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Swelling Pressures of Dilute Na-Montmorillonite Pastes

Published online by Cambridge University Press:  01 January 2024

B. P. Warkentin
Affiliation:
Department of Agricultural Physics, Macdonald College, McGill University, Canada Department of Agriculture, University of Oxford, UK
R. K. Schofield
Affiliation:
Department of Agricultural Physics, Macdonald College, McGill University, Canada Department of Agriculture, University of Oxford, UK
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Abstract

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Swelling pressures calculated from diffuse double-layer theory previously had been experimentally verified for Na-montmorillonite at clay concentrations above 10 percent, but published data at clay concentrations less than 5 percent consistently showed osmotic pressures much lower than the maximum of about 40 cm water calculated from theory. Swelling pressures of Na-montmorillonite in 4–5 percent orientated suspensions were therefore measured in an specially constructed osmometer in various solutions of NaCl up to 1.25 mN. The osmometer construction allowed solutions of desired concentration to be flushed continually across the membrane separating solution from clay. It was found that soluble impurities present in the clay decreased swelling pressures to about 1 cm of water. When these were removed during sample preparation, most efficiently by ultrafiltration through a dialysis membrane, swelling pressures measured were in satisfactory agreement with calculated values. The impurities were not identified chemically, but buffer curves of the solution toward HCl were determined.

Type
Article
Copyright
Copyright © Clay Minerals Society 1958

Footnotes

Work done during tenure of a National Research Council of Canada Fellowship at the University of Oxford.

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