Production of chlorine dioxide

ClO2 and Cl2 are produced by continuously adding an alkali metal chlorate and chloride and a strong acid to a reaction vessel, maintaining a partial pressure of water such as to ensure crystallization of the alkali metal salt of the acid within the vessel, and continuously withdrawing the product gases and solid. The acid may be H2SO4 or H5PO4 and the alkali metal may be Na, K or Li. The chlorate and chloride may be added dry or as solution, separately or together, in a ratio of 1 : 1 to 1 : 6 respectively. H2SO4 used may be above 100%. The reaction mixture produced may be 0.005-3 M in chlorate, 0.001-2 M in chloride, and less than 6 M in H2SO4, and may be at a temperature of - 25 DEG to + 100 DEG C. The partial pressure of water may be maintained by means of a water jet eductor (which produces a partial vacuum and also dissolves the ClO2 and Cl2), or by using a stream of inert gas, e.g. air or N2. Liquid effluent withdrawn from the vessel and wash water may be recycled. The crystals produced may be, for example, NaHSO4, NaHSO4.H2O,