Biography of Berzelius. 201 



But when it was attempted to prove this preconceived law 

 by demonstrating the composition of the decomposed salts, 

 all the proofs brought forward were either altogether in- 

 sufficient or very incomplete, — a circumstance resulting from 

 the then imperfect methods of separation, by means of which 

 it was impossible to attain to such accurate analyses that 

 the calculated results of the decomposition of two neutral 

 salts could correspond with experiment. 



The attention of chemists was soon diverted from this 

 subject when in the eightieth year of the past century the 

 theories of Lavoisier gave a new direction to the whole science. 

 The attack upon the phlogistic theory, and the establishment 

 of the antiphlogistic system, took undivided possession of all 

 thinking minds. None had time to occupy themselves with 

 any other than the qualitative changes which bodies under- 

 went by their mutual decomposition. It was also necessary 

 that Lavoisier's theory should have gained a complete ascen- 

 dency before the doctrine of simple chemical proportions could 

 be fully recognised and appreciated. 



In addition to this, the development by Berthollet, one of 

 the most gifted chemists of the time, of a theory apparently 

 in total opposition to that of definite chemical proportions, 

 tended to withdraw attention from the latter. Berthollet 

 endeavoured to prove, that bodies which possess an affinity 

 for each other are capable of combining in all proportions 

 between certain maximum and minimum quantities, and that 

 when the combination took place in definite proportions this 

 was owing to special circumstances, particularly the power 

 of crystallising or of cohering in any form, in consequence of 

 which compounds could separate from a solution, as precipi- 

 tates or crystals ; or else owing to the expansion taking place 

 on passing into the gaseous state, by which they removed 

 themselves from the sphere of action of solid or fluid 

 bodies. The most important law established by Berthollet 

 was, however, that of the so-called chemical mass, according 

 to which the deficiency of a body in chemical affinity may be 

 replaced or made up for by increasing its quantity : and it is 

 indisputable that this law, although it has latterly been more 

 and more forgotten, is perfectly correct. 



