抄録
Electrolytic oxidation of chromium (III) in chromic acid solutions was studied as functions of the electrolyte composition and the conditions of electrolysis. For a lead (IV) oxide anode, the current efficiency for the oxidation of chromium (III) to chromium (VI) was found to decrease with increasing current density and decreasing chromium (III) concentration. The cathodic polarization measured with an iron cathode was affected strongly by the concentrations of sulfate and chromium (III). In solutions without sulfate, the cathode reaction was solely evolution of hydrogen. In solutions containing sulfate, the reduction of chromium (VI) to chromium (III) was dominant at cathode potentials more noble than-1.0-1.1V (vs SCE), while the evolution of hydrogen, deposition of metallic chromium and reduction of chromium (VI) to chromium (III) were observed to occur simultaneously at less noble potentials. For the purpose of recovering chromic acid from chromium (III) using an electrolytic cell without diaphragm, it was found desirable that the electrolysis was carried out in a solution of high chromium (III) concentration with sulfate as low as possible, and using lead (IV) oxide as the anode. The current density must be low at the anode and sufficiently high at the cathode.
