Abstract: At the production of alkali metal chlorate by electrolysis of alkali metal chloride in an electrolyser a part of the liquid phase from the electrolyser is brought to a crystallizer for precipitation of alkali metal chlorate crystals. The hydrogen gas formed in the electrolyser is purified from contamination of chlorine gas by contacting it with the outgoing mother liquor from the crystallizer, which has a pH in the interval 7.5 to 14. The mother liquor is then brought back to the electrolysis system.

Abstract: The present invention relates to a process for production of chlorine dioxide from an alkali metal chlorate, a mineral acid and a volatile reducing agent. The process is carried out in a vessel operated under subatmospheric pressure, whereby water is evaporized and withdrawn together with chlorine dioxide and the alkali metal salt of the mineral acid is crystallized within the reaction vessel and withdrawn therefrom. According to the invention the utility of the volatile reducing agent is enhanced by the addition of the agent to the region of crystallization in the reaction vessel.