Abstract: Apparatus for electrolyzing a liquid having an electrolytically regeneratable ionic oxidizing agent, the apparatus including an anode having a tubular portion and a cathode having a cylindrical portion inside the tubular portion of the anode. The opposing surfaces of the tubular anode portion and the cylindrical cathode portion are substantially uniform and concentric about a common axis. In one embodiment, the anode and cathode are each made of a plurality of portions, with means for electrically connecting anode-cathode pairs of said portions in series.