8 Meldrum, Development of tJic Atomic TJieory. 



different workers and even by the same worker. He was 

 able to maintain his teaching by quoting able chemists 

 such as Vauquelin and Klaproth, whose results a priori 

 were as probable as Proust's."' 



Proust had to maintain his own analyses in the face of 

 Berthollet's teaching and of the analyses of other 

 chemists. It is quite a mistake to suppose that his results 

 were specially accurate. E. von Meyer surmises that if 

 he had only " calculated the result of his experiments on 

 the composition of binary compounds otherwise than he 

 did, he would have discovered the law of multiple pro- 

 portions."" As a matter of fact he frequently ex- 

 pressed his results in a way that must have revealed the 

 law in question, supposing that he had known what to look 

 for, and that his data were approximately correct. For 

 the composition of black oxide of copper he gives copper 

 lOO and oxygen 25, and this is correct, and for the com- 

 position of the red oxide copper 100, and oxygen 17 — 18 

 instead of I2'5.'' These figures prove that for the deter- 

 mination of the composition of chemical substances it is 

 not sufficient to have good intentions and a strong con- 

 viction that substances are formed in invariable propor- 

 tions. 



In truth the odds against Proust were heavy. He 

 had no principle of the same calibre as the doctrines of 

 mass-action and chemical equilibrium with which to 

 encounter Berthollet. He had to trust to the purely em- 

 pirical method, and there is no reason to think that it 

 was by means of this method that the doctrine of constant 

 proportion was ultimately established. 



-' Jour, dc Phys., vol. 6o, p. 349, 1805. 



-^ Op. cil., pp. 195 — 196; see also Airhenius to llie same effect, 

 "Theories of Chemistry," Eng. Trans., p. 16, 1907. 



"" Journ. de Phys., vol. 65, p. 80, 1807. 



