Electrolysis of aqueous salt solutions

Claim 1

In a process for producing chlorine and sodium hydroxide wherein aqueous sodium chloride is electrolyzed in a bank of a plurality of electrolytic cells, each cell having a cathode compartment and an anode compartment separated by a cationic permeable membrane, the improvement which comprises: (a) transferring the catholyte serially from the cathode compartment of one or more preceding cells to the cathode compartment of at least one succeeding cell in the bank and providing electrical isolation between the cathode compartment by means of a gas-lift in which hydrogen produced in the cathode compartment rises through the sodium hydroxide catholyte solution in a confined space and lifts said catholyte solution to a disengaging point where the hydrogen is separated and the catholyte is allowed to fall freely through a confined void space to a predetermined point where it is collected and fed by gravity to the cathode compartment of a succeeding cell; and (b) maintaining the electric current on the cathode in said preceding cells such that C d K=D/H, wherein C d is the current density, D is the depth of the cathode compartment, H is the height of the cathode compartment and K is a proportionality constant having a value between 0.01 and 2.0.