LECTURE III.] HISTORY OF CHEMISTRY. 35 



place, however, long after his death, and therefore I postpone 

 the consideration of this matter to a later lecture. We must 

 occupy ourselves here with another attack upon Lavoisier, 

 which was eventually decided in his favour; and is of im- 

 portance on this account, that through it a strict separation of 

 mixtures from compounds was first brought about. 



This attack had to do with the question whether chemical 

 combinations are possible in all proportions, or whether sub- 

 stances can combine in certain fixed proportions only. The 

 latter view, as is evidenced by many of his investigations, 

 was assumed by Lavoisier ; and indeed it seems to have been 

 accepted as self-evident by all the chemists of his time, without 

 having been proved. But a book appeared in 1803 which 

 attracted the greatest attention in the scientific world, both on 

 account of its contents and of the form in which these were set 

 forth ; and in this book, amongst other things, the constancy 

 of chemical proportions was denied, on the ground both of 

 theoretical speculation and of experimental investigations. 



The work to which I refer is Berthollet's Statique Chimique, 

 and if I am to render intelligible the importance of the attack 

 which it contains, I must give at least a slight sketch of 

 Berthollet's extremely interesting general theoretical ideas. I 

 extract these from the work just mentioned, and from some 

 scattered essays by its author upon the same subject. 6 



Berthollet's book will always be of importance in chemistry, 

 chiefly because the fundamental doctrines to which the author 

 subordinates all chemical reactions, are the principles of me- 

 chanics and of physics ; and these must necessarily possess a 

 value in chemistry. And even although many of Berthollet's 

 conclusions do not harmonise with experiment, and have long 

 since been disproved, still this does not damage the basis of his 

 conceptions. 



The work as a whole is chiefly directed against the false 

 view which had been adopted with regard to the affinities of 

 substances ; and against the misuse which was made at the 



6 Ann. Chim. 36, 302 ; 37, 151 and 221 ; 38, 113 ; 39, 3. 



