Demixing Pressure Measurements of Aerosol-OT in Supercritical Ethane and Ethane + Benzene Mixtures

The demixing pressures (dew point pressures) for sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in ethane and in ethane + benzene cosolvent mixtures were 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 linearly increase with temperature while the demixing pressure was found to linearly decrease with increasing benzene concentration at constant temperature. It was observed that the addition of benzene to SCF ethane affects the demixing pressure of AOT primarily through its influence on the solvent density. A minimum solvent density is required to solubilize 1.6 mass % AOT, which remains constant as the solvent composition is changed at constant temperature. This demixing density was found to decrease slightly with an increase in temperature.