This invention provides a method for purifying a chlorine supply that includes a chlorine component, a bromine component, and nitrogen trichloride. The method includes the steps of introducing the chlorine supply into a vaporizer, heating the chlorine supply in the vaporizer to form a vapor, and introducing the vapor into a distillation system to provide purified chlorine gas, a distillate that includes liquid chlorine and the bromine component, and a bottoms component including the nitrogen trichloride. The method also includes the steps of condensing the vapor in a reflux condenser, heating the condensate in a reboiler, removing the purified chlorine gas from the distillation system, and removing the distillate from the distillation system.