Anodic current efficiency in the counterflow electrolysis of uranyl chloride solutions

Abstract

.-"-!lodic cu rrent effi ciency or the chlorine-oxygen ratio in the electrolysis of aq ueous sol u t ions of uranyl chloride \\'as determined by a counterflow method at a temperat.u;e of 250 C. Because of the hyd rolysis of dissolved chlorine, measu rements we re made only a fte r suffi cient time had elapsed to ass ure a state of eq uilibrium. Different concentrations of elect rolyte, various elec- t rode materials, an d several current densit ies were employed to ascertain the effects of such changes. T he s lalldard potent ials of t he oxyge n a ncl chlorin e electrodes a re such that oxygen should be evolved at a nodes in t he electrolysis of ch lo rides. However, chlorine is liberate:! because of the relative magn it udes of t he oxygen a nd chlorin e overvoltages. The value of overvoltage is dependent on t he electrode material a nd the na ture of the electrode surface. For uranyl chloride t.he current effi ciencies inc rease in t he order : magnetite, a rc carbon, graphite, metall ic ca rbides. and the p lat inum metals. Magnetite, the cD rbiries, a rc carbon, a nd graphite e rode or pencil d uring elect rolysis. Palladium black a nd platinum black become dispersed in the electrolyte. The highest current effi ciency obtained was 97 perccll i; , and the data ind icated that cll rrent efficiencies of 100 percent cannot be realized for aq ueo us solu tions of IIranyl chloride at 250 C. The mcthod is gene ral a nd may be llsed in the determination of the current e ffi ciency of mallY electrode proceSties. The method may also be ada pted to th e continllous produ ct ion of gases of known purity.