3? 8 Exflatiatbn nf thi EffeS of 



du£Hve of fubfequent cventf , and have been denoted for fome years by tbe name of difpofing. 

 afGnities. Thus it is that the attradlion of acids for the metallic oxides favours the decom- 

 pofition of water by means cf the metals, which do not in faft become oxided to unite to acids, 

 but at the cxpence of the oxygcne which tlicy take from the hydrogene. Thus likewife it 

 is, tlut tlic affinity of tlie cauOic earths and alkalis for the fulphuric acid determines the 

 conibullion of the fulphur of fulphurcts by means of water, and the feizure oi oxygene from 

 the latter, which would not t;ike place without the exiftence of this difpofing affinity. When 

 the long confidcration of chemical phenomena, the habit of beholding them, and cf appre- 

 ciating their refulfs, has defiroyed this firft repugnance in the mind of the chemift, he foon 

 conceives that it is not more difficult to admit and explain this difpofing affinity, than it is 

 in natural philofophy to adopt, and admit as proved, the attraction at great diftances which 

 takes place between the planetary bodies. 



We may exprefs the refults of the chemical efTcft as it has here been at length explained 

 by a fimple formula, which in reality is nothing more than an argument difpofed in a clofe 

 arrangement, like all the algebraic forniulx; and this method, by prcfenting chemical phe- 

 nomena in a concife language, will polTcfs ilie advantage, when more generally employed, of 

 reprefenting, with clearnefs and precifion, every thing that happens in the mod complicated 

 operations. Thus we may fay. 



Aqueous fulphuric acid + liquid acetous acid + precipitated carbone — concentrated 

 fulphuric acid + entire vegetable matter. In this manner it was that Lavoifier exhibited the 

 whole myftery of the vinous fermentation in this fimple form of an equation : — Juice of 

 grapes = carbonic acid + alcohol; becaufe, in faft, the refult of this interelling obfervation, 

 formerly fo obfcure, but at prefent fo pcrfpicuous, is the converfion of mud, or liquid £ac- 

 charine matter, into alcohol and carbonic acid. 



If the efTefls be truly fuch as we have here explained, it muft be neceffary for their ejt- 

 jftence that the fulphuric acid (hould be concentrated, and the vegetable matters in the dry 

 {late : for, if they contained water ready formed, this, by its immediate application to the 

 fulphuric acid, would faturate it, and prevent its re-aQion upon the principles of thefe fub- 

 (tances. The fame thing would happen if the acid employed was already weakened by the 

 previous addition of water. This, in faft, takes place in both cafes, as the experience of every 

 chemift mud fhew. It mud, however, be obferved in this place, that in order that the a£lion 

 between vegetable matter and fulphuric acid combined with water diould be nothing, the 

 water ought to be enough to faturate the acid : for, if its tendency to combination with 

 water be not entirely fatisfied, its decompofing a£lion on vegetable fubdances mud be in 

 proportion to its want of faturation. In fa£l,.the decompofition here mentioned, namely 

 the formation of water and vegetable acid witli the precipitation of carbone, cannot be ob- 

 tained but by increafing the quantity of acid. This alfo is confirmed by experience, which 

 (hews that the quantities of fulphuric acid neceflary to produce the required decompofi- 

 tion, do not follow the fimple ratio of the quantities of water they contain, but are at lead in 

 proportion to the fquares of tliofe quantities. So that if we fuppofe, for example, that the 

 mbd concentrated fulpliuricacid contains a quantity of water equal to two, and that another 

 acid contain a quantity equal to four, there will be required not only the double of this lad 

 to produce the fame efTeiS upon a vegetable fubdance, but it will be found neceflary to ufe 

 at lead fixtcen times as much. And this agrees very well with reafoning, fmcc it is known 



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