54 



ordinary aluminium, whicli is iherefore an enobled state of aluminium, 

 we ger what fellows. 



The ordinary aluminium is at first the negative pole with respect 

 to the mercury. It becomes, however, noble by the dissolving, and 

 it is soon as noble as mercury. Nobler than mei-cury it can, howe- 

 wer, not become then, since in this case, the current would be 

 reversed, which would change the state of the aluminium again in 

 the base direction. This is the reason that ordinary non-amalgamated 

 aluminium immersed in mercury, assumes the potential of the mer- 

 cury. This experiment can however not be continued for any length 

 of time, because the alummium in contact with mercury slowly 

 amalgamates, as we have seen, in consequence of which finally also 

 the part which is not in contact with the electrolyte, will become 

 active, so that the same things will be observed as in case of well- 

 amalgamated aluminium. 



In a following communication the investigation of the other metals 

 will be treated, after which a critical summary will be given of the 

 theories which have been proposed by others up to now as an ex- 

 planation of some of the facts discussed here. 



SUMMARY. 



In the foregoing pages the theory of allotropy was applied to the 

 electromotive behaviour of the metals A<j, Cu, Ph, Ni,Cd, Bi, Fe, Al. 



We have come to the conviction that the newly obtained point 

 of view, as we hope to prove further, enables us to survey the 

 widely divergent cases, and gives a deeper insight into the signifi- 

 cance of the observed phenomena. 



Anorg. Chein. Lah. of the University. 



Amsterdam, April 23, 1914. 



Chemistry. — ''The Allotropy of Cadmium:' II. By Prof. 

 Ernst Cohen and W. D. Helderman. 



(Communicated in the meeting of April 24, 1914). 



J. In our first paper on this subject') we concluded from measure- 

 ments with the pyknometer and the dilatoraeter that cadmium has 

 a transition temperature at 64°. 9 and that this metal as we have 

 known it until now, is a metastable system in consequence of the 

 very strongly marked retardation which accompanies the reversible 



1) Tiiese Proc 16, 485 (1913). 



