STUDIES IN COLLOIDAL CLAYS. I¹

Abstract

Only in recent years has it been possible to produce for the purpose of further studies well-defined monodisperse fractions of colloidal clays by rational supercentrifugal separation (2, 3).The lack of data concerning, primarily, clay sols of low concentration and varying particle sizes made highly desirable a closer study of freshly prepared natural suspensions of the clay mineral montmorillonite (the major constituent of bentonite) in concentrations from about 0.06 to 2 per cent by weight.Of special interest was the question whether any signs of structure could be detected in such low concentrations and, if so, how these change with particle size of the suspension and also what effect certain pretreatments of the original suspensions, as, for instance, thermal concentration at different temperatures, would have on their properties. Changes due to the addition of electrolyte have not been considered in this investigation, but will be discussed separately in a later publication.The particular bentonite used in this work was of the Wyoming type, mined by the American Colloid Co., Chicago, Illinois. (For further details as to location of the deposit, see reference 3.)The analysis of the finest fraction of this bentonite gave the values in table 1.The different particle size fractions were produced according to a method described by Hauser and Reed (2). Six fractions were obtained. The gels produced by supercentrifuging had about 10 per cent dry weight content. They were stored in the condition in which they were scraped from the liner of the centrifuge. The overflow of the finest and final fraction was collected and stored as a sol of 0.46 per cent dry weight. It will be referred to as fraction 7.The following experiments were carried out with fraction 6 containing particles of an average apparent diameter of 14 µ. Comparative studies

Effect of the Dielectric Constant on the Double Layer on Clays

“…As these data show, the Gouy model gives a much slower decay in the values of the potential as a function of the distance than the multimedia model presented in this paper. For example, at a distance of (Hauser and Le Beau, 1941;Oakes, 1960;Swartzen-Allen and Matijevic, 1975) represent the potential at a plane of shear separated by thicknesses of one or two water molecules from a clay surface, the values of the potential obtained from the present model are more in line with the experimental values of clays than the Gouy model.…”

Electrophoresis in a dilute dispersion of colloidal spheres

“…The O('p2) term would be small except in the case of concentrated dispersions. The existing experimental data concerning the concentration effect on electrophoresis (Hauser and LeBeau, 1941;Maron et al, 1948;Zukoski and Saville, 1987) also indicate that the particle velocity decreases slightly as p increases at small values of p.…”

Soil Components

“…Early work ineludes that of TSCAPEK [1934], HAUSER and LEBEAU [1938], and NITZSCHE [1940. Hence, density of elay-water systems has been extensively studied as a function of elay content.…”