GB345190A - Improvements in or relating to the preparation of chlorine dioxide - Google Patents

Abstract

Chlorine dioxide is prepared by the action of sulphuric acid on prepared lumps of a mixture of a chlorate with substances which are inert with regard to chlorates and sulphuric acid such as gypsum or pumice. Inert gases may be introduced during the reaction and these gases may be charged with gaseous organic reducing agents such as formic acid or formaldehyde. Alternatively, the inert gas may be formed in situ by adding salts which react with sulphuric acid to the mixture of chlorate and inert substance. Catalysts such as manganic oxide, or the oxides of vanadium, iron or osmium may also be added. Organic reducing agents such as oxalic acid, formic acid, or carbohydrates may be added to the prepared lumps and sulphuric acid. According to examples, (1) potassium chlorate is made into a paste with gypsum and water, lumps of the resulting hard product being treated with sulphuric acid; (2) sodium bi-carbonate or chalk is added to a mixture of potassium chlorate and gypsum which is treated according to example (1); (3) lumps of sodium chlorate and gypsum made as in example (1) are treated with sulphuric acid while air charged with formaldehyde vapour passes through the reacting mixture; (4) a small proportion of osmium oxide is added to a mixture of potassium chlorate and gypsum, further treatment being as in example (1); (5) pumice is saturated with a solution of potassium chlorate, the dried product being treated with sulphuric acid.