THE EFFECT OF TEMPERATURE UPON THE BASE-EXCHANGE CAPACITY OF CLAYS

Abstract

The purpose of this work was to obtain data that would throw light upon the nature of the changes brought about by heat on the base exchange capacity of soils. The clay fraction of a Crowley silt loam soil was obtained, divided into five equal portions, and each of these portions was saturated with the chlorides of potassium, sodium, calcium, magnesium and hydrogen (HCl), respectively. Each of the so saturated portions was subdivided into smaller fractions which were heated at 25°, 50°, 75°, and 100° C. for 0, 5, 12, and 46 days respectively. The amount of the particular replaceable base with which the clay had been saturated and the total exchangeable bases were determined after each thermal treatment. It was found that the amounts of replaceable potassium, calcium, and acid hydrogen decreased with prolonged treatment, whereas that of sodium and magnesium increased. The amount of total exchangeable bases showed an increase in the potassium and acid hydrogen clays, and a decrease in the sodium, calcium, and magnesium clays upon prolonged thermal treatment. The reasons for these markedly different behaviours of clays saturated with different cations are not well understood at present. An interpretation based on ionic radii is proposed.