A solution model, based on the regular solution theory coupled with Flory-Huggins entropy term, was developed for the calculation of solubilities of inorganic compounds in water vapor under high temperatures and pressures. The solubilities of sodium chloride (NaCl), potassium hydroxide (KOH), sodium sulfate (Na2SO4), lead oxide (PbO), silicon oxide (SiO2), lithium nitrate (LiNO3), sodium nitrate (NaNO3) and potassium nitrate (KNO3) were correlated by optimizing internal energies and molar volumes of inorganic compounds which give their solubility parameters. (C) 2001 Elsevier Science B.V. All rights reserved.