Chemical Affinity in terms of Electromotive Force. 391 



error limits) with that calculated in this way, the values of a 

 and b being deduced from the above table by interpolation. 

 Thus the following values were obtained: — 



Different Solutions of the same Salt mixed. 



Stronger solution 



Weaker solution 



Observed contraction 

 Calculated „ 



CuS0 4 47H 

 CuS0 4 163 H~0 



1-12 



113 



ZnS0 4 19-3 H 2 

 ZnS0 4 148 H 2 



3-84 



3-83 



OdS0 4 15-81 H 9 

 CdS0 4 171 h;o 



4-88 



4-66 



Difference 



+ -01 



- -01 



- -22 



Solutions of different Salts used. 



Stronger solution 



ZnS0 4 19-3 H 2 

 CuS0 4 163 H 2 

 4 4-37 2 

 4-23 



CuS0 4 47H 9 

 ZnS0 4 148 HlO 



•92 



•99 



Weaker solution 



Observed contraction . . . 

 Calculated „ 



Difference 



-•14 



+•07 





CdS0 4 15-81 H 2 

 CuS0 4 163 H 2 



4-39 



4-36 



CdS0 4 15-81 H 2 

 ZnS0 4 148 H 2 



4-19 



4-11 



ZnS0 4 19-3 HO 

 CdS0 4 171 H 2 



4-41 



4-42 



- -03 | - -08 



+ -01 



Since but little difference exists between the contractions 

 on dilution through given ranges, whether zinc, copper, or 

 cadmium sulphate be employed, it results that the amounts of 

 contraction on intermixture when two different solutions of 

 the same salt are mixed will not differ greatly whichever of 

 the three salts be employed. It would hence seem that there 

 is a much closer connexion between the amount of contraction 

 taking place on intermixture, and the potential difference 

 thereby developed, than there is between either of these values 

 and the heat-evolution simultaneously taking place. For 

 varying solution-strengths, the first two values alter fairly 

 concurrently and to extents not widely different, whether zinc, 

 copper, or cadmium sulphate be used. But this is by no 

 means the case with the heat-values, the cadmium value 

 largely exceeding the corresponding zinc and copper values, 

 which latter two are substantially identical. 



