A titrimetric method for determining total sulphur in mineral soils

A rapid method for the determination of total sulphur in mineral soils is described. The various sulphur compounds in soil are first oxidised to sulphate by potassium dichromate in phosphoric acid, and the sulphate thus formed is then reduced to sulphur dioxide by heating with activated charcoal. The evolved sulphur dioxide is trapped in hydrogen peroxide, barium perchlorate added to the resulting sulphuric acid to precipitate barium sulphate, and the excess of barium determined by titration against standard potassium sulphate, with sulphonazo III as indicator. The proposed method gave acceptable results when tested on pure compounds and on soils of known sulphur content. No interferences are to be expected from normal soil constituents.