CRITICAL STUDY OF METHODS OF DETERMINING EXCHANGEABLE BASES IN CLAYS *

Abstract

A bstract A study was made of analytical methods of determining exchangeable bases in clays and similar ceramic materials. Total exchange capacity can be determined by electrodialysis or by the teaching‐distillation method. The time required for electrodialysis can be materially reduced by agitation of the clay slip during dialysis. Electrodialysis effects decomposition of bentonite and similar materials unless extremely low current densities are applied. Exchangeable cations of clays and similar materials are replaced slowly by percolation methods, but an agitation leaching‐centrifuging procedure was developed which effects a rapid replacement. In ultimate analyses by leaching methods, correction must be made for soluble sulfates. Aqueous 1 N ammonium acetate is a satisfactory leaching solvent for most clay bodies, but for those containing appreciable amounts of calcium carbonate, alcoholic ammonium acetate should be employed. Details of recommended analytical procedures are given.