131 



be expecled tlial the potential of such a inatei'ial aj^aiust Ccuhnium 

 which has been foriued by electrolysis should be zero. In order to 

 test this conclusion we carried out the following experiment : We 

 prei)ared a certain quantity of electrolytic cadmium (Prep. A) (Comp. 

 our second paper ^ 8) and determined (at 40°) the potential dilie- 

 rence between this material in a solution of cadmium sulphate which 

 was half-saturated at 15° C and : 



1. Cadmium, which we received from Kahlbaum (molten) in a 

 linely divided state (Prep. B), 



2. Cadmium which we had used in our dilatometric measurements; 

 in this material the presence of /-cadmium was presumed. (Prep. C). 



Making use of the small apparatus shown 

 in Fig. 3 we first determined the potential 

 (liiTerence between two samples of the same 

 material, subsequently that between samples 

 of diiferent preparations. In this way we found: 



E. iM.K. of A against A = 0.000037 Volt. 



Fig. 3. 

 Utrecht, May 1914. 



E. M. K. 



„ B 



„ C 



„ A 



„ A 



B=: 0.000018 Volt. 

 C = 0.00000 Volt. 

 Bz=: 0.000037 Volt. 

 C = 0.000037 Volt. 



From these measurements we see that y- 

 cadmium is really present in our preparations, 

 as the dilatometer had shown. 



VAN 't E.OFF- Laboi'((t07'y. 



[July 3, 1914). 



