I. ORGANIC CONTAMINAT ION ON THE SURFACE OF WET-GROUND MUSCOVITE

ABSTRACT: The surface properties of wet-ground muscovite were studied by thermodynamics of water adsorption. The surface appears to be covered by con-taminating material, probably organic, which is strongly held; it was not removed at 350 ~ C and under a vacuum of 10- ~ tort. Attention is directed to the difficulty of maintaining freshly made silicate surfaces without contamination and to the importance of surface conditions in the interpretation of silicate properties which involve surface phenomena. The present studies have arisen from previous work aimed at obtaining a better understanding of naturally occurring fine-grained micas and mica-like minerals (Brindley, Takeshi & Wentworth, 1963; Wentworth & Brindley, 1965). By using finely powdered materials obtained from macrocrystalline micas, it was considered that important advantages might accrue from knowing the initial condition of the mica before its comminution. This paper describes a thermodynamic study of water vapour adsorption on the surfaces of fine-grained muscovite. Previously Gaines (1958, 1961) and Rouxhet & Fripiat (1966)have studied gas adsorption on mica surfaces. Water adsorption on montmorillonite, silica gel, and ground glass has been studied by Fripiat et al. (1965); the heat of adsorption and its variation as a function of the degree of coverage can indicate the presence of cations and whether the surface is composed of oxygens or hydroxyl groups. Thermodynamics of water adsorption by differen