UC-NRLF 4. SYSTEM CHEMISTRY IN FIVE VOLUMES. BY THOMAS THOMSON, M.D. F.R.S.E. THE FOURTH COITION, VOL. I. EDINBURGH: PRINTED FOR BELL & BRADFUTE. >OT D BY JOHN MURRAY, LONDON; AND GILBERT & HODGE9; DUBLIN. 1810. Y/IT8IM3HO #O8MQHT 8AKOHT iftto JOHN BARCLAY, M. D. \1 I LECTURER ON ANATOMY. SIR, THE motives which induced me to prefi* your name to the first Edition of this Work, still con- tinue to operate with undiminished force. Your gene- ral knowledge, your particular views, and the intimate connection between Chemistry and that science of which you are so great a master, qualify you in a peculiar manner to judge of the merits of a Work which yQU originally suggested, and which you will receive as a pledge of that intimate friendship which we have so long enjoyed. I am, DEAR SIR, Your sincere Friend, Arid humble Servant, THE AUTHOR, EDINBURGH, April aoth, a ol . PREFACE. THE general attention which is at present paid to Chemistry in Britain cannot escape the most superficial observer. The sale of three large Editions of a Work so extensive as the present, within a year after the pub- lication of each> is a decisive proof that the votaries of the science are numerous and daily increasing. Indeed, it possesses such attractive charms, and sheds so benefi- cial an influence over the arts and manufactures, that to be welcomed and cultivated it requires only to be known . and if we consider the number of eminent chemists at present in the British Empire, we cannot but indulge the most flattering hopes of the future progress of the science. Some years ago it was affirmed in a continen- tal journal, and a chemist of eminence attached his name to the assertion, that Britain possessed scarcely a scientific chemist. The remark was prefixed to an ac- count of a set of experiments on a subject of importance. In this account many interesting facts and observations are stated as new, though they had been almost all an- ticipated three years before by Dr Wollaston. The experiments of the British chemist must have been un- known to the continental philosopher, as he observes with regard to them the most profound silence ; yet they had appeared in the Philosophical Transactions, the most celebrated work in England, or even in Eu- rope. X PREFACE. AT present it is not likely that any man, how par- tial soever to his own circle or his own country, would hazard the ridicule of such an assertion. We can reckon the names of not a few philosophers still worthy of the country of BACON and of NEWTON, where Philosophi- cal Chemistry first originated, who cultivate the science with assiduity and success, and who have already en- riched it with the most important discoveries. Nor is it meant to depreciate the illustrious Chemists on the Continent 3 the science has been deeply indebted to their genius, and still requires their fostering care. Indeed, so important, so difficult, so vast, so infinite are the ob- jects of Chemistry, that it can only be rapidly and sue* cessfully improved by the united exertions of all na- tions, tongues, and languages. THE object of this Work was to facilitate, as much as possible, the progress of Chemistry, by collecting into one body the numerous facts whkh lay scattered through a multiplicity of writings, by blending with them the history of their gradual development, and by accompanying the whole with exact references to the original works in which tbe discoveries have been re- gistered. The avidity with which the wprk was re- ceived, and the private or public approbation of most of our most eminent Chemists, are flattering proofs tbat it was not considered as useless. SEVERAL circumstances have retarded the appear, ance of this Edition much longer than was origin ally .intended or expected. Meanwhile the science has been advancing in all its departments. A numerous band of philosophers are devoted to it in almost every part of PREFACE. 3U Europe ; and new and important discoveries are the na- tural consequences of their enlightened exertions. No pains have been spared by the Author to collect these improvements as they made their appearance, and to render this Edition as complete a register as possible of the present state of the science. Much curious ad- ditional matter has been inserted in it, which was un- known at the publication of the last Edition. The dif- ficult communication with the Continent, and the re- cent discovery of several very important facts, htve swelled the Appendix to an unusual size. IT was the intention of the Author to have collected all these alterations and improvements, and to have printed them in a separate volume, for the sake of the purchasers of the former Editions ; but this plan has been abandoned with regret, as impracticable. The addi- tions are so numerous, that, had they been thus collect- ed, they would have amounted to a size too nearly ap- proaching that of the original work, and would have been too expensive to answer the purpose of an Appen- dix ; nor would it have been possible, without perpe- tual repetitions, to have wrought them into any thing like a connected series. MUCH pains have been taken to render every part of this Edition, and especially the numerous Tables which it contains, as correct as possible : But in a work of such extent, and necessarily embracing such a vast va- riety of matter, errors, both from ignorance and inat- tention, are perhaps unavoidable. The Author lay under considerable obligations to several of his friends, and likewise to different men of eminence with whom he ill fREFACE. was not personally acquainted, who took the trouble to send him lists of mistakes committed in the former Edition, and thus enabled him to correct errors which might otherwise have passed undiscovered by the Au- thor himself. To some of the same gentlemen he is indebted for a variety of new and important chemical facts, which had not been previously published to the world. THE last volume, in consequence of the great length of the Appendix, swelled out unexpectedly to such a size, that it was thought expedient, for the sake of unifor- mity in the bulk of the volumes, to place the Index at the end of the first rather than of the last volume, where it usually stands. CONTENTS OF VOLUME FIRST. PART I. PRINCIPLES OF CHEMISTRY 15 BOOK I. OF SIMPLE SUBSTANCES 16 DIVISION I. Of Confinable Bodies 18 CHAP. I. Of simple supporters - 19 SECT. l. Of oxygen 20 CHAP. II. Of simple combustibles - 30 SECT. 1. Of hydrogen - - 31 2. Of carbon and diamond 38 3. Of phosphorus 65 4. Of sulphur 79 CHAP. III. Of simple incombustibles 103 SECT. 1. Of azote 104 2. Of muriatic acid . 117 CHAP. IV. Of metals - - 131 CLASS I. Malleable metals - 147 SECT. 1. Of gold - - 148 2. Of platinum - - i<>7 3. Of silver . . 165 4. Of mercury - - 172 CONTENTS. Page, SECT. 5. Of palladium - - 185 6. Of rhodium - - 192 7. Of indium - - 196 8. Of osmium - - 20a 9. Of copper - - 204 10. Of iron - - 216 11. Of nickel - - 250 12. Of niccolanum - - 256 13. Of tin - - 258 14. Of lead - 270 15. Of zinc 285 CLASS II. Brittle and easily fused metals 303 16. Of bismuth 304 17. Of antimony - 312 18. Of tellurium - 323 19. Of arsenic - 325 CLASS III. Brittle and difficultly fused metals - - 337 20. Of cobalt - - 338 21. Of manganese * 345 . Of chromium - 352 23. Of uranium - - 355 24. Of molybdenum - 361 25. Of tungsten - - 371 CLASS IV. Refractory metals - 377 26. Of titanium - - 378 27. Of columblum - 381 28. Of cerium - - 383 29. General remarks - 387 DIVISION II. Of unconfinable Bodies - 401 CHAP. I. Of light - r 403 II. Of caloric * - . 423 CONTENTS. XV Page. SECT. 1. Nature of caloric - 424 2. Motion of Caloric 435 3. Equal distribution of tem- perature - - 478 4. Effects of caloric - 486 I. Changes in bulk ib. II. Changes in state 516 III. Changes in composition 546 5. Quantity of caloric in bodies 547 6. Sources of caloric - 582 I. The sun - 583 II. Combustion - 588 III. Percussion 611 IV. Friction 615 V. Mixture - 622 CHAP. III. Of simple bodies in general 626 BOOK II. OF COMPOUND BODIES, Vol. II. i DIVISION I. Of Salifiable Bases - 3 II. Of Primary Compounds 112 III. Of Secondary Compounds 517 BOOK III. OF AFFINITY, Vol. III. 417 PART II. CHEMICAL EXAMINATION OF NATURE, Vol. IV. - i BOOK I. OF THE ATMOSPHERE - 2 II. OF WATERS - 128 III. OF MINERALS - - - isi IV. OF VEGETABLES - - 635 V. OF ANIMALS, Vol. V. - 423 S Y S T E M OF CHEMISTRY. .S soon as man begins to think and to reason, the dif- ferent objects which surround him on all sides naturally engage his attention. He cannot fail to be struck wi their number, diversity, and beauty ; and naturally feels nature a desire to be better acquainted with their properties and uses. If he reflect also, that he himself is altogether de- pendent upon these objects, not merely for his pleasures and comforts, but for his very existence, this desire must become irresistible. Hence that curiosity ^ that eager thirst for knowledge^ which animates and distinguishes generous minds. Natural objects present themselves to our view in two Divided in- different ways ; for we may consider them, either as se -ad fierce parate individuals, or as connected together and depend^ ing upon each other. In the first case, we contemplate Nature as in a state of restj and consider objects merely as they resemble one another, or as they differ from one another : in the second, we examine the mutual action of substances on each other, and the changes produced by that action. The first of these views of objects is distin* VOL, I. A 2 A SYSTEM OF guished by the name of Natural History ; the second, by that of Science. Science Natural science, then, is an account of the events which take place in the material world. But every event, or, which is the same thing, every change in bodies, indi- cates motion ; for we cannot conceive change, unless at the same time we suppose motion. Science, then, is in fact an account of the different motions to which bodies are subjected, in consequence of their mutual action on eacli other. of two Now bodies vary exceedingly in their distances from each other. Some, as the planets, are separated by many millions of miles ; while others, as the particles of which water is composed, are so near each other, that we cannot, by our senses at least, perceive any distance between them ; and only discover, by means of certain properties which they possess, that they are not in actual contact. But the quantity of change or of motion, produced by the mutual action of bodies on each other, must depend, in some measure at least, upon their distance from one another. If that distance be great enough to be perceived by the eye, and consequently to admit of accurate measurement, every change in it will also be perceptible, and will ad- mit of measurement. But when the distance between two bodies is too small to be perceptible by our senses, it is evident that no change in that distance can be percep- tible ; and consequently every relative motion in such bo- dies must be insensible. Mechanic*! Science therefore naturally divides itself into two great ScT-ivus branchcs : tne ^ rst > comprehending all those natural events try. which arc accompanied by sensible motions ; the second, all those which are not accompanied by sensible motions. The fin>t of these branches has been long distinguished in CHEMISTRY. d Britain by the name of Natural Philosophy, and of late by the more proper appellation of Mechanical Philosophy ; the second is known by the name of Chemistry. CHEMISTRY, then, is that Science which treats of those Definition -....., of chemis- events or changes in natural bodies which are not accom~ tr y % panied by sensible motions. Chemical events are equally numerous, and fully as Us Import- important as those which belong to mechanical philoso- phy : for the science comprehends under it almost all the changes in natural objects with which we are more immediately connected, and in which we have the great- est interest. Chemistry therefore is highly worthy of our attention, not merely for its own sake, because it increases out knowledge, and gives us the noblest display of the wisdom and goodness of the Author of Nature ; but be- cause it adds to our resources, by extending our dominion over the material world, and is therefore calculated to promote our enjoyment and augment our power.- As a science, it is intimately connected with all the phenomena of nature ; the causes of rain, snow, hail, dew, wind, earthquakes, even the changes of the seasons, can never be explored with any chance of success while we are ignorant of chemistry : and the vegetation of plants, and some of the most important functions of animals, have received all their illustration from the same source. No study can give us more exalted ideas of the wisdom and goodness of the Great First Cause than this, which shows us everywhere the most astonishing effects produced by the most simple though adequate means, and displays to our view the great care which has everywhere been taken to secure the comfort and happiness of every living creature. As an art, it is intimately connected with all our manufactures : The glass-blower, the potter, the smith., A2 4 A SYSTEM OF and every other worker in metals, the tanner, the soap- maker, the dyer, the bleacher, are really practical che- mists ; and the most essential improvements have been introduced into all "these arts by the progress which che- mistry has made as a science. Agriculture can only be improved rationally, and certainly, by calling in the assist- ance of chemistry ; and the advantages which medicine has derived from the same source, are too obvious to be pointed out. Origin. The word CHEMISTRY seems to be of Egyptian origin, and to have been originally equivalent to our phrase natural philosophy in its most extensive sense, compre- hending all the knowledge of natural objects which the ancients possessed. In process of time it seems to have acquired a more limited signification, and to have been confined to the art of working met ah* . This gradual change was no doubt owing to the immense importance attached by the ancients to the art of working metals. The founders and improvers of it were considered as the great- est benefactors of the human race ; statues and temples were consecrated to their honour ; they were even raised above the level of humanity, and enrolled among the num- ber of the gods. How long the word chemistry retained this new signi- fication, it is impossible to say; but in the third century we find it used in a still more limited sense, signifying the art of making gold and silver. The cause of this new limitation, and the origin of the opinion that gold can be made by art, are equally unknown. Chemistry, in this new sense, appears to have been cultivated with consider- Our English word ptysida* has undergone a similar change. CHEMISTRY. able eagerness by the Grecian ecclesiastics, to have pass- ed from the Greeks to the Arabians, and by the Arabians to have been brought into the west of Europe. Those who professed it gradually assumed the form of a sect, under the name of ALCHYMISTS; a term which is sup- The Al- posed to be merely the word chemist, with the Arabian c ' I8ti * article al prefixed. The alchymists laid it down as a principle, that all metals are composed of the same ingredients, or that the substances at least, which compose gold, exist in all mr- tals, contaminated indeed with various impurities, but ca- pable, by a proper purification, of being brought to a perfect state. The great object of their researches was to find out the means of producing this change, and conse- quently of converting the baser metals into gold. The substance which possessed this wonderful property they called lapis philosophorum, " the philosophers stone ;" and many of them boasted that they were in possession of that grand instrument. Chemistry, as the term was used by the alchymists, sig- Their opi nified the art of making the philosophers stone. They ni< affirmed that this art was above the reach of the human capacity, and that it was made known by God to those happy sages only whom he peculiarly favoured. The fortunate few who were acquainted with the philosophers stone called themselves adepti, " adepts j" that is, per- sons who had got possession of the secret. This secret they pretended they were not at liberty to reveal ; affirm- ing, that dire misfortune would fall upon that man's head, who ventured to disclose it to any of the sons of men without the clearest tokens of the divine authority. In consequence of these notions, the alchymists made it a rule to keep themselves as private as possible. They A SYSTEM OF concealed, with the greatest care, their opinions, their knowledge, and their pursuits, In their communications with each other, they adopted a mystical and metaphori- cal language, and employed peculiar figures and signs, that their writings might be understood by the adepts on- ly, and might be entirely unintelligible to common read- ers. Notwithstanding all these obstacles, a great number of alchymistical books made their appearance in the dark ages ; many of them under the real names of the authors ; but a still greater number under feigned titles, or ascribed to the celebrated sages of antiquity. How far alchymy had extended among the. ancients, or whether it had even assumed the form of a sect, cannot be ascertained. Traces of it appear among the Arabians, who turned their attention to literature soon after the con- quests of the Caliphs, and who communicated to our bar- barous ancestors the first seeds of science. The principal chemical writers among the Arabs were Geber and Avi- cenna j and in their writings, such of them at least as we have reason to consider as authentic, there appears but lit- tle of that mysticism and enigma which afterwards as- sumed a systematic form- The alchymists seem to have been established in the west of Europe as early at least as the 9th century. Be- tween the llth and 15th centuries, alchymy was in its most flouri&hing state. The writers who appeared during that period were sufficiently numerous, and very different from each other both in their style and abilities. Some of their books are altogether unintelligible, and bear a stronger resemblance to the reveries of madmen, than to the sober investigations of philosophers. Others, if we make al- lowance for their metaphorical style, are written with Comparative plainness, display considerable acuteness, and CHEMISTRY. indicate a pretty extensive acquaintance with natural ob- jects. They often reason with great precision, though generally from mistaken principles ; and it is frequently easy enough to see the accuracy of their experiments, and even to trace the particular circumstance which led to their wrong conclusions. The principal alchymists who flourished during the dark ages, and whose names deserve to be recorded, either on account of their discoveries, or of the influence which their writings and example had in determining the public taste, were Albertus Magnus, Roger Bacon, Arnoldus de Villa Nova, Raymond Lully, and the two Isaacs of Hol- land*. The writings of the greater number of Alchymists are And remarkable for nothing bat obscurity and absurdity. They all boast that they are in possession of the philoso- * Albertus Magnus was a German. He was born in the year 1205, and died in 1280. His works are numerons ; but the most curious of them is his tract entitled DC Ahlym'ia, which contains a very distinct view of the state of chemistry in the I3th century. Roger Bacon was born in the county of Somerset in England in 1224. His merit is ton well known to require any panegyric. The greater num- ber of his writings are exceedingly obscure and even mystical; but he ge- nerally furnishes us with a key for their explanation, ^ome of them ex- hibit a wonderfully enlightened mind for the age in which he wrote. His tract De mirabili Pciettttlc Att'n et Natura would have done honour to Lord Bacon himself. Arnoldus de Villa Nova is believed to have been born in Provence, a- bout the year 1240. His reputation was very high ; but all of his writings that I have examined are exceedingly obscure, and often net intelligible. Raymond Luily was born at Barcelona in izjij His writings are still more obscure than those of Arnold. It is not known at what period the Isaacs of Holland lived, though it i? supposed to have been in the I3th century. I A SYSTEM OF phers stone ; they all profess to communicate the method of making it ; but their language is enigmatical, that it may be understood by those adepts only who are favoured with illumination from heaven. Their writings, in those benighted ages of ignorance, gained implicit credit ; and the covetous were filled with the ridiculous desire of en- riching themselves by means of the discoveries which t, they pretended to communicate. This laid the unwary open to the tricks of a set of impostors, who went about the world, affirming that they were in possession of the secret of the philosophers stone, and offering to com- municate it to others for a suitable reward. Thus they contrived to get possession of a sum of money ; and af- terwards they either made off with their booty, or tired out the patience of their pupils by intolerably tedious, ex- pensive, and ruinous processes. It was against these men that Erasmus directed his well-known satire, entitled, " The Alchymist." The tricks of these impostors gra- dually exasperated mankind against the whole fraternity of alchymists. Books appeared against them in all quar- ters, which the art of printing, just invented, enabled the authors to spread with facility j the wits of the age direct- ed against them the shafts of their ridicule j men of sci- ence endeavoured to point out the impracticability, or at least the infinite difficulty of the art ; men of learning rendered it probable that it never had been understood , and men in authority endeavoured by laws and punish- ments to guard their subjects from the talons of alchymis- tical impostors. Universal Chemists had for many ages hinted at the importance idicme. discovering a universal remedy, which should be capa- ble of curing, and even of preventing all diseases ; and several of them had asserted that this remedy was to be CHEMISTRY. found in the philosophers stone, which not only con- verted baser metals to gold, but possessed also the most sovereign virtue, was capable of .curing all disea- ses in an instant, and even of prolonging life to an inde- finite length, and of conferring on the adepts the gift of immortality on earth. This notion gradually gained ground ; and the word chemistry, hi consequence, at length acquired a more extensive signification, and im- plied not only the art of making gold* but the art also of preparing the universal medicine *. Just about the time that the first of these branches was sinking into discredit, the second, and with it the study of chemistry, acquired an unparalleled degree of celebrity, and attracted the attention of all Europe. This was owing to the appearance of Theophrastus Paracelsus. This extraordinary man, who was born in 1493, near Zurich in Switzerland, was, in the 34th year of his age, after a number of whimsical adven- tures, which had raised his reputation to a great height, appointed by the magistrates of Basil to deliver lectures in their city ; and thus was the first public Professor of chemistry in Europe. In two years he quarrelled with the magistrates, and left the city ; and after running through a complete career of absurdity and debauchery, died at Salzburg in the 47th year of his age. The character of this extraordinary man is univer- sally known. That he was an impostor, and boasted * The first man wh formally applied chemistry to medicine was Btsil Valentine, who is said to have been born in 1394, and to have been a Benedictine Monk at Erford in Germany. His Currus triumptalit An- timonii is the most famous of his treatises. In it he celebrates the virtues or antimonial medicines, cf v/h:ch he \vs the original discoverer. 10 A SYSTEM OF of secrets which he did not possess, cannot be denied j that he stole many opinions, and even facts, from others, is equally true : his arrogance was unsupport- able, his bombast ridiculous, and his whole life a con- tinued tissue of blunders and vice. At the same time, it must be acknowledged that his talents were great, and that his labours were not entirely useless. He con- tributed not a little to dethrone Galen and Avicenna, who at that time ruled over medicine with absolute power ; and to restore Hipp- crates and the patient ob- servers of Nature to that cha r, fom which they ought never to have risen. He certa-'.!y gave chemistry an eclat which it did not before -.ossess , and this.must have induced many of those laborious men, who succeeded him, to turn their attention to the science. Nor ought we to forget that, by carrying his speculations con- cerning the philosophers stone, and the universal medi- cine, to the greatest height of absurdity, and by exem- plifying their emptiness and uselebsness in his own per- son, he undoubtedly contributed more than any man to their disgrace and subsequent banishment from the science. Van Helmont, who was born in 1517, may be con- sidered as the last of the alchymists. His death com- pleted the, disgrace of the universal medicine. His contemporaries, and those who immediately succeeded him, if we except Ciollius and a few other blind admi- rers of Paracelsus, attended solely to the improvement of chemistry. The chief of them were Agricola, Be- guin, Glaser, Erkern, Glauber, Kuncke], Boyle, &c. Origin of The foundations of the alchymistical system being c cmwtry |jj us shaken, the facts which had been collected soon as a science. became a heap of rubbish, and chemistry was left with* CHEMISTRY. 11 out any fixed principles, and destitute of an object. It was then that a man arose thorougly acquainted with the whole of these facts, capable of arranging them, and of perceiving the important purposes to which they might be applied, and able to point out the proper ob- jects to which the researches of chemists ought to be directed. This man was BECCHER. He accomplished the arduous task in his work entitled Physica Sulter- ranea, published at Francfort in 1669. The publica- tion of this book forms a very important era in the his- tory of chemistry. It then escaped for ever from the trammels of alchymy, and became the rudiments of the science which we find it at present. Ernest Stahl, the editor of the Physica Subterranea, adopted, soon after Beccher's death, the theory of his master ; but he simplified and improved it so much, that he made it entirely his own ; and accordingly it has been always distinguished by the name of the Stahlian Theory. Ever since the days of Stahl, chemistry has been cul- Itaprogrest, tivated with ardour in Germany and the North ; and the illustrious philosophers of these countries have con- tributed highly towards its progress and its rapid im- provement. The most deservedly celebrated of these are Margraf, Bergman, Scheele, Klaproth, &c. In France, soon after the establishment of the Aca- demy of Sciences in 1666, Homberg, Geoffrey, and Lemery, acquired celebrity by their chemical experi- ments and discoveries ; and after the new-modelling of the Academy, chemistry became the peculiar object of a part of that illustrious body. Rouelle, who was made Professor of chemistry in Paris about the year 1745, contrived to infuse his own enthusiasm into the whole 12 A SYSTEM OF body of the French literary men ; and from that mo- ment chemistry became the fashionable study. Men of eminence appeared everywhere, discoveries multi- plied, the spirit pervaded the whole nation, extended itself over Italy, and appeared even in Spain. After the death of Boyle and of some other of the ear- lier members of the Royal Society, little attention was paid to chemistry in Britain except by a few indivi- duals. The spirit which Newton had infused for the mathematical sciences was so great, that for many years they drew within their vortex almost every man of eminence in Britain. But when J)r Cullen became Professor of Chemistry in Edinburgh in 1756, he kin- dled a flame of enthusiasm among the students, which was soon spread far and wide by the subsequent disco- veries of Black, Cavendish, and Priestley j and meet- ing with the kindred fires which were already burn- ing in France, Germany, Sweden, and Italy, the sci~ ence of chemistry burst forth at once with unexampled lustre. Hence the rapid progress which it has made during the last fifty years, the universal attention which it has excited, and the unexpected light which it has thrown on several of the most important arts and ma- nufactures. Andpre- The object of this Work is to exhibit as corn- *ctjt state. plete a view as possible of the present state of che- mistry ; and to trace, at the same time, its gradual progress from its first rude dawnings as a science, to the improved state which it has now attained. By thus blending the history with the science, the facts will be more easily remembered, as well as better understood j and we shall at the same time pay that tribute of re- CHEMISTRY. 13 spect, to which the illustrious improvers of it are justly intitled. A complete account of the present state of chemistry must include not merely a detail of the science of che- mistry strictly so called, but likewise the application of that science to substances as they exist in nature, constituting the mineral, vegetable, and animal king- doms. This Work, therefore, will be divided into two Parts. The first will comprehend THE SCIENCE OF CHEMISTRY, properly so called ; the second will con- sist of A CHEMICAL EXAMINATION OF NATURE. PART FIRST. PRINCIPLES OF C H EMISTR Y. I HE object of chemistry is, to ascertain the ingre- Object of dients of which bodies are composed ; to examine the c ^ i compounds formed by the combination of these ingre- dients; and to investigate the nature of the power'* which occasions these combinations. The science therefore naturally divides itself into three parts : 1. A description of the component parts of bodies, or of simple substances as they are called. 2. A description of the compound bodies formed by the union of simple substances. 3. An account of the nature of the power which occasions these combinations. This power is known in chemistry by the name of AFFINITY* These three particulars will form the subject of the three following Books. BOOK I. OF SIMPLE SUBSTANCES. ^ Book I. jg Y s j m p] e substances is not meant what the ancient philosophers called elements of bodies, or particles of matter incapable of farther diminution or division. Definition. They signify merely bodies which have not been de- compounded, and which no phenomenon hitherto ob- served indicate to be compounds. Very possibly the bodies which we reckon simple may be real compounds ; but till this has actually been proved, we have no right to suppose it. Were we acquainted with all the ele* ments of bodies, and with all the combinations of which these elements are capable, the science of chemistry would be as perfect as possible ; but at present this is very far from being the case. Division. The simple substances at present known amount to about 48, and naturally divide themselves into two classes. The bodies belonging to the first class can be confined in proper vessels, and of course exhibited in a separate state. Those which belong to the second class are of two subtile a nature to be confined by any of the vessels which we possess. They cannot, therefore, be exhibited in a separate state ; and their existence is SIMPLE SUBSTANCES. inferred merely from certain phenomena which the first class of bodies and their compounds exhibit in particu- lar circumstances. Hence it is obviously necessary to be acquainted with the properties of the first set of bo- dies before we can investigate the second. It will be exceedingly convenient to consider these two classes se- parately. And for want of better terms we shall distin- guish the first set by the title of confinable bodies, the se- cond by that of vnconfinable bodies *. * An apology may be deemed necessary lor these two words, which have not been hitherto used by any British writer. I employ them, b and this name we shall Division I. w v - afterwards employ . Oxygen gas may be obtained likewise by the follow- ing process : D (in fig. 5.) represents a wooden trough, the inside of which is lined with lead or tinned copper. C is the cavity of the trough, which ought to be a foot deep. It is to be filled with water at least an inch above thq shelf AB, which runs along the inside of it, about three inches from the top. In the body of the trough, which may be called the cistern, the jars destined to hold gas are to be filled with water, and then to be lifted and placed inverted upon the shelf at B. This trough^ which was invented by Dr Priestley, has been called by the French chemists the pneumatico-cbemical, or simply pneumatic apparatus, and is extremely useful in all experiments in which gases are concerned. Into the glass vessel E put a quantity of the black oxide of manganese in powder, and pour over it as much of that liquid which in commerce is called oil of vitriol, and in chemistry sul- phuric acid, as is sufficient to form the whole into a thin paste. Then insert into the mouth of the vessel * The word gat WGS first introduced into chemistry by Van Helmont ; He seems to have intended to denote by it every tiling which is driven < iTfrom bodies in the state of vapour by heat. He divides gaits into five classes. *' Nescivit, inquam, schola Galenica hactenus diifcreuthm inter gas ventosum (quod mere aer est, id est, ventus per syderum bias com- motus), gr.s pingue, gas siccurn, quod snbhmatum dicitur, pas fuligino- Mim, sive cndimirum, et gas sylvestre, iive incoercibile, quod in corpu* rogi non potest visibile." Van Helmont de Flat'ibus^ 4. Macquer seems "o have introduced the word into tLe language of modern chemistry. OXYGEN. 23 the glass tube F, so closely that no air can escape except , Gha P- L through the tube* This may be done either by grind- ing, or by covering the joining with a little glazier's putty, and then laying over it slips of bladder or linen dipped in glue or in a mixture of the white of eggs and quicklime. The whole must be made fast with cord*. The end of the tube F is then to be plunged into the pneumatic apparatus D, and the jar G, previously filled with water, to be placed over it on the shelf. The whole apparatus being fixed in that situation, the glass vessel^E is to be heated by means of a lamp or a candle. A quantity of oxygen gas rushes along the tube F, and fills the jar G. As soon as the jar is filled, it may be slid t6 another part of the shelf, and other jars substi- tuted in its place, till as much gas has been obtained as is wanted. The last of these methods of obtaining oxygen gas was discovered by Scheelef, the first by Dr Priestley ^. * This process/4>y which the joinings of vessels are made air-tight, i* called luting, and the substances used for that purpose are called lutes. The lute most commonly used by chemists, when the vessels are exposed to heat, is fat lute, made by beating together in a mortar fine clay and boil- ed linseed oil. Bees wax, melred with about one-eighth part of turpen- tine, answers very well, when the vessels are not exposed to heat. The accuracy of chemical experiments depends almost entirely in many cases upon securing the joinings properly with luting. The operation is al- ways tedious ; and some practice is necessary before one can succeed in luting accuratery. Some very good directioi.s are given by Lavoisier. See his Elements, Part iii. chap. 7. Jri many cases luting may be avoided altogether by using glass-vessels properly fitted to each other by grinding *hem with emery. f On Air and Fire, p. 43. Engl. Trans, J PriestUy en A':r, v. 154, SUPPORTERS OF COMBUSTION. Eook I. Division I. Discovered by Priestley and Schcele. Properties of oxygen. Supports flamu And life. The gas which we have obtained by the above pro- cesses was discovered by Dr Priestley on the 1st of August 1774, and called by him depL logistic at ed air. Mr Scheele of Sweden discovered it before 1777, without; any previous knowledge of what Dr Priestley had done . he gave it the name of empyreal air*. Condorcet gave it first the name of vital air ,- and Mr Lavoisier after- wards called it oxygen gas ; a name which is now ge- nerally received, and which we shall adopt. 1. Oxygen gas is colourless, and invisible like com- mon air. Like it, too, it is elastic, and capable of inde- finite expansion and compression. 2. If a lighted taper be let down into a phial filled with oxygen gas, it burns with such splendour that the eye can scarcely bear the glare of light, and at the same time produces a much greater heat than when burning in common air. It is well known that a candle put in- to a well-closed jar filled with common air is extinguish- ed in a few seconds. This is the case also with a candle inclosed in oxygen gas; but it burns much longer in an equal quantity of that gas than of common air. ?'. It was proved long ago by Boyle, that animals cannot live without air, and by Mayow that they can- not breathe the same air for any length of time without suffocation. Dr Priestley and several other philoso- phers have shown us, that animals live much longer in the same quantity of oxygen gas than of common air. Count Morozzo placed a number of sparrows, one af- ter another, in a glass bell filled with common air, and inverted over water. *' fHieele on Air and Fire, p. 34. Engl. Trans. CXTGEN. II. 3VI. The first sparrow lived 3 The second 3 The third , 1 He filled the same glass with oxygen gas, and repeat- ed the experiment. The first sparrow lived 5 23 ; The second 2 10 The third 1 30 The fourth 1 10 The fifth 30 The sixth 47 The seventh 27 The eighth 30 The ninth 22 The tenth . ,... . 21 He then put in two together ; the one died in 20 mi- nutes, but the other lived an hour longer. 4. It has been ascertained by experiments, which Exists in shall be afterwards related, that atmospherical air con- tains 21 parts in the hundred (in bulk) of oxygen gas; and that no substance will burn in common air previ- ously deprived of ail the oxygen gas which it contains. But combustibles burn with great splendour in oxygen gas, or in other gases to which oxygen gas has been added. Oxygen gas, then, is absolutely necessary for combustion. 5. It has been proved also, by many experiments, 26 SUPPORTERS OF COMBUSTIOK. Book I. that no breathing animal can live for a moment in any Division I. . . . , , . . . . ^ air or gas which does not contain oxygen mixed with it. Oxygen gas, then, is absolutely necessary for re- spiration. 6. When substances are burnt in oxygen gas, or in any other gas containing oxygen, if the air be examined after the combustion, we shall find that a great part of the oxygen has disappeared. If charcoal, for instance, be burnt in oxygen g-s, there will be found, instead of part of the oxygen, another very different gas, known by the name of ca bonic acid gas. Exactly the same thing takes place when air is respired by animals ; part of the oxygen gas disappears, and its place is occupied by substances possessed of very different properties. Oxygen gas then undergoes some change during com- bustion, as well as the bodies which have been burnt 5 and the same observation applies also to respiration. Its specific 7. Oxygen gas is somewhat heavier than common gravity. a j r> If the specific grav ity of common air be reckon- ed 1*000, that of oxygen gas, as determined by Mr Kirwan, is 1'103*. With this result the statement of Lavosierf agrees exactly. But Mr Davy found it a little heavier ; and Fourcroy, Vauquelin, and Seguin, found it a little lighter. Its specific gravity, accord- ing to Mr Davy's experiments, is l*127j; according * u* } ' bloghtin, p. 25. j- Elemfnf!, Appendix. See also K : rwan on phlogiston, p. 37. of Nichol- son's translation. \ Davy's Researches, p. 8. Mr Davy's oxygen ga? was procured from oxide of manganese. It is possible that it contained a little carbonic acid gat. The tests used would not have excluded that body. This would ; its greater specific gravity. OXYGEN. 27 to the French chemists, 1'087*. At the temperature Chap. I. ^ of 60, and when the barometer stands at 30 inches, 100 cubic inches of common air weigh very nearly 31 grainsf. ) 00 inches of oxygen gas, at the same tem- perature and pressure, weigh, according to Kirwan and Lavoisier, 34 grains; according to Mr Davy, 34*74 grains ; and according to Fourcroy, Vauquelin, and Se- guin, 33*69 grains. S. Oxygen gas is not sensibly absorbed by water, Combiru- t*Oll Wltil though jarfuls of it be left in contact with that liquid, water. It has been ascertained, however, that water does in reality absorb a small portion of it, though not enough to occasion any perceptible diminution in the bulk of the gas. When water is freed from all air by boiling, and the action of the air pump, Dr Henry ascertained, that 100 cubic inches of it will imbibe 3*55 inches of oxygen gas.|. By forcing oxygen gas into a bottle of water by means of strong pressure, the water may be made to absorb about half its bulk of that gas, and to retain it in solution. This experiment was first made by Mr Paul, a celebrated preparer of mineral waters, now settled in London. Water thus impregnated does not sensibly differ from common water either in taste <;r smell, yet it has been found a valuable remedy in several diseases}. * Ann. de Chlm. ix. 34. f Sir John ShucUburgh Evelyn, as quoted by Kirwan on fllogn P- 23- \ Phil. Trans. 1803, p. 174. \ See DrOdier's observations on it in the 8th and loth vols of the &iliet}.efj-ac "Britanaigtie ; ar,d the Appendix to Mr Paul's little publica- tion on his Arttfcial Zluxrzl V/utcrt. ;>& SUPPORTERS OF COMBUSTION. Book r. 9. Oxygen is capable of combining with a great num- \ - , - ber of bodies, and of forming compounds. As the com- f substances with each other is of the utmost importance in chemistry, before we proceed farther it will be proper to explain it. When common salt is thrown into a vessel of pure water, it melts, and very soon spreads itself through the whole of the liquid, as any one may convince himself by the taste. In this case the salt is combined with the water, and cannot afterwards be separated by filtration, or any other me- thod merely mechanical. It may, however, by a very simple process : Pour into the solution a quantity of spirit of wine, and the salt falls slowly to the bottom in the f.i.ate of a very fine powder. Why does the salt dissolve in water ? and why does it fall to the bottom on pouring in spirit of wine ? These questions were first answered by Sir Isaac New- ton. There is a certain attraction between the particles of common salt and those of water, which causes them, to unite together whenever they are presented to one another. There is an attraction also between the par- ticles of water and of spirit of wine, which equally dis- poses them to unite, and this attraction is greater than that between the water and salt ; the water therefore leaves the salt to unite with the spirit of wine, and the salt, being now unsupported, falls to the ground by its gravity. This power, which disposes the particles of different bodies to unite, was called by Newton at- traction, by Bergman elective attraction, and by many of the German and French chemists affinity * , and * The word mffinity seems first to have l>een introduced into science by Dr Hooke. See his Microgrofbia, OXYGEN. 2 this last term is now employed in preference, because t Chap. I. the other two are rather general. All substances which are capable of combining together are said to have an affinity for each other : those substances, on the con- trary, which do not unite, are said to have no affinity for each other. Thus it is said that there is no affinity Between water and oil. It appears from the instance of the common salt and spirit of wine, that substances differ in the degree of their affinity for other substan- ces, since the spirit of wine displaced the salt and uni- ted with the water. Spirit of wine therefore has a stronger affinity for water than common salt has, In 1719, Geoffroi invented a method of representing the different degrees of affinities in tables, which he called tables of affinity. His method consisted in pla- cing the substance whose affinities were to be ascer- tained at the top of a column, and the substances with which it united below it, each in the order of its affini- ty ; the substance which had the strongest affinity next it, and that which had the weakest farthest distant, and so of the rest. According to this method, the affinity of water for spirit of wine and common salt would be marked as follows : WATER. Spirit of wine Common salt. This method was universally adopted, and has contri- buted very much to the rapid progress of chemistry. We shall see as we proceed the order which sub- stances follow in their affinity for oxygen. SO SIMPLE COMBUSTIBLES. Book f. Division F. CHAP. II. OF SIMPLE COMBUSTIBLES, BY combustibles I mean substances capable of combus- tion ; and by simple combustibles, bodies of that nature which have not hitherto been decompounded. These Number. bodies are only four in number ; namely, HYDROGEN, CARBON, PHOSPHORUS, and SULPHUR. The metals might indeed be classed among combustible bodies ; but the greater number of their properties are so differ- ent from those of the four bodies just mentioned, that it is proper to consider them by themselves as a distinct class of bodies. All our classifications are in fact arti- ficial ; Nature does not know them, and will not sub- mit to them. They are useful, however, as they ena- ble us to learn a science sooner, and to remember it bet- ter ; but if we mean to derive these advantages from them, we must renounce a rigid adherence to arbitrary definitions, which Nature disclaims. HYDROGEN. SECT. I. OF HYDROGEN. HYDROGEN, the first of the simple combustibles, may be procured by the following process. Into a retort having an opening at A* (fig. 7.), put Howprc- one part of iron filings ; then shut the opening A with a cork, through which a hole has been previously drilled by means of a round file, and the bent funnel B passed through it. Care must be taken that the funnel and cork fit the retort so as to be air-tight. Plunge the beak of the retort C under water ; then pour through the bent funnel two parts of sulphuric acid previously diluted with four times its bulk of water. Immediate- ly the mixture begins to boil or effervesce with violence, and air-bubbles rush abundantly from the beak of the retort. Allow them to escape for a little, till you sup- pose that the common air which previously filled the retort has been displaced by the newly generated air. Then place an inverted jar on the pneumatic shelf over the beak of the retort. The bubbles rise in abundance and soon fill the jar. The gass obtained by this process is called hydrogen gas. It was formerly called inflam- mable air, and by some chemists phlogiston. It may be procured also in great abundance and pu- rity, by causing the steam of water to pass through a * Such retorts ve called tubulated by chemists. SIMPLE COMBUSTIBLES. Bbok I,' Division ! Discovery Its proper ties. red hot iron tube. This gas being sometimes emitted in considerable quantities from the surface of the earth in mines, had occasionally attracted the notice of ob- servers*, and indeed was the dread of miners under the name ofjire damp. Mayowf, Boyle!, and Hales, pro- cured it in considerable quantities, and noted a few of its mechanical properties. Its combustibility was known about the beginning of the .18th century, and was often exhibited as a curiosity $. But Mr Caven- dish ought to be considered as its real discoverer; since it was he who first examined it, who pointed out the difference between it and atmospheric air, and who ascer- tained the greatest number of its properties ([. They were afterwards more fully investigated by Priestley, Scheele, Sennebier, and Volta. 1. Hydrogen gas, like air, is invisible and elastic, and capable of indefinite compression and dilatation. When prepared by the first process it has a disagreeable smell, similar to the odour evolved when two flint stones are rubbed against each other. This smell must be ascri- bed to some foreign body held in solution by the gas; for the hydrogen procured by passing steam through red hot iron tubes has no smell. * See an instance related in Phil. Trans. Abr. i. 169, f Tractatus qitinyue, p. 163. } Shaw's Boyle , iii. ai. Cramer's Elementa Docimatit, i. 45. This book was published in 1739. Wasserberg re lates a story of an accidental explosion which ter- rified Professor Jacquin*s operator, Wasserberg's Institution^ i. 184. || PLil. Trans* 1766, vol. Ivi p. 141, HYDROGEN 33 It is the lightest gaseous body with which we are t cha F T |- . acquainted. If the specific gravity of common air be Weight, reckoned I'OOO, the specific gravity of hydrogen gas, as determined by Mr Kirwan, will be 0.0843*. Mi- Lavoisier states it as only 0'0756f, while Messrs Fsur- croy, Vauqueiin, and SeguinJ, make it O.OSS7. Mr Kirwan's estimate appears to me the most correct. At the temperature of 60, while the barometer stands at 30 inches, 100 cubic inches of hydrogen gas weigh, according to Kirwan, 2'613 grains troy ; according to Lavoisier, 2'?>72 grains; and according to Fourcroy, Vauquelin, and Seguin, 2' 75 grains. It is very nearly 12 times lighter than common air. 3. All burning substances are immediately extin- Action cri guished by being plunged into this gas. It is incapable ^^ therefore of supporting combustion. 4. When animals are obliged to breathe it, they soon on animate, die. A mouse put into a jar of it by Dr Gilby of Birmingham lived 30 seconds without inconvenience ; but in 1 minute 33 seconds it was dead. Dr Beddoes kept a rabbit in it 7 mintttes 5 it was much distressed and weakened, but recovered^. Scheele found that he could make 20 inspirations of it without much in- convenience || ; but Fontana, who repeated the experi- ment, affirmed that this was owing to the quantity of common air contained in the lungs when he began to breathe ; for on expiring as strongly as passible before * On Pbloghion, p. 26. f Element!. Appendix. | Ann. de Cblm. iy. 294. Btddoes on Factitious A'n, p. 31, H Scheele on A' r and Vnyp. 60. Vol. /. C 34 SIMPLE COMBUSTIBLES. Book F. drawing in the hydrogen gas, he could only make tlnree Division I. . i_v - respirations, and even these three produced extreme feebleness and oppression about the breast *. The as- sertion of Scheele was fully verified by Pilatre de Ro- zierf and Mr Watt|. The ingenious Mr Davy, professor of chemistry in the Royal Institution, to whom we are indebted for many curious and important, but rather hazardous ex- periments on respiration, made chiefly upon himself, after a complete voluntary exhaustion of his lungs, found great difficulty in breathing this gas for so long as half a minute. It produced uneasy feelings in the chest, momentary loss of muscular power, and some- times a transient giddiness . But when he did not previously empty his lungs, he was able to breathe it for about a minute without much inconvenience [(<. When much diluted with common air, it may be breathed without injury. * 'Jour, de Ptys. xv. 99. t He breathed hydrogen gas six or seven times from a bladder with- out inconvenience. To demonstrate that it was really hydrogen gas which he was breathing, he made a strong inspiration, and expired the ?.ir slowly through a long tube. On bringing a lighted taper to the end of the tub/:, the gas took fire, and continued to burn for some tune. It was objected to him, that the gas which he breathed was diluted witb common air. To show that this was not the case, he mixed together one part of common air and nine parts of hydrogen gas ; and having drawn the mixture into his lungs, he threw it out the same way. On applying a taper to the tube, the whole of the gas exploded in his mouth, and almost stunned him. At first he thought that the whole of his teeth had been driven out ; but fortunately he received no injury whatever, See Jour, dc ?bys. xxviii. 425. f Beddoes in the Use and Production of Factitious Airs, p, HO. f Davy '9 Rettartltf, p. 409. \\ Ibid. p. 466= HYDROGEN. 25 5. If a phial be filled with hydrogen gas, and alight- t Chap. 11^ ed candle be brought to its mouth, the gas will take fire, Combusti* and burn gradually till it is all consumed. If the hy- drogen gas be pure, the flame is of a yellowish white colour ; but if the gas hold any substance in solution, which is often the case, the flame is tinged of different colours, according to the substance. It is most usually reddish f. A red hot iron likewise sets fire to hy- drogen gas. From my experiments it follows, that the temperature at which the gas takes fire is about 1000. If pure oxygen and hydrogen gas be mixed together, they remain unaltered ; but if a lighted taper be brought into contact with them, or an electric spark be made to pass through them, they burn with astonishing rapidi- ty, and produce a violent explosion. If these two gases be mixed in the proportion of one part in bulk of oxy- gen gas and 2*05 parts of hydrogen gasj, they explode Exrfodt over water without leaving any visible residuum ; the gen gas,' vessel in which they were contained (provided the gases water were pure) being completely filled with water. This important experiment was made by Scheele $ ; but for want of a proper apparatus he was not able to draw the proper consequences. Mr Cavendish made the ex- periment in dry glass vessels with all that precision | Hydrogen always holds in solution a certain portion of the metal by means of which it was produced. This affects the colour of its flame very much at first ; but when the gas is kept, most of the metallic mat- ter is deposited. J Ann. de Chira. ix. 41. Scheele ** A' When charcoal is heated to about S02f, or when by combus- ft is made nearly red hot. and then plunged into oxy- tion into carbonic gen gas, it takes nre ; and, provided it has been pre- acid gas. viously freed from the earths and salts which it ge- nerally contains, or if we employ lamp black, which is charcoal nearly pure, it burns without leaving any residuum. But the air in which the combustion has been carried ort has altered its properties very consider- ably, for it has become so noxious to animals that they cannot breathe it without death. If small pieces of dry charcoal be placed upon a pedestal, in a glass jar filled with oxygen gas, and standing over mercury, they may be kindled by means of a burning glass, and consumed. The bulk of the gas is not sensibly altered by this combustion, but its properties are greatly changed. A great part of it will be found converted into a new gas quite different from oxygen. This new gas is easily detected by letting up lime-water into the jar : the lime water becomes milky, and absorbs and condenses all the new- formed gas. This new gas has received the name of carbonic acid. Mr Lavoisier as- certained, by a very laborious set of experiments, that it is precisely equal in weight to the charcoal and oxy- * Nicholson, Ibid, and Jour, de Phys. Ivli. 467. The increase of weight cf charcoal had been observed >lso by Dr Watson, See his Essays, iii. 42. f I estimated this temperature by ascertaining the time at which char- coal ceased to burn on an iron plate which had been heated to redness, and measuring the rate of cooling by Sir Isaac Ntwton's method, *o be de Bribed hereafter. CARBOX. 48 gen which disappeared during the combustion. Hence Chap. II. he concluded, that carbonic acid is a compound of char- coal and oxygen, and that the combustion of charcoal is nothing else than its combination with oxygen *. Mr Lavoisier concluded from his experiments, that every 28 parts of charcoal, during their combustion, united with 72 parts of oxygen, and that carbonic acid is composed of these two bodies combined in that pro- portion. The experiment is of difficult execution ; yet it has been made by other philosophers with nearly the same result. The mean of five experiments made with great care by Messrs Allen and Pepys, gives for the constituents of carbonic acid, charcoal 28*6 oxygen 71 '4 100'Of This result differs so little from that obtained by Lavoi- sier, that in the present state of chemistry we may adopt the numbers of that illustrious philosopher as sufficient- ly precise. When considerable quantities of charcoal are con- sumed in oxygen gas, some time after the commence- ment of the combustion a quantity of water deposites itself and trickles down the inside of the glass. This happens however dry the oxygen was, and however well the charcoal was prepared : but after the combus- tion has continued for a certain time the water is taken up again and disappears $. This deposition of water * Mem. Par. 1781, p. 448. f Pbil. Trans. 1807. J Berthollet's Statijuc Cbimiyve, ii. 42-. SIMPLE COMBUSTIBLES. Book I. Division f. Properties of the Uia- tnond t Burn*. induced Mr Lavoisier to conclude that charcoal is not a simple substance, but that it is a compound of at least two bodies, both of which, during the combustion of charcoal, unite to oxygen, and form, the one water, and the other carbonic acid. The first we know to be 'hydro- gen ; the second Lavoisier called carbon. Charcoal then, according to Lavoisier, is a compound of hydrogen and carbon. He even estimated the hydrogen in common charcoal as -Jth of the whole. The subsequent experi- ments of other chemists, especially those of Priestley, Cruikshanks, and Berthollet junior, have amply con- firmed this deduction of Lavoisier. Charcoal, then, is not pure carbon ; but as the greatest part of it consists of that body, we may consider it as capable of giving us some idea of its properties. We are acquainted with carbon, however, in a state apparently very different : in that state it constitutes the diamond. 5. The diamond is a precious stone, which has been known from the remotest ages. When pure, it is per- fectly transparent like crystal, but much more brilliant. Its figure varies considerably j but most commonly it is crystallized in the form of a six-sided prism, termi- nated by a six-sided pyramid. It is the hardest of all bodies ; the best tempered steel makes no impression on it j diamond powder can only be obtained by grind- ing one diamond against another. Its specific gravity is about 3*5. It is a non-conductor of electricity. 6. As the diamond is not affected by a considerable heat, it was for many ages considered as incombustible. Sir Isaac Newton, observing that combustibles refract light more powerfully than other bodies, and that the diamond possesses this property in great perfection, suspected it, from that circumstance, to be capable of combustion. This singular conjecture was verified in CARBON. 45 1694 by the Florentine academicians, in the presence ^Chap. II. of Cosmo III. Grand Duke of Tuscany. By means of a burning-glass they consumed several diamonds. Francis I. Emperor of Germany, afterwards witnessed the destruction of several more in the heat of a furnace, These experiments were repeated by Darcet, Rouelle, Macquer, Cadet, and Lavoisier ; who proved that the diamond was not merely evaporated, but actually burnt, and that if air was excluded it underwent no change*. Mr Lavoisier prosecuted these experiments with his usual precision ; burnt diamonds in close vessels by means of powerful burning glasses ; ascertained, that during their combustion carbonic acid gas is formed ; and that in this respect there is a striking analogy be- tween them and charcoal, as well as in the affinity of both when heated in close vesselsf. A very high tem- perature is not necessary for the combustion of the dia- mond. Sir George Mackenzie ascertained that they burn in a muffle when heated to the temperature of 14 of Wedgewood's pyrometer ; a heat considerably less than is necessary to melt silver . When raised to this temperature they waste pretty fast, burning with a low flame, and increasing somewhat in bulk ; their surface too is often covered with a crust of charcoal, especially when they are consumed in close vessels by means of burning glasses ||. * Alcm. Tar. 1/66, 1770, 1771, IJJZ. f Lavoisier's Opuscules, ii. as quoted by Macquer. Diet, i, 337. t A m-ajjii is a kind of small earthen-ware oven, cpen at one em?, and fitted into a furnace. Nicholson's Quarto Jour. iv. 104. * Macquer and Lavoisier, Macquer'? Diet. Ibid. 46 SIMPLE COMBUSTIBLES. Book I. In 178 5, Guyton-Morveau found that the diamond is ... combustible when dropped into melted nitre ; that it burns without leaving any residuum, and in a manner analagous to charcoal *. Mr Smithson Tennant repeat- ed this experiment with precision in 3797. Into a tube of gold he put 120 grains of nitre, and 2*5 grains of diamond, and kept the mixture in a red heat for half an hour. The diamond was consumed by the oxygen, which red hot nitre always gives out. The carbonic acid formed was taken up by means of lime, and after- wards separated from the lime and measured. It oc- . . cupied the bulk in one experiment of 10*3 ounces of verted into water, and in another of 10*1: the mean is equal to c j coal*, borne inaccuracy, therefore, must nave crept into Morveau's experiment, As far as experiment has gone, the constituents of diamond and charcoal are abso- lutely the same. Now as the presence of hydrogen has been demonstrated in the latter, we must admit it also in the former ; a conclusion which corresponds with the previous deductions of Biot, founded on the power of the diamond to refract light. At the same time, it must be admitted that considerable obscurity still hangs over this subject. The properties of dia- mond and charcoal are different in almost every re- spect ; if their composition be the same, it is impossible to explain upon what that difference depends. Such are the facts that have been ascertained re- specting the combination of carbon with oxygen. Let us now examine the compounds which it forms with hydrogen. 7. When charcoal is exposed to a strong heat in an iron retort, there is disengaged from it a gas which has the property of burning with a blue flame, and which is considerably heavier than hydrogen gas ; hence it received the name of heavy wjla?iTmcibls air. A gas possessed of similar properties is obtained by causing steam to pass through a tube filled with red-hot char- coal ; by passing spirit of wine, ether, or camphor, through red-hot tubes; by distilling oils, wood, bones, or indeed almost any animal or vegetable body what* ever. These heavy inflammable airs were occasionally sollected by Dr Priestley, but they were first parties Heavy in- flammable airs, Pli!. CARBON. 49 larly examined by Mr Lavoisier, Dr Higgins, and Dr cha P- Austin, who ascertained, that when they are mixed with oxygen gas and burnt, the products are only wa- ter and carbonic acid. Hence it was concluded, that they are composed of carbon and hydrogen; and the term carbureted hydrogen gases, indicating their consti- tuents, was applied to them. These gases, in conse- quence of the experiments of Dr Priestley, have Three spe- cies of hea- lately attracted the attention of chemists ; and many im- V y inflam- portant additions have been made to our knowledge of mablc atr * them, chiefly by the Dutch chemists, by Mr Cruik- shanks, Mr Bertholler, and Dr William Henry. But notwithstanding the merit and sagacity of these philo- sophers, the nature of the gases is still involved in considerable obscurity, owing in a great measure to our uncertainty of the proportion of carbon in carbonic acid. The opinion of Dr Henry and Mr Dalton, that there are only three species of heavy inflammable air, and that all the variety which we obtain is produced by mixtures of these in various proportions, seems to me much more probable than the opinion of Berthollet, that their number is indefinite. Let us endeavour to state the facts respecting these three species of gas as distinctly as possible. 8. There is a gas which rises spontaneously in hot i. Carbur weather from marshes and stagnant water, and which e cn * may be easily collected in considerable quantities ; this gas was examined by Dr Priestley, and more lately by Mr Cruikshanks and Mr Dalton. It is invisible and elastic, like common air, and it burns with more brilliancy than hydrogen gas. Its specific gravity, ac- cording to Cruickshanks, is 0.67774; that of common air being rooo. One hundred cubic inches of it, at Vol. ,L D 50 SIMPLE COMBUSTIBLES. Book T. 60% weigh 21 grains *. When mixed with oxygen Division f. i y > gas and fired by electricity, it explodes, and leaves a residue more bulky than the original mixture ; but lime-water absorbs the greatest part of it. The sub- stances formed during this combustion are carbonic acid and water. Hence it is obvious, that the gas is composed of carbon and hydrogen. It is therefore en- titled to the name of carbureted hydrogen. But after the carbonic acid has been removed (supposing it had been mixed with oxygen in the exact proportion to consume the whole of that body), Mr Dalton has as- certained, that there always remains a residue amount- ing to about --th of the gas from stagnant water originally used. This residue possesses the properties of the gas called aKote^f which we shall examine in a subsequent chapter. The gas from stagnant waters, then, is a mix- ture of four parts of carbureted hydrogen, and one part of axote. Dr Henry has ascertained, that if the azote be supposed separated, the carbureted hydrogen re- quires for combustion twice its bulk of oxygen gas; and there is produced a quantity of carbonic acid just equal in bulk to the carbureted hydrogen . Hence it is easy to determine its constituents. Itscompoai- One hundred inches of it require 200 inches of oxygen gas, 100 of which form carbonic acid; and the remaining 100 must enter into the composition of the water form- ed, and of course combine with a quantity of hydro- gen equal in bulk to 200 inches. Now 100 inches of carbonic acid contain 13*02 grains of carbon, and 200 tton. * Nicholson's 410 Jour. v. 8. f Henry, Nicholson's Jour. xi. 68, \ Ibid 23 of hydrogen weigh 5*2 grains. This would give ( Chap. If. us the gas composed of nearly 28 v hydrogen Tli carbon .100 A result which accords pretty riearly with the weight of the gas, as ascertained by Crulkshanks. One hun- dred inches of carbureted hydrogen (freed from azote) ought to weigh, according to him, 18*6 grains ; and the constituents, as stated above* weigh 1S'22 grains. The gas obtained by distilling acetate of potash*, Gas from acetate of seems to be the same very nearly with the carbureted potash; hydrogen above described. It was this gas that was subjected to experiment by Drs Austin and Higgins. When common pit-coal is distilled in close vessels, From pit- i vast quantity of inflammable air is evolved, which c has rather an unpleasant smell, burns with a fine yel- iowish white flame like oil, and yields a very bright light. This gas has been substituted for oil in lamps, and has been used successfully to light up rooms f. Il * A salt described in a subsequent part of this Work. f Many successive exhibitions of it were made at the Lyceum in Lot- 'ion in 1 804, and it had been publicly proposed in France for the sam^ purpose? about the year 1801 ; but-the real discoverer of the use of th* gas was Mr Murdoch of Birmingham, Dr William Henry has publish- ed the following detail of the discovery : * In the year 1792, at which time Mr Murdoch resided at Redruth in Cornwal, a* Boulcon and Watt's principal agent and manager of engine* an that county, he commenced a series of experiments upon the quantity and quality of the gases contained in different substances. In the coursm. Par. 1781, p, 453. f Nicholson's 4to Jour. r. 8. SIMPLE COMBUSTIBLES. Gas from wood. Gas from peat. Book I. ted hydrogen present. But in the present state of im~ Division r. f . . .. v ' certainty, it is unnecessary to proceed any farther with the investigation, 13. The gas obtained by the distillation of wood burns with a much whiter flame than that from char- coal : yet Dr Henry found, that 100 measures of gas from oak required only 54 measures of oxygen to sa- turate it, and produced 33 measures of carbonic acid. This result induces him to consider it as a mixture of the same gases as the last, but in different proportions. The gas from dried peat differs considerably in its- properties, according to the qualities of the peat, and the mode employed in procuring it. I have obtained no less than four kinds, and Dr Henry procured and exa- mined another altogether different. Its specific gravity varies from 0.813 to 0'608. It burns sometimes with a white, sometimes with a blue flame; 100 cubic inches of the heaviest kind consume 100 inches of oxy- gen, and form 80 inches of carbonic acid; 100 inches of the lightest kind consume 160 inches of oxygen, and form 60 inches of carbonic acid gas *. It is pro- bably a mixture of two different gases, and its different properties are most likely owing to a variation in their proportions* One of these gases I conceive to be car- bonic oxide ; but I think I have shown that the other is a gas not yet obtained or examined in a separate state. If this last gas shall be found to contain oxygen as a constituent, which is not unlikely, it will constitute a triple compound, to which the name of oxy- carbureted hydrogen may be applied. * See my experiments on it in Nicholson's Jour. xvi. 241, PHOSPHORUS. <55 The gas obtained by distilling coal burns with great Chap. II. brilliancy. Dr Henry considers it as a mixture of car- pitcoal. bureted hydrogen with some carbonic oxide and ole- iiant gas. The gases obtained from oil and wax by distillation Oils and are carbureted hydrogen gas ; but the first contains -j- of its bulk, and the other $ its bulk of olefiant gas. The olefiant gas is present also in the gases obtained by passing camphor, ether, or alcohol, through hot tubes *. SECT. III. OF PHOSPHORUS. PHOSPHORUS, the third of the simple combustibles, may Method of be procured by the following process : Let a quantity pj" P 3 "ng of bones be burnt, or, as it is termed in chemistry, cal- cined, till they cease to smoke, or to give out any odour, and let them afterwards be reduced to a fine powder. Put 100 parts of this powder into a bason of porcelain or stoneware, dilute it with four times its weight of water> and then add gradually (stirring the mixture after every addition) 40 parts of sulphuric acid. The mixture becomes hot, and a vast number of air-bubbles are extricated f. Leave the mixture in this state for 24 hours ; taking care to stir it well every now and * Henry, ib!d. | The copious emission of air-bubbles is called in chemistry effe VoL I. E 66 SIMPLE COMBUSTIBLES. Book I. then with a glass or porcelain rod to enable the acid to Division I. act upon the powder *. The whole is now to be poured on a filter of cloth ; the liquid which runs through the filter is to be recei- ved in a porcelain bason ; and the white powder which remains on the filter, after pure water has been poured on it repeatedly, and allowed- to strain into the porcelain bason below, being of no use, may be thrown away. Into the liquid contained in the porcelain bason, which has a very acid taste, nitrate of leadf, dissolved in wa- ter, is to be poured slowly > a white powder immediate- ly falls to the bottom: the nitrate of lead must be added as long as any of this powder continues to be formed. Throw the whole upon a filter. The white powder which remains upon the filter is to be well washed, al- lowed to dry, and then mixed with about one-sixth of its weight of charcoal powder. This mixture is to be put into the earthen ware retort (fig. 5. .) The re- tort is to be put into a furnace, and the beak of it plun- ged into a vessel of water, so as to be just under the surface. Heat is now to be applied gradually till the re- tort be heated to whiteness* A vast number of air- bubbles issue from the beak of the retort, some of which take fire when they come to the surface of the water. At last there drops out a substance which has * Fourcroy and Vauquelin, Mem. de /' Jnst. ii. i8a f A salt to be described in a subsequent part of this Work. It an- swers better than acetate of lead, as was first pointed out by Gioberr ai.d more lately by Mr Hume. See Giobert's process, Ann. de CA/w, xiL 15. and PHI. Mag. xx. 160. its disco* PHOSPHORUS. 67 the appearance of melted wax, and which congeals un- Chap. II. der the water*. This substance is phosphorus. It was accidentally discovered by Brandt, a chemist History of of Hamburgh, in the year 1669 1, as he was attempt ing to extract from human urine a liquid capable of converting silver into gold. He showed a specimen of it to Kunkel, a German chemist of considerable eminence, who mentioned the fact as a piece of news to one Kraft, a friend of his at Dresden. Kraft im- mediately repaired to Hamburgh, and purchased the secret from Brandt for 200 dollars, exacting from him at the same time a promise not to reveal it to any other person. Soon after, he exhibited his phosphorus pub. licly in Britain and France, expecting doubtless that it Xvould make his fortune. Kunkel, who had mentioned to Kraft his intention of getting possession of the pro- cess, being vexed at the treacherous conduct of his friend, attempted to discover it himself; and about the year 1674 he succeeded, though he only knew from Brandt that urine was the substance from which phos- phorus had been procured J. Accordingly he is always reckoned, and deservedly too, as one of the discoverers of phosphorus. Boyle likewise discovered phosphorus. Leibnitz in- deed affirms, that Kraft taught Boyle the whole pro- * The theory of this process will be explained afterwards. f Homberg, Mem. Par. 1692. An acc> unt of it is published in the Philosophical Transactions for 1681, first by Sturmios, and then by Dr Slare. | This is KunkeTs own account. See his Laboratorium Ctymieum, p. 660. See also Wiegleb's Getchicbte det Wacbttbums and der Erfindungci s det Cbcmir t Vol. i. f . 4 X. E2 OS SIMPLE COMBUSTIBLES. Book I. C e S s, and Kraft declared the same thing to Stahl. But Division I. y t surely the assertion of a dealer in secrets, and one who had deceived his own friend, on which the whole of this story is founded, cannot be put in competition with the affirmation of a man like Boyle, who was not only one of the greatest philosophers, but likewise one of the most virtuous men of his age > and he positively as- sures us, that he made the discovery without being pre- viously acquainted with the process*. Mr Boyle revealed the process to his assistant God- frey Hankwitz, a London apothecary, who continued for many years to supply all Europe with phosphorus. Hence it was known to chemists by the name of English phosphorus \. Other chemists, indeed, had attempted to produce it, but seemingly without successt, till in 1737 a stranger appeared in Paris, and offered to make phos- phorus. The French government granted him a re- ward far communicating his process. Hellot, Dufay, GeofFroy, and Duhamel, saw him execute it with suc- cess ; and Hellot published a very full account of it in the Memoirs of the French Academy for 1737. It consisted in evaporating putrid urine to dryness, heating the inspissated residue to redness, washing it with water to extract the salts, drying it, and then rai- sing it gradually in stone-ware retorts to the greatest intensity of heat. It was disgustingly tedious, very expensive, and yielded but a small quantity of produce. The celebrated Margraf, who informs us that he had * Boyle's Works abridged by Shaw, iii. 174. f See Hoffman's experiments on it, published in 1722 in his Plys. Cbyw. Select, p. 304. } Stahl's Fundament. Ct>ym ii. 58. PHOSPHORUS, ft devoted himself at a very early period to the investiga- Chap. II. tion of phosphorus, soon after published a much more expeditious and productive process ; for the first hint of which he was indebted to Henkei. It consisted in mixing a salt consisting chiefly of lead with the inspis- sated urine. He even found that urine contained a pe- culiar salt*, which yielded phosphorus when heated with charcoal f. In the year 1769, Gahn, a Swedish chemist, disco- vered that phosphorus is contained in bones $ ; and Scheele , very soon after, invented a process for ob- taining it from them. Phosphorus is now generally procured in that manner. The process described in the beginning of this Section is that of Fourcroy and Vau- quelin. The usual process followed by manufacturers pf phosphorus is an improvement on that of Scheele. Soon after the discovery of phosphorus, many experiments on it were made by Slare and Boyle. Hoffman published a dissertation on it, containing some curious facts, in 1122 ; but Margraf was the first who investigated its effects upon other bodies, and the na- ture of the combinations which it forms. The subject was resumed by Pelletier, and continued with much in- dustry and success. Lavoisier's experiments were still * Known at that time by the name offusdte talt of vrie t now called f bos f bate of ammonia, f Misctl. Btrolin, 1740, vi. 54. ; and Mem. Acad* Berlin* 1746, p. 84; and MargraPs Of use. i. 30. J Bergman's Notes on ScLeffir. Crell, in his life of Scheele, informs us, that Scheele himself was the discoverer of the fact. This, he says, appears clearly from a printed let- ter of Scheele to Gahn, who was before looked upon as the discoverer. See Crell's Annals , English Trans, i. 17. Book I. .Division I. v_ v Its proper- ties. Burns when exposed to .Ac air. SIMPLE COMBUSTIBLES. more important, and constitute indeed a memorable era in chemical science. 1. Phosphorus, when pure, is semi-transparent, and of a yellowish colour ; but when kept some time in water, it becomes opaque externally, and then has a great resemblance to white wax. Its consistence is nearly that of wax. It may be cut with a knife, or twisted to pieces with the fingers. It is insoluble in water. Its mean specific gravity is I'll 0. 2. It melts at the temperature of 99*. Care must be taken to keep phosphorus under water when melted ; for it is so combustible, that it cannot easily be melted in the open air without taking fire. When phosphorus is newly prepared, it is always dirty, being mixed with. a quantity of charcoal dust and other impurities. These impurities may be separated by melting it under water, and then squeezing it through a piece of clean shamois leather. It may be formed into sticks, by putting it j into a glass funnel with a long tube, stopped at the bot- tom with a cork, and plunging the whole under warm water. The phosphorus melts, and assumes the shape of the tube. When cold, it may be easily pushed out with a bit of wood. If air be excluded, phosphorus evaporates at 219*, and boils at 554 f. 3. When phosphorus is exposed to the atmosphere, it emits a white smoke, which has the smell of garlic, and is luminous in the dark. This smoke is more a- bundant the higher the temperature is, and is occasioned Pclletier, Journal /e fbylqvt t ixxv. 380. f Ibid. PHOSPHORUS. by the gradual combustion of the phosphorus, which at last disappears altogether. 4. When a bit of phosphorus is put into a glass jar Soluble in filled with oxygen gas, part of the phosphorus is dis- solved by the gas at the temperature of 60 ; but the phosphorus does not become luminous unless its tem- perature be raised to 80*, Hence we learn, that phosphorus burns at a lower temperature in common air than in oxygen gas. This slow combustion of phos- phorus, at the common temperature of the atmosphere, renders it necessary to keep phosphorus in phials filled with water. The water should be previously boiled to expel a little air, which that liquid usually contains. The phials should be kept in a dark place ; for when phosphorus is exposed to the light, it soon becomes of a white colour, which gradually changes to a dark brown. 5. When heated to 148, phosphorus takes fire and Converted burns with a very bright flame, and gives out a great quantity of white smoke, which is luminous in the dark j at the same time it emits an odour which has some resemblance to that of garlic. It leaves no resi- duum ; but the white smoke, when collected, is found to be an acid. Stahl considered this acid as the muri- atic f. According to him, phosphorus is composed of muriatic acid and phlogiston J, and the combustion of * Fourcroy and Vauquelin, Anndc, de C&imte, xxi. 196. f This acid shall be afterwards described. J The term pklogiiton was applied by Stahl and his followers to a substance which, according to them, exists in all combustible bodies, and separates during combustion. A sketch of their theory will be given in the next Section, in which we shall treat of sulphur, on which the hy- pothesis was founded. f* SI1TPLE COMBUSTIBLES. Book I. it j$ merely the separation of phlogiston. He even de- Divreion ! . t v clared, that to make phosphorus, nothing more is neces- sary than to combine muriatic acid and phlogiston *. These assertions having gained implicit credit, the compo'sition and nature of phosphorus were considered as completely understood, till Margraf of Berlin pu- blished his experiments in the year 1740. That great man, one of those illustrious philosophers who have con- tributed so much to the rapid increase of the science, distinguished equally by the ingenuity of his experi- ments and clearness of his reasoning, attempted to pro- duce phosphorus by combining together phlogiston and muriatic acid: but though he varied his process a thou- sand ways, presented the acid in many different states, and employed a variety of substances to furnish phlo- giston, all his attempts failed, and he was obliged to Into phos- &* ve U P *ke combination as impracticable. On exa- phoricaad; mining the acid produced during the combustion of phosphorus, he found that its properties were very dif- ferent from those of muriatic acid. It was therefore a distinct substance f. The name of phosphoric add was given to it ; and it was concluded that phosphorus is composed of this acid united to phlogiston. But it was observed by Margraf, that phosphoric acid is heavier than the phosphorus from which it was produced ; and Boyle had long before shown that phos- phorus would not burn except when in contact with air. These facts were sufficient to prove the inaccuracy of. the theory concerning the composition of phosphorus ; but they remained themselves unaccounted for, till La-' * Stehl's Three Hundred Exferimtntt. f Margraf 's Ofutc. I 56, PHOSPHORUS. 73 voisier published those celebrated experiments which t Chap. II. threw so much light on the nature and composition of / acids*. He exhausted a glass globe of air by means of an which i* air-pump ; and after weighing it accurately, he filled it with oxygen gas, and introduced into- it 100 grains of phosphorus. The globe was furnished with a stop- g cock, by which oxygen gas could be admitted at plea- sure. He set fire to the phosphorus by means of a burning glass. The combustion was extremely rapid, accompanied by a bright flame and much heat. Large quantities of white flakes attached themselves to the inner surface of the globe, and rendered it opaque ; and these at last became so abundant, that notwithstanding the constant supply of oxygen gas the phosphorus wa$ extinguished. The globe, after being allowed to cool, was again weighed before it was opened. The quantity of ocygen employed during the experiment was ascer- tained, and the phosphorus, which still remained un- changed, accurately weighed. The white flakes, which were nothing else than pure phosphoric acid, were found exactly equal to the weights of the phosphorus and oxygen which had disappeared during the pro- cess. Phosphoric acid therefore must have been form- ed by the combination of these two bodies ; for the ab- solute weight of all the substances together was the same after the process as before itf. It is impossible, then, for phosphorus to be composed of phosphoric acid and phlogiston, as phosphorus itself enters into the com- position of that acid. * Mtm. Par. 1778 and 1780. f Lavoisier's CLtmistry, Part I. chap. 14 SLMPLE COMBUSTIBLES. Book I. Thus the combustion of phosphorus, like that of hy- Bivision I. . " . . . t v > drogen and carbon, is nothing else than its combination with oxygen : for during the process no new substance appears, except the acid, accompanied indeed with much heat and light. From Lavoisier's experiment it follows, that 100 parts of phosphorus, during this combustion, unite with 154 parts oxygen. So that a grain of phosphorus con- denses no less than 4^ cubic inches of oxygen gas ; and five grains are capable of depriving 102-J cubic inches of air of all its oxygen gas. 6. Though pure phosphorus does not take fire till it be heated to 148, it is nevertheless true, that we Oxide of meet with phosphorus which burns at much lower phosphorus, temperatures. The heat of the hand often makes it burn vividly ; nay, it sometimes takes fire when merely exposed to the atmosphere. In all these cases the phosphorus has undergone a change. It is believed at present, that this increase of combustibility is owing to a small quantity of oxygen with which the phosphorus has combined. Hence, in this state, it is distinguished by the name of oxide of phosphorus. When a little phosphorus is exposed in a long narrow glass tube to the heat of boiling water, it continues moderately lu- minous, and gradually rises up in the state of a white vapour, which lines the tubes. This vapour is the ox- ide of phosphorus. Thi oxide has the appearance of fine white flakes, which cohere together, and is more bulky than the original phosphorus. When slightly heated it takes fire, and burns brilliantly. Exposed to the air, it attracts moisture with avidity, and is con- PHOSPHORUS. 15 verted into an acid liquor*. When a little phosphorus , cha P- IL is thus oxidized in a small tin box by heating it, the oxide acquires the property of taking fire when exposed to the air. In this state it is often used to light candles under the name of phosphoric matches ; the phosphorus being sometimes mixed with a little oil, sometimes with sulphur. When phosphorus is long acted on by water, it is covered at last with a white crust, which is also consi- dered as an oxide of phosphorus ; but it differs consi- derably from the oxide just described. It is brittle, less fusible, and much less combustible than phosphorus itselff. Phosphorus, when newly prepared, usually contains some of this last oxide of phosphorus mixe4 with it ; bi|t it may be easily separated by plunging the mass into water heated to about 100. The phos- phorus melts, while the oxide remains unchanged, and swims upon the surface of the melted phosphorus. 7. When bits of phosphorus are kept for some hours zed hydro- in hydrogen gas, part of the phosphorus is dissolved, gen gas. This compound gas, to which Fourcroy and Vaque- lin, the discoverers of it, have given the name of phos- phorized hydrogen gas> has a slight smell of garlic. When bubbles of it are made to pass into oxygen gas, a very brilliant bluish flame is produced, which per- vades the whole vessel of oxygen gas. It is obvious that this dame is the consequence of the combustion of the dissolved phosphorus . When phosphorus is introduced into a glass jar of Phospfco- hydrogen gas standing over mercury, and then melted * Steuiachcr,^n. similar to the smell of pu- trid fish. When it comes into contact with common air, it burns with great rapidity ; and if mixed with that air, it detonates violently. Oxygen gas produces a still more rapid and brilliant combustion than com- mon air. When bubbles of it are made to pass up through water, they explode in succession as they reach the surface of the liquid ; a beautiful coronet of white smoke is formed, which rises slowly to the ceil- ing. This gas is one of the most combustible substan- ces known. It is obvious, that its combustion is mere- ly the combination of its phosphorus and its hydrogen with the oxygen of the atmosphere ; the products, of course, are phosphoric acid and water. These two sub- stances mixed, or rather combined, constitute the coronet of white smoke. * Mem. Scav. Etrang. x, f Ann. ie dim. x. 19. t Ibid. xxxv. 2)5. PHOSPHORUS. 77 Pure water, when agitated in contact with this gas, Chap. H. dissolves at the temperature of between 50 and 60 about the fourth part of its bulk of it*. The solu- tion is of a colour not unlike that of roll sulphur ; it has a very bitter and disagreeable taste, and a strong unpleasant odour. When heated nearly to boiling, the whole of the phosphureted hydrogen gas is driven off unchanged, and the water remains behind in a state of purity. When exposed to the air, the phosphorus is gradually deposited in the state of oxide j the hydrogen gas makes its escape ; and at last nothing remains but pure water f. When electric explosions are passed through this gas, its bulk is increased precisely as happens to car- bureted hydrogen. The water which it contains is de- composed, phosphoric acid formed, and hydrogen gas evolved j. We are neither acquainted with the specific gravity, nor with the proportion of the constituents of this gas. 8. Phosphorus is capable of combining with car- ph os phuret bon. This compound, which has received the name of carbon, of phosphuret of carbon, was first examined by Mr Proust, the celebrated professor of chemistry in Spain. It is the red substance which remains be- hind when new-made phosphorus is strained through shamois leather. In order to separate from it a small quantity of phosphorus which it contains in excess, it Such was the result obtained by Raymond, Dr Henry found that xoo inches of water took up only 2*14 inches of this gat at the tempera- ture of 60. See PL'il. Tram. 1803, p. 474^ f Raymond, Ann. de Cbim. xxxv. 333. | Henry, Nicholson's quarto Js,ur. ii. 347. 78 SIMPLE COMBUSTIBLES. Book I. Division Phosphtl- rets. Apgiton. Composi- lion. should be put into a retort, and exposed for some time to a moderate heat. What remains behind in the retort is the pure phosphuret of carbon. It is a light, flocky powder, of a lively orange red, without taste or smell. "When heated in the open air it burns rapidly, and a quantity of charcoal remains behind. When the retort in which it is formed is heated red hot, the phosphorus comes over, and the charcoal remains behind*. 9. Such are the properties of phosphorus, and the compounds which it forms with oxygen, hydrogen, and carbon. It is capable likewise of combining with many other bodies: the compounds produced are called pbospbttrtts . 10. Phosphorus, when used internally, is poiso- nousf . In very small quantities (as one fourth of a grain), when very minutely divided, it is said by Leroi to be very efficacious in restoring and establish, ing the force of young persons exhausted by sensual indulgence J ; that is, I suppose, in exciting the vene- real appetite. 11. Though nobody has hitherto succeeded in ascer- taining the constituents of phosphorus, there is every reason to consider it as a compound. When acted upon by a powerful galvanic battery, Mr Davy found that it emitted hydrogen in considerable quantity. Hence it is not unlikely that hydrogen is one of its constituents. The other has not yet been observed in a separate state, but analogy renders it not improbable that it will be found to be of a metallic nature. * Ann. de Cb'im. xxxiv. 44. \ Nicholson's Journal^ iii. 85. SULPHUR. SECT. IV. OF SULPHUR. SULPHUR, distinguished also by the name of brimstone^ was known in the earliest ages. Considerable quanti- ties of it are found native, especially in the neighbour- hood of volcanoes, and it is procured in abundance by subjecting the mineral called pyrites to distillation. The ancients used it in medicine, and its fumes were employed in bleaching wool*. 1. Sulphur is a hard brittle substance, commonly of a yellow colour, without any smell, and of a weak though perceptible taste. It is a non-conductor of electricity, and of course be- comes electric by friction. Its specific gravity is 1*990. Sulphur undergoes no change by being allowed ta remain exposed to the open air. When thrown into water, it does not melt as common salt does, but falls to the bottom, and remains there unchanged : It is therefore insoluble in water. 2. If a considerable piece of sulphur be exposed to a Action of sudden though gentle heat, by holding it in the hand, heat< for instance, it breaks to pieces with a crackling noise. When sulphur is heated to the temperature of about Flowers of 170, it rises up in the form of a fine powder, which * u ' p Uf " * Pliny, lib. xxrr c. 15. 80 SIMPLE COMBUSTIBLES. BookT, may b e easily collected in a proper vessel. This pow- Divisjon I. J . J * -Y > der is called Jtowers of sulphur^. When substances fly off in this manner on the application of a moderate hear, they are called volatile ; and the process itself, by which they are raised, is called volatilisation. When heated to the temperature of about 218 of Fahrenheit's thermometer, it melts and becomes as li- quid as water. If this experiment be made in a thin glass vessel, of an egg shape, and having a narrow, mouth*, the vessel may be placed upon burning coals without much risk of breaking it. The strong heat soon causes the sulphur to boil, and converts it into a brown coloured vapour, which fills the vessel, and is- sues with considerable force out from its mouth. Sulphur ca- 3< There are a great many bodies which, after being ^ ssolved * n water or melted by heat, are capable of as- suming certain regular figures. If a quantity of com- mon salt, for instance, be dissolved in water, and that fluid, by the application of a moderate hear, be made to fly off in the form of steam ; or, in other words, if the water be slowly evaporated, the salt will fall to the bottom of the vessel in cubes. These regular figure* are called crystals. Now sulphur is capable of crystal- lizing. If it be melted, and as soon as its surface be- gins to congeal, the liquid sulphur beneath be poured out, the internal cavity will exhibit long needle-shaped crystals of an octahedral figure. This method of crys- tallizing sulphur was contrived by Rouelle. If the ex- t It is only in this state that sulphur is to be found in commerce to- lerably pure. Roll sulplur usually contains a considerable portion of fo- reign bodies. * Such vessels are usually called receivers or fiasli by chemist*. SULPHUR. 81 periment be made in a glass vessel, or upon a flat plate Chap. II. ^ of iron, the crystals will be perceived beginning to shoot when the temperature sinks to 220. 3. When sulphur is heated to the temperature of 560 Converted in the open air, it takes fire spontaneously, and burns tionintoan with, a pale blue flame, and at the same time emits a acidt great quantity of fumes of a very strong suffocating odour. When set on fire, and then plunged into a jar full of oxygen gas, it burns with a bright violet colour- ed flame, and at the same time emits a vast quantity of fumes. If the heat be continued long enough, the sul- phur burns all away without leaving any ashes or resi- duum. If the fumes be collected, they are found to consist entirely of sulphuric acid. By combustion, then, sulphur is converted into an acid*. This fact was known several centuries ago ; but no intelligible expla- nation was given of it till the time of Stahl. That chemist undertook the task, and founded on his experi- ments a theory so exceedingly ingenious, and support- ed by such a vast number of facts, that it was in a very short time adopted with admiration by the philosophic world, and contributed not a little to raise chemistry to that rank among the sciences from which the ridiculous pretensions of the early chemists had excluded it. According to Stahl, there is only one substance in nature capable of combustion, which therefore he call- ed PHLOGISTON ; and all those bodies wh,ich can be set tij1 *' * Acids are a class of compound bodies, to be afterwards described. They are distinguished by a sour taste, and by tbe property which they pr sess of changing the blue colour of many vegetable infusions (of the Sowers of mallows, for instance, or red cabbage) to red. L F 82 SIMPLE COMBUSTIBLES. Book I. on fire contain less or more of it. Combustion is Division I. u_ -v ' merely the separation of this substance. Those bodies which contain none of it are of course incombustible. All combustibles, except those which consist of pure phlogiston (if there be any such), are composed of an incombustible body and phlogiston united together. During combustion the phlogiston flies off, and the incombustible body remains behind. Now when sul- phur is burnt, the substance which remains is sulphuric acid, an incombustible body. Sulphur therefore is composed of sulphuric acid and phlogiston. To establish this theory completely, it was necessary to show that sulphuric acid can be obtained by separa- ting the phlogiston from sulphur, and that sulphur can be actually formed by combining together sulphuric acid and phlogiston. Both of these points Stahl undertook to demonstrate. If potash* and sulphur be mixed to* gether and heated, they melt and form a brittle mass of a brown colour, consisting of the two substances combined together. Put this compound, previously re- duced to powder, into a flat open vessel, and expose it to a gentle fire, the sulphur gradually disappears, and sulphuric acid is found in its place combined with the potash. In this case, said Stahl, the gentle heat dis- sipates the phlogiston and leaves the acid. To form the sulphur anew, it is only necessary to present to the acid a body containing phlogiston. Lamp black or charcoal is such a body : for it is combustible, and therefore, according to the theory of Stahl, contains phlogiston : when burnt, it leaves a very inconsiderable residuum. * The nature offetast shall afterwards be explained; SULPHUR. 83 and consequently contains hardly any thing else than Chap. IL ^ phlogiston. He mixed together in a crucible the com- pound consisting of sulphuric acid and potash, and one- fourth part by weight of pounded charcoal, covered the crucible with another inverted over it, and applied a strong heat to it. He then allowed it to cool, and ex- amined its contents. The charcoal had disappeared, and there only remained in the crucible a mixture of potash and sulphur combined together, and of a darker colour than usual from the residuum of the charcoal. Now there were only three substances in the crucible at first, potash, sulphuric acid, and charcoal ; two of these have disappeared, and sulphur has been found in their place. Sulphur then must have been formed by the combination of these two. But charcoal consists of phlogiston and a very small residuum, which is still found ia the crucible. The sulphur then must have been formed by the combination of sulphuric acid and phlogiston*. This simple and luminous explanation appeared so satisfactory, that the composition of sulphur was long considered as one of the best demonstrated truths in chemistry. There are two facts, however, which Stahl either did Unsatifac- not know, or did not sufficiently attend to, neither of tQr ^* which is accounted for by his theory. The first is, that sulphur will not burn if air be completely exclu- ded ; the second, that sulphuric acid is heavier than the sulphur from which it was produced. To account for these, or facts similar to these, suc- *Stahl*3 Qpm;. Cbymic as was 6 rst ascertained by Margraff. Pel- letier afterwards examined the combination with carej. Some curious observations were published on the for- mation of this compound by Mr AccumJ ; and soon af- ter the circumstances under which it takes place were explained with precision by Dr Briggs|[. All that is necessary is to mix the two substances together, and apply a degree of heat sufficient to melt them, as Pelletier first observed. The.compound has a yellowish white colour, and a crystallized appear- ance 1J. The combination may be obtained by heating the mixture in a glass tube, having its mouth properly * Mem. D'Arcueil, i 324. f Of use. i. ir. t Jour, dt Pbys. xxxv. 381. Nicholson, vi, !) IbiJ. vii. 58. ^ Briggs, Ibid. SULPHUR. stcured from the air. The sulphuret of phosphorus^ . cha P; Ir - thus prepared, is more combustible thn phosphorus. If it be set on fire by means of a hot wire, allowed to burn for a little, and then extinguished by excluding the' air, the phosphorus, and perhaps the sulphur, is oxi- dized, and the mixture acquires the property of ta- king fire spontaneously as soon as it comes in contact with air*. The combination may be procured also by putting the two bodies into a retort, or flask, filled with water, and applying heat cautiously and slowly* They com- bine together gradually as soon as the phosphorus is melted. It is necessary to apply the heat cautiously, because the sulphuret of phosphorus has the property of decomposing water, as had been observed by Mar- graf, and ascertained by Pelletier. The rate of decom- position increases very rapidly with the temperature, a portion of the two combustibles being converted into acids by uniting to the oxygen : the hydrogen at the moment -of its evolution unites with sulphur and phos- phorus, and forms sulphureted and phosphoreted gases. This evolution, at the boiling temperature, is so rapid as to occasion violent explosions, as I 'accidentally ob- served some years ago. Mr Accum has lately exami- ned the circumstances attending this explosion, and found that the gas emitted burns spontaneously> and leaves phosphoric and sulphuric acids. The sulphuret of phos- phorus formed under water has a yellow colour. It gives to the water in which it is kept an acid taste, and the smell of sulphureted hydrogen. It burns, ac- * BriggS, Hid. L 98 SIMPLE COMBUSTIBLES. Book I. cording to Dr Briggs, at a temperature considerably Division I. . . ., , . . , lower than a similar compound made m the dry way. This induces him to conclude, that during the combi- nation a little water is decomposed, and the oxygen ex- pended in converting the sulphur and phosphorus into oxides. The sulphuret of phosphorus may be distilled over without decomposition. Indeed it was by distillation that Margraf first obtained it. Sulphur and phospho- rus, by combining, acquire a considerable tendency to liquidity ; and this tendency is a maximum when the two bodies are combined in equal proportions. The following table exhibits the result of Pelletier's expe- riments on the temperatures at which the compound be- comes solid when the substances are united in various proportions * : 8 1 8 Phosphorus 7 Sulphur 5 Phosphorus ") congeals at 7T at 59 2 S Sulphur 5 Phosphorus 7 at 50 4 8 Sulphur 5 Phosphorus ......... at 41 8 4 Sulphur 5 Phosphorus ') ......... at 54'5 S Sulphur y Phosphorus") at QQ'S " 8 Sulphur j * Ann. de Cbim. iv. IO. StTLPlftfR; When the sulphur predominates, this compound may- be called photphuret of sulphur ; when the phosphorus exceeds, it may be called sulphur -et of phosphorus. 10. From an experiment of Mr Clayfield made in 1799, and lately described by Mr Davy*, and from si- milar experiments performed still more lately by Ber- thollet junicrf, there is reason to conclude that sulphur contains hydrogen rts a constituent. Mr Clayfield dis* tilled a mixture of three parts copper filings, and one part powdered sulphur* both well dried, and obtained a quantity of sulphureted hydrogen gas. Berthollet dis- tilled sulphur mixed with copper, and with iron, and with mercury, and obtained the 1 same gasj especially when mercury was used. Sulphur, then, is in all pro- bability a compound. But as we are ignorant of the other constituent of this substance, and as we do not know whether the hydrogen enters into the composi- tion of sulphuric acid, we cannot venture as yet to place it in the class of compound combustibles. Such are the properties of the simple combustibles, and such the combinations which they form with oxy- gen and with each other. Hydrogen, as far as we know at present, is really a simple body ; but charcoal, phos- phorus, and sulphur, are certainly compounds containing hydrogen as a constituent. Whether this hydrogen enters into the acid compounds which these three bodies form * On the de com petition and composition of tie fixed alkalies. Pbil, dm. iSc8. f Mem. D'Arcueil, i 337. G2 100 SIMPLE COMBUSTIBLES. Book I. W1 *th oxygen ; cr whether these acids consist merely of Division I. the other unknown constituent combined with oxygen, has not been determined. But the first of these sup- positions is probable, though it would be difficult to as- certain its truth by actual experiment. Hydrogen in a separate state can only be exhibited in the state of gas, and cannot therefore be compared with the rest in its properties. Carbon is always solid, and cannot be fused, far less volatilized, by any degree of heat which we can raise. Sulphur and phosphorus bear a striking resemblance to each other* They are both solid, both fusible by heat, both volatilizable, and both boil and assume the form of vapour when suffi- ciently heated. It is the combustibility of these bodies, and the strong tendency which they have to unite with oxygen, which constitutes their charateristic property. They are all capable of condensing a certain determinate portion of this principle ; and when once they have combined with that portion, they cannot unite with any more. In che- mical language, they are then said to be saturated with oxygen.- Now the proportion of oxygen with which each is capable of uniting, is exceedingly different, as- will appear from the following table : TOO hydrogen unites with 597*7 oxygen 100 carbon 257*0 100 phosphorus 154*0 10O sulphur , 138*7 J^ffiniry for This difference claims particular attention. Bertholkt has ingeniously supposed that the affinity of one body for another is proportional to the quantity of it which it is capable of condensing. The phenomena of che- Co-nbina- tions with oxygen. SULPHUR. mistry agree well with this supposition. But if we ad- Chap. u. rait it, we must suppose the affinity of the simple com- bustibles for oxygen to be in the order which we have followed in describing them. Hydrogen will have the greatest affinity, carbon will be next, then phosphorus ; and sulphur will have the weakest affinity of all. Hydrogen when saturated with oxygen forms water; the other three combustibles form acids, the corrosive qualities of which become stronger, the smaller the quantity of oxygen necessary to saturate the combusti- ble. This fact is curious. Berthollet supposes that the properties of oxygen are" disguised best when it is combined with those bases for which it has the strong- est affinity, and that its predominant qualities begin to display themselves as the affinity of the base diminishes. This notion, which is ingenious enough, if applied to oxygen, would lead us to conclude, that when in a con- densed state it is of a corrosive nature, unless when its action is checked by the body to which it is united. A notion that accords well with the great activity of this important substance. Hydrogen combines only with oxygen in one proper- Hydrogen tion ; but all the rest are capable of uniting with vari- conTp'ound; ous doses of it. Carbon is believed to be capable of uniting with three Carbon, doses of it. The first compound is supposed to be a black powder resembling charcoal. It is rather hypo- thetical at present. When ascertained it may be called carbonous oxide. The second compound is carbonic ox- ide gas j the third carbonic acid. Phosphorus when imperfectly burnt is convered into phospho- oxide of phosphorus. When left exposed to the open air, nis> ee ; it gradually combines with oxygen, and is converted 1012 SIMPLE COMBUSTIBLES. Book I. Division I. Sulphur, three. Combina- tion of the combusti- bles with each other. into an acid liquid called phosphorous acid When set on fire, it combines with a maximum of oxygen, and is converted into white flakes, destitute of smell, called phosphoric acid. Sulphur, when kept long in a state of fusion, com- bines with a small dose of oxygen, and is converted in- to oxide of sulphur . When heated to 560 in the open air, it burns with a blue flame, combines with oxygen, and forms an acid which has a peculiarly suffocating odour, and is called sulphurous acid. When mixed with nitre and set on fire, it combines with a maximum of oxygen, and forms an acid without smell called sul* phuric acid. All the simple combustibles are capable of combining with each other. Chemists have agreed to give to all such combinations a name ending in uret, and derived from that ingredient which is supposed to characterize the compound. Thus we have s-ulphuret of phosphorus, of carbon, and of hydrogen ; but the last compound be- ing gaseous, is usually denominated sulphureted hy~ drogen gas. We have likewise phosphuret of sulphur, of carbon, and of hydrogen, or phosphureted hydrogen gas. We have also two species of carbureted hydra- gen gas. All these compounds retain their combustii. bility. SIMPLE INCOMBUSTIBLES, GHAP. III. F SIMPLE INCOMBUSTIBLES, 1HE characteristic property of those substances which Characters. i term simple incombustibles, is a strong tendency to unite to oxygen ; the combination is not accompanied by the emission of heat and light, and the compounds formed are capable of supporting combustion. Only two substances possess this character j namely, azote and muriatic acid. There are indeed two other incom- bustible bodies not hitherto decompounded ; but they do not combine with oxygen at all : and at present ana- logy leads us to place them among the compounds. .Book I. Division SXMFLE INCOH3USTIBLES, procuring azotic gas. SECT. I. p F A "L O T E. I. AZOTE, called also NITROGEN, by some chemists, may be procured by the following process : If a. quantity of iron filings and sulphur, mixed together, and moistened with water, be put into a glass ves- sel full of air, it will absorb all the oxygen in the course? of a few days ; but a considerable residuum of air will still remain incapable of any further diminution*. This residuum has obtained the appellation of azotic gas^ There, are other methods of obtaining it more speedily. If phosphorus, for instance, be substituted for the iron- filings and sulphur, the absorption is completed in less than 24 hours. The following method, first pointed out by Berthollet, furnishes very pure azotic gas, if the proper precautions be attended to. Very much diluted aquafortis, or nitric acid as it is called in chemistry, is poured upon a piece of muscular flesh, and a heat of about 100 applied. A considerable quantity of azotic gas is emitted, which may be received in proper ves- sels. This gas was discovered in 1T72 by Dr Rutherford, now professor of botany in the university of Edinburgh f , * This experiment was first made by Dr Hales. | See his thesis De Aerc Mtphitico, published in 1772." Sed aer sa* lubrisetpurus respirationcm animali non modo ex partc fit mephiticui, eed AZOTE. Schcele procured it by the first mentioned process es Ch?p. II r. early as 1776, and proved that it was a distinct fluid*. 1. The air of the atmosphere contains about 0*79 parts (in bulk) of azotic gas ; almost all the rest of it is oxygen gas. Mr Lavoisier was the first philosopher who published this analysis, and who made azotic gas known as a component part of air. His experiments were published in 1773 f. Scheele's Treatise on Air and Fire, in which his analysis is contained, was not i published till 1777. 2. Azotic gas is invisible and elastic like common Weight. air, which it resembles in its mechanical properties. It has no smell. Its specific gravity, according to Kir- wan, is 0*985 t, tnat f a * r being 1*000. Lavoisier makes it only C*97S , and with this the statement of Davy coincides exactly ||. According to Mr Kirwan, 100 cubic inches of it, at the temperature of 60, ba- rometer 30 inches, weigh 3 0'535 grains ; according to Lavoisier and Davy, they weigh 30*338 grains. 3. It cannot be breathed by animals without suffoca- Destroy* tion. If obliged to respire it, they drop down dead -til- ' et aliam indd'n ;ux mutatlonem i nde fatitur. Postquam emm omnis aer mephiticus {carbonic acid gas~) ex eo, ope lixiyii caustic! secretusct abduc- tus fuerit, gut tamerr resiai nullo modo salubrior inde evadit ; nam quam- vis nullam ex aqua calcis praecipitationem faciat baud minus quam antea etf^mmamet vitar* ext'mguit" Page 17. When Hauxbee passed air through red-hot metallic tubes, he must have obtained this gas ; but at that time the difference between gases was ascribed to fumes held in solution. See flil.trani. Abr. v. 613. # On Air and Fire, p. 7. | See his remarks on Scheele's works, Mem. Par. 1781, p. 397, | Qn Phlogiston, p. 27. Lavoisier's Elements. K Rttearctcs, p. 565. 106 SIMPLE INCOMECSTIBLES. Book L most instantly *. No combustible will burn in it. Division'!. ....... i~-v-^ rlence the reason why a candle is extinguished in at- And pre- vents com- bustu n. Absorption by water. mospherical air as soon as the oxygen near it is con- sumed. Mr Goettling, indeed, published, in 1794, that phosphorus shone, and was converted into phos- phoric acid, in pure azotic gas. Were this the case, it would not be true that no combustible will burn in this gas; for the conversion of phosphorus into an acid, and even its shining, is an actual though slow combus- tion. Mr Goettling's experiments were soon after re- peated by Drs Scherer and Jaeger, who found, that phosphorus does not shine in azotic gas when it is per- fectly pure j and that therefore the gas on which Mr Goettling's experiments were made had contained a mixture of oxygen gas, owing principally to its having been confined only by water. These results were af- terwards confirmed by Professor Lampadius and Pro- fessor Hildebrandt. It is therefore proved beyond a doubt, that phosphorus does not burn in azotic gas j and that whenever it appears to do so, there is always some oxygen gas present f . 4. This gas is not sensibly absorbed by water ; nor indeed are we acquainted with any liquid which has the property of condensing it. Dr Henry ascertained, that when water is previously deprived of all the air which it contains, 100 inches of it are capable of ab- sorbing only 1*47 inches of azotic gas at the tempera- ture of 60 J. * Hence the name azote, given it by the French chemists, which sig- nifies " destructive to life." f Nicholson's Journal, ii. 8. \ Phil. front. 1803, p, 274. AZOXE. 107 II. 1. When electric sparks are made to pass through Chap. ill. common air confined in a small glass tube, or through a mixture of oxygen gas and azotic gas, the bulk of the air diminishes. This curious experiment was first made Combines by Dr Priestley, who ascertained at the same time, g en , that if a little of the blue infusion of litmus be let up into the tube it acquires a red colour * ; hence it fol- lows that an acid is generated. Mr Cavendish ascer- tained, that the diminution depends upon the propor- jion of oxygen and azote present ^ that when the two gases are mixed in the proper proportions they disap- pear altogether, being converted into nitric acid. Hence And form* fce inferred that nitric acid is formed by the combination ni * nc of these two bodies. This important discovery was communicated to the Royal Society on the 2d June 1785. The combination of the gases, and the forma- tion of the acid, was much facilitated, he found, by introducing into the tube a solution of potash in water. This body united with the nitric acid as it was pro- jiuced, and formed with it the salt called nitre. In Mr Cavendish's first experiments there was some uncer- tainty, both in the proportion of oxygen gas and of common air which produced the greatest diminution in a given time, and in the proportion of the two gases which disappeared by the action of the electricity. The experiment was twice repeated in the winter 1787-8 by Mr Gilpin, under the inspection of Mr Cavendish, and in the presence of several members of the Royal $ociety. The last of these experiments, which was conducted with every possible precaution to ensure ac- Priestley on Air, ii. 1CS SIMPLE JNCOMBUST1BLES. curacy, I shall consider as nearest the truth. It lasted rather more than a month. During the course of it there were absorbed 4090 measures of oxygen gas contaminated with ^ part of azote, and 2588 mea- sures of common air. Now if we suppose that com- mon air contains 22 parts in the 100 of oxygen gas, and make the necessary corrections, we shall have 4532 measures of oxygen gas, and 2146 measures of azotic gas, or very nearly 2 measures of azotic gas to 4J- of oxygen. 453*2 inches of oxygen weigh about 154 grains, and 214*6 measures of azote about 65 grains. proportion According to this statement, we have nitric acid com- P osed of 10 P arts bv wei g ht of a *te united to 236 of oxygen ; or in the hundred parts 29*77 azote 70*23 oxygen 100*00* This result agrees almost exactly with the subsequent experiments of Mr Davy, according to which the con- stituents of nitric acid are 29*5 azote 70 s 5 oxygen Two oxide* te ; 100-0 f 2. Nittic acid is a heavy liquid, usually of a yellow colour, which acts with great energy upon most sub- stances, chiefly in consequence of the facility with which it yields a portion of its oxygen. If a little phospho- rus or sulphur, for instance, be put into it, the acid Phil. Tram. 1788, p, l66. f Researches, p. j6j. AZOTE. 109 when a little heated gives up oxygen to them, and con- Chap, m. verts them into acids precisely as if the two bodies were subjected to combustion. In this case the nitric acid, by losing a portion of its oxygen, is changed into a species of gas called nitrous gas, which flies off and oc- I Nitrous casions the effervescence which attends the action of S as; nitric acid on these simple combustibles. Nitrous gas is procured in greater abundance, as well as purity, by dissolving copper or silver in nitric acid. The gas may "be received in a water trough in the usual way. It possesses the curious property of combining with oxy- gen the instant it comes in contact with it, and of form- ing nitric acid. Hence the yellow fumes which appear when nitrous gas is mixed with common air. This combination furnishes a sufficient proof that the consti- tuents of nitrous gas are azote and oxygen, and that it contains less oxygen than nitric acid. It is therefore an oxide of azote. 3. When iron filings are kept for some days in ni- 2. Gaseous P. . f . oxide. trous gas, they deprive it or a portion ot its oxygen, and convert it into a gas which no longer becomes yel- low when mixed with common air, but in which phos- phorus burns with great splendour, and is converted into phosphoric acid. This combustion and acidifica- tion is a proof that the new gas contains oxygen. Its formation demonstrates that it contains azote, and that it has less oxygen than nitrous gas. It is therefore an oxide of axote as well as the last described gas. The name gaseous oxide of azote has been given to it. Thus we learn that azote is capable of uniting with three dozes of oxygen, and of forming two oxides and one acid. We shall find afterwards that there is still another acid composed of the same ingredients. 110 SIMPLE INCOMBUSTIBLES. Book I. Division I. Combines with hy- drogen. III. The combinations of azote with simple combus- tibles are scarcely so numerous; but some of them are of great importance. 1. When putrid urine, wool, shavings of horn, and many other animal substances, are subjected to distilla- tion, among other products there is obtained a substance* which has a very pungent odour, and which is well known under the names of hartshorn and 'volatile al- kali*. It may be procured in greatest purity from the salt called sal ammoniac. Pound this salt, and put it into a flask together with thrice its weight of ground quicklime, and luting on a bent tube, plunge the ex- tremity of it into a mercurial trough, and apply heat to the flask. A gas comes over, which is hartshorft in a state of purity ; by chemists it is usually called ammonia. It is light, absorbed in great abundance by water, has a pungent taste, and gives a green colour to vegetable blues. When electric sparks are passed through this gas, its bulk is doubled, and it is converted into a mixture of hydrogen and azotic gases. This was considered as a demonstration of its com- position ; but from the late experiments of Mr Davy, there is reason to conclude, that besides hydrogen and azote it contains also a portion of oxygen f. It is difficult to form ammonia by uniting its constituents artificially. However, Dr Austin succeeded in com- bining them. * The term alkali is applied in chemistry to a variety of substances which have the property of giving a green colour to vegetable blues, f The details will be given when we come to treat of ammonia. AZOTE. Ill When they are in the gaseous state, the union does Chap. Hi. not take place ; but when hydrogen, at the instant of its evolution, comes in contact with azotic gas, ammonia is formed. Dr Austin filled a jar with azotic gas,, placed it over mercury, and let up into it some moistened iron filings. Now iron filings have the property of decom- posing water. They unite with its oxygen, and allow its hydrogen to escape. There was suspended in the jar a paper tinged blue with radish. In a day or two it became green, and thus indicated the formation of ammonia ; for no gas but ammonia has the property of changing vegetable blues to green. When nitrous gas was substituted for azote, the ammonia was evolved more speedily. The experiment succeeded also with common air, but more slowly *. When nitrous gas and sulphurated hydrogen are mixed, ammonia is form- ed, as Kir wan first observed f. In this case the de- compositions and new combinations are more com- plicated. 2. No compound of azote and carbon is at present Dissolves known ; but if we believe Fourcroy, azotic gas has the property of dissolving a little charcoal. For according to him, azotic gas, obtained from animal substances by Berthollet's process, when confined long in jars, depo- sites on the sides of them a black matter, which has the properties of charcoal t 3. Phosphorus plunged into azotic gas is dissolved in a small proportion. Its bulk is increased about , * Phil. Tram. 1788, p. 382. f Jj,d. p. 384 \ Fourcror, Ann. J f Cbim. i. 45. j BertholleL 112 SIMPLE 1NCOMSUSTIBLES. Book I. and plosphuretcd azotic gas is the result. When this Division I. gas is mixed with oxygen gas, it becomes luminous, in consequence of the combustion of the dissolved phos- phorus. The combustion is most rapid when bubbles of phosphureted azotic gas are let up into a jar full of oxygen gas. When phosphureted oxygen gas, and phosphureted azotic gas, are mixed together, no light is produced, even at the temperature of 82* *. Ami sul- " "*" Fourcroy informs us, that when sulphur is melted in phur. azotic gas, part of it is dissolved, and sulplureted axotid gas formed. This gas has a fetid odour. Its properties are still unknown f. It is said to have been lately dis- covered by Gimbernat in the waters of Aix-la-Cha- pelle J. Attcmptsto IV. As azote has never yet been decompounded, it azote. must, in the present state of our knowledge, be consi~ dered as a simple substance. Dr Priestley, who ob- tained azotic gas at a very early period of his experi- ments, considered it as a compound of oxygen gas and phlogiston, and for that reason gave it the name ofpblo- gisticatedair. According to the theory of Stahl, which was then universally prevalent, he considered combus- tion as merely the separation of phlogiston from the- burning body. To his theory he made the following addition: Phlogiston is separated during combustion by means of chemical affinity: Air (that is, oxygen ga^ <; has a strong affinity for phlogiston : Its presence is .ne- cessary during combustion, because it combines with the phlogiston as it separates from the combustible^ y * Fourcroy and Vauquelin, Ann. de Cb'tm. xxi. 19*. f, Fourcroy, i. ZOO. J Jour, de Cbim. ii. 1 14. AZOTE. 113 and it even contributes by its affinity to produce that Chap. Hf. separation : The moment the air has combined with as Supposed, much phlogiston as it can receive, or, to use a chemi- ^Ljof*" cal term, the moment it is saturated with phlogiston, oxygen and . phlogiston, combustion necessarily stops, because no more phlogis- ton can leave the combustible*: Air saturated with phlogiston is azotic gas. This was a very ingenious theory, and, when Dr Priestley published it, exceed- ingly plausible. A great number of the most eminent chemists accordingly embraced it : But it was soon af- ter discovered, that during combustion the quantity of air, instead of increasing, as it ought to do if phlogiston be added to t, actually diminishes both in bulk and weight. There is no proof, therefore, that during com- But erratic- bustion any substance whatever combines with air, but ousl y* rather the contrary. It was discovered also, that a quantity of air combines with the burning substance du* ring combustion, as we have seen to be the case with sulphur, phosphorus, carbon, and hydrogen ; and that this air has the properties of oxygen gas. These dis- coveries entirely overthrew the evidence on which Dr Priestley's theory was founded. More lately a new theory concerning the composition of azote has been proposed, and variously modified \)J different chemists. As this theory has occasioned a controversy which has been maintained in Germany * This icgenio^s theory was first conceived by Dr Rutherford, as ap- pears from the following passage of his thesis. " Ex iidem etiam dedu- cere licet quod aer iile nullgnus (azotic gas) componitur ex acre atmo- jpttritf cum pblogisto unito et quasi taturato. Afojie idem confirmatur eo, quod aer qui metal iortim calcination! jam inserviit, et phlogiston ab. iis "r, ejusdem ptar? !ir indo'is" De Aert Miftitin, p. 40. Vol. I. H 114 SIMPLE INCOMBUSTIBLES. Book I. with a good deal of keenness, and which has eontribu- Division I . . 1 i _ v ' ted towards explaining several very curious chemical phenomena, I shall give a short account of the whole in this place. In the year 1783 Dr Priestley discovered, that when earthen ware retorts, moistened with water in the in- side, or containing a quantity of moist clay, are heated above the boiling temperature, very little water issues from their beak in the form of vapour ; but instead of it a quantity of air nearly equal to the weight of the water employed. As this air scarcely differed in its properties from common air, he concluded at first that the water by this process was converted into air. But he afterwards ascertained, by the most ingenious and de- cisive experiments, that the water which had disappear- ed, had made its way through the pores of the vessel, while at the same time a quantity of external air was forced by the pressure of the atmosphere into the ves- sel,. and that this was the air which issued out of the beak of the retort*. 2. Of water This conclusion was objected to by Achard of Ber- andSre. jj n j n j^g^ w ho endeavoured to prove by experiment, that whenever steam is made to pass through red hot earthen tubes, or even metallic tubes, it is converted in- to azotic gasf. Mr Westrumb drew the same conclu- sion from an experiment of his own ; and hence infer- red, that azotic gas is composed of water and "beat com- bined together:}:. In 1196, Wiegleb published a long paper on the same subject ; in which he endeavours,. * Priestley on A : r, il 407. f Crell's Annals, 1 785, i. 304, | UiJ. p. 499. AZOTE. 115 "both by reasoning and experiments, to prove the truth Chap III. of Westrumb's theory*. This paper drew the atten- tion of the associated Dutch chemists, Deimann, Troost- vvich, and Lawerenburg ; and induced them to make a very complete set of experiments, an account of which they published ITQSf. Their experiments coincided exactly with those of Dr Priestley. No gas made its appearance except when the instruments employed were of earthen ware, arid of course capable of being pene- trated by air. Wiegleb's method of making the ex- periment was to lute the tube of a tobacco pipe to a re- tort containing some pure water. The tobacco pipe \vas heated red hot by means of a charcoal fire j and then the water in the retort being made to boil, the steam passed through the red hot pipe. The Dutch chemists found, that when instead of a tobacco pipe a glass or metallic tube was used, or when the tobacco pipe was covered with a glass tube, no gas appeared, unless the tube was cracked : and that when gas was obtained, it was always the same with the air on the outside of the tube ; that is to say, a mixture of carbo- nic acid and azotic gas, when the tube was heated in a charcoal fire, and common air when the tube was with- drawn from the fire. Thus their experiments coincided precisely with those of Dr Priestley, and led them to the same conclusion. Mr Wiegleb attempted to an- swer the objections of the Dutch chemists, and to esta- blish his own theory by new experiments ; but he has 67. f Aatr. de Cbim. xrvi. JIC. H2 116 SIMPLE INCOMBUSTIBLES. Book I. Division I. 3. Of oxy- pen and hy- drogen. But with- out proof. Its compo- nent parts unknown. by no means succeeded ; he has not been able to satisfy even himself*. Soon after Dr Girtanner published a dissertation on the same subject, in the 34th volume of the Annales dc Cbimie. His experiments coincide pretty nearly with those of Wiegleb and his associates; but he drew from them very different consequences, and founded on them a theory almost diametrically opposite. According t& him, azotic gas is obtained whenever water in the state of vapour comes into contact with clay. Thus, it is obtained when water is boiled in an earthen retort, or in a glass retort containing a little clay, or ending in an earthen tube. Hence he concludes, that azotic gas is composed of hydrogen and oxygen gas combined toge- ther, and differs from water or vapour merely in con- taining a smaller proportion of oxygen f . These very singular assertions were put to the test of experiment by Berthollet and Bouillon Lagrange. But though they adhered implicitly to the directions of Girtanner, and even varied the process every conceivable way, they did not obtain a particle of azotic gas J. Girtanner therefore either never performed these experiments at all, or he must have been misled by some circumstance or other. His theory of course falls to the ground. Thus as all the attempts to decompose azote have hi- therto failed, we must of necessity consider it as a sim- ple substance. It must be acknowledged, however, that there are several chemical phenomena altogether inexplicable at present ; but which might be accounted * Crcll's Annals, 1799, i. 45, &c. t Ibid. XXXV. 23. f Ann. tie C/jim. XXXl'v. 3 MURIATIC ACID. 117 for if it were possible to prove that azote is a compound, Chap. m. and that one of the component parts of water enters in- to its composition. One of these phenomena is the for- mation of RAIN, which will come under our considera- tion in the Second Part of this Work : Another is the constant disengagement of azotic gas when ice is melt- ed. Dr Priestley found, that when water, previously freed from air as completely as possible, is frozen, it emits, when melted again, a quantity of azotic gas. He froze the same water nine times without exposing it to the contact of air, and every time obtained nearly the same proportion of azotic gas *. SECT. II. OF MURIATIC ACID. L MURIATIC acid, the second of the simple incom- bustibles, may be procured by the following process : Let a small pneumatic trough be procured, hollowed Prepara- out of a single block of wood, about 14 inches long, 7 * broad, and 6 deep. After it has been hollowed out to the depth of an inch, leave 3 inches by way of shelf on one side, and cut out the rest to the proper depth, gi- ving the inside of the bottom a circular form. Fig. 8. represents a section of this trough. Two inches from each end cut a slit in the shelf to the depth * Nicholson** Journal, iv. 193 118 SIMPLE INCOMBUSTIBLES. Book T. of an inch, and broad enough to admit the end of small Division I. . .., -y glass tuoes, or the points of small retorts. This trough is to be filled with mercury to the height of -J inch a- bove the surface of the shelf. Small glass jars are to be procured of considerable thickness and strength, and suitable to the size of the trough. One of them being filled with mercury by plunging it into the trough, is to be placed on the shelf over one of the slits. It ought to be supported in its position ; and the most con- venient method of doing that is, to have a brass cylin- der two inches high screwed into the edge of the trough just opposite to the border of the shelf. On the top of it is fixed two fiat, pieces of brass terminating each in a semicircle, moveable freely upon the brass cylinder, and forming together a brass arm terminating in a circle, the centre of which is just above the middle of the slit in the shelf, when turned so as to be parallel to the edge of the shelf. This circle is made to embrace the jar; be- ing formed of two distinct pieces, its size may be increa- sed or diminished at pleasure, and by means of a brass slider it is made to catch the jar firmly. The apparatus being thus disposed, two or three oun- ces of common salt are to be put into a small retort, and an equal quantity of sulphuric acid added ; the beak of the retort plunged below the surface of the mercury in the trough, and the heat of a lamp applied to the salt in its bottom. A violent effervescence takes place; and air bubbles rush in great numbers from its beak, and rise to the surface of the mercury in a vi- sible white smoke, which has a peculiar odour. After allowing a number of them to escape, till it is supposed that the common air which previously existed in the retort has been displaced, plunge its beak into the slit MURIATIC ACID. Up in the shelf, over which the glass jar has been placed. Chap.W. The air bubbles soon displace the mercury and fill the jar. The gas thus obtained is called muriatic acid gas* This substance in a state of solution in water was known even to the alchymists ; but in a gaseous state it was first examined by Dr Priestley, in an early part of that illustrious career in which he added so much to our knowledge of gaseous bodies. 1. Muriatic acid gas is an invisible elastic fluid, re- Properties, sembling common air in its mechanical properties. Its specific gravity, according to the experiments of Mr Kirwan, is 1'929, that of air being I'OOO, at the tempe- rature of 60, barometer 30 inches; 100 cubic inches of it weigh 59*8 grains. Its smell is pungent and pe- culiar ; and whenever it comes in contact with common air, it forms with it a visible white smoke. If a little of it be drawn into the mouth, it is found to taste ex- cessively acid ; much more so than vinegar. 2 Animals are incapable of breathing it ; and when Does not plunged into jars filled with it, they die instantaneous- combustion ly in convulsions. Neither will any combustible burn nor e * in it. It is remarkable, however, that it has a consi- derable effect upon the flame of combustible bodies ; for if a burning taper be plunged into it, the flame, just before it goes out, may be observed to assume a green colour, and the same tinge appears the next time the taper is lighted *. 3. If a little of the blue coloured liquid, which is ob- T ^ e vc " tained by boiling red cabbage leaves and water in a tin blues red, vessel, be let up into a jar filled with muriatic acid Priestley, u. 1'JO SIMPLE INCOMBUSTIBLE. Book I. Division I. Absorbed by water. gas, it assumes a fine red colour. This change is con- sidered by chemists as a characteristic property of acids. 4. If a little water be let up into a jar filled with this gas, the whole gas disappears in an insiant, the mercury ascends, fills the jar, and pushes the water to the very top. The reason of this is, that there exists a strong affinity between muriatic acid gas and water ; and whenever they come in contact, they combine and form a liquid j or, which is the same thing, the water absorbs the gas. Hence the necessity of making expe- riments with this gas over mercury. In the water cis- tern not a particle of gas would be procured. Nay, the water of the trough would rush into the retort and fill it completely. It is this affinity between muriatic acid gas and water which occasions the white smoke that appears when the gas is mixed with common air. It absorbs the vapour of water which always exists in common air. The solution of muriatic acid gas in water is usually denominated simply muriatic acid by chemists. In thi$ state it appears to have been known to the alchymists ; but Glauber was the first who extracted if from common salt by means of sulphuric acid. It was first called spirit of salt, afterwards marine acid, and now, pretty generally, muriatic acid*. It is prepared for commercial purposes, by mixing together one part of common salt and seven or eight parts of clay, and distilling the mixture ; or by distilling the usual pro- portion of common salt and sulphuric acid, and re*. * From mafia., MURIATIC AC1J). 121 ceiving ihe product in a receiver containing water. For Chap. HI. chemical purposes it may be procured pure in the fol- lowing manner. A hundred parts of dry common salt are put into a glass matrass, to which there is adapted a bent glass tube that passes into a small Wolf's bottle. From this bottle there passes also a glass tube into another larger bottle, containing a quantity of water equal in weight to the common salt employed. When the apparatus is properly secured by luting, 75 parts of sulphuric acid are poured into the common salt through a mouth of the matrass, furnished with a proper stopper. Heat is then applied. The sulphuric acid displaces the muri- atic acid, which passes over and is condensed in the wa- ter of the large bottle, while any sulphuric acid that may be driven over by the heat is condensed in the smaller bottle, and thus does not injure the purity of the muriatic acid. A cubic inch of water at the temperature of 60, ba- Proportion rometer 29'4, absorbs 515 inches of muriatic acid gas, which is equivalent to 308 grains nearly. Hence wa- ter thus impregnated contains 0'548, or more than half its weight of muriatic acid, in the same state of purity as when gaseous. I caused a current of gas to pass through water till it refused to absorb any more. The specific gravity of the acid thus obtained was 1*203. If we suppose that the water in this experiment absorb- ed as much gas as in the last, it will follow from it, that six parts of water, by being saturated with this gas, expanded so as to occupy very nearly the bulk of 11 parts ; but in all my trials the expansion was only to nine parts. This would indicate a specific gravity of 1*477 ; yet upon actually trying water thus satura- 122 SIMPLE INCOMBUSTIBLES. ted, its specific gravity was only 1*203. Is this dif- ference owing to the gas that escapes during the taking of the specific gravity ? During the absorption of the gas, the water becomes hot. Ice also absorbs this gas, and is at the same time liquefied. The quantity of this gas absorbed by water diminishes as the heat of the water increases, and at a boiling heat water will not absorb any of it. When water impregnated with it is heated, the gas is again expelled unaltered. Hence muriatic acid gas may be procured by heating the common muriatic acid of com- merce. It was by this process that Dr Priestley first obtained it. Properties. The acid thus obtained is colourless : it has a strong pungent smell similar to the gas, and when exposed to the air is constantly emitting visible white fumes. The muriatic acid of commerce is always of a pale yellow colour, owing to a small quantity of iron which it holds in solution. As muriatic acid can only be used conveniently when dissolved in water, it is of much consequence to know how much pure acid is contained in a given quantity of Strength. liquid muriatic acid of any particular density. Now the specific gravity of the strongest muriatic acid that can easily be procured and preserved is 1*196: it would be needless, therefore, to examine the purity of any muriatic acid of superior density. Mr Kirwan calcu- lated that muriatic acid, of the density of 1*196, con- tains 0*2^28 of pure acid : then, by means of experi- ments, he formed the following TABLE* : * Nicholson's quarto Jour. iii. 213. My experiments, as the reader wiQ observe, are not reconcilcable with this table. MURIATIC ACID. r lOJ Farts Sp. Gravity. Rea'i Acid. 25-28 100 Parts Sp. Gravity. Real Acid. i-196 1-1282 16-51 1-191 24-76 1-1244 15*99 1-187 24-25 1-1206 15-48 1-183 23-13 1-1168 14-96 1-119 23-22 1-1120 14-44 1-175 22*70 1-1078 13-93 1-171 22*18 1-1036 13>41 1-167 21-67 1-0984 12-90 1-163 21*15 1-0942 12*38 1-159 20-04 1-0910 H'86 1-155 20-12 1-0868 11-35 1-151 19-60 1-0826 10-83 1-147 19-09 1-0784 10*32 1-1414 18-57 1-0742 9*80 1-1396 18-06 1-0630 8-25 1-1358 17-54 1-0345 5-16 1-1320 17-02 1-0169 2'58 II. Muriatic acid is capable of combining with oxy- Combine* gen, and forms with it compounds which have a con- ^ oxy " siderable analogy to the compounds of azote with the same principle. 1. When muriatic acid is poured upon black oxide A "d forms, of manganese, an effervescence takes place ; and by the rratic acid : assistance of heat a gas comes over, which may be re- ceived over water. Scheele, the discoverer of this gas, called it dephlogisticated muriatic acid ; but it is now known by th^name of oxy-muriatic acid. It has a green colour, a most detestable odour, and is very readily absorbed by water, to which it communicates its colour and properties. Berthollet filled a bottle with this im- pregnated water, fitted a bent tube to its mouth, con- nected it with a water trough, and exposed it to sun- 124 SIMPLE INCOMBUSTIBLES. Book I. shine ; the liquid gradually lost its colour, bubbles ot Division I. ..... rp., ^^..wy-^^, gas separated, and were collected in a jar. 1 ne gas on examination was found to be oxygen, and the water was impregnated with common muriatic acid. This experiment demonstrates, that the constituents of oxy- muriatic acid are oxygen and muriatic acid. By esti- mating the bulk of the oxygen that escaped, and the weight of the acid that remained, Berthollet concluded that oxymuriatic acid is composed of about 89 muriatic acid 11 oxygen 100 But Mr Chenevix has more lately, from an experiment to be described hereafter, made the proportion of oxygen much higher. According to him the gas is composed of about 77*5 muriatic acid 2 2' 5 oxygen 2. Hyper- oxymuria- tic acid. 100-0 2. When a current of oxymuriatic acid is passed through water holding potash in solution, a number of flat shining crystals are at last deposited. They were first obtained by Dr Higgins, but first examined and analysed by Berthollet. These crystals are called hyper- exymuriate of potash. When this salt is exposed to a suf- ficiently strong heat, it gives more than |d its weight of oxygen gas : the residue is a compound of muriatic acid and potash. The acid in this salt, of course, con- tains much more oxygen than oxymuriatic acid, Ac- MURIATIC ACID. 125 cording to Chenevix, who has lately examined it, the cha P* nr -, constituents are 34 muriatic acid (36 oxygen 100 III. The action of muriatic acid on the simple combustibles has not bee.n examined with much at- tention. 1. Hydrogen, as far as we know at present, does not unite with muriatic acid. 2. Carbon is not supposed to combine with it. Char- coal has the property of absorbing it very rapidly j but the change produced by the absorption has not been ascertained. 3. Phosphorus, according to Dr Priestley's experi- ments, absorbs very little muriatic acid *. 4. Sulphur, according to Dr Priestley, imbibes it Sulphuret. slowly f. When a current of oxy muriatic acid gas is passed over flowers of sulphur in a glass vessel, the sulphur is gradually converted into a fine red liquid, which I consider as a compound of muriatic acid and oxide of sulphur ; and which, therefore, may be termed * ?riestley en Ah; ii. 283. He affirms.that the phosphorus smokes atut gives light in muriatic acid gas as in common air ; but on repeat- ing- the experiment I perceived no such effects. Priestley's gas, of course, contained air. f Ibid. He says sulphur imbibed r-jth, and left a residue of 4-jths inflammable air, burning with a blue flame. This experiment requires- repetition. 126 SIMPLE INCOMBUSTIBLES. Beak I. sul bljureted muriatic acid *. It weighs more than triple Division I. ^ v - ' the sulphur employed. It is perfectly liquid ; its colour is a fine red, interme- diate between scarlet and crimson. When streaks of it run down the inside of the phial, they appear green by transmitted light. Its specific gravity is 1-623. When exposed to air it smokes very much. It is very volatile, disappearing very rapidly when exposed to a moderate heat. Its smell has a strong resemblance to that of sea- plants, but is much stronger. The eyes, when exposed to its fumes, are soon filled with tears, and acquire the same painful feeling as when exposed to the smoke of wood or peat. Its taste is strongly acid, hot, and bitter, affecting the throat with a painful tickling. It converts vegetable blue papers to red ; but the. change takes place slowly, unless the paper be dipt into water ; the paper is not corroded unless heat be applied. If a drop of it be let fall into a glass of wafer, the * Rerthollet Junior has lately repeated my experiments on this curious compound {Mem. D'Arcueil, i. 161.) He endeavours to prove that the sulphur is not in the state of an oxide, but that the liquor is a tripk com- pound of oxygen, sulphur, and muriatic acid, and thinks that his experi- ments are inconsistent with mine, because he extracted the sulphur pure, arid not in the state of an oxide. It is plain from this that he has ne\'er consulted my paper published in Nicholson's Jour. vi. 104. He would have seen that I always obtained the sulphur in the same state, and inferred the presence of oxygen from the formation of sulphuric acid when- ever the] liquid is decomposed. A fact confirmed by his own ex- periments. MURIATIC ACID. 121 .surface of the water becomes immediately covered with Chap. Hi. a film of sulphur ; a greenish red globule falls to the bottom, which remains for some time like a drop of oil, but at last is converted into yellow flakes. These flakes have an acid taste, which they do not lose, though allowed to remain in water for several days ; they are very ductile, and continue so, though left exposed to the air. When thrown into warm nitric acid, a very violent effervescence takes place, and the whole mixture is thrown, with a kind of explosion, out of the vessel. If the acid be cold, the effervescence is at first slow, but heat is very soon evolved, and the same effects produ- ced. When the proportion of nitric acid is great, and the sulphuret dropt in very slowly, the effervescence continues moderate ; nitrous gas and oxymuriatic gas being evolved. It dissolves phosphorus cold with great facility. No effervescence takes place ; the solution has a fine am- ber colour, and is permanent. When evaporated, the phosphorus remains behind with a little sulphur, and at last takes fire. When the solution is mixed with liquid potash, the whole becomes beautifully luminous, and phosphuret of sulphur is precipitated. According to my analysis, it is composed of 44*00 oxide of sulphur 35*75 muriatic acid 20'25 loss 100*00 * * See Nicholson's Jour. vi. 104 128 SIMPLE INCOMEUSTIBLES. Book T. Division 1 Action of electricity. Destroys putrid miasmata. IV. We are not acquainted with any combination of muriatic acid and azote ; but when mixed with nitric acid it forms a compound possessed of very remarkable properties : it was formerly called aqua regia, but is now better known by the name of nitro-muriatic acid. V. When electric explosions are made to pass through muriatic acid gas, its bulk is diminished, and hydrogen gas is evolved. At the same time, if the experiment be made over mercury, a quantity of muriate of mercu- ry is formed. These changes continue to take place for a limited time only ; after which electricity ceases to produce any farther change. They are always propor- tional to the moisture of the gas, and have been shown by Dr Henry to be owing to the decomposition of the water held in solution by the gas. The oxygen of the water combines with part of the acid, and forms oxy~ muriatic acid, while its hydrogen is set at liberty. Dr Henry has shown that 100 cubic inches of muriatic acid gas, after being made as dry as possible, by stand- ing over quicklime or other bodies which absorb mois- ture, still contain 1-4 grains of \vater in solution: but this water maybe completely decomposed and removed by means of electricity. Here then is a method of de- priving this gas altogether of water *. When muriatic acid gas and carbureted hydrogen gas are mixed, elec- ^ricity decomposes the water, and carbonic acid and hy- drogen gas are evolved. After the water is completely decomposed, electricity produces no farther effect f- Vi. Morveau first showed that muriatic acid, in the State of gas, neutralizes putrid miasmata, and by that Nicholson's Journal, iv. 209. f Henry. Jbid. MURIATIC ACID, means destroys their bad effects. In 1775, the cathe- dral of Dijon was so infected bj putrid exhalations, that it was deserted altogether after several unsuccessful at- tempts to purify it. Application was made to Mr Morvean, at that time professor of chemistry at Dijon, to see whether he knew any method of destroying these exhalations. Having poured two pounds of sulphuric acid on six pounds of common salt, contained in a glass capsule, which had been placed on a few live coals in the middle of the church, he withdrew precipitately, and shut all the doors. The muriatic acid gas soon filled the whole cathedral^ and could even be perceived at the door. After twelve hours, the doors were thrown open, and a current of air made to pass through to remove the gas. This destroyed completely every putrid o- ilour *. Chap. HI. SUCH are the properties of the simple incombustible bodies. Like the combustibles, their predominant cha- racter is their affinity for oxygen. But they unite with- out the phenomena of combustion ; hence the com- pounds which they form with oxygen are supporters of combustion. The quantity of oxygen which each is Combina* capable of condensing does not differ nearly so much as ' we observe in the cas of the combustibles. 100 muriatic acid condenses 194 oxygen 100 azote 236 oxygen If we judge of the affinity by the power of condensa- tion, it will follow, that azote has a stronger affinity for Vol. I. * Jour, di Pbyt. i. 436. 130 SIMPLE INCOMBUSTIBLES. Book I. Division I Azote unites with three dozes. Muriatic acid, with two. oxygen than muriatic acid. If the properties of the oxygen predominates most in those compounds in which the base has the least affinity for it, then, in that case, hyperoxymuriatic acid ought to be a better supporter of combustion, and to act with more energy, than nitric acid ; which is the case. Azote unites with three doses of oxygen at least, and formsj 1. Nitrous oxide 2. Nitric oxide 3. Nitric acid. Muriatic acid unites with two, and forms, 1. Oxy muriatic acid 2. Hyperoxymuriatic acid. The combinations of the simple incombustibles with the combustibles have not hitherto excited much of the attention of chemists. Analogies, to be pointed out hereafter, lead us to sup- pose both azote and muriatic acid to be compounds ; but till some fortunate experiment ascertain their com- ponent parts, we are under the necessity of considering them as simple. METALS. CHAP. IV. OF METALS, -j -r- I. J1TALS may be considered as the great instru- Properties ments of all our improvements : Without them, many raeta1 ' 3 of the arts and sciences could hardly have existed. So sensible were the ancients of their great importance, that they raised those persons who first discovered the art of working them to the rank of deities. In che- mistry, they have always filled a conspicuous station t at one period the whole science was confined to them ; and it may be said to have owed its very existence to a rage for making and transmuting metals. 1. One of the most conspicuous properties of the metals is a particular brilliancy which they possess, and which has been called the metallic lustre. There are other bodies indeed (niica for instance) which appa- rently possess this peculiar lustre; but in them it is con- fined to the surface, and accordingly disappears when they are scratched ; whereas it pervades every part of the metals. This lustre is occasioned by their reflect- ing much more light than any other bodies ; a property which seems to depend partly on the closeness of their texture. This renders them peculiarly proper for mir- rors, of which they always form the basis. 12 132 COtfFINABLE BODIES. Book I. Division I. Opacity. Fasibility. Weight. 2. They are perfectly obaque, or impervious to light, even after they have been reduced to very thin plates. Silver leaf, for instance, - n5 - 5 T T5 _ 5 -. 5 . of an inch thick, does not permit the smallest ray of light to pass through it. Gold, however, when very thin, is not absolutely o- paque : for gold leaf T - r5 - 1 ._ of an inch thick, when held between the eye and the light, appears of a lively green ; and must therefore, as Newton first remarked, transmit the green coloured rays. It is not improbable that all other metals, as the same philosopher supposed, would also transmit light if they could be reduced to a sufficient degree of thinness. It is to this opacity that a part of the excellence of the metals, as mirrors, is owing ; their brilliancy alone would not qualify them for that purpose. 3. They may be melted by the application of heat, and even then still retain their opacity. This property enables us to cast them in moulds, and then to give them any shape we please. In this manner many ele- gant iron utensils are formed. Different metals differ exceedingly from each other in their fusibility. Mer- cury is so very fusible, that it is always fluid at the or- dinary temperature of the atmosphere ; while other metals, as platinum, cannot be melted except by the most violent heat which it is possible to produce. 4. Their specific gravity is exceedingly various, more so indeed than that of any other class of bodies at present known. The greater number of them are heavier than any other known substances. This in- deed, till very lately, was considered as a character be- * Davy en tke Decomposition rftle Fixed Alkalies, fb'il. Trans. 1808. METALS, 133 longing to them all. But several very singular me- Chap, iv. tals, discovered by Mr Davy, are not so heavy as water, and of course much lighter than most stony bodies. Platinum, the heaviest of the metals, is 23 times heavier than water ; while the specific gravity of potasium is only 0'6, that of water being 1. 5. They are the best conductors of electricity of all Conducting power, the bodies hitherto tried. 6. None of the metals is very hard ; but some of Hardness, them may be hardened by art to such a degree as to exceed the hardness of almost all other bodies. Hence the numerous cutting instruments which the moderns make of steel, and which the ancients made of a combi- nation of copper and tin. 7. The elasticity of the metals depends upon their Elasticity, hardness ; and it may be increased by the same process by which their hardness is increased. Thus the steel of which the balance- springs of watches is made is al- most perfectly elastic, though iron in its natural state possesses but little elasticity. 8. But one of their most important properties is mal- Malleabi- leability, by which is meant the capacity of being ex- tended and flattened when struck with a hammer. This property, which is peculiar to metals, enables us to give the metallic body any form we think proper, and thus renders it easy for us to convert them into the va- rious instruments for which we have occasion. All metals do not possess this property ; but it is remark- able that almost all those which were known to the an- cients have it. Heat increases this property consider- ably. Metals become harder and denser by being ham- mered. 0. Another property, which is also wanting in many Ductility. 134 CONFINABLE BODIES. Book I. Division I. Tenacity. Combine with oxy- gen. Oxides or calces. Reduction, of the metals, is ductility ; by which we mean the ca- pacity of being drawn out into wire by being forced through holes of various diameters. 10. Ductility depends, in some measure, on another property which metals possess, namely tenacity; by which is meant the. power which a metallic wire of a given diameter has of resisting, without breaking, the action of a weight suspended from its extremity. Me- tals differ exceedingly from each other in their tenaci- ty. An iron wire, for instance, -r^th of an inch in di- ameter, will support, without breaking, about 5QOlb. weight ; whereas a lead wire, of the same diameter, will not support above 29lb. 11. When metals are exposed to the action of heat and air, most of them lose their lustre, and are gradu- ally converted into earthy-like powders of different co- lours and properties, according to the metal and the de- gree of heat employed. Several of them even take fire when exposed to a strong heat ; and after combus- tion the residuum is found to be the very same earthy- like substance. 1. All metals, even the few that resist the action of heat and air, undergo a similar change when exposed to acids, especially the sulphuric, the nitric, and the mu- riatic, or a mixture of the two last. All metals, by these means, may be converted into powders, which have no resemblance to the metals from which they were obtained. These powders were formerly called calces ; but at present they are better known by the name of oxides. They are of various colours according to the metal and the treatment, and are frequently ma- nufactured in large quantities to serve as paints. 2. When these oxides are mixed with charcoal pow- METALS. 135 der, and heated in a crucible, they lose their earthy ap- Chap. IV.^ pearance, and are changed again into the metals from which they were produced. Oil, tallow, hydrogen gas, and other combustible bodies, may be often substituted for charcoal. By this operation, which is called the reduction of the oxides, the combustible is diminished, and indeed undergoes the very same change as when it is burnt. In the language of Stahl, it loses its phlogis- ton / and this induced him to conclude that metals are composed of earth and phlogiston. He was of opinion, SM *eo- that there is only one primitive earth, which not only component forms the basis of all those substances known by the name of earths, but the basis also of all the metals. He found, however, that it was impossible to combine any mere earth with phlogiston ; and concluded, therefore, with Beccher, that there is another principle besides earth and phlogiston which enters into the composition of the metals. To this principle Beccher gave the name of mercurial earth, because, according to him, it exists most abundantly in mercury. This principle was sup- posed to be very volatile, and therefore to fly off during calcination ; and some chemists even affirmed that it might be obtained in the soot of those chimneys under which metals have been calcined. A striking defect was soon perceived in this theory. The original metal may be again produced by heating its oxide along with some other substance which con- tains phlogiston. Now, if the. mercurial earth flies off during combustion, it cannot be necessary for the for- mation of complete metals, for they may be produced without it : if, on the contrary, it adheres always to the calx, there is no proof of its existence at all. Che- mists, in consequence of these observations, found them- 136 CONFINABLE BODIES. Book I. selves obliged to discard the mercurial principle alto- Division I. u v ^ gether, and to conclude, that metals are composed of earth only united to phlogiston. But if this be really the case, how comes it that these two substances can- Improved not be united r by art? Henkel was the first who at- by Henkel, tem p te d to so j ve fa^ difficulty. According to him, earth and phlogiston are substances of so opposite a nature, that it is exceedingly difficult, or rather it has been hitherto impossible for us to commence their union ; but after it has been once begun by Nature, it is an easy matter to complete it. No calcination has hitherto deprived the metals of all their phlogiston ; some still adheres to the calces. It is this remainder of phlogiston which renders it so easy to restore them to their metallic state. Were the calcination to be con- tinued long enough to deprive them altogether of phlo- giston, they would be reduced to the state of other earths ; and then it would be equally difficult to convert them into metals, or, to use a chemical term, to reduct them. Accordingly we find, that the more completely a calx has been calcined, the more difficult is its re- duction. This explanation was favourably received. Anaiv'> Boy/e, 5i. 394. f It is remarkable that John Rey, a physician of Perigord, had ascri- bed it to this very cause as far back as the year 1630: but his writings had excited little attention, and had sunk into oblivion, till his opinion had been incontestibly proved by Lavoisier. Mayow also, in the year 1694, ascribed the increase of weight to the combination of the metals with exygen. " Quippe vix concipi potest (says he), i>nde augmentum illud antimonii (calcinati) nisi a particulisnitro-aereis igneisque inter calcinan- dum FIXIS procedat." Tract, p. 28. " Plane ut antimonii fixatio non tarn a sulphuris ejus exttrni assumptione, quam particulis nitro-aereis, ojuibus flamma nitri abundat, EI IN FIXIS provenire vitkatur." Jl/iJ.f. 29. METALS. 139 ascertained, that the residuum of the air, after calcina- Chap.iv. tion has been performed in it, is always pure azotic gas : It follows, therefore, that it is only the oxygen which combines with calces ; and that a metallic calx is not a simple substance, but a compound. Mr Lavoisier observed, that the weight of the oxide was always equal to that of the metal employed, together with that of the oxygen absorbed. Hence he corn- eluded, that the oxide is nothing else than a combina- tion of the metal with oxygen : that the metals, as far as we know, are simple substances ; that what Stahl considered as the escape of phlogiston from metals was, in reality, their combination with oxygen ; and that the oxygen, reduction of metals, instead of restoring the lost phlo- giston, consisted, in fact, in the separation of oxygen by means of some combustible which has a strong affinity for it. These conclusions were supported in the most ingenious and satisfactory manner. 3. No metal can be converted into an oxide except pome substance be present which contains oxygen 5 and during the oxydizement a portion of that oxygen dis- appears. 4. There are some metallic oxides which can be re- duced by the application of heat in close vessels. Now whenever they are reduced in that manner they yield oxygen gas ; and the weight of the oxygen, together with that of the metal obtained, is equal to the weight of the original oxide. Thus when the oxide of mercury is heated in a retort, to which a pneumatic apparatus is attached, to the temperature of 1000, it is converted into pure mercury ; and, at the same time, a quantity of oxygen separates from it in a gaseous form. As this process is performed in a close vessel, no new sub* 140 CONFINABLE BODIES. Book T. stance can enter : The oxide of mercury, then, is re- i duced to the metallic state without phlogiston. The weights of the metal and the oxygen gas are together equal to that of the oxide ; the calx of mercury, there- fore, must be composed of mercury and oxygen ; con- sequently, there is no reason whatever to suppose that mercury contains phlogiston. Its calcination is merely the act of its uniting with oygen *. Gold, platinum, silver, nickel, and even lead, may be reduced in the same way, and with the same evolution of oxygen gas. To them therefore the same reasoning applies. Se- veral other oxides may be brought nearer the metal- lic state, though they cannot be completely reduced by heat*; and this approach is accompanied by the escape of oxygen gas. Manganese, zinc, and probably also iron, are in this predicament. 5. All the oxides are reduced by means of combus- tible bodies ; and during the combustion the combustible unites to oxygen. This is the reason that charcoal- powder is so efficacious in reducing them : and if they * This experiment was performed by Mr Bayen in 1774. This philo- sopher perceived, earlier than Lovoisier, that all metals did not contain phlogiston. " Ces experiences (jays he) vont nous detromper. Je ne tiendrai plus le langage des disciples de Stahl qui seront forces de restrein- dre la doctrine sur le phlogistique, ou d'avouer que les precipites mercu- rials, dont je parlc, ne sont pas des chaux metalliques, ou enfin qu'il y a des chaux qui peuvent se reduire sans le concours du phlogistique. Les experiences que j'ai faites me force de conclurer, que dans la chaux mercu- riale dont je parlc, le rnercure doit son etat calcaire, non a la perte du fbh~ fistigue qu'il n'a pas essuye, mats a sa \combinaison intime avec le fluide etas- titjuty dont le poids ajoute a celui du mercure est la seconde cause de 1'augmentation de pesanteur qu'on observe dans les precipites que j'ai is a ramen." Jour, de P/^v. 1774. pages 288, 295. METALS. 141 are mixed with it, and heated in a proper vessel fur- t Chap. IV. nished with a pneumatic apparatus, it will be easy to discover what passes. During the reduction, a great deal of carbonic acid and carbonic oxide comes over. These, together with the metal, are equal to the weight of the oxide and the charcoal : they must therefore con- tain all the ingredients ; and we know that they are composed of carbon and oxygen. During the process, then, the oxygen of the oxide combines with the char- coal, and the metal remains behind. In the same man- ner, when oxide of iron is heated sufficiently, in Con- tact with hydrogen, the iron is reduced, and water formed, as \vas ascertained by the experiments of Dr Priestley. 6. It cannot be doubted, therefore, that all the me- tallic calces are composed of the entire metals combi- ned with oxygen ; and that calcination, like combus* tion, is merely the act of this combination. Metals, then, in the present state of chemistry, must be consider- ed as simple substances ; for they have never yet been decompounded. The words calx and calcination being evidently im- _ , . , oxidizement proper, because they convey false ideas, the words oxide explained. and oxidizement *, which were invented by the French chemists, are substituted for them. A metallic oxide signifies a metal united with oxygen ; and oxidixcmext implies the act of that union. * Oxidation was the word formerly used by British chemists. Eot the reasons assigned by Mr Ghenevix in his Remark* on tie Chemical No- mttulaturt, page 163. have induced me to prefer the terms which he has there substituted for it. 142 CONFINABLE BODIES. Book I. Division I -V Metals combine with oxy- gen. Nomencla- ture of ox- ides. 7. Metals, then, are all capable of combining with oxygen ; and this combination is sometimes accompa- nied by combustion and sometimes not. The new compounds formed are called metallic oxides, and in some cases metallic acids. Like the two last classes of bo- dies, they are capable of combining with different doses of oxygen, and of forming different species of oxides or acids. These were formerly distinguished from each other by their colour. One of the oxides of iron, for instance, was called black oxide, another was termed red oxide / but it is now known that the same oxide is capable of assuming different colours according to cir- cumstances. The mode of naming them from their colour, therefore, wants precision, and is apt to mis- lead ; especially as there occur different examples of two distinct oxides of the same metal having the same colour. As it is absolutely necessary to be able to distinguish the different oxides of the same metal from each other with perfect precision, and as the present chemical no- menclature is defective in this respect, I shall, till some better method be proposed, distinguish them from each other, by prefixing to the word oxide the first syllable of the Greek ordinal numerals. Thus the protoxide of a metal will denote the metal combined with a mini- mum of oxygen, or the first oxide which the metal is capable of forming ; deutoxide will denote the second oxide of a metal, or the metal combined with two doses of oxygen.* When a metal has combined with' as * The same explanation will ?.pply to tr'.toxide- (third oxide), tetoxidc (fourth oxide), fento.\-Ve (fifrh oxide), tecioxiJe (sixth oxide), whenever they become necessary. METALS, .143 much oxygen as possible, I shall denote the compound Chap. IV. formed by the \ermperoxide ; indicating by it, that the metal is thoroughly oxidized f. Thus we have the term oxide to denote the combina- tion of metals with oxygen in general ; the terms pro- toxide and peroxide to denote the minimum and maxi- mum of oxidizement ; and the terms deutoxide, tritoxide, &c. to denote all the intermediate states which are ca- pable of being formed. III. Metals are capable of combining with the simple ^ b ^ combustibles. The compounds thus formed are deno- bustibles, ted by the simple combustible which enters into the combination, with the termination uret added to it. Thus the combination of a metal with sulphur, phos- phorus, or carbon, is called the su/pburet, phosphuret, or carburet of the metal. The compounds formed by the metals with the three combustibles just mentioned are usually solid ; but when hydrogen unites with them, it still retains its elastic state. These solutions of me- tals in hydrogen have been but slightly examined. They are usually distinguished by an epithet, indica- ting the metal, prefixed to the word hydrogen. Thus arsenical hydrogen gas means hydrogen holding arsenic in solution. * Etymologists will doubtless object to this term, that it is a hetero- geneous compound of a Greek and Latin word ; but this fault, if it be one, has been already committed -rery frequently in the formation of chemical terms. My object was, not to prevent the objections of etymo- logists, but to employ a word perfectly precise, which could not mislead and which was not unwield} nor unsuitable to the genius of the Ergli.h language. 144 CONFINABLE BODIES. Book I. IV". The simple incombnstibles, as far as is known Division I. . . , < v i at present, do not combine with the metals. ach other ^' ^ ie metals, in general, unite very readily to one another, and form compounds, some of which are ex- tremely useful in the manufacture of instruments and utensils. Thus pew tcr is a compound of lead and tin ; brass, a compound of copper and zinc j bell-metal, a compound of copper and tin. These metallic com- pounds are called by chemists alloys, except when on of the combining metals is mercury. In that case the compound is called an amalgam. Thus the compound of mercury and gold is called the amalgam of gold. Number of VI. The metals at present known, or concluded from analogy to exist, amount to about 40. But 12 of these, newly discovered by Mr Davy, and constituting the bases of the alkalies and earths, are still so imperfectly known, or possess such peculiar properties, that I shall defer giving an account of them till I come to treat of those bodies hitherto known by the names of alkalies and earths. In this chapter, then y we have to consider the properties of 28 metals. Of these only 7 were known to the ancients as metals, and no fewer than 17 have been discovered since the year 1730. Their num- ber has multiplied exceedingly within these few years : but the more recently discovered metals, with a small number of exceptions, are so scarce as to be of com- paratively small importance. Metals may be conve- niently arranged under four classes ; namely, 1, Malle- able metals j 2. Brittle and easily fusible metals ; 3. Brittle and difficultly fusible metals ; 4. Refractory metals. Under which last name I comprehend all those metallic bodies which are only known at present in the state of combination ; chemists not having sue- METALS: 145 ceeded hitherto in reducing them to the metallic state,. Chap. The metals which belong to each of these heads will be seen from the following Table : I. MALLEABLE. classic*. tion. 1. Gold. 9. Copper. 2. Platinum. 10. Iron. 3. Silver. 11. Nickel. 4. Mercury, 12. Nicolanum, 5. Palladium. 13. Tin. 6. Rhodium. 14. Lead. 7. Iridium. 15. Zinc. 3. Osmium. II. BRITTLE AN T D EASILY FUSED. 1. Bismuth. 3. Tellurium, 2. Antimony. 4. Arsenic. III. BRITTLE AND DIFFICULTLY FUSED. 1. Cobalt. 4. Molybdenum, 2. Manganese. 5. Uranium. i; Chromium. 6. Tungsten, IV. REFRACTORY. 1. Titanium. 3. Cerium, 2. Columbium, The medals of the first class were formerly called metals by way of eminence, because they are possessed either of malleability or ductility, or of both properties together : the rest were called semimetals, because they are brittle. But this distinction is now pretty general- ly laid aside ; and, as Bergman observes, it ought to be Vol. L K CONFIKABLE BOMBS. Book I. so altogether, as it is founded on a false hypothesis, and -^ conveys very erroneous ideas to the mind. The first four metals were formerly called noble or perfect metals^ because their oxides are reducible by the mere applica- tion of heat ; the rest were imperfect metals, because their oxides were thought not reducible without the ad- dition of some combustible substance * ; but this dis- tinction also is now very properly exploded. The different metals, in the order in which they have been enumerated, will occupy our attention in the fol- lowing Sections. * Nickel and lead are reducible by mere heat* and of course entitled to the name of noble metal* also. METALS, CLASS I. MALLEABLE METALS. THE metals belonging to this Class, from their mal- leability, are of much more importance than the rest ; all those known to the ancients belong to it, and five more which have been discovered by the moderns. Besides these five, I have included in this class three other recently discovered metals ; the malleability of which has not been ascertained, but which may be in- ferred, perhaps, from the great analogy which they bear to the most perfect of the malleable metals. 14?S MALLEABLE METALS. Book f. Division I. SECT. I. 6 F GOLD. I. (JTOLD seems to have been known from the verf beginning of the world. Its properties and its scar- city have rendered it more valuable than any other metal*. 1- It is of an orange red, or reddish yellow colour, and has no perceptible taste or smell. Its lustre is con- siderable, yielding only to that of platinum, steel, sil- ver, and mercury. 2. Its hardness is 6ft . ~~ * The fullest treatise on gold hitherto published is that by Dr Lewis in his Pbihsr.pbical Commerce of the Arts. The account of gold in Was- scrberg's Inttitutiones Cksmie, vol. i. is, a great part of it at least, nearly a translation of Dr Lewis ; but it contains likewise several discoveries of posterior date, chiefly made by Bergman. Mr Hatchett's Experi- ments and Observation: on the Alloys > Specific Gravity, and (.omparatii'i ivear of Gold, published in the fill. Trans, for 1803, are of the utmost impor- tance, on account of the care with which they were made, and the many mistaken notions which they have enabled us to rectify. f Mr Kirwan's method of denoting the different degrees of hardness by figures has been adopted in consequence of its brevity, jjdr Kirwan's plan will bo understood from his own explanation, which is here sub- joined. 3, Denotes the hardness of chalk. 4, A superior hardness, but yet what yields to the nail. 5, What will not yield to the nail, but easily, and without grlttincssy to the knife. 6, That which yields more difficultly to the knife, 7, That which scarcely yields to the knife-, GOLD. 149 Its specific gravity is 19' 3 *. ^Chap. IV. 3. No other substance is equal to it in ductility and Malleabi- znalleability. It may be beaten out into leaves so thin, y * that one grain of gold will cover 56 J square inches. These leaves are only TTT ^^ 5 . of an inch thick. But the gold leaf with which silver wire is covered has on- ly TT of that thickness. An ounce of gold upon silver wire is capable of being extended more than 1300 miles in length f . 4. Its tenacity is considerable ; though in this respect Tenacity, it yields to iron, copper, platinum, and silver. From the experiments of Sickingen, it appears that a gold wire 0*078 inch in diameter is capable of supporting a weight of 150'07lbs. avoirdupois, without breaking . 8, That which cannot be scraped by a knife, but does not give fire with steel. 9, That which gives a few feeble sparks with steel. 10, That which give* plentiful lively sparks. Kirivans Mineralogy t i. 3 8. The same meaning, however, is not affixed here to the figures ; but a series of degrees of hardness is conceived, descending from steel to arse- nic, each of which is denoted by arbitrary figures. The specific gravity of gold varies somewhat according to its state, that being heaviest which has been hammered or rolled. Dr Lewi* informs us that he found, on many different trials, the specific gravity of pure gold, well hammered, between 19-300 and 19-400. The specific gravity of one mass which he specifies was 19*376, (Philosophical Com- merce of the Arts, p. 41). Brisson found the specific gravity of another specimen of fine gold, hammered, I9'36i. Mr Hatohett tried gold of 23 carats 3^ grains, (or gold containing 1-96 of alloy); its specific gra- gravity was 19-277. f See Shaw's Boyle t i. 404, and Lewis's Pbilosopb. Commerce aftle Arts t .44. J Ann. de Chlm. XXV. 9. 153 MALLEABLE METALS. Book I. Division I. Action of beat. 5. It melts at 32 of Wedgewood's pyrometer*. When melted, it assumes a bright bluish green colour. It expands in the act of fusion, and consequently con- tracts while becoming solid more than most metals ; a circumstance which renders it less proper for casting into moulds f. It requires a very violent heat to volatilize it ; it is therefore, to use a chemical term, exceedingly Jixed. Gasto Claveus informs us that he put an ounce of pure gold in an earthen vessel, into that part of a glass-house furnace where the glass is kept constantly melted, and kept it in a state of fusion for two months, yet it did not lose the smallest portion of its weight , Kunkel relates a similar experiment attended with the same re- sult $ ; neither did gold lose any perceptible weight, after being exposed for some hours to the utmost heat of Mr Parker's lens [| . Homberg, however, observed, that when a very small portion of gold is kept in a vio- lent heat, part of it is volatilized ^f. This observation was confirmed by Maccjuer, who observed the metal rising in fumes to the height of five or six inches, and attaching itself to a plate of silver, which it gilded very sensibly ** ; and Mr Lavoisier observed the very same thing when a piece of silver was held over gold melted * According to the calculation of the Dijon academicians, it melts at tahrenheit ; according to Mortimer, at 1391. Lewis's Philosophical Commerce, p. 67. " Nee minimum, de pondere decidisse conspexi " Gastonis Clavei Argyropoeix, et Cbrytopoear advenits Tbomam Erattum, Theatrum Chemicum, ii. 17. Lewis, Philosophical Commerce, p. 70. 8 Kirwan's Mineralogy, i. 94. f Mem. Par. IJ07,, p. 147. ** Dietioneire de Clii7ile t ii. 14? , GOLD. 151 by a fire blown by oxygen gas, which produces a much Chap. IV. greater heat than common air *. After fusion, it is capable of assuming a crystalline form. Tillet and Mongez obtained it in short quadran- gular pyramidal crystals. 6. Gold is not in the least altered by being kept ex- posed to the air ; it does not even lose its lustre. Nei- ther has water the smallest action upon it. II. It is capable, however, of combining with oxy- Oxide*, gen, and even of undergoing combustion in particular circumstances. The resulting compound is an oxide of gold. Gold must be raised to a very high temperature before it is capable of abstracting oxygen from common air. It may be kept red hot almost any length of time without any such change. Homberg, however, observed, that when placed in the focus of Tschirnhaus's burning-glass, a little of it was converted into a purple coloured oxide ; and the truth of his observations were confirmed by the subsequent experiments of Macquer with the very same burning-glass f. But the portion of oxide formed in these trials is too small to admit of being examined. Electricity furnishes a method of oxi- dizing it in greater quantity. If a narrow slip of gold leaf be put, with both ends hanging out a little, between two glass plates tied toge- ther, and a strong electrical explosion be passed through it, the gold leaf is missing in several places, and the glass is tinged of a purple colour by the portion of the metal which has been oxidized. This curious experi- Kirwan's Min, ii. .92. f D/c/.ii. r^j. Peroxide. MALLEABLE METALfc. racn-t was first made by Dr Franklin * ; it was cpn- firmed in 1173 by Camus. The reality of the oxidize- ment of gold by electricity was disputed by some phi- losophers, but it has been put beyond the reach of doubt by the experiments of Van Marum. When he made electric sparks from the powerful Teylerian ma- chine pass through a gold wire suspended in the air, it took fire, burnt with a green coloured flame, and was completely dissipated in fumes, which when collected proved to be a purple coloured oxide of gold. This combustion, according to Van Marum, succeeded not only in common air, but also when the wire was sus- pended in hydrogen gas, and other gases which are not capable of supporting combustion. The combustion of gold is now easily affected by exposing gold-leaf to the action of the galvanic battery. I have made it burn with great brilliancy, and a green coloured flame, by exposing a gold wire to the action of a stream of oxygen and hydrogen gas mixed together and burning. Now in all cases of combustion the gold is oxidized. We are at present acquainted with two oxides of gold : the protoxide has a purple or violet, the peroxide a yellow colour. 1. Of these the peroxide is most easily procured; it is therefore best known. It may be procured in the fol- lowing manner : One part of nitric and four of muriatic acid are mixed together f, and poured upon gold : an * Lewis's Pbilosofb. Commerce, p. 175. This work was published in 1763- f This mixture, from its property of dissolving gold, was formerly cal- led aqua regii (for gold, among the alchymists, waathe king of metals) ; it is now called nitre-muriatic acid. GOLD. 153 effervescence takes place, the gold is gradually dissol- t Chap. IV. yed, and the liquid assumes a yellow colour. It is easy to see in what manner this solution is produced. No znetal is soluble in acids till it has been reduced to the state of an oxide. There is a strong affinity between the oxide of gold and muriatic acid. The nitric acid furnishes oxygen to the gold, and the muriatic acid dis- solves the oxide as it forms. When nitric acid is de- prived of the greater part of its oxygen, it assumes a gaseous form, and flies off in the state of nitrous gas, It is the emission of this gas which causes the effer- vescence. The oxide of gold may be precipitated from the nitro-muriatic acid by pouring in a little potash dis- solved in water, or even by lime water. It subsides slowly, and has a yellowish brown colour, and some- times, indeed, approaches to black. When carefully washed and dried, it is insoluble in water and tasteless. Bergman found that 100 parts of gold, when treated in this manner, weigh 110. Were we to suppose this estimate correct, but Bergman himself expresses his doubts of its accuracy, it would follow from it, that the peroxide of gold is composed of about 91 gold 9 oxygen 100* When this oxide is moderately heated, it becomes pur- ple. A stronger heat expels the whole of the oxygen, and reduces it to the metallic state. 2. The properties of the protoxide of gold are but Protoxide. * Bergman's Ojwic. ii. aoi. 154 MALLEABLE METALS, Book f. Division I. Solphnret. little knoxvn. It is formed when the metal is subject- ed to combustion, or to the action of electricity, and likewise by exposing the peroxide to the proper degree of heat, or even by placing it in the rays of the sun. Its colour is purple. Various preparations containing it are used in the arts. The oxides of gold are still but imperfectly known > and all the attempts hitherto made to investigate them with more accuracy have been unsuccessful. Proust, in a dissertation which he has recently published, en- deavours to show, that what has been called the purple oxide of gold, is in reality gold in the metallic state *. But his experiments do not appear to me satisfactory. From Proust's experiments compared with some of my own, it is probable that there are three oxides of gold, composed respectively of 100 parts gold combined with 8, 16, and 32 parts of oxygen. But from the great readiness with which they are decomposed and altered, it is extremely difficult to estimate their composition with precision. III. Hitherto gold has been united artificially to none of the simple combustibles except phosphorus. Hydro- gen and charcoal are said to precipitate it from its solu- tions in the metallic state. 1. Sulphur, even when assisted by heat^ has no ac- tion on it whatever ; nor is it ever found naturally- combined with sulphur, as is the case with most of the other metals ; yet it can scarcely be doubted that sul- phur exercises some action on gold, though but a small * Nicholson's Jour. riv. 238, and 324. GOLD. 155 one : for when an alkaline hydro- sulphur t * is dropt ^Chap. 1V - into a solution of gold, a black powder falls to the bot- tom, which is found to consist of gold and sulphur, merely, as Proust informs us, in a state of mixture f j and when potash, sulphur, and gold, are heated together, and the mixture boiled in water, a considerable portion of gold is dissolved, as Stahi first discovered. Three parts of sulphur, and three of potash, are sufficient to dissolve one of gold. The solution has a yellow colour. When an acid is dropt into it, the gold falls down, united to the sulphur in the state of a reddish powder, which becomes gradually black . From the experiments of Bucholz, it seems to be composed of about one part of sulphur to 4*5 of gold, or of about 82 gold 18 sulphur 1GO 2. Margraf failed iu his attempts to unite gold with phosphorus || j but Pelletier was fortunate enough to succeed by melting together in a crucible half an ounce pf gold and an ounce of phosphoric glass {, surrounded with charcoal. The phospjwret of gold thus produced phosptu- was brittle, whiter than gold, and had a crystallized ap- ret * pearance. Jt was composed of 23 parts of gold and * By this is understood a combination of sulphurated hydrogen and an alkali. These compounds will be described hereafter. f Nicholson's Jour.ziv. 241. J Stahl's Op u,c. Clym.-Pbys.-Mcd. p. 6c6. $ Bucholz, Beitrage xur ertvtiterungund Bcricbtigung Jer Ctemle t iii. I7I |1 Ofusc. i. 2. \ Phosphoric acid evaporated to dryness, and then fused, 136 MALLEABLE METALS Action of incom- fcustibles. Alloys. Book I. one of phosphorus *. He formed the same compound Division f. . r . \ y by dropping small pieces or phosphorus into gold in fusion f. By the application of a sufficient heat, the phosphorus is dissipated and the gold remains. IV. Gold does not combine, as far as is known, with either of the simple incombustible bodies. V. But gold combines readily with the greater num- ber of the metals, and forms a variety of alloys. This metal is so soft that it is seldom employed in a state of purity. It is almost always mixed with small quantities of copper and silver. Goldsmiths usually announce the purity of the gold which they sell in the following manner : Pure gold they suppose divided in- to 24 parts called carats. Gold of 24 carats means pure gold ; gold of 23 carats means an alloy of 23 parts gold, and one of some other metal ; gold of 22 carats means an alloy of 22 parts of gold, and two of another metal. The number of carats mentioned, specifies the pure gold ; and what that number wants of 24, indicates the quantity of alloy. Thus gold of 12 carats would bean alloy containing 12 parts gold, and 12 of some other metal. In this country the carat is divided into four grains j among the Germans into 1 2 ; and by the French it was formerly divided into 32 J. * Ann."d c - Clitn.i, 71. f Ibid, xiii. 104* \ Lewis's fkilosofl . Commerce, p. 1 15. FLATIKrW, SECT. II. OF PLATINUM, GOLD, the metal jnst described, was known in the earliest ages, and has been always in high estimation, on account of its scarcity, beauty, ductility, and inde- structibility. But platinum, though perhaps inferior in few of these qualities, and certainly far superior in others, was unknown in Europe, as a distinct metal, be- fore the year 1749 f- f Father Cortinovis, indeed, has attempted to prove that this metal vras the tlectrum of the ancients. See the Chemical Annals of Brugnattlli, 1 790. That the clectrum of the ancients was a metal, and a very valuable one, is evident from many of the ancient writers, particularly Homer. The following lines of Glaudian are alone sufficient to prove it : M Atria cinxit ebur, trabibtis solid^tur ahenis a Culmen et in celsas surgunt tlutra columnas." L. I. v. 164. Pliny gives us an account of it in his Natural History. He informs us that it was a composition of silver and gold ; and that by candle-light it ihone with more splendour than silver. The ancients made cups, statues, and columns of it. Now, had it been our platinum, is it not rather ex- traordinary that no traces of a metal, which must have been pretty abun- dant, should be perceptible in any part of the old continent ? As the passage of Pliny contains the fullest account of electrum to b found in any ancient author, I shall give it in his own words, that eve?y one may have it in his power to judge whether or not the description will apply to the platinum of the moderns. * Qmniaufo incst argentura vaiio ponderc. Ubicur.que quinta argr.- 158 MALLEABLE METALS. Book t. I. It has hitherto been found only in America, in Choco Division * . . . , v t in Peru, and m the mine of Santa Fe, near Carthagena. Satinum f Vauquelin has lately discovered it in considerable quantity in the silver mines of Guadalcanal, in the pro- vince of Estremadura in Spain *. The workmen of the American mines must no doubt have been early acquainted with it ; and indeed some of its properties are obscurely mentioned by some of the writers of the 16th century. Mr Charles Wood, assay-master in Ja- maica, saw it in the West Indies about the year 1741* He gave some specimens of it to Dr Brownrigg, who presented it to the Royal Society in 1750. In 1748 it was noticed by Don Antonio de Ulloa, a Spanish ma- thematician, who, in 1735, had accompanied the French academicians to Peru in their voyage to measure a de- gree of the meridian. A paper on it was published by Mr Wood in the 44th volume of the Philosophical Transactions for 1749 and 1750. Dr Lewis began a set of experiments on it in 1749, the result of which was published in four papers in the Philosophical Tran- sactions for 1754, and afterwards two other papers were ti portio est, elcctrum vocatur. Scrobes ese reperiuntnr in Canaliensi. Fit et cura electrum argento addito. Quod si quintam portionem excessit incudibus non restitit. Et electro auctoritas, Homero testc, qui Menelai regiam auro, electro, argento, ebore fulgere tradit. Minervae tempium habet Lindos insulse Rhodiorum in quo Helena sacravit calirem ex elec* tro. Electri natura est ad lusernarum lumina clarius argento snlendere. Quod est nativum et venena deprehendit. Namque discurrunt in caliq* bus arcus coelestibus similes cum igneo stridore, et gemina rationc prd* cunt," Lib. xxxiii. cap. iv. * Ann. dt Ctim. Ix. 317. PLATINUM. 15P added *. These experiments demonstrate its peculiar nature and its remarkable properties. In 1752, Schef- fer of Sweden published a dissertation on this metal, remarkable for its precision, if we consider the small quantity of ore on which he had to work, which was not more than 40 grains. The experiments of Lewis were repeated, and many curious additions made to them by Margraf in 1757f. These dissertations ha- ving been translated ii.cO French, drew the attention of the chemists of that country, and induced Macquer and Baume to make a set of experiments on platinum, which were soon followed by the experiments of Buf- fon, Tillet, and Morveau$ ; Sickengen ||, Bergman ^[, Lavoisier **, and more lately Mussin Puschkin ft, and Morveau Jt ? an d several other chemists of eminence have added to our knowledge of this mineral. Crude platina comes from America in small flat grains of a silvery lustre. In this state it is exceeding- ly impure, containing, either mechanically mixed, or chemically united, no less than nine other metals ; but it may be reduced nearly to a state of purity by the following process. Dissolve the grains in diluted nitro- Purifier muriatic acid with as little heat as possible. Decant the solution from the black matter which resists the ac- tion of the acid. Drop into it a solution of sal ammo* tion, * Pbil. Trans, xlviii. 638, and 1. 148. See also Ptil. Com. p. 443, for * Cull detail of all the experiments on this metal made before 1763. \ Mem. Jkrlin, 1757, p. 31. and Margraf's Opasc. ii. aa6. $ Mem. Par. 1758, p. U$. Jour, de Pbys. iii. 324. (t Macquer's Dictionary . ^ Of use. ii. 166. ** Ann. de Ctim, V. 137, \\ J&J. TXlV. 2Of . |$ ttuk XXV. 3. 160 MALLEABLE METALS. Book f. n lac * t Aii orange yellow-coloured precipitate falls id Division I. v the bottom. Wash this precipitate; and when dry; expose it to a heat slowly raised to redness in a porce- lain crucible. The powder which remains is platinum nearly pure. By redissolving it in mtro-muriatic acid, and repeating the whole process, it may be made still purer. When these grains are wrapt up in a thin plate of platinum, heated to redness, and cautiously hammer- ed, they unite, and the whole may be formed into an ingot f. properties. i. Platinum, thus obtained, is of a white colour like silver, but not so bright J. It has no taste nor smell. 2. Its hardness is 8. Its specific gravity, after being hammered, is 23 '000 5 so that it is by far the heaviest body known J. 3. It is exceedingly ductile and malleable; it may be hammered out into very thin plates, and drawn into wires not exceeding -r-^Vs- inch in diameter. In these * This salt will be described afterwards. It is .7 combination of muri- atic acid and ammonia. f Phil. 3fo. xxi. 175. | To this colour it owes its name. Plata, in Spanish, is " silver ;'* and platina, " little silver," was the name first given to the metal. Bergman changed that name into platinum, that the Latin names of all the metals might have the same termination and gender. It had been, however, called platinum by Linnaeus long before. Kirwan's Miner, ii. 103. Authors differ considerably in their esti- mate of the specific gravity of this metal. Lewis did not obtain it. hea- vier than gold ; but his trials were made on impure specimens, Schef- fer, from the specific gravity of the alloys made by Lewis, calculated the specific gravity of platinum at ai ; but this theory wis Erroneous. Sick- ingen found it aro6i. I have a crucible whrse v^-fic gravity at first was near 22. Chabanau found the specific er ". hsmmere<& platinum no less than 24. PLATINUM. 161 properties it is probably inferior to gold, but it seems t cha iy to surpass all the other metals. 4. Its tenacity is such, that a wire of platinum 0*078 inch in diameter is capable of supporting a weight of 274' 31 Ibs avoirdupois without breaking*. 5. It is one of the most infusible of all metals, and cannot be melted in any quantity at least, by the strong- est artificial heat which can be produced. Macquer and Baume melted small particles of it by means 'of a blow- pipe, and Lavoisier by exposing them on red hot charcoal to a stream of oxygen gas. It may indeed be melted without difficulty when combined or mixed with other bodies, but then it is not in a state of purity. Pieces of platinum, when heated to whiteness, may be welded together by hammering in the same manner as hot iron. 6. This metal is not in the smallest degree altered by the action of air or water. II. It cannot be combined with oxygen and convert- Oxide*, ed into an oxide by the strongest artificial heat of our furnaces. Platinum, indeed, in the state in which it is brought from America, may be partially oxidized by exposure to a violent heat, as numerous experiments have proved ; but in that state it is not pure, but com- bined with a quantity of iron. It cannot be doubted, however, that if we could subject it to a sufficient heat, platinum would burn, and be oxidized like other me- tals : For when Van Marum exposed a wire of plati- num to the action of his powerful electrical machine, it burnt with a faint white flame, and was dissipated in- * Morveau, Ann, efe Cllm* nv. j. Vol. I. L 162 Book I. Division I. Peroxide. Protoxide. MALLEABLE METALS. to a. species of dust, which proved to be the oxide of platinum. By putting a platinum wire into the flame produced by the combustion of hydrogen gas mixed with oxygen, I caused it to burn with all the brilliancy of iron wire, and to emit sparks in abundance. 1. To obtain the oxides of this metal, it is necessary to have recourse to the action of an acid. When the deep brown solution of platinum in nitro- muriatic acid is treated with lime water, a yellowish-brown powder falls. Dissolve this powder in nitric acid j evaporate to dryness, and apply a heat sufficient to drive off the acid. The brown powder which remains is the per- oxide of platinum. It is tasteless and insoluble jn wa- ter. When heated to redness, the oxygen is driven off', and the oxide reduced to the metallic state. One hun- dred and fifteen parts of oxide, by this treatment, leave 100 parts of metal. Hence the oxide is composed of 81 platinum 13 oxygen 100* 2. If the heat in this experiment be very cautiously raised, the oxide, before it is reduced, assumes a green colour. This change is occasioned by the separation of a portion of the oxygen. The green-coloured powder is, according to Chenevix, a protoxide of platinum. From his experiments, we learn that it is composed of 93 platinum 7 oxygen 100 f * Cfeenevix on Palladium, Phil Trans. 1803, f Hid. PLATINUM. 163 I III. The action of the simple combustibles on this i cha P- IV - t ietal is not more remarkable than their action on gold. 1. Neither hydrogen nor carbon have been hitherto combined with it. 2. Phosphorus unites without difficulty, and forms a phospburet. By mixing together an ounce of platinum, an ounce of phosphoric glass,* and a dram of powdered charcoal, and applying a heat of about 32 Wedge- wood, Mr Pelletier formed n plospluret weighing more than an ounce. It was partly in the form of a button, and partly in cubic crystals. It was covered above by a blackish glass. It was of a silver white colour, very brittle, and hard enough to strike fire with steel. When exposed to a fire strong enough to melt it, the phospho- rus was disengaged, and burnt on the surface *. He found also, that when phosphorus was projected on red hot platinum, the metal instantly fused and formed a phosphuret. As heat expels the phosphorus, Mr Pel- letier has proposed this as an easy method of purifying platinum f. 3. Platinum cannot be made to unite to sulphur by Sulphutct, heating them together J. In this respect it resembles gold. Yet there seems to be an affinity between the two substances ; for when the metal is heated with a mixture of potash and sulphur, it is corroded and ren- dered partly soluble in water, as was proved by the experiments of Lewis J and Margraf||. And when sulphureted hydrogen gas is passed into a solution of platinum in an acid, the metal is thrown down in dark * Ann. de Cb'tm. \. Jl. f Hid. liii. 105, | Lewis, Phil. Com. p. 498, Ibid. p. 499, (1 Qpust. ii. 284. L2 164 MALLEABLE METALS. Book I. brown flakes, apparently in combination with sulphur. [Division I. < -y Indeed, if we believe Mr Proust, a sulphuret of Ihia metal occurs sometimes mixed with native platina *. IV. Platinum, as far as is known, does not combine with the simple incombustibles. Alloys. Y". It combines with most of the metals and forms alloys, wh ; jh were first examined by Dr Lewis. i. Gold. 1. Dr Lewis found that gold united with platinum when they were melted together in a strong heat. He employed only crude platina ; but Vauquelin, Hatchett, and Klaproth, have since examined the properties of the alloy of pure platinum and gold f. To form the alloy, it is necessary to fuse the metals with a strong heat, otherwise the platinum is only dispersed through the gold. When gold is alloyed with this metal, its co- lour is remarkably injured ; the alloy having the ap- pearance of bell metal, or rather of tarnished silver. Dr Lewis found, that when the platinum amounted only to ^th,. the alloy had nothing of the colour of gold ; even one forty-second part of platinum greatly injured the colour of the gold. The alloy formed by Mr Hatchett of nearly eleven parts of gold to one of pla- tinum, had the colour of tarnished silver. It was very ductile and elastic. From Klaproth we learn, that if the platinum exceed -rV^ 1 f tne g^> tne colour of the alloy is much paler than gold ; but if it be under T * T th, the colour of the gold is not sensibly altered. Neither * Ann. de Cbim. xxxviii. 149. It is not unlikely that this ingenious chemist took for a sulphuret of platinum some one of the numerous me- tallic bodies that have been lately discovered in crude platina. f Vauquelin, Manuel de i'Etiayeur, p. 44. Hatchett on the Alloys of Gold, &c. Pbit. Trans. 1803, Klaproth, Journal de Ctimtf^iv:. Z% SILVER. 165 is there any alteration in the ductility of the gold. Chap. IV. Platinum may be alloyed with a considerable propor- tion of gold without sensibly altering its colour. Thus an alloy of one part of platinum with four parts of gold can scarcely be distinguished in appearance from pure platinum. The colour of gold does not become predominant till it constitutes eight-ninths of the al- loy *, From these facts it follows, that gold cannot be al- loyed with -y^th of its weight of platinum, without ea- sily detecting the fraud by the debasement of the co- lour ; and Vauquelin has shown, that when the plati- num does not exceed T Vth, it may be completely sepa- rated from gold by rolling out the alloy into thin plates, and digesting it in nitric acid. The platinum is taken up by the acid while the gold remains. But if the quantity of platinum exceeds V^th, it cannot be separa- ted completely by that method f. SECT. III. OF SILVER. I. OILVER seems to have been known almost as early as gold. 1. It is a metal of a fine white colour with a shade of yellow, without either taste or smell ; and in point * Klaproth, Journal de Ciitnie, ir. 29. f Manuel de rEttajtar, p. 48. 166 MALLEABLE METALS. Book I. of brilliancy is perhaps inferior to none of the metallic Division I. * <,. v i i bodies, it we except polished steel. 2. Its hardness is 7. When melted, its specific gra- vity is 10*474 * ; when hammered, 10'510 f. 3. In malleability it is inferior to none of the me- tals, if we except gold. It may be beat out into leaves only T ^- 5 I 5 .-^. inch thick. Its ductility is equally remarkable : it maybe drawn out into a wire much finer than a human hair ; so fine indeed, that a single grain of silver may be extended about 400 feet in length. 4. Its tenacity is such, that a wire of silver 0*078 inch in diameter is capable of supporting a weight of 187'13lbs avoirdupois without breaking J. 5. Silver melts when it is heated completely red hot ; and while melted its brilliancy is much increa- sed. According to the calculation of Mortimer and Bergman, its fusing point is 1000 of Fahrenheit. Dr Kennedy ascertained, that the temperature at which it melts corresponds to 22 of Wedgewood's pyrometer J. If the heat be increased after the silver is melted, the liquid metal boils, and- may be volatilized ; but a very * Brissonand Hatchett. Fahrenheit found it 10-481. (Phil. Trans. 1 724, vol. xxxiii. p. 114.) I found pure silver melted and slowly cooled of the specific gravity 10-3946; when hammered it became 10-4177; when rolled out into a plate it became 10-4812. Nicholson's Jour. xiv. 3P7- f According, to Brisson. Musehenbroeck found the specific gravity of hammered silver 10-500. Dr Lewis makes it no less than 10-980, (Phil. CM*, p. 549.) | Ann. tie Glim. XXV. 9. Sir James Hall, Nicholsons Jour, ix. 99. SILVER. 167 Itrong and long-continued heat is necessary. Gasto Chap. IV. Claveus kept an ounce of silver melted in a glass-house furnace for two months, and found, by weighing it, that it had sustained a loss of T V of its weight *. When cooled slowly, its surface exhibits the appear- ance of crystals ; and if the liquid part of the metal be poured out as soon as the surface congeals, pretty large crystals of silver may be obtained. By this method Tillet, and Mongez junior, obtained it in four-sided pyramids, both insulated and in groups. II. Silver is not oxidized by exposure to the air: Oxides. it gradually indeed loses its lustre, and becomes tar- \ uished ; but this is owing to a different cause. Nei- ther is it altered by being kept under water. But if it be kept for a long time melted in an open vessel, it gradually attracts oxygen from the atmosphere, and is converted into an oxide. This experiment was first made by Junker, who converted a quantity of silver into a vitriform oxide f . It was afterwards confirmed by Mac- quer and Darcet, Macquer, by exposing silver 20 times successively to the heat of a porcelain furnace, obtained a glass~$. of an olive green colour . Nay, if the heat be sufficient, the silver even takes fire, and burns like other combustible bodies. Van Marum made electric sparks from his powerful Teylerian ma- chine pass through a silver wire ; the wire exhibited 2 * Tleatrum Cbem. ii. 17. f Junker's Conspectus Cbem. i. 887. \ Metallic oxides, after fusion, are called glass, because they acquire a good deal of resemblance, in some particulars, to common glass* Macquer's Dictionary 1 11.571. 168 MALLEABLE MATALS. Book!, greenish white flame, and was dissipated into smoke. Division I. >. v Before a stream of oxygen and hydrogen gas, it burns rapidly with a light green flame. By means of the galvanic battery it may be burnt with great brilliancy. The oxide of silver, obtained by means of heat, is of a greenish or olive colour. When silver is dissolved in nitric acid, and precipitated by lime water, it falls to the bottom under the form of a powder of a dark olive brown colour. From the experiments of Klaproth we learn, that this oxide is composed of 100 parts of silver united to 12*8 of oxygen*, or per cent. of about 89 silver 11 oxygen 100 which differs but little from the previous statements of Bergman f and Wenzel. But Proust, from an experi- ment, which however he thinks requires repetition, considers this oxide as a compound of 100 silver and $4- oxygen J. This oxide is tasteless and insoluble in water. When exposed to the light, part of its oxygen is separated, as Scheele first ascertained, and it is con- verted into a black powder, which contains but a very small portion of oxygen, and may be considered as sil- ver reduced. By exposing the solution of silver in ni- tric acid to sunshine, the silver precipitates in the form of a flea-brown powder* * Bcitrage, iii. 199. f Of use. iii. 391 | Nicholson's Jour. xv. 375. SILVER. The oxide now described, as far as we know at pre- Chap IV sent, is the peroxide of silver ; the protoxide, as Proust has discovered, may be formed by dissolving silver in nitric acid, and heating the solution in contact with a portion of the metal in the state of powder. Its colour resembles that of the peroxide ; but its combination with nitric acid is much more soluble *. III. Neither carbon nor hydrogen have been com- Combina- bined with silver ; but it combines readily with sulphur and phosphorus. ^les. 1. When thin plates of silver and sulphur are laid al- Sulphurct. ternately above each other in a crucible, they melt rea- dily in a low red heat, and form sulphur et of silver. It is of a black or very deep violet colour ; capable of being cut with a knife ; often crystallized in small needles ; and much more fusible than silver. If suf- ficient heat be applied, the sulphur is slowly volatilized, and the metal remains behind in a state of purity. This compound frequently occurs native. It has a dark grey colour, a metallic lustre, and the softness, flexibi- lity, and malleability of lead. Its specific gravity is about 7*2. According to the analysis of Klaproth, it is composed of 85 silver 15 sulphur 100 f Hence 100 parts of silver unite with about 17*6 parts of sulphur J. * Nicholson's Jour. xv. 376. f Beitrage,i. 162, \ In Wenzel's trials, 100 parts of silver took up only 14'; parts of sul- phur. But probably the heat was too great. Vtrwandtutaft, p, 279. Grindel's edition. JP10 MALLEABLE METALS. I. It is well known that when silver is Ion? exposed to Division I. w _ y the air, especially in frequented places, as churches, theatres, &c. it acquires a covering of a violet colour, which deprives it of its lustre and malleability. This covering, which forms a thin layer, can only be detach- ed from the silver by bending it, or breaking it in pieces with a hammer. It was examined by Mr Proust, and found to be sulphuret of silver *. Phosphu- 2. Silver was first combined with phosphorus by Mr Pelletier. If one ounce of silver, one ounce of phospho- ric glass, and two drams of charcoal, be mixed together, and heated in a crucible, pbosphuret of silver is form- ed. It is of a white colour, and appears granulated, or as it were crystallized. It breaks under the hammer, but may be cut with a knife. It is composed of four parts of silver and one of phosphorus. Heat decom- poses it by separating the phosphorus f. Pelletier has observed that silver in fusion is capable of combining with more phosphorus than solid silver : for when phosphuret of silver is formed by projecting phospho- rus into melted silver, after the crucible is taken from the fire, a quantity of phosphorus is emitted the mo- ment the metal congeals!. IV. Silver does not combine with the simple incom- bustibles. Alloys V. Silver combines readily with the greater number of metallic bodies. 1. When silver and gold are kept melted together, With gold, they combine, and form an alloy composed, as Homberg * AHH. de Ctim. i. 142. f Pelletier, Ann. de Clioi. i. 73. AH ft. de Cllm\ jiii. IlO< SILVER. 17t ascertained, of one part of silver and five of gold. He Chap.iv. kept equal parts of gold and silver in gentle fusion for a quarter of an hour, and found, on breaking the cruci- ble, two masses, the uppermost of which, was pure sil- ver, the undermost the whole gold combined with of silver. Silver, however, may be melted with gold in almost any proportion ; and if the proper precau- tions be employed, the two metals remain combined together. The alloy of gold and silver is harder and more so- norous than gold. Its hardness is a maximum when the alloy contains two parts of gold and one of silver *. The density of these metals is a little diminished f, and the colour of the gold is much altered, even when the proportion of the silver is small ; one part of silver pro- duces a sensible whiteness in twenty parts of gold* The colour is not only pale, but it has also a very sen- sible greenish tinge, as if the light reflected by the sil- ver passed through a very thin covering of gold. This alloy, being more fusible than gold, is employed to sol- der pieces of that metal together. 2. When silver and platinum are fused together (for with plad- which a very strong heat is necessary), they form a nunu mixture, not so ductile as silver, but harder and less white. The two metals are separated by keeping them for some time in the state of fusion ; the platinum sinking to the bottom from its weight. This circum- stance would induce one to suppose that there is very little affinity between them. Indeed Dr Lewis found, that when the two metals were melted together, they * Muschenbroeck, f Hztchett. 172 Book I. Division I. MALLEABLE METALS. sputtered up as if there were a kind of repugnance be- tween them. The difficulty of uniting them was no- ticed also by Scheffer *. SECT. IV. OF MERCURY. Fropcrtiea. I. MERCURY, called also QJJICKSILVER, was known iti the remotest ages, and seems to have been employed by the ancients in gilding and in separating gold from other bodies just as it is by the moderns. 1. Its colour is white and similar to that of silver ; hence the names hydrargyrum, argentum vivvm, quick- silvery by which it has been known in all ages. It has no taste nor smell. It possesses a good deal of brillian- cy : and when its surface is not tarnished, makes a very good mirror. 2. Its specific gravity is 13*568 f. When in a solid state its density is increased ; its specific gravity, according to the experiments of Schulz, * Lewis's Pbilosopb. Commeree, p. 542. f Cavendish and Brisson. The specific gravity varies considerably li ke that of all other metals. Fahrenheit found it 13-575. (PhiL Trans. 17 24. vol. xxxiii. 114.) Mr Biddle found it 13*613 at the temperature of 50. (PhiL Mag. xix. 134). MERCURY. 113 being 14*391*, according to the experiments of Mr Chap.IV.^ Biddle 14-465 f. 3. At the common temperature of the atmosphere it is always in a state of fluidity. In this respect it dif- fers from all other metals. But it becomes solid when exposed to a sufficient degree of cold. The tempera- Point of ture necessary for freezing this metal is 39, as was ascertained by the experiments of Mr Hutchins J at Hudson's Bay. The congelation of mercury was acci- dentally discovered by Professor Braun at Petersburgh in 1759. Taking the advantage of a very severe frost, he plunged a thermometer into a mixture of snow and salt, in order to ascertain the degree of cold there- by produced. Observing the mercury stationary, even after it was removed from the mixture, he broke the bulb of the thermometer, and found the metal frozen in- to a solid mass. This experiment has been repeated very often since, especially in Britain . Mercury con- tracts considerably at the instant of freezing ; a circum- stance which misled the philosophers who first witnes- sed its congelation. The mercury in their thermome- ters sunk so much before it froze, that they thought the cold to which it had been exposed much greater than it really was. It was in consequence of the rules laid down by Mr Cavendish, that Mr Hutchins * Gchkn's Jour. 1^434. f Pbil. Mag. m. 134. t Pbil. Trans. 1783, p. 303. See also Mr Cavendish's observations on Mr Hutchin's experiments in the same volume of the Transactions. The method of performing this experiment will be described in the Second Division of the fifst part of this "Work. JL74 MALLEABLE METALS. Book I. was enabled to ascertain the real freezing point of the Division I. . metal. 4. Solid mercury may be subjected to the blows of a hammer, and may be extended without breaking. It is therefore malleable ; but neither the degree of its mal- leability, nor its ductility, nor its tenacity, have been ascertained. Boiling 5. Mercury boils when heated to 656 *. It may point. therefore be totally evaporated, or distilled from one vessel into another. It is by distillation that mercury is purified from various metallic bodies with which it is often contaminated. The vapour of mercury is invisible and elastic like common air : like air, too, its elasticity is indefinitely increased by heat, so that it breaks through the strongest vessel. Geoff- roy, at the desire of an alchymist, inclosed a quan- tity of it in an iron globe strongly secured by iron hoops, and put the apparatus into a furnace. Soon after the globe became red hot, it burst with all the violence of a bomb, and the whole of the mercury was dissipated f. Oxide*. II- Mercury is not altered by being kept under wa- ter. When exposed to the air, its surface is gradually tarnished, and covered with a black powder, owing to its combining with the oxygen of the atmosphere. But this change goes on very slowly, unless the mercury be either heated or agitated, by shaking it, for instance, in a large bottle full of air. By either of these processes * Crichten, Pitt. Mag. xiv. 49. f Macqucv's / 7 MERCURY. 175 the metal is converted into an oxide : by the last, into Chap. IV. a black coloured oxide ; and by the first, into a red coloured oxide. This metal does not seem to be capable of combustion; at least no method which I have hither- to tried to burn it has succeeded. It is the only metal I have hitherto had an opportunity of examining which may not, by peculiar management, be made to burn. The oxides of mercury at present known are four in number. 1. The protoxide was first described with accuracy ft-otoxide. by Boerhaave. He formed it by putting a little mer- cury into a bottle, and tying it to the spoke of a mill- wheel*. By the constant agitation which it thus under- went, it was converted into a black powder, to which he gave the name of ethiops per se. It is a black pow- der without any of the metallic lustre, has a coppery taste, and is insoluble in water. According to the ex- periments of Fourcroy, it is composed of 96 parts of mercury and four of oxygenf. According to Messrs Braamcamp and Siquiera-Oliva, it is composed of 92*5 mercury and V5 oxygen J. When this oxide is exposed to a strong heat, oxygen gas is emitted, and the mercury reduced to the metallic state. In a more mo- derate heat it combines with an additional dose of oxy- jen, and assumes a red colour. This black oxide may be procured by shaking pure * This experiment was first made by Homberg in 1699. He at- tached a bottle holding some mercury to the clapper of a mill. tyn's Abrldg, of tie Par. Mem. vol. i. f Jtur. de Mists, An. x. p. 283. \ Ann.de Cblm. liv. 1 1C, 1"76 MALLEABLE METALS. Book r. mercury in oxygen gas or common air, or by triturating i v 1. 1 it with water*. 2. When mercury is dissolved in nitric acid without the assistance of heat, and the acid is made to take up as much mercury as possible, it has been ascertained by the experiments of Mr Chenevix, that an oxide is formed, composed of 89*3 mercury and 10*7 oxygenf . In this case, 100 parts of mercury unite with about 12 of oxygen. This oxide cannot be separated complete- ly from the acid which holds it in solution without un- dergoing a change in its composition ; of course we are at present ignorant of its colour and other properties. Indeed it is believed by many to be the same with the black oxide just described under the name of protoxide; but as this has not been proved, and as experiments have given a different proportion of oxygen for each, it would be improper at present to confound them to- gether. Besides, during the formation of the red oxide of mercury by heat, three stages may be observed : The metal first assumes the form of a black powder ; this powder becomes afterwards yellow, and at last red. The yellow powder may be the very oxide which is formed by nitric acid in the above process. Red oxide. 3. When mercury, or its protoxide, is exposed to a heat of about 600, it combines with additional oxy- gen, assumes a red colour, and is converted into an ox- ide, which, in the present state of our knowledge, we must consider as a tritoxide. This oxide may be form- ed two different ways : 1. By putting a little mercury * Sec Wasserberg's Imtitutionct Cbemi \\. a6, f fkil. Trent. l8oa. MERCURY. 177 into a flat-bottomed glass bottle or matrass, the neck of Chap. IV. which is drawn out into a very narrow tube, putting the matrass into a sand bath, and keeping it constantly at the boiling point. The height of the matrass, and the smallness of its mouth, prevents the mercury from making its escape, while it affords free access to the air. The surface of the mercury becomes gradually black, and then red, by combining with the oxygen of the air: and at the end of several weeks, the whole is converted into a red powder, or rather into small crystals of a very deep red colour. The oxide, when thus obtain- ed, was formerly called precipitate per se. 2. When mercury is dissolved in nitric acid, evaporated to dry- ness, and then exposed to a graduated heat, it assumes a brilliant scarlet colour. The powder thus obtained was formerly called red precipitate, and possesses ex- actly the properties of the oxide obtained by the for- mer process*. This oxide has an acrid and disagreeable taste, pos- sesses poisonous qualities, and acts as an escharotic when applied to any part of the skin. It is somewhat ^soluble in water. When triturated with mercury, it gives out part of its oxygen, and the mixture assumes various colours according to the proportion of the in- gredients. When heated along with zinc or tin filings, it sets these metals on fire. According to Fourcroy, it is composed of 92 parts of mercury and eight of oxygenf. But the analysis of Mr Chenevix, to be * See a description of the method of manufacturing thii oxide, by Paysse, Ann.de Cbim. li. 202. f Jtur, de Mints, Aj). X. p. 283. Fbl. L M 178 MALLEABLE METALS. D?ri?on"l. described hereafter, gives, for the proportion of its "v -' component parts, 85 parts of mercury and 15 parts of oxygen. Messrs Braamcamp and Siquiera-Oliva, on the other hand, found it a compound of 90 mercury and 10 oxygen*. 4. When a current of oxymuriatic gas is passed through water in which there is red oxide of mercury, the oxide gradually assumes a dark brown colour, and a portion of it is dissolved. This brown powder re- tains the form and crystalline appearance of the red oxide. It dissolves in nitric acid without effervescence ; with muriatic acid it forms the very same compound as the red oxide ; and from both it is thrown down in the state of a yellow powder by potash, as is the case with the red oxide when similarly dissolved. We have therefore no proof, except the new colour, to lead us to suppose that the brown powder is a different oxide from the red. Mr Chenevix, however, to whom we are in- debted for all these facts, is rather inclined to consider them as distinct f. But Messrs Braamcamp and Si- quiera-Oliva have rendered it extremely probable, that the dark colour is owing merely to the presence of a portion of muriatic acid, and not to any difference in the state of oxldizementif. III. Mercury does not combine with carbon nor hy- drogen ; but it unites readily with sulphur and with phosphorus. 1. When two parts of sulphur and one of mercury are triturated together in a rnortar, the mercury gradually Combina- tion with combusti- bles. Black sul- phuret. Ann. di Cbim. Hv. 1 1 8. Anni di dim. liv. 129- Pbil. Tram. 180*. MERCURY*. disappears, and the whole assumes the form of a black powder, formerly called etbiops mineral. It is scarcely possible by this process to combine the sulphur and mercury so completely, that small globules of the me- tal may not be detected by a microscope. When mer- cury is added slowly to its own weight of melted sul- phur, and the mixture is constantly stirred, the same black compound is formed. When this substance is heated, part of the sulphur is dissipated, and the compound assumes a deep violet co- lour. Fourcroy had suggested, that in this compound the mercury is in the state of black oxide, absorbing the necessary portion of oxygen from the atmosphere du- ring its combination with the sulphur*. But the late experiments of Proust have shown that this is not the case f . Berthollet had conjectured that it contains sul- phureted hydrogen ; but Seguin has ascertained that this opinion is not well founded %. Ethiops mineral, then, is merely a sulphuret of mercury. The union is probably less intimate, and the proportion of sulphur greater, than in red sulphur -et of mercury. 2. When ethiops mineral is heated red hot, it sub- Red ul limes ; and if a proper vessel be placed to receive it, a p u cake is obtained of a fine red colour. This cake was formerly called cinnabar ; and when reduced to a fine powder, is well known in commerce under the name of * Fourcroy,. v. 298. f Jour, de Pbys. liiL 92. \ Stat!j*e Cllntquf, ii. 438. M 2 180 MALLEABLE METALS. Book r. vermilion *. It has been hitherto supposed a compound oxide of mercury and sulphur. But the experi- ments of Proust have demonstrated that the mercury which it contains is in the metallic state. According to that very accurate chemist, it is composed of 85 parts of mercury, and 15 of sulphur f. It is therefore a sul- phur et of mercury. This sulphuret of mercury has a scarlet colour, more or less beautiful, according to the mode of preparing it. Its specific gravity is about 10. It is tasteless, inso- luble in water, and in muriatic acid, and not altered by exposure to the air. When heated sufficiently, it takes fire, and burns with a blue flame. When mixed with half its weight of iron filings, and distilled in a stone ware retort, the sulphur combines with the iron, and the mercury passes into the receiver, which ought to contain water. By this process mercury may be ob- tained in a state of purity. The use of this sulphuret of mercury as a paint is well known J. Cinnaber may be prepared by various other proces- ses. One of the simplest of these is the following, lately discovered by Mr Kirchoff. When 300 grains of mercury, and 68 of sulphur, with a few drops of so- lution of potash to moisten them, are triturated for * The word vermilion is derived from the French word vermei, which comes from vermictilui , or ocrmiculum : names given in the middle ages to the tcrmes or eoccvt illicit, well known as a red dye. Vermilion originally signified the red dye of the kermes. See Bedmann't History of Ditcovcr'm t ;i. i So f Jour, de Phyt. liii. 91. t See a description of the process of making it by Paysse, Ann. de Ctim. )i. 196, and by Tuckert, \b\d % iv, 25, MERCURY. 181 some time in a porcelain cup by means of a glass pestle, Chap. IV. ethiops mineral is produced. Add to this 160 grains of potash dissolved in as much water. Heat the ves- sel containing the ingredients over the flame of a can- dle, and continue the trituration without interruption during the heating. In proportion as the liquid evapo- rates, add clear water from time to time, so that the ox- ide may be constantly covered to the depth of near an inch. The trituration must be continued about two hours ; at the end of which time the mixture begins to change from its original black colour to a brown, which usually happens when a large part of the fluid is evapo- rated. It then passes very rapidly to a red. No more water is to be added ; but the trituration is to be con- tinued without interruption. When the mass has ac- quired the consistence of a jelly, the red colour becomes more and more bright, with an incredible degree of quickness. The instant the colour has acquired its ut- most beauty, the heat must t>e withdrawn, otherwise the red passes to a dirty brown. Count de Moussin Pousch- kin has discovered, that its passing to a brown colour may be prevented by taking it from the fire as soon as it has acquired a red colour, and placing it for two or three days in a gentle heat, taking care to add a few drops of water, and to agitate the mixture from time to time. During this exposure the red colour gradu- ally improves, and at last becomes excellent. He dis- covered also, that when this sulphuret is exposed to a strong heat, it becomes instantly brown, and then pas- ses into a dark violet ; when taken from the fire, it pas- ses instantly to a beautiful carmine red *. * Nicholson's Journal,, it, i, 182 MALLEABLE METALS. Book T. 3. fylr Pelletier, after several unsuccessful attempts Division I. L y ~>- to combine phosphorus and mercury, at last succeeded 3 08 P huret - b r distilling a mixture of red oxide of mercury and phosphorus. Part of the phosphorus combined with the oxygen of the oxide, and was converted into an acid ; the rest combined with the mercury. He observed, that the mercury was converted into a black powder be- fore it combined with the phosphorus. On making the experiment, I found that phosphorus combines very readily with the black oxide of mercury, when melted along with it in a retort filled with hydrogen gas to prevent the combustion of the phosphorus. As Pelle- tier could not succeed in his attempts to combine phos- phorus with mercury in its metallic state, we must conclude that it is not with mercury, but with the black oxide of mercury, that the phosphorus combines. The compound therefore is not phosphuret of mercury, but black phosphureted oxide of mercury. It is of a black colour, of a pretty solid consistence, and capable of being cut with a knife. When exposed to the air, it exhales vapours of phosphorus *. IV. Mercury does not combine with the simple in- combustibles. Araal arm ^" Mercury combines with the greater number of metals. These combinations are known in chemistry by the name of amalgams f. Of Gold. i. The amalgam of gold is formed very readily, be- cause there is a very strong affinity between the two * Ann. de Cbim. xiii. 113. f This word is supposed to be derived from apct and y^t a ; of course it signifies literally intermarriage. MERCURY. 183 metals. If a bit of gold be dipped into mercury, its Chap. IV. surface, by combining with mercury, becomes as white as silver. The easiest way of forming this amalgam is to throw small pieces of red hot gold into mercury heated till it begins to smoke. The proportions of the ingredients are not determinable, because they combine in any proportion. This amalgam is of a silvery white- ness. By squeezing it through leather, the excess of mercury may be separated, and a soft white amalgam obtained, which gradually becomes solid, and consists of about one part of mercury to two of gold. It melts at a moderate temperature ; and in a heat below redness the mercury evaporates, and leaves the gold in a state of purity. It is much used in gilding. The amalgam is spread upon the metal, which is to be giit ; and rhen by the application of a gentle and equal heat, the mer- cury is driven off, and the gold left adhering to the me- tallic surface ; this surface is then rubbed with a brass wire brush under water, and afterwards burnished*. 2. Dr Lewis attempted to form an amalgam of pla- platinum, tinum, but succeeded only imperfectly, as was the case also with Schefferf. Guyton Morveau succeeded by means of heat. He fixed a small cylinder of platinum at the bottom of a tall glass vessel, and covered it with mercury. The vessel was then placed in a sand-bath, and the mercury kept constantly boiling. The mercury gradually combined with the platinum ; the weight of the cylinder was doubled, and it became brittle. When heated strongly, the mercury evaporated, and left the * Gcllert's Metallurgy CAemittry, 375, and Lewis, P/v'/T Coat. p. 75. f Lewis, Pill. Com. p. 508. 184 . Book I. Division T. Silver. MALLEABLE METALS. platinum partly oxidated. It is remarkable that the platinum, notwithstanding its superior specific gravity, always swam upon the surface of the mercury, so that Morveau was under the necessity of fixing it down*. The simplest and easiest way of combining plati- num and mercury was pointed out by Muschin Push- kin. It consists in triturating with mercury the fine powder obtained by precipitating platinum from nitro- muriatic acid by sal ammoniac, and exposing the pre- cipitate to a graduated heat. Some trituration is ne- cessary to produce the commencement of combination ; but when once it begins, it goes on rapidly. Small quan- tities of the platinum and mercury are to be added alter- nately till the proper portion of amalgam is procured. The excess of mercury is then separated by squeezing it through leather. The amalgam obtained is of a fine silvery whiteness, and does not tarnish by keeping. At first it is soft, but gradually acquires hardness. It ad- heres readily to the surface of glass, and converts it into a smooth mirror. 3. The amalgam of silver is made in the same man- ner as that of gold, and with equal ease. It forms den- dritical crystals, which, according to the Dijon acade- * Ann. de Ch\m. xxv. 12. This was doubtless owing to the strong co- hesion which exists between the particles of mercury. If you lay a large mass of platinum upon the surface of mercury, it sinks directly on ac- count of its weight ; but a small slip (a platinum wire, for instance) swinw, being unable to overcome the cohesion of the mercury. How- ever, if you plunge it to the bottom, it remains there in consequence of its superior weight. If heat be now applied to the bottom of the vessel, the wire comes again to the surface, being buoyed up by the hot mercury, to which it has begun to adhere. These facts explain the seeming anomaly observed by Morreau. PALtADIUM. 135 micians, contains eight parts of mercury and one of sil- ^Chap. iv.^ ver. It is of a white colour, and is always of a soft consistence. Its specific gravity is greater than the mean of the two metals. Gelhrt has even remarked, that when thrown into pure mercury, it sinks to the bottom of that liquid *. When heated sufficiently, the mercury is volatilized, and the silver remains behind pure. This amalgam is sometimes employed, like that of gold, to cover the surfaces of the inferior metals with a thin coat of silver. SECT. V. OF PALLADIUM. THIS metallic body, recently discovered by Dr Wol- laston in crude platina, has given birth to a very ex- traordinary controversy, which is not yet settled. In the month of April 1803, a printed paper was par- History, tially circulated in London, announcing, that a new me- tal called palladium, or new silver, was sold at Mr Forster's, Gerrard- street. Several of the properties of the metal were stated ; but the name of the discoverer, and every thing which could lead to the knowledge of the substance from which it was obtained, were * Gellert's Metallurgy dentistry^ 186 MALLEABLE METALS. Book I. omitted. This unusual mode of proceeding led Mr Division L . . & _ , ,. * v^ ' Chenevix to suspect imposition on the part 01 the dis- coverer, and induced him to undertake a very labori- ous set of experiments to detect what he considered as a fraud. The result of his inquiries was published in the Philosophical Transactions for 1803. He concluded palladium to be a compound of platinum and mercury. He pointed out various methods of uniting the two me- tals together ; but could not succeed in again decompo- sing them, or in reducing palladium to its constituents. The very extraordinary consequences that followed from these experiments and assertions of Chevenix, imme- diately attracted the attention of all chemists to the sub- ject. Dr Wollaston and Mr Smithson Tennant very soon announced, that they considered Mr Chenevix as mistaken, as his experiments in their hands did not succeed. Dr Wollaston informed him, that he had detected small quantities of palladium in crude pla- tina, and endeavoured to convince him that the pal- ladium in his experiments had been derived from that source. Mr Chenevix, however, still persisted in his original opinion. Some months after, a letter was pub- lished by the unknown discoverer, denying the accu- racy of Chenevix's experiments, affirming that palladi- um cannot be made artificially, and offering a reward of twenty guineas to any person who could produce twenty grains made either by means of the formula of Chenevix or any other. The money was actually de- posited, but nobody appeared to lay claim to the re- ward. In France some of Mr Chenevix's experiments were repeated by Morveau, who exhibited several ot his re- sults before the National Institute, and affirmed that PALLADIUM. 1S7 they coincided in general with those of the British che- t ch *P- 1V mist. But Fourcroy and Vauquelin investigated the subject farther, and were led to conclude that mercury does not enter into the composition of palladium. In Germany the investigation was taken up by Rose and Gehlen, and by Richter ; but none of these chemists succeeded in forming palladium artificially. Neither were the attempts of Trommsdorf and Klaproth atten- ded with better success. My own trials to obtain the results of Chenevix were not more fortunate. This uniform failure led the generality of chemists to suspend their judgment, and even to suspect that Mr Chenevix had allowed himself to be deceived. This naturally induced him to resume the subject, to exa- mine with more precision the mutual action of platinum and mercury, and to ascertain the circumstances upon which their union depends. These new experiments were sent to the Royal Society, and read at one of their meetings in January 1805. The week following Dr Wollaston read a paper on palladium, vindicating the conduct of the unknown discoverer, and assigning his reasons for believing that he had procured it from crude platina. He finished, by acknowledging that he him- self was the discoverer ; that he had separated it during a long continued series of experiments on crude platina ; and that the occurrence of several anomalous circum- stances had induced him to act as he did, that he might have leisure to examine and explain the whole of the phenomena, before he ventured to publish an account of them in his own name. This avowal of Dr Wollaston entirely destroyed the presumption which had induced Chenevix to under- take his original experiments ; namely, that palladium 1S8 MALLEABLE METALS. Book T. wf P latino, Phil, Trans. lSe>4. Dea- not succeed in obtaining it in a separate state ; but lie showed OSMIUM. 201 nrarkable properties, but they confounded it with iri- Chap. iv. dium. Osmium is separated from indium by the process described in the last Section, and obtained in the al- kaline solution, to which it communicates a yellow colour. When the alkaline solution is first formed, a pungen^ and peculiar smell is perceived, \\hich Four- eroy and Vauquelin compare to that of oxymuriatic acid. As this smell constitutes one of the most remark- able properties of the metallic oxide, Mr Tennant was induced by it to call the metal osmium. I. To obtain the oxide in a separate state, we have Kowob- only to mix sulphuric acid with the alkaline solution, and distil with a moderate heat. A colourless liquid comes over, consisting of the oxide dissolved in water. This liquid has a sweetish taste and a strong smell. It does not give a red colour to vegetable blues. The oxide of osmium may be obtained also in a more concentrated state by distilling the black powder from crude platina with nitre. With a degree of heat under redness, there sublimes into the neck of the retort a fluid apparently oily, but which on cooling concretes into a solid semi-transparent mass, soluble in water ; and the solution exhibits the same properties as that obtained by the preceding process. When mercury is shaken in either of these solutions, that the red colour which the precipitates of platinum sometimes assume, is owing to the presence of iridium. See his paper, Ann. de Cbim. xlviii. 153. Fourcroy and Vauqueiin confounded together the properties of osmium and iridium, ascribing both to one metal; to which they have jivcn the name of tienc. See Ann. J: Cbim. xlix. 177. and I. /. 202 MALLEABLE METALS. their peculiar smell ; and the osmium, reduced to the metallic state, forms an amalgam with the mer-. cury. By distilling the mercury from this amalgam, the osmium remains in a state of purity. Properties. It has a dark grey or blue colour, and the metallic lustre. When heated in the open air, it evaporates with the usual smell; but inclose vessels, when the oxidize- ment is prevented, it does not appear in the least vo- latile. When subjected to a strong white heat in a char- coal crucible, it did not melt nor undergo any apparent alteration. It, is not acted upon by any acid, not even the nitro- rouriatic, after exposure to heat ; but when heated with potash it combines with that alkali, and forms with it an orange yellow solution. Oxides. U* The facility with which osmium is oxidized when heated in the open air, or when fused with pot- ash, though it resists the action of acids, forms one of the singular characters of this metal. Jn these respects osmium differs from all other metallic bodies. The great volatility of this oxide, its peculiar smell, its solubility in water, its sweet taste, and the yellow colour which it assumes with potash, are not less ano- malous. Its solution stains the skin of a dark colour, which cannot be effaced. The infusion of galls immediately produces a purple colour, becoming soon after of a deep vivid blue. By this means a mixture of iridium and osmium may be easily detected. The solution of iri- 1 dium is not apparently altered by being mixed with the oxide of osmium ; but on adding an infusion of galls, the red colour of the first is instantly taken away, OSMIUM. 203 and soon after the purple and blue colour of the latter Chap. IV. appears. When alcohol or ether is mjxed with the solution of oxide of osmium in water, the colour becomes dark, the oxide is reduced, and the osmium precipitates in black films. This oxide appears to part with its oxygen to all the metals excepting gold and platinum. Silver being kept in a solution of it for some time, acquires a black co- lour ; but does not entirely deprive it of smell. Cop- per, tin, zinc, and phosphorus, quickly produce a black or grey powder, and deprive the solution of all smell, and of the power of turning galls of a blue colour. This black powder, which consists of the osmium in a metallic state and the oxide of the metal employed to precipitate it, may be dissolved in nitro-muriatic acid, and then becomes blue with infusion of galls. III. The action of the simple combustibles on os- mium has not been tried. IV. Neither do we know much of its combination Alloy*, with metals, It amalgamates with mercury. Heated with copper and with gold in a charcoal crucible, it melted with each of trjese metals, forming alloys which were quite malleable. These compounds were easily dissolved in nitro-muriatic acid, and, by distillation, afforded the oxide of osmium with the usual pro- perties *. * All the facts in this Section were ascertained by Mr Tennant. It was impossible to use the experiments of the French chemists, because they have confounded iridium and osmium. 204 Book I. Division f. MALLEABLE METALS, SECT. IX, OF COPPER. Properties of copper. I. IF we except gold and silver, copper seems to have been more early known than any other metal. In the first ages of the world, before the method of working iron was discovered, copper was the principal ingre- dient in all domestic utensils and instruments of war. Even during the Trojan war, as we learn from Homer, the combatants had no other armour but what was made of bronze, which is a mixture of copper and tin. The word copper is derived from the island of Cyprus, where it was first discovered, or at least wrought to any extent, by the Greeks. 1. This metal is of a fine red colour, and has a great deal of brilliancy. Its taste is styptic and nauseous ; and the hands, when rubbed for some time on it, ac- quire a peculiar and disagreeable odour. 2. Its hardness is 7*5. Its specific gravity varies according to its state. Lewis found the specific gravi- ty of the finest copper he could procure S'830*. Mr Hatchett found the finest granulated Swedish copper * Neuman's Chemistry, p. 61. Trans .17*4. vol. xxxiii. p. 114. Fahrenheit had found it 8-834. COPPER. 2*05 8*895*. It is probable that the specimens which have Chap. FV. been found of inferior gravity were not quite pure f. Cronstadt states the specific gravity of Japan copper at 9*000. 3. Its malleability is great : it may be hammered out into leaves so thin as to be blown about by the slight- est breeze. Its ductility is also considerable. Its te- nacity is such that a copper wire 0*078 inch in diame- ter is capable of supporting 302'26 Ibs. avoirdupois without breaking^:. 4. When heated to the temperature of 21 Wedge- wood, or, according to the calculation of Mortimer $, to 1450 Fahrenheit, it melts ; and if the heat be in- creased, it evaporates in visible fumes. While in fu- sion it appears on the surface of a bluish green, nearly like that of melted gold ||. When allowed to cool slowly, it assumes a crystalline form. The Abbe Mon- gez, to whom we owe many valuable experiments on the crystallization of metals, obtained it in quadran- gular pyramids, often inserted into one another. II. Copper is not altered by water : It is incapable of decomposing it even at a red heat, unless air have free access to it at the same time ; in that case the sur- * On the Alloys of GoU y p. 50. It would have been heavier had it been hammered or rolled. Bergman states the specific gravity of Swc dish copper at 9-3143. Of use. ii. 263. f The following are the results of Mr Hatchett's trials : Finest granulated Swedish copper, 8-895 Do. Swedish dollar do. - - 8-799 Do. sheet British do. - - - 8-785 Fine granulated British do. - 8-607 1 Sickengen, Ann. de dim. xxv. 9. \ Phil. Trans, xllv, 673. 8 Dr Lewis, Neunian's Chemistry, p. 61. 206 MALLEABLE METALS. Book I. Division I. Oxides, face of the metal Becomes oxidized. Every one must have remarked, that when water is kept in a copper vessel, a green crust of verdegris, as it is called, is form- ed on that part of the vessel which is in contact with the surface of the water* When copper is exposed to the air, its surface is gra- dually tarnished ; it becomes brown, and is at jiast co- vered with a dark green crust. This crust consists of oxide of copper combined with carbonic acid gas. At the common temperature of the air, this oxidizement of copper goes on but slowly ; but when a plate of me- tal is heated red hot, it is covered in a few minutes, xvith a crust of oxide, which separates spontaneously in small scales when the plate is allowed to cool. The copper plate contracts considerably on cooling, but the crust of oxide contracts but very little ; it is therefore broken to pieces and thrown off, when the plate con- tracts under it. Any quantity of this oxide may be ob- tained by heating a plate of copper and plunging it al- ternately in cold water. The scales fall down to the bottom of the water. When copper is kept heated be- low redness, its surface gradually assumes beautifully variegated shades of orange, yellow, and blue. Thin plates of it are used in this state to ornament children's toys. In a violent heat, or when copper is exposed to a stream of oxygen and hydrogen gas, the metal takes fire and burns with great brilliancy, emitting a lively green light of such intensity that the eye can scarcely bear the glare. The product is an oxide of copper. There are two oxides of copper at present known 5 and it does not appear that the metal is capable of be- ing exhibited in combination with more than two doses COPPER, 201 f oxygen. The protoxide is found native of a red co- Chap. lour, but when formed artificially it is a fane orange j but the feroxide is Hack, though in combination it assumes various shades of blue, green, and brown. 1. The protoxide of copper was first observed by Protoxide. Proust j but we are indebted to Mr Chenevix, who found it native in Cornwall, for the investigation of its properties. It may be prepared by mixing together 51'5 parts of black oxide of copper, aud 50 parts of copper reduced to a fine powder by precipitating it from muriatic acid by an iron plate. This mixture is to be triturated in a mortar, and put with muriatic acid into a well-stopped phial. Heat is disengaged, and almost all the copper is dissolved. When potash is dropt into this solution, the oxide of copper is precipitated orange. But the easiest process is to dissolve any quantity of copper in muriatic acid by means of heat. The green liquid thus obtained is to be put into a phial, together with some pieces of rolled copper, and the whole is to be corked up closely. The green colour gradually dis- appears ; the liquid becomes dark brown and opaque ; and a number of dirty white crystals, like grains of sand, are gradually deposited. When this liquid, or the crystals, are thrown into a solution of potash, the orange coloured oxide precipitates in abundance. This oxide is composed of 88*5 parts of copper and 11*5 oxygen*. It attracts oxygen with such avidity, that it can scarcely be dried without becoming bluish- green, at least on the surface j but when once dry, it retains its colour pretty well. Chercvix, Phil. Trans. 1801, p 227 208 MALLEABLE METALS. Book I. 2. The peroxide of copper is easily procured pur '_v from the scales which are formed upon the surface of red hot copper. These scales have a violet red colour^ owing to the presence of a little metallic copper upon their under surface ; but when kept for some time red hot in an open Vessel, they become black, and are then pure peroxide of copper. The same oxide may be ob- tained by dissolving copper in sulphuric or nitric acid, precipitating by means of pntash, and then heating the precipitate sufficiently to drive off any water which it may retain. The peroxide of copper is composed of 80 parts of copper and 20 of oxygen f. When mixed with some- what less than its own weight of copper in powder, and heated to redness, the whole is converted into prot- oxide. The oxides of copper are easily reduced to the me- tallic state when heated along with charcoal, oils, or other fatty bodies ; and even with some of the metals, especially zinc. Smb"sti" h **** Copper has never been combined artificially bles. with hydrogen or carbon ; but it combines readily with sulphur and phosphorus, and forms with them com- pounds called sulphur et and phosphuret of copper. Sulphuret. i. When equal parts of sulphur and copper are stra- tified alternately in a crucible, they melt and combine at a red heat. Sulphuret of copper, thus obtained, is a brittle mass, of a black or very deep blue grey colour, much more fusible than copper, and composed, accord- ing to the experiments of Mr Proust, of 78 parts of * Ann. de Ckil*. XXXli, COPPER, 209 coppef: and 22 of sulphur *. The same cotnpound may Chap. be formed by mixing copper filings and sulphur toge- ther, and making them into a paste with water, or even by merely mixing them together without any water, and allowing them to remain a sufficient time exposed to the air, as I have ascertained by experiment, If eight parts by weight of copper filings, mixed with three parts of flowers of sulphur, be put into a glass receiver, and placed upon burning coals, the mix- ture first melts, then a kind of explosion takes place ; it becomes red hot; and when taken from the fire, con- tinues to glow for some time like a live coal. If we now examine it, we find it converted into sulphuret of copper. This curious experiment was first made by the associated Dutch chemists, Dieman, Troostwyk, Nieuwland, Bondt, and Laurenburg, in 1793 f. They found that the combustion succeeds best when the sub- stances are mixed in the proportions mentioned, above ; that it succeeds equally, however pure and dry the sul- phur and copper be, and whatever air be present in the glass vessel, whether common air, or oxygen gas, or hydrogen, or azotic gas, or even when the receiver is filled with water or mercury. This experiment ha excited great attention, and has been very often repeat- ed $ because it is the only instance known of apparent combustion without the presence of oxygen. The dif- ferent attempts to explain it will be considered in a sue* ceeding chapter. 2. Mr Proust has shown that the sulphuret of cop- per is capable of combining with an additional dos^of P hurct * # Ann. de Cijim. I. \ Jour, de Mln. No. ii. 85. o 210 MALLEABLE METALS. Book I. Division 1 Phosphu- ret. sulphur, and of forming a new compound, which be called supersulphuret of copper. It is brittle, has a yellow colour, and a metallic lustre, and is found na- tive abundantly, being well known to mineralogists by the name of copper pyrites *. 3. Mr Pelletier formed phosphuret of copper by melt- ing together 16 parts of copper, 16 parts of phosphoric glass, and one part of charcoal f. Margraf was the first person who formed this phosphuret. His method was to distil phosphorus and oxide of copper together. It is formed most easily by projecting phosphorus into red hot copper. It is of a white colour ; and, accord- ing to Pelletier, is composed of 20 parts of phosphorus and 80 of copper t- This phosphuret is harder than iron. It is not ductile, and yet cannot easily be pulve- rised. Its specific gravity is 7*1220. It crystallizes in four-sided prisms J. It is much more fusible than copper. When exposed to the air, it loses its lustre, becomes black, falls to pieces; the copper is oxidated, and the phosphorus converted into phosphoric acid. When heated sufficiently, the phosphorus burns, and leaves the copper under the form of black scoriae ||. Sage has shown that this compound does not easily part with the whole of its phosphorus, though frequent- ly melted, but retains about a twelfth* In this state it may be considered as a sub-phosphuret. It is more fusible than copper, and has the hardness, the grain, * Jour, de Pbys. liii, 95, \ Ann. de Cbim. xiii.. 3. 1 Fourcroy, vi. 252. f Ann. dt Cbim. i. 74. $ Sage, Jour, de Pbyt, Xixviii. 468, and the colour of steel, and admits of an equally fine polish *. IV. Copper does not unite to azote. Muriatic acid, when assisted by heat, converts it into an oxide, with which it enters into combination. V. Copper is capable of combining with most of the Alloys with metals ; and some of its alloys are of very great uti- lity. 1. The alloy of gold and Copper is easily formed Gold, by melting the two metals together. This alloy is much used, because copper has the property of increa- sing the hardness of gold without injuring its colour. Indeed a little copper heightens the colour of gold with- out diminishing its ductility. This alloy is more fusible than gold, and is therefore used as a solder for that precious metal f. Copper increases likewise the hard- ness of gold. According to Muschenbroeck, the hard- ness of this alloy is a maximum when it is composed of seven parts of gold and one of copper f. Gold al- loyed with -j^th of pure copper by Mr Hatchett, was per- fectly ductile, and of a fine yellow colour, inclining to red. Its specific gravity was 17'157. This was be- low the mean. Hence the metals had suffered an ex- pansion. Their bulk before union was 2732, after union 2798. So that 916 T of gold and 83y of copper when united, instead of occupying the space of 1000, as would happen were there no expansion, become 1024 t. * Nicholson's Jour. ix. a68, t Waiserberg, i. ill. J Hatchet on the Alloys ofGold> p. 66. The gold was already al~ toyed with i-cj6th of copper ; the expansion, had the gold been pur 3 02 212 MALLEABLE METALS. Gold coin, sterling or standard gold, consists of pare gold alloyed with -rV tn f some other metal. The metal Gold coin. t i , f used is always either copper or silver, or a mixture ot both, as is most common in British coin. Now it ap- pears that when gold is made standard by a mixture of equal weights of silver and copper, that the expansion is greater than when the copper alone is used, though the specific gravity of gold alloyed with silver differs but little from the mean. The specific gravity of gold alloyed with T T T th of silver and ^th of copper was 17*344. The bulk of the metals before combination was 2700; after it 2767*. We learn from the expert- would have been 'greater. For the specific gravity of an alloy of H gold and one copper, (supposing the specific gravity of gold 19-3, of cop- per 8-9), should be by calculation 17-58. Its real specific gravity is only *7'I57- * The first guineas coined were made standard by silver, afterwards copper was added to make up for the deficiency of the alloy ; and as the proportion of the silver and copper varies, the specific gravity of our gold coin is various also. The specific gravity of gold made standard by silver is ..... 17*9/27 silver and copper 17*344 The following trials made by Mr Hatchett, will show the specific gra- vity of our coins in different reigns. Reign. Date. Specific gravity, CHARLES II. a five-guinea piece - - 1681 17-825. JAMES II. a two-guinea piece - - 1687 17*634. WILLIAM III. a five-guinea piece - - 1701 17710. GEORGE I. a quarter-guinea - 1718 16-894. GEORGE II. a guinea ... 1735 17*637. -- a two-guinea piece - - 1740 17-848, GEORGE III. one guinea * . . 1761 '7737. - one guinea ... 1766 17-655. onejuiaaa - 1774 COPPER, 213 tocnts of Mr Hatchett that our standard gold suffers less i cha P- r from friction than pure gold, or gold made standard by any other metal besides silver and copper ; and that the stamp is not so liable to be obliterated as in pure gold. It therefore answers better for coin. A pound of standard gold is coined into 444- guineas, 2. Platinum may be alloyed with copper by fusion, Platinum, but a strong heat is necessary. The alloy is ductile, hard, takes a fine polish, and is not liable to tarnish. This alloy has been employed with advantage for com- posing the mirrors of reflecting telescopes. The pla- tinum dilutes the colour of the copper very much, and even destroys it, unless it be used sparingly. For the ex- periments made upon it we are indebted to Dr Lewis *. Strauss has lately proposed a method of coating copper vessels with platinum instead of tin ; it consists in rub. blng an amalgam of platinum over the copper, and then exposing it to the proper heat f. Reign. Date. Sfeclfic gravity. CEOXGE III. one guinea - one guinea - one guinea - one guinea - .- one truinea one guinea ... five guineas ... ten half-guineas i j seven-shilling pieces { - || Supposing guineas, half-guineas, and seven shilling pieces, to be made from the same metal, there is reason to expect (in a given comparative sum of each) an increase of specific gravity in the smaller coins, as a natural consequence of rulling, punching, annealing, blanching, milling, and stamping ; the effects of which must become more evident in pro- portion to the number of the small pieces required to form a given sum of the larger coins. The average specific gravity of our gold coin, at the ptesent time, jnay probably be estimated at ifjtq. ). Commerce, p. 529. f Nicholson's Jour. it. 303. 1775 17-698. 1776 17-486. 777 17-750. 1782 17-201. 1^86 17-465. 1788 17-418. 1793 17712. 1801 17750. 1802 I7793. 214 MALLEABLE METALS. Book I. Division I. Silver. 3. Silver is easily alloyed with copper by fusion. The compound is harder and more sonorous than silver, and retains its white colour even when the proportion of copper exceeds one-half. The hardness is a maximum when the copper amounts to one-fifth of the silver. The Silver coin, standard or sterling silver of Britain, of which coin is made, is a compound of I2y silver and one copper. Its specific gravity after simple fusion is 10*200 *. By cal- culation it should be 10'35l. Hence it follows that the alloy expands, as is the case with gold when united to copper. The specific gravity of Paris standard sil- ver, composed of 137 parts silver and seven copper, ac- cording to Brisson, is 10*1752 ; but by hammering, it becomes as high as 10'3765. The French silver coin, at least during the old government, was not nearly so fine, being composed of 261 parts of silver and 27 of copper, or one part of copper alloyed with 9y of silver. Jts specific gravity, according to Brisson, was 10-0476 ; but after being coined, it became as high as 10*4077. The Austrian silver coin, according to Wasserberg, contains - T T \- of copper f. The silver coin of the an- * Cavallo's Nat. Pbil. ii. 76. Dr Shaw makes it 10*535 after ham- mering, as it appears from his table. Shaw's J3oyte, ii. 345. f Wasserberg, i. 155. The following table exhibits the composition of different European coins, according to my experiments. Alloy per Weigbt of Silver, that of cent. the Copper being I . --7'5- 12-5 - - - 8 11-5 -..9 ...... lo-i - - - 9'5 9'5 - - - 9'5 9'5 r 10-5 ------ 8j liS'S - - - - . 5'5 British - Dutch French - Austrian Sardinian Spanish - - COJPER,. 215 f dents was nearly pure, and appears not to have been Chap. \\ mixed with alloy. This seems to be the case also with coins of the East Indies ; at least a rupee which I ana- lysed contained only T * T part of copper ; a proportion so small that it can scarcely be supposed to have been added on purpose. A pound of standard silver is coin- ed into 62 shillings. 4. Mercury acts but feebly upon copper, and does not dissolve it while cold ; but if a small stream of melted copper be cautiously poured into mercury heated near- ly to the boiling point, the two metals combine and form a soft white amalgam *. Boyle pointed out the follow- ing method, which succeeds very well : triturate to- gether two parts of mercury, 2j parts of verdigris, and one part of common salt, with some acetous acid, and keep them for some time over a moderate fire, stirring them constantly, and supplying acid as it evaporates ; then wash the amalgam and pour it into a mould ; it is at first nearly fluid, but in a few hours it crystallizes and becomes quite solid f. This amalgam may be form- ed also by keeping plates of copper in a solution of mer- Alloy per Wrgfo of S the r, ilat the Coffer let Q \*g I. - - 1-6 The first column of this Table gives the supposed proportion of alloy In 100 parts of the respective coin; the second gives the weight of silver contained in each coin, on the supposition that the weight of the copper with which the silver is alloyed is always I. Nicholson's Jour. xiv. 409. * Lewis, Ncvmant Cutm. p. 65, f Shaw's Beyle, i. 343- 216 MALLEABLE METALS. v' CUr ^ * n n * tr * c ac "*' ^e plate * s soon i m P re g nate d with mercury. The amalgam of copper is of a white colour, and so soft at first that it takes the most delicate im- pressions ; but it soon becomes harder when exposed to the air. It is easily decomposed by heat ; the mercury evaporates, and leaves the copper. 5. All that is known respecting the combination of copper with palladium, rhodium, iridium, and osmium, has been mentioned in the preceding Sections. SECT. X. OF IRON. History. * I RON > tlie most abundant and most useful of all the metals, was neither known so early, nor wrought so easily, as gold, silver, and copper. For its discovery we must have recourse to the nations of the East, among whom, indeed, almost all the arts and sciences first sprung up. The writings of Moses (who was born a- bout 1635 years before Christ) furnish us with the am- plest proof at how early a period it was known in Egypt and Phoenicia. He mentions furnaces for work- ing iron*, ores from which it was extracted f; and tells us, that swords t, knives J, axes ||, and tools for cut- ting stones ^f, were then made of that metal. How many ages before the birth of Moses iron must have * Deut. iv. ao. f Ibid, viil 5. J Numb. xxxv. x6. J Levit. i. T;. |j Deut. xviii. 5. f Ibid, xxvii, Sf IRON. 21 1 been discovered in these countries, we may perhaps Chap. conceive, if we reflect, that the knowledge of iron was brought over from Phr jgia to Greece by the Dactyli *, who settled in Crete during the reign of Minos I. about Z431 years before Christ; yet during the Trojan war, which happened 200 years after that period, iron was in such high estimation, that Achilles proposed a ball of it as one of his prizes during the games which he celebrated in honour of Patroclus. At that period none of their weapons were formed of iron. Now if the Greeks in 200 years had made so little progress in an art which they learned from others, how long must it have taken the Egyptians, Phrygians, Chalybes, or whatever nation first discovered the art of working iron, to have made that progress in it which we find they had done in the days of Moses ? 1 . Iron is of a bluish white colour ; and when po- Propertiei lished, has a great deal of brilliancy. It has a styptic ofiron ' taste, and emits a smell when rubbed. 2. Its hardness is 9. Its specific gravity varies from 7'6 to T8f. 3. It is attracted by the magnet or loadstone, and is itself the substance which constitutes the loadstone. But when iron is perfectly pure, it retains the magnetic vir- tue for a very short time. * Hesiod, as quoted by Pliny, lib. vii. c. j 7. f Kirwan's Mia. ii. 155. Dr Shaw states the specific gravity of iron at 7*645. Shaw's Boyle, ii. 345. Brisson at 7-788. Mr Hatchett found a specimen 77o. On the Alloy t of Geld, p. 66. Swedenburgh states it at 7-817. According to Muschenbroeck, hammered iron softened by heat i of the specific gravity 7-600 ; the same hammered hot, becomes 7*7633 ; and the same hammered cold, becomes 7-875. Watserbtrg> i. 168. 218 MALLEABLE METALS. Book I. Division I. Combina- tion with oxygen. Decompo- ser water. 4. It is malleable in every temperature, and its mallea- bility increases in proportion as the temperature aug- ments ; but it cannot be hammered out nearly so thia as gold or silver, or even copper. Its ductility, how- ever, is more perfect ; for it may be dra\vn out into wire as line at least as a human hair. Its tenacity is such, that an iron wire, 0*018 of an inch in diameter, is capable of supporting 549*25 Ibs. avoirdupois without breaking *. 5. When heated to about 158 Wedgewood, as Sir George M'Kenzie has ascertained f, it melts. This temperature being nearly the highest to which it can be raised, it has been impossible to ascertain the point at which this melted metal begins to boil and to evaporate. Neither has the form of its crystals been examined: but it is well known that the texture of iron is fibrous ; that is, it appears when broken to be composed of a number of fibres or strings bundled together. II, When exposed to the air, its surface is soon tar- nished, and it is gradually changed into a brown or yel- low powder, well known under the name of rust. This change takes place more rapidly if the atmosphere be moist. It is occasioned by the gradual combination of the iron with the oxygen of the atmosphere, for which it has a very strong affinity. 1. When iron filings are kept in water, provided the temperature be not under 70, they are gradually con- verted into a black powder, while a quantity of hydro- gen gas is emitted. This is occasioned by the slow decomposition of the water. The iron combines with its oxygen, while the hydrogen makes its escape under the * Sickingen, Ann. dt Chim. xxv. 9, f Nicholson's 4to Jour- iv. 109. IRON. form of gas*. If the water be made to boil, it is de- Chap. IV composed much more speedily. Very perceptible bub- bles of hydrogen gas rise from the iron, and may be collected at the top of the vessel. This experiment may be made in a glass retort. The iron filings are to be put in first, and then the retort is to be completely filled with water, and its beak plunged into an open vessel of water. The retort is then to be made to boil by applying under it a lamp. If the steam of water be made to pass through a red hot iron tube, it is decomposed instantly. The oxygen combines with the iron, and the hydrogen gas passes through the tube, and may be collected in proper ves- sels. This is one of the easiest methods of procuring pure hydrogen gasf. 2. These facts are sufficient to show that iron has a Combus? strong affinity for oxygen, since it is capable of taking u it from air and water. It is capable also of taking fire and burning with great rapidity. Twist a small iron wire into the form of a cork-screw, by rolling it round a cylinder ; fix one end of it into a cork, and attach to the other a small bit of cotton thread dipt in melted tallow. Set fire to the cotton, and plunge it while burning into a jar filled with oxygen gas. The wire catches fire from the cotton and burns with great bril- liancy, emitting very vivid sparks in all directions. For this very splendid experiment we are indebted to Dr Ingenhousz. During this combustion the iron com- bines with oxygen, and is converted into an oxide. * This fact was known to Bergman (Opiuc. iii. 95.) and to Scliccle (on Fire, p. 180.) ; but it was first explained by Lavoisier. f Lavoisier and Meusnier, Mem, Par, 1781, p. 260,. MALLEABLE METALS; Book r. The number of oxides which iron is capable of pivision I. f , f forming has not yet been ascertained in a satistactory manner. Proust has proved that there are two very well characterised ; the first having usually a black colour, the second, considered at present as the peroxide, having a red colour. Thenard has endeavoured to prove that there are three oxides of iron, which he distin- guishes by the epithets white, green, and red*. But the difference between his first and second oxides, as far as he has pointed it out, is not sufficient to charac- terise each as containing a peculiar quantity of oxygen. Accordingly, his opinion has been called in question by Mr Darso, who has endeavoured to prove, that the green, colour of Thenard's second oxide is owing to the presence of hydrogen, while he insinuates that the sup- posed white oxide always retains a portion of acid, and owes its colour to that acidf. Though Mr Darso's experiments are not sufficiency decisive to establish his own opinion, they serve to shake our confidence in the conclusions of Thenard, which cannot be admitted till they be supported by more exact experiments than those which he has adduced. ox- 3. The black oxide of iron may be obtained by four different processes : 1. By keeping iron filings a suffi- cient time in water at the temperature of 70. The oxide thus formed is a black powder, formerly much used in medicine under the name of martial ethiops, and seems to have been first examined by Lemeri J. 2. By * Ann. de Cbim. Ivi. 59. f Nicholson's Jour- xvii. 268. t The best process is that of De Roover. He exposes a paste formed of iron filings and water to the open air in a stoneware vessel ; the past$ becomes hot, and the water disappears. It is then moistened again, and JROfl; 221 ttiaking steam pass through a red hot iron rube. The Chap, iv^ iron is changed into a brilliant black brittle substance, which xvhen pounded assumes the appearance of martial cthiops. This experiment was first made by Lavoisier*. 3. By burning iron wire in oxygen gas. The wire as it burns is melted, and falls in drops to the bottom of the vessel, which ought to be covered with water, and to be of copper. These metallic drops are brittle, very hard, and blackish, but retain the metallic lustre. They were examined by Lavoisier, and found precisely the same with martial ethiopsf. They owe their lustre to the fusion which they underwent. 4. By dissolving iron in sulphuric acid^ and pouring potash into the so- lution. A green powder falls to the bottom, which as- sumes the appearance of martial ethiops when dried quickly in close vessels. This oxide of iron, however formed, is always composed of 73 parts of iron and 21 of oxygen, as Lavoisier and Proust have demon stratedj. It is attracted by the magnet, and is often itself mag- netic $. It is capable of crystallizing, and is often native in that state. 4. The peroxide or red oxide of iron may be formed Peroxide, by keeping iron filings red hot in an open vessel, and agitating them constantly till they are converted into a dark red powder. This oxide was formerly called the process repeated till the whole is oxidized. The mass is then pounded, and the powder is heated in an iron vessel till it is perfectly dry, stirring it constantly. See Ann, d Cblm, xliv. 329. * Mem. Par. 1781, p. 269. The iron is converted into a substance not unlike specular iron ore. f Arai.de Cbim. i. 19. J Ibid. i. 19. and x?iii, 8;. $ Bergman 4 iii.ica. 222 MALLEABlE METALS. Book I. sdffron of Mars. Common rust of iron is merely thifc ... y ' oxide combined with carbonic acid gas. The red oxide may be obtained also by exposing for a long time a di- luted solution of iron in sulphuric acid to the atmos- phere, and then dropping into it an alkali, by which the oxide is precipitated. This oxide is also found native in great abundance. Proust proved it to be composed of 48 parts of oxygen and 52 of iron*. Consequently the black oxide, when converted into red oxide, absorbs 0*40 of oxygen ; or, which is the same thing, the red oxide is composed of (36*5 parts of black oxide and 33*5 parts of oxygen. One hundred parts of iron, when converted into a black oxide, absorb 37 parts of oxygen, and the oxide weighs 137 ; when converted into per- oxide, it absorbs 55 additional parts of oxygen, and the oxide weighs 192. The peroxide cannot be completely decomposed by aeat; but when heated along with its own weight of iron filings, the whole, as Vauquelin first observed, is converted into black oxide f. * Ann.de Cbim. xxiii. 87. f Mr Chenevix, in his excellent paper on the animates of copper, has given it as his opinion, that iron is susceptible of four different degrees of oxidizement. The first oxide, according to him, is of a tvbitt colour, the second is green, the third black t and the fourth red. His opinion i* chiefly founded upon the different colours which minerals containing iron are observed to possess; namely, white (or colourless), green, black t red t brown, and blue. But it is more likely that these different colours are the results of the various combinations into which rhe two oxides of iron enter. Difference ef colour is a very uncertain mark of difference in the proportion of oxygen combined with a metal. The black oxide of iron dissolves in acids without effervescence, and therefore without any sensible dbange.in the proportion of it* oxygen ; yet with potash it IROJT. 223 The peroxide of iron is not magnetic. It is con- , cha P' 1V \ verted into black oxide by sulphureted hydrogen gas and many other substances ; which deprive it of the second dose of oxygen, for which they have a stronger affinity, though they are incapable of decomposing the black oxide. 5. Among the ores of iron there occurs an oxide Protoxide, which is by no means uncommon, and which appears to contain only Jjalfthz oxygen of the black oxide. It has the metallic lustre, the colour of iron, but darker, and is brittle and magnetic. I have attempted in vain to form it artificially from iron, always obtaining the common black oxide above described. This native oxide I consider as the real protoxide of iron. The- nard's white oxide is, I presume, the black oxide dis- guised by the presence of foreign matter. If that philosopher succeeds in establishing the existence of his green oxide, the reality of which is still doubtful, we shall be acquainted with four oxides of iron ; namely, the protoxide, the black oxide, the green oxide, and the red oxide. Cutting instruments of steel, after being finished, are Tempering hardened by heating them to a cherry red, and then plunging them into a cold liquid. After this harden- ing, it is absolutely necessary to soften them a little, or jives uniformly a greenish-coloured precipitate, which becomes deeper and deeper coloured when exposed to the light ; and no difference is ob- servable when the experiments are performed in vatuo, or in a close ve&- el under water. The same oxide yields with phosphoric acid a white precipitate, which becomes blue when dried in the open air; and with prussic acid, a white precipitate, which retains its colour as long as the contact of air is withheld 224f MALLEABtfc METAL^? Book I. to temper them as it is called, in order to obtain a fine < and durable edge. This is done by heating them tilF some particular colour appear on their surface. The usual way is to keep them in oil, heated to a particular temperature, till the requisite colours appear. Now these colours follow one another in regular succession ac- cording to the temperature. Between 430 and 450, the instrument assumes a very pale yellowish tinge ; at 460, the colour is a straw yellow, and the instru- ment has the usual temper of pen-knives, razors, and other fine edge tools. The colour gradually deepens as the temperature rises higher, and at 500 becomes a bright brownish metallic yellow. As the heat in- creases, the surface is successively yellow, brown, red, and purple, to 580, when it becomes of a uniform deep blue, like that of watch-springs*. The blue gra- dually weakens to a water colour, which is the last shade distinguishable before the instrument becomes red hotf. These different shades of colour are supposed to be owing to the combination of the metal with oxy- gen, and to indicate a succession of oxides ; but the hypothesis is unsupported by proof, and is unnecessary, because the colours might be equally well explained by supposing the coat of oxide gradually to increase in thickness. The fact that the colours appear while the iron is under the surface of oil, a liquid which readily decomposes the oxides of iron, is scarcely consistent with the supposition that the colours are owing to oxidizement. * See the curious experiments of Mr Stoddart, as related by Mr Ni- cholson. Nicholson*! Quarto Jour. iv. 129. f Lewis, Nwmant Cbem, p. 79. 225 III. Iron is capable of combining with all the simple Chap, iv combustible bodies. 1. Hydrogen, indeed, has never been united to it in Union witL a. solid state ; but when hydrogen gas is obtained by the [ uatt solution of iron filings in diluted sulphuric acid, it car- ries along with it a little of the iron, which is gradu- ally deposited in the form of a brown powder on the sides of the jars in which the hydrogen gas is confiaed. With carbon, phosphorus, and sulphur, iron forms com- pounds known by the name of carburet, phosphuret, and sulphur et of iron. 2. Carburet of iron is found native, and has been Carburei long known under the names of plumbago and Hack lead. It is of a dark iron grey or blue colour, and has something of a metallic lustre. It has a greasy feel, is soft, and blackens the fingers, or any other substance to which it is applied. It is found in many parts of the world, especially in Britain*, where it is manu- factured into pencils. It is not affected by the most violent heat as long as air is excluded, nor is it in the least altered by simple exposure to the air or to water. A moderate heat produces no effect upon it, and occa- sions but little change in its bulk. It is used, in conse- quence, in making the crucibles called black lead* It was long supposed to be incombustible. But Mr Quist published a set of experiments in the Swedish Trans- actions for 1754, from which it appeared, that when plumbago was exposed to a strong heat in a scorifying dish, under a muffle, it yielded sulphureous flowers, and was all wasted away except from ^th to ^th ; which * The chief mines v at Kerwitk in Cumberland, r<>i. L p 226 MALLEABLE METALS. Book I. residuum, according to him, was a mixture of iron anci _ . y tin*. Dr Lewis repeated the experiment. The black lead gradually wasted away on the surface precisely like charcoal, and left behind it -^th part of a dark brown matter, chiefly attracted by the magnet. This result led Dr Lewis to compare plumbago and char- coal with each other, and to consider them as analo- gous substances f. The experiments of Dr Lewis were carried much farther by Scheele, who published a dis- sertation on it in 1779, He found that none of the acids tried had any effect upon it ; that it reduced li- tharge, and other metallic oxides,, precisely as charcoal; that it detonated with nitre, emitted abundance of car- bonic acid j and that 10 parts of nitre were necessary to consume it completely, and in that case it left only a little- oxide of iron J. The experiments of Scheele were confirmed and elucidated by those of Pelletier, and of Vandermonde, Monge and Berthollet, who ex- posed it in glass jars filled with oxygen gas to the ac- tion of a powerful burning-glass. Nine-tenths of it were consumed and converted into carbonic acid ; the remainder was iron. Hence they concluded that plum- bago is a compound of 90 carbon 10 iron 100 It is probable that the portion of iron contained in plumbago is considerably less than this. In a recem * Mr Quist, in fact, used molybdena instead of plumbago in his expe- riments; hence the anomalous result which he obtained. ] tfcL Conttxerte, p. 336. \ ScheelijY Of use, ii. 10. IRON. experiment made by Messrs Allen and Pepys, 100 parts , cha P' IV ; of .plumbago, burnt in oxygen gas, left only five parts of oxide of iron *. Plumbago is formed artificially in a variety of pro- cesses, especially in iron works. 3. Phosphuret of iron may be formed by fusing in Phosphuret, a crucible 16 parts of phosphoric glass, 16 parts of iron, and half a part of charcoal powder. It is mag. netic, very brittle, and appears white when broken. When exposed to a strong heat, it melts, and the phos- phorus is dissipated f. It may be formed also by melt- ing together equal parts of phosphoric glass and iron filings. Part of the iron combines with the oxygen of the phosphoric glass, and is vitrified ; the rest form* the phosphuret, which sinks to the bottom of the cru- cible. It may be formed also by dropping small bits of phosphorus into iron filings heated red hot J. The proportions of the ingredients of this phosphuret have not yet been determined. It was first discovered and examined by Bergman, who took it for a new metal, and gave it the name of siderum. There is a particular kind of iron known by the History of name of cold short iron, because it is brittle when cold, lts f 1S though it be malleable when hot. Bergman was em- ployed at Upsal in examining the cause of this proper- ty, while Meyer || was occupied at Stetin with th * On the quantity of Carbon in Carlor.ic Acid, PhiL Trans. 1 807. f Pelletier, Ann. de Cbim. i. 105. f Id. Ibid. xiii. 113. Op use. iii. 109. || Scbr'ftet far ~Berlin:r Gtitllscl}. Naturf, Frtunde, 1780, ii. 334, and iij- 22B MALLEABLE METALS. Same * nves % at i n J and both of tjletn discovered, nearly at the same time, that by means of sulphuric acid, 2 white powder could be separated from this kind of iron, which by the usual process they converted into a metal of a dark steel grey, exceedingly brittle, and not very soluble in acids. Its specific gravity was 6*700 ; it was not so fusible as copper; and when combined with iron rendered it cold short. Both of them concluded that this substance was a new metal. Bergman gave it the name of siderum, and Meyer of kydrosiderum. But fclaproth soon after, recollecting that the salt composed of phosphoric acid and iron bore a great resemblance to the white powder obtained from cold short iron, sus- pected the presence of phosphorus in this new me- tal. To decide the point, he combined phosphoric acid and iron, and obtained, by heating it in a crucible along with charcoal powder *, a substance exactly re- sembling the new metal f. Meyer, when Klaproth communicated to him this discovery, informed him that he had already satisfied himself, by a more accu- rate examination, that siderum contained phosphoric acid f. Soon after this, Scheele actually decomposed the white powder obtained from cold short iron, and thereby demonstrated that it is composed of phosphoric acid and iron . The siderum of Bergman, however, fs composed of phosphorus and iron, or it is phosphu* * Thi* process in chemistry is called nductlor, f Crell's Annals, 1784. i. 390. t Ibid. 195. $ Crell,i, nz, Bug.- Trans. ret of iron ; the phosphor. 'c acid being deprived of J<: oxygen during the reduction*. 4. Suiphuret of iron may be formed bv n. gather in a crucible equi.l parts of iron fiii:i',j> nn.. dered sulphur. It is of a blade, or ver, lour, brittle, and remarkably haul. \Vi-t:, red powder, and moistened with water, the sulphur i dually converted into sulphuric acid by a gen, while at the same time UK iron is oxLrzf.d. same compound may be formed by mixing together three parts (by weight) of iron filings, and one part of powdered sulphur, and putting the mixture in a glass vessel upon burning coals. This mixture, as the Dutch chemists first ascertained, melts, and burns without the presence of air, just as copper filings and sulphur, though not with such brilliancy t- -But the combus- tion, as I have observed, is remarkably brilliant, and even accompanied by an explosion, if a considerable mixture of iron filings and sulphur be melted togelher in a covered cracible. It continues much longer than that of copper and sulphur. If equal quantities of iron filings and sulphur be mix- ed together, and formed into a paste with water, the sulphur decomposes the water, and absorbs oxygen so rapidly that the mixture sometimes takes fire, even though it be burred under ground. Tiiis phenomenon was first discovered by Lemeri ; and it was considered * Rmman has sK >wn th.it the brittleness and bad qualities of cold short may be removo ' by h at.ng it strongly with lime>t"ne, and with this th. i xperiments o Lr.avasietir correspond- See Ann. de Qkim. zliL r. dt Min. N ' :! !. 230 Book I. Division I. Supersul- phuret. MALLEABLE "METALS. affording an explanation of the origin of vol- canoes *. From the experiments of Proust it appears that 100 parts of iron unite by fusion to 60 of sulphur. Hence the sulphuret of iron is composed of 62'5 iron 37*5 sulphur 100-Of. Mr Hatchett has lately discovered that this sulphu- ret exists native in considerable quantities, and that it had been long known to mineralogists under the name of magnetic pyrites. Its colour is that of bronze. It has a metallic lustre ; but its powder is blackish grey. Its specific gravity is 4'518. It strikes fire with steel, and easily melts when heated. He found it composed of 63 iron and 37 sulphur, which agrees almost exactly with the analysis of Proust. He has made it probable that the iron is not altogether in the metallic state, but contains about T ' T part of its weight of oxygen J. This sulphuret dissolves readily in sulphuric and muriatic acids, emitting abundance of sulphureted hy- drogen. When heated with nitric acid, a considerable portion of the sulphur is separated . 5. Iron is capable of combining with an additional dose of sulphur, and of forming a new compound, * When this experiment was repeated by Bucquet, it did not succeed, Fourcroy's Systeme ties Connais* Cbim, vi. 171. f Jour. Je Pbys. liii. 89. i Hatchett's Analysis of Magnttical Pyrites, Pbil. Trans. 1804. Hatchett, Ibid. 231 which may be called supersulpluret of iron. This^com- Chap. IV. pound is found native in great abundance, and has been long known by the name of pyrites. This substance is of a yellow colour, and has the metallic lustre. It is brittle, and sufficiently hard to strike ire with steel. Its specific gravity is about 4*5. It usually crystalizes in cubes. When heated it is decomposed. In the open air the sulphur takes fire : ia close vessels filled with charcoal, part of the sulphur is volatilized ; and a black substance remains, retaining the original form of the mineral, but falling to powder on the slightest touch. Mr Proust has demonstrated that this black substance is common sulphuret of iron. Pyrites, according to him, when thus treated, gives out 0*20 parts of sulphur, and 0'80 parts of sulphuret remain behind *. Hence pyrites is composed of 80 sulphuret of iron 20 sulphur 100 But this method is not susceptible of great accuracy. Mr Hatchett has lately subjected various specimens of pyrites to analysis with that precision for which he is distinguished. The following Table exhibits a view of the results which he obtained f : * Jour, de Phyt. liii. 89. | Hatchett, Phil. Trais. 1834. MALLEABLE METALS. Bock r. pjvision I. 1st Pyrites. Specific gravity. Constituents. Iron, 47-85 Sulphur. Total. In dodecahedrons 4-830 5215 100 2d Striated cubes 47-50 52*50 100 sd Smooth cubes 4'831 4T30 46*40 45-^fi 512-70 53*60 54-34 100 4th Radiated 4'6Q8 100 5th Smaller do. 4-175 100 From this table we learn, that the regularly crystal- lized pyrites contains least sulphur, and the striated most; but the greatest difference is only 2'19fier cent. Common sulphuret of iron is not only attracted by the magnet, but may be itself converted into a magnet by the usual methods; but pyrites is not in the least obedient to the magnet, neither is it susceptible of the magnetic virtues *. It has been long known that pure iron is not suscep- tible of retaining the properties of a magnet ; but steel, when once magnetized, continues permanently magnetic. Now steel, as we shall see immediately, is a combina- Magnets, tnmpound? tion of iron and carbon. When the proportion of carbon united to iron is increased to a certain proportion, as in plumbago, the iron loses the property of being acted on by the magnet. The addition of a certain por- tion of sulphur likewise renders iron susceptible of Becoming a permanent magnet. The sulphur may of iron tfrtchctt, PM. Trans, 1804. IRON. 233 amount to 46 per cent, without destroying this property ; , cha P- iv r. but when it is increased to 52 per cent, the magnetism vanishes completely. Iron may be made permanently magnetic also when united to phosphorus j but whether the magnetism disappears when the proportion of phos- phorus is increased, has not been ascertained. Thus it appears that pure iron is not susceptible of And aw permanent magnetism. United to a portion of carbon, tamprppot* it forms a compound more or less brittle, soluble in simple coal, muriatic acid, and susceptible of magnetic impregna- tion. Saturated with carbon, it becomes brittle, inso- luble in muriatic acid, and destitute of magnetic pro. perties. Iron, united to a portion of sulphur, forms a brittle compound, soluble in muriatic acid, and susceptible of magnetic impregnation. Saturated with sulphur, the compound becomes brittle, insoluble in muriatic acid, and destitute of magnetic properties. Iron, united to phosphorus, is brittle, and susceptible of magnetic impregnation in a great degree, and in all probability, by saturation, would lose its magnetic pro- perties altogether. For these facts, which are of the utmost importance, we are indebted to Mr Hatchett, who was led to the discovery of them by his experiments on magnetic py- rites. " Speaking generally of the carburets, sulphu- rets, and phosphurets of iron, I have no doubt," says this sagacious philosopher, " but that, by accurate ex- periments, we shall find that a certain proportion of the ingredients of each constitutes a maximum in the mag- netical power of these three bodies. When this max- imum has been ascertained, it would be proper to com- pare the relative magnetical power of steel (which hi- 5*4 MALLEABLE METALS. Book T. therto has alone been employed to form artificial IS vision I. . * v_ y- nets) with that of sulphuret and phospnuret or iron ; each being first examined in the form of a single mass or bar of equal weight, and afterwards in the state of compound magnets, formed like the large horse- shoe magnets, by the separate arrangement of an equal num- ber of bars of the same substance in a box of brass. ** The effects of the above compound magnets should then be tried against others, composed of bars of the three different substances, various in number, and in the mode of arrangement ; and lastly, it would be in- teresting to make a series of experiments on chemical compounds, formed by uniting different proportions of carbon, sulphur, and phosphorus, with one and the same mass of iron. These quadruple compounds, which, ac- cording to the modern chemical nomenclature, may be called carburo-sulphuro phosphurets, or phosphuro-sul- phuro carburets, &.c. of iron, are as yet unknown as to their chemical properties, and may also, by the investi* gation of their magnetical properties, afford some cu- rious results. At any rate, an unexplored field of ex- tensive research appears to be opened, which poss bly may furnish important additions to the history of mag- netism ; a branch of science which of late years has been but little augmented, and which, amidst the present ra- pid progress of human knowledge, remains immersed in considerable obscurity." Varieties of 6 * There are a great many varieties of iron, which >" artists distinguish by particular names ; but al of them may be reduced under one or other of the three fol- lowing classes Cast Iron y Wrought or Soft Iron, and Steel. x.Castlron, CAST IRON, or PIG IRON, is the name of the metal IROK. . 235 when first extracted from its ores. The ores from which Chap. iron is usually obtained are composed of oxide of iron inc , and adds to the mix. * Pill. Com. p, 534, and 551. f Wanerberg, i. 156. \ Jour, de P&yt. 1788. (j Ann, de Cbim. xJiii. 47. IRON. . 49 ture a solution of iron in muriatic acid. By kneading Chap. IV. this mixture, and heating it, the iron and mercury which combine together gradually assume the metallic lustre *. 5. Iron may be united to copper by fusion, but not Copper, without considerable difficulty. The alloy has been applied to no use. It is of a grey colour, has but little ductility, and is much less fusible than copper. The- nard has ascertained, that it is attracted by the magnet, even when the iron constitutes only ^th of the alloyf. Mr Levavasseur has published some observations,which render it probable that the variety of iron called lot short iron, because it is brittle when red hot, sometimes owes its peculiarities to the presence of copper. This variety possesses a greater degree of tenacity than com- mon iron, and therefore answers better for some pur- poses. It may be hammered when white hot. As soon as it cools, so far as to assume a brown colour, the forging must be stopt till it becomes of an obscure cherry red, and then it may be continued till the iron is quite cold J. Pill. Mag. xiii. 416. f AM. dt Clim. 1. BookL Division I, MALLEABLE METALS, i SECT. XL OF NICKEL. I. THERE is found in different parts of Germany a, heavy mineral of a reddish brown colour, not unlike copper. When exposed to the air, it gradually loses its lustre, becomes at first brownish, and is at last co- vered with green spots. It was at first taken for an ore of copper ; but as none of that metal can be ex- tracted from it, the miners gave it the came of Kupfer- Bickel t or " false copper." Hierne, who may be con- sidered as the father of the Swedish chemists, is the first person who mentions this mineral. He gives a description of it in a book published by him in 1604, on the art of detecting metals. It was generally con- sidered by mineralogists as an ore of copper, till it was examined by the celebrated Cronstedt. He con- cluded from his experiments, which were published in the Stockholm Transactions for 1751 and 1754, that it contained a new metal, to which he gave the name of nickel. This opinion was embraced by all the Swedes, and indeed by the greater number of chemical philosophers. Some, however, particularly Sage and Monnet, affirm- ed that it contained no new metal, but merely a com- pound of various known metals, which could be sepa. rated from each other by the usual processes. These assertions induced Bergman to undertake a very labo- rious course of experiments, in order if possible to ob- NICKEL. 251 tain nickel in a state of purity ; for Cronstedt had not Chap. IV. been able to separate a quantity of arsenic, cobalt, and iron, which adhered to it with much obstinacy. These experiments, which were published in I*n5*, fully confirmed the conclusions of Cronstedt. Bergman has shown that nickel possesses peculiar properties ; and that it can neither be reduced to any other metal, nor formed artificially by any combination of metals. It must therefore be considered as a peculiar metal. It may possibly be a compound, and so may likewise many other metals ; but we must admit every thing to be a peculiar body which has peculiar properties, and we must admit every body to be simple till some proof be actually produced that it is a compound ; otherwise we forsake the road of science, and get into the regions of fancy and romance. Nickel is rather a scarce mineral, and it occurs al- ways in combination with several other metals, from which it is exceedingly difficult to separate it. These metals disguise its properties, and account in some mea- sure for the hesitation with which it was admitted as a peculiar metal. Since the great improvements that have been introduced into the art of analysing minerals, chemists of eminence have bestowed much pains upon this metal, and a variety of processes have been pub- lished for procuring it in a state of purity. For the brittle metal that is sold under the name of nickel con- tains abundance of iron and arsenic, and some cobalt, copper, and bismuth. The first set of experiments, af- ter those of Bergman, made expressly to purify nickel, * Bergman, ii. 13 1, 52 MALLEABLE METALS. Book I. are those of the School of Mines of Paris, of which i v * Fourcroy has published an abstract *. Their method was tedious and incomplete. Since the publication of these experiments, no less than six other processes have been proposed by chemists, all. of them ingenious, and attended each with peculiar advantages and inconve- niences f. properties. I. Nickel, when as pure as possible, is of a fine white colour resembling silver ; and, like that metal, it leaves a white trace when rubbed upon the polished surface of a hard stone . Its hardness is 8^, so that it is rather softer than iron. Its specific gravity, according to Richter, after being melted, is 8 '279 ; but when hammered, it becomes 8-666 . It is malleable both cold and hot ; and may without difficulty be hammered out into plates not exceeding the hundredth part of an inch in thickness || . It is attracted by the magnet at least as strongly as iron. Like that metal, it may be converted into a mag- net; and in that state points to the north when freely suspended precisely as a common magnetic needle ^f . * Discourt Preliminatrf, p. 117* f Mr Philips published a process in Phil. Mag. xvi. 314 ; Proust ano- ther in Jwr. de Phys. Ivii. 169; Thenard another, in Ann.de r bim. 1. 117 ; Bucholz another, in Gehlen's Jour. ii. a8a, and iii. aoi; Richter a fifth, Ibid. iii. 244; and Proust a sixth, Ann. de Cbim. he 275. These processes will come under our consideration in a subsequent part of this Work. It is to Richter that we are indebted for the most precise ac- count of the properties of the metal. | Fourcroy, Discourt Prcliminaire, p. 117. Gehlen's Jour. iii. 35*. II Richter, Ibid. ^ Bergman, Klaproth, Fourcroj, Richter, &c. Mr Chenevix had announced a method of procuring nickel which was not magnetic ; but 233 It requires for fusion a temperature at least equal to Chap, i v, 160 Wedgewood *. It has not hitherto been crystal- lized. It is not altered by exposure to the air, nor by keep- ing it under water f. II. Nickel, when moderatly heated, is soon tarnish- Oxide* ed ; and if in powder, it is even converted into an ox- ide ; but a strong heat reduces it again to the metallic state. For the oxides of nickel, like those of gold, are decomposed by heat J. We are at present acquainted with two oxides of Nickel ; the colour of the protox- ide is greenish, that of the peroxide black. 1. The protoxide is easily procured by means of ni- Pratoxids. trie acid. In that acid it dissolves with effervescence, and forms a fine grass coloured solution. Carbonate of potash throws it down of an apple green colour, and pure potash of a deeper green. When dried and expo- sed to a faint red heat, its colour darkens to olive green, or even to blackish grey. In this state it maybe considered as the protoxide of nickel nearly pure. By this treatment 100 parts of nickel are converted into 123 of oxide ||, of nearly 78 nickel 22 oxygen 100 fie afterwards ascertained, that it owed this peculiarity to the presence of arsenic. * Bergman, ii. 269. According to Richter, it .melting point is as high as that of manganese. f Richter, Ibid. J Ibid. p. 154. $ Olive green wa the colour in my trials. Richter obtained it grey- ish black. P Richter, fift 254 MALLIABLE METALS. Book t According to the experiments of Proust, the proportion Division I. _ .... . t \ i of oxygen which it contains is not quite so much. He obtained from 100 parts of nickel 125 or 126 of prot- oxide, indicating a compound of 80 nickel and 20 oxy- gen*. This oxide is tasteless, soluble in the acids, and forms with them a grass green solution. It is soluble also in ammonia, and the solution, according to Richter, is pale blue. Peroxide. 2. The peroxide of nickel was first examined bjr Thenard* It may be formed by causing a current of oxymuriatic acid to pass through water holding prot- oxide of nickel suspended in it ; a portion is dissolved, and the rest acquires a black colour. This oxide is soluble in ammonia as well as the last ; but the solu- tion is accompanied with effervescence, owing to the de- composition of a part of the ammonia by the combina- tion of its hydrogen with part of the oxygen of the ox- ide. A similar effervescence accompanies its solution in acids, occasioned by the separation of a portion of its oxygen in the state of gas. This oxide is soluble like- wise in ammonia f. The proportion of its oxygen has not been ascertained. Union with HI. Nickel has not been combined with| carbon nor combusti- hydrogen ; but it combines readily with sulphur and phosphorus. Sulphuret. Cronstedt found, that sulphuret of nickel may be ea* sily formed by fusion. The sulphuret which he ob- tained was yellow and hard, with small sparkling fa- cets; but the nickel which he employed was impure. # Ann. J< C&irn, Ix. 172. \ Thenard, Ann. Jt Ckim* I UJ. KICKEL. 255 Phosphuret of nickel may be formed either by fusing nickel along with phosphoric glass, or by dropping phosphorus into it while red hot. It is of a white co- lour ; and when broke, it exhibits the appearance of very slender prisms collected together. When heated, the phosphorus burns, and the metal is oxidated. It is composed of S3 parts of nickel and 17 of phosphorus *. The nickel, however, on which this experiment was made, was not pure. IV. Nickel is not acted upon by azote, nor does it combine with muriatic acid. V. The alloys of this metal are but very imperfectly Alloy* wIA known. ~ Mr Hatchett melted a mixture of 11 gold and one Gold, nickel, and obtained an alloy of the colour of fine brass. It was brittle, and broke with a coarse-grained earthy fracture. The specific gravity of the gold was 19' 172 ; of the nickel 7*8 ; that of the alloy 17*068. The bulk of the metals before fusion was 2792, after fusion 2812; Hence they suffered an expansion. Had their bulk be- fore fusion been 1000, after fusion it would have be- come 1007. When the proportion of nickel is dimi- nished, and copper substituted for it, the brittleness of the alloy gradually diminishes, and its colour approach- es to that of gold. The expansion, as was to be expect- ed, increases with the proportion of copper introduced f. With copper this metal is said to form a white, hard, other aie- brittle alloy, easily oxidized when exposed to the air : ul< * with iron it combines very readily, and forms an alloy whose properties have not been sufficiently examined ; * Pellctier, Ann. de Cbim. xiii. 135. f Hatchett on the Albjj of GtU, p. ar. 255 MALLEABLE METALS. Book I. with tin it forms a white, hard, brittle mass, which _ swells up when heated : with lead it does not combine without difficulty : with silver and mercury it refuses to unite : its combination with platinum has not been tried*. But as all these trials were made with impure nick- el, little dependance can be placed upon their precision* SECT. XII. OF NICCOLANUM. 1 HO UGH this metal, announced some years ago by Richter, has not hitherto been examined nor recogni- zed by other chemists ; and though Richter does not appear quite satisfied with respect to its peculiar nature j yet as the properties which he pointed out seem to be peculiar, and as it may throw light on the composition of the ores of nickel hitherto but imperfectly analysed ; it ought not to be omitted in this place. Richter gave it the name of niccolanum y because it always accompa- nies nickel in the ores of that metal f. He had been occupied for a considerable time in pu- rifying nickel, and had collected about half a pound of the oxide of that metal, from which he expected at least a quarter of a pound of metallic nickel. But upon ex* * Cronstetft. { See XJchlea's /wder, mixed with charcoal, and exposed for 18 lours to the strongest heat of a porcelain furnace. By this means, under a blackish brown scoria > there was found a metallic button which weighed 2j ounces. It to this metallic button thus obtained that Richter [ave the name of niccolanu?7ti 1. Its colour is steel grey with a shade of red. It Properties exhibits a coarse granular structure when broken. It is slightly malleable when cold, but not when red hot. It is attracted by the magnet, but not so powerfully as nickel, though (according to Ritter f) more powerful- ly than cobalt. Its specific gravity after fusion is 8*55 when hammered 8*60* 2. It dissolves in nitric acid more readily than nick- el. The solution has a blackish green colour ; and^ when concentrated, gelatinizes. When the acid is dri- ven off, a blackish powder remains, which is the per- oxide of niccolanum. 3. This oxide is insoluble in nitric acid, unless some sugar or alcohol be added to the mixture. It dissolves in muriatic acid, while oxymuriatic acid exhalesi The solution is dark green ; when evaporated to dryness, it assumes a red colour, but becomes again green as it at- tracts moisture from the atmosphere* % ' 4. The sulphate of niccolanum exhibits the same phenomena. 5. Carbonate of potash throws down niccolanum * Gehlon'j Jour, v. 394. > x. 258 MALLEABLE METALS, Book I. from its solutions of a pale blue colour ; pure potasfr- Division I. 4 v^-J of a dark greenish blue. Ammonia renders the solu- tion of niccolanum red, but occasions no precipitate. 6. There are two oxides of niccolanum ; the first is greenish blue, the second black. Neither of them is reducible per se\ The last does not combine, with acids *. Properties. SECT. XIII. OF TIN. J. 1 IN was known to the ancients in the most re- mote ages. The Phoenicians procured it from Spain f and from Britain, with which nations they carried on a very lucrative commerce. At how early a period they imported this metal we may easily conceive, if we recollect that it was in common use in the time of Moses J. 1. This metal has a fine white colour like silver; and when fresh, its brilliancy is very great. It has a slightly disagreeable taste, and emits a peculiar smell when rubbed. 2. Its hardness is 6 . Its specific gravity is 7*291 j after hammering, T299 If. 3. It is very malleable : tin leaf, or tinfoil as it is * Gehlen's Jour. iv. 393. f Pliny, lib. i v. cap. 34, and lib, xxxiv. cap. 47. | Numbers xxxi. 21. Kirwan's Miner, ii. 194, ^ Brisson. TI*. fcalled, is about -rg^ part of an inch thick, and It might CHap. IV. be beat out into leaves as thin again if such were want- ed for the purposes of art. Its ductility and tenacity are much inferior to that of any of the metals hitherto described. A tin wire .-5- i nc h in diameter is Capable of supporting a weight of 31 pounds only without breaking *. Tin is very flexible, and produces a re- markable crackling noise when bended. 4. When heated to the temperature of 442 f it melts but a very violent heat is necessary to cause it to eva- porate. When cooled slowly, it may be obtained crys- tallized in the form of a rhomboidal prism t. II. When exposed to the air it very soon loses ifs Oxides, lustre, and assumes a greyish white colour, but under- goes no farther change ; neither is it sensibly altered by being kept under cold water ; but when the steam of water is made to pass over red hot tin, it is decom- posed, the tin is oxidated, and hydrogen gas is evol ved. When tin is melted in an open vessel, its surface be- 4>omes very soon covered with a grey powder, which is an oxide of the metal. If the heat be continued, the colour of the powder gradually changes, and at last i: becomes yellow. When tin is heated very violently in an open vessel, it takes fire, and is converted into a fine white oxide, which may be obtained in crystals. Mr Proust has demonstrated, that tin is capable of combining with three different proportions of oxygen, and of forming three oxides ; the two last of which are * Muschenbroeck. f Crichton, Pkil. Mag. xv. 147. % Pajot, Jour, tie Pbys. xxxviii.JZ. j Bouillon La Grange, Ann. d: Cbim. xxxv. aoS. R2 60 MALLEABLE METALS, Beok I. usually distinguished, on account of their colour, by the Division I. v - y J names of the yellow and the white oxide \\ j though the first when pure has a grey colour, and a good deal of the metallic lustre. Grey oxide. 1. The grey oxide is formed when tin is exposed to a moderate beat for some time j but in that case it is never pure. It may, however, he obtained in a state of purity by the following method : Dissolve tin in muriatic acid, either by means of heat, or by adding a little nitric acid occasionally. When the solution is com- pleted, add to it an excess of potash ; a white powder falls, but is partly taken up again. But the remainder, on standing, assumes a dark grey colour, and even a metallic lustre ; this remainder is pure grey oxide of tin*. It is tasteless, readily soluble in acids, and gra- dually in potash ; and when united to other bodies, it ab- sorbs oxygen with great avidity. According to the ana- lysis of Proust, 100 parts of tin, when reduced to the state of grey oxide, combine with 25 of oxygen. Hence it is composed of SO tin 20 oxygen 100 Peroxide. 2. The peroxide may be obtained by heating tin in concentrated nitric acid. A violent effervescence en- sues, and the whole of the tin is converted into a white powder, which is deposited at the bottom of the vessel, It is composed of about 28 parts of oxygen and 72 of j! IbM. xxviii. 213. * See Proust, Ibid, and Berthollet, junior, Sfefi ) if, 457, TIW. tin. This oxide is not altered by exposure to the air. t Chap. IV It dissolves very readily in potash, and likewise in mu- riatic acid. 3. The existence of the third oxide, which is in fact Protoxide, a protoxide of tin, has been lately ascertained by Proust, though he has not succeeded in obtaining it in a sepa- rate state, nor in ascertaining the proportion of oxygen which it contains. The salt composed of muriatic acid, and the grey oxide of tin previously reduced to a dry mass, was fused in a retort and mixed with sulphur. The oxide of tin was divided into two parts. One 'por- tion sublimed in combination with the muriatic acid, in the state of peroxide of tin, another portion combined with sulphur, and formed the compound called aurum musivum or mosaic gold. Pelletier had demonstrated that the tin in this-compound is in the state of an oxide. It is obvious from the experiment of Proust, that it con- tains less oxygen than the grey oxide, as it must have resigned a portion of the oxygen which it originally con- tained, in order to convert the portion of tin which sub- limed into peroxide. This conclusion Mr Proust con- firmed by several additional experiments *. But no- thing farther is at present known respecting the pro- perties of this protoxide of tin. III. Tin combines with sulphur and phospho- TT " ?-sf wit , , combusti- rus ; but it has never been united to carbon nor hy. bles. drogen. 1. Sulphuret of tin may be formed by throwing bits Sulphuret. of sulphur upon the metal melted in a crucible, or by fusing the two ingredients together. It is brittle, hea- * Nicholson's Jour, lir. 39. MALLEABLE METALS. Book I. vier than tin, and not so fusible. It is of a bluish co- u / lour and lamellated structure, and is capable of crystal- lizing. According to Bergman, it is composed of 100 parts of tin and 20 of sulphur ; According to Pelletier, of 85 parts of tin and 15 of sulphur *. Proust's ana- lysis coincides with that of Bergman f. Sulphuret- 2. When equal parts of white oxide of tin and sul- jcd oxide. phur are mixed together, and heated gradually in a re- tort, some sulphur and sulphurous acid; are disengaged, and there remains a substance composed of 40 parts of sulphur and 60 of oxide of tin, formerly called aurum musivum, musicum, or mosaicum, and now sulphureted oxide of tin. It consists of beautiful gold coloured flakes, exceedingly light, which adhere to the skin. The process for making this substance was formerly very complicated. Pelletier first demonstrated its real composition, and was hence enabled to make many im- portant improvements in the manner of manufacturing it. Its nature has been still farther investigated by Proust, who has shown that the oxide in combining with the sulphur loses a portion of its oxygen, and is converted into protoxide. According to him it contains a smaller proportion of sulphur than was assigned by Pelletier. Neither nitric nor muriatic acids act upon it, but if nitromuriatic acid be boiled upon it, the mosaic gold is slowly converted into sulphate of tin, consisting of sul- phuric acid combined with the peroxide. It explodes violently when heated with twice its weight of nitre. * Ann. de Cbiat. xiii. 287. f Nicholson's Jwr. xiv. ? See his Memoir, Ann, de Cbim. xiii, 280. TIN. ft dissolves in liquid potash when assisted ty heat. The Chap, iv.^ solution is greenish. It appears from the experiments of Proust, that during this solution water is decom- posed, the oxygen of which converts the tin to a per- oxide, while its hydrogen combining with the sulphur forms sulphureted hydrogen, which unites with the per- oxide *. 3. Phosphuret of tin may be formed by melting in a crucible equal parts of filings of tin and phosphoric glass. Tin has a greater affinity for oxygen than phosphorus has. Part of the metal therefore combines with the oxygen of the glass during the fusion, and flies off in the state of an oxide, and the rest of the tin combines with the phosphorus. The phosphuret of tin may be cut with a knife ; it extends under the hammer, but sepa- rates in laminse. When newly cut, it has the colour of silver ; its filings resemble those of lead. When these filings are thrown on burning coals, the phospho- rus takes fire. This phosphuret may likewise be form- ed by dropping phosphorus gradually into melted tin. According to Pelletier, to whose experiments we are in- debted for the knowledge of all the phosphurets, it is composed of about 85 parts of tin and 15 of phospho- rus f. Margraf also formed this phosphuret, but he was ignorant of its composition. IV. Tin does not combine with azote nor muriatic acid ; though the last substance converts it into an oxide. V. Tin is capable of combining with most of the me- Alloys with * See Proust, Nicholson'i Jour. xiv. 43. f Ann, de Cbiif. xiii. 1 1 6. 264 MALLEABLE METALS, Book I* tals, and some of its alloys are much employed. The Division I. v ' ' greater number of them are brittle. The older metal- lurgists considered it as a property of tin to render other metals brittle. Hence they called it (liabolus me- tailor um *. 1. It unites readily with gold by fusion, and was supposed by the older chemists to have the property of communicating brittleness to the alloy in how small a portion soever it was united to the precious metal ; but later and more precise experiments have shown that this opinion was ill founded, The mistake was first removed by Mr Alchorne, in a set of experiments on this alloy published in the Philosophical Transac- tions for ITS 4 ; and these have been amply confirmed by the subsequent trials of Mr Hatchett. An alloy of 11 gold and one tin has a very pale whitish colour j brittle when thick ; but when cast thin, it bends easily, but breaks when passed between rollers. The frac- ture is fine grained, and has an earthy appearance. The specific gravity of this alloy was 4- 7*307. Tbe bulk of the two metals before fusion being reckoned 1000, after fusion, it was reduced to 981 ; so that the metals contract very considerably by uniting together f. When gold was made standard by equal parts of tin and cop- per, an alloy was obtained of a pale yellow colour, and brittle ; but when the tin amounted only to -^ of the whole, the alloy was perfectly ductile J. Indeed, from the experiments of Mr Alchorne, we learn^ that when gold is Alloyed with no more than T ' T th of tin, it retains its due- * See Etmuller's Clemit1r\, p. 332. I Hatchett OB the Alh^ of Gold, p. 3 ^ \ Hatchett, Ibid. *n; TIN. 265 tility sufficiently to be rolled and stamped in the usual Chap. IV. way. But Mr Tillet showed, as was indeed to have been expected, that when heated to redness, it falls to pieces, owing to the fusion of the tin. Both of these facts have been confirmed by the late experiments of Mr Bingley. He found that an alloy of gold with ^-th of tin, when annealed in a red heat, just visible by day- light, which is equal to 5 of Wedgewood, was quite ductile, and capable of being worked into any form ; but when heated to a cherry red, or to 10 Wedge- wood, blisters began to appear on the surface of the bar ; its edges curled up ; and at last it lost its conti- nuity, and fell into a dark-coloured mass, with little of the metallic lustre*. 2. From the experiments of Dr Lewis we learn, that Platinum, tin and platinum readily melt, and form an alloy which is brittle and dark coloured when the proportions of the two metals are equal, and continues so till the plati- num amounts only to th of the alloy ; after this the ductility and white colour increase as the proportion of platinum diminishes. When this alloy is kept, its sur- face gradually tarnishes and becomes yellow, but not so readily if it has been polished f. 3. The alloy of silver and tin is very brittle and SUvcr, hard. It was examined by Kraft and Muschenbroeck. According to them, one part of tin and four of silver form a compound as hard as bronze. The addition of more tin softens the alloy. It has a granular appear- ance, and is easily oxidized. According to Gellert, * Hatchctt on tbf Alloy of GoU, p, f fbilotofb. Commerce, p, jio, 266 MALLEABLE METALS. Book I. these metals contract in uniting*. Mr Hatchett found Division I. < Y that silver made standard by tin was brittle, and did not ring well f. Mercury, 4. Mercury dissolves tin very readily cold ; and these metals may be combined in any proportion by pouring mercury into melted tin. The amalgam of tin, when composed of three parts of mercury and one of tin, crys- tallizes in the form of cubes, according to Daubenton ; but, according to Sage, in grey brilliant square plates, thin towards the edges, and attached to each other, so that the cavities between them are polygonal. This alloy is used in silvering the backs of looking glasses. A sheet of tinfoil is spread upon a table, and mercury rubbed upon it with a hare's foot, till the two metals incorporate ; then a plate of glass is slid over it, and kept down with weights. The excess of mer- cury is driven oiF, and in a short time the tinfoil ad- heres to the glass and converts it into a mirror J. Copper. 5* Tin unites very readily with copper, and forms an alloy exceedingly useful for a great variety of pur- poses. Of this alloy cannons are made : bell metal, bronze, and the mirrors of telescopes, are formed of different proportions of the same metals. The addition of tin diminishes the ductility of copper, and increases its hardness, tenacity, fusibility, and sonorousness. The specific gravity of the alloy is greater than the mean density of the two metals. It appears from the experiments of Mr Briche, that this augmentation of * Mttatlurgic Cbtm. p. 140. f On the Alloys of Gold, p. 33. \ See Watson's Cbtm. Essays, p. 240. Dr Watson has rendered it probable that the art of forming mirrors by coating giass with a plate of metal, was known at least as early a$ the first century. TIN". sity increases with the tin ; and that the specific gravity, when the alloy contains 100 parts of copper and 16 of tin, is a maximum : it is 8'87. The specific gravity of equal parts of tin and copper is 8' 79, but it ought only to be 8 ; consequently the density is in- creased 0'79 *. In order to mix the two metals ex- actly, they ought to be kept a long time in fusion, and constantly stirred, otherwise the greater part of the cop- per will sink to the bottom, and the greater part of the tin rise to the surface ; and there will be formed two different alloys, one composed of a great proportion of copper combined with a small quantity of tin, the other of a great proportion of tin alloyed with a small quan- tity of copper. Bronze and the metal of cannons are composed of Gun metal* from 8 to 12 parts of tin combined with 100 parts of copper. This alloy is brittle, yellow, heavier than copper, and has much more tenacity ; it is much more fusible, and less liable to be altered by exposure to the air. It was this alloy which the ancients used for sharp-edged instruments before' the method of working iron was brought to perfection. The x aXK f of the Greeks, and perhaps the &s of the Romans, was no- thing else. Even their copper coins contain a mixture of tinf. The term brass is often applied to this alloy, though, in a strict sense, it means a compound of copper and zinc. Brass guns are made in no other part of Bri- tain except Woolwich. The proportion of tin va- nes from 8 to 12 to the 100 of copper; the purest cop- *//r.df Mi.An.v.88r. t Sec Dizc's Analysis, Jour, de Pbyt. 1790, 268 MALLEABLE METALS. pCr re ^ uirIn S tne most > and the coarsest the least. This alloy is more sonorous than iron ; hence brass guns give a much louder report than those made of cast iron *. Bell metal Bell metal is usually composed of three parts of copper and one part of tin. Its colour is greyish white; it is very hard, sonorous, and elastic. The greater part of the tin may be separated by melting the alloy, and then pouring a little water on it. The tin decom- poses the water, is oxidized* and thrown upon the sur- face. According to Swedenburg, the English bell metal is usually made from the scoriae of the brass gun foun- dery, melted over again f. The proportion of tin in bell metal varies. Less tin is used for church bells than clock bells ; and in small bells, as those of watches, a little zinc is added to the alloy According to Ger- bert, the conch of the East Indians is composed of tin and copper, in the same proportions as in bell metal }. Mirror me- The alloy used for the mirrors of telescopes was em- ployed by the ancients for the composition of their mir- rors. It consists of about two parts of copper, united to one part of tin. Mr Mudge ascertained that the best proportions were 32 copper to 14*5 of tin ; a specimen of an ancient mirror analysed by Klaproth was com- posed of 62 copper 32 tin S lead 100 * See Watson's Ckem. Essays , iv. 127. f Wtuterberg) i. 262. J Watton'8 ftayt, iv< X33. 5 Wesierbtrgi i. a6l, TIN. f69 But the lead he considers as accidental *. This alloy is Chap very hard, of the colour of steel, and admits of a fine polish. But besides this, there are many other com- pounds often used for the same purpose f . Vessels of copper, especially when used as kitchen utensils, are usually covered with a thin coat of tin to prevent the copper from oxidating, and to preserve the food which is prepared in them from being mixed with any of that poisonous metal. These vessels are then said to be tinned. Their interior surface is scraped very clean with an iron instrument, and rubbed over with sal ammoniac. The vessel is then heated, and a little pitch thrown into it, and allowed to spread on the surface. Then a bit of tin is applied all over the hot copper, which instantly assumes a silvery whiteness. The intention of the previous steps of the process is to have the surface of the copper perfectly pure and me- tallic ; for tin will not combine with the oxide of cop- per. The coat of tin thus applied is exceedingly thin. Bayen ascertained, that a pan nine inches in diameter, and three inches three lines in depth, when tinned, only acquired an additional weight of 21 grains. Nor is there any method of making the coat thicker. More tin indeed may be applied ; but a moderate heat melts it, and causes it to run off. 6. Tin does not combine readily with iron. An al- loy, however, may be formed, by fusing them in a close crucible, completely covered from the external air. We are indebted to Bergman for the most precise experi- * Phil* Mag. Xvii. 294. f Sec Watttritrfr \, ate, and Watson's Cbcm. Essay,, iv. 270 MALLEABLE METALS. Book I. ments on this alloy. When the two metals were fused Division I. ._. together, he always obtained two distinct alloys : the first, composed of 21 parts of tin and one part of iron ; the second, of two parts of iron and one part of tin. The first was very malleable, harder than tin, and not so brilliant ; the second but moderately malleable, and too hard to yield to the knife *. Ti/jplate. The formation of tinplate is a sufficient proof of the affinity between these two metals. This very useful alloy, known in Scotland by the name of white iron, is formed by dipping into melted tin thin plates' of iron, thoroughly cleaned by rubbing them with sand, and then steeping them 24 hours in water acidulated by bran or sulphuric acid. The tin not only covers the surface of the iron, but penetrates it completely, and gives the whole a white colour. It is usual to add about - r ^th of copper to the tin, to prevent it from forming too thick a coat upon the iron f. Properties. SECT. XIV. OF LEAD. I. JLjEAD appears to have been very early known. It is mentioned several times by Moses. The ancients seem to have considered it as nearly related to tin. 1. Lead is of a bluish white colour; and when newly melted is very bright, but it soon becomes tarnished by * Bergman, iii. 471. f See Watson's Cb:m. Essays, iV. LEAD. 211 exposure to the air. It has scarcely any taste, but chap. r emits on friction a peculiar smell. It stains paper or the fingers of a bluish colour. When taken internally it acts as a poison. 2. Its hardness isS^; its specific gravity is 11'3523*. Its specific gravity is not increased by hammering ; so far from it, that Muschenbroeck found lead when drawn out into a wire, or long hammered, actually diminished in its specific gravity. A specimen at first of the spe- cific gravity 11*419, being drawn out into a fine wire, was of the specific gravity 11'317 ; and on being ham- mered, it became 11'2187 : yet its tenacity was nearly tripledf. 3. It is very malleable, and may be reduced to very thin plates by the hammer ; it may be also drawn out into wire, but its ductility is not great. Its tenacity is such, that a lead wire ^4.3- inch diameter is capable of supporting only 1S'4 pounds without breaking. 4. From the late experiments of Mr Crichton o Glasgow we learn, that lead melts when heated to the temperature 612 . When a very strong heat is ap- plied the metal boils and evaporates. If it be cooled slowly, it crystallizes. The Abbe Mongez obtained it in quadrangular pyramids, lying on one of their sides. Each pyramid was composed, as it were, of three layers. Pajot obtained it in the form of a polyhedron with 32 sides, formed by the concourse of six quadrangular py- ramids . * Brisson. Fahrenheit found it 11-3500, Phil. Trans. 1724. Vol. xxxiii. p. 114. I found a specimen of milled lead 1 1*407 at the temperar Cure of 64. | Wasserhrgt i. 44 1. \ PM. Mag. i7i. 49, Jour, de Pbys. xxxviii. 53. 272 MALLEABLE METALS. Book I. II. When exposed to the air it soon loses its Division f. i i _ - v * and acquires first a dirty grey colour, and at last its sur- Oxidcs. ace b ecomes a l m ost white. This is owing to its gra- dual combination with oxygen, and conversion into an oxid : but this conversion is exceedingly slow ; the external crust of oxide, which forms first, preserving the rest of the metal for a long time from the action of the air. Water has no direct action upon lead ; but it facili- tates the action of the external air : for, when lead is exposed to the air, and kept constantly wet, it isoxida- red much more rapidly than it otherwise would be* Hence the reason of the white crust which appears upon the sides of leaden vessels containing water, just at the place where the upper surface of the water usually ter- minates. It is believed at present, that lead is capable of uniting with at least four doses of oxygen, and of forming four different oxides. Yellow ox- * The yellow oxide of lead, which has been longest *** known, and most carefully examined, may be obtained by dissolving lead in a sufficient quantity of nitric acid, so as to form a colourless solution, and then supersatu- rating it with carbonate of potash. A white powder falls, which when dried, and heated nearly to redness, as- sumes a yellow colour. It is pure ^ lour of gold, but is rather more pale. It is exceedingly brittle, breaking like glass, and exhibiting a fine-grain- ed fracture, of a pale brown colour, without any me- tallic lustre, and having the appearance of porcelain. The brittleness continues even when the proportion of lead is so far diminished that it amounts oaly to -r^^th 290 MALLEABLE METALS. Book T. O f the a li y 4 Even the fumes of lead are sufficient to Division i. J u y J destroy the ductility of gold. The specific gravity of the alloy of 11 gold and one lead is 18*080, which is somewhat less than the mean ; so that the metals under- go an expansion. This expansion increases as the lead diminishes (the gold remaining the same, and the defi- ciency being supplied by copper), and becomes a max- imum when the lead amounts only to T foth of the al- loy. The following Table exhibits a view of this re- markable expansion : Metals. , Grains, Specific gra- vity ot alloy. Bulk be- fore -Do. after, union. 1 Expan- sion. Gold 442 Lead ; 38 is-oso 1000 1005 5 Gold 442 Lead 19 17-7CJ5 1000 1006 G Copper 19 Gold : 442 Copper Lead 30 S 17-312 1000 1022 22 Gold 442 Copper Lead 34- 4 17'032 1000 1035 35 Gold 442 Copper Lead 37'5 0-5 16'(i27 1000 1057 57 Gold 442 Copper Lead 3T75 0-25 17-C39 1000 1031 31* * SCQ Hatchctt on the A'.loys of GoJJ, \, 29 and 67, 1EAD. 281 2. Dr Lewis fused crude platina and lead together Chap. IV. in various proportions ; a violent heat was necessary to platinum, enable the lead to take up the platinum. Hence a por- tion of the lead was dissipated. The alloys had a fi- brous or leafy texture, and soon acquired a purple co- lour when exposed to the air. When equal parts of the metals were used, the alloy was very hard and brittle ; and these qualities diminished with the propor- tion of platinum. When the alloys were melted again, a portion of the platinum subsided *. Many experi- ments have been made with this alloy, in order, -if pos- sible, to purify platinum from other metals by cupel- lation, as is done successfully with silver and gold: But scarcely any of the experiments have succeeded ; because platinum requires a much more violent heat to keep it in fusion than can be easily given f. 3. Melted lead dissolves a great portion of silver at Silver, a slightly red heat. The alloy is very brittle $ ; its colour approaches to that of lead ; and, according to Kraft, its specific gravity is greater than the mean den- sity of the two metals united. The tenacity of silver, according to the experiments of Muschenbrceck, is di- minished by the addition of lead. This alloy is easily decomposed, and the lead separated by cupellation. 4. Mercury amalgamates readily with lead in any M proportion, either by triturating with lead filings, or by pouring it upon melted lead. The amalgam is white and brilliant, and when the quantity of lead is suffi- cient, assumes a solid form. It is capable of crystallU * Pli'.e-s. Commtrce, p 513. f Ibid. p. 561. f Lewi", iVfaCTCfl'.- Qbsrr. p. 57. 2.S2 MALLEABLE METALS. Book f. zing. The crystals are composed of one part of lead Bivision L J an d ne a d a halt of mercury . 5, Copper does not unite with melted lead till the fire is raised so high as to make the lead boil and smoke, and of a bright red heat. When pieces of copper arc thrown in at that temperature, they soon disappear. The alloy thus formed is of a grey colour, brittle when eold, and of a granular texture f. According to Kraft, it is rarer than the meanj. The union between the two metals is very slight. When the alloy is exposed to a heat sufficient only to melt the lead, almost the whole of the lead runs off, and leaves the copper near- ly pare J. The little lead that remains may be scori- fied by exposing the copper to a red heat. If the lead that runs off carries with it any copper, on melting it the copper swims on the surface, and may be easily skimmed off|(. This alloy is said to be employed sometimes for the purpose of making printers types for very large characters If . ._ 6. The older chemists affirm, that iron is not taken up by melted lead at any temperature whatever, but that it constantly swims upon the surface. Muschen- broeck, however, succeeded in uniting by fusion 400 parts of iron with 134 parts of lead, and formed a hard alloy, whose tenacity was not one-half of that of pure * Dijon Academicians. f Lewis, Ibid. } Wasserberg. i. 263. Lewis, Neuman's Chemistry , p. 57. This curious mode of separation Is called in Chemistry eliquation. || Lewis, Ibid. ^ Fourcroy, vi. 266. It has been lately ascertained by Mr Hatchctt, that copper cannot be used to alloy gold unless it be free from lead. The smallest portion of this metal, though too minute to affect the cop- per itself, produces a sensible change on the ductility of gold. LEAD. 283 iron. The specific gravity of an alloy often iron and one lead, according to him, is 4*250*. The experi- ments of Guyton Morveau have proved, that when the two metals are melted together, two distinct alloys are formed. At the bottom is found a button of lead con- taining a little iron ; above is the iron combined with a small portion of lead f. 7. Lead and tin may be combined in any proportion Tin, by fusion. This alloy is harder, and possesses much more tenacity than tin. Muschenbroeck informs us that these qualities are a maximum when the alloy is composed of three parts of tin and one of lead. The presence of the tin seems to prevent in a great measure the noxious qualities of the lead from becoming sensi- ble when food is dressed in vessels of this mixture. This mixture is often employed to tin copper vessels, and the noxious nature of lead having raised a suspi- cion, that such vessels when employed to dress acid food, might prove injurious to the health, Mr Proust was employed by the Spanish government to examine the subject. The result of his experiments was, that vine- gar and lemon juice, when boiled long in such vessels, dissolve a small portion of tin, but no lead, the presence of the former metal uniformly preventing the latter from being acfed on. The vessels of course are inno- cent J. The specific gravity of this alloy increases with the lead, as might be expected. Hence the proportion of the two metals in such alloys may be estimated near- ly from the specific gravity, as will appear from the * Watitrberg. 1.1,12. f Ann. dt Ckim. IviL 47, | Ann. de Cbim. IviL 73. 284 MALLEABLE METALS. Book I. following Table, drawn up by Dr Watson from his Division I. i_ ' own experiments . Pewter. Tin. Lead. Sp. Grav. 100 11'270 100 7-170 32 1 T321 16 1 T438 8 1 7-560 5 1 7-645 3 1 7-940 2 1 8-160 1 1 8-817 What is called in this country ley pewter is often scarce- ly any thing else than this alloy f. tinfoil, too, al- most always is a compound of tin and lead. This al- loy, in the proportion of two parts of lead and one of tin, is more soluble than either of the metals separately. It is accordingly used by plumbers as a solder. * Cbtmtcal Estays, iv. 165. f There are three kinds of peivtcr in common use; namely, ffate, trifo, and ley. The plate pewter is used for plates and dishes ; the trifle chiefly for pints and quarts ; and the Icy metal for wine measures, &c. Their relative specific gravities are as follows: Plate, 7248; trifle, 7-359 ; ley, 7-963. The best pewter it said to consist of loo tin and 1 7 antimo- ny. See Watson's Chemical Etsays, iv. 167. ZINC, SECT. XV. OF ZINC. I. 1 ME ancients were acquainted with a mineral to History, which they gave the name of Cadtnia, from Cadmus, who first taught the Greeks to use it. They knew that when melted with copper it formed brass ; and that when burnt, a white spongy kind of ashes was volati- lized, which they used in medicine *. This mineral contained a good deal of zinc ; and yet there is no proof remaining that the ancients were acquainted with that metal f. It is first mentioned in the writings of Alber- tus Magnus, who died in 12SO ; but whether he had seen it is not clear, as he gives it the name of mafca- site of gold, which implies, one would think, that it had a yellow colour . The word zinc occurs first in the * Pliny, lib. xxxiv. cap. 2. and 10. f Grignon indeed says, that something like k was discovered in the ruins of an ancient Roman city in Champagne ; but the substance which he to'.-k fur it was not examined with any accuracy. It is impossible therefore to draw any inference whatever from his assertion. Bulletin, dc fouillts d'une viUe Rtrrraine, p. II. t The pa>?j^fs in which he mentions it are as follows: They prove, I trrr.k u'contestiMy, that it was not the metal, but the ores of the metal, \vit.h wh'ch Albertus was acquainted. JDe Mineral, lib. ii. cap. ir. havta, five marchasida ut quidam dicunt, est lapis in substantia, et h?be<- multas specie?, quare colorem accipit cujuslibet metalli, et sic diuturmarchasitaargcr.tea et aurea, et sic dicitur aliis, Metallum tamen coiorat cum nun distillat ab ipso, sed evaporat in ignem, t sic 28(3 MALLEABLE METALS* Book I. writings of Paracelsus, who died in 1541. He inform^ Division!. us very gravely, that it is a metal, and not a metal, and that it consists chiefly of the ashes of copper** This metal has also been called spflter. Zinc has never been found in Europe in a state of purity, and it was long before a method was discovered of extracting it from its ore f* Henkel pointed out one in 1721 ; Von Swab obtained it by distillation in 1742 j and Margraf published a process in the Berlin Me- moirs in 1746 J. At present there are three works in this country in which zinc is extracted from its ore j two in the neighbourhood of Bristol, and one. at Swan- relinquifurcinis inutilis, et hie lapis notus est apud alchymicos, et inmul- tis locis veniuntur. Lib. iii. cap. ro. " /Es amem invenitur in venis lapidis, et quod est a- pud locum qui dicitur Goselaria est purissimum et optimum, ettoti sub- stantias lapidis incorporatum, ita quod totus lapis est sicut marchasita au- rca, et profun datum est melius ex eo quod purius. I-ib. v cap. 5. " Dicimusigitur quod marchasita duplicem habet in sui ereatione substantial!!, argenti vivi scilicet mortificati, et ad fixionem ap- proximantis, et sulphuris adurentis. Ipsam habere sulphureitatem com- perhnus manifesta experientia. Nam cum sublimatur, ei ilia emanat substantia sulphurea manifeste comburens. Et sine sublimatione simili- ter perpenditur illius sulphureitas- u Nam si ponatur ad ignitionem, non suscipit illam priusqnam inflr.m- matione sulphuris inflammetur, et ardeat. Ipsam vero argenti vivi sub- stantiam manifestatur habere sensibiliter. Nam albedinem prxstat Ve- neri meri argenti, quemadmodum ct ipsum argentum vivum, et colorem in ipsius sublimatione cx;.'siium prxstare, et luciditatem manifestam me- tallicam habere videmus, qua: certum reddunt artificem Alchimiac, illam has substantias continere in race sua." * " : ce vol. vi. of his Works in quarto. f The real discoverer of this method appears to have been Dr Isaac Lawson. See Pott, iii. diss. 7. and Watson's Cbvnicxl En ays* j Bergman, ii. 309. ZINC. 2S1 Sey. The ore (sulphuret of zinc) is roasted and re- Chap, iv.^ duced to powder, mixed with charcoal, and exposed to a strong heat in large closed clay pots. The zinc is re- duced, and gradually drops down through an iron tube issuing from the bottom of the pot, and falls into a ves- sel of water. The zinc is afterwards melted and cast into ingots. A considerable quantity of zinc is yearly exported from Britain, chiefly to the north of Europe *. 1. Zinc is of a brilliant white colour, with a shade Propertae* of blue, and is composed of a number of thin plates adhering together. When this metal is rubbed for some time between the fingers, they acquire a peculiar taste, and emit a very perceptible smell. 2. Its hardness is 6f . When rubbed upon the fingers it tinges them of a black colour. The specific gravity of melted zinc varies from 6'S61 to 7*1 f ; the lightest being esteemed the purest. When hammered it becomes as high as 7'190Sj. 3. This metal forms as it were the limit between the brittle and the malleable metals. Its malleability is by no means to be compared with that of the metals al- ready described ; yet it is not brittle, like the metals which are to follow. When struck with a hammer, it does not break, but yields, and becomes somewhat flatter ; and by a cautious and equal pressure, it may be reduced to pretty thin plates, which are supple and * See an account of the manufacture of this metal in Watson's Clem. Euays, ir. I. f Brisson and Dr Lewis. A specimen of Goslar zinc was found by Dr Watson of the specific gravity 6-953 ; Bristol zinc 7-028. Chemical Etsays, iv. 41. A specimen of zinc tried by Mr Hatchett was 7-065. On the Alloys of Cold, p. 67. J Brisson. 288 MALLEABLE METALS. I. ^Division T. Cnmbina- t on with oxygen. elastic, but cannot be folded without breaking. This property of zinc was first ascertained by Mr Sage *". Wben heated somewhat above 212, it becomes very malleable. It may be beat at pleasure without break- ing, and hammered out into thin plates. When care- fully annealed, it may (it is said) be passed through rollers. It may be very readily turned on the lath. When heated to about 400, it becomes so brittle that it may be reduced to powder in a mortar. 4. It possesses a certain degree of ductility, and may with care be drawn out into wiref. Its tenacity from the experiments of Muschenbroeck, is such, that a wire whose diameter is equal to T yh of an inch, is capable of supporting a weight of about 26 Ibs J. 5. When heated to the temperature of about 680 , it melts ; and if the heat be increased, it evaporates, and may be easily distilled over in close vessels. When allowed to cool slowly, it crystallizes in small bundles of quadrangular prisms, disposed in all directions. If they are exposed to the air while hot, they assume & blue changeable colour ||. II. When exposed to the air, its lustre is soon tar- nished, but it scarcely undergoes any other change. When kept under water, its surface soon becomes black r the water is slowly decomposed, hydrogen gas is emit- ted, and the oxygen combines with the metal. If the heat be increased, the decomposition goes on itore ra- Jour, de Mia, An. V. 595. f Black's Lectures, ii. 58.3 - t He found a rod of an inch diameter to support 2600 lb. Now if the cohesion increase as the square of the diameter, the strength of a wire of i-ioth inch, will not differ much from that assigned in the text, Black's Lertvresj ii. ^Sj. j: Mr ptdly ; and if the steam of water is made to pass over . Cha P' .* zinc at a very high temperature, it is decomposed with great rapidity *. When zinc is kept melted in an open vessel, its sur- face is soon covered with a grey- coloured pellicle, in consequence of its combination with oxygen. When this pellicle is removed, another soon succeeds it ; and in this manner may the whole of the zinc be oxidized. When these pellicles are heated and agitated in an open vessel, they soon assume the form of a grey powder^ often having a shade of yellow. This powder has been called the grey oxide of zinc. When zinc is raised to a strong red heat in an open vessel, it takes fire, and burns with a brilliant white flame, and at the same time emits a vast quantity of very light white flakes; These are merely an oxide of zinc. This oxide was well known to the ancients. Dioscorides describes the me- thod of preparing it. The ancients called it pompholyx : the early chemists gave it the name of nihil album, lana philosophic a y and flowers of xinc. Dioscorides compares it to wool f. Two different oxides of zinc are at present known. 1. The peroxide, or white oxide of zinc, is the oxide Peroxidcv usually formed in the different processes to which the metal is subjected. We are indebted to Mr Proust for an exact analysis of this oxide and its Combinations. It is composed of 80 parts of zinc and 20 of oxygen |. It may be formed not only by burning zinc, but also by dissolving it in diluted sulphuric or nitric acid, and prt- * Lavoisier, Mem. P*r. 1781, p. 174. f Epiov TOXvrou apcfiottiTXi, V. 85. p. 352. \ Ann. d: Cbim. XXXV. 51. I. T 290 Book r. Division f. Protoxide. TAtiion with simple com- bustibles. Hydrogen. MALLEABLE METAL3. cipitating it by potash. This oxide has been proposed as a paint ; but its colour must be perfectly white. When pure it is light, and has a considerable resem- blance to chalk. It is tasteless and insoluble in water, and not liable to be changed by exposure to the atmos- phere. 2. The protoxide, or zinc combined with a minimum of oxygen, is obtained by exposing the peroxide to a strong heat in an earthen ware retort or covered cru- cible. From the experiments of Desormes and Cle- ment, it appears, that by this process the zinc loses a portion of its oxygen, and assumes a yellow colour. According to the analysis of these chemists, the prot- oxide of zinc is composed of 88 parts zinc and 12 parts of oxygen *. 3. The reduction of the oxides of zinc is an opera- tion of difficulty, in consequence of the strong affinity which exists between zinc and oxygen, and the conse- quent tendency of the zinc after reduction to unite with oxygen. It must be mixed with charcoal, and exposed to a strong heat in vessels which screen it from the con- tact of the external air. III. Most of the simple combustibles combine with zinc. 1. Hydrogen gas dissolves a little of it in certain si- tuations. It is usual to procure hydrogen gas by dis- solving zinc in diluted sulphuric acid. The gas thus obtained carries along with it a little zinc in solution ; but it deposites it again upon the sides of the glass jars, and on the surface of the water over which it stands. * Ann. tfe dim. xxxix. 32. ZIftC. The gas thus mpregnated was recommended by Mr , Cha P* Watt as likely to be serviceable in cases of diseased lungs. 2. Hydrogen gas procured from zinc by means of diluted sulphuric acidj when burnt, produced a certain portion of carbonic acid. Hence it was inferred that it contained originally some carbureted hydrogen *. As the zinc dissolves, a black powder makes its appear- ance in the solution. This black powder the French chemists affirm to be plumbago, and to its presence they ascribe the cause of the formation of carbureted hydrogen ; but this opinion has not been verified by accurate experiments, and is indeed unlikely to be truef. 3. Zinc maybe combined with phosphorus, by drop- Phosphuret; ping small bits of phosphorus into it while in a state of fusion. Pelletier, to whom we are indebted for the experiment, added also a little resin, to prevent the oxi- dation of the zinc. Phosphuret of zinc is of a white colour, a metallic splendour, but resembles lead more than zinc. It is somewhat malleable. When hammer- ed or filed, it emits the odour of phosphorus. When exposed to a strong heat, it burns like zinc J. 4. Phosphorus combines also with the oxide of zinc ; a compound which Margraf had obtained during his experiments on phosphorus. When 12 parts of oxide * See the experiments of Fourcroy, Vauquelin and Seguin, Ann. de Cbim. viiL 230. f Proust has ascertained, that this black powder is often not carburet of iron, but a mixture of arsenic, copper, and lead. Ann. de Cbim. xixv. 51. On separating this black powder and drying it, I found that it as- ^ sutned an olive-green colour. It proved in all my trials to be a mixture of copper and lead. \ Ann. dt Cbim. xiii. 139. T 2 V .-v -- .--- . ~ r --<- ^* ,'-w^-..<- ~ MALLEABLE METALS. Book I. of zinc, 12 parts of phosphoric glass, and 2 parts of Division I. ........ , v v- i charcoal powder, are distilled in an earthen ware retort, retedoxicie anc ^ a stron ^ eat applied, a metallic substance sublimes of a silver white colour, which when broken has a vi- treous appearance. This, according to Pelletier, is phosphureted oxide of zinc. When heated by the blowpipe, the phosphorus burns, and leaves behind a glass, transparent while in fusion, but opaque after cooling *. Phosphureted oxide of zinc is obtained also when two parts of zinc and one part of phosphorus are di- stilled in an earthen retort. The products are, l. Zinc ; 2. Oxide of zinc ; 3. A red sublimate, which is phos- phureted oxide of zinc ; 4. Needleform crystals, of a metallic brilliancy, and a bluish colour. These also Pelletier considers as phosphureted oxide of zinc f. Sulphuret. 5. Sulphur cannot be artificially combined with zinc ; but when melted with the oxide of zinc, a combination is formed, as was first discovered by Dehne in 1781 The experiment was afterwards repeated by Morveau J. A similar compound is formed when, sulphureted hy- drogen, in combination with an alkali, is dropt into a so- lution of zinc. It is at first white, but becomes darker on drying. It was considered by chemists as sulphur united to the oxide of zinc ; but experiment does not confirm the opinion. The zinc seems to be in the me- tallic state. One of the most common ores of zinc is a foliated miner-- J, usually of a brown colour, called blende ; * Pelletier, Ibid. 128. f Ann. de Chim. xiii, I2J. | Clem. Jour. p. 46. and CrelPs Annals, 1786, i. 7. $ Mem. de V Ajtad. de D'jon, 1783. ZINC. 293 tasteless, insoluble in water, and of a specific gravity ' ha P- lv \ about 4. Bergman showed that this ore consisted chiefly of zinc and sulphur. Chemists were disposed to consider it as a sulphureted oxide of zinc, in conse- quence chiefly of the experiments of Morveau, above referred to ; but the analyses of Bergman vere incon- sistent with this notion. Proust gave it as his opinion, that blende is essentially a compound of zinc in the metallic state with sulphur *. Upon examining several specimens of blende, I found the phenomena and the proportion of the constituents to agree exactly with thU opinion, and cannot therefore hesitate to embrace it. IV. Zinc does not combine with azote. Muriatic acid readily converts it into an oxide. V. Zinc combines with almost all the metals, and Alloys wit^ some of its alloys are of great importance. 1. It may be united to gold in any proportion by fu- sion. The alloy is the whiter and the more brittle the greater quantity of zinc it contains. An alloy, consist- ing of equal parts of these metals, is very hard and white, receives a fine polish, and does not tarnish rea- dily. It has therefore been proposed by Mr Hellot f as very proper for the specula of telescopes. Mr Hat- chett united 1 1 parts of gold and one of zinc. The al- loy was of a pale greenish yellow like brass, and very- brittle. Its specific gravity was 16'937. The bulk of the metals before union was 1000 ; after it, 997nearly. Hence the union is accompanied with a small degree of contraction. The brittleness continued though the zinc was reduced to ^th of the alloy, ^ ths of copper being de Phyt. Ivi. 79, f Mem. Acad. Par. 1735. 294; MALLEABLE METALS. Book T. Pivision I. platinum, Silver, ^Jcrcury, added to reduce the gold to the standard value. Even the fumes of zinc near melted gold, are sufficient to ren- der the precious metal brittle *. Hellot affirms, that when one part of gold is alloyed with seven of zinc, if the zinc be elevated in the state of flowers, the whole of the gold rises along with it. 2. Dr Lewis found that platinum unites with the fumes of zinc reduced from its ore, and acquires about ^-d of additional weight. The two metals very readily melt, even when the zinc does not exceed ^th of the platinum. The alloy is very brittle, of a bluish white colour, and much harder than zinc. One-twentieth of platinum destroys the malleability of zinc, and one- fourth of zinc renders platinum brittle f. 3. Silver unites to zinc with facility, and produces a brittle alloy of a bluish white colour, and a granular texture. Its specific gravity, according to Gellert, is greater than the mean. When an alloy of 11 zinc and one silver is sublimed in open vessels, the whole of the silver arises along with the flowers of zinc J. 4. The amalgam of zinc was examined by Malouin. According to him, it is formed most readily by pouring mercury upon zinc, heated so as to char paper, but not to burn it. Its consistence varies with the proportion of zinc. Eight parts zinc, and one mercury, form a white very brittle compound. One zinc and 2^ mer- cury form an alloy, which, when melted and cooled slowly, crystallizes. This amalgam is used to promote the excitement of electric machines J. * Hatchett on the Alloys of Gold, p. 1 7. \ Pbil. Commerce , p. 520. f Was ser berg, i. 160. 5 It was first recommended for that purpose by Dr Higgins. Sec ~ *.I778,P.W*. ZINC. 255 5^ Xinc combines readily with copper, and forms one Chap, IV. of the most useful of all the metallic alloys. The me- tals are usually combined together by mixing granula- ted copper, a native oxide of zinc called calamine, and a proper proportion of charcoal in powder. The heat is kept up for five or six hours, and then raised suffi- ciently high to melt the compound. It is afterwards poured into a mould of granite edged round with iron, and cast into plates. This compound is usually known in this country by the name of brass. The metals are capable of uniting in various proportions, and according to them, the colour and other qualities of the brass vary also. According to Dr Lewis, who made a large set of experiments on the subject, a very small portion of zinc dilutes the colour of copper, and renders it pale ; when the copper has imbibed one-twelfth of its weight the colour inclines to yellow. The yellowness increases with the zinc, till the weight of that metal in the alloy equals the copper. Beyond this point, if the zinc be increased, the alloy becomes paler and paler, and at last white *. The proportion of zinc imbibed by the copper varies in different manufactories according to the process, and the purposes to which the brass is to be applied. In some of the British manufactories the brass made contains yd of its weight of zinc. In Germany and Sweden, at least if the statements of Swedenburg be ac- curate, the proportion of zinc varies from -f th to ^th of the copper f. Brass is much more fusible than copper ; it is malleable while cold, unless the portion of zinc be excessive ; but when heated it becomes brittle. It is Ciim. p. 6j. f H'esserktrv, \. 367. 296 MALLEABLE METALS. Book!. ductile, may be drawn out into fine wire, and is much Division 1. . . . c Vir- l - --. ' tougher than copper, according to the experiments ot Muschenbroeck. According to Gellert, its specific gravity is greater than the inean. It varies considerably according to the proportion of zinc. Dr Watson found a specimen of plate brass from Bristol S'441 * : while Brisson makes common cast brass only 7*824. Brass may be readily turned upon the lath, and indeed works more kindly than any other metal. When zinc in the metallic state is melted with cop- per or brass, the alloy is known by the names oi pinch- beck, princess vietal) Prince Ruperts metal, &c. The proportion of zinc is equally variable in this alloy as in brass ; sometimes amounting nearly to one half of the whole, and at other times much less. The colour of pinchbeck approaches more nearly to that of gold, but it is brittle, or at least much less malleable tha'n brass, Brass was known, and very much valued, by the an- cients. They used an ore of zinc to form it, which they called cadmia. Dr Watson has proved that it was to brass which they gave the nsur.e of onchalcwn f. Their tes was copper, or rather bronze {. * C&em. Essays, iv. 58. f Manchester 1'ramaciions, vol. ii. p. 47. 4 The arcients do not seem ro have known accurately the difference Vetween copper, brass, and bronze, Hence the confusion observable in their names. They considered brass as only a more valuable kind of cop- per, and therefore often used the word #s indifferently to denote either. It was not till a late period that mineralogists began to make the distinc- tinn. They called coppers cyprium, and afterwards only cyprium, which in process of time was converted into cuprum. When these changes took j'lace, is not knpwn accurately. Plir.y uses c^fi'iuM, l.b. juxvi. cap. 26, ZINC. 297 (j. It is difficult to combine zinc with iron, because Chap. IV. the heat necessary to melt the latter metal dissipates the lion, former. The alloy, according to Lewis, when formed, is hard, somewhat malleable, and of a white colour ap- proaching to that of silver*. Malouin has shown that zinc may be used instead of tin to cover iron plates ; a proof that there is an affinity between the two me- tals f. 6'. Tin and zinc may be easily combined by fusion. Tin, The alloy is much harder than zinc, much stronger than tin, and still ductile. This alloy, it is said, is often the ; principal ingredient in the compound called peiuter. 8. The alloy of lead and zinc has been examined by Lead, Wallerius, Gellert, Muschenbroek, and Gmelin. This last chemist succeeded in forming the alloy by fusion. He put some suet into the mixture, and covered the cru- cible, in order to prevent the evaporation of the zinc. When the zinc exceeded the lead very much, the alloy was malleable, and much harder than lead. A mixture of two parts of zinc and one of lead formed an alloy more ductite and harder than the last. A mixture of equal parts of zinc and lead formed an alloy differing little in ductility and colour from lead; but it was har- der, and- more susceptible of polish, and much more so- norous. When the mixture contained a smaller quan- tity of zinc, it still approached nearer the ductility and colour of lead, but it continued harder, more sonorous,, and susceptible of polish, till the proportions approach- The word cuprum occurs first in Spartian, who lived about the year 3. tic says, in his life cf Caracalla, cancelli tx are vel cupro. * Xturtmut Ghent, p. 69. f Mtm. Par. 1/42. MALLEABLE METALS. Book r. Division I. Names and marks gi- ven to the metals by the anci- ents, ed to one of zinc and 1 6 of lead, when the alloy dif- fered from the last metal only in being somewhat harder *. 9. Zinc does not appear capable of combining with nickel by fusion f. SUCH are the properties of the malleable metals, the most numerous and by far the most important of the four classes into which we have divided them. Eight of them have been discovered by modern chemists ; namely, platinum, palladium, rhodium, indium, osmium, nickel, niccolanum, and zinc. The remaining seven were known to the ancients. To these last the names of the planets were formerly assigned, and each was denoted by a particular mark which represented both the planet and the metal. Gold was the Sun, and represented by Silver . , Moon, , . . . . J> Mercury ..... Mercury, Copper Venus, ? Iron Mars, .., d* Tin ........ . Jupiter, If Lead ........ Saturn, > It seems most probable that these names were first * Ann. de ;/*. il. 95. f The Chinese, however, seem to be in possession of some method is sup- posed to represent the scythe of Saturn ; "U the thunder- bolts of Jupiter ; c? the lance of Mars, together with his shield j the cross stands at the top, and the silver character is only sus- pended on the right hand behind it. Brofessor Beckmann, however, who has examined Origin ao . . , . , , , cording to this subject with much attention, thinks that these cha- Beckraann. racters are mere abbreviations of the old names of the planets. " The character of Mars (he observes *), ac- cording to the oldest mode of representing it, is evi- dently an abbreviation of the word oi^ec, under which the Greek mathematicians understood that deity ; or, in other words, the first letter e, with the last letter c placed above it. The character of Jupiter was origi- nally the initial letter of z? ; an d in the oldest manu- scripts of the mathematical and astrological works of Julius Firmicus, the capital Z only is used, to which the last letter e was afterwards added at the bottom, to render the abbreviation more distinct. The supposed looking-glass of Venus is nothing else than the initial letter distorted a little of the word Gurfopoy, which was the name of that goddess. The imaginary scythe of Saturn has been gradually formed from the two first letters of his name x.pwy , which transcribers, for the sake of dispatch, made always more convenient for use, but at the same time less perceptible. To discover in the pretended caduceus of Mercury the initial letter of his Greek name 2T * Jour, de Af/'n. An. v. p. 582. \ Irvine, Nicholson's Jour. iz. 46, VoL L f Brisson and HatchctC, u S06 BRITTLE METALS. Beok I. Division I. Combina- tion with oxygen. Peroxide. but scarcely undergoes any other change. It is not al- tered when kept under water. When kept melted in an open vessel, its surface is soon covered with a dark blue pellicle ; when this is removed, another succeeds, till the whole metal is oxi- dized. When these pellicles are kept hot and agitated in an open vessel, they are soon converted into a brown- ish or yellowish powder. When bismuth is raised to a strong red heat, it takes lire and burns with a faint blue flame, and emits a yel- low smoke, as was first observed by Geoffrey. When this is collected, it is a yellow powder, not volatile, which has been called yellow oxide of bismuth. When bismuth is dissolved in nitric acid, if water be poured into the solution, a white powder precipitates, which was formerly called mctgistry of bismuth. This powder is used as a paint, under the name of pearl or flake white. Bucholz has demonstrated that this pow- der is a ^compound of oxide of bismuth and nitric acid. From his experiments, compared with those of Kla- proth*, we learn that the yellow oxide of bismuth is composed of 100 bismuth and 12 oxygen, or per cent, of about 89*3 bismuth 10*7 oxygen lOO'O This is the only oxide of bismuth at present known with precision. It is tasteless and insoluble in water, In the fire it is fixed, but melts readily into a brown. * Klaproth's ii, 294. Bucholz's Beitragt, iii. 3. BISMUTH. 307 glass. In this respect it resembles the oxides of lead. Chap. iV. Bismuth is sometimes used in the process of cupella- tion instead of lead. It was first proposed for that pur- pose by Dufay in 1727, and his experiments were af- terwards confirmed by Pott. These oxides are easily reduced when heated along with charcoal or other combustible bodies ; for the af- finity between bismuth and oxygen is but weak. III. Bismuth has riot been combined with carbon phosphutei nor hydrogen. Neither does it seem capable of combi- ning in any notable proportion with phosphorus. Mt Pelletier attempted to produce the phosphuret of bis- muth by various methods without success. When he dropped phosphorus, however, into bismuth in fusion, he obtained a substance which did not apparently differ from bismuth, but which, when exposed to the blow- pipe, gave evident signs of containing phosphorus *. This substance, according to Pelletier, did not contain above four parts in the hundred of phosphorus, and even this small portion seems Only to have been me- chanically mixed. 2. Sulphur combines readily with bismuth by fusion. The sulphuret of bismuth is of a bluish grey colour, It crystalliz.es in beautiful tetrahedral needles, which cross each other. It is very brittle and fusible, and bears a strong resemblance to sulphuret of antimony, but is rather brighter coloured. One hundred parts of bismuth, according to WenzePs experiments, unite by fusion to IV 5 of sulphur; Hence the sulphuret of bis- muth is composed of about * Anr. de Ceim. xiii. 30. U 2 30* BRITTLE METALS. J? 00 ! cr ' f 85 bismuth Division 1. v v ' ,..- j 15 sulphur 100* V. Bismuth combines readily with most metallic bo- dies, and forms compounds, few of which have been ap- plied to any useful purposes. Alloys with 1. Gold combines very readily with bismuth by fu- sion. An alloy composed of 11 gold and one bismuth was found by Hatchett to have a greenish yellow co- lour, like bad brass. It was very brittle, and had a fine grained earthy fracture. Its specific gravity was 18*038. The bulk of the metals before fusion was 1000, after it only 988. They had suffered, therefore, a considera- ble contraction. The properties of the alloy continued nearly the same when the bismuth amounted to ^th of the compound ; the requisite quantity of copper to reduce the gold to standard being added. When the bismuth was diminished beyond this proportion, the co- lour of the alloy became nearly that of gold ; but its brit- tleness continued even when the bismuth did not exceed T^Vcfth f tne mass. As the proportion of bismuth di- minished, and that of the copper increased (the gold being always standard), the contraction disappeared, and an expansion took place, which was soon much greater than when copper alone was used to alloy the gold. This curious progression will appear evident from the following Table f. * Verwandtschaft, p. a8o. f The specific gravity of the gold was 19-1^ (it was 23 carats 8 graina fine), of the bismuth 9-82;, of the copper 8-895, BISMUTH. Metals. Grains. Specific gra- vity ot alloy. Bulk be- fore fusion. Do. after. Change of bulk. Gold Bismuth 442 38 lS-038 1000 988 12 Gold Copper Bismuth 442 30 8 17-302 1000 1018 +13 Gold Copper Bismuth 442 34 4 / 16*846 1000 1044 +44, Gold Copper Bismuth 442 37'5 0-5 16*780 1000 1047 +47 Gold Copper Bismuth 442 37-75 0-25 1TC95 1000 1027 +27 So great is the tendency of bismuth to give brittleness to gold, that the precious metal is deprived of its ductU lity, merely by keeping it, while in fusion, near bis- muth raised to the same temperature *. 2. Bismuth and platinum readily melt and combine when exposed rapidly to a strong heat. Dr Lewis fu- sed the metals in various proportions, from one of bis- muth to 24 with one of platinum. The alloys were all as brittle, and nearly as soft as bismuth ; and when broken, the fracture had a foliated appearance. When this alloy is exposed to the air, it assumes a purple, vio- * See Hatchett on the Atttyt of Gdd t p. 36. 310 BRITTLE METALS. Bookr. let. or blue colour. The bismuth can scarcely be ss- iJivision I. 1 v ' parated by heat *. Silver, 3. Bismuth combines readily with silver by fusion. The alloy is brittle; its colour is nearly that of bis- muth ; its texture lamellar ; and its specific gravity greater than the mean. According to Muschenbroeck, the specific gravity of an alloy of equal parts bismuth and silver is 10*7097 f. 4. Mercury combines readily with bismuth, either by triturating the metals together, or by pouring two parts of hot mercury into one part of melted bismuth. This amalgam is at first, soft, but it becomes gradually hard. When melted and cooled slowly, it crystallizes. When the quantity of mercury exceeds the bismuth considerably, the amalgam remains fluid, and has the property of dissolving; lead, and rendering it also fluid. This curious fact was first described by Beccher, who af- firmed that a mixture of three parts mercury, one lead, and one bismuth, form a perfectly fluid amalgam. This triple compound may be filtered through shamois lea- ther without decomposition. Mercury is sometimes adulterated with these metals ; but the imposition may be easily detected, not only by the specific gravity of the mercury, which is too small, but because it drags a tail, as the workmen say ; that is, when a drop of it is agitated on a plain surface, the drop does not remain sphericle, but part of it adheres to the surface, as if it were not completely fluid, or as if it were inclosed in a thin pellicle. This amalgam is used hot for silvering glass balls. 5. Copper forms with bismuth a brittle alloy of a * PbiloscfJj. Commerce, p. 509 and .573. f Wasscrberg, i. 160, BISMUTH. Sll pale red colour, and a specific gravity exactly the mean Chap. 1V.^ of that of the two metals alloyed *. 6. Bismuth combines but imperfectly with iron f. Iron, The alloy is brittle, and attracted by the magnet even \vhen the bismuth amounts to ^ths of the whole t- The specific gravity of this alloy is less than the mean }. 7. Bismuth and tin unite readily. A small portion Tin, of bismuth increases the brightness, hardness, and so- norousness of tin : it often enters into the composition of pewter, though never in Britain. Equal parts of tin and bismuth form an alloy that melts at 280 : eight parts of tin and one of bismuth melt at 390 : two parts of tin and one of bismuth at 330 {] 8. The alloy of lead and bismuth is of a dark grey Lead, colour and close grain ^[. It is ductile, unless the bis- muth exceeds the lead considerably **. Bismuth in- creases the tenacity of lead prodigiously. Muschen- broeck found, that the tenacity of an alloy, composed of three parts of lead and two of bismuth, was ten times greater than that of pure lead. The specific gravity of this alloy is greater than the mean ff. 9. When eight parts of bismuth, five of lead, and three of tin, are melted together, a white coloured al- loy is obtained, which melts at the temperature of 212, and therefore remains melted under boiling water. 10. The alloy of bismuth and nickel is brittle, and Nickel, formed of thin plates t- 11. Bismuth does not combine with zinc. v * Gellert. f Muschenbroeck. \ Henkel. $ Gcllert, ]| Dr Lewis, Neumjn's Cbem, p. in. ^ Va'leriu-r. ** JBaunie. f f Gclkrt. JJ Cronstcdt. BRITTLE METALS, Book T. Division I. SECT. XVII. OF ANTIMONY. History. I. 1 HE ancients were acquainted with an oxide of an- timony, to which they gave the names of biloiofherum t magnetia saturni, jilius and notlut 3,14 BRITTLE METALS. Book I. and sometimes assuming the appearance of imperfect i_ T r crystals. Hauy has with great labour ascertained, that the primitive form of these crystals is an octahedron, and that the integrant particles of antimony have the figure of tetrahedrons*. When rubbed upon the fin- gers, it communicates to them a peculiar taste and smell. 2. Its .hardness is 6| . Its specific gravity is, accord- ing to Brisson, 6'702; according io Bergman, 6'86. Hatchett found it 6' 112 f. 3. It is very brittle, and may be easily reduced in a mortar to a fine powder. Its tenacity, from the experi- ments of Muschenbroeck, appears to be such, that a rod of y^th inch diameter is capable of supporting about 10 pounds weight. 4. When heated to 810 Fahrenheit, or just to red- ness, it melts J. If after this the heat be increased, the metal evaporates. On cooling, it assumes the form of oblong crystals, perpendicular to the internal surface of the vessel in which it cools. It is to this crystallization that the laminated structure which antimony always as- sumes is owing. Oxides, II- When exposed to the air, it undergoes no change except the loss of its lustre. Neither is it altered by be- ing kept under water. But when steam is made to pass over red hot antimony, it is decomposed so rapidly that a violent detonation is the consequence $. When heated in an open vessel, it gradually com- bines with oxygen, and evaporates in a white vapour. This vapour, when collected, constitutes a white colour- * Jour, de Min. An. v. 601. f On the Alloys of Gold, p. 68. } Mortimer. Lavoisier and Meusder, Mem. Par. 1781, p. 374. ANTIMONY. ed oxide, formerly called argentine flowers of antimony. Chap. IV. When raised to a white heat, and suddenly agitated, antimony burns, and is converted into the same white coloured ^oxide. According to Thenard *, who published an excel- lent dissertation on antimony some time ago, this metal is capable of combining with no less than six different Closes of oxygen, and of forming six oxides, which may be exhibited in a separate state. But his method of obtaining most of these bodies, namely, by the appli- cation of heat, does not seem capable of leading to any very precise result ; while at the same time several of his oxides differ from each other only by one or two hundredth parts of oxygen j a degree of precision much greater than chemists are able at present to attain. Proust has lately examined this important question, and has found antimony capable of forming only two ox- ides, agreeing in this respect with most of the other metals. 1. The protoxide of antimony may be obtained by p rotox jde. the following process. Dissolve antimony in muriatic acid, and dilute the solution with water : a white pre- cipitate appears, composed of the protoxide of antimo- ny combined with a little muriatic acidf. Wash this precipitate with water, and boil it for some time in a solution of carbonate of potash. Then wash it well, and dry it on a filter J. * Ann. de Cbim. xxxii. 259. t The white powder thus obtained was formerly called po-wJt garoth, from Victor Algarothi, a physician in Verona, who first procured it in that manner from muriate of antimony. } Proust Jour, de Pfyt. lv. 328. BRITTLE METALS. D?visJon"l ^e P rotox ^ e tnus procured is of a dirty white co- u - NT ' lour, without any lustre. When raised to a moderate red heat it melts, and may be kept for a long time in fusion in a retort. When allowed to cool, its surface becomes covered with small opaque crystals lying close together, and of a yellowish white colour. It is indeed extremely fusible, and always becomes opaque on cool- ing. A part of it is volatilized with a moderate heat, provided air be present. It is composed of 81" 5 antimony 18*5 oxygen 100*0 This oxide may be kept melted in contact with anti- mony any length of time without alteration *. peroxide. 2. The peroxide of antimony may be obtained by exposing the metal in the open air to a violent heat : it takes fire, and a white oxide is sublimed, formerly called argentine flowers of antimony* It is obtained al- so by causing nitric acid to act upon antimony, and by throwing the metal into red hot nitre. After the com- bustion there remains in the crucible a white mass, con- sisting of the oxide of antimony combined with the potash of the nitre. Water dissolves a part of this compound : when an acid is poured into this solution, a white powder precipitates, which is the peroxide of antimony. This oxide is of a white colour ; it is insoluble in water, and not nearly so soluble in acids as the prot- oxide. Neither is it so fusible as that oxide, requiring # Proust Jour, de Pbys. Iv. 328. 'ANTIMONY. Sit a, pretty violent heat ; but it is volatilized at a lower t cha P- temperature, forming white prismatic crystals of a sil- very lustre. It is composed of 77 antimony 23 oxygen 100 When melted with a fourth part of antimony, the whole is converted into protoxide*. III. Antimony has never been combined with car- Union whfe combusti- bon nor hydrogen. When its oxides are heated along bles. with charcoal or oils, they are reduced, but imperfect- ly, unless some body (as potash) be present to favour the fusion of the metal. The greater part remains in the state of a black spongy mass, which often takes fire when exposed to the air. Antimony combines readily with sulphur and with phosphorus. 1. Sulphuret of antimony may be formed by mixing its two component parts together, and fusing them in a crucible. It has a dark bluish grey colour, with a lustre approaching the metallic. It is much more fusible than antimony, and may be crystallized by slow cooling. It is composed, according to Bergman, of 74 parts of antimony and 26 of sulphur f. With this es- timate the late experiments of Proust coincide almost exactly. According to that very accurate chemist, suU phuret of antimony is composed of 75 antimony 25 sulphur 100$ * Proust, Jour, de PLys. lv, 328. f Berg. iii. 167, J Jour, dt Phys. lv. 325^ 318 BRITTLE METALS. Book r. This substance is found native in great abundance, and Division f. . v > indeed is almost the only ore of antimony. It was to this sulphuret that the term antimony was applied by the earlier chemists ; the pure metal was called regulus of antimony *. Glass of 2. The protoxide of antimony has the property of dissolving different proportions of sulphuret when in a state of fusion. The resulting compound is a semitran- sparent substance of a brownish red colour, differing considerably in its appearance according to the propor- tion of its ingredients. When it is composed of about eight parts of oxide and one part of sulphuret, it has a red colour, and is semitransparent. It is then called glass of antimony. When it contains eight parts oxide and two sulphuret, it is opaque, and of a red colour in- clining to yellow. This is the crocus metallorum of apothecaries. Eight parts of oxide and four of sulphur- et form an opaque mass of a dark red colour. This is the liver of antimony of apothecaries f. When sulphur is heated with either of the oxides, it reduces them to the metallic state, if sufficient in quan- tity ; if too small for that, it deoxidizes a portion, com- bines with it, and the sulphuret formed unites with the remaining oxide, always converted to a protoxide. Her.ce the reason that these different compounds may * Sulphuret of antimony is sometimes used to separate the baser me- tals from gold. When heated along with gold, it carries off all the other jr.etals, while part of the antimony combines with the gold. This is re- moved by oxidizing the gold by means of heat andjnitre. This proper- ty of sulphuret of antimony induced the alchy mists to give it the name of the tvo/f t quia ferocia sua omuia metalla prseter leonem, h. e, auruia, sunlit, ffomeri Poppii Batilica Antimoaii, c. T. f Proust, Jour, ds Ptyt. !v. 334. ANTIMONY. 319 be formed by a great variety of processes. The glass Chap. IV of antimony is usually prepared by exposing sulphuret of antimony in powder to a gentle heat for a consider, able time in an open vessel. By this process, which is called roasting, the greater part of the sulphur is driven off, and the metal is reduced to a protoxide. In this state it is put into a crucible, and melted by a sud- den heat into glass. If the roasting has been carried so far as to drive off the whole of the sulphur, only dark coloured scoriae are obtained ; but on the addition of a little sulphur or sulphuret of antimony, the glass may be easily formed *. The glass sold by apothecaries is seldom or never pure, containing almost always, as Vauquelin has demonstrated, about 0*09 f parts of si- lica \ ; derived undoubtedly from the crucibles in which the oxidized sulphuret is fused ; for these crucibles con- tain a very great proportion of siliceous earth. The peroxide of antimony is incapable of dissolving any sulphuret. Of course it does not form a glass. 3. When equal parts of antimony and phosphoric glass are mixed together with a ^little charcoal powder, rct * and melted in a crucible, phosphuret of antimony is produced. It is of a white colour, brittle, appears la- minated when broken, and at the fracture a number of small cubic facettes are observable. When melted it emits a green flame, and the white oxide of antimony sublimes. Phosphuret of antimony may likewise be prepared by fusing equal parts of antimony and phos- * Bergman, iii. 166. f Ann. de Cbim. xxxiv. Ijp. | An tartb which will be described in the next Book, $20 BRITTLE METALS. BookT. phoric glass, or by dropping phosphorus into meltea Division F. . u Y ' antimony *% IV. Antimony does not combine with azote, nor with muriatic acid. Alloys with V. Antimony combines readily with most of the metals ; but the greater number of its alloys have not been applied to any use,* Gold, ! Antimony and gold may be combined by fusion, and form a brittle compound of a yellow colour. Great attention was paid to this alloy by the alchymists, who affirmed, that the quantity of gold might be increased by alloying it with antimony and then purifying it f. Gold made standard by antimony, in Mr Hatchett's experiments, was of a dull pale colour, not unlike tu- tenague. It was exceedingly brittle, and in the frac- ture was of an ash colour^ with a fine close grain, not unlike that of porcelain. Its specific gravity was 16*929. The bulk of the two metals before fusion being 1000, after fusion it was 987. Hence they suf- fer a considerable contraction. A very small propor- tion of antimony destroys the ductility of gold ; the al- loy was perfectly brittle when the antimony did not ex- ceed -r^Wth P art f tne mass. Even the fumes of an- timony, in the neighbourhood of melted gold, are suffi- cient to destroy its ductility J. platinum. 2. Platinum easily combines with antimony. The alloy of equal parts is brittle, and of a much duller * Pellctier, Ann. de Chim. xiii. 132. f This made them give antimony the name 6f balneum regale. The cause of their mistake is obvious ; tl- ?y did not separate the whole of the antimony from the gold ; hence the increase of weight. \ Hatchett en the Alloys of Gold, p. 13, AX TI MO NY. 321 Mercfirrj colour than antimony. The antimony cannot after- , chap ' lv ^ wards be completely separated by heat. When the antimony exceeds, the platinum is apt to subside in slow cooling *. 3. Silver may be alloyed with antimony by fusion, silver, - The alloy is brittle, and its specific gravity, as Gellert has observed f, is greater than intermediate between the specific gravities of the two metals which enter into it. 4. Pott first observed, that antimony, reduced from its sulphuret by means of iron and chalk, unites rea- dily with mercury by trituration. Antimony may be easily amalgamated by pouring it while in fusion into mercury almost boiling hot |. When three parts of mercury are mixed in this manner with one part of melted antimony, a soft amalgam is obtained, which very soon decomposes of itself . Gellert also succeed- ed in forming this amalgam ||. 5. Copper combines readily with antimony by fu- sion. The alloy is brittle when it consists of equal parts of the two metals, is of a beautiful violet colou^ and its specific gravity is greater than intermediate ^f. This alloy was called ngultts of Venus by the alchy- mists. 6. Iron combines with antimony by fusion, and forms a brittle hard white coloured alloy, the specific gravity of which is less than intermediate. The mag- rietic quality of iron is much more diminished by being alloyed with antimony than with most other * Lewis, Pill. Com. p. 521. \ Lewis, Neumjti's Cbem. p, j Mftall. Cbem.v. 141, f Metallurg^ Chemistry, p. 136.- Waller! us. <[ Gellert, p. 13 6, BRITTLE METALS. Book I. metals*. This alloy may be obtained also by fusfngf _y-L^> in a crucible two parts of sulphuret and one of iron. It was formerly called martial regulus. Tin, 7. The alloy of tin and antimony is white and brit- tle ; its specific gravity is less than intermediate f. This alloy is employed for different purposes ; particularly for making the plates on which music is engraved J. Pewter often consists chiefly of this alloy. Thenard has pointed out a remarkable property ia this alloy. If its solution in muriatic acid be de- luted with water the whole of the two metals is preci- pitated . Lead, 8. When equal quantities of lead and antimony are fused, the alloy is porous and brittle : three parts of lead and one of antimony form a compact alloy, malleable, and much harder than lead : 12 parts of lead and one of antimony form an alloy very malleable, and a goodi deal harder than lead : 16 parts of lead and one of an- timony form an alloy which does not differ from lead except in hardness ||. This alloy forms printers types. Its tenacity is very considerable ^[, and its specific gra- vity is greater than the mean **. 9. Zinc may be readily combined with antimony by fusion. The alloy is hard and brittle, and has the co- lour of steel. Its specific gravity is less than inter- diateff. Bismuth ** Antimony forms a brittle alloy with bismuth 4, * Gellert,p. 136. f Ibid. J Fourcroy, vi. 25. Ann. de Cbim. lv. |j GmeYm, Ann. de dim, viii. 319. ^ Muschenbroeck, ** Gellen,p. 136, jj- Ibid. TELLURIUM. 323 to maiaganese it unites but imperfectly * : the com* Chap. IV. pounds which it forms with nickel and cobalt have not been examined. SECT. XVIII. OF TELLURIUM* J. THE mine of Mariahilf, in the mountains of Fatz- History, bay, near Zalethna, in Transylvania, contains an ore of a bluish white colour and a metallic lustre ; concerning the nature of which mineralogists were for a long time doubtful. That it contained a little gold was certain ; but by far the greatest part of it consists of a metallic substance, which some supposed to be bismuth, others antimony. Muller of Reichenstein examined it in 1182 f ; and concluded, from his experiments, that this ore, which had been distinguished by the names of au- rum problematiaim^ auruin paradoxicum, and aurum al- bum, contains anew m-tal different from every other. Being still dissatisfied with his own conclusions, he sent a specimen of it to Bergman; but the specimen was too small to enable that illustrious chemist to decide the point. He ascertained, however, that the metal in question is not antimony. The experiments of Muller appeared so satisfactory, that they induced Mr Kirwan, in the second edition of his Mineralogy , published in * Gmelin, Ann, de Cbim. ill. 367. X2 f Born, ii. 468* 324 Book I. Division I. Properties, Oxides. BRITTLE METALS. 1796, to give this metal a separate place, under the* name of syhanite. Klaproth published an analysis of the ore in 1798, and completely confirmed the conclu- sions of Muller *. To the new metal, which consti- tutes 0-925 of the ore, he gave the name of tellurium ; and this name has been generally adopted. Gmelin ex- amined the ore in 1799 f ; and his experiments coin- cide almost exactly with those of Muller and Klaproth. By these philosophers the following properties of tel- lurium have been ascertained. 1. Its colour is bluish white,, intermediate between that of zinc and lead ;. its texture is laminated like an- timonv, and its brilliancy is considerable. 2. Its hardness has not been ascertained. Its specific gravit^y, according to Klaproth, is 6*115 J. S.It is very brittle, and may be easily reduced to powder. 4. It melts when raised to a temperature somewhat higher than the fusing point of lead. If the heat be in- creased a little, it boils and evaporates, and attaches it- self in brilliant drops to the upper part of the retort in which the experiment is made. It is therefore, next to mercury and arsenic, the most volatile of all the metals,,.. When cooled slowly, it crystallizes. II. When exposed to the action of the blow-pipe up- on charcoal, it takes fire, and burns with a lively blue flame, the edges of which are green ; and is completely volatilized in the form of a white smoke, which, ac- * Crell's Annals, 1798, i. 91. f Ibid- *799> 175. and 36.5, | Mulkr found it 6-343 5 but probably his specimen was not pure. AUSENTC, 325 cording to Klaproth, has a smell not unlike that of ra- ^hap.iv^ dishes J. Tlu;> white smoke is the oxide of tellurium, "which may be obtained also by dissolving the metal in nitro- muriatic acid, and diluting the solution with a great quantity of water. A white powder falls to the bot- tom, which is the oxide. It may be procured also by dissolving the metal in nitric acid, and adding potash slowly till the oxide precipitates. This oxide is easily melted by heat into a straw-coloured mass of a radiated texture. When made into a paste with oil, and heated in charcoal, it is reduced to the metallic state so rapidly, that a kind of explosion is produced. III. Tellurium may be combined with sulphur by Sulphuret. fusion. This sulphuret has a leaden grey colour, and a radiated rexture: on red hot coals it burns with a blue flame. Tellurium may be amalgamated with mercury by trituration. Its other properties have not yet been ex- amined. SECT. XIX. OF ARSENIC. I c 1 HE word arsenic (apamx.ov) occurs first in the xvorks History. of Dioscorides, and of some, other authors who wrote Gmelin could not perceive this smell 326 BRITTLE METALS. Book I, about the beginning- of the Christian era. It denotes Piyision I. . * Y - in their works the same substance which Aristotle had called c-avJapa;^*, and his disciple Theophrastus a/^wjiov, which is a reddish coloured mineral, composed of arse- nic and sulphur, used by the ancients in painting, and as a medicine. The white oxide of arsenic, or what is known in com- merce by the name of arsenic, is mentioned by Avicen- na in the llth century ; but at what period the metal called arsenic was first extracted from that oxide is un- known. Paracelsus seems to have known it ; and a process for obtaining it is described by Schroeder in his Pharmacopoeia, published in 1649 f. But it was only in the year 1733 that this metal was examined with chemical precision. This examination, which was per- formed by Mr Brandt, demonstrated its peculiar nature ; and since that time it has been always considered as a Distinct metal, to which the term arsenic has been ap- propriated. Its properties were still farther investiga- ted by Macquer in 1746 t by Monnet in 1773 {, and by Bergman in 1777 ||. To the labours of these philo- sophers, and to those of Mr Scheele ^[, we are indebted for almost every thing known about the properties of this metal. 1. Arsenic has a bluish white colour not unlike that of steel, and a good deal of brilliancy. It has no sen- sible smell while cold ; but when heated it emits a strong odour of garlic, which is very characteristic. * Pliny seems to m*ke a distinction between samlaracha and arsenic, gee lib. xxxiv. cap. 18. t Bergman, ii. 278. J :\rlem. P T. 1746, p. J23, and I 748, p. 35. Sur I' Arsenic. [} Cifutft ii. 373, 1 Scheele, i. 129. ARSENIC. 2. Its hardness scarce!/ exceeds 5. Its specific gra- Chap. IV. Vity is 8'31 *. 3. It is perhaps the most brittle of all the metals, falling to pieces under a very moderate blow of a ham- mer, and admitting of being easily reduced to a very fine powder in a mortar. 4. Its fusing point is not known, because it is the most volatile of the metals, subliming without melting, when exposed inclose vessels, to a heat of 356 f. When sublimed slowly, it crystallizes in tetrahedrons, which Hauy has demonstrated to be the form of its in- tegrant particles. II. It may be kept under water without alteration ; Oxides, but when exposed to the open air, it soon loses its lus- tre, becomes black, and falls into powder. Arsenic is capable of combining with two doses of oxygen, and of forming two compounds, which might be termed the protoxide and peroxide of arsenic, were it not that they possess several of the properties of acids. 1. When exposed to a moderate heat in contact with Protoxide air, it sublimes in the form of a white powder, and at the same time emits a smell resembling garlic. If the heat be increased, it burns with a pale blue flame. Arsenic indeed is one of the most combustible of the metals. The substance which sublimes was formerly called arsenic or white arse?iic t and is still known by these names in the commercial world. It is a combi- nation of arsenic and oxygen ; and is now denominated white oxide of arsenic, and by Fourcroy arsenious acid, because it possesses several of the properties of an acid. Bergman, ii. 2^9. According to Brandt, 8-308. J lergman, ii. 5179. 23 BRITTLE METALS, ^Eopkt. It is seldom prepared by chemists, because it exists na-> u^^ , live, and is often procured abundantly during the ex- traction of the other metals from their ores. When obtained by these processes, it is a white, brittle, compact substance, of a glassy appearance. It has a sharp acrid taste, which at last leaves an impres- sion of sweetness, and is one of the most virulent poi- sons known. It has an alliaceous smell. It is soluble in 80 parts of water at the temperature of 60, and in 15 parts of boiling water *. This solution has an acrid taste, and reddens vegetable blues. When it is slowly evaporated, the oxide crystallizes in regular tetrahe- drons. It is soluble also in between 70 and 80 times its weight of alcohol, and in oils. This oxide sublimes when heated to 383 : if heat be applied in close ves- sels, it becomes pellucid like glass ; but when exposed to the air, it soon recovers its former appearance. The specific gravity of this glass is 5*000 ; that of the ox- ide in its usual state, 3*106 f. This oxide is capable of combining with most of the metals, and in general renders them brittle. From the experiments of Proust ? it appears that it is composed of 75*2 arsenic 24'S oxygen 100'OJ When the white oxide of arsenic is mixed with black flux, and slowly heated to redness in a matrass or retort, the arsenic is reduced into the metallic state, and slow- ly sublimes. By this means the metal may be procured * Bergman, ii. 291. f Ibid. ii. 286. J Jour, de ARSENIC, in a state of purity. This method of reducing arsenic Chap. 1V.^ was first pointed out by Brandt, to whom we are in- debted for most of the properties of the white oxide above described. 2. Arsenic is capable of combining with an addi- Peroxide or . arsenic acid. tional dose of oxygen, and of iormmg another com- pound, first discovered by Scheele, known by the name of arsenic .acid. The process prescribed by hcheele, is to dissolve three parts of white oxide of arsenic in se- ven pans of muriatic acid, to add five parts of nitric acid, to put the mixture into a retort, and distil to dry- ness. The dry mass is to be merely brought to a red heat, and then cooled again. It is solid arsenic acid, Mr Bucholz has lately shown, that the whole quantity of muriatic acid prescribed by Scheele is not necessary. , The formula which he considers as the best is the fol- lowing : Mix together in a crucible 2 parts of muri- atic acid of the specific gravity 1*200, 8 parts of white oxide of arsenic, and 24 parts of nitric acid, of the specific gravity 1'25. Evaporate to dryness, and expose the dry mass to a slight red heat *. The acid thus prepared has no very strong taste when dry ; but when dissolved in water, it acquires an ex- cessively sour taste, and remains liquid even when eva- porated to the consistence of a jelly. It is as noxious as the white oxide of arsenic. From the experiments of Proust, it follows, that it is composed of 65*4 parts of arsenic, and 34*G parts of oxygen: and with these proportions the determination of Bucholz very nearly corresponds. But Thtnard makes the oxygen to a- mount to 36 parts in the hundred of oxide f. # Van MOD'S Journal de Cbimie t iv. 1 6. \ Ann, de C&iin. 1. 539 BRITTLE MET ALS. Book I. Division I. Union with combust! Wes. Arsenical hydrogen gas. III. Arsenic combines readily with all the simple combustibles, except carbon, with which it has not hi- therto been united by chemists. 1. That hydrogen gas has the property of dissolving arsenic, and retaining it in the gaseous form, was disco- vered by Scheele during his experiments on arsenic acid*. It was afterwards noticed by Proust, during his experiments on tin. Trommsdorf has lately exa- mined it in detail, and published an account of its pro- perties f. The easiest method of procuring it, according to the last mentioned chemist, is to mix together four parts of granulated zinc and one part of arsenic, and to treat them with sulphuric acid diluted with twice its weight of water. Hydrogen gas is disengaged in abundance, which, coming in a nascent state in contact with the ar- senic, dissolves it, and forms the gas wanted. Stromey- er, who examined this gas more recently, recommends an alloy composed of 15 parts of tin and one of arsenic. When this alloy is digested in muriatic acid, the hydro- gen evolved carries off the whole of the arsenic, and leaves the tin pure J. Arsenical hydrogen gas, thus formed, is colourless, has a nauseous smell, is not sensibly absorbed by wa- ter ; extinguishes flame, and destroys animal life. Its specific gravity (barometer about 30 inches) is 0*5293, that of air being one: hence 100 cubic inches of it weigh 16'4 grains. #5cheele's Opuie. i. i8s. French translation. Nicholson'* Jour. vi. 300, \ Ibid xix. 381. ARSENIC. 331 It burns with a blue flame ; and if the neck of the Chap. IV. vessel containing it be narrow, the arsenic is deposited. When two parts of this gas, mixed with three of oxy- gen, are brought in contact with a lighted taper, an ex- plosion takes place, and water and white oxide of arse- nic are formed. Equal parts of these gases do not ex- plode so loudly, but give a more vivid flame. Two parts of this gas and one of oxygen leave a small resi- due. According to Stromeyer it requires for com- t bustion 0'72 parts of its bulk of oxygen gas. Arsenical hydrogen gas is not altered by common air, azotic gas, nor hydrogen. Nitrous gas occasions a di- minution of about ivfo per cent. Sulphureted hydrogen gas occasions no change in it ; but if oxymuriatic acid be added to the mixture of these two gases, the bulk di- minishes, and yellow-coloured flakes are deposited. Hence these two gases furnish us with a delicate test for detecting the presence of arsenical hydrogen. Concentrated nitric acid, when suddenly mixed with this gas, causes an evolution of red fumes, and an ex- plosion accompanied with flame. When the acid is di- luted, it oxidizes and removes the arsenic, leaving the hydrogen pure. Trommsdorf, to whom we are indebt- ed for all these facts, did not succeed in analysing this gas, though it appears from his experiments, that it is a compound of arsenic and hydrogen *. Stromeyer in- forms us that he succeeded in analysing it by means of nitric acid, and that he found it composed of 106 parts arsenic and 2'19 hydrogen f. Proportions which do * See Nicholson's Journal^ vi. 200. f Ibid, xbc, 383. $32 BRITTLE METALS, accorc * w * th tne s P ec " lfic stated by Trommsdorf. of the gas, as Galphurets. 2. Sulphur combines readily with arsenic. If we put a mixture of these two bodies into a covered cruci- ble and melt them, a red vitreous mass is obtained, which is obviously a sulphuret of arsenic. It may be formed also by heating together the white oxide of arse- nic, or arsenic acid and sulphur; but in that case a por- tion of the sulphur absorbs the oxygen from the arse- nic, and makes its escape in the form, of sulphurous acid gas *. This sulphuret of arsenic is found native Ju Realgar, in different parts of Europe. It is usually called realgar '. It has a scarlet colour, and is often crystallised in tran- sparent prisms. Its specific gravity is 3*225 f. It is tasteless, and not nearly so hurtful as the oxides of arse- nic, though Macquer affirms that it is poisonous J. It is sometimes used as a paint. According to the experi- ments of Westrumb, this sulphuret is composed of 80 parts of arsenic and 20 of sulphur J. According to Thenard, it consists of .60 parts of arsenic and 30 of sulphur |[ . 3. If the white oxide of arsenic be dissolved in mu- riatic acid, and a solution of sulphureted hydrogen in water be poured into the liquid, a fine yellow-coloured powder falls to the bottom. This powder is usually called orpiment. It may be formed by subliming arse- nic and sulphur by a heat not sufficient to melt them. This substance is found native. It is composed of thin a. Orpi- ment. * Proust, Jour, de Plys, liii. 94. f Bergman, ii. 298. } Hoffman informs us, that he gave two scruples ot it to a dog with- out any bad effects whatever. Qbscrv. Pbysico-Cbemico-Select. p. 236. Crell's Annals t 1785, i. 2^9. |1 Ann. de Cblm. lix. 290, ARSENIC. 333 plates, which have a considerable degree of flexibility. Chap. iv. Its specific gravity is 5*315. It has been supposed by some chemists, that orpiment differs from realgar merely in containing a smaller proportion of sulphur; by others, that the arsenic exists in it in the state of an oxide ; by others, that it contains sulphureted hydrogen. But Mr Proust has ascertained, that when heated suf- ficiently it melts without emitting any gas, and on cooling assumes the appearance of realgar *. Hence he concludes, that like realgar it is merely a sulphuret of arsenic. This opinion has been confirmed by the ex- periments of Thenard, who found orpiment a compound of three parts of sulphur and four of arsenic f. 4. Arsenic combines readily with phosphorus. The pftospBat* phosphuret of arsenic may be formed by distilling equal ret " parts of its ingredients over a moderate fire. It is black and brilliant, and ought to be preserved in water. It may be formed likewise by putting equal parts of phos- phorus and arsenic into a sufficient quantity of water, and keeping the mixture moderately hot for some timej. IV. Arsenic does not combine with azotic gas nor muriatic acid; neither is it readily oxidized by the ac- tion of that acid. V. Arsenic unites with most metals, and in general Alloys whir renders them more brittle and more fusible. 1. There appears to be a strong affinity beeween gold Gold, and arsenic ; but in consequence of the great volatility of the latter metal, it is difficult to unite them by fusion. * Jour. Je Pbys. liii. 94. f Ann. de Cliff*.. lx. 290, t Pelletier, Ann. deCltim. xiii. 139. 334 BRITTLE RlETAtS. Book I. Division I. Platinum, Bergman succeeded in making gold take up ^V tn f ^ 8 weight of arsenic *. Mr Hatchett added 453 grains of arsenic to 5307 grains of melted gold, and, stirring the whole rapidly with an iron rod, poured the mixture in- to an iron mould. Only six grains of the arsenic was retained ; so that the alloy contained only -g-f-j-th of arsenic. It had the colour of fine gold j and though brittle, yet it bent in some measure before it broke. When once united to gold, arsenic is not easily expelled by heat. Mr Hatchett discovered that gold readily im- bibes, and combines with, arsenic, when heated to red- ness. A plate of gold was exposed red hot to the fumes of arsenic by suspending it near the top of a dome, made by luting one crucible inverted over another. In the lower crucible some arsenic was put, and the whole exposed to a common fire for about 15 minutes. The arsenic had acted on the gold, and combined with its sur- face. The alloy being very fusible had dropt off as it formed, leaving the gold thinner, but quite smooth. The alloy of gold and arsenic formed a button in the undermost crucible. This button had a grey colour, and was extremely brittle f. 2. The alloy of arsenic and platinum was first exa- mined by Scheffer, and afterwards by Dr Lewis. The addition of white oxide of arsenic causes strongly heat- ed platinum to melt ; but the mixture does not flow thin, and cannot be poured out of the crucible. The alloy is brittle and of a grey colour. The arsenic is mostly expelled in a strong heat, leaving the platinum in the state of a spongy massj. # Of use. ii. 28l. \ Phil.. Com. p. J On the -4%-r of Gott, p. 7, ARSENIC. 335 ?. Melted silver takes up T^th of arsenic*. The alloy Chap. IV.^ is brittle, yellow-coloured, and useless. Silver, 4. Mercury may be amalgamated with arsenic by Mercury, keeping them for some hours over the fire, constantly agitating the mixture. The amalgam is grey-coloured, and composed of five parts of mercury and one of ar- senic f. 5. Copper may be combined with arsenic by fusing Copper, them together in a close crucible, while their surface is covered with common salt to prevent the action of the air, which would oxidize the arsenic. This alloy is white arid brittle, and is used for a variety of pur- poses ; but it is usual to add to it a little tin or bismuth. It is known by the names of white copper and white tombac. When the quantity of arsenic is small, the al- loy is both ductile and malleable J. 6. Iron and arsenic may be alloyed by fusion. The TroDj alloy is white and brittle, and may be crystallized. It is found native, and is known among mineralogists by the name of mispickfl. Iron is capable of combining with more than its own weight of arsenic . 7. Tin and arsenic may be alloyed by fusion. The Tin, allov is white, harder, and more sonorous than tin, and brittle, unless the proportion of arsenic be very small. An alloy, composed of 15 parts of tin and one of arsenic, crystallizes in large plates like bismuth ; it is more brittle than zinc, and more infusible than tin. The ar- senic may be separated by long exposure of the alloy te heat in the open air \\ . * Bergman, ii. aSi. f Ibid, $ \tumant Clem. p. 144. Bergman, ii. 281. |! Bay en. 336 Book I. Division T. Antimony, Bismuth. BRITTLE METALS. S. Lead and arsenic may be combined by fusion. The alloy is brittle, dark-coloured, and composed of plates- Lead takes up -J-th of its weight of arsenic *. 9. Nickel combines readily with arsenic, and indeed is seldom found without being more or less contamina- ted by that metal. The compound has a shade of red, considerable hardness, and a specific gravity consider- ably under the mean. It is not magnetic. Arsenic possesses the curious property of destroying the mag- netic virtue of iron, and all other metals susceptible of that virtue. 10. Zinc may be combined with arsenic by distilling a mixture of it and of white oxide of arsenic f. This alloy, according to Bergman, is composed of four parts of zinc and one of arsenic. 11. Antimony forms with arsenic an alloy which is very brittle, very hard, and very fusible ; and compo- sed, according to Bergman, of seven parts of antimony and one part of arsenic. 12. Bismuth may be combined with about -fth of its weight of ^arsenic | ; but the properties of this alloy have not been examined. * Bergman, f Malouin. Bergman, ii. 281 1 BRITTLE METALS. CLASS III. BRITTLE AND DIFFICULTLY FUSED METALS- 1 HE metals belonging to this class are six in number. They were all unknown to the ancients, and were not examined till chemical analysis had acquired a consider- able degree of perfection. None of them are of much value in the metallic state ; their brittleness and difficult fusion rendering it impossible to work them with fa- cility : But some of them are of considerable import- ance in the state of oxides. Vol. I. BRITTLE METALS. Book I. Division I. SECT. XX. OF COBALT. History. I. A MINERAL called cobalt *, of a grey colour, and very heavy, has been used in different parts of Europe, since the 15th century, to tinge glass of a blue colour. But the nature of this mineral was altogether unknown till it was examined by Brandt in 1733. This celebra- * The word cobalt seems to be derived from cobalus, which was the name of a spirit that, according to the superstitious notions of the times, haunted mines, destroyed the labours of the miners, and often gave them a great deal of unnecessary trouble The nrners probably gave this name to the mineral out of joke, becaase it thwarted them as much as the sup- posed spirit, by exciting false hopes, and rendering their labour often fruitless ; for as it was not known at first to what use the mineral could be applied, it was thrown aside as useless. It w8, when a paper on it was published by Mr Tassaert . In the year 1800, a new set of experiments were made upon it by the School of Mines at Paris, in order to procure it perfectly pure, and to ascertain its properties when in that state ||. In 1802, a new series of trials was published by Thenard, which throw considerable light on its combinations with oxygen ^f. And in 1806, Mr Proust published a set of experiments upon the same subject**. Considerable attention has been lately paid to the purification of this metal ; but hitherto no one seems to have been fortunate enough to hit upon a me- thod altogether free from objections ff. 1. Cobalt is of a grey colour with a shade of red, and by no means brilliant. Its texture varies according to the heat employed in fusing it. Sometimes it is com- posed of plates, sometimes of grains, and sometimes of small fibres adhering to each other JJ. It has scarcely any taste or smell. * Acta Uftal, 1733 and 1742. f Cadmialogia, od^r Geubicfae dts Farbcn-Kcbolds. i Opusc. ii. 444, 501 an T j;i. Ann. de Chin, xxviii. IOI. Fourcroy, Disc-,un Pr?!im:na:rs, p. 114. 5 Ann. de Cbim. xlii. HO. ** Ibid. ll. 260. ft- See Richter, Gehleii'a Jour. ii. 53 ; Bucholz, IbiL iii. 20 j ; Philips? Phil. Wag. xvi. 312. ^ L'Ectie tti Mints. Y2 340 BRITTLE METALS. Book I. 2. Its hardness is 6. Its specific suavity, according Division I. . *" . . i v " to Bergman and the School of Mines at Pans, is 7*7. Mr Hatchett found a specimen "7*645 *. 3. It is brittle, and easily reduced to powder j but if we believe Leonhardi, it is somewhat malleable when red hot. Its tenacity is unknown. 4. When heated to the temperature of 130 Wedge- wood, it melts ; but no heat which we can produce is sufficient to cause it to evaporate. When cooled slowly in a crucible, if the vessel be inclined the moment the surface of the metal congeals, it may be obtained cry- stallized in irregular prisms f. 5. Like iron, it is attracted by the magnet ; and, from the experiments of Wenzel, it appears that it may be converted into a magnet precisely similar in its proper- ties to the common, magnetic needle. Oxides. II. When exposed to the air it undergoes no change ; neither is it altered when kept under water. Its affini- ty for oxygen is not sufficiently strong to occasion a de- composition of the water. When kept red hot in an open vessel, it gradually imbibes oxygen, pjid is converted into a powder at first blue, but which gradually becomes deeper and deeper, till at last it becomes black, or rather of so deep a blue that it appears to the eye black. If the heat be very violent, the cobalt takes fire and burns with a red flame. From the experiments of Thenard, it follows that cobalt is capable of combining with three doses of oxy- gen at least, and of forming three distinct oxides, which may be exhited in a separate state. * On the Alloy* of Gold, p. 68. f Fourcroy, v. i .? "< COBALT. 341 1. The protoxide of cobalt has a blue colour. It > Gha P- lv - t may be obtained by dissolving cobalt in nitric acid, and Protoxide, precipitating the cobalt from the solution by means of potash. The precipitate has a blue colour, but when dried in the open air it gradually becomes black. This black powder is to be kept for half an hour in that de- gree of heat knpwn to manufacturers of iron utensils by the name of cherry red. This heat expels the oxygen which it had absorbed in drying, and converts it into a fine blue colour. This oxide dissolves in acids with- out effervescence. The solution of it in muriatic acid, if concentrated, is green ; but if diluted with water, it is red. Its solution in sulphuric and nitric acids is always of a red colour *. According to the analysis of Proust, this oxide is composed of 33| of cobalt, and 16J- of oxygen f. 2. When the protoxide of cobalt, newly precipitated Deutoxide. from acids by potash, is exposed to the air, it gradually combines with an additional dose of cxygen, as The- nard ascertained by experiment, and assumes an olive green colour ; and by cautiously drying it without the aid of heat, it may be obtained in that state. This is the deutoxide of cobalt. When this oxide is treated with diluted muriatic acid, a moderate heat developes oxymuriatic acid gas, and a red coloured solution is ob- tained. Hence we see that the deutoxide of cobalt loses a portion of its oxygen during its solution in muriatic acid J. ij. When the protoxide or deutoxide of cobalt, newly Peroxide. precipitated from an acid, is dried by heating it in the * Anti.de C&IM. ilii. 213.' f Ibid. lx. 26;. \ Ibid. xlH. 342 BRITTLE METALS. Book I. open air, it assumes a flea-brown colour, which 'grada* Division I. r i* Y ' ally deepens till at last it becomes black. This is the peroxide of cobalt. It dissolves with effervescence in muriatic acid, and a great quantity of oxymuriatic acid gas is exhaled. Mr Thenard considers the brown co- lour which the oxide of cobalt first assumes before it becomes black as a tritoxide , but his experiments are not sufficient to decide that point. According to the experiments of Proust, the peroxide is composed of SO parts cobalt and 20 parts oxygen *. But it is not unlikely, from the method employed by this ingenious chemist, that the proportion of oxygen which he obtained was too small. With respect to the reddish precipitate which is spmetimes obtained by precipitating cobalt from acids, and which has been considered as a peculiar oxide of cobalt, Mr Thenard suspects, that it is a combination of the oxide of cobalt with arsenic acid f. Proust however has shown that the blue oxide has the property of combining with water, and forming what he calls a hydrate of cobalt, and this hydrate has a red colour. Union with ^' * Cobalt does not combine with carbon nor hy- combusti- drogen. 2. It cannot be combined with sulphur bv fusion. Sulphuret. But sulphuret of cobalt may be formed by melting the metal along with sulphur previously combined with potash. It has a yellowish white colour, displays the rudiments of crystals, and can scarcely be decomposed by heat. # Ann. df Cbim, lx. 367. f Ann, de Cbim, xlii. 214, OBALT. 343 The sulphuret of cobalt, according to Proust, may be Chap. IV. formed by heating together the oxide of cobalt and sul- phur. It is composed, according to his experiments, of 71| parts of cobalt, and 28^ of sulphur*; but he does not place much confidence in the accuracy of this result. 3. Phosphuret of cobalt may be formed by heating Phosphu- the metal red hot, and then gradually dropping in small ret * bitsof phosphorus. It contains about th ot phospho- rus. It is white and brittle ; and when exposed to the air, soon loses its metallic lustre. The phosphorus is separated by heat, and the cobalt is at the same time oxidated. This phosphuret is much more fusible than pure cobalt f. IV. Cobalt does not combine with azotic gas nor muriatic acid gas. V. Cobalt seems capable of combining with most Alloys with of the metals, but its alloys are very imperfectly known. 1. Mr Hatchett melted together 11 parts of gold Gold, and one part of ccbalt. The alloy was of a dull yel- low colour, very brittle, and the fracture exhibited an earthy grain. Its specific gravity was 1T112. The bulk of the metals before tusion being 1000, after fu- sion, became 1001. Hence they experienced a very small degree of expansion. The brittleness of gold al- loyed with cobalt continues when the cobalt does not exceed -g-^th of the whole ; but when it is reduced be- * 4. de CLlm. h. 274. f Pellctier, Hid. xiii. 134. 344? BRITTLE METALS. Book I. low that proportion, the gold becomes somewhat due- Division I. , i tile*. 2. The alloy of cobalt and platinum has not been ex- amined. Silver, 3. When two parts of cobalt and one of silver are melted together, the two metals are obtained separately after the process ; the silver at the bottom of the cru- cible, and the cobalt above it. Each of them, how- ever, has absorbed a small portion of the other metal : for the silver is brittle and dark coloured, while the cobalt is whiter than usual f. 4. Cobalt does not combine with mercury J. 5. The alloy of copper and cobalt is scarcely known. Iron, 6. The alloy of iron and cobalt is very hard, and not easily broken. Cobalt generally contains some iron, from which it is with great difficulty separated. Tin, 7. The alloy of tin and cobalt is of a light violet colour, and formed of small grains. Lead, 8. It was supposed formerly that cobalt does not combine with lead 'by fusion ; for upon melting equal parts of lead and cobalt together, both metals are found separate, the lead at the bottom and the cobalt above. Indeed when this cobalt is melted with iron, it appears that it had combined with a little lead ; for the iron combines with the cobalt, and the lead is separated ||, But Gmelin has shown that the alloy may be formed. He put cobalt in powder within plates of lead, and co- vered them with charcoal to exclude the air. He then applied heat to the crucibles containing the mixtures. * Hatchett on the Alloy i of Gold, p. 19. | Gellert, p, 137. J Cronstedt, jj Gellert,p. 137. MANGANESE. 345 Equal parts of lead and cobalt produced an alloy, in Chap. IV. which the metals appeared pretty uniformly distribu- ted, though in some cases the lead predominated. It was brittle, received a better polish than lead, which metal it resembled rather than cobalt ; its specific gra- vity was 8*12. Two parts of lead and one of cobalt produced an uniform mixture, more like cobalt than lead, very little malleable, and softer than the last. Its specific gravity was 8'28. Four parts of lead and one of cobalt formed an alloy still brittle, and having the fracture of cobalt, but the polish of lead. It was harder than lead. Six parts of lead and one of cobalt formed an alloy more malleable, and harder than lead. Its spe- cific gravity was 9' 65. Eight parts of lead and one of cobalt was still harder than lead, 'and it received a bet- ter polish. It was as malleable as lead. Its specific gravity was 9*18 *. 9. Cobalt is often found naturally combined with Nickel nickel. 10. It does not seem capable of combining with bis* muth nor with zinc by fusion. SECT. XXL OF MANGANESE. I. THE dark grey or brown mineral called manganese, . in Latin magnesia (according to Boyle from its resem- # Ann. de Cbim. xix. 357. 346 BRITTLE METALS. Division I. blance t tne magnet}, has been long known and used v - V" - J in the manufacture of glass. A mine of it was disco- vered in England by Boyle. A few experiments were made upon this mineral by Glauber in 1656 *, and by Waiz in 1705 f ; but chemists in general seem to have paid but very little attention to it. The greater num- ber of mineralogists, though much puzzltd what to make of it, agreed in placing it among iron ores : but Pott, who published the first chemical examination of this mineral in 1740, having ascertained that it often contains scarcely any iron, Cronstedt, in his System of Mineralogy^ which appeared in 1758, assigned it a place of its own, on the supposition that it consisted chiefly of a peculiar earth. Rinman examined it anew in 1765jj and in the year 1770 Kaim published at Vienna a set of experiments/ in order to prove that a peculiar metal might be extracted from it $. The same idea had struck Bergman about the same time, and induced him to re- quest of Scheele, in 1771, to undertake an examination of manganese. Scheele's dissertation on it, which ap- peared in 1774, is a master piece of analysis, and con- tains some of the most important discoveries of modern chemistry. Bergman himself published a dissertation on it the same year ; in which he demonstrates, that the mineral, then called manganese, is a metallic oxide ||. He accordingly made several attempts to reduce it, but without success ; the whole mass either assuming the form of scorise, or yielding only small separate globules * Prosperity Germania. f Welgleb's Gctcbicltt, i. 127. | Mem. : iockhrlm, 1765, p, 735. De Mctallis ditbiis, p. 48. I Opusc. ii. 201. MANGANESE. 341 attracted by the magnet. This difficulty of fusion led ^Chap. 1V.^ him to suspect, that the metal he was in quest of bore a strong analogy to platinum. In the mean time, Dr Gahn, who was making experiments on the same mi- neral, actually succeeded in reducing it by the follow- ing process : He lined a crucible with charcoal powder moistened with water, put into it some of the mineral formed into a ball by means of oil, then filled up the crucible with charcoal powder, luted another crucible over it, and exposed the whole for about an hour to a very intense heat. At the bottom of the crucible was found a metallic button, or rather a number of small metallic globules, equal in weight to one-third of the mineral employed *. It is easy to see by what means this reduction was accomplished. The charcoal attract- ed the oxygen from the oxide, and the metal remained behind. The metal obtained, which is called manganese, was farther examined by Ilseman in 1782, Hielm in 17S5, and Bindheim in 1789. 1. Manganese, when pure, is of a greyish-white co- Properties lour, and has a good deal of brilliancy. Its texture is granular. It has neither taste nor smell. 2. Its hardness is 9, or equal to that of iron. Its specific gravity, according to Bergman, is about 6'850 f . 3. It is very brittle ; of course it can neither be ham- mered nor drawn out into wire. Its tenacity is un- known. 4. It requires, according to Morveau, the tempera- ture of 160 Wedgewood to melt it j it is therefore somewhat less fusible than iron. # Bergman, ii. an. f Of use. ii. 203. 345 BRITTLE METALS. Book!. Division I. Oxides* protoxide. Pcutoxide. 5. When reduced to powder, it is attracted by the magnet, owing probably to a small portion of iron, from which it can with difficulty be parted. II. Manganese, when exposed to the air, attracts oxy- gen with considerable rapidity. It soon loses its lustre, and becomes grey, violet, brown, and at last black. These changes take place still more rapidly if the me- tal be heated in an open vessel. This metal seems capable of combining with three different proportions of oxygen, and of forming three different oxides, the white, the red, and the black. 1. The protoxide or white oxide maybe obtained by dissolving the black oxide of manganese in nitric acid by adding a little sugar. The sugar attracts oxygen from the black oxide, and converts it into the white, which is dissolved by the acid. Into the solution pour a quantity of potash ; the protoxide precipitates in the form of a white powder. It is composed, according to Bergman, of 80 parts of manganese and 20 of oxygen. When exposed to the air, it soon attracts oxygen, and is converted into the black oxide *. 2. The deutoxide or red oxide may be obtained by dissolving the black oxide in sulphuric acid, without the addition of any combustible substance. When black oxide of manganese, made into a paste with sulphuric acid, is heated in a retort, a great quantity of oxygen gas comes over, while the oxide, thus deprived of part of its oxygen, dissolves in the acid. Distil to dryness, and pour water upon the residuum, and pass it through a filter. A red coloured solution is obtained, consist* * Of use. ii. an. MANGANESE. 349 ing of the sulphate of manganese dissolved in the water. Chap. IV, On the addition of an alkali, a red substance precipi- tates, which is the red oxide of manganese. According to Bergman, it is composed of 74 parts of manganese and 26 of oxygen *. This oxide likewise attracts oxy- gen when exposed to the atmosphere, and is converted into the black oxide. 3. The peroxide or black oxide of manganese exists Peroxide, abundantly in nature ; indeed it is almost always in this state that manganese is found. It was to the black ox- ide that the appellation manganese itself was originally applied. It may be formed very soon by exposing the metal to the air. This oxide, according to Fourcroy, is composed of 60 parts of manganese and 40 of oxy- gen f. When heated to redness in an earthen retort, it gives out abundance of oxygen gas, which may be collected in proper vessels. By this operation it is re- duced nearly to the state of red oxide. If it be expo- sed to the air, and moistened occasionally, it absorbs a new dose of oxygen ; and thus the same process may again be repeated J. No oxygen gas can be obtained from the white oxide : a proof that its oxygen is re- tained by a stronger affinity than the additional dose of oxygen which constitutes the black oxide. Seguin has observed, that in some cases the black oxide of manga- nese emits, before it becomes red, a quantity of azotic * Oputc. ii. 115. t Fourcroy, v. 177. t It may be necessary to mention, that with me this absorption hat succeeded but imperfectly, unless when the red or white oxides of man- ganese hare been precipitated from an acid. BRITTLE METALS. Book I. g as *. When long exposed to a strong; heat, it assumes Division I. * Y ' a green colour. In that state it is whitened by sul- phuric acid, but not dissolved f. A very violent heat fuses this oxide, andt converts it into a green coloured glass. Union with III. 1. Manganese does not combine with hydrogen. combusti- TTr , ,. . . . bj cl> When dissolved in sulphuric acid, a black spongy mass of carburet of iron is left behind. Hence it has been supposed capable of combining with carbon ; but it is more probable that the carbon is combined with the iron, which is almost always present in manganese. It seems pretty clear, however, that carburet of iron is capable of combining with this metal, and that it always forms a part of steel. Sulphurct. 2. Bergman did not succeed in his attempt to com- bine manganese with sulphur ; but he formed a sulphu- reted oxide of manganese, by combining eight parts of the black oxide with three parts of sulphur. It is of a green colour, and gives out sulphureted hydrogen gas \vhen acted on by acids J. It cannot be doubted, how- ever, that sulphur is capable of combining with man- ganese ; for Proust has found native sulphuret of man- ganese in that ore of tellurium which is known by the name of gold ore of Nagyag . Phosphiiret. 3. Phosphorus may be combined with manganese by melting together equal parts of the metal and of phos- phoric glass 5 or by dropping phosphorus upon red hot * Owing most likely to the filtration of air through the earthen war; retort, in which the manganese was heated. I have never observed anjr azotic gas when manganese is heated in an iron bottle. f Bergman, ii. 216. $ ibid. p. aai. Jour, de Pbyt. Ivi. r. MANGANESE. 351 manganese. The phosphuret of manganese is of a Chap. IV.^ colour, brittle, granulated, disposed to crystallize, red bj exposure to the air, and more fusible than manganese. When heated the phosphorus burns, and the metal is oxidized*. IV. Manganese does not combine with either of the simple incombustibles. V. Manganese combines with many of the metals, Alloys, and forms with them alloys which have been but very imperfectly examined. 1. We are indebted to MrHatchett for some curious Gold, experiments on the alloy of manganese and gold. Olive oil was repeatedly mixed and burned with black oxide of manganese, after which a piece of gold was imbed- ded in the oxide, placed in a crucible lined with char- coal, and well luted. The crucible was exposed for three hours to a strong heat. By this means a portion of manganese was reduced and combined with the gold. The alloy was externally of a pale yellowish grey co- lour, with a considerable lustre, almost equal to that of polished steel. It was very hard, and possessed some ductility. The fracture was coarse, very spongy, and of a reddish grey colour. It was not altered by expo- sure to the air. From the analysis of Mr Bingley, the alloy was found to vary in the proportion of manganese from -^th to -th of the whole. It is more difficult of fusion than gold. When kept melted with access of air, the while manganese is oxidized, and swims on the surface. The manganese may be separated by cupel- Jation with leadf. * Pelletier, Air., de Cbim. xiii. 137. J Hatchett on the Alloys of GoU, p. 22, 352 Book r. Division I. Copper, Iron, Mercury. BRITTLE METALS. Manganese unites readily with copper. The cocri* pound, according to Bergman, is very malleable, its co- lour is red, and it sometimes becomes green by age* Gmelin. made a number of experiments to see whether this alloy could be formed by fusing the black oxide of manganese along with copper. He partly succeeded, and proposed to substitute this alloy instead of the al- loy of copper and arsenic, which is used in the arts *. It combines readily with iron ; indeed it has scarcely ever been found quite free from some mixture of that metal. Manganese gives iron a white colour, and ren- ders it brittle. It combines also with tin, but scarcely with zinc f. It does not combine with mercury nor with bismuth. Gmelin found that manganese cannot be alloyed with bismuth without great difficulty ; and that it unites to antimony very imperfectly J. Chemists have not at- tempted to combine it with platinum, silver, nickel, nor cobalt. SECT. XXII. OF CHROMIUM, History, I. IN the year 1766, Lehman, in a letter to Bui published the first description of a beautiful red mine- * Gottingen Comment. 1787, vol. ix. p. 75. f Bergman, ii. W>$ $ Ann. de Gbim. six. 366, CHROMIUMa 353 tal with a shade of yellow, crystallized in four-sided Chap rv\ prisms, which is found in the mine of Beresof, near E- katerirabourg in Siberia. This mineral, known by the name of red lead ore of Siberia, was used as a paint, and is now become exceedingly scarce and dear. It was examined soon after by Pallas, who considered it as a compound of lead, arsenic, and sulphur. Macquart, who in 1183 was sent upon a mineralogical expedition to the north of Europe, having brought a quantity of it to Paris, analysed it in 1789, in company with Mr Vauquelin. These gentlemen concluded, from their analysis, that it is a compound of the oxides of lead and of iron. On the other hand, Mr Bindheim of Moscow concluded from an analysis of his own, that its ingre- dients are lead, molybdic acid, and nickel. These dis- cordant analyses destroyed each other, and prevented mineralogists from putting aqy confidence in either. This induced Vauquelm, who had now made himself a consummate master of the art of analysing minerals, to examine it again in I19~i *. He found it a combination of the oxide of lead and an acid, with a metallic basis, never before examined. By exposing this acid to a violent heat along with charcoal powder, he reduced it to the metallic state ; and to the metal thus obtained he gave the name of chromium f. The experiments of Vauquelm have been since repeated and verified by * Ann. de Cbim. XXV. 21. and 194. f From ^^a.^z, because it possesses the property of giving colour to other bodies in a remarkable degree. Vol. /. Z 354 BRITTLE METALS, Book I. Division I. Properties. Oxides. Klaproth *, Gmelin f, and Moussin Pouschkin J . Rich- ter has lately succeeded in reducing chromium to the metallic state, and in ascertaining some of its most im- portent properties . The colour of chromium is white, intermediate be- tween that of tin and steel. Its specific gravity is only 5'90. It is extremely brittle, assumes a good polish, and, according to the observation of Ritter, is magnetic, but inferior in this respect to iron, nickel, and cobalt ||. Acids act upon it with great difficulty. According to Richter, neither nitric nor muriatic acid dissolve it, even at a boiling heat ; but nitro- muriatic acid converts it very slowly into muriate of chromium. It requires a very high temperature to melt it ; but the precise degree has not been ascertained. Richter succeeded in melting it in small grains in a porcelain furnace. II. Chromium is not altered by exposure to the air : but when heated it is gradually converted into an oxide, Whether it is altered by being kept under water has not been ascertained. Chromium seems capable of combining with three different proportions of oxygen, and of forming three oxides ; namely, the green, the brown, and the yellow or chromic acid. * Crell's Annals, 1798, i. 80. Mr Klaproth had examined the red lend ore in consequence of the analysis of Bindheim. His experiments led him to conclude, that the metallic acid, combined with the lead, was not the molybdic, bu the acid of some new unknown metal ; but his specimen was too small to enable him to decide the point. In the mean time,. Vauquelin's experiments were published, t Ibid. 1799, i. 275. j Ibid. 1798, i. 355, & c . Gehlcn's Jour. v. 35 r. }| Ibid, v~ 394. URANIUM* $53 1. The protoxide, or green oxide, may be obtained t Chap. IV. by exposing chromic acid to heat in close vessels ; oxy- gen gas passes over, and the green oxide remains be- hind. 2. The deutoxide, or brown oxide, is intermediate between the green oxide and chromic acid. Moussin Pouschkin, who first described this oxide, compares it to the brown oxide of iron. He has not given an ac- count of the method by which he obtained it*. 3. The peroxide, or chromic acid, is found native in the red lead ore. It is a red or orange yellow powder, soluble in water, and composed of 33 parts of chromi- um and 67 of oxygen. The remaining properties of chromium have not beea examined. SECT. XXIII. OF URANIUM. I. 1 HERE is a mineral found in the George Wagsfort Historf, mine at Johnan-Georganstadt, in Saxony, partly in a pure or unmixed state, and partly stratified with other kinds of stones and earths. The first variety is of a blackish colour, inclining to a dark iron grey, of a mo- derate splendor, a close texture, and when broken pre- sents a somewhat even, and (in the smallest particles) * CrelTi Annals , 1798, ii. 445. Y 2 BRITTLE METALS. Book I. a conclioidal surface. It is quite opaque, tolerably Division L w ^ hard, and on being pounded yields a black powder. Its specific gravity is about 7*500. The second sort is di- stinguished by a finer black colour, with here and there a reddish cast : by a stronger lustre, not unlike that of pitcoal ; by an inferior hardness ; and by a shade of green, which tinges its black colour when it is reduced to powder *. This fossil was called peMknde ; and mineralogists, misled by the name f, had taken it for an ore of z.inc, till the celebrated Werner, convinced from its texture, hardness, and specific gravity, that it was not a blende, placed it among the ores of iron. Afterwards he sus- pected that it contained tungsten ; and this conjecture was seemingly confirmed by the experiments of some German mineralogists, published in the Miners Jour- nal t. But Klaproth, the most celebrated analyst in Europe, examined this ore in 1789, and found that it consists chiefly of sulphur, combined with a peculiar metal, to which he gave the name of uranium J. Uranium was afterwards examined by Richter, and more lately an elaborate set of experiments has been published on it by Bucholz ||. Howob- To obtain uranium from its ore, the mineral is to be treated with nitric acid, which dissolves the metallic new # Kfaprotb, Crell's Jour. Engl. transl. i. 176. f ~Bler.de i* the name given to ores uf zinc. t Ibid. From Uranus (Ouftzvr,{ ), the name given by Mr Bode to the planet discovered by Herschel ; which name the German astronomers have adopted. Mr Kiaproth called the metal at first uranite ; but he af- terwards changed that name for uraniuw, \\ Gehlen's Jour. iv. 17. URANIUM. 357 portion, and leaves the greater part of the foreign bo- . cha P- ' f r.ies. The solution usually contains iron, copper, and lime as well as uranium. By evaporating it to dryness, and exposing the dry mass to a moderately strong heat, the iron is rendered insoluble, while the other ingredi- ents are taken up by distilled water. Ammonia pour- ed into this solution, and digested in it for some time, retains the copper, but throws down the uranium. The precipitate is to be well washed with ammonia till the liquid comes off colourless ; it is then to be dis- solved in nitric acid, concentrated by evaporation, and set by to crystallize. The green coloured crystals that form are to be picked out, dried on blotting paper, olved in water, and the liquid again crystallized. By this means the whole of the lime, should any be pre- sent, is gradually left behind, and the crystals consist at last of pure oxide of uranium, united to nitric acid. They are to be exposed to a red heat ; a yellow pow- . which is oxide of uranium. This powder is to be mixed with a small quantity of charcoal powder, and exposed to a violent heat. By this method it is re- duced to the metallic state *. 1. Hitherto uranium has not been obtained in masses Properties, of any considerable size ; the heat requisite to melt it being much greater than can be raised in furnaces. It follows, from the trials of Bucholz, that no flux is of any service in facilitating the fusion of this metal; that its refractoriness does not, as Richter suspected, proceed from the presence of iron ; that charcoal powder, when See Klaproth's Butr*gt t 11.476. Ecg.tfans. and Bucholz, Gtblt*t ' 35S BRITTLE METALS. Beok I. mixed in a large proportion, obstructs the success ; and Division I. 6 . r U y ~j that we accomplish our purpose best when the oxide is mixed with a portion of charcoal not exceeding ^th of the weight. This mixture is to be inclosed in a char- coal crucible, to exclude the air, and exposed to the strongest heat that can be raised. Klaproth, in a heat of 170 Wedgewood, obtained a porous, metallic mass, firmly cohering ; and Bucholz procured it nearly in the same state. 2. Its colour, when thus obtained, is iron grey ; it has considerable lustre, and is soft enough to yield to the file. Its malleability and ductility are of course unknown. Its specific gravity, in Klaproth's trials, was only 8*100. But Bucholz obtained it as high as 9*000. II. From the experiments of Bucholz, we learn that uranium is capable of uniting with various doses of oxygen. 1. When uranium is heated to redness in an open vessel, it undergoes a species of combustion, glowing like a live coal, and is soon converted into a greyish black powder, which undergoes no farther change, though the heat be continued. This powder is the prot- oxide of uranium. One hundred parts of the metal, when thus oxidized, increase in weight so as to become 105*17. Hence this oxide is composed of about 95*1 uranium 4*9 oxygen Combina- tion with oxygen. protoxide. 100-0 * * Bucholz, Ibid, p. 35, URANIUM. 359 2. When uranium or its oxide is dissolved in nitric P' . acid, and the solution is treated with an alkali, the me- Peroxide. tal is precipitated in the state of a peroxide. The same peroxide is procured by precipitating uranium from sul- phuric or muriatic acids, and exposing it while moist to the air. The peroxide thus obtained, when well washed and dried, is yellow, tasteless, and insoluble in water. When treated with muriatic acid, it dissolves with effervescence, oxymuriatic acid gas being disen- gaged. This oxide, according to Bucholz, is composed of from 76 to 80 parts of uranium, united with from 14 to 20 of oxygen. Hence 100 parts of the metal, when peroxidized, increase in weight so as to become between 126 and 13 1. Experiment has not hitherto ascertained the exact proportion *. 3 . Bucholz is of opinion, that besides these two oxides Other there are several intermediate degrees of oxidizement of which the metal is susceptible, each of which is cha- racterized by a peculiar shade of colour. When the black oxide is dissolved in sulphuric acid, and thrown down by ammonia, it is at first blackish grey, but soon assumes a violet colour. When the solution of ura- nium in nitric acid is evaporated to dryness, and expo- sed to a red heat, a yellowish brown powder remains, inclining to green. All these colours Bucholz consi- ders as indicating so many degrees of oxidizement. The following, according to him, is the suite of colours through which the oxides of uranium pass, every one including a peculiar oxide f. Protoxide Greyish black. * Sucholz, Ibid. p. 37. -f Ibid. p. 40, 360 BRITTLE METALS. Book T. Division I. Sulphuret. Second oxide. . . .Dark grey, inclining to violet. Third oxide Greenish brown. Fourth oxide Greyish green. Fifth oxide Orange. Peroxide Lemon yellow. III. No experiments have been made to ascertain the compounds which uranium is capable of forming with any of the simple combustibles, except with sulphur. 1. Klaproth mixed the peroxide of uranium with twice its weight of sulphur, and heated it in a retort till most of the sulphur was driven off. The residuum was a blackish brown compact mass. By increasing the heat, the whole of the sulphur was driven off, and the uranium remained in the metallic state in the form of a black heavy coarse powder*. Bucholz's experiments though made in a different way, led nearly to the same result. He boiled a mixture of sulphur and oxide of uranium in an alkaline solution to dry "ess, heated the residue to redness, and then treated it with distilled wa- ter. A blackish brown powder remained behind, and small needles of a red colour appeared in the solution. In one trial, the compound which he obtained gave out some sulphureted hydrogen when dissolved in muriatic cid. Tins is a proof that it was not a sulphureted oxide, but a sulphuret of uranium f. IV. Uranium is but imperfectly soluble in muriatic acid. Azote, we may infer from analogy, does not act upon it, V. Nothing is known respecting the combinations of uranium with the other meu;Js ; Bucholz having been * f f Gthlen's Jour. iy. 47. MOLYBDENUM. 361 hitherto prevented from making any experiments on that J_ part of the subject, by the want of a sufficient quantity of uranium. . SECT. XXIV. OF MOLYBDENUM. I. J. HE Greek word /Ai> ( 3ja/a, and its Latin transla- History, tion plumbago, seems to have been employed by the an- cients to denote various oxides of lead ; but by the mo- derns they were applied indiscriminately to all substan- ces possessed of the following properties : Light, fria- ble, and soft, of a dark colour and greasy feel, and which leave a stain upon the fingers. Scheele first examined these minerals with attention. He found that two very different substances had been confounded together. To one of these, which is composed of carbon and iron, and which has been already described, he appropriated the word plumbago ; the other he called molybdena. Molybdena is composed of scaly particles adhering slightly to each other. Its colour is bluish, very much resembling that of lead. 8cheele analysed it in me, and obtained sulphur and a whitish powder, which pos- sessed the properties of an acid, and which, therefore, he called acid of ??iolybdena *. Bergman suspected this acid, from its properties, to be a metallic oxide j and at * Sdccle, i. 23*. - r ;52 BRITTLE METALS. Book I. his request, Hielm, in 1782, undertook the laborious Division I. L * v *J course of experiments bj which he succeeded in obtain- ing a metal from this acid. His method was to form it into a paste with linseed oil, and then to apply a very strong heat. This process he repeated several times successively *, To the metal which he obtained he gave the name of molybdenum f . The experiments of Scheele were afterwards repeated by PelletierJ, Use- man J, and Heyer || j and not only fully confirmed, but many new facts discovered, and the metallic nature of inolybdic acid was put beyond a doubt : though, in consequence of the very violent heat necessary to fuse molybdenum, only very minute grains of it have been hitherto obtained in the state of a metal. Still more lately Mr Harehett has published a very valuable set of experiments, which throw much new light upon the nature of this metal fl". We are indebted to Bucholz for the last and not the least elaborate and important set of experiments on this refractory metal and its com- pounds **. Kawpro- The simplest method of procuring molybdenum in a state of purity, seems to be that put in practice by Hielm, Molybdena is roasted in a moderate red heat slowly and repeatedly, till the whole is reduced to the state of a fine powder, and passes through a sieve. The powder is to be dissolved in ammonia, the solution fil- tered, and evaporated to dryness. The residuum being moderately heated (adding a little nitric acid) leaves a * Bergman's Sclagraplia, p. 19, Eng. transl. f Crell's Annals, 1790, i. 39, &c. \ Jour, de P/jys. 1785, Decembre, Crell's Annals, 1787, i. 407. || Ibid. 1787, ii. 21. and 124. * Ptit. Trans. 1795, p. 333. #* Gehlen's Jour. iv. 39&. MOLYBDENUM. 36$ white powder, which is^the pure oxide of molybde- t c " a P- IV t num *. By mixing this oxide with some oil or char- coal powder, and exposing it to a violent heat, it is re- duced to the metallic state. The method followed by Bucholz was nearly similar. He has shown that heat reduces the oxide to the metallic state without its bejng necessary to add any charcoal. But no heat which he could raise was high enough to melt this refractory metal into a solid button. The experiments of preceding chemists had been equally unfortunate. I. Hitherto the metal has been obtained only in small Properties, grains, or in pieces imperfectly agglutinated, and which break readily when struck. Its colour, from the ob- servations of Bucholz, seems to be silvery white, but it frequently has a shade of yellow. Hielm found its specific gravity only 7'400 ; but Bucholz, whose spe- cimens had doubtless been exposed to a more violent heat, and were more compact, found it as high as S-611 f. Molybdenum is brittle. It is not altered though kept under water. The effect of exposure to the air has not been ascertained in a satisfactory manner. II. When exposed to heat in an open vessel, it gra- Oxides. dually combines with oxygen, and is converted into a white oxide, which is volatilized in small brilliant needle-form crystals. This oxide, having the proper- ties of an acid, is known by the name of molybdic acid* From the experiments of Bucholz, compared with the previous observations of Hatchett, we learn that molybdenum is capable of combining with at least four * CrelT* Annals^. 338. Eng. trans. f Gehlen's Jour. iv. 364 BRITTLE METALS. Book I. Division I. Protoiiile. Second ox- ide. Blue oxide. different doses of oxygen, and of forming four oxides 5 namely, 1. the brown ; 2, the violet ; 3. the blue ; and 4. the white, commonly known by the name of mo- lybdic acid. 1. The brown oxide is obtained by exposing molyb- denum in powder to a red heat. Nothing is known respecting the proportion of oxygen which it contains. Indeed Bucholz inferred from the colour merely that it is a peculiar oxide, without subjecting it to a particular examination. 2. By exposing the metal to a longer and rather a more violent heat, it assumes a violet brown colour, which Bucholz considers as the second oxide. When the molybdate of ammonia is exposed to a violent heat in a crucible, a violet brown mass remains behind, ha- ving more or less cohesion according to the tempera- ture, and a considerable degree of metallic lustre. This residue Bucholz. considered at first as the metal reduced, but a more complete investigation convinced him that it was a peculiar oxide. Probably it is the same with the second oxide obtained directly by heating the metal. 3. The blue oxide may be obtained by carrying the heating of the molybdenum a little farther. But Bu- cholz found this a very tedious and uncertain method. The following process succeeded much better : Mix together one part of molybdenum in powder and two parts of molybdic acid, and triturate them in a porce- lain mortar made into a pap with hot water till the mix- ture becomes blue, then add eight or ten parts of water, and boil the whole for a few minutes. Filter the sol*u- tion, and evaporate in a temperature not exceeding 120. The blue oxide remains in the state of a fine powder. If the whole of the mixture of molybdenum and mo- MOLYBDENUM* bdic acid be not dissolved, the process may be repeat- ed with the residue as often as is necessary. This blue oxide possesses in fact the properties of an acid. It con- verts vegetable blues to red, is soluble in water, com- bines with the saline bases, and forms salts. The name of molybous acid may be given to it. Molybdenum appears always to be converted into this oxide when left in contact with water and air, or when water mix- ed with it is slowly evaporated. The blue oxide seems to be composed of about 100 parts metal and 34 oxy- gen. 4. The white oxide, or molybdic acid, is obtained Molybdic most easily from native molybdena, by roasting it for SCI * some time, and then dissolving the grey residue in am- monia. Nitric acid dropt into the solution precipi- tates the molybdic acid in a state of purity *. The acid thus otvained is in fine white scales ; but when melted and sublimed it becomes yellow. Its properties were first investigated by Scheele. It converts vegetable blues to red ; but according to Bucholz, not with so much readiness as the blue oxide, which in his opinion is the more powerful acid of the two. It is composed, accord- ing to his experiments, of about 66y parts metal, and 33y oxygen, or of 100 metal and 50 oxygen. Bucholz supposes, that between the blue and the white oxides there is an intermediate oxide, the colour of which is bluish green, and which likewise possesses acid properties. III. l. Molybdenum combines readily with sulphur; Union with and the compound has exactly the properties of mo- mbusti - Bucholz, GeMtn't Jour, iv. 604. BRITTLE METALS. Book I. lybdena, the substance which Scheele decompounded *. v/ Molybdena is therefore sulplmret of molybdenum. The reason that Scheele obtained from it molybdic acid was, that the metal combined with oxygen during his pro- cess. Sulphuret of molybdenum may be formed also by distilling together one part of molybdic acid and five parts of sulphur. From the experiments of Bucholz. we learn, that it is composed of about 60 metal 40 sulphur lOOf. 2. Molybdenum is also capable of combining with phosphorus J. IV. Muriatic acid has but little effect upon molyb- denum ; but it dissolves its oxide. The action of a- zote has not been examined. Alloys with V. To the indefatigable industry of Hielm, we are indebted for a set of experiments on the alloys of mo- lybdenum with other metals. Gold *' With gold it melts only imperfectly, and forms a blackish brittle mass, from which a considerable por- tion of the gold eliquates when it is kept in a strong heat. The alloy is attacked by nitric acid. The gold subsides in the state of a fine powder, and the molyb- denum lies over it in the form of white oxide. The proportions tried were Gold 6, 4, 2. Molybdenum 2, 2, 2. * Pelletier, Jour, de Piys. 1785. f Gehlen's Jour. iv. 603, f Pelletier, Ann. de Cbim< xiii. 137. MOLYBDENUM. 367 None of these compounds could be brought into per- , cha ^ > iv ' f feet fusion even by the assistance of borax *. 2. Equal parts of platinum and molybdenum melt- Platinum, ed into a hard irregular brittle mass, of a close texture, a light grey colour, and a metallic lustre. Three parts of molybdenum, and one of platinum, did not melt com- pletely. The same difficulty of fusion was experienced when the proportion of platinum was augmented. The specific gravity of this alloy was found by Hielm to be 20 f. 3. Four parts of silver and two of molybdenum were strongly heated in a crucible, but did not yield a button. By continuing the heat a portion of the silver eliqua- ted, still retaining a part of the molybdenum, and be- coming bluish when heated. The residuum being melted again in charcoal, became more compact, was brittle, of a grey colour, and a granular texture. When melt- ed by itself silver eliquated. By nitric acid the silver was taken up from this alloy, and the molybdenum converted into white oxide. Four parts of silver and one of molybdenum gave a malleable compound, but it could not be melted into a round button. It was of a silver colour and granular texture. One part of silver and two of molybdenum melted into a granular, brittle, greyish lump. When heated on charcoal the molybdenum evaporated, and the silver remained. The molybdenum may be separated from silver by cupellation, especially if the alloy has been previously calcined J. * Hielm, Crell's Annats, in. 356. Eng. trans. | Ibid. p. 53, and Ann, d: Cbim* iv. 17. J Crell's Axnals, iii. 361, 368 BRITTLE METALS, Book T. Division I. Copper, Iron, Nickel, 4. Hielm could not succeed in his attempts to unite mercury and molybdenum *. 5. Equal parts of molybdenum and copper formed an alloy which yielded to the hammer a little, but at length broke in pieces, exhibiting a granular texture, and a bluish colour mixed with red. It admitted of being filed ; and the surface thus exposed was paler than copper, and did not lose its lustre by exposure to the air. Four parts of copper and 1^- molybdenum formed an alloy not very different in its properties ; but when the metals were mixed in the proportion of one part copper and two molybdenum, the alloy was brit- tle, and of a reddish grey colour. Nitric acid dissolved the copper, and left the white oxide of molybdenum f. 6. Equal quantities of iron and molybdenum melt readily, and form a brittle alloy, of a bluish grey co- lour, and considerable hardness. Its fracture was fine, scaly, and granular. Before the blow-pipe it melted with intumescence, but without sparks. One part of iron and two of molybdenum formed a brittle alloy, of a fine grained texture, and light grey colour. It was magnetic, and did not melt before the blow-pipe. Of all the metals, iron seems to unite most readily with molybdenum 7. Equal quantities of molybdenum and nickel melt- ed into a button, internally of a light grey colour, yield- ing somewhat to the hammer before it broke, and ex- hibiting a granular texture. It was not magnetic, and did not melt before the blow-pipe. When the propor- tion of molybdenum is increased, the fusion of the al- * Crell's Annals, Hi. 358. f Ibid. p. 366- J Ibid. p. 370^ MOLYBDENUM. 36$ loy becomes more difficult ; in other respects, its proper- f Chap. iv.^ ties continue nearly the same *. 3. Equal parts of tin and molybdenum melted into Tin. a blackish grey, granular, brittle, soft mass. When two parts of tin and one of molybdenum were melted together, the alloy was harder than the preceding, but in other respects agreed with 1 it. Four parts of tin and one of molybdenum formed a still harder alloy, which ad- mitted of being hammered a little, did not crackle like tin when bent, and in its fracture exhibited a greyish colour and granular texture. When strongly heated, the tin did not eliquate till the alloy was pressed with the forceps f. 9. Ten parts of lead and one of molybdenum, when melted together, form an alloy which is somewhat malleable, and whiter than pure lead. When kept heated, the lead partly eliquates. When the propor- tion of molybdenum is increased, the alloy becomes brittle, dark coloured, and more difficult of fusion J. 10. The volatility of zinc renders it difficult to alloy that metal with molybdenum. Equal parts ot the two metals, strongly heated in a covered crucible, left a black mass almost in a powdery state J. 11. The combination of bismuth and molybdenum is equally obstructed by the volatility of the former metal. When they are melted together, the bismuth is driven off, and a black brittle mass remains, consisting chiefly of molybdenum. Four parts of bismuth and one of molybdenum, being melted together in a bed of charcoal, gave a black brittle mass, together with a but* * Crell's A".na!s, ii'. 367. t Ib;d. p. 373. J Ibid. p. 388. Ibid. p. 375. . /. A a 370 BRITTLE METALS. Antimony, Book I. ton of bismuth^ which retained a portion of molybde- num. This button bore a few strokes of the hammer, but at length broke in pieces. Its texture was closer than bismuth, and it was very fusible*. 12. When antimony and molybdenum were melted together, the antimony exhaled, leaving the molybde- num in the state of a black mass. By adding antimo- ny to this mass, and repeating the fusion twice, a por- tion of the antimony adhered to the molybdenum, and formed an alloy of a yellowish grey colour and brittle f . 13. When arsenic and molybdenum are melted to- gether, the whole of the arsenic sublimes ; but when oxide of arsenic is employed, a combination takes place, from which the arsenic is not easily separable again J. 14. Equal parts of cobalt and molybdenum melted into a button of a grey colour, brittle, and of difficult fusion. Two parts of cobalt and fqur of molybdenum gave an alloy of a sparkling reddish grey colour, hard, brittle, not attracted by the magnet, internally granular, and of a bluish grey colour .. Manganese. 15. Equal parts of manganese and molybdenum melted into an irregular button, not fusible before the blow-pipe, and not colouring borax till after it had been roasted I! . Arsenic* Cobalt, * Crell's Annalt, p. 363. t Ibid. p. 377. $ Ibid. p. 36^. Ibid. p. 371. [1 Ibid. p. 376, SECT. XXV. OF TUNGSTEN. J 4 THERE is a mineral found in Sweden of an opaque white colour and great weight ; from which last cir- cumstance it got the name of tungsten, or ponderous stone. Some mineralogists considered it as an ore of tin, others supposed that it contained iron. Scheele ana- lysed it in 17S1, and found that it was composed of lime and a peculiar earthy. like substance, which he cal- led from its properties tungstic-acid*. Bergman con- jectured that the basis of this acid is a metal f; and this conjecture was soon after fully confirmed by the experiments of Messrs D'Elhuyar, who obtained the same substance from a mineral of a brownish black co- lour, called by the Germans wolfram J, which is some- times found in tin mines. This mineral they found to contain -f~ of tungstic acid ; the rest of it consisted of manganese, iron, and tin. This acid substance they mixed with charcoal powder, arid heated violently in a crucible. On opening the crucible after it had cooled, they found in it a button of metal, of a dark brown co- lour, which crumbled to powder between the fingers. On viewing it with a glass, they found it to consist of a congeries of metallic globules, some of which were as * Scheele, ii. 8r. f Ibid. if. 91. \ Wolfram had been analysed in 176 by Lehmann. He imagined & a compound of iron and tin. See his Probierlunst, p. 9. A a 2 372 BRITTLE METALS. Book I. large as a pin-head. The metal thus obtained is called Division I . i. i y ' tungsten. The manner in which it is produced is evi- dent : tungstic acid is composed of oxygen and tung- sten ; the oxygen combined with the carbon, and left the metal in a state of purity *. The experiments of the Elhuyarts were repeated in 1796 by Vauquelm and Hecht, in general with suc- cess ; but they were unable to procure the metal com- pletely fused, though this had been accomplished by the Spanish chemists f. Nor is this to be wondered at, as Dr Pearson $ and Mr Klaproth had made the same attempt before them without succeeding. The fusion of this metal has been also accomplised by Messrs Allen and Aiken of London. They succeeded by applying a strong heat to the combination of the oxide of tungsten and ammonia ||. Properties. j Tungsten, called by some of the German che- mists scheelium, is of a greyish- white colour, or rather like that of steel, and has a good deal of brilliancy. 2. It is one of the hardest of the metals j for Vau- quelin and Hecht could scarcely make any impression upon it with a file. It seems also to be brittle. Its spe- cific gravity, according to the D'Elhnyarts, is 17'6 ; according to Allen and Aiken, 17*33 ^[. It is there- fore the heaviest of the metals after gold and plati- num. * Mem. TLoulomey ii. 141, This memoir has been translated int English- f Jur. de Mifj. No.xix. 3. | Transt. of the Cbem. Nomenclature* Obtetv. on tf>e Fossils of Ccrnwall, p. T], \, Aiken's Dictionary of CLemistry, ii. 445. ^ Ibid* TUNCSTtN. 375 2. It requires for fusion a temperature at least equal &&$ IV. to 170 Wedgewood. It seems to have the property of crystallizing on cooling, like all the other metals ; for the imperfect button procured by Vauquelin and Hecht contained a great number of small crystals. 3. It is not attracted by the magnet. II. When heated in an open vessel, it gradually ab- Oxides, sorbs oxygen, and is converted into an oxide. Tung- sten seems capable of combining with two different pro- portions of oxygen, and of forming two different oxides ; the blue and the yellow. 1. The protoxide, or blue oxide, may TDC obtained Protoxide, by heating the yellow oxide for some hours in a cover- td crucible. It is formed when a muriate of tin is poured into a solution of molybdate. 2. The peroxide or yellow oxide, known also by the Peroxide, name of tungstic acid*, may be obtained by boiling three parts of muriatic acid on one part of wolfram. The acid is to be decanted off in about half an hour, and allowed to settle. A yellow powder gradually pre- cipitates. This powder is to be dissolved in a?nmonia, the solution is to be evaporated to dryness, and the dry mass kept for some time in a red heat. It is then yel- * The tungstic acid of Scheele is different from this oxide. It is a white powder of an acid taste, and soluble in water. The D'Elhuyarts have demonstrated that it is a triple salt, composed of the yellow oxide of tungsten, potash, and the acid employed to decompose the mineral from which it is obtained. BRITTLE METALS. Book T. low oxide in a state of purity *. This oxide has n^ 1)5 vision [. T ...... , -i t . ^ taste. It is insoluble in water, but remains long sus- pended in that liquid, forming a kind of yellow milk, which has no action on vegetable colours. When heat- ed in a platinum spoon it becomes green ; but before the blow-pipe on charcoal it acquires a black colour. It is composed of 80 parts of tungsten and 20 of oxygen. Its specific gravity is 6*12. Union with IH- * The sulphuret of tungsten is of a bluish black combusti- colour, hard, and capable of crystallizing. 2. Phosphorus is capable of combining with tung- sten f. But none of the properties of the phosphuret* have been ascertained. IV. The simple incombustibles do not seem capable of uniting with tungsten. V. The Elhuyarts alone attempted to combine tung- sten with other metals. They mixed 100 grains of the metals to be alloyed with 50 grains of the yellow oxide of tungsten nnd a quantity of charcoal, and heated the mixture in a crucible. The result of their Experiments is as follows : * A more economical process for procuring this oxide has been pro- posed by Bucholz. His formula is as follows : Mix one part of wolfram in fine powder with two parts of subcarbonate of potaih ; keep the mix- ture melted in a crucible for an hour, stirring it occasionally. Then pour it into an iron cone. Before the mass be quite cold, reduce it to powder, and boil water on it repeatedly till the liquid comes off tasteless. Mix all the watery solutions together, and pour muriatic acid into them as long as any precipitate appears. Wash the precipitate ; dissolve it in bo;ling carbonate of potash, precipitate again by muriatic acid, wash the precipi- tate, and dry it upon filtering paper. It is pure peroxide of tungsten-. See Jour, de Cblm. iii. 22O. f Pclletier, Ann. ds Cbim. xiii, 137. TUNGSTEN. j. With gold it did not melt completely. The but- ton weighed 139 grains. By cupellation with lead the gold was reduced to its original purity. With platinum it refused likewise to melt. The mass obtained weigh- cd 140 grains. 2. With silver it formed a button of a whitish-browa colour, something spongy, which with a few strokes of a hammer extended itself easily, but on continuing them it split in pieces. This button weighed 142 grains. 3. With copper it gave a button of a copperish red, v which approached to a dark brown, was spongy, and pretty ductile, and weighed 133 grains. 4. With crude or cast iron, of a white quality, it gave a perfect button, the fracture of which was compact,, and of a whitish brown colour : it was hard, harsh, and weighed 137 grains. 5. With lead it formed a button of a dull dark brown, with very little lustre, spongy, very ductile, and split- ting into leaves when hammered; it weighed 127 grains. 6. The button formed with tin was of a lighter brown than the last, very spongy, somewhat ductile, and weigh- ed 138 grains. 7. That with antimony was of a dark brown colour, shining, something spongy, harsh, and broke in pieces easily : it weighed 108 grains. 8. That of bismuth presented a fracture, which, when seen in one light, was of a dark brown colour, with the lustre of a metal, and in another appeared like earth, without any lustre ; but in both cases one could distin- guish an infinity of little holes over the whole mass. BRITTLE METALS. Book I. This button was pretty hard, harsh, and weighed 6$^ Bivision I." -i* y ' grains. 9. With manganese it gave a button of a dark bluish- brown colour and earthy aspect ; and on examining the internal part of it with a lens, it resembled impure dross of iron : it weighed 107 grains *. * Chemical analysis of Wolfram, translated by Cullen,p. 59* REFRACTORY METALS, CLASS IV. REFRACTORY METALS, ALL of the metals belonging to the preceding class, if we except cobalt and manganese, are so difficult of fusion, that it has been impossible to procure them in large masses, but merely in the state of pgglutinated grains. The remaining metals are still more refractory, so much so indeed, that they are still unknown in the metallic state ; their oxides only, and the compounds which they form with other bodies, having been examined. Per- Jiaps titanium may be an exception ; but as the reduc- tion of this substance to the metallic state is still some*. what doubtful, it was thought better to arrange it a- mong the refractory metals. SFERACTORY METALS. Boolt T. Division I. SECT. XXVI. O F T I T A N I U M. KIstoryv J. \yj the valley of Menachan, in Cornwall, there is found a black sand, bearing a strong resemblance to gun- powder. It was examined in 1781 by Mr Gregor, who found it composed almost entirely of iron and the oxide of a new metal, to which he gave the name of menachine * . He attempted in vain to reduce this oxide to the metallic state ; but his experiments were suffi- cient to demonstrate the metallic nature of the sub- stance, and to show that it contained a metal till then absolutely unknown. This curious and ingenious ana- lysis seems to have excited but little attention, since no- body thought of repeating it, or of verifying the conclu- sions of Mr Gregor. But in 1795 Klaproth published the analysis >of a brownish red mineral, known to mineralogists by the name of red shorL He found it entirely cornposed of the oxide of a peculiar metal, to which he gave the name of titanium f. He failed indeed in his attempts to reduce this oxide ; but his experiments left no doubt of its metallic nature. On examining in 1197 the black mineral analysed by Mr Gregor, he found it a compound of the oxides of iron and titanium J. Consequently the analysis of Mr Gregor was accurate, and his mena- * Jour, de Pbys. xxxix. 72. and 152. f Beitragc, i. 233, $ Ibid. ii. 226. TITANIUM. 379 flint is the same \vith titanium, of which he was un- . cha P- Iv ^ doubtedly the original discoverer. The term titanium has been preferred by chemists, on account of the great celebrity and authority of the illustrious philosopher who imposed it. Klaproth's experiments were repeat- ed, confirmed, and extended by Vauquelin and Hecht in 1196, who succeeded in reducing a very minute por- tion of the oxide of titanium to the metallic state *. They were repeated also and confirmed by Lowitz of Petersburgh in 1798 f. By these philosophers, and by Lampadius, the following properties of titanium have been ascertained. I. Lampadius is said to have reduced it by exposing the oxide with charcoal to a violent heat. Its colour is that of copper, but deeper. It has considerable lustre. It is brittle, but in thin plates has considerable elasti- city. It is highly infusible J. II. When exposed to the air, it tarnishes, and is easi- Oxide* ly oxidized by heat, assuming a blue colour. It deto- nates when thrown into red hot nitre . It seems capable of forming three different oxides; namely, the blue or purple, the red, and the 'white. 1. The protoxide, which is of a blue or purple colour, Protoxide, is formed when titanium is exposed hot to the open air, evidently in consequence of the absorption of oxy- gen. 2. The deutoxide or red oxide is found native. It Dcutoxide is often crystallized in four- sided prisms ; its specific gravity is about 4' 2 ; and it is hard enough to scratch glass. When heated it becomes brown, and when ur- * Jour, de Min. No. iv. 10. f CrelPs Annals, 1799, i. 183, + Nicholson's Jour, vi. 62. Lampadius, ibid. SSO REFRACTORY METALS. Book I. ged by a very violent fire, some of it is volatilized. Division I. . J *.' V ' ' When heated sufficiently along with charcoal, it is re- duced to the metallic state. Peroxide. 3i The peroxide or white oxide may be obtained by fusing the red oxide in a crucible with four times its weight of potash, and dissolving the whole in water. A white powder soon precipitates, which is the white oxide of titanium. Vauquelin and Hecht have shown that it is composed of 89 parts of red oxide and'll parts of oxygen . tfnion with III. i. Titanium does not seem to be capable of com- eombusti- . . . . . , , bles. bming with sulphur . Phosphuret. 2. Phosphuret of titanium has been formed by Mr Chenevix by the following process. He put a mixture of charcoal, phosphate of titanium (phosphoric acid combined with oxide of titanium}, and a little borax, into a double crucible, well luted, and exposed it to the ^heat of a forge. A gentle heat was first applied, which was gradually raised for three quarters of an hour, and maintained for half an hour as high as possible. The phosphuret of titanium was found in the crucible in the form of a metallic button. It is of a pale white colour, brittle, and granular ; and does not melt before the blow-pipe f. IV. Vauquelin and Hecht attempted to combine ic with silver, copper, lead, and arsenic, but without suc- cess. But they combined it with iron, and formed an alloy of a grey colour, interspersed with yellow colour- ed brilliant particles. This alloy they were not able to fuse. * Gregor. | Nicholson's Jour. v. 134. COLUMBIUM. SECT. XXVII. OF COLUMBIUM. I. IN the year 1802, while Mr Hatchett was engaged History, in arranging some minerals in the British Museum, a dark-coloured heavy substance attracted his attention, on account of some resemblance which it bore to chro- mate of iron. The specimen was small. It was descri- bed in Sir Hans Sloane's catalogue as " A very heavy black stone with golden streaks 5" and it appears that it was sent along with various specimens of iron ores to Sir Hans Sloane by Mr Winthrop of Massachusets. Its colour was a dark brown grey ; its longitudinal frac- ture imperfectly lamellated, and its cross fracture show- ed a fine grain. Its lustre was glassy, and in some parts slightly metallic. It was moderately hard, but very brittle. By trituration it yielded a powder of a dark chocolate brown, not attracted by the magnet. Its spe- cific gravity, at the temperature of 65, was 5'91S. By an ingenious analysis of this mineral, Mr Hat- chett ascertained that it was composed of one part o oxide of iron, and rather more than three parts of a white coloured substance which possessed the proper- ties of an acid, and exhibited undoubted proofs of being composed of oxygen united to a metallic basis. The properties of this metallic acid will be described here- after. Mr Hatchett demonstrated, that it differs from all the metallic acids hitherto examined; of course its metallic 382 REFRACTORY METALS. Division 1 ! ^asis must ^ e a ^ so P ecu liar, and required a distinct name* * . Accordingly he gave k the name of columlium. Attempts Various attempts were made to reduce this acid to to reduce it. . the metallic state, but none or them succeeded com- pletely. A portion of it was put into a crucible lined with charcoal, and exposed to a violent heat in a small wind furnace for about an hour and a half. The oxide was found in a pulverulent state, and had assumed a Llack colour. Mr Hatchett ascertained, that, like most of the other metals, it is capable of combining with different doses of oxygen, distinguished from each other by their dif- ferent colours and different actions upon the acids. Though strongly heated with sulphur, it showed no disposition to combine with the substance, or to form a sulphuret. Thosphuret. In order to form a phosphuret some phosphoric acid was poured upon a portion of the white oxide ; and be- ing evaporated to dryness, the whole was put into a cru- cible lined with charco-al. It was then exposed for half an hour to the heat of a forge. The inclosed matter was spongy, and of a dark brown : it in some measure resembled phosphuret of titanium *- Ekeberg has announced his opinion, that this metal is the same with tungsten, buthe has not communicated the experiments upon which this opinion is founded f. The o-*e of columbium was reported some years ago to have been discovered in Switzerland, but we -do not know how far that report was correct. * PltL Trans, 1802. f Gehlen's Jour. v. 48* CERIUM. SECT. XXVIIL OF CERIUM. IN the year 1750 there was discovered, in the copper History, mine of Bastnas at Ridderhytta, in Westmannland in Sweden, a mineral which, from its great weight, was for some time confounded with tungsten. This mine- ral is opaque, of a flesh colour, with various shades of intensity, and very rarely yellow. Its streak is greyish white, and when pounded it becomes reddish grey. It is compact, with a fine splintery fracture, and fragments of no determinate form ; moderately hard ; its specific gravity, according to Cronstedt, 4'9SS *, according to Klaproth 4'6V30 f, according to Messrs Hisinger and :Berzelius r from 4'4S9 to 4*619 J. This mineral was first examined by M. D'Elhuyar : the result of whose analysis was published by Bergman in 1784 }. It as- certained that the mineral in question contained no tungsten. No farther attention was paid to this mineral till Kla- proth published an analysis of it in 1804, under the name of Ochroits ||, and announced that it contained a new earth, to which he gave the name of oclroita. He sent a specimen of this new product to Vauquelin, who made a few experiments on it, but hesitated whether to * Gehlen's Jour. ii. 305. f Ibid. \ Ibid. 21. 398, 5 Optisc. vi. 1 08. |j Gehlen's Jour. ii. 303, 384 REFRACTORY METALS. Book!. Division I. How ob- tained. consider ochroita as an earth or a metallic oxide * Meanwhile the mineral had undergone a still more com- plete examination in Sweden by Hisinger and Berze- iius, who gave it the name of cerit ; detected in it a pe- culiar substance, which they considered as a metallic oxide, and to which they gave the name of cerium, from the planet Ceres, lately discovered by Piazzi f. But the attempts of these chemists to reduce the supposed oxide to the metallic state were unsuccessful. Nor were the subsequent trials of Gahn, to reduce it by vio- lent heat along with charcoal, or to alloy it with other metals, attended with greater success |. Vauquelin has re-examined it lately ; but his attempts have been only partially successful . They demonstrate, however, that the substance in question is a metal ; though from its refractory nature, and its volatility, only minute glo- bules of it were obtained. I. To obtain the metal, the combination of oxide of cerium with tartaric acid was mixed with some lamp-black and oil, and exposed to the violent heat of a forge in a crucible lined with charcoal, and in- closed in another filled with sand. Only a small me- tallic buttpn was obtained, not exceeding the 50th part of the oxide of cerium exposed to heat. It was white, brittle, dissolved with great difficulty in nitro- muriatic acid, and proved a mixture of iron and cerium. An- other attempt to obtain the metal by heating its tartrate in a porcelain retort was not more successful. Most * Ann. de Cbim. 1. 140. :, de Cbint. liv. 28. Gehlcn's Jour. iJ. 297- 4 Ibid in. 217- 38$ it was dissipated, small globules only remaining, Chap. IV. which proved as before a mixture of cerium and iron *. */ I. To procure oxide of cerium in a state of purity, How pro* the Swedish chemists employed the following method : curc ' The mineral was reduced to a fine powder, and digested in nitric acid till every thing soluble was taken up. The solution being decanted off is evaporated to dry* ness, and the residue dissolved in water. Into this so- lution ammonia is poured, till every thing precipitable by means of it is thrown down. This precipitate be- ing well washed is redissolved in nitric acid j the acid is neutralized ; and then tartrate of potash f is added to the solution. The precipitate which is separated being heated to redness, and well washed with vinegar, and dried, is pure oxide of cerium J. 1. When first procured it has a white colour, but when heated to redness it becomes reddish brown. v 2. When made into a paste with oil, and heated in a Reduction* charcoal crucible, it loses weight. When urged by a strong fire on charcoal, it does not melt, but continues in powder. It exhibited, however, brilliant particles, and dissolved in muriatic acid, disengaging at first sul- phureted hydrogen, and afterwards pure hydrogen gas. 3. According to the Swedish chemists, it is suscepti- ble of various degrees of oxidizement. This they con- clude from the various colours which it assumes in dif- ferent circumstances ; namely, white, yellow, red, and dark brown. That it contains oxygen they have ren- dered manifest : by digesting muriatic acid upon it, a * Ann. de Clint, liv. 59. f A salt to be described hereafter, j Gehlen's Jour. ii. 401. 5 Hisinger and Berzelius, Ibid, Vol. I. B b .iS6 REFRACTORY METALS. Book I. Division I Action of combusti- bles. portion is driven off in the state of oxymuriatic acid gas. Vauquelin considers it as capable of two states of oxidizernent ; the protoxide of a white colour, and the peroxide reddish brown *. 4. The oxide of cerium does not melt by itself; but when treated with borax before the blow-pipe, it melts readily, and swells. The globule heated by the outer- most flame assumes the colour of blood, which, by cool- ing, passes into yellowish green, and at length becomes colourless, and perfectly transparent. Melted by the blue flame, these changes do not take place ; the glo~ bule at once assuming the state of colourless glass f. These phenomena serve to distinguish it from every other metallic substance. II. Few experiments have been made on the combi- nations of cerium with the simple combustibles. 1. When a stick of phosphorus was put into a solu- tion of cerium in muriatic acid, and kept for some days on a stove, the bottom and sides of the vessel were co- vered with a white precipitate, and the phosphorus was covered with a hard brown crust, which was tenacious, and shone in the dark. When heated it took fire, and left a small quantity of oxide of cerium. But this ex- periment did not succeed when repeated J. 2. Hydro-sulphuret of ammonia throws down cerium * Ann. de Chim. liv. 46. f Hisinger and Berzelius, ibid. The phenomena described by Kla- proth are different. According to him, borax does not dissolve the ox- ide, but acquires from it a brown yellow colour. Vauquelin says nif re- ly, that it tinges borax yellow, and that the globule becomes opaque *vhen saturated with the oxide. \ Hisinger and Berzelius, ibid, CERIUM, 387 at first of a brown colour, but it becomes deep green as Chap. IV.^ we continue to add the reagent. The precipitate when dried becomes bright green. When heated it burns, and leaves the yellow oxide of cerium ; but the colour of the precipitate varies according to the state of the cerium held in solution *. III. The attempt made by Gahn to unite cerium with lead did not succeed, and h-kherto no other combination of it with metals has been tried, if we except the alloy of cerium and iron obtained by Vauquelin* SECT. XXX. GENERAL REMARKS. \\ E have omitted, in the preceding sections, the metallic substance discovered by Ekeberg, and announ- ced by him as a peculiar metal under the name of Tan- Tantaluntf talum ; because this chemist has lately published an acknowledgement that the supposed peculiar oxide was in reality an oxide of tin. As the result of his experi- ments has not hitherto been published, we do not know the real constituents of the minerals to which he gave the names of tantalite and yttrotantalite. The object of the preceding Sections has been to describe the properties of the metals, and to examine the compounds which they form with oxygen, with simple combustibles, and with each other. It will be Hisinger and Bcrzelius, Ibid. With Vauquelin the result was' different. The precipitate winch he obtained was white, and contained no mlphureted hydrogen. Bb2 388 METALS, Book I. attended with considerable advantage to exhibit a sy- v.. 1 '" * noptical view of the most remarkable of these proper- ties and combinations. This will be the business of the present Section. I. The principle properties of the metals, as far as they have been ascertained, will be found in the follow- ing Table : Properties of the me- tals. Metals. Colour. Hard- ness. o- n~ 1! Melting bp. trra- \\ vit y- ||Fahren. Point. II Tenacity. Wedge. II Gold Yellow 6-5 19-36l|| 32 ||150-07 Plat. White 8 23-000 || 170+ 274-31 Silver White 7 10-510 || | 22 18T13 Mer. White 13-568 II -39 | | Pallad. White 9+ 11-871 || 160+H Rhod. White 11-+ | - 160+H Irid. White I 160+H Osrn. Blue II - 160+H Copper Red 7-5 8'805|| 27 ||302'26 Iron j Grey j 9 7'8 || 158 ||549-25 Nickel White 8'5 8-666 1| 160+ Nicol. Grey 1 8'6 1 II Tin White 6 T299 | 442 || 31-0 Lead Blue 5-5 11-352||612 = (1 18-4 Zinc White 6-5 6-861 ||680 II 18-2 Bism. Red white 7 9'822||476 || 20-1 1 Antim. Gr. white 6-5 6-712||810 - II 7 Tellur. Bl. white 6-ll5|i612+ ~ II Arsen. Bl. white 5 8-31 ||400+ ~ II Cobalt Grey 6 7*7 || 130 || Mang. Grey Q 6'850|| 160 I) Chro. White 5-90 || 170+H Qran. Iron-grey 9-000|| 170+H Molvb. Y. white 8-GllH 170+H fun p. | Gr. white 9+ 17-6 || 170+H Titan. Red. II 170+H Colum. II - 170+H Ceri. White II - 170+H METALS* 339 II. All the metals are capable of combining with t Chap. iv^ cxygen ; and this property constitutes one of their most Oxides, striking characters. This combination takes place in a variety of circumstances. 1. Some metals absorb it from the atmosphere, and By the air, gradually crumble into a powder when left exposed to the open air. Arsenic, manganese, and iron, are the only metals known at present to possess that property. The effect is not proportional to the affinity of the me- tals for oxygen, but is owing to the combined action. of a variety of agents. The air, water, and carbonic acid, are the most conspicuous of these. Most metals, when they are left exposed to the air, lose their bril- liancy, which can only be preserved by frequent clean- ing. They are then said to be tarnished. This tar- nish-is supposed at present to be a commencement of oxidiz-ement ; and the tenacity of the metal is consider- ed as the reason why it proceeds no farther than the surface. Gold and platinum are not liable to tarnish ; neither is mercury in a perceptible degree. Silver tar- nishes not from oxidizement, but from the action of B heaf sulphur. 2. When the metals are heated, their combination with oxygen is much facilitated. This is ascribed at present to the effect of heat in diminishing the cohe- sion of the metallic particles. If the heat be sufficiently high, it appears that all metals are oxidized more or less. The metals when sufficiently heated take fire, and tion, burn with more or less brilliancy. Arsenic is the most combustible of the metals ; then comes zinc. Anti- mony and bismuth likewise burn at a red heat, but with little brilliancy. Tin has a more brilliant com- bustion. Iron requires a white heat, but it burns with IvIETALb. Book I. Division I. By decom- posing wa- ter. Table of metallic oxides, great splendour. The combustibility of the remaining metals is much inferior to these. When metals burn, they always combine with a determinate quantity of oxygen. Some metals, as iron and arsenic, are capa* ble, after combustion, of uniting with more oxygen j while others, as zinc, antimony, and bismuth, combine during combustion with a maximum of oxygen. 3. Some metals have the property of taking oxygen from water when the action is assisted by heat. Zinc, iron, tin, and antimony, are the only metals hitherto ex- amined which have that property. When they are heated to redness, and steam passed over them, they are oxidized, while hydrogen gas is evolved. 4. Metals vary exceedingly from each other in the proportion of oxygen with which they are capable of combining ; but in every particular metal the dose seems determinate. Most metals have likewise a mi- nimum of oxygen with which they unite, and in several there are one or more states of oxidizement equally well determined between the protoxide and peroxide j while in others no such determinate intermediate states can be discovered. The following Table exhibits a view of the number of oxides known to be formed by each metal, of the colour of each when known, and of the proportion of oxygen united to 100 of metal by weight, which consti tutes each particular oxide. METALS. Metals. Colour. bO I > Vi O Metals. Colour. s B Gold i 3 urple Yellow 2 Zrinc Yellow White 3'G 5-0 'latin. 2 G^reen Srown 7'5 5 ism. Yellow 2 \ntim. White White 2*7 Silver o Dlive 2'8 Tellur. White Mercury Black Yellow Red 16 2 T6 ~> 3 Arsenic White Acid 3 53 Pallad. 1 2 Hue Yell. ? Cobalt ^ 3 Blue Green Uack 19*7 25 Rhod. P- Yellow Vlangan. 1 2 3 White Red Black 25 35 (56'6 ridium 1 2 Blue? Red? Osmium ) Transp Chrom. 1 2 3 Green Srown Red 200 Copper 1 2 Red Black 13 25 1 2 Black Yellow 5 17 2-0 ron 1 2 3 Grey Black Red 18 37 92-3 Uran. Mol^b. 1 2 3 4 irown Violet Blue White 34 50 Nickel 1 2 Green Black 28 Siccola 1 2 1 <-> Blue Black Tungst. 1 2 Black Yellow 15 25 Tin Grey White 25 38' Titan. 1 T 3 Blue Red White 16 33 49 Lead 1 Yellow Red Brown 8 13' 25 Colum. P 1 t - White Cerium White Red Tlie letter P, in the second co- lumn, signifies peroxide. 392 METALS. Book r. 5. From this Table, it appears that the metals, with Division f. ' v v-*-j respect to the quantity of oxygen which they are capa- o/oxygen" ^le of condensing, observe the following order : absorbed by Chromium ...... 2QO metal?. Iron ..... .... ...... 92-3 Manganese 1 ...... 66 Arsenic ......... 53 Tin ............... 38*8 Antimony ..... , 30 Zinc ............... 25 Copper ......... 25 Lead ............... 25 Tungsten ..... ,... 25 Mercury.. ....... 17'6 Platinum ......... 15 Silver ............ 12'8 Bismuth ., ...... . 12 Were we to suppose with Berthollet, that the affinity of 'these bodies for oxygen is proportional to the quantity of that principle which they are capable ot condensing, without acquiring acid properties, in that case the pre* ceding Table, omitting chromium, arsenic, and tung- sten, would indicate the order of the affinities. But there are many circumstances which militate against this supposition. Probably, indeed, the comparison is not fair, unless the metals compared are oxidized in the same circumstances, and by the same agents. For ex- ring com- ample, when the seven most combustible metals are ex- pu&Uon. posed to a strong heat, they take fire, and unite with pxygen in the following proportions : Iron ............ 37 Arsenic......... 33 METALS. 303 Antimony 30 Tin 25 ? Zinc 25 Bismuth 12 Lead 8 Here the circumstances being the same, it is more ro- bable that the dose bears some relation to the afftity for oxygen. When the same metals are exposed tcthe By the ac- tion of in- action of nitric acid, they combine with different oses tricackL of oxygen, but follow notwithstanding nearly thesame rder, as is obvious from the following Table ; Iron 92 Arsenic 53 Antimony 30 Tin 38-8 Zinc 25 Bismuth 12 Lead 8 5. The metallic oxides differ very conside>bly from Propettici, each other. The greater number of them ?e tasteless powders ; but some of them are acrid, and thers have even the properties of acids. The peroxide of mercu- ry and osmium, and the protoxide of arseic, are solu- ble in water. The peroxides of arseni, chromium, molybdenum, tungsten, and Columbia'* belong to the class of acids. It was formerly Je opinion of chemists, that all metals are susceptibleof acidification by combining them with a sufficient ciantity of oxy- gen ; but subsequent experience has nt confirmed this opinion. 6. When heat is applied to the peoxides, they give out a portion, or the whole, of their ojgen : but in this respect they differ exceedingly from ach other. A mo- METALS. Book I. derite heat reduces the oxides of gold, platinum, silver, "Division . mer , urv ^ an( j nicke^ to tne metallic state; and the same thin: would happen also to the oxide of lead, were it not $> susceptible of melting into a glass. The other metas require a violent heat, and are but imperfectly reducd. Were we to arrange them according to the difficulty of separating their oxygen by heat, the metals wouldassume an order not very different from the fol- lowing* : J .Refractory metals 12. Chromium 2. Manganese 13. Bismuth 3.?iinc 14. Lead 4. ron 15. Copper 5. *in 16. Tellurium 6. Iranium 17. Nickel 7. Molybdenum 18. Platinum 8. Ttigsten 10. Palladium Q. Coalt 20. Mercury 10. Anlmony 21- Silver 11. Arsnic 22. Gold Union with HI. Of tl four simple combustibles, there is one, combusti- narne ly carle, which has been hitherto combined only with one of th metals, iron. 1. Hydrogeigas dissolves arsenic, zinc, and iron, and holds them sus^nded seemingly in the metallic state. Phosphu- 2. Phosphoru combines with most of the metals hi- ret$t therto tried. Te metallic phosphurets have been ap- plied to no use. Most of them have the metallic lus- tre, and all of thex are brittle, except those of tin, lead, * Vaucjuek, Patrin's Minerahtf, v- 189. METALS. 395 and z.inc. The phosphorus may be expelled by heat Chap. IV The following Table exhibits a view of the proportion of phosphorus united to 100 parts of the metals in the phosphurets hitherto examined. Silver 25 Copper 25 Iron 25 Tin 25 Nickel 20 Lead 15 Cobalt 7 Gold 4*3 Bismuth 4 3. More attention has been paid to the metallic sul- phurets, because they occur often native, and have been applied to a variety of useful purposes. Sulphur unites in different proportions with some of the metals. The following table exhibits a view of the colour and speci- fic gravity of the suiphurets, and of the proportion of sulphur combined in tach with 100 of the metal, as far as the point has been ascertained. 36 METALS. Su 7 01 Colour. Decide gravity. bul- shflr. ulphuret* of L'olour. pecific ravhy. Sul- ( r r-ur. Gold Piatin. Un- known ^ismutli Leaden g e > 6-131 1T5 Silver Black.. grey T2 1T6 Antim. Leaden grey 4-368 33-3 Mercury 1. Black 2. Red 1 - 17-6 Tellur. Leaden grey Pallad. White Arsenic 1 Red ~\T 11 3'225 25 Rhod. White 2. Yell. 5'315 43 Indium Un- Lobait Yellow 39'8 Osmium known .ia'-gan rK-.- Un- I. Grey flfi'? <^nrom. known Copper 2. Yell. Uran. Brown Iron 1. Yell. 2. Yell. 4-518 4'83 60 112 Molyb. Leaden grey 4-73 66 N kel Yellow Tungst. Bluish b__ Tin Blue 17*6 i- ck TT Lead Leaden grey 1 16 Litan. Golum. Un- known r> Zinc Lienum Decomposi- tion of sui- phurets. The metals are capable of taking sulphur from each other when assisted by heat. They all follow, in this respect, a determinate order. Thus iron is capable of depriving lead, antimony, silver, and mercury, of sul- phur ; but neither lead nor any of the other metals can decompose the sulphuret of iron. The following, ac- cording to Bergman, is the order that the metals follow METALS. 397 in depriving each other of sulphur ; every metal being Chap, understood to be capable of decomposing the sulphurets of all the metals that follow it in the column. 1. Iron 6. Bismuth 2. Copper 7. Antimony 3. Tin 8. Mercury 4. Lead 9. Arsenic 5 Silver 10. Molybdenum IV. Almost all the metals are capable of combining Alloy* with each other, and of forming alloys; many of which are of the greatest utility in the arts. This property was long reckoned peculiar to metals, and is at present one of the best criterions for determining the metallic nature of any substance. Much is wanting to render the chemistry of alloys complete. Many of them have never been examined ; and the proportions of almost all of them are unknoxvn. Neither has any accurate method been yet discovered of determining the affinities of metals for each other. These alloys are much bet- ter known to artists and manufacturers than to chemists: But an examination of them, guided by the lights which chemistry is now able to furnish, would undoubtedly contribute essentially to the improvement of some of the most important branches of human industry. Their most interesting qualities,in an economical point of view, are their brittleness or malleability ; while the change of bulk which they undergo during their combination is of considerable importance to the che- mist. The three following tables exhibit a view of Table O f these properties, as far as ascertained in all the metallic alloys. The first comprehends the alloys of the mal- leable metals with each other ; the second, the alloys 393 METALS. Book I. of the brittle metals; and the third, the alloys of the malleable with the brittle metals *. * In these tables, the letter M signifies malleable; B, brittle; S, submnl- leable, used when the alloy is malleable in certain proportions, but brit- tle in others. O is used when the metals do not unite. The sign -f- is used when die alloy occupies a greater bulk than the separate me- tals j the sign , when ths alloy occupies a smaller bulk. The first indicates an expansion, the second a condensation. METALS, Zinc M M 1 ead Vl-f 'in B Vf i Ntckt M . m I ron AL.L, 3opp< M KAJiJUB HiJbYAVM ;r ridaum B+ B B s I M Osmii im Rhodium p; B B B B + B B S ~ B M-f M Vl-h M Palladium O B Mercury M M B Silver B B S O VI M B JM M-f B M-f Platinum B- B-f S M + M-f |M MM B M-f M-f |Gold II. BiJTTLE MZTALS. itanium -~-~" ' r ^ "ung^tcn Chromium Uranium Molybdenum B B Mang me B Cobalt B B LAncafc Tellurium h B B B Antimony B S O |B B Ifiism^th 400 METALS. Book 1. Division I, TABLE III. Bismuth . Antimony. Tellurium. | o *S < 1 o U OJ > 'o Uranium. Chromium. | S 1 5 Titanium. Gold B B B B M B Platin. B B B B Silver B B B B B M Merc. B B B O Pallad. B B Rhod. Osmi. Iridium Copper B = B M M S M Iron B + B + B B S B B S Nickel B B+ B S Tin M M? + B B? S Lead M M B B S M Zinc B + B O O o tJNCON FINABLE fiODIES. DIVISION II. OF UNCONFINABLE BODIES 1 HE substances described in the preceding Chapters are of such a nature that they can be collected together in quantities* and retained and confined in proper ves- sels, in order to be subjected to the test of experiment, and examined with accuracy. But the substances which are now to occupy our attention are very different, We have no method of collecting and retaining them till we submit them to our examination. They are of too subtile a nature to be confined in our vessels, and have too strong an affinity for other bodies to remain a moment in a separate state. These peculiarities have rendered the investigation of them particularly intricate, and have given birth to a great many theories and hypotheses concerning them, which have been sup- ported with much ingenuity and address by several dis- tinguished philosophers. The number of them which are at present known, or supposed to exist, amounts to four ; namely, Light, Heat, Electricity, and Magne- tism : But the last of these is scarcely at present con- sidered as belonging to chemistry ; and the third I pro* . 1. C c 402 UNCONFINABLE BOIMES. Bookf. pose to consider in a separate work. I shall therefore Division 17. * -v confine myself to the first two bodies, which I shall consider in the following Chapters. Their intimate connection with combustion, the most important problem in chemistry, has procured them the highest attention, and rendered the investigation of their properties the most interesting part of chemistry. Let us begin with the consideration of light, because its nature has been more completely examined than that of heat, and its properties ascertained with greater precision. LIGHT, CHAP. I. OF LIGHT; person is acquainted with the light of the sun, the light of a candle, and other burning bodies ; and every one knows that it is by means of light that bodies are rendered visible. Concerning the nature of this light, two different the- Nature of ories have been advanced by philosophers. Huygens considered it as a subtle fluid filling space, and render- ing bodies visible by the undulations into which it is thrown. According to his theory, when the siin rises it agitates this fluid, the undulations gradually extend themselves, and at last, striking against our eye, we see the sun. This opinion of Huygens was adopted also by Euler, who exhausted the whole of his consummate mathematical skill in its defence, The rest of philosophers, with Newton at their head, consider light as a substance consisting of small parti- cles, constantly separating from luminous bodies, mo- ving in straight lines, and rendering bodies luminous bjr passing from them and entering the eye. Newton es- tablished this theory on the firmest basis of mathemati- cal demonstration ; by showing that all the phenomena of light may be mathematically deduced from it. Huy- Cc2 04 UNCONFItfAELE BODIES. . Rook Ip fl g ens and Euler, on the contrary, attempted to support J,7ivision I/* 9 < v *J their hypotheses, rather by starting objections to the theory of Newton, than by bringing forward direct proofs. Their objections, even if valid, instead of esta- blishing their own opinions, would prove only that the phenomena of light are not completely understood ; a truth which no man will refuse to acknowledge, what- ever side of the question he adopts. Newton and his disciples, on the contrary, have shown, that the known phenomena of light are inconsistent with the undula- tions of a fluid, and that on such a supposition there can be no such thing as darkness at all. They have also brought forward a great number of direct arguments, which it has been impossible to answer, in support of their theory. The Newtonian theory therefore is much more probable than the other. Taking it for granted, then, that light is constantly moving in straight lines from luminous bodies, let us proceed to examine its properties. Its velocity. 1- It was first demonstrated by Roemer*, a Danish .philosopher, that light takes about eight minutes in moving across one half of the earth's orbit ; consequent- ly it moves at the rate of nearly 200,000 miles in a second. The discovery of Roemer has been still far- ther confirmed and elucidated by Dr Bradley's very in- genious theory of the aberration of the light of the fix- ed stars f. Slz f Jt3 2> From this astonishing velocity we are enabled to particles. form some notion of the size of the particles of light, Mechannical philosophers have demonstrated, that the * Phil. Trans, xii, 8j. f Ibid. xxxv. 637, and xlv, i. LIGHT. 405 ce with which a body strikes another depends upon Chap. I. its size and the velocity with which it moves. A 24 pound ball, if thrown from the hand, makes no impres- sion upon a common wall ; but when discharged from "a cannon with the velocity of 1300 feet in a second, it will shatter the wall to pieces. The greater the velo- city therefore with which a body moves, the greater the effect which it is capable fof producing. Conse- quently to produce any effect whatever by a body, how- ever small, we have only to increase its velocity suffi- ciently ; and in order to prevent a body from producing a given effect, its quantity must be diminished in pro- portion as its velocity is increased. Now the velocity of light is so great, that if each of its particles weighed the 1000th part of a grain, its force would be greater than that of a bullet discharged from a musket. Were it even the millionth part of a grain in weight, it would destroy every thing against which it struck. If it even weighed the millionth part of that, it would still have a very sensible force. But how much less must be the weight of a particle of light, which makes no sensible impression upon so delicate an organ as the eye ? We are certain, then, that no particle of light weighs -r,^c^,-To4,^^,^rth of a grain ; but were we even to suppose it of that size, the addition of 900 millions of particles to any body, or their abstraction, would make no difference of weight capable of being detected by the most sensible balance. Every attempt then to ascer- tain the accumulation of light in bodies by changes in their weight must be hopeless. 3. While a ray of light is passing through the same Refraction medium, or when it passes perpendicularly from one medium to another, it continues to move without chan- 406 UNCONFIKABLE BODIES. Book I. Ping its direction ; but when it passes obliquely from Division IT. 5 5 _ v one medium to another of a different density, it always bends a little from its old direction, and assumes a new one. It is then said to be refracted. When it passes into a denser medium, it is refracted towards the per- pendicular ; but when it passes into a rarer medium, it is refracted from the perpendicular. In general, the quantity of refraction is proportional to the density of the medium ; but if the medium be combustible, the refraction is greater than it would otherwise be *. In the same medium the sines of the angles of incidence and of refraction have always the same ratio to each other. Reflection. 4. When a ray of light enters a transparent medium, as a plate of glass, with a certain obliquity, it continues to move on till it comes to the opposite surface of the glass ; but then, instead of passing through the glass, it bends, and passes out again at the same surface at which it entered ; just as a ball would do if made to strike obliquely against the floor. The ray is then said to be reflected. The angle of iefi< ction is always equal to the angle of incidence. When the surface of a me- dium is polished, as glass or mirrors, oblique rays dp jiot enter them at all, but are reflected when they ap- proach the surface of the body. All surfaces are capa- ble of reflecting a greater or smaller number of oblique rays. Rays are only reflected at surfaces. Inflection. 5. When a ray of light passes within a certain dis- tance of a bocjy parallel to which it is moying, it is * ft was the knowledge of this law that led Newton to suspect the diamond to be combustible, and wattr to contain a combustible ingre- client. Optus, p. 72. LIGHT. 407 fcent towards it. Thus if a ray of light be let into a . Cha P- ^ dark room through a small hole in the window shutter, and received upon paper, it will form a round luminous spot. If two pen knives, with their edges towards each other, be placed on opposite sides of the hole, and made to approach each other, the luminous spot will gradu- ally dilate itself on the side of the knivts, indicating that those rays which pass nearest the knives have been drawn from their former direction towards the knives. This property of light is called inflection. 6. The ray, when its distance from the body parallel Deflection; to which it moves is somewhat greater, is bentyroffz it. It is then said to be deflected. Newton has demonstrated, that these phenomena are owing to the attraction between light and the medium through which it is moving, the medium towards which it is approaching, or the bodies in its neighbourhood. 7. Some substances, as water, are transparent, or al- Opacity and trans- low light to pass freely through them ; others, as iron, patency. are opaque, or allow no light to pass through them. Now, it can scarcely be doubted that the component particles of all bodies are far enough distant from each other to allow the free transmission of light j conse- quently opacity and transparency must depend, not up- on the distance of the particles of bodies, but upon something else. Newton has shown, that transparency can only be explained by supposing the particles of transparent bodies uniformly arranged and of equal density. When a ray of light enters such a body, be- ing attracted equally in every direction, it is in the same state as if it were not attracted at all, and therefore pas- ses through the body without obstruction. In opaque bodies, on the contrary, the particles are either not uni- 46S UNCONFINABLE BODIES Decompo- seven rays Book I. formly arranged, or they are of unequal density. Hencs *_ v ' the ray is unequally attracted, obliged constantly to change its direction, and cannot therefore make its way through the body. 8. When a ray of light is made to pass through a tr i an g u l ar prism, and received upon a sheet of white paper, the image, or spectrum as it is called, instead of being circular, is oblong, and terminated by semicircu- lar arches. In this case the refraction of light is in- creased considerably by the figure of the prism. Con* sequently if light consists of a congeries of rays differ- ing in refrangibility, they will be separated from each other : the least refrangible occupying the luminous circle which the ray would have formed had it not been for the prismatic form of the glass ; the others going to a greater or smaller .distance from this circle, accord- ing to their refrangibility. The oblong figure of the spectrum is a proof that light consists of rays different- ly refrangible ; and as the spectrum exhibits seven co- lours, these rays have been reduced under seven clas- ses. The colours are in the following order ; RED^ ORANGE, YELLOW, GREEN, ^BLUE, INDIGO, VIOLET. The red is the least refrangible, the violet the most ; the others are refrangible in the order in which they have been named. Newton ascertained, by actual measurement, that if the whole of the spectrum be di- vided into 360 parts, then The red will occupy 45 of these parts orange. ...... .27 yellow green blue indigo.. violet . 48 60 60 40 LIGHT. 409 But they have been since observed to differ somewhat t Chap. T * t in their relative lengths in the spectrum, according to the refracting medium. 9. These coloured rays differ from each other in re- flexibility and inflexibility, precisely as they do in re- frangibility : the red rays being least reflexible and in- flexible, the violet most, and the rest according to their order in the prismatic spectrum. 10. Every one of these coloured rays is permanent ; not being affected nor altered by any number of refrac- tions or reflections. The properties of light now enumerated constitute the object of the science called OPTICS. They prove, in the most decisive manner, that light is attracted by other bodies ; and not only attracted, but attracted un- equally. For combustible bodies, provided all other things be equal, refract light more powerfully than other bodies, and consequently attract light more powerfully. But it is variation, in point of strength, which consti- tutes the characteristic mark of chemical affinity. Hence it follows that the attraction which subsists between light and other bodies does not differ from chemical affinity. The importance of this remark will be seen hereafter. 11. The rays of light differ in their power of illumi- illumlna- nating objects : For if an equal portion of each of these rays, one after another, be made to illuminate a minute object, a printed page for instance, it will not be seen distinctly at the same distance when illuminated by each. We must stand nearest the object when it is il- luminated by the violet : we see distinctly at a some- what greater distance when the object is illuminated by the indigo ray j at a greater when by the blue; at a still 410 UNCONFINABLS BODIES. Book I. greater when by the deep green ; and at the greatest Division II. ' ' - y > or all, when bj the lightest green or deepest yellow : We must stand nearer when the object is enlightened by the orange ray, and still nearer when by the red. Thus it appears that the rays towards the middle of the spec- trum possess the greatest illuminating power, and those at the extremity the least ; and that the illuminating power of the rays gradually diminishes from the mid- dle of the spectrum towards its extremities. For these facts we are indebted to the experiments of Dr Her- schel*. n htcn- 12t kight is capable of entering into bodies and re- ters bodies, maining in them, and of being afterwards extricated without any alteration. Father Beccaria, and several other philosophers,have shown us, by their experiments, that there are a great many substances which become luminous after being exposed to the light f. Tins pro- perty was discovered by carrying them instantly from the light into a dark place, or by darkening the cham- ber in which they are exposed. Most of these substan- ces, indeed, lose their property in a very short time, but they recover it again on'being exposed to the light ; and this may be repeated as often as we please. We are indebted to Mr Canton for some very interesting expe- riments on this subject, and for discovering a composi- ti6n which possesses this property in a remarkable de- gree J. He calcined some common oyster shells in a good coal fire for half an hour, and then pounded and sifted the purest part of them. Three parts of this * Plil. Trw. i Poo, p. 255, \ Ibid, Ixi. aiz. J ibid. Iviii. 337. LIGHT. 411 powder were mixed with one part of the flowers of sul- Chap. I. phur, and rammed into a crucible which was kept red hot for an hour. The brightest parts of the mixture were then scraped off, and kept for use in a dry phial well stopped *. When this composition is exposed for a few seconds to the light, it becomes sufficiently lumi- nous to enable a person to distinguish the hour on a watch by it. After some time it ceases to shine, but recovers this property on being again exposed to the light. Light then is not only acted upon by other bo- dies, but it is capable of uniting with them, and after- wards leaving them without any change. It is well known that light is emitted during com- bustion ; and it has been objected to this conclusion, that these bodies are luminous only from a slow and imperceptible combustion. But surely combustion can- not be suspected in many of Father Beccaria's experi- ments, when we reflect that one of the bodies on which they were made was his own hand, and that many of the others were altogether incombustible ; and the phe- nomena observed by Mr Canton are also incompatible with the notion of combustion. His pyrophorus shone only in consequence of being exposed to light, and lost that property by being kept in the dark. It is not ex- posure to light which causes substances capable of com- bustion at the temperature of the atmosphere to become luminous, but exposure to air. If the same tempera- ture continues, they do not cease to shine till they are * Dr Higgins has added considerable improvements to the method [ef preparing Canton's pyrophorus. He stratifies the oyster shells and sul- phur in a crucible without pounding them ; and after exposing them to the proper heat, they are put into phials furnished with ground stoppers. 412 UNCO N FIN ABLE BODIES, Book I. consumed ; and if they cease, it is not the applicalioia < -yJ of light, but of caloric, which renders them again lu- minous : but Canton's pyrophorus, on the contrary, when it had lost its property of shining, did not recover it by the application of heat, except it was accompa- nied by light. The only effect which heat had was to increase the separation of light from the pyrophorus, and of course to shorten the duration of its luminous- iiess. Two glass globes hermetically sealed, containing each some of this pyrophorus, were exposed to the light and carried into a dark room. One of them, on being immersed in a basin of boiling water, became much brighter than the other, but in ten minutes it ceased to give out light: the other remained visible for more than two hours. After having been kept in the dark for two days, they were both plunged into a basin of hot water : the pyrophorus which had been in the wa- ter formerly did not shine, but the other became lumi- nous, and continued to give out light for a considerable time. Neither of them afterwards shone by the appli- cation of hot water ; but when brought near to an iron heated so as scarcely to be visible in the dark, they sud- denly gave out their remaining light, and never shone more by the same treatment : but when exposed a se- cond time to the light, they exhibited over again pre- cisely the same phenomena ; even a lighted candle and electricity communicated some light to them. Surely these facts are altogether incompatible with combustion, and fully sufficient to convince us that light alone was the agent, and that it had actually entered into the lu- minous bodies. It has been questioned, indeed, whether the light emitted by pyrophori be the same with that to which 413 fhey are exposed. Mr Wilson has proved, that in many Chap. T. ^ cases at least it is different ; and in particular that on many pyrophori the blue rays have a greater effect than any other, and that they cause an extrication of red light. Mr de Grosser has shown the same thing with regard to the diamond, which is a natural pyropho- rus *. Still, however, it cannot be questioned that the luminousness of these bodies is owing to exposure to light, and that the phenomenon is not connected with combustion. 13. But light does not only enter into bodies, it also And corn- combines with them, and constitutes one of their com- WI ponent parts. That this is the case, has been rendered very evident by a set of experiments made long ago by Mr Can ton f, and lately repeated and carried a great deal farther by Dr Hulme It has been long kno\vn that different kinds of meat and fish, just when they are beginning to putrefy, become luminous in the dark, and of course give out light. This is the case in par- ticular with the whiting, the herring, and the mackerel. When four drams of either of these are put into a phial containing two ounces of sea water, or of pure water holding in solution -i a dram of common salt, or two drams of sulphate of magnesia, if the phial be put into a dark place, a luminous ring appears on the surface of the liquid within three days, and the whole liquid, when agitated, becomes luminous, and continues in that state for some time. When these liquids are fro- zen, the light disappears, but is again emitted as soon as ie PLyt. xx. a-o. f "Bill. Tram* lir. 446. \ Ibid. iScxxp. i6r. 414 UNCONFINABLE BODIES, , they are thawed. A moderate heat increases the luflit- Division II. * y ' nousness, but a boiling heat extinguishes it altogether. The light is extinguished also by water, lime water, water impregnated with carbonic acid gas, or sulphure- ted hydrogen gas, fermented liquors, spiritous liquors, acids, alkalies, and water saturated with a variety of salts, as sal-ammoniac, common salt, sulphate of magne- sia ; but the light appears again when these solutions are diluted with water. This light produces no sen- sible effect on the thermometer*. After these experi- ments, it can scarcely be denied that light constitutes a component part of these substances, and that it is the first of the constituent parts which makes its escape when the substance containing it is beginning to be de- composed. 14 ' Almost a11 b^ies tve the property of absorb- ing light, though they do not all emit it aeain like the pyrophori and animal bodies. But they by no means absorb all the rays indiscriminately : some absorb one coloured ray, others another, while they reflect the rest. This is the cause of the different colours of bodies. A red body, for instance, reflects the red rays, while it ab- sorbs the rest ; a green reflects the green rays, and per- haps also the blue and the yellow, and absorbs the rest. A white body reflects all the rays, and absorbs none ; while a black body, on the contrary, absorbs all the rays, and reflects none. The different colours of bodies, then, depend upon the affinity of each for particular rays, and its want of affinity for the others. * The same experiments succeed with Canton's pyrophorus, as Hulme has shown. LIGHT. 415 15. The absorption of light by bodies produces very ._^ ha P- L . sensible changes in them. Plants, for instance, may be Light pro made to vegetate tolerably well in the dark ; but in that case their colour is always white, they have scarce- ly any taste, and contain but a very small proportion of combustible matter. In a very short time, however, after their exposure to light, their colour becomes green, their taste is rendered much more intense, and the quantity of combustible matter is considerably increa- sed *. These changes are very obvious, and they de- * The following very curious observation by Professor Robinson de- serves particular attention : "Having occasion, in autumn 1774, to go down and inspect a drain in a coalwork, where an embankment had been made to keep off a lateral run of water, and crawling along, I laid my hand on a very luxuriant plant, having a copious, deep-indented, white foliage, quite unknown to me. I inquired of the colliers what ic was ? None of them could tell me. It being curous, I made a sod be carried up to the day-lighr , to learn of the workmen what sort of a plant it was. But nobody had ever seen any like it. A few days after, looking at the sod, as it lay at the mouth of the pit, I observed that the plant had languie.hr-d and died for want of water, as 1 imagined. But looking at it more attentively, I observed that a new vegetation was be- ginning with little sproutings from the same stem, and that this new growth was of a green colour. This instaatly brought to my recollec- tion the curious observations of Mr Dufay j and I caused the sod to be set in the ground and carefully watered. I was the more incited to this, because \ thought that my fingers had contracted a sensible aromatic smell, by handling the plant at this time. After about a week, this root set out several stems aud leaves of common tansy. The workmen now recollected that the sods had been taken from an old cottage garden hard by, where a great deal of tansy w.^.* still growing among rhe grass. 1 now sent down for more of ths same stuff and several sods were brought up, having the same luxuriant white foliage. This, when bruised be- tween the fingers, gave no aromatic smell whatever. Ail these plants withered and died down, though carefully watered, and, in each, there sprouted from the same stocks fresh stems, and a copious foliage, and produced, among others, common tansy, fully impregnated with th$ or- 416 UNCONFINABLE BODIES. Book f. pend incontestibly upon the agency of light. Another Division IT. ' c-~ y ~i very remarkable instance of the agency of light is the reduction of the metallic oxides. The red oxide of mercury and of lead become much lighter when expo- sed to the sun ; and the white salts of silver, in the same situation, soon become black, and the oxide is re- duced. The oxide of gold may be reduced in the same manner. Light, then, has the property of separating oxygen from several of the oxides. Scheele, who first attended accurately to these facts, observed also, that the violet ray reduced the oxide of silver sooner than any of the other rays* ; and Sennebier has ascertained, that the same ray has the greatest effect in producing the green colour of plants f. Berthollet observed, that during the reduction of the oxides, a quantity of oxygen gas makes its escape . Contains -^ was supposed till lately, that those reductions of deoxidizing metallic oxides were produced by the colorific rays of rays, not colorific. light j but Messrs Wollaston, Ritter, and Bockmann, have lately ascertained, that muriate of silver is black- dinary juices of that plant, and of a full green colour. I have repeated the same experiments with great care on lovage (levistiatm vulgare], mint, and caraways. As these plants throve very well below, in the dark, but with a blaiiched foliage, which did not spread upwards, bur lay flat on the ground ; in all of them there was no resemblance ot shape to the ordinary foliage of the plant. All of them died down when brought into day-light ; and the stocks then produced the proper plants in their usual dress, and having all their distinguishing smells." Dr IlLck'^ Lectures, i. 532. * On Firfy p. 78. and 98. f Mem. Phisko-cllm. ii. 72. \ Jour, de Pi>\s. xxix. 8 1. When muriate of sliver is exposed to the so- lar lij^ht, it blackens almost instantaneously. In that case it is not oxygen gas which is emitted, but muriatic acid, as has bsen observed also by Bcrtholiet. See' Jour, de Phys, Ivi. 80. LIGHT. 411 ned most rapidly when it is placed beyond the violet Chap. T rav, and entirely out of the prismatic spectrum. Hence it follows, that the change is produced, not merely by the colorific rays, but by rays which are incapable of rendering objects visible ; neither do they produce any- sensible heat. We see that they are more refrangible than the colorific rays, as they extend beyond the violet end of the spectrum. From these remarkable experi* ments it follows, that the solar light is composed. of at least two sets of rays 5 one set which renders bodies risible, and another set which blackens muriate of sil- ver, and reduces metallic oxides. It is by no means unlikely, that all the other chemical changes produced on bodies by solar light, is owing to the second set of rays, which hitherto have obtained no name. As the effect of the different prismatic colours on metallic ox- ides increases with their refrangibility, and as the effect is greatest at a certain distance beyond the violet ray # we can scarcely hesitate to admit, that the colorific rays have no influence whatever in the phenomena ; but that it is owing to the other or deoxidizing rays, which of course are mixed with the colorific, and increase in quan- tity with the refrangibility. We shall find afterwards that solar light, besides these two sets, contains also a third species of ray, different from both in its nature and effects. 16. Such are the properties of light as far as they have been examined. They are sufficient to induce us to believe that it is a body, and that it possesses many qualities in common with other bodies. It is attracted by them, and combines with them precisely as other bodies do. But it is distinguished from all the substances hitherto described, by possessing three peculiar proper- FoL I. D d 41S UNCONFINABLE BODIES. Book T. Division II. I^ight pos- sesses three peculiar properties. Sources of ties, of which they are destitute. The first of these properties is the power which it has of exciting in us the sensation of vision, by moving from the object seen, and entering the eye. The phenomena of colours, and the prismatic spectrum, indicate the existence of seven different species of light ; but to what the difference of these species is owing, has not been ascertained. We are altogether ignorant of the component parts of every one of these species. The second peculiar property of light is the prodi- gious velocity with which it moves whenever it is se- parated from any body with which it was formerly combined. This velocity, which is but little less than 200,000 miles in a second, it acquires in a moment ? and it seems to acquire it too in all cases, whatever the body be from which it separates. The third, and not the least singular of its peculiar properties, is, that its particles are never found cohering together, so- as to form masses of any sensible magni- tude. This difference between light and other bodies* can only be accounted for by supposing that its particles repel each other. This seems to constitute the grand distinction between light and the bodies hitherto descri- bed. Its particles repel each other, while the particles of the other bodies attract each other ; and accordingly are found cohering together in masses of more or less magnitude. 17. It now only remains to consider the different me- thods by which light may be procured ; or, to speak more precisely, the different sources from which light is emitted in a visible form. These sources are four : 1. The sun and stars ; 2. Combustion ; 3. Heat ; and 4. Percussion. LIGHT. 419 The light emitted by the sun is familiarly known t Ch a P- 1- 1 by the names of sunshine and light of day. The light Jt The sun, of the stars, as has been ascertained, possesses precisely the same properties. With respect to the cause why the sun and stars are constantly emitting light, the question will probably for ever bame the human under- standing ; at any rate, it is not considered as connected with the science of chemistry. 18. Light is emitted in every case of combustion, a. Combus Now combustion, as far at least as regards simple com- bustibles and metals, is the act of combination of the combustible with oxygen. Consequently the light which is emitted during combustion must have existed previously combined either with the combustible or with the oxygen. But this subject will be resumed in the next Chapter, where the nature of combustion will be particularly considered. 19. If heat be applied to bodies, and continually in- 3. Heat, creased, there is a certain temperature at which, when they arrive, they become luminous. No fact is more familiar than this ; so well known indeed is it, that little attention has been paid to it. When a body be- comes luminous by being heated in a fire, it is said in common language to be red hot. As far as experiments have been made upon this subject, it appears that all bodies which are capable of enduring the requisite de- gree of heat without decomposition or volatilization be- gin to emit light at precisely the same temperature. The first person who examined this subject with atten- tion was Sir Isaac Newton. He ascertained, by a very ingenious set of experiments, first published in 1701, that iron is just visible in the dark when heated to D d c 42$ UNCONFINARLE BODIES* Book I. 635 * ; that it shines strongly in the dark when raised Division II. & J . . . . i. ^ __ to the temperature of 152 $ that it is luminous in the twilight just after sunset when heated to 884 ; and that when it shines, even in broad day-light, its temperature is above 1000. From the experiments of Muschen- broeck and others, it appears, that what in common lan- guage is called a red heat, commences about the tempe- rature of 800. A red hot body continues to shine for some time af- ter it has been taken from the fire and put into a dark place. The constant accession, then, either of light or heat, is not necessary for the shining of bodies : but if a red hot body be blown upon by a strong current of air, it immediately ceases to shine f. Consequently the moment the temperature of a body is diminished by a certaut number of degrees, it ceases to be luminous. Whenever a body reaches the proper temperature, it becomes luminous, independent of any contact of air ; for a piece of iron wire becomes red hot while immer- sed in melted lead |. To this general law there is one Remarkable excep- tion. It does not appear that the gases become lumi- nous even at a much higher temperature. The follow- ing ingenious experiment of Mr T. Wedgewood seems to set the truth of this exception in a very clear point of view. He took an earthen ware tube B (fig. 9.), bent so in the middle that it could be sunk, and make several turns in the large crucible C, which was filled' Dr Irvine has shown that this point is rather too low. For mer- cury, which he found to boil at 572, does not become the least luminous at that temperature. Irvine's Essayi t ^. 33. f T. Wedgewood, P&U. Tram. i 791. J Id, Ibid, LIGHT. 421 with sand. To one end of this tube was fixed the pair Chap. i. of bellows A ; at the other end was the globular vessel D, in which was the passage F, furnished with a valve to allow air to pass out, but none to enter. There was another opening in this globular vessel filled with glass, that one might see what was going on within. The crucible was put into a fire ; and after the sand had be- come red hot, air was blown through the earthen tube by means of the bellows. This air, after passing through the red hot sand, came into the globular vessel. It did not shine ; but when a piece of gold wire E was hung at that part of the vessel where the earthen ware tube entered, it became faintly luminous : a proof that though the air was not luminous, it had been hot enough to raise other bodies to the shining temperature. 19. The last of the sources of light is percussion. It 4; is well known, that when flint and steel are smartly struck against each other, a spark always makes its ap- pearance, which is capable of setting fire to tinder or to gunpowder. The spark in this case, as was long ago ascertained by Dr Hooke, is a small particle of the iron, which is driven off, and catches fire during its pas- sage through the air. This, therefore, and all similar cases, belong to the class of combustion. But light of- ten makes its appearance when two bodies are struck against each other, when we are certain that no such thing as combustion can happen, because both the bo- dies are incombustible. Thus, for instance, sparks are emitted, when two quartz stones are struck smartly a- gainst each other, and light is emitted when they are rubbed against each other. The experiment succeeds equally well under water. Many other hard stones also emit sparks in the same circumstances. sion. 422 UNCOKFINABLE BODIES. Book T. If they be often made to emit sparks above a sheet Division .. Q w hite paper, there are found upon it a number of small black bodies, not very unlike the eggs of flies. These bodies are hard but friable, and when rubbed on the paper leave a black stain. When viewed with a microscope, they seem to have been melted. Muriatic acid changes their colour to a green, as it does that of lavas*. These substances evidently produced the sparks by being heated red hot. Lamanon supposes that they are particles of quartz combined with oxygen. Were that the case, the phenomenon would be precisely simi- lar to that which is produced by the collision of flint and steel. That they are particles of quartz cannot be doubted j but to suppose them combined with oxygen is contrary to all experience ; for these stones never show any disposition to combine with oxygen even when exposed to the most violent heat. La Metherie made experiments on purpose to see whether Lamanon's opinion was well founded ; but they all turned out un- favourable to it. And Monge ascertained, that the par- ticles described by Lamanon were pure crystal unalter- ed, With a quantity of black powder adhering to them. He concludes, accordingly, that these fragments had been raised to so high a temperature during their pas- sage through the air, that they set fire to all the mi- nute bodies that came in their way f. The emission of the light is accompanied by a very peculiar smell, having some analogy to that of burning sulphur, or more nearly to burning gunpowder. * Lamanon, Jour, dt Ply,. 1785. f Ann. de Cl>im.vti. CALORIC. CHAP. II. OF CALORIC* -N OTHING is more familiar to us than leaf ; to attempt Definition, therefore to define it is unnecessary. When we say that a personnels heat, that a stone is hot, the expres- sions are understood without difficulty ; yet in each of these propositions, the word leaf has a distinct mean- ing* In the one, it signifies the sensation of heat y in the other, the cause of that sensation. This ambiguity, though of little consequence in common life, leads una- voidably in philosophical discussions to confusion and perplexity. It was to prevent this that the word calo- ric has been chosen to signify the cause of heat. When I put my hand on a hot stone, I experience a certain sensation, which I call the sensation of heat , the cause of this sensation is caloric. As the phenomena in which caloric is concerned arc the most intricate and interesting in chemistry ; as the study of them has contributed in a very particular man- ner to the advancement of the science ; as they involve some of those parts of it which are still exceedingly ob- scure, and which have given occasion to the most im- portant disputes in which chemists have been engaged- they naturally lay claim to a very particular attention. I shall divide this Chapter into six Sections : The first 424 VNCONTINABLE BODIES. Book I. w iH fog occupied with the nature of caloric ; in the sc- Division II. f.i.n. y i cond, I will consider its propagation through bodies ; in the third, its distribution ; in the fourth, the effects "which it produces on bodies ; in the fifth, the quantity of it which exists in bodies j and in the sixth, the dif- ferent sources from which it is obtained. SECT. I. NATURE OF CALORIC, CONCERNING the nature of caloric, there are two opi- nions which have divided philosophers ever since they turned their attention to the subject. Some suppose that caloric,, like gravity, is merely a property of mat- ter, and that it consists, some how or other, in a pecu- liar vibration of its particles ; others, on the contrary, think that it is a distir f ct substance. Each of these opi- nions has been supported by the greatest philosophers ; and till lately the obscurity of the subject has been such, that both sides have been able to produce exceed- ingly plausible and forcible arguments. The recent im- provements, however, in this branch of chemistry, have gradually rendered the latter opinion much more pro- bable than the former : And a recent discovery, made by Dr Herschel, has at last nearly put an end to the dispute, by demonstrating, that caloric is not a proper- ty, bur a peculiar subsiance ; or at least that we have the same reason for considering it to be a substance, a$ fye have for the believing light to be material, CALORIC. 402 1. Dr Herschel had been employed in making qbser- t Chr.p. n. vations on the sun by means of telescopes. To prevent Discovery the inconvenience arising from the heat, he used colour- f ed glasses ; but these glasses, when they were deep enough coloured to intercept the light, very soon crack- ed and broke in pieces. This circumstance induced him to examine the heating power of the different co- loured rays. He made each of them in its turn fall upon the bulb of a thermometer, near which two other thermometers were placed to serve as a standard. The number of degrees, which the thermometer exposed to the coloured ray rose above the other two thermome- ters, indicated the heating power of that ray. He found that the most refrangible rays hare the least heating power j and that the heating power gradually increases as the refrangibility diminishes. The violet ray there- fore has the smallest heating power, and the red ray the greatest. Dr Herschel found that the heating power of the violet, green, and red rays, are to each other as the following numbers : Violet = 16 Green rr 22*4 Red - 55 It struck Dr Herschel as remarkable, that the illumi- nating power and the heating power of the rays follow such different laws. The first exists in greatest perfec- tion in the middle of the spectrum, and diminishes as we approach either extremity ; but the second increases constantly from the violet end, and is greatest at the red end. This led him to suspect that perhaps the heat- ing power does not stop at the end of the visible spec- trum, but is continued beyond it. He placed the ther- mometer completely beyond the boundary of the red 426 NATURE OF Book I. ra y but still in the line of the spectrum : and it rose Division II. . . u-~y ' still higher than it had done when exposed to the red ray. On shifting the thermometer still farther, it con- tinued to rise ; and the rise did not reach its maximum till the thermometer was half an inch beyond the ut- most extremity of the red ray. When shifted still far- ther, it sunk a little ; but the power of heating was sensible at the distance of l^ inch from the red ray. These important experiments have been lately re- peated and fully confirmed by Sir Henry Englefield *, in the presence of some very good judges. The appa- ratus was very different from that of Dr Herschel, and contrived on purpose to obviate certain objections which had been made to the conclusion drawn by that illus- trious philosopher. The bulbs of the thermometers used were mostly blackened. The following TABLE exhibits the result obtained in one of these experi- ments. Thermometer in the blue ray rose in 3' from 55 to 56* green 3 54.. ..58 yellow 3 .... .56 .... 62 full red 2^ .... 56 .... 72 confines of red 2!.. ..58....73-- beyond the visible light 2-J- .... 61 .... 79 The thermometer, with its bulb blackened, rose much more when placed in the same circumstances, than the thermometer whose bulb was either naked or whitened with paint. This will be apparent from the following TABLE : * Journal of the Royal Institution , i. 2O3. CALORIC, Time. From To Red ray Black therm. White therm. 3' 53 55 61 58 Dark Black therm. White therm. 3 59 58 64 58^ Confines of red Black therm. ; White therm. 59 57| 71 60^ Both Dr Herschel and Sir Henry Englefield take no- tice of a faint blush of red, of a semioval form, visible when the rays beyond the red end of the spectrum were collected by a lense. From these experiments it follows, that there are rays emitted from the sun, which produce heat, but have not the power of illuminating ; and that these are the rays which produce the greatest quantity of heat. Consequently caloric is emitted from the sun in rays, and the rays of caloric are not the same with the rays of light. On examining the other extremity of the spectrum, Dr Herschel ascertained that no rays of caloric can be traced beyond the violet ray. He had found, however, as Sennebier had done before him, that all the coloured rays of the spectrum have the power of heating : it may be questioned therefore whether there be any rays which do not warm. The coloured rays must either have the property of exciting heat as rays of light, or they must derive that property from a mixture of rays of caloric. If the first of these suppositions were true, light ought to excite heat in all cases ; but it has been long known to philosophers that the light of the moon does not pro- duce the least sensible heat, even when concentrated so 425 NATURE 6F stron gty as to surpass, in point of illumination, the brightest candles or lamps, and yet these produce a very sensible heat. Here then are rays of light which do not produce heat : rays, too, composed of all the seven prismatic coloured rays. We must conclude, from this ivell-known fact, that rays of light do not excite heat : and consequently that the coloured rays from the sun and combustible bodies, since they excite heat, must consist of a mixture of rays of light and rays of caloric. That this is the case was demonstrated long ago by Dr Hooke*, and afterwards by Scheelef, who separated the two species from each other by a very simple me- thod. If a glass mirror be held before a fire, it reflects the rays of light, but not the rays of caloric ; a metallic mirror, on the other hand, reflects both. The glass mirror becomes hot ; the metallic mirror does not alter its temperature. If a plate of glass be suddenly inter- posed between a glowing fire and the face, it intercepts completely the warming power of the fire, without cau- sing any sensible diminution of its brilliancy ; conse- quently it intercepts the rays of caloric, but allows the rays of light to pass. If the glass be allowed to remain in its station till its temperature has reached its maxi- mum, in that situation it ceases to intercept the rays of caloric, but allows them to pass as freely as the rays of light. This curious fact, which shows us that glass on- ly intercepts the rays of caloric till it be saturated with them, was discovered long ago by Dr Robison, pro- fessor of natural philosophy in the university of Edin- burgh. These facts are sufficient to convince us that the * Birchc's History of the Royal Society^. 137. f Qn Fh-ft p. 70. Eng. Edit. CALORIC. 42g rays of light and of caloric are different, and that the co- Chap. II. ^ loured rays derive their heating power from the rays of caloric which they contain. Thus it appears that solar light is composed of three sets of rays, the colorific, the calorific, and the deoxidizing. 2. The rays of caloric are refracted by transparent Refracted bodies just as the rays of light. We see, too, that, like the rays of light, they differ in their refrangibility ; that some of them are as refrangible as the violet rays, but that the greater number of them are less refrangible than the red rays. Whether they are transmitted through all transparent bodies has not been ascertained ; neither has the difference of their refraction in different medi- ums been examined. We are certain, however, that they are transmitted and refracted by all transparent bo- dies which have been employed as burning-glasses. Dr Herschel has also proved, by experiment, that it is not only the caloric emitted by the sun which is refrangible, but likewise the rays emitted by common fires, by can- dles, by hot iron, and even by hot water. 3. The rays of caloric are reflected by polished sur- Reflected* faces in the same manner as the rays of light. This was lately proved by Herschel ; but it had been demonstra- ted long ago by Scheele, who had even before ascertain- ed that the angle of their reflection is equal to the angle of their incidence. Mr Pictet also had made a set of very ingenious experiments on this subject, about the year 1790, which led to the same conclusion *. He placed two concave mirrors of tin, of nine inches focus, * A similar set of experiments had been made by Mr King as early as 1785 : See his Montis of Critithm, vol. 1st. 43 Q NATURE OF Book I. at the distance of twelve feet two inches from one ano- -.. ther. In the focus of one of them he placed a ball of iron two inches in diameter, heated so as not to be visi- ble in the dark ; in the other was placed the bulb of a thermometer. In six minutes the thermometer rose 22. A lighted candle, which was substituted for the ball of iron, produced nearly the same effect. In this case both light and heat appeared to act. In order to separate them, lie interposed between the two mirrors a plate of clear glass. The thermometer sunk in nine minutes 14 : and when the glass was again removed, it rose in seven minutes about 12 ; yet the light which fell on the thermometer did not seem at all diminished by the glass. Mr Pictet therefore concluded, that the caloric had been reflected by the mirror, and that it had been the cause of the rise of the thermometer. In another experiment, a glass matrass was substituted for the iron ball, nearly of the same diameter with it, and contain- ing 2044 grains of boiling water. Two minutes after a thick screen of silk, which had been interposed be- tween the two mirrors, was removed, the thermometer rose from 47 to 50^, and descended again the moment the matrass was removed from the focus. The mirrors of tin were now placed at the distance of 90 inches from each other ; the matrass \vith the boil- ing water in one of the foci, and a very sensible air thermometer in the other, every degree of which was equal to about ^-th of a degree of Fahrenheit. Exact- ly in the middle space between the two mirrors there was placed a very thin common glass mirror, suspended in such a manner that either side could be turned to- wards the matrass. When the polished side of this mir- ror jvas turned to the matrass, the thermometer rose on- lr to CALORIC. 431 y to 0*5 ; but when the side covered with tinfoil, and Chap. II which had been blackened with ink and smoke, was turned towards the matrass, the thermometer rose to 3*50. In another experiment, when the polished side of the mirror was turned to the matrass, the thermometer rose 3, when the other side 9*2. On rubbing off the tin- foil, and repeating the experiment, the thermonafiter rose 18. On substituting for the glass mirror a piece of thin white pasteboard of the same dimensions with it, the thermometer rose 10*. 4. All the phenomena concur to show that the rays Their of caloric move with a very considerable velocity ; cit y- though the rate has not been ascertained in a satisfacto- ry manner. The experiments of Mr Leslie would lead us to conclude that they move with the same velocity as sound. But they will come under our consideration in a subsequent Section. The following experiment of Mr Pictet indicates a very considerable velocity. He placed two concave mirrors at the distance of 6& feet from each other ; the one of tin as before, the other of plaster gilt, and 18 inches in diameter. Into the focus of this last mirror he put an air thermo- meter, and a hot bullet of iron into that of the other. A few inches from the face of the tin mirror there was placed a thick screen, which was removed as soon as the bullet reached the focus. The thermometer rose the instant the screen was removed without any percep- tible interval ; consequently the time which caloric takes in moving 69 feet is too minute to be measured f. 5. As caloric radiates from luminous bodies like light, s ; zc< * Pictet, sur Is F/, chap. iii. f See a dissertation on this subject in Pin. Mag. xix. 309. 432 NATURE O* Book I... and without any sensible diminution of their weight, it Division II. . _^ is reasonable to conclude that its particles must be e- qually minute. Therefore neither the addition of calo- ric nor its abstraction can sensibly affect the weight of bodies. As tnis follows necessarily as a consequence from Dr Herschel's experiments, were it possible to prove by experiment that caloric affects the weight of bodies, the theory founded on Dr Herschel's discove- ries would be overturned : But such deductions have been drawn from the experiments of De Luc *, Fordycef, Morveau , and Chausier J. According to these philosophers, bodies become absolutely lighter by being heated. The experiment of Fordyce, which seems to have been made with the greatest care, was conduct- ed in the following manner : He took a glass globe three inches in diameter, with a short neck, and weighing 451 grains ; poured into it 1700 grains of water from the New River, London, and then sealed it hermetically. The whole weighed 21504--*- grains at the temperature of 32. It was put for twen- ty minutes into a freezing mixture of snow and salt till some of it was frozen ; it was then, after being wiped first with a dry linen cloth, next with clean washed dry leather, immediately weighed, and found to be -g'jth of a grain heavier than before. This was repeated exactly in the same manner five different times. At each, more of the water was frozen, and more weight gained. When the whole water was frozen, it was -r'g-th of a grain heavier than it had been when fluid. A thermo- meter applied to the globe stood at 10. When allow- * Svr fa Modif, Je rAttKospl, f PbiL Trans. 1785, part ii. $ Jour. 4e Pty. 17^5, Oct. Jeur. dt Scawns, 1785, p. 493, tALORIC* 43* *d to remain till the thermometer rose to 32, it weigh- t cha P n ed T Vths of a grain more than it did at the same tempera- ture when fluid. It will be seen afterwards that ice contains less caloric than water of the same tempera- ture with ir. The balance used was nice enough to mark h part of a grain. This subject had attracted the attention of Lavoisier, philosopher distinguished by the uncommon accuracy of his researches. His experiments, which were pub* lished in the Memoirs of the French Academy for 1183^ led him to conclude that the weight of bodies is not al- tered by heating or cooling them, and consequently that caloric produces TO sensible change on the weight of bodies. Count Rumford's experiments on the same subject, which were made about the year 179"?, are per- fectly decisive. He repeated the experiment of Dr Fordyce with the most scrupulous caution ; and, by a number of the most ingenious contrivances,demonstrated that neither the addition nor the abstraction of caloric makes any sensible alteration in the weight of bodies *i 0. Caloricagrees with light in another property no less peculiar. Its particles are never found cohering together .sses ; and whenever they are forcibly accumu- lated, they fly off in all directions, and separate from each other with inconceivable rapidity. This property necessarily supposes the existence of a mutual repulsion between the particles of caloric. Thus it appears that caloric and light resemble each other in a great number of properties. Both are emit* ted from the sun in rays with a very great velocity > * Phil. 'Tram. 1799, p. 179. I. E e 43* NATURE OF Book r. both of them are refracted by transparent bodies, and Division II. < v ~ reflected by polished surfaces ; both of them consist of particles which mutually repel each other, and which produce no sensible effect upon the weight of other bodies. They differ, however, in this particular :- light produces in us the sensation of vision; caloric,, on the contrary, the sensation of heat. Upon the whole, we are authorised by the above statement of facts, to conclude that the solar light is composed of three distinct substances, in some measure separable by the prism on account of the difference of their refrangibility. The calorific rays are the least re- frangible, the deoxidizing rays are most refrangible, and the colorific rays possess a mean degree of refrangibili- ty. Hence the rays in the middle of the spectrum have the greatest illuminating power, "those beyond the red end the greatest heating power, and those beyond the violet end the greatest deoxidizing power ; and the heating power on the one hand, and the deoxidizing power on the other, gradually increase as we approach that end of the spectrum where the maximum of each is concentrated*. These different bodies resemble each other in so many particulars, that the same reasoning respecting refrangibility, reflexibility, &c. may be ap- plied to all ; but they produce different effects upon those bodies on which they act. Little progress has yet been made in the investigation of these effects; but we may look forward to this subject as likely to cor- rect many vague and unmeaning opinions which are at present in vogue among chemists. CALORIC. SECT. II. OF THE MOTION OF CALORIC. r ROM the preceding account of the nature of caloric^ we learn that it is capable, like light, of radiating in. all directions from the surfaces of bodies ; and that when, thus radiated, it moves with a very considerable velocity. Like light, too, it is liable to be absorbed when it im- pinges against the surfaces of bodies. When it has thus entered, it is capable of making its way through all bo- dies ; but its motion in this case is comparatively slow* Heat then moves at two very different rates. 1. It es- capes from the surfaces of bodies. 2. It is conducted^ or passes through bodies. It will be proper to consider each of these separately. I* ESCAPE OF HEAT FROM SURFACES. WHEN bodies artificially heated- are exposed to the open air, they immediately begin to emit heat, and con- tinue to do so till they become nearly of the tempera- ture of the surrounding atmosphere* That different substances when placed in this situation cool down with very different degrees of rapidity, could not have es- caped the most careless observer ; but the influence of the surface of the hot body in accelerating or retarding the cooling process, was not suspected till lately. For this curious and important part of the doctrine of heat, we are indebted to the sagacity of Mr Leslie, who has already brought it to a great degree of perfection. His Ee2 436 MOTION OF Beokl. Inquiry into the Nature of Heat, published in 1804, Division II. ' * J . . contains a great number of original experiments and views on this subject. It is remarkable, that a few weeks after the publication of this work, a dissertation by Count Rumford on the same subject, and containing si- milar experiments, appeared in the Philosophical Trans- actions. This dissertation displays, in a remarkable degree, that ingenuity and happy talent of illustra- tion for which the Count is so remarkable. But as Mr Leslie informs us that his leading experiments had been made in 1801, and as his work appeared first, he is certainly entitled to the merit of priority and origin- ality. Effect of the i. Mr Leslie filled with hot water a thin globe of surface in . cooling. bright tin, four inches in diameter, having a narrow neck, and placed it on a slender frame in a warm room without afire. The thermometer inserted in this globe sunk halfway from the original temperature of the water to that of the room in 156 minutes. The same experi- ment was repeated, but the outside of the globe was now covered with a thin coat of lamp black. The time elapsed in cooling to the same temperature as in the last case was now only 81 minutes*. Here the rate of cooling was nearly doubled ; yet the only differ- ence was the thin covering of lamp black. Nothing can afford a more striking proof than this of the effect of the surface of the hot body on the rate of its cool- ing. Count Rumford took two thin cylindrical brass ves- sels of the same size and shape, filled them both with # Leslie's Inquiry into the Nature of Heat, p. 26$* CALORIC. 437 hot water of the same temperature, and clothed the one t Chap. II. vwith a covering of Irish linen, but left the other naked. The naked vessel cooled ten degrees in 55 minutes, but the one covered with linen cooled ten degrees in 36-J- minutes *. In this experiment, the linen produced a si- milar effect with the lamp black in the preceding. In- stead of retarding the escape of heat, as might have been expected, they produced the contrary effect. The same acceleration took place when the cylinder was coated with a thin covering of glue, of black or white paint, or when it was smoked with a candle. 2. The variation in the rate of cooling occasioned by Greatest Jo still air. coating the hot vessel with different substances is great- est when the air of the room in which the experiments are made is perfectly still. The difference diminishes when the atmosphere is agitated, and in very strong winds it disappears almost entirely. Thus two globes of tin, one bright, the other covered with lamp black, being filled with hot water, and exposed to winds of various degrees of violence, were found by Mr Leslie to lose half their heat in the following times f: Clean Globe. Blackened Globe. In a gentle gale 44' 35' In a pretty strong breeze 23' 20^' In a vehement wind...... 9*5' 9' This is sufficient to convince us, that the effect of the lamp black in accelerating cooling cannot be owing to any power which it has of conducting heat, and com- * Nicholson's Jour. IT. 60. f Inquiry into the Nature of Heat, p. 271, 438 MOTION OF Book I. municating it to the air, but to the property which it Division II. p ,. . ,. has or radiating heat (to use the common expression J in a greater degree than clear metallic bodies. That this is in reality the case is easily shown. 3. When a canister of tin, of a cubic shape and con- siderable size, is placed at the distance of a foot or two from a concave mirror of bright polished tin, having a delicate thermometer in the focus, the thermometer ex- periences a certain elevation. If the canister be coated with lamp black, the thermometer rises much higher than when the metal is left bright. Here we perceive that more heat radiates from the lamp black than the clear metal ; since the elevation of the thermometer is in some degree the measure of the radiation. A com- mon thermometer does not answer well in similar ex- periments, because it is affected by every change of temperature in the room in which the experiments are made. Bat Mr Leslie has invented another, to which we are indebted for all the precision that has been in- troduced into the subject. He has distinguished it by Differential the name of the differential thermometer. It was em- thermome- p i oyed a i so ty Count Rumford in his researches. This thermometer consists of a small glass tube bent into the shape of the letter U, and terminating at each extremity in a small hollow ball, nearly of the same size ; the tube contains a little sulphuric acid tinged red with carmine, and sufficient to fill the greatest part of it. The glass balls are full of air, and both communi- cate with the intermediate tube. To one of the legs of the tube is affixed a small ivory scale divided into 100 de- grees; and the sulphuric acid is so disposed, that in the graduated leg its upper surface stands opposite to the part of the scale marked 0. The glass ball attached to the leg CALORIC. 439 -of the instrument to which the scale is attached, is, by way Chap-IL of distinction, called ihefocal ball. Suppose this ther- mometer brought into a warm room, the heat will act equally upon both balls, and expanding the included air equally in each, the liquor in the tube will remain stationary. But suppose the focal ball exposed to heat while the other ball is not, in that case the air in- cluded in the focal ball will expand, while that in the other is not affected. It will therefore press more upon the liquid in the tube, which will of course advance towards the cold ball, and therefore the liquid will rise in the tube above 0, and the rise will be proportional to the degree of heat applied to the focal ball. This thermometer, therefore, is peculiarly adapted for ascer- taining the degree of heat accumulated in a particular point, while the surrounding atmosphere is but little affected, as happens in the focus of a reflecting mirror. 3STo change in the temperature of the room in which the instrument is kept is indicated by it, while the slightest alteration in the spot where the focal ball is placed is immediately announced by it. In making experiments on the radiation of heat, Mr Leslie employed hollow tin cubes, varying in size from three inches to ten, filled with hot w 4 ater, and placed before a tin reflector, having the differential thermo- meter in the focus. The reflector employed was of the parabolic figure, and about 14 inches in diameter o This apparatus afforded the means of ascertaining the effect of different surfaces in radiating heat. It was only necessary to coat the surface of the canister with the various substances whose radiating properties were to be tried, and expose it, thus coated and filled with hot water, before the reflector. The heat radiated in MOTION OF BookT. e{lc h case would be collected into the focus where the I)iVision IT. focal ball of the differential thermometer was placed, and the rise of this instrument would indicate the pro* portional radiation of each surface. These experiments were conducted with much address. The following are the principal results obtained. 4. When the nature and position of the canister is ent<- he- the same, the rise of the differential thermometer is al- tenr'cra- 6 wa y s proportional to the difference between the tem- ture oi the perature of the hot canister and that of the air in the Jior iody and th air. room in which the experiment is made *. Effect on 5^ When the temperature of the canister is the same, the thermo- meter in- the effect upon the differential thermometer diminishes jthe*1istance as ^ e distance of the canister increases from the reflec- gomthere- tor, the focal ball being always understood to be placed in the focus of the mirror. Thus if the rise of the thermometer, when the canister was three feet from the mirror, be denoted by 100, it will amount only to 57 when the canister is removed to six feet. On sub- stituting a glass mirror for the reflector, and a charcoal fire for the canister, when the fire was at the distance of 10 feet the thermometer rose 37, and at the distance of 30 ieet it rose 21 C f. From Mr Leslie's experiments ' it follows, that the effect on the thermometer is very nearly inversely proportional to the distance of the cani- ster from the reflector. He found likewise that when ca- nisters of different sizes were used, heated to the same point, and placed at such distances that they all sub- tended ti'C bame angle at the reflector ; in that case the effect of each upon the differential thermometer was nearly the same. Thus a canister of * Leslie, p. 14. f Ibid. p. 51. CALORIC. 441 3 inches at 3 feet distance raised the thermometer 50 Cha^ll^ 4 inches - 4 feet 54 6 inches - 6 feet 57 10 inches 10 feet 59 From these experiments we learn, that the effect of the canister upon the thermometer is nearly proportional to the angle which it subtends, and likewise that the heat radiated from the canister suffers no sensible diminution during its passage through the air. 6. Heat radiates from the surface of hot bodies in Proportion- all directions; but from Mr Leslie's experiments we sine of the learn, that the radiation is most copious in the direction "l 01 " 13 " 10 " perpendicular to the surface of the hot body. When surface to ... ... . . the refleo the canister is placed in an oblique position to the re- ton Hector, the effect diminishes, and the diminution in- creases with the obliquity of the canister. Mr Leslie has shown, that the effect in all positions is proportional to the visual magnitude of the canister as seen from the reflector, or to its orthographic projection. Hence the action of the heated surface is proportional to the sine of its inclination to the reflecter. Such are the effects of the temperature, the distance, and position of th^ canister with respect to the reflec- tor. None of these, except the first, occasion any va- riation in the quantity of heat radiated, but merely in that portion of it which is collected by the mirror and sent to the focal ball j but the case is different when the surface of the canister itself is altered. 7. Mr Leslie ascertained the power of different sub- Radiating stances to radiate, by applying them in succession to a side of the canister, and observing what effect was pro- dies ' duced upon the differential thermometer. The follow- ing Table exhibits the relative power of the different 442 MOTION OF , Book f. substances tried by that philosopher, expressed by the Division II. . r i i i J L. y elevation 01 the* differential thermometer produced, x Lamp black 100 Water by estimate.... ;.100-f- A ''" Writing paper 98 \ Rosin. 96 Sealing wax.... 95 Crown glass 90 China ink ..r. 88 Ice 85 t Minium 80 Isinglass 80 Plumbago 15 Tarnished lead 45 Mercury 20+. * Clean lead 19 Iron polished 15 Tin plate 12 Gold, silver, copper ... 12 From this Table it appears, that the metals radiate much x worse than other substances, and that tin plate is one of the feeblest of the metallic bodies tried. Lamp Hack radiates more than eight time^ as much as this last metal, and crown glass .7*5 times as muqh. The experiments of Count Rumford do not coincide exactly with those of *Mr Leslie respecting the radiating power . * of the metals. The Count found all that he tried equal in this respect ; while the preceding table indicates a considerable difference in power. But the method a- dbpted by the Count was not susceptible of the same precision with that of -Mr Leslie ; the latter therefore has a much greater chance of being correct. CALORIC. 443 8. Such are the radiating powers of different sab- Stances. But even when the substance continues the same, the radiation is very considerably modified by ap- parently trifling alterations on its surface. Thus me- Increased , ,. , by taruisk* tals radiate more imperfectly than other bodies ; but ing> this imperfection depends upon the .brightness and smoothness of their surface.- When; by exposure to the air, the metal acquires that tarnish which is usually ^ ascribed at present to oxidizernent, the power of radi- ating heat is greatly increased. Thus it appears fro#i the preceding table, that the radiating power of lead while bright is only 19 ; but when its surface becomes tarnished, its radiating power becomes no Jess than 45. The same change happens to tin, and to ail the metarls tried. When the smoothness of the surface is destroyed by And i i : crat4 hing scratching the metal, its radiating power is increased. .^ uf f a ce Thus, if the tffcct of a bright side ot the -canister bt 12, 1 metal* it will be raisi c! 22 by rubbing the side in 6ne direc- tion with a bit oi fine sand paper*. But when the ' surface is rubb'd across with sand paper, so as to form a new set ot tiur ws ii ter*secting the former ones, the radiating prwer is again scmewhat diminished, 9. The radiating power of the different substances Increases , , , . . . ordiniinish- examined, was ascertained by applying a thin cover- esast h e ine of each to one ot the sides of the canister. Now thickness of the coat m- this coat may vary in thickness in any given degree, creases. It becomes a question of some importance to ascertain, whether the radiating power is influenced by the thick- ness to a given extent, or whether it continues the same. * Leslie, p. 8i; 444 MOTION OF Book I. whatever be the thickness of the covering coat. This question Mr Leslie has likewise resolved. On a bright side of a canister he spread a thin coat of liquified jelly, and four times the quantity upon another side ; both dried into very thin films. The effect of the thinnest film was 38, that of the other 54. In this case the ef- fect increased with the thickness of the coat. The augmentation goes on till the thickness of the coat of jelly amounts to about T-sVg-th of an inch ; after which it remains stationary. When a surface of the canister was rubbed with olive oil, the effect was 51 : a thick- er coat of oil produced an effect of 59. Thus it ap- pears that when a metallic surface is covered with a coat of jelly or oil, the effect is proportional to the thickness of the coat, till this thickness amounts to a certain quantity ; but when a vitreous surface is co- vered by very thin coats of metal, no such change is perceived. A canister was employed, one of the sides of which was a glass plate. Upon this plate were ap- plied, in succession, very fine coats of gold, silver, and copper leaf. But notwithstanding their thinness, the effect was only J 2, or the same that would have been produced by a thick coat of these very metals. But when glass enamelled with gold is used, the effect is somewhat increased ; a proof that varying the thickness of the metallic coats, would have the same effect as va- rying the thickness of jelly, provided they could be procured of sufficient tenuity*. As long as an increase of thickness alters the radiating power of the coat, it is obvious that the surface of the canister below exerts * Leslie, p. CALORIC. 445 a certain degree of energy. And the action exerted by t Chap- " j metallic bodies appears to be greater than that exerted by vitreous bodies. 10. Such are all the circumstances connected with the radiating surface hitherto observed, which influence its power. For hitherto it has been impossible to ascer- tain the efficacy of hardness and softness^ or of colour, upon radiation ; though it appears, from Mr Leslie's experiments, not unlikely that softness has a tendency to promote radiation *. But as the effect, as far at least as measured by the differential thermometer, de- pends ruot only upon the radiating surface, but likewise upon the surface of the focal ball, and likewise of the reflector ; it will be necessary also to consider the modi- fications produced by alterations in the surface of these bodies. This inquiry, for which, like the preceding, we are indebted to Mr Leslie, will throw considerable light on the nature of radiation. 11. When the focal ball is in its natural state, that Surfaces ra- ,, . , . dn.te ?^d ' is to say, when its surface is vitreous, it has been al- absorb heat ready observed, that the side of the hot canister coated inthe "I" 11 * proportion. with lamp black raises the thermometer 100. If the experiment be repeated, covering the focal ball with a smooth surface of tinfoil, instead of rising to 100, the thermometer will only indicate 20. A bright side of the canister will raise the thermometer, when the focal ball is naked, 12; but when the ball is co- vered with tinfoil, the elevation will not exceed 2~ de- grees f. From these experiments it is obvious, that metal not only radiates heat worse than glass, but like- * Leslie, p. 90. f Ibid. p. 19. 445 MOTION OF Book I. wise that it is not nearly so capable of imbibing it Division II. ., - TT i T_ ' when the rays strike against its surface. Ir the surtac6 of the tinfoil be furrowed by rubbing it with sand pa- * per, the effect produced when the focal ball is exposed in the focus will be considerably increased *. It has been already observed that the radiating power of tin is likewise increased by scratching it. These facts entirle us to conclude, that those surfaces which radiate heat most powerfully, likewise absorb it most abund- antly when it impinges against them. Reflection 12. The very contrary holds with respect to the re- radiation. Sectors, as mi^ht indeed have been expected. Those surfaces which radiate heat best, reflect it worst ; while the weakest radiating surfaces are- the most powerful reflectors. Metals of course are much better reflectors than glass. When a glass mirror was used instead of the tin deflector, the differential thermometer rose only- one degree; upon coating the surface of the mirror with lamp black*, all effect was destroyed ; when co- vered with a sheet of tinfoil the effect was 10 f. Reflecting To compare the relative intensity -of different sub- vark>usbo- stances as reflectors, Mr Leslie- placed thin smooth *' es * plates of the substances to be tried before the principal reflector, and nearer *than the proper focus. A new re- flection was produced, and the rays were collected in a ; focus as much nearer 'the reflector than the plate as the old focus was farther distant. The comptra: ve pLwer of the* different substances tried was as follows J. Brass 100 Silver .90 * Leslie, p. 81. f Ibid. p. 30. \ Ibid. p. 98. CALORIC. 447 Tinfoil 85 t Chap.IT^ Block-tin v * . 80 Steel 70 Lead 60 Tinfoil softened by mercury 1 Glass 10 Do. coated with wax or oil 5 When the polish of the reflector is destroyed by rub- bing it with sand paper, the effect is very much di- minished. , When the reflector is coated over with a so- lutjon of jelly, the effect is diminished in proportion as the thickness of the coat increases, till its diameter a- mounts to -j-^V^th. part of an inch. The following Ta- ble exhibits the intensity of the reflector coated with jelly of various degrees of thickness *. Thickness of coat. Effect. Naked reflector 127 I QQ roooo 93 87 61 39 29 15 AH these phenomena are precisely what migltf have been expected, on the supposition that the intensity of reflection is inversely that of radiation'. Mr Leslie has shown that it is the anterior surface of reflectors only Leslie, p. 106, 448 MOTION OF Book I. Division If. Radiation takes place only in elas- tic medi- that acts. For when a glass mirror is employed, its power is not altered by scraping off the tin from its back, nor by grinding the posterior surface with sand or emery *. 13. Such are the phenomena of the radiation of heat as far as the radiating surface, the reflector, and the fo- cal ball are concerned. It cannot be doubted from them, that heat is actually radiated from different surfaces, and that bodies vary considerably in their radiating power. We have seen also that substances differ no less from each other in their power of reflecting heat, and that the intensity of the latter power is always the inverse of the intensity of the former. Before we can be able to form a judgment of the way in which the heat is conveyed in these cases, it will bejiecessary to examine the effect of the different mediums in which the radiation may take place, and the obstructions oc- casioned by putting different substances between the radiating surface and the reflector. Both of these points have been examined by Mr Leslie with his usual acute- ness. 14. In all common cases, the medium through which the heat is radiated is the air ; and from Mr Leslie's experiments it appears, that no sensible radiation can be observed when the canister, reflector, and differen- tial thermometer, are plunged into water. Hence he concludes, that no radiation takes place except when the radiating body is surrounded with an elastic medium. But the experiments which he adduces are scarcely sufficient to decide the point. Substances cool so fast * Leslie, p. CALORIC, * when plunged into water, that there is scarcely time for the thermometer to be aff^cied j and, besides, the heat could scarcely accumulate in the focal ball in such quantity as to occasion a sensible rise *. Heat radiates through all the gaseous bodies tried ; and from Mr Leslie's experiments, it does not appear that the rate of radiation is much influenced by alter- ing the surrounding medium. The rate is the same, at least, in air and hydrogen gas ; and oxygen and azotic gas appear to have the same properties in this respect as air. Mr Leslie has shown also that the rarefaction Diminished of the surrounding air diminishes somewhat the radia ting energy of surfaces ; but the radiation diminishes at different rates in different gases. The following Table, calculated from his trials, shows, according to him, the diminution of the power of radiation in air and hydrogen gas of different degrees of rarity. * Wo shall find, however, hereafter, that other experiments of Mr J-eslie leave no doubt that heat does not radiate through solid bodies, Vol. L F f 450 MOTION OF Book r. Division H. Rarity. AIR. HYDROGEN, Radia Glass. ion of Metal. Radial Glass. ion of Metal, 1 5114 714 5714 714 2 5519 690 5584 698 4 5332 667 5456 682 8 5150 644 5331 666 16 4975 622 5210 651 82 4805 601 5091 637 64 4641 5SO 4974 622 128 4483 560 4861 608 256 4331 542 4750 594 512 4183 523 4641 580 1024 4041 505 4538 567 Intercept- ive power of a screen. Such is the effect of different mediums as far as they have been examined by Mr Leslie ; but the experiments on which his conclusions were founded would require to be repeated. 15. When a substance is interposed by way of screen between the hot canister anH the reflector, the effect is either diminished or destroyed altogether, ac- cording to circumstances. These circumstances have been examined by Mr Leslie with great sagacity. In- deed, the developement of the effect of screens constitutes perhaps the most curious and important part of his CALORfC. 451 whole work. A screen may affect the radiation of heat . cha P- ll - t three ways: 1. By its distance from the hot canister ; 2. By its thickness ; and, 3. By the nature of the sub- stance of which it is composed. Let us take a view of each of these in succession. First, From all Mr Leslie's trials, it appears that a screen diminishes the effect of radiation upon the differ- ential thermometer situated in the focus of the reflector, in proportion to its distance from the canister. When placed very near the canister, the effect is comparatively small ; but it increases rapidly as the screen is drawn Increases away from the canister ; so that the elevation of the differential thermometer is soon prevented altogether. * he hot ^* When the canister is at the distance of three feet from the reflector, if the side painted with lamp black pro- duce an effect equivalent to 100, this effect upon in- terposing a pane of glass at the distance of two inches from the canister will be diminished to 20. When the pane is advanced slowly forward towards the reflector, the effect of the radiation gradually diminishes j and when it has got to the distance of one foot from the screen, the radiation is completely intercepted*. Second* When a screen of thin deal board is used in- stead of the pane of glass, and placed at the distance of two inches from the canister, the radiation is diminish- ed, and the diminution is proportional to the thickness thickness!" of the board. With a board -J- inch thick the effect is 20 .... ...... 4- inch ....... e ..... . 15 . . ........ 1 inch ........ ..... 9 * Leslie, p.. a$. Ff2 452 MOTION OP Book I. Thus the radiation diminishes very slowly as the thick- Division IF. J J (.-y ness increases . heat inter- Third > When a sheet of tinfoil is substituted for the cepted by glass pane, and put into the same position, the effect, instead of 20, is reduced to j and this happens how- ever thin the tinfoil is ; even gold leaf of the thickness of y-oo-Woth P art f an inch, though pervious to light, completely stops the progress of radiating heat. When a sheet of writing paper is substituted for tinfoil, the effect is 23 f. Thus it appears, that substances vary considerably from each other in their property of intercepting radiating heat ; and likewise that the power of intercepting heat is inversely as the power of radi- ating it. Those substances which radiate most heat, intercept the least of it when in the situation of screens j and those which radiate the least heat, on the contrary, intercept the most. But it was formerly observed, that the power of absorbing heat was the same with that of radiating it. Hence those substances which absorb least heat are the most powerful interceptors of it, and the contrary. These facts lead naturally to the opinion, that the property of absorbing heat depends upon the surface . of the substance which is interposed as a screen ; an opinion which Mr Leslie has established by the follow- ing experiments. He took two panes of glass, and coated one side of each with tinfoil, leaving the other side bare. These two panes were pressed together j the tinned side of each being outmost, and applied as a screen at two inches distance from the canister. The whole of the rays of heat appeared to be intercepted, * Leslie, p. 38. | Ibid CALORIC. 453 for this thermometer was not acted upon at all. But Chap, n.^ tvhen the glass side of the screen was outmost, the effect of radiation was equivalent to 18. Here we find the very same screen, in the very same position, intercept- ing very different proportions of the radiated heat, ac- cording to the nature of Us external surface. When the tin was outmost, the whole heat was stopped ; but when the glass was outmost, about |th passed on to the reflector. The effect was analogous when two sheets of tin, each painted on one side with a thin coat of lamp black, were employed as a screen, and placed two inches from the canister. Pressed together, and having their metal sides outmost, the radiation produced no effect upon the thermometer; but when the blacken- ed sides were outmost, the effect was equivalent to 23. When only one of the plates is used, and its blackened side turned to the canister, the effect is equal to 4. If the two plates be used with their blackened sides out- most, and at the distance of two inches from each other, all effect is destroyed *. 1(5. Such are the phenomena of the radiation of heat as far as they have been ascertained. Let us see how far they will enable us to ascertain its nature. The only other radiation with which we are familiarly ac- quainted is that of light. This seems to have induced R a jj at j on philosophers to consider them bota as similar, without " J - tric i.ot similar any minute examination ; but the tacts ascertained by to that of Mr Leslie, supposing them correct, demonstrate mat & l " there is no such similarity between them as has been supposed. Light passes through diaphanous bodies, as glass, with only a small diminution of its intensity ; * Leslie, p. 35, 454; MOTION OF Book I. and the effect is the same in whatever part of the course Division II. ,, . , ,. . , y ' the glass pane is placed. But with radiating heat the case -is very different ; when the pane is placed very near the canister, a portion of the effect still takes place ; but as the pane is removed towards the reflector, the intensity gradually diminishes, and at last disap- pears. Neither does the intensity of surfaces radiating heat vary at the same rate as that of luminous bodies ; the first being very nearly inversely as the distance, the second inversely as the square of the distance. These, and several other particulars pointed out in the prece- ding pages, indicate a decided difference between the radiation of heat and of light. Mr Leslie's experiments on the effect of screens leave no doubt that every solid body interposed between the canister and the reflector, however diaphanous or thin, completely intercepts all the rays of heat. For when such bodies are interposed, the remaining intensity is always proportional to the disposition of the screen to receive and radiate heat; and the effect constantly di- minishes as the screen is removed to a greater dis- tance from the canister : that is to say, that the screen imbibes a certain portion of heat from the canister, and radiates again the excess which it has thus acquired. Thus a screen is precisely the same as another canister heated to a smaller temperature. The rays of heat then cannot pass through solid bodies, however thin and transparent, in the state of rays. They enter the screen, are retained by it, and only a small portion sent off from the other surface, in proportion as its heat is great- er than that of the air. In this respect the radiation of heat differs materially from that of light. Hence CALORIC. 455 the reason why radiation takes place only when the hot cha P- I! body is surrounded with an elastic medium. But provided the medium be elastic, it does not ap- pear that its chemical nature occasions any difference ; at least in the few trials made by Mr Leslie, the radi- ation in air was nearly the same as in other gases. But when the medium is artificially rarefied, the effect if di- minished. It does not appear that the rays of heat suffer a di- minution during their passage through air, how great soever the distance be through which they pass ; for the effect on the thermometer is proportional to the vi- sual magnitude of the canister. In this respect they resemble the rays of light, and seem to differ in se- veral circumstances from the aerial pulses which con- stitute s.ound. Thus it appears, that rays of heat are sent off in dif- ferent quantities from different surfaces ; that they can pass only through aerial bodies, being intercepted by all solids ; that their intensity diminishes inversely as their distance ; and that no part of them is lost during their journey. So far seems to be sufficiently esta- blished ; but beyond it every thing is still hypothetical. Mr Leslie supposes that the heat is conveyed from one Ascribed to surface to another by means of the air, and that the supposed radiation is nothing else than a series of aerial undulations. The radiation of heat, according to this hypothesis, is analogous to the propagation of sound. A hot body, according to him, communicates a certain portion of heat to the stratum of air immediately in its neighbourhood ; the stratum immediately expands, and the vibration into which it is thrown occasions a simi- lar vibration in the next stratum, which is propagated in 456 MOTION OF Book I. the usual manner, and with the velocity of sound. The J portion of he^t which produced the fiiot vibration, passes from the first stratum of air to the second, and from the second to the third, with the same rapidity as the undulations themselves. The amount of the effect will depend upon the povtion of heat communicated at each successive moment to the stratum of air in the neighbourhood of the hot body; and this will depend upon the nearness of the air to that substance. Those bodies to which air approaches the ciosest will there- fore radiate heat more powerfully than those to winch it cannot approach so near. Hence glass, and those other bodies which raciiate best, have the greater af- finity tor air ; and metals, which lacliate worst, have the least affinity for air. Hence, also, those bodies which radiate heat best, must absorb it most readily ; because the pulses of air loaded with heat will approach them more nearly. Scratching the surface of a metal in- creases its radiating power by allowing the particles of air to approach more nearly in consequence of the pro- minences produced ; and the same reason accounts for the increasing effect produced by repeated coats of jel- ly applied to metallic surfaces. Such is an imperfect sketch of Mr Leslie's ingenious hypothesis. For a fuller detail it will be necessary to consult his work. Several objections naturally present themselves to this view of the subject ; but as the au- thor has not hitherto advanced any proof in confirma- tion of his peculiar opinions, except their convenience in accounting for the phenomena, it is not necessary to enter upon a particular examination of them. They Cannot be admitted without direct proof; especially as they do not appear consistent with the experiments of CALORIC. 457 Herschel, Wollaston, Ritter, and Bockmann. Count t cha P- IL Rumford has advanced an hypothesis not very dissimi- lar, but has not succeeded so well in giving it an im- posing aspect. II. PASSAGE OF CALORIC THROUGH BODIES. 1. CALORIC, we have seen, is incapable of moving in rays through solid bodies. Yet it is well known that all bodies whatever are pervious to it. Through so- lids, then, it must pass in a different manner. In gene- ra; its passage through them is remarkably slow. Thus if we put the end of a bar of iron, twenty inches long, into a common fire, while a thermometer is attached to the other extremity j four minutes elapse before the thermometer begins to ascend, and 15 minutes by the time it has risen 15. In this case, the caloric takes four minutes to pass through a bar of iron 20 inches. When caloric passes in this slow manner, it is said to be conducted through bodies. It is in this manner alone that it passes through non-elastic bodies; and though it often moves by radiation through elastic media, yet we shall fi;id afterwards that it is capable of being conduct- ed through them likewise. 2. As the velocity of caloric, when it is conducted Conducting through bodies, is greatly retarded, it is clear that it does * C ,!/ X ~ not move through them without restraint. It must be detained for some time by the particles of the conduct- ing body, a-,d consequently must be attracted' by them. Hence it follows that there is an* affinity or attraction between caloric and every conductor. It is in conse- quence of this affinity that it is co Ducted through the body. This pcrLaps will be better understood by the following illustration ; 458 MOTION OF Book I. Let M be a body (a mass of X Division IT. iron, for instance) composed of l an indefinite number of parti- 2 . cles, arranged in the strata, 1, 3 > 2, 3, 4, 5, 6, 7, &c. Let calo- 4 M ric be communicated to it in 5 _____ the direction X. The first stra- <3 turn of particles 1 combines 7 with a dose of caloric, and forms a compound which we shall call A. This compound cannot be decomposed bj the second stratum, because all the strata before the application of the heat were at the same temperature ; consequently the affinity of all for caloric must have been equal. Now it would be absurd to suppose a com- pound destroyed by an affinity no greater than that which produced it. If therefore only one doze of calo- ric combined with stratum 1, no caloric could pass be- yond that stratum. But the compound A has still an affinity for caloric ; it therefore combines with another dose of it, and forms* a new compound, which we shall call B. This stratum is now combined with two doses of ca- loric ; the second of which, according to the general law already explained, is retained by a weaker affinity than the first. Stratum 2, therefore, is capable of ab- stracting this second dose. Accordingly it combines with it, and forms the compound A. Here are two strata combined each with a dose of caloric, and conse- quently constituting compound A. The third stratum is unable to decompose the second, for the same reason that the second was unable to decompose the first while only combined with one dose. Stratum 1 again com- bines with a doze of caloric, and forms compound B CALORIG. 45f Stratum 2 is unable to decompose this compound, be- t cha P- 1T - cause being already combined with one dose, its affinity for the second dose cannot be greater than that of stra- tum 1 for the same second dose. But stratum 1 combines with a third dose of caloric, and forms a new compound which we shall call C. The affinity of this third dose being inferior to that of the second, stratum 2 abstracts it and forms compound B. This second dose is abstracted from stratum 2 by stratum 3, which now forms compound A, Stratum 1 again forms compound C, to be again decomposed by stratum 2, which stratum forms a new compound B. Compound C is a third time formed by stratum i. Three strata are now heated. Stratum 1 is combined with three doses, stratum 2 with two doses, and stratum 3 with one dose. The caloric can pass no farther: for stratum 4 cannot decompose compound A, nor stratum 3 compound B, nor stratum 2 compound C. But stra- tum 1 combines with a fourth dose of caloric, and forms a new compound which we shall call D. This new dose is abstracted by stratum 2, which forms compound C. It is again abstracted from stratum 2 by stratum 3, which forms compound B. From stratum 3 it is ab- stracted by stratum 4, which forms compound A. Stratum 1 again combines with a new dose, and forms compound D ; which is abstracted first by stratum 2, and then by stratum 3, which last stratum forms com- pound B. Stratum 1 a third time forms compound D ; but the dose is immediately abstracted by stratum 2, which forms with it compound C. Compound D is a fourth time formed by stratum 1, and is not de- composed any more. Here are four strata combined with caloric j stratum 1 with four doses, stratum 2 with 460 MOTION OF Book I. three doses, stratum 3 with two doses, and stratum 4 Division II. . u -v- with one close. In this manner may tne heating process go on till any number of strata whatever are combined with caloric. 3. Bodies then conduct caloric in consequence of their affinity for it, and the property which they have of .combining indefinitely with additional doses of it. Hence the reason of the slowness of the process, or, which is the same thing, of the long time necessary to heat or to cool a body. The process consists in an al- most infinite number of repeated compositions and de- compositions. 4. We see, too, that when heat is applied to one extre- mity of a body, the temperature of the strata of that body must diminish equably, according to their dis- tance from the source of heat. Every person must have observed that this is always the case. If, for in- stance, we pass our hajid along an iron rod, one end of which is held in the fire, we shall perceive its tempera- ture gradually diminishing from the end in the fire, which is hottest, to the other extremity, which is coldest. Hence the measure of the heat transmitted must always be proportional to the excess of tempera- ture communicated to that side of the conductor which is nearest the source of heat. Has a limit. 5. The passage of caloric through a body by its con- ducting power must have a limit ; and that limit de- pends upon the number of doses of caloric with which the stratum of the body nearest the source of heat is ca- pable of combining. If the length of a body be so great that the strata of which it is composed exceed the num- ber of doses of caloric with which a stratum is capable of combining, it is clear that caloric cannot possibly be CALORIC. 461 conducted through the body ; that is to say, the strata t Chap.u farthest distant from the source of heat cannot receive any increase of temperature. This limit depends, in, all cases, upon the quantity of caloric with which a bo- dy is capable of combining before it changes its state. All bodies, as far as we know at present, are capable of combining indefinitely with caloric ; but the greater number, after the addition of a certain number of doses, change their state. Thus ice, after combining with a certain quantity of caloric, is changed into water, which is converted in its turn to steam by the addition of more caloric. Metals also, when heated to a certain degree, melt, are volatilized, and oxidated : wood and most other combustibles catch fire, and are dissipated. Now whenever as much caloric has combined with the nrst stratum of a body as it can receive without changing its state, it is evident that no more caloric can enter the body ; because the next dose will dissipate the first stratum. 6. As to the rate at which bodies conduct caloric, that depends upon the specific nature of each particular body; the best conductors conducting most rapidly, and to the greatest distance. The goodness of bodies as con- ductors appear to be in some measure dependent upon their density ; but not altogether, as the specific affinity of each for caloric must have considerable influence. When bodies are arranged into sets, we may lay it down as a general rule that the densest set conduct at the greatest rate. Thus the metals conduct at a greater rate than any other bodies. But in considering the indivi- duals of a set, it is not always the densest that conducts best. 7. As bodies conduct caloric in consequence of their 462 MOTION OF Book I. affinity for it, and as all bodies have an affinity for calo* Division II. . . J J *< v ' ric > *t follows as a consequence, that all bodies must be conductors, unless their conducting power be counter- acted by some other property. If a body, for instance, were of such a nature that a single dose of caloric suf- ficed to produce a change in its state, it is evident that it could not conduct caloric ; because every row of par- ticles, as soon as it had combined with a dose of ca- loric, would change its place, and could not therefore communicate caloric to the strata behind it. All solids 8. All solids are conductors; because all solids are ca- pable of combining with various doses of caloric before they change their state. This is the case in a very re- markable degree with all earthy and stony bodies ; it is the case also with metals, with vegetables, and with animal matters. This, however, must be understood with certain limitations. All bodies are indeed con- ductors ; but they are not conductors in all situations. Most solids are conductors at the common temperature of the atmosphere ; but when heated to the tempera- ture at which they change their state, they are no long- er conductors. Thus at the temperature of 60 sul- phur is a conductor ; but when heated to 218, or the point at which it melts or is volatilized, it is no longer a conductor. In the same manner ice conducts calorie when at the temperature of 20, or any other degree below the freezing point ; but ice at 32 is not a con- ductor, because the addition of caloric causes it to change its state. 9. With respect toliquidsand gaseous bodies, it would appear at first sight that they also are all conductors y for they can be heated as well as solids, and heated too considerably without sensibly changing their state. But CALORIC, 463 fluids differ from solids in one essential particular : ^hap. I r. their particles are at full liberty to move among them- selves, and they obey the smallest impulse ; while the particles of solids, from the very nature of these bodies, are fixed and stationary. One of the changes which caloric produces on bodies is expansion, or increase of bulk ; and this increase is attended with a proportional diminution of specific gravity. Therefore, whenever caloric combines with a stratum of particles, the whole stratum becomes specifically lighter than the other par- tides. This produces no change of situation in solids ; but in fluids, if the heated stratum happens to be below the other strata, it is pressed upwards by them, and being at liberty to move, it changes its place, and is buoyed up to the surface of the fluid. In fluids, then, it makes a very great difference to Fluidcarry what part of the body the source of heat is applied. If it be applied to the highest stratum of all, or to the surface of the liquid, the caloric can only make its way downwards, as through solids, by the conducting power of the fluid : but if it be applied to the lowest stratum, it makes its way upwards, independent of that conduct- ing power, in consequence of the fluidity of the body and the expansion of the heated particles. The lowest stratum, as soon as it combines with a dose of caloric, becomes specifically lighter, and ascends. New par- ticles approach the source of heat, combine with caloric in their turn, and are displaced. In this manner all the particles come, one after another, to the source of heat; of course the whole of them are heated in a very short time, and the caloric is carried almost at once to much greater distances in fluids than in any solid whatever. Fluids, therefore, have the property of carrying or 464 MOTION OF Book T. transporting caloric ; in consequence of which they ac- V J quire heat independent altogether of any conducting power. 10. The carrying power of fluids was first accurately examined by Count Rumford. This ingenious philo- sopher was so struck with it the first time he observed it, that he was led to conclude, that it is by means of it alone that fluids acquire heat, and that they are alto- gether destitute of the property of conducting caloric. In a set of experiments on the communication of heat, he made use of thermometers of an uncommon size. Having exposed one of these (the bulb of which was near four inches in diameter) filled with alcohol to as great a heat as it could support, he placed it in a win- dow to cool, where the sun happened to be shining. Some particles of dust had by accident been mixed with the alcohol: these being illuminated by the sun, became perfectly visible, and discovered that the whole liquid in the tube of the thermometer was in a most rapid mo- tion, running swiftly in opposite directions upwards and downwards at the same time. The ascending cur- rent occupied the axis, the descending current the sides of the tube. When the sides of the tube were cooled by means of ice, the velocity of both currents was accele- rated. It diminished as the liquid cooled ; and when it had acquired the temperature of the room, the motion ceased altogether. This experiment was repeated with linseed oil, and the result was precisely the same. These currents were evidently produced by the particles of the liquid going individually to the sides of the tube, and giving out their caloric. The moment they did so, their specific gravity being increased, they fell to the bottom, and of course pushed up the warmer part of CALORIC. 465 the fluid, which was thus forced to ascend along the . cha P- "-, axis of the tube. Having reached the top of the tube, the particles gave out part of their caloric, became spe- cifically heavier, and tumbled in their turn to the bot- tom. As these internal motions of fluids can only be dis- covered by mixing with them bodies of the same spe- cific gravity with themselves, and as there is hardly any substance of the same specific gravity with water which is not soluble in it, Count Rumford had recourse to the following ingenious method of ascertaining whe- ther that fluid also followed the same law. The speci- fic gravity of water is increased considerably by dissol- ving any salt in it ; he added, therefore, potash to water till its specific gravity was exactly equal to that of am- ber, a substance but very little heavier than pure wa- ter. A number of small pieces of amber were then mixed with this solution, and the whole put into a glass globe with a long neck, which, on being heated and exposed to cool, exhibited exactly the same phenomena with the ether fluids* A change of temperature, a- mounting only to a very few degrees, was sufficient to set the currents a-flowing ; and a motion might at any time be produced by applying a hot or a cold body to any part of the vessel. When a hot body was applied^ that part of the fluid nearest it ascended ; but it de- scended on the application of a cold body. These observations naturally led Count Rumford to examine whether the heating and cooling of fluids be not very much retarded by every thing which diminishes the fluidity of these bodies. He took a large linseed- oil thermometer with a copper bulb and glass tube 2 the bulb was placed exactly in the centre of a brass cy* Vol. I. G K 46(5 MOTION OF Book T. linder ; so that there was a void space between them u y ! J all around 0'25175 of an inch thick. The thermo- meter was kept in its place by means of four wooden pins projecting from the sides and bottom of the cy- linder, and by the tube of it passing through the cork stopper of the cylinder. This cylinder was filled with pure water, then held in melting snow till the ther- mometer fell to 32% and immediately plunged into a vessel of boiling water* The thermometer rose -from 32 to 200 in 597". It is obvious that all the caloric which served to raise the thermometer must have made its way through the water in the cylinder. The experiment was repeated exactly in the same manner ; but the water in the cylinder, which amount- ed to 2276 grains, had 192 grains of starch boiled in it, which rendered it much less fluid. The thermometer now took 1109" to rise from 32 to 200. The same experiment was again repeated with the same quan- tity of pure water, having 192 grains of eiderdown mixed with it, which would merely tend to embarrass the motion of the particles. A quantity of stewed ap- ples were also in another experiment put into the cy- linder. The following Tables exhibit the result of all these experiments. CALORIC. Time tie caloric was in passing into the Thermometer, Tempera- ture. Through the Water and Starch. ,:h til; Water an,; Eiderdown. Through stewed App'n-s. Through pu : c W Seconds. Seconds. Seconds. Seconds. Therm. r f?e from 33 to 1109 9J9 1096^ 597 aoo c in Therm, rose 80- V tx, 341 269 335 112 So 3 to 1 60, in Time the Caloric ivas in passmg cut of the Thermometer. Tempera- ture. Through Through the the Water Water and and Starch. Eiderdown. Through .ved Apples Through pure Water. Seconds. Seconds. Secon.is. Seconds. Therm, f- 11 from : to 43 ii) 1548 1541 17494- 1032 Th rm. fell 8o r , nearly equal, Tin, J t Platinum,^) Iron, ' c i [>much inferior to the others* Lead. gtones, 13. Next to metals, stoner, pevm to be the best cofl- ductois ; but this property vanes* consiqerablj in dif- ferent ?rones. Bricks are much worse conductors than most stones. {JIass, 14. Gi^ss seems not to differ much from stones in its conducting power. Like them, it is a bad conductor. T'c.'s is the reason thai it is so apt to crack on being suddtnh Seated or cooled. One part of it, receiving or parting with its caloric before the rest, expands or con- tracts, and destroys the cohesion. Woofo 15 Next to these come dried woods. Mr Mey- er f has made a set of experiments on the conducting power of a considerable number of woods. The result may be seen in the following Table, in which the con- ducting power of water is supposed =1. Bodies. C Po^r. ng Water ................................. I'OO Diaspyrus ebenum ......... . ........ n: 2*17 f Jour, d: Pbys. 1789, p. 68t f Ann. de Cbim. XXX. 3J. CALORIC. Conducting Power. Bodies. Pyrus mains = -*~i Fraxinus excelsior 3*08 Fagus sylvatica = 3*21 Carpinusbetulus 3*23 Prunus domestica 3*25 Ulmus = 3-25 Quercusrobur pedunculata ...... = 3*26 Pyrus communis = 3'32 Betula alba 3'41 Quercus robur sessilis 3'63 Piuus picea 3*75 Betula alnus rr 3'S4 * Pinus sylvestris =r 3*86 Pinus abies 3*89 TileaEuropaea 3*90 Charcoal is also a bad conductor : According to the :periments of Morveau, its conducting power is to lat of fine sand : : 2 : 3 *. Feathers, silk, wool, and lair, are still worse conductors than any of the sub- stances yet mentioned. This is the reason that they answer well for articles of clothing. They do not al- low the heat of the body to be carried off by the cold external air. Count Rumford has made a very ingeni- ous set of experiments on the conducting power of these substances f. He ascertained that their conducting power is inversely as the fineness of their texture. 16. The conducting power of liquid bodies has not been examined with any degree of precision. I find Charcoal, feathers, &c, Rektive conducting po; r.s oi liquids. r': Cbim, XX vi, 22J. f Pbll. Trans, 476 MOTION OF Book!. by experiment, that the relative conducting powers of Division II. ... , .. r .. mercury, water, and linseed oil, are as loilow : I. EQJJAL BULKS. Water i Mercury 2 Linseed oil 1*111 II. EQJJAL WEIGHTS. Water 1 Mercury 4*8 Linseed oil 1*085 Ofgasc*. 17. With respect to gaseous bodies, it is well known that bodies cool much more slowly in them than in li- quids. But as the cooling of hot bodies in gases is pro- duced by a variety of causes besides the conducting power of these fluids, it is difficult to form an estimate of their relative intensities as conductors from the time that elapses during the cooling of bodies in them. Count Rumford found that a thermometer cooled near- ly four times as fast in water as in air of the same tem- perature ; but no fair inference can be drawn from that experiment, as it is known that the rate of cooling va- ries with the temperature much more in water than in air*. The same philosopher ascertained, that rarefac- tion diminished the conducting power of air, and that hot bodies cool slowest of all in. a Torricellian vacuum. Mr Leslie was enabled, by the delicacy of his instru- ments, to examine the conducting power of gases with Phil. Trans. 1786. CALORIC. 477 more precision than had been previously done. The Chap. II. following are the facts which he ascertained. The conducting power of all gases is diminished bj rarefaction. He has endeavoured to deduce from his experiments, that the conducting power of air is nearly proportional to the fifth root of its density. But Mr Dalton has rendered it probable that it varies nearly as the cube root of its density. Vapours of all kinds, and every thing that has a ten- dency to dilate air, diminish its conducting power. The conducting powers of common air, oxygen, and azote, are nearly equal. The conducting power of car- bonic acid gas is rather inferior to that of air ; but bo- dies cool in hydrogen gas more than twice as fast as in common air. By analysing the process of cooling, and ascertaining that the radiation is the same in air and hydrogen gas, Mr Leslie has rendered it probable that the conducting power of this ;gas is four times as great as that of air *. Mr Dalton has lately investigated the rate of cooling of hot bodies in different gases. He filled a strong phial with the gas to be examined j introduced in- to it a delicate thermometer through a perforated cork, and observed the time it took to cool 15 or 20. The following Table exhibits the result of his trials f. Gases TJme pooling, Carbonic acid, 112" Sulphureted hydrogen, 1 Nitrous oxide, ^...ICO-f- Olciiant gas, * Leslie's Tnjairy into ibe Nature of Heat, p. 473. f Dalton *8 N'e-a S'jstfvi of C&g*rL-al Pbilstofly, p. 1 1 7. 478 DISTRIBUTION OF Time of Gases Cooling. Common air, I Oxygen, ^ 100 Azotic gas, j Nitrous gas 90 Gas from pit-coal 70 Hydrogen gas 40 SECT. III. OF THE EQUAL DISTRIBUTION OF TEMPERATURE,, WE have seen, in the preceding Section, that caloric is capable of moving through all bodies, though with different degrees of facility. The consequence of tnis property is a tendency which it has to distribute itself among all contiguous bodies in such a manner, that the thermometer indicates the same temperature in all. Contiguous 1 * We can easily increase the temperature of bodies, bodies as- whenever we choose, by exposing them to the action of same tern- our artificial fires. Thus a. bar of iron maybe made red hot by keeping it a sufficient time in a common fire : but if we take it from the fire, and expose it to the open air, it does not retain the heat which it had received; but becomes gradually colder and colder, till it arrives at the temperature of the bodies in its neigh- bourhood. On the other hand, if we cool down the iron bar, by keeping it for some time covered with snow, and then carry it into a warm room, it does not TEMPERATURE. 479 retain its low temperature, but becomes gradually hot- Chap. I f.^ ter, till it acquires the temperature of the room. Thus it appears that no body can retain its high temperature xvhile surrounded by colder bodies, nor its low tempe- rature while it is surrounded by hotter bodies. The caloric, however combined at first, gradually distributes itself in such a manner, that all contiguous bodies, when examined by the thermometer, indicate the same tem- perature. These changes occupy a longer or a shorter time, according to the size or the nature of the body ; but they always take place at last. This law is familiar to every person. When we wish to heat any thing, we carry it towards the fire ; when we wish to cool it, we surround it by cold bodies. The caloric in this last case is not lost ; it is merely distri- buted equally through the bodies. When a number of substances are mixed together, some of them cold and some of them hot, they all acquire the same tempera- ture ; and this new temperature is a mean of all the first temperatures of the substances. Those which were hot become colder, and those which were cold become hotter. This property of caloric has been called by phi- losophers the equilibrium of 'caloric ; but it might, with greater propriety, be denominated, the equal distribu- tion of temper atttre. 2. From the experiments of Kraft and Richmann*, Law of made with much precision, and upon a great number of bodies, the following general conclusion has been drawn. " When a body is suspended in a medium of a temperature different from its own, the difference be- . C->mm t Petrnp. i. 195 480 DISTRIBUTION OF Book f. tween the temperature of the body and the medium di- Divisionll. ...,.. .,.,.., . VY/ mimsnes in a geometrical ratio, while the time increa- ses in an arithmetical ratio.^' Or, " In given small times the heat lost is always proportional to the heat remaining in the body." This law had been first sug- gested by Sir Isaac Newton, who calculated by means of it several temperatures above the scale of thermo- meters f. The caloric which leaves hot bodies till they are reduced to the temperature of the substances around them, is partly conducted away by the surrounding me- dium, partly abstracted by currents produced in that : medium (supposing it fluid), and, in the atmosphere, ' f This proposition applies, perhaps, strictly only to bodies cooling in air. Let H be the temperature of a hot body above the atmosphere, and d its loss of heat in one minute. It follows from the law stated in the text, that at the end of m minutes, the temperature will be H (^ j and at the end of n minutes E (^ - J . Supposing these two tempera- tures found by experiment, and that the first is ~ A y and the second r= B ; from these two equations we obtain I . H= - , or Log. H r= -^ ( Log. Am Log JB rr-nl ^ . r =: rate of cooling rr { "JT ) Log. H~d Log. //. See Nicholson's j^v^r/0 7r. i* 187* TEMPERATURE. 481 partly radiates from the surface of the hot body. The t cha P- !L process of cooling, both in air and in water, has been Cooliugi analysed with much address and success by Mr Leslie, ^ ' though he has neglected to notice the labours of his predecessors in that investigation. The following facts have been ascertained. The effect of the conducting power depends upon the The con* medium, and is therefore constant, supposing the tern- powerf peratures and the medium constant ; but it gradually diminishes as the temperature of the hot body approach- es that of the medium. The effect of radiation depends upon the surface of The radj "^ the hot body, and is therefore constant when the same surface is heated to the same degree : but, like the con- ducting power, it diminishes as the hot body approaches to the temperature of the medium. Radiation, being confined to cooling in elastic mediums, does not operate when the hot body is surrounded by liquids. That portion of the medium which is in contact with Andcur the hot body receiving a certain portion of its heat, ac- quires a different density, and in consequence gives place to a new portion, which, being heated in its turn, follows the preceding portion ; and in this manner a current is produced, which very much accelerates the rate of cool- ing. It is obvious, that the velocity of this current will be the greater the higher the temperature of the hot body is. Hence the effect of these artificial currents will diminish as the temperature of the hot body ap- proaches that of the medium. If these currents be artificially increased, it is obvi- ous that the rate of cooling will be proportionably ac-. celerated. Hence the effect of winds in cooling hot bo- dies. From Mr Leslie's experiments it appears that, Vol. I. Hh 482 DISTRIBUTION OF Book I. other tilings being the same, the rate of coaling is al- Division II. w v _, ways proportional to the velocity of the current, or y which is the same thing, to the velocity with which the hot body moves through the cold medium. Thus a hot ball, that in calm air cooled down a certain number of degrees in 12C/, when moved in the same air with different velocities, lost the same quantity of heat in times which diminished as the velocity increased, as will be obvious from the following Table : Velocity. Time of cooling. 6y feet per second 60' 20 30 CO 12 When the ordinary influence of cooling is deducted, thr acceleration of cooling in these degrees is found to in- crease exactly as the velocity *. Attemptsto 4 - As soon as it was discovered that contiguous bo- explain the ^j es assume the same temperature, various attempts ecjuilibri^jj-j oi heat. were made by philosophers to account for the fact. De Mairan, and other writers in the earlier part of the 18th century, explained it, by supposing that caloric is a fluid which pervades all space, and that bodies merely float in it as a sponge does in water, without having any affinity for it whatever. The consequence of all this was a constant tendency to an equality of density. Of courbe, if too much caloric is accumulated in one body, it must flow out ; if too little, it must flow in till the equality of density be restored. This hypothesis is inconsistent with the phenomena which it K intended to explain. Were it true, all bodies * Leslie, p. 281. TEMPERATURE. 483 ought to heat and to cool with the same facility ; and Chap. U. the heat ought to continue as long in the focus of a burning glass as in a globe of gold of the same diame- ter. It is equally inconsistent with the nature of calo- ric ; which has been shown in the first Section of this Chapter, to be a body very different from the hypothe- tical fluid of De Mairan. 5. Another explanation of the equal distribution of Hypothesis temperature, and a much more ingenious one, was pro- Ktet ' posed by Mr Pictet. According to this philosopher, when caloric is accumulated in any body, the repulsion between its particles is increased, because the distance between them is diminished. Accordingly they repel each other ; and this causes them to fly off in every di- rection, and to continue to separate till they are oppo- sed by caloric in other bodies of the same relative den- sity with themselves, which, by repelling them in its turn, compels them to continue where they are. The equal distribution of temperature therefore depends on the balancing of two opposite forces : the repulsion be- tween the particles of caloric in the body, which tends to diminish the temperature ; and the repulsion between the caloric of the body and the surrounding caloric, which tends to raise the temperature. When the first force is greater than the second, as is the case when the temperature of a body is higher than that of the sur- rounding bodies, the caloric flies off, and the body be* comes colder. When the last force is stronger than the first, as is the case when a body is colder than those which are around it, the particles of its caloric are obli- ged to approach nearer each other, new caloric enters to occupy the space which they had left, and the body- becomes hotter. When the two forces are equal, th Hh2 44 DISTRIBUTION OF Book r. bodies are said to be of the' same temperature, and no Division II. . w- v ' change takes place *. But this theory, notwithstanding its ingenuity, is in- consistent with the phenomena of the heating and cool- ing of bodies, and has accordingly been abandoned by the ingenious author himself. Of Prevort, 6. The opinion at present most generally received, and which accounts for the phenomena in the most sa- tisfactory manner, is that of Prevost, first published in the Journal de Physique for 1791, in an essay on the tqvilibrium of caloric ; and afterwards detailed at great- er length in his Recherckes sur la Chaleur f. It was soon after adopted by Mr Pictet J, and has been lately applied by Prevost with much address to the experi- ments of Herschel and Pictet}. According to him, caloric is a discrete fluid, each particle of which moves with enormous velocity when in a state of liberty. Hot bodies emit calorific rays in all directions ; but its par- ticles are at such a distance from each other, that vari- ous currents may cross each other without disturbing one another, as is the case with light. The consequence of this must be, that if we suppose two neighbouring spaces in which caloric abounds, there must be a con- tinual exchange of caloric between these ^wo spaces. If it abounds equally in each, the interchanges will ba- lance each other, and the temperature will continue the same. If one contains more than the other, the exchan- ges must be unequal ; and by a continual repetition of # See Pictet, *ur It F/ K chap. i. 4 Geneva, 1794. \ miittb. Brita*. iv, 30. f PbiL Trant. i8oa, p. 401;, TEMPERATURE. 485 this inequality, the equilibrium of temperature must be t Cha P- Ir restored between them. If we suppose a body placed in a medium hotter than itself, and the temperature of that medium constant, we may consider the caloric of the medium as consisting of two parts ; one equal to that of the body, the other equal to the difference between the temperature of the two. The first part may be left out of view, as its ra- diations will be counterbalanced by those of the body. The excess alone requires consideration ; and relatively to that excess the body is absolutely cold, or contains no caloric whatever. If we suppose that in one second the body receives ^th of this excess, at the end of the first second the excess will be only -^ths. One tenth of this excess will pass into the body during the next second, and the excess will be reduced to /& of ^, or (>)*. At the end of the third second, the excess will be (i^-) 3 ; at the end of the fourth, (A) 4 ; and so on : the time increasing in an arithmetical ratio, while the excess diminishes in a geometrical ratio, according to Richmann's rule. Such is a sketch of Prevost's theory. It is founded altogether upon the radiation of caloric, and leaves the effect of the conducting power of bodies out of sight. The reality of the radiation cannot be doubted ; and it is exceedingly probable that the equal distribution of temperature is the consequence of it. Were caloric mere- ly conducted, its progress would be excessively slow, and indeed absolute equality of temperature would scarcely ever take place. At the same time, it must be allowed that this property of bodies has very consi- derable influence in regulating the time which elapses before the temperature of contiguous bodies is brought 486 EFFECTS OF Book I. t equality ; and in so far as Mr Prevost's hypothesis Division If. r . * v ' overlooks this circumstance, which obviously depends upon the affinity existing between aloric and other bo- dies, it must be considered as imperfect. SECT. IV. OF THE EFFECTS OF CALORIC. HAVING in the preceding Sections considered the na- ture of caloric, the manner in which it moves through other bodies, and distributes itself among them ; let us now examine, in the next place, the effects which it produces upon other bodies, either by entering into them or separating from them. The knowledge of these effects we shall find of the greatest importance, both on account of the immense additional power which it puts into our possession, and of the facility with which it enables us to comprehend and explain many of the most important phenomena of nature. The effects which caloric produces on bodies may be arranged un- der three heads, namely, 1. Changes in bulk ; 2- Changes in state ; and, 3. Changes in combination. Let us con- sider these three sets of changes in their order. I. OF CHANGES IN BULK. Ji Jjpansion. IT may be laid down as a general rule to which there is no known exception, that every addition or abstrac- tion of caloric makes a corresponding change in the bulk CALORIC. 4S*7 of the body which has been subjected to this alteration Chap. IJ. in the quantity of its heat. In general, the addition of heat increases the bulk of a body, and the abstraction of it diminishes its bulk ; but this is nor uniformly the case, though the exceptions are not numerous. Indeed these exceptions are not only confined to a very small number of bodies, but even in them they do not hold, except at certain particular temperatures ; while at ail other temperatures these bodies are increased in bulk when heated, and diminished in bulk by being cooled. We may therefore consider expansion as one of the most general effects of heat. It is certainly one of the most important, as it has furnished us with the means of measuring all the others. Let us, in the first place, con- sider the phenomena of expansion, and then turn our at- tention to the exceptions which have been observed. 1. Though all bodies are expanded by heat and con- Differs in tracted by cold, and this expansion in the same body is always proportional to some function of the quantity of caloric added or abstracted ; yet the absolute expan- sion or contraction has been found to differ exceeding- ly in different bodies. In general, the expansion of gaseous bodies is greatest of all ; that of liquids is much smaller, and that of solids the smallest of all. Thus, 100 cubic inches of atmospheric air, by being heated from the temperature of 32 to that of 212, are in- creased to 13V 5 cubic inches ; while the same augmen- tation of temperature only makes 100 cubic inches of water assume the bulk of 104*5 cubic inches : and 100 cubic inches of iron, when heated from 32 to 212, assume a bulk scarcely exceeding 100*1 cubic inches. From this example, we see that the expansion of air is snore than eight times greater than that of water ; and the 48S EFFECTS OF CALORIC. Book I. expansion of water about 45 times greater than that of Division II. . i_-v ~ iron. Expansion 3. An accurate knowledge of the expansion of ga- of gases. ,. . . seous bodies being frequently of great importance in chemical researches, many experiments have been made to ascertain it ; yet, till lately, the problem was un- solved. The results of philosophers were so various and discordant, that it was impossible to form any opi- nion on the subject. This was owing to the want of sufficient care in excluding water from the vessels in which the expansion of the gases was measured. The heat which was applied converted portions of this wa- ter into vapour, which, mixing with the gas, totally dis- guised the real changes in bulk which it had under- gone. To this circumstance we are to ascribe the dif- ference in the determinations of Deluc, General Roy, Saussure, Divernois, &c. Fortunately this point has lately engaged the attention of two very ingenious and precise philosophers ; and their experiments, made with the proper precautions, have solved the problem. The experiments ot Mr Dalton of Manchester were read to the Philosophical Society of Manchester in October 1801, and published early in 1802 *. To him there- fore the honour of the discovery of the law of the dili- tation of gaseous bodies is due : for Mr Gay Lussac did not publish his dissertation on the expansion of the gases f till more than six months after. Mr Dalton 's experiments are distinguished by a simplicity of appa- ratus, which adds greatly to their value, as it puts it ia the power of others to repeat them without difficulty. It consists merely of a glass tube, open at one end, and Mandestcr Memoirs, v. 593. f Ana. de Cbim. xliii. IJ7* EXPANSION. 489 divided into equal parts ; the gas to be examined was t Cha p. U- introduced into it after being properly dried, and the tube is filled with mercury at the open end to a given point ; heat is then applied, and the dilatation is ob- served by the quantity of mercury which is pushed out. Mr Guy Lussac's apparatus is more complicated but equally precise ; and as his experiments were made on larger bulks of air, their coincidence with those of Mr Dalton adds considerably to the confidence which may be placed in the results. From the experiments of these philosophers it follows, The amc that all gaseous bodies whatever undergo the same ex- m ' pansion by the same addition of heat, supposing them placed in the same circumstances. It is sufficient, then, to ascertain the law of expansion observed by any one gaseous body, in order to know the exact rate of dilata- tion of them all. Now, from the experiments of Gay Lussac we learn, that air, by being heated from 32 to 212, expands from 100 to 137*5 parts: the increase of bulk for 180 is then 37*5 parts ; or, supposing the bulk at 32 to be unity, the increase is equal to 0*375 parts : this gives us 0*00208, or 7 4"o tn P art > f r ^ e ex " pansion of air for 1 of the thermometer. Mr Dalton found that 100 parts of air, by being heated from 55 to 212, expanded to 132*5 parts : this gives us an ex- pansion of 0-00207, or T | T d part, for 1; which differs as little from the determination of Lussac as can be ex- pected in experiments of such delicacy. From the experiments of Mr Dalton, it appears that And nearly the expansion of air is almost perfectly equable ; that is to say, that the same increase of bulk takes place by the same addition of caloric at all different temperatures. It is true, indeed, that the rate of diminution appears to 490 EFFECTS OF CALORIC, Book I. diminish as the temperature increases. Thus the ex* Division IF. * v^ ' pansion from 55 to 1334-, or for the first 77| degrees, was 167 parts; while the expansion from 133 to 212, or for the next 77^-, was only 158 parts, or nine parts less than the first. But this difference, in all likeli- hood, is chiefly apparent ; for Deluc has demonstrated, that the thermometer is not an accurate measure of the increase of heat. Indeed Mr Dalton has shown that the expansion of air follows a regular geometrical pro- gression, if we suppose that mercury expands as the square of the temperature from the freezing point. From the experiments of Gay Lussac, it appears that the steam of water, and the vapour of ether, undergo the same dilation with air when the same addition is made to their temperature. We may conclude, then, that all elastic fluids expand equally and uniformly by heat ; The following Table gives us nearly the bulk of a given quantity of air at all temperatures from 32 to 212. EXPANSION. Temp. ii;.lk. Tcnij). iiuifc. . 2 100000 59 105616 86 111232 33 100208 60 105824 87 111440 I 1<'.0416 61 106032 88 lllo4S 35 100624 62 106240 89 111856 36 100832 63 106448 90 112064 37 101040 64 106656 91 11227J 38 101248 65 186864 112480 39 101456 66 107072 93 112688 40 101664 67 107280 94 112890 41 101S72 68 1074S8 95 113104 42 102080 69 107696 96 113312 43 1C22SS 70 107<)04 97 113520 44 102496 71 108112 98 113728 45 102704 72 108320 99 113936 46 102912 73 108528 100 114144 47 103120 74 108736 110 116224 48 103328 75 108944 120 118304 49 103536 76 109152 130 120384 50 103744 77 109360 140 122464 51 103952 78 109568 150 124544 52 104160 79 109776 160 126624 53 104368 80 109984 170 128704 54 104576 81 110192 ISO 130784 55 104784 82 110400 190 132864 56 104992 83 110608 200 134944 57 105200 84 110816 210 137024 58 105408 85 111024 212 137440 Expansion of air. 3. The expansion of liquid bodies differs from that of Expansion the elastic fluids, not only in quantity, but in the want c of uniformity with which they expand when equal addi- tions are made to the temperature of each. This diffe- rence seems to depend upon the fixity or volatility of the component parts of the liquid bodies ; for in gene- ral, those liquids expand most by a given addition of Not u heat, whose boiling temperatures are lowest, or which form> 492 EFFECTS OF CALORIC. Book f. contain in them an ingredient which readily assumeg Division II. & * > ' the gaseous form. Thus mercury expands much less when heated to a given temperature than water, which boils at a heat much inferior to mercury ; and alcohol is much more expanded than water, because its boiling temperature is lower. In like manner, nitric acid is much more expanded than sulphuric acid ; not only because its boiling point is lower, but because a portion of it has a tendency to assume the form of an elastic fluid. This rule holds at least in all the liquids whose expansion I have hitherto tried. We may consider it therefore as a pretty general fact, that the higher the temperature necessary to cause a liquid to boil, the smaller the expansion is which is produced by the ad- dition of a degree of heat ; or, in other words, the ex- pansibility of liquids is nearly inversely as their boiling temperature. Increases 4. Another circumstance respecting the expansion of tempera" %uids deserves particular attention : The expansibility twre. o f every one seems to increase with the temperature ; or, in other words, the nearer a liquid is to the tempe- rature at which it boils, the greater is the expansion produced by the addition of a degree of caloric : and, on the other hand, the farther it is from the boiling temperature, the smaller is the increase of bulk produ- ced by the addition, of a degree of caloric. Hence it happens, that the expansion of those liquids approaches nearest to equability whose boiling temperatures are highest ; or, to speak more precisely, the ratio of the expansibility increases the more slowly the higher the boiling temperature is. Unconnect- 5. These observations are sufficient to show us, that their'den- ^ e expansion of liquids is altogether unconnected with EXPANSION. 4r/3 their density. It depends upon the quantity of heat ne- Chap. IT. cessary to cause them to boil, and to convert them into elastic fluids. But we are altogether ignorant at pre- sent of the reason why different liquids require different temperatures to produce this change. 6. The following Table will give the reader a pre- Table rf cise notion of the rate of expansion of those liquids which have been hitherto examined by chemical philo- sophers. Temp. Mcrcu- ry*. Linseed oilf. Sulphu- ric Acidf Nitric Acid \. Water . Oil of Turpen. f. Alco- hol}. 32 100000 100000 _ _ - 100000 40 50 100081 100183 99752 100000 99514 100000 100023 100000 100539 101105 60 100304 100279 100486 100091 100460 101688 70 100406 100558 100990 J00197 100993 102281 80 100508 J00806 101530 100332 101471 102890 90 100610 101054 102088 100694 101931 103517 100 100712 102760 101317 102620 10090S 10244C 104162 110 100813 101540 103196 102943 120 100915 101834 103776 101404 103421 130 101017 102097 104352 103954 140 101119 102320 105132 104573 150 101220 102614 102017 160 101322 102893 170 101424 103116 180 101526 103339 T 190 101628 103587 103617 200 101730 103911 212 101835 107250 104577 * This is the result of De Luc's experiments. Philosophers have given very different statements of the expansion of mercury from 31 tc ai. According to General Roy it is 0-0168. Haelistroem make* it O'i 7583 (Gilbert's Atnaitn. 4:r Pkytik, xvii. 107}. Lalandc affirms 494 EFFECTS OF CALORIC. Book T. Division II. 7. Mr Dalton has rendered it probable that the cxi pansion of water and mercury is as the square of the temperature of each, reckoning from their respective freezing points. He finds, if this law be supposed, that that the experiments of Delisle and his own make it 0-0150 (Ibiil. p. 102.) Mr Delue has shown, that the expansion of mercury from 32 to 122 is to its expansion from 122 to the temperature of boiling water a 14 to 15. f The expansion of linseed oil was determined by Sir Isaac Newton. J The expansion of these three liquids is given from my experiments. They were made by filling thermometers with the liquids, and noting down the degrees at which the liquids stood at the different tempera- tures marked. The weight of liquid equivalent to one degree of the tube was then ascertained, and the weight of the whole liquid whose ex- pansion was tried. From these data, it was easy to ascertain the rate of expansion. The degrees were marked corresponding to a good mercu- rial thermometer. But as the expansion of mercury is not equable, it is obvious that the numbers gradually deviate from accuracy in proportion to the temperature. It was the consciousness of this that induced me to. omit the higher parts of the scale altogether. The correction for the ex- pansion ot the glass was not inserted. The expansion of these liquids was ascertained by Sir Charles Blag- tlen and Mr Gilpin. My experiments give the expansion of both consi- derably less. Thus I found the expansion of water as follows : Temp. Expansion. Temp. Expansion. 42-5 IOOOOO 112- 100777 52-5 1000^0 122-5 ioico6 62-5 100106 32-5 IOI17.O 73-5 100182 142-5 IOI495 82-< 100273 I52-5 IOI755 92-5 100471 162-5 IO2O4O 102-5 100624 I72-5 10226 The strength of the alcohol in the Table was 0-825. Mr Dalton found jooo parts of alcohol of O'8i7 at 50 became 1039 at 110, and 1079 at 170. The expansion diminishes when the alcohol is made weaker. Mr Deluc, by mixing together equal quantities of water at 32 and boiling water, ascertained the medium temperature between that of boiling and freezing water. Suppose the whole expansion from th EXPANSION. 495 the expansions of water and mercury correspond. Chap. II. Hence he infers that all liquids follow the same law, or that they expand as the square of the temperature from the freezing point of each . 8. The expansion of solid bodies is so small, that a Expansion micrometer is necessary to detect the increase of bulk, f solids. As far as is known, the expansion is equable, at least the deviation from perfect equality is insensible. The following Table exhibits the expansion of most of the solids which have hitherto been examined. Most of the experiments were made by Smeaton. Temp. Plati- num ^. Gold . Antimo- ny. Cast Iron f. Steel f. 32 212 100000 100087 100000 100094 100000 100109 100000 100111 100000 100112 Temp. Iron. Bismuth. Copper. Cast Brass j|. Silver . 33 212 100000 100126 100000 100139 100000 100170 100000 100188 100000 10ttlS9 temperature of freezing water to that of boiling water to be divided into 80 parts ; he found that the expansion from 31 to that medium temperature (which would be ill , if the expansion of mercury were equable), and from that temperature to that of boiling water, indifferent liquids, to be as follows : From 32 to M. Temp. Mercury 38-6. . . . Olive and linseed oil .... 37-8 . . . Oil of camomile 37'2 Water saturated with salt 34-9 45-1 II-6 : Rectified spirit of wine . . 33-7 46-3 10-9 Water 19*2 6c-8 47 ; New System of Chemical Philosophy, p. IO. ^ Borda. * Bougucr. f The expansion of blistered steel from 33 to *ia, was found by From M. Temp. n . to boiling Water. Ratlos * 4I'4 X 4 : 15 42'* I.V4: 15 42-8 13 : 15 '5 15 15 496 EFFECTS OF CALORIC. Book I. Division r Expansion of glass. Temp. Brass Wire Tin. Lead. , Zinc. Hammer- ed Zinc. 32 212 100000 100194 100000 100238 100000 100281 10000( 100296 100000 100308 Temp. /.inc 8 Tin i Lead a Tin i Brass i Zinc I I'ewter. Copper 3 Tin* i 32 r 212 100000 100259i 100000 1002M 100000 10020^ 100000 100228 100000 100,82 The expansion of glass is a point of great importance, as it influences the result of most experiments on tem- perature. It has been examined with much precision by Mr Deluc. The rate of its expansion, as settled by that philosopher, may be seen in the following Table : Temp. 32 Bulk f 100000 Temp. 100 Bulk. 100023 Temp. 167 . Bulk. 100056 50 100006 120 100033 190 100009 70 100014 150 100044 1 212 10U083 From this Table, it appears, that when glass is ( heat- ed one degree, it undergoes an expansion which amounts Smeaton 100115. Gen. Roy fonnd that of a steel rod i'OOH499. By the late very precise trials of Mr Dalby, roo feet of blistered steel ex* panded 0-007492 inches when heated i of Fahrenheit. Phil. Trans. 17 95, p. 418. | Ramsden. Herbert. H Ramsden found the expansion of a brass scale from 32 to 211, 0-0122646; of English plate brass, in f.rm of a ro , 0-0227136 ; of the same in form of a trough, 0*0227386. The original bulk being . 4*0000. The metal whose expansion is hr.re yiven was an allo composed of three parts of copper and one of tin. The figure-, in some of the prece- ding columns are to be understood in the same manner. Thus in the last column but two, the metal conisted of two parts of brass alloyed with one of zinc. EXPANSION. 497 nearly to T^OITOIT f tne whole bulk. The glass exa- t cha P- "_ mined by Deluc was of the kind employed for making barometer and thermometer tubes. But the expansion of this substance must vary considerably according to circumstances. Thus a solid glass rod expanded, ac- cording to Ramsden, 0*0096944 when heated from 32 to 212, and a glass tube 0*0093138. Smeaton found a barometer tube, exposed to the same degree of heat, 0*0100*. The original bulk in these was 12'000. Mr Dalton has rendered it probable that thin glass bulbs expand nearly as much as iron when heated. 9. The property which bodies possess of expanding, when heat is applied to them, has furnished us with an instrument for measuring the relative temperatures of bodies. This instrument is the thermometer. A ther- Nature of mometer is merely a hollow tube of glass, hermetically " sealed, and blown at one end into a hollow globe or lulb. The bulb and part of the tube are filled with mercury. When the bulb is plunged into a hot body, the mercury expands, and of course rises in the tube ; but when it is plunged into a cold body, the mercury contracts, and of course^//.? in the tube. The rising of the mercury indicates an increase of heat ; its falling a diminution of it ; and the quantity which it rises and falls indicates the proportion of increase or diminution. * On the supposition that metals expand equably, the expansion of a mass of metal, by being heated a given number of degrees, is as follows Let a = the expansion of the mass in length for i, which must be found by experiment ; b = the number of degrees whose expansion is required; i = the solid contents of the metallic mass; *= the expansion sought j then * = 3 b a s, 1. I i 498 EFFECTS OF CALORIC. Beok I. Xo facilitate observation, the tube is divided into a num- Di vision II. < v , .1 ber of equal parts called degrees. The thermometer, to which we are indebted for al- most all the knowledge respecting caloric which we possess,, was invented about the beginning of the nth century ; and is supposed by some to have been first thought of by Sanctorio, the celebrated founder of sta- tical medicine. The first rude thermometer was impro- ved by the Florentine academicians and by Mr Boyle ; but it was Sir Isaac Newton who rendered it really use- ful, by pointing out the method of constructing ther- mometers capable of being compared together. How gra- If we plunge a thermometer ever so often into melt- ing snow, it will always stand at the same point. Hence we learn that snow always begins to melt at the same temperature. Dr Hooke observed also, that if we plunge a thermometer ever so often into boiling water, it al- ways stands at the same point, provided the pressure of the atmosphere be the same ^ consequently water (other things being the same) always boils at the same tempe- rature. If therefore we plunge a new made thermo- meter into melting snow, and mark the point at which the mercury stands in the tube; then plunge it into boil- ing water, and mark the new point at which the mer- cury stands ; then divide the portion of the tube between the two marks into any number of equal parts, suppose 100, calling the freezing point 0, and the boiling point 100 ; every other thermometer constructed in a simi- lar manner will stand at the same degree with the first thermometer, when both are applied to a body of the same temperature. All such thermometers there- fore may be compared together, and the scale may be EXFANSION. 490 extended to any length both above the boiling point and t Chap. II. below the freezing point. Newton first pointed out the method of making com- parable thermometers* ; but the practical part of the art was greatly simplified by Mr Fahrenheit of Amsterdam and Dr Martine of St Andrew's f. From the different methods followed by philosophical instrument makers in determining the boiling point, it was found, that thermometers very seldom agreed with each other, and that they often deviated several degrees from the truth. This induced Mr Cavendish to suggest to the Royal Society the importance of publishing rules for construct- ing these very useful instruments. A committee of the society was accordingly appointed to consider the subject. This committee published a most valuable set of directions, which may be consulted in the Philo- sophical Transactions . The most important of these di- rections is, to expose the whole of the tube as well as the ball of the thermometer to steam^ when the boiling wa- ter point is to be determined. They recommend this to be done when the barometer stands at 29' 8 inches. Mercury is the liquid which answers best for ther- mometers, because its expansion is most equable, owing to the great distance from its boiling and freezing points. There are four different thermometers used at present Different in Europe, differing from one another in the number of degrees into which the space between the freezing and boiling points is divided. These are Fahrenheit's, Cel- sius's, Reaumur's, and De Lisle's. * PLiL Trans. Abr. iv. I. f On tie Conduction and Graduation of Tbermometttt. | PtH, Trans, 1777. p. 816, 500 EFFECTS OE CALORIC. Book I. Fahrenheit's thermometer is used in Britain. The Division II. i y _/ space between the boiling and freezing points is divided into 180 ; but the scale begins at the temperature pro- duced by mixing together snow and common salt, which is 32 below the freezing point ; of course the freezing point is marked 32, and the boiling point 212 *. The thermometer of Celsius is used in Sweden ; it has been used also in France since the Revolution, un- der the name of the thermometre centigrade. In it the space between the freezing and boiling points is divided into 100. The freezing point is marked 0, the boiling point 100 f. The thermometer known by the name of Reaumur, which was in fact constructed by De Luc, was used in France before the Revolution, and is still used in Italy and Spain. In it the space between the boiling and freezing points is divided into 80. The freezing point is marked 0, the boiling point 80 J. De Lisle's thermometer is used in Russia. The space between the boiling and freezing points is divided into 150 j but the graduation begins at the boiling * This is the thermometer always used throughout this Work, unless when some other is particularly mentioned. f Consequently the degrees of Fahrenheit are to those of Celsius, as 180: 100 = 18 : 10 = 9:5. That is, 9 of Fahrenheit are equal to 5 of Celsius. Therefore, to reduce the degrees of Celsius to those of Fahrenheit, we have F = 2' + 3*. J Consequently 180 F = 80 R, or 18 F - 8 R, or 9 F = 4 R ; there- fore F= EXPANSION. 501 *nd increases towards the freezing point. The boiling t Chap. n ^ point is o.arked 0, the freezing point 150 *. 10. In making experiments with the thermometer, I> oe s not measure the we ought always to remember that, when graduated in increase of the common way, it does not give us an exact measure of the increase of heat : For as the expansion of mercu- ry for every degree of temperature increases with the temperature, it is obvious that, unless allowance be made for that increase, the degree indicated by the ther- mometer will not mark the number of degrees of heat added to or abstracted from a body, but another number, deviating more and more from the true one the higlier the temperature indicated happens to be. Thus sup- pose the medium temperature between that of boiling and freezing water to be denoted by 122 ; if we ex- tend the scale upwards, the boiling water point will not be 212, as it would be if the scale were equable, but 218'4; On the other hand, if we fix the boiling and freezing points, as is commonly done, and mark them 212 and 32, then the medium temperature between these two will not be 122, but 118*8. If Mr Dalton's opinion, that the expansion of mer- cury is as the square of the temperature, reckoning from its freezing point, be correct, it is obvious, that the ther- mometer, to indicate equal measurements of tempera- ture, ought to be graduated differently ; the present de- * Hence 180 F = 150 D, or 6 F = 5 D. To reduce the degrees of De Lisle's thermometer under the boiling point to those t-f Fahrenheit, we have F == 212 ; to reduce those above the boiling point, F 4 6 D = 2 12 . 502 EFFECTS OF CALORIC. Boole T. grces are too large at the beginning of the scale, and too u -Y*~> small at its upper extremity. The following Table shows the degrees of Mr Dalton's new thermometer cor- responding with those of the common, supposing the freezing point to be 32, and the boiling water point to be 212. Balton'* New therm. Com. therm. New therm. Com. therm, new gradu- ation. 175 C ' ...... 40-00 172 163'2 68 ...... 21-12 182 175 58 17-06 192 ...... 186*9 48 ,..,,. 12'96 202 199^2 38 - 8*52 212 212 28 ...... 3-76 222 225 4-1-34 232 OQfi/S JL O 8 6*78 4vq9^3 242 A. *) O \j 252'6 + 2 12-63 252 266-8 12 18*74 262 281*2 22 25-21 272 296-2 32 32 282 311*5 42 39'3 292 327 52 ...... 47 302 342-7 62 55 312 ...... 359*2 72 * 63*3 322 375-8 82 72 332 3Q2-7 92 ... 81 342 409-S 102 90*4 352 , 427*3 112 100-1 362 445*3 122 110 372 AfiQ.fi 132 120'1 *P f 4B 382 T*U O (3 482*2 142 130-4 392 501 152 141*1 402 520'3 i62 ...... 152- 412 539*7 EX*ANStOtf. $03 New therm. Cam. therm. New therm. Com. therm. Chap. IF. 422 559-8 452 621'6 432 580'1 462 642 442 600'7 11. Having now considered the phenomena and laws Exceptions of expansion as far as they are understood, it will be ,1 " P< proper to state the exceptions to this general effect of heat, or the cases in which expansion is produced, not by an increase, but by a diminution of temperature. These exceptions may be divided into two classes. The Of tw first class comprehends certain liquid bodies which have a maximum of density corresponding with a certain temperature ; and which, if they be heated above that temperature, or cooled down below it, undergo in both cases an expansion or increase of bulk. The second class comprehends certain liquids which suddenly be- come solid when cooled down to a certain tempera- ture ; and this solidification is accompanied by an in- crease of bulk. 12. Water is considered at present, by th greater * W^tcr number of chemists, as furnishing a remarkable exam- imumdensi- pie of the first class of bodies. This liquid is supposed l ^ to be at its maximum of density when nearly at the temperature of 40. If it be cooled down below 40, it expands as the temperature diminishes ; if it be heated above 40, it in like manner expands as the tempera- ture increases. Thus two opposite effects are produ- ced by heat upon water, according to the temperature of that liquid. From 40 to 32, and downwards, heat diminishes the bulk of water; but from 40, to 212, and upwards, it increases its bulk. Such is the opi- nion at present received by most persons, and which is considered as the result of the most exact rnents. - 504 EFFECTS OF CALORIC. Book r. The facts which led to this conclusion were first ob- Division II. served by the Florentine academicians. An account ^ t * lc * r ex P er i men ts was published in the Philosophical very- Transactions for 1670*. They filled with water a glass ball, terminating in a narrow graduated neck, and plunged it into a mixture of s,now and salt. The water started suddenly up into the neck, in consequence of the construction of the vessel, and slowly subsided again as the cold affected it. After a certain interval it began to rise again, and continued to ascend slowly and equa- bly, till some portion of it shot into ice, when it sprung up at once with the greatest velocity. The attention of the Royal Society was soon afterwards called to this remarkable expansion by Dr Croune, who, in 1683, exhibited an experiment similar to that of the Floren- tine philosophers, and concluded from it, that water be- gins to be expanded by cold at a certain temperature a- bove the freezing point. Dr Hooke objected to this conclusion, and ascribed the apparent expansion of the water to the contraction of the vessel in which the ex- periment was made. This induced them to cool the glass previously in a freezing mixture, and then to fill it with water. The effect, notwithstanding this pre- caution, was the same as before f. Mr De Luc was the first who attempted to ascertain the exact temperature at which this expansion by cold begins. He placed it at 41, and estimated the expansion as nearly equal, when water is heated or cooled the same number of de- grees above or below 41. He made his experiments * PM. Tram. No. 66. or vol. v. p. 3020. Abridgement t f. 540, f Birche's Hitt. of the F.oyal Society, iv. 253, EXPANSION. 505 in glass thermometer tubes, and neglected to make the Chap. ir. correction necessary for the contraction of the glass ; but in a set of experiments by Sir Charles Blagden and Mr Gilpin, made about the year 1790, this cor- rection was attended to. Water was weighed in a glass bottle at every degree of temperature from 32 to 100, and its specific gravity ascertained. They fixed the maximum of density at 39, and found the same ex- pansion very nearly by the same change of tempera- ture either above or below 39. The following Table exhibits the bulk of water at the corresponding degrees on both sides of 39, according to their experiments*. Specific Gra- vity. Bulk of Wa^ ttr. Tempera- ture. 39 Bulk of Wa- ter. 6p. Gravity of Ditto. 100094 1-00094 1*00000 94 38 40 94 1-00000 0-99999 93 37 41 93 0-99999 0-99998 92 36 42 92 0-99998 0-99996 90 35 43 90 0-99996 0-99994 88 34 44 45 88 0*99994 0-99991 85 33 86 0-99992 0-99988 82 32 46 83 0-99989 Rate of ex- pansion. Mr Dalton, in a set of experiments published in 1802, obtained nearly the same result as De Luc. He placed * PLil. Trans. 179*, p. 428. 503 EFFECTS OF CALORIC. Book I. the maximum density at 42'5 , not making any corrco Division II. . ^ Y > tion for the contraction of the glass ; and observed, as Blagden had done before him, that the expansion is the same on both sides of the maximum point, when the change of temperature is the same, and continues how- ever low down the water be cooled, provided it be not frozen *. All these experiments had been made by cooling water in glass vessels; but when the French were forming their new weights and measures, the subject was investigated by Lefebvre-Gineau in a different manner. A determinate bulk of water at a given tem- perature was chosen for the foundation of their weights. To obtain it, a cylinder of copper, about nine French inches long, and as many in diameter, was made, and its bulk measured with the utmost possible exactness. This cylinder was weighed in water of various tempe- ratures. Thus was obtained the weight of a quantity of water equal to the bulk of the cylinder ; and this, corrected by the alteration of the bulk of the cylinder itself from heat or cold, gave the density of water at the temperatures tried. The result was, that the densi- ty of the water constantly increased till the tempera- ture of 40, below which it as constantly diminished f. These experiments seem to have been made about the year 1795. More lately a set of experiments were tried by Haellstroem exactly in the same way ; but he substituted a cylinder of glass for the one of metal. The result which he obtained was the same. The ne- # Manchester Mon. v. 374. f iaur. tie Pbyt. xlix. 171 ; and Hauy's Trait e dt F/ysiqut, I fj. and Ir/ EXPANSION. 507 cessary corrections being made, he found the maximum t Chap. II. density of water lie between 4 and 5 of Celsius, or nearly at 40 of Fahrenheit . Still more lately, a set of experiments have been pub- lished by Dr Hope, which lead to the same result in a different way. He employed tall cylindrical glass jars filled with water of different temperatures, and having thermometers at their top and bottom. The result was as follows ; 1. When water was at 32, and exposed to air of 61, the lottom thermometer rose fastest till the water became of 3S P , then the top rose fastest. Just the reverse happened when the water was 5^*, and ex- posed to the cold water surrounding the vessel ; the top thermometer was highest till the water cooled down to 40, then the bottom one was highest. Hence it was inferred, that water when heated towards 40 sunk down, and above 40 rose to the top, and vice versa. 2. When a freezing mixture was applied to the top of the glass cy- linder (temp, of air 41), and continued even for se- veral days, the bottom thermometer never fell below 39 ; but when the freezing mixture was applied to the bottom, the top thermometer fell to 34 as soon as the bottom one. Hence it was inferred, that water when cooled below 39 cannot sink, but easily ascends. 3. When the water in the cylinder was at 32 C , and warm water applied to the middle of the vessel, the bottom thermometer rose to 39 befofe the top one was affected ; but when the water in the cylinder was at 39*5, and cold was applied to the middle of the vessel, the top $ Gilbert's Annalat tfer Pfytlt, xvil Itj. SOS EFFECTS OP CALORIC. Book T. thermometer cooled down to 33 before the bottom one Division u. u Y^ / was affected . Count Rumford has lately published a set of experi- ments conducted nearly on the same principles with those of Dr Hope, and leading to the same results. They are contrived with his usual ingenuity ; but as they are of posterior date, and add nothing to the facts above stated, I do not think it necessary to detail themf. Dr Hope's experiments and those of Count Rumford coincide with those above related, in fixing the maxi- mum density of water at between 39 and 40. Ascribed to Such are the experiments upon which the belief of this thecontrac- remarkable property of water is founded, and they seem tion of the \ J vessels. at first sight to leave no doubt respecting "its reality. Doubts, however, have been entertained by men of acknowledged candour and capacity ; and it will now be necessary to state the grounds upon which these doubts have been founded. Liquids, as is obvious from the preceding part of this Section, expand when heated at a much greater rate than solids. It has been the opinion of many philoso- phers, that the expansion of liquids is proportional to the squares of the temperatures measured from the free- zing point of each ; and that the deviations from this law are only apparent, and owing to the thermometer not being an exact measurer of the increase of heat. Among others, Mr Daltan has stated this opinion as coinciding with his experiments, and Mr Leslie has made it the foundation of some of his mathematical * See Edln. Trans* vol. vi. The paper was published before October 1804. f See Nicholson's Journal^. 328, Aug. 1805. EXPANSION. 509 reasonings, without any explanation whatever of the ( Chap. H. grounds of his conviction of its truth. On the other hand, the expansion of solids is sensibly only propor- tional to the temperature, setting out from any given point. When cold is applied to solids and liquids, their contractions will follow the same rate as their ex- pansions*. But as the diminution of bulk, when cold is applied to water, is as the difference between the squares of the temperatures, and the diminution of so- lids simply as the difference of the temperatures, it is obvious, that the contraction which water experiences when cooled a degree is constantly diminishing as we approach the freezing point, while that of solids conti- nues sensibly the same. Therefore, at some particular point, the contraction of water will be precisely equal to the contraction of a given solid, and below that point, the contraction of the solid will be greatest. Sup- pose water to be exposed to cold in a glass ball and tube, * With respect to the expansions of water, it certainly follows, pretty nearly at least, the law stated in the text. From the table given in page 494, it appears that the expansion of water, the original bulk being looco, may be expressed pretty nearly by the following numbers : Temp. Expan. 82-s .... 6* 101-5 .... 8* 122-5 .... io* . . . . I2 a if 2-5 , . . . 14* The greatest deviation from these numbers is towards the beginning of the scale, when, owing to the smallness of thefexpansion, it is difficult to measure it with precision. It leads us to this remarkable conclusion, that the squares of the natural numbers beginning at 6 indicate the in- crease of bulk which 10000 parts of water experience for every ten de- grees they are heated above 8a\5 c . 510 EFFECTS OF CALORIC. Book I. it will continue to sink in the tube as long as the con* ^ .vision . tract j on w hj c h i t suffers by cooling is greater than that of the glass ; but when it comes to the point at which the contraction of both is the same, it will not sink farther though cooled, because the diminution of bulk in the water will be just counterbalanced by the con- traction of the vessel. When we pass that point, the water will rise in the tube by the application of cold, because the contraction of the glass will now surpass that of the water. The rise of the water then may be only apparent, and occasioned by this cause ; but an easy method occurs to ascertain the point. Make the experiment in vessels of different kinds, which are dif- ferently contracted by heat, the point of the greatest density of the water ought to vary with the vessel. This accordingly has been done by Mr Dalton. The following Table exhibits the result of his experiments. The first column contains the substances in which the water was contained, and the second the degree of the thermometer at which the water began to rise when cooled in these substances, or its apparent point of great- est density. Brown earthen ware 38 Queen's ware 40 Flint glass 41^ Iron 424- Tin plate. 42 Copper , 45-1' Brass 46 Pewter 46 Zinc 48 Lead 491 These experiments coinciding with what would EXPANSION, if the supposed expansion of water were only apparent, have been considered by Mr Dalton as decisive of the point j and Mr Leslie has advanced a similar opinion. This coincidence, however, is merely apparent. If we Bat this calculate, from the table of expansion given in a pre- coau"foHtl ceding part of this Section, the temperatures at which the expansion of the various bodies in the table coin- cide with the expansion of water, we obtain the follow- ing results : Lowest Point Do. by Dalton's nffm by Calculation. Experiments. Glass..... ..41'5 41'5 Iron 46 42*5 S.fr Copper 52 45*5 6*5 Brass 54 46 8 Pewter 59 46 13 Lead 64 49'5 14'5 The^glass indeed coincides with Mr Dalton's experi- ments, but the other bodies deviate as their expansion increases. This destroys all the consequences that have been drawn from similar experiments, and points out, besides, some error in the data from which the calcula- tions were drawn. The error no doubt consists in setting out from the supposition that water expands from the freezing point. The experiments of Lefebvre-Gineau and Haell- stroem, above related, were in some measure free from the uncertainty resulting from the contraction of the Tessels in which the bulk of the water was estimated. The copper cylinder^ weighed by the former, was hol- low, and every possible precaution was taken to esti- mate the change of bulk occasioned by heat and cold ; and as the instruments were delicate, and the object of 512 EFFECTS OF CALORIC. Book I. great importance, it seems unreasonable to conclude Division H. * y^ that he allowed himself to be deceived. The experiments of Dr Hope and Count Rumford appear at first sight to lead to the same result in a still less ambiguous manner ; but it must be acknowledged that there are circumstances connected with them suf- ficiently puzzling. I shall mention one. If different strata of coloured watery liquids be put into tall glass jars, they will remain separate, if not agitated (as Count Rumford himself observed long ago), for at least a month, notwithstanding all the vicissitudes of tempera- ture to which they are exposed ; vicissitudes often great- er than those to which the liquids were exposed in the trials of Dr Hope and Count Rumford. Now, how can the currents, which their experiments indicate, take place without mixing these strata together in the course of a few hours ? This is a difficulty which I at least have not been able to solve in a satisfactory manner. Mr Dalton has lately reconsidered the subject, and has shown by arguments, which to me appear convin- cing, that the real temperature at which the density of water is a maximum is 36. Thus the singular ano- maly of the expansion of water by cold seems to be completely made out ; but no satisfactory explanation of the cause of this expansion' has been yet offered. We might ascribe it to a commencement of congelation, were it not that in glass tubes water may be cooled down almost to zero before it begins to freeze, and du- ring the whole progress it expands with the utmost re- gularity. I tried a considerable number of liquids, to ascertain whether any of them, like water, have a temperature ia EXPANSION. 513 vhich their density is a maximum, and which expand t p hai. IT when cooled below that temperature. Sulphuric acid has no such point, neither have the oily bodies ; but I thought I could perceive some solutions of salt in wa- ter beginning to expand before they became solid. But these solutions, when cooled down sufficiently, crystallize with such rapidity, that it is extremely difficult to be certain of the fact, that they really do begin to expand before they crystallize. 13. That class of bodies which undergo an expansion 2. Many & when they change from a liquid to a solid body by the diminution of temperature, is very numerous. Not c rystalli only water when converted into ice undergoes such an expansion, but all bodies which by cooling assume the form of crystals. The prodigious force with which water expands in Expansion the act of freezing has been long known to philosophers. * icc> Glass bottles filled with water are commonly broken in. pieces when the water freezes. The Florentine acade- micians burst a brass globe, whose cavity was an Inch in diameter, by filling it with water and freezing it. The force necessary for this eff ct was calculated by Muschen- broeck at 27720 Ibs. But the most complete set of experiments on the expansive force of freezing water are those made by Major Williams at Quebec, and pub- lished in the second volume of the Edinburgh Transac- tions. This expansion has been explained by supposing it the consequence of a tendency which water, in con- solidating, is observed to have to arrange its particles in one determinate manner, so as to form prismatic crys- tals, crossing each other at angles of 60 and 120, The force with which they arrange themselves in this manner must be enormous, since it enables small quaxv<* Vol. L K k 514 EFFECTS OF CALORIC, Book I. Cities of water to overcome so great mechanical pres- Divisc n II. sures. I tried various methods to assenain the specific gravity of ice at 32 ; the one which succeeded best was, to dilute spirits of wine with water till a mass of solid ice put into it remained in any part of the liquid without either sinking or rising. I found the specific gravity of such a liquid to be 0*92 ; which of course is the specific gravity of ice, supposing the specific gravi- ty of water at 60 to be 1. This is an expansion much greater than water experiences even when heated to 212. We see from this, that water, when converted into ice, no longer observes an equable expansion, but undergoes a very rapid and considerable augmentation of bulk. The very same expansion is observed during the crystallization of most of the salts ; all of them at least which shoot into prismatic forms. Hence the reason that the glass vessels in which such liquids are left usually break to pieces when the crystals are formed. A number of experiments on this subject have been pub- lished by Mr Vauquelin *. Several of the metals have the property of expanding' at the moment of their becoming solid. Reaumur was the first philosopher who examined this point. Of all the metallic bodies that he tried, he found only three that expanded, while all the rest contracted on becoming so- lid. These three were, cast iron, bismuth, and antimo- ny^. Hence the precision with which cast iron takes, the impression of the mould. * Ann. de Chlm, xiv. 286, f Mtm. Par. 1726. Berthollet's Statijae Chlmi^ue, ii. 34$, EXPANSION. 5l5 This expansion of these bodies cannot be considered t Cha P- as an exception to the general fact, that bodies increase in bulk when heat is added to them ; for the expansion is the consequence, not of the diminution of heat, but of the change in their state from liquids to solids, and the new arrangement of their particles which accompa- nies or constitutes that change. 14. It must be observed, however, that all bodies do 5? me bo " dies con- not expand when they become solid. There are a con- tract in siderable number which diminish in bulk ; and in these the rate of diminution in most cases is rather increased by solidification. When liquid bodies are converted into solids, they either form prismatic crystals, or they form a mass in which no regularity of arrangement caa be perceived. In the first case, expansion accompanies solidification ; in the second place, contraction accom- panies it. Water and all the salts furnish instances of the first, and tallow and oils are examples of the second. In these last bodies the solidification does not take place instantaneously, as in water and salts, but slowly and gradually ; they first become viscid, and at last quite solid. Most of the oils, when they solidify, form very- regular spheres. The same thing happens to honey and to some of the metals, as mercury, which Mr Ca- vendish has shown from his own experiments, and those of Mr Macnab, to lose about ^d of its bulk in the act of solidification *. When sulphuric acid congeals, it does not perceptibly expand, nor does it in the least alter its appearance. Sulphuric acid, of the specific gravity 1'8, may be cooled down in thermometer tubes , * fbil. Trjns. 1783, p. Kk2 EFFECTS OF CALORIC. Book I. to 36 before it freezes ; and during the whole pro- Division II. < v - cess it follows exactly the rate of expansion given in the table of expansions. At 36, or about that tem- perature, it freezes > but its- appearance is so little altered, that I could not satisfy myself whether or not the liquid was frozen till I broke the tube^ It was perfectly so- lid, and displayed no appearance of crystallization. On the other hand, cast iron, and probably sulphur also, expands in the act of congealing. Bodies change their state by heat. II. CHANGES IN THE STATE OF BODIES. ALL substances in nature, as far as we are acquaint- ed with them, occur in one or other of the three follow- ing states ; namely, the state of solids, of liquids, or of elastic fluids or vapours. It has been ascertained, that in a vast number of cases, the same substance is capa- ble of existing successively in each of these states. Thus sulphur is usually a solid body ; but when heated to 218, it is converted into a liquid; and at a still higher temperature (about 570), it assumes the form of an elastic vapour of a deep brown colour. Thus also water in our climate is usually a liquid ; but when cooled down to 32, it is converted into a solid body, and at 212* it assumes the form of an elastic fluid. All solid bodies, a very small number s excepted, may be converted into liquids by heating them suffi- ciently ; and, on the other hand, every liquid, except spirit of wine, is convertible into a solid body by ex- posing it to a sufficient degree of cold. All liquid bo- dies may, by heating them, be converted into elastic fluids, and a great many solids are capable of undergo- ing the same change ; and, lastly, the number of elastic FLUIDITY. 517 fluids which by cold are condensible into liquids or so- ^hap. IT.^ lids is by no means inconsiderable. These facts have led philosophers to form this general conclusion, " That all bodies, if placed in a temperature sufficiently low, would assume a solid form ; that all solids become li- quids when sufficiently heated ; and that all liquids, when exposed to a certain temperature, assume the form of elastic-fluids." The state of bodies then depends upon the temperature in which they are placed ; in the low- est temperatures they are all solid, in higher temperatures they are converted into liquids, and in the highest of aill they become elastic fluids. The particular temperatures at which bodies undergo those changes, are exceedingly various, but they are always constant for the same bo- dies. Thus we see that heat produces changes on the state of bodies, converting them all, first into liquids, and then into elastic fluids. I. When solid bodies are converted by heat into li- Conversion quids, the change in some cases takes place at once. " There is no interval between solidity and liquidity ; but in other eases a very gradual change may be per- ceived : the solid becomes first soft, and it passes slowly through all the degrees of softness, till at last it becomes perfectly fluid. The conversion of ice into water is an instanta- instance of the first change ; for in that substance there is no intervening state between solidity and fluidity. The melting of glass, of wax, arid of tallow, exhibits instances of the second kind of change ; for these bo- dies pass through every possible degree of softness be- fore they terminate in perfect fluidity. In general, those solid bodies which crystallize or assume regular prismatic figures, have no interval between solidity and fluidity 5 while those that do not usually assume such 518 EFFECTS OF CALORIC. rature. Table of nieifing points. Book r. shapes, have the property of appearing successively m Division II. v v ' all the intermediate states. Takes place 1. Solid bodies never begin to assume a liquid form l *^ ^J" are heated to a certain temperature : this tem- perature is constant in all. In the first class of bodies it is very well defined ; but in the second class, though it is equally constant, the exact temperature ot fluidity cannot be pointed out with such precision, on account of the infinite number of shades of softness through which the bodies pass before they acquire their greatest possible fluidity. But even in these bodies we can easily ascertain, that the same temperature always produces the same degree of fluidity. The temperatures at which this change from solidity to liquidity takes place, re- ceive different names according to the usual state of the body thus changed. When the body is usually ob- served in a liquid state, we call the temperature at which it assumes the form of a solid itefree&ing point, or con- gealing point. Thus the temperature in which water becomes ice, is called the freezing point of water ; on the other hand, when the body is usually in the state of a solid, we call the temperature at which it liquifies its melting point : thus 218 is the melting point of sulphur; 442 the melting point of tin. 2. The following Table contains a list of the melting points of a considerable number of solid bodies: Substance. Melting Point. Lead. 594 Bismuth 476 Tin ..*...,. 442 Substance. Melting Point. Sulphur .......... 21 8 Wax .. , Spermaceti .112 Bleached wax, 155. Nicholson. FLUIDITY. Substance. Melting Point. Phosphorus 100 Tallow 9J Oil of anise 50 Olive oil 36 Ice 32 Milk 30 Vinegar 28 Substance. Melting Point. Blood 25 Oil of Bergamot 23 Wines 20 Oil of turpentine. .... 14 Mercury 39 Liquid ammonia.... 46" Ether.., ,. 46 3. Though the freezing point of water be 32, yet Water may be cooled it may be cooled down in iavourable circumstances con- under the siderably below that temperature, before it begins to shoot into crystals. Experiments were made on this subject by Mairan and Fahrenheit ; but it is to Sir Charles Blagden that we are indebted for the fullest in- vestigation of it. He succeeded in cooling water down to 22 before it froze, by exposing it slowly to the ac- tion of freezing mixtures. The experiment succeeds best when the water tried is freed from air. It ought also to be transparent ; for opnque bodies floating in it cause it to shoot into crystals when only a few degree* below the freezing point. When a piece of ice is thrown into water thus cooled, it causes it instantly to shoot out into crystals. The same effect is produced by throwing the liquid into a tremulous motion ; but not by stirring it. It freezes also when cooled down too suddenly *. 4. When salts are dissolved in water, it is well known Freezing O f that its freezing point is in most cases lowered. Thus tion*. sea-water does not freeze so readily as pure water. The experiments of Sir Charles Blagden have given us the point at which a considerable number of these solutions * Biagden, Pkil, Trans* 1788, p. 125- 520 EFFECTS OF CALORIC. Book I. congeal. The result of his trials may be seen in the following Table. The first column contains the names of the salts ; the second the quantity of salt, by weight, dissolved in 100 parts of water ; and the third, the freezing point of the solution*. Names of Salts. Propor- tion. trcezing point. 25 4 20 s Rochelle salt 50 21 Sulphate of magnesia . Nitre 41*6 12*5 25'5 26 Sulphate of iron Sulphate of zinc 41-6 33-3 28 28-6 From this table it appears that common salt is by far the most efficacious in lowering the freezing point of water. A solution of 25 parts of salt in 100 of water freezes at 4. These solutions, like pure water, may be cooled down considerably below their freezing point without congealing ; and in that case the congelation is produced by means of ice just as in common water, though more slowly. When the proportion of the same salt held in solution by water is varied, it follows from Sir Charles Blag, den's experiments, that the freezing point is always proportional to the quantity of the salt. For instance, if the addition of -^th of salt to water lowers its free- zing point 10 degrees, the addition of ^ths will lower it 20. Hence, knowing from the preceding table the ef^ feet produced by a given proportion of a salt, it is easj See PW. Trans, 1788, p. 277, FLUIDITY. to calculate what the effect of any other proportion will be. The following Table exhibits the freezing points of solutions of different quantities of common salt in 100 parts of water, as ascertained by Blagden's trials, and the same points calculated on the supposition that the effect is as the proportion of salt. Chap. If, (Quantity t" salt to , CO water. Breezing point by xpcrim. Do. by calcula- tion. 3-12 8+ 28-o 4*16 27-5 27'3 6-25 25-5 25 10-00 21-5 20-75 12-80 18-5 iT6 16'1 13-5 14 20 9-5 0-8 22'2 T2 7 25 4 4 5. The strong acids, namely, sulphuric and nitric, of strong which are in reality compounds containing various proportions of water according to their strength, have been shown by Mr Cavendish, from the experiments of Mr Macnab, to vary in a remarkable manner in their point of congelation according to circumstances. The following are the most important points respecting the freezing of these bodies that have been ascertained. When these acids diluted with water are exposed to cold, the weakest part freezes, while a stronger portion remains liquid ; so that by the action of cold they are separated into two portions differing very much in strength. This has been termed by Mr Cavendish the aqueous congelation of these bodies. When they are very much diluted, the whole mix- ture, when exposed to cold, undergoes the aqueous con- 522 EFFECTS OF CALORIC. Book I. gelation : and in that case, it appears from Blagden's Division II. . experiments, that the freezing point ot water is lowered by mixing it with acid rather in a greater ratio than the increase of the acid. The following Table exhibits the freezing point of mixtures of various weights of sul- phuric acid, of the density 1'8.*7 (temperature 62), and of nitric acid of the density 1 454, with 100 parts of water. SULPHURIC ACID, i NITRIC ACID. Pro por- tion of acid. Freezing point. 'ropor tion of acid. Freezing point. 10 24'5 10 22 20 12*5 20 10*5 25 7'5 23'4 7l The concentrated acids themselves undergo congela- tion when exposed to a sufficient degree of cold ; but each of them has a particular strength at which it con- geals most readily. When either stronger or weaker, the cold must be increased. The following Table, cal- culated by Mr Cavendish from Mr Macnab's experi- ments, exhibits the freezing points of nitric acid of va- rious degrees of strength f. * P/T. Trans. 1788, p. 308. f The strength is indicated by the quantity of marble necessary to a- tyrate icoo parts of the acid. Ptil. Trans. 1788, p. 174. FLUIDITY. Strength. Freezing point. Differ- ence. 568 45-5 + 15-4 538 508 478 448 30-1 18-1 94 + 12 + 8-7 + 5-3 + 1-7 418 2'4 1-8 388 4'2 5-5 358 9'7 8 328 1T7 10 298 27'7 The following Table exhibits the freezing points of sul- phuric acid of various strengths $. Strength. Freezing point. 977 918 846 758 + i 26 + 42 45 Mr Keir had previously ascertained that sulphuric acid of the specific gravity 1*780 (at 60) freezes most easi- ly, requiring only the temperature of 46. This agrees nearly with the preceding experiments, as Mr Caven- dish informs us that sulphuric acid of that specific gra- vity is of the strength 848. From the preceding table we see, that besides this strength of easiest freezing, sulphuric acid has another point of contrary flexure at a superior strength ; beyond this, if the strength be in- creased, the cold necessary to produce congelation be- gins again to diminish. Ibid. p. 181. 524 EFFECTS OF CALORIC. Book!. 6. Before Dr Black began to deliver his chemical Division II. , ^i t^-y^.j lectures m Glasgow in 1757, it was universally sup- Dr Black's p ose d that solids were converted into liquids by a small opinion, * addition of heat after they have been once raised to the melting point, and that they returned again to the so- lid state on a very small diminution of the quantity of heat necessary to keep them at that temperature. An attentive view ef the phenomena of liquefaction and solidification gradually led this sagacious philosopher to observe their inconsistence with the then received opi- nions, and to form another, which he verified by direct experiments ; and drew up an account of his theory, and the proofs of it, which was read to a literary socie- ty in Glasgow on April 23d, 1762* ; and every year after he gave a detailed account of the whole doctrine in his lectures. Thatfluidi- The opinion which he formed was, that when a solid sLnedbyla- body ^ s converted into a liquid, a much greater quanti- tem heat, ty of heat enters into it than is perceptible immediate- ly after by the thermometer. This great quantity of heat does not make the body apparently warmer, but it must be thrown into it in order to convert it into a liquid ; and this great addition of heat is the principal and most immediate cause of the fluidity induced. On the other hand, when a liquid body assumes the form of a solid, a very great quantity of heat leaves it without sensibly diminishing its temperature ; and the state of solidity cannot be induced without the abstraction of this great quantity of heat. Or, in other words, when, ever a solid is converted into a fluid, it combines with * Black'i lerturx, Preface, p, 38. FLUIDITY. 525 a eertaitt dose of caloric without any augmentation of Chap, ir.^ its temperature ; and it is this dose of caloric which oc- casions the change of the solid into a fluid. When the fluid is converted again into a solid, the dose of caloric leaves it without any diminution of its temperature ; and it is this abstraction which occasions the change. Thus the combination of a certain dose of caloric with ice causes it to become water, and the abstraction of a certain dose of caloric from water causes it to become ice. Water, then, is a compound of ice and caloric ; and in general, all fluids are combinations of the solid to which they may be converted by cold and a certain- dose of caloric. Such is the opinion concerning the cause of fluidity, taught by Dr Black as early as 1762. Its truth was- established by the following experiments : First. If a lump of ice, at the temperature of 22, be Proved by brought into a warm room, in a very short time it is ex r enmcnt * heated to 32, the freezing point. It then begins to melt ; but the process goes on very slowly, and several hours elapse before the whole ice is melted. During the whole of that time its temperature continues at 32 ; yet as it is constantly surrounded by warm air, we have reason to believe that caloric is constantly entering into it. Now as none of this caloric is indicated by the thermometer, what becomes of it, unless it has combi- ned with that portion of the ice which is converted into, water, and unless it is the cause of the melting of the ice? Dr Black took two thin globular glasses four inches in diameter, and very nearly of the same weight. Both were filled with water ; the contents of the one were frozen into a solid mass of ice, the contents of the other 526 EFFECTS OF CALORIC. Book I. were cooled down to 33 ; the two glasses were then Division II. 1 suspended in a large room at a distance from all other bodies, the temperature of the air being 41. In half an hour the thermometer placed in the water glass rose from 33 to 40, or seven degrees : the ice was at first four or five degrees colder than melting snow; but in a few minutes the thermometer applied to it stood at 32. The instant of time when it reached that temperature was noted, and the whole left undisturbed for ten hours and a half. At the end of that time the whole ice was melted, except a very small spongy mass, which floated at the top and disappeared in a few minutes. The tem- perature of the ice- water was 40. Thus 10! hours were necessary to melt the ice and raise the product to the temperature of 40. During all this time it must have been receiving heat with the same celerity as the water glass received it during the first half-hour. The whole quantity received then was 21 times 7, or 147 ; but its temperature was only 40: therefore 139 or 140 degrees had been absorbed by the melting .ice, and remained concealed in the water into which it had been converted, its presence not being in- dicated by the thermometer *. That heat is actually entering into the ice, is easily as- certained by placing the hand or a thermometer under the vessel containing it. A current of cold air may be perceived descending from it during the whole time of the process. But it will be said, perhaps, that the heat which en- * Black's Lectures, i. iao, FLUIDITY. 521 the ice does not remain there, but is altogether destroyed. This opinion is refuted by the following experiment. Second. If, when the thermometer is at 22, we ex- pose a vessel full of water at 52 to the open air, and beside it another vessel full of brine at the same tem- perature, with thermometers in each ; we shall find that both of them gradually lose caloric, and are cooled down to 32. After this the brine (which does not freeze till cooled down to 0) continues to cool without interruption, and gradually reaches 22, the tempera- ture of the air ; but the pure water remains stationary at 32. It freezes indeed, but very slowly ; and du- ring the whole process its temperature is 32. Now, why should the one liquid refuse all of a sudden to give out caloric, and not the other? Is it not much more probable that the water, as it freezes, gradually gives out the heat which it had absorbed during its liquefac- tion ; and that this evolution maintains the temperature of the water at 32, notwithstanding what it parts with to the air during the whole process ? We may easily satisfy ourselves that the water while congealing is con- stantly imparting heat to the surrounding air ; for a delicate thermometer suspended above it is constantly affected by an ascending stream of air less cold than the air around *. The following experiment, first made by Fahrenheit, and afterwards often repeated by Dr Black and others, affords a palpable evidence, that such an evolution of caloric actually takes place during con- gektion. # Black's Lectures, i. EFFECTS OF CALORIC. BookT. Third. If when the air is at 22, we expose to it a quantity of water in a tall beer glass, with a thermo- meter in it and covered, the water gradually cools down to 22 without freezing. It is therefore 10 below the freezing point. Things being in this situation, if the water be shaken, part of it instantly freezes into a spongy mass, and the temperature of the whole instant- ly rises to the freezing point ; so that the water has ac- quired ten degrees of caloric in an instant. Now, whence same these ten degrees ? Is it not evident that it must have come from that part of the water which was fro- zen, and consequently that water in the act of freezing' gives out caloric ? From a good many experiments which I have made on water in these circumstances, I have found reason to conclude,, that the quantity of ice which forms suddenly on the agitation of water, cooled down below the free- zing point, bears always a constant ratio to the coldness of the liquid before agitation. Thus I find that when \vater is cooled down to 22, very nearly -^ of the whole freezes *; when the previous temperature is> 27, about ~-j of the whole freezes. I have not been able to make satisfactory experiments in temperatures lower than 22 ; but from analogy I conclude, that for every five degrees of diminution of temperature below thefree- zing point, without congelation, T f T of the liquid freezes suddenly on agitation. Therefore, if water could be cooled down 28 times five degrees below 32 without congelation, the whole would congeal instantaneously on agitation, and the temperature of the ice would be 32% # A medium of several experiment* FLUIDITY. 519 ISfow it deserves attention, that 5X28 = 140, gives us precisely the quantity of heat which, according to Dr Black's experiments, enters into ice in order to convert it into water. Hence it follows, that in all cases when water is cooled down below 32, it loses a portion o the caloric which is necessary to constitute its liquidity. The instant that such water is agitated, one portion of the liquid seizes upon the quantity of caloric in which it is deficient at the expence of another portion, which of course becomes ice. Thus when water is cooled down to 22, every particle of it wants 10* of the ca- loric necessary to keep it in a state of* liquidity . Thir- teen parts of it seize ten degrees each from the four- teenth part. These thirteen of course acquire the tem- perature of 32 ; and the other part being deprived o 10 X 13 =r 130, which with the ten degrees that it had lost before constitute 140, or the whole of the caloric necessary to keep it fluid, assumes of consequence the frm of ice. Fourth. If these experiments should not be consi- dered as sufficient to warrant l)r Black's conclusion, the following, for which we are indebted to the same philosopher, puts the truth of his opinion beyond the reach of dispute* He mixed together given weights of ice at 32 and water at 190 of temperature. The ice was melted in a few seconds, and the temperature pro- duced was 53. The weight of the ice was 119 half* drams ; That of the hot water, 135 of the mixture, .......... 264 of the glass vessel, ....... 16 Sixteen parts of glass have the same effect in heating cold bodies as eight parts of equally hot water. There-* Vol* I. 1 1 530 EFFECTS OF CALORIC. * re > i nstea d of the 16 half- drams of glass, eight of wa* ter may be substituted, which makes the hot water a- mount to 143 half- drams. In this experiment there were 158 degrees of heat contained in the hot water to be divided between the ice and water. Had they been divided equally, and had the whole been afterwards sensible to the thermo- meter, the water would have retained 4-|4 parts of this heat, and the ice would have received 4-s-r parts. That is to say, the water would have retained 86, and the ice would have received 72 : and the temperature af- ter mixture would have been 104. But the tempera- ture by experiment is found to be only 53 ; the hot water lost 137, and the ice only received an addition of temperature equal to 21. But the loss of 18 of temperature in the water is equivalent to the gain of 21 in the ice. Therefore 15S 18 = 140 Q of heat have disappeared altogether from the hot water. These 140 must have entered into the ice, and converted it into water without raising its temperature *. In the same manner, if we take any quantity of ice, or (which is the same thing) snow at 32, and mix it with an equal weight of water at 172, the snow in- stantly melts, and the temperature of the mixture is only 32. Here the water is cooled 140, while the tempe- rature of the snoxv is not increased at all ; so that 140 Q of caloric have disappeared. They must have com- bined with the snow; but they have only melted it without increasing its temperature. Hence it follows * Black's Ltcture^l 123, FLUIDITY. 431 irresistibly, that ice, when it is converted into water, t Chap. absorbs and combines with caloric. It is rather difficult to ascertain the precise number of degrees of heat that disappear during the melting of ice. Hence different statements have been given. Mr Cavendish, who informs us that he discovered the fact before he was aware that it was taught by Dr Black, states them at 150 ; Wilkeat 130* ^ Black at 140; and Lavoisier and Laplace, at 135. The mean of the whole is very nearly 140. Water, then, after being cooled down to 32, cannot Latent heat freeze till it has parted with 140 of caloric : and ice, after being heated to 3^, cannot melt till it has ab- sorbed 140 of caloric. This is the cause of the ex- treme slowness of these operations. With regard to water, then, there can be no doubt that it owes its flu- idity to the caloric which it contains, and that the calo- ric necessary to give fluidity to ice is equal to 140. To the quantity of caloric which thus occasions the fluidity of solid bodies by combining with them, Dr Black gave the name of latent heat , because its presence is not indicated by the thermometer : a term sufficient- ly expressive, but other philosophers have rather cho- sen to call it caloric of fluidity. Dr Black and his friends ascertained also, by expe- riment, that the fluidity of melted wax, tallow, sperma- ceti, metals, is owing to the same cause.' Landriani proved that this is the case with sulphur, alum, nitre, and several of the metals f ; and it has been found to be the case with everj substance hitherto examined. * PHI. Tram. 1783, p- 313- t ^"^ ^ *h' 9 xxv - L 12 532 EFFECTS OF CALORIC, cons * dei? * fc therefore as a general lato, that' whenever a solid is converted into a fluid, it combines- with caloric, and that this is the cause of its fluidity. ** ^ e on ^7 experiments to determine the latent Latent heat ofothcrbo- of other bodies besides water, that have been hitherto published, are those of Dr Irvine f and his son Mr Wil- liam Irvine J. The following Table exhibits the results of their trials, Softness and ductility owing to the same cause. Bodies. } Latent heat. Do. reduced to the specific icat of water 143'68 2T14 Spermaceti..... Lead 145 162 V6 Bees wax Zinc 115 493 48*3 Tin '500 33 550 23'25 The latent heat of spermaceti, wax, and tin, were deter- mined by Dr Irvine, that of the rest by his son. Tho latent heatinthe second column expresses the degrees by which it would have increased the temperature of each of the bodies respectively when solid, except in the case of spermaceti and wax ; in them it expresses the in- crease of temperature which would have been produced upon them while fluid. 8. Dr Black has rendered it exceedingly probable al- so, or rather he has proved by his experiments and ob- servations, that the softness of such bodies as are ren- dered plastic by heat, depends upon a quantity of la-. f Black , i. 187. | Nicholson's Jwr- i* 4*v FLUIDITY. 53S tent heat which combines with them. Metals also owe their malleability and ductility to the same cause. Hence the reason that they become hot and brittle when iiammered. 51. Thus it appears,, that the conversion of solids in- to liquids is occasioned by the combination of a dose of caloric with the solid. But there is another change of state still more remarkable, to which bodies are liable when exposed to the action of heat. Almost all liquids, when raised to a certain temperature, gradually assume the form of an elastic fluid, invisible like air, and pos- sessed of the same mechanical properties. Thus water, by boiling, is converted into steam, an invisible fluid, 1800 times more bulky than water, and as elastic as air. These fluids retain their elastic form as long as their temperature remains sufficiently high ; but when cooled down again, they lose that form, and are con- verted into liquids. All liquids, and even a consider- able number of solids, are capable of undergoing this change when sufficiently heated. 2. With respect to the temperatures at which liquids Some bo- undergo this change, they may "be all arranged under two ^** ^ c ^ t me divisions. There are some liquids which are gradual- U tempera* ly converted into elastic fluids at every temperature ; not!** -while others again never begin to assume that change till their temperature reaches a certain point. Water is a well known example of the first cla*ss of bodies. If an open vessel, filled with water, be carefully examined, we find that the water diminishes in bulk day after day, and at last disappears altogether. If the experiment be made in a vessel sufficiently large, and previously exhausted of air, we shall find, that the water will fill the vessel in the state of invisible vapour, in whatever 534 EFFECTS OF CALORIC. Book I. temperature it be placed : alcohol likewise, and ethet ~t__y _/ and volatile oils, gradually assume the form of an elas- tic fluid in all temperatures. But sulphuric acid and the fixed oils never begin to assume the form of vapour till they are raised to a certain temperature. Though left in open vessels they lose no perceptible weight; neither does sulphuric acid lose any weight though kept ever so long in the temperature of boiling water* When liquids gradually assume the form of elastic fluids in all temperatures, they are said to evaporate spontaneously, The second class of liquids want that property altogether. Boiling ex- % When all other circumstances are the same, the plained. evaporation of liquids increases with their temperature ; and after they are heated to a certain temperature, they assume the form of elastic fluids w 7 ith great rapidity. If the heat be applied to the bottom of the vessel con- taining the liquids, as is usually the case, after the whole liquid has acquired this temperature, those par- ticles of it which are next the bottom become an elastic fluid first : they rise up, as they are formed, through tK" liquid, like air- bubbles, and throw the whole. into violent agitation. The liquid is then said to boil. - - Every particular liquid has a fixed point at which this boiling commences (other things being the same) j arid, this is called the boiling point of the liquid. f Thus water begins to boil when heated to 212. It is remarkable, that after a liquid Iras begun to boil, it ne- ver becomes any hotter, however strong the fire be to which ii is exposed. A strong heat indeed makes it boii oiore rapidly, but does not increase its temperature. r Tins was first observed by Dr Hooke e '. FLUIDITT. 535 The following Table contains the boiling point of , cha P- I! a number of liquids. Boiling point*, Bodies. Boiling Point. I Ether 98 Ammonia 140* Alcohol 174 Water 212 Nitric acid 248 Carbonate of potash 260f Bodies. Boiling Point* Muriate of lime ... 264 Sulphuric acid ...... 59Q* rhosphoru. ; ; 54 Sulphur 57O Linseed oil 600 jMercurj 660 5, It was observed, when treating of the melting Vary with the prcfr 1 point of solids, that it is capable of being varied consi- sure, derably by altering the situation of the body. Thus water may be cooled down considerably lower than 32 without freezing. The boiling point is still less fixed, depending entirely on the degree of pressure to which the liquid to be boiled is. exposed. If we dimi- nish the pressure, the liquid boils at a lower tempera- ture ; if we increase it, a higher temperature is neces- sary to produce ebulition. From the experiments of Professor Robison, it appears that, in a vacuum, all liquids boil about 145 lower than in the open air, under a pressure of 30 inches of mercury ; therefore water would boil in vacuo at 67 and alcohol at 34. In a Papin's digester, the temperature of water may be raised to 300, or even 400, without ebulition : But the instant that this great pressure is removed, the boiling commences with prodigious violence. * Dalton. | When so much concentrated as to become nearly solid, a8o*. \ By my trials. EFFECTS OF CALORIC. Book I. <$. The elasticity of all the elastic fluid* into which Division II. .... . . liquids are converted by heat, increases with the temperature ; and the vapour formed, when the li- create* with quid boils in the open air, possesses an elasticity just raturw. equal to that of air, or capable at a medium of balancing column of mercury 30 inches high. The following very important TABLE, drawn up by Mr Dalton* from his own experiments, exhibits the elasticity of steam or the vapour of water of every temperature, from 40 to 325. The elasticities of all the temperatures from 32 to 212 9 were ascertained by experiment; the rest were calculated by observing the rate at which the elas- ticity increased or diminished according to the tempo- rat ure. FLUIDITY, 531 t K~ I V 4 ill ill! 013 -40 -30 020 -20 030 -10 043 064 1 066 2 068 3 071 4 074 5 016 6 079 7 082 8 085 9 087 10 090 11 093 12 096 13 100 14 104 15 108 16 112 17 116 18 1^0 19 124 20 129 21 134 22 139 24 144 24 150 25 156 26 162 27 168 28 174 29 180 30 186 Chap. IL Table of the elasticity of steam. 533 EFFECTS OF CALORIC. Book I. Division IT. TABLE continued. u * cL *. Cu cL, Tu 3 rt J>*8 . 1 C tM 3 ^li 1 l_ "is. U ^ .C 3* 4> * JC 3 1 * JC 3 | 'o 2 K *** 3 >> * 1 1 1*1 6 -S.SS3 I] H *1"S 2 ^.S w C S, 1 111 312 1 ' ~ 269; 76-82 |[284 C 93-23 298 109*48 125-85 270 77-85 285 94-35 299 110-64 313 127-00 271 78-89 286 Q5-48 300 111-81 314 128-15 272 273 274 79-94 287 80-C8 1288 82-01 ;2S9 96-64 9T80 98-96 301 302 303 112*98 114-15 115-32 315 316 317 129-29 130-43 131-57 275 83-13 J290 100-12 304 116-50 318 132-72 276 277 84-35 L291 85-47 .92 101-28 102-45 305 30d 117-68 118-86 319 320 133-86 135-00 278 86-50 [293 103-63 307 120-03 321 136-14 279 280 87-63 T294 88-75 1*95 104*80 105*97 308 309 121-20 122-37 322 323 137-28 138-42 281 89 87 296 10T14 310 123-53 324 139-56 282 90-99 ;297 108-31 311 124-69 325 140-70 283 92-11 | 7, Mr Dalton has shown, that if we consider the ex- Elasticity of pansion of mercury as according to the square of the c temperature, then the force of vapour increases in a geometrical progression, by equal increments of tern- perature, reckoning these increments upon his new thermometric scale. The ratio of the progression he finds to be 1-321. In like manner the force of the va- pour of ether increases in a geometrical progression, the ratio of which is 1*2278. But the increase of the force of the vapour of alcohol, of the specific gravity 0'87, he finds to be irregular. He has drawn as a conclusion from his experiments, that the vapour of all pure liquids increases in force in a geometrical progression to th^ 640 EFFECTS OF CALORIC. Book I. temperature, but the ratio is different in different fluids, Division il. r The vapour of alcohol differs from this law, because it -is in reality a mixture of two distinct vapours, narne?- ly, that of water, and that of alcohol. The following Table exhibits the force of vapour of ether and alcohol, for every ten degrees of Mr Dalton's new thermometer from the freezing to the boiling point of water, as as- certained by that gentleman's experiments *. 1 O O ti_, c. a 13 1 1 fi 8 'J 111 1 2w s sS's-S 1^ 32 | 6-1 0'80 132 46-54 8-2 42 T57 0-93 142 57*03 10-2 52 9-16 1-08 152 69-88 13-9 62 11-22 1-3 162 85'62 17*9 72 13-77 1-6 172 104*91 22-4 82 16-85 2*1 182 128^5 29*3 92 20-65 2-8 192 157-5 102 25-30 3-6 202 193- M2 31* - 4-7 212 236-5 122 37*98 6-3 Vapotirsare 7. Such are th phenomena of the conversion of li- qu^s into elastic fluids. Dr Black applied hi$ theory j a t en t heat to this conversion with great sagacity, and demonstrated that it is owing to the very same, clonc. * Dalton's New System of cbtmical philosophy, p. 14. f The corresponding degrees of the tommon thermometer will be found in page 501 of this rolume. The degrees in the table were pre- served to show the geometrical progression in the force of the vapour of ether. FLUIBITT. <&use as the conversion of solids into liquids ; namely, Chap. H. to the combination of ascertain dose of caloric with the liquid without any increase of temperature. The truth of this very important point was established by the fol- lowing experiments. First. When a vessel of water is put upon the fire r tke water gradually becomes hotter till it reaches 212 afterwards its temperature is not increased. Now ca- loric must b^ constantly entering from the fire and com- bining with the water.- But as the water does not be- come hotter, the caloric must combine with that part of it which flies off in the form of steam : but the tempe- rature of the steam is only 212 : therefore the caloric combined with it does not increase its temperature. We must conclude, then, that the change of water to steam is owing to the combination of this caloric j for it produces no other change.. Dr Black put some water in a tin-plate vessel upon a red hot iron. The water was of the temperature 50 r in four minutes it began to boil, and in 20 minutes it was all boiled off. During the first four minutes it had recei- ved 162, or 40i per mmute. If we suppose that it received as much per minute during the whole process of boiling, the caloric which entered into the water and converted it into steam would amount to 40f X 20 810 *. This caloric is not indicated by the thermome- ter, for the temperature of steam is only 212 y there- fore Dr Black called it latent beat. Second. Water may be heated in a Papin's digester to 400* without boiling ; because the steam is forcibly Black i Licturstfl. 157. 542 EFFECTS OF CALORIC. Book I. compressed, and prevented from making its escape. It * -v ' the mouth of the vessel be suddenly opened while things are in this state, part of the water rushes out in the form of steam, but the greater part still remains in the form of water, and its temperature instantly sinks to 212 ; consequently 188 Q of caloric have suddenly disappeared. This caloric must have been carried oft' by the steam. Now as only about f th of the water is converted into steam, that steam must contain not only its own 188, but also the 188 lost by each of the other four parts ; that is to say, it must contain 188 Q X 5, or about 940. Steam, therefore, is water combined with at least 940 of caloric, the presence of which is not indicated by the thermometer. This experiment was first made by Dr Black, and afterwards, with more precision, by Mr Watt. Third. When hot liquids are put under the receiver of an air pump, and the air is suddenly drawn off, the liquids boil, and their temperature sinks with great ra- pidity a considerable number of degrees. Thus water, however hot at first, is very soon reduced to the tem- perature of 70 ; and ether becomes suddenly so cold that it freezes water placed round the vessel which con- tains it. In these cases the vapour undoubtedly carries off the heat of the liquid ; but the temperature of the vapour is never greater than that of the liquid itself: the heat therefore must combine with the vapour, and become latent. Fourth. If one part of steam at 212 be mixed with nine parts by weight of water at 62, the steam instant- ly assumes the form of water, and the temperature af- ter mixture is 17S'6 ; consequently each of the nine parts of water has 'received 116'6 Q of caloric; conse* quently the steam has lost 9 X 116*6 = 1049'4 9 of FLUIDITY. 545 caloric. But as the temperature of the steam is dimi- . a ^' '* nished by 33*3, we must subtract this sum. There will remain rather more than 1000, which is the quan- tity of caloric which existed in the steam without in- creasing its temperature. This experiment cannot be made directly ; but it may be made by passing a given weight of steam through a metallic worm, surrounded by a given weight of water. The heat acquired by the water indicates the caloric which the steam gives out during its condensation. From the experiments of Mr Watt made in this manner, it appears that the la- tent heat of steam amounts to 940. The experiments of Mr Lavoisier make it rather more than 1000. By the experiments of Dr Black and his friends, it was ascertained, that not only water, but all other liquids during their conversion into vapour, combine with a dose of caloric, without any change of temperature; and that every kind of elastic fluid, during its conversion into a liquid, gives out a portion of caloric without any change of temperature. Dr Black's law, then, is very general, and comprehends every change in the state of a body. The cause of the conversion of a solid into a liquid is the combination of the solid with caloric; that of the conversion of a liquid into an elastic fluid is the combination of the liquid with caloric. Liquids are solids combined with caloric ; elastic fluids are liquids combined with caloric. This law, in its most general Generallaw form, may be stated as follows : Whenever a body byDrBlack, changes its state, it either combines with caloric or sepa- rates from caloric. No person will dispute that this is one of the most important discoveries hitherto made in chemistry. Sci- ence seems indebted for it entirely to the sagacity of Dr 544 EFFECTS OF CALORIC. Gases. Book I. Black. Other philosophers indeed have laid claim id revision IT. . . . . _ _ it ; but these claims are either without any foundation, or their notions may be traced to Dr Black's lectures, or their opinions originated many years posterior to the public explanation of Dr Black's theory in the chemical chairs of Glasgow and Edinburgh. III. A very considerable number of bodies, both so- lids and liquids, may be converted into elastic fluids by h.eat ; and as long as the temperature continues suffi- ciently high, they retain all the mechanical properties of gaseous bodies. It is exceedingly probable, that if we could command a heat sufficiently intense, the same change might be produced on all bodies in nature. This accordingly is the opinion at present admitted by philosophers. But if all bodies are convertible into elastic fluids by heat, it is exceedingly probable, that all elastic fluids in their turn might be converted into solids or liquids, if we could expose them to a low enough temperature. In that case, all the gases must be sup- posed to owe their elasticity to a certain dose of calo- ric : they must be considered as compounds of caloric with a solid or liquid body. This opinion was first stated by Amontons ; and it was supported, with much ingenuity, both by Dr Black and by Lavoisier and his associates. It is at present the prevailing opinion 9 and it is certainly supported not only by analogy, but by several very striking facts. 1. If its truth be admitted, we must consider all the gases as capable of losing their elasticity by depriving them of their heat : they differ merely from the vapours in the great cold which is necessary to produce this change. Now the fact is, that several of the gases may be condensed into liquids by lowering their tempe* Supposed to be liquids c om bined with aaio- fk. Condensed by cold. i'LUIBITT. 545 ratures. Oxy-muriatic acid gas becomes liquid at a t Chap. IL^ temperature not much under 40 ; and at 32 it even forms solid crystals. Ammoniacal gas condenses into a liquid at 45. None of the other gases have been hitherto condensed. 2. It is well known that the condensation of vapours Andpre* sure. is greatly assisted by pressure ; but the effect of pres- sure diminishes as the temperature of vapours increases. It is very likely that pressure would also contribute to assist the condensation of gases. It has been tried without effect indeed in several of them. Thus air has been condensed till it was heavier than water ; yet it showed no disposition to lose its elasticity. But this may be ascribed to the high temperature at which the experiment was made relative to the point at which air would lose its elasticity. 3. At the same time it cannot be denied, that there Jjtl to the opi* are several phenomena scarcely reconcileable to this con- nion. sritution of the gases, ingenious and plausible as it is. One of the most striking is the sudden solidification which ensues when certain gases are mixed together. Thus when r.mmoniacal gas and muriatic acid gas are mixed, the product is a solid salt : yet the heat evolred is very inconsiderable, if we compare it with the dif- ficulty of condensing these gases separately^ and the great cold which they endure before losing their elasti- city. In other cases, too, gaseous bodies unite, and form a new gas, which retains its elasticity as power- fully as ever. Thus oxygen gas and nitrous gas com- bined form a new gas, namely, nitric acid, xvhich is per- manent till it comes into contact with some body on which it can act. Pol. L M rn 546 EFFECTS OF CALORIC. Division 'ii. UI CHANGES IN COMPOSITION. Caloric de- CALORIC not only increases the bulk of bodies, and composes bodies. changes their state from, solids to liquids and from li- quids to elastic fluids ; but its action decomposes a great number of bodies altogether, either into their elements, or it causes these elements to combine in a different manner. Thus when ammonia is heated to redness, it is resolved into azotic and hydrogen gases* Alcohol, by the same heat, is converted into carbureted hydro- gen and water. I* This decomposition is in many cases owing to the difference between the volatility of the ingredients of a compound* Thus when weak spirits, or a combination of alcohol and water, are heated, the alcohol separates, because it is more volatile than the water. 2. In general, the compounds which are but little or not at all affected by heat, are those bodies which have been formed by combustion. Thus water is not decom- posed by any heat which can be applied to it ; neither are phosphoric or carbonic acids* 3. Almost all the combinations into which oxygen enters without having occasioned combustion, are de- composable by heat. Thjs is the case with nitric acid, hyperoxymuriatic acid, and many of the metallic ox- ides. 4. All bodies that contain combustibles as compo- nent parts are decomposed by heat. Perhaps the me- tallic alloys are exceptions to this rule ; at least it is not in our power to apply a temperature high enough to produce their decomposition, except in a few cases. 5. When two combustible ingredients and likewise oxygen occur together in bodies, they are always very BECOMFOSITON. easily decomposed by heat. This is the case with the greater number of animal and vegetable substances. But it is unnecessary to enlarge any farther on this subject, as no satisfactory theory can be given. The de- compositions will all be noticed in describing the differ- ent compounds which are to occupy our attention in the subsequent part of this Work. SECT. V. OF THE QJJANTITY OF CALORIC IN BODIES. HAVING, in the second Section of this Chapter, shown that caloric is capable of moving through all bodies 3 and in the third, that it gradually diffuses itself through all contiguous bodies in such a manner that they as- sume the same temperature the next point of discussion which presented itself was the quantity of caloric in bo- dies. When different bodies have the same tempera- ture, do they contain the same quantity of caloric? Is the same quantity necessary to produce the same change of temperature in all bodies ? What is the point at which a thermometer would stand if it were plunged into a body deprived of heat altogether ? or what is the com- mencement of the scale of temperature ? But these questions could not be examined with any chance of success while we were ignorant of the effects which ca- loric produces on bodies ; because it is by these effects alone that the quantity of caloric in bodies is measured. This rendered it necessary for us to employ the fourth M m 2 543 QJJANTITY OF CALORIC, Book I. Section in the examination of these effects. Let us now Division II. ' apply the knowledge which we have acquired to the in- vestigation of the quantity of calorie in bodies. This investigation naturally divides itself into three parts : 1. The relative quantities of caloric in bodies, or the quantities in each necessary to produce a given change of temperature. This is usually termed specific caloric, 2. The absolute quantity of caloric which exists in bo- dies. 3. The phenomena of cold, or the absence of ca- loric. These three topics shall be examined in orden Specific ca- loric ex- plained* I, Or THE SPECIFIC CALORIC OF BODIES. IF equal weights of water and spermaceti oil, at differ- ent temperatures, be mixed together and agitated, it is natural to expect that the mixture would acquire the mean temperature. Suppose, for instance, that the temperature of the water were 100, and that of the oil 50, it is reasonable to suppose that the water would be cooled 25 and the oil heated 25, and that the tem- perature after the mixture would be 75. But when the experiment is tried., the result is very far from an- swering this apparently reasonable expectation: for the temperature after mixture 13 83y ^ consequently the water has only lost 16^-> while the oil has gained 33}. On the other hand, if we mix together equal weights of water at 50, and oil at 100, the temperature, after agi- tation, will be only 66|, so that the oil has given out 33-', and the water has received only 1(3~. This ex- periment demonstrates, that the r;ame quantity of caloric is not required to raise spermaceti oil a given number of degrees which is necessary to raise water the same number. The quantity of caloric which raises the oil SPECIFIC. 54$ -I2y, raises water only 6^; consequently the caloric t cha P- 1L t which raises the temperature of water 1 will raise that of the same weight of spermaceti 2 r '. If other substances be tried in the same manner, it will be found that they all differ from each other in the quantity of caloric which is necessary to heat each of them to a given temperature ; some requiring more than the same weight of water would do, others less ; but every one requires a quantity peculiar to itself. Now the quantity of caloric which a body requires, in order to be heated to a certain temperature, (one degree for instance), is called the specific caloric of that body. We do not indeed knew the absolute quantity of calo- ric which is required to produce a certain degree of heat in any body ; but if the unknown quantity neces- sary to heat water (l for instance) be made ], we can determine, by experiment, how much more, or how much less caloric other bodies require to be heated the same number of degrees. Thus if we find by trial that the quantity of caloric which heats water 1, heats the same weight of spermaceti oil 2, it follows, that the specific caloric of water is two times greater than that of the oil ; therefore if the specific caloric of water = 1, that of spermaceti oil must be 0*5. In this man- ner may the specific caloric of all bodies be found. That the specific caloric of bodies is different, was History, first pointed out by Dr Black in his lectures at Glasgow between 1760 and 1765*. Dr Irvine afterwards in- vestigated the subject between 1765 and 1770 f ; and Dr Crawford published a great number of experiments * Black's Lectures, i. 504. 550 QUANTITY OF CALORIC. Book. r. on i t i n hJ s Treatise on Heat. These three philosophers Division H. w v denoted this property by the phrase capacity of bodies for leaf. But Professor Wilcke of Stockholm, who published the first set of experiments on the subject, introduced the term specific caloric ,- which has been generally adopted, because the phrase capacity for calo- ric is liable to ambiguity, and has introduced confusion into this subject *. The experiments of Mr Wilcke were first published in the Stockholm Transactions for 1772, but had been read to the Swedish Academy as early as 1771. The manner in which they were conducted is exceedingly ingenious, and they furnish us with the specific caloric of many of the metals. The metal on which the experi- ment was to be made was first weighed accurately (ge- nerally one pound was taken), and then being suspend- ed by a thread, was plunged into a large vessel of tin- plate, filled with boiling water, and kept there till it ac- quired a certain temperature, which was ascertained by a thermometer. Into another small box of tinplate ex- actly as much water at 32 was put as equalled the weight of the metal. Into this vessel the metal was plunged, and suspended in it so as not to touch its sides or bottom ; and the degree of heat, the moment the metal and water were reduced to the same tempera- ture, was marked by a very accurate thermometer. From the change of temperature, he deduced, by a very in- genious calculation, the specific caloric of the metal ? that of water being considered as unity f. * The term ipectfe caloric has been employed in a different sense by Se- uin. He ysed it for the whole calorie which a body contain?, f The following is the process of reasoning by which he was led to SPECIFIC. 551 Next, in point of time, and not inferior in ingenious t Chap. IT. contrivances to ensure accuracy, were the experiments of Dr Crawford, made by mixing together bodies of his conclusions. He first calculated what the temperature would have been if a quantity of water, equal in weight to the metal, and of the same temperature with it, had been added to the ice-cold water instead of the metal. Let M be a quantity of water at the temperature C, m another quan- tity at the temperature c, and let their common temperature after mixture be x ; according to a rule demonstrated long ago by Richman, K = M , . In the present case the quantities of water are equal, there- fore M and m are each = i ; C, the temperature of the ice-cold water, = 32 ; therefore T*~= 3 *f Now c is the temperature of the metal. Therefore if 31 be added to the temperature of the metal, and the whole be divided by a, the quotient will express the temperature of the mixture, if an equal weight of water with the metal, and of the same temperature with it, had been added to the ice-cold water instead of the metal. He then calculated what the temperature of the mixture would have been, if, instead of the metal, a quantity of water of the same tempera- ture with it, and equal to the metal m bulk, had been added to the ice-cold water. As the weights of the ice-cold water arid the metal are equal, their volumes are inversely as their specific gravities. Therefore the v- lume of ice-cold water is to a quantity of hot water equal in volume to the metal, as the specific gravity of the metal to that of the water. Let M = volume of cold water, m = volwmeof hot water, = specific gravity of the metal, I = specific gravity of water ; then m : M : : I : g ; hence = =(M being made =i)-. Substituting this value of m in the formula, A/r ^ = x, in which M = I and C = 31, will be = . ^ . Therefore if the specific gravity of the metal be multiplied by r-H 32, and the temperature of the metal be added, and the sum be divided by the specific gravity of the metal -J- i, the quotient will express the tem- perature to which the ice-cold water would be raised by adding to it a 552 QUANTITY OF CALORIC. Boolc T - different temperatures. These were published in his Divis.on H \ ^ i Treatise on heat. In the first edition many errors had crept into his deductions, from his not attending to the chemical changes produced by mixing many of the sub- jects of his experiments. These were corrected by his volume of water t ;ua to that ot' chc metal, and of the same temperature with it. He then calculated how much water at the temperature of the metal it xvould take to raise the ice-cold water the same number of degrees which the metal had raised it. Let the temperature to which the metal had raised the ice-cold water be N, if in the formula rr~r- =* K M -\-m be made = N, M = i, C -?a, m will he = ^-.Therefore c N if from the temperature to which the ice-cold water was raised by the metal 31 be subtracted, and if from the temperature of the metal be sub- tracted the temperature to which it raised the water, and the first re- mainder be divided by the last, the quotient will express thf quantity of water of the temperature of the metal which would have raised the ice- cold wattr the same number of degrees that the metal did. JsJ , a Now -jj expresses the specific caloric of the metal, that of water being = I . For (neglecting the small difference occasioned by the differ- rence of temperature) the weight and volume of the ice-cold water are to the weight and volume of the hot water as i to , and the num. c - W her of particles of water in each are in the same proportion. But the metal is equal in weight to the ice-cold water ; it mu;erimen$i id the calculations founded on them, as above described. GOLD. Specific gravity 19-040. 1 i 1 * a 'H 1 -5-J5-S 2 1 r 1 1 *Js ^S| = IbL C "o S-| S-S'S-B* 8-J v 3 ? II hi s Ji ' tu > P t- rt 2 3 J5 % W tr ^ *^ ; u rt ^ II o >3 2 l_ ^ c^ u ^3 rt r3 * - .5 & I p- l-s i> *^ i3 ^ ?-5^.f ^ ^~ J 1 * I 3 c 3 U * O <-* t-4 5 * *O l-< ^ 3 "^ "t3 ""^ C^ u fc H 3 H-S S H .ti S - Js h.s K^-5 Q -5 -5 I 163-4 38-3 97.70 3^555 y ^9-857 '44-5 37-4 88-25 37-58 19-833 3 117-4 36-5 79'7 36-68 *0- S Or 4 118-4 36-05 75^ 36-15 ao-353 5 103-1 35-6 65-75 35*4* 18-750 6 95 34-45 63-5 35-o6 19-000 Mean 1071* QUANTITY OF CALORIC. T. considered as inversely proportional to its specific cs Division If. 1 . lone *. LEAD. Specific gravity 11-456^ < i S * J3 c ? g A ^ c I*** *'S |-P: l^^si g a.MJ o s.?e.s: g 515 3 fl -5JSg.fi ^ U 1 1 I 1 86-8 32-3 109-4 44-425 23-571 2 181-40 37-85 106-7 43'473 24-538 3 163-2 37-4 98-6 42-672 23-666 4 163-4 37-4 977 42-548 23-333 5 136-4 36-5 84-2 40-344 22'2OO 6 131 36-05 8i-5 39*947 24-700 7 126-5 36-05 79-25 39-585 22-333 8 107-6 35-15 69-8 38-339 23-COO 9 94-1 34-7 63-05 36-985 22-OOO Mean 23^5 1 5 It i needless to add, that the last column marks the denominator of the 1 specific paloric of the metal ; the numerator being always I, and the speci- fic caloric of water being I. Thus the specific caloric of gold is - In exactly the same manner, and by taking a mean of a number of ex- periments at different temperatures, did Mr W ilcke ascertain the specific caloric of a number of other bodies. * The specific caloric of water being considered as i, the formula was a? follows : Let the quantity of water (which usually constituted one of the substances mixed) be W, and its temperature iv> Let the quantity of the other body, whose specific caloric is to be ascertained, be B, and its temperature b. Let the temperature after mixture be m. The sped- - SPECIFIC. 555 To the labours of this ingenious and correct experU t cha P- " menter we are indebted for some of the most remark- able facts respecting specific caloric that are yet known*. Several experiments on the specific caloric of bodies were made also by Lavoisier and Laplace, which from the well-known accuracy of these philosophers cannot but be very valuable. Their method was exceedingly simple and ingenious; it was first suggested by Mr Laplace. An instrument was contrived, to which Lavoisier gave the name of ca- lorimeter. It consists of three circular vessels nearly in- scribed into each other, so as to form three different a- partments, one within the other. These three we shall call the interior, middle, and external cavities. The in- terior cavity ffff (see section of the instrument fig. 11.) into which the substances submitted to experiment are put, is composed of a grating or cage of iron wire, sup. ported by several iron bars. Its opening or mouth LM is covered by the lid HG, which is composed of the same materials. The middle cavity 1 3 b I is filled with ice. This ice is supported by the grate mm, and under the grate is placed a sieve. The external cavity aaaa is also filled with ice. We have remarked already, that fie caloric ofB is - ^ ; or t when the water is the hotter of the _ bodies mixed, the specific caloric of B is -^ ?J=A See Black's Lee- *^*^m b tares, i. 506. * To form an adequate notion of the delicacy of Dr Crawford's er- periments, it will be necessary to peruse his own account of the precau- tions to which he had recourse. See his Experiments on Animal Hc.t and Combuttten, p. 96. Seguin, in his Essay on Heat, Ann. ds Cbita. iii. 148, has done littie else than translate Crawford. $56 ^UANrm OF CALORIC. Book I. no caloric can pass through ice at 32. It can enter ice* Division II. . c -v indeed, but it remains in it, and is employed in melting it. The quantity of ice melted, then, is a measure of the caloric which has entered into the ice. The exterior and middle cavities being filled with ice, all trie watef is allowed to drain away, and the temperature of the interior cavity to come down to 32. Then the sub- stance, the specific caloric of which is to be ascertained, is heated a certain number of degrees, suppose to 212% and immediately put into the interior cavity inclosed in & thin vessel. As it cools, it melts the ice in the mid- dle cavity. In proportion as it melts, the water runs through the grate and sieve, and falls through the coni- cal funnel ccd and the tube x into a vessel placed be- low to receive it. The external cavity is filled with ice, in order to prevent the external air from approaching the ice in the middle cavity and melting part of it. The water produced from it is carried off through the pipe ST. The external air ought never to be below 32, nor above 41. In the first case, the ice in the middle cavity might be cooled too low ; in the last, a current of air passes through the machine, and carries off some of the caloric. By putting various substances at the same temperature into this machine, and observing how much ice each of them melted in cooling down to 32, it was easy to ascertain the specific caloric of each. Thus if water, in cooling from 212 to 32, melted one pound of ice, and spermaceti oil 0'5 of a pound ; the specific caloric of water was one, and that of the oil 0'5. This appears by far the simplest method of making ex- periments on this subject, and must also be the most accurate, provided we can be certain that all the melted snow falls into the receiver. But from an experiment 557 of Mr Wedgewood, one would be apt to conclude thit Chap, ir. this does not happen. He found that the melted ice, so far from flowing out, actually froze again, and choak- ed up the passage. A Table of the specific caloric of various bodies was likewise drawn up by Mr Kirwan, and published by Magellan in his Treatise on Heat. Mr Meyer has late* ly published a set of experiments on the specific caloric of dried woods ; and Mr Leslie, in his Essay on Heat, has given us the result of his experiments on various bodies. The experiments of Meyer were made by as- certaining the rate of cooling of the same bulks of dif- ferent bodies. From this he deduced their conducting power for heat ; and he considered the specific caloric as the reciprocal of the product of the conducting pow- er multiplied into the specific gravity of the body *, Mr Leslie likewise made his observations by ascertain- ing the time that various bodies of equal bulks took up in cooling in the same circumstances. He then multi- plied the proportional numbers thus got into the speci- fic gravity of the various bodies tried f, Mr Dalton has also turned his attention to this import- ant subject, and has lately published a table of the spe- cific hears of different bodies. His method was similar to that employed by Leslie ; and Mr 'Dalton informs us that he found that method susceptible of considerable precision. * Let L be the conducting power, A the specific caloric, and M the specific gravity. According to Meyer we have A =rT;- Sec Ann.d* Cbim. xxx. 46. f See Leslie on Hiat y p. 240, 558 QJJANTITY OF CALORIC, Book I. Xhe following Table exhibits a view of the specific Division II. y . * heats of various bodies, as they have been obtained by different philosophers . Table of I. GASES. Sp. Caloric. Sp. Caloric. specific ca- Muriate of amO lorics. Hydrogen . . . 21*4000* monia . . i C 0*79Sf Oxygen .... 4'7490* Water . . 1*5 j Common air . . 1*7900* Tartar . . 1 7 Carbonic acid . 1-0454* Water . 237'3 5 ' 765t Azote 0-7936* Sulphate of 1 II. WATER. iron . . 1 Vi;. 0'734f \\T i - V Water . 2*5 j Ice . fo-eooof Sulphate of ^ L -800(a) soda . i C . o728f W^ater 1*0000 Water . 2*9 j Alum . . 1 7 Water . . 2-9 5 ' 649f III. SALINE SOLUTIONS. Nitric acid 94- 7 . Lime ... 1 5 ^ 189 t Carbonate of 7 1-85 if Ditto (l40) . . 0*62 (D) ammonia 5 0*95 (D) Sulphuret of 7 anfm. (0-818) S' 994 t Sulphate of ^ Solution of br. 7 sugar $ ' 086 t Ditto (l*17) . . 0'77(D) magnesia . i > 0*844f IV. ACIDS AND ALKALIES. Water . . . 2 J Common salt 1 7 Water . . . 8J ' 832 + Ditto (1-197) . 0*78 (D) Vinegar .... 0-92(D) fpale . . . 0-844f (1-20) . 0-76(D) Nitre 1 1 [\itnc (1*2989 J \ /T\ Water 8 j ' ' ' 81G ^ 1-30 . . . 0-66(D) Nitre 1 ? Water 3 $ ' ' ' 646 t Carbonate of 7 < ._ . potash (l*30) 3 (1-355) 0-57df (1-36). . 0*63(D) Muriatic J(l'i22)o-680t c 1*153 O-GOfD^ $ Instead of giving the average, as in the former edition of this work, it has been thought more useful to insert the result as obtained by eacfe experimenter. SPECIFIC. 559 Sulph. Sp. Caloric. r(l-SS5) 0-758f 1-844 0-35(D) 0-3345J 0-333 (a) O'GGSlJ 0'603li 0*52(D) Bo. 4, Water 5 Do. 4, do. 3 . Do. equal bulks Aceticfacid(l-056)o-66(D) Potash (l*346) 0'759f (0-997) CO-708-f- (0-948) l-03(D) V. INFLAMMABLE LIQJJIDS. f 0-930 (a) 0-6666* 0-64 (L) Alcohol <{ 0-602* I (-en) o-70(D) i-oset K-S4S) Sulphuric e- 7 ther (0-76)5 Oil of olives Linseed oil . . Spermaceti oil Oil of turpent. Spermaceti . . Ditto fluid . -76(D) 0'66(D) 0-71Sf 0-50 (L) 0'528f 0-5000* 0'52(D) 0'472f 0-400 (a ) 0-399f 0.320 (a) VI. ANIMAL FLUIDS. Arterial blood Venous blood Cows milk . 1-0300* 0-8928* 0-9999* 0-98(D) VII. ANIMA'L SOLIDS. Ox-hide with hair 0'7370* Sp. Caloric. Chap. II Lungs of a sheep 0-7690* * v Lean of ox-beef 0-7100* VIII. VEGETABLE SOLIDS. Pinus sylvestris Pinus abies . . Tilea Europsea Pinus picea . . Pyrus malus . Betula alnus . Quercus robur 0-57TJ" 0-53^ Fraxinus excelsior 0*51^]" Pyrus communis 0-50^f Rice ..... 0*5060* Horse beans . . 0*5020* 0-48]" Peas ..... 0-4920* Fagus sylvatica . Carpinus betulus Betula alba . . . Wheat ..... 0-4770* Elm ...... 0-471! Q^iercus robur 7 pedunculata 3 Prunus domestica 0* Diaspyrusebenum 0- Barley ..... 0'421G* Oats ..... 0-4160* Pit-coal . . 0-45f Charcoal Cinders 0-2777* 0*2631* 0-1923* IX. EARTHT BODIES, STONEWARE AND GLASS. Hydrate of lime 0-40(D) Chalk. . . . (0-27(D) (_ 0-2564* 0'30(D) Quicklime . . < 0-2229 r 0'30(D . . < 0-2229* /0-216SJ 560 QJJANTITY OF CALORIC, F Book I. Sp. Caloric. [Division II. Ash es of pi t- coal 0-1855* h ""~ v Ashes of c-.lin Agate . . Stoneware . Crownglass Crystal . . Swedish glass Flint glass Vl9(D) 0*lS3f 0'23(D) 0-1402 0'195 0-195f 0-200(a) 0-1929J 0'1S7$ 0-19(1)) X. Sulphur . Muriate of soda XI. METALS. Platinum Iron Bras Copper . Sheet iron Gun metal Nickel . Zinc Silver . . Tin. 0-13(a) fo-143(a) d-!3(D) LO-126'} C 0*1123* r ] (. o-iiii* ("114$ o.ii(D) o-jicoj) o-io(D) 0'094-S* O't S2 o-os(D) o-oesf 0-0704* 0-07(D) Antimony . . Gold . . . . Lead . . . . Bismuth . . . Mercury . . Sp. Caloric. '0'086f 0-0645* 0-063$ 0'06(D) '0*050$ 0*05(D) 0'050f 0-0352* 0'04(D) 'o.043} 0'04(D) 0'033f 0-0357* 0'0290t 0'0496(D) XII. OXIDES. Oxide of iron. . 0*320f Rust of iron . . 0*2500* Ditto nearly free "7 from air j White oxide of 7 0'220f antim. washed 3 0-2272* Do. nearly freed from air Oxide of copper, do. Oxide of lead and, , tin Oxide of zinc, do. 0*1369* 0-099Q* 0-096f 0-0680* 0-068f 0*2272' ly -reed froi air Yellow oxide of lead, do. * Crawford ; f Kirwan ; J Lavoisier and Lspiacc ; <> W^icke ; f Meyerj ceding table, were determined by Dr Crawford with much ingenuity and patient industrj ; yet from the ex- treme difficulty of the subject, there is little reason for believing that the results which he obtained are very near approximations to the truth. If any confidence can be put in the hypothesis of Gay-Lussac, w.e are certain that some of the numbers of Crawford must be very er- roneous. When the density of any gas is suddenly changed, it always undergoes a corresponding change of temperature. If the gas becomes rarer, a thermo- meter placed in it sinks ; but if the gas becomes den- ser, or if it rushes into a vacuum, the thermometer rises. Now Gay-Lussac supposes, that in these cases (other things being equal) the change of temperature will be proportional to the specific heat of the gas. He procured two globular glass vessels of the same capa- city, put into each a delicate spirit thermometer, then exhausted each by means of an air-pump, filled one of them with the gas to be examined, and after waiting till they had acquired the temperature of the room, opened a communication between them by means of a stopcock and tube, so contrived that the aperture could be diminished at pleasure, in order that each gas might be made to occupy the save time in passing from the one vessel to the other. The thermometer in the full glass vessel immediately subsided, while that in the va- cuum rose; aad in Gay-Lu^sac's experiments the fall of the one thermometer was very nearly the same as the rise in the other. The greatest change of temperature was produced when hydrogen gas was employed: com- mon air produced a smaller change than hydrogen, oxy- gen gas a smaller change than common air, and carbo Vol. /. JST n 562 QUANTITY OF CALORIC. Boole I. nic acid a smaller than oxygen p-as. From these exoe- Division I f. . {? -_ K riments Gay-Lussac considers it as probable, that the greater the specific gravity of a gas, the less is its spe- cific heat *. Mr Dalton has lately turned his attention to the specific heats of gaseous bodies, and has calcu- lated, from data furnished by a theory of his, to be ex- plained in a subsequent part of this work, that the spe- cific heats of the different gases ought to be as in the following Table, supposing as usual the specific heat of water =r I f* Gases. Sp. Caloric. Hydrogen gas 9*382 Azotic 1*866 Oxygen 1*333 Air 1*759 Nitro.us gas. .*..... 0*777: Nitrous oxide. ..... 0-549 Carbonic acid..........0.*491 Ammonia... 1.555 Carbureted hydro. 1*333 Gases. Sp. Calork, Olefiant gasr 1*555 Nitric acid 0*491 Carbonic oxide 0*777 Sulphureted,, hydro. 0*583 Muriatic acid 0*424 Aqueous vapour ....1*166 Ether vapour 0*848 Alcohol vapour 0*586 If any confidence can be put in the accuracy of this table, it is clear that the hypothesis of Gay-Lussac is without foundation. Indeed, a few simple considera- tions on the phenomena of combustion, are sufficient to show us that the specific heat of gaseous bodies cannot be inversely as their specific gravity. The following are the most important points respect- ing the specific caloric of bodies hitherto investigated. General re- 1 Dr Crawford made a great many experiments re- sults. * Mem.tTArcueil, i. 180. New Syttcm of Chemical Pbiluofby, p. 74,.. SPECIFIC, 563 lative to the specific caloric of bodies at different tern- t Chap. II. ^ peratures, and the result of them was, that it is nearly permanent in the same body, while that body remains in the same state. His reasoning is founded upon two suppositions, neither of which have been sufficiently proved : 1. That the mercurial thermometer is an ac- curate measure of heat ; 2. That heat does not unite chemically to bodies. With these data he shows, that the specific caloric of water does not vary at different temperatures. And, finally, by mixing bodies at various temperatures with water, he established the permanen- cy of their specific calorics *. As this reasoning i* founded on inadmissible suppositions, it is not quite le- gitimate. Mr Dalton has lately endeavoured to show that the specific heat of all bodies increases with their temperature ; and his reasoning, though not quite con- elusive, is at least very plausible and probable, 2. Whenever a body changes its state, its specific ca- loric changes at the same time, according to the follow- ing law. When a solid becomes a liquid, or a liquid an elastic fluid, the specific caloric increases ; when an elastic fluid becomes a liquid, or a liquid a solid, the specific caloric diminishes. This very important disco- very was made by Dr Irvine, and applied by him, with much sagacity, to the explanation of a great variety of curious and important phenomena. 3. The specific caloric of bodies is increased by com- bining them with oxygen. Thus the specific caloric of metallic oxides is greater than that of metals, and of acids than of their bases. This fact was discovered by * Crawford Heat, p. 53 Nns 564 QJJANTITY OF CALORIC. Book I. Dr Crawford, and constituted the foundation of his Division H. * -y . theory of animal heat. 4. The specific caloric of oxygen is diminished when it enters into combination with inflammable bodies. This was also established by Dr Crawford, though not in a manner quite so satisfactory. II. OF THE ABSOLUTE QUANTITY OF HEAT IK BODIES. THUS we see that the relative quantity of caloric is very different in different bodies, even when they are of the same temperature by the test of the thermometer. It is obvious, therefore, that the thermometer is not capable of indicating the quantity of caloric contained in bodies : since,- not to mention the specific caloric, the presence of the caloric which occasions fluidity is not indicated by it at all. Thus steam at 212 contains 1000 more caloric than water at 212, yet the tempe- rature of each is the same. Is there then any method of ascertaining the absolute quantity of caloric which a body contains ? At what degree would a thermometer stand (supposing the thermometer capable of measuring so low), were the body to which it is applied totally deprived of caloric ? or, What degree of the thermome- ter corresponds to the real zero ? The first person, at least since men began to think accurately on the subject, who conceived the possibility of determining this question, was Dr Irvine of Glas- gow. He invented a theorem, in order to ascertain the real zero, which has, I know not for what reason, been ascribed by several writers to Mr Kirwan. 1 It is obvious, that if the specific caloric of bo* ABSOLUTE. 565 dies continues the same at all temperatures, the abso- t Chay>. IT. late quantity of caloric in bodies must be proportional Hypothesis to the specific caloric. Thus if the specific caloric of ^ ne r spermaceti oil be only half of that of water, water must contain twice as much caloric as spermaceti oil of the same temperature. Let us suppose both bodies to be totally deprived of caloric, and that we apply to them a thermometer, the zero point of which indicates absolute cold or a total deprivation of heat. To raise the oil and water one degree, we must throw in a certain quantity of heat, and twice as much heat will be ne- cessary to produce the effect upon the water as on the oil. To produce a temperature of two degrees, the same rule must be observed ; and so on for three, four, and any number of degrees. Thus at all tempe- ratures the water would contain twice as much caloric as the oil. 2 This supposition, that the specific caloric of bodies continues the same at all temperatures, was the founda- tion of Dr Irvine's reasoning. He had ascertained, that when a body changes from a solid to a liquid, its specific caloric at the same time increases ; and that the same increase is observable when a liquid is converted into an elastic fluid. The constancy of the specific caloric of bodies, on which he founded his the- ory, was true only while they remained in the same state. He supposed likewise, that when a solid body is converted into a liquid, the caloric absorbed without any increase of temperature, or the latent heat, is merely 1he consequence of the increase of the specific caloric of the body. Thus when ice is converted into water, 140 of caloric are absorbed, because the specific caloric of Mater is so much greater than that of ice, as to require $66 QUANTITY OF CALORIC* Book I. 140 additional of caloric to preserve the same tempe* Division IT. . 1 '. u -v^-j rature which it had when its specific caloric was less. The same supposition accounted for the absorption of caloric when liquids are converted into elastic fluids. 3. Dr Irvine's theory of the absolute caloric of bo- dies depended upon these two opinions, which he con- sidered as first principles. The first gave him the ratio of the absolute calorics of bodies ; the second, the dif- ference between two absolute calorics. Having these data, it was easy to calculate the absolute quantity of caloric in any body whatever. Thus let us suppose that the specific caloric of water is to that of ice as 10 to 9, and that when ice is converted into water the quan- tity of caloric absorbed is 140. Let us call the abso- lute quantity of caloric in ice at 32 j it is obvious that the absolute caloric in water at 32 is = x -f- 140. We have then the absolute caloric of ice rr x t that of water ~x -|- 140 But these quantities are to each other as 10 to 9. Therefore we have this proportion 10 : 9 : :. tf-f- 140 : x. By multiplying the extremes and means we get this equation 10 x ~ 9 x -f- 1260, from which we deduce A: =r 1260. Thus we obtain the absolute quantity of caloric in ice of 32, and find it to amount to 1260. Water at 32 of course contains 1400 degrees of caloric. Or, to state the proposition differently ; as the specific caloric of water is to that of ice as 10 to 9, it is obvious that the 140 degrees of heat which are evolved when water is frozen are equal to -r^th of the ivhole heat in the water. Therefore the heat of the water is equal to 140 X 10, or 1400. Such was the ingenious method proposed by Dr Ir- vine for ascertaining the real zero, or the degree at which a thermometer would stand when plunged into a ABSOLUTE. 567 body altogether destitute of caloric. We see, that by Chap-ir. the above calculation it would be with regard to ice 1260 degrees below 32 of Fahrenheits scale, or 1298 degrees below 0. Dr Crawford, however, who made his experiments upon a different set of bodies, places the real zero at 1500 below of Fahrenheit. Mr Dalton, who has also turned his attention to the same question, has found the mean of his experiments to give 6000 below the freezing point as the real zero *. 4. Unfortunately the truth of the principles on which this theory of Dr Irvine is founded is by no means established* The first proposition, that the specific ca- loric of bodies continues the same at all tempera- tures, has by no means been ascertained by experi- ments ; so far from it, that the very contrary has been proved by Dr Irvine himself to hold in the case of spermaceti and wax, and has been observed by Craw- ford in other cases f. But even if it did hold at all tem- peratures while bodies comiuue in the same state, still as every change of state is confessedly attended with a corresponding change of specific caloric, we have no right to affirm that the specific caloric is proportional to the absolute caloric. For instance, though the speci- fic caloric of ke be to that of water as 9 to 10, it does not follow that their absolute calorics bear the same pro- portion : nor can any reason be assigned for supposing that this ratio ought to hold, unless we suppose that ca- loric is incapable of uniting chemically to bodies j in which case indeed it might be admitted. 5. The second proposition, namely, that the caloric * Ne-w System f cttmifal flihsefly, p. 9-, f On Hrat, p. 47*. $68 QUANTITY OF CALORIC, Book !. absorbed by a body, during its cha'.ge of state, is mere* owing to the change of the specific caloric of the bo- dy, is equally unsupported by direct proof, and indeed cannot be admitted, if we allow that caloric is capable of combining chemically with bodies. It assigns no reaso . for the change of state which the body has un*> dergone, while the theory of Dr Black accounts for that change. The 940 degrees of heat which disappear when water becomes steam, according to Dr Irvine, are merely tne consequence of the increased specific caloric of steam above thai of water. But why does water be* come steam, and why does it shew a tendency to absorb hen? before it has actually become steam ; a tendency causing it to exert a force \\hich at last overcomes the most powerful obstacles ? If the change be produced by the combination of heat, as all th? phenomena an- nounce, then the hypothesis of Irvine is inadmissible* Accordingly, both Irvine and Crawford laid it down as tin axiom, ;that heat is incapable of combining with bodies. .6. Another set of phenomena from which Dr Irvine drew his conclusions, is more susceptible of investiga- tion. When bodies unite together chemically, a change of temperature is almost constantly produced ; the com- pound either giving out heat or absorbing it. Dr Ir- vine ascertained, by a variety of experiments, that the combination is attended with a similar change in the Specific heat of the compound*. When the specific ca- loric increases, the compound generates cold ; when the specific caloric diminishes, heat is evolved. & Crawford on Heat, p. 455. ABSOLUTE. 569 He inferred, in consequence of his opinion formerly Chap. IT. explained, that the heat evolved or absorbed in these cases was proportional to the change of specific caloric, and the consequence of that change. Hence it was easy, knowing the specific caloric of two bodies before com- bination, the specific caloric of the compound, and the heat evolved or absorbed, to ascertain upon that hypo- thesis the absolute heat of the body. For example, let the specific caloric of two bodies before combination be :*-= 2, and after it = 1, it is obvious, that during com- bination they must have parted with half of their absolute heat. Let the heat evolved be 700 ; then we know that the whole heat contained in the bodies is twice 700, or 1400. Suppose equal weights of the two bodies A, B to be combined together. Let the specific caloric of A be G, aod that of B, c ; and let the specific caloric after combination be K -f- k, then, according to Dr Irvine, .we have C+c K + k : K -f k : : I the heat evolved : S absolute heat. Hence we have S zr / ( K I \ c , __ ^ _ : If the weights of the bodies com* bined be not equal, then let Q^be the weight of A, and q that of B ; we have as before, C Q^-f c q K ::/:S. Hence S = This hypothesis can be true only on the supposition that the quantity S, found by mixing substances toge- ther in different proportions, turns out always the same quantity. If it does not, the opinion falls to the ground. Thus if we mix together various proportions of water and concentrated sulphuric acid, tire heat evolved at each trial, compared with the change of the specific ca- 570 QJJANTITY OF CALORIC. Book T. loric, ought to give us the same value of S. But from ^ 'vision _.' the experiments that have been made upon this subject, it does not appear that any such constant value of S is observed. The experiments indeed of Gadolin ap- proach somewhat to it, but those of Lavoisier and La- place are very anomalous, as will appear from the folr lowing statement. From the experiments of Lavoisier and Laplace on a mixture of water and quicklime, in the proportion of 9 to 16, it follows that the real zero is 3428 Q be- low 0. From their experiments on a mixture of four parts of sulphuric acid and three parts of water, it follows that the real zero is 7262 below 0, Their experiments on a mixture of four parts of sul- phuric acid and five of water place it at 2598 below Q. Their experiments on 9y parts of nitric acid and one of T ft ft Q lime place it at I below 32, =r + 23837* *, 0-01783 The mean result of Gadolin's experiments on mix- tures of sulphuric acid and water, place it at 23Op be- low 0. Mr JDalton's results vary from 4150 Q to 1100 ; the mean of the whole places the real zero at 6150 below 32f, Dr Irvine's own experiments ld him to fix the real zero at 900 below 0. Dr Crawford, from his experiments, placed it at 15 00* below 0. These results differ from one another so enormously, and the last of those obtained by Lavoisier and Laplace, * See Scguin, Ann. dc Chim. v. 131. I New System of Clcmicul Plitiosfhy, p, 97, ABSOLUT?. 571' which places the real zero far above a red heat, is so ab- Chap. n. surd, that if xve suppose them accurate, they are alone sufficient to convince us that the data on which they are founded are not true. Nor can the hypothesis be maintained till the anomalies which they exhibit be ac- counted for. 7. Another method of determining the absolute quan- MrDalton's tity of caloric in bodies has been lately proposed by h n> othe s - Mr Dalton *, a philosopher whose ingenuity and saga, city leave him inferior to none that have hitherto turn- ed their attention to this difficult subject. He supposes that the repulsion which exists between the particles of elastic fluids is occasioned by the caloric with which these particles are combined, and that it is always pro- portional to the absolute quantity of caloric so combi- ned. Now the diameter of the sphere over which the influence of a particle extends, is the measure of the repulsion, and it is proportional to the cube root of the whole mass. The repulsion exerted by the particles of an elastic fluid, at different temperatures, is proportion- al to the cube root of the bulk of the fluid in these temperatures. Therefore, according to this hypothesis, the absolute quantity of caloric in elastic fluids, at dif- ferent temperatures, is proportional to the cube roots of these bulks at these temperatures. To give an ex- ample : The bulk of air at 55 being 1000, its bulk at J12 is 1325; therefore the absolute heat in air at 55 is to its heat at 212 as ^1000 to J x/1325, or nearly as 10 to 11. Let us call the -absolute heat of air at 55 x ; then the absolute heat of air at 212 is x -f- * Manchester Memoirs t *t 512 QUANTITY OF CALORIC. B i- v .1 supposed rays of heat are aerial pulses, he would ac- count for the phenomena in a satisfactory manner. A very great degree of cold may be produced by mixing together different solids,, which suddenly become liquid. The cause of this has been already explained*, But as such mixtures are often employed in chemistry, in order to be able to expose bodies to the influence of a low temperature, it will be worth while to enumerate the different substances which may be employed for that purpose,, and the degree of eold which each of them. ., is capable of producing. Of freezing "The fj rst person who made experiments on freezing mixtures was Fahrenheit. But the subject was much more completely investigated by Mr Walker in various papers published in the Philosophical Transactions from-1187 tolSOl. Several curious additions havebeen made by Professor Lowitz, particularly the introduc- tion of muriate of lime 9 which produces a very great de- gree of cold when mixed with snow *. The experi- ments of Lowitz have been lately repeated and extend- ed by Mr Walker f. The result of all these experi- ments may be seen in the following Tables, which I transcribe from a paper with which I have been lately favoured by Mr Walker. * Ann. deClltn. XXli. 297. and f PUL Trans. l8oi, p. I2O. ' COLD. 579 TABLE I. Frigorific mixtures without tee. Chap. II. Mixtures. Thermometer sinks. Degree of cold produced. Parts- Muriate of ammonia ... 5 titrate of potash 5 Water . 16 From +50 to +10. 40 VTuriate of ammonia . 5 titrate of potash 5 From +50 to +4. 46 Water 16 SJitrate of ammonia ... 1 From +50 to +4. 46 titrate of ammonia ... 1 Carbonate of soda 1 Water 1 From -f 50 to -7. 57 Sulphate of soda ...... 3 Diluted nitric aoid 2 From -f-50 to 3 C . 53 Sulphate of soda Q Muriate of ammonia ... 4 Nitrate of potash 2 Diluted nitric acid .... 4 From 4-50 to 10 . 60 Sulphate of soda ...... 6 titrate of ammonia ... 5 Diluted nitric acid ...'4 From -f 50 to 14. 64 Phosphate of soda 9 Diluted nitric acid 4 From +50 to 12. 62 Phosphate of soda y Nitrate of ammonia ... 6 Diluted nitric acid ...... 4 From -f-5Q D to 21. 71 Sulphate of soda 8 Muriatic acid ........... 5 From +50 to O 9 50 Sulphate of soda 5 Diluted sulphuric acid . 4 From +50 to -f-3. 47 N B. If the materials are mixed at a warmer temperature than that expressed in the table, the effect will be proportionably greater ; thus, if the most powerful ot these ir.ixtures be made, when the air is -J-Sj , it will sink the thermometer to + 580 Book r. Division IT. QJJANTITY OF CALORIC.- TABLE H. Frigorific Mixtures with Ice. Mixtures. Thermometer sinks. Degree of cold produced. Parts. Snow, or pounded ice 2 Muriate of soda ...... 1 | I to 5 9 * Snow, or pounded ice . 5 Vluriate of soda 2 Muriate of ammonia . . 1 to 12 * * Snow, or pounded ice 24 Vluriate of soda .... 10 Muriate of ammonia . . 5 ^itr.ate of potash . . . ., 5 to -18 Q Snow, or pounded ice 12 Muriate of soda 5 to 25 * Nitrate of ammonia . . 5 From +32 to 23 55 Diluted sulphuric acid 2 From -(-32 to 27 59 Muriatic acid ...... 5 From +32 to 30 62 Diluted nitric acid ... 4 Snow 4 From -}-32 9 to 40 ! 72 Muriate of lime 5 From +32 to 50 Q 82 Chryst. muriate of lime 3 From +32 to 51 83 Potash 4 COLD. TABLE III. Combinations of Frigorific Mixtures. 531 Chap. H. Mixtures. Thermometer sinks. Degree of cold produced Parts, Phosphate of soda 5 Nitrate of ammonia ... 3 Diluted nitric acid ...... 4 From to 34 34 Phosphate of soda 3 titrate of ammonia ... 2 Diluted mixed acids ... 4 From 34 to 50 16 Snow ................... 3 Diluted nitric acid ...... 2 From to 46 46 Snow ..,... 8 Diluted sulphuric acid 3 ? Diluted nitric acid ... 3 ) From 10 to 56 46 Snow 1 Diluted sulphuric acid . 1 From 20 to 60 40 From +20 to 48 68 From +10 to 54 64 From 15 to 63 53 Snow 1 Chryst. muriate of lime 2 From to 66 66 Chryst. muriate of lime 3 Frqm 40 to 73 53 Diluted sulphuric acid 10 From 68 to 91 23 SOURCES OF CALORIC. I. I n order to produce these effects, the salts employed Division II. * must be fresh crystallized, and newly reduced to a very fine powder. The vessels in which the freezing mix- ture is made should be very thin, and just large enough to hold it, and the materials should be mixed together as quickly as possible. The materials to be employed in order to produce great cold ought to be first reduced to the temperature marked in the Table, by placing them in some of the other freezing mixtures ; and then they are to be mixed together in a similar freezing mix- ture. If, for instance, we wish to produce a cold =: 46, the snow and diluted nitric acid ought to be cooled down to 0, by putting the vessel which con- tains each of them into the first freezing mixture in the second Table before they are mixed together. If a still greater cold is required, the materials to produce it are to be brought to the proper temperature by being pre- viously placed in the second freezing mixture. This process is to be continued till the required degree of cold Jias been procured *. SECT. III. F THE SOURCES OF CALORIC. PAVING in the preceding Sections examined the na- tui\ . properties, and effects of caloric, as far as the sub- ject Jias been hitherto investigated, it now only remains * WaJker,/^/. irans. 1795, . THE sra. r>85 for us to consider the different methods by which calo- t CIia P- ] * ric may be evolved or made sensible, or the different sources from which it may be obtained. These sources may be reduced to five : It radiates constantly from ^the sun ; it is evolved during combustion ; and it is ex- tricated in many cases by percussion, friction, and mix- lure. The sources of heat, then, are the sun, combus- tion, percussion, friction, mixture. Let us consider each of these sources in the order in which -we have enume- rated them. 1. THE SUN. THE sun, which constitutes as it were the vital part Nature of of the whole solar system, is an immense globe, whose diameter has been ascertained by astronomers to be no less than 888,246 miles, and which contains about 335,958 times as much matter as the earth. Philoso- phers long supposed that this immense globe of matter was undergoing a violent combustion ; and to this cause they ascribed the immense quantity of light and heat which are constantly separating from it. But the late very curious and important observations of Dr Herschel leave scarcely any room for doubting that this opinion is erroneous *. From these observations it fol- lows, that the sun is a solid opaque globe, similar to the earth or other planets, and surrounded by an atmosphere of great density and extent. In this atmosphere there float two regions of clouds : The lowermost of the two is opaque and similar to the clouds which form in our * Phil. Trant, ISOT, p. 365, 584 SOURCES OF CAI llow s that transparent bodies al- ress of their low these rays to pass through them ; but that they are colcyr. detained, at least in part, by opaque bodies. The deep- er the colour of the opaque body, the greater is the rise of temperature which it experiences from exposure to the sun's rays. It has been long known, that when co- loured bodies are exposed to the light of the sun or of combustible bodies, their temperature is raised in pro- portion to the darkness of their colour. To ascertain this point, Dr Hooke made a curious set of experiments, which were repeated long after by Dr Franklin. This philosopher exposed upon snow pieces of cloth of diffe- rent colours (white, red, blue, black) to the light of the sun, and found that they sunk deeper, and consequently acquired heat, in proportion to the darkness of their co- lour. This experiment has been repeated with more precision by Mr )avy. He exposed to the light six THE SUN* 585 equal pieces of copper painted white, yellow, red, green, t Cha P- n t blue, and black, in such a manner that only one side of the pieces was illuminated. To the dark side of each was attached a bit of cerate, which melted when heated to 7b. The cerate attached to the blackened copper bepame first fluid, that attached to the blue next, then that attached to the green and red, then that to the yel- low, and last of all, that attached to the white *. Now it is well known that dark coloured bodies, even when equally exposed to the light, reflect less of it than those which are light- coloured ; but since the same quantity falls upon each, it is evident that dark-coloured bodies must absorb and retain more of it than those which are light-coloured. That such an absorption actually takes place is evident from the following experiment. Mr Thomas Wedgewood placed two lumps of luminous or phosphorescent marble on a piece of iron heated just under redness. One of the lumps of marble which was blackened over gave out no light ; the other gave out a great deal. On being exposed a second time in the same manner, a faint light was seen to proceed from the clean marble, but none at all could be perceived to come from the other. The black was now wiped off, and both the lumps of marble were again placed on the hot iron : The oae that had been blackened gave out just as little light as the other f. In this case, the light which ought to have proceeded from' the luminous marble disappeared : it must therefore have been stop- ped in its passage out, and retained by the black paint. Now black substances are those which absorb the most Bcddoes's Contributions > p. 4. f Pbil. Trent. 1792. $86 SOURCES OF AUORIft. Book I. light, and they are the bodies which are most heated by Division H. f *_y^j exposure to light. Cavallo observed, that a thermome- ter with its bulb blackened stands higher than one which had its bulb clean, when exposed to the light of the sun, the light of day, or the light of a lamp *. Mr Pic- tet made the same observation, and took care to ascer- tain, that when the two thermometers were allowed to remain for some time in a dark place, they acquired precisely the same height. He observed, too, that when both thermometers had been raised a certain num- ber of degrees, the clean one fell a good deal faster than the otherf, ffeatpro- 3. The temperature produced in bodies by the direct the rays of action of the sun's rays seldom exceeds 120; but a much higher temperature would be produced if we were to prevent the heat communicated from being car- ried off by the surrounding bodies. Mr Saussure made a little box lined with fine dry cork, the surface of which was charred to make it black and spongy, in or- der that it might absorb the greatest possible quantity of the sun's rays, and be as bad a conductor of caloric as possible. It was covered with a thin glass plate. When this box was set in the sun's rays, a thermometer laid in the bottom of it rose in a few minutes to 221 ; while the temperature of the atmosphere was only *Z5 * Professor Robison constructed an apparatus of the same kind, employing three very thm vessels of flint glass, which transmit more caloric than any of the other species of glass. They were of the same shape, * PM. Tram. 1780. f Sur le Feu, chap. iv. svr let Afrs, ii 93 1. THE SUN. 5&1 arched above, with an interval of -f inch between them. , cha P- ir They were set on a cork base prepared like Saussure's, and placed on down contained in a pasteboard cylinder. With this apparatus the thermometer rose often in a clear summer day to 230, and once to 231. Even when set before a bright fire, the thermometer rose to 212*. 4. Such is the temperature produced by the direct rays of the sun. But when its rays are concentrated by a burning-glass, they are capable of setting fire to combustibles with ease, and even of producing a tem- perature at least as great, if not greater, than what can be procured by the most violent and best conducted fires. In order to produce this effect, however, they must be directed upon some body capable of absorbing and retaining them ; for when they are concentrated upon transparent bodies, or upon fluids, mere air for Instance, they produce little or no effect whatever. Count Rumford has shown by direct experiment, that the heating power of the solar rays is not increased by concentrating them into a focus, but that the intensity of their action is occasioned by a greater number of them being brought to bear upon the same point at once t 5. These facts, which have been long known, indu- ced philosophers to infer, that the fixation of light in bodies always raises their temperature. On the other * Black's Lectures, i. 547. When the apparatus was carried to a damp cellar before the glasses were put in their places, so that the air within was moist, the thermometer never rose above 208. Hence Dr Robison concluded, that moist air conducts better than dry ; a collusion fullr tonfirmed by the subsequent experiments of Count Rumford. I Jour, de Pbjs, Ixi. 3:. 5&S SOURCES OF CALORIC. Book. I. hand, it was known that the fixation of a certain quan* Division IT. . r . ' . -'- v tity or caloric always occasions the appearance or light $ for when bodies are raised to a certain temperature they always become red hot. Hence it was concluded that light and caloric reciprocally evolve each other ; and this was explained by supposing that they have the pro- perty of repelling each other. Owing to 6. But the recent discoveries in this part of chemis- of fabric. 11 trv ^ ave destroyed all the evidences on which these con- clusions were drawn. Not only light, but caloric also, radiates from the sun. We cannot therefore ascribe the rise of temperature to the absorption of light, but to the absorption of caloric j especially as the rays of the moon, though lumineus, occasion no rise of temperature. The facts, then, oblige us to conclude, that the sun emits rays of caloric ; that these rays are absorbed by opaque bodies, and detained by them ; and that the absorption, other tilings being equal, is proportional to the darkness of the colour of the absorbing body. Thus it appears, that when a body is acted on by rays of caloric, the change of temperature depends upon its opacity and co- lour. In this respect caloric agrees with light. But when caloric is conducted to a body, its opacity or colour does not influence the subsequent change of tempera- ture. II. COMBUSTION. Phenomena THERE is perhaps no phenomenon more wonderful { n itself, more interesting on account of its utility, or which has more closely occupied the attention of che- mists, than comlustian. When a stone or a brick is COMBUSTION. 580 heated, it undergoes no change except an augmentation t cha P- of temperature ; and when left to itself, it soon cools again and becomes as at first. But with combustible bodies the case is very different* When heated to a certain degree in the open air, they suddenly become much hotter of themselves, continue for a considerable time intensely hot, sending out a copious stream of ca- loric and light to the surrounding bodies. This emis- sion, after a certain period, begins to diminish, and at last ceases altogether. The combustible has now un- dergone a most complete change ; it is converted into a substance possessing very different properties, and no longer capable of combustion. Thus when charcoal is kept for some time at the temperature of about 800, it kindles, becomes intensely hot, and continue to emits light and caloric for a long time. When the emission ceases, the charcoal has all disappeared, except an in- considerable residuum of ashes ; being almost entirely converted into carbonic acid gas, which makes its escape unless the experiment be conducted in proper vessels. If it be collected, it is found to exceed greatly in weight the whole of the charcoal consumed. 1. The" first attempt to explain combustion was crude and unsatisfactory. A certain elementary body, called fire^ was supposed to exist, possessed of the property of devouring certain other bodies, and converting them into itself. When we set fire to a grate full of charcoal, we bring, according to this hypothesis, a small portion of the element of fire, which immediately begins to devour the charcoal, and to convert it into fire. Whatever part of the charcoal is not fit for being the food of fire is left behind in the form of ashes. 2. A much more ingenious and satisfactory hypothe- 590 SOURCES OF CALORIC. Baokl. sis was proposed in 1665 by Dr Hooke. According Division H. ^_y--^ to this extraordinary man, there exists m common air a theory 'of certain substance which is like, if not the very same combus- w ith that which is fixed in saltpetre. This substance has the property of dissolving all combustibles ; but on- ly when their temperature is considerably raised. The solution takes place with such rapidity, that it occasions both heat and light; which in his opinion are mere mo- tions. The dissolved substance is partly in the state of air, partly coagulated in a liquid or solid form. The quantity of this solvent present in a given bulk of air is incomparably less than in the same bulk of saltpetre. Hence the reason that a combustible continues burning but for a short time in a given bulk of air: The solvent is soon saturated, and then of course the combustion is at an end. Hence also the reason that combustion suc- ceeds best when there is a constant supply of fresh air, and that it may be greatly accelerated by forcing in air with bellows *. Adopted by About ten years after the publication of Hook's Mi- Mayow. crograpbia t His theory was adopted by Mayow, without acknowledgement, in a tract which he published at Ox- ford on saltpetre f. We are indebted to him for a num- ber of very ingenious and important experiments, in which he anticipated several modern chemical philoso- phers ; but his reasoning is for the most part absurd, and the additions which he made to the theory of Hooke are exceedingly extravagant. To the solvent of Hooke he gives the name of spiritus nitro-acreus. It consists, * Hook's Mlcrograplia, p. 103. See al^o { Dt Sal-nitre ft Sfiritu Nitro-arrco* COMBUSTION. 591 he supposes, of very minute particles, which are con- t Cha P- " stantly at variance with the particles of combustibles, and from their quarrels all the changes of things pro- ceed. Fire consists in the rapid motion of these parti, cles, heat in their less rapid motion. The son is mere- ly nitro-aerial particles moving with great rapidity. They fill all space. Their motion becomes more languid according to their distance from the sun ; and when they approach near the earth, they become pointed, and con- stitute cold *. 3. The attention of chemical philosophers was soon Theory off drawn away from the theory of Hooke and Mayow to one of a very different kind, first proposed by Beccher, but new-modelled by his disciple Stahl with so much skill, arranged in such an elegant systematic form, and furnished with such numerous, appropriate, and convin- cing illustrations, that it almost instantly caught the fancy, raised Stahl to the highest rank among philoso- phers, and constituted him the founder of the Stahlian theory of combustion. According to Stahl, all combustible substances con- tain in them a certain body, known by the name of PHLOGISTON, to which they owe their combustibility. * Though Mayow's theory was not original, and though his additions to it be absurd, his tract itself displays great genius, and contains a vast number of new views, which have been fully confirmed by the recent discoveries in chemistry. He pointed out the cause of the increase of weight in metals when calcined ; he ascertained the changes produced upon air by respiration and combustion ; and employed in his researches- an apparatus similar to the present pneumatic apparatus of chemists. Perhaps the most curious part of the whole treatise is his fourteenth chap- ter, in which he displays a much more accurate knowledge of affinities^ than acy of his contemporaries, or even successors for manj years. 592 SOURCES OF CALORIC. Book I. This substance is precisely the same in all combusts Division II'. . ^ bles. Ihese bodies or course owe their diversity to other ingredients which they contain, and with which the phlogiston is combined. Combustion, and all its at- tendant phenomena, depend upon the separation and dis- sipation of this principle ; and when it is once separated, the remainder of the body is incombustible. Phlogis- ton, according to Stahl, is peculiarly disposed to be af- fected by a violent whirling motion. The heat and the light, which make their appearance during combustion, are merely two properties of phlogiston when in this state of violent agitation. Improved. 4. The celebrated Macquer, to whose illustrious la- bours several of the most important branches of chemis- try owe their existence, was one of the first persons who perceived a striking defect in this theory of Stahl. Sir Isaac Newton had proved that light is a body ; it was absurd, therefore, to make it a mere property of phlogiston or the element of fire. Macquer accordingly considered phlogiston as nothing else but light fixed in bodies. This opinion was embraced by a great num- ber of the most distinguished chemists ; and many in- genious arguments were brought forward to prove its truth. But if phlogiston be only light fixed in bodies; whence comes the heat that manifests itself during com- bustion ? Is this heat merely a property of light ? Dr Black proved that heat is capable of combining with, or becoming fixed in bodies which are not combustible, as in ice or water ; and concluded of course, that it is not a property but a body. This obliged philosophers to take another view of the nature of phlogiston. *>. According to them, there exists a peculiar matter, COMBUSTIOKo 593 extremely subtile, capable of penetrating the densest bodies, astonishingly elastic, and the cause of heat, light, magnetism, electricity, and even of gravitation. This matter, the ether of Hookc and Newton, is also the substance called phlogiston, which exists in a fixed state in combustible bodies. When set at liberty, it gives to the substances called caloric and light those peculiar motions which produce in us the sensations of heat and light. Hence the appearance of caloric and light in every case ef combustion ; hence, too, the rea- son that a body after combustion is heavier than it wa$ before ; for as phlogiston is itself the cause of gravita- tion, it would be absurd to suppose that it possesses gravitation. It is more reasonable to consider it as en- dowed with a principle of levity,; 6. Some time after this last modification of the phlo- Modified gistic theory, Dr Priestley, who was rapidly extending the boundaries of pneumatic chemistry, repeated many experiments formerly made on combustion by Hooke, Mayow, Boyle, and Hales, besides adding many of his own. He soon found, as they had done before him, that the air in which combustibles had been suffered to burn till they were extinguished, had undergone a very remarkable change ; for no combustible would after- wards burn in it, and no animal could breathe it with, out suffocation, He concluded that this change was owing to phlogiston ; that the air had combined with that substance ; and that air is necessary to combustion/ by attracting the phlogiston, for which it has a strong affinity. If so, the origin of the heat and light which appear dring combustion remains to be accounted for? . Pp $9* SOURCES OF CALORIC. Book I. since pnlogiston, if it separates from the combustible iHvision If. ... merely by combining with air, cannot surely act upon By Craw- ford, And Kir- wan. those bodies in what state soever we may suppose them, 7. The celebrated Dr Crawford was the first person who attempted to solve this difficulty, by applying to the theory of combustion Dr Black's doctrine of latent heat. According to him, the phlogiston of the com,- bustible combines during combustion with the air, and at the same time separates the caloric and light with which that fluid had been previously united. The heat und the light, then, which appear during combustion, exist previously in the air. This theory was very dif- ferent from Stahl's, and certainly a great deal more sa- tisfactory. But still the question, What is phlogiston ? remained to be answered. 8. Mr Kirwan, who had already raised himself to the first rank among chemical philosophers, by many im- portant discoveries, and many ingenious investigations of some of the most difficult parts of chemistry,, attempt- ed to answer this question, and to prove that phlogiston is the same with hydrogen. This opinion, which Mr Kirwan informs us was first suggested by the discoveries of Dr Priestley, met with a very favourable reception from the chemical world,, and was adopted either in its full extent, or with certain modifications, by Bergman, Morveau, Crell, Wiegleb, Westrumb, Hermbstadt, Karsten, Bewley, Priestley, and Delametherie. The object of Mr Kirwan was to prove, that hydrogen ex- ists as a component part of every combustible body ; that during combustion it separates from the combusti- ble body, and combines with the oxygen of the air. This COMBUSTION. he attempted in a treatise published on purpose, intitled, An Essay on Phlogiston and the Constitution of Acids *. * I have omitted, in the historical view given in the text, the hypo- thesis published in 1777 by Mr Scheelc, one of the most extraordinary men that ever existed. When very young, he was bound apprentice to an apothecary at Gottenburgh, where he first felt the impulse of that ge- nius which afterwards made him so conspicuous. He durst not indeed devote himself openly to chemical experiments; but he contrived to make himself master of that science by devoting those hours to study which were assigned him for sleep. He aiterwards went to Swede, and settled as an apothecary at Koping. Here Bergman first found hum, saw his merit, and encouraged it, adopted his opinions, defended him with zeal, and took upon himself the charge of publishing his treatises. Encouraged and excited by this magnanimous conduct^ the genius of Scht e!c, though unassisted by education or wealth* burst forth with astonishing lustre ; and at an age when most philosophers are only rising into notice, he had finished a career of discoveries which have no parallel in the annals of chemistry. Whoever wishes to behold ingenuity combined with simpli- city, whoever wishes to see the inexhaustible resources of chemical ana- lysis ; whoever wishes for a model in chemical researches has only to peruse and to study the works of Scheele. In 1777, Scheele published a treatise, entitled Chemical Experiments on Air and Ffre t which perhaps e%hibits a more striking display of the et- tent of his genius than all his other publications put together. After a vast number of experiments, conducted with astonishing ingenuity, he concluded, that caloric is cwmpcsed of a certain quantity cf oxygen com- bined with phlogiston ; that radiant heat, a substance \vhich he supposed tapable of being propagated in straight lines like light, and not capable of combining with air, is composed cf oxygen united with a greater quan- tity of phlogiston, and light of oxygen united v.-ith a still greater quan- tity. He supposed, too, that the difference between the rays depends upon the quantity of phlogiston : the reJ, according to him, contains the least ) the violet the most ph.o*iston. By phlogiston^ Mr Scheele seems to have meant bydrogr'n. It is needless therefore to examine his theory, as it is now known th^t the combination < he pursued with unwearied industry, assisted by the nu- merous discoveries which were pouring in from all quarters; and by, a long series of the most laborious and accurate experiments and disquisitions ever exhibit- ed in chemistry,, he. fully established the existence of this general law "In every case of combustion, oxy- gen combines with the burning body." This noble dis- covery, the fruit of genius, industry, and penetration, has reflected new light on every branch of chemistry, has connected and explained a vast number of facts former- ly insulated and inexplicable, and has new-model led the whole, and moulded it into the form of a science. After Mr Lavoisier had convinced himself of the ex* istence of this general law, and had published his proofs- to the world,, it was some time before he was able to gain a single convert, notwithstanding his unwearied assidu- ity, and the great weight which his talents, his reputa- tion, his fortune, and his situation naturally gave him. At last Mr Berthollet, at a meeting of the Academy of Sciences in 1785, solemnly renounced his old opinions,, and declared himself a convert, Mr Fourcroy, profes- sor of chemistry in Paris, followed his example. And in 1787, Morveau, during a visit to Paris, was prevail- ed upon to relinquish his fotmer opinions, and embrace CCMSUST10N. 591 those of Lavoisier and his friends. The example of t Chap. 1 1. these celebrated men was soon followed by all the young chemists of France. Mr Lavoisier's explanation of combustion depends upon the two laws discovered^by himself and Dr GBlack. When a combustible body is raised to a certain tempe- rature, it begins to combine with the oxygen of the at- mosphere, and this oxygen during its combination lets go the caloric and light with which it was combined while in the gaseous state. Hence their appearance -during every combustion. Hence also the change which the combustible undergoes in consequence of combustion. Thus Lavoisier explained combustion without having recourse to phlogiston ; a principle merely supposed to exist, because combustion could not be explained with- out it. No chemist had been able to exhibit phlogis- ton in a separate state, or to give any proof of its ex- istence, excepting only its conveniency in explaining combustion. The proof of its existence consisted en- tirely in the impossibility of explaining combustion with- out it. Mr Lavoisier, therefore, by giving a satisfacto- ry explanation of combustion without having recourse to phlogiston, proved, that there was no reason for sup- posing any such principle at all to exist. 10. But the hypothesis of Mr Kirwan, who made phlogiston the same with hydrogen, was not overturn- ed by this explanation, because there could be no doubt that such a substance as hydrogen actually exists. But hydrogen, if it be phlogiston, must constitute a compo- nent part of every combustible, and it must separate from the combustible in every case of combustion. These were points, accordingly, which Mr Kirwan un- dertook to prove. If he failed, or if the very contrary 508 SOURCES OF CALORIC. Book I. of his suppositions holds in fact, his hypothesis of course Division II. _ .. '_;- y - ._- fell to the ground. Lavoisier and his associates saw at once the import* ant uses which might be made of Mr Kirwan's essay. By refuting an hypothesis which had been embraced by the most respectable chemists in Europe, their cause would receive an eclat which would make it irresist- ible. Accordingly the essay was translated into French, and each of the sections into which it was divided was -accompanied by a refutation. Four of the sections were refuted by Lavoisier, three by Berthollet, three by Fourcroy, two by Morveau, and one by Monge. And, to do the French chemists justice, never was there a re- futation more complete. Mr Kirwan himself, with that candour which distinguishes superior minds, gave up his opinion as untenable, and declared himself a con- vert to'the opinion of Lavoisier. 11. Thus Mr Lavoisier destroyed the existence of phlogiston altogether, and established a theory of coin- imstion almost precisely similar to that which had been proposed long ago by Dr Hooke. The theory of Hooke is only expressed in general terms ; that of Lavoisier is much more particular. The first was a hypothesis or fortunate conjecture which the infant state of the science did not enable him to verify ; whereas Lavoisier was led to his conclusions by accurate experiments and a train of ingenious and masterly deductions. Theory of According to the theory of Lavoisier, which is now almost generally received, and considered by chemists as a full explanation of the phenomena, combustion consists in two things : first, a decomposition ; second, a combination. The oxygen of the atmosphere being in the state of gas, is combined with caloric and light. COMBUSTION. 99 Ouring combustion this gas is decomposed, its caloric Chap. H and light escape, while its base combines with the com- bustible and forms the product. .This product is in- combustible ; because its base, being already saturated with oxygen, cannot combine with any more. Such is a short historical detail of the improvements gradually in- Iroduced into this interesting part of the science of che- mistry. Let us now take a more particular view of the subject. 12. By combustion Js meant a total change in the nature of combustible bodies, accompanied by the co- pious emission of heat and light. Every theory of combustion must account for these two things 4 name- ly, the change which the body undergoes, and the emis- sion of heat and light which accompanies this change. 13. Mr Lavoisier explained completely the first of Difference these phenomena, by demonstrating, that in all cases vvecn .,_ oxygen combines with the burning body: and that the men t and J combustion, substance which remains behind, after combustion, is the compound formed of the combustible body and oxygen. But he did not succeed so well in accounting for the heat and the light which are evolved during -combustion. Indeed this part of the subject was in a great measure overlooked by him. The combination of oxygen was considered as the important and essential part of the process. Hence his followers considered the terms oxygeni%ement and combustion as synonymous : but this was improper ; because oxygen often unites to bodies without any extrication of heat or light. In this way it unites to azote, muriatic acid, and mercury ; but the extrication of heat and light is considered as es- sential to combustion in common language. The union of oxygen without that extrication is very different SOURCES o* CALORIC. Bookl. from its union when accompanied by it, both in the Division II. , . - phenomena and in the product ; they ought therefore to be distinguished. I employ the term combustion in this Work in its usual acceptation. Difficulty j^ To account for the emission of heat and light, respecting e ; t the origin which constitutes a part of combustion, Mr Lavoisier and light. had recourse to the theory of Dr Crawford. The heat and the light was combined with the oxygen gas, and separated from it, when that gas united to the combus- tible body. But this explanation, though it answers pretty well in common cases, fails altogether in others* Heat and light were supposed to be combined with the oxygen of the atmosphere, because it is in a gaseous state ; and to separate from it, because it loses its ga- seous state, But as violent combustions take place when the oxygen employed is solid or liquid, as when it is in the state of a gas Thus if nitric acid be poured upon linseed oil, or oil of turpentine, a very rapid combus- tion takes place, and abundance of caloric and light is emitted. Here the oxygen forms a part of the liquid nitric acid, and is already combined with azote 5 or, ac- cording to the language of the French chemists, the azote has undergone combustion. Now, in this case, the oxygen is not only in a liquid state, but it has also undergone the change produced by combustion. So that oxygen is capable of giving out caloric and light, not only when liquid, but even after combustion ; which is directly contrary to the theory. Farther: Gunpowder, when kindled, burns with great rapidity in close vessels, or under an exhausted recei- ver. This substance is composed of nitre, charcoal, and sulphur : the two last of which ingredients are combustible ; the first supplies the oxygen, being com= COMBOSTJOlf. 60| posed of nitric acid and potash. Here the oxygen is t cha P- TL ., not only already combined with azote, but forms a com- ponent part of a solid ; yet a greater quantity of caloric and light is emitted during the combustion, and almost the whole product of the combustion is in the state of gas. This appears doubly inconsistent with the theo- ry ; for the caloric and light must be supposed to be emitted from a solid body during its conversion into gas, which ought to require more caloric and light for : ' its existence in the gaseous state than the solid itself contained. jLp. Mr Brugnatelli, the celebrated professor of che- Removed rnistry at Pavia, seems to have been the first who saw this objection in its proper light*. He has endeavoured to obviate it in the following manner : According to this very acute philosopher, the substance commonly called oxygen combines with bodies in two states : 1. Retaining the greatest part of the caloric and light with which it is combined when in the state of gas ; 2. Af- ter having let go all the caloric and light with which it was combined* In the first state he gives it the name of tbermoxygen ; in the second, of oxygen. Thermoxy- gen exists as a component part, not only of gaseous bo- dies, but also of several liquids and solids. It is only in those cases where thermoxygen is a component part of liquids or solids that caloric and light are emitted. All metals, according to him, combine with thermoxy- gen ) those substances, on the contrary, which by com- * Berthollet, in a note upon this passage in the first edition of this "Work, informs us that the subject had been examined long before th* period assigned in the text. See Jour. d< JF%/. IK. afy. 602 SOURCES OF CALORIC. Book I. bustion are Converted into acids, combine with oxygen *. Division H. . 5 f i ' y -> This ingenious theory obviates the objection complete- ly, provided its truth can be established in a satisfacto- ry manner. But as the evidence for it rests almost en- tirely upon its convenience in explaining several difficult points in the phenomena of combustion, we must con- sider it rather in the light of an ingenious conjecture than as a theory fully established f. Bodies divi- 16. All bodies in nature, as far as combustion is con. "upponers, cerned, may be divided into three classes j namely, sup- eombusti- p Qr ters 9 cotJibustibles, and incombustible*. bles,and in- * eombusti. By supporters I mean substances which are not them- selves, strictly speaking, capable of undergoing combus- tion ; but their presence is absolutely necessary, in or- der that this process may take place. Combustibles and incombustibles require no definition. Supporters. Oxygen gas is the only simple supporter known ; but vvhen incombustible bodies are united to oxygen, they also become supporters. The only incombustible bo- dies which possess this property are azote and muriatic acidt. It was this singularity which induced me to separate these two substances from all the rest, and place them among the simple bodies. The first of these bodies unites with four doses of oxygen, the second with two. Thus we have one simple supporter' and six compound ; namely, * Ann. de Cblm. Xxi. l8a. f The reader will find this theory very fully detailed in the Journal Je Climie of Van Mons, vols. ad and 3d. I avoid entering into particu- lars, because I can perceive no evidence whatever for the truth of most of the assertions which constitute this theory. t Perhaps mercury might be added to this list. I have failed ia ail mv attempts to cause it to undergo combustion. COMBUSTION. 1. Oxygen gas ; Chap. 2. Air ; 3. Nitrous oxide ; 4. Nitric oxide (nitrous gat) * 5. Nitric acid j 6. Oxy muriatic acid ; *?. Hyperoxy muriatic acid. 17. The combustibles are of three kinds ; namely, simple, compound, and oxides. The simple are the four simple combustibles described in the second Chap, ter of the first Division of this Part ; and the whole, or at least almost the whole of the metals. The com- pound are the various bodies formed by the union of these simple substances with each other ; most of which are denominated by terms ending in uret, as the sul- phurets, phosphurets, carburets, &.c. ; and also the al- loys, and some other compounds which will be descri- bed hereafter. The combustible oxides consist of com* binations of the combustible bodies, or their compounds with oxygen without undergoing combustion. They are very numerous, constituting the greater part of ani- mal and vegetable substances. 18. During combustion the oxygen of the supporter Products. always unites with the combustible, and forms with it a new substance, which I shall call a product of combus- tion. Hence the reason of the change which combusti- bles undergo by combustion, as has been sufficiently de- monstrated by Lavoisier. Now it deserves attention, that every product is always one or other of the three following substances: 1. Water; 2. An acid; 3. A me* tallic oxide. 19. Some of the products of combustion are capable Partial w of combining with an additional dose of cxygen $ but $04" SOURCES OF CALORIC. Book I. this combination is never attended with the phenomena Division II. - - v y of combustion, and the product by means of it is con- verted into a supporter. This is the case with several of the metallic oxides. Such compounds may be called partial supporters, as it is only to a part of the oxygen which they contain that they owe that property. The following oxides are partial supporters : 1 . Peroxide of gold ; 2. Peroxide of silver ; 3. Red oxide of mercury ; 4. Peroxide of mercury j 5. Peroxide of|iron ; 6. Red and brown oxides of lead j 7. Peroxide of manganese. These bodies, ; however, never attract oxygen except from supporters* 20. Since oxygen is capable of supporting combustion only when in the supporters and partial supporters, it tannot 'be doubted that it is in a different state in these bodies from the state in which it exists in other bodieso Now as light and heat ,are always emitted during com- bustion, but never when oxygen combines without com- bustion, it is natural to suppose that the oxygen of supporters contains either the one or the other of these bodies, or both of them ; while ,the oxygen of other bodies wants them altogether. I am disposed to believe that the oxygen of support- ca- ers contains only caloric, while that body in other cases is wanting, or at least not present in' sufficient quantity. My reason for this opinion is, that the caloric which is evolved during combustion is always proportional to the quantity of oxygen which combines with the bur n- COWBTJSTIOif. tng body $ but this is by no means the case with respect Chap. 11. to light. Thus hydrogen combines with more oxygen than any other body ; and it is now known, that the heat produced by the combustion of hydrogen is great- er than can be produced by any other method ^ yet the light is barely perceptible- 21. It was long the general opinion of chemists, that Combusti- light exists in a fixed state in all combustible bodies. The discoveries of Lavoisier induced the greater num- ber of them to give up this opinion, on the supposition that combustion could be explained in a satisfactory manner without it. Indeed the followers of that illus- trious philosopher considered it as incumbent upon them to oppose it with all their might ; because the fixed light, which had been supposed to constitute a part of combustibles, had been unfortunately denominated phlogiston ; a term which they considered as incompa- tible with truth. The hypothesis, however, was occa- sionally revived j first by Richter and Belametheric., and afterwards in a more formal manner by Gren. Buc little attention has been paid to it in this country till lately. The very curious phenomena observed by Mr henevix in his experiments on the hyperoxymuriatic acid, induced him to incline to the same opinion ; and I endeavoured to support it in some observations on com- bustion, which were published in Nicholson r s Journal*, * Nicholson's Jovmal, 1805, p. 10. Some very proper remarks wcra made upon these observations of mine by Mr Portal, and several objec- tions, -which certainly deserve to be particularly considered. In prosecu- ting the subject farther, I hav obtained w>me singular enough resultt, which have indeed removed several objections that had occurred to me as peculiarly formidable; while they have raised in their own room a. greater aumber of others which ! could not have cipected, Otf SOURCES OF CALORIC* Book I. That the light exists combined With the combustible, u. - w ' will appear exceedingly probable, if \ve recollect that the quantity which appears during combustion depends altogether upon the combustible. Phosphorus emits a vast quantity, charcoal a smaller, and hydrogen the smallest of all ; yet the quantity of oxygen which com- bines with the combustible during these processes, is greatest in those cases where the light is smallest. Be- sides, the colour of the light depends in all cases upon the combustible that burns ; a circumstance which could scarcely be supposed to take place unless the light were separated from the combustible. It is well known, too, that when vegetables are made to grow in the dark, no combustible substances are formed in them j the pre- sence of light being absolutely necessary for the forma- tion of these substances. These facts, and several others which might be enumerated, give a considerable degree of probability to the opinion that light constitutes a component part of all combustible substances ; but they by no means amount to a decisive proof: nor indeed would it be easy to answer all the objections which might be started against this opinion. At the same time, it will be allowed that none of these objections to v. ,ich I allude amount to a positive proof of the false- hood of the hypothesis. It is always a proof of the dif- ficulty of an investigation, and of the little progress which has been made in it, when plausible arguments can be brought forward on both sides of the question. 22. Were we to suppose that the oxygen of support- ers contains caloric as a component part, while com- bustibles contain light, it would not be difficult to ex- plain whai takes place during combustion. The com- ponent parts of the oxygen of supporters are two ? COMBUSTION. 07 namely, 1. A base ; 2. Caloric: The component parts t Chap. of combustibles are likewise two: namely, 1. A base; 2. Light. During combustion the base of the oxygen combines with the base of the combustible, and forms the product ; while at the same time the caloric of the oxygen combines with the light of the combustible, and the compound flies off in the form of fire. Thus com- bustion is a double decomposition ; the oxygen and com- bustible divide themselves each into two portions, which combine in pairs j the one compound is the product^ and the other thejfov which escapes. Hence the reason that the oxygen of products is un- fit for combustion. It wants its caloric. Hence the reason that combustion does not take place when oxy- gen combines with products or with the base of sup- porters. These bodies contain no light. The caloric of the oxygen of course is not separated, and no fire ap- pears. And this oxygen still retaining its caloric, is ca- pable of producing combustion whenever a body is pre- sented which contains light, and whose base has an affi- nity for oxygen. Hence also the reason why a com- bustible alone can restore combustibility to the base of a product. In all such cases a double decomposition takes place. The oxygen of the product combines with the base of the combustible, while the light of the com- bustible combines with the base of the product. 23. But the application of this theory to the phena- rnena of combustion is so obvious, that it requires no particular explanation. It enables us to explain, with equal facility, some curious phenomena which occur during the formation of the sulphurets and phosphu- rets. Sulphur and phosphorus combine with the me- tals and with some of the earths. The combination ii 08 SOURCES OF CALORIC. Book L not formed without the assistance of heat. ^This melttf .' the sulphur and phosphorus. At the instant of their combination with the metallic or earth bases, the com- pound becomes solid, and at the same time suddenly acquires a strong red heat, which continues for some time". In this case the sulphur and phosphorus act the part of a supporter ; for they are melted, and therefore contain a great deal of caloric : the metal or earth acts the part of a combustible ; for both contain light as a component part. The instant of combination, the sul- phur or phosphorus combines with the metal or earth ; while the caloric of the one, uniting to the light of the : other, flies oiF in the form of fire. The process there- fore may be called semicombustion, indicating by the term that it possesses precisely one half of the charac- teristic marks x>f combustion. To estimate the quantity of heat evolved during the burning of different combustibles is not only important in a philosophical point of view, but of considerable consequence also as an object of economy. A set of ex- periments on this subject was made by Lavoisier and Laplace* They burnt various bodies in the calorime- ter, and estimated the heat evolved by the quantity of ice melted in each experiment. Dr Crawford made a similar set of experiments. He estimated the heat e- volved by the increase of temperature which the water experienced with which he contrived to surround the burning bodies *. A still more numerous set of expe- riments has been made by Mr Dalton, chiefly on the heat evolved during the combustion of gaseous bodies, * See his experiments on animal heat, p. 454, 330, COMBUSTION. He filled a bladder capable of holding 30,000 grains of Chap.li. water with the gas : this bladder was fitted with a stop- cock and a pipe. A tinned vessel was procured capa- ble of holding 30,000 grains of water ; the specific heat of which being ascertained, and as much water ad- ded as made the specific heat of both equivalent to that of 30,000 grains of water, the gas was squeezed out of the - bladder, lighted, and the extremity of the flame made to play upon the bottom of the tinned vessel. The quantity of heat evolved was estimated by the increase of tempera- ture produced upon the water in the vessel *. The fol- lowing Table exhibits the result of all these experi- ments, estimating the heat evolved by the quantity of ice which it would melt. The first column gives the sub- stance burnt, and one pound weight is always supposed to be consumed ; the second, the weight of oxygen in, Ibs. which unites with the combustible during the pro- cess ; and the third the weight of ice in Ibs. which was melted, according to the different experimenters. * Dalton'* New System of Chemical PbU caloric or a body to be diminished without an evolution of caloric taking place at the same time. 5 These observations are sufficient to explain why 15 OCCaSLOil* J ed hyper- caloric is evolved by percussion. It is forced out from ciission. the particles of the body struck with which it was for- merly combined. But a part of the caloric which is evolved after percussion often originates in another manner. By condensation, as much caloric is evolved as is sufficient to raise the temperature of some of the particles of the body high enough to enable it to com- bine with the oxygen of the atmosphere. The combi- nation actually takes place, and a great quantity of ad- ditional caloric is separated by the decomposition of the gas. Thai this happens during the collision of flint and steel cannot be doubted ; for the sparks produced are merely small pieces of iron heated red hot by uni* ting with oxygen during their passage through the air, as any one may convince himself by actually examin- ing them. Mr Hawksbee f and others have shown, that iron produces no sparks in the vacuum of an air- pump ; but Mr Kir wan affirms, that they are produced under common spring water, It is not so easy to account for the emission of calo- ric on the percussion of two incombustibles. In the last Chapter, mention was made of the light emitted durirg the percussion of two stones of quartz., flint, felspar, or any other equally hard. Caloric is also emitted durirg this percussion, as is evident from the whole of the phenomenon. Mr T. Wedgewood found, * T, Wtcigefvpcd, PLU. Trans. 1792. f ibid. HIV. 3i6j YRICTIOtf* that a piece of window-glass, when brought in contact with a revolving wheel of grit, became red hot at its point of contact, and gave off particles which set fire to gunpowder and to hydrogen gas *. We must either suppose that all the caloric is produced by mere con. densation, which is not probable, or acknowledge that we cannot explain the phenomenon. This is almost the only instance of the evolution of caloric and light where the agency of oxygen cannot be demonstrated or even rendered probable. The luminous appearance which follows the percus- sion of certain bodies in vacua, or in bodies which are not capable of supporting combustion, seems to be con- nected with electricity ; for Mr Davy has observed that all such bodies are electrics. They are frequently also phosphorescent ; which property may likewise contri- bute to the effect f. IV. FRICTION. CALORIC is not only evolved by percussion, but also by friction. Fires are often kindled by rubbing pieces friction. of dry wood smartly against one another. It is well known that heavy-loaded carts sometimes take fire by the friction between the axle-tree and the wheel. Now N c owing to condcn- in what manner is the caloric evolved or accumulated sation, by friction ? Not by increasing the density of the bo- dies rubbed against each other, as happens in cases of percussion; for heat is produced by rubbing soft bodies * Pkil. Trtnt. I?5>J, p, 45. J Jtur. nfttt JRtyfl Inttit. i, a 616 SOURCES OF &or to de- crease of pecific ca- loric. Book T. against each other ; the density of which therefore can- Division II. ' T - not be increased by that means, as any one may con- vince himself by rubbing his hand smartly against his coat. It is true, indeed, that heat is not produced by the friction of liquids ; but then they are too yielding to be subjected to strong friction. It is not owing to the specific caloric of the rubbed bodies decreasing ; for Count Rumford found that there was no sensible de- crease *, nor, if there were a decrease, would it be suf- ficient to account for the vast quantity of heat which is sometimes produced by friction. Count Rumford took a cannon cast solid and rough as it came from the foundry ; he caused its extremity to be cut off, and formed, in that part, a solid cylinder attached to the cannon 7j inches in diameter and 9^ inches long. It remained joined to the rest of the me- tal by a small cylindrical neck. In this cylinder a hole was bored 3' 7 inches in diameter and 7*2 inches in length. Into this hole was put a blunt steel borer, which by means of horses was made to rub against its bottom ; at the same time a small hole was made in the cylinder perpendicular to the bore, and ending in the solid part a little beyond the end of the bore. This was for introducing a thermometer to measure the heat of the cylinder. The cylinder was wrapt round with flannel to keep in the heat. The borer pressed against the bottom of the hole with a force equal to about 10,000 Ibs. avoirdupois, and the cylinder was turned round at the rate of 32 times in a minute. At the be- ginning of the experiment the temperature of the cy~ * Nicholson's Jou rttal, ii. 106. FRICTIOK. 017 was 60 ; at the end of 30 minutes, when it had made 960 revolutions, its temperature was 130. The quantity of metallic dust or scales produced by this fric- tion amounted to 837 grains. Now, if we were to sup- pose that all the caloric was evolved from these scales, as they amounted to just 7 ^ T part of the cylinder, they must have given out 948 to raise the cylinder 1, and consequently 6b360 to raise it 10 Q or to 130, which is certainly incredible *. Neither is the caloric evolved during friction owing Nor to to the combination of oxygen with the bodies them- tion . selves, or any part of them. By means of a piece of clock-work, Mr Pictet made small cups (fixed on the axis of one of the wheels), to move round with consi- derable rapidity, and he made various substances rub against the outsides of these cups, while the bulb of a very delicate thermometer placed within them marked the heat produced. The whole machine was of a size sufficiently small to be introduced into the receiver of an air-pump. By means of this machine a piece of a- damantine spar was made to rub against a steel cup in air : sparks were produced in great abundance during the whole time, but the thermometer did not rise. The same experiment was repeated in the exhausted recei- ver of an air-pump (the manometer standing at four lines) ; no sparks were produced, but a kind of phos- phoric light was visible in the dark. The thermometer did not rise. A piece of brass being made to rub in the same manner against a much smaller brass cup in air, the thermometer (which almost filled the cup) rose * Nicholson's Journal* n. 106. 18 SOURCES OF CALORIC, Book T, o*3 9 , but did not begin to rise till the friction was over. Division II. _, <_ Y-~-J I his shows us that the motion produced in the air car- ried off the caloric as it was evolved. In the exhausted receiver it began to rise the moment the friction began, and rose in all 1*2. When a bit of wood was made to rub against the brass cup in the air, the thermometej- rose 0*1, and on substituting also a wooden cup it rose 2*1, and in the exhausted receiver 2'4, and in air con- densed to l atmospheres it rose 0'5 *. If these experiments be not thought conclusive, I have others to relate, which will not leave a doubt that the heat produced by friction is not connected with the de- composition of oxygen gas. Count Rumford contrived, with his usual ingenuity, to inclose the cylinder above described in a wooden box filled with water, which ef- fectually excluded all air, as the cylinder itself and the borer were surrounded with water, and at the same time did not impede the motion of the instrument. The quantity of water amounted to IS'lllbs. avoirdupois, and at the beginning of the experiment was at the tem- perature of 60. After the cylinder had revolved for an hour at the rate of 32 times in a minute, the tempe- rature of the water was 107 j in 30 minutes more it was 178 ; and in two hours and 30 minutes after the experiment began, the water actually lotted. According to the computation of Count Rumford, the caloric pro- duced would have been sufficient to heat 26'58lbs. a- voirdupois of ice cold water boiling hot ; and it would have required nine wax-candles of amoderate size, burn- ing with a clear flame all the time the experiment last- * Pictct, wr le Feu, cb, ix. FRICTION. 619 ed to have produced as much heat. In this experiment Chap, all access of water into the hole of the cylinder where the friction took place was prevented. But in another experiment, the result of which was precisely the same, the water was allowed free access *. The caloric, then, which appears in consequence of And conse- friction, is neither produced by an increase of the den- present in- sity, nor by an alteration in the specific caloric of the substances exposed to friction, nor is it owing to the de- composition of the oxygen of the atmosphere Whence then is it derived ? This question cannot at present be answered : but this is no reason for concluding, with Count Rumford, that there is no such substance as ca- loric at all, but that it is merely a peculiar kind of mo- tion ; because the facts mentioned in the preceding part of this Chapter demonstrate the existence of caloric as a substance. Were it possible to prove that the accu- mulation of caloric by friction is incompatible with its being a substance, in that case Count Rumford's conclu- sion would be a fair one ; but this surely has not been done. We are certainly not yet sufficiently acquainted with the laws of the motion of caloric, to be able to af- firm with certainty that friction cannot cause it to ac- cumulate in the bodies rubbed. This we know at least to be the case with electricity. Nobody has been hi- therto able to demonstrate in what manner it is accu- mulated by friction ; and yet this has not been thought a sufficient reason to deny its existence. Indeed there seems to be a very close analogy be* tween caloric and electric matter. Both of them tend * Nicholson's Journal, ii. 106. $20 SOURCES OF CALORIC. Book T. to diffuse themselves equally, both of them dilate bo- TN* * " t T T . 1V1S |" ' dies, both of them fuse metals, and both of them kindle Analogy combustible substances. Mr Achard has proved, that between ca- loric and e- electricity can be substituted for caloric even in those cases where its agency seems peculiarly necessary ; for he found, that by constantly supplying a certain quan- tity of the electric fluid, eggs could be hatched just as when they are kept at the temperature of 103. An accident indeed prevented the chickens from actually corning out ; but they were formed and living, and with- in two days of bursting their shell. Electricity has al- so a great deal of influence on the heating and cooling of bodies. Mr Pictet exhausted a glass globe, the ca- pacity of which was 1200*199 cubic inches, till the ma- nometer within it stood at 1*75 lines. In the middle of this globe was suspended a thermometer, which hung from the top of a glass rod fixed at the bottom of the globe, and going almost to its top. Opposite to the bulb of this thermometer two lighted candles were pla- ced, the rays of which, by means of two concave mir- rors, were concentrated on the bulb. The candles and the globe were placed on the same board, which was supported by a non-conductor of electricity . Two feet and a half from the globe there was an electrifying ma- chine, which communicated with a brass ring at the mouth of the globe by means of a metallic conductor. This machine was kept working during the whole time of the experiment; and consequently a quantity of elec- tric matter was constantly passing into the globe, which, in the language of Pictet, formed an atmosphere not on- ly within it, but at some distance round, as was evident from the imperfect manner in which the candles burned. When the experiment began, the thermometer stood at 621 49 % B. It rose to 70*2 in 732". The same experiment was repeated, but no electric matter thrown in j the ther- mometer rose from 49'8 to 70*2 in 1050" ; so that the electricity hastened the heating almost a third. In the first experiment the thermometer rose only to 71*3, but in the second it rose to 77. This difference was doubt- less owing to the candles burning better in the second than the first experiment ; for in other two experiments made exactly in the same manner, the maximum was equal both when there was and was not electric matter present. These experiments were repeated with this difference, that the candles were now insulated, by pla- cing their candlesticks in vessels of varnished glass. The thermometer rose in the electrical vacuum from 52' 2 to 74*7 in 1050" ; in the simple vacuum in 965". In the electrical vacuum the thermometer rose to 77 ; in the simple vacuum to 86. It follows from these ex- periments, that when the globe and the candles com- municated with each other, electricity hastened the heat- ing of the thermometer ; but that when they were in- sulated separately, it retarded it *. One would be apt to suspect the agency of electricity in the following ex- periment of Mr Pictet : into one of the brass cups for- merly described, a small quantity of cotton was put to prevent the bulb of the thermometer from being broken. As the cup turned round, two or three fibres of the cotton rubbed against the bulb, and without any other friction the thermometer rose five or six degrees. A greater quantity of cotton being made to rub against the bulb, the thermometer rose 15 f. * Pictet tur It Feu, chap. vi. f Ibid, chap, ix. <322 SOURCES OP CALORIC. Book I. Division II. I do not mean to draw any other conclusion from these facts, than that electricity is very often concerned in the heating of bodies, and that probably some such agent is employed in accumulating the heat produced by friction. Supposing that electricity is actually a substance, and taking it for granted that it is different from caloric, does it not in all probability contain ca- loric as well as all other bodies ? Has it not a tendency to accumulate in all bodies by friction, whether conduc- tors or non-conductors ? May it not then be accumu- lated in those bodies which are rubbed against one ano- ther ? or, if they are good conductors, may it not pass through them during the friction in great quantities ? May it not part with some of its caloric to these bodies, either on account of their greater affinity or some other cause ? and may not this be the source of the caloric which appears during friction ? V. MIXTURE. Mixtures Water-es- sential. IT is well known that in a vast number of cases, when two substances enter into a chemical union, a change of temperature takes place. In some instances the mix- ture becomes colder than before, while in others it be- comes much hotter. In the third division of the pre- ceding Section, a very copious list has been given of the first set of mixtures. It remains for us to consider the nature of the second set, and to endeavour, if possible, to ascertain the cause of the change of temperature. 1. It deserves particular attention, that water consti- tutes an essential part of almost all mixtures in which a change of temperature takes place. The most remark- MIXTURE. fluidity or density of the two bodies before mixture, theft the temperature sinks; but when the fluidity or the den- sity of the new compound is less than that of the two bo* dies before mixture, the temperature rises ; and the rise is pretty nearly proportional to the difference. Thus And the when snow and common salt are mixed together, they gradually melt, and assume the form of a liquid. Du- ring the whole process of melting, the temperature con- tinues at zero or lower ; but 'whenever the solution is 624 SOURCES OF CALORIC. Book I. Division II. Solidifica- tion of wa- ter evolves heat. Depends on latent heat. completed, the temperature rises. On the other hand> when spirits and water are mixed together, a condensa- tion takes place ; for the specific gravity is greater than the mean. Accordingly the mixture becomes hot. When four parts of sulphuric acid and one part of water are mixed together, the density is very much increased ; ac- cordingly the temperature of the mixture suddenly ri- ses to about 300. 4. We now see the reason why those salts which contain water in abundance produce cold during their solution : the water, while it constituted a part of them, was in a solid state ; but when the salt is dissol- ved, it becomes liquid. Since these salts, if they be de- prived of their water, produce heat during their solu- tion, it cannot be doubted that the water, before it dis- solves them, combines first with them, so as to form a solid, or at least a solution of considerably greater den- sity. 5. Whenever water is solidified, a considerable pro* portion of heat is evolved. Hence the reason that a great deal of heat is produced by sprinkling water upon quicklime. A portion of the water combines with the lime, and forms with it a dry powder totally destitute of fluidity. For the same reason heat is produced when quicklime is thrown into sulphuric acid. 6. The whole of these phenomena, and likewise the evolution of heat during putrefaction and fermentation, are sufficiently explained by Dr Black's theory of latent heat. Fluidity, in all cases, is produced by the combi- nation of caloric with the body that becomes fluid. Hence a mixture, when it becomes fluid, must absorb ca- loric j which is the same as saying that it must produce cold. On the other hand, when a fluid body becomes MIXTURES 625 solid, heat must be evolved ; because a fluid can only ^hap. IT. become solid by parting with its caloric of fluidity. But the application of the theory to all cases of changes in temperature by mixture is so obvious, that it is quite unnecessary to give any farther illustration. 7. In most combinations which evolve heat or cold, a change takes place in the specific caloric of the bo- dies combined. To this change Dr Irvine ascribed the whole of the heat or cold evolved. Though he ap- pears to me to have carried this doctrine too far, the change must doubtless be allowed to have considerable effect. SUCH is the present state of our knowledge respecting the sources of caloric, one of the most interesting part? of the science. It is perhaps the most intricate part also. Hence the doubt and uncertainty in which it is still involved, notwithstanding the industry and abili- ties which have been employed in clearing them up. It deserves attention, that the sources of light and heat are exactly the same ; and that these two bodies affect aU ways to accompany one another. . /, R r 626 SIMPLE BODIES, Book I. Division II. CHAP. III. OF SIMPLE BODIES IN GENERAL, WE have now finished the examination of both divi- sions of Simple Bodies. Their number amounts to 37. But all the substances which chemists have not yet suc- ceeded in decompounding are by no means included in this first Book. Eleven metallic substances have been omitted for reasons formerly specified, and there are two acids besides, with the bases of which we are not yet ac- quainted. So that the number of undecompounded bo- dies at present known amounts to about 50. The 31 simple substances, in the order in which I have described them, are all concerned in combustion, and contribute to explain it. The knowledge of their properties is necessary to understand that complicated process ; and considered in this point of view, they constitute a beautiful whole, which has much more of scientific arrangement than any other part of chemistry is yet capable of assuming. Let us consider them a lit- tle in that point of view. Oxygen is capable of uniting with all the other sim- ple confinable bodies, and it unites with them all in dif- ferent proportions. With the simple incombustible bo- dies it uaites without the extrication of heat or light ; IN GENERAL. 627 and th ew compounds are all supporters of combus- Chap. III. tion. With the simple combustibles it unites, and the union is accompanied by the extrication of heat and light ; and the compounds are products of combustion. With the metals it unites both with and without the ex- trication of heat and light, and two classes of compounds are formed ; namely, products and supporters. The simple unconfinable bodies are always extricated during combustion. Thus combustion is occasioned by the mutual action of the simple confinable bodies on each other ; and the consequence of this action is the extri- cation of the simple unconfinable bodies. It deserves attention, that the metals and simple com- May be di- vided into bustibles approach each other by insensible degrees in f ou r classes. their properties. Thus the difference between the pro- perties of arsenic and sulphur is by no means so great as between those of arsenic and gold : they might there- fore, without any great impropriety, be reductd under one class. In that case we would have the whole con- finable bodies divided into three sets ; namely, 1. Sup- porters ; 2. Combustibles ; and, 3. Incombustibles. The union of the first and second constitutes products ; of the first and third supporters. Such is the present state of our knowledge of simple substances. But it w r ill be worth while to take a view of the theories of the ancients, the various modifications which they underwent, and the steps by which chemists have been gradually led to the opinions at present re- ceived. It seems to have been an opinion established among Elementsof philosophers in the remotest ages, that there are only thcanciems * four simple bodies: namely, fire, air, water, and earth. To these they gave the name of elements, because they Rr 2 SIMPLE BODIES f Book T. believed that all substances are composed of these four, Division H. . . . ,/-, . ' <__ yj Ihis opinion, variously modified indeed, was maintain- ed by all the ancient philosophers. We now know that all these supposed elements are compounds : fire is com- posed of caloric and light ; air of oxygen and azotic gases ; water of oxygen and hydrogen 5 and earth, as will appear afterwards, of nine different substances. Elements of The doctrine of the four elements seems to have con- knttt* ' tinned undisputed till the time of the alchymists. These men having made themselves imich better acquainted with the analysis of bodies than the ancient philoso- phers had been, soon perceived that the common doctrine was inadequate to explain all the appearances which were familiar to them. They substituted a theory of their own in its place. According to them, there are three elements, of which all bodies are composed ; name- ly, salt, sulphur, and mercury, which they distinguished loy the appellation of the triaprima. These principles were adopted by succeeding writers, particularly by Paracelsus, who added two more tp their number; namely, phlegm and caput mortui, It is not easy to say what the alchymists meant by salt, sulphur, and mercury : probably they had affixed no precise meaning to the words. Every thing which is fixed in the fire they seem to have called salt, every inflammable substance they called sulphur, and every substance which flies ofF without burning was mercury.. Accordingly they tell us, that all bodies may by fire be decomposed into these three principles ; the salt re- mains behind fixed, the sulphur takes fire, and the mer- cury flies of in the form of smoke. The phlegm and caput mortuum of Paracelsus were the water and earth of the ancient philosophers. IN GENERAL. 629 Mr Boyle attacked this hypothesis in his Sceptical Chap. III. Chemist, and in several of his other publications ; proved that the chemists comprehended under each of the terms salt, sulphur, mercury, phlegm, and earth, substances of very different properties ; that there is no proof that all bodies are composed of these principles ; and that these principles themselves are not elements but compounds. The refutation of Mr Boyle was so complete, that the hypothesis of the trio, prima seems to have been almost immediately abandoned by all parties. Meanwhile a very different hypothesis was proposed Altered by by Beccher in his Physica Subterranea ; a hypothesis to, which we are indebted for the present state of the science, because he first pointed out chemical analysis as the true method of ascertaining the elements of bodies. According to him, all terrestrial bodies are composed of water, air, and three earths ; namely, the fusible, the inflammable or sulphureous, and the mercurial. The three earths, combined in nearly equal proportions, compose the metals ; when the proportion of mercurial earth is very small, they compose stones ; when the fu- sible predominates, the resulting compounds are the precious stones ; when the sulphureous predominates, and the fusible is deficient, the compounds are the co- lorific earths; fusible earth and water compose a uni- versal acid, very much resembling sulphuric acid, from which all other acids derive their acidity ; water, fu- sible earth, and mercurial earth, constitute common salt; sulphureous earth and the universal acid form sul- phur. Stahl modified the theory of Beccher considerably. And Stahl. He seems to have admitted the universal acid as an ele- ment j the mercurial earth he at last discarded altoge- 30 SIMPLE BODIES Beniate, iii. 47 azotite, ii. 159 benzoate, iii. 70 borate, ii. 612 eamphorate, iii. 75 carbonate, ii. 640 chromate, iii. 57 citrate, iii. 102 columbate, iii. 58 uuate, ii. 605 .gallate, iii. 115 Potash, hydrosulphurtt, iii. 377 hyperoxymuriate, iii. 38 malate, iii. 110 mellate, iii. S9 moiybdate, iii. muriate, ii. 574 nitrate, iii. 10, audit. 376 nitrite, iii. 34 oxalate, iii. 81 phosphate, ii. 619 phosphite, ii. 634 prussiate, iii. 117 quadroxalate, iii. 83 saccolate, iii. 107 sebate, iii. 108 silicated, ii. 100 soap of, iii. 401 auccinate, iii. 71 subcarbonate, ii. 590 suberate, iii. 113 sulphate, ii. 659 sulphite, iii. '.: Fuper-arseniate, iii. 47 superoxalate, iii. 82 superphosphate,ii.609 supersulphate, ii. 660 supertartrate, iii. 92 tartrate, iii. 91 tungstate, iii. 54 nitrated,iii. 56 urate, iii. 108 Potassium, ii. 33 action of, in salts v. 807 Potato, v. 272 Potential cautery, ii. 28 Pots, ii. 541 Pot^tone, iv. f'OS Pounxii, if Powder ot'aigoroth, i. 315 653 INDEX, Prase, iv. 253 Precipitate per se, f. 177 Precipitants, table of, iii. 664? Precipitation, iii. 675 Prehnite, iv. 273 Prince's metal, i. 296 Principle, vegetative, v. 383 animal, v. 755 Products of combustion, i. 603 Propolis, v. 482 Prostate concretions, v. 661 Protoxide, i. 142 Prussian alkali, ii. 365 blue, ii. 363 native, iv. 4-56 Prussiate of ammonia and iron, iii 127 barytes and iron, iii. 119 lime and iron, iii. 120 magnesia and iron, iii. 127 potash and iron, iii. 121 soda and iron, iii. 1 26 strontian and iron, iii. 120 Pnissiates, iii. 116 Prussic acid, ii. 362, and iii. 547, and v. 823 plants containing it, iv. 644 Pmssous acid, v. 823 Pulmonary concretions, v. 660 Pumice, iv. 270 Purple of amorgos, v. 284 Putrefaction, v. 426 in air, v. 759 under ground, v. 761 of accumulated matters, v. 762 preventatives from, v. 764 Pus, v. 691 Pus, how distinguished from mucus, v. 693 Pyrites, i. 230, and iv. 437 magnetic, iv. 439 arsenical, iv. 497 capillary, v. 844 cppper, L 210, and iv. 420 Pyro-acetic spirit, v. 818 Pyrolignous acid, ii. 353 Pyromachus, iv. 256 Pyrometer of Wedgewood, ii. 81 Pyromucous acid, ii. 353 Pyrophori, i. 410 Pyrophorus, Homberg's,iu675 Canton's, i. 410 Pyrophysalite, iv. 236 Pyrotartarous acid, ii. 318 and 353, and iii. 93, and v. 82* Pyroxen, iv. 215 Pyrop, iv. 223 Q Quartz, iv. 250 milk, iv. 252 Quassia, experiments on its in- fusion, v. 31 Queen's ware, ii. 542 Quercitron, v. 221 Quicklime, ii. 47 Quicksilver, i. 172 Quinquina, v. R Radiant heat, i. 439 Radiating power of bodies, i. 442 Radical vinegar, ii. 282 Radicle, v. 297 Rain, iv. 80 quantity of, iv. 83 INDEX. 659 Rancidity, ii. 498 Kay* of light, i. 4-08 caloric, i. 4-25 Kayonnante, iv. 332 Realgar, i. 332, and iv. 499 Red antimonial ore, iv. 492 cobalt ore, iv. 507 copper ore, iv. 425 chalk, iv. 449 flowers, v. 232 iron ore, iv. 443 lead, i. 275 lead ore of Siberia, iv. 472 ochre, iv. 444 ore of manganese, iv. 512 precipitate, i. 177 sanders, v. 208 silver ore, iy. 405 Reddle, iv. 449 Reduction, i. 134 Reflection of heat, i. 446 light, i. 406 Refraction of light, i. 405 Regulus of antimony, i. 312 martial, i. 322 of Venus, i. 321 Repulsion, iii. 435 Resin, v. 91 Botany Bay, v. 96 from bitumen, v. 1 1 1 green, v. 100 of bile, v. 478 of urine, v. 635 Pesins, v. 83 animal, v. 478 Respiration, v. 714 of fishes, v. 728 Priestley's theory, of, v. 734 Lavoisier's theory of, v. 735 Lagrange's the- ory of, v. 735 changes on air by, v. 720 Respiration, changes on blood by, v. 731 Respirations, number of, v. 718 Rete mucosum, v 534 Retinasphaltum, ii. 509, and iv. 384 Rhodium, i. 192 salts of, iii. 191 Rhomb spar, iv. 353 Rhubarb, v. 201 Rke, v. 254 Roasting, i. 319 Rock crystal, iy. 252 soap, iv. 318 Rocks, iv. 531 structure of, iv. 532 Roestpne, iv. 345 Roots, v. 196 absorb oxygen, v. 369 Rosa mallos, v. 127 Rosacic acid, v. 489 Rosin, v. 91 Rouge, v. 234 Ruby, iv. 225, 227 balass, iv. 225 occidental, iv. 234 octahedral, iv. 225 oriental, iv. 227 spinell, iv. 225 Rum, ii. 410 Rust, iii. 234 Ruthile, iv. 522 Rutilite, iv. 524? Rye, v. 246 Sacar-nambu, iv. 671 Saccharine acid, ii. 305 Saccolates, iii. 107 Saclactic acid, ii. 327, and v. 821 Saffron, v. 238 of Mars, i. 222 Sagapenum, v. 145 660 INDEX. Sagenite, iv. 522 Sago, iv. 708 Sahlite, iv. 336 Sal alembroth, iii. 187 ammoniac, ii. 579 secret, ii. 663 catharticus amarus, ii. 665 de duobus, ii. 659 gem, ii. 577 mirabile, ii. 661 polychrest Glaseri, ii. 659 perlatum, ii. 621 Salifiable bases, i. 3. Saline solutions, action of salt on, iii. 585 table of,iii.577 freezing of, L 519 Saliva, v. 581 of the horse, v. 583 Salivary concretions, v. 659 Salop, iv. 709 Salsola, ii. 39 Salt, ii. 565 arsenical, neutral, iii. 47 common, ii. 577 digestive, ii. 574 of Sylvius, iii. 59 diuretic, iii. 59 Epsom, ii. 665 febrifuge, ii. 574 Glauber's, ii. 661 microcosmic, ii. 625 narcotic, ii. 222 of amber, ii. 297 of Saturn, iii. 271 of Seignette, iii. 96 of Sylvius, ii. 574 of tartar, ii. 27 of wisdom iii. 187 of wood sorrel, iii. 82 perlated, ii. 621 Rochelle, iii. 96 sedative, ii. 222 Salt, Seydler, ii. 665 petre, iii. 10 regenerated sea, ii. 574 rock, iv. 379 sulphureous, of Stahl,iii.3 Salts, ii. 565, and iv. 408, and v. 828 alkaline and earthy, ii. 570 calcareous, iv. 342 combustible, iii. 59 compound, ii. 565 incombustible, ii. 574 metalline, iii. 127 neutral, ii. 566 nomenclature, ii. 568 simple, ii. 565 solubility in alcohol, ii. 429 solubility in water, iii. 577 and 672 triple, ii. 567 food of plants, v. 318 Sandarach, v. 94 Sandaracha, i. 320 Sandstone, iv. 559 Sap of plants, v. 183 and 331. motion of, v. 330 Saponaceous extract of urine, v. 463 matter of putre- faction, v. 762 Saponules, ii. 484 Sappare, iv. 335 Sapphyr, iv. 227 oriental, ibid, occidental, iv. 23 i Sarcocoll, iv. 673 Saturation, iii. 631 Saturn, i. 298 sugar of, iii. 271 extract of, iii. 275 Saussurite, iv. 326 Savonule, ii. 483 Scales offish, v. 521 IND' X. 661 Scales of serpents, v. 522 Scammony, v. 146 Scapolite, iv. 291 Schalstone, iv. 337 Schaumearth, iv. 349 Scheelium, i. 372 Schiefer spar, iv. 349 Schillerstone, iv. 327 Schmeltzstein, iv. 280 Schrifterz, iv. 494 Scorpion, venom of, v. 620 Sea-froth, iv. 321 salt, ii. 577 salt, regenerated, ii. 57* wax, ii. 504 Seas, temperature of, iv. G6 Sebacic acid, ii. 293 Sebates, lii. 108 Secretions, v. 496 morbid, v. 690 Sedative salt, ii. 222 Seeds of plants, v. 243 Selenite, ii. 679, and iv. 363 Semen, v. 607 Semimetals, i. 145 Semiopal, iv. 261 Senna, v. 225 Serpentine, iv. 327, 548, 551 Serosity, v. 557 Serum of blood, v. 557 Seydler salt, ii. 665 Shale, iv. 304 Shells, v. 507 porcellaneous, v. 509 mother-of-pearl, v. 509 Shistus, argillaceous, iv, 305 Shorl, iv. 242 common, iv. 243 red, iv. 522 white, iv. 238 Shorlite, iv. 241 Siberite, iv. 245 Siderite, iv. 283 Siderocalcite, iv. 352 Siderum, i. Sienite, iv. 551 Silica, ii. 96 borate of, ii. 617 chromate of, iii. 58 fluate of, ii. 610 Silicated potash precipitates gum, iv. 681 Silicium, ii. 105 Silk, v. 550 Silver, i. 165 alloys of, i. 170, 191, 195, 200, 214, 248, 265, 281, 294, 310, 321, 335, 344, 367, 9 375 salts of, iii. 145 acetate, iii. 157 amalgam of, iv. 412 antimonial, iv. 401 arseniate, iii. 160 arsenical, iv. 402 auriferous, iv. 401 benzoate, iii. 158 black, iv. 410 borate, iii. 157 carbonate, iii. 156, and iv. 410 chromate, iii. 161 citrate, iii. 159 fluate, iii. 157 fulminating, ii. 13 glance, iv. 403 hyperoxymuriate, lit. 150 malate, iii. 159 mellate, iii. 159 molybdate, iii. 161 muriate, iii. 151, and iv. 408 native, iv. 400 nitrate, iii. 146 ores of, iv. 400 oxalate, iii. 158 oxides, i. 167 phosphate, iii. 15o 6G2 INDEX. Silver, saccolate of, iii. 159 soap, iii. 407 succinate, iii. 158 sulphate, iii. 154 sulphite, iii. 155 sulphuret, iv. 403 tartrate, iii. 158 white, ore, iv. 404 Silvery looking glasses, i. 266 Simple combustibles, i. 30 incombustibles, i. 113 substances, i, 16 supporters, i. 19 Smovia, v. 603 Size, v. 439 Skin, v. 528 whether it absorbs, v. 744 Slate, adhesive, iv* 299 drawing, iv. 304 polishing, iv. 299 whet, iv. 304 Slate clay, iv. 298 spar, iv. 340 Smaragdite, iv. 333 Soap, iii. 396 hard, iii. 397 soft, iii. 401 Starkey's, ii. 484 Soaps, iii. 396 alkaline, iii. 396 acid, ii. 485, 497 earthy, iii. 4-04 metallic, iii. 405 Soda, ii. 39 acetate of, iii. 61 arseniate, iii* 48 axotite, ii. 160 benzoate, iii. 70 borate, ii. 612 camphorate, iii* 76 carbonate, ii* 643, and iv. 377 chromate, iii. 57 . citrate, iii. 108 Soda, fluatc of, ii. 606 gallate, iii. 115 hydrosulphuret, iii. 378 hyperoxymuriate, iii. 41 malate, iii. 110 mellate, iii. 90 molybdate, iii. 52 muriate, ii. 576, and iv. 379 nitrate, iii. 16 oxalate, iii. 83 phosphate, ii. 620 phosphite, ii. 635 prussiate of* iii. 117 saccolate, iii. 108 feoap of, iii. 397 sub-borate, ii. 613 subcarbonate, ii. 644 suberate, iii. 118 succinate, iii. 72 sulphate, ii. 661 sulphite, iii. 4 supersulphate, ii. 663 tartrate, iii. 95 tungstate, iii. 54 unite, iii. 109 how extracted from common salt, ii. 596 Sodium, ii. 41 Softness, i. 532 Soil, v. 314 Solids, iii. .593 table of, iii. 623 expansion of, i. 495 specific gravity of, iiL 624 combination of, iii. 623 Solution, iii* 568 Sommite, iv. 238 Sooty silver ore, iv. 410 Sory, iii. 223 So wins, iv. 709 Spar, ponderous, iv. 368 fluor, iv. 350 calcareous, iv. -846 INDEX. 665 Sparry iron ore, iv. 4-46 Spath perle, iv. 352 Specific caloric, i. 548 Specificum purgans, ii. 659 Spectrum, prismatic, i. 4-08 Specular iron ore, iv. 441 Spelter, i. 286 Spermaceti, v. 4-72 oil, v. 476 Sphene, iv. 524- Spiders webs, v. 55 4 venom, v. 620 Spinell, iv. 225 Spirit of nitre, ii. 229 mindererus, iii. 62 sal ammoniac, ii. 6 salt,i. 117,andii.665 urine, ii. 6 wine, ii. 4-09 Spirit, proof, ii, 4-23 Spirits, ardent, ii. 410 rectified, ii. 410 Spodumene, iv. 292 Sponges, v. 518 Squills, v. 280 Starch, iv. 699 plants containing it, iv. 707 potato, iv. 708 Staurolite, iv. 278 Staurolithe, iv. 222 Staurotide, ibid. Steam, iL 117 elasticity of, i. 537 Steatite, iv. 322 Steel, i. 237 natural, i. 243 of cementation, i. 243 cast, i. 244 tempering, i. 223 Stibium, i. 312 Stilbite, iv. 276 Stinking sulphureous air, i. 90 Srones, analysis of, iv. 588 Stones, saline, iv. 340 earthy, iv. 201 from the atmosphere^ iv. 119 Stonewane, ii. 539 Storax, v. 129 Strahlstein,. iv, 332 Strontian, ii. 73 acetate of, iii. 66 borate, ii, 615 carbonate, ii. 653, and iv. 370 citrate, iii. 105 hydrosulphuretj iii, 377 gallate, iii. 115 hyperoxymuriate, iii. 4-5 muriate, ii. 589 nitrate, iii. 23 oxalate, iii. 87 phosphate, il 631 sulphate, ii, 684, and iv. 371 tartrate, iii. 99 urate, iii. 109 water, ii. 75 Strontianite, iv. 370 Strontites, ii. 74 Strontium, ii. 77 Styrax, v. 126 Subcarburets of iron, i. 246 Suber, v. 153 Suberates, iii. 113 Suberic acid, ii. 344, and v. 822 Subsalts, ii. 567 Subsoap, iL 484 Succinates, iii. 71 Succinic acid, ii. 297 Sugar, iv. 646 acid of, ii. 305 alcohol from, v. 412 cane, juice of, iv. 653 664 JXDhX. Sugar liquid, iv. 663 of beet, iv. 66G of diabetic urine, v. 471 of grapes, iv. 664 of lead, iii. 271 of milk, v. 469 acid of, ii. 328 of Saturn, ibid, plants containing, iv. 670 Sulphate of cobalt, iv. 507, and v. 844 indigo, v. 10 lead, iv. 473 zinc, iv. 484 Sulphates, ii. 658 uses of, ii. 685 Sulphites, iii. 1 Sulphur, i. 79, and v. 772 auratum, iii. 394 flowers of, i. 79 combustion of, i. 81 in animals, v. 486 native, iv. 382 Sulphureous salt of Stalil, iii. 3 Sulphuret of ammonia, ii. 9 antimony, i. 317 arsenic, i. 332 barytes, ii. 70 bismuth, i, 307, and iv. 485 cobalt, i. ' 42 copper, i. 208 gold, i. 154 iron, i. 229 lead, i. 278, and v. 784 lime, ii. 51 magnesia, ii. 62 manganese, i.350 mercury, i. 178 molybdenum, i. 366 muriatic acid, i. 125 Sulphuret of nickel, i. _'.>!< palladium, i. 190 phosphorus, i. 9o platinum, i. 163 potash, ii. 29 silver, i. 169 soda, ii. 40 strontian, ii. 76 tellurium, i. 325 tin, i. 261 tungsten, i. 374 uranium, i. 360 zinc, i. 292 Sulphureted hydrogen gas, i. 89, and iii. 471, 474 alcohol, ii. 427 azotic gas, i. 112 muriatic acid, i. 126 oxide of manga- nese, i. 350 oxide of tin,i. 263 Sulphurets, iii. 627 metallic, i. 395 Sulphuric acid, i. 81, ii. 177 glacial, ii. 197 phlogisticated, ii. 193 in animals, v. 487 Sulphurous acid, i. 87, and ii. 193 Sulphurs, i. 88 Sumach, v. 209 Sun, nature of, i. 583 emits three kinds of rays, i. 584 a source of heat, i. 584 heat of its rays, i. 586 Supercarbureted hydrogen, i. 56 Supersalts, ii. 567 Supersulphuret of copper,i.209 iron, i. 230 lead, i. 279 INDEX. Supersulphureted hydrogen, i. 9* Supporters of combustion, i. 602 partial, i. 603 Surface of minerals, iv. 190 Surturbrand, iv. 386 Swamp ore, iv. 4-52 Sweat, v. 624 Swimming bladders of fishes, air contained in, v. 621 Swinestone, iv. 354? Sylvanite, i. 324? Syrup, iv. 656 Tacamahac, v. 95 Tafelspath, iv. 337 Talc, iv. 328 Venetian, ibid. Talcite, iv. 328 Tallow, v. 4-73 mineral, ii. 504 Tamarinds, v. 270 Tannin, ii. 383, and v. 38 artificial, ii. 399 natural, ii. 385 species of, v. 4*0 Tanning, v. 531 principle, ii. 384 Tantalite, iv. 527 Tantalum, i. 387, and v. 791 ores of, iv. 527 Tar, mineral, ii. 507 Tartar, iii. 92 cream of, iii. 92 vitriolated, ii. 659 chalybeated, iii. 244? emetic, iii. 315 regenerated, iii. 59 of the teeth, v. 660 secret foliated earth of, iii. 59 salt of, ii. 27 and 640 Vol. I. Tartar, soluble, h'L 92 Tartarin, ii. 27 Tartaric acid, ii. 315 plants contain- ing it, iv. 640 Tartrates, iii. 91 Tears, v. 594 Tectum argenti, i, 304? Teeth, v. 506 Telesia, iv. 227 Tellurium, i. 323 salts of, iii. 317 muriate of, iii. 318 native, iv. 494 nitrate, iii. 318 ores of, iv. 493 oxides of, i. 324 sulphate, iii. 319 Temperature, equal distribu- tion of, i. 478 of the atmospliere, iv. 51 Tempering of steel, i. 223 Tenacity, i. 134 Tendons, v. 5:36 Terra ponderosa, ii. 66 Test, i. 277 Thallite, iv. 245 Thermometer explained,!, 497 differential,i.438 varieties of, i.499 Dalton s, i 501 Thermoxygen, i. 601 Thummerstone, iv. 247 Thus, v. 91 Tile ore, iv. 426 Tiles, ii. 540 Tin, i, 258 alloys, i. 263, 283, 297, 311, 322, 335, 344, 369, 375 salts of, iii. 245 acetate, iii. 256 arseniate, iii. 258 benzoate, iii. 257 Uu 666 INDEX. Tin, borate, iii. 255 carbonate, iii. 255 fluate, ibid. hydrosulphurets, iii. 390 muriated, iii. 248 nitrated, iii. 246 ores, iv. 461 oxalate, iii. 257 oxides of, i. 259 phosphate, iii. 254 pyrites, iv. 462 succinate, iii. 257 soap, iii. 407 sulphate, iii. 253 sulphite, iii. 254 tartrate, iii. 258 Tinea), ii. 221 and 613 Tinfoil, i. 258 Tinning, i. 269 Tinplate, i. 270 Tinstone, iv. 462 Titanite, iv. 522, 524 Titanium, i. 378 carbonate, iii. 349 muriate, iii. 348 nitrate, ibid, ores of, iv. 520 oxides of, i. 379 oxalate, iii. 349 salts of, iii. 347 sulphate, iii. 348 tartrate, iii. 349 Tobacco, v. 226 and 847 Tolu, balsam of, v. 122 Tombac, white, i. 335 Topaz, iv. 212, 234 occidental, iv. 234 oriental, iv. 227 rock, iv. 548 Saxon, iv. 234 Tortoise-shell, v. 521 Touchstone, iv. 256 Tourmaline, iv. 242 Tracheae, v. 333 Train oil, v. 476 Transmission of caloric, i. 457 Transparency, i. 407 Transpiration of plants, v. 347 Traps, primitive, iv. 545 floetz, iv. 565 transition, iv. 556 Tremolite, iv. 333 Tria prima of the alchymists, i. 628 Triphane, iv. 292 Tripoli, iv. 300 Trona, ii. 644 Truffles, v. 289 Tube of safety, ii. 229 Tufa, iv. 567 Tungstate of lime, iv. 519 Tungstates, iii. 53 Tungsten, i. 371 alloys, i. 374 salts of, iii. 346 ores of, iv. 518 oxides of, i. 373 Tungstic acid, ii. 266 Turmeric, v. 203 Turpentine, v. 91 Turpeth mineral, iii. 178 nitrous, iii. 166 Type metal, i. 322 U Ulcers in plants, v. 292 Ulmin, iv. 695 Umber, iv. 318 Unconfinable bodies, i. 401 Uran mica, iv. 515 ochre, iv. 516 Uranitic ochre, ibid. Uranium, i. 355 ores of, iv. 514 oxides of, i. 358 salts of, iii. 340 acetate, iii. 346 arseniate, ibid* INDEX. 6C7 Uranium, fluate of, ibid, muriate, iii. 344 nitrate, iii. 34-1 phosphate, iii. 346 sulphate, iii. 344 tartrate, iii. 346 Urates, iii. 109 Urea, v. 463 Uric acid, ii. 331 sublimate from, ii. 334 Urine, v. 630 fusible salt of, ii. 625 spirit of, ii. 6 changes produced on, by diseases, v. 641 of the ass, v. 644 camel, v. 645 cow, v. 645 guinea pig, v.647 horse, v. 643 rabbit, v. 647 Urinary calculi, v. 669 of inferior ani- mals, v. 687 Valerian, v. 204 Vapour, vesicular, iv. 69 explained, i. 533 elasticity of, i. 537 state of, in the atmo- sphere, iii. 46.3 Vapours, nature of, iii. 451 Varec, ii. 40 Variegated copper ore, iv. 419 Varnishing, v. 101 Vegalkali, ii. 27 Vegetable substances, iv. 635 Vegetables, iv. 635 ingredients of, iv. 637 decomposition of, V. 384 Vegetation, v. 295 Veins, iv. 574 Venus, i. 298 salts of, iii. 194 Verdigris, iii. 207 Vermilion, i. 180 Verjuice, iv. 664 Vessels of plants, v. 336 Vestium, v. 787 Vesuvian, iv. 216, 219 Vinegar, ii. 278 distilled, ii, 281 radical, ii. 278 of Saturn, iii. 275 of Venus, ii. 282 Viper, poison of, v. 617 Vital air, i. 24 Vitreous copper ore, iv. 418 silver ore, iv. 403 Vitriol, green, iii. 223 blue, iii. 201 white, iii. 292 Vitriolic acid, ii. 177 Volatile and volatilization, i. 80, and iii. 682 liniment, iii. 403 Volcanic ashes, iv. 574 Volcanite, iv. 215 Volta's eudiometer, i. 37, and v. 17 W Wacke, iv. 315 Wash, v. 409 Wasp, venom of, v. 620 Water, i. 35, ii. 116, and iv. 128 as the food of plants, v. 308 composition of, i. 35, and ii. 126 decomposed by iron, i. 218 of nitre, ii. 229 Uu2 6G8 INDEX, Water, expansion by cold, i. 503 sea, iv. 135 in the atmosphere, iv. 24 Waters, iv. 128 acidulous, iv. 151 aeratedalkaline,ii.211 analysis of, iv. 155 chalybeate, iv. 151 common, iv. 130 hepatic, iv. 152 mineral, iv. 143 rain, iv. 130 saline, iv. 152 snow, iv. 131 Wavellite, iv. 271 Wax, v. 59 myrtle, v. 64? punic, v. 61 Wedgewood ware, ii. 542 Wenurite, iv. 292 Wheat flour, v. 245 Whet slate, iv. 304 Whey, v. 572 Whisky, ii. 410 White cobalt ore, iv. 503 copper ore, iv. 420 flowers, v. 233 gold ore, iv. 494 lead, i. 274 lead ore, iv. 470 ore of antimony, iv. 491 silver ore, iv. 404 tombac, i. 335 Willow, v. 220 Winds, iv. 87 trade, iv. 88 velocity of, iv. 103 Wine, v. 415 essential salt of, iii. 59 its fermentation, v. 415 component parts, v. 418 Wines, table of their compo- nent parts, v. 421 Witherite, ii. 652, and iv. 367 Woad, v. 230 Wolf, i. 318 Wolfram, iv. 518 Wood, v. 154, 196 gas from, Yttria, ii; 88 acetate o iii. 67 arsemate, iii. 50 carbonate, ii. 655 muriate, ii. 592 hydrosulphuret, iii. 360 nitrate, ui. 26 oxalate, iii. 88 phosphate, ii. 632 suet-mate, iii. 73 sulphate, ii. 677 tartrate, iii. 100 Yttrotantalite, iv. 527 ' INDEX- 669 Zeolite, iv. 274- foliated, iv. 276 radiated, iv. 275 Zero, real, i. 564? Zinc, i. 285 alloys, i. 293, 322, 336, 369 salts of, iii. 289 acetate, iii. '298 arseniate, iii. 300 benzoate, iii. 298 borate, iii. 297 butter, iii. 291 carbonate, iii. 296 hydrous, 482 chromate, iii. COO citrate, iii. 299 flowers of, i. 289 fluate, iii. -^7 hycirosulphur-, % 'ii. lactate, iii. :juJ rrrlate, ibid. jnuiybdate, iii. 300 v. Zinc, muriate, iii. 290 nitrate, ibid, ores of, iv. 477 oxalate, iii. 299 oxides of, i. 288 phosphate, iii. 296 soap of, iii. 406 succinate, iii. 298 sulphate, iii. 291 sulphite, iii. 294 tartrate, iii. 299 tungstate, iii. 300 Zingiberic acid, v. 825 Zircon, iv. 208 Zi^ cilia, ii. 93 how freed from iron, ii. 594 acetate, iii. 67 cnrV'^iiiit.- a. 656 rii-t^, ii. L'j"2 nitrate, iii. 27 sulphate, ii. 678 Zirconium, ii. 96 Zoisite, iv. 246 Zoonic acid, ii. 352 Zoophites, v. 513 EDINBURGH* Printed by JOHN BROWK. r rJ I I i? FipJl RETURt ^'|C^ 642-3405 A!,!,IAMPm.civ7 BERKELEY, CA94720 BE ** U.C. BERKELEY LIBRARIE! n m