LIBRARY OF THE UNIVERSITY OF CALIFORNIA PROF, WJB. RISING Class ELEMENTS OF CHEMISTRY, IJf THK <>RIH:K or TIM: LECTURES GIVEN YALE COLLEGE. BY liK \JAMIK SIL.LJMAN, PROCESSOR or :HEMIS TRY, PHARMACY, MINERALOGY AND GKOLOOT. IN TWO VOLUMES, NEW HAVEN: KD AND PUBLISHED BY UEZEKIAH HOWE. DISTRICT OF CONNECTICUT, ss. ********* BE IT REMEMBERED, That on the eighteenth day of February in * L. S. ! tne nft y fourth year of the Independence of the United States of Amer- * ica, BENJAMIN SILLIMAN, of the said District, hath deposited in this ********* O ffi ce the title of a Book, the right whereof he claims as Author in the words following, to wit : " Elements of Chemistry, in the order of the lectures given in Yale College. By Benjamin Silliman, Professor of Chemistry, Pharmacy, Mineralogy and Geology. In two volumes." In conformity to the Act of Congress of the United States, entitled, " An Act for the encouragement of learning, by securing the copies of Maps, Charts, and Books, to the authors and proprietors of such copies, during the times therein mentioned." And also to the Act, entitled, "An Act supplementary to an Act, entitled, 'An Act for the encouragement of learning, by securing the copies of Maps, Charts, and Books, to the Authors and Proprietors of such copies during the times therein men- tioned,' and extending the benefits thereof to the arts of designing, engraving, and etching historical and other prints." CHARLES A. INGERSOLL, Clerk of the District of Connecticut. A true copy of Record, examined and sealed by me, CHARLES A. INGERSOLL, Clerk of the District of Connecticut, PREFACE. THE object of this work is to present the science of Chemistry in the most intelligible form, to those who are learning its elements ; and for the convenience of the classes in Yale College, the topics are arranged in the order in which they are now discussed, in the lectures given in that Institution. As the Medical Class constitutes a part of the audience, the most important pharmaceutical prepara- tions, and leading uses of such substances as belong both to the Ma- teria Medica, and to Chemistry, are briefly mentioned ; and in gen- eral, throughout the work, practical facts are interwoven with scien- tific principles. The attempt has been made, to unite copiousness with condensation ; perspicuity with brevity ; and a lucid order, and due connexion of subordinate parts, with a general unity of design. By numerals* and letters, the topics have been digested under appropriate heads ; and by the use of large and small capitals, and italics, the writer's impression, as to the relative importance of the leading facts and propositions, has been indicated. It is supposed that these mechanical helps, not novel indeed, but in this work, more extensively employed than usual, may facilitate the progress of the student, by enabling him to take, at pleasure, a more general, a more particular, or a detailed review ; and the same facility is, of course, presented to the instructor. Exact accounts of processes and manipulations have been given ; and Dr. Hare, having kindly permitted the introduction of the cuts,f from his Compendium, his own language, sometimes abridged, has been generally employed in the descriptions of his figures. The val- uable illustrations, thus derived from his liberality, render it unne- cessary to apologize for the frequent use of his name. * Adopted, to some extent, by Dr. F. Bache, in his System of Chemistry for Med- ical Students, and more fully by Dr. Henry. t The more complex figures have been omitted. 237474 IV PREFACE. The materials of this work have been gradually accumulating since 1802. They have been drawn from Scientific Journals, from the Transactions of Learned Societies, and from the principal writers who have flourished since the middle of the last century the Augustan age of Chemistry. From works of an earlier date, light has been oc- casionally derived, as well as from notes and recollections of the in- structions of the distinguished teachers, to whom the author was formerly so happy as to listen. In this view, he takes particular satisfaction in naming the late Dr. Murray, of Edinburgh, and Prof. Thomas C. Hope, still a distinguished ornament of the University in the same city. Various notices, derived from the author's own experience, and from his personal communications with others, are introduced, with occasional figures, for illustration ; and in the notes, many miscella- neous facts are preserved. In the immediate preparation of this work for the press, the origi- nal memoirs of authors and discoverers have been often consulted, and the abstract has been frequently drawn from them, rather than from the elementary books ; but the analyses contained in the latter have not unfrequently been adopted ; sometimes even after a careful ex- amination of the original, and for this reason, among others, that the statements contained in them could be often, without injury, still farther abridged. In such cases, several eminent elementary writers have been diligently compared, on the same subject ; and thus omissions have been supplied, and obscurity has been removed, either by the comparison, or by resorting to the first record. References to the original memoirs have always been preserved, where such memoirs were attainable ; and when the books contain- ing them were not at hand, the citations have been copied from the latest systematical writers. Credit has also, in most instances, been given to elementary writers, for materials drawn from their pages ; but for brevity, and especially where the facts are the common stock of the science, the references have been sometimes omitted, or an initial letter only retained. There are, however, some works to which a more particular acknowledgment is due. Those of Bergman and Scheele ; the Lectures of Dr. Black, by Robison ; the System of Dr. Thomson, in all its editions, and also his more recent work on the First Principles of Chemistry ; the Dictionaries PREFACE. V of Nicholson, Aikins, and Ure, the Compendium of Dr. Hare, the Dispensatory of Dr. Coxe, the Technology of Dr. Bigelow, the Operative Chemist of Gray, and the Chemical Manipulation of Mr. Faraday ; the System of the late Dr. Murray, and his Elements, ably edited by his son ; as also the writings of Mr. Dalton ; the works of Lavoisier, Chaptal, Berthollet, and Fourcroy, the System of Thenard, in its most recent edition, and his miscellaneous writings, especially in connexion with Gay-Lussac ; and those of Dr. Priestley, Bishop Watson, Mr. Parkes, Prof. Berzelius, and Sir H. Davy, including also his Elements these are among the leading authorities, although it would be easy to increase the catalogue.* A recent work by Dr. Turner, of the London University, has been of great utility. It is highly scientific and very exact, particu- larly on the facts and doctrines of definite and multiple proportions, and combining equivalents ; and many of its details have been adopted. But the work to which, more than to any other, the author of this is indebted, is the Elements of Dr. Henry. All its numerous edi- tions have been attentively studied, and among the facts that have been cited from it, the statements of the proportions of bodies, and especially of the salts, are the most prominent. In numerous critical comparisons, made between it and the original memoirs, abundant evidence has been obtained of the great exactness of the respectable author, whose abstract always reflects an image of the original, diminished indeed, but perfect in every feature. No writer on chemistry, in the English language, surpasses Dr. Henry in fidelity, perspicuity and good judgment. For twenty years, his work was the text book of the classes in this Institution, and it ceased to be used here only when, on account of its increased size and cost, it ceased to be reprinted. Three editionsf of it with notes, were published ex- pressly for the students of Yale College ; there have been three English editions since the latest American, J and the author's eleventh, with his last revision, has, through his kindness, been just received. * Many French as well as English Journals of Science have been also examined. t Besides two subsequently, by Professors Coxe and Hare, of the Univ. of Penn. t Since it has become difficult to obtain this work, the valuable Manual of Dr. Webster, on the basis of Brande, has 'been recommended to the classes. Few works on Chemistry contain so much important information. VI PREFACE. To the following gentlemen, the author of this work tenders his acknowledgments; to Prof. Edward Hitchcock and Prof. J. W. Webster, who were consulted in the revisal of the earlier proofs ; but to Professors Griscom, Torrey and Olmsted, and to Mr. C. U. Shepard, assistant in the chemical department of Yale College, a more particular expression of thanks is due, for the trouble which they, by request, have taken, in reading nearly all the proofs. Their individual suggestions are occasionally designated ; and while the work has been much benefitted by their judicious criticisms, they are fully exonerated from any responsibility either for its errors, or its deficiences. The errors that have been detected, and which were of such a character as to affect the sense, have been registered, as usual, in a table of errata, although the corrections for most of them are generally obvious from the context. As other errors will doubtless be observed, the author requests, as a particular favor, that they may be promptly communicated to him. If it does not excuse, it may account for, some inadvertencies, when it is known, that an arduous and responsible work was written and printed, under the unremitting pressure of absorbing and often conflicting duties. Life is flying fast away, while, in the hope of discharging more perfectly our obligations to our fellow men, we wait in vain, for continued seasons of leisure and repose, in which we may refresh and brighten our faculties, and perfect our know- ledge. After we are once engaged in the full career of duty, such seasons never come ; our powers and our time are placed in inces- sant requisition ; there is no discharge in our warfare ; and we must fight our battles, not in the circumstances and position which we would have chosen, but in those that are forced upon us, by impe- rious necessity. Yale College, 1830. CONTENTS OF VOLUME I. Page. PLAN OF THE WORK, - - 1 INTRODUCTION, - - . - 7 PART I. IMPONDERABLE AGENTS. Sec. I. LIGHT, . . 35 Its materiality velocity, - -25 Its refraction, . - 26 Solar phosphori, - - - 29 Its chemical agency, - 31 " action on animals and vegetables, - - - 32 " " " mineral bodies, - 33 " connection with magnetism sources of light Leslie's Photometer, - - - 34 Sec. II. HEAT OR CALORIC, . 35 General nature, - ~ " Conclusions, - 42 Effects, . 44 1. Expansion, - " Thermometers, - - - 54 2. Distribution of Temperature, - 63 Conduction Radiation, - - 65 3. Congelation and Liquefaction, - 82 4. Vaporization and Gasification, - 84 Steam Engines, 92 5. Spontaneous evaporation, - - 104 Effects cold, &c. 105 Wollaston's cryophorus, - 116 6. Ignition or Incandescence, 117 7. Capacity for Heat Specific Heat, - 1 19 8. Combustion, - 126 Sec. III. APPENDIX TO CALORIC SOURCES OF HEAT AND COLD, 127 Blowpipe, 128 Table of freezing mixtures, - 136 Sec. IV. ATTRACTION, - 137 Gravitation, - Magnetism Galvanism, - 138 Cohesion and Aggregation, - 139 Crystallization, - 141 Chemical Attraction or Affinity, 151 Definite proportions, 160 Vlll CONTENTS. Page. Chemical equivalents, 164 Appendix to Attraction, 172 Rules of Philosophizing, - 173 Apparatus and Operations, - 174 Specific gravity, method of ascertaining, - 177 Pneumatic Cisterns, - 181 Gazometers, - 183 PART II. PONDERABLE BODIES. Sec. I. OXYGEN, Action on Combustibles, - 187 Relation to animal life, 190 Sec. II. NITROGEN OR AZOTE, - r - 193 Atmosphere, - 195 Sec. III. HYDROGEN, - 201 Properties, &c. 202 Water synthesis, - - 207 " analysis, 209 " its properties, - 211 Deutoxide of Hydrogen, 215 Eudiometry by Hydrogen, - 217 " " spongy Platinum, 221 Hare's Oxy-Hydrogen Blowpipe, - - 224 ALKALIES. Preliminary Remarks and Statement, - 228 Sec. I. AMMONIA, - - 230 Composition, - 233 Sec. II. POTASSA, - - 238 Properties, 240 Uses, &c. - Potassium, - . Decomposition of Potassa and Soda, - 244 Properties of Potassium, 247 Sec. III. SODA, - 251 Sodium, 253 Sec. IV. LITHIA, - - 257 EARTHS. Introductory Remarks, 259 EARTHS. I. LIME, ... - 261 Calcium, 264 II. BARYTA, - - 267 Barium, 268 HI. STRONTIA, 270 Strontium, .... 271 CONTENTS. IX Page. IV. MAGNESIA, - 272 Magnesium, - 274 V. SILICA, - 274 Silicon, - 277 Glass, - 279 VI. ALUMINA, - 283 Porcelain and Pottery, - - - 286 Aluminium, - - 293 VII. ZIRCONIA, 295 Zirconium, ..... 297 VIII. GLUCINA, ...... 298 Glucinium, 299 IX. YTTRIA, - - " Yttrium, 301 X. THORINA Thorium, - " SIMPLE INFLAMMABLE AND ACIDIFIABLE BODIES, (not metallic,) AND THEIR COMBINATIONS WITH THE PRECEDING BODIES. Sec. I. HYDROGEN, (see p. 201,) - 302 Sec. II. SULPHUR, ..... ACIDS. Preliminary Remarks, - 305 General Properties their nomenclature, 307 Sulphuric Acid, - ' Sulphurous " - - - - - 313 SALTS. Introductory Remarks, - - 318 Nomenclature, - - 319 Sulphates of Alkalies and Earths, - 321 Sulphate of Potassa, " Bi-sulphate of do. - - 323 Sulphate of Soda, 324 " Ammonia, - - 325 " Lime, - - - 326 " Baryta, - - 328 " Strontia, 330 " Magnesia, - - 331 " Alumina and Alum, - - 334 Sulphites of Alkalies and Earths, - - 337 Sulphite of Lime of Baryta, - " " Strontia, Magnesia, Alumina, Potassa, Soda, and Ammonia, - - 338 Hypo-Sulphurous Acid, - 339 Hypo-Sulphites, - - " Hypo-Sulphuric Acid and Hypo-Sulphates, 340 Sulphuretted Hydrogen, - - 341 Bi-Sulphuretted Do. - 344 VOL. II. 2 X CONTENTS. Page. Hydro-Sulphurets, 345 " of Potassa, 346 " ^ of Soda, Ammonia, Lime, Baryta, 347 " of Strontia, Magnesia, 348 Sulphuretted Hydro-Sulphurets General Characters, " of Potassa, of Soda, Ammonia, Lime, 349 of Baryta, Strontia, - 350 of Magnesia, 351 Sulphurets of Alkalies and Alkaline Earths, Sec. III. CARBON, 355 Charcoal, - 356 Uses, - 360 Sulphuret of Carbon, Carbonic Acid, - 365 Carbonates, 375 of Potassa, 376 Bi-Carbonate of Do. Carbonate of Soda, (soda-water) 379 Bi-Carbonate of Do. Carbonates of Ammonia, " Lime, 387 Baryta, 389 Strontia, - 391 " Magnesia, 392 Carbonic Oxide, - - 395 Carburetted Hydrogen Gases Olefiant Gases, 399 Naphthaline, - 407 Coal and Oil Gas, - - 408 Davy's Safety Lamp, - Cyanogen, 417 Prussic or Hydro-Cyanic Acid, Sec. IV. PHOSPHORUS, History preparationproperties, - 418 Atmospheric Eudiometer by Phosphorus, 420 Phosphoric Acid, - Phosphorous Acids, 425 Hypo-Phosphorous Acid, - Phosphates, 429 Phosphate and Bi-Phosphate of Potassa, - - 430 Phosphate of Soda, 431 " and Bi-Phosphate of Ammonia, 433 " of Soda and Ammonia of Lime, - 434 " of Baryta, - 437 " of Strontia of Magnesia, - 438 " of Ammonia and Magnesia, 439 CONTENTS. XI Page. Binary Compounds of Phosphorus with various bases, - 440 Phosphuretted Hydrogen and varieties, " Phosphuret of Sulphur, - 444 " Lime, - 445 Sec. V. NITROGEN its Combinations with preceding simple bodies, - 446 Nitric Acid, - Deutoxide of Nitrogen or Nitrous Gas, - 453 Nitrous Acids general explanation, - 456 Hypo-Nitrous Acid, - 457 Nitrous Acid, - 459 Appendix to History of the Nitrous Acids, - 461 Nitrates of Alkalies, 464 " Potassa, - " Soda, - - 473 " Ammonia, - 474 Nitrous Oxide or Protoxide of Nitrogen, 476 Nitrates of the Earths, - - 486 Baryta, - Strontia, - 486f Lime, - 487 Magnesia, .... 43$ Magnesia and Ammonia of Alumina, 489 Nitr tes, - - - - * Recapitulation of Compounds of Oxygen and Nitro- gen, ..... Sec. VI. BORON and BORACIC ACID, 491 Boracic Acid, - " Boron, - . 494 Borate of Potassa Bi-Borate of Soda or Borax, - 496 " Ammonia Baryta Strontia, - 498 " Lime Magnesia Alumina, - 499 Sec.VII.-FLUORic ACID, " Fluo-Silicic Acid Gas, - - - 502 Fluo-Boric Acid Gas, - 505 Fluoric Principles, - 506 Fluates General Characters, - 508 Fluate and Bi-Fluate of Potassa, - - - 509 " of Soda of Ammonia, - 510 " Baryta Strontia Lime, - 511 " Magnesia Alumina, 512 Silica, - - 513 Sec. VIII. SELENIUM, " Oxide of Selenium, - 515 Selenious Acid, 516 Selenic Acid, - 517 ERRATA VOL. I. Page 49, 1. 6 fr. top, after with, dele one of; and after another, insert of the same. p. 58, 1. 7 fr. bot. dele or melting snow. p. 128, 1. 15 fr. bot. for illustrating, read illustrated. p. 139, (g.) after chlorine, read and bromine. p. 148, 1. 19 fr. top, after which, read have. p. 155, 1. 4 fr. top, dele except the first. p. 161, 1. 3 and 4 fr. top, for 40, read 78 ; and for 78, read 40. p. 162, 1. 7 fr. top, for 1, read 2. p. 168, 1. 10 fr. top, after + 0.0694 x 3 =, add 1.1804. p. 169, 1. 27 fr. top, before acid, read oxygen of the. p. 180, 1. 5 fr. top, for x 18, read +18. p. 186, 4(c.) before for, read grs. p. 201, 2(a.) after muriatic, read acid. p. 202, 4(c.) for 0.694, read .0694 ; and p. 310, 1. 11 fr. bot, 373, 1. 5 and 6 fr. bot., 403, (6.), 408, 1. 9 fr. bot. tbe dec. point is either misplaced or omitted. p. 232, (6.) for weight 18.17 grs., read weight of 100 cub: in. is, 18.17 grs. p. 241, 1. 15 fr. top, after of the, read ashes of the. p. 248, 1. 18 fr. top, before potash, read nitrate of. p. 262, 1. 17 fr. top, after 32 for . A read , a. p. 288, 1. 10 from bot. before conical, read and. p. 297, (c.) (in a few copies,) for zirconia, read zirconium. p. 315, (fe.) for - 31, read + 31. p. 326, 1. 2 fr. top, interchange 1 and 2. p. 332, (i.) dele carbonate of. p. 337, 1. 1 fr. bot. for 40, read 32. p. 338, 1. 11 and 12 from bot. for 9 = 108 = 172, read 8 = 72 = 136. p. 339, 1. 16 and 17 fr. top. for 32, read 16 and for 40, read 24. p. 340, 1. 4 fr. bot. for 1, read 2; 1. 25 fr. top, for ous, read ic, and vice versa, p. 426, 1. 10. p. 355, 2 (a.) 1. 18 fr. top, for it, read charcoal. p. 357, 1. 20 fr. top, for oxide 35, read acid 35. p. 361, (kk.) 1. 16 fr. top, for of iron, read of lime. p. 371, 1. 21 fr. top, (n.) for fluid, read ice and omit the paragraph ( the knowledge that we present to him. He is, ordinarily, no judge of our theoretical views with re- gard to classification and arrangement ; he will, in most cases, even fail to understand us, when we discuss them ; and he will be best sat- isfied, with that course which, in the most interesting and intelligible manner, presents to him the greatest amount of useful knowledge. Both in my public courses of lectures, and in the present work, I have therefore, considered this object as paramount in importance to ev- ery other. 5. The simple , non-metallic combustible bodies are next intro- duced, both because their history is remarkably interesting and in- structive, and because they are the bases of the most important acids, whose history is easily and naturally developed, in connexion with that of these combustibles. Hydrogen, already described along with water, comes again into view as the basis of muriatic , acid. Nitrogen,f although, in a popular sense, strictly a non-combustible ; * Since the metallic oxides include bodies of such widely different properties, I can see no impropriety in distributing them into classes. I am supported in this ar- rangement by the late edition of Murray. t The new vegetable alkaline principles are so peculiar in most of their properties, that there would be no advantage in classing them with the alkalies commonly so called. t Also before described in coanexion with the history of the atmosphere. 4 PLAN OF THE WORK. still, because it possesses affinities, and produces in combination, re- sults entirely similar to those of the combustibles, is thrown into the same class, for the purpose of bringing forward the important acids and oxides of which it is the basis. Two of the least important of the simple combustibles, boron and selenium, are reserved until this period : their history bears no very important relation to that of most of the other bodies, but, as they too form acids, they are disposed of in the train of the other combustibles, and of the great agents that sustain combustion. Fluoric acid, which although undecomposed, has without doubt, a combustible base, is naturally assigned to the same place, in the class- ification, and from its combining, in an interesting manner, with boron, it comes immediately after that body, and before selenium, whose character is rather anomalous, but more allied perhaps to the combus- tibles than to the metals, where many have placed it. 6. Chlorine and Iodine and Bromine are introduced after the ele- mentary non-metallic combustibles have been described, and at a pe- riod when, as already intimated, their history becomes intelligible. The history of bodies, thus far described, embraces a great part of the philosophy of chemistry, and no small part of the most im- portant facts of the science. If we were to name any portion of chemistry, that is more splendid in its experiments, and more afflu- ent in important results, than another, it would be that which is in- cluded in the history of the elementary combustible bodies, especial- ly when we add their relation to chlorine and iodine, which follow im- mediately after the simple inflammables. 7. The metals come next, and their history includes all the re- maining elementary bodies. There is a general agreement among authors, as to the place which most of the metals are to occupy in a systematic arrangement, and no one at present thinks of presenting them, as some formerly did, in the beginning, along with other ele- mentary bodies. It is true that some of them are used in the de- monstrations that precede, but as most of the facts are familiar, and the phenomena intelligible, this creates no difficulty ; every one can understand, for instance, how iron decomposes water, and he will comprehend how sulphuric acid aids in that process, just as well be- fore as after he has studied the properties of iron and of the other metals. II. ORGANIC BODIES. They owe their particular modes of existence, to the joint action of the laws of life and of matter. There is, of course, nothing elementary in this part of the subject. Both animals and plants must derive their elements from the unor- PLAN OF THE WORK. ganized kingdom; and, in relation to them, our most interesting task is, to trace the various proximate principles, in which the ele- ments are combined. This part of chemistry is less splendid than the preceding ; but it is fruitful in important information, and much of it is applicable to common wants and occurrences. 1. Vegetable Bodies. We have here only oxygen, carbon, and hydrogen, as essential to the constitution of most plants ; nitrogen is found in some, and the number containing it is greater than was formerly supposed ; but the proximate principles are numerous and important, and the student is astonished to find, that such diversified results are obtained from the union, in different modes and proportions, of three or four .elements. 2. Animal Bodies. The few remarks, just made, are applicable here with some quali- fications. The same elements are found as in vegetables; and nitrogen, instead of being an occasional, is nearly a constant principle. The number of proximate principles is however more limited than in the vegetable kingdom, but their history is instructive and important. All are agreed in giving a late place to the chemistry of organ- ized bodies ; for it is obvious, that it would not be intelligible at an earlier period. GALVANISM. It has been already stated, that this power, although mentioned and described, generally, among the imponderable agents, is better understood, after the student has been made acquainted with all the Qther facts in chemistry. As a general power, its most important function is, in the decom- position of bodies, ending in the transfer of their elements and prin- ciples, to its respective poles. This being, in the begining, ex- plained, and experimentally proved, in connexion with the history of the other imponderable agents, there is no difficulty in marking and understanding the polarity of each body as we proceed, and when we come to present Galvanism, in form and in fulness, at the end of the course, thislgeneral arrangement of both elements and prox- imate principles can be recapitulated, and experimentally illustrated in detail, with great advantage. (3 PLAN OF THE WORK. Neither is there any thing in the earlier parts of the course that renders it necessary to exhibit the deflagrations, ignition,* and mus- cular shocks produced by this agent ; and which, when presented at the conclusion, with the aid of powerful apparatus, terminate a long course of demonstrations and reasoning, with the most brilliant finish that can be desired. So far as the natural history of bodies, and their analysis, and ap- plications to use are proper subjects of attention in a concise Manual, I have thought it better, in general, to give the facts, in connexion with the different articles to which they belong, rather than at the end of the work. The numerical tables that are not given in the body of the work, are of course contained in an appendix. They are necessarily se- lected from different authors, and although little used by the student of mere elements, are important for occasional reference. * Dr. Hare however uses a small calorimotor to explode gases ; and his larger in- struments exhibit results, more splendid and interesting, than any other Galvanic apparatus with which I am acquainted. INTRODUCTION.* I. PHENOMENA AND SCIENCES CONNECTED WITH NATURAL OB- .'JECTS. As man is, necessarily and constantly, conversant with natural objects, he cannot, if he would, be wholly withdrawn from the physical phenomena, which are perpetually exhibiting the relations of material things. In ancient times, every thing relating to natural bodies was inclu- ded under PHYSICS, and this term therefore, comprised NATURAL HIS- TORY, NATURAL PHILOSOPHY, and CHEMISTRY. Since the more ex- tended cultivation of natural science, and particularly since the time of Bacon and Newton, the external appearances! of natural bodies have been included under NATURAL HISTORY, and their analysis and composition are assigned to CHEMISTRY. 1 . NATURAL PHILOSOPHY occupies itself with the general affections and mechanical laws of bodies, with the physical f laws of light, heat, magnetism and electricity, and in short, with all that is not inclu- ded in the two other great divisions of natural science. It is a science of high importance ; it is in every university, a regular branch of education, and in every enlightened country, an object of diligent cultivation. It is founded on observation and experiment, and the application of the mathematics, in aid of its researches, has given them both dignity and certainty. The mathematics are applied to most of the physical sciences, not excepting Chemistry. They are founded on intuitive truths, and embrace the relations of magnitude and number. In these relations, every one is interested, and were there no other use in mathematics than to supply us with precise ideas and terms, for the forms of external things, and with correct expressions for the distances and positions of objects, they would relieve us from much obscurity and confusion. The study of the mathematics, greatly invigorates and sharpens the understand- ing, by establishing habits of patient investigation, of exact method, and close reasoning, besides conducting us also to many important practical results. The mensuration of heights and distances, the computations of quantity, both superficial and solid, and the linear * Revised and abridged from an introductory lecture of the author, published iu October, 1828. t In part also under Natural Philosophy. i As distinguished from the chemical laws. $ INTRODUCTION, and angular measurements of perspective, and of navigation, survey- ing and astronomy, are among its most familiar and obvious ap- plications. To return to Natural Philosophy, the student in this science learns, with pleasure and surprise, that the same power which retains Jupi- ter in his orbit, precipitates a falling drop ; that a feather, a balloon and a ship of the line are floated by statical pressure ; that the same power causes a narrow column of water, sustained in a tube, to raise a weight, many thousand times greater than its own ; that by its means a cascade falls through the atmosphere, which in its turn, raises a column of water in a pump ; and that gravity exerts an uninterrupted dominion over atoms, planets and systems. It is seen also by the learner, that the mechanical powers, so indispensable to our existence and efficiency, and that the motions of animals are de- pendent upon similar principles, and gravity is not unfrequently the immediate agent. The phenomena of LIGHT are among the most beautiful and in- structive of those belonging to Natural Philosophy. The rainbow is a splendid example of the decomposition of the solar beam, ef- fected by the refractive power of the drops of water ; still, magnifi- cent and beautiful as it is, it excites perhaps less astonishment in the beholder, than the colors exhibited by the common prism in a darkened room, where the iris, although very small, compared with the bow, is more intense, and is brought within our more immediate view. The astonishing results produced by the solar focus, in which the concentrated beams melt and dissipate metals and stones ; the surprising and beautiful effects of the common, the lucernal, and the solar microscope, in whose fields of vision motes become beams, and animalculse rival the gigantic animals ; the wonderful illustrations of the eye, on whose retina, either uncovered by dissection, or imi- tated by art, are seen painted distinctly, in all their varieties of color and of form, the fields, the groves, the sky, the faces of men, and all the objects that surround us ; the power of the telescope, by which we penetrate into the awful darkness of space, and look through the veil that covers the heavenly bodies ; these are a few of the won- ders which natural philosophy teaches respecting light, that incom- prehensible emanation, without which the creation would become cheerless and desolate, and animated beings would dwindle and die. THE ATMOSPHERE, in tranquillity, is little regarded except as af- fording the means of comfortable respiration to the whole animal world ; but, disturbed in its statical pressure, by the influence of heat, it generates not only land and sea breezes, monsoons, and trade winds, but the hurricane and the tornado. Navies are overwhelmed in the waves ; the oak and the cedar are prostrated ; and man and his works, his towers of strength, ami his pinnacles of pride are level- INTRODUCTION. 9 led with the dust. The same atmosphere, although invariably the residence of the electric fluid, exhibits, only occasionally, decisive proof of an energy, which pervades the material world. Excited by causes, which, except in their proximate operation, are unknown to us, the electric fluid fills the atmosphere with thunder and light- ning. It was reserved for Dr. Franklin to prove, that lightning is identical with the spares which are obtained by friction from glass or resin, or from dry fur, from our apparel of silk or woollen, and from many other sources. In short, we now know that all things are full of the electrical influence ; that we can bring it down from the clouds by kites, metallic rods and wires ; that we can evolve it by our machines of glass and metals, and that by the power called Galvan- ism, using certain arrangements of metals, acids, and other substances, we can produce it at pleasure, connected more or less with the other imponderable fluids, in entire independence of the weather, and of the state of the atmosphere ; and at the same time we can render sensible the attraction and repulsion, which are inseparable from its excitement. Although the experiments, exhibiting these facts, are sufficiently curious, the importance of the subject has, only within a few years, been perceived in its full extent ; for it is now believed, that the par- ticles of matter are constantly under the influence of these attractions and repulsions, and that they are producing, without cessation, de- compositions and new arrangements. Associated, every where, with electricity, HEAT both modifies its effects, and produces peculiar phenomena. The mild radiations of the sun, and the gentle fluctuations of temperature are subjects of common experience, and excite no particular surprise. But the amazing energy of VOLCANIC ACTION, far surpasses every other ex- ample of natural heat. Science is now in a condition to reason, with considerable probability, as to the causes of volcanic heat, and still more, regarding those of the accompanying phenomena of earth- quakes : but leaving these for the present out of view, our attention is arrested by the grandeur of the events, associated with volcanic agency. The convulsion of the ground, not only in the immediate vicinity, but often in distant countries ; the subterranean noises, like internal thunder, and the grating sound produced by the rending of the solid strata ; the violent emission of gases, steam, ashes, sand, ignited stones and rocks, and eventually of the current of lava, which flows in a stream of fire down the mountain, and over the nether country ; the overthrow of the structures of man, or their inhumation beneath the lava and ashes ; the lightning and thunder, in and above the cra- ter ; the violent flux and reflux of the tides and the strong agita- tion of the sea, alternately inundating and draining the adjacent 10 INTRODUCTION. shores ; the deluging torrents of rain and mud, and the delusive pe* riods of repose, between the eruptions, sometimes extending to years, and centuries, are among the principal circumstances which charac- terise volcanos. ATTRACTION AND REPULSION, although less obvious than some of those phenomena that have been mentioned, are undoubtedly, more important in relation to the system of things, than any or all other natural causes and events. Gravitation is the bond which connects, equally, the greatest and the minutest parts of our system. Every particle of matter gravi- tates towards every other ; every mass, however large, is attracted by every particle ; every member of our system, and every sys- tem, in the great system of systems is affected, reciprocally, by every other : projectile power, or immense distance and counter- balancing attractions keep them from rushing together in ruinous col- lision ; and the whole creation of matter is afloat in space, suspend- ed and sustained by the energy of almighty power. It would be foreign to our present purpose, to designate the de- tails of the various kinds of attraction the gravitating, the electri- cal, the cohesive, the chemical, and the magnetic. The magnetic is universally known, and by its aid we traverse the ocean and pathless deserts. It presents the most striking and famil- iar example of repulsion, a power, which, springing from various causes, and operating under various forms, is, although unseen, every where active around us. We do not certainly know, that magne- tism can be permanently attached to any other substances than iron and nickel,* although we can no longer entertain a doubt, that it holds a permanent connexion with heat, light and electricity. Attraction is only a name for an unknown cause, of which we have no other knowledge than that it depends on the will of God. Mys- terious indeed It is, but it is not more so than the connexion of our intelligent minds with our living bodies. The Creator can endue mat- ter with any properties, and there are, undoubtedly, many possible qualities, which he has not bestowed, and many actual ones, which we have not discovered. ASTRONOMY examines the heavenly bodies, and the construction and relations of the celestial systems. It has taught us that the diffuse light of the Galaxy is composed of the mingled effulgence of innumerable stars, each of which is, probably, the centre of a system, and the con- tinually increasing power of penetrating into space, acquired by the modern improvements of the telescope, evinces, that we have only begun to number the stars, and that we shall never be able to call Some add cobalt. INTRODUCTION. 1 1 them all by their names. But we have measured the distances and the dimensions of the planets and the periods and the rapidity of their revolutions ; and we have ascertained their absolute and relative weight. We know not where discovery will stop ; the noble science of astronomy is now cultivated with an ardor not surpassed even by that of the age of Newton, and with means far superior. Innumera- ble discoveries of new stars have been made ; and it is ascertained, that a part of the fixed stars have a revolution indicating the move- ments of the members of particular systems. This is true, especial- ly of what are called the double stars, and the sublime conception is entertained, that the whole stellary system, with its myriads of planetary worlds, revolves in the course of ages around a common centre. Astronomy is, not without reason, regarded, by mankind, as the sublimest of the natural sciences. Its objects, so frequently visible, and therefore familiar, being always remote and inaccessible, do not lose their dignity. Although Newton, a century ago, unfolded the structure of the universe ; Herschel, La Place, La Lande, and other distinguished astronomers have continued to enlarge our knowledge of the heavens* and the Astronomical Society of London diligently collects and com- pares all discoveries, while some of its members are ardently engaged in making new observations. The practical applications of astronomy, in determining the latitude and longitude especially at sea, are highly important ; the exact cal- culation and prediction of some of its more striking phenomena have removed the superstitious dread of eclipses, and substituted a rational comprehension of their cause ; while the transits of the planets and the measurement of arcs of great circles of the heavens in different latitudes, have been thought sufficiently important to justify voyages and journeys to the most distant and inhospitable regions. It may be mentioned also, without impropriety, that the observation of the heaven- ly bodies is a rational source of amusement. In a fine night, the teles- cope, although not like that of Herschel, of immoderate size and ex- pense, is an interesting companion, and we contemplate with delight the mild lustre of the evening star, the fiery face of Mars, the silver orb of Jupiter, his belts and his satellites, and the incomprehensible rings of Saturn. f * Chalmers, with his own peculiar eloquence, has arrayed astronomy in new at- tractions, by connecting its physical features with our moral instruction. t In this connexion we ought not to forget Dollond, Lerebours, Fraunhofer and other distinguished artists without whose aid the science of astronomy must have t>een arrested in its course. 12 INTRODUCTION. 2. NATURAL HISTORY describes the external appearance or at least the distinctive characters of all natural bodies. Its numerous sub-divisions, are all included under Zoology, Mineralogy and Botany. ZOOLOGY, which includes the whole animal world, comprehends also a great number of subdivisions, e. g. ornithology, ichthyology, herpetology, entomology, conchology, &c. As it is conversant about animated beings, it inquires also into their habits, their food, their re- production, their decay and their death. Strictly, man is at the head of this department of Natural History. Zoology begins with man and ends with the snail and the oyster ; and in its course it embraces the elephant and the mouse, the lion and the mole, the whale and the minim, the eagle and the gnat. Among gigantic animals, the whale, the larger seals, the rhinoce- ros, the hippopotamus, the wild buffalo, the giraffe, the camel and the elephant, are signal examples, and among the reptiiia, the boa constrictor and the anaconda are sometimes of enormous size. In zoology, living animals are of course more interesting and more in- structive subjects of study than dead ones, however w r ell preserved. A menagerie, is one of the most gratifying kinds of museums, and these exhibitions, as regards especially the larger and more perfect wild animals, afford very fine opportunities for the study of zoology. The panthers and the elks of America, the rein deer of Lapland, the lions, the camelopards and the zebras of Africa, and the royal tigers, the hyenas and the elephants of Asia, torn from their native forests and dens, are imprisoned not only in the apartments of Exe- ter 'Change, of the Tower of London, and of the Garden of Plants of Paris, but in the cages of the travelling caravans which have now become common in this country. But, where all opportunities from museums, whether of dead or living animals, are wanting, zoology may still be studied, with good advantage, by the aid of the numerous works on this science, illus- trated as most of them are by accurate engravings. MINERALOGY AND GEOLOGY comprise all that relates to the satehil constitution of our planet, including its atmosphere and variiik gases, as well as its waters, its metals, its salts, its combustibles, arftfitEJ garthy combinations. The study embraces not only mountain^ #dd conti- nents, but the pebbles under our feet, the sand ofl'M Chores and the dust that is borne on the winds. It attempts to account for the origin and causes of the present state of things, and it contemplates the impending changes, decay and dissolution of the firm substratum of our globe. Minerals, although to some extent constantly before us, are, for the greater part, far more inaccessible than vegetables and animals. Many of them are drawn from the recesses of the earth, from the caverns and mines remote from the light of day. In this department then, although something may be done with the INTRODUCTION. 13 aid s of such things as we can every where obtain, still, a cabinet or museum is peculiarly necessary, and as this study is acknowledged to be both important and interesting, collections in mineralogy are found in colleges and universities more generally than any other sub- jects of natural history. They have the very important advantage of being, with few exceptions, not liable to destruction, nor to any spontaneous changes. They need no preparation, but when detach- ed from their native situations, and reduced to a proper size, are ready for the museum. This department of nature affords much of the wealth of nations, many of the comforts of civilized and polished society, nearly all the instruments of physical and philosophical re- search, and most of those of the ornamental and useful arts. Civili- zation, social refinement and science cannot exist where the mine- ral kingdom is not explored and understood, and especially where iron and some of the other metals are not known and used. Although no aliment for living beings is obtained from this king- dom, very important remedies are derived from it, especially from several of the earths and metals. Plants and animals are probably more attractive to the eyes of most persons than the greater part of minerals ; still, among crystals are found objects of extreme beauty, whose polish and whose form rival the finest works of art, and some of the gems have ever been selected to adorn diadems and crowns. GEOLOGY, which reveals to us the actual structure of the globe, and the natural position, relation and associations of its productions, affords important light in the research for useful minerals ; and it ex- hibits, in the arrangement and contrivance of the mineral strata, de- cisive proofs of the power, wisdom and design of its author. BOTANY is the natural history of plants. It is a beautiful and em- inently useful branch of knowledge. It is constantly extending its re- searches and adding new species to the great number,* which have been already discovered. The loftiest forest tree and the humblest shrub are equally within its domain, and every climate, and every continent and island, are visited for the discovery of new species. The plants that grow in mountains indicate, with great accuracy, the climates that belong to the different elevations ; the plants and fruits of tropical regions may grow at the foot, and the stunted evergreens of the polar circle may crown the summit. In this elegant department of knowledge, a sufficient number of its subjects is scattered every where around us, to afford the means of comprehending the outlines of the science and of prosecuting it with Fifty-six thousand, or more. 14 INTRODUCTION. considerable advantage. Its dried specimens are preserved with in-' comparably more ease than those of animals, and it is thought to be an object worthy even of princely munificence to found collections of living plants, and to preserve them in the Botanical Gardens, as is seen in the Royal establishment of Kew in England, and of the Gar- den of Plants in Paris. Even public spirited individuals* have, either by their own efforts, or by the assistance of private citizens, like them- selves, formed botanical gardens, of signal beauty and utility ; pre- senting in one grand perspective, the vegetable glories of the world. The study of the science is thus facilitated, in a surprising degree, and the botanical student finds, within the bounds of at most a few acres, the plants, to have seen which, in their native soils, would have demanded a life of adventure. The vegetable kingdom affords most of the food of men and animals, many medicines, and many materials for the arts. 3. CHEMISTRY. The remaining branch of science relating to nat- ural bodies, begins where Natural Philosophy and Natural History stop. As the gleanings of its early history may be found in the pre- faces of the larger elementary works on chemistry, we shall here omit the vague annals of its infancy, and the delusions of its middle age. . It would exceed our limits to trace the progress of chemistry from age to age ; to unfold the delusions of ALCHEMY, whose ob- ject was to discover the philosopher's stone, an imaginary substance, which, it was supposed, would convert the baser metals into gold and silver ; or, to speak of the equally delusive pursuit, after the GRAND CATHOLICON, or universal remedy, which was to remove eve- ry disease ; to avert death, and confer terrestrial immortality upon man ; or to mention the imaginary ALCAHEST, or universal solvent;, whose power it was supposed nothing could resist. The alchem- ist indeed imagined, that these miraculous virtues resided in one and the same substance, and during the dark ages, most of the cut tivators of what was then called chemistry, smitten with the deli-, rium of alchemy, pursued their occult processes, in cells and caverns, remote from the light of heaven, and wasted their days and nights, their talents and their fortunes, in a vain pursuit. The alchemist however accumulated many valuable facts, which have been em- ployed, with good advantage, in laying the foundations of modern chemical science. Some knowledge of chemical arts is coeval with the earliest stages of human society, and it has happened with this, as with other branch- es of natural knowledge, that many facts were discovered, and accu- *As was done by Mr. Roscoe and Dr. Currie of Liverpool, Dr. Hope of Edin- burgh, Mr. Bartram of Philadelphia, and Dr. Hosack of New York. INTRODUCTION. 15 mulated, in the practice of the arts, and in domestic economy, long before any general truths were established, by a course of inductive reasoning, upon the phenomena. The arts are all either mechanical or chemical, and not unfrequent- ly both are involved in the same processes. The practices of the arts may be regarded as experiments in natural philosophy and chem- istry. The object of the artist is usually gain ; but he, or any other person, who views the facts correctly, may reason upon them advan- tageously, and thus obtain important instruction. Glass is a chemical compound, usually of siliceous earth and fixed alkali, or in a more extended view, of alkaline, saline, metallic and earthy materials. These, after being duly proportioned, are com- bined by the effect of fire, and various adventitious matters are added, to impart color or to discharge it, to increase the density, or to dimm- ish the hardness, or for various other purposes. The production of the materials of the glass depends therefore upon chemical principles, and is thus far, a chemical art. But, the fabrication of the vessels depends upon mechanical causes, principally the breath of the artist, injected through an iron tube, to which the melted glass is made to adhere. The subsequent cutting, grinding, and polishing of the glass are also mechanical, and thus glass is a production both of chemistry and mechanism. Soap, (except the mere act of mingling the oil and the alkali,) is a production of chemistry alone ; a watch is a result of mechanism, but the metals of which it is made are prepared by chemistry and me- chanism united ; wool is carded, spun, woven, fulled and sheared by mechanical means, but it is scoured and dyed by chemical processes, and thus through a multitude of instances, the purposes of society are accomplished, by the application of the principles of one or of the other, or of both of these sciences. The science of chemistry considered as a collection of elementary truths derived from the study of facts, can scarcely be referred to a pe- riod much beyond the commencement of the last century, and its prin- cipal triumphs have been achieved, since the middle of that period. It would be premature, to detail, on the present occasion, the partic- ular discoveries, which, like stars, rising successively, above the hor- izon, have broken forth in rapid succession. Those discoveries, their periods and authors will be mentioned, in giving the history of each particular substance. At present, it would not be proper to attempt any thing more than to convey to those to whom the subject may be new, a general conception of the nature, extent and objects of the science of chemistry, reserving the details for the time when they will be both the most intelligible and the most interesting. > 16 INTRODUCTION. DEFINITION.* CHEMISTRY is THAT SCIENCE WHICH INVESTI- GATES THE COMPOSITION OF ALL BODIES, AND THE LAWS BY WHICH IT IS GOVERNED. Remark. This, of course, includes every possible combination and decomposition. Chemistry, taking into view the properties discovered by Natural Philosophy, begins its appropriate work where the sister science stops. The distinction between chemistry and natural philosophy is illus- trated by the familiar examples of 1. Water, 2. The atmosphere, 3. Gunpowder. Thus, water is composed of the bases of two gases ; the air of at least two, and gunpowder of combustible and metallic matter and the ponderable part of gases. Natural History, Natural Philosophy and Chemistry are all ne- cessary to complete the scientific history of any thing. Natural History explains the external appearance of bodies ; Natural Philosophy the mechanical properties ; Chemistry the constitution. This general position is easily illustrated by reference to amber, tool, calc-spar, fossil salt, and other familiar bodies. Chemistry is distinguished as an art or a collection of arts, from chemistry as a science : the former is empirical, the latter is guided by established principles, and they are now, in numerous instances, happily united, in the hands of both practical and scientific men. Chemical arts are numerous ; glass and soap-making, have been already mentioned, and pottery, metallurgy, and dyeing, may be ad- ded ; the latter depends on the affinity of coloring matter for fibre, or for the mordant, or for both. The vinous fermentation produces cider, wine, perry, bear, me- theglin, &ic. Carbonic acid gas is evolved, while alcohol is formed, and the rapidity of the process depends on the temperature. Leather, is formed from skins and tannin contained in the astrin- gent vegetables; the tannin of the latter uniting with the gelatine of the skin. Bread, is produced by a peculiar fermentation : its sourness, ow- ing to excessive fermentation, is corrected by an alkali and the carbon- ic acid which is evolved, renders it lighter than before. * For various definitions the student may see the principal authors, Thomson. Fourcroy, Henry, Murray, La Grange, Thenard, Davy, Brande, Turner, Hare and others. INTRODUCTION. ] 7 Ink ; the theory of its formation is, that the astringent principl& unites with the oxide of iron, and gum Arabic or sugar suspends the precipitate. The burning of lime consists in the expulsion of the carbonic acid, by heat ; the acid gas forms nearly one half of the weight of the limestone, marble, and chalk. Art and science mutually aid each other, because art furnishes hands and science eyes ; science without art is inefficient ; art with- out science is blind. The philosophical chemist must understand the principles of the chemical arts, and the more of the practice he knows the better. Chemical artists should understand the science, at least of their own arts, and practical knowledge is of- course indispensable. Not satisfied with the knowledge of the external properties and the mechanical relations, which are unfolded by Natural History and by Physics, but taking them into view, and retaining and using their principal discoveries, chemistry proceeds to investigate the hidden constitution of every species of material existence, in earth, sea and air. Earth, air, fire and water, were the four elements of the ancient school. They have however, yielded to analysis, and water, bland and simple as it seems, contains two bodies, whose properties, are en- tirely different from its own and from those of each other ; burning, when mingled and ignited in large quantities, with violent explo- sion ; and in a small stream, with a heat, which melts and dissipates the firmest substances. We should never have conjectured that water, whose great prerogative it is, to extinguish fire, contains both a combustible and a supporter of combustion. The air, the pabulum of life to the whole animal and vegetable creation, mild and negative like water, is not simple but contains inci- dentally many bodies, essentially however only two ; one of which and that, constituting four fifths of the whole, is, and was intended to be, in a high degree noxious and even deadly to animal life and fatal to combustion. The air does not destroy life instead of invigorating our frames, and extinguish instead of inflaming combustion, because the prevalent noxious principle of the air (nitrogen) is balanced by a life and fire-sustaining principle (oxygen) too vigorous to be trusted alone, and therefore, diluted exactly to the proper degree, by the op- posite principle, both being, by another extraordinary provision, sus- tained, in constant proportion, and thus producing a salubrious and unchanging atmosphere. The earth, under our feet, the soil, the sand, the gravel, the firm substance of the rocks, is not simple. In this ancient but assumed element, we have a double complexness. The one imagined, simple 18 INTRODUCTION. earth contains at least nine, and each of these is again complex, con- taining for one principle, oxygen, the same that exists both in wa- ter and in the atmosphere, united to nine or ten varieties of met- als or combustibles none of which are known in common life. He who is acquainted with the wonderful effects of chemical com- bination, will not think it strange that half the weight of marble is carbonic acid, and that metals, when combined with oxygen, resemble, very exactly, the earthy substances. Light as well as heat, is contained in common fire, and therefore it is not simple, unless fire and heat are varieties of one and the same thing. Modern research has proved that, besides light, which in its seven prismatic colors, is contained in the solar beam, there is also, in this emanation, an opake, radiant principle, which accompanying light and heat, neither warms nor illuminates, but acts to decompose certain chemical compounds ; that there are opake rays which warm but do not illuminate, and illuminating rays which are cold to the sense of living animals, but impart to the universe its splendid drape- ry of colors ; and that, associated with one or more -of these emana- tions, there is a surprising power, which imparts magnetism to a needle, and gives it the properties of the loadstone. But we have used the word element without defining it. An element is an undecomposable body it is therefore simple, or in other words not reducible to any other form of existence. We must however, carefully distinguish, between real elements, and those which are such, only in relation to the present state of our knowledge. When modern science speaks of a body as elementary, it intends nothing more, than that it has not been decomposed. It is therefore simple as far as we know, but it is possible that, by future efforts, it may be decomposed. Although we have no reason to doubt, that there are real elements, we cannot say, that we are certainly in pos- session of any one element. It is, however, perfectly safe to reason upon bodies as elementary, until they are proved to be compound. Iron is, as far as we know, a simple body ; we cannot as yet, exhibit it In any simpler form ; all we can do, is to alter its figure and size, without at all changing its nature. But iron rust, or the scales which fly off, when red hot iron is hammered, are not simple ; they consist of iron, combined with oxygen, one of the principles of the atmosphere ; we can exhibit these substances in a simpler form; the iron, which they contain can be separated from the aerial principle, and both can be exhibited apart, and thus the proof will be complete ; red lead and red precipitate are still better examples, because the former can be partially, and the latter wholly, brought back to the condition of metals, by simply heating them. INTRODUCTION. 19 The four ancient elements, earth, air, fire and water, were assum- ed at hazard, because they are so conspicuous and important ; the conception was grand but it was wholly erroneous. Instead of four elements, we have at the present time not less than fifty, nearly four fifths of which are metals ; the remainder are chiefly combustibles, and bodies, which, combining with com- bustibles and metals with peculiar energy, are generally called support- ers of combustion.* Our simple bodies then are 1. Metals, about 40f 2. Combustibles not metallic, 7-j- 3. Principles or supporters of combustion, 2 or 3 4. One body, or possibly two { of an undetermined char- acter; in all 50 or 51 5. Imponderable bodies, light, heat and electricity; besides the power called magnetism and the other varieties of attraction. The principal object of chemistry is to display first, the great powers upon which its phenomena depend ; and secondly, the proper- ties of the elements, the mode and energy of their action, the combi- nations which they are capable of forming, the properties of the result- ing compounds, and the laws by which they are governed. This statement, obviously, includes all bodies natural and artificial. There are many chemical compounds made by art, which, as far as we are informed, do not exist in nature, and there are many natural bodies which art has not yet been able to imitate. The philosophical chemist studies both the properties of the ele- ments, and the constitution of the intermediate or proximate com- pounds of the whole material world, as far as it is tangible by man. Of the chemical constitution of the planetary and stellary bodies, we have no knowledge, except from the hints that are afforded by the occasional projection to our earth, of stony masses, severed by ex- plosion from luminous meteors or fire balls, which occasionally pass, with great velocity, through our atmosphere. It will be easily understood, that the philosophical chemist under- takes an arduous and responsible duty, involving much manual skill and labor and mental effort, but the reward is rich and gratifying. * Some object to this phrase, preferring to consider combustion as being only an ex- ample of intense chemical action ; this view is philosophical ; but combustion is so fre- quent an occurrence and involves so many imporant chemical events, that it is con- venient, in accordance with the general practice of mankind, to designate it and the bodies concerned in it, by a peculiar phraseology. t It is perhaps doubtful where some of these bodies ought to be classed whether among metals, or combustibles. t Perhaps silicon and bromine ; we have however classed them where they ap- pear to belong. 20 INTRODUCTION. The veil is withdrawn from the face of nature, and a constitution of things, not at all suspected by those ignorant of chemistry, is un- folded. The pupil in this science discovers that he has, all his life, walked unconsciously amidst powerful, although unseen energies ; that like a child scattering sparks among gun-powder, he has often heen sport- ing with dangerous elements, and that, with all his curiosity and in- telligence, he has known only the surface of things. He finds, eve- ry where, innumerable applications of his knowledge to purposes of practical utility, to those of domestic life, to the arts which enrich and adorn society, and to the illustration of the wisdom, power and goodness of that great being, whose pleasure called the physical uni- verse into existence and constantly sustains it in order and beauty. To exhibit the proof of these statements, even in outline, would require a distinct recital, and might well occupy a treatise ; but op- portunities will occur in the progress of this work, when these truths may be, to a certain degree, illustrated. It would be premature, to attempt, at this time, to exhibit the na- ture of the evidence upon which chemical deductions are founded, and the mode in which the study and exhibition of the science are prosecuted. It is sufficient to say, that like the other physical sciences, chemis- try derives its evidence, from experiment, and the observation of. facts ; but, as a great proportion of the facts are such as do not occur in common life, and still, as they all have their foundation in the consti- tution of things, it becomes necessary for the philosophical chemist to perform a great number of experiments ; in other words to exhibit numerous facts ; for, an experiment is nothing but the exhibition of a fact, happening according to natural laws, which it is not in our power either to create, to cancel or to modify. Hence, the necessity of be- coming well acquainted with those laws. Whenever all of them shall be fully understood, then chemistry will have reached its perfec- tion, and in relation to the science, the greatest service which we can perform, is to extend and perfect its general laws. At some future day, it will not be necessary to study facts so much in detail as now : selections will be made to illustrate general principles, and thus chem- istry will be assimilated to natural philosophy. Chemistry may be regarded in three views, all of which are inter- esting and important. 1 . As a branch of general philosophy. 2. As a school for the chemical arts and for many of those of do*- rnestic economy. 3. As an important auxiliary to the profession of medicine and to pharmacy. INTRODUCTION. 21 In accordance with all these views, it is now ardently and perse- veringly cultivated, in every enlightened country. In every university and medical school ; in every college ; in many academies ; in volunta- ry associations, in larger and smaller towns, supporting Lyceums* and Athenaeums ;* in popular courses of lectures, sustained by private indi- viduals ; and even in manufacturing establishments, fostered by the zeal of the operative artizans ; chemistry, with the sister sciences, natural philosophy and natural history, is assiduously and advantage- ously cultivated. It would in this age, be as disreputable for any per- son, claiming to have received a liberal education, or to possess liberal knowledge, to be ignorant of the great principles and the leading facts of chemical as of mechanical philosophy. Many intelligent artizans now resort to philosophical lecture rooms, to learn more per- fectly the principles of their respective arts ; and the great familiarity with the practical facts of their callings which they, of course pos- sess, and ordinarily in a degree superior to that attained by teachers- of science, enables them to apply with great advantage the general principles which they acquire. Domestic economy is greatly benefitted by a correct knowledge of the principles of natural science and especially of chemistry. Besides the instances that have been already named the combus- tion of fuel ; the equal and economical distribution of heat and light ; the preservation of delicate fruits and of their extracts or jellies ; the preparation of food by steaming, boiling and roasting ; the extraction of animal gelatine ; the manufacture of starch ; the separation of butter and cheese from the milk ; the bleaching and dyeing of stuffs and many more domestic arts depend upon the prin- ciples of science, and chiefly upon those of chemistry. It is true that these things are accomplished, with more or less skill, by per- sons unacquainted with science, but they would be better and more effectually done, were the artists enlightened more generally in its principles. To insist on no other instance, there is no doubt that in the common modes of using fuel, a large part is wasted, and that part skilfully applied would be more effectual than the whole, as it is in most cases actually used. There is now, generally, but one opinion as to the importance of chemical science to the profession of medicine. This opinion is sufficiently evinced by the fact, that there is no medical school in which chemistry is not taught, nor any medical examination in which this topic is omitted. It is true that medicine may be practised, em- pirically, by those who understand neither the structure- of the human frame, nor the nature and properties of the substances, which they * Popular names in this country for certain institutions having for their object, the dissemination of useful knowledge. 22 INTRODUCTION. administer. But who would choose to trust such men ; or those, who, equally uninformed, as to the nature of things, mix, compound and vend, by precept and example alone ? Both may indeed do it, to a certain extent, successfully, but it is travelling blindfold, and, at the same time, leading others. Medicine and pharmacy both need the aid of scientific chemistry ; then they can proceed with intelli- gence and confidence they can shun and rectify errors, discard abuses, and add new resources to the healing art. They will avoid mixing inconsistent and mutually subversive ingredients ; they will reject the spurious and inert scrutinize, w^ith skill and knowledge, the genuineness of medicines, and avoid painful sometimes fatal mistakes. The principles of natural and experimental philosophy as well as of chemistry, should enter into the education of a medical man ; and if he has not been already initiated into these elements, he should neglect no favorable opportunity of acquiring them. They are constantly brought into view, along with the principle of life, in reasoning upon the phenomena of the human frame ; and in surgery, a correct knowledge of mechanical principles is of the utmost import- ance. A knowledge of natural philosophy should every where be and in some seminaries it is an indispensable qualification for medi- cal privileges and honors. The enlightened medical man will regard his profession in a high- er view, than as being merely a business, by which he may live. The true physician is a man of extensive scientific acquirements. No other profession demands so much scientific knowledge ; and when this is possessed, by a man of powerful and ardent mind, and united to habits of persevering and industrious exertion, the medical man may become entitled to a distinguished rank among philoso- phers. Probably, science is more indebted to medical men than to those of any other profession. Every young man, who, with com- petent talents, enters upon the study of this profession, should aim at acquiring enlarged views of general as well as of medical science, and should endeavor to add something to the common stock of know- ledge. The physician, who possesses the true spirit of his profession, will aim at a still higher excellence, that of being a good man. Familiar in the confidence of families, having access to all, in the hour of sor- row, and of tenderness, and weakness, he is, if virtuous and amiable, regarded as the common friend of mankind. It is however in his power, to sow moral contagion, or to diffuse the happiest influence. In concluding, we may observe for the sake of the general stu- dent, that, LITERATURE adorns and illustrates science, adding much to its attractions, and to the method, perspicuity, and effect of its communi- INTRODUCTION. 23 cations. It cannot be entirely neglected, by any one who would claim an elevated rank in physical science. The accounts of the most valuable researches and discoveries are, to a degree disgraced, by being clothed in a coarse and slovenly style, and communicated without good arrangement, and without logical clearness and pre- cision. It sometimes happens, that able philosophers and mathe- maticians are accomplished scholars, and then the utmost finish is given to the solid structures of physical science. No one who has had opportunity to appreciate their attractions, and their utility, can be insensible to the advantages and pleasures of polite literature, and of miscellaneous knowledge presenting as they do, a rich field for investigation, and affording to the student, ample remuneration. But ars longa, vita brevis, meets us at every turn ; and, although the general student, in the regular progress of a university education is of course, made acquainted with the outlines of the principal branches of human knowledge ; in after life, we are obliged to say, non omnes omnia possumus, while reluctantly giving up the rest, we select and pursue some one art, science, or practical profession. But our previous efforts are not lost ; the commune vinculum which connects all the departments of human knowledge, still re- mains unbroken ; the intellect which has been enriched by the ele- ments of science and literature, continues to shed a portion of their lustre over its own particular pursuit, and occasionally to aid, by use- ful suggestions and partial efforts, those who are travelling upon some other route. Knowledge is said to be power ; it is indeed, power of the most comprehensive and efficient kind. Knowledge is nothing but the just and full comprehension of the real nature of things, physical, intellectual, and moral ; it is co-ex- tensive with the universe of being ; reaching back to the dawn of time, and forward to its consummation. It is inseparable from the incomprehensible existence of the creator, who alone intuitively sees the whole. Human life is sufficient for the acquisition of only a very small part of universal knowledge, and the greatest and the most enlightened mind, measuring its acquirements by this standard, will find no cause for pride. It is useful when we are about entering on the study of a particular science, and especially of one of so great extent and interest as chemistry, to remember that there are many other inter- esting and useful branches of knowledge, and that we always assume too much, if we claim all importance and every attraction, for a par- ticular pursuit. This is necessarily the feeling of every one who insulates himself within his own peculiar dominion ; but he who takes a comprehensive survey of human knowledge, will learn to appre- 24 INTRODUCTION. ciate justly his own acquisitions, and to concede to others the favor which he would claim for himself. #*# * * # * Probably the greatest step that has been made in chemical science since the discovery of oxygen and chlorine, is in the establishment of the doctrine of definite proportions, depending on the combina- tion of the elements and of the proximate principles in certain fixed ratios, thus unexpectedly, giving to chemistry a mathematical basis. PART I. IMPONDERABLE AGENTS. Sec. I. LIGHT. " LIGHT is THE AGENT OF VISION." The history of its mechanical affections belongs to Optics, but some general facts may be advantageously stated here. 1. ITS MATERIALITY. By some it is supposed to result from the vibration of subtile elastic media ; but every thing goes to counte- nance the idea of its materiality, and this was admitted by Newton.* It cannot be weighed, because our balances and organs of sense are not sufficiently delicate. 2. ITS VELOCITY is two hundred thousand^ miles in a second ; it is seven or eight minutes in coming from the sun, and were its weight the million-millionth, or billionth part of a grain, it would, by its impetus, destroy the firmest bodies. Nine millions of particles of that size would not affect our most delicate balances. J Thorn. Momentum, being made up of velocity and quantity of matter, it results, that any degree of momentum may be produced by increas- ing either the quantity of matter, or the velocity ; it therefore follows that the particles of light must be inconceivably small. 3. Its velocity is progressive, and has been measured, by ob- serving the eclipses of Jupiter's satellites, when the primary is nearest Dr. U re has given a different view of this subject. Diet. 3d Ed. p. 563. I One hundred and ninety-five thousand. L. U. K. \ " The materiality of Light is sufficiently proved. Its motion, though inconceiv- ably rapid, is progressive, and may be measured ; it may be stopped in its progress, or its direction may be changed ; it may be condensed into a smaller, or dispersed over a larger space ; it is inflected when passing near to any body, which proves it to be subject to gravitation ; it produces chemical changes in many bodies, exists in them in a state of combination, and is disengaged by the exertion of new affinities, when it appears in its original form." " There is no physical point (says Melville,) in the visible horizon, which does not send rays to every other point ; no star in the heavens which does not send light to every other star. The whole horizon is filled with rays from every point in it, and the whole visible universe with a sphere of rays from every star. In short, for any thing we know, there are rays of light joining every two physical points in the universe, and that in contrary directions, except where opake bodies intervene." A ray of light, coming from any of the fixed stars to the human eye, ' has to pass, in every part of the intermediate space between the point from which it has been projected, and our solar system, through rays of light flowing in all directions, from every fixed star in the universe ; and in reaching this earth, it has passed across the whole ocean of the solar light, and that light which is emitted from the planets, satellites and comets. Yet in this course its progress has not been in- terrupted." Mur. 4 26 LIGHT. to and farthest from the earth. Seven minutes are now allowed by calculation, for the passage of light from the sun to the earth, and one twenty fourth of a second for its passage, from pole to pole, of our earth. L. u. K. A body cannot be seen through a bent tube, except by reflection, and the shadows of bodies are exact copies of the form of the original. 4. It moves in right lines ; never in curves ; if turned, it is always at an angle. 5. Its rays are mutually repellent, as they always diverge,* if mov- ing uncontrolled ; as observed when they are let into a darkened room, through a hole in the shutter especially when the dust is raised in the room, so as to render the progress of the rays visible. 6. IT OBEYS THE LAWS OF ATTRACTION. It is refracted in passing from one transparent medium into an- other ; going obliquely from a denser into a rarer medium the re- fraction is always from the perpendicular, and vice versa ; there is a constant ratio between the sine of the angle of incidence, and that of refraction. A piece of money being placed in a bowl, and the eye so situated as just to lose sight of it, is rendered visible by pouring in water. A stick, standing out of transparent water, appears bent at the surface. A river, or other transparent water, is deeper than it appears to be, because the image of the bottom appears too high. 7. The amount of refraction is proportioned directly to the density of the body. Inflammable bodies refract in a higher ratio, and of course, inflam- mable gases refract more than those that are not. At 32 Fahr. and pressure 30, the refractive power of the following gases is as follows ; Atmospheric air, .00000 Carbonic Acid, .00476 Azotic Gas, .03408 Muriatic Gas, - - .19625 Oxygen Gas, .86161 Sub-carburetted hydrogen gas, - 2.09270 Ammonia, 2.16851 Hydrogen Gas, - 6.61436f In general, the refractive power increases with the density of the body ; but inflammable bodies, hydrogen, phosphorus, sulphur, dia- mond, bees-wax, amber, spirit of turpentine, linseed oil, olive oil, camphor, &c. have a refractive power, from two to seven times greater, in respect to their density, than most other substances. * Rays from the sun and fixed stars, although divergent, are regarded as parallel., because the immense distance renders the angle of divergence indefinitely smalk t Henry, Biot, Arago. LIGHT. 27 Sir Isaac Newton observed this fact with respect to the diamond, which he thought was probably "an unctuous substance coagulated," thus anticipating the discovery of its inflammability.* L. u. K. 8. Light suffers reflection. The angles of incidence and reflection are always equal, as is observed in a common plane mirror ; when two persons on opposite sides, standing each at the same angle, see each others images. 9. All objects seen by refraction or reflection appear in the direc- tion of the refracted or reflected ray. This is confirmed by constant experience. 10. Light undergoes polarization. f " This name has been given to a property of light, which causes it often to be divided into two portions, one of which is transmitted, the other reflected by the same pane of glass : or one portion sus- tains refraction in an ordinary degree, the other in an extraordinary degree. Again, all these properties are found to be commutable ; so that the portion of the rays which is reflected in one case, may be transmitted in another ; or that which in one case sustains the or- dinary refraction, in another, may undergo the extraordinary refrac- tion, and vice versa. These phenomena are ascribed to the different positions assumed by different sets of rays ; certain poles, which they are supposed to possess, being variously directed at different times, so as to de- termine their reflection, or transmission, or the degree of their refrac- tion.'^ This topic belongs to optics.^ 11. Light produces little or no heat. The Lunar focus has always been said to exhibit no heat that can be indicated by the most delicate thermometer ; and that whether the rays were collected by a lens or mirror. No heat was felt in the pupil of Sir Joseph Banks' eye, from the lunar rays collected by Parker's great burning lens. But Dr. Howard, of Baltimore, by using his very delicate differ- ential thermometer, filled with etherial vapor, || apparently found a little heat in the moon's rays. The lunar light is composed of all the seven colors, as is evident in the lunar bow, and in the lunar circles. IT * Dr. Brewster states that realgar, (red sulphuret of arsenic,) and chromate of lead, exceed the diamond in refractive power, and all other substances in dispersive power. PA. Tr. 1813. t For an account ot this curious property of light, the reader is referred to Henry's Chemistry, 10th Edit. Vol. I. p. 154. Also Edin. Enc. Article Optics. Nich. Jour. Vol. XXIII, p. 334, and 94th Vol. of the Annales de Chimie, Ure's Diet. 3d Edit. 568, and Cambridge Course of Mathematics. t Hare's Comp. All transparent crystals polarize light, except those whose primary form is the cube or regular octohedron. Iceland crystal (rhomboidal calc-spar) is by far the most energetic. }1 Am. Jour. Vol. II. p. 329. and condensed, and falls in the tem- perate and polar regions, to go through the same round again.* (q.) Currents upward and downward, both in gross and aerial fluids, produce a vast and salutary effect on the comfort of the globe. The warm ocean imparts its heat to the chilled land, of the polar regions, and the hot land of the tropical countries gives its heat to the water of the cool ocean ; the monsoons and trade winds and common winds produce a similar effect in the atmosphere. f Without currents, the atmosphere would become fatally hot, in tor- rid, and fatally cold in frigid climates; and similar inequalities in the ocean and other great waters would be deadly to the aquatic animals. (R.) RADIATION OF HEAT is ITS (apparently) INSTANTANEOUS PASSAGE THROUGH TRANSPARENT MEDIA. We can perceive no progress, and therefore regard the passage as instantaneous : there can be no reasonable doubt that it passes as ra- pidly as light. (s.) Caloric or heat radiates from the sun, from fires, and volca- nos, and probably from all bodies. All our experience confirms this statement, and particular experiments to prove it will be mentioned hereafter. (t.) Solar heat radiates more or less, through all transparent media, whether solid, fluid or aerial, and generally without heating them materially. J (u.) Culinary, or artificial heat radiates only through air, and other aerial fluids, and not through transparent solids, or transpa- rent gross fluids, as water, alcohol, fyc. The cause of this difference is not known. (v.) The transparent bodies through which artificial heat does not * See Dr. Hare's essay on the gales of the Atlantic States of N. Ain.Am. Jour. Vol. V, p. 352. t Murray, 2d Edit. Vol. I, p. 276. \ The lower regions of the air would be quite as cold as the upper, did they not receive heat from the earth. There is a difference in this respect, among media; water arrests abgut half the I'ays, and alcohol more than half, and of course heat is acquired by these fluids, 70 HEAT OR CALORIC. radiate, are heated by it, but they derive little heat from the solar rays, which permeate them easily. For the most important facts respecting the radiation of heat, see the section on the nature of heat and light. A few facts may be added here. (iv.) Polished surfaces, of all bodies that are not transparent, re- flect radiant solar heat, and do not transmit it.* (a?.) Caloric not only radiates freely in a vacuum,^ but it is not impeded by currents or agitation of the air. Winds do not disturb sunshine, and the solar focus is equally distinct and powerful, in a windy as in a still day. Bellows blowing across a current of radiant culinary heat, do not divert the rays. (Y.) Surface has a great effect on the radiation and reception of heat independently of the nature of the material. Blackf and rough surfaces, radiate and receive heat the best ; bright and polished surfaces, the worst. Glass, however, although naturally polished, radiates and receives heat very well, and so do paper, skin, and animal membrane ; the latter radiates and receives twenty five times as powerfully as polished metal. (2.) The radiating and absorbing powers are alike and equal; but the radiating and reflecting powers are directly opposed, and are inversely as each other. In a cubical vessel of tin, one of whose sides was blackened, another papered, and another glazed, the radi- ation was in the following proportion from the black side, 100 " " papered, - 98 " " glazed, - 90 " " bright metallic, - 12 Leslie. (aa.) The thermometer indicates more or less of heat, according as 'its surface is blackened, covered with tinfoil or other good reflector, or is in its natural state. For a comparative result, it should be at the same temperature, in the beginning of different experiments. Jbb.) All mirrors lose their power of reflecting heat if blackened become heated. Glass mirrors, not reflecting culinary heat, do reflect it, if covered with tin foil. * In order that this should be strictly true, the solids must be supposed to be per- fectly smooth, of which we have perhaps n'o examples. Scratched metallic surfaces receive and emit more heat, if the scratches cross one another, than if they are parallel ; the difference is attributed to the formation of points, by the intersection, through which points, the heat more readily passes. t As ascertained by Pictet and Rumford. In the experiments of the latter it per- vaded the Torricellian vacuum. Sir Humphrey Davy found that a thermometer was heated by radiation, from charcoal, ignited by galvanism in a vacuum, three times as much as it would have been in the air ; there being no cooling effect from currents. t Dr. Turner doubts whether color has any effect on the absorption of heat unless the latter is accompanied by light, in which case he calls it luminous caloric : but then he allows that the effect is great. HEAT OR CALORIC. 71 PRACTICAL QUESTIONS. (cc.J Why are black* clothes hotter in the summer and in the sun, than in the winter and in the shade ? In order to settle this ques- tion, it is necessary to ask another, that is, in what circumstances will the absorption exceed the radiation of heat ? This will plainly be in the summer, and the reverse will be true in the winter. (dd.) Why do black people endure heat better, and cold worse, than white people / The answer depends on the same cause, taking into view the average animal temperature. (ee.) Why should steam, which we wish not to condense, be con- veyed in bright tubes, and vice versa ? Because such surfaces radi- ate heat badly. (ff.) Why does a common rolled iron stove pipe diffuse heat bet- ter than a bright tinned one ? Because its surface is rough, and therefore radiates heat powerfully, f (&&) Why does water keep hot longer in a bright polished vessel than in a dark and rough one ? J The answer is the same as in ee. (M.) Why does water become heated rapidly in a rough iron kettle, and slowly or not at all in one of bright copper ? The answer is the same as in jf, reception being substituted for radiation. (ii.) Why would an earthern ware tube, when gilded, preserve steam longer uncondensed, than the same tube with its natural sur- face, or than bright tinned iron ? Because the substance is a bad conductor, and the surface a bad radiator. (./}) Why does snow melt rapidly where the dirt is thrown upon or mixed with it, as in the travelled path, and slowly, or not at all, * Quere, (communicated )" Are black clothes, when worn in the shade during summer, warmer or cooler than white clothes in the same circumstances ?" The answer will depend on the radiating and receiving power of the surfaces, and on the temperature of the air, compared with that of the body. i In neither of these cases, is the final cause assigned ; it is unknown. t Experiment in Yale College Laboratory, Nov. 10th. 1826. A blackened and a polished canister of plated tin of the same form and size, being filled with water at 200 their times of cooling were as follows. Blackened Canister cooled in the 1st 12 minutes, 2d 12 3d 12 4th 12 5th 12 6th 12 7th 12 8th 12 96 min. In one hour and thirty six minutes, the blackened canister cooled 61, during which time the polished one cooled but 35. (At two hours Trona the completion of the above experiment*, viz. three hour^ and thirty six minutes from the commencement, the water in the polished canister was still 20 warmer than in the blackened one.) Accumulating Polished Canister cooled Dif. differences. in the 1st 12 minutes, 6 4 4 s 2d 12 5 3 7 7 3d 12 5 2 9 6 4th 12 3 3 12 8 5th 12 3 5 17 9 6th 12 5 4 "21 8 7th 12 5 3 24 5 8th 12 3 2 26 T~ 96 min. 35 i 72 HEAT OR CALORIC. where it is clean, and especially if glazed, by frozen rain'} Because snow is a good reflector, and dirt, from its rough dark surface, absorbs heat rapidly. (kk.) Why on copper plates painted black, white, gray, fyc. does wax melt soonest on the black and other dark colors, and scarcely at all on the white* when they are exposed to the sun *? The answer is founded on the general effect of colors on the absorption and radi- ation of heat. (II.) Why do pieces of cloth of different colors, black, white, and intermediate shades, when laid on snow in the sunshine, sink into the snow very differently, the black deepest, and the white not at all ? The answer is the same as under kk. (mm.) Why in summer, is the temperature of the earth several de- grees lower than that of the air, especially in a clear night ? It is owing chiefly to radiation, as beautifully illustrated by Dr. Wells. (nn.) Why, in hot weather, is a house cooler if kept dark, than if light and air are freely admitted ? Because the radiant heat, flow- ing, not from the sun only, but from all external objects, some of which are often much heated, is also excluded. (oo.) Why is white a good color for the roof of an ice house, and black a bad color for any roof? Because the former reflects, and the latter absorbs the heat rapidly. EXPERIMENTAL ILLUSTRATIONS. i. Inequality of conducting power. Dr. Hare, from I to 11, ex- cept 3, 4, and 8. " Let there be four rods, severally of metal, wood, glass, whale bone, each cemented at one end to a ball of sealing wax. Let each rod, at the end which is not cemented to the wax, be successively exposed to the flame excited by a blow pipe. It will be found, that the metal be- comes quickly heated throughout, so as to fall off" from the wax but, that the wood, or whale- bone, may be destroyed, and the glass bent, by the ignition, very near to the wax, without melt- ing it, so as to liberate them." * The colored surfaces receiving the rays, and the waxed side being downwards. HEAT OR CALORIC. 2. Glass so heated by the friction of a cord, as to separate into two parts, on being subjected to cold water. " Some years ago, Mr. Lukens showed me, that a small phial tube, might be separated into two parts, if subjected to cold water, after being heated by the friction of a cord made to circulate about it by two persons alternately pulling in opposite directions. I was subsequently enabled to employ this process, in dividing large ves- sels, of four or five inches in diameter, and likewise to render it, in every case more easy, and certain, by means of a piece of plank forked like a boot jack as represented in the preceding figure and also having a kerf, or slit, cut by a saw, parallel to, and nearly equi-distant from, the principal surfaces of the plank, and at right angles to the other incisions." " By means of the fork, the glass is easily held steady by the hand of one operator. By means of the kerf, the string, while circulating about the glass, is confined to the part, where the separation is de- sired. As soon as the cord smokes, the glass is plunged into water, or if too large to be easily immersed, the water must be thrown upon it, This method is always preferable when the glass vessel is so open, that on being immersed, the water can reach the inner surface. As plunging is the most effectual method of employing the water, in the case of a tube, I usually close the end which is to be sunk in the wa- ter, so as to restrict the cooling to the outside." 10 iter, 74 HEAT OR CALORIC, 3. METALS, &tc. Provide as many equal cylinders of metals as may be desired ; fix them vertically in a perforated copper or iron plate, their lower ends resting on a similar and parallel plate connected with the upper one at a small distance by metallic posts. Place upon each metallic cylinder a thin slice of phosphorus, and set the apparatus upon hot sand contained in an iron pan ; the pieces of phosphorus will successively take fire, in the order (caeteris paribus) correspon- ding with the conducting power of the metals. I f * b * a 8 lass cy?d 76 *e others the phosphorus upon that will not take fire.* 4. METALS AND WOOD. A solid piece of metal one and a half inches in diameter, and eight inches long, closely wrapped in clean writ- ing paper, will bear to be immersed in the flame of a spirit lamp, for a considerable time, without scorching the paper ; but if the paper be applied to a piece of wood, and heated in a similar manner, the paper will immediately burn. L. u. K. 5. Liquids almost destitute of conducting power. That liquids are almost devoid of power to conduct heat is proved by the inflammation of Ether, over the bulb of an air ther- mometer, protected only by a thin stratum of water. "The inflammation of ether, upon the surface of water, as represented in this fig- ure, does not cause any movement in the li- quid included in the bore of the thermom- eter at L, although the bulb is within a quar- ter of an inch of the flame. Yet the ther- mometer may be so sensitive, that touching the bulb, while under water, with the fin- gers, may cause a very perceptible indica- tion of increased temperature." " By placing the sliding index I, directly opposite the end of the liquid column in the stem of the thermometer, before the ether is inflamed, it may be accurately dis- covered whether the heat of the flame cau- ses any movement in the liquid." * Sometimes the phosphorus will melt in the air, without taking fire, but on jarring the apparatus, it will blaze ; a thin film of oxidized phosphorus apparently protects the phosphorus below from combustion. HEAT OR CALORIC. 75 CIRCULATION INDISPENSABLE, TO AN EFFECTUAL COMMUNICATION OF HEAT IN LIQUIDS. 6. Different effects of heat on the upper or lower strata of a liquid. H B "A glass jar, about 30 inches in height, is supplied with as much water as will rise in it within a few inches of the brim. By means of a tube* descending to the bottom, a small quantity of blue coloring matter is introduced below the col- orless water, so as to form a stratum as represented at A, in the engrav- ing. A stratum, differently colored, is formed in the upper part of the vessel, as represented at B. A tin cap, supporting a hollow tin cylin- der, closed at bottom, and about an inch less in diameter than the jar, is next placed as it is seen in the drawing, so that the cylinder may be concentric with the jar, and de- scend about 3 or 4 inches into the water." " The apparatus being thus pre- pared, if an iron heater, H, while red hot, be placed within the tin cylinder, the colored water, about it, soon boils ; but the heat pene- trates only a very small distance be- low the tin cylinder, so that the col- orless water, and the colored stra- tum, at the bottom of the vessel, remain undisturbed, and do not But if the ring, R, be placed, while red hot, upon the iron mingle. R stand which surrounds the jar at S S, the portion of the liquid, color- ed blue, being opposite to the ring, will rise until it encounters the warmer, and of course lighter particles, which have been in contact with the tin cylinder. Here its progress upwards is arrested ; and in * e. g. A dropping tube. 76 HEAT OR CALORIC consequence of the diversity of the colors, a well defined line of separation is soon visible.*' " The phenomena of this interesting experiment may be thus ex- plained." " If the upper portion of a vessel, containing a fluid, be heated ex- clusively, the neighboring particles of the fluid, being rendered light- er, by expansion, are more indisposed, than before, to descend from their position. But, if the particles, forming the inferior strata of the fluid in the same vessel, be rendered warmer than those above them, their consequent expansion and diminution of specific gravity, causes them to give place to particles above them, which, not being as warm, are heavier. Hence, heat must be applied principally to the lower part of a vessel, in order to occasion a uniform rise of tempe- rature in a contained fluid." " This statement is equally true, whether the fluid be aeriform, or a liquid, excepting that in the case of aeriform fluids, the influence of pressure on their elasticity, may sometimes co-operate with, and at others oppose, the influence of temperature." 7. Process by which caloric is distributed in a liquid before it boils. "On the first application of heat to the bottom of a vessel con- taining cold water, the particles in contact with the bottom are heated and expanded, and con- sequently become lighter in pro- portion to their bulk, than those above them. They rise therefore, giving an opportunity to other particles to be heated, and to rise in their turn. The particles which were first heated, are soon, comparatively, colder than those by which they were displaced, and, descending to their primi- tive situation, are again made to rise, by additional heat, and en- largement of their bulk. Thus the temperatures reversing the situations, and the situations the * "I used to perform this experiment with an inclined tube, as suggested in Henry's Chemistry. The modification here given, is so far a contrivance of my own, as relates to the use of the heater, tin cap, and iron ring ; and the employment of two colors instead of one. On account of the liability of the glass to crack, I found the old method very precarious, when a tube was used large enough to show the phenomena advantageously." HEAT OR CALORIC. 77 temperatures, an incessant circulation is supported, so long as any one portion of the liquid is cooler than another ; or in other words, till the water boils ; previously to which, every particle must have combined with as much caloric, as it can receive, without being con- verted into steam." " The manner in which caloric is distributed throughout liquids by circulation, as above described, is illustrated advantageously by an ex- periment contrived by Rumford, who first gave to the process, the at- tention which it deserves." "Into a glass nearly full of water, as represented by the foregoing figure, some small pieces of amber are introduced, which are in spe- cific gravity so nearly equal to water, as to be little influenced by grav- itation." " The lowermost part of the vessel being subjected to heat, while thus prepared, the pieces of amber are seen rising vertically in its axis, and after they reach the surface of the liquid, moving towards the sides, where the vessel is colder from the influence of the exter- nal air. Having reached the sides of the vessel, they sink to the bottom, whence they are again made to rise as before. While one set of the fragments of amber, is at the bottom of the liquid, some are at the top, and others at intermediate situations ; thus demonstra- ting the movements, by which an equalization of temperature is ac- complished in liquids." " When the boiling point is almost attained, the particles being nearly of one temperature, the circulation is retarded. Under these circumstances, the portions of the liquid which are in contact with the heated surface of the boiler, are converted into steam, before they can be succeeded by others ; but the steam thus produced, can- not rise far before it is condensed. Hence the vibration and singing, which is at this time observed." 8. Provide a glass tube twelve or fifteen inches long and from two to two and a half wide, closed at one end, and that end thin, so as to bear heat ; nearly fill the tube with alcohol, and then with a dropping tube, convey to the bottom some alcohol, colored by turmeric or cochineal and rendered a little heavier by water ; if dexterously done, there will be a well defined line of separation ; then apply heat at the bottom, and the color will be rapidly diffused. Now repeat the experiment, only place the colored alcohol* on the surface ; the color on the top will be scarcely disturbed till the fluid begins to boil. * Jt is hardly necessary to say, that no water should be added to it. 78 HEAT OR CALORIC. 9. Model for illustrating the operation of concave mirrors. "The object of the model repre- Asented by this dia- gram, is to explain the mode in which two mirrors oper- ate, in collecting the rays of radiant heat emitted from one focus, and in concentrating them in another." " The caloric emitted by a heated body in the focus of the mirror A, would pass off in radii or rays lessening their intensity, as the space into which they pass enlarges; or, in other words, as the squares of the distances. But those rays which are arrested by the mirror, are reflected from it in directions parallel to its axis.* Be- ing thus corrected, of their divergency, they may be received, with- out any other loss, than such as arises from mechanical imperfections, by the other mirror ; which should be so placed, that the axes of the two mirrors may be coincident ; or, in other words, so that a line drawn through their centres, from A to B, may at- the same time pass through their foci, represented by the little balls supported by the wires, WW." " The second mirror, B, reflects to its focus, the rays which reach it from the first ; for it is the property of a mirror, duly concave, to render parallel the divergent rays received from its focus, and to cause the parallel rays which it intercepts, to become convergent, so as to meet in its focus." " The strings, in the model, are intended to represent the paths, in which the rays move, whether divergent, parallel, or convergent." 10. Phosphorus^ kindled at the distance of twenty, or even at six- ty feet, by an incandescent iron ball. Dr. Hare. " The annexed figure represents the mirrors, which I employ in the ignition of phosphorus, and lighting a candle, by an incandescent iron ball at the distance of about twenty feet." " I have produced this result at sixty feet, and it might be always effected at that distance, were it not for the difficulty of adjusting the foci with sufficient accuracy and expedition. I once ascertained that a mercurial thermometer, when at the distance last mentioned., was raised to 110 degrees of Fahrenheit." * " The axis of a mirror is in a line drawn from its centre through its focus." t Especially if enveloped in cotton, which is a bad conductor. HEAT OR CALORIC. 79 80 HEAT OR CALORIC. " Some cotton, imbued previously with phosphorus, is supported by a wire over a candle wick, placed as nearly as possible, in the focus of one of the mirrors. A lamp being similarly situated with respect to the other mirror ; by receiving the focal image of the flame on any small screen, it will be seen in what way the arrange- ment must be altered to cause this image to fall upon the phos- phorus." " The screen S, placed between the mirrors, is then lowered so as to intercept the rays. The iron ball being rendered white hot, is now substituted for the lamp, and the screen being lifted, the phos- phorus takes fire, and the candle is lighted." " Description and construction of the mirrors. The mirrors rep- resented by the figure, are sixteen inches in diameter, and were turned in the lathe, the cutting tool being attached to one end of an iron bar two feet long, which at the other end turned upon a fixed pivot." " Of course the focal distance, being one half the radius of con- cavity, is one foot." " I designed these mirrors, and proposed to have them made out of castings ; but pursuant to the advice of Dr. Thomas P. Jones, I resorted to sheet brass, which was rendered the more competent by strengthening the rims with rings of cast brass, about three fourths of an inch thick each way. For the idea of these rings, and the execu- tion of the mirrors, I am indebted to Mr. Jacob Perkins." " I believe there are none superior, as the face is reflected by them much magnified, but without the slightest distortion." " For die rationale of the operation of the mirrors, I refer to the preceding article." 11. Diversity of radiating power in metals, wood, charcoal, glass t pottery, fyc. E HEAT OR CALORIC. 81 u At M, in the preceding figure, a parabolic mirror is represented. At B, a square glass bottle, one side of which is covered with tinfoil, and another so smoked by means of a lamp, as to be covered with carbon. Between the bottle and mirror, and in the focus of the lat- ter, there is a bulb of a differential thermometer, protected from re- ceiving any rays directly from the bottle, by a small metallic disk. The bottle being filled with boiling water, it will be found that the temperature in the focus, as indicated by the thermometer, is greatest when the blackened surface is opposite to the mirror ; and least, when the tinfoil is so situated ; the effect of the naked glass being greater than the one, and less than the other." " When a polished brass andiron is exposed from morning till night to a fire, so near as that the hand, placed on it, is scorched intolera- bly in a few seconds, it does not grow hot."* " Fire places should be constructed of a form and materials to fa- vor radiation : flues, of materials to favor the conducting process." 12. A cork thrust into a candlestick ; some black wool pushed by a knife into a slit in the cork ; some thin slices of phosphorus or sul- phuret of phosphorus, laid upon the wool or wrapped in it, the focus being previously ascertained by the light of a candle, will hardly ever fail of success,! an ignited iron ball or a few live coals being placed in the other focus. A screen of glass or metal may be held between the mirrors till we are ready for the result. 13. Fulminating mercury, or silver, or gunpowder, maybe sprink- led on the wool or on charcoal, but they will by their explosion soil the mirror : the effect is otherwise agreeable. 14. Boiling water being in one focus and a delicate air, or differen- tial thermometer in the other, there is an evident movement of the fluid, and the glass screen being interposed, arrests and soon reverses the effect. 15. A bright metallic mirror, held before a common fire, remains cold, but, if blackened by candle smoke or India ink, it becomes hot. 16. Provide two bright tin flasks or polished metallic tea pots ; black- en one with candle or lamp smoke, then pour boiling hot water from a tea kettle into both ; examine the temperature, at intervals of five minutes, and it will be found that for more than an hour, the bright vessel will remain decidedly the hottest, and sensibly so for several hours. J 17. Fill them with cold water and place them before a bright fire ; the blackened vessel will become hot, and the other will remain cold. * Except that a little heat passes by slow communication along the iron bar. t A mouse trap without the bottom, supported by the ring of a retort stand, makes a good fire grate, and a sheet of copper, zinc, or iron, will protect the table from the falling coals. t See the statement of experiments, page 71. 11 82 HEAT OR CALORIC. With a mask coated with tin foil, our faces may safely encounter the; blaze of a glass house furnace. lire's Die. 277. 18. Hot water cools faster in a glass, than in a polished metallic- vessel. 19. "Radiation of cold. -A thermometer, placed in the focus of a mirror, indicates a decline of temperature, in consequence of a mas? of ice or snow being placed before it, in the situation occupied by the bottle, in the preceding figure. This change of temperature has been ascribed to the radiation of cold, and has been considered a? demonstrating the materiality of that principle. For, since the trans- fer of heat, by radiation, has been adduced as a proof of the exis- tence of a material cause of heat ; it is alleged that the transmission of cold, by the same process, ought to be admitted in evidence, of a material cause of cold."* But, it is necessary to suppose only that the heat flows from the thermometer, which is relatively the hotter body, to the ice, which is constantly absorbing the radiant heat of the room and that of the thermometer more than of any other body, because the heat is there concentrated by the mirrors, and thence flows in greater quantities than is true of any other place. f III. CONGELATION AND LIQUEFACTION. (a.) Dr. Black first proved that fluidity depends on a peculiar com- bination or operation of heat or caloric. (b.) The sensible heat of both melting ice and freezing water is at all times and places 32 of jFoAr.J H. The water, when first formed by melting, is at 32, and the heat absorbed during liquefaction has merely melted the ice, and has not raised its temperature. If ice is colder than 32% it cannot melt till it attains that temperature, and the sensible heat will neither rise nor fall during the process of melting. (c.) The quantity absorbed is 140 A pound of snow at 32 and a pound of water at 172, if quickly mingled, will give the tempera- ture of 32, therefore 140 have been absorbed to melt the ice, and are not discoverable by the senses or by the thermometer.^ * Dr. Hare. 1 Ice at 32,. is a radiant point of heat in an atmosphere of 0, and a freezing mix- ture, e. g. salt and snow producing a cold of 0, would be, relatively, a warm point in a medium of 40 below 0. t The freezing and melting points of all bodies are the same lor each particular body, but no two coincide, unless by chance ; c. g. solid mercury melts at 39 solid water or ice at-j-32. Most bodies, as the metals, melt without becoming pre- viously soft, but others which are bad conductors, become soft first, as butter and sulphur. Several other experiments of Dr. Black, go to prove the same result, namely thai while ice is melting, a quantity of heat enters into it, without raising its tempe- rature, which would raise that of water 140. HEAT OR CALORIC. 83 (d.) Freezing water gives out 140 of heat. This warms the in- cumbent air, which rises and affects a delicate thermometer, suspend- ed above the freezing fluid. Freezing is therefore a warming process, and sensibly mitigates the severity of winter ; the 140 being near- }y the whole difference between the extreme climates of the globe, and being given out from the extensive surface of the freezing waters and plants, which are imbued with moisture, it greatly mitigates the atmospheric cold. (e.) Melting ice, especially if suspended ', is attended by a descend- ing current of cold air, which is perceptible even to the hand, and still more, by means of a delicate thermometer. Liquefaction is therefore a cooling process, as is perceived also from the chilly air produced by melting snow in a bright day. (/*.) Water cooled beloiu 32, if agitated, congeals into a spongy mass of ice; the evolved latent heat raises the temperature to 32, and, a part of the ice slowly melts again. Water may be cooled 20 or more below the freezing point, or 32 of Fahr. This is best done in a tall vessel, with a narrow mouth, and with a film of oil over the surface of the water ; it happens often accidentally in domestic ves- sels, in cold weather. Water thus cooled, immediately commences freezing, if a particle of ice or even a crystal that is floating in the air, happens to enter the fluid. (g.) All solids absorb heat when becoming fluid and retain it while in that state. The quantity of heat is different in different cases, and is to be learned only by experiment. Sulphur absorbs 143.68 of Fahr. spermaceti 145, lead 162, beeswax 175, zinc 493, tin 500, bismuth 550. Black, Henry. (h.) The particular quantity of heat which renders a substance fluid, is called its latent heat, or caloric of fluidity. The word latent was used by Dr. Black, merely to denote the condition in which the heat exists ; latet, it lies concealed. It is not a different kind of power, but merely heat in an insensible condition and manifesting its character by a peculiar effect, that of producing fluidity. (i.) Freezing mixtures, depend upon these principles. One ingre- dient in them, is always a solid, and in producing the effect of gene- rating cold, this solid always melts or liquefies, and thus absorbs heat. When both substances are solid, as snow and muriate of lime, or snow and caustic potash, or snow and common salt, the effect is of course greater. (j.) Heat is evolved during the conversion of fluids into solids. This is well illustrated by the slacking of lime and the mixing of wa- ter with burned plaister of Paris, in both of which cases, the water becomes solid and heat is evolved. 84 HEAT OU CALORIC. A saturated solution of sulphate of potash precipitated hy alcohol evolves considerable heat, when the salt congeals. Henry. !/.) Were there no absolution of heat to become latent during the ting of ice, countries covered with snow might be instantaneously devastated. The torrents are even now, very destructive ; then, they would be ruinous. Snow and ice would instantly melt, as soon as the temperature rose above 32, but as the absorption of 140 of heat is indispensable, the process is necessarily a slow one. (/.) The heat absorbed in liquefaction, is given out again in freezing. Thus one cause tends to correct the effect of the other, and both causes conspire to regulate the temperature ; for thawing is a cooling, and freezing is a warming process. IV. VAPORIZATION AND GASIFICATION OR THE FORMATION OF AERIFORM BODIES. Introductory Remarks. Weight and pressure of the atmosphere. This subject belongs to mechanical philosophy,* but it is impossible to make any progress in investigating the nature of aerial agents, without taking into view the pressure of the atmosphere. Its existence is fully demonstrated, by the rise of water in a pump, and by the stationary condition of the column of mercury in a barometer tube, as w r ell as by many com- mon occurrences. f The pressure, in any given place, varies at dif- ferent times, but the mediuni is about fifteen pounds on the square inch, corresponding to a column of thirty inches in the barometer ; to about thirty three feet of water, and to columns of other fluids varying in height according to their specific gravity. Taking the doctrine of atmospheric pressure for granted, we pro- ceed to aeriform bodies. (a) Jin atriform body is one having the mechanical properties of air ; J a vapor is a transient aeriform body, condensible by cold, or pressure, or both united ; a gas is supposed to be permanently aeriform under eve- ry degree of pressure and cold. Some latitude is allowed in the use of these terms, and a few bodies continue to be called gases, which have been condensed ; e. g. ammonia, euchlorine, sulphurous acid. * Consult EnfielcPs Philosophy, and any other treatise on Natural Philosophy. This subject and that of statical pressure in general, is ably illustrated by Dr. Hare, in his Compendium, p. 25. t It is now said that flies and other insects walk on the ceiling of a room with iheir backs downwards, in consequence of the peculiar webbed structure of their feet, which enables them to press the wall so closely, that little or no air intervenes, and thus the pressure of the atmosphere keeps them in their places. L,. u. K. $ Atmospheric air has, by pressure, been reduced to T l^ part of its volume, with- out losing its clastic form. HEAT OR CALORIC. 85 sulphuretted hydrogen, carbonic acid, nitrous oxide, cyanogen, muri- atic acid, and chlorine.* Strictly, the distinction between vapors and gases, although conven- ient in description, is unimportant. A vapor is derived from a body whose vaporific point is within our reach ; but that of a true gas, is lower than our means will enable us to go. (b.) Caloric converts both^ solids and fluids into gases, and vapors. Camphor, benzoic acid, and carbonate of ammonia, are easily converted into vapor, by being thrown upon a warm iron ; a bell glass may be placed over them to catch the vapor. Some solids are volatilized without previous fusion sal ammoniac and arsenic are of this number. (C.) WlTH EQUAL PRESSURE AND PURITY, EVERY LIQUID HAS A FIXED BOILING OR VAPORIFIC POINT ; c. g. water, the barometer be- ing at 30 inch, boils at 212 ; ether, at 96 or 98 ;{ alcohol, 173 to 176. Water in a glass vessel boils at 214 or 216 in a metallic ves- sel, at 212. The boiling point in most liquids, is lowered several degrees by putting in chips of wood, coils of wire, metallic filings, pounded glass, &c. The bubbles of steam are thus broken, and the heat escapes more rapidly. Dr. Bostock thus reduced the boiling point of ether, 50, and that of alcohol, 30. || (d.) The steam or vapor, is of the same temperature with the boil- ing liquid. (E.) PHENOMENA OF EBULLITION explained by the instance of water. As the water is warming from the common temperature, it is first thrown into currents by the change of specific gravity, and when it arrives at 2 12, IT elastic vapor then forms at the bottom of the fluid, and from its levity ascends, is condensed and disappears ; it is followed by other bubbles, and when the water is thus all heated to the boiling point, the vapor passes through uncondensed, and is dissipated at the top. The water remains at 212 till the last drop is exhaled. The old theories of palpable fire, or matter of caloric, of air bub- bles passing through the water, and thus causing its agitation, &c. are untenable, and unworthy of discussion. Water, in the aeriform * See Mr. Faraday's experiments in Philos. Transac. part II. for 1822, and Am. Jour. Vol. 7 pa. 352. t Dr. Black laid the foundation of the philosophy of vapors and gases, or in other words, of aeriform bodies, by his discoveries respecting latent heat, and by proving the distinct existence of an auriform body, different from common air, namely, carbo- nic acid gas, called by him, fixed air. The period of this discovery was 1757. t Dr. tire says 100. For exceptions, See Henry, 10th Lond. Ed. Vol. I. pa. 114 ; Ann. Philos. new series, IX. 296. Ann. de Chim. et de Phys. torn, VII. pa. 307; and Jour. Science, Vol V. pa. 361. || Ann Phil. N. S. Vol. IX. IT And also, when the vapor has acquired elastic power sufficient to lift both the atmosphere and the superincumbent fluid. 36 HEAT OR CALOKIC. 4 state, or steam, is the true cause of the mechanical movements in liu-: boiling fluid, and the cloud which we see in the air near the surface is the vapor condensed into minute drops resembling a fog or mist. The singing arises from the escape of innumerable air bubbles, and the crackling noise, that precedes boiling, and ceases when it begins, is owing to the formation of elastic vapor, and its immediate conden- sation by the colder fluid above. (/.) Perfectly formed vapor is invisible. If water or other fluid be boiled in a glass flask, the space above the water, appears as if the vessel were empty, and the cloud at the mouth consisting of con- densed steam, in the form of mist, would not be seen, if the air were of the temperature, 212. Ether, in thin glass vessels, is easily vaporized by applying boiling water, and condensed again by cold water. (G.) The latent heatof steam is about 950 orfromthatto 1000. Dr. Ure adopts the latter number, which is probably correct. This is proved, by distilling one gallon of water, and condensing the vapor in a worm immersed in ten gallons of the same fluid, each of which will receive nearly 100 of heat, and this multiplied by 10, gives the above result very nearly.* Or one gallon of water in steam, will heat six gallons from 50 to 212 ; 212^-50x6 = 972=: latent heat of steam very nearly. Hence, steam is an excellent vehicle of heat, and is very useful in cookery, in heating manufactories, drying gunpowder, and chemical precipitates, in heating baths, dye vats, and apartments for invalids 5 in making pharmaceutical extracts, and in many other cases. Large vessels of wood are employed with great economy because they can be heated by steam. (H.) PRINCIPLE OF DISTILLATION. Caloric, combining ivith the more volatile part of a fluid, raises it in vayor; it is again condensed by the cold water of the refrigeratory, which thus becomes rapidly hot, and must be often changed ; this is usually done by a stream of cold water conveyed into the condenser ; on one side, hot water runs out, and on another, cold water runs in.f A retort and receiver is the simplest distilling apparatus ; the fluid in the retort is made to boil, and the vapor is condensed in the re- ceiver, which is kept cold for that purpose. Sublimation is the same thing in principle, as distillation, but the vapor is condensed in the solid form ; this is seen, in the case of camphor, sulphur, benzoic acid, corrosive sublimate, calomel, arsenic, &c. * Due allowance being made for the sensible heat, and for waste. Henry, 10th Lond. Ed. Vol. I. p. 127. t Col. Wm. Moseley of New Haven, ingeniously avails himself of the cold water at the bottom and of the hot water at the top of the condensing tub, to supply baths conveniently and economically. HEAT OR CALORIC. 87 Distillation in vacuo, although it is attended by no economy of heat, is a good mode of conducting the process, where the product would be injured by a high temperature. Vinegar as commonly distilled, has often an empyreumatic taste, but if distilled in vacuo, it requires only 130 of heat, and the pro- duct is pellucid and fine. L. u. K. In these cases, the vacuum is obtained either by driving out the air by the vapor, and then closing the aperture of the receiving ves- sel, or, by applying a syringe or air pump to the receiver, cold being also of course in all cases applied to the receiver.* (i.) The specific heat of the vapors of different fluids is different, and can be ascertained by experiment only. Table of latent heat of vapors.^ Despretz, Ann. de Ure's Die. 17. Chim. &c. xxiv. 329. Vapor of Water, at 212 1000. 955.8 Alcohol, sp. gr. 0.825, 457. (sp. gr. .793, Sul. ether, boiling point 104, 312.9 ( " " .715, Spt. turpentine, " about 310, 183.8 (" " .872, 373.86 163.44 138.24 Petroleum, 183.8 Nitric acid, (sp. gr. 1 .494- boiled at 165,) 550. Liquid ammonia, (sp. gr. 0.978,) 865.09 Vinegar, (sp. gr. 1.007,) 905. The force of vapor at the boiling point is the same in all fluids ; it is equal to 30 inches of mercury, and in all fluids, is the same for * In consequence of a tax laid by the English parliament on the Scotch stills, by wffich they were to pay thirty shillings a year on every gallon of the capacity of their stills, it became their interest to make them work as fast as possible, and they made such improvements in the construction of their stills, that, although the tax was augmented by degrees from thirty shillings a year on a gallon, to fifty four pounds, they still continued to carry on the business with advantage. The improve- ments consisted chiefly iu making the still very broad and very flat, so that only a small depth of wash could be In it at once, leaving a very large orifice for the escape of the vapor, having an internal moving apparatus for agitating the wash, to prevent its burning, and another in the upper part of the still to break the frothy effervescence, when it would be in danger of boiling over. The fire was applied to a very large surface ; the ebullition was very rapid and general ; no pressure was opposed to the escape of the vapor, and thus they arrived at such astonishing rapidity in the distilla- tion, as to run off their stills of forty or fifty gallons capacity, three times in an hour, or seventy two times in twenty four hours, (see report on the Scotch Distillery, Phil. Mag. Vol. VI. pa. 76,) and by improvements still subsequent, they brought the pro- cess to such perfection, that a still of the capacity of forty gallons in the body, and three in the head, charged with sixteen gallons of wash, could be worked four hun- dred and eighty times in twenty four hours, viz. seven thousand six hundred and eighty gallons of wash could be distilled, and as the wash would afford eighteen per cent of spirit, it follows, that one thousand, three hundred and eighty two gallons could be distilled from a still of this capacity in twenty four hours, the still could be worked off therefore, twenty times in an hour, or once in three minute;?, and gave about fifty eight gallons an hour, or near a gallon in a minute. * Quoted from Henry, 10th London edit. Vol. I. p. 125. 88 HEAT OR CALORIC. an equal number of degrees above and below ebullition, but fixed oils, sulphuric acid and mercury, afford no readily appreciable vapor under the boiling point. (j.) By being converted into steam, a cubic inch* of water be- comes nearly a cubic foot or 1728 cubic inches. Dr. Black and Mr, Watt estimated the enlargement at nearly 1800 times. According to Gay Lussac it is 1698 times. Alcohol, in vapor, under the common pressure, occupies 659 times the volume that it did when liquid, and ether 443 times. The specific gravity of steam is 623, air being 1000, but the vapor of alcohol is half as heavy again as air, and that of ether more than twice and a half as heavy, and generally with a few exceptions, the lower the boiling point of a fluid, the more dense is the vapor formed from it. (K.) THE PRESSURE OF THE ATMOSPHERE, AND PRESSURE IN GENERAL, EXERTS AN IMPORTANT INFLUENCE ON VAPORIZATION. As already observed, no correct conclusions respecting aeriform bodies can be formed, without taking this subject into view. (/.) The pressure of the atmosphere is measured by the column of mercury which it is capable of sustaining. A glass tube not less than 32 inches long nor over half an inch in diameter, closed at one end, being filled with mercury, and having its mouth first closed by the finger, and then inverted and opened under the surface of mercury, exhibits die amount of atmospheric pressure, vibrating on both sides of 29 or 30 inches, which is about the medium of different cli- mates, seasons and countries. f (m.) At the, medium pressure, pure water boils at 212 ; if the pressure be diminished, water and all fluids boil at a lower tempera- ture. This is shewn by the air pump, and by the Torricellian vacuum. J Natural variations of atmospheric pressure vary the boil- ing point about 5. (n.) According to Dr. Slack, fluids boil in vacuo ivith 124 less of heat than under the pressure of the atmosphere ; others say with 145 less, if estimated in the Torricellian vacuum.^ As we ascend, it requires less heat to make water boil ; on the top of Mount Blanc, it boils at 187, || and on the range of Pasco, Peru, at 180.1T In the Rev. Mr. Wollaston's thermometer, each * Weight 252 grains. The specific gravity of steam at 212 and of the force of 30 inches of mercury, in pressure, is to dry air as 10 to 16. Henry. t See Dr. Hare's experiments, in his Compendium. t For a table, see Henry, Vol. I, p. 116, Lon. Ed. 10. The space above the mercury in a barometer tube : it was called after its discov- erer Evangelista Torricelli. || The monks at one of the highest monasteries on the Alps, complain that they cannot make good Bouillie, (milk porridge,) because the water boils so soon. Paris' Pharmacologia. A digester would remove the difficulty. 1F Am. Jour. Vol. XVII. p. 50. HEAT OR CALORIC. 89 degree near the boiling point is divided into 1000 parts. Each de- gree of Fahr. is equivalent to 0.689 of an inch of the barometer, in- dicating an elevation of 530 feet. The 1000th part of a degree in Wollaston's thermometer is therefore equivalent to about six inches, and the height of a common table produces a manifest difference in the boiling point of water.* This delicate instrument therefore answers the purpose of a bar- ometer, it being necessary only to make water boil in order to deter- mine the elevation of the place. The boiling point of water is raised by having salt dissolved in it, and the steam has the temperature of the boiling fluid, and so in other cases.f (o.) Slight variations of pressure may be exhibited in glass vessels. Boil water in a flask until the air is all expelled by the steam ; cork it while boiling ; if tight, it will continue to boil, and the more rapidly, if it be cooled, as by touching it with or immersing it in cold water, and the boiling will be repressed or stopped by hot water. In a retort corked in the same manner, the same phenomena are still more strikingly exhibited ; the water, if shaken after all is cold, falls like lead, thus illustrating the principle of the water hammer.f Water, boiled in a flask, furnished with a stop cock, has its ebulli- tion repressed by closing the key for a very short time ; on opening it, it boils violently again, and so vice versa. This must be done with caution, the operator avoiding exposure both to the mouth and bottom of the vessel. All these effects depend on variations of pressure. (P.) GREAT VARIATIONS OF PRESSURE ARE SAFELY EXHIBITED IN STRONG METALLIC VESSELS. In Papin's digester, or any strong boiler, fitted with a cover, stop- cocks and valve, the vapor of boiling water or other fluids may be confined ; then the temperature of the fluid will rise as the pres- sure increases, and the ebullition will be repressed or stopped. Wa- ter may be heated in this manner to 400 of Fahr. or more ; the danger of explosion is of course greater in proportion to the heat ; the machine being suddenly opened, a jet of steam rushes out with great violence, and the temperature of the water falls. Mr. Southern's table of pressure and temperature is copied from Henry. || Henry, and Phil. Trans. t Eng. Quar. Jour. Vol. XVIII. t This is owing to the want of atmospheric resistance, and shews that rain would fall like shot if it were not resisted hy the air. As formerly helieved, although now controverted by Mr. Perkins ; see Jones' Journal, and American Jour. Vol. XIII, p. 52. Mr. Perkins thinks that the pres- sure of steam will not be in proportion to the temperature, unless there be an abund- ant supply of water to generate new steam and thus add to the quantity. Aside from this, the steam is no more expanded "by increased heat, than air or any other elastic fluid would be. || Vol. I, p. 122, Lond. Ed. 10. 12 90 HEAT OR CALORIC. Pressure in inches Temperature* Atmospheres. of mercury. P'ahr. 1 29.8 - 212.0 2 - - 59.6 - - 250.3 4 - 179.2 - 293.4 8 - 238.4 - - 343.6 (q.) The latent heat of steam may be shewn by the digester. Five- gallons of water are heated to 400 ; the orifice being opened, one gallon flies away in the form of steam ; the resulting temperature is 212 ; therefore one gallon in steam has carried away heat repre- sented by 5 X 188 940= nearly the latent heat of steam; for 400 C 212 -- 188, and there were five gallons of water. (r.) The latent heat of condensed steam, if suffered to pads into cold water, makes it boil quickly, and it soon melts ice. Great noise is produced by steam striking' cold water; this is owing to its sud- den condensation, and the noise grows less as the water becomes hotter, till finally the steam passes almost silently through water, at or near 212, like a gas, and is not condensed.* The better way to heat water, is to surround by steam, the vessel containing the water to be heated. Mr. Parkes heated twenty gal- lons in this manner, in six minutes, from 52 to 190, in eight minutes to 200, in ten minutes to 208, and in eleven to 212. L. u. K.f High steam does not scald, because it is cooled by its sudden ex- pansion, and it blows along with it a mass of cold air ; indeed it is no longer high steam, but common steam partly condensed. It also blows a burning brand powerfully, but if held too near, it extinguishes the fire in consequence of the condensation of the steam ; it does not scald the hand, at a few inches from the orifice. The agent in the combustion is not so much the steam as the air which it blows along ; still, at a very high temperature, the steam may be, and probably is decomposed, giving oxygen to the carbon, and hydrogen to the flame. There is a popular impression that a boiling tea kettle does not burn the hand, but that, if it ceases boiling, it will produce that effect ; perhaps there is a mistake in the fact ; and this is the more proba- ble, as the trial is of course made in a hurried and imperfect manner. (s.) The density of steam confined over water, is directly as its elasticity ; that is, the higher the temperature and the greater the elasticity, the greater is the quantity of water contained in steam of the same volume. J * It is said however that water heated in this way is still two or three degrees short of the boiling point. L. tr. K. t Quoting Parkes' Chern. Essay. t Henry, Vol. I, p. 122, Lond. Ed. 10, HEAT OR CALORIC. 91 (T.) " The same weight of steam contains, whatever may be its density, the same quantity of caloric ; its latent heat being increased, in proportion as its sensible heat is diminished ; and the reverse."* Henry. Water distilled in vacuo at 70, gave a vapor which, when condensed, indicated latent heat amounting to 1200 or 1300. Hence there is no economy of heat in distilling in vacuo, for, as the sensible heat is diminished, the latent heat is increased. (U.) But steam formed at temperatures above 212, suffers a di- minution of latent heat by the increase of its sensible heat.^ Hence there is no economy of fuel in the use of high steam, for more heat passes off by the chimney than where low steam is generated. There may be convenience and economy of room and money, in the ar- rangements of the machinery, and obviously the higher the temper- ature at which the steam is formed, the more of it there is in a given space, or the more water in the state of steam, and consequently the greater is the moving power. (V.) Fluids under vast pressure, maybe converted into vapor with only a small augmentation of volume. This was done by M. de la Tour,{ in glass tubes ; alcohol of thesp. gr. .837, and occupying about | of the capacity of the tube, became transparent vapor by expand- ing to a little over three times its first volume, and with a pressure of 119 atmospheres, or 785 Ibs. on the square inch; the temperature was 404.6 Fahr. Ether at 369 of Fahr. became vapor, under 38 or 39 atmos- pheres = 576 Ibs. to the square inch, and the vapor occupied less room than that of alcohol or naptha. Water, with a trace of carbonate soda, required a little over four volumes to become vapor. In these experiments, the presence or absence of atmospheric air made no difference, and on cooling the tubes, the fluids reappeared, the vapor being condensed. At these high temperatures, water can decompose glass, by sepa- rating its alkali, and thus causing the glass to become cloudy. * That is, e converse, as the sensible heat increases, the latent heat diminishes, so that equal weights of steam incumbent over water, at whatever temperature, contain the same quantity of heat; or the total heat of steam is a constant quantity. A giv- en quantity of vapor of the same substance, whatever may be its temperature, and e-lasticitj imparts to cold water the same quantity of heat t Manchester Memoirs, Vol. II, now series. Brewster's Edit, of Prof. Robinson's works. ; Annales de Chimie and de Physique, XXI. 127178. XXII. 400. Annals of Philos. V. 290. HEAT OR CALORIC. (W.) OF THE STEAM ENGINE. Dr. Hare. The principle of Savarifs Steam Engine illustrated, i " A matrass, situated as in the above figure, and containing a small quantity of water, being subjected to the flame of a lamp, the water will soon, by boiling, fill the matrass with steam. When this is ac- complished, bubbles of air will cease to escape from the neck of the' matrass, through the water in the vase." "The apparatus being thus prepared, on removing the lamp, the water of the vase will quickly rush into the vacuity, in the matrass, arising from the condensation of the steam." Of Savary' s Engine.* "The celebrated engine of Savary, which led to the invention of that of Newcomen, and finally to the almost perfect machine of Bol- ton and Watt, consisted essentially of a chamber in which steam, after being introduced from a boiler, was condensed by a jet of cold water, as in the experiment above described." "Just before the condensation of the steam, the communication with the boiler was cut off, and a cock or valve, was opened in a pipe descending into a reservoir of cold water. The chamber was con- sequently filled with water, which was expelled through an aperture opened for the purpose, by allowing the steam to enter again above the water. The aperture through which the water escaped, and that through which the steam entered, being closed simultaneously, the operation of condensing the steam and filling the chamber with * The Marquis of Worcester in 1663 published in his book (whimsically entitled,; The Century of Inventions, an obscure hint of the contrivance, which Savary car- ried into effect in 166& HEAT OR CALORIC. 93 water was reiterated, as likewise in due succession the other steps of the process, as above stated." Of Newcomen's Engine. " The great objection to Savary's engine, was the waste of steam arising from its entrance, over the water, into a cold moist chamber. So great is the power of cold water in condensing steam, that had the steam been introduced, below the water, it could not have been expelled until ebullition should have been excited ; but heat, being; propagated downwards in liquids with extreme difficulty, the steam entering from above was not condensed so rapidly as to paralyze the engine." " To diminish the very great loss sustained in the engine of Sa- vary, Newcomen, instead of causing the vacuum produced by the condensation to act directly upon water, contrived that it should act upon a piston, moving, air tight, in a large cylinder, like a pump chamber. The piston was attached to a large lever, to the end of which, on the other side of the fulcrum, a pump rod and a weight were fastened. By the vacuum arising from the condensation, the piston, being exposed to the unbalanced pressure of the atmosphere, was forced down to the bottom of the cylinder, drawing up, of course, the rod and weight at the other end of the lever." "The cylinder being replenished with steam, the weight on the beam drew up the piston in the cylinder, and pushed down the pump rod, and thus by the alternate admission and condensation of steam, the piston and pump rod were made to undergo an alternate motion, by which the pump, actuated by the rod, was kept in operation. Although less caloric was wasted by Newcomen's engine than by Savary's, there was still great waste, as the cylinder was to be heated up to the boiling point each time that steam was admitted, and to be cooled much below that point as often as condensation was ef- fected." In Watt and Bolton's Engine,* steam from the boiler lifts the pis- ton, and steam let in above, depresses it ; condensation of the steam taking place at the same time, by communication with a cold vacuum,, connected with an air pump ; thus the stroke and condensation are alternate, the cylinder is kept constantly hot, and the condenser cold y by water pumped in by the working machinery, from below ; the hot water, formed from the condensed steam, is returned to the boiler. * This engine, the most splendid present ever made by science to the arts, is, ic common with other steam engines, far from using the whole power that is genera- ted ; for Clement and Desormes conclude, from their own experiments that the best steam engines have brought to bear not more than one twelfth part of the power of steam, as calculated by theory. Then. I. 85, 5th Edit. 4 HEAT OR CALORIC. by the operation of the machinery ; the atmosphere does not ope rate, except on the horizontal section of the rod of the piston. In this machine, the steam is constantly working, while in Newcomen's it was inert half the time, and not only was the cylinder below the piston, chilled at every stroke, by the cold water, but above the pis- ton, by the cold air. Mr. Watt's great improvement consisted in shut- ting out the atmosphere entirely, and in causing the condensation of the steam, at a distance from the cylinder, which is in that way main- tained at the boiling point. Thus both the upward and downward movement of the piston, is caused by the elastic effort of the steam. Wolf's, Evans's or the high Pressure Engine. There is no con- densation of the steam, which is driven out alternately, above and be- low the piston, against the atmosphere. As these engines work simply by dead lift of expansive steam, great strength is necessary in the machinery. The principal advantage is in economy of machinery, and room ; not of fuel. On account of the strength and smaller size of the boilers, explosions are less frequent, than in the low press- ure engines, but they are more destructive. Dr. Hare remarks, that " the engines in our steam boats, generally combine the two prin- ciples using steam that will support a weight, of from seven to fif- teen pounds, per square inch, and that a true Bolton and Watt steam engine, having an ample supply of water, cannot explode while the safety valve is of a proper size, and not improperly loaded."* Perkin's Generator.-^ The pressure is far beyond any thing here- tofore used ; eight hundred pounds, and even one thousand pounds, on the square inch, is not an uncommon pressure and fifteen hun- dred has been frequently used. The generator is very small ; it is heated in a furnace ; there is no boiler, but water is injected by the machinery, as it is wanted, about one gallon at a time. At Woolwich of late,J the steam was so heated, as to set fire to wood, tow, &c. and to ignite the iron generator, at the orifice made for the emission of the steam. Mr. Perkins says, that 4000 atmospheres = 6 5, 000 Ibs. on the square inch, is the maximum pressure of steam.< (#.) Mr. Perkins states that his high steam will not issue from an orifice, in his generator, one fourth of an inch in diameter, the pressure * If these conditions were observed, all steam engines would be much safer than they are ; but in the high pressure engines, the metal is necessarily exposed both to the weakening effect of heat, and to the mechanical strain arising from vast pres- sure ; while in the low pressure engines, these causes are comparatively feeble in their operation. The rule for loading the valve in Mr. Watt's original engines, was two and a half pounds for each square inch. t See Am. Jour, especially Vol. XIII. t Jones' Journal, Nov. 1827. The elastic energy of common steam is derived from the latent heat X ^P- gr. -{- the temperature or thermometric tension. Ure. HEAT OR CALORIC. 95 being SOOlbs. on the square inch, but when cooled down to the com- mon working temperature, it issues with a roaring noise, so as to be heard ii: U a mile, and powerfully blows a burning brand which it would not do before.* (y.) Cause of >h.e explosion of steam boilers. According to Mr. Perkins and Mr. Hazard, of Philadelphia, it is caused mainly by the fact that the boiler, by want of water, becomes heated unduly, and heats the steam excessively ; the water then dashing up in jets, caus- ed by the ebullition, or even by the spontaneous or intentional lifting of the valve, is converted into steam, in such great quantities, that it cannot be retained, and therefore bursts the boiler. A boiler full of steam, without access to water, it is said, may be heated even to red- ness, without explosion, steam being no more expansible than an equal volume of air, but if there be water present to form more steam, then the pressure becomes uncontrolable. Red hot iron boil- ers, by decomposing water, doubtless generate hydrogen gas, when the water is suddenly let in, and this, being incapable of condensa- tion, of course, greatly increases the tendency to explosion, which the boiler, thus rapidly oxidized, is unable to resist. STEAM ARTILLERY. Mr. Perkins, by applying steam to the propulsion of cannon balls, is able to throw sixty, four-pound balls, in a minute, " with the cor- rectness of a rifled musket, and to a proportionate distance." A musket may be made to throw, by means of steam, from one hundred to one thousand balls in a minute, and it is not doubted that a constant stream of balls may be discharged during a whole day,^ if required. From five hundred to one thousand bullets have actu- ally been thrown per minute, the steam, all the while blowing off at the escape valve. f It is said, however, that the range of shot, pro- pelled by steam, is much more limited than if fired in the usual way. Principle of Cupping. A cup partially exhausted of air, by burning paper in it,{ and sud- denly applied to the soft parts of the body, allows the flesh to be forced into it, by atmospheric pressure, and after scarification, the renewal of the process, causes the blood to ooze out. The emission of blood, at great heights, as experienced by Humboldt and his companions on the Andes, was probably owing to the prevailing force of vas- cular action, under a greatly diminished pressure, on the surface of the body. * Mr. Perkins supposes that heat is matter and that its accumulation at the fice imprisons the steam. t Am. Jour. Vol. XIII. pp. 44, 45. - Exhausting syringes are said to be now occasionally used. HEAT OK CALORIC. A ADDITIONAL EXPERIMENTAL ILLUSTRATIONS OF THE NATURE OF AERIFORM BODIES. 1. Aeriform bodies can displace gross fluids or pre- vent their entrance into cavities which they occupy. The figure represents a cylindrical glass containing a colored fluid, upon which is a taper floating upon a wide, flat and thin cork ; a narrow and tall bell glass is placed carefully over the light, and depressed as far as it can be, without making the fluid overflow ; the light is then seen at b b which is the surface of the fluid, within the jar, while a a, shows its position on the outside. It is hardly necessary to mention that this is the principle of the diving bell. 2. The candle bomb is a spherule of glass contain- ing a little alcohol, ether or water ; it has a stem, which is stuck into a candle, so that the ball shall be in, or just above the wick, which is touched with oil of tur- pentine, that it may be lighted promptly ; when this is done, the fluid is vaporized, and the glass soon explodes ; it should be placed behind a screen. 3. A glass flask containing water over an Jlrgand or spirit lamp. or over a few burning coals, shews the phenomena of boiling. 4. The Eolipile. A copper ball with a recurved tube, shews the force of steam, issuing from a capillary orifice ; it will vigorously blow a burning brand, or the entire fire, if placed on the hearth. If ether, or alcohol, or oil of turpentine be substituted for the water, the jet of vapor is then inflammable. The fluid is introduced as it is into the thermometer ball. 5. Ether is easily vaporized. (a.) In a flaccid bladder, furnished with a stop cock and tube, let a little ether be heated by contact with hot water ; it will soon in- flate the bladder, which being compressed, will give a jet of inflam- mable vapor ; or cold water applied to the bladder will condense it. (b.) A tall thin glass jar, filled with water, and standing in the pneu- matic cistern, has a little ether introduced, by turning up beneath it, a vial filled with that fluid : the jar should be secured by recurved tongs, of this form, or by a ring on a stand : boiling hot water, from a tea kettle, being poured on the top of the jar, the ether boils, and drives the water out ; if the jar be quickly lifted out of the water, the etherial vapor 'may be inflamed by a candle, or if allowed to stand, the water will condense the vapor and will again fill the jar, except a small space occupied by extract- ed air. HEAT OR CALORIC. 97 (c.) Such a flask, as that represented at No. 11, p. 100, is filled with water, except an inch or two of the neck, which is occupied by ether ; its mouth being covered by the thumb, it is inverted and se- cured in the pneumatic cistern, and treated as in (6.) and with the same result, only the return* of the water especially if the neck of the flask is plunged deep, so that the water which comes in is very cold, may be sudden ; it produces a violent whirl of the injected water, which, if it does not break the flask, makes a very pleasing experiment ; if, when the etherial vapor fills the vessel, the thumb be used as a stopper, the ball of the flask may then be cooled, and the water let in gradually, without endangering the vessel, but the effect is much less striking. (d.) Ether boils instantly at the common temperature, in the Tor- ricellian vacuum. Form this vacuum by using a strong tube, thirty- three or thirty-four inches long, and a half or three quarters of an inch in the bore, and then introduce a little ether through the mercury, in which the tube stands, by depressing a small essence vial full of that fluid, beneath the mouth of the tube, and turning it up ; as soon as the ether arrives near the top of the tube, it flashes into vapor, with violent ebullition and drives the mercury half or two thirds down the tube ; if the tube be then inclined in a position as nearly horizontal as possible, without removing its mouth from the mercury, a great part of the ether will be recondensed, and the va- por will be formed anew on raising the tube. The above experiment is very strikingly exhibited by filling the tube with mercury, except an inch at the top, which is filled with ether, and then the orifice being closed with the thumb or the hand, it is introduced, in an inverted position, into the mercurial cistern, when as soon as the hand is withdrawn, the tube, at that moment occupied by the mercury and ether, becomes instantly, in a great measure filled with etherial vapor, which, as before, drives the mercury down. 6. A glass tube, six or eight feet long, and one inch wide, closed at one end, and the other fitted with a stop-cock, being screwed to the plate of the air pump, may be exhausted to the greatest degree that the pump is capable of; if the pump is a good one, the atmosphere, when the tube is unscrewed and opened beneath water, will force it up in a jet and nearly fill it : a colored fluid gives the most beauti- ful experiment. 7. If the exhausted tube be opened under mercury, a jet of that fluid will be thrown in, and the column that is formed may be thirty inches high. On lifting the tube out of the mercurial cistern, the atmosphere will enter, and, because there is still a good vacuum above the mercury, the latter fluid will be pushed up nearly or quite, to the top of the tube, and will then fall, and the same effect will 13 98 HEAT OR CALORIC. be exhibited several times, but each time in a diminishing degree, until it ceases. 8. CULINARY PARADOX. Ebullition by Cold* Dr. Hare, 8 to 14. " A matrass, half full of water, being heated until all the contained air is ex- pelled by steam ; the orifice is closed so as to be perfectly air tight. The matrass is then supported upon its neck, in an inverted position, by means of a circular block of wood. A partial con- densation of the steam soon follows, from the refrigeration of that portion of the glass which is not in contact with the water. The pressure of the steam upon the liquid of course be- comes less, and its boiling point is ne- cessarily lowered. Hence it begins again to present all the phenomena of ebullition ; and will continue boiling, sometimes for nearly an hour." " By the application of ice, or of n sponge soaked in cold water, the ebullition is accelerated ; because the aqueous vapor, which opposes it, is in that case more rapidly condensed : but as the caloric is at the same time more rapidly ab- stracted from the water, by the increased evolution of vapor, to re- place that which is condensed, the boiling will cease the sooner." * This fact is pleasingly exhibited, by providing two cylindrical glass vessels, of one quart or two in capacity, (the quart or three-pint tumblers, sold in the shops, answer very well) ; into one of them pour cold, and into the other hot water ; then immerse alternately in each, a flask which contains water that was, just before, while boiling, cut off, by a good cork, from the atmosphere ; in the cold water it will boil vehemently, and in the hot it will cease boiling. A retort if treated in a similar manner, is a still better instrument, because it pre- sents in the ball, a large surface for warming or cooling; and a little cold or hot water poured on cautiously, while the retort is hanging in a ring, produces a very striking effect. If the retort be very thin, and especially if large, there is danger of its being crushed by the pressure of the atmosphere. I have repeatedly met with this accident, with both retorts and flasks $ but it is not dangerous, as the fragment do not fly about. HEAT OR CALORIC. 9. AERIFORM STATE DEPENDENT ON PRESSURE. FIG. 1. Proof that some Liquids would always be aeri- form, were it not for the Pressure of the Atmosphere. "A glass flask, fig. 1, being nearly filled with water, and having the remaining space occupied by sulphuric ether, is inverted in a glass jar, covered at bottom by a small quan- tity of water, to prevent the air from entering the neck of the flask. The whole being placed upon the air pump plate, under a receiver, and the air exhausted, the ether assumes the aeriform state, and displaces the water from the flask. Allowing the atmospheric air to re- enter the receiver, the ethereal vapor is con- densed into its previous form, and the water reoccupies its previous situation in the flask." FIG. 2. " The return of the ether, to the fluid state, is more striking, when mercury is employed, as in fig. 2 ; though, in that case, on account of the great weight of this metallic liquid, the phenomenon cannot be exhibited on so large a scale, without endangering the vessels, and risking the loss of the mercury."* * It is pleasing to see so dense a fluid as mercury, especially as it is also brilliant andopake, becoming a truly transparent, invisible, and elastic vapor, and then by a slight depression of temperature, returning again to the fluid state. The boiling of the mercury in the thermometer ball and tube, during the construction of that in- strument, exhibits this fact in perfection. 100 HEAT OR CALORIC. 10. Atmospheric pressure opposes and limits chemical action, where elastic fluids are to be generated or evolved. " Water would boil at a lower temperature than 212, if the at- mospheric pressure were lessened ; for when it has ceased to boil in the open air, it will begin to boil again in an exhausted receiver ; and those who ascend mountains find, that for every five hundred and thirty feet of elevation, the boiling point is lowered one degree of Fahrenheit's thermometer." The boiling point is lowered by a diminution of atmospheric pressure. " Water heated to ebullition in a glass ves- sel, having ceased to boil in consequence of its removal from the fire, will boil again under a receiver, as soon as the air is withdrawn." 1 1 . Boiling point raised by pressure. Jls the Boiling Point is lowered by diminution of Pressure, so it is raised if the Pressure be increased. " Into a small glass matrass, with a bulb, of about an inch and a half in diameter, and a neck of about a quarter of an inch in bore, introduce nearly half as much ether as would fill it. Closing the orifice with the thumb, hold the bulb over the flame of a spirit lamp, until the effort of the generated vapor to escape, becomes difficult to resist. Removing the matrass, to a distance from the lamp, lift the thumb from the orifice : the ether, previously qui- escent, will rise up into a foam, produced by the rapid extrication of its vapor." " This experiment may be performed more securely, by employing a vessel of hot water, instead of a flame, to warm the matras," HEAT OR CALORIC. 101 12. Column of Mercury raised by vaporized Ether. Jin increase of Pressure results from constrained Ebullition. " Having supplied a small flask with a little mercury, and a minute portion of sulphuric ether : through the neck, let there be a glass tube, so introduced, and firmly luted, as that it may be concentric with the vertical axis of the vessel, and extend downwards until nearly in contact with the bottom. If the flask thus pre- pared, be held cautiously over a spirit lamp, the ether will be more or less converted into vapor. The vapor being unable to escape, will soon cause the mercury to rise to the top of the tube. On the removal of the lamp, the mercury gradu- ally falls to its previous situation." It is better, as Dr. Hare has before recom- mended, to plunge the flask cautiously into hot water (of about 150', or 180,) as the pressure sometimes blows out the bottom of the flask, when, if over fire, a dangerous combustion would ensue. 13. HIGH PRESSURE BOILER. That the temperature of Steam is directly as the pressure, may be demonstrated by a small Boiler, such as is represented in the fol- lowing cut. " The glass tube in the axis, passes below the water in the boiler, and enters a small quantity of mercury at the bottom. The junc- ture of the tube, where it enters the boiler, is made perfectly tight. On the opposite side of the boiler, a tube, not visible in the draw- ing, descends into it. This tube consists of about two inches of a musket barrel, and is closed at bottom. The object of it is to contain some mercury, into which the bulb of a thermometer may be inserted, for ascertaining the temperature." " When the fire has been applied during a sufficient time, the mercury will rise in the glass tube, so as to be visible, above the boiler ; and continuing to rise, during the application of the fire, it will be found that with every sensible increment in its height, there will be a corresponding rise of the mercury in the thermometer. In front of the tube, as represented in the figure, there may be ob- served a safety valve, with a lever and weight, for regulating the pressure." 102 HEAT OR CALORIC. " It has been found, that when the effort made by the steam to escape, in opposition to the valve thus loaded, is equal to about fif- teen pounds for every square inch, in the area of the aperture, the height of the column of mer- cury, C, C, raised by the same pressure, is about equal to that of the column of this metal, usually supported by atmos- pheric pressure, in the tube of a barometer." " Hence the boiler, in this predicament, is conceived to sustain an unbalanced press- ure equivalent to one atmos- phere, and for every additional fifteen pounds per square inch, required upon the safety valve to restrain the steam, the pressure of an atmosphere is alleged to be added. To give to steam at 212, or the boil- ing point, such an augmenta- tion of power, a rise of 38 is sufficient, making the tem- perature equal to 250. To produce a pressure of four at- mospheres, about 293 would be necessary. Eight atmos- pheres would require nearly 343." " When, by means of the cock, an escape of steam is allowed, a corresponding de- cline of the temperature and pressure ensues." " If the steam, as it issues from the pipe, be received un- der a portion of water of known temperature and weight, the consequent accession of heat will appear surprizingly great, when contrasted with the ac- cession of weight, derived from the same source. It has in fact been ascertained, that one HEAT OR CALORIC. 103 measure of water converted into aqueoils vapor, will, by its conden- sation, raise about nine measures of water in the liquid form, one hundred degrees." 14. EXPLOSIVE POWER OF STEAM. " If a small glass bulb, hermetically sealed, while containing a small quantity of water, be suspended by a wire over a lamp flame, an explosion soon follows, with a violence and noise which is surprising, when contrasted with the quantity of water, by which it is oc- casioned. " In order to understand this, suppose that the bulb were, in the first instance, merely fill- ed with steam, without any water in the liquid form. In that case the effort of the steam to enlarge itself, would be nearly in di- rect arithmetical proportion to the tempera- ture ; but when water is present in the liquid form, while the expansive power of the steam, previously in existence, is thus increased, more steam is generated, with a like increased power of expansion. It follows, that the in- crements of heat being in arithmetical proportion, the explosive power of the confined vapor will increase geometrically, being actually doubled, as often as the temperature is augmented, somewhat less than forty degrees of Fahr." Miscellaneous uses of steam.* 1. For warming apartments, especially large manufactories. There is no danger from fire ; the boiler may be even in another room, and as the steam is transmitted in tubes, it is thus condensed and gives out its heat. " Every cubic foot in the boiler is equal to heating two thousand feet of space to an average temperature of 70 or 80," and each square foot of surface of steam pipe will warm two hundred cubic feet of space. 2. For drying muslins and calicoes and other goods. Either the stuffs are hung up in rooms and dried by steam pipes giving a heat of 100 or 130, or they are made to pass around cylinders filled with steam. Delicate colors, such as scarlet and crimson, formerly faded by stove drying, are thus preserved from injury, although heated to 165, and the people are healthy, which was said not to have been the fact when the rooms were warmed by stoves. Concisely mentioned before. 104 HEAT OR CALORIC. 3. Gunpowder is safely dried, in a similar manner. 4. By surrounding the vessels with steam, pharmaceutical extracts are made, without injury to delicate principles. Chemical precip- itates are sometimes dried in the same mode. 5. Steam is employed in bleaching. Instead of boiling the stuffs with solution of potash, they are steeped in that alkali, and then hung up while wet, in a chamber which is afterwards filled with steam, which enables the alkali to dissolve and remove the coloring matter more effectually and more rapidly than in the old way.* 6. It is applied to cookery. It is neat and effectual, and the same water may in fact be used twice ; once in the boiler as water, and once, as steam, in another vessel, which may be made of tinned iron, and placed in any convenient situation, with which a communication should be established by a bright tin tube ; the boiler must be fur- nished with a lid and a safety valve. 7. It is used for heating baths and dye vats. The steam may be made to pass either through tubes, immersed in the water, or, it may be thrown directly into the water, which it will heat very rapidly. There should be a valve in the tube of communication to prevent the reflux of the water into the boiler. Very large quantities of water may be thus heated in vessels of wood, and in one third part of the usual time. 8. For creating a vacuum. This is perhaps more easily done by the action of steam than in any other way. The first effect when the steam engine is put into operation, is to expel the air, and large vessels may, in this manner, be almost instantly filled with steam, which, being quickly condensed, leaves a pretty good vacuum, containing little else than a feeble vapor of water. An ingenious still has been constructed by Mr. Barry, for making vegetable extracts in vacuo ; both still and receiver are freed from air, and as water will then boil at a temperature below 100, the veg- etable extracts are obtained stronger and without empyreuma or de- composition, f (V.) NATURAL OR SPONTANEOUS EVAPORATION. (a.) This is the gradual wasting of fluids and of some solids at atmospheric temperatures. It takes place at the surface, and there- fore is not attended with ebullition ; it differs not at all in principle from vaporization ; it is only more gentle and never produces any agitation. Sb.) Not only all waters, but all animals and vegetables and men, the entire surface of the earth give out moisture by evaporation. Place almost any thing, even ice itself, under an inverted glass which * Murray's Elements, 6th Edit. Vol. I, p. 237. t Ibid, p. 143. HEAT OR CALORIC. 105 is kept cold, and vapor will be condensed in dew or frost if the cold be considerable. Camphor, carbonate of ammonia, and other vola- tile solids give off vapor so rapidly, that when placed in equilibrio in balances, they are soon found to lose weight. (C.) The cause of natural evaporation is caloric. It produces from, water, at every temperature, an elastic invisible vapor, whose elasticity increases with the temperature, and which sustains a corres- ponding column of mercury. Dalton and Gay Lussac have fully es- tablished this position. The theory, formerly so prevalent, that evap- oration depends on the solution of water in air, is no longer tenable as the sole and sufficient cause, but it is still very possible,* that va- por may be dissolved in air. The lower the boiling point of a fluid, the more readily it evaporates. (d.) It has already been stated, (p. 87 J that the force of vapor is the same at the boiling point for every fluid ; it equals thirty inches of mercury, and is the same, in all cases, for an equal number of degrees above and beloiv ebullition.-\ This is a curious fact ; per- haps it would have hardly appeared probable, for instance, that the vapor of ether at its boiling point, 98, of water at 212, and of mercury itself at 656, should each exert a power capable of sus- taining in a tube, a column of that metal thirty inches in altitude. EFFECTS OF NATURAL EVAPORATION. (e.) Evaporation produces cold because heat must be absorbed to form vapor. The evaporation of ether under the receiver of the air pump freezes water in contact with it, or having only a thin vessel between ; so a stream of ether falling upon a thin glass tube, freezes water contained in it. The sensation of cold in coming out of a bath, especially if warm, is owing to the absorption of heat to form vapor. The formation of vapor is a cooling process ; it goes on extensively, and thus regulates natural temperature. In the hottest climates, evaporation from ex- tensive surfaces of water, mitigates the heat, but where there is little or no water, as in the great African desert, the heat becomes intolerable. Excessive degrees of heat have been occasionally endured by hu- man beings in consequence of evaporation from their own surfaces. " Sir Joseph Banks and Sir Charles Blagden, breathed for some time an atmosphere in a room prepared by Dr. Fordyce, which * Nor is it impossible or even highly improbable, that water may be, to a certain ex- tent soluble in air, as there is obviously an affinity between the atmospheric gases and water ; but the fact, if admitted, will not account for all the phenomena, without admitting the formation of vapor at all temperatures. It is even said that vapor formed at atmospheric temperatures, has the same amount of heat as that formed at the boiling point; the latent heat increasing as the sensible heat is diminished. t See Dalton's tables. 14 106 HEAT OR CALORIC* was 50 higher than that of boiling water," viz. at 262 Fahr. *' The temperature of their bodies was not at all raised, though their watch chains and every thing else metallic about their persons were so heat- ed, that they could not bear to touch them.* The thermometers which hung in the rooms always sunk several degrees when either of the experimentalists touched them, or breathed upon them. Some eggs and a beefsteak were placed on a tin frame ; the eggs were roasted hard in twenty minutes, and the beefsteak was overdone in thirty three minutes. Water placed in the same room did not how- ever acquire a boiling heat until a small quantity of oil was dropped on it, when it soon began to boil briskly. The evaporation from the surface of the water had prevented it from acquiring the heat of 212 ; but when that surface became covered with a film of oil, the evapora- could not go on, and ebullition commenced. "f " The oven girls in Germany often sustain a heat of from 250 to 280, and one of these girls once breathed for five minutes, in air heated to 325 of Fahr. When the air of such rooms is damp, or the skin is rubbed over with varnish, the heat cannot be borne an instant. " J In the case of Sir Joseph Banks and Sir Charles Blagden, it is stated that there was no remarkable evaporation from the skin ; the insensible perspiration was doubtless greatly increased, and in such cases an immense perspiration usually happens, and it is this chiefly which either in a sensible or insensible form, renders such trials safe. , A well varnished man would probably soon die in such circumstan- ces, and probably could not live long at the common temperature.^ The cooling of liquors in hot countries, is effected by evaporation from skins containing water, from porous jars, &c. Mr. Leslie, with the aid of sulphuric acid to absorb the vapor, froze water by its own evaporation under the exhausted receiver ; some- times he employed merely porous solids, as clay, or parched oat meal or flour, porous and burnt whin stone,\\ and porous, and ignited pieces of muriate of lime.lT If the water has been previously boiled, the ice formed is firmer, although the process is slower. An earthen ware vessel is pre- * " The heat of metals at 120, is scarcely supportable ; water scalds at 150, but air may be heated to 240, without being painful to our organs of sensation." Davy. t Phil. Trans. Vol. LXXVI, p. 271, Ann. 1775. Quoted by Mr. Parkes. Es- says, 2d Lond. Edit. Vol. I, p. 70. t Parkes, quoting Hist. Acad. Sciences, 1764. Communicated. Since reading " Wells on Dew," I have doubted whether the power of the animal system to endure such a high temperature were owing entirely to the cooling effects of evaporation. Physiologists maintain that this power of the animal system to endure a high heat, is connected with the vital principle. V. Sir Everard Home, in Phil. Tran. || The Scotch colloquial name for greenstone and other trap rocks. IT The Pacha of Egypt procured a fine air pump for the manufacture of ice by Mr. Leslie's process. HEAT OR CALORIC. 107 ferred for holding the water. A hemispherical earthen vessel, con- taining three pints of water, was placed by Mr. Leslie over a body of parched oat meal, one foot in diameter, and one inch deep, and the whole of the water was frozen by working the pump. By the skilful management of evaporation and radiation, ice is obtained at Benares, in a climate where, in the summer, the ther- mometer is never under 100 n , and is often 1 10. Shallow pits or beds are made four or five feet wide, and about four inches deep, separated from one another by narrow borders, and so numerous as to cover an extent of about four acres. These pits are filled with dry straw in the middle of then 1 winter, when the ther- mometer is about 40 of Fahr. On the straw are placed rows of shallow earthen pans containing a few inches of water introduced at evening. In the morning they find a little ice, which at sun rise is wrapped in flannel and carried to the ice house. Near Calcutta, a similar process is adopted. In the plains, excavations are made about thirty feet square and two feet deep, and covered about a foot deep with dried stalks of Indian corn or sugar cane. Unglazed earthern pans about 1 J inch deep, are filled with soft water which has been boiled, and in the three winter months, some of it is frozen, every night, when the weather is clear. At sun rising it is carried, wrapped in flannel, to the ice house, which is a deep pit, lined with straw and coarse blankets, and covered by a thatched roof the mouth is closed with straw. L. u. K. Quicksilver may be frozen by the united influence of evaporation, rarefaction and absorption. If a pear shaped mass of ice containing the metal, be suspended over a large surface of sulphuric acid, and a good exhaustion obtained, it will freeze the quicksilver, which may be kept solid for several hours. L. u. K. The freezing of wet clothes exposed to the air when the thermom- eter is not so low as 32, is occasioned by evaporation. Plants are often injured by the frost when the thermometer is above freezing ; this is the joint effect of evaporation and radiation. Wine coolers are usually made of porous earthern jars unglazed ; they cool the wine by evaporation from the surface ; several of them on a table have an effect on the air around, which is perceptible to the guests. Rooms are cooled by sprinkling water around them, in hot weather. In India, drapery is suspended around their dining halls, which are roofed, but open at the sides, and water being dashed on the cur- tains, the evaporation generates cold. (/.) Evaporation contributes to health, by imparting moisture to the atmosphere. The driest air contains moisture, which is often condensed upon cold objects, especially if they are good conductors. 108 HEAT OR CALORIC. During hot weather, cold water, in almost any vessel, but soonest in a metallic one, produces drops of condensed vapor upon the out- side and a freezing mixture will generate hoar frost from the driest air. If the air were deprived entirely of moisture, it would, during res- piration, parch the membranous lining of the passages, and thus produce great inconvenience, and eventually serious mischief, in breathing. (g.) Evaporation injures health by raising into the air miasmata, produced by animal and vegetable putrefaction. This is too evident to need illustration ; the effect is dependent on a certain degree of heat, aided by moisture, as is seen in the rice swamps of our south- ern states. Fever and ague* probably arise chiefly from this cause. In cold countries extensive swamps do little or no mischief, and even in those that are temperate, they are comparatively harmless. The region about the river Sorel, in Lower, and the Welland Canal, in Upper Canada, are examples. In particular seasons, however, such countries become sickly. (h.) Evaporation supplies the moisture necessary to form rmn 1 snow, hail, hoar frost, dew, fogs, mist, fyc. This precipitation takes place according to the state of the atmosphere ; it is much influenc- ed by the mingling of currents of air, differing in temperature, and in the quantity of vapor they contain. Precipitation of dew, hoar frost, &c. is much affected by radiation, from the surface of the earth, and this depends greatly on the pre- valence or absence of clouds. Radiation is most abundant in a clear night, when the temperature of the ground is often several degrees lower than that of the air. The frost is often caused, principally, by radiation from the ground ; hence, it frequently freezes on the ground when the air is not as low as 32. This subject has been fully illustrated by Dr. Wells, and he has explained, why condensation of atmospherical vapor takes place when there is not cold enough in the air to produce it ; it is because the surfaces on which the vapor is precipitated, are colder than the air ; those surfaces that radiate the best, will therefore be the coldest ; hence, glass will be colder than metals. This radiation from the earth's surface is of the utmost importance to vegetation, especially in hot climates ; plants radiate heat very powerfully, and hence, they are often covered with dew, when the naked ground is scarcely moist. This effect is much favored by the clear, cloudless skies, of hot climates, while in colder regions, there is more cloudy weather. The earth is there cold and damp and * Malaria is the classical word now applied to all such effects, and to their causee- wbether understood or not. HEAT OR CALORIC. 109 needs much less moisture and there radiation is much less ener- getic.* It has been already mentioned that a principal cause of the per- manency of snow on high mountains, is the diminution of capacity for heat in the air, in consequence of its rarefaction ; it rises often, highly charged with aqueous vapor, which the cold precipitates abundantly. (i.) Circumstances which influence evaporation. Surface'. As natural evaporation proceeds from the surface only, the more extensive the surface, other things being equal, the more rapid is the evaporation. Water in a bottle, with a narrow open mouth, will waste away very slowly, but the same quantity of water, in a wide and shallow basin, will evaporate much more rapidly. In a narrow-mouthed vessel, also the pressure of the vapor which is formed, will react to retard the evap- oration. Agitation promotes evaporation by enlarging the surface, and by exposing warmer particles successively. Temperature. The effect of increased temperature on evapora- tion, is very familiar ; hot fluids evaporate more rapidly than cold ones, in proportion as their temperature is higher. Vapor in the air. As a given temperature can raise only a given quantity of vapor into the air, it follows that evaporation will be more or less rapid, according as the quantity of vapor already in the air, is more or less considerable. In a very dry air, the evaporation is always more rapid than in a moist air, and when the vapor already in the atmosphere, is the maximum, that the given temperature can sustain, there will be no evaporation. Pressure. The principles that have been established under the head of vapor, are applicable here. Evaporation is more or less rapid, as the pressure is greater or less. Atmospheric pressure re- tards evaporation ; hence, it is remarkably accelerated in the vacu- um of the air pump ; but the same quantity of vapor is raised in the end, whether the atmosphere be present or not ; the only difference is in the rapidity of the process. "Mr. Dalton found that the tension or elasticity of vapor, is always the same, however much the press- ure may vary, so long as the temperature remains constant, and liquid enough is present for preserving the state of saturation, proper to the temperature. If, for example, in a vessel containing a liquid, the space occupied by its vapor, should suddenly dilate, the vapor it con- tains will dilate also, and consequently suffer a diminution of elastic force ; but its tension will be quickly restored, because the liquid yields an additional quantity of vapor, proportional to the increase of space. Again, if the space be diminished, the temperature re- * For a description of Mr. Leslie's ^Ethrioscope, See Murrays' Elements 6th Ed- Vol. I. pa. 199. 110 HEAT OR CALORIC. maining constant, the tension of the confined vapor, will still continue unchanged ; because a quantity of it will be condensed, proportional to the diminution of space, so that in fact, the remaining space con- tains the very same quantity of vapor as it did originally. The same law holds good, whether the vapor is pure or mixed with any other gas."* (j.) Mode of estimating the force of vapor. This has been al- ready explained under the head of vaporization. Water is introdu- ced into the Torricellian vacuum, and the depression of the mercury measures the force of the vapor. Vapor being produced at every temperature, even below freezing, a table was constructed by Mr. Dalton to express the force through a wide range of temperature. This table, and the results since obtained by Dr. Ure,f may be in- serted at the end of the volume. At the same distance from the boiling point, the force of vapor is the same in all fluids. (k.) Effect of vapor upon gases. It enlarges their volume, and that directly, in proportion to the temperature. J Gases are freed from their hygrometric moisture either by intense cold, or what is more usual, by exposing them to substances, which powerfully attract moisture ; muriate of lime, which has been ignit- ed, is the substance which is almost always used, and it is very ef- fectual. (/.) Hygrometers. These depend, generally, upon a change of dimensions, in consequence of absorbing or giving out moisture. A human hair becomes elongated by imbibing moisture, and returns to its former dimensions, when the moisture is withdrawn ; this change is measured by an instrument, usually furnished with an index, and a graduated arc. Wood, cord, membrane, whalebone, &c. are simi- larly affected. Cords are shortened in wet weather ; this appears to be owing to the enlargement of their diameter, at the expense of their length. It is often observed in a common clothes line ; most remarkably at sea, in the great tension of a ship's rigging during a rain storm, and in the relaxation when dry weather returns. The amount of vapor in the air, is estimated with considerable accu- racy by covering the bulb of a thermometer with a piece of linen or silk, and exposing it to the air, when the rapidity and extent of the fall of the mercury will indicate the amount of vapor. Upon this principle, is constructed a little instrument,^ called the Rosometer. It is a thermometer, || with a ball of black glass, the up- * Turner's Chem. p. 56. t Phil. Trans. 1818. \ For Mr. Dalton's formula to correct this result, See Turner's Chemistry, first Eng. Ed. pa. 58. Invented by Mr. Jones of London, and Mr. Coldstream, of Leith. ]| Filled either with mercury or alcohol. HEAT OR CALORIC. n per part of which, is covered with muslin ; a little ether being drop- ped upon this part of the ball, dew soon begins to be deposited on the other, and the temperature at which this happens, is called the dew point.* Mr. Pollock of Boston constructs this instrument with two balls, one immediately below the other ; the upper one is cov- ered with muslin, and moistened with ether and the dew is deposited on the lower ball. EXPERIMENTAL ILLUSTRATIONS OF THE LAWS OF EVAPORATION. 1 . Loss of weight. Water balanced in scales, loses a perceptible weight in a short time ; with alcohol and ether the effect is still more remarkable. 2. Heat applied to the fluid gives a much quicker result. 3. Camphor, carbonate of ammonia, and other very volatile solids, in the same circumstances, lose weight, although more tardily. 4. Dip a finger successively into water, alcohol, and ether, and observe that the sensation of cold, is stronger and quicker, the more evaporable the fluid. 5. Production of cold. When the atmosphere is apparently still, we discover which tvay the wind is, by wetting the finger in the mouth and holding it up to the air, it will feel coldest on the windward side, the evaporation being there the most rapid, and consequently, heat being there most absorbed, from the finger, to form the vapor. 6. Water is frozen by the evaporation of ether, j- in the air ; this '19 conveniently done, by placing the water in a glass tube, sealed at one end ; it may be one third or one half of an inch in diameter, and the water may occupy two or three inches in depth ; a coiled wire may be pushed into the tube to lift the ice out, (and perhaps to aid by its conducting power, in the extrication of the latent heat ;) if the water be colored, the effect will be the more pleasing ; now let a capillary stream of ether, from a dropping tube or otherwise fall upon the tube containing the water, which may be either naked or may have a little gauze wrapped around it ; in a few minutes the water will be frozen solid, and a momentary pressure of the tube in the hand will thaw the outside of the ice, so that it may be withdrawn by the wire. 7. Cold produced by the Palm Glass. Dr. Hare, from 7 to 13. " Two bulbs are formed, at each end of a tube, one having a perforated projecting beak. By warming the bulbs, and plunging the orifice of the beak * Phil. Trans. 1826 Edin. Phil. Jour. No. XVII. pa. 155. i This fact was mentioned on p. 105. 112 HEAT OR CALORIC. into alcohol, a portion of this fluid enters, as the air within contracts by returning to its previous temperature. The liquid, thus introdu- ced, is to be boiled in the bulb which has no beak, until the whole cav- ity of the tube, and of both bulbs not occupied by liquid alcohol, is filled with its vapor." " While in this situation, the end of the beak is to be sealed, by fusing it in a flame excited by a blow pipe." "As soon as the instrument becomes cold, the vapor which had filled the space within it, vacant of alcohol in the liquid form, is con- densed, and a vacuum is produced ; excepting a slight portion .of va- por, which is always emitted by liquids when relieved from atmos- pheric pressure." "The instrument, thus formed, has been called a palm glass ; be- cause die phenomena, which it displays, are seen by holding one of the bulbs, in the palm of one of the hands." "When thus situated, the bulb in the hand being lowermost, an appearance of ebullition always ensues in the bulb, exposed to view, in consequence of the liquid, or alcoholic vapor, being pro- pelled into it from the other bulb subjected to the warmth of the hand." " This phenomenon is analogous to the case of ebullition in vacuo, or the culinary paradox ; but the motive for referring to the experi- ment here, is to state, that as soon as the last of the liquid is forced from the bulb, in the hand, a very striking sensation of cold, is expe- rienced by the operator." "This cold is produced by the increased capacity of the residual vapor for caloric, in consequence of its attenuation." Remark. A little ether dropped on either of the balls, immediately produces a rush of the fluid into that ball, and the other ball being then treated in a similar manner, the fluid as rapidly returns. The appearance of ebullition in the palm or pulse glass is evidently much increased by the fact that the thin film of fluid, lining the upper part of the ball, to which the hand is applied, is rapidly converted into vapor, drives the fluid before it, and then rushes through it ; that there is no ebullition of the mass of the fluid, is proved by the fact, that if w r e reverse the position of the ball, placing it uppermost, and allow the fluid .to rest in the palm of the hand it remains entirely quiet. 8. Cold consequent to a relaxation of pressure. " It is immaterial whether a diminution of density, arise from re- lieving condensed air from compression, or from subjecting air of the ordinary density to rarefaction. A cloud similar to that which has been described as arising in a receiver partially exhausted, may usu- ally be observed in the neck' of a bottle recently uncorked, in which a quantity of gas has been evolved in a state of condensation by a fermenting liquor." HEAT OR CALORIC. 113 Apparatus for showing the influ- ence of Relaxed Pressure, on the capacity of Mr for Heat, or Moisture. " A glass vessel with a tubulure and a neck, has an air thermom- eter, fastened air tight, by means of a cork into the former, while a gum elastic bag is tied upon the latter, as represented in this fig- ure. Before closing the bulb, the inside should be moistened. Under these circumstances, if the bag, after due compression by the hand, be suddenly releas- ed, a cloud will appear within the bulb, adequate in the solar rays, to produce prismatic colors. At the same time the thermome- ter will show that the compres- sion is productive of warmth the relaxation of cold." " The tendency in the atmosphere to cloudiness, at certain el- evations, may be ascribed to the rarefaction which air inevitably un- dergoes, in circulating from the earth's surface to such heights."* * In connexion with this effect on the transparency of the atmosphere, it may be interesting to recollect, the important influence of barometrical pressure on our health and comfort. If we were to regard (a supposition which is not exactly true, but which may be made for the sake of illustration,) the muscular power of the heart and arteries as a constant force, propelling the blood regularly in the circulation ; then it is obvious, that the varying pressure of the atmosphere must necessarily af- fect both our feelings and our safety. With a diminished pressure, there must be a more rapid and hurried circulation, and with it we might expect faintness and op- pression as is experienced on high mountains. The oppression and lassitude expe- rienced in what is called a heavy air, (which is really a lighter air, our feelings alone being heavy,) is probably owing, in part, to this cause. At moderate elevations, we do not experience oppression, for there is generally a clearer and a cooler atmos- phere, and our moral energy is invigorated by the scenery, and our physical force by the exercise. The subject is perhaps worthy of some attention in selecting situa- tions for invalids, but many other causes must be taken into view, such as the exha- lations, the temperature, &c. 15 114 HEAT OR CALORIC. 9. Influence of pressure on the escape of gaseous substances from combination. " When one of the ingredients of a Solid, or Liquid, is prone to assume the aeriform state, its extrication will be more or less easily effected, in proportion, as the Pressure of the Atmosphere is increas- ed, or diminished." " If a tall cylindrical jar, containing a car- bonate undergoing the action of an acid, be placed under a receiver, and the air with- drawn by an air pump, the effervescence will be augmented. But if, on the other hand, the same mixture be placed in a receiver, in which the pressure is increased, by condensa- tion, the effervescence will be diminished. In the one case, the effort of the carbonic acid to assume the gaseous state, is repressed ; in the other, it is facilitated. Hence the necessity of condensation, in the process for manufac- turing mineral water. Beyond an absorption of its own bulk of the gas, the affinity of the water is inadequate to subdue the tendency of the acid to the aeriform state ; but when, by exterior mechanical pressure, a great number of volumes of the gas are condensed into the space ordinarily occu- pied by one, the water combines with as large a volume of the con- densed gas, as if there had been no condensation." If a gas, under the ordinary pressure of the atmosphere, will com- bine with water in the proportion of equal volumes, the pressure be- ing doubled, the water will combine with two volumes of the gas, and if this last pressure be doubled, the volume of gas combined will be again doubled ; that is, it will be quadrupled, compared with the first quantity combined under the ordinary atmospheric pressure, and so on. When thus charged, if suddenly relieved from all the extra pressure, by simply opening the vessel, as in drawing soda water, the fluid is violently agitated, because the gas that was forcibly com- bined, then resumes its elastic form. HEAT OR CALORIC. 10. Cold produced by vaporization in vacuo, by boiling ether. Water frozen " Let a portion of water, just adequate to cover the bottom, be introduced into the ves- sel, represented in the subjoined .drawing, as suspended within a receiver. Over the wa- ter, let a stratum of ether be poured, from an eighth, to a quarter of an inch in depth. If, under these circumstances, the receiver be placed on the air pump plate, and sufficiently exhausted, the ether boils and the water freezes." 1 1 . Congelation of water in an exhausted receiver, by the aid of sulphuric acid. " In the preceding experiment, water is frozen by the rapid ab- straction of caloric, consequent to the copious vaporization of ether, when unrestrained by atmospheric pressure. In vacuo, water un- dergoes a vaporization analogous to that of the ether in the preced- ing experiment ; but the aqueous vapor evolved in this case, is so rare, that it cannot act against valves with sufficient force, to allow of its being pumped out of a receiver with the rapidity requisite to pro- duce congelation. However, by the process which I am about to describe, water may be frozen by its own vaporization." * This experiment is neatly performed by placing water in a watch glass upon a stand, and covering it with a thin metallic cup into which the ether is poured : on working the pump, the ether will boil, and the water will freeze ; thug freezing and boiling are coincident, and the boiling is the cause of the freezing, and yet the boil- ing fluid is as cold as that which is freezing. These experiments "are more apt to succeed promptly if the ether be good ; it is well to wash it two or three times with water in a bottle, in a mode to be de- scribed hereafter, and if the water which is used for freezing, has been just formed from melted ice or snow, it freezes so much the quicker as it has less sensible heat no HEAT OR CALORIC. " A thin dish, or pane oi glass, covered by a small quantity of water, and situ- ated over some concentra- ted sulphuric acid, in a broad vessel, is placed on the air pump plate within a receiver, as represented in this engraving. Under these circumstances, the exhaus- tion of the receiver causes the congelation of the wa- ter." 12. Wollaston's Cryophorus. " The adjoining figure represents the Cryophorus, or frost bearer ; an instrument, invented by the celebrated Wollaston, in which congelation is produced in one cav- ity, by the rapid condensation of vapor in another." " In form, this instrument obviously differs but little from the palm glass, already described (46.) It is sup- plied by the same process, with a small portion of water, instead of alcohol ; so that there is nothing included in it, unless water, either liquid, or in vapor." , , " The Cryophorus being thus made, if all the water be r j allowed to run into the bulb near the bent part of the tube, ^ "* and the other bulb be immersed in a freezing mixture, the water will freeze in a few minutes." " So long as no condensation is effected, of the thin aqueous vapor, which occupies the cavity of the instrument, that vapor prevents, by its repulsion, the production of more vapor : but when, by means of cold, the vapor is condensed in one bulb, its evolution in the other, containing the water, being unimpeded, proceeds rapidly. Mean- while the water becomes colder, and finally freezes, from losing the caloric which the vaporization requires." " According to Wollaston, one grain of water, converted into va- por, holds as much caloric as would, by its abstraction, reduce thirty one grains from 60 Fahr. to the freezing point ; and the caloric re- quisite to vaporize four grains more, if abstracted from the residual twenty seven grains, would convert them into ice. HEAT OR CALORIC. H7 13. Large Cryophorus. " This figure represents a very large Cryophorus, the blowing of which 1 superintended ; and by means of which I have successfully repeated Wollaston's experiment." " This instrument is about four feet long ; and its bulbs are about five inches in diameter." VI. IGNITION OR INCANDESCENCE. (a.) Bodies become luminous in consequence of the accumulation of heat in them.* In common language, this is expressed by saying that bodies become red hot, as a bar of iron does among burning coals. Some bodies melt during their ignition ; this is the fact with stones and most metals, and the melted stone or metal is as truly red hot as the bar of ignited iron. Some bodies evaporate during ignition ; such are antimony, bismuth, lead and tin ; some evaporate before ig- nition, as water and most fluids, not excepting the most fixed fluids, as quicksilver, and sulphuric acid, and dense oils ; the latter are de- composed before ignition. Gases do not become luminous at any temperature, although they may cause solid bodies, as gold, &tc. immersed in them, to become luminous, the reason appears to be, that there is not matter enough in any one point to project the light to the eye, although from their communicating ignition to solid bodies, it is certain that they have the requisite heat. Mr. Perkins' high steam, it would appear, is capable of igniting other bodies, (as already stated under steam and vapor ;) it kindled tow and ropes, and it even ignited the bored orifice in the generator from which it was issuing ; still it does not appear certain that it was itself luminous, nor is it certain that it was not, because we cannot inspect the steam formed in opake vessels, like those of metal, and when the steam issues into the air, it is no longer high steam ; just at the orifice of emission, it is elastic and invisible, but a little way from it, it forms a cloud of mist. (b.) Bodies become luminous by friction. Glass, or agate, or quartz, held against a revolving gritstone or grindstone, become hot and luminous. Metals are affected in the same manner. The parts of gun locks and other pieces of steel emit sparks when held firmly against grindstones or revolving wheels, covered with emery powder * They are not supposed to undergo decomposition during their ignition. 118 HEAT OR CALORIC, spread upon oiled leather straps, which serve as bands to the wheels.* (c.) Jill bodies begin to shine by heat at the same temperature. This fact was first discovered by Sir Isaac Newton, and has been confirmed by others. In genera], redness, that is the emission of red rays, commences at about 800 of Fahr. and is fully established in broad day light at 1000 in the direct sun's light, perhaps about 1100, or possibly 1200. The appearance is of course much influenced by the quan- tity of the surrounding light. A body might be luminous in the dark, that would not be at all so in the light. There are many cases of phosphorescence or emission of light which are not attended by any considerable increase of heat ; these have been already mentioned under the head of light. (d.) A white heat is only a greater degree of ignition. White light, that is, light containing a due proportion of all the colored rays, is emitted when the accumulation of heat is the greatest ; a welding heat of iron is a white heat. The artists have many terms to de- note the various degrees of heat connected with their processes ; thus, they speak of a cherry red, a worm red, &c. and of a white heat, a blue white, a red white, &tc. and there are many degrees of heat between, commencing with the feeblest redness visible only in the dark, and ending with a full white light, distinctly visible even in the blaze of the meridian sun.f (e.) Ignition affords one of the strongest arguments for the iden- tity of light and heat. If they are different substances or powers, then the heat when accumulated to a certain degree, expels the light, previously lodged in the body ; or, it may be said, that as most cases of ignition are produced by burning bodies, the light from the fire enters the body along with the heat, and thus obtains a transit ; or, if heat and light are merely modifications of each other, then it may be supposed that at a certain temperature heat becomes light, or pos- sibly a certain accumulation or intensity of radiant heat affects the optic nerves so as to produce the sensation of vision. J * This is beautifully seen at the gun manufactory, at Whitneyville, near New Haven ; the sparks fly off in innumerable tangents, and the hand, unless brought very near, may be held in the fiery stream without inconvenience ; this is doubtless owing to the strong current of air which the revolution of the wheels produce. It is curious that while coarse emery is used, gunpowder is inflamed by the sparks at any distance to which they extend ; but, when very fine emery is used, coarse gun- powder is not kindled, but if finely pulverized, it then flashes with the minutest sparks. (Communicated by Mr. Eli Blake of Whitneyville.) t Although it is called a white heat, there are more red rays than are contained in the sun beams. The very mild heat which causes the emission of light from some bodies, e. g. fluor spar, countenances the opinion that light is lodged in them ; and light may be imparted to some bodies to such a degree, that they become partially transparent without producing, upon them, the effects of ignition ; thus, eggs, the human fingers, and other bodies are illuminated, through and through, by an electrical discharge. HEAT OR CALORIC. H9 If we suppose that the entrance of heat continues to expel light from a body for an indefinite time, this difficulty is perhaps removed by adverting to the fact, already suggested, that at the temperature of ignition, the light enters the body along with the heat, and that both bodies thus find a transit through it. This however does not ac- count for the indefinite ignition produced by friction ; even allowing that it is indefinite, which has not yet been proved, there is no great- er difficulty than attends the indefinite emission of heat under the same circumstances. Perhaps it would not be useful, in a concise text book, to intro- duce the speculations of the learned and able philosophers who would make heat, and perhaps light, to depend upon the internal motions of the particles of bodies ; one kind of effect depending upon sup- posed vibratory, or expansive, or retrocessive, and another upon gy- ratory motions of uncognizable particles.* We might quote the great names of Newton, Boyle, Hooke, Rumford, Davy, Leslie, and others. The question can perhaps never be decided ; but in dis- cussing the nature of light and heat, the statements of facts and the reasonings can be exhibited most conveniently upon the supposition that these agents are material, and that they are different from each other. This course may therefore be pursued provisionally, until other views shall be conclusively established, f VII. CAPACITY;); FOR HEAT, AND SPECIFIC HEAT. (a.) The capacity of a body for heat, is its power of containing a given quantity of heat at a given temperature. $ The comparative estimate between different bodies is usually made, by taking them hi equal weights ; but it may be made also upon bodies in equal volumes ; the numerical results will of course be different, but are capable of being intelligibly compared. (6.) The specific heat of a body, is the particular quantity of that power which it contains at a given temperature. * See Davy's Chemistry. t See Dr. Hare's paper on the materiality of heat, Am. Jour. Vol. IV. p. 142, and the ingenious discussions between him and Professor Olmsted, in the same Jour- nal, Yols. XI, XII, XIII. Dr. Hare has shewn that the phenomena of heat are inconsistent with the opinion that they depend upon corpuscular motion. There seems then to be no other alternative than that there must be a material cause of heat, although that cause is too subtle to be recognized by us in any other way than by its effects. t The term is evidently figurative, and alludes to the capacity of a containing vessel. The use of the word, in relation to heat, implies merely a power, without deciding on the mode. For a description of that elegant intrument, the Calorimeter of Lavoisier, see his elements, and most of the larger chemical works. The quantity of water ob- tained by the fusion of ice, during certain changes in bodies surrounded by that substance, was made the criterion of the quantity of heat ; but there were some, perhaps inherent, sources of error, and the instrument is now very little, if at all used. 120 HEAT OR CALORIC. The experiments are commonly made by comparing fluids* or com- minuted solids, after they have been mingled at different tempera- tures. That body which, in a given short time, has lost the greatest number of degrees, has the smallest capacity, and the smallest spe- cific heat, and vice versa. The resulting temperature is always nearest to that body, whose capacity or specific heat is the greatest, and therefore the greater the capacity the less the changes of temperature. Boerhaave first dis- covered this remarkable fact, with respect to quicksilver, and water, but Dr. Black first established the law ; many other able men have investigated it, among whom are Wilcke, Irvine, Crawford, Lavoisier, Berard, and Delaroche, Petit, and Dulong, Clement and Des- ormes, &c. (c.) Different bodies, whether taken in equal weights, or volumes., contain different quantities of heat or caloric. This could never have been known by reasoning a priori; the conclusions are founded entirely upon experiment. (d.) Different bodies exposed to the same heating or cooling cause, undergo different changes of temperature, in equal short times, and the capacities are inversely as the change of temperature. Thus fifty spheres, or cubes, equal either in weight or diameter, of as many dif- ferent kinds of matter, if plunged into boiling water, and examined after an interval of five minutes, would be found very differently heated ; or, if already arrived at the temperature of 212, if they were exposed to a freezing air, and examined as above, they would be found very unequally cooled, although in the end, they would in both cases ac- quire a common temperature. (e.) In homogeneous bodies, mingled at different temperatures, the resulting temperature is always the arithmetical mean. A pint of water at 100, and a pint at 200, would on being mingled, give 150 as the resulting temperature, and the same would be true of any other fluids, or minutely divided solids. (/.) In heterogenous bodies, the resulting temperature is never the mean. The capacity of water is 23 that of mercury 1, for the changes which they undergo, when mingled at different temperatures, and in equal weights or volumes, are inversely as the changes the) suffer. One pint of mercury at 100 Fahr.+one pint of water at 40,= not 70, the arithmetical mean, but only 60 ; the metal loses 40, which raises the water only 20 ; hence, in equal volumes, water has the greater capacity. If the pint of water be 100, and the mercury at 40, the temperature will be about 80, because the water con- tains more heat than is necessary to raise the mercury to the mean. * Always taking it for granted that they do not act chemically on each other. HEAT OR CALORIC. 121 Water 1 in volume, and mercury 2,= always the arithmetical mean ; e. g. 70 3 , if the extremes be 100 and 40; hence, in equal vol- umes, water has twice the capacity of quicksilver. In equal weights, one pound of water at 100,-f-one pound of mer- cury at 40-~97j; therefore the 2| lost by the water have raised the mercury 57 J, which is in the proportion of 1 : 23, viz, water has twenty three times the specific heat that is contained in an equal weight of mercury, and its capacity is in the same proportion.* (g.) Formula. 1 . By weight. If the weight be multiplied into the change of temperature, the capacity will be inversely as the change, that is, the greater the change, the less the capacity, and vice versa. 2. By volume ; the capacity found as above, X into the sp. gr. = the capacity by volume. f (h.) Comparing classes of bodies, the capacities for heat are, in general, inversely as their density. Solids have less capacity than fluids fluids less than gases, and vice versa. When the capacity is enlarged, heat is absorbed, and when dimin- ished, it is given out. ft;) The sudden expansion of air always produces cold. "This striking occurrence takes place on a vast scale at the fountain of Hiero ; at the mines of Chemnitz, 'in Hungary. A part of the machinery for working these mines, is a perpendicular column of water, two hun- dred and sixty feet high, which presses on a quantity of air enclosed in a tight reservoir. The air is consequently condensed to an enor- mous degree by this height of water, which is equal to eight or nine atmospheres, and when a pipe, communicating with this reservoir of condensed air, is suddenly opened, it rushes out with extreme ve- locity, instantly expands, and in so doing absorbs so much caloric, as to precipitate the moisture it contains in a shower of very white com- pact snow, or rather hail, which may be readily gathered on a hat, held in the blast. The force of this is so great, that the workman who holds the hat is obliged to lean his back against the wall to re- tain it in its position. If the cock of the pipe is only partly opened, the snow is still more compact."{ By condensing aeriform bodies into a small space, cooling them by freezing mixtures, and liberating them suddenly, great cold is produced by the rarefaction. We have found occasion more than once to remark that similar effects probably happen in the higher regions of the atmosphere, from the sudden liberation of the ascending currents of rarefied air from pressure, and from their mixture with colder currents. (j.) Great and sudden increase of pressure upon common air, evolves so much heat as to ignite very combustible bodies. This was exhibit- * Henry's Chemistry. The author quotes Dalton ; the numbers usually stated are as 1 to 28. f Murray. 1 Aikin, I, 213. 10 122 HEAT OR CALORIC. ed by a brass syringe, furnished at one end with a little chamber, containing tinder, agaric, or other combustible, which is heated by the compression produced by the quick stroke of the piston, so that the combustible, on being suddenly brought to the air, by the turn- ing of a key, took fire. More recently, the combustible is contained in the piston itself, which, after the stroke, is quickly withdrawn from the tube. The instrument is now made of glass, which enables one to see the flash. (k.) Changes of capacity for caloric have an intimate connexion with the regulation of natural and artificial temperature. The me- dium heat* of the globe is usually placed at about 50 of Fahr. and is found, as has been heretofore believed, at about 1000 feet below the surface of the ground. Medium heat of the atmosphere at New Haven, about 50. f " " " the Torrid zone, 70 to 80. " " " moderate climates, 50 to 52. " " " near the polar regions, about 36. The extremes of the globe are from about 50 sometimes 70 to 100, 105, 110; and even 120, or perhaps in some situa- tions, still more. The extremes of artificial temperature* are much greater, from 91, to 35127, (Henry.) which is the highest estimated heat, but we know that it is not the highest heat that has actually been produc- ed. We have no measure for it, and probably can never have any other than the effects which such heats produce in fusion, &c. The real zero has never been discovered. { ( /.) Freezing mixtures act by enlargement of capacity. A solid, as already observed, is always one ingredient in these compositions ; it becomes fluid by uniting, chemically, with some other agent, and thus absorbs heat and produces cold. Salts and acids, as Glauber's, eight ounces, and muriatic acid, five ounces, are most commonly em- ployed, and sink the thermometer from 50 to 0. When both in- gredients are solid, the mixture is still more powerful, as in the case of muriate of lime and snow ; and of muriate of soda and snow ; by the former, mercury is frozen. Snow, or pounded ice, two parts, and common salt, one part, depress the thermometer from 50 to 5. The mere solution of a salt in water produces cold. Nitre, in large quantities, added to water, sinks the thermometer 17 ; ni- - Should the views of Prof. Cordier, as to the increasing heat of the interior of the earth, be established, the result stated in the text cannot be correct ; but it will require numerous and often repeated observations, extending to many countries, and through many years, to establish a conclusion so extraordinary See Am. Jour. Vol. 15. p. 109. t Pres. Day, in Trans, of Conn. Acad. t We think it useless to reiterate the fruitless discussions on this subject ; they may be found in all the larger chemical works. It is evident that no reliance can be placed upon the results, widely discordant as they are. For a more copious table of freezing mixtures, see p. 136. HEAT OR CALORIC. 12.; trate of ammonia, 28 ; muriate of lime three parts, and water two, 37 ; muriate of ammonia, and nitre in powder, with from five to eight parts of water, from 50 to 11 ; and the salts, recovered by evaporation, answer as well as before. Diluted acids with salts, are more powerful than water only. Sul- phate of soda, with sulphuric acid, diluted with as much water, re- duces the temperature from 50 to 5, and with diluted nitric acid, from 51 to 1. With mixed salts the cold is still greater. Phos- phate of soda, nitrate of ammonia, and diluted nitric acid, reduce the thermometer from 50 to 21, and mercury has been frozen by a mixture of nitrous acid, sulphate of soda, and nitrate of ammonia.* By these, or similar means, all fluids have been frozen, except al- cohol, and several of the gases have, by the aid of strong pressure, been condensed into fluids. The salts should be previously well crystallized, and should retain their full proportion of water ; they should be well pulverized ; they should be mixed in vessels which are bad conductors of heat ; the access of the external air should, as much as possible be cut ofF, and the materials may be previously cooled by being placed sepa- rately in other freezing mixtures, taking care that they be not cooled below that degree at which the materials act on each other.f (m.) Many heat-producing , or calorific mixtures, act by diminu- tion of capacity.-. Sulphuric acid and water combine with increase of specific gravity, and diminution of specific heat, and therefore with increase of sensible heat. Many other acids, e. g. the nitric, muriatic, fluoric, &tc. act in the same way ; even alcohol and water, in considerable quantities, grow- sensibly warm by being mixed. The heat evolved in those cases in which the products of the chemical action are chiefly gaseous, does not appear to be well accounted for in this way. Nitric acid and oils, gunpowder and fulminating compositions generally, and mixtures of the chlorates with the combustibles, result in the conversion, more or less, of solids into aerial matter, and cold should therefore be genera- ted, instead of heat, which is always evolved in great quantities. Dr. Turner sums up our knowledge of specific heat under the fol- lowing heads. 1. " Every substance has a specific caloric peculiar to itself, whence it follows that a change of composition will be attended by a change of capacity for caloric." 2. "A change of form, the composition remaining the same, is likewise attended with a change of capacity. It is increased when a solid liquifies, and diminished when a fluid passes into a solid." 3. " It is certain that the specific caloric of all gases increases as their density diminishes, and vice versa. * Graham. * Murray. 124 HEAT OR CALORIC. Mr. Dalton contends that this law prevails also in solids and fluids,* and Petit and Dulong have proved it with respect to several solid?. The specific heat of Iron was found to be Centigrade. Specific heat. From to 100 - 0.1098 " .0 200 - - 0.1150 " o " 300 0.1218 " 350 - - 0.1255 And so of other bodies. Spec, heats-, from to 100 cent. 0.0330 - 0.0927 0.0507 - 0.0557 0.0049 - 0.0355 0.1770 Spec heat from to 30" iif 0.0350 - 0.1015 0.0549 - 0.0611 0.1013 - 0.0355 0.1900 Mercury, Zinc, Antimony, Silver, Copper, Platinum, - Glass, - 4. " Petit and Dulong have rendered it probable that the atoms of all simple substances have the same specific caloric. "f This is illustrated by a pretty copious table, for which see the Ann. de Chimie et de Physique, Vol. 10. 5. " A change of capacity for Caloric always occasions a change of temperature. An increase of the former is attended by a diminu- tion of the latter ; and a decrease of the former is attended by an in- crease of the latter." The specific heat of the cording to Dela Roche and follows. Under equal volumes. Atmospheric Air, 1.0000 Hydrogen Gas, 0.9033 Oxygen Gas, 0.9765 Nitrogen Gas, 1.0000 Nitrous Oxide, 3.3503 OlefiantGas, 1.5530 Carbonic Oxide, 1.0340 Carbonic Acid, 1.2583 'ases is an interesting erard, several of them Under equal weights. 1.0000 - 1.2340 0.8848 - 1.0318 0.8878 - 1.5763 1.0805 - 0.8280 problem. Ac- stand related as Specific gravities. - 1.0000 0.0732 - 1.1036 0.9691 - 1.5209 0.9885 - 0.9569 1.5196 * Chera. Phil, part 1. p. 50. t By comparing the equivalents of twelve principal metals, and of sulphur, as given by Petit and Dulong, and by Dr. Turner, in his Chemistry, it has been found thai the product arising from the multiplication of those equivalents into the spe- cific heat of the bodies, gives results so widely differing from uniformity, as " would Beem to take all plausibility froTj the hypothesis that the atoms of simple bodies har.'* the same specific heat." Bache, in Jour. Jlcad. Nat. Sci. Phil. Jan. 1829. HEAT OR CALORIC. 125 Water being unity, the specific Specific heat of metals, accord- heats of the gases are as fol- ing to Petit and Dulong. lows. Bismuth, - - 0.0288 Water, - - - - 1.0000 Lead, 0.0298 Atmospheric Air, 0.2669 Gold, - - - 0.0298 Hydrogen Gas, 3.2936 Platinum, 0.0314 Carbonic Acid, 0.2210 Tin, - - - - 0.0514 Oxygen Gas, - - 0.2361 Silver, - - 0.0557 Azote, - - - - 0.2754 Zinc, - 0.0927 Protoxide of Azote, 0.2369 Tellurium, 0.0912 Olefiant Gas, - - 0.4207 Copper, - 0.0949 Oxide of Carbon, 0.2884 Nickel, - - 0.1035 Steam, - - - - 0.8470 Iron, - - 0.1100 Cobalt, - - 0.1498 Sulphur, - 0.1880 It is worthy of observation that all the gases, excepting hydrogen, have, according to Petit and Dulong, less specific heat than water ; this is the fact even with steam. It would seem that they had some doubts as to the correctness of this result. Apparatus for illustrating capacities for heat. Dr. Hare. " Let the vessels A,B,and C, be sup- plied with water thro ugh the tube T. which commmuni- cates with each of them, by a hori- zontal channel in the wooden block. The water will rise to the same level in all.' Of course the resistance made by the wa- ter, in each vessel, to the entrance of more of this liquid will be the same, and will be measured by the height of the column of water in the tube T. Hence if the height of this column were made the in- dex of the quantity received by each vessel, it would lead to the im- pression that they had all received the same quantity. But it must be obvious, that the quantities severally received, will be as different as are their horizontal areas. Of course we must 'not assume the resistance exerted by the water within the vessels against a further accession of water from the tube, as any evidence of an equality in the portions previously received by them." 126 HEAT OR CALORIC. VIII. COMBUSTION. (a.) In common language it means the same as burning ; that is, in most cases, the apparent consumption* of a body, and an entire change in its properties, with the emission of heat and light. (b.) In what was catted the new or French theory, combustion was synonymous with a combination of oxygen with a combustible body, attended by augmentation of its weight, and change of its nature, heat and light being at the same time emitted. Now, Chlorine is added as another agent possessed of similar powers with oxygen ; also, by some, Iodine ; and many even regard every case of intense chemical action, with the emission of heat and light, as combustion. " Whenever the chemical forces that determine either combina- tion or decomposition, are energetically exercised, the phenomena of combustion, or incandescence, with a change of properties, are dis- played."! In general we shall use the word combustion in its common and more restricted sense, taking due notice, however, of the other cases as we come to them. (c.) It would be premature to consider combustion fully at pre- sent ; for its theory and phenomena are best developed progressively as we proceed. We mention combustion in this place merely to complete our list of the effects of heat; for, as commonly seen, it sustains a very close connexion with heat, since an exalted temperature is usually neces- sary to its existence. Heat is, however, often the consequence, as well as the cause of combustion. (d.) Phlogiston is a name formerly given to a principle of com- bustion, supposed to reside in all inflammable bodies ; dissipated, as was imagined, in the form of heat and light, during combustion ; the body being thereby rendered uninflammable, and its inflammability being again restored by recombining with phlogiston, as when red lead is heated with charcoal which causes the incombustible metallic oxide to become again combustible in the form of metallic lead. This theoryf is now obselete, but in its time, it rendered important, service to the science of Chemistry, and was in vogue for a century. Phlogiston comes very near to the modern idea of combined and free caloric. If we substitute a combination of oxygen for the extrication of phlogiston, and the extrication of oxygen for the combination of phlogiston, we translate, very nearly, all the common cases of com- bustion, from one theory into the other. * Sometimes the body remains, but in an incombustible state. i lire's Chem. Die. Invented by Becher, and more fully illustrated by StaML SOURCES OP HEAT AND COLD. 127 APPENDIX TO CALORIC. SEC. III. SOURCES OF HEAT AND COLD. I. SOURCES OF HEAT ; most of which are also sources of light. (a.) The sun. b.) Combustion. ) Chemical action without combustion. ? Electricity and Galvanism. Condensation of aeriform bodies by pressure. ) Condensation of solids, by mechanical action, including friction and percussion, (g.) Vital action. (a.) The solar rays. The intensity of the solar heat being in pro- portion to the rays that can be collected upon a given spot, there ap- pears to be no other limit to our power of generating heat in this manner, than what is found in the size of our instruments, and the difficulty of using them, for it has been long known, that the effect is much increased by lenses and mirrors.* This is especially true if the focus he received on a black and rough surface, e. g. on charred cork lining a box, and covered by glass ; thus a heat of 221, was produced while the air was only 75. Saussure. In another case, the heat generated by similar meanSj was from 230 to 237, while a bright fire gave, at the same time, 212. Black, Thomson. Dr. Hare remarks, that previously to the discovery of the heat ex- cited by oxygen, by the compound blowpipe, or by the Voltaic series, there was no known mode of rivalling the heat produced by large burning glasses and mirrors. These have been already mentioned, perhaps sufficiently, in the account of heat and light. It is not in our power to say what is the nature of the sun, and for aught we know, the popular opinion that his body is a globe of ignited matter, may be correct.f (b.) Combustion. After the solar influence, this is the most im- portant source of heat ; it is very completely under our command $ it can be applied when and where we please, and varies from ex- * Dr. Hare. t Dr. Herschel's ideas of the nature of the sun, were peculiar. He supposed the sun's body to be opake ; that his atmosphere has two strata of clouds ; the one opake and the other phosphorescent ; the latter he supposes to be the highest, and that they emit the light ; that when the clouds are broken and ragged, the sun's opake body is seen through the clouds. The fruitfulness of different seasons he supposed to be connected with the quantity of light emitted fvom the luminous clouds of the sun. Phil. Trans. 1801.. ' 128 SOURCES OF HEAT AND COLD. treme mildness to extreme intensity. Common fires, in fire places and stoves ; ' Argarid's lamp ; oil lamps ; spirit lamps ; gaslights; a smith's forge ; the furnaces of the arts and of the laboratory ; can- dles ; the mouth blowpipe, and that fed by oxygen and hydrogen gases, are all familiar instances, in which combustion is seen. Combustion is mentioned with propriety, both as a source and as an effect of heat ; for generally, it does not commence and proceed without an augmented temperature, and it raises the temperature in turn. I shall omit the description of common furnaces, and subjoin that of the following instruments. 1. The Mouth I L . Dr. Hare, Itol. J. J. ? " As fire is quickened, by a blast from a bellows, so a flame may be excited by a stream of air propelled through it from the blow- pipe." " The instrument, known by the abovementioned appellation, is here represented in one of its best forms,. It is susceptible of vari- ous other constructions ; all that is essential being a pipe of a size at one end suitable to be received into the mouth, and towards the other end, having a bend, nearly rectangular, beyond which the bore converges to a perforation, rather too small for the admission of a common pin. There is usually, however, an enlargement, to catch .the condensed moisture of the breath, as in this figure." Berzelius has in an octavo volume, illustrating, the extreme utility of the mouth blowpipe, with which Gahn discovered tin in a mineral containing only one per cent., which had escaped detection by an- alysis ; and he extracted also copper from the ashes of a quarter of a sheet of paper. -t 2. Lamp without a flame.* r j " About the wick of a spirit lamp, a fine wire oi platina is coiled, so as to leave a spiral interstice be- tween the parts of the spiral formed by the wire ; a few turns of which should rise above the wick." " If the lamp be lighted ; on blowing out the flame, the wire will be found to remain red hot, as it re- tains sufficient heat to support the combustion of the alcoholic vapor, although the temperature be inade- quate to constitute, or produce inflammation." See Am. Jour. Vol. IV. p. 328. SOURCES OF HEAT AND COLD. 129 " Instead of blowing out the flame, it is better to put an extin- guisher over it, for as short a time as will cause the flame to disap- pear. For this purpose, a small phial, or test tube, is preferable to the metallic cap usually employed." " The metallic coil appears to serve as a reservoir for the caloric, and gives to the combustion a stability, in which it would otherwise be deficient." " There is some analogy between the operation of the wire, in act- ing as a reservoir of heat in this chemical process, and that of a fly wheel, as a reservoir of momentum, in equalizing the motion of ma- chinery." Dr. Hare introduced a blowpipe, in which the air was propelled by hydrostatic pressure ; and in this manner he used also the oxygen and hydrogen gases.* I have found such a blowpipe very useful, and it will be mentioned again in this work. The blowpipe of the enameler and of the thermometer maker, is fed by a double bellows, worked by the foot, and terminates in a pointed tube, which rises above a table, and thus supplies a lamp. 3. Alcohol Blowpipe,. " A flame resembling that of the enameler's lamp, may be produced by a small boiler, A, containing alcohol, in which alcoholic vapor is generated, as steam is, by the boiler of a steam engine." " The vapor thus generated is substituted for air in the blast of the blowpipe, being directed upon the flame of a lamp in the same way, by means of a pipe proceeding from the boil- er, and terminating in a beak, with a capillary orifice, B. the boiler is furnished with a safety valve, V." " It may be objected to flame thus excited, that as the oxygen is not so copiously supplied, as when a stream of air is used, the oxide of lead in flint glass tubes is reduced by it, and the glass consequently blackened." ' The apparatus here represented, is furnished with an adjusting screw, S, by which the height of the boiler is regulated ; while the See his Compendium, p. 73. 17 130 SOURCES OF HEAT AND COLD. communication is preserved between it and the beak, by means of G tube sliding through a stuffing box, C, which surmounts a larger tube to which the beak is soldered."* 4. A new modification of the Blowpipe by Alcohol. 11 This figure represents an improv- ed blowpipe, by alcohol. In the ordi- nary construction of that instrument, the inflammation is kept up, by pass- ing a jet of alcoholic vapor through the flame of a lamp, supported, as is usual by a wick. The inflammation of the jet cannot be sustained with- out the heat of the lamp flame ; since the combustion does not proceed with sufficient rapidity to prevent the in- flamed portion from being carried too far from the orifice of the pipe ; and being so much cooled by an admix- ture of air, as to be extinguished. By using two jets of vapor in opposi- tion to each other, I find the inflam- mation may be sustained without a lamp. If one part of oil of turpen- tine, with seven of alcohol be used, the flame becomes as luminous as a gas light." " In order to equalize and regulate the efflux, I have contrived a boiler like a gasometer. It consists of two concentric cylinders, open at top, leaving an interstice of about one quarter of an inch between them ; and a third cylinder, open at bottom, which slides up and down in the interstice. The interstice being filled with boiling water, and alcohol introduced into the inner- most cylinder, it soon boils and escapes by the pipes. These pass through stuffing boxes in the bottom of the cylinder. Hence their orifices, and of course the flame, may be made to approach to or re- cede from the boiler. It must be obvious that the introduction of the alcohol requires the temporary removal of the intermediate cylinder.'' * "Stuffing box is the technical name given by mechanics to a small hollow me- tallic cylinder, in which, by means of another cylinder acted upon by screws, some cotton, tow, leather, or other elastic substance, is packed about a rod, 50 as to allow it to move to and fro without permitting any fluid to escape from the vessel into which it may enter/" SOURCES OF HEAT AND COLD. 13] (c.) Chemical action without combustion; that is to say, without combustion to begin with ; combustion is not used as a means of rais- ing the heat, although this mode of evolving heat may end in com~ bustion, provided any ingredient in the mixture is combustible ; e. g. as in the case of nitric acid acting on alcohol or oils, dense or vola- tile. Fermentation of hay may produce combustion. Spontaneous combustions proceed in many instances, from chem- ical action, as in cases where oils, tallow, paints, and similar sub- stances, are in contact with flax, cotton or hemp. Tanner's bark and horse manure, by fermentation, produce heat for the green house, and for some processes in the arts. Most of the cases under this head belong to capacity and specific heat, and the doctrine has been partly anticipated. Many more in- stances will follow. At present I add only the following from Dr. Hare. 5. Boiling heat produced, by the mixture of sulphuric acid vnth water. " Into the inner tube, represented in the adjoining figure, introduce about as much alcohol, colored, to render it more discern- ible, as will occupy it to the height of three or four inches. Next pour water into the outer tube, till it reaches about one third as high as the liquid within ; and afterwards add to the water, about three times its bulk of concentrated sulphuric acid. The liquid in the inner tube will soon boil vio- lently, so as to rise in a foam." 6. Chemical combination, attended by decomposition, as the means of evolving caloric. " Instances of that species of corpuscular reaction, which comes un- der this head, will be hereafter mentioned in their proper places. The extrication of caloric, which is usually more or less a consequence of 132 SOURCES OF HEAT AND COLD. intense chemical reaction, is a collateral, rather than a necessary con- sequence of it. "As an example in which caloric is rendered sensible, by the method in question, the inflammation of turpentine by a mixture of nitric acid, with sulphuric acid, may be adduced." " The inflammation of alcohol, or oil of turpentine, by means of a chlorate and sulphuric acid, as represented by this figure, affords another exemplification perfectly in point." " About as much chlorate of potash as may be piled upon a half c'ent, being deposited in a heap, in the inflammable liquid, and con- centrated sulphuric acid being poured upon the heap, the liquid is in- flamed." " As portions of the liquid are sometimes projected into the air, in a state of inflammation, it is expedient, for the security of the opera- tor, to have the glass, used to convey the acid, fastened to the end of a rod." (df.) Electricity and Galvanism. The modes of excitement are peculiar ; generally they are well known, but they belong either to a different science, or to a different part of this science. The applications of the heat evolved in this way, are extremely useful to the chemist ; the power is conveyed, conveniently, into and through the interior of vessels, and thus gives us a furnace heat with- out its inconveniences. The heat is mild or intense at pleasure ; no heat, probably not even that of lightning, exceeds that produced by electrical and galvanic arrangements. The decomposing powers con- nected with common and galvanic electricity, produce the most curi- ous and important results, dividing the material world between the opposite poles, but this part of the subject is not appropriate to the present topic. The facts and the instruments relating to Galvanism are reserved for another place, except that I shall introduce here from Dr. Hare, an instrument equally simple and useful. SOURCES OF HEAT AND COLD. The galvanophorus, or galvanic substitute for the electrophones " The preceding figure represents an instrument for igniting a. lamp, by means of a galvanic discharge, from a calorimotor." " The plunger, P, being depressed, by means of the handle at- tached to it, some acid, contained in the box, B, is displaced, so as to rise among the galvanic plates. By the consequent evolution of the galvanic fluid, a platina wire (fastened between the brass rods forming the poles of the calorimotor, and projecting over the lamp, as seen at R,) is rendered white hot, and a filament of the wick, pre- viously laid upon it, is inflamed." " The weight, W, acts as a counterpoise to the plunger, and keeps it out of the acid, when it is not depressed by the hand." (e.) Condensation of aeriform bodies by pressure and cold. This topic is already anticipated under specific heat and vapors. Vapors and gas mechanically condensed, as by the syringe and piston, give out heat ; vapors impart heat to colder bodies, as in the distill- ing apparatus with its condenser, already mentioned. Compressed oxygen and chlorine give out light, and these gases are said to be the only simple ones that become luminous by pressure. (/.) Condensation of solids by mechanical action including fric- tion and percussion. The flint and steel in collision, or two quartz stones struck forcibly together ; any hard stone firmly held upon a revolving grit stone ; the vigorous rubbing together of two sticks ; the friction of branches of trees in stormy weather ; of axles in carts and wagons and of various pnrts of powerful machinery ; of the axles in 134 SOURCES OP HEAT AND COLD. sheaves or blocks of running tackle* on board of ships ; of ropes, pass- ing rapidly over a gunwale, as when a whale is harpooned ; friction in the boring of cannon and muskets j of a rope running rapidly through the hand ; of the hand rubbed on a stair rail, or on one's woolen coat sleeve ; all these and many others are instances of heat evolved on this principle. The rotary match box gives sparks by the collision of a rapidly revol- ving steel with flint, and a similar instrument called the steel mill, was used to give light in coal mines before the invention of the safety lamp. An iron bar grows hot enough, by vigorous hammering, to kindle shavings, and lead will by the same treatment kindle phosphorus. Wood, in rapid revolution, " may be carbonized throughout the circle of contact, by holding against it another piece properly sharp- ened, and one cork rubbed against another will become hot enough to kindle phosphorus. "f A disk of soft iron rapidly revolving by ma- chinery, will easily cut in twof the hardest steel saw plate, or the best file. (g.) Vital action. This is evidently a source of heat, although in a way not perhaps fully understood. There can be no doubt that oxygen, acting in respiration, is an important agent in producing and sustaining it ; it appears probable also that secretion, connected with the influence of the nerves, is concerned, and some facts countenance the opinion that galvanic agencies are not dormant. Whatever may be usefully said on the latter subject, belongs to a more advanced stage of this work. II. THE SOURCES OF COLD. 1. Evaporation, 2. Rarefaction, 3. Chemical action. 1. Evaporation. The general facts on this subject have been al- ready stated. Whenever a body passes to the aeriform state, it ab- sorbs heat to turn it into vapor, and thus cools the contiguous bodies. Sensible cold is produced by the evaporation of water, more by that of alcohol, and most of all by that of ether or carburet of sulphur, or liquid sulphurous acid, whether measured by our organs or by the thermometer. We have already seen that water is frozen by the evaporation of ether, both in the exhausted receiver of the air pump, and in a tube in the atmosphere. The mercury in a thermometer ball, wet with water and having a current of air blowing upon it, will fall 5 ; if with alcohol, 12, and if with ether, 30. -Murray. * See Lt. Glynn in Am. Jour. Vol. XIV, p. 196, and Capt. Parry's 2d Voyage, New York Ed. p. 212. " The weight of the ice every moment increasing, obliged us to veer on the hawsers, whose friction was so great as nearly to cut thtough the bit heads, and ultimately set them on fire, so that it became requisite for people to at- tend with buckets of water." Parry. t Dr. Hare. t See Am. Jour. Vol. VI, p. 336. SOURCES OF HEAT AND COLD. 135 With a rapid exhaustion by the air pump, mercury in a thermome- ter ball, if the ball be wrapped in flannel or fleecy hosiery and dipped n ether ior sulphuret of carbon, will be frozen in two or three minutes. Evaporation is very extensive in its natural operation, and its uni- versal prevalence is one of the great causes which prevents the accu- mulation of heat on our globe, and which therefore tends very much to preserve the equilibrium of its temperature. It is also occasion- ally of use in the operations of art, and is sometimes employed as we have already seen, to depress the temperature of particular bodies. 2. Rarefaction. This is intimately connected with evaporation, and depends upon the same principle. As condensation produces heat, so rarefaction generates cold. It is seen chiefly in the aeriform fluids. The remarkable example at the fountain of Hiero, has been already mentioned. In air pump experiments, the thermometer falls several degrees, and Dr. Darwin observed, "that if, in the stream of air issuing from the receiver of an air gun, in which it had been compressed, a thermometer were placed, it sunk from 5 to 7." In the first instance, it produces heat by its condensation, and in- stantly after, cold by its rarefaction. Air, condensed into a reservoir and suddenly liberated from an or- ifice, produces a considerable degree of cold : Gay Lussac found it equal to 50 of Fahr.* If heat must be absorbed in evaporation or gazification, in order to produce an aeriform body, more heat is required to enlarge its bulk after it is produced, and, as its particles are repulsive, when the pres- sure which retains them within a certain distance is diminished, the particles recede and caloric is absorbed, for, otherwise their repellent power could not be maintained at increasing distances, and they would again approach ; when they are forcibly brought together anew by compression, the heat is again given out. 3. Chemical action. Cold is produced during the chemical ac- tion of those substances whose capacity is by the union enlarged, and which therefore absorb caloric. The immediate effect of chem- ical union is a mutual penetration of particles, and therefore an in- crease of specific gravity, and of course an emergence of heat ; but it often happens also that there is an enlargement of capacity and the absorption of heat which follows from this cause, is frequently suffi- cient to generate a considerable degree of cold. Sulphuric acid and snow afford us an illustration of both these remarks ; when first min- gled they produce heat for an instant, owing to the energy of their combination, but immediately after, cold is produced because water is of the capacity of ten for caloric, while ice is only nine. * Probably from the medium of temperature. " The cold will, however, depend on the previous condensation of the air." Dr. Torrey informs me that he makes this experiment with Newman's blowpipe, and that, with an air thermometer, the e:ffect can be witnessed at a considerable distance. 136 SOURCES OF HEAT AND COLD. s CO * 15*2 si? of soa ammoni xed acid I s I o I I e I QC CO 02 Snow Diluted Diluted ! S. CO -f Snow Muri I o CO CO c g if o -^ S-5 --S! S d) 3 * a, S = in o * "3 II I uio.tj sjjuis Snow, or Muriate o m Snow Diluted i% i S S 2 2 Snow Diluted nitric aci S. Snow Muri g 5 ** $a$ 9 % hb S .2 c S a vt '" 3 2 , SJ'oS' SS S C 05 g 3 C O |.S2-o ^ji*l* 2.i5|| ^ " = > ' f-\ nj 53 (Q cr 1 3 S S ATTRACTION. 137 SEC. IV. ATTRACTION.* By attraction, we mean the tendency of bodies to approximate, and also the unknown cause of that tendency. In its most general sense, it extends to atoms and masses reciprocally, and to every distance. It is the bond of the universe.; it appears to depend in general on no proximate cause, but to emanate at once from the will of the Deity. Counteracted and modified by the powers of repulsion and pro- jection, it keeps every thing in harmonious equilibrium. It is unknown whether it arises, in all its varieties, from the modifi- cations of one cause, or whether there are several, giving origin to the different kinds of attraction. However this may be, it is most convenient to consider the sub- ject under different heads. 1. GRAVITATION. 2. MAGNETISM. 3. GALVANIC ELECTRICITY. 4. COHESION AND AGGREGATION. 5. CHEMICAL ATTRACTION OR AFFINITY. 1. GRAVITATION. (a.) It extends to every thing, to all quantities of matter, and to all distances. (6.) Its force is directly as the quantity of matter, and inversely as the square of the distance. The quantity of matter, in different cases, being as 1.2. 3. 4, the attracting force at a given distance, will be as those numbers directly ; but the same body being placed suc- cessively at the distances 1. 2. 3.4, the attracting force will be ex- pressed inversely, by 1. 4. 9. 16, that is, at the distance 2 it will be J, at 3, i, and at 4, ,',,, as great as it was at the distance 1. We are familiar with the effects of gravitation, and therefore re- gard them as natural ; they are so to our habits, but only in obedi- ence to an established law ; if the law had been different, our habits would have been accommodated to it. Were there no attraction towards the earth, a stone thrown into the air would not return, and would stop only from the resistance of some medium, or of some other body which it might encounter. (c.) The projectile power modifies the gravitating force, so that the planets move in elliptical orbits, and neither fall to the centre of motion, nor move off in tangents to the curve of the orbit. * I have been accustomed to give, in my lectures, a very general sketch of the different varieties of attraction, that affinity may be the better understood, and shall pursue the same course in this work. 18 IBS ATTRACTION. 2. MAGNETISM. (a.) This is a power usually manifested in iron or steel, after hav- ing received particular treatment, or after having been for some time in a particular position. (b.) It belongs also to nickel, and to cobalt, which like nickel, is found to be the more magnetic, the purer it is made. (c.) Magnetism resides also in the earth. The magnetic poles are not coincident with the poles of revolution. In the Arctic region, the magnetic pole is* in 69 16' of N. lat. and 98 8' W. lon.f d.) Repulsion as wdl as attraction is predicable of magnetism, e.) Similar magnetic poles repel, and opposite poles attract. f.) Magnetism is connected, in some mysterious manner, with the other imponderable powers, light, heat, and electricity. Sg.) The solar rays, especially the violet, magnetize a needle.^ h.) The calorimotor evolves heat with great energy, but its elec- tricity is of a very low intensity ; still, it magnetizes needles power- fully, when there is no light perceptible. (i.) Similar effects, in a greater or less degree, are produced by all the varieties of galvanic apparatus ; all the known imponderable fluids being occasionally present together. 0/0 ^ e cannot say, therefore, whether magnetism is a distinct power, or a property or appendage of one or more, or of all the other imponderable powers. The magnetic power, both in its attractions and repulsions, is pleasingly exhibited by magnetic needles, fish, boats, and balls, by the horse shoe magnet, bar magnet, &c. Many articles of iron and steel become magnets spontaneously, especially such as have stood long vertically or nearly so, and more especially, if in the magnetic meridian. Magnetism is excited also by rapid rotary mo- tion. 3. GALVANISM 1. Requires, and will receive a distinct statement near the end of this work, but as this remarkable power actually arranges in a natural method, all the elements and compound principles of matter, it is mentioned here among the general powers. (a.) Mode of excitement. Nearly as various as matter, almost all substances of different natures, or sometimes the same substance in different conditions, arranged in a particular connexion, will serve to * Or was at the lime of Captain Parry's late voyages ; I Icnow cot whether any observations have since been made, to ascertain its constancy in latitude ; the varia- tions of the needle E. and W., eecm to prove that the magnetic pole varies in longi- tude, t Am. Jour. Vol. XVI, p. 149. t Morrichini's and Mrs. Somerville^s experiments on magnetizing needles, arc said to have failed in skilful hands ; it is suggested that the needles might have been magnetized before. The editor of the Pbi]os. Magazine, new series, Vol. IV, p 221, thinks that, at least, the magnetism was increased. ATTRACTION. 139 render this power perceptible. Common electricity is also excited in many ways, but most usually by the friction of glass or resin. (6.) Mode of exciting the Voltaic power. Certain combina- tions of metals, usually zinc and copper, with fluids, especially saline and acid fluids, producing opposite polarity at the two extremes of the series. (c.) .Mode of receiving and transmitting the power. By conduc- tors, uniting the poles ; they are commonly wires, and are often pointed with well prepared charcoal. (d.) Nature of the power. It has been commonly regarded as the same with electricity ; like that it is attended by light, heat, and magnetism, variously modified and combined in different proportions, in different kinds of apparatus ; so that one predominates in one kind and another in another. It is clear that it is not electricity merely. (e.) Sensible and demonstrable effects. Attractions and repul- sions, as in common electricity ; similar poles repelling and opposite attracting. All elements and all compound principles, when placed in the electro-galvanic circuit, being for the time endued with polari- ty, chemical decompositions are thus produced. ' Muscular shocks are also among the effects produced by this power, as well as light, heat, and magnetism, which have been already mentioned. (/*.) Mode of effecting the decompositions, by bringing the con- necting points into contact with the particular substance. (g.) Classification of the elementary bodies. Oxygen, iodine, and chlorine, are attracted to the positive pole, and are therefore said to be electro-negative. The combustibles and metals are attracted to the negative pole, and are therefore said to be electro-positive. (h.) Classification of the principal proximate principles in the com- pound bodies. The acids go to the positive pole ; the earths, alka- lies and oxides of metals, to the negative. (i.) Galvanic electricity is a powerful agent in decomposition ; it is more energetic, and it is also more manageable than common elec- tricity. (j.) The arrangement of the principles of bodies under this pow- er, will be mentioned as we come to them individually. (k.) The other effects are not material in our present state of ad- vancement ; they will be mentioned in their proper place. It is supposed, that the electrical and magnetic attractions are gov- erned by the same general law with gravitation. 4. COHESION ADHESION AGGREGATION. (a.) Cohesion is a union of parts, without change of properties. The particles of a bar of iron cohere ; this force gives the iron its strength ; those of water cohere but feebly ; hence it has no strength ; those of moist dough cohere more than water, &c. These 140 ATTRACTION. are examples of union where the minutest parts are of imperceptible magnitude. Adhesion.* Two plates of glass or two of metal, or one of glass and one of metal, when moistened or oiled, adhere, with considerable force ; with still more force, two leaden hemispheres made by split- ting a bullet, and pressing the surfaces together with a wringing or twisting motion. If furnished with hooks, the parts of the bullet may be suspended, and will support a considerable weight that may be gradually increased for some time, before the hemispheres will part.f (b.) The cohesion of homogeneous^ particles is often termed aggre- gation, and masses made up in that manner are said to be aggregates. (c.) The word adhesion may be used to denote the union between surfaces of perceptible magnitude, whether similar or dissimilar in their nature. (d.) Cohesion produces augmentation of volume, and frequent- ly a change inform, but no change in properties. The dust of mar- ble is the same substance with the stratum or mountain of marble which afforded it ; it contains the same elements, and in the same proportions. The elements are united by affinity or chemical attrac- tion ; the compound particles produced by the union of the elements, are united by cohesion. (e.) Mhesion of surfaces of perceptible extent produces no change in properties. Generally the union of such surfaces is feeble. That particular mode of corpuscular union which is called cohesion, is the source of the different strength of materials, as of lead, iron, wood, &ic. (/.) The attraction which produces the union of particles is often called corpuscular attraction. It is quite immaterial whether the par- ticles be simple, as those of single metals, or compound as those of metallic alloys or wood ; in either case, the state of the body results from the union of minute particles, which are for this purpose regard- ed as mechanically simple, whether chemically so, or noU The union of dissimilar particles, as will be hereafter seen, is re- ferred to chemical action. Chemical union may first connect dis- similar particles, as zinc and copper ; and the compound, which is in that case called brass, is composed of panicles, that are regarded as mechanically simple, and are called integrant particles ; while the others are called constituent particles. * Jldhesion is merely a word of convenience ; the power that unites surfaces of perceptible magnitude, and that which unites particles in aggregation, is doubtless the same. t This effect evidently depends, in part, upon the furrows on the surface of the lead which are brought into close contact by the twist that is given in pressing them to- gether, with a screwing motion ; when polished, it is difficult to make thorn adhere. I Heterogeneous particles will also unite, but the result is not an aggregate ; it is a new body, whose particles are connected not by mechanical but by chemical at- traction. ATTRACTION. 141 (G.) CRYSTALLIZATION is THE RESULT OF THE ATTRACTION OF AGGREGATION. (h.) A crystal is a symmetrical solid, produced by the union of in- tegrant particles.* (i.) Natural crystals are numerous, and art produces many more; every good mineral cabinet exhibits great numbers of the former, and every good chemical collection of the latter. (j.) Destruction or great diminution of the power of cohesion is an indispensable preliminary. This is effected either by so- lution in a fluid, or by the aid of heat producing fluidity or the state of vapor. In the former case, it is necessary to drive off part of the solvent by heat ; in the latter, merely to allow the fluid to cool, or the vapor to be condensed, in order that crystals may be formed. Cer- tain circumstances are, however, necessary to be attended to in order to success. If the solvent be very rapidly expelled by the aid of a high temperature, or, if the fused body be suddenly exposed to an in- tense cold, either a shapeless mass will be formed, or only confused and irregular crystals. In general, fine crystals are obtained only by slow evaporation and by slow cooling. Water and most of the metals are examples of bodies that crystallize by a mere reduction of tem- perature. A saturated solution of sulphate of soda, boiled and cork- ed in that state, does not become solid on cooling, but on letting in the air ; agitating it by a jerk or jar, or dropping in a crystal, it con- geals and heat is evolved, sufficient to melt it again. If a string or mark be placed on the neck of the vessel, it will be seen that the mass has been expanded by the crystallization. It does not appear that it is the mere pressure of the air, as was formerly supposed, that pro- duces the crystallization ; the air seems to act as a disturbing force, or perhaps by the introduction with it, of some foreign body, which may serve as a nucleus. f A gentle waving motion does not cause it to congeal. The salts are crystallized generally by diminishing the quantity of the solvent, that is, by evaporation, or by conjoining both, diminishing the solvent by evaporation and reducing the tem- perature ; or, when a particular portion of a salt has been sus- pended by the aid of an elevated temperature, a simple reduction of temperature is sufficient, without evaporation. For, an elevated temperature increases the power of most solvents. Common salt, however, being dissolved in nearly equal quantities by cold as by hot * That is of particles of the same kind, but these particles may be chemically, either simple or compound. t A point or almost any solid frequently determines incipient crystallization ; so a jar or sudden vibratory motion brings the particles into such a position, that their polar attractions become effectual, and the negative pole of the galvanic series produces crystallization, while the positive pole counteracts it. Light also causes camphor to crystallize from its alcoholic solution, and it is rcdi^sojvcd in a dark dav Dr. Ure. 142 ATTRACTION. water, no advantage is gained by the aid of heat, except in speed, nor does a reduction of temperature cause it to crystallize. The only method in which this can be effected, is by diminishing the solvent by evaporation. It is found that crystallization is much facilitated by supplying a nucleus ; and Le Blanc, a Parisian apothecary, has even founded upon it a method of obtaining large and beautiful crystals, by selecting the best, replacing them in the solution, and turning them daily j as the lower side does not increase. (k.) An increase of bulk is commonly an effect of crystallization, but sometimes the bulk is diminished, as in the case of mercury. Substances which have been deposited from an aqueous solution, generally retain, intimately combined, a portion of water, which is called their water of crystallization. The efficacy of freezing mix- tures is owing, in a considerable degree, to this water of crystalliza- tion, which, by becoming fluid, absorbs caloric ; when, with the aid of heat, it causes the salt to become fluid, the salt is said to suffer the aqueous fusion. When it escapes spontaneously, into the atmosphere, the salt is said to effloresce, for the crystalline form is destroyed, and it falls into powder. When the salt attracts water from the air, and becomes more or less fluid, it is said to deliquesce* When it splits and crackles by heat, it is said to decrepitate. (I.) All bodies, in crystallizing, assume a determinate form. Thus the crystal of alum is an octahedron ; that of common salt a cube ; of the beryl, a hexahedral prism, &c. It must not be understood, however, that these forms are invariable. The same substance will sometimes assume one form, sometimes another, according to cir- cumstances. But, to this apparent caprice there is a limit, for a given substance will always crystallize in one of a given number of forms, which are appropriate to it. Prisms and pyramids are among the most common forms of crys- tals, but they admit of great diversity. (m.) Ml the forms of crystals are reducible either by dissection or by calculation, to six primitive forms, namely, the hexahedron, includ- ing the cube, parallelopipedon and rhomboid ; the regular octahedron ; the prism of six sides ; the regular tetrahedron ; the dodecahedron with rhomboidal faces, and the dodecahedron with isosceles triangu- lar faces. This very curious subject has been developed by the suc- cessive labors of Rome de L'Isle, Gahn, Bergman, Bournon, and Haiiy. Haiiy completed what Bergman had begun, by extracting the primitive form of calcareous spar in the following manner. * Sometimes portions of the fluid from which crystals have been precipitated, are lodged mechanically between the plates, and it may be even a portion of a fluid con- taining a different substance, if other salt* or compounds were present in the solution. ATTRACTION. 143 Dr. Hare, Fig. 1 to 14. >~J f "As each of the sides of an hexagonal prism of calca- reous spar, is bounded by two edges, one at each end of the prism ; there are six edges at each end, and in all, twelve edges. If to every one of the twelve edges a knife be forcibly applied, in the direc- tion indicated in figure 1 , one of the edges, a b c, a b c, bounding each side, will yield so as to expose a smooth nat- ural facet, making an angle of 45 with the adjoining side. The alternate edges will not split off so as to present surfaces corresponding either in smoothness, or obli- quity, with those above described, so that the six facets will be equal- ly divided between the two ends of the prism, each having three facets alternating with three remaining edges." " If the dissection be continued, by applying the knife in directions parallel to the facets, finally a rhomboid R will be developed, which exists not only in the hexagonal prism, but in many other crystalline forms of calcareous spar." "All these other forms are called secondary. The rhomboid, which is their common nucleus, or primitive form, is beautifully ex- emplified in the Iceland spar." FIG. 2. L " The same author teaches us that a cu- ^ bic crystal of fluor spar, can be split only in directions parallel to the faces of an oc- tohedral nucleus, whose situation, relatively 1 to the containing cube, is represented by figure 2." " By various dissections, analogous to those which have been adduced, it is ren- X " J dered highly probable that every crystalli- zable substance has an appropriate form, which it assumes in the first instance, and which is the basis of all its other forms." " The nuclei may sometimes be obtained by percussion, sometimes by heat ; in other cases by heat followed by refrigeration." " Although a nucleus cannot be extracted in every instance from crystals, the existence in them of primitive forms, is usually inferred 144 ATTRACTION. by analogy. The angles which the sides make with each other, are always the same in a nucleus, however obtained ; and such crystals are always divisible in directions parallel to all their surfaces, where- as there are some surfaces of secondary forms, parallel to which, by cleavage, new facets cannot be obtained." " Haiiy enumerates six primitive crystalline forms, the parallele- piped, (including the cube, rhomboid, and four sided prism,) the reg- ular tetrahedron, regular octohedron, hexahedral prism, rhombic dodecahedron, and dodecahedron with triangular faces." FIG. 3. Quadran- gular or four- sided prism. FIG. 4. Cube. FIG. 5. Rhomboid. FIG. 6. Tetrahedron. FIG. 7. Octohedron FIG. 8. Hexangular or six sided prism. FIG. 9. Rhombic dode- cahedron. ATTRACTION. i4,j FIG. 10. Dodecahedron FIG. 11. Triangular or with triangular faces. three sided prism. " The primitive forms, by a further dissection of the octahedron, hexangular prism, and dodecahedra, in directions, not parallel to the sides, may be reduced into three forms : the tetrahedron, or simplest solid, the triangular prism, or the most simple prism ; and the paral- lelopiped, including the cube, rhomboid, and four sided prism. As it is in size only, that integrant atoms can be altered by cleavage ; it it is inferred that if the dissections were continued until the smallest integrant atom should be developed, its form would be the same as that of the parent mass. Hence also the inference has arisen, that the only forms, which belong to integrant atoms, are those above mentioned." It is remarkable that (the sphere and spheroids only being except- ed,) these three forms are the simplest of solids. As three lines are the smallest number that can include a superficies, so four planes are the smallest number that can include a solid ; the integrant molecules above named have successively, four, five, and six faces. (n.) The actual or secondary forms are built up, by the union of Integrant particles, to produce the primitive form, and then by the addition of other particles, single or in groups, upon the faces of the primitive form . (o.) The dev elopement of these processes, constitutes the theory of crystallization, proceeding according to the laws of decrement. 1. Parallel to the edges 2. Parallel to the diagonal 3. Par- allel to a line intermediate between the side and the diagonal ; or, parallel to either of the above, but proceeding by three in breadth, and two in height, or the reverse, or by such a ratio that the relation of height and breadth, in the ranges of particles, shall be expressed by a proper vulgar fraction ; this supposed arrangement of integrant particles is called 4. Mixed decrement. (p.) A minute, consideration of this subject, belongs to mineralogy but the following illustrations will render the descriptions of incre- ment and decrement intelligible. Conversion of a cube into a dodecahedron. " If a cube be increased by layers of particles, applied to all its sides, the edges of the layers being parallel to those of the cube, and 19 140 ATTRACTIONS . each layer being made less than that immediately preceding it, by one row of particles on each of its edges, a dodecahedron, or twelve sided solid, with rhombic faces, will be produced." FIG. 12. "If, instead of diminishing every layer one row, on every edge, they be made less, at each addition, by two rows on two parallel edges, while, upon the other two edges, each layer is made alternately the same as the preceding, alternately less by one row, a dodecahedron, or twelve sided solid, with pentagonal or five sided faces, will be pro- duced." FIG. 13. ATTRACTION. 141 "One surface (C) of the cube, in each figure, is represented as if no addition were made to it, in order that the situation of the nucleus, relatively to the pyramids raised upon it, may be understood. It must be evident that each rhombus, R R R R, in fig. 12, and penta- gon, PPPPP, in fig. 13, is made up of the surfaces of two adjoin- ing pyramids, built upon a cubic nucleus." ; ' The decrements may proceed only on two sides, or a diminution of two, three, or more rows may take place on all the sides ; yet in either case, secondary crystalline forms may be built upon the com- mon nucleus, or primitive form." FIG. 14. Of tJiP. Goniometer, or instrument for measuring the an- gles of crystals. " The goniometer is founded upon the 1 5th proposition of Euclid^ which demonstrates that the opposite angles, made by any two lines in crossing each other, are equal. Hence it follows that the angles made by the legs BB, BCB, of this instrument, fig. 14, above and below the pivot on which they revolve, are equal to each other. Consequently, if they be made to close upon any solid crystalline angle, presented to them at C, they will comprise a similar angle on the other side of the centre about which they turn. This angle is evidently equivalent to that of the crystal, and is ascertained by in- specting the semicircle A, graduated into 180 degrees precisely in the same manner as a protractor." "The construction of goniometers is usually such as to allow the legs to be detached from the arch, in order to facilitate their appli- cation to crystalline angles ; and yet, so that they may be reapplied to the semicircle, without deranging them from the angle to whicla they may have been adjusted." I4b ATTRACTION. " The piece of brass, in which the pivot is fastened, slides in a slit in each leg, so as to permit them to be made of the most suitable length, on the side on which the crystal is applied." The reflective Goniometer of Dr. Wollaston, depends upon the reflection of the rays of light from the brilliant surfaces of contigu- ous crystalline plates, uncovered by cleavage, or of natural surfaces. The pieces or crystals to be examined are fixed upon an axis whose revolution carries around a graduated wheel, which measures the an- gle contained between two contiguous surfaces, when they have ar- rived successively in the position to reflect an image of the bar of a window or of some other definite line.* This instrument is much more accurate than that of Carangeau, used by Hauy, (See the fig- ure above,) and has corrected a number of errors, some of which were important. Mr. Daniell has contrived a method of discovering the structure of crystals by solution. In a mass of alum lying in water, there will be discovered, after some -time, upon its lower part in high relief, both octahedral forms and sections of octahedra. Borax gives similar results. Even shapeless metals, which a peculiar tendency to crys- tallization, will reveal their crystalline forms by the action of acid sol- vents; bismuth exhibiting with dilute nitric acid, cubes, antimony, rhomboidal plates, and nickel, regular tetrahedra.f Very different views of crystallization are taken by more recent authors, among whom Mr. Brooke f and Professor Mohs are the most distinguished. Crystalline forms that have an intimate connex- ion with each other, are considered as forming certain natural groups or systems of crystallization. They are called, the tessular system which comprehends the cube, the tetrahedron, the regular octahe- dron, the rhombic dodecahedron, &c. ; the pyramidical system, con- taining the octahedron with a square base and the right square prism ; the prismatic system including the rectangular and rhombic octahe- dron, and the right rectangular and right rhombic prisms ; the hemi- prismatic system, embracing the right rhomboidal and the oblique rhombic prisms ; the tetarto-prismatic system containing the oblique rhomboidal prism, and the rhombohedral system comprehending the rhombohedron and the regular hexagonal prism. || This complex system seems to present no advantage to compen- sate for the absence of the simplicity and perspicuity which charac- terizes the system of Hauy. * A more particular description with a plate maybe found in Phillips' Mineralogy t English Jour. Sci Vol. I. p. 24. t Familiar Introduction to Crystallography Treatise on Mineralogy, translated by Mr. Haidinger. it Turner, 2d Ed. p. 555. ATTRACTION. 149 It is worthy of observation, that Professor Mitscherlich of Berlin, in 1819,* discovered "that certain substances are capable of being substituted for each other in combination, without influencing the form of the compound. The neutral phosphate and biphosphate of soda, have exactly the same form as the arseniate and binarsemate of soda ; the phosphate and biphosphate of ammonia with the arseniate and binarsemate of ammonia, the biphosphate and binarsemate of potash ; each arseniate has a corresponding phosphate, possessed of the same form and containing the same number of equivalents of acid, alkali and water, and differing in nothing but in one's containing arsenic, and the other phosphoric acid." It appears then that certain substances, when combined in the same manner with the same body, are disposed to assume the same crys- talline form, and this discovery has given origin to the phrase isomorphous crystals. The arseniates are isomorphous with the phosphates ; the oxide of lead and baryta and strontia form iso- morphous salts with the same acid. The isomorphous crystals ap- pear to contain the same quantity of waterf of crystallization, and there are many other very curious circumstances in the constitution of these bodies, which are too minute to be introduced into this work, but which are thought to give great support to the atomic theory to be mentioned hereafter. THEORY OF DR. WOLLASTON. It has been already remarked, that among solids bounded by plane faces, the tetrahedron, the triangular prism, and the cube, are the simplest ; these are the three integrant molecules of Hauy, and it would seem that their simplicity and their capability of being so ar- ranged as to produce, perhaps, all other solids, afforded a strong pre- sumption in favour of their being the real integrant particles of bodies. But a different view has been taken of this subject by Dr. Wollaston ; for this reason among others, that in " crystallograpy we meet with appearances which Haiiy's theory but imperfectly explains. A slice of fluor spar, for instance, obtained by making two successive and parallel sections, may be divided into acute rhomboids ; but these are not the primitive forms of the spar, because by the removal of a tetrahedron from each extremity of the rhomboid, an octohedron is obtained. Thus, as the whole mass of fluor may be divided into te- trahedra and octohedra, it becomes a question which of these forms * Ann. de Chimie and de Physique, Vol. XIV, p. 172, XIX, p. 850, and XXIV, pp 264 and 355, Turner. t And when the quantity of water is different, the crystals assume a different form. Turner. 150 ATTRACTION. is to be called primitive, especially as neither of them can fill space without leaving vacuities, nor can they produce any arrangement suffi- ciently stable to form the basis of a permanent crystal." " To obviate this incongruity, Dr. Wollaston (Phil. Trans. 1813,) has very ingeniously pro- posed to consider the primitive particles as spheres, which, by mutual attraction, have as- sumed that arrangement which brings them as near as possible to each other. When a num- ber of similar balls are pressed together, in the same plain, they form equilateral triangles, with each other ; and if balls so placed were cemented together, and afterwards broken asunder, the straight lines in which they would be disposed to separate, would form angles of 60 with each other. A single ball placed any where on this stratum, would touch three of the lower balls, and die planes touching their surfaces would then include a regular tetrahedron. A square of four balls, with a single ball resting upon the centre of each surface, would form an octohedron ; and upon ap- plying two other balls at opposite sides of this octohe- dron, the group will represent the acute rhomboid. Thus the difficulty of the primitive form of fluor, above alluded to, is done away, by assuming a sphere as the ultimate molecula. By ob- late and oblong spheroids, other forms may be obtained."* Dr. Wollaston has demonstrated, geometrically, that by assorting spheres and spheroids in particular groups and modes, all the solids of crystals may be constructed. The cannon balls in an arsenal, are often arranged in such a manner as to illustrate this subject. One group forms a square and another a triangle, and by piling them * Brande, quoted by Hare. ATTRACTION. 151 they become pyramids, shewing half a tetrahedron, half an octohe- dron, &tc. which would be completed, by continuing the group down- ward, in the same form. The marbles used for play, by children, may be made use of for similar illustrations. But it is obvious that the truth of this view, beautiful and probable as it is, cannot be de- monstrated, nor is it perhaps inconsistent with that of Haiiy ; for if the ultimate integrant particles of bodies are spheres or spheroids ; as they may, by the supposition, be grouped so as to produce Hauy's in- tegrant molecules, and these may be the last term of mechanical analysis, although the ultimate particles of which they are composed, may be spheres ; and when they are inconceivably small, there will be no appreciable difference between the plane and curved faces. Indeed, in Hauy's theory, the passage by increment and decrement, is supposed to be by particles so minute, that the steps cannot be or- dinarily perceived, although the imperfection of the process some- times renders them more or less obvious.* 5. CHEMICAL ATTRACTION OR AFFINITY. (a.) It is exclusively, a corpuscular power. (6.) Its three principal characteristics, are : it is exerted at insen- sible distances ; between particles only ; and those particles are al- ways heterogeneous. (c.) Its effects are, a change of properties more or less complete : it is unlike cohesion, which induces no change of properties, but merely of bulk or form. (d.) The change of properties, in the cases where weak affinities are exerted, is often slight ; giving in many instances only the mod- ified properties of the parent substances ; as examples, we can men- tion watery solutions generally, as of salts, gum and sugar, and often alcoholic solutions, as of resins ; and among fluids, alcohol and water, and water and acids ; the union in such cases, is quiet, and attend- ed with no remarkable appearances. (e.) But the union is permanent and cannot be destroyed by mechan- ical means. Solutions of salts, sugar, gum, and alcohol, in water, are instances in point ; they are not decomposed by repose, by agitation or by filtration, thus proving that the union is not merely mechanical. (f.) This class of compounds should be considered as midway be- tween mere aggregation and energetic chemical combination ; The union is chemical, inasmuch as it is not subverted by mechanical means ; but these compounds partake of the nature of aggregates, in- asmuch as they present the mitigated properties of the parent sub- stance and no new properties. * Mr. Daniel, in a paper in the Eng. Jour, of Science, Vol. I, p. 24, has with great ability, illustrated Dr. Wollaston's theory ; but the limits of this work do not allovv ns to go farther into these metaphysics of crystallization ; a subject which is per* Jiap) In order that numbers may express correctly the combining power of bodies, they must refer to a common unit. -Oxygen and hy- drogen are the bodies which have been selected for this purpose : dif- ferent philosophers have adopted, some the one and some the other 5 but there is in my view a decided advantage in adopting hydrogen, and in expressing its lowest combining proportion by 1 We thus avoid fractional expressions, for it would appear from the researches of Prout and others, that the combining powers of all bodies may be expressed by numbers which are multiples or reduplications of that which expresses the combining power of hydrogen. We go upon the supposition that hydrogen enters into combination with oxygen to form water, in a smaller proportion than it enters into the constitution of any other body ; and also that there is no body whatever that en- ters into combination in so small a proportion as hydrogen* We have, it is true, only negative evidence in support of either of these propositions, although the presumption that they are true amounts al- most to certainty. But should it be hereafter discovered that hydro- gen enters into some combination in a less proportion than it exists in water ; or that some other element enters into combination in a pro- portion still smaller than any known proportion of hydrogen ; even * This most remarkable fact evidently depends upon the original constitution of things ; and is as truly a law of the physical universe, as that its gravitation is direct- ly as the quantity of matter, and inversely as the square of the distance. 21 162 ATTRACTION, then the numerical relations would not be in the least disturbed, only the numbers expressing them would be doubled, tripled or quadru- pled, &ic. according as the unit was placed lower in the scale. For instance, should we find a compound in which hydrogen exists in half the weight that it does in water ; then the composition of water, (the lowest known proportion of hydrogen being still unity,) would be ex- pressed by 1 of hydrogen and 16 of oxygen, and in the same manner all other numbers expressing combining ratios would be doubled. (qq-) The foundation of the doctrine of definite proportions is therefore laid in the constitution of things, and the facts discovered by analysis, have been confirmed by calculation. If discovery had pro- ceeded no farther, the knowledge obtained would have been both highly valuable and interesting, but it was reserved for Mr. Dalton,* to discover the next law which, although built upon that which has been already announced, is perhaps still more extraordinary. (RR.) IF TWO SUBSTANCES UNITE, IN SEVERAL DIFFERENT PRO- PORTIONS, THE LOWEST COMPOUND WILL CONTAIN ONE, OR BOTH PRINCIPLES IN THEIR SMALLEST COMBINING PROPORTION ; AND IN THE HIGHER, THE PROPORTIONS WILL BE SUCH AS ARE PRODUCED BY MULTIPLYING THE LOWEST BY SOME WHOLE NUMBER. In a word, the higher proportions are multiples of the lowest, by a whole number, or, the difference will be expressed by a whole number, and the lowest is generally a divisor of the higher without a remainder. In compounds of A-fB, supposing the first compound to be of the smallest proportions of each, and that A remains constant, then the other compounds will be A+2B, or -f 3B, or -f 4B. " The following tablef will illustrate the subject. Water is composed of hydrogen 1. oxygen Deutoxide of hydrogen do. 1, do. 16 Carbonic oxide, carbon 6, do. 8 Carbonic acid, do. 6, do. 16 Nitrous oxide, nitrogen 14, do. 8 Nitric oxide, do. 14, do. 16 Hyponitrous acid, do. 14, do. Nitrous acid, do. 14, do. 32 Nitric acid, do. 14, do. 40" In the two first lines, the proportion of hydrogen is the same, while in the second that of the oxygen is doubled ; in the third and fourth lines, similar relations exist between carbon and oxygen, and in the * Of Manchester, England, who is still living. i Turner, 2d ed. p. 151. ATTRACTION. four last, while the proportion of nitrogen is constant, that of the oxygen is double, triple, quadruple, and quintuple. This is the law that has usually been called the law of multiples, or of multiple proportions, and there can be no doubt that it is true to a very great extent, although, at present, we are prevented, by a very few apparent exceptions, from regarding it as quite universal. Thus, hydrogen being 1, lead is represented by the number 104, and manganese by 28, and each of these metals has three oxides, which are found to contain respectively, 8, 12, and 16 of oxygen, which is in the proportion of 1 1.5 and 2 ; so iron, whose equivalent is 28 has, in its two oxides, 8 and 12 of oxygen, which also are in the proportion of 1, and 1.5. This does not correspond with the doc- trine of multiple proportions ; the difficulty would, however, be re- moved, should an oxide of each of these metals be discovered, with 4 of oxygen, instead of 8 ; or possibly there may have been a mix- ture of oxides, as of the protoxide and peroxide of lead, thus giving origin to an apparent deutoxide, which may not really exist.* Should these cases, however, prove in the end to be exceptions, they will not invalidate the truth of the general doctrine. (ss.) The number representing any compound body is composed of the sum of the numbers representing its parts. Thus in sulphate of potash, whose equivalent is 88, sulphur 16, -f- 3 proportions of oxygen 24=40, and potassa is composed of potassium 40, and 1 pro- portion of oxygen, 8=48, which + 40=88; this will hold true of the most complicated as well as of the most simple compounds. This truth is well illustrated by all the salts. (tt.) " The respective quantities of any number of alkaline, earthy, and metallic bases required to saturate a given quantity of any acid, are always in the same ratio to each other, to what acid soever they may be applied "\ Soda 2 parts, and potassa three parts respective- ly, these numbers always bearing the same relation to each other, and to some unit, saturate every acid ; soda is represented by 32, and potassa by 48, hydrogen being one, and 32 : 48 : : 2 : 3, as above, and these numbers therefore constantly represent the combining power of these two alkalies ; but the proportions of the different acids which will combine with these, and with other bases, will of course vary. (uu.) " The respective quantities of any number of acids requir- ed to saturate a given quantity of any base, are always in the. same ratio to each other, to what base soever they may be applied."^ This is only the converse of the other proposition, the relative pro- portions of any two acids that saturate a given base, will saturate any * Turner. t Prof. Olmsted, in Am, Jour, Vol. XII, p. 1. J64 ATTRACTION. other base, and are therefore called chemical equivalents, and the same is true of the bases, in relation to the acids. Wenzel, a German chemist, proved, in a work published in 1777, that two neutral salts that decompose each other, still preserve their neutrality ; neither acid nor base being in excess,* and Richter, of Berlin, illustrated this truth more fully in 1792. This could not have been true, had not the relations of acids and bases been con- stant, as stated in the two last propositions. Thus, in sulphate of potassa, the acid is in the proportion 40, and the alkali 48=88, and in nitrate of baryta the acid is 54, and the earth 78 = 132. Now when these salts are, by double decomposition, converted into sul- phate of baryta, and nitrate of potassa, the 54 parts of nitric acid in the nitrate of baryta will saturate and be saturated by the 48 parts of potassa in the sulphate of potassa, making 102 of the new salt, the nitrate of potassa, and the 40 of sulphuric acid in the sulphate of potassa, will saturate and be saturated by the 78 of baryta, in the nitrate of baryta, making 118 of the sulphate of baryta. The facts may be concisely expressed thus. Before decomposition. Sulphuric acid 40 -f potassa 48= 88 sulphate of potassa. Nitric acid 54 -j- baryta 78 = 132 nitrate of buryta. "220 Jlfter decomposition. Sulphuric acid 40 -f baryta 78 = 118 sulphate of baryta. Nitric acid 54-}- potassa 48 = 102 nitrate of potassa. 220~ The sum of the constituents being the same after decomposition as before, it is obvious there can be no excess of either. Thus then, hydrogen being unity, we are to infer that 40, or a multiple of it by a whole number, will always express the combining power of sulphuric acid, and so of other principles. (W.) CHEMICAL EQUIVALENTS ARE THOSE DEFINITE QUANTI- TIES OF PARTICULAR SUBSTANCES THAT SATURATE DEFINITE QUAN- TITIES OF OTHER SUBSTANCES. This is only expressing in the form of a proposition, what has been already stated ; namely, that a unit being chosen, it becomes possible to express the combining power of all bodies, both simple and com- pound, by numbers. Thus, if the combining power of hydrogen be * For an interesting account of the progress of the doctrine of definite proportions see the introduction to Dr. Thomson's First Principles of Chemistry. ATTRACTION 165 expressed by 1, that of oxygen will be 8, that of carbon 6, that of sulphur 16. If hydrogen and oxygen unite in one proportion of each, the compound will be expressed by 9, this is the number repre- senting water, and every combination of water will be expressed by 9, or 18, or 27, or 36, and so on, even to ten proportions, which would be expressed by 90. (ww.) The combining weight or power of a body being once ascer- tained, it will always remain the same ; or it will sustain the same ra- tio in every combination. If the combination takes place in different proportions with a given body, the number expressing the lowest pro- portion will be constant, and the higher proportions will be multiples of it, by a whole number. Thus, hydrogen being unity, oxygen will always enter into combination in the proportion 8, 16, 24, 32, &c. ; carbon in the proportions 6, 12, 18, 24, &ic. The combining weights or powers of bodies, both simple and compound, may therefore be per- manently registered in a table of chemical equivalents. Such a ta- ble is now attached to every treatise on chemistry, and is constantly referred to in practical operations, both of science and art. It is an important auxiliary, for we discover by inspection what quantities of particular bodies saturate, or are equivalent to each other. In the present work the chemical equivalents, as far as they are ascer- tained, will be found connected with each body, in its proper place, and they will be collected in a table at the end.* Dr. 'Wollaston 1 s Scale of chemical equivalents.^ This is a table of combining or proportional weights, embracing those bodies that are most frequently used in practical chemistry. It differs from other tables only in this, that while the names of the substances are station- ary, those of the numbers are placed on a sliding rule, divided logo- metrically, according to the principle of that of Gunter. The advan- tage of the instrument is, then, that it not only presents a table of chemical equivalents, but by moving the sliding rule in a proper man- ner, many proportions can be mechanically worked, without the trouble of calculation. Thus, it has been already stated, that sul- phate of potassa is composed of acid 40+ potassa 48, and therefore 88 is the number expressing the composition of the salt ; hydrogen being the unit, all this will be seen, by placing the scale in such a po- sition that 8 is opposite to oxygen ; but if we wish to know what would be the proportion of the acid and alkali, in 100 parts of sul- phate of potassa, we have only to bring the scale into such a posi- tion, that 100 will be opposite to sulphate of potassa, when we shall * A very valuable table is annexed to Dr. Thomson's First Principles of Chem- istry, and Mr. Brande has published, in a separate work, the equivalents of all bodies as far as they are known. t For a description of this beautiful instrument, see the Phil. Tr. for 1814. lt>6 ATTRACTION. read opposite to potassa 54.5, and to sulphuric acid 45.5, which is the composition in 100 parts. Dr. Wollaston called oxygen 10. When this number was oppo- site to oxygen, the other numbers, therefore, estimated by that scale, represented " the combining weights of the bodies opposite to which they may be found." " By mere inspection of this scale, we dis- cover the quantity of one body which enters into combination with another, the proportions of the elements of compounds, and the quantities of these which enter into the composition of any particu- lar weight of a compound ; the quantity of any substance required to decompose a compound, by combining with either of its ingredi- ents, and the quantity of the products that will be formed." The progress of analysis has shewn that the numbers attached to Dr. Wol- laston's scale are, in many instances, incorrect, but these errors have been rectified in more recent editions of the scale,* in which, also, the more convenient unit of hydrogen has been adopted. It is now ascertained that the foundations of chemical combination are laid in mathematical relations, and the proportions of bodies have therefore become subjects of mathematical calculation, as well as of analytical experiment. The mathematical relations are proved by analysis, to be true, and analysis is, in its turn, guided and corrected by calculation. We may be assured that an analysis is wrong if it does not correspond with numerical ratios, and we may predict that the result will be expressed by one of a certain set of numbers, rela- ted to each other by the same ratio, provided we are correctly ac- quainted with any one combination of the same principles ; the new compound of these principles will bear a relation to them which may be expressed by whole numbers, although we cannot be certain whether it will be double, triple, quadruple ; or a half, or a third, or a fourth, &c. of the one known ; it will be certain, or in the highest degree probable, that it will not be expressed by any inter- mediate number. This beautiful discovery, as its foundations are laid in the exact relations of quantity, places chemistry upon a mathematical basis. Mr. Higgins gave the first hint of this subject in 1788, in his view of the phlogistic and anti-phlogistic theory, but Mr. Dalton first clear- ly explained the doctrine. COMBINATION BY VOLUMES. (XX.) GASEOUS BODIES UNITE BY VOLUME, IN THE SIMPLE RATIO OF 1 TO 1, 1 TO 2, 1 TO 3, 1 TO 4, &c. This law was es- * As by Mr. Reid, in Britain, and by Messrs. Henry and Beck, of the Rensselaer School at Troy, N. Y., and by Dr. Barrat, at Middletown, Con. ATTRACTION. 1(57 tablished by Gay Lussac, and Humboldt,* and the first fact of the kind observed, was in the case of the elements of water, two vol- umes of hydrogen combining with one volume of oxygen. The following tablesf exhibit a number of facts of this class. Volumes. Volumes. 100 muriatic acid gas combine with 100 ammoniacal gas. 100 carbonic acid gas, " " 100 do. do. 100 do. do. " 200 do. do. 100 nitrogen gas, " " 50 oxygen gas, 100 do. " " 100 do. 100 do. " " 150 do. 100 do. " " 200 do. 100 do. 250 do. 100 Chlorine gas, " " 100 hydrogen gas. 100 nitrogen gas, " " 300 do. 100 oxygen gas, " " 200 do. This table needs no comment ; supposing it to be accurate, of which there can be no reasonable doubt, it fully supports the propo- sition stated above. (yy.) Bodies in the state of vapor obey the same law. 11 100 vols. hydrogen + 100 vols. vapor of sulphur = sulph'd hydrogen, 100 " oxygen -j- 100 " " = sulphurous acid. 100 " " -f-100 iodine = hydriodic acid."J This view is carried so far as even to embrace solids, which, per- haps, have never been in the aeriform condition, except in a state of combination ; it is supposed that in that state, they would obey the same rule. In the compound gases just mentioned, it is obvious that the specific gravity and proportion of the oxygen in sulphurous acid, and of the hydrogen in sulphuretted hydrogen being known, the balance of the weight of the gas under a given volume, must represent the sulphur in the state of vapor ; and the same remark will apply to the hydriodic acid ; we may include the carburetted hydrogen gases in the same view, for the specific gravity of the hydrogen which they contain, and its proportion being known, it is obvious that the remain- der of the weight in a given volume must be carbon in a state of vapor. (zz.) When gases suffer condensation, in consequence of com- bining, it is always in a simple ratio to the volume of one of them. Ammonia is composed of 3 vols. of hydrogen -f 1 vol. of nitrogen, contracted into 2 vols. and in the formation of nitrous oxide gas there Memoires d'Arcueil. t Murray, 6th Ed. Vol. 1, p. 67. 168 ATTRACTION. is a contraction to two thirds. In the formation of sulphuretted hy- drogen, and sulphurous acid, there is also a contraction to one half ; and the same fact is seen in many other cases. (aaa.) By knowing the specific gravity of the gases composing a compound gas, and the degree of condensation which they undergo, the specific gravity of the compound gas may be calculated. Dr. Turner has given the following instances among others. Ammonia, as just observed, contains 3 vols. hydrogen, and 1 of nitrogen, condensed into 2 vols. The sp. gr. of hydrogen is 0.0694, air being 1, and that of nitrogen is 0.9 722 therefore the latter number +0.0694X3 = =0.2951, the sp. gr. which ammoniacal gas would have, 4 were there no contraction of the gases ; but as they contract one half, the sp. gr. will be double of that, or 0.5902, which is its weight, as ascertained by experiment by Sir H. Davy. Nitric oxide gas, be- ing composed of 100 vols. of oxygen, and 100 of nitrogen, united without contraction, must form 200 volumes of the compound, and of course the sp. gr. must be the mean of its components, or 3LJ _ = 1.0416, which accords with the average results of the best experiments. (bbb.) The combinations by volume coincide accurately with the law of multiple proportions, for it is obvious that double, triple, fyc. of the volume of a gas must also be double, triple, fyc. of the weight. There is also an additional coincidence, that is not possessed by the compounds that are not aeriform. Although in them there is an arithmetical relation between the weights of the different proportions of the same principle, there is no such correspondence between the dif- ferent principles of the same compound. Thus, between the 14 parts by weight, of nitrogen, and the 8 of oxygen, contained in nitrous oxide ; and the 14 and 16 parts of the same principles, in nitric ox- ide ; and the 6 of carbon, and 8 of oxygen, in carbonic oxide ; and the 6 and 16 of the same principles in carbonic acid, there is no mul- tiple relation. (ccc.) In combinations of aeriform bodies, there is a multiple re- lation, not only between the different proportions of the same princi- ple, but of the different principles, that are united in the same com- pound. The table on page 167 proves this proposition to be true. (ddd.) In general, a volume of a gas represents a combining pro- portion. Oxygen is the only exception ; in that gas, half a volume represents a combining proportion. This arises from the fact that in the lowest combination of oxygen known, it unites with two volumes of hydrogen, which are supposed to contain only one combining pro- portion, and therefore the combining proportion of oxygen is consid- ered as contained in half a volume of that gas. ATTRACTION. 169 (eee.) .Although, in general, there is no arithmetical ratio between the combining proportions of different bodies, hydrogen forms an ex- ception. According to Dr. Prout,* and Dr. Thomson, f "in -every one of the compounds of hydrogen, the proportion of the body united with it, is an exact multiple, by a whole number, of its own weight." J Thus, in water, (protoxide of hydrogen,) the oxygen is just 8 times the weight of the hydrogen, while in the deutoxide, it is 16 times ; and in sulphuretted hydrogen, the sulphur is just 16 times the weight of the 1 hydrogen. (fff') Berzelius^ has discovered that oxygen contained in different proximate principles of the same compound, exists in a multiple ratio, or in equality. Thus, hydrate of potassa is composed of potassa 48, and of water 9, and there is 8 of oxygen in each of them. This law holds in earthy minerals, containing several oxides, and in the salts. Carbonate of potassa consists of carbonic acid 22, containing oxy- gen 16, and of potassa 48, containing oxygen 8. Where water of crystallization is present, there is a similar rela- tion. Crystallized sulphate of soda contains sulphuric acid 40, in which the oxygen is 24; soda 32, with oxygen 8, and water 90, with oxygen 80; and these numbers, 8, 24, and 80, consist of one, three, and ten proportions of oxygen. Compound salts obey the same law. In tartrate of potassa and soda, the oxygen in the acid, and in the two alkalies is the same. (ggg.) " In each series of salts the same relation always exists between the oxygen of the acid and of the base." In the neutral sul- phates, the ratio is as 1 to 3 one in the alkali, and three in the acid. In the carbonates the acid is double, and in the bi-carbonates, quad- ruple the oxygen of the base. The illustrious discoverer of these most remarkable laws, says that in the course of several years that have passed since he first observ- ed them, he has not detected any exception, and he therefore relies upon them implicitly, and is in the habit of calculating the compo- sition of bodies upon this principle. || * Annals of Philosophy, Old Series, Vol. VI, p. 321. t First Principles. t This is denied by Berzelius, who asserts that it is inconsistent with the results of his analysis. This account of the discoveries of Berzelius, is abridged from Dr. Turner s Chemistry, 2d Ed. || For an able view of this subject, see Dr. Turner's Chemistry, 2d Ed. p. 177. He gives the following generalization. Most of the neutral sulphates, all the alka- line and earthy, and several metallic sulphates of common metals, as iron, zinc, and lead, consist of 1 proportion of acid, and 1 of base ; the acid contains 1 proportion of sulphur, 16, and 3 of oxygen, 24, and every protoxide consists of metal 1 propor- tion, and oxygen 1=8. It will be seen by comparing the numbers that 1. " The oxygen of the acid is a multiple of that of the base." 2 The acid contains three times as much oxygen as the base," 22 170 ATTRACTION. THEORY OF ATOMS. For a complete view of this curious and interesting speculation, re- course must be had to the writings of Higgins^ Dalton, Berzelius, Thomson and others.* In the sketch that has been given of definite proportions, I have in- tentionally avoided the use of the word atom, because it may be mis- understood, and may lead beginners to confound facts with hypothe- sis. The doctrine of definite and multiple proportions is established on the basis of experiment, and is fully confirmed both by analysis and calculation. The expressions, combining weight, combining quantity, or combin- ing proportion, and chemical equivalent, all mean the same thing ; and it may be added, that atom, and atomic constitution and atomic weight, are used by most writers in the same sense. The atomic hypothesis, first suggested by Mr. Higgins, (1789,) was so fully detailed and illus- trated by Mr. Dalton, in his Chemical Philosophy, that the theory is usually considered as his. It is ingenious and beautiful, and there can be no reasonable doubt that matter has an atomic constitution ; but, that it is such as the atomic theory now in discussion supposes, although highly probable, cannot be demonstrated ; and it is there- fore important for the student to be able to distinguish it, or any other atomic theory that may be proposed, from the luminous and demon- strated verity of definite and multiple proportions. (AM.) If we assume that bodies, in the combination in which they exist in the smallest proportions, unite atom and atom, then their re- lative weights in those cases, will represent those of their atoms. This assumption is the foundation of the atomic theory. (Hi.) There being no combination in which hydrogen is known to exist in smaller proportion than in water, and the specific gravity of hydrogen to oxygen being as 1:16, if these elements unite atom to atom, and a volume of each represents an atom, then the relative 3. " The sulphur of the acid is just double the oxygen of the base." 4. The acid itself is just five times as much as the oxygen of the base. Metallic sulphurets often contain one proportion of each element, and when con- verted into a salt, the sulphuric acid and the protoxide will be exactly in the propor- tion for forming a neutral sulphate of a protoxide. In the carbonates, the oxygen of the acid is generally double that of the base, and a similar mode of reasoning is applicable to the various genera of salts ; but no con- stant ratio exists between the quantity of oxide and that of the acid, or of the oxygen in the acid, because the combining weights of the metals themselves are different. All these facts are arranged naturally under Mr. Dalton's principle of multiple pro- portions. An attempt has been made to extend the same views to the constitution of miner- als. See Ann. of Philosophy, N. S. Vol. IX, Mr. Children. * See Henry, 10th London Ed. Vol. I, p. 42. Thomson's First Principles of Chemistry, and Turner and Murray. ATTRACTION. 171 weights of the atoms will be as those numbers ; but as it requires two volumes of hydrogen gas to saturate one volume of oxygen gas, it follows that if the two volumes of hydrogen be expressed by 1, viz. be regarded as one atom, half a volume of oxygen must be the equivalent of the hydrogen, arid will be expressed by 8.* (jjj>) Either of these elementsf being taken as unity, then the weights of the atoms of other bodies may also be expressed by numbers, having an arithmetical relation to those attached to these two elements, and thus we may construct a table of atomic weights. (kkk.) If we could be certain that we actually know the lowest pro- portions in which bodies combine, and that in them the constituents are united atom and atom, then their definite proportions and their atomic weights would correspond ; or at least they would be multiples and divisors, generally, of each other, and always by whole numbers. (III.) But we can never be certain, that we either know the small- est combining quantities of bodies, or that those quantities, if known, are relatively in the proportion of atom and atom, or of one atom of one and of two of another, or vice versa, or of some other pro- portion ; we cannot therefore be certain that our atomic hypothesis is true. (mmm.) This however does not affect the truth of the theory of multiple proportions ; that great discovery is independent of hypothe- sis, because the exactness and arithmetical relation of the proportions is a matter of fact, and will still be true, whether the lowest combin- ation is formed by atom and atom of different bodies, or by one atom of one and two of another, or the reverse ; or by any other assort- ment that may be imagined. (nnn.) The atomic theory is an elegant hypothesis, framed to ac- count for definite and multiple proportions, and may be either true or false without affecting that sublime truth, which deserves to be in- scribed on the same tablet with the laws of gravitation and projection. (ooo.) Still the hypothesis is highly probable, and the probability of its truth is much increased by its surprising coincidence with facts. (ppp-) No student in chemistry, should however, imagine that the doctrine of definite and multiple proportions must stand or fall with the atomic theory. The latter may be discarded, without in the least affecting the former ; but the truth of the former is indispensable to the existence of the latter. I shall, as much as possible, avoid the use of the word atom, since we have no positive knowledge of the nature, forms, number and weight of the atoms of any thing ; as the word is short, it may however * See Mr. Finch's paper on the atomic theory, Am. Jour. Vol. XIV, p. 24. t Other elements might have been used for this purpose ; but none are equally oxygen and hydrogen. 172 ATTRACTION. be convenient to use it occasionally, but it will be understood by the reader, that nothing more is intended by it than combining weight, combining proportion, or chemical equivalent.* It will doubtless be thought by some, that the atomic theory should be presented more in detail. There can be no objection to its be- ing studied fully by those who are well versed in chemistry, but the learners of elements, for whom chiefly this work is intended, will, if they have mastered the doctrine of definite and multiple proportions, be able to go forward in their studies without the atomic theory, and to understand that theory the better, the farther they proceed in the science. We do not, however, hold it in small consideration, and a sufficient number of opportunities of illustrating its nature, will pre- sent themselves in the study of the particular bodies. f APPENDIX TO ATTRACTION. Terrestrial and artificial magnetism, has an evident effect on chem- ical action. Before leaving the subject of attraction, it ought to be remembered, that magnetism appears to be connected with it. Tinc- ture of purple cabbage placed in a syphon tube, is changed in fifteen minutes to green, by being connected by an iron wire, with the two poles of a magnet, and when the liquor was in two connected tubes, the same thing happened, but it required two days to effect the change. J A' syphon tube, half an inch wide, and four and five inches long, having mercury poured into the bend, but not sufficient to cut off the communication between the two branches ; the tube is then nearly filled wijth an acid solution of nitrate of silver. The tube being placed in the plane of tlie magnetic meridian, the precipitation of the arbor dianse is much more rapid than when it is at right angles with it; and it is much more abundant at the north than at the south end, and the crystals are more brilliant and longer, and more perfect. A bent tube placed across the magnetic meridian, and in which the crystallization has made little progress, exhibits it in increased activity, when two artificial magnets are approached, the north pole *Dh "VVollaston, in a paper on the finite extent of the atmosphere, published in the Phil. Transactions for 1822, has rendered it probable that there are atmospheri- cal atoms incapable of farther division. The question as to the indivisibility of atoms, is a physical topic, entirely independent of the mathematical speculation as to the infinite divisibility of matter ; a speculation which seems however to have little utility, and some would say, meaning, except with reference to physical elements. t Thenard has followed this course, Vol. I, Chem. p. 24, Ed. 5. I heard Mr. Dalton explain his own theory in his lecture room at Manchester, and while I was entertained with the arrangement of his atomic symbols, I was forcibly struck with the stiil greater value of his discovery of multiple proportions. i The spontaneous change is to red and not to green. A fanciful name given to this peculiar crystallization of silver; the disposition of the crystals being in branches, and silver was formerly called Luna or Diana. ATTRACTION. 173 of one to one leg, and the south pole of the other to the other leg of the syphon tube. Circles of tallow being formed on glass plates, so- lution of nitrate of silver was placed within, and a circular piece of zinc in the centre ; the precipitation of silver was much more active towards the north, and the oxide of zinc inclined to the south ; a strong magnet being brought within two inches of a plate prepared, as before, the precipitation took place in one fourth of the time, that it did on the plates that were beyond its influence.* * * * * -x- We have now taken a preliminary view, perhaps sufficiently ex- tensive and detailed, of the general doctrines of chemistry. This was indispensable, to enable us to understand the history of particular bo- dies, which is to follow ; and in giving it, I have endeavored, as far as practicable, to avoid anticipation ; still it is possible that some pas- sages may be unintelligible to a beginner ; as they are, however, not numerous, they may be omitted in the first reading, and being mark- ed in the margin by a pencil, they can be examined again at a more advanced stage of the subject, when the pupil has become more familiar with chemical facts and reasoning. The preceding account of the general doctrines, although proba- bly sufficient for an introduction, is far from being complete, and ad- ditional illustrations will be given, when the proper facts come in our way. Before proceeding to the history of particular bodies, it will be useful to say something of the rules of philosophising, and of the ap- paratus and operations. I. RULES OF PHILOSOPHISING. LIMITS OF HUMAN REASON. 1. GOD IS THE FIRST CAUSE OF EVERY THING. (a.) Ml our observations, experiments and reasonings, make us acquainted only with second causes* (b.) Theproximate cause of an effect, is the one immediately an^- tecedent to the event, or which is principally operative in produc- ing it. (c.) To every proximate cause, there may be another proximate cause, and to that cause another ; but the series will end at last in the power of the Creator, in immediate agency ; and this will still be the fact if we discover ever so many proximate causes, constitu- ting a series or chain apparently endless. (d.) When we have classified similar phenomena, and have dis- covered their modus operandi ; we say that we have found out the law that governs them ; but still this harmony of facts and operations, we must trace to the same source. * Am. Jour. Vol. XVI, p. 262, and Ann. de Chim. et de Physique. 174 ATTRACTION, (e.) Natural science is to be studied by observing facts, and making experiments, and then drawing conclusions ; this is the inductive or Baconian method of reasoning, and is the foundation of legitimate theory. An experiment is nothing but the exhibition of a fact. (f.) Hypotheses may be introduced in the absence of true theory founded on induction ; but they can be admitted only provisionally, until something better can be done.* (g.) We will add from Sir Isaac Newton, that, " ive are to admit no more causes of natural things, than such as are both true and suffi- cient to explain their appearances." ( h.) " Therefore, to the same natural effects we must, as far as possible, assign the same causes."^ (i.) The range of human reason is the whole extent of second causes. (j.) The final reason of a particular law is sometimes discovered by us, and always magnifies the author. The unvarying proportion of oxygen gas in the atmosphere ; and the means by which it is pro- bably sustained ; the exception in the expansion of water between 32 and 40 ; the phosphorescence of marine animals and of fish gener- ally in the ocean, and the circulation of fluids and of aeriform bodies in currents to equalize temperature, are striking instances among mul- titudes that might be adduced. f (k.) The moral effect of physical study upon every mind which has been correctly disciplined, is altogether happy, and augments the vigor of every proper feeling. It is not, however, to be denied, that an op- posite effect is sometimes produced upon certain minds ; but this is the fault of the individual and not of the study. Even moral study sometimes produces the same effect. (/.) The greatest mental power and the longest life, joined with the greatest industry, can enable man to compass only a small part of universal knowledge. Of this, the wisest and the greatest men are the most sensible. Newton was not more distinguished for his vast powers and acquirements, than for his singular modesty. The im- portant suggestions at the end of his optics are in the form of queries. The whole amount of the knowledge of such a man, compared with all that a savage knows, is indeed great ; but, compared with univer- sal knowledge, it is an evanescent point. II. APPARATUS AND OPERATIONS. Under the head of apparatus, we include all the instruments and utensils employed in chemical experiments. An experiment being, (as already observed,) only the exhibition of a fact, we want such * See Lord Bacon's Novum Orgaiium, and Do Augment. Scientiarum. i Principia, Vol. II, Ed. 1803. t See Paley's Natural Theology. ATTRACTION. 175 instruments as will enable us to show facts ; they are for utility, and not for mere parade, but in a public establishment, elegance may be in a good degree, combined with utility. An apparatus is best explained, when it is used ; but a few facts may be stated advantageously in this stage of our progress, and the names of some leading instruments and operations may be given. A considerable number of instruments has already been mention- ed, but they have been chiefly those which illustrate general princi- ples, and the greater part have been very intelligible. For private re- search, and for the instruction of only a lew persons at once, a compli- cated and expensive apparatus is not necessary. Much may be done by cheap and simple means. * Still, it is an error to suppose that re- fined analysis and difficult researches that demand great precision, can be accomplished without proper instruments, and various and sometimes expensive reagents ; nor can full effect be given before a large audience, to the fine experiments with which chemistry abounds, without an apparatus, and materials corresponding in some measure, to the splendor and dignity of the subject. For a full account of chemical apparatus and operations, the stu- dent is referred to Mr. Faraday's excellent work on chemical mani- pulations, where all the information that can be desired is given. Apparatus names of things heads and hints. Instruments of chemistry, to be perfect, should be, (a.) Transparent. Ib.) Incapable of corrosion. (c.) Incapable of fracture by heat and cold. ( d.) Strong to confine elastic vapors. (e.) Not liable to be melted or otherwise injured by heat. Glass, metal, and earthen ware, collectively possess these properties. Glass has the two first characters, in a sufficient degree, but not the rest; Metal, has sufficiently the third an,d fourth, and Porcelain or earthen ware, the fifth, provided the heat is careful- ly managed. 1. Means of producing heat. (a.) Fuel, fyc. Charcoal, coak, anthracite and other coals ; wood, oil, alcohol, ether, hydrogen gas ; this gas and oxygen ; friction, per- cussion, fermentation, chemical mixtures. 2. Instruments in which, and means by which the application is to be made. * I heard Dr. Priestly say, that his principal instruments were gun barrels, glass tubes, flasks, vials and corks, and it is well known that few men have made more discoveries. Still he was a pioneer ; he was always on travels of discovery, and his operations were not in general so remarkable for refinement, as for sagacity and effect. 176 ATTRACTION. (a.) Furnaces, Black's, crucible furnace, table furnaces, Lewis', air (furnaces, forge furnace. The general principles of all furnaces are the same. The principal parts are an ash pit and register, a grate, a body, a top, and a chimney. Argand's lamp, spirit lamp, mouth blowpipe, table blowpipe or Artists', Dr. Hare's, compound and hydrostatic, electric and galvanic apparatus, and burning lenses, and mirrors are useful means of producing heat. 3. Vessels to be used with heat. (a.) For fusion. Crucibles, Hessian, Wedgewood, Austrian or black lead, charcoal, platinum, gold, silver. (b.) For mixture. All vessels may be employed for these pur- poses, provided the agents do not act on them. For the solution of salts in the cold, most vessels will answer ; with heat, they must bear expansion and contraction. For metallic solutions, they must generally be of glass or earthen ; a platinum crucible may however be employed for many metallic solutions. (c.) For evaporations, distillations, sublimations. For evapora- tion. Earthen pans, glass dishes, watch glasses, saucers, plates, and porcelain, and metal capsules ; those of platinum are very valuable ; bottoms of retorts and mattrasses are useful. Almost all vessels an- swer for crystallizations. For distillations. Common still, with its worm and refrigeratory, mattrasses, oil flasks, tubulated and plain retorts and receivers of glass, iron, earthen ware, lead, silver, and gold or platinum ; bent glass tubes, closed at one end. For concentration, decoction, digestion. Papin's digester, or other strong boiler with tubes and stop .cocks ; occasionally, almost all ves- sels are used for boiling. (d.) For sublimation.-*- Most of the vessels last named. Baths of writer, sand, ashes, steam, oil, mercury, hot air, alcohol, brine, &c. Alembics of glass, metal, &c. 4. PNEUMATIC APPARATUS AND MISCELLANEOUS ARTICLES. !a.) Hydro-pneumatic cistern and air jars. b.) Mercurial trough, usually of stone, furnished with tubes of glass. Sc.) Air pump and its appendages. Condensing syringes. d.) Gazometers of different sizes for different purposes. Eudi- ometers and graduated glass jars, graduated tubes, detonating tubes, Woulfe's apparatus, and Dr. Hare's improvements ; do. for impreg- nating with carbonic acid gas. Stands, supports, &c. of iron and brass ; barometer and thermometer ; instruments for specific gravity. 5. MECHANICAL OPERATIONS PREPARATORY. (a.) Trituration. Mortars of marble, iron, steel, glass, porcelain, jr, porphyry, agate, wood, granite. (b.) Levigation. The rubbing stone and muller. [c.) Pulverization. Rasps, files, graters, hammers, anvil. ATTRACTION. J77 d.) Weighing. Scales, coarse and fine, very sensible balances. e.) Sifting. Selves, of various fineness, with andwithout covers. /.) Decantation. Syphons, coffee pots, &ic. g.) Filtration. Unsized paper of various quality, pounded glass, flannel, filtering stones, sand, &c. Filtering funnels and stands. 6. LUTES. Flour and water, rye paste ; sand, flour and clay ; fat lute, com- posed of clay and oil, lime and white of an egg. 7. VESSELS FOR KEEPING PRODUCTS. Ground glass stopped bottles for deliquescent salts ; wide mouth- ed bottles ; common vessels of any description. Tin cases for phos- phorus bottles. Drawers, mineralogical cabinet, bladders and silk bags, for the pur- pose of administering gases. 8. LABORATORY general idea of one. Any convenient, light, dry, and well ventilated place for the performance of experiments. Neat- ness, order, and care of one's person and clothes and premises are in- dispensable. Necessity of caution and presence of mind. Unreasonable fears of chemical experiments. Frequent ventilation of a laboratory ne- cessary. Specific gravity. The specific gravity of a body is its weight under a given volume. It is often necessary in chemical experiments, to take the specific gravity of bodies. Ample instructions are given on this subject, in every book of Natural Philosophy, and for the present, mention will be made only of its application to gaseous bodies. It may however be stated, for the sake of those who have not more delicate apparatus, that common money scales are sufficiently exact for most purposes. A fragment of the substance to be weigh- ed, may be suspended by a fine thread or piece of sewing silk, from the point of bearing of one arm of the balance, the thread being long enough to allow the fragment to swing below the scale so as to admit of immersion in pure water ; we then proceed as is usual in similar cases. Dr. Hare has several ingenious contrivances and in- ventions for taking specific gravities, which may be seen in his com- pendium, and in the American Journal of Science, and if there is room, they may be given in an appendix to this work. The specific gravity of fluids is easily taken by weighing them in a thin vial with a narrow neck, having a mark upon it so that the same volume may be easily taken ; it is most convenient that the vial should hold 1000 grains of distilled water. 23 178 ATTRACTION. Method of ascertaining the specific gravities of the gases. Dr. Hare. " Suppose the globe, A, to be removed from the receiver, R, and exhausted during a temporary at- tachment to an air pump, by means of a screw with which the globe is fur- nished, and which serves also to fasten it to the re- ceiver, as represented in the figure. Being pre- served in this state of ex- haustion, by closing the cock, let it be suspended from a scale beam, and accurately counterpoised ; air being then admitted, will cause it to preponde- rate decidedly. If in lieu of admitting air, the globe be restored to the situation in which it appears in this figure, so as to be filled with hydrogen from the receiver, R, anjl after- wards once more sus- pended from the beam, in- stead of preponderating de- cidedly, as when air was allowed to enter ; unless the balance be very deli- cate, the additional weight, arising from the admission of the hydro- gen, will scarcely be perceptible. Supposing, however, that the ad- ditional weight thus acquired, were detected ; and also the weight gained by the admission of exactly the same bulk of atmospheric air, after a similar exhaustion of the globe, the weights of equal volumes of hydrogen and air, would be represented by the weights thus ascer- tained. The specific gravity of atmospheric air is the unit, in mul- tiples, or fractions of which, the specific gravities of the gases are ex- pressed. Hence the weight of any given bulk of hydrogen, divided by the weight of an equal bulk of air, gives the specific gravity of ATTRACTION 179 hydrogen. By a similar process, the specific gravity of any other gas may be discovered." " The apparatus for ascertaining specific gravities, above represent- ed, is that which is recommended by Henry. The gas may be more accurately measured, by using one of the volumeters."* " The weight of any given number of cubic inches of air or gas, as one hundred, for instance, may be known by introducing a certain quantity into the globe, as above described, and noticing the acces- sion of weight : then, as the number of cubic inches introduced, is to the weight gained by its introduction, so is one hundred to the weight of one hundred cubic inches of the fluid." " The number of cubic inches introduced, may be known by means of the graduation on the receiver, R." If there be a column of water or mercury standing in the jar, the gas will be less compressed than if there were no such column. Therefore, the density will be inversely the volume directly as the height of this column. Hence, to ascertain the volume, say H : H h'_ \v : x. Here, H is the height of the barometer, h the height of the column,f v the observed volume, and x the volume re- quired. In weighing the gases in order that the result may be correct, the gas should be pure ; it should be dry, or due allowance should be made for watery vapor, and if the experiment is not made when the barometer is at 30 inches, and the thermometer at 60, the observ- ed volume should be reduced by calculation, to what it would be, at the medium temperature J and pressure. The purity must be secured and ascertained by the modes appro- priate to each particular gas. Moisture must be removed, as far as possible, by exposure to dry muriate of lime, quick lime recently ignited, or fused potash ; or other substances that powerfully attract water. For temperature ; the volumft of a gas is as the temperature direct- ly, and as operations on gases are almost always carried on above 32, we first ascertain the volume that the gas would occupy at that tem- perature, which is done by multiplying the total volume by|| 480, and dividing the product by|| 480, -f- the number of degrees that the * See Dr. Hare's Compendium. t The column being of mercury, or due allowance made if it is water; a foot of water representing nearly an inch of mercury. | Gloves should be worn while handling the vessels, or they should be lifted by the keys of the stop cocks, that the warmth of the hands may not cause expansion in the gas. For a general formula, see Henry, 6th Ed. Vol. I, p. 25, and Turner, 2d Ed. Vol. I, p. 71. [| Because a gas expands ^ j^ part of its volume by every degree of heat. 180 ATTRACTION. temperature is above 32 Fahr. Then to determine its volume at any other temperature, " add T | of the volume at 32, for each de- gree that the temperature required, exceeds 32 Fahr. Thus, to find what space 100 cubic inches of gas at 50 would occupy, if raised to COo _-%.4, the volume at 32, and 96.4+ 96.4X28 = 102 the j t C0 o*_ Henry. 480 For pressure ; the volume of a gas is inversely as the pressure. To reduce the volume to what it would be at 30 inches, the mean pressure, " as the mean height is to the observed height, so is the observed volume 'to the volume required. Suppose the barometer to stand at 29 inches, and that we wish to ascertain what volume 100 cubic inches of gas would occupy at 30 inches, 30 : 29 : 1 100 : 96.66, which last number is the answer required. For both pressure and temperature. Suppose the question is, what volume would 100 cubic inches of gas, estimated at 50 of Fahr. and 29 inches of the barometer occupy at 60 and 30 inches. By first correcting the temperature, we find that the 100 cubic inches, would be 102, and then, 30 : 29: : 102 : 98.6. The weight of a given volume of gas being known at any temper- ature, to learn ivhat would be the weight of an equal volume at the mean temperature. The volume being given, the weight will be di- rectly as the pressure. Correct the bulk to the mean temperature ; " then say, as the corrected bulk is to the actual weight, so is the ob- served bulk to the number required." 100 cub. in. of gas weighing 50 grains at 50 Fahr. would at 60 occupy 102 cub. in. and 102 I 50: : 100 : 49.02, which would be the weight of 100 cub. in. at 60. From the weight of a given volume of gas at an observed pressure, to ascertain what would be its weight under the m,ean pressure ; say, " as the observed pressure is to the mean pressure, so is the observed weight to the corrected weight." 100 cub. in. of gas at 29 of the barometer, weight 50, what would it weigh at 30 inches pressure. 29 ! 30: :50 : 51.72, the fourth term being the answer. To combine both the last calculations. 100 cub. in. of gas, at 50 Fahr. and 29 in. pressure, weight 50 grains, what would it weigh at 60 Fahr. and 30 inches pressure ; first make the correction for temperature, which gives for the weight under a given volume, 49.02, then, 29 : 30: : 49.02 : 50.71, which is the answer required, f * For a general formula, see Turner, 2d Ed. p. 34. \ These rules are cited substantially from Henry, 10th Ed. Vol. f, p. 23 ATTRACTION. 181 Pneumatic Cisterns. Dr. Hales, more than a century ago, employed an apparatus upon the principle of the modern pneumatic cistern, which was introduced by Dr. Priestley. This instrument is little else than a vessel suffi- ciently capacious, filled with water or quicksilver, and furnished with fixed shelves and a sliding shelf. The apparatus for mercury is usu- ally small, on account of the weight and expense of the metal, and ounce measures are used where, in the other apparatus, we employ quarts or gallons of water. In both, for the purpose of expelling the air, the vessels are filled with the fluid, and then, they being inverted with their mouths under it, the gas is introduced from below. The an- nexed cut represents the mercurial cistern used by Dr. Hare ; it is, however, five or six times larger than those generally employed. This kind of cistern is rarely used, except when the gases are rapid- ly absorbable by water. That in the laboratory of Yale College, is of marble,* and of a similar construction, but holds not over two hun- dred pounds of mercury, and usually from one hundred and fifty to- one hundred and sixty pounds. Mercurial Cistern for gases. IB - " B B, is a wooden box, which encloses the reservoir so as to catch any of the metal which maybe spilled over the margin of the cistern. This box is bottomed upon stout pieces of scantling, tenant- ed together and grooved so as to conduct the mercury towards one corner, where there is a spout to allow it to escape into a vessel, situ- ated so as to receive it. The cistern itself, is made out of a solid block of white marble. It is twenty seven inches long, twenty four inches wide, and ten inches deep." " The ledges, S S, answer for the same purposes as the shelves in the common pneumatic cistern. The excavation, w, is the well in which vessels are filled with mercury, in order to be inverted and placed, while full, on the ledges. There are some round holes in * Prof. Hitchcock, of Amherst College, has one of soap stone. 182 ATTRACTION. the marble for introducing upright wires to hold tubes, or Eudiome- ters ; also some oblong mortices, for allowing the ends of tubes, duly recurved, to enter under the edges of vessels to be filled with gas ; and in cases of rapid absorption, to afford a passage for the mercury, into vessels, from which it might otherwise be excluded, in conse- quence of their close contact, with the marble of the reservoir." " This reservoir requires nearly six hundred pounds of mercury to fill it completely." Water ^cistern for gases. Any vessel containing water in sufficient depth to admit of filling the air glasses, will answer in some good degree. There is in the laboratory of Yale College, a pneumatic cistern constructed in 1803, of which an engraving was given in the editions of Henry's Chemis- try published by me, and which has been found very convenient. It is furnished with air cells, which may be understood by an inspec- tion of Dr. Hare's figure below. In mine, there were only the up- per cells here represented under A A, but divided each into two compartments, and nearly beneath them and under water, were hy- drostatic bellows, for throwing in air and gas. From the cells, also, proceeded tubes for the compound blowpipe, but the apparatus in front, representing the arched tubes and the inverted kettle and its treadle, and also the other lower cells under C C, were not in mine. Hydro-pneumatic Cistern of Dr. Hare. " The figure, here given, is such as would be presented to the eye, were the front of the cistern removed." " A A, are two shelves formed by two inverted chests, which are used as cells to contain gas : B is a sliding shelf, over a deep place between the shelves, A A, which is called the well of the cistern." ATTRACTION, 183 Fig. 2. " Fig. 2 affords a view of the lower side of the sliding shelf, in the wood of which it will be seen that there are two excava- tions, converging into two holes, one of which is seen at A, fig. 1. This shelf is loaded with an ingot of lead at L, to prevent it from floating in the water of the cistern." " Besides the chests abovementioned, there are two others, C C, near the bottom of the cistern, but not so close as to prevent the wa- ter from passing freely into and out of them." Referring to Dr. Hare's Compendium for the remainder of the description, I will add only, that the inverted kettle by a treadle be- low, and by the aid of a peculiar internal construction, is made to throw in air through the lower arched tubes, into the cells under C C, which are intended for regulating the height of the water ; while it is allowed to escape through the upper arched tubes at their com- mon orifice at/. The cells under A A, are for receiving any gas not absorbable by water, and it is easily drawn off at the cocks at e e, into vessels standing in the shelves A A. The student will not suppose that, strictly, any thing more is ne- cessary for a pneumatic cistern, than a water vessel with a fixed shelf or shelves as at A A, and a sliding shelf as at B, and even the latter may be dispensed with by making holes through one of the fixed shelves, and introducing an inverted funnel. GAZOMETERS. Gazometers are important in many chemical experiments. In contriving the pneumatic cistern mentioned above, it was one object to furnish gazometers in the cistern itself, where most of the gases are prepared ; and there was, for many purposes, great utility in the contrivance ; but the gases being always under pressure, were of course liable to escape at any leak. There is so much convenience, however, in occupying with air cells, this otherwise useless space, that I should still recommend this mode of construction, of the pneumatic cistern, so far as the cells are concerned ; without attempting any thing farther, except the neces- sary appendages to draw off the gases. On the' whole, I have found the most useful species of gazometer to be the following, which, it will be perceived, is only a modifica- tion of the form generally used. 1. The containing air vessel is made of tinned iron, or the thin- nest sheet copper, painted and varnished : the form is cylindrical, as at 184 ATTRACTION. 1* A, and there is a smaller cylinder, a,* rising in the centre to receive an interior gas pipe ; the rings are to receive the cords that are to suspend the cylinder by passing over pully wheels at c c, fig. 2. 2. D is a slightly conical cask, to be filled with water in which A is suspended by the cords already mentioned, and which are weight- ed at d d, so as to keep the air vessel in equilibrio. 3. Fig. 3 represents a tube of copper or lead, which is fastened within the cask D, so that the limb / rises in the center and passes up into a, fig. 1, when the air vessel is down, and the stop cock m is open, for the escape of the common air. The other limb e is fas- tened firmly to the cask at the side. 4. Fig. 4 represents the mouths of two of the interior tubes with additional tubes fitted air tight, with corks through the trumpet shap- ed orifices, i i, and terminating, after curvature, in a frustrum of pla- tinum at/. This apparatus of tubes is used for the compound or oxy-hydrogen blowpipe of Dr. Hare, and can be taken off by double jointed screws at o o, and also at i i, and any other apparatus can be attached. At b 6, is a thin slip of wood, acting both as a guide and a scale to the air vessel. It is obvious that if there are two casks and two air vessels, they will form convenient reservoirs for oxygen and hydrogen. Mine contain together fifty gallons, and by means of weights laid on the air vessels, the gases are made to issue at j 9 with all necessary force. Nothing can be more convenient for the compound blowpipe ; for the oxygen or the hydrogen blowpipe alone ; for the common air blowpipe ; for gas lights ; for musical tones with hydrogen ; for communicating oxygen and hydrogen through a tube to the pneumatic cistern, and for many other purposes, sufficiently obvious to a practical chemist. Smaller instruments upon this principle, are convenient for the respi- ration of gases, a proper mouth piece being fitted to e g, fig. 3. Which may be furnished with a small stop cock, to let off common air. OXYGEN. 185 PART IL PONDERABLE BODIES. Introductory Remark. I SHALL here repeat what was stated in the Introduction, p. 18, that a real element is an undecomposable body ; that, in relation to our knowledge, an element is merely an undecomposed body. Our evidence on this subject being only negative, it follows that any body and all bodies, now admitted as elementary, may hereafter be decomposed. Should we, for argument's sake, admit the improbable result, that all compound bodies may be hereafter reduced to two, the smallest number of principles with which it is possible to form a third body, we should even then not be certain, that these two were real ele- ments ; for they might be decomposed into two, three, or four others, and they again into five, six, seven, or eight others, and so on ; pro- ceeding from the greatest apparent simplicity, to the greatest com- plexness. It is proper to recal to the recollection of the student, that the an- cient hypothetical elements, earth, air, fire and water, have all been proved to be compound, and that there are now more than fifty* un- decomposed bodies, among which are three supporters of combustion, oxygen, chlorine and iodine ; about forty metals, and seven combusti- bles, that are not metallic, namely, phosphorus, carbon, hydrogen, sul- phur, nitrogen, boron and selenium. Nitrogen, as already observed, is thrown into this class, as resembling them very much in its relations and character, although it is not in the popular sense a combustible. INORGANIC BODIES. SIMPLE SUPPORTERS OF COMBUSTION. SEC. I. OXYGEN. 1. NAME, Oxygen^ derived from ogus and ysivopat or /svvaw, signi- fying, therefore, the generator of acids ; a name imposed by the framers of the new nomenclature ; the former names were, dephlo- * Dr. Turner's 2d edition, gives fifty two, including bromine and selenium. t Several authors, (as Thenard, 5th Ed. Vol. I, p. 166,) consider the name oxygen as improper, because it is not the sole acidifier ; but it is the great ruling acidifier, it being the sole agent in almost all cases, and therefore the name is proper. We might as well reject the name chlorine, because it is not the only greenish yellow body. 24 186 OXYGEN, gisticated air, vital air, empyreal or fire air, and pure air, which have all yielded to the name oxygen. 2. PROCESSES. (a.) There are several ; the most useful is by igniting the purest* black oxide of manganese in an iron bottlef or earthen retort ; one ounce of the oxide affords about one hundred and twenty eight cubic inches of gas. (6.) Sulphuric acid 1 part, mixed with the same mineral 2 parts, to the consistence of a paste, and heated moderately, affords this gas ; the theory of these experiments will be given hereafter. (c.) Other modes will be mentioned farther on, such as that of heating the chlorate or nitrate of potash,{ or a mixture of red lead and sulphuric acid ; and that from green leaves placed in water in the sun's light, &c. The gas is received in inverted glasses full of water. 3. DISCOVERY (a.) By Dr. Priestley,^ in England, August, 1774, by heating red oxide of mercury, in a bell glass by the solar focus. (6.) By Scheele, in Sweden, the year after, and without a knowl- edge of Dr. Priestley's discovery ; and also by Lavoisier, at Paris, in the same year. 4. PHYSICAL PROPERTIES. (a.) Transparent, colorless, tasteless, inodorous, not condensible by pressure and cold, a non-conductor of electricity. (b.) Sp. gr. 1.1111, air being 1. Thomson. (c.) Wei^ ight 33.8888 for 100 cub. in. at the medium temperature and pressure. Id. (d.) Refracts light less powerfully than any other gas. (e.) Becomes luminous || as well as hot, by sudden condensation. (/.) It is a non-conductor of electricity. 5. CHEMICAL PROPERTIES. (a.) It possesses more extensive powers of combination than other substance. * It is sometimes previously washed with a weak mineral acid, to decompose car- bonate of lime, if any is present. t A wrought iron bottle, with a wide tube about two feet long welded to it, is much the best instrument ; it should be coated, every time it is used, with a lute of clay, sand, and flour, applied with the hand and dried before using. A gun barrel answers for a small experiment. t Dr. Thomson says that the first 5th of the gas from nitre is quite pure, and Dr. Hare confirms the statement, that the first portions are quite pure. See Priestley's account in his work on air. || All the gases become hot by sudden pressure, but chlorine and oxygen are the only simple gases that become luminous in this manner ; common air becomes luminous by the same treatment, but in a less degree than oxygen, to which gas, this property in air is owing. OXYGEN. 187 (B.) IT ACTS ON COMBUSTIBLE BODIES WITH INTENSE ENERGY, and this is one of its great characteristic, but not altogether peculiar properties. (c.) Generally the temperature must be raised, in order to bring on the action. (d.)* A lighted candle burns brilliantly in oxygen gas. If extin- guished, (fire remaining on the wick,) it is instantly relighted with a slight report, and that many times in succession, j- Candle in air, in vacuo, and in oxygen gas. Dr. Hare. " Let there be two bell glasses, A and B, communicating with each other by a flexible leaden pipe, a cock intervening at C. Sup- pose A, to be placed over a lighted candle on the plate D, which communicates with an air pump plate as represented at E. It will be found that the candle will gradually burn more dimly, and will at last go out, if no supply of fresh air be allowed to enter the contain- ing bell ; if on repeating the experiment, the air be withdrawn by means of the pump, the candle is rapidly extinguished. It is thus demonstrated, that a candle will not burn in vacuo, and that it can burn only for a limited time, in a limited portion of atmospheric air." " Let the experiment be repeated with the following change. Let the air be exhausted from both vessels, the cock, C, remaining open, * For the experiments under d and /, a common glass bottle answers suf- n ficiently well. t A quart of oxygen gas, well managed in a bottle, will relight a candle more than fifty times ; the bottle should be held mouth upwards, and gent- ly inclined each time the candle wick is presented to it ; as the oxygen is consumed or expelled, the bottle must be turned down more and more. A candle in a socket, fixed to a wire, is easily let down into a jar of gas, as rep- resented in the cut. 188 OXYGEN. until the bell, B, is filled with water from the shelf of the pneumatic cistern, on which, for this experiment, it must be placed. The cock being closed, fill the bell, last mentioned, with oxygen gas, from the cell of the cistern. Now lift the bell A, which may be easily done, the pipe having a due flexibility, and introducing a candle, set the bell again on the plate. Next exhaust the air until the candle is nearly extinguished, and then open the cock, so as to allow the oxygen to enter. The candle will now burn brilliantly for a much longer time, than it had done, when the bell contained atmospheric air." (e.) Ignited charcoal burns intensely in this gas, and the bark with vivid scintillations. (f.) Iron wire or a watch spring, with a lighted sulphur match on the end, burns with bright ignition and sparks, but without flame. Combustion of iron wire in oxygen gas. Id. 11 Place over the cock of one of the cells of the pneu- matic cistern, sufficiently supplied with oxygen gas, a glass vessel, such as is usu- ally employed to shelter can- dles from currents of air. Let the upper opening of the vessel be closed, by a lid with a central circular aperture, as here represent- ed. Leaving this aperture open, by turning the key of the cock, allow the gas to rise into the vessel from the cell. Next apply a ta- per to the aperture, and as soon as it indicates by an in- creased brilliancy of com- bustion, that oxygen has taken place of the air pre- viously in the vessel, cover the aperture.* Wind a fine wire round any hard cylin- * Or, any vessel, large or small, may be rilled with oxygen gas, by simply con- veying the orifice of a curved tube to the bottom of the vessel, the other end of the tube being connected with a gazometer or other reservoir, from which the gas is allowed to flow ; the atmosphere is thus lifted out and the oxygen takes its place. OXYGEN. 189 drical body of about an inch in diameter.* By these means, the wire is easily made to assume the form of a spiral. Near the end of the spiral, wind it about a piece of spunk about as large as a pin. Hav- ing lighted the spunk, remove the cover from the aperture in the lid of the vessel, and lower the end of the wire to which the spunk may be attached, into the oxygen gas. The access of the oxygen causes the spunk to be ignited so vividly, that the wire takes fire and burns with great splendor, forming a brilliant liquid globule, which scintil- lates beautifully. This globule is so intensely hot, that sometimes on falling, it cannot immediately sink into the water ; but leaps about on the surface, in consequence of the steam which it causes the water to emit. If it be thrown against the glass of the containing vessel, it usually fuses it without causing a fracture, and has been known to pass through the glass, producing a perforation without any other injury." (g.) A stream of oxygen gas from a gazometer and blowpipe, di- rected upon burning charcoal, melts and burns many bodies, as iron, copper and tin, with brilliant appearances, and the evolution of much heat. (H.) EFFECT OF THE COMBUSTION. The oxygen gas is diminished ; its ponderable part combines with the combustible body, and both changes its properties and increases its weight; one grain being gained in weight for every three cubic inches of gas absorbed. Combustibles, which like oil, candles, and charcoal, disappear while burning, are not destroyed ; they have only passed off in gas, and other diffused forms ; with proper care, all the products can be collected again ; we can neither create nor an- nihilate an atom. (i.) Products of the combination. They are either acids, alkalies, oxides or earths ; the three last may strictly be included under one head, but it is convenient to divide them. The process of combin- ing with oxygen, is called oxidation or oxidizement, and the corres- ponding verb is oxidate or oxidize.-^ The oxides are sometimes dis- tinguished by terms derived from their colors, but Dr. Thomson has introduced a nomenclature founded on the Greek numerals, as pro- toxide, deutoxide, tritoxide, viz. first, second, and third oxide, &c. and Jperoxide, for the oxide with the most oxygen. (j.) Water, at the pressure of 30 inches, and temperature 60, if freed from air by boiling, absorbs 3.5 cubic inches of oxygen gas, for every 100 cubic inches of water; by pressure, the quantity is in- * I use a ram rod and binding wire. t Some use oxygenize or oxygenate, oxygenizement or oxygenation ; these terms are rather more genera), and do not decide whether the product is an oxide or an acid. t From the Latin preposition. 190 OXYGEN creased, and by great pressure, water will absorb half its bulk, but without any change of properties. 6. Relation to animal life. (a.) Oxygen supports life eminently in respiration, and is the only agent that is adapted to this purpose ; but it is necessary that its great energy should be mitigated by dilution, as will be mentioned again farther on. (b.) A bird will live five or six times as long in a confined portion of oxygen gas, as in the same volume of common air ; and several birds will live a short time in oxygen gas, in which others have died ; each successive one will, however, in general, live a shorter time than its predecessor. " Count Morozzo placed a number of sparrows, one after another, in a glass bell filled with common air, and inverted over water : The first sparrow lived - - 3^. Om. The 2d " " - - 03 The 3d " " - 1 " The water rose in the vessel, eight lines during the life of the first ; four during that of the second, and the third produced no ab- sorption. He filled the same glass with oxygen gas, and repeated the experiment. The first sparrow lived - - 5h. 23m. The 2d " " - - 2 10 The 3d " 1 30 The 4th . - 1 10 The 5th " " - 30 The 6th - - 47 The 7th " " 27 The 8th " - - 30 The 9th " " 22 The 10th " " - - 21 He then put in two together, the one died in twenty minutes, but the other lived an hour longer." Chaptaland Thomson. 7. Relation to disease. Oxygen gas is eminently salutary in some cases, especially in diseases of the thorax, in paralysis, general de- bility, &c.* * Oxygen gas, when respired in the human lungs, generally produces a sen- sation of agreeable warmth about the region of the chest, and some say that they ex- perience a comfortable sensation through the whole body. Chaptal relates the fol- l^wing instance of its effects on a man in consumption. " Mr. De B." says this writer, " was' in the last stage of a confirmed pthisis. Extreme weakness, profuse sweats, and in short, every symptom announced the approach of death. One of my friends, Mr. De P , put him on a course of vital air. The patient respir- ed it with delight, and asked for it with all the eagerness of an infant at the breast. During the time that he respired it, he felt a comfortable heat which distributed it- self through all his limbs. His strength increased with the greatest rapidity ; and OXYGEN 191 8. Effect on the color of the blood. If blood be suspended in oxygen gas or agitated with it, or even with common air in a glass tube, it turns it of a brilliant vermilion color; the nature of the change is to be mentioned hereafter more particularly ; we may how- ever remark at present, that it acts on the blood principally, by im- parting oxygen and detaching carbon. 9. It is found in more combinations and in greater quantities than any element.* It is found in the atmosphere, in all waters and watery fluids, and in all natural fluids, except perhaps naptha and mercury. It exists in animals and plants; in stones, rocks, and metallic oxides, and in acids, salts, earths, and alkalies ; it possesses therefore the highest importance, and without knowing this agent, we could under- stand little of the real constitution of things. What has been called the modern theory of chemistry, was occupied principally in unfolding the agencies of oxygen, and this exposition still constitutes the most important part of the science. 10. Polarity. It goes to the positive pole in the electro-galvanic circuit, and is therefore considered as electro-negative. f 11. Its combining weight. Hydrogen being unity, J oxygen is represented by 8, because these are the proportions in which these elements exist in water. As its combining weight is " smaller than that of most bodies, it is inferred that it approaches nearer than they to the elementary or in six weeks, he was able to take long walks. This state of health lasted for six months ; but after this interval he relapsed ; and being no longer able to have re- course to the use of vital air, because Mr. De P had departed for Paris, he died. I am very far, adds Mr. Chaptal, from believing that the respiration of vital air ought to be considered as a specific, in cases of this nature. I am even in doubt whether this powerful air is perfectly adapted to such circumstances ; but it in- spires cheerfulness, renders the patient happy, and in desperate cases, it is certainly a most precious remedy, which can spread flowers on the borders of the tomb, and prepare us in the gentlest manner for the last dreadful effort of nature." Thenard relates that of three men who had been suffocated by sulphuretted hy- drogen gas, in cleaning a privy, two died almost immediately, and the third being almost dead, was made to respire oxygen gas from a bladder, and it rallied his pow- ers so that he sat up for a moment, but soon fell back and died. In a case related in the Am. Jour. Vol. XVI, p. 250, by Dr. Muse, of Cambridge, Maryland, there was the most complete success, a favorite hound that had been for several hours com- pletely drowned, having been perfectly restored to life, and gradually to all his func- tions in consequence of the injection of oxygen gas into his lungs ; the very first in- flation of the lungs produced a shrill yelp from the animal. For other remarkable cases, see also Am. Jour. Vol. I, p. 95, and Dr. Thornton's various Reports in Til- loch's Philos. Mag. * Limiting our estimate, of course, to the bodies with which we are acquainted^ t Several respectable modern authors make this fact the foundation of an arrange- ment of chemical bodies. t Several authors have adopted oxygen for unity ; Dr. Thomson makes it 1, Dr, Wollaston 10, Berzelius 100, &c. 192 OXYGEN. simple state ;"* this might have been said with still greater truth, of carbon and hydrogen. Remarks. Oxygen unites with every simple body, but it has neither acid nor alkaline properties. It is the agent in all common cases of combus- tion, which in most instances, is nothing more than rapid oxidation, with the emission of heat and light ; and a slow combination of ox- ygen often goes on without either ; common iron rust is produced in that manner. Combustion and respiration have the same effect in vitiating the air ; the air in which an animal has died, will not support combus- tion, and the air in which a combustible will not burn, will not sup- port animal life. Oxygen is involved in the chemical study of all bodies, simple and compound. The term oxygen means strictly the ponderable part of oxygen gas ; the material part is known only in combination ; it has never yet been isolated so as to exhibit it separately ; in its gaseous form, it is combined with caloric and light, and probably with electricity. It appears to exist no where in nature, in a pure and disengaged state, and we always obtain it for use by evolving it from one of its combinations. Healthy leaves of vegetables, acted upon by the di- rect sun beams, throw it off incessantly into the atmosphere, and it is supposed to be a principal means of recruiting the waste of oxygen which arises from combustion, respiration, and other natural processes. In the dark, a different gas, the carbonic acid is said to be disengag- ed ; the subject will be resumed in giving the history of that gas. It is fortunate that oxygen gas can be easily and abundantly ob- tained from the native oxide of manganese, as there is scarcely any other from which it could be obtained at all, and no other which could supply the demands of chemistry and the arts. Nitre is perhaps the easiest resource for affording oxygen gas, but only the early portions are pure ; a little may be heated to low red- ness in a gun barrel, but we should avoid the mouth, as the melted nitre is apt to boil up, congeal above the ignited portion of the tube, and thus acting like a wad, by and by, after a cessation, the gas causes an explosion, by which the hot nitre is driven about. Every thing connected with the history of oxygen, is elegant, beautiful, and in- structive ; without it there would be no beginning of animal life, nor any adequate means of producing and regulating heat. * Murray, Vol. I, p. 407. NITROGEN. SEC. II. NITROGEN OR AZOTE. THE ATMOSPHERE. NITROGEN. 1. Name. As it is the basis of nitric acid, it is now called nitro- gen ; its former name was from a, a Greek privative, and w?j, life, signifying that which destroys life ; but the name is not distinc- tive, many other gases being azotic. 2. Discovery by Dr. Rutherford, at Edinburgh, 1772 ; Lavoi- sier first separated it from the atmosphere, in 1775, and Scheele, about the same time. 3. Mode of obtaining. (a.) Burn phosphorus in a floating saucer or other earthen dish under a bell glass over water ; the acid fumes are absorbed in half an hour by the water, and sooner, if agitated with it ; and nitrogen gas slightly phosphorized, remains. Solution of caustic potash, agitated with the gas in a bottle, quickly separates both the phosphoric acid, and a little carbonic acid which is sometimes mingled with it. (b.) With a gentle heat, dilute nitric acid, sp. gr. 1.20, acting on lean muscle in a glass retort, evolves nitrogen. (c.) Iron filings and sulphur being mixed and moistened, and placed in a saucer under a bell glass ; the oxygen is absorbed in three or four days, and nitrogen remains. Other methods will be mentioned farther on. 4. PHYSICAL AND CHEMICAL PROPERTIES. (a.) Transparent, colorless, inodorous, tasteless, not sensibly ab- sorbed by water. (b.) Sp. gr. .9722, air being 1. (Thomson.) 100 cub. in. weigh 29,652 grains. (c.) Its refractive power is very feeble. (d.) Combines with oxygen, and forms several very important compounds nitric acid, the nitrous acids, nitric oxide gas, and ni- trous oxide gas. (e.) No combination results from a mere mixture of the oxygen and nitrogen ; owing to the repelling power of caloric, they would probably remain forever in mixture, without change ; but they will unite, if in the nascent state, or, if one of them is in that condition. (f.\ Combined with oxygen by electricity, nitrogen forms nitric acid.. (jr.) Still it is not a combustible in the common sense of that word ? it does not fire by the approach of a candle to the mouth of a vessel containing it, nor if previously mixed with oxygen gas. (h.) It is fatal to combustion. A burning match, candle, phos- phorus, or any burning body is extinguished by immersion in this 25 194 NITROGEN. gas ; even potassium, although intensely heated by galvanism in nitro- gen, produces no change ; it is therefore not a supporter of combus- tion. (i.) Water deprived of its air by boiling, absorbs about one and a half per cent, of this gas ; or, according to Dr. Ure, 100 volumes of water absorb about one of this gas ; Mr. Dalton states it at 2.5. 5. EFFECTS ON ANIMAL LIFE. (a.) Fatal, if breathed pure ; an animal immersed in it, immedi- ately dies. (6.) Kills by suffocation merely ; it is not directly noxious, and ex- erts no positively injurious influence on the lungs; an animal is drown- ed in it as it would be in water. 6. COMPOSITION. (a.) Unknown; but it is suspected to be compound; Berzelius believes it to be an oxide of an unknown base.* (b.) Contained in animal matter, and is equally abundant in her- bivorous and graminivorous, as in carnivorous animals. (c.) Plants do not generally contain it. (d.) It is an element, according to the present state of our knowl- edge.! 7. IMPORTANCE AND DIFFUSION. (.) It forms the basis of animal substances ; of them it is the char- acteristic element, and it gives origin to the ammonia and the prus- sic acid, which are generated during their decomposition. (6.) It is found in the cruciferous plants, cabbage, mustard, &LC. ; in the fungous tribe, mushrooms, &c. and in all plants that putrefy with an animal odor. (c.) Its properties are interesting principally in combination; es- pecially in animal matter ; in the nitric compounds ; in ammonia^ and with chlorine and iodine ; for an account of which, see the sections containing those subjects. 8. POLARITY. It resorts to the negative pole in the electro-gal- vanic circuit, and is therefore considered as electro-positive. 9. Its combining weight is 14, hydrogen being 1. Nitrogen is possessed rather of negative than of positive proper- ties, but in combination, it produces bodies of a highly active and in- * Thomson's Annals, II, 284. t When ammonia, an alkali which contains nitrogen, (or either of its salts,) is gal- vanized with mercury, it converts that metal into an amalgam, which creates a sus- picion that its base is metallic ; but Gay Lussac and Thenard say, that this amalgam is immediately resolved into mercury, ammonia, and hydrogen, even when water is not present, and that, therefore, it is composed of these three substances directly united ; but, there may be metallic matter in both ammonia and hydrogen, or in hy- drogen alone, because it is contained in ammonia, and it is possible that even ni- trogen may be an oxide of hydrogen. NITROGEN. 195 teresting character ; some of the most powerful fulminating com- pounds contain it.* THE ATMOSPHERE. PHYSICAL PROPERTIES. (a.) Transparent, colorless, inodorous, only slightly absorbed by water; a bad conductor of heat and of electricity ; the latter when ac- cumulated, passes through the air in a spark, but is diffused through a vacuum in the form of a luminous cloud. (b.) The azure color and other hues in the atmosphere, are pro- duced by reflected light. (c.) As we ascend, the sky grows darker, and at a great height, the stars with the lustre of silver, are contrasted with a basis of black. (d.) Specific weight, 1.; it is unity for all other aeriform fluids ; 100 cubic inches, at the medium temperature and pressure, weigh 30.50 grains. f Compared with water, it is ji^ of the weight of that fluid. Gallileo ascertained in 1640, that it has weight, and Tor- ricelli introduced the barometer tube in 1643. (e.) Absolute weight ; at the ocean level, about fifteen pounds on the square inch, equal to thirty four feet of water, and thirty inches of mercury. Henry. (f.) Jls we ascend, the heights being in an arithmetical ratio, the weight decreases in a geometrical ratio ; at three miles elevation, it sustains 15 inches of mercury; at six miles, 7.5 inches; at nine miles, 3f inches ; at fifteen miles, about 1 inch. Id. Air is compressed in direct proportion to the force applied. Dou- ble the force will reduce it to half the volume ; double the force again, and its volume will be again reduced one half, that is, to one quarter of its first volume, and so on. A force has been applied to it, equal to 110 atmospheres, and the law stated above, was found still to hold good.J * In the Eng. Jour, of Science, Vol. XIX. 17, Mr. Faraday has given an ac- count of an ingenious method of detecting minute portions of nitrogen, by the for- mation of ammonia. D is a glass tube, four or five inches long, and one fourth of an inch in the bore. At a, there is some zinc foil ; at b, a piece of potash ; at c, a piece of turmeric paper moistened with pure wa- ter, at the lower end, which is two inches above the potash ; heat the ft lower end of the tube only in the spirit lamp so a? to melt the potash, and almost instantly, the moistened paper will be reddened, indicating an al- kali, and it is evident that it is ammonia, because the color is discharged when the paper is withdrawn, and the colored part laid on the warm tube. Sea sand handled after ignition, yields ammonia, which is discovered by this treat- ment. Ib. t Shuckburgh 30.199. Brande, t Ed. Jour. Science, No. VIII, 224, 196 NITROGEN. Mr. Perkins states, that he has applied to it a pressure of 2000 atmospheres, and he supposed that he had thus compressed it into a liquid, but as this liquid was permanent under the common pressure, it is probable it was water only. As we descend below the surface of the earth, the density and pressure of the air continue to increase in the same ratio. " In very deep mines, water will not boil till heat- ed 3 or 4 degrees above 212*. Murray. (g.) The greater part of the atmosphere is within three or four miles of the earth's surface. (h.) The phenomena of refraction indicate that the atmosphere is at least forty or forty five miles high. (i.) Dr. Wollaston thinks that the atmosphere has limits fixed by gravity, counteracting the elasticity imparted by caloric, (Phil. Trans. 1822,f) and on account of the absence of refraction, (the heavenly bodies not being disturbed in their apparent position,) it is asserted that neither the sun nor Jupiter has any atmosphere ; hence the earth's atmosphere is not indefinitely divisible, and does not extend to those bodies, and therefore it is thought that its ultimate atoms must be indivisible, and this is regarded as a direct proof of the truth of the atomic theory, or, in other words, of the existence of indivisi- ble atoms or particles. (/.) WINDS are produced by the ascent of rarefied air arising from the pressure of colder and heavier air towards the heated place. Thus, as already stated, page 68, are produced the trade winds, monsoons, and land and sea breezes, and the irregular winds. (k.) The draught of a chimney is owing to atmospheric pressure; the column of air in the chimney rarefied by heat, is lighter than the adjacent column of colder air, and therefore ascends from the pre- ponderance of the latter. (I.) The refractive power of the air is observed in the elevation of ships and other objects near the horizon, and in the effect on the heavenly bodies in the same situation, causing them to emerge sooner when rising, and to linger later when setting. (m.) It has been already stated that the higher regions of the at- mosphere are cold ; the temperature in the lower regions, dimin- ishes at the rate of one degree for every three hundred feet. 2. CHEMICAL PROPERTIES. (a.} Air supports combustion, as every one knows. b.) It generates acidity in vinous fluids. (c.) It oxidizes some of the metals, at the common temperature, and most of them at ignition. * It is calculated, that at 46 miles below the surface, air would have the density of quicksilver. t For an excellent analysis of this curious paper, see Murray, 6th Edit. Vol. I, p. 413. NITROGEN. 197 (d.) Very great rarefaction diminishes, and even destroys its pow- er of supporting combustion. (e.) Great condensation does not increase the intensity of the com- bustion, although it is sustained for a longer time. (f.) Mixture with various gases diminishes it.* 3. COMPOSITION, IN VOLUME, 80 NITROGEN, 20 OXYGEN BY WEIGHT, oxygen 22.22 nitrogen - - 77.77 100.00 very nearly. f This proportion of oxygen is undoubtedly that which is best adapt- ed to the support and comfort of human life, and to the convenience of all the animal creation. Experiments have proved that animals compelled to breathe oxygen gas alone, soon become feverish from excess of stimulus, and life is eventually destroyed by the intense- ness of its own functions ; just " as a candle burns brighter in oxygen gas, and is more quickly consumed, so in this gas, the flame of life would be more vivid, but sooner burnt out." Most chemists have stated the composition of air at 21 per cent, of oxygen. Dr. Henry states that he could never satisfy himself wheth- er it was 20 or 21 ; Dr. Hare obtained very constantly 20.66, but 20 corresponds with the theory of volumes, viz. 1 to 4, and also of definite proportions by weight, that is, 1 proportion of oxygen 8, to 2 of nitrogen 28. Still the greater number of chemists do not admit that the atmosphere is a chemical compound. 4. MEANS OF ANALYSIS. They are numerous ; every substance which abstracts oxygen with- out returning any thing ^ may be employed for this purpose. (a.) Phosphorus is effectual, either by slow or rapid combustion ; the latter is the most convenient process, and if we subtract T \f of the volume on account of the vapor of phosphorus dissolved, in the nitrogen, the result will be accurate. (b.) Iron filings and sulphur moistened, and standing in contact with a confined portion of air remove the oxygen.^ (c.) Quicksilver heated in the confined air of a retort, forms oxide of mercury. (d.) Many other things to be mentioned in their place, produce a similar effect ; see hydrogen, nitric oxide gas, hydro-sulphurets, &c. In all these cases, oxygen is abstracted and nitrogen gas is left, and we know of nothing which will remove the latter gas, and leave the * See Henry, 10th Lon. Ed. Vol. I, p. 296. t Thomson's Principles of Chemistry, Vol. I, p. 100. t Turner. If they stand too long, hydrogen may be evolved from the decomposition of water. 198 NITROGEN. oxygen. The process of analysis of the air is called eudiometry, the instrument, an eudiometer.* 5. CONDITION OF THE ELEMENTS OF THE ATMOSPHERE. (a.) It has been already stated, that most chemists suppose the at- mosphere to be a mixture of the two gases. In favor of this view, it may be said that there is not, as in most cases of chemical combi- nation, any change in volume ; 4 volumes of nitrogen and 1 of oxy- gen, forming precisely 5 volumes of the mixture ; the refractive pow- er and the agency in combustion and respiration, is just what would arise from the operation of the mixed gases, and even water, in a de- gree, separates them, because ebullition expels from rain water more than 28 per cent, of oxygen ; j- the extended surface of the drops of rain being peculiarly favorable to the efficiency of a weak affinity ; also, a small quantity of air agitated with a large quantity of water, has all its oxygen absorbed, and but little of its nitrogen. On the other hand, as the proportions, both by volume and weight, corres- pond with the theory of definite proportions ; as there is no inequality in the mixture arising from the difference in specific gravity, the at- mosphere being every where the same ;{ even if the gases are not com- bined, the winds would tend greatly to preserve, in equable mixture, aeriform fluids whose gravity is so nearly equal. (b.) Perhaps it is, rather, a feeble combination. Analogous to the many which exist between palpable substances where the properties are not altered. (See p. 159.) There is no improbability that gases may be united by a very feeble affinity, and a strong one would, in this case, be incompatible with the exigencies of animal and vegeta- ble life, and with the demands of combustion. It is indispensable that the atmosphere yield up its elements readily. 6. Constancy of the proportions. (a.) They never vary, except from the operation of limited local causes, such as combustion and respiration. The air which Gay Lussac brought down from 21.735 feet above the earth, contained * The term alludes to the health of the atmosphere, as it was supposed to be af- fected by the proportion of oxygen ; the Greek particle i>, signifying well, and Atoj, the atmosphere, derived from Jupiter, which in Greek is Zev$, Gen. Awj, used for the atmosphere, t Edin. Jour. No. 8, p. 211, quoted by Dr. Turner. t Mr. Dalton's views of the constitution of the atmosphere and of mixed gases, are opposed to this opinion. See Henry, Vol. I, p. 299, 10th Lon. Ed. In a vertical tube, or in two vials thus connected by a tube, hydrogen gas will in a few hours de- scend, and carbonic acid gas ascend, so as to mix with each other contrary to gravity. Still, in chemical experiments, we find it important to favor the mixing of gases of remarkably different specific gravity, by adding the lightest, last; otherwise the mixture will be imperfect and tardy. The great mobility of gases, and the waves and currents so easily produced in them by even slight variations of temperature, might be expected to favor their mixture in the course of time. At that height, an exhausted bottle was opened, filled with air, and then closed ; after his descent, it was opened under water, which rushed in and filled half of it, thus proving the great rarity of the air. NITROGEN. 199 the regular proportion of oxygen 5 so does that obtained in the deepest mines ; that transported from Egypt and the African sands, and from Mont Blanc and Chimborazo, had the same constitution.* (b.) This constancy, as has been generally supposed, is maintained by the agency of the vegetable kingdom. See carbonic acid and veg- etables. Living vegetables in the sun's light, give out oxygen gas and decompose carbonic acid for food ; in the night, they absorb oxygen and give out carbonic acid, but Priestley and Davy say, that they give out more oxygen than they consume, and therefore they purify the air. (c.) According to Prevost, 100 years would consume only T ^Vo tn part of the weight of the oxygen in the atmosphere, making due allow- ance for all the consuming processes that are going on, and therefore if they had gone on even at the same rate from the creation of man, the consumption would have been but the T ^ part, and doubtless it has not been half of that, that is, o-j-^. Some have supposed, that volcanic fires expel oxygen from various mineral bodies ; some, that nitrogen is absorbed into the bodies of animals, and others, that hy- drogen is obtained by plants from the decomposition of water ; all of which processes would either throw oxygen into the air, or tend to give it a preponderance, but none of these suggestions are proved to be true. 7. AGENCY IN RESPIRATION. (.) Animal life universally, in all its forms, is sustained by the oxygen of the air. (6.) The nitrogen appears to be merely a diluent,^ and not to act except under certain peculiar' circumstances, but it is not improbable that it answers some positive purpose in the animal economy, whose nature is not yet understood. (c.) The principal effect in respiration, appears to be the abstrac- tion of carbon from the blood. See carbonic acid and respiration. 7. THERE ARE OTHER BODIES IN THE ATMOSPHERE. (a.) Perhaps the only ones that are constant, are carbonic acid, about ToW or sVu an ^ it never exceeds yj^ and aqueous vapor; T^ot by weight. Saussure found carbonic acid at the top of Mont Blanc, and it exists at every height hitherto attained, but the aque- ous vapor varies with the temperature; air at 60 may contain 10 grains of water to a cubic foot, and 4.5 at 43, and the quantity in- creases in a high ratio as the temperature is raised. On high mountains, * Mr. Faraday's analysis of air from the Arctic regions, shows a decided and con- stant difference between it and the air of London, of at least 1.374 per cent. See Appendix to Parry's 3d voyage, Lond. Ed. p. 240. No explanation is given to ac- count for the cause of this difference, but ! have little doubt that it is owing to the deficiency of vegetation in high northern latitudes. (Communicated.) J. T. t \Ve cannot be positive on this point ; it is certainly possible that it has some more important agency. t Mr. Dalton found it rather more than this in the air which an assembly of two hundred people had breathed for more than two hours. 200 NITROGEN. it is very small ; caustic potash remained dry on the peak of Ten- erifFe, at 12,176 feet above the sea. (b.) These adventitious things probably vary in their proportion. (c.) Besides these, there are other bodies. Various inflammable gases, from marshes and stagnant waters, from putrefaction, &c. Jlmmonia, from the latter cause, and from some plants. Vapors and effluvia, from every volatile thing, from fluids, flowers, &c.producmg odors and aroma. The matter of contagion. It is too subtile as yet for our processes, doubtless it is something aerial, more subtile than any gas yet known. It is combated successfully by chlorine, and to a degree, by acid gases. " Seguin examined the infectious air of a hospital, the odor of which was almost intolerable, and could discover no appreciable de- ficiency of oxygen, or other peculiarity of composition." Turner. Upon the usual estimation of 21 per cent, of oxygen in the air, its contents will be, including only those bodies whose existence has been proved to be constant. Nitrogen gas, 77.5 by measure, 75.55 by weight. Oxygen gas, 21. " 23.32 " Aqueous vapor, 1.42 " 1.03 Carbonic acid gas, .08 " .10* " Dr. Prout discovered that the specific gravity of any gas is ob- tained by multiplying its combining weight by .555, which is half the sp. gr. of oxygen gas, air being 1. or 10. ; half the sp. gr. of oxygen is taken because half a volume of oxygen represents its combining power. The above rule applies to gases whose equivalents are es- timated with reference to oxygen as unity ; if hydrogen be unity, then multiply the equivalent by that scale, by .555 as before, and di- vide the product by 8, which is the combining weight of oxygen upon that scale. Or the same result will be obtained by multiplying the equivalent upon the hydrogen scale, by the number expressing the sp. gr. of hydrogen, namely, 0.0694. Id. Remarks. If we could suppose our atmosphere to be removed, (the laws of heat and of pressure remaining as they now are,) another atmosphere would be immediately formed, consisting of aqueous vapor, and of every thing else that could, at the given temperature, assume the ae- riform condition 5 this process would go on until the pressure react- ed with sufficient power to become mechanically a substitute for the present atmosphere. With similar physical laws, we cannot there- fore understand, how any of the heavenly bodies can be without at- mospheres, of some kind or other. * Murray, I, 433. HYDROGEN, 201 SEC. III. HYDROGEN WATER HAREMS BLOWPIPE. HYDROGEN. The name is derived from u^wp and ysvvaw, or ysivofwu, signifying the generator of water ; the popular name is inflammable air ; the miners call it wild fire. 1. DISCOVERY. It was probably known to the ancients, but Mr. Cavendish, A. D. 1766, first proved it to be a distinct gas,* as Dr. Black had done nine years earlier with respect to carbonic acid gas, which was the first aeriform body, other than common air, whose existence was established, and hydrogen was the second. f 2. PROCESS. It is always obtained, directly or indirectly, from the decomposi- tion of water. (a.) Fragments of zinc, or iron filings, or turnings, 1 part, sul- phuric acid 2 parts, water 5 or 6 parts ; add the water to the metal ; then the acid by separate portions, with intermediate agitation, the vessel being held under a chimney, till the effervescence comes on, when the gas must be received over water, in inverted vessels filled with that fluid. A glass retort, or a glass flask, furnished with a bent tube is all the apparatus that we need. A vessel of lead, or even of plate tin, will answer very well, but its opacity is an inconvenience. Muriatic answers nearly as well as sulphuric in obtaining this gas, but the latter is much cheaper. (6.) It is obtained still purer, by the decomposition of water, by iron ; see water. (c.) A purer gas. Hydrogen gas as obtained by the above pro- cesses, is not quite pure ; if washed with a little lime water, or caustic potash, it is deprived of carbonic acid, and of sulphuretted hydrogen, which sometimes arises from sulphur in the zinc, and by being passed through alcohol, it loses its odor, which is probably owing to a volatile oil,{ supposed to be generated between the carbon in the metal and the hydrogen. A little carburetted hydrogen is very apt to remain ; and to have the gas absolutely pure, the zinc must be pre- * Phil. Trans, v. 66. p. 144. t Carbonic acid gas was discovered in 1756 or 7; hydrogen in 1766 ; nitrogen in 1772 ; oxygen and chlorine in 1774. These important discoveries laid the found- ation of the pneumatic chemistry. t Which, on diluting the alcohol, makes its appearance, after a few days, upon the surface of the water. Other authors suggest that arsenical particles derived from the zinc, cause the smell. 26 202 HYDROGEN. viously distilled. It sometimes has a little zinc or iron suspended or dissolved in it. 3. THEORY OF THE PROCESS. The acid is not altered, but the water is decomposed ; its oxygen passing to the iron, converts it into an oxide, and its hydrogen is evolved ; the acid unites with the oxide of iron, and forms sulphate of iron, which appears in green crystals, as soon as the mixture is cold. How the acid operates to favor the decomposition is not al- together clear. * 4. PHYSICAL PROPERTIES. (a.) It is colorless and transparent. As commonly obtained, it has a smell slightly fetid. If obtained over mercury, the odor is much diminished. It is scarcely absorbed by water, unless it has been freed from common air, when 100 cubic inches of that fluid take up 1 J inches of the gas ; with strong pressure the water absorbs one third of its volume. (6.) It refracts light more powerfully than any gas, agreeably to the general law with respect to inflammable bodies; ratio 6.6 air being l.f (c.) Specific gravity 0.694, air being 1, just 16 times lighter than oxygen ; weight 2.116 grs. for 100 cub. in. at the medium tempera- ture and pressure. f One cubic inch weighs but little more than j\ of a grain, and fifty cubic inches but little more than one grain ; it is the lightest form of matter hitherto obtained. " It is about 200,000 times lighter than mercury, and 300,000 times lighter than platina." Hare. * This used to be called a case of disposing affinity ; the acid being disposed to unite with the oxide of iron about to be formed, by the transfer of the oxygen of the water to the iron ; this explanation appears to be no more than verbal, as the oxide of iron cannot exert an attraction before it is in existence ; but if, as suggested by Murray, the acid be supposed to exert, simultaneously, an attraction, both for the oxygen of the water, and for the iron, it may thus aid the combination of the former with the latter, and then the acid will combine with the oxide of iron. But there is no evidence, except that which is afforded by the fact in question, that such an attraction exists between the acid and the oxygen, and the acid and the iron. It ap- pears to me better to say that we do not understand it, and to wait till we do, be- fore we attempt to explain the fact. The heat generated by the action of the acid and water, will not explain the decomposition, for the cold diluted acid will rapidly evolve hydrogen gas from iron; it grows hot, it is true, during the action, but the heat is not the cause, it is the effect of the action. There is another theoretical diffi- culty in this experiment. The rapid evolution of gas, and especially of one whose capacity for heat exceeds that of all known bodies, ought not, upon the received theory of heat, to evolve that power; the mixture ought to grow cold. Again, the crystallization of the sulphate of iron is rapid, and begins even before the mixture is cold, and proceeds the more rapidly the colder the liquor grows; but the evolu- tion of a solid from fluids ought to produce heat. I Henry, vol. l.p. 154. I Thomson. HYDROGEN. 203 (d.) Balloons* are filled with it. The principle of balloons is very- well exhibited by filling soap bubbles with hydrogen gas, or, better still, with the explosive mixture of oxygen and hydrogen ; they will rise in the atmosphere ; the former rapidly, the latter more quietly, and the flame of a candle will fire them as they pass ; in the latter case there is a considerable explosion. The solution of soap should be strong, and used cold, and a metallic pipe will allow the bubbles to be more easily disengaged than one of clay. If a dish of strong soap water be blown up full of bubbles of the mixed gases, it detonates powerfully, when fir- ed by throwing a burning match into it. A bladder, filled in the same manner, may be fired by piercing it with a sharp wire, fixed to a pole, and having, appended to the wire, a burning rag moistened with spirit of turpentine. (e.) Musical tonesf are produced when a small jet of this gas is burned in a glass or other tube. They are produced also by car- bonic oxide, coal gas, olefiant gas, and vapor of ether, burning in a jet ; the sounds are produced in bottles, flasks, and vials ; and globes, from seven to two inches in diameter, give very low tones. The re- port is considered by Mr. Faraday, agreeably to the views of Sir H. Davy, as only a continued explosion. J 5. CHEMICAL PROPERTIES. (a.) Hydrogen possesses extensive powers of com- bination, as will be seen in the history of other bo- dies, especially of chlorine, iodine, sulphur, carbon, &c., and of animal and vegetable substances. (6.) ITS INFLAMMABILITY IS ITS MOST IMPORT- ANT PROPERTY. (c.) A candle kindles a jar of it, but is itself ex- tinguished by immersion in the gas, and is relighted if the wick again touch the flame ; see the an- nexed figure of Dr. Hare, which needs no explana- tion. * For some curious and amusing speculations respecting the possible uses of bal- loons, see the Am. Jour. Vol. XI, XII and XIII. Gay Lussac, who ascended till the mercury in the barometers stood at 11 inches, ascertained, that magnetism and elec- tricity existed at that height, in undiminished energy, and that the proportion of oxygen and nitrogen, was the same as at the surface of the earth. t A. jet of flame from one of the gazometers, p. 184, is admirably adapted to insure the success of this pleasing experiment. By turning the key, the jet is accurately regulated, and a great variety of tones, from the most acute to the most grave, is easily produced by using tubes of different materials, diameters, length and thick- ness; hardly any "tube comes amiss, and the same tube will give a variety of tones, if moved up and down, while the flame is in it. t Eng. Jour, of Science, No. 10. 204 HYDROGEN. It is plain from this experiment, that hydrogen gas is a combustible, but not a supporter of combustion ; it burns where it is in contact with the air, but will not permit a candle to burn in it ; on the contrary, oxygen gas causes the candle to burn more rapidly, but, when it is withdrawn, the gas does not itself burn. (d.) Hydrogen gas burns in jets and in many pleasing forms, as is illustra- ted by the following figure. The bottle contains the materials to afford the gas, which is kindled at the orifice of the tube, (the common air having been allowed previously to es- cape,) and the jet is called the philo- sophic candle. The flame is very pale, but Dr. Hare, whose cut is annexed, ascertained, that the addition of one seventh of spirit of turpentine to the materials, would " obviate this defect." (e.) If mingled with common air, 5 or 6 volumes, and hydrogen gas 2, it explodes on contact with the flame of a candle. (/.) More violently with oxygen gas 1 part, and hydrogen 2, by volume. This mixture should not be exploded in glass vessels, un- less in small quantities, and unless the glass is strong, and well an- nealed. It is better to use tubes of tin plate, or sheet copper ; a cylinder of the latter, closed at one end ;* or two cones joined at the base, and furnished with a mouth that can be corked firmly, and with a touch hole, make a good discharging pistol. It is first filled with water ; then with the mixed gases, and then kindled by a burning candle, or sulphur match, applied at the touch hole.f Hydrogen gas burns in volume with a yellowish flame, sometimes with points and sparks of red. (g.) Hydrogen gas, from its levity,, escapes rapidly from vessels held with their mouths upward ; but it remains a good while in con- tact with the air, without escaping, if their mouths are in the reverse * If this mixture be allowed to escape from beneath water, the bubbles explode violently on touching a flame at the surface ; a glass vessel should never be used in this experiment. t If the double cone be filled with hydrogen and held with the mouth downward, leaving the touch hole at the top open, the gas will slowly escape and may be kin- dled, being gently pressed upwards by the atmosphere. If when partly burned, the instrument be turned upwards, the mixed gases will explode. J. G. HYDROGEN. 205 position. It may be turned upward into a vessel full of air, and will expel it, and take its place. (A.) Suspend, out of the water of the pneumatic cistern, a tall nar- row jar, full of the gas, keeping a glass plate over its mouth, until it is fixed in its place : then withdraw the plate without agitation ; on putting a burning candle to the mouth, a quarter of an hour after, the gas will take fire with the usual slight explosion, and will then continue to burn quietly away, thus proving that owing to its levity, the pressure of the atmosphere had kept it in its place. (i.) Reverse the experiment, by filling the same jar again with the same gas ; cover its mouth with the glass plate, and turn it up ; let an assistant hold a candle a foot above, and when the plate is withdrawn, the gas, now rapidly rising, will take fire as it is passing upward, and will exhibit a volume of flame in the air : the same pressure which in the former experiment kept it in its place now forces it to rise. 6. EFFECTS ON ANIMAL LIFE. It is hostile to life, but not instantly fatal. (a.) The lungs may be inflated with it a few times in succession, and it may be blown out without injury.* It produced in Mr. Mau- noir and Mr. Paul, at Geneva, a soft, shrill, and squeaking voice, when they attempted to speak, after breathing it. (b.) Frogs placed in hydrogen gas will suspend their respiration; they have been known to do it for 3J hours at a time. (c.) In mixture with oxygen, it may be substituted for the nitro- gen, and a respirable atmosphere might thus have been made ; but, the mixture would have been explosive, and the hydrogen would probably have separated from the oxygen in consequence of its levity. (d.) It kills by suffocation, merely or principally, as water does. (e.) It is not noxious to plants, and some, it is said, even absorb it. 7. NATURE OF HYDROGEN. It is an element in relation to our knowledge, and probably it is a real element. It is a simple combustible. 8. ITS IMPORTANCE AND DIFFUSION. (a.) It is probably, next to oxygen, the most important element ; it is exceedingly abundant, and its compounds meet us almost every where. (b.) It exists in water, and all fluids used by men and animals for drink or diluents. * Pilatre de Rozier was accustomed, not only to fill his lungs with hydrogen gas, but to set fire to it as it issued from his mouth, where it formed a very curious jet of flame. He also mixed pure hydrogen gas with one ninth of common air, and re- spired the mixture as usual ; " but when he attempted to set it on fire, the conse- quence was an explosion so dreadful, that he imagined his teeth were all blown out." 206 HYDROGEN. (c.) It is a constituent of all animal and vegetable bodies, and is found in almost every part of them. (d.) It exists in mineral coal of every variety, and most abundant- ly in the bituminous coal. 9. Its combining weight, when it is made unity for other bodies, is of course expressed by 1 ; if oxygen be unity, then hydrogen will be .125. These are Dr. Thomson's numbers, but I have already stated the reasons why I prefer making hydrogen unity, as most wri- ters now do. 10. POLARITY. Hydrogen, in the galvanic circuit, resorts to the negative pole, and is therefore considered as electro-positive. Self regulating reservoirs, for hydrogen and other gases, are occasionally convenient ; the following are from Dr. Hare, being im- proved upon the original contrivance of Gay Lussac.* "Suppose the glass jar without, to contain diluted sulphuric acid ; the invert- ed bell, within the jar, to contain some zinc, support- ed on a tray of copper, sus- pended by wires, of the same metal, from the neck of the bell. The cock be- ing open, when the bell is lowered into the position in which it is represented, the atmospheric air will escape and the acid, entering the cavity of the bell, will, by aid of the zinc, cause hy- drogen gas to be copiously evolved. As soon as the cock is closed, the hydro- gen expels the acid from the cavity of the bell ; and consequently, its contact with the zinc is prevented, until another portion of the gas is withdrawn. As soon as this is done, the acid re-enters the cavity of the bell, and the evolution of hydrogen is renewed, and continued, until again arrested, as in the first instance, by preventing the escape of the gas, and consequently causing it to displace the acid from the interior of the bell, within which the zinc is suspended." * Dr. Hare states that he used an apparatus of this kind, at Williamsburgh, Va. before he had heard of that of Gay Lussac. It will be seen farther on, that such a contrivance is admirably adapted for obtaining light, instantaneously, by allowing the jet of flame to flow upon spongy platinum. WATER. 207 Large self-regulating reservoir, for Hydrogen. " This figure represents a self- regulating reservoir, for hydrogen gas; it is constructed like that described in the preceding arti- cle, excepting that it is about 50 times larger, and is made of lead instead of glass." " This reservoir is attached to the compound blowpipe, in or- der to furnish hydrogen ; and may, of course, be used in all experiments, requiring a copious supply of that gas." On account of the extensive uses of oxygen and hydrogen gases, in a philosophical labora- tory, it is highly convenient, to have them always on hand, in large quantities ; and, of course, in separate reservoirs, between which there is no possibility of communication. WATER. SYNTHESIS. 11. THE COMBUSTION OF HYDROGEN PRODUCES WATER, and pTC>- vided the gases be pure,* it produces nothing else. (a.) Burn a jet of hydrogen gas in a tall glass tube, and water, in visible drops, will soon line the tube. (b.) The same may be done in a bottle, filled either with common air, or with oxygen gas. . (c.) Or burn a double stream of the two gases, coming from distinct reservoirs, and mingling at the moment of exit. In these cases the receiver should be kept cold. (d.) If a bladder, furnished with a stop cock, and a bent tube, be filled with hydrogen gas, and the gas, kindled in a. jet, be allowed * Sometimes a little nitric acid or nitric oxide, is formed at the expense of the ni- trogen; or carbonic acid, from carburetted hydrogen, these being accidental im- purities in the gases. 208 WATER. to burn under a jar of common air, or better of oxygen gas, standing over mercury, there will be a rapid rise of the metal, and water will appear, first in vapor, and then in minute drops, lining the interior of the jar. (e.) I find it perfectly easy to fill a large glass globe with oxygen gas, by allowing it to flow from a reservoir through a tube descend- ing to the bottom of the globe, and it is known when the latter is full by applying a taper, blown out, and having a little fire on the wick, which is then rekindled at the mouth of the globe. This arrangement saves air-pump exhaustion. The hydrogen gas is then lighted in a jet, and allowed to flow from a gasometer as long as it is needed. As I employ the compound blow-pipe in this experiment, it is easy to let in either oxygen or hydrogen as it is needed, and thus the com- bustion is continued at pleasure. The production of water in this mode is immediate and palpable. I subjoin a figure of a beautiful but more complicated apparatus. Lavoisier's apparatus for the recomposition of water. " This apparatus con- sists of a glass globe, with a neck cemented into a brass cap, from which three tubes pro- ceed, severally com- municating with an air pump, and with reser- voirs of oxygen and hy- drogen. It has also an isulated wire, for pro- ducing the inflamma- tion of a jet of hydrogen, by means of an electric spark. In order to put the apparatus into op- eration, the globe must be exhausted of air, and then supplied with oxy- gen to a certain extent. In the next place, hy- drogen is to be allowed to enter it in a jet, which is to be inflamed by an electric spark. As the oxygen is consumed, more is to be admitted." WATER. 200 " I have employed a wire ignited by galvanism, to inflame the hy- drogen in this apparatus, and conceive it to be a much less precari- ous method than that of employing an electric machine, or electro- phorus." Hare. (f.) Oxygen and hydrogen may be combined by explosion. This happens of course, in all cases where they are fired together ; the product is lost, if the explosion finds vent into the open air, but if confined to an eudiometer tube, over mercury, a little water will be obtained ; this is never done except for the purposes of eudiometry, which will be mentioned again. (g.) Oxygen and hydrogen combine by pressure. -The two gases, will remain forever in mere mixture, at the common temperature and pressure, without combining ; but by sudden and violent com- pression in a syringe, they will explode, probably on account of the heat which is thus evolved, for " an equal degree of condensation, slowly produced, has not the same effect." These gases combine slowly above the temperature of boiling mer- cury, and below that of glass when ignited, so as to be just visible in the dark. 12. PROPORTION OF THE ELEMENTS. (a.) By volume, 2 hydrogen, and 1 oxygen, by weight, 88.9 oxygen, > , -, " 11.1 hydrogen, $ veryi The combining weight, if there be one proportion of each, Combining weight of water, 9* or 11.25 (b.) The proportions of the elements in water, have been settled after the most rigorous and often repeated analysis. The atomic hy- pothesis, and the theory of definite and multiple proportions, are built upon the result of this analysis. All chemists take either oxygen or hydrogen for unity, and of late the weight of opinion and authority is evidently in favor of hydrogen. WATER ANALYSIS. 1 . If water, in the state of steam, be passed over clean ignited iron, in an iron, or in a luted glass or earthen tube, the iron absorbs the ox- ygen, and hydrogen gas is obtained ; the weight of the hydrogen added to the increased weight of the iron equals that of the water de- composed. Zinc, antimony, and several other metals will answer the same purpose more or less perfectly. The common arrangement for decomposing water is represented by the following figure from Dr. Hare. * 9 is the number now generally adopted. 27 210 WATER, Steam decomposed by ignited iron. " Having introduced some turnings of iron or refuse card teeth, into a clean musket-barrel ; lute into one end of the barrel, the beak of a half pint glass retort, about half full of water. To the other end of the barrel, lute a flexible leaden tube. Lift the cover off the furnace, and place the barrel across it, so that the part containing the iron turnings, may be exposed to the greatest heat. Throw into the furnace, a mixture of charcoal, and live coals ; the barrel will soon become white hot. In the interim, by means of a chauffer of coals, the water being heated to ebullition, the steam is made to pass through the barrel in contact with the heated iron turnings." " Under these circumstances, the oxygen of the water unites with the iron, and the hydrogen escapes in the gaseous state through the flexible tube." For 1 grain of hydrogen evolved, the iron gains 8 grs. 2. Galvanism with gold or platina wires, gives an elegant result; the two gases, in exact proportion, being obtained in mixture, if the two wires are in the same tube ; if in different tubes communicating by a fluid or a wet fibrous solid, then the oxygen will be in one tube and the hydrogen in the other. If the wire is oxidable, hydrogen gas alone is obtained while the wire is in the meantime oxidized. 3. Water is readily decomposed by ignited carbon, but the results are more complicated ; carbonic acid gas, carbonic oxide, and carbu- retted hydrogen gases being obtained. WATER. 211 In this account of the composition of water, as a matter of conven- ience, the synthesis has been given before the analysis, while the re- verse order would have seemed more natural. The synthesis was, however, first discovered, although in every instance of obtaining hy- drogen for the experiment, it must have been preceded by an actual, although unknown analysis of water. In 1776, Macquer and De la Fond, at Paris, burned a jet of hy- drogen, and observed that drops of water were condensed from it on a white China saucer, which was not soiled, and in the following year, a similar experiment was made by Bucquet and Lavoisier, who could not satisfy themselves as to what was produced, but ascertained that it was not carbonic acid. In the spring of 1781, Mr. Warltire and Dr. Priestley fired the mixed gases, but the water produced was supposed to be accidental, or to have been merely deposited from a state of suspension. In the summer of the same year, and afterwards, more particular- ly in 1783, Mr. Cavendish burned hydrogen on a large scale, and proved that the product was water ; an opinion which had been be- fore entertained by Mr. Watt, and communicated to Dr. Priestley and to De Luc. Mr. Cavendish, without any knowledge of Mr. Watt's opinion, had drawn the same conclusion, and is therefore the discoverer of the composition of water. Among the innumerable ex- periments which have confirmed this result, that made by Fourcroy and his companions, is worthy of particular commemoration ; the gases were kept burning more than a week, 37500 cubic inches were consumed, and fifteen ounces of pure water were obtained precisely equal in weight to that of the gases employed. The decomposition of water was first effected, understandingly, by Lavoisier, in 1783, by passing the steam of water over ignited iron; the increase of weight in which, added to the weight of the hydrogen gas obtained, precisely equalled that of the water decomposed. The iron is found to be in the same condition as if it had been burned in oxygen gas or common air, it being a protoxide. WATER. ITS PROPERTIES. 1. It absorbs spontaneously, a small quantity of air, which escapes by the action of the air pump, or by boiling, and in the Torricellian vacuum. Water absorbs oxygen, rather than nitrogen from the air ; water that has been exposed to the air, contains over 31 per cent, of oxygen ; this fits water to support the life of fishes, and gives it pun- gency and vivacity to the taste. The air obtained by ebullition from rain water, contains 32 per cent, of oxygen ; that from snow water 34.8, but if the atmosphere be excluded during its melting, it is near- ly free from air ; this is not contradictory, for during the freezing of water, the air is expelled, and is again absorbed when it melts. When 212 WATER. water absorbs any other gas, the air which it contains is more or less ex- pelled ; hence, gases confined over water, are soon contaminated in this manner. In boiling water, the first portions expelled contain the most oxygen ; the nitrogen comes more tardily, and, if after boiling and air pump exhaustion have ceased to evolve any more gas, electri- cal discharges be passed through water, more nitrogen will be evolved along with oxygen and hydrogen, proceeding from the decomposition of the water. 2. Boiled water, absorbs a portion of every gas.* The quantity absorbed is increased by pressure and by cold, and the facts will be more particularly stated in giving the history of each particular gas. 3. Water always exists in the atmosphere, in the driest weather. Sa.) Deliquescent substances attract it, as potash, sulphuric acid, muriate of lime. (b.) Cold bodies condense it, in dew or hoar frost. (c.) Porous bodies absorb water from the air. -Dry earth, dry oat meal, and dry metallic filings, afford examples. 4. Water, by combination becomes solid. This is seen in the hy- drated alkalies, potash and soda,, in the hydrated oxides, and in many crystals, especially artificial ones ; when crystals contain water, it is always in definite quantity. 5. Water, dissolves a great variety of bodies, more, probably, than any other fluid acids, alkalies, salts, gum, sugar, alcohol, &c. It is the most general solvent to bring substances together, under such circumstances as to promote the various chemical processes of nature, and as it alters their properties very little, it is favorable to chemical action by bringing many solids into a state of fluidity. But in some cases, its chemical action is highly important. 6. The solution of a solid in water generally produces cold. Bi-carbonate of potash and caustic potash crystallized, produce cold ; but caustic potash that has been recently ignited, or which after that operation has not again absorbed water, dissolves with a rise of tem- perature. 7. Jlir is disengaged during the solution of bodies in water. It is partly contained in the crevices of the bodies, and partly dissolved in the water. 8. Water, when pure, is perfectly transparent, tasteless, colorless, and inodorous. According to Professor Robinson, a cubic foot of water at the temperature of 55, weighs 998. 74f oz. Avoirdupois, or 62.42 Ibs. A cubic inch at 60, and at 30 inches pressure, weighs 252.525 grains. Pure or distilled water, at the temperature of 60, is always taken as the unit, when we speak of the specific gravity of other bodies. * See n table, Henry, Vol. 1, p, 225. i In round numbers 1000. WATER. 213 The refractive power of water is very high, owing, as is supposed, to the hydrogen which it contains. By a vigorous stroke in a syringe, water emits a flash of light. Thenard. Water has generally been regarded as incompressible, but Mr. Per- kins applied to it a force of 2000 atmospheres, and stated the com- pression at y 1 ,-, but Prof. Oersted* justly considers this estimate as far too great. It would appear from a note by the late Prof. Fisher,f of Yale College, that the subject is not quite new, and Mr. Canton, so far back as 1764, ascertained that water expands ^TTT o P art > by the removal of the pressure of the atmosphere, and that an additional atmosphere reduces its volume in an equal degree. No natural water is quite pure ; it always holds saline and earthy matters dissolved be- sides gases; rain or snow water obtained away from population, as on a mountain, is the purest. It is obtained pure by distillation, espe- cially in vessels of gold, silver, or platinum. Distilled water is indis- pensable in all accurate chemical operations. 8. Utility of water. It is far more abundant than all other fluids ; it is indispensable to animal and vegetable life, and no other fluid would answer the same purposes. Water enters into the composition of all the solids and fluids which we consume for food and drink ; it imparts that humidity to the air which in breathing moderates animal heat ; it affords by its pressure and motion, the means of great mechanical operations, and it facilitates commerce and friendly communication between nations. It is ne- cessary that its properties should be negative, or it would be injurious. Gazometer for oxygen or any gas not absorbed by water. Dr. Hare. " The engraving on p. 214, represents a section of the gazometer for oxygen, which is capable of holding between five and six cubic feet of gas. It is placed in the cellar beneath the lecture room. The wooden tub, V, is necessarily kept nearly full of water. The cylin- drical vessel, T, of tinned iron, is inverted in the tub, and suspended and counterpoised, by the rope and weight, in such manner, as to re- ceive any gas which may proceed from the orifice of the pipe, in its axis. This pipe passing, by means of a water-tight juncture, through the bottom of the tub, rises through the floor, F, is furnished with a cock at C, and terminates in a gallows screw. This is fixed in a cavity made in the plank forming the table of the lecture room, in the vicinity of the pneumatic cistern. Hence by means of it, and a lead- en pipe soldered to a brass knob, properly perforated, a communica- tion may be established between the cavity of the gazometer, and any other vessel, for the purpose either of introducing or withdrawing the gas. The counter-weight being made heavier than the vessel, by appending additional weight to the ring, K, the gas may be sucked * Edin. Jour. No. 12, p. 201. t Am. Jour. Vol. Ill, p. 347. 214 WATER. in from a bell glass, (situated over the pneumatic cistern,) as fast as it enters the bell, from the generating apparatus." " Gazometers which contain 40 or 50,000 cubic feet, have been constructed upon this principle, for holding the gas from oil or coal." l"V WATER. 215 Deutoxide of Hydrogen. 1 . HISTORY. Until 1818, water was believed to be the only com- pound of hydrogen and oxygen ; but in that year, Thenard published in the Transactions of the Academy of Sciences of Paris,* an ac- count of this singular substance, and hitherto little has been added to the facts stated in the original memoirs by this celebrated chemist. 2. PREPARATION. f From the peroxide of barium, by the action of diluted muriatic acid, and then of sulphuric acid, both, a number of times repeated ; followed by that of sulphate of silver, and then by * Thenard's Chem. 4th Ed. Vol. V, p. 41. t The principal steps of this complicated process, which the student will not be ex- pected fully to understand until farther advanced, are as follows : 1. Prepare nitrate of baryta ; this may be done by decomposing the sulphate ot barytes by igniting it with charcoal, by which it is turned into a sulphuret; this is decomposed even in an iron vessel by nitric acid, and any iron that is taken up is precipitated by baryta, and the nitrate of baryta is then crystallized. 2. The nitrate is decomposed by ignition in a porcelain retort ; (if the heated ni- trate be withdrawn from the fire in proper time, it will be left in the state of a fine deutoxide, but*) it is commonly oxygenized by passing the dry pure oxygen gas over the ignited baryta contained in a luted glass tube ; the oxygen is rapidly absorbed, and we obtain the deutoxide or peroxide of barium ; it is this very portion of oxygen thus absorbed, which is to be transferred to water or rather to its hydrogen, and it is done in the following manner. 3. Take water, six or seven ounces, and strong muriatic acid sufficient to dissolve 230 grains of baryta, and add 185 grains of powdered peroxide of barium ; the so- lution is without effervescence, because, although the acid combines only with the protoxide, the excess of oxygen is not disengaged, but unites to the water or to the hydrogen of the water ; the water thus becomes oxygenized, but in too small a pro- portion to be observed. 4. Sulphuric acid is now added, just enough to precipitate the barytes, and the muri- atic acid is thus liberated, and is again ready to act upon more of the peroxide, which, as before, is now added in the proportion of 185 grains; this is dissolved; the excess of oxygen is added to the water ; the barytes is again precipitated by sulphuric acid, and the insoluble sulphate is separated by the filter ; thus the process is repeated a sufficient number of times, until about three ounces of the peroxide have been em- ployed, when the liquid will contain from twenty five to thirty times its volume of oxygen gas. 5. The solution is now a mixture of muriate of baryta with oxygenized water, and to remove the salt, its acid is first separated by sulphate of silver, which forms mu- riate of silver, and liberates the sulphuric acid, which, in its turn, is removed by so- lid baryta in powder and by filtration. 6. The solution is now the oxygenized water, or, as it is more properly called, the peroxide of hydrogen, but still containing more water than is necessary for its solu- tion ; this is removed by the air pump ; the vessel containing the peroxide of hydro- gen is placed in another about two thirds full of sulphuric acid, and the vacuum is formed over it, which occasions the evaporation of the water, and leaves eventually nothing but the peroxide, which, if continued in the vacuum, is finally, but very slowly volatilized unchanged. Thenard says, " au bout de deux jours la liqueur contiendra peut-etre deux cent cinquante fois son volume d' oxygene." The per- oxide, as thus obtained, has the specific gravity of 1.452, and it did not grow any denser by continued exposure to the vacuum, although it diminished considerably in quantity. Minute as this abridged statement may appear, there are many details necessary to success, for which recourse must be had to Thenard's own account in his Chem- istry, or in the Ann. de Chim. et de Phys. Veils. VIII, IX and X ; or Ann. of Phil. Vols. XIII and XIV. * The clause in parenthesis communicated by Dr, J. Torrey. 216 WATER. baryta, and finally by concentration by air pump exhaustion, aided by the affinity of the vapor of water for sulphuric acid. 3. PROPERTIES. (a.) They are remarkably different from those of water. The fluid is colorless and inodorous ; destroys gradually the color of litmus and turmeric paper ;* is somewhat corrosive to the skin, bleaches it, and if abundantly applied, destroys it. It bleaches the tongue, makes it tingle, and gives a peculiar taste resembling that of metallic solutions. (b.) Although much more fixed than water, it may be entirely evap- orated in a vacuum, without decomposition. At 59 Fahr. it is de- composed into water and oxygen gas. It can therefore be scarcely preserved except surrounded by ice ; but it remained fluid at every degree of cold applied to it. (c.) At 212, it is decomposed explosively, oxygen gas being lib- erated, and therefore if we would decompose it by heat, it must be previously diluted. Diffuse day light has no effect upon it, and di- rect solar light very little. (rf.) It is decomposed by nearly all the metals, and by most of their oxides, these substances being in a state of minute division. (e.) Those that powerfully attract oxygen combine with a portion of it; such are potassium, sodium, arsenic, zinc, &ic. and in this way several metallic protoxides become peroxides, and on the same prin- ciple hydriodic acid, sulphurous acid and sulphuretted hydrogen, at- tract oxygen from this fluid and bring it to the condition of water. (/.) Oxide of silver]- decomposes the oxygenized water with ex- plosion. This happens if the fluid falls on the silver, drop by drop, and if the place be dark, light is seen. (g.) Several other peroxides decompose this oxygenized compound. Such are those of manganese, cobalt, lead, platinum, gold, iridium, rhodium, and palladium ; the oxygen of the water is always disen- gaged, and sometimes that of the oxide. The decomposition is complete and instantaneous, and sometimes ignition is produced in the glass tube containing the materials. * Some have supposed that the bleaching powers of chlorine may depend on the mixture with it, of a small quantity of oxygenized water. t In the Am. Jour. Vol. XVII, p. 34, Dr. Ed. W. Faust has suggested, that this curious phenomenon of the decomposition of oxygenized water by oxide of silver, may be accounted for upon galvanic principles : thus "When any metal is placed in the peroxide of hydrogen, a galvanic effect is pro- duced. The hydrogen having less affinity for the excess of oxygen, than the metal has, the liquid becomes negative, thus acting the part of the copper plate of a bat- tery, while the metal becomes positive, supplying the place of the zinc plate. The liquid is thus resolved into water and oxygen. If the metal be very oxydable, it retains the oxygen, which is evolved if gold, platina, &c. be used. We need scarce- ly refer to the wires of a battery, for a parallel case. " When the peroxide of hydrogen conies in contact with the oxide of silver, the oxygen escapes from both, and the latter is reduced to the metallic state." Far a fuller account, see the paper of Dr. Faust. WATER. (h.) Water and acids, especially the more powerful, render the compound more permanent : if the liquid has begun to effervesce by heat, a drop of the stronger acids, and even of the principal vegeta- ble acids, will cause it to cease, and the addition of an alkali will cause the effect to be renewed. (i.) Peroxide of hydrogen is decomposed by heating carefully the diluted solution: its composition as ascertained by its discoverer, Thenard, is hydrogen 1 proportion and oxygen 2 = 16, and 17 is there- fore its representative number. From its great specific gravity, it sinks in common water as sulphuric acid does, although it has a great affinity for that fluid. Thenard suggested an application of it to remove dark spots from pictures, in which white lead paint had become tarnished by sulphuret- ted hydrogen : this it effected instantly by the agency of the oxygen of the oxygenized water, which converted the sulphuret into a sulphate. Many other particulars might be added respecting this curious com- pound, but they would be inconsistent with the extent of this work. There does not appear any positive proof that the combination of the oxygen is with the hydrogen directly, rather than with the entire water, but the fact that the oxygen bears a multiple relation to that contained in water, affords a strong presumptive proof; perhaps a satisfactory one, in support of the former view. EUDIOMETRY BY HYDROGEN. Eudiometry has been already mentioned in giving the history of the atmosphere, and it remains to describe, as fast as we come to them, the action of the various substances that operate to remove oxygen from the air, or from any mixture of gases. Hydrogen is one of the most effectual. 1 . Modes of application. (.) In a common eudiometer tube. This kind of tube is made very stout, as in the annexed figure : the glass is well . .. annealed, its mouth is usually trumpet shaped, it is graduated and furnished, towards the top, with two wires, cemented into the glass, and approaching, but not touching each other. In this manner, an electric spark is easily made to pass through the mixed oxygen and hydrogen gases, and an explosion and diminution of volume follow. (b.) Dr. lire's eudiometer, of which a figure is annexed, is very simple. It is a syphon tube, clos-. ed at one end, and with platinum wires hermetically inserted : it is of course graduated : its legs are both from six to nine inches long, and the interior diame-. ter is from two to four tenths of an inch : it will receive safely one fourth of an inch of the mixed oxygen and hydrogen gases, and nearly an equal volume of olefiant gas mixture : the water or mercury in the 28 218 WATER. bend is brought to the same level, and two inches or more of air is left in the leg, which is held in the hand. The thumb is pressed firmly upon the orifice, and the spark taken either through the hand as a part of the conducting substance, or by a wire : the elastic spring of the confined air prevents all danger of explosion, only a very slight pressure being felt at the moment.* (c.) Volttfs eudiometer. I give, from Dr. Hare, a figure of this elegant, but expensive, and rather complicated in- strument, which is now little used, and I therefore omit the detailed description, which may be found in Dr. Hare's Com- pendium. A and G are graduated glass tubes : each division of the 200 parts of A cor- responding to 10 of G, which holds 10 measures of A. C is a funnel-shaped foot, with a stop cock and cap for intro- ducing gas from the measure, k, which is furnished with a slide so as to give al- ways the same measure. I is an insu- lated electrical conductor. F, a basin shaped cap for pouring in water, and to admit of introducing G, air tight, with a finger on the orifice, so that (F being filled with water y ) it may be screwed to its place, or removed from it without loss of its contents. There is of course a communication through B and E, and the whole apparatus having been first filled with water, the mixed gases are introduced ; the spark taken ; B opened under water to ascertain the diminution, and the residual gas being let up into G is there accurately measured. (d.) Dr. Hare's eudiometer. To produce the explosion of the gases, this gentleman has availed himself of the ig- nition produced by a small calorimeter, in a slender platinum wire, forming a part of the connexion in the interior of the eudiometer tubes : he measures the gas conveniently and accurately, by a graduated rod, sliding air tight in the instrument, * For a more detailed description, see lire's Dictionary, art. Eudiometer; also Edin. Phil, Trans. Jan. 1818, WATER. 219 and also by some separate instruments called volumeters, and sliding rod gas measures. To one of his eudiometers a barometer gage is attached, by which the amount of absorption is accurately ascertain- ed. The ignition of the platinum by the calorimotor, for the purpose of inflaming the gases, is an elegant and novel method of operating ; the various modes of measuring the gases are ingenious and accur- ate, and the detailed description of all the instruments and operations may be found in Dr. Hare's Compendium, and in the Am. Journal. We subjoin the figure, and an abridged description of the simplest of these eudiometers. Hydro-oxygen Eudiometer of Dr. Hare. A A W W W W Two brass wires passing through the socket S, and appear- ing within the glass detonating tube G, where they are connected at the top by a soldered arc of platina wire, visible in the drawing. One of the brass wires is soldered to the socket. The other is fast- ened by means of a collar of leathers, packed by a screw, so that it has no metallic communication with the other wire, unless through the filament of platinum, which is called the igniting wire. At A is a capillary orifice in the glass tube, which is opened and closed by the lever and spring, seen in the drawing, and it may be guarded by a gallows screw, in the iron staple A A, which may be ap- pended to the instrument by pivots at S, and the opposite point, and may be dropped out of the way when the eudiometer is to be charged. R The sliding rod, is acurately graduated to about 160, and to diminish the chance' of leakage, a stop cock may be interposed be- tween the sliding rod and the detonating tube. B represents a detonating tube, to be discharged by an electric spark ; it may be screwed into the socket S, instead of the tube G. 220 WATER. The sliding rod eudiometer being ascertained to be tight, is filled with water, free from air bubbles, the rod being introduced to its hilt, and the valve at A being open, the rod is drawn out and the instrument being in the atmosphere, common air of course en- ters, or the eudiometer is placed under a bell glass, and the gas- es, either successively, or previously mixed in the proper propor- tions, are then introduced by suction of the graduated rod A, and the wires W W being applied to the two poles of a calorimotor, at the moment in action, the explosion takes place. The valve be- ing opened under water, this fluid enters to supply the place of the gases consumed, and any residuary air being excluded by the sliding rod, the portion of the latter remaining without, will, by the gradua- tion, indicate the deficit, which is to be apportioned by the rules given below ; that is, f of the diminution is hydrogen, and is oxygen.* For the purpose of the general student, any mode in which the mixed gases can be exploded conveniently and the diminution easily ascertained, will answer every valuable purpose. USE OF THE HYDRO-OXYGEN EUDIOMETER. If we mix accurately 2 volumes of hydrogen with 1 of oxygen, and inflame them in any of the above named eudiometers, provided the gases are pure, there will be a total condensation. As it is however rare that the gases are quite pure, it is often best to employ an excess of that gas which is used to detect the other. In examining oxygen gas, if we take three volumes of hydrogen, one third of the diminution being oxygen, it will not injure the result, if there should be a residuum. If 100 measures of oxygen gas are fired with 300 hydrogen, and there is a residuum of 130, it follows that 270 have disappeared, and 90 is one third of this, and of course it appears that there is 10 per cent, of foreign gas, it may be nitrogen, or carbonic acid ; for there is an excess of 100 of hydrogen. Suppose, on the other hand, that we fire equal measures of oxy- gen and hydrogen, say 100 of each; if the 200 are reduced to 80, the diminution will have been 120, and two thirds of this, that is 80, is owing to hydrogen ; it follows of course, that there is in the hy- drogen 20 per cent of foreign gas most probably nitrogen. Henry. If 100 measures of common air are mingled with 50 of hydrogen, and exploded, the 50 volumes will generally be reduced to 87, giv- ing a diminution of 63 measures, one third of which, 21, is the pro- portion of oxygen usually assigned to the atmosphere. * The figure of the calorimotor used in these experiments will he given under the head of Galvanism. For a more detailed account, and various particulars to in- sure accuracy, see Dr. Hare's Compendium. Not being in possession of the wood cuts of the barometer gage eudiometer, and of the sliding rod gas measure, I have been obliged to omit an account of those in- struments which 1 had prepared. WATER. Dr. Thomson (First Principles,) employed 42 volumes of hy- drogen to 100 of air, and always obtained a reduction of 60, one third of which, 20, corresponds with the theory of volumes, and also of multiple proportions by weight, and granting that atmospherical air is a feeble compound, this would appear to be, in all probability, the true proportion ; and if this is the true proportion, this fact in its turn strengthens very much the opinion that in the atmosphere, the elements are not merely mixed, but slightly combined. The electric spark will no longer cause explosion in the mixture of 2 volumes of common air, and 1 of hydrogen gas, when there are 12 parts of common air, or 9 of hydrogen added to the mixture, or when it is rarefied 16 times by diminution of pressure, or 6 times by heat. Oxygen and hydrogen gases in the proportion to form water, if rarefied mechanically 1 8 times, will not explode by electricity ; according to Sir H. Davy, rarefaction by heat causes the mixed gases to explode more readily by the temperature of ignition. In the analysis of atmospheric air by hydrogen gas, 5 volumes of air should be , sufficient for 2 of hydrogen; but it is better to employ a small excess ; here, as before, one third of the dimi- nution will be owing to oxygen. Dr. Hare says, that in a great number of experiments, performed by means of his instruments, he obtained very constantly 20.66 as the quantity of oxygen in 100 parts of the air, and that in twenty experiments, the greatest discord- ance did not amount to T oVo- m 100 measures of air. Comp. ACTION OF PLATINUM. (a.) A very effectual eudiometer was unexpectedly presented to us by a discovery of Dobereiner, of Jena. The muriate of platinum and ammonia, when ignited, leaves the metal in the state of spongy platinum,* upon which, if a stream of hydrogen be directed, the metal, if air has access, becomes ignited, and the gas soon takes fire. (6.) It is necessary that the oxygen gas of the air be let in at the same time, and water is the result, as if the gases had been kindled in any other way. (c.) If spongy platinum be introduced into a mixture of oxygen, or common air, with hydrogen gas, in explosive proportions, they de- tonate ; in other proportions they slowly combine and form water. (d.) The spongy platinum being formed into a paste, with about an equal weight of alumine, or china clay, and water, with the addition of some muriate of ammonia, to preserve the porosity, and made into * Or the sub-oxide of platinum, prepared by Mr. E. Davy's process, answers, per- haps equally well. t See Henry, Vol. I. p. 238, and Ann. de Chimie et de Phys. 23, and 24. WATER. balls of the size of peas, and dried, at first slowly, and afterwards more rapidly, the balls will act in the same manner as the sponge, and their power is renewed by heating them in the blowpipe flame ; being thus treated, they will, if preserved from dust, answer a thousand times, and more ; their size need not be over 2, 4, or 6 grains. If one of the balls, fastened for convenience, to a piece of platinum wire, be introduced into a mixture of air 100, and hydro- gen gas 50 measures, it will in a few minutes be reduced to 87 ; the diminution, 63, divided by 3=21, the proportion of oxygen. (jf.) In general, the platinum at common temperatures does not act upon the gases that are found mixed with hydrogen ; but if the ball is hot, it sometimes acts upon the residuary nitrogen to form ammonia, and produces a diminution greater than 63. (g.) Moist platinum sponge has the same power as dry, only it re- quires a longer time. If some of the ammonio-muriate of plati- num be ignited in the sealed end of a glass tube, or if its solution be decomposed there, by a rod of zinc, a thin film of the metal will ad- here firmly to the interior of the tube. In such a tube, a mixture of oxygen and hydrogen, or of the latter and common air, will be de- composed in a few hours : and if the hydrogen prevail, all the oxy- gen will disappear ; in this manner hydrogen can be perfectly puri- fied from oxygen ; even one part in 100 will be abstracted, which much exceeds the power of hydrogen alone, aided by the electric spark. (A.) Dobereiner supposed this to be a peculiar galvanic arrange- ment, in which the hydrogen represents the zinc, and the platinum the copper ; but it appears that no heat is produced, unless oxygen or atmospheric air is present ; so that the office of the metal appears to be to produce a combustion of the hydrogen. (i.) Platinum, in fine powder, produces no action, not even a slow one ; the laminated metal and its wire are equally inert, but thicker leaves and wire acted, although slowly, when heated to between 200 and 300, Centigrade. A very thin film of platinum, rolled round a glass tube, or suspended freely in a detonating mixture, pro- duced no effect in several days ; but when crumpled like the wad- ding of a gun, it produced instant detonation. (j.) Platinum sponge strongly ignited, loses the property of becom- ing incandescent ; but produces slowly, and almost imperceptibly, the combination of the two gases. (k.) This phenomenon appears still more remarkable, when it is considered that it happens between the lightest and the heaviest body known. (L) If, upon a mixture of spongy platinum, and nitrate of platinum, and ammonia, a jet of hydrogen be directed, the mixture reddens, crackles, and emits inflamed sparks. WATER. 223 (m.) Alcohol is turned into acetic acid and water, by the action of the sulphuretted oxide of platinum ;* the same effect is produced by the black powder which zinc precipitates from the platinum solution. (n.) Several metals act in a similar manner upon mixtures of oxy- gen and hydrogen ; among them, palladium is the most effectual ; this metal, and iridium inflamed the mixed gases at common tempe- ratures, and gold and silver acted efficiently at a heat below 212, Modes of preparing Platinum sponge. (a.) According to my own experience, when common crude gram platinum is dissolved in nitro-muriatic acid, and precipitated by muriate of ammonia ; this orange precipitate being collected by subsidence, may be partially dried in a Wedgwood's or other dish, and then transfer- red into a platinum crucible, which may be gradually heated in a little earthen furnace, till the fumes of muriate of ammonia cease to appear. The cover of the crucible may now be put on, and the whole buried in burning coals, which may be blown by hand bellows, both above and below, until it is fully ignited ; it need remain in this state not more than two or three minutes, when it may be withdrawn and cooled. (b.) The orange precipitate maybe thrown upon a filter, the filter dried, and introduced directly into the crucible. A greater division of the platinum takes place in consequence of the mixture with the carbon of the burnt paper, and causes the platinum to ignite more readily in a jet of hydrogen ; neither is there any waste of the pre- cipitate, f (c.) If a stream of hydrogen from the compound blowpipe, or other jet, fall upon the sponge, it will be ignited, and the hydrogen will take fire.J (d.) If the oxygen be let in at the same time, or immediately af- ter, the mixed gases are instantly lighted with a slight explosion. * Procured by precipitating the muriate of platinum by sulphuretted hydrogen-. t The above circumstance was observed in the laboratory of Yale College, by Mr. C. U. Shepard, and noted Feb. 17, 1827. In the Journal of the Royal Institution, for April, 1829, it is mentioned that Mr. Pleischel recommends that a piece of paper be three times immersed in the solution of murrate of platinum, and then burnt, which leaves the platinum in the best state for producing ignition. The Editors of the Jour- nal say, that a little of the ammonio-muriate of platinum being heated upon platinum foil, in a spirit lamp, with the mildest heat that will dissipate every thing volatile,, the platinum will be left in a fit state to inflame a mixture of oxygen and hydrogen, at the lowest possible temperature. Dr. Webster recommends dipping a cotton cloth in the solution of the muriate of platinum, and then burning it to tinder, which, if kept dry, will ignite as readily as the sponge. t This contrivance is so good a substitute for the complicated, although elegant in- strument of Volta, in which a jet of hydrogen is fired by a spark from an electropho- rus, that I have not thought it best to give a drawing and description of this instru- ment, both of which may be seen in Dr. Hare's Compendium, p. 65. 224 COMPOUND BLOWPIPE. (e.) These facts are best exhibited in public, by placing the pla- tinum in a wine glass, but as it is liable to break from the sudden heat, it is well to place a dish beneath. (/.) After precipitation of the orange precipitate, the yellow su- pernatant fluid still contains platinum, as is indicated by muriate of tin and hydriodic acid on evaporation, a solid is obtained, consisting principally of the muriate of ammonia, and probably the foreign met- als ; for on heating this residuum in a platinum crucible, as in the case of the sponge, a little metallic matter is obtained, which, however, does not ignite the hydrogen. 1. Dr. ROBERT HARE, of Philadelphia, invented this instrument in 1801 ; and in December of that year, the discovery was com- municated to the chemical society of that city; in 1802, an account of it was published in a pamphlet.* 1 It was used by Dr. Hare and the author of this work, in 1802 3, and full accounts of their experi- ments were published in the Phil. Trans, of Philadelphia, Vol. VI. In Dec. 1811, an extensive series of experiments was performed by the author, and published in 1812, in Dr. Bruce's Journal, several years before Dr. Clarke's experiments were performed. j- 2. Dr. Hare is entitled exclusively to the merit of the discovery. The contrivance of mixing the gases before hand in explosive pro- portions, is all that has been added, and this is not an improvement; it introduces a serious danger where there was none before, and as regards the heat produced, is attended with no important advantage. 3. The principle of Dr. Hare's instrument is, that the oxygen and hydrogen gases coming from distinct reservoirs, mingle at the mo- ment of their exit from a capillary orifice, and are there ignited with perfect safety. 4. Dr. Hare first ascertained, that oxygen and hydrogen gases can be made to burn together in this manner; that the heat thus evolved, surpasses that produced by any other mode of combus- tion, and that it is scarcely exceeded even by that produced by Vol- taic electricity ; this might perhaps have been anticipated from the great capacity of the gases, especially of hydrogen for heat.J * Which was republished in Vol. XIV, of Tilloch's Phil. Mag. Lond. and in Vol. XLV, of the Ann. de China. Paris. t See Am. Jour. Vol. I, p. 98, and Vol. II, p. 181. t Being an independent original witness to the early use, (in 1802,) of this fine in- strument by its inventor; and having been in the habit of using it frequently, for several years before Dr. Clarke's experiments were published, as well as ever since ; I embrace this opportunity to say, that no other name, than that of Dr. HARE, can be, in my view, rightfully associated with the invention of the Compound Blowpipe. COMPOUND BLOWPIPE. 225 5. The apparatus which I employ, is that represented in the annexed figure, the parts of which are described at page 184 ; it is convenient and effectual, and has, for many years, enabled me to per- form all these interesting experiments with great facility, and on a large scale. By adverting to the strictures of Dr. Hare,* and to the statement of the edi- tors of the Annales de Chimie et de Physique, f it will be apparent, that in point of effect, no advantage is gained by mingling the gases, previously to their combustion, f and a serious danger is necessarily encountered, notwithstanding the wire gauze, and oil, and mercury valves that have been interposed in the apparatus of Newman or Brooke, whose figure is annexed. \ It is a small copper box, (here represented on the left of the page,) * Am. Jour. Vol. II, p. 281. t Ibid, Vol. Ill, p. 87. t In the apparatus which 1 employ, stout tubes of cast silver are screwed into a piece of platinum, shaped like the lower frustrum of a pyramid, and this is the part of the instrument where the gases issue ; but common brass tubes hard soldered and screwed into a silver frustrum, will answer; care must however be used, that the silver is not melted, which it certainly will be, if allowed to sink into the hole burned into a charcoal support, on which any thing is melting or burning. Professor Griscom was so good as to bring this instrument to Yale College, some years since, and we made a series of experiments with it, but with no results differ- ent from those produced by Dr. Hare's blowpipe. In point of pressure, we carried it so far that the copper parallelepiped, was swollen (ill its sides were convex, but no advantage appeared to be gained bv great pressure. 29 226 COMPOUND BLOWPIPE. furnished with an injecting syringe, for the introduction of the gases, previously mingled in the proportions to form water ; it is furnished also with an internal valvular apparatus of wire gauze, to guard against explosions,* and with a tube of efflux mounted with a stop cock and a platinum orifice. Great pressure may be a convenient means of bring- ing more of the gases into the reservoir, but it is of no avail as regards the heat, for not being at their efflux, adequately resisted by the air, it amounts to nothing more than supplying the gases in sufficient quan- tity. The previous accurate adjustment of the proportions, may at first view seem to be a point of importance, but after a little experi- ence, there is no practical difficulty in hitting this proportion, when the gases come from different reservoirs ; the eye will easily perceive, by the color and size of the flame, and the appearance of the focal point, when the proper proportion is attained ; and the effects have proved that there is no important difference in the power of the in- struments. Mr. Brooke's blowpipe has the advantage in neatness and convenience of size, but its contents being soon exhausted must be frequently renewed. It is obvious that the security of Dr. Hare's contrivance may be easily connected with that of Mr. Brooke, by simply providing two condensing boxes of proper size, one for hy- drogen and the other for oxygen, and connecting them in the manner represented in the cut on page 225. On account, both of strength and capacity, two globes of metal would be most convenient ; and an instrument, like that in the figure above referred to, would unite all the most important advantages of the different varieties of appara- tus, hitherto constructed for this purpose, and be at the same time, free from their inconveniences, and from the danger attending Mr. Brooke's. 6. The figure in the note below represents the form of the instru- ment, at present, used by Dr. Hare. It is less simple than those that have been described, but the inventor says, that he has found it equally convenient in use, as the most simple form, " while its parts are peculiarly susceptible of advantageous adjustment."! * On a principle which will be illustrated under the history of the safety lamp, in the section on the carburetted hydrogen gases. t '* B is a brass ball, with a vertical perforation, terminating in a male screw above, and in a female screw below. Another perforation, at right angles to this, causes a communication with the tube, t, which enters the ball at right angles. A simi- lar, but smaller brass ball, may be observed above, with perforations similar to those in the larger ball, and a tube, in like manner, entering it laterally. This ball ter- minates in a male screw below, as well as above. The thread of the lower screw is curved to the left, while that of the screw of the larger ball, which enters the same nut, n, is curved to (he right. Hence the same motion causes the male screws to ap- proach, or recede from each olher, and thus determines the degree of compression given to a cork which is placed between them, in the nut. At S, -above the ball, a small screw may be observed, with a milled head. This is connected with a small tube which passes through the cork in the nut, and reaches nearly to the external orifice, o, from which the flame is represented as proceeding. This tube is for the COMPOUND BLOWPIPE. 227 Effects of the compound blowpipe. 1. Every variety of mineral matter has been melted by it, except the diamond ; it is evident that this substance and charcoal are ex- ceptions, merely on account of their combustibility. 2. All combustible bodies burn in the focus, not excepting any of the metals : the latter exhibit beautiful phenomena, depending on the color of their oxides and of the flame : platinum, because it is too fixed a substance to form vapor, burns, not with flame but with scintillation. 3. Peculiar facilities are afforded by having two separate reser- voirs for the gases. (.) We use the hydrogen flame alone if we wish a lower degree of heat. most part of brass, but at its lower end terminates in a tube of platina. It communi- cates by lateral apertures with the cavity of the upper ball, but is prevented by the cork, from communicating with the cavity in the other ball. Hence it receives any gas which may be delivered into the upper ball from the lateral pipe which enters that ball, but receives none of the gas which may enter the lower ball, B." " Into the female screw of the latter, a perforated cylinder of brass, c, with a cor- responding male screw, is fitted. The perforation in this cylinder, forms a continu- ation of that in the ball, but narrows below, and ends in a small hollow cylinder of platina, which forms the external orifice of the blowpipe, 0." " The screws, s s s s, are to keep, in the axis of the larger ball, the tube which passes through it, from the cavity of the smaller ball. The intermediate nut, by compressing, about the tube, the cork which surrounds it, prevents any communf- cation between the cavities in the two balls. By the screw, s, in the vertex, the orifice of the central tube may be adjusted to a proper distance from the external orifice. Three different cylinders, and as -many central tubes, with platina orifices of different calibres, were provided, so that the flame might be varied in size, agree- ably to the object in view." S G 228 ALKALIES. (b.) We let in a portion of oxygen, more or less, as we wish the heat to be increased to any degree, till we reach the maximum. (c.) We ignite charcoal by the compound flame, and then shut off the hydrogen, if we wish to have the effects of oxygen gas alone. (d.) This is beautifully seen in burning the metals ; we first raise the heat by the compound flame, and when the globule of metal is heated very intensely, we cut off the hydrogen and permit the oxy- gen alone to flow, which at that high temperature sustains, and even increases the combustion of the metals, not excepting cobalt, nickel, silver and gold. 4. Most intense light is exhibited, by bringing incombustible bodies, such as the earths, and particularly lime and argil, in the form of a pipe's stem, or of porcelain, into the focus : the naked eye cannot endure the light : and in this focus the most refractory substances, the rocks, the pure earths and the gems, are melted ; the diamond alone excepted, which burns with great intensity, and is soon exhaled in the form of carbonic acid gas.* THE ALKALIES. Preliminary Remarks. Several eminent writers at the present time, have broken up the long established class of alkalies, and distributed them according to relations derived from their composition : ammonia is described in connexion with hydrogen and nitrogen, and potassa, soda and lithia, under the metals. Similar remarks are applicable also to the earths. This course is logical, but it is highly inconvenient; for it is scarcely possible to take more than a few steps in the chemistry of particular bodies, without calling in the aid of the alkalies, in our experiments * For the details of these and of numerous other experiments, see Dr. Hare's ori- ginal pamphlet, and his and my own various memoirs in the Phil. Trans, of Phila- delphia; in Tilloch's Phil. Mag. ; in the Annales de Chimie el de Physique ; in Dr. Bruce's Journal, and in the American Journal. Dr. Hare remarks, (Comp. p. 77,) that excepting the republication of his memoir in Tilloch's Phil. Mag. and in the Ann. de Chim. et de Phys. and a quotation of his results in Murray's System of Chemistry, they had been generally neglected. "Hence, (adds Dr. Hare,) a modification of the hydro-oxygen blowpipe was con- trived by Mr. Brooke. Dr. Clarke, by means of this modification, repeated my ex- periments and those of Prof. Silliman, without any other notice of our pretensions than such as was calculated to convey erroneous impressions." I regret to say that this omission, although made known, was never corrected, and* that the experiments of Dr. Clarke, most of which had been, years before, performed and accounts of them published by Dr. Hare or myself, were entitled to no credit for originality ; while the almost identity (in many cases) of the language in which they were described, with that used by us so long before, proves that the results with the two instruments were the same. It is not pleasant to transgress the kind maxim, nil de mortuis nisi bonum; but truth obliges me in this instance to do it. The claims of Dr. Clarke respecting the compound blowpipe were entirely un- founded. ALKALIES. 229 and reasoning : this remark is perhaps equally true of the principal acids, and both these important classes of bodies should be placed as early as possible in the hands of the student. It has been already stated, in the plan of the work, that in teaching, I have found the most convenience in introducing the alkalies before the acids ; al- though my preference is not so decided that I should have any seri- ous objection to the opposite course. But, I am not willing to post- pone the history of the alkalies and earths until we come to that of the metals, and to treat of them merely as appendages of those bodies ; and I should be still more reluctant, for the sake of avoiding this diffi- culty, to bring in the metals first, or in connexion with the simple combustibles, as some authors have done ; nor is it a sufficient reason, that the alkalies* and earths then fall in naturally as metallic oxides. It is true that modern discovery has increased the difficulty of giving a strictly logical definition of an alkali ; but the bodies that have usu- ally been called by this name are, in some of their forms, familiarly known ; they have also a sufficient number of properties in common, to distinguish them from other classes of bodies,f and this is the most important point to be attained in our arrangements. It is true also that their properties graduate into those of some of the earths; but it is sufficient to designate the latter as alkaline earths, and to leave the remainder of them to be called earths proper. Explanatory Statement. The alkalies, when they are to be prepared pure for chemical pur- poses, are generally extracted from their saline combinations, and it is therefore necessary to premise, that a salt is composed of an acid and a base : the alkaline salts have, of course, an alkaline base, and the object of our processes is to separate the acid, and leave the base isolated, and free also from accidental bodies, commonly called im- purities. In giving the history of potassa, soda and ammonia, only two acids need be mentioned : potassa and soda, as they occur in commerce, are usually found combined with the carbonic acid ; and ammonia both with that and with the muriatic acid. The carbonic acid, com- posed of carbon and oxygen, is a gaseous body, which when com- bined with the alkalies, blunts their properties, but it is easily remov- ed from these combinations, partially by heat and completely by the superior affinity of lime. It is also entirely expelled by stronger acids, but a new salt is, in that case, formed ; and in general the form- ing of such a compound, would rather retard than advance our pro- * Ammonia excepted, which no one arranges under the metals. i It is scarcely necessary to add, that I do not include the new alkaline vegetable proximate principles, morphia, delphia, quinia, strychnia, &c. 230 ALKALIES. gress towards obtaining the pure alkali. The muriatic acid is also a gaseous body : it cannot be expelled from the alkalies by heat : it can be displaced by the sulphuric acid, but that will only engage the alkali in a new combination : to remove it entirely, we employ lime in this case also, which will attract it away and leave the alkali free and pure.* AMMONIA POTASSA SODA LITHIA. GENERAL CHARACTER OF ALKALIES. !a.} Caustic to the animal organs. 6.) Volatilizable by heat, but, except ammonia, not decomposable by heat alone. (c.) Combine with acids and form salts $f acids and alkalies are antagonists. (d.) Very soluble in water, even in the state of carbonate ; solu- ble also in alcohol. (e.) Turnf most blue, purple, and other dark vegetable colors, to green ; as tincture or infusion of violets, and of purple cabbage. (f.) Turn most yellow vegetable colors to brown ; as turmeric and rhubarb ; and red to purple, as tincture of brazil wood. (g.) The colors altered by an alkali, are generally restored by a due proportion of an acid. (h.) Unite with oils and form soaps ; corrode woollen cloth ; and are generally powerful solvents of animal matter. (i.) Taste, acrid and peculiar; particularly different from that pro- duced by acids ; it is called the alkaline taste, and in a milder form, is observed in pearl ashes and soda. SEC. I. AMMONIA. || Remark. This alkali is placed first because of its relation to ni- trogen, and hydrogen, which have been described. * Had we begun with acids, an explanatory statement would have been necessary respecting alkalies and salts, as two of the most important of the acids, the nitric and muriatic, are extracted from saline combinations. t The definition of alkali proposed by Dr. Ure, founded on the power of " com- bining with acids, so as to neutralize or impair their activity," would confound them with the earths and metallic oxides. t The power to affect vegetable colors, continues even after combination with carbonic acid, which distinguishes the alkaline from the earthy carbonates. Ammo- nia being a volatile alkali, sometimes escapes by evaporation, and the original color is thus restored. Bibulous paper, wet with these colored solutions, forms test papers, by which the application of colors is easily made. Litmus is not changed by alkalies, but if previously reddened, it is turned back by an alkali to its original color, and thus be- comes a test. || Called also the volatile alkali. Popular name hartshorn, because it was an- ciently distilled from the horns of the hart or deer, which, in common with other animal matter contain its elements. ALKALIES. 231 1. THE NAME is derived from that of sal ammoniac, or the mu- riate of ammonia, and this from the sandy country of Lybia,* (a^orf,) where the salt was first procured. 2. DISCOVERY. The gas was discovered by Dr. Priestley, by heating the aqueous solution of the shops ; he collected the gas in vials filled with mercury, which was expelled by the gas. Process for obtaining gaseous Ammonia. 3. PREPARATION. (a.) From equalparts of powdered muriate of ammonia, and dry- slacked-\ quick lime, in- timately mingled, and heated moderately in a glass retort ;{ we receive the gas over mercury, as in the an- nexed cut of Dr. Hare. It is very convenient to displace the com- mon air, by conveying the gas, by a glass tube into an inverted glass vessel 5 as in the annexed figure, where a is the flask containing the materials ; b a spirit lamp, for heat ; c the recipient, and d the connecting tube. It is obvious that this pro- cess is founded on the levity of the gas, which displaces the air of the vessel. (b.) Heat the aqueous solution of ammonia to expel the gas ; but this is not an eligible mode, as the water dis- tils over, is condensed above the mercury, and reab- sorbs the gas. In the process 3, (b.) we know when the recipient is full, both by the pungent smell, and by bringing a feather dipped in muriatic acid near the mouth of the vessel, when, if the gas is overflowing, there will be a white cloud of regenerated muriate o fgrjL ammonia. When it is important to have the gas very dry, unslacked lime should be used ; but it is apt to adhere to the glass and break it. 4. PHYSICAL PROPERTIES. * Called Ammonia. Some say in allusion to the sand ; others to the temple of Jupiter Ammon. t That is, slacked with such a portion of water, as to remain dry. . In all operations for collecting gases over mercury, ground, tubulated glass re- torts are better than flasks, as, from the pressure, the latter are apt to leak at the cork, ALKALIES. (a.) Transparent and colorless ; smell, highly odorant and pun- gent. Agreeable, if largely diluted with air ; it causes a sharp prick- ly sensation in the hands, and if the skin is moist, it is absorbed, and is almost corrosive ; combining with the moisture on the eye-balls, it causes a sensation of intolerable pain. It is therefore decidedly caus- tic, and could it be made solid without combination, it would doubtless act on animal matter with as much energy as the fixed alkalies do. (6.) Specific Gravity 0.5957, air being I. -Weight, 18.17, at the medium temperature and pressure. (c.) Hostile to animal life. An animal immersed in it instantly dies. It kills by suffocation and excoriation ; admitted into the fauces it is intensely painful ; it causes a violent spasm as soon as it reaches the glottis, and produces the most distressing coughing, and a lasting irritation. 5. CHEMICAL PROPERTIES. (a.) Instantly absorbed by water, a drop of which being admitted and agitated with the gas, the mouth of the vessel being closed by the finger, and then opened under the fluid, it rushes in as it would into a vacuum. Ice melts in the gas more rapidly than it would in the fire ; if passed up into ajar of gas standing over mercury, the metal rises rap- idly as the ice melts, and the gas is absorbed to form liquid ammonia. (b.) Ice-cold water absorbs 780 times its volume of this gas. (Thomson.) Sir H. Davy has stated its absorbability at 475 ; water easily absorbs this quantity, and then holds about one third of its weight of the gas. Sir H. Davy's more recent statement was, that 670 times its volume of this gas, was condensed into one of water. (c.) Aqua jlmjnonice is prepared in pharmacy and in chemistry, by passing am- moniacal gas, from equal parts of slacked lime, and muriate of ammonia, heated in an iron bottle, through ice cold water, contained in Woulfe's bottles, the contents of the first being rejected as impure. For a figure of Woulfe's apparatus, see mu- riatic acid. I annex a cut from Dr. Hare, of an appa- ratus which will answer for a common experiment. It needs no explanation. (d.) The aqua ammonia smells like the gas; it is a very useful reagent, and an efficacious medicine. ALKALIES, 233 The more highly water is impregnated with ammonia, the lighter it is,* as appears from the following table of Sir H. Davy, in which the proportions are by weight. Sp. gr. Ammonia. Water. 0.8750 32.50 67.50 0.8875 - - 29.25 - - 70.75 0.9000 26.00 74.00 0.9054 - - 25.37 - - 74.63 0.9166 22.67 77.93 0.9255 - - 19.54 - - 80.46 0.9326 17.52 82.48 0.9385 - - 15.88 - - 84.12 0.9435 14.53 - 85.47 0.9476 13.46 - - 86.54 9.9513 12.40 87.60 0.9545 - - 11.56 - 88.44 0.9573 10.82 89.18 0.9597 - 10.17 - - 89.83 0.9619 9.60 90.40 0.9692 - 9.50 - - 90.50 Dr. Uref has given another table ; he thinks the numbers in Sir H. Davy's too high by about 1 per cent. A vial containing 224 grains of distilled water, will contain only 216 grains of strong aqua am- moniae. (e.) Alcohol can be impregnated in the same manner, and it may be done at the same time, in a separate bottle of the apparatus. (/.) Jlmmoniacal gas extinguishes flame, but burns slightly ; very evidently, if taken in quantities not less than a pint, and having at the same time access to the air, when it burns as it rises, with a a voluminous yellow flameff If it were collected in large jars, in the manner already described, 3. (a.), it would doubtless burn with a flame still more conspicuous. (g.) If introduced into oxygen gas, in the form of a jet, it burns, and the products are water and nitrogen gas ; the hydrogen uniting with the oxygen, and leaving the nitrogen behind. 6. ANALYSIS, COMPOSITION, AND PROPORTION OF ELEMENTS. (a.) By the electric spark, passed through the gas, standing in a detonating tube, over mercury. It requires two or three hundred discharges to effect the decomposition. * The same fact is observed in the solutions of its salts. t Diet. 24 Ed. p. 142. t Am. Jour. Vol. VI, p. 185. 234 ALKALIES. (b.) By furnace heat, the gas being driven through a porcelain tube ; but the decomposition, is in this way very tardy, and requires an in- tense heat to produce a few bubbles of gas.* It is much better done in an iron tube, filled with coils of iron wire, or copper, silver, gold, or platinum; their relative energy corresponds with the order in which they are named above, but iron is by far the most power- ful. The explanation of this decomposition, appears, at first, not very easy ; since the metals do not combine with either of the con- stituents of ammonia, and are not altered. Probably they act by transmitting heat ; the metals neither gain nor lose in weight, and appear to act as conductors only. The result of the experiment gives 3 volumes of hydrogen and 1 of nitrogen gas, in mixture ; electrization gives the same result ; by weight, 17.64 hydrogen, 82.35 nitrogen ; as the gases are condensed into half their volume, the specific gravity of ammonia is not that of nitrogen, .9782 + 3 hydro- gen .2083=1.1865, but half of this =.593.f A soft, pasty, semi crystallized mass is obtained, when a globule of mercury is galvanized, or a piece of potassium laid, in a cavity, in a solid ammoniacal salt, particularly in muriate of ammonia; it resembles an amalgam, and hence it has been supposed that either hydrogen or nitrogen, or both, has a metallic base ; but the sub- stance has never been obtained isolated, and no satisfactory conclu- sion can be built upon it, (c.) By oxygen. 100 measures of ammonia +50 of oxygen, being detonated over mercury in a tube, the oxygen disappears ; then add 30 or 35 measures more of oxygen ; detonate again ; one third of the entire diminution is oxygen, and double this is the hydro- gen ; the nitrogen remains, deducting any that may have been intro- duced with the oxygen gas ; this result corresponds with that under (b.) giving 3 volumes of hydrogen, and 1 of nitrogen, which, as they exist in a state of combination in ammonia, are condensed into 2 vol- umes ; the decomposition of ammonia, therefore, doubles its volume ; it is, however, no longer ammonia, but a mixture of its constituent gases, hydrogen and nitrogen. (d.) The mixed hydrogen and nitrogen gases, obtained by igne- ous or electrical decomposition, may be analyzed in the same man- ner, by detonation with oxygen, and will give the same result.} * As the ammonia is instantly absorbed by water, none of it will pass through that fluid, and the mixed gases obtained, are of course hydrogen and nitrogen. I have re- peatedly carried this experiment, by the aid of bellows, almost to the fusion of the porcelain tube, without obtaining a cubic inch of gas; while if there be iron in the tube, the gases come over, abundantly. t .595 is the number which we have quoted, p. 232 ; Dr. Thomson states it at .590. \ The analysis by chlorine is very elegant and easy. See that topic. The chlo- rine removes the hydrogen, and leaves the nitrogen. ALKALIES. 235 7. SYNTHESIS. (a.) Hydrogen gas and nitrogen gas, mingled in the proper pro- portions, do not form ammonia, nor would they ever do it their spe- cific caloric opposes the union ; they would remain always a mere mixture. (6.) Hydrogen in its nascent state, meeting with nitrogen, forms ammonia ; this happens when hydrogen is disengaged from moistened iron filings, included in a jar of nitrogen. (c.) Nitric acid, acting on tin or on phosphorus, forms ammonia ; water furnishing the hydrogen and the acid the nitrogen ; it is then disengaged by a little lime which arrests the acid, and the ammonia is perceived by its odor, and by a white fume with muriatic acid.* (d.) Ammonia is formed during animal decomposition ; both its elements being evolved from the animal matter, and uniting at the instant ; this is the origin of ammonia in stables, privies, and other similar places. 8. ACTION ON COLORS. f (a.) Red tincture of alkanet becomes blue ; { blue infusion of cab- bage, green ; diluted yellow tincture of rhubarb or turmeric, brown. * Ann. de Chim. et de Physique, XXIV. 295. t I am not aware that any reason has been suggested for these changes of color ; certainly none has occurred to me that is satisfactory. As a general fact, permanent changes of color depend on changes of composition, as is evinced in innumerable cases ; for instance, red lead and red precipitate contain oxygen, a colorless body, and metals, one of which is white and the other gray; indigo is intensely blue, but becomes green by losing oxygen. In the case of the test colors, the color is permanent, as long as the coloring matter is not decomposed, which happens event- ually, and perhaps we may say that a peculiar combination takes place between the coloring matter and the acid or alkali, although we can give no reason, any more thaa in other cases, why these particular colors should result, or why there should be any change of color. The autumnal hues of the leaves of trees probably depend on similar causes ; that is to say, on the fuller developement of acid or alkali, by the variations of temperature ; for these agents always exist abundantly in vegetable bodies, and particularly in their fluids. It is not impossible that galvanic principles, may aid in producing and mod- ifying the effects. If any person would examine the leaves of the sugar maple, for instance, just be- fore the first autumnal frosts, and while they are still green, he could easily decide whether acid or alkali were predominant, or whether either was to be found in a state of freedom ; then let him examine the leaves after they have turned red, a color which we should of course attribute to the developement of acid. A similar exa- mination should be made of the chemical condition of leaves exhibiting other col- ors produced by decay, as the yellow of the hickory, the brown of several species of oak. &c. and so of the different colors observed in leaves of the same trees in the va- rious stages of decomposition. In the American Journal, Vol. xvi, p. 215, there is a reference to an essay on this subject, in the Ann. de Chim. et de Phys. Aout, 1828, in which it is stated, that the colored parts of vegetables, appear to contain a particular substance, called by Prof. De Candolle, chromule, and the autumnal change in the color of leaves is attributed to the fixation of oxygen, and to a sort of acidification of the chromule. J We owe this very convenient test, to Dr. Hare. 236 ALKALIES. &c. ; acids bring the colors back, as has been stated in giving the general characters. (b.) In applying these colors, we may fill a small tube stopped at one end, or an essence vial, with the colored fluid, and with a finger on the mouth, turn it upward into a jar of the gas standing over mer- cury ; instantly the color will change, and the gas be absorbed. 9. CONDENSATION OF THE GAS, BY COLD AND PRESSURE. This was accomplished by Mr. Faraday,* by disengaging it in sealed syphon tubes, from chloride f of silver which absorbs it in large quantities, 100 grains absorbing 130 cubic inches of the gas. The leg of the syphon containing the chloride, was heated to 100 Fahr. and the other leg kept cold by ice. Ammoniacal gas was evolved, and part of it was by the pressure of the rest, reduced to the liquid state. It was a colorless fluid ; its refractive power was great- er than that of water, and at 50, its pressure equalled 6.5 atmos- pheres ; its specific gravity was 0.76, water being 1. 10. PROCESS IN THE ARTS. By the distillation of bones, and other firm parts of animal sub- stances, ammonia is generated, by the reaction of its elements, but it is more or less combined with carbonic acid. Among the ele- ments of animal matter, we always find hydrogen and nitrogen. The ammonia obtained is impure, mixed with animal oil, &c. and is pu- rified by combining it with the muriatic or sulphuric acid, and then decomposing this ammoniacal salt by quick lime, in the manner alrea- dy described. In the manufactories, bones and horns are commonly employed, and sometimes the refuse of the slaughter houses. An iron retort, or still is generally used ; the bones are introduced rough- ly broken, and a strong heat applied. A tar like substance, oil, and very fetid gases, are evoked, which should always be burned as they are both noxious and disgusting. Valves are sometimes fixed in the apparatus to prevent the return of common air ; this would of course happen when the apparatus grows cold, and the air by ming- ling with the inflammable gases, might occasion an explosion, when the fire is lighted again. Animal charcoal, mixed with phosphate of lime, remains in the iron vessel. J 11. PHARMACEUTICAL PROCESS. To procure aqua ammoniae, we may employ either a still or Woulfe's bottles ; the latter are always used in philosophical laborato- ries ; the proportions of the materials are 1 to 2 parts of slacked lime, and 1 of pulverized sal ammoniac, and the gas is received in water, * Phil. Trans. 1823, p. 196. I Muriate. t Gray's Op. Chem. In the large way, one ofiron is used with a stone-ware head, and stone- ware bot- tles may be used for the condensation. ALKALIES, 237 equal in weight to the salt employed ; it is kept cold by ice or snow, or at least by cold water often renewed. When the gas ceases, the addition of a little water to the materials in the retort, will renew the flow of gas, and produce complete decomposition ; ten pounds of sal ammoniac should produce thirty pounds of aqua ammonia?, sp. gr. .950, and containing about 12 per cent, of ammonia.* The Edin- burgh college prepare it of the strength, .989 ; that of London, .960. Ure. 12. NATURAL SOURCES. From the decomposition of animal substances, as in privies and stables,f &tc. ; it is probable that ammonia is produced generally during the spontaneous decomposition of animal bodies ; a pungent, reviving, and antiseptic gas thus springs up, from the very bosom of putrefaction. The Chenopodium vulvaria emits this gas in the act of vegetation, and many flowers, even those with an agreeable odor| do the same. 13. GENERAL INFERENCE. In destructive distillation, and in spontaneous decomposition, the appearance of ammonia indicates nitrogen, and of course hydrogen. This remark will apply not only to animal substances, but to plants, when they afford ammonia, as all those do which putrefy with an an- imal odor. 14. POLARITY. Ammonia is attracted to the negative pole in the galvanic circuit, and is therefore electro-positive. 15. COMBINING WEIGHT 17 made up of 1 proportion of nitro- gen 14, and 3 of hydrogen =17. 16. MEDICAL AND OTHER USES. These are important; taken in- ternally, in the proportion of 8 or 10 drops to a wine glass full of wa- ter, ammonia is a powerful and valuable stimulant, producing the most useful effect of alcohol, but without its mischiefs. It is also an ant- acid. Externally, it is a rubefacient, but it is generally used in the form of volatile liniment, made by agitating aqua ammonias in a vial with olive oil. Ammonia is a very valuable antidote to poison. Either the aqua ammoniae, the carbonate, or the volatile liniment may be used externally, and the two former internally.^ * The iron bottles in which quicksilver is brought, answer very well for the de- composition of sal ammoniac, and the muriate of lime is easily extracted from them by hot water. t In these places, the ammonia is mixed with fetid gases; the pungency belongs to the former, and the disagreeable odor to the latter. The ammonia is often so abundant as to produce a white cloud, when, in these places, the stopper is withdrawn from a vial of muriatic acid. In Europe, ancient hotels are sometimes tilled with ammoriiacal exhalations, arising from the privies within the premises. t Jour, de Phar. Feb. 1824, p. 100 ; also, Am. Jour. Vol. X, p. 190. $ See Am. Jour. Vol. XVI, p. 183. 238 ALKALIES. It is given to animals, to relieve the inflation occasioned by eating excessively of green grass, clover, lucerne, &c. It is of the most im- portant and extensive use in practical chemistry. Remarks. Ammonia is one of those gases which destroy animal life, when it is mingled, in only a small proportion, with the air that is respired. It was found by Chevallier in iron rust, in situations exposed to animal effluvia ; it was formed when clean iron that had been ignited was boiled in pure water, and it appears to be always formed when iron decomposes water in contact with air ; the water affording the hydrogen, and the air the nitrogen. It appears also to exist in natural iron ores, such as the red hema- tite of Spain, the micaceous ore, and the Jenite of Elba.* It has already been mentioned that ammonia is formed when mois- tened iron filings are placed in nitrogen over mercury, as ascertained by Dr. Austin, in 1788. SEC. II. POTASSA. 1. NAME. From the potashes of commerce ; and their name is obviously derived from ashes, and the pots (called potash kettles,) in which the lixivium is boiled down. Some of the old names were, vegetable alkali salt of tartar salt of wormwood, and alkali of nitre, in allu- sion to the principal sources from which the alkali is obtained. 2. PROCESS OF THE ARTS.f The watery lixivium J of the ashes mixed with quick lime, being boiled down in the iron pots or kettles, the residuum is ignited, and then constitutes the potashes of commerce. Placed in a reverbera- tory furnace, and stirred while the flame plays upon it, it becomes white, and is then the pearlashes of commerce ; it is thus purified by fire only, by the destruction of extractive and other combustible mat- ter, and the dissipation of volatile principles, gases, &c. ; it loses gen- erally about 10 or 15 percent, of its weight. || The purest alkali is obtained from the mutual action, in a red hot iron pot, of nitre 1, and tartar 2 ; the basis of both salts being potash, * Am. Jour. Vol. XIII, p. 181. t To render this process intelligible, nothing more need be premised than that be- sides impurities, the potash of commerce is found combined with carbonic acid, which the lime detaches by its superior affinity, and thus liberates the alkali. \ This word is used to denote a lye made with ashes, and is derived from the Latin word lix, denoting this preparation, and Lixa is a worker in this branch of the Arts. Parkes. When wood is burned, the ashes constitute about l-200th part of its weight. lire's Diet. || See Dr. Roger's account in Am. Jour, Vol. VIII, p. 304. ALKALIES. 239 and the acids being destroyed by their action on each other ; also by igniting nitre in a crucible of gold. 3. PREPARATION OF POTASSA, OR PURE POTASH. Take 1 part potashes, or pearl ashes, and good quick lime 2, with abundance of water ; boil for an hour, in an iron or copper kettle, till the fluid neither effervesces with acids, nor precipitates lime water.* Strain it through a coarse brown towel, stretched on a frame with ten- ter hooks, and hot water should be repeatedly passed through, until we have used ten times as much as the weight of the carbonate of pot- ash employed. The caustic fluid may be put up in black bot- tles, and allowed to settle over night ; the next morning it may be drawn off by a glass syphon. To avoid burning the rnouth, the sy- phon tube may be filled with water, and the finger being pressed up- on the mouth of the longer leg, the shorter may be dexterously turn- ed into the bottle's mouth, without breaking the column in the sy- phon, the water in which maybe allowed to run off, and the fluid is then saved for evaporation. In general, filtering succeeds badly with caustic alkalies, unless very weak, as they are apt to corrode the filters, and paper can scarcely be used, unless for small assays. If the filtering is slow, the car-- bonic acid of the air is apt to combine with the alkali, and to prevent this, Mr. Donovan contrived the an- nexed apparatus, in which A is the filtering funnel, whose mouth is obstructed by folds of linen ;f D is the receiving vessel, and c is a connecting tube, to prevent, at once, any communication with the exter-D| nal air, and any accumulation of pressure in the lower vessel. { (b.) Boil the solution^ down to dryness in a clean iron kettle ; fuse the mass in a silver crucible ; pour it out on a marble slab ; break it up, without delay, and cork it tight from the air in a glass bottle. Cream of tartar, ignited in a crucible, dissolved in water, filtered, boiled with sufficient lime, obtained clear by subsidence and decantation, and solid by evaporation in a silver vessel, to the consistence of oil, gives a cake of the pure hydrate of potassa, without the trouble of using alcohol. It must be put up immediately, in close bottles. Ure. * Taking care, provided the solution of alkali is strong, to dilute it with pure water; otherwise it may precipitate the lime, by seizing the water, and thus give a delusive indication. t Better by fragments of glass, coarser below and finer and finer above ; water is passed through, both before and after an experiment, to remove impurities, and thus a permanent filter is obtained for acids and other corrosive fluids. D. O. t Ann. Phil. 26, 115, and Turner, 2d Ed. p. 405. For a table shewing the real quantities of alkali in aqueous solutions, see Henry. Vol. I, p. 528, 10th London Ed. 240 ALKALIES. This substance, mixed with lime, and fused and cast in cylindrical moulds, forms the caustic called lapis infernalis, or lapis causticus of the shops. It is said that' oxygen gas is disengaged, during its so- lution in water, and that it varies apparently with the impurity of the specimen. (c.) It is now caustic, but contains all the soluble impurities, chief- ly salts, carbonate, muriate, and sulphate of potassa, silex, and oxide of iron and manganese, &c. ; to purify it, dissolve it in good alcohol ; the solution will be wine red ; the watery solution of the salts be- low is immiscible with the alcoholic solution of the alkali, and the solid impurities are at the bottom. Evaporate the alcohol,* and finish the process in a silver basin or crucible, with moderate ignition ; then break up the mass, and secure it from the air. It still contains a little carbonic acid, arising from the reaction of the alkali on the alcohol, or absorbed from the air. The addition of barytic water, previous to the last evaporation, will entirely remove the carbonic acid. (d.) Hydrate of Potassa. This is the substance above described. If the whole of the alcohol be not expelled, the alkali will, on cool- ing, crystallize in single or double plates, needles, or tetrahedral py- ramids. This hydrate contains one proportion of water, 9, and one of potassa, which, as we shall see under potassium, is represented by 48, and its equivalent is therefore 57. Heat alone will not separate the water from it ; if it is urged, the alkali will rise along with the water, which can be separated only when it enters into new combina- tions. 4. PROPERTIES. (a.) Solid at common temperatures ; melts at 300, and is vola- talized at low ignition, with a visible cloud of caustic fumes, highly acrid ; color, white or gray ; taste, when strong, burning and in- tolerable ; corrodes and destroys animal and vegetable substances, subverting completely the organic texture, and in a word, it posses- ses, in perfection, and in full energy, all the characters of alkalies, mentioned in the introduction to their properties. (6.) It affects vegetable colors as ammonia does ; in addition to the colors enumerated under ammonia, it may be mentioned that a strong infusion of the dried flowers of the red rose, answers very well. Parkes. (c.) Deliquesces rapidly in the air, and by absorbing carbonic acid, becomes partially mild again. It acquires moisture so rapidly, * Or distil off and save the first half of it, in a receiver, as it will be alcohol of a good quality ; the remainder will contain more water, and is scarcely worth sa- ving ; there is danger, besides, if we evaporate too low in a glass vessel, that it will be attacked by the alkali. ALKALIES. 241 from the air, as speedily to change the color of any of the alkaline test papers upon which it is laid. Turmeric paper shews it well. Crystallized hydrate of potassa, produces cold during its solution in water, while the solid alkali evolves heat. 5. COMPOSITION. See potassium. 6. POLARITY. Electro positive ; it is attracted to the negative pole in the galvanic circuit. 7. ORIGIN. From vegetables that have no connexion with salt water. Plants yield more than trees ; the branches more than the trunk ; the small branches more than the large, and the leaves most of all. Her- baceous plants yield more ashes and more alkali than wood. Fumi- tory* is said to yield more salt than any other plant, and wormwood more alkali than any other vegetable. One thousand pounds of the following vegetables yielded saline matter in the following proportions. Wormwood, 748 Fumitory, 360 Stalks of sunflower, 349 Beech, - 219 Stalks of Turkey Wheat, or Elm, 166 Maize, - 198 Fir, - - 132 Vine branches, - 162 6 Oak, - 111 Fern, cut in Aug. ^ - 116 Heath, - - 115 Sallow, - . - 102 Aspen, - 61 Box, - 78 Kirwan. Fern leaves are used in Yorkshire, in England, in cleaning cloth for fulling, and appear to afford alkali already developed. In the Highlands of Scotland, soap is made from the alkali ob- tained from the ashes of peat. The resinous and odorous woods afford little alkali ; hence the ashes of pine wood are regarded in families, as worthless for soap- making. Potatoe tops yield a great deal of alkali. The alkali of ashes arises principally from salts existing in the veg- etable juices, and modified by the fire.f 8. HISTORY. In an impure state, it was known to the ancients ; Pliny states that the Gauls and Germans formed soap of ashes and tallow ; and Dr. Thomson thinks that their ashes were the same with our potash. * In Mr. Kirwan's table, quoted in the text, Fumitory is stated to yield but about half as much saline matter as wormwood. t As the alkali of vegetables is not an essential constituent, and is derived from the soil, the quantity which any plant will afford, will depend on the qualities of the earth, in which it is raised. Hence we can account for the discrepancies of different experimenters respecting the relative quantities of alkali afforded by different plants. J. T. 31 242 ALKALIES. Indeed it was not known in purity until 1786, when Berthollet gave the process by alcohol. In the ruins of Pompeii, which was overwhelmed by an eruption of Vesuvius, A. D. 79, " a complete soap boiler's shop was discov- ered, with soap in it, which had evidently been made by the combi- nation of oil and alkali," and it was perfect, although it had been made more than seventeen centuries.* 9. TESTS FOR POTASH. j- 1 . With an excess of tartaric acid, it forms a precipitate, which, when stirred with a glass rod, forms peculiar white streaks. 2. Muriate of platinum gives a yellow precipitate, a triple salt of platinum and potash, forming, by gentle evaporation to dryness, and the addition of cold water, " small shining crystals." 3. Potash is precipitated by nothing. Turner. 10. PHARMACEUTICAL PREPARATION AND MEDICAL USE. The pharmaceutical preparation does not differ materially from that which has been already described for the purification of the alkali. The principal use of caustic potash is as an escharotic ; the cylin- drical masses found in the shops, are often impure, and partially car- bonated and deliquesced, and will sometimes disappoint the practi- tioner. That which is carefully prepared by the process 3. (a.) and (6.) is much more powerful. Potash is mixed with lime to render it milder, and less deliquescent ; this is the kali causticum cum calce, of the pharmacopeias. The pure alcoholic potassa, prepared by the pro- cess 3. (c.) is a very certain caustic, and if fused at ignition, in the conclusion of the process, broken up immediately, and put up in close vials, it discovers, even in several years, no disposition to deliques- cence, and preserves its crystalline structure. J Caustic alkali has been used as a lithontriptic. When the concre- tions consist of uric acid, or urate of ammonia, there is often a favor- able effect produced, but it is difficult to persist long in the use of such a remedy, either by the mouth or by injection into the bladder. When there is to be a long perseverance in the use of alkaline remedies, they must be taken in a milder form, as will be mention- ed under their carbonates. * Parkes' Chem. Essays. t The nitrate, oxalate, or oxide of nickel, fused with borax, will give a blue color with nitre, feldspar, or any substance containing potash, and the presence of soda does not prevent the appearance of the color ; if nickel contains cobalt, the glass will have a brown color. Am. Journal, Vol. XVI, p. 387. $ The late celebrated Dr. Nathan Smith used to obtain this alkali from the lab- oratory, in all cases when he wished an energetic and certain effect, and it never dis- appointed him. I have many times gone through the whole labor of preparing it and although the processes are troublesome, the result is very valuable, both to chemistry and medicine. ALKALIES. 243 Remarks. Common ashes effervesce powerfully with acids, and they easily give a solution with hot water, which affects the taste with the perception of alkalinity, and the test colors with their appropriate changes. The most familiar use of a lye in families, is in soap making, and a principal cause of failure is, that the alkali is not rendered caustic by the application of a sufficient quantity of good quick lime. The den- sity of the solution is ascertained by the family hydrometer, an egg, which floats when the solution is sufficiently dense ; but it may be dense without being caustic, and if it is not caustic, it will act but partially in forming soap. It should not effervesce with acids ; if it does, it is proof that the carbonic acid has not been all withdrawn, and it may be necessary to pass it through more lime. If it is too weak from having too much water in it, this is easily removed by boiling it down. The subject of saponification will be mentioned again under oils, vegetable and animal. Lye has a valuable antisep- tic effect, and is often used in families, as a part of poultices, and also to counteract the tendency of wounds towards tetanus. This alkali, as it separates almost every base from acids, and as it acts with great energy upon many substances, is of great utility in chemistry. It is an immediate antagonist of acids, and forms salts with them. JHkalimeter. This simple instrument is founded upon the fact that 100 grains of pure subcarbonate of potash, are saturated by 70 of strong sul- phuric acid. The acid is placed in a glass tube graduated into 100 equal parts, and the tube to the extent of the graduations, is then filled with water. The purity of the alkali to be tried, will be as- certained by the proportion of this diluted acid which it requires for perfect saturation ; if there be 60 per cent, then 100 grs. will require 60 divisions, and so in proportion ; if pure, it will require it all. If we would ascertain the proportion of pure potassa in the salt, then we must employ 102 grains of the acid, and dilute it with the same quantity of water, requisite to fill the tube. Ure. This alkali is of vast importance in glass making, soap making, in medicine, in domestic economy, and in various arts, and it constitutes an important article of commerce, especially from the United States to Europe. POTASSIUM. 1. DISCOVERY by Sir H. Davy, in October, 1807.* * See the Bakerian lecture for that year, in the Philos. Trans. Although soda has not been, as yet, described in this work, I will give the account of the discovery of its decomposition in connexion with that of potassa, as the facts in the two cases are very similar, and are in both perfectly intelligible. A more particular state- ment of the properties of sodium will be afterwards given. 244 ALKALIES- 2. PROCESS. DECOMPOSITION OF POTASH AND SODA. 1. By galvanism. The first attempts of Sir H. Davy were made upon aqueous solutions of potash and soda, but the water alone was decomposed. He then kept the potash in perfect fusion by an in- genious contrivance ; it was contained in a spoon of platinum, which was, in the first instance, connected with the positive side of a battery of one hundred pairs of six inches, highly charged, and the connexion from the negative side was made by means of a wire of platinum. A most intense light was exhibited, at the negative wire, and a column of flame arose from the point of contact. When the spoon was made negative, and the wire positive, a vivid and constant light appeared at its point, and aeriform globules which inflamed in the at- mosphere rose through the potash. A small piece of pure potash, slightly moistened by the air, so as to give it conducting power, was placed on an insulated disc of pla- tinum, connected with the negative side of the battery of the power of 250 pairs of 6 and 4 inches, in a state of intense activity and a platinum wire, communicating with the positive side, was brought in contact with the upper surface of the alkali. The whole apparatus was in the open atmosphere. There was a fusion of the potash at both surfaces a violent ef- fervescence at the upper, and at the lower, i small globules, having a high metallic lustre, and being precisely similar, in visible characters, to quicksilver, appeared, some of which burnt with explosion and bright flame, as soon as they were formed, and others remained and were merely tarnished and finally covered by a white film which formed on their surfaces. These globules were the basis of the potash ; they did not pro- ceed from the platinum, for they appeared equally, whether copper, silver, gold, plumbago, or even charcoal, was employed for com- pleting the circuit. The air had no agency in producing the glo- bules, for, they were evolved when the alkali was placed in a vacuum.* The substance was likewise produced from potash, fused by means of a lamp, in glass tubes, confined over mercury, and furnish- ed with hermetically inserted platinum wires, by which the electrical action was transmitted. But the glass was so rapidly decomposed by the substance that the operation could not be carried far. The substance produced from potash remained fluid at the tem- perature of the atmosphere, at the time of its production. * I repeated these experiments in 1S10, and then obtained the metalloids ; see Bruce's Journal. Dr. (now Pres.) Cooper first decomposed pota?h in this country by the gun barrel and furnace. ALKALIES. 245 THEORY OF THE PHENOMENA. These decompositions agree perfectly with those which have been before described ; oxygen is evolved at the positive wire, and the combustible with which it was united at the negative. When the solid potash or soda was decomposed in glass tubes, the new sub- stances were always evolved at the negative wire, and the most deli- cate examination proved that the gas liberated at the positive wire was pure oxygen, and, unless more water was present than was ne- cessary to give conducting power to the alkali, no gas whatever was given out at the negative wire.* The synthetical proofs were equal- ly satisfactory. The bases of both alkalies, when exposed to the atmosphere, be- came tarnished and covered with a white crust, which immediately deliquesced ; water was decomposed, a farther oxidizement took place, more white matter was formed, and the whole became a sat- urated solution of fixed alkali. When the metallic globules were confined over mercury in oxygen gas or common air, an absorption took place, a crust of alkali instantly formed, and, for want of mois- ture the process stopped, the interior being defended from the action of the gas. " When the substances were strongly heated, confined in given portions of oxygen, a rapid combustion with a brilliant white flame was produced ; and the metallic globules were found convert- ed into a white and solid mass, which, in the case of the substance from potash was found to be potash, and in that from soda, soda." 2. BY THE FURNACE. (a.) The next spring, 1808, potash was decomposed in a gun barrel, in Paris, by Gay Lussac and Thenard. S6.) Vary many precautions are necessary to secure success. -\ c.) Principal particulars. Provide a clean sound gun barrel bent, so that the middle shall be curved a little downward, while the end in which the potash is to be placed, shall incline gently upward, and the other end downward ; it must be protected by a very refrac- tory lute, made of coarse siliceous sand and potter's clay, with as much sand as can possibly be worked in, and dried with extreme slowness ; place the tube across a furnace ; potash in fragments is put into the elevated end out of the furnace ; this is the breech of the gun barrel, and the breech pin is now put in with a lute ; clean iron turnings are introduced into the belly of the tube in the part which lies in the fur- * Some have supposed that the hydrogen combines with the pure alkali to form the metals. i Sec Recherchcs Physico-Chimiqucs; also, my translation of the Memoir of Gay Lussac and Thenard, in the Boston Edition of Henry's Chemistry, 1814 ; also An- nales de Chimie, LXV, 325; Memoires d' Arcueil, H, 299. 246 ALKALIES. nace ; a stop cock and tube of glass bent downward at right angles, are fixed at the other end ; the glass tube dipping into oil ; both ends are kept cold by water or ice, till a great heat is raised by a powerful bellows blowing with a large orifice, so as to introduce abundance of air ; the potash which should have been previously ignited, before its introduction into the tube, is then slowly melted by a portable furnace, and running down upon the ignited iron, is decomposed ; its oxygen is fixed in the iron, and hydrogen gas being abundantly disengaged from the tube, holding potassium in solution, and being spontaneously inflammable, it flashes frequently and with intense brightness ; the potassium rises in vapor and congeals in the cold end of the tube ; it is then cut out by a knife dipped in naptha and is preserved under that substance. It may be melted beneath it, and is readily moulded by the fingers smeared with naptha, into any form and into pieces of convenient size. The great difficulty is in preserving the gun barrel from oxidation and fusion.* Curaudau of Geneva, in the same year, shewed that potash might be decomposed by charcoal alone, by mixing it in powder with twice its weight of dry carbonate of potash, and heating the mixture strong- ly in an iron tube or spheroidal iron bottle. Prof. Brunner has im- proved this process. His apparatus is a spheroidal wrought iron bottle, of one pint in capacity, and half an inch thick ; a bent gun barrel, ten or twelve inches long, screws into the mouth of the bottle ; the apparatus is well luted, and the gun barrel protected by iron wire wound around it, dips into a vessel of naptha, kept cold by ice. In one experiment, 6 oz. of iron filings, 2 of charcoal, and 8 of fused carbonate of potash, were intimately mingled and heated in a furnace, when 140 grains of potassium were obtained. It appears, accord- ing to the original observation of Sir H. Davy, that " potash or pearl- ash is easily decomposed by the combined attractions of charcoal and iron ; but, it is not decomposable by charcoal, or, when perfectly dry, by iron alone. Two combustible bodies seem to be required by their * For improved processes, see Ann. of Phil. New Series, VI, 233 ; Quarterly Journal of London, XV, 379; and Annales de Chim. XXVII, 340; also, Am. Jour. Vol. VIII, p. 372. It would be difficult, without an amount of detail which is in- consistent with the limits of this work, to state all the circumstances that influence the success of this difficult process. Soon after the discovery of this method of ob- taining potassium, and for several years after, I labored much in this field, having gone many times, through every part of the operation, from the preparation of the caustic alkali to its decomposition, and the evolution of its metal ; I was a coadju- tor at different periods, in these experiments, with Dr. Hare, Prof. Dewey, and Prof. Olmsted. The statements of Gay Lussac and Thenard, are extremely pre- cise and very full ; perhaps I might have added some things from my own expe- rience, but it is rendered unnecessary by the fact, that easier means have been discovered, and potassium, from being one of the dearest of all substances, is now within the reach of every one. ALKALIES. 247 combined affinities for the effect ; thus, in the experiment with the gun barrel, iron and hydrogen are concerned." It would seem, however, that charcoal alone has succeeded in the hands of Wohler, who employed the cream of tartar, after being heated to redness in a covered crucible. The tartar may be calcined in the same iron bottle in which it is to be decomposed, and it is ad- vantageous to mix a little charcoal with the tartar previous to calcin- ation ; 300 grains have been obtained from 24 oz. of crude tartar. Prof. Berzelius is said to have obtained half a pound at one opera- tion.* 4. PROPERTIES. (a.) At 60 or 70 Fahr. it is imperfectly fluid ; perfectly so at 100, and of course at a higher temperature; when melted under naptha, it cannot be distinguished from mercury; at 150, two glo- bules will run into one ; at 50, it is a soft solid, plastic in the hand ; at 32 or lower, it is brittle ; breaks with brilliant lustre ; and when broken, exhibits through a microscope, a crystallization in facets very white and splendid ; at about the heat of ignition, it is volatile, rises in vapor and if air and moisture are excluded, condenses unaltered. (b.) It is a perfect conductor of heat and electricity. (c.) Sp. gr. about 0.865, (G. L. and Th.) 0.876, Bucholz or from .8 to .9, water being 1 . Davy. That obtained by chemical means, is a little heavier, owing to carbon or iron combined with it, but it is suf- ficiently pure for experiments. (d.) In the air or by moisture, it is oxidized and becomes again caustic potash ; it cannot be preserved except under naptha ; if that fluid has been recently distilled, and the vial is full of the fluid, the potassium may be kept under it for years, only it will collect a film of soap around it ; the metal may be examined in the air, if cover- ed with a film of naptha. 5. OXIDES. (a.) The protoxide is formed by the action of water, the air being excluded ; in that case, there is great effervescence, but no flame ; 40 grains of potassium decompose 9 grs. of water and evolve 1 gr. of hydrogen gas, while the other 8 grs. combine with the metal ; thence the quantity of oxygen is inferred ; also, from the oxygen absorbed by potassium when it is exposed to dry air ;f if it is in thin slices, the protoxide is formed in this manner also. Proportions, potassium, 83.34, oxygen, 16.66 = 100.00, This being nearly in the proportion of 100 potassium to 20 oxygen, it follows, that 20 : 100: : 8 : 40 ; 8 being the representative num- * Graham, and Bib. Univ. XXII, 36. t According to Thenard, it is the only metal that is acted upon by perfectly dry oxygen gas. 248 ALKALIES. her of oxygen, 40 becomes that of potassium, and therefore the num- ber for protoxide of potassium is 48. (6.) Properties of the protoxide, free from water ; this is its con- dition when it is formed in dry air or in dry oxygen gas. It is white, very caustic, and fusible a little above a red heat, but it requires a very high heat to volatilize it. Dissolved in water and obtained again, it becomes even after igni- tion, a hydrate, containing protoxide of potassium, 84, water, 16 = 100. Potassium being represented by 40, oxygen by 8, and water by 9, it follows that the equivalent of hydrate of potassa is 57. This is the substance described under potassa. We know riot whether the solid anhydrous protoxide is caustic or not, because its properties cannot be examined in this particular, without admitting water to it, when it becomes a hydrate. It has already been observed, that the hydrate melts at a low heat, (360,) and is easily volatilized. The protoxide is formed also by acting on potassium with a small quantity of water, or by heating potassium with common caustic potassa, and by igniting potash in a crucible of gold. (C.) PEROXIDE. (a.) The white dry protoxide heated in oxygen gas, absorbs two additional proportions, and becomes of an orange color. It may be formed also by heating and burning potassium in oxygen gas, or in common air. (b.) Its properties. Color yellow ; fusible with less heat than hy- drate of potassa, and crystallizes in laminae by cooling. When plunged into water, the two additional proportions of oxygen are evolved, and it becomes hydrate of potassa. Heat greater than that at which it was formed, expels the excess of oxygen, and brings it to the state of protoxide or true anhydrous potash.* The heating must be per- formed in a platinum tray, and the oxide covered with muriate of pot- ash. When mixed with combustible bodies, and heated, it acts vig- orously upon them in consequence of the two additional proportions of oxygen which it contains, and it thus becomes potassa. The com- position of the peroxide is potassium, one proportion 40, and oxygen 3=24, and its equivalent number is 64. Nitrogen and potassium have no action upon each other, but if potassium be heated in ammoniacal gas, a fusible olive colored com- pound is formed, which consists of nitrogen and potassium, and of this compound and ammonia, and at the same time, hydrogen gas is liberated. As it appears not to be particularly important, we refer * This is said to be so fixed as to sustain the heat of a wind furnace without being volatilized ; it attracts water very powerfully, and generates intense heat during its solution. The hydrate of the protoxide is easily volatilized by heat. ALKALIES. 249 for a more full account of its properties to Thenard, Vol. II, p. 413, 4th Ed. 6. MISCELLANEOUS PHENOMENA. (a.) When thrown upon water, potassium floats , melts , becomes a polished sphere, runs briskly about, takes fires, and emits brilliant white red, and violet light, with fumes of caustic potash ; sometimes rings of white smoke, from the combustion of potassuretted hydro- gen are formed in the air, and the regenerated alkali, by becoming red hot, often produces a slight explosion ; if the piece is as large as a pea, the explosion is sometimes violent, and jets of the burning metal are thrown about the room, followed by white streaks of caustic potash. The moving power that impels the floating metal, is potassuretted hydrogen gas, aided by steam, both being generated beneath the globule ; the explosion is caused by the ignited caustic potash, com- bining with the water. (b.) On ice, potassium acts in a similar manner ; it burns and melts a hole, in which, the existence of a solution of caustic potash is easi- ly ascertained by turmeric paper ; it sometimes explodes on ice. (c.) Placed on ignited iron, it burns in common air, and brilliantly in oxygen gas, producing abundant white alkaline fumes, which are soon condensed on the interior of the glass vessel. (d.) On all the test fluids cabbage, turmeric, alkanet, fyc. it burns and produces the effect of an alkali, and that although they may have been first changed red by an acid : the experiment is strikingly exhib- ited in a small glass flask, containing the watery solution of these colors. (e.) It flames on the three strong minerals acids, producing with them salts of the respective acids : the sulphate of potash, on ac- count of its insolubility, sinks through the fluid in white streaks. (f.) It dances about on alcohol and ether, gradually wasting away, but generally without flaming, and the globule looks like polished silver : in the very best ether it sinks, and when it rises it does not of course prove that it is lighter than the ether, as it is often made buoyant by the hydrogen generated beneath it. It discovers and decomposes even the small quantities of water contained in alcohol and ether, and being insoluble in the latter, it forms in it, a turbid cloud of potash, while hydrogen is disengaged. (#) With M S it slowly forms soap, and when kept even under naptha, in vials carelessly closed, it, in the course of some time, be- comes entirely saponified ; absorbing oxygen first to form alkali, and this uniting with the naptha to form soap. Potassium, when heated in the concrete oils, (tallow, spermaceti, wax, &c.) acquires oxygen even from them, gas rises, the base is slowly converted into potash, and a soap is formed. (h.) On test papers, if moist, it runs about, changes the color, and fires if there be moisture enough. We should never touch it with 32 250 ALKALIES. moist hands, as it immediately blazes, and we have in that case, both the actual and potential cautery. (i.) Hydrogen gas, heated in contact with potassium, dissolves it, and becomes spontaneously inflammable, but loses this property by standing, and deposits potassium again. A solid compound of potas- sium and hydrogen, is formed by heating the gas and metal together, with a spirit lamp. It is gray, dull, infusible, and not inflammable, except at a high heat, when it burns vividly. 7. POWERS OF COMBINATION. They are almost universal, as will appear farther on ; it unites with iodine, chlorine, the metals and most of the combustibles, &c. and it decomposes the acids, most of the oxides and salts, and animal and vegetable bodies, and few substances, simple or compound, are un- affected by it. Its greatest prerogative however is to attract oxygen, which it takes from every thing, even from glass and stones, and from the firmest compounds, both natural and artificial. 8. In relation to the state of our knoivledge, it is an element. The most singular circumstance in the character of potassium is its levity : it resembles the metals very much in the greater number of its prop- erties, but differs from them remarkably in specific gravity, while in its extreme inflammability it is assimilated to the most combustible bodies.* 9. POLARITY AND COMBINING PROPORTION. Like other inflammable and metallic bodies, it resorts to the nega- tive pole in the galvanic circuit, and is therefore electro-positive. Its combining number or chemical equivalent has already been stated to be 40, hydrogen being l.f 10. USES. As yet they are exclusively philosophical. In the hands of the chemist, it is a fine instrument of analysis, especially in the agencies which it exerts upon oxygen. It is a splendid substance for experiment, admitting of many beautiful and instructive modes of exhibition. From the improved modes of obtaining it which have been discovered, there seems little reason to doubt that it may be manufactured to any extent that may be required, and its introduction as a new means of annoyance and destruction, would perhaps not be improbable, were it not that it might prove nearly equally dangerous to friend and foe. * These properties, with the remarkable fact, that during the galvanic decomposi- tion of the alkali, although oxygen is evolved at the positive pole there is no hydrogen given off at the negative, led to the presumption that potassa is not a compound of oxygen and potassium, but of potash and hydrogen; the oxygen arising from the decomposition of water, and the hydrogen of that fluid going into union with the alkali to produce potassium. For an ingenious discussion of these and some other similar views, see Murray, 6th ed. Vol. II, p. 27. t Mr. Murray has stated some reasons why it may rather be supposed to be 41, see as above. ALKALIES. 251 SEC. III. SODA. 1. NAMES. The caustic soda was always, and is still unknown to commerce ; anciently, the carbonate was called natron, natrum and nitrum, whence the nitre of the Scriptures. It is mentioned in the Bible, as a detergent, and as disagreeing (effervescing ?) with vin- egar ; both of which qualities belong to the carbonate of soda, but neither of them to nitre. In Africa, they call it trona; on the shores of the Mediterranean, soda and barilla. It has been called marine and mineral alkali. The term soda is now universally used. 2. HISTORY. Indicated by Geber, an Arabian chemist, in the ninth century, but confounded with potash till after the middle of the last century; and unknown in its pure state until the discovery of the carbonic acid. Effervescence with acids was formerly considered as characteristic of soda as well as of the other alkalies, but it be- longs to them in the state of carbonate only, and not in the pure state. 3. POINTS OF SIMILARITY BETWEEN IT AND POTASSA. (a.) Their history is so nearly the same, that it is necessary only to indicate the difference. (b.) All that respects the preparation is identical, and their prop- erties are very similar. 4. SODA ORIGINATES FROM *MARATIME AND MARINE PLANTS, the algae fuci, salsola soda, &LC. : the plants are dried, burned and lixivi- ated, and the lixivium evaporated to dryness. The crude soda of commerce, called barilla, is the incinerated salsola soda: kelp, a coarser variety, is the incinerated sea weed, and often contains only from 2 to 5 per cent of alkali ; white good barilla contains 20 per cent. The crystallized carbonate of soda of commerce is obtained either from the calcination of the sulphate with charcoal and chalk in a reverberatory furnace, or by decomposing the muriate of soda by carbonate of potash. Ure. 5. PROPERTIES. (a.) Caustic soda is at first deliquescent in the air, like potassa, but unlike that alkali it never runs into the consistency of an oily fluid ; for it soon becomes efflorescent, from combination with the carbonic acid contained in the atmosphere : a change which potash never un- dergoes. (b.) Caustic soda is in the form of gray sub-crystalline masses, which can scarcely be distinguished from potassa, by the eye or by any sensible properties. 6. The force of attraction in soda for the acids, is inferior to that of potassa: the soda salts are decomposed by potassa. * Salsola is a maratime plant, (i. e. it grows on the sea shore,) but the algae are marine; the carbonate of soda of truly marine plants only, yields iodine. J. T. $52 ALKALIES. 7. Soda with oil forms hard soap potash soft; and soda is per- haps a little less caustic than potassa. 8. Distinctive characters. (a.) It forms different combinations with acids ; for instance, the sulphate of soda is very soluble in water ; that of potash the opposite. (b.) Its salts, suspended upon platinum wire, impart a rich yellow color to the blowpipe flame. Turner. (c.) Muriate of platinum and tartaric acid give no precipitates with salts of soda : the opposite is true of potash. 9. USES AND IMPORTANCE. Soda is scarcely inferior in this re- spect to potassa : in soap and glass making it is largely used, and it is preferred for the finest articles. In the form of carbonate it is much used in medicine as an antacid : in medicine the caustic soda, is not used, having no advantage over potash. 10. The distinction of vegetable and mineral* alkali is unfounded; for both are found in plants, and both also in stones and various min- erals. Still it is true that potash is found in most plants, and soda in those only which are connected with saline sources ; on the other hand, solid mineral salt, the ocean and other saline waters, and the soda lakes and incrustations, present great quantities of that alkali in the mineral kingdom. f 11. POLARITY. In the galvanic circuit, soda goes to the negative pole, and is therefore electro-positive. Its combining weight is 32. REMARKS. In commerce, we never see caustic soda ; in its pur- est form, in the shops, it is always in semi-crystalline masses of car- bonate, called sal soda. The purest fossil alkali, obtained from the efflorvescence on plaster walls, contains about 60 J of its weight of alkali in crystals. Alkali manufactured at Liverpool, - 49 Fossil alkali from India, - 28 Best Alicant Barilla, - 26 J Sicilian Barilla, - 23 The richest Kelp, made in Norway, the Orkney Islands, and Skye, 6 The general produce of Scottish Kelp, - 2J There are associated with the soda in sea-weed, muriate and sul- phate of soda, hydriodate of potash, or soda, and portions of lime, magnesia, silica, and alumina. There is also more or less of sul- * Potash was formerly culled the vegetable alkali, and soda the mineral. t As felspar, which constitutes so large a proportion of granite, whose detritus forms a considerable part, oi our soils, contains, on an average, at least 10 per cent, of potassa, this alkali may after all be more abundant than soda. J. T. and C. U. S. t Black's Lect. ALKALIES. 253 phur, which is often to a degree separated by the efflorescence of the soda,* in the form of carbonate. When soda plants are made to vegetate away from saline sources, the quantity of soda constantly diminishes, and eventually they afford only potash. Murray. Although soda is separated from its com* binations with acids by potash, it exceeds that alkali in its power of neutralizing acids, in the proportion of 4 to 6, or 2 to 3, its equiva- lent being 32, and that of potash 48. Mode of ascertaining the proportion of real alkali in the soda of Commerce. Take sulphuric acid of the specific gravity of 1.10, w^hich is gene- rally prepared by mixing one part, by weight, of the best acid of the shops, with six of water. Pulverize finely, an average sample ; take, say 100 grains, and add to it 2 oz. measures of pure water, agitating it occasionally, for a few hours ; after subsidence, decant, add more water, and again allow the solid matter to subside ; decant again, and filter the fluids, and lastly, wash the solid residuum on a filter, until the water drops tasteless, and no longer affects the test colors. Mix the different fluids, and concentrate them, by boiling, to the volume of 2 or 3 oz. measures. In a vial of known weight, place 2 oz. of the acid, sp. gr. 1.10, and then add it cautiously to the alkali, till effervescence ceases, and the test papers are no longer altered. Sulphur will be precipitated. Now see how much acid remains. It having been ascertained by previous trials, that 100 grains of dry alcoholic potas- sa, require 520 grains of the acid, of the sp. gr. 1.10, for saturation, and that 100 grains of alcoholic soda require 812 grains of the same acid, it is easily calculated how much real alkali there was in the por- tion subjected to examination. Trial is made also, for potash, and the test used is muriate of platinum ; there will be a yellow precipitate if potash is present ; otherwise none. If muriate of potash should be suspected, since the muriate of platinum detects all the salts of potash, it may be knovvn by adding a little sulphuric acid to the alka^ line lixivium, when there will be fumes of muriatic acid gas, if the muriate of potash is present. f SODIUM. 1. DISCOVERY. By Sir H. Davy, at the same time with potas- sium, October, 1807. * Mr. Parkes, in his essays, mentions that some dealers refuse to buy theefflores- ced carbonate of soda, thinking it to be spoiled, whereas it is really in a good degree purified. t Parkes' Cheru. Essays, Vol. II. 254 ALKALIES. 2. MODES OF OBTAINING. The same as those described for po- tassium ; only the decomposition of soda is more difficult, requir- ing a higher voltaic power, and in the process by the furnace, a greater degree of heat ; a mixture of potash and soda is more easily decomposed, and affords an alloy of the two metals. Dry muriate of soda or chloride of sodium is decomposed by po- tassium, with the aid of heat, and sodium is evolved ; it is done in an iron tube. 3. PROPERTIES. (a.) Extremely similar to those of potassium. (b.) Rather more solid at the common temperature under naptha, brilliant like silver, and quite as white. (c.) Very malleable ; by pressure of a platina blade, a globule T V or y'g- of an inch in diameter, is made to cover of a square inch, and this property does not diminish even when it is cooled down to 32. (d.) Several globules, by strong pressure, unite into one, and it is therefore capable of being welded at the common temperature, while iron and platinum require full ignition. (e.) It merely floats on ivater; the sp. gr. at 59 Fahr. is sup- posed to be 0.972, water being 1. (f.) Less fusible than potassium ; softens at 120, is perfectly fluid at 180 or 200, and readily melts under naptha. (g.) J^aporizable, but at what exact temperature is unknown, for it does not rise in vapor at the fusing point of plate glass, but is dis- tilled at an intense heat. (A.) Tarnished by common air, but not by air artificially dried, un- less heated in it. f i.) Heated to fusion, it burns with scintillations and white flame. ) On ivater, it melts, appears like a globule of floating silver, and wastes rapidly away, but without emitting light, unless the water be hot, when it scintillates and flames ; there is no combination of the sodium with the hydrogen evolved by the decomposition of the wa- ter, on the surface of which it has a rapid motion, owing to the causes mentioned under potassium. It burns in chlorine gas with bright red scintillations, and muriate of soda is the result. When plunged be- neath it, it decomposes water with violent effervescence, and a loud hissing noise ; soda is formed, and hydrogen evolved, but there is no luminous appearance. On moistened paper, or in contact with a small globule of water, as there is nothing to carry off the heat, the sodium usually inflames. The action on alcohol and ether, is the same as that of potassium. In the action of sodium on the oils, and on naptha, on sulphur, and phosphorus, on mercury and sev- eral other metals, there is almost a perfect similarity with the ac- tion of potassium. The soaps are of a darker color, and less solu- ble ; the combination with sulphur, (effected as in the case of potas- sium in close vessels filled with the vapor of naptha,) is attended with ALKALIES. 255 very vivid light, and much heat, and often explosion. The amalgam of mercury and sodium seems to form triple compounds with other metals; Sir H. Davy thought that the mercury remained in combina- tion with iron and platinum, after the sodium was alkalized, and sep- arated by deliquescence. The amalgam forms a triple compound of a dark gray color with sulphur. (k.) Inflames on the strong acids, forming salts with soda for a basis ; the nitric acid, as usual, acts with the most energy. 4. OXIDES. (a.) Protoxide. Sodium combines spontaneously with oxygen re- producing soda,* but its attraction for oxygen appears to be less en- ergetic than that of potassium ; the process is slower, and the deli- quescence of the alkali produced is not so rapid. The combination is accelerated by heat, but combustion in oxygen gas does not take place till near ignition ; it then burns beautifully with a white flame and bright sparks, and, in common air, the flame is similar to that from burning charcoal, but much brighter. Sodium heated with so- da, is said to divide the oxygen between them, producing a deep brown fluid, which, on cooling, becomes a dark gray solid, and at- tracts oxygen again from air and water.f The protoxide is produced also by burning sodium in dry common air, the sodium being in excess, or by the action of water. This protoxide is caustic soda; its color is gray, fracture vitreous, does not conduct electricity, fusible at a red heat, combines with water, with great heat, and produces hydrate of soda, which is white, crys- talline and more fusible and volatile than before. Its constitution is, 1 proportion of sodium, 24 1 " oxygen, 8 And the equivalent of anhydrous soda is 32 It combines with water, as already remarked, with great energy, be- coming a hydrate, and the water cannot be expelled by ignition. The constitution of the hydrate, 1 proportion of protoxide, 32 per cent. 22 J water. J 1 " water, 9 41 (b.) Deutoxide of sodium. Burn sodium in an excess of oxygen gas, or heat the protoxide in that gas ; the protoxide is always formed * This happens, of course, if it is not carefully kept; I have lost masses of sodium in this manner; the metal turns into white caustic soda, and eventually effloresces in the form of carbonate, at the same time enlarging its volume very much. t It is doubted whether it is not a mixture of the metal with soda. J See Mr. Dalton's table of the quantities of soda, in different solutions, Henry, Vol. I, p. 558, 10th Lon. Ed. 256 ALKALIES. first, and then more oxygen is absorbed, and the peroxide is generated. The color of this oxide is yellowish green or orange; it is fusible ; a non-conductor of electricity, and when thrown into water, it gives out its excess of oxygen. Its composition according to Davy, is sodium, - 75 oxygen, - 25 100 Its constitution is stated to be 1 proportion of sodium 24, and 1J of oxygen =12 = 36, but as this introduces a fraction, it is probable that our knowledge is not precise. The peroxide acts upon most combustible bodies with deflagration. According to some, the peroxide is composed of two proportions, of Sodium, 48 Oxygen 3, - =24 72 would then be its equivalent or representative number ; of the truth of this view, there seems to be no direct proof. 5. POWERS OF COMBINATION. They are very extensive, like those of potassium ; to which how- ever it yields an energy of affinity, as is evident in the case of the decomposition of common salt by potassium. 6. POLARITY. Like potassium, it is attracted to the negative pole in the galvanic series, and in this way it was first discovered. 7. DIFFUSION. Sodium exists very extensively in the carbonate, sulphate, muriate and other forms of soda salts ; it is found in some plants, especially marine ones, and in many stones and rocks. Remarks. The great prerogative of sodium is to attract oxygen, in which function, it is inferior only to potassium. Both these re- markable bodies are endued with such a degree of activity, and their chemical relations, are so numerous, as almost to realize the brilliant suggestion of their illustrious discover,* that they approach to the char- acter of the imaginary alkahest of the ancient alchemists. Their dis- covery has placed in our hands new means of investigation, and of beautiful and splendid experiment. Nothing could be more unex- pected, than that common salt and sea weed should contain a metal, or wood ashes another. In the present state of our knowledge, we must regard potassium and sodium as elements. As they exist abundantly in minerals, we can understand how, in the processes of * Applied by him more particularly to potassium. ALKALIES. 257 vegetable life, they should become constituent parts of plants. It has been already stated, that hydrogen has been supposed by some, to be one of their constituent principles ; a suggestion which is coun- tenanced by their levity, and by the fact, so contrary to what is found to be true in most other cases, that their oxides are heavier than the metals which they contain.* SEC. IV. LITHIA. 1. NAME. From Xidos, a stone, or Xidsios, stony. 2. DISCOVERY. Detected in the year 1818, by Mr. Arfwedson, in the petalite, which contains from 3 to 8 per cent. ; in the triphane or spodumene, ) there is 8 per cent, and in crystallized lepedolite, 4 per cent. ; it has been found also in the green and red tourmaline, and in several varieties of mica. 3. PROCESS. (a.) Fuse the powdered petalite, 1 part, with carbonate of pot- ash 3 parts, dissolve in muriatic acid evaporate to dryness digest in alcohol, which takes up the muriate of lithia and little else ; this so- lution is evaporated to dryness, and the residuum again dissolved in alcohol, which gives the muriate pure ; it is then digested with car- bonate of silver, to form carbonate of lithia ; this being decomposed by lime or barytes, gives pure lithia, which must be evaporated to dryness, away from the air.J (6.) Another process by Berzelius, is as follows : Mix 2 parts of fluor spar, and 3 or 4 of sulphuric acid, with 1 of powdered petalite or spodumene, and apply heat till the acid vapors, consisting princi- pally of silicated fluoric acid, have ceased ; thus the silica is remov- ed, and the alumina and lithia unite with the sulphuric acid, in the form of sulphate ; that of alumina is decomposed, and the earth pre- cipitated by boiling with pure ammonia. Ignition expels the sul- phate of ammonia, and the pure sulphate of lithia remains, which is easily converted into the carbonate, and the carbonic acid being ex- pelled from this, we obtain the pure lithia. * It is however sufficient to caution us against admitting conjectures in such cases, that soda was formerly suspected to be composed of magnesia and nitrogen, and Fourcroy, in his large work, has stated the reasons why he with some other chem- ists, conjectured that potash was composed of lime and nitrogen, and soda of magne- sia and nitrogen. t In the spodumene and petalite, the lithia is combined with silica and alumina; but in the lepidolite and in the lithion mica, it is combined also with potassa, and to avoid contamination with this alkali, the lithia should be prepared from the spodu- mene and petalite. Turner. t For other processes, see Ann. de Chim. et de Phys. X. 86 ; also, Henrv, Vol. I, p. 572, and Thenard, Vol. II, p. 323,4th Ed. ; Ure's Diet. 3d Ed. p. 582. * 33 258 ALKALIES. 4. PROPERTIES. (a.) Color white ; not deliquescent, but absorbs carbonic acid by exposure to the air, and becomes a carbonate. (&.) Very soluble in water, but less so than potassa and soda, and scarcely soluble at all in alcohol ; acrid, caustic, acts on colors as the other alkalies do. (c.) Heated with platinum, it acts on the metal ; place on platinum foil, with a small excess of soda, a piece of a lithia mineral as large as a pin's head, and heat it with the blowpipe for two minutes ; a dark color or dull yellow trace appears near the fused alkali, and the met- al is oxidized by aid of the lithia and the air, while it is not affected under the soda. The soda, by combining with the other principles of the stone, liberates the lithia. (d.) Lithia has a higher neutralizing power than potassa and soda, or even than magnesia ; its phosphate and carbonate are sparingly soluble, its chloride is deliquescent and soluble in alcohol, and this solution burns with a red flame ; all the salts of lithia give a red color when heated on a platinum wire before the blowpipe. " Lithia is distinguished from the alkaline earths by forming soluble salts with sulphuric and oxalic acids," and the carbonate, * although difficultly soluble in water, stains turmeric paper brown. The muriate and ni- trate are deliquescent ; the concentrated lithia salts mixed with a strong solution of carbonate of soda, deposit carbonate of lithia. Bcrzelius. Some of these properties have been mentioned in anticipation, and others are omitted or reserved for their more appropriate place. 5. DECOMPOSITION. The metallic base was evolved by Sir H. Davy, by galvanism, but it was too rapidly oxidized to be collected ; and the metal was, how- ever seen to be white like sodium, and burned with bright scintilla- tions. Composition supposed to be lithium, 56.50, oxygen, 43.50 = 100.00, or by Dr. Thomson, lithium 10, which he supposes to be its equivalent number, and oxygen 1 proportion 8 = 18, for the equivalent of the alkali. * Like the earthy carbonates, and it therefore forms an exception to the general characters, stated p. 230, (d.) I:\KTFLV 259 EARTHS. LIME BARYTA STRONTIA MAGNESIA SILICA ALUMINA GLU- CINA ZIRCONIA AND YTTRIA. Introductory Remarks. In the plan of this work, and in connexion with the alkalies, some objections have been stated to the prevailing mode of arranging most of them, and all the earths, under the metals. With . respect to the earths, this course, though highly inconvenient, would perhaps be somewhat less so than in relation to the alkalies ; but I decidedly pre- fer to preserve the old division of earths, notwithstanding the inter- esting discovery that most, if not all,* of them are metallic oxides. Here, as in the case of the fixed alkalies, there can be no difficulty in pursuing the analytical course, by proceeding from the compound to its principles, first describing the earth, and then its composition ; and reverting again to the metallic bases of the earths, when we come to the metals. The great advantage proposed in pursuing this course is, that we are, as early as possible, put in possession of a knowledge of the properties of these important bodies, and that the natural order of earths will remain unbroken ; for, as Dr. Ure (Diet.) very justly remarks, " whatever may be the revolutions of chemical nomenclature, mankind will never cease to consider as earths, those solid bodies composing the mineral strata, which are incombustible, colorless, not convertible into metals by all the ordinary methods of reduction, or when reduced by scientific refinements, possessing but an evanescent metallic existence, and which either alone, or at least when combined with carbonic acid, are insipid, and insoluble in water." Nearly the whole crust of our planet is composed of these bodies ; for, the combustibles, and alkalies, and the metals, properly so called, form but a very small proportion of the whole. Nine bodies have been distinguished by chemists, to which the name earth has been given ; they are, as enumerated at the head of this division, Lime, Baryta, Strontia, Magnesia, Silica, Alumina, Glucina, Zirconia, and Yttria. The three latter are of little consequence, either in a scientific or practical view, and seem chiefly important in determining the con- stitution of some few gems, and of a few other minerals, most of them rare. Of the remaining six, the most abundant is silica ; lime, is in this respect, the next ; then follows alumina, and then magnesia ; * The base of silica seems to have no claim to be called a metal ; should it be melted it may, perhaps, exhibit metallic properties. 260 EARTHS. these four earths constitute the great mass of our mountains, rocks, stones, gravel, and soil, and yere the five others annihilated, it would not sensibly diminish the volume of the crust of the globe. Baryta and strontia exist, however, in some quantity, and baryta, especially combined with sulphuric acid, is of frequent occurrence, although it is generally confined to veins in the rocks. As chemical reagents, lime and baryta are of signal utility ; stron- tia possesses similar properties, but has, in comparison with those earths, little that is peculiar, or that gives it a ground of preference. Silica, alumina, and magnesia are of limited use in scientific chem- istry, but they are of vast importance in the arts, and along with lime, are the foundation of the vegetable kingdom, and of agricul- ture ; as our best soils consist of different proportions of these earths ; and the varying qualities of soils, although modified in an important degree by moisture and by animal and vegetable matter, and other causes, are characterized chiefly by the predominant earths. The preceding sketch has been presented, that the student might not fail to obtain a just idea of the important natural order of earths, which it is difficult to define by unexceptionable chemical characters ; but there is no difficulty in giving clear discriminations, provided we divide the earths into groups.* The divisions under which the earths will be described, are 1. Alkaline earths. 2. One earth of a sub-alkaline character. 3. Earths proper. ALKALINE EARTHS. LIME BARYTES STRONTIA. THEIR GENERAL CHARACTERS. (a.) Soluble in water, but much less so than the alkalies. (b.) Acrid and caustic ; in light powder, irritate the nostrils, and produce sneezing. (c.) Test colors affected by them, as by the alkalies. (d.) Differ from the alkalies in their very difficult fusibility, but fu- sible by the compound blowpipe, and by galvanism. * Perhaps the only characters that will strictly apply to them all, are these 1. They are, when prepared pure by art, white powders. 2. They are not volatile by heat, and are remarkably difficult to melt, and are, both when pure, and when in combination with each other, in the stones and rocks, the most infusible and unalter- able bodies that are generally known to mankind. 3. They have oxygen for a com- mon principle, united, in each earth, to a peculiar metallic or combustible base. It is true (as suggested by a friend,) that some of the proper metallic oxides, would be covered by these characters, e. g. the oxides of columbium, titanium and cerium; but still, most of our artificial divisions, fail of rigorous exactness; the oxides them- selves graduate into the acids, but no one for that reason thinks, of blending them. There can be no good objection to dividing the numerous class of oxides into con- venient orders, which are also in a great measure natural. See Introduction, p. 3. EARTHS. 261 (e.) Not volatile by any heat hitherto applied. tf.) Form soaps with oils. (g.) In common with the other earths, combine with acids and form salts.* EARTH OF A MIXED CHARACTER. NAMELY, MAGNESIA. a.} Not acrid or caustic. b.) Applied in substance, affects the vegetable colors. c.) Nearly insoluble in water, but absorbs it. d.) Equally difficult to fuse as lime, not volatile. e.) Combines readily with acids to form salts. /.) Combines indirectly with oils to form soap. EARTHS PROPER. SILICA ALUMINA GLUCINA ZIRCONIA YTTRIA.f Destitute of alkaline properties, except that (.) They unite with acids, and form salts ; silica combines per- manently with only one acid ; i. e. the fluoric. b.) Insoluble in water ; but most of them absorb it, c.) Tasteless, innoxious, inodorous. d.) No effect on test colors. e.) Very difficult to melt, but less so than the alkaline earths $ still the alkaline earths are powerful fluxes of the earths proper, and of common metallic oxides. (/.) Not volatile by heat. (g.) In their pure state, do not combine with oils to form soap. SEC. I. LIME. 1. DISCOVERY. Familiarly known from the remotest ages. 2. PREPARATION. (a.) By thoroughly igniting, in a good furnace, in a covered crU" cible, small fragments of marble, chalk, J or shells, or other pure cal- careous carbonate of lime, (Carrara and Parian marble are prefer- red,) these substances lose half their weight or more in the form of gas and water, and if fully calcined, they will not effervesce with acids. (b.) As the natural carbonates of lime are not always pure, we may dissolve them in dilute muriatic acid ; then add ammonia, which * Even silica combines permanently with fluoric acid, and transiently and slightly with some other acids ; this earth differs in several respects from the rest, and some have even regarded it as an acid. t It is scarcely necessary to remark that Thorina, which was transiently admit- ted among the earths, has been found to be a sub-phosphate of Yttria. t Chalk is the least pure of the three. EARTHS. will precipitate the magnesia and alumina, and not the lime ; we then decompose the filtered solution by carbonate of potash, and the pre- cipitated carbonate of lime, after being washed and dried, is decom- posed by a strong heat. Common good quick lime, that has not been air slacked, answers every purpose for demonstrating the pro- perties of lime. 3. PROPERTIES. (a.) Color, white, and the masses recently from the furnace are rather hard, but brittle. When dry, not active on the animal organs, but if moistened, lime acts as a caustic ; taste astringent and alkaline. (6.) Specific gravity 2.3. (c.) Soluble in water: writers vary in stating the proportion, be- tween 450 and 778 parts of water for the solution of 1 part of lime, or 558 for the hydrate : 500 is the number heretofore adopted ; pro- bably 700 may be near the truth ; but it appears that only a weak lime water is obtained by using water at 212, which dissolves only TTTTF f ^ e H me ana " JT f th e hydrate, while at 32. Accor- ding to Mr. Dalton* and Mr. R. Phillips, it takes up i^, or nearly double, and when the solution is heated, it becomes troubled, and lime is deposited. These facts are not in accordance with the gen- eral laws of solution when it is aided by heat. (c?.) Lime water: its taste is acrid and disagreeable, and it produ- ces upon test colors the effects of alkalies ; it is not however caustic, and there is so little of it contained in the water that it may be swal- lowed with safety, and often with advantage. It is a valuable reagent and medicine ; it is prepared by simple solution of lime, in w r ater ; it must be preserved in close bottles from the atmosphere, } otherwise it precipitates as a carbonate. (e.) Lime water^ is made to afford crystals, if placed in a vacu- um, under the receiver of an air pump, the evaporation being aided by sulphuric acid, contained in another vessel; the process is gradual, and depends on the same principle as the congelation of water by the same means, (see page 116.) The crystals are transparent hexahedra, and are true hydrates, containing lime, 76.26, water, 23.74=100.00.J Lime water forms an imperfect soap with oil. * Ann. Phil. N. S. I. 107. t Place in a clean carboy, a quantity of good hydrate of lime ; fill the vessel with rain water ; agitate it, and allow the lime to subside over night ; it will be dissolved in one fourth of an hour, and in the morning it may be drawn off clear by a syphon, or filtered through paper if it is wanted immediately ; if the cork be good, and the water is not allowed to freeze, the same arrangement, adding water from time to time, will answer for years. t Ann. de Chim. et de Phys. I. 335. EARTHS. 263 (/.) Slacking of lime. In this familiar process, the earth com- bines with about one third of its weight of water, forming a true hy- drate ; and in this condition, lime kept secluded from the air, is in the most useful state for the laboratory. The water may be again expel- led by a red heat, contrary to the fact in the case of the hydrates of potassa and soda, and of baryta and strontia. The heat, (about 800, Dalton,) arises from the solidification of the water, and is much more than the latent heat of the water, because ice or snow and lime slack, with energy, and give out a heat of 212. Light sometimes appears, when the slacking is performed in a dark place ; I have seen it from the Carrara marble.* If fragments of good lime be placed in a quart tumbler, filling not more than one third of it, the tumbler resting in a dish, the proper quantity of water being sprinkled over it, and a tall bell glass covering the whole, the vapor will rise in a dense cloud ; it will soon produce currents like rain, down the sides of the bell, which will become clear, as soon as it attains the boiling heat, and the steam will then blow out powerfully under its sides: when the bell is lifted out of the dish, the cold air will again produce a thick cloud. (g.) Milk or cream of lime, is the hydrate brought to the consist- ence of paste with water, and thus mechanically suspended : it is very useful in purifying gases from carbonic acid ; they are, for this purpose, made to pass through the milk of lime, the large quantity of the earth being much more effectual than lime water, which is how- ever, very convenient in small experiments. (A.) Lime is mechanically raised in slacking, as is perceived by the odor, and by the effect on test paper, placed in the steam that ri- ses from it. (i.) Lime absorbs moisture from the air, falls to powder, and be- comes a true hydrate, f (/.) The mere water-slacking of lime does not destroy its activity ; its peculiar powers are blunted or suspended by air-slacking, the cause of which will be explained under the history of the carbonate. 4. FUSIBILITY. Extremely infusible; first partially melted by Dr. Hare's compound blowpipe, in Philadelphia, and in 1812 more perfectly, in the laboratory of Yale College. J The lime must be shaped into the form of an acute cone, not over the size of a large pin, and the focus of heat must be directed upon the apex ; when it softens, subsides, and is soon covered with a vitreous glaze. Fusible also in the galvanic current. The light emitted by lime, in the focus of heat, is most intense ; it has been used with a stream of oxygen gas, * Jn a dark cellar, in JMr. Acoum's house, in London, some lime of Carrara mar- ble, during its slacking, showed luminous points of mild white light. 1 It also absorbs carbonic acid, and loses its causticity. t Afterwards by Sir H. Davy, by Galvanism. 264 EARTHS. directed through the flame of an alcohol lamp, for the purpose of producing a signal light, which can be seen at a great distance. 5. POLARITY. It is attracted to the negative pole in the galvanic circuit, and is therefore electro-positive. 6. Combining weight, 28, as will be seen more particularly under calcium, the basis of lime. 7. PHARMACEUTICAL PREPARATION. This is the same that has been already described in giving the process for quick lime. CALCIUM. 1. DISCOVERY. In 1808, in Sweden, by Prof. Berzelius and Dr. Pontin ; afterwards obtained by Sir H. Davy in England. The- nard attributes the first observation to Dr. Seebeck. 2. PROCESS. (a.) A cup or capsule, made of moistened lime, or sulphate of lime, containing a globule of mercury, is placed on a metallic dish; the negative wire of the galvanic battery of 100 pairs, in good action, is made to touch the mercury, and the positive wire is brought in contact with the under side of the metallic support. An amalgam of mercury and calcium is formed, but the process must be continued a good while in order to obtain any manageable quantity ; in a small (green*) glass retort, or tube closed at one end, this amalgam is dis- tilled, with naptha, which rises first, then the mercury, and the cal- cium remains in an atmosphere of vapor of naptha, for which nitro- gen may be substituted. (b.) When potassium, in vapor, was passed through quick lime heated to whiteness, the potassium acquired oxygen, and became potash, and a dark gray substance, with metallic lustre, was found imbedded in the potash, and it was evidently calcium, more or less perfectly reduced, because it effervesced violently in water, and formed a solution of lime. 3. PEROXIDE. This is formed when oxygen gas is passed over lime ignited in a tube ; the exact proportions are not known, but it is supposed to contain twice as much oxygen as the protoxide. In the moist way, the oxygenized water of Thenard forms the same peroxide. 4. PROPERTIES. Little known. (a.) Color, white, like that of silver, and with the same lustre ; sinks in water. (b.) Ignited in a tube in which the distillation of the amalgam was going on, it took fire when the tube broke, and burnt with an intense * Because white glass contains oxide of lead, whose oxygen would change the calcium to the state of oxide, or lime. EARTHS. 265 white light, into quick lime. When the amalgam of calcium was thrown into water, hydrogen gas was evolved, and lime water re- mained. (c.) Lime is the protoxide, of calcium. Its composition is estima- ted by Berzelius at calcium, 71.73, oxygen, 28.27 = 100.00. Thenard says, that it ought to contain by calculation, 39 of oxygen. 5. ITS EQUIVALENT WEIGHT is stated at 20, and therefore, oxygen being 8*, lime, or the protoxide is represented by 28. 6. POLARITY. Electro positive ; it goes to the negative pole in the galvanic series. 7. USES OF LIME. They are numerous and important. In med- icine, the caustic earth is not used, except to prepare lime water ; in the solid form, the pure earth is too acrid for internal use ; it was formerly used as an escharotic, and its caustic properties are still employed in removing the hair from skins, preparatory to tanning. It is almost constantly used in the laboratory ; in the form of lime water, it is an important reagent, and we have seen that it is employ- ed to disengage the alkalies in a caustic state ; it is largely used for the same purpose in soap making. In a word, it is of great value in medicine, in architecture, in agriculture, and in many arts. Mortar is a mixture of sand, or gravel, or both and lime ; in the proportions of fine sand 3 parts, coarse sand 4, quick lime 1, recent- ly slacked with as little water as possible. It is well to add some pulverized lime, that has not been slacked ; it absorbs water, and solidifies the other ingredients. Roman mor- tar was made of the same materials as the modern, but of the best quality, and accurately proportioned ; time has done much to give it hardness. According to Pliny, the Romans made their best cement a year before it was used, so that it was partly combined with carbonic acid before it was laid in the work. In old Roman stone buildings, the stone will often break as soon as the mortar. Another recipe for mortar. Fine sand, 3, brick powder, 3, (well baked,) slacked lime, 2, unslacked lime 2. If very little water be used, the mortar sets the sooner. Burnt bones, not exceeding one fourth part, improve the tenacity of mortar. Manganese and puzzolana cause mortal- to harden beneath the water. Puzzolana is decomposed lava, and consists of silica, alu- mina, and oxide of iron. The mortar for the Eddystone light-house on the S. W. coast of 'Cornwall, (Eng.) was composed of equal parts of slacked lime and puzzolana. For 71.73 : 28.27 : : 100 : 39.4 and 39.4 : 100 : : 8 : 20.3. Henry. 34 266 ' EARTHS. Manganesian and ferruginous limestones are valuable in this respect, and a portion of silica and alumine in the composition of the lime- stone improves it for these purposes.* Recipe for water mortar. f Blue, clay, 4 parts, manganese, 6, limestone 90, and all in powder ; calcine, mix with sand 60 parts, and form it into a mortar, with water. The tarras,J used for the con- struction of dykes in Holland, is merely an ancient decomposed lava from the extinct volcanos on the Rhine ; some call it a decomposed basalt, and it is certain that the rocks of this family, are effectual in this way, if previously decomposed, or calcined, so that they can be broken down and intimately mixed with the lime. Parker's ce- ment is composed of silica, 22, alumine, 9, oxide of iron and manga- nese, 13, carbonate of lime, 55 = 99, and there was in the analysis a loss of 3.25. The white cement used in New Haven to cover stone houses, is composed of the best slacked lime, 1 part, by measure, and from 3 to 5 measures of coarse siliceous sand and some hair, well beaten together, and laid on with a trowel ; the workmen pre- tend to add sugar, and various salts, particularly the sulphate of pot- ash ; but having tried the mortar, both with and without these addi- tions, I am persuaded that they are of no importance, and that the cement of coarse sand, hair and lime, alone, will stand any length of time, provided water does not get beneath ; if it does, the first freez- ing will crack the mortar, and throw it off. Lime is of great use in Agriculture. In the form of carbonate of lime, it is often mixed with soils, and will be mentioned again. In the state of quick lime it is largely used in England, where it is com- mon to see extensive tracts covered with heaps of it. || It appears to be a part of the food of plants, as it is found in the ashes of most of them, and it may be also a stimulus to vegetable life. Its immedi- ate action, when caustic, is to destroy vegetable organization, and it appears to act as a manure, principally by decomposing hard dry * Hydraulic lime of the state of New York, contains according to Dr. Hadley's analysis, carbonic acid 35.05, lime 25, silex 15.05, alumine 16.05, water 5.03, oxide of iron 2.02. Am. Jour. Vol. Ill, p. 231. t Hydraulic lime is found at Southington, Connecticut, near the canal, and in many places on the Erie Canal. See Am. Jour. Vol Xlll, p. 382. i The proportions said to be used in Holland, are tarras 1 part, and slacked lime 2 parts. I saw them preparing the trap rocks in this manner, at Greenock, where (1806,) they were making hydraulic mortar for a dock. The porous and vesicular trap which they used was from the neighboring isle of Arran. That in East Haven, which is crumbly, and used for mending the roads, and the vesicular trap near Hartford, (see Am. Jour. Vol. XV 11, No. 1,) would in all probability answer the same purpose, and it may be found of the same character in many other places in our trap regions. Th more vesicular, and the more decomposed it is, the better, because it is the more easily pulverized by calcination and grinding. I) Extensively used in Pennsylvania, and highly valued. J. G. Not much used in New England. EARTHS. 267 vegetable fibres, and thus rendering them soluble ; even tanner's bark is decomposed by lime, and rendered useful as a manure ; it is thought to be injurious with animal manures, unless they are too rich, and need to be in part decomposed.* SEC. II. BARYTA. Name from the Greek /3apu, heavy. f 1. DISCOVERY. By Scheele, in Sweden, in 1774; formerly confounded with lime. 2. PROCESS. (a.) Native, or artificial carbonate, in powder, mixed with lamp- black and oil, in a ball, is strongly calcined in a crucible, for one hour, by the heat of a forge or wind furnace, and the carbonic acid is thus decomposed, or expelled. Boiling water dissolves out the caustic earth. The theory of the process will be rendered more in- telligible hereafter. (b.) By calcination of the nitrate of Barytes ; see that salt. 3. PROPERTIES. (a.) Color, gray before slacking; consistency, porous ; after slack- ing, a white powder ; sp. gr. 4. (b.) Taste acrid and caustic ; poisonous. (c.) Affects the test colors, as lime and the alkalies do. (d.) The hydrate is fusible in its own water, of which it contains about 9 or 10 per cent. (e.) Baryta, even when obtained from the nitrate, is fusible by the compound blowpipe.f (f.) Water causes it to slack with much greater energy than lime ; the phenomena and theory are the same, but much more strik- ing, and light is said to be sometimes emitted. The water slacked baryta, is a true hydrate, and as the earth is represented by 78, and there is one proportion of water in the hydrate, the equivalent num- ber is of course 87. It slacks in the air, as lime does, and for the same reason. It dissolves readily in 20 parts of water at 60, and if boil- ing, in 2 parts. (i.) On cooling, it forms regular crystals flattened hexagonal prisms. *a 13 vi if:} * See Davy's Agricultural Chemistry, and Ure's Diet. t The natural sulphate is known to the miners, by the name of heavy spar. t Respectable authors state that baryta thus prepared is infusible, but they had probably not tried the compound blow-pipe. The observation is attributed to Dobereiner, and it will not appear very extraor- dinary, since lime sometimes exhibits light while slacking, although the energy of the action is much less remarkable. 268 EARTHS. i/.) They contain, according to Dalton, 70 per cent, of water, lose 50 by ignition ; their constitution is, according to the same author, baryta 1 proportion 78, and water 20 proportions or 180, and their equivalent number is 258 ; they melt in their own water, or suffer the aqueous fusion ; after ignition, the dry powder which remains, slacks again with great energy. (k.) Crystals soluble in 17J times their weight of water. (/.) Burning alcohol, although it does not dissolve this earth, re- ceives from the crystals a yellow tinge, but this is better exhibited in the flame of the compound blowpipe, in the focus of which, every form of baryta, not excepting the sulphate, exhibits this characteristic color in the most striking manner. (m.) Barytic water is a very useful reagent ; it should be kept stopped from the air, otherwise it is precipitated in the form of an in- soluble carbonate. It produces all the effects of the alkalies upon the test colors. (n.) Solution of baryta forms a soap ivith oils ; its salts also form soaps if mingled with aqueous solutions of alkaline soaps. (0.) Dust of the earth irritates the nostrils as it rises. 4. POLARITY electro-positive, it resorts to the negative pole of the galvanic battery. 5. COMBINING WEIGHT, 78, the elements of which may be seen under barium. BARIUM. 1 . Obtained in the same manner as calcium, using native carbonate of baryta or the pure earth,* made into a paste with water, a globule of mercury being placed in a little hollow made in its surface ; the paste was laid upon a platinum tray in connexion with the positive wire of a galvanic battery, while the negative wire touched the mer- cury. The mercury is distilled off in the same manner, but it is very difficult to obtain the metal, f 2. PROPERTIES. (a.} Metal of a dark grey color,'^ with less lustre than cast iron. (b.) Solid at the ordinary temperature, but becomes fluid below ignition. (c.) Near redness, rises in vapor, and acts violently on the glass. * Oxide of mercury may be used in obtaining the metals of the earths; one third partis mixed with two thirds of the earth, and galvanized, when an amalgam is formed with the metallic base. t Dr. Clarke states that he obtained the metal from the nitrate, by the compound blowpipe. I mentioned in the memoir published in Bruce's Journal, in 1812, that the metallic bases of both baryta and strontia, appeared to me to be evolved, and to dart out in bright scintillations, when the earths were in the focus of the instrument, but as they always burned away, I was notable to collect the metals. t " White color, with metallic liK-fie, having a resemblance to silver.". Murray. EARTHS. 269 (d.) In air, becomes covered with a film of baryta, and in water un- dergoes the same change; effervesces violently and evolves hydro- gen. If gently heated in air, it burns with a deep red light and be- comes baryta. (e.) Sinks in water, and even in sulphuric acid, although surround- ed by gas ; hence its sp. gr. cannot be less than 2, probably over 3. (/.) Flattened with difficulty by pressure. (g.) Constitution of the protoxide, about 89.75, metal, 10.25 oxygen=100.00. Barium, 1 proportion, 70, oxygen, 1 proportion, 8=78. (h.) PEROXIDE OR DETJTOXIDE. Baryta, prepared by ignition of the nitrate, is placed in fragments as large as a hazel nut, in a coated glass tube, and heated to low redness, when it rapidly absorbs dry oxygen gas as it is passed over it and becomes peroxide with prob- ably two proportions of oxygen ; it is formed also by heating ba- ryta in contact with oxygen or common air resting upon it, but in the latter case some carbonate is also formed. Concentrated barytic water becomes filled with pearly plates of the deutoxide of barium, when oxygenized water, containing ten or twelve times its volume of oxygen is poured into it. Thenard. Composition of the peroxide. Barium, 70, oxygen, 2 proportions, 16 = 86; the peroxide contains twice as much oxygen as the pro- toxide. It has been found that the nitrate of baryta may be decomposed by heat with such care, that the deutoxide is left ; it is done in a lu- ted porcelain retort, connected by a Welter's safety tube with an in- verted jar of water. The heat is gradually raised to redness, as long as nitric oxide or nitrogen gas is disengaged, and when they cease and pure oxygen comes, it is a proof that all the nitrate is decompos- ed, and then the deutoxide will remain in the retort. Turner. (i.) The deutoxide of barium is scarcely sapid, it is grayish white, loses its excess of oxygen by an intense heat, and acts with the aid of the same agent upon various combustible bodies, and thus becomes a protoxide. In contact with hydrogen near a red heat, there are luminous jets from the surface of the deutoxide, but the water that is formed is all retained in the state of hydrate, and the baryta thus becomes very fusible. Boiling water causes the excess of oxygen to escape in the form of gas. (/.) This substance was employed, (July, 1818,) by Thenard, for the oxygenation of water.* Baryta is poisonous ; its natural carbonate is employed in Lan- cashire, (Eng.) as a ratsbane. * See this work, p. 215, and Henry, Vol. I, p. 264, 10th Lond. Ed. ; also, Ann. dc Chim. et de Phys. VII. IX ; Ann. of Philos. XIII, XIV, XV, and Quarterly Eng. Jour, of Science, VI. 150, 379, VIII. 114, 154. 270 EARTHS. Pure baryta is useful to the chemist as a test, particularly for the discovery of carbonic acid, either free or combined. Its muriate is used by physicians in scrofula, &ic. The sulphate is the most abund- ant form, and it is convertible into every other, by certain processes which will be mentioned in their proper place. 3. POLARITY Electro-positive ; it resorts to the negative pole in the galvanic circuit. 4. COMBINING WEIGHT, 70. This is the number of Dr. Thom- son. Berzelius states it at 50.66, but the former number is gene- rally adopted. SEC. III. STRONTIA. 1. NAME. From the lead mine of Strontian, in Argyleshire in Scotland, whence the minerals containing it were first brought. 2. DISCOVERY. By Dr. Thomas Hope,* then and still, professor of chemistry in the Univ. Edin. Anno. 1791. 3. PREPARATION. The same as that of baryta. f 4. PROPERTIES. (a.) The result of the igneous decomposition of the nitrate is a grayish porous substance ; sp. gr. approaching that of baryta. (b.) With water, slacks violently, like baryta and lime, and the theory is the same ; the powder of the dry substance irritates the nostrils and lungs. (c.) After slacking, no more water being used than is necessary, the earth remains in the form of white powder ; it is then a hydrate consisting of strontia, one proportion, 52, and one of water 9=61. The hydrate fuses readily at ignition, but is not decomposed by the strongest heat of a wind furnace. (d.) More water being added, it dissolves in about 40 parts ; if the water be boiling hot, it dissolves in 20 parts of that fluid, and crys- tals are formed on cooling, having the form of thin quadrangular plates, sometimes square, oftener parallelograms, not over J of an inch in diameter.J (e.) After being heated, the dry earth remaining, is about 32 per cent. ; the crystals contain 1 proportion of earth, 52, and 12 of wa- ter, 108=160. (/.) At 60, soluble in 51 J parts of water ; boiling water takes up half its weight. * Dr. Crawford observed a difference between the muriate of strontia and that of baryta, in 1790. Klaproth confirmed the views of Dr. Hope. t Vide Edin. Trans. IV, 44. t In both cases, the decomposition of the sulphate is the cheapest process ; see the articles sulphate of baryta and sulphate of strontia. The carbonate is managed with the greatest ease. EARTHS. 271 The composition of the hydrate of strontia according to Dalton, is 1 proportion of earth and 12 of water. (g.) Strontia imparts to the flame of boiling alcohol, a blood red color ; its effects on the test colors are the same as those of baryta, lime, &ic. !h.) No union with fixed alkalies or baryta. i.) Heat readily separates the water from the hydrate, and from the crystals. ( /.) The compound blowpipe melts the earth itself,* with the char- acteristic red flame. (k.) This blowpipe produces a similar flame from every combination of strontia, even from the native minerals. (L.) DISTINCTIVE CHARACTERS cannot be confounded with any thing except baryta, but it is lighter than that earth, less caustic, and attracts acids less powerfully ; the strontitic salts being decomposed by baryta, produce different combinations with acids, are less poison- ous, and give a different colored flame. 5. POLARITY. Like that of baryta, electro-positive, and of course it is attracted to the negative pole in the galvanic series. 6. COMBINING WEIGHT, 52 composed of strontium one propor- tion, 44, and oxygen one, 8 = 52. STRONTIUM. 1 . Obtained from native carbonate of strontia, by the same pro~ cesses as those which afford barium; discovered by Sir H. Davy, in 1808. 2. PROPERTIES. (a.) Similar to those of barium ; has less lustre ; difficult to fuse ; not volatile. (b.) Action of air and of water, converts it into strontia; in wa- ter, it produces hydrogen gas. (c.) Proportions of the constituents of the protoxide. Strontium, 84.54, or 1 equivalent, 44 Oxygen, - - 15.46, or 1 - 8 100.00 52 3. THE DEUTOXIDE OR PEROXIDE of strontium is obtained in pre- cisely the same manner as that of barium. According to Thenard, (II, 314,) it is best obtained by the action of the oxygenized water, or deutoxide of hydrogen upon strontia water; the peroxide of strontium precipitates in brilliant pearly crystals. This oxide, by * First effected by Dr. Hare, 18023. See Phil. Trans, of Philad. It is one of the most refractory of natural substances. 272 EARTHS. heat, even that of a lamp, gives up its excess of oxygen, and becomes protoxide. It acts like the nitrates upon burning coals, causing in- creased combustion. When it is moist, it gradually loses the oxygen, and rapidly in hot water. It appears to contain just twice as much oxygen as the protoxide or strontia. 4. COMBINING WEIGHT. This is estimated at 44. 5. POLARITY. Electro-positive; resorts to the negative pole of the galvanic battery. 6. USES, &tc. Strontia has the same uses in chemistry as baryta. It is a test for carbonic and sulphuric acids ; as a natural production, it is more rare, especially its carbonate ; its sulphate is found abund- antly in Put-in-Bay, Lake Erie ; at Detroit, Mackinaw, Lockport, &c. The salts of strontia are not poisonous ; the pure earth is acrimoni- ous like the other alkaline bodies. The natural and artificial compounds of baryta, are heavier than those of strontia, and there are various points of difference found in their combinations. The nitrate of strontia is used to give a blood red color to artificial fire works.* SEC. IV. MAGNESIA. 1. DISCOVERY. In the beginning of the eighteenth century, ex- posed for sale as a panacea at Rome, by a canon, who called it pow- der of Count Palma ; but Dr. Black, in 1755, was the first person who distinguished it clearly from other substances. 2. PREPARATION. (a.) In the arts. From the muriate and sulphate of magnesia, found in sea and saline water ; they are decomposed by alkalies, or usually by their carbonates ; magnesia may be extracted by acids from magnesian stones, and the salts thus obtained can be decomposed as above. (&.) In Chemistry. Ignite the common carbonate of the shops, or dissolve the sulphate and decompose it by any alkali or alkaline carbonate, wash thoroughly, and ignite the precipitate. 3. PROPERTIES. (a.) In light spongy masses, or in a friable powder, which forms with water a paste destitute of cohesion ; the carbonate is commonly seen in cubical cakes. (b.) Sp.gr. 2.3; still the cakes float awhile on water, till they are filled by absorption. (c.) Taste insipid, or slightly earthy ; lime mixed with it some- times communicates to it a slight degree of acrimony. (d.) Mild, harmless, and without corrosive action on the living or dead animal organs. * Ure, 2d Ed. 743. EARTHS. 273 (e.) Effects the most delicate test fluids ; if mixed with them in substance* e. g. cabbage infusion, violet tincture, and that of tur- meric ; but it is not sufficiently soluble in water, to impart the same power to that fluid. (/.) Does not slack ivith water. (g.) Nearly insoluble in that fluid, which takes up about 5 T Vj at 60, and at 212 ^i^.f (A.) Absorbs water, so that 100 becomes, in weight, 118; heat drives the water off, and the magnesia contracts again. It forms a hydrate with water, but it unites with this fluid without any sensible heat, and it is easily driven off at ignition. (i.) Precipitated from acids in the state of hydrate containing probably one third water. (/.) This hydrate, dried by a very gentle heat, is transparent: it is supposed to contain 1 equivalent of magnesia 20, and 1 of water, 9=29. (k.) Native hydrate, of Hoboken, New Jersey, contains about 30 per cent, of water. (I.) Alkalies do not combine with magnesia ; alkaline earths unite with it by heat. (m.) Of very difficult fusion; first melted by Dr. Hare's blow* pipe, in the laboratory of Yale College. J (ra.) Those minerals in which it is a large ingredient, are very infusible ; hence soapstone is used in furnaces. (0.) With lirne, in excess, it melts in furnaces ; for the lime, al- though itself infusible, acts as a flux. 4. POLARITY. Magnesia goes to the negative pole, and is there- fore electro- positive. 5. COMBINING WEIGHT. Theory estimates it at 20 ; of which 12 is assigned to magnesium and 8 to oxygen, being 1 proportion of each. 6. CHARACTERISTICS. Its sulphate is very soluble, while those of lime, baryta and strontia, are very insoluble : its nitrate and mu- riate are very deliquescent,^ and soluble in alcohol : the bi-carbonates of potassa and soda do not precipitate it, on account of the carbonic acid. || Oxalate of ammonia, which readily precipitates lime, does not precipitate magnesia, if the solution is moderately diluted. Turner. 7. USES. Magnesia is a very useful article of the materia medica; it is used as an antacid and cathartic. It seems however to be nearly inoperative, unless there is acid in the stomach, or unless acid is taken after it: all the salts of magnesia are bitter and cathartic. * Probably this effect is, in some cases, owing to the fact, that the alkali used in decomposing the raagnesian salt has not been perfectly removed by washing. t Fyfe, quoted by Henry. t Con. Acad. Trans. Am. Jour. Vol. II, p. 290. The nitrate of lime is deliquescent. The same is true, in a good degree, of liinc. 35 274 EARTHS. The carbonate is most commonly used, but the pure earth, sold un- der the name of calcined magnesia, is sometimes preferred, because no gas is extricated from it in the stomach. Magnesia sometimes forms large and dangerous accumulations in the bowels, of several pounds weight, particularly when its use has been long persevered in, and the earth has not been duly evacuated, by acids, forming with it saline combinations. It sometimes enters into the clays, and other materials which go to form porcelain, in the fabrication of which, on account of its infusibility, it serves a valuable purpose. It is one of the four earths which form a large part of the crust of this planet. Soapstone owes its peculiar properties to magnesia, particu- larly its infusibility : magnesian stones, such as soapstone and talc, are much employed, not only to resist fire, but because they are so easily wrought by tools into any desired form.* They are used in building- MAGNESIUM. 1 . Obtained in the same way as the other metals of the earths. 2. A white and brilliant solid ; (a little mercury still remaining in combination with it.) 3. Sinks rapidly in water, although surrounded by bubbles of gas. 4. Both in air and water reproduces magnesia ; in air gains weight, as the balance proves, both with respect to this and other earths. 5. POLARITY. Magnesium goes to the negative pole, and is there- fore electro-positive. 6. The combining weight is estimated by Dr. Thomson at 12, and this, with 1 proportion of oxygen, forms magnesia, which is the only known oxide of magnesium, whose equivalent is of course, 26. There can be no doubt that magnesia is a metallic oxide. Hitherto chemists have been unable to make it absorb more oxygen. SEC. V. SILICA. 1. NAME. Sttev is the Latin for flinty which is composed of this earth, nearly pure ; limpid rock crystal is almost pure silica, and sev- eral other siliceous minerals, as chalcedony, carnelian, opal,, agate, &c. consist principally of this earth. The purest white sand contains little else : in the form of quartz it constitutes mountain masses, and ki that of sandstone vast strata. * Savage nations are acquainted with these uses : many of their containing ves- sels, especially vessels for cookery, are made of these minerals. After the abori 4 - gines of this country became acquainted with the Europeans, they made bullet moulds of soapstone ; they were ingeniously arranged in halves, with a regular mouth , and were tied together by withes ; I have such a specimen. Soap stone is also used fte diminish friction in machinery. Am* Jour. Vol. XIV, p. 376. EARTHS. 275 2. PREPARATION. (a.)Flint or rock crystal, ignited, thrown into water, and pulver- ized, affords silica sufficiently pure for every common purpose. (b.) But the more correct process is, to mix these powders with 3 or 4 parts of carbonate of potash or soda,* and to melt the mixture in a crucible, giving a higher heat, for half an hour or an hour, to- wards the last, and stirring it to prevent overflowing. f (c.) Caustic potash or soda is, of course, more energetic in its ac- tion, but is more expensive ; there is however an advantage in using caustic alkali, as it does not intumesce ; if a silver crucible is used, it should be thick, that there may be the less danger of melting it. (d.) Dissolve the melted alkalino-siliceous mass in water, filter, and add diluted muriatic or sulphuric acid as long as precipitation continues ; the acid must be added in excess. J (e.) The solution was formerly called liquor silicum, liquor of flints; the vitreous mass from which it is obtained is deliquescent, and if the solution formed from it is dilute, and the acid is added gradually, the alkali may be saturated without precipitating any of the silica, but by evaporation to dryness the silica is rendered insoluble ; the salt formed by the alkali may be dissolved out, and the earth thus obtained pure after ignition. (/.) If the proportions of alkali and earth are reversed, then the compound produced is glass ; of which mention will be made again. 3. PROPERTIES. White, insipid, harsh. 7V0 effect on test colors, no causticity, or any alkaline proper- ty, except its union with a single acid, the fluoric. (c.) Water does not directly dissolve silica, nor is it absorbed by that earth, but when it is newly precipitated, it retains 26 per cent, of water, at 70 Fahr. (d.) When dry it is insoluble in water, but when just precipita- ted, it is dissolved by that fluid, in the proportion of about ToVT$ an( ^ and if taken in its nascent state, || it is even largely dissolved, and a * Dry pearl ashes will do. t It is recommended to dissolve the alkali first, in as little water as may be, to mix it with the silica, evaporate to dryness, and then fuse it, which may be done in a silver crucible. From my own experience, I should however recommend caution in the use of silver vessels, as they melt at about the degree of heat which produ- ces the combination between the silica and the fixed alkali. t Dr. Henry remarks, " the alkaline liquor must be added to the acid, and not the reverse ; for, in the latter case, the precipitate will be glass and not silica." Vol. I. p. 642, Mh ed. Found naturally dissolved, as in the Geysers in Iceland, in which the solution is aided by soda, contained in the water: in the similar hot fountains of the Azores, silica is found in solution, &c. there are natural hydrates, and the immense num- ber of crystals of quartz, evince that silex has been in solution on a great scale. || Particularly when the sulphuret of silicium is dissolved in water, and the silica is regenerated by the oxygen of that fluid, while its hydrogen is evolved, combined with sulphur. 276 EARTHS. bulky gelatinous hydrate is obtained, by a gentle evaporation : it is decomposed at a common temperature, but entirely at ignition. Dr. Thomson,* has shown that there are several hydrates of silica. (e.) Insoluble in acids, except the fluoric, which attacks it with great energy. (f.) When newly precipitated, soluble to some extent, in several acids, and readily forms triple salts. Dr. Marcet recommends to precipitate it with muriate of ammonia. (g.) Specific gravity 2.66, (h.} "" Infusible in any furnace, but readily melted by the compound blowpipe ; this was done originally by Lavoisier, with oxygen gas directed upon burning charcoal ; afterwards, and often, by Dr. Hare, and in the laboratory of Yale College :f it forms a perfect glass. (h.) Silica, minutely divided, is dissolved at a boiling heat, by caus- tic fixed alkali; the alkali should be twice the weight of the silica; after evaporation, the white puffy mass forms a clear solution with warm water, as already mentioned under (e.) (i.) Silica is hard, and when rubbed between two plates of glass wears them so as to spoil their polish. 4. POLARITY. I believe it is not distinctly determined. Several chemists of eminence regard silica as being an acid rather than an earth. This opinion is founded upon the fact that it satu- rates the fixed alkalies, and that in its natural combinations, it sat- urates the other earths. It has therefore been called the silicic acid, and its compounds, silicates. This however, appears to be a forced arrangement. In every other particular, silica is quite foreign from the nature of acids, and as regards its combinations with earthy and alkaline bases, it is not uncommon for one oxide to unite with another ; the alkalies dissolve many metallic oxides, and potassa and soda readily dissolve alumina, and should therefore, upon this prin- ciple be called acids. The student will, however, do well to remem- ber that the silicates mentioned in modern books, and frequently in the analyses of minerals, are compounds of silica with bases. Wheth- er we regard silica as an earth or an acid, there appears no reason why these combinations should not take place in definite proportions, such as are actually found to exist. 5. COMBINING WEIGHT. According to Dr. Thomson, it is 16, of which one proportion is oxygen, 8, and one silicium, 8. Accord- ing to Berzelius, it is 1 proportion of silieinm, and 3 of oxygen. * First Principles, Vol. I, p. 191. t Not first by Dr. Clarke, as stated by Dr, Henry. Vol. I, p. 643. 10th London cd. EARTHS, 277 SILICIUM, OR SILICON.* Remark. The student may omit this head until he has studied the fluoric acid, and its compounds. 1. PROCESS. (a.) Iron seven parts, silica five, and from { to f of soot, fused in a blast furnace, gave an alloy of silicium and iron. (b.) Purified potassium, when heated in silicated fluoric acid gas ? burns, condenses the gas, and gives a brown substance. (c.) This boiled in water, and dried, burns in oxygen gas, and produces only silicated fluoric acid, and silica. (d.) " The residue, treated with fluoric acid, gave silicated fluoric acid, and its color was rendered much darker." (e.) " Thrown on a filter, washed and dried, it was pure silicium, which may be obtained also by heating potassium in a glass tube, with dry silicated fluate of potash." (/.) " The product by being well washed with water, yields a compound of silicium and hydrogen, from which the latter may be detached by heating in a crucible. "f 2. PROPERTIES. (a.) Color, deep nut brown, without lustre, and acquires no bril- liancy from a burnisher ; no resemblance to a metal ; resists friction like an earthy substance. Incombustible, in common air, or even in oxygen gas.J * Sir H. Davy, (as already mentioned with respect to lime,) by driving the potassi- um through the earths heated intensely, succeeded so far in decomposing several of them, that the mass exhibited metallic points, and the potassium became potash. No considerable masses of metals were obtained in this way, but in general there was sufficient evidence that they were decomposed, and in this manner he was the first to ascertain that silica is a compound of oxygen and a base. t Ann. de Ch. etde Phys. Vol. XX VII, 337. Am. Jour. Vol. IX, p. 377. Hen- ry, Vol. I, p. 641, 10th Ed. The best method of decomposing silica, is by taking it in the form of double fluale of silica and potash or soda; the latter is preferred, because it contains the greatest quantity of silica. To prepare it, the; aqueous solution of silicated fluoric acid is mixed with the carbonate of soda, when the double salt, which is nearly insoluble, precipitates, and is washed and dried at a heat above 212. This is stratified with thin slices of potassium, in a glass tube, hermetically sealed at one end, and the mass must be uniformly heated, and at once, by a spirit lamp. Even before ignition the silica is reduced with a hissing noise, and some appearance of heat, but if the matter is dry no heat is evolved. The resulting brown mass, after being thoroughly freed from acid and saline mat- ter, by water repeatedly applied, at first cold, and in abundance, and at last boiling- hot, is then ignited, to expel hydrogen. It is then washed in diluted hydro-fluoric acid, to remove any siliceous particles, and is again washed and dried. For the de- tails see Ure's Diet 2d Ed. p. 718, and Ann. of Phil. Vol. XXVI, p. 116. t When first obtained, and before it is freed from hydrogen, it burns when heated, even in the open air, but if carefully ignited first, in seclusion from the air, to expel the hydrogen, it becomes uninflammable. 278 EARTHS. (b.) Not attacked by water, or sulphuric, nitric, or nitro-muriatic acid. Infusible, and unalterable by the blow pipe, and apparently one of the most infusible of bodies. (c.) Fluoric acid, with a little nitric, attacks it vigorously. (d.) After ignition, chlorate of potash does not affect it at any temperature. Nitre acts upon it violently at a white heat. If a frag- ment of carbonate of soda be introduced into the mixture, it detonates. (e.) Vapor of sulphur unites with the ignited silicium, and becomes incandescent. (/.) The resulting sulphuret decomposes water rapidly, and evolves sulphuretted hydrogen ; silica is generated, and the water dissolves it, and becomes gelatinous, but after it is dry, it remains a cracked mass, and is entirely insoluble in acids. It is observed that this solu- bility of silica just formed, may explain the existence of siliceous crystals in closed cavities, which could never have contained water enough for the solution of the materials, unless they were originally in a much more soluble state. (g.) Silicium burns in chlorine at a red heat, and forms a yel- low volatile liquid, smelling like cyanogen, and depositing silica on the addition of water. (h.) Detonates when heated with carbonate of potash, and with the hydrates of fixed alkalies, and of baryta, producing at a tempe- rature below redness, vivid incandescence ; it acts upon the alkali of nitre, after the acid is destroyed by heat. (i.) JL non-conductor of electricity. j.) Alloys of silicium are obtained by heating silica along with other metals, but silicium once extricated from oxygen, does not form alloys. (k.) It stains, and sticks strongly, even when dry, to the glass vessels in which it is kept. (1.) When silicium is heated in vapor of potassium it takes Jire, producing a compound of silicium and potassium. Remarks. It is not easy to class silicium. It can scarcely be called a metal, as it is infusible, is a non-conductor of electricity, and has none of the physical properties of a metal. It may be re- garded as a combustible, since it burns in chlorine, and those who choose to consider its combination with sulphur and potassium, with emission of heat and light, as a combustion, will of course add those instances as proofs of its combustibility. On the whole, it is perhaps more allied to boron and carbon, than to the metals ; but carbon has two metallic properties ; it is a conductor of electricity, and in the form of- plumbago, and of fused charcoal, it has the metallic lustre. Some of the metals, as uranium, titanium, and columbium, are rather * See Aim. de Chem. et de Phys. Vol. XXVII, p. 337, and Ure's Diet. p. 719, EARTHS. 279 remote in their properties from those usually assigned to metals.- Berzelius. GLASS.* 1. HISTORY. Known to the ancients. Glass beads were found among the ornaments of mummies in the catacombs, near Memphis, supposed to be 1600 years older than the Christian era ; glass was known to the Romans, and glass vessels were discovered in the hous- es of Herculaneum, and a coarse glass in the windows of the houses in Pompeii, which were destroyed by an eruption of Vesuvius, A. D. 79 ; glass lachrymatories are found in the tombs of the ancient Greeks. f Glass was however, with the ancients, merely an article of luxury and curiosity, and it is only in modern times that it has come into general use. In Europe, it was first made at Venice, and its use, in windows of private houses, was introduced into England in the tenth century, nor was it common until the 13th or 14th century. 2. COMPOSITION. Essentially a compound of silica, and fixed alkali, with however, various adventitious ingredients; sometimes glass is made of lime, or of the coarsest refuse ashes, and sand. 3. Principal kinds.' Flint glass ; crown, or window glass ; broad r or coarse window glass ; 'plate glass ; green bottle glass. (a.) Flint Glass.^ 120 parts clean white sand, 40 purified pearl ashes, 35 litharge, or minium, 13 nitre, and a little oxide of manga- nese ; or 100 white sand, 80 to 85 red oxide of lead,. 35 to 40 of pearl ashes, 2 or 3 of nitre ; or, (in England,) purified Lynn sand tOO* parts? litharge, or red lead, 60, purified pearl ashes 30. To remove the- color, derived from combustible matter, or oxide of iron, a little nitre,., or black oxide of manganese, or arsenic is added ; the oxigen con~ tained in these substances, either burns the combustible matter, or brings the metallic oxides that may be present, to such a state that they do not color the glass. The fusion takes about thirty hoursv The lead gives to this species of glass greater toughness and softness,* so that it can be cut, ground, and highly polished, and greater densi- * Glass is an example of what is called a vitrification. Many earthy and saline substances, and metallic oxides, either alone, or mixed, become by fusion, dense, hard, brittle, shining bodies, usually breaking with aconchoidal fracture, and having more or less of transparency. The slag and scoriae of furnaces are imperfect vitrifications. t Specimens were brought out by Mr. Jones, author of " Naval Sketches," anrf are now in the Cabinet of Yale College; they are supposed to be 2200 years oldV Some of them are beautifully irised ; the glass is perfect, and is a little greerrin its shade of color. | Called flint glass, because it was formerly made from flints ; and it has beei* called crystal glass, being sometimes made from rock crystals ; both are ignited and thrown into water to crack them, and they are then pulverized. 280 EARTHS. ty, and higher refractive power. It is the glass of our tables, of op- tical instruments, and lustres. (b.) Crown Glass. 200 parts of good soda, (or pearl ashes,) 300 pure sand, 33 lime, 250 to 300 ground fragments of glass ; this last addition is not essential ; or, by measure, fine sand purified 5, best kelp, ground, 1 1 ; by weight, sand 200, kelp 330. Professor Sweigger discovered that sulphate of soda might be used in the man- ufacture of glass, and his proportions are, sand 100, dry sulphate of soda 50, dry quick lime, in powder, 17 to 20, charcoal 4. There- suit is a good glass ; the sulphate of soda, aided especially by the charcoal, is decomposed, and its soda combines with the silica and the lime aids in producing the vitrification. The materials of glass are combined, in part, by a preliminary operation, called fritting, performed in a furnace, by which sulphur and other volatile mat- ters are expelled, previous to the full fusion, and the alkali is brought into combination with the silica, so that it is not volatilized by a higher heat. (c.) Broad glass. Soap maker's waste 2,* sand 1, kelp 1, mix- ed, dried and fritted ; or, soap boiler's waste, 6 bushels, 3 of kelp, and 4 of sand ; these form a pretty good broad glass. The materi- als are calcined for 20 or 30 hours before fusion, and then it requires 12 or 15 hours to melt them into perfect glass. (d.) Plate glass 300 Ibs. sand, 200 soda, 30 lime, 32 oz. man- ganese, 3 oz. azure, and 300 Ibs. fragments of glass ; or pure sand 43, dry soda 26.5, pure quick lime 4, nitre 1.5, broken plate glass 25 = 100, from which 90 parts of good plate glass may be obtained. (e.) Bottle glass. Common sand,f 100 parts, 30 of varec or coarse kelp, 160 leached ashes, 30 pure ashes, 80 of brick clay, about 100 broken glass ; or, soap maker's waste and river sand, in proportions determined by practice. Common sand and lime, with some common clay, and sea salt, form a good mixture for bottle glass. 3. Pastes are artificial imitations of the gems. They are very fine glass, rendered fusible by borax and other fluxes, and stained by oxides of metals. Rock crystal, or other very pure siliceous mat- ter, is selected, pulverized very fine, and mixed with the other sub- stances ; the following examples will shew the composition. Pulverized rock crystal, or flint, 8 oz. purified pearl ashes, 24 oz. these are fritted together, and then mixed with 12 oz. of white lead, * Consisting of refuse lime, that had been used to give causticity to the alkali, the insoluble part of the kelp or barilla, and some salt and water, all in a pasty state. Ure. N t lu England, the government will not permit any but coarse sand to be used in this manufacture, lest (lie common glass should be so good that the sale of the flint and other superior kinds of glass, which pay a higher duty, should be diminished. Parkes. EARTHS. 281 and 1 oz. of borax after fusion, 5 drachms of nitre are added ; or, rock crystal pulverized, 3 oz., white lead, 8 oz., and borax, 2 oz., and half a grain of manganese. This is a paste in which the lead and borax answer the purpose of a flux. Some principal colors are given by the following oxides of metals. Antimony gives yellow, and the same is produced by muriate of sil- ver, and by oxide of zinc, white clay, and yellow oxide of iron ; manganese produces violet ; gold, many shades of violet, red and purple ; cobalt, blue ; chrome, green, or red ; iron, red, and a great many other colors and shades ; and many varieties are imparted by mixtures of different oxides. Fluxes for the colors are made of borax, pearl ashes, lead, &c. These imitations of the gems, except in lustre, are often equal in beauty to the originals, but they are soft, and easily defaced. (g.) Stained glass. The art of staining glass was introduced into England, in the 13th century, in the reign of king John. Many of the ancient Gothic churches in Europe, are ornamented by stained glass, the panes of the windows having pictures painted upon them. The glass used for this purpose, is made without oxide of lead, be- cause that addition would make it too fusible, so that it would lose its shape during the second heating. The colors, ground in water, are laid on the glass, which is heated under a muffle, until the colors are melted, and united to the glass ; and the pieces, to prevent their bending, are supported upon the biscuit of unglazed porcelain, or some other suitable substance.* (h.) Medallions encased in glass. They appear to be something like the biscuit of porcelain introduced into the glass, while in fusion ; they are called crystallo ceramie, and are very beautiful. f (i.) Enamels are glasses, more or less opake, stained with various colors ; one of the most common is stained by oxide of tin or oxides of tin, arsenic and lead more or less mixed, as in watch faces. Dr. Bigelow informs us,J that the beautiful imitation of porcelain, made in Boston, and now seen in the shops, is flint glass, containing a portion of white arsenic, upon which its opacity depends. Remarks. Green glass is much harder and less fusible than white flint, and as it contains no lead, it is also much fitter to contain cor- rosive chemical agents. Glass is very ductile, as is proved by its being spun into the most delicate threads ; it is highly elastic, form- ing the finest toned bells and musical instruments ; it expands and contracts less than any other substance by variation of temperature, * I have seen modern stained glass in the windows in the University, Cambridge Eng. and in Hartford, Conn, (the latter of Boston manufacture,) less beautiful, however, than the ancient. t Heads of Washington, Franklin, Napoleon, and other distinguished persons, have been executed in this way. t Technology, 460. 36 282 EARTHS. and might therefore be used for clock pendulums ; it is a bad con- ductor of heat, and a large mass of it poured in fusion into water, will remain red hot in the inside, for several hours after the outside is solid. 3. MECHANICAL OPERATIONS. It would exceed the limits of a work like this, to describe even the outlines, of the ingenious opera- tions by which glass is fabricated into the various forms in which we see it. In general, it is blown by the breath of the artist, injected through an iron tube, to which the melted glass is made to adhere, by dipping and rolling one of its ends, repeatedly in the crucible ; and in the early part of the operation, while it is inflated, it is rolled on a smooth iron plate. I will briefly describe a few cases, most of which I have seen, and they will serve as examples for the rest. A porter bottle is partly blown, and then allowed to drop into a mould of copper, brass, or iron, in which, by a vigorous inflation, it receives its form ; the bottom is indented to make it stand ; the mould opens with a hinge, and another workman attaches a rod, having a little melted glass upon it to the bottom of the bottle ; the neck is cracked off by touching it with an instrument wet with cold water, and the broken mouth, being again heated, is shaped by introducing a revolv- ing iron into it, and a coil of melted glass is wound around to give it strengh ; it is then carried away to the annealing furnace, to be gradually cooled. Glasses consisting of several parts, are blown sep- arately, opened, moulded, shaped and stuck together while hot ; the foot of a wine glass is blown, as well as the conical part. A glass tube is drawn, by blowing a little into a mass of melted glass on the end of the iron tube, and then an assistant pulls the mass with iron pincers, and moves off rapidly or slowly, as the tube is to be coarser or finer. Plate glass is cast on an iron table ;* an iron cylinder of five hundred pounds weight or more, is passed over it to spread it smoothly, and it is finished by being ground and polished. Plates have been made of twelve feet by six. The smaller glass plates are blown, opened by a chisel and mallet, and cut, while hot, by shears, spread open upon a table, and afterwards annealed and cut by the diamond. Plates can be made in this way, of four or five feet, by two or three. Window glass is blown, and either cut open and spread ; or in the best kinds, after being blown into a huge globe, this is fixed at the bottom, to another iron tube, or rather an iron rod ; the neck is cracked off, and the mouth is heated at a flaming furnace, while the bottle is made to revolve rapidly, and by the cen- trifugal force, the mouth opens and widens, and the globe suddenly expands into a wheel, forty eight or fifty inches in diameter, called by the workmen, a table ; this operation is called flashing, and is * Copper tables and rollers were formerly employed, but the copper is apt to crack. EARTHS. 283 very beautiful. The glass, after being annealed, is cut up into squares by a diamond ; the centre piece by which the wheel was supported, is called the bull's eye, and is often seen in entry windows. Broad glass is blown into a conical form ; cracked longitudinally while hot, by touching it with a cold wet iron, and it is then spread out on a ta- ble, whence its name ; it is afterwards annealed and cut. The annealing of glass, which means the cooling of it, very slow- ly, in a peculiar kind of furnace, is important to prevent its crack- ing by slight movements, or jars, or variations of temperature. Prince Rupert's drops are made by pouring melted green glass into water, when the portions assume a tadpole shape ; they will bear the moderate blow of a hammer, if lying on a smooth table, but if the point is broken off, they explode into a thousand pieces. That this peculiarity depends on an unequal contraction produced by sud- den cooling, is evident, because if the drops are gradually heated red hot, and gradually cooled, they will no longer fly on having the point broken. The Bologna vial is blown with a thick bottom, but is cooled in the air, without being annealed ; it will bear to be struck upon a table with some force, but if a fragment of glass or sand be dropped into it, it flies to pieces, and frequently it does so by slight changes of tem- perature ; even, as I have observed, by the warmth of the hands. Cups of green glass, unannealed, have been made three inches thick at bottom, which were not broken by a musket ball falling from a considerable height, but were shivered, by a piece of flint of two grains weight falling into them. SEC. VI. ALUMINA. 1. NAME. From alumen, the latin of alum, which has this earth for its basis ; called also the argillaceous earth. Indicated by Geof- froy, in 1727, established by MargrafF, of Berlin, 1756. Formerly called argil, because it was the basis of clays. 2. PREPARATION. (a.) To a solution of alum,* in 20 parts of water, add liquid ammo- nia till precipitation ceases : or, precipitate by bicarbonate of potash ; as a little sulphuric acid is apt to adhere, it may be re-dissolved in nitric acid, and the solution tried for sulphuric acid, by nitrate of ba- rytes ; when there is no farther milkiness, it may again be precipi- tated by the above reagents, or the nitrate may be decomposed by heat.f (0.) Or, alum purified from iron, by repeated crystallizations, is dissolved in 4 or 5 parts of water, at 212 ; add carbonate of potash * Alum is apt to contain iron, which will remain when the salt is decomposed, and the earth dissolved by potassa ; or, if dissolved, it will, after a few hours, precipitate in brown flocks. t Ann. de Chim. XXXII, p. 64. 284 EARTHS. in slight excess, to prevent the formation of sub-sulphate ; digest a little while, filter and wash the precipitate with boiling water, to re- move the acid entirely ; but as some alkali may adhere to the earth, re-dissolve it in dilute muriatic acid, and decompose by ammonia, or its carbonate ; wash the precipitate thoroughly, and give it a white heat, when it will be pure. (c.) When alum is composed of 'sulphuric acid and alumina, with ammonia, and without any other alkali, the earth may be obtained by heat alone, which expels the ammonia, and decomposes the acid. (d.) Galvanism discovers minute portions of the fixed alkalies and acids in the alumina prepared as above, but not when it is dissolved in muriatic acid, and precipitated by ammonia.* 3. PROPERTIES. (a.) Tasteless, inodorous, insoluble in water ; no effect on test flu- ids ; infusible in furnaces. Sp. gr. 2. No alkaline property, ex- cept that of uniting with acids. (b.) Although insoluble in water, it attracts it powerfully ; when dry, it adheres to the tongue ; when precipitated, and moderately dried, it is a hydrate, half of whose weight is water, which cannot be expelled except by a white heat. After ignition, it attracts water so fast from the air, that balances show the increase of weight, f Henry. Dr. Thomson states that there are two hydrates; the one composed of 1 equivalent of alu- mina, and 2 of water, forming a bi-hydrate ; the other containing one equivalent of each. (c.) Easily diffusible in water, and forms with it a plastic mass ; and whether dry or moist, is impalpable between the fingers, or teeth, not being harsh and gritty, like silica ; nor alkaline like lime, baryta, and strontia ; nor rough, like magnesia. (d.) If precipitated from a concentrated solution of an alkali, it is a light friable powder, and adhesive to the tongue. (e.) If from a dilute solution, the dried precipitate is transparent, yellow, and brittle, compact, not earthy, and does not adhere to the tongue; this retains water forcibly, and has .15 of it, even after in- candescence. (/.) Infusible in furnaces, but fused by pure oxygen gas, on char- coal, and by the flame of the compound blowpipe, into an enamel, or a glass. (g.) Dissolved in the humid way by the fixed alkalies, but very imperfectly by ammonia ; the earth precipitated from alum, potash or soda, is re-dissolved by adding those alkalies in excess, and pre- cipitated again by an acid. * Phil. Trans. 1800, Davy. t In Berzelius' hands, 15 1-2 per cent, were gained in a dry, and 33 in a humid air. EARTHS. 285 (h.) Alumina and baryta, in equal parts, boiled together in water, 'are dissolved. (i.) Five parts of strontia being boiled on 1 of alumina, a portion is dissolved, and a compound of strontia and alumina is left undissolved ; they unite also by fusion. (j.) Alkaline solution of alumina, added to lim_e water, produces an insoluble precipitate of lime and alumina. (k.) The same alkaline liquor boiled on lime dissolves no more than the water alone will dissolve ; if alumina be mixed with the lime, much more lime is taken up than before. (I.) Mixture of alumina and lime, the latter being in excess, melts under oxygen gas, directed upon burning charcoal, but in no propor- tions in a common furnace. (m.) Alkaline solution of silica, with alkaline solution of alumina, on being mixed, gives a precipitate of silica and alumina, which fuses with an intense heat, into a milky glass or enamel. (n.) Not soluble in alkaline carbonates. (o.) Alumina unites by fusion with the fixed alkalies, and with most of the earths. Henry. (p.) This earth attracts coloring matter powerfully see dyeing, under vegetables. (q.) CONTRACTS PERMANENTLY IN THE FIRE ; and becomes so hard as to give fire with steel. This is from an intimate union of the molecules, and especially when silica is present, as in the natural clays. Wedgewood's pyrometer depends on this fact. See heat, and the means of measuring heat. 4. POLARITY. Electro positive ; it is separated at the negative pole in the galvanic circuit. 5. COMBINING WEIGHT. 18 according to Dr. Thomson and Gay-Lussac, but chemists are not perfectly agreed as to this number. 6. DISTINCTIVE CHARACTERS. (a.) Plastic with water, and imparts this property to large mix- tures of other earths. (b.) Precipitated as a hydrate, by alkaline carbonates, and by pure ammonia. (c.) Precipitated by pure potassa and soda, and immediately re- dissolved by an excess of those alkalies ; some choose to call this an acid property, but the alkali is not fully neutralized. 6. NATURAL HISTORY AND USES. In various forms and combinations, it is one of the most abundant substances in nature. Clays are composed of alumina, for their characteristic ingredient, mixed with silica, oxide of iron and other substances. Those clays which, when burned, become red, contain oxide of iron, as is seen in our red bricks. 286 EARTHS. Alumina enters more or less into the composition of most soils, and it generally forms strata in valleys and low grounds and plains, where it arrests the water which has filtered down from the hills, and causes it to issue from the ground, in springs and rivulets. On ac- count of its impermeability to water, clay is employed in the con- struction of tanner's vats, of artificial mill ponds, &c. where it is wish- ed to retain the water. In soils, this earth is of the first importance ; perhaps it is not too much to say, that there cannot be a good soil without it. Its pe- culiar office appears to be, to retain moisture, and to prevent the waste of the soluble parts of animal and vegetable manures, which so rapidly filter through siliceous sand and gravel. Still, a soil may contain too much alumina ; it will then be stiff, cold, and difficultly penetrated by the roots of plants ; but if it is mixed with a good pro- portion of siliceous sand and gravel, it will be warm, still retentive of moisture, and sufficiently mellow. Lime is an excellent ingredient in soils, as will be mentioned more particularly under the carbonate of that earth. Alumina exists abundantly in rocks, especially in felspar, which is a constituent of granite and gneiss ; in clayslate, steatite, asbestus, and serpentines, and in a great variety of minerals. It is nearly pure in the sapphire, and all the most precious oriental gems ; it forms nearly the whole of corundum ; it exists in a vast proportion of min- erals, and forms a large part of the crust of the globe. PORCELAIN AND POTTERY. In all the manufactures which go under the general name of pot- tery, from the coarsest tile or water pot, to the most beautiful porce- lain in chemical lutes, in fuller's earth, and bricks, silica and alu- mina, in certain proportions, are the essential ingredients. History. Known from the remotest antiquity ; the most barbarous nations fabricate rude vessels of baked earth, as well as by hollowing out soft stones ; bricks were employed in the tower of Babel,* two thousand years before the Christian era, and they are found in the an- cient Roman structures in Britainf and elsewhere. Earthen lach- rymatories are discovered in the tombs of the ancient Greeks and * In Yale College, are some Babylonish bricks brought out by the late Mr. E. Lewis, of N. Haven ; they were never baked ; they contain straw and bitumen, and some of them have " inscriptions in the arrow headed character ;" the dimensions of the largest are twelve and three fourths inches square by three and a half thick. t In the Roman wall at York, the bricks are seventeen inches long, eleven broad, and two and a half thick ; and there is in Yale College, a piece of brick and mortar, trom Roman baths at Paris, presented by Mr. Joel Root, who obtained it from the ruins. EARTHS. 287 Romans ;* the celebrated Etruscan vases were found in the tombs of lower Italy, f Water pipes were made by the ancients. I have one from Smyr- na, sent out by the American missionaries, which indicates its anti- quity by numerous layers of carbonate of lime, accumulated in the tube to the thickness of three or four inches, and evidently deposited from the water which ran through it. The Egyptians ornamented the mummies in their catacombs, not only with glass, but with earthen figures, some of which were cover- ed with a blue glazing made by the oxide of cobalt, the same mate- rial that is now used for this purpose. Porcelain was made by the Persian, and other eastern nations, before the Christian era, and the art is of high antiquity in China and Japan. It was introduced into Europe, early in the late century, and fabricated first in Saxony and France ; it was established in England, about the middle of the late century, and the manufacture was brought to great perfection, by the late Mr. Wedgwood.f The manufacture of porcelain has been within a few years, begun in the United States,^ and beautiful porcelain is now made at Philadelphia, by Hulme and Tucker. Materials of porcelain. The Romish missionary, father D'En- trecolles, early in the 18th century, sent home some of the materials used by the Chinese, and called by them petuntze and kaolin, the former being undecomposed felspar, and of course fusible ; the lat- ter decomposed and infusible, in consequence of the loss of the al- kali, which is one of its constituent principles. The felspar is composed of silica about 60 or 70, alumina from 15 to 25, and from 10 to 12 per cent, of potash or soda. Porcelain differs from stone ware in having a vitreous fracture and delicate translucence, which arises from its being composed of one fusible ingredient, while the infusible one preserves the vessels from losing their form in the fire. Porcelain clays abound in this country, and the materials from Chester County, near Philadelphia, now used there, are of the first order in point of excellence. Such clays should be free from iron, or the ware will be colored. Materials of pottery. There is no difference in principle between the materials of pottery and those of porcelain, except that the latter * Specimens are in Yale College, brought out by Dr. Howe and Mr. Jones. Some of them are supposed to be of the age of Pericles, particularly those from the tombs near Athens. Dr. Howe informed me that he was present when they were taken from the tombs. t I saw a collection of these in the British museum, sent out from Italy by the late Sir Wm. Hamilton. t The common pottery had been manufactured in England, time out of mind. I believe that Dr. Meade, of New York, was the first person who succeeded in, this country in making true porcelain. 288 EARTHS. and contain one fusible ingredient, and are purer. The pottery being opake, needs not tbe felspar, and it has a dull earthy fracture instead of a vitreous one. The most common earthen ware is made of pipe clay, often con- taining iron, which of course colors the ware when it is burned. A clay, much used in this country, is obtained from Amboy, N. Jersey, and is gray, both before and after it is burned. The plastic property possessed by moist clay, and by means of which it is moulded, depends on the alumina ; but the pieces would crack and be destroyed by shrinkage, were not the alumina correct- ed by the silica, which is not prone to shrink in the fire. If natural clays then have the requisite proportions of the two earths, and are free from iron, they have all the properties that are essential ; and if a color is produced by burning, it does not prevent the clay from forming a useful ware, although it may not be beautiful. Magnesia frequently enters into the composition of clays, and is a valuable in- gredient, as it is a very infusible earth, and contracts but little in the fire ; but if there is much lime, it will act as a flux, and produce a dis- torted ware. As the natural clays do not always contain a sufficient portion of siliceous earth, it is usual, in such cases, to mix with them siliceous sand or ground flints, the clay being first blended with water into a paste, and it is then uniformly mixed with the siliceous ingredient.* Fabrication of porcelain and pottery. There are important dif- ferences between the two, and there are many varieties of operations relating to both, but a few general facts may be stated. There is no analogy between these processes and those by which glass is made ; they are in fact directly opposite ; glass is " softened by heat, and wrought at a high temperature, whereas the clay is wrought while cold, and afterwards hardened by heat." Bigelow. There is much labor in preparing the materials, the detail of which would be foreign from the object of this work, in which only a few of the most important operations can be mentioned. Circular conical vessels are moulded upon the potter's wheel, a very ancient instrument, mentioned by the earliest writers, sacred and profane. A mass of the prepared clay is placed in the centre, and it revolves by a movement given by the foot, or by some other power ; the potter, his hands being moistened, to prevent adhesion, one hand being on the outside, and the other within, gives it a circu- lar form, and he employs sometimes a rude instrument, like a knife, to aid in finishing the piece. Many articles, modeled in this way, being too thick, are afterwards turned in the lathe, to make them thinner. * Pottery contains silica, two thirds, alumina, from one fifth to one third, and sometimes one five hundredth or one two thousandth of lime, and iron from the smallest portion to 15 or 20 per cent. Vauquelin, quoted by Parkes. EARTHS. 289 Handles, spouts, and other appendages are made separately, and are stuck on afterwards, with a thin paste of the clay, called slip. Vessels that are to have a peculiar form, oval, scalloped, fluted, &c. are made in moulds, usually of calcined plaster of Paris, which, by its absorbing power, aids in drying the articles, and the moisture is expelled from the moulds by heat, so that they are soon rendered serviceable again. Burning or Baking. The vessels, after they are dried, either in the air, or in stove rooms, are placed in earthen cases, called seg- gars, and these are so arranged that one covers another, in the oven or furnace, where they are gradually heated for about 12 hours, by flues, communicating from without, and the full heat is maintained from 24 to 48 hours ; more or less, according to the size of the es- tablishment, and the nature of the ware.* The furnace being grad- ually cooled, the pieces are withdrawn, and are then in the state of biscuit, as it is called : it will be a perfect pottery, only it is ab- sorbent of fluids, and therefore cannot be used, except for promoting evaporation, when it is desired that the fluid should pass through the pores and be exhaled from the outside. It adheres to the tongue, because it absorbs its moisture. Porcelain contracts so much in baking, that some tablets which I have from the Royal Manufactory at Sevres,f in France, which were marked off into ten equal parts, are shrunk one division, comparing them with those that have not been baked. Magnesia very much diminishes the shrinkage of the porcelain, and, in the form of steatite, is now employed by the English manufacturers. Great quantities of bones are consumed in the English potteries ; it is done for economy, for the quality of the ware is injured, as to firmness and weight, although it is white and translucent. Ornamenting. In the state of biscuit, the figures are usually put on ; in the finer kinds, by the pencil, and in the most beautiful por- celain, by the best artists, with exquisite taste and skill ; and often a separate figure or scene is painted upon every piece of an extensive set : the colors are metallic oxides. The ground oxide, in fine pow- der, is intimately mixed with gum water, acid of tar, oil of turpentine, or some other essential oil, and after the color is laid on, the fluid is entirely evaporated. The colors employed are the same as those mentioned under glass. * Trial pieces are withdrawn, from time to time, to enable the manufacturer to judge of the state of the ware. t This is a part of a very instructive collection, containing a complete suite of all the materials used in the manufacture of French porcelain, and in all their stages of preparation and fabrication, from the decomposed granite, up to the perfect vessel ; em- bracing also a series of colors, applied upon the porcelain, and accompanied by ex- planatory and descriptive catalogues. It was presented to me by Mr. Alexander Brongniart, the superintendant of the manufactory, a gentleman well known for his valuable researches, and excellent works in mineralogy and geology. 37 90 EARTHS. Very beautiful designs are now fixed upon the common ware by &id of the copperplate printing press. The design, first painted, and then engraved upon copper, is printed with a metallic color, mix- ed with prepared linseed oil, upon silver paper, which, with the figure upon it, is immediately applied to the biscuit, and then rubbed with a hard roll of flannel, to make it adhere, and after about an hour, the article is immersed in water, which softens the paper, so that it is easily removed, and leaves the colored figure ; the piece is next heated moderately in an oven, to dissipate the oil, and is then prepared to receive the glaze. The porcelain is not always painted in the biscuit ; sometimes it is painted on the glazing, and I believe this is generally done, on the most beautiful porcelain ; it is then necessary to heat the vessels again, in the enameller's oven, that the coloring matter may be melted, and incorporated with the glazing. Glazing. To prevent the absorption of fluids, and to make the ves- sels more cleanly, they are covered with a vitreous coat, a thin glassy film, which, as long as it lasts, protects the ware below. In the case of the common stone ware, it is produced by throwing into the hot furnace, common salt, which is raised in vapor, by the heat, when the soda vitrifies the outside and forms a perfect covering, which is also safe and cheap. The glazing, used on the common yellow ware, is composed of 40 pounds of ground flints, and 100 of litharge,* or of 100 of litharge, and 80 of Cornish granite. For porcelain and the finer kinds of earthen ware, it is composed of white lead, ground flint glass, ground silex, and common salt, The materials of the glaze are reduced to an impalpable powder, and suspended by agitation in water ; the vessels are dipped in them, and they retain enough to form a perfect covering when they are again exposed to the heat of the furnace. This glazing is dangerous 5 on account of the poisonous nature of lead : lava and pumice stone, have been substituted in France with good success ; and even ground flint glass, mixed with clay and water, has been found to an- swer | indeed, no protection would be better than the common mate- rials of glass, was not the ratio of its contraction and expansion by heat, different from that of pottery, which would cause it to break. Metals and their oxides are sometimes mingled with the materials of the glaze, to give it color, in certain parts, as on the edges of plates, copper being used for green, and manganese for black. Porcelain is occasionally covered with gold or platinum in sub- stance. The gold is dissolved in nitro-muriatic acid, which is evap- prafed, leaving the metal in a state of minute division ; it is next mix-- The French use galena, the native sulphuret of lead, thence called potter"* EARTHS. 9 i ed with borax 4 and gum water, and by means of a volatile oilj applied to the article ; it is then baked, and afterwards burnished. ' The lustre ware is made by applying an oxide of gold,* with a volatile oil, which is laid upon the vessels, colored by umber or red clay ; this appears through the gold, and gives the copper tint. The steel colored ware is covered with the precipitate by muriate of ammonia, from the muriate of platinum, which is applied in a similar way, but upon a cream colored basis ; and in both cases, it is introduced into the enameller's oven, where the heat dissipates the volatile principles, and the metals being left in their dull state, are afterwards burnished. The ware is glazed before the gold and platinum are applied. When prints are made to adhere to the biscuit, in the manner al- ready described, as the glaze is applied afterwards, it is important that it should be transparent, that the colors may be seen through it. It should be mentioned that the glazing on the best porcelain, par- ticularly that of China, is composed entirely of feldspar, finely pulver- ized, and suspended in an aqueous fluid^ which is said to be in China,- a lye of fern ashes ; no lead, or other metallic matter, enters into its composition, and it requires a very great heat to produce its fusion ; it is much harder than the glaze on most European porcelain. The Chinese ware is made so firm that it is merely dried before dipping it into the glaze, and does not require a previous baking ta- bling it to the state of biscuit. In general, the European porcelain, although superior to the Ori- ental in whiteness and beauty, and in its exquisite ornaments, is in- ferior in hardness, infusibility, weight, capability of enduring sudden changes of temperature, and in the permanency of its glazing. Some of the Saxon porcelain is said to be equal to the Chinese. Crucibles are made of the most infusible ckys, arid pipes and tiles are manufactured upon similar principles with those that have been explained. f Bricks, of every variety, are merely rude pottery. Fire Bricks are made of very refractory clay, called fire clay, and are both more infusible and worse conductors of heat than common bricks. They are sometimes prepared so as to be soft, or capable of being cut, in order that they may be adapted to different purposes,- and the fire, as they are used, hardens them afterwards 5 at other times they are burned hard at first* Those manufactured at New * A private letter to the author from Mr. Accum, in 1809, mentioned, that fulmina-* ting gold was applied in this way ; if so, doubtless its explosive character was de- stroyed by the combustible matter of the oil of spike, with which it was said to be t See Parkes' Essays, Vol. II ; Gray's operative Chemist, and Bigelow's Tech- nology. 292 EARTHS. Haven are made by using a fire clay, brought from Amboy, and found near the pipe clay ; an equal measure of rather coarse silice- ous sand is added, and they are baked in a potter's oven, with less heat than is employed for stone ware. Such bricks endure the intense heat raised in the cylindrical furnace stoves, in which the anthracite, and particularly the Lehigh coal is burned. On the side exposed to the fire, they become vitrified, and the impurities of the coal, consisting of earths, and oxide of iron, attach themselves to the bricks, in the form of a slag, and if the accumulated matter is not frequently detached, it eventually chokes the furnace. The common bricks are burned in huge piles, called, in this coun- Iry, Kilns, in England, Clamps. They are constructed of the moulded and sun-dried bricks, laid up with interstices, for the flame and hot air, and there are cavities left at the bottom, crossing the structure, in an arched form ; in these the dried wood is laid, and the fire being kindled, is gradually increased, for the first twelve hours, after which it is kept at a uniform height for several days and nights, until the bricks are sufficiently hardened. Some are exter- nally vitrified, or covered with a glaze, which is nothing but the melted materials of the bricks, and is not desirable, as good bricks can be made without vitrification. Some bricks are soft, and ab- sorbent of water, and will split with the frost : others are firm, and will endure a great length of time. There is a great diversity in the elays of different places, as regards the goodness of the bricks made from them. Bricks, after being partially dried in the sun, are some- times pressed hi iron machines, which forces out water and air, and makes them more firm and handsome. Terracotta, or Terre cuite, (burnt earth,) is used by the moderns, as it was by the ancients, in making ornamental designs, " vases, imitations, and architectural decorations. n The finer kinds of clay are employed, and they are with great facility moulded into any de- sired form. Reamur's Porcelain* This curious production might have been mentioned under glass, of which it is only an alteration,- effected by the action of continued heat to the point of softening, and followed by slow cooling, when the glass loses its transparency, and under- goes a kind of crystallization. The change is most easily effected upon green bottle glass ; it is found to be owing to the loss of the alkali by the heat, and that the glass thus changed will endure sud- den changes of temperature, as well as the best porcelain. It is usually prepared by filling a common green glass bottle with white sand and gypsum ; it is buried and pressed down in this mixture, in a covered and luted crucible, and baked in a potter's kiln, during the usual time of firing the ware, at the end of which period, it will be found changed into a kind of porcelain. Bigelow's Tech. EARTHS. 293 ALUMINIUM.* 1. HISTORY. (a.) Discovered by Sir H. Davy, who obtained, by galvanic pow- er, a compound of iron and this metallic base, which effervesced in water, and produced alumina, and oxide of iron ; also, by passing potassium, in vapor, through alumina heated to whiteness, the potassi- um was converted into potash, and metallic particles were obtained, which became white in the air, and effervesced in water ; when the temperature was only at a red heat, an alloy of the two metals ap- peared to be obtained, which effervesced violently in water, and took fire spontaneously in the air. 2. NEW PROCESS. (a.) Of late, Dr. JVohler has obtained aluminium pure. ^ (The student may omit this process until he has studied chlorine.) Chlo- ride of aluminium is formed by passing dry chlorine gas through an ignited porcelain tube, containing very dry alumina, intimately blend- ed with charcoal, in consequence of its having been mixed in the state of hydrate, and then ignited in a covered crucible, with char- coal, sugar, and oil 5 the hydrate is made by adding an excess of carbonate of potash, to a hot solution of alum. (b.) Carbonic oxide gas ivas evolved, and after the chlorine gas had passed for an hour and a half, the sublimed chloride of alumini- um had collected in such quantity as to choke the tube. (c.) The chloride was in greenish yellow translucent scales, resem- bling talc, deliquescing into a clear liquid, and combining with water r with heat, and even ebullition, if the quantity of water was small, and muriate of alumina was formed. (d.) Potassium decomposes the chloride of aluminium, and evolves the metal. The action is too violent for glass, which is [destroyed by the heat disengaged. It succeeds in a platinum crucible, the cover being secured by wire, and the heat of a spirit lamp applied } but the crucible becomes red hot.} (e.) The potassium should be free from carbon, and the quantity not over the size of ten peas> and so proportioned, that none of the chloride may sublime, during the decomposition, nor the resulting mass be alkaline. * Aluminum would seem preferable, but I adopt the orthography already intro- duced. i The first hint was given by Prof. Oersted, in consequence of his having obtain- ed what he believed to be aluminium, by acting upon chloride of alumina, by an amalgam of potassium. t To prevent the possibility of deception, the experiment was repeated in a porce- lain crucible, and with complete success. 294 EARTHS. (/.) The mass in the crucible is found to be melted, and of a dark gray color, and when put into water after it is cold, the saline matter is dissolved, an offensive hydrogen gas is evolved, and metallic scales remain, which after being thoroughly washed in cold water,* are pure aluminium. 3. PROPERTIES; (a.) A gray powder very simitar to that of platinum, in small me- tallic scales or spangles, or in slightly coherent spongy masses, hav- ing in some places a tin white lustre, rendered more distinct by pres- sure on steel, or in an agate mortar. (b.) In fine powder, a non-conductor of electricity, but becomes a conductor after fusion, f (c.) Fusible at a higher heat than that which melts cast iron. (d.) Ignited in the air, it burns vividly, and the product is alu- minous earth, white and considerably hard ; sprinkled in powder, in the flame of a candle, it gives bright scintillations, like iron in oxygen gas. (e.) Ignited in pure oxygen gas, it burns with great heat and light, and the resulting alumina is partially vitrified, yellowish, and hard as corundum ; it even cuts glass. When burning in glass, it appeared to reduce the silicium, producing a semi-fused brown spot. ^/.) Near ignition, it burns in chlorine gas, and chloride of alu- minium is formed. (g.) Not oxidized nor tarnished by cold water ; near ebullition, hydrogen gas is feebly evolved, and scarcely any oxidizement is ob- served. (h.) No action with strong sulphuric or nitric acid in the cold, but with heat, the former is decomposed, and sulphurous acid gas evolved ; it is dissolved in dilute muriatic and sulphuric acid, and hydrogen gas extricated. (i.) Dissolved readily and entirely in dilute solution of potash, and even in ammonia, hydrogen gas being evolved, and much alu- mina held in solution.j 4. COMBINING WEIGHT. Not accurately ascertained ; it has been already stated, that the number 10 has been adopted, and that it combines with one proportion of oxygen, 8, to form alumina, whose equivalent is of course, 18* * The solution is neutral, and contains some alumina, formed, as it is said, in con- sequence of a combination between chloride of potassium, and chloride of aluminium. t It is remarkable, as Dr. Wohler observed, that metallic iron, in fine powder, is a non-conductor of electricity, so that this property of metals seems to depend on their form, or, possibly, on intervening air. Perhaps if silicium were melted, it might become a conductor, and thus be assimilated to the metals. J Dr. Brewster's Journal, No. 17, p. 178. EARTHS'. 295 5. POLARITY. Electro-positive, as appears from the original ex- periment of Sir H. Davy, in which it was attracted to an iron wire connected with the negative pole of the galvanic series. Remark. That alumina so extensively diffused and so familiarly known, should contain a metal, distinct and remarkable in its pro- perties, and with the aid of potassium, so easily obtained, is a very interesting confirmation of the views of the illustrious Davy,* and must give celebrity to that of Dr. Wohler. Should the basis of the most important of the earths, namely, si- licium, which Prof. Berzelius has, by the aid of the same agent, potassium, now placed fully within our reach, eventually prove, after fusion, to be truly metallic, it would be an interesting addition to the series ; but in any event, the great fact that the earths are all oxides, is sufficiently established. SEC. VII. ZIRCONIA. 1. NATURAL HISTORY AND DISCOVERY. Never found pure in nature; discovered first in 1789, by Klap-< roth, in the jargon or zircon, a precious stone from Ceylon, in which he found 37.5 silica, .5 nickel and iron, and 68. of the new earth, which from its parent mineral, he called zirconia. In 1795, found by him in the hyacinths of Ceylon, and in 1796, discovered by Mor- veau, in those from the brook of Expailly, in France ; Vauquelin confirmed the discovery by farther experiments, f 2. PROCESS. (a.) To the pulverized zircon, add three or four times its weight, J of caustic potash, and fuse it in a silver crucible, throwing in the mix- ture, spoonful by spoonful, and waiting for the fusion of each portion before another is added t and after all are fused, increase the heat and maintain it for an hour and a half. Wash the contents of the cru- cible abundantly in boiling hot water, to remove the alkali. Now add muriatic acid to dissolve the zirconia, some silica is taken up by the acid, which is precipitated by heating the fluid, and removed by filtration. Lastly, add potassa ; the zirconia precipitates ; or it may be thrown down by carbonate of soda, and must then be washed sufficiently with pure water. * Whose premature death, the friends of science and mankind will long deplore. t Dr. Thomson, of Glasgow, has discovered 18 per cent, of zirconia, in the Silli- manite, a new prismatic mineral species fpund at Chester, in Saybrook, Conn, and first analyzed, named, and described by the late Prof. Bowen, who found it to consist of alumina, 54.11, silica, 42.66, iron, 1.99, and water .51. Dr. Thomson found a sim- ilar constitution, except that he discovered the zirconia as above stated. Am. Jour. Vol. VIII, 195. 217; Vol. XII, 159, and Vol. XVI, 207. t Five or six times, Four. II, 210 nine times, Ure's Pict. 815. 296 EARTHS. (b.) Or, to 1 part powdered zirconia, add 2 of potassa, and heat it for one hour in a silver crucible ; add distilled water, filter and wash well the insoluble part, which will be a compound of zirconia, silica, potash and oxide of iron. Dissolve in muriatic acid, and evaporate to dry- ness, to separate the silica. Redissolve the muriates of zirconia and iron in water, and having washed the remaining silica with weak mu- riatic acid, to remove any adhering zirconia, add it to the fluid. Fil- ter and precipitate tlie zirconia and iron by pure ammonia ; wash the precipitates well, and then boil them in oxalic acid ; this dis- solves the iron and leaves the zirconia an insoluble oxalate, which is to be washed until no more iron can be detected in the washings. The oxalate of the earth, which, when dry, is of an opaline color,* is then to be decomposed by heat in a platinum crucible. f 3. PROPERTIES. (a.) A fine white powder, tasteless and inodorous, resembles alu- mina, but somewhat harsh to the touch ; sp. gr. after being heated vi- olently on charcoal, 4.3. (b.) Infusible before the common blowpipe, but heated in a char- coal crucible protected by an earthen one, in a good forge fire, for some hours, becoming a substance like porcelain, insoluble in acids, suffering a partial fusion, and acquiring a gray color. In this state, it will scratch glass gives fire with steel, and has the specific gravity of 4.3. (c.) Perfectly fusible before the compound blowpipe of Dr. Hare, producing a white enamel.f (d.) Insoluble in water, but is absorbent of it, and when dried slowly after being precipitated form a solution, it has a yellow color ; retains about one third of its weight of water ; has a small degree of transparency, and resembles gum arabic. When heated red in a cru- cible of silver, it loses .37 of its weight. (e.) No action on combustibles, or oxygen, or nitrogen. (f.} Insoluble in alkalies, but dissolved in alkaline carbonates. (g.) Insoluble in acids, until it has been acted upon again by caustic potash, and washed till the alkali is removed ; it is next dis- solved in muriatic acid, precipitated by ammonia and the washed hy- drate, is then easily soluble in acids, forming salts, and those with the sulphuric, carbonic, and phosphoric acids, are insoluble in water. In general, the salts of zirconia are insoluble, and those that are solu- ble, have a sweetish astringent taste. * For a third process, see Thenard, Vol. II, p. 295, and Ann. de Chim. et de Phys. T. XIII, p. 245. t Ann. de Chim. et de Phys. T. XIV, p. 110. t Am. Jour. Vol. II, p. 292. The hydrate heated by a spirit lamp in a glass capsule, becomes red hot, as if it were on fire. Thenard. EARTHS. 297 (A.) Zirconia differs from silica, in being much more soluble in acids, and in being insoluble in alkalies, but it is soluble in alkaline carbonates ; in this last property it differs from alumina and glucina. ('.) There is a great resemblance between oxide of titanium and zirconia, in most of their properties ; but tincture of galls precipi- tates oxide of titanium reddish brown zirconia in yellow flocks.* 4. POLARITY. From analogy, supposed to be electro-positive; and to be attracted to the negative pole of the galvanic series. 5. COMBINING WEIGHT, 48, consisting of zirconium, 1 proportion, 40, and oxygen, 1 proportion, 8. Thomson. It has been supposed from some experiments of Berzelius, that it is 30 or 33. ZIRCONIUM. 1. HISTORY AND PROCESS. Sir H. Davy discovered, that when zirconia is ignited with po- tassium, the latter is oxidized, and dark metallic particles are diffused through the alkali. Berzelius has more recently procured this base, as he did sili- cium ; that is, by heating with a spirit lamp, in a tube of glass or iron, a mixture of potassium and hydro-fluate of zirconia and potassa, care- fully dried ; at a temperature below ignition, the earth is reduced to the metallic state, and without any luminous appearance ; the mass is next washed with boiling water, and then digested for some time in pure muriatic acid ; the residue is pure zirconium, f 2. PROPERTIES. (a.) Black as charcoal; it is a powder. (6.) Not oxidized by boiling water, or sulphuric or muriatic acid, but dissolved by aqua regia, and hydro-fluoric acid, the latter evolv- ing hydrogen. (c.) Zirconium burns intensely in the open air, with a slight in- crease of heat, but far below luminousness, and produces zirconia. (d.) It combines with sulphur, forming a chesnut brown sulphuret, insoluble in muriatic acid, and alkalies ; but which burns brilliantly, regenerating the earth, and evolving sulphurous acid.J (e.) Does not conduct electricity ; it is capable of being pressed out into scales of a dark gray color, having somewhat of the metal- lic appearance, but it is not perfectly settled whether it ought to be called a metal. 3. COMBINING WEIGHT not accurately determined. See zirco- nia, 5. * Ann. of Philos. XIII, 83. Turner, and Eng. Quar. Jour. XV111, 157. t Ann. of Philos. N. S. VIII, 123. 38 298 EARTHS. SEC. VIII. GLUCINA. 1. NAME NATURAL HISTORY DISCOVERY. From /Xuxuj, sweet, because its salts have that taste. Discovered in the beryl and emerald, in 1798, by Vauquelin, who at the request of Haiiy, analyzed the beryl to discover whether its chemical in- gredients were the same with those of the emerald, as from physical considerations, he had conjectured that they were. The analysis proved the suspicions of Haiiy to be well founded. 2. PROCESS. (Th. I, 530.) Fuse pulverized emerald or beryl 1 part, with potassa 3 parts ; dilute the mass with water, dissolve in muriatic acid, and evaporate to dryness, stirring the matter towards the end. Mix it with much water, and filter to separate the silica, which is more than half. The muriates of glucina and alumina are in solution ; precipitate them by carbonate of potash,* wash the pre- cipitate, and dissolve it in sulphuric acid. Add to the solution sul- phate of potash ; evaporate and obtain crystals of alum. When no more are formed by adding sulphate of potash, add carbonate of ammonia in excess, shake the mixture, and let it stand till the gluci- na is dissolved by the carbonate of ammonia, and nothing but alumina is left, then filter, and evaporate to dryness, when a white powder is obtained, which, after slight ignition in a crucible, is glucina, in the proportion of 16 per cent, of the stone. Euclase also contains 21.78 of this earth ; and by Mr. Seybert's analysis, the chrysoberyl of both Haddam and Brazil, has as much as the emerald, f that is 15.80 glucina for the chrysoberyl of Haddam, and 16, for that of Brazil ; the other constituents were for the latter, alumina 68,66, silica 5.99, oxide of titanium 2.66, oxide of iron 4.73, and water ; for that of Haddam, 73.66 alumina, 4 silica, 1 oxide of titanium, 3.38 oxide of iron, and a little moisture. The existence of glucina in chrysoberyl had been overlooked by the first analysts, until it was discovered by Mr. Seybert. 3. PROPERTIES. (a.) Inodorous, tasteless, and insoluble in water ; but forms with it a paste of some tenacity. It is a fine white powder, resembling alumina, and like that adheres to the tongue. b.) Does not contract in the fire, nor affect the test colors. c.) Specific gravity 3. d.) Infusible by the common blow pipe, but perfectly fusible by that of Dr. Hare. * The latter part of this process may be conducted differently from the descrip- tion in the text. After precipitating the alumina and glucina, dissolve them in water acidulated by muriatic acid, and precipitate again by pure ammonia; then dissolve this in carbonate of ammonia, and proceed to the end as already directed. Or, start- ing from the same point: add to the precipitated earths pure potassa, which will dis- solve the alumina, and a portion of the glucina, but that which remains, is this earth sometimes slightly colored by iron. For the mode of extracting glucina from the chrysoberyl, see Am. Jour. Vol. Vill,p. 105. I Am. Jour. Vol. Vlll, p. 105, EARTHS. 299 (e.) Combines with potassa and soda, but not with ammonia, al- though it is soluble in the carbonate of that, and of other alkalies, and in the caustic fixed alkalies. (/*.) With all the acids forms salts, with a sweetish astringent taste ; they are decomposed by the alkalies, even by ammonia, which does not precipitate alumina, which glucina considerably resembles. (g.) Resembles alumina in attracting coloring matter. (A.) It is not precipitated by prussiate of potash. (i.) It absorbs carbonic acid, at the ordinary temperature of the air. 4. COMBINING WEIGHT. Stated by Dr. Thomson, and by Ber- zelius as 26. 5. POLARITY. From analogy supposed to be electro positive. GLUCINIUM. 1. This base has not been distinctly obtained, but the analogy which would lead us to admit its existence, is strongly supported by the following fact. 2. Sir H. Davy ascertained that by igniting potassium with glu- cina, the metal is converted into potassa, thus proving the existence of oxygen in the earth ; dark colored particles, with a metallic aspect also appeared in the mass, and regained the earthy character by be- ing heated in the air, and by the action of water, hydrogen gas being, in the latter case, evolved. 3. COMBINING WEIGHT. Dr. Thomson concludes that the num- ber for the earth must be 26, and if it consists of 1 proportion of me- tallic base, and 1 of oxygen, the latter being 8, the former will of course be 18.* 4. POLARITY. Supposed from analogy to be electro positive. SEC. IX. YTTRIA. 1. NAME NAT. HISTORY DISCOVERY. Name, from Ytterby, a quarry in Sweden, where the mineral was found, from which Yttria was first extracted. Discovered by Prof. Gadolin, in 1794, during his analysis of this mineral, called after him, the Gadolinite, and confirmed by several eminent chemists since. Yttria has been found, not only in the mineral mentioned above,-)" which yielded it in the proportion of 35 to 45 per cent., but also in another mineral, consisting of the metal tantalum, and yttria, called yttrotantalite, containing about 20 per cent., and in the yttrocerite, which has about 8 or 9 per cent. These minerals, as well as Ga- dolinite are found only in the quarry of Ytterby. 2. PROCESS. * Thomson's First Principles, Vol. I, p. 318. t Combined with black oxide of iron and silica. 300 EARTHS. (a.) *Let the Gadolinite be repeatedly digested in muriatic acid, and silica remains. To the fluid, add liquid ammonia, boil the pre- cipitate in solution of potash, and filter. Dissolve the insoluble resi- due of the last process in diluted sulphuric acid, evaporate to dry- ness, ignite, and redissolve it in water ; a precipitate falls down, which must be separated by the filter. The filtered solution, when mingled with liquid ammonia, yields a precipitate which is Yttria.f (b.) Fuse the Gadolinite 1 part, with caustic potash 2, wash the mass with boiling water, and filter the liquor, which will be of a fine green ; evaporate till the oxide of manganese, in the form of a black powder, ceases to fall ; then saturate the liquid with nitric acid. Digest the undissolved sediment in dilute nitric acid, which will dis- solve the earth with much heat, leaving the silica undissolved, and the iron highly oxidized. Mix the two liquors, evaporate to dryness and redissolve and filter, which will separate any silica or oxide of iron that may have been left. A little carbonate of potash will separate any lime, and hydro-sulphuret of potash will precipitate any mangan- ese ; but if too much be added, it will throw down the yttria too. Lastly, ammonia will precipitate the yttria, which must be well wash- ed and dried. } 3. PROPERTIES. (a.) Ji fine white, powder ', infusible alone, but with borax melts into a glass. (6.) Tasteless, smooth, and inodorus no effect on vegetable colors. (c.) Sp. gr. 4.842, greater than that of any earth. (d.) Insoluble in water, but absorbs it, and loses .31 of its weight when heated to redness. (e.) Soluble in alkaline carbonates, but not in pure alkalies, like alumina and glucina ; requires to dissolve it 5 or 6 times as much carbonate of ammonia as glucina does. (/.) With acids forms sweet tasted salts, with some degree of austerity, and several of them are said to be colored, a fact not ob- served in any other metallic salts, but there can be little doubt that the color is owing to the adhering iron and manganese. (g.) Solution of Yttria in muriatic acid, evolves chlorine after be- ing long heated. (A.) Oxalic acid, and oxalate of ammonia, precipitate yttria like muriate of silver. 4. POLARITY. Supposed from analogy to be electro positive. 5. COMBINING WEIGHT, 42. * Accum. Mineral, p. 137. t For the process of Vauquelin, see Ann. de Chim. p. 150, XXXVI, and Henry, 10th Ed. Vol. I, p. 625. J Ure'sDict. EARTHS. 301 YTTRIUM. 1. Not yet obtained isolated. 2. Yttria converts potassium into potassa, when aided by heat, thus proving the existence of oxygen in the earth, which also exhibits ap- pearances of metallization, so that there can scarcely be a doubt that this earth consists of oxygen and inflammable or metallic matter. 3. COMBINING WEIGHT. Dr. Thomson assigns 42 as the repre- sentative number of yttria, and supposing that the earth is composed of 1 proportion of oxygen, and 1 of metal, he states the latter at 34, for 34+8=42. # # * * # * # Since the account of the earths was in type,* Prof. Griscom has been so kind as to forward to me the following notice of a new earth, which, as it is so named by its discoverer, I insert here rather than under the metals. The learner will observe that it is a different thing from the substance formerly called Thorina. See note, p. 261. Discovery of a new earth, named Thorina, and its metallic base, named Thorium. M. Dulong communicated to the Academy of Sciences at Paris, on the 26th of July last, in a letter from M. Ber- zelius, the discovery of a new earth. " I have just discovered," says the Swedish Savant, " a new earth, which possesses almost all the properties of that which bore the name of Thorina, and which has been ascertained to be only a phosphate of Yttria. It is in con- sequence of this striking analogy, that I have retained the name of Thorina, for this new substance. This earth is white, and irreduci- ble by charcoal and potassium. After being strongly calcined, it is attacked by none of the acids, except concentrated sulphuric, even after being treated with caustic alkalies. The sulphate of Thorina is very soluble in cold water, and almost insoluble in boiling water, so that it may be freed from many other salts, by washing the mix- ture with boiling water. Thorina dissolves easily in carbonate of ammonia. An elevation of temperature occasions a precipitation of a part of the earth ; but on cooling, the precipitate disappears. All the salts of Thorina have a very pure astringent taste, very similar to that of tannin. The chloride of Thorium, treated with potassium, is decomposed with a triple deflagration. There results a gray metallic powder, which does not decompose water, but which, raised above a red heat, burns with a splendor almost equal to that of phos- phorus in oxygen gas. Nevertheless, Thorium is feebly attacked by nitric and sulphuric acids. The hydrochloric, on the contrary, dissolves it with a brisk effervescence. Thorina, or the oxide of Thorium, contains 11.8 oxygen. Its specific gravity is 9.4. Tho- rina exists in a new mineral which has been found in very small quantities at Brevig, in Norway. Bib. Univ. Juillet, 1829. * But before it was struck off. 302 INFLAMMABLES. SIMPLE INFLAMMABLE AND ACIDIFIABLE BODIES, (not metallic,) AND THEIR COMBINATIONS WITH THE PRECEDING BODIES. HYDROGEN SULPHUR CARBON PHOSPHORUS NITROGEN BO- RON UNKNOWN BASE OF FLUORIC ACID SELENIUM. SEC. I. HYDROGEN. (a.) This inflammable body has been already described under the head of water, and is here mentioned again only for the sake of classing it. (b.) With oxygen, it forms no acid, but it forms one with chlorine, as will be shewn in its place. SEC. II. SULPHUR. 1. HISTORY. Known from the remotest antiquity. 2. SOURCES. (a.) Volcanos, active, dormant or extinct ; sublimed by the sub- terranean heat, collects in craters and solfaterras, as near Naples, in Gaudaloupe, &c. (b.) Combined with metals, forming numerous species of native sulphurets, as of iron, copper, lead, silver, &ic. sublimed from them by artificial heat, but is not in this manner obtained pure ; it is con- taminated with the metals, with which it was combined. (c.) In sulphureous mineral waters imparting a disgusting odor, and the property of blackening white metals and their solutions; be- ing suspended by hydrogen, it is deposited as that gas is exhaled, and is found in the channels, through which the waters pass.* (d.) In animals and plants found more or less in all animal bo- dies, as is proved by the production of sulphuretted hydrogen, dur- ing their decomposition. Among plants, in the rumices or docks, in the cruciform plants, as scurvy grass and cresses. Sulphur was sublimed by Deyeux, from roots of horse radish and of dock. J (e.) In rocks and stones, along with gypsum and sulphate of stron- tia, and even with the primitive rocks in veins, and sometimes in in- durated marl and compact limestone ; arising perhaps from the de- composition of sulphurets. * At Niagara, it oozes from the bank near the north side of the great Horse Shoe fall. Own observations, Oct. 1827. I Exists in eggs, in privies, in pits in which flax has been steeped, &c. INFLAMMABLES. 303 (/.) In sulphuric acid, forming a constituent of the natural sul- phates of lime, baryta, strontia, soda, &c. and in the free sulphuric and sulphurous acids. 3. PROPERTIES. (a.} Sp.gr. 1.99. (b.) Electric by friction ; color lemon yellow, but precipitated sul- phur is at first white, and it becomes white if water be dropped on it while in fusion, and also if sublimed with watery vapor ; the whiteness is supposed to be owing to a combination with water ;* electricity, negative or resinous ; a non-conductor of heat. Hence, a roll of it, grasped in the hand, crackles in consequence of its brittleness, and of its unequal expansion by heat. (c.) Emits a peculiar odor when rubbed or heated. Brittle and fracture brilliant ; it has a considerable refractive power. (d.) Evaporates at 170, with a disagreeable smell ; fuses at 185 or 190 ; fluid at 220, most perfectly fluid between 230 and 280, when it is of an amber color. (e.) It begins to thicken at 320 ; at 350, stiffens and acquires a deeper color ; f is very tenacious between 428 and 482, but from that to its boiling point, it grows fluid again, and on cooling, also, it recovers its fluidity ; this may be repeated by sudden transitions of temperature in close glass vessels ; otherwise the sulphur is volati- lized. J Evaporates at 290 ; it can be distilled from a glass retort into a re- ceiver. (/.) Sublimes at 600. The sulphur being thrown on an ignited iron, and covered suddenly with a bell glass, the latter is instantly lined with the sublimate called flowers of sulphur ; melted, skimmed, de- canted, and cast in moulds, this forms the best roll sulphur .$ * It is said also to acquire a paler color from adulteration with rosin, flour, &c. i In this state, or when heated to 428, it is poured into hot water, and is used to copy medals, they being impressed upon it while it is warm. I Thenard, I, 107, quoted by Henry, Vol. I, p. 380. Rough sulphur is purified by melting it in cast iron bodies or retorts, covered with earthen ware heads ; about six cwt. at once, and the distilled sulphur is drawn off into water, at the lower of three holes in the receiver; one being for the admission of the retort, and one for the escape of the vapors ; the refined sulphur is cast in moulds made of beech wood. In subliming sulphur, the furnace is below, and the sulphur, melted in iron pots, rises into a room placed above, where it is con- densed in flowers or sublimate. It is sublimed also from thick iron pots, of the capacity of 10 or 12 cwt. by a lateral communication from its dome into a chamber, which, if intended for roll sulphur, rnay be not more than one fifth the size that would be requisite, if flowers of sulphur were to be made. Gray's Op. CJiem. If the distillation is rapid and incessant, it will condense in the liquid form, and will be made into roll sulphur ; if slow and with suspension at night, it will be in the form of flowers. Formerly, crude sulphur was merely melted, and when the impuri- ties had subsided, it was ladled out and cast in moulds; the sulphur thus obtained was impure, and much was lost in the sediment; the best roll sulphur, as well as flower:?, has been distilled or sublimed. 304 INFLAMMABLES. (g.) In the arts, to form the flowers, it is sublimed in rooms lined with sheet lead. (h.) Examined by the test fluids, to ascertain whether it is acid ; agitate it with infusion of cabbage or litmus. (i.) Crystallization natural in volcanos often beautiful modi- fied octahedra ; by art sulphur melted in a broad deep vessel, sev- eral pounds at once, (a crucible or earthen pot will answer,) when its surface congeals, break it and pour out the liquid interior. (j.) The cavity will be found lined with prismatic or needle form crystals, of which the basis is an oblique rhombic prism. (k.) With water no action ; if the sulphur be pure, it comes off tasteless ; but precipitated sulphur is a hydrate, and is white ; it was formerly called lac sulphuris. (I.) With liquid alcohol no action ; in vapor they unite, a vial of alcohol being suspended in an alembic in which sulphur is sublim- ed, the spirit rises too, and a union results ; water precipitates the sulphur. (m.) Boiling essential oil of turpentine dissolves sulphur entirely, but not the usual impurities ; hence, used to detect its adulterations ; when properly purified, it has a fine sparkling brilliant yellow color.* 4. An element in relation to our knowledge. (a.) Sir H. Davy evolved sulphuretted hydrogen from it, by gal- vanism but is not certain that the gas did not come from decom- posed water, lodged in the interstices. f (b.) Potassium evolves sulphuretted hydrogen, with intense heat and light. 7. USES. (a.) An important article in the materia medica, both internally, as a laxative, and externally, as a remedy against cutaneous dis- eases. b.) The basis of the manufacture of sulphuric acid, c.) Used with iron filings as a cement, and for matches. d.) In its viscid form for copying medals, &tc. e.) The chief use is in the fabrication of gunpowder, of which it visually forms 15 per cent. For these and other purposes it is large- ly imported into this country from Italy, whose volcanic regions abound with sulphur, particularly in the Solfaterra near Naples, and it comes, in perhaps larger quantities, from Sicily than from Naples. * Aikin's Diet. Vol. II, p. 353. i Berzelius found that when metals combine with sulphur, as dry as possible, little or no sulphuretted hydrogen is exhaled. INFLAMMABLES. 305 (h.) To divide a bar of iron ; when at ignition, or better at a white heat, if rubbed with a roll of sulphur, the iron melts and falls in drops of liquid sulphuret. " If a gun barrel be heated red hot at the but-end, and a piece of sulphur be thrown into it, on closing the muzzle with a cork, or blow- ing into it, a jet of ignited sulphurous vapor will proceed from the touch hole. Exposed to this, a bunch of iron wire will burn as if ignited in oxygen gas, and will fall down in the form of fused glob- ules, in the state of proto-sulphuret. Hydrate of potash, exposed to the jet, fuses into a sulphuret of a fine red color." Dr. Hare. 5. POLARITY Electro positive; it goes to the negative pole in the galvanic circuit. 6. COMBINING WEIGHT, 16, hydrogen being 1. 8. PHARMACY. No peculiar preparation is necessary to fit the best roll and flowers of sulphur for medical use. Whether it is acid may be learned from its taste, and from its effects on the test colors ; if it turns the blue vegetable color red, it must be washed abund- antly with hot water, and the addition of a little alkali will aid in re- moving the acid. ACIDS. Preliminary Remarks. One of these bodies, vinegar, seems to have been always known to mankind. In the progress of time ; accident, art and science have either developed or formed many more. There can be no doubt, that the acids are all compound bodies, and that the only one which remains undecomposed, the fluoric, has an inflammable base, like the rest : for, with this exception, all of the hundred or more that are 39 306 INFLAMMABLES. known to chemistry, have inflammable or metallic matter, as their basis, and with only a few exceptions, it has been proved to be com- bined with oxygen, which, instead of being regarded as the exclusive acidifying principle, may still be viewed as sustaining this agency in nearly all cases. Thirty years ago, there were three acids whose composition was unknown, namely, the muriatic, the boracic, and the fluoric. Although the latter is still undecomposed, the boracic acid has followed the general analogy, having yielded a new combustible body, boron, united to oxygen. The muriatic acid is now believed to be composed of hy- drogen and chlorine. Sulphuretted hydrogen has most of the proper- tes of an acid, but contains only sulphur and hydrogen ; the hydriodic acid consists of iodine and hydrogen, and the prussic acid of carbon and nitrogen, united to form a compound base, which is however not acid, until it unites with hydrogen. Thus, there are four* acids in which hydrogen appears to be essential to the acidity, and oxygen is not present ; while the bases of three of these acids, namely, sulphur, io- dine, and chlorine, form other acids, by uniting with oxygen ; and even the compound basis of the prussic acid, consists of elements which, individually, form acids with oxygen. Some chemists are now inclining to the opinion, that no one princi- ple can be regarded as being endowed with the peculiar prerogative of being an acidifier, but that acidity may, and often does arise from a balanced or conjoined effect of several principles. f Oxygen exists, as we have seen, in all the alkalies, except ammonia, and in all the earths and metallic oxides, so that we cannot attribute to it the ex- clusive property of producing either acidity or alkalinity, although it is in most instances concerned in both ; still, that body without which another would not be acid, must be considered as its acidifier. Most of the acids that have been discovered, are of very little im- portance ; but several of the principal acids are eminently valuable, and their history, being equally instructive and interesting, will be developed with sufficient detail, in connexion with that of the in- flammable bodies that form their bases. In giving the history of the principal acids, I shall therefore pursue the synthetical course, as being the most convenient and intelligible, although the analytical was, for the same reasons, adopted in the account of the alkalies and earths; or, in other words, the bases of the most important acids will be presented first, whereas those of the fixed alkalies and earths were presented last. * Besides others of a most doubtful character, as that composed of hydrogen and tellurium. t For an ingenious discussion of this view, see Murray's Elements, 6th Ed. Vol. II, Art. Acids. Mr. Murray is inclined to think that even the water, usually re- garded as combined with acids and alkalies, acts rather by its element?, than in the character of water, a fact which it m;iy be difficult either to prove or disprove. INFLAMMABLES. 307 GENERAL PROPERTIES OF ACIDS. THEIR NOMENCLATURE. 1 . Most of them sour. 2. Soluble in water ; most of them largely some very sparingly. 3. Redden most of the vegetable blues restore the colors that have been changed by alkalies or alkaline earths. 4. Combine with alkalies, earths, and other metallic oxides, and form salts. 5. The stronger acids corrosive. 6. They consist generally, of an inflammable base, combined with oxygen ; in a few cases hydrogen takes its place.* 7. Exist solid, fluid and gaseous, in different cases. NOMENCLATURE OF THE ACIDS. (a.) In the new or French nomenclature, acids are named from the inflammable bases. (b.) The termination ic denotes the higher combination with oxy- gen ; ows, a lower, and the proportions in both are definite. (c.) Where there is only one proportion of oxygen the termination is in ic. (d.) Where the base is complex, as in the animal and vegetable acids, the termination ic means nothing, and the acid is usually named from the substance which affords it ; as tartaric acid, from tartar, &c. (e.) The names of the hydracids, as they are called, terminate in 1C, as hydrochloric, hydriodic, &c. SULPHURIC ACID. 1. NAME. Derived from sulphur, the inflammable base, which affords also other acids. Oil of Vitriol is the name of the shops.f 2. HISTORY. Discovered by Basil Valentine, at the close of the 15th century. 3. EARLY PROCESS. By distilling sulphate^ of iron, (copperas,) whose water of crystallization, amounting to about one half its weight, had been previously dissipated by a moderate heat. This process is still followed in Saxony ; 600 Ibs. of copperas gave Bernhardt but 64 of the acid, and when no water was put into the receiver, 52 pounds of a dry concrete acid were obtained, formerly called glacial oil of vitriol. Glauber says that sulphate of zinc affords a purer and better acid, and with less heat. * Sulphuretted hydrogen and prussic acid, consist wholly of combustible elements. Chloric acid is composed of two supporters of combustion and some would refer the oxiodic and the chloriodie acids to the latter class. t Because it was distilled from green vitriol, and has an oily consistence ; it was called spirit of vitriol, when it was less concentrated. t It is the sulphate of the protoxide, which passes to the condition of peroxide. Parkcs' Essays, Vol. I. p. 468. 308 INFLAMMABLES. 4. MODERN PROCESS.* (a.) Carried on in chambers, lined throughout, with sheet lead ; usual size, 20 feet long, and 12 wide or 40 to 60 by 16 or 18; in one case, in England, 120 by 40, and 20 high contents 96000 cubic feet. (b.) Sulphur, 7, 8 or 9 parts, coarsely bruised, and 1 part of common nitre, are mixed. One pound of the mixture for every 300 cubic feet of air, is placed in separate portions upon iron or leaden plates, supported by stands of lead. The sulphur is lighted by a hot iron and the door closed, f The combustion continues 30 or 40 minutes, and in three hours the acid gas is absorbed by the water on the floor of the room, which is usually about six inches deep ; or sometimes the acid vapors are carried by the current of air that sup- ports the combustion, into another leaden room, where they are con- densed by water, f (c.) The room is then ventilated, and the process repeated every four hours, day and night, until the water at the bottom is sufficiently acid. (d.) Then it is drawn off by a syphon, into a leaden reservoir. (e.) It is pumped from this into leaden boilers, and there concen- trated|| by heat, until it is of the sp. gr. 1.350 to 1.450, or 1.560. (f.) It is finished in glass retorts, placed in sand baths, and the retorts are now generally furnished with platinum wire to prevent the concussion in boiling ; water, and nitrous and sulphurous acid gas be- ing expelled, it then has the specific gravity 1.850, or, as Dr. Ure says, 1.842, if pure. For economy, the concentration of sulphuric acid is now often performed in platinum boilers, placed within iron ones of the same size and form. The conversion of sulphur into an acid, is easily proved by burning it in a pendent metal spoon, introduced into a bottle of oxygen or common air, on the bottom of which is some litmus infusion.^ 5. PROPERTIES. (.) Thick, oily looking fluid ; pours slowly from vessel to ves- sel ; corrosive, and, with or without heat, destroys all animal and vegetable bodies ; the first sensation when it is rubbed on the skin, is that of lubricity, but immediately after, there is extreme burning. * Begun by Dr. Ward, in England, before 1746, by combustion in glass bells or globes; in 1746 Dr. Roebuck introduced the leaden chambers at Birmingham. Parkes' Essays, Vol. I, p. 476. t A red hot cannon ball is sometimes rolled in through a trough lined with iron. t The theory of this process cannot be fully elucidated until we have become ac- quainted with the nitric compounds, when it will be resumed. It may be stated, however, that sulphurous acid is formed from the sulphur, and nitric oxide gas from the nitre ; this obtains oxygen from the air, becomes nitrous acid vapor, then oxy- genizes the sulpburous acid, and turns it into sulphuric acid. The sulphurous. || Concentration is when a volatile ingredient is driven off, and a more fixed one is Saved. Distillation when the volatile ingredient is saved. INFLAMMABLES, 309 (b.) When pure; colorless, limpid, inodorous; intensely sour, even when largely diluted with water. (c.) Sp. gr. as already stated, 1.850, or (Ure,) 1.842 ; ac- cording to Dr. Thomson, 1.847 ; if heavier, it may contain sulphate of lead, or sulphate of potash, or both ; 2 J per cent, of sulphate of potash gives it the sp. gr. of 1.860, and Dr. Ure states* that the best acid of commerce contains from J to f of 1 part in 100, of foreign matter, which is sulphate of lead, in the proportion 4, to sulphate of potash l.f (d.) Its purity is decided by saturating it by an alkali. Dry car- bonate of soda, 100 grains, neutralizes 92 grains of pure liquid sul- phuric acid, and 100 of the acid require 108, or 108.5 of the car- bonate. J Henry. (c.) Produces heat, when mingled with water in every proportion ; 4 acid -f 2 water =300 Fahr. ; or better, 2 acid to 1 water, or by measure, If, or 1 acid to 1 water. Place a thin glass tumbler in a dish pour in the water provide a thin glass tube, 8 or 10 inches long, and fill it two thirds with colored water, add the acid in a slow stream, stirring with the glass tube, and soon after, the water in the tube will boil, and another tube, filled with alcohol, will also be made to boil. Explanation. Increase of specific gravity, and diminution of ca- pacity for heat. Two by measure, of acid -f-1 of water, starting from 50 =300, and the concentration =^. (/.) With ice. Ice 1-f- acid 4=212. ice 4-f- acid 1 produce intense cold. In both instances, the affinity of the acid for the water produces fusion, as the two cannot unite while the water is solid. The excess- of acid then goes, in the first case, to produce heat with the water form- ed ; in the second case, there being no more acid than is wanted for the fusion, cold is produced, upon the general principle that fluidity requires heat, and that the absorption of heat produces cold. (g.) Absorption of water from the air. Rapid, especially if ex- posed with a large surface ; in one day 3 parts became 4, and 1 oz. in twelve, months gained 6^ ; a drachm gained in five successive days, 68, 58, 39, 23, and 18 grains, and in five days more only, 5, 4, 3, 4 ; in one case, in fifty six days a drachm became 6 J drachms. * Diet. 2d Ed. p. 91. t The acid of commerce often contains 3 or 4 per cent, of salts, and sometimes more arising from the use of nitre, to remove the brown color; evaporation in a pla- tinum dish gives a prompt result, and if there are more than 5 grains in 500, the acid is sophisticated. Ure. \ These numbers do not correspond with the equivalents of sulphuric acid and carbonate of soda, as they stand in our modern works. 100 acid should neutralize very nearly 110 of carbonate soda. (49 liq. sul. acid : 54 carb. soda : : 100 S. A.: 110.2 C. S.) Communicated. Seventy three acid to twenty seven water, or very nearly 3 acid to 1 water. Ure. 310 INFLAMMABLES. (h.) Discoloration from the air, fyc. All common combustibles, even the floating dust in a room, will discolor this acid ; a drop of oil of turpentine does it instantly ; it is decomposed by the acid, and carbon developed. (i.) The pure acid is not rendered turbid by dilution with water. The impurities are chiefly sulphate of potash, and sulphate of lead ; the latter being very insoluble, is precipitated, renders the acid milky, and in time subsides ; hence dilution is a means, to a certain extent, of purifying the acid.* (/.) The acid is purified by distillation. Dr. lire's method is good, and avoids the danger which was encountered in the old way. Arrangement. A retort of from 2 to 4 quarts capacity ; acid 1 pint, adopter 3 or 4 feet long, terminating in a large receiver ; apply a charcoal fire to the naked retort, which should contain along with the acid, a few pieces of broken glass, or some platinum wire,f or platinum foil, which will prevent the heavy recoil upon the glass, produced by the sudden condensation of vapor, and^ by the great weight of the fluid. (k.) Boiling point. Acid of sp. gr. 1.850 containing 81 per cent, real acid, boils at 620, and at a lower temperature, in proportion as it is mingled with more water; that of sp. gr. 1.849, boils at 605, and contains 80 per cent real acid ; that of sp. gr. 1.838 containing real acid 75 per cent, boils at 530, &c. It is rendered stronger by heating, until the acid itself rises in vapor, and if mingled with combustible matter, this is burned off by heating it. (Z.) The freezing point. This depends on the dilution of the acid. If of sp. gr. 1780,{ it congeals at 45 ; viz. with 13 degrees less than causes water to freeze ; it freezes at 32, if any where be- tween 1.786, and 1.775; if 1.843, or like that of commerce, it freezes at 15 ; and if half water, at 36. When once frozen, it does not easily melt ; it sometimes forms regular prismatic crystals. (m.) Effects on the test fluids, the same that were mentioned under the general properties of acids ; infusion of litmus is very sensible, and that of purple cabbage sufficiently so ; alkanet tincture, previ- ously blued by a little ammonia, is instantly turned red again by a drop of the diluted acid. * Dr. Ure, by evaporating 100 parts of sulphuric acid, in a platinum dish, obtained three quarters of a part of solid matter, of which 2 (*4 ? p. 309, c.) was sulphate of potash, andl sulphate of lead. Jour. Science, Vol. IV, p. 115. For a table of the boiling point of acid of different densities, see Henry, Vol. I, p. 386, and Eng. Jour. Science, VoL IV, p. 127. t I have found it to succeed well without this precaution, which, however, it might be advisable to take. t Easily brought to this specific gravity by mingling 6 1-8 parts of the acid of commerce with 1 1-8 of water. Thomson's First Principles, Vol. I, p. 214. See Am. Jour. Vol. VI, p. 186. INFLAMMABLES. 311 6. DECOMPOSITION. (a.) Driven in vapor through a red hot platinum tube, or a small tube of glass or porcelain, this acid is decomposed, and affords sul- phurous acid gas, two volumes, and oxygen gas one volume. (b.) Its decomposition is best effected upon one of its salts, as will be mentioned under sulphate of baryta, from which we can obtain the sulphur. (c.) Heated with charcoal powder, it is decomposed, and various gases are evolved, as will be mentioned farther on. (d.) When it chars any animal or vegetable substance, it suffers decomposition. Se.) Decomposed by galvanism sulphur appears at the negative, oxygen at the positive pole, platinum wires being used. (/.) By being passed through an ignited porcelain tube along with hydrogen, which unites with its oxygen and precipitates the sulphur, and perhaps evolves sulphurous acid gas. 7. PROPORTION OF ITS CONSTITUENTS AND COMBINING WEIGHT. (a.) Centesimal ratio. Writers vary between 43.28 sulphur, and 56.72 oxygen, and 40 sulphur and 60 oxygen. Dr. Wollaston ad- mits the latter numbers, and Berzelius those that approximate to them ; 40 and 60 are probably correct. Murray. (b.) Equivalent numbers. The proportions of 40 and 60, corres- pond with 1 6 of sulphur, 1 proportion, and 24 of oxygen, 3 propor- tions, making 40 for the representative number of the dry acid, and liquid sulphuric acid = 1 real acid, 40, and 1 of water 9 49. It is supposed that by volume, the sulphur would be represented by 100, and the oxygen gas by 150, for oxygen gas is considered as combining in the proportion of half a volume which would be 50, if the 1 proportion of sulphur is called 100, and there are 3 of oxygen, which would of course be 150. 8. ANHYDROUS ACID. (a.) The dark fuming acid, already mentioned as being obtained by distilling green vitriol, has a sp. gr. of 1.896 or 1.90, and boils from 102 to 122 Fahr. (b.) Heated in a glass retort to which a receiver is attached, sur- rounded by snow and salt, half of the acid passes over in a state re- sembling asbestos, and is regarded as sulphuric acid without water, or the anhydrous acid, and the acid remaining in the retort is like the common oil of vitriol, composed of acid one proportion, and water one. (c.) It is the pure acid without water. (d.) It smokes violently when exposed to the air, and is dissipated too speedily to admit of being weighed. It is less corrosive than common sulphuric acid. It crystallizes in tough silky filaments like 312 INFLAMMABLES. asbestos, or in flat transparent rhomboids, of which the large angles are but little above 90. Thrown into water, it acts like red hot iron. It liquifies at 66, is more fluid than the common acid, and has a specific gravity of 1.97. 9. IMPORTANCE AND USES OF SULPHURIC ACID. (a.) Largely used in chemistry, being the most common agent in decompositions, where other acids are to be separated from their com- binations. (6.) For generating hydrogen, with the aid of zinc or iron, and water, for filling balloons. (c) For the manufacture of soda water, to evolve the gas from marble powder. (d.) For manufacturing nitric, muriatic, citric and tartaric acids. () In dyeing, bleaching, cleaning metals from oxide, and hVpre- paring chlorine for disinfection. (jf.) In forming metallic sulphates, as those of copper, zinc, and iron ; in making calomel, and corrosive sublimate, and sulphuric ether ; in dissolving indigo, extracting phosphorus, &c. (g.) In medicine, largely diluted 50 or 60 parts of water to 1 of acid.* Used as an antifebrile drink, and as a tonic and stimulant. It is also used externally as a caustic, and in the composition of elixir vi- triol, &c. Externally, as a gargle in putrid sore throats, and apthous mouths, and as a wash in cutaneous diseases. In its concentrated state, it is a violent poison, and the person who swallows much of it, dies in agony ; chalk and carbonate of magnesia, are the best rem- edies. 10. DIFFUSION IN NATURE. Largely in combination, as in the earthy and metallic sulphates, but not much known in a free state 5 occurs in that condition in the cra- ter of a volcano at Mount Idienne, in Java, &c. ; also, observed by Baron Humboldt, in the river Vinagre, in the Andes of Popayan.f Found in the cavities of a small volcanic hill, called Zoccolino, near Sienna ; also, in the state of New York.f 11. TEST. Muriate of barytes ; it acts by giving its earth to this acid, and by thus taking it from every combination, it affords us an infallible test for the sulphuric acid ; the precipitate is a heavy white powder. 12. POLARITY. Electro-negative ; it is attracted to the positive pole in the galvanic series. * Or, as much as will make it agreeable, and it may be qualified with sugar. To prevent its injuring the teeth, it is usual to suck it through a quill, but a glass tube would be better. I Boston Jour. Vol. II, p. 460. J By Prot. Eaton Am. Jour. Vol. XV, p. 23. INFLAMMABLES. 313 Remark. According to Berzelius, a minute quantity of titanium exists in the English acid, and of tellurium in that of Sweden. SULPHUROUS ACID. 1. HISTORY. This gas being produced whenever sulphur is burned, it has proba- bly always been known, although it was not recognized as a distinct chemical agent, until noticed by Stahl ; but it was first obtained pure by Dr. Priestley.* 2. PREPARATION. (a.) In a glass globe or bottle, burn sulphur in common air, either in a pendent spoon, f or by means of a sulphur match ; sulphurous acid gas will be formed, and if there be litmus or cabbage infusion in the bottle, it will be reddened, and eventually the color will be des- troyed, (b.) The same result is obtained with oxygen gas ; the combus- tion is brilliant, with a blue and white light, and the product is entire- ly sulphurous acid. There is no change in the volume of oxygen gas, but the weight is doubled. One volume of sulphur vapor unites with one volume of oxygen. (c.) Red oxide of mercury and sulphur, equal parts, or sulphur 12, and peroxide of manganese, 100 parts, mingled in powder and heated, produce sulphurous acid gas; in the former case, one cubic inch is obtained for every 5 grains of the oxide ; the latter pro- cess is recommended as being a very good one. (d.) The best process is, by mercury 1 part, with 6 or 7J of sul- phuric acid, in a small glass retort ; apply the heat of a lamp or of a few coals, and obtain the gas over mercury, or by a recurved tube passing to the bottom of a jar or bottle, and displacing the common air, as exhibited in the figure on p. 232, only substituting an empty bottle for the bottle of water theory, the mercury detaches 1 pro- portion of oxygen, and leaves the whole of the sulphur combined with the remaining two proportions of oxygen, and thus evolves the sulphu- rous acid gas ; the sulphate of mercury which is formed, may be sav- ed for future use. (e.) Sulphuric acid is decomposed by many other things ; it may be boiled on charcoal, wood, straw, cork or almost any vegetable * On Air, Vol. II, p. 1. t Pendent spoons are easily made by cutting a slip of sheet copper, into the form of a very acute isosceles triangle, the sharp end may be tlmist through a cork, and the other be hammered into a spoon and turned at right angles. I Metal 2. acid 3. (Turner,) with so small a proportion of acid, there might be danger of breaking the retort; it is better to use an excess of acid which can be af- terwards poured off. Thenard directs 6 or 7 of acid to 1 of mercury. 40 314 INFLAMMABLES. substance, and sulphurous acid gas will be obtained ; but there are other gases produced, and the process is much less neat than when mercury or copper is employed ; tin answers equally well. 3. COMPOSITION AND PROPERTIES. (a.) Sulphurous acid gas is composed of 1 volume of sulphur in vapor, and 1 volume of oxygen condensed into one volume, f or we may say that the volume of the oxygen gas is not changed, but an equal weight of sulphur is added to it. Its sp.gr. being 2.22,* and that of oxygen gas 1.11, therefore the weight of the gas is divided equally between the oxygen, and the sulphur. (6.) 100 cubic inches weigh nearly 68 grains ; accurately, it should be 67.776 grains, containing 33.888 of sulphur, that is, just half.f (c.) It is fatal to life, producing spasms of the glottis, and killing both by suffocation and excoriation ; used to destroy bees. Intol- erably suffocating, disgusting, and distressing, even when breathed in moderate quantity, and mixed with much air ; it creates a cough and a stricture of the breast. (d.) Extinguishes combustion ; best shewn by a pendent candle let down into a jar of the gas, as exhibited in a note to p. 187 ; it may be extinguished many times, and then the gas may be poured upon other candles, and will run down like water and extinguish them. (e.) Fugaciously reddens, and soon bleaches the dark vegetable col- ors. A red rose becomes white in it, as may be beautifully shown by holding a red rose over a burning sulphur match, when it will be- come first variegated and then white, and immersion in water re- stores the color ; litmus paper is first reddened and then becomes white. The color is not decomposed, for it can be restored by a stronger acid or by an alkali. Turner. ^ (f.) The aqueous solution is prepared by passing the gas, with a recurved tube, through water, which, when kept cold by snow, ab- sorbs 33 times its volume ;|| or 100 grains absorb 8.2 of the gas. (g.) The gas is spontaneously disengaged into the air ; rapidly by sulphuric acid. (A.) Sulphuric acid, saturated ivith the sulphurous, crystallizes with a moderate reduction of heat ; when distilled, it crystallizes and becomes solid. (i.) Not decomposed by heat. * 2.234, Thenard 2.25, Th. and G.-Lus. t Thomson's First Priu. I. 216. t Ann.de Chim. et de Phys. Vol. V. A gratuitous cruelty, as they can be transferred to another hive, and thus, both the bees and the honey can be saved. |j At 61. I'ic. INFLAMMABLES. 315 .00 If tw o measures of sulphurous acid gas and one of oxygen be mingled in a jar, standing over mercury, and a little water be added, sulphuric acid will be formed ; the same result is obtained by passing the mixed gases through a red hot tube, or causing the electric spark to pass through them. (k.) Becomes liquid by great cold ; or by moderate cold, 31, if aided by pressure. (/.) Decomposed when passed over ignited charcoal, or with hy- drogen, through a red hot tube ; water and sulphur are the products (m.) Liquid sulphurous acid does not give up its gas by freezing, and becomes so heavy as to sink in water. (n.) Boiling expels the gas, although the water remains acid, from the formation of sulphuric acid. (o.) Exposed to the air, the liquid acid becomes slowly sulphuric acid, absorbing oxygen gas from the air ; its smell is like that of the gas. (p.) Decomposed, by potassium* heated in it ; products, probably potassa and sulphuret of potassium ; also, at ignition, by hydrogen, forming water and leaving sulphur ; and by carbon, producing carbo- nic acid and carbonic oxide, and liberating sulphur. (q.) Sulphurous acid attracts oxygen powerfully ; it converts the peroxide into the protoxide of iron ; the same with manganese, and it precipitates gold, platinum, and mercury in the metallic state, be- cause their affinity for oxygen is feeble ; it becomes itself, in the mean time, sulphuric acid, by acquiring one proportion of oxygen. (r.) Condensation of sulphurous acid gas. Mr. Faraday,f by confining, in a bent glass tube, both sulphuric acid and mercury, and applying heat, caused the sulphurous acid gas which they produced by their reaction, to pass into the other end of the tube, cooled by a freezing mixture, and thus obtained the sulphurous acid in a liquid state. The pressure was about two atmospheres. (s.) Mr. Bussy\ also obtained the liquid anhydrous acid, from the above named materials, by passing the dried gas into a vessel cooled by ice or snow, then through a tube containing melted muri- ate of.lime, and finally into a matrass surrounded by a mixture of ice 2 parts and common salt 1 ; in this, the gas is condensed into a liquid, at the common atmospheric pressure.^ * It is decomposed in the same manner by sodium. t Phil. Trans. 1823, p. 190. i Ann. Phil. Vol. VIII, p. 307, N. S. & M. A. de la Rive (Bib. Univ. Mars, 1829, and Am. Jour. Vol. XVII, p. 166,) directs that a second tube, filled with muriate of lime, should pass from the second to a third vessel cooled like the others, and from this a tube may proceed to the mer- curial cistern. The junctures must be luted tight. The gas having been disenga- ged during 8 or 10 hours, white crystals, (hydrates) are found in the vessel No. 1 ; they resemble the hydrate of chlorine ; they are said to remain solid at 4 or 5 (centi- grade ) and in Nos. 2 and 3, is the liquid sulphurous acid, which must be immediately 316 INFLAMMABLES. (t.) Sir H. Davy, substituting the pressure of the vapor of ether for that of the gas itself, and causing the former, through the medium of mercury in the bend of the tube, to press upon the latter in the other leg, while cold was applied, succeeded in condensing the sulphurous acid into a fluid.* 4. PROPERTIES OF THE LIQJJIFIED GAS. (a.) Limpid, colorless, refractive power similar to that of water ; when the tube was opened it evaporated rapidly, but without explo- sion. (b.) Sp. gr. 1.45 bolls at 14 Fahr. and evaporates rapidly, but without explosion, cooling the residuary fluid to 0, so that it re- mains some time liquid under the pressure of the atmosphere. (c.) JY0 visible fumes, but a strong smell of sulphurous acid, eventually leaving the tube dry. (d.) Ice dropped into the fluid, proved so much warmer, that the ice made the fluid boil. (e.) Mercury is frozen by the cold produced by the evaporation of sulphurous acid ; for this purpose the ball of a thermometer tube is surrounded with cotton, and kept wet with the liquid. (jf.) By its aid, and that of a moderate pressure, several addition- al gases have been liquified. f The cold was carried to 60, but absolute alcohol and ether did not freeze. One part of the acid in a watch glass, freezes, by the spontaneous evaporation of the other. 5. COMBINING WEIGHT. Sulphurous acid consists of 1 proportion of sulphur 16, -f-2 of oxy- gen 16 = 32, which is therefore its equivalent number. 6. POLARITY. Like other acids, it is electro negative, as it is attracted to the positive pole in the galvanic arrangement. 7. SULPHUROUS ACID IN VOLCANOS AND SOLFATERRAS. It is constantly emitted wherever volcanic fires are active. This arises from the combustion of sulphur, raised by the subterranean heat r and burned by the air in its passage. Those who visit volcanic cra- ters and solfaterras are constantly incommoded by this gas, and ^often find it necessary to mount some elevation in order to escape from suffocation. corked tight, and the vessel must be constantly surrounded by a freezing- mixture, else the gas will escape, or the vessel explode. A few drops of the liquid sulphu- rous acid thrown upon water, produces a crust of ice. If mercury, of the volume of a hazlenut, is moistened by a few drops of the acid, and the apparatus placed under an exhausted receiver, the metal will freeze solid, and a considerable mass may be thus frozen and preserved for a few minutes. It is found that solid mercury is a much better conductor of electricity than the fluid metal. In its pure liquid state, it was not decomposed by electricity, but if a little water was added, sulphuretted hydrogen appeared at one pole, and oxygen at the other. * See Faraday's Chemical Manip. p. 205. t Ann. Phil. N. S. Vol. VIII, p. 307, INFLAMMABLES. 317 8. USES, INT BLEACHING, and for other purposes* Jz.) It bleaches straw, woolen and silk y and gives silk lustre* ulphur is burned in a barrel, in family operations ; the articles to be bleached are hung up in the barrel, and moistened with water or solution of pearlashes.f It also discharges iron moulds and vegeta- ble stains from linen. For this purpose, the places must be made thoroughly damp, and then two or three sulphur matches must be burned close to them ; liquid sulphurous acid will thus be formed, and the spots will soon disappear. (b.) A similar process is practised on a large scale in the arts ; the sulphur is burned in chambers lined with sheet lead, and the moistened articles are hung upon frames. J (c.) Prepared of a proper strength for liquid bleaching, by dis- tilling in a glass retort 1 Ib. of wood shavings, with the same weight of sulphuric acid, and placing two gallons of water in the receiver ; if to be used to stop the fermentation of wine, only two quarts of water are placed in the receiver. (d.) A rag, imbued with sulphur, is sometimes burned in cider casks to preserve the cider from too rapid fermentation. (e.) The fumes of burning sulphur, (or in other words, sulphurous acid gas,) were employed 1600 years ago in bleaching wool; but the gas whitens only the surface, and therefore the liquid acid is pre- ferred. (/.) Thenard says that the sulphurous acid is beginning to be used to cure diseases of the skin that there are in various hospit- als in Paris, baths of this kind that a few applications suffice to remove psora, and that the tetters yield to the continued use of this remedy. It is said that Dr. Gules, of Paris appliesj| the vapor of burning sulphur mixed with air, to the surface of the body, as an air bath, with much advantage in many chronic diseases of the joints, the glands, and the lymphatics. Ure. ******* Dr. Torrey informs me that he has made the liquid sulphurous acid before his class, and that tubes of it may be sealed by the blow- pipe, while immersed, (except the capillary extremity,) in a freezing mixture. The hypo- or sub-sulphurous, and the hypo- or sub-sulphuric acids will be mentioned after the sulphates and sulphites* * Sec Parkes on Bleaching. Essays, Vol. II, p. 337. t Water would probably be better, as the alkali would neutralize a part of the- acid gas, and withdraw it from action. I Verbal communication to the author while in England, from a manufacturer. Fifth Ed. VII, p. 195. fl In an apparatus called Boite Fumigatoire. 318 SALTS. SALTS. Introductory Remarks. That the student may not be fatigued by a too frequent reiteration of similar properties, the history of saline bodies will be given, in di- visions, under that of the acids, which they respectively contain, in the same manner as that of the principal acids is given, under combustibles. We shall thus dispose of the salts in convenient groups, and the most important will be brought into view, as early as possible. As many of the salts are unimportant, the history of some of them will be abridged, and that of others omitted, or included in a general statement of the properties of the genus to which they belong. Some of the salts are, however, eminently important and interesting, and therefore the history of such salts will be developed, with all the ne- cessary details. Under the head of attraction and crystallization, many things have been stated respecting saline bodies, which need not be repeated here, and various generalizations will be prefixed to the first genus. It remains, to make a few other observations, by way of introduction to the history of saline bodies generally. As salts consist of acids and salifiable bases ; alkalies, earths, and metallic oxides, we observe that the powers of saturation differ very widely among these agents ; it takes much more of some bases to satur- ate a given acid than of others, and vice versa, of different acids to saturate a given base. This evidently depends upon the number ex- pressing the combining powers of those different bodies ; or rather the formation of salts is only a mode of ascertaining and expressing this very fact, in relation to acids and bases. For instance, the com- bining power of nitric acid is expressed by 54, that of lime by 28, and that of baryta by 78 ; to form then anhydrous nitrate of lime, 54 parts of nitric acid will unite with 28 of lime, and the chemical equivalent of nitrate of lime will be 54+28=82; but to saturate 54 of nitric acid, requires 78 of baryta, and therefore the chemical equivalent of nitrate of baryta will be 54+78 = 132. Now, suppose lime and baryta to be combined, each with two acids ; say the nitric and the sulphuric ; the numbers expressing the combining powers of these earths being as above stated, and that of sulphuric acid being 40, the sulphate of baryta will be expressed by 40+78=118, and that of the sulphate of lime by 40+28 = 68, the salts being supposed anhydrous. It was suggested by Berthollet, and the idea was adopted, more or less, by many chemists, that the strength of affinity is inversely as the saturating power ; but this idea is inconsistent with facts ; e. g. 40 parts of sulphuric acid require 28 of lime and 78 of baryta for saturation, and therefore baryta should attract sulphuric acid less powerfully than lime, which is not true. SALTS. Triple Salts are those which have two bases united to one acid, as the phosphate of soda and ammonia ; this may be regarded as two phosphates combined, or as a phosphate of two bases ; some prefer to call such combinations double salts. Neutral Salts were formerly regarded as those in which the pro- perties of the acid and base are both entirely lost, as in sulphate of potassa ; but sometimes there are peculiar characters imparted by the acid or base, more commonly by the latter ; e. g. the salts of am- monia are volatile ; of magnesia bitter ; of alumina styptic ; and of glucina sweet. The nitrates are cooling, and they deflagrate with red hot charcoal. In general, a salt is said to be insoluble, if it requires 1000 parts of water for its solution. Salts are not only compound bodies, but the acids and bases of which they consist, are also compound. Thus, in sulphate of soda, the acid is composed of oxygen and sulphur, and the base of oxygen and sodium. It has been imagined by some, that in salts, the ele- ments, losing the form of acids and bases, are directly united to each other, so as to produce ternary or quaternary compounds. Thus, in sulphate of soda, the oxygen, which exists in the acid, in the base, and in the water of crystallization ; the sulphur of the acid ; the sodium of the base, and the hydrogen of the water, are regarded as being in immediate union, to form a quaternary compound; but of the truth of this speculation there is no direct proof; and it is extremely improbable that it is true, because the acid, the base and the water can be combined synthetically, to form the salt ; the water can be expelled by heat and recovered, and the galvanic power will separate the acid and alkali unaltered, in full proportion, and we know not of any affinity which should unite^these bodies in a quaternary combination, and then resolve them again into binary compounds. NOMENCLATURE AND CHARACTER OF SALTS. 1. As almost every acid unites with nearly every base, and some- times in more than one proportion, it follows that the salts are very numerous. 2. They are said to exceed 2000, although not more than thirty were known fifty years ago. 3. The old names were sometimes barbarous, absurd, or false, im- plying incorrect ideas. 4. The nomenclature of the French chemists,* is eminently use- ful in the study of the salts. 5. Every salt consists of an acid and a salifiable base, and the bases, except ammonia, are all oxides of metals or of inflammable bodies. * See page 35. 320 SALTS. 6. The genera are derived from the acids ; the species from the bases, thus all that contain sulphuric acid are sulphates ; all that con- tain nitric acid are nitrates, &ic. 7. The bases are the oxides* of which there are three divisions ; the alkalies, the earths, and the other metallic oxides. 8* Every base that combines with acids, furnishes a species ; thus sulphuric acid with potassa, soda, and ammonia forms a sulphate of each of those bases. 9. The termination ate, corresponds with the acid, whose termina- tion is in ic, and the termination ite, with the acid whose termination is in ous ; thus, sulphuric acid gives sulphates ; sulphurous acid sulphites. 10. There are some acids containing less oxygen than those that terminate in ous ; in such case, the word hypo is prefixed ; thus we have hypo-sulphurous acid, hypo-nitrous acid, giving also salts that are called hypo-sulphites, and hypo-nitrites. 11. It was formerly supposed, that there is sometimes an excess of acid in a salt, in which case, the preposition super or hyper was pre- fixed ; and on the other hand, that there is, in particular cases, a de- ficiency of acid or an excess of base, and then the preposition sub was prefixed ; thus, there was a super-sulphate of potassa. and a sub- carbonate of potassa. Now, salts with excess of acid are distinguished by the prefix, bis or bi; thus we have fo'-sulphate and 6i-carbonate of potas- sa ; because in these salts, there is just twice as much acid as in the carbonates of the same base. In some salts, the double propor- tion is again doubled, and then the word quadro is prefixed ; thus there is oxalate, 5w-oxalate and quadr-oxalate of potash, implying one, two, and four equivalents of the acid to one of the base. The word super is now banished from the nomenclature of salts ;f but sub is still retained by some, where there are two or more propor- tions of the base. But, Dr. Thomsonf has proposed to use the Greek numeral words, dis, tris, tetrakis, to denote the proportions of base in a sub-salt ; thus, 6?i-sulphate of alumina contains one propor- tion of acid and two of the earth, but this nomenclature has not yet obtained general currency. 12. Salts are generally, but not always sapid. The first idea was derived from common salt ; but many earthy salts are insipid, e. g. sulphate of lime, carbonate of lime, &c. and such salts are generally insoluble. 13. Salts are generally, but not universally soluble in water ; the alkaline salts are all soluble, but earthy and metallic salts have some- times one character and sometimes the other. A salt is said to be * Ammonia excepted. i It may be, and often is still used in a vague and popular sense. } Dr. Thomson has introduced the word sesqui, where there is supposed to be a half of an equivalent. SALTS SULPHATES. 321 insoluble, if it requires more than 1000 parts of water for its solu- tion. 14. Incombustible, with a few exceptions. 15. Crystallizable, either by natural or artificial processes. 16. Saturation between acid and base is determined (a.) By the taste, which, when there is one equivalent of each, becomes saline, or at least, ceases to be acid or alkaline. '.^ By the absence of any effect on test colors. c.) In the case of a carbonate; by the cessation of effervescence. d.) A scale or table of chemical equivalents, furnishes at once the information desired, as to the quantity of the one agent necessary to saturate the other. 17. Salts precipitate, if they are insoluble in water,* or much less soluble than their constituent principles (a.) In powder, as sulphate of baryta. (b.) In crystals, as sulphate of potassa, if formed from concentra- ted acid and alkali. 18. If soluble, they remain in solution, as most alkaline, and many earthy and metallic salts do. 19. The name of a salt expresses its composition, and the knowl- edge of the composition recals the name. 20. The nomenclature is therefore founded upon the most correct logical principles. 21. The salts are, on the whole, very important, to arts, science, and domestic economy. Some of them exist in vast abundance. SULPHATES OF ALKALIES AND EARTHS. General Characters. 1. Formed by sulphuric acid and a base. 2. Generally crystallizable. 3. Not decomposable by heat, or only partially so, (except the sul- phate of ammonia.) 4. Decomposable, (with the same exception,) by ignition with charcoal, being converted into sulphurets. 5. Have generally a bitter taste, if any. 6. Decomposed by all the barytic salts, except sulphate of baryta ; the precipitate is insoluble in acetic acid. 7. Precipitated from their aqueous solutions, by alcohol, and in general, crystallized. SULPHATE OF POTASSA. 1. PREPARATION. (a.) By sulphuric acid and dilute solution of potassa, or of carbo- nate of potassa, mingled till test paper is no longer affected, or effer- vescence ceases. * Supposing the bases, or perhaps both acids and bases, to have been previously in aqueous solution. 41 322 SALTS SULPHATES. (b.) Evaporation gives regular crystals, whose form is that of six sided prisms, sometimes crowned by six sided pyramids. 2. HISTORY. Long known, and had formerly a multitude of names,* which were banished when it received its present denomina- tion. 3. PROPERTIES. (a.) Taste, acrid and bitter sp. gr. 2.29, or 2.40, easily pulve- rized. (b.) At 212, requires five times, and at 60, sixteen times its weight of water for solution. (c.) Not affected by the air. On burning coals, or red hot iron, it decrepitates. (d.) Contains no water of crystallization. 4. COMPOSITION. Acid, 45.45 ; potassa, 54.55, or acid, 1 propor- tion, 40 ; potassa, 1 proportion, 48 = 88, which is its equivalent number. 5. DECOMPOSITION. (a.) By acids. Although the sulphuric acid has a stronger affinity for potassa, than any other acid has, still the nitric and muriatic acids, in large quantities, decompose it in part ; the products are much bi- sulphate of potassa, and some nitrate and muriate of potassa. Not owing to the capriciousness of chemical attraction, but accord- ing to Berthollet, to the influence of quantity, compensating for infe- rior force of attraction. !b.) By barytic and strontitic water, attracting the sulphuric acid, c.) Also, by nitrate and muriate of lime, by double elective at- traction. (d.) By heating it with charcoal powder, when it becomes a sul- phuret, and can be decomposed in the palm of the hand, by vinegar or other weak acid, thus fulfilling Stahl's boast, but not as it was in- tended by him, that others should understand it. (e.) Other processes. Saw dust substituted for charcoal, and py- roligneous acid for the vinegar, and the acid is afterwards decom- posed by heat. Dundonald. Sulphate of potassa, 100 parts, chalk 100, charcoal 50, heat them sulphuret of lime is formed, and the alkali being liberated, may be obtained by lixiviation.f 6. USES, &ic. Called in the shops, vitriolated tartar, and used as a purgative or alterative dose, half an oz. or less ; the effect less transient than that of sulphate of soda. The sal polycrest of the old physicians was made by deflagrating nitre and sulphur, and was a * Vitriolized and vitriolated tartar, sal de duobus, arcanum duplicatum, sal pol- ycrest, salt of Glazer, vitriol of potash, vitriolated vegetable alkali, &c. but vitri- olated tartar was the most general name. Hence, and from similar cases, the ne- cessity of the new nomenclature of the salts. t Ann.de Chim. Vol. XIX. SALTS SULPHATES. 323 c&mpound of sulphate and sulphite of potassa. The finest neutral crystals of this salt are obtained when acid predominates in the mix- ture. Not found among mineral bodies, but exists in some animal fluids, and in the ashes and juices of some vegetables, as tobacco.* BI-SULPHATE OF POTASSA. 1 . PREPARATION. By heating together three parts of sulphate of potassa, and one of sulphuric acid ; discovered by Rouelle senior ; may be obtained in needle formed crystals, and even in six sided prisms. 2. PROPERTIES. (a.) Soluble in 2 parts of water, at 60, and in less at 212. (b.) Melts readily, with the appearance of oil, but becomes of an opake white on cooling ; heated for a long time, its superfluous acid is dissipated, and it becomes sulphate of potassa. !c.) Taste acrid ; reddens the blue test colors. d.) The bi-sulphate is usually obtained in the process for nitric acid. (e.) With ice, it generates cold.f Of little use, except to form the sulphate, which is done by neutralizing the excess of acid by chalk ; it may be used in crystallizing alum, and is sometimes employed as a flux. After the process for nitric acid, if the salt, while still fluid, is pour- ed into a pan, it effloresces most beautifully in the course of a few months, presenting a delicate downy coating of crystalline filaments, which make their way over and down the sides of the vessel ; if it is glazed, the glazing will peal off and leave the naked biscuit. It contains two proportions of sulphuric acid, and one of potassa, 40X2=80 acid, -f 48 potassa = 128 for its equivalent. SULPHATE OF SODA. 1. NAMES. Named Glauber's salt, after a German chemist, who discovered it in the residuum of the process for muriatic acid. 2. NATURAL HISTORY. (a.) Found in sea water, and in the ashes of marine vegetables, and in kelp. (b.) In the earth, near ASTRACHAN.{ (c.) In salt and mineral springs. (d.) Often effloresces at the surface of the ground, upon the walls of subterraneous edifices and other buildings. * Four. III. 33. t Four. Ill, 39. t Kirw. Mfti 324 SALTS SULPHATES. (e.) Found in the ashes of old wood, and in some plants, particu- larly tamarisk.* (/.) In large proportion in the Glauberite of Spain. 3. PREPARATION. By saturating a solution of soda or its carbo- nate with sulphuric acid, but the quantity produced in the manufac- ture of muriatic acid, and chlorine, and that can be made from sea water, is much greater than can be consumed. 4. PROPERTIES. (a.) Crystallizes in transparent six sided prisms, with dihedral summits, usually striated at the edges, and often very irregular. (b.) Taste bitter, and dissolves easily in the mouth ; suffers readily, the watery fusion ; then dries and melts, with the true igneous fusion. (c.) Effloresces in the air loses half its weight, and thus becomes, as a medicine, twice as strong ; by a high heat, a part of the acid is driven off. (d.) Soluble in 2.67 of water at 60, and in .8, at 212 ;f in this respect, strongly contrasted with sulphate of potassa. The hot solu- tion of sulphate of soda, crystallizes by cooling, { and when the quan- tity is great, the crystals are very large, sometimes half a yard in length, and several inches in diameter. 5. COMPOSITION. When anhydrous, Acid, 55.55 or 1 proportion 40 Soda, 44.45 or 1 " 32 100. 72 its representative number. * Four. Ill, 42. t In judging of the solubility of a salt, we must not put the salt into water, and expose that water directly to heat, but immerse the vessel containing the salt in a water bath, in which the thermometer is placed. t At 70, water dissolves nearly half its weight, twice its weight at 88, and 3.2 of its weight at 106, at any higher degree, some of the salt is deposited in opake anhy- drous crystals, so that it grows less soluble with more heat. Turner. If the saturated boiling solution of this salt be made with care in a matrass or flask, and free from agitation, it may be reduced to the temperature of the air with- out crystallizing. Close the vessel by a stop cock at the top, or a good cork, the in- stant before it is withdrawn from the fire, and while still boiling. Sometimes on open- ing or on agitating the solution, and always on throwing in a crystal, (any crystal or solid will do, but better one of the same salt,) nearly the whole fluid will rapidly crys- tallize, and the temperature will rise considerably. The balance offerees between cohesion and repulsion is disturbed by agitation, or by a crystal affording a nucleus. The pressure of the atmosphere acts only as a disturbing force, and any other disturb- ing forces produce the concretion ; for it happens in vacuo if a crystal be dropped in. Mr. Graham, (Phil. Mag. New Series, Vol. IV, p. 215,) has discovered that a saturated solution of sulphate of soda, placed over mercury, previously heated to 110 or 120, will cool without crystallizing, but that if a bubble of air, or of any gas, especially of those that are soluble in water, or a portion of any fluid that attracts water, as alcohol, be thrown up into the solution, it will immediately crystallize. Hence it is concluded that the influence of air in causing the crystal- lization in this well known experiment, is owing to the solution of a portion of it, which thus deprives the salt of a part of its water, and causes the crystallization to begin. SALTS SULPHATES. 325 The crystals, Acid, 24.70 or 1 proportion =40 Soda, 19.75 1 " =32 Water, 55.55 10 " =90 100. 162 its equivalent number. 6. DECOMPOSITION. (a.) By combustibles, especially charcoal ; the same as that of sul- phate of potassa. Immense quantities are produced in making muri- atic acid, and in other manufactures ; therefore its cheap and effectual decomposition is an object of vast importance for the sake of the soda. (b.) Potassa will do it. but the price of labor forbids, although soda is dearer than potash. (c.) Decomposed (via humida,) by no acid, but it dissolves readily in the nitric, muriatic and sulphuric acids, producing cold. 4 parts sulphuric acid with 5 of this salt produce 47 of cold ; 2 parts nitric acid with 2 water and 3 of this, produce more cold than the last mix- ture ; 5 muriatic, and 8 of this salt, form a considerably powerful mixture. .) Baryta and strontia decompose it, taking its acid. SES. It is the most common domestic cathartic, and is called salts; dosel oz. perhaps more, often 1 J oz. Used also in small diluted doses, as a diuretic and aperient. The effloresced salts must be given in half the quantity. It is now used in the manufacture of glass, p. 280 (b.) BISULPHATE OF SODA. * ' Formed by adding sulphuric acid to a hot solution of sulphate of soda; product, large rhomboidal crystals ; efflorescent, soluble in twice their weight of water at 60 ; lose their excess of acid by heat. Henry* SULPHATE OF AMMONIA. 1. HISTORY, NAME, &tc. Discovered by Glauber, who called it secret sal ammoniac ; other names vitriolated ammoniac, vitriol- ated volatile alkali, &c. Found in the vicinity of volcanos, and in the waters of the Tuscan lakes ; also in the ashes and soot of pit coal.* 2. PREPARATION. By mingling sulphuric acid 88 parts, and compact carbonate of ammonia 100 parts, to mutual saturation, or by decomposing muriate of ammonia, by sulphuric acid. 3. PROPERTIES. (a.) The crystals are long six sided prisms, crowned with six sided pyramids ; sometimes in plates, silky fibres, or clusters of needles. f (" u.. * It is not probable that the ammonia exists in the coal, but the nitrogen of the air and the hydrogen of the coal form the ammonia ; the oxygen of the air, with the sulphur of the coal, forms the sulphuric acid, and this is doubtless the origin of the sulphate of ammonia in the soot and ashes. t Tour. Vol. Ill, p. 55. 326 SALTSSULPHATES. b.) Taste sharp and bitter. c.) Solubility at 60 ; water 1, salt 2 ; at 212, equal parts. d.) During its solution it produces cold. e.) Little affected by the air, or slightly efflorescent. /.) Heated, suffers watery fusion, sublimes in part, and is then sour, and reddens vegetable blues. By a still higher heat, com- pletely decomposed, and resolved into nitrogen, water, and sulphu- rous acid. 5. COMPOSITION. Acid, 53.1 or 1 propor. =40 Ammonia, 22.6 1 " =17 Water, 24.3 2 " =18 100.0 75 its equivalent number. If water be subtracted, it leaves 57 for anhydrous sulphate, which is known only in theory. Dr. Thomson admits but one proportion of water, in the crystallized salt, which would reduce its equivalent to 66. 6. DECOMPOSITION. The nitric and the muriatic acids decompose about J of the salt. Potassa and soda, baryta, strontia and lime, liberate the gas ammonia, forming a sulphate of the base. Sulphate of soda, and sulphate of ammonia, when mingled, form a triple crystallizable salt.* (c.) Deflagrates with melted nitre, being resolved into water and nitrogen. SULPHATE OF LIME. 1. PREPARATION, NATURAL HISTORY, &c. Formed by the mu- tual action of diluted sulphuric acid and marble, or chalk, or by the same acid and any soluble calcareous salt, or lime water; the sul- phate precipitates. 2. PROPERTIES. Melts before the blowpipe, and in furnace heats. Solubility in cold water, 500 parts to 1, in 450 at 212, and crystallizes on cooling. Soluble entirely in dilute nitric acid. (c.) Causes waters to be hard, decomposing the soap that is mingled with them ; the acid unites with the alkali, and the oil with the earth, to form an earthy soap ; by adding solution of soap to so- lution of sulphate of lime, this effect is manifested. (d.) Thrown down by alcohol from its aqueous solution. (e.) Decomposed by boiling with baryta, strontia, potassa and soda, and by their carbonates, or at least by those of the fixed alkalies ; see those articles. Th. Ill, 362. to SALTS SULPHATES. 327 (/.) Insipid and harmless ; sp. gr. of the native salt about 2.26 to 2.31. 3. COMPOSITION. According to Dalton, 58.60 acid, 41. 40 base. Berzelius and Thomson 58. and 42. Dr. Henry thinks its true con- stitution is, Acid, 58.42, or 1 proportion, - - = 40 Lime, 41. 58, or 1 " - -28 100.00 68 Crystallized sulphate of lime is composed of, Sulphate of lime, 79.07, or 1 proportion, (anhydrous,) 68 Water, - 20.93, or 2 " 18 100.00 86 4. USES AND MISCELLANEOUS REMARKS. (a.) The native salt is abundant, in the form of alabaster, gypsum, or plaster stone, selenite crystals, &c. Found in the ashes of vege- tables, in the sea, and in many natural waters ; producing incrusta- tions upon the pans of the salt boilers.* There is a native variety without water, called the anhydrite, but it is rare, and its properties are different from those of the common kind.f Sb.) Heated, it loses weight .22, and if in a retort, water may be ected. (c.) Exhibits a false appearance of boiling, in consequence of the escape of the water ; this is best shewn in a glass retort, with the la- mellated variety ; it may be seen in a crucible with a forge heat. (d.) Thus prepared for statuary and stucco work. Heat the plas- ter thoroughly, pulverize it fine, mix with a little good quick lime in fine powder, and form into a paste with water. (e.) To copy a medal or coin, pour the paste into a box, oil the surface of the medal to prevent adhesion, and brush it over with the cream of the plaster to prevent air holes ; then impress it upon the paste and let it harden. (f.) To copy a face, living or dead, or a statue ; the process is the same, only laying the figure on a table, oiling the surface, and if a living person, putting paper tubes in the nostrils, tying the hair back, and pouring on the plaster of the consistence of a thick cream. The muscles are kept composed, and in about 20 minutes, the cast will grow firm, when it is removed. After forming the concave copy, the convex is cast in it, and any mistakes are corrected or additions made ; then a new concave is made upon this and serves as a permanent mould ; statues are cast in parts and then joined. For stucco work, * And in the boilers of the steam boats, that use salt water. t It is found to be much more common than was formerly supposed. 328 SALTS SULPHATES. the plaster is cast in moulds, or figured on the spot to which it is ap- plied. Sometimes used to adulterate flour. Discovered by weighing a given measure, by grittiness be- tween the teeth, by alcohol throwing it down from water that has been boiled on the flour, by the tests for lime and sulphuric acid, by burn- ing the flour in the open air, and examining the residuum and by forming heavy bread. Besides the uses of this salt for statues, &c. it is employed in -cer- tain proportions with common lime plaster, to give it firmness and beauty, and such walls will bear washing and cleaning with soap. It is largely and most advantageously employed in agriculture as a manure, on sandy soils and grass lands. * It is extensively used in Switzerland, but very little, if at all, in Great Britain. It need not be burned, but merely pulverized. At Paris, and in Minorca, it is employed in building houses. Abundant in Nova Scotia, and in many of the Western American States ; a very beautiful transparent va- riety is found at Lockport, and the compact variety exists extensive- ly in other places in the state of New York. SULPHATE OF BARYTA. 1. NAME, &c, (a.) The native mineral formerly called ponderous spar ; its sp. gr. being from 4.3 to 4.7. (b.) Its composition first ascertained by Ghan. 2. NATURAL HISTORY. (a.) Found native, in almost every country, particularly in metal- lic veins, of which it often forms the gangue ; it is frequently amorphous, compact or granular, and of a pure white, or red, brown, yellow, &c. (b.) Often crystallized, or fibrous, translucent, transparent or opake.f 3. PREPARATION. By mingling barytic water or any soluble salt of baryta, with sulphuric acid or any soluble salt containing it ; there is an immediate dense precipitate. 4. PROPERTIES. (a.) By heat, the foliated natural sulphate decrepitates, and melts under the blowpipe, at about 35, Wedg. (b.) Tasteless and inodorous, insoluble in water ; or requires ac- cording to Kirwan, 43,000 parts of water. * The popular opinion that it will not answer near the sea, appears to be erroneous, as was proved by the late Mr. M. Rogers, at his place, near Stamford, Conn, where, as I heard him say, it produced the most striking effects on land washed by the salt water. Dr. Black says its effects last two years, and he asserts, contrary to our impressions in this country, that it is most efficacious on strong and rich lands. t Found sometimes in sandstone, in Scotland ; rarely, in the same country, in granite, in the place of the felspar ; occasionally in the interior of Scotch agates, and in the ludus helmontii, of England. SALTS SULPHATES. 329 (c.) Soluble in concentrated sulphuric acid, especially if boiling, but again precipitated by water.* (d.) Decomposed by ignition with charcoal ; its oxygen is separated in the form of carbonic acid, and sulphuret of barium is left. (e.) Pulverized, kneaded up with flour and water, formed into a thin cake and exposed to ignition, it becomes phosphorescent in the dark.f 5. COMPOSITION. Dr. Henry, after citing several analyses, con- cludes that the true composition is, Acid, 33.90, 1 proportion, - 40 Earth, 66.10, " - 78 100.00 11 8, its equivalent. As baryta is used to separate sulphuric acid from all its combina- tions, this salt is very important in analysis. The quantity is deter- mined by weighing the precipitate, previously washed and dried, and allowing 33.9 per cent, of its weight, " for real sulphuric acid," thus shewing the quantity in any sulphate. J Sulphuric acid or any solu- ble sulphate occasions a sensible precipitate in a solution containing sVo o f baryta, or of any of its soluble salts. 6. DECOMPOSITION. The mode by charcoal has been already mentioned. Sa.^ Not decomposed by any acid or alkali.\\ b.) Readily by double elective attraction, with carbonate of po- tassa, or of soda, or ammonia, IT after long continued boiling. (c.) But much more readily, by ignition with the carbonate of an alkali. Mix pure, decrepitated and pulverized sulphate of baryta, with twice its weight of dry, pure carbonate of fixed alkali, and ex- pose them in a crucible to a violent heat. A double decomposition * Easily shown by adding sulphuric acid to solution of baryta, or any of its soluble salts ; the precipitate will be redissolved by more sulphuric acid, and then thrown down by water, and thus it may be alternately redissolved and precipitated by acid and water. t First observed, in the variety called Bologna stone, by an Italian shoemaker, named Vincen/o Casciarolo. This man found a Bologna stone at the foot of mount Paterno, and its brightness and gravity made him suspect that it contained silver. Having heated it to extract the silver, he observed that it was afterwards luminous in the dark, and on repeating the experiment, it constantly succeeded. It is evident that by the calcination, it must be converted, at least in part, into sulphuret. Prof. Olmsted informs me, that a granular sulphate of baryta from North Carolina, (Crow- der's mountain,) when heated, phosphoresces with a clear white light. t Henry, 10th Ed. Vol. I, p. 604. Thenard, III, 171. || Fourcroy asserts, (III, 32,) that the phosphoric and boracic acids, decompose it by ignition. IT After boiling for two hours, about one fourth of it will be found to be decomposed, and the result will be carbonate of baryta, sulphate of the alkali, and undecomposed sulphate of baryta. 42 330 SALTS SULPHATES. results, and carbonate of baryta and sulphate of alkali remain mixed in the crucible ; wash out the soluble sulphate with water, dissolve the carbonate of baryta in muriatic acid ; decompose it by the car- bonate of an alkali, and thus, after strong ignition, especially in con- tact with charcoal powder, the pure earth will be obtained. (d.) Native carbonate of baryta dissolves in sulphuric acid, with a very slow and scarcely perceptible effervescence. 7. USES. (a.) To afford baryta by its decomposition, and for the prepara- tion of a phosphorescent substance. (b.) It has been used in the manufacture of porcelain, particularly by the late Mr. Wedgwood.* (c.) The artificial sulphate, under the name of permanent white, is applied in painting in water colors, and is the most delicate and per- manent white known, f The carbonate is employed for the same Qose. Either of them may be used with advantage in labelling es in a laboratory, where acid vapors are so apt to destroy common writing ink.J [d.) The sulphate of baryta is the only salt of this earth that is not poisonous. If the carbonate, which is a virulent poison, has been swallowed, diluted sulphuric acid would therefore be an antidote ; and if any soluble salt of baryta has been taken, a solution of sulphate of soda or other alkaline or earthy sulphate would be the best remedy. SULPHATE OF STRONTIA. 1. DISCOVERY. By Dr. Hope and Mr. Klaproth, about the year 1793. 2. NATURAL HISTORY. (a.) Exists naturally in considerable abundance ; usually called ce- lestine, from a delicate tinge of sky blue, which it frequently has ; first observed at Strontian, in Scotland ; found at Bristol, England ; at Bouvron, France, and at Montmartre, near Paris ; in splendid crystals in Sicily ; also very beautiful at Put-in-Bay, Mackinaw, and Detroit, on the Great Lakes, and at Lockport, N. Y. (b.) Found crystallized, massive, or in veins, "composed of nee- dles, or very fine rhomboidal prisms;" sometimes foliated, fibrous, or granular ; occasionally in sulphur beds. * He employed it in what was called the jasper ware, which, for a long time, was made by Mr. Wedgwood alone ; but the secret having been discovered and sold by a faithless servant, both the price and beauty of the vessels were soon much re- duced by inferior artists. Parkes* Essays, Vol. I, p. 317. t Parkes. t Artificial sulphate mingled with lampblack, painter's oil and spirits of turpentine, for light colored bottles, drawers, &c. without the lampblack, for black bottles, &c. c.u. s. Thenard, Vol. Ill, 172, says, " Le sulfate de bavyte est employe en Angleterre eomme mort-aux-rats." This appears to be a mistake; th carbonate is the sub- stance actually used for this purpose. SALTS SLPHATES. 33 1 (c.) Frequently confounded with sulphate of baryta, but easily distinguished from it, by its sp. gr. which is 3.85 ; it is always below 4. and sulphate of baryta always above 4.25 3. PREPARATION. (a.) By mingling sulphuric acid and strontian water, when it is precipitated in the form of a white and tasteless powder. (b.) Or by mixing any soluble form of strontia, with any soluble sulphate. 4. PROPERTIES. (a.) Tasteless and inodorous ; nearly insoluble; requiring 3000 or 4000 parts of cold, or 3840 of boiling water. (b.) Dissolved in boiling sulphuric acid, and thrown down again by water ; or in the additional mode named under sulphate of baryta, 4. (c.) note. 5. COMPOSITION. Acid, 42 4- earth 58=1 00. Wollaston. " 46 -f " 54=100. Fauquelin. 43 4- " 57 = 100. Stromeyer. According to Dr. Thomson, it is composed of 1 proportion of strontia 52, and one of acid 40=92 for its equivalent, and this would require this salt to consist of 43.47 acid, and 56.53 base. 6. DECOMPOSITION. (a.) JVb acid decomposes it,* nor does air affect it. At a high temperature it melts. (b.) JVb base except baryta can separate its acid; but carbonates of the fixed alkalies decompose it with the aid of heat. (c.) Decomposed by ignition with charcoal, in the same manner as sulphate of baryta is. It has not been applied to any use.f SULPHATE OF MAGNESIA. 1. NAME AND PREPARATION. (a.) That of the shops, called Epsom Salts, from a mineral spring at Epsom, in Surrey, (Eng.) where, mixed with some sulphate of soda, it was first obtained by Dr. Grew, A. D. 1675. But Dr. Black first distinguished it from Glauber's salt, with which it had, till his time, been confounded. (b) Formed, by dissolving the carbonate of magnesia, or calcined magnesia, in sulphuric acid, somewhat diluted ; it is then evaporated and crystallized. (c.) Strong sulphuric acid and calcined magnesia, produce great heat, and sometimes light ; but this acid evolves no heat with the carbonate, because the gas carries it away. * The phosphoric and boracic effect its decomposition, if aided by a red heat* Fourcroy, Vol. Ill, p. 48. t Except in pyrotechny, for preparing the nitrate of strontia an ingredient of red re.-3. T. 332 SALTS -SULPHATES 2. PROPERTIES. (a.) Crystals four sided prisms, with quadrangular pyramids, having dihedral summits.* The prismatic form, according to Mr. Brooke, is a right rhom- boidal prism, of 90 30, and 89 30. (b.) The Epsom salt of the shops is in the form of confused needle like crystals. (c.) When pure, unchanged in the air; but sometimes deliques- cent, from mixture with the muriate. (d.) Suffers aqueous fusion at low redness ; and loses about half its weight, but is not volatilized, except a little of the acid. (e.) Soluble at 60, in 1 part of water, in f of its weight at 212, the water is expanded J. (/.) Solution precipitated by carbonates ofpotassa and soda, (see those articles.) Equal weights of the salts, in equal weights of boil- ing hot water ; or, crystallized sulphate 4 parts, carbonate of potassa 3 parts, in solution ; 100 grains dry sulphate give about 71 carbonate of magnesia, or 33. pure earth. (g.) The carbonate is, in this case, preferable to the bi-carbonate of an alkali, because abundance of carbonic acid suspends the mag- nesia ; heat would however, eventually throw down a precipitate. (h.) Carbonate of ammonia does not precipitate the earth, unless heat is applied. (i.) Barytic, strontitic, and lime water throw down a mixed pre- cipitate of carbonate of magnesia and a sulphate of the other earth. (y.) Decomposed by charcoal at ignition ; producing a sulphuret, which is, however, feeble in its properties. (&.) Jit a high heat completely fusible, but without decomposition. (I.) Taste bitter, but less disgusting than that of sulphate of soda. (m.) JLn excellent cathartic; dose, 6 or 8 drachms, dissolved in water; and, by many, preferred to Glauber's salts. 3. COMPOSITION. 1 proportion of magnesia 20 33.04 1 sulphuric acid, 40 66.96 its equivalent number, 60 100.00 The crystals contain, Magnesia, 16. or 1 proper. 20 Acid, 32.57 or 1 " 40 Water, 51.43 or 7 " 63 100.00 123 the equivalent for the crystals. * For some varieties of the crystals, see Henry, Vol. I, p. 621. SALTS SULPHATES. 333 (a.) With pure ammonia, a part of the earth is precipitated ; by evaporation a triple salt, called the amrnoniaco-raagnesian sulphate, is obtained, consisting of Sulphate of magnesia, 1 proportion 60 Sulphate of ammonia, 1 " 57 Water, 7 " 63 180 its equivalent number. (b.) Ji compound sulphate of magnesia and soda is obtained, by evaporating the bittern of sea water ; it crystallizes in transparent rhombs, and consists, according to Dr. Murray's analysis, of sul- phate of magnesia 32, sulphate of soda 39, and water 29 ; and its proportions are very nearly those of 1 equivalent of sulphate of mag- nesia 60, 1 of sulphate of soda 72, and 6 of water, 54=186 for its equivalent number. It is a cathartic, not disagreeable to the taste, and is sold at Lymington, England.* (c.) A sulphate of potassa and magnesiaf is obtained, when 1 equivalent of sulphate of magnesia and 1 of sulphate of potassa are mixed ; they crystallize with 6 of water, and there is a double salt of 1 equivalent of sulphate of magnesia, and 1 of sulphate of ammo- nia, with 8 of water, which is obtained by spontaneous evaporation of the mixed solutions. 4. ORIGIN OF SULPHATE OF MAGNESIA. (a.) Found abundantly in sea water, ancf obtained from the bit- tern, after the evaporation for crystallizing common salt ; it is boiled down, until, on cooling, in clear and cold weather, it affords the sul- phate of magnesia, in acicular crystals, in the proportion of 4 or 5 parts to 100 of common salt, obtained from the same water; or sul- phate of iron is added, to decompose the muriate of magnesia, and thus increase the quantity of sulphate. J (b.) Manufactured from magnesian minerals, especially the mag- nesite ; 1.500,000 Ibs. are made annually in Baltimore, from a mag- nesite found near Chester, Penn. (c.) Found native and crystallized, in remarkable quantity, in a great cave, at Corydon, Indiana ; also in many other limestone cav- erns, in Kentucky, Virginia, and Tennessee, &c. (d.) Effloresces occasionally on brick walls. (e.) Formed by the decomposition of rocks, which contain mag- nesia, and sulphuret of iron ; the latter affords the sulphuric acid, which combines with the magnesia, and effloresces, and is extracted by a process, for which see Thenard, 5th Ed. Vol. Ill, p. 169. * Murray, 6th Ed. Vol. II, p. 94, and Edinburgh Trans. t See Phil. Trans. 1822, p. 455, also Henry, 10th Ed. Vol. I. p. 625. t See muriate of magnesia. Am. Jour. Vol. XIV, p. 10. See also Vol. IV, p. 22. 334 SALTS SULPHATES. (/.) Also by calcining the magnesian limestones; treating them with muriatic acid to dissolve the lime, and then with sulphuric acid, or sulphate of iron, to form the sulphate of magnesia.* SULPHATE OF ALUMINA AND ALUM. Common alum. 1. PREPARATION. Always prepared in the large way; rarely by the chemist , unless in analysis. 2. PROPERTIES. (a.) Its properties are always shown by the alum of commerce, which is a triple salt, and not mere sulphate of alumina, which has characters entirely different. (b.) Crystals formed from a hot concentrated solution, filtered ; a frame of sticks or some hairs or strings or wires are often suspended in it, for the crystals to adhere to ; they form a beautiful group, and are handsomely exhibited in a bottle. (c.) Aqueous fusion and subsequent desiccation by heat, on an ignited iron ; the product was formerly called alumen ustum ; there is a par- tial expulsion of the acid so that the solution of the desiccated alum does not easily redden blue vegetable colors. f By a very violent heat, most of the acid is expelled. The solution of the crystals red- dens litmus liquor decidedly, cabbage liquor slightly, " but blue tinc- tures, from the petals of plants, are generally turned by it green."f (?.) Air has generally no action sometimes produces a slight efflorescence. (e.) Taste, sweetish, acid, and astringent; rather agreeable to most persons. Specific gravity 1.71. (/.) Water 5 parts at 60 dissolves 1 of the salt; at 212 1 part of water dissolves three fourths of its weight. Or-) Pyrophorus. Take 3 parts of alum and 1 of flour or brown sugar, heat the mixture, and stir it constantly, in an iron pot or ladle, tiU it has ceased to swell, and has become dry ; powder the mixture finely, and introduce it into a vial coated with clay ; set this in a sand heat, and continue the heat till gas ceases to be inflamed, by bringing a lighted paper to the mouth ; we are usually directed to in- troduce a small tube, through a perforated cork, into the vial's mouth ; when the operation is over this may be removed and a cork substituted. (h.) This pyrophorus fires in the air ; more vividly, in ajar of oxygen gas ; it fires also in chlorine and nitric oxide gas. * Id. and Ann. de China, et de Phys. T. VI, p. 86, and Gray's Op. Chem. t It is suggested that the effect of alum on blue colors, may be owing to a feeble affinity between the acid and the earth, and of course to an attraction between the acid and the coloring matter, rather than to an excess of acid. t Quarterly Jour. XVIII, 396. SALTS SULPHATES. The foregoing process for pyrophorus, which is the usual one, is of rather uncertain success, and the theoretical reasoning formerly given respecting it being imperfect, I do not repeat it here ; but proceed to state a better process, furnished me by Dr. Hare, and one which rarely fails to succeed. Take lampblack 3 parts, calcined alum 4$ pearl ashes 8, mix them thoroughly, and heat them for one hour, in a coated iron tube, to a bright cherry red, or full red, but not to a white heat. Black's fur- nace, filled with charcoal thoroughly ignited, the flues being then shut, and when the fuel is half burnt down, again filled, and allow- ed to burn quietly out, with the flues still cloesd, or nearly so, will give a good pyrophorus. The tube must not be opened until it is cold, and then very cautiously. The pyrophorus may be jarred out, by inclining the tube, and gently striking it with a hammer. If good, it fires on falling out, especially if the air is damp, or if breathed upon ; caution should be observed lest the little explosions injure the eyes. If a ramrod be introduced to detach the pyrophorus, the operator should be on his guard, as a violent explosion sometimes happens, discharging the whole contents at once, with a loud report.* This pyrophorus fires brilliantly, if a large stream of oxygen gas be direct- ed upon it from a gazometer, or if it be poured into oxygen, or chlorine or nitric oxide gas. It fires also, if thrown upon water or fuming nitrous acid . There can be little doubt that sulphuret of po- tassium must be formed in this process, and that to potassium, in some state or other, the principal phenomena must be attributed. (i.) All the, alkalies and soluble alkaline earths decompose this salt, and if ammonia enter into its constitution, it is perceived by the odor r when either of the other alkaline bodies is added and heat applied, and by the cloud formed with the fuming acids. (/.) Jill the alkalies throw down the alumina; potassa and soda redissolve it, if added in excess, and yield it up again if detached by an acid. (k.) Ammonia precipitates the earth without redissolving it, or only very slightly, and heat would throw down even this little. (I.) The soluble alkaline earths throw down a mixed precipitate, of alumina and the earths, combined with the sulphuric acid. (m.) Baryta and strontia, are proper for the discovery of potassa; if present, it would remain in solution, and could be detected by muriate of platinum. (n.) The carbonates of alkalies decompose this salt, with a slight effervescence at first, and throw down a carbonated earth. (0.) Crystals of alum are usually octahedral; * See Am. Jour, of Science, Vol. X, p. 366, and the same thing has often occur- red to me since. 336 SALTS SULPHATES. (p.) But they become cubical, by letting a solution of common alum stand for some time upon either alumina or potassa ; still, with a great excess of potassa, alum does not crystallize. (q.) Saturate alum, with alumina, by boiling a solution of common alum upon it ; it becomes a tasteless insoluble powder. (r.) Digest natural clays in sulphuric acid; they dissolve only partially, and scarcely saturate the acid ; dissolve newly prepared alumina (added in excess) in sulphuric acid, and a neutral sulphate is formed, which crystallizes in thin flakes, and becomes alum by adding potassa or its sulphate. 2. COMPOSITION AND VARIETIES. (a.) The most common variety of alum is that which contains po- tassa, but there has been considerable diversity in the statements made of its constitution : the following is the average of six analyses.* Sulphuric acid, 33.22 5 aluminous earth, 1 1 .07 ; potassa, 9.88 ; water, 45.92 = 100. (b.) According to Mr. R. Phillips, alum consists of 1 proportion of bi-sulphate of potassa, 128; 2 of sulphate of alumina, (67 X2) =134; 25 of water, (9x25) =225=487,f its equivalent number. Dr. Thomson supposes alum to be composed of 1 proportion of sulphate of potassa, 88; 3 of sulphate of alumina,{ (58x3) 174; 25 of water, 225=487. The difference between these two views is, that in the former the equivalent of alumina is taken at 27, and in the latter at 18; and adding 40 in each case for the sulphuric acid, we have 67 and 58 for the equivalent of sulphate of alumina, of which 2 proportions are taken in Mr. Phillips' statement, and 2 in that of Dr. Thomson. (c.) Alum with basis of ammonia,^ consists of 1 proportion of sul- phate of ammonia, 57 ; 3 of sulphate of alumina, 58 X 3 = 174 ; 24 of water, 9 X24=216 ; and of the acid, 26.979 are united to 11.906 of the earth, and 9.063 are united to 3.898 of ammonia. (d.) Jllum with basis ofsoda.\\ Its composition is stated as being water, 51.21; acid, 32.14; earth, 10.; soda, 6.32: or, 2 propor- tions of sulphate of alumina, 1 of bi-sulphate of soda, 28 of water. A native soda alum is found in the isle of Milo, Greece, and in South Am erica. TT * As given by Dr. Henry, Vol. I, p. 632, 10th ed. t In this statement, the experimental results are slightly changed, to accommo- date them to definite proportions, and the equivalent of alumina is taken at 27. t The equivalent of alumina being taken at 18. The chemical equivalent of alu- mina is not yet ascertained with certainty, but Mr. Murray remarks, (II. 182,) that from the analysis of salts and minerals containing alumina, it is more probable that 18 is the true number. According to Riffault, Ann. de Chim. et de Phys. IX, 106. II Quarterly Jour. VIII- 386, and XIII. 276. I have prepared a lithia alum, in large quantities, from the Sterling spodumene, in following Berzelius' process for extracting lithia. It is deliquescent, hut in other respects resembles the potassa alum, J. T. IT Am. Jour. Vol. XVI. p. 203. SALTS SULPHITES. 337 (e.) Magnesia also appears to form a variety of alum, but it has not been applied to use. (/.) For a notice of a neutral sulphate of alumina, and for one of a sub-sulphate of alumina and potassa, &ic. see Henry, Vol. I, p. 634, 10th ed. Ann. de Chim. et de Phys. VI, 201 and XVI, 355, and Dr. Thomson's First Principles, I, 313. SULPHITES OF ALKALIES AND EARTHS. General characters. 1. Taste and smell like that of burning sulphur. 2. Heat expels sulphurous acid and water, and finally sulphur, which, when inflamed, burns violently, and a sulphate remains.* 3. Solution slowly absorbs oxygen from the air and becomes sul- phate. 4. Chlorine and nitric acids convert the sulphites into sulphates ; and nitric acid gives out red fumes. Sulphuric and muriatic acids expel the sulphurous acid with effervescence. 5. The sulphites are not precipitated by solution of baryta or strontia, or by any of their salts. 6. They are formed by passing a stream of sulphurous acid gas through the base, dissolved or suspended in water. 7. The alkaline sulphites are most soluble and crystallizable. 8. A neutral sulphite, when its acid is oxygenized, always forms a neutral sulphate. SULPHITE OF LIME. 1 . Besides the general method, already mentioned, this salt may be formed from the carbonate. 2. Insoluble at first, but is dissolved by continuing to pass sulphur- ous acid through it. 3. Crystallizes in six sided prisms, acuminated by six planes. 4. Requires 800 parts of water for solution, unless there be an excess of acid. 5. Proportions, lime 28, sulphurous acid 32, by theory. Brande. SULPHITE OF BARYTA. 1. It may be formed by passing sulphurous acid over carbonate of baryta. 2. A white powder, little soluble, becomes more so by passing sulphurous acid gas in excess through the powder. 3. Composition. Baryta 78, acid 40 ; by theory, one proportion of each. Except the sulphate of ammonia, which is entirely exhaled 43 338 SALTS-SULPHITES. SULPHITE OF STRONTIA. This salt is most easily formed, by mingling an alkaline sulphite with a solution of the earth in an acid, when there will be a precipit- ate of the sulphite of strontia, which is insoluble. SULPHITE OF MAGNESIA. 1. Formed also by diffusing the carbonate in water, and passing sulphurous acid gas through it. 2. Insoluble till there is an excess of the acid ; gives crystals which are flattened tetrahedra. 3. Requires 20 parts of cold water for solution. 4. Taste sweetish and earthy. SULPHITE OF ALUMINA. 1. A white soft insoluble powder. 2. Soluble in an excess of acid. SULPHITE OF POTASSA. 1. Formed with ease, from a saturated solution of the carbonate. 2. Crystals, long rhomboidal plates or divergent needles. 3. Soluble in water, 1 part at 60, in less at 212. 4. Composition, 43.5 acid, 54.5 potassa, 2 water; (Thomson) by theory, 1 potassa, 48; 1 acid, 32 = 80, its equivalent. 5. Slightly effloresces in air, and becomes sulphate; decrepitates. 6. Decomposed by baryta and lime. SULPHITE OF SODA. 1. Crystals, tetrahedral prisms, with dihedral summits. 2. Dissolves in 4 parts of cold water, in less than 1 at. 2 12. 3. Effloresces ; suffers aqueous fusion, and is decomposed at last by heat. 4. Composition, soda 1 proportion 32, acid 32, water 9=108; = 172 for the equivalent. 5. Potash decomposes it, attracting its base. SULPHITE OF AMMONIA. 1. Crystals, six sided prisms, terminated by pyramids with the snme number of sides, or rhomboidal prisms with trihedral summits. 2. Soluble in 1 part of cold water, and in less at 212. 3. Deliquesces, and becomes converted into a dry sulphate. 4. Fused and volatilized by heat. 5. Composition, 17 ammonia, 32 acid, for the anhydrous salt, giving 49 for its equivalent ; and when crystallized, 2 equivalents of the salt, = 98 -f 1 of water, 9=107 by theory. Brande. HYPO-SULPHUROUS ACID. 339 HYPO-SULPHUROUS ACID. HYPO-SULPHURIC ACID. HYPO-SULPHITES. HYPO-SULPHATES. Remarks. In the present advanced state of chemistry, the most serious inconvenience encountered by the student, is found in the great extent and variety of details. In a concise elementary work, it is im- possible to present them all, and there seems to be no better course than to omit, or to notice slightly the least important, and to enlarge upon those of the opposite character, giving at the same time, sufficient references to original sources of information. Were it not that it is desirable to preserve the chemical history of bodies unbroken, and particularly to display the extent and precision of definite and multiple proportions, I should hardly have thought it best to say any thing of the preceding sulphites or of the acids and their compounds which stand at the head of these remarks. HYPO-SULPHUROUS ACID. 1. Composition. 1 proportion of oxygen, 8, and 1 of sulphur, 32 =40, for its equivalent. 2. Preparation. Difficult to obtain and preserve in an isolated state. It is done, (a.) By decomposing the dilute solution of hypo-sulphite of stron- tia, by dilute sulphuric acid ; the earth is precipitated and the acid liberated. (5.) By digesting sulphur in a solution of any sulphite, when an ad- ditional proportion of sulphur is dissolved, and hypo-sulphurous acid formed ; or by decomposing hydro-sulphuret of lime* or strontia, by a stream of sulphurous acid gas, when there is an exchange of one pro- portion of the oxygen of the sulphurous acid for one proportion of the sulphur of the hydro-sulphuret, water being formed, and thus two proportions of sulphur remain in union with one of oxygen. 3. Properties. A transparent, colorless, inodorous acid ; decom- posed spontaneously, sulphur precipitated, and sulphurous acid re- mains. HYPO-SULPHITES, OR SULPHURETTED SULPHITES. 1. Preparation. (a.) The hypo-sulphites of the alkalies and alkaline earths are best obtained by passing a stream of sulphurous acid gas through a lixi- vium of those bodies that has been boiled with sulphur ; the sulphurous acid is converted into hypo-sulphurous, and the excess of sulphur pre- cipitated. (6.) By boiling a sulphite with sulphur. (c.) By double decomposition ; an alkaline hypo-sulphite being mixed with an acid solution of some other base. *Seep. 347. 340 HYPO-SULPHURIC ACID. 2. Properties. (a.) Generally soluble in water, and have a bitter taste ; precipi- tate nitrate of silver and mercury black, in the form of sulphurets of those metals ; salts of lead and baryta are thrown down as white in- soluble hypo-sulphites of those bases. (6.) Muriate of silver, recently precipitated, is dissolved by the hypo-sulphites, and especially by that of soda, and a fluid is formed sweeter than honey, and entirely void of metallic taste. The hypo- sulphite of ammonia forms with muriate of silver, a white salt of which 1 grain imparts a perceptible sweetness to 32,000 grains of water.* HYPO-SULPHURIC ACID. 1. Discovery. In 1819, by Welter and Gay-Lussac.f 2. Preparation. Black oxide of manganese in fine powder, is suspended in water, and a stream of sulphurous acid gas passed through ; two acids are formed by the oxygen of the manganese ; the sulphuric and hypo-sulphuric, and both unite with the base, form- ing sulphate and hypo-sulphate of manganese ; both are decomposed by adding solution of baryta slightly in excess, which precipitates manganese and sulphate of baryta, and leaves hypo-sulphate of baryta in solution. Carbonic acid gas is then passed through, to remove any excess of baryta ; the solution is boiled to expel the carbonic acid, and by evaporation, hypo-sulphate of baryta is obtained in crys- tals. To a solution of these crystals, sufficient sulphuric acid is cau- tiously added to saturate the baryta, which is precipitated in the form of sulphate, and the hypo-sulphurous acid remains in solution. 3. Properties. (a.) A colorless, inodorous acid, changes the test fluids ; concen- trated by heat, or under the receiver of the air pump, its sp. gr. is 1.347, but if attempted to be carried farther, especially by heat, it is decomposed and converted into sulphurous and sulphuric acids. (6.) Suffers no change from the air or from nitric acid ; it dis- solves zinc like the stronger acids, and forms hypo-sulphate of zinc, while hydrogen gas is evolved. (c.) It forms soluble salts with baryta, strontia, lime, lead, and silver, which completely distinguishes it from sulphuric acid. 4. Composition. Ascertained by decomposing the hypo-sulphate of baryta by heat, and the proportion of sulphur appears to be 1=32, and of oxygen, 5=40=72, for its equivalent. HYPO-SULPHATES. 1. Preparation. Formed by direct combination with bases. * For numerous additional particulars, see Ann. de China. Vol. LXXXV ; Edin. Philos. Jour. Jan. 1819, Vol. 1, 8, and 396, and Ure's Diet. 2d Ed. p. 97. t Ann. de Chim. et de Phys. Vol. X. SULPHURETTED HYDROGEN. 341 2. Properties. (a.) All soluble; decomposed by a moderate heat, sulphurous acid gas being exhaled and sulphates remaining. (b.) Strong sulphuric acid decomposes the acid of the hypo-sul- phates, at the instant when it is decomposing the salts which contain it ; a weak acid, applied cold, separates the hypo-sulphuric acid with- out decomposition. (c.) Not changed by the air, or only slightly absorb oxygen. The hypo-sulphate of baryta crystallizes in square prisms of pecul- iar brilliancy ; that of potassa in a cylindroidal form ; that of lime in hexagonal, and that of strontia in very small hexahedral laminae. Composition of the acids of sulphur. Sulphur. Oxygen. Hypo-sulphurous acid, - 16 -f 8 1 and 1 proper* Sulphurous acid, - 16 -f 16 1 and 2 " Sulphuric acid, - 16 + 24 1 and 3 " Hypo-sulphuric acid, - 32 + 40 2 and 5 " Thus these compounds beautifully illustrate the laws of definite and multiple proportions. COMPOUNDS FORMED BETWEEN SULPHUR, HYDROGEN, AND THE AL- KALIES AND EARTHS. SULPHURETTED HYDROGEN. 1. NOMENCLATURE. The termination uret is appropriated to combinations of simple combustible, non-metallic* bodies, with each other and with the metals, alkalies, and earths. Thus, in the case of sulphur and phosphorus, we have sulphuret of phosphorus, or phosphuret of sulphur, sulphuret or phosphuret of lime, and of calci- um, of potassa, and of potassium, of iron, &tc. To denote different proportions of the principles, terms are derived either from some sensible property, usually the color ; e. g. we have a black and red sulphuret of mercury, yellow and red sulphuret of arsenic, &tc. ; or it is now more usual to prefix the same terms that are applied to the oxides, as proto-sulphuret, deuto-sulphuret, &c. implying one or two- proportions of sulphur, &c. Where the compound is gaseous, it is usual to add ted to the ter- mination uret ; as sulphuretted hydrogen and phosphuretted hydro- gen, instead of sulphuret and phosphuret of hydrogen. 2. HISTORY. Known to Rouelle, but first investigated by Scheele, A. D. 1777 ; afterwards by many distinguished chemists. 3. PROCESSES. (a.) By heating sulphur in hydrogen gas, by the solar rays ; or by subliming sulphur, repeatedly, in hydrogen gas ; or, by passing this gas over sulphur heated in a porcelain or coated glass tube. * The compounds of metallic bodies with each other are called alloys. 342 SULPHURETTED HYDROGEN. (b.) Better by the aid of sulphuret of iron, to prepare which, min- gle flowers of sulphur and iron filings, equal parts ;* heat them in an iron pot or skillet, under a chimney, not merely till the sulphur melts, which happens almost immediately, but until an intimate chemical union is indicated, by incandescence pervading the entire mass ; it begins with a little luminous spot or spots, and gradually ex- tends through the whole, while the vessel containing the materials is perhaps not even red ; at this moment, the boiling and combustion of sulphur cease, for it is now detained by its affinity for the iron. The sulphuret being pulverized, is fit for use, and will not disappoint the experimenter.f (c.) To one part of the sulphuret of iron thus made, add 2 of mu- riatic acid, with 4 of warm water, and when the gas begins to come languidly, a little heat may be applied. (d.) Powdered sulphuret of antimony, with 5 or 6 times its weight of muriatic acid, (sp. gr. about 1.160,) apply the heat of a lamp ; this process, although strongly recommended, has not succeeded well with me. (e.) Add diluted sulphuric or muriatic acid to almost any alkaline sulphuret, preferably of potassa, but the gas comes too rapidly to be easily managed ; process (c.) is the best. 4. PROPERTIES. (a.) Sp.gr. 1.18, air being 1; 100 cub. inch, weigh nearly 36 grains. { (b.) Smell very offensive, like that of rotten eggs, or of sulphureous mineral waters. (c.) When kindled in contact with air, it burns quietly, with a bluish white flame, and deposits sulphur on the glass vessel. Sd.) Mixed with common air, it burns more rapidly. e.) With oxygen, three measures to two of this gas, it detonates, producing water and sulphurous acid. (jf.) Water absorbs its own volume or, if the gas be pure, even two or three times its volume, and then resembles exactly, the native sulphureous waters. * Or sulphur 1 part, iron 2. t The mere melting of iron filings and sulphur, and still more the mere mingling of them will not answer ; for, when the acid is added, the gas produced will be merely a mixture of sulphuretted hydrogen, and common hydrogen gas. The pro- cess by rubbing roll sulphur upon a bar of iron heated to whiteness, till liquid drops fall, gives also a true sulphuret which will afford the gas, but the manipulation is more troublesome, and the product of sulphuret of iron is small. The following process was communicated. Heating the native yellow pyrites, in a close crucible, till 1 proportion of sulphur is expelled ; and a fine proto-sulphuret will be left. J. T. t 35.89, according to Dr. Thomson. Different authors have stated its sp. gr. dif- ferently. SULPHURETTED HYDROGEN. 343 (g.) This fluid tarnishes metallic solutions, and bright metals; e. g. silver, mercury ; also, white paint, acetate of lead, muriate of bismuth, nitrate of silver, &ic. (A.) Write with a solution of silver or lead on cards, and expose them to this gas ; Dr. Henry found that T F7F part of this gas, mix- ed with common air, or hydrogen, or carburetted hydrogen, pro- duced a sensible discoloration of white lead, or of oxide of bismuth, mixed with water and spread upon a card. (i.) Moisten the entire surface of cards with the solution, and ex- pose them as above, when they will be entirely tarnished. (j.) Aqueous solution reddens infusion of violets or litmus liquor or paper, and in this respect resembles the acids. (k.) Sulphuretted hydrogen being mixed with sulphurous acid, either liquid or gaseous, sulphur is deposited by mutual decomposi- tion ; if 3 volumes of sulphuretted hydrogen be mixed with 2 of sul- phurous acid gas, both being dry, they are entirely condensed into an orange yellow substance, having acid properties, and consisting, according to Dr. Thomson, of 5 proportions of sulphur, 4 of oxygen, and 3 of hydrogen.* (/.) Liquid sulphuretted hydrogen deposits sulphur, by exposure to air, or even in a bottle, and in the channels where the sulphureous mineral waters run. Fuming nitrous acid precipitates the sulphur, but the colorless acid does not. (m.) Fuming nitrous acid, being poured into a wide mouthed re- ceiver, filled with sulphuretted hydrogen, decomposition happens, and a beautiful flame spreads through the interior of the vessel.f (n.} Chlorine decomposes this gas and precipitates the sulphur. (o.) Very hostile to life ; if pure, kills almost instantly ; or even if mingled with a large proportion of air, it is very noxious. Air containing only T1 V o- killed a bird, jfa a dog, and ^ j -$ a horse. J A young rabbit, whose head was in the pure air, and its body en- closed in a bladder filled with sulphuretted hydrogen, died in 15 or 20 minutes ; old rabbits lived longer. It is fatal, therefore, when ap- plied to the surface of the body. (p.) Sulphuretted hydrogen precipitates all the metals, except iron, nickel, cobalt, manganese, titanium, and molybdena. (q.) Electricity and galvanism throw down sulphur, and an equal volume of hydrogen gas remains ; sulphuretted hydrogen is partially * Ann. Phil. Vol. XII, p. 441. A similar decomposition is supposed by Prof. Daubcny to be the principal source of volcanic sulphur. See his lectures on Volcanos, Am. Jour. Vol. XIII, No. 2. t Ann. of Phil. Vol. VIII, p. 226, and Henry, Vol. I, p. 449, 10th Ed. ; Thenard, Vol. I, 723. 344 BI-SULPHURETTED HYDROGEN. decomposed, by being passed through an ignited porcelain tube, or over ignited charcoal. Thenard. (r.) Alkalies absorb it readily, and thus it is easily separated from common hydrogen. (s.) Potassium and sodium, heated in this gas burn brilliantly ; i. e. much heat and light are evolved, and a sulphuret of the metal is formed, while as much hydrogen gas is produced as the metal would have liberated from water. Diluted muriatic acid produces from the sulphuret the original quantity of sulphuretted hydrogen gas. 5. COMPOSITION. According to Dr. Thomson, it is composed of 1 volume of the vapor of sulphur =1 proportion 1.111, +1 vol. of hydrogen gas, 0.069 ; these numbers being almost exactly in the ratio of 1 : 16, give the equivalent weight of sulphur very nearly the same as that deduced from the composition of sulphuric acid.* 6. LIQUEFACTION OF SULPHURETTED HYDROGEN. (a.) Mr. Faraday, by disengaging this gas in a recurved tube, sealed, before the materials were brought into contact, the end oppo- site to that in which they were contained being kept cold by a freez- ing mixture, succeeded in condensing it into a liquid. (b.) It was limpid, colorless, and more fluid than ether ; equally fluid at as at 45 Fahr. and its refractive power greater than that of water. (c.) The tube being opened under water, the fluid rushed instant- ly into gas, which was sulphuretted hydrogen. The pressure of its vapor, at 50 of Fahr.f was equal to seventeen atmospheres, or 255 Ib. to the square inch. Remarks. Sulphuretted hydrogen gas exists abundantly in the sewers and privies of great cities. I have observed, in London, that a sudden and heavy rain would force it out in great quantities, taint- ing the atmosphere, and tarnished white lead paint. In great cities, especially in Paris, it is often fatal to those who clear away the filth of the sewers : the best antidote and remedy is chlorine, especially in the form of chloride of lime. BI-SULPHURETTED HYDROGEN. 1. DISCOVERY. By Scheele originally, and afterwards examined by Berthollet. J 2. PREPARATION. Boil flowers of sulphur with liquid potassa ; pour this reddish brown solution, by little and little, into muriatic acid ; very little sulphuretted hydrogen escapes, and a part of it combines with more sulphur, and precipitates, of an oily appearance ; or, fill one third of a vial with muriatic acid, of the sp. gr. 1.07, and pour * Henry, Vol. I. p. 446, 10th Ed. f Phil. Trans. 1823, p. 192. * Ann. de Chim. XXV, and Phil. Trans. HYDRO-SULPHURETS. 345 in an equal bulk of the above named compound of sulphur and al- kali ; the vial being corked and shaken, the peculiar fluid gradually subsides to the bottom, in the form of " a brown, viscid, semi-fluid mass." Henry. The hydrogenized sulphuret of lime is also used, in the same manner, for obtaining this compound. 3. PROPERTIES. (a.) Odor like that of putrid eggs ; heavier than water ; burns with the smell of sulphurous acid. (5.) A gentle heat causes sulphuretted hydrogen to exhale, and sulphur only is left. (c.) It unites with alkalies and earths, and produces the sulphu- retted hydro-sulphurets, or hydroguretted sulphurets. (d.) If kept in a vial, floating on water, it exhales sulphuretted hy- drogen, whenever the stopper is withdrawn. (e.) If placed on the tongue, it gives a pungent bitter taste, exhales sulphuretted hydrogen, and leaves sulphur in the mouth. 4. COMPOSITION. According to Mr. Dalton, 2 proportions of sul- phur =32-f-l of hydrogen =33. In centesimal proportions,* it con- sists of sulphur 96.75, hydrogen 3.25 = 100. Its combinations with alkalies will presently be considered. HYDRO-SULPHURETS. f COMPOUNDS OF SULPHURETTED HYDROGEN AND BASES. Introductory Remarks. It has been already observed, that sulphuretted hydrogen performs the functions of an acid. It is not sour to the taste, but it reddens the infusion of vegetable blue colors, or at least that of litmus or radishes ; its most important character, as an acid, is, that it com- bines with the alkalies and alkaline earths, neutralizing their alkaline properties, and forming crystallizable compounds, analogous to the salts. Some have therefore enrolled sulphuretted hydrogen among the acids, but, in a free state, except a feeble effect upon some of the blue test colors, its properties are so different from those of acids, that I prefer to consider it as merely a compound combustible gas, adding a notice of those properties that assimilate it to acids. { 1. PREPARATION of hydro sulphurets. Formed, by passing sul- phuretted hydrogen gas through the base, suspended or dissolved in water, in Woulfe's or other convenient apparatus. * Henry, Vol. I, p. 447. t Called .by some authors hydro-sulphates, but it would seem, unhappily; as the learner is in danger of confounding them with the sulphates: the old name appears to be unexceptionable. See Dr. Turner's Chemistry, 2d ed. p. 603. \ It has been called the hydro-thionic, and the hydro-sulphuric acid ; neither name has obtained much currency, and the latter confounds this body with the com- mon sulphuric acid. 44 346 HYDRO-SULPHURETS. 2. GENERAL PROPERTIES. (a.) Soluble in water, recent solution colorless, by exposure to the air become greenish or yellowish, and deposit sulphur on the sides of the vessel. (b.) If the bottle in which they are kept contains lead, it is redu- ced, and coats the interior with a metallic lining, probably a sulphuret. (c.) By long exposure to the air, and even by long keeping, they pass to the state of sulphites, and ultimately to that of sulphates, which are sometimes precipitated, and sometimes remain, in part or in whole, in solution. (d.) Acids liberate sulphuretted hydrogen, but do not precipitate sulphur ; (e.) Except* the nitric acid, which combines with the hydrogen to form water, and thus liberate sulphur ; (f.) Except also when the hydro-sulphurets have been partially decomposed by careless keeping, when they throw down sulphur. (g.) Precipitate all metallic solutions, and also alumina and zir- conia, but no other earths. (A.) Generally crystallizable. (t.) Take up an additional dose of sulphur, by digestion, upon it, but do not suffer it to be again precipitated by a stream of sulphuret- ted hydrogen. (/.) After exposure, for some time, to the air, exhale sulphurous acid gas along with sulphuretted hydrogen, and precipitate sulphur. (k.) Absorb oxygen, and therefore used in eudiometry. (I.) If there is no more sulphuretted hydrogen than is necessary to saturate the base, they are inodorous ; but they usually have the odor of sulphuretted hydrogen, because it not only saturates the base, but combines with the water of the solution, which after the superfluous gas is expelled, by heat, will no longer have any odor. (m.) The hydro-sulphurets are decomposed by heat, and the base remains ; ammonia excepted, which is exhaled. (w.) It is said that sulphuretted hydrogen combines with alkalies, in a double proportion, forming bi-hydro-sulphurets. HYDRO-SULPHURET OF POTASS A. 1. Crystallizes in large transparent crystals, similar to those of sul- phate of soda ; four sided prisms acuminated by four planes, or six sided prisms with six planes, at the ends. 2. Taste alkaline and bitter, inodorous when dry, but becomes odorant by moisture ; is deliquescent. 3. Forms a syrupy liquor, which imparts a green color to bodies in contact with it. 4. Dissolves, not only in water but in alcohol, producing cold. * Chlorine produces the same effect by seizing the hydrogen. HYDRO-SULPHURETS. 347 HYDRO-SULPHURET OF SODA. Crystals formed with more difficulty than the preceding ; trans- parent, quadrilateral prisms, acuminated by four planes, bearing a close resemblance to the hydro-sulphuret of potassa.* HYDRO-SULPHURET OF AMMONIA. 1 . The two gases mixed over mercury, or in a bottle, or other- wise, combine ; in equal volumes, they are almost completely con- densed into an odorous cloud, which forms a soft white crystalline deposit on the inside of the vessel, and if it is kept cold by ice, acic- ular crystals will be formed. 2. The liquid solution is easily formed, but does not crystallize. 3. It is an excellent test, in examining metallic solutions. 4. Admitted into the Pharmacopaeia, as a depressing and nausea- ting remedy, in cases of too great action introduced by Dr. Rollo, and used chiefly in diabetes ;f dose, 5 or six drops, three or four times a day, gradually increased, and mitigated, when nausea and giddiness supervene. HYDRO-SULPHURET OF LIME. 1 . Formed, by passing the gas, either through lime water, or milk of lime. 2. It is formed when sulphur is boiled with lime and water ; but there is also another product soon to be described. 3. I have often seen distinct prisms formed in the solution made by boiling lime and sulphur to saturation in water ; I am not aware that they have been examined ; if not hydro-sulphuret, may they not be hypo-sulphite of lime ? HYDRO-SULPHURET OF BARYTA. 1 . Formed, as mentioned in the general characters ; but by far the best method is to obtain it from the decomposed sulphate, by char- coal, as described under sulphate of baryta, and soon to be mention- ed again, with particular reference to this subject. 2. It crystallizes, confusedly, in brilliant plates, which must be dried between folds of blotting paper, and if immediately dissolved in distilled water, they form a colorless solution. * It was formerly said to be distinguished, by not forming alum when added to sulphate of alumina, which the other salt would do, but this distinction was indica- ted, probably, before it was known that there is a triple soda^alurn. t The physician can prepare this remedy by extricating the gas, under a chim- ney, in the manner already described under sulphuretted hydrogen, and passing it from an oil flask, or bottle, through the aqua ammonia? of the shops, contained in a vial immersed in cold water, or better, surrounded by ice. This remedy has still considerable reputation, and conjoined with a diet of animal muscle, is thought to have produced the most salutary results. I have repeatedly prepared it for phy- sicians, and have always heard a favorable report of its effects, if conjoined with a rigorous diet. 348 SULPHURETTED HYDRO-SULPHURETS. HYDRO-SULPHURET OF STRONTIA. In every respect as the last, only the decomposition of the sul- phate is not so striking. HYDRO-SULPHURET OF MAGNESIA. 1. Formed by passing the gas through the magnesia suspended in water. 2. It is a feeble and imperfectly characterized compound. SULPHURETTED HYDRO-SULPHURETS. * General Characters. 1. Formed, by boiling flowers of sulphur with the base, dissolved or suspended in water. 1 . Caustic heavy fluids, of a greenish yellow, or brownish color. 2. Stain the cuticle black, have an acrid taste, and an offensive smell. 3. Deposit sulphur when kept in close vessels, and become more transparent, and lighter colored. 4. Absorb oxygen gas, and therefore used in eudiometry. 5. Sulphuric and muriatic acids throw down sulphur, and evolve sulphuretted hydrogen. 6. Exposed to the air they are slowly changed into sulphates. 7. Have a soapy feel. 8. Sulphuretted hydrogen, passed through them, precipitates the excess of sulphur, and converts them into hydro-sulphurets. 9. Sulphuretted hydro-sulphurets, are formed also, by digesting a hydro-sulphuret upon sulphur, but they do not throw down sulphur when sulphuretted hydrogen is passed through them.f SULPHURETTED HYDRO-SULPHURET OF POTASSA. 1. Boil sulphur, 1 part, with 3 of the solution of caustic potash, of the common strength. J 2. Or, decompose the sulphate of potassa, by heating it red hot along with J- of charcoal, in a crucible : dissolve every thing soluble in hot water, and filter ; the theory of these facts will be given farther on. * Called also hydrogenized, hydroguretted, and hydrogenated sulphurets, but the name in the text is preferred, because it expresses correctly the composition of these bodies. t Aikin, Vol. 2. p. 364. t Pearl ashes, water, and sulphur boiled together, produce hydrogenized sulphu- ret of potassa of a very good quality, so that it is not necessary to use caustic potash ; probably sal soda would also answer instead of caustic soda. SULPHURETTED HYDRO-SULPHURETS, 349 3. The color varies in intensity according to the degree of con- centration. 4. The principal use made of this preparation is in eudiometry ; but the compound with lime is most used, which see. SULPHURETTED HYDRO-SULPHURET OF SODA. 1 . It is almost perfectly identical with the last. 2. The sulphate may be decomposed by charcoal in the same manner, but the appearances are less striking. SULPHURETTED HYDRO-SULPHURET OF AMMONIA. 1. If liquid ammonia be digested upon sulphur, the action is fee- ble and not much sulphur is dissolved. 2. But ammonia in its nascent state, dissolves sulphur readily. 3. A preparation of this kind was formerly called Boyle's fuming liquor ; 3* parts slacked lime, 1 muriate of ammonia, 1 flowers of sulphur, and half a part of water, are mingled and a gentle heat ap- plied ; the first drops are watery, and as they become deeper colored, the heat is raised till the bottom of the retort becomes slightly red. 4. White fumes are abundantly extricated in the more early stages of the operation, and must have vent from the receiver. 5. The fumes may be all collected in a Woulfe's apparatus; they are more abundant and incoercible in proportion as less water is added. 6. The liquor fumes, as soon as the stopper is withdrawn from the bottle in which it is kept. 7. The fuming is owing to the ammonia in excess, meeting with sulphuretted hydrogen,f for when the fuming liquor is digested on sul- phur, the ammonia becomes saturated and the fuming ceases. SULPHURETTED HYDRO-SULPHURET OF LIME. 1. Boil slacked lime with JJ sulphur and 10 parts of water, for half an hour or an hour, and shake frequently during the boiling. 2. The fluid is of a fine orange yellow, and deposits crystals one cooling. 3. Decomposition of the sulphate by charcoal and heat, succeeds but imperfectly. 4. For the rest, see general properties. 5. This preparation and the parallel one of potassa are much used in eudiometry, and this is rather preferred, because it affords the most concentrated solution. * 1, Ure. \ Proceeding, doubtless, from the decomposition of water, by the compound of am- monia and sulphur. t Equal weights of lime and sulphur. Murray, This is much more sulphur than is needed. 350 SULPHURETTED HYDRO AND LIQUID SULPHURETS. EUDIOMETER OF DR. HOPE. " This eudiometer consists of a graduated glass tube, sealed at one end, and at the other fitted, by grinding, into the mouth of a tubulated glass bottle, so as to be air tight. Manipulation, with this instrument, is very simple. The tube is filled with gas, the bottle with the liquid which is to act upon the gas. The tube being, under these circumstances, inserted into the mouth of the bottle, by inverting both, the contained gas is made to pass into the bottle. Agitation is next to be resorted to, and time allowed for the absorption to be completed. In the interim, the tubulure is to be occasionally opened under water, by removing a ground stopple with which it is furnished. The gas absorbed, is conse- quently replaced by water. " Finally, the stopple must be removed, the tube being previously depressed into water, till this liquid is as high on the outside as within. The graduation being at the same time inspected, the deficit produced by the absorption of oxygen, is thus ascertain- ed.''!^. Hare. SULPHURETTED HYDRO-SULPHURET OF BARYTA. 1 . This compound is formed either by boiling pure baryta (4 parts.) in powder, or in crystals, with water upon sulphur, 1 part, or by de- composing the sulphate of baryta by igniting it along with one sixth charcoal powder for half an hour ; then dissolving it in hot water and filtering. 2. This a mixture of sulphuretted hydro-sulphuret and of hydro- sulphuret, which last will crystallize on cooling. 3. See general characters for the rest. This compound is very useful in preparing the salts of baryta ; see the muriate and carbo- nate. SULPHURETTED HYDRO-SULPHURET OF STRONTIA. The same in every respect as the last, only the decomposition of the sulphate by charcoal is less striking. LIQUID SULPHURETS. 1. This name is often given to the hydrogenated sulphurets, 2. Indeed they seem to consist generally of a solution of sulphur in an alkali, combined with more or less of sulphuretted or of bi-sul- phuretted hydrogen. SULPHURETTED HYDRO-SULPHURETS. 351 3. According to Proust, a pure liquid sulphuret, without sulphuret- ted hydrogen, may be formed, by withdrawing the latter by red ox- ide of mercury.* SULPHURETTED HYDRO-SULPHURET OF MAGNESIA. By processes similar to those pointed out above, magnesia gives but feeble indications of combining with sulphur, &c., and is the last of the earths that gives any. Remarks. The elaborate researches of Berthollet, (1798,) for- merly led us to suppose, that when a base is boiled with sufficient sulphur, a fluid sulphuret was produced, which decomposed water, and generated sulphuretted hydrogen, part of which was exhaled, thus producing the peculiar odor of these preparations, and that the remainder of this gas combined with the sulphuret, and formed what was called hydrogenized sulphuret ; and it was thought to be a suf- ficient proof of the truth of this opinion, that an acid decomposed the preparation, evolving sulphuretted hydrogen and precipitating sulphur abundantly, both of which facts were supposed to arise from the acid seizing the base to form a salt. More recently, we are taught, that bi-sulphuretted hydrogen is gen- erated in these cases, and that the excess of sulphur is contained in that mode of combination. But I think this cannot be all that hap- pens ; for there is great variety in the quantity of sulphuretted hydro- gen, which acids evolve, and of sulphur which they precipitate from these preparations. Sometimes, although sulphur is abundantly pre- cipitated, very little gas makes its escape, and at other times it is very abundant. I am persuaded that there is often much sulphur in solution, which is simply dissolved by the entire compound, and is not merely combined with the hydrogen in the form of sulphuretted or bi-sulphuretted hydrogen'. My experience would lead me to ac- cord with the following opinion of Dr. Ure.f 1. Sulphuretted hydrogen, sulphur and the alkalies have the pro- perty of forming very variable triple combinations. 2. All these combinations contain less sulphuretted hydrogen than the hydro-sulphurets ; and 3. The quantity of sulphuretted hydrogen is inversely as the sul- phur they contain, and reciprocally. SULPHURETS. I. Sulphurets of alkalies and alkaline earths. Remarks. Until within a few years, it was supposed that the fu- sion of dry sulphur with the fixed alkalies and alkaline earths, produ- ced a true sulphuret of the alkaline body, and it is still by no means certain that, under particular circumstances, this is not the fact. It is the opinion of Gay Lussac, that a true sulphuret of an oxide is form- ed, provided the temperature is kept below ignition. "A une tem- * Aikin's Diet. Vol. II, p. 363. t Diet. 2d Ed. p. 756. 352 SULPHURETS. perature pen elevee, qui n'atteigne jamais la chaleur rouge, ce corps se combine avec les alcalis sans les decomposer, et forme des sul- fures d' oxide." This appears to me so probable, that I shall here preserve a notice of what were, heretofore, regarded as alkaline sulphurets. 1 . Formed by fusion of sulphur with the base, or decomposition of a sulphate by ignition with charcoal powder.' 54 ' 2. Of a liver\ color, if formed with caustic alkalies, or greenish yellow, if with their carbonates. 3. Inodorous, ivhile dry. 4. Decomposed by a higher degree of heat than that by which they were formed, sulphur being sublimed, and the base left in the bottom of the vessel. Chemists and physiciansj were accustomed to use these prepara- tions in solution, but they then ceased to be true sulphurets ; for sul- phuretted hydrogen was generated, and they passed to a new condi- tion ; that of the sulphuretted hydro-sulphurets. In making the preparations, it is of little importance whether we boil the base and sulphur together, or melt them together, and then dissolve them ; or whether we dissolve, in hot water, the residuum from the decomposi- tion of the sulphates, by ignition with charcoal ; for, in either case, by the decomposition of water, we obtain a compound containing sulphuretted or bi-sulphuretted hydrogen ; it is fetid, and acrid, and liberates by the action of acids, precipitated sulphur and sulphuret- ted hydrogen gas. In all these cases also there is a generation, probably from the oxygen^ of the water, of some of the acids of sul- phur, and by spontaneous decomposition, especially if the solution is kept in loosely stopped vessels, the substances pass to the condition of sulphite or sulphate, || and thus lose their peculiar properties. II. Sulphurets of the metallic bases of the fixed alkalies and alka- line earths. * In the latter case they were left in mixture with the charcoal, and could scarce- ly be exhibited pure ; it now appears that a metallic sulphuret is produced in this manner. t Therefore called, in the old language of chemistry, hepar sulphuris or liver of sulphur. t Physicians prepare the sulphuret of potash by taking flowers of sulphur and potash or pearl ashes, equal quantities ; they are melted in a covered crucible or skillet, and then kept in a close vessel, but are dissolved for use, in the proportion of two drams in a pint of rain water, and this is used as an external wash. A. table spoonful is taken for a dose, twice in a day ; used for a variety of eruptions, scald head, psora, &c. In pulmonary consumption it may be given, in the above manner or in form of pills, from two to live grains for a dose, repeated two or three times in a day. It removes or diminishes the hectic fever: it has been used internally as an antidote against metallic poisons and to check excessive salivations from mercury. Coni'd. Vauquelin supposed from the oxygen of the alkali. Jl The preparation from the decomposed sulphate of baryta, is particularly re- markable for passing back to the condition of sulphate, and it often presents distinct prismatic crytals. SULPHURETS. 353 It cannot.be doubted, that many of the compounds which were formerly regarded as sulphurets of the oxides of metallic bases, were really sulphurets of the metals themselves, and it is now clearly as- certained that they are formed in the following modes and circum- stances. 1. By fusion of the metallic base with sulphur, or by passing its vapor over the metal, ignited in a porcelain tube; the union often takes place with the disengagement of much heat and light, resem- bling a combustion, and by many it is regarded as such. Potassium and sodium are the only alkaline bases which we are able to try in this way ;* the same thing happens with silicium. 2. By heating the metallic bases in sulphuretted hydrogen gas, when the sulphur combines with the metal, often with appearance of combustion, and the hydrogen gas is liberated ; potassium and sodi- um exhibit this phenomenon remarkably. 3. By passing the same gas, or its solution in water, into the metal- ic solution, when sulphurets are precipitated ; those metals that are not affected by sulphuretted hydrogen, namely, iron, manganese, nickel, cobalt and uranium, are, like all the other metallic solu- tions, precipitated as sulphurets, by the hydro-sulphurets of potassa and ammonia. 4. By heating sulphur to ignition with the oxide of the metal; the oxygen escapes in sulphurous acid, and the remainder of the sulphur combines with the metal. 5. By igniting the sulphate of an alkaline oxide with charcoal powder, j- or by passing the hydrogen gas over the ignited sulphate ; all the sulphates of these bodies are thus reduced at a white heat and if fusible, very quickly. Perhaps the true limit between the sul- phurets of the fixed alkalies and alkaline earths, and of their metallic bases, will be found below a red heat for the former, and at or above it for the latter. There cannot be any doubt that true metallic sul- phurets are formed, when the alkalies and alkaline earths are igni- ted with sulphur, or when a sulphate is decomposed, at a similar temperature, by charcoal or hydrogen. { It is remarkable that during the decomposition of the sulphates by charcoal, the gases disengaged are found to contain the whole of the * Of the common metals a number, as iron, copper, lead and bismuth, exhibit this phenomenon in a striking manner; the two former shew it in a glass vessel. t Mr. Berthier enclosed the sulphate in a covered crucible lined with a mixture of clay and charcoal powder. t The limits of this work do not allow me to cite more in detail, the labors of Vau- quelin, Ann. de Chim. et de Phys. Vol. VI, 1817, or those of Gay-Lussac, Id. or of Berthier, Id. Vol. XXII, or of Berzelius, Vol. XX. A perspicuous statement drawn from these authorities, may be found in Dr. Turner's Chemistry, 2d Ed. p. 388 ; I find that it contains every thing of importance in the original memoirs. 45 354 SULPHURETS. oxygen that existed, both in the oxidized base and in the sulphuric acid ; and when hydrogen is employed, the water produced, accounts in the same manner, for the whole of the oxygen, and there is in either case, no loss of sulphur, as it all remains combined with the metallic base forming a true metallic sulphuret. When the sulphurets of the metallic bases of the alkaline sub- stances are dissolved in water, they pass at once, to the condition of hydro-sulphurets and sulphuretted hydro-sulphurets. The decom- position of the water appears to be the means of effecting these changes ; its oxygen causes the metal to pass to the state of oxide, and its hydrogen with a part of the sulphur forms sulphuretted or bi-sul- phuretted hydrogen ; some of the acids of sulphur are also formed. When a sulphuret is obtained by the decomposition of sulphate of baryta by charcoal and heat, and subsequent addition of boiling wa- ter, there is produced, from a strong solution, a very copious and sudden deposition of white crystalline plates of hydro-sulphuret of baryta, while a part of the fluid appears to remain in the condition of sulphuretted hydro-sulphuret or bi-hydro-sulphuret of baryta. Sul- phurous acid or hypo-sulphurous acid is also produced, and combin- ing with a portion of the oxidized base contributes to expel more sul- phuretted hydrogen. In concluding this rather complicated subject, it may be well to call to the recollection of the learner, that the following are its great divisions. 1 . Sulphuretted and U-sulphurettcd hydrogen, containing sulphur dissolved in hydrogen ; one proportion in the former, and two in the latter. 2. Hydro-sulphurets, consisting of sulphuretted hydrogen, and an oxidized metallic base* of an alkaline substance ; in other words, of an alkali or an earth. f 3. Sulphuretted hydro-sulphurets, consisting of bi-sulphuretted hy- drogen, and oxidized metallic bases, viz. alkalies and earths ; pro- bably containing also variable proportions of sulphur dissolved, besides what is united to the hydrogen. 4. Sulphurets of the alkalies and earths, formed below ignition. 5. Sulphurets of metallic bases, formed above ignition and con- taining no sulphuretted hydrogen, nor any uncombined sulphur. * Ammonia being always exceptecl as having a different constitution, but still, it forms a true hydro-sulphuret, and one of the most useful, t The common metals are not here brought into view. CARBON, 355 SEC. II. CARBON carbo Latin. 1. ITS IMPORTANCE AND WIDE DIFFUSION. (a.) An element of great interest, diffused through the animal and vegetable kingdoms, and largely in the mineral, either in the form of carbon or carbonic acid, free or combined. (b.) Known to the ancients. Theophrastus Eresius, pupil and suc- cessor of Aristotle, mentions charcoal 300 hundred years before Christ, and Pliny describes the process of burning it.* 2. PRINCIPAL NATURAL FORMS AND VARIETIES. (a.) DIAMOND. It differs from charcoal, in being a non-conduc- tor of electricity, and in nearly all its physical properties ; still it is pure crystallized carbon. The proof rests on the fact, that it is entirely combustible ; that it is converted into carbonic acid gas, without any other product ; and that it forms steel by cementation with soft iron.f The combustion is effected without difficulty, in pure oxygen gas ; under the compound blowpipe, and in melted nitre. It differs from charcoal more in its state of aggregation,! than in its chemical relations. Still it is much harder than we imagine ; a mass of vegetable charcoal is light, because a great quantity of matter has been expelled in the aeri- form state, and thus the substance is made to appear both soft and light ; but its integrant particles^ are hard, as will be peceived by grinding them between plates of window glass which they will scratch, and it is stated on the authority of Prof. Leslie, that the sp. gr. of charcoal is really greater than that of the diamond. Carbon exists in a transparent state, in the oils and in alcohol, and in crystals of white sugar, from all of which it is easily developed, by heat, acids, and other agents ; it is found also in several gases. (b.) PLUMBAGO, or black lead. The proof that this is nearly pure carbon, is the same ; it produces carbonic acid by combustion, and there is only a small residuum of iron and earthy impurities. || (c.) ANTHRACITE. The same remark may be made of this ; it is nearly pure carbon. There seems no reason to doubt that the globules which I obtained in 1823, from the plumbago and anthracite, by the deflagrator, arose in part, from the earths present in these minerals ; but with charcoal, I conceive it to have been otherwise, (see note, p. 358,) and the * Parkes' Essays, Vol. I, 396. t Phil. Trans. 1815, p. 371. | Charcoal is not more different from diamond, than clay or pure pulverulent alu- mina is from the sapphire ; or chalk from Iceland crystal ; or pulverulent magnesia, from the same in the boracite ; or than quartz nectique, (swimming flint,) from rock crystal. So, the integrant particles of pumice stone and tripoli are hard, although the mass is soft, and that of the former is very light. || For its analysis, see Am. Jour. Vol. X, p. 102. 356 CARBON. compound blowpipe, evidently effected, the fusion of the entire plum- bago, including the carbon, the earths and iron.* (d.) BITUMINOUS COAL. The basis of this is carbon, which, un- der the name of coak, is obtained, after the bitumen, the inflammable gas, and other volatile ingredients have been expelled by heat. It contains some earthy and metallic impurities, but burns away almost entirely in oxygen gas, producing carbonic acid. 3. ARTIFICIAL CHARCOAL. (a.) CHARCOAL is, after the diamond, the purest form of carbon ; it is prepared in the large way, by a smothered combustion of billets of wood, properly arranged, so as to admit a very partial supply of air, through holes at the bottom ; the pile is covered with turf, earth or clay, except a few spiracles, or one hole at the top ; and these are stopped, when the dark smoke is replaced by clear whitish clouds. The emission of volatile matter, consisting of inflammable gases, va- por of oils, and water, and pyroligneous acid, and other things, chem- ically or mechanically raised, finally ceases; and the heap is suffered gradually to cool, which takes several days or weeks, according to its size. The principle of the process is, that the combustion of a por- tion of the wood produces strong ignition in the remainder, and thus expels every thing volatile. (b.) Its formation may be shewn, by plunging small pieces of wood beneath melted lead or tin,-\ or beneath sand heated to redness in a crucible, in a furnace ;J when cold, it should be immediately removed, and corked up for use. (c.) Prepared also in cast iron cylinders, for the manufacture of gun powder,^ and the charcoal is the same from whatever wood pre- pared, although alder, dog-wood, and willow have been heretofore preferred. The cylinders are placed across a furnace, and there is vent only for the aerial matter, consisting of inflammable gas, pyro- ligneous acid || and tar, all of which are useful products. 4. PROPERTIES. (.) Slack, brittle, shining, inodorous, and easily pulverized ; it is so porous that it is easy to blow through it. * See Am. Jour. Vol. VI, p. 352. t Arrangement for class exhibition. A small earthen furnace, filled with burn- ing charcoal, is supported by bricks or a stone upon a table, and upon this rests a large ladle nearly full of melted lead, which should be nearly red hot, and the wood held by small tongs is plunged beneath it; the fluid metal will boil vehemently, and the inflammable gas, may be fired as it rises ; when all is quiet, the charcoal is devel- oped, and maybe cooled beneath mercury. t Aikin, Vol. If, 235. Or still more neatly, by wrapping a piece of wood in platiua foil, and holding in the flame of alcoholic lamp. The liberated gases take fire and burn brilliantly, and well formed charcoal remains within. J. G. || 'The charcoal made in this manner, is kept from the air when it is to be used for the manufacture of gun powder ; it has not more than half the specific gravity of CARBON. 357 (b.) Unchanged by heat, in closed vessels, except that it grows firmer, and harder, and blacker, and shrinks ; it will then very de- cidedly scratch glass, and wear a file.* With the best pieces, one can write his name on window glass. !c.) Unaltered by air and water, and exempt from decay. d. If well prepared, it conducts electricity, but is a bad conduc- tor of heat.f (e.) When once thoroughly made, it retains for a long time, its power of conducting electricity. Heated without contact of air, it emits inflammable gases and nitrogen^ % (f.) Jlfter being ignited, it absorbs gases without alteration ; this is shewn by placing on the quicksilver bath, a piece recently extin- guished, and covered by a jar. This power is much diminished by pulverizing the charcoal. The following are the results of Saus- sure, with box wood charcoal, the most powerful species ; the time was from 24 to 36 hours ; the charcoal was first ignited, cooled in mercury, and then placed in the gas. Gaseous ammonia 90 times the volume of the charcoal ; do. mu- riatic acid 85 ; sulphurous acid 65 ; sulphuretted hydrogen, 55 ; nitrous oxide, 40 ; carbonic oxide, 35 ; olefiant gas, 35 ; carbonic oxide, 9.42 ; oxygen, 9.25 ; azote, 7.5 ; light gas from moist charcoal 5. ; hydrogen, 1.75 ; very light charcoal scarcely absorbs at all. The power of absorption in charcoal bears no relation to its chemi- cal attraction for the gas or vapor, which, by heating the charcoal, is in general recovered unaltered. Those gases that cannot be condensed into the liquid state, are the least absorbed by charcoal, and the reverse is true, very nearly in proportion to the ease with which they are condensed. Vapors- common charcoal ; although better for gun powder, it is not preferred by the iron manufacturer. The loppings'of young trees, called crop wood, are now generally used in England. Abundance of a substance like tar is produced, which Mr. Parkes says is an excellent preservative of wood, against decay and insects. Essays, Vol. I, p. 399. The proportion of charcoal obtained from different woods varies from 15 to 26 per cent ; the average of 21 trials gave nearly 20 per cent. Parkes* Essays, Vol. I, p. 408. Fir gave 18.17, lignum vitae 17.26, box 20.25, beech 15, oak 17.40, mahogany 15.75. Allen and Pepys. For a fuller table, see p. 363. Wood, burned in the open air leaves only about l-200th, or l-250th of the wood, but the charcoal is said to contain l-50th of its weight of alkaline and earthy salts. Turner. * Even in its common state, good charcoal will wear window glass. t Lampblack is prepared from the combustion of oils and resins. We may col- lect it by receiving the smoke of a lamp upon a saucer, or by burning a piece of pine knot or rosin, under suspended sacking. In the arts, the refuse resin and pitch are burned in a peculiar furnace, furnished with long flues, terminating in a close chamber, the ceiling of which is covered with porous cloth to catch the soot. t Mem. d' Arcueil, T. II, p. 484. Jour, de Phys. T. XXIII, and LVIII, and Ann. de Chim. T. XXXII. 358 CARBON. are more easily absorbed than gases, and liquids more easily still. It evidently depends upon the porous form of the charcoal, and plum- bago does not possess it at all. The power seems to be analagous to that of capillary attraction in other solids. When oxygen is ab- sorbed, carbonic acid is formed at the end of several months ; if char- coal is impregnated with sulphuretted hydrogen, and exposed to the air or to oxygen gas, sulphur is evolved, and water formed, the gas being destroyed, and considerable heat produced, so as, in some cases, to produce in a few minutes, detonation with oxygen gas, and more or less heat is always evolved when gases are absorbed by char- coal.* In general after 24 hours, the absorption is not increased, ex- cept in the case of oxygen gas, which goes on absorbing for years, in consequence of the formation of carbonic acid. The gas is easily extracted by the air pump, and during its extrication, cold is pro- duced. Charcoal which has absorbed a gas will give it out en- tirely by being heated again, and very strikingly with ebullition, by plunging it into boiling hot water. The charcoal can be as effect- ually prepared for absorbing gases by the air pump as by ignition. f This property is common more or less to all porous bodies ; asbes- tos, silk, meerschaum, adhesive slate, agaric mineral, wool, linen thread, plaster of Paris solidified by water, &c. have been made sub- jects of similar experiments. { (g.) By exposure to the air, charcoal increases in weight, by ab- sorption of water, air, &c., f of which is water. By a week's ex- posure, lignum vita3 gained 9.6 per cent., fir 12.0, box 14.0, beech 16.3, oak 16.5, mahogany 18.0. Allen and Pepys. (h.) Infusible by any heat which we can apply, except that of gal- vanism. \\ (i.) Insoluble in water, although at a red heat, it decomposes that fluid, (vide carburetted hydrogen.) * Proportioned to the rapidity and amount of absorption ; 25 in the case of car- bonic acid. t Quere Whether also for conducting- galvanism, and for antiseptic agency ? \ Turner, 2d Ed. p. 235, and Vasel,in Sweigger's Jour. Charcoal absorbs from air more oxygen than nitrogen ; when recently ignited and confined in air, over mercury, it left only 8 per cent. ; and if from a state of full ignition, it be plunged into water, and then confined in air over mercury, the oxygen is nearly or quite all absorbed, leaving, as is said, pure nitrogen. We are not informed whether the pure oxygen can be recovered by heating the charcoal. || Fusion of char codify the use of Dr. Hare's Deflagrator. The poles being ter- minated by well prepared charcoal, a knob of fused matter appears on the copper or negative pole, sometimes half an inch in length, while a cavity, corresponding in position, appears on the zinc or positive pole, and if the pieces are made to change places, the knob and cavity are transferred from side to side. The knob appears to come from the opposite pole, and is evidently derived from the charcoal. It is very difficult to burn, but if heated either in oxygen gas by the sun's rays, or in common air, or mixed with nitrate or chlorate of potash, it produces carbonic acid. On an ignited iron in the air, it wastes slowly away. It is smooth and glis- tening, with semi-metallic hues; its color gray, or almost black; not fibrous or CARBON. 359 (j.) Plunged into mercury, or merely resting on it, it absorbs much of that metal into its pores. (k.) Heated in contact with common air, it burns away entirely ; very rapidly r , and wholly, if immersed in oxygen gas in sufficient quantity. A piece of charred bark burns best, and with lively scin- tillations. (/.) Sulphuric acid boiled on charcoal powder is decomposed, and sulphurous acid gas is liberated. (m.) The decomposition of the sulphates by charcoal, is a striking instance of its action on sulphuric acid. (n.) To prepare charcoal for clarification; take that which is well burned, pulverize and sift it ; heat it strongly away from the air, as in a crucible with a small hole in the cover, or covered with sand ; it must then be bottled tight, till it is wanted. (0.) Tincture of alkanet, diluted with water, mixed with well pre- pared charcoal, and simmered over the fire, and then thrown upon a fil- ter, comes through perfectly limpid. Mixed with common vinegar or wine, a thick froth rises, and the liquors are clear after filtration. It is sometimes necessary to boil the vinegar upon the charcoal. (p.) Ditch, sink, or puddle water, or even that of a surgeon's tub is thus rendered limpid, inodorous, and insipid ; and rancid oils are restored by repeated filtration through charcoal. (q.) The prepared charcoal is an excellent dentifrice ; that from the shell of the cocoa nut is preferred ; the charcoal of the kernels of nut fruit is very delicate, and that of carbonized wheat bread is very good.* (r.) Solutions of impure acid of tartar, crude tartar, crude nitre, and other salts are rendered colorless by being boiled with charcoal powder, and are thus made to crystallize in snow white purity. (5.) Impure carbonate of ammonia, sublimed from an equal weight of charcoal powder, is rendered white and deprived of its foetid smell. Charcoal also destroys the heavy sickening odor arising from oiled and gummed silks, such as those of which hat cases and um- brella coverings are made, and it speedily removes any unpleasant porous ; it has no resemblance to charcoal ; sinks as readily in strong sulphuric acid, as it before floated on water with its volume half out ; its gravity was there- fore increased four times, compared with the charcoal in mass. This observation was first made by myself in March 1823, and has been repeat- ed many times since ; with a powerful deflagrator, it constantly occurs. The sub- stance resembles greatly, the residuum found in the iron gas bottles, and there seems no reason to doubt that it proceeds from the volatilization and fusion of the charcoal along with whatever foreign substances it may contain. The objections of Prof. Vanuxem seem to have related to a different substance. Am. Jour. Vol. IV, p. 371. * Soot is one of the very best dentifrices ; for, besides the carbon, there are the detergent ammoniacal salts, and a bitter principle, and other active agents. 360 CARBON. % effluvium from clothes, &c. by being wrapped in them. "It also sweetens bilge water." (t.) Malt spirits, distilled from charcoal are deprived of their disa- greeable flavor ; if too much charcoal is used, the spirit is decom- posed, as is vinegar also. Charcoal, for this purpose, is prepared by heating it red hot in a furnace ; it is then ground in a mill and barrelled or put to immediate use by having the spirit placed over it. (u.) Eight or ten pounds of the spirit macerated for eight or ten days on two ounces of charcoal, is improved in flavor. (v.) Water become putrid in casks, is restored by filtration through charcoal, especially if a few drops of sulphuric acid be added. (w.) The odor of alcoholic solutions of resins and balsams is not destroyed by charcoal, although their color is ; essential oils do not lose their smell. ( a?.) Distilled waters and many vegetable tinctures, and litmus, and indigo, and other lakes and pigments, become colorless when their aqueous solutions are filtered through charcoal. (y.) Gum-resins, as opium, assafoetida, &ic. suspended in water, lose their odors. (z.) Tainted meat is restored by rubbing or boiling it with charcoal powder ; and if daily renewed, it preserves meat from putrefaction. (aa.) The inside of water casks is charred to preserve the water from putridity in long voyages, and the ends of posts to keep them from rotting. (bb.) The facts under (t.) and (u.) are true of rum and other varieties of ardent spirit. (cc.) Proper proportion is essential to success in these experiments. (dd.) The same portion of charcoal, if re-ignited, may be used repeatedly. (ee.) Minimal charcoal is a more powerful antiseptic than vegeta- ble ; it is obtained by calcining bones in close vessels.* (ff.) Charcoal, if undisturbed when in the act of being formed, preserves the organization of the substance from which it is derived; " the wire marks of paper and the thread of linen, are still seen with distinctness," after being carefully burned. Grains of wheat and rye charred in Herculaneum, by the volcanic eruption, A. D. 79, were easily distinguished from each other, and an arrow head has been charred so as to preserve the form of the feather. ParJces. (gg.) The charcoal of the heaviest wood requires most air, and gives the most heat, and is best fitted for the reduction of metallic oxides ; " while lighter wood preserves a glowing heat with a less draught of air." If wood be stripped of its bark before it is carbon- * Ann. de Chiin. 79, 80 ; Jour, of Science, IV, 367. CARBON. 361 ized, it does not crackle and fly. For black crayons, willow affords the best charcoal, it being uniformly soft. Ivory black is the coal of ignited ivory prepared in close vessels ; the common ivory black is often made from bones. (hh.) The durability of charcoal is seen in the figures on the dial plates of steeples, which often stand out in bold relief, while the rest of the wood, painted white, is worn away. (ii.) Lampblack, ignited in a crucible, and cooled before it is un- covered, and the charcoal which Is procured by passing the vapor of oils or of alcohol through ignited tubes, is the purest carbon that art can prepare. It is an impalpable black powder, and more than twice as heavy as water.* (jj.) Bistre, a beautiful brown pigment, is prepared from an aqueous infusion of wood soot. (kk.) Animal charcoal is more dense and less combustible than ve- getable, and contains phosphate of iron ; it is distinguished from ve- getable, as the latter burns on an ignited iron into white ashes, form- ing a bitterish liquor with sulphuric acid, but the residuum of animal matter is much less soluble, and forms a compound having a very dif- ferent taste. f (II.) Charcoal is very effectual in depriving treacle or molasses of its peculiar taste ; twenty four pounds, diluted with an equal weight of water, and boiled for half an hour with six pounds of pulverized charcoal, were entirely deprived of the empyreumatic taste and smell, and being strained and evaporated to a proper consistence, had the flavor of good sugar. { Honey may be treated in the same manner, and with the same effect.^ (mm.) The due preparation of charcoal is of the last consequence to success in these operations. Common charcoal is almost inert ; it is indispensable that it be fresh made ; or re-ignited, and that it be secluded from the air till it is used. (nn.) Charcoal is used in polishing brass and copperplates and lanthorn leaves ; in tracing the outlines of drawings, and in giving some peculiar tints to glasses colored in imitation of the gems.|| (oo.) The ancients knew that charcoal will not decay. The piles driven, more than than two thousand years ago, in founding the tem- ple of Ephesus, were charred, and those that support the houses * Davy's Elements, p. 299. A very pure charcoal is prepared also from sugar and starch. t Parkes' Essays, Vol. I, p. 414. t Charcoal has been applied to the refining of sugar, and a patent was taken out for it some years ago in London. Mr. Parkes says, that finer loaves of sugar than were manufactured at any other establishment in London, were as he supposes, pro- duced in this manner. Parkes' Essays, Vol. I, p. 419. || Parkes. 46 ,J62 CARBON. in Venice had undergone the same process. Dr. Robinson, in his in- troduction to Dr. Black's lectures, says, "About forty years ago, a number of pointed stakes were discovered in the bed of the Thames, in the very spot where Tacitus says that the Britons fixed a vast number of such stakes, to prevent Julius Ca3sar from passing his army over by that ford. They were all charred to a considerable depth, and retained their form completely ; and were so firm at the heart, that a vast number of knife handles were manufactured from them, and sold as antiques, at a high price."* 5. POLARITY. Electro-positive; it is attracted to the negative pole. 6. COMBINING WEIGHT 6, hydrogen being 1. 7. MEDICAL AND OTHER USES. A preference is entertained by some for charcoal made from particular substances, as from cedar or cork ; it should be newly prepared or recently heated, j- It is thought to correct a vitiated state of the stomach and bowels, and has been celebrated in some stages of dyspepsia, and in dysentery and other diseases of the alimentary canal. The dose cannot be critical ; from 10 grains to a table spoonful may be given, two or three times a day.J It is applied with much advantage to foul ulcers, whose fetor it cor- rects, and in the form of poultice to sores that are tending to gan- grene. 8. MISCELLANEOUS. (a.) Charcoal is said to be better if the bark is left on the wood, which should not be split ; pieces of six or seven inches in diameter are easily charred. Coak is the carbon of mineral coal ; it is pre- pared by a process resembling in principle that for charcoal ; it pro- duces an intense fire, and is much used in England in the manufac- tures, especially of iron. || A charcoal is also extracted from peat. The following table shows the proportion of volatile matter, charcoal and ashes, in 100 parts of different woods. Ure. * I saw one of these stakes in the British Museum ; the charcoal on the outside and the wood within, were apparently as perfect as the day it was driven. t If it is to be applied on a foul ulcer or sore, it should be taken red hot from the fire, pulverized immediately in a metallic mortar, and used as soon as cold, and any ,that remains should be bottled, tight from the air. + Coxe. It is conjectured that in the charring of wood, portions of it are sometimes con- verted into pyrophorus, and that explosions in powder mills may occasionally be owing to this cause. || One ton of bituminous coal yields from 700 to 1100 Ibs. of coak. Much bitumen and other volatile products are lost in the usual way of charring, but Lord Dundo- nald, by heating the coal in a range of eighteen or twenty stoves, with as little ac- cess of air as possible, and conducting the smoke through horizontal tunnels, and finally into a brick tunnel 100 yards long, and covered at top by water, succeeded in obtaining nearly 3 per cent, of bitumen in the form of tar ; 28 barrels of it yielded 21 of tar, and the volatile parts gave materials for varnish, besides ammonia. Ure. SULPHURET OF CARBON, 563 Oak, Ash, Birch, Norway Pine, Mahogany, Sycamore, Holly, Scotch Pine, Beech, Elui, Walnut, American Maple, Do. Black Beech, Laburnum, Lignum Vitae, Sallow, Volatile Matter. 76.895 81.260 80.717 80.441 73.528 79.20 Charcoal. Ashes. Charcoal by 22.682 17.972 17.491 19.204 25.492 19.734 0.423 0.768 1.792 0.355 0.980 1.068 78.92 19.913 1.162 83.095 79.104 79.655 78.521 79.331 77.512 74.234 72.643 80.371 16.456 19.941 19.574 20.663 19.901 21.445 24.586 26.857 18.497 0.449 0.955 0.761 0.816 0.768 1.033 1.180 0.500 1.132 Proust. 20. 17. 20. Black Ash, 25. Willow. 17. Heart of Oal 19. Guaiacum. 24. Kumford. 43.00 44,18 76.304 23.280 0.416 43.27 42.23 Poplar. 4357 Lime, 43.59 the s Chesnut, (b.) Charcoal, in the form of lampblack and plumbago, is among t most enduring of paints, and forms a firm body with oil. Plumbago used for lubricating machinery, for making crucibles, for protecting iron from rust, and to give it lustre. Charcoal with oil forms print- er's ink ; with sulphur and nitre, gunpowder ; with iron, by cementa- tion, steel ; it is used to exclude or to confine heat ; it is a very ex- cellent fuel, and it is employed with advantage, after being thorough- ly ignited, to surround that part of lightning rods which enters the ground . Thenard. (c.) Charcoal is of great utility in reducing the metals, both in raising the necessary heat and in detaching oxygen from the oxides. Carbon, in the form of diamond is the most beautiful of ornaments, and the best substance to cut glass, and to afford a cutting powder to polish the hardest bodies, diamond itself not excepted. The water of the Seine, rendered turbid by mud in the winter, is purified and made potable, by passing through charcoal, placed between two layers of sand, and these between two others of gravel and pebbles. Id. (d.) It is exceedingly abundant in nature ; it exists in all animal and vegetable bodies ; in all the varieties of natural coal, and bitumens, and petroleum and naptha ; in the carbonates of lime, and other min- eral carbonates ; in carbonic acid, both free in the air, and dissolved in water.; and in the carburetted hydrogen gases and carbonic oxide ; and its chemical and natural history involves a vast number of inter- esting and important facts. SULPHURET OF CARBON. 1. PREPARATION. (a.) A porcelain tube, one inch and a half in diameter, coated with fire lute, and partly filled with fragments of recently ignited charcoal^ 364 SULPHUREt OF CARliON. is placed a little inclined across a furnace ; at one end a recurved glass tube dips into water, and the other end is open. The furnace being in action, a fragment of sulphur is pushed along by a wire till it is near the charcoal, taking care to exclude the air as much as possible ; the open end of the tube is then stopped, gas passes in abundance, and a liquid collects beneath the water ; more bits of sulphur may be introduced, till enough of the liquid is obtained, and it is said that half a pint may be procured in a day. (b.) The following process I find to be a good one, A tube of iron is placed across Black's furnace, as a protection to a tube of porcelain which is passed through it. A glass flask containing flowers of sulphur, coated with lute of sand, clay and rye flour, is connected with one end of the iron tube, and at the other is a glass tube passing into water, contained in a vessel surrounded by ice. Pieces of charcoal, recent- ly ignited, are placed in the porcelain tube, and heat is applied by a chafing dish under the flask ; the sulphur is slowly volatilized through tire charcoal ; the two combine, and the desired yellow liquid drops from the mouth of the tube. The principal point is to bring- the sulphur into contact with the charcoal when it is very hot and has ceased to emit gases. (c.) Another process, stated also to be a good one, is to distil na- tive iron pyrites, (bi-sulphuret of iron,) with one fifth of its weight of charcoal powder. 2. PROPERTIES. (.) After being re-distilled at a heat not exceeding 100 or 110 Fahr., from some dry muriate of lime placed in a retort, it is color- less, transparent and limpid;* its refractive power very high. {b.) Taste acrid, pungent, and somewhat aromatic; smell nauseous and fetid, but unlike that of sulphuretted hydrogen. Inflammable, and its combustion produces sulphurous and carbonic acid gases. Insoluble in water. (c.) Sp. gr. 1.27; boils at 106 or 110, does not freeze at 60; very volatile, at 63.5 Fahr. its vapor sustains a column of mercury 7.36 inch high, and during its evaporation produces so much cold as to freeze mercury. The thermometer ball is covered with fine lint, moistened with the liquid, and placed under the receiver of an air pump. A spirit thermometer at the same time indicated 80. (d.) Not decomposed, by heat alone, at any temperature ; but it is decomposed by being transmitted over ignited iron or copper turn- ings ; also by peroxide of iron ; or by heating potassium in its vapor, when there is a brilliant ignition ; the sulphur always combines with the metal and liberates the carbon. (e.) It is very combustible, and produces sulphurous and carbonic acid ; a little sulphur remains unburnt. Placed in oxygen gas or * Sometimes a little milky and opaque at first, but becomes limpid the next day. CARBONIC AC1U 365 deutoxide of nitrogen, it renders it explosive. Soluble in volatile oils, in ether and in alcohol, and precipitable by water. (f.) Evaporation from water causes it to congeal. 3 t COMPOSITION. 85 sulphur to 15 carbon, and it is supposed to contain 2 proportions of sulphur 1 6 X 2 = 32 and 1 carbon 6 = 38 for its chemical equivalent. This compound was called alcohol of sulphur by Lampadius, its discoverer.* HYDRO-XANTHIC ACID. (favdo?, yellow.) The sulphuret of carbon is generally unaffected by acids, but the nitro-muriatic acid produces from it a yellow acid, whose nature is not yet exactly ascertained. f Its discoverer, M. Zeise, (Copenha- gen,) regards it as a compound of sulphur and carbon for a base, with hydrogen for an acidifier. It combines with alkalies, neutral- izing them, and forming peculiar crystallizable salts. The subject seems to need farther examination. J Remark. It was announced last year, in Paris, that phosphorus, remaining six or eight months in bi-sulphuret of carbon, attracted away the sulphur, and left the carbon to crystallize into true dia- mond ; it was sajd that the Parisian jewellers pronounced it to be genuine, but the latest accounts state that the small crystals obtained appear to be siliceous. CARBONIC ACID. 1. COMBUSTION OF CARBON IN VARIOUS FORMS. (a.) It has been already mentioned, that Sir Isaac Newton sup- posed the diamond to be a coagulated combustible, because it re- fracted light so powerfully. This sagacious conjecture has been con- firmed by the actual combustion of the diamond, and the products having been collected are found to be carbonic acid. * Crell's Annals, 179G, II. Cited by Turner. t Berzelius supposes it to be a compound of muriatic, carbonic and sulphurous acid gases. t Ann. de Chim. et de Phys. Vol. XXI, and Ann. Phil. N. S. Vol. IV. The- nard, 5th ed. Vol. I, p. 440. The Emperor Francis I, exposed a quantity of diamonds and rubies to an intense heat, the rubies remained unaltered, but the diamonds disappeared. The Florentine academicians, by means of the large burning glass of Tschirhaucen, in the pres- ence of Cosmo III, Duke of Tuscany, dissipated several diamonds in the year 1694. These experiments were repeated with equal success by Darcet, Rouelle, Macquer, and other French chemists, who ascertained that the diamond was not merely dis- sipated, but that it actually burnt with a visible flame. Count de Sternberg, a Bohemian gentleman, fastened a diamond to red hot iron, and plunged it into oxygen gas, when the combustion of the iron set fire to the diamond, which burnt with a very brilliant flame. Lavoisier and Cadet proved that the diamond does not burn after the oxygen gas is exhausted. But these experiments went only to prove that the diamond is combustible. No attention had been paid to the products of the combustion, until Lavoisier, in 1777, undertook a series of experiments on a large scale, to ascertain this point. The result was found to be, that the diamond when "burnt in oxygen gas, is converted wholly into carbonic acid gas. The conclusion 366 CARBONIC ACID. (b.) A coated glass or porcelain tube filled with charcoal that has been heated till it has ceased to yield any gas, is placed across a fur- nace and ignited ; one end being connected with a gazometer to af- ford oxygen gas or common air ; the other with a pneumatic appar- atus to receive the gas ; by adding another gazometer, the gas may be made to pass repeatedly back and forward. (c.) Diamond, charcoal, plumbago and anthracite, or any varieties of carbon may be treated in the same manner, as was done by Messrs. Allen and Pepys, in their celebrated experiments ; they used a pla- tinum tube to contain the diamond and other forms of carbon, and their gazometers were placed over mercury. (d.) Burn charcoal in a bottle or jar of oxygen gas ; if a piece of well charred bark be used, the combustion is attended with brilliant scintillations ; otherwise with only a bright glow. (e.) Burn any kind of wood, or a taper, in a bottle of common air, or of oxygen gas, and carbonic acid will be formed, as may be evinced by the test of lime water, which produces a milky precipi- tate. (f.) Diamond is easily made to burn under the compound blow- pipe,* and wastes entirely away. If the combustion be stopped in its progress, the surface of the diamond will be found, not carbonized, but indented and dull, as if it had been corroded and then washed. In my experiments it had the appearance of superficial fusion. (g.) An elegant apparatus for the combustion of diamond, is fig- ured by Mr. Brande, in his elements, and copied by Dr. Henry,f by which the diamond may be burned, and the products collected. By combustion, it is rapidly diminished, and carbonic acid is abundantly precipitated by admitting lime water. (h.) According to the experiments of different eminent chem- ists, J 28 or 29 grains of any pure carbon, require 71 or 72 of oxy- gen and give 100 carbonic acid; 201 cubic inches of oxygen by bulk, require 28 or 29 grains of charcoal. Mr. Dalton assumes the composition of carbonic acid to be, in round numbers, 28 carbon to that diamond is carbon, was unavoidable. In 1785, Guyton Morveau, found that the diamond, when dropped into melted nitre, burns without any residuum, and in a manner analogous to charcoal. Dr. Tennant also burnt the diamond in nitre, and found that carbonic acid gas was the only product. (Phil. Trans. 1797.) Guyton Morveau observed, that the diamond burns at three different temperatures, and al- though some of his conclusions were erroneous, for instance, that the diamond can be converted into a substance resembling charcoal, and that charcoal is an oxide of carbon, still he fully established the fact that diamond is by combustion, converted into carbonic acid. * See Am. Jour. Vol. VI, p. 349. t Vol. I, p. 342, 10th Ed. t Carbon, 28.60; oxygen, 71.40=100. Carbon, 27.376; oxygen, 72.624=100. Allen and Pepys, Clement and Desormes, Wollaston, Gay-Lussac, and Berzelius. See Henry, 10th Ed. Vol. I, p. 344. 4 The precise proportions appear to be 72.72 of oxygen, and 27.27 of carbon, which corresponds with 2 proportions of oxygen and of 1 carbon. Murray. CARBONIC ACID. 367 72 oxygen, and all the results come so near to this, that we may venture to neglect the fractions. The composition of carbonic acid is a problem of great importance, for whenever it is produced, we infer the presence of carbon in the proportion now stated. (i.) Oxygen gas, by uniting with charcoal, suffers neither contrac- tion nor expansion, but increases- in specific gravity, so that 100 cubic inches weigh, at the medium temperature and pressure, 46.59 grains, or about one and a half the weight of common air.* These methods of obtaining carbonic acid gas, are put in practice only to demonstrate its composition ; they are never resorted to when the object is to obtain the gas in large quantities ; then it is always extracted from some of its natural combinations. 2. OTHER MODES OF OBTAINING CARBONIC ACID GAS. (a.) Procured from marble poivder, or chalk with dilute sulphuric or muriatic acid.^ The proportions with sulphuric acid, may be about 6 parts by weight, of water, to 1 acid, and 1 J marble powder ; apparatus a retort, flask, or bottle, with a glass tube, bent twice at right angles, and turned up at the end of delivery ; it may be thrust through a cork bored by a tapering hot iron ; the residuum will be sulphate of lime. (b.) Heat marble powder or chalk, red hot, in an iron bottle; a quart affords a barrel of gas, and the residuum is brought almost to the condition of quick lime. 3. DECOMPOSITION. (a.) Decomposed by repeated electrical discharges, over mercury; becomes carbonous oxide, J and oxygen gas. The undecomposed carbonic acid, being washed out by lime wa- ter, or potassa, and an electric discharge passed through the remain- der, it explodes and becomes again carbonic acid. (b.) A mixture of hydrogen and carbonic acid, being heated in the same manner, water and oxide of carbon are obtained. (c.) Carbonic acid, as it exists in the carbonate of lime, and of baryta, and probably strontia, is easily decomposed by igniting the pulverized carbonate with iron filings, when oxide of carbon is pro- duced, as will be shewn in connexion with that substance. (d.) Potassium heated in carbonic acid gas, in the proportion of 5 grains to 3 cubic inches, inflames, and charcoal is precipitated. || * For the statements of different writers, see Henry. t Muriatic acid, mixed with 2 or 3 parts of water, is perhaps preferable, be- cause the sulphuric acid forms an insoluble compound with the lime, and clogs the effervescence. t Whose propertes will be soon explained. || I am accustomed to exhibit this beautiful experiment by the following arrange- ment. A flask, with dilute sulphuric acid and marble powder, is fitted with a cork and tube bent twice at right angles, through which carbonic acid gas flows to the bottom of another flask, and expels the air, or the gas may be introduced in a similar manner 368 CARBONIC ACID. (e.) Carbonic acid, contained in carbonate of lime, or of soda, is decomposed by phosphorus, and the carbon appears in the form of charcoal. (/.) It is done by taking a glass tube J of an inch wide, and 20 inches long; it is sealed at one end, and coated with sand and clay, to within an inch of the end ; phosphorus is placed there, and mar- ble powder, or better, carbonate of soda, dried in a sufficient heat ; the part containing the carbonate is heated red hot, and then the phosphorus is sublimed through it, and the heat continued for some minutes ; charcoal is found mixed with a phosphate.* (g.) In Dr. Pearson's experiment, 200 grains of phosphorus, and 800 carbonate of soda, gave 40 grains charcoal. f (A.) If phosphorus be boiled in a solution of carbonate of soda, it becomes black in consequence of the developement of charcoal ; it is done in a small flask, and the process occupies an hour. 4. PROPERTIES. (a.) Carbonic acid gas is fatal to animal life ; if we confine a mouse or other small animal in this gas, it will speedily die. But- terflies and other insects may be killed in this manner, or hy heat alone, without injuring their beauty. This gas kills both by suffoca- tion and by a deadly influence of its own. (b.) It extinguishes combustion ; lower a pendent candle into it, and withdrawing it immediately, drop it into oxygen gas ; it is ex- tinguished and relighted alternately. Gun powder burns in this gas.f from a small gazometer. A tray of platinum, with a lump of potassium, is slipped into the flask, taking care at the same time, not to let in the air or spill the carbon- ic acid; a tube, twice bent at right angles, is then adapted, and dips into a glass containing mercury ; live coals are applied beneath the tray of potassium, and just at the point of the fusion of plate glass, the potassium inflames with bright light, regenerated potassa fills the flask with white fumes, and charcoal precipitates, mix- ed with the potassium. A green flask would probably be better, as enduring more heat ; sometimes the experi- ment succeeds with difficulty, and the bottom of the flask is indented. N. B. The second tube and the mercury may be dispensed with, provided we cork the flask rath- er loosely, so as to allow the gas to escape a little by ex- pansion. * Phil. Trans. 1791, p. 182. t Phil. Trans. 1792, p. 289. t A, Large gJass globe with a wide neck filled with carbonic acid gas. 6, Iron or copper spoon with gun powder in it. C, An iron rod heated red hot at the lower end to in- flame a few grains of gunpowder. d, Orifice stopped with a cork, which being with- drawn, the gas runs in a visible current and fluctuates. A candle cannot burn in atmospherical air, containing one fourth part, by measure, of carbonic acid. CARBONIC ACID. 369 (c.) Mix smoke with this gas, by extinguishing in it a burning chip or paper, or by burning a cork with a red hot iron borer, at the ves- sel's mouth, or better by exploding gun powder in a pendent spoon, in ajar, or globe filled with carbonic acid ; see the figure on p. 368. (d.) The gas is thus rendered visible, and exhibits distinct fluc- tuations and currents. (e.) Butterflies and other insects of delicate colors are killed in this gas, and better than by sulphurous acid gas.* (f.) By a cylindrical jar, containing carbonic acid gas and a little water, with the aid of a pendent candle, we may show the phenome- na of the damp in wells and caverns. In the annexed apparatus, two ounces of the carbonate of am- monia, and half as much deep orange colored nitrous acid, being placed in the three necked bottle, will evolve carbonic acid gas, which will thus be rendered visi- ble in its ascent, and in its over- flow beneath the cover of the up- per vessel. This being removed and a candle introduced, it will be extinguished. The gas can be drawn off at A ; its current will be visible, and it will extin- guish a burning taper held in its course ; or it can be drawn like a liquid into any other vessel con- taining a lighted candle which it will thus put out. If either ori- fice of the bottle be opened, all the gas in the upper vessel will flow out. Dr. Hare. A long necked funnel may be substituted for the upper vessel. (g.) Sp. gr. 1.527 ; 100 cub. inch, weigh at 60 Fahr. and 30 in. Bar. 46.59, whereas air weighs 30.50.f (h.) We may pour the contents of one jar into another, and exa- mine by a pendent candle how high the gases rise. (i.) We may collect it by a bent tube passing into a bottle filled only with common air, which it will expel. * Entomologists prefer to kill them simply by means of heat, immersing them in boiling water, in close vessels. t It is said that Dr. Prout has recently ascertained that it is as high at least as 31 grs. Addenda to Turner, 2d edition. 47 370 CARBONIC ACID. (j.) The absorption of this gas by water, is slow if merely stand- ing over it, but rapid, if agitated with the water in a bottle. (k.) Noo^s apparatus is an elegant one for impregnating water with this gas ; it combines agitation and moderate pressure. A, The pedestal and containing vessel for the marble powder and acid ; , an orifice for pouring in the diluted acid which should be mixed previ- ously with water and allowed to cool. B, The neck of the vessel to contain the water which is to be impregnated ; this neck contains a glass cylinder pierced longitudinally with capillary ducts, and also a plano-convex lens, which oper- ates as a valve. D, The containing vessel furnished with a stop cock at C. E, A vessel of retreat for the water. As the gas rises into the middle vessel, it causes the fluid, by means of the bent tube e, to mount into E, thus producing hydrostatic pressure, and favoring the combination of the water with the gas. Much more powerful instruments are known in the arts.* The following is from Dr. Hare. IMPREGNATION OF WATER WITH CARBONIC ACID. " A condenser, A, is fastened at bottom, into a block of brass, which is furnished with a conical brass screw, by means ol which, it Phil. Trans. 1803; Dr. Henry's Apparatus. CARBONIC ACID. 371 is easily attached firmly to the floor. In this brass block are cavities for the two valves, one opening inwards from the pipe, B, the other outwards, towards the pipe, C. The pipe, B, communicates with a reservoir of gas which the condenser draws in, and forces through the other pipe into a strong copper vessel containing the water. The front part is represented as removed in order to expose the inside to inspection." " If due care be taken to expel all the air in the vessel before the impregnation is commenced, the water will take up as many times its bulk of gas, as the pressure employed exceeds that of the atmosphere." " When duly saturated, the water may be withdrawn at pleasure, by means of the syphon, D, of which one leg descends from the vertex of the vessel, to the bottom, while the other is conveniently situated for filling a goblet." (Z.) The gas washed to free it from any sulphuric acid, and passed up into litmus infusion, reddens it fugaciously. (m.) Liquid* carbonic acid gives up its gas by boiling , and by being placed under the exhausted receiver. (n.) Litmus water, reddened by this acid, is restored by air pump exhaustion, or by boiling. -\ This gas is liberated from water by freezing, which gives the fluid a spongy appearance. (o.) Lime water is a test of carbonic acid; it is applied by pour- ing the liquid acid into it by suffering the gas to pass into a tall in- verted tube closed at the top and filled with lime water, or by re- ceiving the gas in a bottle and washing it with lime water. (p.) An excess of carbonic acid redissolves the precipitate, and then more lime water precipitates it again, and so on without limit. (q.) Burn a candle, a stick, or any common combustible, in a bot- tle of air or oxygen gas, and examine by lime water for carbonic acid ; if present there will be a milky precipitate. (r.) Carbon is a principle of those substances which, by burning, give a gas not rapidly absorbed by water, and which precipitates lime water; the precipitate being soluble in muriatic acid, with effervescence. (s.) This gas is an antiseptic, and therefore useful in putrid dis- eases, and externally in ulcers. Cataplasms are made with yeast and other fermenting materials. (t.) Meat suspended in carbonic acid, especially if the gas be frequently renewed, keeps much longer than in common air. (u.) Carbonic acid promotes vegetation, especially when in the liquid form and applied to the roots ; also, as an atmosphere, pro- * At a common temperature and pressure, water absorbs its own volume of gas ; twice its volume under a double pressure, and so on in the same ratio. t Tincture of alkanet diluted and slightly blued by ammonia, is decidedly redden- ed when agitated in a vial with carbonic acid gas. When the above solution is boiled so as to expel the carbonic acid, it resumes its original blue color. 372 CARBONIC ACID. vided it does not exceed one eighth of the whole ; beyond that it is injurious. (v.) This gas exists in fermented liquids ; we may collect it from any fermenting mixture, or from bottled cider, beer, porter, &LC. and it will prove to be carbonic acid. (iv.) This may be shewn by drawing the cork under water the mouth of the bottle being immersed, the gas, at least what is spon- taneously disengaged, will collect at top, and the rest may be obtain- ed by boiling the fluid in a proper gas apparatus. 5. MISCELLANEOUS. (a.) Carbonic acid gas, on account of its gravity, is often found at the bottom of wells and caverns, as in the grotto Del Cani, near Naples, and thus often destroys those who incautiously descend into them ; by letting down a candle, it may always be determined whether the place is safe. (b.) Jls the combustion of charcoal, and other carbonaceous sub- stances, always generates carbonic acid, it is unsafe ever to remain in a confined situation, in such an atmosphere ; in both these modes many lives are destroyed. When it is pure, it produces a spasm of the glottis, and suffocation ensues ; if so much diluted as to pass in- to the lungs, it operates as a narcotic poison.* (c.) There are many other gases evolved in combustion, and all of them are deadly ; nitrogen is always present in such cases, and frequently carburetted hydrogen, gaseous oxide of carbon, ammonia, and various vapors, as of pyroligneous acid, &tc. (d.) Fire should, therefore, always be made under a good drawing vent. (e.) Carbonic acid is eminently salutary in the stomach, although fatal in the lungs ; witness the native and artificial acidulous waters ; its action in the primae viae is that of a mild stimulant. With com- mon air, it exists, dissolved, in all natural waters, and imparts to them pungency ; hence the flatness of boiled water, or of that which has been exposed to air pump exhaustion. (/.) Carbonic acid gas. is the principal agent in raising bread ; it is generated in the fermenting mixtures, as yeast, the sediment of beer,f &c., and the native or artificial acidulous waters will inflate dough and make it light. (g.) Carbonic acid exists every where in the atmosphere ; it was found on the top of Mount Blanc, by Saussure,J and aeronauts have brought it down from the greatest heights to which man has as- * It is supposed by many, that charcoal, when burning without smoke, is harm- less, and that the anthracite coal does not produce a noxious gas ; both these are very dangerous popular errors ; the deadly carbonic acid gas is rapidly formed from both, during the whole time that they are burning. t Called in this country emptyings. t Jour, de Phys. XVII, p. 202. CARBONIC ACID. 373 cended ; in general, the proportion is very uniform. A pellicle is formed on lime water, by exposure to the air ; it contains T | carbo- nic acid, as formerly stated ; according to Dalton, T T7r , or even less. (h.) Although produced in enormous quantities by respiration, combustion, and other processes, it is scarcely found to exist in great- er proportion in large towns than in the country ; doubtless the winds prevent its accumulation. At sea, however, only two leagues from Dieppe, there was so little that it scarcely affected barytic water.* (i.) Caustic alkalies absorb carbonic acid gas entirely, and thus separate it from other gases. (/.) Vegetation appears to be the grand means of preserving the purity of the atmosphere ; it decomposes the carbonic acid, absorbs its carbon for food, and lets loose its oxygen. It is true that vegetables emit carbonic acid in the night, but in smaller quantity than that which they decompose in the day.f (k.) Carbonic acid is visible in the sunshine, as it descends into a vessel of common air, because, on account of its great weight, it produ- ces unequal refraction in the light, and thus creates a disturbed image. 6. RESPIRATION. (a.) About 8 or 8J per cent, of carbonic acid is thrown from the human lungs in respiration, at every expiration, and only 10 per cent, when the contact is rendered almost as frequently as possible ; a similar result happens with the whole animal creation. (b.) About 11 oz. Troy, of carbon, are thus daily detached from the blood, and of course more than twice the weight of a living man in a year. (c.) Thus one great office of respiration is, the decarbonization of the blood. (d.) The production of animal heat is also intimately connected with this process ; venous blood becomes arterial in the lungs, and there acquires its florid color, and emits its excess of carbon, and its capacity for heat, according to the experiments of Dr. Crawford, J is enlarged from .892, which expresses the capacity of venous blood, to .1030 ; thus the heat that would be evolved from the union of the carbon with the oxygen, is absorbed, and again given out when the arterial blood becomes venous, that is, all over the body.|| (e.) There can be no doubt that animal heat is connected also with the nervous power, with secretion, and perhaps with other vital agencies. * Ann. Phil. N. S. VI, p. 75. t See Thomson's Chemistry. t The experiments of Dr. J. Davy, do not appear to have set aside those of Dr. Crawford. || In a note on respiration, in Parkes' Chem. Chat, the following facts are stated. The human heart gives 100,000 strokes in 24 hours, 4000 strokes in an hour, and 66 or 67 in a minute, and 350 pounds of blood pass through it in that time ; 25 pounds is the whole amount in the body of a common sized man ; this passes through the heart 14 times in an hour. The aorta of a whale is one foot in diameter, and 10 or 15 gallons of blood (half a barrel,) are sent out at every stroke with vast force. 374 CARBONIC ACID. (/.) Lime or barytic water is precipitated by blowing through it with a tube ; or by agitation in air which has been breathed. 7. COMBINING WEIGHT. The weight of carbon is 6, and carbonic acid being a compound of 2 proportions of oxygen, and 1 of carbon, its equivalent will be 16-f-6=22. In volumes, Gay-Lussac estimates it constitution to be 1 gaseous carbon, and 1 oxygen, condensed into 1 volume. As oxygen under- goes no change of volume, by combining with carbon, and as 100 cu- bic inches of carbonic acid weigh 46.597 grains, it follows that the amount of carbon in vapor will be 46.59733.888, the weight of 100 cubic inches of oxygen, =12.709 grs. of carbon ; and as 12.709 : 33.888 : : 6 to 16, and 6 being the combining proportion of car- bon, it follows that carbonic acid is composed as above. * 8. POLARITY. Like other acids, it is evolved at the positive pole, and is therefore electro negative. 9. LIQUEFACTION OF CARBONIC ACID. Mr. Faraday\ effected this by cold and pressure. He contrived to extricate the carbonic acid gas from sulphuric acid and carbonate of ammonia, brought together at the moment, and after the bent glass tube in which they were contained was sealed, the other end of the tube was kept cold by a freezing mixture, and the gas, subjected to its own enormous pressure, aided by cold, became fluid. These ex- periments are very hazardous, as it is a more difficult gas to con- dense than any with which Mr. Faraday succeeded ; very strong tubes were required and yet they often exploded. 10. PROPERTIES. (a.) Limpid, colorless, very fluid ; floating on the other fluids in the tube ; distils readily and rapidly between and 32 ; refractive power less than that of water, not altered by increase of cold. When it was attempted to open the tubes, they always burst with powerful explosions ; at 32 the pressure was equal to 36 atmos- pheres. Sir H. Davy, in a communication to the Royal Society, suggested the application of condensed gases as a moving force, capable of be- ing increased or diminished by slight variations of temperature. It would be necessary only to let loose a little of the condensed carbonic acid, to produce a powerful movement ; condensed nitrogen would be still more powerful, and hydrogen would exert a tremendous force. No furnaces would be necessary, but mere variations between sun- shine and shade might perhaps be sufficient to vary the energy of the power. It is obvious, however, that the danger of explosion would be great. 11. DISCOVERY. Dr. Black discovered carbonic acid in 1755, or 6, and thus laid the foundations of the pneumatic chemistry; he called * Turner. t Phil. Trans. 1823, p. 193. CARBONATES. 375 it fixed air.* Its composition was first demonstrated in 1772, by Lavoisier, who, as already stated, proved that the diamond, by being burned, becomes carbonic acid gas. 12. NATURAL ORIGIN. Carbonic acid gas is formed abundantly by the respiration of ani- mals; from our candles and lamps, and from our fire-places, and from furnaces, from fermentation and putrefaction it is perpetually rising into the air. It forms nearly half, T 4 /o j of the beds and moun- tains of marble and limestone, and exists in various other natural car- bonates, and abundantly in shells. Its fatal prevalence appears to be prevented by the fact that vegetables during their growth decompose this gas, absorbing its carbon for food, and liberating the oxygen to recruit the waste of the atmosphere. The late Dr. Woodhouse, proved by many experiments, that when- ever vegetables emit oxygen gas, it is from the decomposition of car- bonic acid present in the air, and dissolved in the waters which they imbibe. He justly rejected the idea that they give out oxygen gas of themselves, or from the decomposition of water. f 13. MEDICAL AND ECONOMICAL USES. It is highly salutary in the brisk and acidulous natural mineral wa- ters, such as those of Saratoga and Ballston, and in imitations of them by art, either with or without saline substances ; in fermented li- quors, to which this agent imparts life and pungency, and in a de- gree to all natural waters. It operates as a tonic, diuretic and an- tiseptic remedy. It is said to be very useful in the hemorrhoids or piles ; it is a reagent in the laboratory. CARBONATES. General facts and characters. Some of them have been long known, and were used before the discovery of the power of carbonic acid to neutralize the alkalies. The carbonates effervesce with acids, and emit carbonic acid. They are decomposed by heat, more or less violent ; the gas being expelled, and the base remains.} Potassa, soda and lithia, are exceptions. (c.) Alkaline carbonates turn the vegetable blues green, and have an alkaline taste. ( Do. in the hydrate, - - -11.00$- Carbonic acid, - - 36.32 Water, - - - 19.75 100.00 Berzelius found the common magnesia of the shops, after being thor- oughly washed in boiling hot water, to be composed of magnesia 44.58, carbonic acid 35.70, water 19.72 = 100.00. CRYSTALLIZED CARBONATE OF MAGNESIA. \ 1. PROCESS. By diffusing magnesia in water, and passing a cur- rent of carbonic acid gas through it to saturation. 2. PROPERTIES. (a.) Much more soluble than the carbonate, requiring only 48 parts of cold water, and water impregnated with carbonic acid takes up 13 grains to the ounce. (b.) When the solution is heated, although transparent before, it becomes turbid, and again resumes its transparency on becoming cold.f (c.) It crystallizes, in transparent hexagonal prisms, terminated by a hexagonal plane ; partly in groups and partly solitary ; length about 6 lines, and breadth 2. (d.) Effloresces in the air, and decrepitates in the fire ; it loses about .75 of its weight, while the common carbonate loses only .50. * Thomson's First Principles, Vol. II, p. 303, and Henry, 10th ed. Vol. I, p. 617. t The heat must be discontinued just at the point where the solution becomes tur- bid, or the carbonic acid will be driven off. The reason of this turbidness is sup- posed to be the elasticity of the gas, tending to escape, and thereby beginning to let go its hold on tho magnesia. Dr. Hope, Note Book. CARBONIC OXIDE. 395 (e.) During the disengagement of the gas, die powder seems as if boiling, and is said to emit, towards the end, a bluish phosphoric light.* Remark. The above described salt has been regarded as a bi- carbonate, but Dr. Henry is of opinion, from his own analysis and from that of Berzelius, that it is a hydrated carbonate and that its composition is 1 equivalent of magnesia, - 20 28.60 1 do. carbonic acid, - - 22 32. 3 do. water, - 27 39.40 Its equivalent 69 100.00 It appears that, although the anhydrous carbonate has been found native, (see note p. 392,) it has not yet been formed by art. Berzelius has formed a carbonate of magnesia and potassa, by mingling bi-carbonate of potassa and muriate of magnesia. It seems to be of little importance, f 3. MISCELLANEOUS. ~/w the arts, the carbonate of magnesia is pre- pared from the bittern of the salt pans, remaining from the crystalli- zation of common salt, which contains much muriate and sulphate of magnesia. Carbonate of either of the alkalies, by double exchange, affords carbonate of magnesia, whose precipitation is hastened by boiling. 4. USES. As an antacid and cathartic. (See magnesia, p. 273.) On account of the flatulency sometimes produced by the carbonate of magnesia, calcined magnesia is used. Dr. Black says that it is liable to contain a portion of quick lime, derived from the sul- phate of lime of the bittern. No other earth has cathartic powers ; most of the rest are austere and astringent, particularly lime. CARBONIC OR CARBONOUS OXIDE. 1. HISTORY. Discovered by Dr. Priestley; who obtained it from dry metallic oxides with dry charcoal, and thought it was, at least in part, hydrogen, or that hydrogen entered into its composi- tion ; it therefore revived, for a season, the once favorite notion of a phlogistic f principle in the metals, charcoal, &c. and an animated con- * Four. IV. 67. t Edin. Phil. Jour. II. 67, and Henry, I. 619. t I happened to be in Philadelphia, as a pupil of Dr. Woodhouse, in the winter of 1802-3, when Dr. Priestley, who, as is well known, passed the latter years of his life in Pennsylvania, came in person, to the laboratory of Dr. Woodhouse, who was himself a disciple of Lavoisier, and who performed various experiments on this topic, at that time keenly controverted. It was the last effort to sustain the doctrine of phlogiston, and to produce from metals and inflammables a real substance, to which it was supposed that the name of phlogiston could be applied. Hydrogen had been before called phlogiston, but it was impossible to prove its existence in all inflammable bodies and metals, (unless the discovery of this gas should establish it,) and it was distinctly proved that it forms water by its combustion. Indeed Dr. Priestley was one of the first to perform that interesting experiment, but he did not eventually ad- mit the conclusion. 396 CARBONIC OXIDE. troversy respecting it was for some time maintained, but its true na- ture was soon pointed out, by the late Mr. Cruickshanks, of Wool- wich, England ;* Clement and Desormesf completed the demon- stration, and the refutation of the ideas of the associated Dutch chemists and others, who took it for a variety of carburetted hydro- gen gas-t 2. PREPARATION. All the processes mentioned below, are in- structive. They all shew, (that under (g) excepted,) the formation of an oxide of carbon, either by the combination of 1 equivalent of oxy- gen with 1 of carbon, or by the removal of 1 equivalent of oxygen from carbonic acid, leaving 1 of carbon and 1 of oxygen in combina- tion. To the former belong the processes (a) (e), and (/.) to the latter (6), (c), and (d) ; (g) is peculiar. (a.) Heat white oxide of zinc with J of charcoal powder or iron filings; (6.) Or iron filings with an equal weight of chalk, previously heat- ed moderately red. (c.) Or dry carbonate of lime or of baryta^ with } charcoal pow- der, previously ignited; or heat the same carbonates with J or J of dry iron filings or metallic zinc. (d.) Bypassing carbonic acid over charcoal or iron filings, ignited in an earthen or perhaps iron tube.|| (e.) Heat equal parts of the scales of iron with dried charcoal powder. (jf.) Manganese, after ceasing to give oxygen by heat alone, mix- ed with an equal weight of charcoal, previously ignited. IF (g.) Still another process has been introduced, by mixing salt of sorrel 1 part (bin-oxalate of potash) with 5 or 6 of sulphuric acid, and heating the mixture to ebullition in a retort ; decomposition of the oxalic acid ensues, and carbonic acid and carbonic oxide are evolved in equal measures ; the former is easily absorbed by a caustic alkali or by lime water, and leaves the latter pure. The sulphuric acid is not decomposed ; it remains limpid, and operates by uniting * Nich. Jour. 4to, Vol. V. t Ann. de Chim. Vol. XXXIX. t Ann. de Chim. XXXIX, 26, and XLIII. The dry carbonate of baryta and dry iron filings give the purest gas, and nearly free from carbonic acid. The process with oxide of zinc and iron filings, is one ol* the best, and affords abundance of gas which is easily purified by washing it with caustic alkali or lime water. || See Nich. Jour. Vol. II, p. 116, for BarueFs apparatus. IT Any carbonate, that will sustain ignition, without decomposition, will give car- bonic oxide, if heated with half its weight of iron filings or charcoal ; iron is of course, oxidized by the oxygen withdrawn from the carbonic acid which undergoes decomposition, giving up just half its oxygen; and charcoal is turned into carbonic oxide by the same process. The carbonates of strontia, soda, potassa and lithia, utay be employed in addition to those that have been named, and the oxide of lead aad copper may be used with charcoal, as well as the oxide of zinc or iron. CARBONIC OXIDE. 397 with the alkali of the salt and with the water of the oxalic acid, which being thus left at liberty, is decomposed as above. * 3. PROPERTIES. (a.) Smell offensive; colorless; sp. gr. 972, common air being 1000. 100 cubic inches weigh 29.65 grains, at medium tempera- ture and pressure ; having the same weight as nitrogen. (b.) Does not support combustion; a candle will not burn in it. Inflammable, burning with a blue flame; it takes fire at a low tem- perature, and an iron wire, at dull redness, kindles it ; w^hile the hy- drogen gases require a full ignition or a white heat. (c.) It must be washed with lime water, or passed through milk of lime or caustic alkali, as it always comes over with carbonic acid gas. (d.) Burn, in a bottle of air, a jet of this gas, issuing from a jar with a stop cock, and it will form carbonic acid.-^ (e.) Mixed with common air, it burns more rapidly, but does not explode, except in a few proportions, as 3 of the oxide gas to 1 of air. (/.) With oxygen gas 100 volumes and this gas about 200, it ex- plodes by electricity, and the product is 200 of carbonic acid ; the two gases being mixed in the above proportions, when a candle is brought to the mouth of the vessel, burn rapidly, with a whistling noise, but scarcely explode. (g.) Fire a jet of it and burn it in a tube, when it will produce feeble musical tones ; and if burnt in a bottle of oxygen gas, over lime water, no water is formed but carbonic acid is produced. (h.) It is well to burn and explode some hydrogen, and also varie- ties of carburetted hydrogen, for comparison with this gas, when it will be seen to be very different ; it is less combustible, burns with a different flame and produces carbonic acid only, without water, while the former produces water only, and the latter both water and car- bonic acid. The formation of water in this experiment, is owing to the hydrogen, and that of carbonic acid to the carbon contained in the gas. * Edin. Jour, of Sci. No. xii, p. 350. Turner and Dumas. t The carburetted hydrogen gases require iron in actual combustion, or the flame of some burning body, in order to set them on fire. t When this gas is burned in a bottle of common air, by means of ajar with a stop cock and tube, as in the annexed figure, no water is formed ; but it is otherwise when hydrogen is burned. A. Jar of common air. B. Jar with a stop cock and tube, containing the gas. 398 CARBONIC OXIDE. (i.) It is immediately fatal to animal life; a bird put into it is not withdrawn alive. (j.) It produces giddiness and fainting in the human subject, even when mixed with common air. Sir H. Davy was so daring as to take three inspirations of it, mixed with J of common air, and it had near- ly proved fatal ; apoplectic symptoms were induced in Mr. Welter, who fell senseless, but was restored by inhaling oxygen gas.* k.) But little soluble in water; about 1 volume to 50. I.) Not absorbed by caustic alkalies, nor by lime water. m.) Not altered by electricity. n.) Passed in equal volume with hydrogen, through an ignited tube, it is decomposed, water is formed and charcoal thrown down, lining the tube. (o.) Potassium and sodium, heated in it, decompose it, and pre- cipitate the charcoal. 4. COMPOSITION. (a.) 43 carbon, 57 oxygen, (Gay Lussac ;) or 55.72 oxygen and 44.28 charcoal, (Berzelius.)f Carbonic acid is composed of 1 vol- ume of gaseous carbon and 1 of oxygen condensed into 1 volume. This gas is composed of 1 volume of gaseous carbon and half a vol- ume of oxygen, condensed into 1 volume ; or of 1 equivalent of carbon =6-}-l of oxygen J =8 = 14, for its equivalent. As it con- tains just the same quantity of carbon as carbonic acid, occupies the same volume, and has only half as much oxygen, therefore, if from the specific gravity of carbonic acid, which is 1.527, we take 0.555, which is half the sp. gr. of oxygen, we have 0.972, the number stated under 3 (a), which corresponds with the results of experiment. (6.) The discovery of the singular agencies of spongy platinum, has brought to light some new facts respecting oxide of carbon. Car- bonic oxide, with more than half its volume of oxygen, in contact with spongy platinum, over mercury, begins to be converted into carbonic acid, at a temperature from 300 to 310 Fahr. and at a few degrees higher is acidified in a few minutes ; at a common tem- perature there is little action. (c.) Hydrogen and oxygen gases, in explosive proportions, mixed with an equal volume of carbonic oxide, do not detonate, when spon- gy platinum is added, but water and carbonic acid are slowly formed ; if the proportion of the explosive mixture be larger, the metallic sponge always causes detonation.^ * Phil. Mag. V. 43. Ure, 2d ed. 299. t And Clement and Desormes, nearly the same as Berzelius. i As half a volume of oxygen represents an equivalent. Phil. Trans. 1824, p. 271, quoted by Dr. Henry, Vol. I, p. 355, 10th ed. CARBURETTED HYDROGEN GASES. 399 REMARK. Frequently the oxide of carbon is produced at the same time with carbonic acid. The pale blue flame which arises from burning charcoal, especially when the fire is nearly burnt out, ap- pears to be produced from the ignition of the nascent oxide of car- bon. As fast as this gas is formed, it takes fire and burns away, being converted into carbonic acid gas. Oxide of carbon appears to be formed in those combustions of carbon, where the oxygen is supplied slowly and with difficulty ; carbonic acid gas, where it is supplied rapidly and in large quantities. Hence, when we heat the oxides of mercury with charcoal, we obtain carbonic acid ; when the oxides of iron, we evolve oxide of carbon. We have every reason to believe that oxide of carbon is one of the gases produced during animal and vegetable decomposition, and as it is highly noxious, it may contribute to their injurious effects. It is observed, that as oxygen } by combining with carbon to form carbonic acid, becomes heavier, we might naturally expect that car- bonic oxide, containing twice as much carbon, should be heavier still ; but this does not follow. Carbonic acid is heavier than oxy- gen, by precisely the additional weight of the carbon, because this last has assumed the aeriform condition, within the same volume as the oxygen. The sp. gr. of carbonic acid being 1.527, if we deduct that of the oxygen, 1.111, we have .416 for the sp. gr. of aeriform carbon in the gas, and as this is combined with only half a volume of oxygen, which is expressed by .555 this added to the weight of the carbon =.97 If for the gravity of the carbonic oxide, which is to be regarded, therefore, not as a mere solution of carbon in oxygen, but as a combination of fieriform carbon with oxygen gas. CARBURETTED HYDROGEN GASES. 1. HISTORY. Some of these gases must have been for a long time, more or less known to mankind; as their occurrence is fre- quent in the mud of marshes, in coal mines, in the matter emitted from burning combustibles, and from the ultimate results of animal digestion, &ic. But we owe the accurate knowledge of them to a few modern philosophers, among whom Mr. Dalton, Dr. Henry, and Dr. Thom- son, are conspicuous.* 2. GENERAL VIEW. It seems, at first, as if there must an immense number of carburetted hydrogen gases ; since we can scarcely ope- rate by destructive processes, upon any animal or vegetable matter * The following statements of facts are drawn principally from the writings of Dr. Henry and Dr. Thomson. I .972 is the number we have hefore stated. 400 CARBURETTED HYDROGEN. without obtaining inflammable gases, that differ in sp. gr. ; in combus- tibility ; in the quantity of oxygen required to saturate them ; in the in- tenseness of light emitted while they are burning, and in many other particulars. The ablest analysts, however, among whom none stand higher than the gentlemen already named, are of the opinion that only a few species have been distinctly established, and that the apparent diversity arises from innumerable mixtures of these with each other, with other gases, and with various vapors derived from the substances employed. According to this opinion, which is probably correct, the compounds of carbon and hydrogen exist in definite proportions only, " with this peculiarity, that they differ from each other, not so much in the relative proportions of their elements, as in the number of volumes or atoms, condensed into a given volume."* 3. CONSTITUTION OF THE THREE VARIETIES THAT ARE BEST KNOWN. Dr. Henry. Prop, by Prop, in weight, vol. carb. Sp. gr. carb. hyd. hydro. 1. Carburetted hydrogen, 0.555, 6:2 1:2 } condensed 2. Olefiant, 0.972, 12:2 2 : 2 > into one 3. Super-olefiant, 1.458? 18:3 3:3 ) volume. In the olefiant and the super-olefiant the carbon and hydrogen of each gas hear the same relation to each other, and the gases differ only in the condensation of their elements. In the olefiant gas, one volume contains two of each of the elements ; in the super-olefiant three. The gases that are best known, are divided conveniently into light and heavy carburetted hydrogen gases ; of the former, there is one variety ; of the latter, there are two or more. LIGHT CARBURETTED HYDROGEN.f 1. PREPARATION. (a.) By stirring with a stick, the mud at the bottom of any stag- nant water ; bubbles of gas will rise, which may be inflamed by a lighted taper at the surface, or they 'may be collected by an inverted pitcher, filled with water, or by a bottle filled in the same manner, and having a funnel in its mouth. This gas contains in mixture, about V f carbonic acid, which may be removed, by washing with lime water, or with solution of caustic potash ; there is also present from yV to ^ - of nitrogen gas. * Dr. Henry. t Formerly called hydro-carburet and carbonated hydrogen. It is also called proto-carburet of hydrogen, heavy inflammable air of marshes, &c. but the name in the text is generally used. CARBURETTED HYDROGEN. 401 b. The gas distilled from mineral coal after purification with li- quid potash to remove the carbonic acid, and with chlorine* to re- move the olefiant gas, is also sufficiently pure, and probably the same would hold nearly true of the gases obtained by heating the follow- ing substances. (c.) Anthracite of Pennsylvania and of Rhode Island, the latter moist ;f kernels of the hickory nut, and of other oleaginous nuts and seeds ; common woods, as oak, and maple, pine and pine knots ; tar^ tar ; recent bone ; moist charcoal ; acetate of lead, and acetate of copper ; spermaceti ; tallow, wax, &c. (c?.) In these mixed gases, there are variable proportions of car- bonic acid of olefiant, and perhaps sometimes of super-olefiant gas, and various vapors. 2. PROPERTIES OF LIGHT CARBURETTED HYDROGEN GAS.J (a.) Colorless and tasteless, not absorbable by water, which, how- ever, after having been previously boiled, takes up about V f ^ volume. (b.) Odor slight when it is otherwise, it is derived from mixture with other gases and vapors, especially when the gas is distilled from bituminous coal. (c.) Sp. gr. .555, air being 1 ; consequently, 100 cubic inches weigh, at mean temperature and pressure, 16.944 grains, just half as much as oxygen gas. Its sp. gr. is thus obtained by calcula- tion; it consists of 1 vol. vapor of carbon, which weighs .4166-f 2 vol. of hydrogen, .0694x2 = . 1388 = . 555, which is exactly the weight of carburetted hydrogen obtained by experiment. (d.) Extinguishes burning bodies, but is itself inflammable ; burns from a jet, with a flame, which is yellow or variously tinged; its power of illuminating is much greater than that of hydrogen gas. (e.) Mixed with from 6 to 12 volumes of atmospherical air, it ex- plodes with violence by contact of a lighted taper. (f.) More violently with oxygen gas the latter must exceed the inflammable gas in volume, but must not be over two and one fourth times its bulk. (g.) Loses its combustibility, if rarefied, so that the pressure is less than one fourth part that of the atmosphere. * Chlorine has the property of removing the heavy species of carburetted hydro- gen, to form with it a peculiar compound, the chloric ether, which has been regard- ed, but erroneously, as an oil. This property of chlorine must be repeatedly men- tioned in giving the account of the carburetted hydrogen gases, and will be again illustrated In its proper place. t See Am. Jour. Vol. X, p. 331. t That obtained from the marshes is the purest variety. For carbonic acid has the sp. gr. 1.527, from which deduct that of the 1 vol. of oxygen which it contains, 1.111, which leaves .416 for the weight of the carbon in vapor. 51 402 OLEFIANT GAS. (h.) Carbonic acid and other gases, also diminish its inflamma- bility. (i.) Its complete combustion requires more than two volumes of ox- ygen two are consumed, and carbonic acid, equal in volume, to the inflammable gas, is produced and water is formed. (/.) There being in carbonic acid exactly its volume of oxygen, it follows that half the gas used went to form water along with the hy- drogen, of which there were therefore 2 volumes, and this, along with 1 of gaseous carbon, existed in the compass of 1 volume. (k.) It hence* results that the light carburetted hydrogen gas is composed for 100 cub. inches, at med. temp, and pressure, of charcoal, 12.69 grains, 74.87 grains, hydrogen, 4.26 " 25.13 " 16.95f 100.00 (/.) On respiration and animal life, its effects are eminently noxious, and speedily fatal. (m.) Not decomposed by electricity, nor by heat in ignited tubes, unless very intense, as stated above. 4. CONSTITUTION. Two volumes of hydrogen and one volume of gaseous carbon, condensed into one volume ; 1 equivalent of char- coal, = 6-}-2 of hydrogen, =8 for the equivalent of the compound. OLEFIANT GAS.J 1. HISTORY. Discovered at Haarlem, in Holland, in 1796, by the associated Dutch chemists ; but Mr. Dalton, of Manchester, gave the first accurate account of its composition. 2. NAME. With chlorine, in equal volumes, it is condensed into a substance resembling an oil ; hence the name, from oleum Jio ; the compound substance produced, being however, not an oil, the name was unappropriate, but it is still generally retained. 3. PREPARATION.^ (a.) Alcohol 1 measure, sulphuric acid 2 or 3 ; mix them cau- tiously, in a retort, of which they must not occupy more than J of the body. Gentle heat is gradually applied the mixture soon be- * 16.93. Dr. Turner. 16.94, on p. 401, (e.) of this work. t For carbonic acid, with 1 vol. carbon and 1 of oxygen, weighs 46.597 grains for the 100 cub inches, deduct the weight of the oxygen, 33.888, leaves 12.70 nearly, for the weight of the carbon in vapor, and the weight of hydrogen being, for 100 cu- bic inches, 2.118 ; twice that sum is 4.236, and this*+12. 70 =16.936. These numbers are taken from Brande's Tables, and vary slightly from those quoted elsewhere in the pages of this work. I Or heavy carburetted hydrogen gas, bi-carburetted, and per-carburetted hydro- gen, and hydroguret of carbon. The first name, that of olefiant gas, is generally employed. By passing the vapor of alcohol over ignited siliceous, or argillaceous earth, nearly pure olefiant gas is obtained. OLEFIANT GAS. 403 comes black, froths, and emits gas, which, when it burns quietly with a bright flame, may be saved ; it is received over water. (6.) As the mixture puffs up very much, especially towards the end of the process, the heat must be very carefully managed, and should never exceed that of a chafing dish. (c.) Sulphurous acid comes over, which the water will absorb, and carbonic acid is formed, but this, as well as the other gas, is remov- ed by solution of caustic alkali. (d.) The olefiant gas is derived from the alcohol, whose consti- tution is altered by the sulphuric acid, principally, as is imagined, by its uniting with the water.* 4. PROPERTIES. (a.) Invisible little odor, except from sulphuric ether, which is formed in the process ; I have always observed however, that it re- tains the ethereal smell for a long time. Water 8 vols. absorbs 1 of this gas. (6.) Sp. gr. 972, f air being 1. It is remarked that nitrogen gas, carbonic oxide, and olefiant gas have the same gravity ; { and that 100 cubic inches, at the medium temperature and pressure therefore weigh 29.64 grains. As it consists of 2 vols. of vapor of carbon, and 2 vols. of hydrogen, its sp. gr. is easily obtained by calcula- tion, thus. Twice the sp. gr. of hydrogen gas, 0694 x2 = 1388-{- twice the sp. gr. of the vapor of carbon, 4166x2=8333, and this number 4-1388 = .972. (c.) Extinguishes burning bodies, but issuing from a jet, and kindled by a candle, this gas burns with extreme brilliancy, the flame resembling that of the brightest lamp ; it far surpasses simple carbu- retted hydrogen. (d.) Mixed, 1 vol. with 3 vols. of oxygen gas, and inflamed, it de- tonates with great violence, and much care is requisite to avoid ac- cidents. If done in glass vessels, they should be small and strong, but it is better to use plate tin, or copper tubes. (e.) The explosion may be made in a detonating eudiometer tube, by electricity, but only a cubic inch of the mixed gases should be employed. (f.) One volume of this inflammable gas, requires 3 of oxygen for saturation, and gives two volumes of carbonic acid gas. (g.) Dr. Henry remarks, that in order to insure the perfect com- bustion of the gas, it should be mixed with 5 volumes of oxygen gas, of at least 90 per cent, purity. * For a more particular view of the theory, see alcohol. t Thomson's First Principle, Vol. I, p. 149. t The Dutch chemists made that of olefiant gas, .909 Dr. Henry, some years ago, .967 Saussure Jr. .9852. 404 OLEFIANT GAS. 5. MODE OF ESTIMATING ITS COMPOSITION. (a.) If too little oxygen be used, charcoal precipitates unburnt, and the volume of the residue is greater than that of the original gases. (b.) Upon the same principles of calculation as those upon which the composition of the light carburetted hydrogen gas was determin- ed, it follows that in 100 cubic inches there are Charcoal, 25.38 85.63 grains, 100. Hydrogen, 4.26 14.37 " 16.71 29.64* 100.00 116.71f (c.) Olefiant gas has therefore 100 grains of charcoal united to 16.71 of hydrogen, while the light carburetted hydrogen has the same weight of carbon, with 33.41 of hydrogen, just double ; in other words, the carbon being given, it has half the hydrogen, and the hydrogen being given, it has double the carbon. 6. CONSTITUTION. As, in the combustion of olefiant gas, 3 vols. of oxygen disappear, water is formed, and 2 vols. of carbonic acid are produced, it is evi- dent that as oxygen does not change its volume by combining with carbon, to form carbonic acid, 2 volumes of the oxygen have gone into the carbonic acid with 2 volumes of carbon ; the other volume of oxygen has formed water, and as two volumes of hydrogen are demanded for this purpose, it follows that each volume of olefiant gas contains 2 volumes of carbon, -f-2 volumes of hydrogen, =2 equivalents of each. The compound will therefore weigh 12 -f 2 = 14, its equivalent.J If 2 grains of sulphur be heated over mercury, with 1 cubic inch of olefiant gas, 2 cubic inches of light carburetted hydrogen will be obtained, and charcoal precipitated. Ure. 7. MISCELLANEOUS.^ (.) In olefiant gas there is so large a proportion of carbon, that when a jet of the flame is permitted to play against a white earthen plate, it covers it with charcoal, and the jet burning freely in the air, emits a column of lamp black. (b.) Olefiant gas is decomposed by electricity ; and by ignition in porcelain tubes ; products, charcoal and hydrogen, the latter in a volume double -to that of the gas decomposed. In the experiment with the tube, by varying the heat, we can cause it to deposit more or less charcoal. * Dr. Turner states this number at 29.65, and that for two volumes of hydrogen at 4.23. t See p. 403, (4. &.) JHenry, Vol. I, p. 425, 10th Ed. The action of chlorine and iodine upon the carburetted hydrogen gases, will be considered under those heads. CARBON AND HYDROGEN. 405 SUPER-OLEFIANT GAS. 1. REMARK. We mention this gas, (whose distinct existence is highly probable, but not perhaps fully proved,) out of respect to Mr. Dalton, and Dr. Henry, to whom science is so much indebted, es- pecially in relation to the inflammable gases. 2. HISTORY. Dr. Henry, in the Phil. Trans, for 1821, has given an account of the discovery of this gas by Mr. Dalton, which has not been obtained in a separate form, but mingled with other varieties, in the gases obtained from oil, coal, &c. 3. PROPERTIES. (a.) For complete combustion, 1 volume requires 4j of oxygen, and produces 3 of carbonic acid. (b.) Sp. gr. estimated at 1.4, but Dr. Henry thinks that if con- stituted as he supposes, of 3 volumes of gaseous carbon, and 3 vol- umes of hydrogen, condensed into 1 volume, its specific gravity must be 1.458, derived from multiplying the sp. gr. of hydrogen, .0694, and that of gaseous carbon, .4166, each by 3, and adding the pro- ducts together. (c.) A portion of a gas which contained more than 40 per cent, of the super-olefiant, was cooled by muriate of lime and snow, but no liquid was deposited from it ; it was condensible by chlorine, but the product has a peculiar odor, unlike that of chloric ether. OTHER COMPOUNDS OF CARBON AND HYDROGEN. It is believed that there are four or five more of these compounds, in which the constituent principles bear the same proportion to each other, but differing in the degree of condensation. 1 . It is supposed that a compound may exist of 1 volume of car- bon, and of 1 of hydrogen, condensed into 1 : the sp. gr. of this would be, for the carbon vapor, .4166, and for the hydrogen, .0694, the sum of which would be, .4860 ; but this has not yet been dis- covered, although Dr. Thomson and Dr. Henry, concur in suggest- ing that it may yet be found.* 2. Dr. Thomson inferred that another compound might exist in the vapor of ether, in union with 1 volume of aqueous vapor. He supposed that it might consist of 4 volumes of vapor of carbon, and 4 volumes of hydrogen, condensed into 1 volume ; it would of course have twice the sp. gr. of olefiant gas, that of 1.9444 : it would require 6 vols. of oxygen, for its entire combustion, and would produce 4 vols. of carbonic acid.f Its equivalent would of course be 28, composed of 4 X 6 for the carbon, and 4X1 for the hydrogen. Dr. Thomson gave it the provisional name of quadro-carburet. This compound has since been discovered by Mr. Faraday. In Mr. * Perhaps as a constituent of coal gas. t Hence, adding the number representing the sp. gr. of aqueous vapor, Dr. Thom- son inferred that the sp. gr. of the vapor of ether must be 1.9444+06250=2.5694. 406 CARBON AND HYDROGEN. Gordon's patent oil gas lamp, the gas is compressed by a force of 30 atmospheres, and a limpid fluid* is obtained, which appears to contain several compounds of carbon and hydrogen. If this fluid be heated by the hand, and the vapor condensed into a tube, cooled to 0, it becomes a fluid, which remains such only below 32 Fahr. and even before that temperature is attained, it is reconverted into vapor, which burns with a brilliant flame. Its sp. gr. is 1.9065, very near that calculated for it by Dr. Thomson, before its discovery. It is slightly absorbed by water ; more by alcohol, but is evolved from the latter, with effervescence, by water. At it is again condensed, and the fluid having the sp. gr. of 0.627, is the lightest known. Sulphuric acid absorbs 100 times its volume, and its color is dark- ened, but no sulphuric acid is disengaged. Its analysis by oxygen is exactly what was predicted by Dr. Thomson ; as to the quantity of gas required, the carbonic acid pro- duced, the proportions of its constituents, and the equivalent num- ber, as already stated. 3. Dr. Thomson supposes that the vapor of the fluid distilled from coal tar, and which is, from its similarity to mineral naptha, called by the same names, consists t)f 6 equivalents of vapor of carbon +6 of hydrogen, condensed into 1. Its equivalent number is of course 42 ; it requires 6 vols. of oxygen for its complete combustion, and there are produced 6 of carbonic acid. This 'compound is supposed to exist in the coal gases, and as their light is in direct proportion to the quantity of carbon which they contain, it is obvious that upon this view, the vapor of naptha will give three times as much light as defi- ant gas. Its sp. gr. must, of course be 2.9166. In pure naptha, potassium remains unoxidized,. which proves the absence of oxygen. 4. In the liquid obtained by the condensation of coal gas, Mr. Fa- raday discovered another compound of carbon and hydrogen. This fluid, when recent, boils at 60 Fahr. ; one tenth being exhaled, the boiling point rises to 100, and the whole is not evaporated till it rises to 250. It thus appeared probable that there were different com- pounds, differing in volatility, and by condensing the vapor at differ- ent temperatures, he attempted to obtain them separate. The boil- ing point appearing more constant between 176, and 195, than any where else, he carried on the distillation within those limits, and by repeating it, and condensing the vapor at 0, he obtained a fluid which he called bi-carburet of hydrogen. Its properties are as follows ; it is a transparent colorless fluid, smells like oil gas, or almonds; at 60, sp. gr. .850, and that of its vapor 2.776. At 32, it becomes solid and crystalline ; at trans- parent and crumbles into grains, having nearly the hardness of loaf * About 1 gallon for 1000 cubic feet of good gas. Phil. Trans. 1825, p. 441. NAPTH ALINE: 407 sugar. Boiling point, 186, evaporates spontaneously ; soluble, in fixed and volatile oils, and in ether and alcohol, from which it is thrown down by water. It burns readily and brilliantly, and with much smoke ; in oxygen gas its vapor rises and forms a detonating mixture. Potassium re- tains its lustre in it, even when heated. By passing it in vapor through an ignited tube, charcoal is deposited, and carburetted hy- drogen obtained. Its analysis was performed by detonation with oxygen ; and by passing it over ignited oxide of copper ; carbonic acid and water were the only products, and as there is no oxygen in it, it follows that it is composed of carbon and hydrogen only. It requires 750 measures of oxygen to burn 100 of its vapor; 600 unite with 600 of carbon vapor, and 150 with 300 of hydrogen, and therefore its constitution is 6 equivalents of carbon, and 3 of hydrogen, and of course the equivalent of the compound is 6x636 + 1x3=39. The sp. gr. of its vapor is easily inferred ; for the weight of the va- por of carbon -4166 X 6=2.4996, and that of hydrogen .0694 X 3 = 0.2082=2.7078, and this is very near to the number obtained by Mr. Faraday. NAPHTHALINE. A substance to which this name has been applied, was first ob- served by Mr. Garden and afterwards examined by Dr. Kidd of Ox- ford Univ. * It is obtained from coal tar ; the naptha passes first by a very gen- tle distillation, and afterwards the naphthaline in vapor, which con- denses in the neck of the retort, in the form of a white crystalline solid. Properties. Sp. gr. 1 .048 ; taste pungent and aromatic ; odor peculiar, and said to resemble that of narcissus; to the touch smooth and unctuous; color white; lustre silvery; soluble in alcohol and ether, in olive oil, in oil of turpentine, and in naptha ; not very in- flammable, but, when kindled, burns rapidly, with much smoke ; fusible at 180; evaporates at the common temperature and boils at 410; its condensed vapor readily crystallizes in thin trans- parent laminae. By Dr. Thomson's analysis, naphthaline consists of one equivalent and a half of carbon 9, and of 1 of hydrogen, and its own equivalent is therefore 10. According to Dr. Thomson's views it is, therefore, a scsqui-carburet. It appears to form, with sulphuric acid, another peculiar acid, to which the name of sulpho-naphthalic has been given, and its compounds have been called sulpho-naph- thalates. There is also an acid, apparently formed by the action of nitric acid. It is scarcely necessary to detail the particulars of these unimportant compounds.* * Phil. Trans. 1825, Part II, and Ann. of Philos. XXVII, 44, and New Series, VI, 136. Eng. Quar. Jour. VIII, 289. Murray. Turner. 408 MIXED GASES. MIXED GASES ; obtained by heating various combustible bodies, as tallow, alcohol, ether, bituminous coal, &ic. Remark. Although, as has been already observed, these gases are, in all probability, mixtures of the varieties that have been de- scribed, they do, in practice, present some peculiarities worthy of be- ing noted. I. COAL GAS. (a.) There is so much variety in the properties of the gases ob- tained by heating mineral coal, that they are hardly worthy of being grouped together, except on the ground that they are obtained from a common material. (6.) Bituminous coal, distilled in an iron retort, affords, besides the permanent gases, tar and solution of carbonate of ammonia. (c.) The gas varies in quality, even from the same coal, at dif- ferent stages of the process, according to the degree of heat and the manner of applying it ; of course, it varies with different specimens of coal. (d.) Dr. Henry remarks, "within certain limits, the more quickly the heat is applied, the greater is the quantity and the better the qual- ity, of the gas obtained from coal ; for, too slow a heat expels the inflammable matter in the form of tar."* (e.) The gas declines much in quality towards the end of the oper- ation, although we still continue to obtain large quantities. K) The useful part of the gas is composed of mixtures of light leavy carburetted hydrogen, in endlessly varied proportions. (g.) The useless gases are carbonic acid, oxide of carbon, nitro- gen and sulphuretted hydrogen,f and sometimes ammonia, (and sul- phurous acid gas?) (h.) The disagreeable smell arising from sulphuretted hydrogen, and probably a little sulphuret of carbon, may be washed out by cream of lime, without injuring the combustibility of the gas. (i.) The best gas has the sp. gr. of at least 650, air being 1, " and each volume consumes about 2J volumes of oxygen and gives 1 J vol- ume of carbonic acid." (/.) " The last portions have a sp. gr. as low as .340, and each volume consumes about .8 of a volume of oxygen gas and gives about .3 of a volume of carbonic acid." (k.) Chlorine, applied in a manner hereafter to be pointed out, detects from 13 to 20 per cent of olefiant gas; the rest is chiefly light carburetted hydrogen. * Phil. Trans. 1808, 1820, 1824. t Dr. Henry refers us, for the method of separating them, to his memoirs above quoted, to Manchester Memoirs, and Annals of Philosophy, XV. MIXED GASES. 409 (/.) The last portions contain hardly any olefiant gas; they con- sist of light carburetted hydrogen, and much hydrogen and carbonic oxide, which is the reason that they afford so little light during their combustion. (m.) There is great uncertainty and variety in the quantity and quality of gas obtained from coal. Dr. Henry considers it as an ap- Eroximation to truth, to suppose, that 112 Ibs. of good coal may af- >rd from 450 to 500 cubic feet of gas, "of such quality, 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." (n.) I have often obtained a very bright burning gas from Rich- mond (Va.) coal ; at other times a gas producing a very pale flame. * (o.) Anthracite of Pennsylvania and of Rhode Island,* afford much gas,f chiefly light carburetted hydrogen, but it is unfit for illu- mination; most authors state that the anthracties afford little or no gas. That of Wilkesbarre gave, in my trials, 40 wine pints from 886 grains of the coal, while the specific gravity of the coal was in- creased from 1.65 to 1.77,J and several other varieties of American anthracite yielded large quantities of inflammable gas. II. OIL GAS. 1. HISTORY. (a.) The familiar use made of animal oils, to afford by their combustion, artificial light, naturally suggested the project of decom- posing them to obtain gas. (6.) Dr. Henry, in a memoir in Nicholson's Journal for 1805, ap- pears to have first brought this subject into notice, and to have proved that next to the pure olefiant, the gas from oil is the best adapted for artificial illumination. 2. PREPARATION AND PROPERTIES. (a.) By allowing spermaceti oil, or even refuse whale oil, (as the purity of the oil is not material,) to fall drop by drop, from a reser- voir furnished with a stop cock, and connected by a tube with an iron bottle or cylinder, upon fragments of bricks, or, as practised in New York, fragments of anthracite, heated to a cherry red. (6.) A condensing vessel should be interposed between the fur- nace and the gazorneter, to receive the undecomposed oil. (c.) A wine gallon of oil affords 100 cubic feet of gas, whose specific gravity exceeds .900 ; more than .40 of this gas is condensi- ble by chlorine ; 100 volumes require 200 of oxygen to saturate them and produce 158 of carbonic acid. * The latter must be moist. t It is not easy to say how much of this gas arises from water ; the increase of sp. gr. in consequence of ignition, seems however to imply that a lighter constituent of the mineral has been expelled. J Am. Jour. Vol. X, p. 355, and Vol. XI, p. 78. 52 410 MIXED GASES. (d.) Wigan coal has been esteemed the hest in England ; the gas from this coal, required, on an average, only 155 volumes of oxygen to 100 of the coal gas, and gave 88 measures of carbonic acid. (e.) As the inflammable gases produce light just in proportion to the quantity of carbon they contain, it follows, that oil gas is nearly or quite as powerful as gas from Wigan coal. 3. MISCELLANEOUS. (a.) Mr. Brande estimates, that to produce a quantity of light equal to that of ten wax candles, burning for one hour, there are re- quired 2600 cubical inches of olefiant gas, 4875 of oil gas and 13120 of coal gas. (b.) Dr. Henry suggests that this estimate is, as regards coal gas, rather low, and is disposed to consider 1 volume of oil gas as equiva- lent to 2 or 2J of coal gas. (c.) The late Mr. Creighton, of Glasgow, considered 2 volumes good coal gas as equal, in affording light, to only one of oil gas, and valuing the quantity of light given by one pound of spermaceti candles at 1 shilling, he estimated the cost of an equal effect from sperm oil, burning in an Argand's lamp, at 6 JJ. that from whale oil at 4jc?. and that from coal gas at 2jdf. " Twenty cubic feet of coal gas, or ten of oil gas, he considers as equivalent to a pound of tallow, and 5000 grains of spermaceti oil to 7000 of tallow or 1 Ib. avoirdupois." (d.) Dr. Henry sums up the comparative claims of oil and coal gas, by saying, that for oil gas, vessels and tubes of half the size are sufficient ;* no washing is needed ; there is no residuum ; the light is brighter and the heat less ; but that still, in large establishments and in countries where coal is cheap, the latter will be preferred on the score of economy. (e.) The best criterion of the illuminating power of a gas is the quantity of oxygen required for its perfect combustion,! and the amount of carbonic acid produced ; specific gravity is deceptive, for it may be affected by foreign gases, for instance, by carbonic oxide or by carbonic acid. J (/.) It appears that a very valuable illuminating gas is obtained by decomposing cotton seed by a well managed heat. Prof. Olmsted lias shewn that it is both economical and effectual^ (g.) Coal gas is obtained by decomposing coal in an iron retort ; the tar is received in a condensing vessel, and more continues to be deposited by the passage of the gas through vertical tubes kept cold. The gas, under strong pressure, is passed through lime diffused in * Oil gas, being; free from sulphuretted hydrogen, needs no purification, and is therefore peculiarly fitted for dometic use. t It is suggested that condensation by chlorine niay be a test equally decisive. Comm. I Henry's Chem. Vol. I, p. 432, 10th ed. Am, Jour, Vol. XIII, p. 194, and Vol. X. MIXED GASES, 411 water, or through successive layers of hydrate of lime, to remove carbonic acid, sulphuretted hydrogen, &c. ; it is finally received in a gazometer, (see p. 214,) thence distributed by tubes, and burned at proper orifices furnished with stop cocks. (h.) It is now evident, that the illuminating power of gases is de- pendent not only upon the quantity of olefiant gas in them but upon the other compounds containing still more carbon, as the quadro- carburet, the vapor of naphtha, &c. (*.) Mr. Daniel employs resin,* dissolved in oil of turpentine ; it falls, drop by drop, into the retort, and the volatile oil, by passing over in vapor, is recovered. This gas is employed by Mr. Gordon in his portable lamps, and is said to be equal to oil gas. PORTABLE GAS LIGHT. "One of the greatest obstacles to the general employment of gas lights, as a sub- stitute for candles and lamps, is the neces- sity of pipes leading from gazometers, to all situations where the light is wanted. The condensation of the gas in strong metallic receivers, has been resorted to in order to obviate this difficulty. This process may be illustrated by means of the apparatus described for the impregnation of water with carbonic acid. "It is only necessary to exchange the communication with the reservoir of car- bonic acid gas, for a similar communication with a reservoir of olefiant gas, and the cop- per vessel being first exhausted of air, to condense the gas into it. The syphon used to draw off the carbonated water, is repla- ced by a tube and cock, terminating in a capillary perforation. Through this, the gas may be allowed to escape in a proper quantity to produce a gas light when inflamed." Dr. Hare. SAFETY LAMP OF SIR H. DAVY. 1. REMARKS. (a.) It has long been notorious that a deadly gas infests the mines of bituminous coal, called by the miners, the fire damp or wild fire, * Dr. Hare, several years ago, employed common rosin, in New York, and it is now used there to afford gas light; he. obtained also a substance, rising in distilla- tion, which not a little resembled naphthaline. 412 MIXED GASES. and that the most deplorable accidents have frequently resulted from its explosion.* (b.) It probably 'arises from the decomposition of water by the coal, and issues from the crevices of the rocks and of the coal strata, particularly from places called blowers ;f it is but little more than half as heavy as common air, and therefore it occupies first the roof of the mine.f 2. HISTORY. (c.) The first scientific account of the gas of coal mines, was pub- lished in 1806, by Dr. Henry, $ who proved that it is the same as the light carburetted hydrogen. (d.) Sir Humphrey Davy, some years later, visited the coal mines in person, descended with the miners into the regions of the fire damp, obtained specimens of the gas and subjected them to a chem- ical examination. || (e.) He discovered several important facts, and by a train of in- genious and philosophical reasoning, was led to a happy conclusion in the discovery of the safety lamp. * In the Felling Colliery, 92 miners perished at one time, and 23 at another, and in another 57 were killed in the same way. Murray. t These are fissures laid open in working the mines. t When mixed with the air of the mine, it is said to produce a misty appearance, as I had opportunity of observing at the mines of Newcastle, in England, in Nov. 1805. If the quantity of gas in the mines is small, it is harmless; but if great the consequences are sometimes extensively fatal. The catastrophe proceeds from the extreme in- flammability of this gas, and its disposition to explode when mixed with the atmos- phere. Unhappily, in these dark regions, no work can be done without artificial light. In some places, they work by the feeble sparks produced by rubbing flint against a jagged steel wheel. In other places, they carry a candle or a torch, and whenever the fire is communicated to a large quantity of this gas mixed with common air, the explosion is as sudden and violent as that of gun powder. Some- times, the mine, machinery, and miners are blown up, with the loss of all their works, and of course of the lives of a large proportion of the people. If the walls and roof of the mine are so strong as not to give way, the expansive force of the steam and of the elastic vapors rarefied by the sudden heat, forces every thing along the narrow chamber of the mine, as a bullet is driven from a gun. In the mines where the production of this gas is not very rapid, the miners set fire to it frequently, and thus explode it in small quantities without danger. This they do by means of a candle tied to the end of a long pole, which they elevate into those parts of the roof where the gas commonly collects. Sometimes they tie a candle in the mid- dle of a rope, and two men, by pulling the rope at the two ends, bring the candle into contact with the gas. But where it is produced too copiously to be managed in this way, the miners fix wooden pipes all along the roof of the mine, with branches carefully communicating with those places from which the gas issues, and all these pipes are connected with one main shaft which terminates in a chamber where is a fire place with a very tall chimney. Here a fire is constantly maintained, and the rarefaction of the air produces a constant stream from all parts of the mine to this spot, where the gas burns quietly away without injury. When the inflammable air is very copious, it is said to burn at the top of the chim- ney, and to produce heat enough to maintain the combustion without any additional fael. Nichok?on's Jour. XIX, 149. || Phil. Trans. 1816; History of the Safety Lamp, 1818; Phil. Mag. I, 50. 387. MIXED GASES. 413 3. SOME PECULIAR PROPERTIES OF THE FIRE DAMP. (a.) The most explosive mixture of this gas with common air ', was found to be 1 measure of the inflammable gas to 7 or 8 of air ; it ex- plodes feebly with 5 or 6 volumes of air, and with only 3 or 4, it does not explode at all ; it is still explosive with 14 volumes of air, but with more, a taper burns in it only with an enlarged flame. (6.) Charcoal in active combustion, and iron heated to redness or even to whiteness, did not kindle this mixture ; it was, however, ex- ploded by iron in a state of brilliant combustion, and the smallest point of flame, owing to its high temperature, produced instant ex- plosion. (c.) The fact which led immediately to the discovery of the safe- ty lamp, had been observed before by Dr. Wollaston, and was this, " that an explosive mixture cannot be kindled in a glass tube so nar- row as one seventh of an inch in diameter." (d.) Two separate reservoirs filled with an explosive mixture, be- ^ing connected by a metallic tube one sixth of an inch in diameter, a*nd one and a half inch in length the explosion could not be made to pass into the one, when the other was set on fire. (e.) It was also discovered that fine wire sieves, or wire gauze being in fact only short tubes, form, upon the same principle, an effec- tual barrier between two portions of explosive gas, which will not communicate through such a partition. (/.) It was found also that " a mixture of fire damp and air, in ex- plosive proportions, was deprived of its power of exploding by the addition of about one seventh of its bulk of carbonic acid or nitrogen gas."* (g.) Sir Humphry Davy was thus led to an attempt to combine both these principles by the construction of a lamp, which being fed with only a limited supply of air, might be occupied more or less by carbonic acid and nitrogen, and which, by having small metallic aper- tures, might prevent the spreading of combustion into the surround- ing atmosphere, should that be in an inflammable or explosive state. (A.) After various modifications and improvements, the safety lamp is now constructed of wire gauze, that is, the flame is surrounded by a wire sieve, so fine as to have at least 625 apertures in a square inch. (i.) It is a cylinder 2 inches in diameter ; it rises 10 or 12 inches above the flame ; the wire gauze is double at the top, where the greatest heat exists, and no part of it is impervious to air, except that which contains the oil, and which is furnished with means of * Many miners perish from the prevalence of these gases after the explosion ; carbonic acid being formed and mixed with the nitrogen which is left. 414 SAFETY LAMP. raising and trimming the wick, and recruiting the oil, without open- ing the lamp in the explosive atmosphere. 0*0 When the proportion of the fire damp in the air is T ' the wick of the lamp is seen surrounded by a faint blue flame. (k.) When the proportion is increased to |, j, or j, the lantern is filled with the flame, burning green, as I have observed it in labo- tory experiments ; still, the flame, even when the wire is red hot, does not communicate to the exterior air, although it should be in an explosive state.* (I.) Should danger arise from a current of explosive gas passing through so rapidly as to heat the wire to such a degree that it might inflame the air ; still the increase of the cooling surface, either by di- minishing the size or increasing the number of the apertures, would obviate the danger, for the safety of the instrument is supposed to consist in the cooling powers of the wire, reducing the explosive gas below that temperature at which it is inflammable, which tem- perature is stated to be far above a white heat.f (m.) Even when the- noxious gases prevail, so as to extinguish the lamp, and thus threaten life by suffocation, a small coil of plati- num wire, hung above the lamp, within the wire gauze cylinder, will continue to glow, and will enable the miner to grope his way through regions otherwise perfectly dark. This combustion is owing to the fire damp, but it does not communicate to the external air ; and on com- ing into better air, the lamp will frequently be rekindled spontaneously. * The miner should, however, then withdraw, because the wire may be so rapidly oxidized as to fall to pieces, and he may be in danger also of suffocation, from the prevalence of irrespirable gases. t Sir H. Davy's theory of the safety lamp is called in question by M. G. Sibri, (Bib. Univ. Mars, 1827, and Am. Jour. Vol. XIII, p. 179.) who contends that it is not owing to the cooling power of the metal, but to a repulsion existing between flame, and any substance that may be brought near it. It is repelled equally by a rod of glass or porcelain, as by one of metal, and the effect depends not on the nature of the body, but is proportioned directly to its bulk, and inversely to its distance ; even two flames will repel each other, and so gross a flame as that of a candle, will refuse to pass between two rods of any kind, (even wood,) brought near to each other on opposite sides of the flame, and near the summit. The repulsion is not all affect- ed by the temperature of the substance. I have repeated these experiments, and find them exact, and the cause is obvious ; the repulsion appears to be occasioned by the gas, which is incessantly blowing out from flame, and which striking against any obstacle, reacts, to inflect the flame ; just as a current of lava will sometimes stop short, at a wall, rise parallel to, and finally cascade over it, without touching it ; this well ascertaained fact is owing to the great quantity of ae'rial matter blown out by lava, and which, meeting with an obstacle, reacts upon it as above described, with respect to flame. Mr. Sibri conceives that the number of wires in the metallic gauze of the safety lamp, is by far too great, and that the same security would be af- forded by such a number as would merely give strengh to the instrument, without so much impeding the light. I have never felt satisfied with this part of the theory of the safety lamp, given by its illustrious inventor, and am disposed to think that the one suggested above is the principal source of protection ; in this opinion I am supported by Prof. J. Griscom, to whom I am indebted for the notice of Mr. Sibris' SAFETY LAMP. 415 A, is a large bell of common air, held by the hand, or suspended by a string. B, is a lighted safety lamp, held by an as- sistant within the jar. C, An air jar, with cap, stop cock, and tube, filled with carburetted hydrogen, and depressed into the water of the pneumatic cistern, D D, so that by gently turning the key^*, the inflammable gas flows through the tube, mixes with atmospheric air, pene- trates the lamp, and enlarges the flame ; it even fills the whole lamp with a delicate blue or green flame, which ultimately ex- tinguishes the light of the lamp ; but if, when the lamp is nearly extinguished, it be lowered a little, so as to better the condi- tion of the air, it will be rekindled, and then may again be raised into the jar, and so on. Comm. Figure and Description from Dr. " The lamp is seen within a large glass cylinder upon a stool. The cylinder is close- ly covered by a lid, which will not permit the passage of air between it and the cylin- der, and which is so light as to be easily blown off. Ex- cepting the cage alluded to above, the safety lamp differs not materially from those which are ordinarily used. The upper surface of the re- ceptacle for the oil, forms the bottom of the cage, which is so closely fitted to it, and so well closed every where, as to allow air to have access to the flame only through the meshes of the wire gauze. The cage is enclosed within three iron rods, surmounted by a cap, to which a ring for holding the lamp is attached, as seen in the drawing." " If while the lamp is burn- in , as represented in the Hare. 416 SAFETY LAMP. figure, hydrogen, either pure or carburetted, be allowed, by means of the pipe, to enter the glass cylinder, so as to form with the air in it an explosive mixture, there will, nevertheless, be no explosion. It will be found that as the quantity of inflammable gas increases, the flame of the lamp enlarges, until it reaches the wire gauze, where it burns more or less actively, according as the supply of atmospheric air is greater or less. It will, under these circumstances, often ap- pear as if the combustion had ceased, but on increasing the propor- tion of atmospheric air, the flame will gradually contract, and finally settle upon the wick, which will burn as at first, when the supply of hydrogen ceases." "If the cage be removed from the lamp, and the experiment repeat- ed in all other respects as at first, an explosion will ensue, as soon as a sufficient quantity of hydrogen is allowed to enter the cylinder." It appears that Mr. Stevenson invented a lamp, whose light was enclosed in a lantern, to which air was admitted by a number of tubes, and any explosion within did not communicate to the air with- out. The principal inconveniences of Sir H. Davy's lamp are, its lia- bility to injury, on account of its delicate texture, and if there is a hole made in it, the explosive atmosphere without may be readily fired ; it is evident also that it does not afford a strong light, and the work- men are sometimes tempted if possible, to open it, even in dangerous situations, and accidents are said to have occurred from that cause. Dr. Murray invented a safety lamp, of which an account is given by his son,* founded upon the well known fact, that the inflammable gas occupies principally the upper cavities, and that the air on the floor is ordinarily good. The air for the support of the flame is drawn from the floor, by a flexible tube, passing from the bottom of the lamp, while the chimney at the top, by the strong current which it is constantly discharging, prevents the entrance of gas from that direction. The lamp is also of sufficient strength, and being furnish- ed with a good mirror and lens, it throws a strong light, and it is said that if an explosion should happen in it, it would merely extin- guish the light, but would not extend to the atmosphere without. f * Elements, 6th Ed. Vol. I, p. 609. t Trans. Roy. 8oc. Edin. Vol. VI, p, 31. CYANOGEN. 417 COMPOUND OF NITROGEN AND CARBON. This compound is named here, because, in the strictness of logi- cal arrangement, this is the place for its introduction ; but its fuller developement, and that of the connected topics, will be reserved to a more advanced stage of this work, because the subject is compli- cated and difficult, and requires the previous knowledge of the most important facts of elementary chemistry. These topics will be touched upon again under iron, and the other metals, and finished under the chemistry of animal bodies, from which the principal agents of this family are derived. CYANOGEN. 1. NAME. xuavo^, blue.* 2. PROCESS. If prussian blue, 8 parts, be boiled with red oxide of mercury, 1 1 parts, a crystallizable salt will be obtained, the prus- siate or cyanuret of mercury, by heating which, in a dry state, in a retort, we obtain over mercury a gas called cyanogen, which burns with a superb purple and violet flame. It is composed of 2 equiva- lents of carbon, and 1 of nitrogen. PRUSSIC ACID, OR HYDRO-CYANIC ACID. 1. NAME. Called prussic acid, from prussian blue, the parent substance, from which, as above, the cyanuret or prussiate of mercury is obtained, which affords this agent. The term, hydro-cyanic, refers to the union of hydrogen with cyanogen, to form this acid. 2. PROCESS. Decompose the prussiate, or cyanuret of mercury, in a retort by muriatic acid, and condense the volatile product in an ice cold receiver. 3. PROPERTIES. It is the most diffusive and virulent poison known ; it kills small animals when a drop is applied to the tongue, and a few drops are more than sufficient to extinguish life in a vigor- ous man. It exists ready formed in the vegetable kingdom, in peach blossoms, and peach kernels, in the bitter almond, in the lauro cerasus, &ic. It, or its radical, combines with alkaline and earthy bases, and the prussiates or cyanurets of these bodies furnish us with tests that are highly useful in detecting the metals. The prussic prin- ciple is transferred to them, front prussian blue, and these applications may be occasionally mentioned before the subject is fully exhibited. There are two acids composed of cyanogen and oxygen, call- ed, the one cyanic, and the other fulminic acid ; and one of them is supposed to exist inthe fulminating silver, and in fulminating mercury. In allusion to Prussian blue. 53 418 PHOSPHORUS. SEC. IV. PHOSPHORUS. 1. HISTORY AND NAME. (a.) Brandt, an alchemist of Hamburgh, has the credit of discov- ering Phosphorus, A. D. 1669, while endeavoring to transmute metals ;* Brandt sold the secret to his friend, Kunckel, but deceiv- ed him with a false process. Kunckel, having however learned that it was obtained from urine, avenged himself by making the dis- covery anew. Mr. Boyle also discovered it in England, and Godfrey Hankwitz, a man instructed by him, vended it at a high price, in a shop still shown in London, near Covent Garden Theatre. (b.) In 1737, a committee of the French Academy of Sciences was instructed in the process by a stranger ; it was then, as at first, ob- tained by evaporating bogheads of putrid urine to dryness, and after- wards distilling the residuum with a strong heat, in a stone ware retort. (c.) JVLargrajf, of Berlin, by adding muriate of lead to tlie urine, precipitated phosphoric acid, in union with oxide of lead, and this was decomposed by distillation with charcoal. (d.) In 1769, Ghan, of Sweden, a pupil of Scheele, having dis- covered that phosphate of lime is the basis of bones, invented the pro- cess now generally followed. The name signifies light bearer, $5 To render the common or bi-phosphate neutral, Mr. Dalton says that its sodaf must be doubled, when it will acquire much more sol- ubility, and crystallize in fine needles. Mr. Dalton recommends this form of the salt as a test. Dr. Hen- ry remarks, that fresh experiments are necessary to reconcile these discordant statements.^ By heat on a sand bath, the crystals loose 12 equivalents of water, without changing their properties. It is said that they still retain an equivalent of water, which they give up at ignition ; and then being redissolved in water, and the solution spontaneously evap- orated, irregular four sided prisms are obtained, whose primary is a rhombic octahedron ; they do not effloresce, are much less soluble than before, and consist of 1 equivalent of acid, and 1 of soda, with 5 of water. The solution precipitates nitrate of silver, white, and not yellow, like the common phosphate. A phosphate of soda has also been obtained, from a solution evaporated at 90, con- taining 7 J equivalent of water ; they are permanent in the air, and have a different form from the common phosphate. || 4. MISCELLANEOUS. (a.) Exists in human urine, with phosphate of ammonia and, the concrete salts, obtained by evaporation, are principally these two ; formerly, under the name of microcosmic salt, much employed as a flux, with the blowpipe. (b.) The phosphate of soda is used for the same purpose, and be- sides its use in medicine, it is advantageously employed as a substi- tute for borax in the soldering of metals. (c.) It is useful in chemistry ; by double exchange, we can thus form almost all other phosphates. * 35.71, Mitscherlich, quoted by Turner, 2d Ed. p. 581. t Thomson's, First Prin. I, 201. t By adding as much again caustic soda. Turner, Vol. I, p. 568. {I Turner, 2d Edition, p 281, and Edin. Jour. XIV, No. p. 298. PHOSPHATES. 433 PHOSPHATE OF AMMONIA. 1. PREPARATION. (a.) By saturating pure phosphoric acid with ammonia. (b.) By decomposing, by carbonate of ammonia, the acidulous liquor proceeding from the action of sulphuric acid upon bone ashes. (See phosphate of lime.) 2. PROPERTIES. (a.) Its crystals are rhombic prisms, terminated by dihedral sum- mits ; the primary form is an oblique rhombic prism, whose smaller lateral angle is 84, 30' ; sometimes it is obtained in needles. (b.) Its taste is sharp, cooling, and ammoniacal. re.) Sp. gr. 1.8051. (d.) Soluble in 4 parts of water at 60, and in less at 212; crystallizes on cooling, but not beautifully, unless by spontaneous evaporation. (e.) Not affected by the air. (/.) Suffers the aqueous fusion, and is decomposed by heat; the ammonia is exhaled, and the phosphoric acid melts into a vitreous globule. (g.) This is one mode by which the phosphoric acid is obtained pure, or nearly so. (h.) On account of the facility with which this salt is decomposed by heat, it affords phosphorus when heated with charcoal. 3. COMPOSITION. Acid 28 -{-17 ammonia, or 62.22, and 37.78. There is said to be also Ij equivalent of water.* 4. MISCELLANEOUS. (a.) It exists in urine, mixed with the phosphate and muriate of soda, from which it is difficult to free it ; in that state it forms the long famed microcosmic salt. . (b.) In its pure state not employed; but the microcosmic salt has been much used as a flux for the mineralogist, and in the composi- tion of the pastes. BI-PHOSPHATE OF AMMONIA. 1 . PREPARATION. By adding to phosphoric acid, ammonia or its carbonate, till the solution ceases to precipitate muriate of baryta. 2. PROPERTIES. Less soluble than the natural phosphate ; no change in the air ; primary form, an octahedron, with a square base, but the right square prism, with a rhombic base is most frequent.f 3. COMPOSITION. Acid, 2 equivalents, 56+2 of ammonia, 34 + 3 of water, 27=117 for its equivalent. * Turner, quoting Mistcherlich. t Turner. 55 434 PHOSPHATES. PHOSPHATE OF SODA AND AMMONIA. 1. PREPARATION. By dissolving in a little boiling water, 1 equivalent of muriate of ammonia, and 1 of phosphate of soda ; the double phosphate crystallizes as the fluid cools, and muriate of soda remains in solution. 2. PROPERTIES. (a.) Primary form, the oblique rhombic prism ; effloresces, losing ammonia, and passes to the condition of bi-phosphate of soda. (6.) Decomposed by heat ; the ammonia and water are dissipated and a very fusible bi-phosphate of soda remains. 3. COMPOSITION. 1 equivalent phosphate of soda, 60, -{-1 of phosphate of ammonia 45,-f 10* of water in the crystals =90 = 195. Remarks. This is the microcosmic salt, in a state of purity. According to Fourcroy, this salt effloresces, loses its ammonia, and passes to the condition of bi-phosphate of soda. It turns tincture of violets green. The ammonia is said to be dissipated by repeated so- lutions and crystallizations. PHOSPHATE OF LIME. 1. DISCOVERY. By Gahn and Scheele, in 1774, who found that hones consist principally of this substance, with some other salts, cemented by gelatine ; it exists in bones, in the proportion of 86 per cent. 2. PREPARATION. (a.) By precipitating lime water, by liquid phosphoric acid (b.) Or, phosphorus burned beneath a bell glass inverted over lime water, becomes phosphoric acid, and precipitates the lime !c.) Or, by mingling solutions of phosphate of soda, and muriate ime, adding the muriate lastf (df.) Or, we may purify the phosphate of lime of bones or. lix- iviate bone ashes with abundance of hot water, to remove muriate and phosphate of soda, and the carbonate of lime may be dissolved by acetic acid ; or, dissolve the phosphate by muriatic acid and precipi- tate by ammonia ; the phosphate falls without decomposition, and after being dried is pure. J 3. PROPERTIES. (a.} A white powder, never crystallized except as a native mineral, (b.) Insoluble in water, tasteless and inodorous. (c.) Melts by the most intense heat into an opake white enamel, (d.) Unaffected by the air. (e.) Formed with water, into a paste, it is made into cupels for ithe assay ers. * Mistcherlich quoted by Turner. 1 Otherwise the .precipitate will have excess of base, and the liquor will be acid. Berzelius. + Fourcroy. PHOSPHATES. 435 (/*.) Partially decomposed by acids, especially the stronger, and even by the vegetable acids. 4. COMPOSITION. One equivalent of acid, 28, and one of lime, 28. BI-PHOSPHATE OF LIME is easily formed by dissolving phosphate of lime in as much phosphoric acid as the salt contains, and it is always formed, (or at least a phosphate with excess of acid,) in the decom- position of bone ashes, as will appear more particularly farther on. The bi-phosphate is very soluble in water and does not crystallize.* It melts before the blowpipe into a transparent globule ; it is insoluble, and doubtless, by the heat, loses the excess of acid. Remark. For a notice of Mr. Dalton's views respecting the bi- tri- quadri- octo- and dodeca-phosphate of lime, containing, as is sup- posed, 2, 3, 4, 8 and 12 equivalents of acid, reference may be had to Henry's Chemistry, 10th ed. Vol. I, p. 591. 5. MINERAL AND ANIMAL PHOSPHATE. Found as a mineral in many countries ; in Estremadura, in Spain, forms extensive rocky strata ; it is there used in building. Most of the natural phosphates are highly phosphorescent by heat ; animal phosphates are not. Occurs crystallized in Saxony, Bohemia, Eng- land, United States, &c. in six sided prisms and tables ; it is called apatite and asparagus stone. It exists in most animal fluids; in human urine, in the form of bi-phosphate, and is precipitated by lime water and the alkalies ; in milk and blood ; it is found in the muscles and in jelly ; in preter- natural ossifications, and in most of the calculi, whether in the kid- neys or the bladder. It exudes through the skin, and is found in the solid excrements of animals whose urine does not contain it. It is found also in the ashes of both vegetable and animal substances. 6. PROCESS FOR PHOSPHORUS. f (a.) Burn bones in a furnace, or even in a common fire; the oils, gelatine, &ic. will be consumed and the osseous part will be easily pulverized. In an earthen pan or dish, place bone ashes 2 parts, water 20 and sulphuric acid 1 ;J digest them upon embers or by a sand heat, and stir thoroughly, with a glass rod during ten or twelve hours ; throw the mass upon a coarse linen filter, stretched over a frame with tenter hooks; wash the insoluble residuum with boiling water till it comes orT tasteless ; the fluid will be turbid ; let it settle, and then draw it off clear ; evaporate in a clean copper or tin vessel to dryness ; or, it will answer if still moist. * Fourcroy says it can be made to crystallize in brilliant micaceous scales. t For a series of years, I was in the habit of manufacturing all the phosphorus required in the experiments of the laboratory, and nearly every part of the annexed statement I have repeatedly verified by my own experience. t There will be a considerable effervescence owing to carbonate of lime, and as is said, carbonate of soda. 436 PHOSPHATES. (6.) The fluid obtained by the filtration is acidulous phosphate and acidulous sulphate of lime;* the two neutral salts being held in solu- tion by an additional quantity, probably an equivalent of their respec- tive acids. To free the fluid from the earthy matter thus dissolved, the liquor may be decomposed by acetate or nitrate of lead, and the precipitate of phosphate of lead may be decomposed by heating it in an earthen retort, with half its weight of charcoal powder. The phosphorus, obtained in this way, may be contaminated with sulphur, because sulphate of lead is thrown down by the acetate or nitrate ; this may be got rid of, by decomposing the phosphate of lead by sul- phuric acid, and then the liberated phosphoric acid by charcoal. (c.) This process is complicated, and it is better to decompose the .acidulous phosphate by adding carbonate of ammonia; the phosphate of ammonia, on being evaporated and heated to low redness, gives up its ammonia ; sulphate of ammonia, if present, is volatilized, and the phosphoric acid is obtained nearly or quite pure. But even this is unnecessary, if the object is merely to obtain the phosphorus ; for that purpose the acidulous phosphate may be at once decomposed. (d.) The purified acid, mixed ivith one half its weight of charcoal powder and heated in a furnace, affords about one fourth of its iveight of phosphorus.^ (e.) The solid residuum from (b) is commonly employed to afford phosphorus. (/.) It is mixed with from J to J its weight of dry powdered char- coal and distilled. (g.) The acidulous solution, when considerably evaporated, must be suffered to cool, and sulphate of lime will subside, which must be separated. (A.) The earthen retort is glased with lime, 1 part, slacked ivith a solution of 2 parts of borax; and with this mixture the retort is wash- ed thoroughly, inside and out ; when it is heated it will melt and fill the pores through which the phosphorus would otherwise escape. (i.) The retort is carefully coated with fire lute, and its neck dips into water ; the heat is very gradually raised, and much gas is pro- duced ; it burns spontaneously, with brilliant flashes ; we continue the heat some time after gas has ceased to come. (/.) If the neck of the retort is choked, which is ascertained by a wire, a hot iron bar is applied to it externally to melt the phosphorus. (/c.) Some phosphorus may come over into the water, but most of it condenses in the neck of the retort, and must be got out by heating it with water poured from a tea kettle. * Perhaps bi-phosphate and bi-sulphate. t It is said not to be so good for (his purpose as the acidulous phosphate, because- it is more liable to be volatalized. PHOSPHATES'. 437 (/.) Phosphorus is purified by straining it through leather under hot ivater; or better by distillation in vessels filled with hydrogen gas. It is melted under hot water, in a retort, and suffered to congeal ; the retort is then filled with hydrogen gas, its mouth plunged into warm water, and the distillation is performed by a sand heat or even by a naked fire : it is a delicate and difficult process ; I have been suc- cessful with it, but have had the retort break from the regurgitation of the water ; in such a case there is a violent and even dangerous combustion. (m.) It is cast into sticks in the throat of a funnel, or drawn up into tubes by suction ; the finger, protected by leather, is slipped over the end of the tube, and the latter is then placed in cold water. (n.) Phosphorus may be obtained by precipitating the phosphoric acid from urine, or from phosphate of soda, by nitrate or acetate of lead; we distil the concrete residuum with charcoal. About 14 or 18 parts of phosphorus are afforded by 100 parts of phosphate of lead ; less heat is necessary in this than in the process with bones. (o.) The product of phosphorus is greatest ivhen the materials are dry and the distillation is slow. Pelletier obtained 60 ounces at one operation, from the acid of 36 Ibs. of bones, (576 ounces,) decom- posed by 30 Ibs. of sulphuric acid ; at another time he procured only half this quantity. (p.) Phosphorus is purified by liquid chlorine. It should be pre- viously granulated, which is done by melting it beneath water and shaking it as the water cools ; then by shaking it in solution of chlo- rine the color is in a few minutes removed.* PHOSPHATE OF BARYTA. 1. PREPARATION. The muriate or nitrate of baryta, mixed with the phosphate of soda or ammonia, produces a precipitate of phos- phate of baryta. * By estimates made thirty years ago, the acids which decompose the phosphate of lime, take up uo more than _*_"_ of the lime it contains, and separate from it less than half the phosphoric acid ; " 100 parts, treated by an acid, afford only .33 of acidulous phosphate of lime, containing only .17 of disengaged phosphoric acid out of the .41 of this acid which exists in the 100 parts of phosphate of lime ; so that by the distillation of this substance with charcoal, we obtain only about .05 of phosphorus, instead of .16 which exist in the 100 parts of the bases of bones." It would seem, however, (o.) that Pelletier obtained double this quantity. Neutral phosphate of lime remains in the retort after the distillation of phosphorus ; its origin is obvious. We decompose no more phosphoric acid than what goes to hold in solution the phosphate of lime. In the process of the older chemists, the solid extract of urine was distilled to obtain phosphorus ; only the phosphoric acid of the phosphate of ammonia was decomposed by the combustible matter present, and therefore very little phosphorus was obtained ; the product is increased by the ad- dition of charcoal. 438 PHOSPHATES. 2. PROPERTIES. White, insipid, pulverulent, insoluble in water, soluble in nitric and muriatic acids ; applied to no use. 3. ITS COMPOSITION, after being washed and dried, is, according to Berzelius Phosphoric acid, 31.8 100. Baryta, - - 68.2 214.46 100. Dr. Henry suggests that if it be constituted of 1 equivalent of acid and 1 of base, its composition will be expressed by Phosphoric acid, 28 26.62 100 Baryta, - - _ 78 73.38 280 Its equivalent, 106 100.00 Berzelius, by dissolving baryta in phosphoric acid, and evaporating the solution, obtained acidulous crystals, which, if composed of 2 equivalents of acid, =56, and 1 of base, =78 = 1<34 3 and would be a bi-phosphate. From a solution of these crystals, alcohol precipi- tates a bulky white and tasteless substance, which appears to be com- posed of 2 equivalents of base, and 3 of acid, or if we say 1 of the former and l of the latter, it would be called a sesqui-phosphate.* PHOSPHATE OF STRONTIA. 1. FORMATION AND PROPERTIES. Every thing in the last article is applicable to this, except that it is soluble in phosphoric acid, gives a purple flame with charcoal before the blowpipe, is totally decom- posed only, by the sulphuric acid and partially by the nitric and mu- riatic acids. It is fusible by the blowpipe, into a white enamel ; it is soluble in 2000 parts of water. 2. COMPOSITION. Acid, 36.565, base, 63.435 = 100.00. Dr. Henry remarks, that " if a true binary compound, it should consist of very nearly 65 base, -f- 35 acid ; and that there is a bi- phosphate consisting of 2 atoms of acid, 1 atom of base, and 2 of water." PHOSPHATE OF MAGNESIA. 1. PREPARATION. By digesting phosphoric acid on magnesia or the carbonate. By mixing equal quantities of the concentrated solutions of sulphate of magnesia and phosphate of soda ; in a few hours, crys- tals of phosphate of magnesia are formed. . (a.) (6.) * Henry, Vol. I, p. 605. See Berzelius on two sub-phosphates, Ann. of Phi!. XV, 277. PHOSPHATES. 439 2. PROPERTIES. (a.) They are compressed prisms; speedily effloresce and re- quire 1 5 parts of cold water for solution ; hot water dissolves so much that crystals form as the solution cools. (b.) Lose water of crystallization by heat; melt by a still higher heat into a glass. (c.) Decomposed entirely by sulphuric, nitric, and muriatic acids, and by fixed alkalies and alkaline earths. Ammonia forms a triple salt, which exists in urine. (d.) Composed of acid, 1 equivalent, 20; base 1, 28=48, and when crystallized, water 7 = 63 = 111. Thomson. PHOSPHATE OF AMMONIA AND MAGNESIA. 1 . DISCOVERY. Found by Fourcroy, in the calculus of a horse; ex- ists in the bones of most animals, and is common in the human subject. 2. PREPARATION. (a.) Formed by adding phosphate of ammonia, or ammonia, or its carbonate to phosphate of magnesia; or carbonate of ammonia and afterwards phosphate of soda to solution of sulphate of magnesia, when the double phosphate subsides in the form of minute grains. (b.) Magnesia is detected when in solution in an acid, with or without other earths, in the following manner. (c.) Add to the solution bi-carbonate of ammonia, (formed by ex- posing common carbonate to the air, till it has lost its smell ;) the other earths will be precipitated, but not the magnesia. (d.) Add a cold saturated solution of phosphate of soda ; a white powder precipitates which is the ammoniaco-magnesian phosphate. (e.) Ammoniacal phosphate of magnesia is a white powder which lines the cavities of some calculi in the form of crystals^ and is fre- quently deposited in crystals. (f.) Tasteless, insoluble in water, soluble in acids, even in the acetic, and is precipitated unchanged when the acid is saturated by ammonia ; decomposed by heat, the ammonia and water flying away,, and leaving the phosphate of magnesia ; composed of equal weights of phosphate of ammonia, phosphate of magnesia, and water.* PHOSPHATE OF ALUMINA. Phosphoric acid combines with alumina, to saturation, forms a white insipid powder which melts before the blowpipe into a transpa- rent globule. & & * # & * The phosphates of the other earths are comparatively unimportant. * Its composition is said to be otherwise not accurately determined. Stromeyer states the magnesia at .37. Turner. But Thomson states it at 1 equiv. phosphate of magnesia, 48, 1 equiv. phosphate of ammonia, 45, 4 of water, 36 ; its equivalent being 129, the salt being dried without heat. 440 PHOSPHURETTED HYDROGEN. BINARY COMPOUNDS OF PHOSPHORUS WITH VARIOUS BASES. PHOSPHURETTED HYDROGEN.* 1. PREPARATION. (a.) Hydrogen gas may be partially phosphuretted, by heating phosphorus in it by the solar rays. (b.) The better mode is to heat a strong alkaline solution, (potash or soda,) with phosphorus ; the retort may be previously filled with hydrogen gas. (c.) To do this properly, introduce the phosphorus and fill the retort with hot water as it cools, the phosphorus will congeal, and adhere to the bottom, so that it will not fall out ; throw in the hydrogen gas by means of a bladder and tube, or by a tut>e coming from an air jar, or a gazometer ; keep the mouth of the retort down, and with the finger upon it, dip it into the alkaline solution ; now expel so much gas, by warming the retort, that when it cools, the requisite portion of fluid may enter. (d.) Or, fill the retort with the alkaline solution, and throw out by hydrogen gas, as much as you choose. f (e.) Or, we may mix lime with a strong solution of pearl ashes find add the phosphrous ; or, use solution of caustic potash, phos- phorus, and quick lime ; or quick lime only, and phosphorus, and wa- ter. Either of these methods will succeed. The first and the last of the three now named, are easy and cheap, and answer as well as the more troublesome modes usually described ; the last process, which is the easiest, is little inferior to any other. In all cases, it would be better to wait till ebullition, when the vapor will have expelled the air ; then through the tubulure of the retort, drop in the phosphorus ; this saves the necessity of any other precaution. (/.) Phosphuret of lime, with dilute muriatic acid, and a mod- erate heat ; to prevent explosion, the retort may be entirely filled with the diluted acid. * Discovered in 1783, by Gengembre. It is called also phosphuretted and bi- phospuretted hydrogen gas. t My method is to fill a small retort, (holding from 4 to 6 or 8 oz.) with a strong alkaline solution. Drop in the phosphorus, then from a small vial with a bent tube and a little iron filings and diluted acid, throw up as much hydrogen gas, as will dis- place the greater part of the fluid, keeping the mouth of the retort in a bowl of the same solution, then place the neck of the retort under the shelf of the tub, and ap- ply a lamp. It never fails. A bottle full of the solution will last for years, as but little is expended at a time. Communicated, J. G. I would add, that even when the air is not removed, the only precautions necessary to be observed, are not to immerse the beak of the retort until it has ceased flashing in the interior, "and begins to shew flame at the mouth not to immerse it deeply at all, and to watch that the water does not go back by regurgitation, Author. PHOSPHURETS. 441 In these cases water is decomposed ; its hydrogen, with a portion of phosphorus, forms phosphuretted hydrogen, and its oxygen, with other proportions, forms phosphorous, and hypo-phosphorous acid. 2. PROPERTIES. (a.) Smell alliaceous ; fires spontaneously, with a beautiful ring of smoke, rising and enlarging for some distance ; it is vapor of water and phosphorous acid ; similar appearances are sometimes seen dur- ing the discharge of artillery. (b.) Detonates with oxygen, 1^ of oxygen to 1 measure of phos- phuretted hydrogen ; only one bubble of either gas must be let up into the other at once. The combustion is very brilliant.* If only 1 measure of oxygen be used, the product is phosphorous acid, if 1 J, it is the phosphoric. (c.) In chlorine and nitrous oxide gases, phosphuretted hydro- gen explodes. In all these cases, the same effect is produced, if the gas supporting combustion be let up into the phosphuretted hy- drogen, and with oxygen this course is rather safer. (d.) Sulphurous acid gas, and phosphuretted hydrogen mutually decompose each other. (e.) Phosphuretted hydrogen loses its spontaneous inflammability, after standing a short time ; a part of the phosphorus is deposited ; but it still burns, and with a very bright light, when kindled by a candle. (/.) In the dark, and over mercury, it retains its inflammability a long time. (g.) It is lighter than common air. Air being 1, its sp. gr. is ac- cording to Thomson, .9027, theory and experiment coinciding, for sp. gr. of hydrogen, - 0.0694 And of phosphorus vapor, 0.8333 0.9027f Dumas gives it at 1.761 5 Dalton at 1.1. * A, represents an air jar, with a few cubic inches of oxygen gas, standing over a column of water. B, is a retort, with slacked lime, phos- phorus, and strong solution of pearl ashes, the bubbles of gas coming singly, but rather rapid- ly on depressing the mouth of the retort, (on a particular occasion,) a little gas accumulated, and one bubble hung in the glass jar without explosion, but the next blew up the whole with great violence, broke all the contigu- ous glass vessels, shot some of their fragments to the distance of 40 feet, among a large au- B dience, and slightly wounded several specta- tors ; this shews the necessity of extreme caution. See Am. Jour. Vol. VI, p. 187. t Henry, Vol. 1, p. 489. 56 442 PHOSPHURETS. (h.) Water absorbs a portion of this gas, by agitation ; if thorough- ly deprived of air at 55, it absorbs j- of its bulk, (Dalton ;) ^ (Thomson.) (i.) Heat, below boiling, expels it unaltered and inflammable. (j.) Spontaneously decomposed by exposure to the air; oxide of phosphorus is precipitated, and the gas rises uninflammable, (spon- taneously.) (&.) Solution of this gas does not change the test colors. This gas being readily absorbed by sulphate of copper, and chloride of lime, a sure method is thus afforded of ascertaining whether it is con- taminated with common hydrogen. SI.) Precipitates many metallic solutions in the state of phosphuret. m.) Potassium does not inflame in phosphuretted hydrogen gas, even when heated, but the potassium is converted into a phosphuret, and 2 measures of the gas become 3. (n.) Decomposed by heat, by electricity, and by vaporizing sul- phur through this gas; it then becomes sulphuretted hydrogen.* Phosphuretted hydrogen collected in a jar with a cap and stop cock, blazes when the jar is depressed into the water and the orifice opened ; or if a bent tube be attached to the cap, and the bubbles be allowed to issue from beneath the water, they flash as they break into the air.f OTHER VARIETIES OF PHOSPHURETTED HYDROGEN. 1. Sub-phosphuretted hydrogen gas. (a.) This is the gas, already named, which remains after the com- mon phosphuretted hydrogen has deposited J of its phosphorus,^, and has thus lost its spontaneous inflammability ; it is called at present, gub-phosphuretted hydrogen, and by some proto-phosphuretted hy- drogen. (b.) For perfect combustion it requires 1.25 volumes of oxygen; ,75 saturates the phosphorus, and .50 the hydrogen ; as the vapor of phosphorus requires its own volume of oxygen, this gas is inferred to consist of 1 vol. of hydrogen, 0.0694 + 0.75 of a vol. of phosphorus, 0,6250 = .(5944, * We are not informed what becomes pf the phosphorus ; whether it is precipitated or remains suspended in vapor. t It is supposed that many of these fires which are said to be seen at night, around burying grounds, and other place? where animal and vegetable substances are un- dergoing decomposition, arise in part at least, from phosphuretted hydrogen. Trav- elling once, through a deep valley, in a dark night, between Wallingford and Durham, Conn. I was surrounded by multitudes of pale lambent lights; they were every moment changing their position, and some of them were within the reach of my whip ; they were yellowish and not intense. I Thomson. Dumas says one third, PHOSPHURETS. 443 2> Hydro-phosphoric gas. Davy ; bi-hydroguret of phosphorus. Thomson. (a.) Obtained by heating solid phosphorous acid away from air ; the hydrogen of the water of crystallization unites with a part of the phosphorus to form this gas, and the oxygen with another part to form phosphoric acid. (b.) JL distinct gas, not spontaneously inflammable ; smell fetid, but less so than that of the phospburetted hydrogen. c.) JLt 300 Fahr. it detonates violently with oxygen gas. ) Explodes in chlorine with a white flame. Water absorbs j- of its volume. /.) Sp. gr. .87* more than twelve times as much as that of hy- drogen gas. (g.) Potassium heated in it becomes a phosphuret, and the volume of the gas is doubled. (A.) Sulphur in the same manner produces sulphuretted hydro- gen gas, equal to twice the original volume. (i.) 3 volumes of this gas condense 5 of oxygen, 1 volume re- quires 2 of oxygen for its complete combustion, 1 for each of its constituent principles, forming phosphoric acid ; and with 1 J vol. oxygen, phosphorous acid. (j.) 1 volume of this gas absorbs 4 of chlorine. Remarks. Mr. Dalton says that there is only one variety of the phosphuretted hydrogen, that the others quoted are merely mixtures of this with common hydrogen, and that they may be separated by chloride of lime, which absorbs the former. He says that phosphu- retted hydrogen requires 2 volumes of oxygen for saturation, and 8 volumes of water for its solution, f &c. It is inconsistent with the design of this work to discuss the views of different writers on the subject of these compounds, particularly the elaborate researches of M. Dumas. { A full abstract of them is given by Dr. Ure, in his Dictionary, 2d Ed. p. 658, and the views of Prof. Rose are briefly stated by Dr. Turner, 2d Ed. of his Chemistry, p. 355. It is sufficient for the general student to know that there are either several varieties of phosphuretted hydrogen, or that the gas which has been so long known by that name, is mixed in different proportions with common hydrogen gas, which as al- ready stated, is the opinion of Mr. Dalton. * Davy. .9653 Thomson. Theory would give it at .9721 ; twice the sp. gr. of hydrogen, = 0.1388,+ sp. gr. of phosphorus vapor, 8333. .9721. Henry. Mr. Dumas states it as 1.214. t Thomson's Annals, Vol. XI, p. 7. i Ann. dc Chirn. et de Phys. Vol. XXXI, p. 158-. 444 PHOSPHURETS. PHOSPHURET OF SULPHUR, OR SULPHURET OF PHOSPHORUS.* 1. PREPARATION. (.) It is unsafe to form this compound by melting the materials under water, unless in very small quantities, say 60 or 80 grains, and with a heat not over 160 Fahr. (6.) Mix the ingredients, the phosphorus in slices- the sulphur in flowers, and place them in a tube sealed at one end, and loosely corked ; immerse this in water, and heat it gradually, till the com- bination is formed, f Or, melt phosphorus, not exceeding 30 or 40 grains, in a tube from J to f of an inch wide, and 4 or 5 inches long ; the sulphur may be thrown in, in successive small pieces. In all the modes, sulphuretted hydrogen is evolved. 2. PROPERTIES. (.) Fusibility greatest when the proportions are equal or 1J of sulphur to 2 phosphorus, J congeals at 41 ; 1 of sulphur to 2 phos- phorus, at 50 ; with 1 to 4 at 60 ; sulphur prevailing, it becomes less fusible ; 1 of phosphorus to 2 sulphur congeals at 56, 1 to 3 at 99. Phosphorus 1, and sulphur 8, or even 30, give a solid and good compound for lighting matches, but they unite in every propor- tion. (b.) Decomposes water, becomes acid, emits fetid gases, and if heated in contact with water to 210, it explodes. (c.) Less inflammable when formed in the dry than in the humid ivay ; becomes very inflammable by kindling it by a hot wire in the tube, and suffering it to burn for a few minutes. (d.) Olive oil, rubbed with this compound, and suffered to stand in the cold, dissolves it, as do the essential oils. (e.) When the solution is perfectly clear, it may be rubbed on the hands with safety, and appears very luminous in the night. (f.) The solution in olive oil, mixed in equal parts with oil of turpentine, gives a beautiful shower of fire, when poured out in the dark. * For many interesting particulars, see Nich. Vol. VI, and VII ; Accum and Briggs ; Ann. de Chim. Vol. IV, p. 10 ; Quar. Jour. IV, p. 361. t The young chemist should be very much on his guard in forming this dangerous compound ; the mode in which I have succeeded the best, has been to prepare the materials as stated t in the text, and then to hang the tube through a piece of board laid across a common tea-kettle, whose lid is removed ; it con- tains cold water, and is placed over live coals contained in a table furnace, and left to itself; it ought not to be approached until the water has boiled and grown cold again. I have, when even all these precautions were taken, known several violent explosions, throwing the kettle to a distance. Prof. Olmsted remarks, that if the phosphorus is dried by blotting paper, and the sulphur in a saucer, the danger of explosion is greatly diminished. \ Thenard says 2 of phosphorus and 1 of sulplur. ftl 9 PHOSPHURETS. 445 PHOSPHURETS OF THE ALKALIES are scarcely formed, except the transient combination by which phosphuretted hydrogen is pro- duced ; they have but a momentary existence, and pass to the saline condition. PHOSPHURET OF LIME. 1. PREPARATION. (a.) A coated glass or earthen tube is partly filled with good lime, in pieces, occupying the middle ; phosphorus is placed at one end, which is stopped with fire lute ; the other end is closed with solid chalk ; lay it across a furnace, and when the lime is red hot, draw the phosphorus into the heat, it sublimes, and the compound is form- ed ; it must be kept close from the air. 2. PROPERTIES. Of an auburn brown color. Thrown into water, emits phosphuretted hydrogen, which flashes in the air. (c.) Place some of it in a dish of water, and bring over it quickly a jar of common air, which produces a pretty fire work ; we should be on our guard against explosion, which, especially if oxygen gas be used, is very liable to happen. (d.) It is said,f that lime and phosphorus stratified in a long vial, buried in sand to the neck, and gradually heated, keeping just be- low redness till the combination is formed, will answer as a substi- tute for the tube experiment, and then the phosphuret may be kept in the same vial.J (e.) It is very possible that this substance is, at least in part, a phosphuret of calcium ; but no accurate experiments have been made to determine this point. (/.) If phosphorus be sublimed through carbonate of lime, the carbonic acid is decomposed, and charcoal deposited. Remark. From half an ounce of good phosphuret of lime, 60 cubic inches of phosphuretted hydrogen gas are obtained, by the agency of muriatic acid. ####*## The phosphurets of baryta and strontia may be formed in the same manner, but they possess no properties that are peculiar, ex- cept that the phosphuret of baryta^ is employed for the formation of the hypo-phosphorous acid. * If languid, warm water makes it succeed brilliantly, and sulphuric acid, (strong) added to the mixture, has the same effect. Muriatic acid has a similar effect, but not with so much energy. t Aikins' Diet. Vol. II, p. 214. + This has not succeeded well with me ; the phosphorus is vaporized before the lime is sufficiently heated. See Dr. Pearson's account of the phosphurets in the Phil. Trans. 446 NITROGEN. SEC. V. NITROGEN. COMBINATIONS OF NITROGEN AND PRECEDING SIMPLE BODIES. COMPOUNDS OF NITROGEN WITH OXYGEN, AND THE COMBINA- TIONS OF THESE WITH PRECEDING BODIES. Remarks. As it seemed difficult to advance at all without a knowledge of the composition of the atmosphere, the history of nitro- gen was given in connexion with that subject. It now remains to detail the history of the other Compounds into which nitrogen enters, in connexion with oxygen, and it seeins to me that the properties of this very singular class of bodies will be best understood by taking them in the following order. NITRIC ACID. -NiTRic OXIDE GAS, (nitrous gets.) NITROUS ACIDS. NITRATES OF ALKALIES. NITROUS OXIDE, (exhilirating gas.) NITRATES OF EARTHS. NITRITES ; to be concluded by a recapitulation of the composition, fyc. of the nitric compounds. NITRIC ACID. 1. HISTORY. First obtained by distilling a mixture of nitre and clay. The discoverer was Raymond Lully, a chemist of the island of Majorca, born in 1235. Basil Valentine, in the fifteenth century, describes the process more minutely, and calls the acid water of nitre ; subsequently it was called spirits of nitre and aquafortis ; the latter is still the name in the shops. Called nitric acid by the French chemists, in 1782; because it is obtained from nitre.* On the prin- ciples of the nomenclature, it would, at that time, have been called azotic acid, and the name azote was altered to nitrogen to make the terminology consistent. 2. PREPARATION. (a.) For information merely, the original experiment of Mr. Cav- endish may be repeated. f In that case, it was formed by electrizing for a great length of time, with many thousand shocks, a mixture of oxygen and nitrogen gases, in the proportion, by measure, of 5 parts of oxygen to 3 of common air, or 7 oxygen to 3 nitrogen, or common air by itself. J It may be done, over quicksilver, in a glass tube, furnished with gold or platinum wires ; caustic potash, introduced before electrization, will absorb the acid as it is formed, and thus * Familiarly called saltpetre. t See Phil. Trans. Vol. LXXV, 1785. ' t Oxygen and azotic gas were mixed by Mr. Cavendish, in the proportion of 416 of the former, to 914 of the latter, in bulk, in one experiment, and in another, in the proportion of 1920 : 4860, and (Phil. Trans. 1785,) he converted them totally into WITRIC ACID. A distinguished chemist, in London, informed me, in 1805, that he and a noble- man who was his pupil, had labored during a month to produce nitric acid by the ori- ginal experiment of Mr. Cavendish^ but without success. This goes only to prove that it is a difficult process, for the name of Mr. Cavendish is sufficient authority for any thing which he asserts. NITRIC ACID. 447 nitre will be produced, from which the acid may be extracted. Min- gled in proper proportions, the gases nearly disappear, in conse- quence of their combination. (b.) The usual process for nitric acid.* A large retort, with an adopter, tubulated receiverf and sand heat ; the lute, is clay 5 sand and flour, equal measures, mixed and kneaded together ; proportions of the salt and acid, nitre 6, sulphuric acid 4 to 6 ; the nitre in fragments : if the receiver is not tubulated there should be an opening through it for gas to escape; heat slowly raised, receiver kept cool; there should be no water in it, if we would obtain a strong acid ; the pro- cess lasts one hour, or two or more, according to the quantity ; there is some red gas at the beginning, and much towards the end ; the retort is clear in the middle of the experiment, and when the residuum puffs up, we stop the process. To extract the caput mortuum, J warm water is poured in very cautiously, and, at first, in very small portions, for there is great heat and ebullition ; proceed carefully till the super- sulphate of potassa is thus dissolved ; if left in, it almost infallibly breaks the retort by crystallizing ; the excess of acid may be driven away by heat, or neutralized by chalk, and then crystals of sulphate of potassa will be obtained. (c.) Nitric acid is freed from muriatic, and in a good degree from the sulphuric, by nitrate of silver ; the sulphuric acid is better re- moved by distilling it again from J of the original quantity of very pure nitre. (d.) Nitrate of baryta also separates the sulphuric acid ; it must be re-distilled off from the precipitate, leaving J or T \ in the retort. (e.) Pure nitre is prepared by dissolving and crystallizing nitre several times, the last time with the addition of nitrate of silver, to precipitate the muriatic acid. Such nitre will, if the salt does not soil the neck of the retort, and the heat is cautiously raised, and is not raised too high, give pure nitric acid in the first process. (/.) The colored acid may be made clear by long and cautious heating, to expel the nitric oxide gas, and a receiver may be used to save any acid that rises. The acid is more easily cleared by a little black oxide of manganese, placed in the retort which imparts oxygen and converts the nitrous into nitric acid. Probably any other nitrate would answer to afford nitric acid, but the nitrate of potash is the best.|| * Nitre may be decomposed by sulphuric acid in small quantities, with a naked glass retort, over a lamp or live coals, and the adopter is not indispensable, as the receiver is very little heated in the process. t Furnished with a bent tube if you wish to collect the gases evolved. t An old fanciful name given to the solid residuum from distillation. Or nitrate of lead ; but nitrate of silver is preferable. |) Dr. Thomson, (First Principles, Vol. I, p. 107,) says that pure nitre is anhy- drous, and that if a little water be mechanically lodged between the plates of the crystals, it is easily dissipated by a moderate heat or by fusion. When such nitre in the proportion of 12| parts is decomposed by 6 \ parts of the strongest sulphuric 448 NITRIC ACID. 3. PROPERTIES. (a.) Its sp. gr. is usually 1.5 or 1.55 ; it has been obtained as high as 1.62, by Proust ;f supposed to be in its pure state an acid gas of sp. gr. 2440, air being 1000 ; this acid gas with water forms the common acid; that having the sp. gr. 1.55, contains nearly 86 per cent, of acid, and 14 water. Table of the strength of nitric acid, from Thomson's First Prin- ciples, Vol. I, p. 114. Equiv. of acid. Equiy. of water. Acid in 100. Sp. Gr. 1 - - 1 - - 85.714 - - 1.5500 1 2 - 75.000 - - 1.4855 1 - 3 - 66.668 - - 1.4546 1 - - 4 - - 60.000 - - 1.4237 1 - 5 - 54.545 - - 1.3928 1 - - 6 - 50.000 - - 1.3692 1 - 7 - 46.260 - - 1.3456 1 8 - 42.857 - - 1.3220 1 - 9 - 40.000 - - 1.3032 1 - - 10 - - 37.500 - - 1.2844 1 - - 11 - - 35.294 - - 1.2656 1 - - 12 - - 32.574 - - 1.2495 1 - - 13 - - 31.579 - - 1.2334 1 - - 14 - - 30.000 - - 1.2173 1 - - 15 - - 28.571 - - 1.2012 (b.) Hydro-nitric acid, as it is called, is a pale colorless fluid, like water, with a pungent odor, and it emits smoke in the air. (c.) It has all the acid properties in perfection. (d.) Highly corrosive, and turns the skin yellow, (e.) Boils at 248, and is distilled without change ; but this boil- ing point belongs to acid of the sp. gr. 1.42, containing acid .60 and water 40. acid,* we obtain the strongest nitric acid, with sp. gr. 1.55. When the proportion of sulphuric acid is doubled, the retort is not so liable to be broken, but the nitric acid, obtaining a larger supply of water from the sulphuric acid, is of course weaker. When 12| parts sulphuric acid are mixed with 12| parts of pure anhydrous nitre, the whole of the nitric acid is obtained, but of the sp. gr. 1.4855, and its composition is 1 equivalent acid and 2 water. In the London Pharmacopeia, equal parts of nitre and sulphuric acid are ordered ; this contributes to the formation of a bi-sulphate of pot- ash, which is said to be necessary to the entire decomposition of the nitre, and af- fords two proportions of water, which are required to condense the whole of the nitric acid. The Edinburgh Pharmacopeia and the manufacturers use three fourths or four fifths of sulphuric acid, and these proportions are the best. * It is well, before using it, to heat the sulphuric acid nearly to its boiling point, to expel the water it may have imbibed. t Gay-Lussac says, (Ann. de Chim. et de Phys. Vol. I, p. 396,) that 1.510, at 18 centigrade, is the heaviest that had then, (1816,) been obtained. NITRIC ACID. 44Q Jlny acid, either weaker or stronger, boils at a lower temperature; if weaker, it is strengthened, if stronger, it is weakened by boiling ; and acids of all degrees of strength come, by continued boiling to sp. gr. 1.42, which seems to be the strongest combination of acid and water. Acid of sp. gr. 1.369, contains half its weight of water ; that of sp. gr. 1.30, has acid 40 and water 60, and boils at 236.* (/.) Frozen at 2 below 0, Fah. if of sp. gr. 1.3. When either stronger or weaker, it requires a much more intense cold, as much, in some cases, as to freeze mercury. f (g.) Exposure to light, colors it red, while oxygen gas is given out, provided it be strong ; and this happpens when it is weak, if it be previously mixed with sulphuric acid. (A.) Decomposed into oxygen and nitrogen gases, or nitric oxide gas, by being passed in vapor through a red hot earthen tube, and the stronger the acid the more readily it is decomposed. A pendent candle just blown out, is promptly relighted by being plunged into the mixed oxygen and nitrogen ; these may be analyzed by any of the eudiometrical methods, and their proportion ascertained. They will be found to be in nearly the reversed proportions of the atmosphere. Some nitric oxide gas usually comes over and produces red fumes of nitrous acid, which are soon absorbed by the water, and leave the ox- (gen and nitrogen mixed. The decomposition of the solid nitrates y ignition affords similar results ; nitrate of ammonia, is however an exception, as will appear in its proper place. (i.) Causes ice and snow to melt, producing cold ; 4 parts strong- est nitric acid with 7 of snow, sink the mercury from -f 32 to 30 , see tables of freezing mixtures. (j.) Attracts water from the air and becomes weaker, but not in an equal degree with sulphuric acid. (/c.) Acid 2, -f- water 1, at common temperature, raise the therm. 112, but if more water is added, this mixture lowers the tempera- ture. Nitric acid, 58 measures, of sp. gr. 1.5, mixed with 42 of water, raises the temperature from 60 to 140, Fahr. and on cool- ing, the 100 measures occupy 92.65.J (I.) More or less affected and decomposed by all combustibles, and by most metals. (m.) It explodes with hydrogen at a high degree of heat ; caution is required ; it is best shown by passing the hydrogen gas from a flask, by means of a tube bent twice at right angles, through nitre melted in a crucible, when there is a slight explosion, and a flash at the passage of every bubble of gas ; some caution is requisite. Dalton. Thomson. Henry. t Cavendish, Phil. Trans. 1788. Ure, quoted by Turner. 57 I 4f>0 NITRIC AC It). (?i.) Boiled on sulphur, sulphuric acid is formed, but without combustion. (o.) Poured on charcoal, there results a vivid inflammation; it is best to pound ignited charcoal taken immediately from the fire ; put it into a worthies glass vessel or a crucible, and add the acid gradu- ally. Lamp black, or the charcoal of oils inflames more easily than common charcoal, but a mixture of the two more easily than either alone. (p.) Phosphorus is converted into phosphoric acid by the nitric ; if weak, it merely boils with red fumes of nitrous acid $ if very strong, and especially if warm, it burns with a splendid combustion; it is thrown about in jets of fire and requires great caution ; to render it the more beautiful, a tall narrow deep vessel should be used, but when the quantity of both substances is considerable, there is some- times a dangerous explosion.* (q.) If phosphoric acid is desired^ the common aquafortis is strong enough ; it may be gently heated ; the phosphorus is added in pieces, and when they are no longer dissolved, and readily take fire on com- ing to the surface, the process is through. (r.) Heat will expel any remaining nitric acid, and if pushed far enough in a platinum vessel, we obtain glacial phosphoric acid. (s.) The easily oxidable metals, iron, tin, zinc, copper, &ic. de- compose the acid powerfully, especially if hot. (t.) Very strong nitric acid, poured from a glass fixed to a pole, fires oil of turpentine, and other volatile oils the pole is for safety. A little sulphuric acid is mixed with the nitric, to concentrate it by re- moving a portion of water which it contains. The drying oils do not need the addition of sulphuric acid. 4. COMPOSITION AND COMBINING WEIGHT. When we have fin- ished the history of the compounds of nitrogen and oxygen, we will review that of nitric acid, which cannot perhaps be fully understood without an acquaintance with all the acids and oxides, which have nitrogen for their basis. We may state at present, that the propor- tions of the elements of nitric acid, by weight, are, 74.13 oxygen, - - 286 by volume, nearly 250 25.87 nitrogen, 100 " " ' 100 100.00 386 * This circumstance has happened so often in my own experience, with nitric acid distilled from very pure nitre, with two thirds its weight of sulphuric acid, and with- out any water in the receiver, that I cannot but repeat the caution that the operator should be much on his guard. With a stick of phosphorus as long as a finger drop- ped into 2 or 3 oz. of strong nitrous acid, 1 have known explosions like those of a swivel, and the fragments of glass have wounded persons at a considerable distance. See Am. Jour. for'Dr. Hare's experience. NITRIC ACID. 451 and its constitution, 5 equivalents of oxygen 40, and 1 of nitrogen = 14, its own equivalent being therefore 54.* Liquid nitric acid, sp. gr. 1.50, contains 2 proportions of water, 18 + 54 = 72 for the representative number. Dr. Thomson assigns the sp. gr. 3.75, to the dry gaseous acid, and this number is produced by multiplying .06944, the specific weight of hydrogen, by 54, that of nitric acid. 5. POLARITY. In the galvanic circuit, this acid is attracted to the positive pole, and is therefore electro-negative. C. USES. (a.) The nitric acid is a very important agent in chemistry. From its yielding its oxygen with so much facility, it is often em- ployed to oxidate substances of various kinds, and particularly several of the acids are formed in this way. It attacks and decomposes all vegetable and animal substances, giving oxygen to their carbon, to form carbonic acid, and to their hydrogen to form water. (b.) It is also much used in the arts ; by engravers in etching their copper plates ; in the solution of metals, and in dyeing ; es- pecially with muriatic acid, to prepare tin as a mordant for cochineal, to produce the scarlet ; and in forming and fixing other fine colors. It is employed in medicine, particularly in liver diseases ; as an auxili- ary in some other cases, both internally and externally, but in the latter case, diluted, so as merely to prick the skin ; as a very valuable remedy in fevers typhus, petechial and malignant ; and as a tonic. It is diluted to such a degree, as to be only agreeably acid, and it may be qualified By sugar and aromatics. The diluted nitrous acid of the Edinburgh and Dublin pharmaco- peias, is composed of equal weights of nitrous acid and water. (c.) Vapor of nitric acid expelled from nitrate of potassa by sul- phuric acid, is used in fumigations to counteract febrile effluvia ; it appears to possess a good deal of efficacy in that way, and is not inconvenient to the patient, to whose bed side it may be carried without harm ; no heat should however be applied, as it will then emit very suffocating vapors of nitrous acid. Half an ounce of nitre is mixed with 2 drachms of sulphuric acid, and the vapor from this will fill ten cubic feet. For this application, Dr. Carmichael Smith received from the British Parliament, a reward of 5000 pounds ster- ling. (d.) It is one of the great acids of commerce. It forms nitrates with the salifiable bases. All its salts are soluble ; it is separated from them all in a state t)f decomposition, by heat, and the bases, ammonia excepted, are left behind. * Henry, Vol. I, p. 324; Thomson's First Priii. Vol. I, p. 112; Ann. of Philos. N.S. VIII, 299. 452 DEUTOXIDE OF NITROGEN. 7. MISCELLANEOUS In the arts, copperas calcined to redness, is mixed in equal quantities with dried and purified nitre ; the distilla- lation is performed in an earthen retort or an iron pot with an earth- en head, and a very strong fuming acid is thus obtained, called aqua fords. If the materials have not been before heated, they will afford water and a diluted acid which fumes very little ; it is called single aqua fortis. The sulphate of potassa is separated by solution, and the oxide of iron is sold for polishing metals ; it is called colcothar. On the continent of Europe, they use clays, boles and other earths containing silex ; the affinity exerted by these earths, towards the al- kali of the nitre decomposes the latter at a red heat. As crude nitre is employed, the acid which is called spirit of nitre, is contaminated with muriatic acid. The French distil the nitric acid in large cast iron cylinders, but when iron is used, more of the nitric acid is decomposed, and there is of course more nitrous acid produced. The corrosive fumes of nitrous acid are carefully avoided in the manufactories; they sometimes cause the workmen to spit blood. The double aqua fortis is half as strong as pure nitric acid ; and sin- gle aqua fortis being half as strong as double, is of course one fourth the strength of the strongest acid. Nitric acid is distinguished by its ready action on copper and mercury ; by forming nitre with potash, and nitro-muriatic acid with muriatic acid, and thus becoming capa- ble of dissolving gold,* by bleaching a very dilute solution of indigo, if in the proportion of 7 |oj or turning it yellow if ^^, when a few drops of sulphuric acid are added ; also by the scintillation which it produces when dropped upon ignited charcoal. For economical purposes, 100 good nitre, 60 strong sulphuric acid, and 20 of water, form a good proportion. Dr. Ore states, as the result of his own experiments, that if the respective terms of dilution of nitric acid with water, be taken as an arithmetical, the densities will be in a geometrical series. f In its concentrated state, it is a deadly poison, corroding and de- stroying the animal organs. NITRIC OXIDE GAS NITROUS GAS OR DEUTOXIDE OF NITROGEN. 1. REMARKS. In the strictness of logical arrangement, this oxide should be described after the protoxide or exhilirating gas, and both of them before nitric acid, but as it is obtained by the decomposition of the latter, its history will probably be most intelligible if intro- duced here. * But muriatic acid produces a similar iluid with the chlorates and bromates. t Diet, 2d Ed. p. 57. DEUTOXIDE OF NITROGEN. 2. HISTORY AND NAME. It appears from Dr. Hole's vegetable statics, that he obtained this gas more than a century ago, hut Dr. Priestley first examined its properties with attention in 1772.* He called it nitrous air; it is called also nitrous gas, and nitric oxide gas, and deutoxide of nitrogen. The two last names being the most proper will be employed, and for brevity the term nitric oxide will be commonly used. 3. PREPARATION. (a.) It is best obtained by the action of nitric acid upon mercury or copper: for both economy and purity the latter is preferred. (b.) Nitric acid, sp.gr. 1.2 or 1.3, is poured upon cuttings of copper. With shears like those used by the tinmen, cut sheet copper into pieces of such size that they will easily slide into a glass retort ; add common aqua fortis, or any of the varieties of nitric acid of the shops, till the copper is more than covered ; then add hot water, by little and little, till the action comes on ; let the first red vapors es- cape, and when the neck of the retort is nearly clear of the red color the gas may be saved. f (c.) If any of the copper clippings are left, they may be rinsed with water and allowed to remain in the retort for another operation. (d.) If a diluted acid be used, the heat of a lamp or of a few coals may be employed. In general, the gas comes rather suddenly; con- tinues to flow rapidly for a few minutes and then remits; it is of little use to urge it with heat beyond this point ; some gas may indeed be obtained, but it appears to be principally that which was dissolved in the nitric acid, and, although there may be an active ebullition, little is disengaged besides aqueous vapor. (e.) Jin economical process for obtaining nitric oxide gas is, to mix sulphuric acid and nitre in the proportions to afford nitric acid, and then to add to the mixture some pieces of copper. J (f.) THEORY of the process. The nitric acid imparts oxygen to the copper and converts it into peroxide, which unites with a portion of acid that has not been decomposed and forms nitrate of copper ; the nitric oxide contains all the nitrogen of the acid decomposed and as much of the oxygen as remains after the oxidation of the cop- per. * Priestley on Air. t The contrast presented by the green solution of the copper and the red vapor of nitrous acid is very striking; the solution, which will be nitrate of copper, (usu- ally with excess of acid,) should be saved for future uses. t In some of the processes for nitric oxide, a portion of nitrous oxide, and even of nitrogen, is evolved. 454 DEUTOX1DE OF NITROGEN. (g.) Specific gravity ; air being 1. it is 1.041, and 100 cubic inches at 60 Fahr. and 30 inches of the barometer weigh 31.770* grains ; compared with hydrogen its weight is 15. 4. COMPOSITION. (a.) Potassium, heated in this gas, abstracts 50 per cent, of oxy- gen and leaves the same quantity of nitrogen; as 50 cubic inches of oxygen weigh 16.944 grains, and 50 of nitrogen 14.826, its weight is plainly, for 100 cubic inches, 31.770, as stated above. As there is no condensation attending the union of the gases which unite in equal volumes, we easily obtain the specific gravity by calculation ; thus the specific gravity of oxygen gas, air being 1, is - 1.1111 that of nitrogen gas is .9722 - .9722 The sum of which 2.0833 divided by 2 = 1.041. By volume, therefore, this gas consists of 50 oxygen and 50 nitro- gen; by weight of 53.4 oxygen and 46.6 nitrogen; the difference between the number expressing the weight and the volume is owing to the difference in the specific gravity of the two gases. (b.) Heat, applied in porcelain tubes, and electric sparks decom- pose this gas ; the product resembles common air, and a portion of the original gas is left undecomposed. (c.) Iron, zinc, tin, arsenic, phosphorus, charcoal and the alkaline sulphurets, by abstracting oxygen, convert it either into nitrous oxide or nitrogen. 5. CONSTITUTION. The equivalent number of this gas is obtain- ed by adding 14, which is the number for nitrogen, to 16, which represents two equivalents of oxygen, and 30 therefore represents the nitric oxide. 6. PROPERTIES. (a.) Invisible, colorless, and permanently elastic. (b.) Not much absorbed by water, unless previously boiled, when it takes up, by agitation, about T V of its bulk, which is again expelled by ebullition. f Dr. Turner states the absorption at 1 or about 11 per cent. J (c.) Very hostile to life; warm blooded animals, immersed in it, are killed almost instantly, and it destroys the irritability of the heart. It kills by suffocation and by excoriation. It becomes nitrous acid * Its weight was formerly stated by Sir H. Davy at 34.26 grains. t The impregnated water is said to generate nitrate of ammonia after long keep- ing ; this is perhaps not extraordinary, as all the elements are present, namely, hy- drogen and oxygen in water, arid oxygen and nitrogen in the nitric oxide. 1 Elements, p. 186. DEUTOXIDE OF NITROGEN. 455 by meeting with the oxygen in the air, in the cavities, and excites the glottis to violent spasmodic action with most distressing irritation.* (d.) Action on combustibles. This is very various; some com- bustibles that burn in common air, do not burn in this gas, as a candle, sulphur, and most common combustibles, which, although on fire, are extinguished by immersion in nitric oxide. Phosphorus, if previously kindled, burns with great energy, but it may be melted in this gas without inflaming. Homberg's pyro- phous is spontaneously inflamed. Charcoal, previously ignited, takes fire, but burns feebly.-^ Hydro- gen gas, mingled with the nitric oxide, does not explode by a lighted candle, but burns quietly, with a greenish white flame, of peculiar and agreeable hue, which is modified between that of the yellow vapors of nitrous acid, and the pale bluish flame of the hydrogen. Carburetted hydrogen no explosion, except between 7 measures of nitric oxide gas, and 1 of the olefiant. Spongy platinum acts upon a mixture of hydrogen gas with nitric oxide, in proper proportions ; acid and nitrogen and watery vapor are evolved. Ammonia 100 parts, and this gas 150, detonate by the electric spark, and by a spontaneous action, nitrogen is liberated in the course of a month. J (e.) Action on oxygen ga&. This is the most interesting of all the relations of nitric oxide gas. Wherever it meets with oxygen gas, either alone, or in mixture with other gases, it produces deep brownish red fumes of nitrous acid. This property need be indicated here, only in a general way, be- because it will be more fully stated under the nitrous acid. 1 . Fill a tall glass tube with infusion of litmus, or purple cabbage'; pass up some bubbles of nitric oxide gas, that have stood for an hour or two over water ; there will be no alteration in the color of the litmus ; now add some oxygen gas, or common air ; there will still be no change till the bubbles reach the nitric oxide ; then red fumes will be produced, which will promptly change the color of the liquid to red, and the water will rise rapidly, on account of the absorption of the acid vapor. 2. The above experiment may be repeated, only using a tall air jar, and common air. The observer who sees the result for the first * As I once experienced, having breathed some of it, for nitrous oxide, from an air vessel. Insects that will live in some of the other noxious gases die in this, and fishes die in water impregnated with it. Murray. t Murray. Most authors say brilliantly, but in numerous trials, I could never make it burn at all. It will never answer for a class experiment. May it not be that nitric oxide gas has been in this case confounded with nitrous acid vapor, which is more energetic in supporting combustion ? t Henry. 450 NITROUS ACIDS. time, is astonished at the deep blood red color of the fumes, and the rapid absorption, especially when oxygen gas is employed. In this case, the hand laid upon the jar, in which the combination is going on, is sensible of considerable heat. 3. Lift out of the pneumatic cistern, a large air jar, filled with ni- tric oxide gas, having previously slipped under it a pane of window glass ; reverse its position, and suddenly remove the glass plate ; im- mediately a dense cloud of red nitrous acid vapor will rise from the mouth of the jar, and the hand placed in the current, will be warm- ed. The acid will soon disappear, being absorbed by the watery vapor in the atmosphere. NITROUS ACIDS. 1. General Explanation. It is obvious, from the statements that have been made, that whenever nitric oxide gas is mingled with free oxygen gas, nitrous acid is produced, and thus these gases become very delicate tests of the presence of each other. It is also true, that nitric oxide willl sometimes detach oxygen gas from combina- tion, and form with it nitrous acid. (a.) Prepare a flask with a tube bent twice at right angles, thus : in the flask A, place the copper and diluted ni- tric acid : in the bottle B, some pale colorless nitric acid. As soon as the nitric oxide gas be- gins to be evolved, the pale acid will change its color, and pass rapidly through many shades of yellow, ending with deep green, while blood red fumes will rise from the surface. These chang- es are owing to the absorption of the nitric ox- ide gas, by the nitric acid ; this is at the same time partially decomposed, giving oxygen to the nitric oxide gas, which is thus converted into nitrous acid, and in this state mingles with the still undecomposed nitric acid, and thus presents a variety of shades of color ;* " even a little more than 1 per cent, being sufficient to impart a pale yellow color." (b.) In the process for nitric acid from the nitrate of potash and sulphuric acid, as already described, p. 447 it is now obvious that the red fumes which appear slightly at the beginning, and abundantly at the end of the distillation, are owing to the decomposition of a por- tion of nitric acid, giving both nitric oxide, and oxygen gas, which again unite in different proportions from the original ones, and thus produce fuming nitrous acid. * Heat, gradually and long applied, will discharge this color, and dilution with water does it instantly, while red fumes are emitted. HYPO-NITROUS ACID. 457 In the middle of the process, when the first effects of the sulphu- ric acid are over, and the materials have not as yet become very hot, the nitric acid passes, without decomposition, and by changing the receiver, we obtain it nearly colorless. If any combustible is mixed with the materials, the red fumes are much increased, as the acid is then decomposed more rapidly than before. (c.) In all cases where nitric acid acts on combustibles, or on metals, it becomes colored, and emits red fumes, especially if in con- tact with the atmosphere ; this is owing to the generation of nitrous acid, in consequence of the extrication of nitric oxide gas, and its subsequent reoxigenation to produce nitrous acid. (d.) It follows, that nearly all the acids of the nitric family, found in the shops, and in the arts, and all that are colored, are mixtures of nitric and nitrous acids ; but the nitric acid usually pre- vails, and such acids by uniting with bases, form true nitrates ; still it is true that the purest and strongest nitric acid, and the purest and strongest nitrous acid are scarcely known, except in the hands of the philosophical chemist ; the pale acid of the shops is usually a nitric acid, diluted, more or less, with water ; and all the colored acids, may, by additional dilution, or by the proper application of heat, be brought to the condition of nitric acid. (e.) Still, although there are many varieties in the weight, color, fuming properties, and energy of the nitrous acids of the arts, we must not suppose that there is a great diversity of real nitrous acids, and that the nitric oxide and oxygen " can unite in every propor- tion" within certain limits. " The true explanation is, that the mixture of these gases may give rise to three compounds, the hyponi- trous, the nitrous, and the nitric acids, and that if certain precautions are adopted, either of them may be formed, almost if not entire- ly, to the exclusion of the others."* HYPO-NITROUS ACID. 1. NAME AND HISTORY. Called by some per-nitrous, but hypo- or sub-nitrous seems the most proper name, since it is less energetic as an acid than the nitrous and nitric, and also contains less oxygen. First obtained by Mr. Dalton,f and Gay-Lussac.f 2. PROCESS. (a.) Mingle over mercury, in a glass tube, containing a strong so- lution of pure potassa, 400 measures of nitric oxide gas, with 100 of oxygen. The compound thus formed, will be absorbed by the alkali, and is supposed to be the hypo-nitrous acid. (6.) If 100 measures of nitric oxide gas be exposed for three months to a solution of pure potassa, over mercury, 25 measures of * Turner. t Thomson's Ann. Vol. X. * Ann. de Chim. et de Phys. Vol. I, p. 400. 58 458 HYPO-NITROUS ACID. nitrous oxide (protoxide) will be left, the remainder having com- bined with the alkali in the form of hypo-nitrous acid, oxygen having been afforded by one portion of the nitric oxide, which was thus re- duced to nitrous oxide, while the other, by the aid of the oxygen, became nitrous acid. (c.) Gay-Lussac supposes that he obtained the same acid by dis- tilling the nitrate of lead, the volatile product being condensed in a receiver, kept cold by a freezing mixture.* But it is perhaps, not certain that the hypo-nitrons acid has yet been obtained in a state of freedom. 3. PROPERTIES. (a.) The acid obtained by Gay-Lussac, from the destructive dis- tillation of nitrate of lead, boiled at 79 Fahr. and was dissipated in very dense red fumes. (6.) Poured into water, nitric oxide gas ivas abundantly liberated^ " and the water became blue, green, and yellow, according to the proportion added." (c.) Sulphuric acid, either strong, or a little weakened, and at a moderate temperature, forms with the hypo-nitrous acid, four sided prisms, which, as well as the fluid in which they are produced, emit nitric oxide gas by the contact of water. (d.) Nitrous acid vapor, passed into sulphuric acid gives also a similar compound.-^ 4. CONSTITUTION. Hypo-nitrons acid appears to consist, by measure, of 200 of nitrogen to 300 of oxygen, or of 100 to 150 ; for since 100 measures of oxygen (see 2,) are mingled with 400 of nitric oxide to produce hypo-nitrous acid, and as nitric oxide consists of equal volumes of nitrogen and oxygen, it follows that the propor- tions are as above stated. Also, in the experiment 2. (b.) " deduct- ing from the nitrogen and oxygen originally contained in the nitric oxide gas, the quantities constituting 25 of nitrous oxide, we shall find that 25 volumes of nitrogen, and 37.5 of oxygen had disappear ed and formed a new compound, which was absorbed by the potassa. Thus 100 nitric oxide gas =50 nitrogen +50 oxygen, 25 nitrous oxide gas =25 " -j-12.5 " 25 37.5 and 25 : 37.5 : 100 : 150." H. These are exactly the proportions assigned by Gay-Lussac to the hypo-nitrous acid. * Dulong and Dr. Thomson, however, suppose that the acid obtained in this case was the real nitrous. Murray. t Also by mingling oxygen gas, sulphurous acid, nitric oxide gas, and aqueous vapor, a similar compound is produced. Clement and Desormes, its discoverers, supposed it to consist of sulphuric acid and nitric oxide gas. H. NITROUS ACID. 459 The representative number of hypo-nitrous acid is 38, made up of 1 proportion of nitrogen, 14, and 3 of oxygen, 24 ; thus answer- ing to 1 volume of nitrogen, and l of oxygen 1 volume of oxygen representing two proportions, viz. 16. 5. The hypo-nitrous acid cannot be obtained from its alkaline combinations in the isolated form, for whenever a stronger acid is added, to separate it from the alkali, it is decomposed into nitrous acid, and nitric oxide gas. NITROUS ACID. It has been already explained, in what sense this term has been generally used by chemists. It now appears that there is a distinct and peculiar acid, to which the term may be properly applied. 1. PREPARATION. (a.) According to Dr. Thomson* the distillation of dry nitrate of lead into a receiver kept cold by a mixture of snow and salt, affords this acid in purity ; Gay-Lussac considers it as the hypo-nitrous.f (b.) Sir Humphry Davy obtained it by mixing in a vessel deprived of air, 2 volumes of nitric oxide and 1 of oxygen, the gases being both dry. The condensation, according to Davy, is into one half; ac- cording to Gay-Lussac and Dr. Thomson, into one third of their original volume. (c.) The correct performance of this experiment requires a glass globe adapted to the air pump, and also to glass jars from which the two gases can be introduced in their proper proportions. (d.) The common class experiment of mingling the gases by pour- ing them into glass jars through water, in the pneumatic cistern, gives a mixed acid ; composed probably of the three varieties nitric, ni- trous, and hypo-nitrous. 2. PROPERTIES. (a.) In dry glass vessels, it forms a deep blood red vapor, or per- haps it might be called a gas. (b.) It is, however, condensed into a liquid by a low temperature. The density of the anhydrous acid is 1.451. (c.) We have the authority of Dulong and of Dr. Thomson, that the red fuming acid distilled into a cold receiver from nitrate of lead, is really anhydrous nitrous acid. (d.) ItJ is very corrosive intensely acid odor very pungent, color, yellowish orange at common temperatures, it is a fuming li- quid, but evaporates rapidly and boils at 82 Fahr. The exhala- tions are the common nitrous acid vapors, which, when once mingled with other gases, require a very intense cold to condense them. * Elements, Vol. I, p. 120. t Ann. de Chira. et de Phys. Vol. I, p. 405. i It will be observed that this description applies also to what Gay-Lussac consid- ered as hypo-nitrous acid ; see his memoir, Ann. de Chim. etde Phys. T. I, p. 405. Berzelius remarks that nitrous acid of the same density with nitric that boils at 236, boils at 160. 460 NITROUS ACID. (e.) Action of water. To form liquid nitrous acid, nothing more is necessary than to add this vapor to water mixed with a large quantity of this fluid, it becomes nitric acid, which remains colorless in the water, while a quantity of nitric oxide gas escapes into the air, producing the usual red fumes. But if the nitrous acid is added to a very little water, the gas is retained and the fluid becomes green ; with an intermediate quantity of water, the anhydrous nitrous acid, when dropped in, emits at first, a considerable quantity of red fumes, which however diminish as more acid is added, and finally cease. In the progress of the addition of the acid to the water, (as has been already stated under the hypo- nitrous acid,) the liquid passes through shades of greenish blue, and green of various tints, and be- comes at length, orange yellow, which is the color of the acid itself. These changes of color are evidently owing to a mixture of differ- ent proportions of the three acids, and of the nitric oxide.* (f.) Action on animals; highly irritating and suffocating in the glottis ; it should be avoided as much as possible. In the nu- merous experiments of the laboratory, in which nitrous vapors are dis- engaged, it sometimes produces permanent injury, and often a dis- tressing stricture of the chest, with a continued sense of pressure and suffocation. (g.) Action on combustibles. A candle burns in this vapor with some brilliancy, and phosphorus burns with splendor ignited charcoal continues to burn, but with a dull red light. (h.) By calculation from the weight of the elements and their con- densation, this acid, in the aerial form, must iveigh 65.3 grains, at a medium temperature and pressure.' (*".) Action on colors. It is scarcely necessary to add that this acid reddens litmus and affects the other test colors, as the acids gen- erally do. (j.) The nitrous acid cannot be combined directly with the bases; it affords with potassa, for instance, nitrate and hypo-nitrite, without any proper nitrite. f 3. Test for nitrous acid. We owe to Gay-Lussac the know- ledge of the fact that the red sulphate of manganese becomes instantly colorless by the action of the nitrous acids ; which, by detaching oxy- gen, bring it to the state of w r hite sulphate, while nitric acid has no such effect. 4. REPRESENTATIVE NUMBER AND CONSTITUTION. As nitrous acid is formed from 2 volumes of nitric oxide, consisting of equal volumes of oxygen and nitrogen, with the addition of one volume of * For an ingenious theoretical explanation, more in detail, see Turner's Elements, 2d Ed. p. 225. t Ann. de Chim. et de Phya. T. I, p. 410. NITROUS ACIDS. 461 oxygen, it consists obviously of 4 equivalents of oxygen 32, and 1 of nitrogen 14, which make the number representing it, 46. 5. USES. Most of the acids of this class used in chemistry and the arts, and even in medicine, are, as already stated, rather nitrous than nitric acids, or rather mixtures of the two or even three varieties.* In medicine, this fact is of no moment, because the acid is always given largely diluted with water, and in this state, it is a weak nitric acid ; and indeed, in most of the arts, it is used in a state of dilution. For the purposes of oxidation and combustion, the nitrous acids are used indiscriminately with the nitric ; and the highly fuming acids, if equally concentrated, are thought to be even better for some brilliant experiments, such as the combustion of oils, of charcoal and of phos- phorus. In chemical analysis, the nitric acid is generally employed ; the nitrous is resorted to only occasionally. APPENDIX TO THE HISTORY OF THE NITROUS ACIDS. 1 . Application of nitric oxide gas. It is obvious, from the pre- ceding statements, that nitric oxide gas and oxygen gas, are mutu- ally tests. To know whether there is in any gas a mixture of free oxygen or of common air, it is necessary only to add a little nitric ox- ide, when, if there is any uncombined oxygen gas present, the red fumes will appear. So far as this fact goes, the nitric oxide is an im- portant agent in the hands of the chemist, but, as regards the amount of oxygen present, there has been much diversity in the results obtained in different modes of operating. As the causes of this diversity could not be fully understood until we had become acquainted with the ni- trous acids, this subject has been reserved for the present place. 2. Common air. When, in a glass receiver over ivater, nitric oxide fas is mixed with common air, the red fumes appear, and by ming- ng them in proper proportions and in a proper manner, the ivhole of the oxygen will be withdrawn, and the nitrogen will be left the ni- trous acid being absorbed by the water. 3. Oxygen gas. In the same manner, oxygen gas ivill be absorb- ed only with more energy, and it can be known in either case, which gas is in excess, by adding cautiously and in small quantities, either oxygen gas or nitric oxide ; if there is a residuum of either gas, there will be red fumes, on adding the other. If pure oxygen gas is em- ployed, and pure nitric oxide, in proper proportions over water, the absorption will be entire, and either gas, by adding the other, can be completely withdrawn from any mixture of gases. * They are generally, described as nitric acid, holding in solution variable quan- tifies of nitric oxide gas ; but the more correct view appears to be that in the text (and on p. 457 d.) I have always found that the fumes obtained by heating or dilu- ting the colored and fuming acids, are still more red and fuming, and indeed, it seems impossible that nitric oxide gas, should be in contact with nitric acid, without de- composing it, and taking enough of its oxygen, both to form and to leave nitrous acid, and the same effect will of course be produced by any combustible body. 462 NITROUS ACIDS. 4. Apparent caprice. (a.) It has been found, however, that the amount of oxygen ab- sorbed, is very different in different cases, and that it is influenced by the proportion in which the gases are mixed the time that elapses after they are mixed the size and form of the vessels the greater or smaller surface of the water over which, and the rapidity with which, the mixture is made ; and perhaps by other causes, such as agitation, temperature and order of mixture. (b.) According to Davy, when large quantities of nitric oxide gas are added to small quantities of oxygen in vessels of large diameter, the absorption is from 2 to 3 of nitric oxide for 1 of oxygen but if large quantities of oxygen are added to small quantities of nitric ox- ide gas in narrow tubes, the absorption is from 1 to 1.5 of oxygen in volume, and 2 of the nitric oxide gas. (c.) Surface of water. In general, the larger the surface of the water, the more rapid the absorption and therefore for want of time, less oxygen is combined ; in such case, more of the nitrous and less of the nitric acid will be formed. (d.) Cause of the variable absorption. Dr. Priestley, supposing that the nitric oxide and oxygen combined in only one proportion, very early employed them in eudiometry but he was ignorant of the fact that they combine in three proportions ; producing hypo-nitrous, nitrous and nitric acids, and that it is the varying production of one or another of these, and in different proportions, that creates the ap- parent caprice. (e.) Can the uncertainty be removed ? Dr. Henry, in his Ele- ments Mr. Dalton, in the 10th Vol. of the Annals of Philosophy, and Gay-Lussac, in the 2d Vol. p. 247, of the Memoires d'Arceuil, have given minute directions how this may be with more or less certainty effected. (/.) The process of Gay-Lussac, resembling the original one of Dr. Priestley, is worthy of being mentioned. In a wide jar, a common tumbler glass, or a tube not less than 1 J inch in diameter,* add 100 measures of nitric oxide, to 100 of com- mon air ; the absorption will be complete in half a minute or a min- ute ; the residue being measured in a graduated tube, will indicate a diminution of 84 measures out of the 200 ; one fourthf of the di- minution is oxygen, =21, and 8421 = 63, the proportion of nitric oxide gas that has been acidified. In applying this process to mixed gases, containing sometimes more and sometimes less than the oxygen in the air, the result was found to be correct. When the proportion of oxygen was greater than in * Murray. t The division by four seems to be founded on experience only, as no reason ap- pears why that number should give in this case a uniform result. NITROUS ACIDS. 453 the air, the quantity of nitric oxide should of course be increased, that it may be present in excess. (g.) The processs of Davy. Nitric oxide gas being largely and readily absorbable by the green sulphate, and the green muriate (proto,) of iron, in that condition will attract powerfully the oxygen of the air. The nitric oxide which is to be used, should be previously agita- ted in a tube, with one of these solutions, in order to determine whether there is nitrogen mixed with it. A strong watery solu- tion of one of the salts just named, the acid being also saturated with the oxide of iron, is next to be fully impregnated with the ni- tric oxide ; it should be kept in small divided portions in close vials, and applied as it is wanted, in Dr. Hope's Eudiometer, or in some other adequate instrument. The protosulphate of iron is preferred, but the solution is liable to spontaneous decomposition, the protoxide of iron attracting oxygen, both from the water and the nitric oxide, and the nitrogen of the lat- ter, combining with the hydrogen of the former, ammonia is gener- ated. Gas is said also to be emitted. See Davy's researches. Dr. Hare remarks, " as nitric oxide consists of a volume of nitro- gen and a volume of oxygen uncondensed, to convert it into nitrous acid which consists of a volume of nitrogen, and two volumes of ox- ygen, would require one volume of oxygen. Of course, if nitrous acid be the product, one third of the deficit produced, would be the quantity of atomspheric oxygen present. This would be too much to correspond with the formula of Gay-Lussac." " Supposing hyponitrous acid produced, only half as much oxygen would be required, as is necessary to produce nitrous acid ; so that instead of the two volumes of nitric oxide taking one volume, they would take only a half volume. The ratio of J in 2.j, is the same as 1 in 5, or one fifth, which is too little for Gay-Lussac's rule." " The formula recommended by Dr. Thomson, agreeably to which, J of the deficit is to be ascribed to oxygen gas, is perfectly consist- ent with the theory of volumes, and much more consonant with the results of my experiments, than that recommended by the celebrated author of that admirable theory."* * " The late Professor Dana ingeniously reconciled Gay-Lussac's statement, with the theory of volumes, by suggesting that a half volume of oxygen may take one volume of the nitric oxide, and another half volume of oxygen, two volumes. Vol. Vol. oxygen takes 1 oxide and forms nitrous acid. & oxygen 2 oxide and forms hyponitrous acid. Deficit due to oxygen is as 1 to 3 This result is evidently dependent upon the contingencies, which may prevent nitrous acid from being the predominant product." 464 NITRATES. Antiseptic properties of nitric oxide. Nitric oxide is thought to be an antiseptic. Dr. Priestly says that it renders bladders in which it has been kept imputresible. He tried many experiments on the preservation of meats by this gas. It generally saved them from putrefaction, and even stopped the progress of putrefaction already begun, but meats preserved in it had always a bad taste. NITRATES OF ALKALIES. A highly important and interesting class of salts ; the principal ni- trate, that of potash, having been known from remote antiquity. GENERAL CHARACTERS. 1. Soluble, and crystallizable by the cooling of the hot solution. 2. At a red heat, detonating with combustibles. 3. Decomposed by sulphuric acid, nitric or nitrous acid being evolved. 4. Producing chlorine and dissolving gold leaf, when decomposed by muriatic acid. 5. Totally decomposed by heat, and (nitrate of ammonia except- ed,) affording oxygen, mixed more or less with other gases. NITRATE OF POTASSA. 1. SYNONYMES. Nitre salt petre. The nitre of the scriptures is carbonate of soda.* 2. HISTORY. Known to the Romans; to the Chinese, from re- mote antiquity, and to the earliest chemists. (b.) Roger Bacon, in the thirteenth century, mentions it under the name of nitre. Although the subject of experiments for many centuries, Hooke and Mayhow, in the 17th century, having come very near discovering its real character, and Hales, in the beginning of the 18th, having extracted from it by heat, a great quantity of gas, its nature was not understood till the era of the modern chemistry. 3. PREPARATION. By saturating pure nitric acid with potassa, or its carbonate, and then evaporating and crystallizing. But it is not necessary to prepare it, as it is found abundantly in commerce, and sufficiently pure for most purposes in chemistry. 4. PHYSICAL PROPERTIES. (a.) The most common form of the crystals is that of the six sided prism, with a wedge-shaped termination. * The word nitre is mentioned only twice in the sacred writings, viz. Prov. xxv, 20. and Jeremiah, ii, 22. It has been already mentioned (p. 251, Soda,) that in the first intsance, allusion is made to an effervescence produced by an acid, and in the second to a detergent, or cleansing property ; neither of which belong to nitrate of potash, but both of them to the carbonate of soda the natron of the Greeks the nitrum of the Latins. With this understanding, the allusions are appropriate and beautiful ; otherwise unmeaning ; and this use is sustained by Pliny, and other ancient authors. The carbonate of soda is used largely in Great Britain in washing. NITRE. 465 (b.) More commonly, however, it is in crystalline, striated or channeled masses, which, when of considerable length, are called stick nitre. Sc.) Primitive form, a right rhombic prism incidence of the lat- planes, 109.50; ratio between one side of the base and the height, nearly : 1 : 0.48. Cleavage, " parallel to all the faces of the primitive, and also to a plane passing through the two short diagonals of the bases.* Nitre sometimes crystallizes in tables, or laminae, and in the prism of six sides, the two opposite ones are commonly broad ; the prism is sometimes terminated by 18 faces at each extremity, arranged in three rows, each having six faces, " as if three truncated pyramids were piled on each other." Sp. gr. 1 .9603. (d.) Taste, bitterish and cool. (e.) Brittle, and easily pulverized. CHIEF CHEMICAL PROPERTIES. 1. ACTION OF HEAT. This salt is anhydrous, and the small portion of water that is lodged mechanically between the plates of the crystals is easily dissipated by low ignition. (a.) It melts quietly into an oil-like liquid, and if cooled, congeals into a smooth white mass.f (b.) If the heat be increased to redness, we obtain oxygen gas, to the amount of about J of the weight of the nitre employed. The first portions are pure, but after about } part has been withdrawn, it is obtained more or less mixed with nitric oxide gas, and with nitrogen, which prevail most towards the end. (c.) If the heat be continued, the decomposition is entire, and po- tassa remains behind. If the salt be removed from thejire, when only a part of the oxygen gas has made its escape, it is found reduced to the state of nitrite. This is an easy process for oxygen gas, and answers very well, where we do not want it very pure. It is usually saved, when it is so good as to re-light a candle just blown out, but having a red wick. In a gun barrel or iron bottle, the salt should be melted at the up- per part first, and then the remainder by degrees ; otherwise there is danger of an explosion. One pound of nitre yields about 1200 cubic inches of oxygen gas. 2. ACTION OF WATER. (a.) Soluble in 7 parts of water at 60 Fahr. and in nearly its own weight of boiling water ;{ crystallizes on cooling. When mixed with * Levy, Quart. Jour, Vol. XV, 284, and Henry. t When melted, it is sometimes poured into moulds, and sold in round lumps like bullets, under the name Sal prunella. In this state it is preferred by jewellers, for heightening the color of their wares. J. G. \ According to Dr. Hope, it is soluble in 4 or 5 times its weight of water at 60. 59 466 NITRE. water it sinks the thermometer 19 during its solution. With ice it produces a still greater degree of cold. It is used in hot countries for cooling wine ; and the same portion of salt by evaporating and crys- tallizing, may be used again and again. 3. ACTION ON COMBUSTIBLES. The phenomena are brilliant and instructive. (a.) Action of charcoal. If into melted nitre, charcoal powder be thrown, it deflagrates ; and if 3 parts of nitre be employed to 1 of charcoal, the action is very energetic.* (b.) The product of the detonation of charcoal and nitre is always carbonic acid gas, mixed with nitric oxide and nitrogen, and probably with oxide of carbon, and carbonate of potassa remains. If igni- ted charcoal be held above melted nitre, it will burn with increased brilliancy, owing to the disengagement of oxygen gas. (c.) Jlction of sulphur. Thrown into a red hot crucible, in the proportion of 3 parts of nitre to 1 of sulphur, the latter burns away very completely and rapidly ; the products are sulphuric and sulphurous acid, sulphate of potassa, nitrogen and nitric oxide gas; the theory is obvious. It has been already mentioned, that in the manufacture of sulphuric acid a small quantity of nitre, usually about \ or {, is added to the sulphur, and it was known only that the sulphur was thus made to burn in such a manner as to form sulphuric rather than sulphurous acid. Now it is known that the sulphur decomposes the nitric acid of the nitre, by attracting such a proportion of its oxygen as leaves nitric oxide, which is displaced by the sulphuric acid. The nitric oxide meeting with oxygen in the air, forms red nitrous acid vapor ; in the mean time the greater part of the sulphur has become sulphurous acid ; the floor of the leaden chamber is covered with water several inches in depth ; so that aqueous vapor, sulphurous acid and nitrous acid, are present, in mixture. When the two latter are mingled in a dry state, there is no decomposition, but with the aid of water the nitrous acid transfers oxygen to the sulphurous acid and converts it into the sulphuric ; it thus becomes again nitric oxide ; again attracts oxygen and transfers it to the sulphurous acid ; and thus it becomes a vehicle for oxygen between the atmosphere and the sul- phurous acid. A small quantity of water enables the sulphurous acid and the nitrous to unite and form a crystalline solid, as appears when a drop of water is admitted into a globe containing the two agents in a dry state ; the same thing is supposed to happen in the leaden chamber, and the abundant water on the floor decomposing this com- * The Alchemists performed this deflagration, in a series of tubulated receivers, connected with each other, and with a tubulated retort, into which, when red hot, they projected their mixture of charcoal and nitre, immediately closing the aperture of the retort; their apparatus often blew up, but it sometimes escaped, and they then carefully collected the liquid condensed in the receivers ; this they called clyssus of nitre, and imagined that it possessed the most wonderful properties in alchemy. NITRE. 467 pound, enables the nitrous acid to oxygenize the sulphurous and form sulphuric, while the nitric oxide is again evolved, to perform the same function anew.* At Fahlun, in Sweden, they are enabled to manu- facture sulphuric acid in small leaden chambers, by placing upon the floor flat glass vessels containing nitric acid, which is decomposed by the sulphurous acid gas, thus evolving nitric oxide gas and answering the purpose of nitre, which is here omitted. This mode is less eco- nomical than the common one, but it produces a purer acid, contain- ing only . 1 or .2 of foreign matter, consisting entirely of sulphate of lead, while the common acid contains .5 or .6 of foreign bodies.f 4. GUNPOWDER, &tc. (a.) History. First known to the Chinese ; neither its European discoverer nor the period of the discovery is exactly ascertained ; attributed to Roger Bacon and to Swartz, a German, in 1320.J (b.) Composition. Gunpowder is an intimate mixture of nitre, sulphur and charcoal; the proportions vary in different manufacto- ries, and for different purposes ; but those employed in the Royal Mills of England, are 75 nitre, 15 charcoal, 10 sulphur.^ These are the proportions generally employed in other countries. The nitre, being the most expensive article, is sometimes stinted ; this of course injures the quality of the powder. Common gunpowder often contains not more than .50 of nitre. || (c.) Process in the Royal Mills of England. The ingredients are as pure as possible. The nitre is carefully purified. Common salt, uncombined potassa and sulphate of magnesia,1F are the most common impurities, and cause the powder to deliquesce. The charcoal is made in ignited iron cylinders, and the sulphur must be free from acid. The ingredients are separately pulverized ; then * Ann. de Chim. Vol. LIX, and Davy's Elements, Am. ed. p. 1. t Berzelius, Ann. de Chim. et de Phys. Tome IX, p. 162. The acid made near New York, contains only .1 or .2 of foreign matter. J. T. $ Gunpowder was not known in Europe before the end of the thirteenth century, probably not before 1320 ; it was well known in the middle of the fourteenth cen- tury, and cannon were used in Germany before 1372 ; first used by the English at the battle of Agincourt, A. D. 1415. See Nicholson's Journal, 8vo. series. In France 75. nitre, Sweden 75. Poland 80. Italy 76.5 9.5 sulphur, 16. 12. 12.5 15.5 charcoal, 9. 8. 12.5 100. 100. 100. 101.5 Dr. Watson's essays. At present, both in England and France, 7 JVitre. Charcoal. Sulphur. common powder contains $ " - 75 12 12 Shooting powder for the sportsman, 78 12 10 Or, 76 15 9 Powder for blasting in mines and quarries, 65 15 20 M. Bouchet's patent powder, 78 12 9 The shooting powder is glazed by the mutual friction of the grains in a barrel, revolving on an axis ; the proportion of nitre and charcoal is large, to insure its quick action. Gray's Op. Chem. p. 495. || Black, Vol. I, p. 432. IT Id. 468 NITRE. mixed, moistened and pounded in mortars, or ground, to the consist- ence of a thick paste, by large wheels of stone or cast iron, shod with copper. This mass is granulated, by passing it through a series* of parchment or wire sieves, turned by cranks and covered by a heavy piece of wood, usually lignum vitae, whose motion and pressure force the powder through, in the form of grains. It is next sifted, and then dried, in drawers with canvass bottoms, by hot cylinders or stoves of iron placed on one side of the apartment, of which the shelves occupy the other three ; or, as now practised in some manu- factories, by steam, or by warm air thrown in from another apartment. f Gunpowder, although frequently injured by dampness, can be pre- served a long time, as appears from the fact that, in 1782, "there were discovered, at Purfleet, (England,) some barrels of very small grained powder, manufactured by Sir Polycarpus Wharton, surveyor of the ordnance in Charles the second's reign. "J (d.) Theory of its combustion. Gunpowder is merely a mechan- ical mixture; no chemical action takes place between its ingredients at common temperatures.^ Jit a red heat the oxygen of the nitre acts on the sulphur and carbon, with which it is intimately blended ; the combustion is therefore intensely rapid and violent, and it happens equally in a vacuum, in a mephitic gas, or in a dry cavity under water, and quite independently of air or of any foreign aid. The sulphur produces a rapid combustion, the charcoal contributes largely to the formation of gas, and a good gunpow r der cannot be made without both these combustibles. The power is produced by the sudden formation and disengagement of a vast volume of gases, greatly ex- panded by the heat. Gunpowder , wet and crushed in the manner of a squib, maybe safely although imperfectly burned in a gun or pistol barrel, and the gases may be caught in an air jar filled with water. They are prin- cipally carbonic acid, nitrogen and nitric oxide ; sulphurous acid gas and sulphuretted hydrogen, and some ammonia ; perhaps also carbu- retted hydrogen and oxide of carbon. Sulphuric acid is produced and forms sulphate of potassa, which with some sulphuret, a little carbonate of potassa and charcoal, remains. The smell of sulphu- retted hydrogen gas is perceived in fire arms, especially when in the act of being cleaned. (e.) The volume of gases produced from gunpowder is, at 60, 250 times, and at the moment of discharge 1000 times, greater than that * Said to be, in the Royal Mills of England, 24 in number. t For an account of the mode of making gunpowder in France, see Thenard, 5th ed. Vol III, p. 251. t Gray's Op. Chem. See Am. Jour. Vol. XVII, p. 132, where it appears that it may sometimes ex- plode in consequence of the heat given out by sudden compression of air, if not of its own ingredients. NITRE. 469 of the powder.* As each additional volume of gas exerts a force equal to that of the atmosphere, 1000 X 15 = 15000 pounds on a square inch, which will project a bullet with a force of 2000 feet in a second, j- The general rule for powder for heavy shot is one third of the weight of the shot, for lighter artillery one fourth. Count Rumford found that 18 grains of gunpowder raised a weight of 18000 Ibs. The goodness of gunpowder is judged of by the force with which it impels projectiles ; it is measured in an instrument called an eprouvette. A rude analysis of gunpowder is easily effected by dis>- solving the nitre by water and then subliming the sulphur out of the charcoal. J (f.) Pulvis fulminans or fulminating powder. $*It is made of 3 parts of nitre, 2 pearl ashes and 1 sulphur, well dried and thor- oughly mixed, by gentle trituration in a warm mortar. It is placed in a spoon and heated by a candle or the embers till it gradually blackens and melts, when it explodes, with a sharp and loud report. If the heat is raised too high or too rapidly, the powder is decompo- sed and does not explode. (g.) Theory. Similar to that of gunpowder, but the explosion happens only when all the mass is melted, and the gases are disen- gaged instantaneously, whereas the grains of gunpowder || burn suc- * Vide Robbing' Essay on Gunnery, and Nich. Jour. IV, 258. t Murray. t For an accurate method by Gay Lussac, see Ann. de Ch. et de Phys. XVI, 434. This powder is used by sportsmen for priming, to insure the discharge of their fowling pieces. For this purpose it is slowly melted over the fire, care being taken to stir it frequently. When the fusion is complete, it is taken off and stirred until cool, which leaves it in the state of a fine powder. It must be kept in close vessels, since it rapidly attracts moisture from the atmosphere. || Composition formerly used for firing artillery is 60 nitre, 40 sulphur and 20 gunpowder; rammed into a small pasteboard cylinder. Chinese blue lights for signals, 28 nitre, 7 sulphur, 2 arsenic, & apart rice flour, and water enough to knead them into a stiff paste ; the water and flour retard the combustion ; this paste is rammed into little earthen pots and kept in pitched cloths. Fire balls to be thrown into an enemy's camp, 40 nitre, 15 charcoal, 3 pitch and a little sulphur. It is not consistent with the object of this work to enter into the details of pyro- techny, which may be found in many works, Gray's Op. Chemist ; Cutbush, in Am. Jour. Vol. VIII. p. 118, &c. The following may be taken as examples of prepa- rations for rockets. Powder for rockets. Rockets of one or two ounces 8 parts gunpowder, 1 fine soft charcoal. Somewhat larger 10 ounces gunpowder, 3 saltpetre, 3 charcoal. Of five or six ounces weight 37 ounces gunpowder, 8 saltpetre, 2 sulphur, 6 charcoal, 2 iron filings. Ten to twelve ounces weight 17 ounces gunpowder, 4 saltpetre, 3 sulphur, 1 charcoal. One pound weight 16 ounces gunpowder, 1 sulphur, 3 charcoal. Four to seven pounds weight 31 saltpetre, 4 sulphur, 10 charcoal. Still larger 8 pounds saltpetre, 1| sulphur, 2| charcoal. The contents of a Congreve rocket, analysed by Gay Lussac, were in the propor- tion of 720 nitre, 16 charcoal and 234 sulphur. A rocket made upon this result had the same properties with the English. 470 NITRE. cessively, although rapidly.* This powder has little effect on a ball when fired in a gun. (A.) Another pulvis fulminans has been recently proposed, consist- ing of nitre 2 parts, neutral carbonate of potassa 2, sulphur 1 and marine salt 6, all finely powdered. It explodes with great energy. f (i.) Phosphorus. If a mixture of phosphorus and nitre be struck forcibly with a hot hammer, a violent detonation takes place, and jets of flaming phosphorus dart out laterally with danger to the spectators. It is not a proper experiment before a class. (/.) Hydrogen gas. If a stream of this gas be passed, by a bent tube, through melted nitre, the salt is decomposed with detonation, and water formed ; the experiment requires caution. (k.) Powder of fusion 3 parts nitre, 1 sulphur, and 1 fine saw dust, thoroughly mixed. If this mixture is surrounded by a rim of sheet copper, and set on fire, the copper instantly melts, being con- verted at the same time into a sulphuret. (/.) White flux equal parts of nitre and crude wine tartar, mixed and deflagrated in a red hot crucible. (m.) Black flux 1 part nitre and 2 tartar, deflagrated in the same manner ; it is a mixture of carbonate of potassa and charcoal. The substances, under ;, k, and Z, (especially the last,) are em- ployed as fluxes, and for other purposes in small metallurgic operations. 5. ACTION OF ACIDS. Decomposed by phosphoric and boracic acids, aided by heat. Muriatic acid with heat, evolves nitrous acid and chlorine, a mix- ture with which the alchemists, used to dissolve gold. (See chlorine.) Sulphuric acid. The action of this acid has been mentioned. 6. COMPOSITION. The equivalent of nitrate of potassa is 102 ; it being an anhydrous salt, is composed of 1 proportion of dry nitric acid 54-f 1 proportion of potassa 48 = 102. For 100 parts, of the acid 52,94 -f alkali 47.06 = 100. In full detail, its constitution is, Oxygen 5 proportions, 5x8=40+ 1 prop, nitrogen, 14 = 54 Potassium 1 proportion, 40 -}-l proportion oxygen, 8 =48 102 Thus we see how in a complex compound the numbers expressing the combining powers of all the principles are united, according to an admirable law. * Vide Black's Lectures, 1, 433, note 32. The difference is seen when a train is fired on a board and another between two boards with weights upon them : the ra- pidity of the combustion is greatly increased by the reaction of the flame, as in the chamber of a gun. I Ferussac's Bulletin, Aout, 1828. 9 NITRE. 471 7. SOURCES OF NITRATE OF POTASSA. (a.) Tliere are some soils which contain so much of it that they are catted saltpetre grounds. In Italy and Spain, and in the latter es- pecially, it is found, even in the dust of the roads ; and when the crops of wheat fail, the farmers frequently obtain an indemnity, by lixiviating the soil for nitre.* In India, in China, and in the eastern parts of Persia, saltpetre earths are very common, and the salt even effloresces on the surface ; and from these countries a great part of the nitre used in Great Britain and America is brought. It is found in pasture grounds, near Lima, in South America, and in Podolia, a province of Poland, in little hillocks, being the ruins of habitations, in a plain country, formerly populous. (b.) Nitre is usually found in places where there has been an accu- mulation of animal and vegetable matters, or an abundance of animal effluvia, having free communication with the air, and with alkalies or lime ; as in the ruins of old houses, in the earth of cellars, and sta- bles, and in pigeon lofts, in which places it often effloresces, pro- vided the walls be of lime, and in general in low situations, which have been frequently impregnated with animal or vegetable fluids in a putrescent state. Nitre is produced in grounds much trodden by cattle, and frequently impregnated with their excrements. Ure. In such places the nitre is constantly reproduced, after being remov- ed, especially if the place have a northern exposure. In France the richest part of the vegetable mould is often found to contain nitre,f and in this country, such sources were resorted to, to afford nitre during the war of the revolution. The earthy floors of the tobacco houses were found to be particularly rich in this salt. (c.) Nitre is also found in marly and calcareous grounds ; or rather another salt is found in such places, greatly resembling nitre, and into which it is easily con verted. J (d.) In the calcareous caverns of the Western and South Western States of the United States of America, there are vast resources for manufacturing nitre, derived from the nitrate of lime, found in these caves. It is changed into saltpetre by wood ashes one bushel of earth, in some instances, yielding from 3 to 10 pounds of the salt. In Kentucky, there are masses of ready formed nitre, mixed in sand- stone rocks. (e.) In vegetables. Nitre is found in borage, bugloss, parietaria, hemlock, and the sunflower ; and in the dried branches of this last, * Black, Vol. II, p. 444. t They prefer the earths that are at a little distance from the surface of the ground ; they are distinguished by their sharp taste ; it is a rich nitre ground that contains 5 per cent. t The wells of great cities also afford this salt. In Peale's Museum, in Philadel- phia, is deposited a quantity of nitre, obtained along with other salts, during the analysis of the pump water of that city. 472 NITRE. as well as of other plants, it is sometimes found crystallized in nee dies. It exists in tobacco ; and sometimes the stalks of this plant contain so much nitre that when dried, they will burn like a squib. The nitre in plants appears to be derived from the soil. How is nitre formed ? (/.) During the decomposition of bodies containing nitrogen, this principle has been supposed to combine with the oxygen of the air, to form this acid, and this unites with any proper base. Lime is often present, and forms in this manner nitrate of lime, which by a substitution of the alkali, from weeds, ashes, &c. is chang- ed into nitrate of potassa. (g.) There seems great reason to believe that the atmosphere is, to a certain extent, converted by electrical agencies, into nitric acid, as nothing more is necessary, than that the elements should unite in nearly the reversed proportions in which they exist in the air. There is a popular impression that thunder and lightning, and also clear frosty weather, are favorable to the production of nitre. That its production depends upon atmospherical phenomena, seems to be proved from the fact, that the lixiviated saltpetre earth becomes im- pregnated again in a year or or two, by exposure to the air. (h.) Jlrtificial nitre beds. Most of the nitre used on the continent of Europe, is produced from composts, formed of garden mould, lime rubbish, ashes, and marly earths, and animal and vegetable sub- stances, of every description. The bed is screened by a thatched roof, through which the air has access, although it does not circulate very freely. The heap is frequently stirred, and moistened from time to time with the drainings of the barn yards, and of the kitchen. To favor the process, situations are sometimes chosen on the de- clivities of hills. Moderate light, moderate moisture, a temperature from 65 to 90, and (as asserted,) additions of common salt, pro- mote the production of nitre. 8. EXTRACTION. The nitrous earths, mixed with quick lime and ashes, are placed in large vats or barrels, with perforated bottoms, cov- ered with straw, and sometimes there is a second bottom, below the first, with a stop cock between. Water dissolves the nitrates, the ashes decompose the nitrates of lime and magnesia, and the nitrates of potash, and other soluble salts, are drawn off below. In the re- fining of nitre, eggs, milk, soap, and twigs of euphorbia, are used. The solution is then concentrated by heat, and suffered to crystallize. It is at first a dirty mass with many impurities, particularly common salt. From these it is purified by successive solutions, evaporations, and crystallizations. The earthy bases are precipitated by potassa, or ashes. Such salts as are less soluble than nitre, are separated during the evaporation, and such as are more soluble, are drawn off with the mother water. These operations are repeated three or four NITRATE OF SODA. 473 times before the nitre is sufficiently pure for the manufacture of gun- powder. 9. USES. Nitre* is an important substance. It is nearly indis- pensable in the manufacture of the nitric and sulphuric acids. In medicine it is given as .a diuretic, and cooling remedy ; it is a pow- erful antiseptic, and is much used in the salting of beef, to the fibre of which it gives a fine red color, and great firmness. f It is given only in inflammatory states of the body, 5 to 20 grains at a time, and not exceeding 1 or lj drachms in a day ; it di- minishes heat and vascular action, and is cathartic. In a dose of an ounce, it is a violent poison, and has often been sold and given by mistake, for sulphate of soda. It can always be distinguished by throwing it on burning coals, when if genuine, it will deflagrate ; and by the emission of fumes of nitric acid, when sulphuric acid is added to it. In Chemistry, it affords oxygen gas ; it imparts oxygen to many substances which- cannot be made to combine with it in any other way, as to metallic titanium, which resists even nitro-muriatic acid. It is employed in metallurgic operations, in the assaying of ores, and it is used to determine, by deflagration, the proportion of carbonace- ous or other combustible matter contained in a soil, in coal, &c. It has^changed the whole art of war ; and in naval conflicts, gunpowder is, and must remain, the principal means of annoyance. NITRATE OF SODA. 1 . NAME AND PREPARATION. Formerly called cubic nitre, from the obtuse rhomboidal form of its crystals. It is prepared by saturating soda, or its carbonate, with nitric acid; it is not known in the shops. 2. PROPERTIES. (a.) Taste more bitter than that of nitre, but its general proper- ties very similar. J^.) Rather more soluble, requiring only 3 parts of water at 60, less than its own weight at 212. (c.) Effected by heat, acids and combustibles, in the same manner as nitre, but is less fusible. (d.) Slightly deliquescent, and therefore unfit for making gunpow- der. 3. COMPOSITION. According to Dalton, 57.6 and 42.4 base, but Dr. Henry remarks that these numbers do not agree with equivalent proportions. On the authority of Wenzel, quoted by Brande,{ it is * For the sake of brevity, I have generally, in this article, used the word nitre in- stead of nitrate of potassa. t Muscular fibre after being thoroughly impregnated with salt, especially with the addition of nitre and dried, becomes nearly imputrescible. In the Leverian museum, in London, I saw beef in 1805^ a remnant of the provisions with which Lord Anson performed his circumnavigation, from 1739 to 1744. \ Tables of definite proportions. 60 474 NITRATE OF AMMONIA. composed of 1 proportion of soda 32, and \ of nitric acid 54 = 86, its equivalent. 4. USES. Proust suggested that, for economy, it might be em- ployed in artifical fire works, and that 5 parts of it, with 1 of char- coal and 1 of sulphur, will burn three times as long as common gun- powder, and of course make a more enduring exhibition. When thrown on a shovel full of burning coals it produces a peculiar orange yellow flame. 5. NATURAL SOURCES. It had been thought that this salt was un- known as a natural production, but it has been, within a few years, discovered in Peru, in the district of Atacama, near the port of Yquique ; it is in strata of variable thickness, under clay, extending fifty leagues, and in some places it is quite pure. The proprietor had, at the date of the account, obtained from it 40000 quintals.* NITRATE OF AMMONIA. 1. HISTORY AND NAME. Long known ond formerly called nitrvm flammans and semivolatile. Our accurate knowledge of its properties is derived, principally, from Berthollet and Davy. 2. PREPARATION. (a.) Bring into contact, in a glass globe with two necks, the vapor of strong nitric acid and ammoniacal gas, (in an apparatus like that on p. 385,) when nitrate of ammonia will be precipitated, at first concrete, but which will soon deliquesce and then crystallize in prisms. (b.) The best mode is to saturate diluted nitric acid with con- crete carbonate of ammonia; evaporate with a gentle heat and crys- tallize, f If the evaporation has been performed between 70 and 100 Fahr. the crystals are hexahedral prisms crowned by long hexahedral pyramids; if at 212, they are in silky fibres; if at 300, the solution concretes without crystallization. 3. PROPERTIES. (a.) Taste, bitter and cool. Sp.gr. 1.5785. (b.) Soluble at 60, in twice, and at 212, in half its weight of water ; f deliquescent. (c.) The acids, especially the sulphuric, decompose it. The fibrous or prismatic crystals melt at 230, or below 300 ; ebullition, but without decomposition, commences between 360 and 400 ; decomposition begins at 450, and between that and 500, it affords the pure protoxide of nitrogen. * Ann. de Chim. et de Phys. XVIII, p. 442, and Thenard, III, 265. t A few embers, under an earthen dish, are sufficient: hot coals would volatilize and decompose the salt. The common aquafortis need not be diluted. The solu- tion is in a good state to crystallize, when a twitching pellicle forms on the surface, and when a knife blade dipped in the solution and waved in the air is speedily cov- ered with small crystals. t Dr. Hope says, that it dissolves at 50, in its own weight of water, and gener- ates 46 of cold. NITRATE OF AMMONIA. 475 (d.) The compact nitrate suffers no change below 260 ; from 275 to 300, it sublimes slowly, without suffering decomposition or becom- ing fluid; at 320 it melts, and from 340 to 380, is decomposed partly sublimed, and yields the above mentioned gas.* If the tem- perature does not rise above 500, the salt is ivholly decomposed and converted into nitrous oxide and water, in the proportion of about 3 parts of gas to 1 of water. 100 grains of the salt afford 84 cubic inches of the gas. The hydrogen of the ammonia, ivith one proportion of the oxygen of the nitric acid forms water ; the remainder of the oxygen and of the nitrogen, forms the nitrous oxide gas. (e.) At 600 and above, this salt explodes by the reaction of its own elements, being converted into nitrous acid, nitric oxide gas, wa- ter and nitrogen gas. (/.) On red hot iron or any other ignited body, it deflagrates beauti- fully with a rich yellow flame, and exhibits a singular instance of a burning saline body ; the reaction of the oxygen of its acid with the hydrogen of its base, produces the rapid combustion. Hence its old name of nitrum ,flammans. 4. USES. They are limited to the formation of nitrous oxide, and to some cases in chemistry, when we wish, by heat, to oxidize substances, and to have no residuum ; the nitrate of potassa always leaves that alkali free or combined, but the nitrate of ammonia when deflagrated, leaves nothing behind. 5. ALKALIES AND EARTHS. Baryta, strontia, potassa, soda, and lime, by trituration in the cold, attract the acid and liberate the am- monia. 6. EQUIVALENT NUMBER AND COMPOSITION. This salt is com- posed of acid, 1 proportion, 54, ammonia, 17 = 71, for the dry salt, and according to Berzelius, 1 proportion of water 9, for the prismatic variety, =80. The proportions of Berzelius, are for the 100 parts acid, 67.625, base, 21.143, water, 11.232 = 100.00f The composition according to Davy, is for the Prismatic crystals, 69.5 Fibrous, 72.5 Compact, 74.5, acid. " " 18.4 " 19.3 " 19.8, ammonia. " " 12.1 " 8.2 " 5.7, water. 100. 100. 100. * According to my experience, the compact nitrate, if not very carefully dried, (which is difficult on account of the fluid imbibed by its pores,) is apt to puff up in. the retort, with a violent effervescence of aqueous vapor ; while the dry prismatic nitrate is perfectly manageable, and is decomposed with great steadiness and unifor- mity. t Ann. de Chim. T. LXXX, p. 182. 476 NITROUS OXIDE. NITROUS OXIDE PROTOXIDE OF NITROGEN. Remarks. It has already been stated that this oxide has been re- served for the present place, because it will be best understood in con- nexion with the salt from ivhich it is always obtained. Otherwise it would naturally have been introduced after nitrogen and before its deutoxide, the nitric oxide gas. 1. HISTORY. Discovered by Dr. Priestley, in 1772, by whom it was called dephlogisticated nitrous air ; Mr. Davy examined it with more particular care, and called it nitrous oxide. 2. PREPARATION. (a.) The nitric oxide can be converted into the nitrous oxide, by the action of various substances which will abstract half the oxygen ; they will be mentioned in an appendix to this article. (b.) But the only eligible method is by the decomposition of the nitrate of ammonia by heat.* (c.) The solid nitrate, which should be as dry as possible, should not Jill more than one quarter the body of the retort a good Ar- gand's lamp or a few live coals are sufficient for the decomposition, which is known to be proceeding well, when the melted materials boil quietly and emit small bubbles ; a thin snowy vapor revolving in the retort, and no red fumes appearing. If the heat is raised too high, the bubbles will be very large, and a reddish tinge in the retort will indicate the formation of nitrous acid vapor. 3. THEORY OF THE DECOMPOSITION AND EQUIVALENT NUMBER. (.) The nitrate of ammonia is composed entirely of the pondera- ble part of gases, and the effect of the heat is so to rearrange them, by the exertion of new affinities, that the solid is converted, wholly, into aerial products ; steam, and nitrous oxide. (b.) The nitrate of ammonia is composed of one proportion of ni- tric acid 54, and one of ammonia 17=71. The acid is composed of nitrogen, 1 proportion, 14, and oxygen, 5 proportions, 8x5=40=54. The alkali consists of nitrogen, 1 proportion, 14, and hydrogen, 3 proportions, 1x3=3=17. (c.) The representative or equivalent number of nitrous oxide is 22, made up of I proportion of nitrogen 14, and 1 of oxygen, 8=22. (of.) During the decomposition, 71 grains of the salt afford 27 of water, consisting of 3 proportions, viz. 9x3, and water is composed of I proportion of hydrogen I, and 1 of oxygen, 8=9; there are produced also, 44 grains of nitrous oxide, consisting of two propor- tions, or 22x2. * In addition to what has been already said under the nitrate of ammonia, we will observe that, notwithstanding the statements under 2, (c, d, and e,) it is not necessa- ry to use a thermometer to regulate the decomposition of this salt. NITROUS OXIDE. 477 The three proportions of water consist ofoxy. 24+hydrog. 3=27 two " nitrous oxide 1 6 -\-nitr og. 28=44 71* (e.) This view supposes the nitrate of ammonia to be anhydrous, and all the water that appears during the decomposition, to be gener- ated and not evolved. It is a beautiful example of the arrangement of principles in defi- nite proportions, so that with a complete decomposition and a forma- tion of new products, there is no loss. 4. PROOFS OF THE PURITY OF THE GAS. (a.) When the mouth is applied to a bottle of it, a distinctly sweet- ish taste is perceived, without any corrosiveness or peculiar smell.f (I.) Entirely absorbed by agitation ivith about its own volume of water, that has been previously boiled, and become cold without the access of air. The saturated water will have a sweetish taste, and faint agreeable odor, and the gas will be expelled, unaltered, by boil- ing ; the solution does not redden the vegetable blue colors, or pro- duce any exhilirating effects. (c.) JVb red fumes are produced by mingling this gas with oxygen gas or common air, which would happen if nitric oxide gas were present ; (d.) Nor, on the other hand, does nitric oxide gas produce any change of color or absorption, as it would do if free oxygen gas were mingled with it. (e.) It is not diminished by agitation with green sulphate of iron, which would be the fact if nitric oxide were present. (/.) It is not acid. 5. PHYSICAL, PROPERTIES. (.) Colorless transparent. (b.) Specific gravity, 1.5277, common air being 1. (c.) Weight for 100 cubic inches of the gas at medium tempera- ture and pressure, 46.596 ; this appears also from its constitution, which is nitrogen 100 cubic inches, weighing 29.652 grains, and ox- ygen, 50 cubic inches, weighing 16.944 grains, =46. 596, J the 150 volumes of gases being condensed into 100. * Turner. t Provided it has stood long enough over water to 'absorb any saline or acid vapor, for which one hour and sometimes half an hour is sufficient. t Dr. Prout, as has been already observed, introduced the rule that the atomic or representative number of a gas multiplied into the specific gravity of oxygen, if that be unity, or of hydrogen, if that be unity, will give the specific gravity of the gas in question thus, if oxygen be unity, then the representative number of nitrous oxide is 2.75 and 2.75 X by .555 =1.526 or the equivalent hydrogen being unity, is 22, which X .0694 = 1.526. 478 NITROUS OXIDE. 6. ACTION OF COMBUSTIBLES. (a.) JL lighted candle burns, with increased brilliancy in this gas, and with a white flame, which, before extinction, appears edged with blue. (b.) Dr. Turner states, that an extinguished candle retaining " a red wick," is lighted again by immersion in this gas.* (c.) Sulphur burning with a blue flame, is immediately extinguish- ed; but with a white flame, that is, at a higher temperature, it hums vividly, and the flame becomes rose-colored. (d.) Phosphorus may be melted, and if touched with a red hot wire, it may be even sublimed in this gas without burning ; but if touched with a white hot iron the phosphorus burns almost explosively. The jar should be strong, not more than one eighth filled with the gas, and the wire well curved, so that it may be expeditiously withdrawn ; not unfrequently the jar bursts in the experiment. The combustion ceases when about one half the gas is consumed, and the product is phosphoric acid, nitrogen being evolved. (e.) If the phosphorus be already on fire when it is introduced, it continues to burn but with increased splendor, greater than we should infer from the proportion of oxygen which the gas contains. (f.) Charcoal, vividly ignited, is said to burn in this gas more bril- liantly than in common air,f and if properly managed to produce, for each measure of nitrous oxide, one of nitrogen, and half a meas- ure of carbonic oxide, equivalent to half a measure of oxygen.f (g.) Hydrogen gas, mingled, volume for volume with this gas, ex- plodes by the contact of flame, and by its acid, the nitrous oxide is decomposed by spongy platinum at the common temperature. With 40 hydrogen to 39 nitrous oxide, there remains only nitro- gen, and if the proportion of hydrogen is smaller, some nitric acid is produced. In general, the products of the combustion of hydro- gen in nitrous oxide, are the same as in oxygen, or in common air, and nitrogen remains equal in volume to the original gas. (h.) Pyrophorus does not take flre spontaneously in this gas, but it takes fire if touched with an iron strongly heated, but not to igni- tion. It is the only body which burns in this gas, at a temperature below ignition. Si.) Phosphuretted hydrogen flashes in this gas. j.) Potassium and sodium decompose it below a red heat, evol- ving nitrogen, and forming alkali. * This has never succeeded with me. t In this experiment I have never been able to succeed. * Henry. Ibid. NITROUS OXIDE. 479 (k.) "An iron wire burns in this gas nearly as well as in oxygen gas." 7. COMPOSITION. (a.) The equivalent number of this gas has been already stated to be 22. (b.) As two volumes of nitrous oxide require, for decomposition, two volumes of hydrogen, which can saturate only one volume of oxygen ; it follows that the residuary nitrogen, which is found to be expanded into two volumes, was combined with 1 measure of oxygen, and that the three were condensed into two ; or one volume of ni- trogen combines with half a volume of oxygen, and the volume and a half occupy one volume, as before stated under specific gravity ; one volume of nitrogen, or 1 proportion, is 14, and half a volume of oxygen is 8, and 8 + 14=22. (c.) Ammoniacal gas 100 measures -\-15Q nitrous oxide, produce a combustible mixture ; the oxygen of the oxide uniting with the hy- drogen of the ammonia. (d.) Olejiant gas burns, when mingled with this gas and ignited. (e.) Carbonic oxide 1 vol. -{-nitrous oxide 1 vol. fired by the elec- tric spark, over mercury, produce 1 vol. carbonic acid, and 1 vol. of nitrogen. This method of analysing nitrous oxide was introduced by Dr. Henry.* Let 1 100 measures of nitrous oxide, proved, by agitation with green sulphate of iron, to be free from nitric oxide, be fired with a slight excess, say 110 or 115 measures of pure carbonic oxide, f and 100 measures of carbonic acid will be obtained. (f.) If this gas be electrized in a tube over mercury, it is partially decomposed, being converted into nitrous acid, and common air, and a similar effect is produced by passing it through a thoroughly ignited porcelain tube, glazed within and without. 8. CONDENSATION OF NITROUS OXIDE. (a.) Effected by Mr. Faraday,^ by means similar to those that have been already described in the case of other gases. Some nitrate of ammonia, rendered very dry, by a partial decomposition by heat, in the air, was placed in the end of a recurved tube, sealed at both ex- tremities ; the end containing the salt was then heated, while cold was applied to the other end, by a mixture of ice and snow. (b.) Two fluids were obtained, the one water, with a little nitrous, acid and oxide, and the other, floating upon it, being very mobile > limpid, and colorless, was the liquified nitrous oxide. * Ann. of Phil. N. S. Vol. VII, p. 299. t Previously washed with a solution of caustic potash. t Phil. Trans. 1823, p. 195. 480 NITROUS OXIDE. (c.) It was so volatile } that the warmth of the hand, although un- der so great a pressure, converted it into vapor, and it boiled readily by the difference between and 50. In refractive power it was in- ferior to any known fluid, not excepting even the other condensed gases. It remained fluid at 10. When the tube was opened in the air, the fluid instantly burst into gas, and another tube being opened under water, the fluid rushed again into the form of gas, which was collected. (d.) To estimate the pressure, a trumpet shaped capillary tube, containing a globule of mercury, after being graduated, by the pas- sage of the mercury through the different parts of the tube, was seal- ed at one end, and introduced into the larger tube, before it was closed. The movement of the mercury indicated the pressure, and when it became stationary, the force, at 45, appeared to be equal to 50 atmospheres, and 50 X 15 = 750 Ibs. upon the square inch. At 32 the pressure was 44 atmospheres, and 15 X 44 =660 pounds on the square inch ; 12 degrees of temperature having added to its pressure 7 atmospheres, or 105 pounds, or nearly 9 pounds for each degree. Mr. Faraday always subtracted 1 atmosphere for the air in the tubes when the experiment began. 9. EFFECTS ON ANIMAL LIFE. (a.) Warm blooded animals, confined in nitrous oxide speedily die* and fishes expire in water impregnated with it.f For many years after its discovery, no suspicion was entertained that it was res- pirable. (b.) This gas is not only respirable, but it is the most powerful stimulant known. ,f (c.) This was first ascertained by Sir H. Davy, in a series of trials on respiration, some of them very hazardous, which he made upon his own person ; the results may be found in his Researches, from which the following passage is extracted, p. 487. " Having previously closed my nostrils, and exhausted my lungs, I breathed four quarts of nitrous oxide from and into a silk bag. The first feelings were similar to those produced in the last experi- ment, (giddiness) ; but in less than half a minute, the respiration be- ing continued, they diminished gradually, and were succeeded by a sensation analogous to gentle pressure on all the muscles, attended by a highly pleasurable thrilling, particularly in the chest and the ex- * Dr. Ure, (Diet. 2d Ed. p. 619,) says that mice die more speedily than when im- mersed in nitrogen, hydrogen, or carbonic acid. t The blood acquires a purple color in consequence of the respiration of this gas, and after death the muscles of animals are found to have lost their irritability. t It is said that if a little sulphate or muriate of ammonia be mixed with this ni- trate, this salt will not afford an exhilirating gas. Ure. NITROUS OXIDE. 481 tremities. The objects around me became dazzling, and my hear- ing more acute. Towards the last inspiration the thrilling increased, the sense of muscular power became greater, and at last an irresist- ible propensity to laughter was indulged in ; I recollect but indis- tinctly what followed ; I know that my motions were various and violent. These effects soon ceased after respiration. In ten min- utes I had recovered my natural state of mind. The thrilling in the extremities continued longer than the other sensations." (d.) " The effects of the nitrous oxide on the human system are analagous to a transient, peculiar, various, and generally very viva- cious ebriety." Dr. Hare. (e.) It differs from all other diffusible stimuli in not being attend- ed by any subsequent depression ; in general, on the contrary the violent effects gradually subside into cheerfulness, and manifest them- selves by gayety and activity, which sometimes continue for hours, and even in particular cases for days. (f.) The general dose is from 4 to 6 or S quarts of the gas. JIX (g.) It is breathed into and from a silk bag, or an air jar furnished with a stop cock, of a wide bore, or with a arge bent tube, as in the annexed cut : and the action ofl the lungs may be relieved by having an assistant to hold the jar over the well of the pneumatic cistern, so that it, may rise and fall; a small gasometer is still more con-= venient. (h.) The effects are not always agreeable. Some persons are not excited, but are rather depressed, and also fatigued, by the constrained mode of breathing. Some become faint and fall as in a Jit or swoon; but they in general soon recover, as if from a troubled dream or a turn of nightmare ; some are rendered apparently, apoplectic, and others are thrown into a temporary, but often violent delirium, and in such cases the subsiding feelings are disagreeable. (i.) There is good ground for caution, and it would now be proper that the practice of breathing the nitrous oxide should be dis- continued, except for medical purposes.* Remark. Although we can offer no satisfactory theory to account for the action of the nitrous oxide, it cannot but be regretted, that so powerful a stimulus both of our physical and inellectual powers should * Among multitudes to whom I have administered this gas, about 6 out of 8 have been agreeably affected ; but there has been very great variety in the appearances, influenced, in most cases, apparently, by the physical and moral temperament of the subject. I have seen not a few cases attended by symptoms so violent and alarming that I have been very glad when they have subsided. I have personally known no instance of fatal effects, either immediate or remote ; but some have thought themselves injured for a considerable period, and it has always been a subject of anxiety lest some idiosyncrasy should,) produce an unhappy termination. The ex- perience of Thenard, Vanquelin, and their companions was altogether painful. See Thenard's Chem. 61 482 NITROUS OXIDE. remain a subject of mere curiosity or merriment. Differing from every other stimulus, in not producing depression correspondent to the excitement; why should it not be employed as a general tonic and as a comforting reviving remedy ? In cases of great debility, it clear- ly ought not to be used in such doses, as to produce violent effects, but rather such as are gentle and longer continued, which might then be more frequently renewed. It would be proper to begin with di- luting the gas one half or more, with common air, and the strength and quantity might thus be graduated to the state and strength of the patient. A larger gasometer being employed, the desired dose might be drawn off into a smaller one, and the gases being used over the same water, there need be no loss by absorption. In the Ameri- can Journal, Vol. V, p. 196, may be seen an account of a person whose health of body and mind was restored by the respiration of this gas; and although it was attended by the singular circumstance, that he had acquired suddenly such a taste for sweets, that he cra- ved sugar and molasses on all his food, even that of an animal kind, and this taste was freely indulged, still his health was permanently invigorated, and the acquired taste gradually left him.* * Apparatus for evolving and preserving nitrous oxide gas. Dr. Hare. A, represents a copper vessel of about 18 inches in height, and nine inches in diameter, which is represented as heing divided longitudinally in order to show the inside. The pipe, B, proceeds from it obliquely, as nearly from the bottom as possible. Above that part of the cylinder from which the pipe proceeds, there is a diaphragm of copper, perforated like a cullender. A bell glass is surmounted by a brass cock, C, supporting a tube and hollow ball, from which proceed, on opposite sides, two pipes, terminating in gallows screws, D D, for the attachment of perforated brass knobs, soldered to flexible leaden pipes communicating severally with leathern bags, F F. The larger bag, is capable of holding about fifty gallons, the smaller one about fifteen gallons. The beak of the retort must be long enough to eriter the cylinder, so that the gas in passing from the mouth of the beak, may rise under, and be caught by the dia- phragm. This is so hollowed as to cause it to pass through the perforations already mentioned, which are all comprised within a circle, less in diameter, than the bell glass. The gas is, by these means, made to enter the bell glnss, and is, previously to its entrance, sufficiently in contact with water, to be cleansed from the acid vapor which usually accompanies it. On account of this vapor, the employment of a small quantity of water to wash the gas, is absolutely necessary ; and for the same reason, it is requisite to have the beak of the retort so long, as to convey the gas into the water, without touching the metal; otherwise, the, acid vapor will soon corrode the copper of the pipe, B, so as to enable the gas to escape. But while a small quantity of water is necessary, a large quantity is productive of waste, as it absorbs its own bulk of the gas. On this account, I contrived this apparatus, in preference to using gazometers or air holders, which require larger quantities of water. The seams of the bags are closed by means of rivets, agreeably to the plan of Messrs. Sellers & Pennoch for fire hose. The furnace is so contrived, that the coals, being situated in a drawer, G, may be partially, or wholly removed, in an instant. Hence the operator is enabled, without difficulty, to regulate the duration or the de- gree of the heat. This control over the fire, is especially desirable in decomposing the nitrate of ammonia, as the action may otherwise become suddenly so violent, as to burst the retort. The iron netting, represented at N, is suspended within the furnace, so as to support the glass retort, for which purpose it is peculiarly adapted. The first portions of gas which pass over, consisting of the air previously in the re- 484 NITROUS OXIDE. APPENDIX RELATING TO NITROUS AND NITRIC OXIDE GAS. 1 . Sulphite of potash, pulverized and retaining its water of crys- tallization, 100 grains, in 1 hour, reduced 16 cubic inches of nitric oxide gas to 7.8 of nitrous oxide. 2. Dry muriate of tin, dry alkaline sulphurets and iron filings, in a few days, convert the nitric oxide gas into nitrous oxide. 3. Dry nitric oxide gas and dry sulphuretted hydrogen, slowly decompose each other ; sulphur is deposited and nitrous oxide formed. 4. In all the above cases, the presence of water aids the decom- position. 5. Zinc, in contact with water and nitric oxide gas, converts the latter into nitrous oxide, and ammonia is also produced. 6. Nitrous oxide is produced during the solution of several of the metals in nitric acid. 7. Zinc or tin dissolved in nitric acid, diluted with five or six times its weight of water, gives this gas ; zinc in large pieces gives nitrous oxide, till the acid begins to be of a brown color, when nitric oxide gas is formed ; the gas from the solutions of the metals is never pure. 8. Iron produces it mixed with nitric oxide gas. 9. A cold saturated solution of nitrate of iron gives out much of it. 10. Nitrate of zinc, distilled to dryness the same. 11. If sulphite of potash, mixed with caustic potash, retaining its water of crystallization, be immersed in an atmosphere of nitric oxide gas, the latter will become nitrous oxide and this will combine with the potash ; the sulphate of potash and remaining sulphite are crys- tallized out, and the compound of nitrous oxide and potash is ob- tained pure, except some carbonate of potash.. 12. This salt is very soluble in water ; is caustic and pungent to the taste ; turns green the alkaline test liquors, and contains about J nitrous oxide, which is not expelled by boiling ; powdered charcoal mixed with it burns with scintillation, and all acids expel the nitrous oxide. 13. By similar means a compound with soda may be formed, em- ploying the sulphite of soda, &c. tort, are to be allowed to escape through the cock, H. As soon as the nitrous oxide is evolved, it may be detected by allowing a jet from this cock, to act upon the flame of a taper. To obtain good nitrous oxide gas, it is not necessary that the nitrate of ammonia should be crystallized ; nor does the presence of a minute quantity of muriatic acid, interfere with the result. I have employed advantageously in the production of this gas, the Concrete mass formed by saturating strong nitric acid, with carbonate of ammonia. The saturation may be effected in a retort, and the decomposition accomplished by exposing the compound thus formed to heat, without further preparation. NITRATES OF EARTHS. 485 NITRATES OF THE EARTHS. General characters. 1. Similar to those of the nitrates of the alkalies, but their action on ignited combustible bodies is less vigorous ; they rather scintillate than deflagrate on burning coals, but are eventually decomposed both by heat and by hot combustibles. 2. In some of them, as the nitrates of strontia and baryta, the acid is decomposed at once into nitrogen and oxygen, without the formation of a nitrite ; the base being left behind. 3. Sulphuric acid evolves the nitric acid. 4. Only two of the earthy nitrates* are found native, the rest be- ing formed by art. NITRATE OF BARYTA. 1. DISCOVERY. First formed by Scheele and Bergman, in 1776. 2. PREPARATION. (a.) By decomposing the carbonate of baryta, native or artificial, by the nitric acid, diluted with from 8 to 16 times its volume of water ; the effervescence is moderate. (b.) By decomposing, by the nitric acid, the artificial hydro-sulphu- ret of baryta, formed from the decomposition of the sulphate by char- coal ; or, a carbonate may first be formed by precipitating the baryta from the solution of the sulphuret by the carbonate of an alkali, and then this may be decomposed by nitric acid. 3. PROPERTIES. (a.) Crystals are easily obtained from the evaporated solution ; primitive form, the octahedron sometimes in brilliant triangular plates, with truncated angles ; sometimes grouped in stars. (b.) Sp. gr. 2.9. Taste, sharp and acrid. (c.) Insoluble in alcohol, but soluble in 12 parts of water at 60, and in about 3 or 4 at 212. Least soluble of all the nitrates ; nitric acid being poured into a concentrated solution of muriate of baryta, causes a precipitate of the nitrate which more water redissolves. Solution of nitrate of baryta should not cause a precipitate with nitrate of silver. !d.) Air produces little change upon this salt, e.) Decrepitates and feebly scintillates on burning coals, (f.) Decomposed by ignition in a crucible, and affords pure baryta,^ by a theory already explained. If decomposed in a porce- * Those of lime and magnesia. t If the heat is urged too far, it vitrifies in an earthen crucible. 486 NITRATES OF EARTHS. lain retort, by a regulated heat, the deutoxide may be obtained. (See note, p. 215.) (g.) Strength of affinity. Not decomposed by any single base or acid, except by the sulphuric and the phosphoric ; decomposed by all the soluble sulphates, and by the carbonates of the alkalies. 4. PROPORTIONS. This salt is anhydrous. If it is a compound of 1 proportion of nitric acid, and 1 of baryta, its composition should be baryta, 78, per cent. 58.4 nitric acid, 54, 41.6 Its equivalent, 132 100. From this result, the analyses of several of the most eminent chem- ists are not very remote. Clement and Desormes, 40 acid, 60 base. Jas. Thomson, 40.7 59.3 Berzelius, 41.54 58.46* 5. USE. !a.) To afford pure baryta by its decomposition by heat. b.) To detect sulphuric acid. In examining the nitric acid for this purpose by the nitrate of baryta, the latter must be dilute unless the former is so, otherwise the strong nitric acid will precipitate crys- tals of nitrate of baryta, presenting a false indication of impurity ; their ready solubility in more water will however distinguish them. Remark. After the expulsion of the nitric acid by the compound blowpipe, the earth of this salt, if urged by the heat, exhibits on char- coal a deep yellow flame, and ultimately melts. NITRATE OF STRONTIA. 1. DISCOVERY. By Dr. Hope, of Edinburgh. 2. PREPARATION. (a.) By dissolving carbonate of strontia, 1 part, in nitric acid 1, and water I ; the action is rapid; carbonic acid is disengaged, and the nitrate of strontia, being evaporated over a lamp, the crystals pre- cipitate during the process. (b.) JBy decomposing the sulphate of strontia by ignition with char- coal and then decomposing the resulting sulphuret by nitric acid ; or it may first be turned into a carbonate by a carbonate of an alkali. 3. PROPERTIES. (a.\ The crystals are octahedra or six sided prisms.-^ (b.) Taste pungent and cooling, (c.) Sp. gr. 3. * Quoted by Henry. t See Ann, of Phil. N. S. VII, 288. NITRATES OF EARTHS. 487 (d.) Jit 60, dissolves in 1 part of water, and at 212, in some- what more than half its weight. (e.) Alcohol does not dissolve it. (/.) Deliquescent in moist air ; efflorescent in a dry air. (g.) Slightly scintillates on burning charcoal, but with sulphur and charcoal in the proportions of gunpowder, it burns slowly and emits purple sparkles, and a fine green flame. (h.) Decomposed by ignition, and pure strontia remains.* (i.) A cry 'Stalin a burning candle produces a beautiful blood red flame. (j.) The flame of boiling alcohol also acquires a red color from this salt. (k.) Decomposed by the sulphuric and muriatic acids, and by baryta, potassa, and soda, 4. PROPORTIONS. According to Richter, this salt contains, (ex- clusively of water,) acid 5 1. 4 -f 48. 6, base. Stromeyer gives acid 50.62 + 49.38, base. These proportions agree with the equivalent weight of the acid 54, and of the base 52. Henry. 5. USE. To afford pure strontia, and as a test for sulphuric acid ; it is to be used with the same precautions as the nitrate of baryta. NITRATE OF LIME. 1. NATURAL SITUATIONS. In the nitre beds ; in the nitrous earths, and particularly in those of the caverns in the limestone of the wes- tern American States ; in the calcareous cement and plaster of old buildings that have long been inhabited. Its origin, as regards the acid, appears to be from the atmosphere, aided at least in some cases, by nitrogen from animal effluvia. 2. PREPARATION. (a.) By dissolving lime or its carbonate in nitric acid, diluted with 5 or 6 parts of water, evaporating to a syrupy consistence, and then allowing it to cool and crystallize. 63 parts of carbonate of lime are decomposed by 90.23 of nitric acid of the density 1.5 and produce 103.05 parts of dry nitrate of lime. 3. PROPERTIES. (a.) The crystals are six sided prisms, very acutely terminated ; more frequently it is in fine brilliant needles. !b.) Taste acrid and bitter. c.) Sp.gr. 1.6. Suffers the aqueous fusion ; if kept melted for fae or ten minutes and then poured into a heated iron pot, it becomes phosphorescent, and was formerly called Baldwin's phosphorus. f * If at the instant of decomposition, a combustible substance be brought into contact with it, a deflagration with a very vivid red flame is produced. Dr. Hope, t From the discoverer, Baldwin, who published an account of this fact in 1675. 488 NITRATES OF EARTHS. It is to be broken up and preserved in tight bottles. After "being exposed to the sun for a few hours, it emits in the dark a beautiful white light." Henry. (d.) With a strong heat it is completely decomposed, and lime remains. (e.) It contains so much water that it scarcely acts on combusti- bles unless previously dried. (f.) .More deliquescent than any other salt.* (g.) Water at 60 dissolves 4 parts ; boiling water any quantity ; and boiling alcohol its own weight. Although difficult to crystallize, it will, when evaporated to a thickish consistence, often become solid and hot by the slightest agitation. (h.) J^cids, and alkalies and earths decompose it in the same man- ner as the other nitrates. If potassa is added to a concentrated so- lution it throws down the lime nearly solid, because it absorbs the water. 4. PROPORTIONS. Exclusive of water, the equivalent number of nitrate of lime would be 82, i. e. acid 54, lime 28, and this would give for its con- stitution in the 100 parts, Acid 65.86 Mr. Dalton found acid 61.3 base 38.7 Base 34.14 Philips " 65.6 34.4 100.00 The result of Mr. Philips is very near to the regular constitution. Id. NITRATE OF MAGNESIA. (a.) Of very little importance; exists in the mother waters of nitre, and it may be formed synthetically; crystallizes in minute nee- dles or in rhomboidal prisms; its taste is very bitter; sp. gr. 1.73; soluble in half its weight of water at 60, and in less at 212; deli- quescent; suffers the aqueous fusion; by more heat is decomposed, like the other nitrates, leaving magnesia. (b.) Emits nitrous fumes with sulphuric acid. (c.) The alkalies precipitate the magnesia. (d.) Action on combustibles very feeble; it only scintillates slightly on burning charcoal. (e.) Composition. According to Dr. Thomson, acid 1 propor- tion, 54 ; 1 of base 20 ; 6 of water 54 = 128, its equivalent, which gives percent, acid 42.2, base 15.6, water 42.2=100.0. * Hence it is kept very dry in close vessels, and used to dry the gases ; being for that purpose placed in tubes through which they are made to pass. Impure deli- quescent nitre, generally contains this salt. NITRITES. 489 NITRATE OF MAGNESIA AND AMMONIA. 1. PREPARATION. Formed by a partial decomposition of nitrate of magnesia by ammonia, or of nitrate of ammonia by magnesia, or better by a mixture of the two nitrates. 2. PROPERTIES. Slender acicular crystals; Utter. Little deliquescent; soluble in 11 parts of water at 60, in less at 212, and the solution deposits crystals as it cools.* NITRATE OP ALUMINA. 1. PREPARATION. The fresh precipitated earth is washed and heated with dilute nitric acid. 2. PROPERTIES. (a.) The solution, which is always acid, deposits, after evapora- tion, thin crystalline ductile plates. (b.) Taste sour and astringent ; extremely soluble and deliques- cent; decomposed by heat without decomposing the acid. (c.) Decomposed by most alkalies and earths. 3. COMPOSITION. Nitrate of alumina, when dried between folds of blotting paper, is composed of acid 1 proportion, base 2, water 10, and by a stronger heat it loses a portion of its acid. Thomson. The nitrates of the other earths are unimportant. NITRITES. They cannot be formed synthetically, and the only distinct one is that of potassa. 1. PREPARATION. Fuse nitre in a crucible till one proportion of its oxygen has escaped, or partially deflagrate it with charcoal. 2. PROPERTIES. Deliquescent, and emits red fumes of nitrous acid even with vinegar, and very strikingly with a strong acid. It is not certain whether this salt is a nitrite or hypo-nitrite. RECAPITULATION Of some principal facts relating to oxygen and nitrogen. 1 . Remark. Even a limited acquaintance with chemistry is suffi- cient to enable us to see that the properties resulting from chemical combination are such as we cannot always foresee, nor account for when known ; and that the different results, obtained from combina- tions of the same elements in different proportions and in various de- grees of condensation, are very surprising. * See Thenard, 2d ed. Vol. Ill, p. 240. 62 490 RECAPITULATION. Perhaps the truth of this observation is no where more manifest than with respect to the bodies composed of oxygen and nitrogen. These elements constitute the air that we breathe, and also one of the most powerful of the acids ; they give us two other acids scarcely inferior to the other in energy, but possessed of peculiar and charac- teristic properties ; they produce also a gas eminently deadly, and which, by acquiring more oxygen, passes instantly to the condition of one, or of the other of these acids ; and finally another gas, deadly to animals that are confined in it, but which, when breathed for a short time, by human beings, is exhilirating beyond any other agent. These differences, which have been fully unfolded in the preceding pages, are attributable solely, so far as we know, to difference of proportion and to different degrees of condensation. 2. Dr. Henry, Gay-Lussac, Dalton, Davy and Thomson, have contributed the most important facts, from which have been deduced the proportions, both by volume and weight, of the compounds of oxygen and nitrogen. Gay-Lussac gave us the law, to which no certain exception has yet been ascertained ; "that compounds, whose elements are gaseous, are constituted either of equal volumes of those elements, or that, if one of the elements exceeds the other, the ex- cess is by some simple multiple of its volume," It is obvious that if gases sustain this relation by volume, they must sustain a similar one by weight, for twice, thrice, &LC. the volume must be also twice, thrice, &c. the weight ; the temperature and pressure being the same. 3. The following numerical statements exhibit the proportions of oxygen and nitrogen by volume and by weight. By weight Rep. No. Rep. for 100 Equivalent of the No. of Measures of By weight. parts, proportions, elements, the nit. ox. nit. ox. nit. ox. nil. ox. nit. ox. cornp's Nitrous oxide contains 100 50 100-f 57 63.5836.42 +1 14-j- 8 22 Nitric oxide, 100 100 100 114 46.68 53.40 2 14 16 30 Hypo-nitrous acid, 100 150 100 171 36.81 63.20 3 14 24 38 Nitrous acid, 100 200 100 228 30.40 69.60 4 14 32 46 Nitric acid, 100 250 100 285 25.97 74.03 5 14 40 54 It will be perceived that the smallest number in the first, second, fourth and fifth tables, is a divisor of all the larger numbers in that column, and that those other numbers are of course multiples of the smallest number. Most chemists regard common air as a mixture rather than a compound ; but the fact that it corresponds with definite propor- tions, both in volume and in weight, is perhaps the strongest argument that it is a compound and not a mixture, and perhaps no good reason can be assigned why it should not be added to the acknowledged compounds of oxygen and nitrogen. See p. 197-8. BORACIC ACID. 491 4. It is thought that all the compounds of nitrogen and oxygen are, essentially, gaseous bodies ; the two oxides are certainly so, and can be combined with water in only small proportions. Other com- binations have so strong an affinity for water that they have never been entirely separated from it. Nitric acid is of this description, and the two other acids unite very largely with water. 5. In all the combinations of oxygen and nitrogen the elements are in a state of condensation, excepting in the nitric oxide ; in this gas, according to the opinion of Gay-Lussac, the oxygen and nitro- gen have exactly the same density as in their free state ; but in the other compounds the condensation is such that the oxygen gas does not add to the volume ; or in other words the contraction is equal to the volume of the oxygen gas. 6. As among gases, the combining proportions correspond with the volumes ; the least volume that enters into combination represents the equivalent or smallest combining quantity. In the case of oxygen, however, as already stated, the smallest combining proportion is con- sidered as corresponding with half a volume, as in the composition of water. 7. It is obvious that, as the compounds of oxygen and nitrogen differ from each other only in the proportion of oxygen which they contain, they may be converted into each other by adding or abstract- ing oxygen. This has been rendered apparent in the statements that have been already given. Nitric acid, by its action on combustibles and metals, is often converted into nitrous acid and nitric or even ni- trous oxide ; and nitric oxide, by the addition of oxygen, forms the nitrous acids and perhaps the nitric. SEC. VI. BORON AND BORACIC ACID. Remark. BORON being a substance unknown in common life, it will be most convenient to describe first, the acid from which it is obtained. BORACIC ACID. 1. NAME AND DISCOVERY. The composition of this acid being unknown when the nomenclature was formed, it was therefore named from the Borax of commerce, its parent substance. The ancient name of sedative or narcotic salt was given to it by Homberg, a chemist of the Academy of Sciences of Paris, who, in 1702, obtained it by distilling sulphate of iron and borax. 2. NATURAL SOURCES. (a.) In the saline form, borax, from which chemists always obtain boracic acid, is a native alkaline salt, having soda for its basis. It 492 BORACIC ACID. is brought to Europe from the East Indies, under the name of tin- ea], and is obtained from Boutan and Thibet ; sometimes in small crystalline masses, found two yards under ground ; it is procured also from natural lakes, whose waters, containing the salt in solution, yield it it by evaporation, and deposit it in the solid form, at the bot- tom or in artificial reservoirs. In Europe, the salt goes through re- fining processes, formerly confined to Holland but now practised in England. (6.) In the free state, found in the hot springs of Lipari and , and in the hot waters of Lake Cherchiago, and Castlenuovo, in Italy. By evaporating 120 Ib. of the water, 3 oz. of the concrete acid are obtained ; 12280 grs. of the water of Lake Castlenuovo yielded 120 grains of acid. Boracic acid is also found in the vicinity of these lakes, adhering to the rocks in crystals. The boracic acid is now obtained in such quantities from Tuscany that it forms an important article of commerce, and is used to form borax by a direct combination with soda. (c.) In minerals. Found in the Boracite of Luneberg, a hard cubical stone, imbedded in gypsum, and containing magnesia as the basis ; also in the Datholite and in Tourmalines, &c. 3. PREPARATION. Obtained from borax, both by sublimation and by precipitation. (a.) By sublimation. A solution of 2 Ibs. calcined sulphate of iton, and 2 oz. of borax, is filtered, evaporated to a pellicle, and sub- limed in an alembic or retort ; the boracic acid, in crystals, lines the upper cavity, and may be swept out with a feather.* (b.) Or, the acid may be obtained of a beautiful whiteness, by ad- ding to the borate of soda J its weight of sulphuric acid, and sub- liming.^ (c*) The usual process is to dissolve borax 2 parts, in water 6 or 8; and to add Ij of sulphuric acid diluted with 1 of water, a gen- tle heat being continued for a short time ; it is set by, and on cool- ing, crystals of boracic acid, in white shining plates or scales, or mi- nute prisms, will be abundantly precipitated. They must be washed with cold distilled water, to remove any adhering sulphuric acid, or sulphate of soda, and dried on blotting paper. The remaining fluid is a solution of sulphate of soda. The crystals obtained in this man- ner are still contaminated by a little of the base of the borax, and of the acid used to decompose it. It is said to be obtained purer by using the muriatic or the nitric acid, instead of the sulphuric. Gay- * Chaptal, Vol. I, p. 265. t The product by sublimation is much less than by precipitation Id. BORACIC ACID, 493 Lussae prefers the muriatic, and the boracic acid must be afterwards ignited in a platinum crucible, to expel any excess of the decompos- ing acid. 4. PROPERTIES. (a.) The form is that ofkexahedral scales, white and brilliant. (b.) Feel, a little unctuous, like spermaceti, which it somewhat re- sembles. The sublimed boracic acid is much more light and volu- minous than the precipitated. !c.) Taste, cool, bitterish, and slightly sour; inodorous, d.) Reddens blue vegetable colors, effervesces with the alkaline carbonates, but turns turmeric brown, like the alkalies. Its sp. gr. 1 .48 after fusion, 1.803. (e.) " When sulphuric acid is poured upon it, a transient odor of musk is produced." (/.) This acid a hydrate, for by ignition it loses about 43 per cent, which is the water of crystallization; if heat be suddenly applied, a large quantity of acid rises with the water of crystallization, and in either case we obtain boracic acid, fused, and becoming when cold, a hard transparent glass, not deliquescent, but partly opaque ; if dissolved in hot water, it crystallizes again on cooling. Authors are exceedingly at variance as regards the solubility of this acid ; but they agree that it is much more soluble in hot than in cold water, the general statement being 12 parts of cold, and 3 or 4 of boiling water.* (g.) When a saturated solution of this acid, in water, is distilled, a part of the acid passes over, and crystallizes in the receiver ; when solid, it will melt into glass, rather than sublime. (h.) Soluble in 5 parts of boiling alcohol, which will then burn with a beautiful green flame ; it is best exhibited by dipping a paper in the solution, and setting it on fire, or by burning it from a watch or wine glass ; but sponge does not shew it well, as the yellow color produced by the salt with which it is impregnated, overpowers the green. If the paper which has been dipped in the alcoholic solution be dried first, it then burns with a yellow flame ; other substances, which burn with a blue flame, as sulphur, burn green when mixed with boracic acid.f 5. COMPOSITION AND POLARITY. In the next article, the de- composition of this acid will be mentioned ; we may now say that it has a combustible base, called boron, which by union with oxygen, forms boracic acid. * According to Murray it requires 5 parts of boiling water, and 2& of cold ; but Davy asserts that it requires 50 parts, even of boiling water, t Aikin'sDict. 494 BORACIC ACID. Boron 1 proportion, represented by the same number as oxygen, namely 8, -{-2 prop, oxygen 1 6, forms dry boracic acid, having 24 for its equivalent ; the crystallized acid consists of dry acid 24 -j- water 2 proportions, 18 =42 for the equivalent of the crystallized acid; and for the 100 parts, 42 : 18 : : 100 : 43 nearly, being the quantity of water in the 100 parts, of course there is 57 of dry acid. According to Berzelius, crystallized boracic acid, contains .44 of water, one half of which is expelled at a heat above 212, and the other half when it combines with bases, but it cannot all be expelled by heat alone, 6, POLARITY. In the galvanic circuit, this acid goes to the posi- tive pole, and is therefore, electro negative. 7. USES. It melts very easily, and by acting as a flux, it favors the fusion of minerals, with the blow pipe. It is used in the analysis of stones, aiding their fusion in the crucible. After it is melted by itself, it endures a white heat without volatilization, and as it cools into a glass, it is called a glacial acid, being one of three that bear that name, viz. the phosphoric, the arsenical, and the boracic. In the dry way, viz. with heat, the boracic acid displaces all the acids except the phosphoric ; this arises from its great fixity and fusi- bility by which it is able to vitrify the bases of the salts, even of the earthy salts. BORON. DECOMPOSITION OF BORACIC ACID. 1. DISCOVERY OF BORON. (a.) The power of 500 pairs of galvanic plates extricates from moistened boracic acid a peculiar olive colored combustible basis, first ascertained by Davy, in 1807. 2. PROCESS. (a.) Better obtained by heating very pure vitreous boracic acid along with potassium, in tubes of green glass or copper, iron or brass ; preferably the last. (b.) 12 or 14 grains of each substance were employed ; but 8 grains of boracic acid will saturate 20 grains of potassium. At 302 Fahr. ignition comes on, a little hydrogen appears, the potassium is con- verted into potassa,* and boron is obtained. * See Recherches Physico-Chimiques, Vol. I. Berzelius employs the fluo-borate of potassa with potassium in a crucible ; the boron is to be washed with sal-ammoniac, and lastly with alcohol ; as water carries some of it through the filter. This process is said to be less expensive in potassium than the other. BORACIC ACID. 495 3. PROPERTIES. (a.) An opake, pulverulent, olive colored mass, does not scratch glass, does not conduct electricity, is tasteless, inodorous, insoluble in water, ether, alcohol and oils, and does not affect blue colors. (b.) Burns in atmospheric air, at a heat below that of boiling olive oil, or at about 600, with a red light, sparkles like charcoal, and produces boracic acid, the coating of which, on the boron, soon stops the combustion. (c.) Not fused or volatilized by a white heat, in close vessels, but becomes dense enough to sink in sulphuric acid of the sp. gr. 1.844, hence its sp. gr. must be nearly 2. (d.) The heat of a spirit lamp makes it burn brilliantly in oxygen gas, and boracic acid sublimes.* (e.) It burns spontaneously in chlorine gas, and forms a new gas, which when brought into contact with atmospheric air, smokes as much as fluoboric gas. Freed from excess of chlorine, by standing over mercury it becomes colorless, and is rapidly absorbed by water ; its composition is chlorine, 90.743, boron, 9.257 = 100. Berzelius. (jf.) Niti'ic acid converts it into boracic acid, while nitric oxide gas is liberated. (g.) It dissolves in hot sulphuric acid with effervescence, and pot- ash throws down a black precipitate. (h.) Muriatic acid acquires a green color, but its action is feeble, and there is no solution. (i.) With fixed alkalies, it forms pale olive-colored compounds, from which muriatic acid throws down dark precipitates. (j.) Sulphur dissolves it by long fusion, and acquires an olive tint little action with phosphorus, none with mercury. (k.) It burns vividly, when mixed with chlorate or nitrate of potash, and thrown into a red hot crucible. (I.) Boron heated in the vapor of sulphur, unites with it, with the appearance of combustion producing a sulphuret, which is white and opake, and which, when thrown into water, gives off sulphuretted hydrogen and forms boracic acid. 4. EQUIVALENT NUMBER AND POLARITY. The equivalent of boron is 8, as already stated. In the galvanic circuit, it goes to the negative pole. 5. NATIVE BORON. Boron is to be regarded as a peculiar combustible ; a little resem- bling carbon in fixity in the fire, but it is unlike it in being a non-con- ductor of electricity. * There is a black residuum which produces more boracic acid by being heated again in oxygen gas. 496 BORATES. BORATES OF ALKALIES AND EARTHS. General properties, 1. In the humid way, decomposed by all acids except the car- bonic. 2. In the dry way, the action is often reversed, especially where the acid of the other body has a tendency to become gaseous. 3. Boracic acid attracts the earths more forcibly than the alkalies. 4. Alkaline borates are very soluble in water ; the earthy the re- verse. 5. The boracic acid being feeble, it neutralizes the alkaline bases imperfectly, and hence the borates of the alkalies have alkaline char- acters. 6. Borates are very fusible. 7. Digested with strong sulphuric acid, the residue imparts to al- cohol the power of burning with a green flame. BORATE OF POTASSA. 1. PROCESS. (a.) Boil boracic acid in caustic potash, either to saturation or so as to leave a slight excess of alkali. (b.) In the latter case, it crystallizes in pretty large four sided prisms taste sub-alkaline. 2. PROPERTIES. (a.) Not altered by the air by heat, swells, foams, and runs into a clear glass. (6.) Decomposed by lime, baryta, and magnesia. BORAX. BI-BORATE OF SODA, formerly called sub-borate. 1. PREPARATION. It can be formed synthetically, but this is un- necessary, as it is abundant in commerce. 2. PROPERTIES. (a.) Turns vegetable blues green; taste, cool, sweetish, and sub- alkaline. (b.) Soluble in 12* parts of cold water, and in 6 of boiling ; slight- ly efflorescent ; deposits crystals by cooling ; prisms with 6 irregular sides. Phosphoresces by collision of its crystals. (c.) Suffers the aqueous fusion, is very much inflated, and at igni- tion becomes a pellucid glass ; soluble again in water. f t Provided it were melted in a silver crucible or hastily in one of earth, for it H prone to corrode earthen crucibles. BORATES. 497 (d.) Sp. gr. 1.74 after fusion, flies and cracks to pieces in cooling. (e.) Action of the acids as already mentioned under boracic acid, and the general characters of the borates. (/.) If only the excess of soda be neutralized by an acid, the whole, by evaporation becomes a confusedly crystallized mass, containing all the ingredients. (g.) The excess of alkali can also be saturated by boracic acid; the salt takes up nearly half its weight, and ceases to affect the blue col- ors, to effloresce, to taste alkaline, and to crystallize in the same form as borax. (h.) Baryta, strontia, lime, and magnesia, decompose borax. (i.) Potash also decomposes it, but there is no precipitate, because soda dissolves borate of potash. (j.) Borax fluxes silica into a transparent, and alumina into an opake glass ; the ingredients being in equal proportions, the com- pound is insoluble in the mineral acids, but a great excess of borax makes it soluble. (k.) The borax of the shops exhibits an imperfect crystallization, with a figure approaching to the hexahedral prism. The crystals are slightly efflorescent. 3. COMPOSITION AND REPRESENTATIVE NUMBER. Gmelin, acid, 35.60, base, 17.80, water, 46.6 = 100 ) , Thomson, 31.51, 20.42, 48.0=100 j n< The representative number of boracic acid has already been stated as being 24. According to Dr. Thomson, this salt is composed of 2 proportions of boracic acid, =48 1 " soda, - - =32 8 " water, - - - =72 Its equivalent, 152 In the 100 parts, acid 31.58, soda 21.05, water 47.37. 4. MISCELLANEOUS. The natural and commercial- history of this salt has been already given under boracic acid. In addition to the localities already named, it is found in China, in Peru, in Transyl- vania and Saxony.* The crude borax brought from the East Indies and the Levant, is al- ways enveloped in an oleaginous matter ; which Vauquelin found to be a soap with soda for its base. It is believed that the natives cover it with a film of oil to prevent its efflorescence, and it is said to be mois- tened by sour milk for the same purpose. It is purified by repeated solutions and crystallizations, in vessels of lead ; they obtain from the tincal .80 of borax, and they expose it * Thenard, III, 90. 63 498 BORATES. to heat as a preparatory operation, to burn off the oily or fatty matter which surrounds it. Formerly the manufacture was confined to Holland, and it seems not to have been known that an addition of soda was necessary to saturate the boracic acid. Borax is now abundantly manufactured in France, by the combi- nation of the boracic acid, obtained from Tuscany, with soda; the French consume, annually, about 25 tons, and they no longer import the tincal. In forming borax in France, they dissolve 1200 Ibs. of carbonate of soda in 1000 Ibs. of water, and add, by 20 Ibs. at a time, 600 Ibs. of Tuscan boracic acid ; the processes are conducted in leaden boil- ers, by repeated solutions and crystallizations, and many circumstan- ces must be attended to in order to obtain large and handsome crys- tals. 100 Ibs. of the best Tuscan boracic acid, containing about half its weight of the pure acid, produce about 150 of refined bo- rax ; but as the acid is not always pure and there is some loss in the processes, the product is ordinarily not more than 140 or 142 Ibs. of borax from 100 of boracic acid.* 5. USES. Formerly used internally as a sedative, and still employ- ed to form a gargle to remove the aphthous crust from the mouths of children ; it is a flux for the blowpipe ; for the vitreous materials of artificial gems or pastes, and for the glazing of porcelain. Known from remote antiquity, and it is mentioned by Pliny as chrysocolla or gold glue, in allusion to its use in soldering the precious metals ; from which it removes impurities, preventing also oxidation. BORATE OF AMMONIA. 1. PROCESS. By digesting boracic acid with ammonia, we obtain small rhomboidal octahedra. 2. PROPERTIES. (a.) Taste sharp ; turns the blue vegetable test liquors green ; undergo slight efflorescence in the air. (b.) The ammonia is expelled by heat and the boracic acid is left; according to Lassone,f the entire salt melts into a grayish glass, and gives after solution, the same crystals as before. (c.) Decomposed by the fixed alkalies both in the moist and dry way, BORATE OF BARYTA. Add boracic acid to barytic water, and a white, insipid, insoluble powder precipitates. BORATE OF STRONT1A. 1. Same mode of formation ; a copious precipitate. 2. Prone to an excess of base; soluble in 130 parts of boiling \vater, and is scarcely affected by cold water. * Gray's Op. Chem. p. 526. t Aikin, Vol. I, p. 156. FLUORIC ACID. 499 BORATE OF LIME. 1. PROCESS. Mix boracic acid or borax with lime water, or any soluble salt of lime. 2. PROPERTIES. (a.) A white, insoluble, insipid powder ; fusible at ignition. (b.) Chalk 2, and boracic acid 1, at ignition, produce a yellow glass so hard as to strike fire ; with the reverse proportions, the mat- ter often runs through the crucible. BORATE OF MAGNESIA. 1. PROCESS. By long digestion of boracic acid with magnesia; or a mixture of any soluble borate with any soluble magnesian salt, produces this combination. 2. PROPERTIES. An insoluble and insipid precipitate, without any crystalline form ; fusible, at ignition, into a white semi-transpa- rent glass. The bi-borate of magnesia is found native at Luneberg, Germany, under the name of the boracite ; it is in small cubical crystals, often highly modified. BORATE OF ALUMINA. 1. Newly precipitated and undried alumina is digested with bo- racic acid. 2. Evaporation gives a viscid mass, through which minute crystals are interspersed ; taste astringent. SEC. VII. FLUORIC ACID. Remark. In order to entitle the fluoric acid to a place here, strict method would require that a combustible basis should have been prov- ed to exist in this acid, and that this base should be described in con- nexion with the acid. But as we have no decisive proof as to the nature of the fluoric radical, the present arrangement can be consid- ered as provisional only ; for it remains yet to be seen whether fluo- ric acid is composed of a combustible basis and oxygen, or of a peculiar principle, analogous to iodine and chlorine, and hydrogen, or whether it has a composition entirely peculiar ; for all analogy leads to the opinion that it is compound. 1. HISTORY. Re-discovered by Scheele, A. D. 1771 ;* for it ap- pears to have been first obtained (A. D. 1670,) by the artist Shank- hard, at Nuremburg; and also by Pauli, at Dresden, A. D. 1725, who employed it, as Shankhard had done, to corrode glass, but Vide Scheele's Essays, Vol. I. 500 FLUORIC ACID. the subject was forgotten, till Mr. Scheele revived it. The acid of Scheele was, however, impure, and it was not till Gay-Lussac and Thenard obtained it,* that it was known in purity. 2. ORIGIN AND NAME. Exists abundantly in the beautiful mine- ral called Derbyshire spar ; it being found in great quantities in tha.t county, in England. This mineral is called also fluor, or fluor spar, because, being fusible, it is used as a flux for ores. It is usually crystallized in cubes, with an octahedral nucleus, which gives, by con- tinued dissection, octahedra and tetrahedra. When pure, it is white, but it is most commonly colored. Jls the fluor spar affords the acid in question, the name, fluoric acid, was bestowed, because the composition was then, as it is still, un- known. 3. PREPARATION. (a.) Gay-Lussac and Thenard employed a leaden cylinder, con- nected by a recurved leaden tube, with another leaden vessel for a re- ceiver ; the latter was kept cold by ice. (b.) Finding lead so liable to fusion, I have used a silver alembic, with a capacity of 16 fluid ounces, its head and tube 2j, and the tube fitted tight to a silver bottle of 3J oz. the latter furnished with a ground silver stopper, to preserve the acid, and to save the necessity of pouring it into another vessel. (c.) In the alembic are placed 2 oz. of pure fluor spar, and 4 oz. of strong sulphuric acid ; the receiver is surrounded by ice or snow, and a few live coals are placed beneath the alembic, whose head is made securely tight by a lute of finely powdered pipe clay, placed in the joint, and a rag, smeared with the same, is bound tightly over it. The receiver should not be pressed hard home, so as to be accurate- ly tight upon the tube, but a little room should be left for the escape of the vapor of the acid. (d.) The apparatus should be under a well drawing flue, the hands protected by thick gloves, and the receiver, when moved, should be grasped by small tongs, furnished with curvatures, to fit the neck of the bottle. f In about half an hour, the process will be through, and * Recher. Phy.-Chim. Vol. II. t As represented in the annexed figures, which being made with corresponding c==o =-~ flexions, and of various sizes, from those that are very delicate and adapted to sustain the minutest flasks by the neck, to such as will lift a heavy crucible, or a basin, are highly convenient. FLUORIC ACID. 501 on shaking the bottle, the movement of the liquid fluoric acid will be distinctly perceived.* 4. PROPERTIES. (a.) An exceedingly volatile fluid; extremely corrosive, suffoca- ting ', and dangerous. (b.) Jit 32 Fahr. it is a colorless fluid. Sp. gr. 1.0609, and by gradual additions of water, its density is increased to 1.25.f (c.) Retains its liquid form at 60, if preserved in well stopped silver bottles :J those of lead answer but imperfectly, as the acid cor- rods them and escapes. Sd.) Does not congeal at 4 Fahr. e.) When strong, emits into the air dense white fumes, which evi- dently arise from a combination with the watery vapor. (f.) Potassium burns, or rather detonates in the liquid fluoric acid ; hydrogen gas is disengaged, and a solid white substance is formed. This experiment must be performed in a metallic vessel ; a platinum crucible or capsule answers well. (.) Dropped into water, it hisses like a hot iron, and there is great agitation, and even ebullition, especially when water is added to the acid. * See Am. Jour. Vol. XVI, p. 354. With the proportion of acid mentioned in the text, (that of Gay-Lussac and The- nard,) the silver alembic is sometimes attacked, and corroded through and through, as I have more than once experienced. If we diminish the quantity of acid, using 3 to 2 of fluor, or even equal weights, the danger to the vessel is much diminish- ed, but the product of fluoric acid is less, and the residuum in the alembic is much more difficult to remove. To a certain extent, the smaller the proportion of sulphu- ric acid used, the stronger and more fuming is the fluoric acid obtained. A similar effect is produced by previously heating the sulphuric acid, for some time, near to its boiling point. The reason is obvious ; it is the water of the sulphuric acid that serves to condense the fluoric acid, otherwise incoercible, at least at the tempera- ture of ice, and under the ordinary pressure, and therefore, the less in quantity, and the stronger the sulphuric acid, (provided it is sufficient for the decomposition,) the more concentrated will be the fluoric acid. I have known the latter so active as to be of very difficult condensation ; blowing out the silver ground stopper with violent puffs, and rapidly wasting away by its own evaporation. A little water in the receiver, however, prevents this, and if our object is to etch on glass, a diluted acid is much preferable. The strong acid of Gay-Lussac is needed only to display its own dangerous and wonderful energy, and too much caution cannot be recom- mended to those who prepare it. t This is said to be unlike other fluids, but is it however, really an exception ? Alcohol and water, and sulphuric acid and water, acquire by union, a gravity great- er than the mean. This acid appears to attract water with more energy than the sulphuric, much more heat is evolved by the condensation, and the density ought to be increased considerably. t In silver bottles, with well ground stoppers, in a cellar, it can'be kept the year round; but from lead bottles, however well ground and luted, it almost always makes its escape, corroding the lead ; and glass vessels in the vicinity are extensive- ly covered with a white deposit of silica, rendering them opake. This eeffct men- tioned by Dr. Thomson, (First Principles, Vol. II, p. 165.) I have often seen. 502 FLUO-SILICIC ACID. (A.) Respiration. The vapor is extremely dangerous in the lungs ; and should be anxiously avoided. (i.) Contact with the body. This also is dangerous ; excepting prussic acid, there is perhaps no agent so deleterious. It instantly disorganises the skin ; painful and obstinate ulcers are formed, for it seems to penetrate into the very tissue of the parts ; there is a general irritation of the system, and sometimes extirpation of the in- jured portion is the only remedy. Even contact with the vapors floating about should be avoided, for they immediately irritate the skin, and may produce permanent injury. J (j.) Fluoric acid, largely diluted in vessels of lead, platinum or silver, has a decidedly acid taste, and reddens the vegetable blues. (&.) It forms salts with the salifiable bases ; " and with acids weak- er than itself, it produces compounds, in which the latter serve as a kind of base." By dilution with water, these acids suffer a partial decomposition, and deposit a portion of their base ; of this description are fluo-boric, and fluo-silicic acids, which will be described in then places. (/.) The constitution and combining weight of fluoric acid will be mentioned at the conclusion of the whole subject. FLUO-SILICIC ACID GAS. The action of fluoric acid upon silica is so peculiar, as to merit a distinct consideration. The strong acid ofGay-Lussac instantly soils glass ; attacking it with as much energy as sulphuric acid does an alkali ; heat is evolved, and instead of having its volatility diminished, it becomes, by this union, permanently aeriform ; a true gas ; although before only a vapor. 1. PREPARATION. (a.) This gas is of course produced, whenever the ordinary process for fluoric acid is performed in glass vessels, but it is usual to add half as much pulverized glass asfluor spar to the mixture of equal parts of the latter, and strong sulphuric acid. (b.) In the latter case, the glass retort will be much less corroded, but in my experiments it has always been attacked in some degree, , I Gay-Lussac and Thenard mention (Recher.-Phys. Chim. Tom. II, p. 11,) that some of their assistants suffered severely for a month, from exposure for a few min- utes to the acid vapor, coming in contact with the fore finger and thumb ; and a dog upon whose back, deprived of hair at that place, six drops of this acid were allowed to fall, suffered extremely, and in a few hours died in agony. They state that the effect is not always perceived till 7 or 8 hours after the contact of the vapor, and that even when it is too feeble to be observed, it produces in a few hours, acute pain, loss of sleep, and fever. Similar results have several times been observed in my laboratory. FLUO-SILIC1C ACID. 503 and if not protected by the mixture of glass, it is usually eaten through and through. (c.) Even with the addition of glass, I have never failed to find the vessels covered by an opake white crust of silica,* less remarkable however than when the fluor and sulphuric acid alone are mingled, 2. PROPERTIES. (a.) Received over mercury, it is a gas, colorless and invisible ; it extinguishes a burning candle, but shows a blue border surround- ing the red flame ; it smokes in the air, producing a dense fog like muriatic acid gas, which, in odor, it strongly resembles ; the cloud is produced by the combination of the acid gas with the atmospheric wa- ter, silica being at the same time deposited, in a state of minute di- vision. (b.) It is fatal to animals confined in it, and is suffocating to the experimenter; but its properties are so repressed by combination with the silica, that it is not particularly dangerous to inhale a little of it mixed with the air of the room. (c.) Sp.gr. 3.6111, air being 1, and 100 cubic inches at 60 Fahr. and 30 inches barometer, weigh 110.138 grains. Thomson. (d.) Dr. John Davy, by decomposing it by liquid ammonia, found that 61.4 of the weight of the gas is silica. Dr. Thomson, from 40 cubic inches of the gas (=44.05 grains,) obtained 27.14 silica, which is at the rate of 61.60 per cent. It is indeed most singular, that a very volatile vapor, by corroding siliceous bodies and becoming charg- ed with more than 60 per cent, of a naturally very Jixed and almost unalterable earth, should become a gas, which, when dry, is perma- nent. (e.) Water. This fluid absorbs about 263 times its volume of 'this gas, and the solution does not corrode glass vessels. During the so- lution, one third of the silica is deposited, and the remainder with the fluoric acid is retained in the water, and was called by Dr. Davy, sub-silicated fluoric acid. It is sour and reddens litmus. (/.) The precipitate is a gelatinous hydrate of silica, and after be- ing washed and ignited, it is regarded by Berzelius as pure. It af- fords perhaps the easiest method of obtaining that earth. (<") Silicated fluoric acid gas, when passing into the receiver, often becomes cloudy from the precipitation of the silica by the moisture of the air. (h.) If distilled into a receiver containing water, it becomes cover- ed with a siliceous crust, which eventually covers the water, and then * This may be presented by covering them with a coat of bees wax, or probably copal varnish, but this last I have not tried. It is said, however, that dry glass is not attacked by silicattd fluoric acid gas. 504 FLUO-S1LICIC ACID. the condensation ceases; but if the receiver be shaken, the crust will break and fall, and the condensation will go on again. (i.) If the gas be let up through water standing over mercury, the silica is deposited in the form of vertical tubes. (j.) When moist substances are placed in an atmosphere of silica- ted fluoric acid gas, they become encrusted with it, so as to resemble petrifactions ; moistened sponge, frogs, lizards, &c. may be envelop- ed in this manner, and covered with a siliceous coat. (k.) Silicated fluoric acid gas condenses ammoniacal gas ; 1 vol. of the former to 2 of the latter ; and it would seem that the combina- tion takes place in no other proportion ; the product is a dry white acidulous salt, from which water precipitates silica, and if the solution be boiled in glass vessels, they are corroded with energy. Henry. (I.) By combining the silicated fluoric acid gas with liquid ammo- nia, a pure fluate of ammonia is obtained, while the silica is all pre- cipitated. This fluate of ammonia may then be decomposed by sul- phuric acid, and fluoric acid obtained free from silica. (m.) This gas unites with other bases, and forms compounds that have been called, as Berzelius thinks improperly, fluo-silicates.* 3. ETCHING UPON GLASS. (a.) In consequence of the energy with which fluoric acid acts upon glass, it is necessary only to protect it where we would not choose to have it corroded, and to expose it in those places where we would wish an indelible trace. (b.) Sees wax^ forms a good protection, but one stilt better is made of this substance and turpentine melted together and spread over the warm glass, until an even coating is obtained ; a rim or border of the same substance is made to surround the glass, and then the pure fluid acid, diluted to such a degree that it does not smoke, may be poured on, and the glass should be carefully turned till the whole is thoroughly moistened. Two or three minutes are ordinarily sufficient to com- plete the etching, and the same portion of acid will etch a number of plates successively.^ (c.) Those who have not a proper distilling apparatus may effect the same object, but much more tardily and imperfectly, by allowing the vapor of the fluoric acid, as it rises from an open vessel of tin or lead to strike the glass plate, but there is danger of corroding it on the wrong side, unless that too is protected ; and also of melting and disfiguring the varnish by the contact of the hot acid. * See his memoir, Ann. de Chim. et de Phys. Tom. XXVII, and Ann. of Philos. N. S. quoted by Henry. t Isinglass is also mentioned by Mr. Murray, as a protection, but this I have never tried. + Am. Jour. Vol. VI, p. 355. I find this process easy and always successful; an engraver prepares the plates, and the etching is done in the laboratory. FLUO-BORIC ACID. 505 (d.) Diamonds and various gems have been exposed to the action of fluoric acid, but without much effect.* FLUO-BORIC ACID GAS. 1. HISTORY. This singular compound was obtained about the same time by Gay-Lussac and Thenard and by Sir H. Davy, although the former gentlemen first published their observations. Both had the same object in view, that of obtaining fluoric acid gas free from water. 2. PROCESS. (a.) A coated iron tube; vitreous boracic acid 1 part and fluor spar 2, with heat. (6.) An easier way is to distil, in a glass retort, 1 part vitreous boracic acid, 2 fluor spar and 12 strong sulphuric acid.\ Common crystallized boracic acid answers perfectly well.f 3. PROPERTIES. (a.) Colorless and transparent, and, over mercury, permanently aeriform. It reddens litmus. (b.) Sp. gr. 2.36; at 60 Fahr. and 30 in. bar. 100 cubic inches of this gas weigh 72.044 grains. (c.) Extinguishes flame and life; very pungent and suffocating, but less so than fluo-silicic acid gas. (d.) The bubbles of this gas break, in a moist air, in dense white fumes almost like snow. (e.) This arises from the strong attraction of the gas for water, which it detects in almost every other gas and precipitates in a cloud, to the density of which the boracic acid, as well as the moisture, probably contributes. (f.) Water absorbs 700 volumes of this gas and acquires the sp. gr. 1.77; although it increases in volume. The acid thus formed is dense, fuming and highly corrosive, and considerably resembles sul- * Other stones were also tried. The agate lost its transparency and color ; the avanturine its brilliant particles, and appeared like a gray pebble ; the bloodstone became soft and brittle, and its beautiful colors were changed and became dull ; garnets were corroded, and assumed a dark red color, and the gypsum of Mont- martre and the sandstone of Fontainbleau were dissolved. Rock crystal is not at- tacked so readily as glass, owing to its stronger aggregation. (Gray's Op. Chem. p. 457.) The minerals generally lost weight, and the effects may be referred either to the affinity of the fluoric acid for silica or for the other constituents of the stones. Fluoric acid is useful in giving indelible labels upon glass for the laboratory ; and attempts have been made, on the score of economy, to substitute glass plates, cor- roded by fluoric acid, instead of copper plates, and a funeral piece in honor of Scheele was executed in that way; but it is difficult to sustain the glass and prevent it from cracking in the press. t J. Davy, Phil. Trans. 1812. t The previous vitrification adds considerably to the trouble of the experiment, nd for a class experiment presents no important advantage. Thomson, First Prin. Vol. II, p. 179. 64 606 FLUORIC PRINCIPLE. phuric acid. It requires a heat above 212 to make it boil, and it condenses again in striae ; it chars animal and vegetable substances like the sulphuric acid; it blackens paper, and forms a true ether with alcohol. On glass it has no effect, its affinity for silica being evi- dently supplanted by that of the boracic acid. (g.) It unites with ammoniacal gas in 3 proportions ; in equal measures, if the ammonia be first introduced into the tube ; the com- pound is then solid and neutral ; if the fluo-boric gas pass in by bub- bles, the combination is liquid, and in the proportion of 2 ammonia to 1 of the acid gas. If to this last more fluo-boric gas be admitted, it is absorbed and the product still remains liquid. Heat expels part of the ammonia from both the fluid compounds, and a solid, volatile &n4 unaltered by heat, is obtained.* Nature of the fluoric principles. 1. REMARK. Three acids, the boracic, the fluoric and the muri- atic, were, for many years, mentioned in connexion, as undecomposed bodies. The boracic, as we have seen, has been satisfactorily de- composed, and the analysis has been confirmed by synthesis. Its constitution is in perfect accordance with that of most of the other acids, as it consists of a combustible base and oxygen.. The muriatic acid, as we shall soon see, is now regarded, by the chemical world, as a compound of an inflammable basis, namely, hydrogen, not how- ever with oxygen, but with chlorine, which is admitted as a principle analogous to oxygen, fluoric remains for 2. COMPOSITION OF FLUORIC ACID. In the researches of Sir H. Davy, of Gay-Lussac andThenard, and of Berzelius, maybe found most of the facts relating to this investigation. It would occupy too much room to recite them here in detail. f Potassium and sodium can both be made to burn vividly in fluo-boric and fluo-silicic acid gas, and a combustible substance makes its appearance, but it is evi- dently the basis of the boracic acid in the first case and of silica in the second j and accordingly, when they are, respectively, made to burn in oxygen gas, boracic acid and silica are reproduced. Those experiments may therefore be regarded as affording a convenient method of decomposing boracic acid and silica ; and in that view they are valuble, and the method by fluo-silicic gas or the fluo-silicate of soda and potassa is the most valuable one which we possess for obtaining the basis of silica. (See p. 277.) Potassium, as already stated, burns vividly, and even with explosion, in the strongest liquid fluoric acid that has hitherto been obtained. As that fluid is always * Henry, Vol. I, p. 366. t See Recherches Physico-Chimiques, Tom. II, Phil. Trans, for 1813 and 1814, d the scientific journals of the day. FLUORIC ACID. 507 procured by the aid of sulphuric acid,* there would seem to be no reason to doubt that it must contain water,f the decomposition of which, according to the opinion of Gay-Lussac and Thenard, affords the hydrogen which is evolved and supplies oxygen to the potassium, by which it becomes potassa and unites with fluoric acid to form an acid fluate of potassa. In this experiment, therefore, there seems no reason to admit that the fluoric acid is decomposed, and it would be premature to say that it consists of oxygen and a combustible basis, although such a constitution is certainly both very possible and very probable. On the whole, we must, for the present, and until additional re- searches shall clear up the difficulty, rank fluoric acid among the un- decomposed bodies :{ although from analogy, I have placed it with bodies known to be compound. EQUIVALENT OF FLUORIC ACID. Dr. Thomson,^* has concluded that the representative number of fluoric acid is 10, and Berzelius has formed the same conclusion 5 this is upon the supposition that the fluates are compounds of fluoric * It would seem that the fluoric acid exists anhydrous in fluo-silicic and fluo-boric gas, and in its own saline compounds, fluor spar, &c. but that it cannot be separated, in its pure state, from its combinations, except by the aid of an acid that contains water. t Especially if the sulphate of lime remaining in the distilling vessel be, as it doubtless is, anhydrous ; for besides the strong affinity of the fluoric acid for water, the residuum in the vessel is usually heated to a degree that expels all water from the natural hydrous sulphates of lime, and 1 have found it very hard to detach. t Deference to the opinions of very able men, and to the practice of some of the most respectable chemical authors, would have led me to place the' hypothetical principle fluorine, in the text and in the tabular arrangement. But it appears plain that fluorine would never have been thought of, but for the supposed analogies with chlorine, which controverted topic was keenly agitated about the time of the princi- pal modern researches upon fluoric acid, and the extension of these analogies, by the discovery of iodine, almost at the same period, seemed to make it, in a sense, neces- sary to admit the existence of a similar principle in fluoric acid. These analogies may be mentioned again, after we have gone through with the history of chlorine and iodine. For the present, however, it may be remarked that there is no decisive experiment, proving the existence of fluorine. When Sir H. Davy galvanized the strongest liquid fluoric acid, an inflammable gas, doubtless hydrogen, was disengaged at the negative pole, and the platinum wire" was rapidly corroded at the positive ; while a chocolate colored powder collected on the wire. As it does not appear to have been examined, we are in na condition to decide whether it was, as imagined, a compound of fluorine with platinum, or an oxide of that metal. We do not know whether the solvent powers of the fluoric acid, great as they are, may not have been so exalted by the galvanic energy, that this agent may have become capable, in its acid character, of attacking even plati- num, while it would be even possible that the oxygen requisite to oxidize the metal may have been derived from the water which would then give out the hydrogen, its other element at the negative pole. To me it appears premature, to place fluorine, a principle purely hypothetical,, along side with chlorine and iodine, whose distinct existence and peculiar energy are manifested in so many remarkable forms. First Prin. Vol. II. 508 FLUATES. acid, and an oxidated combustible or metallic base ; if therefore die fluoric acid contains one proportion of oxygen 8, the base will be ex- pressed by 2.* EQUIVALENT OF FLUO-SILICIC ACID. Reasoning upon the per centage of silica in fluoric acid gas, (61.4 John Davy,) its constitution is inferred to be, 1 proportion of fluoric acid, =10 1 " silica, 16 26, which would ap- pear to be its equivalent number. f EQUIVALENT OF FLUO-BORIC ACID. Upon the same authority, it is stated at 1 proportion fluoric acid, 10 I " boracic acid, - 24 34 FLUATES. General characters. Upon the supposition that they are compounds of fluoric acid and oxidated bases, rather than of fluorine and bases, or that they are fluates and not fluorides. 1 . Formed synthetically, by the union of pure fluoric acid with the base, or by double exchange of a solution of an alkaline fluate with the intended base combined with some acid in a soluble form. 2. The neutral fluates with fixed bases, fusible at high temperatures, and in close vessels ; if dry, not decomposed by any degree of heat. 3. Fluates of alkalies and alkaline earths not decomposed by heat, even when aided by the affinity of combustibles. 4. No anhydrous acid except the vitreous boracic decomposes them by heat alone, and this only by combining at the moment of decom- position with the fluoric acid. 5. Decomposed by being moderately heated with sulphuric, muri- atic, phosphoric and arsenic acids. * If the fluates are regarded as fluorides, that is, compounds of fluorine with a metal or combustible, then its equivalent is obtained by adding to that of fluoric acid the weight of one proportion of oxygen supposed to exist in the metallic base ; upon the supposition that the salts are fluates, this will give 10-1-8=18, for the number representing fluorine. t Thomson's First Prin. Vol. II, p. 176. FLUATES. 509 6. The vapor, which rises, corrodes glass ; this effect is decisive as to the presence of fluoric acid. 7. Alkaline fluates deliquescent and difficult to crystallize. 8. There are five native fluates , namely a.) Fluor-spar or fluate of lime the most important. b.) The double fluate of soda and alumina, called the cryolite, c.) The fluate of cerium. d.) The double fluate of cerium and yttria, and what some choose to call (e.) The fluo-silicate of alumina the topaz. Turner. FLUATE AND BI-FLUATE OF POTASSA. 1 . PREPARATION. FLUATE . (a.) Caustic potash and fluor spar do not produce this compound by heat, but carbonate of potash and fluor do by double exchange. (b.) Water being added, the carbonate of lime is precipitated, and the fluate ofpotassa is dissolved. (c.) Formed by saturating pure liquid fluoric acid with potassa,* much heat is disengaged. 2. PROPERTIES. (a.) JL gelatinous deliquescent mass, difficult to crystallize as- sumes a foliated form if evaporation is pushed to dryness. (b.) Suffers the aqueous, and afterwards the igneous fusion, by heat. (c.) Fluate of potassa acts upon silica and glass, especially when aided by heat, and even spontaneously in the course of a day or two, and a triple compound is formed of earth, acid, and alkali. (d.) The sulphuric acid expels the fluoric with brisk effervescence. BI-FLUATE. 1. FORMATION AND PROPERTIES. This salt is readily formed by leaving the acid in excess, and is easily converted into the neutral fluate by heating it to redness, which expels one proportion of fluoric acid. The bi-fluate crystallizes in square tables with the edges re- placed ; it is very soluble in water. 2. COMPOSITION. 1 proportion neutral fluate, and 1 of fluoric acid; by ignition, it leaves 74.9 of neutral fluate, and the remainder is composed of 11.5 of water, 13.6 acid.f * Or its carbonate. t Berzelius, Ann. ele Chim. etde Phys. Tom. XX VII. Addition to fluate of potassa. It is common in laboratories, to pass silicated flu- oric acid gas through water ; gelatinous silica is deposited, containing fluoric acid, and an acid fluate of silica remains in the water. If to this fluid, caustic potash, or its carbonate, be added, there is formed an acid fluate of silica and potassa soluble 510 PLUATES. FLUATE OF SODA. 1. PREPARATION. (a.) In the same manner as the preceding, and also by decompos- ing the acid fluate of silica by soda.* (b.) Dr. Thomson formed itf by passing fluo-silicic gas, to satura- tion, through solution of carbonate of ammonia, which was then de- composed by carbonate of soda, added by little and little ; after evap- oration to dryness in a silver vessel, resolution and filtration to get rid of a little silica, it was again evaporated and crystallized. The crys- tals are small and crackle between the teeth. 2. PROPERTIES. (a.) In transparent crusts like ice; after the expulsion of the water of crystallization forms opaque white crusts, becoming again transpa- rent by immersion in water. (b.) Not deliquescent or efflorescent ; a little more soluble in hot than in cold water ; effervesces vigorously with sulphuric acid ; taste bitter and styptic ; but not so strong as the fluate of potassa ; suffers the aqueous fusion. FLUATE OF AMMONIA. J 1. PREPARATION. (a.) Pulverized fluor 1 part and sulphate of ammonia 2 ; heat them in a subliming apparatus ; ammoniacal gas is liberated at first, and then fluate of ammonia sublimes and incrusts the capital. in 6 or 7 hundred parts of water; the filtered fluid, on evaporation, gives a fluate of silica and potassa, gelatinous, very transparent, tasteless, without effect on blue colors becoming pulverulent with a mild heat, and with ignition, exhales silicated fluoric acid gas. Both the powder and the jelly effervesce vigorously with sulphuric acid. Caustic potash, soda and ammonia, in the cold, do not decompose it in 24 hours; potassa and soda dissolve it with heat. It is not possible, by potash, to extract pure silica from silicated fluoric acid gas, for it forms with it an insoluble triple salt. Gay-Lussac and Thenard, in Recher. Ph. Ch. T. II, p. 20. * The effect of soda upon the acid fluate of silica, is very different from that of po- tassa. There -is no prompt precipitate, but boiling produces readily a transparent jelly of pure silica, while the fluid is pure fluate of soda. In this manner, pure silica may be advantageously prepared even from the insoluble fluate of silica, which is completely decomposed by soda, with the same results as are obtained from the acid fluate. Id. t First Principles, Vol. II, p. 168. J Ammonia affects the acid fluate of silica in a manner very different from potassa, and even from soda. It promptly precipitates pure gelatinous silica, opake, and white, but a little silica remains in solution in the fluate of ammonia, as appears from its repeated precipitation, on the addition of pure ammonia, from lime to time, after evaporation. Ammonia also decomposes the solid acid fluate of silica, as perfectly as the fluid. Pure silica then can be obtained by ammonia, from either of them, although we cannot in this way obtain a pure fluate of ammonia, as we do a pure fluate of soda in the parallel process with that alkali. Id. FLUATES. 5J1 (b.) Saturate pure liquid fluoric acid with caustic or carbonated ammonia; it is at first neutral, but by evaporation becomes acid, and does not crystallize. 2. PROPERTIES. By a continued heat it evaporates, in thick white vapors ; the taste is sharp, It is a useful fluate, being in a convenient form to be employed as a test of lime, &LC. FLUATE OF BARYTA.* 1. PROCESS. (a.) By mingling pure fluoric acid with barytic water, solid pure baryta, or the native or artificial carbonate. (b.) To nitrate or muriate of barytes, add fluoric acid, or any alkaline fluate. 2. PROPERTIES. (a.) A pulverulent, fleecy precipitate, sparingly soluble in water, decomposed by lime water, and by sulphuric acid. (b.) Soluble in an excess of fluoric acid, and in the nitric and muriatic acids. (c.) Sometimes fluoric acid is used to distinguish between lime and baryta, because the compound with the latter is more soluble than with the former. FLUATE OF STRONTIA. Substituting strontia and its soluble salts, for baryta and its similar salts, the facts with respect to this fluate are the same as with re- spect to the preceding, and their properties are very similar. FLUATE OF LIME. Remark. As ths native fluate of lime exists in abundance, there is no occasion to form it by art. 1. PREPARATION. It may however be done, by processes per- fectly analogous to those which have been stated with respect to baryta and strontia, substituting lime water, with fluoric acid, or bet- ter, the soluble salts of lime, with solutions of the alkaline fluates ; perhaps the best is fluate of ammonia, with nitrate of lime ; the in- soluble precipitate is washed and dried, 2. PROPERTIES. (.) Lime and fluoric acid reciprocally take each other from every thing else,\ and are therefore mutually tests ; the soluble alkaline * If the acid fluate of silica be poured into a solution of the muriate, or nitrate of baryta, in a few minutes a multitude of small crystals are precipitated ; they are very hard, insoluble in water, and in nitric and muriatic acids, and suffer no alter- ation from being heated with lampblack. There can be no doubt that they are a triple compound of fluoric acid, silica, and baryta. t Some doubt is intimated relative to fluate of magnesia. Aikins, Diet. Vql. I, p 441. 512 FLUATES. fluates are generally used for this purpose, especially the fluate of ammonia. (b.) Soluble in fluoric acid, and in the nitric and muriatic. (c.) The native fluate is phosphorescent on hot iron. (d.) Insipid not affected by air at 51 W. fuses into a trans- parent glass. (e.) Decomposed by sulphuric acid, with evolution of fluoric acid gas, as already stated. NATURAL HISTORY. This belongs to mineralogy, and the uses of the mineral to the arts ; but it may be briefly stated here, that hitherto only one mine has been discovered that affords the massive fluor, in pieces of sufficient size and firmness to admit of their be- ing wrought. This mine it at Castleton, in Derbyshire, England, and is called the spar rnine.J I saw it in 1805, when it was far from being exhausted. FLUATE OF MAGNESIA. 1. PREPARATION. (a.) Carbonate of the earth and liquid fluoric acid, with a mild heat ; there is effervescence ; near saturation, the salt falls down chiefly in a gelatinous precipitate, probably mixed with silica. (b.) Soluble salts of magnesia, mingled with liquid fluoric acid or with solutions of alkaline fluates. 2. PROPERTIES. Scarcely soluble in water ; rather more so in alcohol ; not decomposed by heat, nor by any acid, but soluble in the strong acids. The Brucite, or Condrodrite contains a native fluate of magnesia. FLUATE OF ALUMINA. 1. PROCESS. Sa.) The earth precipitated from alum is soluble in fluoric acid. b.) Alum and alkaline fluates decompose each other, and pro- duce fluate of alumina, and sulphate of alkali. 2. PROPERTIES. (a.) The pulverulent compound becomes gelatinous by evapora- tion, but does not crystallize. } In that mine, it is not, as every where else, mixed with other spars, and with metallic matters, but constitutes entire veins by itself; these veins lie imbedded in solid limestone, and are wrought for the sake of the fluate of lime only, which is manufactured into articles of furniture, as candle sticks, salt-cellars, ink stands, &c., and into the most beautiful ornaments for houses and palaces, as urns, vases, pyra- mids. In this mine, attached to the walls and roofs, are the most beautiful crystallized incrustations, and regular stalactites of carbonate of lime, some of which last have reached the floor, and form continued pillars, and as they, and the incrustations are generally of a snowy whiteness, they present a very brilliant spectacle when those dark regions are lighted up with candles. SELENIUM. 513 (b.) Insipid, insoluble in water, but soluble in an excess of acid. (c.) The compound of alumina, fluoric acid, and soda, may be made to crystallize, and is even found native in the cryolite; and in the topaz, fluoric acid is combined with fluoric acid. The properties of the t fluate of silica have been incidentally detail- ed, perhaps to a sufficient extent. The following facts may how- ever be advantageously recapitulated. FLUATE OF SILICA. 1. This compound is always formed when fluoric acid is obtained in glass vessels ; more perfectly if a little powdered flint or sand be mixed with the materials. 2. Silica is thus suspended in the gaseous form, and is permanent over quicksilver. 3. Water throws down a part of it. 4. Glass vessels are corroded' both by liquid and gaseous fluoric acid ; Bergman obtained crystals from a fluoric solution, which Four- croy regards as fluate of silica. 5. Alkalies decompose the fluate of silica, and triple compounds are often thus formed. 6. A similar compound is formed when fluoric acid attacks glass ; softer siliceous stones that contain no alkali, are attacked by fluoric acid, with more difficulty. 7. Fluate of silica is decomposed by heat. Remarks. It is very probable that the progress of chemical analysis will bring to light more native combinations ,of earths, with the fluoric acid ; a number have been added within a few years. Gay-Lussac and Thenard remark, that they had a quantity of fluor of the purest and most beautiful appearance, in which the eye, aided by a magnifier, did not enable them to discover any silex, which nevertheless yielded silicated fluoric acid gas. The fluates of zirconia, glucina, and yttria are formed upon the same principles as the other earthy fluates, but are of no impor- tance.* SEC. VIII. SELENIUM. 1. DISCOVERY. By Berzelius, in 1818. The iron pyrites of Fahlun, in Sweden, afford by sublimation, sulphur, which being em- ployed in the manufacture of sulphuric acid, a reddish substance f was constantly deposited in the bottom of the leaden chambers. It was principally sulphur, but on burning it, an odor like that of decay- * See Recher. Phys.-Chim. Tom. II, p. 27. t In this substance, besides the selenium, Berzelius found mercury, tin, cop- per, zinc, iron, lead, and arsenic. 65 514 SELENIUM. ed horse radish was j>erceived, and on closer examination, a peculiar substance was discovered, to which the name of selenium was given. It has been discovered in the form of sulphuret of selenium, among the volcanic products of the Lipari islands ; at Clausthal, in the Hartz mountains, in combination with lead, cobalt, silver, mercury and copper ; in several varieties of sulphur, in the sulphuric acid of Nordhausen, and in that manufactured from the sulphur of pyrites, from the isle of Anglesea. 2. NAME. From 2eX>jvif], the moon, in analogy with tellurium, from tellus ; the substance having some resemblance to tellurium, and having at first been mistaken for it by Berzelius.* 3. PROCESS. The process of Berzelius being very long, the shorter one of Lewenau is here abridged. The red deposit 1 Ib. is placed in a 2 quart tubulated retort, whose sides must not be soiled ; it is placed in the sand bath, and connected with a large globular receiver, joined by a Woulfe's tube, to a flask full of water, and all properly luted. Nitro muriatic acid, composed of 8 muriatic, sp. gr. 1.2, to 4 of nitric, sp. gr. 1.5,j* was now introduced by portions, to the bottom of the retort, intervals being allowed for the subsidence of the effer- vescence, and of the heat. Red vapors escaped, the liquid in the retort became dark gray, and that in the Woulfe's bottle, reddish yellow. The fluid being distilled over in the retort, a reddish yellow gas was disengaged, and near the end, small yellow stellated crystals lined the neck of the retort, which disappeared with the increase of the heat ; most of the liquid having thus passed, more acid was ad- ded in portions, and a violent action ensued at every addition, the water in the flask being several times changed, as it became satura- ted with the acid vapors. All the liquors being redistilled from the retort, an insoluble residuum, of a deep red color, supposed to be selenium, now occupied its bottom and sides. To dissolve it, l Ibs. of fuming nitric acid was next added, and distilled nearly to dryness. The residuum was then washed with boiling distilled water, till it came off tasteless, and the filtered fluid was of a light yellow. J This fluid contained the selenium in the form of selenic acid, and to precipitate it, (neglecting the metals that might be in so- lution,) recently prepared sulphite of ammonia, in large excess, was added, which threw down the selenium in the form of large cinnabar * See Ann. de Chim. et de Phys. Vol. IX, and Ann. Phil. Vol. VIII, N. S. and Vol. XIII. t The author speaks of 12 Ibs. of the mixed acid, but this seem? disproportioned Jo the size of the retort. J The distilled fluid was found to be slightly seleniferous. OXIDE OF SELENIUM. 515 colored flakes. When the solution was strong, the precipitation was immediate ; if dilute, it was more tardy, and the color varied from bright red to dark gray. The selenium was washed with 5 or 6 parts of cold distilled water, till muriate of baryta gave no precipitate, and lastly, it was dried in the shade. The selenium still contained in the liquor is obtained by concen- tration, by evaporating to two thirds the bulk, and the addition of more sulphite of ammonia, and finally by immersing bars of zinc, taking care that these do not remain in too long, and thus mix their own substance with the selenium.* 4. PROPERTIES. (a.) Color various ; if rapidly cooled, dark brown, or gray, or of a leaden color, and metallic lustre, it often resembles polished he- matite ; when in powder of a deep red, adheres by pounding, and its surface gray and smooth. (b.) It is not hard, but it is brittle; fracture conchoidal, of the color of lead, and perfectly metallic; lustre vitreous. (c.) Sp. gr. between 4.31, and 4.32. (d.) Jit 212 soft and ductile, like Spanish wax, and may be kneaded between the fingers, or drawn into fine translucent threads, wiiich have a metallic aspect ; " red by transmitted, but gray by reflected light." Becomes quite fluid, at a temperature considera- bly above that of boiling water, and near that of boiling mercury, or about 650, it boils, and may be distilled in a retort, condensing like mercury, in metallic drops, or if a retort with a large neck is used, or sufficient space to mix it with cold air, in a light sublimate, of a fine cinnabar color. Its vapor is of a color between that of chlorine, and that of the vapor of sulphur. If cooled slowly, it assumes a granulated fracture, like that of cobalt. (e.) At the boiling point its vapor is inodorous ; but under the blowpipe a piece not over j\ of a gr. will Jill a large room with the smell of horse radish : it tinges the blowpipe flame of a fine azure blue. (/.) Insoluble in water ; not altered by the air. (g.) A non-conductor of heat and electricity, and does not become electric by friction. OXIDE OF SELENIUM. (a.) The peculiar odor is developed when the exterior flame of the blowpipe is applied, and is caused by the combination of selenium * The sulphureous deposit examined by Mr. Lewenau was from ^ sulphuric acid manufactory, in Hungary : it was much richer than that of Sweden, and afforded 591.82 grs. to the pound of the crude substance, of which 484.16 was from the first precipitate. Ann. Phil. N. S. Vol. VIII, p. 106. In one instance, the material of Sweden gave Berzelius only 0.0015 of its weight. 516 SELENIOUS ACID. with oxygen, forming a gaseous oxide of selenium* and like arsenic it is odorous only while combining with oxygen at a high temperature. (b.) Formed best by heating selenium in a close glass vessel, with a limited quantity of air, which is to be washed to remove the selenic acid, a little of which is formed at the same time ; the water acquires the smell of the gas, and feebly reddens litmus. The oxide of selenium is only sparingly soluble in water, and does not combine with alkalies. Its composition has not been ascertained, but it is supposed to be one proportion of each of the constituents. SELENIOUS ACID. 1. PROPERTIES. (a.) Selenium is combustible. Heated in a flask filled with oxy- gen gas, selenium evaporates with the odor of oxide of selenium,, but without inflaming, and exactly as it would do in common air ; but if heated in a glass ball of an inch in diameter, and supplied with oxygen gas at the moment of ebullition, it burns with a feeble flame, white towards the base, and green, or bluish green on the edges : the selenium is completely consumed, oxygen gas is absorbed, and the remaining ga has the odor of oxide of selenium. The product is a sublimate of selenious acid. (b.) Hot nitric acid dissolves selenium, and forms on cooling large prismatic crystals of selenic acid, longitudinally striated, and resem- bling almost exactly those of nitrate of potash. (c.) This acid is still better prepared by the aid of nitro-muriatic acid. A white residuum is left on evaporation, and by an increased heat the selenious acid sublimes, and is condensed in the colder part of the apparatus in very longf needles of four sides. The vapor of the acid has a deep yellow color much resembling that of chlorine, but not so deep as that of the vapor of the selenium itself. (d.) Selenious acid has a peculiar lustre which it quickly loses on being exposed to the air ; the crystals adhere and it gains weight so fast that it is difficult to weigh it accurately. Taste acid, leaving a slightly burning sensation. (e.) Readily soluble in cold and almost without limit in hot water, from which, by rapid cooling, it crystallizes in grains, and more slow- ly in prisms, and spontaneously in acicular radiated groups. Very soluble in alcohol and giving with that fluid by distillation an etherial odor, intermediate between that of nitre and sulphuric ether. (f.) Sulphuric acid, selenic acid, and alcohol in mixture produce by distillation, a most insupportable odor. Decomposition. Easily af- * Which Berzelius thinks analogous to the oxide of carbon, although ho has not been able to isolate and shew it separately. t In a large retort they are sometimes two inches or more long. SELENIC ACID. 517 fected by all bodies having a strong affinity for oxygen, as sulphurous and phosphorous acids, alkaline sulphites, and sulphuretted hydrogen, and metallic zinc,* by all of which it is precipitated. Zinc throws it down in the form of red, brown, or blackish flakes : sulphuretted hydrogen in an orange precipitate, fusible a little above 212, sub- limed in close vessels, burning in the air and producing selenic and sulphurous acids. (g.) Selenium is soluble in oils; it unites with the metals usually with ignition, forming seleniurets commonly of a gray color and metallic lustre. The seleniuret of potassium is soluble in water with efferves- cence. The acids disengage from it seleniuretted hydrogen, whose odor is like that of sulphuretted hydrogen but excessively offensive. This gas is soluble in water, combines with the alkalies, and pre- cipitates metallic salts of a dark color. 2. EQUIVALENT NUMBER. Berzelius from his investigations con- cludes that selenious acid consists of Selenium, 71.261 100.00 Oxygen, 28.739 40.33 If it is composed of one proportion of base and two of oxygen, the equivalent number of selenium will be 40+2 oxygen 16=56ybr tht equivalent of selenic acid. SELENIC ACID. The acid just described has been hitherto called by this name, but another acid has been discovered containing an additional equivalent of oxygen, and which is therefore called selenic acid. 1. PREPARATION. Omitting the tedious process upon the selenitic ores,f we may describe that which commences with the preceding acid, the selenious. (a.) It is neutralized by soda, and by fusion with nitre or with ni- trate of soda it is converted into seleniate of soda and crystallized. (b.) This seleniate is decomposed by nitrate of lead, which gives an insoluble seleniate. (c.) This is decomposed by a stream of sulphuretted hydrogen, which precipitates the lead as a sulphuret and liberates, without de- composing the selenic acid ; the excess of sulphuretted hydrogen be- ing expelled by heat, the selenic acid remains diluted with water. 2. PROPERTIES. (a.) Colorless; not decomposed below 576 Fahr. but above that emits oxygen and becomes selenious acid. (b.) Sp. gr. When concentrated at 329, it is 2.524 ; if at 512, it is 2.60 ; and if at 545, it is 2.625 ; but a little selenious acid is Mixed with muriatic acid. Edin. Jour, of Science, No. XVI, p. 294, and Turner, 2d ed. p. 350. 518 SELENIUM. then present. Concentrated at a heat above 576, and deducting the selenious acid present, it appeared to contain 15.75 water. (c.) Attracts water powerfully, and by combining with it, evolves as much heat as sulphuric acid. (d.) Boiled with muriatic acid, selenious acid is deposited and chlorine liberated, and the solution dissolves gold but not platinum ; it resembles aqua regia, and probably contains it. It unites with alkaline bases and forms salts, which are with diffi- culty decomposed by sulphuric acid, which it appears strongly to re- semble. (jf.) Selenic acid dissolves iron and zinc, with disengagement of hydrogen gas. 3. ITS EQUIVALENT. It appears to contain 3 equivalents of oxy- gen, 24-f-l of selenium, 40 = 64. CLASSIFICATION. Selenium resembles the metals in sp. gr., and metallic lustre, and in most of its chemical properties, but it is a non- conductor of heat and electricity. Berzelius ranked it with the met- als, and it has a considerable resemblance to tellurium, but it is rather more like sulphur, and on the whole seems to form a connecting link between the combustibles and the metals. Its combination with hy- drogen appears to be particularly noxious, and it is probable that it often renders sulphuretted hydrogen more noxious, since there is reason to believe that it is not unfrequently present i*that gas, as sulphur is often contaminated by it. It is obtained by heating the seleniuret of iron with muriatic acid, by an obvious theory. The gas is acid and has been called hydro-selenic acid and seleniuretted hydrogen. It is colorless, fetid, irritates and paralyses the membrane of the nose for some hours, so that the sense of smell is destroyed ; it is dissolved by water and stains the skin brown. It is decomposed by the air and leaves selenium. With all the metallic solutions it forms seleniurets.* Selenium being as yet a substance very difficult to be obtained, we must refer, for numerous additional particulars and for the history of the seleniates,, to the elaborate mempir of Berzelius, in the ninth vol- ume of the Annales de Chimie et de Physique. * Turner, 2d ed. p. 356. END OF VOL. 1. RETURN TO: CIRCULATION DEPARTMENT 198 Main Stacks LOAN PERIOD 1 Home Use 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS. Renewals and Recharges may be made 4 days prior to the due date. Books may be renewed by calling 642-3405. DUE AS STAMPED BELOW. Mfw 1 4 ?nn? "'UV 1 OJuL * FORM NO. DD6 UNIVERSITY OF CALIFORNIA, BERKELEY 50M 6-00 Berkeley, California 94720-6000 pV- fe> J> D^/^ :xnpRfffjm'-; -nor*