THE TEMPERATURE DEPENDENT ENTHALPY OF VAPORIZATION OF PURE SUBSTANCES

Abstract

Recently the universal behavior of the temperature dependent enthalpy of vaporization along with the whole liquid–vapor coexistence curve at equilibrium is described and explained by Roman et al.5 The work (called RWVM relation) succeeds in the combination of the linear relation near the triple point and the renormalization group theory result near the critical point. For the convenience of chemical designs and engineering applications, we report its b values yielding the minimum average absolute deviation (AAD) for 74 pure substances from the NIST web-book and compare the results with other correlations. We find that with an adapted b value, the RWVM relation predicts the data of 47 pure substances with an AAD less than 0.0093, with six more than 0.02 and all less than 0.03 except quantum fluid hydrogen, that is clearly better than other correlations. For most pure substances, b covers the range from 0 to 1. Only one negative value stands for the quantum fluid helium because of its enthalpy of vaporization being experimentally not a monotonic function of the temperature in the range near the triple point.