k 



On the Laws of Affinity. 147 



atSlian,) becaufe they ad with a force fo great as to make 

 the influence of little caufcs dlfappear ; becaiiie they often 

 produce comparable degrees of faturation ; and becaufe they 

 gite refults eafy to be obferved/* But the confequences 

 which Berthollet draws from their properties he applies to 

 all combinations ; and feveral examples are adduced to prove 

 that the principle which he eftablifties extends to every che- 

 mical a6tion of bodies. 



After having proved, by direct experiments, that the che- 

 mical adion of bodies, the forces of which are contrary, de- 

 pends not only on their affinity but alfo on their quantity, 

 the author announces, that he means to felcjSl obfervations 

 refpe^ling the different kinds of combinations, which will 

 confirm this principle, and which will prove its extent. 

 i^ I (hall then examine,'* fays he, " the circum fiances by 

 which it is modified, or the affeftions of bodies which favour 

 or leflen their chemical a6lion, and which occafion a variety 

 of proportions in the combinations they can form. I fhall 

 apply thefe confiderations to complex affinities and to thofe 

 of compound bodies ; and, in the lafl: place, I fliall endea- 

 vour to fix the bafis on which the general and particular the* 

 pries of chemical phsenomena depend. 



II. Experiments ivhich prove that in Eif^ive Affinities the 

 . Subftances which exercife oppofite Affinities divide them- 

 felvcs in that which is the Suhjc^ of the Co?iibhiation, 



To demonftrate the truth of this principle, C. Berthollet 

 defcribes feveral experipients, of which we flmll mention the 

 following: ^' I kept ill a ilate of ebullition,'' fays he, " in a 

 fmall quantity of water, an equal weight of potafli, purified 

 by alcohol, and of fulphat of barytes. The operation was 

 performed in a retort, and, confequei>tly, without the conta6l 

 of the air : the mixture u-as reduced to a flate of drynefs, and 

 the refiduum being treated with alcohol, which diflblved the 

 potafli, and after that with water, the latter effcfted a folu- 

 tion which ftill exhibited alkaline properties. The alkali was 

 faturatcd with acetous acid, after which there was formed, 

 by evaporation, a pretty confiderable quantity of fmall cryf- 

 %^\^, which had all the chara6lers of fulphat of potafli ; fo 



T ^ tha^ 



