A generalized method for estimating heats of vaporization

Abstract

Starting from Clapeyron's vapour pressure equation, separate generalized correlations are developed for the gas and liquid phase contributions appearing in this equation. The final equation obtained by combining these correlations is: L/T_c = 4.58 log p_T/₁∫^T_r (1/zT_r²)dT_r = 0.0244 (p_r-1)/₁∫^T_r (ω /T_r)dT_r A rigorous graphical solution of this equation is presented which enables estimations of the heat of vaporization of a substance from a knowledge of its critical temperature, critical pressure and vapour pressure data. The correlation has been tested for a variety of substances up to the critical point and found to be very accurate, particularly for organic compounds and elementary (or simple) molecules for which the average error in the use of this correlation is less than 2 per cent.