Statistical Thermodynamic Study on Vpor-liquid Equilibria of Pure Compounds

A relation between the saturated vapor pressure and the heat of vaporization for pure liquids has been derived by statistical thermodynamic method. The generalized van der Waals partition function is uSed for liquid phase,and internal p＆rtition function of liquid molecules is assumed as the produCt of that of independent molecule and an interaction factor which is only function of density and gradually approach unit wity the decrease of denSity. The results of test show that the relation can describe changing rule of the heat of vaporisation with the temperature satisfactorily for seven typical liquids.