402 



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



uulphate with sulphuric acid. The last method gave the largest difference, but this 

 was of the order of 5 parts in 100,000 only. 



Mr. J. A. SADD, A.C.G.I., a student demonstrator of the Central Technical College, 

 has constructed some cadmium cells in accordance with a specification published by 

 the author* in 1905. These cells contain mercurous sulphate prepared electrolytically, 

 and were forwarded to the National Physical Laboratory for comparison with our 

 standards. There are ten cells in all, and their values at 17 C. are as follows : 



1-01832 volts. 

 34 

 35 

 37 

 38 



1-01839 volts. 

 39 

 40 

 42 

 43 



Mr. H. TINSLEY, of Beckenham, Kent, has also prepared some cadmium cells in 

 accordance with the specification mentioned above. In this case the depolariser was 

 prepared with mercurous sulphate precipitated by adding mercurous nitrate to 

 sulphuric acid (Method II.). Most of Mr. TINSLEY'S cells are also greater in E.M.F. 

 than the N.P.L. standards, the difference being about 1 part in 10,000. 



In May, 1907, 12 cadmium cells prepared by Dr. F. A. WOLFF of the National 

 Bureau of Standards, Washington, were brought to England by Dr. BURGESS, and a 

 direct comparison between the cells of the two institutions was thus rendered possible. 

 Cells which were believed to nearly represent the normal cell were chosen to compare 

 with those from Washington, and the following differences were observed : 



TABLE II. 



F. E. SMITH, 'British Association Rt-port,' Section A, 1905 



