Abstract: This invention relates to an improved method of operating a three compartment electrolytic cell which comprises an anode compartment, a buffer compartment and a cathode compartment. More specifically, it concerns an improved method of operating a three compartment cell used in the electrolytic production of chlorine and caustic wherein the solution produced in the buffer compartment is either chemically or physically treated to optimize the overall operation of the three compartment electrolytic cell.

Abstract: In the electrolysis of an alkali metal chloride brine in an electrolytic cell equipped with a permselective ion exchange membrane between the anode and cathode, which membrane is of the perfluorinated sulfonic acid type, improved anode and cathode current efficiencies are obtained with lower power consumption by introducing the aqueous alkali metal chloride solution into the anode compartment at an alkali metal chloride content of at least 250 grams per liter and a pH which is not in excess of about 4.5, which pH is maintained by the addition of hydrochloric acid to the alkali metal chloride solution, and controlling the rate of flow of the solution through the anode compartments such that the alkali metal chloride content of the solution removed from the anode compartment is at least 25 grams per liter less than that of the solution introduced into the compartment.