Abstract: Electrochemical properties of a cation exchange membrane of a carboxylic acid type fluorinated polymer which is used for an electrolysis of an aqueous solution of an alkali metal chloride is recovered by converting ion exchange groups of --COO).sub.m M; wherein M represents an alkali metal or an alkaline earth metal; and m represents a valence of M; to the corresponding acid or ester groups of --COOR wherein R represents hydrogen or a C.sub.1 - C.sub.5 alkyl group and heat-treating the fluorinated polymer having the groups of --COOR.

Abstract: In an electrodialysis process for aqueous base-containing solutions the improvement which comprises using a cation-exchange membrane made of a copolymer of ethylene and an unsaturated carboxylic acid or a salt thereof having an ion-exchange capacity of 0.7 to 3 m equivalent/g (dry resin).

Abstract: An acid diffusion-dialysis membrane, which can be used for separating an acid from a mixture of an acid and a salt, or a mixture of an acid and a water-soluble organic compound, e.g., glucose, by non-electrolytic dialysis, is prepared by forming a film from the combination of (I) a vinyl group containing benzene monomer or a vinyl group containing pyridine monomer, (II) a non-conjugated divinyl-containing monomer, and (III) a thermoplastic polymer which is swellable or soluble in the monomer mixture, polymerizing said monomer mixture in the film, and then introducing anion exchange groups into the resulting polymerized product. The acid diffusion-dialysis membrane is characterized by a high acid diffusion-dialysis coefficient and a high acid-salt selectivity ratio, and further by a relatively high mechanical strength.