Electrochemical reduction of arsenic acid

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