641 



Table II. 



Temperature 25°.0, 

 E.K. 

 Cell 8 0.04757 Volt 

 Cell 4 0.04839 „ 



Temperature 64°. 5. 

 Cell 8 0.04737 Volt 

 Cell 4 0.04633 „ 



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

 Cell 8 0.04776 Volt 

 Cell 4 0.04789 „ . 



11. From table II it may be seen that we are here at the limit 

 of measurement obtainable in working with cells of so small an 

 E.M.F. the reproducibility of which is 0.5 Millivolt. 



12. From the invei-sion of poles which has been observed, we 

 may conclude that the value 0.048 Volt at 25°.0 really has signi- 

 licance and is to be attributed to the presence of /?-cadmium. 



- 13. As to the bearing of the existence of different modifications 

 of cadmium on the E. M. F. of (he standard cell of Weston, we 

 refer to our paper "On the Thermodynamics of standard cells" 

 (sixth communication), published some months ago ^). 



Utrecht, September 1914. van 't ]Aoyy- Laboratory. 



Chemistry. — -'The Allotropy of Z'mc.'' III. By Prof. Ernst 

 Cohen and W. D. Helderman. 



(Communicated in the meeting of September 26, 1914). 



1. In our first communication on the allotropy of zinc ''), we 

 summarized the earlier literature on this subject as follows: as long 

 as half a century ago various investigators tried to solve the problem 

 whether zinc might be capable of existing in different allotropic 

 modifications. As late as 1890 Le Chatelier proved that this metal 

 does really show a transition point in the neighbourhood of 350°. 

 MöNKEMEYER found tliis poiut at 321°, Benedicks at 330° (melting 

 point of pure zinc 419. °4) whilst the measurements of Max Werner 



1) Chemisch Weekblad 11, 740 (1914). This paper will be published before long 

 in the Zeilschr. f. physik. Chemie. 



2) Proceedings 16, 5G5 (1913). 



