Although alkaline stannate baths for electrorefining of tin have been used for some time, there is still room for improvement The effects of alkali concentration, current density and temperature on the cathodic current efficiency have been studied, and a bath temperature of 75°C is recommended. To avoid unstable conditions in the bath, a special treatment to the anode and application of an auxiliary cathode are necessary. Many of the metallic impurities present in the crude tin anode go into the slimes in the form of hydroxides, but lead impurities can only be tolerated if concentrations are less than one percent.