PROPOSED METHOD FOR THE MEASUREMENT OF EXCHANGE PROPERTIES OF HIGHLY WEATHERED SOILS

The ‘compulsive exchange’ method of Bascomb has been modified to allow the determination of cation exchange capacity and anion exchange capacity of soils containing significant quantities of constant potential surfaces. The soil is equilibrated with unbuffered barium chloride solution at an ionic strength approximating that of the soil solution, so that the conditions under which determinations are made are similar to those found in the field. Barium on the exchange complex is then replaced by magnesium when the latter is added as magnesium sulfate, and this is accomplished without altering the solution ionic strength. If desired, exchangeable basic cations can be determined as an additional step in the procedure. Results obtained by the proposed method are compared with other commonly used procedures for determining cation exchange capacity and exchangeable basic cations. © 1979, CSIRO. All rights reserved.