040 



against the common amalgam electrode B. (12.5 "/„ by weight). It 

 is absolutely necessary to use ?i common electrode as the cadmium 

 amalgam of 12.5 percent hy weight does not form a heterogeneous 

 system at 64^.5; its E.M.F. is then a function of its composition. The 

 use of the two amalgam electrodes B and D might give rise to 

 serious mistakes, if there were only small differences in their com- 

 position. 



The absolute E.M.F. of our amalgam electrode against cadmium 

 in. A and C does not play any role in our measurements. 



10. The determinations of E.M.F. were carried out by the Pog- 

 GENDORFF compensation method. The resistances used, had been checked 

 by the Physikalisch-Technische Reichsanstalt at Oharlottenburg — 

 Berlin. The same was the case with the thermometers used. Our 

 two standard elements (Weston) were put into a thermostat which 

 was kept at 25°. 0. We used as a zero instrument a Deprez-d'Arsonval 

 galvanometer, which was mounted on a vibi-ation-free suspension 

 (Julius). The readings were made by means of a telescope and scale; 

 0.02 millivolt could easily be measured. 



The determinations were continued during several days, until the 

 E.M.F. of the cells had become constant. 



Our table I shows the results. 



Table I. 



Temperature 25°.0. 

 E.M.F. 

 Cell 7 0.04741 Volt 

 Cell 22 0.04815 „ 



Temperature 64°. 5 

 Cell 7 0.04029 Volt. 

 Cell 22 0.03979 „ 



After having brought the cells to 25°.0, we found : 

 Cell 7 0.04741 Volt. 

 Cell 22 0.04806 „ 



The table shows that at 64°. 5 there has taken place an inversion 

 of the poles and that the cells regain their original E.M.F. at 25°. 0. 



A second experiment with two cells (n^ 4 and 8) newly con- 

 structed, gave the following results: 



