<Original Papers>Studies on Electrolytic Refining of Zinc. (IV) : Courses of Lead Transferred to Cathode Zinc

To elucidate the courses of lead coming into the cathode zinc, comparison was made with the lead content of zinc deposited to two cathodes of which one was enclosed in an unglazed cylindrical alumina diaphragm and the other was directly immersed to electrolyte suspending reasonable amount of lead peroxide particles. Electrolyte solution was forcibly circulated through the diaphragm to prevent growth of difference between electrolyte constituents, especially lead ion concentration, of both sides of diaphragm. The lead distribution between lead ion deposition and lead peroxide occlusion was decided by comparing results of these two cathodes. The ratio of lead quantity caused by lead ion deposition to the total amount of lead in the cathode zinc was much higher beyond our expectation. The ratio of lead ion deposition increased with increase in lead ion concentration of electrolyte solution and with decrease in amount of dispersed lead peroxide particles and in electrolyte temperature. The total lead content of cathode zinc takes the minimum value at the some current density which varies with correlation between lead ion concentration and the amount of dispersed lead peroxide, and with other electrolysis conditions. At that current density, it was found that the respective lead quantity that comes into cathode passing through the different course was just same. In higher range than that current density, the occlusion of lead peroxide is the predominating factor in contamination course of zinc, but at a less current density, cathodic contamination is due mainly to the deposition of soluble lead. From comparison of both contamination ratios of lead ion deposition and lead peroxide occlusion, it was found that we had to pay the same attention to lead ion deposition as to the lead peroxide occlusion