Dissolution of Cadmium in Chromic Chloride Solutions

Abstract

The dissolution rate of cadmium has been determined in dilute chromic chloride solutions containing hydrochloric acid up to 4M as functions of concentration, stirring speed, and temperature. A small amount of hydrogen is produced, but the main reaction is the reduction of chromic to chromous ion. Reaction with the violet hexaaquo chromic ion is slow and under chemical or electrochemical control; with the green dichIorotetraaquo ion it is much faster and transport-or diffusion-controlled. In each case, the driving force is only a few millivolts. The potential of the metal in these solutions is essentially that of the cadmium-cadmium ion couple, and there is little if any anodic polarization.