Solubility of Solids in Supercritical Fluids: Consistency of Data and a New Model for Cosolvent Systems

The ability to correlate and predict the solubility of solids in supercritical fluids is important in the design and evaluation of supercritical extraction processes. However, a review of the literature reveals that solid solubility data obtained by different investigators often do not agree within the reported uncertainties of the measurements. We have shown previously that a simple theory of dilute solutions can be used to check the consistency of supercritical CO 2 −solid solubility data and also that such data can be reduced to a single straight line over a significant range of solvent density and temperature. In the present work, we first show that our binary solution model is applicable to systems in which the solvent is not CO 2 . We then extend the approach to ternary cosolvent systems and show that data over a range of temperatures, pressures, and cosolvent concentrations can be correlated within experimental error using a single equation. The new model has three parameters that are independent of temperature, pressure, and cosolvent concentration. The approach may therefore be used to extrapolate limited data sets over a range of these variables.