Quantitative theory of solubility in supercritical fluids

The phenomenon of enhanced solubility of solids in supercritical fluids is analyzed. The entire region of pressures is considered on the basis of the thermodynamic approach, independently of specific models. General aspects of the phenomenon have been discovered by considering the slopes of solubility curves. These slopes are shown to diverge near the two existing critical points, namely the lower and upper critical end points. In the case of dilute solutions, a curve of the locus of maxima of slopes of solubility curves is found in the reduced pressure-reduced temperature plane. All available experimental data are unified under this approach and are found to agree with theoretical analysis. The results obtained can be used to optimize supercritical fluid extraction.