Previously, solubility parameter (SP) values were calculated by the group contribution method, the precision and the reliability of which are not so enough for the QSAR study. On the purpose of improvement of SP estimation method, correlation analysis among the observed value of SP and the other physicochemical properties of liquid compounds was studied. In the case of non-associated compounds, very distinct linear relationship between the energy of vaporization and the square of normal boiling point was found. New estimation method, which calculate SP values from those of the normal boiling point and the density of liquids utilizing this linear relationship, will be presented.
