Study of Water Layers Adsorbed on Na‐ and Ca‐Montmorillonite by the Pulsed Nuclear Magnetic Resonance Technique

The pulsed magnetic resonance technique was applied to the measurement of the longitudinal (T 1 ) and transversal (T 2 ) relaxation time of water molecules adsorbed by Na‐ and Ca‐Montmorillonite, In the Na‐clay the water was adsorbed as a monomolecular layer whilst in the Ca‐clay, the bimolecular layer was formed under specified water vapor pressures. The effect of paramagnetic centers (Fe 3+ ) was corrected and the samples were studied between + 30°C and −80°C. The main contribution to T 1 was the “inter” contribution of protons diffusing from one water molecule to another whilst T 2 results from simultaneous rotational (intramolecular) and diffusional (intermolecular) contributions. The proton diffusion coefficient and the life‐time of a proton on one specified water molecule is derived from T 1 inter. The calculated value at 298°C is equal to 10 −7 times the life‐time in liquid water, suggesting a dissociation degree 10 7 times higher in the adsorbed state than in liquid water. This increase in the dissociation degree as well as the reported activation energies are in good agreement with experimental data obtained from conductimetric and dielectric measurements performed previously.