240 On the Effect of the Quantity of Matter in 



Turner says, " A similar omission [to exclude the atmo- 

 sphere] appears to have been made in the other experiments, 

 where decomposition was attempted by pure potash or soda." 

 Though Berthollet does not state in express terms, at the 

 commencement of every experiment, upon the results, of 

 which the carbonic acid present in the atmosphere could 

 have an influence, that it was excluded, he does make this 

 statement in substance, respecting the second as well as the 

 firat ;* and where we find these marks of scrupulous caution 

 in two cases, it is but a piece of common justice, to suppose 

 they were not wanting in the others, and that the mention of 

 these was omitted, merely because it was supposed to be 

 unnecessary. 



The language of Davy, in the objections he has framed 

 to the seventh, or last and least valuable of Berthollet's ex- 

 periments, shows that he did not recur to the writings of that 

 chemist, to see what the experiments really were ; and 

 though it is barely possible, there might be something like 

 the play of affinities supposed by him : the view of the 

 change taken by Berthollet, is far more simple and has a 

 stronger probability in favor of its correctness. Of the facts 

 long known to chemists and cited by Berthollet — that no 

 amount of quick lime, for instance, will completely decom- 

 pose the carbonate of potash, no explanation is attempted. 



All these arguments and experiments therefore, by which 

 Berthollet was once supposed to have proved, and proved 

 decisively, that the quantity of matter modifies the force of 

 chemical attraction so as to compensate for a weak affinity, 

 remain unanswered and unshaken ; at least so far as Sir 

 Humphrey Davy and the English chemists are concerned. 



Experiments were brought forward by Pfaff", tending to 

 show, that in some cases quantity has no influence. These 

 it was necessary for Berthollet to explain, in accordance 

 with his views, and he published an answer to the paper, 

 in which they were detailed. But' with this dispute we have 

 here no concern., though Pfaff's experiments are sometimes 

 absurdly enough cited to prove that quantity of matter has 



a distinguished chemist, solely on his own misconceptions of the experiments 

 by which that theory is supported, and the error be propagated from one book 

 to another for years, is lamentable. 



* " Le sulfate de potasse ayant 6te soumis k la meme epreuve avec poids 

 6gal de chaux," etc. 



