Correlation of the solubility of ill-characterized solid compounds in supercritical fluids by a cubic equation of state

Abstract A cubic equation of state is applied to correlate the solubility of an ill-characterized solid substance in a supercritical fluid (whose properties are known). By the reasonable assumption that the gas-phase fugacity coefficients are equal to those at infinite dilution, and using the co-volume or the experimental solid volume to calculate the Poynting factor the adjustable parameters are reduced to the solute vapour pressure and co-volume and a binary parameter expressing the solute—solvent interactions (the solute critical constants not being required). By such assumptions, experimental data can be correlated almost within experimental accuracy.