Thermodynamic Properties of Montecellite

Abstract

A thermochemical study of natural calcium and magnesium orthosilicate monticellite (Ca_1.00Mg_0.95\({\text{Fe}}_{{0.05}}^{{2 + }}\))[SiO₄] from the Khabarovsk Territory, Russia, was carried out on a Tian–Calvet microcalorimeter. The enthalpy of formation from elements Δ_f\(H_{{{\text{el}}}}^{^\circ }\)(298.15 K) = –2238.4 ± 4.5 kJ/mol was determined by high-temperature melt solution calorimetry. The enthalpy and Gibbs energy of formation of monticellite of theoretical composition of CaMg[SiO₄] are calculated: Δ_f\(H_{{{\text{el}}}}^{^\circ }\)(298.15 K) = –2248.4 ± 4.5 kJ/mol and Δ_f\(G_{{{\text{el}}}}^{^\circ }\)(298.15 K) = –2130.5 ± 4.5 kJ/mol.