palm oil are now manufactured into soap in very large quantities. The foUowing kinds of fat are employed in phar- macy : — Butter of cacao, the tallow-like white or yellowish fat of the cacao-nut, the cause of the fat particles which rise on boiled chocolate. Oil of nutmegs, the yeUow, agreeably-smelling fat of the nutmeg, having the consistency of butter. Oil of bays, the beautifully green, suet-like fat of the berries of the laurel-tree. B. ANIMAL FATS. 536. Our common domestic animals, cows, goats, and sheep, supply us with several kinds of fat; — a harder, white kind (tallow or suet), which lies in and over the flesh; a softer kind, generally of a yellow color, which separates from their milk (butter); and, besides these, there are the fats of the marrow and the feet. Stag-grease is white and hard, Uke mutton-tallow. Hog's lard, goose-grease, &c, are weU enough known. In earlier times, when it was believed that each single animal fat concealed within itself peculiar properties, numerous kinds of such fats were kept on hand in the apothecaries' shops; but now, plain hog's lard supplies the place of all the others. 46* 546 VEGETABLE MATTER. 537. Fish oil is tried out from the fat of whales, dolphins, seals, and different fishes. The fat, when melted out at a moderate heat, ha3 a yellow color, and a slight odor, which is not disagreeable; but that which is obtained by strong heat, or from fishes that have become putrid, is of a dark-brown color, and has a very disagreeable odor. Fish oil is preferred for greasing leather; it is likewise used in medicine and in the preparation of the black oil-soap. 538. Spermaceti is white, sparkling, and so hard that it may be rubbed into a powder, and is found inclosed in special cavities in the head of the sperm-whale. 539. Wax (cera) occurs in small quantities in all plants, especially in the shining coating of the leaves, stalks, and fruits; for instance, in the skins of ap- ples, and particularly in the pollen of flowers. Some plants of Japan and South America contain so much wax that it may be separated by boiling with water and by pressure, and it is then introduced into com- merce under the name of vegetable or Japan wax. But the purveyors of our common wax are the bees, who gather it from the flowers, and use it in the building of their ceUs. These insects may, perhaps, make their wax in part also from the sweet juices of the plants on which they feed, for accurate experiments have proved that bees have the capacity of exuding from their abdominal sacs the sugar upon which they feed, con- verted into wax. The yellow wax is bleached by cut- ting it into shavings, exposing them to the sun, and frequently watering them. The yeUow^ wax melts at 62° C, the white wax at 70° C. Wax is not only used for imparting stiffness to thread, and in the manufacture of candles, but when dissolved in potash lye it forms the so-called wax-soap, employed for giving a gloss to FATS AND FAT OILS. 547 variegated paper and for polishing floors, and when mixed with oils is made into plasters and ointments (cerates). Paper immersed in hot wax forms a good material for covering vessels, to protect them from moisture. Turpentine is added to wax, in order to ren- der it more pliant and tougher, as we find it in wax candles, and in the wax used for grafting trees. FATS AND ALKALIES (SOAPS). 540. Hard Soap. — Experiment. — Make first a strong lye with one dram of caustic soda Fig. 207. f a r of commerce and one ounce of wa- ter, and next, a weak lye, with one dram of caustic soda and two oun- ces of water. Boil the latter gently with an ounce and a half of beef- tallow, for half an hour, in a vessel only half filled with the mixture, and then add the strong lye gradually while the boiling continues. The fat and lye unite by degrees to a uni- form mass, of a gluey consistency, which after a time becomes thick and frothy. If a drop of this, when pressed between the fingers, presents firm white flakes, then add half an ounce of common salt, boil for some minutes, and let the whole mass quietly cool. We obtain a firm mass (soap) and a watery liquid, in which the common salt and some free soda remain dis- solved (under lye). If the soap, when boiled with water, forms a turbid solution, it contains still some unsaponified tallow, in which case add to it some weak lye, and continue boiling until the sample gives a clear solution in water; add again some table salt, and let it cool. The soap prepared in this manner has the same 548 VEGETABLE MATTER. composition as common house-soap. More recently, palm oil or cocoa-nut oil has been used partly or en- tirely to supply the place of tallow, the palm oil be- cause it is cheaper than tallow, and the cocoa-nut oil because it communicates to the soap the property of forming a strong lather. Experiment — Repeat the former experiment, using olive oil instead of tallow; hard soap is likewise ob- tained (olive oil or Marseilles soap). 541. Soft Soap. — Experiment — Prepare again some oil-soap, as above described, but instead of soda use potassa lye, which is prepared from caustic potassa and water, and omit the addition of common salt; the glu- tinous mass does not hereby pass by boiling into a hard soap, but, after a sufficient evaporation of the water, yields a soft mass (soft soap or potassa soap). This kind of soap is frequently employed in cotton factories for the cleansing of colored fabrics. If whale oil, hemp- seed oil or Unseed oil is used instead of oUve oil, a darker- colored soft soap is obtained, which is usually colored green by indigo and turmeric (green and black soap). Ammonia acts far more feebly than potassa and so- dium upon fats. If some of the unctuous oils are shaken up with ammonia, thick white mixtures, lini- ments, are obtained, which are often applied by friction to the skin. Hard soaps are formed from fats by soda, soft soaps by potassa. The chemical process taking place in both cases may be explained as follows. 542. Fat Acids. — The fats, as was shown in § 533, consist of several simple, sometimes solid, sometimes fluid, kinds of fat, — among which the solid stearine and the fluid oleine are especially predominant. These proximate constituents of the natural fats may be re- FATS AND FAT OILS. 549 garded as saline bodies; that is, as combinations of an acid with a base. Every simple fat contains a peculiar acid, — stearine, stearic acid ; oleine, oleic acid; palmi- tine, palmitic acid, &c.; but all contain one and the same base, to which the name oxide of glyceryle (sweet principle of oil) has been given. Stearine is, accordingly, stearate of oxide of glyceryle. Oleine " " oleate of oxide of glyceryle. ~ .. ci ti S & mixttlre of much stearate, and a little oleate C of oxide of glyceryle, &c. To designate the different acids contained in the fats, the general term " fat acids" will always be used in the following pages. Fats in general are accordingly to be regarded as combinations of fat acids with oxide of glyceryle, or as salts of fat acids and oxide of gly- ceryle. 543. The process of the formation of soap is thus one of simple elective affinity; the stronger bases, soda and potassa, displace the weaker oxide of glyceryle, and combine with the fat acids, forming compounds of fat acids with soda (soda soap), or of fat acids with potassa [potassa soap). From potassa and fat acids with ox- ide of glyceryle are formed fat acids with potassa and free oxide of glyceryle (potassa soap). From soda and fat acids with oxide of glyceryle are formed fat acids with soda and free oxide of glyceryle (soda soap). In the first two experiments the separated oxide of glyceryle, soluble in water, remains in the under lye ; but in the soft soap, when the surplus of water does not separate as a fluid from the soap, but is removed by evaporation, it remains mechanically mixed with the soap. The action of common salt may be seen by try- ing to dissolve hard soap in salt water; no solution 550 VEGETABLE MATTER. takes place, not even on boiling, for soap is insoluble in salt water, and likewise in strong lye; therefore, soap may be precipitated from a solution in water by the addition of common salt. This method of separation is usually employed on a large scale, since it yields a purer soap than when the water is removed by evapo- ration ; for, in the latter case, hydrated oxide of gly- ceryle, surplus of lye, and perhaps, also, some impurities contained in the lye or fat, remain mixed with the soap, while by the former method they are dissolved in the liquid (under lye). 544. Conversion of Potassa Soap into Soda Soap. — Experiment. — Dissolve some of the soft soap obtained in § 541 in boiling water, and sprinkle in some salt; the soap separates, and collects upon the surface of the water, yet, when cold, it wiU no longer be soft, but hard. The salt here acts in another manner; it occa- sions an interchange of the constituent parts; namely, from fat acids with potassa and chloride of sodium are formed fat acids with soda and chloride of potassium (soda soap). Soap-makers often proceed in this way on a large scale; they make a caustic potassa lye of wood-ashes and lime (lye of wood-ashes), boil it with fat, and final- ly convert the soft potassa soap obtained into hard soda soap, by means of common salt. SOAP AND ACIDS. 545. Experiment. — Dissolve some of the hard soda soap in hot water, and add to it vinegar by drops until a turbidness ensues. Vinegar, and other acids, are stronger than the fat acids ; therefore, they withdraw from the latter the base, and the fat acids are set FATS AND FAT OILS. 551 free. As these are lighter than water, and at the same time insoluble in it, so they collect on the surface of the water. The fat acids thus obtained resemble tal- low externally, but it is evident that they are not tal- low, since, even after long washing, they still have an acid reaction, which is not the case with tallow, and they are easily dissolved in hot alcohol, but tallow very difficultly. Three fourths of the mass consists of stearic acid, one fourth of oleic acid. When strongly pressed between blotting-paper, the oleic acid soaks into the paper, and the stearic acid remains behind. Stearic acid is harder and more brittle than wax, brilliantly white, translucent, and melts at the tempera- ture of 70° C. There are now large factories for the preparation of it, and it is used in the manufacture of the stearine candles, which have become so popular. Experiment — Heat some ounces of strong alcohol in a water-bath, and when it boils, add to it as much stearic acid as will dis- solve in it. Pour half of the solution obtained into cold water, and let the other cool quietly ; in the former case the stearic acid is obtained as a light, silky, brilliant mass, while in the latter it takes the form of delicate crystal- line plates. 546. Experiment. — If an acid is added to a solution of oil-soap, an oily fluid separates, which consists prin- cipally of oleic acid. Oleic acid in its external appearance is hardly to be distinguished from olive oil, but it differs from it in the following respects : it has an acid taste and reaction, which olive oil has not, and it readily dissolves even in cold alcohol, while olive oil does not. The oleic acid, 552 VEGETABLE MATTER. procured in stearic-acid factories from tallow, as a sec- ondary product, now frequently occurs in commerce, and on account of its cheapness is employed in the manufacture of soap, and in greasing wool for spinning. 547. Oxide of glyceryle (glycerine, or sweet principle of oil). — Experiment. — Add to the soft soap, prepared according to § 541, a solution of tartaric acid, and leave the watery fluid, after being clarified by filtration, to evaporate in a wTarm place. The saline mass re- maining after evaporation consists of bitartrate of potassa (tartar) and of the base of the fats, oxide of glyceryle; when strong alcohol is added, the latter dis- solves, while the bitartrate of potassa, together with any excess of tartaric acid that may be present, re- mains undissolved. The oxide of glyceryle, which remains after the evaporation of the alcohol, has the appearance of a yel- low syrup. It has not an alkafine taste, but is sweet, Uke sugar; neither does it react basically, although it is soluble in water. It has, accordingly, no similarity to other bases soluble in water, as, for example, potassa or soda. But the reason why it is regarded as a base is evident from its behaviour with acids; it is considered as a base, because it combines with acids in fixed pro- portions, forming compounds having the character of salts. It constitutes only about a tenth or twelfth part of fats; an ounce and a quarter of it, at most, is con- tained in one pound of taUow. Experiment. — Wipe the bowl containing the smaU quantity of the oxide of glyceryle that has been ob- tained with white blotting-paper, and heat the latter in a spoon. During the combustion there wiU be evolved from it an extremely pungent odor, proceeding from the oxyde of glyceryle, which is decomposed by the heat FATS AND FAT OILS. 553 into a volatile, extremely pungent substance (acroleins or oxide of aeryle), which causes lachrymation. Hence is explained the pungent odor which is perceived dur- ing the imperfect combustion of all kinds of fat. This odor is very strikingly manifested, also, when varnished articles are drying; for instance, in the drying chambers of the oil-cloth factories. This volatile matter may be formed also, even at a low temperature, from glycerine. No smell of acroleine is evolved on heating the pure fat acids. PROPERTIES OF SOAPS. 548. Washing with Soaps. — Soaps have two impor- tant properties; — 1st, they dissolve fat and oils ; 2d, they are very easily resolved, merely by mixing with much water, into an acid salt and free alkali; the latter dissolves, as is well known, most organic substances, but the former effects by its lubricity an easy washing away of the dissolved matter from other substances. On these two properties depends the application of soap in washing. The separated acid salt of fat acids with alkali modifies at the same time the action of the free alkali, and keeps the articles pliant which are washed with soap, while they would become fragile if they were cleansed with caustic alkalies alone. To prevent the shrinking of woollen articles, wash them with a weak solution of carbonate of soda, instead of with soap. 549. Soap and Alcohol — Experiment— Pour one ounce of alcohol upon one ounce of the shavings of tallow soap; the soap is completely dissolved on heat- ing in the water-bath, but the solution congeals on cool- ing to a transparent jelly. This jelly-like soap, mixed 47 554 VEGETABLE MATTER. with camphor and ammonia, is called opodeldoc. The white stars separating from this consist of crystallized stearate of soda. All soaps prepared from solid fats (rich in stearine) behave like tallow soap. Experiment. — Dissolve one dram of Naples soap in half an ounce of alcohol; this solution does not coagu- late on cooling; it forms the tincture of soap. By evaporation, a diaphanous soap is obtained (transparent soap). All the soaps made from the fluid fats (rich in oleine) act like the Naples soap. 550. Insoluble Soaps. — Experiment — If some lime- water is added to a solution of soap in water, a pre- cipitate of insoluble lime soap is formed; hence is ex- plained why spring-water, which generally contains lime (hard water), neither dissolves soap nor lathers with it, and accordingly cannot be used for washing. Experiment. — By adding acetate of lead (§ 337) to a solution of Naples soap in hot water, as long as a pre- cipitate is formed, we obtain, by double elective affinity, acetate of soda, which remains dissolved, and a com- pound of fat acid with oxide of lead, which separates as a white, adhesive mass, that may be kneaded with the moist hands, and formed into roUs (lead soap or lead plaster). From the compound of fat acid and soda, and from the acetate of lead, are formed a com- pound of fat acid with oxide of lead (lead plaster) and acetate of soda. In pharmaceutic laboratories, this plaster, generaUy known under the name of diachylon, is prepared in a different manner, namely, by boiling litharge with olive oil and some water. By this method oxide of glyceryle is readily obtained, and in larger quantities, as a secon- dary product; the plaster made has only to be washed with hot water, and the water evaporated after the ox- VOLATILE OILS. 555 ide of lead dissolved in it has been previously precipi- tated by sulphuretted hydrogen. If, instead of litharge white lead (carbonate of lead) is boiled with oil and water, we Ukewise obtain a compound of fat acid and oxide of lead, since the carbonic acid is expelled by the fat acids. In this manner the plaster of carbonate of lead is prepared, which has commonly a whiter color than the former plaster, because it still contains some white lead mechanically mixed with it. X. VOLATILE OR ETHEREAL OILS. 551. Preparation of Volatile Oils. — Experiment.— Put one ounce of turpentine in a dish in a warm place, Fig. 210. and when it has become Uquid transfer it to a capacious flask, pour upon it four ounces of water, and distil until about three fourths of the water has passed over. Pour the residue, while still hot, into cold water, in which the non-volatile portion of the turpentine remaining 556 VEGETABLE MATTER. behind congeals to a solid mass (resin). A strong- smelling, colorless liquid, a volatile oil, commonly known under the name of oil of turpentine, floats on the surface of the water distiffed over. Turpentine, a juice which exudes from pines, larches, and other trees, when the inner bark is cut through, is accord- ingly a mixture of resin and oil of turpentine; the latter is converted by heat, simultaneously with the water, into steam, and on cooUng is again condensed to a liquid. Experiment — Distil in the same manner half an ounce of cum- in-seeds (which have been pre- viously bruised in a mortar), in a retort contain- ing four ounces of water, until two ounces of water have passed over. The drops floating upon the water are likewise a volatile oil, oil of cumin; they have the smell and taste of the cumin-seeds, but in a stronger degree, while the residue remaining in the re- tort has scarcely the least smell or taste of them. All volatile oils possess a burning taste, and are somewhat harsh to the touch; but the fat oils have a mild taste and an unctuous feeling. DIFFERENT KINDS OF VOLATILE OILS. 552. Whenever we perceive an odor in a plant, we may presume that a volatile oil is present, which grad- ually evaporates. But how incredibly diffused and VOLATILE OILS. 557 diluted this must be in many plants may be inferred from the fact, that scarcely a quarter of an ounce of vol- atile oil is contained in one hundred pounds of fresh roses, or orange blossoms. We most frequently find the volatile oils in the flowers and seeds, sometimes in the stalks and leaves, but more rarely in the roots. They are obtained almost in the same way, without exception, as oil of turpentine, by distilling the vege- table parts with water. The oils procured from the skins and peels of some fruits, as the oil of lemons, and bergamot, contained in the rind of lemons, citrons, and oranges, form an exception, since such oils are ob- tained by expression from the fresh rind. 553. Of the more known volatile oils we obtain,— c.) From the flower : — Oil of roses, a yellowish, thick fluid, with flakes re- sembling tallow floating in it. Oil of orange-flowers (ol. neroli), colorless, reddish in the light; contains no oxygen. Oil of camomile, a dark blue, thick liquid; becomes green, and finally brown, by age and light. Oil of lavender, a yellowish, thin liquid. Oil of cloves, yellowish, soon becomes brown; a somewhat thick fluid, heavier than water. b.) From seeds and fruits : — Oil of cumin, colorless ; becomes yellowish, and final- ly brown, by age. Oil of anise-seed, yellowish ; congeals even at 12° C. Oil of fennel, colorless or yellowish; congeals like- wise readily. Oil of dill, yellow; becomes brown in the light. Oil of nutmeg, a pale yellow, thin liquid, has the smell of nutmegs. Oil of bitter almonds, yeUow; heavier than water; 47* 558 VEGETABLE MATTER. contains prussic acid, and consequently is very poi- sonous. Oil of mustard, yellowish, of an extremely pungent smell, causing lachrymation; contains sulphur. Oil of juniper, colorless; contains no oxygen. Laurel oil, white or yellow; a thick fluid. Oil of savin, colorless or yellowish ; a thin fluid; con- tains no oxygen. Oil of parsley, pale yellow; on being shaken with water, separates into a light volatile oil, and into a heavy, solid, crystalline oil. Oil of lemons, from lemon-peels, contains no oxygen. Oil of orange-peel likewise contains no oxygen. Oil of bergamot, from the rind of the bergamot orange, a pale yellow, very thin liquid. c.) From the leaves and branches: — Oil of the curled leaf mint (Mentha crispa), colorless or yellowish ; becomes brown with age. Oil of peppermint, colorless or yellowish, a very thin liquid, now frequently exported to Europe from Amer- ica. Oil of balm, pale yeUow, has an odor Uke that of lemons. Oil of marjoram, yellowish or brownish. Oil of thyme, when fresh, yeUowish or greenish ; when old, brownish-red. Oil of sage, when fresh, yeUowish or greenish; when old, brownish-red. Oil of wormwood, dark green; soon becomes brown or yellow, and viscous in the light. Oil of rosemary (ol. anthos), colorless and very thin, is, next to the oil of turpentine, the cheapest volatile oil. Oajeput oil, from the leaves of a tree growing in the VOLATILE OILS. 559 Moluccas; the oil, when pure, is colorless; the crude oil is commonly green, and often contains camphor; it has a camphorated odor. Oil of rue, pale yellow, or greenish. Oil of cinnamon, yellow; soon becomes brown in the air; heavier than water. Oil of turpentine, the most common of the volatile oils, is contained in aU our fir-trees, and exudes from them, mixed with resin, as turpentine (§568). When purified, it is colorless and thin, and has an agreeable, penetrating odor; it contains no oxygen. An ordinary sort, possessing a disagreeable empyreumatic odor, ob- tained in the preparation of pitch from pine resin, is crude oil of turpentine. Camphor occurs in commerce as a solid white, crys- talline, odoriferous mass, prepared by distillation with water, or by sublimation from the wood of the camphor- tree, growing in Japan and the East Indies. d.) From roots : — Oil of acorus, yellow or brownish. Oil of valerian, pale yellow, or greenish; becomes rapidly brown and viscous on exposure to the air. It is very remarkable, that we sometimes find several sorts of oil in one and the same plant. Thus, for ex- ample, we find in the orange-tree three different kinds of oil; one in the leaves, another in the blossom, and a third in the rind of the fruit. 554. Ferment Oils. — Experiment. — If water is poured on the centaury-plant (Erythraea centaurium), and it is left in a warm place until fermentation com- mences, a very penetrating odor is evolved from the leaves, which were previously scentless; the odor pro- ceeds from a volatffe oil, which was generated during the fermentation. In a similar manner, the fresh, scent- 560 VEGETABLE MATTER. less leaves of the tobacco-plant obtain the well-known nicotian odor by the so-called sweating process. Oils of this kind, which may be generated by fermentation from many other odorless plants, are called ferment oils. In the brandy-distilleries there is evolved also, on the fermentation of potatoes and grain, a disagreeably- smelling oil (fusel oil), which partly distils over with the brandy or spirit, and imparts to these liquids the fusel taste and smell. On filtering through charcoal, it remains behind in the pores of the latter. 555. Empyreumatic Oils. — FinaUy, oily volatile sub- stances are produced by the dry distfflation of vegetable and animal matter; for instance, oil of wood-tar from wood, coal oil from pit-coal, animal oil from bones, oil of amber from amber, &c. They are all distinguished by an exceedingly disagreeable odor, and are mixtures of various volatile substances. They are called empy- reumatic oils. Rock oil, or petroleum (nerpos, rock), is of a similar nature; it oozes out from the earth in many places in Asia, where it is formed in a manner as yet unknown to us. The red color of the oil occurring in commerce is given to it by the addition of alkanet-root. PROXIMATE CONSTITUENTS OF THE VOLATILE OILS. 556. All these oils are volatile at average temper- atures, except camphor, which begins to melt at the temperature of 175° C.; but below this temperature forms a white, solid, crystalline mass. If the volatile oils are cooled, there is frequently separated from them a beautifully crystallized, solid, white, camphor-like sub- ' stance, which has been called stearoptene, in opposition to the liquid portions that remain, which are caUed VOLATILE OILS. 561 eleoptene. Accordingly, the volatile oils, like the fats, consist of two proximate constituents, one of which may be regarded as solid and crystaUized, but the other only as a Uquid. Many oils — for instance, the oils of rose and anise-seed — are so rich in stearoptene, that, when kept in cool cellars, they congeal into a nearly solid mass. ELEMENTARY CONSTITUENTS OF THE VOLATILE OILS. 557. The volatile oils are divided into three classes, according to the elements of which they are com- posed : — a.) Into the non-oxygenated oils (having two ele- ments) ; these consist only of carbon and hydrogen (C, H), so that they may be regarded as condensed il- luminating-gas. To this class belong rock oil and oils of turpentine, juniper, savin, lemons, &c. b.) Into oxygenated oils (having three elements), which, beside carbon and hydrogen, contain also oxy- gen (C, H, O); most of the other volatile oils have this constitution. c.) Into sulphuretted oils, which are composed of carbon, hydrogen, and sulphur (sometimes with and sometimes without nitrogen). The oils of this class are distinguished by a very pungent smell, causing lachry- mation, and by a great acridity, raising blisters on the skin when brought in contact with it. The oils of mustard, horseradish, scurvy-grass, garlic, hops, &c. belong to this class. Of these elements, hydrogen (as regards the number of atoms) commonly predominates; hence, the volatile oils are usually reckoned among the organic substances rich in hydrogen. 562 VEGETABLE MATTER. PROPERTIES OF THE VOLATILE OILS. 558. Experiment — Pour a drop of some volatile off upon a sheet of paper, and let it remain exposed to the air; the paper at first receives an apparent grease-spot, but this disappears after a time, because the oil gradu- ally evaporates. The name volatile or ethereal oil thus explains itself; and the disappearance of camphor, on being exposed to the air, is owing to this volatileness. If the oiled paper is placed upon a warm stove, the evaporation takes place much more rapidly. Aromatic oils are employed in this way for perfuming apartments. Usually a quantity of flowers, wood, and rinds, finely cut up, are moistened with the oil, and scattered as a fumigating powder upon the stove. 559. Experiment. — Heat a quarter of an ounce of oil of turpentine in a vessel to boiling. A thermometer introduced into the Uquid will indicate a temperature of about 150° C.; oil of turpentine accordingly re- quires half as much again heat for boding as water. Other oils often boil with even more difficulty. The vapor may be inflamed by a taper, when it will burn with an intense sooty flame; it is easily extinguished by covering the vessel with a board, but water must on no account be employed for extinguishing burning oils. Then remove the oil from the fire ; after it is cold, mix it with some water, and again heat it; as long as any water is present, the temperature of the fluid will not rise above 100° C. The ascending vapor is a mix- ture of aeriform water and aeriform oil. The same thing occurs here as previously mentioned; the less vol- atile oil evaporates with the more easily volatile water. The oils remain unchanged at the boiling point of water, but at their own boiling point (140° to 200° C.) VOLATILE OILS. 563 they become not unfrequently somewhat empyreumat- ic; this is the reason why water is always added in the preparation of oils, and also in the redistillation of them (rectification). 560. Experiment. — Inflame some drops of oil of tur- pentine put upon a shaving, and also a piece of cam- phor laid upon water; both bodies will ignite, and burn with a highly luminous and sooty flame. The volatile oils are far more easily combustible than the fat oils, which in order to burn with a flame must be heated to 350° C. We have consequently in oil of turpentine a convenient means for speedily lighting oil-lamps; it being merely necessary to smear the wick with a few drops of it. Experiment — Pour a mixture of half an ounce of absolute alcohol with half a dram of oil of turpentine into a spirit-lamp ; the mixture gives, when lighted, a strongly ffluminating, but no longer a sooty flame, since all the carbon of the oil of turpentine is convert- ed by the heat of the burning alcohol, rich in hydrogen, into illuminating gas, and then into carbonic acid (and water). This mixture is now used in lamps construct- ed for the purpose, and which are so made that the liquid evaporates in them, and the vapor ignites as it issues from several small openings. 561. Volatile Oils and Water. — Experiment — Drop some oil of cumin upon water; the oil floats on the surface without mixing with the water, for most of the volatile oils are lighter than water; but there are some, such as oil of cinnamon, oil of cloves, and oil of bit- ter almonds, which are heavier than water, and sink in it. If the mixture is briskly shaken, the water becomes turbid, because the oil is thus divided into small, invis- 564 VEGETABLE MATTER. ible globules, which are kept suspended in the water. The water may be again clarified by filtration, but it retains the smell and taste of the oil, since a small quantity of it remains dissolved. Many such solutions are kept in the apothecaries' shops, under the name of medicated or distilled waters. It is well to keep them protected from the light, and in full vessels, — both light and air having a decomposing action on the vol- atile oils. They are commonly prepared by distilling with water the vegetable substance containing the oil, as thereby a more intimate combination of the water with the oil is effected than by merely shaking it up. 562. Volatile Oils and Alcohol. — Experiment — Add a drop of oil of cumin to one ounce of strong alcohol; it dissolves readily and entirely. All the vol- atile oils are soluble in alcohol, most of them in alco- hol of eighty per cent.; but the non-oxygenated oils, such as oil of turpentine, oil of lemons, &c, only in absolute alcohol. If an ounce of water, in which half an ounce of sugar has previously been dissolved, is added to the solution, we obtain cumin-cordial. In this manner, by the aid of various aromatic oils, the in- numerable cordials occurring in commerce are now gen- erally prepared (preparation of cordial in the cold way). They were formerly manufactured from aromatic seeds, flowers, herbs, &c, by pouring brandy over them, the brandy being afterwards distilled or drawn off, where- by a spirituous solution of volatile oils was likewise obtained. Experiment — If some drops of bergamot, orange- flower, lavender, or rosemary oils are dissolved in half an ounce of strong alcohol, we obtain a spirit of a very pleasant odor. In a similar way the innumerable kinds of perfumed waters are prepared, at the head of VOLATILE OILS. 565 which stands the well-known eau de Cologne. The fumigating spirit also, which, instead of the fumigating powder, is often sprinkled on a warm stove, has a similar composition. Camphor spirit, much used as an external remedy, is Ukewise a solution of camphor in alcohol. 563. The volatile oils are not only dissolved by al- cohol, but also by ether and concentrated acetic acid. A solution of oil of cloves, cinnamon, bergamot, and thyme, in acetic acid, is used as a perfumed vinegar, on account of its refreshing odor. The volatile oils may also be mixed with fat oils, and with some kinds of tallow and lard; hence by means of them an agreeable odor may be imparted to the latter, as, for instance, in hair oils, pomatum, &c, or grease-spots be dissolved and removed by them from various articles. Volatile oils mixed with alcohol yield, when shaken up with olive oil, a turbid, milky liquid, because the alcohol does not dissolve the oUve oil; this behaviour may be taken advantage of for testing the purity of mercantile oils. 564. Experiment. — Rub a piece of sugar some time on the rind of a fresh lemon ; the hard sugar tears the cells in which the oil of lemons is inclosed, and the oil is attracted into the pores of the sugar. This, when re- duced to powder, is called oleosaccharum. Such mix- tures are commonly prepared in pharmacy by triturat- ing together powdered sugar and volatffe oils. 565. Experiment. — If you add some drops of oil of turpentine to iodine, a brisk emission of sparks ensues, since a part of the hydrogen is expelled and replaced by the iodine. The same phenomenon is occasioned by all non-oxidized oils, but not by the oxidized; there- fore iodine may serve as a test, although not a very 48 566 VEGETABLE MATTER. accurate one, for ascertaining whether oils of the lat- ter class have been adulterated with oil of turpentine. 566. Conversion of the Volatile Oils into Resins. — Experiment. — Let some oil of turpentine remain ex- posed to the air for some weeks, in a cup covered with paper, and afterwards put the cup in a warm place to evaporate the oil; it will not entirely volatffize, but will leave at first a viscous, and afterwards a vitreous residue. This residue is resin. All volatile oils are converted into resin, because they gradually absorb oxy- gen from the air ; which, as in the case of the transfor- mation of alcohol into vinegar, first combines with a portion of the hydrogen of the oil, forming water, and then unites with the oil itself. Alcohol, on exposure to the air, is converted by the removal of hydrogen into aldehyde, then by the reception of oxygen into acetic acid; the volatile oils are, in a similar manner, first con- verted by the air into turpentine (mixtures of volatile oils and resin), and then into resins. Oil of turpentine consists of C10 Hi6; resin, of C10 H15 O ; consequently the former has only to relinquish one atom of hydrogen, and receive one atom of oxygen, to be converted into resin. This explains very simply why the volatile oils become gradually viscous and scentless on being kept, and more rapidly in large and only partiaUy filled bottles than in small ones, and why the drops running down on the outside of the bottles dry up first into a sticky, and then into a resinous mass. Old oil of turpentine is, for this reason, not suitable for removing grease- spots ; it dissolves, indeed, the fat or resin dried into the material, but leaves behind new spots of resin in their place. The volatile oils are very rapidly changed by nitric acid into non-volatile resinous substances. There are RESINS AND GUM-RESINS. 567 sometimes simultaneously formed, in this case, pecuUar organic acids; for example, turpentinic acid from oil of turpentine, camphoric acid from camphor, &c. Many such acids are also spontaneously generated together with resin, by long standing in the air; for instance, cinnamic acid in the oil of cinnamon; or are found al- ready formed in the volatile oils; as, for instance, cary- ophyllic acid in oil of cloves, &c. 567. Metallic arsenic has no smell; neither has ar- senious acid (arsenic combined with oxygen). We per- ceive the striking odor like that of garlic only at the very moment when the arsenic is combining with the oxygen. The same thing seems to happen with regard to the odor of volatile oils, so that we may assume that the odor is emitted because the offs are combining with the oxygen of the air, and while they are combining. Fresh oils, and those distilled by exclusion of air, and old resinous oils, either do not smeU at aU, or emit quite an unusual odor. XI. RESINS AND GUM-RESINS (Resinje et GUMMI-RESINJ2). 568. Turpentine and Balsams. — Whoever has been in a forest of fir or pine trees must certainly have no- ticed the yellow, transparent juice, having the consis- tency of honey, which exudes from these trees, and he may perhaps have observed also that it sticks to the fingers, and cannot be washed off again by mere water. This juice is turpentine. It is procured in large quan- tities by incisions made in the trees. That obtained from the European fir-trees is turbid, and has a thick 568 VEGETABLE MATTER. consistency; it is called common European turpentine; but Venice turpentine is the more transparent and more fluid sort, which is procured from larch-trees. A yet finer quality, yielded by the American silver-fir, is caUed Canada balsam. The term balsam is applied also to several other res- inous vegetable juices, which exude from some tropi- cal trees, or are boiled out from them. The best known are the yeUowish balsam of copaiba, an important med- icine, the blackish-brown balsam of Peru, and the brownish-gray balsam of storax (liquid storax), the last two of which are generally used for fumigating, on ac- count of their agreeable odor, which resembles that of vanilla. All these turpentines and balsams are to be regarded as solutions of resin in volatile oils, into which two constituents they are separated when distffled with water (§ 551). The same thing happens when they are aUowed to stand for some time in an open vessel in a warm place, except that in this case the oil volatiUzes, and diffuses itself in the air. 569. Preparation of the Resins. — Experiment. — Spread a little turpentine upon a board, and put the board for some time near a heated stove; the oil of tur- pentine evaporates, but the resin remains behind as an amorphous brittle mass. In some countries, incisions are made through the bark of the pine-trees, and the turpentine which exudes is allowed to evaporate on the trees themselves, and after it has been purified, by melting and straining through a colander, from the woody particles adhering to it, it is brought into mar- ket under the name of resin, white pitch, or Burgun- dy pitch. Large quantities of such resin are now ex- ported from the forests of America (American resin). RESINS AND GUM-RESINS. 569 Two different operations are going on during the evap- oration of the turpentine; a part of the volatile oil found in it evaporates, and occasions the peculiar smell of the pine forests, but another part attracts oxygen from the air, and is converted into resin (§ 556). Resinous juices, which harden in the air, forming solid resins, exude, either spontaneously or through in- cisions made for the purpose, not only from our fir- trees, but also from many other trees and shrubs, partic- ularly those of hot climates. Almost all the resins oc- curring in commerce are procured in this manner. Experiment. — Resin is deposited most abundantly in those parts of the trees where the branches join the trunk; wood 4fl impregnated with such resin is *-^' caUed resinous wood. If a piece of resinous wood is lighted at the upper end, and held by a wire in an oblique position over a basin of water, one portion of the resin burns up with a sooty flame, while an- other part is melted by the heat, and runs down into the vessel beneath. Resin is not sol- uble in water; hence it hardens in the latter without mixing with it. In this manner — by roasting— resins may be prepared from many plants ; but the color of the resins thus prepared is usually dark, because some of the resin has become burnt, and is thereby richer in carbon, according to the general law, that hydrogen is always burnt before carbon. Experiment. — Pour strong alcohol upon some res- inous wood, and let it remain for a day in a warm place; the resin is dissolved, and the woody fibre re- mains behind. The solution is poured into eight times 48* 570 VEGETABLE MATTER. its quantity of water, which is thereby rendered milky, because the resin is precipitated, but in such a state of fine division that it floats about in the water in the form of small globules. If this milky fluid is heated to the boiling point, the resinous particles soften and unite with each other in small lumps, which may be taken out and pressed together in larger masses. This is a third method of extracting resin from vegetable sub- stances. DIFFERENT SORTS OF RESIN. 570. The following are the most important resins: — Pine-resin is the resin of our pine-trees. Galipot is a very clear yellowish-white kind of pine- resin, imported from France. Copal is of a yellowish-white color, turning to brown, and very hard; it comes to us covered with sand and earth, from which it is freed by washing it with lye and by scraping. The copal of the West Indies and Africa has a smooth surface, but that of the East Indies is wrinkled and uneven. It is insoluble in common alco- hol, but it partly dissolves in absolute alcohol, and dis- solves entirely in ether; the East India copal dissolves the most readily. Dammar a resin (Kauri or Cowdee) is colorless or yellowish, tolerably hard; comes from the East Indies. Mastic is yellowish, transparent, comes in rounded tears, and exudes from a species of Pistacia, a tree growing principally in Greece. Sandarach, much resembling mastic, but yet more brittle, is the product of an evergreen tree which grows in Africa. Lac exudes from several species of Ficus growing in the East Indies, through punctures made by a small insect called the Coccus lacca. RESINS AND GUM-RESINS. 571 a.) Stick-lac is the name given to the juice dried upon the twigs. b.) Seed-lac, when it is broken off from the twigs. c.) Shellac, when it is melted and strained through a cloth to remove impurities. The liquefied resin is com- monly made to drop upon large leaves, and cooled; it thus spreads out into thin plates. The finest shellac has an orange color, that of inferior quality a dark- brown color. It is very hard and tenacious, and for this reason is generaUy used in the manufacture of sealing-wax. Benzoin flows from incisions made in a tree of the East Indies. The resin exuding during the first three years forms milk-white grains, but that formed after- wards is yellow or brown. Both sorts are kneaded to- gether; hence the amygdaline appearance of the com- mon benzoin. Its agreeable odor, somewhat like that of vanilla, has rendered it a popular ingredient in fu- migating pastilles, and also in cosmetic lotions for beautifying the skin. One sixth of it consists of ben- zoic acid. Dragon's-blood is a brownish-red colored resin; it is the produce of several palm-trees growing in the East Indies. Guaiacum, a brownish-green resin, and also an olive- colored variety of the same, are obtained by roasting guaiacum-wood, and are considerably used in medicine. Resin of jalap is extracted by alcohol from the root of the jalapa. Many other resins are used in pharmacy, for in- stance, anime, tacamahac, elemi, &c. 571. Bitumen.— Two other resins, amber and as- phaltum, which are obtained from the earth or from the sea, remain to be mentioned. 572 VEGETABLE MATTER. Amber probably proceeds from the forests of a pri- meval age, which have been submerged by floods of water. The resins form an exception to the general rule, — they do not putrefy or decay, like other organic bodies. The amber-resin might accordingly remain for centuries unchanged in the earth, or in the sea, while the trees from which it exuded were changed into mould and earth, or, chemically speaking, became de- composed into carbonic acid, water, &c. Amber is found most frequently in the Baltic and on its coasts, and in many brown-coal mines. Its hardness and te- nacity are well known, since it is formed into various articles which are usually manufactured from glass or horn. It differs from other resins, as it yields on fusion succinic acid, and undergoes a change, in consequence of which it then becomes soluble in alcohol and oils, which scarcely attack it in its unmelted state. By longer fusion it becomes black, and is then called amber-colophany; it yields, at the same time, a very disagreeably smelling empyreumatic oil, oil of amber, which is sometimes used in medicine. Asphaltum, or pitch of Judea, is likewise a mineral resin, which is found in many of the seas of Asia, par- ticularly in the Dead Sea. It has a black color, and great similarity to the black resin which is obtained by the evaporation of pit-coal tar (factitious asphal- tum). Asphaltum is found in other places, and has a soft consistency, and resembles turpentine (Barbadoes tar); this kind has in later times been mixed with sand and lime for making artificial pavements and tiles. It is very probable that these two resins, as also petroleum, are derived from layers of pit-coal which have been heated in the interior of the earth by vol- canic fires. RESINS AND GUM-RESINS. 573 572. Similar resinous substances, of a black color and disagreeable odor, are also artificially formed whenever animal and vegetable substances are heated with an insufficient supply of air, especially during dry distil- lation of the same. When in a fluid form the^ are called tar; in a solid form, black pitch. PROPERTIES OF RESIN. 573. It was stated when speaking of amber, that resins are substances which do not undergo decay; in- deed, they have the power to protect from decomposi- tion other bodies which very readily pass into decay or putrefaction, — for instance, flesh. On this account they were formerly used for embalming dead bodies, which are now found, after the lapse of centuries, dried to mummies, in the pyramids of Egypt. 574. Resin and Water. — The resins as a general rule are insoluble in water, and therefore tasteless ; but some of them in very small quantities may be dissolved, and these usually have a bitter taste. But many of the res- ins which occur in commerce contain some water in a state of minute division, and are thereby rendered dull and opaque; common pine-resin and boiled turpentine furnish examples of this. Colophony or Rosin. — Ex- periment — Heat a piece of the solid turpentine (§ 551), or else some pine-resin, in a spoon, till all the water is evaporated; the anhydrous res- in will now appear perfectly transparent. In this state it is called colophony, or rosin, ^* 574 VEGETABLE MATTER. being vdiite when it is moderately heated, but brown when the heat is so strong as to convert a part of the resin into black pitch. Colophony is so brittle, that it may easily be reduced to a powder. When the bow of a violin is rubbed with it, the rosin powder formed re- mains adhering to the fibres, and these then again ad- here better to the strings of the violin. A similar effect is produced on the cords which sustain the weights in clocks when they are rubbed with rosin to prevent their slipping. The resins, accordingly, exert an effect con- trary to that of oil; by resin, a rough, uneven surface is produced, by oil, a smooth, slippery surface. 575. Action of Heat on Resins. — The experiment first performed reveals at the same time another property of resin, namely, its easy fusibility. Most of the resins require, in order to become fluid, a heat which is some- what higher than that of boiling water. If the melted rosin is poured upon a board, it spreads, and forms after hardening a soUd, briUiant coating on the wood. The resins are hereby well adapted for protecting wood or metal from the penetration of air or "water. For this reason, iron rails and iron ornaments are covered with a coating of pitch, to prevent them from being so quickly oxidized by the oxygen of the air; for the same reason, also, wine-casks and beer-barrels are smeared with pitch, that no air may penetrate into the casks, and that no beer may penetrate into the staves. The wood-work of ships, the hatches, &c, are covered with tar to keep out the sea-water and rain ; and finally, also, the solid and tenacious resin, shellac, is employed in the form of sealing-wax as a protection against curiosity. Sealing-wax. — Experiment — Melt together in a small ladle one fourth of an ounce of pale shellac, one dram of turpentine, one dram of cinnabar, and three RESINS AND GU.M-RESINS. 575 fourths of a dram of prepared chalk ; scrape out the mass while yet ductile, and roll it out into sticks by the hands, moistened with water. The turpentine ren- ders the seaUng-wax more inflammable, and the cinna- bar imparts to it the favorite red color. Various other colors are given to it by chrome-yellow, azure-blue, mountain-green, lamp-black, bronze-powder, &c. 576. Rosin-gas. — Experiment. — When rosin is heat- ed above its melting point, it kindles and burns with a luminous and sooty flame, leaving behind some char- coal. Therefore powdered rosin, when blown into the flame of a lamp, burns vividly. In many places illu- minating gas is prepared from it, by letting it drop in a melted state upon coke, which is heated to redness in an iron cylinder (rosin-gas). Burnt Pitch. — If the rosin, after it has burnt for some time, is extinguished by putting a board over it, we shall have as a residuum a black, burnt resin, ship-pitch, and shoemaker's wax, possessing great tenacity. Lamp-black. — Experiment. — If you hold a cone made of blotting-paper over burning pine-wood, it will soon become Uned with soot. The well known lamp- black is prepared on a large scale by a similar method. Resinous wood, or the resin itself, is burnt with an in- sufficient supply of air in a stove furnished with long flues, or with a chamber in which the smoke deposits its carbon on its passage through. Experiment. — If some amber is scattered on glow- ing charcoal, a vapor having a pleasant balsamic odor is emitted from it as it smoulders away. Amber, frankincense, benzoin, and mastic are on this account frequently used for fumigating purposes. 577. Electrophorus. — Experiment. — Rub a stick of sealing-wax for some minutes upon a piece of cloth, 576 VEGETABLE MATTER. and then approach it to some smaU shreds of blotting- paper ; they will fly up to the sealing-wax, and remain adhering to it for some time. This attraction is effected by electricity (resinous or negative electricity), which is generated in the resins by. friction. If you pour a mix- ture of shellac and rosin into a tin plate in order to obtain a larger surface, you will be enabled to extract the electricity from it in the form of sparks, and to col- lect it; this is called an electrophorus (bearer of electri- city). This mysterious power has received the name of electricity from rfXcurpov, the Greek word for am- ber, in which the electrical phenomena were first ob- served. 578. Resin and Alcohol. — Experiment — Wrap half an ounce of sandarach in paper, and break it with a hammer into smaller pieces; then mix it with an eighth of an ounce of sand, which has been previously freed from its pulverulent particles by washing, and after- wards thoroughly dried, and pour the mixture into a glass vessel, with two ounces of strong alcohol. Tie a piece of bladder over the vessel, and let it remain for several days in a warm place, frequently stirring it round. The clear solution of resin thus obtained is called lac-varnish, because, when smeared over metal, wood, or paper, it leaves behind, after the alcohol has evaporated, a varnished, shining coat. If alcohol is poured upon the sandarach, unmixed with sand, the resinous powder wiU cake together on the bottom of the vessel, forming a tenacious mass of resin, which dissolves much more slowly. To varnish, then, is to smear the surface of any thing with resin. By this coat of varnish articles not only acquire a beautiful bril- liancy, but are rendered at the same time impervious to air and water. When paper articles — for instance, GUMS AND GUM-RESINS. 577 drawings, charts, &c. — are to receive a coat of varnish, glue or a solution of gum must previously be spread over them several times, as the solution of resin would otherwise penetrate into the fibres of the paper, and render it gray and transparent. This imbibition is usually prevented in wooden articles by smearing them with linseed oil before putting on the varnish. When the varnish is applied on places that are wet, white opaque spots are formed, because the resin is separated by the water as a dull white powder. Experiment.— Dissolve half an ounce of sheUac in strong alcohol; a turbid liquid is obtained, as the shel- lac contains, besides the resin, small quantities of wax and mucilaginous substances, which float about undis- solved in the solution of resin. This solution is also employed as a lac varnish, but much more frequently as the so-called polish of the cabinet-makers ; that is, as a solution of resin, which they rub continuously upon the wood with a ball of linen, until the alcohol has evaporated. By this means a yet smoother and finer polish is obtained than by merely applying the resinous solution .with a brush, the marks of which frequently remain visible. The finer articles of furniture are usually polished, the more ordinary ones varnished. 579. Resins and Oils. — Experiment. — Mix half an ounce of dammara resin with some sand, and pour over the mixture two ounces of oil of turpentine; after a few days you will obtain an almost complete solution, as the volatile oils are likewise able to dissolve resins. These solutions are also frequently employed as lac varnishes; they dry, indeed, more slowly, but form a more tenacious coating, which is less liable to crack. The paler and finer varieties of varnish are principally prepared from amber, copal, dammara, shellac, sanda- 49 578 VEGETABLE MATTER. rach, and mastic; the inferior and darker kinds, from amber-colophony, common colophony, turpentine, as- phaltum, &e. A yellow color is sometimes given to the pale varnishes by the addition of dragon's-blood, or gamboge. The resins are likewise soluble in fat oils. Many ointments and plasters of the apothecaries consist of mixtures of fats and resins, and it is the latter which communicate to the former the property of adhering to the skin. Turpentine is usually employed for this pur- pose. 580. Resinous Soap. — Experiment. — Boil in a jug a quarter of an ounce of rosin, with one ounce of strong potassa or soda lye, and then gradually add lye by spoonfuls, until a sample of the mixture dissolves in hot water, forming a clear liquid. The mass hardens, on cooling, into a solid soap (a compound of the resinous acid and potassa, or soda). The resins, as we see, comport themselves towards strong bases like the fat acids, and hence have an extensive application in the manufacture of soap, being mixed with the fats in dif- ferent proportions in the manufacture of the cheaper kinds of soap. Experiment — Mix a solution of resin soap with a solution of alum ; an insoluble combination of resinous acid and alumina is formed. Resin soap is employed for the sizing of paper; it is first introduced into the vat containing the pulpy mass of which the paper is to be made, and then the solution of alum is added. There is thus formed round each fibre of the paper a thin layer of insoluble alumina soap (resinous acid and alumina), which prevents the spreading of the ink. According to the old method, the sheets of paper were passed through a solution of glue, whereby only a thin GUMS AND GUM-RESIXS. 579 layer of glue was formed on the surface of the paper. This kind of paper allows the ink to spread, when the coat of glue has been scraped off by erasure ; but this may be prevented by rubbing some resin — sandarach is the best — upon the spots erased. Resins combine with bases, and their solutions red- den litmus-paper. Accordingly, they may be regarded as acids. 581. Composition of the Resins. — By alternate treat- ment of the resins with cold or hot, weak or strong al- cohol, or with ether, various kinds of resin may be ex- tracted from most of them, which have been designated by the terms alpha (a), beta (j9), or gamma (y) resins. The natural resins are accordingly to be regarded as mixtures of several simple resins. Only the three elements carbon, hydrogen, and oxy- gen (C, II, O) occur in the resins. That they contain somewhat more oxygen, and less hydrogen, than the volatile oils, has already been stated (§ 566) ; but, never- theless, they belong to the bodies rich in hydrogen, since they burn with a strong flame. GUM-RESLNS. 585. If you divide a stem of poppy, lettuce, or celan- dine, a white or yellow juice exudes, which dries up in the air or by the heat of the sun, forming a yellow or brown amorphous mass. This milky juice consists of a solution of gum, intimately mixed with minute drops of resin; thus it forms a natural emulsion. This kind of dried, half-resinous, half-gummy vegetable juice is called, from these two proximate constituents, gum-resin. Many plants of hot climates are especially rich in such resins, and from them are principally obtained the gum- 580 VEGETABLE MATTER. resins occurring in commerce, which have various ap- plications, particularly in pharmacy. Among the most important are, — Ammoniac (gum ammoniac), the inspissated milky juice of an African umbelliferous plant; it has a yel- lowish or brown color, and a strong, peculiar smell and taste. Assafcetida (stercus diaboli), the juice of a Persian umbelliferous plant, having a very unpleasant smell, like that of garlic; it has a milk-white appearance when freshly broken, but quickly changes in the air and light into a pink color. Aloes, which has a brown or black color, and is ex- ceedingly bitter; it is the dried juice of the aloe-plant, which grows in great abundance on the Cape of Good Hope and the adjacent islands. Euphorbium, which comes in brownish-yellow tears from the African plant Euphorbia Canariensis, and con- tains a very acrid substance, in consequence of which it vesicates the skin, and, when snuffed, excites inflam- mation of the nostrils and the most violent sneezing. Galbanum, a yellowish or brownish substance, having a strong and peculiar odor; it is obtained from an ever- green plant of Persia. Gamboge, which occurs in orange-colored masses or sticks ; it is obtained from the leaves of an East Indian plant, and is principally used as a yellow water-color in painting. Myrrh; the better sorts occur in pale, brownish-yellow fragments, the inferior sorts in dark brownish-red pieces; it has a bitter taste and a balsamic odor, and exudes from incisions made in a tree growing in Arabia. Frankincense (olibanum), which comes in yellowish- white, brittle, roundish fragments; the juice, inspis- GU.MS A.\D GUM-RESINS. 581 sated in the air, is obtained from a tree in Persia. It yields an agreeable odor upon glowing coals, and hence is much used for fumigating purposes. Opium, a milky juice, which exudes from incisions made in the heads of unripe poppies, and is inspissated by exposure to the air; it occurs in large lumps of a dark brown color, having a bitter taste and an offensive nar- cotic odor. The soporific effects of it are well known. Lactucarium, of a brown color, and having somewhat the odor of opium; it is the inspissated juice of several kinds of lettuce. Opoponax, Sagapenum, Scammony, and many others. PROPERTLES OF THE GUM-RESLNS. 583. Experiment. — Triturate some one of the gum- resins with water; the gum is hereby dissolved, and a turbid, milky liquid (emulsion) is obtained. If this is boiled for some time, the softened particles of resin cake together, and separate as lumps; the liquid, having be- come clear, contains now only the gum in solution. Experiment — If strong alcohol is poured over the gum-resins, and they are digested together for some time, the resin only is dissolved, while the gum remains undissolved. The well-known tincture of myrrh is a solution in alcohol of the resinous particles contained in the myrrh. Most of the gum-resins contain, besides resin and gum, a small quantity also of volatile oils, to which they owe their peculiar odor. CAOUTCHOUC (GUM ELASTIC). 584. There exudes from several large South Amer- ican trees, when incisions are made in them through 49* 582 VEGETABLE MATTER. the outer and inner bark, a milky juice, which dries in the air into a white elastic mass, quite insoluble in wa- ter and alcohol. It is gum elastic, or caoutchouc. The drying proceeds more rapidly when the milky juice is spread upon moulds of clay or Ume, and then suspended over a fire. If, after the gum is dry, the clay or lime is removed by washing, hoUow articles of caoutchouc are obtained, but which have a black or sooty appearance on account of the soot mixed with them. Experiment — Caoutchouc at the ordinary tempera- ture is hard and stiff, but it becomes soft when it is put into hot water or in a warm oven. Cut from one of „. „,. these caoutchouc bottles, softened Fig. 214. ' by heat, a square piece, apply it evenly round the ends of two glass tubes, and then cfip off with a pair of scissors the ends of the strip in the direction marked out in the annexed figure: the fresh surfaces of the caoutchouc adhere firmly to each other (but still more closely when they are pressed together with the nail, yet without touching the freshly cut surfaces), and Fig 215. thus is formed a tube, which, firm- ly tied at both ends, binds the two glass tubes air-tight with each other. In this manner, the glass tubes occurring in chemical apparatus are made pliant and flexible, and the risk of breaking them is thereby diminished. Experiment. — Pour some petroleum upon a few pieces of caoutchouc ; the caoutchouc will swell up in it, and may then be converted into a homogeneous mass. When melted with shellac, the mass affords a very permanent cement for wood, stone, and iron (ship- glue). :tEEh ca GUMS AND GUM-RESINS. 583 Experiment. — If ether, oil of turpentine, or oil of pit- coal tar is poured upon caoutchouc, a complete solu- tion is obtained. Solutions of this kind are now fre- quently employed for rendering fabrics waterproof (Mackintosh). When strongly heated with alcohol, caoutchouc forms a homogeneous, tenacious, black mass, which is very well adapted for smearing shoe- leather. Experiment — When caoutchouc is held in a burn- ing lamp, it takes fire and burns with a vivid, sooty flame, Uke petroleum or oil of turpentine, and melts into a black, glutinous residue. This melted caout- chouc is very serviceable for preventing the sticking of glass stoppers in bottles, in which lye, &c, is kept; the stoppers, when coated with it, remain lubricous for a long time. Caoutchouc acquires an extremely high degree of elasticity by intimately mixing it with sulphur, or sul- phuret of arsenic (vulcanized caoutchouc). Caoutchouc is one of the few solid bodies which con- tain no oxygen; it consists only of carbon and hydro- gen, so that it may be regarded, as it were, as con- densed petroleum, or as condensed iUuminating-gas. Gutla Percha. — Under this name, within a short time, a substance resembling caoutchouc has occurred in commerce, which is procured from the milky juice of several East Indian trees; it has the advantage over caoutchouc, that it becomes quite soft and plastic by moderate heating, but hard again on cooling, and has found already various applications in the arts. 584 VEGETABLE MATTER. RETROSPECT OF THE FATS, VOLATILE OILS, AND RESINS. 1. The fats, volatile oils, and resins are among the very generally diffused substances of the vegetable kingdom; most of them comport themselves like indif- ferent bodies, many like feeble acids. 2. As occurring in nature, they are mixtures of sev- eral similar substances with each other, which are, — a.) The fats ; mixtures of solid fats (stearine, marga- rine) and of fluid fats (oleine, glycerine). b.) The volatile oils; mixtures of solid stearoptene and fluid oleoptene. c.) The resins; mixtures of several different kinds of resin (alpha, beta, gamma resins, &c.). 3. As respects their elementary constitution, they consist only of the three elementary substances, carbon, oxygen, and hydrogen; but they are always poor in ox- ygen and rich in hydrogen. (Some volatile oils contain no oxygen.) 4. On account of the excess of hydrogen, — a.) They burn, when ignited, with a brisk flame, and yield, on decomposition by a glowing heat, much com- bustible gas. b.) Most of them are so light that they float upon water. c.) They are dissolved only in Uquids which are like- wise rich in hydrogen and poor in oxygen ; for instance, in alcohol and ether, but not in water. 5. They are either liquid, or are easily rendered so, even when gently heated. 6. The fats of animals have exactly the same consti- tution as the vegetable fats. 7. By the addition of oxygen many kinds of fat be- EXTRACTIVE MATTER. 585 come solid and hard (varnish oils), others, on the con- trary, become rancid without hardening (unctuous oils). 8. The fats are resolved, by strong inorganic bases, into peculiar acids insoluble in water (fat acids), and into an organic base (oxide of glyceryle). The sepa- rated fat acids hereby combine chemicaUy with the in- organic bases, forming soaps. The alkalies form, with the fat acids, soaps which are soluble in water; the ox- ides of the earths and metals, on the contrary, form soaps which are insoluble in water. 9. The volatile oils, by the addition of oxygen, pass into resins ; often also, at the same time, into acids. 10. The resins evince no great affinity for oxygen; at least they do not alter, however long they may be ex- posed to the air. 11. Many of the resins combine with the alkalies, forming soaps soluble in water; with the earths and metallic oxides, forming soaps insoluble in water (resin- ous soaps). 12. Balsams are mixtures of resins with volatile oils ; gum-resins are mixtures of resins with gum. XII. EXTRACTIVE MATTER. 585. Extracts. — The vegetable substances hitherto considered are, if we except the volatile oils and some resins, mostly without taste and without any striking medicinal effect; most of them occur very generally dif- fused in the vegetable kingdom, and are found in al- most all vegetables. But we observe in many plants a peculiar taste, and when swaUowed a peculiar effect 586 VEGETABLE MATTER. upon our bodies; consequently, there must be other special substances present, from which the taste and effect proceed. Wormwood and rhubarb have a bit- ter taste, pepper and henbane a pungent and sharp taste, the roots of couch-grass and of liquorice a sweet taste. When introduced into the stomach, wormwood is stomachic, rhubarb purgative, pepper stimulating, henbane narcotic, &c. These and similar actions must, even at an early period, have excited the attention of man, and led him to extract the tasting and medicinal principles from the plants, and to use them in med- icine. This extraction was effected in a simple man- ner, from the juicy parts of the plants by expression; from the drier parts, by treating them with cold water (maceration), or with hot water (infusion), or by boil- ing them with water (decoction). As the vegetable juices or extracts would soon become sour or mouldy, the water is evaporated away ; by this means, a pulpy or pasty mass, or, on more complete desiccation, a solid amorphous mass, is obtained, which is called an extract (watery extracts), and may be kept for years unchanged and undecomposed. Sometimes, instead of water, al- cohol or ether is used as a solvent (alcoholic and ethe- real extracts). Many of these extracts are always kept on hand by the apothecaries as medicines, and one ounce of them frequently contains as much active matter as one pound, or even several pounds, of the vegetable substance from which they were prepared. It has already been stated, that most of the vegetable juices contain sometimes larger, sometimes smaller, quantities of starch (sediment), mucus, gum, sugar, tannin, chlorophyU, vegetable albumen, salts, acids, &c.; hence, all these substances do not volatilize on evaporation, but some of them must also be present in EXTRACTIVE MATTER. 587 the watery extracts. It is likewise clear, that in the spirituous and ethereal extracts all those substances which can be dissolved from the vegetable substances acted upon by either alcohol or ether must be present; for example, resins, fats, &c. The extracts may, ac- cordingly, be regarded as mixtures of various kinds of vegetable matter, as mixtures of known with unknown vegetable matter, of that having taste with that having no taste, of the active with the inert, of the colorless with the colored, &c. 586. Extractive Matter. — On closer examination of the vegetable juices or extracts, it has been found that after the known substances, such as starch, sugar, albu- men, &c, have been removed from them, a brown or black uncrystallizable, soluble mass remains behind, which generally possesses in a greater degree the taste and the medicinal effect of the plant from which it has been extracted. This mass is called extractive matter, and is distinguished by the following and other prop- erties : — bitter (in wormwood, buckbean, aloes, colo- cynth, &c), aromatic bitter (in the root of the sweet- flag, in hops, &c), acrid (in senega-root, soapwort, &c), meet (in Uquorice-root, root of couch-grass, &c), nar- cotic (in hemlock, henbane, &c). The name was ob- viously a very convenient one, since it applied to aU the innumerable vegetable substances not thoroughly examined, which possessed a dark color and did not crystallize, however different might be their chemical constitution. How great this difference may be we in- fer from this, that most vegetable substances, for in- stance, sugar and gum, when they are boiled for a long time, or merely exposed to the air, are converted into brown, uncrystallizable compounds. 587. The reason why all extracts have a brown or a 588 VEGETABLE MATTER. black color is to be sought for in this ready changeable- ness of vegetable matter. Experiment — Pour upon some ounces of sliced Uquorice-root»six times the quantity of boiUng water, and, after it has stood for some days, express the Uquid; when this has been filtered through blotting-paper, it is clear, transparent, and of a sherry-wine color. Upon evaporation, we obtain from it a black extract, the weU- known Spanish liquorice, which, when redissolved in water, no longer yields a yellowish, but a dark-brown liquid. Not only the color, but the taste also, has per- ceptibly changed. Both changes clearly show, that during the evaporation a chemical decomposition of the dissolved matter has taken place. It is very simi- lar to that which happens during the putrefaction or slow oxidation of wood; namely, oxygen is absorbed from the air, and some hydrogen and carbon are hereby oxidized into water and carbonic acid, whereby sub- stances similar to humus, richer in carbon, and con- sequently darker-colored, are formed. These are in part dissolved in the water, and cause the dark color of the liquid; but they are in part no longer soluble, and therefore separate from the solution as a dark-colored sediment. This sediment has been designated by the likewise very indefinite term, oxidized extractive matter. From this it results as a general rule in the preparation of extracts, that the evaporation of the vegetable juices should be conducted, if possible, with exclusion of air, and at a gentle heat; it is best done over the water- bath. 588. Crystallizable Extractive Matter. — In modern times, several of these peculiar substances have been ob- tained in a crystalline form, consequently as fixed and independent compounds. Many of these behave very EXTRACTIVE MATTER. 589 much like the inorganic bases (potassa, soda, ammonia, &c.); that is, they are able to neutralize acids and to form salts with them: these are the organic bases (§ 596). Others, on the contrary, possess neither basic nor ac,id properties, — they are indifferent, and may be called crystallizable extractive substances, at least until their chemical behaviour shall have been more accu- rately ascertained by further investigations. As yet, too Uttle is known about them to enable us to express any decided opinion concerning them. The number of the plants now known exceeds a hundred thousand, and it. is not improbable that extractive matter is to be found in most of them ; consequently they present a fine field for new discoveries. After what has been said, we may include under the term extractive matter all sorts of chemical substances of indifferent crystalliza- ble, and of indifferent brown, uncrystallizable matter, to which in most cases we ascribe the peculiar taste and the peculiar medicinal effects of plants. Most of them are characterized by a bitter taste, and hence are fre- quently called bitter substances. Some of them, name- ly, those which are insoluble in water, do not evince the taste peculiar to them until they are dissolved in some other liquid, for instance, in alcohol or ether. 589. The best known of these peculiar substances will now be briefly referred to. Their names (as also the names of coloring matters and of the organic bases) are usually formed from the Latin names of the plants, with the addition of the affix in or ine. Absinthine, from wormwood, very bitter; a colorless crystalline mass. Amygdaline, from the bitter almonds, slightly bitter, crystallizes in lustrous silky scales; it has the very re- markable property of being converted into a volatile oil 50 590 VEGETABLE MATTER. containing prussic acid (oil of bitter almonds) when it is mixed with dissolved vegetable albumen. Centaurine, from the Chironia centaurium, bitter; as yet only known as an extract. Cetrarine, from Iceland moss, bitter; a white powder. Columbine, from columbo-root, very bitter, erystaffizes in white prisms. Gentianine, from gentian-root, very bitter, erystaffizes in yellow needles. Imperatorine, from masterwort, very acrid and burn- ing ; in white crystals. Lupuline, from hops, an agreeable bitter; a white or yellowish powder. Meconine, from opium (poppy-juice), acrid to the taste ; in white crystals. Picrotoxine, from the seeds of the Cocculus Indicus, very bitter, narcotic, and poisonous; in white needles. Quassine, from the wood of the quassia, very bitter; in white crystals. Santonine, from worm-seed, bitter, in white crystals. Scillitine, from squill, nauseously bitter; a white amorphous mass. Senegine, from senega-root, acrid and astringent; a white powder. Glycyrrhizine, from liquorice-root, very sweet; a pale-brown amorphous mass. Populine, from the leaves and bark of the poplar, sweet; crystallizable in white needles. Asparagine, from asparagus, having an insipid taste; in white crystals. Smilacine, from the root of the sarsaparilla, tasteless; in white crystals. COLORING MATTER. 591 By far the greater proportion of these substances con- sist of the three elements carbon, hydrogen, and oxygen; some few only contain also a little nitrogen. XIII. COLORING MATTER, OR PIGMENTS. 590. When the peculiar substances which have been treated of in the previous section, under the name of ex- tractive matters, are themselves colored, or become so by the action of other substances, they are called coloring matter, or pigments. Most of those colors whose inim- itable splendor and variety we admire in the flowers of plants are so exceedingly evanescent, that they fade or disappear on withering or drying, and very rapidly, especially when they are exposed at the same time to the sunshine. The same happens when we attempt to extract or separate the coloring matter by expression, or in some other way. A few plants only contain, some- times in the roots or the wood, sometimes in the leaves or fruit, coloring juices of such permanency that they are more difficultly and slowly decomposed by the light; these may be extracted, and then employed for coloring other substances. These colors, however, are turned white by chlorine or sulphurous acid (bleached). Their extraction may be effected in most cases by water, sometimes also by alcohol or other liquids. As some extractive substances in the former section have been obtained in a crystaUine form, so also crystallized coloring substances have been separated from colored extractive matter; but other coloring principles, on the contrary, are only known in the form of extracts. The names which have been given to these coloring sub- 592 VEGETABLE MATTER. stances likewise terminate in ine, and are included in parentheses in the following list of the most impor- tant vegetable coloring matters. 591. Red and Violet Coloring Substances. a.) Madder is the ground-up root of the Rubia tinc- torum. The fresh root looks yellow, but when exposed to the air it becomes red, owing to the absorption of oxygen, and yields a superior permanent or fast red color in dyeing, for instance, the briUiant Turkey-red; also beautiful varnish colors, such as madder-varnish. (Coloring matter, Alizarine, or madder-red, crystallizes in yellowish-red needles, soluble in boiling water.) Madder contains, moreover, a yellow, an orange, and a brown coloring matter. b.) Brazil-wood (Fernambuca), from the heart-wood of several trees growing in South America, imparts to different materials a beautiful but not very permanent (not fast) red color. It is employed also in the prep- aration of red ink, of drop-lake, &c. (Coloring matter, Braziline, crystallizes in orange-colored needles, easily soluble in water.) c.) Saffiower, the flowers of the dyer's saffron, are used for obtaining a brilliant rose-color (for pink-sau- cers). (Coloring matter, Carthamine, soluble in water.) d.) The alkanet-root contains in its bark a resinous coloring matter, which is consequently not soluble in water; cloth is dyed violet with it, but alcohol, oils (as petroleum), and fats (as lip-salve), are colored pink with it. e.) Sandal-wood (red sanders-wood), the rasped blood-red wood of a tree growing in the East Indies, contains likewise a red, resinous coloring matter (Sau- taline). COLORING MATTER. 593 /.) The red pigments occurring in many fruits, as, for instance, cherries, raspberries, &c, are but slightly durable, and only used for coloring confectionery, cor- dials, &c. g.) Cochineal is a dried insect, which is brought to us from Mexico. The weff-known red carmine is obtained from it, and in dyeing establishments a very brilliant scarlet and purple red is prepared from it. (Cochineal- red, reddish-purple, crystalline grains.) h.) Lac-lake, or lac-dye, is a reddish-black, resinous mass, which is obtained in the preparation of shellac (§ 570); it contains a red coloring matter very similar to cochineal-red. 592. Yellow Coloring Substances. a.) Fustic is the rasped trunk-wood of a mulberry- tree growing in the West Indies. (Morine, crystallizes in yellow needles, soluble in water.) b.) Quercitron, a nankeen-yellow powder, mixed with fibrous fragments, is obtained from the bark of the black oak, a tree of North America. (Quercitrine, a yellow powder, soluble in water.) c.) Buckthorn, Persian, or French berries are the fruit of the buckthorn, growing in warm countries, and gathered before they are ripe. (Coloring matter only known as an extract, soluble in water.) d.) Weld and dyer's weed are the names given to the Reseda luteola, dried after it has done blooming. (Lu- teoline, crystallizes in yellow needles, soluble in water.) The four last-mentioned coloring substances are principally used for dyeing silk, wool, cotton, and other materials, yellow. e.) Annotto, orleana, occurs as a brownish-red paste, which is prepared from the pulp surrounding the seeds 50* 594 VEGETABLE MATTER. of the Bixa Orellana, and contains two coloring princi- ples, a yellow and a red. The former is dissolved when the annotto is boiled with water, the latter on boiling it with a weak lye (Orelline). f.) Turmeric, the root of a plant growing in the East Indies, is very rich in a resinous yellow pigment, which is colored brownish-red by alkaUes. Paper stained with it may therefore be used like red litmus-paper for de- tecting alkaUes. (Curcumine, an amorphous yellow mass.) g.) Saffron consists of the dried stigmas of the flow- ers of the Crocus sativus. Its application, in coloring articles of food and cordials yellow, is weU enough known. (Polychroite.) 593. Green Coloring Substances. Leaf-green (chlorophyll) is one of the most widely diffused substances in the vegetable kingdom, since it occurs in all parts of the plant which possess a green color. As found in plants, it is a mixture of wax and of several coloring matters not well known. It need hardly be said, that it is not soluble in water; for if it were, the water would become green on flowing over meadows. The expressed juices of the herbs are in- deed green, but it is obvious from their turbidness that the leaf-green is only mechanically mixed with the liquid. We become still more fully convinced of this by the separation of the coloring matter which takes place when the juices are boiled, or aUowed to remain for some time in repose. If, on the other hand, alcohol, ether, or weak lye, is poured on the green leaves, we obtain green solutions; hence all the tinctures of phar- macy which are prepared from leaves or stalks have a green color. The green color appears only in those COLORING MATTER. 595 parts of the plant which are exposed to the light; it is obvious from this, that the chemical compound which we caU chlorophyll is only generated with the coopera- tion of light. When separated from plants, this color- ing matter is very soon decomposed; it is, therefore, not at all suited for a coloring substance, except, perhaps, for cordials and other liquids. In the autumn it is con- verted in the leaves themselves into leaf-yeUow and leaf-red, probably by a process of oxidation. Sap-green is an extract prepared from the juice of the buckthorn berries, by the addition of alum. 594. Blue Coloring Substances. Indigo. — Several plants of hot cUmates contain a colorless juice, from which, after standing in the air and abstracting oxygen from it, a blue sediment is depos- ited, that, when dried, forms the well-known indigo. This substance, very important to science and the arts, usually occurs in commerce in deep blue, friable cakes, which exhibit, when rubbed by the nail, a coppery color and lustre. Its brilliant blue coloring matter is called indigo-blue; but besides this, the crude indigo contains other foreign substances, such as indigo-gluten, indigo-brown, indigo-red. Indigo is quite insoluble in water, alcohol, ether, &c.; there is only one liquid known which can dissolve it, fuming sulphuric acid (§ 170). The indigo-blue chem- ically combines with the sulphuric acid, forming a blue compound soluble in water, which is called sulphin- digotic acid. What we caU tincture of indigo is prin- cipally a mixture of water, sulphindigotic acid, and free sulphuric acid. The sulphindigotic acid combines like a simple acid with bases, forming salts. The best known of these 596 VEGETABLE MATTER. salts is sulphindigotate of potassa (blue carmine), which is obtained as a deep blue precipitate when the sulphin- digotic acid is neutrafized by potassa. The blue car- mine is indeed soluble in pure water, but not in water containing a salt in solution. Deoxidation of Indigo. — We can also, but in a very different way, render indigo soluble, by mixing it with bodies which have a very great affinity for oxygen ; for instance, with protoxide of iron, protoxide of tin, &c. Experiment — Triturate half a dram of finely pow- dered indigo, with half a dram of green vitriol, and one dram and a half of slaked Ume ; shake up the mixture in a four-ounce bottle; then, having filled the bottle with water and closed it tightly, let it stand for several days; the indigo graduaUy loses its blue color, and dissolves into a clear yellowish liquid. The body which effects the decoloration is the protoxide of iron, which is separated by means of the lime from the green vitriol. This attracts oxygen from the indigo, whereby the latter becomes colorless and soluble in Ume-water (reduced indigo). As soon as the clear liquid is exposed to the air, it again attracts oxygen and becomes blue. If you saturate a piece of blotting-paper with the liquid, and then dry it in the air, it first be- comes green, and then blue, and the blue color formed adheres quite firmly, since it has not only settled upon but in the fibres of the paper. In dyeing establish- ments, such a solution of indigo is called the cold vat. Another method of rendering indigo soluble is by add- ing it, together with hot water, to a mixture of bran, woad, madder, &c, which (carbonate of potassa and lime being present) passes into fermentation. The fermentation is partly acid, and partly putrid; in both processes oxygen is required, which is in part taken COLORING MATTER. 597 from the indigo. The deoxidized, colorless indigo dis- solves in the alkafine liquid (warm vat). By treating indigo with bodies which readily part with oxygen, for instance, with nitric acid, chromic acid, &c, we have in modern times become acquainted with some very interesting products of oxidation (isatine, isatinic acid, anilic acid, picric acid, &c). Wood is a European plant, which Ukewise contains indigo, but in far less quantities than the foreign in- digo plants. Logwood, or Campeachy-wood, the reddish-brown in- terior wood of a tree of tropical America, is one of the most common coloring matters for dyeing blue, violet, and black. (Hematoxyline, in yellowish crystals, which become speedily violet and blue in the air, owing to the ammonia always contained in the latter.) Archil. — Several species of lichens, growing on the rocks in England and France, contain pecuUar sub- stances (orcine, erythrine, &c), which, although in themselves colorless, acquire a beautiful purple-red color when they are acted upon by ammonia. It is com- mon to putrefy the bruised lichens with urine, and then a red or violet-colored paste is obtained (cudbear, persio, orchil). By the addition of lime or potassa, this red is changed into blue (litmus). We have examples of both these coloring matters in red and blue test- paper. 595. Experiments with Coloring Substances. Experiment a. — Take up some sandal-wood on the point of a knife and put it on a filter, and pour over it some alcohol; the alcohol which passes through has a red color, and, when poured upon a piece of wood, im- parts to it an intense blood-red color. Cabinet-makers 598 VEGETABLE MATTER. frequently employ this solution for staining furniture. Alcohol acquires a pink color when a small piece of alkanet-root is put into it. Water wiU not extract a red pigment from either of these substances. Those coloring matters which are soluble only in alcohol are called resinous. Experiment b. — Boil for some time in a jar, — 1st, French berries; 2d, Brazil-wood; and 3d, logwood; each separately, with twrelve times its amount of water ; the decanted decoction of the first is yellow, of the second reddish-yeUow, and of the third brownish-red; a sufficient proof that the coloring matters con- tained in these substances have been dissolved in the water. Dyers call these colored decoctions baths. Experiment c. — Divide these coloring decoctions into two equal parts. Dissolve a quarter of an ounce of alum in one of each of the parts, and then add to them a solution of carbonate of potassa, as long as any pre- cipitate subsides. As was stated in § 260, the hydrate of alumina is precipitated ; but, together with this, the coloring matter is also precipitated, and hence the pre- cipitates are colored. These precipitates are called lakes. The lake obtained from the French berries oc- curs in commerce under the name of yellow lake, that from Brazil-wood as drop-lake. Experiment d. — Prepare a solution of alum (a), another of salt of tin (b), a third of green vitriol (c), a fourth of carbonate of potassa (d), a fifth of tartaric acid (e), and saturate a sheet of white blotting-paper with each solution. When dry, cut each sheet into three strips, smear one of the strips from each sheet with the COLORING MATTER. 599 fustic, another of them with the Brazil-wood, and the third set with the logwood decoction, and again dry them. You wiff find that one and the same coloring matter produces a different color, or shade of color, upon each of the five sheets. This color will be very slight when the colored decoctions are applied to mere blot- ting-paper (/). If you now immerse the colored and dried strips in warm water, the colors will be for the most part dissolved from the three last tests (d, e,f), but not from the former (a, b, c). Those salts which, like alum, salt of tin, and green vitriol, have the power of forming insoluble combinations with the coloring matters, and fixing them firmly in the fibres of the cloth, are called mordants, and are generally employed in dye- ing and calico-printing establishments, to fix the pig- ments upon the various materials, such as silk, wool, cot- ton, linen, &c. That which effects the coloring is an insoluble lake color, that is, a combination of the color- ing matter with alumina, peroxide of tin, or sesquioxide of iron, but which, in order that it may adhere firmly, must first be formed within the pores of the vegetable fibre. If it is formed on the outside of them, it only covers the fibres externaUy, and then merely adheres mechanically upon them; such a color may be removed from the material by rubbing, shaking, and also by washing. The process pursued in the printing of calico, &c, is very similar, with this difference, however, that the mordants are only appUed in spots, or else the whole of the cloth is first covered with the mordant, which is again removed in spots (§ 197). When a piece of cloth thus treated is immersed in the coloring decoction, the coloring matter will be precipitated only in those places covered with the mordant, and thus, instead of one un- 600 VEGETABLE MATTER. interrupted homogeneous color, an interrupted color is obtained, presenting a pattern. XIV. ORGANIC BASES, OR VEGETABLE BASES (ALKALOIDS). 596. It has already been mentioned, under the head of extractive matter, that many plants contain peculiar substances, which, like the inorganic bases, can combine with acids, forming salts; they are called organic bases. Many of them, also, like the alkalies, exert a basic re- action upon red test-paper ; hence the second name, al- kaloids. The organic bases are to the inorganic bases what the organic acids are to the inorganic acids. The organic bases are composed of two, commonly of four elements (carbon, hydrogen, oxygen, and nitrogen), the inorganic of two elements only; they are charred and consumed by heat, — the inorganic bases are not; they undergo, in the presence of water and heat, a pu- trefactive decomposition, — the inorganic bases do not. They are characterized by containing, almost without exception, nitrogen in their composition. Almost all organic bases dissolve with difficulty, or not at all, in water, but more readily in alcohol; their solutions have commonly a very bitter taste. As a general rule, they dissolve, when combined with acids as salts much more easily in water, than they do when in their simple condition. Most of the organic bases known at present are de- rived from those plants which are characterized by their poisonous qualities or by their medicinal effects, and we have strong reasons for attributing to them the poi- ORGANIC BASES. 601 sonous and medicinal properties of the plants. Many of them are virulent and dangerous poisons; but in very small doses they are energetic medicines. One grain frequently possesses the same medicinal power as an ounce, or even several ounces, of the vegetable sub- stances from which they were obtained. The vegetable bases, when they are dissolved, are almost without exception precipitated by tannic acid as nearly or entirely insoluble tannates, for which rea- . son liquids containing tannic acid, such as tincture of i gall-nuts, decoction of green tea, or of oak-bark, &c, are not only employed as reagents for detecting vege- table bases, but also as efficient antidotes in cases of ^ poisoning by them. The vegetable bases occur generally in combination ^.- with vegetable acids. They are separated from these ^ acids, and extracted from the vegetable matter, by add- f ing to the latter some water, and an acid which is ' stronger than the vegetable acid and forms with the '. base an easily soluble salt (muriatic acid, sulphuric acid, &c). If an inorganic base (potassa, lime, ammo- nia, magnesia, &c.) is added to the acid solution, the . organic base is then precipitated. But there are also ,; numerous other methods of preparing these bases ; all of them, however, are long and complicated, for the reason that many other substances are also extracted ^ from the plants at the same time with the bases, which, jxs. very many cases, can be separated and purified only s by laborious operations. 597. Some of the most important organic bases are: — Aconiline, from the Aconitum napellus (monk's- hood), a white, granular powder, extremely poisonous; sV of a grain wHl kill a sparrow. 51 602 VEGETABLE MATTER. Atropine, from the root of the belladonna (deadly nightshade); it crystallizes in white silky prisms; very poisonous. Chelidonine, from the celandine; crystallizes in color- less tables. Quinine is found combined with kinic acid, chiefly in the crown-bark and in the CaUsaya-bark, and crystal- lizes in silky needles ; but it also occurs under the name of quinoidine in the amorphous state, as a dark-brown resinous mass, and is a very important medicine. The basic sulphate of quinine, which occurs in white needles, is most commonly used in medicine. This is very difficultly soluble in water, but is very readily dissolved in it when sufficient sulphuric acid is added to convert it into neutral sulphate of quinine. Another base, very similar to quinine, occurs in the gray cinchona-bark; it crystallizes in white prisms, and has received the name cinchonine. Caffeine, or theine, from the unroasted coffee-bean, or the so-called green tea; crystalUzes in fine white prisms of a silky lustre. Colchicine, from meadow-saffron; crystaUizes in white needles; it causes, when taken, the most violent vomit- ing. Daturine, from the seeds of the thorn-apple, in color- less crystals; highly poisonous. Emetine (from ipecacuanha) occurs when pure as a white powder, when impure as a brown extract; a powerful emetic. Hyoscyamine, from henbane, in radiated groups of white needles; a narcotic poison. The Alkaloid of Opium. About forty years ago the first vegetable base was discovered in opium, — the in- spissated juice of the poppy, — and was called morphine. ORGANIC BASES. 603 It exists in opium combined with meconic acid, and crystallizes in colorless prisms; narcotic and poisonous; in small doses, a very valuable remedy. The acetate of morphine* is much used in medicine. By later investigations there have also been found in opium pseudo-morphine, narcotine, narceine, codeine, and the- baine. Piperine, from white, black, and long pepper; in white crystaUine needles. Solanine, from several species of the solanum, par- ticularly from the white sprouts of the potato; as a white powder, or in crystaUine, colorless needles; a narcotic poison. Strychnine, from the nux-vomica (the seeds of the Strychnos nux-vomica), and from the Indian arrow- poison ; crystalfizes in prisms or octahedrons; very poisonous. There is another base, brucine, occurring along with it. Veratrine, from white hellebore, and the seeds of the sabadffla; a lustrous white powder, extremely poison- ous; when introduced into the nostrils, it excites the most violent sneezing; TV of a grain will kill a cat. The following are volatile and Uquid: — Conicine, from hemlock, principally from the seeds; a colorless oily liquid, of a nauseous, strong odor; very poisonous. Nicotine, from the leaves of the tobacco, colorless, oily, having a smeU like that of tobacco. Highly poi- sonous ; one fourth of a drop will kiU a rabbit. Vegetable bases may also be artificiaUy produced, for instance, — Aniline, from indigo, or from pit-coal tar. Siiiammiue, from mustard, Sec. * In this country the sulphate is most generally employed. 604 VEGETABLE MATTER. RETROSPECT OF THE EXTRACTIVE AND COLORING SUBSTANCES, AND OF THE VEGETABLE BASES. 1. Besides the generally diffused vegetable substances, there occur in almost every plant peculiar principles, upon which, in many cases, the effect, taste, and color, of these plants depend. 2. We find these peculiar principles mixed with va- rious other substances in the inspissated vegetable juices, the so-called extracts. 3. Many of them are non-azotized, others azotized, and still others contain at the same time sulphur. 4. Those combinations which are indifferent, and have no prominent color, are called extractive matter; they are also called bitter-extractive, because they have, for the most part, a bitter taste. 5. Coloring matter is extractive matter which has an absolute inherent color, or is converted by the action of other bodies into colored combinations; it is quickly rendered colorless by chlorine, slowly by Ught and air (bleached). 6. Coloring matter presents a great affinity for some bases, especially for alumina, sesquioxide of iron, and peroxide of tin, and forms with them insoluble col- ored compounds (lake-colors); in dyeing and calico- printing these insoluble precipitates are produced in the fibres of the yarn or material. 7. The vegetable bases can, like potassa or soda, com- bine with acids, forming salts; many of them also exert an alkaUne reaction; most of them are difficultly sol- uble in water, but easily soluble in alcohol. 8. The vegetable bases occur principally in those plants which are characterized by particular poisonous or medi- cinal qualities. Many of them are very violent poisons. 9. Almost all vegetable bases contain nitrogen. ORGANIC ACIDS. 605 XV. ORGANIC ACIDS. 598. The organic acids are found much more fre- quently, and in greater abundance, than the organic bases, in the vegetable kingdom. Several of them occur uncombined, or as acid salts; hence the acid taste which we perceive in so many vegetable substances, especially in unripe fruits. They are frequently, also, completely neutralized by bases, or are insoluble, as in the resins, and in both these cases they are not recognized by the taste. Besides these acids occurring in nature, many also have been discovered, which may be artificially pro- duced from other non-acid vegetable substances; thus, oxalic acid and formic acid are prepared from sugar, acetic acid from alcohol, the fat acids from fats, &c. The general properties of these acids have already been mentioned (§193, &c.); we shall here notice only those which are best known. 599. Racemic acid occurs in the juice of many grapes, and crystallizes like tartaric acid, to which it is very similar, in colorless, very acid-tasted prisms. 600. Citric acid exists in the juice of lemons, and also in that of currants, gooseberries, and many other fruits. By evaporating the juice of the lemon, we only obtain an acid brown extract, because all the other non- volatile constituents, as well as the citric acid, remain behind; but if the juice is neutraUzed with chalk, a difficultly soluble citrate of lime is precipitated, while the foreign substances remain for the most part in solu- tion. We obtain from citrate of lime, by decomposi- tion with diluted sulphuric acid, gypsum and a solu- tion of citric acid, which yields on evaporation colorless prismatic crystals. A mixture of the pleasant acidu- 51* 606 VEGETABLE MATTER. lous-tasting citric acid (or tartaric acid) with sugar is called lemonade-powder. By moderate heating, the citric acid passes into aconitic acid, an acid which also occurs native in monk's-hood. 601. Malic acid is obtained from sour apples, ber- ries of the mountain-ash, and many other plants; it is very deliquescent, and therefore is difficult of crys- tallization. Malic, citric, and tartaric acids are found associated together in almost aU acid fruits. 602. Formic acid occurs in ants, but may be arti- ficially produced from almost aU vegetable matters, when they are treated with bodies rich in oxygen; for instance, nitric acid, chromic acid, black oxide of man- ganese, or sulphuric acid. It is a volatile, colorless Uquid, of a very acid taste, and a very pungent odor. 603. Tannic acid (tannin) is the general name given to that substance, of very frequent occurrence in plants, especially in the barks of trees, which imparts to them the well-known puckering and astringent taste. It is regarded as an acid, because it has an acid reaction, and can combine with bases. These acids are divided, ac- cording to the plants in which they occur, into querci- tannic, mimotannic, &c. acids. The querciiannic acid, wmich is found most abundantly in nut-galls and in the bark of young oak-trees, is best known. In the pure state it forms a white or yellowish gum-Uke mass, which is very easily dissolved in water and alcohol. It forms the principal constituent in the tincture of nut- galls. There are two properties which especially char- acterize tannic acid, and have stamped it as an ex- tremely important substance in the arts: — a.) It yields, with salts of sesquioxide of iron, a blue-black precipitate of tannate of sesquioxide of iron (§ 285), and therefore is generally employed for dyeing ORGANIC ACIDS. 607 all kinds of materials with a gray or black color, and for the preparation of ink, &c. b.) It combines, moreover, with the skin of animals, forming a combination insoluble in water, and no longer subject to putrefaction, — leather; hence the name tannin, and hence the extensive application of the vegetable substances containing tannin (bark of the oak, pine, birch trees, &c.) in the tanner's trade. 604. If a solution of tannic acid remains for a long time exposed to the air, it will be converted into two new acids, gallic and ellagic acids. Consequently, both are to be found in tincture of nut-galls, and in ink, which have been kept for some length of time. Gallic acid crystallizes in white needles or prisms; its solution yields, like tannic acid, a blue-black precipitate with salts of sesquioxide of iron, but it does not tan the skins of animals. 605. Substances containing Tannin. — The following are the principal dye-stuffs and tanning substances which occur in commerce. a.) Nut-galls. They are produced on oak-leaves by the puncture of an insect. The best come from Asia Minor, and consist nearly one half of tannic acid; in- ferior sorts are brought from Italy and Hungary. The gall-nuts formed on trees in Germany contain but Uttle tannic acid. b.) Catechu, the brown, dry extract of the Acacia catechu, is now very frequently used in dyeing and cafico-printing establishments, for the production of a brown color; sometimes, also, for tanning skins. c.) Kino, the brownish-black extract of a tree grow- ing in the East Indies. d.) Sumach, or Rhus, the bruised leaves of several kinds of rhus ; very important in dyeing. 608 VEGETABLE MATTER. e.) Divi-divi, the seed capsules of an African plant. /.) Bablah, the pods of a species of mimosa growing in the East Indies. g.) The rind of the pomegranate, rind of the walnut, &c, &c. 606. The acids just mentioned, together with tar- taric, oxaUc, and acetic acids, previously treated of, are very widely diffused; but besides these there are many others, which are found only in particular plants or vegetable substances, or are artificially prepared from them; as, — Succinic acid, in amber; white crystals, volatile in the heat; it is formed also by the oxidation of stearic acid. Benzoic acid, in benzoin; white crystalline needles, volatile in the heat; it is formed also in many ethereal oils, when long kept. The bitter oil of almonds, on exposure to the air, is oxidized, and completely convert- ed into crystallized benzoic acid. Cinnamic acid, in old oil of cinnamon and in balsam of Peru ; white crystals. Caryophyllic acid, in the oil of cloves; an oily Uquid. Valerianic acid, in the root of valerian ; an oily liquid of a pungent odor. May be prepared, also, from the fusel oil of potatoes. Suberic acid is prepared by heating cork or fat acids with nitric acid. Fumaric acid, in fumitory and in Iceland moss; it is formed also by heating malic acid. Chelidonic acid, in celandine. Meconic acid, in opium. Kinic acid, in cinchona-bark. Lactic acid, in whey, sour-krout, juices of flesh, &c. Uric or lithic acid, in urine, &c. ASHES. 609 XVI. INORGANIC CONSTITUENTS OF PLANTS (ASHES). 607. If we review the proximate constituents of plants treated of in the preceding section, it will be seen that they are composed either of three elements (C, H, O), or of four elements (C, H, O, N). We may accordingly regard the organogens, carbon, hydrogen, oxygen, and nitrogen, as the four main pillars of the vegetable world. Next to them, sulphur appears wide- ly diffused in the vegetable kingdom, since it forms a constituent of the albuminous substance never fail- ing in any plant. But the Ust of the chemical sub- stances occurring in plants is not yet finished; for were it so, plants would be completely consumed by heat without any thing being left behind. But on the combustion of every plant a residue remains, which neither burns up- nor volatilizes; consequently there must also be present, besides the combustible organic compounds, some incombustible inorganic substances. The latter are termed ashes. 608. The term ashes is just as indefinite as that of hu- mus. Hunt us is the term generally applied to all those black or brown substances formed during the decay of organic matter; but by ashes are understood aU the non- volatile and incombustible substances which remain be- hind after the incineration of organic matter. How very different these may be, both in quantity and quality, is obvious from even a superficial observation of the three best known kinds of ashes, those of wood, peat, and pit-coal. From a hundred pounds of wood we obtain only half a pound, or at most three pounds, of ashes • from a hundred pounds of pit-coal or peat, twenty or thirty pounds of ashes. Wood-ashes contain very 610 VEGETABLE MATTER. many parts soluble in water, pit-coal and peat-ashes very few parts; the former yields with water a power- ful alkaline lye, the latter does not; the former always acts on our fields and meadows as an exceUent ma- nure, the latter only in a smaU degree. Great differ- ences also appear when the ashes of other plants or parts of plants are compared with each other, as may be seen from the foUowing table: — Yield Of which are soluble in water about 100 lbs oak-wood 2 to 4 lbs. ashes 1 3' 100 « oak-bark 5 " 6 " u _1_ 1 3' 100 « oak-leaves (in spring) 5 " a 1 2' 100 « " (in fall) 5i« u 1 6' 100 " dried potatoes 8 " 9 « « 4 5- 100 « potato-tops 15 « cc 15 lo 2 5 • 100 « wheat-grain 2 " 3 " u 1 2' 100 " wheat-straw 4 " 6 « u 8 LU 1 0 • The quantity, as weU as the nature, of the inorganic matter in plants consequently varies in the most re- markable manner, and not only according to the differ- ence of the plants, but according to the difference of the individual parts of one and the same plant; indeed, even in the latter according to the difference of age. We always find the largest quantities of it in the younger vegetable organs, where the progress of growth is most active, namely, in the leaves and twigs. 609. If we ask what is the constitution of vegetable ashes, chemical analysis replies, that they consist prin- cipally of potassa, soda, lime, magnesia, and sesquioxide of iron, combined with carbonic acid, silicic acid, phos- phoric acid, sulphuric acid, and muriatic acid (chlorine). Of these combinations there are principally, — ASHES. 611 a.) Soluble in water, the alkaline salts (salts of po- tassa and soda). b.) Soluble in diluted muriatic acid, the earthy salts (salts of lime, of magnesia, and of sesquioxide of iron). c.) Insoluble in water and acids, the silicates. The character of the prevailing inorganic constitu- ents of a plant may be ascertained, though only in an approximative manner, by merely treating the ashes first with water, and then with diluted muriatic acid. 610. The above-named inorganic substances are often contained in the living plants in quite a different form from that in the ashes; namely, sulphur as a con- stituent of the albuminous matter, but the bases mostly as vegetable acid salts. That the latter are converted on ignition into carbonates (carbonate of potassa, of soda, of lime, &c.) has previously been shown under the heads of tartrate and oxalate of potassa (§§ 194, 197), and thus is explained why almost aU ashes effervesce with acids. The sulphur, on the incineration of the plant, is partly converted into sulphurous acid, which escapes, and partly into sulphuric acid, which unites with one of the bases present, and remains behind in the ashes. 611. It has already been mentioned under the heads of phosphoric and silicic acids (§§ 176, 183), and of po- tassa and lime (§§ 214, 240), that these substances are able to exercise a very favorable influence upon the growth of plants, and that many plants will not flour- ish in a soil in which salts of potassa are wanting, and that others wiU not thrive in a soil which contains no lime, or no silicates or phosphates. The occurrence of inorganic substances in all plants must lead to the conclusion, that every plant requires a certain quantity of them for its existence, and for its complete develop- 612 VEGETABLE MATTER. ment. If the plant does not find them in the soil as- signed to it, it is obstructed in its growth; it pines and withers away before attaining maturity. It is highly probable that basic bodies, as Ume and potassa, act here in a predisposing manner, similar to that in the formation of nitric acid; that they effect by their pres- ence the formation of organic acids, with which they afterwards enter into combination. On the further growth and ripening of the plants, there are formed, as it appears, from these acids, the indifferent substances starch, sugar, gum, &c.; for, as is well known, the acid taste is lost in many vegetable parts, especially in the fruits at the time of ripening, while a mealy, sweet, or mucilaginous taste suppUes its place. It foUows from what has previously been stated, that the inorganic salts requisite for the growth of each indi- vidual plant may be ascertained most simply by burn- ing the plant, and examining the ashes which remain; it requires the same substances which are found in its ashes. If we now examine the soil on which plants of this kind are to be cultivated, we shall find by compar- ison which of the constituents of the ashes are already present in it, and what constituents must be added to it that the plants may find therein all the mineral sub- stances requisite for their development and growth. 612. Arable land, or arable soil, that is, the upper thin layer of the surface of our earth, in which plants ger- minate and take root, consists chiefly of two different kinds of matter; namely, inorganic substances, belong- ing to the mineral kingdom (silica, combinations of silicic, phosphoric, carbonic, and sulphuric acids with alumina, lime, magnesia, potassa, soda, and iron), and organic substances, derived from the animal and vege- table kingdom (humus-like substances). ASHES. 613 The ground and soil which are adapted to vegetation are principally formed of mineral substances, more or less finely divided, which consist of rocks that have been disintegrated by the operation of the atmosphere, or weathered, during the lapse of centuries (§ 265). This weathering is going on uninterruptedly, even now, in the soil of the earth, and so much the more rapidly in proportion as the soil is loosened and penetrated by air and water (fallow). But during this process, the masses of rock are not merely mechanically broken into small fragments, but they are also chemically changed, since from their several insoluble constituents soluble salts — for instance, salts of potassa, soda, lime, &c. — are gen- crated, which may be absorbed by the roots of the plants. Every thing which promotes the weathering and dissolution of the rocks — for instance, burning of the soil (§ 258), mixing it with lime (§ 240) or acids (§§ 173, 186, &c.) — will accordingly, as a general rule, exercise a beneficial influence upon the growth of plants. The organic substances contained in arable soil have always a brown or black color, and are designated by the general term humus (§ 411). They partly consist of decaying leaves and branches, which have fallen off, and of decaying roots of plants remaining behind in the earth, and partly of decomposing vegetable or ani- mal manure put upon the soil. It has already been previously mentioned, that these products of decay are gradually still further decomposed into carbonic acid, ammonia, and water, and for this reason cause a more vigorous growth of the plant. They likewise act favor- ably on vrgetation, because by reason of their dark color the soil is heated more strongly by the rays of the sun, because they loosen the soil, and finally, because 52 614 VEGETABLE MATTER. the weathering of the rocks is promoted by the carbonic acid which is set free from them. XVII. NOURISHMENT AND GROWTH OF PLANTS. bo J Electricity, ■+a d (» •£ o HI fc ^ ' s „ o c a a bC SP o ^3 bo >-> o Si bO o CS X >> u O w £ Silica, Alumina, Lime, Salts, Humus. 613. Carbon, oxygen, hydrogen, and nitrogen, — these are the four elements which the Divine Power has established as main pillars for the structure of the whole organic creation ; from them, and also from sul- phur, phosphorus, and some other inorganic substances, all the numberless wonderful forms of the animal and vegetable world are produced. We as yet know but little about the interior chemical workings by which GROWTH OF PLANTS. 615 these results are effected, but we have nearly ascer- tained the external conditions under which they take place, and the sources from which the above-named elementary substances are taken. That plants require for their germination and devel- opment soil, water, air, warmth, and light — those universal conditions of vegetable life — is well enough known; while the chemical investigations of modern times, and particularly those instituted by Liebig, have first diffused a clearer light as to what single constitu- ents are taken up from the earth, the water, and the air by the plants, and serve them as means of nourishment. UNCULTIVATED PLANTS (MEADOWS, FORESTS, &c). 614. Food of Plants. — Plants absorb their nourish- ment partly by the roots, partly by the leaves. It fol- lows from this, that the nourishment must either be liquid or aeriform; for in these two forms only can it penetrate into the fine pores of the root-fibres and leaves. Plants receive their hydrogen and oxygen from the water, their carbon from carbonic acid, their nitrogen principally from ammonia, their inorganic constituents chiefly from the earth. Water, carbonic acid, ammonia, and a small number of inorganic salts, are accordingly to be regarded as the nourishment of plants. a.) Water furnishes the plants with oxygen and hy- drogen.— The plants imbibe it as a liquid, by their roots, from the earth, and as vapor, through their leaves, from the air. Water is moreover essential to plants, in so far as it occasions, by its fluid condition, the for- mation of the solid vegetable parts; for all the solid ingredients of the plants are developed from the juice, rendered liquid by water. 616 VEGETABLE MATTER; b.) Carbonic acid furnishes the plants with carbon. — This is principally absorbed (§ 167) by the leaves from the air, which is constantly suppUed with it by the processes of combustion, decay, and respiration. More- over, the roots of the plants find carbonic acid in every soil which contains humus, for humus consists of de- caying organic matter, that is, organic matter resolving itself into carbonic acid and water (§444). From this limited source the young plants especiaUy draw their nourishment, before they have leaves enough by means of which to appropriate to themselves the carbonic acid from the free air. The changes which the latter under- goes by the action of living plants are shown in the fol- lowing experiments: — Experiment. — Fill a glass funnel with the fresh leaves of some plant, and invert it in a wide glass vessel filled with water, in such a manner as quite to cover the funnel with water. Now close the upper opening of the fun- nel with a cork, suck out, by means of a glass tube, a part of the exterior water, and expose the vessel to the sun; bubbles of air will soon rise from the leaves, and collect in the tube of the funnel. When the water is so far pressed down within the fun- nel that it stands on a level with the exterior water, then uncork the funnel, and hold a glowing shaving in the gas evolved from the leaves; the shaving will inflame briskly, just as it would in oxygen gas. In- deed, this gas is really oxygen, which is derived from the carbonic acid contained in the water. Thus, in the plants, the carbonic acid has been resolved into its constituent parts, by the influence of light; its oxygen GROWTH OF PLANTS. 617 becomes free, and escapes, but its carbon remains be- hind in the plants. The plants inhale carbonic acid, and in the light exhale oxygen. Experiment. — Repeat the experiment, but with this alteration, — pour, instead of common water, Selters water over the leaves; this contains a greater abun- dance of carbonic acid, and the consequence is, that the evolution of oxygen gas proceeds more briskly, and continues longer. The principal mass of plants consists of vegetable tissue, starch, gum, mucus, sugar, &c, each composed of three elements; all these may be produced from car- bonic acid (C Oa) and water (H O), when the elements of the water combine with the carbon of the carbonic acid. If this happens, the oxygen of the latter must necessarily be liberated. From Carbonic acid = Carbon, Oxygen, and Water = Hydrogen, Oxygen, are formed Hydrogen, Oxygen, Carbon -|- Oxygen Vegetable tissue, starch, mucus, sugar, &c. (is liberated), It is also, perhaps, possible that the elements of the carbonic acid combine with the hydrogen of the water, and that accordingly the oxygen which becomes free is derived from the water; the chemical process would then be different from that just stated, but the results would be exactly the same. From Water, = Hydrogen, Oxygen, and Carbonic acid = Carbon, Oxygen, are formed Carbon, Oxygen, Hydrogen -|- Oxygen Vegetable tissue, starch, mucus, sugar, &c. (is liberated). 6'.) Ammonia furnishes plants with nitrogen. — When vegetable and animal matters decay, ammonia (N H3) 52* 618 VEGETABLE MATTER. is formed from their nitrogen, carbonic acid from their carbon; both of these products combine with each other, forming a volatile salt which escapes in the air. It is condensed again from the air, partly by the loam or clay (§ 256) and the humus of the soil (§ 444), partly by the dew, rain, and snow, and returned again to the earth, and then with the water absorbed by the plants. If organic substances decay in the soil where plants are growing, the ammoniacal salt is, immediately after its formation, absorbed by their roots. Whether ammonia can be formed directly from the nitrogen of the air, where the latter is in contact with decaying substances in the moist earth, and can be of service to the plants, has not yet been ascertained with certainty. In what manner the assimilation of ammonia takes place in the vegetable kingdom is, indeed, not yet known, but it is probably the ammonia from which plants take the nitrogen requisite for the formation of their azotized constituents, such as albumen, gluten, caseine, organic bases, &c. From Carbonic acid = Carbon, Oxygen, Water = Hydrogen, Oxygen, Ammonia = Nitrogen, Hydrogen, are formed Nitrogen, Hydrogen, Oxygen, Carbon -f- Oxygen <.------------^_---------------; Albumen, gluten, caseine, organic bases, &c. (is liberated). Carbonic acid, water, and ammonia accordingly con- tain in their elements the essential constituents for the formation of all vegetable substances (carbon, hy- drogen, oxygen, and nitrogen). On decay and putre- faction, animal and vegetable matter is decomposed into carbonic acid, water, and ammonia. What seems to us to be annihilation is, however, only decay; the form only passes away, the matter itself is unchange- GROWTH OF PLANTS. 619 able. From the disgusting substances of decay are formed again the living wonders of the vegetable world. Fig. 218. Dead animals and plants. Living plants. d.) Plants are furnished, through the soil and water, with the requisite inorganic matters. — Our arable land is constantly undergoing changes ; the organic matter contained in it decays, the inorganic is decomposed by the action of time and weather. By the last process soluble salts are always forming from insoluble rocks, which salts may now be absorbed by the roots of plants. Weathering takes place also beneath the surface of the earth, and indeed wherever air and water can pene- trate into the mass of rocks. The substances thus rendered soluble are taken up by the rain-water, and constitute the salts contained in our common spring and river waters; accordingly, in many places plants can receive from water also inorganic matter. Finally, the air likewise contains inorganic substances which have been conveyed into it by evaporation (§ 182), especially from the ocean, and also by the force of the winds, and which are diffused by it over the whole earth. These are returned again to the earth in rain, dew, snow, &c, and thus we can no longer wonder at finding in plants salts (for instance, common salt) not existing in the rocks from which the soil serving as a habitation for these plants has been formed. The changes which these substances undergo in Uving plants have already been noticed in the preceding section. 620 VEGETABLE MATTER. It should still be expressly stated, that a plant can grow vigorously, thrive, and attain complete maturity, only when the substances mentioned at a, b, c, and d are all four presented to it simultaneously. As the life of man ceases if only a single condition necessary for his continued existence is withdrawn, for instance, the air (oxygen), or water, — as a clock stops if only a single wheel is taken from it, — so also the complete development of a plant is obstructed when one of the above-mentioned means of nourishment fails. CULTIVATED PLANTS. 615. If we give abundant and invigorating food to an animal, it becomes vigorous and fat; on scanty and slightly nourishing food, it remains poor and lean. Just the same thing occurs also with plants. When they find an abundance of all the substances which they require for their development in the soil and in the air, they will grow up more vigorously, and put forth more branches, leaves, flowers, and fruits, than when they do not find these substances, or find only a part of them, in sufficient quantity. Consequently, the way of obtaining from our fields and meadows the largest produce consists in presenting to the plants which are to be cultivated upon them all the materials requisite for their nourishment in sufficient quantity. We do this by manuring the soil. 616. Nature, by means of rain and dew, decay and putrefaction, provides that the three universal means of nourishment, water, carbonic acid, and ammonia, shall not be wanting to plants ; and man also, without exactly intending it, contributes his share by the act of breath- ing and by the fires he kindles. The air contains an in- GROWTH OF PLANTS. 621 exhaustible provision of these substances, since the pro- cesses by which they are generated on the earth never suffer an intermission. The air alone would accordingly suffice for the nourishment of plants, if they could only find in the soil the necessary inorganic salts in solution. But as a structure advances more rapidly when it is worked upon at several parts at the same time, so the growth of a plant proceeds more rapidly and more lux- uriantly when it can take up nourishment from sev- eral different sources, not only by the leaves, but at the same time also by the roots. All vegetable and animal substances are converted by decay into water, carbonic acid, and ammonia; hence it is quite natural that such substances, when they decay in a moist soil, should promote the growth of the plants sown in that soil. Hereby is explained, but in part only, the beneficial in- fluence exerted upon vegetation by the universally used animal and vegetable manures, as, for* instance, the so- called humus-like substances formed from excrements, urine, horn-shavings, bone-dust, guano, straw, leaves, &c. 617. But the reception of these universal means of nourishment, and their transformation into organic mat- ter by the vital activity of the plants, can, as already mentioned, only take place by the aid of the inorganic salts. If these are wanting in a soil, the seeds sown in it may indeed germinate and grow for a while, because they contain within themselves a certain quantity of those inorganic constituents which the plants require for their growth, Dut the growth will cease when the constituents are exhausted in the development of the young plants. Nature provides, indeed, for the forma- tion of soluble substances in the earth, by the gradual action of the weather; but these are not sufficient to yield a rich harvest year after year from the same fields, 622 VEGETABLE MATTER. and it is therefore indispensable to mix these constit- uents artificially with the soil in order to maintain its fertility. This is done, either directly by those mineral substances which contain lime, potassa, soda, phosphoric acid, &c, as, for instance, by Ume, gypsum, marl, wood-ashes, bone-ashes, animal charcoal, common salt, &c.; by the overflowing of meadows with water, &c.; or indirectly, by the salts contained in most kinds of manure. The soluble salts existing in the food are re- moved again from the animal body by the urine of an- imals, the insoluble by the solid excrements; and thus is explained, in a simple manner, why the excrements of animals fed upon oats are the most appropriate and most powerful manure for oats; those of animals fed upon peas, clover, or potatoes, the best manure for peas, clover, or potatoes. In these saline or inorganic sub- stances consists the second mode of operation of the an- imal and vegetable manures. Since the different kinds of plants require different in- organic substances, and different quantities of them, for their nourishment, — some, for instance, principally salts of potassa, others salts of lime, and others again phos- phates or silicates, — so it is advantageous in the culti- vation of plants to make such an alternation (rotation of crops) that a potassa plant shall be foUowed by a lime plant, and this again by a silica plant, &c. In this way, it is possible to obtain from a field which is ex- hausted for one kind of plant a second or a third crop consisting of a different species of plant, without the necessity of manuring it each time. 618. It is clear from these hints, that chemistry alone can give to the farmer a knowdedge of the constituents of his soil, of the constituents of the plants which he wishes to cultivate upon this soil, and of the substances RETROSPECT. 623 which must be added to it in order that the plants may find there all that is necessary for their nourishment. Inducement enough is hereby offered to every farmer to cultivate a more intimate acquaintance with this sci- ence, as the only guide to be reUed upon in his prac- tical experiments and occupations. RETROSPECT OF VEGETABLE MATTER IN GENERAL. 1. While a plant lives, a constant motion, and a constant reception, change, and surrendering of certain aeriform and Uquid substances, are continually taking place in it. If these substances are wanting to the plant, its growth and Ufe cease; we therefore regard them as food for the plant. 2. These substances aU belong to the inorganic com- pounds ; they consist, — a.) Of a combination of hydrogen and oxygen (water). b.) Of a combination of carbon and oxygen (carbonic acid). c.) Of a combination of nitrogen and hydrogen (am- monia). d.) Of inorganic acids and bases (salts). 3. From these substances are formed, in an incom- prehensible manner, the juices of the plants, and from these the single parts of the plants (organs), together with the innumerable vegetable substances which we find in them. 4. The vegetable substances may be classified by dif- ferent methods. We may classify them, — I. According to their more or less general diffusion: — 624 VEGETABLE MATTER. a.) Into such as occur in almost all plants; for in- stance, vegetable tissue, starch, sugar, gum, mucus, fats, many acids, chlorophyll, albuminous matter, &c. b.) Into such as occur only in certain kinds of plants; for instance, extractive matter, coloring matter, volatile oils, resins, many acids, organic bases, &c. II. According to their chemical character: — a.) Into vegetable acids. b.) Into vegetable bases. c.) Into indifferent vegetable matter. The indifferent combinations predominate in the veg- etable and animal kingdoms, the acids and bases in the mineral kingdom. III. According to their composition: — a.) Into non-azotized substances, and, moreover, a. into those rich in oxygen, namely, organic acids, &c.; j3. into those rich in hydrogen, namely, fats, vol- atile oils, resins, &c.; y. into those rich in carbon, namely, vegetable tissue, sjtarch, sugar, gum, mucus, &c. b.) Into azotized substances; for instance, organic bases, many of the coloring matters, &c. c.) Into those containing nitrogen and sulphur; for instance, albumen, gluten, caseine, &c. The non-azotized compounds predominate in the vegetable kingdom, the azotized and sulphurized com- pounds in the animal kingdom. 5. The vegetable substances produced by nature may be transformed and decomposed in various ways into new combinations. They may be changed, — a.) By the addition of oxygen; as, a. by combustion with free access of air (carbonic acid, water, nitrogen) ; RETROSPECT. 625 /3. by decay (humus, carbonic acid, water, ammo- nia, acidification of spirituous liquids, and of oth- er vegetable substances; grass-bleaching, &c.); y. by mere exposure to the air (drying or becoming rancid of fats, conversion into resin of the vola- tile oils, &c.); S. by evaporation (the becoming brown of ex- tracts, &c.); e. by the action of nitric acid, chromic acid, and other bodies rich in oxygen (conversion of sugar into saccharic acid, oxalic acid, &c). b.) By the abstraction of oxygen (reduction of indigo- blue). c.) By the abstraction of hydrogen (bleaching with chlorine). d.) By combining with sulphurous acid (bleaching with this acid. e.) By the abstraction of hydrogen and oxygen (trans- formation of alcohol into ether or olefiant gas, and also of oxaUc acid into carbonic oxide and carbonic acid by sulphuric acid; charring of wood by sulphuric acid, &c.). /.) By the addition of hydrogen and oxygen (putre- faction of vegetable matter with exclusion of air, as, for instance, under water; that is, the conversion of vege- table matter into carbonic acid, carburetted hydrogen [marsh gas], water, ammonia, mud, peat, brown-coal, pit-coal; conversion of starch or sugar into lactic acid, &c) g.) By heating with exclusion of air (charring or dry distillation of wood, of pit-coal, of the fats, of the acids, &c, that is, their conversion into carbonic acid, car- buretted hydrogen [iUuminating gas], water, wood-vin- 53 626 VEGETABLE MATTER. egar [empyreumatic acids], ammonia, tar [burnt oil, burnt resin], creosote, wood-coal, coke, &c). h.) By the peculiar action, not yet thoroughly investi- gated, of an easily decomposed body or ferment (spir- ituous fermentation, that is, decomposition of sugar into alcohol and carbonic acid). i.) By the transposition, not yet explained, of one vegetable substance into another isomeric (equally con- stituted) compound; for example,— a. conversion of starch into gum and sugar by sulphuric acid; /3. conversion of starch into gum and sugar by diastase; y. conversion of starch into gum by moderate heat- ing; 8. conversion of crude sugar into liquid sugar by heating or long boiling with water; e. coagulation of albumen by heating, &c. k.) By the operation of strong bases upon vegetable matter; for example, — a. formation of cyanogen (§ 291); /3. formation of ammonia (§ 232); y. formation of nitre (§ 207); 8. formation of soap from fats (§ 540). I.) By the action of light (formation of chlorophyll, bleaching of colors, &c). These are only a few of the more important meta- morphoses of vegetable matter as yet known to us; but their extent is unUmited, and increases every day, since extraordinary industry and zeal are now devoted to the investigation of this very department of chem- istry. ANIMAL MATTER. 619. The chemical processes which take place in the living animal are far more mysterious and more com- plex than even those which take place in plants. That such actions really do occur in the animal body, who can doubt ? We here see that which peculiarly char- acterizes these processes, the conversion of bodies into new^ bodies with entirely new properties, far more dis- tinctly and more forcibly than in plants and minerals. For can there be a more striking metamorphosis than that of the constituents of the egg (albumen, yolk, and egg-shell) into the constituents of the young bird (flesh, blood, bones" feathers, &c.) ? or the conversion of milk, which constitutes the sole nourishment of many young animals, into flesh, blood, &c. ? That chemical force alone cannot effect these changes has already been stated in the earlier part of this work; it is merely the instrument, the means, which the Divine Power has employed, in a way as yet concealed from us, to form, during the life of the vegetables and animals, all the different parts of the vegetable and animal kingdom. That which principally distinguishes animal life from vegetable life is, that during the former oxygen is in- cessantly inhaled, but during the latter it is exhaled; and also, that, with the exception of water and some 628 ANIMAL MATTER. salts, organic substances only are appropriated to the support of the former. 620. The chief mass of vegetable matter consists of non-azotized substances, consequently of substances which contain only three elements; but in the animal body, on the contrary, the azotized and sulphurized substances (albuminous substances), consequently far more complex combinations, predominate. Water and fat are almost the only substances, composed of only two or three elements, that occur in the animal body; aU the others, for instance, flesh, cartilage, blood, hair, nails, &c, are rich in nitrogen, sulphur, and also in phosphorus. It is also characteristic of these substan- ces that they do not assume a crystalline form; we find crystaUine combinations — as, for instance, in urine (urea, uric acid, &c.)—in those animal Uquids only, which, being unfit for assimilation, are again separated from the body. Most animal substances, when viewed under the microscope, exhibit the form of smaU glob- ules. Accordingly, the globular form is the funda- mental form for the composite, more highly organized types of the animal kingdom, while in the more simple, lifeless productions of the mineral kingdom, the angu- lar form (crystaUine form) prevails. In the vegetable kingdom, holding a middle position between the two, we find both forms, namely, the globular or spherical in starch, yeast, &c.; the crystalline in sugar, in organic acids, bases, &c. 621. The elementary matter from which the proxi- mate constituents, and from which again the organs of the animal body, are formed, is exactly the same as that which occurs in the vegetable kingdom, namely, oxygen, hydrogen, carbon, nitrogen, sulphur, phosphorus, and chlorine; and the metallic substances, lime, potas- the egg. 629 sium, sodium, and iron. These must be introduced into the animal body in order that it may grow and live. How this happens may be shown most simply in the constitution of the egg and of milk. I. THE EGG. The egg, as is known, consists of the albumen, the yolk, and the shell. 622. Albumen. — The white in the hen's egg consists of cells, in which is contained a colorless alkaline Uquid, the albumen. On evaporation, we obtain from it one eighth of soUd albumen; the rest is water. When burnt, it leaves behind common salt, carbonate, phos- phate, and sulphate of soda, and phosphate of lime. That albumen, when briskly beaten up, yields a po- rous Ught froth, that it becomes insoluble and coagu- lates by heating, &c, are well known facts. On ac- count of the latter property, it is used for clarifying turbid liquids, especially the juices of sugar. Experiment. — Stir up some honey in warm water, add a little albumen to the turbid solution obtained, and heat the mixture to boiling. The albumen seizes upon the foreign substances floating in the liquid, bears them to the surface, and incloses them within itself as it coagulates; the liquid thereby becomes clear and transparent, and may be separated by a strainer from the coagulated albumen. The constituents of animal albumen are just the same as those of vegetable albumen (§ 477). 623. The yolk of eggs consists of albumen holding in suspension yellow drops of oil. On account of the albumen contained in it, it coagulates when heated, and the fat (oil of yolk of eggs) may be extracted from 53* 630 ANIMAL MATTER. it by strong pressure, or by agitation with ether. Phos- phorus is contained in the oil of yolk of eggs. 624. Egg-shells. — Experiment. — Pour some diluted muriatic acid upon some egg-sheUs; with the exception of some membrane, they will entirely dissolve, with the evolution of gas. The gas which escapes is carbonic acid; but lime is contained in solution in the muriatic acid, as we may ascertain by the addition of sulphuric acid, which throws down gypsum from it. The shells have accordingly the same constitution as chalk, name- ly, they consist of carbonate of lime. There are in the egg-sheUs smaU pores, through which the air penetrates into the interior of the egg, and graduaUy effects a change (putrefaction) of the latter. If these openings are stopped up, — for in- stance, by packing the eggs in ashes, or by smear- ing them with oil, — the eggs will keep much longer unchanged, as the penetration of the air is thus pre- vented. II. MLLK. Milk consists of a solution of caseine and sugar of milk in water, in which solution small globules of oil are held suspended. The latter render the milk opaque, and give it the appearance of an emulsion. 625. The Oil- Globules. — Experiment. — These glob- ules cannot be separated from the milk by filtration alone, as they are so small that they pass with it through the pores of the finest paper; but it may be accomplished in the following manner. Dissolve an ounce of Glauber salts and a couple of grains of carbon- ate of soda in half an ounce of lukewarm water, and agitate the solution with half an ounce of fresh milk. MILK. 631 If you now transfer this mixture to a filter, the fatty portions (cream) remain behind, while a liquid, only slightly opalescent, passes through. The saline solu- tion added does not act chemicaUy upon the constitu- ents of the milk, but it only acts mechanically, causing the globules to form a more compact mass, and to be more readily separated from the watery liquid. 626. Caseine. — Experiment. — If you add to the filtered liquid a few drops of muriatic acid, the caseine separates from it as a white flaky mass; accordingly, the animal caseine is likewise coagulated and rendered insoluble by acids in the same manner as vegetable caseine (§ 452), with which it exactly agrees in consti- tution. Pure caseine is insoluble in water, but it dis- solves in it when alkalies are present; these always exist in the milk, and keep the caseine in solution. The alkali (soda) is withdrawn from the caseine by the acids which are added, and the caseine then separates in the familiar form of new cheese. Caseine is an albuminous substance, that is, it contains, besides car- bon, hydrogen, and oxygen, also some nitrogen and sul- phur in its constitution. 627. Albumen. — Experiment. — If you filter the ca- seine from the liquid, and then boil the latter, it again becomes turbid, although less so than before. It is the albumen which separates, smaU quantities of it being present in aU milk. 628. Experiment. — Let a small piece of the dried membrane of the stomach of a calf (rennet) remain standing one night in a spoonful of water, and after- wards pour this water upon a quart of new milk; the milk, after having stood for some hours in a warm place, will coagulate into a gelatinous mass, which is to be'put upon a filter. What remains behind consists 632 ANIMAL MATTER. of an intimate mixture of the curdled caseine with glob- ules of fat. By pressing and drying, we obtain from it the so-called cream or new-milk cheese (Swiss, Dutch, Chester, &c. cheese). 629. Sugar of Milk. — Experiment. — Separate the filtered Uquid (sweet whey) from its albumen by boil- ing, and, having again filtered it, evaporate till only a few ounces of it remain. If left in a warm place, hard, prismatic white crystals of sugar of milk will be deposited (§ 473). By this method sugar of milk is procured in Switzerland on a large scale. Consequently the sweet whey is to be regarded principaUy as a solu- tion of sugar of milk (together with some albumen and some salts) in water. Experiment — Dissolve again in water the sugar of milk obtained, and put a piece of rennet in the solu- tion ; the liquid will soon become sour in a warm place, because the sugar of milk is converted into lactic acid. 630. Experiment. — The coagulation of the milk, which was produced by the rennet in a few hours, is effected instantaneously by the addition of acids, as is rendered obvious by adding a few drops of some acid to heated milk. In this curdled mass are contained all the caseine and fatty particles of the milk (cheese and butter). 631. Experiment. — Fill a flask with fresh milk, close it, and keep it, inverted, from twenty-four to thirty- six hours in a cool place; then loosen the stopper a little, so that the lower, thinner portion of the milk (blue or skim milk) may run off, but the upper, thicker part (cream) remain behind. On standing, the lighter oil- globules of the milk ascend, and form on the surface the well-known fatty, thick cream. If this is shaken for some time, the membranes of the oil-globules are torn, MILK. 633 and the latter then unite together, forming masses of butter. The thin mihk which passes off from beneath may be separated, in the way already described, into caseine, albumen, and sugar of milk. Butter, Uke the vegetable fats, consists of a solid fat (margarine) and a fluid (oleine), and it has also exactly the same properties (§ 533). But besides these two kinds of fat, butter contains a smaU quantity of a pe- culiar fat (butyrine). If butter remains exposed some time to the air, some volatile fat acids having a dis- agreeable smeU and taste will be generated in it; these cause the rancidity of butter. If butter that has become rancid is boiled several times with double its quantity of water, these acids will be removed from it, and the butter, on cooling, will have regained its agree- able flavor. 632. If you let milk stand for some time in open ves- sels, its sugar of milk is gradually converted into lactic acid, and this, like every other acid, causes a curdling of the milk, and at the same time its well-known sour taste. But the curdUng first commences after most of the oil-globules have collected on the surface (sour cream). From this cream butter is most usually pre- pared with us, and therefore the buttermilk remaining (a mixture of curdled caseine, lactic acid, and water, with some particles of butter remaining behind) has an acid taste. The so-called curd beneath the cream con- tains only some traces of fat, and consists accordingly of water, lactic acid, and coagulated caseine. By press- in o- we obtain from it the sour whey, and, as a residuum, the coagulated caseine, from which our common skim- milk cheese is made. When kept damp this under- goes a decomposition (putrefaction), by which ammo- nia is generated, which forms with the caseine a soft 634 ANIMAL MATTER. saponaceous mass. If the putrefaction advances still farther, there will be finaUy generated also volatile com- pounds of a very offensive odor (sulphuretted hydrogen, volatile fat acids, &c). 633. Fermentation of Milk. — Experiment — Let milk stand in a flask till it begins to curdle, and then put the flask furnished with a tube for the evolution of gas (Fig. 188) in a place the temperature of which ranges from 24° to 30° C. A brisk evolution of carbonic acid will commence, because the sugar of milk, which has not yet passed into lactic acid, is converted, at a higher temperature, first into grape sugar, and then into alcohol and carbonic acid. But there is also formed at the same time some butyric acid, which imparts a disagreeable taste to the spirit, obtained by the distffla- tion of the fermented Uquid after it has been strained and squeezed off. The koumiss prepared by the Cal- mucs is a liquor obtained by the fermentation of mare's milk. 634. Ashes of Milk. — If milk is burnt with access of air, there remain behind, after all its carbon, hydro- gen, oxygen, and nitrogen have been converted into aeriform combination, ashes, which consist of potassa, soda, lime, magnesia, and sesquioxide of iron, and also of phosphoric acid, sulphuric acid, and chlorine. 635. Digestion, — If we reconsider the constituents of the egg and the milk, as just stated, we find in them the following elementary substances : — The egg consists of Milk consists of Water = H, 0. Water = H, O. Oil of eggs = II, O, C, P. Butter £ = H O C Albumen = H, O, C, N, S, P. Sugar of milk $ ' ' Caseine > = 11, O, C, N, S, P. Albumen y Shells and other in- > Ca, Na, K, Fe, Inorganic sub- ) =Ca, Na, K, Mg, Fe, organic substances S P, S, CI, O. stances \ P, S, CI, O. MILK. 635 But exactly the same, and only the same, elementary substances are found also in the animal body; accord- ingly, it must be concluded that the constituents of the hen's egg are used, in the hatching of the egg, for the development of the young chicken, and the constituents of the milk which forms the food of the young Mam- malia are used for the growth and nourishment of the latter. It is the same, also, with the constituents of the vegetable and animal substances, which serve us as food. The food is mixed up in the stomach with the gastric juice (a Uquid containing free muriatic acid and common salt, which liquid is secreted by the inner skin of the stomach,—mucous membrane), and is thereby softened into a soluble, white, pulpy mass (chyme). The muriatic acid is likewise formed by a decomposi- tion of common salt taking place in the body, and it is indispensable for the solution (digestion) of the food. The explanation of this action is, that water, rendered feebly acid by muriatic acid, is able (after it has been previously left in contact for a day with a piece of rennet) to dissolve, at a temperature of from 30° to 40° C, hard-boiled albumen, flesh, and other food. All of the chyme which has become soluble is, during its passage through the intestines, absorbed and introduced as nourishment (chyle) into the blood. The changes which the food experiences in the animal body are there- fore the following: from the food is formed chyme, from this chyle, from this blood, and from the blood all the numerous organs and parts of the animal body are generated, just as all the organs and parts of plants are generated from the vegetable juices. 636 ANIMAL MATTER. ID. THE BLOOD. Like milk, the blood also consists of a liquid as clear as water, in which small globules are held suspended; but these globules (blood corpuscles) have, however, a yeUowish-red color. 636. Experiment. — If you let the blood of an animal remain standing quietly in a vessel, it will, in a short time, undergo a change ; it coagulates, forming a dark- red jelly (the clot, coagulum), which contracts on longer standing, and a yeUowish-Uquid is separated (serum). When the latter is heated to boiling, it coagulates to a white jelly ; the serum consists of a solution of albumen. There are two substances combined together in the coagulum, one of which dissolves by long washing in water, communicating to it a red color (coloring matter of the blood, the principal constituent of the blood cor- puscles), while the other remains behind as a white fibrous mass (animal fibrine). Accordingly, the most important proximate constituents of the blood are water, albumen, blood corpuscles, and animal fibrine, which, on the standing of the blood, are transposed in the following manner: — From Water, Albumen, Blood Corpuscles, Fibrine, are formed Serum and Coagulum. It is a distinguishing peculiarity of the coloring mat- ter of the blood, that it always contains iron. 637. Experiment. — If the blood freshly drawn from the veins is beaten up during cooling, it does not coagulate; the fibrine is indeed insoluble, and exists as a thread-like coherent mass, which, when knead- ed for some time with water, becomes finally white, and, after drying, resembles the muscular fibre. In- THE blood. 637 deed, it may be regarded as half-formed flesh, since it has entirely the same composition, and at any rate the flesh of the animal body is formed from it. The blood remaining behind retains, after the separation of the fibrine, its red color, and coagulates on boiUng to a jelly of a dark-red color, as may be perceived in the so-called black-pudding* The metamorphosis of the blood just treated of is, accordingly, as follows: — Water, Albumen, Blood Corpuscles Fibrine remain'liquid. becomes solid. Fibrine belongs to the albuminous substances; it is very rich in oxygen, and contains also sulphur and phosphorus in organic combination. 638. The Ashes of Blood. — If blood is evaporated to dryness, and heated for a long time in the air, it will finally burn up, with the exception of some ashes. These ashes consist of alkaline phosphates (much soda, little potassa), phosphates of the alkaline earths (lime, magnesia), phosphate of the sesquioxide of iron, com- mon salt, and the alkaline sulphates; consequently, of the same constituents which we find in the ashes of our principal articles of nourishment (eggs, milk, bread, &c). In the vegetable kingdom we find these ash-constituents most abundant in those vegetable parts which are rich in albuminous matter, especially in the seeds of our grains and leguminous plants. 639. Respiration and Means of Nourishment — As long as an animal lives, its blood is in a state of con- stant motion and of constant change. Light-red blood streams out from the heart, through the arteries, into all * " Mixed with fats and aromatics, and inclosed in the prepared intes- tines, the blood of this animal [the pig] constitutes the sausages sold in the shops under the name of black-puddings." — Pereira on Food and Diet. 54 638 ANIMAL MATTER. parts of the body, from which it returns, darker colored, through the veins, back again to the heart. But before the latter blood recommences its circulation, it is im- pelled through the lungs, in which it comes in imme- diate contact with the inhaled air, and by means of which it experiences a most remarkable change. When in contact with the air, the dark venous blood is con- verted again into light-red arterial blood, and thereby the air loses a part of its free oxygen, and receives in return carbonic acid and vapor; the exhaled air is ac- cordingly poor in oxygen, but rich in carbonic acid and vapor. This change of the air is obviously very much like that which the air undergoes by the process of com- bustion ; for in this case, too, its free oxygen is convert- ed into carbonic acid and water. Indeed, this similarity is rendered still more apparent, when we consider, more- over, that heat becomes free also in the animal body, as long as it Uves and breathes, and that the food received into it, like wood in the stove, entirely disappears, with the exception of a small portion which passes off in the form of excrements. Its disappearance takes place in exactly the same way as that of wood, with which we heat our apartments; this disappearance is caused by a change of the food into aeriform combinations, into carbonic acid and vapor, which are partly exhaled by the lungs, and partly evaporated from the skin. For this purpose, as it seems, non-azotized food, namely, starch, sugar, gum, fat, lactic acid, and other organic acids, beer, wine, &c, are principally employed, and are therefore called elements of respiration. It is different with those substances which contain nitrogen and sulphur (and phosphorus); these serve for the production of blood, the constituents of which are the same. These substances, albumen, fibrine, &c, THE FLESH. 639 afterwards pass with the blood into aU parts of the animal body, and are transformed into flesh, nerves, muscle, hair, nails, &c. For this reason, they have been called the plastic elements of nutrition. Those azotized, sulphurized, and other substances, such as salts, which can no longer be used in the animal body, are removed from it again by the solid excrements and the urine. IV. THE FLESH. What is commonly caUed meat (muscle) is likewise (see § 637) animal fibrine or muscular fibre. In this form it consists of bundles of fine fibres, which are in- terwoven with cellular tissue, nerves, and veins, and are thoroughly penetrated with a watery liquid, the so- called juice of flesh. 640. Juice of Flesh. — Experiment. — Mince a quar- ter of a pound of lean meat very fine, pour over it a quarter of a pound of water, and, after letting it stand fifteen minutes, press out the liquid through a linen cloth ; pour over the residue the same quantity of wa- ter, squeeze out the liquid, and mix this with the former liquid. In the reddish juice are contained almost all the soluble, and, at the same time, all the savory and odorous constituents of the flesh. If this juice is heated to 60° C, a frothy mass separates from it, which con- sists of coagulated albumen. When the liquid filtered off from this is boiled for some time, a turbidness again ensues, which is caused by the coloring matter and fibrine (§ 636) of the blood extracted also from the flesh, which likewise coagulate at a boiling heat. The acid broth or decoction (bouillon) now remaining behind contains free phosphoric and lactic acids, phosphate and 640 ANIMAL MATTER. lactate of the alkalies (much potassa, Uttle soda), phos- phate of magnesia, together with several organic mat- ters, a crystalline, indifferent organic body (creatine), and a crystalline, basic, organic body (creatinine), nei- ther of which has been yet thoroughly investigated. By evaporation the broth becomes yeUow, and finaUy brown (roast-broth); if evaporated to dryness, a dark- brown soft mass (extract of fiesh) remains behind, half an ounce of which is sufficient to convert one pound of water, to which some common salt has been added, into a strong and savory soup. 641. Fibrous Tissue. — Experiment— If you boil the fleshy residue left after the former experiment with water for some hours, you obtain a liquid which coag- ulates in the cold to a jelly, and consists principally of a solution of gelatine; the fat floating on the surface proceeds from the tallow, or fat of the flesh. What re- mains is fibrous tissue, a milk-white, hard, tasteless, and odorless fibrous mass ; in this hardened state it is diffi- cultly digestible, and but slightly nutritious. The annexed grouping gives a probable idea of the quantitative composition of the flesh. From one thou- sand pounds of beef were obtained, — a.) By expression with water (consisting one half of albumen), . • • 60 lbs- b.) By five hours' boiling with water (con- sisting chiefly of gelatine), . 6" c.) Lean, juiceless, and tasteless fibrine, . 164 " d.) Fat or tallow,.....20 " e.) Water,.......J^_ " 1000 lbs. 642. Boiling of Meat. — To obtain by boiling an ex- cellently tender, savory, and nutritious meat, care must THE FLESH. 641 be taken that the juice is not extracted from the flesh during boiling, but remains in it, and that the boiling is not continued too long. If the albumen contained in the juice remains in the interstices of the animal fibres, a tender roasted or boiled meat is obtained; but if, during the boiling or roasting, the juice goes into the broth or gravy, then the meat becomes tough and hard. It is best to put the meat to be boiled into boiling wa- ter, continue the boiUng for several minutes, and then let it stand for some hours in the kettle on the hearth of the stove, where the temperature is about 70° C. In this way the albumen in the external layers of the meat is immediately coagulated by the boiling water, and forms, in this coagulated state, a coating which prevents the escape of the liquid, and likewise the pen- etration of the external water into the interior of the meat. 643. Preparation of Broth, or Soup. — We must man- age in just the contrary way if we wish to obtain a good and abundant soup from the meat. To effect this, mince the meat fine, mix it uniformly with an equal weight of cold water, heat it slowly to ebullition, let it boil for a few minutes, and finally strain off and squeeze out the liquid. By adding to this liquor some common salt, and other ingredients with which soups are commonly seasoned, and then coloring it somewhat darker with onions burnt brown, or with burnt sugar, to give it the ordinary favorite brownish color, we ob- tain the best soup which can, in general, be prepared from a given quantity of meat. Hitherto, it has been frequently assumed that gelatine formed the most im- portant, most characteristic constituent of animal soup; but this is a mistake, since the gelatine itself is quite tasteless, and forms but a very insignificant part of the 54* 642 ANIMAL MATTER. soup. And for this reason, the so-caUed portable soup prepared in England and France cannot yield a really good animal broth. 644. Salting of Meat. — A universally known method of preserving meat is to salt it down, that is, to rub into it and strew over it some common salt, and let it remain piled up, or pressed together, for some time. The common salt extracts from the flesh one third to one half of the juice, dissolves in it, and forms with it the so-called brine. Since, consequently, a large por- tion of the nutritive albumen, and of the lactates and phosphates essential to digestion and nourishment, and also of the creatine and creatinine, are removed with this brine from the meat, the latter must lose in nutri- ture, and it is not improbable that this is the reason why a long continued dieting on salt meat — for in- stance, during sea-voyages — is followed by scurvy and other maladies. Hence, it would be better not to let the salting of the meat continue till a brine is formed. V. THE BLUE. 645. The bile separates in the Uver from the venous blood ; it consists of a thickish, greenish-yellow liquid, and possesses a very bitter taste. Its chief constituents are choleic acid and soda, which, combined with each other, have a saponaceous character. If you shake up bile with water the solution froths like soap-suds; it also comports itself like this towards greasy substances, and therefore is frequently used for washing silks, which, by the application of soap, would lose their color. The dried gall-bladder of the carp forms an ar- ticle of commerce. Experiment. — Dissolve a little carp-gall, or some THE SKIN. 643 drops of fresh ox-gall, in a little water, and add grad- ually to the solution sufficient common sulphuric acid entirely to redissolve the precipitate formed ; if you now add a few drops of sugared water, or thin starch-paste, the liquid, unless rendered too hot by the addition of sulphuric acid, assumes a splendid violet-color. In this way, extremely small quantities of sugar or starch, or, inversely, of bile, may be detected. VI. THE SKIN. 646. The whole body of the animal is externally sur- rounded by the solid elastic skin, which consists of a thick tissue of cells, between which are smaU openings (pores). The annexed figure Fis- 219- represents a piece of human skin about the size of a mustard-seed, as it appears under a powerful magnifying-glass. Partly an oily substance, and partly a watery perspiration, together with some carbonic acid, are separated from the body through the pores. Experiment — Put a piece of fresh animal skin in water; it sweUs up in it without dissolving; if kept for some time, it passes over into an offensive putrefaction. If however, the skin is boiled for some hours with wa- ter, the largest part of it dissolves, and we obtain a liquid which, on cooling, coagulates into a tremulous jelly. When dried, this forms the well-known glue. The skin does not contain glue ready formed, but a tissue, which first, after long boiling, passes over into glue, and has received the name of gelatinous tissue. 644 ANIMAL MATTER. 647. Gelatine forms a principal constituent of the animal body, for it is found in almost aU parts of it which do not belong to the albuminous substances; for instance, in the interior skin, the muscles, the ten- dons and ligaments, the bones, horns, &c. Its com- position is very nearly that of albumen or animal fibrine; Uke these, it is very rich in nitrogen, and con- tains also some sulphur, but it is distinguished from them essentially by its properties, and its behaviour to- wards other substances. Glue. — The common, amorphous glue is mostly prepared from refuse skins or bones, either by extrac- tion with hot water, or, better, by the pressure of steam (digesting). The concentrated hot solution is then al- lowed to settle, and the thin liquor yields, on cooUng, a stiff jelly, which is cut by wires into thin cakes, and placed to dry upon packthread nettings, which give it the well-known grooved appearance. Experiment. — If you aUow glue to lay in cold water, it swells up into an opaque soft mass; if you then heat it, you obtain a complete transparent solution, which, even when a hundred times diluted, stiffens on cooling. The application of glue as an adhesive me- dium is well known; its adhesive power is much in- creased by adding to it white lead (Russian glue) or borax (about an ounce or an ounce and a half to a pound of glue). Isinglass, also, is one of the gelatinous substances. This consists of the inner skin of several fishes, par- ticularly of the sturgeon, which, after being cleansed, is dried and brought into the market in the form of plates, or of sticks twisted into the shape of a horseshoe. On boiling, a colorless or odorless gelatinous solution is obtained from it, which is much used as an adhesive THE SKIN. 645 medium, or when smeared upon taffety as court-plaster, or mixed with the juices of fruits and sugar for the preparation of jellies. The antlers of the deer are likewise rich in gelatine, and on this account, when rasped, yield, by long con- tinued boiling with water, a liquid which stiffens in the cold (hartshorn jelly). Small quantities of gluten occur also in broth, and in roast-broth, and impart to them, especially to the latter, the property of stiffening in the cold to a tremu- lous jeUy. 648. Gelatine and Tannic Acid. — Experiment — If you pour some tincture of galls upon a solution of gelatine, or upon a decoction of meat, you obtain a flaky precipitate, a combination of gelatine with tan- nic acid, which is insoluble in water, and may remain exposed to the moist air without passing into putrefac- tion. For this reason, gelatine is an excellent means for clarifying liquids, for instance, wine, &c, from any tannin that they may contain. But this action of tannic acid upon gelatine is of far more importance, as it may be used for converting animal skins into leather. The gelatine of the skin is thus altered, as the gelatine in the experiment was, when the skins are packed in layers with ground oak or pine bark (tan) in vats, and allowed to remain moistened with water till they are quite saturated with the brown tannin of the bark (tanning). This penetra- tion takes place more rapidly by forcibly pressing the liquid containing tannin into the skin (quick-tanning). The brown sole and upper leather consist, accordingly, of cellular tissue, the gelatine of which has become in- timately combined with the tannic acid; it is now, especially when it is saturated with oil or fat, pUable, 646 ANIMAL MATTER. supple, and almost impervious to water; nor when moist does it undergo putrefaction. Skins are converted in another manner into leather, by means of certain salts, most frequently by laying them in a solution of alum and common salt, and afterwards working them with fish-oil and other fats; the leather prepared in this way is white, and is softer and more supple than the former (tawing). The still softer wash or chamois leather is obtained by working the skins a long time with fat. In this way the Indians also convert the skins of animals into soft leather, by kneading them with the brains of animals that have been steeped in hot water, until the fat contained in the brains has been absorbed by the skin. If the softened and scraped skins are stretched in frames, and rubbed, while drying, with pumice-stone, till they are quite smooth, the thin, translucent, stiff, and elastic parchment is obtained (hog-skin). By rub- bing with chalk, the parchment becomes white and opaque, by smearing with white lead and varnish, pol- ished and smooth (writing-parchment). 649. Before the animal skins can be subjected to either of the operations just described, they must be freed from the hair. This is easily done by scraping, after the skin has been decomposed either by the influ- ence of moisture and heat, or by caustic potassa. Sul- phuret of calcium may also be used for this purpose (§ 405). 650. Gelatine, like other animal substances in the presence of air and water, very readily passes into de- cay or putrefaction, and yields thereby, since it is very rich in nitrogen, much ammonia ; therefore it will not appear strange that it powerfully promotes the growth of plants. Its effect may be observed in a truly sur- THE SKIN. 647 prising manner in the hyacinth, if it is occasionally watered with a thin solution of glue, or if the bulbs are surrounded with horn-shavings when planted in the earth. 651. If gelatine is boiled for some time with potassa lye, there is formed from it, together with some other products of decomposition, a peculiar substance, crys- tallizing in needles ; it has a very sweet taste, and has received the name of sugar of gelatine, or glycocoll. 652. There is a kind of gelatine which varies some- what in its properties from common gelatine; it is ob- tained from young, not yet fully hardened bones, and from the cartilaginous parts of the animal body, — for instance, from the cartilages of the windpipe, of the nose, &c, — by long boiling with water. This kind of gelatine has received the special name of chondrine. 653. Horny Matter. — The hair, wool, bristles, feath- ers, nails, claws, hoofs, horns, scales, &c, which often cover the skin of animals, are not dissolved by boiling with water into gelatine; they very much resemble the latter in their constitution, but, besides nitrogen, they contain also some sulphur. Their containing sulphur is the reason why they become black, when heated with a solution of lead, since a dark sulphuret of lead is formed Wool consists of hollow yellowish tubes, cov- ered with fat. By washing with putrid urine, or soap- water, the fat may be removed; but by sulphurous acid the yellow color is converted into white (chlorine is no aDDlicable to the bleaching of wool). The fibres of wool as well as those of silk, likewise having an am- mal origin, have a far greater affinity for coloring mat- t^n the vegetable fibres linen or cotton have; and ter than the vege ^ ^ ^ may be 648 ANIMAL MATTER. By boiUng with lye, all the above-named animal sub- stances, consisting of horny matter, may be entirely dissolved. VII. THE BONES. The bones forming the soUd skeleton of the animal body consist, one third of organic gelatinous matter, and two thirds of inorganic matter (bone-earth). 654. Bone-earth. — Experiment — Put a piece of beef-bone, which has been weighed, into a furnace-fire, and take it out again when it has entirely recovered its white color; the gelatine burns up, but the bone-earth remains behind. The bone burnt to whiteness, which has become one third Ughter, consists principally of phosphate of Ume mixed with some carbonate of Ume (magnesia, fluoride of calcium, and chloride of sodium). This proportion between gelatine and bone-earth is, however, not unchangeable; it varies in different ani- mals, and indeed even in one and the same animal, ac- cording to its age. 655. Bone-black. — Experiment. — If you heat a bone for some hours in a crucible which is well covered with a piece of slate, it assumes a black color; it becomes bone-black (ivory-black, &c). As the air in such cases does not have access to the bones, only an imperfect combustion takes place, a charring of the gelatine; the bone-earth, intimately mixed with the carbon, re- mains behind. Experiment — If you add some diluted muriatic acid to the bone-black, and let it remain some time in a warm place, the bone-earth will be dissolved, and the carbon may be separated by filtration, washed, and dried. From one ounce of bone-black only half or THE BONES. 649 three fourths of a dram of carbon is obtained; but this, on account of its minute state of division, possesses such a striking bleaching power, that one ounce of bone-black acts far more powerfully than the same quantity of wood-coal. If ammonia is added to the filtered Uquid, the dissolved phosphate of lime is again precipitated from it as a white powder, because the muriatic acid is neutralized by the ammonia, and thereby loses the capacity of holding the bone-earth in solution. 656. Experiment — Put a bone in a glass vessel, and pour over it some diluted muriatic acid; the bone will gradually become soft and transparent, and finally pass into a cartilaginous translucent mass. The way in which the muriatic acid acts is obvious from the former experiment; it dissolves the bone-earth, and the gelatine remains behind, since it is insoluble in muriatic acid and in water. If the gelatine is taken from the acid, and, after having been washed, is boiled for some time with water, it passes over into glue, and a solution is obtained which coagulates on cooling. This method is employed in many factories for preparing glue from bones. The acid solution of bone-earth makes an ex- cellent manure. That bone-earth is in fact dissolved in the acid is readily ascertained by the addition of am- monia. 657. In boiling out the bones with water, not only the fat present in all bones, but also the gelatine lying in the external part, is extracted, and the latter may be entirely extracted when the boiling is performed in tight vessels, as in this case the Water is forced by the increased pressure into the interior of the bones. Steam, also, at a great tension, operates in the same way. Glue is prepared on a large scale, according to both of these methods. 55 650 ANIMAL MATTER. 658. Bone-dust. — Unburnt bones ground to a coarse powder (bone-dust), and also white or black burnt bones, have for many years been regarded in England as an excellent manure; in Germany it is only in more recent times that their economical value has been rec- ognized. It is very obvious how they enhance the fertility of land; the burnt bones furnish the soil, by means of the bone-earth, with two inorganic sub- stances, lime and phosphoric acid, which every plant requires for its development; the unburnt bones, more- over, by means of their gelatinous matter, furnish am- monia. VLTI. THE SOLID EXCREMENTS AND URINE. 659. Those ingredients of the food consumed, which are not appUcable to nourishment, that is, which can- not be converted into the constituents of the animal body, and those parts which are separated from the body (as no longer serviceable to the vital process) by the incessant process of renovation, which we caU life, are either removed from the body in an aeriform state, by breathing or insensible perspiration, or in a Uquid form, as urine, or, finaUy, in a solid form, that of the solid excrements. Both of the last-named substances are of great consequence in medicine and domestic economy; in medicine, because the physician, in cases of sickness, is frequently able, by their condition, to ascertain the nature of a disease; in domestic economy, because the farmer makes use of them for promoting the growth of plants. The solid excrements (faeces) consist, for the most part, of those constituents of the food which are not dissolved in the stomach, — not digested; in the her- THE SOLID EXCREMENTS AND URINE. 651 bivorous animals, principally of vegetable tissue, chlo- rophyll, wax, and insoluble salts; in the carnivorous animals, dogs, for instance, frequently almost wholly of inorganic substances, as phosphate of lime, magnesia, &c, mixed with but a very small quantity of organic matter. The beneficial influence of solid excrements on vegetation is principally owing to the inorganic compounds contained in them (lime and magnesia, phosphoric acid, and silicic acid). 660. By the urine, which is separated in the kid- neys from the arterial blood, the soluble salts contained in food, and also the nitrogen, no longer necessary for the vital process, are removed again from the body; it is natural, therefore, that the constituents of it, as like- wise of the fasces, should correspond exactly with the food consumed. If this is rich in soluble salts, the urine will also be rich in them; if this contains only a few soluble, but many insoluble salts, the urine will be poor in soluble salts, while the fasces will be rich in in- soluble salts. Consequently, the amount of inorganic substances in the animal excrement or manure may be just as accurately ascertained from the food which the animal consumes, as from the manure itself. The food has only to be burnt, and the remaining ashes ex- amined ; those parts of it which are soluble in water correspond with the salts in the urine; those which are insoluble, to the organic substances of the fasces. We find in the urine of cows and horses principally alka- line carbonates, muriates, and sulphates (potassa, soda, and ammonia); in the urine of men, moreover, some alkaline phosphates. 661. Nitrogen is contained in the urine, either in the form of urea^m-ic acid, or hippuric acid. Urine, like the juice of flesh, contains, moreover, creatine and creatinine (§ 640). 652 ANIMAL MATTER. Urea occurs in the greatest abundance in the urine of the higher animals, especiaUy in the carnivorous quadrupeds. It crystallizes in colorless needles, or prisms, and is easily soluble in water. This substance has excited great scientific interest, as it is the first or- ganic compound which has been artificially prepared. Thus, it was found that cyanate of ammonia, without losing any of its constituents, or receiving any new ones, was converted merely by heat into urea. From Cyanic Acid = Carbon, Oxygen, Nitrogen, and Ammonia = Nitrogen, Hydrogen, * i------------' was formed Urea. In a practical point of view, that decomposition which urea undergoes in urine, when the latter putre- fies by long standing in the air, is of great importance. During this decomposition, the urea combines with the constituents of two atoms of water, and becomes there- by carbonate of ammonia; from Urea = Carbon, Oxygen, Nitrogen, Hydrogen, and Water = Oxygen, Hydrogen, are formed Carbonic Acid and Ammonia. 662. Uric acid (lithic acid) predominates in the urine of the lower animals; the white excrements of birds and snakes (a mixture of fasces and urine) consist chiefly of urate of ammonia. In the pure state, it consists of fine white crystalline scales, which are dis- solved in water only with extreme difficulty. On ac- count of this difficult solubifity, they sometimes sepa- rate spontaneously from the urine (gravel and urinary calculi). If the excrements, which are rich in uric acid, are allowed to remain for some time exposed to the air they will absorb oxygen, and afterwards contain oxalate of ammonia; if the latter takes up more oxygen, it THE SOLID EXCREMENTS AND URINE. 653 passes over into carbonate of ammonia. Thus is ex- plained why we frequently find in some sorts of guano only traces of uric acid, but instead of it large quan- tities of oxalates. 663. Guano (bird-manure).— Guano, which in recent times has been in such demand as a manure, owes its efficacy in part to the uric acid contained in it, or, in so far as this has already undergone decomposition, to the ammoniacal salts formed from it, and in part also to inorganic salts (sulphate, phosphate, and muriate of potassa, soda, lime, magnesia, &c.) present in it. On account of the great difference in the article, it is indis- pensable that the farmer should test it before its appli- cation. This is done with sufficient accuracy for agri- cultural purposes in the following way. Experiment a. — Pour some strong vinegar over guano; no perceptible effervescence should ensue. A brisk effervescence would indicate an admixture of car- bonate of lime. Experiment b. — Heat half an ounce of guano in an iron spoon over an alcohol lamp, or upon glowing char- coal, till it is burnt to a white ashes; good guano should only leave behind, at the most, one dram of ashes. How much alkaline salt this ashes contains may be ascertained by extraction with hot water; what remains are earthy (lime and magnesia) salts. Experiment c — Treat half an ounce of pulverized guano several times with hot water, and decant the Uquid after it has become clear on settUng; then dry and weigh the muddy mass which finally remains; it should not weigh more than a quarter of an ounce. 664. Hippuric Acid. — This azotized acid always oc- curs in the urine of herbivorous animals; it crystalUzes in long white needles, and is difficultly soluble in water. 55* 654 ANIMAL MATTER. On the putrefaction of the urine, it is converted into benzoic acid and ammonia. Human urine contains the above-named compounds rich in nitrogen, — urea, uric acid, and hippuric acid ; the first, urea, in the largest quantity. 665. When urine remains for some time exposed to the air, it undergoes a decomposition, by which volatile substances having a disagreeable odor are formed; it passes into putrefaction. It is obvious from what has been stated, that carbonate of ammonia is to be regarded as the principal product of this decomposition (putrid urine contains, moreover, creatine). Putrid urine may, therefore, be employed for the cleansing of wool, and for the preparation of chloride of ammonium (§ 233). This change takes place when the urine is coUected in manure-heaps, or is poured upon the soil. To prevent the evaporation of the volatile carbonate of ammonia, it is well to add gypsum, diluted sulphuric acid, or green vitriol, from time to time, to the manure-heaps, by which means sulphate of ammonia is formed, which does not escape at the ordinary temperature. In this respect, also, an addition of substances rich in carbon, for instance, bone-black, earthy-brown coal, peat, &c, acts very beneficially, because the coal first retards the putrid decomposition, and afterwards retains the gases hereby formed (carbonic acid, ammonia, sulphuretted hydrogen, &c). The inorganic salts of the urine, and of the solid excrements, are not essentiaUy changed by the putrefaction. To these salts and to the nitrogen are principally to be ascribed the beneficial effects which animal manure exercises on the fertility of our fields. RETROSPECT. 655 RETROSPECT OF ANIMAL MATTER LN GENERAL. 1. A constant motion is taking place in the Uving animal, as well as in the living plant, — an incessant receiving (eating, drinking, and breathing), changing (digestion, assimilation), and separating (secretion, ex- cretion) of aeriform, liquid, and solid bodies. 2. In a chemical point of view, animal life is distin- guished principally from vegetable life by the uninter- rupted reception of oxygen, and separation of carbonic acid and water. (Among the Infusoria, however, there are some which exhale oxygen.) During the life of plants, on the contrary, carbonic acid and water are re- ceived, and oxygen separated. 3. Besides water, air, and some salts, those substances only serve for the nutrition of the animal body which are produced by means of vegetable or animal life. The plant consumes carbonic acid, the animal vege- table tissue, sugar, gum, fat, &c.; the plant consumes ammonia, the animal albuminous substances, for in- stance, gelatine, albumen, caseine, flesh, blood, &c. 4. The first series of the above-named means of nourishment, those rich in carbon, serves for the main- tenance of the respiratory or destructive processes, and for the generation of animal heat (elements of respi- ration) ; the second class, that of the means of nourish- ment rich in nitrogen, serves for the maintenance of the nutritive or formative process (plastic elements of nutrition). 5. Animal substances may be divided : — I. According to their composition, — a.) Into non-azotized substances (fat, sugar of milk, &c). b.) Into azotized, albuminous substances (albumen, caseine, flesh, fibrine, &c). 656 ANIMAL MATTER. c.). Into azotized gelatinous substances (gelatine of the bones, ligaments, gristle, &c). , d.) Into azotized excretory substances (urea, uric acid, hippuric acid, &c). II. According to their occurrence and their production in the animal body, — a.) Into products of the process of digestion. b.) " " " " breathing. c.) Constituents of the red blood. d.) " of the white blood (lymph). e) " of the flesh, &c. /.) " of the bones, &c. g.) " of the skin, hair, &c. h.) " of the secretory and excretory prod- ucts (gaU, milk, urine, &c). 6. The changes of animal matter by the influence of heat, water, air, acids, bases, &c, exceed in variety those of vegetable matter, since they are far more com- plex than the latter; they mainly agree with those which the azotized and sulphurized vegetable substan- ces experience. 7. The spontaneous changes of animal and vege- table matter may be arrested, — a.) By removal of the water (drying, baking, &c). b.) By exclusion of air (Appert's method of preserva- tion, bottling of beer, wine, &c). c.) By reducing the temperature below the freezing point (refrigerators, &c). d.) By antiseptics; for instance, common salt, nitre (salting), wood-vinegar, creosote (smoking), alcohol, sugar, charcoal, and arsenical, mercurial, and other metaUic compounds. THE END. yA*^ f^^^stv (. if h, to