on Chemical Equivalence. 179 



IV. Discussion. 



The precipitability of nickelous sulphate being, asjieretofore, 



represented by <f>= -, we find our experiments in accordance 



with the equation 



= 1-53106 (1) 



Probable error of a single experiment, '034802: of nine expe- 

 riments. -011601. 



In a similar manner, the precipitability of cadniic sulphate, 



4>= s, proyes to be 



<f>= 1-19462 --25763c? (2) 



Probable error of a single experiment. '025793: of nine expe- 

 riments, -008598. 



In order to ascertain under what conditions the two sul- 

 phates are equally precipitable, we must have 



l'19462-'25763c7=l'53106, 



which leads to —1-3059 as the value off/. To this negative 

 result no chemical interpretation can be assigned. We con- 

 sequently infer that, in these experiments, nickelous and caclmic 

 sulphates are not comparable in point of precipitability. 



To calculate in what proportions the sulphates should be 

 mixed in order to yield equal weights of precipitate, we must 

 solve the quadratic 



n 1-53106 v 



d (l'19462-'25763f?)6 



} 



[The condition gives ~ = 1], The deduced values are d= '4153 



and /i = '5847. Inserting these quantities in the primitive 

 equations, we obtain v=S='3819, a result evidently in ac- 

 cordance with experiment. 



Our present inference with regard to the precipitability of 

 nickelous-cadmic salt will lead (if confirmed by the action of 

 reagents other than sodic carbonate) to the following important 

 criterion: — Two elements belong to the same group when, in 

 saline solutions of identical genus, they may be equally preci- 

 pitable. 



