<Original Papers>Studies on Electrolytic Refining of Zinc. (III) : Behavior of Lead Peroxide Suspended in Zinc Electrolyte

To determine the effect of lead peroxide dispersed in electrolyte on the lead content of cathode zinc, the following investigation was conducted. For comparison with results in the previous work, experiments were carried out in the same manner as the previous one except the use of pure lead or 1% Ag alloy anode and the variation of the amount of lead peroxide kept in suspension. By comparing with the previous results it was found that the lead peroxide was occluded to the cathode zinc, as is well known as the major course of zinc contamination. In some examples, an assumption was made on the ratio of lead quantities transferred to zinc from lead ion deposition and from the occlusion of lead peroxide respectively. Results are summarised in the following four points : (1) Distribution of lead on the cathode surface depends on the amount of lead peroxide in suspension. When its quantity is large, lead distribution is not uniform, contaning more lead in the surrounding part ; on the other hand, when less quantity of lead peroxide is dispersed, the result approches to that of lead ion deposition only. (2) At low current dencity the influence of lead ion deposition is intensified, while at high current dencity the occlusion of lead peroxide is accelerated with increasing electrolyte agitation by bubbles. (3) Rising temperature is favorable to increasing lead ion concentration, and furthermore, the occlusion of lead peroxide. High current density accelerates the influence of elevated temperature. (4) It is impossible from comparison with the previous results to presume the contamination course of zinc in all runs except in some examples, because the lead peroxide particles dissolve relatively easily while electrolysis is going on