Abstract: Method and apparatus for cyclic control of both potential and current in electrolysis, called Cyclic, Controlled-potential, controlled current Electrolysis. The method can be used with a two-electrode cell (W and C), or a three-electrode set-up using a reference electrode R to form two half cells. The method involves supplying a controlled current, preferably a constant current, to the W and C electrodes to operate the electrolysis within well-defined upper and lower potential limits. In a first embodiment (called the constant-current, preset-voltage mode), when a predetermined voltage is reached, the current is reversed until a second predetermined voltage is reached. The cycle is then repeated continously. In a second embodiment (called the preset-voltage, preset-time mode) the current is maintained constant until the predetermined voltage is reached. Then the voltage is maintained constant by reducing the current until a predetermined time of operation has elapsed.