The extent of vicinal water: Implications from the density of water in silica pores

Abstract

In this paper the densities of water confined to the pores of silica gels and porous glasses are reported. These densities are consistent with a model for vicinal (interfacial) water reported earlier by the senior author (F.M.E.). From these average pore densities the density of water is calculated as a function of distance from the silica surface at 10, 20, 30, 40°C. The results, at all studied temperatures, suggest that water is structurally modified by propinquity to surfaces to distances up to 3–5 nm from the surface. The results of the present experiments are consistent with the thermodynamic properties of water in clays as reported by Low ( Soil Sci. Soc. Amer. J. 43, 652 (1979); J. Colloid Interface Sci. 95, 45 (1983); J. Colloid Interface Sci. 96, 229 (1983) ), the results of disjoining pressure measurements by Peschel et al. ( Z. Naturforsch. 26a, 707 (1971); Naturwissenschaften 11, 1 (1969); J. Colloid Interface Sci. 34, 505 (1970); Colloid Polym. Sci. 260, 444 (1982) ) and the properties of intracellular water as discussed by Clegg ( in “Cell Associated Water” (W. Drost-Hansen and J. S. Clegg, Eds.), Academic Press, New York, 1979; in “Biophysics of Water” (F. Frank, Ed.), Wiley, New York, 1982); Amer. J. Physiol. 246, R133 (1984); Cell Biophys. 6, 153 (1984) .