ARMY MEDICAL LIBRARY WASHINGTON Founded 1836 . Section—- Number .../_0_?_96_/ Fobm 113c, W. D., S. G. O. 3—10543 (Revised June 13, 1936) !&*■ I I; u PRINCIPLESiOF CHEMISTRY. THE PRINCIPLES OF CHEMISTRY, ILLUSTRATED BY SIMPLE EXPERIMENTS. Dr. JULIUS ADOLPH STOCK El ARDT, PROFESSOR IN THE ROYAL ACADEMY OP AGRICULTURE AT THAUAND, AND ROYAL INSPECTOR OP MEDICINE IN SAXONY. TRANSLATED BY C. H. PEIRCE, M. D. MM'H AMERICAN, FROM THE SIXTH GERMAN EDITION. CAMBRIDGE : PUBLISHED BY JOHN BARTLETT. BOSTON: PHILLIPS, SAMPSON, & CO. MIILADELPHIA: LIPPINCOTT, GRAMDO, & CO. 18 52. Entered according to Act of Congress, in the year 1851, by John Baetlett, in the Clerk's Office of the District Court of the District of Massachusetts. QD CAMBRIDGE: STEREOTYPED AND PRINTED BY METCALF AND COMPANY, PRINTERS TO THE UNIVERSITY. w 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 a* VI 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. Cambridge, Sept. 1, 1850. NOTE THIRD AMERICAN EDITION. The first American edition of Stockhardt's " Princi- ples of Chemistry," translated from the third German edition, has been thoroughly revised with the fifth, re- cently published, and many alterations and additions have been made; among which are those that refer to Dobereiner's lamp, the section giving a Synopsis of Chemical Tests, and the Index. For the sake of convenience, we have also added a table showing the corresponding degrees of the Cen- tigrade and Fahrenheit's thermometers; likewise a ta- ble of the symbols and equivalents of the chemical elements, from the "Annual Report of the Progress of Chemistry, &c, No. V., by Justus Liebig, M. D., &c." In this table the equivalent numbers are in accordance with the hydrogen instead of the oxygen scale, the lat- ter, having oxygen as 100, being employed in the body of the work, as in the original, while the scale with hydrogen as 1 is that generally adopted by English and American chemists. C. H. P. Cambridge, January 1, 1851. 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 X INTRODUCTION7. of essays on operative surgery, or the solutions ol 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. XI 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, Rumford Professor in the University at Cambridge. I CONTENTS. _____________________ C/i ( V - 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,..........M Composition of Water,.........55 b XIV 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,.......... _ j3- Phosphorus,......... j3g Phosphuretted Hydrogen (predisposing affinity, water-bath, &c), . 145 Retrospect of the Pyrogens. Tldrd Group : Halogens. Chlorine (nascent state, degrees of oxidation, of sulphuration, of chlorination, &c ),....... 150 Iodine,............155 Bromine, Fluorine,...... 156 Cyanogen,...........157 Retrospect of the Halogens. Fourth Group: Hyalogens. Boron and Silicon,...... j ,g Retrospect of the Metalloids. Acids. First Group: Oxygen Acids. Nitric Acid (acids, bases, neutralization, &c), Nitrous Acid, Nitric Oxide, Nitrous Oxide, CONTENTS. XV Carbonic Acid (diffusion, mineral water, &c),.....164 Sulphuric Acid (anhydrous, Nordhausen, common, &c), . . 168 Sulphurous Acid,..........174 Phosphoric Acid,..........176 Phosphorous Acid, Oxide of Phosphorus,.....177 Chloric Acid, Hypochlorous Acid, &c, ..... 178 Cyanic Acid, Fulminic Acid,........179 Boracid Acid (glass, blow-pipe, volatilization of fixed substances, &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,...........I96 Acetic Acid,...........198 Retrospect of the Vegetable Acids. Radicals,............199 Capacity of Neutralization,........200 Light Metals. First Group: Alkali Metals. 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),..........2U Ammonia (dry distillation, chloride of ammonium, carbonate of am- monia, &c.),........... 231 Lithium,.......... Retrospect of the Alkalies. XVI CONTENTS. Second Group: Metals of the Alkaline Earths. Calcium (chalk, quicklime, burning of lime, mortar, gypsum, chloride of lime, &c),...........237 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),....... 27g 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,...... 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 of lead, white-lead, lead-tree, sulphuret of lead, &c.)....... ' Bismuth (fusible metal, oxide of bismuth, &c.),' . 3!! Copper (oxide of copper, colors of copper, reduction of metals, salts ' of copper, blue vrtriol, verdigris, sulphuret of copper, alloys of copper, brass, &c),... r ' ' "' Mercury^oxideofmercury.salts'ofme'rcury.ciunabar.'amalgams^c.)' 365 Silver (alloys, lunar caustic, &c), . ;' Gold (alloys, solution of gold, &c), . • . 379 ' 383 CONTENTS. XV11 Platinum (solution of platinum, spongy platinum, &c), . . 390 Palladium, Iridium, Rhodium, Osmium,......395 Retrospect of the Second Group of Heavy Metals. TJiird Group of the Heavy Metals. Tungsten, Molybdenum, Tellurium, Titanium, &c., .... 396 Chromium (salts of chromium, chrome yellow, chromic acid, &c), 397 Antimony (tartar emetic, Kermes mineral, golden sulphuret, type- metal, &c),...........402 Arsenic (fly-poison, white arsenic, Schweinfurth green, orpiment, Marsh's arsenical test, &c),........410 Retrospect of the Third Group of Heavy Metals. Retrospect of all the Metals (metals, metallic oxides, sulphurets, chlorides, oxygen salts, occurrence of the metals, &c.). Classification of the more common Chemical Elements. PART II. ORGANIC CHEMISTRY. Vegetable Matter. Vegetable Life (constituents of plants, organic radicals, &c), . . 419 I. Vegetable Tissue (germination, woody tissue, linen, cotton, bleaching, &c),........426 Changes of the Vegetable Tissue by Acids (gun-cotton, &c), 433 Changes of the Vegetable Tissue by Alkalies, . . .434 Changes of the Vegetable Tissue by Heat with free Access of Air,..........435 Changes of the Vegetable Tissue by Heat without Access of Air (charcoal, illuminating gas, wood-vinegar, creosote, wood-spirit, wood-tar, pit-coal tar, tar-water, coke, &c), . 436 Changes of the Vegetable Tissue by Air and Water, or Pu- trefaction and Decay (humus, marsh gas, pit-coal, brown coal, peat, &c),.........443 H. Starch, or Fecula (starch from potatoes, wheat, and peas; al- buminous substances ; sago, inuline, &c), ... 450 Changes of Starch into Gum and Sugar (starch-gum, dex- trine, starch-syrup, malt, diastase, mashing, &c), . . 458 ttt. Gum and Vegetable Mucus (gum Arabic, tragacanth, cerasine, pectine),......... c 464 Mil CONTENTS. IV. Sugar (grape-sugar, cane-sugar, liquid sugar, sugar of milk, mannite),........' Changes of Sugar by Heat and Acids, . • • • 4'J Retrospect of the Vegetable Tissue, Starch, Gum, and Sugar. V. Albuminous Substances (albumen, caseine, gluten), • -4,7 Changes of the Albuminous Substances by Decay and Putre- faction (formation of ammonia and nitre), • • .479 Retrospect of the Albuminous Substances. VI. Conversion of Sugar into Alcohol (alcoholic fermentation), 482 Wine,...........484 Beer (surface fermentation, bottom fermentation, yeast, &c), 487 Brandy (rectification, fusel oil, &c),.....491 Spirit of Wine, or Alcohol (tinctures, cordials, &c), . 438 VII. Conversion of Alcohol into Ether (talefiant gas, sulphuric ether. ether, naphtha, &c),.......502 Organic Radicals (ethyle),......508 VIII. Conversion of Alcohol into Vinegar (vinegar from brandy, wine, beer, starch, and sugar. Quick method of making vinegar. Aldehyde, acetyle, &c), . . . . • • • 509 Conversion of Sugar into Lactic and Butyric Acids (muci- laginous fermentation), .......515 Formation of Alcohol, Acetic Acid, and Lactic Acid, on the Baking of Bread,........ 516 Retrospect of the Changes of Sugar and Alcohol. IX. Fats and Fat Oils (oil, lard, tallow, emulsion, &c), . . 520 Changes of Fat by Heat (olefiant gas, illumination, &c), . 528 Composition of Fats (stearine, oleine, &c), .... 532 Vegetable Fats (drying oils, unctuous oils, &c), . . 534 Animal Fats (tallow, butter, fish oil, spermaceti, wax, &c), . 536 Fats and Alkalies, Soaps (hard soap, soft soap, fat acids, oxide of glyceryle, &c),.......540 Properties of Soaps ; Insoluble Soaps (plaster), . . 54 S X. Volatile or Ethereal Oils (preparation of them, varieties of vol- atile oils),..........551 Composition and Properties of the Volatile Oils (burning fluids, perfumed distilled water, oleo-saccharum, conversion of the volatile oils into resin, &c), ..... 556 XI. Resins and Gum-Resins ("turpentine and balsams, prepara- tion of the resins, kinds of resins, &c ), . . . 56g Composition and Properties of the Resins (sealing-wax, lamp- black, lac-varnish, resin soap, &c), ..... 573 Gum-Resins, ..... . Kg2 CONTENTS. XIX 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 Dyes,.......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 XVII. 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. The 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. T/ie 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 VII. Tlie Bones (bone-earth, animal coal, bone-dust, &c), . . 654 VIII. The Solid Excrements and Urine (urea, uric acid, guano, &c), . 659 Retrospect of Animal Matter in General. A Synopsis of the most Important Chemical Tests, . Thermometrical Table,...... Chemical Symbols and Equivalents, . . . • Index,........... 666 668 669 PART FIRST. INORGANIC CHEMISTRY. (mineral chemistry.) 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 altered wine; it has an acid smell and taste, and has lost its spirituous flavor, as well as its exhilarating 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, imbibing 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 tissue, 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 green coloring matter, — chlorophyll; and in the ripe tubers, a mealy substance, — starch. None of these sub- stances are injurious to health; but if the potatoes 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. The potato forms one of our most important articles 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 1* 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 is self-evident how improving and instructive for every thinking man must be that science which explains to him this vicissi- tude, and opens to him a clearer insight into the won- ders 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 conveniences of life that were not enjoyed by our fathers. It can- not be doubted that the farmer must at once regard chemistry as his indispensable friend, for it is this alone which acquaints him with the constituent parts of his soil, with the proper nutriment of the plants he wishes to cultivate, and with the means whereby he can en- hance the fruitfulness of his fields. i 5. Chemical Force or Affinity. — If a ball of iron be heated to redness, till a thick crust of scales is formed around it, and then weighed, it will be found to have increased in weight; consequently, it must have been supplied with something ponderable from the air. This ponderable substance is a species of gas, called oxygen; by its union with the iron it has become fixed, yet by other chemical processes it can be reconverted into its gaseous form. If this crust of iron is now exposed for a time to moisture, it will gradually become rust, and again weigh more than before; it has attracted and united to itself water, and more oxygen from the air. Accordingly, the crust consists of iron and oxy- gen, the rust, of iron, oxygen, and water, which have become most closely united with each other; — 8 CHEMICAL ACTION. they are chemically combined. There is a peculiar power, which is considered the cause of this intimate union, as, in general, of all chemical changes; it is called chemical power or affinity, and bodies that possess this capacity of uniting with each other are said to have an affinity for each other. Accordingly, iron at a red heat has an affinity for the oxygen of the air, and at an ordinary temperature it has also an affinity for water. A ducat changes neither its color nor its weight, whether at a glowing heat, or exposed to moisture; we con- clude that gold possesses no affinity for oxygen or for water. v 6. A force cannot be seen or grasped; we notice it only in the effects which it produces. If we would know whether a piece of steel possesses magnetic power, we apply a needle, and try whether this is attracted by it or not; we then conclude from its be- haviour as to the absence or presence of magnetism. Precisely the same course, that of experiment, must be taken, in order to become acquainted with the chemi- cal forces, the affinities of bodies for each other. Every experiment is a question put to a body, the answer to which we receive through a phenomenon, that is, through a change which we observe, sometimes by the sight or the smell, sometimes by the other senses. The question has just been put to iron and gold, whether they have an affinity for oxygen; the iron, converted in- to black oxide, gave an answer to this question, the un- changeable gold did not. Every change which we per- ceive, every new property which we observe in a body, is a letter in the language of chemistry. To learn this easily and thoroughly, it is above all things useful for the beginner to exercise himself in spelling, that is, in mak- ing experiments. To give directions for this is the ob- CHEMICAL ACTION. 9 ject of the present little work. Those experiments only have been introduced, which, on the one hand, can be performed easily, safely, and without great expense, and, on the other hand, seem best adapted to illustrate the chemical doctrines and laws, and to imprint them on the memory. 7. There are four leading questions which the chem- ist puts to the different natural bodies. a.) Of what are they composed? 'Take, for instance, a piece of bone. How is it affected when strongly heat- ed in a furnace ? It becomes whiter, lighter, and less solid than before (bone-ashes). But how is it affected when heated in a covered vessel ? It becomes lighter, and black (bone-black). If exposed to boiling water, or to steam, how is it affected ? It becomes lighter, and re- mains white; but in the water is dissolved glue. How in muriatic acid ? It becomes transparent; the bone- earth is dissolved, and a gristly mass remains, which, when boiled with water, turns to glue. What is the action of fire upon the glue ? In a covered vessel it is converted into coal, in an open one it burns and dis- appears. These few experiments show that the bone contains a glue which is combustible, and an earth which is not so; they show, at the same time, that it is the carbonized glue which, in the second experiment, colors the bone-earth black, and makes it bone-black; that this glue is dissolved in water, but not in muri- atic acid, &c. Glue and bone-earth are called the proximate constituents of bone, but by continued chemi- cal processes these can be resolved still further, that is, separated into simpler constituents. In bone-earth are found phosphorus, a metal (calcium), and oxygen; in the glue, besides carbon, three other bodies, —oxygen, hydrogen, and nitrogen. These bodies can be de- 10 CHEMICAL ACTION. composed no further by any known method of analysis, and are therefore called simple bodies, or chemical ele- ments. There are now about sixty known elements, and almost every year adds to their number; but this in- crease is of little importance to chemical science or its applications, for it consists of elements which but very seldom occur. This separating of compounded bodies into simple ones is designated by the name of analysis.' b.) Wliat changes do bodies undergo, when placed in contact with other bodies ? ) Phosphorus, which is ob- tained from bones, is luminous in the air, and is grad- ually converted into an acid liquid; it unites with the oxygen of the air, as the iron did on being heated to redness. If the phosphorus is gently heated, this union is attended with a vivid combustion, and there is formed an acid body which is different from the former; to which, if chalk be added, a new body is formed, very similar to bone-ashes ; it is in fact artificial bone-ashes. The number of new bodies which may be produced by the union of the elements with each other, or with com- pound bodies, is infinite, and entirely different sub- stances are often formed, according as the combination takes place under the influence of cold or heat, in water or in air, in greater or smaller quantities. This is combination or synthesis. c.) Wliat useful applications can be made of chemical theory and practice?. When the chemist discovers a new body, or a new property in one already known or a new method of synthesis or analysis, he imparts his discovery to the apothecary, the physician, the farmer, the manufacturer, and the tradesman, that ex- periments may be instituted for the purpose of ascer- taining whether any advantage, facility, or improve- ment can be derived for pharmacy, medicine, agricul- CHEMICAL ACTION. 11 ture, or the arts. Phosphorus ignites spontaneously at a gentle heat; it is used in friction-matches. Taken into the stomach it acts as a violent poison; it is at present the most common means for the extirpation of rats and mice. Bone-ashes and gluten are the constitu- ents universally found in the seeds of different kinds of grain; the chemist concludes from this, that pulverized bones must yield an excellent manure for grain; the agriculturist demonstrates this by experiments on a large scale. In bone-black the property has been dis- covered of attracting many substances held in solution in liquids, and of condensing them in itself: on account of this property, it is used for making impure water potable; the sugar-refiner employs it to make brown syrup colorless; with it the distiller purifies brandy from fousel oil. This is applied or practical chemistry. d.) Wliat are the causes of chemical changes, and according to what laws do they take place? If chemical experiments are performed, as they should be, with the balance in the hand, it will soon be observed, that when two different bodies which can unite with each other are brought together, sometimes a part of the one, sometimes a part of the other, remains free. Further experiments will show how much of one body, in weight, can be united with the other. If all bodies are tested in the same manner, the certainty is finally attained, that all chemical combinations take place only in fixed, unchangeable proportions, and that to every individ- ual body is assigned a definite weight, with which it always enters into any combination whatever. (§ 268.) This certainty is called a natural law. Many such laws of nature have already been ascertained, and they serve as a certain guide to the chemist in his labors, since they cannot, like human laws, be arbitrarily evaded or 12 WEIGHING AND MEASURING. changed. By them alone we attain to a scientific in- sight into the chemical processes, and to the capability of putting direct questions to bodies by experiment, and of testing the truth of the answers received. An explanation of the chemical processes based on natural laws, which presents a clear idea of the subject to the mind, is called a Theory. WEIGHING AND MEASURING. 8. Weighing.— The balance is to the chemist what the compass is to the mariner. The ocean was indeed navigated before the discovery of the compass; but not till after this could the sailor steer with confidence to a certain place, and recover his proper course, however often lost. And so, in chemistry, no systematic method of study could be pursued before the introduction of the balance. The balance is the standard, as well as the test, of chemical experiments; it teaches us how to ascertain the true composition of bodies, and shows us whether the questions put, the answers received, or the conclusions drawn from them, are correct or false. Hence it cannot be too strongly recommended to those commencing the study of chemistry to use the balance even in simple experiments. For the experiments de- scribed in this book, a common apothecaries' balance is all that is requisite. Such a balance consists of a brass beam, with arms of equal length, through the centre of which passes a steel wedge-shaped axis, resting on a hardened plate, so that the beam, to the extremities of which the pans are attached, may easily vibrate. It is essential WEIGHING AND MEASURING. 13 that the axis should be in the right place of the beam, a little above its centre of gravity, as in Fig. 1, a. The centre of gravity can be found by balancing the beam on its flat side, with the index attached to it, on a needle, and when the beam rests horizontally, the point of the needle desig- nates the centre of gravity. If the axis be placed too low, beneath the centre of gravity, as in Fig. 1, b, the beam will over- set, if one of the pans is more heavily loaded than the other. If placed directly in the centre, of gravity, the balance itself will cease to vibrate when the beam is in an oblique position. When the axis is too high above the centre of gravity, the balance loses much of its sensibility. This latter defect occurs most frequently, but is easily remedied by lowering the axis. 9. The apothecaries' weight and the French decimal weight are those commonly used. The following is the table of the apothecaries' weight, which will an- swer for all the experiments given in this book: — , Pound. Ounces. Drachms. Scruples. Grains. 1 = 12 = 96 = 288 = 5760 1 = 8 = 24 = 480 1 = 3 = 60 1 = 20 10. The new French system of weights and meas- ures, which is now almost universally adopted by chemists, is characterized by great simplicity, all its divisions being made by ten; hence the name decimal 2 14 WEIGHING AND MEASURING. Fig. 2. weight and measure. Its unit is derived from the size of our globe. In order to define the different localities on this globe, imaginary circles, as is well known, have been drawn around it. Those which pass round the earth from east to west, the largest of which is the equator, are called parallels of latitude (circles of latitude); those which pass round the earth lengthwise, intersect- ing at the poles, meridians (circles of longitude). The parallels of latitude grad- ually become smaller to- wards the poles; the me- ridians, on the contrary, are all of equal size. The circle, N E S W N repre- sents a meridian or circle of longitude. The fourth part of this circle, or, what is the same thing, the fourth part of the cir- cumference of our earth, as N E, is the basis of the French system. This quadrant was divided info ten million parts, one of which was taken as the unit, under the name of meter. A meter is about three feet and a quarter in length. The smaller measures are produced by dividing by ten, and are designated by Latin terms; the larger ones by multiplying by ten, and are designated by Greek terms. Smaller Measures. Meter. Decimeter = ^ meter. Centimeter = jjs " Millimeter =^ " Larger Measures. Meter. Decameter = 10 meters. Hectometer = 100 " Kilometer = 1,000 " Myriameter =10,000 " 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 = ^5 " Hectogramme = 100 " Milligramme = %$m " 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. 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, -r(ro, or, in decimals, 0.80; it is therefore -5- lighter than water. Ice, -v9^-, or, in decimals, 0.90; it is therefore iV lighter than water. Iron, Yoh or5 in decimals, 7.50; it is therefore 1\ times heavier than water. Quicksilver, ■1ro^-, 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 13y 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 18 SPECIFIC GRAVITY. flask from the pan, and put the nails into the flask. A bulk of water will be displaced equal to that of the nails; 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 \^- = 7.5, is the specific gravity of iron, of which the nails were made. 14. Experiment. — If we have to determine the specific grav- Flg# 3" 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 \-£- = 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, i 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- cific gravity of liquids,/ the hydrometer 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 ori 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. 5. 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, liquid, 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 stronger 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, and 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 lighter 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. . 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: — Reaumer's (R.), divided into eighty degrees; the centigrade of Celsius (C), into one hundred ; and Fahrenheifs (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 80D; 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 Germany, Reaumer's thermometer is used, Fig. 8 . R. C. F. Soil^W.^^-n 10ft—r 2/2 - '• Y ■ ;K J' *"; • v.:-*-..'^ -,:■ .-.;:• .'. ' '*: ->S ■$% ■",%' V'-J /:', if 40°--+ 60-—+ /22° T '§£ ■"'V- "'''''-' r'":J* ■■"''TV-j;;-:, -.:';.<'-&■'■.■..; .-j'Y'-V;-, cT&JP o '4' 0-^-+._ ' 0 S2 . "£*.%.,._ n%y o9- '~bt 7% > 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, 323 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 1 to a perforated cork, and then fitted to a flask, in P| 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* 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 -f4° 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. Were 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. Experiment. — 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 -{-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 become 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 whicn 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 Fig. 13. 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 as a convenient stand for annexed them. gure, serves Fig. 14. Experiment. — Repeat the former experi- ment, using instead of the tube a flask, and omit the sawdust, so that the water 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. C It is almost 1700 times lighter than water, because a measure 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 long 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 0° 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. i l* LIQUID. 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 atO° 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.f 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 f **J 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 AxND 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 are called hygrometers. 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. J It explains, also, how man is enabled to support the scorching sun 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- Fig. 18. ' 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. J 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, &c.; as they are often cracked by sudden cooling and contraction, which is also frequently caused by a current of cold air. Doors of furnaces, ladles, &c, are provided with wooden handles to prevent those using them from being burnt. Should a person desire to hold a flask or a test-tube while liquids are boiling in them, he must wrap round DIFFUSION OF HEAT. 45 them several folds of paper, or tie round them a piece of twine, in order that they may serve as a non-con- ductor between the glass and his fingers. By inclos- ing substances in non-conductors, the entrance of cold, or, more correctly, the departure of heat, may be pre- vented ; this principle is illustrated in our method of clothing, in the protection given to our wells and trees by covering them with straw, in the preservation of the seeds of plants by snow, and in numerous other phe- nomena of daily occurrence. Hence non-conductors are frequently called preservers of heat. 43. Radiation of Heat. — By conduction, bodies can communicate or abstract heat only when in contact. But heat is felt even at some distance from a fire or from a heated stove, and the earth is warmed by the sun, although a space of millions of miles is between them. This sort of heating is called radiation of heat. Experiment. — Envelop three tumblers with paper, one with silver paper, another with white, and a third with dull black paper, and place them in the sun; a thermometer will indicate that the tumbler with the black paper is heated the most, and that with the silver paper the least, and yet all these vessels have been equally exposed to the rays of the sun. This differ- ence is explained on the principle, that the sun's rays are reflected from light-colored and shining bodies, whilst they are absorbed by those which have a dull, dark color. From this absorption it would seem that the light of the sun's rays is converted into heat. It explains why black clothes keep us warmer than white ones; why the snow melts more rapidly when soot or dark earth is scattered upon it; and why grapes and other fruits ripen quicker against dark walls than against those having a light color. 46 WATER AND HEAT. If hot water is poured into the tumblers enveloped with paper, and the cooling of it noted by the ther- mometer, the contrary effect will be observed; the glass covered with black paper will first become cold, and that wrapped in silver paper the last; because bodies with dull surfaces radiate the heat more rapidly than those with polished surfaces. For this reason, coffee retains heat longer in a bright than in a tarnished pot; a stove of glazed Dutch tiles remains hot longer than another of unglazed tiles; a smooth sheet-iron stove, longer than a similar one of rough cast-iron, &c. The radiation of heat enables us to explain some of those common natural phenomena which otherwise would remain obscure. Why do not the rays of the sun, even in the hottest summers, melt the snow upon the tops of high mountains, which are nearer than the level portions of the earth to the sun ? Because they only heat those bodies which can absorb their warmth, as the rough surface of the earth. The snow is indeed struck by the rays of the sun, but being a white and shining body it reflects them and remains cold. 44.{Formation of Dew.— When the surface of the earth has become warm, the air is heated by it; hence, during the day the lower strata will always be warmer than the upper. But a change takes place after the sun has gone down. The earth continues to radiate heat without receiving any in exchange, and its tem- perature consequently diminishes. Neither does the air so readily part with its heat, and therefore it attains dur- ing the night a higher temperature than the surface of the earth ; it is only cooled where it comes in contact with the colder earth. If this cooling should reach the dew-point of the air (§ 38), then the vapors are con- densed, on the soil or on vegetation, in the form of SOLUTION AND CRYSTALLIZATION. 47 small drops, just as a tumbler is covered with vapor when brought from a cold into a warm room, — dew forms. If the temperature of the earth sinks in the night to the freezing point, or below it, the aqueous vapor is deposited in a solid form, and is called frost. The radiation of heat from the earth is greatest when the weather is clear and serene; but it is obstructed by clouds and wind. Thus the most copious deposit of dew takes place only in clear and quiet nights. The clouds serve as a screen in reflecting back to the earth the rays of heat, so that it can only cool gradually. The same effect is produced by the mats, straw, and boards with which the gardener covers his young plants to protect them from the late frosts of spring, or from freezing. The annexed figure, in which arrows denote the direction of heat, will serve to render this process more intelligible. J Sunbeams. Fig. 20. SOLUTION AND CRYSTALLIZATION. 45. Solution. — Water can dissolve many bodies, and unite intimately with them, without losing its transpar- 48 WATER AND HEAT. ency. Such combinations are called solutions. If rain- water meets with soluble substances, either in the earth or in the rocks through wmich it oozes, it dissolves them; and this explains why almost all spring-water, as it evaporates, yields an earthy or saline residue. Frequently this residue, particularly when it contains lime, is so altered during evaporation, that it can no longer be dissolved in water, and forms a hard in- crustation round the inner sides of the vessels used in cookery. The springs of Carlsbad deposit so much residue, that articles immersed in them appear in a short time to be externally petrified or incrusted. If water is unusually rich in soluble substances, especially such as possess medicinal properties, as, for example, iron, sulphur, &c, it receives the name of mineral water, and the springs from which it issues are called mineral springs. A pound of sea-water contains about half an ounce of substances in solution. 46. Experiment. — Pour a teaspoonful of slaked lime (§ 33) into a bottle, and fill it with water, cork it up, and, after shaking it for some minutes, let it stand until the water has become perfectly clear. By care- fully inclining the bottle, most of the liquid may be poured off free from the sediment. This operation is called decantation, and the clear liquid is lime-water. Lime is but slightly soluble in water, three hundred ounces of water being required to dissolve half an ounce of lime ; the excess remains undissolved, and as lime is heavier than water, it settles at the bottom. That a por- tion of it has been dissolved is known by the peculiar taste imparted to the liquid. This taste is called alkaline. Keep a part of the lime-water in a well-stopped bottle for future use; it will remain transparent and clear. Pour the remainder into a tumbler, and expose SOLUTION AND CRYSTALLIZATION. 49 it to the air; the water soon becomes turbid and cov- ered with a film, which gradually grows thicker, and settles at the bottom. If after some days the water has become clear again, it will have lost its alkaline taste; the lime dissolved in it, having been chemically changed by the air and rendered insoluble, will be found as a powder at the bottom of the tumbler. 47. Experiment. — Put into a flask half an ounce of litmus, pour over it three ounces of water, and let it remain in a warm place until the liquid has obtained a dark-blue color. Litmus consists of a blue coloring- matter, which is soluble in water, and is hence taken up by it; it also contains some earthy matter, which is insoluble, and is deposited as a slimy mass. These two substances might be sepa- Fi?.21. Fig. 22. 6 V rated from each other, as in the former experiment, by decantation, but it can be done more readily by filtra- tion. For this purpose, cut a piece of blotting-paper into a circular shape, fold it together twice, and then place this filter into a glass funnel. That the paper and the glass may not come into too close contact, place between them thin pieces of wood or glass; a piece of cord must also be inserted between the funnel and the neck of the flask into which the liquid is to be filtered, to allow an opening for the escape of the air from the flask, as otherwise the fluid could not flow in. The filter, which must never be higher than the top of the funnel, is first moistened with water before the fluid is poured upon it. Blotting-paper consists of fine linen or cotton fibres matted together, between which are 5 50 WATER AND HEAT. small interstices or pores, through which liquids, but no fine solid particles, can pass; these remain on the filter. Writing-paper cannot be used for filtration, as its pores are filled up by glue or starch. £ 48. Experiment. — Pour 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 acid (has an acid reaction). Experiment. — Mix cautiously another portion of the solution with lemon-j uice, until the blue color appears distinctly red; this also serves to color 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, j 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. u_ 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 long 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. 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 salt, treated like Glauber salts, lose nothing in weight, neither do they become opaque nor pulverulent; they contain no chemically combined water. 5* 54 WATER AND HEAT. COMPOSITION OF WATER. 55. Besides that electricity, which we admire on a grand scale in the majestic phenomena of lightning, or which we generate on a small scale by rubbing various 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- istry, 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 -j- 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 may be obtained in great quantities from water, by means of the galvanic battery; but in a more simple manner as follows. Experiment. -L Introduce into a somewhat tall, but not too thin, test- 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. A retort-holder is a wooden stand provided with a mov- 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. J 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 Fig. 27. . a b force is sufficient to hold them to- (g) (§) gether (a, Fig. 27); but at an increased (q)(o) 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.j 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. If you mix, by merely rubbing together with the fingers upon a sheet of paper, chlorate of potas- sa with its own weight of black oxide of manganese, the evolution of gas will be vastly accelerated. 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, Fi?. 28. . 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 60 METALLOIDS. instrument. When wanted for use, pour into the vessel as much water as will be sufficient to cover the shelf an inch deep, and then invert the vessel intended for the reception of the gas, with its mouth exactly over 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 contrivance is called a pneumatic trough. In order to collect and pre- serve larger quantities of gas, and to experiment with them more conveniently, special contrivances, called gasometers, are used in chemical laboratories. 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.) anc* $ Oxygen—-—'^* _____—Chloride of potassium t OtaSSa ^ 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- ' 'g, ' 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 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. f 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 Missing Pages: P. 63-70 missing HYDROGEN. 71 Fig. 36. 84. Experiment. —uIf 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 common sulphuric acid, pour this 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 inte- rior of the vessel, but only on the outside, where it is surrounded by atmospheric 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 ex- periment the lower vessel must not be immediately ex- posed to the lighted taper, because, if all the hydrogen is not displaced, an explosion might ensue that would break the flask; but if the taper be applied after ten minutes 72 METALLOIDS. have elapsed, the flask will be found no longer to con- tain any combustible gas, this having entirely escaped, j Hydrogen is the lightest of all gases; 14| measures of it weigh only as much as one measure of atmospheric air. On account of its levity, it is used for filling balloons. _. 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* , 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 L~ platinum, and is employed as tinder in the ^. ~-Jf-' well-known Dobereiner's inflammable lamp. The apparatus here represented consists of a flask, having the bottom broken off, and to the neck of which the cover of the glass vessel, c, with the cock, e, is fastened air-tight. A piece of zinc is suspended in the flask by means of a wire. If diluted sulphuric acid is now poured into the vessel, c, upon which the cover with the flask at- tached is placed, then, the cock being opened, that the air contained in the flask may be displaced by the acid from beneath, hydrogen is immediately evolved by the contact of the zinc with the acid, which hydrogen must be collected in the flask by closing the cock, e, the acid being thereby forced into the exterior vessel, until it no longer touches the zinc. Upon opening the stop-cock, e,the gas issues from the fine jet, and is directed against HYDROGEN. 73 Fig. 39. the spongy platinum, /. As the gas es- capes, the sulphuric acid passes again into the interior vessel, and generates fresh hydrogen upon reaching the zinc. Spongy platinum possesses, in a high degree, the power of absorbing oxygen and condensing 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 chemically combine to form water, and the heat thus liberated is sufficient to ignite the platinum tinder, and to inflame the gas, which subsequently 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. 86.1 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. ,40. 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 j 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.) fEvery chemical combination or decomposition is /jf "attended with liberation of heat. S r \ Exact experiments have shown that two measures of Fig. 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- sult of the combination is water. rBut two measures of hydrogen and one of oxygen do not yield three meas- ures of vapor; they afford two measures only. Thus the two gases condense one third by chemical union. \ If both the hydrogen and oxygen were suddenly mixed 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 weight, 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-j 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 -{-, 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 -4- sign. H2 signifies accordingly two atoms of hydrogen, H,, three atoms, &c.; but 2 H O 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, tnd filter them. A black residue will remain on the filter, which principally consists of carbon that was con- tained 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, transparent crystals. The formation of it is ex- plained in the following diagram : — Water = oxygen and hydrogen Iron_________I = oxide of iron 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,J that V, simple bodies unite only with simple bodies,)jand com- ^- f 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 78 METALLOIDS. affinity for a base, cooperates with it and enables it to overpower the water, and a base is formed (protoxide 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; it is called the atmosphere, and is supposed to extend about forty-five miles above the solid earth. The air pos- 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 that 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. Fig. 43. a AIR. 79 Fig. 44. 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. In 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 and down in the cylinder of many 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, Fig. 45. 80 METALLOIDS. 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 beaker-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, —f 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 13y times light- er than quick silver. \ The Surface of the earth. instrument by which the amount of atmospheric pressure can be determined is called the (barometer.) Fig. 47. j^r 45 miles high yfater 34 feet high. -^S^^^incheshigh. V AIR. 81 Fig. 48. V 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 inches, perhaps to s (Fig. 48). The height of the quicksilver, from a & to 5, amounts to about 30 inches. The quicksilver does not fall lower, on account of the external pressure of the atmosphere, which is ex- erted on the quicksilver at a b, and not at s, since this end is closed. The col- umn of quicksilver in the tube may be regarded as the counterpoise to the at- mospheric pressure, and it is hence con- cluded that the latter exerts just as much 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 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 Fig. 49. ! 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 syphon 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 r>$ 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. 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 air 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 than in the valley below, f On the top of Mont Blanc quicksilver rises only to the height of 16 inches in the barometer, and water boils at 84° C. Hence the barom- eter and the boiling point of water may be employed for calculating the heights of mountains^ 96. As water boils more easily under diminished pressure, so it boils with more difficulty when the pres- sure is increased. An increase of pressure can be pro- duced, not only by the air, but by the steam of the wa- ter itself, if new steam be constantly generated, while AIR. 85 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 110° to 120° entirely penetrates the bones, and extracts the gelatine also from the interior of them. — 97. Air and Heat. —rfHeal 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 trader 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. Tf 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 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 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 fa^ life), from its inability to support respiration. / It forms the chief element of at- 0, mospheric air; this consisting of four measures of /'*'■■•' nitrogen, and only one of oxygen, j 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. I 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.j (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; land 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 S* 90 METALLOIDS. cloudiness in the liquid; it is the affirmative answer to the question put by the lime-water to the air. If you ask, What is the source of this carbonic acid ? the re- ly is, CIt is formed wherever substances are burning, wherever men and animals are breathing, and wherever decay and putrefaction are taking place, j In 100 measures of atmospheric air are contained, — 79 measures of nitrogen, or N. 21 " " oxygen, " O. 3o-i5 " " carbonic acid, " CO,. and variable quantities of water, " H O. r In crowded rooms, and other confined places, the air becomes deteriorated ; that is, poorer in oxygen and richer in carbonic acid, h J! That the air also contains other foreign ingredients is 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). At. Wt. = 75. 103. If a piece of wood be placed on the hot hearth of a stove, it becomes brown, and finally black, — it is charred. If water be poured over a burning chip, the latter is extinguished, — it is likewise charred. A piece of linen, when inflamed and immediately smothered, becomes tinder. Tinder is charred linen. In the first CARBON. 91 case, the heat was not sufficiently strong entirely to consume the wood; in the second, the complete burn- ing was prevented by quenching, and in the third by the exclusion of air. i All animal and vegetable substan- " l) j ces, if only partially ournt, are converted into coal. \ As coal, on exclusion of the air, cannot be melted, even in the strongest heat, so the exterior of it is very different, according to the character and structure of the sub- stance from which it was prepared; indeed, this differ- ence often extends itself throughout the interior struc- ture, as in charcoal, soot, coke, bone-black, &c. ( In the charring of organic bodies the coal is not generated, but it previously existed in them, though in chemical combi- f "fa Q . nation with other substances, which are principally driv- en off by heat, as is obviously the case from the fact that the charred body weighs much less than the orig- inal substance. \ All animals and plants consist, there- fore, partly of coal; or, in chemical language, of Car- bon = C. rCarbon also exists in the mineral kingdom. It forms the principal element of pit coal, brown coal, &c, which / U «-> have all been formed from the vegetation of an earlier * i period.*} [It is found almost pure in the diamond and ' in the graphite, \ and, (combined with oxygen, is con- ^ tained in limestone, marble, chalk, / 0 and various other minerals, j 104. Charcoal (C containing a little ashes.) Experiment. — Gradually intro- duce a burning splinter of wood into a test-tube. The part out- side of the tube only will burn with a flame, while that within merely chars, because the air is 92 METALLOIDS. excluded. On the same principle, charcoal is prepared on a large scale. ^ Piles of wood (charcoal kilns) are erected, which are covered with turf and moistened earth, and the wood is then kindled. This would be extinguished, however, for want of air, if holes were not made, by wooden pokers, at different parts of the kiln, through which fresh air may be admitted, and the burnt air may escape. Only so much air should be ad- mitted as is necessary for carbonizing or half-burning the wood. When this has been accomplished in the neigh- bourhood of the holes, they must be closed, and new ones made at other points. At last all the openings are carefully stopped, that the fire may be suffocated. When cold, the wood will be found thoroughly burnt to black- ness and charred, the shape of the knots and rings being still perceptible. One pound of wood yields about one quarter of a pound of charcoal. / 105. Experiments with Charcoal. Experiment a. — Weigh a piece of freshly-burnt char- coal, and let it remain for a day in a moist place; it will now weigh more than before, owing to its having imbibed air and moisture. If the coal be now put into hot water, the air will escape from the coal in numerous bubbles, being expelled by the heavier water, which re- places the air in the small interstices or pores of the coal. The snapping of such coals when placed upon the fire is hereby easily explained ; the gases and vapors are expanded to such an extent by the sudden heat, that the coal is forced asunder, with a sort of explosion. Polished steel articles are often packed up in charcoal dust, that the air in the interior of the package may be kept dry, thus protecting the steel from rusting. Pulver- ized charcoal, on account of its absorbing power, may CARBON. 93 also be used for purifying sick-rooms, and other apart- ments filled with deleterious vapors and gases. Experiment b. — Grind freshly-burnt charcoal to a coarse powder, and place it on a filter. Then pour over it some red wine, or some water colored black by a few drops of ink ; the liquid will pass through the filter nearly or quite colorless, the coal hav- ing absorbed or retained the coloring matter. Sugar-refiners take advantage of this property of charcoal in bleaching their brown syrups. Experiment c. — Foul stagnant water is deprived of its bad taste, and islrendered clear / ;) and colorless, by being filtered through char- coal, i /In some large cities, where there is a scarcity of potable water, it is not unusual to filter it / through charcoal, j Grain, likewise, which has become musty, may be rendered sweet by intimately mixing it with pulverized charcoal, and allowing them to re- main some weeks in contact. Coal will also retard decay in vegetable and animal substances for a long period, and water remains pure for years in vessels which have been charred upon the inside; potatoes may be kept in cellars longer, without sprouting or rotting, when laid in with coal-dust; and meat, when packed in it, passes more slowly into a state of putrefaction. Experiment d. — Charcoal renders ordinary brandy pleasanter in taste and smell, by absorbing into its pores an acrid volatile oil, fusel oil, with which some crude brandy is contaminated. Coal deprives beer of its bitterness, by absorbing certain component parts of the hops. 106. /The cause of this remarkable power of coal to attract and retain within itself such various substances, depends on its spongy, porous character. If a plate of 94 METALLOIDS. glass be dipped into water and immediately removed, some of the water will remain adhering to its surface, showing that the water and glass have an attraction for each other. This power is called surface-attraction, or adhesion. This adhesion can be better illustrated by dipping a glass tube with a fine bore into water; the water rises in it, and the rise in the tube will increase Fig. 57. in proportion to the decrease of the di- ameter. Such tubes present a great sur- face of glass to a small amount of liquid, and the sides are in such close proximity, that they aid each other in drawing up the water into the tube. This sort of adhesion is called capillary attraction. It is this which causes oil to rise in the lamp-wick, the spreading of water in blotting-paper, and the diffusion of moisture through sugar and plastered walls. In the same man- ner, all solid bodies which have many pores, and conse- quently much surface, attract fluids and gases. A piece of charcoal, the size of a walnut, is intersected by many hundreds of partitions, which, if they could be placed by the side of each other, would cover a space a thousand times larger than the piece of coal itself covered. The force of attraction of this large surface is so powerful, that the coal can absorb from 80 to 90 times more than its own bulk of many species of gas. It is very probable that these gases, by such a compres- sure into 80 or 90 times smaller space within the coal, become fluid or solid. In the case of spongy platinum (§ 85, c), a yet more porous substance than coal, heat is produced, in con- sequence of the absorption of oxygen and hydrogen rendering the platinum red-hot. Heat, also, but to a CARBON. 95 less extent, is developed in charcoal when it absorbs gases ; the charcoal may be heated even to redness, undergoing spontaneous combustion, by heaping to- gether large masses of it in a pulverized state, and many an unfortunate accident has occurred from this cause, especially in factories for the manufacture of gunpowder. Hydrogen and oxygen, however long they remain in contact, do not enter into chemical union, but when the mixture is brought into contact with spongy platinum they instantly unite, forming water. This will be easily understood, when it is remembered that chemical force acts only at insensible distances, and consequently only when substances are in the very closest contact. In spongy platinum, as in other porous bodies, gases can be condensed to the 80th, and indeed, in the former case, to the 800th part of their volume ; they must there- fore touch each other from 80 to 800 times more closely than in their natural condition. ,~- 107. Not only charcoal, but the following varieties of coal, have many different applications. i Soot, or lamp-black, (C containing empyreumatic matter,) is coal in a state of minute division, which is deposited from carbonaceous gases, commonly from il- luminating gas ; for instance, from the flame of pit- j ' * coal, wood, oil, rosin, &c, when during the combustion there is an insufficient supply of air. One variety of superior quality is called lamp-black. (§ 116.) The soot must be freed from the empyreumatic substances, either by igniting it thoroughly in a well-closed vessel, or by treating it with strong alcohol. Soot is well known as a most important black coloring substance (Indian ink, printing-ink). \ i Coke, or charred pit-coal, (C generally containing II' ' 96 METALLOIDS. considerable quantities of ashes,) has a gray color, is more or less porous, is very hard, and has a metallic lustre; it burns without forming soot, and gives out an intense heat; hence it is an excellent fuel, and es- pecially adapted for the smelting of iron, and for the heating of locomotive boilers. Coke is obtained as a secondary product in the preparation of illuminating gas from pit-coal. (§ 118.) f Bone-black (C intimately mixed with bone-ashes, and generally also with some azotized substances) is obtained by heating bones in close vessels. The coal contained in it amounts only to about one tenth part of the whole, the other nine tenths being bone-ashes ; but notwithstanding this, its decolorizing power is so strong, that it is preferred to all other kinds of coal as a means of abstracting color from the syrup of brown sugar, or from other dark liquids. Two sorts of carbon found in the mineral kingdom, viz. graphite and the diamond, possess very remark- able, yet different, properties. ( Graphite, or plumbago, (crystallized black carbon,) a gray substance, having a metallic lustre, imparts its color so readily to other bodies, that it is used for mak- ing lead pencils, and for giving a black polish to iron articles, such as stoves, &c.; it is so soft and lubricating, that it is added to grease for the purpose of preventing friction in wheels and machinery; it is also so nearly in- combustible, that crucibles are made of it, which endure the strongest fire without burning (blue-pots)y j Diamond (crystallized colorless carbon) is the hardest of all bodies. In external appearance it has not, indeed, the slightest resemblance to coal, yet it can be entirely burnt up in oxygen, and carbonic acid is the only prod- uct obtained from it, and exactly so much is obtained CARBON. 97 as would have resulted from the combustion of an equally heavy piece of charcoal or coke. In order to crystallize a substance, it must first be rendered fluid, which is done either by melting or dissolving it. Coal can neither be melted by the strongest heat, nor dis- solved in any known liquid. Should a method ever be discovered for rendering it liquid, then diamonds could certainly be artificially imitated. \ 108. Carbon shows very clearly how one and the same body can have quite different forms and different properties, i In charcoal, soot, coke, and animal carbon, it is black without any determined shape (amorphous), and very combustible!; in graphite it is black, with a j j crystallized foliated structure, and is nearly incom- bustible ; in the diamond it is colorless, and is crystal- lized as a four-sided double pyramid (octahedron), and is likewise almost incombustible, f Hence carbon is said to be dimorphous, having two different crystalline forms, j If a body can assume more than two crystalline forms it is said to be polymorphous, having many forms. This property, which many elements have, of as- suming different forms, is also called allotropic (from aAAorpoW, different nature), and it is designated by an- nexing Greek letters to the chemical symbols. Accord- ingly carbon occurs in the three following allotropic states or modifications ; as Co in diamond, C0 in graphite, and C y in charcoal. The cause of this difference depends upon the relative position of the particles or atoms constituting the body towards each other. The same fibres of cotton, which, after carding, are parallel to each other, when matted to- gether without order, constitute paper or paste-board ; when loosely woven together, wadding; when twisted, yarn or thread, and when they are made to intersect 9 98 METALLOIDS. each other regularly, or in some intricate manner, cloth, stockings, velvet, &c. Nature also impresses different forms upon the same substance, but in a still more varied and artistical manner. The adaptation of the atoms to each other is not rendered visible to us, even by the aid of the strongest microscope; but this theory may be regarded as correct, since it explains the sub- ject in a simple and natural manner. 109. Coal and Oxygen. —■ Coal undergoes no change on exposure to the air, or when imbedded in the ground. It is not decomposed at common temperatures, that is, ' * ^ it does not enter into combination with the oxygen of the air or of water.\ 'But this, as is well known, takes place very readily, when heated to redness. It then burns and disappears, with the exception of a small quantity of ashes. The heat thus developed is the re- sult of the chemical union of the carbon with the Oxygen of the air. The gas generated is called carbonic acid, which forms, with lime-water, a white precipitate (carbonate of lime), as has been stated previously. * *7 Carbonic acid consists of one atom of carbon and two atoms of oxygen, consequently its formula is = C 02. It may also be obtained as follows, j Carbonic Acid. — Experiment. -^-Mix 109 grains of oxide of mercury with four grains of charcoal, and heat them in a test-tube (§ 56). A lighted taper introduced into the gas is extinguished, a sign that it contains no free oxygen. If you shake it with lime-water, the liquid becomes turbid, and on shaking the flask the : . finger is sucked in, or rather it is pressed into the neck of the flask by the atmospheric air, a proof that the gas was absorbed by the lime-water, and that a vacuum was produced within the vessel. If the oxide of mer- cury had been heated by itself (§ 56), it would have CARBON. 99 separated into mercury and ox- ygen ; and this also happens in the present ex- periment, but the oxygen does not escape as such, it having previous- ly united with part of the coal; the gas evolved is carbonic acid. The mercury is found, as a metallic mirror, at the upper part of the test-tube. After the experiment is finished, some coal still remains in the test-tube, for only 3 grains of it have united with the 8 grains of oxygen con- tained in the oxide of mercury; consequently, in the same proportions as in the burning of charcoal in pure oxygen. (§§ 63, 70.) We see that 3 grains of carbon combine with as much oxygen as 101 grains of mer- cury, or (§ 70) with as much oxygen as 8 grains of sul- phur, 6 grains of phosphorus, 23 grains of sodium, or '20 grains of iron. These numbers are called equiva- lents; they indicate that 3 grains of carbon have the same chemical value as 101 grains of mercury, or as 8 grains of sulphur, &c. In the same sense, when we see a steam-engine perform, in one day, the work for which four horses or twenty-four men were required, we say that the power of the steam-engine is equivalent to the power of four horses or twenty-four men. (§ 164). J 110. Carbonic Oxide Gas.—-.When charcoal, during combustion, has a sufficient supply of air, then carbonic / 100 METALLOIDS. acid, or C 02, is formed; but if there is a deficiency of air, then 3 grains of charcoal unite with only half as much oxygen, namely, with 4 instead of 8 grains, and there is produced but half-made carbonic acid, as it were, which is called carbonic oxide gas =CO. Car- bonic oxide gas is extremely poisonous when inhaled, and constitutes what the miners call coal-gas. This gas is always formed when charcoal burns slowly, for example, in a chafing-dish, because the ashes, accumu- lating round the coals, obstruct the access of air; and it is also formed when the damper of a stove is closed, before the coal is burnt out, since in this case the draught of air, and consequently the supply of sufficient oxygen, is prevented. Notwithstanding repeated warn- ings, accidents not seldom occur from the fumes of burning charcoal. Carbonic oxide burns, when kindled, with a blue flame; it takes up the deficiency of oxygen not supplied to it by the air while forming, and is con- verted into carbonic acid; that is, it takes up as much again oxygen, and C O becomes C 0*. \ The blue flame which is always perceived on feeding the fire with fresh /v coals, or in large masses of glowing coals, is burning ' - carbonic oxide gas. ^ COMBUSTION. lll.jjEvery combustion with which we are familiarly / acquainted is caused by a rapid chemical union of com- 7 bustible bodies with the oxygen of the air, and the pro- cess may be regarded as one of oxidation. \ The con- sumed or oxidized combustible substances, that is, the compound of the fuel with oxygen, are mostly aeriform. We call them smoke, which will not support combus- tion. \It follows from this, that, in order to maintain COMBUSTION. 101 combustion, fresh air must be continually supplied to the fire, and the smoke conducted off. This is effected by a current of air. | Experiment. — Place the glass cylinder of a lamp over a lighted candle, which will soon be extinguished, because no fresh air can enter from be- low. The candle is also extin- guished when the cylinder is covered at the top, although the cylinder is so held that the air can gain admittance from/be- low; it is extinguished in this case, because the escape of the burnt gases is prevented. If the cylinder is placed uncovered on two pieces of wood, the candle continues to burn quietly, and by holding a taper recently extinguished near the lower opening, it will be obvious, from the direction of the smoke, that air rushes in at the bottom, but escapes at the top, having become hot and lighter during the process of combustion. The hand can be held quite close over the flame of a lamp without being burnt, but if the flame be surrounded by the glass cylinder, the heat cannot be borne, unless the hand be much farther removed from the flame. In the former case the hot air radiates in all directions, while in the latter it is confined within the walls of the cylin- der ; consequently the hot air must issue from the top more rapidly, and the cold air enter more rapidly from below to replace it. Owing to this increased current of air, cylinders effect a brisker and more perfect combus- tion, and cause a brighter and stronger illuminating flame. Chimneys are to fire-places what cylinders are to 9* 102 METALLOIDS. lamps, tit is well known that narrow chimneys draw better than wide ones; the air escapes from the former hotter and more rapidly; hence a greater quantity of cold air is supplied to the fire, causing it to burn more freely. \ Experiment. — If the upper part of the cylinder of a lamp be divided into two channels by a partition down the middle, the candle will then burn, even if access of air be cut off from below. The smoke of a glimmering taper will be drawn inwards on one side and expelled from the other, as indi- cated by the arrows in the fig- ure ; a draught of air sets in from the top to the bottom, which supplies the oxygen requisite for combustion; that this current of air exists is also made evident by the quiver- ing motion of the flame. 112/. In common lamps air has access only to the outside of the flame; hence combustion goes on only at the circumference, and not simultaneously in the interior, as is indicat- ed by the dark central portion. But if air be admitted into the interior of the flame, this dark portion disappears; then a more complete combustion is effected, with the production of increased light. On this principle the so-called Argand lamps are constructed, to which are adapted circular wicks, so that the air has access, not only to the exterior surface of the flame, but is ad- mitted from below directly through the cen- COMBUSTION. 103 tre of the flame, causing it to burn in the form of a hol- low ring. They are also called lamps with a double draught. J The so-called Berzelius Spirit-Lamp, universal- ly employed in chemical laboratories, when a higher heat is required jjthan a common spirit-lamp can yield, is constructed on this principle. It is made of brass plate, is attached to a brass stand, and is provided with several rings of various sizes for holding porcelain dishes, crucibles, and other vessels, that are to be heated. In using this lamp, care must be taken that sufficient space be left between the vessels and the chimney for the escape of the hot air, and for the diffu- sion of the upper part of the flame. If this be not done, the combustion will be imperfect, and consequently less heat be given out. When it is desired to feed the lamp with more alcohol, the flame must first be extinguished, as otherwise the alcohol might take fire and cause seri- ous inconvenience. 113. In order to kindle a substance, and to keep it continually burning, it must first be heated to a certain point, and then maintained at this temperature. Experiment. — Heat in a small ves- sel some ashes or sand, on which a few friction-matches have been placed; the latter, or more correctly the phos- phorus on them, will not inflame until the ashes are heated to about 65 -70° C, which can be readily ascertained by the thermometer. 114. Slow and rapid Combustion. — Experiment. — If Fig. 63. 104 METALLOIDS. a coil of fine platinum wire, being raised to a white heat in the flame of a spirit-lamp, be plunged quickly into a heated goblet into which a teaspoonful of strong alcohol has been poured, it will continue to glow in the va- por of the alcohol, whilst it would soon have ceased glowing in the air. / The alcohol un- dergoes a slow combustion, that is, it unites '"' Sit w a smau quantity of oxygen, and the ^====^ heat thus liberated is sufficient to keep the wire red-hot. \ A disagreeable sour smell will also be perceived, proceeding from the new combination formed between the alcohol and oxygen during the slow combustion, and which may be regarded as partially burnt alcohol. When alcohol is kindled, it burns briskly and completely, and the products emit no smell; there- fore the combinations formed during the rapid or com- plete combustion must be different from those formed during the slow or incomplete combustion. Something similar to this is perceived with all other combustible bodies. |The unpleasant odor caused by the singeing of the hair, the scorching of wool, the boiling over of milk, and the dull burning of blotting-paper, is the conse- ' 1 ^ q»ence of incomplete combustion; if they had been com- pletely burnt, no bad smell would have been observed, J If in the last experiment ether be substituted for alco- hol, and the wire be brought to a white heat, it will cause it to burst into flame; but the red-hot wire will not kindle it. The temperature of the red-hot wire is not sufficient to produce rapid combustion of the ether, but a stronger heat is required. As phosphorus did not inflame until it was heated to 70^ C. nor ether un- til a higher temperature was attained, so all combusti- ble substances require a certain degree of heat at which COMBUSTION. 105 to enter into rapid combustion, some a higher and some a lower degree. When burning bodies are cooled below this temperature, they are extinguished. Red-hot iron will continue to burn in oxygen, but not in common air; heat enough is evolved during the combustion in oxygen to keep it burning, while, in the five times slow- er combustion in the air, sufficient heat is not evolved for the continuance of this process. Pit-coal requires for sustained combustion a stronger heat than wood; therefore the pieces must lay close upon each other in the grate or stove, or they will cool off too much and cease burning; wood continues to burn, even when spread loosely about on the hearth of the stove. A glowing coal is extinguished much sooner when placed on iron than on wood, for the iron, a good conductor of heat, withdraws the warmth more rapidly than wood, a bad conductor. Even the flame of a candle, or of a spirit-lamp, can be cooled to such a degree by iron as to be extinguished. Experiment. — If you introduce a piece of wire gauze, such as is used for sieves, into the flame of a lamp, this will be sup- pressed as though a piece of tin- plate were held over it, and smoke, but no flame, passes through the net-work. This smoke, if kindled by a match, will again burn. The smoke in passing through the iron gauze has become cooled down be- low the temperature necessary for burning; if this temperature be restored by the applica- tion of a taper, or by the gauze having reached a white heat, the smoke is again kindled. • An illustrious English chemist has made a successful 106 METALLOIDS. application of this principle for the prevention of the ex- plosions so often occurring in coal mines. In many mines a combustible gas (fire-damp, or light carburetted hydrogen) issues from the fissures of the coal, which, mixing with the atmospheric air, forms an explosive gas, which might be fatal to the miner who should carry a burning lamp into a vein filled with such a gas. But I U." if the flame be inclosed within an iron net-work, the ex- plosive gas would only burn within the cage ; the miner thus warned has time to withdraw, and this dangerous gas is afterwards expelled by appropriate means. (Da- vy's Safety-lamp.) \ - ■-Z- 115. Complete Combustion. — In the combustion of hydrogen, water is formed (§ 87), and in the combustion of carbon, carbonic acid (§§ 63, 109). Both of these products are also formed in the combustion of most other substances familiar to us, as these generally con- tain hydrogen and carbon, on which depends their ca- pacity for burning. Experiment. — Invert an empty flask over a burning candle, so that it may receive the hot gases as they form; it becomes clouded on the in- side, from the deposition of moisture which is condensed from the smoke upon the cold sur- face of the glass. This smoke consequently contains vapor. This explains why, on heat- ing a vessel over a lamp, moisture is depos- ited on the outside as long as it remains cold. Pour lime-water into the flask, and agitate it. The liquid will become turbid, and deposit, on standing, a white powder (carbonate of lime); thus the smoke contains also carbonic acid; some nitrogen also must of course be present, as it existed in the at- mospheric air which was used in maintaining the fire. COMBUSTION. 107 These component parts exist likewise in the smoke which issues from the chimneys of houses, whether formed from the combustion of wood, pit-coal, or brown coal; and are contained in the invisible current which ascends from an alcohol or oil flame. 116. Incomplete Combustion.— Experiment.—\Jf you extinguish a lighted candle having a long snuff, you can rekindle the smoke ascending from the wick, even at some distance ; this smoke <& consists of the combustible gases jpi into which the tallow has been I'' 1 converted by heating. It is par- tially consumed tallow, and has an unpleasant smell. On being extinguished, sufficient heat is not retained for its complete combustion, but this commences again when the smoke is heated and kindled by a match. Completely burnt tallow, that is, tallow converted into carbonic acid and water, has no smell. Experiment. — If you stop up the draught of a burn- ing astral or Argand lamp (§ 112) with a piece of paper, the flame will immediately become dark and red, emitting a thick black smoke, which has a very dis- agreeable odor, and which covers a piece of paper held over it with soot. There is an incomplete combustion of the oil, owing to the exclusion of the air; a part of the carbon contained in the oil remains unconsumed, and escapes as soot. Experiment.—Refrigeration gives rise to the same phenomenon, as, for example, when an iron spoon is held over the flame of a com- 108 METALLOIDS. mon oil-lamp, so as partly to suppress it. The iron, being a good conductor, not only cools the flame, but it also obstructs the draught of air; a part of the car- bon, therefore, remains unconsumed, and is deposited as soot upon the spoon. In this way watchmakers pre- pare lamp-black for marking their dial-plates. A tal- low candle yields an invisible and scentless smoke when allowed to burn quietly, but, on the contrary, a sooty and disagreeably smelling smoke when the flame is cooled by blowing upon it, or moving the lamp about. In order to smoke meat rapidly, green or wet wood is burnt; this yields a thick, black smoke, because it can- not be heated above 100° C. as long as it contains water, and at this low temperature it is only incom- pletely consumed. 117. Illuminating Gas and Flame. — Experiment. — i To acquire a clearer understanding of the products of incomplete combustion, put into a large test-tube some wood-shavings, and heat it, having previously adapted to the opening a cork, provided with a glass tube or a piece of pipe-stem (Fig. 69). The gaseous matter which is formed will pass through the tube, and, on be- ing kindled, will burn with a luminous flame. Previously to being kindled, the shavings emit a sour and empyreumatic odor; this smell, however, vanishes en- tirely on burning. Flame, then, is caused by burning gas. Substances which do not become gaseous on combustion can only glow, but cannot burn with a flame. Some charcoal will remain un- burnt in the test-tube, owing to a deficiency in the sup- ply of air. An application of this principle is made COMBUSTION. 109 on a large scale in the preparation of illuminating gas by the heating of pit-coal, rosin, &c, in closed iron ves- sels. Every candle and every oil-lamp, when burning, are generators of gas on a small scale. \ 118. Experiment. — Repeat the experiment with pul- verized pit-coal, Fis-m but conduct the gas, through a bent glass tube, into a jar placed over the pneuma- tic trough, and collect it as al- ready described. The gas is color- less, and on be- ing ignited burns like hydrogen,but with a far more luminous flame. Its chief constit- uent is indeed hydrogen, chemically united with some carbon (carburetted hydrogen gas). During combus- tion, both constituents of illuminating gas unite with the oxygen of the air, and are converted into carbonic acid and water. Coke, already alluded to, which is a tolerably pure carbon, remains behind in the tube. | Carbon forms with hydrogen a very numerous class of chemical compounds ; those with which we are best acquainted are, — a) light carburetted hydrogen (EL C), which issues from the fissures of many coal-beds (fire- damp, § 114), and is likewise always generated wher- ever vegetable matter is putrefying under water (marsh 10 110 METALLOIDS. gas, § 446); owing to its larger proportion of hydrogen, it is lighter, and, on account of its smaller proportion of carbon, it burns with a paler flame, than b) heavy car- buretted hydrogen (H4 C,), commonly called olefiant gas (§503). These two gases (H2 C and H4 C<) form the principal constituents of the common illuminating gas.""} 119. Experiment.— Heat some pieces of wood, and conduct the volatile matter through a tube into a flask immersed in cold water, and adapt to the cork of the lat- Fig. 71. ter another open tube, for the escape of the illuminating gas. (Two fluids will be condensed at the bottom of the flask; one a very thick viscid fluid, and the other a thinner watery substance. The first is called wood- tar ; it is resinous, and is therefore insoluble in water. The other is called wood-vinegar, or pyroligneous acid; both its taste and action upon blue test-paper in- dicate that it is an acid. ) ^Illuminating gas, wood-tar, and wood-vinegar did not previously exist in the wood, but Were formed during the incomplete combustion from its constituent parts, carbon, hydrogen, and oxy- gen. ^ Such new-formed substances are called products; and in the present case, moreover, products of the in- COMBUSTION. Ill complete combustion (dry distillation) of wood. Hy- drogen predominates in illuminating gas ; oxygen in pyroligneous acid; and carbon in wood-tar; all of them, owing to the deficient supply of air, were but partially burnt, and they are hence capable of undergoing further combustion in the air, and, like the wood from which they originated, of being fully converted into carbonic acid and water. A portion of wood always remains in- completely consumed in our fire-places, and therefore soot is deposited in the funnels and chimneys; the tar and acid are also deposited, as a black shining sub- stance, upon the jambs of the chimney. The operation by which, as in the present case, liquid products may be obtained from a solid substance, is called dry distillation. Most of these liquids have a brown color, and a peculiar, unpleasant, empyreumatic smell and taste. — — — — _ ~___- 120. It has been previously stated that hydrogen burns very easily, and with a flame, while carbon burns more difficultly, and without flame; thus is easily explained why fuel burns with a flame at the com- mencement of the combustion, but finally only glows ; it is the hydrogen which first burns with a flame, and afterwards the carbon, with a mere glow, without flame. All combustible substances that contain hydro- gen and carbon burn in a similar manner. Burning wood presents the most convincing illustration of this fact. 121. The alcohol flame consists of two parts; the dark central part is alcohol vapor, and the bright envelope is alcohol vapor uniting chemically with the oxygen of the air. The tapering form of the flame is ow- ing to the ascending of the hot gases, and 112 METALLOIDS. the rushing in of cold air from below. The alcohol is drawn up from the lamp by the capillarity of the wick (§ 106); it burns with a feeble lustre, but if a twisted wire or some other solid body be introduced into it, it will then burn vividly. If a thin wire is placed across the flame, it will be heated to redness near the margins of the flame, while in the interior it will remain dark ; consequently, the external part is much hotter than the central part of the flame. The point of greatest heat is indicated by the mark in the figure, and vessels to be heated over the spirit-lamp should never be placed below this point. This may be rendered very evident by applying a friction-match to this part of the flame, when it will take fire at once; but not so quickly if thrust into the centre of the flame. 122. An the flame of a lamp or candle, three portions can be distinguished; in the middle (a, Fig. 73), the dark centre, consisting of illuminating gas (decomposed tallow); around this (b), the luminous cone, consisting of burning hydro- gen, intimately mixed with carbon at a white heat; and on the very outside (c), a thin, scarcely perceptible veil, in which carbon is burning. If a horizontal section, through the centre of the flame, be supposed, it would present nearly the same appearance as in Fig. 74. The middle circle is carburetted Fig. 74. hydrogen, or illuminating gas ; the hydrogen of which burns first, and the great warmth thus evolved brings the carbon to a white heat (this is indicated by the second circle); and finally, in the exterior circle, the carbon is consumed. The heated 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 will 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. \ I 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 light, but, on the contrary, a brilliant light when heated to a white glow, j 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 called 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 liquid 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 solid 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 all, 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 living 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 weight. 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 (in the wider sense) 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 (oxides in the narrower sense). 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 concisely the constitution of the com- pound bodies. SECOND GROUP OF METALLOIDS: PYROGENS. 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- l r-, 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) L 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 solid 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 ^' stand till a crust has formed over the surface; \K 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 {nose 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. Fig. 76. If the sulphur is allowed to cool quietly, without de- canting the liquid 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, like 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, Fig. 77. 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, glue, &c. /128. Experiment.— If the sulphur in the test-tube be heated still more strong- 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. Clf 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 sublimation, 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 called 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 will be dissolved, imparting to the liquid a yellowish-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 0} sulphur, or precipitated sulphur, land 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 02). If another atom of oxygen be added to this, there is then formed the common and very important acid, called sulphuric acid (S 06). 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. 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 haye 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- ers call them glance, blende, or pyrites. The pyrites having the lustre of brass, and found in almost all pit- coal, is sulphuret of iron; red cinnabar is sulphuret of mercury, &c. The sulphuret of copper, artificially 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 small 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 will be perceived ; a chemical compound, sulphuret of iron, is formed. If the two substances be mixed together 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 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; a.nd 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. Fig. 80. JT 1 K 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 Volatile. of and this unites iron, 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 liquefied, 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 small 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 ^jj 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 litharge, 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 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 tree, 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 Insoluble. black c()lor> The added Fluid. base effects, what other- wise would not have oc- ^iey 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. Lead paper is used for the detection of sulphuretted hydrogen, by which it is colored brown or black. It is made by passing strips of paper through a weak solu- tion of sugar of lead in water. 135. It is well known, that during the decomposi- tion of animal substances, blood, urine, excrements, white of eggs, &c, a putrid odor is evolved; this is owing to sulphuretted hydrogen, which is formed SELENIUM.--PHOSPHORUS. 129 from the small quantity of sulphur contained in most 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 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, &c<)— and in some acrid plants, such as mustard and horseradish. If these are suffered to decay, sulphu- retted hydrogen is evolved from them. 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 nauseous sulphuretted water; by removing the rot- ten pipe, the water will again become odorless and potable. 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). 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 130 METALLOIDS. violence, and might occasion dangerous wounds. It may catch fire even when lying upon blotting paper, par- 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- ,v 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. 7 139. 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, like 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, but after a time it becomes yellow, and coated over with a hydrated white crust. I Phosphorus is insoluble in water, but soluble in ether, / alcohol, sulphuret of carbon, and oils. J Phosphorus is an exceedingly violent poison, and is for this reason frequently employed for the extirpation of rats and mice. The rat electuary, so called, (phosphorus dough,) is composed of 1 dram of phosphorus, 8 ounces of hot water, and 8 ounces of flour. (See p. 682.) 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 PHOSPHORUS. 131 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 to shine in the dark; hence its name,phosphorus, from 4>Z>s, light, and fopav, 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 liquid. 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 volatilizes 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 phosphoric acid, which is always generated when phosphorus is completely burnt, that is, with a flame, as has already been explained. 132 METALLOIDS. 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. 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 is prepared from hot mucilage (70° C), to which small pieces of phos- phorus are added, being thoroughly incorporated with it by constant rubbing till cold. But as the mass, becom- ing hard on drying, would prevent the admission of air to the phosphorus, there must be added some substance rich in oxygen, as black oxide of manganese, nitre, or red-lead, from which the phosphorus can abstract the oxygen necessary for its ignition. If parts of phos- phorus, 4 of gum Arabic, 4 of water, 2 of nitre, and 2 of red-lead, form a good inflammable mass. A tempera- ture of 65-70° C. is requisite for kindling matches (§ 113); in this case the temperature is caused by fric- tion. 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 access of air is prevented by the PHOSPHORUS. 133 Fig.; Fig. 8i. 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- cially in the dark. The phos- phorus enters at once into oxida- tion, but with the formation of a lower compound; it swims as a red-hot powder in the liquid, and is called oxide of phosphorus, con- taining 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 D 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 fee- ble and imperfect, because the heavy smoke, consist- ing of phosphoric and phosphorous acids, passing off slowly, allows the admission of only a small quantity of air. Some red oxide of phosphorus is also deposited on the upper part of the tube. But the combustion becomes at once more vivid by in- clining the tube, and when the tube is held perpen- dicularly it is complete, as then the draught of air is most powerful. In this way phosphorus may be oxidized to either degree required; it must be slowly burnt to form phosphorous acid, imperfectly to form oxide of phosphorus, and completely to form phos- 12 134 METALLOIDS. phoric acid. The experiment is also well adapted for illustrating the principle of draughts in chimneys, &c. (§111). - 144. 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. The lime is removed by sulphuric acid. Sulphate of lime is formed. f The oxygen (Os) is expelled by igniting Phosphoric J the bones with charcoal (carbonic acid acid. 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, escapes 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 (C O), 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 (P H3). 145. Experiment. — Put into an ounce flask a quarter 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 PHOSPHURETTED HYDROGEN. 135 it in a small vessel containing a strong solution of salt, prepared by adding half an ounce of salt to an 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 will be evolved, which, as it issues from the tube and comes in contact with the air, inflames spontaneously. This gas is called phosphuretted hydrogen, and consists of several combi- nations of phosphorus and hydrogen, chiefly of P H3. If you collect it in a small jar filled with water, it im- mediately ignites upon the admission of air. Both the phosphorus and the hydrogen combine with the oxygen of the air, and there results phosphoric acid (P Os) and water (3 H O). 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 accomplish, 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 stron^ base, for instance, lime, with which the acids 136 METALLOIDS. 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- 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 shall 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 RETROSPECT OF THE PYROGENS. 137 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 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 boiling 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 saline 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 especially 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 chemically on each other, one of them must, as a general rule, be liquid or gaseous. 12* 138 METALLOIDS. 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- 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 called reactions. 11. Taste is perceived only in soluble bodies, odor only in volatile ones. CHLORINE. 139 THIRD GROUP OF METALLOIDS: HALOGENS. CHLORINE (CI). At. Wt. = 443. — Sp. Gr. = 2.5. 150. Experiment. — Pour one ounce and a half of muriatic acid upon a quarter of an ounce of finely powdered black oxide of manganese, and heat it grad- ually in a flask, to which is adapted a bent glass tube; a yellowish-green gas lis disengaged, which is collected by a process already described. This gas is called chlorine (from xa*> part), or similarly constituted bodies. BORON AND OXYGEN. Boracic Acid, B03. 180. Experiment. — Dissolve in a porcelain dish half an ounce of borax in an ounce and a half of boiling water, and add muriatic acid by drops to the solution, until the liquid gives a strong acid reaction; on grad- ually cooling, 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 will first melt and swell in its water of crystallization 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, litharge, 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 volatilizing, 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 smaller interior cone, of a blue color, and a larger exterior cone, of a yellowish ap- pearance ; the former is called the reducing flame, the lat- ter 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 interior 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, like 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 called flint is called in chemistry silicic acid. We find it tolera- Fig. 99. fciy pUre jn qUartz and flint5 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 cornelian, the violet amethyst, the green chrys- oprase, the variegated agate and jasper, the opal and chalcedony, — these well-known pre- cious stones consist, likewise, of silica; their colors are chiefly owing to the presence of metallic oxides. Com- mon sand is rendered, by hydrated oxide of iron (rust), yellow or brown colored silica. In its natural state, silica is so hard as to give sparks with steel, and is quite in- soluble 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 liquid with from ten to twelve times its quantity of water, and then remove 188 ACIDS. the potassa by muriatic acid, the liquid will remain clear, and the silicic acid remain dissolved in the water. But this solubility is destroyed as soon as the solution is evaporated to dryness, and the silicic acid is then thrown down as a white powder, which is completely in- soluble in water. Thus, as is obvious, silicic acid exists also in two quite dissimilar isomeric modifications, one insoluble, as occurring in siliceous stones and rocks; and another soluble, as found in plants and water. Almost all our springs, as well as our plants, contain small quantities of silicic 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. \ Silica 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 silica, (or if there is not enough potassa, which renders the silica soluble,) these properties will be wanting to the stalk, and it will bend over. The horse-tail plant (Equise- tum) contains so much silica that it may be used for polishing wood. Silicic acid is found even in the animal kingdom, particularly in the class of Infusorise, which are only visible under the microscope; the shells of many Infusorise 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-volatility, 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. r* /. .ti _ . ... • '* .1 : - J r. //f- ^RETROSPECT OF THE OXYGEN ACIDS. 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 chemically 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 called oxy-salts. SECOND GROUP: HYDRACIDS, 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 ACDD (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. j 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 in 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 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 gas, 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 muriatic 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 F's-10L 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 - Volatile. de- composed by the more powerful sulphuric acid, which combines with the base, and expels the hy- drochloric acid. The sulphate of soda (Glauber salts) 17 Non- volatile. 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 fill 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 light 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 (thefiltrate) 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 called sesquichlo- ride of iron (Fe2 Cl3). This salt contains one half more chlorine than the former. Muriatic acid is very often used for dissolving metallic 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 will 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, like 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 metallic oxide (§ 152). 3.) By the solution of a metal in a hydrogen acid (§ 186). 4.) By the solution of a metallic 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 + H O is the same as Na O, H CI.) AQUA REGIA. 197 Formerly the combinations of chlorine with the met- als were universally 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 -f- H O = Fe O, H CI.) Sesquichloride of iron and water, the same as the muriate of the sesquioxide of iron. (Fe2 Cl3-l-3HO=Fe203 + 3HCl.) AQUA REGIA, OR NITRO-MURIATIC ACID (2HCI + NO5). 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 liquids 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 FLUORINE, + 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. —Hub 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 the bowl with a piece of window- 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 small 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 small 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 ACIDS. 1. The haloids or halogens — chlorine, bromine, io- dine, fluorine, and cyanogen — form acids, not only with oxygen, but also with hydrogen. 2. The halogens have a greater preference for hydro- 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. 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 called protochlorides, protobromides, &c. The former correspond with the peroxide salts, the latter with the protoxide salts. RETROSPECT OF THE COMBINATIONS OF THE METAL- LOIDS WITH OXYGEN AND HYDROGEN. 192. The combinations which hydrogen forms with the halogens have been here grouped together, because they have the greatest similarity to each other. These 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 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 metalloids, 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- metallic 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 Oa), 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- Affinity for Oxygen. Metalloids. Affinity for Hydrogen. Fig. 103. Silicon. Boron. Carbon. Phosphorus. Sulphur. Selenium. Nitrogen. Cyanogen. Iodine. Bromine. Chlorine. Fluorine. 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 called inorganic or mineral acids, because they are prin- cipally found in the mineral kingdom, or prepared artifi- cially 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 may 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 will be considered in the second and third parts of this work. TARTARIC ACID (HO, 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 peculiar 204 ACIDS. empyreumatic odor. If, during the Fig. 104. process of charring, you hold over 4^ K?^n\ *ne ac^ a ^T'co^ glass vessel, it ^N^" Xrv.. will become lined with globules ^""""■^fc// 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 wTood. 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 essentially distinguished from the inorganic, wmich consist only of two elements, and which are neither charred nor consumed in the fire. Experiment. — Pour a little warm water over some tar- taric acid; it will 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, slimy flakes will be deposited, and the acid taste will gradually be lost,—it putrefies. In a similar manner, all organic acids, when they are diluted with water, decompose after a time. Experiment. — Mix gradually a solution of tartaric acid with ammonia; there will 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 potassa with a solution of tartaric acid; the carbonic • TARTARIC ACID. 205 acid escapes; the liquid, however, remains clear, because the neutral tartrate of potassa (K O, T) formed is an easily soluble salt. But by adding yet more tartaric acid, the liquid becomes turbid, and deposits a quantity of small, 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 crystallization. These crystals are called acid tartrate of potassa, or bitartrate of potassa (K O, 2 T 4- H O); 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 generally 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 lime, which forms with sulphuric acid an insoluble, or at least very difficultly soluble compound. By boiling 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 lime, 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 obliged 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, finally remain a white powder, which has an alkaline taste, a basic reaction, and which, on the addition of an acid, will 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 still ignorant how they are formed in plants and animals. All 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- plish in his retorts 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. OXALIC ACID (H O, 6, or HO, C2O3). 196. 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 yellow- ish-red fumes (N 03) will commence. Con- tinue boiling until these vapors cease, and then put the liquid 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, like most acids, contains water chemically 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 Os). 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 will 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 oxalic 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 C02, 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 all 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- pally burns, because it is very readily combustible; at last principally 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 principally 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 oxalic 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 Oa. 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 will be depos- ited on cooling, which have an acid reaction ; they are called acid oxalate, or binoxalate 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 called 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 (Oxalis), 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 and let the liquid settle; the decanted water contains a small quantity (^) 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 lime; consequently oxalic acid has a greater affinity for lime than sulphuric acid has, since it is able to displace the latter acid. The decomposition takes place more rapidly and perfectly when the oxalic 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 lime and lime salts. Experiment e. —r Add some spoonfuls of water to a piece of green vitriol of the size of a pea, and moisten 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 oxalic acid with water into a thin paste, and dot the yellow paper with it in several places; the color will soon dis- appear from those spots, and you obtain a white pattern on a yellow ground. Oxalic acid easily dissolves ses- -HO, SO3 CttOCoOg ) __jfONH3 S03 HONH3.C^CctO,C203 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 application for the re- moval of ink-spots from linen 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 oxalic acid, or an oxalate containing a free acid, causes the white spots on fabrics dyed yellow by peroxide of iron, and also why it removes ink-spots from garments, paper, &c. ACETIC ACID (HO, A). 198. Vinegar is likewise a vegetable acid. It is often formed spontaneously, producing mischievous conse- quences. It is formed when sweet or spirituous liquors, 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 will 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 following manner. Experiment. — Add to one pound of colorless vinegar 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 called 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 metallic 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 metallic 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 smell. The strongest acetic acid (hydrated acetic acid) crystallizes on cooling; 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 well 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 smell will be evolved. 214 ACIDS. RETROSPECT OF THE VEGETABLE ACIDS. 1. Almost all vegetable acids consist of carbon, hy- drogen, and oxygen (oxalic acid being an exception.) 2. They are generated during the growth of plants, 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- cially imitated, but as a general rule this is effected by the metamorphosis of other vegetable substances. 5. All 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 (water of constitution); 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 metalloids 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 called 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 clement 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 neutralization 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 litharge. 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 0xyScn' 100 oz. are neutralized by 118 oz. of potassa ; these contain 20 oz. 100 « « « « 70 " " lime; " " 20 " 100 « « « " 90 " " protoxide of iron;" " 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 called the capacity of neutralization of sulphuric acid. The action of bases upon all the other acids has been examined in the same manner, and the capacity of neutralization of the latter determined. That of nitric acid, for example, is 14f; that of carbonic acid, 36}; 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| " " " " " 1*1" 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 all neutral sulphates, as 60 to 20, or as 3 to 1. « " nitrates, " 732 « 14|, " " 5 " 1. " " carbonates, « 72| " 36|, " " 2 « 1. Water acts also as a base when chemically com- bined with an acid. In common sulphuric acid (H O, S O,), 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 05), as 5 to 1, &c. LIGHT METALS. FIRST GROUP: ALKALI-METALS. POTASSIUM (K). At. Wt. = 489. — Sp. Gr. = 0.8. 201. Potash, or Carbonate of Potassa (K O, C Oa). Experiment. — Fit into a funnel a filter of blotting- paper, and place upon it a handful of wood- Fig. 107. ashes, and gradually 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 finally 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 (§ 607) all the sub- stances which the plants received from the soil during their growth ; they are not volatile, and therefore remain behind 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 (silica, 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 liquid 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 will be deposited in crystals. Again filter the liquid and evaporate to dryness, continually 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 solubility 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 that in the damp air of the cellar. Potash is a very hygro- scopic salt. POTASSIUM. 219 Experiment b. — Boil for some time, in a vessel containing a quarter of an ounce of potash and two ounces of water, a piece of gray linen, and some dirty or greasy linen or cotton rags; the liquid will become of a dark color, while the rags are made white and clean. Dirt, as it is commonly called, is dust, which adheres to the skin, garments, &c, particularly after they have become moistened by perspiration, or have come in contact with greasy or other adhesive substances. These last-mentioned substances may be dissolved and removed by potash; on this depends the various appli- cation of this substance in cleaning and washing. Experiment c. — Pour a teaspoonful of potash into a tumbler containing vinegar; there escapes with brisk effervescence a gas, in which a burning taper is ex- tinguished. This gas is the well-known carbonic acid; it is chemically combined in the potash with the basic oxide of potassium or potassa. Potash is consequently a salt, carbonate of potassa (K O, C 02); but beside this, the crude potash contains also several other foreign salts, as silicate, sulphate, muriate, and phosphate of potassa, and many others. The feeble carbonic acid is not able to destroy completely the basic properties of the potassa; therefore the carbonate of potassa has an alkaline taste, and colors red litmus-paper blue. Vin- egar can completely neutralize potassa. If you add so much of it to the potassa, that neither blue nor red test-paper is altered, and then filter and evaporate the liquid, you will obtain a white saline mass, — acetate of potassa. We might suppose that the carbonic acid, which so willingly assumes a gaseous form, might easily be ex- pelled by heating; but it is a striking fact, that its friendship for the potassa stands the proof even of the 220 ALKALIES. Fig. 108. hottest fire. The potash does not lose its carbonic acid at the strongest red heat. The potash of commerce possesses very different de- grees of goodness and purity. To test its value, or to compare several sorts with each other, weigh one hundred grains of each sort, and neutralize them with an acid. A good article requires more acid than a bad one; consequently the value of the potash may be estimated according to the quantity of the acid consumed. An alkalimeter is a useful instrument for those who have frequently to determine the value of potash. It consists of a glass cylinder, divided into degrees (graduated), in which the quantity of acid is measured instead of being weighed. For this purpose a test-acid must be prepared, of such a strength that one degree of it will exactly neutralize one grain of pure carbonate of po- tassa. The number of degrees of the acid consumed will then indicate at once, in per cent., the quantity of pure carbonate of potassa in the sample tested. The value of soda may be ascertained in a similar way. Bicarbonate of Potassa (K O, 2 C 02 -f- HO). If carbonic acid is conducted into a solution of car- bonate of potassa, the latter will take up as much again carbonic acid as it previously contained, and crystals will be deposited, consisting of one atom of potassa, two atoms of carbonic acid, and one atom of water. This combination belongs, accordingly, to the acid salts. On heating, the second atom of carbonic acid, together with the water, escapes; and the same happens, in part, on boiling a solution of this salt. POTASSIUM. 221 203. Oxide of Potassium, or Potassa (KO). If you withdraw the carbonic acid from the potash, potassa remains behind. Experiment. — Place half an ounce of quicklime in a plate, drench it with warm water, and let it stand until it is slaked, that is, until it be- comes a fine dusty powder. Then put half an ounce of potash into an iron basin with six ounces of water, and boil it, and gradually add by spoonfuls, during the boil- ing, half of the slaked lime. After the mixture has boiled for some time, put a teaspoonful of it upon a paper filter, and pour the filtrate into vinegar. If it effervesces, still more lime must be added; but if no effervescence en- sues, pour the whole into a bottle, close it up, and let it remain quiet for some hours, that the sediment may subside. Decant the clear liquor, and preserve it in a well-stoppered bottle. It consists of water in which potassa is dissolved, and is called solution of caustic po- tassa, or lye. The carbonic acid previously combined with the potassa has soluble, d^ing the boiling pass- ed to the lime, as may Not easily be seen by the soluble. J J effervescence which en- sues when vinegar or some other acid is poured on the white sediment of lime. From the lime, carbonate of lime is formed, but potassa from the carbonate of potassa. The carbonate of lime is insoluble, and is deposited as a white powder; the potassa is soluble, and it combines with the water present. 19* K 0, HO ■CaQCO,, 222 ALKALIES. It would thus appear as if lime were a stronger base than potassa, since it takes from the latter the carbonic acid; but this is not correct, for in all other cases the potassa is stronger than lime. But a weaker base, when it forms with an acid an insoluble salt, always takes this acid even from a much stronger base. Thus the lime abstracts the carbonic acid from the potassa, not because it has a greater affinity for the acid, but be- cause it forms with it an insoluble compound (chalk). In the same way a weaker acid is often able to over- come a stronger one. Experiment. — Evaporate a portion of the caustic potassa in an iron vessel (glass and porcelain are at- tacked by it); all the water but one atom escapes, and a white mass finally remains behind, hydrate of potassa. This may be melted at a stronger heat, and cast into sticks or plates (lapis infemalis, or fused potassa). Potassa consists of a metal (potassium) and oxygen (§ 166). It also contains one sixth of its weight of water, which cannot be expelled even by the strongest heat; its proper name is, accordingly, hydrate of potas- sa (K O, HO). This water, as though it were an acid, is chemically combined with the potassa. Water, be- ing an indifferent body, acts with strong bases like an acid, and with strong acids like a base (§ 200). 204. Experiments with Hydrate of Potassa. Experiment a. — Expose some dry potassa to the air; it will soon become moist; indeed, it will deliquesce, and on longer exposure it will effervesce upon the addi- tion of an acid. Potassa has two strong affinities: 1st, for water; 2d, for carbonic acid. It absorbs both from the air, and is then converted into carbonate of potassa. Experiment b. — Heat in one test-tube some white, and in another some brown blotting-paper, with some POTASSIUM. 223 potassa lye; both papers will be decomposed and dis- solved, the vegetable fibres of the white paper (linen or cotton) more slowly than the animal fibres of the brown paper (wool). Potassa exerts a very corrosive action, especially on animal substances. The slippery feeling caused by rubbing lye between the fingers is owing to a gradual solution of the skin. Experiment c. — Boil in a test-tube a little tallow or fat with a solution of caustic potassa; a union grad- ually takes place ; soap is formed. The soap prepared from potassa is soft, and is called barrel-soap or soft- soap. Experiment d. — If some potassa be melted with sand on a piece of charcoal, before the blow-pipe, we obtain a vitreous, amorphous compound of silicate of potassa. Much sand and a small proportion of potassa yield an insoluble glass, — the common bottle or window glass; but much potassa with a small proportion of sand, a soluble compound, called soluble glass. A solution of the latter may be em- ployed as a fire-proof varnish for wood, canvas, and other combustible materials. Experiment e. — Dissolve a piece of blue vitriol (sul- phate of copper) in water, and add to it some potassa lye. Potassa is the strongest base known; therefore it abstracts the sulphuric acid from the blue vitriol, and forms with it sulphate of potassa, which remains in solution. The oxide of copper, not being soluble in 224 ALKALIES. water without an acid, is precipitated as a hydrate; that is, chemically combined with some water in the form of a delicate blue powder, and may be collected on a filter. This method is very frequently employed for separating metallic oxides from metallic salts. 205. Potassium (K). If the oxygen is withdrawn from the potassa, then potassium remains behind, —a metal which has so strong a tendency to combine again with oxygen that it can only be protected against oxidation by keeping it in petroleum, a liquid which contains no oxygen. The usual method of preparing potassium is by putting carbonate of potas- sa and charcoal into an iron vessel, provided with an iron I voiiu/e! exit-tube, and exposing them to the strongest white heat. At this extremely high temperature, the coal combines with the oxygen of the carbonic acid and of the po- tassa, forming carbonic oxide gas, which escapes. The liberated potassium is also converted into vapor, which is conducted into petroleum, where it condenses into a solid mass, resembling silver. It has been shown under carbonic acid (§ 166), that potassium, at a moderate heat, can withdraw the oxy- gen from the carbon; while here, at a higher temper- ature, the contrary takes place. Similar incongruities in chemical actions are not unfrequent; they show that the affinities of bodies for each other are greatly altered by the temperature. Experiment. — Put a piece of potassium of the size of a pea into a basin of water ; itfioats with a whizzing noise upon the water, and burns at the same time with 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 will 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 sulphuric acid; evaporate the filtered liquid 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. 226 ALKALIES. Acid Sulphate, or Bisulphate of Potassa (KO, 2 S03 -f 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 06). 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 will be deposited from it, which have a cooling 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 will 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 Os, and 2\ C are formed K O, C Oz, and 1\ C 02. 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 Volatile. 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 wfll 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; the explosion follows even more quickly than with the pulverized gunpow- der, because the granulat- 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 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 strong- er evolution of gas; since it combines with the po- tassium of the nitre, forming sulphuret of potassium, whereby three atoms of free carbonic 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 Volatile. 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 will 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 well adapted for converting metals into metallic 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 lime 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 (NH3) ; this, after a time, unites with the oxygen of the air, forming nitric acid (and water), which acid is immediately neutralized by the lime. 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 still 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 small 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 ot 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 with sulphuric acid. The asbestos serves to prevent the too deep immersion of the match. 10 parts of sul- phur, 8 of sugar, 5 of gum Arabic, 2 of cinnabar, and 30 of finely powdered chlorate of potassa, form with water a good inflammable mass, with which the piece of wood previously dipped in melted sulphur is coated. e. — Chlorate of potassa, like nitre, oxidizes the metals 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. POTASSIUM. 231 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 simultaneously, chloride of potassium and chlorate of potassa; the first is easi- sparingiy ly, the latter more spar- ingly soluble in water; they may therefore be Easily if U soluble. separated irom 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, KCI -f- HO, being the same as KO, HCI. 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, will be given off. The chemical action is the same in both cases. 211. Tartar, or Bitartrate, of Potassa (K 0,2 T-f H O). 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 well 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 liquid, 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 neutralized 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. " " " -f- " " oxide of antimony = tartar emetic. 212. Salt of Sorrel, Acid Oxalate, or Binoxalate of Potassa (K O, 2 C2 Oa -f 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 oxalic 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 Tersulphuret of Potassium (3KS3+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- 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 yellowish- green solution. If to this you add diluted sulphuric acid, a strong evolution volatile, of Sulphuretted hydrogen takes place, and the liquid becomes milky from the precipitation of two thirds Soluble °^ ^e sulpnur (milk of sulphur). A decomposi- insoiubie. 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 well 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 of potassa and charcoal, which latter abstracts the oxygen HO, SOo K<^; 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, lime, &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 universally 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 all 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 all 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 will 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, HC1. 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 like 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 expelled by evaporation. In some places springs are found contain- ing salt in solution, the so-called 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 filled up with fagots (graduation-house), and from which it is made to fall 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. All 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 called 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 (NaO, S 03 -f 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- Fig. ii7. direct process must often be resorted to, since ]Hn chlorine is not so easily removed from sodium I as carbonic acid is from potassa. The chloride of sodium must first be converted into sulphate I I of soda. We are already acquainted with this L|, salt, it having remained in the retort after the SJ—^ 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 crystallized 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 crystallization. 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 allowed 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 crystallization (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 crystallization undergo only the latter kind of fusion. Experiment. — Heat in a small flask half an ounce of water to 33° C, and keep it at this temperature, gradually add- a ing crystallized Glauber salts, as long as they are dissolved, amounting to about an ounce and a half. If a stronger heat be now applied to the saturated solution, a salt will separate (anhydrous crystals); if you let it cool, a salt will likewise 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 peculiar property of being most soluble in water, not at the boiling 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 will observe exactly the same phe- 21 242 ALKALIES. Fig. 119. 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 lime (§ 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 liquid. 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 ol sodium. If you drop muriatic or diluted sulphuric acid into NaO SO ---N„S Volatile. Non- volatile. SODIUM. 243 the solution, the dis- voiatiie. agreeable smell of sulphuretted hydrogen ,£L will 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 -f 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 shallow glass dish, leaves behind a white powder, which has an alkaline reaction and effervesces with muriatic acid, but yet without emitting any disagreeable odor; it is carbonate of soda. The Soluble7 sulphur has thus passed to the calcium of the B^ubl7 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 C«OC0,----^NttO,COj 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 essentially the same as that already described, except that the two operations, described as separate above, are unit- ed into one; the chalk or limestone 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, hot 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 readily, — or calcined, consequently anhydrous. The latter, accordingly, when it occurs pure, is of more than twice the strength of the crystallized. 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, 2COa -f 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. 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 called 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, like caustic potassa, for which it is often substituted in preference in the arts. 222. Sodium (Na). On abstracting oxygen from the soda metallic sodium is obtained. This metal is prepared like 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 following 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 crystallization. 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 will 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 0). The hard, colorless crystals commonly called borax, and generally 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 alkaline 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 will 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 excess of manganese. The metallic 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 silicates of metallic 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, polished 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 is 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 little finely pulverized sand; upon placing it again in the blow-pipe flame, effervescence will ensue, and afterwards a clear bead will 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 boiling; 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) lime 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 all 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 till it boils, and then allowing 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 (yellow sand and wood-ashes) used in the preparation of the ordinary sorts of glass. 252 ALKALIES. SYSTEMATIC ARRANGEMENT OF THE COMPOUNDS OP POTASSIUM AND SODIUM. Oxy-salts. Metals: Potassium. Oxides: Oxide of potassium, or caus- tic potassa. Sulphurets: Sulphuret of potassium, or Liver of sulphur. Haloid Salts: Chloride of potassium. Iodide of potassium. Carbonate of potassa. Bicarbonate of potassa. Chlorate of potassa. Nitrate of potassa, or salt- petre. Sulphate of potassa. Bisulphate of potassa Silicate of potassa, or glass. Basic silicate of potassa, or 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. Sodium. Oxide of sodium, or caustic soda. Sulphuret of sodium. Chloride of sodium. Iodide of sodium. Carbonate of soda. Bicarbonate of soda. Nitrate of soda, or Chili salt- petre. Sulphate of soda, or Glauber salts. Bisulphate of soda. Sulphite of soda. Phosphate of soda. Silicate of soda, or glass. Biborate of soda, or borax. AMMONIA (NH3). At. Wt. = 213. — Sp. Gr. [as gasj = 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. 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 lighted 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 VoiaiHe. filings at the same time with two grains of po- Non. tassa and two grains of nitre, in an open volatile. 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 possesses an alkaline character; we call it ammonia. 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 NH3. 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 Dippell's ani- mal oil. After the completion of the dry distillation, 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 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 neutralized by the acids, that you can no longer recognize it by the smell. 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 called 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 filling smelling-bottles. Experiment d. — Put a piece of tin, the size of a pea, upon a bright cent, and Fig. 125. r ° . hold it, by means ol 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 smell of free ammonia. Ammonia and the ammoniacal salts are commonly prepared from sal 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 lime 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 lighter 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 limb 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 accidentally 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 wTater, 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 called caustic ammonia. AMMONIA. 259 231. Hydrosulphuret of Ammonia, or Sulphuret of Am- monium (NH3, 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 will be shown here- after. 232. Carbonate of Ammonia (2 NH3, 3 C 02 -j- 2 H O). The crude carbonate of ammonia has al- ready been treated of; the pure is prepared from sal ammoniac and chalk, by sublima- tion. Experiment. — Introduce a mixture of half an ounce of chalk and a quarter of an ounce 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 a somewhat larger flask over the former, and the fumes will soon condense into a white saline 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- nate of ammonia. This salt is frequently used by bakers, instead of yeast, for raising gingerbread, spice- 260 ALKALIES. cakes, &c. (§ 519); it escapes in the heat as a gas from the dough, and renders it light 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 distillation). 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 not volatilize 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 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 really 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 called 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- ide of potassium is commonly called potassa, or caustic potassa; the oxide of sodium, soda, or caustic soda; and ammonia may also be regarded as caustic ammonia. 3. These three oxides are commonly called alkalies, also caustic alkalies. Formerly potassa was called vegetable alkali; soda, mineral alkali; and ammonia, volatile alkali. 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 alkaline 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. 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 crystallization, 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 will often remove the acid from a stronger base, when it forms with this acid an insol- uble compound. SECOND GROUP: THE ALKALINE EARTHS. CALCIUM (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-shells, &c. There are whole ridges of mountains consisting of limestone, and extensive districts having a lime or calcareous soil; carbonate of lime is one of the principal constituents of our earth. We also find it in transparent crystalline forms, rhom- 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 tallized in candy, granular-crystalline in loaf-sugar, amor- phous in bonbons, and pulverulent in pounded sugar. All limestones effervesce when treated with an acid, and may thus generally 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 called lithographic stones. Experiment. — Blow air into lime-water, through a glass tube; a precipitate of carbonate of lime is formed (see Fig. 81); continue 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. almost all spring-water contains carbonate of lime (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 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 solid mass- es, called stalactites. The walls of cellars and bridges are sometimes found covered with an incrustation of sta- lactites. The calcareous tufa deposited from the Carls- bad waters also consists principally of carbonate of lime. 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, Ca 0). 238. Experiment. — Put a piece of chalk upon coal, and heat it strongly before the blow-pipe for several minutes; it will 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 litmus-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 limestone; conse quently the lime cannot be rendered impure by the ashes of the fuel. A kiln is usually provided with several such furnaces, c and /are the dis- charge outlets for extracting the lime, when it is well 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 lime combine with one pound of water, forming a fine powder of hydrate of lime (CaO-J-HO), or slaked lime. 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 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 quicklime 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, wells, mines, or in cel- lars in which fermenting liquors, as must, wort, brandy mash, &c, are kept. Milk of lime is also commonly used for abstracting from crude illuminating gas its carbonic acid, as well as the admixture of sulphuretted hydrogen. It is likewise in general use for white- washing ; it becomes quickly white and dry, and then it is no longer hydrate of lime, 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 consolidation 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 lime 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 gradually 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 will certainly possess the same de- gree of firmness, provided good quartz sand has been employed in its preparation, and not the argillaceous 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 lime, carbonate of lime, silicate of hme, and silica (sand). If you burn a limestone in which clay is contained, or an intimate mixture of chalk with one fifth of clay, you will obtain a burnt lime, 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 called hydraulic cement, and is well 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 with silicate of alumina. 240. Further Experiments with Lime. Experiment. — Wrap a piece of quicklime in paper or in a linen rag, and set it aside for some weeks ; the paper and the linen will become, after a time, so rotten as to be easily torn; the lime, to use a common ex- pression, has eaten them. Thus quicklime, like potassa or soda, exerts a corrosive action upon organic sub- stances, and for this reason it is also frequently called caustic lime. If you rub between the fingers lime 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, lime is mixed with weeds, such as couch-grass, &c, to accelerate their de- composition. It is, however, altogether wrong to mix Hme with manure that is already in a state of decay 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 will, 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 lime is as indispensable for the life of many plants, as common salt is for that of animals. Thus agriculturalists possess in lime an excellent ma- nure for those fields where lime is deficient. Experiment. — Dissolve a little soap in hot water, and add lime-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 lime, the so-called hard water, cannot be used for washing. The viscous mass which separates is lime soap, a combination of the fatty substances con- tained in the soap with lime. Potassa and soda soap are soluble in water, lime soap is insoluble. Caustic lime 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, SO34-2H0). 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 called ealcined gypsum. The loss of weight is owing to the CALCIUM. 271 water of crystallization 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 a strip of paper, firmly securing the loose end of it by sealing-wax. A box is thus made, the bottom of which is formed by the dollar. 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, 6mear 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 walls and ceilings various ornamental figures and designs, called stucco-work. Gypsum is a mineral of very frequent occurrence in nature, and in some localities, as at Jena, it forms entire ranges of hills. When crystallized in tables it is termed selenite, and the white, compact, granular variety is called alabaster. It is also frequently contained in spring-water. Gypsum is very sparingly soluble in water, half an ounce of the latter dissolving only half a grain of gvpsum. 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 oxalic acid, by which the presence of lime is shown. Oxalic acid is the most certain test for lime salts (§ 197). That gypsum, as weU as quicklime, is a valuable manure for many plants, especially for the leguminous plants, is well known to farmers, who frequently spread it over their barley and clover fields. The plants here- by 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 am- monia contained in the air and in rain-water, and fixes it in the soil, these two salts being converted respective- ly into sulphate of ammonia and carbonate of lime. When gypsum is heated to redness with charcoal, sulphuret of calcium is obtained, which, like the liver 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 Os) 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 lime 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.* * " 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 will evolve from two ounces of muriatic acid and half an ounce of black oxide of manganese. The liquid, clari- fied 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 lime releases its oxygen, and is converted into calcium, which, being a simple body, combines with chlorine; the oxygen, liberated 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 lime. Thus are formed a haloid ^eacT salt> chloride of calcium, and an oxygen salt, hy- pochlorite of lime. The latter is the essential agent, the bleaching power, in the chloride of lime; 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 lime, 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 lime is used, which is spread upon hurdles in chambers, and which, like milk of lime, absorbs the chlorine. Chloride of lime, 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 hme; 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 will 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 lime, the vegetable fibres will 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 lime, so much the more indigo it is able to deprive of its color. Experiment d. — Chloride of lime, as well 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 liquid, known as Labarraque1 s disinfecting liquor. Chloride of Calcium, or Muriate of Lime (Ca CI, or CaO, HC1). 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 will 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 tube with frag- ments of it, and adapt to each 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). v BARIUM AND STRONTIUM. .277 BARIUM AND STRONTIUM (BaandSr). 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 aU 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 crystallizes 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 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 metallic 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. Chloride 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 I (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 finally decant the warm clear liquid. Nob, SO.,—T^BaO'$03| MAGNESIUM. 279 It will have a green tint, owing to the presence of some protoxide of iron. When boiling, 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, called magnesia (Mg O). The taste of all the soluble salts of magnesia is bitter. This base is combined in the serpentine with silicic acid, which the stronger sulphuric acid displaces and com- bines with, forming a soluble salt, while the silica re- mains behind undissolved. We find silicate of magne- sia also in other minerals; for instance, in meerschaum, soap-stone, talc, asbestos, hornblende, and in several varieties resembling mica, &c. All these minerals have a slippery 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 small acicular crystals, owing to the evaporation having been carried on after the formation of the pel- licle, and to the stirring of the mass while cooling. 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 likewise 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 liquid is now heated to boiling, filtered, and the precipitate washed and dried; it is very light and white, and is known as the magnesia alba of the apothecaries' shops. During the ebullition, some carbonic acid escapes. Carbonate of magnesia is also found in many kinds of marble and limestone, called dolomite. Magnesia (Oxide of Magnesium) (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 called calcined magnesia (oxide of magnesium). It is nearly insoluble in water, and consists of a metal, mag- nesium, and of oxygen. Chloride of Magnesium, or Muriate of Magnesia (MgCl, orMgO, HC1). 251. Experiment. — Add to carbonate of magnesia some diluted 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 little Epsom salt, and then add to it a solution of phosphate of soda ano 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. RETROSPECT OF THE ALKALINE EARTHS (LIME, BARYTA, STRONTIA, AND MAGNESIA). 1. The metals of the alkaline earths have, like 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; alkaline, because they have a basic reaction. (The alkalies 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 alkaline earths are quite 24* 282 METALS OF THE EARTHS. insoluble in water (the carbonates of the alkalies 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 alkalies soluble soap). THIRD GROUP: METALS OF THE EARTHS. ALUMINUM (Al). At. Wt. = 17l. — Sp. Gr. 1. Clay and Loam. 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 will not co- here, but remain friable. Common clay contains more sand than plastic clay, and, owing to the presence of iron ochre, has a yellow or brown color. There is still a coarser variety of clay, mixed with still more sand, commonly called loam. Experiment. — Hollow out a piece of clay, and pour Fig. 133. some water into the 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 silica, or sand, one 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 France, where the nature of the soil is peculiarly adapt- ed to such works. Experiment. —Yut 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 still 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 still 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 liquid 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 hence 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 cloth 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 weeks, 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 slight odor, on being treated in the same manner. Thus is explained, also, the peculiar smell 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 build- ings, are valued by the experienced farmer as excellent manure. Clay, when gently burnt, also experiences a similar change (§258). Constituents of Arable Land. 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 wholly composed either of sand or of clay is totally unproductive; but a mixture of them affords a fertile soil. A clayey or 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 will not allow of a free circulation of air. By showers of short duration it becomes baked; that is, a crust forms on the surface, which prevents the water from penetrating into the soil; but after long continued rains it becomes muddy, 286 METALS OF THE EARTHS. and then it allows 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. 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 liquid into a tall glass, rinsing out with water what remains in the mortar. On stand- ing, the earthy particles will 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 bottom. The residue is again stirred up with water, and the lat- ter decanted, and these processes continued until all the clay is washed out from the sand. While decant- 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 will 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. It is frequently employed to separate finely crushed ores from the admixture of the lighter particles of stone and earth. 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 well-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 yellowish filtrate till it has a decided smell of it; the brown flaky precipitate which is hereby separated consists of hydrat- ed oxide of iron and alumina, which you must remove by a second filtration. The clear solution obtained is then boiled in a flask, and a concentrated solution of carbonate of ammonia or carbonate of potassa is added, as long 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 (==i 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 cylinder. If you have more liquid than the cylinder 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 lime, but also alumina, since this is partially precipitated at the same time with the carbonate of lime. 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 still 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 (Wedgewood's pyrometer). Though earthen-ware acquires by baking great hardness and solidity, yet it still 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. 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 verifiable 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 linen. The residue on the latter consists principally of silicic acid, but a base called alumina (Alz 03) is found dissolved in the liquid. Clay is, accordingly, an insoluble salt, silicate of alumina. Before the clay is heated, the silicic 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, lime, &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 (Al2 03, 3 S03 -j- 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 crystallize 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 calico-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 liquid reacts basically; a brisk efferves- cence ensues, and Volatile. 3Wd.O,COiJ— *coi Al ,0 3 SO —>*3(JSTaO, SO, Al„0„ 3H0 Soluble. Insoluble. a gelatinous pre- cipitate is formed, which, after repeat- ed washings with 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, = A1.2 Os. Experiment. — Heat in a test-tube some alumina with potassa; it dissolves in it completely, since it enters into combination with the potassa. We call 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 metallic 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 polishing metals and glass. Alum (Sulphate of Alumina and Potassa). (KO, S03-f- Al, 03, 3 S 03-j- 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 till 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, Fis-m 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. AL_ O,, 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 brilliant 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 similar 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 all 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 similar 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),ox 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-called 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 following kinds of alum: — Potassa alum, consisting of sulphate of alumina -\- sulphate of potassa. Soda alum, " " " -j- " " soda. Ammonia alum, " " " -f- " " ammonia. Chrome alum, " sulphate of chrome -f- " "potassa (soda or ammonia). Iron alum, " sulphate of iron -\- sulphate of potassa (soda or ammonia). These combinations are said to be isomorphous (from itror, equal, and popfyt), form), or having the same form, because they possess a similar constitution and the same crystalline form (octahedron). The term alum is now applied, also, to some of the double salts, in which no alumina is present. The three first of the alums mentioned, have a white color, chrome alum, a deep red, and iron alum, a pale violet color. They may easily be prepared by dissolving together in water their simple constituent salts, in proper proportions, and putting the solution aside to crystallize. 296 METALS OF THE EARTHS. Occurrence of Alumina in Nature. 265. Next to silica, alumina occurs most frequently in nature, and, indeed, not only in clay and loam, but also in rocks and minerals; for instance, in the well- known gray-colored clay-slate, porphyry, &c. Felspar must be regarded as the most important of the alumina minerals, and is found in greater or less quantity in granite, gneiss, mica-slate, and other rocks. In its con- stitution it has the greatest similarity to alum, except that it contains silicic, instead of sulphuric, acid. Alum (anhydrous) (K O, S 03 -f Al, 03, 3 S 0,); Felspar (K 0, Si 03 + Al, 03, 3 Si 0a). Felspar, like all other stones, is finally disintegrated by the influence of air and water, and by heat and cold; it weathers, as the miners say, or is dissolved, and the sili- cate of potassa is thereby gradually removed by the water, so that, as the result of this decomposition, clay or loam remains behind (Al, 03, 3 Si 03). When the farmer lets his ploughed land lie fallow, that is, remain uncultivated for some time, he by this means acceler- ates the weathering; soluble salts of potassa, soda, lime, and other salts, are thereby formed from the constitu- ents of the soil, and to these salts especially is to be at- tributed the greater fertility of fallow land over that which has been exhausted by cultivation. 266. Glucinum, Yttrium, Zirconium, Thorium, and the recently discovered Erbium, Terbium, and Norium, are very rare elements, the combinations of which with oxygen are white, insoluble, and earthy, like aluminum, and are called 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 alkalies and alkaline 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 crystalline 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 called 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 silica, 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 alkalies, and of the alkaline earths, are the strongest bases (alkalies, 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 alkalies 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 likewise 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. When 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 124 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 12j ounces of hydrogen, orH. 489 ounces of potassium, orK. 175 nitrogen, " N. 290 it sodium, " Na. 75 carbon, " C 225 " ammonium, KNHi. 200 " sulphur, " s. 250 it calcium, " Ca. 400 " phosphorus, " p. 855 it barium, " Ba. 443 " chlorine, " CI. 158 !< magnesium, " Mg. 1000 " bromine, " Br. 171 i< aluminum, " Al. 1586 " iodine, " I. 350 11 iron, " Fe. 325 " cyanogen, " Cy. 345 a manganese, " Mn. 136 " boron, " B. 368 !( cobalt, " Co. 278 " silicon, " Si. 369 U nickel, " Ni. 407 " zinc, " Zn. 1350 C( silver, "Ag. 735 " tin, " Sn. 1232 a platinum, " Pt. 1294 " lead, " Pb. 2458 " gold, " Au. 1330 " bismuth, " Bi. 328 u chromium, " Cr. 396 " copper, " Cu. 937 11 arsenic, " As. 1250 " mercury, " Hg. 1613 C( 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. 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-g- 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, 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. When in a chemical combination one element replaces an- other, it always happens in the quantities specified by the combining proportionals. For 100 dollars 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 -j- 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 vabr, 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 Ou). 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 Oa) 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 sulphuric acid are water are 1 eq. sulphur = 200 1 eq. hydrogen = 124 and 3 eq. oxygen = 300 1 eq. oxygen = 100 Eq. of S 03 is thus =500 Eq. of HO is thus = 112^ Consequently, the combining proportion of common sulphuric acid is 612^. 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 crystallization; its constituents are, conse- quently, — 1 eq. of Ca O = 350 1 eq. of S Os = 500 and 2 eq. of H O = 225 Equivalent number of cryst. gypsum = 1075 = Ca O, S O3 + 2 H O. 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 likewise 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, 2\, 3, or Z\, but never in ratios of 1^, or If, or \\, &c. The ascent takes place, as it were, only by whole or half steps; thus, for instance,— „. f k f 100 oz. of oxygen, carbonic oxide =C0. form.wui^i150 " " oxalic acid =C20, (.200 " « carbonic acid =C02. f 100 oz. of oxygen, nitrous oxide = N 0. 75 oz. of nitro-j 200 " " nitric oxide =N02. gen form, with | 300 " " nitrous acid = N 03 [500 « " nitric acid =N05. f 100 oz. of oxygen, protoxide of manganese, = Mn 0. [ 150 " " sesquioxide of manganese = Mn« O3. •?, -l 200 " " hyperoxide of manganese = Mn Oj. nese form, with i OAn (( .. ... ,, ~ 300 " " manganic acid = MnOj. [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} 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 calling 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 all 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 immutability is sought for. A thinking man, when he knows that a thing happens, and how it happens, will always inquire, Why 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 to 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 specifically 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 liquid 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 : Lime : 3.) These small particles, of which the mass of a body consists, cannot be further divided into yet smaller par- CHEMICAL PROPORTIONS. 307 tides. Thus is explained the name atomus (that which cannot be divided). 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 balls may be put in the fol- lowing positions, — ooco88c§3(i^8cxD so atoms also may lie 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, crystallizes from its solutions in octahedrons; but when fused, it crystallizes on cooling 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 ball of lead of the same size as the pea is substituted for it, though the square will 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, — 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 illuminating gas, afford a striking example of ex- ternal difference and interior conformity. They have the same constituents (carbon and hydrogen) both in quality 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 million 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 lime 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. Finally, 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 list 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 valleys 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 mental 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 all 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 find 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^ grains of iron filings 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 1\ 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 until 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, 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 silicic 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 (Fe2 Oa). 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 of oil of vitriol; this forms an article of commerce under 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 crystallized, as in iron-glance; sometimes compact, as in red iron-stone; or radiated, as in red hematite; 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 fill 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 all spring-water, and slowly ox- idize the iron. These gases are expelled 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 Os, 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 soil, will now no longer appear strange; the black protoxide of iron contained in them is grad- ually oxidized into a yellow hydrated 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 pellicle, the color of which gradually changes to yellow, then to red and violet; finally, the pellicle assumes a yellowish-brown color, and falls as 316 HEAVY METALS. rust to the bottom. Protoxide of iron attracts oxygen with great avidity, and is converted into magnetic oxide of 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 pellicle of magnetic oxide of iron gives a yellow 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 called 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 is prepared on a large scale. They are the following: — Fe O -f- Fe2 Oa, or magnetic iron ore. IRON. 317 Fe O, C O^, or spathic iron (clay iron-stone, sphe- rosiderite). Fe, 0„, or specular iron (red hematite, iron-glance, &c). Fe2 Oj -j- 3 H O, or brown iron ore (yellow iron-stone, yellow 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 generally 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 (gangues); for in- stance, silica, clay, lime, manganese, phosphorus, &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 will 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 slasr. 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, called 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 silica, lime, and clay; these form a slag, which floats on the molten iron, and is drawn off at i. The melted iron is suffered to flow off from time to time, by a small 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 slag are removed from beneath, fresh charges of ore, lime, 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 + Carbon, Silica (clay). Lime (clay). Product, Carburetted Iron (cast-iron). Carbonic Oxide and Carbonic Acid. Silicate of Lime and > o. 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. It is fre- quently formed into square blocks, and used for build- ing-stones. 279. Cast or 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 likewise some silicon 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 malleability, 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-crystalline 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. 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 rolled 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. All 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 silicate of magnetic oxide of iron. The iron mass becomes gradually 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 usually hammered or rolled into bars or bands. This method of converting brittle cast-iron into ductile and malleable 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 intelligible. Iron |, Cast Iron, Air, Sand, Products, Wrought Iron, Iron i, Oxygen, Silica, Slag, Carbon. Oxygen. 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. hi. 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 (like cast-iron); if cooled some what more slowly, it is rendered elastic, and if cooled very slowly, it is soft, ductile, and malleable (like 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, especially for cut- ting instruments, since it may be made soft or 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 order 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 yelloiv appearance, but gradually 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 yellow 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 gradually 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), i IRON. 325 Steel may be ornamented by corroding its polished surface with acids, whereby a variety of light and dark colored shades and impressions will be pro- duced. 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 well in this place to remind the student that a solution of a metal does not contain a metal as such, but always a metallic salt in solution (§ 160). 285. Green Vitriol, or Sulphate of Protoxide of Iron (Fe O, S 03 -f 6 H O). This salt, which is always formed when iron is dis- solved in diluted sulphuric acid, is often called 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- tallization. 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 will gradually change to green, while the iron is covered with a red coating of copper. The stronger iron takes from the copper its IKON. 327 oxygen and sulphuric acid, and combines with both of them; 32 grains of me- tallic copper are de- Soluble. l l posited, while 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 crystallized 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-yellow substance,* hydrat- ed sesquioxide of iron, is deposited. All the other salts of protoxide of iron do the same; namely, they attract oxygen from the air, and are gradually converted into salts of 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 falls 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 arc 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 boiling, the nitric oxide escapes, and is converted in the air into nitrous acid, forming the yellow 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 metallic oxides are insoluble in water. If the metallic oxides, at the moment of their IRON. 329 separation from a combination, meet with water, they readily com- bine with it, form- soiubie. ' 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 well 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 finally 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- 2S* 'IFeO, sq^^^HQNHj S03 F&O.HO h^oSso^^o^so^l j^HjHO; ^03,3^0 330 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, will have a brownish-yellow 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 will be formed, which assumes at first a violet, and finally a black color ; but in the second liquid 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 gallate and tannate of iron in suspension. The combination of tannin and gallic 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. 286. Nitrate of sesquioxide of iron (Fe2 03,3 N05) 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 still 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 (pyrolignite 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- (Fe2 Cl3), a brown salt, volatile. . ,. , . 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 + 2 Fe2 Cy3). 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 each other, for prussiate of protoxide of iron is the same as cyanide of iron -f- water, IRON. 333 Fe O + H Cy = Fe Cy + HO; and prussiate of sesquioxide of iron is the same as sesquicyanide of iron -j- water, Fe, 03 + 3 H Cy = Fe2 Cy3 + 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 2C 02 and N), and you finally 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 (2KCy, FeCy-f-3HO). 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 Fig. 142. tne ciear yellowish liquid; they are commonly called yellow prussiate of potassa, but in chemical language fer- rocyanide of potassium. This double salt is formed as follows: — Prussian blue: iron with more cyanogen -f iron with less cyanogen, Potassa: oxygen and potassium, Water: water, C cyanide of potassium -f- pro- Products : hydrated sesquioxide of iron, £ t0Cyanide 0f 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 commonly 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. More recently the nitro- gen of the air has been successfully used for the forma- 336 HEAVY METALS. tion of cyanogen, whereby animal substances have become quite superfluous in the preparation of ferrocy- anide of potassium. 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 of Prussian blue is produced; for from Ferrocyanide of potassium: protocyanide of iron -j- cyanide of potassium, and Sulphate of sesquioxide of iron: ------ iron, oxygen, and sulphuric acid, , , ( protocyanide of iron -f- sesquicyanide of iron are tormed £ (insoiuble), and sulphate of potassa (soluble). Experiment b. — Mix a solution of ferrocyanide of potassium with a solution of green vitriol; a light 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 gradually 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, IRON. 337 and sulphate of potassa remains dissolved in the liquid. This is the most accurate test for detecting the presence 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 durability. 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- 29 338 HEAVY METALS. tains a red heat, which rapidly pervades the whole mass. The yellowish-brown substance obtained is sesquisul- phuret of iron. Another method of preparing this sub- stance, and of applying it to the evolution of sulphuret- ted hydrogen, has been described (§ 131). This com- bination also occurs native (magnetic pyrites).* Experiment. — If you moisten protosulphuret of iron with water, and let it remain exposed to the air for some weeks, small green crystals will be found dissem- inated throughout the mass, both the iron and the sul- phur having gradually 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 called iron pyrites or bisulphuret of iron. It has quite Fig. 143. the appearance of brass, and usually oc- curs in cubic crystals. If heated in a re- tort, half of the sulphur distils over, and is collected, and a black sulphuret of iron remains behind; accordingly sulphur may be prepared from it. Green vitriol is pre- pared from this residue, by piling 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 lixiviation and evaporation. The salts of iron may be detected by their behaviour before the blow-pipe, by ammonia, tincture of galls, sulphuret of ammonium, and ferrocyanide of potas- sium. # The composition of magnetic pyrites generally corresponds to the formula Fe7 S* = 5 Fe S + Fe* S3.— Cours Elementaire de Chirme par Begnault. 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 -{- 5 per cent, of carbon). c.) Steel, a mixture of both. Sulphurets of Iron. a.) Sulphuret of iron, black. 6) 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. 6) 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). Ferricyanide 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. cially 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 hy peroxide of man- ganese is excellently adapted for combining other bodies with oxygen, as was shown in the preparation of chlorine, when the oxygen of the hyperoxide of manganese oxi- dized the hydrogen of the muriatic acid, forming water, and thereby liberated the chlorine of the muriatic acid. Glass-makers often add hyperoxide of manganese to 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. On this account, black oxide of manganese is called glass-makers' soap. 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 litharge, 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 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 of sulphuric acid, and expose the mixture to a gentle heat for fifteen minutes, and then to a strong heat for an hour. After cooling, boil the 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, S03 + 4 HO). 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 follow- 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 all the sesquioxide in solution. Experiment b. — If some ammonia or potassa is added to another portion of the solution, the stronger bases will overpower the sulphuric acid, and hydrated pro- toxide of manganese (MnO -f HO) will separate as a white precipitate. On filtering and drying, it will be- come converted into dark-brown hydrate of sesquioxide of manganese (Mn2 03 -j- 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 will adhere firmly to the fibres of the cloth, and will ac- 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 metallic 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 Oz is converted into Mn 0J5 which latter compound comports itself as an acid; that is, it combines with the base present, forming a salt (K O, Mn Oa). 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 Os), however, on being deprived of its base, immediately separates into two parts, one of which contains less oxygen (hyperoxide of manganese, Mn O-,), and the other more oxygen (per- manganic acid, Mn, 07) ; 3 Mn Os is converted into Mn 02 and Mn* 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, will 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. 345 lbs. of manganese form with 100 lbs. of oxygen Protoxide of man- or 1 at. Mn u u lat. 0 ganese, = Mn 0. 345 lbs. of manganese form with 150 lbs. of oxygen Sesquioxide of man- or 1 at. Mn (C (1 lj at. 0 ganese, = Mn2 03. 345 lbs. of manganese form with 200 lbs. of oxygen Hyperoxide of man- or 1 at. Mn U. 11 2 at. O ganese, = Mn 02. 345 lbs. of manganese form with 300 lbs. of oxygen Manganic acid, or 1 at. Mn n it 3 at. O = Mn O3. 345 lbs. of manganese form with 350 lbs. of oxygen Permanganic acid, or 1 at. Mn " " 3i at. O = Mn2 (V 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 call 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. COBALT (Co) AND NICKEL (Ni). At. Wt.=368.— Sp. Gr. = 8.5. At.Wt. = 369.— Sp. Gr. = 9. 303. During the Middle Ages, when the miner held intercourse with earth-spirits and goblins in the solitary COBALT AND NICKEL. 345 depths of his mines, ores were occasionally found, par- ticularly in the mines of Schneeberg, in Saxony, resem- bling, in brilliancy and solidity, the finest silver ores, which, however, yielded in the smelting furnaces no silver, but crumbled away to a gray ashes, a disagree- able odor of garlic being at the same time emitted. In accordance with the superstitious notions of those times, the miner attributed the disappearance of the supposed silver to the malicious jests of the earth-spirits, and contemptuously rejected these ores, which he baptized by their names, — cobalt and nickel. But now they are held in high estimation, cobalt being used for impart- ing a beautiful blue color to glass and porcelain, and nickel for giving to brass the appearance of silver. As these metals are melted only with great difficulty, the heat of the old furnaces was not sufficient to fuse them. The odor of garlic was occasioned by the arsenic, which always accompanies the ores of cobalt and nickel. 304. Smalt, Azure, or Cobalt-blue. — The ores (white cobalt, cobalt pyrites, cobalt glance, &c.) containing arsenical cobalt and nickel are now worked in the fol- lowing manner. The stamped ores are first roasted in a reverberatory furnace, to expel any arsenic that may be present, and to convert the cobalt into oxide of cobalt; then it is mixed with sand and carbonate of po- tassa, and the mixture fused in clay crucibles. Thus a glass is produced, in which the oxide of cobalt dis- solves, imparting to it a deep blue color; but the arseni- cal nickel, together with some silver and bismuth pres- ent, collects at the bottom of the crucible as a fused metallic lump (speiss). The melted blue glass is ren- dered brittle and friable by pouring it into cold water, after which it is ground to an impalpable powder, and elutriated. It is much used, under the name of smalt 346 HEAVY METALS. and azure, not only as a vitrifiable pigment for glass, porcelain, and pottery, but for coloring paper, and also in washing, for giving a blue tint to linen and muslin. 305. White Copper, or German Silver. — The speiss, which remains after the fusion of the cobalt ore, is now generally used in the preparation of German silver. The arsenic being first expelled, the bismuth, silver, and nickel are melted with from four to five times as much brass (copper and zinc), whereby a metallic mixture (an alloy) of a silvery-white color, beautiful brilliancy, and great malleability, is obtained. This alloy is extensively used, as a substitute for silver, in the manufacture of a great variety of articles, not only of convenience, but of luxury. 306. As pure metals, cobalt and nickel have a great similarity to iron, both in their external appearance and in their combinations; but they are nobler met- als, that is, they do not attract oxygen with such avidity, and they do not rust so readily as iron. The three metals, iron, cobalt, and nickel, constitute, as has been already mentioned, the magnetic trio; they alone, of all the metals, are attracted by the magnet. It is, moreover, remarkable, that- just these three metals al- ways occur in meteorites, which occasionally fall to the earth, we know not whence, in a glowing state (meteoric iron, meteoric stones). The fly-poison of the apothecaries is also frequently called cobalt, but most inappropriately, as it does not contain a particle of cobalt; it is metallic arsenic. 307. Both these metals, like iron, form with oxygen a protoxide and a sesquioxide. Protoxide of cobalt (Co O) is of an ash-gray color, and its hydrate is pink; sesquioxide of cobalt (Co2 03) is black. These oxides are frequently employed in painting on porcelain and glass. ZINC. 347 Protoxide of nickel (Ni O) is of a greenish-gray, and its hydrate of a beautiful apple-green color; ses- quioxide of nickel (Ni2 03) is black. Chrysoprase, known as an ornamental stone, is quartz, colored green by protoxide of nickel. 308. The salts of protoxide of cobalt are of a pink color. A solution of the nitrate of protoxide of cobalt is often used in blow-pipe experiments, especially for the detection of alumina (§ 262); a solution of protochlo- ride of cobalt is employed as a sympathetic ink, as it possesses the property of becoming blue by evaporat- ing the water, and again pink on absorbing water. Cobalt forms, with phosphoric and arsenious acids, red insoluble compounds, which are now employed as ve- rifiable pigments in glass and porcelain painting. The salts of protoxide of nickel have a light-green color. The salts of cobalt and nickel, like those of iron, are not precipitated by sulphuretted hydrogen, but they are by sulphuret of ammonium, as black sulphuret of cobalt and nickel. ZINC (Zn). At. Wt. = 407.—Sp. Gr.= 6.8. 309. Not very long ago, zinc was hardly used except for making brass and pinchbeck; but since the art of rolling it out into plates, of forging it, and of drawing it out into wire, has been acquired, it is used also for the manufacture of many articles which were formerly made of lead, copper, and iron; for instance, for making nails, gasometers, gas-pipes, gutters, and for covering roofs of houses, for lining refrigerators, &c, as it is hard- er, and yet lighter, than lead, cheaper than copper, and less liable than iron to be destroyed by air and water. 348 HEAVY METALS. It usually occurs in commerce in the form of sheets, which are so brittle, that they may be broken by the hammer into small pieces ; the fresh fracture exhibits a hackly* crystalline structure, and a bluish-white color. 310. Experiments with Zinc. Experiment a. — When polished zinc remains ex- posed to the air for some time, it loses its lustre, and is covered with a gray film. This film consists of zinc combined with a small quantity of oxygen, and is called suboxide of zinc. Experiment b. — If a piece of polished sheet zinc be alternately exposed to the action of water and of air, it will become gradually covered with a white film; it rusts like iron, but the rust of zinc has a white color. In iron the oxidation proceeds rapidly towards the inte- rior, but not in zinc, or only very slowly; therefore articles made of zinc, when exposed to the wind and weather, last much better than those made of iron, and for this reason, also, iron articles are frequently coated with zinc (galvanized iron). Iron-rust is hydrated ses- quioxide of iron, zinc-rust is hydrated oxide of zinc. Zinc attracts not only oxygen, but also some carbonic acid, from the air, and this may be recognized by the effervescence which follows when some acid is dropped upon the rusted zinc; consequently, the white film is a double compound of hydrated oxide of zinc with car- bonate of oxide of zinc (basic carbonate of the hydrated oxide of zinc). Experiment c. — Hold a piece of zinc by means of a pair of tongs or pincers in the alcohol-flame, until it hisses if you touch it with a piece of moist wood; if you now quickly hammer it upon a stone or anvil pre- * " Hackly fracture; when the elevations are sharp or jagged, as in brok- en iron." — Dana's Manual of Mineralogy. ZINC. 349 viously heated, it does not break, but spreads out like lead into a thin, coherent sheet. Zinc has the singular property of being ductile from 100° C. to 150° C, but below or above this temperature it is brittle. Ever since it has been known that zinc is thus affected by heat, it has been found easy to overcome the difficulties which formerly opposed the conversion of this metal (which is unpliant when cold) into sheets and wire. Experiment d. — Zinc, when heated to about 400° C, melts, as may easily be seen by holding a small piece of it in an iron spoon over an alcohol flame. In this case a gray film of suboxide is likewise formed; but this after a time assumes a yellow color, and is con- verted into oxide (Zn O). On cooling, the yellow color passes to white; the oxide of zinc belongs to those substances which present a color in the heat different from the color at the ordinary temperature. Experiment e. — In chemical experiments, especially for the evolution of hydrogen, it is very convenient to use zinc in the form of small grains (granulated). It is very easily obtained in this state, by pour- ing the melted metal through a moistened broom, gently shaking it while it is held over . a basin of water. In this way the other ea- sily fusible metals al- so, such as lead, tin, bismuth, &c, may be subdivided into smaller parts, and with much more fa- cility than by filing or cutting. Experiment f. — At a still stronger heat, zinc evapo- 30 -®— 350 HEAVY METALS. rates, and burns at the same time, with a bluish flame. In this experiment, the spoon containing the zinc must be placed on red-hot coals, that it may become hotter than by the spirit-lamp. A beautiful appearance is presented, even on a small scale, by heating a piece of zinc upon charcoal, before the blow-pipe; the metal is soon converted into a loose, spongy mass of oxide, and during the combustion, blue flames burst forth from the oxidized coating. The oxide is not volatile, for if it were, nothing at all would remain behind. The flame is caused by the burning fumes of zinc; the substance formed by the combustion is oxide of zinc. This is called oxide prepared in the dry way, or flowers of zinc, and it may be freed from any admixture of me- tallic particles by elutriation. Zinc has only this one degree of oxidation. Zinc and Acids. 311. All diluted acids dissolve zinc with ease, with the evolution of hydrogen, and form with the oxide produced salts of zinc. The hydrogen liberated in this way is much purer than that prepared with iron; on this account, zinc is generally employed in the prepara- tion of hydrogen, namely, for Dobereiner's hydrogen- lamp, balloons, &c. If, as is usually done, diluted sul- phuric acid is taken for dissolving the zinc, we obtain on evaporation the best known of the salts of zinc, the sulphate of the oxide of zinc. 312. White Vitriol, or Sulphate of Oxide of Zinc (ZnO, SO,-f7HO). This salt crystallizes in colorless, rhomboidal prisms, which contain nearly half their weight of water of crys- tallization. Sulphate of the oxide of zinc, called also ZINC. 351 white vitriol, is easily soluble in water, and is often em- ployed as a cooling application, particularly in inflam- mation of the eyes. Tolerably large quantities of this salt may be prepared without much trouble, by evaporating the waste liquids left after generating hydrogen from zinc and sulphuric acid. The black substance which deposits from the solution of zinc is for the most part charcoal, a little of which always unites with zinc on the smelting of it from its ores. As it is not soluble in acids, it must remain be- hind on dissolving the metal. All the salts of zinc are poisonous, and ex- cite, when introduced into the stomach, vio- lent vomiting; milk, white of eggs, and coffee are em- ployed as antidotes. Experiments with White Vitriol. a.) Prepare a solution of white vitriol, and add to it ammonia or potassa. A white precipitate of hydrated oxide of zinc is formed, which dissolves again in an excess of the alkali. b.) Sulphuret of ammonium; here also a white pre- cipitate is produced; this is sulphuret of zinc. This behaviour of zinc is taken advantage of to distinguish and to separate it from other metals. Sulphuret of zinc also occurs native, but then it has a red or a brown color, and is called zinc blende. From this ore, by roasting, weathering, and lixiviation, white vitriol is prepared, precisely in the same manner as green vitriol is obtained from sulphuret of iron. c.) Carbonate of soda; carbonate of the hydrated oxide of zinc is obtained likewise in the form of a white precipitate. If this is dried, after having been 352 HEAVY METALS. previously washed with water, full one half of the car- bonic acid passes off; when heated to redness, all the carbonic acid and the oxide of zinc remain behind. The oxide thus prepared is called oxide of zinc pre- pared in the moist way. 313. Carbonate of zinc occurs also in nature most abundantly, in Silesia, Westphalia, and Belgium ; it is the most important zinc ore, and from it the metallic zinc is always prepared in the above-mentioned places. The miner calls this ore calamine. 314. Preparation of Zinc. — In order to convert the calamine into metallic zinc, the carbonic acid and ox- ygen must be expelled. The first is effected in the same way as with carbonate of lime, by calcining in furnaces, and the latter in the same way as with the iron ores, by heating to redness with charcoal. But the process of reduction cannot be conducted in open fur- naces, for in them the reduced zinc would evaporate and burn up in the air, forming again oxide of zinc, so that from oxide of zinc in the furnace we should only obtain oxide of zinc in the air. It is rather a pro- cess of distillation than of melting that we must under- take. Clay cylinders or muffles are employed for con- Fig H7 ducting the distillation. Several of these are ranged in circles, or are piled one above the other in a furnace. The annexed figure is a representa- tion of a muffle. On the front side of it is a projection made of bent clay, through which the two gaseous substances, car- bonic oxide gas and zinc fumes, which form during the heating of the roasted ore and charcoal, may escape. 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 small 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° C, 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 brought 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 flexibility, — 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 fusibility, which renders it peculiarly well adapted for casting, and for coating other metals (tinning). It has, indeed, lost much of its earlier 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 called Jupiter, and has the symbol 2f. 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 yellow 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 polishing 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 lively motion, and con- tinues to glow even when it is removed from the fire. In this manner the potter prepares Fis-148- 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 called coarse solder; it is so thick that it does not spread of itself, but must be applied by smearing. For soldering those metallic 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 tin, 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 tinfoil, 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 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. Perchloride 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 Ck, or perchloride of tin. This combination can also be obtained by boiling 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 verifiable 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- 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-called 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 convert 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 easily 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 yellow 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 metallic 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 metallic lustre (Sn S). If you sprinkle the glass, while still 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 S_). — 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 sublimate 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. Finally, it is fused with charcoal in a blowing-furnace, and carbonic oxide gas and metallic 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 crystalline 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- ^-^L^L^. lamp, till the tin is melted; then /If UiiRni quench it with water, that the tin I ^B—Hal I may harden quickly. The surface I ^llHMi °^ *ne P^a^e has a dull §rav asPect, ^j^^ggp^ ^^= for it is covered with a film of oxide ; but the most beautiful crys- talline figures will very soon appear upon it by rubbing it alternately with balls 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 metallic 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 boiling 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 liquid 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 boiling this tin will 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 allowed 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 (U> At. Wt. = 750.— Sp. Gr. = 1 328. 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 rarities. RETROSPECT OE THE EIRST 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 (all 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 b,. 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 generally used instead of wooden pumps. 331. Experiment. — If lead is heated before the blow- pipe in the exterior flame, it melts at about 320° C, and is thereby coated with a gray film ; indeed, it is finally 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 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 brilliant scales, the well- 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 peculiar 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 1295 pounds of it is able to accomplish 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 silver. 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 silicic acid came from the crucible. 332. Red Oxide of Lead. — Experiment. — Heat in a ladle one dram of litharge and a quarter of a dram of 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 Oz). — 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 O*), 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. Even in a solution of lead more than 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 brilliant, 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. . & /j. water of crystallization, forms the most im- ^ j portant soluble salt of lead, sugar of lead \ (§ 198), which commonly crystallizes in four- ; sided prisms. On exposure to the air, some [ of its acetic acid is driven off by the carbonic ^-J/ 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 Goulard's 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. — Fill 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 yellow 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 small 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 expelled, 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. 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 metallic 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 metallic lead. 343. 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 (Bi2 Oa). 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 boiling water. Bismuth melts at 250° C, lead at 320° C, tin at 230° C, and yet the mixture of these three metals melts below 100° C. By increasing the quantity of lead, alloys may be prepared which readily become liquid at any temperature desired above 100° C. 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 burn the wood, they are also very well adapted for making metallic copies of engraved wooden moulds, for calico-printing, and block-impressions. This alloy is called Rose's metal, after the inventor. 347. Experiment. — Bismuth is most easily dissolved by nitric acid. Dissolve some bismuth at a moderate heat in this acid, and pour the solution into a large quan- tity of water; it becomes very turbid, and after stand- in°- quietly, a white precipitate subsides, which contains 32 374 HEAVY METALS. Acid salt Soluble. Bi203, 3 NO, 3 NO, 3 NO, Bi203, Bi203, Bi203, 3 NO, 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 of 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 dilution 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 (Cn). 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 9. Copper possesses several excellent properties, which have rendered it an exceedingly useful metal. a.) It is ductile and at the same time very strong and tenacious, so that it may be hammered out into plates, which, even when very thin, still hold firmly together. b.) It fuses with difficulty (its point of fusion being COPPER. 375 1200° C.); therefore it is excellently adapted for such articles as are to be exposed to a great heat, for in- stance, kettles, pans, boilers, moulds for casting, &c. c.) When exposed to the air, it suffers from rust much less than iron; for this reason, copper utensils are much more durable than iron ones. Sheet-copper is em- ployed for sheathing ships, and for roofing towers and other buildings. d.) It is quite hard, and therefore wears out but slow- ly on use, as in copper plates for engravings, and rollers of print-works. e.) With zinc, tin, and nickel, it forms very useful alloys, such as brass, tombec, bronze, bell-metal, cannon- metal, German silver, &c. /.) It is precipitated from its solutions by the gal- vanic current as a firm coherent mass; on this princi- ple, impressions of other bodies are produced by the modern process of electro-metallurgy. g.) It yields with oxygen and several acids insoluble combinations of a beautiful green and blue color, of va- rious application in painting. Although copper possesses no smell, yet it imparts to moist hands and to the water which has long been standing in vessels made of it (as boilers or kettles), a peculiarly disagreeable odor. Experiments with Copper. 349. In the moist air, copper slowly turns gray and afterwards green (native mineral-green). Copper, like zinc, attracts, not merely oxygen and water, but also carbonic acid from the air; the green coating is the hydrated basic carbonate of copper. In Siberia this com- bination occurs in large beds in the earth, and is then called malachite. The celebrated Russian copper is prin- 376 HEAVY METALS. cipally obtained from it; and its beautifully mottled va- rieties are, like marble, formed into works of art, and are used for ornamenting palaces, &c. This green body, on receiving yet more carbonic acid, acquires a beautiful blue color, and is converted into sesquibasic carbonate of copper, which likewise occurs native as a copper ore, under the name of blue carbonate of copper. The arti- ficially prepared is called mountain blue, and is em- ployed as a pigment, particularly for painting walls, its color not being changed, like Prussian blue, by the lime of the walls. 350. Experiment. — Hold a brightly polished copper coin over the flame of a spirit-lamp ; the color changes from yellow to crimson, violet, and blue, and finally passes over to a dark gray. Flg-154- These iridescent hues pre- ^*gg=I=:^s^ sent a particularly beautiful appearance by holding the coin obliquely in the mid- dle of the flame, and mov- ing it to and fro; in the cen- tre of the flame the coating vanishes, but it instantane- ously reappears, as soon as the coin reaches or extends beyond the external border of the flame. On speed- ily quenching the coin in water, it becomes brownish- red ; this red coating is suboxide of copper (Cu20). Such a coating is often intentionally produced upon copper medals, as it is less liable to change in the air than the brilliant metallic copper (bronzing of copper, bronze medals). Suboxide of copper, when thrown into melting glass, colors it blood-red; in this manner a beautiful red color is flashed on glass in the glass fac- tories. This accounts, also, for the red color of the slag COPPER. 377 which forms during the calcination and fusion of cop- per. 351. Protoxide of Copper (CuO). — If the copper coin is left for some time in the point of the flame, it acquires a black appearance; protoxide of copper is formed, which has a black color, and contains as much again oxygen as the red suboxide. If suddenly quenched, the oxide flies off, and the red appearance of the coin shows that the suboxide is also present beneath the film of the protoxide. By long-continued ignition the whole mass of the coin may be converted into suboxide, and by still longer heating, completely, at last, into protoxide. The glowing cinders, which fall off in the workshops of the coppersmith (copper scales), consist of a mixture of the suboxide with the pro- toxide. Experiment. — Triturate a small quantity of borax with a scale of the black oxide of copper, and melt it into a bead on a platinum wire before the blow-pipe; the oxide of copper will dissolve in the borax, and form a green glass. Oxide of copper is made use of in glass and porcelain painting. If introduced into the interior flame, the green color passes over to red, because the oxide is there reduced to suboxide of copper. Oxides of copper may also easily be prepared in the humid way, but they have then a very different color. 352. Hydrated Oxide of Copper (Cu O, H O). — Ex- periment. — Add to a solution of the previously men- tioned blue vitriol, or sulphate of copper, a solution of caustic potassa; a greenish-blue powder is precipi- tated ; it is hydrated oxide of copper. The black oxide yields, also, chemically combined with water, a blue body. Mixed with gypsum this forms a light powder, the well-known Bremen blue. Boil a portion of the 32* 378 HEAVY METALS. liquid; the precipitate will become black, because at the boiling point the combination between the oxide of copper and the water is destroyed; — another exam- ple of chemical decomposition occasioned by mere ele- vation of temperature. 353. Ammoniated Oxide of Copper. — Experiment. — Repeat the former experiment, but instead of potassa take ammonia; here also the hydrated oxide of cop- per is first precipitated, but this is redissolved by adding more ammonia, forming a superb blue liquid. Ammonia is therefore a test for salts of copper. Pour upon the blue liquid an equal quantity of strong alcohol, and direct the stream against the side of the glass, so that the alcohol may float on the surface; after the lapse of twenty-four hours, a mass of dark- blue acicular crystals is perceptible, which consist of a combination of sulphate of copper with ammonia, and are called ammonio-sulphate of copper. By dissolv- ing them in water, the blue liquid of the apothecaries' show-bottles is prepared. The alcohol effects that which is otherwise attained by boiling, namely, a re- moval of the water; it withdraws from the blue liquid a portion of its water, and the double salt, which is in- soluble in alcohol, is separated. The water may be abstracted, also, in this way from other solutions of salts, which would undergo a decomposition on the evaporation of the water by heat. 354. Experiment. — Add to a diluted solution of blue vitriol a small quantity of pulverized sugar of milk, and then rather more liquid potassa than is necessary to precipitate the hydrated oxide of copper, and heat the mixture; the blue color will soon pass into a yellow- ish-red. The yellowish-red precipitate is suboxide of copper, which is formed from the protoxide of copper, COPPER. 379 because the sugar is able to abstract from the latter half its oxygen. The same compound, but of a more beautiful red color, is obtained by boiling verdigris with vinegar, and then adding some honey to the solution obtained, and again boiling. Thus is easily explained why a red deposit always subsides from the oxymel of subacetate of copper in the apothecaries' shops ; in the slow separation which occurs in the latter case, small distinct crystals are frequently formed. Reduction of the Copper Compounds to Metals. 355. Experiment. — Rub together some grains of blue vitriol, carbonate of soda, and charcoal; ignite the mixture strongly for some minutes before the blow- pipe, and then elutriate the black mass with water; numberless small spetngles of metallic copper will re- main behind on the bottom of the vessel. The car- bonate of soda takes the sulphuric acid from the blue vitriol, and the charcoal the oxygen from the oxide of copper. 356. Experiment. — If half an ounce of blue vitriol is heated to boiling with an ounce and a half of water in a porcelain bowl, and then boiled a few minutes with some granulated zinc, the metallic copper separates as a powder, since the zinc has a greater affinity than copper for oxygen and for sulphuric acid. The pow- der obtained is washed, and then boiled with water and a few drops of sulphuric acid, in order to remove all the zinc. It must be dried quickly, but not at a high heat, for copper in this state of minute subdi- vision attracts oxygen with more avidity than when it is in a compact mass. 357. Experiment. — Introduce some hydrated oxide of copper into a test-tube, the bottom of which is 380 HEAVY METALS. Fig. 155. Fig. 156. broken out, heat it, and then pass over it a stream of hydrogen, which is evolved by zinc and di- luted sulphuric acid; in the heat, the hydrogen abstracts from the oxide of copper its oxygen, and forms with it water, which escapes in company with the hydrated water. This method is frequently employed for the reduction of ores on a small scale. 358. Experiment. — Push an iron rod into a good- sized, large-mouthed phial, forcibly enough to break out the bottom, file off the sharp edges of the fractured part, and bind a moistened bladder over the mouth of the phial. Then twist a wire firmly round the phial, in such a manner as to form two or three supports, by means of which it may be suspended in a tumbler. Let a strip of strong sheet-zinc, of the width of the finger, and five inches long, be soldered to a strip of thin copper plate, ten inches long, and bend the strip of cop- per as represented in the annexed figure- Put a coin upon the lower horizontal part of the copper strip, — for instance, a bright dollar, — or some other metallic object, the impression of which you wish to have. Now fill the phial three quarters full with very diluted sulphuric acid (one dram of sulphuric acid to two ounces of water), introduce the zinc, and sus- pend the apparatus in a tumbler, in which a saturated solution of blue vitriol, and also a few whole crystals Fig. 157. COPPER. 381 Fig. 158. of blue vitriol, have been put. In the course of a few minutes the coin will be covered with a thin film of metallic copper, and after several days with a layer several lines in thickness, which may be removed as a coherent mass. Tallow and wax must be smeared over those parts of the coin and plate on which the copper is not to be deposited. The sunk impression thus obtained may be used in the same way again, instead of the coin, as a mould for obtain- ing a raised impression. When the evolution of the gas in the phial has ceased, a few drops of strong sul- phuric acid may be stirred in, or the liquid, which con- tains sulphate of zinc in solution, may be replaced by a fresh supply of diluted sulphuric acid. Salt water may also be used instead of sulphuric acid, but then the separation of the copper takes place more slowly. The decomposition of the blue vitriol has, in this case, been effected by the galvanic current, which is always generated when different kinds of metals come in contact, or are introduced into different liquids. The bladder is a porous substance, through which the gal- vanic current may pass. Galvanism here takes the place of the plastic artist, and hence the term galvano- plastic, applied in Germany to electro-metallurgy. A solution of gold or silver may be decomposed in the same manner (galvanic gilding and silvering). Copper and Acids. 359. Chloride of Copper (Cu CI). — Experiment. — If muriatic acid is added to oxide of copper, a green so- lution is obtained, and from it, by evaporation, a green salt, chloride of copper, or muriate of oxide of copper. 382 HEAVY METALS. Introduce some of it into the wick of a spirit-lamp; it dissolves in the alcohol, and colors the flame green. Write on paper with a very diluted solution of it; the color of the writing changes on heating, and again on cooling, as in the case of chloride of cobalt (§308). Metallic copper is dissolved, but very slowly, and with access of oxygen. For Sulphate of Oxide of Copper, or Blue Vitriol, see §175. 360. Nitrate of Oxide of Copper (Cu O, N 05 + 5 HO). Copper dissolves very readily in nitric acid, forming a blue liquid (§ 162); if the solution is set aside in a warm place, blue crystals of nitrate of copper are depos- ited, which deliquesce in the air. The accompanying diagram serves to illustrate the pro- cess attending the solution of copper, as well as of most other metals, in ni- tric acid. It is al- ready known that the nitric oxide gas which escapes becomes nitrous acid on coming into contact with the air. Experiment. — Envelop quickly in tinfoil some crys- tals of nitrate of copper, moistened with a drop of wa- ter, and press the parcel compactly together, and put it upon a stone; flames and smoke will soon break forth from the bubbling mass, because the tin overpowers the nitric acid, and by means of its oxygen becomes oxidized into oxide of tin. Oxide of copper forms, with phosphoric, arsenic, ox- alic, and silicic acids, insoluble blue or green com- pounds, in the same way as with carbonic acid. 3(HO,NOr) 3^O,N0j) Volatile. Non- volatile. COPPER. 383 361. Verdigris. — Experiment. — By sprinkling a copper coin from time to time with vinegar, it becomes gradually covered with a green coating. When copper is rusted merely by exposure to the moisture of the at- mosphere, or of the earth, basic carbonate of copper is formed; but when the rusting is effected by vinegar, basic acetate of copper is formed. The latter is the ver- digris of commerce. It is prepared on a large scale, either directly from copper and vinegar (green or Ger- man verdigris), or indirectly by packing sheets of cop- per with the refuse of pressed grapes, since the juice yet adhering to the mash gradually passes over into vin- egar (blue or French verdigris). Verdigris boiled with vinegar gives a blue solution, from which, on cooling, dark green crystals of neutral acetate of oxide of copper (Cu O A -f- H O) are deposited (crystallized or distilled verdigris). Verdigris, like all the salts of copper, is very poison- ous; the white of eggs and milk are efficacious anti- dotes. Polished iron, ammonia, sulphuretted hydrogen, and especially ferrocyanide of potassium (§ 292), serve for the detection of salts of copper. Copper and Sulphur. 362. Experiment. — If some sulphuretted hydrogen water is added to a solution of any of the copper salts, a black precipitate of sulphuret of copper is produced (§ 131). Heat this, after it has settled and the liquid has been decanted, with some drops of nitric or muriatic acid; the sulphuret of copper is decomposed and dis- solved, while nitrate or muriate of copper is formed. This mode is universally employed on a small scale, especially in analysis, in order to convert metallic sul- phurets into soluble salts. 384 HEAVY METALS. 363. Preparation of Copper. — The sulphuret of cop- per is the most common ore from which copper is ex- tracted. It is seldom found pure, but mostly combined with sulphuret of iron, as in copper pyrites. The pro- cess of the reduction and smelting of copper is, accord- ingly, very tedious, as not only the sulphur, but also the iron, must be got rid of. This is effected, — 1st, by roasting in the air, whereby the copper is converted into oxide of copper, the iron into black oxide of iron, and the sulphur into sulphurous acid; 2d, by melting the roasted ore with charcoal and some silicious sub- stance, by which means metallic copper and carbonic oxide are formed from the oxide of copper and the char- coal, and silicate of protoxide of iron (iron slag) from the protoxide of iron and quartz. What appears thus simple is, in reality, so difficult an operation, that the roasting and melting must often be alternately repeated ten or twenty times in order to remove all the iron and sulphur. The melted mass, which is obtained when about half the iron and sulphur is abstracted, is called matte (crude copper); and black copper, when it contains only about five per cent, of these two substances. The complete refining of black copper is effected by melting the metal again, exposing it at the same time to the action of the air, whereby the iron, sulphur, and other foreign metals which may be present, as lead and anti- mony, are oxidized before the copper. When the black copper contains silver, it is subjected to the process of liquation. The operation of working the copper is much easier when the ores are combined with oxygen instead of sulphur, as they yield the metallic copper by merely heating with coal; but such ores are of too rare occur- rence in nature to yield sufficient copper to meet the demand. MERCURY. 385 364. Alloys of Copper. — Copper forms very impor- tant alloys with several other metals. Gold and copper form the common gold, silver and copper the common silver, from which gold and silver articles and coins are made. The well-known brass, and other metallic compounds having the appearance of gold, such as tombac, sim- ilor, prince's metal, red brass, &c, are composed of zinc and copper. Spurious gold-leaf is made by ham- mering out tombac into exceedingly thin leaves, which, when finely pulverized, constitutes the so-called gold bronze. Purple or copper bronze is prepared by gently heating the gold-colored bronze till it turns to a purple- red color. Zinc, nickel, and copper constitute the ingredients of German silver (packfong, white copper). Tin and copper form a very hard gray alloy, from which statues, cannons, bells, mirrors, &c, are cast (bronze, gun-metal, bell-metal, speculum metal). MERCURY, HYDRARGYRUM (Hg). At. Wt. = 1250. —Sp. Gr. == 13.5. 365. We have in mercury the only metal which is fluid at ordinary temperatures; for this reason, and also on account of its silver-white brilliancy, it has been called hydrargyrum (water-silver or liquid silver). But subsequently, from its mobility, it was dedicated to Mercury, the most active of the ancient gods, and re- ceived his name, the symbol $ being at the same time assigned to it. Even now, quicksilver and its various medicinal preparations, such as calomel and corrosive sublimate, are called mercurial remedies. In the north- ern parts of Siberia mercury becomes solid every winter, 33 386 HEAVY METALS. whenever the cold reaches —40° C, or —32° R., but in our climate it can only be solidified by artificial frigo- rific mixtures. Its action in the heat also corresponds with this; namely, it boils at 360° C. (consequently with only three and a half times greater difficulty than water), and it is therefore easily volatilized and dis- tilled. Experiment. — Fasten to the cork of a phial contain- ing mercury a piece of wood, affixing to the bottom of the latter some genuine gold-leaf; the gold, after some days, will have assumed a white color, and be converted into an alloy of gold and mercury. It is obvious from this, that fumes of mercury must be contained in the air of the phial, and that mercury, like water, evaporates slowly even at ordinary temperatures. The vapor of mercury, and the preparations of mercury, are very in- jurious ; they first produce involuntary salivation, and afterwards lingering, dangerous maladies ; therefore, in experimenting with mercury, not only the inhalation of the fumes should be avoided, but it must be weighed and decanted over a bowl, so that, if any portion of it should happen to be spilt, it may not fall upon the floor. Spirit-thermometers only should be suspended in sleep- ing-apartments and sitting-rooms, since, from the acci- dental breaking of the mercurial thermometer, the at- mosphere would be vitiated by the mercury running into the chinks of the boards, from which it could be removed only with great difficulty. The same rule applies, too, to green-houses, as the fumes of mercury are also poisonous to plants. As, in comparison with water, mercury boils at a very high, and freezes at a very low temperature, and as it has a great specific weight, it is for these reasons excellently adapted to the construction of thermometers, barometers, areometers, MERCURY. 387 &c. (§§ 16, 24, 93). Its chief use in areometers is to lower the centre of gravity, thereby forcing the instru- ment to float in an upright position. In the less ac- curate areometers, lead shot are frequently substituted for mercury. Mercury and Acids. 366. Mercury, if quite pure, retains its metallic lustre in the air and water, and it is therefore ranked among the noble metals; but if it is mixed or adulterated with other metals, as lead, tin, or bismuth, a gray film will gradually form upon its surface. On account of the slight affinity of the noble metals for oxygen, their ox- ides cannot be prepared directly by exposing them to the air, or by heating them to redness, but only indi- rectly, the best way being to treat the metals with acids. The most powerful solvent for mercury is nitric acid; the cheapest is sulphuric acid. 367. Nitrate of Suboxide of Mercury (Hg2 O, N O,). __Experiment. — Pour into a porcelain dish one ounce of mercury, one dram of water, and half an ounce of nitric acid; cover the vessel and place it aside for sev- eral days ; you will then find the mercury covered with white crystals; they are the nitrate of the suboxide of mercury. In the cold, two atoms of mercury take up only one atom of oxygen from the nitric acid. Put a part of the crystals into a phial, and pour over them some water; a milky turbidness is produced, as in the solution of bismuth (§ 347), but it disappears again on the addition of a few drops of nitric acid. This solution of suboxide of mercury serves for the following experiments : — 368. Suboxide of Mercury (Hg2 O). — Experiment. — To a part of the solution of suboxide of mercury is 388 HEAVY METALS. added a solution of potassa ; a black precipitate of sub- oxide of mercury is formed. This preparation must be kept in an opaque phial, because it is resolved by the light into oxide of mercury and metallic mercury. If ammonia is used instead of the potassa, a triple com- bination is obtained of suboxide of mercury, ammonia, and nitric acid, — black or Hahnemann's suboxide of mercury, used in Germany as a medicine. 369. Experiment.— If a drop of the solution of mer- cury is rubbed upon a copper coin, the mercury separates as a metal, and effects a false silvering of the copper. Experiment. — Make a stroke across a brass plate with a wooden stick that has been dipped in the solu- tion of mercury ; if the plate is afterwards bent at this place it will break, as though it had been cut; because the reduced mercury penetrates the brass with great quickness, and renders it brittle. Thus the brazier can make use of this solution instead of shears. 370. Subchloride of Mercury (Hg2 CI). — Experiment. — Add some muriatic acid, or a solution of common salt, to a part of the diluted solution of the suboxide of mercury; a heavy white precipitate of muriate of sub- oxide of mercury, or subchloride of mercury, is produced, which is insoluble in water. When finely washed and dried, this salt of mercury forms the highly important medicine known as calomel (precipitated). If some of it is moistened with potassa or lime water, it becomes black, owing to the suboxide of mercury being set free; thus is explained the Greek name calomel (ko\6s, beau- tiful, ^\as, black). This combination is also slowly decomposed by light. Formerly, subchloride of mer- cury was universally prepared from chloride of mercury and metallic mercury, which were rubbed together and sublimed (sublimed calomel). By this process Hg CI MERCURY. 389 and Hg are converted into Hg2 CI, a heavy, crystalline, white mass, which is pulverized and washed out many times with boiling water. The powder thus obtained has a slight yellowish tinge. 371. Nitrate of the Peroxide of Mercury (Hg O, N 03). — Experiment. — Dissolve in a flask, at a moder- ate heat, some mercury in nitric acid, and when com- pletely dissolved, boil the liquid briskly for some min- utes. While boiling, the mercury combines with as much again oxygen as in the cold, and accordingly ni- trate of peroxide of mercury is produced, which crystal- lizes from the liquid on cooling. A solution of this salt gives, with potassa or lime-water, a yellowish-red pre- cipitate of peroxide of mercury, but it is not rendered turbid by muriatic acid or common salt. 372. Peroxide of Mercury (Hg O). — Experiment.— Heat gradually in a test-tube some of the crystals of the nitrate of peroxide of mercury, till they cease to give off fumes; the nitric acid escapes, partly decom- posed into nitrous acid, the oxide of mercury remains behind. Its red color, however, appears first on cool- ing ; as long as it is hot, it looks black. It is resolved by too strong a heat into oxygen and metallic mercury (§56). 373. Perchloride of Mercury (Hg CI).—Experiment.— Heat some peroxide of mercury with muriatic acid, and continue adding the latter till a complete solution is obtained; the white prismatic crystals which separate on cooling are muriate of peroxide of mercury, or per- chloride of mercury, — one of the most violent poisons. The same compound is obtained on a large scale, in white, transparent, heavy masses, by the sublimation of the sulphate of oxide of mercury with common salt; hence its common name, corrosive sublimate (mercurius 33* 390 HEAVY METALS. sublimatus corrosivus). Potassa turns calomel black, but corrosive sublimate yellowish-red. Poisonous sub- stances commonly have the property of protecting veg- etable and animal substances from decay, and perchlo- ride of mercury possesses this power in a high degree. For this reason, wood for ship-building, and sleepers for railroads, are saturated with a solution of it in water (Kyanizing) ; the plants of herbariums are passed through a solution of it in alcohol, &c. It must not be forgotten, that these things themselves are thereby ren- dered poisonous. In cases of poisoning, large quan- tities of whites of eggs must immediately be adminis- tered, as the albumen forms with the chloride of quick- silver an insoluble compound. 374. If ammonia is added to a solution of perchloride of mercury, then red oxide is not precipitated, but a white body, which is likewise (as in § 368) a triple compound, consisting of mercury, chlorine, and am- monia. It is kept in the apothecaries' shops as an ex- ternal remedial application, under the name of white precipitate. 375. Experiment. — Add some salt of tin (protochlo- ride of tin) to another portion of the solution, and heat the liquid ; a gray powder will separate; this is mercury in a state of extreme comminution. If you boil it with muriatic acid, after having decanted the liquid, the powder finally forms into globules. The protochloride of tin has so strong a tendency to pass over into per- chloride, that it abstracts the chlorine from the chloride of mercury. This action is made available in analysis for detecting the salts of mercury. Mercury may be minutely divided also by long tritu- ration with viscous substances, as fat, tallow, wax, &c, so that no particles of it can be discerned by the naked MERCURY. 391 eye. In this manner, mercurial ointment and mercurial pla ters are prepared by the apothecaries. Mercury and Sulphur. 376. Sulphuret of Mercury (Hg S).— Experiment — If a solution of chloride of mercury is agitated with a little sulphuretted hydrogen water, or sulphuret of am- monium, a white precipitate is formed, which, on add- ing more of the precipitating body, becomes yellow, brown, and finally black; the black substance is sul- phuret of mercury. This compound is also obtained by mixing mercury with melted sulphur, or indeed by rub- bing it for a day with flowers of sulphur (Ethiops min- eral). If this black sulphuret of mercury is sublimed in a glass tube, then a blackish-red crystalline mass is obtained, the color of which, by friction, passes over into the most magnificent scarlet-red. The sulphuret of quicksilver in this state is called vermilion, or cinna- bar. The red and the black sulphuret of mercury have precisely one and the same composition, and yet a very great difference in appearance; they afford one of the finest examples of isomeric combinations. In both the red and black sulphuret of mercury, one atom of sul- phur is always combined with one atom of mercury, or one ounce of sulphur with 6| ounces of mercury. Ver- milion is also frequently prepared in factories in the moist way, bv triturating together for a day mercury, sulphur, and a solution of potassa. When vermilion is pure, it volatilizes completely on a glowing coal, emit- ling, at the same time, a blue sulphurous flame; but if adulterated with minium, beads of metallic lead remain behind. On account of its insolubility, it is far less prejudicial to health than the other compounds of mercury. 392 HEAVY METALS. Cinnabar also occurs in nature, and we have in it the most important ore, from which we obtain mercury on a large scale. Small globules of pure mercury are also found in many porous stones. 377. Preparation on a Large Scale. — Experiment. — Mix a little vermilion with half its quantity of iron filings, and heat the mixture in a dry test-tube; small globules of mercury will soon deposit themselves on the upper cooler portions of the glass, while the sul- phur remains combined with the iron. Mercury is ob- tained in a similar manner from native cinnabar, by distilling it with iron or lime in large iron retorts; the foreign earths remain behind in the latter. This heavy liquid is imported either in leather bags, iron flasks, or hollowed out bamboo-canes. 378. Amalgams. — Experiment. — Introduce a glob- ule of mercury into a porcelain dish, put upon it a piece of lead, and let them remain for some time in contact; both metals will intimately combine together. If the proportion of mercury is small, a friable mass is produced, but by increasing the quantity, a paste, and, if still more is added, a liquid solution, is ob- tained. Mercury will combine in a similar manner with most of the metals, forming what are called amal- gams. The amalgam of tin is especially important for silvering glass, so that the rays of light falling upon the surface of the glass may be reflected by the bright coat- ing of the amalgam. Such glasses are called mirrors. SILVER, ARGENTUM (Ag). At. Wt. = 1350. — Sp. Gr. = 10.5. 379. Silver conveys to us a distinct conception of what is understood by a noble metal. We can let a SILVER. 393 dollar of pure silver remain exposed to the air, we can throw it into the water, or bury it in the earth; it does not rust. We can subject it to the greatest heat; it may perhaps change its form, and melt (at about 1000° C), but it does not oxidize nor volatilize. Silver has also a higher value than most other metals, not only on account of its unchangeableness, but because its ores are of comparatively rare occurrence in nature, and the process of obtaining them is more costly than that of other ores. A pound of silver is worth about fifteen dol- lars. It is principally on account of these two circum- stances that silver and gold have been made to serve as the medium of exchange in the sale and purchase of commodities, — that they are used as money. The beau- tiful lustre of silver, and its extraordinary ductility, have moreover rendered it a favorite and appropriate metal for various articles of luxury, and for plating other metals. The old name for silver is Luna (D ). Alloys of Silver. — As pure silver is very soft, and would quickly wear out in using, it is generally alloyed with copper, whereby it is rendered harder, without losing its ductility. If the proportion of copper is only one fourth, the silver still retains its beautiful white col- or ; but if more copper is added, the alloy becomes yel- low, and finally red, by use. It has been agreed to call a quantity of pure silver, weighing 8 ounces, a fine mark. If the sample is an alloy of silver and copper, the question is always asked, What is the proportion of pure silver in 8 ounces ? If it amounts to 7^ ounces, the silver is said to be 1\ ounces fine; if 6, or 4, or 2 ounces of silver are contained in it, it is understood to be 6, or 4, or 2 ounces fine. Accordingly silver 6 oun- ces fine contains three fourths of silver and one fourth of copper, from which plate and the larger coins, for in- 394 HEAVY METALS. stance, dollars, are made.* In the two-ounce silver, on the contrary, the proportions are one fourth of silver and three fourths of copper; this is used for some of the smaller modern German coins, for instance, grosch and half-grosch pieces, &c. When recently stamped, they are yellow, but the surface of them is rendered white by boiling them with cream of tartar and water, be- cause some of the copper is thereby dissolved, and con- sequently a thin coating of pure silver is produced. By due weight is understood the weight of a coin; by value, the fineness of the silver employed. Experiments with Silver. 380. In order to oxidize silver, it must be treated with acids; it dissolves most readily in nitric acid. In the following experiments, care must be taken not to touch the solution of silver with the finger, as the skin is stained black by it. Nitrate of Oxide of Silver.— Experiment. — Add some nitric acid to a silver coin placed in a beaker-glass, which must be put in a warm place; if after a few days the coin is not entirely dissolved, add more nitric acid, and wait till the solution is completed. The blue solution consists of oxide of silver and of oxide of cop- per, both combined with nitric acid. To separate these two metals from each other, put some bright copper coins into the solution, and set it aside in a warm place for a few days, occasionally giv- ing it a circular motion. The separated laminae are pure silver, which are to be digested with ammonia, until this ceases to be colored blue. The silver, after being washed and dried, is dissolved for the second * " The gold and silver coins [Federal Moneyl contain nine tenths pure metal, and one tenth alloy." SILVER. 395 time in nitric acid, and the liquid, diluted with water, is kept as solution of silver. Lunar Caustic. — By evaporating this solution, nitrate of oxide of silver (Ag O, N OJ is obtained, in white tab- ular crystals. When these are fused and formed into slender sticks by casting in brass moulds, they consti- tute lunar caustic, known as a corrosive agent, em- ployed for removing proud-flesh, warts, &c. (fused ni- trate of silver). It not only attacks the texture of the skin and dyes it black, but also other organic sub- stances; on account of this property, it is often em- ployed for dyeing black the hair, and also bones and ivory, as in chess-men, &c. The black color proceeds from the separation of the oxide of silver. Nitrate of silver forms also the indelible ink used for writing on linen. 381. Experiments with Nitrate of Silver. Experiment a. — Place a small piece of lunar caustic upon charcoal, and heat it before the blow-pipe; it de- flagrates and yields metallic silver, which may be easily fused at a stronger heat. Experiment b. — Add some ammonia to a solution of lunar caustic; the dark-gray precipitate is oxide of silver (Ag O). If more ammonia is added, it is redissolved. It would be dangerous to continue this experiment any further, as the oxide of silver combines with ammonia and forms fulminating silver, which explodes violently on percussion or friction. Another explosive compound may be prepared by uniting the oxide of silver with ful- minic acid. Experiment c —Chloride of Silver. — Dilute with wa- ter part of the solution of silver obtained in § 380, and add to it muriatic acid, or a solution of common salt; 396 HEAVY METALS. you obtain a white curdy precipitate of chloride of silver (Ag CI). This precipitate is so insoluble in water, that it will impart a cloudiness to a solution of silver diluted a millionfold (§ 187); it is, however, easily dissolved by ammonia (test of salts of silver). This relation of the solution of silver to common salt is made use of by silversmiths for testing silver alloyed with copper, as the quantity of pure silver in the alloy may be esti- mated from the amount of the solution of salt required for its complete precipitation (humid assay of silver). Chloride of silver is also called horn-silver, having for- merly received this name from the horn-like appearance it assumes on melting. Experiment d. — After having decanted the superna- tant liquid, rub the chloride of silver with a cork upon a sheet of paper, and let it dry in a dark place, — in a drawer, for instance; it remains white. Now inclose the sheet in a book, so that one half may be exposed to the light; this part soon acquires a violet, and finally a black color, while that protected from the light remains white. Thus light alone is capable of destroying the affinity between silver and chlorine; the chlorine es- capes, but the silver remains, and in this state of fine subdivision its color is black. On this action of the so- lar light on certain substances were founded the experi- ments made some years since by the natural philoso- pher Daguerre, who at length succeeded in making use of the sun as delineator, and of the salts of silver (espe- cially the compounds of silver with chlorine, bromine, and iodine) as crayons or India ink, in producing the so-called Daguerreotype or photographic impressions. Experiment e. — Sulphuret of silver. — If you add sul- phuretted hydrogen to a solution of silver you obtain a black precipitate of sulphuret of silver (Ag S). This SILVER. 397 compound occurs in nature as the most important sil- ver ore; it is called silver-glance. Silver is likewise found in a pure state, or in combination with arsenic and antimony, as red silver ore. 382. Preparation of Silver on a Large Scale. — The preparation of silver from its ores is adapted to the oth- er ores with which the silver ores are commonly mixed. The three following methods are those most frequently resorted to. a.) Cupellation. — Galena generally contains small quantities of silver. In order to extract this, the galena is first reduced, by roasting and smelting with charcoal, to metallic lead, in which the silver is also contained. This mass, containing silver, is then put into a kind of reverberatory furnace, called the refining hearth, and which is hollowed out like a kettle; it is there heated for a day, while a constant current of air is passed over the metal, until all the lead is at last converted into ox- ide. The oxide of lead melts in the heat, and flows off partly as litharge through a tube, and partly soaks into the porous mixture of clay and lime, which has been firmly beaten down on the hearth of the furnace; but the silver, which is not oxidized, remains behind in a metallic state (refined silver). This is rendered still purer by being again fused in clay-basins (smaller cu- pels), which absorb the remainder of the litharge (fine silver). If other less noble metals are present in the silver ore, they are likewise oxidized and carried down into the cupel by the litharge. These methods can also be employed on a small scale for estimating the allovs of silver (assay by the cupel). b.) Liquation Process. — Many of the copper ores also contain silver, and yield, on reduction, a copper con- taining silver (§ 363). The silver is fused and extracted 34 398 HEAVY METALS. from this ore by means of lead, in the same way as potassa is dissolved and extracted from wood-ashes by water. The calcined ore is mixed with a large propor- tion of lead, and then fused and run into pigs, called liquation-cakes, which are placed, with layers of char- coal, upon an inclined hearth. When the coal is ignited, the heat is indeed sufficient to melt the lead, but not the copper; consequently the lead flows off, and carries with it the silver, whilst the copper remains behind. This mixture of lead and silver is finally, as described at a, converted into metallic silver and oxide of lead in the refining-hearth. c.) Process of Amalgamation. — Silver is often ex- tracted by means of mercury from the ores containing pure silver or sulphuret of silver, but no admixture of lead. But in the case of silver-glance the metallic sil- ver must first be separated from the sulphur. This is done by two operations. In the first, the stamped ore is roasted with common salt, by which process chloride of silver and sulphate of soda are formed; in the second, the roasted ore is mixed with water, iron, and mercury, and kept in constant agitation for some time in closed casks. Chloride of iron and metallic silver are thereby formed, the latter of which is dissolved in the mercury. The excess of mercury is then filtered off, and a solid silver amalgam is obtained by subjecting it to pressure, and the mercury is at last completely removed from the amalgam by distillation. GOLD, AURUM (An). At. Wt. = 2458. —Sp. Gr. = 19 2. 383. Though gold is found in most countries, yet it is disseminated so sparingly, and the separation of it gold. 399 from the rocks or the river-sand in which traces of it occur is attended with so much labor, that it is ren- dered the most costly of our metals. The value of gold is about fifteen times greater than that of silver.* Its unchangeableness, its beautiful color, its high lus- tre, and great density, have stamped it as the noblest metal, —the king of metals. It was formerly regarded as the symbol for the king of the stars, and was called Sol, or Sun (©)• It surpasses even silver in ductility, may be beaten out into extremely thin leaves (gold- leaf), and a single grain of gold may be drawn out into a wire five hundred feet in length. As it always exists in a metallic state in nature, and has a very great specific weight, the most simple method of sep- arating it from the sands, or from the stamped ores, is either by washing with water or by amalgamation with mercury. Pure gold, like pure silver, is exceedingly soft, and quickly wears out in using; therefore, when it is to be manufactured into coins or articles of luxury, it is alloyed with other metals, usually silver and copper, to render it harder. The quantity of pure gold contained in a mass is expressed by the word carat, the standard number not being 8, as in silver, but 24. A mark of gold (8 ounces) is divided into 24 parts or carats. If gold is said to be 18 carats fine, it is understood that the mass consists of three fourths (18 parts) of gold, and one fourth (6 parts) of alloy ; if 6 carats fine, of one fourth (6 parts) of gold, and three fourths (18 parts) of alloy, &c. 384. Parting of Gold. — In order to obtain fine gold from alloyed gold, or to separate it from silver con- * " Gold is regularly purchased by the Bank of England at the rate of £3 17s. 9d, and issued at the rate of £ 3 17s. 10|c?. per ounce of 22 carats (eleven twelfths) fine." — Waterston's Cyclopaedia of Commerce. 400 HEAVY METALS. taining gold, it is boiled with concentrated sulphuric acid, which must be done in iron kettles ; the concen- trated sulphuric acid does not dissolve iron. The sil- ver and copper are dissolved with the formation of sul- phurous acid, while the gold remains behind undis- solved, as a brown powder. From the solution of silver and copper, the silver is precipitated by copper, and blue vitriol is obtained as a secondary product. This operation is called refining. Formerly, with the same view, silver containing gold was dissolved in nitric acid, which does not dissolve the gold, though it does silver. In this case the remark- able fact was observed, that the silver was completely dissolved only when three fourths of silver were present to one fourth of gold (two thirds of silver, however, is an adequate proportion); hence the term quartation. If more than one fourth or one third of gold is contained in the alloy, the gold exerts a protecting influence upon the silver, so that the latter is not attacked and dis- solved by the nitric acid. The most simple mode of testing gold is to rub some of it off upon a black flint slate (touchstone), and ap- ply to the mark a drop of aqua-fortis. If the gold is pure the yellow stroke remains unchanged, but if al- loyed it partly disappears; if it is only an imitation of gold, for instance, tombac, it entirely dissolves. 385. Gold and Acids. — None of the common acids alone can dissolve gold, since this metal is in a high degree indifferent towards oxygen and acids. Chlorine is the only means of rendering it soluble (§ 152). Commonly the chlorine is obtained for this purpose by mixing muriatic with nitric acid; in this mixture, the well-known aqua regia, the gold dissolves completely by sufficient heating, and a brownish-yellow liquid is GOLD. 401 obtained (solution of gold). By evaporating this solu- tion to dryness, ter chloride of gold (Au Cl3) is ob- tained, as a brownish-red deliquescent salt. Metallic gold separates from it on exposure to the light, and like- wise separates by introducing phosphorus, iron, zinc, and other metals, into a solution of it. Experiments with Gold. 386. Gilding. — Experiment a. — Dip a dry test-tube into a diluted solution of gold, so as to moisten the bot- tom of it, and then heat it over the flame of a spirit- lamp ; it will become gilded, — a proof that gold has only a very feeble affinity for chlorine, since it releases it at a mere gentle heat. Experiment b. — Drop some of the solution of gold upon blotting-paper ; let the paper dry, and then hold it by means of a wire over the flame of a spirit-lamp; you obtain finely-divided gold, mixed with the ashes of the paper as a coherent loose mass. If you rub this for some time upon a bright silver spoon, with a soft cork which has been dipped in salt water, the silver be- comes gilt (cold gilding). There are other methods of gilding; — the moist gilding, in which the copper, brass, or silver articles are boiled with a very diluted solution of gold, to which some bicarbonate of soda, or cyanide of potassium, has been added; the hot or quicksilver gilding, by which these articles are smeared with a so- lution in mercury, and afterwards heated ; the galvanic gilding, which is done in the same manner as the gal- vanic coppering. The silvering of metals is conducted on the same principle. 387. Gold Powder. —Experiment. —Drop into a weak solution of sulphate of iron some muriatic acid, and then some of the solution of gold; the liquid im- 34* 402 HEAVY METALS. mediately assumes a changeable dark and brownish color, but it appears of a beautiful blue color by trans- mitted light. On standing, a brown substance is de- posited, which is gold in the state of minutest subdi- vision (gold powder). The green vitriol is at the same time converted into the sulphate of the sesquioxide of iron, and into sesquichloride of iron ; decomposition is thus produced, by the great tendency of the protoxide of iron to pass over into the sesquioxide of iron. In this way the workers in gold precipitate that metal from liquids containing it. By triturating gold powder with oil of lavender, the color made use of by painters for gilding porcelain, glass, &c, is obtained. 388. Gold and Oxygen. — If the solution of gold is applied to the skin, or to any other organic substance, it imparts to it on drying a dark purple-colored stain, proceeding from the protoxide of gold (Au O). This protoxide of gold is also formed on the addition of the solution of gold to protochloride of tin (purple of Cas- sius). That the most beautiful purple color is produced by this on glass and porcelain has already been men- tioned, under the head of tin (§ 322). Gold may be recognized in its solutions by salt of tin. Teroxide of gold (Au 03) is of a brownish-black color, and com- ports itself like an acid towards bases. It combines with ammonia, like the oxide of silver, forming fulmi- nating gold. 389. Sulphuret of Gold. — When sulphuretted hydro- gen is added to a solution of gold, a black precipitate of sulphuret of gold is produced, which is soluble in sul- phuret of ammonium. Gold cannot be united directly with sulphur, by fusing them together. PLATINUM. 403 PLATINUM (Pt). At. Wt. == 1232. —Sp. Gr. = 21.5. 390. Platinum, a metal of still greater density than gold, was brought in the last century from America, where it was found, in the form of small, flattened grains, mixed with the sands from which the gold was washed. It received the name platinum, derived from the Spanish word plata, silver, on account of its re- semblance to silver in color and ductility. It was afterwards found also in the sand of the Ural Moun- tains, in compact lumps, from the size of a flax-seed to that of a man's fist. Platinum, like gold, is a noble met- al, and, like iron, is tenacious, ductile, and can be welded, and is, moreover, infusible at the strongest furnace heat. These properties have rendered platinum an in- valuable metal to the chemist. Sulphuric and hydro- fluoric acids can be distilled in platinum retorts, aqua- fortis can be boiled in platinum capsules, and substances can be subjected to the strongest white heat in plati- num crucibles, or on platinum foil or wire, without the platinum articles being broken or melted. It is only necessary to be careful that no metal be heated with platinum, as a fusible alloy might thus be formed, and the platinum apparatus be melted or broken even at a moderate heat. The value of platinum is intermediate between that of gold and silver, and in Russia it has been coined into money. It is less adapted for articles of luxury than either of these two metals, its color not being of a pure, but of a grayish white, and its lustre far inferior to that of silver. It can be fused by the oxy- hydrogen blow-pipe, or by the galvanic battery. 391. Platinum, like gold, is dissolved by heating it for a long time with aqua-regia ; and a dark-brown so- 404 HEAVY METALS. lution of chloride of platinum = Pt Cl2 is obtained (solution of platinum). A small quantity of this solu- tion can easily be prepared from one or several pieces of spongy platinum, such as are employed in the Do- bereiner hydrogen-lamp. Experiments with Platinum. 392. Finely divided Platinum. — Experiment. — Add a few drops of a solution of platinum to a solution of sal ammoniac ; the two salts will combine together, forming a yellow insoluble double salt, which is called chloride of platinum and ammonium. After settling, decant the supernatant liquid; let the precipitate partly dry in a dish, so that it forms a moist paste; affix it to a plati- num wire, several times bent, and hold it in the flame of a spirit-lamp. The sal ammoniac flies off, but the platinum remains behind as a gray, loosely coherent, porous mass, the so-called spongy platinum. When held in hydrogen, it becomes red-hot, and inflames the gas (§ 85). The porous platinum acts on gases in the same manner as the pump of an air-gun, only far more rapidly and vigorously ; it absorbs them, and condenses them so powerfully together into its pores, that the atoms of two different gases often approach each other sufficiently near to combine together chemically. As hydrogen and oxygen are in this instance compelled to unite, so the spongy platinum can force many other gases, which will not directly combine with each other, to enter into combination. Pure platinum is commonly prepared from spongy platinum, which is heated to whiteness and then quick- ly compressed by strong pressure. A compact mass is thus obtained, which, on being again heated, may be hammered out into uniform pieces, and afterwards PLATINUM. 405 rolled into plates, drawn out into wire, or moulded into crucibles, capsules, &c. By proper chemical means, platinum may be divided still more minutely than in the case of spongy plati- num ; it is then obtained in the form of a delicate black powder, which possesses, in a still higher degree than spongy platinum, the power of condensing gases into its pores ; it is called platinum black. If some alcohol be dropped upon this platinum black, ignition takes place, with an almost instantaneous conversion of the alcohol into acetic acid. The reason of this change is to be sought for in a combination of the alcohol with the oxygen of the air, which is effected by means of the porous platinum black. 393. Experiment. — If you perform the experiment described in §386 with a solution of platinum, you obtain a coating of metallic platinum upon the glass. The combination between this metal and chlorine is likewise so feeble, that heat alone is able to destroy it. 394. Experiment. — Dissolve one of the salts of po- tassa, and add to it some drops of solution of platinum; here also, as in § 392, a yellow insoluble precipitate is formed, consisting of potassium, platinum, and chlorine. The solution of platinum serves, therefore, as a test for the salts of potassa (and salts of ammonia). The solu- tion of platinum is precipitated black by sulphuretted hydrogen (sulphuret of platinum). Platinum forms with oxygen a peroxide and a pro- toxide; likewise with chlorine, a perchloride and a pro- tochloride. Palladium, Iridium, Rhodium, and Osmium. 395. These four metals are, as it were, the satellites of platinum ; they are always found in small quantities 406 HEAVY METALS. in the crude platinum sand, and are obtained on the purification of the latter, by a somewhat elaborate pro- cess. They also have the character of noble metals. RETROSPECT OF THE SECOND GROUP OF THE HEAVY METALS. 1. The metals lead, bismuth, copper, mercury, silver, gold, and platinum do not possess the power of decom- posing water, that is, of abstracting its oxygen, like the metals of the first group; therefore, concentrated acids must be employed for their solution. 2. Their lowest degrees of oxidation are bases, while their higher degrees comport themselves sometimes like bases, sometimes like acids. 3. These metals most frequently occur in nature uncombined, or as sulphurets, rarely as oxides. 4. They have a greater specific weight than the metals previously described; it varies from 8.8 to 21.5. (That of iridium is indeed 23.0). 5. They are all precipitated as black sulphurets by sulphuretted hydrogen and sulphide of ammonium; the sulphurets of gold and platinum are redissolved by the latter reagent. 6. The metals mercury, silver, gold, and platinum, together with the last-named associates of platinum, are called noble metals, because they remain bright in the air or in water. When oxidized by other means, by acids, for instance, the oxides may be again resolved merely by heat into metal and oxygen. This is effected with the ignoble metals only by the addition of a re- ducing agent, as by charcoal. CHROMIUM. 407 THIRD GROUP OF HEAVY METALS. TUNGSTEN, MOLYBDENUM, TELLURIUM, TITANIUM, TANTALUM, VANADIUM, NIOBIUM, PELOPIUM. 396. These metals occur only as chemical rarities, and have not yet found any useful application. Their highest degrees of oxidation are clearly defined acids. The first two are the most common, as they are some- times dug out from tin mines, — tungsten as wolfram ore, and molybdenum as sulphuret of molybdenum, or molybdate of lead. CHROMIUM (Cr). At. Wt. = 328. — Sp. Gr. = 6. 397. Chromium has only been known within a few decades, and already several of its combinations have become common and valued articles of commerce. The cause of this rapid extension is owing to the beau- tiful color of many of the preparations of chromium, on account of which they are excellently adapted for pig- ments. This also has given rise to the name chromium (color). The most important ore of chromium, chromale of iron, an insignificant looking black mineral, is mostly obtained in North America, and is manufactured into a red salt, which consists of potassa and chromic acid. The other compounds of chromium are prepared from this salt. 398. The Red Chrornate or Bichro- mate of Potassa (K O, 2 Cr 03) is an acid salt, for it contains two atoms of chromic acid and one atom of po- tassa, and commonly occurs in beau- 408 HEAVY METALS. tiful tabular or prismatic crystals. Rub an ounce of it with ten ounces of water; it will dissolve in it, forming an orange-yellow solution. Experiment. — Add to one half of this solution a dram of pure carbonate of potassa, and concentrate by evaporation the liquid, which has become of a clear yellow color; on cooling, yellow crystals will be de- posited. These consist of neutral chromale of potassa (K O, Cr 03). The potassa of the carbonate of potassa has, while the carbonic acid escaped, combined with the second atom of chromic acid. If nitric acid is added to a solution of the yellow salt, the liquid be- comes darker, and on evaporation red crystals are ob- tained, mixed with crystals of nitre. It is obvious that the nitric acid has abstracted half of the potassa. 399. Chromate of Oxide of Lead (Pb O, Cr03).— Experiment. — Add to a portion of the solution of the red salt a solution of sugar of lead, as long as there is any precipitate; this precipitate, when washed and dried, is the well-known chrome yellow, and is the richest and most vivid of all the yellow pigments. By mixing it with white substances, — for instance, chalk, talc, clay, gypsum, &c, — numerous other shades of yellow are obtained, as new-imperial, king's, Paris, &c., yellow; but by mixing it with Prussian blue, the well- known cheap green pigments are obtained, called olive green, Naples green, green cinnabar, &c. Experiment. — If chrome yellow is stirred up with water and heated with some carbonate of potassa, it passes into chrome orange, which is also used as a paint- er's color. This contains somewhat less chromic acid than the chrome yellow; accordingly, the potassa ab- stracts from the chrome yellow a portion of the chromic acid, which is rendered apparent by the yellow color of the liquid filtered off from the chrome orange. CHROMIUM. 409 By fusing with nitre, still more, even a half, of the chromic acid may be withdrawn from the chrome yel- low ; in this way we obtain a beautiful red color, al- most rivalling that of cinnabar, chrome red, or basic chromate of oxide of lead (2 Pb O, Cr Os). Thus we see that the colors of the combinations of lead comport themselves inversely to those of the combinations of potassa; the chrome yellow passes into orange and red by abstracting chromic acid, while yellow chromate of potassa, on the contrary, becomes red by adding more chromic acid, or, what amounts to the same, by with- drawing potassa. Experiment. — Chrome yellow has obtained also a very important application in the dyeing and printing of yarns and fabrics. First dip a piece of cotton into a solution of chromate of potassa, then, after it has be- come dry, into a solution of sugar of lead; it is dyed yellow. If you now boil a little quicklime with water in a vessel, and then dip the cotton dyed yellow into it for a few moments, it will acquire a reddish-yellow col- or, because the lime, just like the carbonate of potassa, abstracts some chromic acid from the chrome yellow. It is scarcely necessary to explain any further why chrome yellow cannot be used for painting the walls of apartments. Salts of zinc and baryta are precipitated yellow, salts of suboxide of mercury a brick-red, and salts of silver a purple-red, by chromate of potassa. 400. Sesquioxide of Chromium (Cr2 03). — Experiment. —Boil some chrome yellow in a test-tube with muriatic acid; it becomes white, and the liquid green; the white residue consists of muriate of oxide of lead (chloride of lead), but the liquid holds in solution muriate of the sesquioxide of chromium (sesquichloride of chromium). A piece of moistened litmus-paper, or of paper smeared 35 410 HEAVY METALS. with ink, introduced into the tube during the boiling, is bleached, as chlorine gas escapes at the same time. The process is analogous to that of the evolution of chlorine from black oxide of manganese, or from aqua- regia; the chromic acid gives up half its oxygen, and becomes green sesquioxide of chromium, but the oxygen, becoming free, abstracts from a portion of the muriatic acid its hydrogen, and liberates its chlorine. Decant the green solution, dilute it with water, and add to it ammonia; the ammonia combines with the muriatic acid, and the sesquioxide of chromium is precipitated as a hydrate having a bluish-green color. Dried and ignited, it becomes a dark green anhydrous oxide. A fine green is produced by it on porcelain and glass; ac- cordingly it is esteemed as a valuable vitrifiable pig- ment. Experiment. — The ease with which chromic acid gives up half of its oxygen may also be shown with chromate of potassa. Dissolve in a test-tube a few grains of red chromate of potassa in warm water; add a few drops of sulphuric acid, and heat the solution still more strongly. If you now add a little sugar or some drops of alcohol to it, a brisk ebullition ensues, and the color of the solution is changed from red to green; sulphate of potassa and sulphate of sesqui- oxide of chromium are now contained in the liquid. 401. Chromic Acid (Cr 03).—Experiment. — Re- duce to powder half an ounce of red chromate of potassa, put it into a porcelain dish, and then add half an ounce of water and half an ounce of sulphuric acid, and heat the whole, with constant stirring, for five minutes. If a drop of it is CHROMIUM. 411 put on blotting-paper, it effervesces, and changes its yel- lowish-red color to green. When the vessel is entirely cold, add an ounce of cold water to the thick saline mass, stir it a few minutes, and then carefully decant the liquid into a beaker-glass. What remains in the dish is sulphate of potassa; but we have in the liquid a solution of chromic acid, which is precipitated as a red mass by adding to it from one and a half to two ounces of common sulphuric acid. Cover the beaker- glass with a small board, set it aside for twenty-four hours, and then carefully pour off the supernatant acid into a glass vessel, and transfer the red paste remaining behind to a new brick, by which the fluid portion is completely absorbed. After twenty-four hours, during which time the precipitate is kept covered with a dish, you obtain the chromic acid, as a crystalline, red powder, which must be scraped off from the brick with a glass rod, and put into a wide-mouthed phial, provid- ed with a glass stopper. The following experiments will illustrate the extreme ease with which this highly interesting body decomposes into sesquioxide of chro- mium and oxygen. Experiment a. — Rinse out a tumbler with strong alcohol, then throw into it a few grains of chromic acid; the alcohol which remains adhering to the tum- bler will combine with half the oxygen of the chromic acid, with such energy, that it ignites and instantane- ously bursts into flame. The change which the alcohol has hereby undergone is at once revealed by the odor, similar to that of the vinegar apartments; in the latter, the alcohol contained in the brandy, beer, &c. slowly imbibes oxygen from the air, and is converted into vinegar; in the present case this conversion is instan- taneously produced by the oxygen of the chromic acid. 412 HEAVY METALS. Experiment b. — Mix in a small mortar as much chromic acid as can be taken up on the point of a knife with about one quarter as much of powdered camphor (without pressing upon it strongly), and then let some drops "of alcohol fall from a considerable height into the mortar; instantaneous ignition and deflagra- tion ensue, almost as if you were burning gunpow- der. The residue in the mortar presents, after the decomposition, the appearance of an elegant green mossy vegetation; it consists of sesquioxide of chro- mium, which at the moment of its formation was scat- tered by the burning camphor fumes, and was thereby most delicately subdivided. It is obvious from this action, that chromic acid may be classed under one and the same category with nitric acid, chloric acid, manganic acid, hyperoxide of man- ganese, hyperoxide of lead and chlorine (and the finely divided platinum); it possesses in a high degree the property of forcing other bodies into a combination with oxygen. ANTIMONY, STD3IUM (Sb). At. Wt. = 1613.—Sp. Gr. = 6.7. 402. Antimony has a lamellar crystalline texture, and a white metallic lustre, like bismuth, but without the red tint of the latter; it far exceeds it in brittleness, for it may be easily rubbed to powder in a mortar. The sol- uble preparations of antimony are undisguised enemies to animal life, and consequently the stomach exerts it- self to remove from the body all such compounds intro- duced into it. This is effected by vomiting, and for the very reason of its emetic properties, antimony has become a very important medicine. 403. Oxide of Antimony (Sb Os). — Experiment.— ANTIMONY. 413 Antimony does not alter in the air, but if a piece of it is heated on charcoal before the blow-pipe, it soon melts, and burns with a white flame, forming an oxide, which partly escapes as a white vapor, and is partly deposited as a coating on the charcoal. If you let the melted metallic globule slowly cool, the oxide con- denses into crystals, which form around the metal an espalier of white points. When thrown into a paper capsule, the white glowing globule will burst into a multitude of small spheroids, which skip about for some time, leaving in their trail a pulverulent oxide. Anti- mony generally contains traces of arsenic; hence the smell, like that of garlic, which almost always accom- panies its fusion. 404. Antimonic Acid (Sb 03). — If antimony is treat- ed with nitric acid, it takes up two more atoms of oxy- gen, and becomes antimonic acid, a yellowish powder, insoluble in water and acids. At a glowing heat one atom of oxygen is expelled from this, and a com- pound of antimonic acid with oxide of antimony re- mains behind, which may be regarded as antimonious acid (Sb 04). It is not volatile at a glowing heat, and has the property of imparting to glass and porcelain a yellow and orange color. Experiment. — If some powdered antimony be heated with nitric acid, the same thing occurs as with tin; namely, the metal is converted into a white powder, which consists of a mixture of both degrees of oxida- tion, antimonic acid and oxide of antimony. A similar process takes place by mixing powdered antimony with nitre, and throwing the mixture into a glowing hot crucible; in this case only antimonic acid is formed, which remains behind combined with the potassa. The antimoniate of potassa may be dissolved by boiling 35* 414 HEAVY METALS. in water, and is then used as a test for the salts of soda, the antimonic acid forming with the soda a very spar- ingly soluble salt. 405. Chloride of Antimony. — Antimony is dissolved only with great difficulty by muriatic acid ; a solution is more readily obtained by employing sulphuret of an- timony instead of metallic antimony. Experiment. — Put half an ounce of sulphuret of an- timony into a capacious flask; pour over it two ounces and a half of muriatic acid, and heat it in a sand- bath, at first moderately, but afterwards to boiling; the sulphuretted hydrogen, escaping in large quantities, is conducted either into water or into milk of lime, by which it is completely absorbed. The sulphuret of an- timony and the muriatic acid are converted into sul- phuretted hydrogen and chloride of antimony (muriate of oxide of antimony). After several days' repose, de- cant the clear liquid; it contains chloride of antimony in solution, and was formerly called butter of antimony. By continuously rubbing some drops of it upon an iron plate, a very strongly adhering coating of oxide of iron is produced, which imparts to the iron a brown appearance, and renders it less liable to rust. In this way the well-known color (browning) is given to gun- barrels. The liquid obtained as a secondary product, filtered from the milk of lime, is to be regarded as hydrated sulphuret of calcium; it has the property of rendering hair so loose in the skin, that it may easily be pulled out, as will appear if a piece of calf-skin is softened in it for some time. Experiment. — By pouring one ounce of the liquid muriate of antimony into ten ounces of hot water, a decomposition and turbidness are produced, as in the ANTIMONY. 415 case of the solution of bismuth; the precipitate is ox- ide of antimony combined with a little muriatic acid. Wash it several times with water, by settling and de- canting the liquid, and then digest it for an hour with a solution of a quarter of an ounce of carbonate of soda in two ounces of hot water, whereby the muriatic acid is completely removed. The precipitate, being again washed, yields, when dry, a white powder of oxide of antimony. The same preparation is thus obtained in a moist way, as by igniting the metallic antimony (§403). 406. Tartar Emetic (K O, T -f- Sb Os T + 2 H O).— Experiment. — Boil in a porcelain dish two ounces of distilled water, and during the boiling stir in a mixture of one dram of oxide of antimony, and one dram of cream of tartar. When the liquid is half boiled away, filter it while boiling, and pour one half of it into one ounce of strong alcohol, but set the other half aside. In both cases you obtain a white salt, tartar emetic; in the latter case in the form of crystals, but in the former as a fine powder, because tartar emetic is insoluble in alcohol, and consequently is precipitated by it from its solutions. The process in this case is a very simple one. Cream of tartar is an acid salt, that is, a combi- nation of tartrate of potassa with free tartaric acid; this free tartaric acid combines with the oxide of antimony. Thus we obtain tartrate of potassa and tartrate of ox- ide of antimony, which unite together, forming a double salt, tartar emetic. The name indicates the medicinal application of this double salt; it is the most usual means of inducing vomiting. One grain of it, dissolved in half an ounce of Teneriffe or Sherry wine, forms the well-known wine of antimony. One ounce of tartar emetic requires fifteen ounces of cold water for so- lution. 416 HEAVY METALS. 407. Sulphuret of Antimony. — Experiment. — Add some sulphuretted hydrogen to a solution of tartar emetic in water: an orange-colored precipitate of sul- phuret of antimony (Sb S3) is obtained, which becomes darker on drying. Thus the combination of antimony may be very well recognized, as no other metal yields a sulphuret of this color. We most frequently find antimony in nature having this composition ; but the native sulphuret of antimony has quite another color, namely, steel-gray, and in other respects likewise a very different exterior condition, as it occurs in heavy compact masses, which on the frac- tured surface appear as if they were composed of small shining needles or points. On account of this appear- ance, it has received the name of prismatoidal antimony glance. It melts even in the flame of a candle, and hence may be obtained from the different sorts of rock with which it is associated, merely by liquation. When pulverized, it forms a black gray shining powder, which is employed by the farmer as a familiar remedy in the diseases of domestic animals. It is commonly, but er- roneously, called antimony, by which term sulphuret of antimony is implied. Experiment. — Boil a small quantity of pulverized gray sulphuret of antimony with a solution of potassa, let it settle, and add an acid to the decanted liquid: a brownish-red precipitate is produced, likewise sulphuret of antimony, which was dissolved by the potassa. This sulphuret of antimony (containing an oxide), which in the apothecary's shop is called Kermes mineral, is much more finely divided (§ 129) than the gray, and thereby acquires the red color; the division is still greater in the orange-colored sulphuret, prepared from the tartar emetic. ARSENIC. 417 These three combinations, the orange, the red, and gray sulphurets of antimony, have quite a similar com- position ; they are one and the same body, only existing in different isomeric states. A still higher sulphuret of antimony (Sb S5) occurs in the pharmacopoeias, under the name of the golden sul- phuret, as an important medicine; it has an orange color, and corresponds in its constitution to antimonic acid, as the gray or red sulphuret corresponds to the oxide of antimony. For Antimoniuretted Hydrogen, see § 418. 408. Preparation of Antimony. — In order to sepa- rate metallic antimony from the sulphuret, it is only ne- cessary to fuse it with iron, which has a greater affinity for the sulphur, and unites with it, forming sulphuret of iron. On cooling, the heavy metallic antimony settles at the very bottom. 409. Alloys of Antimony.— Of the alloys which anti- mony forms with other metals, that with lead, from which types are cast, deserves especial notice. Lead alone is much too soft to be employed for this purpose, but if from an eighth to a twelfth part of antimony is mixed with it, it acquires such a degree of hard- ness, that types cast from it may be used for printing many thousand times without losing their distinctness. ARSENIC, ARSENICUM (As). At. Wt. = 937. — Sp. Gr. = 5.7. 410. Poisonous as arsenic, is almost a proverbial ex- pression, and it shows, in this respect, at least, that arse- nic is well known, and in sufficiently bad repute. In fact, it is placed among the metallic poisons, and a very small quantity of it produces a fatal effect, unless antidotes 418 HEAVY METALS. are quickly administered. Happily, in recent times a means has been discovered, in the hydrated sesquioxide of iron (iron-rust), by which most of the combinations of arsenic may be rendered, even in the stomach, insol- uble, and thereby harmless. Before this remedy and the aid of the physician can be procured, it is well in cases of poisoning by arsenic, as in cases of poison generally, to administer milk, white of eggs, soap suds, or sugar. On account of the dangerous effects of arse- nic, the greatest care must be taken, in experimenting with it, not to inhale its dust or vapor; the vessels that contain it must also be most carefully washed, and the water used for this purpose should be emptied into some place not accessible to domestic animals. 411. Metallic Arsenic. — Metallic arsenic is not unfre- quently found in the earth, as a lead-gray ore, of strong metallic lustre. The artificially prepared metallic arse- nic, which soon tarnishes and assumes motley colors in the air, and finally falls into a coarse gray powder, is kept on hand in the apothecaries' shops, under the name of fly-poison. If boiled with water, the film of oxidized arsenic dissolves, and a very poisonous liquid is ob- tained (fly-poison). A fresh film of oxide is produced upon the metal which remains, and thus is very easily explained why, after a time, a new poisonous solution can again be prepared from it, without any perceptible decrease of the original powder. Fig. 161. Experiment. — Put a piece x of arsenic of the size of a mil- fl ^ => let-seed into a glass tube, hold the latter by one end, and heat it; the arsenic volatilizes at 180° C, and deposits itself on the upper portion of the tube ARSENIC 419 as a brilliant black mirror; the smell of garlic, peculiar to the fumes of arsenic, being at the same time given off. These two tests are employed as very accurate for detecting the presence of arsenic in other bodies. Phosphorus, when exposed to the air, emits, likewise, the odor of garlic. If this indicates a similarity in these two bodies, the resemblance is rendered still more striking, since arsenic behaves very much like phosphorus in its combinations with other substances. 412. White Arsenic, or Arsenious Acid (As 03). Experiment. — Let the arsenical mirror obtained in the above experiment be heated once more, but in an open tube; it is converted into a vapor, which condenses on the colder parts of the tube, partly in small white crystals, partly as powder. Before the magnifying-glass these crystals appear as four-sided double pyramids (octahedrons); their constituent parts are arsenic and oxygen, and they are called arsenious acid, white ar- senic, or ratsbane. When arsenic is spoken of in a popular sense, the white arsenic is always implied. It is obtained on a large scale, — a.) as a secondary prod- uct in the roasting of tin, silver, and cobalt ores ; b.) as a principal product, by heating arsenical ores with access of air (in the arsenical furnaces in Saxony and Silesia). In both cases the arsenious acid passes off as vapor, with the smoke, which must therefore be conducted through long, horizontal chimneys, till it cools, and the arsenious acid condenses as a powder (white arsenic). White arsenic is often re-sublimed in some appropriate apparatus, and is then obtained as amorphous arsenious acid, in solid transparent pieces. These after a time become opaque and milk-white, like porcelain, without changing their constitution ; another 420 HEAVY METALS. example that, even in solid bodies, atoms can alter their relative situations (§ 280). Arsenious acid is especially distinguished from the other metallic oxides by its solubility in water, which, indeed, is not very great, since one grain of it requires fifty grains of cold water, or from ten to twelve grains of boiling water, for solution; but it is sufficiently soluble to render these solutions exceedingly dangerous poisons. White arsenic is generally employed for killing rats, moles, and other troublesome house or field animals; for this purpose colored arsenic only should be pur- chased, as the white arsenic looks very much like sugar or flour, and might easily be mistaken for it. In order to prevent its being carried off, it is best to strew pow- dered arsenic over broiled rinds of pork, or broiled fish, nailed upon boards. If the poison is put in stables, the fodder-troughs should be carefully covered over, that the poisoned rats may not vomit the poison into them. Arsenious acid, like 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 hares. 413. Reduction of Wliite Arsenic. Experiment. — Draw out a glass tube into a point, ARSENIC. 421 Fig. 162. introduce into it a very little arsenious acid, and 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 oxygen is withdrawn from the vapors of the 7 arsenious acid while they pass over the glow- ing coal. This is one of the surest methods of detecting small quantities of arsenic. 414. Combinations of White 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- 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- 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 Os). — If arsenious acid is boiled with nitric acid, it takes from the latter '°~ ' two additional atoms of oxygen, and becomes the 1st period, ( half.burnt wood. the 1st period, ( humus . from the half- ( ,,., . . „ , burnt woodin the < wa*r .(httle)' fr0m the humUS 5 water ' ^ § C7 > V £ '£ „ o £ £ A a" ^ •N 0) c c S3 be > o •— bo o J3 cd X >> O O M 55 Silica, Alumina, Limt ;, 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 TLANTS. 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, ivater, 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- drolen __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 sohd mgredients 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 supplied 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 especially 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 O.) 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). c) Ammonia furnishes plants with nitrogen. — When vegetable and animal matters decay, ammonia (N H.) 8 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; whereas it may be regarded as proved that plants have the power of withdrawing nitrogen even from nitrates when these are present in the arable soil. 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 -j- 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 GROWTH OF PLANTS. 619 to us to be annihilation is, however, only decay; the form only passes away, the matter itself is unchange- 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 620 VEGETABLE MATTER. changes which these substances undergo in living plants have already been noticed in the preceding section. 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, but 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 lime, gypsum, marl, wTood-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 followed 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 knowledge 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 relied 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 liquid substances, are continually taking place in it. If these substances are wanting to the plant, its growth and life cease; we therefore regard them as food for the plant. 2. These substances all 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.; £. into those rich in hydrogen, namely, fats, vol- atile oils, resins, &c.; y. into those rich in carbon, namely, vegetable tissue, starch, 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 0. 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.); 8. 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 oxalic 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 [illuminating 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; 0. conversion of starch into gum and sugar by diastase; y. conversion of starch into gum by moderate heat- ing) b. conversion of crude sugar into liquid sugar by heating or long boiling with water; t. coagulation of albumen by heating, &c. k.) By the operation of strong bases upon vegetable matter; for example, — a. formation of cyanogen (§ 291); 0. formation of ammonia (§ 232); y. formation of nitre (§ 207); b. 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 unlimited, 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; all 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 assi (ne a crystalline form; we find crystalline combination — as, for instance, in urine (urea, uric acid, &c.) — in those animal liquids only, which, being unfit for assimilation, are again separated from the body. Most animal substances, when viewed under the microscope, exhibit the form of small 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 (crystalline 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, i ilphur, phosphorus, and chlorine ; and the metallic subs ances, lime, potas- THE EGG. 629 slum, 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 liquid, the albumen. On evaporation, we obtain from it one eighth of solid 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- ious light 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-shells; 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-shells small pores, through which the air penetrates into the interior of the egg, and gradually 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 chemically 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, small quantities of it being present in all milk. 628 Experiment — Let a small piece of the dried membrane of the stomach of a calf (rennet) remain ^Tdinc one night in a spoonful of water, and after- Talp-Ls water upon a quart of new milk; the milk, after having stood for some hours in a warm 1U will coagulate into a gelatinous mass which s 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 liquid (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 principally 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 coagujation 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 milk which passes off from beneath may be separated, in the way already described, into caseine, albumen, and sugar of milk. Butter, like 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 small quantity of a pe- culiar fat (butyrine). If butter remains exposed some time to the air, some volatile fat acids having a dis- agreeable smell 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 curdling 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^ 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 finally 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 distilla- tion of the fermented liquid 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 = H, O, C, P. Butter > _ Albumen = H, 0, C, N, S, P. Sugar of milk ] ~ H' °' C- Caseine > „ _ „ Albumen £ = H'°> C, N, S, P. Shells and other in- ) Ca, Na, K, Fe, Inorganic sub- ) =Ca, Na, K, Mg, Fe, organic substances SP, S, CI, O. stances \ P, S, CI, 0. 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 liquid 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 303 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. III. 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 yellowish-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 yellowish-liquid 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 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 boiling 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 lives 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, 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 all 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 called 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 6oagulated 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, little 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 yellow, and finally 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,.......750 « 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 boiling 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-called 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 BILE. 645. The bile separates in the liver 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 dome 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. Fig. 219. VI. THE SKIN. 646. The whole body of the animal is externally sui- rounded by the solid elastic skin, which consists of a thick tissue of cells, between which are small openings (pores). The annexed figure 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 swells up in it without dissolving; if kept tor 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 iellv When dried, this forms the well-known glue The skin does not contain glue ready formed, but , 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 all 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; like 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 cooling, 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 allow 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 jelly. 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 ot 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, pliable, 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). y v 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 not applicable to the bleaching of wool). The fibres of wool, as well as those of silk, likewise having an ani- mal origin, have a far greater affinity for coloring mat- ter than the vegetable fibres linen or cotton have ; and this is the reason why woollen and silk stuffs may be more easily or permanently dyed than cotton or linen. 648 ANIMAL MATTER. By boiling with lye, all the above-named animal sub- stances, consisting of horny matter, may be entirely dissolved. VII. THE BONES. The bones forming the solid 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 lighter, consists principally of phosphate of lime mixed with some carbonate of lime (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 liquid, 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 he external part, is extracted, and the latter maybe entirely extracted when the boiling is performed in ^hr vessels, as in this case the water is forced by hf inl ea d preSsure into the interior of the bone, cf u at a great tension, operates in the same ^'Glue' is prep-d 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. VHI. THE SOLLD EXCREMENTS AND URINE. 659. Those ingredients of the food consumed, which are not applicable 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 call life, are either removed from the body in an aeriform state, by breathing or insensible perspiration, or in a liquid form, as urine, or, finally, 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. 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-;^ is natural, therefore, that the const— of it, ahke wise of the feces, should correspond exac ly w*h the food consumed. If this is rich in soluble salts the. urine will also be rich in them; if this contains on y a few soluble, but many insoluble salts, the urine will be poor in soluble salts, while the feces will be rich in in- soluble salts. Consequently, the amount of inorganic substances in the animal excrement or manure may be ust as accurately ascertained from the food which£a animal consumes, as from the manure itself. The food has only to be burnt, and the remaining ashes ex- A those parts of it which are soluble in water amined , those P«* ^ those which are C°r7Ph^ tit tglt ^nees of the feces. We ^^ the u" cows and horses principally alka- r "bonateTmuriates, and sulphates (potassa, soda, Ime carbonates, m moreover? some and ammonia); in tne alkaline phosphates. either in lhe 661. Nitrogen, —^^ acid.' UrinCj like forn of urea^tZ^eo.er, creatine and the juice ot nesu, creatinine (§640). 652 ANIMAL MATTER. Urea occurs in the greatest abundance in the urine of the higher animals, especially 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, 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 feces 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 solubility, 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 chiefly 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 ot ashes How much alkaline salt this ashes contains may be ascertained by extraction with hot water; what remains are earthy (lime and magnesia) salts. The in- ferior sorts of guano often yield after burning three ^txTert^Tc.'- Treat half an ounce of pulverized guano several times with hot water and decant the fiquid after it has become clear on settling; then dry and wefeh the muddy mass which finally remains; it should not weigh more than a quarter of an ounce 664 Hippuric Acid.-'^s azotized acid always oc- 654 ANIMAL MATTER. curs in the urine of herbivorous animals; it crystallizes in long white needles, and is difficultly soluble in water. 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 collected 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, ccc, 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 essentially 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 IN GENERAL. 1. A constant motion is taking place in the living 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 ot 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.— T According to their composition,— a.) Into non-azotized substances (fat, sugar of milk, &C^ 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 (gall, 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 metallic compounds. A SYNOPSIS OF THE MOST IMPORTANT TESTS FOR ASCERTAINING THE PRESENCE OF THE MORE COMMON CHEMICAL COMPOUNDS, ESPECIALLY WHEN IN SOLUTION. 1. Alkalies and their Salts. These are not precipitated by carbonate of ammonia, sulphuretted hydrogen (H S), or sulphuret of ammo- nium (N H3, H S). 2. Salts of Potassa. Tartaric acid, in excess and in a concentrated solu- tion, produces, especially after violent agitation, a white crystalline precipitate. (Tartar, § 194.) Platinum solution gives a yellow crystalline precipi- tate. (Chloride of platinum and potassium, § 394.) 3. Salts of Soda. Antimoniate of potassa produces, in neutral or alka- line solutions of soda salts, a white precipitate. (Anti- moniate of soda, § 404.) 4. Salts of Ammonia. Caustic lime or caustic potassa, especially on heating, 658 CHEMICAL TESTS. liberates the ammonia, which is easily recognized by its pungent odor. Heated on platinum foil, the salts of ammonia are readily volatilized. (§ 229.) Platinum solution reacts in the same manner as with potassa salts. (§ 392.) 5. Alkaline Earths. These are precipitated by carbonate of ammonia, as carbonates of a white color, but not by H S or N Ha, HS. 6. Salts of Baryta and Strontia. Sulphuric acid produces a white precipitate, insoluble in acids (sulphate of baryta and of strontia). The ba- ryta salts impart a yellowish color, and the strontia salts a crimson color, to the flame of alcohol. (§ 248.) 7. Salts of Lime. Sulphuric acid produces only in concentrated solu- tions of lime a precipitate, which is redissolved in a large proportion of water. (§ 241.) Oxalic acid and ammonia indicate mere traces of lime by a milky turbidness. (Oxalate of lime, § 197.) 8. Salts of Magnesia. Sulphuric acid causes no precipitate or turbidness (§ 249.) Phosphate of soda and ammonia produce, but not im- mediately, in diluted solutions, a white crystalline pre- cipitate. (Phosphate of magnesia and ammonia, § 251.) 9. Salts of Alumina. These are precipitated by ammonia, carbonate of am- monia, and also by NH3, H S, as hydrate of the oxide CHEMICAL TESTS. 659 of alumina. Potassa in excess dissolves the hydrate of oxide of alumina, which is again precipitated by chloride of ammonium. (§ 260.) They are colored blue on being heated to redness with cobalt solution. (§ 262.) 10. Metallic Salts. Ammonia precipitates from their solutions the oxides as hydrates; carbonate of ammonia also precipitates them (partly as carbonates, and partly as hydrated ox- ides). HS added to an acid solution precipitates the fol- lowing metallic oxides as sulphurets : — a.) Black; lead, bismuth, copper, silver, mercury, platinum, gold. b.) Dark brown ; tin (protoxide). c.) Orange; antimony. d.) Yellow ; tin (peroxide), cadmium, arsenic. Of these, the sulphurets of platinum, gold, tin, anti- mony, and arsenic, are soluble in N HJ? H S. N H3, H S precipitates also as sulphurets the follow- ing, which are not precipitated by sulphuretted hydro- gen alone from their acid solutions: — 3 a.) Black; iron, cobalt, nickel. b.) Flesh-colored; manganese. c.) White; zinc (also alumina and oxide of chro- mium as hydrates). 11. Salts of Protoxide of Iron. Ammonia; a greenish-white precipitate, passing to dark green, and finally to reddish-brown. (Hydrated orotoxide of iron, § 285.) Ferrocyanide of potassium; a light blue precipitate, becoming finally dark blue. (§ 292.) Zctwre of nutgalls; a violet precipitate, passing 660 CHEMICAL TESTS. gradually to blue-black. (Tannate of protoxide of iron, §285.) 12. Salts of Sesquioxide of Iron. Ammonia; a reddish-brown precipitate. (Hydrated sesquioxide of iron, § 285.) Ferrocyanide of potassium; a dark-blue precipitate. (Prussian blue, § 292.) Tincture of nutgalls ; a blue-black precipitate. (Tan- nate of sesquioxide of iron, § 285.) 13. Salts of Manganese. Ammonia ; a white precipitate, soon passing to light and then dark brown. (Hydrated protoxide of manga- nese, § 300.) H S ; a flesh-colored precipitate. (Sulphuret of man- ganese, § 300.) 14. Salts of Cobalt. Potassa; a blue precipitate, gradually becoming green. (§ 307.) Blowpipe ; melted with borax, they give a blue bead. (Cobalt glass, § 304.) 15. Salts of Nickel. Potassa; a light green precipitate. (Hydrated pro- toxide of nickel. § 307.) 16. Salts of Zinc. Ammonia; a gelatinous white precipitate (hydrated oxide of zinc), which redissolves in an excess of ammo- nia; white sulphuret of zinc is precipitated from this solution by N H3, H S. Blowpipe; heated with carbonate of soda upon char- CHEMICAL TESTS. 661 coal, a yellow incrustation is formed, which becomes white on cooling. (Oxide of zinc, § 310.) 17. Salts of Tin. Solution of gold causes in solutions of protoxide of tin a purple-red color or precipitate. (Gold purple, § 322.) H S ; in the protoxide solutions, a dark-brown pre- cipitate (protosulphuret of tin) ; in the perchloride so- lutions, a yellow precipitate. (Bisulphuret of tin, § 325.) 18. Salts of Lead. Sulphuric acid; a white precipitate insoluble in acids. (Sulphate of lead.) The same is rendered black imme- diately by N H3, H S. (§ 335.) Blow-pipe ; heated with carbonate of soda upon char- coal, malleable metallic beads are formed, together with a yellow incrustation upon the coal. (§ 331.) 19. Salts of Bismuth. Water, added largely to solutions of bismuth, causes a white turbidness, with a precipitation of a basic salt of bismuth. (§ 347.) Blowpipe; if heated with carbonate of soda upon charcoal, we obtain brittle metallic beads. (§ 345.) 20. Salts of Copper. Ammonia causes a greenish-blue precipitate, which redissolves in an excess of ammonia, forming a deep blue liquid. (§ 353.) Ferrocyanide of potassium; a purple-red precipitate. (Ferrocyanide of copper, § 292.) Polished iron; a deposition of metallic copper. (§ 152.) vv ' 56 662 CHEMICAL TESTS. Blowpipe ; when heated with carbonate of soda upon charcoal, and washed with water, spangles of metallic copper are obtained. (§ 355.) 21. Salts of Mercury. Potassa precipitates from protoxide salts black pro- toxide of mercury (§ 368); from the peroxide salts, yel- lowish-red peroxide of mercury. (§ 371.) Protochloride of tin precipitates on boiling metallic mercury. (§ 375.) Copper, on being rubbed with a solution of mercury, assumes a silvery appearance. (§ 369.) 22. Salts of Silver. Muriatic acid; a white, curdy precipitate, soluble in ammonia. (Chloride of silver, § 381.) Blowpipe ; heated with carbonate of soda upon char- coal, glistening malleable metallic beads are formed. (§ 381.) 23. Salts of Gold. Protochloride of tin ; a purple-red precipitate. (Gold purple, § 388.) Green vitriol; a precipitate of gold powder. (§ 387.) 24. Salts of Platinum. Potassa; a yellow crystalline precipitate. (Chloride of platinum and potassium, § 394.) Blowpipe ; reduces the salt to a metal. (§ 393.) ' 25. Salts of Sesquioxide of Chromium. Potassa; a bluish-green precipitate (hydrated oxide of chromium), soluble in an excess of potassa, forming a dark green solution. (§ 400.) CHEMICAL TESTS. 663 26. Salts of Chromic Acid. Sugar of lead; a yellow precipitate. (Chrome yel- low, § 399.) Sulphuric acid and alcohol; conversion of the yellow or red color into green by heating. (§ 400.) 27. Compounds of Antimony. H S ; an orange-colored precipitate. (Sulphuret of antimony, § 407.) Blowpipe; heated with carbonate of soda, brittle metallic globules are formed ; and also white fumes and a white incrustation upon the charcoal. (§ 403.) Marsh's test (§ 418). 28. Compounds of Arsenic. H S ; a yellow precipitate. (Sulphuret of arsenic, § 416.) Reduction test (§ 413). Marsh's test (§ 417). 29. Salts of Sulphuric Acid. Chloride of barium ; a white pulverulent precipitate, insoluble in acids. (Sulphate of baryta, § 171.) Sugar of lead; a white precipitate insoluble in di- luted acids. (Sulphate of lead, § 335.) 30. Salts of Sulphurous Acid. Sulphuric acid evolves a gas having the odor of burn- ing sulphur. (§ 174.) - 31. Salts of Phosphoric Acid. Chloride of barium; a white precipitate soluble in acids. 664 CHEMICAL TESTS. Silver solution; a yellow precipitate. (Phosphate of silver, § 176.) Solution of magnesia and ammonia; a white precipi- tate. (See No. 8.) 32. Salts of Boracic Acid. Chloride of barium; a white precipitate soluble in acids. Sulphuric acid and alcohol, when heated with them, present a green flame. (§ 182.) 33. Salts of Nitric Acid. Indigo solution and sulphuric acid ; by boiling, the feeble blue-colored liquid is changed in color by the liberated nitric acid. Glowing charcoal causes a deflagration of the nitrates. (§ 207.) 34. Salts of Chloric Acid Act like the nitrates towards solution of indigo, and upon glowing charcoal; but, when heated with muri- atic acid, they evolve the odor of chlorine. (§ 150.) 35. Chlorides or Salts of Muriatic Acid. Silver solution; a white, curdy precipitate of chloride of silver, readily soluble in ammonia. (§ 186.) Peroxide of manganese and sulphuric acid; evolution of chlorine on heating. (§ 151.) 36. Iodides. Silver solution; a yellowish precipitate of iodide of silver difficultly soluble in ammonia. Peroxide of manganese and sulphuric acid evolve iodine in violet fumes. (§ 210.) CHEMICAL TESTS. 665 Starch paste and nitric acid; blue color. (Iodide of starch, § 155.) 37. Sulphurets. Muriatic acid evolves from most of them a gas hav- ing the odor of rotten eggs. (H S, §§ 132, 213.) 38. Salts of Carbonic Acid. Muriatic acid liberates from them with effervescence an odorless gas. (§§ 202, 237.) Lime-water is rendered milky by them. (CarDonate of lime, §115.) 39. Salts of Oxalic Acid. Solution of gypsum causes a white precipitate. (Ox- alate of lime, § 197.) Heated upon platinum foil, they are decomposed without charring. (§ 197.) 40. Salts of Tartaric Acid. Potassa precipitates tartar, as in No. 2. (§ 194.) Heated on platinum foil, they are decomposed with separation of much carbon, and give off the odor of burnt sugar. (§ 194.) 41. Salts of Acetic Acid. Sulphuric acid produces on heating an odor of vin- eg7dphuric acid and alcohol, an odor of acetic ether. (§ Mated, they are charred, and give off the odor of vin- egar. (§193.) 56 TABLE, Showing the Corresponding Degrees of the Centigrade and Fahrenheit's Thermometers. Cent. Fahr. Cent. Fahr. Cent. Fahr. Cent. Fahr. o 0 0 0 o c o —50 —58.0 —7 19.4 36 96.8 79 174.2 —49 —56.2 —6 21.2 37 98.6 80 176.0 —48 —54.4 —5 23.0 38 100.4 81 177.8 —47 — 52.6 —4 24.8 39 102.2 82 179 6 —46 —50.8 —3 26.6 40 104.0 83 181.4 —45 —49.0 —2 28.4 41 105.8 84 183.2 —44 —47.2 —1 302 42 107.6 85 185.0 —43 —45.4 0 32.0 43 109.4 86 186.8 —42 —43.6 +1 33.8 44 111.2 87 188.6 —41 —41.8 2 35.6 45 113.0 88 190.4 —40 —40.0 3 37.4 46 114.8 89 192.2 —39 —38.2 4 39.2 47 116.6 90 194.0 —38 —36.4 5 41.0 48 118.4 91 195.8 —37 —34.6 6 42.8 49 120.2 92 197.6 —36 —32.8 7 44.6 50 122.0 93 199.4 —35 —30.0 8 46.4 51 123.8 94 201.2 —34 —29.2 9 48.2 52 125.6 95 203.0 —33 —27.4 10 50.0 53 127.4 96 204.8 —32 —25.6 11 51.8 54 129.2 97 206.6 —31 —23.8 12 53.6 55 131.0 98 208.4 —30 —22.0 13 55.4 56 132.8 99 210.2 —29 —20.2 14 57.2 57 134.6 100 212.0 —28 —18.4 15 59.0 58 136.4 101 213.8 —27 —16.6 16 60.8 59 138.2 102 215.6 —26 —14.8 17 62.6 60 140.0 103 217.4 —25 —13.0 18 64.4 61 141.8 104 219.2 —24 —11.2 19 66.2 62 143.6 105 221.0 —23 — 9.4 20 68.0 63 145.4 106 222.8 —22 — 7.6 21 69 8 64 147.2 107 224.6 —21 — 5.8 22 71.6 65 149.0 108 226.4 —20 — 4.0 23 73.4 66 150.8 109 228.2 —19 — 2.2 24 75.2 67 152.6 110 230.0 —18 — 0.4 25 77.0 68 154.4 111 231.8 —17 + 1-4 26 78.8 69 156.2 112 233.6 —16 3.2 27 80.6 70 158.0 113 235.4 — 15 5.0 28 82.4 71 159.8 114 237.2 —14 6.8 29 84.2 72 161.6 115 239.0 — 13 8.6 30 86.0 73 163.4 116 240.8 — 12 10.4 31 87.8 74 165.2 117 242.6 —11 12.2 32 89.6 75 167.0 118 244.4 —10 14.0 33 91.4 76 168.8 119 246.2 — 9 15.8 34 93.2 77 170.6 120 248.0 — 8 17.6 35 95.0 78 172.4 121 249.8 667 Cent. Fahr. Cent. Fahr. Cent. Fahr. Cent. Fahr. o o o o 0 0 o o 122 251.6 172 341.6 222 431.6 272 521.6 123 253.4 173 343.4 223 433 4 273 523.4 124 255.2 174 345.2 224 435.2 274 525.2 125 257.0 175 347.0 225 437.0 275 527.0 126 258.8 176 348.8 226 438.8 276 5288 127 260.6 177 350.6 227 440.6 277 530-6 128 262.4 178 352.4 228 442.4 278 532.4 129 264.2 179 354.2 229 444.2 279 534 2 130 266.0 180 356.0 230 4460 280 5360 131 267.8 181 357.8 231 447 8 281 537-8 132 269.6 182 359.6 232 449.6 282 539.6 133 271.4 183 361.4 233 4514 283 5414 134 273.2 184 363.2 234 453 2 284 543.2 135 275.0 185 365.0 235 455 0 285 5450 136 276.8 186 366.8 236 4568 286 546.8 137 278.6 187 368.6 237 458 6 287 548.6 138 280.4 188 370.4 238 460.4 288 550.4 139 282.2 189 372.2 239 4622 289 552.2 140 284.0 190 374.0 240 4640 290 554.0 141 285.8 191 375.8 241 465-8 291 555.8 142 287.6 192 377.6 242 467 6 292 557.6 143 289.4 193 379.4 243 469 4 293 559.4 144 291.2 194 381.2 244 471.2 294 561.2 145 293.0 195 383.0 245 4730 295 563.0 146 294.8 196 384.8 246 474.8 296 564.8 147 296.6 197 386.6 247 476.6 297 566.6 148 298.4 198 388 4 248 478.4 298 568.4 149 300.2 199 390.2 249 480.2 299 570.2 150 302.0 200 392.0 250 482.0 300 572.0 151 303.8 201 393.8 251 483.8 301 573.8 152 305.6 202 395.6 252 485.6 302 575.6 153 307.4 203 397.4 253 487.4 303 577.4 154 155 309.2 204 399.2 254 489.2 304 5792 311.0 205 401.0 255 491.0 305 581.0 156 157 158 159 160 161 162 163 164 165 166 312.8 314.6 316.4 318.2 320.0 321.8 323.6 325.4 327.2 329.0 330.8 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 402.8 404.6 406.4 408.2 410.0 411.8 413.6 415.4 417.2 419.0 420.8 422.6 256 257 258 259 260 261 262 263 264 265 266 267 492.8 494 6 496.4 498.2 500.0 501.8 503.6 505.4 507.2 509.0 510.8 512.6 306 582.8 307 584.6 308 586.4 309 5882 310 5900 311 5918 312 5936 313 595.4 314 597-2 315 599.0 316 6008 317 602.6 167 168 169 170 171 332.6 334.4 336.2 338.0 339.8 424.4 426.2 428.0 429.8 268 269 270 271 514.4 516 2 518.0 519.8 318 6044 319 6062 320 6080 CHEMICAL SYMBOLS AND EQUIVALENTS. Aluminum Al = 13.7 Nickel Ni = 29.6 Antimony Sb =129 Niobium Nb Arsenic As= 75 Nitrogen N = 14 Barium Ba= 68.5 Norium No Bismuth Bi =213 Osmium Os = 99.6 Boron B = 10.9 Oxygen 0=8 Bromine Br = 80 Palladium Pd = 53.3 Cadmium Cd= 56 Pelopium Pe Calcium Ca = 20 Phosphorus P = 32 Carbon C = 6 Platinum Pt = 98.7 Cerium Ce = 47 Potassium K = 39.2 Chlorine CI = 35.5 Rhodium R = 52.2 Chromium Cr = 26.7 Ruthenium Ru= 52.2 Cobalt Co = 29.5 Selenium Se = 39.5 Copper Cu= 31.7 Silicium Si = 21.3 Didymium D Silver Ag =108.1 Erbium E Sodium Na = 23 Fluorine Fl = 18.9 Strontium Sr = 43.8 Glucinum G = 4.7 Sulphur S = 16 Gold Au = 197 Tantalum Ta=184 Hydrogen H = 1 Tellurium Te = 64.2 Iodine I =127.1 Terbium Tb Iridium Ir = 99 Thorium Th= 59.6 Iron Fe = 28 Tin Sn= 59 Lanthanium La Titanium Ti = 25 Lead Pb =103.7 Tungsten W = 95 Lithium Li = 6.5 Uranium U = 60 Magnesium Mg= 12.2 Vanadium V = 68.6 Manganese Mn= 27.6 Yttrium Y Mercury Hg = 100 Zinc Zn = 32.6 Molybdenum Mo= 46 | Zirconium Zr = 22.4 N. B. — The atomic weights and equivalents are assumed to be equal. INDEX. INDEX. [The numbers refer to the sections.] A. Absinthine, 589. Acetic acid, 198. " ether, 507. Acetometer, 514. Acetyle, 513. Acid oxides, 66. " radicals, 199. " salts 197. Acids, 66,'76, 159, 199, 267 " fat, 542. " hydrogen, 184. « organic, 193, 598. " oxygen, 159. Aconitine, 597. Acroleine, 547. Adhesion, 106. Affinity, chemical, 5, 89, 146, 192. . " disposing, 89, 146. " of the metalloids, 192. After-fermentation, 488. Aggregation, 19. Air, 90. " composition of, 100, 101. " current of, 98, 111. " expansion of, 97. Albumen, 477, 622. Alcohol, 482, 498. " burning of, 121. » flame, 121. « lamp, 112, 121. " weighing of, 500. Alcoholometer, 500. Aldehyde, 512. Alizarine, 591- Alkalies, 201, 236. Alkali-metals, 201. Alkalimeter, 202. Alkaline earths, 237, 251. Alkaloids, 596. Alkanet-root, 591. Allotropv, 108. Alloys, 305, 317, 346, 364, 378, 379, 383, 409. Almonds, oil of, 535. Aloes, 582. Alum, 261. Alumina, 260. " silicate of, 258. " sulphate of, 259. Aluminum, 252. Amalgamation, process of, 382. Amalgams, 378. Amber, 571. Ammonia, 227, 230. " as food of plants, 614. " by dry distillation, 228. " carbonate of, 232, 665. " from decay, 233, 479, 665. " liniment, 541. " salts of, as manure, 235. " water of, 230. Ammonium, 236. " chloride of, 229. " sulphuret of, 231. Amorphism, 127, 129,475. Amygdaline, 589. Analysis, 7. " elementary, 435. Aniline, 597. Animal fats, 536. " fibrine, 636. " life, 619. 67:3 INDEX. Animal matter, 620 Animals, food of, 639. Anthracite, 442. Antichlorine, 174. Antimoniuretted hydrogen, 418. Antimony, 402. " oxide of, 403. Antimony-glance, prismatoidal, 407. Antlers of the deer, 647. Aqua regia, 188. Arable land, 255, 612. " " estimation of, 256. " " humus in, 444, 612. " " inorganic matter in, 612. " " lime in, 612. Archil, 594. Areometer, 16. Arrack, 496. Arrowroot, 455. Arsenic, 410. " test for, 413, 417. " white, 412. Arseniuretted hydrogen, 417. Artesian wells, 252. Ashes, 201, 608. " of plants, 607. Asphaltum, 442, 571. Assafoetida, 582. Assaying, 382. Atmosphere, 90. pressure of, 91. Atomic weights, 274. Atoms, 274. " changes of, 274, 280, 475. " grouping of, 274. Atropine, 597. Aurum musivum, 325. B. Baking, 516. Balsam, 568. Barium, 248. Barley, germination of, 426. Barm, 488. Barometer, 93. Baryta, 248. " compounds of, 248. Bases, 69, 267. " organic, 596. Basic radicals, 199. " oxides, 69. Bast, 430. Beans, germination of, 426. Beer, 487. Bees-wax, 539. Bell-metal, 364. Benzoin, 570. Bismuth, 345. Bitumen, 571. Bleaching, 152, 174, 429. Blood, 636. " coloring matter of, 636. Blowpipe, 181. Blue liquid, 353. Bogs, 252. Boiling, 34. " by steam, 36. " of meat, 642. " of water, 34, 95, 96. Bone-black, 107. Bone-dust, 658. Bones, 144, 176, 654. Boracic acid, 180. Borax, 225, 351. Brandy, 491. Brass, 364. Braziline, 591. Brazil wood, 591. Bread, 517. Bremen blue, 352. Bromine, 156. Bronze, 364. Broth, 643. Buckthorn berries, 592. Butter, 631. Butyric acid, 515. " ether, 507. C. Cadmium, 315. Caffeine, 597. Calamine, 313. Calcium, 237. " and chlorine, 24 Calico-printing, 595. Calomel, 370. Campeachy-wood, 594. Camphor, 401, 553. Candy, 470. Cane-sugar, 470. Cannon-metal, 364. Caoutchouc, 584. Capillary attraction, 106. Caput mortuum, 276. Carat, 383. Carbon, 103, 166. INDEX. 673 Carbonic acid, 63, 109,164. " as nutriment of plants, 614. " from respiration, 167. " " in the air, 101. Carbonic oxide gas, 110. Carbonization, 104, 119, 436. Carmine, blue, 594. " red, 591. Carthamine, 591. Caseine, 477, 626. Cassel yellow, 336. Catalysis, 459. Cement, hydraulic, 239. Chalk, 237. Charcoal, 104. Cheese, 632. Chemical combination, law of, 70,267. " force, 5. " processes, 1. " symbols, 88. Cherry gum, 467. Chloric acid, 178. Chloride of antimony, 152, 405. " barium, 248. " calcium, 246. " copper, 152, 359. « gold, 152, 385. " iron, 186, 289. " lead, 336. " lime, 244. " magnesium, 251. " manganese, 150, 299. " mercury, 370, 373. i: platinum, 391. « potassium, 209. " silver, 381. « sodium, 153, 215. " tin, 319. " zinc, 152. Chlorides, different, 154. metallic, 152, 186. u " retrospect of, 41 Chlorine, 150. » water, 150. Chlorophyll, 593. Chondrine, 647. Chromate of potassa, 398. Chrome-yellow, 399. Chromic acid, 401. Chromium, 397^^^^ Cinchonine, 597. Cinnabar, 376. Citric acid, 600. Clay, 252. " ware, 257. Coal, 104, 107. " brown, 448. ," pit, 448. Cobalt, 303. Cochineal, 591. Cocoa-nut oil, 535. Cognac, 486. Cohesion, 19. Coke, 107, 118,441. Colchicine, 597. Cold, 28, 40, 246. Colophony, 574. Coloring matter, 590. Combination, laws of, 70, 148, 267. Combining proportionals, 269. Combustion, 111, 114. " complete, 115,435. " incomplete, 116, 436. " in chlorine, 152. " in oxygen, 58, 63. " slow, 140. " spontaneous, 106, 140. " with sulphur, 131. " under water, 142. Conductors of heat, 42. Conicine, 597. Contact, 459. Copper, 348. " alloys of, 364. « and sulphur, 131, 362. " oxide of, 349. " salts of, 173, 359. Cordials, 501, 562. Corrosive sublimate, 373. Cotton, 431. Creosote, 438. Crystallization, 50, 125, 155. " interrupted, 51. « water of, 54. Cudbear, 594. Curcumine, 592. Cyanic acid, 179. Cyanide of potassium, 291. Cyanogen, 157. D. Daguerreotype, 381. Dammara resin, 570. Daturine, 597. Davy's safety-lamp, 114. Decay, 443. 674 INDEX. Decimal weights and measures, 10. Deoxidation, 144, 198. " retrospect of, 418. Dephlegmator, 191. Detonation, 160. Dew, 44. " point, 38. Dextrine, 460. Diamond, 107. Diastase, 461. Diffusion of gases, 165. Digestion, 635. Dimorphy, 108, 126, 274. Disinfectants, 105, 152. Distillation, 41. " dry, 119, 436. Dobereiner's lamp, 85. Dragon's-blood, 570. Dyeing, 595. Dyes, 591. E. Earths, 252. " alkaline, 237. " metals of the, 252. Egg-shells, 624. Elayle, 502. Electrophorus, 577. Elements, ancient, 19. " retrospectof chemical,418. Elutriation, 256. Emetine, 597. Emulsion, 525. Epsom salt, 249. Equivalents, 270. Ether, 504. " sulphuric, 503. " varieties of, 507. Ethyle, oxide of, 504. Euphorbium, 582. Evaporation, 37, 40. Excrements, 659. Expansion, 22, 27. Explosive gas, 86. Extractive matter, 586, 588. Extracts, 585. Faeces, 659. Fat acids, 542. Fats, 520. Felspar, 265. Fermentation, alcoholic, 482. " artificial, 519. " mucilaginous, 515. " of bread, 516. " putrefactive, 445. " vinegar, 509. Ferment oils, 554. " sediment, 489. Fibrine, 636. Filtration, 47. Fine mark, 379. Finery process, 281. Fire and coal, 103. Fire, to extinguish, 111, 530. Fire-damp, 114, 118. Fish-oil, 537. Flame, 117, 121, 122. " of a candle, 122. " shining of, 117, 529, 560. Flax, 429. Flesh, 640. Floating of bodies, 16. Fluids, rising and falling of, 92. Fluoric acid, 190. Fluorine, 156. Fluor-spar, 247. Fly-poison, 411. Forces, 6, 20. Formic acid, 602. Formulae, chemical, 88. Frankincense, 582. Frost, 44. Fulminic acid, 179. Fumigation, 438, 558, 576. Fumigating spirit, 562. Fusel oil, 554. Fusible metal, 346. Fustic, 592. G. Galena, 341. Galipot, 570. Gallic acid, 604. Gall, 645. Galvano-plastic, 358. Gamboge, 582. Gases, 99. " collection of, 56. Germination, 426. Gilding, 386. Glass, 180,226. INDEX. 675 Glass, etching of, 190 soluble, 204, 226. " to break, &c, 27. Glauber salts, 218. Glazing, 226, 257,317. Glue, 647. Gluten, 453, 477. Glycerine, 547. Glyceryle, oxide of, 547. Glycocoll, 651. Gold, 383. " combinations of, 386. " mosaic, 325. " parting of, 384 Golden sulphuret, 407. Goulard's extract, 337. Gramme, 10. Granulation, 310. Grape-juice, 484. Graphite, 107. Guano, 663. Gum Arabic, 465. " cherry. 467. " elastic, 584. " resins, 582. " starch, 458. " tragacanth, 466. Gun-cotton, 433. Gunpowder, 207. Gutta percha, 584. Gypsum, 211. " solution of, 197. H. Hasmatoxyline, 594. Hair, to remove, 405. Haloid salts, 157, 187, 276. Halogens, 150, 157. Hartshorn, spirit of, 228. Heat, 22. " conduction of, 42. " destruction of chemical combi nations by, 57. . Heat, expansion of air.oy> 97- « « solids by, 27. » " water by, 22. " free, 36, 86. " latent, 32, 36. ' " of chemical combination, Sb. " radiation of, 43. Hemp, 429. Hippunc acid, 664. Hoffmann's anodyne liquor, 506. Honey, 469. Hom-silver, 381. Horny matter, 653. Humus, 444. Hyalogens, 158. Hydrates, 54. Hydraulic cement, 239. Hydriodic acid, 189. Hydrobromic acid, 189. Hydrochloric acid, 184, 185. Hydrocyanic acid, 191. Hydrofluoric acid, 190. Hydrogen, 81, 87. " reduction by, 357. Hydrometer, 16. Hydrothionic acid, 132. Hyperoxide, 77, 79. Hypochlorous acid, 178. I. Ice, formation of, 29. Illuminating gas, 117. Illumination, 115, 529, 560. Indigo, 173, 594. " blue, 594. Ink, 285, 603. Inuline, 457. Iodine, 155. Iron, 275. " and chlorine, 289. " " cyanogen, 290, 293. " " sulphur, 131, 133, 294. " bar, 280. " cast, 279 " crude, 279. " magnetic oxide of, 276. " malleable, 280. " ore, 276. " " bog, 276. " " brown, 276. " " spathic, 276. " oxide of, 276, 285. « " dyeing with, 197. " rust of; 276. 14 scales, 68. " saltsof, 83, 173, 186, 284-288. " specular, 276. " vitriol, 89, 285. Isinglass, 647. Isomerism, 179, 274, 424. Isomorphism, 264, 274. 676 INDEX. K. Kermes, 407. Kindling purposes, 130. Lac-lake or Lac-dye, 591. Lactic acid, 457, 515. Lactucarium, 582. Lac varnish, 578. Lakes, 595. Lamp-black, 107, 116, 576. Lard, 521. Laws, chemical, 70, 148. Lead, 329. " and sulphur, 341. " glass, 331. " glazing, 257. " oxide of, 331. " plaster, 550. " salts of, 160, 198, 334. " subacetate of, 337. " sugar of, 198,337. " tree, 340. " white, 339. Leaf-green, 593. Leather, 648. Lichenine, 457. Lime, 239. " and chlorine, 244. " as mortar, 239. " burnt, 238, " carbonate of, 237, 271. " caustic, 238. " muriate of, 246. " nitrate of, 243. " phosphate of, 242. " slaked, 33. " soap, 240. " sulphate of, 241, 271. " water, 46, 238. Linen, 429. Liniment, 541. Linseed oil, 534. Liquation process, 382. Liqueurs, 501, 562. Litharge, 337. Lithographic stones, 237. Litmus, 594. " paper, 48. " solution, 47. Loam, 252. Logwood, 594. Lunar caustic, 380. Lupuline, 598. Lye, caustic, 203, 221. M. Madder, 591. Magnesia, 250. " compounds of, 249. Magnetic pyrites, 295. Malachite, 349. Malic acid, 601. Malt, 426, 460. Manganese, 298. " acids of, 301. " black oxide of, 297 " oxide of, 297. " salts of, 299. Mannite, 474. Manuring by ammoniacal salts, 235. " bones, 658. " gelatine, 650. " guano, 663. " gypsum, 241. " inorganic matter, 617. " lime, 240. " muriatic acid, 186. " organic matter, 616. " potassa-salts, 214. " sulphuric acid, 173. Mark, fine, 379. Marsh-gas, 445. Marsh's arsenical test, 417. Mashing process, 461, 487. Mastic, 570. Matches, 208. Matter, 18. Meal, 516. Melting, 30. " point, 31. Mercury, 365. " and sulphur, 376. " oxide of, 56, 368. " salts of, 366. Metalloids, 56. " and hydrogen, 192. " " oxygen, 192. Metallic alloys. See Alloys. " oxides, retrospect of, 418. Metals, 201. " heavy, 275. " light, 201. " negative, 133. " noble, 379. INDEX. 677 Metals, positive, 133. " retrospect of the, 418. Meter, 10. Milk, 625. Minium, 332. Moir.'; metallique, 326. Molybdenum, 396. Mordant, 197, 595. Morine, 592. Morphine, 597. Mould, 514. Mountain blue, 349. Muriatic acid, 185. " ether, 507. Myrrh, 582. N. Naphtaline, 441. Naphtha, 442, 555. Nascent state, 150. Neutralization, 71, 160, 186. " capacity of, 199. Nickel, 303. Nicotine, 597. Nitre, 207. " formation of, 480. Nitric acid, 159, 161. " oxide, 162. Nitrogen, 101. Nitro-muriatic acid, 188. Nitrous acid, 161. " ether, 507. " oxide, 163. Non-conductors, 42. Non-metallic elements, 56. Nutrition, plastic elements of, 639. O. Odor, 123. CEnanthic ether, 485. Oil, burning, to refine, 535. '; gas, 528, 560. " lamp, 529, 560. " soap, 540. Oils, empyreumatic, 555. " ethereal, 551. " fat, 520. " ferment, 554. " volatile, 552. Olefiant gas, 502. Oleic acid, 546. Oleine, 533. Oleo-saccharum, 564. Olive oil, 535. Opium, 582. Orchil, 594. Orelline, 592. Organic acids, 193, 598. " bases, 596. " radicals, 508, 513. Organogens, 56, 122. Orleana, 592. Orpiment, 416. Oxalates, 197, 212. Oxalic acid, 196. Oxidation, 66. " by chlorine, 152, 186. " by chlorate of potassa,332. " by nitre, 207. " by nitric acid, 160. " by oxygen, 500. " degrees of, 75, 154, 272. Oxides, 69, 77. " retrospect of, 418. Oxidizing flame, 181. Oxygen, 56, 80. " acids, 159. " circulation of, 167, 614. " salts, retrospect of, 183,418. P. Palm oil, 535. Papin's digester, 96. Parchment, 648. Paste, 457. Peas, starch of, 452. Peat, 446. Pectine, 468. Perchlorides, 154. Permanganic acid, 301. Persio, 594. Phosphoric acid, 65, 176. Phosphorous acid, 177. Phosphorus, 138, " oxide of, 177. Phosphuretted hydrogen, 145. Pigments, 590. Piperine, 597. Pitch, 569, 575. " burnt, 576. Plants, cultivated, 615. " food of, 614. 678 INDEX. Plants, growth of, 613, 614. " inorganic constituents of, 607 " uncultivated, 614. Platinum, 390. " spongy, 392. Plumbago, 107. Pneumatic trough, 60. Polish, 578. Polychroite, 592. Porosity, 106. Potash, 201. " lye, 203. " soap, 541. Potassa, 203. " acetate of, 202. " antimoniate of, 403. " carbonate of, 201. " caustic, 203. " chlorate of, 59, 203. " chromate of, 398. " muriate of, 209. " nitrate of, 207. " oxalate of, 197, 212. " silicate of, 204, 226. " sulphate of, 206. " tartrate of, 194, 211. Potassium, 205. " and chlorine, 209. " iodine, 210. " sulphur, 213. " ferricyanide of, 293. " ferrocyanide of, 291. Potato-starch, 451, 462. Precipitation, 129. Preservation of organic matter, 449. Proportions, chemical, 272. Proteine, 477. Protochlorides, 150. Prussian blue, 290. Prussiate of potassa, 291, 293. Prussic acid, 290. Puddling process, 281. Putrefaction, 445. " to prevent, 105, 449. Pyrogens, 123, 149. Pyrometer, 26. Pyrophorus, 338. Pyroxylic spirit, 439. Q. Quartation, 384. Quartz, 183. Quercitron, 592. Quinine, 597. R. Racemic acid, 599. Radicals, 199. " compound, 508, 513. Rape-oil, 535. Rat electuary, 139. Reagents, 133. " for acetic acid, 198. ammonia, 229. antimony, 407. arsenic, 413, 416, 417. bismuth, 347. carbonic acid, 46, 102. chlorine, 186. copper, 152, 192. gold, 388. hydrosulph. acid, 479. iodine, 155. iron, 296. lead, 335. lime, 197, 241, 256. magnesia, 251. manganese, 300. mercury, 375. muriatic acid, 186. nitric acid, 160. oxalic acid, 197. phosphoric acid, 176. platinum, 394. potassa, 211. silver, 381. soda, 404. starch, 457, 645. sugar, 645. sulphuric acid, 171,240. tartaric acid, 194. the metals, 133. tin, 322, 325. zinc, 312. " retrospect of the, 149. " synopsis of, page 657. Realgar, 416. Rectification, 492. Reduction by hydrogen, 357. dry, 144, 198, 355. " flame, 181. " galvanic, 358. " humid, 285, 356. Refining, 384. Rennet, 628. Resin, 569, 570. Respiration, 167, 639. " elements of, 639. Retrospect of alcohol, &c, 519. INDEX. 679 Retrospect of animal matter, 665. the albuminous sub- stances, 481. Retrospect of the alkalies, 236. " " alkaline earths, 251. " " earths, 266. " extractive and col- oring substances, 597. Retrospect of the halogens, 157. " " heavy metals, 328, 395,418. " " hydrogen acids, 191. " " light metals, 266. " *' metallic sulphurets, 418. " " metalloids, 158. " " metals, 266. " " organogens, 122. " " oxygen acids, 183. " " pyrogens, 149. " " resins and oils, 584. " " vegetable acids, 198. " " vegetable bases, 597. " of vegetable matter, 618. " of vegetable tissue, starch, sugar, &c, 476. Rotation of crops, 617. Rum, 484. Rum-ether, 507. Safety-lamp, 114. Safety-tube, 92. Safflower, 591. Saffron, 592. Sago, 446. Sal-ammoniac, 229. Salt, common, 215, 216. « " volatilization of, 182. " double, 261, 267. Salting of meat, 644. Saltpetre, 207. Salt radical, 199. " springs, 216. Salts, 71, 160, 267. « acid, 194, 197. » basic, 202, 347. Sandal-wood, 591. Sandarach, 570. Sap-green, 593. Scheele's green, 414. Schweinfurth green, 414. Sealing-wax, 575. Selenium, 137. Selters water, 165. Shellac, 570. Shot, 343. Silica, 183. Silicon, 158. Silver, 379. " alloys of, 379. Silvering, 386. Silver, oxide of, 381. " salts of, 380. Sirup, 459, 472. Smalt, 304. Smell, 123. Smelting, 278. Smoking of meat, 438. Snow, 43. Soap, 540. " resinous, 580. Soda, 220, 221. " biborate of, 225. " carbonate of, 220. " caustic, 221. " lye, 221. " muriate of, 173, 186, 215. " nitrate of, 224. " phosphate of, 223. " silicate of, 226. " soap, 540. " sulphate of, 173, 218. " sulphite of, 174. Sodium, 222. " and chlorine, 153, 210. " " oxygen, 67, 81. " " sulphur, 219. Solanine, 597. Soldering, 225. Solution, 45. Soot, 107, 116, 576. Soup,643. Spar, heavy, 248. Spermaceti, 538. Spirit, 498. Spritz-bottle, 94. Stalactites, 237. Starch, 450. " gum, 458. " sirup, 459. " sugar, 459. Steam, 35. » Stearic acid, 545. Stearine, 533. Steel, 282. Stick-lac, 570. Stochiometry, 70, 267. 680 INDEX. Strontium, 248. Strychnine, 594. Sublimate, 128, 373. Sublimation, 128. Suboxide, 77. Succinic acid, 606. Sugar, 469. " burnt, 475. " cane, 470. " fermentation of, 482. " liquid, 472. " of gelatine, 651. " of milk, 473, 629. " of starch, 469. " sorts of, 459, 469. Sulphur, 123. " amorphous, 127, 129. Sulphuret of ammonium, 231. " antimony, 407. " arsenic, 416. " calcium, 220, 405. " copper, 362. " iron, 131, 133, 294. " lead, 133, 341. " manganese, 300. " mercury, 376. " potassium, 213. " silver, 381. " tin, 325. " zinc, 312. Sulphuret: sulphide, 131, 154. Sulphurets, metallic, 133. " " retrospect of the, 418. Sulphur, flowers of, 128. " liver of, 213. " springs, 137. Sulphuric acid, anhydrous, 169. " " common, 168, 172. " " fuming, 170. " «' hydrated, 172. " " mixing of, with water, 84, 173. Sulphuric acid, Nordhausen, 170. " ether, 506. Sulphurous acid, 64, 174. Superficial fermentation, 488. Symbols, chemical, 88. Synthesis, 7. T. Tallow, 522. " soap, 540. Tannic acid, 603. Tannin, 603. Tanning, 648. " substances, 605. Tar, pit-coal, 441. Tartar, 194, 211. " emetic, 406. Tartaric acid, 194. Tartarus, 195. Taste, 123. Temperature, 24, 113. Test-paper, 48. Test-tubes, 34. Theory, 7. Thermometer, 24. " spirit, 25. Tin, 316. " alloys of, 318. " and sulphur, 325. " glaze, 317. " moire, 326. " oxide of, 317, 326. " proof, 318. " salts of, 319. Tinning, 229, 327. Tombac, 364. Tragacanth, 466. Train oil, 537. Tufa, calcareous, 237- Turmeric, 592. Turpentine, 568. " oil of, 551. Type-metal, 409. U. Uranium, 328. Urea, 661. Uric acid, 662. Urine, 660. Value, 379. Vapor, 37, 99. " cold, 40 Varnish, 534. " lac, 578. Vat, cold, 594. Vegetable acids, 193, 598. " albumen, 451. " ashes, 607. " caseine, 452. INDEX. Vegetable fats, 534. " growth, 614. " jelly, 468. " life, 419. " mucus, 466. " tissue, 427. Veratrine, 597. Verdigris, 361. Vermilion, 376 Vinegar, 198, 509. " aromatic, 198, 563. " mother, 527. " quick method of making. 511. Vital air, 80 " force, 80. Vitriol, 285. " blue, 175. " green, 89, 285. " oil of, 170. " white, 312. W. Water, 21. " as food for plants, 614. « bath, 149. " boiling of, 34, 95, 96. " chemically combined, 54. " composition of, 55, 87. u decomposition of, 55, 82, 83. « distilled, 41, 561. " expansion of, by cold, 28. « « by heat, 22. " in the air, 100, 102. " mineral, 165, 447. " of constitution, 159, 196. Water of crystallization, 54. " soft and hard, 237. Wax, 539. Weather-prophets, 93. Weighing, 81. Weight, absolute, 10. " due, 379. " specific, 11. Weights, 9. " apothecaries', 9. Weld, 592. Wheat-starch, 453. Whey, 629. White precipitate, 374. Wine, 484. Woad, 594. Wolfram, 396. Wood, 427, 433. " tar, 119,430. " vinegar, 119, 437. " white rotten, 449. Woody fibre, 428. Wool, 653. Y. Yeast, 488. " bottom, 489. Yellow berries, 592. Yolk of eggs, 623. Z. Zinc, 309. " oxide of, 310. " saltsof, 311. CORRECTIONS. The following corrections have been made in the sixth German edition of the Chemistry. Page 66, section 75 should read as follows : — "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 defi- ciency of oxygen. According to a late discovery, oxygen, by remaining for some time in contact with wet phosphorus, or by being electrified, ac- quires a very great inclination to combine with other bodies. The name Ozone has for the present been given to this ' chemically excited' oxygen, the nature of which has not yet been fully investigated. Many elements consume a greater quantity of oxygen at a high than at a low temperature, and when the supply is copious than when it is deficient; and this excess or diminution of consumption is likewise prescribed by fixed laws. The different proportions in which substances unite with oxygen are called its degrees of oxidation." Page 130, insert immediately before section 140 : — "According to a late discovery, phosphorus undergoes a remarkable change by being kept dur- ing several days at the temperature of 240° ; it then acquires a red color, neither ignites nor dissolves so readily, and has lost its luminous power ; but exposure to a stronger heat restores it to its original state." RECOMMENDATIONS. Extract from a Letter of S. L. Dana, M. D., LL. D. " The name of the author of the above work, so well known among practical men as one of the editors of the Polytechnisches Centralblatt, would alone authorize the conclusion, that this book is preeminently clear, concise, practical in all its allusions to art, simple in its ar- rangements, and illustrated by experiments requiring no array of costly apparatus. It is a work worthy of its author. It is a work not written for those only who know the position of Dr. Stockhardt, and who therefore would be prepared to welcome it, in its excellent English dress, because it approaches with the prestige of a good name. It is a work which will bear the character we have given to it, even when subjected to the severest scrutiny of critical strangers." From A. A. Hayes, M. D., Assayer to the State of Massachusetts. "After reading this work in the translation by Dr. Peirce, I have formed the opinion that, as an easy introduction of the student to the principles of chemistry, it is unrivalled by any book in our language. The author has adapted his illustrations with great sagacity to the wants which students feel in first entering upon the subject of this science, and there is a directness and accuracy in his mode of teaching which leads one forward with great rapidity. Rarely is it possible to find an elementary work, which, without being voluminous, discusses so many subjects clearly. The thanks of instructors and pupils are truly deserved by Dr. Peirce, for placing this book within their reach." From John A. Porter, Professor of Chemistry applied to Art, in Brown University. " Stdckhardt's 'Principles of Chemistry' occupies the first rank amon" introductions to the science of which it treats. In Germany, where5 works of the kind abound, it is held in the highest estimation. 2 I hope, for the interest of the science, that it may be generally intro- duced in this country. I concur entirely in the views of the work expressed by Professor Horsford in the Introduction, and shall recom- mend it to those pursuing the study of chemistry under my direction." From Elbridgk Smith, Master of the Cambridge High School. "Cambridge, Oct. Uth, 1850. " Mr. Bartlett : — " Dear Sir, — Of the ' Principles of Chemistry,' which you sent me some time since, I can hardly speak too highly. It is unquestionably the best book on elementary chemistry that has been published in the United States. On first examining the volume, I was inclined to think that for common schools it might with advantage be abridged. A more intimate acquaintance with the work has convinced me that not a page can be safely dispensed with." From David A. Wells, Assistant in the Chemical Department of the Lawrence Scientific School. " Cambridge, Feb. 1st, 1851. " I consider Stockhardt's ' Principles of Chemistry,' as an elemen- tary book, superior to any work of the kind hitherto published. I have recommended its introduction in a number of cases, and in all has it given perfect satisfaction. It has, moreover, an advantage over all otr^er works, that it is at present as complete as the rapid advance of chemical science will admit." Extract from Professor Horsford's Introduction. " 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 chapter, 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 teachers 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 without the aid of an instructor."