The solubility of solids in supercritical fluids

The ability to correlate and predict the solubility of solids in supercritical fluids is important in many applications, including solid deposition in natural gases and the supercritical extraction of natural products. We show below that a simple linear expression, based on the theory of dilute solutions, can be used to correlate solid solubility data. The linear relationship may also be used to check the consistency of experimental data. The proposed equation for solid solubility requires a knowledge of the sublimation pressure of the solid of interest. Since sublimation pressures of 'nonvolatile' solids are often not available, we have developed another relationship for the solid solubility that incorporates a Clausius-Clapeyron equation for the sublimation pressure. Although the resulting expression contains three parameters, we have found that these parameters are independent of temperature and pressure. The proposed expression may therefore be used to extrapolate data to temperatures where experimental information may not be available. (C) 1999 Elsevier Science B.V. All rights reserved.