the vessel 12 in accordance with conventional r3 practice such catalysts include ag mn cr pd and pt in the form of metals and compounds and complexes the relative proportions of the reduction of chlorate effected with added chloride ions and with methanol may vary widely generally from 0 1 by methanol with the balance by chloride ions to 100 by methanol as the proportion of reductant which is chloride ions increases more co produced chlorine appears in the product gas stream a 10 tpd chlorine dioxide generating plant is set up as illustrated in fig1 and 2 4000 usgpm of recycle liquor having an acidity of about 7 n and a sodium chlorate concentration of 4 molar enters the venturi pipe 30 the aperture at the upstream end of the pipe 38 is sized to permit a flow of 10 usgpm into the pipe 1 0 usgpm of 36 n sulphuric acid and 0 3 usgpm of methanol are flowed to the pipe 38 through pipe 44 to establish therein an acidity of 9 38 n the pipe 38 is sized to permit a residence time of 0 5 seconds which is sufficient for complete reaction of the sodium chlorate to chlorine dioxide to occur in the pipe chlorine dioxide of purity 98 at a chemical efficiency of 98 is recovered from the generator.