Thermodynamic studies on adsorption at interfaces. II. One surface-active component system: Tetradecanol at hexane/water interface

Abstract

In order to show that the thermodynamic [ J. Colloid Interface Sci. 64, 348 (1978)] treatment developed in Part I is useful in studying the adsorption of surface-active substances at interfaces, comparison has been made with a system consisting of water and dilute solution of tetradecanol in hexane. As the system is trivariant, we have chosen the temperature, pressure, and mole fraction of tetradecanol in hexane for the thermodynamic independent variables and measured the interfacial tension as their functions. By means of the thermodynamic equations derived in Part I, the interfacial concentration of tetradecanol and thermodynamic quantities of interface formation have been determined from the experimental results. Further, the partial molar thermodynamic quantity changes at the adsorption have been calculated. It has been observed that the thermodynamic quantities of interface formation decrease, while the interfacial concentration increases with increasing the mole fraction of tetradecanol. The results are explicable in terms of negative values of the partial molar quantity changes.