Differentiation of Hydrogen Clays and Identification of their Mineral Constituents by Electrochemical and Viscous Methods

Abstract

A NUMBER of publications1,2,3,4 from this Laboratory have dealt with the acid character of hydrogen clays isolated from Indian soils as revealed from a study of their titration curves with bases, buffer indices and base-exchange capacities calculated at the inflexion points of the titration curves. An 'electrochemical method' for differentiating hydrogen clays and identifying clay minerals contained in them has been developed, based on a comparison of their electrochemical properties with those of hydrogen colloids isolated from natural deposits of the clay minerals. Hydrogen kaolinites (prepared by repeatedly leaching entire clay fractions with 0·04 N hydrochloric acid and washing free from chlorides) from four different samples of kaolin and a number of hydrogen clays known, from X-ray and dehydration studies carried out by Mr. S. N. Bagchi, to contain kaolinitic minerals have a dibasic acid character within the range of pH 4–11·05,6, The first inflexion usually occurs between pH 7·0 and 8·0 and the second between pH 8·0 and 9·5 (see diagram). The ratio of the base-exchange capacities at the two inflexion points is nearly 2·0, though the actual value of the base-exchange capacity varies in the case of different hydrogen clays and hydrogen kaolinites from 12·0 m.e. to 23·0 m.e. per 100 gm. at the first inflexion point; and from 20·0 to 45·0 m.e. per 100 gm. at the second inflexion.