High-temperature i.r. spectroscopy of the vapour over AlCl3 The thermodynamic properties of AlCl3(g) and Al2Cl6(g)

Abstract

The infrared spectra of the vapour above AlCl3(s) under saturated as well as superheated conditions have been measured. From the results for the saturated-vapour phase the infrared-active vibrational wavenumbers of Al2Cl6 have been obtained. In the superheated vapour above AlCl3, an appreciable amount of monomeric molecules was found, enabling the assignment of the three infrared-active fundamentals of AlCl3(g). Combining the results with quantities from the literature, the thermal functions of AlCl3(g) and Al2Cl6(g) have been calculated, yielding for the standard molar entropies S°m(AlCl3, g, 298.15 K) = (312.7 ± 2.0) J·K-1·mol-1 and S°m(Al2Cl6,g,298.15 K) = (470.2 ± 3.0) J·K-1·mol-1. Third-law evaluation of the available vapour pressures yielded ΔfH°m(AlCl3,g,298.15 K) = -(585.7±1.8)kJ·mol-1 and ΔfH·m(Al2Cl6,g,298.15 K) = -(1299.0±1.9)kJ·mol-1. © 1992 Academic Press Limited All rights reserved.