Expansion of the Montmorillonite Lattice on Hydration

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Abstract
When exposed to water vapor, water, or some non‐aqueous solvents, montmorillonitic clays display expansion of their lattices. Assuming that the expansion on hydration is a uni‐dimensional swelling phenomenon, a thermodynamic analysis has been made which furnishes quantitative evaluation of interplanar forces. This analysis indicates that for lattice expansions of 3 or 4A from the dehydrated contracted state, the force between montmorillonite lattice layers is substantially constant; but for greater expansions the force diminishes in a complex manner. The analysis also indicates the possibility of determining quantitatively the forces exerted by molecules of solvents which expand the lattice, providing ion exchange does not occur. Problems in determining molecular forces and structure are discussed.