Interfacial tension and vapor-liquid equilibria in the critical region of mixtures
88 (12):
7772-7780 (1988)DOI: 10.1063/1.454290
Abstract
In the critical region, the concept of two‐scale‐factor universality can be used to accurately predict the surface tension between near‐critical vapor and liquid phases from the singularity in the thermodynamic properties of the bulk fluid M. R. Moldover, Phys. Rev. A 31, 1022 (1985). In the present work, this idea is generalized to binary mixtures and is illustrated using the data of Hsu, Nagarajan, and Robinson for CO2+n‐butane. We fit the pressure‐temperature‐composition‐density data for coexisting, near‐critical phases of the mixtures with a thermodynamic potential comprised of a sum of a singular term and nonsingular terms. The nonuniversal amplitudes characterizing the singular term for the mixtures are obtained from the amplitudes for the pure components by interpolation in a space of thermodynamic ‘‘field’’ variables. The interfacial tensions predicted for the mixtures from the singular term are within 10% of the data on three isotherms in the pressure range (Pc−P)/Pc<0.5. This difference is comparable to the combined experimental and model errors.