METHOD FOR ELECTROLYSIS

PROBLEM TO BE SOLVED: To obtain an electrolysis method in which membrane electrolysis and amalgam electrolysis can be operated with the use of the same salt water circuit by mixing each of anodic liquid flows from a membrane electrolysis device having a mercury-resistant cathode which can consume oxygen and from an amalgam electrolysis device. SOLUTION: Salt water 9 of NaCl 12 concentrated in a salt dissolution station 1 is supplied to a common precipitation/filtration station 2, sulfate, calcium, and magnesium are separated/removed, and impurities are allowed to remain. the main flow 10 of the salt water 9 is supplied to amalgam electrolysis 5. The subordinate flow, with free chlorine removed in a dechlorination station 7, with Al, Fe, and Mg reduced in a hydroxide precipitation station 6, and after obstructive Ca/Mg impurities being removed by a Ca/Mg ion exchanger 3, is supplied to membrane electrolysis having a cathode 4 which can consume oxygen. After that, an anodic liquid flow 13 is circulated to the salt dissolution station 1 as a combined anodic liquid flow 14.