Abstract: In a method for electrolyzing hydrochloric acid in an electrolysis apparatus, the improvement which comprises the electrolysis apparatus comprising at least two electrolysis cells, each electrolysis cell having at least one anode, at least one cathode and at least one cation exchange membrane therebetween to define an anode compartment and a cathode compartment therein, and the method comprising the steps of(a) feeding hydrochloric acid aqueous solution as a starting material into the anode compartment of a first electrolysis cell and electrolyzing the hydrochloric acid aqueous solution therein,(b) feeding hydrochloric acid aqueous solution discharged from the anode compartment of the first electrolysis cell into the anode compartment of a second electrolysis cell and electrolyzing the hydrochloric acid aqueous solution therein,(c) feeding hydrochloric acid aqueous solution discharged from the anode compartment of the last electrolysis cell of the electrolysis apparatus into the cathode compartment of each of

Abstract: A cathode for use in electrolysis comprising (1) a substrate of iron or an alloy thereof; (2) a compact interlayer of Fe.sub.3 O.sub.4 formed on the substrate, and (3) a coating of activating nickel comprising principally nickel or an alloy thereof formed on the Fe.sub.3 O.sub.4 layer. In another embodiment, the interlayer (2) may be heat-treated to convert a part of the interlayer (2) into a nickel ferrite. The cathode is especially suitable for use in the electrolysis of an alkali metal halide, such as sodium chloride, using an ion exchange membrane method.

Abstract: A method for electrolyzing a molten chloride which comprises electrolyzing a molten bath of a chloride of a metal more base than hydrogen, such as sodium, magnesium, calcium or aluminum, in an electrolytic cell containing an anode and a cathode to form chlorine at the surface of the anode and the metal at the surface of the cathode,wherein the anode comprises an electrically conductive substrate resistant to corrosion by the molten bath of the metal chloride and the electrolysis products thereof and having thereon a coating of a noble metal oxide, andwith the electrolysis being carried out in the presence of an oxide or oxychloride of a metal more base than the metal formed at the cathode where the concentration of the oxide or oxychloride of the metal present in the molten bath, expressed as the mole fraction of free oxygen ion, is at least about 1.times.10.sup.-4.