64 HISTORY OF CHEMISTRY. [LECTURE IV. 



explained by the fact that the hypothesis only led to decisive 

 results as to the number of atoms contained in the molecule 

 (and thus to the determination of the atomic weight) in the 

 case of gaseous substances, and was not applicable to solids 

 and liquids. Chemists, therefore, looked for new generalisa- 

 tions, and the next impulse in this direction was given by 

 Wollaston. 



Wollaston had carried out an investigation on the carbonates, 

 in i8o8, 35 which appeared simultaneously with an examination 

 of the oxalates by Thomson. 36 It was shown in the papers of 

 these chemists that carbonic acid can form compounds with 

 one and with two parts, and oxalic acid with one, with two, and 

 with three parts of potash. These experiments produced a 

 great impression, because at that time there were few facts of 

 this kind known which had been minutely examined ; on this 

 account, they formed an important support to the law of 

 multiple proportions. But if Wollaston, on the one hand, thus 

 exerted an influence upon the rapid recognition which the 

 atomic theory met with, and consequently came to be regarded 

 even by authorities as an adherent of the theory, 37 still, by a 

 later paper, 38 he contributed to the abandonment of the atom 

 by a section of chemists, as too indefinite a basis for chemical 

 considerations. 



In 1814, Wollaston, not without justice, represents to Dalton 

 how uncertain and arbitrary is his estimation of the number of 

 atoms in a compound ; and how, in consequence, the atomic 

 weights are wholly hypothetical numbers, so that, in his opinion, 

 they should not be adopted. He advised, instead of the con- 

 ception of the atom, the introduction of the equivalent, which 

 word he employs for the first time. Wollaston was well 

 acquainted with Richter's works, 39 and he derives the concep- 

 tion of the equivalent principally from his investigations. I 

 must at once remark, further, that, with him, not only are those 



35 Phil. Trans. 1808, 96 ; A.C.R. 2, 34. 36 Phil. Trans. 1808, 63 ; 



A.C.R. 2, 41. 37 Kopp, Geschichte. 2, 373. ** Phil. Trans. 1814, 

 i ; Ann. Chim. 90, 138. ^ Even Wollaston remarks (loc. cit.) that 

 Wenzel's analyses do not agree with the law of neutrality. 



