A study of techniques for the determination of sulphate in soil, was made and a new method was developed. This method made use of the insolubility of barium sulphate to separate the sulphur from interfering substances. The barium sulphate was determined, via reduction to hydrogen sulphide, as methylene blue.
A method was also developed for the determination of the sulphur status of a series of basaltic soils. (Sulphur status was measures by the growth of Phalaris tuberosa L. in pots.) Reducible sulphur, determined by digesting the soil with a mixture containing hydriodic acid, red phosphorus, and formic acid was found to be strongly correlated with plant growth, and was therefore a reliable indicator of the sulphur status of this series of soils.
The reducible sulphur was found to be sulphate sulphur which was tightly bound up in the organic matter. It can not be extracted by any of the normal extractants used for the determination of “available” nutrients in soil.