<Original Papers>Redissolution of Cadmium in Zinc Sulfate Solution

Experiments were carried out in the hope of making clear the mechanism of redissolution of cadmium in zinc sulfate solution. In some cases cadmium redissolves even in the neutral zinc sulfate solution, and in other cases it does not dissolve even in the solution saturated with air at the atmospheric pressure. Different behaviors of cadmium depend upon the presence of impurities such as ions which lower hydrogen-over-voltage or which have an adverse effect on electrolytic deposition of zinc. However, redissolution does not occur, so long as cadmium holds the adhesion to metallic zinc. The tentative mechanism of cadmium redissolution is proposed as follows : Cadmium is detached from zinc by the mechanical impact given from stirring or filtration of the solution. Discharge or reduction reaction of hydrogen ion and oxygen occurs on the detached cadmium sponge. Under these conditions cadmium is capable of dissolving anodically, but the rate of redissolution is regulated by the diffusion of hydrogen ion or oxygen dissolved in the solution