Abstract: The invention relates to an aqueous electrolytic cathode and/or anode in which an aqueous solution of alkaline metal hydroxide is used or an active nickel or nickel alloy electrode having greater stability and smaller overvoltage under the condition of high current density for use in electrolysis of aqueous solution of alkaline metal halide, and the method for producing the same. Electrode material consisting of nickel or nickel alloy or electrode material of multiple layers comprising said electrode material coated with nickel or nickel alloy powder is forcibly subjected to oxidization and reduction treatments in repetition under a selected treatment temperature and atmosphere so that the surface area is expanded by the production of surface openings, thereby enabling to obtain an electrode having the said high properties.

Abstract: An electrode having a lead dioxide coat electrodeposited on a porous ceramic substrate is manufactured by soaking a porous ceramic substrate in an aqueous lead (II) salt solution and thereby allowing lead oxide to be deposited in the porous surface layer and on the surface of the substrate thereafter soaking said porous ceramic substrate in a persulfate solution to cause oxidation of the lead oxide so deposited therein and thereon and effecting electrolysis in an aqueous lead (II) salt solution by using said lead dioxide-coated substrate as the anode and the aqueous solution as the electrolyte and thereby causing lead dioxide to the additionally electrodeposited on said lead dioxide coat.The electrode manufactured as described above excels in corrosion-resisting property and therefore proves quite advantageous as an electrode for use in the electrolysis of aqueous solutions.

Abstract: Single crystals of .beta.-PbO.sub.2 are formed when an intermediate oxide of lead represented by the generic formula, PbO.sub.x wherein x denotes a value falling in the range of 1.4 to 1.7, is heated in an aqueous alkali hydroxide solution under a pressure exerted by use of oxygen or an oxygen-containing gas. The single crystals are in the shape of slender rods, have a black color and have a metallic gloss.