The electrochemical reduction of dichromate

Abstract

The reduction of dichromate to chromic ion has been studied in sulphuric and perchloric acid solutions, in connection with the possible use of dichromate as a depolariser in a primary battery. Gold and pyrolytic graphite electrodes have been used. At a gold electrode the current increases rapidly to a limiting value. Potential-sweep experiments and electron diffraction studies indicate that the rate of reduction is controlled by the properties of surface film. The nature of this film is altered by potential and is also modified by addition of foreign anions. On a pyrolytic graphite electrode in perchloric acid, film deposition and modification again considerably modify the rate of reduction. In sulphuric acid solutions, however, the form of the current-potential curves obtained is not determined primarily by the properties of a surface film. Under these conditions it was shown that dimeric CrVI species are reduced at more positive potentials than the monomeric species. The kinetics of the reduction of the monomeric species has been investigated.