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To avoid the formation of arsine (arsenic hydride) during the purification of waste copper electrolyte, electrowinning by controlling cathodic potential is suggested. By controlling the value of cathodic potential, copper and arsenic can first be separated and arsine and hydrogen will not form. In small-scale tests, the current efficiency reached 80%. After electrowinning, the copper content in the solution was less than 1 g/l and arsenic less than 0.5 g/l., To avoid the formation of arsine (arsenic hydride) during the purification of waste copper electrolyte, electrowinning by controlling cathodic potential is suggested. By controlling the value of cathodic potential, copper and arsenic can first be separated and arsine and hydrogen will not form. In small-scale tests, the current efficiency reached 80%. After electrowinning, the copper content in the solution was less than 1 g/l and arsenic less than 0.5 g/l.

The effects of temperature, time, atmosphere, reductant content, basicity, etc. on the volatility of Sn, Pb, Cu, Zn and As in pellets of tin middling have been studied and optimum conditions for roasting determined. The mechanism of chloridising volatilisation of metals in pellets is discussed in relation to the thermodynamics of the chemical reactions involved., The effects of temperature, time, atmosphere, reductant content, basicity, etc. on the volatility of Sn, Pb, Cu, Zn and As in pellets of tin middling have been studied and optimum conditions for roasting determined. The mechanism of chloridising volatilisation of metals in pellets is discussed in relation to the thermodynamics of the chemical reactions involved.