284 Dr. C. E. A. Wright on the Determination of 



is very far superior, a well-constructed cell giving absolutely 

 the same value (when used in conjunction with a quadrant 

 electrometer only) for months and months together. 



110. The above described experiments having given results 

 indicating the average values of the electromotive forces 

 developed with different characters of plates when the specific 

 gravities of the solutions surrounding the plates are the same, 

 further series of observations were made with cells in which the 

 zinc- and copper-sulphate solutions were not of the same 

 specific gravity, the mode of operating being otherwise the 

 same as before. As predicable from Moser's figures, and as 

 previously observed by H. F. Weber, it was found that when 

 the copper-sulphate solution was the more dense of the two, 

 the E.M.F. was higher than with solutions of equal density, 

 and vice versa when the zinc-sulphate solution was the stronger. 

 The average results of various observations, mostly lasting 

 over four hours as before, are contained in the following table ; 

 in every case the zinc plate employed was of pure metal and 

 amalgamated with pure mercury. 



Effect of increasing the strength of the Zinc-sulphate solution 

 relatively to that of the Copper-sulphate. 



Specific gra- 

 vity of solu- 

 tions used. 



Zinc 

 sul- 

 phate. 



, Copper 

 jsulphate. 



1-145 



1-175 



*l-395 



*l-395 



1-010 { 

 1-050 [ 

 1-050 [ 

 1010 [ 

 •1-175 f 



Nature of 

 copper 

 plate. 



Electro. 

 Bright. 



Electro. 

 Bright. 



Electro. 

 Bright. 



Electro. 

 Bright. 



Electro. 

 Bright. 



Average E.M.F. at 18° of 

 combination. 



Ob- 

 served 



1-099 

 1107 



1102 

 1-108 



1096 

 1103 



1-077 

 1-086 



1-097 

 1-104 



Previously 

 found for 



solutions of Differ- 



equal spe- 

 cific gra- 

 vity. 



1-114 

 1120 



1-114 

 1-120 



1114 

 1-120 



1-114 



1120 



1-114 

 1120 



•015 

 013 



•014 



•012 

 •012 



•012 



•018 

 •017 



•0175 



•037 

 •034 



•0355 



•017 

 016 



•0165 



Ratio of differ- 

 ence in E.M.F. 

 to difference in 

 specific gravity. 



S-« 



Si«<™ 



^=•083 



•0386- W - 



•0165 cv .. 



