Elementary Lectures on Chemistry and Natural Hiftory. Tranflated from the French of M. Fourcroy. By Thomas Elliot. With many Additions, Notes, and Illuftrations, by the Tranflator. In Two Volumes. 8vo. 125. in Boards. Robinfon.

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F a science, improving with great rapidity, it is necessary, at different periods, to ascertain the ftate, by collecting what has been hitherto discovered, and pointing out those subjects which are imperfectly understood, and may repay the labour of the difcoverer by the importance of the acquifition. In England, a work of this kind was more wanted, fince the foreign chemifts have lately been very fuccefsful in particular branches of their art: the chemical mineralogy, which arofe under the auspices of Cronstedt, has flourished very successfully under thofe of Scheele, Bergman, and fome of the French chemifts; while we can claim the laurel for the dif covery of the different airs. Our labours have been extended through the continent, and received with avidity; but we have not been equally eager in appropriating the fuccefs of our competitors; and fome English works, in this luminous period of chemistry, have been lame, imperfect, or erroneous. Mr. Kirwan's mineralogy, and the tranflation of Bergman's Effays, have been valuable additions to this fcience, from fources to which we could not have easily had accefs; and the prefent volumes will alfo materially contribute to our knowlege. The characters of M. Bucquet, and of his favourite pupil M. Fourcroy, are well known; we are not therefore furprised to find the lectures before us equally accurate, clear, and comprehenfive. There are very few omiffions or errors, and many circumstances either ftated in a new light, or which have been hitherto little known. The notes of the translator are juft and valuable: fome of these feem to belong to the author; and no mark of diftinétion is fubjoined. The tranflation itself is not executed with elegance: in a few places it is unintelligible; but, in general, we cannot impeach its accuracy.

The plan of thefe Lectures is fimple, but not the most convenient. After examining what have been usually called the chemical elements, viz. fire, air, water, and earth, our author proceeds to the different fubjects of the mineral kingdom,' concluding with the mineral waters. He then confiders the vegetable and animal kingdoms. The great difadvantage of his plan is, that by this artificial arrangement, he separates fubjects the moft nearly allied. After he has explained the combinations of mercury, v. g. with the mineral acids, he leaves its relations to the oils and vegetable acids, till he ar rives at a very distant part of the work; and this is more inConvenient, as the aerial and marine acids' are, in fome re

fpects, very analogous in their action to the acetous. The chemical history of each fubject should have been completed under its proper head.

It is not eafy, in a work containing fo great a variety of fubjects, to give a regular analyfis. We fhall mention only fome of the peculiar features, which feem to pervade the whole, and influence the refemblance, as well as a few of the most important obfervations. We had lately fome occafion to hint at an hypothefis of Mr. Lavoifier, concerning the change which takes place in the combuftion of combustible, and the calcination of metallic fubftances. This has been usually attributed to the escape of phlogifton, a principle incomprehenfible in its properties, and which art has not been able to fix in a separate state*. Its exiftence was firft fuggefted by Stahl, and received with the reft of his reveries (for many of his chemical opinions, though very ingenious, deferve this title) by the elder French chemifts; and from them derived to their fucceffors, and to the English. Its escape seemed to increase the weight of bodies; and there was certainly a period when a principle, poffeffing specific levity, was not only hinted at, but attempted to be fupported by argument. This apparent abfurdity ftartled many refpectable philofophers; yet a flight attention to the experiments of Dr. Hales foon explained the difficulty. In combuftion and calcination, a great quantity of air was evidently abforbed; and Monf. Lavoifier feems inclined to abolish entirely, the fuppofition of a phlogistic principle, and to explain every appearance from the abforption of pure air only. Thus a calx is not a decompofed metal, but a combination, of which the metal is only one of the component parts. Sulphur is not a compound of phlogifton and acid, but a fimple fubftance, capable of forming an acid when combined with pure air. We fhall extract monf. Fourcroy's analyfis of monf. Lavoifier's opinion.

According to Stahl, a combuftible body is a compound, which contains fixed fire or phlogifton. According to his theory, combustion is only the feparation of this fixed fire, and converfion of it into free fire; a separation which is manifested by light and heat. M. Macquer has greatly increased the proba bility of this fyftem, by fubftituting, in the room of the phlogifton of Stahl, the existence of which can no way be demonitrated, light, which exifts with the characteristic properties, and whofe influence in the chemical phenomena is begun to be perceived.

According to the new doctrine, a body is only combustible, because it tends ftrongly to unite with pure air. Combustion is

*Unless Mr. Kirwan's opinion be established respecting the identity of inflammable air and phlogiston.

nothing

nothing but the act of that combination. This opinion is. founded on the four following facts: 1. A body cannot burn without air. 2. The purer the air is, the more rapid the combuftion. 3. In combuftion there is an abforption of air, and an increase of weight in the body burnt. 4. Laftly, the body burnt contains the portion of pure air which it abforbed; and fometimes that air may be extracted by different methods, which will be more fully explained hereafter.

This doctrine which we have delivered, is very different from that which M. Lavoifier published, as an hypothefis indeed, in the memoirs of the academy for the year 1777. That chemist thinks, that pure or dephlogisticated air is compofed of a base, of which he does not defign the nature, and which is held diffolved by the matter of fire or of light. When a combuftible body is heated in this fluid, fuch body decompofes the air by feizing upon its bafe; aud then the matter of fire having become free, affumes all its qualities, and efcapes with the characters which diftinguish it; namely, flame, heat, and light. According to this hypothefis, pure air is the true and only combuftible body. But let us obferve, that this manner of explaining combuftion is as difficult to prove as that of Stahl, fince it differs from Stahl's only as to the place of the phlogiston or fixed fire, which M. Lavoifier admits to be in the body which is employed for kindling, while Stahl admitted it in the combuftible body. It cannot then be admitted, but fo far as the existence of the matter of fire in pure air can be demonftrated; and in that cafe, we shall find the fame difficulties which occur in the theory of phlogifton. We likewife think that it ought to be obferved, that the opinion of the fimple fixation of pure air in the combuftible body, feems to agree with every fact.'

The former hypothefis, of 1777, differs in a flight degree from the new doctrine;' and, though our author does not decide, yet the language of thefe volumes is entirely confonant to the latter. Since our first mentioning it, we have not loft fight of the opinion; and think, that in many respeЯs, it is highly probable. It will explain the greater number of facts, with more confiftency and probability, than the theory of Stahl fome however cannot yet be reconciled to it, particularly the reduction of lead by inflammable air, without leaving a refiduum. In this cafe no air can escape, and a principle is evidently abforbed. There is great reafon alfo to fuppofe, that it is the atmospheric air, and not its dephlogisticated portion, which combines with the calces; for the pure air is generally obtained only by the affiftance of the nitrous acid, which powerfully attracts its noxious parts. If M. Lavoifier contends, that the air comes entirely from the acid, any abforption during the calcination is a gratuitous fuppo

fition.

fition. It is indeed not always, though in many inftances, neceffary.

This theory has induced our author to give a diftinct place among the acids, to aqua regia, which has been ufually fuppofed to be a very pure marine acid; the nitrous acid only ferving to attract its phlogifton, fo that it may more fuccefsfully diminish the union of this principle with the calx of the gold. M. Fourcroy allows the fact, but differs about the explanation. It is, he says, marine acid combined with pure air, and confequently a very different body, which deferves a particular enumeration. The calx of manganese is known to be very greedy of phlogiston; or, in other words, to contain a large proportion of pure air. Marine acid therefore, diftilled from it, has all the properties of aqua regia. It will diffolve regulus of antimony, and in this way the butter of antimony is fometimes prepared, for the purpofe of making emetit tartar, and is faid to fhorten the operation very confiderably. The annotators feem to be mistaken, in supposing that Bergman recommends the glass of antimony for this purpose. We shall now leave this new theory for future confideration, and beg leave to return to our former term of phlogiston. Language has little effect on opinions; and, in this inftance, we would wish to be understood to continue it only as a language to which we have been accustomed, till the fyftem fhall appear more unexceptionable.

The different fubjects in this work are examined with accuracy there are fome fubjects which we wish had been more fatisfactorily explained; but as they have not hitherto been investigated with fufficient attention, we ought not to blame the author for the defect. The animal and vegetable subftances are hitherto little understood; and much is not added, in thefe volumes, to our former knowlege: even the existence of manganese in the latter, a fact pretty well known, is not mentioned. It would amply repay the labours of a chemist, if he traced the changes of the food from its state of imperfect animalization, to the different forms which it afterwards affumes; from the fimple combination of chyle to its firft change into milk, when it feems only to have been inveloped by a more vifcid oil, till it ultimately appears as a highly phlogisticated fluid, the bile, as an earthy falt, or an excrementitious fluid, with a fimilar acid. The phofphoric acid is now found in all the kingdoms of nature; combined with iron and lead, in the mineral; in the charcoal of mustard or wheat, and probably in the glutinous parts of farina, in the vegetable; but its great fource is the animal kingdom. From

hence

hence it may be fparingly derived, in obvious ways, to the others; but we have great reason to think, if its analogy to the marine acid be confuted, that it will be found a new form only of fome well known body.

The natural history of these Lectures contains only fo much, of the fcience as is connected with chemistry. The appearance of the different bodies are well described; and their origin is in general traced with accuracy. We do not however agree with the author, in referring all calcareous earth to marine bodies. We fhall infert his account of the different ftates; for if the premises are allowed, the account of the fubfequent changes is clear and exact.

The waters of the fea, in poifing themselves according to the laws of a motion, with which we are as yet unacquainted, are imperceptibly difplaced, and change their bed. This fact is demonftrated in the learned theory of the earth, by M. le Comte de Buffon. As the waters quit a part of their bed, they expose to view the grounds on which their varied motions, fo well explained by the celebrated man we have just now mentioned, have formed beds by the fucceffive depofition of folid particles, or the skeletons of fea-animals. Thefe beds are almoft entirely filled with fhells; the putrefaction of which very foon destroys the animal-gluten, and afterwards having loft their colours, the polish of their internal furface, and particularly their confitence, they become friable, earthy, and pafs into the late of foffils. Hence the production of the shell-earths, and ftones of the fame nature.

• These ftones, being wafted by the rains, gradually lofe the organic form, become friable, and very foon form a subftance, in grains very little adhering, called chalk. When a fhell-tone has acquired enough of hardness to be fufceptible of polish, and when the fhells which compofe it have put on dif ferent colours, preferving their organization, it then conftitutes the lumachelles. If the organization is deftroyed, if the ftone is hard and fufceptible of polish, we give it the name of marble. The water which is charged with chalk, depofites it on all the bodies over which it runs, and forms incrustations. When it is filtrated through the vaults of fubterranean cavities, it lets fall white and opaque depofitions, formed of concentric layers, refembling pendulous conical maffes. Thefe are the ftalactites. If thefe laft, re-united into a great mafs, and filling caverns, remain for a long time in the earth, they acquire a confiderable hardnefs, and give rife to alabafter. Laftly, when the water, which holds a very fine and attenuated chalk in folution, flowly penetrates the ftony cavities, it will depofite this fubftance, molecules on molecules; and thefe fmall bodies, approaching one another with the furfaces which will fuit beft, will af fume a fymmetrical and regular arrangement, and form hard transparent crystals, refembling thofe of the faline fubftances. VOL. LIX. March, 1785.

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