CHEMICAL D ISSOLUTION TECHNIQUES IN THE STUDY OF SOIL CLAYS: PART I

ABSTRACT: The mineralogy of the clay fractions of two soil profiles repre-sentin ~ the end-members of a catena developed on a glacial till derived from basic lavas has been determined. Particular attention has been given to the assessment of the nature of the amorphous inorganic material in the clay fraction of these soils. Chemical dissolution techniques were used and their effects on the clay fraction were followed by X-ray diffraction, differential thermal, infrared absorption, electron-optical nd surface area measurements. The principal conclusion is that the soil clays are a continuum from completely disordered, through poorly ordered to well crystallized material. The clay fraction of soil contains the finest and therefore the most surface-reactive particles. Consequently, many of the properties of the soil are determined by the nature of this fraction even when the amount present may be merely a few per cent. Although it is inevitable that chemical pretreatment will result in some alteration of these properties (Harward & Tlieisen, 1962; Farmer & Mitchell, 1963), this need not necessarily be disadvantageous and indeed careful and controlled degradation o