mercury cathode process all require the introduction of water or a dilute aqueous caustic solution into the cathode compartment of an electrolytic cell during electrolysis and such addition results in a loss of current efficiency as noted above in the practice of this invention water or dilute alkali metal hydroxide solution is usually introduced to the cathode compartment only initially and added subsequently only if optionally desired the brine solution introduced into the anode compartment may vary widely from about 100 g l to about 325 g l of nacl concentration but preferably is maintained at from about 160 g l to the saturation concentration of nacl also excellent results may be obtained in the practice of this invention when either high purity or impure alkali metal halide solutions are employed as the anolyte during either batch or continuous operation alkali metal halide is usually introduced to the anode compartment as an aqueous solution of desired concentration however the alkali metal halide may obviously be introduced as a combination of dry halide salt and water in amounts calculated to provide a desired predetermined concentration in some cases after the initial introduction of alkali metal solution to the anode compartment the addition of dry halide to the anode compartment may be desirable during either batch or continuous operation to maintain the concentration of the alkali metal halide anolyte at a desired level the cell of the present invention is constructed in two hollow sections which allows the fluorinated copolymer cation exchange resin film to be positioned and maintained in closely spaced.