Method for restoring the current efficiency.

摘要

In the electrolysis of sodium chloride by means of a perfluoro cation exchange membrane for the production of sodium hydroxide having a concentration of from 32 to 40% by weight, a method for restoring the current efficiency, which comprises suspending the electrolysis when the current efficiency of the perfluoro cation exchange membrane has dropped to a predetermined level, and maintaining the catholyte concentration at a level of not higher than 30% by weight.