IDENTIFICATION OF CLAY MINERALS FROM ACID SOILS

Abstract

A technique is described for the identification of clay minerals, the layers of which are difficult to expand or collapse by the usual treatment with glycerol and KCl. Samples are extracted for 3 to 6 hours in normal sodium citrate at pH 7–3 and 100° C. The citrate is renewed hourly. After the citrate extraction the inter- layer spaces of some minerals can be expanded with glycerol and CaCl₂ Basal spacings of minerals previously identified as ‘dioctahedral vermiculite’ expand to 16–18 A. after this treatment; hence, their identity is questioned. The widespread occurrence in the north-eastem United States of clay minerals with 14-A. spacing necessitates this extraction for correct identification.