Revised values for the thermodynamic properties of boehmite, AlO(OH) , and related species and phases in the system Al-H-O

Heat capacity measurements are reported for a well-characterized boehmite that differ significantly from results reported earlier by Shomate and Cook (1946) for a monohydrate of alumina. It is suggested that the earlier measurements were made on a sample that was a mixture of phases and that use of that heat-capacity and derived thermodynamic data be discontinued. The entropy of boehmite derived in this study is 37.19 ?? 0.10 J/(mol.K) at 298.15 K. Based on our value for the entropy and accepting the recommended Gibbs free energy for Al(OH)-4, the Gibbs free energy and enthalpy of formation of boehmite are calculated to be -918.4 ?? 2.1 and -996.4 ?? 2.2 kJ/mol, respectively, from solubility data for boehmite. The Gibbs energy for boehmite is unchanged from that given by Hemingway et al. (1978). -from Authors