Dispersion of Mineral Colloids in Soils using Cation Exchange Resins

Abstract

THE techniques for particle size distribution analysis of soils which have gained general acceptance are those which include a pre-treatment with an oxidizing agent such as hydrogen peroxide¹ or sodium hypobromite² to destroy, as completely as possible, the organic materials present. It is customary also, where hydrogen peroxide has been used, to add a peptizing or dispersing agent, usually in the form of a soluble salt such as sodium metaphosphate³, before the oxidized soil material is shaken in water suspension to obtain separation of the mineral particles. However, for a realistic investigation of the processes of dispersion and aggregation in soils, a method is required which results in complete separation of the mineral particles without the destruction or irreversible alteration of any organic materials present and without degradation of the mineral colloids⁴. These requirements preclude the use of bases or soluble salts, since those which are efficient dispersing agents invariably dissolve soil constituents, and the materials solubilized can be lost from the system along with the added chemicals if desalting is attempted. These stringent requirements led to the development of the method of dispersion described here.