Abstract: Cell and process for operating chlor-alkali brine electrolysis cell which contains an anode, a cathode, and a non-rigid permionic membrane. Non-rigid, non-impregnated membrane is disposed against the cathode face by a positive pressure differential maintained between the anolyte and catholyte contrary to prior art suggestions. The cathode face is shaped such that it presents a substantially non-flattened surface so that there is no more than a slight surface-to-surface contact between the membrane and the cathode. This allows the membrane to be disposed against the cathode with a much smaller voltage penalty than is taught would be expected to occur while at the same time the greater anolyte pressure prevents the explosive problem encountered by hydrogen gas entering the anolyte compartment when a leak occurs in the membrane and the catholyte pressure is greater than the anolyte pressure.