Comparison of interfacial tension and capillary constant for argon + krypton, CH4 + krypton, and C2H6 + krypton using two independent methods of measurement

Abstract

Abstract Interfacial tension and capillary constant data were experimentally determined by two independent methods for the systems argon+krypton, methane+krypton, and ethane+krypton. Six to eight isotherms from 125 K to the critical point of the less volatile component were obtained for each system. The interfacial tension data were used to test an improved differential bubble tensiometer against the traditional differential capillary rise method and were used to further support the “field variable” based corresponding states theory. A brief description of the apparatus is presented. Comparisons of the results show that the differential bubble pressure method is as accurate as the differential capillary rise method with better repeatability. Potentially, the improved tensiometer can be automated and used with systems where visual measurements are not possible. The interfacial tension and capillary constant data were used to compare two versions of a corresponding states theory. One version incorporates a scaling law along lines of constant liquid mole fraction and the other along lines of constant fugacity fraction which is a “field variable” in the Griffiths-Wheeler sense. In order to reduce the amount of interpolation necessary to correlate the data, measurements were concentrated at liquid compositions rich in the less volatile component. The results show that the fugacity fraction based corresponding states theory better representated of the data.