Redox control in the electrodeposition of metals

In one embodiment, a method of electrowinning a metal from an electrolyte comprises the steps of measuring the redox potential of the electrolyte to obtain a measured value, comparing the measured value with a predetermined optimum value and adding a redox agent to the electrolyte to adjust the redox potential of the electrolyte to the optimum value. One embodiment of apparatus (10) for carrying out the method comprises a redox potential measuring device (20) having a housing for the flow of electrolyte therethrough and including a pair of electrodes (22, 24) for measuring the redox potential of an electrolyte flowing through the housing to produce an output measurement value and a redox controller (26) responsive to the output measurement value for controlling the addition of redox agent to the electrolyte of an electrolysis cell (12).