LECTURE IV.] HISTORY OF CHEMISTRY. 51 



b of another base. The mode of expressing this which Richter 

 employs is remarkable. He says : 8 



" If P is the mass of a determining element, where the 

 masses of the elements determined by it are a, b, c, d, e, etc., 

 and <2 is the mass of another determining element, where the 

 masses of the elements determined by it are a, ft, y, 8, e, and 

 so on, but where a and a, b and ft c and y, d and S, e and e, 

 always represent one element, and the neutral masses P+a 

 and Q + P ; P+ b and Q + y ; P+ c and Q + a, etc., decompose 

 by double affinity in such a way that the products obtained are 

 again neutral, then the masses a, b, c, d, e, and so on, have ex- 

 actly the same quantitative ratio amongst themselves as the 

 masses a, ft y, 8, e, and conversely." 



I must observe that by the determining element, and the 

 element determined, Richter understood the quantities of acid 

 and of base that mutually neutralise each other. Richter well 

 understood the importance of the foregoing statement. He 

 remarks : 9 "This rule is a true touchstone of the experiments 

 instituted with regard to the relations of neutrality ; for, if the 

 proportions ascertained empirically are not of the nature that 

 the law of decomposition by double affinity requires, where the 

 decomposition actually taking place is accompanied by un- 

 altered neutrality, they are to be discarded without further ex- 

 amination, since an error has then occurred in the experiments 

 tried." 



Richter tabulated the quantities of the bases which are 

 neutralised by the same weight of sulphuric acid, of hydro- 

 fluoric acid, etc., and these he calls neutrality series, or series 

 of masses ; 10 he also determined the quantities of the acids 

 which are saturated by the same quantity of different bases. 11 

 In doing this, he thought he had discovered certain regularities, 

 but this subsequently proved to be fallacious. Thus, accord- 

 ing to him, the series of masses in the case of the bases formed 

 an arithmetical, and that in the case of the acids, a geometrical 



8 Neuere Gegenstande (1795). 2, 66, 9 Ibid. 2, 69. 10 Ibid, 



2, 70, n Ibid. 2, 92; 3, 176. 



