Mechanism of adsorption and desorption of water vapor by homoionic montmorillonite. 1. The sodium-exchanged form

The structural changes which occur during the intracrystalline swelling of a well-characterized Wyoming sodium montmorillonite have been investigated using controlled-rate thermal analysis, nitrogen adsorption volumetry, water adsorption and desorption gravimetry, immersion microcalorimetry in water, and X-ray diffraction under controlled humidity conditions. The experimental X-ray powder patterns of the 001 reflections have been compared with the theoretical simulations to determine the structural change of the montmorillonite during hydration and dehydration. 85 refs., 13 figs., 4 tabs.