Chemistry. — " Volta- Luminescence" . By Dr. J. Lifschitz. (Com- 

 municated by Prof. F. M. Jaeger). 



(Communicated at the meeting of June 3ü, 1923). 



^1. On the passage of electric current.s through Voltaic cells 

 phenomena of light are often observed at the electrodes. This "elec- 

 trolytic", or rather this "electrode" light can appear botii at the 

 anode and at the cathode, as well on use of continuous current and 

 of alternate current. The nature of the emitted light has seldom 

 been investigated, and then only unsatisfactorily. Consequently so 

 far only little could be said witli certainty about the nature of the 

 process. Some researchers (1, 2, 3) have interpreted some of these 

 phenomena of liglit as reaction luminescence phenomena — hence 

 as belonging to the phenomena of chemi-luminescence. If this should 

 appear to be true, this would be of importance, because, as is known, 

 ionic reaction is hardly ever attended with luminescence (4, 5). Besides 

 the [)henomena in question are of importance spectroscopically and 

 eleclro-cliemically. The light emissions under consideration may 

 certainly not be considered as of an exclusively thermal character. 

 For, as earlier experimenters already observed, the phenomenon of 

 light is as a rule the more intense, as electrode and electrolyte have 

 a lower temperature. Often the luminescence only occurs at very 

 small intensity of the current. The spectrum is mostly discontinuous, 

 or it presents at least a maximum of intensity, as is not pos- 

 sible with purely thermal radiation. At any rate an incandescence of 

 the electrode metal can he distinguished with perfect certainty from 

 the luminescence proper. Hence we are justified in distinguishing 

 the phenomena in what follows as "Volla-luminescences" ; ai)d it 

 will appear that inter se these are of very different characters, though 

 on the other hand they resemble each other more or less in the 

 following respects: 



1. There is mostly a considerable increase of the resistance of 

 the cells, as long as the electrode emits light. 



2. Formation of solid or gaseous layers at the luminescent elec- 

 trode, which sometimes enliiely prevent the passage of the current. 



3. Often an abnormal course of the electrolysis can be observed. 



37 



Proceedings Royal Acad. Amsterdam. Vol. XXVI. 



