Interfacial Adsorption of Dibutyl Ester of Sodium Sulphosuccinic Acid at the Liquid Hydrocarbon Mixture — 0.1 M KCl Interfaces

Abstract

Interfacial tension (γ) measurements were determined by using a modified drop volume technique at mixture of benzene and toluene – 0.1 M KCl interfaces with varying concentration of dibutyl ester of sodium sulphosuccinic acid (BSS) using AGLA micrometer syringe. The value of interfacial tension regularly decreases with increase in concentration of BSS. The values of surface excess (Γs) at different concentrations of BSS have been calculated from the gradients of γ - log C curves and appropriate form of Gibb's adsorption equation. From these data, number of surfactant ions adsorbed per cm² of interface area occupied per surfactant ion have also been calculated. From π - A curves, it is clear that at low surfactant concentration, slight increase in surface pressure (π) reduces the area to a greater extent but at higher concentrations a large increase in surface pressure produces little decrease in surface area. At low surface pressure the film of surfactant ions is fully expanded and ions are stretched out in disorder manner. The surface area occupied per surfactant ion does not appreciably decrease when surfactant ions are tightly packed together which is seen from the vertical portion of π - A curves. It has been observed that as the mole fraction of benzene in hydrocarbon mixture increases, the area occupied per surfactant ion corresponding to closest packing of mono-molecular film increases.