MANUAL OF CHEMISTRY ; CONTAINING A CONDENSED VIEW OF THE PRESENT STATE OF THE SCIENCE, WITH COPIOUS REFERENCES TO MORE EXTENSIVE TREATISES, ORIGINAL PAPERS, &c. INTENDED AS A TEXT-BOOK FOR MEDICAL SCHOOLS, COLLEGES AND ACADEMIES. Br LEWIS C. BECK, M. D. PROFESSOR OF CHEMISTRY AND BOTANY IN THE UNIVERSITY OF THE CITY OF NEW-YORK, AND IN RUTGERS COLLEGE, NEW JERSEY ; -MEMBER OF THE ROYAL PHYSICAL SOCIETY OF EDINBURGH ? OF THE LINNvEAN SOCIETY OF PARIS; OF THE NATURAL HISTORY SOCIETY OF MONTREAL; OF THE PHILADELPHIA ACAD- EMY OF NATURAL SCIENCES ; OF THE NEW-YORK LYCEUM; OF THK ALBANY INSTITUTE, &C. &C. SECOND EDITION, REVISED AND ENLARGED. MripMBBOb ,\6RA* OF THE ^ UNIVERSITY OF isg^UFQRN^ ALBANY: PRINTED AND PUBLISHED BY E. W. $ C. SKINNER, L AND SOLD BY THE PRINCIPAL BOOKSELLERS. M.DCCC.XXXIT Entered according to 'Act of Congress, in the year 1831, by LEWIS C. BECK, in the ClerVs Office of the District Court for the Nortliern Dis- trict of the State of New- York. TO T. ROMEYN BECK, M. D. PROFESSOR OF THE INSTITUTES OF MEDICINE AND MEDICAL JURISPRUDENCE, IN THE UNIVERSITY OF THE STATE OF NEW-YORK, $c. fa THIS VOLUME IS INSCRIBED, AS A SLIGHT TRIBUTE OF RESPECT FOR HIS SCIENTIFIC ATTAINMENTS, AND OF GRATITUDE FOR THE MANY PROOFS OF KINDNESS WHICH HAVE BEEN RECEIVED FROM HIM BY HIS BROTHER, THE AUTHOR. PREFACE TO THE SECOND EDITIOX. THE adoption of this work as a Text Book in several of our most respectable Institutions, and the rapid sale of a large Edition, are gratifying evidences of public favour, the con- tinuance of which I have endeavoured to ensure by the im- provements which have now been introduced. In this edition I have adhered to the original plan of the work, which was to set forth in a concise and perspicuous manner the principal facts of the science to which it is devot- ed ; and at the same time to furnish the student with such references to other works and memoirs as may give direction to his inquiries in cases of doubt or difficulty, In the revision of this volume, I have constantly consulted the latest editions of the elaborate treatises of Berzelius, The- nard, Thomson and Henry ; and of the smaller, though not less valuable ones, of Brande and Turner. I should state, however, that the work of Dr. Turner has been used more freely than any other, and may in some respects be considered the basis of the present Manual. The method of arranging the subjects is essentially that ori- ginally proposed by Professor Brande ; which I have adopted from the conviction, that although not entirely free from ob. jection, it is upon the whole more easily acquired by the stu- dent than any which to my knowledge, has hitherto been fol- lowed. In the description of individual substances, I have studied brevity as far as was consistent, and have employed in many instances the style usually pursued in Natural History. I have in general omitted descriptions of apparatus, and the more delicate manipulations, as these would have increased the size of the book beyond the limits assigned to it. This department, moreover, has been made the subject of a separ- ate treatise by Mr. Faraday, and will probably hereafter hold VI PREFACE. a place distinct from the views of the science to which text books must now be confined. The improvements in the present edition consist in the in- troduction of many interesting facts discovered within the last three years, which are inserted in their proper places ; the adoption of atomic numbers, founded on the experiments of Berzelius and Turner; and the employment of symbols to de- note chemical substances and their compounds. The number of references has also been increased and the results of origi- nal investigations have in several cases been introduced. With regard to the atomic weights and symbols employed in this edition, some explanation may be necessary. It is well known that two sets of chemical equivalents or atomic weights have for some years been current among chemists. The one, founded upon what appears to be an incorrect hypothesis, that the atomic weights of bodies are multiples by a whole number of the atomic weight of hydrogen, has until recently, been al- most exclusively adopted in England and in this country The other, proposed by Berzelius, and founded upon numerous and most accurate analyses, has been sanctioned by the Con- tinental Chemists, and is now beginning to be employed in the English chemical treatises. It is this last which 1 have now adopted, for the simple reason that it is based upon experi- ment and not upon hypothesis. But in order to avoid the nu- merous and inconvenient decimals of Berzelius, I have used the numbers given by Dr. Turner, in the Fourth Edition of his " Elements of Chemistry,' 5 as being more simple, and for all ordinary purposes sufficiently near the truth. These numbers the author states to be founded on his own experiments and on those of Berzelius. Symbols have not heretofore found much favour among our chemists, and an opinion unfavourable to them is expressed in this work, which I at first intended to carry through the press without introducing them, although I had observed that they were employed by several English chemists. But a more attentive examination of the subject induced me to change my plan in this respect. The symbols which I have adopted are placed at the head of each article, so that their meaning will at once be understood, and cannot occasion the least embar- PREFACE. Vll rassment to the student. I have, moreover, used them in ac- cordance with the rules of algebra. The atomic weight of each element is denoted hy the first letter of its Latin name, and when the names of two or more elements begin with the same letter, the distinction is drawn by adding an additional letter. Thus, B is the symbol for Boron, Ba for Barium. When bo- dies combine atom to atom, as in the case of Protoxide of Chlo- rine, the symbol is Cl+O ; but when more than one atom oi an element is contained in a compound, a figure indicates the number of atoms. Thus, 4O-f Cl denotes Peroxide of Chlo- rine, and indicates that it consists of 4 atoms of Oxygen com- bined with I atom of Chlorine. Degrees of oxydation are some times expressed by Berzelius and others by dots placed over the symbol ; but in order to avoid confusion I have uniformly adhered to the plan of expressing them by figures. In those cases where the symbol is complex, abbreviations are sometimes employed. Thus, Aq for water, (Aqua) and Ac for Acid, will be occasionally noticed in the descriptions the salts. It only remains for me to acknowledge the important assist- ance which I have received from my brother, Dr. T. Romeyrr Beck. To him I am indebted for many useful suggestions as well with regard to the general plan of the work, as to its more minute details. By the use of his manuscript book of chemi- cal references, the labour of one part of the work was muck abridged. The entire articles on the action and tests of Arsenic, Corrosive Sublimate, and Tartar Emetic, were furnished by him. And in consequence of my engagements at a distance from the publishers, he has rendered me an equally important service, by assuming the task of revising and correcting the sheets as they passed through the press. UNIVERSITY OF THE CITY OF NEW- YORK, December, 1834. CONTENTS. Page. DEFINITION OF CHEMISTRY. ... .13 CHAPTER I. ATTRACTION. SECTION I. Cohesion Crystallization, . . .14 SECTION II. Affinity, ..... 22 SECTION III. Of the proportions in which bodies combine. Ato- mic theory, . ..... 27 CHAPTER II. CALORIC OR HEAT. SECTION I. Nature of Caloric, . ... 35 SECTION II. Communication of Caloric Radiation. Conduc- tion, ... . . . . .36 SECTION III. Distribution of Caloric, ... 43 SECTION IV. Effects of Caloric Expansion, Liquefaction, Vapor- ization, ....... 46 SECTION V. Specific Caloric, .... 59 SECTION VI. Sources of Caloric, .... 60 CHAPTER III. LIGHT, . . . . . . 65 CHAPTER IV. ELECTRICITY. Galvanism, 70 CHAPTER V. MAGNETISM. Electro- Magnetism. Thermo-Electricity, . . 83 CHAPTER VI. ELECTRO-NEGATIVE BODIES. General Remarks, explanation of the Nomenclature, &c. . 96 X CONTENTS. Page. SECTION I. OXYGEN, ..... 98 SECTION II. CHLORINE Protoxide of Chlorine, Peroxide of Chlo- rine, Chloric Acid, Perchloric Acid, SECTION III. BROMINE Bromic Acid, Chloride of Bromine, 104 SECTION IV. IODINE lodous Acid, lodic Acid, Chloriodic Acid, Bromides of lodifie, ..... 106 SECTION V. FLUORINE, ... CHAPTER VII. ELECTRO-POSITIVE BODIES. SECTION I. HYDROGEN Water, Deutoxide of Hydrogen, Muri- atic Acid, Hydriodic Acid. Hydrobromic Acid, Hydrofluoric Acid, . . '. . . . >im 110 SECTION II. NITROGEN Atmospheric Air, Protoxide of Nitrogen, Deutoxide of Nitrogen, Hyponitrous Acid, Nitrous Acid, Ni- tric Acid, Nitro- Muriatic Acid, Chloride of Nitrogen, Iodide of Nitrogen, Ammonia, Salts of Ammonia and the foregoing Acids, . *'. . , . . . .123 SECTION III. SULPHUR Hyposulphurous Acid, Sulphurous Acid, Hyposulphuric Acid, Sulphuric Acid, Chloride of Sulphur, Bromide of Sulphur, Iodide of Sulphur, Hydrothionic Acid, Hydrothionous Acid, Salts of Ammonia and the acids contain- ing Sulphur, ..... ,*\ 143 SECTION IV. PHOSPHORUS Oxide of Phosphorus, Hypophospho- rous Acid, Phosphorous Acid, Phosphoric acid, Pyrophospho- ric Acid, Salts of Ammonia and the acids containing Phos- phorus, Chlorides of Phosphorus, Bromides of Phosphorus, Iodide of Phosphorus, Hydruret of Phosphorus, Bihydruret of Phosphorus, Sulphuret of Phosphorus, . . v 156 SECTION V. CARBON Carbonic Oxide, Carbonic Acid, Salts of Carbonic Acid and Ammonia, Chlorides of Carbon, Chloro- carbonic Acid, Bromide of Carbon, Iodide of Carbon, Hydru- rets of Carbon, Naptha from Coal Tar, and Naphthaline, Coal and Oil Gas, Fire Damp &c., Chloride of Hydrocarbon, Bromide of Hydrocarbon, Iodide of Hydrocarbon, Cyanogen, Cyanous Acid, Cyanic Acid, Chlorides of Cyanogen, Bro- mide of Cyanogen, Iodide of Cyanogen, Hydrocyanic Acid, Hydrocyanate of Ammonia, Cyanide of Sulphur Sulpho-cy anicAcid, Bisulphuret of Carbon, Xanthogen and Hydroxan- thic Acid, Phosphuret of Carbon, . . . 164 SECTION VI. BORON Boracic Acid, Bichloride of Boron, Fluo- boric Acid, Sulphuret of Boron, * ... 188 CONTENTS. XI Page. SECTION VII. SELENIUM Oxide of Selenium, Selenious Acid, Selenic Acid, Chloride of Selenium, Bromide of Selenium, Hydroselenic Acid, Sulphuret of Selenium, Phosphuret of Se- lenium, . ... 191 CHAPTER VIII. METALS. General properties of the metals, . . 195 SECTION I. POTASSIUM Oxides, Chloride, ] Bromide, Iodide, Hy- druret, Nitruret, Sulphuret, Phosphuret, and Cyanide of Po- tassium, Alloys and Amalgams, Salts of Potassa, . 208 SECTION II. SODIUM Oxides, Chloride, Iodide, &c. Alloys and Amalgams, Salts of Soda, Disinfecting Liquid, . . 223 SECTION III. LITHIUM Oxide, Chloride, Salts of Lithia, 223 SECTION IV. BARIUM Oxides, Chloride, Bromide, &c. Salts of Baryta, ..... 235 SECTION V. STRONTIUM Oxides, Chloride, Iodide, &c., Salts of Strontia, ..... 240 SECTION VI. CALCIUM Oxides, Chloride, &c., Chloride of Lime, Salts of Lime, ..... 243 SECTION VII. MAGNESIUM Oxide, Chloride, &c., Salts of Mag- nesia, 249 SECTION VIII. ALUMINUM Oxide, Chloride, &c., Salts of Alu- mina, ....... 254 SECTION IX. GLUCINUM Oxide, &c., . . . .257 SECTION X. YTTRIUM Oxide of Yttrium, . . . . 258 SECTION XI. ZIRCONIUM Oxide, &c., .... 259 SECTION XII. SILICIUM Oxide, Chloride, Bromide, Fluoride, &c, 260 SECTION XIII. THORIUM Oxide of Thorium, ... 263 SECTION XIV. MANGANESE Oxides, Acids, Chloride, &c., Salts of Manganese, ..... 264 SECTION XV. IRON Oxides, Chlorides, Bromides, Carburets, &c., Alloys, Ferrocyanic Acid, Salts of Iron, Ferrocyanates, 270 SECTION XVI. ZINC Oxide, Chloride, Iodide, and Sulphuret, Al- loys, Salts of Zinc, 279 SECTION XVII. TIN Oxides, Chlorides, &c., Alloys, Salts of Tin, 284 SECTION XVIII. CADMIUM Oxide, Chloride, &c., Alloys, Salts of Cadmium, 288 SECTION XIX. NICKEL Oxides, Alloys, Salts of Nickel, . 290 SECTION XX. COBALT Oxides, Chloride, &c. Salts of Cobalt, 293 xil CONTENTS. Page. SECTION XXI. ARSENIC Arsenious and Arsenic Acids, Chloride of Arsenic, Bromides, Iodide, Hydruret, and Sulphurets, Al- loys of Arsenic, Arsenites, Arseniates, . " . 296 SECTION XXII. MOLYBDENUM Oxides of Molybdenum, Molybdic Acid, Chloride of Molybdenum, Fluoride and Sulphuret, Molybdates, 303 SECTION XXIII. CHROMIUM Oxides of Chromium, Chromic Acid, Chlorochromic Acid, Fluochromic Acid, Sulphuret and Phosphuret of Chromium, Chromates, . 305 SECTION XXIV. VANADIUM Oxides of Vanadium, Vanadic Acid, Chlorides of Vanadium, Sulphurets, &c, . . 309 SECTION XXV. TUNGSTEN Oxide of Tungsten, Tungstic Acid, Chlorides of Tungsten, &c., . . .312 SECTION XXVI. ANTIMONY Oxide of Antimony, Antimonious and Antimonic Acids, Chlorides of Antimony, Sulphurets, Al- loys, Salts, 313 SECTION XXVII. URANIUM Oxide and Sulphuret of Uranium, Salts of Uranium, ..... 318 SECTION XXVIII. COLUMBIUM Oxide of Columbium, Columbic Acid, Chloride of Columbium, Fluocolumbic Acid, Sulphuret of Columbium, 320 SECTION XXIX. CERIUM Oxides and Sulphuret of Cerium, Salts of Cerium, 321 SECTION XXX. TITANIUM Oxide of Titanium, Titanic Acid, Bi- chloride and Bisulphuret of Titanium, ... 322 SECTION XXXI. TELLURIUM Tellurous Acid, Telluric Acid, Chlorides of Tellurium, Telluretted Hydrogen, . . 324 SECTION XXXII. BISMUTH Oxide, Chloride, Bromide, Iodide, and Sulphuret of Bismuth, Alloys, Salts, . . 326 SECTION XXXIII. COPPER Oxides, Chlorides, Sulphurets, and Phosphuret, Alloys, Salts, 329 SECTION XXXIV, LEAD Oxides, Chloride, Iodide, and Sulphu- rets, Alloys, Salts, ..... 335 SECTION XXXV. MERCURY Oxides, Chlorides, Bromides, Io- dides, Sulphurets, and Bicyanide of Mercury, Amalgams, Salts of Mercury, ..... 340 SECTION XXXVI. SiLvln Oxides, Chloride, Bromide, Iodide, Sulphuret, and Cyanide of Silver, Alloys, Salts of Silver, 348 SECTION XXXVII. GOLD Oxides, Chlorides, Bromide, Iodide, Sulphuret and Phosphuret of Gold, Alloys, . 353 SECTION XXXVIII. PLATINUM Oxides, Chlorides, and Sulphu- ret, Sulphate of Platinum, Alloys, . . .356 SECTION XXXIX. PALLADIUM Oxides of Palladium, . 359 CONTENTS. Xlii Page. SECTION XL. RHODIUM Oxides of Rhodium, . 359 SECTION XLI. OSMIUM Oxides, &c. 360 SECTION XLII. IRIDIUM Oxides, &c. . . 360 CHAPTER IX. VEGETABLE SUBSTANCES. Preliminary Remarks, . . . 362 SECTION I. VEGETABLE ACIDS Acetic Acid, Pyroligneous Acid, Kreosote, Acetates, Oxalic Acid and the Oxalates, Oxamide, Tartaric Acid and the Tartrates, Racemic or Paratartaric Acids, Citric Acid and the Citrates, Malic Acid and the Mal- ates, Benzoic Acid and the Benzoates, Benzule, Gallic and Pyrogallic Acids and the Gallates, Ellagic Acid, Aspartic, Boletic, Camphoric, Carbazotic, Chloroxalic, Caincic, Crame- ric, Croconic, Igasuric, Indigotic, Kinic, Laccic, Lactucic, Meconic, Mellitic, Moric or Moroxylic, Mucic or Saccholic- tic, Pectic, Phosphoric and Hydrocyanic, Suberic, Succinic, Ulmic, Valerianic, and Zumic Acids, . . . 363 SECTION II. VEGETABLE ALKALIES Morphine and its Salts, Nar- cotine, Cinchonine, Quinine, Strychnine, Brucine, Emetine, Veratrine, Sanguinarine, Atropine, Buxine, Corydaline, Cro- tonine, Curarine, Cynapine, Daphnine, Daturine, Delphine, Digitaline, Essenbeckine, Eupatorine, Hyoscyamine, Nico- tine, Solanine, Violine, .... 377 Substances somewhat allied to the preceding, but not alkaline Amydalin, Asparagin, Bassorin, Caffein, Cathartin, Chloro- phyle, Colocyntin, Columbin, Conein, Cytisin, Dahlin, Dra- cin, Fungin, Gentianin, Hematin, Imperatorin, Inulin, Legu- min, Liriodendrin, Lupulin, Madarin, Medulin, Olivile, Paraf- fin and Eupion, Picrotoxin, Piperin, Plumbagin, Polychroite, Populin, Rhubarbarin, Salicin, Sarcocoll, Scillitin, Suberin, Tiglin, Ulmin, Zanthopicrite, Bitter Principle, Extractive Matter, ....... 384 SECTION III. SUBSTANCES WHICH IN RELATION TO OXYGEN CONTAIN AN EXCESS OF HYDROGEN Oils, Fixed Oils, Volatile or Essen- tial Oils, Camphor, Coumarin, Resins, Amber, Balsams, Gum, Resins, Caoutchouc, Wax, Alcohol, Alcohol in Wine, &c., Ether,Ethers of the first Class, Sulphuric Ether, Sulphovinic Acid, Phosphoric Ether, Ethers of the second class, Muriatic, Chloric, Hydriodic, Fluoric and Fluoboric Ethers, Ethers of the third class, Nitric and Acetic Ether, Bituminous substan- ces, Bitumen, Naptha, Petroleum, Asphaltum, Mineral Pitch or Maltha, Retinasphaltum, Pit-Coal, Glance Coal or An- thracite, .380 XIV CONTENTS. Page. SECTION IV. SUBSTANCES, THE OXYGEN AND HYDROGEN OF WHICH ARE IN EXACT PROPORTION FOR FORMING WATER Sugar, Man- na, Sugar of Grapes, of the Maple, of Beets, c., Honey, Molasses, Starch or Fecula, Arnidine, Hordein, Gum, Mucil- age, Lignin or Woody Fibre, .... 399 SECTION V. SUBSTANCES WHICH DO NOT BELONG TO EITHER OF THE PRECEDING SECTIONS Colouring Matter and Dyes, Tannin, natural and artificial, Gluten, Yeast, Vegetable Albumen, Fermentation. Panary, Saccharine, Vinous, Acetous, and Pu- trefactive Fermentations, . . . 420 CHAPTER X. ANIMAL SUBSTANCES. Preliminary Remarks. ..... 408 SECTION I. ANIMAL ACIDS Uric, Pyro-Uric, Purpuric, Erythric, Rosacic, Amniotic, Lactic, Formic, Caseic, Sebacic. Choles- teric, Stearic, Margaric, Oleic, Phocenic, Butyric, Caproic, Capric, Hircic, and Cetic Acids, . . 408 SECTION II. OLEAGINOUS SUBSTANCES. Train Oil, Spermaceti Oil, Dippel's Oil, Hogslard, Suet, Butyrine, Phocenine, Hircine, Adipocire, Cholesterine and Ambergris, . . . 411 SECTION III. SUBSTANCES WHICH ARE NEITHER ACID NOR OLEAGIN- OUS Fibrin or Animal Gluten, Albumen, Gelatin, Urea, Su- gar of Milk, Sugar of Diabetes, . . . 413 SECTION IV. THE MORE COMPLEX ANIMAL PRODUCTS The Blood and its constituents, Respiration, Animal Heat, Saliva, Pan- creatic Juice, Gastric Juice, Bile, Biliary Calculi, Chyle, Milk, Eggs, Humours of the Eye, Tears, Mucus, Pus, Sweat, Urine and Urinary Concretions, Solid parts of Animals, Bones, Teeth, Shells of Eggs, Lobsters, &c., Horn, Tendons, Hair, Wool and Feathers, Muscle. 414 APPENDIX. TABLE of Atomic Weights and Symbols. . . . 425 TABLE showing the Proportions in which several Gaseous Bodies combine by Volume, ..... 428 f UNIVERf ITY \ r* OF jUFQR^bX ; '- ; MANUAL OF CHEMISTRY. DEFINITION OP CHEMISTRY. CHEMISTRY* has been variously defined. By Dr. Black it was de- nominated " the science of heat and mixture.'* Modern chemists, however, have given it a wider range. Thomson calls it the sci- ence which treats of those events and changes in natural bodies, which are not accompanied by sensible motions. Syst. of Chem. i. 18. Brande considers it "the object of chemistry to investigate all changes in the constitution of matter, whether effected by heat, mix- ture or other means." Man. of Ckem. 1. According to Berzelius, " chemistry is the science which makes us acquainted with the com- position of bodies and with the manner in which they act upon each other." Trait, de Chim. i. 31. Chemistry borders closely in many instances upon Natural Philoso- phy ; but the distinction can be easily drawn. It is the office of natural philosophy to investigate the sensible mo- tions of all bodies ; whereas chemistry studies the constitution and qualities of these bodies. The natural philosopher contemplates whole masses and ascertains their properties ; while the chemist notices the operations of their par- ticles, observes their reciprocal actions and seeks to discover all the changes that may occur. Thus in examining our atmosphere, when studied as a whole, its weight, pressure, density and elasticity, are subjects falling within the province of natural philosophy'; but when we endeavor to dis- cover the elements of which this air is composed, the changes which it undergoes, by heat or combination, and the phenomena which at- tend these changes, we are within the boundaries of chemistry. The business of the chemist, therefore, is to interrogate nature, and thus to make himself acquainted with the ultimate constitution of bodies. When this is effected, he is furnished with the means of imitating her in some of her most interesting operations, and thus in many instances, of contributing largely to individual as well as to na- tional wealth and prosperity. Chemistry is divided into I. The general forces, or powers productive of chemical phenome- na and the laws which govern them : or the general theory of the science. II. The particular effects which are produced in different bodies by the agency of these general powers ; or the chemical history of in- dividual substances. *The term chemistry is probably derived from the Greek word Chemia, originally applied to the art of making gold and silver. The Arabians by prefixing the article gave' it the name of Alchemy. Thomson's History of Chemistry. B 1 4 ATTRACTION COHESION. The general powers, or as they are sometimes called, general pro- perties of matter, or imponderable substances, are - ATTRACTION. HEAT. LIGHT. ELECTRICITY. MAGNETISM. CHAPTER I. ATTRACTION. The term attraction is employed to express that unknown principla which causes distant bodies to approach each other, and to resist a separation with some degree of force. Attraction may be, I. Remote ; when it acts on masses of matter at sensible distances ; as in gravitation, electricity, and magnetism. II. Contiguous ; when it acts on masses of matter at insensible dis- tances ; as in cohesion and in chemical affinity. Contiguous attraction is of two kinds, viz : homogeneous and hetero- geneous, or cohesion and affinity. The former takes place between bodies of the same nature, and the latter between those which are different. SECTION I. COHESION. SYNONYMES. Attraction of Aggregation Cohesive Affinity Corpus- cular, or Molecular Attraction Homogeneous Affinity. Cohesion may be denned to be that force or power by which parti- cles or atoms of the same kind are brought into contact and retained in that situation. Cohesion is exerted in different bodies with different degrees of force. In solids, its force is exerted with the greatest intensity; in liquids, it acts with much less energy; and in aeriform bodies it is doubt- ful whether it exists at all. Thus water in a solid state has considera- ble cohesion, which is much diminished when it becomes liquid, and is entirely destroyed as soon as it is changed into vapour. The force of cohesion in solid bodies which is denominated tenacity, is measured by the weight necessary to break them, or rather to pulj them asunder. Heat is excited at the same time, a good illustration of which occurs in the process of wire drawing. [An abstract of Mr. Rennie's elaborate experiments on the cohesive force of various solids will be found in Ure's Chem. Dictionary. ] In liquids the force of cohesion is demonstrated by the spherical figure which they assume when suffered to form drops, The drop is COHESION. 15 spherical, because each particle -of the fluid exerts an equal force in every direction, drawing other particles towards it on every side, as far as its power extends. To the same cause is owing the property possessed by all liquids of remaining heaped up above the brims of the vessels which contain them. Other examples of cohesion. 1. Similar portions being cut off with a clean knife from two lead- en bullets and the fresh surfaces being brought into contact with a slight turning pressure, the bullets cohere, almost as if they had been originally cast together. 2. Fresh cut surfaces of India rubber adhere in a similar manner. 3. Two pieces of perfectly smooth glass or marble laid upon each other adhere with great force. It has been supposed that in some of the above cases the attractive force is confined to the surfaces of the masses, and it has been called adhesion. Mr. Ruhland has given a table exhibiting the weights which were found necessary to separate equal surfaces of different bodies from the same liquids. [Gorhams Chem. i. 6. Ann. of Phil. vii. 20.] Dr. Thomson considers adhesion as exhibiting the charac- teristic marks of chemical affinity and as affording a particular case of the action of that power. Cohesion is weakened by the following causes : I. By Heat. When a fusible body is exposed to the influence of heat, its volume is at first augmented, and this increase of bulk is in conse- quence of the separation to a certain degree of its constituents. Co- hesion is thus lessened, though not destroyed, and hence if heated zinc be struck with a hammer, much less force will be required to dis- integrate it, than if it were at the ordinary temperature of the air. If the heat be continued, the particles of the metal will be so far re- moved from each other, as to allow of free motion, and it will become liquid. By raising the heat still higher, while the metal is not in con- tact with the air, all cohesion will be removed and it will be resolved into vapour or an elastic fluid. II. By Mechanical violence. Under this head may be arranged seve- ral processes which are highly useful in the laboratory, as Pulverization and trituration ; by which substances are reduced to powder, generally performed by means of pestles and mortars. Levigation ; a process similar to trituration, except that the rubbing is assisted by the addition of a liquid in which the solid matter under operation is not soluble. Granulation; effected either by pouring the substance while in fusion into cold water, or by agitating it in a box. Sifting ; employed for the purpose of obtaining bodies in powder of an equal degree of fineness throughout, performed by instruments termed sieves. III. By the influence of a more powerful attraction. Thus if a mass of lime be immersed in vinegar, it gradually lessens and finally disappear!. Here an attractive force has been introduced which is superior to the attraction of the particles of lime for each other, and consequently they are separated. 16 CRYSTALLIZATION. The effects of the exertion of cohesion are, 1. To unite the particles of bodies in a confused manner, without any regularity of form. 2. To bring them together in a determinate mode so as to form regular geometrical figures or crystals. The latter is the most fre- quent. CRYSTALLIZATION. When we diminish in any manner the cohesion of a solid body so as to render it liquid or gaseous and afterwards remove the cause of this change, the body returns to its former state and the molecules ar- range themselves in a determinate manner, or in the form of crystals. Hence when a body passes from a gaseous or liquid state to that of a solid, it crystallizes; but if this passage be too rapid, the crystallization will be confused. The most common agents employed to crystallize bodies are water and heat ; alcohol is also sometimes made use of in certain analyses. I. Water. This agent is employed in two ways, viz. a. To dissolve the body by the aid of heat and then to allow the solution to cool. In this case it will generally be only necessary to continue the process of evaporation until a drop of the solution when placed upon a cold body shows a tendency to crystallize ; or at least until a film or pellicle appears on its surface. This proves that the at- traction of the saline particles for each other is becoming superior to their attraction for the water. In this case, crystallization takes plaee because hot water generally dissolves a greater quantity of a salt than cold water, and when it has become saturated a portion is necessarily deposited as the water cools. There are, however a few exceptions to the law that salts are more soluble in hot than in cold water, and Mr. Graham suggests that the efflorescent salts generally belong to this class. Phil. Mag. and Ann. i. 7. b. To leave the cold solution to spontaneous evaporation. In this case the water by evaporation is brought to the point at which it is unable to hold the salt in solution. In both of the above cases, crystals generally retain a portion of water, which is termed the water of crystallization, and the salts con- taining it are denominated hydrous salts. These salts when heated liquify and undergo a process which is called watery fusion. Alum offers a familiar example. In a few casea however, salts do not retain any water of crystalliza- tion and they are then termed anhydrous salts. Salts, in crystallizing, frequently enclose mechanically within their texture particles of water, by the expansion of which, when heated, the salt is burst with a crackling noise into smaller fragments. This phenomena is known by the name of decrepitation ; and it is observed to be most powerful in those crystals which contain no water of cry s- tallization ; as the nitrates of baryta and of lead. Some salts part with their water of crystallization by a simple ex- posure to a dry air, when they are said to effloresce ; but there are other salts which deliquesce or attract water from the atmosphere. Car- bonate of potash is a deliquescent salt ; carbonate of soda an efflores- cent one. [For a table of the action of the atmospheric air, on some of the most common salts, see Parke's Chem. Catechism, 231, 8th ed.] CRYSTALLIZATION. 17 II. Heat. There are two methods of employing this agent, viz. a. To expose the body to heat until it has melted, then to let it cool slowly and without agitation, till a crust has formed on its surface, to pierce this crust and decant the liquid contained in the interior. We then obtain the outer portion in the form of a solid crystalline bed, sometimes resembling a geode. This effect can be finely exhibited by treating in such a manner sulphur, or lead, bismuth and some other of the semi-crystalline rnetals. b. To reduce the body to a state of vapour and to condense it gradu- ally. This however, is not always practicable, because few of the solids can be volatilized. The process is generally called Sublimation. Exp. Put powder of corrosive sublimate or arsenic in a dry flask, obstruct the mouth slightly and apply heat. The vapour rises and forms crystals in the upper part. More heat is required in the case of arsenic than in that of corrosive sublimate. III. Alcohol. This is generally employed by applying heat ad then allowing the solution to cool as above. The great utility of this agent depends upon the fact, that a few salts only are soluble in it. Hence it is often made use of to separate such sails from others with which they may be combined, It is scarcely necessary to observe that in such cases the purest alcohol must be employed. [For a table of substances soluble in alcohol, see Henry's Chcm. llth ed. ii. 653.] Several circumstances affecting the process of crystallization de- serve to be noticed. Among these are, 1. Rapidity of evaporation. When the heat is high and the evapo- ration very rapid, the crystallization is confused. 2. The access of atmospheric air. This under certain circumstances produces instant crystallization in some saline solutions. Those which are the most remarkable on this account are carbonate and sulphate of soda. Hot saturated solutions of these salts in well cork- ed phials may be cooled down without the deposition of any crystals, but as soon as the corks are withdrawn, crystals begin to form and at the same time the temperature rises. Dr. Thomson has satisfactorily proved that the water of crystallization of the salt which crystallizes, gives out its latent heat, and that this evolution is the cause of the in- crease of temperature observed.* Ann. of Phil. xix. 169. * The theory of this singular phenomenon hat riot yet been well settled. That it does not depend on atmospheric pressure is proved by the fact that the solution may be cooled in open vessels without becoming solid, provided its surface be covered wi'h a film of oil, as first shown by Gay Lussac ; and, as Dr. Turner states, that the experiment also succeed? without the use of oil by causing the air of the flask to communicate with the atmosphere by means of a moderately narrow tube. Mr. Graham supposes the effect of air to arise from a certain chemical ac- tion upon water. He has shown that gases which are more freely absorbed than atmospheric air, act more rapidly in producing crystallization. And it would seem from his experiments that the rapidity of crystallization, occa- sioned by the contact of gaseous matter, is proportional to the degree of its affinity for water Upon this principle also, he accounts for the fact that so- lutions of sulphate of soda which have not been boiled are less affected by exposure to the air than well boiled solutions; for the former still retain most of their air, and do not absorb air so eagerly on exposure as solutions which have been boiled. Phil. Mag. and Annals, iv. 215. On the other hand, Dr. H. O^den contends that the access of air is not neces- 18 CRYSTALLIZATION. 3. The, nature of the, liquor in which the crystals are, formed. Dr. Woolner has ascertained that this often influences the fundamental or primitive forms of crystals. Thus he says that when a small portion of solution f sulphate of iron is poured into a solution of alurn and the whole allowed to crystallize, the sulphate of iron assumes the octa- hedral form of the alum, although these octahedral crystals contain scarcely a trace of alum. Edin. Neio Phil. Jour. i. 189. 4. \The immersion of some foreign body into the saline solution. This serves as a nucleus or attracting point around which the parti- cles as they are deposited may be attached. Hence many of the salts are found concreted around sticks or twigs, and the crystals of sugar are arranged around threads. A crystal of the same kind as that held in solution also answers the purpose. 5. Light. Of this, instances are observed in the bottles of camphor placed in druggists' windows, where the crystals are always most co- pious on the side exposed to the light. Chaptal found that by using a solution of a metallic salt, and shading the greater part of the vessel with black silk, capillary crystals shoot up the uncovered sides, and that the extent of the exposed partis distinctly marked by the limit of crystallization. The phenomenon termed saline vegetation, consist- ing in the creeping of the salt around the edge of the vessel, is also re- ferred by Chaptal to the influence of light. For the perfect success of this experiment, the edges of the vessel should be smeared with oil. 6. Electricity. It has been repeatedly remarked that saline solu- tions which have not yielded crystals, after having been sufficiently concentrated and left undisturbed for several days, have suddenly de- posited an abundant crop, during, or immediately after a thunder storm. Dr. lire has shown that negative electricity facilitates, and positive electricity retards the formation of crystals. Erandes Jour. iv. 106. Crystallographers have observed that certain crystalline forms are peculiar to certain substances. Thus, calcareous spar crystallizes in rhombs ; fluor spar in cubes, and quartz in six sided pyramids ; and these forms are so far peculiar to those substances, that fluor spar is never found in rhombs or six-sided pyramids, nor does calcareous* spar or quartz ever occur in cubes. Crystalline form may, therefore, serve as a ground of distinction between different substances. It is accordingly employed by mineralogists for distinguishing one mine- ral species from another } and it is very serviceable to the chemist as affording a physical character for salts. A notice of this subject there- fore should form part of every treatise on chemistry. The surfaces which limit the figure on crystals are called the planes or Jaces, and are generally flat. The lines formed by the junction of two planes, are called edges, and the angle formed by two such edges is a plane angle. A solid angle is the point formed by the meet- sary lo the process* of crystallization. Me asserts that it often occurs when the vessel is closed, by mere agitation, without opening it, (a fact which I have also observed, and to this he also ascribes the results of Mr. Graham.) He also shows that tins pecu'iar property of resisting crystallization is not con- fined to any gonns of salts in particular, but enumerates several alkaline, earthy and metallic sails which will exhibit this property. Among 1 which are the sulphate, carbonate, acetate, and phosphate of soda, the tartrate of potash and soda, ferrocyanate of potnsh, sulphate ef magnesia, the muriates of lime and barytes and the sulphate of copper. New Edin. Jour. xiii. 309. CRYSTALLIZATION. 19 ing of at least three planes. The planes which terminate a prism are called terminal planes ; those at the sides lateral planes ; the face on which a crystal is supposed to stand is called a base. When the end of a crystal is formed by two planes inclined to each other like the roof of a house, it is said to be culminated ; if three or more planes meeting in a solid angle, terminate the prism, they form a pyramid which is called the summit ; the planes which form the sum- mit are called acuminating planes, and the edges produced by their junction, edges of the pyramid. When an edge or solid angle is cut off and replaced by a single new face, it is said to be truncated ; if by two or more new faces, it is bevelled. A very short prism is called a table. The forms of crystals are very various. They are divided by crys- tallographers into what are called primitive, primary, derivative, or fun- damental forms, and into secondary or dsrived forms. The number of primary forms is differently stated by different au- thors, according to the system which they adopt. The most simple, however, is that which reduces these forms to the following, viz. 1. The cube. 2. The tetrahedron. 3. The Octahedron. 4. The six-sided prism. 5. The rhombic dodecahedron. 6. The dodecahedron with isosceles triangular faces. 20 CRYSTALLIZATION. 7. The rhomb. These primitive forms by farther mechanical analysis may be redu- ced to three integral elements. 1. The parallelepiped, or simplest solid having six surfaces, paral- lel, two and two. 2. The triangular or simplest prism, bounded by five surfaces. 3. The tetrahedron or simplest pyramid, bounded by four surfaces. The secondary forms are supposed to arise from decrements of par- ticles taking place on different edges and angles of its primitive forms. Thus a cube, having a series of decreasing layers of cubic particles upon each of its six faces, will become a dodecahedron, if the decre- ment be upon the edges ; but an octahedron, if upon the angles ; and by irregular, intermediate, and mixed decrements, an infinite variety of secondary forms would ensue. There are some appearances in crystallography to which the above explanation will not apply. A slice of fluor spar, for instance, ob- tained by making two successive and parallel sections, may be divid- ed into acute rhomboids ; but these are not the primitive forms of the spar, because by the removal of a tetrahedron from each extrem- ity of the rhomboid, an octahedron is obtained. Thus as the whole mass of fluor may be divided into tetrahedrons and octahedrons, it be- comes a question which of these forms is to be called primitive, es- pecially as neither of them can fill space without leaving vacuities, a structure not adapted to form the basis of a permanent crystal. To obviate this difficulty, Dr. Wollaston suggested that the integrant par- ticles of all crystals might be considered as spheres or spheroids, which by their mutual attraction have assumed that arrangement which bringsjthem as near as possible to each other ; and this view of the subject has been confirmed by the experiments of Mr. Daniell. [Wollaston in Phil. Trans. 1813. Daniell in Brandt's Jour. i. 24.] But although the preponderance of evidence is rather on the side of the spherical form of atoms, this opinion is attended with difficulties which in the present state of our knowledge cannot be obviated. Such are some of the facts developed by Isomorphism. See Thom- son 1 s Inorganic Chcm. i. 16. The primitive forms of crystals can be ascertained 1 st, by me- chanical division or cleavage ; and 2d, by the action of fluid men- strua. For our knowledge of the latter we are wholly indebted to Mr. Daniell ; and the fact is well shown by plunging into a tumbler full of cold water, a shapeless mass of alum, the surface of which becomes in a few days, eaten and carved out into a variety of regular cryst- alline forms. The process called cleavage consists in separating thin layers or slices from the sides, edges or angles of a crystallized substance in a CRYSTALLIZATION. 21 given direction. Many crystallized substances are very obviously composed of thin plates or laminae, which by a careful operation may be separated from each other, without presenting the appearance of a fracture. The planes in which these laminae are applied to each other, are called the natural joints of a crystal. The direction in which it may be cleaved is called the direction of cleavage. Some times a crystal is cleavable only in one direction, and is then said to have a single cleavage. Others may be cleaved in two, three, four or more directions, and are said to have a double, treble, fourfold cleavage, and so on according to their number. 8. It was at one time supposed that substances of different composition never assumed precisely the same primitive form. But the researches of Professor Mitscherlich have proved, that certain substances are capable of being substituted for each other in combination without influencing the crystalline form of the compound. This discovery has led to the formation of groups, each comprehending substances which crystallize in the same manner, and which are hence said to be isomor- phous. One of the most instructive of these groups includes the salts of arsenic and of the phosphoric acid. Thus the neutral phosphate and biphosphate of ammonia correspond to the arseniate and biarseniate of ammonia ; and the biphosphate and biarseniate of potash have the same form. Indeed each arseniate has a corresponding phosphate, hav- ing the same form, the same number of equivalents of acid, alkali and water of crystallization, and differing in fact in nothing except that one series contains arsenic and the other an equivalent quantity of phosphorus. Seveial other similar groups occur, and while their stu- dy is of great importance to the chemist, their existence should serve as a caution to the mineralogist, not to place exclusive reliance on crys- tallographic character. In some instances certain groups of crystals approximate in their forms without becoming identical. To this approximation the term plesiomorphism, has been applied. An illustration occurs in the sul- phates of strontia and baryta, the primary forms of both salts are rhombic prisms, very similar to each other ; but on measuring the inclination of corresponding sides in each prism, the difference is found to exceed two degrees. The scope of this work forbids a more detail- ed view of these subjects, and I would therefore refer those who are desirous of a full account of the present state of our knowledge upon the subject of isomorphism, and the allied branches of enquiry, to Mr. J. F. W. Johnston s Report on Chemistry, made in 1832, to the British Association for the advancement of Science. It is of great importance in the examination of crystals to measure their angles with precision ; for this purpose an instrument has been invented, called a goniometer, of which there are two kinds, the com- mon arid the reflective. The reflective goniometer, invented by Dr. Wollaston, is the most useful of these instruments. It enables us to determine the angles even of minute crystals, with great accuracy : a ray of light reflect- ed from the surface of the crystal being employed as radius, instead of the surface itself. See Phillips' Introduction to Mineralogy, and Brandt's Chemistry. REFERENCES On Cohesion Muschenbroecti 's Experiments on the cohe- sive force of solid bodies, in Thomson s Chem. iii. 94. On the means em- ployed by the chemist to prepare the particles of bodies for chemical action, in ChaptaVs Chem. applied to the Arts, i. 51. Boscovich's explanation 22 AFFINITY. of the phenomena of cohesion, in Thomson's Chem. iii. 96. Arnott's Physics. On Crystallography Plauy Traite de Cristallo graphic, i. Brooke's Introduction to Crystallography. Clcavcland's Mineralogy. Phillips' Introduction to Mineralogy. Gorham's Chemistry, i. Moh's Mintralo- gy, i. Leblanc's method of obtaining large artificial crystals, in Thomson's Chemistry, iii. 98. Some valuable directions for crystallizing sails are also to be found in the Encyclopedia Briitannica, iv. 443. Remarks upon DanieWs theory of Crystals, Ann. of Phil. xi. 125, 199, 287. SECTIOiN II. AFFINITY. SYN. Chemical Affinity Chemical Attraction Heterogeneous Attrac- tion. If oil and water, or water, oil and mercury, be agitated together, they do not act on each other, but soon separate and exhibit their ori- ginal characters ; they do not combine and have no affinity for each other. But if olive oil and a solution of potassa be agitated together, they form a milky fluid in which neither of them is recognized ; they unite and form a chemical combination : and bodies which unite chemically are said to have an affinity for each other, and those which do not unite under any circumstances in which they have been placed, are correctly said to have no affinity for each other. Affinity is defined to be that force by which are united the particles or atoms of bodies of different kinds. Like cohesion, it is only effec- tive at insensible distances ; it is mutual and reciprocal between those bodies which it combines thus A cannot be said to have an affinity for B, while B has none for A. Affinity produces, 1. In some cases a compound not materially altered in its properties. Under this proposition, solution is usually offered as an illustration, though it may be doubted whether this is a good example of affinity. Solution is an operation by which a solid body combines with a fluid in such a manner that the compound retains the form of a permanent and transparent fluid. In this case the fluid is termed a menstruum. Solution can easily be distinguished from a mere mechanical mixture or diffusion as follows : Exp. Diffuse a quantity of magnesia in water, the mixture is turbid and finally the magnesia is deposited. If to the turbid mixture a few drops of nitric acid be added, it will become transparent, and the mag- nesia can no longer be separated by any mechanical process or by rest. The nitrate of magnesia is held in solution by the water. Solution is promoted, a. By diminishing the cohesion of the particles of the body to be dis~ solved. Exp. Place a lump of marble in a wine glass, and a small quantity of the same, previously reduced to powder in another ; pour upon each, dilute muriatic acid ; the powdered marble will dissolve much more rapidly than the solid lump. AFFINITY. 23 b. By mechanical agitation. Exp. Put a crystal of tartaric acid into a wine glass containing in- fusion of litmus or of cabbage. The acid if left at rest, produces only a slight effect in its immediate vicinity, but if the liquor be stirred, the whole will become red. c. By heat. There are a few exceptions to this statement which have already been adverted to. In most cases of solution there is a certain point at which the force of affinity between the solid and fluid will be balanced by the cohesion of the solid, and beyond which solution will not proceed : this point is called saturation, and the resulting compound a saturated solution. 2. Affinity produces in most cases a compound zohose prcpei'ties differ essentially from those qftfte components. Exp. Burn phosphorus in oxygen gas or atmospheric air, the result- ing compound is phosphoric acid. Exp. Pass atmospheric air or oxygen gas into a vessel of nitric ox- ide ; the resulting compound is nitrous acid. Affinity sometimes also produces, 3. A change of state. Exp. Two glass vessels, one rilled with ammoniacal gas, and the other with muriatic acid gas, when brought into contact produce solid muriate of ammonia. Exp. To a solution of muriate or nitrate of lime add sulphuric acid ; tolid sulphate of lime will be formed. Exp. Crystals of sulphate of soda and nitrate of ammonia triturated together become a liquid. Exp. Gunpowder, when exploded, is resolved into various gases. 4. A change of colour. Exp. Add liquid ammonia to a solution of nitrate or sulphate of cop- per a rich blue colour is produced. A few drops of sulphuric acid render it colourless. Exp. Sulphate of copper and acetate of lead rubbed together in a mortar assume a green colour. Exp. A few drops of tincture of galls added to a very dilute so- lution of sulphate of iron produce a deep black. In each of these cases, the change of colour is owing to the forma- tion of a new chemical compound. 5. A change in specific gravity and temperature. Exp. Sulphuric acid and water when combined have the specific grav- ity of the compound greater than that of the mean. Exp. Surround a phial with some tow and place a piece of phospho- rus within the tow and against the phial. The phial being half full of water, add a small quantity of sulphuric acid ; the heat produced will be sufficient to fire the phosphorus. 6. Intense ignition. Exp. Add a few drops of sulphuric acid to a mixture of chlorate of potash and sugar. 24 AFFINITY. Exp. Add sulphuric acid to phosphorus and chlorate of potash un- der water. There are several circumstances which influence and modify the op- eration of affinity. 1. A p r evious state of combination. This generally diminishes, and often prevents chemical action. 2. Cohesion. This, as has been already remarked, often acts as an antagonist power to [chemical affinity. Hence the utility of mechani- cal processes which diminish this force. Solid antimony is but slowly acted upon by chlorine gas, but when in the state of fine powder, it takes fire as soon as it touches the gas. Hence also liquidity fa- vours chemical action, the cohesive power being comparatively so tri- fling as to present no appreciable barrier to affinity. There are, however, some instances in which two solids act chemically on each other. 3. Caloric. This has a very important influence over chemical ac- tion : sometimes increasing it, at other times destroying or subverting it. Thus bodies which unite at one temperature refuse to combine or remain combined at another temperature. Lead shavings do not de- compose cold nitric acid, but when heat is applied, rapid decomposition ensues. An increase of temperature favours chemical action by its ef- fect in overcoming the force of cohesion ; but this explanation is not of universal application. 4. The electric state of bodies. Those bodies which are in the same electric state do not combine, those in different electric states do com- bine. Indeed so intimate is the connexion which subsists between electricity and chemical action, that they have been supposed by some to depend upon the same power. Hence the Electro -Chemical Theory of Davy, which will be more fully noticed hereafter. 5. Specific gravity. When two bodies have different specific gravi- ties, they tend to separate. If their affinity is very feeble, they can not be made to combine. Oil and water, and mercury and water, are familiar examples. The influence of specific gravity over chemical ac- tion is, however, quite limited. 6. The intervention of a third body. This sometimes increases and sometimes destroys chemical action. Oil and water are made to unite upon the addition of an alkali. Alcohol added to a saturated solution of sulphate of soda or nitrate of potassa combines with the water, and the crystallization of the salt instantly takes place. This has been called disposing or predisposing affinity, which to say the least, is an extremely vague term. 7. Mechanical action or compression. This frequently modifies chemical action in a great degree, particularly in the case of gases and liquids. Thus water when under high pressure combines with a greater quantity of carbonic acid than when the pressure is less. The com- pound of carbonic acid and lime, known under the name of chalk, may be decomposed by the simple application of an intense heat ; but under strong pressure, a heat may be applied sufficient to melt the chalk without expelling the carbonic acid. It is this principle, (the influ- ence of pressure in opposing chemical decomposition,) that is the foundation of Dr. Hutton's ingenious Theory of the Earth. Henry's Chem. llth ed. i. 65. AFFINITY. 25 8. Quantity of matter or mass. The influence of quantity of matter over affinity appears to be now generally admitted. If one body A, unites with another body B, in several proportions, that compound will be the most difficult of decomposition which contains the smallest quantity of B. Of the three oxides of lead, for instance, the peroxide parts most easily with its oxygen by the action of caloric ; a higher temperature is required to decompose the deutoxide, and the protoxide will bear the strongest heat of our furnaces, without losing a particle of its oxygen. The influence of quantity over chemical attraction may be further illustrated by the phenomena of solution. When equal weights of a soluble salt are added in succession to a given quantity of water, which is capable of dissolving almost the whole of the salt employed, the first portion of the salt will disappear more readily than the second, the second than the third, the third than the fourth, and so on. The af- finity of the water for the saline substances diminishes with each ad- dition, till at last it is weakened to such a degree as to be unable to overcome the cohesion of the salt. The process then ceases and a satu- rated solutiou is obtained. Quantity of matter is employed advantageously in many chemical operations. If, for instance, a chemist is desirous of separating an acid from a metallic oxide, by means of the superior affinity of potassa for the former, he frequently uses rather more of the alkali than is sufficient for neutralizing the acid. He takes the precaution of em- ploying an excess of alkali, in order the more effectually to bring eve- ry particle of the substance to be decomposed in contact with the de- composing agent. But Berthollet has attributed a much greater influence to quantity of matter. His views, however, do not appear to be supported by facts. Berthollet Chem. Stat. Turner's Chem. Davy's Elements. Affinity is of two kinds 1. SIMPLE. 2. ELECTIVE. Simple affinity is the union of the constituent atoms of a compound without causing decomposition. It is sometimes also called combina- tion. Thus the combustion of carbon in oxygen gas produces by the mere union of these two elements carbonic acid. So also sulphur- ic acid and potassa by mere combination form sulphate of potassa. Elective Affinity is of two kinds, simple and compound, or single and double. An important law of affinity, and which indeed is the basis of almost all chemical theory, is that the same body has not the same force of affinity towards a number of others, but attracts them unequally. Thus when sulphuric acid is added to a solution of nitrate of lime, (composed of nitric acid and lime,) the lime leaves the nitric acid and combines with the sulphuric, forming a sulphate of lime. This is an example of what is termed in chemistry, a simple decomposition. The lime in this case is considered as making an election of the sulphuric acid in preference to the nitric ; and this affinity has been called single elective affinity. When one of the substances falls down in the state of powder, it is termed a precipitate. Other illustrations of single elective affinity. Exp. Add sulphuric acid to muriate of soda, muriatic acid is disen- gaged and sulphate of soda remains. 26 AFFINITY. Exp. To a solution of nitrate of silver add mercury ; the nitric acid will in a short time leave the silver and combine with the mercury. To the nitrate of mercury thus formed, add lead, the nitric acid will leave the mercury and unite with the lead. To this last add copper, and nitrate of copper will be produced. Upon the discovery of this important law, it occurred to Geoffrey, a French chemist, that tables might be constructed, which should ex- hibit the relative forces, of the attraction of any body towards others. The substance, whose affinities are to be thus expressed, is merely placed at the head of a column separated from the rest by a horizontal line. Beneath this line are arranged the different substances for which it has any attraction, in an order corresponding with that of their res- pective forces of affinity ; the substance which it attracts most power- fully being placed nearest to it, and that for which it has the least affin- ity at the bottom of the column. The following series exhibiting the affinities of sulphuric acid for the alkalies and alkaline earths, will serve as an example. SULPHURIC ACID. BARYTA, STRONTIA, POTASSA, SODA, LIME, AMMONIA, MAGNESIA. Double Elective Affinity, This kind of affinity takes place when two bodies, each consisting of two principles are presented to each other, and mutually exchange a principle of each ; by which means two new bodies or compounds, are produced, of a different nature from the original compounds. In this case it frequently happens, that the compound of two principles cannot be destroyed, either by a third or a fourth separately applied ; whereas if this third and fourth be combined, and placed in contact with the former compound, a decomposition or change of principles will ensue. Thus when lime- water is added to a solution of sulphate of soda, no decomposition happens, because sulphuric acid attracts soda more strongly than it does lime. If nitric acid be applied to the same compound, still its principles remain undisturbed, because the sulphuric acid attracts soda more strongly than the nitric. But if lime and nitric acid previously combined, be mixed with the sulphate of soda, a double decomposition is effected and two new compounds are produced. These changes may be expressed by the following diagram, contrived by Bergman. Nitrate of Soda. Sulphate \ Soda. Nitric acid. / Nitrate of < V of Soda / Sulphuric acid. Lime. \ Lime. Sulphate of Lime. On the outside of the vertical brackets are placed the original com- pounds, (sulphate of soda and nitrate of lime,) above and below the LAWS OF COMBINATION. 27 horizontal lines, the new compounds produced, (nitrate of soda and sulphate of lime, ) the upper line being straight indicates that the ni- trate of soda remains in solution, the dip of the lower line, that the sul- phate of lime is precipitated. A piece of sheet lead immersed in a solution of sulphate of zinc pro- duces no change, because the sulphuric acid has a stronger affinity for the zinc than for the lead. Neither does acetic acid produce any change. But when acetate of lead is added, two new compounds, viz. sulphate of lead and acetate of zinc are the result. In the above cases, as in many others, we can easily explain the de- compositions which take place. There are two distinct sets of affini- ties, one tending to prevent any change of composition, as between the sulphuric acid and the soda in the former case, and between the nitric acid and the. lime; termed by Kirwan the quiescent affinities. Another set tending to produce a decomposition as between the nitric acid and the soda, and the sulphuric acid and the lime, are termed the divellent affinities, and which in this case are the most powerful. But other cases of double decomposition cannot be explained in this man- ner. As for instance, carbonate of baryta and sulphate of potassa mu- tually decompose each other. 1?. Phillips Quart. Jour. i. 80. Dulong in Phil. Magazine, 41. REFERENCES. The article * Chemical Decomposition/ in the Supplement o the Encyclopedia Britannica^ by Dr. Thomson. Turners Chemistry, sec- tion on Affinity. Murray's Chemistry, Book I, on Attraction. Davy's Ele- tments of Chemical Philosophy. Ure's Chemical Dictionary, Art. Attrac- tion. Branded History of Chemistry. Henrys C Ministry, llth ed. 1. Bishop Watson on the various phenomena attending the solution of salts, in Phil. Trans. 1770, 235, and in Chemical Essays, r. 43. Gay Lussac on the solubility of the salts in water. Ann. of Phil. xv. 1- SECTION III. OP THE PROPORTIONS IN WHICH BODIES COMBINE ; AND OF THE ATOMIC THEORY. In the chemical combination of bodies with each other, the follow- ing circumstances deserve to be mentioned. I. Some bodies unite in all proportions ; for example, water and sul- phuric acid, and water and alcohol. II. Other bodies combine in all proportions, as far as a certain point, beyond which, combination no longer takes place. Thus water will take, up successive portions of common salt, until at length it becomes incapable of dissolving any more. In cases of this sort, as well as in those included under the first head, combination is weak and easily destroyed, and the qualities, which belonged to the components in their separate state, continue to be apparent in the compound. It is necessary however, to remark, that these two deductions, though they appear to be warranted by a general survey of the phe- nomena, are not absolutely and strictly true ; for though some acids, for instance, appear to unite with water in every proportion, yet there are certain relative qualities of water and acid which form the most energetic compounds, distinguished by their permanency and peculiar properties Henry's Chem. i. 43. 28 LAWS OF COMBINATION. III. Some bodies unite in one proportion, or in a few proportions only. Chlorine and hydrogen combine in no other proportions than those constituting muriatic acid. On the other hand, carbon and oxygen unite in two proportions ; oxygen and nitrogen in five proportions, &c. The greatest number of compounds that any two substances are known to produce, is six, if we except those noticed in the preceding paragraphs. The combination of bodies that unite in this manner, is regulated by the following laws : I. The composition of bodies is fixed and invariable. A compound substance so long as it retains it characteristic properties, must al- ways consist of the same elements united together in the same pro- portion. Muriatic acid, for example, is always composed of 35.45* parts by weight of chlorine, and one of hydrogen ; no other elements can form it, nor can its own elements form it in any other proportion. Water, in like manner, is formed of 1 part of hydrogen and 8 of oxygen ; and were these two elements to unite in any other propor- tion, some new compound, different from water, would be the product. The same observation applies to all other substances, however com- plicated, and at whatever period they were produced. Thus, sul- phate of baryta, whether formed ages ago by the hand of nature, or quite recently *by the operations of the chemist, is always composed of 40 parts of sulphuric acid and 76.7 of baryta. This law, in fact, is universal and permanent. Its importance is equally manifest. It is the essential basis of chemistry, without which the science itself could have no existence. Turner's Chem. II. The relative quantities in which bodies unite, may be expressed by proportional numbers. Thus 8 parts of oxygen unite with one part of hydrogen, 16 of sulphur, 35.45 of chlorine, 40 of selenium, and 108 parts of silver. Such are the quantities of these five bodies which are disposed to unite with 8 parts of oxygen ; and it is found that when they combine with one another, they unite either in the proportion expressed by those numbers, or in multiples of them according to the third law of combination. Thus sulphuretted hydrogen is composed of 1 part of hydrogen and 16 of sulphur, and bisulphuretted hydrogen, of one part of hydrogen to 3'2 of sulphur ; 35.45 of chlorine unite with one of hydrogen, 16 of sulphur, and 108 of silver, and 40 .parts of selenium with 1 of hydrogen, and 16 of sulphur. From these examples it is manifest, that bodies unite according to proportional numbers ; and hence has arisen the use of certain terms, such as proportions, combining proportions, proportionals, or equiva- lents to express them. Thus the combining proportions of the sub- stances just alluded to are Hydrogen 1 Oxygen 8 Sulphur 16 Chlorine 35.45 Selenium 40 Silver ........ 108 This law also applies to compound bodies. Thus water is composed of one proportional or 8 parts of oxygen, and one proportional or 1 * I adopt, vrith few exceptions, the equivalent numbers of Dr. Turner. LAWS OF COMBINATION. 29 part of hydrogen, and hence its combining proportion is 9. The pro- portional of sulphuric acid is 40, because it is a compound of one proportion or 16 parts of sulphur, and three proportions or 24 parts of oxygen. And so in all other cases not only of compounds but of two "elements of salts; the latter of which indeed, furnish the most strik- ing illustrations of this subject. III. When one body A unites with another body E in two or more pro- portions, the quantities of the latter, united to the same quantity of the former, bear to each other a very simple ratio. These ratios of B may in all cases be represented by one or other of the two following se- ries : 1st. A unites with 1, 2, 3, 4, 5, &c. of B. 2d. A unites with 1, 1 1-2, 2, 2 1-2, &c. of B. The following table exemplifies the first series. Water is composed of ... Hydrogen 1 . . Oxygen 8 ) 1 Deutoxide of Hydrogen ... Do. 1 . . Do. 16 $ 2 Carbonic Oxide Carbon 6 . . Do. 8)1 Carbonic Acid Do. 6 . . Do. 16 } 2 Nitrous Oxide Nitrogen 14 .. Do. 16 ^ 1 Nitric Oxide Do. 14 . . Do. 16 | 2 Hyponitrous Acid Do. 14 .. Do. 24 } 3 Nitrous Acid ...... Do. 14 .. Do, 32 I 4 Nitric Acid Do. 14 .. Do. 40 j 5 It will be observed that in all the above cases the ratios of the oxy- gen are expressed by whole numbers. In water the hydrogen is combined with half as much oxygen as in the deutoxide of hydrogen, and hence the ratio is as one to two. The same may be said of car- bonic oxide and carbonic acid. In the compounds of nitrogen and oxygen the latter is in the ratio of 1,2, 3, 4, & 5. This ratio also extends to the combinations of combustibles with each other and to the salts. It may be illustrated by a very simple experiment, first made by Dr. Wollaston ; let a given weight of bicarbonate of potassa be thrown into a tube over mercury, and diluted sulphuric acid suffi- cient to cover it, be introduced into the tube, when a certain volume of carbonic acid gas will be disengaged ; let an equal weight of the carbonate be treated in the same way and it will be found to give off exactly half as much carbonic acid gas. The second series is exemplified in the following compounds : Protoxide of iron consists of Iron 28 Oxygen 8)1 Peroxide .... Do. 28 Do. 12 $ H Protoxide of lead . . . Lead 103.5 Do. 8 ) I Deutoxide . . . . Do. 103.5 Do. 12 > H Peroxide . . . . Do. 103.5 Do. 16)2"" Arsenious Acid . . . Arsenic 37.7 Do. 12 ) H Arsenic Acid ... Do. 37.7 Do. 20 $ 2| Hypo-Phosphorous Acid . Phosphorus 15.7 Do. 4 ) Phosphorous Acid . . Do. 15.7 Do. 12j>H Phosphoric Acid . . Do. 15.7 Do. 20 ) 2| Both of these series, which together constitute the third law of com- bination, as Dr. Turner remarks, result naturally from the operation of the second law. The first series arises from one proportion of a 30 LAWS OF COMBINATION. body uniting with 1, 2, 3 or more proportions of another body. The second series is a consequence of two proportions of one substance combining with 3, 5, or more proportions of another. Thus if two proportions of phosphorus unite both with 3 and 5 proportions of. oxygen, we obtain the ratio of 1 1-2 to 2 1-2 ; and should one propor- tion of iron combine with one of oxygen, and another compound be formed of two proportions of iron to three of oxygen, then the oxygen united with the same weight of iron would have the ratio, as in the table, of 1 to 1 1-2. And the compounds of lead and phosphorus with oxygen, afford examples of the same kind. Turner's Chem. 4th ed. IV. Gases or airs unite in the most simple ratios of volume or bulk. This important fact was discovered by Gay Lussac. Thus 1 volume unites to 1, or 1 to 2, or 1 to 3, &e. In combination by weight there is no simple multiple ratio between the weight of the elements in the first compound ; the oxygen for example , is not equal to, or twice or thrice, &c. the weight of the nitrogen in nitrous oxide, or of carbon in carbonic oxide ; it is only when there is a second compound formed of the same elements, that the new proportions of the body which has been added, become a multiple of the first. But in combinations by volume, the bulk of one of the gases in the first, as well as in the other compounds, is always equal to, or is some multiple of that of the other : thus, 100 of oxygen combine with 200 hydrogen. 100 ammonia " " 50 carbonic acid. 100 ammonia " " 100 carbonic acid. 100 nitrogen " " 50,100,150,200. and 250 volumes of oxygen. Another curious fact established by Gay Lussac is that the diminu- tion of bulk, which gases frequently suffer in combining is also in a very simple ratio. Thus the four volumes of which ammonia is con- stituted, (3 volumes of hydrogen and 1 of nitrogen,) contract to one half or two volumes when they unite. There is a contraction to two- thirds in the formation of nitrous oxide, to 1 half in the formation of sulphuretted hydrogen, and to 1 half in that of sulphurous acid &c. [For a more full exposition of this law see Henry's Chem. i. 55.] V. The respective quantities of any number of alkaline, earthy or me- tallic bases required to saturate a given quantity of any add, are always in the same ratio to each other, to ichatsoevcr acid they be applied. This law appears to have been discovered by Richter of Berlin, in 1792, and has been fully confirmed by succeeding chemists. For an illustration of it let us take potassa and soda for the bases, and sulphuric acid for the acid. Having found by experiment that tv/o parts of soda will saturate as much of the acid as three of the potash, their power of saturating every other acid is in the ratio of two to three. Thus if we should ascertain by experiment that it required 4 parts of soda, to neutralize any given quantity of nitric acid, we should know without experiment that it would require 6 parts of potash to neutralize the same amount of nitric acid. Two parts of soda are therefore said to be equivalent to three of potash. This rale applies as well to all the acids as to the bases, and greatly facili- tates chemical investigations. Thus if we have 100 bases and 50 acids, we have only to apply each of these bases to any one of the acids, and one of the bases to all the acids, to ascertain the amount of all the LAWS OF COMBINATION. 31 other bases necessary to saturate all the acids. Hence we need only perform 149 experiments instead of 5000 which we should be obliged to do without a knowledge of this law. By arranging the numbers indicating the relative combining weights or equivalent quantities of different substances on a moveable scale, and writing against them the names of the substances they respectively represent, Dr. Wollaston constructed a Scale of Chemical equivalents, an instrument stamped with the accuracy and ingenuity of its author, and of great value to the practical chemist. Phil. Trans. 1814. In this instrument the slide is a line of numbers on which equal dis tances denote equal ratios. The distance between 50 and an 100, for example, is the same as that between 1 and 2, because 50 : 100 : 1 : 2. Opposite to the numbers on this scale, are written the names of the bodies of which the numbers themselves are the equivalents ; then the distances between these bodies are in like manner the measures of the ratios of their combining quantities, and will be the same with the distances between the numbers. But the chief value of the ar- rangement is, that by means of the slide, we can at once solve a great number of cases which arise out of combinations and decompo- sitions, the solution of which in the ordinary way would require a tedious number of computations. As the proportional numbers merely express the relative quantities of different bodies which unite together, it is of no consequence what figures are employed to express them, provided the relation is strictly observed : Thus Dr. Thomson makes oxygen 1, so that hydrogen is 8 times less than unity, or 0.125, carbon 0.75, and sulphur 2. Dr. Wollaston in his scale of equivalents, fixes oxygen at 10, by which hydrogen is 1.25, carbon 7.5, &c. But the greatest number of chem- ists call hydrogen unity and therefore oxygen 8. This is much the most simple, and has been adopted in the scale of equivalents con- structed by Professor Henry and myself, and also in the present work. A circular table of chemical equivalents is described in Brande's Jour. Hi. 391. The utility of being acquainted with the important laws which have here been given is almost too manifest to require notice. Through their means our knowledge of the composition of bodies is much sim- plified. The exact quantities of bodies necessary to produce a desired effect can also be at once determined with certainty, and these laws thus become highly useful both in the practice of the chemical arts and in the operations of pharmacy. The same knowledge, moreover, affords the best guide to the analyst, by which to judge of the accura- cy of his results. Thus a powerful argument in favor of the accuracy of an analysis is derived from the correspondence of its results with the laws of chemical combination. On the contrary, if it form an ex- ception, it may be considered doubtful, and we may hence be led to detect an error, which might otherwise have escaped notice. It should be observed that these laws are deduced from experiment, and the student should be careful to keep them distinct from the theo- ry which has been proposed to account for them. Whatever may be the fate of this theory, it cannot affect these laws, though the progress of discovery may render it necessary that they should be modified. ATOMIC THEORY. The foregoing are the principal facts, which the experimental ex- aminations of chemical combinations and decompositions have un- 32 ATOMIC THEORY. folded. To account for these facts a theory has been invented which is denominated the Atomic Theory ; which derives much probability from the complete solution it affords of the laws of attraction. For the full developement of this theory we are indebted to the labors of Mr. Higgins and Mr. Dalton. The Atomic Theory proceeds on the supposition that every body is an assemblage of minute, solid particles, without considering whether a farther division of them be possible or not. The question of the in- finite divisibility of matter is not therefore involved ; the theory only assumes that matter is not, in fact infinitely divided. These undivid- ed particles are the atoms in question. It is also assumed that these atoms differ from each other in weight, whether this difference is owing to specific gravity or size, or both together, is not material. Thomson's First Pi in. v. 1. It is further supposed that though we appear, when we effect a chemical union, to operate on masses, the combination only takes place between these ultimate particles or atoms.* To apply this theory, let us take the compounds of nitrogen and oxygen, which are five, differing much from each other ; viz : nitrous oxide, nitric oxide, hyponitrous acid, nitrous acid and nitric acid. If we take a given quantity of nitrogen, say 14 r grains, and combine it with 8 grains of oxygen, we form nitrous oxide ; with 8 more, we have nitric oxide ; with 8 more, hyponitrous acid ; with 8 more, nitrous acid; with 8 more, nitric acid. Now supposing that these several compounds are formed by the union of a certain number of atoms of oxygen, the latter number varying in the several compounds, the first compound is probably formed of an equal number of atoms of each element. It is plain that one atom of nitrogen can combine with no less than one atom of oxygen, because the atoms are, by the hypothesis, indivisi- ble, or at least undivided. Nor is it probable, that, in forming the first compound, one atom of nitrogen combines with any more than one of oxygen ; for this union is the most simple and hence the most natural. The first compound then being formed of one atom of ni- trogen and one of oxygen, it is plain that no new compound can be formed, until we add at least one atom of oxygen ; and hence the reason is evident why in all the higher combinations the quantity of oxygen is just twice, or thrice, or four times that in the lowest, there being respectively just twice, or thrice, or four times as many atoms of oxygen. In cases where two bodies unite only in one proportion, it is assum- ed that they unite atom to atom ; and hence if we determine the rela- tive weights of the masses, which enter into combination, we can easi- ly determine the relative weights of the atoms ; the ratio being the same. Thus chlorine and hydrogen combine only in one proportion, forming muriatic acid. The volume of each is the same, but the weight of the volume of chlorine is 35.45 times greater than that of the volume of hydrogen ; hence the atom of chlorine is to that of hydrogen as 35.45 to 1. * An ingenious method of illustrating this theory has been invented by Professor Hadley of the Medical College of the Western District. Jt con- sists of a box containing a number of cubical blocks, which are variously colored to represent the principal elementary substances. By these represen- tatives of atoms, the laws of combination may be strikingly presented to the student, and many of the more complex chemical decompositions rendered aparent. ATOMIC THEORY. 33 \ The weight of the atoms of all other bodies is ascertained in the same manner. Thus an atom of carbon is six times, and an atom of sulphur 16 times heavier than that of hydrogen ; and this is precisely the reason why they unite with each other in the proportions express- ed by those numbers. What are called proportional or equivalent numbers, are therefore, in fact nothing else but the relative weights of atoms.* The two assumptions, which indeed constitute the basis of this the- ory, would be considered gratuitous, were it not for the complete explanation which they afford of the laws of definite proportions. They are further supported by the fact, that the weight of an atom comes out the same when deduced from different premises. This theory is also confirmed by the observations of Dr. Wollaston, in his essay on the finite extent of the atmosphere. [Phil. Trans. 1822.] And another argument which appears to amount almost to demon- stration, is deducible from the peculiar connexion noticed by Pro- fessor Mitscherlich, between the form and composition of certain substances. Ann. dc, Chim. et de Pkys. xiv. 172, xix. 350. and xxiv. 264 and 365. There is a seeming objection to the atomic theory in those cases where one proportion of one body combines with one proportion and a half of another. In such cases, however, it is supposed that two atoms of the one are combined with three atoms of the other, by which the exact ratio is preserved, and the idea of a fraction of an atom avoided. If the atoms occupied the same space when in a gaseous form, they might be represented by volumes, and their proportional numbers would be identical with their specific gravities. This, however, is not the case. The atom of hydrogen, and several other gaseous sub- stances occupy twice the space of an atom of oxygen ; but in such cases it is easy to calculate the specific gravity by multiplying the atomic weight by half the specific gravity of oxygen. It might at first view appear that the atoms and volumes could be made to correspond, if we considered water as a compound of two atoms of hydrogen and one atom of oxygen. This has been propos- ed by Sir H. Davy, and advocated by other chemists ; but it increas- es instead of removing the difficulty. Thus sulphuretted hydrogen, on this supposition, must be considered as consisting of one atom of sulphur and two atoms of hydrogen, while it is composed of one volume of each of the constituents. Muriatic acid gas would be one atom of chlorine and two atoms of hydrogen, though constituted in like manner of one volume of each gas. And the same remark would be applicable to hydriodic acid, hydrocyanic acid, and indeed to most other compound gases containing hydrogen. For this and other reasons which might be given, water is considered a compound * These terms have been proposed to avoid theoretical annunciations; but the term atom originally proposed by Mr. Dalton is generally employed ia this work as being the most convenient. And 1 thin!; Dr. Thomson has cor- rectly remarked that " unless we adopt the hypothesis with which Da! ton set out, namely that the ultimate particles of bodies are atoms incapable of far- ther division, and that chemical combination consists in the union of these atoms \vith each other, we lose all the new light which the atomic theory throws upon chemistry, and bring our notions back to the obscurity of the days of J3ermau and Bertho!let." History of Chemistry. 34 HEAT OR CALORIC. of one atom of hydrogen and one atom of oxygen, though the vol- ume of oxygen is only one half that of the hydrogen*. The learner will now see the reason why the atomic weight of oxy- gen is fixed at 8 compared to hydrogen 1, although its specific grav- ity is 16 when compared to the same substance as unity. Laws of Berzelius. The peculiar views of this celebrated chemist, are stated in an 8vo. volume entitled, Essai sur la Theorie des Proportions Chimiques. Paris , 1819 ; and also in the article Proportions, Determinate , of Dr. Brews- ter's Edinburgh Encyclopaedia. The facts contributed by this cele- brated chemist, in proof of the laws of definite and multiple propor- tions, are of the highest importance. But in deducing general laws he does not appear to have been equally fortunate. At least they have not gained much sanction. It is to be regretted, moreover, that his nomenclature is shrouded in language and symbols calculated to confuse and perplex the learner. Though I shall constantly avail myself of the experimental investigations of this able chemist, I shall be content with referring those who wish to study his general theories to the works above quoted, and to Turner's Chemistry, 2d edition. Berzelius' Table of Atomic Weights, and the explanation of his symbols, are also contained in the appendix to the 2d volume of Henry's Chemistry. REFERENCES. Turner's Chemistry. Ure j s Cheat. Dictionary, Art. Equi- valent. Professor Olmstead on the present state of Chemical Science. Sillimart's Jour. xii. 1 ; a paper containing a very lucid explanation of the Laws of Combination and of the Atomic Theory, from which some of the ideas in. the above section are obtained. McNevin on the Atomic Theory. Thomson's Fi-st Principles, v, 1. Dalton's neio system of Chemical Philo- sophy, v. 1. Berthollefs Chemical statistics. Some interesting papers con- cerning the Atomic Theory, by Berzelius, Dalton and Thorn-son, will be found in the %d, 3d, 4th and 5lh volumes of the Annals of Philosophy. J9a- vy's Element's of Chem. Phil. Thenard's Traite de Chim. 5th eel. v. 1 and 5. Prout on the relations between the specific gravity of Gaseous Bodies, and the weights of their Atoms. Ann. of Phil. vi. 321. vii. 111. Thomson and Gay Lussac on the same subject same work, vii. 343. ix. 15. Murray on the relation of the Law of Definite Propositions in Chemical Combination, to the constitution of Acids, Alkalies and Earths. Ann. of Phil. xiv. 281. 344.. Daubeny on the Atomic Theory. CHAPTER II. HEAT OR CALORIC. The term Heat, in common language, has two meanings : in the one case it implies the sensation experienced on touching a hot body ; in the other, it expresses the cause of that sensation. To avoid any ambiguity that may arise from the use of the same expression in two such different senses, the word caloric (from the latin color, heat) has been adopted to designate exclusively the principle or cause of the * Mr. Finch in his paper on the Atomic theory, ( Silliman's Jour. xiv. 24.) has evidently overlooked all these difficulties. NATURE OF CALORIC. 35 feeling of heat ; but to prevent repetition, the terms caloric and heat are both occasionally employed to designate the cause in question. This subject will be treated of in the following order : 1. THE NATURE OF CALORIC. 2. ITS COMMUNICATION. 3. ITS DISTRIBUTION. 4. ITS EFFECTS. 5. SPECIFIC CALORIC. 6. THE SOWRCES OF CALORIC. SECTION I. NATURE OP CALORIC. Upon this point philosophers are divided into two sets ; the one maintaining that caloric is a mere property of matter ; the other that it is a distinct substance. The former is an old opinion, but was adopted by Sir H. Davy, and is at the present time quite generally received in France. The latter was maintained by Sir Isaac New- ton ; and as this affords a more easy explanation of most of the chemical phenomena, it will be adopted in the present treatise. Caloric, on the supposition of its being material, is a subtle fluid, the particles of which repel one another, and are attracted by all other substances. It is imponderable ; that is, it is so exceedingly light that a body undergoes no appreciable change of weight, either by the ad- dition or abstraction of caloric. It is present in all bodies, and can not be wholly separated from them. For if we take any substance whatever, at any temperature, however low, and transfer it into an atmosphere, whose temperature is still lower, a thermometer will in- dicate that caloric is escaping from it. That its particles repel one another, is proved by observing that it flies off from a heated body ; and that it is attracted by other substances, is equally manifest from the tendency it has to penetrate their particles and be retained by them. Turner. Caloric has also been defined as the agent to which the phenomena of heat and combustion are to be ascribed. So far as chemical agencies are concerned it is, 1st. An antagonist power to cohesive attraction ; and, 2d. It concurs with, and increases elasticity. Caloric, in many of its properties, resembles light. As for example, in those of refraction, reflection and radiation, and in the repulsion which exists between its particles. This latter property indeed, is so striking that caloric is often treated of under the appellation of calorific repulsion. As the presence of caloric produces the sensation of heat, so its ab- sence produces that of cold. This last sensation, therefore, is not to be considered as produced by any particular agent, but as altogether a negative expression. Caloric exists in two states viz : free or sensible, and, latent or corn- lined. In the former state it is capable of exciting the sensation of heat, and of producing expansion in other bodies, and to it the term caloric of temperature has also been applied. By the term temperature, we are to understand the state of a body relatively to its power of excit- ing the sensation of heat, and occasioning expansion ; effects, which in all probability, bear a proportion to the quantity of free caloric in a 36 COMMUNICATION OF CALORIC. given space, or in a given quantity of matter. Thus what we call a high temperature may be ascribed to the presence of a large quantity of free caloric; and a low temperature to that of a small quantity. We are unacquainted, however, with the extremes of temperature ; and may compare it to a chain, of which a few of the middle links only are exposed to our observation, while its extremities are far re- moved from our view. Henry's Chem. i. 82. In the latter state, caloric exists either in combination with bodies or in something resembling it. Under these circumstances, it does not possess its distinguishing properties cannot be discovered by our senses or by the thermometer, and produces important and sometimes permanent changes in the bodies with which it combines. The dif- ference between these two states may be shown by the following ex- periment : Exp. Place two vessels of thin glass, the one containing water and the other a small portion of sulphuric acid, in contact with the bulb of an air thermometer. Allow them to remain in this situation for a short time, to show that the thermometer is not affected by them. Now empty the sulphuric acid into the water, when it will be seen that the liquid in the thermometer descends, owing to the expansion of the air by the caloric which has been rendered free by the mixture. The common fire syringe offers another striking illustration of the difference between combined and free caloric. REFERENCES. For a notice of facts and reasonings concerning the nature of Caloric, see Thomson's Chemistry, vol. 1 / and Library of Useful Know- ledge, Art. Heat. Professor Hare's paper, on the materiality of Heat, and. the discussion on this subject between him and Prof. Olmslead. Sillimaifs Amer. Jour. vols. iv. xi. xii. xiii. SECTION II. COMMUNICATION OF CALORIC. Caloric is radiated in all directions, and moves with great velocity. It is also absorbed by certain bodies, and when it has thus entered, it makes its way through the body. In the latter case its motion is comparatively slow. Hence caloric is communicated, 1. BY RADIATION. 2. BY CONDUCTION. KADIATION. When the hand is placed above a heated ball, or a fire, the sensa- tion of heat is perceived ; and the same thing also takes place when the hand is placed below the source of caloric. Now as nothing in- tervenes in the last case but the air, and as this fluid, when caloric is communicated to it expands arid rises, the impression cannot be owing to the transmission of hot air to the hand ; but rather to the action of the particles of caloric which are supposed to be thrown off in all directions. Bodies capable of discharging caloric in this way are called Radiating ; and the principle which is thus projected, Radi- ant Caloric. Radiant Caloric is reflected. This fact can be shown in a familiar manner, by standing at the side of a fire in such a position that the caloric cannot reach the face di- COMMUNICATION OF CALORIC. 37 rectly, and then placing a plate of tinned iron opposite the grate and at such an inclination as permits the observer to see in it the reflection of the fire ; as soon as it is brought to this inclination, a distinct im pression of heat will be perceived upon the fa'ce. If a line be drawn from the heated substance to the point of a plane surface from which it is reflected, and a second line from that point to the spot where it produces its effect, the angles which these lines form with a line per- pendicular to the reflecting plane are equal to each other, or in phi- losophical language, the angle of incidence is equal to the angle of re- , flexion. Turner. This may be illustrated in a still more striking manner, by the ex- periment devised by Pictet, which is, to take two concave mirrors of planished tin or copper, and to place them at a distance of from 9 to 12 feet apart, with their concave surfaces towards each other. If now a hot ball or a small basket of coals is placed in the focus of one mirror, it will instantly affect a thermometer in the focus of the other ; or if a piece of phosphorus be substituted for the thermometer, it will soon be kindled. Now these phenomena cannot be explained upon the supposition that the heat of the ball or of the coals is communicated directly to the thermometer through the medium of the air which intervenes ; for upon this hypothesis, a point intermediate between the two mir- rors would be of a higher temperature than that directly in the focus, which is not the case. There must, therefore be something emanating from the ball or the coals which is reflected by the mirrors, and is con- centrated also into a focus, so as to affect the thermometer and the phosphorus. When the heated ball is placed near the mirror, rays of heat fly off from it in straight lines to the mirror, by which they are instantly re- flected again In straight lines to the opposite one, where they are also reflected, and are thus brought to a point where the heating effect is produced. The distance at which this takes place, depends of course on the form of the mirror ; and the effect is much greater when burn- ing charcoal is employed instead of the heated ball. But the thermo- meter is affected even when a glass of boiling water is substituted for the heated ball. Radiant Caloric is absorbed. This may be shown by placing a thermometer before the fire or any heated body, when the mercury will be seen to rise in the stem. And it has been ascertained that the intensity of effect diminishes according to the squares of the distance from the radiating point. Thus the thermometer will indicate four times less heat at two inches, nine times less at three inches, and sixteen times at four inches, than it did when it was only one inch from the heated substance. It is therefore evident that a hot body placed in the air is the centre of a multitude of calorific rays ; that these rays traverse the air almost without resistance ; and that when they fall upon the surface of a sol- id or liquid substance they are either reflected from it and receive a new direction, or lose their radiant form altogether, and are absorbed. With regard to caloric then, three powers may be recognized as belonging to bodies, viz. 1. The power of emitting or radiating caloric ; 2. Tha power of absorbing ; and 3. The power of reflecting caloric. These powers appear to depend chiefly upon the temperature, and polish upon the surface of the body : their nature having but little influence. Temperature. The higher a body is heated, the greater is its radia- 38 COMMUNICATION OF CALORIC- ting power; for then the caloric of the body has greater tension, or in other words, makes more effect to escape. Polish of surface. When even a large quantity of radiant caloric falls upon a metallic body highly polished, the body is scarcely heat- ed ; from which we infer that all the caloric has been reflected. But if we blacken the surface of this body and expose it again to the same amount of caloric, it becomes considerably heated ; and in this case nearly all the caloric will be absorbed. Polish influences the radiating, as well as the absorbing and reflect- ing power. This is strikingly illustrated by the experiment of Mr, Leslie. He coated one side of a canister with lampblack, covered a second with writing paper, applied to a third a pane of glass, and left the fourth bright and polished. The canister was now filled with boiling water and placed in the focus of the mirror. When the me- tallic surface was presented to the reflector, the impression upon the thermometer amounted to 12 Z ; from the glass surface it was equal to 90 ; from the papered side 98 ; and 100 from the lampblack. The powers of bodies to radiate and absorb caloric are directly proportional to each other. Those which absorb with the most ease also radiate with the greatest facility. If in the usual arrangement, the bulb of the thermometer be coated with tin foil, or even gold leaf, the impression of the radiant caloric will be exceedingly slight ; if the bulb be naked, the effect will be much greater, but if it be coat- ed with lampblack, the action on the instrument will reach its maxi- mum. Now experiments have proved that lampblack absorbs more than glass, and glass more than the metals, which is exactly the order of their radiating powers. Leslie's Inquiry. The powers of radiation and reflection are inversely proportional to each other. Those bodies which reflect the most, radiate the least, and those which radiate the most, reflect the least caloric. Thus metals reflect heat with great facility ; but if a glass mirror be substi- tuted for the metallic reflector, the positions of the hot body and the thermometer being the same, the effect will be considerably diminish- ed, and if the surface of the glass be coated with lampblack, no action upon the thermometer will be perceived. The vast superiority of metallic bodies over glass in reflecting ca- loric may be proved by a very simple experiment. In the focus of the commonest tin reflector, if at all approaching to a concave or parabolic form, when held before a large fire, a considerable degree of warmth will be perceived ; whereas the best glass mirror of the same dimensions will hardly collect in its focus heat enough to be felt. On the other hand, glass radiates more caloric than the metals, and lampblack more than glass. If the surface of the metallic mirror be furrowed or roughened, or if it be covered with a thick film of amal- gam, its powers to reflect caloric will be diminished, while the power to radiate will be proportionably increased. Metallic bodies possess this property in different degrees, and it will be seen, by inspecting the table of Mr. Leslie, that those which reflect the most, radiate the least, and that the converse of the proposition is equally true. It also appears as might be expected, that the reflecting and absorbing pow- ers of bodies are in the inverse ratio to each other. In ordinary cases heat is radiated through the medium of the air ; and no sensible radiatiton takes place when the whole apparatus is plunged into water although the experiments on this point are not free from objection. It radiates through all gaseous bodies tried, and it does not appear that the rate of radiation is much influenced by the COMMUNICATION OF CALORIC. 39 surrounding medium. The rate is the same at least, in air, and in hydrogen gas ; and oxygen and nitrogen appear to have the same pro- perties in this respect as air. Mr. Leslie has shown also that the rari- fication of the surrounding air diminishes somewhat the radiating en- ergy of surfaces ; but the radiation diminishes at different rates in dif- ferent gases. He has given a table showing the diminution of the power of radiation in air and in hydrogen gas of different degrees of rari- ty ; but perhaps the experiments require to be repeated. It has bsen supposed that solid bodies are impermeable to radiant caloric, and an experiment is described in some chemical works as a conclusive proof of the difference between caloric and light. It consists in placing a lamp or burning coals in the focus of a mirror, and a pane of glass between it and the opposite mirror : the rays of light will pass through the glass, but the rays of caloric, it is said, will be completely intercepted. But this distinction can scarcely be maintained. It is true indeed that the thermometer is not BO much affected as it would be were no screen interposed, and the glass itself becomes warm. These facts prove that the greater part of the calori- fic rays is intercepted by the glass. But the thermometer is affected to a certain degree, and the question is, by what means do the rays reach it 1 Professor Leslie contends, that all the rays which fall upon the glass are absorbed by it, pass through its substance by its con- ducting power, and are then radiated from the other side of the glass towards the thermometer an opinion, which Dr. Brewster has ably supported with an argument, suggested by his optical researches. [Phil. Trans, for 1816, p. 106.] The experiments of Delaroche, on the contrary, [Biot. Traite de Phys.] lead to the conclusion that glass does transmit some calorific rays, the number of which, in relation to the quantity absorbed, is greater as the intensity of the heat increas- es. This general result has been confirmed by various other philoso- phers. Mr. Leslie has advanced the idea that radiant caloric is not thrown off from hot bodies and darted through the air to distant bodies, but that the air itself is the medium of its transmission. According to this hypothesis, the stratum of air immediately in contact with the heated body acquires a portion of its high temperature, by which it is expanded and made to press upon the next stratum of particles ; this in like manner recedes, and thus an undulation or chain of serial pulsations is produced. "The mass of air, without sensibly chang- ing its place, suffers only a slight fluctuation as it successively feels the partial swell ; but the heat attached to this state of dilatation is actually transported, and with the swiftness of sound." Leslie's In- quiry, p. 140. But the experiments of Delaroche and others, offer insuperable objections to the adoption of Leslie's theory, and indeed go to prove that there is but little difference between the radiation of heat and light. When a cold body, as ice or a vessel containing a mixture of snow and salt, is placed in the focus of one of the mirrors, instead of the hot body, the bulb of the thermometer in the focus of the other mir- ror will indicate a diminution of temperature below that of the sur- rounding air. This fact led some philosophers to advance the opin- ion that cold was a material substance, and subject, like heat, to the laws of radiation and reflection. But this, as well as the other phe- nomena of radiant caloric, will be explained in the section on the dis- tribution of temperature. It should be observed, that in all these ex- 40 COMMUNICATION OF CALORIC. periments upon the radiation of caloric, the Differential . Thermometer, described in Section 4, should be employed. RKFERENCKS. Leslie's Inquiry. PicteCs Essay. Delaroclie on Radi- ant Heat -Ann. of Phil. ii. 100. Ritche in Edin. Phil. Jour. xi. 281. Prof. Powell in Repertory of Inventions, iv. 394 Also Ami. of Phil, xxiv, xxv, and TL\\\.Pou:elPs Report on Radiant Heat to the British Associa- tion, 1832. CONDUCTION. Another method in which heat is communicated, is by what has been aptly termed conduction, which differs considerably from radia- tion. The most striking point of difference, however, is the veloci- ty with which caloric is transmitted. When caloric is radiated, its mo- tion is rapid, nay almost instantaneous ; when it is conducted, its motion is slow. These two modes of communication, however, are seldom perfectly independent of each other. When caloric is radia- ted through the air, a portion is also conducted by the air which comes in contact with the rays. And again, when caloric is conduct- ed through a solid body, for example, radiation at the same time takes place. The difference in the velocity of transmission will explain why, in the former case, only a small portion of heat is conducted, and in the latter case why so large a quantity is radiated. Caloric is conducted through solids, liquids and triform substan- ces ; in each of these bodies, however, there is some peculiarity in the manner of its conduction. Conducting powers of Solids. When a metallic bar, iron for example, is exposed at one end to the heat of a furnace, the heat is gradually transmitted through its whole length, and after a short time the other extremity cannot be touched without danger of our being burnt. But this may be done with perfect safety with a rod of glass or of wood. Hence bodies are said to differ in their power of conducting caloric, and some are called good and others bad conductors. Metals are the best conductors of caloric ; but even among these there is considerable difference. According to the experiments of In- genhouz, silver and gold are the best conductors, next copper and tin, which are nearly equal, and lastly platinum, iron, and lead, which are much inferior to the others. Glass, pottery, clay, &c. have much less conducting power than any of the metals. This is the reason why glass is so liable to break when suddenly heated or cooled ; one part of it is receiving or part- ing with its caloric before the rest expands or contracts, and hence the cohesion is destroyed. It is on this account that the manufac- turers resort to a process called annealing, which consists in putting the glass while hot, immediately after being formed into the required shape, into an oven strongly heated, where the glass remains till it becomes cold by slow degrees. Exp. Put a lamp under the centre of a sheet of copper, and at equal distances from the centre place a piece of silver, copper, iron and por- celain, of the same size and thickness, having on each a small bit of phosphorus. That on the silver will be first kindled, showing that it is soonest heated ; in other words, that the caloric has passed most quick- ly through it. Next comes the copper, then the iron, and lastly the porcelain, the phosphorus on which will remain a long time, without being kindled. COMMUNICATION OF CALORIC. 41 Next to these bodies in point of conducting power, come the dried woods, which also differ materially from each other. According to Professor Mayer, the conducting power of these is inversely as their specific gravities. (See his table in Webster's Brande.) The difference between the conducting power of the metals and wood may be shown as follows : Exp. Take a smooth cylindrical tube, or still better, a solid piece of metal, about an inch and a half in diameter and eight inches long ; wrap a clean piece of writing paper round the metal so as to be in close contact with its surface. When thus prepared it may be held for a considerable time in the flame of a spirit lamp without being in the least affected. Wrap a similar piece of paper around a cylindrical piece of wood of the same diameter, and hold it in the flame ; it will speedily burn. When the paper is in close contact with the metal, the heat which is applied to it in one particular part cannot accumu- late there, but enters into the] metal, and is equally diffused through its substance, so that the paper cannot be burned or scorched, until the metal becomes very hot : but when the paper is wrapped round wood, the heat that is applied in one particular part, not being able to enter into the wood with facility, accumulates in a short time in suffi- cient quantity to burn the paper. L. U. K. Art. Heat. Charcoal is also a bad conductor : but feathers, silk, wool and hair are worse than any yet mentioned. Count Rumford has made ex- periments with a view of determining the conducting power of sub- stances of this nature, from which it appears that those have the least conducting power, in which tfce fibres are finest and most condensed, provided the interstitial air is not expelled by the condensation. Rum- ford's Essays. The substances which form the warmest articles of clothing are those which have the longest nap, fur or down, on account of the air which is involved, resisting the escape of the natural warmth of the body. The imperfect conducting power of snow arises from the same cause, and hence its utility in preventing the surface of the earth from being injuriously cooled in many parts of the world. While the temperature of the air in Siberia has been 70 D F. it is affirmed that the surface of the earth has seldom been colder than 32- F. Despretz has given the following table of the comparative conduct- ing powers of the principal metals and some earthy bodies. Ann. de Chim. et de Pk. xxxvi. 422. Gold, (greatest conducting power,) 1000.0 Platinum, 981.0 Silver, ...... 973.0 Copper, - - - - 898.2 Iron, - - - - - - 374.3 Zinc, 363.0 Tin, 303.9 Lead, 179.6 Marble, 23.6 Porcelain, 32.2 Earth of bricks and furnaces, - - 11.4 The conducting powers of bodies have been investigated by Fourier, by the aid of instruments called a Thermometer of Contact, and a Ther- 42 COMMUNICATION OF CALORIC. moscope of Contact, from the first of which some curious facts have been ascertained. See Henry's Chem. i. 108. Ann. de Ctitm. et dt Ph. xxxvii. 291. Conducting powers of Liquids. Liquids may be said, in one sense of the word, to have the power of communicating caloric with great rapidity, and yet they are very imperfect conductors. The transmission of caloric from particle to particle does in reality take place very slowly ; but in consequence of the mobility of their particles upon each other, there are peculiar in- ternal movements which under certain circumstances may be occa- sioned in them by increase of temperature, and which do more than compensate for the imperfect conducting power with which they are really endowed. "When certain particles of a liquid are heated, they expand, and thus become specifically lighter than those which have not yet received an increase of temperature ; and consequently, according to a well- known law in physics, the colder and denser particles descend, while the warmer ones are pressed upwards. It therefore follows that if caloric enter at the bottom of a vessel containing any liquid, a double set of currents must be immediately established, the one of hot parti- cles rising towards the surface, and the other of colder particles des- cending to the bottom. Now these currents take place with such ra- pidity, that if a thermometer be placed at the bottom, and another at the top of a long jar, the fire being applied below, the upper one will begin to rise almost as soon as the lower. Hence, under certain cir- cumstances, caloric is rapidly communicated through liquids. But if, instead of heating the bottom of the jar, the caloric is made to enter by the upper surface, very different phenomena will be ob- served. The intestine movements cannot now be formed, because the heated particles have a tendency to remain constantly at the top ; the caloric can descend through the fluid only by transmission from parti- cle to particle, a process which takes place so very tardily, as to have induced Count Rumford to deny that water can conduct at all, and to assert that liquids were heated exclusively by their transporting or carrying power. (Rumford's Essays.) The incorrectness of this opinion, however, appears to be quite satisfactorily shown by the ex- periments of Dr. Hope, Dr. Thomson and Dr. Murray ; though they all admit that water, and liquids in general, mercury excepted, possess the power of conducting caloric in a very slight degree.* The transporting power of liquids can be very satisfactorily shown by putting into a vessel of water some small pieces of amber which are in specific gravity so nearly equal to water as to be little influenced by gravitation. The lowermost part of the vessel being subjected to heat, when thus prepared, the pieces of amber rise vertically, and on reaching the surface, move towards the sides of the vessel, which are colder from the influence of the external air ; they then sink and rise again as be- fore. When the boiling point is nearly attained, the particles being nearly of one temperature, the circulation is retarded. The portions on the surface are converted into steam before they can be succeeded by others ; but the steam thus produced cannot rise far, before it is con- * Some ingenious experiments in confirmation of the theory of Count Rura- ford, by Lieut. W. M. Mather, are detailed in Silliman's Jour. xii. 368. DISTRIBUTION OF CALORIC. 43 densed. Hence the vibration and singing observed at this time. Hare's Minutes. The slow conducting power of water can be shown by cementing an air thermometer into a glass funnel, and covering the bulb of the instrument with water. If now a small quantity of ether be poured upon the surface of the water, it may be fired without sensibly affect- ing the fluid in the stem of the thermometer. Conducting powers of ceriform bodies. It is extremely difficult to estimate the conducting power of aeri- form fluids. Their particles move so freely on each other, that the moment a particle is dilated by caloric, it is pressed upwards with great velocity by the descent of colder and heavier particles, so that an ascending and descending current is instantly established. Be- sides, these bodies allow a passage through them by radiation. Now the quantity of caloric which passes by these two channels is so much greater than that which is conducted from particle to particle, that we possess no means of determining their proportion. It is certain, however, that the conducting power of gaseous fluids is exceedingly imperfect, probably even more so than that of liquids. Turner. REFERENCES. Soquet on the power of Fluids as cojiductors of Heat, in Rep. of Art$ t 1st ser. xiii. 277. Dalton on the same subject, in Rep. of Arts, %d ser. ii. 282. Dulong and Petit on the Laws of the communication of Heat, in Ann. of Phil. xiii. 112. Murray's Experiments on the conducting power of Liquids. Syst. of Chem. 1. SECTION III. DISTRIBUTION OP CALORIC. Different theories have been proposed to account for the tendency of bodies to acquire an equilibrium of temperature. I shall content myself with an exposition of the theory of Professor Prevost, of Ge- neva, which though not wholly free from objection, is now very gene- rally adopted. It is altogether founded upon the phenomena of ra- diant caloric. There appears to be no point of temperature at which radiant ca- loric is not given out by bodies. Ice, which is so cold when in con- tact with the hand at ordinary temperatures, becomes hot if it be trans-- ported to a chamber whose temperature is 20 below zero, and a mass of melting ice then presented to the thermometer will cause the fluid to ascend as well as the vessel of boiling water presented to it at the ordinary temperature. Again, a mixture of snow and salt cooled down to 20 below zero, becomes a hot body if it be transported to an atmosphere of 40 below zero. In all these cases, as in our own sensations, there is nothing abso- lute ; all is elative. We are therefore forced to the conclusion that all bodies, atrall temperatures, radiate caloric ; but that the radiation is of unequal intensity, according to their nature, to their surfaces, and to the temperature to which they are brought. The constancy of the temperature of a body depends then upon an equality in the quantity of radiant caloric which it emits and receives during the same time ; and the equilibrium of caloric which takes place among several bodies by mutual radiation, depends upon the perfect compensation of the instantaneous changes which are effected between all and each 44 EISTRIBUTION OF CALORIC. of them. This is the ingenious theory suggested by Prevost, and which, combined with the peculiar properties of different surfaces, ex- plains all the phenomena of radiant caloric. A few experiments will more fully illustrate this interesting subject. Place a thermometer in a chamber which has an equal temperature in all its parts, and allow it to remain until it becomes of the same temperature. In the same chamber have an opake disk of any na- ture and form whatever, also at the same temperature. If now this disk be presented at a greater or less distance to the bulb of the ther- mometer, no effect will be produced upon it. The reason is obvious. Before we employed the disk, the bulb received at each instant from the walls and from the air of the chamber, a certain quantity of heat by radiation and reflection, and itself at the same time, sent back by this double mode an amount exactly equal, since its temperature remained the same. Now when we present the opaque disk to the bulb of the thermometer, we intercept for each point of the bulb all the calorific rays which are comprised in the cone formed by this point, and the whole surface of the disk. But, in exchange, the same point receives from the disk a certain number of rays comprised in the cone just mentioned ; and in consequence of the supposed equality of temperature, this number is exactly equal to that which came from that portion of the wall upon which the disk is projected. Thus after the interposition of the disk, each point of the bulb receives still as much heat in the same time, as it received previously ; and as the quantity which it gives out is not changed, it is evident that its tem- perature and that of the bulb will remain the same. A different result, however, will be observed, if there be presented to the thermometer a disk whose temperature is either higher or lower than that of the chamber; for then the number of caloritic rays radi- ated or reflected by this disk in a given time will be, in the former case greater, in the latter, less than that which came from the portion of the wall which it conceals. The same explanation will apply in the cases where two mirrors are employed. Place a thermometer, the bulb of which is blackened, in the focus of one mirror, and allow it to become of the same tempera- ture as the surrounding air, and in the focus of the other mirror, place any body which is of the same temperature. The thermometer will not be affected. The reason will be readily perceived. When the passage of the rays through this last focus was free, there arrived at this point from all parts of space a certain number of calorific rays, which, after they have crossed, fall upon the second mirror, are reflected from it to the first, and finally are concentrated upon the bulb of the thermometer. These rays are indeed intercepted by the opaque body which we have placed in the focus, but as this is sup- posed to be of the same temperature with the surrounding space, it transmits by radiation and reflection a number of rays exactly equal, which falling upon the second mirror are reflected to the first, and finally to the thermometer ; and hence no change is effected. But this will not be the case when the body placed in the focus is either of a higher or lower temperature than that of the surrounding space and of the thermometer. For then the thermometer, after the interpo- sition, will receive through the medium of the mirrors more or less than it received before, and also more or less than it loses in the same time either by reflection or by radiation. Whence it fol- lows, that the temperature will b^ elevated in the former case, and re- duced in the latter. DISTRIBUTION OF CALORIC. 45 These views are fully confirmed by experiment. For as has al- ready been shown, if we place a hot body in the focus of one mirror, the thermometer in the focus of the opposite one will indicate an in- crease of temperature ; and on the contrary, if we place a piece of ice or a mixture of snow and salt in the focus of one mirror, the thermometer in the focus of the opposite mirror will indicate a di- minution of temperature. All these phenomena can be explained if we only admit that all bodies, however low their temperature, radiate caloric, and in this there is nothing surprising, since our ideas of heat and cold are all relative. Without this admission we should have to adopt the opinion advanced by some philosophers, that cold as well as heat is radiated ; an opinion which is not necessary, nor even war- ranted by the facts. Biot. Precis. Elemental, ii. 642. The theory of radiation as thus unfolded, has been successfully em- ployed by Dr. Wells, in explaining the phenomena of Dew. By his numerous and well directed experiments he has amply proved, that the formation of dew is owing to the radiation of caloric from the ground, and he conceives that all the previous explanations fail in not accounting for the production of cold in the dewed body. He has shown that the degree of cold on the surface of grass, &c. is in pro- portion to the quantity of dew which is formed : that dew appears in the greatest quantity upon those substances which radiate the most caloric ; that the radiation is the greatest, and the dew most copious in calm and serene nights ; that the process is diminished or sus- pended by high winds and by the presence of clouds ; and that in those cases the temperature of the grass, &c. is the same as that of the air. Wells' Essay on Dew, 4c. A similar explanation has been applied by Dr. Wells to various ap- pearances connected with dew, and among these not the least curi- ous is that of the formation of ice during the night in Bengal, when the temperature of the air is above 32 F. This has generally been ascribed to cold produced by evaporation ; an opinion which has been adopted by Davy, Leslie, Thomson and others. Dr. Wells, however, has shown conclusively, that it cannot be owing to this cause ; but that it depends upon the radiation of heat to the heavens. For it is observed that ice is chiefly formed in Bengal during the clearest and calmest nights, when the greatest cold from radiation is observed on the surface of the earth ; and that clouds and winds pre- vent its formation by preventing, or at least diminishing, the radiation of heat.* The study of the laws of radiant caloric has lead to impor- tant improvements in the construction of fire places ; a subject which engaged the attention of Count Rumford. See Rumford's Essays. * Captain Scoresby found that in the Polar Seas, ice was formed in clear nights when the temperature of the air was several degrees above the freez- ing point of water; but that in cloudy nights no ice was formed the tem- perature of the air in both cases being the same. In the last instance there was a constant interchange of caloric between the water and the clouds, by means of which the temperature of the water was preserved nearly equal to the temperature of the air, which was above the freezing point. In the first instance, as there was nothing which could radiate back to the water the ca- loric which was radiated from it, its temperature sunk below the freezing point, and ice was formed. D 46 EFFECTS OF CALORIC. REFERENCES. Prevost's Researches svr la Chaleur. Wells 1 Easy on Dew, Spc. Pictefs Essays. Biofs Precis. Elementaire. Sundry papers on Prevosfs Theory of Radiant Caloric, by R. Davenport, Prof. Prevost, Dr. Wells andJ. Murray, are contained in the Ann. of Phil. v. vi. and vii. SECTION IV. EFFECTS OF CALORIC. The general effects of caloric are 1. EXPANSION. 2. LIQUEFACTION. 3. VAPORIZATION. EXPANSION. This is one of the most remarkable effects of caloric. When bodies are heated they become less compact, are increased in bulk, or in other words, expand ; and as they cool they retuin to their former di- mensions. Hence caloric is inferred to separate their particles, and is regarded as the repulsive power, which is constantly opposed to co- hesion. This being the case, it follows that caloric must produce the greatest expansion in those bodies whose cohesive power is the least; and the inference is justified by observation. Thus the force of co- hesion is greatest in solids, less in liquids, and least of all in seriform substances ; while the expansion of solids is trifling, that of liquids is more considerable, and that of elastic fluids far greater. Expansion of Solids. In proof of the expansion of solids, we need only take the exact dimensions in length, breadth, and thickness of any substance when cold, and measure it again when strongly heated, when it will be found to have increased in every direction. A familiar demonstration of the fact may be afforded by adapting a ring to an iron rod, the for- mer being just large enough to permit the latter to pass through it while cold. The rod is next heated, and will then no longer pass through the ring. This dilatation from heat and consequent contrac- tion in cooling takes place with a force which appears to be irre- sistible. This property of metals has been applied to various useful purposes. The iron band or tire, as it is called, of a carriage-wheel, being pur- posely made a little smaller than the wooden circle, is enlarged by heat so as to embrace the latter, and being then suddenly cooled, by throwing water upon it, is again contracted, and becomes immoveably fixed. An ingenious use of the same principle was made, several years ago, at Paris, by M. Molard, in restoring to the perpendicular,* two opposite walls of a building, which had been pressed outward by the incumbent weight. Through strong holes in the walls, opposite to . each other, several strong iron bars were introduced, so as to cross the apartment, and to project outside the building sufficiently to allow strong iron plates or washers to be screwed upon their ends. The bars were then heated, and the iron plates screwed up. On cooling, the bars contracted, and drew the separated walls together ; and this was repeated till the walls had regained their perpendicular position. EFFECTS OF CALORIC. 47 In riveting together the iron plates out of which steam engine boilers are made, it is necessary to produce as close a joint as possible. This is effected by using the rivets red hot ; while they are in that state the two plates of iron are rivetted together, and the contraction which the rivet undergoes in cooling draws them together with a force which is only limited by the tenacity of the metal of which the rivet itself is made. The degree of expansion, however, is not the same for all solids, and even differs materially in substances of the same class. Thus the metals expand in the following order, the most expansible being placed first, zinc,* lead, tin, copper, bismuth, iron, steel, antimony, palladium, platinum. The experiments of Petit and Dulong, (Ann. of Phil. xiii. 164,) tend to show that unequal degrees of expansion are produced in a bar of metal by a succession of similar increments of heat ; the rate of expansion increasing with the temperature. The expansion of solids has occupied the attention of many experi- menters, whose chief object appears to have been to ascertain the exact quantity that different substances are lengthened, by a given increase of heat, and to determine whether or not their expansion is equable at different temperatures. The Philosophical Transactions of London contain the various dissertations on this subject by Elli- cott, Smeaton, Troughton and General Roy : and Biot in his Traite de rhysique, i. 158, has given the results of experiments performed with great care by Lavosier and La Place. [A table of the linear dilatation of various solids by heat will be found in lire's Dictionary of Chemistry, and in the Library of Useful Knowledge.] Expansion of Liquids. The simplest method of proving the expansion of liquids is by put- ting a common thermometer, made with mercury or alcohol, into warm water, when the dilatation of the liquid will be shown by its ascent in the stem. The experiment is indeed illustrative of two other facts. It proves, first, that the dilatation increases with the temperature ; for if the thermometer is plunged into several por- tions of water heated to different degrees, the ascent will be great- est in the hottest water, and least in the coolest portions. It demon- strates, secondly, that liquids expand more than solids. The glass bulb of the thermometer is itself expanded by the hot water, and therefore is enabled to contain more mercury than before ; but the mercury being dilated to a much greater extent, not only occupies the additional space in the bulb, but likewise rises in the stem. Its as- cent marks the difference between its own dilatation and that of the glass, and is only the apparent, not the actual expansion of the li- quid. Turner. Liquids differ also in their relative expansibilities ; ether is more expansible than alcohol ; alcohol more than water, and water more than mercury. Those liquids are generally most expansible which boil at the lowest temperature. * This is the order usually given, but according to Dr. Lardner, lead is the most expansible of the rnotals, In the solid state. Its bulk is increased one part in 350 by being plunged into inching ice, and the ire then being raised to the temperature of boiling water; or in o'.her words, this takes place bv a change of temperature, amouM'ing to 130 degrees of the common thermome- ter. Treatise on Heat } 23. 48 EFFECTS OF CALORIC. Exp. This may be rendered evident by partially filling several glass tubes of equal diameter, furnished with bulbs, with the different liquids and placing them in hot water ; as the liquids expand, they will rise to different heights in the tubes. To render this more apparent, the li- quids may be tinged with some colouring matter. The expansion of various liquids by heat has been studied with great care by Lavoisier and La Place, Petit and Dulong. Expansion of JEriform bodies. The expansion of&riform bodies by heat may be exemplified by hold- ing near the fire a bladder half filled with air, the neck of which is closely tied, so as to prevent the enclosed air from escaping. The bladder will soon be fully distended, and may even be burst by con- tinuing and increasing the heat. All aeriform bodies, when deprived of moisture, and even condensible vapours, when not in contact with the liquids from which they have been produced, undergo the same expan- sion or contraction at all temperatures hitherto tried, by similar ad- ditions or subtractions of caloric. This for a single degree of Fahr- enheit's thermometer, is ^g-g- part of their bulk, between 32 and 212 C ? as first determined by Mr. Dalton, and afterwards confirmed by Gay Lussac, and by Petit and Dulong, who have extended the law, up to 572 F. (Ann. of Phil, xxix. 117.) This equable expansion of air by equal increments of heat, adapts it for the accurate measurement of temperature. At a cherry red heat, (= about 1035 F.) Sir H. Davy found that a volume of air = 1 at 212 F. became 2.5 volumes. On Flame, 68. Henry's Chem. i. 91. To the general law of the expansion of bodies by heat 7 and their contraction by cold, there are, however, some remarkable exceptions. Thus water when cooled down below the temperature of 39 F. ex- pands and continues to do so, until it is converted into ice.* The most remarkable circumstance attending this expansion is the pro- digious force with which it is effected. The Florentine academicians burst a hollow brass globe, whose cavity was only an inch in diameter. by freezing the water with which it was filled : and it has been esti- mated that the expansive power necessary to produce such an effect is equal to a pressure of 27,720 pounds weight. This fact was confirm- ed by the experiments of Major Williams of Quebec. Trans. Royal Society, Edin. ii. 23. Salts also, in the act of crystallizing, expand ; and some of the me- tals, as cast iron, bismuth and antimony, have their dimensions en- larged on congealing. Hence the precision with which ca^t iron takes the impression of the mould ; and hence also the use of antimony to the type founder. In all these cases, the cause of the expansion is supposed to be the new and peculiar arrangement of its particles. It only occurs in those bodies which upon cooling assume a crystalline or semi-crystalline form, the particles of which, then occupy more space than when they are liquid. In the case of water, where the ex- pansion commences previous to congelation, it is supposed that the water begins to arrange itself in the order it will assume in the solid state, before actually laying aside the liquid form. If these views are correct, the exceptions to the general law of expansion by heat are rather apparent than real. * The mean of the recent determinations of the true point of the maximum density of water by Stampfer, Mu-icke and Crichton is 38.34. Johnston's Report on Chemistry. EFFECTS OF CALORIC. 49 One of the important applications of the principle of expansion is to the construction of instruments which, under the designation of thermometers, or thermoscopes, pyrometers, or pyroscopcs, are now in general use in every part of the civilized world. Their names are de- rived from the Greek terms, thermos, pur, signifying heat, fire, and mc- tron, skopos, a measure, an investigator. Thermometers. The invention of the thermometer is generally ascribed to Sanc- torio of Padua, who flourished about the beginning of the seventeenth century. But the instrument employed by that philosopher, was of a very simple kind, and measured variations of temperature by the variable expansion of a confined portion of air. To prepare it, a glass tube is to be provided, eighteen inches long, open at one end, and blown into a ball at the other. On applying a warm hand to the ball, the included air expands, and a portion is expelled through the open end of the tube. In this state the aperture is quickly inverted in a cup filled with any coloured liquid, which ascends into the tube as the air in the ball contracts by cooling. The instrument is now prepared. An increase of temperature forces the liquor down the tube ; and on the contrary, the application of cold causes its as- cent. These effects may be exhibited alternately by applying the hand to the ball, and theji blowing on it with a pair of bellows. By the application of a graduated scale, the amount of expansion may be measured. The advantages of the Air Thermometer consists in the great amount of the expansion of air, which by a given elevation of temperature, is increased in bulk above twenty times more than mercury. Hence it is adapted to detect minute changes, which the mercurial thermometer would scarcely discover ; and its expansions being uniform for equal additions of caloric, it is better adapted than any liquid for becoming, when properly applied, an accurate measure of temperature. But an insuperable objection to it, in its present form is, that it is affected not only by changes of temperature, but by variations of atmospheric pressure. An ingenious modification of the air thermometer has been invented by Mr. Leslie and employed by him, with great advantage, in his in- teresting researches respecting heat. To this instrument he has given the name of the Differential Thermometer. It consists of two thin glass balls joined together by a tube bent nearly into the shape of the letter U. Both balls contain air, but the greater part of the tube is fill- ed with sulphuric acid coloured with carmine. It is obvious that this instrument cannot be affected by any change of temperature acting equally on both balls ; for as long as the air within them expands or contracts to the same extent, the pressure on the opposite surfaces of the liquid, and consequently its position, will continue unchanged. Hence the differential thermometer stands at the same point, how- ever different may be the temperature of the medium. But the slight- est difference between the temperature of the two balls will instantly be detected ; for the elasticity of the air on one side being then greater than that on the other, the liquid will retreat towards the ball whose temperature is lowest. It is hence admirably adapted to ascertain the difference of the temperatures of two contiguous spots in the same at- mosphere ; for example, to determine the heat in the focus of a concave reflector. Sec Leslie's Essay on Heat. A differential thermometer has been contrived by Dr. Howard of 50 EFFECTS OF CALORIC. Baltimore, resembling that of Mr. Leslie in its general form, but in which the degree of heat is measured by the expansive force of the vapour of ether or alcohol in vacua. It is intended to be applied to the same purposes as that of Mr. Leslie, but is a much more delicate in- strument. Brands s Jour. viii. 219. .Thermometers filled with alcohol or spirit of wine, (a liquid which lias not been congealed by any degree of cold hitherto produced,) are best adapted to the measurement of very low temperatures, at which mercury would freeze. The amount of the expansion of alcohol also, which exceeds that of mercury above eight times, fits it for ascertain- ing very slight variations of temperature. But it cannot be applied to measure high degrees of heat, because the conversion of the spirit into vapour would burst the instrument. Henry, i. 96. The fluid best adapted for filling thermometers is mercury, which, though it expands less in amount than air or alcohol, still undergoes this change to a sufficient degree ; and in consequence of its difficult conversion into vapour, may be applied to the admeasurement of more elevated temperatures. In the construction of thermometers the first object is to select a tube with a small bore, the diameter of which is the same throughout its whole length ; and then by melting the glass to blow a bulb at one end of it. The bulb is now heated, by means of which the air within, it is rarified ; and the open end of the tube is dipped into mercury. As the air cools and contracts, the mercury is forced up, entering the bulb, to supply the place of the air which has been expelled from it- Only a part of the air, however, is removed by this means ; the re- mainder is driven out by the ebullition of the mercury. Having thus contrived that the bulb and about one-third of the tube shall be full of mercury, the next step is to seal the open end hermet- ically. This is done by heating the bulb till the mercury rises very near the summit, and then suddenly darting a fine pointed flame from a blow-pipe across the opening, so as to fuse the glass and close the aperture, before the mercury has had time to recede from it. The graduation of the thermometer, by which alone the observa- tions made with different instruments can be compared together, con- sists of two parts, viz. first to obtain two fixed points which shall be the same in every thermometer : and second, to divide the interval be- tween these two fixed points into any number of equal parts or de- grees. To effect the first of these objects, the practice generally pur- sued, is that introduced by Sir Isaac Newton, and is founded on the fact that when a thermometer is plunged into ice that is dissolving, or into water that is boiling, it constantly stands at the same elevations in all countries, provided there is a certain conformity of circumstan- ces. The point of congelation, or the freezing point, is ascertained by immersing, in thawing snow or ice, the ball and part of the stem ; so that the mercury when stationary, shall barely appear above the sur- face. At this place let a mark be made with a file. To fix the boiling point is a more delicate operation, since the tem- perature, at which water boils is affected by various circumstances, which will be more particularly mentioned hereafter. The general directions are, that the water be perfectly pure, free from any foreign particles, and not above an inch in depth the ebullition brisk, and conducted in a deep metallic vessel, so that the stern of the ther- mometer may be surrounded by an atmosphere of steam, and thus exposed to the same temperature as the bulb that the vapour be al- lowed to escape freely and the barometer to stand at 30 inches* EFFECTS OF CALORIC. 51 The second part of the process, or the division of the interval be- tween the two fixed points, may be effected by marking on the tube itself, by means of a diamond, or by first drawing the divisions upon a piece of paper, ivory or metal, and afterwards attaching it to the thermometer. The number of divisions between these two points is not material, though it would be more convenient if there was greater uniformity in this respect. In the centigrade thermometer, which is perhaps the most convenient, this space is divided into 100 3 , the freezing of water, being marked (P, the boiling point 100^. In the scale of Reaumur the freezing point is D , the boiling point S0\ And in Fahrenheit's scale, generally employed in England and America, the interval is divided into 180 ; but the zero of Fahrenheit is placed 32 below the temperature of melting snow, and on this account the point of ebullition is 212. The temperature expressed by one of these scales can easily be reduced to that of another, by knowing the relation which exists between their degrees. See Turner and Webster's Brande, also L. U. K. Art. Heat, 17. P EFERENCES. Particular directions for the construction of Thermometers Henry's Cke.m, i. 96. The Chevalier Landrianfs directions for construct' ing Thermometers of great sensibility Brandos Jour. vii. 183. Directions for determining the accuracy of Thermometers Faraday's Cheni. Manip. Library of Useful Knowledge Thermometer and Pyrometer. The article Thermometer in the Edinburgh Encyclopaedia Prof. Forbes 1 Report on Me- teorology, to the British Association, 1832. Pyrometers. These are instruments for measuring degrees of heat much higher than those which can be determined by the mercurial thermometer. Of these, there are several. That of Mr. Wedgewood is founded upon the property which clay posse ses of contracting when strongly heated, without returning to its former dimensions as it cools. But the indications of this instrument cannot be relied on, and it is at present, seldom employed. The best pyrometer is per- haps that of Mr. Danieli. A bar of platinum is enclosed in a case made of the same ware as black lead crucibles, and is fixed to it at one end, while the other is left free to move an index, by which means degrees of heat, above ignition, admit of being measured, but not with accuracy, owing to the increasing rate of expansion in metals at high temperatures. Henry, i. 92. Brande s Jour. xi. 309. On the same principle Breguet has constructed a very sensible metallic thermometer, for temperatures between the freezing and boiling points of water. It consists of a slip of silver and another of platinum, united face to face with solder, and coiled into a spiral, one end of which is fixed, while the other is connected with an index which moves over a circular graduated plate. Strictly, two metals only are sufficient for the purpose, platinum and silver, for instance ; but it has been found to be an improvement to employ three, and the instrument is now prepared by interposing between the platinum and silver a metal of mean dilatability, such as pure gold. The unequal expansion of the metals causes the spiral to increase or diminish the degree of its curvature by variations of temperature ; and the needle, being attached at right angles to the axis of the spiral, is thus made to traverse the graduated circle. Experi- ments have shown that the needle, for equal changes of temperature, moves over equal arcs, so that the instrument is comparable, not only with itself, but with others constructed on the same principle. Such 52 EFFECTS OF CALORIC. was found to be its great sensibility, that, when enclosed in a large receiver, which was rapidly exhausted by the air pump, it indicated a reduction of temperature from 66 F. to 25, (=41,) while a sensi- ble mercurial thermometer, similarly situated, fell only 3.6. Henry's Chem. i. 92. Ann. de Chim. et de Phys. v. 312. Instruments have also been constructed for the purpose of ascer- taining the highest and lowest temperature which has occurred during a given interval of time. These have been called Register Thermome- ters ; and one of the best is that described by Dr. John Rutherford. Turner's Chem. and L. U. K. But though the thermometer is one of the most valuable instru- ments of philosophical research, it is by no means an exact measure of the number of degrees of heat in a body. It does not follow, be- cause the thermometer stands at the same elevation in any two bod- ies, that they contain equal quantities of caloric ; nor should we in- fer that the warmer possesses more of this principle than the colder. The thermometer only indicates that condition of a body which is expressed by the term temperature. All that we learn by this instru- ment is, whether the temperature of one body is greater or less than that of another ; and the difference, if there be any, is expressed nu- merically, namely by the degrees of the thermometer. These de- grees, however, it should be remembered, are merely parts of an arbi- trary scale which have no reference whatever to the actual quantity of caloric present in bodies. REFERENCES. WedgewoocPs description of and observations on his Py- rometer Repertory of Arts, 1st series, v. vi. yii. ix. Gazerarfs Memoirs on the method of preparing Pyrometrical Earths of VVedgewood Same work, 1st series, xir. 211. Fourmy on the Thermometer of baked Earth Same \cork, Zd series, vii. 143. xxii. 309. L. U. K. LIQUEFACTION. It has already been shown, that as we apply heat to a body, it in- creases in bulk. In continuing its application, the enlargement also continues, till it arrives at a certain temperature, when a change of a different nature ensues. It now becomes liquid, and the body is said to be melted, liquified or fused, and the change is called fusion, or liquefaction. On the contrary, when we apply cold to a liquid it contracts, and continues to do so till at a certain temperature it be- comes solid, and it is then said to be frozen or congealed. In this way almost every fluid may be made solid and almost every solid fluid ; and both these points, though different for different bodies, are uni- formly the same under similar circumstances in the same body. Under this head the two following general propositions may be stated : 1. Bodies in passing from a solid to a liquid state, absorb caloric. If a pound of water at 32 be mixed with a pound of water at 172, the temperature of the mixture will be intermediate between them, or 102. But if a pound of water at 172 be added to a pound of ice at 32, the ice will quickly dissolve, and on placing a thermome- ter in the mixture, it will be found to stand, not at 102 J , but at 32. In this experiment, the pound of hot water, which was originally at 172, actually looses 140 of caloric, all of which entered into the ice, and caused its liquefaction, but did not affect its temperature ; and it follows, therefore, that a quantity of caloric becomes insensible during EFFECTS OF CALORIC. 53 the melting of ice, sufficient to raise the temperature of an equal weight of water 140 F. This explains the well known fact, on which the graduation of the thermometer depends, that the temperature of melting ice or snow never exceeds 32 F. All the caloric which is added becomes insensible, till the liquefaction is complete. The loss of sensible caloric which attends liquefaction seems essen- tially necessary to the change, and for that reason is frequently called the caloric of fluidity. The actual quantity of caloric required for this purpose varies with the substance, as is proved by the following results obtained by Irvine. The degrees indicate the extent to which an equal weight of each material may be heated by the caloric of fluidity which is proper to it. Caloric of fluidity* Sulphur 143.68 F. Spermaceti ..... 145 Lead 162 Beeswax 175 Zinc 493 Tin 500 Bismuth 550 All the bodies enumerated in this table, require, it may be observed, more caloric to bring them into a fluid state than is sufficient to con- vert ice into water, for which 140 are sufficient. Other examples of the absorption of caloric during the liquefaction of bodies, are furnished by the mixture of snow and nitric acid, or of snow and common salt, both of which, in common language, produce intense cold.* Crystallized muriate of lime, mixed with snow, in the proportion of three parts of the former, to two of the latter, causes the thermometer to sink to 50. Most neutral salts also, during solution in water, absorb much caloric ; and the cold thus generated, is so in- tense as to freeze water and even to congeal mercury. The congela- tion of water may be easily affected on a summer's day, by a mixture of five parts of muriate of ammonia, five of nitrate of potassa, eight of sulphate of soda, and sixteen of water. For further particulars concerning the frigorific mixtures, the reader is referred to Walker's Paper in the Phil. Trans, for 1801. Walker on the artificial Production of Cold, Phil. Mag. and Ann. iii. 401. Pepys and Allen s Account of Experiments on the production of Cold, in one of which Jifty-six pounds of mercury were frozen into a solid mass. Tilloch's Phil. Mag. iii. 76. A convenient apparatus for freezing mercury is de- scribed by Dr. Henry, in the 2d volume of his Chemistry. Parkcs' Es- say on Temperature. 2. Liquids in becoming solid, evolve or give out caloric, or in common language, produce heat. Water, if covered with a thin stratum of oil, and kept perfectly free from agitation, may be cooled down more than 20 degrees below 32 C ; * The Peasants on the Baltic say, thai nothing tends so effectually towards the freezing of the sea as a fall of snow into the salt water. The effects of a snow storm are thus described : " The water becomes turbid, like milk turn- ing to curd, pieces of ice soon made their appearance and were heard rattling against the prow and sides of the vessel." Dr. E. D. Clarke's Travels,'}']. 201, 242. 4 EFFECTS OF CALORIC. but on shaking it, or dropping into it a small fragment of ice, it imme- diately congeals, and the temperature rises to 32. Madden. Phil. Trans. 1788. If we dissolve sulphate of soda in water, in the proportion of one part to five, and surround the solution by a freezing mixture, it cools gradually down to 31. The salt at this point begins to be deposited, and stops the cooling entirely. This evolution of caloric, during the separation of a salt, is exactly the reverse of what happens during its solution. Blagdcn. To a saturated solution of sulphate of potassa or sulphate of magne- sia in water, add an equal measure of alcohol. The alcohol, attracting the water more strongly than the salt does, precipitates the salt, and considerable heat is produced. These phenomena are all easily explained by Dr. Black's doctrine of latent heat. According to this doctrine, caloric in causing fluidity loses its property of acting on the thermometer, in consequence of combining chemically with the solid substance, and liquefaction results because the compound so formed does not possess that degree of cohe- sive attraction on which solidity depends. When a liquid is cooled to a certain point, it parts with its caloric of fluidity, heat is set free, or becomes sensible, and the cohesion natural to the solid is restored. VAPORIZATION. This effect of caloric is conveniently studied under two heads Ebul- lition and Evaporation. In the first, the production of vapour is so rap- id that its escape gives rise to a visible commotion in the liquid : in the second, it passes off quietly and insensibly. Ebullition. The temperature at which vapour rises with sufficient freedom for causing the phenomena of ebullition, is called the boiling point. The heat requisite for this effect varies with the nature of the fluid. Thus, sulphuric ether boils at 96 F. alcohol at 173 J , and pure water at 212 ; while oil of turpentine must be raised to 316, and mercury to 68(P before either exhibits marks of ebullition. The boil- ing point of the same liquid is constant, so long as the necessary con- ditions are preserved ; but it is liable to be affected by several circum- stances. The nature of the vessel has some influence upon it. Thus, Gay Lussac observed that pure water boils precisely at 212 in a met- allic vessel, and at 214 in one of glass. It is likewise affected by the presence of foreign particles. The same accurate experimenter found, that when a few iron filings are thrown into water boiling in a glass vessel, its temperature quickly falls from 214 to 212, and remains stationary at the last point. But the circumstance which has the greatest influence on the boil- ing point of fluids is the variation of atmospheric pressure. In refer- ence to this subject the following propositions may be stated. 1. When atmospheric pressure is diminished, fluids boil at a lower tem- perature than under the ordinary pressure. Thus water which has been removed from the fire, and has ceased to boil, has its ebullition renew- ed, when it is placed under a receiver, the air of which is quickly ex- hausted by an air pump. Alcohol and ether, confined under an ex- hausted receiver, boil violently at the temperature of the atmosphere. In general, liquids boil, in vacuo, with about 124 less of heat than are required under a mean pressure of the atmosphere. [Black's Lectures, i. 151.] Water therefore in a vacuum must boil at 88 and alcohol at 49 F. EFFECTS OF CALORIC. 55 The influence of a diminished pressure in causing ebullition to take place at a lower temperature, may also be shown as follows : Exp. Fill a barometer tube with mercury and invert it in a basin of the same fluid ; then pass up a small quantity of ether by means of a half ounce phial. The ether upon reaching the torricellian vacuum immediately springs into vapour and forces the mercury down the tube. If the tube is inclined, the ebullition ceases. Exp. Place over a lamp a Florence flask, about three-fourths filled with water ; let it boil briskly during a few minutes ; and immediate- ly on removing it from the lamp, cork it tightly, and suddenly invert it. The water will now cease to boil : but on cooling the convex part of the flask, by a stream of cold water, the boiling will be renewed. Applying boiling water to the same part of the flask, the water will again cease to boil. This renewal of the ebullition by the application of cold, (an apparent paradox,) is owing to the formation of an imper- fect vacuum over the hot water, by the condensation of steam ; and the suspension of boiling, on reapplying the heat to the renewed pres- sure on the surface of the hot water, occasioned by the formation of fresh steam. The same fact is illustrated by the common pulse glass, in which the fluid is made to boil by the mere heat of the hand. 2. When, atmospheric pressure, is increased, fluids require a higher temper- ature to produce their ebullition. Water cannot be heated under common circumstances beyond 212, because it then acquires such an expansive force as enables it to over- come the atmospheric pressure, and fly off in the form of vapour. But if subjected to sufficient pressure, it may be heated to any extent with- out boiling. This is best done by heating water while confined, in a strong copper vessel, called Papin's Digester. In this apparatus, on the application of heat, a large quantity of vapour collects above the water, which checks the ebullition by the pressure it exerts upon the surface of the liquid. There is no limit to the degree to which wa- ter may be heated in this way, provided the vessel is strong enough to confine the vapour ; but the expansive force of steam under these cir- cumstances is so enormous as to overcome the greatest resistance. An apparatus for exhibiting the same fact, has been contrived by Dr. Marcet, of which a figure and description will be found in Webster s Brande and Henry's Chcm. i. 126. It should be observed, that during the conversion of a liquid into vapour, caloric is absorbed. This is proved by the well known fact, that the temperature of steam is precisely the same as that of boiling water from which it rises, so tjiat all the caloric which enters into the liquid is solely employed in converting a portion of it into vapour, without affecting the temperature of either in the slightest degree, pro- vided the latter is permitted to escape with freedom. On the other hand, when this vapour is condensed into water, the caloric which was latent, according to the explanation of Dr. Black, becomes free. The exact amount of caloric rendered latent by vaporization, may therefore be ascertained by condensing the vapour in cold water and observing the rise of temperature occasioned by it. From the experiments of Dr. Black and Mr. Watt, conducted on this principle, it appears that steam of 212, gives out as much caloric as would raise the tempera- ture of an equal weight of water by 950 degrees, all of which had pre- viously existed in the vapour without being sensible to a thermometer. The latent heat of the vapours of different liquids has been investi- 56 EFFECTS OF CALORIC. gated by Dr. Ure, and by M. Despretz. From the results, Dr. Ure has constructed a table. [See his Dictionary of Chemistry.'} The only fluid, the vapour of which can be converted to any particu- lar use, is water. Owing to the heat which it gives out when conden- sed into steam, it is often used for heating large quantities of water. It is also employed for heating rooms and for carrying on different chemical processes, in which too great heat would be injurious, as in assisting fermentation and in drying substances gradually, and with- out the risk of burning. In consequence of the great elasticity of steam, it is employed as a moving power in the steam-engine. The construction of this ma- chine depends on two properties of steam, namely, the expansive force communicated to it by caloric, and its ready conversion into water by cold. The effect of both these properties is well shown by a little instrument devised by Dr. Wollaston. It consists of a cylin- drical glass tube, six inches long, nearly an inch wide, and blown out into a spherical enlargement at one end. A piston is accurately fitted to the cylinder, so as to move up and down the tube with free- dom. When the piston is at the bottom of the tube, it is forced up by causing a portion of the water, previously placed in the ball, to boil by means of a spirit-lamp. On dipping the ball into cold water, the steam which occupies the cylinder is suddenly condensed, and the pis- ton forced down by the pressure of the air above it. By the alternate application of heat and cold, the same movements are reproduced, and may be repeated for any length of time. The moving power of the steam-engine is the same as in this ap- paratus. The only essential difference between them is in the mode of condensing the steam. In the steam-engine, the steam is con- densed in a separate vessel, called the condenser, where there is a re- gular supply of cold water for the purpose. By this contrivance, which constitutes the great improvement of Watt, the temperature of the cylinder never falls below 212. Turner. REFERENCES. For a table of the boiling points of the most important liquids, see Ure\t Diet, of Client, and L. U. K. art. Heat, 50. Gay Lussar. Muncke and Biot, on the fixedness of the boiling point of Fluids Ann. of Phil. xii. 129. Lardner^s Popular Lectures on the Steam- Engine, and Professor Remcick's Treatise on the same subject. Evaporation. Evaporation as well as ebullition consists in the for- mation of vapour, and the only assignable difference between them is, that the one takes place quietly, the other with the appearance of boiling. Evaporation takes place at common temperatures, as may be proved by exposing water in a shallow vessel to the air for a few days, when it will gradually diminish, and at last disappear entirely. Most fluids, if not all of them, are susceptible of this gradual dissi- pation ; and it may also be observed in some solids, as for example, in camphor. Evaporation is much more rapid in some fluids than in others, and it is always found that those liquids, whose boiling point is the lowest, evaporate with the greatest rapidity. Thus alcohol, which boils at a lower temperature than water, evaporates also more freely ; and ether, whose point of ebullition is lower than that of alcohol evaporates with still greater rapidity. The chief circumstances that influence the process of evaporation are extent of surface, and the state of the air as to temperature, dry- ness, stillness, and density. EFFECTS OF CALORIC. 57 As a large quantity of caloric passes from a sensible to an insensi- ble state during the formation of vapour, it follows that cold should be generated by evaporation. A very simple experiment will prove it. If a few drops of ether be allowed to fall upon the hand, a strong sensation of cold will be excited during the evaporation ; or if the bulb of a thermometer, covered with lint, be moistened with ether, the production of cold will be marked by the descent of the mercu- ry.* 1 But to appreciate the degree of cold which may be produced by evaporation, it is necessary to render it very rapid and abundant by artificial processes ; and the best means of doing so, is by removing pressure from the surface of volatile liquids. Water placed under the exhausted receiver of an air pump, evaporates with great rapidi- ty, and so much cold is generated as would freeze the water, did the vapour continue to rise for some time with the same velocity. But the vapour itself soon fills the vacuum, and retards the evaporation by pressing upon the surface of the water, t This difficulty may be avoided by putting under the receiver a substance, such as sulphuric acid, which has the property of absorbing watery vapour, and conse- quently of removing it as quickly as it is formed. Such is the prin- ciple of Mr. Leslie's method for freezing water by its own evapora- tion. Edinburgh Encyclopedia, art. Cold. See also Dr. Cullen on the Cold produced by Evaporation, Edinburgh Physical and Literary Es- says, ii. 159. The action of the Cryophorus, an ingenious contrivance of Dr. Wollaston, depends on the same principle. It consists of two glass balls, perfectly free from air, and joined together by a tube. One of the balls contains a portion of distilled water, while the other parts of the instrument, which appear empty, are full of aqueous va- pour, which checks the evaporation from the water by the pressure it exerts upon its surface. But when the empty ball is plunged into a freezing mixture, all the vapour within it is condensed; evaporation commences from the surface of the water in the other ball, and it is frozen in two or three minutes by the cold thus produced. Phil. Trans. 1813. * The production of cold during evaporation, is by no means confined to the more volatile liquids. Koempfer states, that on the borders of the Persian Gulf the winds are so scorching, that travellers are suddenly suffocated, un- less they cover their heads with a wot cloth ; but if this be too wet, they im- mediately feel an intolerable cold, which would become fatal to them if the moisture were not speedily dissipated by the heat. The cold, which is pro- duced by the act of evaporation, ceases as soon as that is finished, by the cloth becoming dry. Watson's Chem. Essays, iii. 126. Wet clothes also are injurious, because the evaporation produces cold on the surface and thus < onstricts the extreme vessels. f [n Glasgow and the neighborhood, soda and alum leys are brought to the requisite degree of concentration, by passing over their surface a brisk current of air which has previously passed through a fire ; so that the flame of the fire plays over the surface of the evaporating liquor. And this process has been found more convenient and economical, than the method of evaporating liquid* by applying heat to the bottom of vessel? containing them. Thomson's Out- lines of Heat, #r. 243. 58 EFFECTS OF CALORIC. Liquids which evaporate more rapidly than water, cause a still greater reduction of temperature. The cold produced by the evapo- ration of ether in the vacuum of the air-pump, is so intense as under favorable circumstances to freeze mercury. Advantage has also been taken of this circumstance in Mr. Howard's plan for refining sugar, and in plans for preparing pharmaceutical extracts in vacua. Repcrtc:y of Arts, 2d Ser. xxiii. 4* xxv. Concerning the cause of evaporation a difference of opinion exists among chemists. It was at one time supposed to be owing to a chem- ical attraction between the air and water. But Mr. Dalton has shown, that caloric is the true and the only cause of the formation of vapour. As our limits do not permit us to enter into these discussions, we shall refer the reader to Turner's Chemistry. Henry's Chem. Dalton, in Manchester Memoirs, v. Ure, in Phil. Trans. 1818. Biot Traite de Pkys. 1. Faraday on ike existence of a limit to Vaporization, PhiL Trans. 1826. The presence of watery vapour in the atmosphere, is owing to evaporation which takes place from the water on the surface of the earth. As this evaporation goes on to a certain extent, even at low temperatures, it is probable that vapour is always present in the air, though its quantity is subject to great variation, in consequence of the changes of temperature to which the air is constantly subjected. But even when the temperature is the same, the quantity of vapour is still found to vary ; for the air is not always in a state of satura- tion. At one time it is excessively dry ; at another it is fully satu- rated ; and at other times it varies between these extremes. Instru- ments have been constructed to determine this variable condition of the atmosphere as to saturation, which are called Hygrometers. These consist for the most part of some substance, such as human hair, or a fine slip of whale bone, which is elongated by a rnoist atmosphere, and shortened by a dry one. The extreme points are attained by placing it, first in air artificially dried, and then in air rendered as humid as possible. The degree of expansion or contraction is rendered more sensible by connecting it with an axis, which moves a circular index, like the finger of a clock. Mr. Leslie, by a slight modification of his differential thermometer, makes it serve the purpose of an hygrome- ter : for if one of the balls be covered with silk, and then moistened with water, the rate of evaporation will be shown by the degree of cold produced, as indicated by the descent of the liquid in the oppo- site leg of the instrument. The drier the air, the quicker will be the evapoiation, and the greater the effect in moving the liquid within the instrument. Henry, i. 280. But the most perfect instrument of this kind, is that invented by Mr. Daniell, for a particular description of which the reader is re- ferred to DaniclVs Meteorological Essays or to the Library of Useful Knowledge, art. Pyrometer and Thermometer, where several modifica- tions of the tfygrtfmtttr are also described. For information on the subject of Hygrometers, sec also Prof. Forbes' Jteport on Meteorology, made to the Brit. Ass. in 1832. I should also mention that Mr. A. Hayes has described a dew-point Hygrometer in Siltimfai's Jour- nal, xvii. 351. SPECIFIC CALORIC. 59 SECTION V. SPECIFIC CALORIC. Equal weights of the same body at the same, temperature, contain the same quantity of caloric. But equal weights of different bodies at the same temperature, contain unequal quantities of caloric. Thus if we add a pint of water at 100 J F. to a pint of the same liquid at 50 a , the mixture will have a temperature of 75, or the mean between the two ; that is, the 25 which the hot water has lost, has been just sufficient to raise the cold by as many degrees. But if one pound of mercury at 185 F. is mixed with a pound of water at 40, the mix- ture will have a temperature of 45 only ; or if the experiment be re- versed by having the water at 185 and the mercury at 40, the mix- ture will have a temperature of 180. In the first case, 140 degrees lost by the mercury served to heat the water by five degrees, and in the second, five degrees lost by the water sufficed to raise the temper- ature of the mercury by 140. It hence appears that 28 times more caloric is required to raise the temperature of water through one or more degrees, than for heating an equal weight of mercury to the same extent. By mixing water with various other substances it has been found that it requires different quantities of caloric to heat them equally. Thus on the addition of warm water to a jar containing a pound of water at 50, the temperature will rise, say 10 ; on adding a similar quantity of warm water to another jar containing a pound of spermaceti oil, it will rise 20 ; and the same addition to a jar containing a pound of powdered glass will cause a rise of 50. Here then it will be observed that equal quantities of caloric added to water, oil and glass, have raised the temperature of the first 10, of the second 20, and of the third 50 degrees. Now it is clear that if we wished to raise them all to the same temperature, say 50, we must add twice and a half as much to the oil, and five times as much to the water. The quantities of caloric which they are capable of receiving, are therefore as glass 10, oil 20, water 50 ; or taking water as the standard, and calling it 1000, they are water 1000, oil 500, glass 200. The term employed, to designate this remarkable difference, by Dr. Black, who first observed it, was capacity for caloric. But as this term is apt to lead to erroneous impressions concerning the cause of this difference, that of specific caloric has been substituted for it, and is now generally employed. When substances can be mixed together, as in the instances above mentioned, their specific caloric can be determined, by ascertaining the relative quantities of caloric which is requisite for heating them by an equal number of degrees. Water is commonly employed as one of the substances, and the specific caloric of other bodies is usually compared with that of water. In some cases, however, the bodies under examination cannot be in- timately mixed. When the specific heat of a solid mass of metal is to be examined, it may be heated throughout to a certain degree, and then surrounded by water, at 32, observing the increase of temperature, which is gained by the water, and calculating the specific heat as be- fore. This was the method of Wilcke, of Stockholm. [Thomson's Chem. i. 100.] Lavoisier and La Place substituted ice for water, placing, by means of an apparatus called the Calorimeter, the heated 60 SPECIFIC CALORIC. body in the centre of a quantity of ice, and determining the caloric evolved, by the quantity of ice melted in each instance. Lavoisier's Elements. It has been ascertained by Petit and Dulong, who have recently in- vestigated this subject, that the specific heats of bodies are greater at high than at low temperatures. They have also deduced from their researches the law, that the atoms of all simple bodies have precisely the same specific heat. [Ann. of Phil. v. 13.] This, however, is to be considered at present, merely in the light of an ingenious speculation, derived from a train of reasoning, a defect in any part of which must be fatal to the conclusions. See Henry, i. 160. Dalton's New Syst. ii. 280. Also, Professor Bache's Strictures on the Table of Petit and Du- long Jour, of the Acad. of Nat. Scien. Phil. Jan. 1829. The determination of the specific heat of gases has successively en- gaged the attention of some of the most profound and ingenious chemical philosophers. Among the most valuable observations on this subject, are those of Delaroche and Berard, De La Rive and F. Marcet. In the experiments of the two latter philosophers which are the most recent, they appear to have avoided sources of fallacy which were not provided against by those who preceded them in these in- vestigations. From a review of their experiments, they consider the following conclusions as legitimately deducible. 1. That under the same pressure, and with equal and constant volumes, (the elasticity alone varying,) all gases have the same spe- cific heat. 2. That, all other circumstances remaining the same, the specific heat diminishes at the same time as the pressure, and equally for all gases, according to a progression but little convergent, and in a much less ratio than that of the pressures. 3. That each gas has a different power of conducting heat. Henry's Chem. i. 163. REFERENCES. For tables of the Specific Htats of some Gases, see Library of Useful Knowledge, Art. Heat, or Thomson's Outline of Heat, fyc. 71. Delaroche and Berard on the Specific Heat of Gases, Ann. of Phil. ii. Herepath on the causes of Heat in Gases, Ann. Phil. xvii. Same author's Tables of Temperature, and replies to him, Ann. of Phil. xvii. & xviii. Meikle on the Specific Heat of Air. Edin. New Phil. Jour. ii. 328. SECTION VI. SOURCES OP CALORIC. The sources of caloric may be reduced to six, viz. 1. THE SUN, 4. MIXTURE, 2. FRICTION, 5. ELECTRICITY, 3. PERCUSSION, 6. COIUBUSTIQN. The Sun. The heat produced by the sun is found to differ according to the surface exposed, and the colour of the surface. Franklin found that when pieces of cloth of various colours were exposed upon snow to the light of the sun, they sunk deeper, and consequently acquired heat, in proportion to the darkness of their colour. This experiment was repeated with more precision by Sir H. Davy, with similar results. The temperature produced by the direct action of the sun's rays sel- dom exceeds 120 ; a higher temperature however, may be produced SOURCES OF CALORIC. 61 if we prevent the heat communicated from being carried off to sur- rounding bodies. But when the sun's rays are concentrated by means of a burning lens, intense heat is produced, provided they are directed upon some body capable of absorbing and retaining them. Some lenses have been constructed of extraordinary power, and among them may be mentioned those of Tschirnhausen and M. de Trudaine, by which many of the most refractory substances were readily fused. [For a description of these and other powerful lenses, see Cliaptal's Chem. app. to the Arts, and Parkes' Chcm. Essays.] According to Count Buffon, however, the only way by which the sun's rays can be made to produce an intense heat at a great distance, is by the com- bination of a considerable number of plain mirrors, so disposed 'as to throw numerous images of the sun upon the same spot. v By an in- strument constructed upon this principle he was enabled to melt the metals and metallic minerals at the distance of forty feet, and to kin- dle wood when at the distance of 210 feet. Parked Chem. Essays. 2. Friction. Fires are often kindled by rubbing pieces of dry wood smartly against one another. So also when parts of heavy machine- ry rub against one another, the heat excited, if the parts in contact are not well greased, is sufficient for kindling wood. The axle-tree of carriages has been burned from this cause, and the sides of ships are said to have takSn fire by the rapid descent of the cable. [Parry's 2d Voyage, N. Y. Ed. 212.] Count Rumford observed, that in the boring of cannon, by the friction of the borer, a very large quantity of caloric is rendered sensible. To ascertain its quantity, he fixed a solid cylinder of brass in a trough filled with water, and having adapt- ed the borer to it, connected with the machinery by which it is turn- ed, it was made to revolve in the usual manner, at the rate of 32 times in a minute. Heat was soon excited, and of course raised the tem- perature of the metal, and of the surrounding water. In an hour the temperature had risen from 60 to 107 ; and in two hours and a half the water was brought to boil, the quantity of this water being 18 Ibs. ; the apparatus itself, which was of course raised to the same tempera- ture, weighed 15 Ibs. From this experiment it may be safely concluded, that the access of atmospheric air is not essential to the evolution of caloric ; an infer- ence confirmed also by the experiment of Pictet who constructed an apparatus by which friction could be excited in an exhausted receiver. The thermometer rose higher than when this friction was going on in open air. Rumford 1 s Essays Pictet' s Essay on Fire. It was hence concluded by these philosophers that caloric was not a material substance, but a kind of motion. The same opinion was adopted by Sir H. Davy. But although these facts present a difficulty in the adoption of the hypothesis that caloric is material, the other phenomena can be more satisfactorily explained upon the latter sup- position, and hence it is quite generally adopted by the chemists of the day. See references under the first Section of this Chapter. 3. Percussion. The heat excited by percussion is equal, and in many cases superior, to that evolved by friction. When a piece of iron is smartly and quickly struck with a hammer, it becomes red hot ; and another familiar illustration is the production of heat by the compres- sion ofair in the common fire-syringe. No heat, however, has been observed to follow the percussion of liquids, nor of soft bodies which easily j'ield to the stroke. 62 SOURCES OF CALORIC. 4. Mixture. We have already given some examples of the effect of mixture in producing heat ; as in the case of the mixture of sulphuric acid and water, and the mixture of sulphuric acid with the chlorate of potash and sugar. [See page 23.] So also some gaseous bodies, which, when united .together, form solids, as ammoniacal and muriatic acid gases, evolve a considerable degree of heat. Some times, how- ever, the temperature of the mixture is reduced, and the sensation of cold produced ; as is remarkably the case in some of the freezing mix- tures. It may be laid down as a rule, to which there are few exceptions, that when the compound formed by the union of two bodies is more fluid or dense than the mean fluidity or density of the two bodies be- fore mixture, then the temperature sinks ; but when the fluidity or the density of the new compound is less than that of the two bodies be- fore mixture, the temperature rises ; and the rise is pretty nearly pro- portional to the difference. Thomson's Chem. i. 143. 5. Electricity. This will be particularly noticed in Chapter 4. 6. Combustion. This may be denned to be the disengagement of heat and light which accompany chemical action. Modern discoveries have shown the insufficiency of former theories upon this subject. But in the present state of our knowledge, we are unable to substitute one that is wholly free from objection ; and we are left to the naked statement of the fact, that combustion is the general result of the actions of any substances which possess strong chemical attractions, or different electrical relations. Ures Chem. Dictionary. I shall notice the leading phenomena of combustion under the fol- lowing heads, viz. 1. The temperature necessary to inflame different bodies. 2. The nature of flame. 3. The heat given out by different combustibles in burning. 4. The causes which modify, promote or extinguish combustion. 1. The temperature necessary to inflame bodies. The temperature necessary for inflammation, is very different in different bodies. Thus, if we heat phosphorus to 150 F. it takes fire ; but sulphur requires a heat of 500 3 for its inflammation. The successive combustibilities of bodies can be shown as follows : Exp. Into a long bottle with a narrow neck introduce a lighted taper, and let it burn till it is extinguished. Carefully stop the bottle and introduce another lighted taper. It will be extinguished before it reaches the bottom of the neck. Then introduce lighted sulphur. This will burn for some time ; and after its extinction, phosphorus will be as luminous as in the air, and if it be heated will burn with a pale yellow flame. The combustibilities of various gaseous bodies are to a certain ex- tent as the masses of heated matter required to inflame them. Thus, an iron wire l-40th of an inch in diameter, heated to a cherry red, will not inflame olefiant gas, but it will inflame hydrogen. A wire of l-8th of an inch, heated to the same degree, will inflame olefiant gas. But a wire l-500th of an inch, must be heated to whiteness to inflame hydrogen, though at a low red heat it will inflame bi-phosphuretted gas. 2. Nature of flame. Flame is the rapid combustion of volatilized matter, or in other words, volatile combustible matter heated so highly SOURCES OF CALORIC. 63 > t as to become luminous. Davy has asserted that the flame of combus- tible bodies must be considered as the combustion of an explosive mixture of inflammable gas or vapour and air, and that this combus- tion takes place in the interior as well as at the surface of contact. A simple experiment, however, proves that no combustion goes on in the interior of a flame. Exp. Place a piece of coin or metal upon an earthen plate ; place a small piece of phosphorus upon the coin, and surround the latter with alcohol. The alcohol may be fired without setting fire to the phosphorus, which remains unaffected in the interior of the flame, but as soon as the external air comes in contact with it, combustion in- stantly takes place. The interior of a flame consists of aqueous vapour, which may be exhibited by an ingenious apparatus contrived by Mr. Blackadder. Edin. New Phil. Jour. i. 224. The light of a flame may be shown by the prism to consist of sev- eral colours. The flame of a candle consists of four portions, al- though these may be considerably modified by various circumstances. A blue portion which extends from the base to about the middle of the flame ; an attenuated opaline brush over the whole exterior surface of the blue part of the flame ; a cone ot yellowish white light, commencing on the inner surface, and at a short distance from the base of the blue portion ; and an interior cone of white light, the base of which is above the upper part of the blue portion. Edin. New. Phil. Jtmr. i. 228. Flame has electric polarity ; that of burning phosphorus being acid, is bent towards the positive pole, and that of a candle containing ig- nited carbon, toward the negative. Brande, Phil. Trans. 1814, noticed in Ann. of Phil. iv. 441. The products of flame are usually water and carbon. The use of a wick is to raise the fluid by capillary attraction. It is not, however, an essential part of the oil or alcoholic lamp. Lamps without wicks have been constructed by Mr. Blackadder, and are supposed by him to possess many advantages. Ed. New Phil. Jour. i. 52. The colour of flame depends upon the presence of various for- eign substances, and an attention to it is of great utility in many analytical researches. Thus the flame of alcohol is tinged with a fine carmine red by nitrate of strontia, yellow by nitrate of baryta, green by nitrate of copper, &c. This is by some supposed to be owing to the reduction of the substances employed, to the metallic state. Flame is supposed to possess a very high temperature. By Sir H. Davy it was estimated at 7000 F. But there can be no doubt that the temperature varies with the combustible, and that it is influenced also by other circumstances ; and it perhaps never reaches the point first mentioned. One of the arguments advanced by Davy, viz. that a fine platina wire becomes white hot in a part of the flame of a spirit lamp where there is no visible light, has been weakened by the fact since discovered, that the mere contact of a jet of hydrogen with spongy platina causes the incandescence of the latter. The other argument of Davy appears also open to objection. 3. Heat given out by different combustibles in burning. On this subject experiments have been made by Lavoisier, Crawford, Dalton, Rumford and Davy. But the results of these experiments are 64 SOURCES OF CALORIC. so discordant that they can scarcely afford any correct guide. They appear to agree, however, that of the numerous substances tried, hy- drogen gives out the most heat and carbonic oxide the least. Ure's Chem. Dictionary. With respect to the heat given out by ordinary combustibles used as fuel, the experiments of Mr. Bull, of Philadelphia, are the most satisfactory. The following results are extracted from his table, in the Transactions of the American Philosophical Society, N. S. iii. 1. Amount of heat given out by various combustibles a cord of shell- bark hickory being equal to 100. Shell-bark hickory 100 White oak 81 Hard maple ...... 60 White beech 65 White pine 42 Lehigh coal (a ton 2240 Ibs.) ... 99 Lacka waxen coal ..... 99 Schuylkill coal 103 4. Causes ichich modify, promote or extinguish combustion. Although the progress of discovery has shown that the general- ization proposed by Lavoisier, viz. that in all cases of combustion, oxygen combines with the burning body, is not of universal applica- tion ; it must be confessed that in most cases the presence of oxygen is essential to the process of combustion. In ordinary cases, the more complete the access of atmospheric air and the more perfect its contact with the combustible, the more perfect will be the combustion. It is upon this principle that most of the modern improvements in the con- struction of lamps and furnaces depend. Upon the same principle also the heat may be greatly increased, by causing a blast through a flame. For this purpose, a blow-pipe,, to be blown either by the mouth or a pair of bellows, is used. The form of this instrument is not material ; and several modifications of it have been proposed. The principle upon which it acts, is that a constant supply of air is brought to the inflammable matter, thus rendering the combustion more complete, and the consequent heat greater. There are other forms of the blow-pipe, as that in which alcohol is employed, and the oxy-hydrogen blow-pipe, which will be noticed hereafter. Flame being gaseous matter so highly heated as to become lumin- ous, will be extinguished by a reduction of its temperature. This can be effected by bringing near it some metallic conductor. Let the smallest possible flame be made by a single thread of cot- ton immersed in oil, it will be found to yield a flame of about l-30th of an inch in diameter. Let a fine iron wire of 1 -180th of an inch, made into a ring 1-lOth of an inch in diameter, be brought over the flame. Though at such a distance, it will instantly extinguish the flame, if it be cold ; but if it be held above the flame, so as to be slightly heated, the flame may be passed through without its being extinguished. That the effect depends entirely on the power of the metal to abstract the heat of the flame, is shown by bringing a glass capillary ring of the same diameter and size over the flame. This being a much worse conductor of heat, will not, even when cold, LIGHT. 65 extinguish it. If its size, however, be made greater, and its circum- ference smaller, it will act like the metallic wire, and requires to be heated to prevent it from extinguishing the flame. Davy on Flame. Ure's Chzm. Dictionary. It is upon this principle that Sir H. Davy constructed his Safety Lamp, one of the most valuable discoveries of the age. In this in- strument there is a succession of metallic orifices forming the wire fauze, which constitutes the cage of the lamp, and thus by cooling own the flame prevents it from communicating with the explosive mixture. The same principle has also been applied by the Chevalier Aldini, to the construction of a robe for the preservation of firemen against fire and flame. [Set SiUiman's Jour, xviii. 177, xx. 96.] M. Libri of Florence ascribes the protection which Davy's lamp affords, to the re- pulsion exerted by the metallic wire upon the flame. Brewsters Edin. Jour. ix. 311. REFERENCES. Graham on the Heat of Friction Ann. of Phil, xxviii. 2(!0. The article Combustion, in fJres 1 Chem. Dictionary, containing an account of the various theories on this subject Also, Thomson*^ Chemistry. Davy on I 'lame. RwmfortPs Experiments on the combustions of Woods See his Essays, and Thoinsoifs Chemistry. Berzlius on the Blow-pipe. Lin- ton on the colour of Flames Emporium of Arts, v. 457. PorretCs observa- tions on the flame of a Candle Ann. of Phil. ix. 337. Sym. on Flame Arm. of Phil. viii. 321. Murray on the same subject Ann. of Phil. xvi. 424. On the construction of Furnaces, and the management of Fuel See Parkes* Essays ; and also, Grains Operative Chemist. GENERAL REFERENCES ON HEAT. Count Rnmford's Essays. Dalian's New System of Chemical Philosophy. Dr. Bla(K t s Lectures, by Robinson. Berthollefs Chemical Statistics. S cheek's Treatise on Air and Fire. Lf she's Experimental Inquiry into the Nature of Pleat. Pictefs Essay on Fire Biot's Precis. Elementaire. Murray 1 s System of Chemistry Thom- son's Outline of the Science of Heat and Electricity. Library of Useful Knowledge, article Heat. Lavoisier's Elements of Chemistry. Aiki/fs Dic- tionary of Chemistry and Mineralogy, article Caloric. AmotCs Physics, \\. Lardnef on Heat. CHAPTER III. LIGHT. When the sun rises above the horizon a mode of communication is established, which in spite of his great distance, acquaints us with his existence. This mode of communication is called Light. And bodies which can thus manifest their existence are said to be lumin- ous, (of themselves, ) as the sun, the stars, &c. Most bodies, however, as we shall hereafter see, become luminous when their temperature is sufficiently elevated, and they lose this property when they be- come cool. But even when they become opaque, if enlightened by 66 LIGHT. a luminous body, they acquire the property of transmitting light in the same way as if they were luminous ; and these bodies are said to be visible by reflection. Concerning the nature of light, philosophers are divided into two classes. The one class consider it to consist of particles of matter actually emanating from the luminous body ; the other conceive it to be transmitted by means of pulsations or vibrations excited in an elastic fluid, in the same way that sound is conveyed through the air. The former opinion was adopted and maintained by Newton, and is now generally received, as best accounting for the phenomena which it exhibits.* 1 The consideration of the laws of light, so far as they relate to the phenomena of its movement, and its effects in producing vision, con- stitutes the science of Optics ; and are the objects, therefore, not of Chemistry, but of Natural Philosophy. We shall, however, briefly notice the physical properties of light, as they bear upon important questions of chemical enquiry. The light of the sun moves with the velocity of 192,000 miles in a second of time, so that it passes through the whole distance from the sun to the earth in about eight minutes. Light is transmitted through the air in straight lines, which are called rays of light, and it is by means of these that vision is effec- ted. When a ray of light falls upon a polished surface, it is thrown off or reflected. And the angles of incidence and reflection are in this case always equal, whatever may be the obliquity of the incident ray. A ray of light passing obliquely from one medium to another, does not proceed in the same direction as before, but is refracted, or bent out of its course. If the new medium be denser than the old, the ray of light is bent or reflected nearer to the perpendicular ; but in passing out of a denser into a rarer medium, it is refracted from the perpendicular, and there is a constant proportion between the sine of the angle of incidence and that of refraction. Transparent media, also, not only cause a change in the direction of a ray, but de- compose it into its constituent parts, an effect which has been call- ed dispersion. When a ray of light, in passing through certain bodies, (Iceland spar for example,) exhibits a double image of any object viewed through them, it is called double refraction. In this case the light is divided into two pencils, the one following the law of ordinary re- fraction ; the other being differently affected, constituting extraordi- nary refraction. Light is not a simple body, but is capable of being divided by the prism into seven primary rays or colours, viz. red, orange, yellow, freen, blue, indigo, and violet. These rays differ in their refrangi- ility, the red being the least, and the violet the most refrangible. The image formed by the different rays, thus separated, is called the * Dr. Brewster thus briefly contrasts the two systems. ** In the Newtonian theory, light is supposed to consist of material particles emitted by luminous bodies; and moving through space nith a velocity of 192,003 miles in a se- cond. In the unduiatory theory, an exceedingly thin and elastic medium, call- ed ether, is supposed to fill all space and to occupy the intervals between the particles of all material bodies." Optics, 134. LIGHT. 67 solar spectrum. According to Dr. Wollaston, the spectrum consists of four colours only, viz. red, green, blue and violet, and these oc- cupy spaces in the proportion of 16.23. 36.25. These different colour- ed rays being collected by a lens into a focus, again produce colour- less light. Again, Dr. Brewster gives a new analysis of solar light indicating three primary colours, forming coincident spectra of equal length. Edin. Jour, of Science, N. S. v. 197. Sir W. Herschel found that the prismatic colours differ in their illu- minating power. The orange possesses this property in a higher de- gree than the red ; and the yellow rays illuminate bodies still more perfectly. The maximum of illumination lies in the brightest yellow or palest green. The green itself is nearly equally bright with the yellow; but from the full deep green, the illuminating power de- creases very sensibly. That of the blue is nearly equal to that cf the red ; the indigo has much less than the blue ; and the violet is very deficient. Phil. Trans. 1800. The heating powers of the rays follow a different order. If the bulb of a very sensible thermometer be moved in succession through the differently coloured rays, it will be found to indicate the greatest heat in the red rays ; next in the green, and so on, in a diminishing progression to the violet. But when it is removed entirely out of the confines of the red rajs, but with its ball still in the line of the spec- trum, it rises even higher than in the red rays, and continues to rise, till removed half an inch beyond the extremity of the red rays. It was hence inferred by Herschel, that there exists in the solar beam a distinct kind of ray, which causes heat, but not light ; and that these rays being less refrangible than the luminous ones, deviate in a less degree from their original direction in passing through the prism. Though the truth of the statement, that the prismatic colours pos- sess different heating powers, has been confirmed by all succeeding experiments, there has been much difference with regard to the spot at which the heat is a maximum. The opinion of Herschel has how- ever been fully confirmed by the recent observations of Mr. Seebeck. Edin. Jour, of Science, i. 358. When the solar rays traverse a biconvex lens, they are collected to- gether in a focus, but the focus of the calorific rays is a short dis- tance behind that of the luminous, showing that they are differently refracted. Berzelius. Beyond the confines of the spectrum on the other side, viz. a little beyond the violet ray, the thermometer is not affected : but in this place it is remarkable that there are also invisible rays of a different kind which produce all the chemical effects of the rays of light, and with even greater energy. It is well known that if chloride of silver is exposed to the direct light of the sun, it is speedily changed from white to black. The rays separated by the prism possess this power of blackening chloride of silver in various degrees. The blue rays for example, effect a change in 15 seconds, which the red require 2& minutes to accomplish ; and, generally speaking, the power diminish- es as we recede from the violet extremity. But entirely out of the spectrum the effect is still produced. Hence it is inferred that there are certain rays which excite neither heat nor light ; and which, from their peculiar agency, have been called Chemical or de-oxidizing rays. It appears, therefore, that a ray of light contains three distinct sets of rays, viz. The illuminating, the heating, and the chemical or deoxi- 63 LIGHT. dizing. It may also be added, that the more refrangible rajs of light seem to possess the property of rendering steel or iron magnetic : a property discovered by Dr. Morichini of Rome, and confirmed by the* experiments of Mrs. Somerville, who succeeded in magnetizing a sew- ing needle by less than two hours exposure to the violet ray. Phil. Trans. 1828. This effect, however, has been much questioned, and is wholly rejected by Priess and Moser. Brewster's Edin. Jour. N. S. ii. 225. There are many bodies in nature which possess the property of giv- ing out light without any sensible emission of heat ; and these arc commonly known by the name of phosphori. The leading divisions of these substances are : 1. Solar phosphori; or those which require a previous exposure to solar or other light to become luminous. Such are Canton's, Bald- win's and the Bolognian phosphori, which will be described hereafter. To the same class belong several natural bodies which retain light arid give it out unchanged. Thus, snow is a natural solar phosphorus. 2. Phosphori from heat; or those which become luminous, by heat alone. Thus powdered fluate of lime becomes luminous, when throwu on an iron plate raised to a temperature rather above that of boiling water, and one of its varieties known to mineralogists by the name of Chlorophane, gives out abundantly an emerald green light, by the mere heat of the hand. The yolk of an egg, when dried, becomes luminous on being heated ; and so also do spermaceti, wax and tallow, during liquefaction. To exhibit the last mentioned fact, it is only necessary to place a lump of tallow on a coal, heated below ignition, making the experiment in a dark room. Brcwster. on the phosphorescence of certain fluids, Edin. Jour, of Science, iv. 178. 3. Spontaneous phosphori ; or those animal and vegetable substances which emit light spontaneously at common temperatures, without the necessity of previous exposure to light. This property is possessed in a remarkable degree by fish and some other marine animals ; and in these it makes its appearance before the commencement of putrefac- tion, and ceases when the latter is completely established. The lumi- nosity of sea water is ascribed to the presence ofanimalcnlac, which arc naturally phosphorescent. Of vegetable matters which become lumi- nous, the most remarkable is decayed wood. The chemical effects of light are very evident in the case of a mix- ture of chlorine and hydrogen, which explodes and produces muriatic acid. Again, chlorine and carbonic oxide have scarcely any tendency to unite, even at high temperatures, when light is excluded ; but ex- Eosed to the solar rays, they enter into chemical union. Chlorine also as but little action on water unless exposed to light. To the same class of the chemical effects of light, may be referred the decomposition of nitric acid, and the decomposition or change of colour of the salts of gold and silver. The green colour of vegetables is also owing to the influence of solar light. [For additional facts on the subject of the chemical influence oi Light, see Phil. Mag. and Ann. vii. 46^.] For measuring the intensities of light from various sources, an in- strument has been constructed which is called the Photometer. That of Mr. Leslie is founded on the principle, that light in proportion to its absorption, produces heat. The degree of heat produced, and con- sequently of light absorbed, is measured by the expansion of a confined portion of air. It is merely a very chlicate and small differential ther- 69 mometer, enclosed in a thin and pellucid glass tube. One of the balls, however, is rendered opake, either by tinging the glass or covering it with a pigment ; and hence this ball, when the instrument is suddenly exposed to light, becoming warmer than the clear bulb, indicates the effect by the depression of the fluid. Leslie s Enquiry. Some objections to this instrument have been stated, for which we must refer the reader to the Rev. Mr. Powell's Historical Sketch of Photometry, in the Ann. of Phil, xxvii. 371, where will also be found a notice of Rumford's Photometer, and of that proposed by Dr. Brew- ster ; and to Mr. Ritchie's paper on Leslie's Photometer, in ihe Edin. Jour, of Science, ii. 321. 339. and iii. 104. Brande's modification ot Leslie's Photometer, is described in his Journal, viii. 220.* The sources of light are, the, Sun and Stars, Chemical action, Heat and Percussion. The first of these we have already noticed. Chemical action. Whenever combustion forms a part of the phe- nomena, light, as is well known, is given out ; but light is also evolved in other instances, where nothing like combustion takes place. Thus, freshly prepared magnesia, added suddenly to highly concentrated sul- phuric acid, exhibits a red light. When the vapour arising from a so- lid, benzoic acid for instance, is condensed, light is evolved, and fused boracicacid, when passing to a solid form, exhibits the same phenome- non. So also some substances, during the process of crystallization give out scintillations of light, as sulphate of potassa and fluoride of sodium. Berzelius, i. 52. But, perhaps the most intense artificial light is that which is obtain- ed by directing the flame of the oxy hydrogen blow-pipe upon a small spherule of lime, about a quarter of an inch in diameter. The lime from chalk is best adapted to this purpose, as it is most easy to give it the proper form. The light thus produced is so brilliant as scarcely to be borne by the naked eye, and its use is therefore suggested for illu- minating light houses. It acts also as solar light does on mixtures of chlorine and hvdrogen, and on chloride of silver. Drummond, Phil. Trans. 1826. "Also Edin. New Phil. Jour. i. 182. Percussion. Light is also evolved by percussion and friction. Thus, two pieces of common bonet cane, rubbed strongly against each other ia the dark, emit a faint light. Two pieces of borax, quartz or sugar, have the same property in a more eminent degree. Some of the gases also, when highly compressed, give out light. Heat. When heat is applied to bodies, and continually increas9d, there is a certain temperature at which they become luminous ; and the body is then said to be red hot, or incandescent. The temperature at which solids in general begin to shine in the dark, is between 600 and 700 3 F. ; but they do not appear luminous in broad daylight, till they are heated to about 1000 F. The colour of incandescent bodies varies with the intensity of the heat. The first degree of luminousness is an obscure red. As the heat augments, the redness becomes more and more vivid, till at last it acquires a full red glow. Should the temperature still continue to increase, the charac- * The indications of these photometers cannot be depended on when there is much difference in the colour of the lights. In such cases the best method of obtaining approximative results, is by observing the d'sfarice from each light at which any given object, as a printed page, ceases to be distinctly visi- ble. The Illuminating power of the lights so cosnpared is as the squares of their distances. ELECTRICITY. ter of the glow changes, and by degrees becomes white, shining with increasing brilliancy as the intensity of the heat augments. Liquids and gases likewise become incandescent when strongly heated ; but a very high temperature is required to render a gas luminous, more than is sufficient for heating a solid body even to whiteness. The different kinds of flame, as of the fire, candles and gas light, are instances of in- candescent gaseous matter. REFFERENCES. Biotas Traite Precis, ii. Brewster's Optics. Library of Useful knowledge, Art. Double Refraction and Polarization of Light. Thomson" 1 s Chemistry, i. Aikiifs C/iem. Diet. Art. Phosphori. Lieut. In- galls on the Luniinousness of the Ocean Trans. Alb. Institute, \. Osann on some New Bodies, which absorb Light strongly Edin. New Phil. Jour. \\. 153. Mr. Powell on Solar Light and Heat, Ann. of Phil, xxiii. and xxiv. Also, remarks by the same author on Light and Heat from Terrestrial Sources, Ann. of Phil. xxir. 181, xxv. 201, 359, 401, and the same author's recent Report on Radiant Heat. RiimforcCs Inquiry concerning the Chemic- al Properties that have been attributed to Light, Phil. Trans, and Repert. of Arts, \st series, x. 189. In this paper the aut/ior attempts to show that the chemical properties usually ascribed to light, are the mere effects of the heat which is generated, or excited, by the ligkt that is absorbed by the bodies in which these changes are supposed to ta/ce place. On the identity of Light and Heat, see also ChaptaVs Client, i. CHAPTER IV. ELECTRICITY. The term Electricity, applied to the unknown cause of a peculiar kind of attraction, is derived from the Greek word electron, amber, be- cause the electric property was first noticed in this substance. In my remarks upon this subject, I shall briefly notice, 1st. The general or elementary facts of the science : 2d. The theory proposed to account for these facts : and 3d. The effects of accumulated elec- tricity. I. The general facts of electricity may be conveniently reduced to the following, viz : EXCITATION ATTRACTION REPULSION DISTRIBUTION TRANSFERANCE and INDUCTION. Library of Useful Knowledge, Art. Electricity. All these facts can be shown with the simple apparatus of a clean and dry glass tube, a dry silk handkerchief, and a few pith balls, sus- pended by silken threads. But they are much more strikingly exhibit- ed if we employ an Electrical Machine, an instrument which consists essentially of a circular plate of glass, or a glass cylinder, fixed upon an axle, and pressed by a cushion or Rubber, which is generally be- smeared with a soft compound, or an amalgam of mercury and tin with grease. At a short distance, is placed a metallic cylinder, sup- ported by glass feet, called the Prime Conductor, which at the end next the glass, has commonly a few projecting teeth made of pointed wire. ELECTRICITY. 71 If now the rubber is connected by a small chain or otherwise, with the table or floor, and the glass cylinder or plate made to revolve upon its axle, a crackling noise is heard, accompanied with a luminous ap- pearance, and on bringing the knuckle or a rounded metallic knob, near the prime conductor, a spark issues, accompanied with a snap or slight report, and with a pricking sensation when the knuckle is pre- sented. The glass is in this case said to be excited, and the substances thus susceptible of excitation are termed Electrics, in contradistinction to such as are not excited by a similar process, and which are termed Non- electrics. This distinction, however, is not founded in nature, for electricity may be excited in all solid bodies by friction, though for this purpose the friction is to be applied in different ways. Attraction and Repulsion. If, while the prime conductor is charged with electricity, a light body, as a pith ball, suspended by a silken thread, be brought near it, it is attracted by the conductor and adheres to it for a certain time ; after which it recedes, or is repelled from it. This change, however, does not take place in all bodies with equal ra- pidity ; some require a considerable time before they begin to recede ; others, and especially metallic bodies, are repelled the instant after contact. The phenomena of attraction and repulsion can also be stri- kingly exhibited by several amusing experiments ; as the electrical bells, the electrical dance, &c. It appears therefore that when bodies are electrified by contact with excited glass, they are repelled by it. The same thing also takes place, when they are electrified by excited resins. But when a body electri- fied by glass is brought near a body electrified by the resins, instead of repelling each other, they are now attracted. From these facts the following general laws have been deduced, viz : Bodies similarly elec- trified, repel each oilier ; bodies differently electrified, attract each other. It should be remarked also, that the production or excitation of one kind of electricity is always attended by the excitation of the other. Thus when glass is rubbed by silk or cloth, they assume opposite elec- trical states. This can be shown very strikingly by insulating the rubber of an ordinary machine. Distribution and Transference. If a pith ball or metallic globe, sus- pended by silk, after having been in contact with a charged conductor, be removed, and the ball be brought near to another ball, suspended in a similar manner, they will approach each other and then again recede. This second ball, when brought near a third, will exhibit the same phenomena, although in a less striking manner, as the amount of elec- tricity becomes gradually diminished by these successive operations. It is evident, therefore, that the electricity communicated to the first ball may be communicated to the second, and that from the second to the third, &c. in the same mariner that heat is transferred from one body to another. If, however, we bring in contact with a ball thus electrified, the hand or a metallic body, we observe, in some instances, a, spark, arid it loses the property of attracting another unelectrified ball, in conse- quence of the electricity having passed into the body. But if a tube of glass be substituted for the hand or the metallic rod, the body touched retains the whole of its electricity. We therefore infer that some bodies, as glass, are incapable of conducting electricity, while others, such as the metals and the human bodv, readily convey that influence. Hence the division of bodies into conductors and non-con- ductors the latter being those which are electrics, and the former ELECTRICITY. non-electrics. The two qualities, of a capability of excitation and a power of conducting electricity, appear to be incompatible with each other; for the one is always found to diminish in proportion as the other increases. The permanence of electricity in metallic bodies, which are suspended in the air by silk threads, shows that the air, as well as silk, is a non-conductor. Bodies which, in this way, are sur- rounded on all sides by non-conductors, are said to be insulated. The air, however, when it contains much moisture, becomes a conductor ; and the conducting powers of most bodies are influenced by changes of form and temperature. The metals are the most perfect conduct- ors ; the resins, amber and gum lac, the most perfect non-conductors. The phenomena of the transference of electricity are modified by the form of bodies. Hence the different effects which are observed when conductors in the form of balls, or pointed ones, are charged with the fluid. In the former case the electricity is equally diffused over the surface of the ball, and it has a low intensity ; in the latter, the intensity is greatly increased at the extremities, and this is accom- panied with a powerful tendency in the fluid to escape.* Induction. It has been shown that when an excited electric is brought near to an insulated ball, the latter is attracted. This arises from the fact that the natural state of the body has been disturbed, and an electricity of an opposite kind has, as it is said, been induced, in that part of the ball nearest to the electric ; whereas that part of the ball which is most distant has the same electrical state as the electric. Attraction, therefore, is in all cases, the result of this principle of in- duction. But when the ball comes in contact with the electric, it soon becomes of the same electric condition, and repulsion is observed. This principle can be more satisfactorily shown by the Leyden Jar. the inner side of which, by communication with the charged conduc- tor of a machine, is rendered positive, whereas the outer side is ren- dered negative by induction. When these two sides are brought into contact, by means of a Discharger, the restoration of the equilibrium * As the terms quantity and intensity or tension are often employed in treating 1 of electricity and galvanism, it may be proper to explain them more particularly. The former implies the actual quantity of electric power in any body; whereas intensity or tension, signifies? the stale of electricity indicated by the electrometer, and ils power of flying off from surfaces and passing through a certain stratum of air or other ill conducting medium. Tension, appears to depend upon the quantity of electricity accumulated on a given space; arid hence the intensity of those substances is the greatest, which have the greatest excess or deficiency of electricity in proportion to their surface. Suppose a charged Leyden jar to give a spark when discharged, of one inch in length, another uncharged jar, communicating with the former, would upon the same quantity of electricity being thrown in, reduce the length of the, spark to half an inch : thus the quantity of electricity remaining the same, its intensity is diminished by one-half, by its distribution over a larger surface. This accounts for the freedom with which electricity is given off by pointed conductors. For though the quantity of electricity accumulated on a sharp point, may be very small, it is still large when compared with the surface. The electric tension of the point is' the re fore very great, and hence x if positive, it gives off electricity to surrounding bodies, and if negative, receives it from them, with extreme velocity. ELECTRICITY. 73 of electricity is attended with a snap or report. These explanations, however, will be better understood, from the following brief exposition of the theory of electricity. II. Theory. The phenomena of electricity are ascribed by some philosophers to the agency of one fluid, and by others to that of two distinct fluids. The latter opinion was originally proposed by Dufay, and is almost exclusively adopted in France ; the former was proposed by Franklin, and is generally received in England and America. It is somewhat singular that most of the phenomena can be equally well explained upon either hypothesis, and as has been remarked, "the selection depends more upon the taste than the judgment of the in- quirer." The former of these theories is adopted in the present work. Electricity, according to the Franklinian hypothesis, is a subtle, highly elastic and imponderable fluid, which pervades all material bodies, and is capable of moving through the pores or substances of various kinds of matter. It moves through bodies with various degrees of facility, through some, as the conductors or non-electrics, passing freely ; through others, as the electrics or non-conductors, with great difficulty. The particles of this fluid repel one another, and attract the particles of all other matter, with a force varying in- versely as the square of the distance. Bodies, on this hypothesis, are supposed to be in their natural state, with regard to electricity, when, the repulsion of the particles of the fluid is exactly balanced by the attraction of the matter for the same particles. In this state bodies are supposed to be saturated with the electric fluid. When they contain a quantity greater than this, they are said to be positively electrified, or over charged with the electric fluid ; when the quantity is less than this, the body is said to be negatively electrified, or under charged. These different states are sometimes re- presented by the terms plus and minus. According to this theory, when a body is positively electrified, or has more than its natural quantity of electricity, the surplus, in con- sequence of the mutual repulsion of its particles, has a tendency to escape, and this continues until the body is reduced to its natural stats. Again, when a body is negatively electrified, or contains less than its natural quantity of electricity, it has a tendency to attract the fluid from all sides, until the neutral state is again restored. When a glass globe or tube is excited by silk, the electricity leaves the silk and is accumulated on the glass ; the silk, therefore, becomes negative and the glass positive. There was however, one defect in the original Franklinian theory, which was detected by Aepinus and confirmed by Cavendish, and which rendered it necessary to add another condition to it. The de- fect was, that while the repulsion which is observed between two po- sitively electrified bodies was easily accounted for, the repulsion be- tween bodies negatively electrified was left without explanation. By the theory, this could not be referred to the repulsion of the particles of electric fluid, for they were supposed to contain less than their na- tural amount. It was necessary, therefore, to annex the additional condition, that particles of matter uncomlined with electricity, exert a re- pulsive action upon one another. Without this, a:s can easily be shown, we are not only unable to account for the repulsion existing between bodies negatively electrified, but also for the want of action between two neutral bodies. The repulsion of two negatively electrified bodies, therefore, can only be considered as the result of the repulsion of the particles of matter. 74 ELECTRICITY. It will now be seen that the theory, as thus developed, satisfactorily explains the elementary facts which have been set forth, and will bear application to all the phenomena which electricity presents. Thus, by the operation of friction, the natural state of bodies is dis- turbed ; and, as the result of this, there is an accumulation of electri- city on one side and a diminution on the other, and the bodies are excited. The phenomena of attraction and ^repulsion, of distribution and transference, can also be readily accounted for. And the law of induction, moreover, is a consequence of the theory. For when a body overcharged with electricity is presented to a neutral body, the repulsive force existing among the particles of electricity in the former has a tendency to drive the electricity from the nearest part of the neu- tral body, if a conductor, to that which is the most remote. The near- est end of the body, therefore, becomes negatively electrified, while the remote end becomes positively electrified. Now if, instead of a positively electrified body, we bring a negatively electrified one near a neutral body, its attraction for the fluid in the second body will cause an accumulation in the nearest end, and of course a deficiency in the remote end. For the purpose of ascertaining when a body is electrified, and also the intensity or degree to which it is excited, instruments have been constructed which are called Electroscopes and Electrometers. Al- though the term electrometer is often indiscriminately applied to both those instruments, the latter denotes the intensity of electricity, the former merely indicates excitement and the electrical state by which it is produced. One of the simplest electroscopes is that of Hauy, which consists of a light metallic needle, terminated at each end by a light pith ball, which is covered with gold leaf, and supported horizontally by a cap at its centre, on a fine point. The attractive or repulsive power of any electrified body, presented to one of the balls, will be indicated by the movements of the needle. In some cases, however, it is more convenient to employ a pair of similar balls, suspended from a brass ball, fixed to the end of a glass handle, by very fine silver wires, or by hempen threads, previously steeped in a solution of salt and after- wards dried. L. U. K. Electrometers are constructed upon the principle, that the more highly an insulated conductor is charged with electricity, the more powerful is the repulsion which it communicates to bodies which are brought near it. Henley's Quadrant Electrometer, is in common use. Bennett's Gold Leaf Electrometer, is not only a more delicate instru- ment, but we are enabled by it to discriminate between positive and negative electricity. It consists essentially of a cylindrical glass bot- tle, with its apertures closed by a brass plate, from the centre of which two slips of gold leaf are suspended. The brass plate, with its slips of gold leaf, are thus insulated, and the latter prevented from be- ing moved by currents of air, by the glass with which they are sur- rounded. The approach of any electrified body, even though feebly excited, to the brass plate, is immediately detected by the divergence of the leaves. If the divergence be increased by the approach of flint glass excited by silk, the electricity is said to be positive ; if the divergence be diminished, they are said to be negatively electrified. This instrument is, strictly speaking, an electroscope. The most perfect electrometer for measuring small quantities of electricity, is the apparatus described by Coulomb, and to which he has given the name of the Torsion Balance, for a description of which ELECTRICITY. 75 we must refer to elementary works on Natural Philosophy, or to the Library of Useful Knowledge, art. Electricity. III. Effects of Electricity upon bodies. Independently of electrical attraction and repulsion, it does not appear that the simple accumula- tion of electricity in any quantity in bodies, as long as it remains qui- escent, produces the least . sensible change in their properties. A person standing on an* insulating stool, may be charged with any quantity of electricity from a machine, without being perceptibly af- fected, until the equilibrium of the fluid is disturbed, by drawing sparks from his body or from the prime conductor with which he may be in communication. It is the passage of electricity therefore, which produces the effects now to be noticed. When this passage is uninterrupted, as is the case in rods of metal, no perceptible change in the mechanical properties of the body is produced. But very considerable effects are produced, either if the body is so small as not to admit the whole quantity of electricity to pass with perfect freedom ; or if the body, though large, is deficient in conducting power. The effect of electricity may be conveniently arranged under the following heads, viz. 1. The mechanical effects, which can be illustrated by various experi- ments ; as by passing a charge of electricity through a capillary tube containing mercury, oil, water, alcohol or ether ; or by passing it through a small plate of glass, a piece of pasteboard, a card, or through the leaves of a book. 2. The evolution of heat. The ignition and fusion of the metals by the electric dischage, are phenomena which have been long observ- ed. Thus a very fine wire may be fused by a powerful Leyden bat- tery, or if the wire be sufficiently fine, by a single jar ; and so also alcohol, ether and spirits of turpentine may be inflamed by the spark from the prime conductor, as well as by the discharge from the jar. Gun-powder may be fired by partly interrupting the electric circuit, as by causing the wire or chain to pass through a vessel of water. Light as well as heat are emitted during the electrical discharge, at every point where the circuit is either interrupted or is occupied by bodies of inferior conducting powers. Thus a moderate charge from a Leyden jar will produce a bright spark when made to pass through water, and the spark is still more luminous in oil, alcohol or ether, which are worse conductors than water ; on the contrary, in fluids of greater conducting power, there is greater difficulty of eliciting elec- tric light. 3. The chemical effects. These will be more strikingly shown when treating of Galvanism ; but they can also be exhibited by powerful electrical machines. Thus when a strong charge is sent through water, it is decomposed and resolved into oxygen and hydrogen, which immediately assume a gaseous form. So also oxides of tin and mer- cury may be reduced to the metallic state. If a narrow glass tube containing chloride of silver be subjected to a series of electric sparks from an ordinary machine for five or ten min- utes, by means of two metallic wires fixed into the end of the tube, the silver will be reduced ; and if potassa be substituted for the chloride of silver, the potassium will be seen to take fire as it is produced. 4. Effects upon animals. When one hand communicates with the negative side of a charged jar, and the other hand is brought into contact with the positive side, a shock is observed more or less pow- ELECTRICITY. erful according to the amount of electricity which has been accumu- lated. This shock is felt, especially at the joints, for the reason pro- bably that the fluid meets with greater resistance in passing from one bone to another. When a shock is passed through the muscles, a con- vulsive motion is produced, even in those cases where the nerves of a limb are completely paralyzed. But upon the nervous system, these effects are still more striking. The Atmosphere is generally in an electrical stnte. This fact can be shown by employing a metallic rod elevated to some height above the ground, and communicating at its lower end with an electros- cope. Or, if we wish to collect electricity from the higher regions of the air, a kite may be raised, in the string of which a slender me- tallic wire should be interwoven, so as to conduct the electricity. The electroscope attached to this, will usually show the prevalence of the positive electricity, which increases as you ascend. This atmospheric electricity, however, varies in quantity at different seasons of the year, and at different times of the day ; and alternates from the posi- tive to the negative. Upon the approach of thunder storms, these alternations succeed each other with great rapidity : Strong sparks are given out by the conductor, and it becomes dangerous to prosecute the experiments with it in its insulated state.* Although the analogy between the electric spark and lightning, had been a subject of remark among the earliest experimenters upon electricity, it remained for Dr. Franklin to prove it directly. He did this by the celebrated experiment of raising a kite during a storm, when he succeeded in obtaining sparks from a key attached to the lower end of the hempen string of the kite. This grand dis- covery excited the attention of philosophers in every part of the world, and the experiment was every where repeated. It was, how- ever, in many instances, attended with risk, and proved fatal to Pro- fessor Richman, of St. Petersburgh, in 1753. The most important practical application of the theory of electri- city, is the protection of houses, ships, &c. from the effects of light- ning. This is effected by means of a metallic conductor, which is called a Lightning-rod,' being a rod of iron or copper, about half an inch in diameter, the extremity of which projects some distance above the building, and is pointed with silver, platinum or gold, the more completely to preserve it from corrosion. No interruption should exist in the rod, and the lower end should be carried into the earth un- til it reaches water, or at least a moist stratum. REFERENCES. Franklin's Workf* Library of Useful Knoioledge, art. Electricity. Priestley's History of Electricity. Cavallo's Philosophy. HioCs Traife de. Physique, or Cambridge Course of P/iysics. Gay Lussac's instructions respecting Par-itonnerret, or Conductors of Lightning, Ann. of Phil. xxiv. 4:27. Pouillefs Eleniens de Physique, ii. Cuthberlsoti's Prac- tical Electricity and Galvanism. * Water rnny be readily decomposed by atmospheric electricity in the man- ner proposed by M. Bonijol. The electricity is gathered by means of a very mie point fixed at the extremity of ;m insulated rod : (he lotte,r is connected with the apparatus, in which the water is to be decomposed, by a metallic \vire, of which the diameter does not exceed l-50th of an inch. In this way the decomposition of the water proceeds in a coritii uous and rapid manner, notwithstanding the electricity of the atmosphere is not very strong. Stormy weather is quite sufficient for the purpose. Bib. Univ. GALVANISM. 77 GALVANISM. The science of Galvanism owes its name and origin to the experi- ments made by Galvani, Professor of Anatomy at Bologna, in Italy, in the year 1790. Being engaged in some researches on animal irrita- bility, he observed that when a piece of zinc was placed in contact with the nerve of a frog, and a piece of silver or copper with the mus- cle, the animal was violently convulsed. In this fact he conceived that he had found a strong confirmation of a theory which he had adopted, that the nervous fluid was somewhat analogous to electricity, and these convulsions were consequently ascribed by him to a discharge of this nervous or electrical energy from the muscles in consequence of the conducting power of the metals. And to this he gave the name of Animal Electricity. The fallacy of the notions of Galvani was first pointed out by the celebrated Volta, of Pavia, who in repeating the experiments, soon es- tablished the fact that electricity is excited by the contact of the me- tals, and that the convulsions are owing to the current passing through the conducting muscle and nerve.* And as it is to him we are in- debted for the first true explanation of this curious fact, so did he first contrive an apparatus for exciting electricity in this manner. The instrument constructed by Volta for this purpose was called the Pile; a description of which was first published in the Philosoph- ical Transactions, for 1800. It consists of any number of pairs of zinc and copper, or zinc and silver, plates, each pair being separated from the adjoining ones by pieces of cloth, nearly of the same size as the plates, and moistened in a saturated solution of salt. The relative position of the metals in each pair must be the same in the whole se- ries : that is, if the copper is placed below the zinc in the first combi- nation, the same order must be preserved in all the others. The pile is contained in a proper frame, formed of glass pillars, fixed into a piece of thick wood, which both supports and insulates it. This form of the galvanic series, soon gave place to the more con- venient one of the Trough, or battery, invented by Mr. Cruickshank. This consists of a trough of baked wood, in which are placed at equal distances, any number of zinc and copper plates, previously soldered together, and so arranged that the same metal shall always be on the same side. Each pair is fixed in a groove cut in the sides and bottom of the box, the points of junction being made water- tight by cement. The apparatus thus constructed is always ready for use, and is brought into action by filling the cells left between the pairs of plates with some convenient solution, which serves the same purpose as the moistened cloth in the pile of Volta. Several modifications in the construction of the battery were after- wards proposed. One of these was suggested by the Couronne des Tasses of Volta ; in which the trough made either of baked wood or * This fact may be illustrated by the following simple experiment Place a piece of silver upon the tongue, and a piece of zinc under it ; upon bringing their ends into contact we immediately perceive a saline taste and a peculiar sensation resembling a slight electric shock. Sometimes, also, when the sur- face of the metals is extensive, a flash of light appears to pass before the eyes ; an effect which may be more certainly produced by placing one metal between the upper lip and the gums, and bringing their ends together as before. P 78 GALVANISM. glazed earthen, is divided into partitions by the same material. A more important improvement was suggested by Dr. Wollaston, who recommends that each cell should contain one zinc and two copper plates, so that both surfaces of the first metal are opposed to one of the second. By this arrangement the plates of copper communicate with each other, and the zinc between them with the copper of the ad- joining cell. An increase of one half the power is obtained by this method. The size and number of plates are subject to every variety. The largest battery ever made, is said to be the one of Mr. Children, the plates of which are six feet long and two feet eight inches broad. [See Ann. of Phil. vii. 11.] The great battery of the Royal Institution, with which Sir Humphry Davy established the true nature of the fixed alkalies and alkaline earths, is composed of 2000 pairs of plates, each plate having 32 square inches of surface. These form a striking con- trast to the elementary battery of Dr. Wollaston, consisting of a sin- gle pair of plates, of very small dimensions, with which he succeeded infusing and igniting a fine platina wire. Ann. of Phil. vi. 209. The fluid generally used for rendering these batteries energetic, is one of the stronger acids, diluted with 20 or 30 times its weight of water. Mr. Children recommends a mixture of three parts of fuming nitrous acid, and one of sulphuric, diluted with 30 parts of water. Directions also respecting the kind and density of acids, for producing galvanic electricity, are given by Mr. Singer. From his experiments it appears that acid of different densities is required for different pur- poses. The best wire-melting charge is formed with ten gallons of water, five pounds of nitric acid and half a pound of muriatic acid. According to Gay Lussac and Thenard, dilute nitric acid is the best where we wish to produce instantly the highest energy of the battery while muriatic acid should be employed when the object is to obtain a prolonged action. The Electric Column may be classed among galvanic arrangements. It was originally contrived by M. De Luc, who formed it of disks of Dutch gilt paper, alternated with similar disks of laminated zinc. These were piled on each other in a dry state, (or at least in a state of dryness at ordinary temperatures, for paper can not be made or preserved absolutely dry, except at a heat nearly sufficient to scorch it.) This instrument, instead of being soon exhausted, like the pile with humid substances, was found to continue active for some years. A similar pile may be formed, by laying a mixture of very finely pow- dered zinc with common glue and a little sugar, by means of a brush, on the back of Dutch gilt paper, and when dry, cutting it into disks, which are to be piled on each other. [Phil. Mag. xlvii. 265.] Zam- boni, of Verona, has constructed a pile of slips of silver paper, on the unsilvered side of which is spread a layer of black oxide of man- ganese and honey. These papers are piled on each other, to the number of 2000; then covered externally with a coating of shell-lac, and enclosed in a hollow brass cylinder. Two of these piles are placed at the distance of four or five inches from each other ; and between them is suspended, on a pivot, a light metallic needle, which is attracted alternately to the one pile and the other, so that it moves between them like a pendulum. This instrument has been applied to the measurement of time, by causing it to give motion to the pen- dulum of a clock. Phil. Mag. xiv. 261. Henry, i. 188. GALVANISM. 79 The more striking effects of the voltaic battery may be reduced to four general heads. I. ITS ELECTRICAL PHENOMENA. II. ITS CHEMICAL AGENCY. III. ITS POWER OF IGNITING THE METALS. IV. ITS ACTION ON THE MAGNET. I. Electrical Phenomena. Galvanism, even when excited by a single galvanic circle only, (such as a piece of zinc, a similar one of copper, and a piece of cloth moistened with a solution of muriate of ammo- nia,) distinctly affects the gold leaf of Bennet's electrometer. If the zinc end be uppermost, and be connected directly with the instrument, the electricity indicated is positive ; if the pin of the electrometer touch the copper, the electricity is negative. A pile consisting of six- ty combinations produces the effect still more remarkably. [For cau- tions necessary to the success of this experiment, see Singer, 317.] The Voltaic apparatus is capable of communicating a charge to a Leyden jar, or even to a battery. If the zinc end of a pile be made to communicate, for a moment, with the inside of a jar, it is charged positively. If the circumstances be reversed, the jar is charged nega- tively. Cuthbertsori 's Practical Electricity and Galvanism, 261. The sensation produced by the galvanic shock is extremely similar to that which is excited by the discharge of a Leyden jar. Both in- fluences, also, are propagated through a number of persons, without any perceptible interval of time. The galvanic fluid passes through the air, and certain other non- conductors, in the form of sparks ; accompanied with a snap or re- port ; and, like the electrical fluid, it may be made to inflame gun- powder, phosphorus, and mixtures of hydrogen and ox v gen gases. It has been found, also, by Mr. Children, that in the voltaic apparatus, there is what is called in electricity, a striking distance. With a power of 1250 pairs of four inch plates, he found this distance to be one 50th of an inch, the thickness of a plate of air, through which the galvanic discharge is able to pass in the form of a spark. By increasing the number of plates, the striking distance will be greater, and the reverse when it is diminished. It is also increased by rarifying the air, through which the spark is transmitted. See Henry's Chemistry on the mutual relations of Electricity and Galvanism, i. 189. For the purpose of exhibiting the effects just mentioned, a number of plates is necessary, without reference to the size. Acid solutions are to be preferred when shocks or sparks are required ; water is pre- ferable for effecting the electrometer or Leyden jar. II. Chemical effects of the battery. The chemical effect of the bat- tery first noticed, was the decomposition of water, which, as we shall hereafter see, is a compound of oxygen and hydrogen. When two gold or platinum wires are connected with the opposite poles of a battery, and their free ends plunged into the same cup of water, but without touching each other, oxygen gas is disengaged at the positive wire, and hydrogen gas at the negative. These gases may be collected at separate tubes, or in a single bent tube, and sub- jected to experiment. [See a very simple apparatus for collecting the gases evolved from liquids submitted to galvanic action, by the Rev. Mr. Robertson, in Edin. New Phil. Jour. iii. 44.] If, however, we em- ploy wires of copper, silver, or any other oxidable metal, the oxygen 80 GALVANISM. no longer appears in the form of gas, but unites with the wire, and oxidates it. If, instead of water, we subject to the action of the poles of the battery, acids or saline solutions, they are, in like manner, decomposed; one of their elements appearing at one pole and the other at the other. There is an exact uniformity in the circumstances attending these decompositions. Thus, in decomposing water or other com- pounds, the same kind of body is always disengaged at the same pole of the battery. The metals, inflammable substances in general, the alkalies, earths, and the oxides of the common metals, are found at the negative pole ; while oxygen, chlorine, and the acids pass over to the positive end. If the conducting wires are plunged into separate vessels of water, and made to communicate with each other by moist fibres of cotton or amianthus, the two gases are still disengaged in the usual order. And if one vessel containing a neutral salt, (sulphate of soda for example,) communicates with the negative pole, and another containing dis- tilled water with the positive, and the two cups be united by moisten- ' ed amianthus, the acid of the salt passes over to the water, and the salt becomes distinctly alkaline. On reversing the pole, the alkali passes over to the water, and the saline solution becomes distinctly acid. These singular results were first obtained by Sir H. Davy, and described by him in the Phil. Trans, for 1807. The same results will still be observed, though a cup of ammonia intervene between those of distilled water and the saline solution ; from which it appears that the galvanic action not only separates the elements of compound bodies, but suspends the operation of affinity so entirely as to enable an acid to pass through an alkaline solution, or an alkali through water containing a free acid, without combination taking place between them. The three cups being arranged as in the last experiment, Sir H. Davy put a solution of sulphate of potassa in one, pure water in another, and a weak solution of ammonia in the intermediate cup, so that no sulphuric acid could find its way to the distilled water, without passing through the ammoniacal liquid in its passage. A battery, composed of 150 pairs of 4-inch plates, was set in action, and in five minutes, free acid appeared at the positive pole. Muriatic and nitric acids were, in like manner, made to pass through strong alkaline solutions ; and on reversing the experiment, alkalies were transmitted directly through acid liquids without entering into combination with them. It has been shown, in our remarks upon electricity, that bodies which are similarly electrified repel each other, while those which are dissimilarly electrified attract each other. Now the invariable ten- dency of oxygen and the acids to the positive pole of the battery and of hydrogen and the alkalies to the negative, can only be explained upon the principle that the former are negatively, and the latter positively electrified at the moment of their separation from each other. This forms the basis of the hypothesis advanced by Davy, which has re- ceived the appellation of the Electro Chemical Theory, and has been adopted by several philosophers, especially by Berzelius. It has been shown by Volta that when two metals are brought into contact, they are, on being separated, in opposite electrical states. Thus, when an insulated plate of zinc is brought into contact with one of silver or copper, the former is found to be in a positive state, and the latter negative. Sir H. Davy also ascertained that a similar effect is produced by the contact of other bodies. A dry alkali or an al- GALVANISM. 81 kaline earth, for example, is excited positively by contact with a me- tal ; dry acids after having touched a metal are negative, and the con- tact of acids and alkalies, in their dry state, render the former negative and the latter positive. He further observed that electrical effects are exhibited by the same bodies, when acting as masses, which produce chemical phenomena when acting by their particles, or atoms. It is, therefore, by no means improbable, that the primary cause of both these phenomena maybe the same, and that the same arrangements of matter which render bodies attractive of each other electrically, may likewise render their particles attractive, and enable them to combine, when they have full freedom of motion. According to the above view, all substances which have a chemical affinity for each other, are in different states of electricity, and the de- gree of affinity is proportional to the intensity of these opposite states. When such a compound body is placed in contact with the poles of a Voltaic battery, the positive pole attracts the constituent which is negative, and repels the positive. The negative acts in the opposite way, attracting the positive constituent and repelling the negative. Thus, when water is subjected to the action of the battery, its oxygen invariably appears at the positive pole, and its hydrogen at the nega- tive. Hence hydrogen and all other substances which like it are at- tracted by the negative pole, are classed together as electro-positive bodies ; and oxygen and other substances which are attracted by the positive pole are called electro -negative bodies. In following out these ideas, Davy conceived that no compound could resist decomposition, if subjected to the action of a battery of sufficient power. He accordingly exposed to galvanic action substances, which, although they had been thought to be compound, had baffled all at- tempts to analyze them. The result was successful. Potash was" proved to consist of a metallic basis in combination with oxygen, and continuing his investigations, he soon decomposed the other fixed alka- lies and alkaline earths, and rendered it almost certain that the earths proper were similarly constituted. Although some of the conditions of the Electro-Chemical Theory have not yet been demonstrated, yet it rests on extensive observation and is supported by numerous facts. It affords also the most easy expla- nation of the phenomena ascribed to affinity. It appears to me, more- over, to furnish principles the most philosophical for the arrangement of chemical substances, and on this account I shall follow the example of Mr. Brande and Dr. Henry, and treat of individual substances in the order of their electrical relations. III. The, igniting effects of the battery. The ignition of the metals seems to depend upon the difficulty with which electricity passes along them. But as they are perfect conductors, this can only take place when the quantity to be transmitted is out of proportion to the extent of surface along which it has to pass. For this purpose, therefore, it is important to excite as large a quantity of electricity in a given time as possible ; and hence a few large plates answer a better purpose than a number of small ones. A strong acid solution should also be used, as an energetic action is more important than its permanence. With regard to the powers of the Voltaic series in igniting the met- als, a very important improvement has been made by Dr. Hare, of Philadelphia. This was suggested by a notice of the fact, that the igniting power of the battery attains its highest intensity almost as soon as the plates are covered with the acid used to excite them. It 82 GALVANISM. must be evident therefore, that a large battery constructed in the or- dinary way, must lose much of its power before it can be used. In the apparatus of Dr. Hare, as at present constructed, the metals are fixed in a box, which is made to revolve on pivots, and thus by a quarter revolution, the acid is thrown entirely off into another box, attached at right angles to the first, and by reversing the revolution at pleasure, the acid returns upon the plates. This instrument is named by the inventor, a Galvanic Deflfigrator, and where the igniting effects are required to be exhibited, it possesses advantages over every other form of the galvanic apparatus hitherto discovered. The metals are readily fused by it, and it produces a vivid ignition in charcoal, and when the points of the charcoal are drawn three-fourths of an inch apart, a most brilliant arc of flame extends between them. It should be remarked, that Dr. Hare is opposed to the opinion above stated, concerning the heat produced by galvanic combinations. He supposes that heat, like electricity, is an original product of galvanic action. According to his views, the relative proportion of the two principles evolved, depends upon the construction of the apparatus, the caloric being in proportion to the extent of the generating surface, and the electricity to the number of the series. In the case of batteries, in which the size and number of the plates are very considerable, both electricity and caloric are presumed by him to be generated in large quantities. When the number of the plates is very great, and their size insignificant, as in De Luc's column, electricity is the sole pro- duct ; and conversely, where the size is very great and the number of the series small, caloric is abundantly produced, and the electrical effects are nearly null. [Fora full account of the theory of Dr. Hare, see Sittiman's Jour. i. 413.] IV. The action on the magnet. This interesting subject will be no- ticed in connection with the general view of the laws of magnetism, in the next chapter. THEORIES OF GALVANISM. There are three leading theories which have been constructed to ac- count for the phenomena of the galvanic pile, and of all similar ar- rangements. The first originated with Volta, who maintained, that the electricity was set in motion and kept up solely by the contact of the metals. But as no very sensible effects are produced, un- less the substances employed have a chemical action on each other, Dr. Wollaston was led to conclude, that the process commences with the oxidation of the zinc, and that the oxidation is the pri- mary cause of the developement of electricity. The theory of Davy is intermediate between the two just mentioned, and is perhaps most conformable to the facts hitherto discovered. He supposes that the contact of the metals disturbs the electric equilibrium, and that the electric action is afterwards kept up by the action of the solution upon the zinc. But in the present state of the science, neither of these theories appears to be altogether satisfactory. The reader who wishes to examine them more in detail, is referred to Bostoch's Remarks on the, Hypotheses of Galvanism, in Ann. of Phil. iii. 32, 85. Sir H. Davy's chapter on Electrical Attraction and Repulsion, in his Chem, Phil. ; and Gay Lussac and Thenard's Rccherches. MAGNETISM. 83 REFERENCES. Cuthbertsorfs Practical Electricity and Galvanism. Sin- ger on Electricity and Galvanism. Several papers by Volta, Singer, De Luc, and Henry, in Nicholson's Journal. Library of Useful Knowledge, Art. Galvanism, by Dr. Roget. Davy on the Chemical Agencies of Electri- city, Phil. Trans. 1807 and 1826, and also Phil. Mag. and Ann. i. Oersted on the Identity of Chemical and Electrical Forces, Ann. of Phil. xiii. 369, 456, xiv. 47. Thomson on Heat and Electridty. The first eight volumes of Silliman's Journal contain sundry papers by Professors Hare and Silli- man, upon Calorinwtors, Dejlagrators, fyc. CHAPTER V. MAGNETISM. Though the consideration of Magnetism belongs, strictly to the de- partment of natural philosophy, I shall advert briefly to its more pro- minent laws, as by this means the reader will be better prepared to understand the facts of Electro-Magnetism. Most of the fragments of iron ore in which a degree of oxidation has taken place, are found to possess, when taken from the earth, the singular property of attracting particles of iron, by an invisible power. The force of this attraction is sometimes so powerful as to raise con- siderable weights. This mineral has received the name of a magnet, from the Greek word magnees ; and hence the term magnetism is used to stand for the phenomena exhibited by this mineral ; in the same way that the term electricity is applied to the unknown cause of elec- trical phenomena. This influence may be communicated to some me- tallic bodies, and particularly to iron and steel. When a magnet is rolled in iron filings, different quantities of the filings are attached to different parts of its surface. This effect is particularly sensible at two opposite points, where the filings are ac- cumulated in the greatest abundance, standing as it were on end, nearly parallel to each other. These parts are called the poles of the magnet. When a magnet is suspended horizontally by an untwisted thread, or bundle of silk fibres, or when it is made to float on water, it takes a determinate direction. This direction, however, differs in different parts of the earth, being in some exactly in the meridian, in others, in- clining towards the west ; and in others again, towards the east. If to one of the poles of a magnet thus suspended, a similar pole of another magnet be presented, they will repel each other ; but if the opposite poles are presented, they will attract each other. This is analogous to what takes place when bodies are under the influence of electricity , and hence similar laws of attraction and repulsion are applicable. To these poles, the names of north and south, or boreal and austral, have been applied ; and by Berzelius, positive and negative. Traite de Chim. i. 170. When a steel bar is suspended freely by its centre of gravity, and afterwards carefully magnetized, it will be found not only to place itself in the magnetic meridian, but to assume a position inclined to the 84 . MAGNETISM. horizon. In northern latitudes, the northern pole of the needle will incline beneath the horizontal plane, and the other will be raised above it. This angle of inclination varies but little at the same place, and is called the dip of the needle. There is a zone not far from the equator, where the magnet hangs in a horizontal position ; to the south of this the northern pole will be elevated, and the southern will dip. Although the magnet exerts its force at the distance of several feet, it decreases in strength as the distances increase, but in very different ratios in different magnets. In some the force of attraction seems to be inversely as the square of the distances ; in others as the cubes of the distances ; and so on in other proportions. Its virtue is exerted in vacua, as well as in open air, and without any sensible diminution of its force by the interposition of the hardest bodies, whose pores it easi- ly pervades. * The magnetic property is found also to reside naturally in nickel and a few other metals. It may be communicated to iron and steel, as follows : 1. By the contact of a natural magnet. This is indeed proved by examining the crest of iron filings attached to the poles of the magnet, which will be found to consist of several minute magnets adhering end to end. Bars of soft iron may be rendered quickly magnetic by the contact of a magnet. Thus, if we suspend a small bar of soft iron to the pole of a magnet, the lower end will immediately acquire all the magnetic properties. A second and a third bar added to this will adhere to one another, until their total weight exceeds that which themagnet is capa- ble of supporting. When the first bar detaches itself they all fall, and lose, in a great measure, their magnetic powers. Bars of steel may also be magnetized by the contact of a magnet or magnets, but this is effected with more difficulty ; though the bars re- tain magnetism much longer. The same magnet may thus successive- ly magnetize any number of steel bars, without losing any portion of its original virtue, if the bars be not too large ; from which it follows that the magnet communicates nothing to the bars, but only developes, by its influence, some hidden principle. [For details of the methods of magnetizing bars of steel, see Blot's Traite Precis, or Cambridge Course of Physics.] 2. Besides the contact of a magnet, magnetism may be communi- cated to iron and steel by placing them in the magnetic meridian by torsion or twisting by the blow of a hammer by pressure by the act of rotation and even, as some have supposed, by mere exposure to certain rays of light. [See p. 69.] The directive power of the magnet is the most important property which it possesses ; and it is this which has led to the construction of the Compass, an instrument wherein a magnetized needle is employed, to ascertain the direction of objects from the point in which it is placed. It is more especially useful in pointing out the course of a vessel when at sea, and out of sight of land : without this valuable invention, it would have been out of our power to have traversed the great oceans, that form so large a portion of the globe. The directive force of the needle is impaired by the vicinity of large masses of iron. In ships this is a source of much inconvenience, espe- cially in high northern or southern latitudes. To remedy the errors of the needle, resulting from this cause, Professor Barlow contrived an instrument, which is called the correcting plate ; the utility of which, MAGNETISM. 85 has been abundantly proved by Capts. Sabine, Parry, and other distin- guished naval officers. Electricity also has the effect of varying the directive power of the needle, and that not only when accumulated, but as excited by the mere friction upon the glass cover of the compass. Hence needles are in this manner very frequently injured. [See Lieut. E. J. Johnson's valuable observations on local and electrical influences on compasses variously constructed, in Brande's Jour. xxi. 274.] There are several practical applications of the laws of magnetism. Among these may be mentioned, the separation of iron filings from the particles of sand and other substances with which they are often mixed. A neat apparatus for effecting this object is described in the 28th volume of the Transactions of the London Society of Arts. The same principle has also been applied to the separation of the magnetic ores of iron from silex, pyrites, and other substances which interfere with the process of smelting. A method was patented in England in 1792, which consisted in reducing the crude ore to a coarse powder by means of hammers, rollers, &c., and of separating the metallic parti- cles by the employment of magnetic attraction. [Repert. of .Arts, 1st Ser. 1.] An American patent has also been issued for a similar appli- cation of this principle, which cannot fail to be useful in those districts where the magnetic ores of iron are abundant. Another beautiful application of the laws of magnetism, is the con- struction of masks of magnetized steel wire, which are now employed by the workmen who are engaged in the pointing of needles ; an oc- cupation which was formerly attended with great hazard, in conse- quence of the fine particles of steel, continually flying off from the grindstones, being inhaled into the lungs. Magnetism is also employed in certain analyses. The method of oscillations suggested by Coulomb, is one of the most accurate for as- certaining the presence of iron, either in natural or artificial products. We have only to form needles of the substances to be examined, and to make them oscillate between two powerful magnets, and to compare their oscillations with those of needles made of iron, combined with some other substance not magnetic, the relative proportions of the iron and the unmagnetic substance being known. It only remains to add to this sketch, a few words concerning Ter- restrial Magnetism. The earth may be considered as a great natural magnet, and many of the phenomena which we have noticed are due to the power of this magnet. From the experiments which have been made upon the earth's magnetism, it results that there is a line (called the magnetic equator,} in which the needle has no dip f that as we proceed from this line, north or south, the dip constantly increases until we arrive at points where the needle is vertical, which are called the poles that there are also lines which cut the magnetic equator, in which the nee- dle has no declination, or points to the true north and south. The earth, therefore, is a great natural magnet, with poles and a point where the influence of the poles is exactly balanced ; hence the directive power and the dip of the needle are due to its influence. It may be remarked, that although the phenomena of magnetism are manifest only in a few substances, Professor Hansteen has drawn from numerous experiments and observations, the important conclu- sion, that every vertical object, of w/iatever material it is composed, has a magnetic south pole above, and a north pole below. Edin. Phil. Jour, for 1826. 86 ELECTRO-MAGNETISM. REFERENCES. Biot, and Cambridge Course of Physics. Renwick's Out- lines of Natural Philosophy. Hobisorfs Nat. Phil Cavallo's Philosophy. For an account of the Experiments on the peculiar magnetic effect induced in Iron, and on the magnetism manifested in other Metals, fyc. during the act of rotation, by Messrs. Barlow, Christie, Babbage and Herschel, See Phil. Trans, for 1825. Also, Ann. of Phil, xxvii. and xxviii. Capt. Kater^s val- uable directions for constructing Compass Needles, Ann. of Phil, xviii. 231. For a description of Barlow's Correcting Plate, see his Essay on Magnetic Attraction, and the value of this Apparatus attested by Capt. Parry, 3d voyage, 65 and 67, Amer. Ed. Professor Hansteerfs Table of the variations of the Magnetic Needle, Breioster's Edin. Jour. ix. 264. This Journal also contains several other papers by the same author. Capt. Sabine, on the Mag- netism of the Earth, Siliiman's Jour. xvii. 145. ELECTRO-MAGNETISM. It has already been observed, that electricity, as developed by fric- tion, has an effect upon the directive power of the needle. The pow- er of lightning also, in destroying and reversing the poles of a magnet, and in giving magnetic polarity to pieces of iron which did not pre- viously possess it, has long been known. Attempts were accordingly made at different times to communicate the magnetic virtue by means of electricity* or galvanism ; but no results of importance were ob- tained until the year 1819, when Professor Oersted made his celebra- ted discovery, which constitutes the basis of the science of Electro- Magnetism or Electro-Dynamics. The fact observed by Professor Oersted was, that an electric cur- rent, such as is supposed to pass from the positive to the negative pole of a Voltaic battery along a wire which connects them, causes a mag- netic needle placed near it to deviate from its natural position, and as- sume a new one, the direction of which depends upon the relative po- sition of the needle and the wire. On placing the wire above the magnet and parallel to it, the pole next the negative end of the battery always moves westward, and when the wire is placed under the needle, the same pole goes towards the east. If the wire is on the same hori- zontal plane with the needle, no declination whatever takes place ; but the magnet shows a disposition to move in a vertical direction, the pole next the negative side of the battery being depressed when the wire is to the west of it, and elevated when it is placed on the east side, t * In a paper published by Dr. Franklin in 1750, he observes, ** By electri- city we have (here at Philadelphia) frequently given polarity to needles, and reversed it at pleasure." " A shock from four large glass jars, sent through a fiae sewing needle, gives it polarity, and it will traverse when laid on water. If the needle, when struck, lies east and west, the end entered by the electric blast points north. If it lies north and south, the end that lay towards the north will continue to point north when placed on water, whether the fire entered at that end, or at the contrary end.'' Franklin's Works, iii. 65. f This term is synonymous with the terms, connecting and communicating wire, employed by some authors. There can be no confusion in regard to them, when it is remembered that the phenomena of electro-magnetism are solely produced by electricity in motion. Whatever, therefore, forms the union between the zinc and copper plates used to exhibit these effects, is, for convenience, called the conjunctive or connecting wire. ELECTRO-MAGNETISM. 87 The conjunctive wire connecting the two poles of the battery, may consist of any metal ; even a tube filled with mercury is effectual : the only difference is, in the amount of effect produced. It continues also, though the conductor be interrupted by water, unless the interruption be of great extent. The influence of the wire extends through all substances, and acts upon the needle beyond, just as with common magnetism. Those forms of the Voltaic apparatus which generate quantity, are such as produce the most decided electro-magnetic effects ; they appear to be independfcit of tension, and hence a single pair of very large plates, is more effectual than a number of small ones. Batteries constructed of one or a few pairs of large plates, have hence been called magnet- omotors. I shall present an outline of the principal facts of electro-magnetism under the following heads, viz. 1. Action of the conjunctive wire upon the magnet. 2. Action of the conjunctive wire upon soft iron and steel. 3. Action of two conjunctive wires upon each other. 4. Action of the electro- and steel magnet upon the conjunctive wire. 5. Action of the earth's magnetism upon the conjunctive wire. I. Action of the conjunctive wire upon the magnets. It has already been observed, that when a wire connects the opposite poles of a Voltaic battery, a magnetic needle placed near it is made to deviate from its natural position. These facts, discovered by Oersted, have been confirmed by the experiments of various other philosophers. It has also been shown by Ampere, that the pile itself acts in the same manner as the conjunctive wire, and his views of the phenom- ena led him to the construction of an instrument which, at the same time that it proved this action, was shown to be of great value in experiments on currents of electricity. This was merely a magnetic needle, but from the uses to which it was applied was called a Galvan- ometer. When placed near a pile or trough, in action, having its poles connected either by a wire, or by introducing them into one cell, it immediately moved, becoming obedient to the battery, in the same manner as to the connecting wire : and the motions were such as if the battery were simply a continuation or part of the wire. The action of the conjunctive wire upon the magnet, can be more advantageously exhibited by the instrument invented by Pro- fesser Schweigger, of Halle, and called the Electro -Magnetic Mul- tiplier. This instrument consists of brass wire, wound with silk, so as to prevent the electricity from passing laterally, and wound upon the hand or a book, fifty, or an hundred or more times ; the delicacy of the apparatus being in proportion to the number of turns. These are now held in their place by threads of silk, and the two ends of the wire are left free. We have thus an oval bundle of wires, through which, when the ends are connected with an active battery, the current of electricity passes. If now we place a freely suspended magnetic needle in the middle of this oval multiplier, and then connect the two ends of the wires with the two opposite poles of a battery, the needle, after several oscillations, becomes stationary at right angles to the oval, the influence of terrestrial magnetism being surmounted by that of the multiplier. When this instrument con- sists of 60 or 100 turns, the needle may be made to deviate by disks of zinc and copper, an inch in diameter, and merely united by paper, 88 ELECTRO-MAGNETISM. moistened by any saline solution, or even by saliva. See Ann. of Phil. xxi. 436. Various modifications of this apparatus have been proposed ; that invented by Professor Henry and described by him in the first volume of the Transactions of the Albany Institute, is one of the most con- venient. It appears therefore, that the wire connecting the two opposite poles of a Voltaic battery, and the battery itself, during the passage of elec- tricity, exerts a certain action upon the magnetic needle and that the force which is thus exerted by the conjunctive wire, is at right angles to its axis. The conjunctive wire is also capable of attracting and repelling the poles of a magnet. If, when the magnet and connecting wire are at right angles to each other, the latter passing across the centre of the former, the wire be moved along the needle towards either ex- tremity, attraction will take place between the wire and the adjacent pole ; and this will occur, though the same point of the wire should be presented in succession to both of the poles. Again if the position of the poles of the needle be reversed, they will be repelled by the same point of the wire which had previously attracted them. See Fara- day" s Historical ^Sketch of Electro- Magnetism, in Ami. of Phil, xviii. 198. Any wire, through which a current of electricity is passing, has a tendency to revolve round a magnetic pole, in a plain perpendicular to the current ; and that, without any reference to the axis of the mag- net, the pole of which is used. A magnetic pole also has a tendency to revolve round such a wire. Suppose the wire perpendicular, its upper end positive, or attached to the positive pole of a Voltaic battery, and its lower end negative ; and let the centre of a watch-dial represent the negative pole ; if it be a north pole, the wire will rotate round in the direction that the watch hands move ; if it be a south pole, the motion will be in the opposite direction. From these two, the motions which would take place if the wire were inverted, or the pole changed or made to move, may be readily ascertained, since the relation now pointed out remains constant. These motions are exhibited in an apparatus devised by Mr. Fara- day, or perhaps still better by the revolving cylinders of Ampere. They consist of a cylinder of copper, about two inches high, and one and three fourths internal diameter, within which is a smaller cylin- der about one inch diameter, also of copper. The two cylinders are fixed together by a bottom, having a hole in the centre the size of the smaller cylinder, leaving a circular cell, which may be filled with dilute acid. A piece of strong copper wire is fastened across the top of the inner cylinder, and from the middle of it rises at right angles a piece of copper wire, supporting a very small metal cup, containing a few globules of mercury. A cylinder of zinc open at each end, and about one and a quarter inch in diameter, completes the Voltaic combination. To the latter cylinder a wire, bent like an inverted U, is soldered at opposite sides, and in the bend of this wire a metallic point is fixed, which, when fixed in a little cup of mercury, suspends the zinc cylinder in the cell, and allows it a free circular motion. On the suggestion of Mr. Barlow, Mr. Newton has fixed an ad- ditional point, directed downwards from the stronger wire, which point is adapted to a small hole at the top of a bar magnet. When the ap- paratus, with one point only, is charged with diluted acid, and set on ELECTRO-MAGNETISM. 89 the end of a magnet placed vertically, the zinc cylinder revolves in a direction determined by the magnetic pole which is uppermost. With two points, the copper revolves in one direction, and the zinc in a con- trary one. The magnet employed should be a powerful one. Henry, i. 215. II. Action of the conjunctive, wire vpon soft iron and steel. It was about the same time ascertained, both by Sir H. Davy and M. Ara- go, that magnetism may be developed in steel, not previously pos- sessing it, by being placed in the electric current, and may even be excited by the connecting wire itself. Both philosophers ascertained, independently of each other, that the conjunctive wire attracts iron filings, and collects sufficient to acquire the diameter of a common quill. As soon as the connection is bioken, the filings drop off, and the attraction diminishes with the decaying energies of the battery. In Sir H. Davy's experiments, similar effects were produced by common electricity. With a Leyden battery of seventeen square feet, discharged through a silver wire one-twentieth of an inch diameter, he rendered bars of steel two inches long and from one-tenth to one- twentieth thick, so magnetic as to lift up pieces of steel wire and nee- dles ; and the effect was communicated to needles at the distance of five inches from the wire, even with the intervention of water or thick plates of glass or metal. Phil. Trans. 1821, or Ann. of Pkil. xviii. 81, xix. 1. The theory of Ampere, that magnets are only masses of matter, around the axis of which electrical currents are moving in closed curves, led M. Arago to expect a much greater effect, if the connecting wires were placed in the form of a spiral, and the piece to be magnet- ized were placed in its axis. This idea was amply verified by experi- ment. Having made some of these helices, one was connected by its extremities with the poles of a Voltaic battery, and then a needle wrap- ped in paper, placed within it ; after remaining there a few minutes, it was taken out and found to be strongly magnetized ; and the effect of a helix above that of a straight connecting wire, was found to be very great. If the wire after being formed into a helix, be bent back, so as to return in a straight course in the interior of the cylinder, with the usual precautions against contact, we obtain a very perfect ac- cordance with the condition of a magnetic cylinder ; and to such ar- rangements the term Voltaic Magnets may be applied as being prefera- ble to that of Electro-Dynumic Cylinders, given to them by Ampere. This application of the theory of Ampere, has led to the most inte- resting and remarkable results having made us acquainted with a me- thod of magnetizing soft iron to an extent heretofore unknown. It was found that when the conjunctive wire was wound around a bar of iron, bent in the form of a horse-shoe, while the battery was in action, the iron became quite powerfully magnetic ; but to produce these effects, it was supposed that powerful Voltaic instruments were required. The first simplification of apparatus for this purpose, was proposed by Mr. Sturgeon, of Woolwich, [Ann. of Pkil. xxviii. 357,]^ who was enabled by his apparatus to render a horse-shoe capable of supporting nine pounds, when the opposite ends of the wires were united with the poles of his Voltaic arrangement. Dr. Moll, of Utrecht, in repeating these experiments, used a large Voltaic surface. He first employed a soft iron wire, bent in the form of a horse-shoe ; the length of the horse-shoe being about eight and a half inches, and one inch in diameter. A copper wire about one- 90 ELECTRO-MAGNETISM. eighth of an inch in diameter was twisted or coiled eighty-three times round the iron, from right to left. The two ends of the wire were connected with the opposite poles of a galvanic apparatus, consisting of one single copper trough, in which a zinc plate, having a surface of about eleven square feet, was immersed. When the Voltaic appara- tus was rendered active, the horse-shoe was capable of supporting fif- ty pounds. A larger horse-shoe, about twelve inches and a half high, and two and a quarter inches in diameter, and weighing about twen- ty-six pounds, coated with silk and wound round, at first, with forty- four turns of brass wire, the acting Voltaic surface being the same as before, supported 135 pounds ; with forty turns of iron wire it support- ed 154 pounds. Brewster's Edin. Jour. N. S. iii. 209, and Sillimans Jour. xix. 329. The most recent, and by far the most interesting experiments of this kind, are those of Professors Henry and Ten Eyck ; the object of which was not merely to impart to soft iron its greatest magnetic ef- fect, but with a very small galvanic surface. Around an iron horse- shoe, about nine and a half inches high and two inches square, and weighing 21 pounds, 540 feet of copper bell-wire, previously covered with silk or cotton thread, were wound in nine coils of 60 feet each. These coils were not continued around the whole length of the bar, but each strand of wire occupied two inches, and was coiled several times backwards and forwards over itself; the several ends of the wires were left projecting, and all numbered, so that the first and last end of each strand might be easily distinguished. In this manner one combination of wire or more, could be made by merely uniting the different pro- jecting ends. With a single battery, consisting of two concentric copper cylin- ders, with zinc between them, having a surface of 2-5ths of a square foot, and which needed one half pint of dilute acid for its submersion, the horse-shoe supported, when the extreme and opposite ends of all the wires were soldered to the zinc and copper, 650 pounds. But when a zinc plate of twelve inches long and six wide, and surrounded by copper, was employed, the horse-shoe supported 750 pounds. Sil- limaris Jour. xix. 400. Still more recently these gentlemen have constructed a magnet, con- sisting of a soft iron horse-shoe, weighing fifty-nine and a half pounds, and coiled with seven hundred and twenty-eight feet of copper bell- wire, in twenty-six strands, which with a zinc surface of four seven- ninth square feet, surrounded by copper, supports, when the battery is in action, 2,063 pounds. Sillimaris Jour. xx. 201. III. Action of two conjunctive wires upon each other. It was ob- served by Ampere, that when two conducting wires were so ar- ranged as that one or both of them were allowed a certain free- dom of motion, they either attracted or repelled each other, accord- ing as the electric current which was transmitted was moving in the same or in opposite directions in the two wires. If, for example, two wires, which are transmitting currents of electricity, be situated with- in a certain distance, and parallel to each other, and if we suppose the current of positive electricity to be passing from left to right, in both the wires, they will manifest an attraction for each other. The same tendency of attraction will also appear when the positive cur- rents are both moving in the contrary direction, that is from right to left. But if the current in one wire be moving in a direction opposite to that of the current in the other wire, in that case a repulsive action will take place between the two wires. These were found to be con- ELECTRO-MAGNETISM. 91 stant and invariable effects of the transmission of electricity along conductors ; and they were manifested equally, whether the two cur- rents were obtained from separate Voltaic batteries, or were only two portions of the same current indifferent parts of its course. Quarterly Review, xxxv. The contrast between these attractions and repulsions, and those usually called electrical, is very striking. These take place only when the circuit is completed ; those only when it is incomplete. The at- tractions take place between the similar ends of the wires, and the repulsions between the dissimilar ends ; but the electrical attractions take place between dissimilar ends ; and the repulsions between sim- ilar ends. These take place in vacua, but those do not. When the magnetic attraction brings the two wires together, they remain in con- tact ; but when electrical attraction brings two bodies together, they separate after the contact. It is evident, therefore, that these effects cannot be ascribed to elec- trical action ; it has therefore been regarded as a magnetic effect, and an attempt has been made to account for it upon the principle of the vertiginous action of magnetism arqund the axis of the conjunctive wire. But this, as we shall presently see, is assumed by Ampere, as an ulti- mate fact. IV. Action of electro- and steel magnets upon the conjunctive wire, or Volta- and Magneto -electric Induction. For most of the facts upon this new and interesting branch of Elec- tro-Dynamics we are indebted to Mr. Faraday. It has been shown that when an excited electric is brought near to an insulated body, electricity is induced in the body. After a series of experiments, the distinguished philosopher just named, succeeded in proving that elec- tro-magnetic phenomena could also be exhibited by induction. A cop- per wire 203 feet in length was passed in the form of a helix round a large block of wood, and an equal length of similar wire was wound on the same block and in the same direction, so that the coils of each helix should be interposed, but without contact, between the coils of the other. The ends of one of the helices were connected with a galvanometer, and the other with a strong Voltaic battery, with the view of ascertaining whether the passage of a Voltaic current through one helix would induce a current in the adjoining helix. It was found that the galvanometer needle indicated a current at the moment both of completing and breaking the circuit, but that in the interval no de- flexion took place ; and similarly the induced current readily magnet- ized a sewing needle, while the Voltaic current along the inducing helix was in the act of beginning and ceasing to flow, but at no other period. By varying the experiment the same result was ob- tained : an electric current transmitted from a Voltaic battery through a conducting helix does not induce a current in an adjoining helix, ex- cept at the moment of making or breaking the Voltaic circuit. In the former case the direction of the induced current is opposite to that of the inducing current, and in the latter case it is the same. This phe- nomenon is distinguished by Mr. Faraday under the name of Volta- electric Induction. In continuing these researches, it was also found that the inducing power of a magnet greatly exceeds that of an electric current. There are various arrangements of apparatus for the purpose of illustrating this fact. Perhaps one of the most convenient consists of a hollow cylinder of pasteboard; round which two compound helices were ad- 92 ELECTRO-MAGNETISM. justed. On transmitting an electric current through one helix, the other deflected the galvanometer and magnetized a needle, as in the experiment jusrdescribed ; but when a cylinder of soft iron was intro- duced into the pasteboard case, and a Voltaic current transmitted as before, the effect on the galvanometer was much greater. The action in this last experiment is distinguished by the name of Magneto -electric Induction. Upon carefully reviewing these experiments and comparing them with those already described, in the remarks concerning the condition of the conjunctive wire and its action upon soft iron, it is evident that the induced wire is in the same electric state as that which unites the two poles of the battery. Thus it magnetizes steel, it deflects the mag- net ; and by connecting a frog's leg with the induced wire it is thrown into spasms, and by arming the ends of that wire with points of char- coal and separating them at the instant the Voltaic circuit is broken or restored, sparks of electricity are obtained. A Voltaic current circulat- ing around a bar of soft iron converts it, as we have seen, into a tem- porary magnet, and it is to this magnet that most of the induced elec- tricity is to be ascribed. Mr. Faraday rendered this certain by sur- rounding a cylinder of soft iron with one helix connected with the gal- vanometer, and converting the soft iron into a temporary magnet, not by a Voltaic battery, but by placing at each end of the cylinder the opposite pole of a magnet. During the act of applying the magnetic poles to the iron, the galvanometer needle was deflected ; and the de- llection was reproduced, but in an opposite direction, when the mag- netism of the iron was ceasing by the removal of the magnet. So al- so when a helix was wound on a hollow cylinder of pasteboard, and a real magnet was introduced, the galvanometer was deflected : the nee- dle then remained quiescent so long as the magnet was left in the cyl- inder ; but in the act of its removal, the needle was again deflected, though as usual in the opposite direction. Thus it appears that while magnetism maybe induced by an electric current, electricity may also be induced in a wire by a magnet. In consequence of the intimate relations which are thus established be- tween galvanic and magnetic action, it was supposed that the electric spark could be obtained from the magnet itself. Several arrangements of apparatus are now constructed, which at first sight seem to con- firm this conjecture. But the electrical phenomena which they exhi- bit, may all be referred to the principle of induction which has just been explained. By surrounding the middle of the keeper or armature of a common steel magnet with a helix ot copper wire wound with silk, and connecting one of the ends of the wire with a cup of mer- cury and removing the other at the moment the armature of soft iron is withdrawn from the magnet, a spark is visible ; as also when the armature is applied and the contact of the conducting wire restored. Of the different forms of apparatus constructed for the purpose of showing these effects, one of the most convenient is that of Mr. Saxton, described in the Journal of the Franklin Institute for 1834. In this apparatus the keeper is made to revolve upon the ends of the magnet and around its axis ; and by a peculiar arrangement of the coils of copper wire which surround it, water may be rapidly decomposed, and shocks communicated to the mouth and tongue. Dr. Emmet, with an other arrangement, has succeeded in giving shocks so powerful that they can scarcely be taken through the arms and shoulders without great inconvenience. [Sittiman's Jour, xxvi, 313.] And Dr. Ritchie has described a neat apparatus for firing an explosive mixture of oxy- ELECTRO-MAGNETISM. 93 gen and hydrogen gases. But I must omit further details and refer those who wish to examine these and other allied topics, to the papers of Mr. Faraday, Dr Ritchie, Mr. Forbes, and others, most of which are published in the recent volumes of the London Phil. Mag. and in Silliman's Journal. The fourth English edition of Dr. Turner's Chemistry also contains a well digested summary of the recent dis- coveries in Electro-Magnetism, to which I acknowledge myself large- ly indebted in the preceding sketch. V. Action of the earth's magnetism upon electric currents. Led by his elaborate views of this subject, Ampere was induced to sub- stitute terrestrial magnetism for the magnet he had previously used in experiments on the wire. His conclusions were verified upon find- ing that a conducting wire, bent into the form of a circle, when free to move, always assumes, by the electro- magnetic action of the earth, a position in a plane which is perpendicular to the magnetic meri- dian. This fact can be shown in a striking manner, by a small instrument called De la Rive's Ring. It consists of a small Voltaic combination, or battery, attached to a piece of cork ; the zinc plate is half an inch wide and three inches long, and passes through the middle of the cork, two and a half inches below and half an inch above it ; the slip of copper is the same width as the zinc, but about twice as long ; it passes through the cork on both sides of it, and being thus opposed to both surfaces, it forms a little battery, on the principle of Dr. Wol- laston's. A piece of copper wire, covered, with silk thread, is rolled five or six times and tied together so as to form a ring, about an inch and a half in diameter ; the ends of the wire are connected, one with the zinc, and the other with the copper slip or plate, above the cork. Now when this little battery is placed in water, slightly acidulated with sulphuric or nitric acid, the ring becomes magnetic, and on pre- senting a magnetic bar to it, which is strongly charged, it will be attracted and repelled, according as one or the other of the poles is opposed, or as one or the other side of the ring is presented to the bar. If instead of connecting the copper and zinc by a ring, it is done by a helix of copper, and the instrument then floated on dilute acid, the helix becomes magnetic ; - its extremities act like the opposite poles of a magnetic needle, being attracted or repelled by the opposite ends of a magnetic bar, and it settles in a north and south position, in the same manner as a common magnetic needle. THEORY OF ELECTRO-MAGNETISM. Different theoretical views of the phenomena of Electro-Magnet- ism have been offered. But those of M. Ampere are the most ex- tensive and precise, and have been tested by the application of facts and calculations very far beyond any of the rest. They have also been found a safe guide in experiment, and many of the most inter- esting facts of the science are direct consequences from them. Of these views the following is a very brief outline ; but as the theory of two electrical fluids is adopted by Ampere, they are here made to con- form with that of one fluid employed throughout this work. When a wire of any metal connects the opposite poles of a Voltaic battery in action, it is supposed that a current of electricity is circu- lating from the positive to the negatilte side of the battery, and it is 94 ELECTRO-MAGNETISM. only when electricity is thus moving, that magnetic phenomena are produced. While others attempt to explain the attraction which is observed between currents when they move parallel to each other in a similar direction, and the repulsion between currents moving parallel to each other in opposite directions, Ampere assumes these as the fundamental or ultimate facts. Ampere supposes that all magnetic bodies, and the globe of the earth among the number, derive their magnetic properties from currents of electricity continually circulating among the parts of which they are composed, and having, with respect to the axes of these bodies, one uniform direction of revolution. In order to render these views more precise, let us conceive a slender cylinder of iron, intersected by an infinite number of planes, perpen- dicular to the axis, so as to divide it into as many circular disks, suc- cessively applied to each other, as represented in the annexed diagram : let us now imagine that, in consequence of some unknown action among the particles composing these circles, a cur- rent of electricity is perpetually circulating in their cir- cumferences, as if they had composed a Voltaic circuit. Let us suppose the direction of these currents to be the same throughout the whole series of circles : the cylinder thus constituted may be considered as a magnetic fila- ment ; that extremity in which, when uppermost, the cur- rent of positive electricity is moving in a direction con- trary to the hands of a watch, being the one which has the northern polarity, that is to say, which, when sus- pended as in a compass needle, points to the north. Setting out then, with the assumptions that parallel cur- rents attract one another when their directions are the same, and repel one another when opposite ; and that a magnet con- sists of an infinite number of circular currents of electricity, all the facts of the science, now known, can be easily explained. We have seen that when the conjunctive wire is brought near to a magnetic needle, it is deflected to the east or west according as the wire is brought above or below the needle. In order to understand this fact, and the course of the deflection, we have only to suppose electric currents passing round the needle from west to east as repre- sented. Now when the conjunctive wire is brought over, and in a direction parallel to the magnetic north and south, the current of positive electricity passing from north to south, the north end of the needle will be deflected to the east, because the current in the wire and those in the magnet will then move in similar directions. For the same reason also, when the wire thus arranged, is brought under the needle, it will be deflected to the west, because then also the currents will be in similar directions. When the position of the conjunctive wire is reversed, that is, when the supposed electric current passes from south to north, it will, when brought over the needle, cause it to de- viate to the west ; when brought under it, to the east. All these re- sults precisely accord with experiments, and they are also supported by the most exact mathematical calculations. The revolutions of the wire around magnets were regarded by most philosophers as indicative of a rotary tendency being an ultimate fact, but they will be found upon an attentive examination to be direct con- sequences of Ampere's theory^ and are indeed, among the strongest confirmations of its truth. So also the phenomena of electro-magnetic ELECTRO-MAGNETISM. 95 induction, and the action of terrestrial magnetism upon electrical cur* rents, are precisely such as might have been deduced from it. REFERENCES. Faraday's Historical Sketch of Electro -Magnetism, up to 1822, Ann. of Phil, xviii. 195, 274, xix. 107. Professor Oersted on Electro- Mugnetisiii, Arm. of Phil, xviii. 321 contains his own account of his theory, and his objections to that of Ampere. Professor Green, of Philadelphia, on Electro-Magnetism. ( This little work contains a good account of the prin- cipal facts of the science up to 1827, with descriptio7is and plates of appara- tus, Sfc.) Art. Electro-Magnetism in the Quarterly Review, xxxv. contains an exposition of the theory of Ampere, shewing its application to all the facts of the science. Professor Cu mining's Manual of Electro- Dynamics. Bar- t iw's Essay on Magnetic Attractions. Walking popular Sketch of Elec- tro Mignetism. The article Electro-Magnetism, in the Library of Useful Knowledge, by Dr. Roget. THERMO-ELECTRICITY. Thermo-electric phenomena are those which result from currents of electricity, which can be excited in metals by mere variations of tem- perature. Seebeck demonstrated the existence of these currents in 1821, and this observation was one of the first, as well as the most in- genious applications, of the discovery of Oersted. If a magnetic needle be placed upon a pivot within a rectangle, formed of a bar of antimony or bismuth, with a slip of copper or a copper wire soldered to each of its extremities, and the heat of a lamp applied to one end of the bar, the needle will be deflected and tend to place itself at right angles to the magnetic meridian. If that end be allowed to cool, the needle returns to its former position, and if now the opposite end of the bar be heated, the needle is deflected in a direc- tion contrary to that in the former case. Similar phenomena will also be observed when either of the ends are cooled down below the natural temperature. Thermo-electricity may also be developed in a homogeneous metallic mass, or in two distinct masses of the same metal unequally heated at their point of contact. Nor is it confined to the simple metals, char- coal, plumbago and some of the metallic sulphurets, are capable of this species of excitation. The metals compose a thermo-electric series, of which bismuth and antimony are the extremes, and are the most efficacious within certain limits. Rotatory motion may also be produced by thermo-electrics, as first shown by Professor Gumming. Platinum and silver wires soldered together in a circular form, rotate, when poised upon a magnet and heated by a lamp. The thermo-electric current appears to be incapable of passing through fluid non metallic conductors, of heating wire placed in its circuit, or of magnetizing steel or forming a thermo-electric magnet ; and it therefore seems to have no assignable tension. Cumming's Re- port. It has been supposed that a thermo-electric combination might be employed as a very delicate thermometer ; and an instrument has been constructed by M. M. Nobili and Melloni, which they denominate a Thermo-multiplier, and which consists of such a combination, susceptible of excitation from the feeblest conceivable application of heat, and 96 ELECTRO- NEGATIVE BODIES. connected with a delicate galvanometer, which gives a measure of the effect produced, and consequently of the heat. [Ann. de Chim. Oct. 1831.] This apparatus they have applied to the examination of the different reflecting, absorbing and radiating power of surfaces. But according to Professor Gumming the ratio between the temperatures and the corresponding deviations of a needle, in the thermo-electric circuit, is not invariable, the deviations increasing slower than the temperature, the law of which deviation is unknown ; and hence a pyrometer constructed on thermo-electric principles gives inaccurate indications. The theoretical views which have been heretofore offered* are appli- cable to the phenomena of thermo-electricity. REFERENCES. Experiments on Thermo- Electricity by Fourier and Oers- ted, Ann. of PhiL xxi. 439. Professor Camming* s Report on the same, published in the Reports of the British Association for 1832. Sturgeon'y papers in the Phil. Mag. and Ann. for 1831. Emmet upon Caloric as a cause of Galvanic Currents. Sill. Jour, xxv. 269. Most of the general referred to under the last head, contain notices of Thermo- Electricity.* CHAPTER VI. ELECTRO-NEGATIVE BODIES. Having now treated of the general powers, &c. I come next to the chemical history of individual substances, and in conformity to the re- marks which have been made, when noticing the electro-chemical the- ory of Davy, I shall adopt that as the basis of their arrangement, at least so far as inorganic chemistry is concerned. The first class of bodies to be examined, are those which being at- tracted by positively electrified bodies, are inferred to be themselves negative. They may be termed, for the sake of brevity, Electro-Nega- tive Bodies. Though highly important, from their influence as chem- ical agents, yet their number is but small, for they consist only of OXY- GEN, CHLORINE, BROMINE, IODINE, and a fifth body, which is only very imperfectly known to us, FLUORINE. These bodies have also been classed together, from another circum- stance of resemblance, that of being what has been termed supporter? of combustion. But the term combustion, is now used to express all chemical combinations which are accompanied with the extrication of heat and light ; phenomena, for the production of which, the presence of these bodies is by no means essential. Before proceeding to a notice of these individual substances, it may be proper to explain the principles upon which the nomenclature, now generally adopted by chemists, is founded. When bodies unite with oxygen, two sets of compounds are pro- duced, differing in many respects from each other : the one called ox- ides or salifiable principles ; the other acids or salifying principles. The oxides differ from the acids in the want of the sour taste which gene- rally belongs to the latter, and in their not changing vegetable blue colours to red ; but they are better characterized by the fact, that they combine with acids and form bodies which are termed salts. In some ELECTRO-NEGATIVE BODIES. 97 cases the oxides possess properties termed alkaline ; but there are both acids and alkalies which do not contain oxygen. Oxygen may combine with a body in several proportions, and form both oxides and acids. If there be many oxides of the same base, the Greek numerals are prefixed to express the different proportions of oxy- gen, as prot-oxide, deut-oxide, trit-oxide, and per-oxide ; the latter al- ways expressing the highest degree of oxidizement in oxides. When two acids are formed by the union of different proportions of oxygen, that which contains the smallest quantity is designated by the termination ous ; the other by the termination ic. Thus, nitrous acid contains four proportions of oxygen ; nitric acid five proportions. The acid containing a still less amount of oxygen than the nitrous, is called the hypo- nitrous. And if, as is the case with the sulphurous and sulphuric acids, there be an acid intermediate, it is called the hypo- sulphuric. The compounds of chlorine are called chlorides ; of bromine, bro- mides; of iodine, iodides; and of fluorine, fluorides; when they do not possess acid properties. When they form more than one such compound with a body, or when the compound is acid, the principles already laid down will apply. Many acids are formed by the union of hydrogen with other bodies. The name of such acids has the usual termination, the term hydro be- ing prefixed ; as hydro-chloric, hydri-odic. In the compounds of non-metallic combustibles, or electro-positive bodies with metals, the termination met is added ; thus sulphur and iron form sulphuret of iron, &c. When an acid combines with any salifiable basis, if the resulting compound does not effect either the tests of acids or alkalies, it is called a neutral salt. Acids terminating in ous, when they combine with alkalies or oxides, change that termination into ite ; and acids terminating in ic change it to ate. Thus, sulphite of soda consists of sulphurous acid and soda ; sulphate of soda, of sulphuric acid and soda. A salt, in which two proportions of an acid are combined with one of a basis, has the same term bi prefixed. Thus we have a carbonate and a ^i-carbonate of soda. When an acid combines with a protoxide of a metal, the salt has the term proto prefixed ; and when with a peroxide, the term per ; thus we have a proto -sulphate and a per-sulphate of iron. By carefully studying the principles which have thus been briefly laid down, the learner will find his progress in the knowledge of chem- ical compounds much facilitated. It should be remarked, however, that although very generally applicable, there are occasional instances of deviation from these rules. The bodies about to be described, exist in one of three forms, viz. solid, liquid and gaseous, or ceriform. The two former of these terms are sufficiently understood. But it may be observed, that the term gas is applied to all permanently elastic fluids, except the atmosphere, to which the term air is appropriated : hence we shall be easily enabled to distinguish between a gas and a vapour. For performing experiments on the gases, various articles of appa- ratus are required, as a pneumatic trough, receivers, gasometers, &c. for descriptions of which we must refer to more extended treatises. Some bodies are called simple or elementary, by which is to be under- stood, not that they are incapable of further decomposition, but only that they have not yet been decomposed. We are at present acquainted with fifty-four of these elementary bodies. 98 OXYGEN. Compound bodies are formed by the union of two or more simple ones, and their nature is determined by two kinds of proof, viz. syn- thesis and analysis. Synthesis consists in effecting the chemical union of two or more bodies ; and analysis, in separating them from each other, and exhibiting them in a separate state. SECTION I. OXYGEN. 'Atom. Num. SSymb. OSjp. gr. 1-111 air=L* SYX. Dephlogisticated Air Priestley. Empyreal Air Scheele. Discovered by Priestley, in 1774 ; but received its present name from Lavoisier. PROPERTIES. In the most simple form in which we can procure it, it is gaseous, insipid, colourless, inodorous, a powerful supporter of respiration and combustion ; sparingly absorbed by water ; when sud- denly compressed, emits light and heat ; refracts light less than any other gas. A supporter of respiration and animal life. This can be shown by confining a small animal, as a mouse, in a vessel of oxygen gas and another in a vessel of the same size, filled with common air. The animal in the former, will live thrice as long as in the latter. Or if we place a glow-worm within ajar of oxygen gas, in a dark room, the insect will shine with much greater brilliancy than it does in atmos- pheric air, and appear more alert. A powerful supporter of combustion. This can be shown by several interesting and brilliant experiments. Thus a lighted taper, when introduced into a vessel of this gas, burns with great brilliancy, and if the taper be blown out, and let down into a vessel of it while the snuff remains red hot, it instantly kindles with a slight explosion. Lighted charcoal emits beautiful scintillations in oxygen [gas, and phosphorus burns with such splendour that the eye cannot bear its im- pression. Even iron wire or a steel watch spring, when formed into a coil and heated at one end to redness, undergoes rapid combustion in it. It is important to notice that in all the foregoing experiments the volume of the oxygen gas has diminished during the combustion. This is owing to its combination with the burning body. Oxygen gas is supposed to be a compound of oxygen, light and heat. During combustion in it, the light and heat are given out, and there remains a compound of solid oxygen with the combustible. Thus when iron wire is burned in oxygen gas, light and heat are evolved, and there remains a substance, which, upon examination, proves to be an oxide of iron, composed of oxygen andiron, and the increase of weight in the iron is exactly equal to the diminution of weight in the oxygen gas. The same thing occurs during the combustion of phosphorus, sulphur, carbon, &c. in this gas, though in these cases acids, instead of oxides, are formed. * I have endeavoured lo consult the convenience of the student by placing under the name of each substance its equivalent or atomic number, the symbol by which it is expressed, and its specific gravity. OXYGEN. 99 Respiration has the same effect upon oxygen as combustion. If an animal be confined in a limited quantity of atmospheric air, it will at first feel no inconvenience ; but as a portion of oxygen is withdrawn at each inspiration, its quantity diminishes rapidly, so that respiration soon becomes laborious, and in a short time ceases altogether. Ano- ther animal introduced into the same air, expires in the course of a few seconds, and if a lighted candle be immersed in it, the flame will be extinguished. NATURAL STATE. Oxygen gas can scarcely be said to exist in a se- parate state in nature. In some saltpetre caves, perhaps, there is an excess of it, over that which commonly forms atmospheric air. EXTRACTION. This gas may be obtained by heating to redness any substance which contains a large proportion of oxygen, as the chlorate or nitrate of potassa, peroxide of manganese and red lead. Chlorate of potassa furnishes the most pure gas ; but this requires more cautious management. Peroxide of manganese is generally employed. This is to be heated to redness in a gun-barrel or iron retort, to which a tube is attached. The gas is collected over water. The first por- tions should be rejected as containing atmospheric air, and some- times carbonic acid, owing to the impurity of the manganese.* The gas should always be tested with a taper before it is collected for ex- periment. The rationale of all these processes accords with the views before given, and will be readily understood. Chlorate of potassa, peroxide of manganese and red lead contain a large proportion of oxygen. Upon the application of heat the oxygen is rendered gaseous and it then escapes. TEST. M. Kastner has proposed protoxide of iron as a test for the presence of oxygen in gaseous mixtures. Phil. Mag. and Ann. v. 235. ACTION UPON THE ANIMAL ECONOMY. Although oxygen gas is essen- tial to the support of animal life, it appears, when pure, to excite so great a degree of excitement in the pulmonary organs as to render it hazardous to breathe it for any length of time. Thenard relates a case in which it proved fatal. And, in an experimental enquiry into the physiological effect of oxygen gas upon the animal system, by Mr. Broughton, the author shows that the symptoms induced by its respir- ation are analogous to those which follow the absorption of certain poisons into the system. Phil. Mag. and Ann. v. 383. Brande's Jour. N. S. vii. 1. REFERENCES. Scheele on air and fire. Priestly on Airs. Lavoisier 1 s Elements of Chemistry. Thenard describes an apparatus for showing the evolution of Light by the compression of Oxygen Gas, Traite de Chim, i. 181. A convenient apparatus for procuring Oxygen Gas, from Chlorate of Potassa, is described anil figured by Berzelius, Traite de Chim. i. 207. On the specific gravity of Oxygen, see Thomson's First Prin. where the esti- mate of Dr. Prout, as above given is confirmed. * The carbonate of lime to which this is due, may be separated by washing the manganese with dilute muriatic acid until effervescence ceases. 100 CHLORINE. SECTION II. CHLORINE. Atom. Num. 35.45 jStymfc. Cl Sp. gr. 2-47 air=L SYN. Dephlogisticated Marine Acid Scheele. Oxymuriatic Acid* This substance was discovered by Scheele, in 1774. It derives its present name from the Greek chloros, green, in allusion to its colour. PROPERTIES. Gaseous, having a yellowish-green colour, an astrin- gent taste and disagreeable odour ; one of the most suffocating of the gases, exciting spasms and great irritation of the glottis, even when considerably diluted with air ; emits light and heat when strongly and suddenly compressed ; under a pressure of four atmospheres becomes a limpid liquid of a bright yellow colour ; is absorbed by cold water, from whence it can again be driven by heat ; supports combustion ; discharges animal and vegetable colours, when water is present ; and is a powerful disinfectant. Chlorine is absorbed by cold water. Cold recently boiled water, at the common pressure, absorbs twice its volume of chlorine. Hence a solution of chlorine may be easily made by transmitting a current of the gas through cold water. It has the taste, colour and most of the other properties of the gas itself. When moist chlorine gas is exposed to a cold of 32 F. yellow cryslals are formed, which consist of water and chlorine in definite proportions. They are composed, according to Mr. Faraday, of one atom of chlorine, and ten atoms of water, and have received the name of Hydrate of Chlorine. Phil. Trans. 1823. Ann. of Phil, xxiii. 89. Supports combustion. Some substances unite with chlorine with the evolution of light and heat, and hence it is called a supporter of com- bustion. In this respect, however, it differs considerably from oxygen gas. If a lighted taper be plunged into a vessel of chlorine gas, it burns for a short time with a small red flame, and emits a large quan- tity of smoke. Phosphorus takes fire in it spontaneously, arid burns with a pale white light, if the temperature of the gas be raised to about 70 F. Several of the metals, such as tin, copper, arsenic, anti- mony and zinc, when introduced into chlorine in the state of powder, or of fine leaves, are suddenly inflamed. Great caution should be ob- served in performing these experiments to prevent the gas from being inhaled. In all these cases of combustion in chlorine gas, the chlorine com- bines with the combustible, and there result a class of compounds named Chlorides or Chlorurets. These are sometimes acid and some- times destitute of that property. Discharges colours. This assertion is correct when applied to chlo- rine as it is usually obtained. But Sir H. Davy proved that chlorine, when perfectly dry, does not bleach. When combined with water, it possesses the property of bleaching in an eminent degree. This may be shown by introducing a solution of indigo or strips of calico into solution of chlorine. In a short time the colours will be com- pletely discharged, and they can never be restored. Hence an im- portant practical application of chlorine, and some of its compounds, in the art of bleaching. CHLORINE. 101 Is a powerful disinfecting agent. The power of chlorine, for the pur- poses of fumigation, was shown by Guyton-Mor\eau, who ascertain- ed that it destroyed the volatile principles given off .by petrifying animal matters. It probably acts in a similar way* on contagious ef- fluvia. It is now extensively employed as a disinfecting agent, either in solution in water, or in the form of those, peculiar corr> pounds, of chlorine and soda, and chlorine and lime, which have received the names of Labarrague's disinfecting liquor, and Tennant's bleaching pow- der, and which I shall notice hereafter. It has been ascertained that the bleaching and disinfecting powers of chlorine are in exact proportion to each other, and it is probable that both these effects are produced in a similar way. During the process of bleaching, water is decomposed, in consequence of the great affinity between chlorine and hydrogen ; the decomposition of the colouring matter is occasioned by the oxygen which is liberated ; at the same time muriatic acid is always generated. The bleaching property of the deutoxide of hydrogen, of which oxygen is certainly the decolourizing principle, strengthens this view. The power of chlorine, as a disinfecting agent, depends also upon its great affinity for hydrogen, a substance entering largely into putrid affluvia, by means of which they are decomposed. This is illustrated in the cases of sulphuretted and carburetted hydrogen, which are in this way de- composed by chlorine, and rendered innoxious. NATIVE STATE. Chlorine exists in nature in great abundance, but always combined with other bodies. Some of these compounds are very abundant, as muriatic acid, which is often thrown out in great quantities by volcanoes, and chloride of sodium which occurs in the form of rock salt, and also in solution in the waters of the sea, &c. PREPARATION. Chlorine gas may be obtained, 1. By mixing concentrated muriatic acid, contained in a glass flask or retort, with half its weight of peroxide of manganese. Upon the application of heat the gas is freely evolved. It should be collected over warm water, in inverted glass bottles filled with the same liquid, and when the water is wholly displaced by the gas, the bottles should be closed with stoppers. In this process a part of the muriatic acid is decomposed ; its hy- drogen combines with one atom of the oxygen of the manganese, and forms water, while the chlorine is disengaged. At the same time also protoxide of manganese combines with an undecomposed portion of muriatic acid and forms muriate of the protoxide of manganese, which remains in the retort. 2. The more common and cheaper method of preparing chlorine, is to mix intimately three parts of common salt and one part of the per- oxide of manganese, and to this mixture add two parts of sulphuric acid, diluted with an equal weight of water. In this case, sulphuric acid acting upon the solution of common salt, disengages muriatic acid, which is decomposed by the peroxide of manganese in the manner just explained. The residuum in this case, however, is the sulphate of manganese and sulphate of soda. TESTS. Chlorine may in general be recognized by its colour and odour. Chemically, it may be detected by its bleaching property, and by the circumstance that a solution of the nitrate of silver/ oc- casions in it a dense white precipitate (chloride of silver,) which be- comes dark on exposure to light, is insoluble in acids, but completely soluble in pure ammonia. 102 CHLORINE. ACTION ON THE ANIMAL ECONOMY. Chlorine in a gaseous state, des- troys those who- breathe it, by producing great irritation of the bron- chia ;* and ev^n wL.en diluted with atmospheric air, it causes cough and inflammation. Pelletier is thus said to have fallen a victim to its effects* . [.Beck's Med. Juris. 3d ed. 503.] The antidote in such cases is.tanmoT'ia. In jsohition, however, chlorine is employed medicinally ; in some cases with great advantage. See Urc's Chem. Diet. REFERENCES. Scheele's Essays. Memoirs on the nature of Chlorine, by Davy, Van Moris, Thomson, Gay Lussat and Berzelius, Ann. of Phil. iii. iv. v. and vi. A comparison of the new and eld theories of Chlorine, by Ber- zelius, Ann. of Phil. v. 7. [The author ivas, until recently, in favour of the old theory.] Papers on the controversy concerning the nature of Chlorine, by Murray, Ure y Berthollet and Davy, Ann. of Phil. x. xi. xii. xiii. For a summary of (his coritroversy up to 1813, see a note of Dr. T. Cooper, in the 1st volume of the Amprican edition of Thomson's Chem. 155. He hoioever inclines to the old theory, now universally abandoned. Berzelius on the nature of Muriatic Acid, Ann. of Phil. ii. 254. CHLORINE AND OXYGEN. These substances unite in four different proportions. The leading character of these compounds depends upon the fact, that chlorine and oxygen have a very feeble affinity for each other. They are therefore never met with in nature ; they can hence also be easily decomposed. These compounds are as follows : Cl. O. Protoxide of Chlorine, - .... 35-45 8.=r43-45. Peroxide of Chlorine, .... 35 -45.... 32.3=67-45. Chloric acid, - 35-45....40.z=75-45. Perchloric acid, 35 -45.... 56. 91 -45. Protoxide of ChlorineAtom. Num. 4345 Symb. O-f-CI Sp. gr. 2417 air=l. Discovered by Sir H. Davy in 1811, and described by him under the name of Euchlorine. PROPERTIES. Gaseous ; colour yellowish-green, similar to that of chlorine, but more brilliant ; odour like that of burned sugar ; bleaches vegetable substances, but gives the blue colours a red tint before discharging them ; is highly explosive ; dissolves in water to eight or ten times its volume ; may be liquified by pressure. Protoxide of Chlorine is highly explosive. The heat of the hand, or the pressure occasioned in transferring it from one vessel to another, sometimes causes an explosion. This effect is also occasioned by phos- phorus, which bursts into flame at the moment of immersion. All * The recent experiments of Mr. Soubeiran, have rendered the existence of this gas doubtful ; and (he same author supports the opinion of Berzelius, that the bleaching compounds contain a lower acid of chlorine, Chlorous acid. But these views are not yet sufficiently settled to warrant the alterations, which by their adoption, would become necessary. See Ann. de Chim. xlviii., or Johnston* s Report on Chemistry, CHLORINE. 103 burning bodies by their heat, occasion an explosion, and then burn vividly in the decomposed gas. With hydrogen, it forms a mixture which explodes by flame, or the electric spark, forming water and mu- riatic acid. The best proportion is fifty measures of the protoxide of chlorine to eighty of hydrogen. PREPARATION. This gas is prepared by adding to two parts of chlorate of potassa, one part of strong muriatic acid and one of water. These ingredients should be put into a small retort, to which gentle heat is to be applied. The gas must be collected over mercury. Prof. Silliman recommends placing the materials in a small glass flask, fur- nished with a tube bent twice at right angles, and passing to the bot- tom of any clean dry phial, flask or tube, rather deep and with a nar- row neck. A gentle heat, applied beneath the flask, soon disengages the euchlorine gas, which, by its great weight, displaces the common air from the recipient and takes its place. By using tongs properly curved, so as to embrace the phials or tubes filled with the gas, the operator may perform all the necessary experiments without danger of causing an explosion by the warmth of the hands. Sill. Jour. vi. 164- REFERENCES. Sir H. Davy, in Phil. Trans. 1811. Faraday, on the liquefaction of Euchlorine, Phil. Trans. 1823, and Ann. of Phil, xxiii. 95. Peroxide of Chlorine Atom. Num. 6745 4O-|-C1 Sp. gr. 2-3-16 air=l. SYN. Chlorous Acid. Berzelius. Qitadrozide of Chlorine. Thom- son. Discovered by Sir H. Davy in 1815, and soon after by Count Sta- dion of Vienna. PROPERTIES. Colour bright yellowish-green ; odour aromatic, with- out any smell of chlorine ; is rapidly absorbed by water ; destroys most vegetable blues without previously reddening them ; does not unite with alkalies ; occasions the combustion and explosion of phos- phorus when introduced into it : explodes violently when heated to a temperature of 212 F. emitting a strong light, and suffering a greater expansion than the protoxide of chlorine ; it can be liquified by pres- sure. PREPARATION. This substance is formed by the action of sulphuric acid upon chlorate of potassa. A quantity of this salt, not exceeding 50 or 60 grains, is reduced to powder and made into a paste by the ad- dition of strong sulphuric acid. The mixture which acquires a deep yellow colour, is placed in a glass retort, and heated by warm water, the temperature of which is kept under 212 F. The gas is to be col- lected over mercury. The changes which take place in this process may be thus explain- ed. The sulphuric acid decomposes some of the chlorate of potassa and liberates chloric acid. The chloric acid, at the moment of sepa- ration, resolves itself into peroxide of chlorine and oxygen ; the last of which, instead of escaping as free oxygen gas, goes over to the acid of some undecomposed chlorate of potassa and converts it into per- chloric acid. The whole products are bisulphate and perchlorate of potassa and peroxide of chlorine. One of the most striking properties of this gas, can be exhibited on a small scale, by adding to a few grains of chlorate of potassa in a test 104 BROMINE. glass five or six drops of strong sulphuric acid. The gas is immedi- ately disengaged. If a piece of cotton dipped in ether, be now brought into contact with the gas, it takes fire with a slight explosion. The eotton should be attached to a wire, and some care is necessary in per- forming the experiment. REFERENCES. Sir H. Davy, in Phil. Trans. 1815. Count Von Stadi- on,in Gilbert's Ann. der Phys. lii. 179, (Feb. 1816. J Berzelius, Trait, de Chitn. ii. 73, where will be found his reasons for calling this an acid. Chloric Acid Atom. Num. 7545 Symb. 50-}-Cl. First obtained in a separate state by Gay Lussac. PROPERTIES. Reddens vegetable blues ; has a sour taste and forms neutral salts, called Chlorates, with alkaline and earthy bases ; distin- guished from chlorine by its not being possessed of bleaching proper- ties ; gives no precipitate with nitrate of silver, and can hence be dis- tinguished from muriatic acid ; is readily known by its forming a salt with potassa which, when thrown on burning charcoal, deflagrates like nitre. PREPARATION. This acid may be obtained by adding to the chlorate of baryta a quantity of weak sulphuric acid, exactly sufficient for com- bining with the baryta. The insoluble sulphate subsides and pure chloric acid remains in the liquid. This may be concentrated by gen- tle heat, till it acquires an oily consistence. REFERENCES. Gay Lussac, in a memoir on Iodine, #c. Ann. of Phil, vi, 129. Perchloric Acid Atom. Num. 91-45 Symb. 7O-fCl &p. gr. 1'65 water=l. PREPARATION. The saline matter which remains in the retort after forming the peroxide of chlorine, is a mixture of perchlorate and bi- sulphate of potassa ; and by washing with cold water, the bisulphate is dissolved, and the perchlorate is left. Perchloric acid may be pre- pared from this salt by mixing it in a retort with half its weight of sulphuric acid, diluted with one third of water, and applying heat to the mixture. At the temperature of about 2^4 F. white vapours rise which condense as a colourless liquid in the receiver. This is a solution of perchloric acid. It has an acid taste, and reddens litmus paper without discharging its colour, and uniting with alkalies, forms Perchlorates. REFERENCES. Stadion, in Gilbert's Ann. der Phys. lii. 213. Berzelius, Trait de Chim. ii. 65. SECTION II L BROMINE. Atom. Num. 78-26 Symb. Dr. Sp. gr. 2-966 water=l. Discovered by M. Balard of Montpelier, in 182(5, and described by him under the name of Muridc. This has since been changed to Bromine, from the Greek bromos, in allusion to its strong odour. BROMINE. 105 PROPERTIES. A liquid of a deep reddish-brown colour ; odour dis- agreeable, somewhat resembling that of chlorine ; taste powerful ; at common temperatures it emits red coloured vapours, which are very similar in appearance to those of nitrous acid ; and at 116'5 F. it en- ters into ebullition ; between the temperature of zero and 4 F. it is congealed, and in that state is brittle, but if combined with water so as to form a hydrate, it affords fine red crystals at 32 ; soluble in water, alcohol and ether, the latter being the best solvent ; does not redden litmus paper, but bleaches it rapidly like chlorine ; supports combustion ; acts with energy upon animal textures, giving the skin a yellow stain, and being highly destructive to life. Bromine is volatile. This can be shown by introducing a few drops of the liquid into a matrass ; the beautiful red vapour will soon fill the vessel. Supports combustion. Antimony and tin, take fire, and potassium causes a violent detonation, when brought into contact with bromine. Its vapour extinguishes a lighted taper, but before going out it burns for a short time with a flame surrounded by a greenish margin topped with red. The compounds formed by the union of combustibles with bromine, are called Bromides or Bromurets. NATIVE STATE. This substance exists in sea water, in the form of hydrobromic acid, in combination probably with magnesia. In this state it apparently forms an essential ingredient in ocean water ; for it has been detected in the waters of the Mediterranean, Baltic, North Sea, and Frith of Forth. It has also been found in the waters of the Dead Sea, and in many lime springs in Germany and in our own country. Finally, it has been detected in the ashes of certain sea weeds, and of some animals, as those of the Janthina violacea. PREPARATION. Bromine is obtained by transmitting a current of chlorine gas through the bittern of sea water, and then agitating a portion of sulphuric ether with the liquid. The ether dissolves the whole of the bromine, from which it receives a beautiful hyacinth red tint, and on standing, rises to the surface. When the ethereal so- lution is agitated with caustic potassa, its colour entirely disappears, owing to the formation of hydrobromate and bromate of potassa, and the former salt is obtained in cubic crystals by evaporation. The bromine may then be set free by means of chlorine, and separated by heat. TESTS. In most cases bromine is easily detected by means of chlo- rine ; for this substance displaces bromine from its combination with hydrogen, metals and most other bodies. The appearance of its va- pour, or the colour of its solution in ether, will then render its pres- ence obvious. Bromine also renders a solution of starch of an orange colour. REFERENCES. Balard on a peculiar substance contained in Sea Water, Ann. de Chim. ft de Phys. xxxii. 337, and in Ann. of Phil. xii. 381, 411 contains also a notice of its compounds. Phil. Mag. and Ann. vii. 234. viii, 225. For a summary of what was known concerning Bromine and its com- pounds up to 1828, see New-York Med. and Phys. Jour. vii. 141. On the presence of Bromine in American saline Waters, Sillimari's Jour, xviii, 142. 106 IODINE. BROMINE AND OXYGEN. Only one compound of bromine and oxygen has been hitherto dis- covered, which is bromic acid, similar in its constitution to chloric acid. ' Bromic Acid -A lorn. Num. 118-26 Symb. 5O+Br. PROPERTIES. Odour scarcely any ; taste very acid, though not at all corrosive ; reddens litmus paper powerfully at first, and soon after destroys its colour ; is not affected by nitric or sulphuric acid, except when the latter is highly concentrated, in which case bromine is set free, and effervescence, probably owing to the escape of oxygen gas, ensues ; unites with bases and forms a class of bodies termed Bro- mates, analogous to the chlorates. PREPARATION. This acid may be procured in a separate state by decomposing a dilute solution of bromate of baryta, with sulphuric acid, so as to precipitate the whole of the baryta. The resulting solution of bromic acid may be concentrated by slow evaporation, until it acquires . the consistence of syrup ; but on raising the tem- perature, in order to expel all the water, one part of the acid is vola- tilized, and the other resolved into oxygen and bromine. The same effect takes place when the evaporation is conducted in vacuo, with sulphuric acid ; and hence all attempts to obtain anhydrous bromic acid have been unsuccessful. BROMINE AND CHLORINE. We are acquainted with one compound of these elements, probably composed of one atom of each. Chloride of Bromine. SYN. Chlorure Bromique. Berzelius. PROPERTIES. A volatile fluid, of a reddish-yellow colour, much less intense than that of bromine ; odour penetrating ; taste very disagree- able ; vapour of a deep yellow, like that of the oxides of chlorine ; so- luble in water, in which state it possesses the colour, odour and bleach- ing properties of the compound. PREPARATION. This compound may be formed at common tempera- tures, by transmitting a current of chlorine'through bromine, and con- densing the disengaged vapours by means of a freezing mixture. SECTION IV. IODINE. Atom. Num. 126 Sijmb. ISp. gr. 4 948 water=l. Discovered in 1812, by M. Courtois, a manufacturer of saltpetre, at Paris ; recognized as a new body, by M. Clement, in 1813, and after- wards shown to be an elementary one, by Gay Lussac and Davy. The IODINE. 107 name is derived from the Greek iodecz, in allusion to the violet colour - of its vapour. PROPERTIES. A soft and friable solid, of a bluish-black colour, and metallic lustre ; a non-conductor of electricity ; produces a yellow stain upon the skin ; smell resembling that of diluted chlorine ; taste acrid ; is extremely volatile, rising into a rich violet coloured vapour, at a temperature of beween 80 and 100 F. ; fuses at 225 F., and en- ters into ebullition at 347 F. ; is sparingly soluble in water, but read- ily so in alcohol or ether ; acts energetically upon the animal system ; destroys vegetable colours, but forms a blue compound with starch ; combines with phosphorus and various other substances. Iodine is very volatile. This can be very easily shown by introducing into a retort or bolt head, a small portion of iodine, and applying a gentle heat. The violet vapours rise and fill the vessel : upon the ap- plication of cold these are again condensed. Is sparingly soluble in water. Water does not hold more than 1- TOOOths of its weight of iodine in solution; but even this communi- cates a brownish tint. The proper solvents are ether and alcohol. It is in these forms that it is often employed for medicinal purposes. Combines with phosphorus. Phosphorus brought into contact with iodine takes fire, if the experiment is performed in the open air ; but in close vessels no light appears. Iodine combines, also, with most of the other non-metallic combustibles, and with the metals, forming a class of compounds denominated Iodides or lodurets. Forms a blue compound with starch. This is a most delicate test for the presence of iodine, and it is said by Prof. Stromeyer, that a liquid containing 1-450,000 of its weight of iodine, receives a blue colour from starch. Two precautions should be observed to ensure success. First, the iodine must be in a free state, for it is the iodine alone and not any of its compounds which unites with starch. Secondly, the solution should be quite ^cold at the time of adding the starch; for boiling water decomposes the blue compound and consequently re- moves its colour. NATIVE STATE. Iodine has been discovered in a great number of the fuci, which grow upon the sea shores, in sponges, in various mollus- cous animals, and in sea water ; and it has been found by Vauquelin, combined with silver, in South America. It has also been found, in a state of combination, in various salt springs in Europe and America. PREPARATION. Lixiviate powdered kelp, (the semi-fused ashes of seaweed,) with cold water. Evaporate the lixivium till a pellicle forms, and then set it down to crystallize. Evaporate the mother liquor to dryness, and pour upon the mass half its weight of sulphuric acid. Apply heat to this mixture in an alembic to which a receiver is attached ; fumes of a violet colour arise and condense in the form of opaque crystals, having a metallic lustre, which are to be washed out of the head of the alembic with a small quantity of water and quickly dried upon bibulous paper. ADULTERATION. Iodine is sometimes adulterated with black lead. This may be detected by dissolving the substance in alcohol, and also by subjecting it to heat. Black lead is not soluble in alcohol, neither is it vaporized by heat. ACTION ON THE ANIMAL ECONOMY. In small doses iodine is employ- ed with success in various diseases, but in larger ones it excites nausea 108 IODINE. and vomiting, and other distressing symptoms. See Magendie's For- mulary and Beck's Med. Juris. 484. REFERENCES. Gay Lussar, Ann. of Phil. iii. 106. Van Mons. ibid. 429. Sir H. Davy, Phil. Trans. 1814, and Ann. of Phil, iii, and \v. Gay Lus- sac's Memoir on Iodine and its compounds, Ann. de Chim. xci. 5, and in Ann. of Phil. v. 101, 207, 296, 401, vi. 124, 183. Crystalline form of Iodine, Branded Jour. v. 364, and Sill. Jour, xviii. 84. Hobsoii's Prize Essay on Iodine. COMPOUNDS OP IODINE AND OXYGEN. Two compounds of iodine and oxygen have been noticed by che- miststhe lodous and lodic Adds. The former, however, as we shall presently see, is involved in some obscurity. lodous Acid. Discovered by Professor Sementini, of Naples, in 1824. PROPERTIES. An oily liquid, having a disagreeable odour ; taste, acid, and astringent ; reddens vegetable blues permanently, without destroying them; is rapidly volatilized at 212 F. arid evaporates slowly at common temperatures ; is decomposed by sulphur ; phos- phorus and potassium take fire as soon as they come in contact with it. PREPARATION. Equal parts of iodine and chlorate of potassa are to be triturated together in a glass or porcelain mortar, until they form a fine pulverulent yellow mass, in which the metallic lustre of the iodine is no longer visible. The mixture is then heated in a glass retort, and as soon as the chlorate begins to lose oxygen, iodous acid rises in the form of a dense white vapour, and condenses in the neck of the retort into a yellow liquid, which falls in drops into the re- ceiver. It is asserted by M. Wbhler that this compound does not consist of iodine and oxygen, but of chlorine and iodine. This has led to new investigations on the part of Sementini, which render it probable that there exists both iodous acid and oxide of iodine. Brandes Jour. N. 8. ii. 203. REFERENCES. SementinVs account, see Branded Jour. xvii. 381 same work, N. S. i. 477. lodic Acid Atom. Num. 166Symb. 5O+I. Discovered about the same time by Gay Lussac and Sir H. Davy ; by the latter of whom it was termed Oxiodine. In its dry state, it constitutes Anhydrous lodic Acid. PROPERTIES. A regular crystalline body which has a strong astrin- gent sour taste, but no odour ; density greater than that of sulphuric acid ; is fused at 500 F. and resolved into oxygen and iodine ; is very soluble in water, and deliquesces in moist air. The liquid acid thus formed, reddens vegetable blue colours, and afterwards destroys them. On evaporating the solution, a thick mass, of the consistence of paste, is left, which is Hydrous lodic Acid, and from which, by the cautious application of heat, the water may be expelled. It acts powerfully on IODINE. 109 inflammable substances; with charcoal, sulphur, sugar and similar combustibles, forms mixtures which detonate when heated ; combines with bases and forms a class of bodies denominated lodates, which are analogous to the chlorates. According to Mr. Connel this acid may be formed by digesting iodine with nitric acid over a spirit lamp, in a large flask, and washing down the iodine as it condenses on the sides of the flask. [Jameson's Jour. 1831, p. 72.] The process recommended by Liebig is to precipi- tate the iodate of soda by chloride of barium ; to every nine parts of the precipitate, well washed and dried, to add two of sulphuric acid diluted with ten or twelve of water, to boil half an hour, filter, evapo- rate to a sirupy consistence, and expose it to the air for several days. Regular transparent crystals are formed to the last drop. Johnston's Report on Chemistry. IODINE AND CHLORINE. Chloriodic Add Atom. Num. 196-90 Symb. 2C1+I. Discovered by Gay Lussac and Sir H. Davy ; and by the former called Chloride of Iodine. PROPERTIES. A solid compound, of an orange yellow colour, when the iodine is fully saturated with chlorine, but of a reddish orange if the iodine is in excess ; by heat is converted into an orange liquid, which yields a vapour of the same tint on increase of temperature ; de- liquesces in the open air and dissolves freely in water ; forms a colour- less solution, which is very sour to the taste, and reddens vegetable blues, but afterwards destroys them. Possesses acid properties. On this point there is still some dispute. Davy gave the compound the name of chloriodic acid, but Gay Lussac on the contrary, conceives that the acidity of its solution arises from the presence of muriatic and iodic acids, which he supposes to be gene- rated by the decomposition of water. The opinion of Davy is most generally received, yet this compound does not unite with alkaline substances, a fact somewhat difficult of explanation upon this suppo- sition. PREPARATION. This compound may be prepared very readily by the direct union of chlorine and iodine. IODINE AND BROMINE. Bromides of Iodine. Bromine and iodine act readily on each other and appear capable of uniting in two proportions. The proto-bromide is a solid, converti- ble by heat in a reddish-brown vapour, which in cooling, condenses into crystals into the same colour, and of a form resembling that of fern leaves. An additional quantity of bromine converts these crys- tals into a fluid, which, in appearance, is like a strong solution of iodine in hydriodic acid. This compound dissolves, without decom- position, in water, but with the alkalies yields hydrobromic and iodic acids. But, as is remarked by Dr. Turner, the existence of two bromides of iodine can scarcely be regarded as satisfactorily estab- lished. 110 HYDROGEN. SECTION V. FLUORINE. Atom. Num. 18-68. Syml. F. The substance to which this name is applied has not heretofore been obtained in a separate state, and hence the properties which are peculiar to it in that state, are entirely unknown. From the nature of its compounds it appears to belong to the class of nega- tive electrics, and like oxygen and chlorine, to have a powerful affini- ty for hydrogen and metallic substances. With hydrogen it consti- tutes a very peculiar acid, the Hydrofluoric Acid, which I shall no- tice hereafter. CHAPTER VII. ELECTRO-POSITIVE BODIES. The electro-positive class of bodies, includes all those substances which have not been previously described. They are sometimes also called Combustibles. As they are quite numerous, it will be convenient to divide them into, 1. Those which are NON-METALLIC. 2. Those which are METALLIC. The non-metallic simple electro-positive bodies are, HYDROGEN, NI- TROGEN, SULPHUR, PHOSPHORUS, CARBON, BORON and SELENIUM. SECTION I. HYDROGEN. Atom. Num. 1Symb. H Sp. gr. 0-0694 air=l. First proved to be a distinct gas by Cavendish, in 1766. It derives its name from the Greek words signifying the generator of water. It is also sometimes called Inflammable Air. PROPERTIES. A colourless gas, having neither odour nor taste, when perfectly pure ; a powerful refractor of light ; the lightest body in nature ; is sparingly absorbed by water ; inflammable in an eminent degree ; cannot support respiration nor combustion ; detonates when combined with oxygen and fired ; takes fire when brought into contact with a platinum sponge ; produces an intense degree of heat when burned under pressure. Hydrogen gas is destitute of odour. This is only true of the most pure form of this substance ; but as commonly obtained, it has a slight- ly disagreeable smell. HYDROGEN. Ill Is the lightest body in nature. 100 cubic inches of this gas weigh 2'118 grains at mean pressure and temperature ; it is 16 times lighter than oxygen gas ; 200,000 times lighter than mercury, and 300,000 times lighter than platinum. The extreme levity of hydrogen can be shown by fitting soap bub- bles with it, which will be found to ascend rapidly. Hence balloons are now filled with this gas. Is highly inflammable. The inflammability of hydrogen can be shown in various ways. A candle kindles ajar of it, but is itself extinguished by immersion into the gas, and is relighted if the wick again touch the flame. To a bottle containing the materials for hydrogen gas attach a tube. if the common air be now allowed to escape, and the gas kindled at the orifice of the tube, the jet is called the philosophic candle. When a stream of hydrogen gas is burned under a tube of from 12 to 20 inches long, musical sounds are produced, owing to the succession of explosions which take place. Faraday in Brandes Jour. v. 274. Hydrogen gas, when combined in the proportion of 2 parts to 1 part of oxygen, explodes violently on contact with the flame of a candle. The same thing takes place, though in an inferior degree, if the hydro- gen be mixed with atmospheric air, in the proportion of 1 of hydro- gen to about 3 of air. In each of these cases the product of combus- tion is water. These experiments may be performed in a strong glass vial or metallic air pistol, and the explosion is equally produced by the electric spark as by the contact of flame, or by a solid body healed to bright redness. It has been discovered by M. Biot that a mixture of hydrogen and oxygen gases may be made to explode by mechanical compression. A mixture of these two gases, was introduced into a strong metallic syringe, furnished with a glass bottom, and a sudden stroke given to the piston, an extremely brilliant light appeared, accompanied with a loud detonation ; and the glass bottom was forcibly driven out. The repetition of this experiment, it is obvious, must be attended with some difficulty and danger. Nicholson'* Jour. 8vo. xii. 212. Henry's Chem. i. 262. Does not support combustion nor respiration. The former of these has already been shown, under the last article. An animal soon per- ishes, when confined in it. Death ensues from deprivation of oxy- gen, rather than from any noxious quality of the hydrogen, since an atmosphere composed of a due proportion of oxygen and hydrogen ases may be respired without inconvenience. It appears, however, according to the trials of Mess. Allen and Pepys, to have the curious property of throwing the animal into a profound sleep. Takes Jire when brought into contact with spongy platinum. This singular fact was discovered by Professor Dobereiner of Jena, in 1824. For the purpose of exhibiting this experiment, let platinum sponge be prepared, by dissolving platinum in nitromuriatic acid, and then pre- cipitating it by means of ammonia. If a jet of hydrogen from some orifice, and under hi^h pressure, be brought into contact with this sponge, it instantly becomes red hot, and the gas soon takes fire. This has been applied in various ways to the construction of lamps for producing instantaneous light. Several metallic bodies produce the same effect ; especially palladium, rhodium and iridium. Produces an intense degree of heat, when burned under pressure. Iron wire can readily be burned by a stream of hydrogen gas, under strong pressure. 112 HYDROGEN. But the most intense degree of heat is occasioned by the combustion of a mixture of hydrogen and oxygen gases, as it issues from a very small jet. This apparatus, commonly known as the Compound or Oxy- kydrogen blowpipe, and first employed by Dr. Hare of Philadelphia, has been variously modified by Dr. Clarke, Mr. Newman, Dr. Wollaston. and others. These modifications were all proposed for the purpose of preventing the recession of the flame and the consequent explosion of the mixed gases : an object which has been most happily attained by the safety tube lately proposed by Mr. Hemming. It consists of a brass cylinder about six inches long and three fourth of an inch in di- ameter, filled with very fine brass wire, in length equal to that of the tube. A metallic rod l-8th of an inch thick is then forcibly driven through the centre of the bundle of wires in the tube, so as to wedge them firmly together. The interstices between the wires thus consti- tute very fine metallic tubes, the cooling and conducting powers of which are so great as entirely to intercept the passage of flame. So com- pletely effectual is this contrivance that the wells and reservoirs ordi- narily employed may be dispensed with and the mixed gases supplied from a common bladder under the arm. Reports of the British Associa- tion for 1832. A very intense heat, quite sufficient for most purposes, may be safe- ly and easily procured by causing a jet of oxygen gas to pass through the flame of a spirit lamp as proposed by Mr. Marcet. [./tfnn. of Phil. ii. 99.] Or still better, by substituting the flame of coal gas for that of alcohol, upon the plan of Mr. Daniell. Phil. Mag. and Ann. for 1833. In all the above cases of combustion the product is water, and the heat produced can be accounted for upon the general principles which have been laid down, viz. that these gaseous substances, in assuming the liquid form, give out the caloric with which they are combined. PREPARATION. Hvdrogen gas may be easily procured in two ways. 1. By passing the vapour of water over metallic iron heated to red- ness. This is done by putting iron wire into a gun barrel, open at both ends, to one of which is attached a retort, containing pure water, and to the other a bent tube. The gun barrel is placed in a furnace, and when it has acquired a full red heat, the water in the retort is made to boil briskly. The gas, which is copiously disengaged as soon as the steam comes in contact with the glowing iron, passes along the Uent tube, and may be collected in convenient vessels, by dipping the iree extremity of the tube into the water of a pneumatic trough. 2. By putting pieces of iron or zinc into dilute sulphuric acid, form- ed of one part of strong acid to four or five of water five are generally preferred. But in neither of these cases is the hydrogen absolutely pure ; it has an offensive odour, derived from impurities in the iron and zinc, as they are met with in commerce. All these impurities, ex- cept carburetted hydrogen, may be removed by passing the gas through a solution of pure potassa. If hydrogen of great purity is desired, dis- tilled zinc should be employed. In both of the above cases water is decomposed ; the oxygen com- bines with the metal and forms an oxide, and the hydrogen escapes in a gaseous form. HYDROGEN. 113 REFERENCES. Cavendish, experiments on Factitious Air, Phil. Trans. 1766. Action of Hydrogen upon. Platinum, fyc. Thenard, Traite de Chint. i. 338. An elaborate account of Dr. Clarke's Compound Blow-pipe, and-of its effects upon numerous refractory substances^ is given in the appendix to the Life of Dr. Ed. D. Clarke. For papers on Dr. Hare's Blow-pipe, see SWwatfs Jour. 1 98, ii. 181, 281. HYDROGEN AND OXYGEN. Two compounds of these bodies are at present known, viz. the Pro- toxide or water , and the Deutoxide. PROTOXIDE OP HYDROGEN OR WATER. Atom. Num. 9Symb. O+HSp. gr. 1. PROPERTIES. A well known liquid, transparent, colourless, inodor- ous and tasteless ; compressible, by very strong pressure ; elastic ; a bad conductor of electricity, and changed by the application of heat into vapour, by the abstraction of it into ice. Its specific gravity is 1, the density of all solid and liquid bodies being referred to it as a term of comparison. One cubic inch, at 60 F. and 30 Bar. weighs 252.525 grains, so that it is 828 times heavier than atmospheric air. The following are among the most important chemical properties of water. I. It contains air. This may be shown by placing a glass vessel of water, fresh from a spring, or even of distilled water that has been ex- posed a few days to the atmosphere, under the receiver of an air pump. During the exhaustion of the receiver, bubbles of air will be seen to as- cend very plentifully. Much air escapes also from water during boil- ing, and may be collected by a proper apparatus ; but it again absorbs it when exposed to the atmosphere. Water which has been deprived of its air, by long boiling, possesses the pi-operty of absorbing every gas, though the quantity which it is capable of absorbing varies considerably with respect to the different gases. Water absorbs, at the mean pressure and temperature, according to the recent investigations of Henry and Dalton, Of carbonic acid gas, . its own bulk. Sulphuretted hydrogen, .... do. Nitrous oxide, do. Olefiantgas, l-8th. Oxygen gas, l-27th. Nitrous gas, ..... do. Carburetted hydrogen, .... do. Carbonic oxide, l-64th. Nitrogen gas, do. Hydrogen gas, do. IHenry. i. 276, Ann. of Phil. vi. 340, vii. 215.] 2. Ft enters into combination with various bodies. Sometimes it is contained in a variable ratio, as in solution ; at others it forms a mere accidental ingredient, as in common salt or sulphate of potassa. In 114 HYDROGEN. many instances, however, it unites in a fixed definite proportion ; as is the case in its combination with several of the acids, and metallic oxides and of all the salts that contain water of crystallization. These compounds are termed Hydrates ; and in some of them the water is held by so powerful an affinity as not to be separated by a very high temperature. The pure alkalies potassa and soda, retain, for example, even after fusion, about one- fifth their weight of water, of which they can only be deprived by some body having a stronger affinity for the alkali. Water is contained in the atmosphere, even during the driest weather. Expose to the air. in a shallow vessel, a little subcarbonate of potassa, or common salt of tartar ; in a few days it will have become moist, or deliquiated, and will have increased considerably in weight. So also when sulphuric acid is added to common salt, dense white fumes are given out, in consequence of the combination of the muri- atic acid with the moisture in the air. There are two different theories of the state in which water pxists in the atmosphere, and in other gases. By most chemists it has been considered as united to air by chemical affinity, and when abstracted by other bodies, the effect has been ascribed to the superior affinity of those bodies for water. According to Mr. Dalton, however, aqueous vapour constitutes a distinct and independent atmosphere, the elastic force of which forms, at different temperatures, different proportions of the elastic force of the whole ; for example, at the temperature of 65 F. it gives to air l~50th of its elasticity. Hence, a volume of air or gas at any temperature, saturated with moisture, contains as much steam as would exist, at that temperature, in a vacuum of equal ca- pacity. This view, confirmed by the experiments of Gay Lussac, is much more probable than that which explains the phenomena by chemical affinity ; and it is supported especially by the fact that the absorption of caloric is precisely the same in amount in spontaneous as in forced evaporation. It steers clear also of the inconsistency at- tending the supposition that the vapour contained in the atmosphere, at ordinary temperatures, is in a different state from that existing in a Toricellian vacuum ; and again, that water below "212 F. is chemi- cally combined with the atmosphere, and above 212 assumes a new form and becomes a distinct elastic fluid, called steam. It is certainly much more reasonable to suppose that water, whenever it exists as an elastic fluid, whether distinct from, or mixed with others, is maintain- ed as such by one and the same cause, viz. by its constituent caloric, and not by chemical solution, in any gas or mixture of gases. Henry, i. 278. The purest water that can be found as a natural product, is produc- ed by melting freshly fallen snow, or by receiving rain in clean vessels at a distance from houses. But this water is not absolutely pure ; for if placed under the exhausted receiver of an air-pump, or boiled brisk- ly for a few minutes, bubbles of gas escape from it. The air obtained in this way from snow water, is much richer in oxygen gas than atmos- pheric air. According to the experiments of Gay Lussac and Humboldt, it contains 34'8 per cent of oxygen, and the air separated by ebullition from rain-water contains 32 per cent of that gas. All water which has once fallen on the ground, becomes impregnated with more or less of earthy or saline matters, and it can be separated from them only by distillation. The distilled water thus obtained, and preserved in clean well slopped vessels, is absolutely pure. In this state it is employed for the purposes of analysis and in pharmacy. HYDROGEN. 115 Ice. When water is exposed to the action of cold, it condenses more and more, until it reaches the temperature of about 39 D F. ; after which it expands to the point of congelation. Hence ice is lighter than water : its specific gravity is not far from 0-93. [See page 48.] Ice exists naturally at the poles, even in the midst of the sea, at all times. Under other parallels it is found in this state only at a certain elevation, which increases as we proceed from the poles to the equa- tor. The masses of snow which accumulate on the summits of moun- tains, being alternately melted and congealed, become at last changed by this process into solid ice, often grouped and fashioned by such irregular action into the most fantastic shapes, constituting what are denominated Glaciers. In its native seat, this icy belt acquires con- tinual additions to its height, till the accumulating pressure at last tears the mass from its base and precipitates its dissevered fragments to a lower level. In its new position, below the inferior boundary of congelation, the enormous pile suffers, on the whole, a very gradual thaw, which is sometimes protracted for several centuries, and gives birth to streams of greater or less magnitude. Meanwhile in the high- er magazine, another icy belt is again slowly collecting, which will in due time repeat the succession, arid maintain the eternal circle of pro- duction and decay. See Art. Climate, in Suppl. Encycl. Brit. Vapour or steam. If water be exposed to the heat of 212, the ba- rometer being 30, it is converted into a transparent gas, which is cal- led aqueous vapour or s!eam } the bulk of which is about 1700 times greater than that of water. Under a diminished pressure, however, water boils below the temperature of 212, while on the contrary, when the pressure is increased, the boiling point is higher. In every case, therefore, the tension of the vapour depends upon the tempera- ture. A table has been constructed by Mr. Dalton, to show the elastic force of vapour at every degree of the thermometer. The boiling of water is influenced in some degree also by its purity. Thus, if it contains a portion of common salt in solution, its specific gravity will be increased, and under the same pressure the boiling point will be several degrees higher than when the water is pure. Composition of water. This may be determined by analysis andsyn- thesis. 1st, by Synthesis. When two volumes of hydrogen are mixed with one volume of ox- ygen gas, and the mixture inflamed in a proper apparatus by the elec- tric spark, the gases totally disappear, and the interior of the vessel is covered with drops of pure water, equal in weight to that of the gases consumed. The same effect is also produced by burning hydrogen in an atmosphere of pure oxygen gas. An apparatus for producing water by the electric spark, is figured in the Library of Useful Knowledge, art. Chemistry. It should be recollected that every gas is a compound of gravitating matter with heat, and perhaps electricity and light. In the above ex- periments the bases of these gases combine to form water, the impon- derable ingredients having for the most part escaped during the com- bustion. 2. The composition of water may be proved analytically as follows : By exposing pure water to the action of the Voltaic battery, it is re- solved into two volumes of hydrogen, disengaged at the negative pole, arid one volume of oxygen, disengaged at the positive ; and hence the atomic constitution is such as has been stated above. Water may also be resolved into its elements by passing its vapour over red hot iron. 116 HYDROGEN. when the oxygen combines with the iron and the hydrogen is liberated in the gaseous form. REFERENCES. TlienarvTs Chem. ii. 2. Berzelius*s very elaborate account^ Trait, de Chim. i. 397. Parkers Chemical Essays, v. 4. Deutoxide or Peroxide of Hydrogen Atom. Num. 17 Symb. 2O+ H Sp. gr. 1-452 water=l. A singular compound discovered by M. Thenard, in 1818. Some- times also called Oxygenized Water. PROPERTIES. A colourless transparent liquid, without odour ; it whitens the skin when applied to it, and even destroys its texture if the application be long continued ; possesses bleaching properties ; is slowly volatilized in vacuo, and hence its vapour is much less elastic than that of water ; it has not been congealed by any degree of cold hitherto applied to it. The most remarkable property of the deutoxide of hydrogen is the facility with which it can be decomposed. A temperature of 58 F. is sufficient to decompose it and to liberate oxygen gas in great abun- dance. The action of heat varies with the degree of concentration. Seven or eight grains of the sp. gr. 1*452, when suddenly heated, are sufficient to occasion a violent explosion ; and therefore to obtain safely the whole of its excess of oxygen above that constituting wa- ter, it is necessary before applying heat, to dilute it with about 20 parts by weight of water. This substance is powerfully acted on by many of the metals and metallic oxides. Tin, iron, antimony and tellurium bring it back ra- pidly to the state of water. Gold, platinum and silver, when finely divided and added to it, liberate its oxygen, without themselves un- dergoing any change. Arsenic, tungsten, potassium, &c. liberate one part of the oxygen and absorb the rest. It is also decomposed by seve- ral of the metallic protoxides, as those of iron, tin, manganese, &c. ; and the peroxides of silver, lead, mercury, gold, and some others act upon it with great energy, exciting an intense heat accompanied with a kind of explosion. On the contrary, the acids have the property of rendering it a more stable compound. PREPARATION. To obtain this substance it is necessary to employ the Peroxide of Barium, a compound which will be described under the article Barium. This compound when acted upon by liquid mu- riatic acid, abandons part of its oxygen, and is reduced to the state of protoxide, which unites with the muriatic acid, while the oxygen unites with the water. Sulphuric acid, added to the compound fluid, carries down the baryta and sets muriatic acid at liberty, which is ready to act upon a fresh quantity of the peroxide of barium. This operation may be several times repeated, and at each repetition the water becomes charged with an additional quantity of oxygen. When the process has been carried far enough, sulphate of silver is added, to precipitate the free muriatic acid, which it replaces by a quantity of free sulphuric acid ; but the latter is easily separated by adding a due proportion of baryta. This is a very general outline of the process, which requires for its success several precautions, and especially the greatest attention to the purity of the peroxide of barium. Minute directions are given by Thenard in the original paper. HYDROGEN. 117 REFERENCES. Ann. deChim. et de Ph. viii. ix. Ann. of Phil. xiii. xiv. XY.'awoJ Branded Jour. vi. 150, 379 viii. 114, 154. Thenard ii. 42. Ber- zelius, i. 451, under the name of Sur-oxide hydrique. I '"or Dr. Thomson's views concerning the action of the metals and metallic oxides upon the above compound, see his Inorganic Chemistry , i. 43. HYDROGEN AND CHLORINE.] Hydrochloric or Muriatic Add Atom. Num. 3645 Symb. Cl+H Sp. gr. 1-269 air=l. Discovered by Priestley in 1772, and for a long time known under the names of Spirit of Salt and of Marine Acid. PROPERTIES. A colourless gas, of a pungent odour and acid taste ; extinguishes burning bodies, and is quite irrespirable, exciting violent spasm of the glottis ; produces a white cloud when brought into con- tact with common air, owing to its union with the aqueous vapour always present in the atmosphere ; is decomposed by being mixed with oxygen and submitted to the action of electricity ; rapidly ab- sorbed by water, forming liquid muriatic acid, under a pressure of 40 atmospheres ; at the temperature of 50 F. it is liquid ; it combines with bases forming a class of salts called Muriates or Hy- drochlorates. 1. It extinguishes a lighted taper. Before the flame goes out, the up- per part of it assumes a greenish hue, the cause of which has not yet been explained. A white vapour also surrounds the extinguished wick, owing to the combination of water produced by the combustion of the candle, with the muriatic acid gas. 2. It is decomposed by electricity. When muriatic acid gas is sub] jected to the action of a galvanic battery, it is readily decomposed, hydrogen appearing at the negative, and chlorine at the positive pole. It is also decomposed by ordinary electricity. The decomposition, however, is incomplete ; for though one electric spark resolves a por- tion of the gas into its elements, the next shock in a great measure effects their reunion. It is not affected by oxygen under common cir- cumstances ; but if a mixture of oxygen and muriatic acid gases is electrified the oxygen unites with the hydrogen of the muriatic acid to form water, and chlorine is set at liberty. Henry, Phil. Trans. 1812 and 1824. 3. Some of the metals effect its partial decomposition. Potassium, by being heated in muriatic acid gas, liberates one third of its volume of hydrogen. Heated zinc and tin disengage a volume of hydrogen equal to one half that of the muriatic acid gas, and chlorides of those metals are obtained. Davy, Phil. Trans. 1810. 4. It is rapidly absorbed by water. A drop or two of water admit- ted to a large jar full of muriatic acid gas, causes the whole instantly to disappear. And on opening a long wide jar filled with it, under water, the absorption of the gas takes place so instantaneously, that the water is forced up into the jar with the same violence as into a vacuum. When a piece of ice is put into a jar full of the gas, con- fined over mercury, the ice liquifies on the instant, and the whole of the gas disappears in the course of a few seconds. 118 HYDROGEN. NATIVE STATE. Muriatic acid is one of the gaseous substances which issue from the craters of volcanoes. It has also been found by Humboldt in a number of warm springs in Mexico. PREPARATION. This may be effected in various ways. 1. If a phial be entirely filled with a mixture of chlorine and hydro- gen gases in equal proportions, and a well ground stopper be intro- duced, no action takes place, provided light is carefully and complete- ly excluded, even by standing some time ; but, on applying a lighted taper, or on passing an electric spark through the mixture, the gases immediately explode. 2. Let a stout and well stopped phial, capable of holding three or four ounce measures, be filled over water with equal volumes of chlo- rine and hydrogen gases, and a ground stopper introduced. Expose it to the ordinary day light, guarding it from the direct rays of the sun, and in twelve or fourteen hours the colour of the chlorine will have disappeared ; and on withdrawing the stopper under water, the phial will be immediately filled with that fluid. 3. If the experiment be repeated, with this difference that the phial is exposed to the direct rays of the sun, the combination will take place rapidly, arid a detonation will ensue, which will probably drive out the stopper. But if this should not happen, the stopper may be removed under water, which will ascend and completely fill the bottle. Prof. Silliman however has related the accidental explosion of a mix- ture of these gases, in the quantity that filled a Florence flask, not only when no direct solar light fell upon it, but when the diffuse light of day was rendered more feeble than common by a thick snow storm. [Amcr. Jour. iii. 342.] This fact serves as a caution against mixing the two gases in considerable quantities. Mr. Brande found [Phil. Trans. 1820] that the intense light, issuing from charcoal points connected with a powerful galvanic battery, was as effectual as solar light in acting on hydrogen and chlorine gases and causing them to detonate ; but he could not produce an analogous ef- fect by any other terrestrial light. The moon's rays, also, he found to foe quite inefficient on a mixture of these two gases. To obtain muriatic acid in sufficient quantity for the exhibition of its properties, the direct combination of hydrogen and chlorine is not an eligible process. It may be procured more conveniently as follows : 1. By putting an ounce of strong liquid muriatic acid into a glass flask or retort, and heating it by means of a lamp till the liquid boils. Pure muriatic acid gas is freely evolved, and may be collected over mercury. 2. By adding concentrated sulphuric acid to an equal weight of com- mon salt, in a tubulated retort or gas bottle. Brisk effervescence en- sues at the moment of making the mixture, and on the application of heat a large quantity of muriatic acid gas is disengaged. In the first process muriatic acid, previously dissolved in water, is simply expelled from the water by increased temperature. In the second, a portion of the water contained in the liquid sulphuric acid is resolved into its elements, the hydrogen unites with the chlorine of the common salt, forming muriatic acid, which escapes in the form of gas ; while soda is generated by the combination of oxygen with the sodium, which combines with the sulphuric acid and forms sulphate of soda. The water contained in the liquid sulphuric acid is therefore HYDROGEN. 119 essential to the success of the operation. The affinities which deter- mine the change are the attraction of chlorine for hydrogen, of sodium for oxygen, and of soda for sulphuric acid. Liquid muriatic add. The liquid muriatic acid may be obtained by passing a current of the gas into water as long as it is absorbed. A considerable increase of temperature takes place during the absorption^ and therefore the apparatus should be kept cool by ice. Sir H. Davy states that water, at the temperature of 40 J F. absorbs 480 times its volume of the gas, and that the solution has the density of 1-2109. According to Dr. Thomson one cubic inch of water, at the tempera- ture of G9 3 F. is capable of absorbing 417*8*22 cubic inches of muriatic acid gas, and when cooled down to the temperature of the air, occu- pies the space of 1*3433 cubic inch. One cubic inch of this acid con- tains 31 1-041 cubic inches of muriatic acid gas, and it has a density of 1-1958 and contains 40-39 per cent, of real acid, united with 50-61 of water. In winter he has obtained muriatic acid of as high a specific gravity as 1-212. Dr. Thomson has constructed a table which exhibits the specific gravit} r of this acid of determinate strength. His method of proceed- ing was to saturate a given weight of the acid with calcarious spar. Every 50 grains of spar, (or pure marble,) dissolved, indicated the presence of 37 grains of muriatic acid. Knowing the exact strength of one particular acid, it was easy, by the addition of determinate weights of water, to form acid of any inferior strength required. Thomson's First Princip. i. 88, 87. Directions for obtaining liquid muriatic acid are given in most of the Pharmacopeias. The process recommended by the Edinburgh college is very good. The proportions they prescribe are equal weights of common salt, water and sulphuric acid, more acid being purposely em- ployed than is sufficient to forma neutral sulphate with the soda, so that the more perfect decomposition of the salt may be insured. To prevent too violent an action at first, the acid is mixed with one third its weight of water, and when the mixture is cool, it is thrown into the vessel containing the salt. The heat of a sand bath or lamp is now applied and the distillation is continued to dryness. The gas that is formed passes into a receiver, which is luted to the retort, arid con- tains about twice the quantity of water used in diluting the sulphuric acid. By this process muriatic acid may be obtained of the specific gravity of 1-170. Liquid muriatic acid has the following properties : 1. It emits white suffocating fumes, consisting of muriatic acid gas, which becomes visible by contact with the moisture of the air. 2. When heated in a retort or glass bottle, muriatic acid gas is dis- engaged, and may be collected over mercury. 3. Liquid muriatic acid is not decomposed by the contact of char- coal, essential oils, or other combustible bodies. 4. When diluted with water, an elevation of temperature is pro- duced, much less remarkable, however, than that occasioned by dilut- ing sulphuric acid; and when the mixture has cooled to its former temperature, a diminution of volume is found to have ensued. 5. In a perfectly pure state, liquid muriatic acid is quite colourless ; but it has frequently a yellowish hue. This may proceed either from a portion of chlorine or muriate of iron, but most commonly of the latter. This colour is instantly destroyed by a few drops of muriate 120 HYDROGEN. of tin ; but this addition, instead of diminishing, obviously increases the impurity of the acid. USES. Muriatic acid is used in large quantities in the preparation of muriate of tin. It is also used in several other arts, and is a valuable re-agent in the laboratory. Views concerning the nature of Muriatic Acid. The theoretical views concerning the nature of muriatic acid, have undergone many and important changes. Scheele considered it a compound of a certain base and an imaginary principle, called phlogiston. It was afterwards supposed to be a simple body, which, by its union with oxygen, form- ed oxymuriatic acid, now called chlorine. And this opinion prevailed until the experiments of Sir H. Davy, Gay Lussac and Thenard left no doubt that chlorine is an undecompounded substance, and that muriat- ic acid is a compound of chlorine and hydrogen. For the discussions on this subject the reader may consult the works and papers referred to under the article chlorine, page 102. REFERENCES. Gay Lussac and Thenard's Recherches, Phys. Chim. v 2, Davy's Elements of Chem. On the quantity of real Acid in Liquid Hydro- chloric, by Dr. Ure, Ann. of Phil. x. 268. The chapter on Muriatic Acid, in ChaptaPs Chem. iii. 83. Far the methods of Manufacture, fyc. see Cray's Operative Chemist, 426. HYDROGEN AND IODINE. Hydriodic Acid Jltom. Num. 127 Symb. I-f H Sp. gr. 4-1092 air=l. This acid was discovered by Gay Lussac, and to him and Davy we are indebted for a knowledge of most of its properties. PROPERTIES. A colourless, transparent gas, of an acid taste and an odour similar to that of muriatic acid ; reddens litmus powerfully ; does not support combustion ; is partly decomposed by a red heat, and completely when mixed with oxygen, forming water and separat- ing the iodine ; forms white fumes when admitted into the air, and is rapidly absorbed by water, resembling, in both these respects, muriatic acid; when brought into contact with chlorine it is decomposed, mu- riatic acid being formed, and the vessel is filled with the vapour of iodine ; it is also decomposed by many of the metals, as potassium, sodium, zinc, iron, mercury, &c. at ordinary temperatures, the iodine combining with the metal, and the hydrogen passing off. NATIVE STATE. Hydriodic acid is found native in several species of Fucus, in sponges, &c. usually in combination with potassa or soda. Vauquelin has also detected it in combination with silver. PREPARATION. This gas may be procured, 1. By passing a mixture of hydrogen gas and the vapour of iodine through a red hot porcelain tube. 2. It may also be obtained quite pure by the action of water on the iodide of phosphorus. For this purpose we introduce into a small re- tort some moistened iodine, and afterwards add to it one-eighth or one-twelfth its weight of phosphorus. An iodide of phosphorus is formed, which instantly reacts upon the water. Mutual decomposition HYDROGEN. 121 ensues ; the oxygen of the water unites with the phosphorus, and the hydrogen with the iodine, giving rise to the formation of phosphoric and hydriodic acids. On the application of a moderate heat the latter passes over in the form of a colourless gas, and is collected in receiv- ers, filled with common air, which, by a proper management, it will expel by its superior specific gravity. Liquid Hydriodic Acid, or the solution of hydriodic acid in water, is fuming, and when saturated has a density of 1 -7. It does not act upon mercury, although in the gaseous state it attacks it powerfully. Chlorine takes the hydrogen from this compound; muriatic acid is formed and iodine is liberated. It is slowly decomposed by contact with air, the hydrogen being attracted by the oxygen of the atmos- phere ; it is also decomposed by galvanic electricity, by concentrated sulphuric and nitric acids, and by those oxides which hold their oxy- gen loosely. With other oxides it combines and forms a genus of neutral salts, called Hydriodates. HYDROGEN AND BROMINE. Hydrobromic Acid Atom. Num. 79'26 Symb. Br+H. Discovered by M. Balard. PROPERTIES. A colourless gas, with an intensely acid taste ; by contact with atmospheric air gives white vapours, more dense than those produced by hydrochloric acid, under the same circumstances ; it has a pungent irritating odour ; is decomposed by chlorine, which instantly liberates abundant vapours, that condense into drops of bro- mine ; decomposed at common temperatures by potassium, in which case a volume of hydrogen remains, exactly equivalent to half that of the original gas. And hence its composition is analogous to that of hydriodic and hydrochloric acids, being equal volumes of bromine and hydrogen without condensation. The salts of this acid are termed Hydrobro mates. Hydrobromic acid is very soluble in water, which, by absorbing the gas, increases in volume, acquires great density, and also the property of emitting white vapours by contact with the air. This solution is colourless and possesses the principal properties of the gas. PREPARATION. Hydrobromic acid is generated by exposing a mix- ture of hydrogen and bromine to the flame of a taper, or what is stil! better, by introducing an ignited iron rod into a bottle containing it. It may also be procured by a process analogous to that used for hydri- odic acid gas. Bromine and phosphorus, placed in contact, and mois- tened with a few drops of water, afford abundantly a gas which is the acid in question. HYDROGEN AND FLUORINE. Hydrofluoric Acid Atom. Num. 19-68 Symb. F+H. The property which Fluor or Derbyshire Spar possesses of corroding glass when mixed with sulphuric acid, is said to have been known at Nuremberg as early as 1670. Scheele, in 1771, pointed out that the property of corroding glass was due to an acid given off by the action 122 HYDROGEN. of sulphuric acid upon fluor spar. Gay Lussac and Thenard, however, first pointed out the method of obtaining the acid in a pure form. PROPERTIES. Hydrofluoric acid at the temperature of 32 F. is a colourless fluid, remaining in that state at 59 F. if preserved in well stopped bottles ; but when exposed to the air flies off in dense white fumes, which consist of the vapour of the acid in combination with the moisture of the air; its specific gravity when first prepared is, 1*06, but is increased, by the gradual addition of water, to 1-55, and there is no known instance of a similar condensation ; its vapours are highly irritating, and when applied to the skin it disorganizes it so rapidly as to occasion dangerous ulcers ; in addition to the usual properties of a powerful acid, it acts strongly on glass and corrodes it deeply ; it also dissolves some bodies which resist the action even of nitro-muri- atic acid, as silicium. zirconium and columbium ; when brought into contact with potassium, violent detonation takes place, hydrogen gas escapes, and a white compound, fluoride of potassium, is generated ; with the alkalies it forms salts, called Hydrofluates. Hydrofluoric acid corrodes glass. When glass is brought into contact with this acid, its transparency is instantly destroyed This effect is produced by the union of the acid with the silex of the glass, and the product is a colourless gas known by the name of jluo-silicic acid. It is in consequence of this affinity for siliceous matter that plates of glass, covered with a composition of beeswax arid turpentine, and drawn upon with a graver, may have those parts which are laid bare etched by exposure either to the vapour or to the diluted acid. PREPARATION. As glass is immediately corroded by this acid, we must employ vessels of lead or silver in procuring it. The following method is suggested by Gay Lussac. A retort of pure lead must be procured, composed of two pieces which slip into each other. To this retort must be adapted a leaden receiver. Take any quantity of pure fluor spar, reduce it to a fine powder, and put it into the re- tort, then mix it well with twice its weight of concentrated sulphuric acid. Lute the joining of the retort and the beak where it enters the receiver with clay, then apply a moderate heat to the retort, taking care that it is not so great as to fuse the lead. The receiver is to be surrounded with a mixture of common salt and snow. The acid is disengaged and collected in the receiver in a liquid state. For the purpose of exhibiting the effects of the vapour upon glass, a small square or oblong leaden vessel will suffice. Into this the fluor spar and sulphuric acid are to be put and gentle heat afterwards ap- plied. Attempts have been made to effect the decomposition of this acid, both upon the supposition that it may be a compound of an electro- positive body, such as sulphur with oxygen, or that it is constituted of a highly electro negative element, like chlorine, in union with hy- drogen. The latter view is, of the two, the best supported by experi- ment and analogy. A strong argument in its favor is derived from the fact discovered by Kuhlman, that fiuor spar is not decomposed by the anhydrous sulphuric acid. [Ann. de Chim. et dc Phys. Feb. 1827.] There being no water to furnish oxygen to the calcium, or hydrogen to the fluorine, the hydrofluoric acid cannot be produced. REFERENCES. Puymaurin on the action of Fluoric Acid on silidons Earth, and engraving with it on Glass, Repert. of Arts. 1st. ser. v. 210, 271. Gay Lussac and Tlwiard on the Fluoric Acid, and Us decomposition ', Jour. NITROGEN. 123 de Phys. Jan-wary, 18(K, and Repert. of Arts, <2d ser. xv. 90. Davifs ex periinents on Fluoric Acid, Phil. Trans. 1812, and in Reper. of Arts, ^d ser. xxii. 72. Berzelius on Fluoric Acid and its most remarkable com- binations, Ann, of Phil. xxiy. and xxv. Also, Traite de Chirn. by the same author. SECTION II. NITROGEN. Atom. Num. USymb. NSp. gr. 0-9722 air=l. First noticed as a distinct gas by Dr. Rutherford, in 1772. But first discovered as a constituent part of the atmosphere by Lavoisier, in 1775, who named it Azote. It has also been called Mephitic Air, but Nitrogen appears to be the most appropriate name. PROPERTIES. A gaseous body without colour, taste or odour ; does not support combustion nor animal life ; is not inflammable like hy- drogen, though under favourable circumstances it may be made to unite with oxygen; is very sparingly absorbed by water. It extinguishes burning bodies. This can be easily shown by im- mersing a lighted taper or candle into a vessel of nitrogen gas. Does not support animal life. Although no animal can live in an atmosphere of nitrogen, yet it exerts no injurious action either on the lungs or on the system at large, the privation of oxygen being the sole cause of death. Indeed this gas is more distinguished by negative characters than any striking quality. NATIVE STATE. Nitrogen gas is sometimes given off by hot springs. Dr. Daubeny has found it in hot springs in Scotland, on the Alps and in France. PREPARATION. Nitrogen gas may be obtained in several ways. 1. By burning a piece of phosphorus in a jar of air inverted over water. The strong affinity of phosphorus for oxygen, enables it to burn till the whole of that gas is consumed. The product of the combustion, pyrophosphoric acid, is at first diffused through the resi- due in the form of a white cloud ; but is rapidly absorbed by water, and disappears in the course of half an hour. The residual gas is nitro- gen, containing a small quantity of carbonic acid and vapour of phos- phorus, both of which may be removed by agitating it briskly with a solution of pure potassa. This process is usually adopted. 2. By introducing a solution of proto-sulphate of iron, charged with the deutoxide of nitrogen, into a vessel of atmospheric air the oxygen will be absorbed in a few minutes. A stick of phosphorus produces the same effect in 24 hours, if exposed to a temperature of 60 F. A solution of the sulphuret of potassa or of lime or a paste made of equal parts of iron filings and sulphur, with water, acts in a similar manner. 3. By exposing a mixture of fresh muscle and nitric acid of spe- cific gravity 1*20 to a moderate temperature, effervescence takes place and nitrogen is liberated, mixed however, with carbonic acid, which may be separated by lime water. 124 NITROGEN. In 'all these processes, except the last, the theory of which is some- what complex, some substance is brought into contact with atmos- pheric air which has a strong affinity for its oxygen, with which it forms a compound and leaves the nitrogen in a separate state. It should be remarked, that nitrogen may also be obtained by the action of chlorine on ammonia, in a manner to be explained when treating of that alkali. USES. Nitrogen is without use in the arts or in medicine. But it must perform some important office in the animal economy, since the only difference between animal and vegetable substances consists in the presence or absence of this principle. NATURE OF NITROGEN. Though nitrogen is ranked among the simple non-metallic bodies, Berzelius, Davy and others have maintain- ed the opinion that it is compound. But this view does not appear to be supported by experiment. Those who are desirous of examining the facts and reasonings in favour of this opinion, are referred to Ber- zelius' paper on the nature of Azote, &c. in Ann. of Phil. ii. 276, and to the 2d volume of his Traite de Chim. ii. 339 ; to Davy in Phil. Trans. 1810, and to J. Miers, on the composition of Azote, in Ann. of Phil. iii. 364, iv. 180, 260. REFERENCES. Rutherford's Dissertation de Acre Mephitica. Scheele on Air and Fire. Lavoisier's Elements. Priestley on Air. For particulars concerning the preparation of Nitrogen, by the decomposition of Ammonia, see Berzelius, i. 240. Atmospheric Air. Atmospheric air was for many centuries believed to be an elemen- tary body. Although many philosophers deserve the merit of having thrown doubts over this opinion, its true nature was demonstrated about the same time by Scheele and Lavoisier. PROPERTIES. Atmospheric air is a gaseous substance, transparent, invisible, without odour or taste, and it is not sensible to the toucli unless in motion ; is perfectly elastic and compressible ; has a pressure at the level of the sea, equal to a weight of about 15 pounds on every square inch of surface, and can support a column of water 34 feet high and a column of mercury of 30 inches ; has a density of 1,000, being the standard with which the density of all other elastic fluids is 1 com- pared ; 100 cubic inches of it in a pure and dry state weigh, according to the recent experiments of Proutand others, 31 grains at 60 F. and 30 Bar. Henry, i. 320. The chemical properties of atmospheric air, are owing chiefly to the oxygen which it contains, the presence of which is necessary to its salubrity ; it is a bad conductor of electricity, for when this fluid has accumulated on the surface of a body, and passes to another body through the air, it is always in the form of sparks ; it is not changed by high degrees of heat or cold ; is changed with few exceptions by the simple combustibles, at various temperatures, absorbing its oxygen and liberating its nitrogen. I shall now briefly notice some of the most important of the above named properties. Compressibility and Elasticity. The compressibility of air is shown by the fact that a quantity of it may be compressed or condensed, into NITROGEiN. 125 a very small compass ; as is exemplified in the common fire syringe, and in the air gun. In these cases, of course, the particles of which the air is composed are brought nearer together by the compression. The elasticity of air may be shown by putting a bladder half full of air, under the receiver of an air pump and exhausting. As we with- draw the air, or in other words diminish the pressure, the bladder be- comes distended in consequence of the expansion of the air within it. This elasticity is a force of considerable energy ; for when air is high- ly compressed its effort to recover its proper bulk is prodigious ; and so great that it will sometimes burst the strongest vessels. Hence the well known danger of forcing too much air into the ball of an air gun : it bursts and occasions great mischief. The extreme compressibility and elasticity of the air accounts for the facility with which it is set in motion, and the velocity with which it is capable of moving. It is subject to the laws which characterize elastic fluids in general. It presses, therefore, equally on every side ; and when some parts of it become lighter than the surrounding por- tions, the denser particles rush rapidly into their place and force the more rarefied ones to ascend. The motion of air gives rise to various familiar phenomena. A stream or current of air is wind, and an undulating vibration excites the sensation of sound. Weight and Pressure. That the air is possessed of weight was first suspected by Galileo in 1640, and afterwards placed beyond doubt by the experiments of Torricelli arid Pascal, in 1643. Torricelli ascer- tained that when a glass tube of about three feet in length and closed at one end, was filled with quicksilver and inverted in a basin of the same fluid, the mercury fell about six inches, so that the atmosphere appeared capable of counterbalancing a column of mercury of about 30 inches. By this experiment the Barometer was in fact constructed ; but it required the observation of Paschal that upon ascending a moun- tain the quicksilver fell in the tube, because there was less air above to press upon the surface of the metal in the basin, to prove that an instrument of great value had thus been invented. The pressure of the air, as is shown by the barometer, is extremely variable. It varies according to the elevation above the level of the sea, and on this principle the height of mountains is estimated. It also varies at the same place, and on this depends the indications of the barometer as a weather-glass. For although we are still ignorant of the cause, observation has fully proved, that the weather is com- monly fair and calm when the barometer is high, and usually wet and stormy when the mercury falls. It is obvious that as the pressure of the air diminishes as we ascend from the surface of the earth, the greater the elevation, the lighter must be the air. But it is not exactly known to what height the at- mosphere extends. From calculations founded on the phenomena of refraction, its height is supposed to be about 45 miles ; and Dr. Wol- laston estimates, from the law of the expansion of gases, that it is 40 miles. How far it extends beyond this point is a subject for specula- tion. Dr. Wollaston, from astronomical observations made by himself and Capt. Kater, infers that the atmosphere is of finite extent. On this point see Wollaston on the finite extent of the atmosphere. PkiL Trans. 1822, and in Ann. of Phil. xx. 151. These properties of the air, are most strikingly illustrated by the Air Pump, an instrument which in its construction resembles the com- mon sucking pump, excepting that all the parts are more accurately made, the object being to exhaust the air as completely and as expe- I 126 NITROGEN. ditiously as possible. If the receiver be placed on the plate of the pump and exhausted, we are unable to move it, because it is kept down by the weight of the air around it. Or if a long tube with a stop-cock be exhausted by the pump, and then have the cock opened under water, the fluid will be forced in by the pressure of the air on the surface of the water in the basin. Constitution of the Air. The researches of Davy, Dalton, Gay Lus- sac, Thomson and others, leave no doubt that pure atmospheric air consists of nearly 21 of oxygen and 79 nitrogen in the 100 volumes. But the atmosphere is never absolutely pure ; or rather, in addition to the above gases, it always contains a variable quantity of aqueous va- pour and carbonic acid. According to Vogel and others, air within a certain distance from the sea, contains a little muriatic acid. [Ann. of Phil. xxii. 25,] and Liebig states that a trace of nitric acid is discover- able in rain which has fallen immediately after lightning. [Henry's Chem. i. 321.] In addition to these, the odoriferous matter of flowers and other volatile substances, are also frequently present in the air. The presence of watery vapour in the air, may be shown by the ex- periments noticed under water, [p. 114 ] The amount varies accord- ing to the temperature, and these variations are determined by the Hygrometer. The presence of carbonic acid in the air may be shown by exposing to it a vessel of lime water. A pellicle soon forms on the surface of the solution, which by agitation sinks to the bottom and is soon suc- ceeded by another. Upon analysing this precipitate, it is found to be carbonate of lime, the carbonic acid of which must have been derived from the air with which the lime water was surrounded. But the quantity of this gas in the air is quite inconsiderable, although it is liable to variation. According to Mr. Dalton it does not usually ex- ceed 1 in 1000 parts ; and T. Saussure has recently found that 10,000 parts of air contain 4*9 of carbonic acid as a mean, 6-2 as a maximum, and 3'7 as a minimum. The knowledge of the composition of the air, and of the importance of oxygen to the life of animals, naturally gave rise to the notion that the healthiness of the air, at different times, and in different places, depends on the relative quantity of this gas. It was, therefore, sup- posed that the purity of the atmosphere, or its fitness for communica- ting health and vigour, might be discovered by determining the pro- portion of oxygen ; and hence the origin of the term Eudiometer, which was applied to the apparatus for analyzing the air. But this opinion, though at first supported by the discordant results of the earlier anal- yses, was soon proved to be fallacious. It appears, on the contrary, that the composition of the air is not only constant in the same place, but is the same in all regions of the earth, and at all altitudes. Air collected at the summit of the highest mountains, such as Mont-Blanc and Chirnborazo, contains the same proportions of oxygen as that of the lowest valleys. The air of Egypt was found by Berthollet to be similar to that of France. The air which Gay Lussac brought from an altitude of 21,735 feet above the earth, had the same composi- tion as that collected at a short distance from its surface.* Even the * Mr. Faradav's analysis of air from the Arctic regions, shows a decided and constant difference between it and the air of London, of at least 1 374 per cent. A pp. to Parry's 3d Voyage, Lond. ed. p. 249. This difference is supposed by Dr. Torrey to bo owing to a deficiency of vegetation in high northern latitudes. Sillimarfs Chemistry, i. 19S. NITROGEN. 127 miasmata of marshes, and the effluvia of infected places, owe their noxious qualities to some principle of too subtile a nature to be detect- ed by chemical means, and not to a deficiency of oxygen*. Seguin examined the infectious atmosphere of an hospital, the odour of which was almost intolerable, and could discover no appreciable deficiency of oxygen, or other peculiarity of composition. Turner. For descrip- tions of various kinds of Eudiometers, see Webster's Brande and Ure's Dictionary. Concerning the nature of the union which exists among the several elastic fluids constituting the atmosphere, two opposite opinions pre- vail. By the greater part of chemists, it has been considered as a chemical compound, chiefly from the uniformity of its composition and from the fact that its several ingredients do not arrange themselves ac- cording to their respective specific gravities. On the other hand, Mr. Dalton has advanced the theory that, of the various elastic fluids con- stituting the atmosphere, the particles of one have neither attractive nor repulsive power towards those of another ; but that the weight or pressure upon any one particle of a fluid mixture of this sort, arises solely from the particles of its own kind. According to this hypothe- sis, oxygen, nitrogen and carbonic acid gases, (or indeed any number,) may exist together, under any pressure, and at any temperature, while each of them, however paradoxical it may at first appear, occupies the space allotted for all. Each ingredient of the atmosphere, on this view, exerts its own separate pressure in supporting the mercury of the barometer. This theory appears to be loaded with fewer difficulties than that which considers the constituents of the atmosphere to be held together by chemical affinity. But our limits will not permit a detail of the arguments in its sup- port. Mr. Dalton has fully explained his views respecting the consti- tution of the atmosphere, in the Phil. Trans, for 1826. On this subject see also the papers of Mr. Graham and Dr. Mitchell of Philadelphia, on the diffusion of the Gases. Journal of the Roy. Ins. ii. 101. Jour, of Science, N. S. vi. 74. REFERENCES. Priestley on Airs. Scheele's Essay on Air and Fire. La- voisier's Elements of Chemistry. Thenard's Traite. de Chitn. i 272. Art- Aeronautics, in the Supplement to the Encyclopedia Britannica, containing an account of the Aerial Ascent of M. M. Biot and Gay Lussac, and of their observations upon the higher Atmosphere, t^c. NITROGEN AND OXYGEN. We are at present acquainted with five definite compounds of these substances, the composition of which, as determined by Gay Lussac, Henry and Davy, is as follows : By volume. By iceight. Protoxide of nitrogen, . . 100 N. 50 O. 14 N. 8 O=22. * An interesting fact was observed by Dr; Prout, while engaged in an ex- tensive series of experiments on the weight of dry atmospheric air: viz. that during the existence of the epidemic cholera in London in 1832, the air uni- formly possessed a weight above the usual standard. " It would seem," gays he, '* as if some heavy foreign bod\ r had been diffused through the lower re. gions of the atmosphere about this period, and which was somehow or other connected with the disease in question." Reports of the Brit. Association fo<- 1832. 128 NITROGEN. Deutoxide of nitrogen, . Hyponitrous acid, . 100 N. . 100 N. 100 N. 100 O. 150 O. 200 O. 14 N. 14 N. 14 N. 16O=30. 24 O=38. 32 O=46. Nitric acid, . 100 N. 250 O. 14 N. 40 O=54. Protoxide of Nitrogen Atom. Num. 22 Symb. O-f-N Sp. gr. 1-527 air=l. This curious substance was discovered by Priestley, in 1772, and has been examined with much care by Berthollet, Davy, Gay Lussac and Thenard. It has successively received the names of Dephlogisticated Nitrous Gas. Nitrous Oxide, and Gaseous Oxide of Azote ; but the ap- pellation above given is in strict conformity with the principles of chemical nomenclature. PROPERTIES. A colourless gas, without odour, and of a slightly sweetish taste ; does not affect vegetable blues, even when mixed with atmospheric air ; supports combustion, most substances burning in it with greater energy than in the atmosphere ; it is respirable, pro- ducing, when breathed, a high degree of excitement, similar to that of the early stages of intoxication ; but when animals are wholly confin- ed in it they die very speedily ; it is absorbed by water at 60 J F. in the proportion of three fourths of its volume, and hence it should be col- lected over warm water; it is decomposed by heat and by the electric spark ; it is liquified by pressure. It also possesses, as well as the deutoxide, the property of combining with the pure alkalies. It supports combustion. The glowing wick of an extinguished taper or candle, when introduced into a vessel of this gas, is immediately kindled by it into a flame. Iron wire and red hot charcoal burn in it, with nearly the same splendour as in oxygen gas, but for a shorter time. Phosphorus introduced into it, in a state of active inflamma- tion, burns with great violence, almost approaching to explosion. When mixed with hydrogen it will detonate, either by the application of flame or the electric spark. In each of the above cases, the combustible combines with oxygen, forming water, an oxide, or an acid, and nitrogen is set at liberty. It is respirable when mixed with atmospheric air. It has been ob- served that animals wholly confined in pure protoxide of nitrogen speedily die. It may, however, be taken into the lungs without be- ing fatal, because it is mixed and diluted with the air present in that organ One of the most extraordinary properties of this gas, first ascertained by the bold experiments of Davy, in 1799, is that it produces, when breathed, a transient intoxication, or violent exhil- aration. To administer the gas, it may be introduced into an oiled silk bag or clean bladder, furnished with a stop-cock, and it may be breathed repeatedly from the bag and back again, as long as it will last. The sensations produced are, in general highly pleasurable and re- semble those attendant on the early period of intoxication. Great exhilaration, an irresistible propensity to laughter, a rapid flow of vivid ideas, and an unusual fitness for muscular exertion, are the ordinary feelings it produces. But the effects of the gas are different upon persons of different temperaments and constitutions. Some interest- ing notices of its operation upon distinguished men in England, are NITROGEN. 129 to be found in lire's Chemical Dictionary. In general these feelings of exhilaration are not followed by any thing more than a slight sensa- tion of languor, probably from the effects of muscular exertion alone; but it should not be concealed that its administration is occasionally attended with unpleasant consequences, and should, upon the whole, be rather discouraged than recommended. Two cases of this sort are related by Professor Silliman, as having occurred at New-Haven. Amer. Jour. v. 194. PREPARATION. The protoxide of nitrogen may be obtained, 1. By exposing deutoxide of nitrogen for a few days to iron filings, or to various other bodies strongly attracting oxygen, the former gas is changed into the protoxide, one half of its oxygen combining with the metal. 2. By the decomposition of the nitrate of ammonia, a salt obtained by the action of pure nitric acid upon the carbonate of ammonia, and subsequent evaporation. When this salt is put into a glass retort and exposed to the temperature of between 4 and 500, it liquifies, bub- bles of gas begin to rise from it, and in a short time a brisk efferves- cence ensues, which continues till the whole of the salt disappears. The heat should be cautiously regulated to avoid explosion, which takes place when the temperature reaches that of a red heat. The gas should be collected over warm water and allowed to stand a short time before it is used. The above process may be easily explained. Nitrate of ammonia consists of Nitric acid, 1 atom=54 Ammonia, 1 atom =17 71 Nitric acid consists of Ammonia consists of Nitrogen, - - 1 atom =14 Nitrogen, - - - - 1 atom=14 Oxygen, - 5 atoms =40 Hydrogen, .... 3 atoms = 3 54 17 Now by the application of heat to the salt the hydrogen combines with so much oxygen as is sufficient for forming water, and the re- maining oxygen converts the nitrogen both of the nitric acid and of the ammonia into protoxide of nitrogen. The decomposition of the 71 grains of salt will therefore yield, Water, 3 atoms =27 Protoxide of nitrogen, - 2 atorns=44 71 REFERENCES. Davy's Elements of Chem. Phil. Gay Lussac and The- nard Phys. Chem. Researches. Faraday on impurities in Nitrous Oxide. Branded Jour. vi. 360. Deutoxide of Nitrogen Atom. Num. 3QSymb. 2O-J-N 8p.gr. l-041air=l. SYN. Nitrous Gas. Nitric Oxide. Binoxide of Nitrogen. The discovery of this substance is due to Hales j but its properties were first investigated by Priestley. 130 NITROGEN. PROPERTIES. A colourless gas, without action upon litmus ; is sparingly absorbed by water ; extinguishes most burning bodies, but charcoal and phosphorus, if immersed in it when in a state of vivid combustion, burn with increased brilliancy ; is quite irrespirable, ex- citing a strong spasm of the glottis, as soon as an attempt is made to inhale it ; is decomposed by heat and electricity ; when mixed with oxygen gas assumes an orange red colour, owing to its combination with an additional quantity of oxygen the same thing takes place when this gas comes in contact with atmospheric air, affording a con- venient test of its presence ; when mixed with hydrogen it burns with a green flame, but does not explode by the electric spark. fiction of Oxygen Gas. When deutoxide of nitrogen is mixed with oxygen gas, atmospheric air or any gaseous mixture that contains oxygen in an uncombined state, dense suffocating vapours, of an orange red colour, are produced, called nitrous acid vapours, which are copiously absorbed by water, and communicate acidity to it. This effect can be shown by the following experiment. Exp. Paste a sheet of litmus paper within a glass jar ; near the bot- tom, and into the jar, filled with and inverted in water, admit so much nitrous gas, previously well washed, as will displace the water below the level of the paper. The colour of the litmus will remain unchanged ; but on admitting oxygen gas it will be immediately red- dened. It is from this property of absorbing oxygen, but no other gas, that nitrous gas has been applied to the purpose of Eudiometry , or of as- certaining the purity of atmospheric air, which was formerly sup- posed to depend upon a varying proportion of that gas. The sources of error, in its employment in this mode, have hitherto been consider- ed such as to forbid our relying implicitly on the results which it may afford. But Dalton and Gay Lussac maintain that it may neverthe- less be employed in eudiometry ; and have described the precautions which are required to ensure accuracy. Mr. Dalton has given his process in the 10th volume of the Annals of Philosophy ; and further directions have been published by Dr. Henry, in his Elements. The method of Gay Lussac, which is preferred by Dr. Turner, may be found in the 2d volume, p. 247, Mernoires d' Arcucil. PREPARATION. The deutoxide of nitrogen may be easily obtain- ed by. pouring upon filings or turnings of copper, put into a retort or gas bottle, some nitric acid, diluted with twice its bulk of water ; an action ensues, red fumes are produced, and there is a copious evolu- tion of the gas which may be collected over water. The first por- tions should be rejected, as containing nitrogen and nitrous acid gases. The deutoxide of nitrogen is presently recognized, by the red fumes which it produces when brought into contact with air. During this process a portion of the nitric acid is decomposed ; part of its oxy- gen uniting with the copper, converts it into the peroxide of copper ; while another part is retained by the nitrogen of the nitric acid, form- ing the deutoxide of nitrogen. The peroxide of copper attaches itself to some undecomposed nitric acid, and forms the blue nitrate of cop- per. Many other metals are oxidized by nitric acid, with the disen- gagement of a similar compound ; but none, mercury excepted, yields BO pure a gas as copper. REFERENCES. Davy's Elements of Chem. Phil. Gay Lussac Mem. d'Arcueily'n. NITROGEN. 131 Hyponitrous Acid Atom. Num. 38 Symb. 30-J-N. From the experiments of Gay Lussac, it appears that there ex- ists an acid formed of 100 measures of nitrogen and 150 of oxygen. When he passed into a glass tube confined over mercury 500 or 600 parts of deutoxide of nitrogen, 100 parts of oxygen, with some solu- tion of pure potassa, there was uniformly an absorption of 500 parts, consisting of the 100 oxygen and 400 deutoxide of nitrogen. These Ibrmed an acid which combined with the potash. JSow as 400 mea- sures of deutoxide of nitrogen consist of 200 oxygen and 200 nitro- gen^ it follows that the acid must be composed of 200 measures ni- trogen and 300 oxygen, or 100 and 150, as above stated. It con- tains therefore, three times more oxygen tlian the protoxide of ni- trogen. This acid is also produced, according to Gay Lussac, by keeping the deutoxide of nitrogen for three months in a glass tube, in contact with a concentrated solution of potassa. At the end of this time 100 parts of the deutoxide are reduced to 25 parts of the protoxide of ni- trogen, and crystals of hyponitrite ofpotash are also formed. The- nard, ii. 193. Hyponitrous acid has not yet been obtained in a separate state. When we attempt to separate it from potassa by means of an acid, it is converted into deutoxide of nitrogen, which is disengaged, and ni- trous or nitric acid which remain in solution. Berzelius does not recognize the hyponitrous as a distinct acid and thinks it ought not to be admitted as such in the nomenclature. Traite. de CJiim. II 41, Nitrous Acid Atom. Num. 48 Symb. 40+N. This acid appears to have been known for some time, but was con- founded with nitric acid, being known under the name of Fuming Nitrous Acid. Its true nature has been made known by Davy, Gay Lussac and Dulong. PROPERTIES. Nitrous acid exists in a gaseous and liquid state. The gaseous acid is characterized by its orange red colour ; is quite irrespirable, exciting great irritation and spasm of the glottis, even when moderately diluted with air ; supports the combustion of burn- ing phosphorus and of a lighted taper, but extinguishes burning sul- phur. The liquid anhydrous acid is powerfully corrosive, has a strong acid taste, and pungent odour ; is of a yellowish orange colour at the ordin- ary pressure and temperature, but at low temperatures becomes colour- less ; has a density of 1-451 ; preserves the liquid form at the ordinary temperature and pressure, and boils at 82 J F. ; evaporates with great rapidity when exposed to the atmosphere, forming common nitrous acid vapours, which when once mixed with air, or other gases, require intense cold to condense them. PREPARATION. This acid never exists in nature. The gaseous acid may be formed by mixing oxygen gas with the deutoxide of nitrogen. The operation, however, must not be conducted over water or mercury. The presence of the former determines the production of nitric acid ; the latter is oxidized by the nitrous acid, and therefore decomposes it Sir H. Davy made this compound by mixing two measures of the 132 NITROGEN. deutoxide of nitrogen, and one of oxygen, free from moisture, in a dry glass vessel, previously exhausted by an air pump. Nitrous acid va- pours were produced, and a contraction ensued, amounting to about one half the volume of the mixed gases. The liquid anhydrous acid may be obtained by a more easy process than the above. For this purpose dry and neutral nitrate of lead is to be exposed to heat in a glass retort. The nitric acid of the salt is in this manner resolved into nitrous acid and oxygen ; and if the pro- ducts are received in vessels kept moderately cool, the greater part of the former condenses into a liquid. REFERENCES. Davy's Elements of Chem. Phil. Dulong, in Ann. de Chim. et de Ph. ii. 317. R. Philips and Dr. Hope^s controversy concern- ing its preparation, Ann. of Phil. xvii. 59, 189. xviii. 24. Nitric Acid Atom. Num. 54Symb. 50+N Sp.gr. 1-510 \vater=l. SYW. Spirits of Nitre. Aqua Fortis. This acid is said to have been discovered about 1225, by Ramond Lully, in distilling a mixture of nitrate of potassa and clay ; but its nature was not well understood until 1785, when it was examined by Cavendish. Since that time, its properties have been investigated by Davy, Dalton and Gay Lussac. PROPERTIES. Nitric acid, in its highest state of concentration, is liquid, odorous, white and very corrosive ; destroys the skin and changes it to a yellow colour ; is eminently poisonous ; possesses acid properties in a high degree, a single drop of it, though largely diluted with water, reddening litmus permanently ; in its most pure and concentrated state has the specific gravity of 1-50 or 1-510, con- taining still in this state a considerable quantity of water, from which it cannot be separated without decomposition or by uniting with some other body ; boils at 248 F. and may be distilled with- out change ; is frozen by cold, the temperature at which congela- tion takes place varying with the strength of the acid, the strongest freezing at 50 below zero ; it is decomposed by solar light and by several of the combustibles ; forms with bases, salts which are called Nitrates. It is decomposed by solar light. When very concentrated, liquid ni- tric acid becomes coloured by exposure to the sun's light, passing first to a straw colour, and then to a deep orange. This effect is produced by the union of the light of the sun with oxygen, in consequence of which the proportion of that principle to the nitrogen is diminished. Henry, i. 353. By exposing it to the sun's rays in a gas bottle, the bent tube of which terminates under water, oxygen gas may be procured. It is decomposed by various combustible bodies. As this acid retains its oxygen with but little force, it is decomposed by all combustibles, which are oxygenized by it, with more or less rapidity, in proportion to their affinity for oxygen. 1. When brought into contact with hydrogen gas at a high tempe- rature, by transmitting them together through an ignited porcelain tube, a violent detonation ensues. This experiment, therefore, re- NITROGEN. 133 quires great caution. Dr. Priestley found also that hydrogen gas, af- ter being used to displace nitric acid from a bottle inverted in that liquid, had become explosive. 2. Poured on perfectly dry and powdered charcoal, it excites the combustion of the charcoal, which becomes red hot, and emits an im- mense quantity of fumes. 3. It also inflames essential oils, (as those of turpentine and cloves) when suddenly poured on them. In these experiments, the acid should be poured out of a bottle, tied to the end of a long stick ; otherwise the operator's face and eyes may be severely injured. 4. Nitric acid is decomposed by boiling it in contact with sulphur, which attracts the oxygen and forms sulphuric acid. 5. This acid is also decomposed by metals ; as iron, tin, copper, &c. with various phenomena, according to the affinity of each metal for oxygen. This may be seen by pouring some strong nitric acid on iron filings or powdered tin. Violent heat, attended with red fumes, will be produced, and the metals will be oxidized. Henry. PREPARATION. This may be effected in the following ways : 1. The direct combination of nitrogen and oxygen, affording a de- cisive synthetic proof of the nature of this acid, may be effected by passing electric sparks through a mixture of nitrogen and oxygen gases. The experiment is an extremely laborious one, and requires for its performance, a powerful electrical machine. See Cavendish, Phil. Trans. Ixxv. Hennjs Chem. i. 346. 2. This acid may be readily produced by passing the deutoxide of nitrogen very slowly into oxygen gas, standing over water. By this operation four volumes of the former combine with three of the lat- ter, and the compound, therefore, must consist of two volumes nitro- gen and five volumes oxygen, or by weight of one proportion of nitro- gen and five proportions of oxygen. This view is confirmed by the experiments of Davy by the analy- sis of nitrate of baryta, by Dr. Henry, and by the analysis of various nitrates, by Dr. Thomson. This, however, is only as it exists in the dry state, when in combination. 3. The liquid nitric acid of commerce is abundantly obtained from the decomposition of the nitrates by means of sulphuric acid ; and common nitre or nitrate of potassa being the cheapest, is always se- lected for this purpose. This salt previously well dried, is put into a glass retort, and a quantity of the strongest sulphuric acid is poured upon it. On applying heat, ebullition ensues, owing to the escape of nitrous acid vapours, which must be collected in a receiver kept cold by moist cloths. The heat should be steadily increased during the ope- ration, and continued as long as any acid vapours come over. There is some difference among chemists as to the best proportions for forming nitric acid. The London college recommends equal weights of nitre and sulphuric acid ; the Edinburgh and Dublin col- leges employ three parts of nitre to two of the acid. According to Thomson, when 61-8 parts of the strongest sulphuric acid of com- merce are mixed with 12 3-4 parts of nitre thoroughly freed from wa- ter and perfectly pure, the acid which comes over is the strongest that can be procured, having a specific gravity of 1-55, and consists of one atom of acid and one atom of water. When 12 1-4 parts of sulphu- ric acid are mixed with 12 3-4 parts of pure anhydrous nitre, the whole 134 NITROGEN. nitric acid may be obtained without loss ; but its specific gravity is only 1'4855, and it is a compound of one atom real acid and two atoms water. First Princip. i. 113. Thenard states that 1800 parts of well dried nitre and 1800 parts of sulphuric acid of commerce, yield 1020 parts of acid of equal strength with that obtained from a larger proportion of sulphuric acid, and he, therefore, prefers these proportions. In the large way, and for purposes of the arts, it is usual to sub- stitute earthen or cast iron retorts, made extremely thick, for those of glass. An earthen head is adopted, and this is connected with a range of proper condensers. The strength of the product is varied also by putting more or less water into the receiver. IMPURITIES. The nitric acid of commerce is seldom perfectly pure. It may contain both sulphuric and muriatic acids ; the former being derived from the acid which is used in the process : the latter from the muriate of soda which is sometimes mixed with the nitre. These impurities can be detected by adding a few drops of a solution of muri- ate of baryta and nitrate of silver to separate portions of nitric acid, diluted with three or four parts of distilled water. If the solution of muriate of baryta cause a cloudiness or precipitate, sulphuric acid must be present ; if a similar effect be produced by nitrate of silver, the presence of muriatic acid may be inferred. Nitric acid is purified from sulphuric acid by re-distilling it from a small quantity of the ni- trate of potassa, with the alkali of which, the sulphuric acid unites and remains in the retort. To separate muriatic acid, it is necessary to drop a solution of nitrate of silver into nitric acid as long as a pre- cipitate forms, and draw off the pure acid by distillation. It should be kept in well stopped glass bottles, and in a dark place, as the light ef- fects its decomposition. TESTS OF NITRIC ACID. Liebig, some time since, proposed the blue colour of the sulphate of indigo as a test for the presence of nitric acid, but this substance is decolourized by so many agents that no reliance can be placed in its indications. A very delicate and apparently un- objectionable test, is the orange red followed by a yellow colour, which nitric acid communicates to morphine. The supposed nitrate is heated in a test tube with a drop of sulphuric acid and then a crystal of mor- phine is added. For this fact we are indebted to Dr. O'Shaugnessy. Lancet 182930. ACTION ON THE ANIMAL ECONOMY. This substance is of course highly poisonous, when taken internally in its concentrated form, causing death speedily, though never suddenly. In these cases neutralizing agents should be administered as soon as possible, to prevent the action of the poison. See Beck's MedicalJuris. 3d ed. 489. USES. Nitric acid is of considerable use in the arts. It is employ- ed for etching on copper, as a solvent of tin to form with that metal a mordant for some of the finest dyes ; in metallurgy and assaying ; in various chemical processes, on account of the facility with which it parts with oxygen and dissolves metals ; in medicine as a tonic, &c. For the purposes of the arts it is co. iii. 476.] These results are also confirmed by the experiments of Despretz. Brande's Jour. J\\ 8. vii. 201. Ammoniacal gas is absorbed by water. A drop or two of water be- ing admitted to a jar full of this gas, confined over mercury, the gas will be immediately absorbed, and the mercury will rise so as to fill the whole of the jar, provided the gas be sufficiently pure. Ice pro- duces the same effect in a still more remarkable manner. Water by- saturation with this gas, acquires its peculiar smell, ar,d constitutes NITROGEN. 139 what has been called liquid ammonia, but which is more properly a solution of pure ammonia in water. Alcohol also absorbs several times its bulk, and affords a solution of ammonia which possesses the strong smell and other properties of the gas. This is commonly called Spirits of Hartshorn. Composition. The composition of ammonia has occupied much of the attention of chemists. Hydrogen and nitrogen gases do not unite directly, and therefore we have no direct synthetic proof of the con- stitution of ammonia. But it is produced synthetically during the decomposition of many animal substances ; it is also formed during the violent action of nitric acid upon some of the metals, and by moistened iron filings exposed to an atmosphere of nitrogen. In these cases the nascent gases unite, so as to form a portion of ammonia. But the composition of ammonia has been determined analytically with the greatest exactness. When a succession of electric sparks is passed through ammoniacal gas, it is resolved into its elements ; and the same effect is produced by conducting ammonia through porce- lain tubes, heated to redness. The late A. Berthollet analyzed am- monia in both ways, and ascertained that 200 measures of that gas, on being decomposed, occupy the space of 400 measures, 300 of which are hydrogen and 100 nitrogen. Dr. Henry has recently made an an- alysis of ammonia by means of electricity, and his experiment proves beyond a doubt that the proportions above given are rigidly exact. Ann. of Phil. xxiv. 346. PREPARATION. Ammonia may be obtained in the form of gas in either of the following ways : 1. Mix together equal parts of muriate or sulphate of ammonia and dry quick-lime, each separately powdered, and introduce them into a small gas bottle or retort. Apply the heat of a lamp, and receive the gas that is liberated, over mercury. 2. To a saturated solution of ammonia in water, or the pure liquid ammonia in a gas bottle, apply the heat of a lamp ; and collect the gas as in the former case. Ammonia has heretofore been found native only in combination, 1 . with muriatic and phosphoric acids in the urine ; 2. with sulphuric acid in some mines of alum ; 3. with carbonic and acetic acid, &c. in putrid animal matter, and in the urine of all animals. Solution of Ammonia in water. This is commonly but incorrectly known by the name of liquid ammonia. The following process is given by Mr. R. Phillips, as preferable to that of the London Phar- macopeia. Remarks on the Lond. Pharm. 34. On nine ounces of well-burnt lime, pour half a pint of pure water, and when it has remained in a well closed vessel about an hour, add twelve ounces of muriate of ammonia (sal-ammoniac) in powder, and three pints and a half of boiling water. When the mixture has cool- ed, pour off the clear portion, and distil from a retort twenty fluid ounces. The specific gravity of this solution is 0'954. A process of Sig. Bizio is described, by which, from every pound of muriate of am- monia, 1 -Gl of a pound of liquid ammonia may be obtained of specific gravity 0-910. See Brande's Jour. N. S. iii. 477. The concentrated solution of ammonia as thus procured is a clear colourless liquid, possessing the peculiar pungent odour, taste, alka- linity and other properties of the gas itself. On account of its great volatility, it should be preserved in well stopped bottles, a measure 140 NITROGEN. which is also required to prevent the absorption of carbonic acid. At the temperature of 130 F. it enters into ebullition, owing to the rapid escape of pure ammonia ; but the whole of the ga,s cannot be expelled by this means, as at last the solution itself evaporates. It freezes at about the same temperature as mercury. Tables are given by Sir H. Davy and Dalton, showing the quantity of real ammonia contained in 100 parts of solutions of different den- sities. Elements of Ch&m. Phil. Henry, i. 429. TESTS. The presence of ammonia may always be detected by its odour, by its temporary action on the yellow of turmeric, and by forming dense white fumes, the muriate of ammonia, when a glas rod moistened with muriatic acid is brought near it. Hydrated oxide of lead is also a test of ammonia. ACTION ON THE ANIMAL ECONOMY. Cases are mentioned where the solution of ammonia caused death in the space of a few minutes, and in a late work, Orfila adds a caution against its too free use with per- sons who have fainted. If inspired too long, the vapour inflames the throat and lungs, and destroys the individual. Beck's Ned. Juris. 498. REFERENCES. For a very elaborate account of Ammonia, and its action on various substances, see Thtnard, Trait, de Chim. ii. 418. Derzelius on the nature of Ammonia, Ann. of Phil. ii. 276, and Trait, de. Chim. ii. 320. Dalton, Ann of Phil. ix. 186, on the same subject. Pfaff on the most sensi- ble reagent of Ammonia, Repert. of Arts. 2c/ ser. xii. 66. Phillips and Hopt?s controversy on the preparation of solution of Ammonia, Ann. of Phil, xv ii. 30, xviii. I'dl. Faraday on the combination of Chlorides icith Ammonia, Branded Jour. v. 7-1. SALTS OP AMMONIA AND THE FOREGOING ACIDS. The salts of ammonia are generally colourless and solid at com- mon temperatures, except the subtiuoborate, which is a liquid. They are mostly neutral ; of an acrid taste ; those with an excess of base having an amrnoniacal odour. A few of them are acid ; almost all crystallizable ; when exposed to heat are either wholly or in part volatilized, depending upon the nature of the acid whether gaseous or fixed. They are decomposed by chlorine at common temperatures, and when mixed with potassa, soda, lithia, baryta, strontia or lime, ammonia is evolved. REFERENCES. Dr. Urt*s experimental researches on the Ammoniacal Salts, Ann. of Plul. x. 203, 278. Chlorate of Ammonia. Crystallizes in fine needles ; of a very sharp taste ; detonates when thrown upon hot coals, and when submitted to a gentle heat in a retort, is rapidly decomposed and is converted into water, chlorine, nitrogen, protoxide of nitrogen, and an acid hydro- chlorate of ammonia. This salt is not found in nature. It may be readily obtained by adding carbonate of ammonia to chloric acid to complete saturation, and then evaporating the liquor. The evaporation should be very carefully conducted ; indeed it should be in a manner spontaneous, to prevent the volatilization of the salt. It is of no use in the arts. REFERENCES. VauqueliiSs description of Chi or. of Am. Arm. de Chim. xcv. 96. Ann. of Phil. vii. 39. **; NITROGEN. 141 lodate of Ammonia. Forms small indeterminate crystals ; when heated is decomposed into oxygen, nitrogen, water and iodine ; when heated in close tubes, the tubes are frequently burst ; but Gay Lussac succeeded in collecting the products, which were equal volumes of oxy- gen and nitrogen gases. He states its composition to be 100 acid and 10-94 ammonia, or two volumes gaseous ammonia, one volume iodine and two and an half volumes oxygen. Thenard, iii. 473. This salt may be obtained by adding ammonia to iodic acid to sat- uration, small crystals being immediately deposited. Hydrochlorate or Muriate of Ammonia Atom. Num. 52'45 Symb. (3H-f N)+CCI+H)-^. gr. 145 water=l. Known in commerce as Sal- Ammoniac, a name given to it by the ancients, because it was found in great quantities near the temple of Jupiter Ammon. Crystallizes ordinarily in long needles, which appear to be hexahe- dral pyramids ; white, of a very sharp taste ; soluble in three parts of water at 60 3 , and in equal parts of boiling water ; exposed to heat it melts in its own water of crystallization, dries and sublimes in the form of white vapours ; is decomposed by the fixed alkalies and alka- line earths ; reddens litmus paper, [Berzelius~\ ; calcined with carbon- ate of lime, it yields solid chloride of calcium, volatile carbonate of ammonia and water. PREPARATION AND NATIVE STATE. Hydrochlorate of ammonia is found native in the dung of certain animals, particularly the camel ; and in human urine. It appears also to exist in small quantities in the vicinity of volcanoes, and Dr. Marcet has ascertained that it ex- ists in sea water, and may be separated by sublimation from the un- cristallizable part, called bitt6rn.~Ph.il. Trans. 1822. 454. This salt may be formed directly, by mixing over mercury equal measures of ammoniacal gas, and muriatic acid gas, which are entire- ly condensed into a white solid. The common sal-ammoniac of the shops is prepared by a circuitous process from an impure carbonate of ammonia, obtained from the dis- tillation of bones and other animal matters. This carbonate of ammo- nia, by being kept in contact with sulphate of lime and water, is convert- ed into sulphate of ammonia. This again is decomposed by muriate of soda, which affords muriate of ammonia and sulphate of soda. The latter salt is separated by priority of crystallization, and the muriate of ammonia is then purified by being once or twice sublimed. In this way it is usually obtained in the form of a hard elastic cake. USES. This salt is employed to furnish ammonia and the carbo- nate of ammonia ; in certain metallurgic operations ; in tinning the surface of copper to prevent its oxidation : it is employed also in small quantities in dyeing ; in medicine as a stimulant, and when dissolved in nitric acid, forms the aqua regia of commerce, employed for dissolving gold, instead of a mixture of nitric and muriatic acids. ACTION ON THE ANIMAL ECONOMY. This salt is poisonous when tak- en into the stomach, or applied in large quantities to wounds. It causes vomiting, convulsions and death. Beck's Med. Juris. 502. REFERENCES. Sal-ammoniac and its manufacture, Encyc. Britannica Suppl. A volcanic product in Centra^sTctcianfy B^nde's Jour. x. 197. J ( UNIVERSH . 142 NITROGEN. Aslley , improvements in the manufacture ofy Repert. of Arts, %d ser. xii. 248. Manufacture of, in Egypt, Clarke's Trav. v. 23. Parkes* Chem. Essays, iv. on Sal-ammoniac. Hydriodate of Ammonia. Crystallizes in cubes, which are more sol- uble than sal-ammoniac, and nearly as volatile, subliming in close ves- sels without decomposition. PREPARATION. The hydriodate of ammonia may be prepared by combining directly, equal volumes of hydriodic acid and ammonia in their gaseous state ; or by saturating liquid hydriodic acid with carbon- ate of ammonia. Hydrofluate of Ammonia. Crystallizes with much difficulty ; has a very sharp taste ; when heated disengages a portion of ammonia, pass- es to an acid state and vaporizes under the form of dense and very disagreeable white fumes, at a temperature scarcely above that of boil- ing water ; is very soluble in water ; is decomposed by sulphuric acid, with brisk effervescence and a great disengagement of heat. PREPARATION, This salt may be prepared by adding a solution of ammonia to the hydrofluoric acid, allowing a slight excess of ammo- nia, and afterwards evaporating the liquor at a moderate heat in a platinum or silver vessel. REFERENCES. Gay Lussacand Thenard, Jour, de Phys. January, 1C09. Repert. of Arts, 2d ser. xv. 90. J. Davy, Repert. of Arts, '^d ser. xxii. 77. Nitrate of Ammonia Atom. Mim. 71 Symb. (3H+N)+ (50+ N.) Known by the older chemists under the name of Nit-rum Flammnns. Crystallizes in various forms according to the manner in which its solution has been evaporated ; if at a temperature below 100 F. in six-sided prisms, terminated by six-sided pyramids ; if boiled down, its crystals are thin and fibrous ; and when the evaporation is carried so far that the salt immediately concretes on a glass rod in cooling, it then forms a compact and shapeless mass ; is deliquescent, (except when evaporated at a high temperature,) and soluble in twice its weight of water at 60 ; has an acrid and bitter taste ; undergoes watery fusion when exposed to heat, giving off its water of crystalliza- tion, and a small portion of its alkali ; when gently heated in a retort is converted into water and the protoxide of nitrogen ; when thrown into a red hot crucible or heated to the temperature of 600 it inflames or explodes, and the products are water, nitrogen and the deutoxide of nitrogen, the inflammation being produced, according to Thenard, by the rapid combination of the oxygen of the nitric acid with the hydro gen of the ammonia. The composition of this salt varies according to the mode of its preparation. Davy. PREPARATION. This salt has not been found native. It may be procured by the direct union of ammonia with nitric acid ; or more easily by saturating dilute nitric acid with carbonate of ammonia, and evaporating the solution until a pellicle appears on the surface. The only use to which it is applied is in the process for obtaining protoxide of nitrogen. SULPHUR. 143 SECTION III. SULPHUR. Atom. Num. 16Symb. SSp. gr. 1'9S water=L This substance has been known from the most remote periods of antiquity. It is met with under two different forms ; a compact solid, which has generally the shape of long rolls or sticks, called roll brim- stone; and a light powder called floicers of sulphur. PROPERTIES. Sulphur is of a light yellow colour, and when melted emits a peculiar odour ; is insoluble in water, and tasteless ; when heated to 170 F. it begins to evaporate, and to produce a very disa- greeable smell ; at 185 or 190 it begins to melt, and at 220 is com- pletely fluid, but if the heat be rapidly increased, it loses, at 350 its fluidity, and becomes firm, and of a deeper colour. It regains its fluid- ity, if we reduce the temperature ; and this may be repeated at pleas- ure, in close glass vessels, if the changes of heat be not too slow ; in which case it is volatilized. When liquified .sulphur, of the temperature of 2*20 is slowly cooled, it forms a fribrous crystalline mass ; it sublimes at the temperature of 60(P ; and according to the greater or less quickness of the process, and the size of the condensing chambers, may be collected either in a solid form, or in that of flow- ers. [Thcnard, i. 197.] It is a bad conductor of electricity, but be- comes negatively electric by heat and by friction j and is in a high de- gree doubly refractive. Sulphur may be crystallized. The crystalline arrangement is gen- erally perceptible in the centre of a common roll of sulphur ; and by some management, regular crystals may be obtained. To attain this end, several pounds of sulphur should be melted in an earthen cruci- ble ; and when partially cooled, the outer crust should be pierced, and the crucible quickly inverted, so that the inner, and as yet fluid parts, may gradually flow out. On breaking the solid mass, when quite cold, crystals of sulphur will be found in its interior. M. Mitscherlich has made the discovery of two primary forms of sulphur. The one, which occurs in nature, is an octahedron, with a rhombic base ; the other produced by the slow cooling of fused sul- phur, is an oblique rhombic prism. Henry, i. 403. Liquified sulphur suddenly cooled, is variously affected, according- to its temperature When the most fluid sulphur is suddenly cooled, it becomes brittle, but the thickened sulphur, similarly treated, remains soft, and more soft as the temperature has been higher. Thus at 230, sulphur is very liquid and yellow, and cooled suddenly by im- mersion in a large quantity of water, it becomes yellow and very friable ; at 374, it is thick and of an orange colour, and by cooling, becomes at first soft and transparent, but soon friable and of the ordi- nary appearance ; at 428 it is red and viscid, and when cooled, soft, transparent and of an amber colour ; and at the boiling point it is of a deep brown red colour, and when cooled, very soft, transparent and of a red brown colour. Dumas, Ann. de Ch. et de P/i. xxxv. 83. Solubility of sulphur. Sulphur is completely soluble is boiling oil of turpentine, which is one of the tests of its purity. It is also soluble in alcohol, if the two bodies are brought into contact when both are 144 SULPHUR. in a state of vapour. On pouring this compound into water, the sul- phur will be precipitated. [For a description of the details of the process, see Henry's Chem. i. 404.] Presence of hydrogen in sulphur. The presence of hydrogen in sul- phur, first inferred by M. Berthollet, jun. has been satisfactorily prov- ed by the experiments of Sir H. Davy. By exposing sulphur to the strong heat of a powerful galvanic battery, he found that sulphuretted hydrogen was disengaged. But the quantity was so small that he was led to consider it nothing more than an accidental ingredient. This view of the subject is also embraced by Berzelius. Ann. de Chim* Ixxix. 119. Milk of sulphur, or precipitated sulphur of the pharmacopeia, some- times used for medicinal purposes, is formed by precipitating sulphur from some of its alkaline solutions, as from the hydro-sulphuret of potas- sa, by an acid. When washed and dried, it is in the form of a yellowish- grey impalpable powder, and is considered, by Dr. Thomson, as a com- pound of sulphur and water. PREPARATION AND NATIVE STATE. Sulphur is found native in large quantities in the vicinity of volcanoes, and as an article of commerce is chiefly brought from Sicily. It is also abundant in combination in a vast number of native sulphurets and sulphates. Among the most important of these are the sulphurets of iron, lead, mercury, antimo- ny, copper and zinc. This substance is prepared artificially by being separated from the earthy substances with which it is combined, in the neighbourhood of volcanoes, or from the compounds which it forms with iron, copper, &c. In the former case it is exposed to heat, in large pots, well cov- ered to prevent the admission of air ; when fluid, the impurities fall to the bottom, and it is then poured into moulds, thus forming the cylin- ders. When further purification is necessary a greater heat is applied and the sulphur is sublimed, the process being conducted in pots hav- ing receivers adapted to them, in which the vapour is condensed. In the latter case the sulphurets are roasted and the fumes received into chambers of brick work r where the sulphur is gradually deposited ; it is then purified by fusion and cast into sticks. In this state it is known in commerce by the name of roll brimstone ,~ when it is further purified by sublimation, it is called sublimed sulphur, or flowers of sul- phur. USES. Sulphur is extensively employed in the manufacture of sul- phuric acid ; in that of gunpowder, &c. When heated to 300 or 350 F. and poured, at that temperature, into water, it becomes tena- cious like wax, and may be applied, [as was done by Mr. Tassie,] to take impressions from engraved stones, seals, &c. In medicine, it is employed both as an external application and as an internal remedy, especially in diseases of the skin. IMPURITIES. Sulphur sometimes contains earthy impurities, which can be readily ascertained by heating it on a piece of platinum leaf when the sulphur will evaporate and leave the earthy substances. Pure sulphur also is perfectly soluble in boiling oil of turpentine. Sometimes arsenic is found in sulphur. According to M. M. Geiger and Reimann the minutest quantity can be detected as follows : A cer- tain quantity of precipitated sulphur, flowers of sulphur, or ordinary- sulphur finely pulverized, is to be digested with ammonia for a con- siderable time, then filtered, and afterwards the clear liquid acted upon SULPHUR. ' 145 by muriatic acid in excess. If a yellow precipitate occurs, it is an in- dication of the presence of arsenic ; if not, the liquid is to be evapo- rated until only a few drops remain. A little ammonia is then to be added ; afterwards a small quantity of muriatic acid ; and finally a little solution of sulphuretted hydrogen. If there be the smallest quantity of arsenic, it will be rendered evident by a yellow precipi- tate. Brande' s Jour. N. S. v. 192. SULPHUR AND OXYGEN. Chemists are at present acquainted with four compounds of oxygen and sulphur, all of which have acid properties. Their composition is shown in the following table. S. O. Hypo-sulphurous acid, . . . . 16-f- 8=24. Sulphurous acid, . . . . . 16+16=32. Hypo-sulphuric acid, .... 32+40=72. Sulphuric acid, 16+14=40. Hyposulphurous Acid fltom. Num. 24 Symb. O-f-S. (or 20+2 S=48.) This acid, like the hypo-nitrous, exists only in combination with salifiable bases, forming compounds, which were first examined in 1813, by Gay Lussac, and were called by him Sulphuretted Sulphites. Besides other methods of preparing these salts, he found that they might be obtained by digesting the solution of a sulphite with sulphur, an additional quantity of which might thus be made to combine with the sulphurous acid. It had also been long observed by Mr. Higgins of Dublin, that liquid sulphurous acid dissolves iron without efferves- cence ; and Berthollet afterwards showed that in this case the iron is oxidized at the expense of the sulphurous acid, and that sulphur is disengaged, which immediately unites with the sulphite of iron, form- ing a sulphuretted sulphite. Dr. Thomson appears to have been the first who took a correct view of these phenomena. The new compound he found to be a neutral salt, containing a peculiar acid of sulphur, to which he gave the name of Hypo sulphurous Acid, and to its compounds, that of Hyposulphites. [Syst. Cham. 5th edit.] This view has been confirmed by Mr. Her- schel. who has examined these compounds with great ability. [Edin. Phil. Jour. i. 8, 396.] He did not, however, succeed in his attempt to exhibit the acid in a separate state ; nor indeed does it appear capable of existing permanently when uncombined with a base. From the experiments of Mr. Herschel and his own, Dr. Thom- son inferred that this acid is a compound of one atom oxygen+one atom sulphur=24. This view of its constitution, although oppo- sed by a subsequent statement of Dr. Thomson, has been confirmed by Rose. It is somewhat remarkable, however, that while its ele- ments are in the proportion of 16 to 8, the atom of the acid is not 24 but 48. Turner. 146 SULPHUR. Sulphurous Acid Atom. Num. 32Sym?). 20+$ Sp. gr. 2222air=l. This acid appears to have been known at a very early period, though first distinguished as a separate substance by Stahl. It was also ob- tained and examined by Priestley in 1774, and has since been accu- rately analyzed by Gay Lussac and Berzelius. PROPERTIES. A gaseous and invisible acid ; has a sour taste and a pungent suffocating odour ; extinguishes burning bodies without being itself inflamed ; is fatal to animal life, producing a violent spasm of the glottis, by which the entrance of the gas into the lungs is prevent- ed, and, even when diluted with air, excites cough and causes a pecu- liar uneasiness about the chest ; slightly reddens litmus paper, and then slowly bleaches it ; destroys most vegetable colours ; is absorbed by water to the extent of 33 times its bulk ; is readily liquified by com- pression ; by combination with bases it forms Sulphites. It discharges vegetable, colours. Vegetable blues are reddened by sul- phurous acid previous to their being discharged. This effect may be illustrated in a striking manner by holding a red rose over the blue flarne of a common match, by which the colour will be discharged wherever the sulphurous acid comes in contact with it, so as to render it beautifully variegated, or entirely white. If it be then dipped into water, the redness, after a short time, will be restored. As the bleach- ing powers of this acid are quite considerable, it is much used in whitening silk and straw work. It also removes fruit stains from woollen cloth. It has a very strong attraction for oxygen. Though sulphurous acid cannot be made to burn by the approach of flame, it has a strong at- traction for oxygen, nniting witli it under favourable circumstances, and forming sulphuric acid. The presence of moisture is essential to this change. A mixture of sulphurous acid and oxygen gases, if quite dry, may be preserved over mercury, for any length of time, without acting on each other. But if a little water be admitted, the sulphurous acid gradually unites with oxygen, and disappears entirely. For this reason, a solution of sulphurous acid in water cannot be kept, unless atmospheric air be carefully excluded. Many of the chemical proper- ties of sulphurous acid are owing to its affinity for oxygen. On being added to a solution of the peroxide of iron, it takes oxygen, and thus converts the peroxide into the protoxide of that metal. The solutions of metals which have a weak affinity for oxygen, such as gold, plati- num and mercury, are completely decomposed by it, those substances being precipita'ed in the metallic form. Nitric acid converts it in- stantly into sulphuric acid, by yielding some of its oxygen. The peroxide of manganese causes a similar change, and is itself convert- ed into the protoxide of manganese, which unites with the sulphuric acid. It is absorbed by water. To show how readily this gas is absorbed by water, let a small bottle be filled with it over mercury and place the thumb on the mouth of the bottle and take it off under water. This fluid will instantly combine with it, and be forced up into the bottle with explosive violence by the pressure of the atmosphere. Water may be easily impregnated with sulphurous acid gas by passing it in a current through this fluid ; for which purpose the best mode is to em- ploy the series of bottles well known by the name of Woulfe's appa- SULPHUR. 147 ratus. From the solution, when recently prepared, the gas may be separated by heat, but not by congelation. It is readily liquified by compression. Of all the gases, sulphurous- acid is most readily liquified by compression. According to Mr. Fara- day, it is condensed by a force equal to the pressure of two atmos- pheres. M. Bussy has obtained it in a liquid form under the usual at- mospheric pressure, b_y passing it through tubes surrounded by a freezing mixture of snow and salt. The Anhydrous Liquid acid has a density of 1-45. It boils at 14 F. From the rapidity of its evapo- ration at common temperatures, it may be used advantageously for producing an intense degree of cold. M. Bussy succeeded in freezing mercury, and liquifying several of the gases, by the cold produced during its evaporation. Ann. of Phil. xxiv. 307. Faraday, Phil. Trans, for 1823, and Ann. of Phil, xxiii. 93. M. de la Rive has recently discovered a solid compound of sulphur ous acid and water, procured by passing moist sulphurous acid gas through a recipient, cooled down to the temperature of from 5 to 14 F. Colourless crystals, of an acid and not unpleasant taste, are con- densed on the inner side of the vessel. This compound is also formed during the evaporation of liquid sulphuric acid ; in this case the moist- ure of the atmosphere contributes to its formation ; but it is then mixed with ice. Berzelius, Trait, de Chim. ii. 25. PREPARATION AND NATIVE STATE. Sulphurous acid is found native only in volcanic countries, and most generally issuing from the fissures of lava. It is constantly disengaged from the Solfatera near Naples, from the summit of Stromboli, &c. It is also found in certain hot springs near volcanoes in Italy. It may be artificially prepared in two ways, viz : 1. By burning sulphur at a low temperature, in common air, under a bell glass or by burning sulphur in dry oxygen gas, in which case it is the sole product of the combustion. 2. By heating red oxide of mercury with one fourth of its weight of sulphur, sulphurous acid is produced, in the proportion of about a cu- bic inch for every five grains of the oxide. 3. By boiling one part by weight of mercury with six or seven of sulphuric acid to dryness in a glass retort, and then raising the heat, sulphurous acid gas is formed, andmay be collected and preserved over mercury. Half an ounce of mercury is sufficient for the production of several pints of the gas. In this instance the mercury becomes oxidated and thus deprives the sulphuric acid of one proportion of oxygen, and reduces it to sulphurous acid. The sawings of wood or powdered charcoal mixed with sulphuric acid in a retort, also, affords upon the application of heat, a large quantity of this gas. USES. Sulphurous acid prepared by the combustion of sulphur, is much used for bleaching cotton goods, and also for whitening silk, wool and straw. In wine countries it is sometimes used to check vi- nous fermentation. In medicine it is employed in some diseases of the skin. REFERENCES. Parkes' Chem. Essays, art. Blenching. For cases illus- trciting its action on the Animal Economy ', see Beckys Medical Juris. 3d ed. 304. 148 SULPHUR. Hyposidplmric Add. Atom. Num. 72Symb. 5O+2S. Discovered by Welter and Gay Lussac, in 1819. Ann. de Chim. et de Phys. x. 312. PROPERTIES. A colourless liquid, without odour even in the great- est state of condensation, by which circumstance it is distinguished from sulphurous acid ; reddens litmus ; has a sour taste, and forms neutral salts with the alkalies ; cannot be obtained free from water ; its solution, if confined with a vessel of sulphuric acid, under the ex- hausted receiver of an air pump, maybe concentrated till it has a den- sity of 1'347, but if an attempt is made to condense it still further, the acid is decomposed, sulphurous acid gas escapes, and sulphuric acid remains in solution, a similar change being still more readily pro- duced if the evaporation is conducted by heat. PREPARATION. The process recommended by Welter and Gay Lussac for obtaining this acid, is to pass a current of sulphurous aeid gas through water containing peroxide of manganese in fine powder. The manganese yields oxygen to the sulphurous acid, thus converting one part of it into sulphuric, and another part into the hyposulphuric acid, both of which unite with the protoxide of manganese. To the liquid, after filtration, a solution of pure baryta is added in slight ex- cess, which precipitates the protoxide of manganese, and forms an in- soluble sulphate of baryta with the sulphuric, and a soluble hyposul- phate with the hyposulphuric acid. The hyposulphate of baryta is then decomposed by a quantity of sulphuric acid exactly sufficient for precipitating the baryta, and the hyposulphuric acid is left in solu- tion. This solution is then concentrated by evaporation, until its density approaches 1'347. M. Heeren advises that when sulphurous acid is passed over black oxide of manganese, the oxide should be finely divided, and the tem- perature low. The largest portion of hyposulphuric acid is formed at the commencement of the operation. Brandes Jour. N. S. ii. 473. REFERENCES. Welter and Gay Lussac, on Hyposulphuric Acid and Hy posulphates, Ann. of Phil. xiv. 352. Sulphuric Add. Atom. Num. WSymb. 3O+S. This acid has been known ever since the time of Basil Valentine, who appears to have discovered it about the close of the fifteenth century. Sulphuric acid exists in two states : 1st, a dry crystalline solid, such as is obtained from the sulphuric acid of Nordhausen ; 2d, a li- quid combined with a certain proportion of water, such as it ordinarily exists and as it is used in the arts, and in the laboratory. I shull no- tice each of these separately. Anhydrous Sulphuric Acid. Sometimes called Glacial or Fuming Sul- phuric Acid. PROPERTIES. A white and opake solid ; liquifies at 66 F. and then has a specific gravity of 1'97, and boils at a temperature between 104 and 122, forming, if no moisture is present, a transparent va- pour ; when exposed to the air unites with watery vapour, and flies off in the form of dense white fumes ; is very caustic and reddens SULPHUR. 149 litmus powerfully ; dissolves sulphur and becomes of a brown, green or blue colour, and upon the addition of water, the sulphur is deposited and the acid is converted into ordinary sulphuric acid ; dissolves indigo with great readiness, the solution assuming a most beautiful purple colour, and hence it is much employed for this pur- pose. PREPARATION. This acid is obtained from a peculiar kind of hy drous sulphuric acid, manufactured at Nordhausen, a small village in Germany, by the distillation of the protosulphate of iron. Gmelin has procured it during the rectification of common sulphuric acid, by changing the receiver at the moment when it is filled by opake vapours, and surrounding the fresh receiver with ice. [Ann. de Chim. et de Phys. xxxii. 223.] Professor Mosander, of Stockholm, proposes the following very simple mode of preparing it. If the oxide of antimony be treated with excess of sulphuric acid till the oxide is saturated, and the excess of acid then driven off by a low temperature, the sulphate is obtained dry and crystallized. If this salt be put into a retort and heated to dull redness, the greater part of the acid is driven off in an anhydrous state and is easily condensed in acool receiver. Johnston's Re/tort. On this acid see also Thomson s First Prin. Bussy in Ann. of Phil. xxiv. 259, and Repert. of Arts, 2d ser. xlvi. 181. Hydrous Sulphuric Acid Oil of Vitriol. PROPERTIES. A colourless, dense, oily fluid, one of the strongest acids with which chemists are acquainted ; is powerfully corrosive ; decomposes all animal arid vegetable substances by the aid of heat, causing deposition of charcoal and formation of water ; has a sour taste, and reddens litmus though greatly diluted with water ; boils at 62(P F and has a specific gravity, in its most concentrated form, of 1'847, or a little higher, never exceeding 1-850 ; has a great affinity for water, uniting with it in every proportion, and producing during the combination, an intense heat ; absorbs watery vapour with avidi- ty from the air, and on this account is employed in the process for freezing water by its own evaporation ; freezes at 15 F. but when diluted with water, so as to have a specific gravity of 1-78, it congeals even above 32 J F. and remains in the solid state, according to Mr. Keir, till the temperature rises to 45 F. but when mixed with ra- ther more than its weight of water, has its freezing point lowered to 36 ^ F. Sulphuric Acid chars animal and vegetable substances. Hence the acid is apt to acquire a brown tinge, from particles of straw, resin or other matter that may accidentally have fallen into it. Its operation in this case as well as in destroying the texture of the skin, and in forming others, is supposed to be owing to its affinity for water. It has a great affinity for water. When this acid is suddenly mixed with water, a considerable degree of heat is produced. Four parts, by weight, of concentrated sulphuric acid, and one of water, when mixed together, each at the temperature of 50 J F. have their tempera- ture raised to 300. The greatest elevation of temperature, Dr. Ure finds to be occasioned by the sudden mixture of 7:i parts, by weight, of strong sulphuric acid with 27 of water. A diminution of bulk also ensues ; one measure of acid and one of water not occupying the space of two measures but about l-17th less. It takes moisture from the air, even at a boiling temperature, when it is concentrated ; and hence it cannot be concentrated so well in 150 SULPHUR. an open as in a close vessel, on which account retorts of glass or platinum, are used for the last stage of its concentration by the manu- facturers. Though sulphuric acid, when mixed with water as in the above cases, produces a high degree of heat, a mixture of 2 parts of acid and 3 of snow reduces the mercury in Fahrenheit's thermometer to 23. Hence this is employed as a freezing mixture. To explain these re- sults, which at first appear contradictory, it is sufficient to observe : 1st, that snow or ice, in passing from the solid to the liquid state, ab- sorbs caloric ; and, 2d, that sulphuric acid, in combining with water, gives out caloric ; hence either heat or cold is produced according as water is employed in the liquid or solid form. Many of the simple non-metallic combustibles decompose sulphuric acid, ichcn assisted by heat. When hydrogen gas and sulphuric acid are made to pass through a red hot porcelain tube, the acid is completely decomposed, and there results water, sulphurous acid or sulphur, ac- cording as the proportion of hydrogen to the acid is greater or less. When the hydrogen is in excess, and the heat is not too high, sul- phuretted hydrogen is also produced. Sulphuric acid is also decom- posed by carbon, phosphorus and sulphur. PREPARATION AND NATIVE STATE. Though sulphuric acid is said to have been found native, it is doubtful whether this is correct. The- rtard supposes that naturalists have mistaken for it an acid sulphate. [Trait, de Chim. ii. 213.] It is, however, frequently found in combi- nation with various bases, as lime, potassa, soda, &c. The process for forming sulphuric acid, at present very generally adopted, is by burning sulphur, previously mixed with one-eighth of its weight of nitrate of potassa. The mixture is burned in a furnace so contrived that the current of air which supports the combustion, con- veys the gaseous products into a large leaden chamber, the bottom of which is covered, to the depth of several inches, with water. The nitric acid yields oxygen to a portion of sulphur, and converts it into sulphuric acid, which combines with the potassa of the nitre ; while the greater part of the sulphur forms sulphurous acid, by uniting with the oxygen of the air. The nitric acid, in losing oxygen, is converted into the deutoxide of nitrogen, which, by mixing with air at the mo- ment of its separation, gives rise to the nitrous acid vapours. The gaseous substances present in the leaden chamber are, therefore, sul- phurous and nitrous acids, atmospheric air and watery vapour. And it appears that the sulphurous is converted into the sulphuric acid, by the oxygen of the air, and that the combination is not effected di- rectly, but through the medium of the nitrous acid. For details of this explanation see Davy's Elements and Webster's Brande. An ac- count of the successive improvements in the manufacture of sulphuric acid, will be found in Parkes' Chemical Essays. Mr. Reid, in his Practical Chemistry, describes an apparatus which illustrates in a very happy manner the theory of the formation of this acid. Although sulphuric acid, as ordinarily prepared, answers in general the purpose of the artist, it is never quite pure. It contains some sulphate of potash and of lead, the former derived from the nitric em- ployed in making it, the latter from the leaden chamber. To sepa- rate these impurities, the acid should be distilled from a glass or pla- tinum retort. The former may be used with safety, by putting some fragments of platinum leaf into it, which causes the acid to boil free- SULPHUR. 151 ly on the application of heat, without danger of breaking the vessel. Faraday, Chem. Manip. sect. 409. The strength of sulphuric acid is best judged of by saturating a known quantity with an alkali, and it may be assumed as sufficiently correct, that 100 grains of dry sub-carbonate of soda neutralize 92 grains of pure liquid sulphuric acid ; or that 1 00 grains of the acid require 108 or 108'5 of the sub-carbonate for saturation. The strength may also be judged of by its specific gravity. Mr. Dalton has pub- lished a table, exhibiting the specific gravity and boiling point of acid of various strengths. New System of Chem. Philosophy. See also Henry s Che^i. ADULTERATION. The presence of sulphuric acid may always be de- tected by the white insoluble precipitate which it forms when added to any soluble salt of baryta. If the acid is coloured it indicates the pre- sence of organic matter. If when diluted with water, it becomes tur- bid, we may infer the presence of sulphate of lime, sulphate of lead or some such salt. But the amount and nature of these impurities may be more satisfactorily determined by heating a portion of acid in a pla- tinum spoon ; the pure acid will be entirely volatilized, but the salts, if it contain any, will remain and may be subsequently examined. USES. The uses of sulphuric acid are very numerous. 1. It is that by means of which we obtain almost all the other acids employed in the laboratory or in the arts. 2. To extract soda from common salt. 3. In the manufacture of alum, sulphate of iron, to dissolve indigo, in the manufacture of chlorine, and in various chemical processes, Indeed it is one of the most common agents employed by chemists and artists. REFERENCES. On the modes of manufacturing Sulphuric Acid, see Chap- tal^s Chemistry ', applied to the Arts, iii. 21, and Par/ces 1 Chemical Essays, ii. 273. SULPHUR AND CHLORINE. Chloride of Sulphur. Atom. Num. 51*15 Symb. Cl+S 8p.gr. 1-687 water=l. This compound was discovered by Dr Thomson in 1804, and was subsequently examined by Bertliollet, Davy and Dumas. PROPERTIES. A liquid appearing red by reflected and yellowish- green by transmitted light; volatile below 200 D F., and condenses again without change on cooling ; emits acrid fumes when exposed to the air, which irritate the eyes powerfully, and have an odour some- what resembling sea-weed, but much stronger ; reddens tincture of turnsol powerfully ; boils readily when heated in a retort, but is not changed ; acts with energy on water, mutual decomposition ensues, the water becomes cloudy from the deposition of sulphur, and a solu- tion is obtained, in which muriatic, sulphurous, and sulphuric acids, may be detected. PREPARATION. Chloride of sulphur may be most conveniently pre- pared by passing a current of chlorine gas over flowers of sulphur gently heated. Direct combination takes place, and the product is obtained under the form of a liquid as above described. Some chemists regard this compound as an acid, and propose to 152 SULPHUR. name it Chloro-sulphuric Acid, because it reddens the tincture of turn- sol. This effect, however, is more properly ascribed to the sudden formation of muriatic or sulphurous acid. Besides, the chloride of sulphur does not combine with salifiable bases. Berzelius describes two compounds of chlorine and sulphur. One of which he calls Cklorure sulfurique ; the other Chlorure sulfur eux. REFERENCES. Thomson on the composition of Chloride of Sulphur, Ann. of Phil. xv. 408. Berzelius, T . de Chim. i. 283. ' raite SULPHUR AND BROMINE. Bromide of Sulphur. On pouring bromine on sublimed sulphur, combination ensues, and a fluid of an oily appearance and reddish tint is generated. In odour it somewhat resembles chloride of sulphur, and like that compound emits white vapours when exposed to the air, but its colour is deep- er. It reddens litmus paper faintly when dry, but strongly if water is added. Cold water acts slowly upon the bromide of sulphur ; but at a boiling temperature, the action is so violent that a slight detonation occurs, and three compounds, hydrobromic and sulphuric acids, and sulphuretted hydrogen are formed. The formation of these substan- ces is of course attributable to decomposition of water, and the union of its elements with bromine and sulphur. Bromide of sulphur is like- wise decomposed by chlorine, which unites with sulphur, and displaces bromine. Turner. SULPHUR AND IODINE. Iodide of Sulphur. ^""Sulphur unites readily with iodine, but with less energy than with phosphorus. A gentle heat is necessary to effect the combination. The resulting compound is in the form of brilliant rays, resembling sulphuret of antimony. It decomposes with facility when exposed to a temperature a little more elevated than that at which it is formed, the iodine separating in the form of vapour. This compound was first described by Gay Lussac. Ann. de Chim. xci. SULPHUR AND HYDROGEN. According to some chemists, these substances combine in two pro- portions, forming what were originally termed Sulphuretted Hydrogen and Supersulphuretted Hydrogen. But the nature of the latter has not been clearly settled. Both, however, are allowed to possess acid pro- perties, and some German chemists have proposed for the former the name of Hydrothionic Acid. This is preferable to the name of Hydro- sulphuric acid, given to it by Gay Lussac, which would be more pro- perly applied to liquid sulphuric acid. Should the supersulphuretted hydrogen prove to be a distinct substance, it may be called Hydrothion- ous Acid. SULPHUR. 153 Hydrothionic Acid. Atom. Num. 17 Symb. H+S * Sp. gr. 1-1805 air=l. SYN. Sulphuretted Hydrogen, Scheele. Hydrosulphuric Acid, Gay Lussac. Su/fide Hydrique, Berzelius. Discovered by Scheele in 1777. PROPERTIES. A colourless gas, having a highly offensive taste and odour, similar to that of putrifying eggs or the water of sulphurous springs ;. is compressed into a liquid under a pressure of 17 atmos- pheres, at 50 F., resuming the gaseous state as soon as the pressure is removed ; is very injurious to animal life ; extinguishes all burning bodies, but the gas takes fire when a lighted candle is immersed in it, and burns with a pale blue flame ; with oxygen gas forms a mixture which detonates by the application of flame or the electric spark ; reddens litmus feebly, and forms salts with the alkalies called Hydro- sulphurets or Hy dro sulphates ; is absorbed by water when agitated, or when recently boiled, from which the gas may be expelled without change ; is partly decomposed when submitted to heat in a porcelain tube, a portion of sulphur and hydrogen separating, the first in a solid and the second in a gaseous state. It is decomposed by Chlorine and Iodine. Sulphuretted hydrogen is decomposed by chlorine and iodine in consequence of their great affini- ty for hydrogen, and the former is often employed as a means of pu- rifying places which have been rendered noxious by this gas. The re- sult of the action of chlorine is muriatic acid, that of the action of iodine, hydriodic acid. It acts upon most of the metals. Sulphuretted hydrogen acts upon most of the metals ; the gas is decomposed, the sulphur combines with the metals, and the hydrogen is liberated. Hence it is used as a test of the presence of metals in solution. It is absorbed by water. Water, when agitated or under pressure, absorbs three times its volume of this gas, forming a transparent and colourless liquid, with the taste and odour of the gas. But when ex- posed to the air, it becomes covered with a pellicle of sulphur. Sul- phur is even deposited when the water is kept in well closed bottles. On the addition of a few drops of nitric or nitrous acid to the wa- tery solution, sulphur is instantly precipitated. In this case the oxy- gen of the acid combines with the hydrogen of the gas, and the sul- phur is separated. The gas itself, also, is decomposed when trans- mitted through sulphuric, nitric or arsenic acids. [BrandesJour.il. 152.] If a drachm of fuming nitric acid is poured into a bottle full of sulphuretted hydrogen gas, a bluish white flame passes rapidly through the vessel, sulphur and nitrous acid fumes make their ap- pearance, and of course water is generated. Liquid Sulphuretted Hydrogen. Mr. Faraday obtained sulphuretted hydrogen in a liquid form by producing it under pressure. It was then colourless, limpid and excessively fluid. Ether when compar- ed with it in similar tubes, appeared tenacious and oily. It did not seem more consistant at than at 45 F., and when raised from the former to the latter temperature, the only effect was, that part of the liquid rose in vapour, and its quantity diminished. When a tube containing it was opened under water, the liquid rushed immediately into gas, which when collected, had all the properties of sulphuret- 154 SULPHUR. ted hydrogen. The refractive power of the liquid appeared rather greater than that of water ; it decidedly surpassed that of sulphurous acid. By a small guage, introduced into the tube in which it was produced, the pressure of its vapour was nearly equal to 17 atmos- pheres at 50 F.Mul. Trans. 1823, 192. NATIVE STATE AND PREPARATION. Sulphuretted hydrogen is given off in small quantities from various springs denominated sulphur- ous. Also from many substances undergoing the process of putrefac- tion, as eggs, &c., and hence its peculiar odour can often be observ- ed in the vicinity of sinks and sewers. Its presence can also be de- tected by its effects in blackening silver or other metallic substances. This gas can readily be prepared by presenting sulphur to nascent hydrogen. Any of the sulphurets of the alkaline metals will furnish it by the mere addition of water. It may also be obtained by adding diluted sulphuric acid to sulphuret of iron ; or more conveniently by heating bruised sulphuret of antimony in muriatic acid. It may be procured over water, though by agitation that fluid absorbs thrice its bulk. The use of metallic vessels should of course be avoided in pro- curing this gas. TESTS. Sulphuretted hydrogen is readily distinguished from other gases by its odour. The most delicate chemical test of its presence is carbonate of lead (white paint,) mixed with water and spread up- on a piece of white paper. So minute a quantity of sulphuretted hy- drogen may by this means be detected, that one measure of the gas mixed with 20,000 times its volume of air, hydrogen or carburetted hy- drogen, gives a brown stain to the whitened surface. Henry's Chcm. i. 467. ACTION ON THE ANIMAL ECONOMY. Sulphuretted hydrogen is one of the most deleterious gases with which we are acquainted. According to the experiments of Dupuytren andThenard, the presence of l-1500th of sulphuretted hydrogen in air, is instantly fatal to a small bird ; . l-800th killed a middle sized dog, and a horse died in an atmosphere which contained 1 -250th of its volume. Chaussier has even proved that if this gas be made on the cutaneous surface of animals, it is suffi- cient to cause their death. Thenard, iv. 575. Jour, dc Medicine, de M. Leroux, fyc. USES. Sulphuretted hydrogen is used sometimes in medicine, as, for example, in the form of baths, for certain cutaneous eruptions. It is also employed by the laboratory as a re-agent for detecting the pres- ence of the metals. REFERENCES. This compound has been the subject of numerous researches by Uertkollet, Chassier, Dnpuytren, Davy, Gay Lussac and Thenard. Berthollet has made it almost a complete study, Ann. de Chim. xxv. Chas- itier, Dupuytren and Thenard /iave examined its deleterious action upon the animal economy Jour, de Medicine. Davy, Gay Lutwc and Thenard, have examined its ehendcal properties Recherches Physico ChLnijites, i. Ilydrothionous Add Atom. Num. 33 Symb. H-J-2S. SYN. Super sulphuretted Hydrogen. Scheele. Per- or Bi-suJphurettcd Hydrogen. This substance was discovered by Scheele, afterwards examined by SULPHUR. 155 Berthollet. ( Ann. de Chim. xxv.) and still more recently by Thenard. (Ann. dc Chim. xlviii. 79, or Johnston's Report.} It may be convenient- ly made by boiling equal parts of recently slacked lime and flowers ot sulphur, with five or six of water, when a deep orange yellow solution is formed, which contains a hydro-sulphuret of lime with excess of sulphur. On pouring this liquid into strong muriatic acid, a copious deposition of sulphur takes place ; and the greater part of the sul- phuretted hydrogen, instead of escaping with effervescence, is retain- ed by the sulphur. After some minutes, a yellowish semi-fluid matter like oil, collects at the bottom of the vessel, which is the bisulphuret- ted or super-sulphuretted hydrogen. PROPERTIES. A viscid substance ; has the peculiar taste and odour of the sulphuretted hydrogen, but in an inferior degree ; unites with salifiable bases, forming salts, denominated, Sulphuretted Hydrosulphu- rets, (or Hydrolhionites); is inflammable and burns in the air with the smell of sulphurous acid ; when gently heated, is resolved into sulphur and sulphuretted hydrogen, and from the facility with which this decomposition is effected, the history of this substance is still im- perfect. The salts of the bi-sulphuretted hydrogen may be prepared by di- gesting sulphur in solutions of the alkaline or earthy hydro-sulphurets. They are also generated when alkalies or alkaline earths are boiled with sulphur and water. These salts absorb oxygen from the air, arid pass gradually into hyposulphites. A similar change is speedily ef- fected by the action of sulphurous acid. Dilute muriatic and sulphu- ric acids produce in them a deposition of sulphur, and evolution of sulphuretted hydrogen. SALTS OF AMMONIA AND THE ACIDS CONTAINING SULPHUR. Hyposulphite of Ammonia. This salt has a pungent and excessively bitter taste ; it does not readily crystallize ; when heated it burns with a feeble flame and evaporates. Edin. Phil. Jour. i. Sulphite of Ammonia. Crystallizes in six-sided prisms, terminated by six-sided pyramids, or in four-sided rhomboidal prisms, terminated by three-sided summits ; has a cool, penetrating and somewhat sul- phurous taste ; is soluble in its own weight of cold water ; or in less than an equal weight of boiling water ; attracts moisture from the air, and rapidly passes to the state of a sulphate. Though this salt usually contains water, it may be obtained anhy- drous. Dobereiner in Phil. Mag. and Ann. ii. 389. Sulphate of Ammonia Atom. Num. 66 Symb. (3H+N) +(30+S)+lAq. SYN. Secret Sal- Ammoniac, Glauber. Viiriolated Ammoniac. PROPERTIES. Crystallizes usually in small six-sided prisms, whose planes are unequal, terminated by six-sided pyramids ; has a sharp and bitter taste ; is soluble in twice its own weight of water at 60 F. and in its own weight of boiling water ; when exposed to the air, slow- ly attracts moisture ; when heated, first decrepitates, then melts, and is converted into an acid sulphate ; at a red heat it is completely de- composed, nitrogen is disengaged, as well as water and the acid sul- 156 PHOSPHORUS. phate of ammonia which vapourizes in the form of a white cloud ; it is also decomposed by potassa, soda, &c. PREPARATION AND NATIVE STATE. This salt is sometimes found na- tive in the vicinity of volcanoes. In the laboratory it is obtained by adding excess of ammonia to dilute sulphuric acid, and evaporating the solution; or by saturating dilute sulphuric acid by carbonate of ammonia, or by decomposing muriate of ammonia by sulphuric acid. In the arts it is obtained in large quantities by treating sulphate of lime with the carbonate of ammonia, procured during the distillation ef animal matter. Hydrothionate of Jlmmonia. Atom. Num. 34 Symb. (3H+N.)+(H+S.) SYN. Hydrosulphuret of Ammonia. Hydrosulphate of Ammonia. Thenard. PROPERTIES. When perfectly pure, this substance occurs in needle form crystals, which are transparent and colourless ; is very volatile, and when kept in a bottle, sublimes gradually to the top of the ves- sel, where it crystallizes in long transparent plates, by which means it is freed from any impurities which it may contain ; when exposed to the air it assumes a yellow colour, absorbs oxygen, and passes to the state of a hydroguretted sulphuret ; mixed with excess of ammonia, it dissolves speedily, and produces a considerable degree of cold. PREPARATION. Pure hydro-sulphuret of ammonia may be obtained by combining ammoniacal gas and sulphuretted hydrogen gas at a low temperature. For details concerning the preparation of this corn- pound, see Thenard, iii. 477. When sulphuretted hydrogen gas is passed through solution of am- monia, a substance is obtained which is commonly called Liquid Hy- drosulphuret of Ammonia ; and which is much employed in the labora- tory as a test. It is of a yellowish colour, and rapidly decomposes when exposed to the air or to heat. Hydrothionitc of Jlmmonia. SYN. Hydroguretted Sulphuret of Ammonia. Thomson and The- nard. A liquid of the consistence of syrup, with a taste and odour similar to that of the hydrosulphuret of ammonia. But this as well as the other compounds of this acid, is still imperfectly understood. See p. 155. And for further particulars, see Thomson's or Thenard' s Chem- istry and HerscheVs Paper in Edin. Phil. Jour. i. 13. SECTION IV. PHOSPHORUS. Atom. Num. 15-7 Symb. P Sp. gr. 1-770 water=l. Phosphorus was discovered by Brandt, an alchemist of Hamburg, in 1669, but it was not until Scheele published his process for obtaining it, nearly a century afterwards, that it became sufficiently common to be accurately examined. PHOSPHORUS. PROPERTIES. Phosphorus is transparent and almost colourless ; is so soft that it may be cut with a knife, and the cut surface has a waxy lustre ; is highly inflammable, undergoing a slow combustion, when exposed to the air at common temperatures ; fuses at the temperature of 108 F. and sublimes at 550 F. ; inflames spontaneously in chlo- rine ; when gently heated, burns very brilliantly in oxygen gas ; is soluble in ether, alcohol, olive oil, &c. and communicates luminosity to these substances ; decomposes nitrous acid, with combustion ; is poisonous when taken into the stomach ; by carefully fusing and cool- ing a large quantity it may be crystallized in rhombic dodecahedrons. Mitschertich, in Phil. Mag. and Jinn. iii. 154. Combustion of Phosphorus in air and in oxygen. Phosphorus when brought into contact with air or oxygen gas at low temperatures, gives out white vapours and a peculiar alliaceous smell, appears luminous in the dark, and is gradually consumed. Hence it should always be kept under water. If a stick of phosphorus be put into a jar of air inverted over water, the volume gradually diminishes, and if the tem- perature of the air is at 6CP F. the whole of the oxygen will be with- drawn in the course of 12 or 24 hours. The residue is nitrogen, con- taining about l-40th of its bulk of the vapour of phosphorus. It is re- markable that the slow combustion of phosphorus does not take place in pure oxygen, unless its temperature be about 80 F. ; but if the oxygen be rarified by diminished pressure, or diluted with nitrogen, hy- drogen or carbonic acid, then the oxydation occurs at 60 F. accom- panied with the extrication of light and heat. The presence of cer- tain gaseous substances, even in very small quantities, has been found by Mr. Graham, to have a remarkable effect in preventing the slow combustion of phosphorus. Jour, of Science, N. S. vi. 83. But though phosphorus, in a solid state, acts with very little energy upon oxygen gas, the case is different when the phosphorus becomes liquid then it absorbs and solidifies this gas with great rapidity and there results phosphoric acid, with much heat, and a very vivid disen- gagement of light. This may be shown by filling a small glass tube with mercury and introducing into it a small quantity of well dried phosphorus. The phosphorus, being lighter than the mercury, ascends to the upper part of the tube, where it may be melted by a small spirit lamp or a piece of burning charcoal. Oxygen gas is now passed into the tube, bubble by bubble, each one on corning into contact with the phosphorus disappearing in an instant, and producing a flash of light, which the eye is scarcely able to support. [ T/ienard. ] This fact may also be shown by throwing some pieces of phosphorus in hot water, and then directing a stream of oxygen gas upon it. Phosphorus is inflamed by the application of a very gentle heat. Ac- cording to Dr. Higgins a temperature of 60 F. is sufficient to set it on fire, when perfectly dry. It burns, when heated to about 148 F. with a very brilliant light, a white smoke, and a suffocating smell, and may be inflamed in an atmosphere rarified sixty times. It may be set on fire by friction. Rub a very small bit between two pieces of brown paper, or of wood ; the phosphorus will inflame and set the paper on fire also. NATIVE STATE AND PREPARATION. Pure phosphorus does not exist in nature, but some of its acid compounds are found in combination with bases, especially in the form of phosphate of lime, which constitutes a large proportion of the solid matter of the bones of animals. 158 PHOSPHORUS. The process for obtaining phosphorus, now generally adopted, is, to ignite bones in an open fire, till they become quite white, so as to de- stroy all the animal matter they contain, and oxidize the carbon pro- ceeding from its decomposition. The calcined bones, of which phos- phate of lime constitutes nearly four fifths, should be reduced to a tine powder, and be digested for a day or two with half their weight of concentrated sulphuric acid, so much water being added to the mix- ture as to give it the consistence of a thin paste. The phosphate of lime is decomposed by the sulphuric acid, and two new salts are gene- rated the sparingly soluble sulphate and a soluble biphosphate of lime. On the addition of boiling water the biphosphate is dissolved, and may be separated, by filtration, from the sulphate of lime. The solution is then evaporated to the thickness of syrup, mixed with one-fourth its weight of charcoal in powder, and heated in an earthen retort well luted with clay. The beak of the retort is put into water, in which the phosphorus, as it passes over in the form of vapour, is collected. When first obtained, it is frequently of a reddish-brown colour, owing to the presence of the phosphuret of carbon, which is generally form- ed during the process. It may be purified by being put into hot water, and pressed, while liquid, through chamois leather ; or the purification may be rendered still more complete by a second distillation. Turner. ACTION ON THE ANIMAL ECONOMY. Phosphorus is a violent and gene- ral excitant. In small doses its effects are very soon manifested, but are of short duration. In large doses it occasions death, by causing violent inflammation. Some physicians have administered it in solu- tion in alcohol, ether and the oils ; others have recommended it in the form of pills. It is stated by Mr. Murray, that if phosphorus be allow- ed to stand in water for some time, it will render that fluid poisonous to animals that drink it. Ann. of Phil. xvi. 232. REFERENCES. Lavoisier's Elements of Chem. Davy's Elements of Chem. Aikiri's Chemical Diet, containing a detailed account of the various processes for obtaining Phosphorus, and of its action upon various substances. For the action of Phosphorus upon various mixtures of oxygen and other gases see Thenard, i. 237. Berzehus, Trait, de Chim. i. 254. For an account of the poisonous effects of Phosphorus, fyc. see Beck's Med. Juris. Dr. Lobxtem on Phosphorus. PHOSPHORUS AND OXYGEN. Oxide of Phosphorus ? When phosphorus is kept under water for some time, a white film forms upon its surface, which some have regarded as an oxide of phos- phorus. The red coloured matter which remains after the combustion of phosphorus, is also supposed to be an oxide. But chemists have not yet succeeded in determining the nature of these substances in a satisfactory manner. The following are the definite compounds of phosphorus and oxygen now generally recognized, viz : P. O. Hypophosphorous Acid, - 31-4 8=39-4 Phosphorous Acid, 15-7 12=27-7 Phosphoric Acid, Pyrophosphoric Acid, PHOSPHORUS. 159 Hypophosphorous Add Atom. Num. 39-4 Symb. O+2P. This acid was discovered by M. Dulong, in 1816, and may be form- ed by the action of water upon the phosphuret of an alkaline metal, as phosphuret of barium. An insoluble precipitate is formed, from which the liquid is to be separated by filtration. To this solution sul- phuric acid is carefully added so long as any precipitate is formed. The sour liquor which remains, after a second filtration, is to be con- centrated by evaporation, when a viscid, uncrystallizable acid fluid will be obtained, to which the above name has been given. It is still doubted, by some chemists, whether it may not be a triple compound of oxygen, phosphorus ,.and hydrogen, or a hydracid, in which case its proper appellation would be hydrophosphorous acid. REFERENCES. Dulong in Phil. Mag. xlviii. 271. Sir H. Davy, Phil. Trans. 1818, and Ann. of Phil. xiii. 210. Rose on the Salts of, Ann. de Chim. etde Phys. July, 1828. Phosphorous Acid. Atom. Num. 27.7 or 55*4 Symb. 1J O+P. Discovered by Sir H. Davy, in examining the action of proto-chlo- ride of phosphorus upon water. PROPERTIES. Phosphorous acid has a very sour taste, and smells somewhat like garlic ; reddens litmus powerfully ; is decomposed by heat, yielding the same products as the hypophosphorous acid ; unites with bases and forms salts, which are termed phosphites ; in solu- tion it absorbs oxygen slowly from the air, and is converted into phosphoric acid ; has a great tendency to unite with an additional quantity of oxygen, and is, therefore, a powerful deoxidizing agent, and hence, like sulphurous acid, precipitates mercury, silver, platinum and gold, from their saline combinations in the metallic form ; by ni- tric acid it is converted into phosphoric acid. PREPARATION. This acid can only be obtained in a state of pu- rity by subliming phosphorus through powdered corrosive sublimate, contained in a glass tube. A liquid comes over which is a com- pound of chlorine and phosphorus. When this substance is put into water, a peculiar change takes place. A portion of water is decom- posed ; its hydrogen unites with the chlorine and forms muriatic acid ; while the oxygen combines with the phosphorus and forms phosphorous acid. The solution is then evaporated to the consistence of a syrup, to expel the muriatic acid ; and the residue, which is the hydrate of phosphorous acid, becomes a crystalline solid on cooling. Phosphoric Add. Atom. Num. 35-7 Symb. 2JO+P. J^seems now to be admitted that under the term phosphoric acid two distinct acids, the phosphoric and pyrophosphoric have heretofore been usually included. These compounds are of great interest as affording an example of a fact but recently noticed, viz : That two bodies may consist of the same ingredients, in the same proportions, and yet differ essentially in their chemical properties. For such compounds, of which several are now known, Berzelius has proposed the general ap- 160 PHOSPHORUS. pellation of isomcric, from the Greek isomercs, expressive of equality, in the ingredients. The phosphoric and pyrophosphoric acids are thus distinguished from each other. Phosphoric acid gives a yellow salt with oxide of sil- ver, but does not affect albumen. Pyrophosphoric acid yields a white salt with oxide of silver and precipitates solution of albumen. These acids as well as the salts which they form are easily converted into each other ; and during these changes there is neither gain nor loss of either of their elements. Thus by a red heat the phosphoric acid is converted into the pyrophosphoric : and the pyrophosphoric is reconverted into the phosphoric in the course of a few days by cold wa- ter, and rapidly by hot water and the acids : and the salts are sub jected to similar changes by the application of the same agents. Phosphoric acid. This acid exists only in solution, for the applica- tion of heat necessary to expel the water converts it into the pyro- phosphoric. It has an intensely sour taste, reddens litmus, and neu- tralizes the alkalies, but does not destroy the texture of the skin. PREPARATION. This acid is readily prepared by boiling an aqueous solution of pyrophosphoric acid. Pyrophosphoric acid. Discovered by Mr. Clarke of Glasgow in 1827, [Brcicster 's Jour. vii. 298.] and distinguished from the preceding by the characters above given. PREPARATION. When phosphorus is burned in a dry vessel of air or oxygen gas, a copious white smoke appears, which soon collects in- to distinct particles and falls to the bottom of the vessel like flakes of snow. This substance which is a white, bulky, rather tenacious solid, is an hydrous pyrophosphoric acid. On exposure to the air it rapidly absorbs moisture, with which it constitutes drops of a densely acid, so- lution. When kept for a day or two, it becomes phosphoric acid. This acid maybe also obtained by the cautious addition of phosphor- us to concentrated nitric acid, evaporating the solution thus obtain- ed and subjecting it to a red heat. But this process requires great care and a cheaper and easier method consists, in mixing biphosphate of lime obtained from bones as already described, with carbonate of am- monia ; boiling the mixture for a few minutes, then filtering, and eva- porating the liquid to dryness and igniting it in a platinum crucible. It will be observed that in the processes just noticed, phosphoric acid exists in solution, but by the application of red heat it becomes pyro- phosphoric acid, which remains in the crucible united with water. It concretes on cooling into a kind of glass, which has long been known under the name of Glacial Phosphoric Acid. REFERENCES. The papers of Sir H. Davy already quoted. For abstract? of researches on the combinations of Phosphorus and Oxygen, by Dulong, Berzelius, Davy and Thomson, see Ann. of Phil. ix. xi. a-nc/xiii. ChaptaPa Chem. iii. 78. Johnston's Report on Chemistry. Also, Tumer's Chem. 4th London ed. SALTS OF AMMONIA AND THE ACIDS CONTAINING PHOSPPIORUS. Hypophosphite of Ammonia. Very soluble both in water and in al eohol. Its composition has not been ascertained. Phosphite of Ammonia. A very soluble salt, which is with difficulty brought to crystallize. PHOSPHORUS. 161 Phosphate of Ammonia. Crystallizes in low four-sided pyramids with square bases ; soluble in twice its weight of water at 55 F. ; when heated it fuses, swells, and if the heat be strongly urged, loses its alkaline base, the phosphoric acid being left in the glacial form. This salt may be formed by saturating phosphoric acid with am' monia. Besides the above, which is a neutral salt, there is also a & phosphate. PHOSPHORUS AND CHLORINE. There are two compounds of chlorine and phosphorus, viz. the Pro- tochloride and the Perchloride. Proto chloride of Phosphorus Atom. Num. 63'87 Symb. 1 JC.1+P % gr. 1-45 water=l. PROPERTIES. A transparent and colourless liquid, it does not affect the colour of litmus paper, but the fumes, which it gives off in abun- dance, are acid, owing to contact with the moisture of the atmos- phere ; acts energetically upon water, the hydrogen combining with the chlorine, forming muriatic acid, and the oxygen with the phospho- rus, by which the phosphoric acid is produced, as before described, (p. 159); in which process the muriatic acid is driven off by heat, and pure phosphorus acid remains. PREPARATION. This compound may be made either by heating th e perchloride with phosphorus, or by passing the vapour of phosphorous over corrosive sublimate, heated in a glass tube. Perchloride of PhosphorusAtom. Num. 104*32 Symb. 2% Cl+P. When phosphorus is introduced into chlorine, it inflames spontane- ously, and burns with a pale flame. The product is a white solid, which condenses upon the sides of the vessel. This solid compound, which is the perchloride of phosphorus, is vo- latile at a temperature below 212 ; but may be fused under pressure, and crystallizes in cooling. It acts with violence upon water, forming with its elements phosphoric and muriatic acids. When transmitted with oxygen gas through a red-hot porcelain tube, chlorine is evolved, and phosphoric acid is formed, showing that at high temperatures, the affinity of oxygen for phosphorus, is stronger than that of chlorine. Henry, i. 40 L. REFERENCES. Davy in Phil. Trans, for 1812, under the names of "Phos~ phorane" and " Phosphorana" Also, his Elements of Chem. Phil. Gay Lussac and Thenard, Recherches, Phys. Chini. ii. PHOSPHORUS AND BROMINE. When bromine and phosphorus are brought into contact in a flask filled with carbonic acid gas, they act suddenly on each other with the 162 PHOSPHORUS. evolution of heat and light, and two compounds are generated ; one a crystalline solid which is sublimed and collects in the upper part of the flask, and the other a fluid, which remains at the bottom. The latter is regarded by M. Balard as a Protobromide, and the former as a Dcu- tobromide of Phosphorus. PHOSPHORUS AND IODINE. Iodine and phosphorous combine readily in the cold, evolving so much caloric as to kindle the phosphorus, if the experiment is made in the open air ; but in close vessels no light appears. The combina- tion takes place in several proportions, which have not been determined. Its most interesting property is that of decomposing water, with the formation of hydriodic and phosphoric acids. REFERENCES. Davy, in Phil. Trans. 1814. Gay Lussac, in Ann. de Chim. xci. 9. PHOSPHORUS AND HYDROGEN. Of all the compounds to which chemists have directed their atten- tion, none are perhaps less perfectly understood than those of phos- phorus and hydrogen. All writers on the subject, with the exception of Mr. Dalton, who contends that there is only one species of phos- phuretted hydrogen, admit the existence of two at least. To these Dr. Thomson has added a third, which does not, however, appear yet to have been examined by other chemists. Berzelius recognizes four compounds of phosphorus and hydrogen, containing different propor- tions of hydrogen united to the same of phosphorus. Traite de Chim. i. 263. Hydruret of Phosphor us* Atom. Num. 167 ? Symb.U+P ? SYN. Perphosphuretted Hydrogen Gas. Phosphure Trihydrique. Berzelius. Discovered in the year 1783, by Gengembre, and since particular- ly examined by Mr. Dalton, Dr. Thomson, M. Dumas and Prof. H. Rose. PROPERTIES. A colourless gas, possessing a highly offensive smell, resembling that of garlic, and a bitter taste ; it is very slightly soluble in water ; does not support flame or respiration ; inflames spontane- ously when mixed with air or oxygen gas ; its specific gravity is !] according to Dalton, 0-9027 according to Dr. Thomson, and 1-761 ac- cording to Dumas. It is slightly absorbed by water. Recently boiled water, according to Dalton, absorbs fully one-eighth of its bulk of this gas, most of which is again expelled by boiling or agitation with other gases ; but Dr. * According to Prof. H. Rose, this gas and the next have the same com- position and specific gravity ; both consisting of one volume phosphorus vapour-j-three volumes hydrogen, condensed into two volumes. And this view is said to be confirmed by a fact noticed by Serullas. Johnstons Re- port on Chemistry. PHOSPHORUS. 163 Thomson states that water takes up only about five per cent of its volume. The aqueous solution does not redden litmus paper, nor does the gas itself possess any of the properties of acids. The gas is free- ly and completely absorbed by a solution of sulphate of copper and chloride of lime, by which means its purity may be ascertained, and the presence of hydrogen detected. When this gas is allowed to stand for a few days over water, it de- posits part of its phosphorus without change of volume, and ceases to be spontaneously combustible when mixed with atmospheric air. Ac- cording to Dr. Thomson, it parts with l-4th of its phosphorus under these circumstances, and a peculiar gas, which he has called Subphos- phuretted Hydrogen, is generated ; but M. Dumas maintains that l-3d of the phosphorus is deposited, and that the new gas is identical with protophosphuretted hydrogen, (bihydruret of phosphorus.) It inflames spontaneously when admitted into air or oxygen gas. This is the most remarkable property of this gas, and by means of which it is distinguished from all other gases. If the beak of the re- tort from which it issues, is plunged under water, so that successive bubbles of the gas may arise through the liquid, a very beautiful ap- pearance takcs place. Each bubble on reaching the surface of the wa- ter bursts into a flame, and forms a ring of dense white smoke, which enlarges as it ascends, and retains its shape, if the air is tranquil, until it disappears. This takes place even at the temperature of freezing mercury, as observed by Rose. [Ann. de Chim. etde Ph. Feb. and Jug. 1827.] If received into a vessel of oxygen gas, the entrance of each bubble is instantly followed by a strong concussion, and a flash of white light of extreme intensity. Hence this experiment should be performed with some caution. Silliman's Jour. vi. 187. PREPARATION. Hydruret of phosphorus may be prepared in several ways : 1. By throwing into water the phosphuret of any metal, which me- tal per se will decompose water, as phosphuret of potassium, sodium, calcium, &c. 2. From a combination of phosphorus and the oxides of these me- tals, as potash, soda, lime, &c., by the application of a sufficient heat to enable the phosphorus to effect a decomposition of the'se oxides. 3. By the addition of a dilute acid to phosphorus and those metals which are usually employed in procuring hydrogen gas, as iron, zinc, &c. Sillimans Jour. xii. 294. Bihydruret of Phosphorus* Atom. Numb.I7'7? Symb. 2H+P? SYN. Protophosphuretted Hydrogen, Dumas. Hydrophosphoric Gas, Davy. Phosphure Bihydrique, Berzelius. Discovered by Sir H. Davy in 1812. * This is now (bought to be a compound of 3 hydrogen-j-1 phosphorus, and to be analogous in its composition to Ammonia. And one of the most curious facts lately made out with regard to it, is that it agrees also with ammonia in its power of forming 1 crystallizable compounds with the hydrogen acids. These compounds are, moreover, similar in constitution and in crystalline form to the analogous salts of ammonia. Johnston's Report on Chemistry. 164 CARBON. PROPERTIES. A colourless gas, of a disagreeable odour, though less fetid than the foregoing ; is absorbed by water ; does not take fire spontaneously when mixed with air or oxygen gas at common tem- peratures, but the mixture detonates with the electric spark, or when heated to 300 F.; admitted into a vessel of chlorine, it inflames in- stantly and emits a white light, a property which it possesses in com- mon with perphosphuretted hydrogen ; its specific gravity is estima- ted by Dr. Thomson at 0-9722 ; but M. Dumas found it to be 1-214. PREPARATION. This gas was prepared by Sir H. Davy by exposing to heat in a retort the solid hydrate of phosphorous acid ; and the same gas is evolved by treating the hydrous hypophosphorous acid in the same manner. It is also formed, according to Dumas, by the action of concentrated muriatic acid on phosphuret of lime ; and likewise by the spontaneous decomposition of perphosphuretted hydrogen gas. REFERENCES. Dalto7t's New Syst. of Chem. Phil. Sir H. Davy in PhiL Trans. 1312, containing the first particular examination of Bihydruret of Phosphorus. Thomson's Experiments on Phos. Hyd. Gas. Ann. of Phil. viii. 87. The Essays of Dumas and of Rose, Ann. do Ch. et de Phys. xxxi. xxxiv. Henry's Chem. ii. 692. PHOSPHORUS AND SULPHUR. Sulphur et of Phosphorus. When sulphur is brought into contact with fused phosphorus, they unite readily, but in proportions which have not been precisely de- termined ; and they frequently react on each other with such violence as to cause an explosion. These substances may also be made to com- bine by agitation under water, the temperature of which should not exceed 160 F. The compound has a reddish brown colour, and is fluid at about 40 F. It is more fusible than phosphorus, and is high- ly combustible. BrandesJour. iv. 361. REFERENCES. Pelletier, Ann. de Chitn. iv. 10. Accum and Briggs* Nicholson's Jour. vi. and vii. SECTION V. CARBON. Atom. Num. 6Symb. CSp. gr. 3 52 water=l. Perfectly pure carbon is rare in nature, and cannot be prepared by arl . 1 only occurs in a precious stone called the diamond. The diamond is found in many parts of the East Indies, especially in tli3 provinces of Golconda and Visapour, in Bengal, and in the island of Borneo. About the year 1720, diamonds were first found in the district of Serra Dofrio, in Brazil. They always occur in detached crystals in alluvial soil. The primitive form of the diamond is the regular octahe- dron, each triangular facet of which is sometimes replaced by six se- condary triangles, bounded by curved lines ; so that the crystal be- comes spheroidal, and presents 48 facets. Diamonds with 12 and 24 CARBON. 165 facets are not uncommon. [Jameson s Mineralogy."] The diamond has been found nearly of all colours ; those which are colourless are most esteemed ; then those of a decided red, blue or green tint. Black dia- monds are extremely rare. Those which are slightly brown or tinged with other colours, are least valuable. It is the hardest body in nature. The best tempered steel does not scratch it. It refracts light pow- erfully, and hence Newton was led to conjecture its combustibil- ity ; a conjecture which was rendered probable by the experiments of the Florentine academicians in 1694, and which was subsequently confirmed by several philosophers. The products of its combustion were first examined by Lavoisier in 177*2, arid subsequently with more precision by Guy ton Morveau, in 1785. [Ann. de C/iim. xxxi.] In 1797, Mr. Tennant demonstrated the important fact, that when equal weights of diamond and pure charcoal were submitted to the action of red hot nitre, the results were in both cases the same ; and in 1807, the combustion of the diamond in pure oxygen, was found by Messrs. Al- len and Pepys to be attended with precisely the same results as the combustion of pure charcoal. Hence the inevitable inference that charcoal and the diamond are substances similar in their chemical na- ture ; differing only in mechanical texture. [Phil. Trans. 1807.] This view was confirmed by Sir H. Davy, [Phil. Trans. 1814,] who com- pared the product of the combustion of the diamond with that derived from different kinds of charcoal. Further proof of the identity of charcoal and the diamond, is furnished by the fact that the diamond converts iron into steel, under circumstances quite free from all sources of fallacy. Phil. Trans. 1815, 371. Next to the diamond the most remarkable and purest forms of car- bon, are 1. Graphite or Black Lead. A mineral of a lead grey colour, from which common crayons are manufactured, found in beds in mountains belonging to primitive formations. As it generally leaves after its combustion a cinder which contains much iron, it was supposed to be a compound of carbon with about 5 per cent, of this metal. But more recent researches, especially those of Karsten, have proved beyond a doubt that it is a peculiar form of carbon, and that the foreign sub- stances which accompany it, are merely accidental. The graphite of Barreros is Brazil, leaves scarcely a trace of residuum when it is burn- ed. Berzelius, i. 313. 2. Anthracite. Another species of fossil carbon, differing from coal in that, when sufficiently heated, it burns without flame, odour or smoke. 3. Cook. A name applied in England to a carbonaceous mass of an iron black colour, and semi-metallic lustre, which remains after coal has been deprived, by means of heat, of ail the volatile parts which it contains. 4. Charcoal. A substance obtained by burying in sand, in a crucible, pieces of oak, willow, hazel, or other woods deprived of bark, and ex- posing them covered to the strongest heat of a wind furnace. For purposes of accuracy, charcoal must be used when recently prepared, and before it has had time to become cold ; or if it cannnot be had fresh made, it must be heated again to redness under sand in a cruci- ble. Different kinds of wood furnish variable quantities of charcoal ; ma- hogany, oak, fir and box are the most highly esteemed. See Allen and Fepys, Phil. Trans. 1807. 166 CARBON. In the large way, charcoal is often prepared by the distillation of wood in cast-iron cylinders. The loppings of young trees, commonly called crop-wood, are generally employed ; and, besides the charcoal, liquid products of value are collected, especially an impure vinegar, known under the name of pyroligneous acid. Parkes' Chem. Essays, ii. 271. The more common method, in this country especially, is to form the wood into a conical pile, which being covered with earth or clay, is suffered to burn with a limited access of atmospheric air, by which its complete combustion, or reduction to ashes, is prevented. 5. Lampblack. This is obtained chiefly by turpentine manufactur- ers, from refuse resin, which is burned in a furnace so constructed that the dense smoke arising from it may pass into chambers hung with sacking, where the soot is deposited, and is swept off from time to time, and sold without further preparation. When heated red hot in a close vessel, it forms a very pure carbon. Lampblack may also be obtained by passing the vapour of the oil of turpentine, or of spirit of wine, through a red hot tube ; or by the combustion of camphor, which forms the basis of a very fine black paint. 6. JUnimal charcoal. This is obtained by subjecting bones to a red heat in a covered crucible. It is a black mass, of a metallic lustre, consisting of charcoal mixed with the earthy matters of the bone. When reduced to powder, it occurs in commerce under the name of Ivory black. 7. A new and curious form of carbon has been described by Dr. Colquhoun of Glasgow. When coal gas is passed over red hot iron, in Mr. Mackintosh's process for converting iron into steel, this variety of carbon is deposited in long capillary threads, very fine, brittle, per- fectly black, and having considerable lustre. In its external appear- ance, though this is the most perfect, many shades of difference oc- cur. Jinn, of Phil, xxviii. 1. PROPERTIES OF CHARCOAL. A black, insoluble, inodorous, insipid, brittle substance ; an excellent conductor of electricity, but a bad con- ductor of heat ;* unchanged by the combined action of air and moist- ure at common temperatures ; infusible, and easily combustible in oxygen gas ; is capable of destroying the smell and taste of a variety of vegetable and animal substances. Lowitz, Crells Annals, ii. 165. Charcoal has the property of absorbing gases icithout alteration. Fill a jar with common air, or any other gas, and place it over dry mercury ; take a piece of charcoal, red-hot from the fire, and plunge it in the mercury of the bath ; when cold, let it be passed into the ves- sel of gas, without bringing it into contact with the atmosphere. A considerable diminution of the gas will be effected ; and in 24 or 36 hours its absorption will be completed. This property of charcoal has been made the subject of valuable sets of experiments by Saussure and Count Morozzo. [Ann. of Phil. * Dr. Thomson states, on the authority of Cheuvreusse, (hat charcoal form- ed under a red heat is a non-conductor of electricity, and cannot be employed as one of the elements of the Voltaic battery. It is also a bad conductor of heat. Charcoal formed by a red heat is an excellent conductor of electricity and of heat, and is not nearly so combustible as the first species. Inorganic Chem. i. 149. CARBON. 167 vi. 241. Henry's Chem. i. 361.] The absorption appears to be a mere mechanical effect ; for even those gases which have an affinity for charcoal, (as hydrogen and oxygen,) are given out unchanged at the heat of boiling water. Thenard, i. 219. It resists the putrefaction of animal substances. Meat which has be- come tainted may even have its sweetness restored by rubbing with charcoal, and may be preserved sweet by being buried in its powder. It also produces the remarkable effect of destroying the colour and smell of many animal and vegetable substances. Common vinegar, by being boiled with it, becomes perfectly colourless ; and red wines, rum or brandy may be bleached by filtration through it. It is largely employed, for this purpose, in the process of sugar refining, and for preparing colourless crystals of citric acid and other vegetable pro- ductions. Charcoal, prepared by calcining animal substances in close vessels, has been found most efficacious for these purposes. Ann. de Chim. Ixxix. 80. Brandes Jour. iv. 367. See also Graham's paper on the effects of Animal Charcoal on solutions. Brandes Jour. N. S. vii. 120. It is a very slow conductor of heat. The experiments of Guyton Morveau have determined, that caloric is conveyed through charcoal more slowly than through sand, in the proportion of three to two. Hence powdered charcoal may be advantageously employed to sur- round substances which are to be kept cool in a warm atmosphere ; and also to confine the caloric of heated bodies. It affords, however, an easy transmission to the electric fluid. Spontaneous inflammation of powdered charcoal. It has long been known that charcoal in a state of fine powder, often inflames sponta- neously. The subject has recently been examined by Col. Aubert of the French artillery, and others, arid some interesting facts have been made known. It appears that spontaneous combustion ensues in al- most all cases when 20 or 30 cwt. of charcoal in a state of minute di- vision, are put together in a heap and left undisturbed. Col. Aubert ascribes the combustion in such cases to the absorption of air which occasions a disengagement of heat ; but it is most probably owing, as is suggested by Mr. Davies, to the action of air and moisture on the minute portions of potassium which charcoal contains. Perhaps this may also account, at least in some degree, for the singular power of absorption which charcoal possesses. See Land, and Edin. Phil. Mag. iii. 1 and 89. REFERENCES. Tennaut on the nature of the Diamond, Phil. Trans. 1797. Repert. of Arts, 1st ser. viii. 113. Mawe's Treaties on Diamonds, fyc. Cheuvreusse's P hy si co- Chemical Researches on Charcoal, Ann de Chim. Aug. 1825, and in Repert. of Patent Inventions, ii. 387. Parkes* Chem. Essays, ii. 249, containing an account of the various forms of Carbon, me- thods of preparing Charcoal, SfC. Spc. Doolittle^s new method of making Charcoal. Killimari's Jour. xvii. 395. CARBON AND OXYGEN. There are two compounds of these substances, the one known un- der the name of Carbonic Oxide, the other of Carbonic Acid, 168 CARBON. Carbonic Oxide. Atom. Num. 14 Symb.Q-\-C Sp.gr. O-9721 air-1. SYN. Gaseous Oxide of Carbon. This gas appears to have been first obtained by Dr. Priestley ; but its true nature was first made known by Mr. Cruickshanks of Wool- wich, in 1802. [Nicholson's Jour. 4to. v.J and it was afterwards more particularly examined by M. M. Clement and Desormes. Ann. de Chim. xxxix. 26. PROPERTIES. A gaseous body, of an offensive smell, colourless and insipid ; very sparingly soluble in water, and it does not in any way af- fect the colour of blue vegetable infusions ; it is inflammable, and when set on fire as it issues from the orifice of a small pipe, burns with a fee- ble blue flame, but a lighted taper plunged into ajar full of the gas is in- stantly extinguished ; is noxious to animal life, when received into the lungs, and when respired for a few minutes produces giddiness and fainting. Phil. Mag. xliii. 367. .Beck's Med. Juris. 305. When a mixture of carbonic oxide and an equal bulk of hydrogen, is passed through an ignited tube, the tube becomes lined with char- coal. At this temperature, the hydrogen attracts oxygen more strong- ly than it is retained by the charcoal, and water is formed. When mixed with half its volume of oxygen gas, and the mixture fired over mercury, in a detonating tube, 150 measures of the mixture will be converted into 100 measures of carbonic acid, if the gases employed be perfectly pure. It was found, also, by Gay Lussac, that carbonic oxide is decomposed by the action of potassium, which combines with the oxygen, and precipitates charcoal ; and Dobereiner by bringing it into contact with sulphuretted oxide of platinum, converted it into half its volume of carbonic acid. PREPARATION. This gas may be prepared in either of the following ways. 1. By introducing into a gun barrel a mixture of equal parts of well dried carbonate of baryta, or of lime, (common chalk,) and charcoal pulverized, or of chalk and dry zinc or iron filings, and exposing them to a strong heat. In this case the charcoal, iron or zinc filings com- bine with one proportion of oxygen in the carbonic acid of the carbon- ate of lime or baryta, and convert it into carbonic oxide. 2. By transmitting carbonic acid gas over charcoal ignited in a por- celain tube, the acid gas combines with an additional dose of charcoal, loses its acid properties, and is converted into a double volume of car- bonic oxide. 3. By mixing binoxalate of potassa, [salt of sorrel,] with five or six times it weight of concentrated sulphuric acid, and heating the mix- ture in a glass bottle. [Dumas, Ann. dc Chim.etde Phys. xxxiii, 110.] The evolved gas, after removing the carbonic acid by washing in lime water or liquid potassa, is pure carbonic oxide. This washing is, in- deed, necessary, from whatever source the gas may have been ob- tained. To understand the theory of this process, we should remark that oxalic acid is a compound of equal measures of carbonic acid and car- bonic oxide, or at least its elements are in the proportion to form these gases ; and that it cannot exist unless in combination with water, or CARBON. 169 some other substance. Now the sulphuric acid unites with both the potassa and water of the binoxalate. and the oxalic acid being thus set free, is instantly decomposed. Oxalic acid may be substituted in this process for the binoxalate of potassa. Carbonic Add Atom. Num. 22Symb. 2O+C Sp. gr. 1-5277 air=L This acid was discovered by Dr. Black, in 1757, and described by him, in his inaugural dissertation, de Magnesia Alba, under the name of Fixed Mr. Its nature was first demonstrated synthetically by La- voisier, and analytically by Mr. Tennant. PROPERTIES. A colourless, inodorous, elastic fluid, possessing all the physical properties of the gases in a high degree, and requiring a pressure of thirty-six atmospheres to condense it into a liquid ; is rather more than by one half heavier than atmospheric air ; it is per- fectly uninflammable, and instantly extinguishes flame ; is speedily fatal to animal life, even when in moderate proportion ; is absorbed by water to the amount of its own bulk, under common pressure and tem- perature, but the quantity taken up may be greatly increased by in- creasing the pressure; the solution has an agreeable subacid taste, and reddens paper stained with the blue colour of litmus. It extinguishes flame. Set a vessel filled with the gas, with its mouth upwards, and let down alighted candle. The candle will be instantly extinguished. The combustion, in this case, does not cease from the want of oxygen only, as appears from the fact that a candle cannot burn in a gaseous mixture composed of four measures of atmospheric air and one of carbonic acid. It appears therefore to exert a positive influence in checking combustion. It is heavier than atmospheric air. From the great specific gravity of carbonic acid, it will remain for some time at the bottom of a jar with its mouth turned upwards ; and may be poured from one such vessel into another like water. It is an amusing experiment to place a light- ed taper in the bottom of the jar, as it will be instantly extinguished by pouring the gas upon it like a liquid. It is owing to the same property that carbonic acid gas is often found at the bottom of grottoes, of deep wells and of mines, the up- per part of which is entirely free from it, and which, from its injurious effects, is called by the miners, choak damp. Hence the precautions, used by the sinkers of wells, of letting down a candle before they ven- ture to descend in person.* It is absorbed by water. This may be easily demonstrated, by agitat- ing the gas with that liquid, or by leaving a jar full of it inverted over water. In the first case the gas disappears in the cburse of a minute ; in the latter it is absorbed gradually. If more pressure be ap- plied, the amount absorbed by water is greatly increased. Dr. Hen- ry has ascertained, from an extensive series of experiments, that the quantity of gas absorbed by water is directly as the pressure ; that * This can generally be depended on ; but Dr. Christison states that some instances have been known of the atmosphere being sufficiently loaded with carbonic acid to produce insensibility, and yet not so impure as to extinguish a burning candle. Treatise on Poisons, 2o? ed. 707. 170 CARBON. is, water dissolves twice its volume, when the pressure is double, and three times its volume, when the pressure is treble, &c. [Henry's Chem. i. 372. Phil. Trans. 1803.] It is by the strong compression of a forcing pump that the common soda water is so highly charged with this gas. The pleasant pungency of brisk and sparkling fermented liquors is owing to the Carbonic acid which they hold in solution, and which they lose upon exposure to the air, and thereby become flat and stale. It possesses acid properties. This may be shown by dipping into wa- ter impregnated with it, a bit of litmus paper, or by mixing with a portion of the liquid about an equal bulk of infusion of litmus ; in both cases the litmus will be reddened. This fact establishes the title of the gas to be ranked among acids. When an infusion of litmus, which has been thus reddened, is either heated or exposed to the air, its blue colour is restored, in consequence of the escape of carbonic acid. This is a marked ground of distinction from most other acids, the effect of which is permanent, even after boiling. It produces turbidness and precipitation when passed through lime water. This is produced by the combination of the lime with the gas, forming carbonate of lime, which, from its insolubility in water, at first renders the solution milky, and afterwards forms a white flaky precipitate. Hence lime water is not only a valuable test of the pres- ence of carbonic acid, but is frequently used to withdraw it altogeth- er from any gaseous mixture that contains it ; but in order to effect its entire absorption, recourse must be had to a solution of caustic potassa or soda. SOURCES AND PREPARATION. Carbonic acid is produced in several cases of combustion ; and also during the process of respiration. It is moreover a constant ingredient of atmospheric air. See page 126. It may be artificially prepared by burning carbon, either pure char- coal or the diamond, in oxygen gas. But it is most conveniently ob- tained, for the purposes of experiment, by the action of muriatic acid, diluted with two or three times its weight of water, on fragments of marble. The muriatic acid unites with the lime, forming a muriate of lime, and carbonic acid gas escapes, with effervescence. It may also be obtained by subjecting any of the carbonates, and especially carbon- ate of lime, to heat in an iron retort. ACTION ON THE ANIMAL ECONOMY. When an attempt is made to in- spire pure carbonic acid, a violent spasm of the glottis takes place, which prevents the gas from entering the lungs. If it be so much di- luted with air as to admit of its passing the glottis, it then acts as a narcotic poison on the system, [t is this gas which has often proved destructive to persons sleeping in a confined room with a pan of burn- ing charcoal. REFERENCES. ChaptaPs Chem. iii. 12, containing a detailed account of Carbonic Acid. Sanssure on the quantity of, in the Atmosphere, Ann. de Ch. et de Ph. ii. 199, and Ann. of Phil. ix. 41. On the quantity of Car- bonic Acid emitted from the lungs during respiration, at different titnes, see the very able papers of Prout, in the Ann. of Phil. ii. 328. and iv. 331. Faraday on the liquefaction of Carbonic Acid. Ann. of Phil, xxiii. 95. Brunei's Apparatus for the condensation of } into a liquid. Repert. of Pat. Invent, ii. 157. CARBON. 171 SALTS OF CARBONIC ACID AND AMMONIA. Carbonate of Ammonia Atom. Num. 39Symb. (3H+N) +(20+C.) r A dry white volatile powder, which has an ammoniacal odour and alkaline properties ; obtained only by mixing dry carbonic acid over mercury with twice its volume of ammoniacal gas. Sesquicarbonate of Ammonia. Atom. Num. 59 Symb. (3H+N)+lJ(20+C)+lAq. SYN. Subcarbonate of Ammonia U. S. Phar. PROPERTIES. When fresh prepared, this salt has a crystalline ap- pearance, and some transparency, and is hard and compact ; it has a pungent smell, and a sharp penetrating taste, and affects vegetable blues as uncombined alkalies do ; it dissolves in twice its weight of cold, or an equal weight of boiling water, but at the latter temperature it gives off part of its acid ; when exposed to the atmosphere it loses weight very fast, ceases to be transparent, and becomes inodorous, brittle, and easily reducible to powder, which is the bicarbonate. PREPARATION. The sesquicarbonate of ammonia is prepared by heating a mixture of one part of muriate of ammonia with one part and a half of carbonate of lime, carefully dried. Double decompo- sition ensues during the process ; muriate of lime remains in the re- tort, and the sesquicarbonate of ammonia is sublimed. The carbonic acid and ammonia are, indeed, in proper proportion in the mixture for forming the real carbonate ; but from the heat employed in the sub- limation, part of the ammonia is disengaged in a free state. Bicarbonate of Ammonia Atom. Num. 61 Symb. (3H-J-N) +2 (20+C). Crystallizes in small six sided prisms, which have no smell, and but little taste. It was formed by Berthollet by transmitting a current of carbonic acid gas through a solution of the common carbonate of am- monia of the shops. On evaporating the liquid, the bicarbonate is de- posited in a crystalline form. REFERENCES. Ure^s Experimental Researches on the Ammoniacal Salts, Ann. of Phil. x. 203, 278. R. Phillips on the Carbonate of Ammonia, fyc. Brande^s Jour. vii. 294. Same author QJI the Bicarbonate of Ammonia, Ann. of Phil. xvii. 110. CARBON AND CHLORINE. For our knowledge of two compounds of these bodies, we are indebt- ed to the able researches of Mr. Faraday. [Phil. Trans. 1821.] An- other was first described by M. Julin of Abo. [Ann. of Phil. xvii. 216.] And recently a fourth has been added by Liebig. The composition of these chlorides will be seen by the following table : 172 CARBON. Subchloride of Carbon, .... C1+2C= 47-45 Protochloride of Carbon, - - - Cl-f C= 41-45 New Chloride of Liebig, - - - - 2iCl-f-2C=100-63 Perchloride of Carbon, .... 3Cl-f-2C=118-35 Subchloride of Carbon. This compound was discovered, in smal quantities, by M. Julin, in a manufactory of nitric acid, from nitre and sulphate of iron, in Sweden. It is in the form of white feathery crys- tals, rather heavier than water, and insoluble in that fluid. It has a pe- culiar smell, resembling spermaceti, and is tasteless. It is soluble in alcohol and ether, and burns in the flame of a lamp, with a greenish colour. It was made the subject of analysis by Messrs. R. Phillips and Faraday. Protochloride af Carbon. A limpid and colourless fluid ; does not assume the solid form even at F. ; is volatilized at 160 J or 170 F. ; may be distilled without change, but is partly decomposed at a red heat; sp. gr. 1-5526. PREPARATION. This compound is obtained by passing the vapour of perchloride of carbon through an ignited glass tube containing frag- ments of glass or rock crystal, to increase the heated surface. The perchloride is partly decomposed, chlorine escapes and a fluid passes over which may be separately condensed and is the protochloride. Perchloride of Carbon. A transparent colourless brittle solid, hav- ing an aromatic odour resembling that of camphor ; sp. gr. 2, being exactly double that of water ; fuses at 320 F., boils at 360 J , and may be distilled without change, assuming a crystalline form as it condens- es ; burns vividly in oxygen gas, and with a red light when held in the flame of a spirit lamp ; is soluble in alcohol, ether, and in the fix- ed and volatile oils, but sparingly so in water. This chloride is obtained by mixing olefiant gas (a compound of chlo- rine and hydrogen,) with chlorine, arid exposing the oily liquid which results from their combination to the direct solar rays, in a vessel full of chlorine gas. The chlorine acts upon and decomposes the liquid, muriatic acid is liberated and the carbon at the moment of separation, unites with chlorine. REFERENCES. Faraday's Memoir, containing a detailed account of the two last compounds, republished from the Plnl. Trans, in the Ann. of Phil. xviii. 104. New Chloride of Licbig. A limpid, colourless liquid, similar in odour and appearance to the oily fluid which chlorine forms with olefiant gas ; density 1-48; boils at 141 F. ; is soluble in alcohol and ether, but not in water ; is feebly combustible and is not changed at moderate temperatures either by acids or alkalies. The new chloride may be conveniently prepared by distilling from a capacious retort, a mixture of 1 pound of chloride of lime, 3 pounds of water, and 2 or 3 ounces either of alcohol or pyro-acetic spirit. CARBON. 173 CARBONIC OXIDE AND CHLORINE. Chlorocarlonic Add Atom. Num. 49*45 Symb. (O+C)+ Cl. Sp.gr. 34421 air=l. This compound was discovered in 1812 by Dr. John Davy, who des- cribed it in the Philosophical Transactions for that year, under the name of Phosgene Gas. It is made by exposing a mixture of equal measures of dry chlorine and carbonic oxide gases to sunshine, when rapid but silent combination ensues, and they contract to one-half their volume. Diffused day-light also effects their union slowly ; but they do not combine at all when the mixture is wholly excluded from light. PROPERTIES. A colourless gas, having a strong odour, and redden- ing dry litmus paper. It combines with four times its volume of am- moniacal gas, forming a white solid salt ; so that it possesses the characteristic property of acids. By contact with water it is changed into muriatic and carbonic acid gases. Several of the metals decom- pose it, and unite with the chlorine, evolving carbonic oxide, equiva- lent in volume to the original gas. Chlorocarbonic acid then affords an example of an acid with a sim- ple base, and two acidifying principles, oxygen and chlorine, which are not often united in the performance of this function. Chloral. This name, derived from the first syllable of the words chlorine and alcohol, has been applied by Liebig to a new compound of chlorine, carbon and oxygen prepared by the mutual action of alcohol and chlorine. It is a colourless, transparent liquid of a penetrating pungent odour, and nearly tasteless, or at most oily ; it boils at 201 F. and may be distilled without change. Liebig considers it to con- sist of 9 atoms of carbon, 6 chlorine, and 4 oxygen. For details con- cerning the properties and mode of preparation of this substance, see Ann. de Chim. et de Phys. xlix. 146. Also. Turner's Chem. 4th Land. Ed. CARBON AND BROMINE. Bromide of Carbon. This compound is formed by mixing together one part of iodide of carbon and two parts of bromine. Bromides of carbon and of iodine are formed, the latter of which is removed by a solution of caustic potash. It is a colourless liquid, at common tem- peratures, but crystallizes at 32 F. It has a sweetish taste, an ethe- real odour, is very volatile and scarcely soluble in water. Berzelius, i. 360. Ann. de Chim. et de Phys. xxxix. 225. CARBON AND IODINE. Periodide of Carbon. When a solution of pure potassa in alcohol is mixed with an alcoholic solution of iodine, a portion of alcohol is de- composed ; and its hydrogen and carbon, uniting separately with iodine, give rise to periodide of carbon and hydriodic acid. The latter combines with the potash and remains in solution. The former has a yellow colour, like sulphur, and forms scaly crystals of a pearly lustre ; its taste is very sweet and it has a strong aromatic odour resembling saffron. Ann. de Chim. and de Phys. xxxvii. 86. L 174 CARBON. CARBON AND HYDROGEN. Chemists have for several years been acquainted with two distinct compounds of carbon and hydrogen, the carburetted hydrogen, and the olefiant gas. Besides these, a third has been pointed out by Mr. Dalton, as entering into the composition of oil and coal gas. to which he proposes that, provisionally, the name of Super- Olefiant Gas should be given ; and Mr. Faraday has further enlarged our knowledge of these compounds, by making us acquainted with at least two others. [Phil. Trans. 1825.] According to Dr. Thomson, naphtha and naph- thaline, are likewise pure hydrurets of carbon. The following is a table of the gaseous compounds of carbon and hydrogen : 1. Hydruret of carbon, (Olefiant gas,) 12 C.+2 H.=14. 2. Bihydruret of carbon, . . . 6 C.-J-2 H.=8. 3. Super-olefiant, .... 18 C.-f 3 H.=21. 4. Bicarb. Hyd. .... 36 C.+3 H.=39. 5. Quadrocarb. Hyd. . . . 24C.+4H.=28. It should be remarked, however, that Thenard does not consider the compounds described by Faraday, as distinct ; and Berzelius, by not noticing them in his treatise in connection with the other compounds, seems to incline to the same opinion. At all events, their nature is by no means clearly established, and I shall therefore only present a brief notice of them, and refer to authorities, as a guide to those who wish to examine the subject more at length. Hydruret of Carbon Atom. Num. H.Symb. 2 H+2 C. Sp. gr. 0-9709 air=l. SYN. Olefiant Gas. Bicarburetted or Percarburretted Hydrogen. This gas was discovered in 1796, by some associated Dutch chem- ists, who gave it the name of Olefiant Gas. But the above name ap- pears to be more in conformity with the principles of chemical no- menclature. PROPERTIES. A colourless elastic fluid, which has no taste, and scarcely any odour when pure ; is absorbed by water to the amount of about one-eighth of the volume of the latter ; it extinguishes flame, is unable to support the respiration of animals, and when set on fire, as it issues from the orifice of a small pipe, burns slowly, with the emis- sion of a dense white light ; when mingled with a proper quantity of oxygen gas, it forms a mixture which may be kindled by flame or the electric spark, and which explodes with great violence ; it is decom- posed by being passed through red hot tubes of porcelain, and it then deposits its carbon, and is expanded into twice its original volume of hydrogen ; it is powerfully acted on by chlorine, uniting with it, as well as with iodine, at ordinary temperatures. When olefiant gas is mixed with oxygen and fired, it explodes. If the mixed gases are fired by electricity in a Volta's eudiometer, it is apt, unless very small quantities be employed, to burst the instrument. One volume requires three volumes of pure oxygen gas, and affords two volumes of carbonic acid gas. But in order to insure the perfect combustion of the inflammable gas, it should be mixed with five times its CARBON. 1 75 bulk of oxygen of at least 90 per cent, purity. If too little oxygen be used, charcoal is apt to be precipitated unburned ; and a small excess of oxygen does no harm, but remains in the mixture. When fired with less than its own bulk of oxygen, the separation of charcoal is evident, and the bulk of the residue is greater than that of the original gases. Henry's Cliem. i. 444. It may be decomposed by heat. When it is passed through a porce^ lain tube at a low red heat, charcoal is deposited, and an equal volume of the bihydruret of carbon is produced ; but at a white heat, the lat- ter is also decomposed, and the gas is greatly increased in volume. It is powerfully acted on by chlorine. When olefiant gas and chlorine are mixed together in the proportion of one measure of the former and two of the latter, they form a mixture which takes fire on the approach of flame, and which burns rapidly with the formation of murialic acid gas, and deposition of a large quantity of charcoal. But if the gases are allowed to remain at rest after being mixed together, a very differ- ent action ensues. The chlorine, instead of decomposing the olefiant gas, enters into direct combination with it, and a yellow liquid-like oil is generated. This substance is sometimes called Chloric Ether; but the term Chloride of Hydrocarbon, as indicative of its composition, is more appropriate. Iodine and bromine also form similar compounds with olefiant gas, all of which we shall notice hereafter. PREPARATION. This gas may be obtained by mixing in a large glass retort, three measures of strong sulphuric acid, and one measure of alcohol, or spirits of wine, and applying heat ; the mixture soon as- sumes a black colour and thick consistence, and a copious disengage- ment of gaseous matter takes place, which may be collected over wa- ter or mercury. After agitation with lime-water or solution of potas- sa, to separate carbonic and sulphurous acids, pure hydruret of carbon remains. In order to understand the theory of this process, it is necessary to state, that alcohol is supposed to consist of one proportion of olefiant gas and one of water. The separation of the water is effected by the sulphuric acid, for which it is known to possess a great attraction. The first portions which escape from the mixture, consist of ether, which will be understood from the fact, that ether consists of two pro- portions of olefiant gas, combined with one of water, differing there- fore from alcohol in the amount of water which it contains, being in this respect intermediate between alcohol and olefiant gas. Pihydruret of Carbon Atom. Num. SSymb. 2 H-f C Sp. gr. 0-5554 air=l. SYN. Heavy inflammable air. -Gas of marshes. Hydrocarburet and Protocarburet of Hydrogen. Light Carburetted Hydrogen. The real nature of this gas was first ascertained by Dal ton, and it has since been examined by Sir H. Davy, Thomson and Henry. PROPERTIES. A colourless, permanent gas, soluble in very minute proportions in water, with little odour ; it extinguishes all burning bodies, and is of course unable to support the respiration of animals ; it is highly inflammable, and when a jet of it is set on fire, it burns with a yellowish flame, and much stronger light than is given out by hydro- gen gas ; when mixed with atmospheric air or oxygen, in certain pro- 176 CARBON. portions, it explodes with violence upon contact with flame ; it is in part only resolved into its elements by the most intense heat. When mixed with oxygen gas and fired, it explodes. To decompose this gas completely, it is necessary to mix it with rather more than twice its bulk of oxygen gas ; but exactly two volumes are consumed. Water and a quantity of carbonic acid are produced, the latter being precisely equal to the original bulk of the inflammable gas. ACTION OF CHLORINE. When the bihydruret of carbon and chlorine are mixed together over water, no action takes place if light be care- fully excluded ; but if exposed to the light of day, and still more rapidly in the light of the sun, a series of decompositions ensue. Mu- riatic and carbonic acids are farmed, the former of which is instantly absorbed. PREPARATION AND NATIVE STATE. This compound of carbon and hydrogen may be obtained, mixed, however, with about 1-20 of car- bonic acid, and 1-15 or 1-20 of nitrogen gas, by stirring the bottom of almost any stagnant pool of water, especially if formed of clay. When this is done by an assistant, the gas is copiously disengaged in bubbles, which may be collected either in an inverted glass jar, or in an inverted bottle filled with water, into the mouth of which a funnel is fixed. It should be washed, when collected, with lime water or liquid potassa. It may also be procured by the purification of gas from coal, by means of chlorine and solution of potassa, applied in succession. Bicarburct of Hydrogen. Atom. Num. 39 Symb. 3H+60. When oil gas is subjected, in proper vessels, to a pressure of thirty atmospheres, a fluid is deposited in the proportion of nearly a gallon from 1000 cubic feet, which may be drawn of and preserved in glass bottles of ordinary strength. By repeated distillations, and by expo- sing the distilled liquid to a temperature of zero, Mr. Faraday obtain- ed a substance to which he has applied the above name. The bicarburet of hydrogen, at common temperatures, is a colour- less transparent liquid, which smells like oil gas, and has also a slight odour of almonds ; its specific gravity is nearly 0.85 at 60 F. ; at 32 it is congealed, and forms dendritic crystals on the sides of the glass ; at zero is transparent, brittle, and pulverulent, and is nearly as hard as loaf-sugar ; when exposed to the air, at the ordinary tempera- ture it evaporates, and boils at 186 ; it is only slightly soluble in wa- ter, but freely so in alcohol and ether, fixed and volatile oils ; it is com- bustible and forms a powerful detonating mixture with oxygen. Quadro carburet of Hydrogen. Atom. Num. 28 Symb. 4H+4C. The second carburet of hydrogen discovered by Mr. Faraday, to which the above name has been applied, was derived from the same source as the preceding. It is obtained by heating with the hand the condensed liquid from oil gas, and conducting the vapour which escapes through tubes cooled artificially to zero. A liquid is thus CARBON. 177 procured, which boils by slight elevation of temperature, and before the thermometer rises to 32- F., is wholly reconverted into vapour. This vapour at 60 F. is highly combustible, and burns with a bril- liant flame ; has the specific gravity of 27 or 28, hydrogen being 1 ; it is sparingly absorbed by water, but alcohol takes it up in large quan- tities, and the solution effervesces on being diluted with water ; olive oil dissolves about six times its volume, and one volume of sulphuric acid condenses above 100 volumes of the vapour with the evolution of great heat ; the acid is much blackened, and on dilution becomes tur- bid, but gives out no gas. The vapour on being cooled down to F. is again condensed into a liquid, which when examined in a tube hermetically sealed, has a specific gravity of 627 at 54 ; it is therefore the lightest fluid known., Henry, 1 , 450. REFERENCES. Faraday in Phil. Trans, for 1825, or Ann. of Phil. xxvii. 44. Naphtha from Coal Tar. And Naphthaline. Both these substances are obtained by distillation from coal tar. The former has received its name from its similarity to mineral naph- tha. It has a strong and peculiar empyreumatic odour, and is highly inflammable. Potassium may be preserved in it without loosing Its lustre. It is composed according to Dr. Thomson, of six atoms carbon and six atoms hydrogen=42. Naphthaline, is a white crystalline solid, heavier than water ; has a pungent aromatic taste, and a peculiar faintly aromatic odour; it freezes at 180 F. and assumes a crystalline texture in cooling ; it volatilizes slowly at common temperatures and boils at 410 F. ; is not very readily inflamed, but when set on fire burns rapidly, and emits a large quantity of smoke ; insoluble in cold and sparingly soluble in hot water, but freely so in alcohol and ether ; is not acted upon by the alkalies, but is dissolved by the acetic and oxalic acids forming pink coloured solutions and combines with sulphuric acid ; it probably con- sists of 1 atom hydrogen and 3 atoms carbon=19. Naphthaline combines with sulphuric acid. By the combination of these two substances an acid is formed which was first described by Mr. Faraday in 1826. under the name of Sulpho-Naphthalic Acid. It has a bitter acid taste, reddens litmus powerfully and combines with bases forming salts which are called Sulpho-Napthalates. Faraday in PhiL Trans, for 1826. MIXED COMBUSTIBLE GASES FROM MOIST CHARCOAL, ALCOHOL, ETHER, COAL, OIL, TALLOW AND WAX FIRE DAMP. The preceding compounds of carbon and hydrogen, are the only ones which are considered as distinct and definite compounds, and perhaps, two of these are not yet entitled to be so considered. It is of a mixture of two or more of these, with occasionally a portion of carbon- ic oxide, that the almost infinite variety of aeriform products are constituted, which are obtainable by the exposure of moistened char- coal, of alcohol or ether, of oil, tallow, wax, resin or coal, to a heat a little above ignition. 178 CARBON. Of these aeriform compounds, the gases from coal and from oil, are of most importance, from their widely extended use in artificial illumi- nation. Coal Gas. By submitting coal to distillation in an iron retort, be- sides a portion of tar and a solution of carbonate of ammonia, which condense in a liquid form, a large quantity of permanent gas is evolv- ed. This gas is very variable in its composition and properties, not only when prepared from different coals, but from the same kind of coal under different circumstances. [Henry, Phil. Trans. J808 and 1820.] The general term of coal gas is, therefore, quite indefinite, and it is probably a mixture of several varieties of carburetted hydro- gen with hydrogen gas, carbonic oxide, carbonic acid, nitrogen, and sulphuretted hydrogen gases. Henry's Chem. i. 452. Coal gas, as generally procured, has a very disagreeable odour, arising from sulphuretted hydrogen, and perhaps a little sulphuret of carbon ; but these may be removed by passing it through lime sus- pended in water, by agitation. The specific gravity of the purified gas varies from 0*450 to 0-700. A large quantity of an impure carbon, called coke, is found in the retorts, after the extraction of the gas. It is scarcely possible to assign the quantity of gas, which ought to be obtained from a given weight of coal, but it may be considered as an approach to a general average to state, that 112 Ibs. of good coal are capable of giving from 450 to 500 cubic feet of gas, of such quali- ty that half a cubic foot per hour is equivalent to a mould candle of six to the pound, burning during the same space of time. Henry's Che,,i. i. 453. Oil Gas. Oil, by being allowed to trickle into a red hot retort, half filled with coke or pieces of brick to increase the heated surface, is de- composed, and yields a large quantity of gas, which is much richer in carburetted hydrogen than coal gas, and is, therefore, much better fit- ted for purposes of illumination. Its specific gravity varies from 0'800 to 0-950. It contains no admixture of sulphuretted hydrogen, and requires no purification. It is, however, more expensive than the coal gas. See an Essay ly Drs. Turner and Christison in the Edin. PhiL Jour. xiii. 1. It has also been ascertained, by Mr. Daniell, that rosin by peculiar treatment, yields an abundance of gas, equal in quality to that from oil, and at about one-fourth of the expense ; its smell moreover is much less offensive than that of either coal or oil gas, and it has been introduced with success in several large establishments in England. L. U. K. Fire Damp. The fire damp of coal mines was proved by an analysis of Dr. Henry, [Nicholson's Jour. xix. 149,] to be identical in compo- sition, with light carburetted hydrogen. This gas often issues in large quantity from between beds of coal, and by collecting in mines, owing to deficient ventilation, gradually mingles with atmospheric air, and forms an explosive mixture. The first unprotected light which then approaches, sets fire to the whole mass, and a dreadful explosion en- sues. These accidents are now, however, comparatively rare, owing to the employment of the Safety-Lamp. For this invention we are indebted to Sir H. Davy ; and its utility depends upon the principles which have already been adverted to in the remarks upon the causes which modify combustion. CARBON. 179 REFERENCES. For the methods of separating the various impurities from Coal Gas, see the papers of Dr. Henry, in the Phil. Trans, for 1808 and 1820, or Ann. of Phil. xiv. An abstract of the analytical part of these papers is given in the %d volume of his Elements of Chemistry. The Essay of Dry. Turner and Chrislison, above quoted, contains much practical information concerning Oil and Coal Gas. The article Gas Lights, in the Supplement to the Encyclopedia Britannica, by Mr. Creighton. DanieWs patent for pre. paring Gas from Rosin, in Brandt's Jour. N. 8. \. 217. The Treatises on Gas Lights, by Mr. Accum and Mr. Peckston and by Dr. Cooper. Davy on the Safety-Lamp for coal miners, Lond. 1818, containing a full history of the Lamp, and of the chemical researches connected with it. OLEPIANT GAS AND CHLORINE. Chloride of Hydrocarbon. Atom. Num. 49*35 Symb. (2H+2C)+Ci. SYK. Hydrocarburet of Chlorine. Chloric Ether. Discovered by the Dutch chemists ; but its true nature was first as- certained by Dr. Thomson, [Mem. Wernerian Soc. 1,] and more fully elucidated by M. M. Robiquet and Colin. Ann. de Chim. et de Phys. i. and ii. PROPERTIES. When pure it is a colourless volatile liquid, of a pe- culiar sweetish taste and ethereal odour ; has a specific gravity of 1-2201 at 45 F.; boils at 152 F. and may be distilled without change; is decomposed by passing its vapour through a red hot porcelain tube, being resolved into charcoal, bihydruret of carbon, (light carbureted hydrogen, ) and muriatic acid gas. PREPARATION, This compound may be obtained, as before stated, by allowing a mixture of chlorine and olefiant gases to remain at rest. The oily liquid which is generated is to be washed with water and then distilled from chloride of calcium, when the compound is obtained in its pure and dry form. OLEFIANT GAS AND BROMINE. Bromide of Hydrocarbon. Atom. Num. 92*26 Symb. ^ (2H+2C)+Br. Discovered by M. Serullas. Ann. de Chim. et de Phys. xxxiv. 95. PROPERTIES. A colourless liquid, heavier than water, very volatile, of a penetrating, ethereal odour, and of a very sweet taste, which it communicates to water in which it is placed, in consequence of being slightly soluble in that liquid ; it is solid at a temperature between 21 and 23 F. and then resembles camphor. PREPARATION. According to Serullas, this compound is best ob- tained by bringing two parts of bromine into contact with one of iodide of hydrocarbon ; the products being bromide of iodine and bro- mide of hydrocarbon. 180 CARBON. OLEFIANT GAS AND IODINE. Iodide of Hydrocarbon Atom. Numb. 140 Symb. (2H+2C)+I. Discovered by Mr. Faraday. Phil. Trans. 1821. Ann. of Phil xviii. 104. PROPERTIES. A solid white, crystalline body, which has a sweet taste and an aromatic odour ; it sinks rapidly in boiling sulphuric acid ; it is fused by heat and then sublimed without change, condens- ing into crystals, which are either tabular or prismatic ; on exposure to heat it is decomposed and iodine escapes ; it burns, if held in the flame of a spirit lamp, with evolution of iodine and some hydriodic acid ; it is insoluble in water and in acid or alkaline solutions, but dissolves in alcohol or ether, and crystallizes upon evaporating the solution. PREPARATION. This compound may be obtained by exposing ole- fiant gas and iodine contained in the same vessel, to the direct rays of the sun. CARBON AND NITROGEN. Nitruret of Carbon, or Cyanogen. Atom. Num. 26 Symb. N+2C 8p. gr. 1-804 air=l. Discovered by Gay Lussac, in 1815. [Ann. de Chim. xcv. and Ann. of Phil. viii. 37.] Its properties have also since been investigated by Vauquelin. Ann. of Phil. xiii. 430. PROPERTIES A colourless gas with a strong, pungent and very peculiar odour; at the temperature of 45 F. and under a pressure of 3*6 atmospheres, it is a limpid liquid, which resumes the gaseous form when the pressure is removed ; it extinguishes burning bodies, but it is inflammable and burns with a beautiful and characteristic purple flame ; it is not decomposed by the strongest heat ; water, at the temperature of 60 F. absorbs 4-5 times, and alcohol 23 times its volume of the gas ; its specific gravity, according to Gay Lussac, is 1-8042; though a compound body, cyanogen has a great tendency to combine with elementary substances. Cyanogen is absorbed by water. The aqueous solution reddens lit- mus ; this, however, is scarcely to be considered as an effect of the gas itself, but is owing to the presence of acids which are generated by the mutual decomposition of cyanogen and water. [ Vauquelin. Ann. of Phil. xiii. 430.] By long keeping, a strong solution was found by Vauquelin to assume a light amber colour, and to deposit orange yel- low crystals, which he proposes to call subcyanogen. Ann. of Phil. N. S. vi. 68. It unites with elementary substances. This property, which is some- what peculiar in the case of a compound body, is illustrated by heat- ing potassium in cyanogen gas ; an energetic action ensues, the metal becomes incandescent, and a cyanide of potassium is generated. On the other hand the affinity of cyanogen for the metallic oxides is com- paratively feeble. Hence it can have no claim to the character of an acid. CARBON. 181 PREPARATION. Cyanogen does not exist in nature, but may be pre- pared by the decomposition of the cyanide of mercury, a compound which will be described hereafter. This substance, well dried, at a temperature below that of boiling water, is put into a small glass retort, or a common test tube, to the open end of which a cork is accurately fitted. Through this is passed a smaller pipe, which may be straight or bent at right angles. The cyanide of mercury is put into the tube, the open end of which is clos- ed by the cork. Heat is now applied ; the cyanide first blackens, then liquifies, and the cyanogen comes over in the form of gaet, which may be collected over mercury ; or its combustibility and the peculiar colour of its flame may be exhibited by bringing a taper into contact with the gas as it issues from the orifice of the pipe. Cyanous Acid. (Cyanic Acid of W older.) First obtained in a state of combination by Wohler, and for some time known only in that form. Subsequently the same chemist dis- covered a method of obtaining the pure cyanous acid. This consists in subjecting to heat the anhydrous cyanic acid. A part of the acid sublimes without change, while another part is transformed into cya- nous acid with the disengagement of nitrogen and of carbonic acid ; when the receiver is properly cooled, the anhydrous cyanous acid con- denses upon the inner side, in the form of a transparent colourless liquid. This acid has a penetrating odour, is very volatile, and irritates the eyes strongly. When combined with water, heat is produced, and it is converted into carbonate of ammonia. Bcrzdius, ii. 155. Cyanous acid may be readily obtained in combination with potassa, by calcining, at a red heat, equal weights of anhydrous ferrocyanate of * The nature of the properties of the compounds of cyanogen arid oxygen is said to have been well cleared up in a recent memoir by M. M. Wohler and Liebig. [Ann. de Chim. xlvi. 25.] But as there is still some uncertainty on the subject, and as it would require much detail to explain these views, I content myself, at present, with the following notice of their investigations from Johnston's Report. They have shown that the cyanic acid of Serullas contains hydrogen according to the formula 1 1-2 (Cy-f-20+H), and have given it the name of Cyanuric Acid. This acid distills over without loss, and condenses in the cooled receiver into a limpid colourless liquid, which is the cyanic acid of Wohler combined with one atom of water. It is repre- sented by the formula (Cy-}-0)-f-(H+0), in which the elements are precise- ly in the same ratio as in the cyanuric acid, from which it appears that by heat the atoms constituting cyanuric acid are arranged so as to produce one atom and a half of a hydrated cyanic acid containing one atom water. But this new arrangement of the atoms is very unstable ; for on acquiring the tempr. rature of the atmosphere it begins to grow turbid, evolves heat, enters into ebullition, and in a few minutes is converted into a dry, compact, brilliant? white solid, of the same composition as the cyanuric and hydrated Cyanic acids, and which, from its insolubility in water and nitric and muriatic acids* has been called insoluble cyanuric acid. 182 CARBON. potassa and peroxide of manganese. Pulverize the remaining mass and boil with alcohol 86 per cent, pure ; on cooling, thecyanite of potassa separates, [in small plates, resembling the chlorate of potassa. [ W'dhler, Ann. de Chim. et de Phys. xxvii. 196.] From its combination with po- tassa the acid may be transferred by double decomposition to other bases ; but we are not yet acquainted with any method of separating the pure cyanous acid from the cyanites. It should be remarked that this acid is identical in its composition with that which was discovered by Liebig, in 1 823, to exist in the ful- minating compounds of mercury and silver, and which he then de- nominated Fulminic Acid, as he called the compounds Fulminates. Ac- cording to an analysis of fulminating silver, made by M. M. Liebig and Gay Lussac, the acid of the salt is composed of 26 parts or one proportion of cyanogen and 8 parts or one of oxygen. [Ann. de Chim. et de Phys. xxiv.] It is, therefore, if this view be correct, a real Cy- anous Acid, and the compounds should be termed Cyanites. Berzelius, however, thinks it difficult to admit, without more proof, the identity of the composition of these two acids. Trait, de Chim. ii. 159. Cyanic Acid. This acid is obtained, according to Serullas, by the action of hot water upon the perchloride of cyanogen, to be presently noticed ; mu- riatic acid and a new acid compound of cyanogen and oxygen are the results. Evaporation expels the muriatic acid and leaves a true cyanic acid, capable of existing in a separate form, and possessing, indeed, considerable stability of composition, since it affords crystals which may be repeatedly dissolved, re-crystallized, and which even dissolve without change, in nitric and sulphuric acids. With bases it forms a distinct class of salts, properly called Cyanates. Carefully analyzed, this acid was found to consist of one proportion of cyanogen and two proportions of oxygen. Serullas, Ann. de Chim. et de Phys. for Aug. 1828. For Wohler's process, see Berzelius, ii. 160. CYANOGEN AND CHLORINE. There appears to be two distinct compounds of chlorine and cyano- gen, which have been termed Chloride and Perchloride of Cyanogen. Chloride of Cyanogen. Atom. Num. 6145 Syrnb. C1-J- (N+2C.) SYN. Cyanide of Chlorine. Chlorocyanic Acid. Chloride Cyaneux. Berzelius. Discovered by Berthollet, and subsequently examined by Gay Lug- gac [Ann. de Chim. xcv. ] and by Serullas [Ann. de Chim. et de Phys. Aug. 1827,] by whom it was first obtained in a state of purity. PROPERTIES. Chloride of cyanogen is remarkable in the circum- stance of its crystallizing in long slender needles, at the temperature of F. (by this it is separated from portions of other gases, with which it would otherwise be liable to be contaminated ;) it becomes liquid at about 8 or 10 F. and at 68 F. is a gas equivalent to four at mospheres ; in the liquid state it is as limpid and colourless as water ; CARBON. 183 it has a very offensive odour, irritates the eyes, is corrosive to the skin, and highly injurious to animal life ; reddens vegetable blue colours, and does not explode when mixed either with oxygen or hydrogen gases. PREPARATION. If cyanide of mercury be mixed with just sufficient water to reduce it to a semi-fluid state, and exposed to the action of gaseous chlorine, in the course of a few hours the colour of the chlo- rine will disappear, and a gas will be found in its place, which is not absorbable by mercury, but instantly taken up by water. This is the chloride of cyanogen or chlorocyanic acid. One portion of the chlo- rine, in this process, expels the cyanogen from the mercury, and forms bichloride of mercury, while another portion combines with the cyanogen and forms* the new compound. For details, see Henry's Cfiem. and Turner. See also, Gay Lussac in Ann. of Phil. viii. 47. Perchloride of Cyanogen. A torn. Num. 96-90 Symb. 2C1+ (N+2C.) SYM. Chloride Cyanique Berzelius. Discovered by Serullas. Ann. de Chim. Aug. 1828. PROPERTIES When carefully purified and dried it is brilliantly white and crystallizes in needles ; its specific gravity is 1 '320 ; it fuses at 140, and boils at 190 ; when kept for some time, it exhales on opening the bottle, an odour of muriatic acid ; it is sparingly soluble in cold water, but dissolves in hot, though with partial decomposi- tion ; it is extremely poisonous, a single grain having proved fatal to a rabbit. PREPARATION. The process of Serullas is to pour about 155 grains of pure hydrocyanic acid of Gay Lussac into a bottle containing about 61 cubic inches of dry chlorine. The bottle being closed with a stop- per, and exposed to sun-light, the hydrocyanic acid is vaporized ; and after a few hours a colourless liquid is seen on the inner surface of the bottle, having the appearance of water, which becomes thicker and thicker, and finally in about twenty-four hours, sets into a white solid, mixed with shining crystals. The process is one of some delicacy, and requires the observance of several precautions, which are given at length in the original memoir, above referred to. Henry, i. CYANOGEN AND BROMINE. Bromide of Cyanogen. Atom. Num. 104-26 Symb. Br.-f- (N+2C.) This compound has been obtained by M. Serullas, by a process anal- ogous to that for preparing chloride of cyanogen. The properties al- so closely resemble those of that compound, as well as of iodide of cy- anogen. Ann. de Chim. et de Phys. xxxiv. and xxxv. 184 CARBON, \ CYANOGEN AND IODINE. Iodide of Cyanogen. Atom. Num. 152Symb. I+(N+2C.) Obtained by Serullas by heating, in a wide mouthed phial, a mix- ture ,of one part iodine and two parts cyanide of mercury, both per- fectly dr y. When the cyanide of mercury begins to be decomposed, and the violet vapour of iodine ceases to be produced, the phial is placed inclined under an inverted bell-shaped glass, the mouth of which is then closed with a piece of paper or disk of glass. White vapours arise from the phial, and are condensed in fine cotton-like flocks on the surface of the paper or glass disk. To purify these from some adhering cyanide of mercury, they are resublimed at the gentlest heat adequate to that effect. The properties of this compound are analogous to those of chloride of cyanogen. Ann. de Chim. et de Pkys. xxvii. CYANOGEN AND HYDROGEN. Hydrocyanic or Prussic Acid. Atom. Num. 27. Symb. H+(N+2C.) Discovered by Scheele in 1782, but, as it was aflerwards found, in solution in water. First procured in a pure state by Gay Lussac. PROPERTIES. Pure hydrocyanic acid is a limpid and colourless fluid, of a strong odour, similar to that of peach blossoms ; its taste is first cool, but soon becomes hot and acrid ; its specific gravity at 45 F., is 0-7058 ; it is highly volatile ; boils at 79 F., and at zero con- geals ; a drop of it placed on a piece of glass becomes solid, because the cold produced by the evaporation of one portion is so great as to freeze the remainder ; it unites with alcohol and water in all propor- tions ; is liable to spontaneous decomposition, and cannot be preserv- ed for any length of time, even when out of contact of air, in well stop- ped bottles ; is highly poisonous ; reddens litmus paper feebly, and combines with bases forming salts, which are called Hydrocyanatcs or Prussiates. PREPARATION. The best process for preparing hydrocyanic acid, is that proposed by Vauquelin. It consists in rilling a narrow tube placed horizontally, with fragments of cyanide of mercury, and caus- ing a current of sulphuretted hydrogen gas to pass slowly along it. The instant that gas comes in contact with the cyanide, double de- composition ensues, the sulphur of the gas combines with the metal, forming black sulphuret of mercury, and the cyanogen, which is lib- erated, unites with the hydrogen. The acid may be expelled by a very gentle heat, and collected in a receiver kept cool by ice. This acid may also be obtained by moistening the cyanide of mer- cury with muriatic acid, and distilling at a low temperature. This is the process adopted at Apothecaries' Hall in London. See Webster's Brande. TESTS. The presence of free hydrocyanic acid is easily recognized by its odour. When in combination, it may be detected by adding to the liquid supposed to contain it, a solution of green vitriol, throwing down the protoxide of iron by a slight excess of pure potassa, and af- CARBON. 185 ter exposure to the air for four or five minutes, acidulating with mu- riatic or sulphuric acid, so as to redissolve the precipitate. Prussian blue will then make its appearance, if hydrocyanic acid had been ori- ginally present. As hydrocyanic acid is sometimes administered with criminal de- signs, the chemist may be called on to search for its presence in the stomach after death. This subject has been investigated experimental- ly by M. M. Leuret and Lassaigne, and the process they have recom- mended is the following. The stomach or other substances to be ex- amined are cut into small fragments, and introduced into a retort along with water, the mixture being slightly acidulated with sulphuric acid. The distillation is then conducted at a temperature of 212 F., the volatile products collected in a receiver surrounded with ice, and the presence of hydrocyanic acid in the distilled matter, tested by the me- thod above mentioned. These gentlemen found that prussic acid may be thus detected two or three days after death ; but not after a long- er period. The disappearance of the acid appears owing partly to its volatility, and partly to the facility with which it undergoes sponta- neous decomposition. Journal de C/dmie Medicate, ti?c. xii. 561. Tur- ner. See also, Christison on Poisons, 555. ACTION ON THE ANIMAL ECONOMY. Pure hydrocyanic acid is a pow- erful poison, producing insensibility and convulsions, which are speedily followed by death. A single drop of it placed on the tongue of a dog causes death in the course of a very few seconds ; and small animals, when confined in its vapour., are rapidly destroyed. On in- spiring the vapour, diluted with atmospheric air, headach and giddi- ness supervene ;. and for this reason the pure acid should not be made in close apartments during warm weather. The distilled water from the leaves of the Prunus lauro ccrasus owes its poisonous quality to the presence of this acid. Its effects are best counteracted by diffusi- ble stimulants, and of such remedies, solution of ammonia appears to be the most beneficial. This acid in its diluted form is sometimes employed in medical prac- tice to diminish pain and nervous sensibility. It may be procured of any strength by dissolving cyanide of mercury in water, and transmit- ting a current of sulphuretted hydrogen gas through the solution till the whole of the cyanide is decomposed ; which may be known by the filtered liquid remaining colourless and transparent when mixed with a solution of sulphuretted hydrogen. REFERENCES. Gay LussaJs experiments on Prussic Acid, Ann. de Chim. xcv. 136, or Ann. of Phil, vii. 350, viii. 37, 108. PorretCs Memoir on Prus- sic Acid, Trans, Lond. Soc. of Arts, fyc, xxvii. 89. For details concerning its action on the human system, and its medical employment, see Magendie's Formulary also Beckys Med. Juris. 540, and Randolph on the deleterious effects of Hydrocyanic Acid^ Amer. Med. Rec. iv. 456. HYDROCYANIC ACID AND AMMONIA. Hydrocyanate of Ammonia. This salt crystallizes in cubes or in very small prisms. Its volatility is such, that at a temperature of 72 F. its vapour supports a column of upwards of 15 inches of mercury ; and at 97 F., it is equal to the 186 CARBON. pressure of the atmosphere. Dr. Thomson finds, that when prussian blue is exposed to a red heat in a copper tube, and the products re- ceived over mercury, the glass receiver is coated with transparent crys- tals of this salt. The solution of this salt precipitates several metal- lic solutions not affected by hydrocyanic acid, which, according to Scheele, acts only on nitrates of silver and mercury, and on carbonate of iron. Ann. of PkiL xv. 394. Henry's Chem. i. 480. CYANOGEN AND SULPHUR. Cyanide of Sulphur. This compound was first formed by Lassaigne. Into a small glass balloon he puts a little cyanide of mercury finely pulverized, and pours upon it half its weight of bichloride of sulphur. At the end of 14 or 15 days of exposure to day-light, the balloon being closed so as to ex- clude air, a minute quantity of crystals rise to the upper part of the balloon, which are the acid in question. Like the sulphocyanic acid, with which it may possibly be identical, it forms crimson coloured salts, with the peroxide of iron. Ann. de Ch. et de Ph. Oct. 1828. Henry, i. 500. Sulphocyanic Acid. Atom. Num. 59 Symb. H+ (N+2C+2S) SYN. Anthrazothionic Acid. Grotthuss. This acid was discovered in the year 1808, by Mr. Porrett, who as- certained that it is a compound of sulphur, carbon, hydrogen, and ni - trogen, and described it under the name of Sulphuretted Chyazic Acid. It is now more commoly called Sulphocyanic Acid, and its salts are termed Sulphocyanates. PROPERTIES. A transparent liquid, which is either colourless or has a slight shade of pink ; odour somewhat similar to that of vinegar ; the strongest solution of it which Mr. Porrett could obtain, had a specific gravity of 1-022 ; it boils at 216-5F. and at 54.5 crystallizes in six-sided prisms, reddens litmus apper, and forms neutral compounds with alkalies ; its presence, whether free or combined, is easily detect- ed by a persalt of iron, with the oxide of which it unites, forming a soluble salt of a deep blood-red colour ; with the protoxide of copper it yields a white salt, which is insoluble in water. PREPARATION. This acid is obtained by mixing so much sulphuric acid with a concentrated solution of the sulphocyanate of potassa as is sufficient to neutralize the alkali, and then distilling the mixture. An acid liquor collects in the recipient, which is sulphocyanic acid dissolved in water, and sulphate of potassa remains in the retort. REFERENCES. The memoirs of T. von Grotthuss , Vogel, and R. Porrett, Jun. in Ann. of Phil. xiii. 39, 89, 101, 356. CARBON. 187 CARBON AND SULPHUR. Bisulphuret of Carbon, or Alcohol of Sulphur. Discovered in 1796 by Professor Lampadius, who regarded it as a compound of sulphur and hydrogen, and termed it Alcofiol of Sulphur. Its true nature was first pointed out by Clement and Desormes. PROPERTIES. A transparent colourless liquid, remarkable for its high refractive power ; specific gravity 1 '272 ; has an acid, pungent, and somewhat aromatic taste, and a nauseous and very fetid smell ; is very volatile, and boils at the common atmospheric pressure at a tem- perature not exceeding 110 F ; owing to its volatility, it may be em- ployed for producing an intense degree of cold ; it has never been con- gealed by the lowest artificial temperature ; is highly inflammable, and burns with a blue flame, emitting copious fumes of sulphurous acid ; dissolves readily in alcohol and ether, and is precipitated from the solution by water ; dissolves sulphur, phosphorus and iodine ; decom- poses chlorine, with the formation of chloride of sulphur ; combines with the alkalies slowly, forming compounds which Berzelius calls Car- bosulphurets. PREPARATION. This compound rnay be obtained by heating in close vessels the native bisulphuret of iron, (iron pyrites,) with one- fifth of its weight of well dried charcoal ; or by transmitting the va- pour of sulphur over fragments of charcoal heated to redness in a tube of porcelain. The compound, as it is formed, should be conducted by means of a glass tube into cold water, at the bottom of which it is collected. To free it from moisture and adhering sulphur, it should be distilled at a low temperature in contact with the chloride of cal- cium. Xanthogen and Hydroxanthic Acid. Professor Zeise, of Copenhagen, has discovered some novel and in- teresting facts relative to the bisulphuret of carbon. When this fluid is agitated with a solution of pure potassa in strong alcohol, the alka- line properties of the potassa disappear entirely ; and on exposing the solution to a temperature of 32 F., numerous acicular crystals are deposited. Zeise attributes these phenomena to the formation of a new acid, the elements of which are derived, in his opinion, partly from the alcohol, and partly from the bisulphuret of carbon. He re- gards the acid as a compound of carbon, sulphur and hydrogen. He supposes it to be a hydracid, and that its radical is a sulphuret of car- bon. To the radical of this hydracid, he applies the term Xanthogen, (from the Greek Xanthos, yellow, and gennao to generate,) expressive of the fact, that its combinations with several metals have a yellow co- lour. The acid itself is called Hydroxanthic Acid, and its salts Hydrox- anthates. The crystals deposited from the alcoholic solution, are the hydroxanthate of potassa. It appears to be agreed that a new acid is generated under the cir- cumstances described by M. Zeise, but he has not obtained it in a se- parate state, and there is considerable uncertainty concerning its na- ture. For details concerningit, see Ann. de Chim, et de Phys. xxi., and Ann. of Phil. xx. 241. 188 BORON. CARBON AND PHOSPHORUS. Phospliuret of Carbon. Atom. Num. 2l.7Symb.~P+C. Discovered by Proust in 1799, but first obtained in a pure state by Dr. Thomson. -Ann. of Phil. viii. 157. PROPERTIES. A soft powder of a yellowish colour, without taste or smell ; when exposed to the air, it slowly imbibes moisture, and ac- quires an acid flavour : burns when exposed to a red heat, gradually giving out phosphorus, the charcoal being prevented from burning by a coating of phosphoric acid. This compound is prepared by allowing phosphuret of calcium to remain in water till it no longer evolves gas ; then add to the liquid excess of muriatic acid, agitate for a few moments, and throw the whole on a filter. The powder which remains is to be washed and dried, and is pure phosphuret of carbon. SECTION YI. BORON. Atom. Num. SSymb. B. First obtained by Sir H. Davy in 1808, by the action of Voltaic elec- tricity on bqracic acid. Subsequently in greater quantity by Gay Lussac and Thenard, by heating boracic acid with potassium. PROPERTIES. Boron is a dark olive-coloured substance, which has neither taste nor smell, and is a non-conductor of electricity ; insolu- ble in water, alcohol, ether and oils ; does not decompose water whether hot or cold ; bears an intense heat in close vessels, without fusing, or undergoing any other change, except a slight increase of density ; its specific gravity is about twice as great as that of water ; it may be exposed to the atmosphere at common temperatures without change, but if heated to 600 F., it suddenly takes fire, oxygen gas disappears, and boracic acid is generated ; it experiences a similar change when heated in nitric acid, or with any substance that yields oxygen with facility. PREPARATION. In addition to the above methods of preparing boron, that of Berzelius should be noticed as the easiest and most economical method of producing it. This consists in heating the potassium in contact with the fluoborate of potassa. Berzelius , Traite. de Chim. i. 361. Ann. of Phil. xxvi. 128. BORON AND OXYGEN. Boracic Add. Atom. Num. 24 Symb. 20+B Sp.gr, 1479. water=l. SYN. ' Homberg's sedative Salt. PROPERTIES. Boracic acid has the form of thin white scales, is destitute of smell and nearly so of taste ; it is sparingly soluble in wa- ter, and the solution reddens vegetable blue colours ; and, what is verjs remarkable, it renders turmeric paper brown like the alkalies. [Fara* BORON. 189 day.'] It is soluble in alcohol, and communicates a beautiful green co- lour to its flame ; fuses when heated, aad gives off its water of crystalli- zation to the amount of 43 or 44 parts in the hundred, and is converted into a hard colourless transparent glass, which is anhydrous boracic acid the hydrous or crystalline acid being supposed to consist of one pro- portion of dry acid and two of water. PREPARATION AND NATIVE STATE. As a natural product, this acid is found in the hot springs of Lipari, and in those of Sasso in the Flo- rentine territory. It is a constituent of several minerals, among which the datholite and boracite may in particular be mentioned. It occurs much more abundantly under the form of borax, a native compound of boracic acid and soda. It is prepared for chemical purposes by ad- ding sulphuric acid to a solution of purified borax in about four times its weight of boiling water, till the liquid acquires a distinct acid reac- tion. The sulphuric acid unites with the soda ; and the boracic acid is deposited, when the solution cools, in 'a confused group of shining scaly crystals. It is then thrown on a filter, washed with cold water to separate the adhering sulphate of soda and sulphuric acid, and still further purified by solution in boiling water and re-crystallization. But even after this treatment it is apt to retain a little sulphuric acid, and on this account, when required to be absolutely pure, should be fused in a platinum crucible, and once more dissolved in hot water and crystallized. REFERENCES. Gay Lussac and Thenard on the decomposition and re- composition of Boracic Acid, Jour, de Phys. 1808, 'and Repert. of Arts, %d ser. xiv. 408. Robiquet on the preparation of Boracic Add from Tincal and the waters of Lakes in Tuscany , Ann. de Chiin. et de Phys. ii. 203, and Re- pert, of Arts, 2o? ser. xxxvi. 123. Faraday on the action of Boracic Acid on Turmeric^ Branded Jour. vi. 152. BORON AND CHLORINE. Bichloride of Boron. Atom. Num. 78-9 Symb. 2C1+B Sp. gr. 3-942. air=l. S YN. Chloride Boriyue. Berzelius. Boron burns with considerable splendour in chlorine gas. The pro- duct Berzelius finds to be a new gas, which may be freed from excess of chlorine by standing over mercury. [Berzelius Traitede Chitn. i. 365-6. Ann. of Phil. xxvi. 129. J It smokes in the atmosphere like fluoboric acid gas ; is rapidly absorbed by water ; is soluble also in alcohol ; unites with ammoniacal gas forming a fluid volatile substance. The combination of these two elements has been better effected by Despretz, by passing chlorine over boruret of iron, and also by trans- mitting the same gas, deprived of water, over charcoal and boracic acid, ignited together in a porcelain tube. PhiL Mag. and Ann. i. 4o9. 190 BORON- BORON AND CHLORINE. Fluoboric Acid, or Fluoride of Boron. SYN. Fluoride Borique. Berzelius. Discovered in 1810 by Gay Lussac and Thenard. Its true compo- sition does not yet appear to be understood. PROPERTIES. Fluoboric acid gas is colourless, has a penetrating pungent odour, and extinguishes flame on the instant ; its specific gravity, according to Dr. Thomson, is 2'3622 ; it reddens litmus pa- per as powerfully as sulphuric acid, and forms salts with alkalies which are called Fluoborates ; it has a singular great affinity for water. When it is mixed with air or any gas which contains watery vapour, a dense white cloud appears, which is a combination- of water and fluoboric acid gas. From this circumstance, it affords an exceedingly delicate test of the presence of moisture in gases* Fluoborie acid gas is rapidly absorbed by water. According to Dr. John Davy, water absorbs 700 times its volume. Caloric is evolved during the absorp- tion and the water acquires an increase of volume. The saturated solution is limpid, fuming, and very caustic. On the application of heat, part of the gas is disengaged ; but afterwards the whole solution is distilled. This acid does not act on glass, but attacks animal and vegetable substances with great energy ; converting them, like sulphuric acid, into a carbonaceous substance. According to Berzelius, when in a certain state of dilution, part of the fluoboric acid and water mutually decompose each other, with formation of boracic and hydrofluoric acids. The latter he supposes to unite with undecomposed fluoboric acid, forming what he has called Hydrqfluoboric Acid. [Traite de Ch~ ii. 189.] A different view, however, is maintained by Gay Lussac and Thenard. PREPARATION. This gas may be obtained by subjecting to strong heat, in an iron tube, a mixture of one part of dry boracic acid, and two parts of powdered fluor spar. It may also be procured by mixing one part of vitrified boracic acid, and two of fluor spar, with twelve parts of strong sulphuric acid, and heating the mixture gently in a glass retort. [Dr. John Davy, Phil. Trans, for 1812.] When thus prepared, however, it contains fluosilicic acid, according to Berzelius, in considerable quantity ; and Dr. Thomson detected in it traces of sulphuric acid. The gas may likewise be formed by the action of hy- drofluoric acid on a solution of boracic acid. REFERENCES. Thenard, Traite de Chim. ii. 533. Berzelius^ in Ann. of Phil. xxvi. 122. BORON AND SULPHUR. Sulpliuret of Boron. SYN. Suljide Borique. Berzelius. This compound may be formed, according to Berzelius, by igniting boron strongly in the vapour of sulphur, and the combination is ac- companied with the phenomena of combustion. The product is a SELENIUM. 191 white opaque mass, which is converted by the action of water into sulphuretted hydrogen and boracic acid ; and the liquid becomes milky at the same time from the deposition of sulphur. Ann. of Phil. xxvi. 129. Berzelius, i. 365. SECTION VII. SELENIUM. Atom. Num. 40 Symb. Se -$p. gr. 4-3 water=l. Discovered by Berzelius, in 1818. PROPERTIES. Selenium at common temperatures, is a brittle solid, of a brown colour and metallic fracture ; it has neither taste nor smell ; when pounded, the particles stick together, and its powder has a deep red colour ; it melts at a few degrees above the boiling point of water, and when warm is very ductile, and may be drawn into fine threads, which are red by transmitted, but grey by reflected light ; it boils at a temperature of about 60(P F. and condenses either in opaque metallic drops, or, when large vessels are used, in flowers of the colour of cinnabar ; its vapour has a deep yellow colour ; when heated in the flame of a candle, urged by a current of air from a blow-pipe, it emits a strong smell of horse-radish. When selenium was first discovered it was regarded, by Berzelius, as a metal ; but, since it is an imperfect conductor of caloric and electricity, it more properly belongs to the class of simple non-metal- lic bodies. It is still very rare, and many accomplished chemists have never yet had an opportunity of seeing it. I shall, therefore, be quite brief in the account of it and of its compounds. NATIVE STATE AND EXTRACTION. In the process for obtaining sul- phuric acid at Fahlun, in Sweden, from a natural combination of sul- phur and iron, called pyrites, it was observed that a reddish mass was deposited, which in burning gave out a peculiar odour. The princi- pal portion of the mass was sulphur ; but it was mixed with a very minute quantity of a substance, to which Berzelius afterwards gave the name of selenium. The process by which it was extracted is gi- ven at length, in Ann. of P kit. xiii. 403. The improved method of M. Lewenau is also given in the 24th volume of that work. It has since been discovered in the volcanic rocks of Lipari ; in several varieties of sulphur ; and in sulphuric acid made with pyrites obtained from the isle of Anglesea. [Ann. of Phil. xxiv. and xxv.] Selenium has also been discovered by M. Henry Rose, in several minerals from the Eastern Hartz, united with lead, cobalt, copper and mercury [Ann. de Ch. ct de Phys. xxix. 113,] and Stromeyer and Haussman have ana- lyzed a seleniui ct of lead from the Laurence mine at Clausthal. Ann. of Phil. xxvi. 233. REFERENCES. On this substance and its compounds, see a detailed notice in Berzelius^ Trait de Chitn. ii. 397 SELENIUM AND OXYGEN. There appear to be three distinct compounds of selenium and oxygen, though the first of these is not yet well understood. 192 SELENIUM. Oxide of Selenium. Atom. Num. 48 ?Sy?nb. O+Se ? Oxide of Selenium is formed by heating selenium in a close phial with common air, which acquires a very strong smell of horse-rad- ish. Water agitated with this air imbibes the odour of the gas, and reddens litmus feebly, but this appears to be owing to the production of a small quantity of selenious acid. Oxide of selenium is a colourless gas, which is very sparingly solu- ble in water, and does not possess any acid properties. Its compo- sition has not yet been determined, but it probably contains an atom of each of its elements. Berzelius, to whom we are indebted for most that is known concerning it, does not seem to have yet obtained it in a perfectly pure state. Ann. de Chim. et de Phys. ix. 176. Selenious Acid. Atom. Num. 56 Symb. 2O+Se. Discovered by Berzelius. PROPERTIES. A white crystalline substance, having a sour and slightly burning taste ; it is very soluble, both in water and in alcohol; it is readily decomposed by all substances which have a strong attrac- tion for oxygen. If sulphurous acid be passed into its solution, pure selenium will be thrown drown in the state of a red powder, and sul- phuric acid formed ; it may likewise be precipitated by the immer- sion of plates of zinc or polished iron ; it combines with bases and forms Selenites. PREPARATION. This acid is most conveniently prepared by digest- ing selenium in nitric or nitro-muriatic acid, till it is completely dis- solved. On evaporating the solution to dryness, a white residue is left which is selenious acid. By increase of temperature, the acid itself sublimes, and condenses again unchanged, in long four-sided needles. It attracts moisture from the air, whereby it suffers imper- fect liquefaction. REFERENCE. Berzelius, ii. 405, Selenic Acid. Atom. Num. 64 Symb. 3O+Se. Discovered by Professor Mitscherlich, and described in Ann. de Chim. et de Phys. Sept. 1827. and in Edin. Jour, of Science, viii. 294. PROPERTIES. A colourless liquid, which may be heated to 536 F. without sensible decomposition, but at 554 F. is resolved into oxy- gen and selenious acid ; its specific gravity, when freed as completely as possible from water, is 2'625 ; but even when of this density, it still contains 15-75 of water in 100 of acid ; like sulphuric acid it evolves great heat when suddenly diluted. When heated with muriatic acid, it affords chlorine and selenious acid, and like aqua regia , dissolves gold. Selenic acid dissolves iron and zinc with a disengagement of hy- drogen ; copper with an evolution of selenious acid, and gold, but not platinum. In its affinities for bases it is a little inferior to sul- phuric acid, but its compounds, (seleniate of baryta for example,) are not entirely decomposed by the latter acid. PREPARATION. This acid may be prepared by fusing nitrate of po- tassa with selenium, with selenious acid or with a seleniuret, such as SELENIUM. 193 that of lead, freed from earthy impurities by muriatic acid. The resi- due, amounting to about one-third of the whole, is mixed with an equal weight of nitrate of soda and projected, by little at once, into a red-hot crucible. The lead is oxidized, and the selenium is convert- ed into selenic acid, which combines with the soda. The purification of the seleniate of soda involves many details, which may be found in the original memoir above quoted. [See also Turner's Chemistry.'] The last step of the process consists in decomposing seleniate of lead in solution, by sulphuretted hydrogen, which precipitates sulphuret of lead, leaving the selenic acid in such a state as to be purified by ebullition. SELENIUM AND CHLORINE. Chloride of Selenium. Selenium absorbs chlorine gas, and becomes hot and forms a brown liquid, which, by an additional quantity of chlorine is converted into a white solid mass. This is stated by Berzelius to be a compound of muriatic and selenic acids, but it is probably composed of chloride of selenium and selenious acid. It has not yet been accurately separat- ed into its component parts, for when heat is applied, both substances are sublimed. Henry, i. 424. SELENIUM AND BROMINE. Bromide of Selenium. This compound is obtained, according to Serullas, by causing sele- nium to fall, in small portions, upon bromine. They combine with violence, and with the disengagement of heat. When cold, the mass is solid, of an orange colour, and soluble in water. Berzelius, ii. 419. SELENIUM AND HYDROGEN. Hydroselenic Acid.- Atom. Num. 41 Symb. H+Se. SYN. Seleniuretted Hydrogen Gas. Selenide Ht/drique. Berzelius. Discovered by Berzelius and found to be analogous to sulphuretted hydrogen. PROPERTIES. A colourless acid, with an odour at first similar to that of sulphuretted hydrogen, but it afterwards irritates the lining membrane of the nose* powerfully, excites catarrhal symptoms, and destroys, for some hours, the sense of smelling ; it is absorbed freely by water, forming a colourless solution which reddens litmus paper, and gives a brown stain to the skin. The acid is soon decomposed by exposure to the atmosphere ; for the oxygen of the air unites with the hydrogen of the hydroselenic acid, and selenium, in the form of a red powder, subsides. All the salts of the common metals are decomposed by hydroselenic acid. The hydrogen of that acid combines with the oxygen of the oxide, and a seleniuret of the metal is generated. 194 SELENIUM. PREPARATION. This gas is disengaged by the action of muriatic acid upon a concentrated solution of an hydroseleniate. It may also be procured by heating the seleniuret of iron in muriatic acid. By the decomposition of water, oxide of iron and hydroselenic acid are gener- ated ; and while the former unites with muriatic acid, the latter escapes in the form of gas. SELENIUM AND SULPHUR. Sulphuret of Selenium. Atom. Numb. 64 Symb. 14 S+Se. When sulphuretted hydrogen gas is conducted into a solution of se- lenic acid, an orange-coloured precipitate subsides, which is a sul- phuret of selenium. It fuses at a heat a little above 212O F. and at a still higher temperature may be sublimed without change. In the open air it takes fire when heated, and sulphurous, selenious, and selenic acids are the products of its combustion. The alkalies and alkaline hydrosulphurets dissolve it. Nitric acid acts upon it with difficulty ; but nitro-muriatic acid converts it into sulphuric and selenic acids. Ann. of Phil. xiv. Berzelivs, ii. 415. SELENIUM AND PHOSPHORUS. PhospJturet of Selenium. The phosphuret of selenium may be prepared in the same manner as the sulphuret of phosphorus ; but as selenium is capable of uniting with phosphorus in several proportions, the compound formed by fus- ing them together can hardly be supposed to be of a definite nature. This phosphuret is very fusible, sublimes without change in close ves- sels, and is inflammable. It decomposes water gradually when digest- ed in it, giving rise to seleniuretted hydrogen and one of the acids of phosphorus Ann. of Phil. xiv. Berzelius, ii. 417. GENERAL PROPERTIES OF METALS. CHAPTER VIII. METALS. 195 GENERAL PROPERTIES OP THE METALS, The metals constitute the most important class of substances with which we are acquainted. They are characterized, by being all con- ductors of caloric and electricity, by appearing, when combined with oxygen, chlorine, iodine, sulphur, or similar substances, and subjected to the action of galvanism, at the negative pole of the battery, by be- ing quite opaque. by being good reflectors of light, and by possessing a peculiar lustre, denominated the metallic lustre. The number of metals at present known to chemists, is forty-two. Some of these were known and made use of in the earliest ages of the world, whereas others were discovered during the present century. The following table designates the names of the metals and the date of the discovery, so far as this is known, together with the name of the discoverer. Names of Metals. 1. Gold, ^ 2. Silver, 3. Iron, 4. Copper, }> 5. Mercury, I 6. Lead, 7. Tin. j 8. Antimony, 9. Zinc, 10. Bismuth, 11. Arsenic, ) 12. Cobalt, I 13. Platinum, 14. Nickel, 15. Manganese, 16. Tungsten, 17. Tellurium, 18. Molybdenum, 19. Uranium, 20. Titanium, 21. Chromium, 22. Columbium, 23. Palladium, > 24. Rhodium, $ 25. fridium, 26. Osmium, 27. Cerium, 28. Potassium, 29. Sodium, 30. Barium, 31. Strontium, 32. Calcium, Authors of the Discovery. Date. Known to the Ancients. Described by Basil Valentine, 15th cent. Described by Agricola, in - 1520. First mentioned by Paracelsus, 16th cent. Brandt, in 1733. Wood, Assay Master, Jamaica, - - 1741. Cronstedt, 1751. Gahn and Scheele, - - - 1774. MM. D'Elhuyart, .... 1781. Muller, 1782. Hielm, 1782. Klaproth, - - - - - - 1789. Gregor, - .... 1791. Vauquelin, 1797. Hatchett, ------ 1802. Dr. Wallaston, .... 1803. Descotils and Smithson Tennant, - 1803. Smithson Tennant, - - - - 1803. Hisinger and Berzelius, 1804. Sir H.Davy, 1807. 196 GENERAL PROPERTIES OF METALS. Names of Metals. 33. Cadmium, 34. Lithium, 35. Silicium, > 36. Zirconium, 5 37. Aluminum, ) 38. Glucinum, > 39. Yttrium, ) 40. Thorium, 41. Magnesium, 42. Vanadium. Authors of the Discovery. Stromeyer, ... Date. - 1818. - 1818 JBerzelius, - Wbhler, .... Berzelius, - ... - 1824. - 1828. - 1829. IQOQ 1820. Metallic Lustre. This property depends upon the opacity of the me- tals, in consequence of which the light is reflected by their surface more completely than it is from other bodies. The metals, however, differ in their lustre. Platinum possesses it in the highest degree ; after which, according to Leslie, are silver, mercury, gold, copper, tin and lead. Specific gravity. Great specific gravity was formerly considered as a distinctive character of the metals ; none being known previous to the decomposition of the alkalies, less than six times heavier than wa- ter. But the metallic bases of most of the alkalies and earth are light- er than that liquid. Indeed the heaviest and the lightest solids are now included in the list of metals. The following is a table of the specific gravity of the principal me- tals compared to water as 1. 1 Platinum, - - 21-00 9 Nickel, - - - 8-27 2 Gold, - - - 19-25 10 Iron, - - - 7-78 3 Mercury, - - 13-56 11 Tin, - - - 7-29 4 Lead, - - - 11-35 12 Zinc, - - - 7-00 5 Silrer, - - - 10-47 13 Manganese, - - 6-85 6 Bismuth, - - 9-82 14 Antimony, - - 6-70 7 Copper, - - 8*89 15 Sodium, - - - 0-972 8 Cobalt, - - - 8-53 16 Potassium, - - 0-865 Malleability. Metals are said to be 7nalleable, which admit of being beaten into thin plates or leaves by the hammer. If when subjected to the process of the hammering, they break, they are said to be brittle. Malleability is one of the most useful properties of the metals. It belongs to the following, in the order in which they are arranged : 1 Gold, 5 Cadmium, 9 Iron, 2 Silver, 6 Platinum, 10 Nickel, 3 Copper, 7 Lead, 11 Palladium, 4 Tin, 8 Zinc, 12 Potassium. Sodium and frozen mercury are also malleable. Gold surpasses all metals in malleability. When perfectly pure it can be beaten into leaves not more than the 1-282, OOOths of an inch in thickness. A grain of it can be beaten out into so fine a leaf as to cover 50 square inches of surface and contain two millions of visible points ; but the gold which covers the silver- wire used in making gold lace, is spread over a surface twelve times as great. The leaves of gold are so thin, that if formed into a book, 1,500 would occupy only the space of a single leaf of common paper; and an octavo volume of an inch thick, would have about as many pages GENERAL PROPERTIES OF METALS. 197 as the books of a well stocked ordinary library containing 1,500 vol- umes of 400 pages in each. Arnott. Ductility. Metals are said to be ductile, when they possess the property of being drawn out into wires. The only ones which are remarkable in this respect, are gold, silver, platinum, iron and cop- per, though some others possess ductility in an inferior degree. Dr. Wollaston devised a method by which gold-wire may be obtained so fine, that its diameter shall be only l-5000ths of an inch, and that 550 feet are required to weigh one grain. He obtained a platinum wire so small that its diameter did not exceed l-30,000ths of an inch. [Phil. Trans. 1813.] It is somewhat surprizing that the ductility and mallea- bility of the same rnetals, are not always in proportion to one another. Iron, for example, cannot be made into fine leaves, but it may be drawn into very small wires. Tenacity. By tenacity is meant the power of supporting weight with- out breaking. According to the experiments of Guyton-Morveau, iron in point of tenacity, surpasses all the other metals. The results which he gives in the Ann. de Chim., are as follows : The diameter of each wire was 0-787 ths of a line. Iron wire supports, .... 549-25 pounds. Copper, - 302-278 Platinum, 274-320 Silver, ------- 187-137 Gold, 150-753 Zinc, 109-540 Tin, 34-630 Lead, - 27-621 Hardness. The metals differ considerably from each other in hard- ness. Among those which are most hard, may be ranked titanium, manganese, iron, nickel, copper, zinc and palladium. Gold, silver and platinum, are softer than these ; lead is still softer, and potassium and sodium yield to the pressure of the fingers. Structure. Many of the metals have a crystalline structure, though this is by no means common to all. Crystals may be most easily pro- cured from those metals which fuse at a low temperature. Bismuth offers the finest illustration, as it affords when fused and treated in the manner described when noticing the crystallization of sulphur, beau- tiful and regular cubic crystals. Arsenic crystallizes in regular tetra- hedrons, and titanium in long slender filaments or prisms. It may be also observed that some metals, as gold, copper, and silver, occur na- turally in the form of crystals. Native state of Metals. When metals occur in the earth in a state of purity, they are called Native. To this class, however, belong only those which have a feeble attraction for oxygen, as gold, silver, platin- um, mercury, &c. Commonly they are, as it is termed, mineralized, by oxygen, sulphur, or arsenic ; and they are sometimes also found in the state of salts. From these compounds the pure metal is extracted by various processes, which, when conducted on a large scale, consti- tute the branch of chemistry denominated metallurgy. But the process- es of determining the purity of metals and other mineral substances by experiments made in a small way, is sometimes termed the art of assaying. 198 GENERAL PROPERTIES OF METALS. Action of heat. The metals are all susceptible effusion by heat, but the temperatures at which they liquify are very various. Mercury is fluid at common temperatures, and requires to be cooled to 39 - F. be- fore it congeals. Potassium melts at 136 F., and sodium at 200; tin at 430 J ; lead at 500; and zinc at about 700. Silver, gold and copper require a bright cherry red heat ; iron, nickel and cobalt, a white heat ; manganese and palladium, an intense white heat. Molybden- um, uranium, tungsten and chromium are only imperfectly agglutina- ted at the highest temperatures of our furnaces ; and titanium, cerium, osmium, iridium, rhodium, platinum and columbium require the in- tense heat of the oxy hydrogen blow-pipe or that of the Voltaic elec- tricity. The metals also differ greatly in their volatility. Mercury, cadmium, arsenic, tellurium, potassium, sodium and zinc are volatile at a red heat and may be easily distilled in close vessels. But many others may be exposed to the most intense heat of a wind furnace without being changed into vapour. It is probable, however, that all of them could be converted into vapour if raised to sufficiently high temperatures, as gold and platinum, which are among the most fixed, evaporate when exposed to the intense heat of the focus of a burning lens. Action of the Electric Fluids. The metals are excellent conductors of electricity, surpassing in this respect all other bodies. When their surface is sufficiently extensive to carry off the fluid, they undergo no change ; but when the contrary is the case, the fluid penetrates the interior, heats, and in some instances melts and volatilizes them. Such is the effect produced by the discharge of a powerful galvanic or Ley- den battery upon very fine wires, or thin plates of any metal, and this is more apparent if the experiment be performed in contact with air, when the combustion is more or less vivid, and the flame assumes dif- ferent colours. For example, iron burns with a very vivid white light, zinc with a whitish or yellowish white light, silver with a green, &c. Action of Oxygen Gas. Oxygen gas, in a dry state is absorbed by but few of the metals at ordinary temperatures. Among these are po- tassium, barium, lithium, strontium, calcium, and the bases of the earths. But at an elevated temperature, it acts upon almost all the metals, except platinum, silver, gold, palladium, iridium and rhodium. In some cases the union of the metals with oxygen is so rapid as to give rise to all the phenomena of real combustion. Zinc burns with a brilliant flame when heated to full redness in the open air, and iron emits vivid scintillations on being inflamed in an atmosphere of oxygen gas. The same will apply to tin, cadmium, arsenic, antimony, tellu- rium and bismuth ; although the combustion of tin, antimony, and bismuth, is the most feeble. The product either of a slow or rapid oxidation of a metal, when heated in the air, has an earthy appearance, and was termed a calx by the older chemists, the process of forming it being called calcina- tion. There are other processes sometimes employed for oxidating the metals, as by deflagration," that is by mixing them with nitrate or chlorate of potassa, and projecting the mixture into a red hot crucible, or by digestion in nitric or nitro-muriatic acid. Some metals combine with oxygen only in one proportion ; but the greater number of them combine with it in two or three proportions. The resulting compounds are either oxides or acids. With the excep- tion of arsenic, the metals all produce oxides by combination with GENERAL PROPERTIES OF METALS. 199 oxygen. But many of them which, when combined with one atom of oxygen, produce oxides, form acids when combined with two or three atoms of oxygen. This occurs in the case of chromium, tungsten, molybdenum and vanadium. When a metallic oxide is deprived of its oxygen and brought to the metallic state, it is said to be reduced, and the operation itself is called reduction. This reduction may be effected in several ways, viz. 1. By heat alone. The oxides of gold, silver, mercury and plati- num, may be decomposed by subjecting them to a red heat, when the oxygen escapes in the form of gas. 2. By the combined action of heat and combustible matter. The reduction is effected in this case by the superior attraction of the com- bustible matter for oxygen. Thus when oxide of lead is heated with charcoal, carbonic acid gas is evolved and metallic lead obtained. Upon the same principle a current of hydrogen gas passed over the oxides of copper or iron heated to redness in a porcelain tube, causes the reduction of the metal, while water is at the same time formed. The metals also are sometimes employed for the same purpose, and it sometimes happens that a metal which at a low temperature decom- poses a metallic oxide, may have its oxide decomposed by that metal at a higher temperature. Thus oxide of iron is reduced by potassium at a very low temperature ; while potassa is reduced by iron when the heat is very intense. 3. By the Voltaic battery. This in some cases effects the reduction of an oxide which resists the preceding agents : as in the case of ba- ryta and strontia. 4. By the action of various agents on metallic solutions. A neutral solution of gold when exposed to the sun's rays has a film of gold formed on the side turned to the light, which gradually increases in thickness. Phosphorous acid when added to a liquid containing oxide of mercury, deprives the oxide of its oxygen, metallic mercury sub- sides, and phosphoric acid is generated. Certain metals also introdu- ced in the metallic state into saline solutions of some others, deprive the latter of their acid and oxygen and precipitate them in a metallic state.* Thus mercury added to a solution of nitrate of silver throws down metallic silver, and oxide of mercury is dissolved by the nitric acid. In these cases the reduced metal is usually obtained in the state of fine powder or cohering together in a porous mass. Occasionally, however, it is met with in a solid malleable state, and even inthe form of regular crystals. Thus it is stated that in the copper pits of An- glesea, where iron is thrown in to reduce the copper from its solutions, malleable and crystallized copper has often been obtained. And it has been recently ascertained by Wach that whenever the process proceeds with sufficient slowness, the metal is deposited in this form. A very convenient method of accomplishing this object is to sew up the metal in two or three folds of bladder, and so immerse it in the solu- * [n a series of experiments which I performed for the purpose of ascer- taining 1 whether the process of crystallization was at all influenced by mag- netism, in which nothing was observed to confirm the views of Murray, I found that the process of metallic precipitation was greatly influenced by solar light. Glass tubes bent in the form of the letter V, and containing solution of nitrate of silver, and metallic mercury, always had the largest and most nu* merous blades of silver in that leg of the tube which was turned to the light. 200 GENERAL PROPERTIES OF METALS. tion to be precipitated, when the metal will be deposited on the outer surface in a massive state. Johnston's Report. The action of atmospheric air upon the metals is analogous, though less powerful than that of oxygen. Those metals which are speedily acted upon by common air and oxygen, are also generally susceptible of decomposing water ; some of them rapidly, others slowly. There are some metals which are not acted upon by air deprived of moisture, nor by water deprived of air ; but moist air, or water containing air, effects their oxidizement ; this appears to be the case with iron. Hall, in Brande's Jour. vii. 55. Water combines with some of the metallic oxides, and produces hydrated oxides, or metallic hydrates. In these, the relative proportion of water is definite. Some are easily decomposed by heat, as hydrate of copper ; others retain water even when heated to redness, as hy- drate of potassa. Every acid, with few exceptions, is capable of uniting with each of the metallic oxides, and of forming compounds, in which the separate qualities of the component principles are no longer apparent, and are hence called neutral salts. Ammonia also combines with several of the metallic oxides, forming what are called Ammoniurets. Some of these are crystalline com- pounds, and those formed by the union of ammonia with the oxides of gold, silver and platinum, detonate when heated. Action of Chlorine. Chlorine has a powerful attraction for metallic substances. It combines readily with many of the metals at common temperatures, and in some cases this combination is attended with the evolution of light. Thus when powdered zinc, antimony or arsenic, is thrown into a vessel of chlorine gas, the metal is instantly inflamed. Indeed the affinity of chlorine for the metals is even superior to that of oxygen ; for if chlorine gas be brought into contact with lime, mag- nesia, baryta, strontia or potassa, at a red heat, oxygen is liberared, and a chloride of the metal is formed. The elements of these com- pounds are so strongly united, that no temperature hitherto tried can separate them. Although the metallic chlorides may, in most cases, be formed by the direct action of chlorine upon the metals, they are perhaps more generally obtained by evaporating a solution of the muriate of a me- tallic oxide to dryness, and applying heat until all the water is driv- en off. When a true metallic chloride is dissolved in water, there are two views which may be taken of the changes that occur. Either the chloride may dissolve as such in water, or a decomposition of that fluid may ensue, the chlorine seizing the hydrogen and forming muriatic acid, while the metal may compose with the oxygen of the water an oxide capable of saturating the newly formed acid. In this way, a chloride may be converted, by the action of water, into a true muriate. The latter appears to be the most correct view, especially in those ca- ses where the chloride contains a metal, which, per se, decomposes water ; as potassium, sodium, &c. On this subject see Jinn, of Phil. xvii.; where the opinions entertained by different chemists regarding the action of the chlorides on water, have been collected together by Mr. Richard Phillips ; and who has adduced satisfactory evidence, that, in many instances, chlorides, by solution in water, are converted into muriates. The same course of reasoning will apply to the metallic iodides, bro- mides and fluorides. GENERAL PROPERTIES OF METALS. 201 Chlorine, in a dry state, does not unite with the pure oxides of the metals ; but if these last contain water, they absorb variable propor- tions of it. These compounds, however, possess very little perma- nency, and none of them can be heated to redness without decompo- sition. Action of Bromine The affinity of bromine for metallic substances is intermediate between chlorine and iodine ; for while chlorine disen- gages bromine from its combination with metals, the metallic iodides are decomposed by bromine. The bromides are formed in the same manner as the chlorides ; that is by the action of bromine upon the metals, or by evaporating solutions of metallic oxides in hydrobromic acid to dryness. Action of Iodine. Iodine has a strong attraction for the metals, and most of the compounds which it forms with them, can sustain a red heat, in close vessels, without decomposition. It is, however, inferior in the force of its affinity to either oxygen or chlorine. Chlorine when brought into contact with the iodides at high temperatures, effects their decomposition in the same manner as it does that of the oxides. Iodine separates oxygen only from potassa, soda, protoxide of lead, and the oxide of bismuth, when heated to redness. In all other cases the iodides are decomposed by exposure to oxygen gas, at the temper- ature of ignition. According to Gay Lussac, when the vapour of iodine is conducted over red hot lime, baryta or strontia, oxygen is not disengaged, but an iodide of these oxides is formed. If this be correct, it differs in this respect from chlorine. Iodine, however, is allowed not to combine with any other oxide under the same circumstances. Action of Fluorine. As this substance has not hitherto been obtain- ed in a separate state, we are unacquainted with the nature of its action on the metals. There is, however, every reason to suppose that the compounds obtained by the evaporation of certain solutions of metallic oxides in hydrofluoric acid, are in reality fluorides of the metals. Action of Hydrogen. Hydrogen combines with few metals. The only compounds, at present known, are those of potassium, zinc, ar- senic and tellurium. These are either solid or gaseous. They are generally obtained by liberating hydrogen in contact with the metals. Action of Nitrogen. Two compounds of nitrogen with metals are now known to exist, viz. the nitrurets of potassium and of sodium. These are obtained by treating the metals with ammoniacal gas. Tkenard, ii. 428. Action of Sulphur. There are but few metals which are incapable of combination with sulphur. These sulphurets, as they are termed, are often found native, and appear to have been known in the earliest ages of the world. They have, therefore, been studied with great care by many chemists. In general, metals form the same number of sulphurets as of oxides and chlorides, and the same law of composition applies to them. Thus a proto-sulphuret consists of one atom of sulphur and one atom of the metal ; a deuto-sulphuret of two atoms of sulphur and one of the rnetal, &c. All the metallic sulphurets are solid and inodorous. All, especially the artificial ones, are brittle, even though the metals which enter in- to their composition are ductile. All are insipid, except those of the 202 GENERAL P-ROPERTIES OF METALS. four first classes. Some, as the sulphurets of iron, lead, antimony, &c. have a metallic lustre ; others, as the sulphuret of mercury, are destitute of it. Most of them are susceptible of crystallization. Their specific gravity is always less than that of the metals which they con- tain, unless indeed the metal itself is lighter than sulphur, as potassi- um and sodium. In those cases where the metal itself possesses the power of de- composing water at ordinary temperatures, the sulphuret of the metal at this same temperature, possesses a similar property. A portion of gaseous sulphuretted hydrogen is at the same time liberated and a hy- drosulphuretted oxide remains. This takes place with the sulphurets of sodium, potassium, &c. An opinion was formerly quite prevalent among chemists that many of the metallic sulphurets were compounds of sulphur and a metallic oxide. This was supposed to be particularly the case with the fixed alkalies and alkaline earths. The more recent investigations of Ber- thier and Berzelius, however, have demonstrated that the metallic bases of these agree with the common metals in their disposition to unite with sulphur. It is now certain that whether a sulphate be de- composed by hydrogen or charcoal, or sulphur ignited with an alkali or alkaline earth, a metallic sulphuret is always the product. It is al- most equally certain that there are no definite compounds of sulphur and the metallic oxides. The metallic sulphurets may be obtained in one or other of the fol- lowing ways. 1. By heating the metal in combination with sulphur in a covered crucible. 2. By mixing sulphur with the oxide of a metal, and exposing the mixture to heat. 3. By depriving the neutral sulphates of the oxygen which they contain, through the agency of heat and combustible matter. 4. By the action of sulphuretted hydrogen upon the metallic salts. Thenard, Trait, de Chim. i. 540. Gay Lussac and Berzelius, Mem. d'Arcueil, i. Action of Phosphorus. The compounds of phosphorus and the me- tals have not yet been very accurately examined, and for the informa- tion we possess concerning them we are chiefly indebted to the re- searches of Pelletier. Phosphorus has heretofore been combined with only twenty-one metals, though it is probable that, like sulphur, it is capable of uniting with all. Pelletier supposed .that it combines only in one proportion with a metal, but this opinion is now abandoned ; it is most probably subject to the same laws of combination as sulphur and selenium. All the metallic phosphurets are solid, inodorous, brittle, and taste- less, except those of the metals which decompose water at the ordinary temperature, and give rise to caustic oxides ; most of them are crys- tallizable and have a brilliant metallic lustre. Many of the metallic phosphurets are, wholly or in part, decompos- ed by high temperatures, and those of the bases of the fixed alkalies and alkaline earths are decomposed by water. Thus when phosphuret of potassium is thrown upon water, protoxide of potassium is formed GENERAL PR OPERTlCTfe^feiS^Btjybf . 203 and phosphuretted hydrogen is liberated, being known by its inflam- mation when coming in contact with the air. None of the metallic phosphurets have hitherto been found in nature. They may be artificially prepared in several ways. 1. By bringing phosphorus either solid or in vapour, in contact with metals at high temperatures. 2. By mixing phosphate of lime and charcoal with the metal and exposing the mixture to heat in a covered ciucible. 3. By passing a current of phosphuretted hydrogen through solu- tions of certain metallic salts in water ; during this process water is formed and the phosphuret is precipitated in the form of flocks. The remarks which have been heretofore made, concerning the compounds of sulphur and the metallic oxides, will apply to phos- phorus. It is very doubtful whether there are any definite com- pounds of phosphorus and these oxides ; although it is asserted, by some chemists, that phosphurets of lime and baryta may be made by conducting the vapour of phosphorus over those earths at a red heat. Action of Carbon. Most of the metals* which have been reduced by charcoal retain a variable, though usually a very small quantity of it, And contrary to the idea formerly maintained, definite compounds are in this manner formed. The most important of these are cast iron and steel, which will be particularly noticed under the head of iron. Action of Cyanogen. Cyanogen, as already stated, (p. 180,) has an affinity for metallic substances. Few of the Cyanides, however, have been hitherto obtained in a separate state, excepting those of potas- sium, mercury, silver and palladium. The three latter are readily de- composed by heat. Cyanogen also unites with some of the metallic oxides. Action of Boron. There is but little known concerning the boru- rets. According to M. Descotils, however, they are solid, brittle, in- sipid and inodorous ; and they are formed by calcining strongly a mix- ture of charcoal, boracic acid and filings of iron or platinum, formed into a paste with oil or fat. In this process the oxygen of the boracic acid unites with the carbon, producing carbonic oxide, which is disen- gaged; at the same time the boron combines with the iron or platinum, forming a boruret. Action of Selenium. It is probable that selenium will unite with most of the metals. The combination is effected by bringing selenium in contact with metals at a high temperature, or by adding hydrosele- nic acid to metallic solutions. The seleniurets have a close resem- blance to sulphurets. Actions of metals upon each other. The union of a metal with one or more metals, is termed an alloy ; and each alloy is distinguished by the name of the metals which constitute it. Thus an alloy of lead and tin is a combination of lead and tin. The name amalgam, however, is applied to combinations of mercury with the metals. Thus when we speak of an amalgam of this or that metal, we express a compound of that metal with mercury. The study of the metallic combination has not yet received that attention which its importance seems to demand. It is probable that each metal is capable of combining in one or more proportions with every other metal, though the number of alloys at present known, 204 GENERAL PROPERTIES OF METALS. does not exceed one hundred and forty. But it may be observed that there are some circumstances which will prevent the number of these .compounds from reaching the limit which theory may designate. Among these may be ranked, in particular, the very different fusibili- ty and volatility of the metals ; causes which oppose obstacles to the formation of alloys. Chemists very generally agree that the metals unite with each other in every proportion, in the same manner as sulphuric acid or alcohol and water ; and that their combination is not governed by those laws which apply to the oxides, acids and other definite com- pounds. An opposite opinion, however, has been maintained by Ber- zelius, as well as by Dalton. Potassium, the former observes, gives, with mercury, two crystallized compounds, one of which contains twice as much potassium as the other. The Arbor Diana? is a defi- nite compound of silver and mercury. When zinc and copper are distilled together, a certain quantity of zinc comes over, but the rest cannot be raised by heat. From a fused mixture of antimony, iron and copper with much tin, metallic crystals separate on cooling, con- taining fixed proportions of the component metals. Indeed, as Mr. Turner remarks, it is possible that the variety of proportions is rather apparent than real, arising from the mixture of a few definite com- pounds with one another, or with uncombined metals, an opinion not only suggested by the mode in which alloys are prepared, but in some measure by observation. Still, however, the present state of our knowledge does not warrant us in considering all the alloys as chemi- cal compounds. The alloys resemble the metals in most of their physical pro- perties. They are solid at ordinary temperatures, except the al- loy of potassium and sodium, and the amalgams in which mercury predominates ; they are opaque ; possess the metallic lustre ; are good conductors of electricity and caloric ; and are more or less crystalline in structure. They often differ in some respects from the metals of which they are composed. The colour of an alloy is some- times different from that of its constituents, of which brass is a re- markable example. The hardness of a metal is in general increased by being alloyed, and for this reason its elasticity and sonorousness are frequently improved. The malleability and ductility of metals, on the contrary, are usually impaired by combination. Alloys formed of two brittle metals are always brittle ; and an alloy composed of a ductile and a brittle metal is generally brittle, especially if the latter predominate. An alloy of two ductile metals is sometimes brittle. The density of an alloy is sometimes less, sometimes greater, than the mean density of the metals of which it is composed. The fusibility of metals is greatly increased by being alloyed. Thus pure platinum, which cannot be completely fused in the most intense heat of a wind furnace, forms a very fusible alloy with arsenic. The tendency of metals to unite with oxygen is considerably aug- mented by being alloyed. This effect is particularly conspicuous when dense metals are liquefied by combination with quicksilver, and is manifestly owing to the loss of their cohesive power. Lead and tin, for instance, when united with mercury, are soon oxidized by ex- posure to the atmosphere ; and even gold and silver combine with oxygen, when the amalgams of those metals are agitated with air. The oxidability of one rnetal in an alloy appears in some instances to be increased in consequence of a galvanic action. Thus Mr. Faraday observed, that an alloy of steel with 100th of its weight of platinum GENERAL PROPERTIES OF METALS. 205 was dissolved with effervesence in dilute sulphuric acid, which was so weak that it scarcely acted on common steel ; an effect which he ascribes to the steel in the alloy being rendered positive by the pres- ence of the platinum. Turner. A number of metallic alloys are found native ; among these may be mentioned those of arsenic, with bismuth, with antimony, with nickel, with iron, and with silver ; of iron and nickel ; of silver and antimo- ny ; silver and lead ; nickel and cobalt, besides a great many others, especially those which are found in the mines of platinum and tellu- rium. Alloys may be prepared artificially, by heating in a crucible the metals of which they are composed. When fusion has been effected they are to be carefully mixed, without which, especially if the metals are of different specific gravities, the alloy will not be homogeneous. If one or both the metals are volatile, care should be taken not to sub- ject the alloy to too high heat. A modification of this process is re- quired for the preparation of alloys of potassium and sodium, which cannot be effected in contact with air. For this purpose we should employ a tube closed at one end ; the potassium or sodium is put into the lower part and covered with the metal with which it is to be alloy- ed ; the tube is then to be heated until both the metals are fused. Amalgams are either liquid or solid; liquid, when the mercury pre- dominates, and generally solid when the quantity of mercury is less than that of the metal to which it is united. There is, however, con- siderable variation in this respect. Thus the amalgam formed of 80 parts of mercury and I of sodium is solid, while that formed of 15 parts of mercury and 1 of tin is liquid. In the liquid state, the amalgams resemble mercury, except that they flow less easily ; in their solid state they are brittle. They are very generally of a white colour. They are all susceptible of crystallization, and of being formed in constant proportions. To effect this it is necessary to dissolve, by heat, a certain quantity of a metal in mercury, and to suffer the com- bination to become cold ; it then separates into two portions, the one solid and crystallized, the other liquid. All the amalgams can be decomposed by a red heat. Almost all the liquid amalgams which contain an easily oxidized metal are decompos- ed by the contact of air ; this is particularly the case with the amal- gams of potassium, barium, strontium and calcium. The amalgams may be prepared by bringing mercury in contact with the metals in a state of minute division. It is well known that mercury instantly combines with gold and assumes a white colour. These combinations, however, may be more advantageously formed by the aid of heat ; indeed the amalgams of zinc and antimony can only be properly formed by melting these metals, and throwing into them the metals slightly heated by little at a time. Some amalgams may also be formed by the action of the Voltaic bat- tery. Thus when a globule of mercury is placed in contact with the negative wire, during the process of decomposing potassa by galvan- ism, an amalgam of potassium is formed. Some of these combinations are of great importance in the arts. 206 GENERAL PROPERTIES OF METALS. CLASSIFICATION OP THE METALS. The study of the metals ought not to be conducted in an arbitrary manner. They may be conveniently divided into the following natural groups or classes, viz : CLASS I. Metals, which wheii combined with oxygen form the fixed al- kalies. Potassium, Sodium, Lithium. These metals have such a powerful attraction for oxygen, that at common temperatures they decompose water at the moment of con- tact, and are oxidized; while at the same time, the hydrogen of the water is liberated in a gaseous form. The resulting oxides are dis- tinguished by their causticity and solubility in water, and by their pos- sessing properties which are denominated alkaline. CLASS II. Metals, which when combined with oxygen form alkaline earths. Barium, Strontium, Calcium, Magnesium. These, like the preceding, decompose water at ordinary tempera- tures. The resulting oxides are called Alkaline Earths / because, while in their appearance they resemble the earths, they are similar to the alkalies, in having a strong alkaline reaction with test paper, and in neutralizing acids. The three first are strongly caustic, and baryta and strontia are soluble in water to a considerable extent. CLASS III. Metals , which when combined with oxygen form earths. Aluminium, Glucinum, Yttrium, Zirconium, Silicium, Thorium. The oxides of these metals constitute the well known substances denominated pure earths. They are white, and of an earthy appear- ance ; in their ordinary state, are quite insoluble in water, and do not affect the colour of litmus or turmeric paper. As salifiable bases, they are quite inferior to the alkaline earths ; and one of them, namely silica, is considered by some chemists, as an acid, for reasons which will hereafter be developed* CLASS IV. Metals, which decompose water only when tfteir temperature is raised to redness. Manganese, Tin, Cobalt, Zinc, Cadmium, Iron, Nickel, GENERAL, PROPERTIES OF METALS. 207 CLASS V. Metals, which do not decompose water at any temperature , and the oxides of which are not reduced to the metallic state by the sole ac- tion of heat. These may be ranged under two heads : 1. Those which, when combined with oxygen, form acids. Arsenic, Tellurium, Chromium, Tungsten, Molybdenum, Uranium, Vanadium, Antimony, Titanium. Columbium, Cerium, 2. Those which do not form acids : Copper, Lead, Bismuth. CLASS VI. Metals, the oxides of which are decomposed by a red heat. Mercury, Silver, Gold, Platinum, Palladium, Rhodium. Osmium, Iridium, 208 POTASSIUM. CLASS I. METALS WHICH WHEN COMBINED WITH OXYGEN FORM THE FIXED ALKALIES. SECTION I. POTASSIUM. Atom. Num. 39-15 Symb. PoSp. gr. O. 865, Discovered by Sir H. Davy in 1807, and particularly examined by him and Gay Lussac and Thenard. PROPERTIES. Potassium is solid at ordinary temperatures ; at 7(P F. it is somewhat fluid, though its fluidity is not perfect, till it is heat- ed to 50 F. ; it sublimes at a red heat without undergoing any change, Erovided the air be completely excluded ; at 50 it is ductile and mal- jable, and of the consistency of soft wax ; at 32 J it becomes a hard and brittle solid ; in colour and lustre itis precisely similar to mercury; is a good conductor of electricity and caloric ; has a great affinity for oxygen gas, oxidizing rapidly when exposed to air or by contact with flu- ids containing oxygen, and decomposing water with the disengagement of heat and light ; burns when heated in the air with a brilliant white light ; it burns spontaneously in chlorine with intense brilliancy. Potassium has a great affinity for oxygen. When exposed to the air or brought into contact with fluids which contain oxygen, this metal is rapidly Oxidized. On this account it must be preserved, either in glass tubes hermetically sealed, or under the surface of liquids, such as naphtha, of which oxygen is not an element. It decomposes water. When potassium is thrown upon the surface of water it decomposes that liquid with great rapidity, and the hydrogen gas evolved carrying with it small particles of the metal, takes fire in the air, and communicating the combustion to the potassium, the whole burns with a kind of explosion, emitting a red light. If a globule of potassium be placed on ice, it instantly burns with a bright flame and a deep hole is made in the ice, filled with a fluid which is found to be solution of potassa. The production of an alkali by the action of water upon potassium is most satisfactorily shown by dropping a globule of the metal upon moistened paper, which has been tinged with turmeric. At the mo- ment when the globule comes into contact with the paper, it burns and it moves rapidly, as if in search of moisture, leaving behind it a deep reddish brown trace, and acting upon the paper exactly like dry caustic potassa. Ezp. The following is an instructive experiment : Take a piece of potassium, wrap it up in a small piece of paper, and introduce it POTASSIUM. 209 quickly into a glass test tube, inverted in a small vessel of infusion of blue cabbage, the tube being filled with the same liquid. The metal will immediately rise to the top, and the moment the water reaches it through the paper, part of it will be decomposed, the oxygen combin- ing with it and forming potassa, which changes the blue of the infusion to a green ; while an equivalent portion of hydrogen gas is found in the tube and may be inflamed by a lighted taper. But perhaps the most striking illustration of the deoxidizing power of potassium is exhibited bj its action on carbonic acid. When heated in contact with that gas, it takes fire, and by uniting with its oxygen, forms potassa, while the liberated carbon is deposited in the form of charcoal. PREPARATION. This metal was first obtained by Sir H. Davy by subjecting moistened hydrate of potassa to the action of a powerful voltaic battery the oxygen of both the water and potassa passed over to the positive pole, while the hydrogen of the former and metallic potassium appeared at the negative. By this process, how- ever, the metal is obtained in small quantity only ; but Gay Lussac and Thenard invented a method by which a larger supply may be ob- tained. This process consists in bringing the fused hydrate of po- tassa in contact with turnings of iron heated to whiteness in a gun barrel. Potassium may also be prepared, as first noticed by M. Curaudau, by mixing dry carbonate of potassa with half its weight of powdered charcoal, and exposing the mixture, contained in a gun-barrel, or spheroidal iron bottle, to a strong heat. An improvement on both processes has been made by M. Brunner, who decomposes potassa by means of iron and charcoal. From eight ounces of fused carbonate of potassa, six ounces of iron filings, and two ounces of charcoal, mixed intimately, and heated in an iron bottle, he obtained 140 grains of potassium. Berzelius has observed that the potassium thus made, though fit for all the usual purposes to which it is applied, contains a minute quantity of carbon ; and, therefore, if required to be quite pure, must be rendered so by distillation in a retort of iron or green glass. A modification of this process has been since described by Wohler, who effects the decomposition of the potassa solely by means of charcoal. The material employed for the purpose is 'carbonate of potassa, prepared by heating cream of tartar to redness in a covered crucible. REFERENCES. Sir II. Davy^s Bakerian Lecture, Phil. Trans. 18,08, Repert. of Arts , Zd ser. xiii. 123, 175. Gay Lussac and Thenartfs im- proved method, Recherches Phys. Chim. i. 74, B runner's process, Branded Jour. xv. 279. Wohlcr^ Branded Jour. xxii. 206. For descriptions of the most approved processes for obtaining potassium, see also Berzelius, ii. 273. and Henry ) i. 544. Dr. Gale on the preparation of Potassium, Sillim. Jour. xix. 205. POTASSIUM AND OXYGEN. Potassium unites with oxygen in two proportions, forming the jPro- toxide or Potassa, or Potash, and the Peroxide. 210 POTASSIUM. Peroxide of Potassium. Atom. Num. 47' 15 Symb. 0+Po. SYN. Vegetable Alkali. PROPERTIES. A white solid, very caustic, heavier than potassium, changing vegetable blues to green ; fusible at a heat below redness, and bears the highest heat without decomposition ; very deliquescent, and hence very soluble in water ; absorbs oxygen at a high tempe- rature and passes into the state of peroxide ; attracts moisture and car- bonic acid from the air, and is converted into a carbonate ; it cannot then be wholly deprived of its water by the most intense heat, having formed with it a solid hydrate of potassa. NATIVE STATE. Potassa occurs in nature as a constituent of differ- ent minerals and in certain organized bodies. It is found in considera- ble quantities in the minerals felspar and mica, from which, indeed, Fuchs has proposed to prepare potash for commercial purposes. It is also contained in the ashes of vegetables, but in these cases it requires a subsequent process to render it pure. Hydrate of Potassa. Atom. Num. 58-15 Symb. (O-j-Po) +CO+H) SYN. Lapis Caustlcus Potassce. Potassa fusa. Lond. and Edin. Phar. PROPERTIES. Solid at common temperatures ; fuses at a heat rath- er below redness, and assumes a somewhat crystalline texture on cooling; highly deliquescent, and requires about half its weight of water for solution; soluble likewise in alcohol; destroys all animal textures, and hence employed in surgery as a caustic ; when in solu- tion, forms the aqua potassce, of the Pharmacopoeias, which possesses properties similar to the hydrate. PREPARATION OF ANHYDROUS AND HYDROUS POTASSA. The protoxide of potassium is always formed when potassium is put into water, or exposed to dry air or oxygen gas. By the first process, even when the solution is evaporated to dryness and exposed to a red heat, it retains a portion of water ; by the second it is anhydrous. The anhydrous oxide may also be obtained according to Berzelius, by fusing one part of potassium with 1-4 of hydrate of potassa ; the water of the hydrate is decomposed, hydrogen gas is disengaged and 2-3 parts of anhydrous potassa are procured. The aqueous solution of potassa is prepared by decomposing car- bonate of potassa by lime. The best process consists in boiling in a clean iron vessel, carbonate of potassa, with half its weight of pure quick lime, in water. The lye is strained through clean linen, con- centrated by evaporation, again strained, and set by in a well stopped bottle, till it admits of being decanted clear from the sediment. If the clear solution is evaporated to dryness, and afterwards cast into sticks, it forms the potassa fusa. This may be further purified by alcohol, which dissolves only the pure hydrate of potassa, and leaves the im- purities ; the alcohol is then driven off by heat. According to Dr. Ure, pure potassa for experimental purposes may most easily be obtained by igniting cream of tartar in a crucible, dis- POTASSIUM. 211 solving the residue in water, filtering, boiling with a quantity of quick lime ; and after subsidence, decanting the clear liquid, and evaporating in a loosely covered silver capsule till it flows like oil, and then pouring it out on a clean iron plate. A solid white cake of pure hydrate of potassa is thus obtained, without the agency of alcohol. It must be immediately broken into fragments, and kept in a well stopped phial. In consequence of the rapid absorption of carbonic acid by pure potassa when it is freely exposed to the atmosphere, it is desirable to filter its solution in vessels containing as small a quantity of air as possible. This object is attained by the apparatus contrived by Mr. Donovan. Ann. of Phil. xxvi. 115. Turner's Chem. 283. Mr. Dalton has constructed a table showing the quantity of real potassa in solutions of different specific gravities. Henry's Chem. L 550. USES. As potassa absorbs carbonic acid gas rapidly it is sometimes employed for withdrawing that substance from gaseous mixtures. It is also employed as a reagent in detecting the presence of bodies, and in separating them from each other. The solid hydrate, owing to its strong affinity for water, is used for depriving gases of hygrometric moisture, and is well fitted for forming frigorific mixtures. REFERENCES. Lowitz's method of obtaining crystallized Potash, perfectly pure, Ann. de Chim. or Rep. of Arts. Zd ser. x. 225. Berthollet on the same subject* Rep. of Arts, 2d ser. xii. 121. Hope and Philips on the preparation of Aqua Potassoz, Ann. of Phil. xvii. CO, 190 ,xviii. 30. Peroxide of Potassium. Atom. Num. 63-15 Symb. 3O+Po. Discovered by Gay Lussac and Thenard. PROPERTIES. Of an orange colour, caustic, changing infusion of litmus to green ; specifically heavier than potassium ; fusible below a dull red heat ; decomposed by the Voltaic battery, but not by heat ; when thrown into water, oxygen gas is evolved, and it passes to the state of protoxide ; when fused and brought into contact with com- bustible bodies, they burn vividly in the excess of its oxygen. PREPARATION. This compound may be prepared by burning potas- sium in open air, or by heating the metal in a vessel of oxygen gas over mercury, or by exposing nitrate of potassa to a red heat. REFERENCES. Thenard^s Chem. ii. 33S. Bridges, in North Am. Med. and Swg. Jour. v. 241. POTASSIUM AND CHLORINE. Chloride of Potassium. Atom. Num. 74 6 Symb. Cl+Po. Long known to chemists under various names, as Febrifuge salt of Sylvius ; Regenerated Sea Salt, fyc. PROPERTIES. Occurs in cubic crystals, which have a saline and bitter taste, and require three parts of water at 60 F. for solution, and rather a less proportion of boiling water. PREPARATION, When small pieces of potassium are introduced into 212 POTASSIUM. chlorine, intense inflammation takes place, and direct combination en- sues. This chloride is also procured by dissolving either hydrate or carbonate of potassa in muriatic acid, and evaporating the solution to perfect dryness. POTASSIUM AND BROMINE. Bromide of Potassium. PROPERTIES. Crystallizes in cubes or in rectangular prisms ; the crystals destitute of water, decrepitating when healed, and entering into fusion without suffering any change ; very soluble in water, and slightly so in alcohol. PREPARATION. Formed by saturating hydrate of potassa with bro- mine ; the solution containing bromate of potassa, and bromide of potassium, is evaporated to dryness, and the residuum heated until it. ceases to evolve oxygen. The bromate is then converted into bro- mide. BerzdiiLS, iii. 374. POTASSIUM AND IODINE. Iodide of Potassium. Atom. Num. 165*15 Synib. I+Po. PROPERTIES. Crystallizes in white cubes ; fuses readily when heat- ed, and is volatilized at a temperature below redness ; deliquesces in a moist atmosphere, and is very soluble in water ; soluble also in strong alcohol. PREPARATION. This compound may be formed by heating potassi- um in a tube of green glass, with excess of iodine. It may also be ob- tained by means of heat from the iodate, and by crystallization, from the hydriodate of potassa. POTASSIUM AND HYDROGEN. These substances unite in two proportions, the one gaseous, the other solid. The latter contains the least hydrogen. Hydruret of Potassium. Discovered by Gay Lussac and Thenard. PROPERTIES. A grey solid, destitute of metallic lustre ; infusible ; not inflammable either in air or in oxygen gas at common tempera- tures, but burns vividly at a high one ; totally decomposed when heat- ed in a close vessel, the hydrogen being liberated in the form of gas, the potassium remaining ; when brought into contact with heated mercury, hydrogen gas is evolved, and an amalgam of potassium and mercury is produced. PREPARATION. This compound may be prepared by heating potas- sium in hydrogen gas ; and the only difficulty consists in regulating the heat, for a high temperature decomposes the compound. REFERENCE. Thenard' s Chem. i. 498, POTASSIUM. 213 Gaseous Hydraret of Potassium. Discovered by Sementini. PROPERTIES. A colourless gas, which, when recently prepared, in- flames by the contact of oxygen gas or air, at the ordinary tempera- ture, but at the end of a certain time, loses this property, because it parts with a portion of its potassium. PREPARATION. According to Sementini, gaseous hydruret of potas- sium is formed when the hydrate of potassa is subjected to a very high temperature in contact with iron. In this case the oxygen of the wa- ter and of the protoxide, combines with the iron, while the hydrogen combines in part with the potassium. Thenard, i. 499. POTASSIUM AND NITROGEN. According to Thenard, when potassium is heated in ammoniacal gas, hydrogen gas is liberated, and a Nitruret of Potassium is formed, con- sisting of 100 parts of potassium, and 11-728 of nitrogen. Thenard, POTASSIUM AND SULPHUR. Sulphuret of Potassium. Atom. Num. 55' 15 Symb S+Po. PROPERTIES. Has a reddish colour : fuses below the temperature of ignition, and assumes a crystalline texture on cooling; dissolves in water, being probably converted with the evolution of caloric into hy- drosulphuret of potassa. PREPARATION. Sulphur and potassium readily unite by the aid of heat, with the evolution of so much caloric, that the mass becomes in- candescent. The best method, however, of preparing this sulphuret, is to reduce in a close vessel, sulphate of potassa with charcoal, or to heat the same salt to redness in a glass or porcelain tube, and then pass over it a stream of hydrogen gas. Besides this protosulphuret, Berzelius has described four other com- pounds, which he obtained by igniting carbonate of potassa with dif- ferent proportions of sulphur. These are composed of one equivalent of potassium to two, three, four, and five equivalents of sulphur. See Berzelius, in Ann. of Phil. xx. 284. Trait, dc C/dm. ii. 300. POTASSIUM AND PHOSPHORUS. Phosphuret of Potassium. This compound may be formed by the action of potassium on phos- phorus with the aid of a moderate heat. It is converted by water into potassa and perphosphuretted hydrogen gas, which inflames at the moment of its formation. 214 POTASSIUM. POTASSIUM AND CYANOGEN. Cyanide or Cyanuret of Potassium. Potassium acts with great energy upon cyanogen ; by the aid of heat it absorbs this gas, with the evolution of light. The compound thus formed is of a yellowish colour ; has a very alkaline taste ; de- composes water, and gives rise to hydrocyanate of potassa. Thenard, i. 473. The process given by Robiquet for procuring this compound, is to subject ferrocyanate of potassa for a considerable time to heat. Pre- pared in this manner, it is proposed as a substitute for hydrocyanic acid, for medical purposes. Magendie's Formulary, 71. POTASSIUM AND THE METALS. The compounds of potassium and the metals are always solid, ex- cept when mercury or sodium form a part of them, when they are often liquid. They are white and generally brittle ; fusible at a tem- perature below redness ; oxidized by exposure to air ; and they decom- pose water when brought into contact with it. These compounds are obtained by heating potassium with the differ- ent metals in a glass tube, or better, by mixing the metals with about half their weight of carbonized cream of tartar, throwing them into a crucible, covering the mixture with powdered charcoal, luting the cover to the crucible, and calcining for about two hours. Serullas, Ann. de Chim. Alloy of Potassium and Sodium. The alloy consisting of 10 parts of potassium and only one of sodium, is liquid at F., and presents the very remarkable property of being lighter than naptha, or rectified petroleum. Alloy of Potassium and Bismuth. This may be obtained by calcin- ing an intimate mixture of 60 parts of carbonized cream of tartar, and 120 parts of bismuth, in the manner before described. This alloy, rich in potassium, scintillates when cut with the scissors, melts and inflames when bruised, and decomposes water. A portion of common charcoal added to it, converts it, according to Serullas, into a pyro- phorus, which, when brought into contact with water, inflames, and produces slight detonations. Alloy of Potassium and Tin. This may be formed by mixing togeth- er 60 parts of tartar, 8 of lampblack, and 100 of oxide of tin. If the quantity of carbon is doubled, a true pyrophorus is produced. Amalgam of Potassium and Mercury. When 1 part of potassium and 145 parts of mercury are heated in a glass tube out of contact of air, an amalgam is formed, which resembles mercury in its appearance ; it absorbs oxygen at common temperatures, and is converted into pure mercury, and into the oxide of potassium. Amalgam of potassium can also be obtained by agitating parcels of potassium on a mercurial bath. When potassium is combined with 60 times its weight of mercury, an amalgam is obtained which is solid, very fusible, white, and which crystallizes easily arid possesses the same properties as the preceding. The liquid amalgam when placed in contact with ammonia, or the ammoniacal salts, produces an ammoniacal hydruret of potassium and POTASSIUM. 215 mercury. This compound is quite remarkable for its metallic aspect, its consistency, and its easy decomposition. A fact noticed by Berzelius concerning the action of amalgam of potassium upon water, deserves to be mentioned. It is, that with water alone it evolves pure hydrogen ; but when the water is acid, or charged with sal ammoniac, the hydrogen gas disengaged has the same odour as that obtained by the use of zinc and dilute sulphuric acid. Thenard, i 619. REFERENCES. Vauquelir), in Ann. de Chim. et de Phys. vii. 32. Serul- las, same Work, xxi. 197, or Repert. of Arts, %d ser. xliv. 376. Tlienard, Traite de Chim. i. 622. SALTS OF POTASSA. Chlorate of Potassa. Atom. Num. 122-6 Symb. (50+CI) f SYN. Hyp erozy muriate of Potash. Chlorate Potassique. Berzelius. PROPERTIES. Colourless, crystallizes in four and six-sided scales of a pearly lustre, the primitive form of which, according to Mr. Brooke, is an oblique rhombic prism ; soluble in sixteen times its weight of water at 60 F., and in two and a half of boiling water ; is quite anhydrous, and when exposed to the temperature of 400 or 500 F. , undergoes igneous fusion, and on increasing the heat almost to redness, effervescence ensues, and pure oxygen is disengaged ; is de- composed by the stronger acids, and exerts powerful effects on inflam- mable bodies. It is decomposed by the stronger acids. If a few grains of the salt are dropped into a little concentrated sulphuric acid in a wine glass, a strong smell will arise : and if larger quantities of the materials be heated in a retort, a violent explosion sometimes ensues. f Muriatic acid disengages chlorine from chlorate of potassa, and the addition of a few grains of the salt to an ounce measure of the acid, imparts to it the property of discharging vegetable colours. It exerts powerful effects on inflammable bodies. To one grain of the powdered salt in a mortar, add about half a grain of phosphorus. The phosphorus will detonate, on the gentlest triture, with a very loud report. The hand should be covered with a glove in making this experiment, and care should be taken that the phosphorus does not fly into the eyes. Charcoal or sulphur may be substituted for the phosphorus in the above experiment, with the same effects ; it requires, however, more powerful triture ; or the experiment may be varied by wrapping the rri'xed ingredients in strong paper or tin foil and then striking them with a hammer. This salt may be substituted for nitre in the preparation of gun- powder, but the mixture of the ingredients requires great care, on ac- count of their liability to explode by trituration. When mixed with sulphur it often detonates spontaneously. PREPARATION. This salt is made by transmitting chlorine gas through a concentrated solution of pure potassa, until the alkali is completely neutralized. The solution, which, after being boiled for a few minutes, contains nothing but the muriate and chlorate of po- tassa, is gently evaporated till a pellicle forms upon its surface, and 216 POTASSIUM. is then allowed to cool. The greater part of the chlorate crystallizes, while the muriate remains in solution. The crystals, after being washed with cold water, may be purified by a second crystallization. USES. This salt is employed in the preparation of percussion poic- der, which is merely a gunpowder in which chlorate of potash is sub- stituted for nitre. A little of it is put into a thin copper thimble, when struck it catches fire and explodes in the piece. It is also employed in the construction of the pocket lights, now so generally employed. For this purpose the end of the match is dipped into a paste made of chlorate of potassa, sulphur, sugar and gum arabic. These when per- fectly dry, take fire by being dipped into bottles containing amianthus which has been soaked into concentrated sulphuric acid. This salt is also used for medicinal purposes in the form of solution and of ointment. See Magendie's Formulary. REFERENCES. For details concerning the preparation of this salt, see Henry's Chemistry , i. 555. Berzelius, iii. 403, who also describes a Chlorite of Potassa. Fourcroy and VauqueUrSs experiments on the explosion of this salt. Ann. de Chim. or Repert. of Arts, 1st ser. viii. 65. CutbusJi's Pyro- techmj, 74. Perchlorate of Potassa. Atom. Num. 138-6 Symb. (70+Cl.)+(0+Po.) PROPERTIES. Crystallizes in elongated octahedrons ; does not change vegetable colours ; requires more than fifty times its weight of water at 60 F. for solution ; distilled at 280 F. with an equal weight of sul- phuric acid, it yields perchloric acid : when heated to 412 F. oxygen is evolved and chloride of potassium remains. PREPARATION. This salt may be formed by mixing one part of powdered chlorate of potassa with three of sulphuric acid, and cau- tiously exposing the mixture to heat till it turns white, when we obtain a mixture of bi-sulphate and perchlorate of potassa. The for- mer being much more soluble than the latter in cold water, their sep- aration may be effected by solution and crystallization. lodate of Potassa. Atom. Num. 213-15 Symb. (5O+I.) -KO+Po.) PROPERTIES. Occurs in small white granular crystals ; when pro- jected on hot coals, acts like saltpetre ; difficultly soluble in water ; when heated to redness, oxygen is given out and is converted into oxide of potassium. PREPARATION. This salt is easily procured by agitating iodine with a solution of potassa ; water is decomposed and gives rise to a solu- ble hydriodate and a difficultly soluble iodate. When evaporated to dryness and afterwards treated by strong alcohol, the hydriodate is dissolved and leaves the iodate in the form of crystals. Hydriodate of Potassa. This salt exists only in solution ; when dry it is the iodide of potassium. It is very soluble in boiling water and requires only two-thirds of its weight of water at 60 F. for solution ; it is also soluble in alcohol. POTASSIUM. 217 PREPARATION This salt is easily obtained by neutralizing hydriodic acid with potassa. But as it is employed quite largely for medicinal purposes, an easier process may be adopted. Perhaps the most eligible of those which have been proposed is to evaporate the mixed iodate and hydriodate of potassa, formed by adding iodine to a warm solution of potassa until the alkali is neutralized, and exposing the dry mass in a platinum crucible to a rather low red heat in order to convert the iodate into the iodide of potassium. The fused mass is then dissolved out by water and crystallized. Turner. REFERENCES. Turner 1 s method of preparing Hydriodate of Potassa, Edin. Med. and Surg. Jour., J/ily, 1825. Hydrofluate of Potassa. Crystallizable and deliquescent ; its solu- tion which is alkaline, attacks glass in a day or two and destroys its polish. When the liquid is rendered neutral by acetic acid, it be- comes on farther dilution with water strongly acid, and vinegar is set at liberty. Prepared by supersaturating carbonate of potassa with hydroflu- oric acid, evaporating the solution to dryness, and expelling the excess of acid by heat. Berzelius, Traite de Chim. iii. 377. The, nard, iii. 324. Bihydrnfluate of Potassa. Forms square tables and is readily soluble in water ; fuses by heat, giving out vapour of hydrofluoric acid, and leaving a portion of neutral salt. Procured by adding to hydrofluoric acid a quantity of potassa, in- sufficient for neutralizing it completely, and concentrating the solu- tion. By slow evaporation crystals are obtained. Berzelius and Thc- nard. These compounds are probably in their dry states Fluorides of Po- tassium. Nitrate of Potassa. Atom. Num. 10M5 %&. (5O+N) + (0+Po.) SYN. Saltpetre. Nitre. PROPERTIES. A colourless salt, crystallizing readily in six-sided prisms, the primitive form of which is a right rhombic prism ; [Levy, in Brandes Jour. xv. 284] taste saline, accompanied with an impres- sion of coolness ; it requires for solution seven parts of water at 60 F. and its own weight of boiling water ; it contains no water of crys- tallization, but its crystals are never quite free from water lodged me- chanically within them ; at 616 F. it undergoes the igneous fusion, and like all the nitrates is decomposed by a red heat ; it is also rapidly decomposed by sulphur, charcoal arid phosphorus. It is rapidly decomposed by charcoal, sulphur, fyc. This may be shown, by mixing two parts of powdered nilre with one of powder- ed charcoal, and setting fire to the mixture in an iron vessel under a chimney. The gaseous product of this combustion, which may be collected by a proper apparatus, is carbonic acid and nitrogen gas. Part of the carbonic acid also remains attached to the residuary al- kali and may be obtained from it, by adding a stronger acid. This residue was termed by the old chemists, Clyssus of Nitre ; if excess 218 POTASSIUM. of charcoal be used, the results are carbonic oxide and acid, nitrogen and subcarbonate of potassa, formerly called nitrum Jixum and white flux. When phosphorous is thrown upon nitre and inflamed, a vivid com- bination ensues, and a phosphate of potassa is formed. Sulphur sprinkled upon hot nitre burns and produces a mixture of sulphate and sulphite of potassa, formerly employed in medicine under the name of Glaser's polychrest salt. Most of the metals, also, when in filings or powder, detonate and burn when thrown on red hot nitre. A mixture of three parts of powdered nitre, two of carbonate of potassa and one part of sulphur, dried and accurately mixed together, forms the Fulminating Powder, which explodes with a loud noise when laid on an iron plate heated below redness. Gunpowder, consists of a very intimate mixture of nitre, sulphur and charcoal. The proportions vary. The following are those usu- ally employed. Common Shooting Shooting Miners' Gunpowder. Powder. Powder. Powder. Saltpetre, 75.0 78 76 65 Charcoal, 12.5 12 15 15 Sulphur, 12.5 10 9 20 The latter contains the smallest quantity of saltpetre, as it requires less quickness or strength. The ingredients are perfectly mixed, moist- ened, beaten into a cake which is afterwards broken up, granulated, dried, and, for the finest powder, polished by attrition. The violence of the explosion of gunpowder depends upon the sudden production of gaseous matter, resulting from the action of the combustibles upon the nitre. Carbonic oxide, carbonic acid, nitrogen and sulphurous acid, are the principal gaseous results, and the solid residue consists of subcarbonate and sulphate of potassa, sulphuret of potassium and charcoal. Nicholson s Journal, iv. PREPARATION. This salt is generated spontaneously in the soil, and crystallizes upon its surface, in several parts of the world, and espe- cially in the East-Indies, whence the greater part of the nitre used in Britain is derived. It is also found abundantly in several caverns hi the western parts of the United States. [Cleav eland' 's Mineralogy.'] In France and Germany, it is prepared artificially from a mixture of common mould or porous calcareous earth with animal and vegetable remains containing nitrogen. When a heap of these materials, pre- served moist and in a shaded situation, is moderately exposed to the air, nitric acid is gradually generated, and unites with the potassa, lime and magnesia, which are commonly present with the mixture. On dissolving these salts in water, and precipitating the two earths by car- bonate of potassa, a solution is formed, which yields crystals of nitre by evaporation. The nitric acid is probably generated under these cir- cumstances by the nitrogen of the organic matters combining during putrefaction with the oxygen of the atmosphere, a change which must be attributed to the affinity of oxygen for nitrogen, aided by that of ni- tric acid for alkaline bases. Turner. USES. The greatest consumption of this salt is in the manufacture of gunpowder. It is also employed in the formation of nitric acid POTASSIUM. 219 and in chemistry as an oxidizing agent. In the East Indies it is used for the preparation of cooling mixtures ; an ounce of powdered nitre dissolved in five ounces of water reduces its temperature fifteen de- grees. It possesses powerful antiseptic properties, and is, therefore, much employed in the preservation of meat and animal matters in gen- eral. ACTION ON THE ANIMAL ECONOMY. This salt is often mistaken for saline laxatives, especially for the sulphate of soda, and has thus been the source of fatal accidents. Cases of this kind are related by Dr. Christison in his Treatise on Poisons, 160. REFERENCES. For a description of the mode of preparing this salty see Thenard, Traite de Chirn. iii. 252. Thomson on the effect of red heat upon Nitrate of Potassa, First Prin. i. 107. On the preparation of Gunpow- der Nicholsons Jour, xxiii. 277. Dr. Ure on the composition of Gun. powder, Journ. of the Roy. Inst. Oct. 1830. Gay Ltissac's process for an- alyzing Gunpowder, Ann. de Chim. et de Phys. xri. 434, and Thenard, iii. 269. Longchamp on Nitrification, Phil. Mag. and Ann. i. 172. The article Gunpowder in the Supplement to the Encyclopaedia Britannica^ by Dr. IWCulloch. CutbusWs Pyrotechny. Watson"* s Chemical Essays. Hyposulphite of Potassa. This salt is best formed by decomposing hydrosulphuret of potassa by sulphurous acid. The salt has a taste at first not unlike that of nitre, succeeded by bitterness, and it is de- liquescent when carefully dried ; it takes fire on raising the heat, and burns like tinder, but with a feeble blue flame ; it dissolves chloride of silver, even when dilute, with great readiness. Henry's Chem. i. 570. Sulphite of Potassa. A salt, occurring in rhomboidal plates of a white colour, and a bitter and sulphurous taste, very soluble, and which by exposure to air is converted into a sulphate. It is prepared by passing sulphurous acid into a solution of potassa and evaporating out of contact of air. Hyposulphale of Potassa. A salt crystallizing in cylindrical prisms terminated by a plane perpendicular to their axis. Little, however, is known concerning it. jinn. Phil. xiv. 355. Brande'sJour. xv. 285. Sulphate of Potassa. Atom. Num. 87-15 Symb. (3O+S) SYN. Sal de duobus. PROPERTIES. White; slightly bitter ; crystallizes in short six-sided prisms, terminated by six-sided pyramids ; it is destitute of water of crystallization and suffers no change by exposure to air ; decrepitates when heated, and enters into fusion at a red heat ; soluble in 16 parts of cold, and five of boiling water ; is decomposed at high temperatures by charcoal, and converted into sulphuret of potassium. PREPARATION AND NATIVE STATE. This salt is found native, but not abundantly, being principally in combination with the acetate and hydrochlorate of potassa, in woody plants. It is artificially prepared by saturating carbonate of potassa with sulphuric acid ; and it is pro- cured abundantly as a product of the operation for preparing nitric acid. 220 POTASSIUM. Bisulphatc of Potatsa. Atom. Num. 127-15 Symb. 2 (30+S.)+(0+Po.) PROPERTIES. Has a sour taste, and a powerful action upon vegetable blues ; one part is soluble in two of water, at 60 F. and in less than an equal weight at 212 F. ; insoluble in alcohol. PREPARATION. This salt may be easily obtained by dissolving in hot water the mass which remains in the retort after distilling nitric acid from equal weights of sulphuric acid and nitre ; or by digesting one proportion of the neutral sulphate with water containing about 50 parts of concentrated sulphuric acid, and evaporating the solution Thomson, Ann. of Phil. xxvi. 439. Ammonia Sulphate of Potassa. A triple salt, crystallizing in bril- liant plates, of a bitter taste. Formed by adding ammonia to bisul- phate of potassa. Thomson, First I'rin. ii. 417. Hypophosphite of Potassa. A very deliquescent salt, soluble in wa- ter and in alcohol, nearly in all proportions. It is formed by the di- rect combination of its constituents. Rose. Ann. de Ch. el de Ph, July 1828. Phosphite of Potassa. A neutral salt, not crystallizable, deliques- cent, and very soluble in water, but not in alcohol. When heated a yellow residue is left, which, with acids gives oat a little phosphuret- ted hydrogen. Phosphate of Potassa. This salt has little taste ; by the action of heat it undergoes igneous fusions ; mixed with 20 or 30 times its bulk of lime water, it preserves all its transparency. It may be obtained by neutralizing a solution of carbonate of po- tassa with phosphoric acid, concentrating the solution and setting it aside for some days to crystallize. Thomson s First Prin. ii. 256. Biphosphate of Potassa. This salt has been very little examined ; it is formed by dissolving the phosphate in phosphoric acid, and evaporating till crystals are obtained, which are prismatic and very soluble. Berzelius describes two other phosphates. Traite de Chim. iii. 402. Carbonate of Potassa. -Atom. Num. GQ-15Symb. (2O+C) +(0+Po) SYN. Suucarlonate of Potash. Salt of Tartar. PROPERTIES. Taste strongly alkaline ; is slightly caustic, and com- municates a green to the blue colour of the violet ; dissolves in less than an equal weight of water at 60 3 F. ; deliquesces rapidly on expo- sure to the air forming a dense solution formerly called oil of Tartar per ddiquium ; it crystallizes with much difficulty from its solution ; in- soluble in pure alcohol ; fuses at a full red heat without decompo- sition. PREPARATION. This salt is procured in an impure form from the potash and pearlash of commerce ; but for chemical purposes it should be prepared from cream of tartar, the bitartrate of potassa. On heat- ing this salt to redness the tartaric acid is decomposed, and a pure POTASSIUM. 221 carbonate of potassa mixed with charcoal remains. The carbonate is then dissolved in water, and after filtration, is evaporated to dryness in a capsule of silver or platinum. It may also be obtained by exposing the bicarbonate to a moderate heat, and dissolving the resulting salt in water ; the solution is then filtered to separate the silicic acid, evapo- rated to dryness, and kept in well stopped bottles. The carbonate pre- pared in this way is preferred by Berzelius in chemical analysis. Commercial Potash and Pearlash. If any vegetable growing in a soil not impregnated with sea-salt be burned, its ashes will be found alka- line from the presence of carbonate of potassa. By lixiviating the ashes thus obtained, with hot or cold water, the alkaline part is dis- solved out and this solution when boiled to dryness, leaves behind a dark brown saline mass, consisting of carbonate of potassa with varia- ble proportions of other salts and a minute quantity of vegetable in- llainrnable matter. In this state it is known in commerce by the name of Potask Calcination at a moderate heat, burns off the colouring particles arid the salt becomes of a spongy texture and beautiful bluish white tinge, and is then called Pearlash. In this process hot water dissolves the alkali more rapidly and com- pletely than cold, and is therefore to be preferred in the manufacture, and advantage is also gained by making use of small leach tubs. If quick lime be mixed with the ashes, previous to lixiviation, the alkali is rendered more caustic, and as some of the other salts of potash are decomposed by it, the value of the resulting mass will be increased. But the addition of common salt or of any soluble matter, to the ashes, previous to lixiviation, or of any substance to the lixivium when un- dergoing the process of evaporation, impairs the quality of the potash, and can only be resorted to through ignorance or for fraudulent pur- poses. Potash and Pearlash being so largely employed in the arts, it is fre- quently of consequence to ascertain the value of different samples ; that is, to determine the quantity of real carbonate of potash contained in a given weight of impure carbonate. The purity of pearlash may in general be judged of by its easy solubility in water, two parts of which should entirely dissolve one part of the salt ; the residue, if any, consists of impurities. But the purity of a given specimen may be more correctly determined by ascertaining its power of saturating an acid. Dilute sulphuric acid may be employed for this purpose. The amount of pure alkali which this test acid will saturate having been determined by previous experiments, it is next to be ascertained how much of this acid is required to saturate a given weight of impure pot- ash, and from this the proportional amount of pure carbonate may be easily ascertained by calculation. Thus if eight ounces of this test acid, neutralizes one ounce of pure carbonate of potassa, and eight ounces of the same acid require for their neutralization two ounces of common potash, the latter contains 1 ounce of impurities. [For a de- scription of a convenient apparatus for ascertaining the purity of corn- commercial potash, and soda, see Faraday's Chemical Manipulation.] 222 POTASSIUM. The following table will exhibit the ingredients of several specimens of potash. The analyses were made by myself under the direction of a committee of the Legislature of New-York, in 1832 and 3, and were confined to such specimens as were met with in our market. See As- sembly Journals, 1832-3. 13 rs" t^ C o "o * ^ j M 0) 2 S S o ^ ei Is * Is |.2.| *S **"> 'Q *-> i-M a! O. cd o S o XI "o 13 rt ^ 3 O 2-5^ ^3 ^ PH "Q - 1 S 02 Pu, .0 g JH 1 11-6 7-5 7-3 73.6 100 2 00-5 6-3 15- 78.2 100 3 2-4 12-2 1Q-8 74.6 100 4 1-6 11 5 10- 76.9 100 5 11-4 4.4 9-2 75 100 6 7-6 10.4 32-8 49.2 100 7 1-7 12-5 6'9> 78.9 100 8 2-5 10-2 U-l 76.2 100 Of these specimens, No. 1 & 7, were manufactured according to the common method. No. 2, 3, 4 r 5, & 8, were made according to a me- thod recently introduced of mixing lime with the ashes, employing hot instead of cold water in the lixiviation, and using small leach tubs. No. 6, was the result of a mistaken idea which was maintained by some manufacturers, that the addition of large quantities of salt and lime to the lye would not only increase the amount of potash, but improve its quality. REFERENCES. Vaiiqnelirfs Experiments on various kinds of Potash, fyc. Ann. de Chim* xl. 273, or Repertory of Arts, 1st ser. xvi. 258, (an important paper.) On obtaining Potash from various substances ChaptaFs Chem. ji. 78. John on the origin of Potash t in vegetables. Ed'm. Phil. Jour, iL 394. Bicarbonate of Pot ass a. Atom. Num. 100-15 Symb. 2. (20-fC)+(0+Po)+laq. PROPERTIES. Crystallizes in eight-sided prisms ; is milder than the carbonate, but is alkaline both to the taste and to test paper ; does not deliquesce on exposure to the air ; it requires four times its weight of water, at 60 3 F. for solution, and is much more soluble at 212 F. but it parts with some of its acid at that temperature, and at a low red heat it is converted into the carbonate. PREPARATION. This salt is made by transmitting a current of car- bonic acid gas through a solution of the carbonate of potassa. By slow evaporation the salt is obtained in the crystalline form. Sesquicarbonate of Potassa, seems to have been obtained acci- dentally in a single instance. Its constitution is stated by Dr. Thorn- SODIUM. 223 son to be H at. carbonic acid-f-1 potassa-f-6 water, First Prin. ii. 255. Sub-borate of Potassa. This salt is little known. It may be formed by the direct combination of liquid hydrate of potassa with boracic acid. Thenard, ill 92. Selenites of Potussa. Selenious acid is capable of uniting with po- tassa in three different proportions, and of composing either a selen- ite, bi-selenite or quadri-selenite. Berzclius, Ann. de C/i. and de Py. ix. 257, and Traite de C/iim. iii. 428. TESTS OF THE SALTS OF POTASSA. 1. A concentrated solution of Tartaric Acid, added in excess to a concentrated solution of potassa or any of its soluble salts, immediately produces a crystalline pre- cipitate of bitartrate of potassa. When the solution is dilute, the precipitate appears only after some time. 2. The spirituous solu- tion of Chloride of Platinum, produces a yellow precipitate of chlo- ride of potassium and platinum. If the salt which is to be tested for potassa, be soluble in alcohol, it is best to mix a spirituous solution of the salt with the spirituous solution of chloride of platinum. See Prof. H. Rose's Manual of Analytical Chemistry, for particulars con- cerning the employment of the above tests and several others of inferior de- licacy. SECTION II. SODIUM. Atom. Num. 23'3. Symb. So. Sp. gr. 0-972 Discovered by Sir.- H. Davy, in 1807, and particularly examined by him, and by Gay Lussac and Thenard. Recherckes Phys. Chim. PROPERTIES. Solid at ordinary temperatures ; white, opaque, and when examined under a thin film of naphtha, has the lustre and gene- ral appearance of silver ; is so soft that it may be formed into leaves by the pressure of the fingers, and possesses the property of welding ; fuses at 200 F. and rises in vapour at a full red heat ; it soon tarnish- es on exposure to the air, though less rapidly than potassium ; when thrown upon water, swims upon its surface, occasions a violent effer- vescence, and a hissing noise, but no light is visible ; the action is stronger with hot water, and a few scintillations appear, but still there is no flame ; in each case, soda is generated, owing to which the wa- ter acquires an alkaline reaction, and hydrogen gas is disengaged. Sodium decomposes water. When sodium is thrown upon pure wa- ter it rapidly decomposes the water, but does not take fire like potas- sium. This Serrulas ascribes to its great mobility compared with that of potassium. Arid he says that if sodium be placed in contact with a little water, thickened by gum, it is then arrested and enough of heat is speedily generated to set the sodium on fire. [Ann. de Chim. et de, Phys. xl. 329.] According to Professor Ducatel sodium inflames with cold water when in contact with, charcoal, and the product is water and sodiuretted hydrogen. \_Silliman' s Jour. xxv. 90.] Sodium burns with a yellowish flame, while that of potassium is reddish. It has al- so been recently observed that when sodium is pushed altogether under 224 SODIUM. water, the disengagement of hydrogen gas is then so sudden and abun- dant as to cause a detonation. PREPARATION. Sodium was first obtained by the action of the Vol- taic battery upon soda ; but it may be procured in much larger quan- tity by chemical processes, precisely similar to those described when treating of potassium. SODIUM AND OXYGEN. Chemists are acquainted with two compounds of sodium and oxy- gen, viz : the protoxide or soda, and the peroxide. Berzelius, how- ever, describes a third, which he calls the sub-oxide ; but it is probable that this is a mere mixture of the metal with soda. Protoxide of Sodium, or Soda. Atom. Num. 31 -3 Symb. O+So. PROPERTIES. Grayish-white ; very caustic ; difficult of fusion ; spe- cifically heavier than sodium ; changes vegetable blues to green ; when exposed to the air it becomes covered with an efflorescent crust of car- bonate of soda. PREPARATION. Soda is obtained by burning sodium in dry atmos- pheric air. It is also formed when soda is oxidized by water. Hydrate of Soda. Atom. Num. 40-3 Symb. (O+So.) With water, soda forms a solid hydrate, easily fusible by heat ; very caustic, soluble in water and alcohol, and has powerful alkaline pro perties. It is prepared from solution of pure soda, exactly in the same manner as the corresponding compound of potassa. Mr. Dalton has constructed a table showing the proportion of real soda, free from water, in solutions of different specific gravities. [See Henrys Chem. i. 580.] Peroxide of Sodium. Atom. Num. 70-6 Symb. 3O+2So. This compound may be formed by burning the metal in an excess of oxygen gas. It is of a deep orange colour, very fusible, and a non-con- ductor of electricity. When acted on by water, its excess of oxy- gen escapes, and it becomes soda. It deflagrates with most combusti- bles. Gay Lussac and Theuard. SODIUM AND CHLORINE. Chloride of Sodium. Atom. Num. 5S'75Symb. Cl+So. PROPERTIES. A crystalline solid, occurring in regular cubes, or by hasty evaporation, in hollow quadrangular pyramids, which, when the salt is pure, are but little changed by exposure to the air ; it dis- solves in twicp and a half its weight of water at 60 F., and is but lit- tle more soluble in hot water ; when heated, gradually fuses and SODIUM. 225 forms when cold, a solid mass ; if suddenly heated, it decrepitates ; is not decomposed by ignition in contact with iflammable substances, except potassium ; is decomposed by carbonate of potassa, sulphuric and nitric acids, and when dissolved in water, is converted into Muri- ate of Soda. PREPARATION AND NATIVE STATE. This compound may be formed directly by burning sodium in chlorine, or by heating it in muriatic acid gas. It is deposited in crystals when a solution of muriate of soda is evaporated ; for this salt, like muriate of potassa, exists only while in solution. In this state it is found abundantly as a natural product in sea water, and in the various brine springs, from which the crystal- line compound is obtained by evaporation. Chloride of sodium is known likewise as a natural product under the name of rock or min- eral salt. Among the most valuable of the brine or salt springs in the United States, are those of Onondaga County, N. Y. The manufacture of salt from these springs commenced about the year 1789, but the quan- tity manufactured has greatly increased within the last ten years. In 1800 it amounted to 42,754 bushels ; in 1814 to 295,215 bushels ; in 1823 to 608,463 bushels ; and in 1833 to 1,838,646. According to an analysis, which I made, of the brine obtained at Salina, in 1825 it contains one-seventh of its weight of chloride of so- dium. 1000 grains of this brine gave 156 grains dry saline residuum, of which there were in 100 parts, Carbonate of Lime, 1*14 Sulphate of Lime, - ... 2-69 Chloride of Calcium, .... 2-25 Chloride of Magnesium, - 1-54 Chloride of Sodium, - - - - 92-38 100-00 The results of my analysis of the different varieties of salt manufac- tured at Salina are as follows, viz : o o o . . CD fl2J aq. SYK. Sal Perlatum. PROPERTIES. Taste saline and not strong ; crystallizes in oblique prisms which effloresce on exposure to the air 7 and require four parts of SODIUM. 229 cold, and two of boiling water, for solution ; when heated it fuses and boils up, and having lost its water of crystallization, runs into a clear glass, which becomes opaque on cooling. PREPARATION. This salt is usually obtained for phamaceutical purposes, by saturating the impure phosphoric acid, obtained from cal- cined bones by sulphuric acid, with carbonate of soda ; the liquor is filtered, evaporated and set aside tQ crystallize. Thomson's First Prin, ii. 270. Pyro-pliosphatc of Soda. This name has been given, by Mr. Clark of Glasgow, to phosphate of soda which has been subjected to a red heat. By this treatment, not only its water is expelled, but the salt appears to undergo some change of constitution, for its solution gives with nitrate of silver, not a yellow precipitate like that of the com- mon phosphate, but a white one ; and when wholly decomposed by the salt of silver, the remaining solution is neutral, not acid, as when the common phosphate has been decomposed. Yet no gaseous or other product can be collected, except water. The crystallized phos- phate was found to contain, to each proportion, 25 proportions of wa- ter, [thus differing from Dr. Thomson] of which 24 were separated by a sand heat, and one by a red heat. The salt had then acquired the new properties which have been just described; and from its solution in water, crystals were obtained, obviously different in form from those of common phosphate of soda, and containing only 10 proper tions of water. These facts, if correctly observed, can only be explained by suppos- ing a new arrangement of the elements of the phosphate, occasioned by the high temperature to which it has been exposed. Henry' Chem. i. 593. Brewsters Edin. Jour. vii. 299. Biphosphate of Soda. Atom. Num. 134-2 %w6. 2(2O+ PJ PROPERTIES. Taste acid and saline ; reddens vegetable blues, and is usually crystallized in four-sided prisms, terminated by four-sided pyramids. PREPARATION. This salt is prepared by adding phosphoric acid to a solution of the neutral phosphate of soda, until the solution ceases to precipitate muriate of baryta. Being very soluble in water, the solu- tion must be concentrated, in order that it may crystallize ; and it re- quires a long time, and a considerable quantity of the solution, to ob- tain large crystals. Thomson s First Pi in. ii. 272. Phosphate of Soda and Ammonia. Atom. Num. 209*7? Symb. (2+ O+O+So)+(2jO+ N+HJ+10 aq. PROPERTIES. Primary form a right rhombic prism ; taste saline and cooling ; quite soluble in water : when heated, pasts with its water of crystallization, and if the heat is raised to redness, the ammonia is likewise disengaged, leaving bi phosphate of soda, which melts into a transparent glass, dissolves in water, and reddens vegetable blues. ' PREPARATION. This salt exists in human urine. It is prepared ar- tificially by dissolving one proportion of muriate of ammonia and two 230 SODIUM. of phosphate of soda in a small quantity of boiling water. As the li- quid cools, prismatic crystals of the double phosphate are deposited, while muriate of soda remains in solution. This salt has long been known under the names of fusible and micro- cosmic snlt. It is sometimes employed by mineralogists as a flux in experiments made by the blow-pipe. Fourcroy, Ann. de Chim. vii. 183. Phosphate of Soda and Potassa. This salt is obtained, according to Mitscherlich, by adding carbonate of soda to a solution of biphosphate of potassa, until effervescence ceases. Upon evaporation the double salt crystallizes. Berzelius, iii. 463. Carbonate of Soda. Atom. Num. 143-3 Symb. (2O+C) +(O+So)+lO aq. SYN. Subcarbonate of Soda of the Pharmacopeia. PROPERTIES. Crystallizes in octahedrons, with a rhombic base, the acute angles of which are generally truncated ; the crystals effloresce on exposure to the air, and. when heated, dissolve in their water of crystallization ; by continued heat are rendered anhydrous without loss of carbonic acid; dissolve in about two parts of cold, and less than their weight of boiling water, and the solution has a strong alka- line taste and reaction. PREPARATION. The carbonate of soda of commerce is obtained by lixiviating the ashes of sea-weeds. The best variety is known by the name ofbarilia, and is derived chiefly from the salsola soda and salicor- niaherbacea. A very inferior kind known by the name of kelp, is pre- pared from sea- weeds on the northern shores of Scotland. The purest barilla, however, though well fitted for making soap and glass, and for other purposes in the arts, always contains the sulphates and muri- ates of potassa and soda, and on this account is of little service to the chemist. A purer carbonate is prepared by heating a mixture of sul- phate of soda, saw-dust and lime, in a reverbatory furnace. By the action of the carbonaceous matter, the sulphuric acid is decomposed its sulphur partly uniting with lime and partly being dissipated in the form of sulphurous acid, while the carbonic acid, which is generated during the process, unites with soda. The carbonate of soda is then obtained by lixiviation and crystallization. It is, however, difficult to obtain this salt quite free from sulphuric acid. [For other processes, see Berzelius, Traite de Chim. iii. 466.] The quantity of real carbonate in the soda of commerce may be con- veniently estimated by its neutralizing power, which may be ascer- tained in the mode described in the remarks upon potash, [p. 222.] REFERENCES. Report on the different methods of extracting Soda from Sea Salt) by Lelievre^ Pelletier. tifc. Jour de Phys. or Repeit. of Arts, 2U ser. x. 230. Gay Lussac and Wetter on the Assay of Samples of Soda and Barilla of commerce , Ibid, xxxvii. 241. On obtaining Soda from Kelp, Muriate and Sulphate of Soda, ChaptaPs Chem. ii. 107. Paikes 1 Chern. Essay s t iii. 121. SODIUM. 231 Sesquicarbonate of Soda. Atom. Num. 82*3 Symb. 1J aq. This salt is found native in Barbary, where it is known by the name of Trona. It constitutes hard masses, which do not deliquesce in the air ; and it is said to be employed in the north of Africa, where rain sel- dom falls, for building the walls of houses. It is manufactured in Lon- don for the use of the soda-water makers, and is sold in the state of a white powder. It does not appear to be susceptible of crystallization. Thomson's First Prin. ii. 267. R. Phillips, in Brandes Jour. vii. 294. Bictirbonate of Soda. Atom. Num. 8'3Symb. 2 (2O+C) +(0+So.) + l aq. PROPERTIES. Taste milder than that of the carbonate; requires 9 or 10 times its weight of water at 603 F. for solution, which when heat- ed liberates a part of the carbonic acid ; affects colour tests in the same manner as the subcarbonate ; by exposure to a low red heat it is rendered anhydrous. PREPARATION. This salt may be prepared by saturating a weak so- lution of carbonate of soda, bypassing through it a stream of car- bonic acid ; or by dissolving 14 parts of carbonate of ammonia in a solution of 100 parts of carbonate of soda and evaporating at a gentle heat. Thomson's First Prin. ii. 267. Compound Carbonate and Chloride of Soda. Disinfecting Soda Liquid of Labarraque. The nature of this compound, sometimes called also the Chloride of Soda, does not appear to have been definitively settled. It has been investigated by Dr. Granville, Mr. Phillips and Mr. Faraday. [See Branded Jour. JV. i. 371. and ii. 84. Phil. Mag. and Ann. i". 376.] It is most probable that this substance consists merely of chlorine held in solution by the dissolved salt and that it is not a definite compound of chlorine and soda, or of chlorine and the carbonate of soda. SUl. Jour. xiv. 251. PROPERTIES. This compound, prepared according to the direc- tions of Labarraque, has a pale yellow colour and a slight odour of chlorine ; taste at first sharp, saline and scarcely at all alkaline, but it produces a persisting biting effect on the tongue ; it first reddens, then destroys the colour of turmeric paper ; when boiled it does not give out chlorine, nor is its bleaching powers perceptibly impaired ; and if carefully evaporated, it yields a mass of damp crystals, which, when redissolved, bleach almost as powerfully as the original liquid ; when rapidly evaporated to dryness, the residue contains scarcely any chlorate of soda or chloride of sodium, but it has nevertheless lost more than half its bleaching power, and therefore chlorine must have been evolved during the evaporation. The solution deteriorates gradually by keeping, chloric acid and chloride of sodium being gene- rated. When allowed to evaporate spontaneously, chlorine gas is gradually evolved, and crystals of carbonate of soda remain. Tur- ner. 232 SODIUM. PREPARATION. This compound is easily prepared by transmitting a current of chlorine gas into a cold and rather dilute solution of caustic soda, or of the carbonate of that alkali. It may also be form- ed easily and cheaply, and of uniform strength, by decomposing chlo- ride of lime with carbonate of soda, as proposed by M. Pa yen. [Brande's Jour. N. 8. i. 236.] The formula of Labarraque is as fol- lows : 2800 grains of crystallized carbonate of soda are dissolved in 1*28 pints of water, and through the solution, contained in a Woulfe's apparatus, is transmitted the chlorine, evolved from a mixture of 967 grains of sea salt and 750 grains of peroxide of manganese, when ac- ted on by 967 grains of sulphuric acid, diluted with 750 grains of wa- ter, the gas being passed through pure water to remove any accom- panying muriatic acid. USES. This compound may be employed for bleaching, and for all purposes to which chlorine gas or its solution was formerly applied. It is now much used in removing the offensive odour arising from drains, sewers, or all kinds of animal matter in a state of putrefaction. Bodies disinterred for the purpose of judicial inquiry, or parts of the body advanced in putrefaction, may, by its means, be rendered fit for examination ; and it is employed in surgical practice for destroying the fetor of malignant ulcers. Clothes worn by persons during pesti- lential diseases are disinfected by being washed with this compound. It is also used in fumigating the chambers of the sick ; for the disen- gagement of chlorine is so gradual, that it does not prove injurious or annoying to the patient. In all these instances, chlorine appears ac- tually to decompose noxious exhalations by uniting with the elements of which they consist, and especially with hydrogen. REFERENCES. An Essay on the use of the Chlorurets of Oxide of Sodi- um and Lime as powerful disinfecting agents, fyc. by Thomas Alcock. The Memoir of Labarraque ^ translated by Dr. Jacob Porter. See also facts stated by the author in a paper on these compounds, in the Neic- York Med. and Phys. Jour. vii. 62. Biborate of Soda. Atom. Num. 151-3 %i&. 2(2O+B)+ (0+So)+8 aq. SYN. Subborate of Soda. Borax. PROPERTIES. Crystallizes in prisms with irregular sides ; efflores- ces in the air ; fuses when ignited, and then loses its water of crystal- lization, and is changed into a white powder, which, on increasing the heat, leaves a transparent mass, called Glass of Borax, a substance of great use in experiments with the blow-pipe ; it changes the colour of svrup of violets to green, and was, therefore, considered as a sub- salt. PREPARATION AN{> NATIVE STATE. This salt occurs native in gome of the lakes of Thibet and Persia, and is extracted from this source by evaporation. It is imported from India, in a crude state, under the name of Tincal, which after being purified, constitutes the refined bo- rax of commerce. Thenard, iii. 87. A new variety of borax is obtained by dissolving, in boiling water, as much common borax as will give a solution of specific gravity 1-246. It forms octahedral crystals and contains only half the water of com- mon borax. M. Pay en, Brande's Jour. N. S. iii. 483. LITHIUM. 233 REFERENCES. Thomson's I irst Prin. ii. 270. MM. Robiquet and Mar* (hand's process for refining Borax. Ann. de Chim. et de Phys. viii. 359. Ann. of Phil. xiii. 61. Berzelpesrw. 469. Selenites and Selenate of Soda. Berzelius describes three distinct se- lenites of soda, differing in the amount of acid which they contain. A Selenate of Soda is also recognized. Traite de Chim. iii. 481. TESTS OF THK SALTS OF SODA. 1. Upon adding sulphuric acid to soda a salt is obtained, which, by its taste and form, is easily recogniz- ed as Glauber's salt, or sulphate of soda. 2. All its salts are soluble in water, and are not precipitated by any re-agent. 3. On exposing its salts, by means of platinum wire, to the blow-pipe flame, they com- municate to it a rich yellow colour. According to M. Harkort, of Freyberg, potash with nickel gives a blue glass before the blow-pipe, while soda gives a brown glass. This is said to be a very delicate test, provided the nickel is perfectly free from cobalt. Ure's Ckem. Diet. SECTION III. LITHIUM. Atom. Num. 10 Symb. L. Lithium is a white coloured metal like sodium, which was first ob- tained fiorn lithia by Sir H. Davy, by means of galvanism ; but it was oxidized and reconverted into the alkali with such rapidity that it could not be collected. LITHIUM A?s 7 D OXYGEN. Oxide of Lithium or Lithia. Atom. Num. 18 Symb. O+L. Discovered in 1818,. by Arfwedson of Sweden, in the mineral call- ed Pctalite, and since that time also found in spodumene, lepidolite, and in several varieties of mica. PROPERTIES. Soluble in water, and like the other alkalies has. an acrid, caustic taste ; changes vegetable blues to green ; when heated in contact with platinum, it fuses and then acts on the metal ; is dis- tinguished from potassa and soda by its greater neutralizing power ; when exposed to the air it absorbs carbonic acid and becomes opaque. PREPARATION. A good process for preparing lithia is to mix pow- dered spodumene with twice its weight of pulverized fluor-spar, and with sulphuric acid ; then to heat the mixture until the hydrofluoric acid with the silica is volatilized, and afterwards to separate the sul- phate of lithia by solution. This salt may be decomposed by the ace- tate of baryta, and the acetate of lithia, thus obtained, is converted into a carbonate by exposure to a red heat By the action of lime the car- bonate may then be brought to the state of caustic hydrate. Berzelius describes other processes for obtaining this alkali. See Traite de Chim. ii. 37. 234 LITHIUM. REFERENCES. Arfwedson, Ann. de Chim. ft de Phys. x. 82. Berzelius on Lithia in Pttalite, S?c. Ann. of Phil. xi. 291, 373, 447. Gmeliifs exam- ination of the chemical properties of Lithia^ Ann. of Phil. xv. 341, 374. LITHIUM AND CHLORINE. Chloride of Lithium. Atom. Num. 45.45 Symb. Cl+L. This compound may be obtained by evaporating the muriate of lithia to dryness and fusing the residne. It is white and semi-transparent, extremely deliquescent, soluble in alcohol, is decomposed when strong- ly heated in the open air, when it parts with chlorine, absorbs oxygen and becomes highly alkaline ; it is very difficultly crystallizable and tinges the flame of alcohol red. In all these respects it differs from the similar compounds of potassa and soda. SALTS OF LITHIA. These have not been very minutely examined, as the basis has not yet been very abundantly obtained. Nitrate of Lithia is very soluble, and by evaporation crystallizes sometimes in regular rhomboids, sometimes in needles. It is extreme- ly fusible ; and at the instant when it has cooled, it attracts moisture from the air and becomes fluid. Sulphate of Lithia crystallizes in small prisms, of a shining white colour. It is more fusible and soluble than sulphate of potassa, and has a saline and not a bitter taste. Bisulphate of Lithia is produced by adding an excess of sulphuric acid to the sulphate. It is more fusible and less soluble in water than the sulphate. Phosphate of Lithia is formed by adding phosphate of ammonia with excess of base to sulphate of Lithia, when an insoluble phosphate falls down. By this property it may be separated from potassa and soda. There exists also a biphosphatc. REFERENCES. On the Salts of Lithia , see Gmeliji 1 ^ paper in the Ann. of Phil, xv., and Berzelius, Traitede Chim. iii. 488. TESTS OF THE SALTS OF LITHIA, Lithia may be distinguished from potassa and soda by forming sparingly soluble salts with carbonic and phosphoric acids ; by affording deliquescent salts with muriatic and nitric acids, which are freely soluble in alcohol. This alchoholic solu- tion burns with a red flame ; and all the salts of lithia, when heated on platinum wire before the blow-pipe, tinge the flame of a red colour, Berzelius on the Blow- Pipe. Rose's Manual of Analytical Chemis- try, 54. BARIUM. 235 CLASS II. METALS, WHICH WHEN COMBINED WITH OXYGEN, FORM ALKA- LINE EARTHS. SECTION IV. BARIUM. Atom. Num. GS'7 Symb. Ba. The metallic basis of baryta was discovered by Sir H. Davy in 1808 ; but it has hitherto been obtained only in small quantities. PROPERTIES. Colour dark grey, with a lustre inferior to that of cast iron ; specific gravity greater than water ; it attracts oxygen with avidity from the air, and is converted into baryta ; effervesces strong- ly, from the escape of hydrogen when thrown into water, a solution of baryta being produced. PREPARATION. This metal was obtained by Sir H. Davy, by a pro- cess suggested by Berzelius and Pontin. It consists in forming car- bonate of baryta into a paste with water, and placing a globule of mercury into a little hollow made in its surface. The paste was laid upon a platinum tray which communicated with the positive pole of a galvanic battery of 100 double plates, while the negative wire was brought into contact with the mercury. The baryta was decomposed, and its barium entered into combination with mercury. This amal- gam was then heated in a vessel free from air, by which means the mercury was expelled, and barium obtained in a pure form. Tamer, See also, Berzelius, Traite de Chim, ii. 346, for a notice of another pro- cess. BARIUM AND OXYGEN. Two compounds of barium and oxygen are at present known. Protoxide of Barium. Atom. Num. 76-7 Symb. O+Ba. Discovered by Scheele in 1774, and called Barytes or Baryta, from the great density of its compounds. PROPERTIES. A gray powder, the specific gravity of which is about 4 ; it requires a high temperature for fusion ; taste sharp and alkaline ; converts vegetable blue colours to green, and neutralizes the strongest acids ; has a strong affinity for water, and when mixed with that liquid it slakes in the same manner as quick lime, but with the evolution of a more intense heat, which, according to Dobereiner, sometimes 236 BARIUM. amounts to luminousness the result being a white bulky hydrate, fusible at a red heat, and which bears the highest temperature of a smith's forge without parting with its water ; evolves light when act- ed on by concentrated sulphuric acid. REFERENCES. Ann. of Phil, xviii. 77. Ann. de Chim. et de Phys. xxxvii. 223, or Repert. of Pat. Invent, vii. 94. Hydrate of Baryta. Atom. Ntmi. 857 Symb. (O+Ba) This hydrate is soluble in twice its weight of boiling water, and in twenty parts of water at the temperature of 6(P F. A saturated so- lution of baryta in boiling water deposites, in cooling, transparent flattened prismatic crystals, which are composed, according to Mr. Dalton, of one proportion of baryta and 20 proportions of water. The Aqueous solution of Baryta is an excellent test of the presence of carbonic acid in the atmosphere, or in other gaseous mixtures. The carbonic acid unites with the baryta, and a white insoluble precipitate, carbonate of baryta, subsides. ,,,, PREPARATION. Baryta may be prepared as above suggested, by ex- posing barium to air. It may also be obtained by decomposing ni- trate of barjta at a red heat ; or, as was ascertained by Dr. Hope, by exposing carbonate of baryta, contained in a black lead crucible, to an intense white heat ; a process which succeeds much better, when the carbonate is intimately mixed with charcoal. Peroxide of Barium. Atom. Num. 84-7 Symb. 2O+Ba. A grayish white substance, employed by Thenard in the preparation of peroxide of hydrogen, (p. 116.) It may be formed by conducting dry oxygen gas over pure baryta at a low red heat. An easier pro- cess, recommended by M. Quesneville, junr., is to introduce nitrate of baryta into a luted retort of porcelain, to which is attached a Welter's safety tube, terminating under an inverted jar full of water. Heat is gradually applied to the retort, and a red heat continued as long as there is any disengagement of nitric oxide or nitrogen gas. When these have ceased and pure oxygen passes over, which is a proof of all the nitrate being decomposed, the process is discontinued. The per- oxide of barium is then found in the retort. REFERENCES. Ann. de Chim. el de Pliys. xxxv. 108. Thenard, Tralte de Chim. ii. 328. Edin. Jour, of Science, ii. 180. Webster's Brande. BARIUM AND CHLORINE. Chloride of Barium. Atom. Nam. 104-15 Symb. Cl+Ba. PROPERTIES. Taste pungent and acrid ; requires five times its weight of water at 60 for solution ; unaltered by exposure to the air ; decomposed by sulphuric acid and the alkaline carbonates ; when dis- solv^d in water, is supposed to be changed into Muriate of Baryta, which may be obtained from the solution by evaporation in the form of tables or eight sided pyramids, applied base to base. These crystals, BARIUM. 237 according to Dr. Thomson, consist of one proportion of muriate of baryta and r one of water. PREPARATION. The chloride is generated when chlorine gas is con- ducted over baryta at a red heat, and oxygen gas is disengaged. It may also be formed by heating to redness the crystallized muriate of baryta. This salt is best prepared by dissolving either the artificial or native carbonate, or the sulphuret, in dilute muriatic acid ; and after- wards evaporating and crystallizing. In this form it is employed as a test for the presence of sulphuric acid. REFERENCES. The prof-esses for the preparation of Muriate of Baryta by La Grange, fyc. Ann. de Chitn., orRepert. of Arts,%dser. iv. 439. viii. 139. Medical and Chemical History of , New-England Med. Jour. iii. 23. On the poisonous properties of f Iiis and other compounds of Baryta^ see Christison on Poisons , 431. BARIUM AND BROMINE. Bromide of Barium. This has been obtained by boiling proto-bromide of iron with moist eaibonate of baryta in excess, evaporating the filtered solution, and heating the residue to redness. The product crystallizes by careful evaporation in white rhombic prisms, which have a bitter taste, are slightly deliquescent, and are soluble in water and alcohol. BARIUM AND IODINE. Iodide of Barium. This compound may be formed by acting upon baryta by hydri- odic acid and evaporating the solution. It m&y also be formed by heat- ing baryta in hydriodic gas ; water and iodide of barium are the re- sults. When thrown into water, it is converted into Hydriodate, of Baryta. BARIUM AND SULPHUR. Sulphuret of Barium. The protosulphuret of barium may be prepared from sulphate of baryta by the action of charcoal or hydrogen gas at a high tempera- ture. It dissolves readily in hot water, forming the hydrosulphuret of baryta. By means of this solution, all the chief salts of baryta may be procured. Thus, by adding an alkaline carbonate, carbonate of baryta is precipitated ; and when muriatic acid is added, sulphuretted hydrogen is evolved, and muriate of baryta produced. A solution of pure baryta may also be obtained from the hydrosulphuret, by boiling it with peroxide of copper, until the filtered solution no longer gives a dark precipitate with acetate of lead. The crystallized hydrate of baryta is easily procured by means of this solution. Turner. 23S BARIUM. BARIUM AND PHOSPHORUS, Phosphuret of Barium. This compound decomposes water and gives out phosphuretted hy- drogen like the preceding phosphurets. It may be formed by heating: to redness anhydrous caustic baryta in a glass matrass, furnished with a long neck, and then throwing pieces of phosphorus into it, Berze- lius, ii. 358* SALTS OP BARYTA. Chlorate of Baryta. Atom. Num. 152-15 Symb. (50+CP, + (0+Ba.) PROPERTIES. Crystallizes in the form of four-sided prisms ; taste pungent and austere ; requires for solution about four times its weight of \\ater at 50 F. y and its solution when pure is not precipitated ei- ther by nitrate of silver or muriatic acid ; by a red heat loses 39 per cent., and the remainder is alkaline. PREPARATION. The readiest mode of preparing this salt is by the process of Mr. Wheeler. On digesting, for a few minutes, a concen- trated solution of chlorate of potassa with a slight excess of silicated hydrofluoric acid, the alkali is precipitated in the form of an insoluble double hydroftuate of silica and potassa, while chloric acid remains in solution. The liquid, after filtration, is neutralized by carbonate of baryta, which likewise throws down the excess of hydrofluoric acid and silica. The silicated hydrofluoric acid employed in the process, is made by conducting fluosiiicic acid gas into water. This salt is of interest, as being the compound employed in the for- mation of chloric acid. lodate of Baryta. Atom. Num. 2427 Symb. (5O+I) + (0+Ba.) An extremely insoluble salt, formed by adding iodine to solution of baryta, from which the iodate precipitates in the state of a white pow- der, and may be edulcorated by washing with distilled water. When strongly heated, oxygen and iodine are evolved from it, and baryta re mains. Nitrate of Baryta. Atom. Num. 130-7 Symb. (5O+N) f(O+Ba.) PROPERTIES. Crystallizes in transparent octahedrons ; not altered by exposure to air ; soluble in 12 times its weight of water, at 60 F. and 3 or 4 parts of boiling water ; insoluble in alcohol ; in a red heat its acid is decomposed, and the earth remains pure. This salt is easily prepared by dissolving the natural or artificial carbonate of baryta in nitric acid, diluted with eight or ten times its weight of water, or by decomposing the sulphuret of barium by nitric acid and evaporating the solution. It is employed as a test, and when mixed with equal parts of charcoal is used for making green fire. BARIUM, 239 Hyposulphite of Baryta. A white shining scaly powder, slightly soluble in water, and obtained by adding muriate of baryta to a con- centrated solution of hyposulphite of lime. Sulphite of Baryta. An insoluble compound, formed by mixing sulphite of potassa and muriate of baryta. Sulphate of Baryta. Atom. Num. 116-7 Symb. (3O+S) +(0+Ba.) PROPERTIES. This salt, sometimes called Heavy Spar, is white, in- sipid, absolutely insoluble in water, sulphuric acid forming a sudden and sensible precipitation in water, which contains 1-20,000 of bary- ta, or even of any barytic salt : it dissolves sensibly in concentrated sulphuric acid, but does not dissolve in the weak acid ; at a very elevated temperature it is fused. [Thenard.'] When heated to redness it ac- quires the property of phosphorescence and is sometimes called Bolog- na Phosphorus. [For details of the process, see Henry's Chem. i. 630.] It is decomposed by being subjected to high heat in contact with char- coal. NATIVE STATE AND PREPARATION. Sulphate of baryta or heavy spar, is found abundantly in nature. It is met with in the mines of Cum- berland and Westmoreland, and in Transylvania, Hungary. Saxony, and Hanover. It also occurs in various parts of the United States, es- pecially in company with galena, in Missouri and Illinois. This salt may be obtained artificially by turning a solution of sul- phate of potassa or of soda into a solution of the nitrate or muriate of baryta. In this state it is used as a pigment under the name of Permanent White. As the sulphate of baryta is a common and abundant native product, it is made use of for obtaining pure baryta and the other salts. For this purpose several processes have been contrived. The most con- venient one consists in mixing the sulphate, finely powdered, in the proportion of six parts, with one part of powdered charcoal, and ex- posing these to a red heat, for half an hour, in an earthen crucible. This converts the sulphate into sulphuret of barium, which is to be dissolved in hot water, and the solution filtered. To this solution we may add dilute nitric acid, if we wish to obtain nitrate of baryta, or muriatic acid, if the muriate is required. The solution is then to be evaporated and crystallized. REFERENCE. Parkes* 1 Chem. Essays, ii. 186. Hypophosphite of Baryta. A very soluble salt, crytallizable with dif- ficulty. Dulong, Ann. de Chim. et de Phys. ii. 142. Phosphite of Baryta. Obtained by Berzelius, by adding muriate of baryta to phosphite of ammonia ; a crust of phosphite of baryta was formed in 24 hours. Phosphate of Baryta. Insoluble in water and formed by mixing so- lutions of muriate of baryta and phosphate of soda. Biphosphate of Baryta. A crystalline salt, with an acid taste and reaction ; obtained by Berzelius by dissolving phosphate of baryta in phosphoric acid and evaporating the clear solution. 240 STRONTIUM. Berzelius describes three other phosphates of baryta. Ann. of Phil xv. 277. Carbonate of Baryta. Atom. Num. 987 Symb. (2O+C)+ (0+Ba.) Exceedingly insoluble in distilled water, requiring 4300 times its weight of water at 60 ^ F. and 2300 of boiling water for solution ; but when recently precipitated it is dissolved much more freely by a solu- tion of carbonic acid ; is highly poisonous. It occurs abundantly in the lead mines" of the north of England, where it was discovered by Dr. Withering, and has hence received the name of Witherite. It may be prepared by way of double decomposition, by mixing a soluble salt of baryta with any of the alkaline carbonates or bicarbonates. See Parkes' Chem. Essays, ii. 186. Selcniates of Baryta. Selenic acid is capable of uniting with baryta in two proportions. The neutral salt which is insoluble consists of 100 acid-f-137 base ; the biselcniate, which crystallizes in round trans- parent grains, and is soluble in water, is composed of 100 acid-f-68 base. Henry, i. 631. TESTS OF THE SALTS OF BARYTA. 1. The soluble salts of baryta are precipitated; as a white carbonate of baryta, by alkaline carbonates, and as sulphate of baryta, which is insoluble, both in acid and alkaline so- lutions, by sulphuric acid or any soluble sulphate. 2. By forming with muriatic acid a salt, which crystallizes readily by evaporation in the form of four, six or eight-sided tables, is insoluble in alcohol, and does not undergo any change on exposure to air. See Rose's Manual of Analytical Chemistry. SECTION V. STRONTIUM. Atom. Num. 4&SSymb. Sr. Strontium may be obtained in minute quantiiies, by the same pro- cess as barium, substituting the carbonate of strontia, which is a na- tive product, for the carbonate of baryta. It resembles barium, is fusi- ble with difficulty, and not volatile. It decomposes water with the evolution of hydrogen, and is converted into an oxide by exposure to the air. STRONTIUM AND OXYGEN. Protoxide of Strontium or Strontia. Atom. Num. 51 -S Symb. O+Sr. PROPERTIES. A gray substance with a pungent, acrid taste, and when powdered in a mortar, the dust that rises irritates the lungs and nostrils ; resembles baryta in appearance, in fusibility and in possess- STRONTIUM. 241 ing distinct alkaline properties ; it may be slaked with water which causes an intense heat. The Hydrate of Strontia fuses readily at a red 1 heat, but the water cannot be driven off by the strongest heat of a blast furnace. It is very soluble in boiling water, which deposits it in crystals upon being allowed to cool undisturbed, and which are composed according to Mr. Dalton of one proportion of strontia and twelve of water. The Solution of Strontia has a caustic taste and an alkaline re-action. Like the solution of baryta, it is^ a delicate test of the presence of car- bonic acid in air and other gaseo'us mixtures, forming with it the insol- uble carbonate of strontia. PREPARATION. Strontia can be obtained by exposing the metal to air, or by subjecting the nitrate or carbonate of strontia to a strong red heat. Peroxide of Strontium. Atom. Num. 59'S Symb. 2O+Sr. A white substance, of a brilliant satiny lustre, inodorous and al- most tasteless. It is formed in the same manner as the corresponding preparation of barium, and also by pouring an aqueous solution of strontia into the deutoxide of hydrogen. For details and preparation, See Thcnard, ii. 322. STRONTIUM AND CHLORINE. Chloride of Strontium. Atom. Num. 79-25 Symb. Cl+Sr. This compound is formed under precisely the same circumstances as the chloride of barium, It is soluble in water, and is then converted into a Muriate of Kirontia, which crystallizes in long slender hexago- nal prisms, which are soluble in two parts of water at GO , and to almost any amount in boiling water. In a very moist atmosphere these crystals dsliquiate. They dissolve in alcohol and give to its -flame a blood-red colour. Iodide of Strontium may be obtained in the same manner as iodide of barium. Dissolved in water and carefully evaporated, it furnishes delicate prismatic crystals, of Hydriodate of Strontia, which, when iieated in close vessels, fuse and become iodide of Strontium by loss of water. Sulphuret of Strontium may be formed by fusing strontia and sul- hur in a green glass tube : or by exposing the powdered sulphate to a red heat with charcoal. It dissolves in water with the same phe- nomena as the sulphuret of potassium, and its solution furnishes, by cautious evaporation, crystals of Hydrosulphuret of Strontia. SALTS OF STRONTIA. Chlorate of Strontia. A deliquescent salt, having an astringent taste, and detonating when thrown upon red hot coals with a beautiful . Gay Lussac on the. same subject, Ann. de Chim. et de Phys. xxxvii. 415, or Branded Jour. N. S. iv. 207. * Sulphate of alumina forms, with sulphate of ammonia and with sul- phate of soda, double salts, which are very analogous to common alum. Riffault, Ann. dc Chim. et de Phys. ix. 106. Ann. of Phil. xvii. 72. Beatson, Brandes Jour. viii. 386. Thomson's First Prin. ii. TESTS OF THE SALTS. Alumina may be recognized as follows : 1 . It is separated from acids as a hydrate, by all the alkaline carbonates, and by pure ammonia. 2. It is precipitated by pure potassa or soda, but the precipitate is completely redissolved by an excess of the alkali. SECTION IX. GLUCINUM. Atom. Num. 17-7 Symb. G. The metallic basis of glucina was first obtained, in a separate state, by Wbhler. PROPERTIES. A dark gray powder, resembling in all respects, a me tal precipitated in the pulverulent form ; under the burnisher, it as- sumes a dull metallic lustre ; its fusing point is very high ; it under- goes no change, either in air or when exposed to boiling water; when heated to redness on platinum foil, it takes fire, and burns with great brilliancy, and glucina is regenerated ; in oxygen it burns with extraordinary brilliancy, and yet the glucina formed gives no indica- tions of fusion ; it burns also in chlorine, and in the vapours of bro- mine and iodine, PREPARATION. The process of Wohler consists in subjecting chlo- ride of glucinum to heat, in contact with potassium, in a platinum crucible. JVohler, Ann. de Chim. et de Phys. xxxix. 77, or Phil. Mag. . Th. The metallic basis of thorina, a new earth discovered by Berzelius, in 1829. PROPERTIES. A gray metallic powder, incapable of decomposing 1 water, but which when heated above redness, burns with a splendour nearly equal to that of the combustion of phosphorus in oxygen ; it is but slightly acted upon by nitric or sulphuric acid, but muriatic acid dissolves it with brisk effervesence. This metal is obtained by decomposing chloride of thorinum by means of potassium. Berzelius, Traite de Chim. ii. 391. THORIUM AND OXYGEN. Oxide of Thorium or Thoria.Jltom. Num. 67-6 ? Symb. O+Th. A constituent of a new mineral found in Brevig, in Norway, to which Berzelius has given the name formerly applied to a substance erroneously supposed by him to be an earth, but which he afterwards ascertained to be a phosphate of yttria. PROPERTIES. Thoria is white and irreducible by charcoal and po- tassium ; specific gravity 9-4 ; when strongly ignited is not attacked by any of the acids except the concentrated sulphuric ; dissolves read- ily in carbonate of ammonia, and on heating the solution a portion of the earth is precipitated, but is afterwards re-dissolved as the solution cools. Berzelius. 264 MANGANESE. CLASS IV. METALS WHICH DECOMPOSE WATER ONLY WHEN THEY ARE HEATED TO REDNESS. * SECTION XIV. MANGANESE. Atom. Num. 27*7 Symb. Mn. Sp. gr. 6*85. Bergman. 8-013 John. Although this substance has been long known, its nature was not understood. By the older chemists it was generally considered as an ore of iron. It was proved to be a distinct metal by Scheele and Gahn in 1774. Scheele' s Chem. Essays. PROPERTIES. A hard brittle metal, of a grayish white colour and granular texture ; when pure is not attracted by the magnet ; is ex- ceedingly infusible, requiring a heat of 160 Wedgewood for fusion ; soon tarnishes on exposure to the air, and absorbs oxygen with rapidity when heated to redness in open vessels ; it is said to decompose water at common temperature, with disengagement of hydrogen gas, though the process is exceedingly slow, but at a red heat decomposition is ra- pid, and protoxide of manganese is the result. EXTRACTION. Manganese, owing doubtless to its powerful affinity for oxygen, has never been found in an uncombined state in the earth ; but the peroxide of manganese occurs abundantly. This metal re- tains its oxygen with such force that its oxides require a stronger heat for reduction than potassa or soda. The method by which Ghan suc- ceeded in procuring metallic manganese, was by exposing the perox- ide, surrounded with charcoal, to the most intense heat of a smith's forge ; and this process has been successfully repeated by others. [Berthier, in Ann. de Chim. et de Phys. xx. Turner.] Dr. Thomson re- capitulates several processes for obtaining metallic manganese. Inorg. Chem. i. 512. MANGANESE AND OXYGEN. Much labour has been employed by chemists in the investigation of the oxides of manganese, a subject of greater difficulty than might have been supposed. Those who have contributed most to our know- ledge concerning them, are John, Berzelius, Forchhammer, Berthier, Arfwedson, Thomson and Turner. MANGANESE. 265 The following are now recognized as distinct compounds of oxygen and manganese : O. Mn. Protoxide, 8+27-7 or O-f Mn.= 35-7 Sesqui-oxide, 12+27-7 30+2Mn.= 79-4 Peroxide, 16+27-7 20+ Mn.= 43-7 Red Oxide, 10-66+27-7 40+3Mn.=115-l Varvicite, 14+27-7 70+4Mn.=166-8 Manganeseous acid, 24+27 -7 30+ Mn.= 51-7 Manganesic acid, 28+27-7 70+2Mn.=lll-4 Protoxide of Manganese. Atom. Num. 35'7 Symb. O+Mn. PROPERTIES. When pure, of a mountain green colour ; according to Turner undergoing no change by exposure to air for nineteen days ; at 600 F. is oxidized with considerable rapidity, and at a low red heat is converted in an instant into the red oxide ; unites readily with acids and forms colourless salts. PREPARATION. This oxide may be formed as was shown by Ber- thier, by exposing peroxide, sesquioxide or red oxide of manganese to the combined agency of charcoal and a white heat ; or by exposing either of the oxides of manganese contained in a tube of glass, porce- lain, or iron, to a current of hydrogen gas at an elevated temperature, as described by Dr. Forchhammer. Ann. of Phil. xvii. 52. Sesquioxide of Manganese. Atom. Num. 79*4 8ymb. 30+2 Mn. PROPERTIES. Colour brownish or nearly black, depending upon the source from whence it is obtained ; it is acted upon by sulphuric and nitric acids ; when exposed to the air absorbs oxygen and is converted into the peroxide. NATIVE STATE AND PREPARATION. This oxide occurs nearly pure in nature, and as a hydrate it is found abundantly, often in large pris- matic crystals, at Ihlefeld in the Hartz. It may be formed artificially by exposing peroxide of manganese for sometime to a moderate red heat, and is therefore the chief residue of the usual process for obtain- ing oxygen gas ; but it is difficult so to regulate the degree of the dura- tion of the heat, that the resulting oxide shall be quite pure. Peroxide of Manganese. Atom. Num. 43"7 Symk . 20+Mn. A very abundant ore, commonly called Black Oxide of Manganese, the nature of which was demonstrated by Scheele, in 1774. PROPERTIES. Occurs massive, of an earthy appearance, mixed with various other substance, or in the form of minute prisms ; it is un- changed by exposure to the air ; is insoluble in water ; does not unite with acids or alkalies ; yields oxygen gas when heated to redness, or 266 MANGANESE. when boiled with sulphuric acid, in the former case it is converted into the sesquioxide, in the latter a sulphate of the protoxide is formed. USBIS. This oxide is employed in the arts for discolouring glass, and in preparing chlorine for hleaching. In the laboratory it is used for procuring chlorine and oxygen gases, and in the preparation of the saj|s of manganese. Red^ Oxide of Mangnnese and Oxidum manganoso-manganicum of Arfwedson. These Dr. Turner has shown to be identical. The oxide of ^-fwedson occurs as a natural product, the other may be formed artificially by exposing the peroxide or sesquioxide to a white heat, either in close or in open vessels. Its colour is variable, but when rubbed to the same degree of fineness, it is always of a brownish red colour when cold, and nearly black, while warm. It does not change its state of oxidation by being ignited in contact with air. It dis- solves in muriatic acid, with a disengagement of chlorine, and com- municates a deep red colour to the acid, which disappears on keep- ing. The red oxide contains more oxygen than the protoxide, and less than the deutoxide. Its elements are in such proportion that it may be regarded as a compound, either of two proportions of protoxide and one proportion of peroxide, or two proportions sesquioxide and one pro- toxide. Turner. Varvicite. A compound known only as a natural production, having been first noticed a few years since by Mr. Phillips among some ores of manganese found in Warwickshire. In the colour of its powder and in its hardness it bears considerable resemblance to the peroxide of manganese for which it was at first mistaken. But it is readily dis- tinguished from that ore by its stronger lustre ; it highly lamellated texture which is very similar to that of manganite. and by its yielding water freely when heated to redness. Its specific gravity is 4-531. When strongly heated it is converted into red oxide, losing 5*725 per cent, of water, and 7'385 of oxygen. It is probably, like the red oxide, a compound of two other oxides; and the proportions just slat- ed justify the supposition that it consists of one atom of peroxide, and one of sesquioxide of manganese, united in the mineral with half an atom of water. Turner Phil. Mag. and Ann. v. 209. vi. 281, and vii. 284. REFERENCES. Dr. Joints Contributions towards a chemical knowledge of Manganese, Ann. of Phil, ii. 172. Serzelius, Traite de Chin. iii. 1296. Gay Lvssac, Ann. de Chim. et de Phys. i. 39. Thenard, Traite de Chim. ii. 341 Arfwedson, Arm. of Phil, xxiii. 267. Berthier, Ann. de Ch. et de Phys. xv Thomson's First Prin. i. 364. Turner, in Phil. Trans. ofEdin.for 1828' or Phil. Mag. and Ann. iv. 22, 96. Manganeseous and Mangancsic Acids. When the peroxide of manganese is mixed with an equal weight of nitre or carbonate of potassa, and the mixture exposed to a red heat, a green coloured fused mass is obtained, which has long been known by the name of Mineral Chamelion. On dissolving this substance in wa- ter, a green solution is obtained ; the colour of which soon changes in succession to blue, purple and red, and ultimately disappears entirely. The experiment may be varied by putting equal quantities of this sub- stance into two glass vessels, arid pouring in the one hot, and into the MANGANESE. 267 other cold water. The hot solution will have a beautiful green colour, and the cold a deep purple. The shades will vary as the temperature alters. From the researches of Dr. Forchhammer it is probable that the green and red colours are produced by two distinct acids, the Manga- neseous and Manganesic ; one of which forms red and the other green coloured salts ; and very recently Mitscherlich has established the ex- istence of these acids and ascertained their composition. He proposes to distinguish them by the names of Manganic and permanganic acids, from the circumstance of his finding the green coloured salts isomor- phous with the sulphates ; and the red salts isomorphous with the per- chlorates. Jinn, de Ckim. et de Phys. xlix. 113. Ann. of Phil. xvi. 130. Henri/ s Chem. ii- 12. Sec also Berzelius, Traite de Chim. iii. 296, and Unverdorben, in Phil. Mag. and Ann. ii. 393. MANGANESE AND CHLORINE. Chemists are acquainted with two compounds of chlorine and man- ganese. Proto chloride of Manganese. Jltom.Num. 63*15 Symb. Cl+Mn. PROPERTIES. A pink coloured semi-transparent substance ; deli- quescent, and, of course, very soluble in water, being converted by that fluid, with the evolution of caloric, into Muriate of Manganese. PREPARATION. This chloride is best prepared by evaporating a solu- tion of muriate of manganese to dryness, by gentle heat, and heating the residue to redness in a glass tube, while a current of muriatic acid as is transmitted through it. The heat of a spirit lamp is sufficient or the purpose. g fo Perchloride of Manganese. Atom. Num. 303-55 Symb.} 7C1+2 MM. A new compound discovered by Dumas. PROPERTIES. A volatile compound, appearing when first formed, as a vapour, of a copper or greenish colour ; but on traversing a glass tube, cooled to 5 or -4 D F. is condensed into a greenish-brown colour- ed liquid ; when the air of a large tube is displaced by the gas, and this is poured into a larger tube, the interior of the latter being first moistened with water, a dense rose-coloured fume appears, and the inside of the vessel acquires a deep purple colour ; a circumstance caused by the instantaneous production of muriatic and manganesic acids. PREPARATION. This chloride is easily prepared by putting a solution of manganese into strong sulphuric acid, and then adding fused sea salt. The muriatic and manganesic acids mutually decompose each other ; water and perchloride of manganese are generated, and the latter escapes in the form of vapour. REFERENCES. Dumas , in Ann. de Chim. et de Phys. xxxvi. 81, or Edin. Jour, of Science, viii. 179. 268 MANGANESE. MANGANESE AND FLUORINE. Fluoride of Manganese. Atom. Num. 186-16 Symb. 7 F+2 Mn. Discovered by Dumas and Wohler, and described in Ann. de Chim. et de P/tys. Jan. 1828. PROPERTIES. A gaseous compound or vapour, of a yellowish-green colour ; when mixed with atmospheric air, it acquires instantly a beautiful purple red colour ; is freely absorbed by water, yielding a so- lution of the same red tint ; it acts instantly on glass, with the for- mation of fluosilicic acid gas, a brown matter being at the same time deposited, which becomes of a deep purple red tint, on the addition of water. PREPARATION. This compound may be prepared by mixing common mineral chamelion with half its weight of fluor spar and decomposing the mixture in a platinum vessel by fuming sulphuric acid. Sulphuret of Manganese. This compound may be procured by ig- niting the sulphate with one-sixth of its weight of charcoal in powder. [Berthier.] It is also formed by the action of sulphuretted hydrogen on the protosulphate at a red heat. [ Arfwedson. ] It occurs native in Cornwall and at Nagyag, in Transylvania. It dissolves completely in dilute sulphuric or muriatic acid, with disengagement of very pure sulphuretted hydrogen gas. Turner. Phosphuret and Carburet of Manganese, may be obtained by heat- ing the metal in contact with phosphorus or carbon. Berzelius, Traite de Chim. iii. 309. MANGANESE AND THE METALS. According to Berzelius manganese combines with silicium, gold, silver, copper and iron. The alloy of manganese and iron is whiter than iron, hard and brittle, and it is said to be most proper for the fabri- cation of steel. SALTS OF MANGANESE. Nitrate of Manganese. Atom. Num. 152-7 Symb. (50+N)+(0+MnO+7 Aq. PROPERTIES. A salt with difficulty obtained in crystals ; colour similar to that of the carbonate ; it deliquiates rapidly when exposed to the air, and on the application of heat melts, and is immediately de- composed. PREPARATION. This salt may be obtained by the action of dilute nitric acid upon protoxide of manganese, or by digesting peroxide of manganese in nitric acid, with some gum or sugar, which abstracts oxygen, carbonic acid is evolved, and the protoxide dissolved by the acid. MANGANESE. 269 Sulphate of Manganese. Atom. Num. 120.7 Symb. (30+S)+(0+Mn.)+5 Aq. PROPERTIES. A rose coloured salt, of a bitter styptic taste, very soluble in water ; crystallizing in very flat rhombic prisms : at a bright red heat it gives out oxygen, and sulphurous acid and sesquioxide of manganese remain. This salt is prepared by dissolving pure carbonate of manganese in moderately dilute sulphuric acid, and setting the solution aside to crystallize spontaneously. With sulphate of ammonia, this salt yields a double sulphate of am- monia and manganese, consisting of one proportion combined with eight of water. It is isomorphous with the analogous salts of mag- nesia and protoxide of iron. Turner. Phosphate of Manganese. Atom. Num. 89.4 Symb. Aq. PROPERTIES. A tasteless white powder, insoluble in water, and pro- ducing no alteration on vegetable blues ; when heated to redness gives out water, and leaves anhydrous phosphate. This salt is obtained by mixing together solutions of sulphate of manganese and phosphate of soda. The phosphate of manganese precipitates in the state of a white powder, which may be collected on a filter, washed and dried in the open air. Carbonate of Manganese. Atom. Nam. 75'7 Symb. (20+C)+(0+Mn.)+2 Aq. PROPERTIES. A snow white tasteless powder, insoluble in water, and when kept for some time is converted into black oxide of manga- nese. This salt is prepared by adding a carbonated alkali to a salt with a base of protoxide of manganese. Dr. Turner thinks it probable that it is strictly anhydrous. TESTS OF THE SALTS OF MANGANESE. The salts of manganese con- taining the protoxide, are mostly soluble in water, and the solution becomes turbid and brown by exposure to air. They are not preci- pitated by hydriodic acid ; they furnish white precipitates with the alkalies, which soon become discoloured by exposure to air ; they are precipitated white by ferro-cyanate of potassa, and yellow by hydro- sulphuret of ammonia. 270 IRON. SECTION XV. IRON. Atom. Num. 28. Symb. Fe. % gr. 7-78. Iron has been known from the most remote periods, and is the most diffused, the most abundant, and the most important of the metals. It was formerly called Mars, and hence the term Martial was applied to its compounds. PROPERTIES. This metal has a bluish- white colour ; it is suscepti- ble of a high polish ; it is very malleable, and is capable of being drawn into very fine wire, though not of being beaten into very thin leaves ; in its pure state is exceedingly infusible, but this disadvantage is counterbalanced for all practical purposes, by its possessing the proper- ty of iceldmg in high perfection ; its hardness exceeds that of most of the metals, and it may be rendered harder than most bodies when con- verted into steel ; it is attracted by the magnet and may itself have the magnetic virtue imparted to it. Iron is malleable and ductile. This metal is malleable in every tem- perature, and its malleability increases in proportion as the tempera- ture augments ; but it cannot be hammered out nearly so thin as gold or silver, or even copper. Its ductility, however, is more perfect, for it can be drawn out into wire as fine, at least, as a human hair. It is acted on by the Magnet. Iron is attracted by the magnet, and it is upon this principle that iron filings are often freed from sand and oth- er impurities. [See page 85} When perfectly pure, iron retains the magnetic virtue for a short time only, but when combined with car- bon so as to form steel it may be rendered permanently magnetic. NATIVE STATE AND EXTRACTION. Iron is rarely found native in its pure state ; the meteoric iron being alloyed with nickel and cobalU It is artificially procured by heating the native oxide with charcoal : but when thus obtained, it is never quite free from carbonaceous mat- ter. The only method of preparing iron absolutely pure, is by pass- ing dry hydrogen gas over the pure oxide, heated to redness in a tube of porcelain. REFERENCES. A notice of a mass of pure native Iron, found m Connecti, cut by Mr. Burrall, see SiUimarfsJour. xii. 154. For a table of the principal Meteoric Stones which have fallen from 1735 to 1815, see Thenard, i. 369; also Cteaveland's Mineralogy. For an account of the various processes for extracting Iron from its Ore?, see Aikirfs or Ure^s Chemical Dictionary.. IRON AND OXYGEN. Iron combines with oxygen in two proportions only, forming the blue or protoxide, and the red or peroxide. Both these compounds are capable of yielding regular crystalline salts with acids. * From the latin word Ferrum* IRON. 271 Protoxide of Iron. Atom. Num. 36 Symb. O-j-Fe. Although the existence of this compound was inferred some years since by Gay Lussac, it was first obtained in an insulated form by Stromeyer. PROPERTIES. A compound of a dark blue colour, which when melt- ed with vitreous substances, communicates to them a tint of blue ; it is attracted by the magnet, though less powerfully than metallic iron ; it is exceedingly combustible, for when fully exposed to air at common temperatures, it suddenly takes fire, and burns vividly, being reconverted into the peroxide ; all its salts, particularly when in so- lution, absorb oxygen with such rapidity, that they may even be em- ployed in eudiometry. NATIVE STATE AND PREPARATION. This oxide is the base of the na- tive carbonate of iron, and of the green vitriol of commerce. It may be obtained in an insulated form, by transmitting dry hydrogen gas over the peroxide of iron, at a very low temperature. REFERENCES. Gay Lussac, Ann. de Chim. Ixxx. 163; Stromeyer, Edin Jour, of Science, v. 300. Peroxide of Iron. Atom. Num. 40 Symb. IJO+Fe. SYN. Crocus Martis Saffron of Mars. PROPERTIES. This oxide is of a brownish red colour, and is not at- tracted by the magnet ; it forms salts generally of a red colour, the solutions of which are precipitated of a fine blue by ferro-cyanate of potassa, and of an intense bluish black, by infusion of galls. NATIVE STATE AND PREPARATION. This oxide is an abundant natur- al product, known by the name of Red Hematite, occurring massive or crystallized. It may be artificially prepared by adding an alkali to a solution of iron in nitromuriatic acid ; a brownish red hydrate subsides, which is identical in composition with the mineral called Broion Hematite, and consists of one proportion of peroxide, and one of water. Black Oxide of Iron. This substance, long supposed to be the pro- toxide of iron, contains more oxygen than the blue, and less than the red. It is most probably, not a definite compound of iron and oxy- gen, but is composed of the two real oxides, united in a proportion which is by no means constant. [Twr/ier.j It occurs native, frequently crystallized in the form of a regular octahedron, which is not only at- tracted by the magnet, but is itself sometimes magnetic, and is then known under the name of Magnetic Iron Ore, which is abundant in va- rious parts of o:ir country. Another variety of this oxide is called Iron Glance and Micaceous Iron Ore. It is from these ores that iron is generally obtained. This oxide is always formed when iron is heated to redness in the open air ; and is likewise generated by the contact of aqueous va- pour with iron, at elevated temperatures. But the composition of the product varies with the duration of the process and the temperature employed. 272 IRON. REFERENCES. On the Oxides of Iron, see Berzelius, Trails de Chim. iii 249; Thenard, ii. 348; Thomson's First Prin. i. 343; Mosander, Edin. Jour, of Science, iv. 137. IRON AND CHLORINE. Iron and chlorine combine in two proportions, forming compounds first described by Dr. John Davy. PM. Trans, for 1812. Protochloride of Iron Atom. Num. 63-45 Symb. Cl+Fe. A compound of a gray colour, metallic splendour, and lamellated texture, requiring a red heat for its fusion, and converted by water in- to the Protomuriate of Iron. It is formed by dissolving iron in dilute muriatic acid, evaporating the solution to dryness, and igniting the precipitate out of contact of air. PercJiloride of Iron. Atom. Num. SI -17 Symb. l|Cl+Fe. A compound of a bright yellowish brown colour, crystallizing in small iridescent plates ; it is" volatile at a temperature a little above 212 ; and when thrown into water is converted into the Permuriate of Iron. It is obtained by burning iron wire in an atmosphere of chlo- rine, or by evaporating the permuriate to dryness. This muriate is formed by digesting the peroxide of iron in muriatic acid, or by expos- ing the protomuriate to air* It forms the basis of the Tinctura Muria- tis Ferri of the Pharmacopeia. IRON AND BROMINE. Bromides of Iron. The union of these two substances may be ef- fected by putting into a porcelain capsule any quantity of bromine with about twenty times its weight of water, and adding iron filings as long as any action continues, accompanied with gentle heat and agita- tion. If the solution is made and evaporated to dryness in close ves- sels, a protobromide is obtained ; but if freely exposed to the air the perbromide is left. IRON AND IODINE. Iodide of Iron. Iodide and iron unite and form a brown fusible com- pound, which decomposes water, and passes to the state of a green Hydriodate of Iron. IRON AND SULPHUR. Two compounds of these bodies are well known. Gay Lussac, how- ever, contends for the existence of three ; Arfwedson of four ; and Berzelius of five. But these require to be further examined before they can be admitted as distinct atomic combinations. IRON, 273 Protositlphuret of Iron. Atom. Num. 44 Symb. S+Fe. PROPERTIES. A yellow, brittle substance, of a metallic lustre, which is feebly attracted by the magnet, and by exposure to air and moisture, is gradually converted into protosulphate of iron. This sulphuret exists in nature, and is known to mineralogists, by the name of Magnetic Iron Pyrites. It may be prepared artificially by igniting the protosulphate of iron with charcoal ; or still more conven- iently, by heating a mixture of iron filings and sulphur. Bisulpliuret of Iron. Atom. Num. 60 Symb. 2S-f-Fe. An abundant natural product known under the name of Iron Py- rites, but which cannot be artificially formed. It is of a bronze yel- low colour, and is often found in crystals ; when heated to redness it loses half its sulphur, and becomes converted into the protosul- phuret. REFERENCES. Proust, en the native and artificial sulphurets of Iron, Jour, de Phys., or Rupert, of Arts, 1st ser. xvi. 411. Thomson's First Prtn- ii. 191, contains a description of a Sesquisulphuret. Arfwedson, in Ann. of Phii. xxiii. 341, describes two new sulphurets. Gay Lussac, Ann.de Chim. Ixxx. 170. Berzelius, Traite de Chim. iii. 357. IRON AND PHOSPHORUS. Phosphuret of Iron. A brittle, gray compound, which acts upon the magnet, and is formed by heating the phosphate of iron with charcoal, or by dropping phosphorus into a crucible containing red hot iron wire Hatchett, in Phil. Trans. 1804. The cold short iron is supposed to owe its peculiar properties to the presence of phosphorus. Dr. Thomson describes three phosphurets of iron. Inorg. Ckem. i. 501. IRON AND CARBON. Carburets of Iron. Carbon and iron unite in very various propor- tions ; but there are four compounds which are distinct from one an- other, viz. cast or pig iron, steel, cast steel, and graphite or plumbago. Cast Iron, being the name applied to iron as it flows from the fur- nace in which it is reduced, contains among other ingredients, a very considerable, but variable proportion of carbon, amounting sometimes, to l-40th of its weight. In this state it is neither ductile nor mal- leable, but very brittle ; and fuses with such facility at a red heat that it cannot be welded. It is highly crystalline and its texture is granu- lar. Cast iron may be converted in malleable or Wrought Iron, by ex- posure in a reverbatory furnace, to the combined action of heat and air, and subjecting the iron while still hot to the operation of rolling or hammering, by which its particles are approximated. But this, though the purest iron of commerce, still contains, according to Ber- zelius, a minute quantity of carbon. There are three varieties of cast-iron commonly distinguished in 274 IRON. commerce ; namely, black cast-iron usually called No. 1, mottled cast- iron called No. 2, and white cast-iron. M. M. Gay Lussac and Wilson have published the results of a series of analyses of carbonaceous irons, which show the carbon in the bar irons examined to vary from fourteen to twenty-nine, and in the steels from sixty-two to ninety-three ten-thousand parts. In gray cast-iron it varied from sixteen to twenty-eight, and in white from twenty -three to twenty-seven thousand parts. Jour, of Science, 1830. Steel is made by exposing bars of the purest malleable iron, sur- rounded with charcoal in powder, to a long continued red heat. Dur- ing this process, the iron unites with about l-150th of its weight of carbon, and acquires new properties. It is much harder than iron ; is more sonorous and elastic, and takes a much higher polish, though it is less ductile and malleable. It bears a strong red heat and may be welded to iron. When combined with an additional quantity of carbon, it forms Cast Steel, which is harder, more elastic and receives a higher polish than common steel, but is so fusible that it cannot be welded. As has already been observed [p. 165] diamonds when heated with soft iron, convert it into steel in the same manner as charcoal. Steel may be distinguished from pure iron by applying a drop of di- lute muriatic or nitric acid to the surface, when the carbon which it contains will be exhibited by a black stain. Wootz, or Indian steel, which is so valuable for the purpose of mak- ing edge tools, owes its excellence to combination with a minute por- tion of aluminum and silicium [Faraday, Brande's Jour. vii. 288J and according to Stodart and Faraday, steel may be much improved for certain purposes, by being alloyed with silver, platinum. fec. Brande's Jour. ix. 319. Graphite or Plumbago, also known by the name of Black Lead, has an iron gray colour, metallic lustre, and granular texture ; and is gen- erally stated to be a compound of 95 per cent, of carbon, with 5 of iron. But this is, perhaps, more correctly to be considered as a pure form of carbon. [See p. 165.] It is an abundant native product, and is used in making pencils and crucibles, and in burnishing iron to protect it from rust. REFERENCES. Mushet on Iron and Steel, TillocJCs Phil. Mag. iL The articles Iron Making, by D. Mushet ; and Cutlery, bij Slodart, in the Supple- ment to the. Encyclopedia Britannica. IRON AND THE METALS. According to Berzelius, iron forms alloys with most of the other me- tals. \Traite, de Chim. iii. 284-] None of these, however, are 1 of much importance, except tin plate, which will be described in the section on tin. Ferrocyanic Acid. PROPERTIES. This acid is neither volatile nor poisonous, in small quantities, and has no odour ; it is gradually decomposed by exposure IRON. 275 to the light, forming hydrocyanic acid, and Prusian blue, but it is far less liable to spontaneous decomposition than hydrocyanic acid ; it red- dens litmus permanently ; unites" with bases and forms salts called Ferrocyanates or Triple Prussiates ; it separates carbonic and acetic acids from their combinations, and even decomposes some salts of the more powerful acids. This substance has, within a few years, been the subject of able re- searches by Mr. Porrett, Berzelius and Robiquet, but its true nature is still involved in some obscurity. The view of Mr. Porrett, which ap- pears to be most consistent with the phenomena, is, that the elements of this acid are carbon, hydrogen, nitrogen and metallic iron, and he proposes for it the name of Ferruretled C/iyazic Acid. From the latest and best experiments on this subject it is probable that ferrocyanic acid is composed of Hydrogen, 2 atoms= 2 ) C Hydrocyanic Acid, 2 atoms =54 Iron, 1 atom =28 > or of ^ Cyanogen, 3 atoms =78 ) ( Cyanide of Iron, 1 atom =54 108 108 Ann. de Chim. et de Phys. xvii. 197. xxii. 322. PREPARATION Mr. Porrett recommends two methods for obtaining ferrocyanic acid, by one of which it is procured in crystals, and by the other in a state of solution. The first process consists in dissolv- ing 58 grains of crystallized tartaric acid in alcohoi, and mixing the liquid with 50 grains of the ferrocyanate of potassa, dissolved in the smallest possible quantity of hot water. The bitartrate of potassa is precipitated, and the clear solution, on being allowed to evaporate spontaneously, gradually deposites ferrocyanic acid in the form of small cubic crystals of a yellow colour. In the second process, the ferrocyanate of baryta, dissolved in water, is mixed with a quantity of sulphuric acid, which is precisely sufficient for combining with the baryta. The insoluble sulphate of baryta subsides, and the ferrocy- anic acid remains in solution. According to Mr. Porrett, every ten grains of the ferrocyanate of baryta require so much liquid sulphuric acid as is equivalent to 2-53 grains of real acid. REFERENCES. Porrett on the Pnissic and Prussous Acids, Repert. Arts, %dser. xvi. 232, 273. Porrett on the Ferruretted Chy&zic Acid. Phil. Trans, for 1814 and 1815. Ann. of Phil. v. 25. xii. 102. xiv. 295. Robiquet, Ann. de Chim. xii. 277, or Branded Jour. ix. 179. Rerzelius, in Ann. de Chim. et de Phys. xv. 144, or Ann. of Phil, xvii and xviii. Robiquet^ Ann. de C/tirn. et de Phys. xvii. SALTS OF IRON. Both of the oxides of iron combine with acids, and form distinct classes of salts. Protonitrate of Iron. Atom. Num. 15-3 Symb. (5O+N) +(0+Fe)+7 Aq. PROPERTIES. Crystallizes in rhomboidal prisms, transparent and of a light green colour ; reddens vegetable blues, as do all the soluble 276 IRON. gaits of iron ; has a sweetish astringent taste, like that of protosul- phate of iron, but harsher. PREPARATION. This salt is obtained by dissolving iron in dilute ni- tric acid, till the acid refuses to take up any more of the metal. The solution is then to be concentrated under the exhausted receiver of an air pump, over sulphuric acid. Thomson's First Prin. ii. 318. Persesquinitrate of Iron. Jltom. Num. 193 Syrnb. 1J (5O+ N)+(l O+Fe.)+8 Aq. When nitrate of iron, as above prepared, is exposed to the at- mosphere, it passes to the state of that in which the oxide is at the maximum ; or we may obtain this salt by leaving nitric acid for a long; time in contact with protoxide of iron. Crystals form spontaneously in the liquid, which are at first transparent and colourless, but become brown by keeping ; their taste is acid and they redden vegetable blues- According to the analysis of Dr. Thomson they are constituted as above. First Prin. ii. 328. Protosvlphatt of Iron. Atom. Num. 139 Symb. (3O+S) +(0+Fe.)+7 Aq. PROPERTIES. This salt, commonly known by the name of Green Vit- riol or Copperas, has a strong styptic, inky taste ; it reddens vegetable blues ; is insoluble in alcohol, but soluble in two parts of cold, and in three-fourths of its weight of boiling water; it oceurs in right rhombic prisms, which are transparent and of a pale green colour; in its anhy- drous state it is a dirty white powder. This salt is sometimes found native, associated with iron pyrites ; it is formed artificially by the action of dilute sulphuric acid on metallic iron, or by exposing the protosulphuret of iron in fragments to the combined agency of air and moisture. It is largely used in the arts, especially in 'dyeing, and in the manufacture of ink-powder. See Aikin's Ohem. Diet, and Henry's Chcm. ii. 33. PersesquisidpJiate of Iron. Atom. Num. 100 Syinb. 1 (30+S)+(lJO+Fe.) When a portion of protosulphate of iron is peroxidized by means of nitric acid, and cautiously concentrated till the whole of the nitric acid is dissipated, we obtain a red coloured mass, which dissolves only partially in water. The solution has a red colour with a tint of yel- low the taste is astringent and very harsh. When evaporated to dry- ness it speedily absorbs moisture, and deliquesces into a liquid. Alco- hol dissolves it readily and it strongly reddens vegetable blues ; and this is the salt to which Berzelius and Thomson have assigned the above constitution. The portion remaining, after the above salt has been extracted, is a red coloured powder, destitute of taste and insoluble in water, to which Dr. Thomson has given the name, Pertetr a sulphate of Iron con- sisting of I atom sulphuric acid and 4 atoms peroxide of iron. When the persulphate of iron is mixed with the sulphate of potassa. IRON. 277 and the solution allowed to crystallize by spontaneous evaporation, crystals are obtained similar to common alum in form, colour, taste and composition. In tbis double salt, the sulphate of alumina is re- placed by persulphate of iron, with which it is isomorphous. A similar double salt may be made with a mixture of sulphate of ammonia and persulphate of iron. Protophosphate of Iron, is a salt of a beautiful pale blue colour, sola ble in most acids, and precipitated again by ammonia without change. It is found native both in the state of powder and of fine blue crystals and may be prepared artificially by mixing solutions of protosul- phate of iron and phosphate of soda. It consists of one atom of pro- toxide of iron, and one atom of acid, with various proportions of wa- ter. There are three species of phosphate of iron which occur native, viz. Hydrated phosphate of iron, Hydrated Subsesquiphosphate and Hydrated Diphosphate. Perphosphatcoflron, is a yellowish white, insoluble powder, formed by mingling the solutions of persulphate of iron and phosphate of soda. Protocarbonate of Iron. Atom. Num. 58 Symb. (2O+C) +(o+Fe.) This salt exists abundantly in nature. It occurs sometimes massive, sometimes crystallized in rhombs or hexagonal prisms. It is also con- tained in most of the chalybeate mineral waters, being held in solution by free carbonic acid. It is very difficult to form it artificially. The Subcarbonatc of Iron, of the London Pharmacopeia, consists of about 40 per cent, carbonate of iron, and 60 of the peroxide. Phillips. We are not acquainted with any compound of carbonic acid with the peroxide of iron. The mineral known by the name of iron stone, or day iron stone, from which almost all the immense quantity of iron manufactured in England is smelted, is a carbonate of iron intermixed with more or less clay, coal and sometimes limestone. Silicate of Iron. The brown coloured hard slag from the smelting of copper ore, is either a silicate or bisilicate of iron, according to cir- cumstances. There occur native no fewer than six species of silicated iron minerals. Ferrocyanate of Potassa. sometimes called Triple Prussiate of Potas- sa A perfectly neutral salt, which is soluble in less than its own weight of water, and forms large transparent four-sided tabular crys- tals, of a lemon-yellow colour ; it is inodorous, has a slightly bitter taste, but quite different from that of hydrocyanic acid, and is perma- nent in the air ; when heated to redness it is decomposed, nitrogen gas is disengaged, and cyanide of potassium, mixed with carburet of iron, remains in the retort. This compound is best formed by digesting pure ferrocyanate of iron in potassa, until the alkali is neutralized, by which means the perox- ide of iron is set free, and a yellow liquid is formed, which yields crystals of the ferrocyanate of potassa by evaporation. It is made on a large scale, in the arts, by igniting dried blood or other animal mat- ters, such as hoofs and horns, with potash and iron. There is much diversity of opinion concerning the constitution of this salt. In the form of crystals, it is most probably, as Berzelius supposes, a double cyanide of potassium and iron ; in solution, aferro- 278 IRON. eyanate of potassa. See a discussion on this subject, ly Mr. R. Phil- lips, in Phil. Mag. and Ann. i. 110, and, also the references under Ferro- cyanic Acid. The ferrocyanate of potassa is employed in the preparation of seve- ral compounds of cyanogen, and as a reagent for detecting the presence of iron and other substances. Red ferrocyanate of Potassa obtained by passing chlorine gas int a moderately strong solution of common ferrocyanate of potassa) which is to be continued until the solution ceases to produce any ef" feet when added to a solution of peroxide of iron. The liquor is then to be concentrated to two-thirds of its volume, and set aside in a mode- rately warm stove to crystallize : after some time, brilliant and slender yellow crystals are obtained in the form of a rose ; by a second crys- tallization, very long needle-form crystals are procured in tufts. These crystals are ruby-coloured, transparent and very brilliant ; their form appears to be elongated octahedrons. The principal character of this salt is that of indicating the proto- salts of iron, precipitating them blue or green, according to the pro- portion in solution ; and on the contrary not precipitating the per salts of iron. This reagent, according to M. Girardin, is much more sensible than the common ferrocyanate of potassa, for ft is capable of detecting one 90,000th of protoxide of iron, while the latter salt does not detect more than one 1800th of the protoxide. Ferrocyanate of Baryta, is soluble in water, and forms yellow crys- tals by evaporation. It is prepared by digesting purified Prussian blue with a solution of pure baryta, and is used in the formation of ferro- cyanic acid. Ferrocyanate of the Peroxide of Iron. This substance, which forms the basis of Pi-ussian Blue, is insipid and inodorous, insoluble in water and in acids, unless they are concentrated and heated ; it is rendered white by strong sulphuric acid ; is decomposed by the alkalies and al- kaline earths, which unite with the ferrocyanic acid, and liberate the peroxide of iron ; is also decomposed by peroxide of mercury, giving rise to bicyanide of mercury ; at a temperature above 307 F. it takes fire and burns like tinder, leaving from 54 to 60 per cent, of the oxide of iron. Henry. This compound, which was an accidental discovery of a colour- maker of Berlin, in 1710, is formed by mixing ferrocyanate of potassa with a persalt of iron in slight excess, and washing the precipitate with water. The Prussian blue, of which this is the colouring mate- rial, is prepared by heating to redness dried blood, or other animal sub- stances, with an equal weight of pearlash, until the mixture has ac- quired a pasty consistence. The residue, which consists chiefly of cyanide of potassium and carbonate of potassa, is dissolved in water, and after being filtered, is mixed with a solution of two parts of alum and one part of the protosulphate of iron. A dirty greenish precipi- tate ensues, which absorbs oxygen from the atmosphere, and passes through different shades of green and blue, until at length it acquires the proper colour of the pigment. The chemical changes which take place in this process are of a very complicated nature, and do not appear to be understood. According to Dr. Turner the precipitate which is at first thrown down, is occa- sioned by the potassa, and consists chiefly of alumina and the protox- ide of iron. The ferrocyanic acid is generated by the protoxide re- acting upon some of the hydrocyanic acid, so as to form water and ZINC. 279 cyanide of iron, the latter of which then unites with undecomposed hydrocyanic acid. The ferrocyanic acid, thus produced, combines with oxide of iron ; and when the latter has attained its maximum of oxi- dation, the compound acquires its characteristic blue tint. This chemist controverts the opinion of Dr. Thomson, that the protoxide of iron enters into the composition of Prussian blue. He states that, in every good specimen of Prussian blue which he examined, the ferro- cyanic acid was in combination with peroxide of iron only. REFERENCES. The first published account of the method of preparing Prussian Blue, will be found in the Phil. Trans, xxxiii. Proust's Essay on Prussian Blue, Jour, de Phys. or Repert. of Arts, 1st ser. xiiL 180. Dr. Cooper on the Manufacture of Prussian Blue, ^Emporium of Arts, iii. 456 On the same subject, see Aikiti's Chem. Diet. ii. Zollickoffer on the medicinal properties of the Prussiate or ferrocyanate of Iron. TESTS OF THE SALTS OF IRON. The salts of iron are mostly soluble in water. Those in which the basis is the protoxide, afford a precipitate of a white hydrate, upon the addition of the pure alkalies, and a white carbonate, by alkaline carbonates, arid a white ferrocyanate, by ferro- cyanate of potassa. The two former precipitates become first green and then red ; and the latter green and blue by exposure to the air. The persalts give a blue precipitate with ferrocyanate of potassa, blood red with the sulphocyanate of potassa, and deep black with in- fusion of galls. The separation of the oxides of iron and manganese is one of the most complex problems in analytical chemistry, and has engaged the attention of many chemists. Berzelius and Rose recommend, for this purpose, succinate of soda, or ammonia, which throws down the iron, and leaves the manganese. For directions concerning the em- ployment of this and other means of separating the oxides of these metals, see Rose's Manual, 55, and Henry's Chem. ii. 590. SECTION XVI. ZINC. Atom. Num. 32-5 Symb. Zn Sp. gr. 7. Zinc has long been known as a metal in China and India, but its extraction from its ores is a comparatively recent discovery in Europe. Henckel first extracted zinc from calamine about the year 1721 ; Von Swab obtained it by distillation in 1742, and Margraff published a pro- cess in the Berlin Memoirs in 1746. PROPERTIES. This metal is of a brilliant white colour with a shade of blue; it is hard, being acted on by the file with difficulty ; at low or high degrees of heat it is brittle : but at temperatures between 210 and 300 F. it is both malleable and ductile, a property which enables it to be hammered into sheets of considerable thinness ; it fuses at 680 F. and when slowly cooled, forms regular crystals ; in its ordinary state it may be pulverized when hot, in a heated iron mortar, the pestle being also healed. Faraday. NATIVE STATE AND EXTRACTION. The zinc of commerce, sometimes called Spelter, is obtained either from Calamine, the native carbonate of zinc, or from the native sulphuret, the Zinc Blende of mineralogists. 280 ZINC. It is procured from the former by heat and carbonaceous matters ; and from the latter by a similar process after the ore has been previously oxidized by roasting, that is, by exposure to the air at a low red heat. When first extracted from its ores, it is never quite pure ; but, contains charcoal, sulphur, and several metals in small quantity. It may be freed from these impurities by distillation, by exposing it to a white heat in an earthern retort, to which a receiver full of water is adapted. USES. Metallic zinc, is employed in the laboratory, for the con- struction of voltaic instruments. It has also been proposed for the purpose of culinary vessels,* pipes for conveying water, sheathing for ships, &c. but it is easily acted on by the weakest acids, and is even- tually, though slowly, oxidized by long exposure to air and moisture. It is hence unfit for these uses. Zinc is, however, employed with ad- vantage when rolled into larjge plates, as a substitute for lead and slates in the covering of buildings. REFERENCES. On the treatment necessary to render Zinc malleable and ductile, see Sylvester^ in Phil. Mag. xxiii., and the Patents granted to him in Rep. of Arts, %d ser. vii. 404. ix. 251. On the danger attending the use of Zinc for culinary purposes, and for measures for liquids, fyc. see the Re- ports of the Medical Faculty of Paris, fyc. Ann. de Chiin. or Rep. of Arts, 2d ser. xxiii. 178, and xxv. 247. Beck's Med. Juris. 467. ZINC AND OXYGEN. Oxide of Zinc. Atom. Num. 4(V5 Symb. O+Zn. Formerly called Flowers of Zinc Pompholix Nihil album Philo- sopher's Wool, fyc. PROPERTIES. White at common temperatures ; but when heated to low redness il assumes a yellow colour, which gradually disappears on cooling ; it is fixed in the fire and very difficult of fusion ; is insoluble in water, and therefore does not affect the blue colour of plants ; it is a strong salifiable base, forming regular salts with acids, most of which are colourless. NATIVE STATE AND PREPARATION. This substance, which is rare in nature, is found at Franklin, New-Jersey. It may be formed by fusing * Vessels of zinc have long been known to be favourable for obtaining; a superior quantity of cream from new milk placed in them, and patents for the manufacture of dairy utensils from this metal have been taken out in England and al>o in this country. The increase i i the quantity of cream is probably owing to the fact that the acetic acid developed in milk by heat and rest, is taken up by the zinc; and thus the coagulation of the milk which would be produced by the action of the free acetic acid is prevented, and the milk by remaining more perfectly fluid, admits the easy ascent of the suspended cream. But the miik must at the saint; time become impregnated with a soluble and deleterious salt of zinc, and is unfit for use. Indeed the ease with which this metal is acted on by the weakest acids, constitutes an insurmountable objec- tion to its employment for culinary purposes. See Lardner^s Cyclopaedia, Manufactures in Metal. ZINC. 281 zinc in open vessels. When the metal is heated to full redness in a covered crucible, it bursts into a flame as soon as the cover is removed, and burns with a brilliant white light. The combustion ensues with such violence, that the oxide as it is formed is mechanically carried up into the air, in which state it has a considerable resemblance to carded wool. By heating metallic zinc in an atmosphere of aqueous vapour, cautiously regulating the heat so as not to fuse the metal, M. Haldat has obtained crystals of oxide of zinc, of a honey colour, almost trans- parent, and of a rhomboidal form. Ann. de Chim. xlvi. 72. Hydrated Oxide of Zinc may be obtained in crystals by uniting a rod of zinc and iron, and placing them in caustic ammonia in a close vessel. Gas is developed, and in a few days the inside of the vessel is covered with small transparent crystals, which are permanent in the air, and consist of one atom oxide of zinc-f- n e atom water=49*5. [Journ. of Science, 1830, p. 204.] The oxide is also precipitated in the form of a hydrate, by the addition of a solution of pure potassa or ammonia to a solution of the sulphate of zinc. According to Berzelius there is a suboxide of Zinc, and Thenard de- scribes a deutoxide; but these do not appear to be recognized by other chemists. ZINC AND CHLORINE. Chloride of Zinc. Atom. Num. 67-95 Symb. Cl+Zn. Formerly called Butter of Zinc. PROPERTIES. A compound fusible under a dull red heat, and on cool- ing goes through several degrees of consistency, being viscid before it becomes solid ; it is very deliquescent and by the action of water pro- duces a Muriate of Zinc. This chloride is obtained by burning leaf zinc in chlorine gas, or by adding muriatic acid to zinc, evaporating the residue to dry ness and then heating it to redness in a glass tube. According to Dr. Thom- son, if the application of heat be stopped at the right point, a muriate of zinc may be obtained, perfectly free from water, of which this com- pound and muriate of ammonia are the only examples. First Prin. ii. ZINC AND IODINE. Iodide of Zinc. Atom. Num. 158'5 Symb. I-J-Zn. A fusible and volatile crystalline compound which, when exposed to the air, deliquesces and is converted into Hydriodatc, of Zinc. It is formed by the union of iodine and zinc. ZINC AND SULPHUR. SulpJmret of Zinc. Atom. Num. 48-5 Symb. S+Zn. This compound exists in nature under the name of Blende, and is frequently found in dodecahedral crystals, or in forms allied to the dodecahedron. Its structure is lamellated, its lustre adamantine, and its colour variable, being sometimes yellow, red, brown or black. It 282 ZINC. may be made artificially by heating to redness a mixture of oxide of zinc and sulphur, by decomposing sulphate of zinc by charcoal, or by drying the white precipitate obtained on adding hydrosulphuret of am- monia to a salt of zinc. The native black Blende, called by the miners Black Jack, is an abundant mineral, and important as the source of the pure metal, which is obtained by roasting the ore, and afterwards exposing it to heat in proper distillatory vessels mixed with charcoal. REFERENCES. Thomson, on the composition of Blende, Ann. of Phil. iv. 89. On the methods of extracting the metal from this and other ores of Zinc, see Bishop Watson's Chem. Essays, iv. 1. Bergman's Works, \\. 309, and Aikin's Chem. Diet. ii. Phosphuret of Zinc, is a compound of a whitish colour, and a me- tallic lustre not unlike lead. It has some malleability, exhales a phos- phoric smell, and at a high degree of heat, burns like common zinc. Cyanide or Cyanuret of Zinc. This compound is obtained by Pelletier by precipitating sulphate of zinc by hydrocyanate of potassa ; forming a triple hydrocyanate of zinc, which being well dried, and calcined at a dull red heat, is converted into a cyanide of zinc. It always contains, however, cyanide of potassium. The above or a similar compound has of late been employed in Ger- many, instead of the hydrocyanic acid, and it has obtained the reputa- tion of possessing decided vermifuge powers. Ma yendie's Formulary. ZINC AND THE METALS. Zinc is capable of furnishing alloys with most of the other rnetals. Of these the most useful, brass, will be mentioned in treating of cop- per. With mercury it forms an amalgam, used for exciting electrical machines. SALTS OF ZIXC. lodateof Zinc, falls down in an insoluble powder, when iodate of po- tassa is added to sulphate of zinc. Nitrate of Zinc. Atom. Num. US'5~Symb. (5O+J\)+ (O-fZn)+6Aq. A salt with an exceedingly disagreeable taste, and which may be obtained with difficulty in Hat four-sided prisms, which deliquesce with great rapidity. It is prepared by the action of dilute nitric acid upon zinc, and subsequent evaporation. Sulphite of Zinc. A crystallizable salt, readily soluble in water, but not in alcohol ; obtained by dissolving zinc in sulphurous acid. Sulphate of Zinc. Atom. Num. 143-5 Symb. (3O+S)+ (0+Zn)+7 Aq. SYN. White Vitriol. PROPERTIES. Taste bitter and styptic ; colour white ; it crystalli- zes by spontaneous evaporation, in transparent flattened four-sided ZINC. 283 prisms, the primary form of which is a right rhombic prism andisomor- phous with epsom salts ; the crystals dissolve in two parts and a half of cold, and are still more soluble in boiling water; it reddens vegeta- ble blues, though, in composition, strictly a neutral salt ; when the crys- tals are deposited from a hot solution, they only contain, according to Thomson, three proportions of water. NATIVE STATE AND PREPARATION. This salt is found native in pla- ces where the sulphuret of zinc occurs ; being probably the result of the decomposition of that ore. It is prepared artificially by the ac- tion of dilute sulphuric acid upon metallic zinc during the process for preparing hydrogen gas ; but for the purposes of commerce, it is made by roasting the native sulphuret of zinc in a reverbatory furnace. The English white vitriol, however, is prepared for the most part by the di- rect action of sulphuric acid on metallic zinc, and is much purer than that obtained by the decomposition of the sulphuret. .4zA;i7i's Chem, Diet. ii. ADULTERATION. Sulphate of zinc is almost always contaminated with iron, and often with copper and lead. Hence the yellow spots which are visible on it ; and hence also the reason why its solution in water lets fall a dirty brown sediment. It may be purified by dissolv- ing it in water, and putting into the solution a quantity of zinc filings ; taking care to agitate occasionally. The zinc precipitates the foreign metals and takes their place. The solution is then to be filtered and the sulphate of zinc may be obtained from it in crystals by proper evap- oration. Thomson. ACTION ON THE ANIMAL ECONOMY. In the dose of a scruple or a drachm, sulphate of zinc is the most immediate emetic we possess ; and it is to be inferred, that if larger doses are rejected, as is the fact, with equal rapidity, they will in general cause no more harm than the medicinal dose. In some instances, however, persons have suffered severely from over-doses of this salt, and a few have even perished- It has also been said to have proved fatal when applied externally. Christison on Poisons, 375. Orfila, Toxicologie Generate. Phosphate of Zinc __ Atom. Num. 96-2 Symb. (2JO+PJ + ( 0+Zn.) A white tasteless powder, insoluble in water and without effect on vegetable blues. It is obtained by boiling carbonate of zinc in phos- phoric acid, after the acid has been saturated in the cold and applying heat to the resulting mass. Dr. Thomson describes a Eiphosphate of Zinc, formed by dissolving carbonate oT zinc in excess of phosphoric acid. Carbonate of Zinc. Atom. Num. SQ'5Symb. (2O+C)+ A white and tasteless salt, found in nature, and commonly known by the name of Calamine, which occurs either anhydrous and crystal- lized, or amorphous, and most commonly stalactitical ; in which state 7 each atom of the carbonate is united with an atomfof water. It is artificially prepared by adding carbonate of potassa to sulphate of zinc. After the precipitate is well washed and dried, it is consti- 284 TIN. tuted as above stated ; but it is difficult to obtain it with exactly the due proportion of water. If dryed at 212 F. it is anhydrous. Ferrocyanate of Zinc appears as a yellowish white precipitate on add- ing ferrocyanate of potassa to sulphate of zinc. TESTS OF THE SALTS OF ZINC. The salts of zinc are mostly soluble in water, and the solutions are colourless and transparent ; they are not precipitated by hydriodic acid. Potassa, soda and ammonia, form white precipitates, soluble in excess of the alkali and in sulphuric acid. Hydrosulphuret of ammonia causes a white precipitate, which is either a hydrosulphuret of the oxide of zinc, or a hydrated sulphuret of the metal. The soluble phosphates, carbonates and borates, produce white precipitates. SECTION XVII. TIN. Atom. Num. 57'9Symb. Sn.* Sp. gr. 7-9. This metal has been known from the remotest ages. It was in com- mon use in the time of Moses, and was obtained at a very early period from Spain and Britain, by the Phenicians. PROPERTIES. Tin has a white colour, and a lustre resembling silver ; is not oxidized by the combined agency of air and moisture, though the brilliancy of its surface is soon impaired by exposure to the atmos- phere ; it is quite malleable, for the thickness of common tin-foil does not exceed 1 -1000th of an inch ; it is soft and inelastic, and when bent backwards and forwards, emits a peculiar crackling noise ; at 442 F. it fuses, and if exposed at the same time to the air, its surface tar- nishes, and a gray powder is formed ; when heated to whiteness, it takes fire and burns with a white flame, being converted into the per- oxide of tin. EXTRACTION. The tin of commerce, known by the name of Block and Grain Tin, is procured from the native oxide by means of heat and charcoal. The best grain tin is almost chemically pure, containing, according to Dr. Thomson, very minute quantities of copper and iron, and occasionally of arsenic. [Awn. of Phil x. 166.] According to Thenard, the tin from Malacca is the only kind which is perfectly pure. [Traite de Chim. i. 372.] Tin foil is said to be almost always a compound of tin and lead. TIN AND OXYGEN. Tin appears to be susceptible of two degrees of oxidation. Both these oxides form salts by uniting with acids; but they are likewise ca- pable of combining with alkalies. Protoxide of Tin. Atom. Num. 65 9 Symb. O+Sn. PROPERTIES. A powder of a gray colour, indecomposable by heat ; * From the htin word Stannum. TIN. 285 Jt is insoluble in water ; when slightly heated in contact with atmos- pheric air or oxygen gas, it is converted into the peroxide with the evolution of heat and light ; its salts not only attract oxygen from the air, but act as powerful deoxidizing agents ; when added to a solution of gold, it occasions a purple coloured precipitate, the purple of Cassius, by which this oxide may be recognized with certainty. PREPARATION. This oxide may be prepared by keeping tin for sometime in a state of fusion in an open vessel. It may also be obtain- ed by precipitation from the protomuriate of tin. But it is difficult to obtain it pure in consequence of the great attraction which it has for oxygen, and its consequent conversion into peroxide. Peroxide of Tin. Atom. Num. ?3'9 Symb. 2O+Sn Sometimes called Stannic Acid. PROPERTIES. White, fusible and undecomposable by heat ; insoluble in water ; it has a feeble affinity for acids, and does not unite with the nitric at all ; it unites with the alkalies forming soluble compounds with them, and when fused with glass forms white enamel. NATIVE STATE AND PREPARATION. This oxide is found native in Cornwall, in Spain, and in Saxony ; it has also been found in Brittany, in France, in the East-Indies, and in South-America. The specific gravity of the native oxide is 7 ; its primitive crystal is an octahedron with a square base. The peroxide of tin may be prepared artificially by treating the metal with nitric acid. There is a violent action, attended with the formation of nitrate of ammonia. Scarcely any of the metal is dis- solved, but remains as a yellowish powder, which may be purified by washing. TIN AND CHLORINE*. Tin unites in two proportions with chlorine ; and the researches of Dr. Davy leave no doubt of these compounds being analogous in com- position to the oxides of tin. Protochloride of Tin. Atom. Num. 93*35 Symb. Cl+Sn. A gray solid substance, of a resinous lustre, which fuses at a heat below redness, and when heated in chlorine gas, is converted into the perchloride. It is prepared either by evaporating the muriate of the protoxide to dryness and fusing the residue in a close vessel, or by heating an amalgam of tin with calomel. Perchloride of Tin. Atom. Num. 12S'8Symb. 2Cl+Sn. SYN. Butter of Tin. Fuming Liquor of Libavius. A colourless volatile liquid, which emits copious white fumes when exposed to the atmosphere ; it has a strong attraction for water, and is converted by that fluid into the Permuriate of Tin. This chloride may be prepared either by heating metallic tin or the protochloride, in an atmosphere of chlorine, or by distilling a mixture UNIVERSITY 286 TIN. of eight parts of tin in powder, with twenty-four of corrosive subli- mate. Both the chlorides of tin possess the characters of an acid, and are capable of combining with chlorine bases, though only a few of these salts have been hitherto investigated. They are denominated Chloro- Stannatcs by Dr. Thomson. See his Inorg. Chem. ii. 824. Tin also combines with bromine and iodine ; with the former in two proportions. TIN AND SULPHUR. Protosulplmret of Tin. Atom. Num.tSQSymb. S-fSn. A brittle compound of a bluish gray colour and metallic lustre ; fu- sible at a red heat, and assuming a laminated structure in cooling. It is best formed by heating sulphur with metallic tin. Bisulphuret of Tin. Atom. Num. 89-9 Symb 2S+Sn. A compound of a golden yellow colour, formerly called durum Musivum, made by heating a mixture of sulphur and peroxide of tin in close vessels. By exposing a mixture of sulphur and protosulphuret of tin to a low red heat, Berzelius obtained a compound of one proportion of tin and one and a half of sulphur. If it be really a definite compound, it should be termed a Sesquisulphuret. TIN AND THE METALS. Most of the malleable metals become brittle and lose their ductility by combination with tin ; and hence tin was formerly called Diabolus MetaUorum. The common tin plate, so extensively employed in the arts, may be considered as an alloy of tin and iron. For forming this valuable article, the iron, .after being rolled into thin sheets, is completely cleansed and freed from oxide, by being steeped in water acidulated with muriatic acid. It is afterwards plung- ed into a vessel of melted fat and oil. At the same time also, the tin is kept melted in an oblong rectangular vessel ; and to preserve its sur- face from oxidation, a quantity of melted fat and oil is kept floating on it. The iron plates are then immersed in the tin for some time, and when withdrawn they are found to have a bright coating of tin. The dipping is repeated twice or more times, according to the thickness of the coat intended to be given, and also to produce a smooth surface, and between these processes the tin is equalized with a brush. See Bishop Watson's Chem. Essays, and Parkes' account of the Manufacture of Tin Plate, Manchester Memoirs, iii. N. S.. or Brandes Jour. viii. 141. When tin plate is exposed to the vapour of muriatic acid, or if the plate is washed with almost any dilute acid, it assumes the appear- ance of what is called Crystallized or Watered Tin. This article is ex- tensively employed to cover ornamental cabinet work, dressing boxes, &c. and is the Fer blanc moire of the French. The best acid solutions for this purpose, are 2 parts of nitric acid, 3 parts of muriatic, and 8 TIN. 287 of water, or citric acid dissolved in a sufficient quantity of water The watered tin is a true crystallization of the alloy ; and the process is much improved by heating the plate in different parts by means of a blow-pipe, or by raising the temperature of the whole plate to near redness, and then pouring the cold acid mixture upon it, or plunging the plate into the liquor. Thenard, i. 635. Bmnde's Jour. v. 368. SALTS OF TIN. lodate of Tin. An orange coloured substance formed either by the direct combination of tin with iodine, or by adding hydriodie acid to protomuriate of tin. The proportion of its elements has not been de- termined. Protomuriate of Tin. Atom. Num. l\l.3o Symb. (Cl-f-H) Aq. This compound, when evaporated out of contact of air, is a white salt which may be obtained in large oblique four-sided prisms, transpa- rent, of a silky lustre, and acid to the taste, and to colour tests. The protomuriate of tin may be obtained by boiling one part of tin with two of muriatic acid, in a tubulated retort. The solution has al- ways an excess of acid, and is perfectly limpid and colourless. It has a tendency to acquire an additional proportion of oxygen, and should therefore be preserved from contact with the air. This property of absorbing oxygen is so remarkable, that it may even be applied to eudio- metrical purposes. It has also the property of reducing to a minimum of oxidation, those compounds of iron, in which the metal is fully oxidized ; for example, it reduces the red sulphate to the green. It is a test also of gold and platinum, and blackens the solution of corro- sive sublimate. With hydros ulphurets it gives a black precipitate. Henry's C/tem. ii. 45. REFERENCES. On tht preparation of Muriate o/'jT/.", see Berard, Ann. de Chini. xviii. 78, or Nicholsoifs Jour. xxvi. and Chaudet, 'Ann. de CLim. et de Phys. iii. 376. The muriates, as well as the oxide of tin, are poisonous. Christison on Poisons. 367. Nitromuriate of Tin. The nitromuriatic acid dissolves tin abun- dantly, and with violent effervescence arid so much heat that it is ne- cessary to add the metal slov, ly by successive portions. The solution is apt to congeal into a tremulous gelatinous mass ; and if water be ad- ded, it is partly decomposed, and some oxide separated. This compound is supposed to be a Permuriate of Tin. It is used to heighten the colours of cochineal, gum lac, and some other red tinctures, from crimson to a bright scarlet. It is prepared by artists with that dilute nitric acid called single aqua-fortis, to each pound of which, are added from one to two ounces of muriate of soda or am- monia. This compound is capable of taking up about an eighth of its weight of tin. Henry. Thenard, iii. 358. Nitrate of Tin. This may be formed by treating the metal with di- lute nitric acid ; a yellow solution, which will not crystallize, is ob- tained ; when exposed to the air it absorbs oxygen, and peroxide of tin 288 CADMIUM. precipitates ; if evaporated, the peroxide falls, and a portion of ni- trate of ammonia is formed, part of the water as well as of the acid be- ing decomposed. Sulphate of Tin. When tin is boiled in sulphuric acid, a solution is obtained which deposits white acicular crystals. A protosulphate of tin is also precipitated by pouring sulphuric acid into protomuriate of tin. TESTS OF THE SALTS OF TIN. These salts are mostly soluble in wa- ter, and are precipitated of an orange colour by hydriodic acid, and by hydrosulphuret ef ammonia, provided no excess of acid be present. Solutions of chloride of gold and of corrosive sublimate, produce pur- ple and black precipitates in the salts containing the protoxide, but none in those containing the peroxide. Ferrocyanate of patassa pro- duces a white precipitate in solution of muriate of tin. SECTION XVIIL CADMIUM. Atom. Num. 55-3 Symb. C<\. Sp. gr. 8-604.] This metal was discovered in 1817, by Professor Stromeyer, of Gottingen, in an oxide of zinc, which had been prepared for medical use from an ore of zinc brought from Silesia. It has since been dis- covered by Dr. Clarke in the zinc ores of Derbyshire, and in the com- mon zinc of commerce, and by Mr. Herapath in the zinc works near Bristol, England. PROPERTIES. This metal is nearly as white as tin, but is somewhat harder and more tenacious ; it is very ductile and malleable, and sus- ceptible of a high polish ; its specific gravity is 8-604 before being hammered, and 8-694 afterwards ; it melts at about the same tempera- ture as tin, and is nearly as volatile as mercury, condensing into glo- bules which have a metallic lustre ; its vapour has no odour. EXTRACTION. The process by which Stromeyer separates cadmium from zinc or other metals is the following. The ore of cadmium is dissolved in dilute sulphuric or muriatic acid, and after adding a por- tion of free acid, a cunent of sulphuretted hydrogen gas is transmit- ted through the liquid, by means of which the cadmium is precipitated as sulphuret, while the zinc continues in solution. The sulphuret of cadmium is then decomposed by nitric acid, and the solution evapo- rated to dryness. The dry nitrate of cadmium is dissolved in water, and an excess of carbonate of ammonia added. The white carbonate of cadmium subsides, which, when heated to redness, yields a pure oxide. By mixing this oxide with charcoal, and exposing the mixture to a red heat, metallic cadmium is sublimed. A very elegant process for separating zinc from cadmium was pro- posed by Dr. Wollaston. The solution of the mixed metals is put into a platinum capsule, and a piece of metallic zinc is placed in it. If cadmium is present, it is reduced, and adheres so tenaciously to the capsule, that it may be washed with water without danger of being lost It may then be dissolved either by nitric or dilute muriatic acid. Turner. CADMIUM. 289 REFERENCES. Stromeyer on Cadmium, Ann. of Phil xiii. 103, xiv. 279. Dr. E. I). Clarke on the discovery of this meted in the Derbyshire ores of Zinc, Ann. of Phil. xv. 272, and\\s.. 1^3. Kerapath on Cadmium, and the sources of procuring it in quantity, Ann. of Phil. xix. 435. CADMIUM AND OXYGEN. Oxide of Cadmium. Atom. Num. 63 % 8 Symb. O+Cd. PROPERTIES. The oxide of cadmium is of an orange yellow colour, and fixed in the fire ; it is insoluble in water, and does not change the colour of violets, but is a powerful salifiable base, forming neutral salts with acids ; it is precipitated as a white hydrate by pure ammonia, but is redissolved by excess of that alkali ; it is precipitated permanently by pure potassa as a hydrate, and by all the alkaline carbonates, as carbonate of cadmium. The oxide of cadmium may be obtained by heating the metal in open air, and also by igniting the carbonate, Chloride of Cadmium, crystallizes in small rectangular prisms, per- fectly transparent, which effervesce when heated, and are very soluble. At high temperatures it sublimes in small micaceous plates. Iodide of Cadmium forms large and beautiful hexahedral tables of a metallic or pearly lustre. At a high temperature the iodine escapes. Sulphuret of Cadmium occurs native in some kinds of zinc blende, and is easily procured by the action of sulphuretted hydrogen on a salt of cadmium. It has a yellowish orange colour, and is distinguished from the sulphuret of arsenic by being insoluble in pure potassa, and by sustaining a white heat without subliming. Phosphuret of Cadmium has a gray colour and feeble metallic lustre, is brittle and very little fusible. CADMIUM AND THE METALS. Cadmium unites readily with other metals, and forms brittle alloys. When these alloys are exposed to a very high temperature, the cadmi- um is volatilized. It also unites with mercury and forms an amalgam which has a silvery appearance, and crystallizes in octahedrons. Ber~ zelius. SALTS OP CADMIUM. Nitrate of Cadmium. Atom. Num. 153-S Symb. (5O+NI +(O+Cd.)+4Aq. This salt crystallizes in needles or prisms, which are deliquescent. Sulphate of Cadmium. Atom. Num. 139-8 %M&. (3O+S) +{0+Cd.)-M Aq. Crystallizes in large rectangular prisms, resembling sulphate of zinc, which are soluble in water, effloresce hi the air, and -at a gentle heat, ^ose their water of crystallization. 290 NICKEL. Phosphate of Cadmium. Atom. Num. 108*5 Syrnb. (2JO+P)+(0+Cd.)+l Aq. A pulverulent and tasteless salt ; insoluble in water, and formed by mixing solutions of nitrate of cadmium and phosphate of soda. Carbonate of Cadmium. Atom. Num. Si'SSymb. (2O+C) +(0+Cd.) A white tasteless powder, having a certain resemblance in colour to white lead ; it is insoluble in water, and readily decomposable by heat ; it is destitute of combined water, but when dried in the open air, re- tains the fifth part of an atom of water, no doubt hygrometrically uni- ted to the salt. Thomson. REFERENCES. I 'or further information concerning the Salts of Cadmium, see the Papers of Strumeyer abuve quoted, and Thomsoifs First Prin. u. 360. SECTION XIX, NICKEL. ? Atom. Num. 29-5- Symb. Tti.Sp. gr. 8 279. Discovered by Cronstedt, in 1751, in the Copper Nickel of West phalia, PROPERTIES. Nickel has a white colour, intermediate between thosv % of silver and iron ; is susceptible of a fine polish ; is both ductile and malleable ; its specific gravity after fusion is^ about 8-279, and is increased to near 9-0 by hammering ; it is attracted by the magnet r and like iron and cobalt may be rendered magnetic; is exceedingly infusible, even more so than pure iron ; suffers no change at cornmoR temperatures by exposure to air and moisture, but absorbs oxygen at a red heat, though not rapidly, and is partially oxidized. EXTRACTION. The principal source from which nickel is obtained, is a substance called Speiss, an artificial arseniuret of nickel, which re- mains at the bottom of the crucibles in which zaffre is prepared. Va- rious processes have been proposed for extracting the metal from this compound, of which that of Dr. Thomson is the most simple and per- haps as successful as any. It consists in reducing the speiss to pow- der and digesting it in a mixture of sulphuric and nitric acids. The crystals obtained by evaporation are free from arsenic, iron, bismuth and antimony, but are contaminated with a little cobalt and copper. The copper is to be precipitated from a watery solution of these crystals by a current of sulphuretted hydrogen, and the oxide of nick- el when washed, but still moist, is to be exposed to chlorine gas, which dissolves the oxide of nickel, leaving that of cobalt untouched, The muriate of nickel is easily convened into sulphate, by the addi- tion of a due proportion of sulphuric acid, and the sulphate, by one or more crystallizations, is obtained pure* From this salt, dissolved in NICKEL. 291 water, carbonate of nickel is precipitated by carbonate of soda, or potassa, and after being well edulcorated, is to be dried and cal- cined. Metallic nickel may be prepared either by heating the oxalate in close vessels, or by the combined action of heat and charcoal, or hydro- gen, on the oxide of nickel. REFERENCES. Thomson, in Phil. Mag. and Ann. ii. 151. Robiquet, in Ann. de Chini. Ixix. Mill, in Ann. of Phil. xix. 201. Laugier, in Ann. de Chim. et de Phys. ix. ; and Berliner, samewor/c, xxv. and xxxiii. Berzelius, Traitede Chim. iii. 210. Hisiiiger and Murray's experiments on jNiccolane- ?tw, Ann. of Phil. i. 116. Dr. Clarke's method of obtaining gure Nickel by the compound blowpipe, same work, xiv. 142. NICKEL AND OXYGEN. Nickel seems to be susceptible of only two states of oxidation ; but Berzelius decribes three oxides. Protoxide of Nickel. Atom. Num. 37*5 Symb. O+Ni. PROPERTIES. This is of an ash-gray colour, but when heated to whiteness, of a dull olive-green ; it is not attracted by the magnet ; is a strong salifiable base, and nearly all the salts have a green tint ; is precipitated as a hydrate, of a pale green colour, by the pure alkalies, but is redissolved by excess of ammonia. It is formed by heating the carbonate, oxalate or nitrate, to redness in an open vessel. Peroxide of Nickel Atom. Num. 41'5Symb. 1 JO+Ni. The peroxide of nickel is of a black colour, and is formed by trans- mitting chlorine gas through water, in which the hydrate of the pro- toxide is suspended. It does not unite with acids ; is decomposed by a red heat, and with hot muriatic acid forms a proto-muriate, with dis- engagement of chlorine gas. Nickel combines with chlorine, iodine, phosphorus, sulphur and car- bon ; but these compounds do not possess any very striking properties. According to Mr. Ross, the carburet of nickel is apt to form when nick- el is reduced from its salts by carbonaceous matter. It resembles iodine, or micaceous iron ore. Ann. of Phil, xviii. 62, 149 ; xix. 201. NICKEL AND THE METALS. Nickel may be alloyed with most of the metals, but few of them are peculiarly interesting. An alloy of iron and nickel has been found in all the meteoric stones that have been hitherto analyzed, however re- mote from each other the parts of the world in which they have fallen. In these it forms from I 1-2 to 17 per cent, of their weight. It enters, also, into the composition of the masses of native iron discovered in Si- beria and South-America ; and was found by Mr. Brande to the ex- tent of 3 per cent, in native iron brought from the arctic regions. Brande s Jour. vi. 369, and ix. 323. 292 NICKEL. Meteoric iron has been imitated by fusing iron with nickel. The alloy of 90 iron with 10 nickel, is of a whitish yellow cast, and not so malleable as pure iron. The alloy with 3 per cent, of nickel, is per* fectly malleable, and whiter than iron. These alloys are less disposed to rust than pure iron ; but nickel alloyed with steel increases the ten- dency to rust. Stodart and Faraday, in Brande's Jour. ix. 324. An alloy of copper and nickel occurs in nature, and is known by the name of Copper-nickel. It is of a copper colour and in addition to its chief ingredients contains sulphur, iron and cobalt. But the most important of the alloys of nickel, is the Tutenag or Packfong of the Chinese. It is a compound of copper, tin, zinc and nickel. It is malleable, and is employed in the fabrication of various utensils. This alloy is now successfully manufactured at Vienna. See an account of the manufacture of Pachfong, in Brewsters Edin. Jour* of Science, N. S. i. 167. SALTS OF NICKEL. Nitrate of Nickel. Atom. Num. I3fr5Symb. (5O+N) This salt crystallizes in four-sided oblique prisms ; has a green co- lour, and does not undergo any change by exposure to the air. Thorn' son's First Prin. ii. 333. Sulphate of Nickel. Atom. Num. 140-5 Symb. (30+8)4- (0+Ni.)+7 Aq. This salt has a beautiful grass-green colour, and crystallizes in rhom* bic and in square prisms. Thomson. Phosphateof Nickel Atom. Num. WQ'2Symb. (2|O+P) + (0+Ni.)+3Aq. A powder of a light pea-green colour, tasteless and insoluble in wa* ter. It is obtained by mixing together solutions of sulphate of nickel and phosphate of soda, in the atomic proportions. Carbonate of Nickel A light green tasteless powder, insoluble in water, but dissolving with effervescence in acids ; formed by precipita* ting a solution of sulphate of nickel by carbonate of soda. REFERENCES. Thomson on the Salts of Nickel, First Prin. ii. 833, and Inorg. Chem. ii. 596. TESTS OF THE SALTS OF NICKEL. The solution of these salts has a fine green colour, and affords a green precipitate with ammonia, so* luble in excess of that alkali, when it assumes a blue colour. Hydrio* date of potassa produces a very characteristic yellowish green precipi- tate ; and the ferrocyanate of potassa, one of a pale gray or greenish white. COBALT. 293 SECTION XX. COBALT. Atom. JVTttw. 29.5 Symb. Co. Sp. gr. 8.538. This metal appears to have been discovered by Brandt. It is met with in the earth, chiefly in combination with arsenic, known by the name of Arsenical Cobalt. It is also, according to Stromeyer, a con- stant ingredient in meteoric iron. PROPERTIES. Cobalt is solid, hard and brittle ; of a reddish gray colour, and weak metallic lustre ; it fuses at about 130 of Wedge- wood, and when slowly cooled it crystallizes ; is attracted by the mag- net, and is susceptible of being rendered permanently magnetic ; ab- sorbs oxygen when heated in open vessels ; is readily oxidized by nitric acid, but is with difficulty attacked by sulphuric or muriatic acid. NATIVE STATE AND EXTRACTION. Cobalt is found in nature in the form of oxide, of sulphate, ofarseniate, and in combination with many combustibles, especially with sulphur and arsenic. From the oxide, metallic cobalt may be obtained by heating it with charcoal, by passing over it a stream of hydrogen gas, or by heating strongly the oxalate of cobalt in close vessels. REFERENCES. Thomson, in Ann. of Phil, xvii. 250. For Trommsdorfs process for obtaining pure Cobalt^ see Repert. of Arts, %d ser. ii. 453, ir. 126, andvm. 154. Laugier^s process for separating Cobalt and Nickel^is describ- ed in Ann. of Phil. xiii. 38, and in Branded Jour. ix. 181. COBALT AND OXYGEN. Chemists are acquainted with two compounds of oxygen and co bait. Protoxide of Cobalt. Atom. Num. 37'5 Symb. O+Co. This oxide is of an ash-gray colour, and is the basis of the salts of cobalt, most of which are of a pink blue ; it absorbs oxygen when heated in open vessels, and is converted into the peroxide. It may be prepared by decomposing carbonate of cobalt by heat, in a close vessel ; and may be easily recognized by giving a blue tint to borax when melt- ed with it. The substance known in the arts by the name of Zaffre, is an im- pure oxide of cobalt, prepared by exposing the native arseniuret of co bait, in a reverberatory furnace, to the united action of heat and air. On heating this substance with a mixture of sand and potassa, a beau- tiful blue coloured glass is obtained, which when reduced to powder, is known by the name of Smalt. In this form it is much employed in the arts for communicating a similar colour to glass, earthen- ware, and porcelain. For details concerning the preparation of this substance and its employment in the arts, see Aikins Chem. Diet, and Parkcs* Chem. Essay's, iii. 338. 294 COBALT. Peroxide of Cobalt. Atom. Num. 4.1-5 Symb. If 0+Co. This oxide is of a black colour, and is easily formed from the protox- ide in the way already mentioned. It does not unite with acids ; and when digested in muriatic acid, the protomuriate of cobalt is generated with disengagement of chlorine. When strongly heated in close ves- sels, it gives off oxygen, and is converted into the protoxide. This compound appears to form salts with bases, especially ammo- nia. Gmelin calls it Cobaltic Acid. Ann. of Phil. 2d scr. ix. 69. COBALT AND CHLORINE. Cobalt takes fire when introduced in a finely divided state, into chlo- rine gas ; but the compound has not been examined. COBALT AND SULPHUR. According to Berzelius, cobalt combines in several proportions with sulphur, but the compounds do not appear to possess any peculiarly in- teresting properties. Berzelius , Traite de Chim. iii. 232. SALTS OF COBALT. Muriate of Cobalt. A deliquescent salt, of a blue-green colour ; when a little diluted the solution becomes pink ; the pale pink solution, when written with, is scarcely visible ; but if gently heated, the writ- ing appears brilliant and green, which soon vanishes, as the paper cools. This solution has been termed HeitoCs Sympathetic Ink. This salt may be prepared by digesting either oxide in muriatic acid. The sympathetic solution may be obtained by digesting one part of cobalt or of zaffre in a sand heat for some hours, with four parts of ni- tric acid. To the solution add one part of muriate of soda ; and di- lute with four parts of water. Characters written with this solution are illegible when cold ; but when a gentle heat is applied they assume a beautiful blue or green colour. Nitrate of Cobalt, occurs in crystals, which have an acrid and bitter taste, redden vegetable blues, and deliquesce rapidly when exposed to the air. It is easily obtained by dissolving cobalt, or its oxide, in nitric acid. Sulphate of Cobalt. This salt has a deep red colour, and crystallizes in rhombic prisms, similar to the form of sulphate of iron. There is also a Bisulphate* Phosphate of Cobalt, is formed by dissolving the carbonate in phos- phoric acid and adding alcohol, or by mixing muriate of cobalt and phosphate of soda. A lilac piecipitate in the last case falls, which if mixed with eight parts of fresh precipitated alumina and dried, forms, according to Thenard, a blue pigment that may be substituted for Ultra-marine, and is known by the name of Thenard' s Blue, or Cobalt Blue. For a full description of the process, see Brandcs Jour. xv. 381; Thenard' s Traite de Chim. iii. 146 ; and Franklin Jour. ii. 3. COBALT. 295 Carbonate of Cobalt a light powder, of a pink colour, tasteless, in - soluble in water, and not altered by exposure to the air. It does not alter vegetable blues, but dissolves in acids with a strong effervescence It is formed by decomposing the nitrate, muriate or sulphate of cobalt with carbonate of potassa, and washing and drying the precipitate. REFERENCES. Thomson on the Salts of Cobalt, First Princip. ii. 341. TESTS OF THE SALTS OF COBALT. All the salts of cobalt contain the protoxide ; oxalic acid throws down from their solutions a rose-colour- ed precipitate ; ferrocyanate of potassa one of a grass green colour ; solution of borax a pink compound ; and hydrosulphuret of ammonia a black hydrosulphuret of cobalt. Henry. 296 ARSENIC. CLASS V. METALS, WHICH DO NOT DECOMPOSE WATER AT ANY TEM- PERATURE, AND THE OXIDES OP WHICH ARE NOT REDUC- ED TO THE METALLIC STATE BY THE SOLE ACTION OF HEAT. ORDER I. METALS, WHICH, WHEN COMBINED WITH OXYGEN, FORM ACIDS. SECTION XXL ARSENIC. Atom. Num. 37-7- Symb. As. Sp. gr 5 70. This metal was known to the ancients, its combination with sulphur being noticed by Dioscorides, under the name of Sfindarac. Its peculiar nature, however, was first demonstrated by Brandt, in 1733. PROPERTIES. An exceedingly brittle metal, of a strong metallic lus- tre, and steel gray colour ; its structure is crystalline ; at 356 3 F. it volatilizes without being fused, and in close vessels may be collected unchanged ; but, when thrown on a red hot iron, it burns with a blue flame and a white smoke, and a strong smell of garlic is perceived, which belongs only to the metal and not to its oxides ; it is speedily tarnished by exposure to air and converted into a black powder, which is a mixture of the metal and oxide. Arsenic decomposes many of the Salts. The nitrates detonate with arsenic, convert it into arsenic acid, and this combining with the base of the nitrate, forms an arseniate that remains at the bottom of the vessel. If three parts of chlorate of potassa be mixed with one part of arsen- ic in fine powder, which must be done with great caution and with a light hand, a small quantity of this mixture, placed on an anvil, and struck with a hammer, will explode with flame and a considerable re- port ; if touched with fire, it will burn with considerable rapidity ; and if thrown into concentrated sulphuric acid, at the moment of contact a flame rises into the air like a flash of lightning, which is so bright a to dazzle the eye. Ures C/iem. Diet. NATIVE STATE ' AND PREPARATION. Metallic arsenic sometimes oc- curs native, but more frequently it is found in combination with other metals, and especially with cobalt and iron. From the oxide obtained ARSENIC. 297 by roasting these ores, the pure metal may be procured by mixing it with oil and subliming at a low red heat in a clean Florence flask, or by mixing it with about twice its weight of black flux, [prepared by detonating, in a crucible, one part of nitre with two of crystals of tar- tar,] and exposing the mixture to a red heat, in an Hessian crucible, over which is luted an empty crucible for receiving the metal. ARSENIC AND OXYGEN. Chemists are acquainted with two compounds of these substances, and as they both possess acid properties, the terms Arsenious and Arsen- ic acid have been properly applied to them. There is, however, some difference of opinion concerning their composition. I shall adopt the views of Berzelius with regard to them, as probably, the most correct. Arsenius Acid. Atom. Num. 49'7Symb. 1 O+As. SYN. White Oxide of Arsenic. White Arsenic. PROPERTIES. A semi-transparent, white and brittle substance, of a sweetish taste ; its specific gravity is 3-7 ; is volatilized at 380 F. yielding vapours, which do not possess the odour of garlic, and which condense unchanged on cold surfaces ; but if suddenly heated it runs into a transparent brittle glass ; it is sparingly soluble in water, and more so in hot than in cold ; it reddens vegetable blue colours, and combines with salifiable bases forming salts, which are termed tfrse- nites. PREPARATION. This compound is always generated when metallic arsenic is heated in open vessels, and it may also be prepared by di- gesting the metal in dilute nitric acid. ACTION ON THE ANIMAL ECONOMY. Arsenious acid acts as a poison not only when taken into the stomach, but when applied to a wound, or when its vapour is inspired. It is the prevailing opinion of writers on this subject, that it produces its deleterious effects more from its constitutional operation than trom the local inflammation which it ex- cites. Inflammation, more or less manifest, is certainly often present, but frequently in fatal cases it is not very striking, and it is difficult to believe that this and its consequences can be the cause of the rapid dis- solution so generally noticed from the exhibition of arsenic. Toxicologists are somewhat divided as to the organ or part which is affected. The opinion of some is, that the action " is a consequence of the poison entering the blood, and so passing to the remote organs acted on," while others consider that "the organ which is remotely affected sympathizes, through the medium of the nerves, with the im- pression made on the organ which is affected primarily." The symptoms vary with the quantity taken and the constitution of the sufferer. The earliest and most common are pain and vomiting ; yet there are exceptions even 'to these. In cases rapidly fatal, extreme faintness, cold sweats, oppression and slight convulsions are seen. If life be prolonged beyond twenty-four hours, the vomiting an.d retching are often succeeded by diarrho3a, burning heat and extreme pain in the stomach and intestines the urinary passages are in many cases affect- ed the pulse is very small the countenance extremely anxious and the skin livid, or sometimes affected with eruptions. In those who 298 ARSENIC. survive, nervous diseases resembling convulsions, palsy or epilepsy are noticed for a length of time. These are the leading symptoms for their variations in different eases, see Christison on Poisons, 214 to 229. TESTS. If the poison be found in a solid state, it should be slowly dried on a filter. It must then be mixed with two parts or more of freshly ignited charcoal, and the whole put into a small glass tube, about two inches long, and blown with a small bulb at the closed end. Apply gentle heat with the spirit lamp, so that the contained moisture may be driven off, and for this purpose, the upper part of the material may be first heated. Then apply the flame to the bottom of the tube, and in a short time a bright metallic crust, resembling polished steel, but darker in colour, will be formed on the inside. This is metallic arsenic, and the test is/ called the reduction of the metal. When heat is cautiously applied to this crust, the metal rises in vapour, and the alliaceous odour will be perceived. 2. If the suspected substance be in a fluid state, after adding as much distilled water as may be deemed necessary, a stream of Sulphuretted Hydrogen Gas should be passed into a portion of it. The solution, if arsenical, will assume a bright lemon yellow colour, and in some cases a yellow precipitate will be thrown down, being the Sulphuret of Arsenic. On account of the probability of the suspected substance containing an alkali, (in which the sulphuret of arsenic is soluble,) it is advisable, previous to the above experiment, to add a little dilute acetic acid. The sulphuret thus formed may be collected, dried and mixed with the black flux, and placed in a tube as above. On applying heat, the polished crust of metallic arsenic is formed. To another portion, a solution of nitrate of silver may be added as long as a white precipitate falls down, and after its subsidence, drop in ammonia ; if arsenic be present, a beautiful yellow precipitate will be produced, being JJrsenite of Silver. This is a modification of the well known test of Dr. Marcet, and proposed by Dr. Forbes, professor of chemistry at Aberdeen, to obviate some of the objections made to it. To a third portion, the ammoniaco-sulphate of copper, in solution, is added, when a precipitate of an apple or grass green colour is per- ceived, being the drscnite of Copper. When these results are obtained from any suspected substance, we need not hesitate in pronouncing it arsenic. No other presents the four characteristic effects now described, and it should be remembered that it is their combination that renders the proof so unequivocal. The reduction is the most satisfactory and decisive, but even here, the metal should be re-oxidized, dissolved in water, and the liquid tests applied, in order to meet every possible objection. Sometimes the presence of organic matters interferes with the pro- cesses just mentioned. Their removal may often be sufficiently effect- ed by adding acetic acid to the solution and separating the coagulated substances by filtration ; but a more complete separation may be pro- duced by evaporating the solution at a moderate heat to dryness, re- dissolving anew by boiling successive portions of distilled water on the residue, and then filtering the solution after it has cooled. By this means most of the organic matters are rendered insoluble. ADULTERATION. Arsenious acid is liable to be mixed with chalk and sulphate of lirne. If the suspected arsenic is heated in an iron spoon, it ought to volatilize. If it contains chalk and sulphate of lime, they remain behind. ARSENIC. 299 REFERENCES. On the solubility of Arsenious Acid, see a notice of the pa* pers of Bucholz and Fisher, in Ann. of Phil. v. 29. vii. 33. Christison on the taste of Arsertic, Edin. Med. and Surg. Jour, xxviii. 95. On the Tests of Arsenic^ see Christison, in Edin. Medico- Chirurgical Trans, ii. and in Edin. Med. and Surg. Jour. xxii. and the Treatise on Poisons by the same author ; Forbes, in Edin. Med. and Surg. Jour, xxxii. ; R. Phillips, in Ann' of Phil. xxvi. 298 ; and Beck's Med. Juris. 383. Arsenic Acid. Atom. Num. 57'7 Symb. 2% O+As. PROPERTIES. A white concrete substance, with a sour metallic taste; it reddens vegetable blues, and combines with bases forming salts, termed arseniates ; attracts moisture from the air, and dissolves in five or six times its weight of cold, and in a still smaller quantity of hot water ; it forms irregular grains when its solution is evaporated, but does not crystallize ; when strongly heated it fuses into a glass which is deliquescent ; but when urged by a very strong red heat it is re- solved into oxygen and arsenious acid : it is an active poison. This acid may be formed by dissolving one part of arsenious acid in six parts of concentrated nitric acid, and distilling the solution to per- fect dry ness. It is found in nature in combination with several of the metallic oxides. ARSENIC AND CHLORINE. Chloride of Arsenic. Atom. Num. 90-87 Symb. 1 J Cl+As. SYN. Fuming liquor of Arsenic. Butter of Arsenic. PROPERTIES. A colourless, very soluble liquid, which fumes very strongly on exposure to the air, and is resolved by water into muriatic and arsenious acids ; by the aid of heat it dissolves sulphur and phos- phorus, which however separate as the liquid cools. PREPARATION. This chloride is prepared by submitting to distilla- tion a mixture of six parts of corrosive sublimate with one of arsenic. The same compound is also formed when arsenic in powder is thrown into a jar full of dry chlorine gas. According to Berzelius there is another chloride of arsenic, con- taining a less proportion of chlorine than the above ; [Traite de Chim. ii. 41 1] and that prepared by the process of Dumas is perhaps also dis- tinct from both. Brandes Jour. N. S. i. 234. ARSENIC AND BROMINE. When arsenic is brought into contact with bromine, the two. bodies unite, according to Serullas, with the disengagement of light. Arse- nic is to be added in small quantities to the bromine until it ceases to produce deflagration, when the mass is to be distilled. The bromide comes over in the form of a colourless and yellowish liquid and crys tallizes in the recipient. Berzelius , ii. 44*2. 300 ARSENIC. ARSENIC AND IODINE. These two bodies unite and form a deep red compound which de- composes water, and affords arsenic and hydriodic acids. It has been made the subject of a memoir by M. Plisson. Ann. de Chim. et de Phys. Nov. 1828. Fluoride of Arsenic is a fuming, colourless liquid, which by the ac- tion of water completely decomposes glass. It has been examined by Unverdorben. Berzelius, ii. 243. ARSENIC AND HYDROGEN. Hydruret of Arsenic^ or Jlrseniuretted Hydrogen. Atom. Num. 39-2 Symb. } H+As. Discovered by Scheele and obtained in a pure form according to Soubeirain, by fusing arsenic with its own weight of granulated zinc, and decomposing the alloy with strong muriatic acid. PROPERTIES. A colourless gas, having a fetid odour like that of gar- lic ; its specific gravity according to Dumas is 2-695 ; it extinguishes bodies in combustion, but is itself kindled by them, and burns with a blue flame ; it instantly destroys small animals that are immersed in it, and is poisonous in a high degree, having proved fatal to a German phi- losopher, M. Gehlen ; water absorbs one-fifth of its volume, and ac- quires the odour of the gas ; it does not possess acid properties ; it is decomposed by various agents, as heat, atmospheric air, chlorine and iodine, and with oxygen it forms an explosive mixture. Gay Lussac has also described a solid compound of arsenic and hy- drogen, separating in the form of chesnut brown coloured flocks, dur- ing the action of water upon an alloy of potassium and arsenic. Its composition is unknown. Tkenard, Traite de Chim. i. 500. ARSENIC AND SULPHUR. % Chemists differ as to the number of definite compounds formed by these bodies. Some assert that there are but two ; others that there are three, while Berzelius, in his treatise, describes no less than five. I shall adopt the view of these compounds contained in Dr. Turner's elements. ProtosuJphuret of Arsenic. Jltoin Num. 53 7 Symb. S-f-As. SYN. Sulfide Hyparscnicux. Berzelius. This sulphuret occurs native, and is known in mineralogy by the name of Realgar. It may be formed artificially by heating arsenious acid with about half its weight of sulphur, until the mixture is brought into a state of perfect fusion. The cooled mass is crystalline, trans- parent, and of a ruby red colour ; and may be sublimed in close ves- sels without change. ARSENIC. 301 Scsquisulphuret of Arsenic. Atom. Num. 61-7 Symb. 1|S -fAs. SYN. Sulfide Arsenieux. Berzelius. Occurs in nature, and known by the name of Orpiment. Formed artificially by fusing together equal parts of arsenious acid and sulphur; or better, by transmitting a current of sulphuretted hydrogen gas through a solution of arsenious acid. PROPERTIES. This compound has a rich yellow colour ; it fuses readily when heated, and becomes crystalline on cooling, and in close vessels may be sublimed without "change. It is dissolved with great facility by the pure alkalies, and yields colourless solutions. USES. Orpiment is employed as a pigment, and is the colouring- principle of the paint called King's Yellow. M. Braconnot has pro- posed it likewise for dying silk, woollen, or cotton stuffs of a yellow colour. For this purpose the cloth is soaked in a solution of orpiment in ammonia, and then suspended in a warm apartment. The alkali evaporates, and leaves the orpiment permanently attached to the fibres of the cloth. Ann. de Cliim. et de P/iys. xii. or Branch? s Jour. ix. 184. Persulphuret of Arsenic. Atom. Num. 77 '7 Symb. 2% S+As. This sulphuret has a colour very similar to orpiment ; it is dissolved by pure alkalies, fuses by heat, and may be sublimed in close vessels without decomposition. It is prepared by transmitting sulphuretted hydrogen gas through a moderately strong solution of arsenic acid ; or by saturating a solution of arseniate of potassa or soda with the same gas, and acidulating with muriatic or acetic acid. The oxygen of the acid combines with the hydrogen of the gas, and the persulphuret of arsenic subsides. The experiments of Orfila have proved that the sulphurets of arse- nic are poisonous, though in a much less degree than arsenious acid. The precipitated sulphuret is more injurious than the native orpi- ment. ARSENIC AND THE METALS. Arsenic combines with most of the metals, which it generally ren- ders brittle, even though in very small quantity. Many of these alloys are found in nature, and are known by the name of jJrseniurcts. The alloy of three parts of tin and one part of arsenic, is white, very brilliant and brittle ; it crystallizes in large plates, is more fusible than arsenic, but less so than tin. It is employed in the laboratory in the preparation of arseniuretted hydrogen, and is formed by heating a, mixture of three parts of tin and two of arsenic in a covered cruci- ble. The alloy of copper and arsenic is white, and so very similar in its appearance to silver, as to be substituted for it. ARSENIOUS ACID AND SALIPFABLE BASES. These compounds, termed Arsenites, have not been much examined. The Ars&nitcs of Potassa, Soda and Ammonia, are soluble and incapa- T 302 ARSENIC. ble of crystallizing; and they may be easily prepared by boiling a so- lution of these alkalies in arsenious acid. The other arsenites are in- soluble, or, at most, sparingly soluble in pure water ; but they are dis- solved by an excess of their own acid, with great facility by nitric acid, and by most other acids with which their bases do not form insoluble compounds. The insoluble arsenites are easily formed by the way of . double decomposition. On exposing the arsenites to heat in close vessels, either the arseni- ous acid is dissipated in vapour, or they are converted, with disen- gagement of some metallic arsenic, into arseniates. Heated with char- coal or black flux, the acid is reduced with facility. The soluble arsenites, if quite neutral, are characterized by forming a yellow Arsenite of Silver when mixed with the nitrate of that base, and a green Arsenite of Copper, Scheeles green, with sulphate of cop- per. When acidulated with acetic or muriatic acid, sulphuretted hy- drogen causes the formation of orpiment. The insoluble arsenites are all decomposed when boiled in a solution of carbonate of potassa or soda. The Artenite of Potassa is the active ingredient in the Liquor Potas- SCE Jlrsenitis of the U. S. Pharmacopeia and in Fowler's mineral solution or tasteless ague drop. ARSENIC ACID AND SALIFIABLE BASES, These compounds, termed Arseniates, resemble the phosphates in this as in other respects, that though carefully neutralized when in so lution, yet when concentrated by evaporation, they crystallize with an excess of base. Arseniate of Ammonia is formed by saturating arsenic acid with am- monia ; rhomboidal prisms are obtained on evaporation, which, when gently heated, effloresce and evolve ammonia. Biarseniate of Potassa. This salt occurs in four-sided rectangular prisms, terminated by very short four-sided pyramids ; is permanent in the air and has a saline cooling taste ; is soluble in about five times its weight of cold water, but is insoluble in alcohol. It may be formed by adding excess of arsenic acid to potassa, or by distilling in a retort equal weights of nitre and arsenious acid. Arseniate of Soda forms large crystals, having the same shape as phosphate of soda, which effloresce by exposure to a dry atmosphere ; it has a cooling taste, resembling that of carbonate of soda, but less strong ; is soluble in about four times its weight of cold water, and the liquid has alkaline properties ; it undergoes watery fusion ; its so- lution when dropped into most earthy and metallic salts, occasions precipitates, the peculiar appearances of which, are exhibited by Dr. Thomson, in a table published in the Ann. of Phil. xv. 83. Arseniates of Lime. According to Mr. Dalton lime and arsenic acid combine in several proportions, forming an insoluble, a soluble and a neutral arseniate. Arseniate of Baryta. An insoluble salt, formed by mixing neutral arseniate of soda with nitrate of baryta. Arseniates of Iron. There are three native arseniates of iron, exactly similar in their composition to the analogous phosphates of iron. MOLYBDENUM. 303 Arteniate of Zinc, is precipitated in the form of a white insoluble powder when arsenic acid or an alkaline arseniate is added to sulphate of zinc. Arseniate of Tin is a white insoluble powder, precipitated by ad- ding arseniate of potassa to muriate of tin. drseniate of Copper, is formed by adding an alkaline arseniate to ni- trate of copper. It is a blue insoluble powder. See Chevenix in Phil. Trans, for 1801. Arseniate of Lead. This salt occurs native in the form of crystals, in Saxony and in Cornwall, Eng. It may be formed artificially by pouring arsenic acid into any of the soluble salts of lead, when it falls in the form of a white powder, insoluble in water, but soluble in dilute nitric acid, by which means we can separate it, in analysis, from sul- phate of lead. REFERENCES. Chevenix in Phil. Trans, for 1801. Thomson on Arse- nic and the Arseniates, Ann. of Phil. xv. 81. Theuard, Traite de Chin. iii. 433. SECTION XXII. MOLYBDENUM. Jitom. Num.. 47-7. Symb. Mo.Sp. gr. 8-625. Discovered by Scheele in 1778, but hitherto has been obtained only in small quantities, and is known imperfectly. PROPERTIES. A brittle metal of a yellowish white colour and very infusible ; it has a specific gravity of 8-615, to 8 '636 according to Bu- cholz ; when heated to a dull red in open vessels, it is converted into an oxide, and at a still higher temperature it is converted into an acid. EXTRACTION. When the native sulphuret of molybdenum, in fine powder, is digested in nitro-muriatic acid until the ore is completely decomposed, and the residue is briskly heated in order to expel sulphu- ric acid, molybdic acid remains in the form of a white heavy powder. From this acid metallic molybdenum may be obtained by exposing it with charcoal to the strongest heat of a smith's forge ; or by conduct- ing over it a current of hydrogen gas, while strongly heated in a tube of porcelain. Berzelius. MOLYBDENUM AND OXYGEN. According to Berzelius there are three compounds of molybdenum and oxygen, viz. two oxides and an acid. Protoxide of Molybdenum.- Atom. Num. 55'7 Symb. O-f- Mo. A dark coloured compound, which forms salts with acids, and when heated in the open air is converted into the deutoxide. It is prepared by adding muriatic acid to the solution of a molybdate, and digesting with distilled zinc. For details, see Berzelius, ii. 470. 304 MOLYBDENUM. Deutoxide of Molybdenum. Jltom. Num. 63-7 Synth. 2O + Mo. This oxide may be obtained in the form of a hydrate, by digesting a mixture of molybdic acid, metallic molybdenum, and sulphuric or muriatic acid, till the colour of the liquid becomes a deep red. When this liquid is treated with ammonia, a rust-yellow hydrated deutoxide is precipitated, which dissolves in acids and yields salts whose solutions are red, but become black, when evaporated to dryness. Berzelius } ii. 473. Molybdic Acid. Atom. JVum. tl'7Symb. 3O+Mo. A white powder, of the specific gravity of 3-4 ; it has a sharp me- tallic taste; reddens litmus paper ; is very sparingly soluble in water ; forms salts with salifiable bases, but as Berzelius observes, it performs the part of a base towards the stronger acids. MOLYBDENUM AND FLUORINE. Fluomolybdic Acid. This acid, which jjM first examined by Berze- lius in 1824, may be obtained by dissolving molybdic acid in fluoric acid. It has an acid, metallic and disagreeable taste, combines with bases and forms Fluomolybdat.es. It is supposed to consist of one atom fluoric acid-f-one atom molybdic acid. Thomson, Jnorg. Chem. ii. 202. MOLYBDENUM AND CHLORINE. With chlorine molybdenum combines in three proportions, forming compounds equivalent to its three oxides. The first is red and a little volatile. The second is black, very fusible, very volatile, and crys- tallizes in a black mass, of a brilliant colour like iodine, which it re- sembles also in the colour of its gas. The third is colourless and crys- tallizes in scales. Berzdius. MOLYBDENUM AND SULPHUll. Bisvlpfiuret of Molybdenum. Atom. JVum. 79-7 Symb. 2$ -ffifa A sectile compound of a metallic lustre, found native, and prepared artificially by heating one part of molybdic acid with five parts of sul- phur. The native mineral resembles graphite or plumbago, and was for- merly confounded with it. It occurs exclusively in primitive rocks, and i found in various parts of the United States. These two mine- rals may be very well distinguished by the streak on white china ; that of plumbago is grayish black, that of sulphuret of molybdenum has an olive green tinge. Cleaveland's Mineralogy. Berzelius also describes another sulphuret of this metal, consisting of one proportion of the metal and three proportions of sulphur. It is of a ruby colour, transparent and crystallized. Traite de Chim. ii. 482. CHROMIUM. 305 MOLYBDIC ACID AND SALIFIABLE BASES. The Molybdotes appear to be numerous, but they have not been at- tentively examined. According to Dr. Thomson the molybdates of potassa, soda, ammonia, lime, magnesia, cobalt and rhodium are solu- ble in water. The other molybdates mentioned in his table are insolu- ble or nearly so. [First Prin. ii. 60.] These salts may be procured in a manner similar to the analagous compounds of chromic acid. Mo- tybdate of Lead is found native, principally in crystals of different shades of yellow. REFERENCES. For further information concerning tJds metal and its com- pounds^ see Scheele's Chem. Essays , the elaborate experiments of Bucholz, in Gehlen's Jour. iv. 618, or Repert of Arts> %d ser. x. 373, 433; and the notices of its Alloys and Amalgams, from CreWs Annals, in Thomson's Syst. of Chem. i. SECTION XXIII. .CHROMIUM. Atom. Num. 2S. Symb. Cr.Sp. gr. 53. Chromium was discovered in the year 1797, by Vauquelin, in a beau- tiful red mineral, the native chromate of lead. It has since been de- tected in the mineral called Chromate of Iron, which occurs abundant- ly in several parts of Europe and America. PROPERTIES. This metal is of a white colour, with a shade of yel- low, and has a distinct metallic lustre ; it is brittle, very infusible, and with difficulty attacked by acids, even by the nitro-muriatic ; its spe- cific gravity has been stated at 5'9 ; but Dr. Thomson found it a little above 5 ; when fused with nitre, it is oxidized, and converted into chromic acid. PREPARATION. Chromium, which has hitherto been procured in very small quantity, owing to its powerful attraction for oxygen, may be obtained by exposing the oxide of chromium, mixed with charcoal, to the most intense heat of a smith's forge. REFERENCES. Vauquelin on Chrome, Ann. de Chim. xxv. or Tilloch's Phil. Mag. i. 279, 361. An elaborate Memoir on Chromium and iis com- pounds, by Dr. Thomson, in the Phil. Trans, for 1827, noticed in Phil. Mag. &nd Ann. i, 452. CHROMIUM AND OXYGEN. Chromium and oxygen combine in two proportions, forming the green oxide, and chromic acid. Protoxide of Chromium. Atom. Num. 40 Symb. IJO- PROPERTIES. A substance of a green colour, exceedingly infusi- ble and suffering no change by heat ; it is insoluble in water, and after 306 CHROMIUM. being strongly heated, resists the action of the most powerful acids ; deflagrated with nitre, it is oxidized to its maximum, and is thus recon- verted into chromic acid; fused with borax or vitreous substances, it communicates to them a beautiful green colour, a property which affords an excellent test of its presence, and renders it exceedingly useful in 'the arts ; it unites with acids and forms salts which have a green colour. PREPARATION AND NATIVE STATE. This compound is found native in France, in the form of a green incrustation. It is the colouring mat- ter of the emerald, and exists in a few other minerals. It is easily ob- tained by calcining to redness chromic acid or the chromate of mer- cury ; the mercury is volatilized with a part of the oxygen, while the protoxide remains. Broicn Oxide. A brown' compound of chromium and oxygen, was first noticed by Vauquelin, and has since been supposed, by some chemists, to be a deutoxide, by others, to be chromous acid. It is pre- pared by passing a current of sulphurous acid gas through a solution of chromate or bichromate of potassa, and washing and drying the pre- cipitate. According to Dr. Thomson it is nothing more than a com- pound of one atom of chromic acid and six atoms of green oxide, and is incapable of forming peculiar compounds. [Phil. Trans. 1827.] This view is, in the main, confirmed by the experiments of Maus. Ann. de Chim. tt dc Phys. xxxv. 216. See also Bcrzelius, ii. 456. C/iromic Acid. Atom. Num. 52Symb. 3O-f-Cr. PROPERTIES. Chromic acid has a dark ruby-red colour, and forms irregular crystals when its solution is concentrated ; it is very soluble in water, has a sour taste, and possesses all the properties of an acid ; is converted into the green oxide, with evolution of oxygen, by expo- sure to a strong heat ; it yields a muriate of the protoxide, when boil- ed with muriatic acid and alcohol, and the direct solar rays have a similar effect when muriatic acid is present. With sulphurous acid, it forms a sulphate of the protoxide ; it is characterized by its colour, and by forming coloured salts with bases, the most important of which is chromate of lead. PREPARATION. This acid may be prepared by digesting chromate of baryta in a quantity of dilute sulphuric acid exactly sufficient for com- bining with the baryta. The sulphate of baryta subsides, and a solu- tion of chromic acid is obtained. Dr. Thomson proposes another me- thod of preparing this acid by acting on the green oxide with nitric acid ; and Maus obtains it by decomposing a hot and concentrated so- lution of bichromate of potassa with fluosilisic acid ; filtering the li- quid and evaporating to dryness in a platinum capsule. The acid thus dried is then dissolved in the smallest possible quantity of water, to exclude a portion of fluosilicate of potassa, which has passed the filter, and the fluid decanted ; for in this state of concentration, chromic acid cannot be filtered, as it attacks paper and is converted into oxide of chromium. Erandes Jour. N. S. iii. 488. CHROMIUM. 307 CHROMIUM AND CHLORINE. Chloro chromic Jlcid Gas, or Chloride of Chromium. Discovered by M. Unverdorben, in 1825. PROPERTIES. A red coloured gas, which may be collected in glass vessels over mercury ; it is instantly decomposed by water, and yields a solution of muriatic and chromic acids ; it may be regarded either as a compound of muriatic and chromic acids, or of chlorine and chromium. This compound is formed by the action of fuming sulphuric acid on a mixture of chromate of lead and chloride of sodium. Edin. Jour, of Science, iv. 129. Dr. Thomson has also described a red coloured liquid under the name of Chloro chromic Acid, which he obtained by the action of con- centrated sulphuric acid on the mixture of dry bichromate of potassa and sea-salt. He supposes it to consist of one atom of chromic acid and one of chlorine, but there are still some doubts with regard to its composition. Thomson, in Phil. Trans, for 1827, and itiorg. Chem. CHROMIUM AND FLUORINE. Fluochrotnic Acid Gas, or Fluoride oj Chromium. PROPERTIES. A gaseous snbstance, acting rapidly upon glass with the deposition of chromic acid, and the formation of fluosilisic acid gas ; it is absorbed by water, and the solution is found to contain a mixture of hydrolluoric and chromic acids ; it is decomposed by the watery vapour of the atmosphere, so that when mixed with air, red fumes appear, owing to the separation of minute crystals of chromic acid. This gas was first obtained by M. Unverdorben, by distilling a mix ture of rtuor spar and chromate of lead with fuming or even common sulphuric acid, in a leaden retort. It may be collected and kept for a short time in glass vessels coated with resin. Berzelius. Sulphuret of Chromium. A dark gray compound, without the me- tallic lustre ; formed by passing the vapour of sulphuret of carbon over the oxide of chromium heated to redness in a porcelain tube. Berzelius, ii. 463. Phosphuret of Chromium. A grayish mass, obtained by subjecting phosphate of chromium to heat in a forge. Berzelius, ii. 465. CHROMIC ACID AND SALIFIABLE BASES. The compounds termed Chromates, are mostly of a red or yellow colour, and on being boiled in muriatic acid mixed with alcohol, the chromic acid is at first set free and is then decomposed, a green muri- ate of the oxide of chromium being generated. 308 CHROMIUM. Chromate of Potassa. ^tom. Num. 99-15 Symb. (30+Cr.)+(0+Po.) PROPERTIES. An anhydrous salt, having a cool bitter, and disa- greeable taste ; it forms crystals, the primary shape of which is a right rhombic prism, [Ann. of Phil. xxii. 120,] and is of an intense lemon yellow colour, with a slight shade of orange ; is soluble to a great extent in boiling water, and in twice its weight of the liquid at 60 F. ; is insoluble in alcohol ; has an alkaline reaction, from which it has been incorrectly supposed to be a sub-salt ; its solution in wa- ter decomposes most of the metallic salts, furnishing some valuable pigments. PREPARATION. This salt, from which all the compounds of chro- mium are directly or indirectly prepared, is made by heating to redness the native oxide of chromium and iron, commonly called Chromate of Iron, with an equal weight of nitrate of potassa, when chromic acid is generated, and unites with the alkali of the nitre. After digesting the ignited mass in water until the chroraate is dissolved, the solution is neutralized by nitric acid, and concentrated by evaporation, in order that the nitrate of potassa should crystallize. The residual liquid is then set aside to evaporate spontaneously, and the chroniate is gradu- ally deposited in small prismatic crystals. Bichromate of Potassa. Atom. Num. 151*15 Symb. 2 (30+Cr.)+(0+Po.) This salt occurs in four-sided tabular crystals, the primary form of which is an oblique rhombic prism ; it is of an exceedingly rich red colour, is insoluble in about ten times its weight of water at 60 F. and the solution reddens litmus paper. Bichromate of f>otassa is made by acidulating the chromate with sulphuric acid, and allowing the solution to crystallize by spontaneous evaporation. It is used in dying. Chromate of Iron is found native in Siberia, France and the United States, in small crystalline grains, of an octahedral form ; but it more commonly occurs massive, of a black colour, with a slight metallic lustre, and hard enough to scratch glass. Chromate of Lead Atom. Num. 163-5 Symb. (3O-f Cr.) +(0+Pb.) This is a very rare mineral found only in Siberia. It is prepared artificially by adding chromate of potassa to a soluble salt of lead. It is of a fine yellow, and is known in commerce by the name of Chrome Yellow. Dichromate of Lead. Atom. Num. 275. Symb. (30+Cr.) + (20+Pb.) A salt, called also the Subchromate of Lead, of a beautiful red co- lour, formed by boiling carbonate of lead with excess of chromate of VANADIUM. 309 potassa. It is recommended by Mr. Badams as a pigment. Ann. of Phil. xxv. 303. Besides the above there are chromates of ammonia, soda, lime and magnesia, which are soluble and crystallizable ; chromates of baryta and strontia, which are difficultly soluble ; and those of silver, mer- cury, copper and uranium, the colours of which are crimson, red, apple-green and yellow. The insoluble chromates are formed by mixing soluble salts of those bases, with chromate of potassa or soda. REFERENCES. For further details concerning the corn-pounds of Chromic Acid with bases, see Vauquelin t Ann. de Cldm. Ixx. Dr. Jo/in, on some unkninvn combinations of Chromic Acid, Ann. of Phil. iv. 424 ; Dr. Thorn, son, in the same work, xvi. 321 ; Grouvelle, Ann. de Clrim. et de. Phys. xvii.S and Stokes, on some new double Chromates, hil. Mag. and Ann. ii. 427. On the Poisonous properties of the Chromates, see Christisoif.cn Poisons* 37'2', and Dr. Duncan, in the Edin. Med. and tiurg. Jour. xxvi. 133. SECTION XXIV. VANADIUM Atom. Num. 68-5. Symb. V. Vanadium, so called from Vtinadis, the name of a Scandanavian di- vinity, was discovered by Sefstrom in 1830, in the iron from the forges of Eckersholm in Sweden ; and in 1831 it was found in an ore of lead from Wanlock Head, by Mr. Jo.hnston of Edinburgh.* It has been obtained by heating vanadic acid in contact with potassium and by the decomposition of the chloride of vanadium. PROPERTIES. This metal as obtained by means of potassium, is a heavy black powder, with very little lustre. But when prepared by the decomposition of the chloride, it has a white colour resembling sil- ver, a strong metallic lustre, but it is extremely brittle. It is not oxid- ized by either air or water, is not acted on by boiling sulphuric, muriat- ic, or hydrofluoric acid, but is attacked by the nitric and nitro-muriat- ic acids, and the solution has a fine dark blue colour. * According to Hurnboldt it appears that this metal had been discovered in Mexico, by M. del Rio, in a brown lead ore, found in the district of Zimam- pa?. M. del Rio gave it the name of Erythronium, but was afterwards in- duced to suppose it merely an impure chrome. Since the discovery of Sefs- trom, however, the brown lead ore of Ziinampas has again been analyzed? and a simple substance, precisely similar to that found in the iron by Sefstrom' obtained from ii.-~Jour. of Royal Institution, ii. 562. VANADIUM. VANADIUM AND OXYGEN. Vanadium combines with oxygen in three proportions. Protoxide of Vanadium. A torn. Num. 76*5 Symb. O+V. A dark brown or black compound, soluble in nitric acid and in aqua regia, but does not form salts. It is obtained by reducing vanadic acid by hydrogen gas. Deut- or Binoxide of Vanadium. Atom. Num. 84'5 Symb. 20+V. A black and pulverulent substance, very infusible and insoluble in water ; heated in the air it attracts oxygen and is converted into vana- dic acid ; forms salts with the acids, which when anhydrous are dark- brown, and when they contain water, of a deep blue like the salts of copper ; it also combines with alkalies, forming brown soluble com- pounds. Vanadic Acid. Atom. Num. 92-5 Symb. 3O+V. PROPERTIES. This compound is a yellow powder, tasteless, sparing ly soluble in alcohol and water, to which liquid it imparts a yellow co- lour ; fuses at a red heat and on cooling crystallizes in beautiful pris- matic crystals, transparent at the edges, of a reddish brown colour and a high degree of lustre ; it forms with bases neutral salts which in general are colourless, and acid salts of a bright orange colour ; gives also saline combinations with the acids ; may be distinguished from all other acids except the chromic by its colour and from this by the ac- tion of deoxidizing substances, which give a blue solution with the for- mer and a green with the latter. Vanadic Add forms colourless as well as coloured Salts. One of the most singular facts with regard to this acid is that its neutral salts are yellow at one time and colourless at another without suffering any ap- preciable change in composition. Thus on neutralizing vanadic acid with ammonia a yellow salt is obtained, the solution of which gradual- ly becomes colourless if kept for some hours, and suffers the same change rapidly when heated. The solution, as it is coloured or colour- less, gives a white residue by evaporation, and a yellow or white pre- cipitate with a salt of lead or baryta.* PREPARATION. By heating the vanadiate of ammonia in an open vessel and well stirred, the whole mass acquires a dark red colour, and * A ne\v and almost indelible ink, is prepared by ISerzelius from vanadium. It is formed by mixing the vanadiate of ammonia with mfu-ion of galls ; a black liquid is produced which is the best writing ink that can be formed. Acids render it blue but do not obliterate it; the alkalies when sufficiently diluted not to act upon the paper do not dissolve it, arid chlorine which destroys the black colour does not, however, efface the writing even when water is after- wards suffered to run over it. Phil. Mag. and Ann. N. S. xi. 16. VANADIUM. 311 pure vanadic acid is obtained ; but a red heat should be avoided, since fusion would thereby be occasioned, and free exposure of every part to the atmosphere prevented. VANADIUM AND CHLORINE. Bichloride of Vanadium is prepared by digesting a mixture of the vanadic and muriatic acids, deoxidizing any undecomposed vanadic acid by sulphuretted hydrogen and evaporating the solution to dryness. A brown residue is obtained, which yields a blue solution with water, part being left as an insoluble sub-salt. It may also be generated by acting directly on the ignited deutoxide with strong muriatic acid. As thus obtained its solution is brown instead of blue, though in composi- tion it seems identical with the preceding. Turner. The ter-C/doride may be formed by transmitting a current of dry chlorine gas over a mixture of protoxide of vanadium and charcoal heated to low redness, when the terchloride passes over in vapour, and condenses in the form of a yellow liquid, from which free chlorine may be removed by a current of dry air. It is converted by water into mu- riatic and vanadic acid, and atmospheric moisture produces the same change indicated by the escape of red fumes. Turner. Compounds of vanadium and bromine, iodine, fluorine and cyanogen, may be formed by dissolving deutoxide of vanadium in hydrobromic, hydriodic, hydrofluoric and prussic acids. VANADIUM AND SULPHUR. Bisulphuret of Vanadium is a compound of a brown colour which becomes black when it is dried and which takes fire when heated. It is obtained by heating the deutoxide of vanadium to redness in a current of sulphuretted hydrogen, or, by mixing with a salt of the deu- toxide of vanadium a hydrosulphuretted alkali until the precipitate at first formed is re-dissolved, and then decomposing the deep purple-col- oured solution by sulphuric or muriatic acid. Ter-sulphuret of Vanadium is formed by acidulating a solution of vanadic acid in a hydrosulphuretted alkali by muriatic or sulphuric acid. It has a much lighter brown colour than the bisulphuret, becomes almost black in drying, and is resolved by a red heat in close vessels into the bisulphuret with loss of water and sulphur. It is soluble in alkalies and alkaline hydrosulphates, and is oxidized by nitric acid. VANADIUM AND PHOSPHORUS. Phosphuret of Vanadium, is of a leaden-gray colour, and may be formed by exposing to a white heat phosphate of deutoxide of vanadi- um mixed with a small quantity of sugar. REFERENCES. Berzelms on Vanadium, Phil. Mag. and Ann. x. 321. xi. 7. Johnston in Brewster's Jour. N. S. v. 318. Reports of the British Asso- ciation for 1832. Turner's Chemistry, 4th ed. 312 TUIN 7 GSTEN. SECTION XXV. TUNGSTEN. Atom. Num. 99'7. Syrnb. Tu. Sp. gr. l?-4. PROPERTIES.' Colour grayish white, like that of iron, with consid- erable lustre ; it is brittle, nearly as hard as steel, and less fusible than manganese ; it is surpassed in density only by gold and platinum ; it is oxidized by the action of heat and air. This metal is obtained by exposing tungstic acid to the action of charcoal, or dry hydrogen gas, at a red heat. TUNGSTEN AND OXYGEX. Chemists are acquainted with two compounds of this metal and oxy- gen, viz : an oxide and an acid. Oxide of Tungsten. Atom. Num. 11 5? Symb. 2O+Tu. PROPERTIES. A compound of a brown or nearly black colour, depend ing upon the mode of its preparation, which does not so far as is known, unite with acids, and which, when -heated to near redness, takes fire and yields tungstic acid ; it combines, according to Wbhler, with soda. Berzelius, ii. 486. PREPARATION. This oxide may be formed by the action of hydro- gen gas on tungstic acid, at a low red heat. But the most convenient process is that described by Wb'hler. A mixture of powdered wol- fram and carbonate of potassa is fused ; the resulting tungstate of potassa is dissolved in water, arid a sufficient quantity of muriate of ammonia then added. The liquor is evaporated to dryness, and the mass is fused in a Hessian crucible, till the muriate of ammonia is en- tirely decomposed and evaporated. By dissolving the fluid mass in water, a black powder separates, which is oxide of tungsten. This is boiled with a weak solution of potassa, to remove a small quantity of acid and difficultly soluble tungstate of potassa, and then washed with abundance of distilled water. Ann. de (.him. ttdcPhys. xxix. Brundu s Jour. xx. ]77. Tungstic Add. Atom. Num. 123 7 Symb. 3O+Tu. PROPERTIES. Tungstic acid is of a yellow colour, is insoluble in water, and has no action on litmus paper ; it forms salts with alka- line bases, called Tungstates, which are decomposed by the stronger acids, the tungstic acid in general falling, combined with the acid by which it is precipitated ; it has a specific gravity of 6' 12 ; is difficult- ly iusible ; calcined in contact with air, its yellow colour becomes deeper and passes to a green, and after some hours to a gray. NATIVE STATE AND PREPARATION. This acid has only been found in nature, combined with bases, in two rare minerals, the tungstate of lime, and the tungstate of iron and manganese, or Wolfram. It is ar- ANTIMONY. 313 OV mine acici ; oy wmcn means me laitiatc ui uiuo is luiiueu, aim me tungstic acid separates in the form of a yellow powder. This is freed from impurities by washing it alternately with ammonia and nitric acid. See Berzelius, ii. 487. TUNGSTEN AND CHLORINE. According to Wohler, these substances combine in three proper* tions. Deuto chloride of Tungsten. A compound, of a deep red colour, which sublimes in delicate needles. It is very fusible, enters into ebu- lition at a slightly elevated temperature, and is converted into a red gas, of a more intense colour than nitrous acid gas. It is obtained by heating metallic tungsten in a current of chlorine gas. Percfdoride of Tungsten. This chloride is generated by heating the oxide of tungsten in chlorine gas. The action is attended with the appearance of combustion, dense fumes arise, and a thick sublimate is obtained in the form of white scales, like native boracic acid. It is volatile at a low temperature without previous fusion. It is con- verted by the action of water into tungstic and muriatic acids, and must, therefore, in composition, be proportional to tungstic acid. Wohler has described another chloride which is formed at the same time as the last ; and though it is converted into muriatic and tungstic acids by the action of water, and would thus seem identical with the perchloride in the proportion of its elements, its other properties are nevertheless different. It is the most beautiful of all these compounds, existing in long transparent crystals, of a fine red colour. It is very fusible and volatile, and its vapour is red, like that of nitrous acid. The difference between this compound and the chloride fir^t described, has not yet been discovered. In addition to the above compounds, Berzelius describes a Fluoride of Tungsten, or Fluo-tungstic acid, and two Sulphurets of Tungsten. Traite de Chim. ii. 489, 492. REFERENCES. Herzelius on Tungsten and some of its compounds, Ann of Phil. iii. 244. Bucholz's experiments on Tungsten and its combinations with Oxygen, Ammonia and other substances, Ann. of P /til. vi. 198. Thomson's First Prin. ii. 6*2. : >v SECTION XXVI. ANTIMONY. Atom. JVi0i. 64-6. %i6. Sb* Sp. gr. 6*7. The date of the discovery of this metal is unknown ; but the man- ner of obtaining it was first described by Basil Valentine, in the fif- teenth century, in a work entitled Currus Triumphal Antimonii. It was called Regulus of Antimony. * From the latin word Stibium. 314 ANTIMONY. PROPERTIES. A brittle metal, of a silvery white colour, scaly tex- ture, and possessing considerable lustre ; it fuses at 810 F. and when slowly cooled, sometimes crystallizes in octahedral or dodecahedral crystals ; in close vessels it may be volatilized and collected unchang- ed, but not, Thenard asserts, if atmospheric air be carefully excluded, and no gaseous matter be generated during the process ; it tarnishes by exposure to the atmosphere, and when placed on ignited charcoal, un- der a current of oxygen gas, it burns with great brilliancy, giving off an oxide in the form of a dense yellow smoke. PREPARATION. Antimony sometimes occurs native ; but its only ore which is abundant, and from which the antimony of commerce is derived, is the sulphuret. This sulphuret was long regarded as the metal itself, and was called Antimony, or Crude Antimony. Metallic antimony may be obtained either by heating the native sulphuret in a covered crucible with half its weight of iron filings ; or by mixing it with two-thirds of its weight of cream of tartar and one- third of nitre, and throwing the mixture, in small successive portions, into a red hot crucible. By the first process, the sulphur unites with iron, and in the second it is expelled in the form of sulphurous acid ; while the fused antimony, which in both cases collects at the bottom of the crucible, may be drawn off and received in moulds. The anti- mony thus obtained is not absolutely pure ; and therefore, for chemic- al purposes, should be procured by heating the oxide with an equal weight of cream of tartar. ANTIMONY AND OXYGEN. The existence of three compounds of antimony and oxygen is now generally admitted ; one of these is a salifiable basis, the other two are acids. Protoxide of Antimony. Atom. Num. 76-6 Symb. } O+Sb. PROPERTIES. A powder of a dirty white colour, which fuses at a red heat and forms on cooling an opaque crystalline mass ; it is very vola- tile, and may be sublimed in close vessels by a strong heat ; when heated in open vessels it absorbs oxygen and is converted into the deutoxide ; it is the basis of all the salts of antimony, and forms the Tartar Emetic when boiled with tartrate of potassa. PREPARATION. Oxide of antimony may be obtained by pouring mu- riate of antimony into water, washing the precipitate (formerly called Poicder of Mgarotk) first with a weak solution of potassa, and after- wards with water, and then drying it ; or by adding to a solution of Tartar Emetic a solution of ammonia, and washing the precipitate with plenty of hot water. It is also formed during the combustion of metallic antimony, though not perhaps perfectly pure. ANTIMONY. 315 Antimonious Acid, or Deutoxide of Antimony. Atom. Num. SO'6Symb. 2O+Sb. PROPERTIES. White ; infusible ; fixed in the fire ; insoluble in wa- ter, arid likewise in acids, after being heated to redness ; combines with bases and forms salts called rfntimonites. This compound is prepared by dissolving metallic antimony in nitric acid and evaporating and igniting the product ; or by dissolving the metal in nitro-inuriatic acid, decomposing by water, washing the pre- cipitate and calcining it in a platinum crucible. Antimonic Add, or Peroxide of Antimony. Atom. Num.81'6 Symb. 2O+Sb. This compound may be obtained by dissolving the metal in nitro- muriatic acid, from which it may be precipitated by throwing the solu- tion into water, as it is insoluble in that fluid. When recently pre- pared it reddens litmus paper, and may be dissolved in water by means of muriatic or tartaric acid. As thus obtained it is a Hydrate, but if exposed to the temperature of 600 F., the water is driven off and the pure peroxide remains. PROPERTIES. This compound, when pure, is of a lemon yellow colour ; is decomposed by exposure to a red heat ; is not soluble in acids, but combines with bases, and forms salts, termed Antimoni- ates. REFERENCES. Ori the compounds of Antimony and Oxygen, see Berzeli- ws, ii. 496, and Thenard, ii. 368, both of whom noiv recognize only three; Prout) in Aim. Jour, de Phys. iv. who reduces them to two. ANTIMONY AND CHLORINE. Two distinct compounds of these bodies are now recognized. Sesquichloride of Antimony. Atom. Num. 117-7 Symb. 1 J Cl+Sb. PROPERTIES. At common temperatures this compound is a soft solid, and hence called Butter of Antimony ; it is liquified by a gentle heat, and crystallizes on cooling ; it deliquesces on exposure to the air, and when mixed with water is converted into muriatic acid, and protoxide of antimony or Muriate of Antimony It may be obtained by throwing powdered antimony into chlorine, or by distilling a mixture of antimony with twice and a half its weight of corrosive sublimate. 316 ANTIMONY. Per chloride of Antimony. Atom. JYitm. 153-22 Symb. 2J Cl+Sb. A transparent volatile liquid, which emits fumes on exposure to the air and when mixed with water is converted into muriatic acid and hy- drated peroxide of antimony. It is obtained by passing dry chlorine gas over heated metallic antimony. Rose, in Jinn, of P /til. xxvi. 416. ANTIMONY AND SULPHUR. The compounds of antimony and sulphur have been examined by M. H. Rose ; according to whom there are three. Jinn, of P hit. xxvi. 419. BesquisiJjjJiurct of Antimony. Atom. Num. 8S-6 Symb. 1J S+Sb. This sulphuret, known by the name of Grade Antimony, is found na- tive of a lead gray colour, and which, though generally compact, sometimes occurs in acicular crystals or in rhombic prisms ; it may be melted in close vessels without undergoing any change, hut when slow- ly roasted in a shallow vessel, it gradually loses sulphur and attracts oxygen, and may then be melted into a glassy substance, transparent at the edges, and called Glass of Antimony. This sulphuret may be formed artificially by fusing together antimo- ny and sulphur, or by transmitting a current of sulphuretted hydrogen gas through a solution of tartar emetic washing and drying the pre- cipitate. This precipitate, according to Gay Lussac and Dr. Turner, in a hydrated sesquisulphuret of antimony. When sulphuret of antimony is boiled in a solution of potassa, a li- quid is obtained, from which, as it cools, an orange-coloured matter, called Kermes Mineral, is deposited ; and on subsequently neutralizing the cold solution with an acid, an additional quantity of a similar sub- stance, the Golden Sulphuret of the Pharmacopeia, subsides. Accord- ing to Berzelius and Rose, kermes is a hydrated sesquisulphuret, differ- ing from the native sulphuret solely in being combined with water. Gay Lussac, however, maintains that it contains both oxide and sul- phurei of antimony. tfnn. de C/dm. ct de Phys. xlii. 88, or Phil. Mag. and Ann. vii. 386. Berzclins, Traite dc Chim. Bisulpkuret of Antimony. Atom. Num. 9G-6 SywJo. 2 S+Sb. This compound is formed, according to Rose, by transmitting sul- phuretted hydrogen gas through a solution of the deutoxide of anti- mony in dilute muriatic acid. ANTIMONY. 317 Per sulphuret of Antimony. Atom. Num. 104 '6 Symb. 2J S+Sb. This compound is formed by the action of sulphuretted hydrogen on a solution of the peroxide, and is identical with the golden sul- phuret prepared by boiling sulphuret of antimony and sulphur, in so- lution of potassa. M. Rose has likewise demonstrated, that the Red Antimony of min- eralogists, is a compound of one proportion of the protoxide, combin- ed with two proportions of the sequisulphuret of antimony. The pharmaceutic preparations known by the terms of Glass, Liver, and Crocus of antimony, are of a similar nature, though less definite in composition, owing to the mode by which they are prepared. They are made by roasting the native sulphuret, so as to form sulphurous acid and oxide of antimony, and then vitrifying the oxide together with the undecomposed ore, by means of a strong heat. The product will of course differ according as more or less of the sulphuret escapes ox- idation during the process. Turner. ANTIMONY AND THE METALS. Antimony may be made to combine with nearly all the metals. The most important of these alloys, is that which it forms with lead, called Type Metal. The composition of this alloy varies ; the smallest types, Mr. Dalton finds, are cast from an alloy composed of nearly one atom of antimony to one of lead ; middle sized types of a compound of one atom of antimony and two of lead ; and the largest size of one atom of antimony and three of lead. New System. Antimony may also be alloyed with tin, but if its proportion in the alloy exceeds one-fourth, the tin loses its ductility. The alloy of one part of antimony and two parts of iron deserves notice, for the singular property which it possesses of giving fire when acted on by the file, T/ienard, i. 644. The alloy of antimony and gold is remarkable in being brittle when it contains only a minute proportion of antimony. According to Hatchett. gold loses its ductility by combination with l-1920ths of its weight of antimony. SALTS OF ANTIMONY. Antimony is soluble in most of the acids. When heated with Sul- phuric Acid, the acid is decomposed ; sulphurous acid is disengaged, and the antimony being converted into protoxide, a subsulphate is the product. Nitric Acid dissolves this metal with great vehemence ; but the most convenient solvent is the nitre-muriatic acid, which acts upon the metal both in a separate state, and as it exists in the black sulphuret. Muriatic Acid acts on the latter compoun^ and evolves sulphuretted hydrogen gas in abundance, and of great purity ; and muriate of ammonia is also lormed, and remains in solution along with the muriate of antimony. Berztlius, Ann. de Chim. el de Phys. xviL Henry, ii. 85. Phosphate of Antimony has not been examined. The medicinal preparation called James' Powder, was found by Dr. Pearson to con- sist of 57 oxide of antimony, and 43 phosphate of lime , and it has u 318 URANIUM. been imitated in the Pulvis Antimonialis of the London Pharmacopeia, which is formed by calcining the native sulphuret with hartshorn shavings. The preparation appears to be uncertain and often even almost inert, and to vary as to the state of oxidation in the antimony, containing sometimes a large proportion of the peroxide. REFERENCES. Pearson, in Phil. Trans. 171)1. R. Phillips, in Ann. of Phil. xx. 266, xxii. 187. Webster's Brande. Tartarized Antimony, or Emetic Tartar, is a triple salt of protoxide of antimony, potassa and tartaric acid, which will be noticed under the head of the Tartrates. The rfniimonites and Antimoniates, are, in general, soluble in water, and easily decomposable by sulphuric, nitric and muriatic acids. Those of potassa, soda and ammonia, are obtained directly ; all the others by double decomposition. Most of these compounds, when heated strongly in a platinum crucible, burn with evolution of light and heat ; this is especially the case with the antimonite and antinio- niate of copper and of cobalt. Berzelius attributes this singular phe- nomenon to the more intimate union of the molecules of these com- pounds ; for he observes, that, after the calcination, the antimonites and antimoniates are with difficulty acted on, even by the strongest acids. Gay Lussac, however, dissents from this opinion. REFERENCES. Thenard, Traite de Cliim. iii. 459. Berzelins, in Ann. de Chim. Ixxxvi. 225. Gay Lussac, Ann de Chim. et de Phys. i. 44, and, same work, v. 158, 160. And for further details concerning the properties of these saline compounds, see Beizelins, in Ann. de Chim. et de Phys. xvii. 1G. SECTION XXVII. URANIUM. Atom. Num. 2i7Symb. U. Discovered by Klaproth, in 1789, in a mineral of Saxony, called from its black colour, Pitchblende, which consists of protoxide of ura- nium and oxide of iron. It is a rare metal, and still imperfectly known. PROPERTIES. This metal, as prepared by Arfwedson, by conduct- ing hydrogen gas over protoxide of uranium, heated in a glass tube, is crystalline, of a metallic lustre and reddish-brown colour ; it is not changed by exposure to the air at common temperatures, but when heated in open vessels absorbs oxygen, and is re-converted into the protoxide. PREPARATION. Metallic uranium may be obtained from the pitch- blende by the following process : reduce it to powder and expose it to heat in a muffle ; then digest in dilute nitro muriatic acid, and precip- itate by excess of ammonia, to retain oxide of copper ; collect and wash the precipitate and dry it at a heat approaching redness. REFERENCES. For the details of this process, see Arficedson's paper on Uranium, in Ann. of Phil, xxiii. 253. For the process of Dr. Thomson, see his First Prin. ii. 2. On Uranium and its compounds, see also the Memoir of Bucholz, in Gehlen's Jour, or Repert. of Arts, 2d ser. viii. 294. URANIUM. 319 URANIUM AND OYYGEN. Chemists are acquainted with two compounds of uranium and oxy- gen, the Protoxide and the Peroxide. Protoxide of Uranium. Jltom. Num. 225 Symb. G-fU. PROPERTIES. A compound of a dark green colour, which is exceed- ingly infusible, and bears any temperature hitherto tried, without change ; it unites with acids, forming salts of a green colour ; by the action of nitric acid it is converted into a solution, which is the nitrate of the protoxide. This oxide is obtained by decomposing the nitrate of the peroxide by heat. It is employed in the arts for giving a black colour to porce- lain. Peroxide of Uranium. Atom. Num. 229 Symb. ] O+U. PROPERTIES. This oxide is of a yellow or orange colour, and per- forms, as was first noticed by Arfwedson, the double function of acid and base ; it is precipitated from acids as a yellow hydrate by pure alkalies, fixed or volatile, but retains a portion of these bases in com- bination ; it is thrown down as a carbonate by the carbonate of soda or ammonia, and is re-dissolved by an excess of the precipitant, a cir- cumstance which affords an easy method of separating uranium from iron. It is employed in the arts for giving an orange colour to porce- lain. URANIUM AND SULPHUR. Sulphur d of Uranium, may be formed according to Rose by trans- mitting the vapour of bisulphuret of carbon over protoxide of uranium strongly heated in a tube of porcelain. It is of a dark gray, or nearly black colour, is converted into protoxide of uranium when heated in the open air, and is readily dissolved by nitric acid. SALTS OF URANIUM. It is difficult to obtain the protosalts of this metal pure, in conse- quence of the tendency of the protoxide to pass to the state of perox- ide. The green solutions of the former, by the action of sulphuric and muriatic acids, become speedily yellowish, green and yellow, in consequence of the formation of peroxide, arid the change is accele- rated by adding a little nitric acid. The Pernitrate of Uranium, is formed by dissolving the protoxide in nitric acid, and from this solution the Percarbonate is thrown down by carbonate of ammonia. The pernitrate crystallizes easily, in large flat four-sided rectangular prisms, of a lemon yellow colour. The Persulphate appears to have a similar constitution to the above ; both consisting of 1 1-2 proportion of acid, and 1 proportion of base. They are, therefore, sesqui-salts. Indeed, as Dr. Thomson remarks the tendency which peroxide of uranium has to form sesqui-salts is very remarkable, First Prin. ii. 40. 320 COLUMBIUM. Among the native compounds of uranium,, may be mentioned the Green arid the Yelloio Uran-mica ; and the Protosulphate and Sub-per- sulphate, discovered by Dr. John. SECTION XXVIII. COLUMBIUM. Atom. Num. 185? Symb. Cb. This metal was discovered in 1801, by Mr. Hatchett, who detected it in a black mineral, supposed to have come from the United States, and, from this circumstance, applied to it the name of Colunibium. About two years after, M. Ekeberg, a Swedish chemist, extracted the same substance from Tantalite and Yttro-tantalite ; and, on the suppo- sition of its being different from columbium, described it under the name of Tantalum. The identity of these metals, however, was es- tablished in the year 1809, by Dr. Wollaston. Phil. Trans. PROPERTIES. This metal, as prepared by Berzelius by heating po- tassium with the double fluoride of potassium and columbium, is a black powder, which does not conduct electricity, but in a denser state is a perfect conductor ; it does not melt at the temperature at which glass is fused ; by pressure it acquires a metallic lustre, and has an iron-gray colour ; it is scarcely acted on by the sulphuric, muriatic or nitro-muriatic acid, but is dissolved with heat and disengagement of hydrogen gas by hydrofluoric acid, and still more easily by a mixture of nitric and hydrofluoric acids ; when heated in open air, it takes fire, and is converted into columbic acid. Berzelius, ii. 515, under the name, of Tantalum. COLUMBIUM AND OXYGEN. These bodies combine in two proportions, forming an oxide and an acid. Oxide of Columbium. Atom. Num. 201 ?Symb. 2O+Cb. This oxide is generated by placing columbic acid in a crucible lined with charcoal, luting carefully to exclude atmospheric air, and expos- ing it for an hour and a half to intense heat. The acid, where in di- rect contact with charcoal, is entirely reduced ; but the film of metal is very thin. The interior portions are pure oxide, of a dark gray colour, very hard and coherent. When reduced to powder its colour is dark-brown. It is not attacked by any acid, even by nitro-hydro- fluoric acid ; but it is converted into columbic acid, either by fusion with hydrate of potassa, or deflagration with nitre. According to Ber- zellus this oxide occurs in combination with protoxide of iron and a little protoxide of manganese, at Kimito, in Finland, Traite de Chim. ii. 527. Columbic Add Atom. Num. 209 ?Symb. 3O+Cb. PROPERTIES. This acid, as obtained in the form of hydrate by fus ing yttro-tantalite with three or four times its weight of carbonate of CERIUM. 321 potassa, and precipitating by acids, is tasteless and insoluble in water, but when placed on litmus paper communicates a red tinge ; it is so- luble in many of the acids, but does not diminish their acidity ; it unites readily with alkalies ; and though it does not neutralize their proper- ties completely, crystallized salts may be obtained by evaporation, call- ed Columbates; on applying heat to the hydrated acid, water is expell- ed, and the anhydrous cQlumbic acid remains., REFERENCES. Thomson's First Prin. ii. 74. JBerzelius, as above. The former chemist adopts a different view of the atomic constitution of these com- pounds from that entertained by the latter. Chloride of Columbium., Columbium burns vividly in chlorine gas, and yields a yellow vapour, which -condenses into a yellowish-white powder. This, by contact with water, is converted with a hissing noise, into columbic and muriatic acids. Fluocolumbic Acid, is prepared by pouring hydrofluoric acid upon the columbic. It forms with bases, salts called Flnocolumbates. Sulphuret of Columbium. Rose first prepared this substance by Seating columbium, at a low redness, in the vapour of sulphur, or by transmitting the vapour of bisulphuret of carbon over columbic acid, in a porcelain tube heated to whiteness. SECTION XXIX. CERIUM. Atom. Nam. 46. Symb. Ce. This metal was discovered in 1803, by Berzelius and Hisinger, in a i-are Swedish mineral, called Cerite. It has since been found, by Dr. Thomson, in a mineral from Greenland, called Allanile. It is but lit- tle known. PROPERTIES. A solid, very brittle metal, of a whitish colour, and almost infusible ; when heated to redness in the open air it is convert- ed into a white oxide, and when heated intensely it is volatile ; it is acted upon by nitro-muriatic acid. Cerium may be obtained by subjecting its oxide to a high heat in combination with charcoaL CERIUM AND OXYGEN. There are two oxides of cerium, which have been studied by Hisin- ger, Vauquelin and Thomson. Protoxide of Cerium. Atom. Num. 54 Symb. O-j-Ce. PROPERTIES. A white powder, which is insoluble in water, and forms salts with acids ; it undergoes no change by exposure to air at common temperatures, but when heated in open vessels it absorbs oxy- gen, and is converted into the peroxide. TITANIUM. PREPARATION. This oxide is obtained by 3 der, and dissolving it in nitro-muriatic acid. The solution is filtered, neutralized with pure potassa, and then precipitated by tartrate of potassa ; or, as Langier recommends, by oxalic acid. This precipitate, well washed and afterwards calcined, is the protoxide of cerium. Peroxide of Cerium. Atom. Num. 58 Symb. IJO+Ce. This oxide is of a fawn-red colour ; it is dissolved by several of the acids, but is a weaker base than the protoxide. It is obtained by de- composing the nitrate of the protoxide, or by heating the carbonate to redness in the open air. REFERENCES. Hisingeron the Oxides of Cerium^ Ann. of Phil. iv. 355. Thomson's First Priu. i. 37S>. CERIUM AND SULPHUR. Cerium may be combined with sulphur in two different ways. 1. By passing the vapour of carburet of sulphur over carburet of cerium, a light porous compound is obtained, of the colour of minium, which is not altered either by air or water. 2. By fusing oxide of cerium with a great excess of sulphuret of potassium, (hepar sulphvris,) the latter of which is removed by washing. Mosander, in Phil. Mag. and Ann. i. 71. Berzelius describes compounds of phosphorus, carbon and selenium, with cerium. Traite de Chim. iii. 315. SALTS OF CERIUM. Permuriate of Cerium, crystallizes confusedly ; is deliquescent, so- luble in an equal weight of water, and in three or four parts of alco- hol. Nitric acid unites most easily with the white oxide. The solution is very sweet, and is not crystallizable. When decomposed by heat it leaves a brick-coloured oxide. Protosulphate of Cerium, occurs in white crystals, of a saccharine taste. It is formed by the action of sulphuric acid upon the white ox- ide. There is also a Persulphate. Carbonate of Cerium, is a white powder, which assumes on drying a silvery appearance. SECTION XXX. TITANIUM. Atom. Mm. 24-3 Symb. Ti.Sp. gr. 5 3. This was first recognized as a new metal by Mr. Gregor, of Corn- wall, in 1791, and its existence was afterwards established by Klap- roth. Its properties, however, were first satisfactorily ascertained by TITANIUM. 323 Dr. Wollaston, in 1822, who found the native metal in a crystalline form. PROPERTIES. Native titanium occurs in cubic crystals, whose colour and lustre are like burnished copper ; it is so hard as to scratch rock crystal ; is exceedingly infusible, but when exposed to the united ac- tion of heat and air, the surface becomes covered with a purple film, which is an oxide ; it is oxidized by being strongly heated with nitre. PREPARATION. Liebig obtains metallic titanium by putting frag- ments of recently made chloride of titanium and ammonia in a glass tube half an inch wide and two or three feet long, transmitting through it a current of perfectly dry ammonia, and when atmospheric air is en- tirely displaced, applying heat until the glass softens. Complete de- composition ensues, nitrogen gas is disengaged, muriate of ammonia sublimes, and metallic titanium is left in the state of a deep blue co- loured powder. If exposed to the air while warm, it is apt to take fire. REFERENCES. Klaproth'* Contribution, i. Wollaston, in Phil. Trans, for 1823. TITANIUM AND OXYGEN. Titanium most probably combines in two proportions with oxygen. Protoxide of Titanium is of a purple colour, and is supposed to exist pure in the mineral called Anatase; but its composition and chemic- al properties are unknown. Titanic Add. Atom. Num. 40-3 Symb. 2O+T1. PROPERTIES. When pure this substance is quite white ; it is ex- ceedingly infusible, and difficult of reduction ; possesses weak acid properties, and according to Rose does not act as a base ; after expo- sure to a red heat it is not attacked by any acid except the hydro- fluoric. NATIVE STATE AND PREPARATION. Titanic acid, or the peroxide of titanium, exists in nearly a pure state in the Titanite or Rutile. From this mineral titanic acid is prepared by fusion with carbonate of po- tassa, dissolving the mass in concentrated muriatic acid, throwing down the oxide by dilution with water, and boiling ; and finally, se- parating the impurities by digesting the precipitate while moist, with hydrosulphuret of ammonia. REFERENCES. Rose in Ann. de Chim. et de Phys. xxiii. For other pro- cesses, see Berzelius, ii. 538 ; and Rose's Manual of Analytical Chemistry. TITANIUM AND CHLORINE- Bichloride of Titanium, was formed by Mr. George by passing dry chlorine over the pulverized native metal. A fluid condensed in the cool part of the tube, which was transparent, colourless, emitted dense white fumes, arid boiled violently at a temperature little exceeding 212 J F. On adding a drop of water to a few drops of this liquid, an almost explosive disengagement of chlorine ensued ; and when the 324 TELLURIUM. water was not in excess, a solid salt was formed, the solution of which had all the properties of Muriate of Titanium. Rose prepared this com- pound by heating a mixture of the peroxide and charcoal in a tube, through which dry chlorine gas was passing: the resulting bichloride was purified from adhering to free chlorine by agitation either with mercury or potassium and repeated distillation. Ann. of Phil. xxv. 18. TITANIUM AND SULPHUR. Eisulphuret of Titanium, was formed by Rose, by passing sulphuret of carbon over titanic acid, strongly heated in a porcelain tube. It is of a deep green colour, and when rubbed with a hard substance, as- sumes a very strong metallic lustre like that of brass. It becomes very hot when nitric acid is poured upon it ; nitrous gas is disengaged and titanic acid is deposited in the state of a fine powder. SECTION XXXI. TELLURIUM. Atom. Num. 61 Symb. Te. Sp. gr. 6-245. Btrzelius. A very rare metal, hitherto found only in the gold mines of Tran- sylvania, and even there in very small quantity. Its existence was inferred by Muller, in 1782, and fully established by Klaproth, in 1798. PROPERTIES. Tellurium has a tin-white colour, running into lead* gray, a strong metallic lustre, and laminated texture ; it is very brit- tle ; when heated to full redness in a close vessel it volatilizes in the form of a yellow gas, which condenses again in drops, and on cooling crystallizes in regular forms ; is, fusible at a temperature below ignition; when heated before the blow-pipe it takes fire and burns rapidly, and is dissipated in gray coloured pungent inodorous fumes. TELLURIUM AND OXYGEN. Berzeliushas obtained two compounds of tellurium and oxygen, both of which possess acid properties. TeUurous Acid. Atom. Num. 80Symb. 2O+Te. When tellurium is exposed to the action of the blow-pipe upon char- coal, it takes fire, and burns with a lively blue flame, the edges of which are green ; and it is completely volatilized in the form of a white smoke. This smoke is the tellurous acid, which may also be obtained by dissolving the metal in nitro-muriatic acid, and diluting the solution with a great quantity of water. It is fusible at a strong heat, and vol- atile at a still higher temperature. It forms a class of salts called Td~ lurites; and can scarcely be made to act as a base. TELLURIUM. 325 Telluric Acid. Atom. Num. SSSymb. 3O-f-Te. This acid is obtained, according to Berzelius by submitting the tel- iurous acid in solution with excess of caustic alkali to a current of chlo- rine, till the precipitate which at first falls, is entirely redissolved. Chloride of barium is added to precipitate any sulphuric or selenic acid which may be present, after which the solution is saturated with ammonia, and the tellurate of barytes precipitated by chloride of ba- rium, collected and washed with cold water. This salt is decomposed by sulphuric acid, and the concentrated solution deposites the telluric acid in beautiful crystals. [For details concerning this and the pre- ceding acid, see a notice of the recent researches of Berzelius in Johns- ton's Report on Chemistry. ~\ TELLURIUM AND CHLORINE. Chlorides of Tellurium. These have been recently examined by Rose. When the metal is gently heated in chlorine gas, a white crys- talline compound is formed, consisting of two atoms chlorine-f- one atom tellurium. It has much resemblance to the solid chloride of se- lenium. When the metal is strongly heated in the same gas, violet va- pours are formed, which condense into a black deliquescent mass. When freed as much as possible from bichloride, this substance was found to consist of one atom chlorine-j-one atom tellurium. TELLURIUM AND HYDROGEN. Tellurctted Hydrogen. A gaseous substance discovered by Sir H. Davy, in 1809. It is colourless, has an odour similar to that of sul- phuretted hydrogen, and is absorbed by water, forming a claret colour- ed solution. As it unites with alkalies it may be regarded as a feeble acid. It reddens litmus paper at first, but loses this property after be- ing washed with water. Berzelius also describes compounds of sulphur, selenium, aluminum and glucinum with tellurium. Traite de Chim. ii. 520. Johnston's Roport. 326 BISMUTH. CLASS V. ORDER II. METALS WHICH DO NOT FORM ACIDS. SECTION XXXII. BISMUTH. Atom. Num. 7l.Symb. Bi. % gr. 9.822. This metal was known as early as 1520 ; but the first satisfactory account of it was published by Geoffry, in 1723. PROPERTIES. Bismuth has a reddish white colour and considerable lustre ; its structure is highly lamellated. and when slowly cooled it crystallizes in octahedrons ; it is brittle when cold, but may be ham- mered into plates while warm; fuses at 476 F.* and sublimes in close vessels at about 3(P of Wedgewood ; is but little changed by exposure to air at common temperatures, but when fused in open vessels it be- comes oxidated, and when heated to the subliming point, it burns with a bluish-white flame, and emits copious fumes of the oxide of bis- muth. NATIVE STATE AND EXTRACTION. Bismuth is rarely found native, but it is often met with in combination with oxygen, sulphur and arse- nic. It may be obtained pure for chemical purposes, by heating the oxide or subnitrate to redness along with charcoal. BISMUTH AND OXYGEN. These two bodies combine only in one proportion, though Berzelius considers the film formed on the surface of the metal, when exposed to the air, as a Subozide. Traitede Chim. iii. 151. Oxide of Bismuth. Atom. Num. tSSymb. O+Bi. A yellow coloured powder, sometimes called Flowers of Bismuth, which, at a full red heat, is fused, and yields a transparent yellow glass, and, at a higher temperature, is sublimed ; it unites with acids, and most of its salts are white. * Marx has ascertained that bismuth at the moment of solidifying 1 expands 1*53 rd of it* volume. He considers also that, like water, it has in the fluid state a point of maximum density. Johnston's Report on Chemistry. BISMUTH. 327 This oxide is formed by exposing the metal to heat, and air, or by heating the subnitrate to redness. REFERENCES. Lijerhielm'i Experiments to determine the proportion in which Bismuth unites with Sulphur and Oxygen, Ann. of Phil, if , 357. Dr. Vary, in Phil. Trans, for 1812. Thomson's I'irst Prin. i. 407. BISMUTH AND CHLORINE. lorideof Bismuth. titom. Num. 106-45- %?&. Cl+Bi. A substance of a grayish-white colour, granular texture, which is opaque, and is not sublimed by heat ; formerly called Butter of Bis- muth. It may be prepared by introducing bismuth, in fine powder, into chlorine gas ; or by heating two parts of corrosive sublimate with one of bismuth, and afterwards expelling the excess of the former, to- gether with metallic mercury, by heat. BISMUTH AND BROMINE. Bromide of Bismuth. A solid, of a steel-gray colour, having the as- pect of iodine, fused into a solid mass. It fuses at 392 F. and then assumes a hyacinth red colour, but resumes its former colour on cool- ing. It may be formed by exposing to heat bismuth in powder with a great excess of bromine in a/long tube shut at one end. The bromide of bismuth is found at the bottom of the tube. Serullas. BISMUTH AND IODINE. Iodide of Bismuth, may be formed by heating that metal with iodine, It is of an orange colour, and insoluble in water. With hydriodic acid, or hydriodate of potassa, nitrate of bismuth affords a deep choco- late coloured precipitate. BISMUTH ANE SULPHUR. SuJphuret of Bismuth. Atom. Num. Q7Symb. S+Bi. Bismuth combines readily with sulphur and forms a bluish-gray sul- phuret, having a metallic lustre. The same compound is also found native in Cornwall, Bohemia, Saxony and Sweden. BISMUTH AND THE METALS. Bismuth is capable of being alloyed with most of the metals, and forms, with some of them, compounds of remarkable fusibility. One of these is Sir Isaac Newton's Fusible Metal. It consists of eight parts of bismuth, five of lead, of three of tin, or, according to Dobereiner. when made in the best proportions, it is a compound of 1 atom of lead, 1 of tin and 2 atoms of bismuth, or an atom of the binary alloy 328 BISMUTH. of bismuth and lead, united with an atom of the binary alloy of bis- muth and tan. [Ann. of Phil. xxv. 389.] When thrown into water it melts before the water is heated to the boiling point. It is from the property of forming fusible alloys, that bismuth enters into the compo- sition of several of the soft solders, which indeed, is its principal use in the arts. Bismuth, like antimony, has the singular property of depriving gold of its ductility even when combined with it in very minute propor- tion. This effect is produced by merely keeping gold in fusion near melted bismuth. It has. nevertheless, been employed, by Chaudet, in eupellation. Ann. de Chim. et de Phys. viii. 113. Henry, ii. 107. SALTS OF BISMUTH. Nitrate of Bismuth. Atom. Num. 160 Symb. (5O+N)+ Aq. A transparent crystalline salt, which is decomposed by water, a white subnitrate being precipitated, which is called Mogistery of Bis- muth, or Pearl White, in which state it is employed in medicine. The solution is also employed for forming a white sympathetic ink. It is prepared by dissolving bismuth in dilute nitric acid, in the pro- portion of one part of the former to one and a half parts of the latter. The bismuth is to be broken into small pieces and added at distant in- tervals. The subnitrate of bismuth, in large doses, is an active poison. See Christison. 371. Sulphate of Bismuth. Atom. Num. 119 Symb. (3O+S)+ (0+Bi.) This salt occurs in the form of a white powder, or in needles ; it is insoluble in water, but is decomposed by it, and converted into a Subsulphate and Super sulphate. [Webster's Erande.~\ It is formed by the action of hot and concentrated sulphuric acid upon metallic bis- muth. Carbonate of Bismuth. Atom. Num. 277 Symb. (2O+C)+ (30+Bi.)+2Aq. A white tasteless powder, quite insoluble in water ; formed by de- composing nitrate of bismuth by an alkaline carbonate. REFERENCES. For description of several other Sails of Bismuth, see Thomson's First Prin. ii. 389, and Inorg. Chem. TESTS OF THE SALTS OF BISMUTH. Water poured into a colourless solution of these salts, produces a white precipitate. Gallic acid occasions an orange yellow, and ferro- cyanate of potassa a yellowish precipitate. COPPER. 329 SECTION XXXIH. COPPER. Atom. Num. 31-5 Symb. Cu. Sp. *gr. 8-695. This metal was known in the earliest ages of the world. PROPERTIES. Copper is distinguished from all other metals, titani- um excepted, by having a red colour ; it receives a considerable lustre by polishing; it is both ductile and malleable, and, in tenacity, is in- ferior only to iron ; it is hard and elastic, and consequently sonorous ; in fusibility it stands between silver and gold ; it undergoes little change in a perfectly dry atmosphere, but is rusted in a short time by exposure to air and moisture, being converted into a green substance, the carbonate of the black oxide of copper ; at a red heat it absorb* oxygen, and is converted into the oxide, which appears in the form of black scales. NATIVE STATE AND EXTRACTION. Native copper is by no means un- common. It occurs in large amorphous masses in the northwestern parts of this continent, and is sometimes found in octahedral crystals, or in forms allied to the octahedron. It also occurs in various states of combination, as the oxide, chloride, sulphuret, &c. Perfectly pure copper may be obtained by dissolving the copper of commerce in muri- atic acid ; the solution is diluted and a plate of iron immersed, upon which the copper is precipitated. It may be fused into a button, after having been previously washed in dilute sulphuric acid to separate a little iron that adheres to it. REFERENCES. For localities of Native Copper, see Cleaveland's Mineral- ogy. Vauquelin on precipitating Copper by Iron and Zinc, Ann. de Chiin. Ixxxvii. 16, or Ann. of Phil. iv. 157. Dr. Cooper on the reduction, SfC. of the Ores of Copper, Emporium of Arts, ii. 215. An article 'on Mining iu Copper and Tm in Cornwall, in the Quarterly Review, xxxvi. 31. COPPER AND OXYGEN. Three distinct oxides of copper are now recognized by chemists. Red or Suboxide of Copper. Atom. Num. 71*2 Symb. PROPERTIES. Orange yellow, in the state of hydrate, red when pure; fusible, below a red heat, into a reddish mass ; absorbs oxygen gas at a temperature slightly elevated and passes into the state of oxide ; it forms a colourless solution with ammonia, which becomes blue by ex- posure to the air. * From the latin Cuprum. 330 COPPER. NATIVE STATE AND PREPARATION. This oxide occurs native in the form of octahedral crystals, and is found, of peculiar beauty, in the mines of Cornwall. It may be prepared artificially by heating in a co- vered crucible a mixture of 31-6 parts of copper filings with 39-6 of the black oxide ; or still better by arranging thin copper plates one above the other with interposed strata of the black oxide, and exposing them to a red heat carefully protected from the air. It may also be obtained by boiling a solution of the acetate of copper with sugar, when the suboxide subsides as a red powder. Black or Protoxide of Copper. Atom. JYum. 39.6 Symb, O+Cu. PROPERTIES. Colour varying from a dark brown to a bluish black 3 according to the mode of formation ; undergoes no change by heat alone, but is readily reduced to the metallic state by heat and combus- tible matter ; is soluble in ammonia, forming with it a deep blue solu- tion, by which it is distinguished from all other substances. NATIVE STATE AND PREPARATION. This oxide of copper, the Cop- per Black of mineralogists, is sometimes found native, being formed by the spontaneous oxidation of other ores of copper. It may be pre- pared artificially, by calcining metallic copper, by precipitation from the salts of copper by means of pure potas^a, and by heating the ni trate of copper to redness. Peroxide of Copper. Atom. Num. 47'6 Symb. 2O+Cu. This oxide was prepared by Thenard by the action of peroxide of hy- drogen diluted with water on the hydrated black oxide. It suffers spontaneous decomposition under water ; but it may be dried in vacuo by means of sulphuric acid. When thrown upon a red hot coal it detonates, and the copper is reduced. It is insoluble in water and does not alter the colour of litmus paper. Acids decompose it into oxide of copper and peroxide of hydrogen. REFERENCES. Prousfs Experiments on Copper and its compounds, Ann, de Chin, xxv. or Repert. of Arts, 1st sfr. xiv. 114, 201, Chenemx, in. Phil. Trans, for 1806. Thenard, Truite de Chin, ii. 379, where three Oxides are described and Berzelius, iii. 128. COPPER AND CHLORINE. From the researches of Proust and Dr. J. Davy, there appears to be no doubt that there are two compounds of these substances, and that they are proportional to the oxides of copper. Subchloride of Copper. Atom. Num. 98-65 Symb. Cl+2Cu. SYN. Rosin of Copper Boyle. White Muriate of Copper Proust. PROPERTIES. Colour varying with the mode of preparation, being COPPER. 331 white, yellow, or dark brown ; it is insoluble in water, but soluble in muriatic acid, and is precipitated unchanged by water ; is fusible at a heat just below redness, and bears a red heat in close vessels without subliming. PREPARATION. This compound may be conveniently prepared by heating copper filings with twice their weight of corrosive sublimate ; or by the action of protornuriate of tin on the muriate of copper; and also by decomposing the muriate by heat. Chloride of Copper. Atom. Num. 67-05 Symb. Cl-j-Cu. A pulverulent substance of a yellow colour, which deliquesces on exposure to the air, and is reconverted by water into the muriate. It is formed by exposing the muriate of copper to a temperature not exceed- ing 400 J F.Dr. J. Davy, in Phil. Trans, for 1812. COPPER AND SULPHUR. Disulphuret of Copper. Atom. Num. 79-2 Symb. S+2Cu. A natural production well known to mineralogists under the name of Copper Glance ; and in combination with sulphuret of iron, it is a constituent of the variegated copper ore. It is formed artificially, by heating copper filings with a third of their weight of sulphur. The combination is attended with such free disengagement of caloric, that the mass becomes vividly luminous. Sulphuret of Copper. Atom. Num. 47*6 Symb. S+Cu. A constituent of Copper Pyrites, in which it is combined with pro- tosulphuret of iron. It may be formed artificially by the action of sulphuretted hydrogen on a per-salt of copper. When exposed to a red heat in a close vessel, it loses half its sulphur, and is converted in- to a protosulphuret. It is from this compound that most of the copper of commerce is obtained. The small quantity of arsenic, and the sulphur which it contains, are separated by roasting ; and the copper is obtained by re peated fusions, in some of which an addiiion of charcoal is made. See R. Phillips on Yellow Copper Ore, Ann. of Phil. xix. 296. COPPER AND PHOSPHORUS. Copper unites by fusion with phosphorus. The phosphuret is white, brittle, and of the specific gravity 7 '122. It consists of one atom phos- phorus-f-2 atoms copper. There are probably several distinct phos- phurets of copper. COPPER AND THE METALS. Many of the alloys of copper are of the highest importance in do- mestic economy and the arts. g le 332 COPPER. Copper may be united to iron by fusion, but not without some diffi- culty. It is an alloy of a gray colour, has but little ductility and is much less fusible than copper. According to Thenard it is attracted by the magnet even when the iron constitutes only 1-10 of the alloy. [Ann, de Cfdm. 1. 131.] And from some observations of M. Levavas- seur it appears probable that the variety of iron, called hot short iron, because it is brittle when red hot, owes its peculiarity to the presence of copper. See Thomson's Inorg. Chem. i. 598. Bronze, is an alloy of 11 parts of tin to 100 of copper. It is of a rayish-yellow colour, harder and more fusible than copper; slightly mal- eable when slowly cooled, and very much so when heated to near redness 'and then plunged into cold water. In consequence of the fu- sibility of this alloy, it is much used in the casting of statues. Ac- cording to Puyrnaurin, the finest French bronze medals consist of from 7 to 11 of tin and 100 of copper. Thenard, i. 629. Bell Metal, is an alloy of 22 parts of tin and 78 of copper. It is solid, fine and close grained, of a grayish-white colour, and more fusi- ble than bronze. The Chinese Tarn-Tain or Gong, so celebrated for the richness of its tones, contains, acccording to the analysis of The- nard, 80 parts of copper and 20 of tin. Speculum Metal, from which the mirrors of telescopes are made, contains about two parts of copper and one of tin. The whiteness of the alloy is improved by the addi- tion of a little arsenic. Brass, consists of copper, alloyed with from 12 to 25 per cent, of zinc ; the proportions differing somewhat in almost every place in which it is manufactured. It has a yellow colour, is very malleable and ductile when cold, but fragile at an elevated temperature. The preparation consists in uniting directly the proper proportions of zinc and copper, in the ordinary way, or in heating a mixture of carbon, copper and calamine, (carbonate of zinc,) which is an abundant natu- ral product. The compounds known under the names of Tombac, Dutch Gold. Prince Rupert's Metal, or Pinchbeck, are alloys, containing more copper than exists in brass, and they are consequently made by fusing various proportions of copper with brass. The art of tinning copper consists in applying to this metal a very thin covering of tin, in order to protect its surface from oxidation. The copper is first sprinkled over with some muriate of ammonia ; it is then heated and rubbed with this salt. When the copper is perfect- ly clean, small fragments of tin are placed upon it, and it is then heat- ed sufficiently for melting the tin ; this, when liquified, is rubbed over the whole sheet of copper, and if the process is dexterously perform- ed, adheres uniformly to its surface.* * According to Mr. Donoran the coat of tinning 1 which is given to the inside of copper vessels is in fact a mixture of had and tin ; and the use of it is to prevent the copper from coming in contact with the food prepared in such a vessel, which might otherwise be impregnated with that poisonous metal. Although lead itself is a poisonous metal, it is singular that the presence of tin renders it innoxious ; the reason of which is that tin prevents the lead from dissolving. Pewter is composed of lead in tin; and on account of the pres- ence of the latter, the former is rendered safe. Donoraifs Chemistry, 249. COPPER. 333 REFERENCES. Bishop Watson's Chemical Essays, ir. Aikin's Chem Diet, article, Brass, #e. Thenard, Traite de Chim. i. 628. The art. Brass, by Mr. C. Sylvester j and the art. on Bronzing, by J. G. Daly ell, in the Supp* totiie Ediri. Encyclopoedia. DaltoiSs New Syst. ii. SALTS OF COPPER. Muriates of Copper. Corresponding with the two chlorides of cop- per we have also a Submuriate and a Muriate. The former is obtained by digesting metallic copper in muriatic acid, with the oxide The latter by dissolving oxide of copper in muriatic acid. Nitrate of Copper. Atom. Nam. 156'6 - Symb. (5O+N.) +(0+Cu.)-j-7Aq. PROPERTIES. This salt crystallizes, though with some difficulty, in prisms, which are of a deep blue colour, and deliquesce on exposure to the air ; by exposing them to heat, a green insoluble Sub-nitrate is form- ed, which contains, exclusive of water, one atom of acid and two atoms of the oxide. When crystals of nitrate of copper are coarsely powdered, sprink- led with a little water and quickly rolled up in a sheet of tin foil, there is great heat produced, nitrous gas is rapidly evolved, and the metal often takes fire. These crystals also detonate when mixed with phos- phorus and struck with a hammer. This salt is prepared by the action of nitric acid on copper. Jmmoniuret of Copper. Copper and its oxides are soluble in ammo- nia. The watery solution of ammonia, at its boiling temperature, acts rapidly on copper. Dry ammoniaca! gas appears also to combine with heated copper. [Brandes Journal, 29, 158.] If ammonia be ad- ded in excess to nitrate of copper, the precipitate which is first formed is re-dissolved. On this property depends the method of separating oxide of copper from other metallic oxides ; from those of iron, for instance, which are not soluble by ammonia. Henry, ii. 112. Oxide of copper digested in ammonia, forms a bright blue liquid ; from which by careful evaporation, fine blue crystals may be obtained, called Ammoniurct of Copper. Suboxide of copper also dissolves in ammonia, and yields a colourless solution, which becomes blue by ex- posure to the air, in consequence of the absorption of oxygen. Plates of copper digested in a solution of muriate of ammonia, are soon incrusted with a green powder, which has been used in the arts under the name of Brunswick Green. Sulphate of Copper. Atom. Num. 124-6 %i&. (3O+S.) +(0+Cu.)+5Aq. SYN. Blue Vitriol Roman Vitriol. This salt is crystalline, of a fine blue colour, and soluble in four parts of water at 60 3 F. ; it slightly effloresces on exposure to the air, and undergoes by a gentle heat the aqueous fusion. The solution of this salt is decomposed by pure and carbonated alkalies. The former, however, re-dissolve the precipitate. Thus on adding pure liquid am- monia to a solution of sulphate of copper, a precipitate appears, which V 334 COPPER. on a farther addition of the alkali is re-dissolved, and affords a beau- tiful bright blue solution. PREPARATION. This salt may be prepared for chemical purposes by dissolving black oxide of copper in dilute sulphuric acid ; but it is pro- cured for sale by roasting the native sulphuret. It is used in medicine as an escharotic ; in the arts, for obtaining Scheele's green, &c. This salt, as well as most of the soluble salts of copper, is poisonous when taken internally. The remedy proposed by Orfila in such cases is albumen, with which oxide of copper forms an inert compound. See Christison on Poisons, 353. There appears to be no sulphate of the suboxide of copper. Disulphate of Copper, is formed by adding solution of potassa to the above sulphate. It is a pale bluish green powder, and is composed of one atom of acid-f-tvvo atoms of the oxide. Phosphate of Copper. This has not yet been formed artificially, but has been found native in a white quartz rock. It is of an emerald- green colour, and is not crystallized. Henry, ii 115. Lunn's Analysis of native Phosphate of Copper, Ann. of Phil. xix. 179. Biphospkate of Copper. A bluish -green salt, formed by mingling to- gether phosphate of soda and sulphate of copper. Carbonate of Copper. According to Mr. Phillips, three native car- bonates of copper are at present known, the green, the blue, and the anhydrous. The green is the beautiful mineral known by the name of Malachite, and consists of one atom of carbonic acid, two atoms oxide of copper, and one of water. A similar compound may be made from the persulphate by double decomposition, or by exposing metallic cop- per to air and moisture. The blue pigment called Vcrditer, said to be prepared by decompos- ing nitrate of copper by chalk, is an impure carbonate. On the Car- bonates of Copper and the preparation of Verditer, sec, the valuable Essay of Mr. Phillips, in Brandes Jour. iv. 273. Ferrocyanate of Copper is a brown compound, obtained by adding ferrocyanate of potassa to a dilute solution of sulphate or nitrate of copper. Mr. Hatchett has recommended this substance as a brown pigment. Repcrt. of Arts, 2d ser. ii. 180. Chromate of Copper. This salt is prepared by precipitating sulphate of copper by chromate of potash. It is of a reddish brown colour, is soluble in dilute solution of ammonia, producing a clear solution of a beautiful and deep green colour. When the solution is evaporated, the reddish chromate of copper appears as the ammonia flies off. The readiest way of preparing this permanent and beautiful colour, is to add solution of chromate of potash to ammoniacal sulphate of copper. The Acetates of Copper will be noticed under Acetic acid. TESTS OF THE SALTS OF COPPER. The cupreous salts are nearly all soluble in water, and of a blue or green colour. Ammonia produces a compound of a very deep blue, when added in excess to these solu- tions ; hydrosulphuret of ammonia forms a black precipitate ; and a, plate of iron plunged into a liquid salt of copper, precipitates metallic copper. Ferrocyanate of potassa is also an excellent test of the pres- ence of copper ; it produces a brown cloud in solutions containing the oxide. All the salts of copper communicate a green tint to inflamma- ble matter in a state of combustion when moistened. LEAD. 335 SECTION XXXIV. LEAD. Atom. JYwwi. 103-5. fifywzA. Pb* Sj). gr. 11-352. Known from the most remote antiquity, and called Saturn by the Alchemists. PROPERTIES. This metal is of a bluish-white colour, and when re- cently cut or melted, exhibits considerable lustre, which soon, how- ever, tarnishes; its malleability is sufficient to allow of its being beat- en into very thin leaves ; and it may be drawn into wire, which has less tenacity, however, than that of most other metals ; it melts, ac- cording to Morveau, at 590 F. but according to Mr. Crichton, of Glasgow, at 612 D ; exposed to a red heat, with free access of air, it smokes and sublimes, and gives off a gray oxide, which collects on surrounding bodies ; it is slowly oxidized also, by exposure to the at- mosphere at common temperatures, and more rapidly when exposed alternately to the action oi f air and water. Many spring- waters, how- ever, owing to the salts which they contain, do not corrode lead. On this subject, see Christison on Poisons, 391. NATIVE STATE AND PREPARATION. Native lead is an exceedingly rare production, but in combination, especially with sulphur, it occurs in large quantity. From the native sulphuret, the Galena of mineralo- gists, all the metallic lead of commerce is extracted. This lead generally contains copper and iron, and sometimes traces of silver. To obtain it in a state of perfect purity, it should be dis- solved in nitric acid, and the solution evaporated and crystallized sev- eral times. The resulting nitrate reduced to powder, is to be strongly heated in a Hessian crucible to drive off the nitric acid, and then melt- ed in contact with a small quantity of charcoal. tierzelius, Trait, de Chiin. iii. 176. LEAD AND OXYGEN. There appear to be three oxides of lead. These have been examin- ed with great care by Berzelius. Protoxide of Lead. Atom. Num. 111-5 Symb. O+Pb. PROPERTIES. Yellow, tasteless, insoluble in water, but soluble in potassa and in acids ; when heated it forms, on cooling-, a yellow semi- transparent glass, called Litharge, which is, to a considerable degree, volatile at a red heat, and has been obtained in regular crystals. [Phil. Mag. and Ann. i. 3J2.] Another form of the yellow oxide is, that which is known in commerce by the name of Massicot. PREPARATION. The yellow oxide may be obtained by decomposing nitrate of lead with carbonate of soda, and igniting the precipitate, or by heating the nitrate to redness in a close vessel. Massicot is pre- pared by collecting the gray film which forms on the surface of melted lead, and exposing it to heat and air, until it acquires a uniform yellow colour. * From the latin word Plumbum. 336 LEAD. Sesquioxide of Lead. Atom. Num. 1155 Symb. l|O-j-Pb. This oxide, which, in an impure form, is the Minium or Red Lead of commerce, does not unite with acids ; when heated to redness it . Gay Lussac on the precipitation of Silver by Copper, in Ann. de Chim. or Report, of Arts, 2d set: xx. 252, Berzelius, Trade de Chim. iii. 88. Det Rio on the reduction of Silver Ores by the method of BecquercL^ Breu-ster's Edm. Jour, of Science, N. 8. v. 222. * From the latin Argentuin. SILVER. 349 SILVER AND OXYGEN. Oxide of Silver. Mm. Num. 116 Symb. O+Aq. This substance is of an olive colour, insoluble in water, and taste- less ; when heated the oxygen is driven off, and the metal is reduced. It is prepared by adding lime-water or solution of pure baryta to solu- tion of nitrate of silver, washing and drying the precipitate. When this oxide of silver, recently precipitated, is left in contact for ten or twelve hours with a strong solution of ammonia, the great- er part is dissolved, but a black powder remains, which detonates vi- olently from heat or percussion. It appears to be a compound of am- monia and the oxide of silver, or of nitrogen and silver. It should be made in very small quantities and dried spontaneously in the air. See Berlhollet, Ann. de (.'him. i. When a solution of the oxide of silver in ammonia is exposed to the air, its surface becomes covered with a pellicle, which Mr. Faraday considers to be a distinct oxide with less oxygen than the one just de- scribed, an opinion which is also confirmed by Dr. Thomson, who calls it a suboxide. Brande's Jour. iv. 270. Thomson's First Prin. i. 433. SILVER AND CHLORINE. Chloride of Silver.- Atom. Num. 14345 Symb. Cl+Aq. PROPERTIES. This compound when formed by precipitation is at first quite white, but by exposure to the direct solar rays, it becomes violet and almost black in the course of a few minutes, arid a similar effect is produced by diffused day light ; it is insoluble in water and very sparingly dissolved by the stronger acids, but is soluble in ammo- nia ; at the temperature of about 500 it fuses, and forms a semi- transparent horny mass on cooling, and hence sometimes called Horn Silver; bears the combined action of heat and charcoal without de- composition, but is readily decomposed by hydrogen gas, with the for- mation of muriatic acid ; it is also rapidly decomposed by tin and zinc. It is decomposed by hydrogen gas. If a few pieces of zinc be put into a test glass and some dilute sulphuric acid be poured over it, an effer- vescence takes place, and hydrogen gas is disengaged. Chloride of silver placed above the zinc in the same glass, is speedily reduced by this hydrogen and converted into metallic silver. Chloride of silver sometimes occurs native in silver mines. It is al- ways generated when silver is heated in chlorine gas, and may be pre- pared conveniently by mixing muriatic acid, or any soluble muriate with nitrate of silver. REFERENCES. On the composition of this substance, see Thomson's First Prin. i. 429; and Berzelius, in Arm. of Phil. xv. 90. Faraday on the de- composition of Chloride of Silver by Hydrogen and by Zinc, Brandos Jour. viii. 374. SILVER AND BROMINE. Bromide of Silver. A light yellow curdy sul n exposure to light, is insoluble in water and i substance which blackens on exposure to light, is insoluble in water and in nitric acid, but solu- 350 SILVER. ble in ammonia. It is formed by adding an alkaline hydrobromate to a solution of nitrate of silver. SILVER AND IODINE. Iodide and Silver. Afom.Nmn. 234 Symb. I+Aq. A compound of a greenish yellow colour, insoluble both in water and ammonia, and formed by mixing hydriodate of polassa with ni- trate of silver. SILVER AND SULPHUR. Rulphnret of Silver. Atom. Num. 124 Symb. S-j-Aq. A compound of a black colour, capable of being 1 cut with a knife, much more fusible than the metal, and from which "the sulphur can be driven off by heat. This substance often occurs native in mines, and is the Silver Glance of mineralogists. It may be prepared by heating to low redness thin plates of silver with alternate layers of sulphur. It is also formed by transmitting a current of sulphuretted hydrogen gas through a solu- tion of nitrate of silver. Cyanide of Silver. Atom. Num 134 Symb. (N-f 2C.)+Aq. A white curdy substance, similar in appearance to the chloride of silver, insoluble in water and nitric acid, and soluble in a solution of ammonia ; is decomposed by muriatic acid, with formation of hydro- cyanic acid and chloride of silver. It is formed by mixing hydrocy- anic acid or an alkaline hydrocyanate with nitrate of silver. SILVER AND THE METALS. Some of the alloys of silver have been noticed ; but the most im- portant is the alloy of silver and copper, as it constitutes plate and coin. The standard silver of Great Britain consists of 0'90 copper, and 11-10 silver. \_Henry.'} The standard silver of the United States consists of 1485 of fine silver and 179 parts of copper ; J3 Troy ounces of standard silver are coined into 15 dollars. This combina- tion, though its colour differs but little from that of pure silver, is much harder, and is better adapted for the purposes of coin, and of domestic implements. The silver of commerce is composed of 37 parts of fine silver and 3 of copper. Amalgam of silver is sometimes employed for plating ; it is applied to the surface of copper, and the mercury being evaporated by heat, the remaining silver is burnished. The quantity of pure silver in any of these alloys is determined by the process called cupellation. This process consists in exposing to heat a clean piece of the alloy, of a given weight, wrapped up in a quantity of sheet lead. This is performed in a cupel, or shallow cruci- ble made of bone earth, which must be previously heated. The whole is then placed under a muffle and heated to bright redness ; the metals SILVER. 351 melt, and, by the action of the air upon the hot surface, the lead and copper are oxidized and absorbed by the cupel, and a button of pure silver ultimately remains. REFERENCES. The article Assay, in Aikiti's Chem. Diet. Gray's Opera. tiveCLenist. Bigelow's Technology. Oersted on determining the composi- tion of Alloys of silver, SfC. by the Magnetic Needle^ Ann. de Chun, et de Phys. Nov. 1828. For an analysis of different European silver coins, see Thom- son's Lnorg. Chem. i. 638. SALTS OF SILVER. Nitrate of Silver. Atom. Num. IW.Symb. (5O+N.) (O +Aq.) PROPERTIES. This salt is crystalline, colourless, bitter and very caustic ; it deliquesces by exposure to air ; is soluble in its own weight of cold, and in half its weight of hot water, and in about four times its weight of alcohol ; it undergoes igneous fusion, when heated, and assumes, on cooling, the appearance of a gray crystalline mass ; at a red heat it is completely decomposed, and metallic silver remains ; its solution produces a black stain upon the skin, and is indelible or peels off with the cuticle ; it may be decomposed by carbon, phosphorus and some of the metals. It is decomposed by some of the combustibles, A clean piece of phos- phorus introduced into a solution of nitrate of silver, becomes cover- ed with a crust of metallic silver. This reduction is also effected by a clean plate of copper, and by mercury. In the latter case the precipi- tation is slow, and produces a peculiar symmetrical arrangement, cal- led the Arbor Diana. PREPARATION. This salt is prepared by dissolving pure silver in ni- tric acid, diluted with from two to four parts of water, and evapora- ting the solution. USES. Nitrate of silver, when fused and poured in this state into heated moulds, forms the common Lunar Caustic, or Lapis Infernalis, employed by surgeons as a cautery. It is also the basis of the Indeli- ble Ink, used for marking linen and cotton, and is sometimes employed for giving a black colour to the hair, but for this purpose it should be used with caution. In the laboratory it is used as a test of chlorine and muriatic acid.* REFERENCES. Bradenbourg on making pure Nitrate of Silver from an Alloy of Silver and Copper. Ann. of Phil. xv. 389. For the mode of ol~ t aining Arbor Di >nce, see Webster's Brandt ; and for another process, which consists in suspending a small knot of fine linen containing Quicksilver, in /.he Nitric Solution of Mercury and Silver, see Repert. of Arts, 2d ser xvii. 381. For a notice of the method of copying engravings, fyc. by nitrate of silver, by T. IVedgewood, see Paris' Life of Davy. i. 161. * The fo' low ing singular fact is stated by Sir John Herschel in his Dig- course on the Study of Natural Philosophy. A solution of nitrate of silver and another of hyposulphite of soda, have each of them separately, whei taken into the mouth, a disgusting bitter taste ; but if they be mixed, or if one be tasted before the mouth is thoroughly cleared of the other, the sensible im- pression is that of intense sweetness. 352 SILVER. Fulminating Silver. Besides the fulminating compound of silver, formed by the addition of ammonia to the nitrate of silver, another one is formed, by a process similar to that noticed under fulminating mercury, viz. by adding alcohol to a solution of silver in nitric acid. Its preparation requires great caution. The same views are entertain- ed concerning its composition as concerning that of fulminating mer- cury. It is probably a Cyanite of Silver. For details concerning its preparation, fyc. see, Henry's Chem. or Webster' s Brande and for some new views concerning it, see Dr. Ellet's Essay upon the compounds of Cyanogen, Sill. Jour, xviii. 335. See also a Report on the Fulminating Powders, capable of being used as Priming for Fire Arms, by MM. Au- oert, Pelissier and Gay Lussac, in which the preference is given to Fulmi- nating Merciiry, Ann. de Chim. xlii. or Repert. of Pat. Invent, ix. 182 307. Sulphate of Silver. Atom. Num. 156 Symb. (3O+S)+ (0+Aq.) v> PROPERTIES. A white powder with a metallic taste ; when heated it melts and is decomposed, being changed into sulphurous acid, oxygen and metallic silver ; soluble in about 88 times its weight of boiling water, and when the solution cools, the salt is partly deposited in the state of small needles. Thomson's First Prin. ii. 406. This salt may be obtained by digesting sulphuric acid over oxide of silver, or by mixing together concentrated solutions of nitrate of sil- ver and sulphate of soda. It is the proper test for ascertaining the presence of muriatic acid where sulphuric acid is also supposed to be present, for the nitrate of silver precipitates both these acids. There is also a Hyposulphite and a Sulphite of Silver, obtained by processes similar to those already described. Phosphate of Sifaer. This salt is obtained by adding solution of phosphate of soda to solution of pure nitrate of silver, washing and drying the precipitate. It is in the form of a yellow powder, fusible at a red heat without any farther loss of weight. It appears to be a subphosphate. Thomson s First Prin. ii. 408. Carbonate of Silver. Atom. Num. 13SSymb. (2O+C)+ (0+Ag.) A white insoluble powder, with a slight shade of blue, which black- ens by exposure to light, and effervesces with dilute nitric acid. It is formed by adding carbonate of potassa to nitrate of silver. Carbonate of ammonia only throws down a portion of the silver from the nitrate,, and forms a triple Ammonio- Carbonate of Silver. Chromate of Silver, is precipitated of a crimson colour by adding" chromate of soda to nitrate of silver. It soon loses its brilliant tint and becomes brown, Phil. Mag. and dnn, i. 345. REFERENCES. On the Salts of Silver, see Thomson's First Prin ii 404. Pro-list 1 s facts relating to the chemical history of Silver, Jour, de Phy&\ or Repert. of Arts, 2d ser. ix. 310, 355. TESTS OF THE SALTS OF SILVER. Those which are soluble are recog- nized by furnishing a white precipitate with muriatic acid, which black- ens by exposure to light, and which is readily soluble in ammonia, and GOLD. 353 by affording metallic silver upon the immersion of a plate of copper. The salts insoluble in water are soluble in liquid ammonia, and when heated on charcoal, before the blow-pipe, they afford a globule of silver. SECTION XXXVI. GOLD. Atom. Num. 200 Symb. Au.* Sp. gr. 19-3. PROPERTIES. This metal, whose history and principal uses are sim- ilar to those of silver, has an orange-yellow or reddish-yellow colour, and may be made to assume a high lustre, only inferior to steel, silver and mercury ; exceeds all other metals in malleability and ductility, (see page 196,) but is less tenacious than several other metals ; is not changed by exposure to air and moisture for any length of time, nor oxidized by being kept in a state of fusion in open vessels ; it is not acted on by any of the pure acids, however concentrated, its only solvents being chlorine and nitro-muriatic acid ; the effect being in both cases ascribed to the agency of chlorine, (see page 135,) ; it is exceedingly soft and flexible when pure ; is less fusible than silver, re- quiring a heat of 32"* of Wedgewood for its fusion. NATIVE STATE AND PREPARATION. Gold occurs in nature in a metallic state, either pure or in combination with other metals. It occurs mas- sive, capillary, in grains, and crystallized in cubes and octahedrons. It is most frequently found in alluvial soils and in the beds of certain rivers, especially those of the west coast of Africa and Peru, Brazil and Mexico. It is also found in various parts of Europe and of North America, especially in North Carolina. This metal may be obtained pure by dissolving standard gold in ni- tromuriatic acid, evaporating the solution to dryness. redissolving the dry mass in distilled water, filtering and adding to it a solution of pro tosulphuret of iron ; a black powder falls, which, after having been washed with dilute muriatic acid and distilled water, affords on fusion a button of pure gold. Vauquelin. REFERENCE. Olmstexd's account of the Gold Mines of North Carolina, Sill. Jour. ix. 5 ; and for other localities see Clcaveland's Mineralogy. GOLD AND OXYGEN. Oxides of Gold. There is still much uncertainty concerning the compounds of gold and oxygen. Berzelius is of opinion that there are three, but their composition is not yet understood. The only well known oxide is that which is supposed to exist in the solution of gold, combined with muriatic acid. According to M. Pelletier, the best method of forming it is by digesting the muriate with pure magnesia, washing the pre- cipitate with water, and removing the excess of magnesia by dilute nitric acid. This is probably a peroxide, consisting of three atoms of oxygen and one atom of gold. Berzelius, Javal, and Thomson. * From the latin Aurum 354 QOLD. The Peroxide of Gold is yellow in the state of hydrate, and nearly- black when pure ; is insoluble in water, and completely decomposed by solar light or a red heat ; it is readily soluble in muriatic acid, yielding the common solution of gold, but it forms no definite com- pound with any acid which contains oxygen ; it has a very feeble affinity for nitric and sulphuric acids, but combines, on the contrary, with alkaline bases, such as potassa and baryta, apparently forming regular salts, in which it acts the part of a weak acid. Hence Pelle- tier proposes the term Auric Acid for the peroxide of gold, and to its compounds with the alkalies he gives the denomination of Anrates. Fulminating Gold. The peroxide of gold is thrown down of a yel- low colour, by ammonia, and the precipitate is an aurate of that alkali. It is a highly detonating compound, analogous to the fulminating sil- ver described in the last section. REFERENCES. Proust's facts relating to the chemical history of Gold, Jour, ae Phya. or Re.pert. of Arts, 2d ser. ix. 289, 350. Pelletier, Ann. (If Chim. et (lc Phys. xv. or Brandos Jour. x. 117. Vauqueliii's experiments on some preparations of Gold, Ann. de Chim. and Repert. of Arts, Ld ser. XX 243. Oberkainpfs memoir on various combinations of Gold, Arm. de Chim. Ixxx., or Repert. of Arts, Zd ser. xxi. 181, 2-19. Berzetius, Traite dt Chim. iii. 1, Javal, Ann* de Chim. el de Phys. xvii. 337, or Brande's Jour. xii. 318. Thomson^ in first Prin. and Phil. Mag. and Ann. vii. 4M. GOLD AND CHLORINE. The same, degree of uncertainty exists with regard to the chlorides , as to the oxides of gold. Gold leaf introduced into chlorine gas taket* fire and burns ; and if it be suspended in water, into which the gas is passed, it is dissolved, and the solution may be concentrated by evaporation. The solution obtained in the manner directed in the last article, consists also, most probably, of the same Perchloride. By exposure to moderate heat, it parts with two-thirds of its chlorine, and is converted into a yellow insoluble Protochloride Chloride of gold is capable of combining with other chlorides. The resulting compounds are called Chloroaurates , and have been examined by Bonsdorf. See Thomson's Inorg. Chem. ii. 831. The solution of gold is decomposed by substances which have a strong affinity for oxygen. On adding protosulphuret of iron, dis- solved in water, the iron is oxidized to a maximum, and a copious brown precipitate subsides, which is metallic gold in a state of per- fect purity. A similar reduction is effected by most of the metals, and by sulphurous and phosphorous acids. So when a piece of char- coal is immersed in the solution of gold, and exposed to the direct solar rays, its surface acquires a coating of metallic gold ; and ribands may be gilded by moistening them with a dilute solution of gold r and exposing them to a current of hydrogen or phosphuretted hydro- gen gas. When a strong aqueous solution of gold is shaken in a phial with an equal volume of pure ether, two fluids result, the lighter of which is an Etherial Solution of Gold. From this liquid, flakes of metal are de- posited on standing, especially by exposure to light, and substance^ moistened with it receive a coating of metallic gold. When the protomuriate of tin is added to a dilute aqueous solution GOLD. 355 of gold, a purple coloured precipitate, called the Purple of Cassius, is thrown down, which is the substance employed in painting on por- celain for giving a pink colour. It appears to be a compound of the peroxide of tin and the purple oxide of gold, in which the former is supposed to act as an acid. REFERENCES. For experiments on the revival of Gold, see Mrs. Fulham-e on or his Essays, 393, and also the papers of Proust and Oberkampf, quoted under the last arti- cle. Johnston on the double Chlorides of Gold, Biewste^s Edin. Jour. N. iii. 131, 2BO. on Combustion, and Count RamfortFs paper in Phil. Trans, for 1798, 449, or his Essays. Dr. Clarke on the Purple of Cassias, Ami. of Phil. xvii. Bromide of Gold. Balard observed the solubility of gold in bro- mine ; and Lampadius found that the dry compound is constituted of equal parts of gold and bromine. It is of a grayish black colour, is soluble in water, and gives a deep-red liquid, which yields crystallized hydrobromate of gold by evaporation. The colour of this salt is so in- tense, that a single grain communicates a perceptible tint to 5,000 grains of water. Brande's Jour. N. S. iii. 489. Iodide of Gold, may be obtained by acting on oxide of gold with hy- driodic acid, or by mixing chloride of gold with hydriodate of potassa, and washing and drying the precipitate. It is insoluble in cold water, and very sparingly soluble in hot. It is decomposed by heated nitric or sulphuric acids, which reduce the gold and set iodine at liberty. It consists, according to Pelletier, of one proportion of each of its elements. Sulphuret of Gold. Sulphur, even when assisted by heat, has no action on gold; but when a current of sulphuretted hydrogen is pass- ed through a solution of that metal, a black precipitate is formed, which is a true sulphuret of gold. The sulphur may be easily expelled from this combination by heat. It appears to be composed of one pro- portion of gold and three proportions of sulphur. Phosphuret of Gold. This compound may be obtained by passing a atreamof phosphuretted hydrogen through a solution of gold. It has a gray colour and metallic lustre. GOLD AND THE METALS. Gold combines with most of the metals. Antimony, tin, zinc and lead, when alloyed with gold, destroy or impair its malleability. It is stated that even the fumes of antimony in the neighborhood of melt- ed gold, are sufficient for this purpose. With copper, (standard gold,) the alloy is perfectly ductile and malleable, but harder than pure gold, and resists wear better than any alloy except that with silver. The sterling or standard gold of Great Britain, consists of gold alloyed with one-twelfth its weight of cop- per, or a mixture of both, as is most common, and according to Mr. Hatchett, the average of its specific gravity is 17-5. The standard gold of the United States consisis of nearly the same proportions of gold and alloy. (For a table of the specific gravity of various gold pieces, see Hatchett' s paper, or Thomson's Jnorg. Chem.) The degree of purity of gold is expressed by the number of parts contained in 24 parts of any mixture. Thus gold, in which 24 such 356 PLATINUM. parts, (termed carats ) contains 22 of the pure metal, is said to be 22 carats fine. Absolutely pure gold, using the same language, is 24 car- ats fine ; and gold alloyed with an equal weight of another metal, 12 carats fine. The process of water gilding consists in applying an amalgam of gold to the surface of silver, and driving off the mercury by heat. In gilding porcelain, Gold Powder, obtained by the decomposition of the chloride, is commonly employed. It is applied with a pencil, and burnished after having been exposed to the heat of a porcelain fur- nace. REFERENCES. Aikirfs Diet. art. Gold, contains an account of the methods of purifying gold, fyc. Lewis' Philosophical Commerce of tJie Arts. Hatch, ett on the various alloys, specific gravity and comparative icear of Gold. Phil. Trans. 1803, abridged in Repert. of Arts, Id ser. iv. 12. The art' Gilding, in Edin. Encyclopedia. The art. Coinage, hy R. Mushet, in Sup. to the Ency. Britamiica. Bigeloufs Technology. For a minute account of the mode of making gold leaf and gilt wire, see Keaumhr's Mem. Paris. 1713, p. 199, and Leivis' 1 Philosophical Commerce. SECTION XXXVII. PLATINUM. Atom. Num. 98*6. Symb. Pt.Sp. gr. 21-5. This valuable metal, discovered by Wood in 1741, is found in vari- ous parts of South- America, in the form of rounded or flattened grains, mixed with sand and other alluvial depositions ; and in the province of Antioquia, in veins associated with gold. Rich mines of gold and platinum have also been recently discovered in the Uralian mountains. ~Edin. Jour, of Science, v. PROPERTIES. Pure platinum has a white colour very much like sil- ver, but of inferior lustre ; it is the heaviest of known metals ; its mal- leability is considerable, though far less than gold and silver ; it maybe drawn into wires, the diameter of which does not exceed the 2000th part of an inch ; it is a soft metal, and, like iron, admits of being weld- ed at a high temperature ; it is a less perfect conductor of caloric than most other metals ; it undergoes no change from the combined agency of heat and air, and may be exposed to the strongest heat of a smith's forge without being oxidated or fused ; is not attacked by any of the pure acids, its only solvent being chlorine and nitromuriatic acid. REFERENCES. Dr. \Vollaston? s process for obtaining pure Platinum, ren- dering it malleable, fyc. Phil. Trans. li>29, or Frankliifs Jour. N. S. iv. 226. For a notice of the Gold and Platinum district in. Russia, see the Jour, of the Royal Institution.,'}. 418. Coinage, fyc. , of Russian Platinum, Edin. New Phil. Jour. iii. 276, vi. 1^7. The Russian method of rendering platinum mal- leable is described by W. Marshall, in the Repertory of Patent Inventions, xlif. 397. PLATINUM. 357 PLATINUM AND OXYGEN. According to Berzelius, there are two oxides of platinum, the oxy- gen of which is in the ratios of 1 to 2. The protoxide is of a black co- lour, reduced by a red heat, and prepared by the action of potassa on the protochloride of platinum. It probably consists of one atom of oxygen and one of platinum. The peroxide has not been obtained pure, but is supposed by Berzelius to exist in the muriate of platinum com- bined with muriatic acid. Dr. Davy has described a third oxide, intermediate between the per- oxide and the protoxide, [P/u/. Trans, for 1820,] and Mr. Copper has also described what he calls a Suboxide, [Brande's Jour. iii. 119,] but this cannot be regarded as a definite compound. PLATINUM AND CHLORINE. Perchloride of Platinum is procured by evaporating the solution of platinum in mtro-miiriatic acid, to dryness at a gentle heat. It is de- liquescent, and is soluble in water, alcohol and ether. The ethereal solution is decomposed by the agency of light, metallic platinum be- ing deposited. The chloride probably consists of one proportion of platinum and two proportions of chlorine. When strongly heated it is converted into the Protochloride. The chlorides of platinum combine with other chlorides and with the muriate of ammonia and form a class of compounds called C/tloro- platinaf.es, which have been investigated by Bonsdorf. [See Thomson's Inorg. Chem. ii. 833.] When a solution of sal ammoniac is added to a liquid chloride of platinum, a beautiful orange-yellow precipitate falls, consisting of one atom of the bichloride of platinum-f-one atom muriate of ammonia. When this compound, which is commonly call- ed the muriate of platinum and ammonia, is heated to redness, chlorine and muriate of ammonia are evolved, and pure platinum remains in the form of a delicate spongy mass, which causes a jet of hydrogen to in- flame, (p. Ill,) and which kindles an explosive mixture of hydrogen and oxygen gases. Various contrivances for the purpose of producing instantaneous light, upon this principle, are now adopted. Dr. Hare states that if asbestos or charcoal be soaked under an exhausted re- ceiver in muriate of platinum, then dried in an evaporating oven for twenty-four hours, and afterwards ignited, the property of ignition in the gaseous elements of water is acquired. Silliman' s Jour, xx. 160. The Bichloro-platinate of Potassium, is obtained by adding pure po- tassa or a salt of potassa to a concentrated solution of chloride of pla- tinum. It consists of very small octahedrons, very little soluble in water and not at all in alcohol. When heated it gives out chlorine and leaves a mixture of platinum and chloride of potassium. The proper- ty of forming this compound with potassa distinguishes platinum from all other substances. 358 PLATINUM. PLATINUM AND SULPHUR. Sulphuret of Platinum. When sulphuretted hydrogen gas is trans- mitted through a solution of muriate of platinum, a black precipitate is thrown down, which Vauquelin regards as a hydrosulphuret of the oxide of platinum. It absorbs oxygen from the air while in a moist state, giving rise to the formation of sulphuric acid. Its composition has not been determined with accuracy. A black sulphuret of platinum was procured by Mr. E. Davy, by heating the rnetal with sulphur ; and Vauquelin obtained a similar compound by igniting the yellow muriate of platinum and ammonia, with twice its weight of sulphur. According to the analysis of these chemists, it contains about 16 per cent, of sulphur. Turner. Sulphate of Platinum. The hydrosulphuret of platinum is convert- ed by the action of nitric acid into a sulphate which possesses remark- able properties. On boiling it in strong alcohol, a black powder is precipitated, which consists, according to Mr. E. Davy, of 96 per cent, of platinum, together with a little oxygen, nitrous acid, and carbon, the last of which is supposed to be accidental. When this powder is placed on bibulous paper moistened with alcohol, a strong action ac- companied with a hissing noise ensues, and the powder becomes red hot, and continues so until the alcohol is consumed. The substance which remains is pure platinum. E. Davy, Phil. Trans. 1820. Fulminating Platinum may be prepared by the action of ammonia m slight excess on a solution of sulphate of platinum. It is analogous to the detonating compounds which ammonia forms with the oxides of of gold and silver. -E. Davy, in Phil. Trans. 1817. PLATINUM AND THE METALS. Platinum combines with other metals and forms alloys which are not in general characterized by useful properties. Its affinity for lead is strikingly shown by the following experiment : If a piece of lead foil, and another of platinum foil, of equal dimensions, be rolled up together, and the flame of a candle be cautiously directed by a blow- pipe towards the edges of the rolls, at about a red heat, the two metals will combine with a sort of explosive force, scattering their melted particles and emitting light and heat in a surprising manner. [Ann. of Phil. xiv. 230.] A small bit of tin. zinc or antimony, rolled in plati- num leaf, and treated in like manner, exhibits similar phenomena. [Henry, ii. 172.] When alloyed with the more oxidable metals, it is remarkable that platinum becomes soluble in nitric acid, which has no action on the pure metal. PALLADIUiM RHODIUM. 359 SECTION xxxviii. PALLADIUM. Atom. Num. 53 Symb. Pd. Sp. gr. 11-5. This metal was discovered by Dr. Wollaston in 1803, in an ore of platinum. PROPERTIES. Palladium resembles platinum in colour and lustre : it is both malleable and ductile ; is harder than wrought iron ; its point of fusion is intermediate between gold and platinum ; is dissi- pated in sparks when intensely heated by the compound blow-pipe ; it is oxidized and dissolved by nitric acid, and by the aid of heat is also acted on by sulphuric and muriatic acids, though its proper solvent is the nitro-muriatic. This metal is obtained by adding to a neutral solution of the ore of platinum, a solution of bycyariide of mercury ; and heating to redness the yellowish white flocculent precipitate of cyanide of palladium, which is gradually deposited. Oxide of Palladium. Jltom. Num. 61 Symb. O+Pd. When potassa is added to solution of palladium, an orange-colour- ed hydrate is thrown down, which becomes black when dried, and is decomposed by a red heat. This oxide forms beautiful red coloured salts, from which metallic palladium is precipitated by protosulphate of iron, and by all the metals described in the foregoing sections, ex- cepting silver, gold and platinum. Berzelius describes two oxides of palladium, and a sulphuret, phos- phuret and carburet. Traitede Chim. iii. 75. REFERENCES. Wollaston, in Phil Trans. 1804 and 1805. Vauqudins Memoir on Palladium and Rhodium., Ann. de Chim. Ixxxviii. 167; or Ann ef Phil. iv. 216. SECTION XXXIX. RHODIUM. Jltom. Num. 52 Symb. R.Sp. gr. 11. This metal, discovered by Dr. Wollaston about the same time as the last, has only been procured in very minute quantities from the so- lutions of crude platinum, in the form of a black powder, which re- quires the strongest heat of a wind furnace for its fusion, and when fused has a white colour and metallic lustre ; it is hard and brittle, and its specific gravity is about 11 ; in its pure state is not attacked by any of the acids, but when alloyed with other metals, is oxidized and 360 OSMIUM IKIDIUM. dissolved by the nitro-muriatic acid ; it is oxidized by ignitibn with nitre. Oxides of Rhodium. Two compounds of rhodium and oxygen are described. The Protoxide, consisting of one atom of each of the ele- ments is black. The Peroxide, which is the bases of the salts of rho- dium, is of a yellow colour ; and all these salts are either red or yel- low, and the muriate is a rose red. See the references under the last Section. SECTION XL. OSMIUM. Atom. Num. 99 ?Symb. Os. Sp. gr. 10. This metai was discovered by Mr. Tennant in 1803, in the black powder left after the digestion of crude platinum in nitro-muriatic acid. Osmium is separated from the iridium which this powder also contains, by alternate and frequent digestions in soda and muriatic acid. It can only be obtained as a metal in a disintegrated state ; it is capable of supporting a white heat, without being volatilized or fused ; it is of a dark gray or blue colour ; if ignited in open vessels, with access of air, it is oxidized and then dissipated in vapour. On agitating the metal with mercury, an amalgam is formed, and with copper, silver and gold, it forms malleable alloys. The pure Oxide of Osmium is soluble in water and volatile ; it emits a peculiar odour, which has something of the pungency of chlorine. The aqueous solution is colourless, and when shaken with mercury, is decomposed, soon loses its smell and forms an amalgam. Berzelius has recently examined this metal and its compounds and has described five oxides and sulphurets and four chlorides. SECTION XLI. IRIDIUM. Atom. Num. 98 6 Symb. Ir. Sp. gr. 18-68. This metal was discovered by Mr. Tennant at the same time with the last. It is the most infusible metal known, having only been fused by the large galvanic battery of Mr. Children ; when it appear- ed as a globule of a brilliant white colour, and metallic lustre ; is at- tacked with great difficulty by nitro-muriatic acid, but is oxidized when heated with nitre. Oxides. The solution of the oxides of iridium in muriatic acid is, when first prepared, of a blue colour ; it afterwards becomes of an olive green, and subsequently acquires a deep red tint. These changes are attributed to its passing through different stages of oxidation. Berzelius has lately ascertained that this metal is capable of forming four oxides and four chlorides. IRIDIUM. 361 The Muriate of Iridium, when deprived of its excess of acid, by heat, may be obtained in crystals of a deep brown colour, by evapo- ration. This salt, when dissolved in water, forms'a red coloured so- lution, which is rendered colourless by pure alkalies or alkaline earths, by sulphuretted hjdrogen, infusion of galls, or by ferrocyanate of po- tassa. It is decomposed by nearly all the metals, except gold and platinum, the iridium being thrown down in a metallic state. Iridi- um may also be obtained from the muriate, by exposing that sail to a red heat. REFERENCES. On the two last Metals, see Tennant, in Phil. Trans, for 1804. Vauqueliri's Memoir on Iridium and Osmium, Ann. de Chim. Ixxxix. J50, or Ann. of Phil, vi, 433. Wollaston, Phil. Trans. 1829. Berzelius. Traite de Chim. iii. 24. 362 VEGETABLE SUBSTANCES. CHAPTER IX. VEGETABLE SUBSTANCES. All bodies which are of vegetable origin are termed vegetable sub- stances. Oxygen, hydrogen and carbon are their principal ingredi- ents, with which a certain portion of nitrogen is sometimes united ; and variations in the proportions and mode of combination of these elements, occasion the great diversity which exists among the pro- ducts of the vegetable kingdom. Every distinct compound which exists ready formed in plants, is called a proximate or immediate principle. Thus sugar, starch and gum are proximate principles. Opium, though obtained from a plant, is not a proximate principle, but consists of several proximate princi- ples, mixed more or less intimately with one another. The proximate analysis of vegetables consists in the separation of these distinct prin- ciples ; but the reduction of the proximate principles into their simp- lest parts, constitutes their ultimate analysis The proximate analysis of vegetables varies considerably with the nature of the substance to be separated ; and some of these processes will be hereafter noticed. The ultimate analysis consists in the de- composition of the body by heat, in contact with some other sub- stance, but it constitutes in its details one of the most delicate opera- tions of analytical chemistry. For the purpose of effecting this ob- ject several processes have been devised. That which is at present most highly approved was proposed by Gay Lussac and Thenard, and consists in mixing three or four grains of the substance to be ana- lyzed with about two hundred grains of the peroxide of copper, heat- ing the mixture to redness in a glass tube, and collecting the gaseous products in a graduated gljss jar, over mercury. For the details of this process, and the manipulations necessary, the reader is referred to the works of T-'teiiard, Thomson, Henry or fierzelius. See also, Gay Lussac and Thenard 1 s Physico-Chem. Kesea.rches, ii.; Front's observa- tion? on tfie analysis of Organic Substances, sinn. of Phil, vi 269, vii. Ill ; and his memoirs on the ultimate composition of Simple Alimentary Substances, #c., Phil. Trans, for 1827, or Phil. Mag. and Ann. iii. 31 and 98. Vegetable substances, and indeed all organic products, are charac- terized as follows : 1. They are composed of the same elements. 2. They are easily decomposed, both spontaneously and by art. 3. They cannot be formed by the direct union of their principles. 4. They are decomposed at a red heat, and often below it. burner. In the present state of our knowledge, vegetable bodies cannot be classified in a purely scientific manner. I shall notice them nearly in VEGETABLE SUBSTANCES. 363 the order proposed by Dr. Turner, on the basis of the general laws de- duced by Gay Lussac and Thenard, viz : 1. Salifying principles or acidr. 2. Salifiable principles or alkalies, and the substances related to them. 3. Substances which, in relation to oxygen, contain an excess of hy- drogen. 4. Substances, the oxygen and hydrogen of which are in exact pro- portions for forming water. 5. Substances which, so far as is known, do not belong to either of the preceding sections. SECTION I. VEGETABLE SALIFYING PRINCIPLES OR ACIDS. These substances are characterized by their having a sour taste, and changing the blue of litmus to red, but more especially by their power oi combining with salifiable bases. Like all organic principles, they are decomposed by a red heat ; though they are in general less liable to spontaneous decomposition than other vegetable substances. They are all colourless, and, with a single exception, solid ; and are nearly all decomposed by hot nitric acid, by which they are converted into carbonic acid and water. Some of the vegetable acids are the products of nature alone ; some are the products of both nature and art; and some are exclu- sively the products of art. I shall present the prominent characters of most of these acids, noticing in detail only the most important. Acetic Acid. Atom. Num. 5lSymb. 3O+3H+4C. NATIVE STATE AND PROPERTIES. This acid exists in the sap of al- most all plants, either free or combined with potassa or lime, and is also abundantly the produce ot art. It is transparent, colour- less, and very volatile ; has a pungent odour, very sour taste, and red- dens litmus powerfully; in its most concentrated form it crystallizes when exposed to a low temperature, retaining its solidity until the thermometer rises to 50 F. It has a specific gravity varying from I -056 to 1-08. PREPARATION. Acetic acid may be obtained by the distillation of common vinegar, which is prepared by exposing malt or vinous liquors to the free access of atmospheric acid, at a temperature slight- ly elevated ; by the purification of pyroligneous acid procured from the distillation of wood ; or still better, by the decomposition of the acetates. The distillation of vinegar is effected in the same manner as that of water. The acid thus obtained is called Distilled Vinegar, and was formerly named Acetous Acid, upon the erroneous supposition that it was chemically different from strong acetic acid. Concentrated acetic acid is best prepared by the decomposition of the acetate of soda by sulphuric acid, and subsequent distillation ; or by subjecting the acetate of copper to heat. The acid, when first 364 VEGETABLE SUBSTANCES. collected, has a greenish tint, owing to the presence of copper, from which it is freed by a second distillation. In addition to the above processes may be mentioned, the exposure of common vinegar to low degrees of temperature, by means of which the water is frozen, and a concentrated acid remains in a liquid state. Pyroligneous Acid. The acid known under this name is an impure acetic acid prepared by the distillation of wood. When first made, it it of a dark colour, holding in solution tar and volatile oil, from which it is freed by mixing it with chalk, decomposing the resulting acetate of lime by digestion with sulphate of soda ; fusing the acetate of soda thus formed at a high temperature, insufficient to decompose the salt, but sufficient to expel or char the impurities ; and finally decomposing the acetate of soda by sulphuric acid. Kreosote. Mr. Reichenbach has recently obtained from pyroligneous acid and also from the tarry matter which distils over with the acid, a new sub- stance which he calls Kreosole, from the greek words meaning flesh, I save. This substance is highly interesting, not only on account of its chemical properties, but from its useful applications to therapeutics. domestic economy and the preservation of provisions for long voyages, Kreosote is an oily, colourless liquid, possessing great refrangibility , has a penetrating, disagreeable odour, similar to that of smoked beef; sp. gr. about 1-037 at 68 F., boils at 397 F., and is not congealed at a temperature of 16'6 F ; burns with a smoky flame ; combines readi- ly with acetic acid, Water, alcohol, ether and with the alkalies ; it also coagulates albumen. Antiseptic properties of Kreosote. When fresh meat is put into a so- lution of kreosote, allowed to remain for half an hour or an hour, withdrawn, and afterwards dried, it may be exposed to the heat of the sun without putrifying, and in the space of eight days it becomes hard, the colour changes to a reddish-brown, and the flavour is that of good smoked beef. Fish may also be preserved by it, Action on the Animal Economy. When kreosote is placed upon the tongue, it occasions violent pain, and when poured in a concentrated state upon the skin it destroys the epidermis. Insects and fish thrown into it, immediately die. Jt has been employed with success in cases of caries, of cancer and of carcinomatous ulcers. Land, and Edin. Phil. Mag. iv. 391. Edin. Med. and Surg. Jour. xli. 248. REFERENCES. CrelUs Annals. Aikirfs Did. art. Acetous Add. For various processes for preparing this add, see also lire's Chem. Diet. 4th ed. 7. Thenard's Traite de Chim. and Chaptal. Despretz' method of making glacial acetic add, by heating a mixture of one atom of acetate of Lead, well dried, with one of concentrated sulphuric acid, Phil. Mag. and Ann. vii. 317. Parked Essays on Pyroligneous Acid. The only correct mode of estimating the strength of acetic acid, is by its neutralizing power ; its specific gravity being no criterion. Sec a Table in Thomsons First Prin. ii. 135. Acetates. These are compounds formed by the union of acetic acid VEGETABLE SUBSTANCES. 365 with bases. They are nearly all soluble in water, and can be decom- posed by sulphuric, muriatic, nitric, hydrofluoric or phosphoric acids. When subjected to destructive distillation, they furnish, in addition to the usual products, a modified vinegar, which has been termed Pyroacetic Acid or Spirit. See M. M. Macaire and Marcel's description and analysis of Pyroxilic and Pyroacetic Spirit, in Ann. of Phil. xxiv. 69. Ace fate of Ammonia. Atom. Num. 131 Symb. (3H-fN)+ Ac*+7 Aq. Crystallizes with difficulty, being deliquescent and very soluble in water and in alcohol ; has a hot and aromatic taste. It may be ob- tained in solution by saturating distilled vinegar with carbonate of am- monia, and it then constitutes the Spirit of Mindtrerus, long used in medicine as a febrifuge. Acetate of Potassa. Atom. Num. 116.15 Synib. (O-fPo.) +Ac+2 Aq. Formerly known by the name of Terra Foliata Tartari, Febrifuge Salt of Sylvius, and Diuretic Saft. This salt, when cautiously evapo- rated, forms irregular crystals, which are with difficulty obtained, ow- ing to their deliquescence. It exists, according to Vauquelin, in small quantity, in the sap of almost all plants, and is formed artificially by neutralizing carbonate of potassa with acetic acid, or by decomposing acetate of lime with sulphate of potassa. Acetate of Soda. Atom. Num. 138-3 Symb. (O+So)+Ac. +6Aq. Formerly known by the name of Terra Foliata Crystallizata. It crystallizes in long striated prisms ; has an acrid and bitter taste ; is soluble in a third of its weight of water, at 60 F. It is prepared by saturating acetic acid with carbonate of soda, and evaporating the so- lution. When it is employed in the manufacture of acetic acid, it is prepared by the decomposition of sulphate of soda by acetate of lime made with pyroligneous acid. Acetate of Baryta is sometimes employed as a re-agent, and Acetate of Alumina is used by dyers and calico printers as a basis or mor- daunt. Acetates of Copper. These salts have been carefully investigaged by Berzelius and Phil- lips. Ann. of Phil. xvii. 217. xviii. 21. xx. 161. xxiv. 192. xxviii. 188. Acetate of Copper. The neutral acetate may be formed either by dissolving oxide of copper or common verdigris in acetic acid or by de- * Ac is used as an abbreviation for the acid of a salt when the symbol is complex. Aq. as heretofore, is an abbreviation for aqua, water. X 366 VEGETABLE SUBSTAN 7 CES. composing sulphate of copper by acetate of lead. Ft crystallizes in oblique rhombic prisms, of a beautiful bluish-green colour, which are soluble in 20 times their weight of cold water, in 5 of boiling water, and in 14 of boiling alcohol. They consist of 1 atom acetic acid, 1 atom of the black oxide of copper and 1 of water=99. Diacetate of Copper. This constitutes the chief ingredient of the pigment called Verdigris, which is prepared in the large way by cover- ing copperplates with cloth soaked in pyroligneous acid, or by cover- ing copper plates with the refuse of the g' ape after the juice has been extracted for making wines, as is practiced in the south of France. The saccharine matter contained in the husk furnishes acetic acid by fermentation, and in four or six weeks the plates acquire a coating of this salt. It consists of 1 atom acetic acid, 2 atoms black oxide of eopper, and 6 atoms of water=144. This salt is decomposed by water and converted into a soluble green sesquiacctate and an insoluble tri-acetate. See the papers above referred to and Thomson's First Prin. ii. 383, and Inorg. Chem. ii. 672. Acetate of Lead. Atom. Num. lSQ'5Symb. (O-f Pb)+Ac. +3 Aq. Known also by the names of Raccharum Saturni and Sugar of This salt, when pure, crystallizes in long six-sided prismatic crys- tals ; it has a taste at first sweet, then astringent ; has no effect upon vegetable blues, being perfectly neutral ; is very soluble in water ; effloresces when exposed to the air, and is partially converted into a carbonate. It is prepared by dissolving either carbonate of lead or li- tharge in distilled vinegar. It is used in medicine as an external ap- plication, &c. ; in the arts, in the preparation of acetate of alurnine ; and in the laboratory as a re-agent. Subacctate of Lead. Jjtom. Num 335*5 Symb. 3(O+Pb)+Ac. This compound, commonly known by the, name of Extractum Satur- m, or Goulard's Extract of Lead, is prepared by boiling one part of neu- tral acetate, and two parts of litharge, deprived of carbonic acid by heat, with 25 parts of water. It crystallizes in white and opaque plates ; has a taste less sweet, and is less soluble in water, than the neutral acetate, and changes to green the syrup of violets. It has a strong attraction for vegetable colouring matter, and upon this princi- ple was employed by Mr. Brande in his analysis of wines. Phil. Trans. 1813. This salt is called by Dr. Thomson the Trisacctatc, and he has also described a Diacetate, formed by boiling with water a mixture of li- tharge and acetate of lead, in atomic proportions. First Prin. ii. 373, and Inorg. Chem. ii. 642. Oxalic Acid. Atom. Num. 36Symb. 3O+2C. STATE AND PROPERTIES. Discovered by Scheele, and exists in the juice of several plants, especially in that of the Rumex Acetosa, L. or common sorrel, and in the Oxaiis Aceiosdla L. or wood sorrel ; but VEGETABLE SUBSTANCES. 367 it almost always occurs in combination either with lime or potassa. It may also be prepared artificially by the action of nitric acid upon various vegetable and animal substances. It crystallizes in slender, flattened four or six-sided prisms, with two-sided summits, the prima- ry form of which is an oblique rhombic prism ; it has a very acrid taste, and reddens litmus strongly ; is soluble in two parts of water at (50 and in its own weight at 2l5 and also in boiling alcohol ; eilior- esces when exposed to the air, and at a red heat is decomposed. It differs, in composition, from all the other vegetable acids, in contain- ing no hydrogen. Berzdius, Ann. dc Chim. ct de Phys. xviii. 155. Thomson's First Prin. ii. 100. See also Dobcreiner, in dnn. de Chim. et de Pliys. xix. Oxalic acid may be easily made artificially, by digesting sugar in iive or six times its weight of nitric acid, and expelling the excess of that acid by distillation, until a fluid of the consistence of syrup re- mains in the retort. The residue, in cooling, yields crystals of oxalic acid, the weight of which amounts to rather more than half the quan- tity of the sugar employed. These crystals are to be re-dissolved in water, and again crystallized, by which the pure acid is obtained. Other processes have been proposed by Braconnot for obtaining this acid from lichens. .inn. de Chim. xxviii. 313. ACTION ON THE ANIMAL ECONOMY. Oxalic ackl is one of the most powerful and rapidly fatal poisons that we possess ; and frequent ac- cidents have occurred in consequence of the resemblance of the crys- tals to those of Epsom salts. Its acidity, however, will be a sufficient mark of distinction, which can be detected either by the taste or by its reddening blue papers. The solution also of a small quantity of this acid, when added to chalk, causfs effervescence, which is not the case with the salt. When the acid has been swallowed, copious draughts of lime-water, chalk or magnesia and water, should be ad- ministered, and vomiting excited as speedily as possible. Christison and CGindet, in Edin. Mud. and Surg. Jour. 1823. TESTS. Oxalic acid is distinguished from all other acids by the form of its crystals, and by its forming, with lime-water, an insoluble pre- cipitate. It is hence employed as a test for lime ; but for this purpose the combination of oxalic acid with ammonia is generally preferred. Oxidates. These compounds are either insoluble or sparingly solu- ble in water, but they are all dissolved by the nitric, and also by mu- riatic acid, except when the latter precipitates the bases of the salts. The only oxalates remarkable for solubility are those of potassa, soda, lithia, ammonia, alumina arid iron. These salts are decomposed at a red heat r but they are with diffi- culty acted upon by the acids. They'are formed either directly or by double decomposition. Oxalatc of Ammonia. A tow. Num. 71Symb. (3H+N) + Ac+2 Aq. This salt crystallizes in long tetrahedrons, terminated by two-sided summits ; it has a very pungent taste ; is soluble in two parts of wa- ter, at 6(P F. insoluble in alcohol. It is prepared by the direct union of its constituents, and is employed in the laboratory as a test for lime. During the decomposition of this salt by heat, a sublimate of a pe- 368 VEGETABLE SUBSTANCES. culiar nature is formed, which is named by Dumas, its discoverer, Oxalammide or Oxamide, compounded of the words oxalic and ammonia.'. It is of a dirty white colour, insoluble in cold water, but is dissolved in boiling water, from which on cooling it is deposited, unchanged, in the form of whitish fiocks of a confused crystalline appearance. when gently heated in an open tube it rises in vapour, and is again condensed on the cold part of the tube ; but when sharply heated, it enters into fusion, and while part sublimes, another portion yields cyanogen gas, and leaves a very bulky carbonaceous residue. It con- sists, according to Dumas, of 2 atoms carbon, 1 atom nitrogen. 2 atoms hydrogen and 1 atom oxygen=36. Ann. de Chim. et de Pliys* xliv. 12&Berzelius, Traite de Chim. Binoxolate of Ammonia. Atom. Num. 161 Symb. (3H+N^ +2Ac+8 Aq. This salt may be formed by adding oxalic, sulphuric, nitric or muri- atic acid to a solution of oxalate of ammonia and setting the solution aside (sufficiently concentrated) for crystallization. Oxalate of Potassa.Atom. Num. 92*15 Symb. (Q+Po) +Ac+Aq. A neutral salt, which crystallizes with some difficulty in flat, ob- lique, four-sided prisms, terminated by diedrai summits ; it is soluble in about twice its weight of water, at 60 F. ; has a cooling and bitter taste. It is prepared by neutralizing oxalic acid with carbonate of potassa. Binoxolateof Potassa. Atom. Num. 137.15 Symb. (O-f-Po) + 2Ac+2 Aq. This salt crystallizes in rhombs, only slightly oblique ; it has a sour . pungent bitterish taste, and reddens vegetable blues ; is soluble in ten times its weight of boiling water. It exists ready formed, in the sorrel and other plants, from which it may be obtained by solution and crys- tallization. Artificially it may be obtained by adding oxalic acid to a concentrated solution of the natural oxalate. It is commonly known by the names of Salt of Sorrel or Essential Salt of Lemons, and is used for the removal of ink stains from linen, &c. Quadroxalate of Potassa. Atom. Num. 254' 15 Symb. (O+Po)+4Ac-f 7 Aq. A salt crystallizing in octahedrons, reddening litmus powerfully and less soluble in water than the preceding. It is obtained by di- gesting the binoxalate in nitric or muriatic acid. On these Oxalatc? consult Wollaston on Super-acid and Sub-add Salts, in Phil. Trans, for 1808, and Berard, in Ann. de Chim. Ixxiii. 271. An Oxalate and Bi noxalate of Soda arc also described by Dr. Thomson, First Prin. ii, VEGETABLE SUBSTANCES. 369 Oxalote ofLimt Atom. Num. 82*5 Symb. (O-f Ca)+ Ac+2 Aq. A white tasteless powder, insoluble in water, but soluble in nitric and muriatic acid ; when heated to 560 F. it becomes anhydrous. It is a frequent ingredient of urinary concretions, and is the basis of what is called the Mulben-y Calculus. Artificially it is prepared by ad- ding any soluble oxalate to a salt of lime. Qxalate of Magnesia. Atom. Num. 70-7 Symb. (O+Mg) -fAc+Aq. A white, tasteless powder, which is sparingly soluble in water. It 'is prepared by adding oxalate of ammonia to a hot concentrated solu- tion of sulphate of magnesia. When the sulphate of magnesia is mod- erately diluted with cold water no precipitate is occasioned by the ad- dition of the oxalate. On this fact is founded one of the best process- es for separating lime from magnesia. Tartaric Acid Atom. Num. ffiSymb. 5O+2H-f-4C. STATE AND PROPERTIES. Thi-s acid was discovered by Scheele in 1770, and exists in combination with lime and potassa in the juice of several acidulous fruits. It occurs in prismatic crystals, the primary form of which is a right rhombic prism ; has a very sour taste, and reddens litmus powerfully : is soluble in five or six times its weight of water at 60 F. ; when exposed to heat it melts, is decomposed, and yields, in addition to the usual products of destructive distillation, a distinct acid, to which the name of Pyrotartaric Acid is applied ; it un- dergoes no change by exposure to air, but its aqueous solution soon be- comes covered with mould. Tartaric acid is prepared by throwing into boiling water a mixture of 197-15 parts or one proportion of cream of tartar, with 50*5 parts or one proportion of chalk, decomposing the tartrate of lime which re- sults, with one proportion of sulphuric acid, filtering and evaporating the solution. This acid combines with bases and forms salts, called Tartrates, and it is distinguished by its forming a white precipitate, the bitartrate of potassa, when mixed with any salt of that alkali. Its great use is by the calico-printers, who thicken it with gum or roasted starch, and apply it to those parts of a piece of calico previously dyed red or blue as are to be rendered colourless by means of chloride of lime. The tartaric acid combining with the lime sets the chlorine at liberty, which immediately destroys the colour of the part of the cloth on which the thickened acid has been fixed. Tartrate of Potassa. Atom. Num. 13M5 Symb. (O-fPo) +Ac-f2 Aq. This salt, frequently called Soluble Tartar, occurs in crystals, the primary form of which is a right rhomboidal prism, and which are so- luble in water, and attract moisture when exposed to the air. It is 370 VEGETABLE SUBSTANCES. formed by neutralizing a solution of the bitartrate with carbonate of potassa. For an account of the forms of its crystals , see Brooke, in .^nn . of Phil. vii. 161. Bitartrate of Poiassa. Atom. Num. 197*15 Symb. (O+Po)+2 Ac+2 Aq. Also called Supcr-tartrate of Potassa, Cream of Tartar, and in an impure form, Tartar. This salt is very sparingly soluble in wafer, re- quiring sixty parts of cold and fourteen of boiling water for solution., from the latter of which it is deposited in small crystalline grains, the primary form of which is either a right rectangular, or a right rhom- bic prism ; it has a sour taste, and reddens vegetable blues. It exist* in the juice of the grape, and owing to its insolubility, is deposited on the sides and bottom of wine casks ; from which source all the tartar of commerce is obtained, and which, by being purified, furnishes the cream of tartar of the shops. It is used in forming the black and white flux, and in the preparation of tartaric acid and the tartrates. For the crystalline form of this Salt, see Ann. 'of Phil. x. 37, and xxiii. 161. The processes commonly adopted in manufacturing tJtis Salt, arz described in Mkins Chem. Diet. ii. art. Tartar. Tartrate of Potassa and Soda. Atom. Num. 282-45. This double salt, which has long been used in medicine under the name of Rochdle Salt, occurs in prismatic crystals, having often ten or twelve sides, the primary form of which is a right rhombic prism : it is soluble in five parts of cold water, and in a less quantity of boiling water. It is obtained by neutralizing bitartrate of potassa with car- bonate of soda. Boro-tartrate of Potassa and Soda. A salt made by dissolving one part of borax in eight parts of boiling water, and adding three parts of tartar, or as much as it is capable of dissolving. It has a place in most of the German Pharmacopoeias under the name Cremor Tartari Soht- Iiilis and Tartras Potassce Boraxatvs. It is said to possess nearly the same properties as cream of tartar. Thomson's Inorg. Chem. ii. 805. Tartrate of Antimony and Potassa Tartar Emetic. Atom, Num. 350-35. PROPERTIES. This salt commonly crystallizes in tetrahedrons, which are transparent when first formed, but become white and opake by exposure to the air. It has a styptic metallic taste ; reddens litmus slightly ; is soluble in fifteen parts of water at 60 F. and in three of boiling water ; its aqueous solution undergoes spontaneous decompo- sition by keeping. PREPARATION. Tartar emetic is obtained by boiling protoxide of an- timony with a solution of bitartrate of potassa. For this purpose, the oxide is variously prepared. The method recommended by Mr. Phillips is to boil 100 parts of metallic antimony in fine powder to dryness, in an iron vessel, with *200 parts of sulphuric acid ; and to boil the residual subsulphate with an equal weight of cream of tartar. The solution is then concentrated by evaporation, and allowed to VEGETABLE SUBSTANCES. 371 cool in order that crystals may form. According to Dr. Thomson, this salt consists of two atoms tarlaric acid, three protoxide of antimony, one atom potassa and two atoms water, =354. First Prin. ii. 441. For a copious abstract of an elaborate memoir on Tartar Emetic, by M. Henrv, of Paris, see the Supplement to Duncan's Edin. New Dispensa- tory, (1829.) ACTION ON THE ANIMAL ECONOMY. Most commonly tartar emetic is evacuated by vomiting, before it can produce any striking consti- tutional effect. But in cases of poisoning when large does have been exhibited, and it remains long on the stomach, burning pain in the stomach comes on, with purging, colic pains, violent and long contin- ued vomiting ; cramp is also common. The resemblance of these symptoms to cholera morbus will strike the physician. TESTS. 1. Sulphuretted hydrogen gives an orange-red precipitate. the Sulphuret of Antimony. 2 Carbonate of potash throws down a white precipitate. 3. The sulphuret obtained as above, after being- dried, is placed in a small glass vessel, a stream of hydrogen is then passed on it from a proper apparatus, heat is afterwards applied by a spirit lamp, and on producing an elevated temperature, metallic an- timony is seen, either in minute globules, or in a spongy mass. This experiment, for which we are indebted to Professor Turner, depends on the property that hydrogen possesses of separating sulphur from antimony. REFERENCES. Dr. Turner, in Edin. Med. and Snrg. Journal, xxviii. Christisoii, on Poisons. Tartrate, of Copper and Potassa. This salt may be formed bj boiling together oxide of copper and tartar in water. The solution yields by evaporation blue crystals, which have a sweetish taste, and contain a great proportion of metal. When tartar and copper, or its oxides, are boiled together, they dissolve, and by evaporating to dryness, a bluish-green powder is obtained, which, according to Leonardi, con- stitutes the better kind of pigment, called Brunswick- green. Thomsons Inorg. Chem. ii. 798. Racemic or Paratartaric Add. Shown to be a distinct acid by John, in 1819, a view which was con- firmed by Gay Lussac and Walckner in 1829. PROPERTIES. This acid occurs in the form of prisms and of large oblique rhombs which are perfectly diaphanous ; is very sour, but with- out odour ; melts easily and becomes yellow when heated. It possesses exactly the same composition and power of saturation as tartaric acid ; in consequence of which Berzelius suggested the name of Paratartaric Acid. PREPARATION. This acid may be prepared by saturating the tartar of sour wine with carbonate of soda, and crystallizing the double tar- trate. The double paratartrate does not crystallize, and remains in the mother water. It is then decolourized as much as possible by animal charcoal and precipitated by a salt of lime or of lead the precipitate, if a salt of lime, is decomposed by sulphuric acid if of lead, by sul- phuretted hydrogen. The solution then contains tartaric and paratar- taric acid ; the last crystallizes first, and the tartaric acid only assumes 372 VEGETABLE SUBSTANCES. the solid form when the mother water becomes of the consistence of syrup. Berzelius, Traite de Chim. v. 83. Berzelius describes several Paratartratcs. Citric Acid. Atom. Num. 5SSymb. 4O+2H+4C STATE AND PROPERTIES. This acid, discovered by Scheele, is found in very large quantity in the juice of the lime and lemon. It crystal- lizes, in large and transparent rhomboidal prisms, which are termina- ted by four plane surfaces, and undergo no change in the air ; when concentrated it has a very sour and almost insupportable taste, and reddens litmus powerfully ; is soluble in an equal weight of cold, and half its weight of boiling water ; when exposed to heat it is decom* posed, and besides the usual products, a peculiar acid sublimes, call* ed Fyrocitric J)cid. It is obtained from lemon juice, by a process very similar to that for obtaining tartaric acid. This acid is sometimes used as a substitute for lemon juice, and when added to the carbonates of potassa or soda, forms an efferves- cing draught. It combines with various bases, and forms Citrates, but these are of little importance. REFERENCES. For a very full account of Citric Acid, see Parked Chtm. Essriys, iii. 3. Lassaigne, on Pyrocitric Acid, Ann. de Chim. ft de Phys of Repert. of Arts, 3d ser. xlii. 251. Malic Acid.Jltom. Num. 57 Symb. 4O+H+4C. lAebig. STATE AND PROPERTIES. This acid, discovered by Scheele in 1785, is found inmost of the acidulous fruits, as grapes, currents, gooseber* ries, &c., and in the Scrnpermvum tectorwn , L. and Sorbus aucvparia, L. and may be formed by digesting sugar with three times its weight of nitric acid. It is white, inodorous, and difficultly crystallizable ; has a sour taste, resembling that of the citric and tartaric acids ; is deli- quescent and soluble in water and alcohol ; has a specific gravity great- er than that of water, and by the action of heat is converted into a distinct and volatile acid, called lyromalic Acid. The compounds of this acid with bases, called Malates, are mostly soluble in water. REFERENCES. Donovan, Le Grange, Vogel and Braconnot, on Malic Acid, in Ann. of Phil. vi. 67; xii. 153; xiii. 51. Braconnot and Labillar- diere's proofs of the identity of the Sorbic and Malic Acid, Ann. de C/tiui. et de Phys. viii. 149 and 214. Thenard, Traite de Chim. iii. 622. Benzole Acid. Atom. Num. 113 Symb. 3O+5H+14C. Flowers of Benzoin of the shops. STATE AND PROPERTIES. Exists in the Styrax Berizoin, Dryand. And in the flowers of the Melilotus officinalis, Lam. It occurs in white opaque, prismatic crystals, of a satin appearance ; has a sweetish and aromatic, rather than a sour taste, though it reddens litmus and unites with bases ; is soluble in about 30 parts of boiling water, and very sparingly so in cold water ; is also soluble in alcohol. It combines with bases and forms a class of salts, called Benzoatcs, most of which are soluble. VEGETABLE SUBSTANCES. 373 PREPARATION This acid may be obtained by heating gum benzoin in an earthen pot, and receiving the acid as it sublimes in a cone of paper placed over it ; or by boiling powdered gum benzoin in a large quantity of water, along with carbonate of potassa or lime, and adding muriatic acid to the solution after being filtered and evaporated. But perhaps the simplest process is to digest gum Benzoin in sulphuric acid, when a great quantity of beautifully crystallized and very pure benzoic acid is sublimed. Benzule. One of the most interesting discoveries lately made in vegetable chemistry, is that of M. M. Wb'hler and Liebig, of the radical of berizoic acid. It is the first example of a radical consisting of three elements, and promises to throw much light on the nature of the vege- table principles in general. The close connexion of benzoic acid and oil of bitter almonds, in which crystals of the acid are often deposited, as it was supposed from the oxidizement of the oil, led the above named chemists to analyze it, when they found it to consist of2O-f-6H-f-14C ; that is, it contains one atom of hydrogen more, and one of hydrogen less, than benzoic acid. Th^y consider both, therefore, to be compounds of the same radical composed of 2O-j-5H-f-14C, which they propose to call Benzule, from the Greek ule, matter or base. If this radical be represented by Bz, then Bz-f-O=benzoic acid and Bz-f-H==oil of bitter almonds. If the oil be exposed to a current of chlorine, there are formed two products. Cl-f-Bz and Cl-jkH, chloride of benzule and muriatic acid. With hydrated bases, it gives a benzoate of the oxide and a chloride of the metal. Distilled with cyanide of mercury, it gives a cyanide of benzule and a chloride of mercury. With sulphuret of lead, and iodide and bromide of potassium, it gives, in the same way, a sulphuret and iodide and a bromide of benzule, while the chlorine unites with the me- tal. The iodide and bromide are crystallizable and volatile, and all three are decomposed by water and bases like the chloride. Johnston's Report on Chemistry. REFERENCES. Vogel, on Benzoic Acid in Melilotus Qffitinalis, fyc. Ann. of Phil, xvi.2^7. Other sources of , Brandos Jour, xviii. 319. Hisinger, on the Bznzontes, Phil. Ma. %. \\. Tromnisdorf and Berzelius, on the same, Ann* de Chim. xi. and xc. Faraday, iuBrande's Jour. vi. 159. Gallic Acid. Atom. Num. 63Symb. 3O+3H+6C. Discovered by Scheele in 1786. STATE AND RROPERTIES. It exists ready formed in the bark of many trees and in gall-nuts. When pure it is in the form of whitish crystals ; has a sour taste and reddens litmus ; is soluble in twenty .parts of water at 6(P, and in three parts at 212 3 . and is also soluble in alcohol and ether ; when heated in the air it exhales a peculiar smell, and at a high heat takes fire. With lime-water, gallic acid yields a brownish-green precipitate, which is redissolved by an excess of the solution, and acquires a reddish tint. It is distinguished from tannin by causing no precipitate in a solution of gelatine. With a salt of iron, it forms a dark blue-coloured corn- pound, which is the basis of ink. The finest colour is procured when the peroxide and protoxide of iron are mixed together. This charac- ter distinguishes gallic acid from every other substance excepting tannin. 374 VEGETABLE SUBSTANCES. When the impure acid obtained from the gall-nut by sublimation is exposed to a temperature of 35(P F. the mass enters into fusion and a volatile matter passes over and condenses on cool surfaces in the form of delicate long scaly crystals. These constitute the Pyrogullic acid of Braconnot. PREPARATION. Pure gallic acid may be obtained, according to Dq- bereiner, in a few minutes by the following process : A concentrated decoction of gall-nuts, mixed with a little acetic acid to decompose the gallate of lime, is shaken for one minute with a quantity of ether. The gallic acid is taken up by the ether, and by spontaneous evapora- tion on a watch glass is obtained in small colourless prisms. If longer digested, the liquid separates into three portions. The lightest con* tains the gallic and acetic acids, if the latter be present in excess ; the next, an ethereal solution of tannin ; and the heaviest, the water and extractive matter. The salts of gallic acid, called Gallates, have been imperfectly ex- amined. The gallates of potassa, soda, and ammonia, are soluble in water ; but most of the other gallates are of sparing solubility. On this account many of the metallic solutions are precipitated by gallic acid. REFERKNCES. B. La Grange s fids towards a history of Gallic Acid, containing a nofic? of various processes for obtaining it, and of sew if t) t e Gallates, Ann. de Chim. or Reperl. of Arts. Zd ser ii. 227, 28 >. Thenard, Traite de Chim. iii. f>53. Berzelins, Ann. of Phil, v 17<\ Ellagic Add Exists, according to Braconnot, along with the gallic acid, in infusion of galls, but its characters have been but imperfectly examined. Its name is derived from the word guile, reversed. See Vauquelin, Ann. de (.him. ct de Fhys. xxxvii. 175. Thcnard, Traite dc Chim. iii. C55. The remaining vegetable acids are arranged alphabetically. Aspartic Add. Discovered and its properties investigated by M. M. Henry and Plisson, in 1829. A white powder consisting of minute crystals, having a slightly acid taste, arid reddening the infusion of litmus. Obtained by mixing acetate of lead with the juice of the shooty of asparagus, washing the insoluble salt which is produced, mixing it with water, decomposing by a current of sulphuretted hydrogen gas, and evaporating the solution. Thomson s ln.org. them. ii. 100. Bidetic Acid Discovered by Braconnot in the Holetus Pscudo-igni- arius. It is in the fortn of prismatic crystals ; reddens litmus, and unites with some bases. Braconnot on Boletic Add and the Boletatcs, Ann. of Phil. ii. 469. Camphoric Add. Obtained from camphor by repeated distillations with nitric acid. It assumes the form of plumose crystals, has a sour and somewhat bitter taste, and an aromatic odour ; reddens litmus ; is very sparingly soluble in cold water more so in hot ; is very solu- ble in hot alcohol ; when thrown upon coals is completely exhaled in the form of thick, white and aromatic fumes. For Licbig's expwimmts on the composition of this add. sec J< vr. of the Roy. Jnst. ii. 630. Bu- cholz on Camphoric Acid and the Camphor ates, Ann. of Phil. ii. 313. Carbazotic Acid. Obtained by the action of nitric acid upon indigo- or silk. When pure this acid is in the form of brilliant crystalline plates, of a yellow colour ; is soluble readily in alcohol and ether, but sparingly soluble in cold water ; is fused and volatilized by heat, with- VEGETABLE SUBSTANCES. 375 out decomposition, but when suddenly exposed to strong heat, in- flames without explosion, and burns with a yellow flame ; reddens lit- mus paper, and is extremely bitter. Brandes Jour. N. S. ii. 210, and ill. 490, ichere several compounds of this acid, icith bases, are also described. Chloroxalic Acid. When crystallizable acetic acid is put into a glass vessel full of dry chlorine, and exposed for a day to bright sunshine, muriatic acid gas is generated, and during the night chloroxalic acid is deposited in dendritic crystals or small rhombic scales. Jn order to ob- tain it pure, the chlorine should be in excess, and the gases subsequent- ly expelled from the flask by dry air. The new acid is very volatile and deliquescent, and when evaporated in vacua yields rhombic crys- tals. Dumas. Caincic Acid Discovered by Pelletier and Caventou in the cainca root Chiococca racemosa, to which the medical properties of the root are supposed to be owing. It may be prepared by acidulating by mu- riatic acid a very concentrated decoction of the root ; and allowing the liquor to repose for several days, when the acid gradually crystallizes. Bcrzc.lius, Traite dc Chirn. v. 99. Cramtric Acid, is obtained according to M. Peschier, fronfthe astrin- gent root of the Crameria triandra. Ann. dc, Chim. Croconic Acid. The gray flaky substance which deposits in cool ves- sels during the preparation of potassium from cream of tartar, when treated with water, becomes red, and on exposure to the air a reddish yellow solution is formed, which by gentle evaporation yields croco- nate of potassa in crystals of the same colour as the solution : the residual liquid contains bicarbonate and oxalate of potassa. In order to separate croconic acid, these crystals, purified by a second crystal- lization and reduced to fine powder, are put into absolute alcohol to which sulphuric acid of the specific gravity 1-78, in quantity insuffi- cient for combining with all the alkali of the croconate, is added. The mixture is gently warmed during several hours, and frequently shaken, until a drop of the solution, mixed with muriate of baryta, causes no turbidity. The yellow alcoholic solution of croconic acid is then sepa- rated from sulphate of potassa by filtration, and the acid obtained by expelling the alcohol. By solution in water and spontaneous evapo- ration, croconic acid yields transparent prismatic crystals of a yellow colour, which are inodorous, have an astringent taste, redden litmus, and neutralize alkaline bases ; the acid as well as its salts are decom- posed at a high temperature, giving a deposit of charcoal. According to the analysis of Gmeliri, the discoverer, this acid consists of 5 atoms carbon -}-4 atoms oxygen. Gmelin's Handbuch. Turner's Ghent. 4th ed. Igasuric Acid Discovered by Pelletier and Caventou, in combina- tion with strychnine, in the SfryrJmos Ignatii, and Strychnos Nux Vomica, though its existence, as different from all other acicte, is doubt- ful, [t closely resembles the meconic acid, but does not, like that, produce a red colour when added to salts of iron ; crystallizes in small hard crystals ; has an acid and very styptic taste ; is soluble in water and in alcohol. Ann. de Chim. etdc Phys. x. 142. Urc's Chem. Diet. 56. Itidigotic Acid First described by Chevreul, and is obtained by the action of nitric acid upon indigo. It appears to be distinct from the carbazotic acid formed by a similar process. Kinic Acid, is found in the bark of the Cinchona ; it is difficultly crystallizable ; has a very acid taste, but when pure wholly destitute of bitterness ; reddens litmus permanently ; is very soluble in water ; 376 VEGETABLE SUBSTANCES. is not altered by exposure to air, and forms no precipitates with the salts of mercury, lead or silver. Vauquelin, in Ann, de Chim. lix. 162. Henry, ii. 256. Laccic Acid Obtained from the White Lac of Madras, by Dr. John* It occurs in crystals of a wine-yellow colour ; has a very sour taste ; is soluble in water, alcohol and ether ; forms white precipitates in so- lutions of lead and mercury, but has no effect upon lime-water, nor the nitrates of silver and baryta. It should in strictness be classed among the animal acids. A full account of the properties of this acid and of the substance that affords it, may be found in Dr. Pearson's paper, in the Phil. Trans. 1794. Lactucic Acid Discovered by Pfaffin the juice of the Lncluca Virosa. It is obtained by precipitating the clarified juice by sulphate of copper or acetate of lead, washing the precipitate and decomposing it by sul- phuretted hydrogen. By the evaporation of the liquor the lactucic acid is deposited in colourless crystals. It closely resembles oxalic acid, but differs, in producing an abundant green precipitate in solutions of the neutral salts of iron, and a brown precipitate with the solution of sulphate of copper. Berzelius, Traite dc Chim. v. 97. Meconic Acid. This acid is found in opium, combined with mor- phine. It occurs in crystals of various forms, which fuse at 212 F., and sublime without decomposition ; reddens litmus ; is very sour ; is soluble in water and alcohol ; produces an intense red colour with so- lutions of the peroxide of iron, without causing any precipitation. For a good account of Meconic Acid, and the Meconiates, see Ure's Chem. Diet. 4th ed. Dr. Hares process for obtaining the acid will be found in Sill. Jour. xii. 293. MtUitic Acid. Found in a rare substance called Honey-stone, occa- sionally met w r ith in Thuringia. in Germany. It crystallizes in hard prisms, or in fine needles, forming sometimes by their re-union, a glo- bular mass ; has a taste first sour and then bitter ; is not very soluble in water ; when placed upon a hot metallic plate it gives off gray fumes which are without odour. Ures Chem. Diet. Moric or Moroxylic Add Discovered by Klaproth, and combined with lime, exists in the bark of the Morus Alba, L., or white mulberry. It crystallizes in fine needles ; has the taste of succinic acid ; reddens litmus ; is not altered by exposure ; is soluble in water and alcohol ; and when heated in a retort is partly decomposed. Klaproth, in Nich- olson's Jour. vii. 129. Henry, ii. 253. Mucic or Saccholactic Acid Discovered by Scheele in 1780. and ob- tained by the action of nitric acid upon gum, manna and the sugar of milk. When pure this acid occurs in the form of white crystals ; has a slightly acid taste, and reddens litmus feebly ; is soluble in sixty times its weight of boiling water, and insoluble in alcohol ; when heated it is decomposed, and yields a volatile white substance, which has been called Pyro-mucic Acid. On this acid and the Mucates, see The- nard, Traite de Chim. iii. 701. Pectic Acid. This acid is found in all vegetables ; it occurs in the form of a colourless jelly ; has no odour, and a slightly acid taste ; is nearly insoluble in hot water as well as cold ; possesses the remarka- ble property of gelatinizing large masses of sugar. It was discovered by Braconnot, though it is still somewhat doubtful whether it is a dis- tinct acid. Bmcomwt, in Ann. de Chim. et de Phys. xxviii. 173. xxx. VEGETABLE SUBSTANCES. 377 96. Thcnard, Traite de Ckim. iii. 669. Dr. Torrey on the Pectic Acid, and its identity with Sclerotin, N. Y. Med. and Phys. Jour. vi. 481 . The Phosphoric and Hydrocyanic rfcids are also found in vegetables. The former in all the varieties of grain, in combination chiefly with potassa and lime. The latter may be distilled from bitter almonds, from the leaves of the laurel, &c. Saussure, in Nicholson's Jour. xxv. 279. Vauquelm, Jinn, de Chim. xlv. 206. Suberic Acid. Formed by digesting cork in nitric acid. When pure it is a white powder ; has a feeble taste, and has little action on lit- mus ; is sparingly soluble in cold water, very much so in boiling water; exposed to gentle heat it melts like fatty matter. Thenard, Traite de Chim. iii. 714. Succinic Acid. Obtained by distillation from amber. When perfect- ly pure it is white, transparent, and crystallizes in prisms ; has a sour and somewhat acrid taste, and reddens litmus ; is not altered by ex- posure ; is sparingly soluble in water ; when exposed to heat it fuses, undergoes decomposition, and in part sublimes, emitting a very pecu- liar and characteristic odour. The compounds of this acid with bases, called Succinates, have been but little examined. The Succinate of Ammonia, easily formed by the direct union of its elements, is employed for separating iron from man- ganese, the succinate of the peroxide of iron being quite insoluble in water, provided the solutions are neutral. The succinate of manga- nese, on the contrary, is soluble. Berzelius, Ann. of Phil. ix. 108. John, same icork, xv. 388. Ulmic Acid. The substance formerly called Ulmin, and shown to be a distinct acid by Boullay in 1830. It exists ready formed in bark, and makes its appearance in a variety of vegetable decompositions. It constitutes the essential ingredient of peat and of umber, and what is usually called vegetable manure. Ann. de Chim. et de Phys. xliii. 273. Valerianic Acid Discovered by Grote in the root of the Valeriana officinalis. It is colourless, oleaginous has an acid, piquant odour. It combines with bases and forms Valerianates , which are distinguished by a peculiar sweetish taste. Zumic Acid Discovered by Bracconnet in several vegetable substan- ces which have undergone the acetous fermentation. It appears from the observations of Vogel to be the lactic acid. Ann. of Phil. xii. SECTION II. VEGETABLE SAL1FIABLE BASES OR ALKALIES. Under this head are classed all those proximate vegetable princi- ples capable of uniting with acids, and of forming with them saline compounds. The existence of this class of bodies was discovered by Sertuerner, in 1805, but they excited no attention until about 1816. Since that time this department has been cultivated with much success by seve- ral chemists, but especially by M. Robiquet, and M. M. Pelletier and Caventou. The vegetable alkalies, according to the researches of Pelletier and Dumas, consist of carbon, hydrogen, oxygen and nitrogen. [Ann. de Chim. et dc Phys. xxiv.] They are all solid, white, bitter or acrid, 378 VEGETABLE SUBSTANCES. without odour, heavier than water, and mostly crystalline ; they change vegetable blues to green ; are insoluble, or nearly so, in cold water, but soluble in alcohol, especially if hot ; most of them are poi- sonous, and many are valuable in medicine. These substances aie never found in a free state in plants, but ap- pear in every case to be combined with an acid, forming a salt, more or less soluble in water. And the process for separating them which is generally applicable, is to digest or macerate the substance contain- ing the alkali, in a large quantity of water, and to add to the solution a more powerful salifiable base, as potassa, soda or ammonia, or to boil it for a few minutes with pure lime or magnesia. The vegetable alkali being thus separated from its union with the acid, and being in- soluble in water, is precipitated. This precipitate, mixed with some animal charcoal, is then dissolved in hot alcohol, and the solution fil- tered while hot and evaporated ; arid the pure alkali is thus obtained. According to Serullas, the vegetable alkalies may be precipitated by iodic acid, which he considers a very delicate test of their presence in solutions. Jinn, de Cliim. xlv. or Jour, of Ike Roy. Inst. ii. 615. Different opinions are still entertained concerning the nature of the vegetable alkalies. They may be reduced to the following : 1. That they combine with acids in the same manner as metallic ox- ides, and give birth to anhydrous salts composed of the two bodies in contact. This is the most generally received. 2. That they contain a certain quantity of ammonia to which they owe their powers as bases, and with which some organic matter is combined in the same way as many vegetable substances are united with sulphuric acid ; and that this substance enters with the ammonia into the salt formed. 3. That the vegetable alkalies like ammonia have the power of act- ing as bases only when combined with water ; in which case the pro- portions in which they saturate the acids depend upon the quantity of water. Or in other words, the vegetable alkalies considered in this point of view, only combine with the hydrous acids, and without set- ting at liberty the water contained in these acids. Bcrzdius, Traitc de Chim. v. 123. Morphine. This is the active principle of opium, (Papaver Somnifcrum , L.) in which it is combined with various other principles. It occurs in crys- tals of a brilliant lustre, which are mostly irregular six-sided prisms, with diedral summits, but the primary form of which, according to Brooke, is a right rhombic prism ; it is insoluble in cold, and sparingly soluble in boiling water; soluble in alcohol, and in solution intensely bitter ; has an alkaline reaction, and forms salts with acids, which are mostly capable of crystallizing. PREPARATION. Various processes have been proposed for separating this alkali. That of Robiquet, which is probably the best, is to boil the concentrated infusion of a pound of opium for a quarter of an hour with about 150 grains of pure magnesia. A grayish crystalline preci- pitate results, which consists ot meconate of magnesia, morphine, iiarcotine, colouring matter and the excess of magnesia. This pow- der is collected on a filter, edulcorated with cold water, and then di- gested at a temperature of 120 or 139 J F, in dilute alcohol, which ro- VEGETABLE SUBSTANCES. 379 moves the narcotine, and the greater part of the colouring matter. The morphine is then taken up by concentrated boiling alcohol, and is deposited in crystals on cooling. A convenient process, suggested by Dr. Thomson, is to precipitate the morphine by ammonia, and to purify it by solution in acetic acid, and digestion in animal charcoal, deprived of phosphate of lime by muriatic acid. Ann. of Phil. xv. 471. ACTION ON THE ANIMAL ECONOMY. It appears that notwithstanding the insolubility of morphine, it is the narcotic principle of opium. Direct experiments have sufficiently proved this. If for example, we make a solution of this substance in oil, we perceive violent narcotic effects, even in a small dose, such as a quarter or half a grain, but these are still more marked when the morphine is combined with acids, probably because its salts are more soluble than it is itself in an uncombined state. Salts of MorpJiine. These salts may be readily obtained by dissolving pure morphine in dilute acid and evaporating the solution. They have long been used for medicinal purposes, and are found to possess all the good qualities of opium, without its inconveniences. Muriate of Morphine Usually crystallizes in tufts of acicular crys- tals, which are neutral and anhydrous. It is obtained by the direct action of muriatic acid gas upon morphine, or by dissolving the alkali in dilute muriatic acid. The process employed by Dr. A. T. Thom- son is to decompose the aqueous solution of opium by muriate of ba- ryta, of which a quantity is used exactly sufficient for precipitating the ineconic acid. The muriates of morphine and narcotine are then sepa rated by crystallization. This salt has recently come into use in medi- cal practice in consequence of its being more uniform in its constitu- tion, than the other salts. [For a detailed account of the mode of preparing this salt, see Edin. Med. and Sitrg. Jour. Nos. 107 and lll.i Sulphate of Morphine, crystallizes in silky tufts, much resembling sulphate of quinine, from which it may be distinguished by its becom- ing red when heated with concentrated nitric acid. It may be obtain- ed by the direct union of sulphuric acid with morphine. Acetate of Morphine Obtained by dissolving morphine in acetic acid. In order to obtain it in the solid state, it must be evaporated to dry- ness. and in this process some of the acid is usually expelled. It is therefore necessary that it should be preserved in the form of solution, and care should be used that the acid is in excess. The compound called Black Drop, consists of opium combined with some vegetable acid, generally in an impure state. Those most com- monly used are the citric and acetic, combined with aromatics and sweet substances. ^REFERENCES. For affecting Ace fate cf Morphine when given for criinina purposes, a process has been described by M. Lasnaignf, for which see Aim. de Chim. et de Phys. xxv. 102, or Turner's Chem. 7f,8 See also Hare's Com pe7id. 206. For the medicinal preparations of Morphine and its Salts, see Magendie s Formulary, Carpenter on the Salts of Morphine, Chapman's Jvur. v 213. 380 VEGETABLE SUBSTANCES. Narcotinc. This substance, though not regarded as a vegetable al- kali,* may be conveniently noticed in connection with morphine. It dissolves in ether and alcohol, the latter, though diluted, acting as a solvent for it by the aid of heat ; and it crystallizes from its solutions in the form of fine needles or rhomboidal prisms ; ^t exerts no action on vegetable colours ', is without taste or smell. Narcotine is easily prepared by evaporating an aqueous infusion of opium to the consistence of an extract, and digesting it in sulphuric ether. From this solvent it may be obtained by evaporation, in the form of crystals. In the same manner morphine may be purified from narcotine. But an easier process is founded upon the property dis- covered by Duflos, that carbonate of potassa precipitates narcotine, but not morphine. The unpleasant stimulating properties of opium are attributed by Magendie to the presence of narcotine, the ill effects of which, ac- cording to the experiments of the same physiologist, are in a great degree counteracted by acetic acid. These results, though they re- quire confirmation, render it probable that the superiority assigned to the Black Drop over the common tincture of opium of the Pharmaco- poeia, is owing to the vegetable acids which enter into its composition. Some physicians, however, discard the medical distinctions gene- rally drawn between morphine and narcotine, and assert that denar- cotized opium or laudanum, in its effect, differs in no respect from common laudanum, except in being considerably weaker. See the views of Prof. Tully and others, in Silliman's Chem. ii. 491. Cinchonine. Discovered by Dr. Duncan jun. in 1803, though its alkaline nature was first settled by Pelletier and Caventou, in 1820. It exists in the Cinchona condaminea, or pale bark, combined with kinic acid. It is white and crystalline, requires 2,500 times its weight of boiling water for solution, and is insoluble in cold water ; is soluble in boiling alco- hol, and in small quantity in oil and ether ; has a bitter taste, though scarcely sensible unless in solution ; it unites with all the acids, and forms salts. It is obtained by a process similar to that described for obtaining morphine. Edin. New Dispensary, \}th cd. 299. Both the Sulphate and Slcetate of Cinchonine are employed in medi- cine ; the first of these salts is very soluble in water, the second much less so ; but an excess of acid dissolves it readily. For a description of several salts of cinchonine. see Berzelius, Traits, de Chim. v. 164. Quinine. Discovered by Pelletier and Caventou. Exists, combined with kin- ic acid, in the Cinchona cordifolia, or yellow bark, and together with cinchonine in the Cinchona oblongifolia, or red bark. It is usu- ble in alcohol, forming a solution which is intensely bitter, and pos- * Berzelius, however, thinks narcotine should be ranked among 1 the vegeta- ble alkalies, because it possesses the property of combining with acids and forming salts, some of which are crystalline. Traite de Chim. v. 137. VEGETABLE SUBSTANCES. 381 sessing distinct alkaline reaction ; is also soluble in ether, but almost insoluble in water ; is distinguished from cinchonine by its habi- tudes with acids, and by the different properties which characterize its salts. Salfikate of Quinine. Though quinine combines with most of the acids, the form in which it is commonly exhibited is that of the Sul- phate. This salt, which consists of 90 parts of the alkali and 10 of the acid, crystallizes in delicate white needles, having the appearance of amianthus. It is less soluble in water than thj6 sulphate of cincho- nine, but is very bitter. It dissolves readily in Strong alcohol by the aid of heat, a character which affords a useful test of its purity. One grain of the sulphate of quinine, when pure, will render nearly a pound and a half of water sensibly bitter. See R. I hillips on the means of ascertaining the purity vf Sulphate of Quinine) Phil. Mag. and Jinn. hi. 111. The presence of cinchonine in the sulphate of quinine may be de- tected by the following method. A grain of the salt in fine powder is shaken with a dram of ether, and a dram of ammonia is added and the whole well shaken. If no cinchonine be present, the line of separation of the two fluids is clean ; if the smallest quantity be present, it is deposited in this line. Kindt, in Urandes Archiv. Johnston's Report. Strychnine. Discovered in 1818, by Pelletier and Caventou, in the fruit of the Strychnos ignatia and Strycknos nux vomica, in which it is combined with igasuric acid ; it has since been extracted by the same chemists from the famous Upas of Java. It occurs in the form of small four-sided prisms ; it is intolerably bitter, and leaves an impression on the or- gans of taste like that of some of the metallic salts ; has no smell, and is not changed by exposure to air ; it is nearly insoluble in water, re- quiring more than 6000 times its weight of cold, and 2500 of boiling water for solution ; has a distinct alkaline reaction and forms salts with acids, most of which are soluble in water. Pelletier and Caven- lou, in Ann. de Chim. ct. de Pkijs. x. and xxvi. Henry, in Jour, de Phar. viii. 401. Strychnine is one of the most virulent poisons hitheito discovered, and is the poisonous principle of the substance in which it is contain- ed. Its energy is so great, that half a grain blown into the throat of a rabbit occasioned death in the course of five minutes. Its operation is always accompanied with symptoms of locked jaw and other teta- nic affections. See Magendie and Christison on Poisons, 637. The salts of strychnine, in consequence of their greater solubility, are more active, and consequently more intensely poisonous than their base. They are, nevertheless, employed medicinally in small doses with decided advantage, Brucine. Discovered by Pelletier and Caventou, in the Brucea antidystnterica, and, in small quantities, also in the Strycknos nux vomica. It crys- tallizes in oblique prisms, the bases of which are parallelograms : in taste and poisonous qualities, it is very similar to strychnine, but is twelve or sixteen times less energetic than that alkali ; it is soluble Y 3S2 VEGETABLE SUBSTANCES. both in hot and cold alcohol, especially in the former ; and it crystal- lizes when its solution is evaporated ; is soluble also in dilute alcohol, by aid of heat, and on this property is formed the method of separat- ing it from strychnine ; it is more soluble in water than most of the other vegetable alkalies, requiring only 850 times its weight of cold, and 500 of boiling water for solution. Emetine. Discovered in 1817, by Pelletier, and is found in the Ccphaelis Ipe- cacuanha, Willd. and VioLi Jpecncutmha. When pure it is white and pul- verulent, and not deliquescent ; lias a bitter and disagreeable taste ; is sparingly soluble in cold, but more freely in hot water ; is insolu- ble in ether, but readily soluble in alcohol ; has a distinct alkaline re- action, arid neutralizes acids, but its salts are little disposed to crystal- lize ; its effects appear to be neutralized by decoction of galls. Ma- gendie's Formularly, 40. It is to this principle that ipecacuanha owes its emetic properties. Veratrint. This alkali, discovered by Pelletier and Caventou, in 1819, exists combined with gallic acid, in the seeds of the Veratrum sabadilla, Itetz, and the roots of Vcnitrum album, L or white hellebore ; and Col- chicum autumnale, L. or meadow saifron. It is white, pulverulent, inodorous, and of an acrid taste ; requires 1000 times its weight of boiling, and still more of cold water for solui on ; is very soluble in alcohol, and may also be dissolved, though less readily, by means of ether ; has an alkaline reaction, and neutralizes acids, but it is a weaker base than morphine, quinine or strychnine ; it acts with singu- lar energy on the membrane of the nose, exciting violent sneezings though in very minute quantity ; when taken internally in very small doses, it produces excessive irritation of the mucous coat of the stomach and intestines, and a few grains were found to be fatal to the lower animals. Jour, de Phar. vi. Mugendies Formulary, 61. . , l Sangitfaarine. Discovered by the late professor Dana, of New-York, in the root of the Sanguinaria canadensis, L. or blood root. It usually occurs in the form of a soft, white powder ; but by the spontaneous evaporation of an alcoholic solution may be obtained in masses which exhibit a crys- talline structure ; has no odour, but a taste bitter and afterwards acrid ; changes the blue of litmus to green, the yellow of turmeric to brown ; combines with acids and forms neutral salts of a red colour. See Dana, in N. Y. Med. and Phys. Jour. vi. 218, and Dr. Tully and Mr. A. A. Hayes, in SiUiman's Chem. ii. 503. According to Dr. Tully the medicinal virtues of blood root reside in this principle, and are not impaired by combination with acids. It is medicinally deobstruent, acrid, narcotic and emetic.- See Professor Tally's Prize Dissertation on Sanguinaria, in the American Med. JRecor der, xiii. V VEGETABLE SUBSTANCES. 383 The remaining vegetable alkalies are arranged alphabetically. Atropine. Discovered by Brandes, in the Atropa belladonna, L. ot deadly nightshade. When pure it is snow-white, when impure yel- lowish ; it has no taste ; is almost insoluble in cold water, except when recently precipitated; it neutralizes acids and forms salts, the watery solutions of which give out by evaporation, vapours which dilate the pupil of the eye and produce violent headache, nausea and giddiness. See Ur&s Chem. Diet. It.k cd. 181. Buxine Announced by Foure as an alkali existing in the box, Ruxus sempcrvirens. It has a bitter taste ; is insoluble in water, but soluble in alcohol and in small quantity in ether. Berzelius, v. 191. Corydafine. Discovered by M. Wackenroder, in the root of the Fu- maria cava, Mil. and (lorydafotubcrosa, De Cande. Ft is obtained from its alcoholic solution in the form of colourless prismatic crystals; it acts as an alkali upon vegetable colours, and combines with acids, forming extremely bitter salts its nitric solution becomes, when heat- ed and concentrated, of a blood-red colour. Phil. Mug. and Ann. iv. 151. Crotonine. Exists according to Brandes in the seed of the Croton tiglium. Bcrzelius, v. 190. Curarine A basis discovered by Boussingault and Roulin, in a matter which the natives of South America employ in poisoning their arrows, and which they call curara or urarL Prepared according to the process of Pelletier and Petroz, it is an uncrystallizable yellowish mass, which has a very bitter taste, and deliquesces upon exposure to the air. It forms neutral salts with the acids. Its poisonous effects are more decided than those of the curara from which it is obtained. Berzclius, v. 181. Cynapine. Discovered by Professor Ficinus of Dresden, in the Aetllusn Cynapium, or lesser hemlock. It is crystallizable, and soluble in water and alcohol, but not in ether. The crystals are in the form of a rhombic prism, which is also that of the crystals of the sulphate. Turner. Daphnine. A basis discovered by Vauquelin in the Daphne Mezcrium. Daturine. Obtained by M. Brandes, from the Datura stramojiium, L. It is similar to atropine, and perhaps indentical with it. Delphine or Delphinine. Discovered by MM. Feneulle and Las- saigne in the Delphinium stnphysagria, L. or Stavesacre. It is in the form of a white powder, crystallizing when moist, but becoming opaque by exposure to dry air ; it has no smell, but a taste at first bitter and afterwards becoming acrid ; is sparingly soluble in water, but freely so in alcohol and ether ; it combines with many acids and forms neutral salts, whose taste is extremely bitter and acrid ; it is precipitated by alkalies in the form of a white jelly. Ann. de Chim. tt de Phys. xii. Mtigendie. Digitaline. Extracted, by M. Le Royer, from the leaves of the Di- gitalis pur pur ea, L. or foxglove. It is a brown, pasty substance, slowly restoring the blue colour of reddened litmus , very bitter and very deli- quescent ; it is difficultly crystallizable ; but seems capable of crys- tallizing from its alcoholic solution ; it combines with acids, and has great activity on the animal system. Brandos Jour, xviii. 178. 384 VEGETABLE SUBSTANCES. Essenbcckine. A supposed basis discovered by Buchner. in Essen- beckia febrifuga. It has a bitter taste like quinine. Berzelius, v. (90. Eupatorine. A basis discovered by Riphini in the Eupatoriujn can- nauinum. Bcrzelius, v. 192. Hyoscyamine. Extracted by Brandes, from the Hyoscyamusniger, L. or black henbane ; it crystallizes in long prisms, is not easily altered in a high temperature, even when heated to redness with charcoal; when saturated with sulphuric or nitric acid forms very characteristic salts. -Ann. of Phil. xvi. 69. Nicotine. The active principle of tobacco Nicotiana tabncum. It is a volatile alkali. Its solution is colourless ; has the peculiar smell of tobacco, and occasions violent sneezing ; has an acrid taste, and pos- gesses poisonous qualities. ( VauqiLelin, in dim. de Cliim. Ixxi. 139.) Berzelins describes several salts of nicotine. Solanine. Discovered by Desfosses. and exists combined with malic acid in the berries of the Solanum vign/jn, L. and in the leaves of the Solunuin dulcamara, L. When pure it occurs in the form of a white, opaque, and sometimes pearly powder; it has no smell, but a slightly bitter and nauseous taste ; is insoluble in cold water, very sparingly soluble in hot, and slightly so in alcohol ; acts faintly on turmeric, but unites with acids and forms neutral salts, which, however, are mostly uncrystallizable. Jour, de Phar. vii. and viii. Nagcndics Form. 79. According to Magendie this alkali, like opium, may produce vomit- ing and sleep, but its emetic powers seem to be more decided, while its narcotic properties are less so than those of opium. Vinline. A vegetable alkali, thought to exist in the Viola odorata' It has properties analogous to emetine and may be extracted from the root, leaves, flowers arid seeds of the plant. Jour, of P liar. Jan. 1824. Urc's Dictionary. Substances somewhat allied to the preceding^ but not alkaline* Amygdatin. A substance extracted in 1830 by Robiquet and Bou* tron Charlard from the bitter almond. Ann. de Cltim. tt de Pnys* xliv. 352. Asparagin. Discovered by MM. Vauquelin and Robiquet, in the juice of the asparagus. It is deposited by evaporation in crystals, having the form of a rectangular octahedron, six-sided prism or right rhombic prism ; has a cool and slightly nauseous taste ; is soluble in water, and has neither an acid nor alkaline reaction. Ann. de (.him* Ivii. 88. Bafisnrin was first noticed in gum bassnra by Vauquelin. Accord- ing to Gehlen arid Bucholz. it is contained, together with common gum, in the gum tragacanth ; and John found it in the gum of the cherry tree. Salep, from the experiments of Caventou, appears to consist almost totally of bassorin. It is characterized by forming with cold water a bulky jelly, which is insoluble in that menstruum, a weil as in alcohol and ether; is not soluble in boiling water, except by long continued ebullition, when the bassorin at length disappears, and is converted into a substance similar to gum arabic. Ccffcin was discovered in coffoe by M. Robiquet in 1821, and wa* VEGETABLE SUBSTANCES. 385 soon after obtained from the same source by Pelletier and Caventou, without a knowledge of the discovery of Robiquet It is a white crys- talline volatile matter, which is soluble in boiling water and alcohol, and is deposited, on cooling, in the form of silky filaments, like amian- thus. It does not affect the vegetable blue colours, nor combine with acids. Jour. de Phar.for May, 18*26. Catkardn. The name has been applied by MM. Lassaigne and Feneulle to the active principle of senna. It is uncrystallizable, of a bitter nauseous taste, reddish yellow colour, and soluble in water and alcohol. Jinn, de Chirn et de Phys. xvi. Cklorophyle. k. name applied by Pelletier and Caventou to the green colouring matter of leaves. It is prepared by bruising green leaves in- to a pulp with water, pressing out all the liquid and boiling the pulp in alcohol. The solution is mixed with water, and the spirit driven off by distillation, when the chlorophyle is left floating on the water. Colocyntin. This name is applied by Vauquelin to a bitter re^inoui matter extracted from colocynth, and to which he ascribes the proper- ties of this substance. Brandes Jour, xviii. 400. Columbin. Obtained from the Columbo root by M. Wittstock. It occurs in colourless prismatic crystals ; is extremely bitter, inodorous, and without effect on vegetable colours ; is soluble in about 30 or 40 parts of boiling alcohol, less so in cold alcohol, ether and water, yet the solutions are intensely bitter ; is decomposed by nitric, sul- phuric arid muriatic acids, as well as by intense heat, without evolu- tion of ammonia. Jour, of the Royal Institution, ii. 631. Condn. the active principle of the Conium w^cuhitum, L., extract- ed by MM. Brandes and Geiseke, half a grain of which is said to hav proved fatal to a rabbit, the symptoms being the same as those produc- ed by strychnine. Brand.es Jour. JV. . iii. 227. Cytisin. A bitter purgative extractive matter similar to cathartin, found by Lassaigne and Chevalier in the Cytisus alpinus. Dahlin is found in the Dahlia, or Georgia of botanists, and in the Hduintlms tuherosus, L. or Jerusalem artichoke. It is a white pul- rerulent substance, more soluble in hot than in cold water, arid inso- luble in alcohol ; appears to have most analogy with starch and inulin. Ijttyen,, Ann. de Chun, et de l j hys. xxiv 209. Henry, ii. 353. Dracin. A principle obtained from the gummi-resinous substance called Drngon's Blood, which has a slight affinity to the vegetable al- kalies. Melandri, in Phil. Mug. and Ann. ii 394. Henry, ii. 363. Fungin. This name is applied by M. Braconnot to the fleshy sub- stance of the mushroom. It is procured in a pure state by digestion in hot water, to which a little alkali is added ; is nutritious in a high degree, and in composition is very analogous to animal substances ; like (lesh, it yields nitrogen gas when digested in dilute nitric acid. Gentianin Obtained from the Geniiana lutea or gentian, about the game time, by M. Henry and M. Caventou. It is yellow, inodorous, possessing strongly the aromatic bitterness of the gentian, more de- cidedly so however, when it is dissolved in an acid ; it is highly solu- ble in ether and alcohol, from which it may be separated in the form of very small, yellow, needle-like crystals : does not sensibly change the colour of litmus when blue, or when reddened by acids, being ap- parently neutral ; it does not possess any poisonous qualities. Ma~ gendies Formulary, 83. 386 VEGETABLE SUBSTANCES. Hematin. The colouring principle of the H&mntoxylon campcrkian- um, or logwood. It occurs in small brilliant crystals, of a reddish- white colour, and slightly bitter, astringent and acrid taste ; soluble in boil- ing water, to which it gives an orange red colour. Chcvreul, Jinn, de Ckirn. Ixxxi. 129. Brundes Jour. xx. 389. Imperatorin. A crystalline principle resembling piperin, discovered by Osann in the root of the Impcraloria Ostruthium. Jtiulin is a white powder like starch, which is spontaneously deposit- ed from a decoction of the roots of the Imila htlenium or elecampane; is insoluble in cold, and soluble in hot water, and is deposited from the latter as it cools, a character which distinguishes it from starch. With iodine it forms a greenish-yellow compound of a perishable na- ture. Its solution is somewhat mucilaginous; but inulin is distin- guished from gum by insolubility in cold water, and in not yielding the saccholactic acid when digested in nitric acid. Legumin is exti acted from the pulp of ripe peas, by steeping in hot water. It is white, and when dried semi-transparent ; forms a mucil- age with tartaric acid ; soluble in all alkalies and their carbonates. Einhof, in Ann. de Chirn et de Phys. xxiv. 209. Henry, ii. 353. Liriodendrin Discovered in the bark of the Liriodendron tulipi- fera, or American tulip-tree, by Professor J. P. Emmet, of Virginia. When obtained from the alcoholic solution by spontaneous evapora- tion, it crystallizes in triangular and rhomboidal plates, interspersed with plumose or stellated prisms ; some are perfectly limpid, others have the micaceous appearance of boracic acid ; in this state it freely dissolves in alcohol; when gently heated the crystals fuse, slightly effervesce (owing to the escape of water,) and then become olive co- loured, without any appearance of crystallization on cooling; in the fused state the alcoholic solution is always olive green, and scarcely gives any indication of a regularly formed deposition, unless the al- cohol employed is dilute. The alcoholic solutions of both varieties possess an intensely bitter taste, but always leave the impression of heat upon the tongue. The crystallized substance is solid, brittle and inodorous at 40, fu- sible at 180-\ and volatile at 270 F. ; it is not acted on by weak acid or alkaline solutions, but is dissolved by concentrated sulphuric and ni- tric acid. According to Dr. Emmet, the properties of this substance appear to place it with camphor as a connecting link between the re- sins and volatile oils. Journal of the. Pliilftdtlphia College of Phar- macy. Lupnlin.A name given by Dr. Ansel W. Ives. to the active princi- ple of the Hnmulns lupiiltts, or common hop. It is contained in all parts of the plant, but chiefly in the female flowers. Silliman's Jour. ii. 302. Madrtrin. An extractive matter obtained by Dr. Duncan from the Ca lop I ris Madari i . M& Jut fin. This name was applied by John to the pith of the sun- flower, but its existence as an independent principle is somewhat du- bious. The term pnllenin has been given by the same chemist to the pollen of tulips. Ann. of Phil. vii. 49. Olimle. When the gum of the olive tree is dissolved in alcohol, and the solution is allowed to evaporate spontaneously, a peculiar sab- itance, apparently different from the other proximate principles hith- VEGETABLE SUBSTANCES. 337 erto examined, is deposited either in flattened needles or as a brilliant amylaceous powder. To this M. Pelletier, its discoverer, has given the name of Olivile. Ann. of Phil. xii. Paraffin and Eupion. Two substances discovered by Reichenbach, in the products of the distillation of vegetable and animal substances. Picrotoxin Obtained by M. Boullay from the fruit of the Cocculus suberosus and C. Plukenetti of Decandolle. It occurs in four-sided prisms, of a silky lustre ; it is inodorous but very bitter ; has no alkaline re- action, nor does it neutralize acidity ; it combines, however, with acids, and with the acetic and nitric acids forms crystallizable com- pounds. See M. Casaseca, in the Edm. Jour, of Science, v. 184, who xhoics that this canaot be ranked among the alkalies. Piperin is the name which is applied to a white crystalline substance extracted from black pepper. It is tasteless, and is quite free from pungency, the stimulating property of the pepper being found to re- side in a fixed oil. [Pelletier, in Ann. de Chim. et de Phijs. xvi. Car- penter, Sill. Jour. xiii. 334.] Dr. A. T. Thomson has extracted it from chamomile flowers. Turner. Plumhagin, extracted by Dulong from the root of the Plumbago Eu- ropcta, is soluble in water, alcohol and ether, and crystallizes from its solutions in acicular crystals of a yellow colour. Its aqueous solution is made cherry red by alkalies, subacetate of lead, and per-muriate of iron ; but acids restore the yellow tint, and the plumbagin is found un- altered. Its taste is at first sweet, but is subsequently sharp and acrid, extending to the throat. Brandes Jour. N. S. vi. 191. Polychroitc The colouring matter of the saffron. It is of a deep yellow colour, deliquescent, readily soluble in water, but insoluble in pure sulphuric ether. Henry, ii. 357. M. Henry of Paris, attributes any medicinal activity of saffron to a volatile oil combined with the colouring matter. Populin A substance found by Braconnot in the bark of the Popu- lus trcmula, analogous in properties and composition to Salicin, if not identical with it. Rhubarbarin is the name employed by Pfaff to designate the princi- ple in which the purgative property of the rhubarb resides. M. Nani of Milan, regards the active principle of this plant as a vegetable al- kali ; but he has not given any proof of its alkaline nature. Brande's Jour. xvi. 172. Salicin. A peculiar compound obtained by M. Leroux from the bark of the Salix alba, L. or white willow. It is a perfectly white body which crystallizes in acicular prisms ; has a very bitter taste ; is solu- l)le in about '20 parts of water at 6(P, more soluble in hot, and to al- most any extent in boiling water ; is soluble also in alcohol, but not in ether, nor in any of the essential oils, except, perhaps, the oil of turpentine ; when treated with sulphuric acid it assumes a fine red colour, perfectly resembling bichromate of potassa; with nitric acid it forms colourless solutions. Pelouze and J. Gay Lussac, in Phil. Mag. and Ann. viii. 303. From the trials which have been made with this substance in France, it appears to possess febrifuge powers scarcely inferior to those of the sulphate of quinine. Gay Lussac and Magendie, who were appointed by the Academy of Sciences to examine the memoir of Leroux, conclude their report by 388 VEGETABLE SUBSTANCES. stating, that this discovery is, without contradiction, one of the most important that has been made for many years in pharmacentical chem- istry. Ann de Chim. xliii. 440, or Jour, of the Royal Institution, i. 178. Sarcocoll is the concrete juice of the Penctn sarcocotta, a plant which grows in the northern parts of Africa. It is imported in the form of small grains of a yellowish or reddish colour like gum arabic, to which its properties are similar. It has a sweetish taste, dissolves in the mouth like gum, and forms a mucilage with water. It is distinguish- ed from gum by its solubility in alcohol, and by its aqueous solution being precipitated by tannin. See Thomson s Chemistry. ScMitin. A crystalline principle discovered by Vogel in the Scilla maritima. Suberin. This name has been applied by M. Chevreul to the cel- lular tissue of the common cork, the outer bark of the cork-oak, (Qutr- cus suber,) after the astringent, oily, resinous, and other soluble mat- ters have been removed by the action of water and alcohol. Suberin differs from all other vegetable principles by yielding the suberic acid when treated by nitric acid. Tiglin. The active principle of Croton-tigllum soluble in alco- hol. Brandes Jour. xx. 331. Ulmin See Ulmic Acid, p. 377. Zanihropicritc Extracted from the bark of a species of Zanthoxi- lum. It forms groups of greenish-yellow crystals, in silky divergent needles ; soluble in water and in alcohol, but not in ether ; it is dis- tinguished by the circumstance, that solution of gold gives with it a precipitate which is quite insoluble in alcohol and in liquid ammonia. Chevftllier and Pclleticr, in jinn, de Chim. et de Phys. Feb. 1827. Henry, ii. 362. Bitter Principle This name was formerly applied to a substance sup- posed to be common to bitter plants, and to be the cause of their pe- culiar taste. The recent discoveries in vegetable chemistry, however, have shown that it can no longer be regarded as a uniform unvarying principle. The bitterness of the nux vomica, for example, is owing to strychnine, that of opium to morphine, that of cinchona bark to cin- chonine and quinine, &c. The cause of the bitter taste in the root of the squill is different from that of the hop or of gentian. The term bitter principle, when applied to any one principle common to bitter plants, conveys an erroneous idea, and should therefore be abandoned. Turner. Extractive Matter. This expression, if applied to one determinate principle supposed to be the same in different plants, is not less vague than the foregoing. It is indeed true that most plants yield to water a substance which differs from gum, sugar, or any proximate principle of vegetables, which, therefore, constitutes a part of what is called an extract in pharmacy, and which, for want of a more precise term, may be expressed by the name of retractive. It must be remembered, how- ever, that this matter is always mixed with other proximate principles, and that there is no proof whatever of its being identical in different plants. The solution of saffron in hot water, said to afford pure ex tractive matter by evaporation, contains the colouring matter of the plant, together with all the other vegetable principles of saffron, which happen to be soluble in the menstrum employed. Turner. VEGETABLE SUBSTANCES. 389 SECTION III. SUBSTANCES WHICH, IN RELATION TO OXYGEN, CONTAIN AN EX- CESS OF HYDROGEN. Oils. Oils are characterised by a peculiar unctuous feel, by inflammabili- ty, and by insolubility in water. They are divided into the fixer' and volatile oils, the former of which are comparatively fixed in the fire, and, therefore, give a permanently greasy stain to paper ; while the latt-r, owing to their volatility, produce a stain which disappears by gentle heat. Fixed Oils. The fixed oils are usually contained in the seeds of plants, as for example, in the almond, linseed, rapeseed, and poppy seed ; but olive oil is extracted from the pulp which surrounds the stone. They are procured by bruising the seed, and subjecting the pulpy matter to pressure in hempen bags, a gentle heat being gene- rally employed at the same time to render the oil more limpid. Fixed oils, the palm oil excepted, are fluid at common temperatures, are nearly inodorous, and have little taste; are lighter than water, their density in general varying from 0*9 to 0-96 ; they are mostly of a yellow colour, and can be rendered nearly or quite colourless, by animal charcoal ; boil at or near 600 ^ F. suffering partial decomposi- tion at the same time, an inflammable vapour being disengaged even below 500 ^ ; they burn in the open air with a clear white light, and are hence employed for the purpose of artificial illumination. By ex- posure to the air, these oils become rancid, in consequence of the acid- ification of the mucilaginous matters which they contain ; they grad- ually also lose their limpidity, and some of them, called on this ac- count drying oils, become so dry that they no longer feel unctuous to the touch, nor give a stain to paper. This property, for which linseed oil is remarkable, may be communicated quickly by heating the oil in an open vessel. The drying oils are employed for making oil paint, and mixed with lampblack constitute printer's ink. Fixed oils do not unite with water, but by the aid of sugar or mu- cilage may be suspended in it, so as to constitute an emulsion; they are sparingly soluble in alcohol and ether ; are thickened by sulphuric acid, and also by chlorine ; are acted on with great energy by nitric acid, giving rise, in some instances, to the production of flame; they unite also with the common metallic oxides, forming varnishes and plasters ; they are readily attacked by alkalies, with ammonia, forming a soapy liquid called rolutile /inament, with the fixed alkalies, soap, the inferior kind being made with potassa, and the hard with soda. The fixed oils and fats are not pure proximate principles, but consist of two substances, called by Chevreul, Stearine and Elaine; the for- mer of which is solid, and abounds in suet, butter and lard ; the latter is fluid, and is found in greater quantity in oils. These substances, however, entirely disappear in the formation of soap, being converted into three compounds, to which M. Chevreul has applied the names of Margaric and Oleic acids, and Glycerine. The two acids enter into combination with the alkali employed, and the resulting compound IB soap. A similar change appears to be effected by the action not cnlj of the alkaline earths, but of several of the other metallic oxides. 390 VEGETABLE SUBSTANCES. Soap is decomposed by acids, and by earthy and most metallic salts. On mixing muriate of lime with a solution of soap, a muriate of the alkali is produced, and the lime forms an insoluble compound with the margaric and oleic acids. A similar change ensues when a salt of lead is employed. From the analysis of Gay Lussac and Thenard it is probable that olive oil consists of 1 Ox. 8-f 11 Hyd. 11+10 Car. 60=79. REFERENCES. The Memoirs of AI. Chevreul are published in the Ann. de Ckim. et de Phys. of which the reader will fin.d an abstract in Vre^s Client. Diet. 4ih e.d. articles Elain and Fat. Lewis 1 Philosophical Commerce of the Arts, contains a history of Pt inters Ink. On Soap, see Aikiifs Chem. Diet. Berzeliaa in his Trai. e de Chim, gives a very elaborate account of the fixed and volatile oils. Volatile or Essential Oik. These substances, to which aromatic plants owe their flavour, have a penetrating odour and acrid taste; are soluble in alcohol, though in different proportions ; scarcely soluble in water ; they are volatilized at a heat below 212 F. by which they may be distinguished from the fixed oils ; they burn in the open air with a clear white light ; are acted upon by strong nitric acid, with the evolution of light and heat ; do not readily combine with alkalies or metallic oxides, but dissolve sulphur and phosphorus. The most interesting of the essential oils are those of turpentine, caraway, cloves, peppermint, nutmeg, anise, lavender, cinnamon, citron, and charnornile- Of these the most important is the first, which is much employed in the preparation of varnishes, and for some medical and chemical purposes. It is procured by distilling common turpentine ; and when purified by a second distillation, it is spirit or essence of turpentine. This oil cannot, without great difficulty, be dis- solved in alcohol, though turpentine itself is easily soluble in that fluid. One part of the oil may be dissolved in seven parts of alcohol ; but on standing awhile the greatest part of the oil separates and falls to the bottom. [6 f /-e.] This compound gives a luminous flame when burned, and has been proposed as a substitute for oil and gas in artifi- cial illumination. The purified oil, according to M. H. Labillardiere, contains no oxygen, but is composed of carbon and hydrogen in such proportions, that one volume of its vapour contains four volumes of olefiant gas, and two volumes of the vapour of carbon. Journal de, Pharmacie, iv. For l/ie anaiyxis of some oils, hy Dr. Ure and several olhtr chemists, see his Dictionary , 4th ed Art Oil. Camphor. An inflammable substance, closely allied to the essen- tial oils, existing ready formed in the Laurvs Cawphora, L. of Japan, and in several other plants. It has a bitterish, aromatic, pungent taste, accompanied with a sense of coolness ; it is unctuous to the touch and brittle, and may be easily reduced to powder by trituration with a few drops of alcohol ; its specific gravity is 0-988 ; is very volatile, fuses at 288 and boils at 400 F.; it is insoluble in water, but freely soluble in alcohol, from which it is thrown down by water ; is solu- ble also in the fixed and volatile oiis, and in strong acetic acid ; is converted by sulphuric acid into a substance resembling tannin, by nitric acid, into camphoric acid. According to Dr. Ure i consists of 1 Ox. 8-f-9 Hyd. 9-f 10 Car. 60 =77. Ure, Chem. Diet. Jrt. Camphor. Coumarin A name applied to the odoriferous principle of the Ton- ka bean, which is the produce of the D plcryx odorata, fVilltl. It is VEGETABLE SUBSTANCES. 391 white, of a hot pungent taste, and distinct aromatic odour ; it crystal- lizes in four sided prisms ; is moderately hard, and is heavier than water ; is sparingly soluble in water, but readily so in ether, alcohol, the fixed and volatile oils. This substance appears to be nearly allied to the essential oils. Boullay and Boutron- Charlard, in Jour, de Phar. for 1825. Turner. Resins. Resins are the inspissated juices of plants, and commonly occur either pure or in combination with an essential oil. They are solid at common temperatures, brittle, inodorous, and insipid; are non- conductors of electricity, and when rubbed become negatively elec- tric ; they are generally of a yellow colour, and semi-transparent ; are fused by heat, and at a still higher temperature are decomposed ; are soluble in alcohol, ether, and the essential oils, and, from the for- mer, they are precipitated by water, in which they are quite insoluble ; they are soluble also in pure potassa and soda, and are decomposed by the acids, the nitric forming with them a kind of tannin. The most important of these substances are common resin, or rosin, copal, lac, sandarach. mastich, elemi and dragon's blood. Resins are the bases of varnishes, and melted with wax and oil con- stitute ointments and plasters. Sealing wax is composed of lac, Ven- ice turpentine and common resin. The resins and gurn resins have been much investigated and with great success by Unverdorben. In a series of very elaborate memoirs he has shown that many of the known resins are mixtures of several substances of the same class, which may in most instances be separ- ated from each other by the action of alcohol and ether. And he has also shown that all the resins possess the power of forming salts with oxides in definite proportions and are therefore analogous to the acids. REFERENCES. Thomson on common Rosin, in Ann. of Phil. xv. 4fi8. Hatchet? s able investigations of the properties uf the Resins will be found in the Phil. Trans, for 1804, 18;J5 and 18>;6. lire's Chem, Diet. Art. Resin. Berzelius, Traite de Chim. v. r. This substance is found plentifully in beds of bituminous wood in some parts of Prussia. It is undoubtedly of vegetable origin, and has the general properties of a resin, but is distinguished by yield- ing succinic acid, when heated in close vessels. For details concerning this substance, see Ure's Chem. Diet. Balsams The balsams are native compounds of resin and benzoic acid, and issue from incisions made in the trees which contain them, in the same manner as turpentine from the fir. Some of them, such as storax and benzoin, are solid ; while others, of which the balsams of Tolu and Peru are examples, are viscid fluids. Gum-Resins. The substances to which this name is applied are the concrete juices of certain plants, and consist of resin, essential oil, gum, and extractive vegetable matter. The two former princi- ples are soluble in alcohol, and the two latter in water. Their proper solvent, therefore, is proof spirit. Under the class of gum-resins are comprehended several valuable medicines, such as aloes, ammonia- cum, assafoBtida, euphorbium, galbanum, gamboge, myrrh, scammo- ny and guaiacum. HatchelL in Phil. Trans. 392 VEGETABLE SUBSTANCES. Caoutchouc, commonly called elastic gum, or Indian rubber, is the concrete juice of the Siphonia elastica, Pers. a native of Brazil, and of several East India trees, as the FICUS mdica, &c. The most re- markable property of this substance is its elasticity. It is inflamma- ble, and burns with a bright flame ; is not soluble in water, but rnay be dissolved, though with difficulty, in pure ether ; it is soluble in pe- troleum, cajeput oil, purified naptha, and the oil of sassafras ; it loses its elasticity by the action of alkalies. This substance is employed for forming varnishes, for covering cloth so as to render it impervious to moisture, &c. Dr. J. K. Mitchell, of Philadelphia, has discovered a mode of mak- ing sheet-caoutchouc, which possesses very singular properties. KEFERF.NCES. /'or a notice of the solubility of Caoutchouc in coal nap~ tha, see Ann. of Phil. xii. Dr. Mitchell's discovery is described in the Jour, nal of t':e Phil. College of Pharmacy, for J in. 1<>3<>, and in a note to Tur ner^s Chem.by Dr. Bache Faraday on pure Caoutchouc, and the substances by which it is accompanied in the state of sap or juice ^ Brande's Jour. xxi. IT- Besides Chemical examinations, this paper contains a list of the most i ttpor* taut memoirs on this curious substance. Caoutchouc found in Arkansas, Sill Jour. iii. 44. Wtx. This principle exists in many plants, and especially in the berries of the Myrica Cerifera, L. In its common form it is always more or les< coloured, but when pure is colourless and insipid ; its specific gravity is 0'96 . it is solid at ordinary temperatures, and some- what brittle, but rnay be easily cut with a knife, when it exhibits a pe- culiar appearance, called the waxy lustre ; it is insoluble in water, sparingly soluble in boiling alcohol and ether ; it is readily soluble in the fixed oils when assisted by heat, and forms a compound of varia- ble consistence, which is the basis of cerates and ointments ; it melts at about 150 ' F. and at a higher temperature it is converted into vapour ; when burned in contact will 1 air it yields a clear white light, and is hence employed for forming candles. According to Dr. John, wax consists of two portions, one of which is soluble in alcohol, the other is insoluble. To the former he has given the name of Cerin, and to the latter that of Myricin. Accord- ing to the analysis of Dr. Ure, it consists of 1 O. 8-4-11 H. 114-13 C. 78=97. REFKRENCES. Ure's Chem. Die/. Thenard, Traite de Chim. iv. Dana's chtintc I examination of the berries of Myrica Cerifera, Sil. Joitr. i. 294. Bran>i/e lie knew the method of re dering it stronger bv an admixture of drv carbonate of potash and of p < paring vegetable mixtures by means of it. Thomson's History of Chemistry. 394 VEGETABLE SUBSTANCES. 1. Alcohol. It can be obtained from wines by distillation invacuo at the temperature of 60 F., which precludes the idea that it is formed by the action of heat upon the elements existing in the fermented liquor. Gay Lussac. Thenard, Traite de Ctiim. iv. 336. 2. When a portion of wine is partly distilled off and the distilled liquor is afterwards added to the residuum in the retort, the specific gravity of the mixture is precisely the same as that of the wine pre- vious to distillation. I confirmed 'the statement of Mr. Brande on this point in the case of three kinds of wine. Alcohol, being much lighter than wine, if it was formed during the process of distillation would have the effect of reducing the specific gravity when added to the resi- duum, which is never the case. 3. When the colouring and extractive matters in the wine are pre- cipitated by sub acetate of lead, the pure alcohol may be separated by the subsequent addition of dry sub-carbonate of potash, in the same manner, as from whiskey, gin and brandy. Brande. It may, therefore, be considered as satisfactorily proved that alcohol exists, as such, in wines and other fermented liquors ; but there is still much doubt whether their intoxicating powers are not materially modi- fied by the acid and other vegetable matters which they contain. I have recently analyzed several varieties of wines and other liquors, chiefly for the purpose of ascertaining the amount of alcohol which they contain. The process adopted was that of slow and careful distillation, and the accurate determination of the specific gravi- ty of the distilled liquor. In the following table of my results, the kind of liquor is designated and the proportion of alcohol per cent, by measure which they were found to contain, is stated. And in order that the strength of these liquors may be easily compared with that of those examined by Mr. Brande, I have taken as the standard, alcohol of the specific gravity of 0-825 at the temperature of 60 J F. VEGETABLE SUBSTANCES. 395 TABLE of tlie proportion of Alcohol per cent. BY MEASURE, contained in several kinds of Wine and other Liquors ; the specific gravity of the standard Alcohol being 0.825 at the temperature of (50 F. Kind of Liquor. l5i - ^7 c ~ ~~ e J5 '5 JO Kind of Liquor. r-H r i = ^ 1. Madeira (common,) 2. Do. (imported from the house of Robt. Seal,) 3. Do. (common,) 4. Do. (imported from the house of H oughton & Co. 5. Do. (" Farquhar," in bottle 40 years,) 6. Do. (20 years old,) 7. Do. (" Edgar,") S. Do. (" Brammin,") 9. Do. (common,) 10. Do. (''Wanderer,") 11. Do. ("Blackburn," old,) 12. Do. (said to be the pure juice, 28 years old,) 13. Sercial Madeira, 14. Do, Do. 25.27 23.11 22.41 22.25 21.79 21.45 21.30 20.91 20.72 20.70 20.68 19.30 25.18 18.96 21. Torres Vedras, 22. Sauterne, 20.51 13.00 23. Claret, (Chateau Mar- geaux,) 24. Do. (Palmer Margeaux,) 11.80 11.04 Average, 11.42 11.25 10.57 10.67 7.38 25. American Wine, (2 years oldj 26. Metheglin, 20 years in bottle, 27. Ale, (Albany, in bottle 2 years, ) 28. Do. (Albany, in barrel,) 29. Cider, (in bottle,) 30. Do. (in barrel, 6 months, ) 31. Do. (in barrel,) 4.80 4.84 4.41 Average of 14 kinds, 21.75 15. London Particular, 16. Bucellas, 17. Brown Sherry, 22.10 18.80 18.03 Average, 468 32. Irish Whiskey, (imported in 1825,) 33. Gin(genuine' 'Hollands'') 34. Brandy, (common.) 35. Whiskey, (common.) 36. Spirits of Wine,(obtained at the druggists,) 37. Do. \ 73.70 55.44 51 01 42.95 93.27 95.35 18. Port, (7 years in bottle,) 19. Do. 20. Do. 22.87 22.35 21.98 Average, 22.60 The results in the above table agree generally with those of Mr. Brande. In all cases where the difference was marked, the trials were repeated several times, and the mean of these is stated. This was par- ticularly so with Nos. 13 & 14, 22, 23 & 24. The ale, IN 6. 27, con- tains more alcohol than any put down in the table of Mr. Brande as ordinarily published ; but in the Journal of Science and the Arts, (Vol. 5, p. 124) he states that Lincolnshire Ale, brewed by Sir Joseph Banks, contained 10-84 per cent, of alcohol. Our cider it would seem contains less alcohol than the lowest average of the specimens exam- ined by Mr. Brande, which is 5-21 per cent. 390 VEGETABLE SUBSTANCES. REFERENCES. For a table of /he specific gravities of Alcohol of different strength, see Henry's Chem. ii. o73. Graham on the concentration of Alco- hol, inEdin. Phil. Trnn*. 1823. On th<< concentration of Alcohol tiy blad- ders, Brande's Jour, xviii. !80. Graham on the Alcoates, Branded Jour. N. 8. iv. 44*2. On Alcohol in u-ines, see Thenard, iv Chaptal on Wine, mid Murray's Chem. For Brandt's table of the quantity of Alcohol in various wines, SfC. see his Manual of Chemistry or Pharmacy. The experimental details are published in Phil. Trans, for 181 1 and 1813. The article distilla- tion in the Supplement to the EHCIJ. Brittannica, by Dr. Thomson. Hender- son on Wines. Ether. The name Elher was formerly employed to designate the volatile inflammable liquid which is formed by heating a mixture of alcohol and sulphuric acid ; but the same term has since been extended to several other compounds produced by the action of acids on alcohol, and which, from their volatility and inflammability, were supposed to be identical or nearly so with sulphuric ether. M. Boullay, sen., divides the ethers into three classes ; 1st. Those obtained by acting upon alcohol with sulphuric, phosphoric and arse- nic acids, which are identical ; 2dly. Those produced by the combi- nation of hydro-carbon with certain hydracids ; 3dly. Those which, according to the experiments of Thenard and of Boullay, are constitu- ted of alcohol and an oxacid. Ethers of the First Class. Sulphuric Ether. Atom. Num. 37$i/mh. 2 (2H+2C)+(O+H.) A colourless fluid, of a hot pungent taste, and fragrant odour ; its specific gravity in its purest form, is about 0*700, and according to Lowitz, 0-632, but the ether of the shops is seldom less than 0*750, owing to the presence of alcohol ; it is extremely volatile, a few drops poured on the hand evaporating instantly with the production of cold ; when of the specific gravity of 713, it boils at 92 Ct 2 F. under the pres- sure of the atmosphere, [Du-mus and Boullny,] and in racuo at 20- be- low ; at 46 J below zero it is congealed ; its vapour has a density of 2-586 compared to air as I ; it. combines with alcohol in all proportions, but not with water ; it is highly inflammable, burning- with a blue flame, and forming carbonic acid arid water ; and with oxygen gas its vapour forms an explosive mixture ; it may be decomposed by being passed through a red hot porcelain tube ; it dissolves many of the re- sins and essential oils, and some of the vegetable alkalies, and when breathed produces effects similar to those produced by nitrous oxide ', but this is sometimes attended with danger. See Brandes Jour. iv. 159. Action of Water. When ether is agitated with that fluid, the great- er part separates on standing, a small quantity being retained, which imparts an ethereal odour to the water ; the ether so washed is very pure, because the water retains the alcohol with which it is mixed. Action of Platinum. When a coil of platinum wire is heated to red- ness, and then suspended above the surface of ether contained in an VEGETABLE SUBSTANCES. 397 open vessel, the wire instantly begins to glow, and continues in that state until all the ether is consumed. During this slow combustion, pungent acrid fumes are emitted, which Mr. Daniel considered as a new acid, and described under the name of Lampic Acid,- but he has since ascertained that its acidity is owing to the acetic acid, which is combined with some compound of carbon and hydrogen, different both from ether and alcohol. Brandes Jour. vi. and xii. If platinum sponge be heated and put into the vapour of ether, it becomes red hot, and continues so as long as any of the vapour is un- consumed According to Dr. Thomson, powdered black oxide of man- ganese, oxide of nickel, oxide of cobalt, oxide of uranium, oxide of tin, &c. when in the loose and porous state in which they are produced by decomposing the oxalates of the several metals by heat in the open air, may be substituted for platinum. Thomson on Heat, tyc. Action of Light If ether is exposed to light in a vessel partially fill- ed, and which is frequently opened, it gradually absorbs oxygen, and a portion of acetic acid is generated. This change was first noticed by M. Planche, and has been confirmed by Gay Lussac. M. Henry, of Paris, attributes its developement to acetic ether, which he believes to be always contained in sulphuric ether. Turner. PREPARATION. Ether may be made by mixing gradually equal parts of strong sulphuric acid and alcohol, and subjecting the mixture to slow distillation, into a receiver surrounded by ice, by a carefully regulated heat. The ether which first passes over is impure, being contaminated with alcohol and with sulphurous acid. To separate these impurities, it should be agitated with a strong solution of potas- sa, which neutralizes the acid, while the water unites with the alco- hol. The ether is then distilled by a very gentle heat, and may be rendered still stronger by distillation from the chloride of calcium. The theory of the formation of ether will be understood, when it is stated that, according to the most correct analysis, ether is supposed to consist of two proportions of olefiant gas and one proportion of water. Now, alcohol is composed of one proportion of olefiant gas and one of water ; so that, if from two proportions of alcohol one of water be withdrawn, the remaining elements are in exact proportion for constituting ether. This is exactly the mode in which sulphuric acid is supposed to operate in generating ether, an effect which it is well calculated to produce, owing to its strong affinity for moisture. Hence, also, when a larger proportion of sulphuric acid is added to alcohol, it combines with the whole of the water, and pure olefiant gas is evolved. Sulphovinic Acid is a peculiar acid formed during the preceding process, and which, according to Mr. Hennel, is composed of sulphur- ic acid and carburet of hydrogen. Phil. Trans. 1826, 247, or Brande's Jour. xxi. 331. Phosphoric Ether is very volatile ; boils at 100 F. ; is soluble in eight or ten parts of water, and burns with a white flame. It is ob- tained by distilling a mixture of thick tenaceous phosphoric acid and alcohol. Boullay, Ann. dc Chim. Ixii. 192. Ethers of the Second Class. Muriatic Ether. This compound is highly inflammable and volatil- izes still more rapidly than sulphuric ether ; when burned it gives out AA 398 VEGETABLE SUBSTANCES. muriatic acid gas. It may be obtained by distilling equal measures of alcohol and concentrated muriatic acid. Chloric Ether, Hydriodic Ether, Fluoric Ether, and Fluoboric Ether may also be obtained by processes analogous to those already describ- ed. See Henry's Chern. ii. 395. Ethers of the Third Class. Nitric Ether. This substance agrees with sulphuric ether in its lead- ing properties, but it is still more volatile ; it usually reddens litmus, and though this property may be destroyed by a little lime, it soon be- comes acid by keeping ; it is highly combustible at common tempera- tures, and under ordinary pressure the specific gravity of its vapour is 2*628. It is prepared by distilling a mixture of concentrated nitric acid with an equal weight of alcohol ; but the process requires great care. Sweet Spirits of Nitre, is a solution of nitric ether in alcohol. When Sure it is colourless, possesses a peculiar odour and a specific gravity of 850. It reddens litmus feebly, and volatilizes without leaving any residue. The presence of muriatic and sulphuric acids may be detect- ed by diluting it with a sufficient quantity of water, and adding solu- tion of nitrate of silver and chloride of barium. Acetic Ether. This compound is volatile ; has a specific gravity of 0*866, being heavier than most other ethers ; it burns with a yellow- ish-white flame, and during its combustion acetic acid is developed. It rs formed by distilling 12 or 15 times in succession concentrated acetic acid (procured from acetate of copper) with alcohol, and return- ing the distilled liquor to charge the retort. REFERENCES. Thomson** System of Chetn,. Thenard, Trailed Chim. \v, 146. Henry's Chem. ii. 383. Brande's Manual of Pharmacy. DanieiL on Lampic Acid and the Lampates. Bran tie's Jour. vi. 318. Harems description of an aparatus for preparing Nitric Ether , Sill. Jour. ii. 326. Daltons Me moir on Sulphuric Ethtr, Arm. of Phil. \v. 117. Thenard on the action of Vegetable Acids on Alcohol, Mem. d 1 Arcueil, ii. 5, or Phil. Mag. xxxvii. 216. Dumas and Boullay, Ann. de Chim. et de Phys. Jan. 13:28. Bituminous Substances. Under this title are included several inflammable substances, which, though of vegetable origin, are found in the earth, or issue from its surface. They may be conveniently arranged under the two heads of bitumen and pit-coal. The first comprehends naphtha, petroleum, mineral tar, mineral pitch, asphaltum, and retinasphaltum, of which the three first mentioned are liquid, and the others solid. The second comprises brown coal, the different varieties of common or black coal, and glance coal. Bitumen Naphtha. A volatile limpid liquid, occurring in some parts of Italy, and on the banks of the Caspian sea ; and produced also by distillation from petroleum. It has a strong peculiar odour, and light yellow colour ; its specific gravity, when highly rectified, is 0-753 at 61 F.; it is very inflammable, and burns with a white flame mixed with much smoke ; at 186 F. it enters into ebullition, and its vapour has a density of 2-833 ; it contains no oxygen, and is hence employed VEGETABLE SUBSTANCES. 399 for protecting the more oxidable metals, as potassium and sodium, from oxidation. Petroleum, found in several parts of the world, especially in coal districts, is of a reddish-brown colour, unctuous to the touch, and less limpid than naptha. Mineral tar is very similar to petroleum, but is more viscid and of a deeper colour. From the petroleum of Rangoon Dr. Christison has obtained a white, pearly, crystalline, inflammable substance, to which he has given the name of petroline. Asphaltum is found on the banks of the Dead sea, and occurs in large quantity in Barbadoes and Trinidad. It is solid, brittle, of a black colour, vitreous lustre and conchoidal fracture ; it melts easily, and is very inflammable. Mineral Pitch or Maltha is likewise a solid bitumen, but is much soft- er than asphaltum. The elastic bitumen, or Mineral caoutchouc, is a rare variety of mineral pitch, found only in the Odin mine, near Cas- tleton, in Derbyshire, England. Retinasphaltum is a peculiar bituminous substance, found associated with the brown coal of Bovey in Devonshire, and described by Mr. Hatchett. It consists partly of bitumen, and partly of resin, a com- position which led Mr. Hatchett to the opinion that bitumens are chiefly formed from the resinous principle of plants. Phil. Trans. 1804. Pit Coal. This is a general term often applied to several varieties, and even distinct species. Brown coal is characterized by burning with a bituminous odour. It sometimes has a fibrous structure, and hence this variety is called bituminous-wood. Pitch coal or jet, which is em- ployed for forming ear-rings and other trinkets, is intermediate between the brown and black coal. Black or common coal, of which there are several varieties, is extensively employed for fuel. Glance Coal or Anthracite, abundant in Pennsylvania, differs from common coal in containing no bituminous substances, and in not yield- ing inflammable gases by distillation. It is nearly pure carbon, and consequently it burns without flame. REFERENCES For localities of the Bitumens above noticed, and further information concerning them, see Cleaveland's Mineralogy. Thomson on the composition of different species of Pit Coal, Ann. of Phil, xiv, 81. Ure's analysis of Splint and Cannel Coal, Phil. Trans. 1822, 471. Karsteiis ob- servations and experiments on different kinds of Coal ; a very valuable trea- tise, of which an abstract trill be found in Jameson's Edin. New Phil. Jour. ji. 280, and iii. 60, 322. SECTION IV. SUBSTANCES, THE OXYGEN AND HYDROGEN OF WHICH ARE IN EXACT PROPORTION FOR FORMING WATER. Sugar. Sugar is an abundant vegetable product, existing in a great many ripe fruits, in the juice of the maple, Acer Sacc/iarinum, L. in the beet root, &c. But the plant which contains it in the greatest quan- 400 VEGETABLE SUBSTANCES. tity is the sugar cane, from which nearly all the sugar used in this country is obtained. When pure, sugar is a white crystalline sub- stance, of a purely sweet taste, and without odour ; it is easily soluble in cold water, and in almost any proportion in hot, the solution con- stituting syrup, which, by long repose deposits crystals of sugar ; it is loluble in alcohol, and large crystals may be obtained from the alco- holic solution ; it combines with alkalies and alkaline earths, forming compounds, in which the taste of the sugar is greatly injured, but which may be restored by the addition of an acid ; when triturated with oil it forms a mixture which is diffusible through water, producing a milky fluid, called an emulsion ; when exposed to the action of nitric acid it is converted into oxalic acid. Manna, Sugar of Grapes, of the, Maple, of Beets, ffC. are varieties of sugar, and possess the same general properties. Honey consists prin- cipally of a crystallizable and an uncrystallizable sugar. Molasses is an uncrystallizable sugar. REFERENCES. For detailed accounts of the manufacture of Sugar, see Edwards 1 History of the West Indies ; and Aikiri's and Ures Chem. Did. For papers on the making of Sugar from Beets, see Repert. of Arts, 2d ser. i. vii. xxii. xxviii. xxix. xl. Ohaptal on the same subject, Ann. de Cliim. xcv. 2o3. or Ann. of Phil. ix. 50. On the same subject, see also Franklin Jour* ii. 183. Howard's celebrated process for preparing and refining Su- gar, are fully described in the Repert. of Arts, xxiii. 129, xxv. 257. On the composition of Sugar > see Prout's Essay on Alimentary Substances, PhiL Mag. and Ami. iii. 98. Starch or Fecula. Starch exists in a great variety of vegetables, being one of the ehief ingredients of most kinds of grain, and of some roots, as the potatoe, from which it may be extracted by diffusing the powdered grain or rasped root in cold water, and separating the grosser parts by a strain- er. It is a white pulverulent substance, without taste or smell ; it i insoluble in alcohol, ether or cold water, but is easily dissolved in boil- ing water ; it forms a blue colour with iodine, by which it may be dis- tinguished from all other substances ; it unites with alkalies, forming a compound, soluble in water, from which the starch is thrown down, by acids ; is decomposed by strong sulphuric acid, and by nitric acid, assisted by heat, is converted into oxalic and malic acids. Amidine, a term applied to torefied starch that is, starch modified by heat, whether in the dry way or by boiling water. It yields a blue colour with iodine, and is soluble in cold water. Hordein. A name given by Proust to a peculiar principle contained in barley, which he supposed to be converted, in malting, partly into starch, and partly into sugar. Dr. Thomson, however, considers it merely a modification of starch. According to Caventou, Indian arrow root, prepared from the root of the Maranta arundinacea, L., has all the characters of pure starch. Sago, obtained from the. pith of an East Indian palm tree, Cycas cir- dnalis, L. and Tapioca, from the root of the Jatropa manihot, L. (Jan- nipha manihot, Kunth,) are chemically the same substance. They both exist in the plants from which they are extracted, in the form of starch ; VEGETABLE SUBSTANCES. 401 feut as heat is employed in their preparation, the starch is more or less converted into amidne. From this it follows that pure potatoe starch may be used instead of arrow root, and that the same material, modi- fied by heat, woud afford a good substitute for sago and tapioca. Tur- ner. REFERENCES. Skrimshire on the quantity of Starch in the different varie ties of Potato?, and the methods of separating it, Nicholson's Jour. xxi. Pearson's experiments and observations on Potatoe Starch, Repert. of Arts, list Ser. iii. 383. Lampadius' analysis of four different varieties of Potatoe t Ann of Phil. v. 39. For a notice of the papers of Saussure, Guibourt, Cat> entou, and others, see Henry's Client, ii. 272. Proufs essay on alimentary substances, Phil. Mag. and Ann. iii. 98. Gum. Of this proximate principle Gum Arabic may be taken as an exam- ple. It is the concrete juice of several species of Mimosa or Acacia, natives of Africa and Arabia. It occurs in small rounded, transparent, friable grains, commonly of a pale-yellow colour, inodorous and nearly tasteless ; it is soluble in water, and forms a solution called mucilage ; is insoluble in alcohol and ether, and the former precipi- tates it from its solution in water ; is soluble in alkaline solutions and in lime water, and is precipitated unchanged by acids ; is decomposed by dilute acids, and by the action of strong nitric acid is converted into Mucic or Saccholactic Acid ; it is not altered by exposure to the air, but its solution at length becomes sour and gives out an odour of acetic acid ; it is precipitated from its solution by several metallic salts, especially sub acetate of lead. Besides gum arabic, there are several well marked kinds of this principle, especially the gum tragacanth, cherry-tree gum, and the mu- cilage from linseed, each of which presents some peculiarities. REFERENCES. For a good Account of the production and gathering of Gum Arabic, see Aikirfs Chem~ Diet. art. Mucilage. For various analyses af Gum, by Ure and others, see Henry, ii.209. Bostock on Vegetable Jelly, Nicholsons Jour, xviii. 28. For a notice of several varieties of gum and vegetable mucilage. See Berzclius, Traite de Chim. v. 214. Lignin. The woody fibrs which remains after the action of water and alco- hol on wood, has been called lignin. [t is insipid and inodorous, un- dergoes no change by keeping ; by the action of sulphuric acid it is converted into a substance like gum, and by diluted sulphuric acid this is converted into sugar ; by destructive distillation it yields Pyro- ligneous acid, and a bright shining charcoal remains. See the references under Acetic Acid. 402 VEGETABLE SUBSTANCES- SUBSTANCES WHICH, SO FAR AS IS KNOWN, DO NOT BELONG TO ANY OF THE PRECEDING SECTIONS. Colouring Matter. The Colouring Matter of Vegetables does not appear to reside in any peculiar principle, and is therefore differently affected by solvents, By the affinity of certain solvents, colouring matter is separated from vegetables, and by the superior attraction of silk, wool, cotton, &c. it is separated from the solvents and attracted to the fibres of the fabric. Colours which are fixed and durable, by the simple attraction of the fibres of ctoth, without the intervention of any other substance, are called Substantive Colours. Those which require the intervention of a third body, which possesses an attraction both for the cloth and the colouring matter, and thus links them together, are called Adjective Colours. The substance which possesses the property of fixing co- lours, is called a mordant or basis. The mordants in most common use are alumina, oxide of iron and oxide of tin. Alumina has a very strong attraction for colouring nmtter, and forms insoluble compounds, called lakes. Though there is a great variety in the tints observable in dyed stuffs, they may all be produced by four simple ones, viz. blue, red, yellow and black. Blue Dyes. The most important of these is Indigo, -the produce of several species of Indigofera. It is a brittle substance, of a deep blue colour, and without either taste or odour ; when heated to 550 F. a fine violet vapour arises, which condenses into acicular crystals, call- ed Indigogene. [Gorham, in JY*. Eng. Jour.'] It is soluble in concen- trated sulphuric acid, and the solution forms the Saxon Blue; it con- tains oxygen in its natural state, and when deoxidized has a green tint, and is then soluble in alkalies, and may be fixed on cloth, which acquires the blue colour by exposure to the air. The indigo of commerce is of a very complex nature, containing, ac- cording to Berzelius, in addition to the salts of magnesia and lime, the following ingredients: 1. A glutinous matter; 2. Indigo-brown ; 3. Indigo-red ; 4. Indigo-blue. Cerulin and Phcnicin, are two compounds of indigo and water, de- scribed by Mr. Crum ; but Berzelius supposes them to be of a more complicated nature. See Crum on Indigo and on certain substances pro- duced from it by means of Sulphuric Acid, Ann, of Phil. xxi. 81. Red Dyes. The chief substances which are employed for giving thfl red dye r are Cochineal, an insect feeding upon several varieties of Cac lus ; archil, the produce of the l } armelia roccella, Ach., a lichen grow ing in the Canary Islands ; madder, the root of the Rubia tinctorum, L.; Brazil-wood, or the wood of the Ccesalpinia echinata, Lam.; log- wood, or that from the Hccmatoxylon campechianum, L. of tropical America : and safflower, or the dried flowers of the Carthamus tinctori- us, L. These are all adjective colours. VEGETABLE SUBSTANCES. 403 The blue pigment called Litmus or Turnsol, used as a test, is a com- pound of the red matter of the archil and an alkali. Cudbear is an ar- ticle of a similar kind manufactured at Glasgow. It is used in dying, and as a chemical test. Yellow Dyes. The chief of these are the quercitron, or Quercus tinctoria, IV.; several species of American hickory ; turmeric, or the root of the Curcuma longa, L.; fustic, or the wood of the Morus tinc~ toria, L., of the West Indies ; all adjective colours. Black Dyes. The black dye is made of the same ingredients as writing ink ; and therefore consists essentially of a compound of ox- ide of iron, with gallic acid and tannin. By the addition of logwood and acetate of copper, the black receives a shade of blue. REFERENCES. For full details on the subject of Dying, 4" c< j see Berthol- Let on Dying; Bancroft's Researches on Permanent Colours, Calico- Print* in.g, . A?i account of the methods of making Isinglass, Glue, tyc. may be found in Johnson's History of Animal Chemistry, i. 311. Urea. This substance is contained in urine, from which it may be obtained by slowly evaporating the liquid to the consistence of syrup; on cooling, a crystalline mass is formed, from which pure alcohol dissolves urea. By the careful evaporation of the alcohol brownish crystals are deposited, which may be purified and rendered colourless. In this state it is soluble in water, especially when hot, and also irt alcohol ; it is decomposed by the fixed alkalies and alkaline earths ; though not alkaline it unites with the nitric and oxalic acids, forming sparingly soluble compounds, which crystallize in scales of a pearly lustre, and by which the presence of urea may be detected. This substance has been formed artificially by Woiiler. Brandes Jour. N. S. iii. 491. Front's process for preparing Urea, differing someiohat from the above, is described in Henry 1 s and Turner's Chemistry. Sugar of Milk. The saccharine principle of milk is obtained by evaporating that liquid to the consistence of syrup, and allowing it to cool. It is afterwards purified by means of albumen and a second crystallization. It has a sweet taste, though less so than the sugar of the cane, from which also it differs in several other respects. Sugar of Diabetes. A kind of sugar which may be obtained in an irregularly crystalline mass, by evaporating the urine voided in the dis- ease called Diabetes. SECTION IV. THE MORE COMPLEX ANIMAL PRODUCTS. The Blood and its Constituents. The blood while circulating in the vessels of living animals, is fluid, of florid red colour in the arteries, and of a dark purple colour in the veins. It has a slightly saline taste, and a peculiar odour, and is some- what unctuous to the touch ; its specific gravity is variable, though generally near 1-05, and in man its temperature is about 98 or 100 F.; when fresh drawn it has the appearance of a homogeneous fluid, but if examined with a microscope of sufficient power, numerous red particles are observed floating in a colourless fluid. The blood, while circulating, is mechanically distinguishable into two parts, one essentially liquid, which may be called liquor sanguinis ,- the other essentially solid, which is merely suspended in the former, and imparts its red colour to the mixture. Both of these constituents of the blood are of a complex nature. Liquor Sanguinis. This is considered by some as serum, but it has been shown by Dr. B. Babington to be similar to chyle, and to consist of fibrin held in solution, along with albuminous, oleaginous and saline ANIMAL SUBSTANCES. 415 matter, by the water of the blood. The liquor sanguinis when set at rest coagulates, and forms a uniform jelly of precisely the same volume as when it was liquid, and possesses the exact figure of the contain- ing vessel ; and in a short time, by the contraction of the mass of coagulated fibrin a yellowish liquid appears, which is the true serum of the blood. It is the liquor sanguinis, thus shown to be spontaneously separable into fibrin and serum, which forms a yellowish liquid stratum at the surface of blood recently drawn from persons in acute rheumatism or other inflammatory fevers. In such affections the liquor sanguinis, from causes not at all understood, generally coagulates with unusual slowness, so that the heavier red globules have time to subside to an appreciable extent, leaving an upper stratum of nearly colourless fluid, which by the cautious use of a spoon may be removed and collected into a separate vessel. The bvffy coat of such blood is pure fibrin se- parated by coagulation from the liquor sanguinis. The coagulable lywpk of Surgeons, which is thrown out on cut surfaces, appears to be the liquor sanguinis ; and this fluid is also not unfrequently exhaled in dropsies, when the fibrin either constitutes a gelatinous deposit, or appears as white flakes floating in a serous fluid. It is poured out by the intestines during an attack of cholera, the rice-water fluid charac- teristic of that disease, consisting of a saline and albuminous solution, in which numerous shreds of fibrin are suspended. Turner. By allowing blood to remain exposed for a short time to the air, it separates spontaneously into two distinct portions : a yellowish li- quid called serum, and which is identical with that obtained from the liquor sanguinis ; and a red solid known by the name of clot, cruor or crassamentum. The relative proportion of these two parts is varia- ble, and depends upon circumstances not at all connected with the state of vigour and health of the animal from which the blood is drawn. Serum. This liquid has a yellowish colour, a saline taste and slight- ly alkaline reaction ; it is somewhat unctuous to the touch, and resem- bles in fluidity warm olive oil ; its specific gravity is from 1-027 to 1-029 ; it is coagulated by heat, and by acids, alcohol and other sub- stances that coagulate albumen. When the coagulum prepared by- heat, is cut into thin slices and subjected to pressure, it yields a small quantity of a colourless, limpid fluid, called serosity which contains according to Dr. Bostock, about l-50th its weight of animal matter, to- gether with a little muriate of soda. The serum of human blood, according to Berzelius, consists in 100 parts of water 90 '59, albumen 8, lactate of soda with animal matter and chloride of sodium 1, modified albumen and an alkaline phosphate and carbonate 0*41. Traite de Chim. vii. 75. Crassamentum or Clot. This is the firm coagulating portion of the blood, and has the specific gravity of about 1-245. It may be resolved into two portions by cutting it into thin slices and washing it repeated- ly in distilled water ; the colouring matter, called the red globules, is gradually dissolved or washed out, and a white fibrous substance re- mains called fibrin. Colouring matter of the blood. To this substance the name of hematosine is now applied. It resembles albumen in most of its pro- perties, except in colour. Its elementary composition is nearly simi- lar to that of fibrin and albumen, but is differs from both, in contain- 416 ANIMAL SUBSTANCES. ing iron. This has been satisfactorily shown by Berzelius. Engelhart and Rose. From the presence of iron in the colouring matter of the blood, some were led to suppose that the peculiar colour of the blood was in some way or other dependant upon that substance. But this view, al- though supported by many plausible arguments, does not seem to be warranted by the facts. Nor can we at present adopt the opinion of Mr. Brande, that the colouring matter is a peculiar animal principle, capable of combining with metallic oxides. With regard to the colour of the blood, a very interesting fact has been stated by Dr. Stevens in his Treatise on the blood, and confirmed by Dr. Turner and others who have repeated the experiment. If per- fectly florid arterial blood be allowed to coagulate, and the clot be washed with repeated portions of pure water, its colour gradually dark- ens so as at last to appear quite black. Exposure to the air does not restore the colour, but a solution of common salt, carbonate of soda, and other neutral salts restore it to the original colour of arterial blood. Dr. Stevens has therefore drawn the conclusion, that the florid colour of arterial blood is not due to oxygen, but to the sa- line matter of the serum. Analysis of the Blood. A very elaborate examination of the blood has been recently made by Lecanu. The following is the mean of the results of two analyses. Water 782-867 Colouring matter 126 313 Albumen 67-252 Fibrin 2-832 Saline, oily, fatty, and extractive matter 20-736 1000.000 Lecanu has observed a difference between the relative proportions of the ingredients of the blood in men and women ; and this observation has been confirmed by Dennis, who has made a more extended exam- ination on this subject. Ann. de Chim. xlviii. 308. Jour, de Pharm. xvii. 522, quoted in Johnston s Report. REFERENCES. Bostock, in Medico-Chirurgical Trans, ii. 166, iii. 231; and also his work on Physiology Brande, in Phil. Trans. 1812, and his "Manual of Chemistry. Engelhart, in Edin. Me.d. and Surg. Jour. Jan. 1827. Scudamore on the Blood. Dr. J. Davy's Observations on the Fibrin, Biiffy Coat, and pres n circumstances. These variations they consider of two kinds, general or diurnal, and particular. It has been generally supposed that the bulk of nitrogen inhaled during respiration is not changed, and that this gas is merely passive in the process, or at least that its only use is to neutralize the ener- getic properties of the oxygen. But it has been shown by that acuts physiologist, Dr. Edwards, that the quantity of nitrogen given out by the same animal, during respiration, is very variable, being at one time increased, at another diminished, and at a third remaining wholly un- changed. These phenomena he has traced to the influence of the sea- sons. It has also been shown by Allen and Pepys, that when animals are confined in vessels of oxygen gas, or in an atmosphere composed of 21 measures of oxygen and 79 of hydrogen, the residual air con- tains a large quantity of nitrogen, and in the latter case a portion of the hydrogen has disappeared. Dulong and Despretz also, in their ex- periments, arrived at the conclusion that in all cases there was an in- crease of nitrogen. It appears therefore little doubtful, that nitrogen is constantly given out by the lungs. From the experiments of Dr. Edwards it appears to be proved, that carbonic acid given out by the lungs, is formed in the blood during its circulation. For on confining animals for some time in an atmosphere of hydrogen, the residual air was found to contain a quantity of car- bonic acid, which was in some instances greater than the bulk of the animal. It may also be inferred from these and other experiments, that nitrogen is absorbed during respiration. And I have elsewhere made the suggestion, that the nitrogen thus absorbed combines with carbon and forms cyanogen, which probably exists in the blood in com- bination with iron. For the facts and arguments in favour of this view, see Sill. Jour, xviii. 52, and N. Y. Med. and Phys. Jour. ix. 288. REFERENCES. Bostock's Physiology. Edwards DeV Influence des Agents Physiques sur la Vie. Prout on the phenomena of Sanguification , and en ie blood in general, Ann- de Phil. xiii. 12, 265. The experiments of Allen and Pcpys, Phil. Trans. 1808. Christison's inquiry on some disputed points in the chemical physiology of the Blood and Respiration, Edin. Med. and Surg. Jour. xxxv. 94. For a good summary of the various opinions, <$<: see Henry's C/iem. ii. For a full account of the former tJieories and views on Chis and various other subjects relating to this department, consult Johnson's History of Animal Chemistry, in three vols. Loud. 1S( ! 3. 418 ANIMAL SUBSTANCES. Animal Heat The production of animal heat appears to be closely connected with respiration. A portion of it, at least, can be satisfac- torily accounted for by the formation of carbonic acid. The remain- der has been ascribed to various other sources, as the processes of nu- trition, secretion, &c. Mr. Brodie, however, refers animal heat alto- gether to the influence of the nervous system. But his results have not been confirmed by other physiologists. There is therefore much obscurity resting upon this subject. REFERENCES. Crawford on Animal Heat, Ellis 1 Inquiry, Dr. J Davy, Phil. Trans, for 1814. The author controverts the opinion of Crawford as to the difference in the capacities of venous and arteiiil Bltod. Brodie, in Phil. Trans. 1811 and 18i2. He ascribes animal Heat wholly to nervous in- Jluence. ' Animal Fluids , Secretions, 8fc. Saliva. The saliva is the fluid secreted by the salivary glands, and is poured into the rnouth during mastication. It is a transparent, colourless and slightly viscid fluid, consisting of albumen and several saline substances dissolved in water. From the recent analysis of Tiedemann and Grnelin, the chief saline constituent is muriate of po- tassa ; but several other salts, such as the sulphate, phosphate, acetate, carbonate, and sulphocyanate of potassa, are likewise present in small quantity. The concretions found in the salivary glands consist chieily of carbonate of lime. REFERENCES. Bostock 9 ^ Physiology, containing the experiments of Tiedt- mann and Gmelin. Pancreatic Juice. This fluid is commonly supposed to be analogous to the saliva, but it appears from the analysis of Tiedemann and Gme- lin, that it is essentially different. The chief animal matters are al- bumen, and a substance like curd ; but it also contains a small quan- tity of salivary matter and osmazome. It reddens litmus paper, owing to the presence of tree acid, which is supposed to be the acetic. Its salts are nearly the same as those contained in the saliva, except that the sulphocyanic acid is wanting. The uses of this fluid are entirely unknown. Gastric Juice. This is a fluid poured out on the mucous coat of the stomach, and appears to be possessed of extraordinary powers as a sol- vent. As collected from the stomach of an animal killed while fast- ing, it is a transparent fluid, which has a saline taste, and has neither acid nor alkaline reaction ; during- the process of digestion however, it appears to be distinctly acid ; it coagulates milk, an effect which is supposed to be independent of the presence of an acid. Its powers cannot be explained upon any known chemical principles. REFERENCES. Prout, in Phil. Trans. 1824. Bostodc's Physiology. Bile. The bile is a yellow or greenish-yellow coloured fluid, of a peculiar sickening odour, and of a taste at first sweet and then bitter, but exceedingly nauseous. Its consistence is variable, being some- times limpid, but more commonly viscid and ropy ; it is rather denser than water, and may be mixed with that liquid in every proportion, it contains a minute quantity of free soda, and is, therefore, slightly al- kaline ; but owing to the colour of the bile itself, its action on test pa- per is scarcely visible. ANIMAL SUBSTANCES. 419 The bile, according to the analysis of Tiedemann and Gmelin, is a- very complex fluid, containing, beside many other ingredients, a pe- culiar acid, called the Cholic, which crystallizes in needles, reddens litmus paper, and has a sweet taste. The peculiar taste of the bile is owing to a substance first obtained, but not in a pure state, by Thenard, and called by him Picromel. This substance, when pure, occurs, according to the above named chemists, in opake crystalline grains ; soluble in water and in alcohol, but not in ether ; its taste is sweet without any bitterness. REFERENCES. Thenard, in Memoirs U'Arcueil, i. or Traite de Cfiim. \v* 398 BeizetiuSj who denies the presence of Picromel in the Bile, Ann.de Chim. Ixxi. 220. Biliary Calculi. The concretions sometimes found in the human gall-bladder, consist, according to M. Chevreul, in general of the yel- low colouring matter of the bile and cholesterine ; the latter predomi- nating and being sometimes in a state of purity. Chyle. The fluid absorbed by the lacteal vessels from the small in- testines during the process of digestion, is known by the name of Ckylc. Its appearance varies in different animals ; but as collected from the thoracic duct of a mammiferous animal, three or four hours after a meal, it is a white opake fluid like milk, having a sweetish and slightly saline taste. In a few minutes after removal from the duct, it becomes solid, and in the course of twenty-four hours separates into a firm coagulum, and a limpid liquid, which may be called the serum of the chyle. The coagulum is an opake white substance, of a slight- ly pink hue, insoluble in water, but soluble easily in the alkalies and alkaline carbonates. Vauquelin regards it as fibrin in an imperfect state, or as intermediate between that principle and albumen ; but Mr. Brande considers it more closely allied to the caseous matter of milk than to fibrin, M'dk. This well known fluid, secreted by the females of the class mammalia for the nourishment of their young, consists of three dis- tinct parts, the cream, curd, and whey, into which by repose it spon- taneously separates. The cream, which collects upon its surface, is an unctuous, yellowish- white, opake fluid, of an agreeable flavour. According to Berzelius, 100 parts of cream of specific gravity 1-0244, consist of butter 4-5, caseous matter 3'5, and whey 92. By agitation as in the process of churning, the butter assumes the solid form, and is thus obtained in a separate state. During the operation there is an increase of temperature amounting to about three or four degrees, oxygen gas is absorbed, and an acid is generated ; but the absorption of oxygen cannot be an essential part of the process, since butter may be obtained by churning, even when atmospheric air is entirely excluded. After the cream has separated spontaneously, the milk soon becomes sour, and gradually separates into a solid coagulum, called curd, and a limpid fluid which is whey. This coagulation is occasioned by free acetic acid, and it may be produced at pleasure either by adding a free acid, or by means of the fluid known by the name of renmt, which is made by infusing the inner coat of a calf's stomach in hot water. When an acid is employed, the curd is found to contain some of it in combination, and may, therefore, be regarded as an insoluble compound of an acid with the caseous matter of milk ; but nothing certain is known respecting the mode by which the gastric fluid, the active principle of rennet, produces its effect. 420 ANIMAL SUBSTANCES. The curd of skim-milk, made by means of rennet, and separated from the whey by washing with water, is caseous matter, or the basis of cheese, in a state of purity. It is a white, insipid, inodorous sub- stance, insoluble in water, but readily soluble in the alkalies, espe- cially in ammonia. By alcohol it is converted, like albumen and fibrin, into an adipocirous substance, of a fetid odour ; and, like tlie same substance, it may be dissolved by a sufficient quantity of acetic acid. REFERENCES. Braconnot, Eclin. Jonr. of Science, viii. 36J>, denies the accuracy of Proust's observations concerning Caseous Oxide and Caseic Acid. Eggs. The shell of eggs is composed principally of carbonate of lime with a little animal matter. The white consists of albumen ; the yolk consists principally of a substance resembling albumen and a semi-fluid oil, which may be separated from the other portions by boiling the egg. The yolk contains a large quantity of phosphorus, which is obviously to supply phosphoric aeid for forming the bones oi" the chick. REFERENCE. Prouf. Phil. Trans. 1822. Humours of the Eye. The aqueous and vitreous humours of the eye, are composed principally of water, with some saline matter, and a trace of albumen. The crystalline lens contains more than half its weight of water and the remainder is a peculiar animal matter, very analogous to albumen, with a trace of salts. REFERENCE. Bostock's Physiology. Tears. The tears are limpid and of a saline taste, dissolve freely i water, and owing to the presence of free soda, communicate a green tint to the blue infusion of violets. Their chief salts are the muriate and phosphate of soda. According to Fourcroy and Vauquelin, the animal matter of the tears is mucus ; but it is more probably either albumen, or some analogous principle. Its precise nature has not however been satisfactorily determined. Mucus. This term appears to have been used in very different sig- nifications. Its properties vary somewhat, according to the source from which it is derived ; but its leading characters are in all cases the same, and are best exemplified in the mucus from the nostrils. It appears to have nearly the same composition as tears, but being more exposed to the air,, it suffers with more rapidity those changes caused by the absorption of oxygen, and hence its greater viscidness and con- sistence. REFERENCE. On the different kinds of Mucus t see Thenard, iv. 592. Pus. This is the fluid secreted by an inflamed and ulcerated sur- face. Its properties vary according to the nature of the sore from which it is discharged. Healthy pus is a yellowish-white coloured liquid, of the consistence of cream, and of a peculiar odour when warm ; under the microscope it appears to be composed of solid glo- bules, floating in a transparent fluid ; its specific gravity is about 1*03: it is insoluble in water, and is thickened, but not dissolved by alcoho-1; it produces no change on vegetable blues, and is dissolved by the stronger acids. It is distinguished from mucus according to Grassmey- ANIMAL SUBSTANCfc;S. 421 er, as follows : triturate it with its own weight of water, then mix it with an equal quantity of a saturated solution of the carbonate of po- tassa. If it contain pus, a transparent jelly forms in a few hours ; but this does not happen if mucus only is present. REFERENCES. For Grassmeyer's test, sse Thomson's Syst. iv. Dr. Young, on Consumptive Diseases, gives a test for distinguishing Pus from Mucus, founded on optical properties. Sir E. Home on Ulcers. Sweat. The excretion which is continually passing off by the skin in the form of insensible perspiration, consists chiefly of water ; but it contains some muriate of soda and free acetic acid, in consequence of which it has a saline taste and an acid reaction. Urine. Urine is an excretory fluid separated from the blood by the kidneys. In its natural healthy state, it is a transparent, limpid fluid, of an amber colour, having a saline taste, while warm emitting an odour which is slightly aromatic, and not at all disagreeable. Its spe- cific gravity in its most concentrated form, is about 1-030. It gives a red tint to litmus paper, a circumstance which indicates the presence either of a free acid or of a super-salt. Though at first quite trans- parent, an insoluble matter is deposited on standing ; so that urine, voided at night, is found to have a light cloud floating in it by the fol- lowing morning. This substance consists in part of mucus from the urinary passages, and partly of the superurate of ammonia, which is much more soluble in warm than in cold water. The urine is yery prone to spontaneous decomposition. When kept for two or three days, it acquires a strong urinous smell ; and as the putrefaction proceeds, the disagreeable odour increases, until at length it becomes exceedingly offensive. As soon as these changes com- mence, the urine ceases to have an acid reaction, and the earthy phos- phates are deposited. In a short time, a free alkali makes its appear- ance, and a large quantity of carbonate of ammonia is gradually gen- erated. Similar changes may be produced in recent urine by contin- ued boiling. In both cases the phenomena are owing to the decompo- sition of urea, which is almost entirely resolved into carbonate of am- monia. According to the researches of Berzelius, the urine is one of the most complex animal fluids, consisting of more than twenty different substances. Of these, water constitutes 933 parts in 1000 of urine. The composition of the urine, however, is much changed by the in- fluence of certain diseases : thus, sugar is found in the urine voided in diabetes ; in some cases of jaundice it is tinged of a yellow colour by the bile ; and in certain kinds of dropsy, albumen is present in it in large proportion. REFERENCES. For the able researches of Berzelius on Urine ^ 8pc. see his general views of the composition of Animal Fluids, in Ann. of Phil. ii. 19, 195, 377, 415, and his Animal Chemistry. Proust, Ann. de Chim. xxxvi. 258. John on the absence of Urea in Hepatitis, Aim. of Phil. v. 424, vi. 392. Prout on the pink sediment from Urine, Medico Chir. Trans, ix. 481. Ann. of Phil. xv. and xvi. Urinary Concretions. The most common kind of urinary concre- tions may be conveniently divided into the following species : 1. The uric acid calculus ; 2. The bone-earth calculus, principally consisting of phosphate of lime ; 3. The ammoniaco-magnesian phosphate ; 422 ANIMAL SUBSTANCES. 4. The fusible calculus, being a mixture of the two preceding species ; 5. The mulberry calculus, composed of oxalate of lime : 6. The cystic oxide calculus ; 7. The alternating calculus ; and, 8. The compound calculus. The Uric Add Calculus, is a hard inodorous concretion, commonly of an oval form, of a brownish or fawn colour, and smooth surface; it consists of layers arranged concentrically around a central nucleus, the laminae being distinguished from each other by a slight difference in colour ; it is sparingly soluble in water, and muriatic acid ; is solu- ble with effervescence, by nitric acid, and the solution yields purpu- rate of ammonia when evaporated ; when digested in pure potassa the acid is dissolved and the other substances remain ; before the blow pipe it becomes black, emits a peculiar animal odour, and is gradually consumed, leaving a very small quantity of white alkaline ashes. The Bone-earth Calculus, is of a pale brown colour, and has a very smooth surface ; it consists of layers, which adhere so slightly that they may be separated with ease into concentric crusts ; in powder, it dissolves easily in dilute nitric or muriatic acid, but is insoluble in potassa ; before the blow pipe it first assumes a black colour, from the decomposition of a little animal matter, and then becomes quite white, undergoing no further changes unless the heat be very intense, when it is fused. The Triple Phosphate Calculus rarely exists quite alone, but is gene- rally associated wilh a small proportion of phosphate of lime. It of- ten occurs in minute crystals diffused over the surface, or between the interstices of other calculus larnince ; is generally white and less com- pact than the preceding ; when reduced to powder it is easily dissolved by cold acetic acid, and still more easily by the stronger acids, the salt being thrown down unchanged by ammonia ; before the blow-pipe a smell of ammonia is given out, it diminishes in size, and melts into white pearl with rather more facility than phosphate of lime. The Fusible Calculus is recognized by the property from which it derives its name. Before the blow-pipe it froths and runs into a glo- bule, which is either perfectly transparent or of a pearly whiteness ; it consists of a mixture of the phosphate of lime and triple phosphate of ammonia and magnesia. The Mulberry Calculus is named from its resemblance in its rough tuberculated surface, to the fruit of the mulberry. It consists of oxa- late of lime, as was first proved by Dr. Wollaston ; when heated be- fore the blow-pipe it becomes black, and afterwards white, and on con- tinuing the heat, a white residuum of pure lime is obtained, which gives a brown stain to moistened tumeric paper. This calculus is sometimes smooth, and when mixed with uric acid becomes more re- fractory, and decrepitates before the blow-pipe. The Cystic Oxide Calculus, is very rare. It resembles the triple phosphate calculus, but is more compact ; before the blow-pipe it emits a peculiarly foetid smell ; it is readily soluble in almost all acids, and in the alkalies ; is insoluble in alcohol, water, acetic, tartaric or citric acids, or in solutions of neutral carbonate of ammonia; it is composed of animal matter, and it is never accompanied with the mat- ter of any other concretion. The Alternating Calculus, is composed of alternate layers of two or more of the substances already mentioned, as constituting calculi ; a ANIMAL SUBSTANCES. 423 fragment of each of the layers may be broken off, and its nature deter- mined by the application of the blow-pipe, and other tests abovemen- tioned. The Compound Calculus, may be known from the equivocal result 8 presented when it is subjected to chemical examination ; it is compos- ed of an intimate mixture of the ingredients of other calculi. Besides the calculi just mentioned, three other species have been no- ticed. Two of these were described by Dr. Marcet, under the names of Xanthic Oxide and Fibrinous Calculus, both of which are exceedingly rare. The former is of a reddish or yellow colour, is soluble in acids and in alkalies, and its solution in nitric acid, when evaporated, as- sumes a bright lemon-yellow tint ; the latter derives its name from fi- brin, to which its properties are closely analogous. The third species consists chiefly of carbonate of lime, and is likewise of rare occur- rence. REFERENCES. Marcels Essay on the chemical history and medical treat- ment of Calcvlous disorders. The papers of Dr. Wallaston and Prof. Braitde, in Phil. Trans. 1797 and 1810. Prout's inquiry into the nature and treatment of Gravel, Calculus, fyc. Dr. Yelloly, in Phil. Trans. 1829. Dr. Henry on Urinary and other Morbid Concretions, Ann. of Phil. xv. 107. See also the ivor/cs of Thomson and Thenard. Solid Parts of Animals. Bones. These consist of earthy salts and animal matter intimately blended, the former of which are 'designed for giving solidity and hard- ness, arid the latter, for agglutinating the earthy particles. The ani- mal substances are chiefly cartillage, gelatin, and a peculiarly fatty matter called marrow. According to the analysis of Berzelius, 100 parts of dry human bones consist of animal matters 33-3, phosphate of lime 51-04, car- bonate of lime 11-30, fluate of lime 2, phosphate of magnesia 1 16, and soda, muriate of soda, and water 1-2. Mr. Hatchett found, also, a small quantity of the sulphate of lime ; and Fourcroy and Vauquelin discovered traces of alumina, silica, and the oxides of iron and man- ganese, REFERENCES. Processes for extracting Gelatine from Bones, by D'Arcet, and Gauthier, Repert. Arts. l ld Ser. xlv. 50. Repert. of Pat. Invent, vi. 321. On the use of (he Gelatine of Bones procured from Butcher^ 1 Meat, as an Alimentary Substance, by M. D'Arcet, Repert. of Pat. Invent, fyc. xi. 25. Teeth are composed of the same materials as bone ; but the enamel dissolves completely in dilute nitric acid, and therefore is free from cartilage. The composition of Ivory is similar to that of the bony matter of teeth in general. The Shells of Eggs and the covering of crustaceous animals, such as lobsters, crabs, and the starfish, consist of the carbonate and a lit- tle phosphate of lime, and animal matter. The shells of oysters, muscles, and other molluscous animals consist almost entirely of car- bonate of lime and animal matter, and the composition of Pearl and Mother of Pearl is similar. Horn differs from bone in containing only a trace of earth. It con- sists chiefly of gelatin and a cartilaginous substance like coagulated 424 ANIMAL SUBSTANCES. albumen. The composition of the nails and hoofs of animals is simi- lar to that of horn ; and the cuticle belongs to the same class of sub- stances. Tendons appear to be composed almost entirely of gelatin ; for they are soluble in fboiling water, and the solution yields an abundant jelly on cooling. The composition of the true skin is nearly the same as that of tendons. Membranes and ligaments are composed chiefly of gelatin, but they also contain some substance which is insoluble in water, and is similar to coagulated albumen. In Hair, Vauquelin found traces of silex, sulphur, iron and manganese and a peculiar oil, which is nearly colourless in white hair, blackish- green in dark hair, and red in red hair. The composition of Wool and Feathers appears analogous to that of hair. The quill part of the feather was found by Mr. Hatchett to con* gist of coagulated albumen. The flesh of animals, or Muscle, consists essentially of fibrin, but independently of this principle, it contains several other ingredients, such as albumen, gelatin, a peculiar extractive matter called Osma- zome, fat and salts ; substances which are chiefly derived from the blood, vessels, and cellular membrane, dispersed through the muscles. APPENDIX. TABLE of the Atomic Weights and Symbols of the Elementa- ry ', and most important Compound, Bodies. The atomic weights are referred to Hydrogen as 1. JV antes of Subs lances. Symbols- At in. || Pittites of Wts. I) Substances. Symbols. Atom. Wts. ALUMINUM i Al 13.7 25.7 49.15 64.6 76.6 80.6 84.6 117.7 153.22 88.6 96.6 377 49.7 57.7 53.7 61.7 77.7 68.7 76.7 84.7 104.15 84.7 71 79 106.45 87 8 78.26 55.8 63.8 91.25 71.8 20.5 28.5 55.95 36.5 36.2 6 14 22 chloride, perchloride, hydruret, bihydruret, bisulphuret, C+C1 2C+3C1 2C+2H C+2H C+2S Ce Ce-fO Ce-l-HO Cl CH-O C1+4O Cl-i-50 C1+7O Cr Cr-f-HO Cr-f3O Cr-j-HCI Cr+3Cl Cr+3F Co Co-fO Co-fHO Co+Cl Co-fS Cb Cb+2O Cb-fSO Cu 2Cu+O Cu+O Cu+2O 2Cu+Cl Cu+Cl 2CU+S Cu+S F G G+O Au Au+O 41.45 118.55 14 8 38 46 54 58 35.45 43.45 67.45 75.45 91.45 28 40 52 81.22 134.35 84.04 29.5 37.5 41.5 64.95 45.5 185 201 209 31.6 71.2 39.6 47.6 98.65 67.05 79.2 47.6 18.68 17.7 25.7 200 208 oxide, (alumina) chloride, ANTIMONY > . . . Al-f-HO Al+Cl Sb Sb+HO Sb-j-2O oxide, deutoxide, peroxide, sesquichloride, perchloride, sesquisulphuret, bisulphuret, Sb+24O Sb+l|Cl Sb-f-2iCl Sb+l4S Sb-f2S As As+UO As+2|O As+S~ As+HS As+2iS Ba Ba+0 Ba+2O Ba+Cl Ba+S Bi Bi+0 Bi+Cl Bi+S B Br Cd Cd+O Cd-t-Cl Cd+S Ca Ca+O Ca-fCl Ca-fS Ca+P C C+O C+2O oxide, peroxide, protoxide, peroxide, chloric acid, perchloric acid, [CHROMIUM .. arseriious acid, arsenic acid, sulphuret, sesquisulphuret, pei sulphuret, BARIUM oxide, chromic acid, chloride, terchloride, terfluoride, protoxide(baryta) peroxide, chloride, sulphuret, oxide, peroxide, chloride, sulphuret, oxide, chloride, sulphuret, oxide, columbic acid, COPPER BROMI'VF .. suboxide, (red) proioxiHf, (black) superoxide, subchloride, chloride, disulphuret, sulphuret, FLUORINE oxide, chloride, sulphuret, oxide, (lime) chloride, sulphuret, phosphuret, GLUCINUM oxide (glucina) carbonic oxide, carbonic acid, oxide, 426 APPENDIX. TABLE OF ATOMIC WEIGHTS AND SYMBOLS CONTINUED. Names of Substances. Symbols. A $%- Names of 1 , / Substance* |%^- A. om Wts. teroxide, chloride, terchloride, tersulphuret, Au-f3O Au+Cl Au+3Cl Au-f3S H H+O H-|-2O H-fCl H+Br H-fl H+F I 1+50 I-T-2C1 Ir Fe Fe+0 Fe-fHO Fe+Cl Fe+HCl Fe+S~ Fe-|-2S Pb Pb+0 Pb+HO Pb+20 Pb+Cl Pb-l-1 PiH-S L L+0 L-I-C1 L+S Mg Mg-fO Mg+Cl Mn Mn+O Mn+HO Mn-f2O 3Mn-r-40 4Mn-f70 Mn-fCl 2Mn-f-7C! Mn-fS Hff Hg+0 Hg+20 Hg+Cl Hg-f-2Cl Hg+I Hg+2I Hg+S Hff-4-2S 1224 235.45 306.35 248 1 9 17 36.45 79.26 127 19.68 126 166 196.90 98.6 28 36 40 63.45 81.22 44 60 103.5 111.5 115.5 119.5 138.95 229.5 119.5 10 18 45.45 26 12.7 20.7 48.15 27.7 35.7 39.7 43.7 115.1 166.8 63.15 303.55 43.7 200 208 216 235.45 270.9 326 452 216 232 MOLYBDENUM Mo Mo-fO Mo-f-2O Mo-r-2S Mo-f3S Ni Ni+0 Ni-fHO Ni+Cl Ni-fS N N+0 N+20 1N-4-3O N-f-40 N-f-50 N+4C1 N+31 N+2C O Os Os+O Pd Pd+0 Pd-f2O P 2P+O P+HO P-f240 P+HC1 P+24C1 P+H" P+2H Pt Pt+O PH-2O Pt-fCl Pt+2Cl Pt+S Po Po+O Po-f3O Po+Cl Po-f-I Po-fS R R-fO R+liO Se 47.7 55.7 63.7 79.7 95.7 29.5 37.5 41.5 64.9? 45.5 14 22 30 38 46 54 155.8 392 26 8 99 107 53 61 69 15.7 39.4 27.7 35.7 68.87 104.32 J6.7? 17.7 98.6 106.6 114.6 134.05 169.5 114.6 39.15 47.15 63.15 74.6 165.15 55.15 52 60 64 40 oxide, deutoxide, bisulphuret, tersulphuret, protoxide, (water deutoxide, hydrochloric acid hydrobromic acid hvdiiodic acid, hydrofluoric acid, oxide, sesquioxide, chloride, sulphuret, protoxide, deutoxide, hyponitrousacid, nitrous acid, nitric acid, chloride, iodide, bicarburet, (cya- nogen) iodic acid, chloriodic acid, IRIDIUM oxide, peroxide, chloride, perchloride, sulphuret, bisulphuret, oxide, PALI ADIUM oxide, sesquioxide, peroxide, chloride, iodide, sulphuret, LITHIUM oxide, deutoxide, PHOSPHORUS hypophosphorous acid, phosphorous acid phosphoric acid ^ pyrophosphor- / ic acid, ; chloride, perchloride, hydruret, bihydruret, PL AT1NUM oxide, (lithia) chloride, sulphuret, oxide, (magnesia) chloride, IVTANG \NESE. oxide, sesquioxide, deutoxide, red oxide, varvacite, chloride, perchloride, sulphuret, oxide, deutoxide, chloride, bichloride, sulphuret, protoxide, (po- tassa, ) peroxide, chloride, iodide, sulphuret, oxide, deutoxide, Chloride, bichloride, iodide, deutiodide, sulphuret, hisulnhuret. oxide, sesquioxide, SELENIUM APPENDIX. 427 TABLE OF ATOMIC WEIGHTS AND SYMBOLS CONTINUED. Names of Substances. Symbols. Atom. Wts. 1 Names of Substances. Symbols, j Atom. Wts. oxide, selenious acid, Se-fO Se-j-2O 48? 56 oxide, TIN Th+0 St 67.6 57 9 selenic acid, SlLICIUM Se-}-30 Si 64 7 5 oxide, deutoxide St+O gt-j-2O 65.9 73 9 oxide, (silica) Si+0 Aff 15.5 108 chloride, bichloride St+Cl st-i-2ri 93.35 128 8 oxide, chloride, iodide, Ag+0 Ag+Cl A61. Fulminating gold, 354. mercury, 347. powder, 218. platinum, 358* silver, 352. Fulminic acid, 182. Fungin, 385. Fusion 52. watery, 16. Fusible metal, 327. Fustic, 403. Galena, 337. Gallates, 374. *& * Gall-nuts, 373, 405. Gall-stones, 419. Galvanic battery, 77. arrangements, 77, 78, Galvanism, 77. how developed, 78. electrical agency of, 79. chemical agency of, 7& igniting effects of, 81, theory of, 82. Gas, definition of, 97. exhilerating, 128. of marshes, 175. from coal and oil, 177. Gastric juice, 418. Gelatin, 413. Gems, artificial, 261. INDEX. 435 Gentianin, 385. Gilding, 356. Glass, of antimony, 317. various kinds of, 261. Glauber's salt, 227. Gliadine, 404. Glucina, 258. Glucinum, 257. oxide of, 258. Glue, 413. Gluten, 404. Glycerine, 389, 412. GoW, 353. oxide of, 353. chlorides of. 354. etherial, 354. bromide of, 355. iodide of, 355. sulphuret of, 355. phosphuret of, 355. alloys of, 355. powder, 356. fulminating-, 354. Gong, Chinese, 332. Goniometers, 21. Goulard's extract, 366. Graphite, 165. Gravity, effect of, on chemical ac- tion, 24. Gum, 401. elastic, 392. Gum resins, 39J. Gunpowder, 218. Gypsum, 247. Hair, 424. Hartshorn, 137. Heat, (see caloric.} animal, 418. Hematin, 386. Hircine, 412. Hogslard, 412. Hombergs phosphorus. 244. Honey, 400. Hoofs, 424. Hordein, 400. Hydrates, metallic, 200. Hydro, how employed, 97. Hydrocarbon, chloride of, 179. bromide of, 179. iodide of, 180. Hydrocyanates, 184. Hydrogen, 110. deutoxio'e of, 116. protoxide of, 113. arseniuretted, 300. Hydrogen, pliosphuretted, 162. carburetted, 174. potassiuretted, 212. seleniuretted, 193. sulphuretted, 153. telluretted, 325. with metals, 201. carburets of, 176. Hygrometers, 58. Hydrosulphurets, 153. Hydrurets, metallic, 201. Hyoseyamine, 384. Ice, 45, 115 Imperatorin, 386. Incandescence, 69. Indigo, 402. Ink, 276. sympathetic. 294, 328. indelible, 351. Inulin, 386. lodates, 109. Iodide of nitrogen, 136. Iodides, metallic, 201. Iodine, 106. and oxygen, 108. arid sulphur, 152.' and phosphorus. 162. bromides of, 109. hydrocarburet of, 186. Ipecacuanha, 382. principle of, 382. Iridium, 360. oxides of, 360. Iron, 270. oxides of. 270. chlorides of, 272. bromides of, 273. iodide of, 272. sulphurets of, 272. phosphuret of, 272. carburets of, 273. cast and wrought, 273. alloys of, 274. Baits of, 275. Isinglass, 413. Isomorphism, 21. Ivory black, 166. James 1 powder, 317. Jelly, animal, 414. Kermes, mineral, 316. Kelp, 230. Kreosote, 364. Labarraque's soda liquid, 231. 436 INDEX. Lakes, 402. Lampblack, 166. Lard, 412. Latent heat, 54. Lateritious sediment, 409. Laws of combination, 28. Law of multiples, 29. Lead, 335. oxides of, 335. chloride of. 336. iodide of, 337. sulphuret of, 337. alloys of. 337. salts of, 338, acetate of, 366. tests of, 339. Legumin, 386. Lemons, acid of, 372. . essential salt of, 368. Lenses, 61. navigation, 15. Leyden jar, 72. Libavius, fuming liquor of, 285. Ligaments, 424. Light, 65. laws of, 66. analysis of, 66. illuminating rays of, 67. heating rays of, 67. chemical rays of, 67. magnetic powers of, 68. sources of, 69. Lightning, 76. rod, 76. Lignin, 401. Lime, 243. hydrate of, 243. chloride of, 245. slaked, 244. salts of 247. oxalate of, 369. Limestone, 249. Linament, volatile, 389. Liquefaction, 52. Liquids, expansion of by heat, 47. conducting power of, 42. Liriodendrine, 386. Litharge, 335. Uthia, 233. salts of, 234. tests of, 234. Lithates, 409. Lithium, 233. oxide of, 233. chloride of, 234. Litmus, 403. Liver of antimony, 317. J^ogwood, 403. Lunar caustic, 351. Lupulin, 386. Madarin, 386. Madder, 402. Magnesia, 250. hydrate of 250. calcined, 250. salts of, 251. tests of, 253. oxalate of, 369. Magnesium, 249. oxide of, 250 chloride of, 250. Magnetism, 83. laws of, 83. terrestrial, 85. electro, 86. Malachite, 334. Mnlates, 372. Maltha, 399. Manganese, 264. oxides of, 264. chloride of, 267. fluoride of, 268. sulphuret of, 268. phosphuret of, 268. salts of, 268. Manna, 400. Marble, 249. Massicot, 335. Matter, properties of, 14. Medullin, 386. Membranes, 424. Menstruum, 22. Mercury, 340. oxides of, 341. bromides of, 344. chlorides of, 342. iodides of, 344. sulphurets of 344. cyanide of, 345. amalgams of, 345. salts of, 346. fulminating, 347. tests of, 847. Metallic combinations, 203. Metals, 195. general properties of, 195. table of discovery of, 195. malleability of. 196. ductility of, 197. tenacity of, 197. hardness of, 197. INDEX. 437 Metals, structure of, 197. native state of, 197. action of heat on, 198. action of electricity on, 198. and oxygen, 198. water, 200. ammonia, 200, chlorine, 200. bromine, 201. iodine, 201. fluorine, 201. hydrogen, 201.* nitrogen, 201. sulphur, 201. phosphorus, 202. carbon, 203. cyanogen, 203. boron, 203. selenium, 203. alloys of, 203. amalgams of, 205. classification of, 206. Meteoric stones, 270, 291. Milk, 419. sugar of, 414. Minder-erus, spirit of, 365. Mineral chamelion, 266. caoutchouc, 399. pitch, 399. tar, 399. Minium, 336. Mixture, heat produced by, 62. Molasses, 400. Molybdates, 305. Molybdenum, 303. oxides of, 303. chlorides of, 304. sulphurets of, 304. Mordant, 402. Morphine, 378. salts of, 379. Mother of Pearl, 423. Mucilage, 401. Mucus, 420. Multiples, law of, 29. Muriatic ether, 397. Muscle, 424. Myricin, 392. Nails of animals, 424. Naphtha, 398. from coal tar, 177. Naphthaline, 177. Narcotine, 380. Neutral salt, 97. Nickel, 290. Nickel, oxides of, 291. alloys of, 291. salts of, 292. Nicotine, 384. Nitre, 217. sweet spirits of, Nitrogen, 123. oxides of, 128. chloride of, 135. iodide of, 136. Nitrous acid, 131. gas, 129. oxide, 128. Nomenclature, 96. Ot7ofDippel, 411. of vitriol, 149. gas, 178. Oils, animal, 411. drying, 389. fixed, 389. vegetable, 389. volatile or essential, 390. Ointment, 392. Olefiant gas, 174. Olivile, 386. Opium, active principle of, 378. Orpiment, 301. Osmazome, 424. Osmium, 360. oxide of, 360. OxaMes, 367. Oxamide, 368. Oxide, cystic, 422. Oxide, xanthic, 423. Oxygen, 98. Oxijgenized water, 116. Oxy-hydrogen blow-pipe, 112. Oxy-muriatic acid, 100. Packfong, 292. Palladium, 359. oxide of, 359. Pancreatic juice, 418. Paraffin, 387. Patent yellow, 336. Pearls, 423. Pearl, white, 328. Pearlash, 221. Percussion, heat evolved by, 61. Perspiration, fluid of, 417. Petroleum, 399. Petroline, 399. Pewter, 337. 438 INDEX. Phenicin, 402. Phocenine, 412. Phosgene gas, 173. Phosphori, 68. solar, 68. from heat, 68. spontaneous, 68. Phosphoric ether, 397. Phosphorus, 156. oxide of, 157. chlorides of, 161. bromides of, 161. iodide of, 162. hydrurets of, 162, 163. sulphuret of, 164. Phosphurets, metallic, 202. Phosphur 'cited hydrogen, 162. Photometer, 68. Picromel, 419. Picrotoxin, 387. Pinchbeck, 332. Piperin, 387. Pitchblende, 318. Pitch, mineral, 399. Pit- Coal, 399. Plaster of Paris, 248. Plasters, 389. Plating, 350. Platinum, 356. oxides of, 357. chlorides of, 357. sulphuret of, 358. sulphate of, 358. fulminating, 358. alloys of, 358. Plesiomorphism, 21. Plumbagin. 387. Plumbago, 274. Pollenin, 386. Polychroite, 387. Populin, 387. Potassa, 210. hydrate of, 210. fusa, 210. salts of, 215. acetate of, 365. oxalates of, 368. tartrates of, 369. tests of, 223. Potassa and Soda, tartrate of, 370. borotartrate of. 370. Potassium 208. oxides of, 210. chloride of, 211. bromide of, 212. Potassium, iodide of, 212. and hydrogen, nitrogen, sulphur, phosphorus, and cyanogen, 212. alloys of, 214. amalgams of, 214. Potatoe, starch of, 401. Pot-metal, 337. Precipitate, red, 341. white, 343. Precipitation, 25. Prism, 66. Proof spirit, 393. Proportions, definite, 28. combining, 28. union of bodies in, 28. Proportionals, 28. Proximate, analysis, 362. principles, 362. of vegetables, 362. of animal substances, 403 Prussian blue, 278. Prussiates, 277. Pulverization, 15. Purpurates, 409. Pus, 420. Putrefaction, 406. Putrefactive fermentation, 406. Pyrites, iron, 273. copper, 331. Pyroxilic spirit, 365. Pyrometers, 51. Quantity, influence on affinity, 25. Quercitron, 403. Quicklime, 244. Quicksilver, 340. Quinine, 380. Radiation, of caloric, 36. Rays, luminous, 67. calorific, 67. chemical, 67. Realgar, 300. Red lead, 336. dyes, 402. precipitate, 341. Reduction, 199. Rennet, 419. Resins, 391. Respiration, 416. Retinasphaltum, 399. Rhodium, 359. oxides of, 360. Rhubarbarin, 387. Rochelle salt, 370. Rum, 405. Saccharine fermentation, 405. INDEX. 439 Safety lamp, 65. Safflower, 402. Sago, 400. Salop, 384. Sal-ammoniac, 141. Saftcm, 387. Salifiabl", principles, 96 Salifying principles, 96. Saliva, 418. iSfa/J common, 224. of sorrel, 368. petre, 217. Salts, crystallization of, 16. hydrous and anhydrous, 16 Sanguinarine, 382. Sarcocoll, 388. Saturated solution, 23. Saxon blue, 402. Scale of equivalents, 31. Scheele's green, 302. Scillitin, 388. Secretions, animal, 418. Sealing wax, 391. Selenium, 191. oxide of, 192. chloride of, 193. bromide of, 193. sulphuret of, 194. : ^.^. phosphuret of, 194. Seleniurets, metallic, 203. Seleniurettcd, hydrogen, 193. Serocity, 415. Serum, 415. Shells, 423. 8jftmg, 15. Silica, or silex, 260. Silicates, 260. SUicium, 260. oxide of, 260. fluoride of, 262. carburet of, 262. Silver, 348. oxides of, 349. chloride of, 349. bromide of, 349. iodide of, 350. sulphuret and cyanide of, o50. alloys of, 350. salts of, 351. fulminating, 352. Smalt, 293. Soap, 389. Soda, 224. hydrate of, 224. salts of, 226. Soda, tests of, 233. acetate of, 365. Sodmm, 223. oxides of, 224. chloride of, 224. ^ iodide, sulphuret, phos-* phuret, 226. Solanine, 384. Solar rays, 60. Solder, plumber's, 337. soft, 328. Solution, 22. Sorrel, salt of, 368. Specific caloric, 59. Speculum metal, 332. Spectrum, solar, 67. Spelter, 279, Spermaceti, 411. Spirit, proof, 393. of wine, 393. Starch, 400. Steam, 55. engine, 56. Stearine, 389. Steel, 274. alloys of, 274. Strontia, or strontites, 240, salts of, 241. tests of, 242. Strontium, 240. oxides of, 240. chloride and iodide of,241 , sulphuret of, 241. Strychnine, 381. Suberin, 388. Succinates, 377. Suet, 412. Sublimation, 17. Sugar, 399. of lead, 366. of milk, 414. of diabetes, 414. ! Sulphocyanates, 186. Sulphur, 143. crystallization of. 143, milk of, 144. flowers of, 143. arsenic in, 144. chloride of, 151. bromide of, 152. iodide of, 152. cyanide of, 186. alcohol of, 187. Sulphurets, metallic, 201. Sulphuretted hydrogen, 153. Sulphuric ether, 396. Sun, heat produced by the, 60. 440 Supporters, of combustion, 96. Sweat, 421. Synthesis defined, 98. Syrup, 400. Tallow, 412. Tannin, natural, 403. artificial, 403. Tanno gelatin, 403. Tantalite, 320. Tantalum, 320. Tapioca, 400. Tar, mineral, 399. Tartar, 370. cream of, 370. emetic, 314, 318, 370. soluble, 369. Tartrates, 369. Tears, 420. Teeth, 423. Telluretfed, hydrogen, 325. Tellurium, 324. oxides of, 324. chlorides of, 325. hydruret of, 325. Temperature, defined, 35. Tenacity of metals, 197. Tendons, 424. Thermo-electricity, 95. Thermometers, 49. air, 49. differential, 49. alcohol, 50. mercurial, 50. register, 52. of contact, 41. Thorium or thorinum, 263. oxide of, 263. Tiglin, 388. Tin, 284. oxides of, 284. chlorides of. 285. sulphuret of, 286. butter of, 285. alloys of, 286. crystallized, 286. salts of, 287. Tin plate, 286. Tincal, 232. Titanite, 323. Titanium, 322. oxides of, 323. chloride of, 323. sulphuret of, 324. Tombac, 332. Train-oil, 411. INDEX. ] Trituration, 15. Trona, 231. Trough, galvanic, 77. Tungsten, 312. oxides of, 312. chlorides of, 313. Turpeth mineral, 347. nitrous, 346. Turmeric, 403. Turnsol, 403. Turpentine, oil of, 390. spirit of, 390. Type metal, 317. Ulmin, 377. Uranium, 318. oxide of, 319. salts of, 319. Uran-mica, 320. Urates, 409. Urea, 414. Urine, 421. Urinary calculi, 421. Vanadium, 309. oxides of, 310. chlorides of, 311. sulphurets of, 311. phosphuret of, 311. Vaporization, 54. Vapour, definition of, 97. latent heat of, 55. in the atmosphere, 126. Varnishes, 389. Vegetable substances, 362. acids, 363. albumen, 404. alkalies, 377. extract, 388. Veratrine, 382. Verdigris, 366. Verditer, 334. Vermilion, 344. Vinegar, distilled, 363. formation of, 406. Vinous fermentation, 405. Violine, 384. Vitriol, blue, 333. green, 276. white, 282. oil of, 149. Volatile alkali, 137. linament, 389. Voltaic instruments, 77. Volumes, combinations, in 30, 428 INDEX. 441 Water, 113. properties of, 113. contained in the air, 114. combines with solids, L13. composition of, 115. expansion of in freezing, 48. Wax, 392. Welding, 223, 270, 356. Wheat, 404. Whey, 419. Whiskey, 405. White lead, 339. Wine, formation of, 393. alcohol in, 393., Wires, tenacity of, 197. Woody fibre, 401. Wool, 424. Xanthic oxide, 423. Xanthogen, 187. Yeast, 404. Yellow, patent or mineral, 336. kings, 301. chrome, 308. dyes, 403. Yttria, 258. Yttrium, 258. Znffre, 293. Za.nthropicrite, 388. Zimome, 404. Zinc, 279. oxide, chloride, iodide and sulphuret of, 280, 281. alloys of, 282. salts of, 282. Zircon, 259. tests of, 260. Zirconium, 259. ERRATA. ge 46, line 1st from top, for " Easy" read " Essay." 65, line 17th from bottom, for " Chemical Statistics," read " Chemica! Statics." 84, line 14th from bottom, for " p. 69," read " p. 68." 105, line 25th from bottom, for " lime springs," read" brine springs." 177, line I7th from top, for " Naphtha from Coal Tar. And Naphtha" line," read " Naphtha from Coal Tar and Naphthaline." 189, line 2d from top, for " aad," read " and." 195, line 5th from bottom, for " Dr. \Vallaston," read " Dr Wollastoru"' 197, line 2d from bottom, for " is," read " are." 210, line 1st from top, for " Peroxide," read " Protoxide." 218, line 4th from top, for " phosphorous," read " phosphorus." 226, line 2d from bottom, for" Chevenix," read " Chenevix ." 223, line 9th from bottom, for" Serrulas," read " Serullas." 245, line 18th from bottom, for " anylitical," read " analytical." 247, Iine22d from top, for " chemica," read "chemical." 297, line 14th from top, for " Arsenius," read " Arseriious." 327, line 7th from top, for u loride," read u chloride." 327, line 12th from bottom, for " ane," read " and " 329, line 3d from top, the asterisk should be placed above "Cu. f * 331, line 15th from top, for " Bisulphuret," read " Disulphuret." 332, lines 1st and 8th from bottom, for ' Donoran," read " Donovan.* 7 345, line 23d from top, for " Bycianide," read " Bieyanide." 349, the Symbol for silver is sometimes printed " Aq" instead of" \g. n 368, line 13th from top, for " Binoxolate," read " Binoxalate." 377, line 16th from bottom, for " Bracconnet,"read " Braconno:." 393, Iite4th from bottom, for" Aquoe vita," read " Aqua vi ae " 394, line 1st, for " Alcohol. It can," read " Alcohol can." 395, line 1st, in the table, for " 25-27," read " 25-77." * c; <' (Z o o ^ * x> c/ i"T T Bcc cc on I. i! I lii 1 to * ~ i I }> s| m ^ Cn hO GO hO o NO 0~ ^ Q GENERAL LIBRARY -U.C. BERKELEY BOOOfl?ba3Q