The interface between ice and silicate surfaces

Abstract

Evidence is developed from observations on the behavior of frozen montmorillonite-water systems and other related observations that indicates the existence of an essentially liquid-like, unfrozen, interfacial layer of water separating ice from the silicate surface. The thickness of the interface is shown to vary greatly with temperature; between 0°C. and about −5°C. the thickness ranges from more than 15 A to about 6 A, but below −5°C. down to liquid nitrogen temperatures the thickness varies only from about 6 A to 3 A. At low temperatures it appears that the mobility of the interfacial water is very much diminished and it may assume properties approaching those of a solid. The question of the presence of anomalous phases of ice is examined, and it is concluded that although the possibility must still be allowed, except for the formation of cubic ice by condensation from the vapor at −80°C. or lower, there is at present no proof of the existence of anomalous ice in frozen silicate-water systems. A phase diagram showing the relationships that exist between the interfacial water, water vapor, and ice is presented. In addition to illustrating the vapor pressure and freezing point depressions, it illustrates in a qualitative way the probable increased effect of pressure on the melting point of the ice present over that of a pure water system. Arguments justifying this point are given together with a discussion of the uncertainties in this conclusion.