Abstract: A process for producing chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity within a range of from about 2 to about 11 N. The reaction medium is subjected to subatmospheric pressure sufficient for evaporating water, a mixture of chlorine dioxide and water vapor being withdrawn from an evaporation zone in the reaction vessel and alkali metal sulfate being precipitated in a crystallization zone in the reaction vessel. A mixture of formaldehyde and methanol is used as reducing agent.

Abstract: A process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, a mineral acid and methanol as a reducing agent in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50.degree. C. to about 100.degree. C. and at an acidity within the interval from about 2 to about 11N and subjected to an subatmospheric pressure. Thereby water is evaporated and a mixture of chorine dioxide, water vapor and gaseous by-products is withdrawn from an evaporation region in the reaction vessel. The alkali metal sulphate is precipitated in a crystallization region in the reaction vessel. The content of formic acid in the reaction vessel is increased by addition of formic acid to a content of formic acid exceeding about 0.3M. The gaseous by-products are condensed to obtain formic acid and the content of formic acid in the reaction vessel is increased by recirculation of the condensate.