﻿Electrical Changes induced by Ultraviolet Lhjld. 413 



compounds in the same way as from metals. This means 

 that here also a slow disintegration is taking place, which 

 is accelerated by the light, and which in compounds depends 

 on the nature and quantity of each constituent. The effect 

 of alloying one metal with another does not seem to give 

 the mean of the two values, as is shown in the case of some 

 amalgams, Table IX. 



Table IX. 



Element. 



Rate of discharge. 



Tin 



128 sees. 



2-4 sees. 



216 sees. 



100-9 sees. 



06 sees. 



7 sees. 



10-0 sees. 



Zinc 



Mercury 





Tin amalgam 



Zinc amalgam 



Copper amalgam ... 



Saturated amalgams, cleaned by the method described for 

 the standard, were used for these experiments. 



C Certain cells only show an electromotive force when 

 one electrode is exposed to the light, whilst the other is kept 

 in the dark. Such differences of potential could easily be 

 explained by the hypothesis used throughout this paper. If 

 this hypothesis is applicable to the case of such an element 

 then a cell consisting of two similar electrodes of the same 

 metal in the same solution should have an electromotive 

 force when one electrode is placed in ultraviolet light, and 



the other is covered up. To investigate this theorem cells 

 were constructed of u viol-glass (fig. 5) ; one limb could be 

 darkened by slipping a blackened tube over it, whilst the 

 other was exposed to the light. The metals used in these 



