Heat Capacities and Thermodynamic Properties of Hungchaoite and Mcallisterite

The heat capacities on two minerals of hungchaoite (MgB(4)O(7)9H(2)O, Hu) and mcallisterite (MgB(6)O(10)7.5H(2)O, Mc) have been measured with a precision calorimeter at temperatures ranging from 306.15 to 355.15 K, experimentally. It was found that there are no phase transition and thermal anomalies, and the molar heat capacities against temperature for the minerals of hungchaoite and mcallisterite were fitted as C-p,C-m,C-Hu = -27019.23675+229.55286T - 0.63912T(2) + (5.95862 x 10(-4)) T-3 and C-p,C-mMc = -9981.88552 + 84.10964T - 0.22685T(2) + (2.0593 x 10(-4)) T-3, respectively. The molar heat capacities and thermodynamic functions of (H-T-H-298.15), (S-T-S-298.15), and (G(T)-G(298.15)) at intervals of 1 K for the two minerals were obtained for the first time. These results are significant in order to understand the thermodynamic properties of those minerals existing in nature salt lakes, as well as applying them to the chemical engineering process design.