GB363215A - Process for the productior of sulphates - Google Patents

Abstract

The process of the parent Specification is modified in the following respects:--(1) In the production of ammonium sulphate by passing air in a very finely divided state into an aqueous medium containing, or to which is added, ammonium sulphite, the latter comprises a mixture of ammonium sulphite and bisulphite with or without ammonium sulphate obtained by combining ammonia and sulphur dioxide, preferably in the presence of air, in such proportions that about 0,5-1 mols. of sulphur dioxide are present to each mol. of ammonia. By using these proportions, escape of ammonia during combination of the gases is minimized. The mixed salts are precipitated electrically and are freed of their excess sulphur dioxide, as by addition of ammonia, before or during the oxidation step. (2) Ammonium sulphate produced in the process is salted out from solution by the addition of solid ammonium sulphite or bisulphite or by treatment with gases containing sulphur dioxide and ammonia, and the mother liquors obtained containing sulphites returned to the process. (3) In the production of alkali sulphates, di- or tri-sodium or potassium phosphates are added to the aqueous medium to provide the base. The sodium or potassium sulphate formed is crystallized out and the mother liquor used cyclically until it is saturated with mono- or di-alkali phosphate, which is then recovered.