DETERMINATION OF EXCHANGEABLE CATIONS AND EXCHANGE CAPACITY OF SOILS—RAPID MICROMETHODS UTILIZING CENTRIFUGE AND SPECTROPHOTOMETER

Abstract

Systematic time-saving microprocedures, especially suitable for routine analytical work, are described for the detn. of the exchangeable cations and the exchange capacity of soils. The exchangeable cations are extracted with 1 [image] ammonium acetate solution. The exchange capacity is detd. by direct nesslerization of the ammonium adsorbed by the soil, subsequent to extraction with NaCl soln. All of the separations in the analysis of the ammonium acetate extract are carried out in a 15-ml. centrifuge tube. Ca is detd. volumetrically as the oxalate. Colorimetric methods utilizing a spectrophotometer are employed in the detn. of Mg, K, Na, and Mn. Because accurate detn. of the small amts. of exchangeable cations by conventional macromethods is attended by considerable analytical difficulties necessitating use of a large soil sample and a large volume of the extracting soln., the more rapid micromethods herein described can be employed to advantage without significant sacrifice of accuracy.