Spreading at the Solid/Oil/Water Interface II. Adsorption of n-Carboxylic Acids at the Chrome/Oil/Water Interface.

Using a film balance technique the surface pressures at which oils and oil solutions of surfactants spread and displace water from a solid surface were measured. Mineral oil solutions of n-alkyl monocarboxylic acids were found to adsorb on chrome oxide immersed in water and result in preferential spreading of the oil phase accompanied by permanent displacement of the water film. The spreading pressures of these mineral oil solutions increased with increasing alkyl chain length of the organic acid and decreased with increasing film thickness of the water layer. Mineral oil solutions of the n-alkyl alcohols did not induce any preferential spreading of the oil phase. A mechanism consistent with experimental results is proposed for the preferential spreading of the mineral oil solutions of n-alkyl monocarboxylic acids on hydrophilic chrome oxide immersed in water.