The Kirkwood correlation factor of dense methanol as a function of temperature and pressure under isochoric conditions and its statistical mechanical treatment

Abstract

Experimental data of dielectric susceptibilities of methanol available in the literature over a wide range of temperature and pressure have been used for constructing a state function of the Kirkwood correlation factor gK of methanol applicable in the homogeneous fluid region between 298 and 580 K and up to 350 MPa. Results of three isochores at 786.32, 820 and 850 kg m-3 of this state function have been compared with predictions made by a statistical mechanical theory developed in previous work. The theory is based on an association model of alcohols accounting for the correlation of effective dipole moments of chains of all length as well as ringlike cluster formations. Most of the parameters such as association constants and association enthalpies have been obtained from quantum mechanical ab initio calculations of methanol clusters up to six members, reducing the numbers of adjustable parameters to three association constants and an averaged value of the angle between dipoles. The theory which has turned out to provide excellent results for alcohol + hydrocarbon and alcohol + CCl4 liquid mixtures at ambient pressure is also able to predict isochoric values of pure methanol up to a pressure of 350 MPa and temperatures of 570 K without adjusting further parameters in satisfying agreement with experimental data. © 2011 Taylor & Francis.