Stability of Thin Aqueous Films on Solid Surfaces, Part I: Ellipsometric Measurement of Disjoining Pressure Isotherms for Aqueous Films Bounded by Glass and Mercury

Experiments were conducted to study thin film stability and measure disjoining pressure isotherms for solid-liquid-liquid systems using ellipsometry. Particular attention was paid to film thicknesses in the range 10 to 1000 Å where relatively few measurements are available. In the glass-brine-mercury system chosen for our studies, the mercury-brine interface offers a unique opportunity to study the effects of the electrostatic component of the disjoining pressure isotherm. It was observed that the surface potential on the mercury electrode as well as the pH and brine concentration had a small but measureable influence on the aqueous film thickness profile and on the resulting disjoining pressure isotherm