X-ray Spectrochemical Determination of Potassium in Clay Minerals*

Leon J. Johnson
Department of Agronomy, The Pennsylvania State University, University Park, Pa. 16802
* Authorized for publication 19 February 1968 as paper no. 3366 of the Journal Series of the Pennsylvania Agr. Exp. Sta., University Park, Pa.

Abstract: An X-ray spectrochemical method is compared with the flame photometer determination of potassium in a series of sixty-five soil clay fractions. Two methods of preparing the clay samples for the X-ray determination were used. In one case a 20 mg sample of clay in suspension was dried onto a plastic disc as a thin film. Potassium was determined by comparing the fluorescence intensity of the unknown with a sample of known composition which was prepared for analysis by the same technique. For the second method a 100 mg sample of dried clay was pressed into a pellet using methyl cellulose as a backing. In this case a National Bureau of Standards sample (NBS-98) was prepared in an identical manner and used as a standard for determining the potassium in the unknown. The results for both techniques were highly significantly correlated with the values as determined by flame photometric analysis. The pellet technique gave a more accurate measure of the potassium content. With the thin films the same sample may be used for X-ray diffraction analysis. In either case the X-ray spectrochemical technique provides a fairly rapid and simple procedure that can be useful for handling large numbers of samples.

Clays and Clay Minerals; December 1968 v. 16; no. 5; p. 373-379; DOI: 10.1346/CCMN.1968.0160506
© 1968, The Clay Minerals Society
Clay Minerals Society (www.clays.org)