Abstract: An alkali metal carbonate substantially free of alkali metal chloride is efficiently produced by electrolyzing an alkali metal chloride in an electrolytic cell having anolyte and catholyte compartments separated by a cation-exchange hydraulically impermeable membrane comprised of a thin film of a fluorinated polymer having pendant sulfononate groups and a cathode spaced apart from the membrane, injecting into the catholyte compartment of the cell carbon dioxide in a quantity sufficient to convert substantially all of the alkali metal hydroxide forming therein to the alkali metal carbonate salt, and utilizing a magnitude of electrolyzing current that reduces alkali metal chloride in the carbonate salt to less than 400 ppm.