Demixing pressure measurements of aerosol-OT in supercritical ethane and ethane plus benzene mixtures

The demixing pressures (dew point pressures) for sodium bis(2-ethylhexyl) s ulfosuccinate (AOT) in ethane and in ethane + benzene cosolvent mixtures we re measured in a variable volume view cell. The temperatures studied ranged from 308 K to 333 K with benzene compositions ranging from 0 to 11.7 mass %. The demixing pressures of AOT in each solvent mixture were found to line arly increase with temperature while the demixing pressure was found to lin early decrease with increasing benzene concentration at constant temperatur e. It was observed that the addition of benzene to SCF ethane affects the d emixing pressure of AOT primarily through its influence on the solvent dens ity. A minimum solvent density is required to solubilize 1.6 mass % AOT, wh ich remains constant as the solvent composition is changed at constant temp erature. This demixing density was found to decrease slightly with an incre ase in temperature.