may be allowed, in the mean time, to concentrate all the information, which we can procure on this fubject, at the hazard of anticipating our accounts of other volumes. The fame author, as we find from this discovery, has been much employed、 in experiments on vinegar and the acetous acid. Common vinegar (that of wine which is common in France, while ours is chiefly prepared from beer) contains fome tartar, the acid of tartar, acetous acid, the mucilage of fugar, and calcareous earth. The empyreumatic acetous acid is compofed of tartarous acid and oily particles (de parties graffes): vinegar, distilled thirteen or fourteen times, with pale dephlogisticated nitrous acid, contains ftill much oily matter; and in fome circumstances it even burns with a very clear flame. By the action of the air alone, a very large quantity of nitrous gas and fixed air are feparated from the refiduum of this diftillation, which ftill adheres to the receiver. The little oxalic acid, which is obtained from the common diftilled vinegar, comes over in the first distillation, where the spirit of wine appears to be very copious; and, in the last, where it is empyreumatic, and contains much tartarous acid and some oily particles. The empyreumatic tartarous acid contains fome of this acid alfo, not decompofed, and furnishes, by this means, fome oxalic acid. If pure pot-afh is put into rectified empyreumatic tartarous acid, fome (tartrite de potaffe) tartarized alkali is formed. In the last volume of the Memoirs of the French Academy, we perceive a memoir by M. Chaptal of the Academy of Montpelier, on the fixed air (carbonic acid) furnished by the fermentation of grapes, and the acetous acid, which refults from its combination with water. If fmall veffels of diftilled water are put within the afmofphere of fermenting grapes, the water is faturated with the air in about forty or forty-eight hours. If it is then put into bottles carelefly corked, after three or four months the taste is changed, and the fmell refembles that of a very weak brandy. The tafte and fmell foon disappear, white flakes are precipitated, fometimes filamentous; at other times, a thick cruft rifes to the top. An acid tafte then appears, which gradually grows ftronger, and the liquor becomes at laft, good vinegar. The operation requires fix or feven months, and fometimes a year: it will occafionally take place only in the warmth of fummer. The accefs of air, and probably vital air, is neceffary, fince in clofe veffels, the operation will not fucceed. The addition of vinegar will occafionally haften it; and it is neceffary, that the fixed air fhould be in its full quantity, as well as that it fhould be procured from fermenting bo dies. In reality we fufpect, that it rifes impure, and carries with it fome of the fpirituous particles, from which the vinegar is formed. Well-water, which contains fome Epfom falt and felenite, is improper for the purpose, fince the fmell of fulphur difguifes that of the vinegar, and fometimes real fulphur is

H 4

formed;

formed; another proof of the presence of phlogistic matter with the air. The floculent fubftance is faid to be carbonic: it is reducible to a cinder, and may almost wholly be reduced to fixed air. M. Chaptal thinks, that it is carried up originally with the air, together with the bafe of the acetous acid, which afterwards requires vital air for its completion; though, when there is any compound which contains the vitriolic acid, the vital air is furnished by its decompofition, and the operation will then fucceed in clofe veffels. The mushrooms which grow in vaults, our author finds to be of a fimilar nature: they are refolvable into coal and into fixed air, leaving only one eighty-ninth of a woody fubftance. By removing them gradually to the light, the fixed air is lefs and the refiduum greater in proportion: the laft has been increased to one twenty-fourth: the vital air of the aerial acid seems to form a new combination with an oily prin ciple, and become a rezin, which gives the yellow colour and augments the refiduum.

M. Hermstadt's experiments on the falt of Benjamin, are not new; but they are fo little known, that we fhall mention them, though much remains to be done on this fubject. It appears to be a very compound acid, united in part to the earthy principle, and fixed by fome oily or phlogiftic matter; when feparate, it is probably not very powerful, on account of its fmall proportion of vital air. Our author endeavoured to feparate the ingredients, by repeated affufions and diftillations of nitrous acid. At laft he fucceeded, in fome degree, and produced a very brown acid liquor, which he stiles the acid of Benjamin; but this refult must be received with fome limitation: it is the acid of Benjamin with an excefs of oxygen, and perhaps contaminated with a little undecompofed nitrous acid. With this liquor, however, he attempted to make æther, and, together with a large proportion of dulcified nitrous acid, he feems to have procured a peculiar fluid of the flavour of bitter almonds, nearly the fame as he perceived in one of the experiments, during the decompofition. There is probably a proportion of tartarous or faccharine acid, in the acid of Benjamin, if it is not entirely a peculiar form of thefe acids, fince it precipitates lime from water, and the calx from acetated lead.

Camphor is an oil, not without the fufpicion of an acid principle; though, what we have collected on this fubject, does not refpect its chemical nature, but its volatility. M. Kunfemuller tells us, that camphor is not nearly so volatile as is commonly fuppofed. He expofed two ounces to the temperature of from 9 to 10° of Reaumur (about 52° to 56° of Farenheit) and as much to the temperature of from 4° to 8° below o (about 23 to-18). The first loft in fourteen weeks, nearly half its weight; and the other, in the fame space, only a drachm and fix grains lefs. The author fhould, however, have remarked, that the lofs is, at firft, much more rapid than

in the later periods; and his conclufion would have been more correct, if he had faid, that the volatility appears to be greatly repressed by forne additional ingredient. The lofs of weight is faid to be in the lower portion of the mass, through the interftices of the pores.'

The reft of our sketch will be chiefly confined to inflam mables, with which we fhall interweave fome obfervations, relating to the great difpute on the compofition of water: we may, therefore, be allowed to begin with Carradoris' theory of heat. This system is contained in his Theoria del Calore publifhed in 788 at Florence, in two volumes, though we have, of late only, received a clear connected account of it. Our author, after explaining the fyftem of Dr. Black, fo ably expanded and applied by M. M. Fontana, Kirwan, Magellan, and Crawford, obferves, that the fenfible heat, loft, appears to be united to the body in different ways. When, for instance, it is loft in the cafe of melting ice, the form is changed, and the addition feems to be required for that change of form: it is then faid to be united by the affinity of compofition. But, when loit by uniting hotter mercury with water, neither ingredient changes its form, and we may conclude, that it is united by the affinity of aggregation.' In this way, air is united to water, and appears when the preffure of the atmosphere is taken off. All the variations, remarkable in the temperature of bodies on their being mixed, depends on the evolution of a quantity of aggregated heat, or the aggregation of a quantity of fenfible heat. Every body, he thinks, contains a different degree of attraction for heat; and in mixing bodies of different temperature, we may not only remark the diffufion of heat to restore the æquilibrium, but the feparation of the aggregated heat, or the abforption of fenfible heat, according to their different affinities. This view then gives occafion to distinguish latent heat into two fpecies. What has been called the capacity for retaining heat is the degree of its affinity for aggregated heat; and this power is leffened by the addition of phlogifton, which feems to give bodies the power of repelling heat. The heat, depofited in refpiration and combustion, our author thinks, is aggregated; but, according to his own fyftem, the latter at least must be fixed' or combined heat.

If this author be favourable to Dr. Crawford, M. Leopold Vacca Belinghieri is little fatisfied with his application of this theory, though, he thinks, his mode of demonstration accurate. In his memoir fur la Chaleur, he replies to an answer, which Dr. Crawford made to fome former obfervations He was accused of neglecting the aqueous vapour in his calculations; but he now endeavours to flow, though, we think, without fuccefs, that this confideration rather ftrengthens than weakens his objection. The calculation would détain us too long. His objections to M. Lavoisier are not on a better foundation. If the molecules of bodies are kept at a distance, by a

repulfion

repulfion occafioned, or at least increased by heat, the diminution of bulk fhould be in the direct proportion of the degree of the diminution of heat; but attraction, he says, acts in the inverfe ratio of the fquares of the diftance: the proportion, therefore, fhould be an increasing one. This would undoubtedly be true, if the attraction of cohesion followed the laws of attraction of gravitation. The laws, which influence the former, can only be afcertained, when we have made the minutest microscopic animal a philofopher. That author's fyftem of combustion, M. Belinghieri thinks, is not on a better foundation. If the heat is derived from the vital air, its intensity should be in the inverfe proportion of its changes of capacity. But, after burning fulphur and phosphorus, the acids which refult should have a lefs capacity than the remains after burning charcoal, viz. the aerial acid: the contrary is, however, true. But our objector has not taken in every part of the experiment, and has unaccountably omitted the different forms of the results: besides, we never understood M. Lavoifier to mean, that the heat extricated in combuftion arofe exclufively from the decompofition of the vital air.

M. de Reboul in his account, or rather in his definition of combuftion, and its defence, though, he feems to be a strenuous advocate for M. Lavoifier, is yet clear and confiftent. He defines it the act in which vital air and a combustible (he fhould have faid inflammable) body, in changing their state, produce fire;' or afterwards a little more accurately, the act in which fire is produced, by the reciprocal combination of vital air and a combuftible body." The fire, he thinks, may, as we have already hinted, come from each, though M. Lavoisier chiefly dwells on the abfolute heat of the vital air. Though we allow his definition, he will find it difficult to reduce every inftance of oxydation and oxygenation under it, unless he defines fire very loosely and vaguely.

M. Lavoisier, himself, is labouring eagerly to fupport his own fyftem, of which the compofition of water forms the chief fupport. His reflections on the decompofition of water by vegetable and animal substances,' are proofs of his ufual acutenefs and ingenuity: at the fame time they afford fome details of curiosity and entertainment. It is well known, that, in difilling charcoal, fome fixed and fome inflammable air are produced, though in a fmall quantity, and without altering the appearance of the coal. This air foon ceafes to come over; but, on expofing the charcoal to the atmosphere, a fimilar pro duct may be obtained in diftillation. On repeating these experiments, it is found conftantly to lofe a little more weight than it had acquired by being expofed to the atmosphere; and, after frequent trials, the whole charcoal is decompofed. It is, however, remarkable, that the airs acquired by thefe repeated trials, is triple of that of the original charcoal; and it is evident, that the additional weight must be derived from the atmosphere,

atmosphere. But, in the air, it is expofed only to air or to water, and it remains to be ascertained, from which the new production is derived. Our author, therefore, expofed it to air deprived, of water and to water deprived of air; but, in the former trial, it derived nothing, in confequence of the expofure, and gave out in the fecond diftillation, neither fixed nor inflammable air. By the fecond method, he decompofed all the charcoal, and produced from it the ufual quantities of air, that is, triple its weight, though it had only been expofed to water deprived of air. We omit the calculations, and particularly the quantity of water decompofed, because the former are too long, and the latter a little fallacious.

With these views our author repeated many of Dr. Hales experiments, and in diftilling woods and plants: in the greater number he found a fimilar refult to that which occurred to him in the experiment with the charcoal; but in the oily plants he found a greater proportion of inflammable air from the decompofition of the oil: on the whole, he chiefly faw, he tells us, the affinity of the oxygen, which joined with the coaly matter (phlogifton), formed fixed air. M. Lavoifier confidered it as a proof of the truth of his fyftem, that wood gradually dried gives no fixed air or hydrogen; while fresh vegetables, which contain much water, give both copiously. At the fame time, the fixed air produced by decompofing vegetable and animal acids, do not proceed, in his opinion, from their formally containing it, but from their containing much water, and its decompofition by the coaly matter, which is one of their principal ingredients. He purfues this fyftem in the analysis of fugar and of fome animal fubstances, where he is almost ready to contend that the oily matters do not formally exift in the body, but are the confequence of a second combination. Of the three principles which enter into the compofition of vegetable and animal fubftances, the coaly matter, he obferves, is in excess; and this, probably, is the cause of their affinity with water. The coaly matter attacks the oxygen of water, forming fixed air, while the hydrogen (inflammable air) is difengaged, or is ⚫ recombined with the coal to produce oil.' At laft, in animal bodies, the azote (phlogisticated air) is added, and produces the volatile alkali.-Perhaps we may have no better opportunity of adding his fyftem of combuftion: This is either effected in the open air, by diftillation in the naked fire in confequence of the bodies containing water, by fermentation either vinous or putrid, or by acids with an excefs of vital air. In the first there is a feparation of heat, in the fecond of the hydrogen, and in the laft, when the dephlogifticated nitrous acid is employed, of nitrous gas. Every kind of oxygenation is, therefore, in M. Lavoifier's opinion, a combuftion; and he diftinguishes the first by the term ardent, and the second by that of obfcure combuftion: an analogous diftinction is already admitted in chemistry, by the terms fenfible and latent heat. As in these combustions

water,