(See p. 75, and 105, vol. iv. &c.) and the explanations might per haps have been useful to the author as well as to his purchasers. Dr. Shaw is proceeding, we underfland, with the fubject of infects, which will include fome other animals, ufually confidered as fifhes; namely, crabs and lobsters. We cannot but with fuccefs to his laborious and useful undertaking; nor ought we to refuse to Mr. Kearsley, the praise most justly due to his fpirit, in commencing and carrying on a work of fuch magnitude and expence.

ART. XV. An Efay on Chemical Statics; with copious explanatory Notes, and an Appendix on vegetable and animal Subftances. Faithfully tranflated from the original French of C. L. Berthullet, Member of the Inftitute, &c. By B. Lambert. In Two Volumes. 472 and 499 Pp. 8vo. 16s. Mawman. 1804.

THE HE object of this work is clearly ftated in the introduction, The leading propofition is, that the phænomena of chemiftry are the effects of the mutual action, or affinity, of the particles of bodies. This affinity is diftinguifhed from the general gravitation of matter (which this author calls aftronomical attraction) by its acting at fmall diftances; whereas the general gravitation of matter acts at all diftances. The former likewife differs in degree according to the peculiar natures of the bodies concerned, befides a variety of other concurring circumstances. The difficulty of determining those circumflances, as well as the proportion of their actions, is what in great measure prevents the poffibility of foretelling the refults, which are likely to arife from a variety of chemical combinations; and it is, therefore, from obfervation alone, that the chemical properties of bodies, or thofe affinities by means of which they exert a reciprocal action in a determinate fituation, can be eftimated.

"The immediate effect" this author fays, " of the affinity which a body exerts is always a combination; hence all the effects produced by chemical action are the confequence of the formation of fome combination.

"Every fubftance which has a tendency to enter into combination, acts in the ratio of its affinity and of its quantity. These facts are the ultimate end of every chemical obfervation.

"But, ift. The different tendencies to combination may be confidered as fo many forces which contribute to a refult, or which partly

deftroy

deftroy it by their oppofition; thefe forces muft, therefore, be diftinguished in order to obtain an explanation of the phenomena which they produce, or to compare them together.

2d. The chemical action of a body does not depend folely upon the affinity peculiar to its component parts and upon the quantity; it alfo depends upon the ftate in which thofe parts are found, whether it be that of actual combination, which caufes a larger or fmaller portion of their affinity to difappear, or that, by their dilatation or condenfation, their reciprocal distances are varied: it is thefe conditions which, by modifying the properties of the elementary parts of a fubftance, form that which I call its conftitution: to obtain the analyfis of chemical action, not only each of thefe conditions must be appreciated, but also every circumftance with which they have any connection." P. viii.

In the fequel he obferves, that in chemical operations, a confiderable part of the refult depends on those properties, which may be particularly called phyfical properties, fuch, for inftance, are the gravity, the temperature, and the peculiar qualities of the atmosphere, in which thofe operations are conducted; alfo the action of light, &c. Hence he naturally infers the neceffity of establishing an intimate relation between the different fciences of phyfics, that they may mutually affift one another. With refpect to the present theory of chemistry, he fays,

Perfuaded that the principles adopted in chemiftry, and the immediate inferences derived from them, with a view to their being made use of as fecondary principles, ought not yet to be admitted as fundamental maxims, I have undertaken a new examination of them, and I have already published, in my Refearches into the Laws of Affinity, the obfervations which have led me to believe that a correct idea of the effects produced by it has not yet been formed.

"The intention of this effay is to extend my firft reflections to all the causes which can produce a variation in the refults of chemical action, or of the product of the affinity and the quantity. I fhall therefore examine what is the mutual dependence of the chemical properties of bodies, compared, at firft, with each other, and afterwards confidered in the different fubftances ? what are the forces which arife from their action in the effects produced by them? and, what are the properties of the forces which contribute to these effects, or which are in oppofition to them?

The effay is divided into two parts: in the first, I confider all the elements of chemical action; and, in the fecond, the fubftances which exercise it, and which contribute the moft to chemical phenomena, claffing them according to their habitudes, or the relations exifting between their affinities."

The firft volume of this work is divided into fix fections, and each fection is fubdivided into chapters. Their titles are as follows:

"Of Chemical Action in General.-Sect. i. Of the Chemical Action of Solids and Liquids.-Chap. i. Of the Force of Cohefion.Chap. ii. Of Solution.-Chap. iii. Of the reciprocal Action of the Subitances which are held in Solution.-Chap. iv. Of Combination. Sect. ii. Of Acidity and Alkalinity.-Chap. i. Of the reciprocal Action of Acids and Alkalis.-Chap. ii. Of the Action of an Acid with a neutral Combination.-Chap. iii. Of the Precipitates produced by Acids or by Alkalis.-Chap. iv. Of the reciprocal Action of neu tral Combinations.-Chap. v. Of the comparative Capacity of Acids and Alkalis for Saturation.-- -Sect. iii. Of Caloric.-Chap. i. Of the Effects of Caloric independent of thofe of Combination.Chap. ii. Of the different States of Caloric.-Chap. iii. Of the Action of Light, and of the Electric Fluid.-Chap. iv. Of Caloric confidered with relation to Combinations.- Sect. iv. Of the Effect of Expanfion and Condensation in Elaftic Fluids.-Chap. i. Of the Characteristic Properties of Elaftic Fluids.-Chap. ii. Of Refulting Affinity.-Sect. v. Of the Limits of Combination.-Chap. i. Of the Proportions of the Elements in Combinations.-Chap. ii. Of the Action of Solvents.--Chap. iii. Of Eflorefcence.-Chap. iv. Of the Propagation of Chemical Action.-Sect. vi. Of the Action of the Atmosphere.-Chap. i. Of the Conftitution of the Atmosphere.-Chap. ii. Of the Elementary Parts of Atmospheric Air.-Conclufion of the Firft Part.-Notes to the First Volume."

Mr. Berthollet's mode of treating thefe fubjects is clear, extensive, and inftructive. But in the difcuffions, into which he enters, he is rather unequal; for he paffes rapidly over thofe fubjects, which though of confiderable importance, are better known, or lefs equivocal; and he dwells with minutenefs on other fubjects, which may feem to be more in need of elucidation. His principal object is to fix general and comprehenfive laws, to illuftrate them, to anfwer the objections to which they are liable, and to point out feveral ufeful applications of the fame. It is alfo neceffary to obferve, that the contents of the chapters are mofly of the fpeculative or theoretical kind, that feveral of the obfervations have been mentioned by other writers on the fubject of chemistry; and that fome of the chapters might have been rendered more methodical and less verbofe. But let us take a nearer view of the contents of this work.

In chapter III. on the precipitates produced by acids or by alkalies, this author expreffes himself in the following manner:

"When

When an acid forms a precipitate, by its combination with an alkaline bafe which it feparates from another acid, the infolubility which caufes the precipitation, belongs to the natural qualities of each of the elements of the combination, the tendency of which to become folid is increased by the condenfation they experience.

The infolubility which derives its origin from this caufe determines the proportions of the elements of the combination precipitated, it only yields, more or lefs, to the acid remaining in the liquid; fo that the operation of the fuperabundant acid is confined to the diminution of the quantity of the infoluble combination; but when an alkaline bafe produces a precipitation, its effect may be different according to the properties of the precipitated bafe, becaufe the alkalis are very different from each other, in refpect of folubility.

"If this bafe is foluble by itself, if it is the combination it forms which becomes infoluble, it is in the fame fituation as the preceding: the combination which feparates muft alfo have determinate proportions; an excess of alkali renders the precipitate more foluble and diminishes the quantity, or diffolves the whole of it.

"But if the bafe, infoluble by itself, requires a certain portion of the acid to become liquid, then another alkaline bafe, by abtracting part of the acid, deprives it of its folubility: it will precipitate by forming an infoluble combination, which may vary in the proportions of its elements.

"An alkali which acts on a solution of a falt with an earthy base, shares, therefore, its action on the acid with this base, but the latter requires all the effect of the acid with which it was combined to preferve its folubility, fuch as it was; in proportion, therefore, as the action of the acid on it diminifhes, infolubility takes place, and increafes until the feparation is accomplished; the acid is divided be tween the alkali and the earthy bafe, in the ratio of the forces which are in action at the moment of the feparation, fo that two combinations are formed, the one foluble and the other infoluble.

Thus, when by means of an alkali, the alumine and magnefia have been precipitated from the foluble combination they formed with fulphuric acid, it is only neceffary to diffolve thefe precipitates again. in an acid, fuch as the muriatic, or nitric acid, and then add a folution of barites to obtain a confiderable quantity of fulphate of barites, which proves that the fulphuric acid was combined with them. The metallic folutions, and particularly thofe of mercury, afford proofs, equally convincing, that the precipitates retain part of the acid.

"It is not, however, to be concluded from this, that precipitates can never be reduced to a fimple ftate: the increase of the force of cohefion in a substance in which it is powerful, is even fufficient, in fome cafes, to feparate an acid from it, with which it has in other refpects but a weak affinity; for example, it is enough that filex, diffolved in any acid but the fluoric, fhould be expofed to a ftrong deficcation, to caufe it to quit the acid and become infoluble: we fhall alfo fee that the force of cohesion of fome metals can determine their precipitation in the metallic ftate, without retaining any of the acid which held them in folution; but it appears that this complete feparation never occurs between the acids and the alkalis: the quantity of the acid alone

may

may be diminished more or lefs, according to the force of the alkali, which tends to abstract it from a precipitate, whofe infolubility does not depend on determined proportions.

"If the quantity of liquid employed as a folvent is fufficient to coun terbalance the infolubility produced by the diminution in the action. of the acid, no feparation takes place, and then each base acts upon the acid in the ratio of its mafs; thus Bergman obferved, that pot afh or foda did not disturb the tranfparency of a falt with base of lime, when the falt was diffolved in fifty times its quantity of water; if the acid did not continue to act on the lime, the precipitate would have appeared in a much greater quantity of water, for it requires nearly feven hundred parts of water to diffolve one of lime.

"If ammonia does not produce a precipitate, like a fixed alkali, with calcareous falts, it is because it has the property of combining with them and forming a triple falt, which is not feparated by evapo ration, unless the action of the liquid is weaker than its infolubility.

"Two fpecies of precipitates may therefore be diftinguished; thofe in which the acid and the bafe acquire, by combination, an insolubility, not poffeffed by either in an infulated ftate, or which they had in a much lefs degree; fuch are the various falts which form precipi tates if the water is not fufficient to hold them in folution, or which cryftalize when that is leffened in which they were diffolved; and thofe precipitates whofe bafe has only acquired folubility by the action of the acid, and which form an infoluble combination whenever that action is diminished. The precipitates of the first fpecies have limited proportions in the elements of their combination, or at leaft thefe proportions are liable to very flight variations, as I fhall notice in another place. Thofe of the fecond may be compofed of very variable proportions, until the quantity of the acid is fuch that the increafing action of the bafe will not allow of its being further diminished; for they can, in precipitation, retain different proportions of the acid according to the state of the forces in action. A proof of this is, that after having formed an infoluble falt with an earthy bafe, even though it hows a ftrong affinity, and though a great force of cohefion has caufed its precipitation, fuch, for instance, as fulphate of barites, a portion of its acid may be abstracted by the action of a concentrated alkali. A ftill greater effect may be obtained by treating phosphate of lime in the fame way.

"It is therefore very probable, that in thefe cafes the precipitates are different according to the circumftances of the operation; according to the energy of the alkali which produced them, and, confequently, according to its degree of concentration; but as the circumftances vary at the commencement and at the end of the precipitation, when the mixture of the liquids is not made fuddenly, the action of the alkali being much stronger at the beginning, than as the fatura

"* De Attract, Elect, § vii.”