639 



contain /?-ca'1minm, those giving 0.047 Volt rt- cadmium, whilst those 

 giving 0.050 Volt have y-cadniinm as a negative electrode. 



5. If this were really the case, it would be possible to construct 

 a transition cell by combining a cell with «-cadmium with one 

 containing /^-cadmium; the E.M.F. of this combination would be zero 

 at the transition temperature of the change f.-cadmium^,^cadmium. 



6. However it is impossible to carry out an exact determination 

 of the transition point in tliis way, as the E.M.F. of the combination 

 is (at 25°.0) only (0.048— 0.047) = 0.001 Volt and the reproducibility 

 of each of the cells is only 0.5 millivolt. 



7. In order to ascertain if the E.M.F. of the /?-celIs .has a real 

 significance, experiments may be carried out on the following lines : 



At temperatures above the transition point of the change «-cad- 

 mium ^ ^-cadmium (which we found in the neighbourhood of 60° 

 by dilatometric measurements) the E.M.F. of «-cells must be higher 

 than that of j^-cells. After cooling the cells below the transition point 

 mentioned, the contrary will occur. 



8. Our experiments in this direction w^ere carried out in the 

 following way : 



We constructed a large number of Hui.ett cells ') ; one of these, 

 the E.M.F. of which had been originally 0.050 Volt at 25\0, had 

 an E.M.F. of 0.047 Volt (at 25°.0) after having been kept for 4 weeks 

 at 47^5. After this time it remai]ied constant. 



We combined this cell (N". 7) with 

 another one (N°. 22) the E.M.F. of 

 which was 0.048 Volt at 25°.0. The 

 two cells AB (N°. 7) and CD (N". 22) 

 were connected by a siphon H, 

 which contained the same sohition 

 of cadmium sulphate as was present 

 in the cells. (Fig. 1). 



The lateral tube E of the siphon 

 was closed by a rubber tube F, iji 

 which was put a glass rod G. The 

 A3 CD little apparatus was brought into a 



Fig. 1. thermostat which could be kept at 



will at 25°.0 or 64°.5. 



9. We measured the E.M.F. l)etween the cadmium which had 

 been electrolytically deposited on the platinum spirals A and C 



•) Proceedings 17, 122 (1914). 



