INTERFACIAL-TENSIONS OF THE BINARY-SYSTEMS CARBON-DIOXIDE OLEIC-ACID, CARBON-DIOXIDE METHYL MYRISTATE, AND CARBON-DIOXIDE METHYL PALMITATE AND OF THE TERNARY-SYSTEM CARBON-DIOXIDE METHYL-MYRISTATE METHYL-PALMITATE AT HIGH-PRESSURES

Interfacial tensions of the binary systems carbon dioxide-oleic acid, carbon dioxide-methyl myristate, and carbon dioxide-methyl palmitate were measured at 40-degrees-C, 50-degrees-C, and 60-degrees-C and at pressures up to 175 bar. The surface tension of subcritical carbon dioxide and the interfacial tension of the ternary system carbon dioxide-methyl myristate-methyl palmitate at 40-degrees-C and 50-degrees-C and at pressures up to 71 bar were also determined. Experiments were performed by observing the rise in a glass capillary placed inside a high-pressure view cell. Interfacial tensions approach zero as the critical point of the system is attained. Higher temperatures at a given carbon dioxide concentration in the liquid phase reduce interfacial tension-the ''temperature effect''. At constant pressure-except near the consolute point-interfacial tension remains nearly unchanged with rising temperature, as the ''temperature effect'' is being counterbalanced by the ''surfactant effect'' of decreasing carbon dioxide concentration. All systems studied are completely wetting. The occurrence of Marangoni instabilities is discussed. The numerical results are given in full detail.