Abstract: A filter press type ion exchange membrane electrolytic cell which comprises an anode compartment and a cathode compartment partitioned by a cation exchange membrane and which is useful for obtaining a halogen, hydrogen and an alkali metal hydroxide from an alkali metal halide aqueous solution, or oxygen and hydrogen from an aqueous alkaline solution.

Abstract: The deterioration of a palladium oxide type anode caused by stopping the operation of a diaphragm type electrolytic cell in the electrolysis of an alkali metal chloride is prevented by increasing the concentration of hypochlorite ions in the anolyte to give a predominant anode potential in short circuit state higher than the reduction potential of palladium oxide.

Abstract: A zoom lens system for a camera comprises a focusable lens, a variator lens for making a focal length of the lens system variable and a compensator lens for compensating the displacement of its image point caused by the variator lens. A zoom operating sleeve is provided which is rotatable about an optical axis and formed on its inner surface with first and second cam surfaces according to which lens holders for the variator and compensator lenses are respectively controlled in relative movement with the aid of a spring for resiliently urging the lens holders against the cam surfaces.