The thermodynamic properties of natural margarite |
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Authors: | L P Ogorodova M F Vigasina L V Mel’chakova |
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Institution: | 1.Faculty of Geology,Moscow State University,Moscow,Russia |
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Abstract: | Thermal, IR spectroscopic, and thermochemical studies of natural brittle mica, margarite Ca1.00Na0.10Mg0.02Al3.89Fe0.013+Si2.03Ti0.01O10(OH)1.74F0.26, were performed. The enthalpy of formation of natural margarite from the elements (−6269 ± 12 kJ/mol) was determined by melt
solution calorimetry on a high-temperature heat-conducting Calvet microcalorimeter (Setaram, France). Enthalpy growth over
the temperature range 298.15–973 K was determined by the drop method. Equations for the temperature dependences of the enthalpy
and heat capacity were obtained, H°(T)−H°(298.15 K), J/mol = 435.21T + 36.46 × 10−3
T
2 + 109.91 × 105/T − 169863 and C°
p
, J/(mol K) = 435.21 + 72.92 × 10−3
T − 109.91 × 105/T
2. The experimental data were used to estimate the thermodynamic properties of margarite of the theoretical composition, CaAl2Al2Si2O10](OH)2. |
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Keywords: | |
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