The relation between some electrical properties and thermodynamic properties of adsorbed water has been studied for two montmorillonites, a silica gel, and a window glass powder at room temperature. A relationship has been found between electrical conduction and the mobility of water molecules in the monolayer. These molecules are immobile on the hydroxylic surface of silica gel and mobile on the oxygen internal surface of montmorillonite. The electrical conduction in the monolayer is believed to be mainly protonic. The dissociation degree of water molecules in this situation seems to be of the order of magnitude of 1%.

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The shift and the change in intensity of the OH stretching bands of decationated near-faujasite (Y) zeolites have been studied with respect to the physical adsorption of N2, 0 2 , CH4, Ar and Kr.The high-frequency OH stretching was assigned to hydroxyls in the supercage and the low-frequency OH stretching to hydroxyls in the cubo-octahedron. A simple electrostatic model allows one to correlate the shift and the change in intensity of the high-frequency OH band to the dielectric constant of adsorbed species. The reaction field of the OH dipole in an ellipsoidal cavity surrounded by the adsorbed molecules seems to be responsible for the perturbation undergone by the OH oscillator when the dielectric constant around the cavity is modified.

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Behandlung von SiO2‐Gelen mit H, bei w 800°C führt in Gegenwart von Metallen wie Ni, Pt, Ta und W (ohne physikalischen Kontakt mit dem SiOQ) durch Reduktion der Siloxanbrücken zu SiH‐Gruppen.

On a étudié l'effet de la température sur l'intensité des bandes de vibration de valence OH des solides suivants : micas, zéolites, boehmite, kaolinite, rnontmorillonite et gel de silice. Pour toutes ces substances, l'intensité de l'absorption diminue réversiblement en fonction de la température pour autant qu'on reste en-deçà des conditions de déshydroxylation. La diminution est attribuée à une augmentation de la mobilité des protons dans la structure. Cette théorie a pu être approfondie dans le cas assez simple de la boehmite où l'on peut estimer raisonnablement les barrières de potentiel séparant les sites accessibles aux protons. La diminution d'intensité peut s'expliquer par la disparition des niveaux discrets de vibration au-delà d'un niveau d'énergie où la probabilité pour le proton de passer à travers la barrière de potentiel est proche de la fréquence d'absorption. Certains minéraux, notamment la gibbsite, la bayérite et la brucite, ne manifestent pas de phénomène de délocalisation.

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Application of statistical mechanics to physical adsorption processes sometimes allows to ascertain the nature of the adsorbed film and therefore the nature of the surface. A study of the state equations, carried out for the case of Na and Ca montmorillonites, seems to prove the existence of two types of "sites". The first type appears to be sites for localized adsorption of water, and may correspond to the region surrounding the cations which balance the lattice charges (1st hydration sphere of these cations) as well as to a part of the external surface (hydroxylic areas of fracture). The second type, consisting of sites for delocalized adsorption, is represented by the remainder of the external surface and the interlamellar space ; the first type of sites covers an area of about 300 m2 g-1, whatever the nature of the cation.