Liquid-vapor Interfacial Tension Research Articles

Critical-point analysis of the liquid-vapor interfacial surface tension.

The interfacial surface tension of the liquid-vapor system is analyzed near the critical point in a manner similar to bulk thermodynamic critical-point analyses. This is accomplished by a critical-point analysis of the single-phase hard-wall surface tension. Both a Landau expansion and a scaling theory equation of state are investigated. Some general exponent relations are derived and, in addition, some thermodynamically defined correlation lengths are discussed.

Equilibrium phase compositions, phase densities, and interfacial tensions for carbon dioxide + hydrocarbon systems. 6. Carbon dioxide + n-butane + n-decane

This paper presents experimental vapor-liquid equilibrium phase compositions, phase densities, and interfacial tensions for the ternary system CO{sub 2} + n-butane + n-decane at 160{degrees} F. Measurements were made on a mixture of constant overall molar composition of 90.2% CO{sub 2}, 5.9% n-C{sub 4}, 3.9% n-C{sub 10} at pressures from 1310 psia to a near-critical dew point state at 1675 psia. Additional data were obtained at a constant pressure of 1600 psia. The measured phase compositions are in agreement with the data of Metcalfe and Yarborough. The phase densities and interfacial tensions represent data not previously available in the literature.

A simple mathematical model of time-dependent interfacial tension

A mathematical model of time-dependent interfacial tension γ( t) is described which couples empirical relationships for concentration-dependent interfacial tension γ( C s) with theoretical expressions for time-dependent surfactant surface concentration C s( t). Method is illustrated with four different diffusion theories and a single γ( C s) model. The applied γ( C s) relationship was different from the Szyszkowski equation and used steady-state interfacial tension as a reference state. Resultant γ( t) formulations were in closed analytical form with a single adjustable kinetic parameter, simple to use in data-fitting applications or computational experiments. Utility was demonstrated by application to dynamic measurements of liquid-vapor interfacial tension for aqueous solutions of a nonionic detergent (Tween-80), three food proteins, and a system of polyvinyl alcohols. Concentration-dependence of fitted kinetic parameters provided adsorption kinetic constants. Distinct kinetic-control regimes were separated and quantified.

Thermodynamics of adsorption and gibbsian distance parameters: II. The pressure coefficient of interfacial tension in ternary two- and three-phase systems

The rigorous thermodynamic theory of the pressure coefficient of interfacial tension, for systems containing a surfactant film at a liquid—vapor interface or a liquid—liquid interface, is developed. It is shown that a thickness parameter, λ 21, can be obtained from this measurement. λ 21 is the thickness of the region from which the major components of the respective bulk phases are excluded. In Gibbsian terms, it is the distance between the Γ 1 = 0 and Γ 2 = 0 dividing surfaces, when substance 3 is surface-active. Experiments in which the theory may be applied are discussed, particularly the measurement of liquid—vapor interfacial tension in the presence of a lipid film at its equilibrium spreading pressure. The physical interpretation of Γ 21, on a microscopic scale, is discussed.

On the surface thermodynamics of a two—component liquid-vapor-ideal solid system

The surface thermodynamics of a two—component three—phase solid—liquid—vapor system is considered. Under the assumption that the solid is ideal, i.e., smooth, homogeneous, rigid, and has no appreciable vapor pressure, it is shown that an equation-of-state type of relation exists between the solid—vapor, the solid—liquid, and the liquid—vapor interfacial tensions. The existence of this relation in conjunction with Young's equation makes it, in principle, possible to determine the solid-vapor and the solid—liquid interfacial tensions from contact angles. A test is described which, on the basis of contact angle data for a solid in contact with several liquids, allows one to decide whether or not adsorption of the vapor of the liquids on the solid is appreciable.