Cohesive pressure of ionized monolayer and thickness of the interfacial phase

Abstract

The cohesive surface pressure for the monolayer of long-chain quarternary ammonium ions has been found to vary linearly with the inverse square of the area per molecule in the lower range of surface concentration. This linear behavior has been explained on the basis of the van der Waals equation for cohesive pressure applied to the surface phase of definite thickness. From the comparison of values of the van der Waals constant for attraction in two and three dimensions, the thickness of the surface phase containing an ionized monolayer has been estimated. At the region of higher surface concentration, the adsorbed long-chain ions have been found to aggregate forming surface micelles. The aggregation number of these micelles has been estimated.