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The thermodynamic properties of dumortierite Si3B[Al6.75 ???0.25O17.25(OH)0.75]

American Mineralogist

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Abstract

The heat capacities of dumortierite have been measured from 7 to 1000 K by quasi-adiabatic low-temperature and differential scanning calorimetry. The corrected calorimeteric entropy at 298.15 K calculated from the experimental data is 330.2 ?? 5.0 J/(mol.K) based upon the chemistry of the sample, average compositions proposed by Alexander et al. (1986), and correction to the structural formula given by Moore and Araki (1978). Moore and Araki (1978) have shown the Al(1) site to be disordered, and chemical analyses suggest that there is some Al substitution for Si. A minimum configurational entropy of 4.74 J/(mol.K) should be added to the corrected calorimetric entropy for third law calculations. The enthalpy and Gibbs free energy of formation of dumortierite from the elements have been estimated from synthesis and decomposition data and are -9109 ?? 20 and -8568 ?? 20 kJ/mol, respectively, at 298.15 K and 1 bar. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The thermodynamic properties of dumortierite Si3B[Al6.75 ???0.25O17.25(OH)0.75]
Series title:
American Mineralogist
Volume
75
Issue:
11-12
Year Published:
1990
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
American Mineralogist
First page:
1370
Last page:
1375
Number of Pages:
6