440 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



In order to correct Patterson and Guthe's results, it became necessary 

 to repeat comparisons of the standard with the voltameter containing 

 old solution saturated with oxide, as used by them. 



TABLE XV. 

 Standard vs. Patterson and Guthe's Method. 



This result is perplexing, and much lower than the average computed 

 from the first two determinations, which was given in the preceding paper. 

 It indicates that the Patterson and Guthe method gives results 0.0G per 

 cent higher than those given by Lord Ravleigh's method, while Patterson 

 and Guthe's own comparisons give a difference of 0.1 1 per cent.* Evi- 

 dently the saturated-oxide method is more variable in different hands 

 even than Lord Rayleigh's. Perhaps the safest number to use in the 

 correction is the average of both, 0.085 per cent above the Lord Ray- 

 leigh method, or 0.135 per cent above the porous cup method. 



We are now in a position to make an approximate correction for the 

 effect of the contaminating anode liquid in each of the more important 

 investigations which bear upon the electro-chemical equivalent of silver. 

 Of these, those of Lord Rayleigh, Fr. and W. Kohlrausch, K. Kahle, 



* Pliys. Peview, 7, 280. Kahle (Wieel. Ann. 67, 32, also Brit. Ass't. A. Sc. 

 1892, 148), found 0.05 per cent, but his solutions were probably fresher. 



