Process for operating a distillation column for the removal of water and lower-boiling components than 1,2-dichloroethane from 1,2-dichloroethane in which at least part of the heat from condensation of the aqueous vapors from the distillation column is used to concentrate caustic soda solution by evaporation; furthermore, at least part of the 1,2-dichloroethane formed when chlorine and ethylene react in a direct chlorination unit is used to heat said distillation column and can subsequently also be used as a heat transfer fluid to concentrate caustic soda solution by evaporation.