Role of Ionic Processes in the Electrolytic Coloration of KBr and KI

Abstract

The possibility that electrolytic coloration of alkali halides be due to electron injection from an alkali metal cathode, formed by ionic transport taking place in the sample prior to electrolytic coloration, has been investigated. The following results have been obtained: On heating the samples from room temperature, the coloration starts at a fixed temperature which is a function of the applied voltage. The relation between that temperature and the applied voltage has been discussed on the light of ionic conductivity mechanisms and it appears to be consistent with the formation of a new alkali metal cathode. The cation vacancy migration seems to play the main role in this process. Furthermore, the increase of the electrical current through the sample at the coloration outset can be explained as due to thermoionic emission from an alkali metal cathode.