Ionic forces in thick films of liquid between charged surfaces

Schofield, R. K.

doi:10.1039/tf946420b219

Cited by 67 publications

(13 citation statements)

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“…It therefore seems reasonable to suggest that while some of the water is directly associated with the surfaces of the clay particles, some is retained by surface tension forces within a gel structure arising from mechanical interactions of the clay particles. The chief experimental difficulty in trying to test the applicability of diffuse double layer theory, as adapted by Schofield (1946), to the swelling of clay systems is to separate the relative contributions of the two mechanisms to the total water content.…”

Section: General Discussion (A) Enmeshed Watermentioning

confidence: 99%

“…These groups of oriented crystals, or domains, are randomly placed with respect to one another throughout the clay matrix; that is, the domains are in turbulent array. Schofield (1946) regarded the swelling of a clay matrix as arising from the development of diffuse double layers by the clay particles. He has presented a theoretical treatment based on the Gouy-Chapman diffuse double layer, to describe the film thickness in terms of the hydrostatic suction within the water surrounding the clay mass and the electrolyte CC~ 8 concentration of the solution external to the double layers of the clay crystals.…”

Section: Introductionmentioning

confidence: 99%

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The Structural Status of Clay Systems

Aylmore

1960

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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Illite and montmoriUonite have been compressed into cores under a pressure of 1200 arm. The structural status of these clays has been examined by means of detailed nitrogen adsorption-desorption isotherms and by means of electron micrographs of fracture surfaces of the clay cores. The subsequent swelling behavior of sodium and calcium clay cores has been analyzed in terms of the model derived from these measurements and the specific surface area of the clay. A generalized theory for the condensation of plate-shaped particles into domains has been proposed.Measurements of the effect of electrolyte concentration and hydrostatic suction on the swelling of sodium-and calcium-saturated clay cores indicate that diffuse double layer theory may play a significant part in determining the swelling of monovalent clay systems but not divalent clay systems.The magnitude of the film thicknesses apparently developed in solutions as concentrated as molar and 4 M, where the condition of ideal solutions required by diffuse double layer theory is certainly not fulfilled, seems to indicate that solution uptake is increased by a relaxation of structural strains within the clay matrix on lubrication by solutions. These strains may arise from the distortion of crystals in packing during the drying process. Such relaxations which appear to occur between p F 4 and 3 could initiate the development of a gel structure.

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Section: General Discussion (A) Enmeshed Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Structural Status of Clay Systems

Aylmore

1960

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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“…It affects the drainage of soils, the hydrology of geological formations, the stability of building foundations, etc. The general view is that swelling is due to excess osmotic pressure in the solution between the superimposed silicate layers and that it can be described by doublelayer theory (Schofield, 1946;Norrish, 1954;Bolt and Miller, 1955;Warkentin et aL, 1957;Norrish and Rausell-Colom, 1963;van Olphen, 1963;Quirk, 1968). A second view, which has been held primarily by Low and his coworkers (Low and Deming, 1953;Hemwall and Low, 1956;Ravina and Low, 1972;Low and Margheim, 1979;Low, 1980Low, , 1981Viani et al, 1983) and by Derjaguin and his coworkers (Derjaguin et al, 1954;Derjaguin and Churaev, 1974) is that surface hydration also contributes to the swelling of clays and other colloids.…”

Section: Introductionmentioning

confidence: 99%

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite

Viani

Roth

Low

1985

Clays and clay miner.

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Abstract--To test the double-layer theory of swelling as applied to layer silicates, the interlayer separation, X, in a Li-saturated vermiculite from Grouse Creek, Utah, was measured as a function of the swelling pressure, II. An oriented sample of the vermiculite (46-105 izm) was placed in an environmental chamber mounted on an X-ray diffractometer and compressed between N2 gas and a porous membrane in contact with a solution draining to the outside atmosphere. After equilibration at each of several successively higher gas pressures, the c-axis spacing was measured by X-ray diffraction, and the corresponding k was calculated by subtracting the thickness of an elementary silicate layer. The results of these measurements showed that: (1) the relation between II and ~ for vermiculite is the same as that previously observed for Na-montmorillonite, i.e., 131 is an exponential function of 1/),; (2) the values of II predicted by doublelayer theory are much smaller than those observed if the surface potential is assigned the appropriate value; and (3) the observed relation between II and ~, does not have the form predicted by this theory. On the basis of these results, a repulsive force not ascribable to double-layer overlap must be primarily responsible for swelling; this force must result from the in-depth perturbation of the water by the surfaces of the vermiculite layers.

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“…The double-layer equation applicable here can be Obtained by integrating the PoissonBoltzmann equation for the condition that there are no interlaminar ions of the same sign of charge as the laminae themselves. The result, obtained independently by Langmuir (1938), Schofield (1946) and Eriksson (1950) where d is the distance between the clay laminae, k is the Boltzmann constant, T is the absolute temperature, e is the protonic charge, z is the valence of the exchangeable ion, D is the dielectric constant and zm is the osmotic pressure mid-way between the laminae. According to the theory, +m is the equivalent of +, the observed osmotic pressure.…”

Section: Experimental Methodsmentioning

confidence: 98%

Thermodynamic Properties of Water in Suspensions of Montmorillonite

Kolaian

1960

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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The partial molar free energies, entropies and heat contents of the water in suspensions of Li-, l~a-, and K-clay were measured relative to pure water by means of a tensiometer. This method of obtaining these thermodynamic properties is far more sensitive than the more common method utilizing adsorption isotherms and a form of the Clausius-Clapeyron equation. The partial molar free energy of the water decreased with time after stirring and increased rapidly upon stirring. This was taken as evidence that a gradual increase in the degree of orientation of water molecules associated with the clay particles occurred as the particles fell into the more random edge-to-surface thixotropie structure. The partial molar entropies and heat contents of the water in the suspensions were found to be less than those for pure water. Hence, this evidence also supported the postulate that an ordered water structure exists in the thixotropic suspensions.

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Ionic forces in thick films of liquid between charged surfaces

Cited by 67 publications

References 0 publications

The Structural Status of Clay Systems

The Structural Status of Clay Systems

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite

Thermodynamic Properties of Water in Suspensions of Montmorillonite

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