fhould be made to his ufing a weak or diluted acid, he rubbed and digefted this powder (we fuppofe without heat) with the moft highly concentrated vitriolic acid, and found that it ftill retained its fulminating property.

No fatisfactory hypothefis has yet been invented to explain the action of this wonderful powder; half a drachm of which, as M. Beaumé informs us (and not half a grain, as the Author fays *), though fired in the open air, produces a louder explofion than even fome pounds of gun-powder fired from a cannon. The opinion which has hitherto been thought the most probable was, that its effects were principally owing to a nitrous ammoniac, or nitrum flammans, as it has been called, or to a nitrous fulphur contained in the compofition: but Mr. Bergman appears to have overturned this manner of accounting for the phenomenon, by producing a genuine aurum fulminans, or a fulminating calx of gold, which, according to him, does not contain any nitrous acid. This, he thinks, he has effected by diffolving a precipitate of this metal (which would not detonate) in vitriolic acid; and then again producing a fresh precipitation by means of volatile alcali, which was found to be poffeffed of a fulminating quality.

We do not however concur in opinion with the Author, in thinking, that Mr. Bergman's trials decifively prove, that no nitrous acid was contained, or could poffibly remain, in the above-mentioned calx, after it had been digefted with oil of vitriol; as the nitrous acid might poffibly be fo intimately combined with the calx, as to refift the means he employed to dif lodge it. We fhall offer the following obfervation, as better adapted to fhew, either that no nitrous acid is contained in the calx; or, at least, not in a fufficient quantity to account for the phenomena presented by this powder.

Mr. Bergman has lately obferved, what has been long ago remarked, that aurum fulminans expofed to heat in ftrong veffels exactly clofed, or without any communication with the external air, does not produce any explosion; the gold being reduced to its metallic ftate without noife. Now it is well known, that in gun-powder, as well as in other combinations of the nitrous acid with inflammable matters (for fuch the volatile alcali, an ingredient in the aurum fulminans, undoubtedly contains), a deflagration, or even a detonation, will take place

* M. Beaumé, of whom the Author very frequently fpeaks not very respectfully, though fo largely indebted to his valuable writings, may here very juftly apply to the Author himself what the latter foon afterwards fays of M. Beaumé, on account of his having committed a mistake in quoting from Mr. Bergman,- Parum fane exacta talis eft auctorum citatio.'

even in close veffels, or without the access of common air, in confequence of the dephlogisticated air generated from the nitrous acid, as hath been of late fully explained by many of Dr. Prieftley's experiments; from whofe mode of experimenting alone, we apprehend a fatisfactory folution of the phenomena of the aurum fulminans, and other powders of a fimilar kind, is to be obtained.

No perfon who writes on the fubject of aurum fulminans, and perhaps excites his readers to the making experiments on it, ought to omit giving them the most earneft cautions with refpect to the handling of fo dangerous a substance. We fhall therefore obferve, that the most dreadful and horrid mischiefs have followed the explofion even of no great quantity of it; and further, that the whole quantity contained in a vial has more than once been kindled by the acceffion of a small unheeded particle that happened to ftick in the neck of the vial, and which has been fired, by its fuffering only the flight friction given it by merely thrusting in the glass stopper.

To what we have already faid of this work, and of its utility with refpect to thofe particularly who wish to enter on the study of chemistry, we fhall only add, that, in the fucceeding volume, the Author propofes to include the Chemical History of the inflammable, and, if poffible, of the faline substances.

ART. VI.

Dictionnaire de Chemie, &c.-A Dictionary of Chemistry, containing the Theory and Practice of that Science; together with its Application to Natural Philofophy, Natural Hiflory, Medicine, and the Arts depending upon Chemistry. Second Edition, revifed, and confiderably augmented. By M. Macquer, M. D. &c. 12mo. Paris. 1778, &c.

TH

4 vols.

HOUGH the fourth and laft volume of the fecond edition of this valuable work (the three firft of which were publifhed in 1778) has been in our hands fome time, we think we fhall do an acceptable fervice to those who intereft themselves in chemical researches, to inform them of the very confiderable additions, and the great improvements, which it has received, and which render its bulk nearly double to that of the first edition. The merit of the work, as first published, is now too well known, to render it neceffary for us to refer to the character of it given in our 46th Volume, March 1772, or indeed rather of Mr. Keir's excellent tranflation of it, enriched with notes, and with new articles added by himself; feveral of which, as well as of those added to the German tranflation by M. Poerner, M. Macquer has adopted in the pre

fent edition.

In this edition the greatest part of the articles has received fome improvement or augmentation. The number of perfons who cultivate chemistry is now fo great, that new lights are almoft daily thrown on various fubjects of that fcience. The moft extenfive additions, however, that have been made to the first edition of this work are to be found under the words, Affinity, Charcoal, Metallic Calces, Quick-lime, Combuflion, Mineral Waters, Cauftic Volatile Alcaline Spirit of Sal Ammoniac, Iron, Fire, Luna Cornea, Nitre, Bones of Animals, Gravity, Phlogifton, Phofphoric Stones, Platina, Salt, Sulphur, Emetic Tartar, Art of Dying, Veffels and Utenfils of Chemistry, Varnish, Wine, Vitrification, and many others.

Befides thefe augmentations of former titles, this edition contains many articles, or rather differtations, that are entirely new; the principal of which, as indicated by the Author, occur under the words, Caufticity, Diamond, Flower, Magnesia, Molybdenum, Nickel, Nitre with a basis of Magnefia, Blood of Animals, Acid Soaps, Soldering, Amber, Sugar, Veffels appropri ated to Cookery, Burning Glass, and several others of lefs confequence.

In the preceding lift we have omitted to mention the most material and bulky of the additions that have been made to this work, and which are prefented in nine or ten large articles, under the title Gas, or (to follow the nomenclature of Dr. Priestley, and the greater part of our countrymen) Air. The interesting and important obfervations that have been lately made on this fruitful fubject, have very juftly excited the particular attention of the Author, who has bestowed above 160 pages in forming, from the obfervations of Dr. Priestley and his numerous fellow-labourers, an excellent compendium of the many discoveries that have been made in this new branch of chemical fcience within thefe few years. The neceffity of fuch an addition had likewife occurred to the English Tranflator, who formed a fimilar epitome, as a neceffary appendix to the fecond improved edition of his tranflation.

Two novelties ought not to be passed over unnoticed, which diftinguish this edition of the Dictionary of Chemistry from the preceding edition, and indeed from all other Dictionaries, and which, in a very confiderable degree, add to the utility of it. The effential articles of the work are of fuch extent, that they might form a regular treatife, were they not, as it were, infulated, and detached from each other, in confequence of their alphabetical arrangement. The Author has therefore planned a certain order, in which the articles are to be read by thofe who would ufe the work as a fyftematical treatife; pointing out the method which the reader is to follow in the perufal of it, and particularly naming the different articles in fucceffion,

in a kind of tabular order; affigning, at the fame time, the reasons on which the propofed train of reading is founded. The Author is fo perfpicuous a writer, that, we apprehend, the chemical student may meet with more information in the propofed mode of perusing this Dictionary, than from many Authors who have treated the fame subjects in a fyftematic form. In fact, however, as the Author himfelf in part obferves, this work is not properly a Dictionary, but a collection of treatises or differtations on fubjects which, however dispersed or separated in confequence of an alphabetical arrangement, have a natural relation to, and an intimate connection with, each other.

The next fingularity, which clofes this Dictionary, is an Index, or Table of Matters, of the most extenfive and comprehenfive kind, and which occupies no lefs than 440 pages. It is executed in such a manner by a Friend of the Author, as not only to answer the common purposes for which Indexes are ufually made; but is, at the fame time, a moft inftructive compendium or abridgement of the whole work. The more extenfive articles of the Dictionary, in particular, are here briefly, but fatisfactorily, analyzed under each head; and, at the fame time, the reader who wishes for information on a particular fubject, which is not to be found in the Dictionary, under a particular title, but lies perhaps concealed in the middle of a long differtation, readily finds the information he wants, by having recourse to this very communicative Index. In short, the Index itself, or the greater part of it, may be read with fatisfaction and improvement, or as a remembrancer, by those who are somewhat converfant in chemistry; as there is scarce an effential paragraph in the Dictionary, the fubftance of which is not there announced, at least in a few words. A fhort account of a few recent obfervations or discoveries contained in fome of the articles added in this edition, may poffibly be new and acceptable to many of our philofophical readers.

Under the articles, Bones of Animals and Phofpbarus, an account is given of a late curious discovery made by Mr. Scheele (who discovered the Acid of Spar), relative to phosphorus, or the phofphoric acid; a fubftance which, on account of its dearnefs, has not hitherto perhaps been fo extensively examined, as it will probably be hereafter, in confequence of this new and eafy method of procuring it. It has been difcovered by him, that the bones of animals contain a large quantity of this acid, which has hitherto been procured, with great difficulty and difguft, from urine; but which may be extracted from bones, by a very simple and eafy procefs. M. Macquer, though he has executed the procefs with fuccefs, does not enter into any particular detail. Though we cannot add any thing with re

spect

fpect to quantities, we fhall fupply a few deficiencies in this article from our reading elsewhere, and indeed from our own experience.

The nature of the earth which forms the bafis of the bones of animals has, till very lately, been entirely unknown to chemifts, who did not fufpect that it was combined with a certain fixed principle, which difguifed it, and which eluded the action of the moft violent heat employed in calcination. Mr. Scheele has ascertained, that bones principally confift of a true calcareous earth, intimately combined with the phosphoric acid. On adding oil of vitriol to bones reduced to powder, or which have even been previously calcined to whitenefs, the vitriolic acid having a greater affinity to the calcareous earth than the phosphoric, immediately combines with that earth, and expels from thence the phofphoric acid. Heating the matter in a proper veffel, hot water is to be fucceffively added to it, till all that is foluble or acid in it be extracted; the water is then to be diftilled or evaporated down to a fmall quantity. It will thus gradually deposit the selenite which is contained in it, and which is to be removed. It is then to be reduced to a pretty thick confiftence, or may be brought into the ftate of a dry vitriform faline mass, in a crucible. It appears now to differ from the phofphoric acid of urine, in a vitreous ftate, only in its still retaining a portion of felenite or earthy matter. If this fubftance be now mixed with a proper quantity of charcoal, and be fubjected to diftillation, even in a heat which a coated glass retort is capable of sustaining, a phosphorus will come over perfectly fimilar to that obtained from urine.

M. Rouelle has obferved, that a greater quantity of the phofphoric falt may be procured from fresh bones, than from fuch as have been calcined. With refpect to the quantity that may be obtained, M. Macquer eftimates, from the experiments which he has made on this fubject, that three or four ounces of it may be procured from each pound of bone, or hartfhorn.

Another, but apparently a more expenfive and operofe, method of extracting this acid from bones is likewife here indicated. Nitrous acid is to be added to them, which will totally diffolve them. Vitriolic acid is then to be gradually added to the folution, till no more felenite appears to be precipitated from it. The liquor is then to be diftilled or evaporated; to expel all the nitrous acid now fet at liberty, and the excess, should there be any, of the vitriolic, together with all the hu midity. The refiduum, thus obtained, will be fimilar to the preceding, and equally fit for the preparation of phosphorus.

An experiment which M. Macquer relates, towards the end of the article Gas, as having been communicated to him by M. Bucquet, deferves notice; as it feems, as he obferves, to