| 摘要 |
PURPOSE:To prevent the rapid rise of cell voltage and the decrease of current efficiency when crudely purified solution is used in electrolysis of the alkali metal salt solution using an ion exchange membrane by a method wherein liquid in anode chamber is maintained at a specific pH and current is passed intermittently. CONSTITUTION:The alkali metal salt solution is roughly treated by a single filter or by settlement using sodium hydroxide or sodium carbonate and therefore contains 3 ppm or more Ca ions. Such solution is introduced into the anode chamber of the ion-exchange membrane type alkali metal salt electrolysis tank, and is subject to electrolysis by intermittently passing current. In this process, the current is halted until Ca ions are dissolved into the anode chamber and reached to sufficient equilibrium, meanwhile solution supply is contained at least in quantity equivalent to the volume of the anode chamber so that the liquid in the chamber is maintained pH 4 or more. The method remorkably relaxes the cell voltage rise and prevents the decrease in current efficiency. |
