A process for producing chlorine dioxide by the reaction of two precursor components, in which the first component contains a solution of a compound containing chlorine in the +1 oxidation state, a source of H+ ions and a source of iodide ions. The second component contains an inorganic base and an inorganic acid salt. The process comprises mixing the two components in a reactor to produce chlorine dioxide. The compound containing chlorine in the +1 state may be in the form of sodium, potassium or calcium hypochlorite. The source of H+ ions may be from hydrochloric acid. The inorganic base may be a hydroxide or carbonate of an alkaline metal or alkaline earth metal. Preferably, the process produces a liquid chlorine dioxide solution for use as a disinfectant.
