A method for electric refining of lead with alternating current in which the basic stage of the process is preceded by two stages, a preparatory stage and an initial stage. The preparatory stage involves pretreatment of the electrode surfaces by means of alternating current of equal width and amplitude of the forward and reverse pulses. During the initial stage there is effected an electric refining with alternating current having reduced current density.
A circuit for electric refining of lead with alternating current has two controllable current rectifiers, each of which is connected to a separate group of electrolytic baths. The groups of electrolytic baths and the controllable current rectifiers are connected in series and opposite to one another. In parallel with the output busbars of each controllable current rectifier there is connected in the same direction a semicontrollable thyristor switch and between the common point of the groups of electrolytic baths and the common point of the controllable current rectifiers there is connected in its conductive direction a common semicontrollable thyristor switch.