Lawrence M. Anovitz Richard A. Robie James J. McGee Bruce S. Hemingway 1990 <p>The heat capacities of dumortierite have been measured from 7 to 1000 K by quasiadiabatic&nbsp;low-temperature and differential scanning calorimetry. The corrected calorimetric&nbsp;entropy at 298.15 K calculated from the experimental data is 330.2 + 5.0 J/(mol.K)&nbsp;based upon the chemistry of the sample, average compositions proposed by Alexander et&nbsp;al. (1986), and correction to the structural formula given by Moore and Araki (1978).&nbsp;Moore and Araki (1978) have shown the Al(l) site to be disordered, and chemical analyses&nbsp;suggest that there is some Al substitution for Si. A minimum configurational entropy of&nbsp;4.74 J/(mol'K) should be added to the corrected calorimetric entropy for third law calculations.</p> <p><br />The enthalpy and Gibbs free energy of formation of dumortierite from the elements&nbsp;have been estimated from synthesis and decomposition data and are -9109 + 20 and&nbsp;-8568 + 20 kJ/mol, respectively, at 298.15 K and I bar</p> application/pdf en Mineralogical Society of America The thermodynamic properties of dumortierite Si₃B[Al_6.75[]_0.25O_17.25(OH)_0.75] article