Chemistry. — ''The Allotropn uf Caihniuin". VI. By Prof'. Ernst 

 Cohen. 



(Communicated in the meeting of December 29, 1917). 



1. Some time ago Frederick H. Getman published a paper ^) on 

 the allotropy of cadmium in which he describes some experiments 

 bearing upon my investigations on this subject. However, in Getman's 

 assumptions as well as in the conclusions he deduces from his 

 careful experimental work some mistakes liave crept in. In the 

 present paper we intend to prove that if these mistakes are removed, 

 Getman's results become identical with those of Cohen and Helderman. 

 As a result Getman's work affords a very welcome control as well 

 as a confirmation of the results formerly got by ourselves. 



2. Having found in our dilatometric experiments that there exist 

 three (at least) different modifications of cadmium to which the names 

 Cd«, Cd^ and Cd.^, respectively, were given, we stated that the 

 transition temperature of the transformation 



Cdai^Cd^ 



is to be found in the vicinity of 60°. We were unable until now 

 to fix this temperature more closely with the dilatometer in con- 

 sequence of the presence of Cdy. 



3. Getman prepared in the same way as we did a nutnber of 

 HuLETT-cells, which were constructed according to the scheme 



Cd 



Cd-amalgam x % 

 by weight. 



Solution of CdS0,.7,H,0 

 7, saturated at 20° 



Whereas x was generally 12.5 in our cells, Getman has chosen 

 x=^S. The negative electi-ode consisted of a platinum spiral covered 

 with an electrolytic deposit of cadmium. If these cells are maintained 

 for some time at 20° they finally give a constant e. u). f. In perfect 

 agreement with our statement Getman found that three different 

 types of cells were formed in this way : 



1) Journal Americ. Ghem. Soc. 39, 1806 (1917). 



