Modifying the force of Chemical Attraction. 237 



exerted by each. This hypothesis admits of the following 

 illustration. 



aaa^aaa^aaa 



The letters (a) represent atoms of lime ; the letters (e) at- 

 oms of carbonic acid, and all of them together, a quantity of 

 carbonate of lime, which has experienced the decomposing 

 agency of heat. The double letters {ce) represent atoms of 

 carbonate of lime undecomposed; upon the carbonic acid 

 (e) of which a force is exerted by the surrounding particles 

 of uncombined hme (a) to prevent its escape. The force 

 exerted by each uncombined (a) upon the (e) of the carbo- 

 nate, is very small when compared with that exerted by the 

 (a) in proper chemical union ; and capable of being overcome 

 by the weak affinity of water or other agent — and yet the 

 united force of all the uncombined (a's) though amounting 

 to only a third, a half, or some other larger or smaller frac- 

 tion of that of the single (a) in chemical combination, is such 

 as to require a considerable elevation of temperature to 

 overcome it. The tendency to definite proportions, in all 

 cases, and its existence in most, is here fully admitted. 



But passing by this, which is merely an hypothesis, desti- 

 tute of proof and incapable of it, we return to the principal 

 subject of this paper: That it is a law of extensive applica- 

 tion, that the quantity of matter modifies the force of chemi- 

 cal attraction, and compensates for a weak affinity. The 

 recollection of every practical chemist, will suggest to him 

 other examples analogous to the above, and pointing to the 

 same conclusion, but perhaps no facts are more to our pur- 

 pose than those collected by Berthollet, and laid by him as a 

 foundation on which to build his theory of chemical affinity, 

 if once the mistakes and misapprehensions prevailing re- 

 specting them are cleared away. 



At the beginning of the present century, few names were 

 more honored and respected amongst chemists than that of 

 Berthollet, He was always spoken of as the profound and 

 accurate. That the quantity of matter modifies the force of 

 chemical attraction, so as to compensate for a weak affinity, 

 was his favorite theory. In support of it when first advanced, 

 he brought forward seven new experiments, instituted by 

 himself for the express purpose of testing at once, and demon- 

 strating its correctness, besides calling into view some im- 

 portant facts with which chemists had long been familiar. 



