Abstract
It is proposed to improve the current efficiency of chlor‐alkali membrane cells by building up a thicker diffusion layer near the anolyte surface of a Nafion membrane. A thicker diffusion layer will decrease the flux of co‐ions (hydroxyl) across the membrane. Experimentally it is shown that improvements in the current efficiency of a chlor‐alkali membrane cell can be achieved by placing the rough side of the membrane toward the anode or by placing a Teflon screen near the anolyte face of the membrane. A correlation has been established between the caustic current efficiency and the anolyte outlet flow rate, based on the hydration of the migrating sodium ions. A lower catholyte flow rate indicates a drop in current efficiency. This correlation can diagnostically serve in identifying cells with low current efficiency.