GB346835A - Improvements in the purification of sulphur - Google Patents

Abstract

Crude sulphur, when free from tarry constituents is purified by heating in the solid or liquid phase with mineral acids, such as sulphuric, hydrochloric, nitric or phosphoric acids, of medium concentration e.g. 40 to 50 per cent. Where the impurities consist mainly of ferrous sulphide, sulphuric acid of a specific gravity of 1,40 may be employed. When tarry matters are present, nitric acid or nitrous fumes may be employed or strong oxidizing agents, such as chromic acid, permanganates, perchlorates, or persulphates may be added to the acids. The sulphur may be in a finely divided form or in the liquid state at temperatures between 120 DEG and 160 DEG C., the increase in temperature being made possible by increasing the pressure, by using acid of the necessary strength or by additions to the acid, such as sodium sulphate or calcium nitrate in the case of sulphuric and nitric acids respectively. Intimate contact between the sulphur and the acid must be effected as by vigorous stirring or by the introduction of inert gases. Examples are given of the use of sulphuric acid and potassium bichromate, sulphuric and nitric acids, sulphuric acid and potassium persulphate or sodium perchlorate, and sulphuric acid alone. Specifications 5838/11, 8097/12 and 10147/12, [all in Class 90, Non-metallic elements], are referred to.