418 



MR F. E. SMITH ON THE NORMAL WESTON CADMIUM CELL. 



the mean (indicated by A) of these six cells is taken as the basis of values given 

 in Table VIII. 



TABLE VIII. 



It will be seen that the American and English cells agree very well among each 

 other. In the first series of measurements : Mean E.M.F. of English cells Mean 

 E.M.F. of American cells =+0'000006 volt, and in the second series of measure- 

 ments the difference is +0'000009 volt. Two cells which Mr. KAYNER of the 

 National Physical Laboratory kindly took from Teddington to the Reichsanstalt, in 

 September, show equally good agreement. 



The German cells mentioned in Table IX. (the series are designated by P, O, 

 and M) were prepared in March, 1907, with three different samples of mercurous 

 sulphate made by the von Steinwehr precipitation method. During the first few 

 months after their preparation these cells showed on the average a decrease in E.M.F. 

 of about 1 part in 10,000, and the E.M.F. had not attained a state of constancy at 

 the commencement of the measurements in question. Drs. JAEGER and LINDECK 

 suggest that the cause of this alteration lies in the fact that the three samples of 

 mercurous sulphate were washed out with dilute sulphuric acid in course of prepara- 

 tion. The relative agreement in the individual groups is, however, very good. In 

 the P group there are eight cells and the difference between any one cell and the 

 mean has at no time exceeded 2 parts in 100,000 ; in the O group there are six cells, 

 and in the M group six cells, and the corresponding differences for these groups are 

 about 1 and 17 parts in 100,000, respectively. Inter comparisons were made with 

 the older cells (1899) of the Reichsanstalt, which were taken as constant during the 

 period June 20 to September 30, 1907. 



