JPS6259187B

PURPOSE:To reduce the replacement times fir diaphragms while maintaining an optimum brine decomposition rate by making the draw-out position of a catholyte draw-out pipe of a vertical electrolytic cell using diaphragm process variable and adjusting the catholyte level freely in correspondence to the change in the state of asbestos diaphragms and the interruption of DC supply. CONSTITUTION:A catholyte 11 flow through a guiding pipe 7 connected to a projecting draw- out pipe 6 in the lowert part of a cathode chamber into an upright pipe 16 which is open by extending beyond the bottom end of the cover body 5 of an electrolytic cell 1. The liquid 11 flows through a valve V2 of a lower branch 19 of the pipe 16 of a height at which asbestos diaphragms 4 are kept free from failure despite the fall in the electrolyte level. The rate of the drawing out of the liquid 11 is determined by the opening of said valve, and the opening can be easily adjusted under the observation of the liquid level in a liquid level indicator 21. Therefore, if the diaphragms 4 are new, the measure of lowering the liquid 11 level without lowering the anolyte level so much can be easily employed. However, if the valve V1 of the middle branch 18 of the pipe 16 is held open, the liquid 11 does not rise higher than this. If this is kept below the discharge port for gaseous H2, the liquid 11 will not fill the part where the gas 13 accumulates and the discharge port despite the rise in its level. When the DC supply is interrupted, the valves V1, V2 are closed, by which a cathode head part 2a is secured in the safe position in the liquid.