xiv THE ATOMIC THEORY 305 



the three proportions of oxygen to nitrogen l were in the 

 ratio 1:2:4, and the two oxides of carbon in which the 

 two proportions of oxygen to carbon 2 were in the ratio 1:2. 



The analytical data which Dalton used were no more 

 exact than those of Proust, and were, indeed, much less 

 exact than those on the strength of which he repudiated 

 Gay-Lussac's Law of Volumes (see below, p. 335). But, 

 guided by his theory, he was able to recognise the existence 

 of simple ratios, even in the imperfect data which were 

 at his disposal. The opinions of Berthollet, " that the 

 chemical agency is proportional to the mass, and that in all 

 chemical unions there exist insensible gradations in the 

 proportions of the constituent principles" (A.C.R. II. 27), 

 was quite incompatible with the atomic theory, according 

 to which one or more atoms of an element could combine 

 with i, 2, 3, etc., atoms of a second element, but not with 

 (any intermediate fractional number. Dalton therefore 

 jdenounced it as inconsistent "both with reason and 

 Observation " (A.C.R. II. 28), whilst Proust was able to 

 show that it had no sufficient experimental basis. 



The law of multiple proportions supported by Thomson 

 (1808), by Wollaston (1808) and by Gay-Lussac (1809). 



As soon as the law of multiple . proportions had been 

 discovered, ample evidence in support of it was forthcoming. 

 Thomas Thomson, whose History of Chemistry is of undi- 

 minished value after being in use for nearly a century, 

 directed attention to the existence of two series of OXALATES, 

 and especially of two potassium oxalates and two strontium 

 oxalates. The composition of these oxalates showed the 

 following simple relationship : 



"Suppose TOO parts of potash; if the weight of acid 



] Dalton gives the proportions as 7 : 10, 7 : 5, 14 : 5. 

 The actual proportions are . . 4 : 7, 8 : 7, 16 : 7. 



Dalton gives the proportions as 7 : 5, 14 : 5. 

 The actual proportions are . .4:3, 8:3. 



