tetrafluoroboric acid and or formic acid acetic acid or citric acid and or the salts thereof can be added to the catholyte in a divided cell or to the electrolyte in a undivided cell the addition of organic bases may also be necessary to produce the ph which is favorable for electrolysis and or may favorably affect the course of the electrolysis primary secondary or tertiary c 2 c 12 alkylamines or cycloalkylamines aromatic or aliphatic aromatic amines or the salts thereof inorganic bases such as alkali metal hydroxides or alkaline earth metal hydroxides such as for example the hydroxides of li na k cs mg ca and ba quaternary ammonium salts with anions such as for example the fluorides chlorides bromides iodides acetates sulfates hydrogen sulfates tetrafluoroborates phosphates or hydroxides and with cations such as for example c 1 c 12 tetraalkylammonium c 1 c 12 trialkylarylammonium or c 1 c 12 trialkylalkylarylammonium but also anionic or cationic emulsifiers in amounts from 0 01 to 25 per cent by weight preferably 0 03 to 20 per cent by weight relative to the total amount of the electrolyte or catholyte are suitable during the electrolysis in an undivided cell compounds which are oxidized at a more negative potential than the halogen ions liberated can be added to the electrolyte in order to prevent the production of free halogen the salts of oxalic acid methoxyacetic acid glyoxylic acid formic and or hydrazoic acid.