Heat capacity of immiscible liquid/fluid interfaces and pressure dependence of the interfacial tension

Abstract

Using a macroscopic thermodynamic approach, the interfacial specific heat capacity is defined and its theoretical formula for two-component, immiscible, liquid–fluid systems is derived. It is found that the interfacial heat capacity depends not only on the bulk phase heat capacity, but also on the interfacial tension, interfacial thickness and interfacial molar densities. By combining a general thermodynamic relation between the interfacial tension and pressure with the extended Cahn–Hilliard gradient theory, a method of evaluating interfacial thickness and interfacial density profile is developed; the interfacial specific heat capacity can then be computed. As examples, the interfacial specific heat capacities of decane–water, dodecane–water, and hexane–water systems are calculated. The significance of the interfacial specific heat capacity is also discussed.