ADSORPTION OF OCTANOATE IONS AT OIL-WATER INTERFACE

The interfacial tension of petroleum ether-water and benzene-water systems has been measured as a function of the increasing concentration of octanoate ions in the presence and absence of excess neutral salt. The pressure-area curve obtained from the analysis of these data has been compared with that for the neutral monolayer of octanoic acid at the oil-water interface. At a given area per adsorbed ion, the surface pressure obtained from the experimental data for the charged monolayer has been found to be considerably smaller than that calculated on the basis of the Goüy model of the electrical double layer. An attempt has been made to explain this deviation on the basis of the discreteness-of-charge effect introduced recently by Bell, Levine, and Pethica. The pressure-area curves for sodium and lithium salts of octanoic acid have also been compared under identical conditions. © 1968.