Electrochemical reduction of arsenic acid

It is found that arsenic acid in aqueous solutions is reduced chiefly to ar sine, whose yield substantially depends on the cathode material nature and electrolysis conditions. The yield increases with the acid concentration an d catholyte temperature. The maximum yield (current efficiency of about 50% ) is obtained on a cadmium cathode. Hydrochloric acid or cationic surface-a ctive substances present in the catholyte raise the arsine yield on a coppe r cathode by more than two times and make no impact on the yield on a cadmi um cathode. A possible mechanism of the observed phenomena is discussed.