Abstract: Vermiculite single crystals swell to the gel state as a consequence of treatment with concentrated solutions of γ-aminobutyric acid.

The amount of swelling was determined, by measuring by X-ray diffraction the separation of the elementary silicate layers in the gel-like crystals.

By application of pressures into the gels along the swelling direction, a direct measure of the swelling pressure is obtained. The relation between swelling pressures and equilibrium interlayer distances is a function of both cationic concentration and dielectric constant of the solution. Measured swelling pressures are consistent with a model based on formation and interaction of diffuse double layers of aminoacid cations around the silicate particles, these having a Stern layer of an approximate thickness of 5 Å. The specific chemical adsorption potential of the system has been estimated as φ = 3·3 ± 0·2 Kcal/mol.