Demixing Pressure Measurements of Aerosol-OT in Ethane + Alcohol Solvent Mixtures

The demixing pressures (dew point pressures) for sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in supercritical ethane + alcohol cosolvent mixtures were measured in a variable-volume view cell. The alcohols studied include methanol, 1-propanol, 1-octanol, and benzyl alcohol. The temperatures studied ranged from 40 to 100 °C with overall alcohol mass fractions ranging from 0 to 0.07. The demixing pressures for AOT (1.6 mass %) in supercritical ethane with methanol, 1-propanol, and 1-octanol were found to linearly increase with temperature. The demixing pressure was found to decrease with increasing alcohol concentration at constant temperature. The differences between methanol and propanol were resolved by calculation of the demixing solvent densities. The addition of 1-octanol decreased the demixing pressure slightly less than the addition of 1-propanol (for 3 mass % cosolvent). For benzyl alcohol as the cosolvent, the demixing pressure increased with increasing cosolvent concentration and showed a very nonlinear dependence on temperature at the highest benzyl alcohol concentration studied.