The interaction of solid surfaces in aqueous systems

The interaction between two high-grade polished fused silica plates separated by a thin layer of aqueous LiCl, NaCl and KCl solution, respectively, was determined by means of a selfdeveloped method. Concerning the repulsion created by overlap of the electrical double layers excellent agreement with the DLVO theory down to separation of about 5 nm were found. For still smaller separations a relatively strong additional repulsion arises which according to experimental evidence might be assigned to the overlap of hydration layers emanating chiefly from the alkali metal halide ions adsorbed onto the silica surfaces. Our results agree well with those obtained by Israelachvili et al. and Pashley, who used mica sheets.