The thermodynamic properties of H2O in magnesium and iron cordierite

Article Abstract:

Thermodynamic study, based on hydrothermal data, enables the determination of cordierite phase relations in an aqueous fluid phase. Experimentation with 31 synthesized cordierite samples helps to demonstrate the pressure-temperature dependence of water in the mineral. Influence of iron and magnesium on water content is discussed. Water models for cordierite facilitate the determination of enthalpy and entropy parameters. Discrepancies in the values of standard enthalpy of hydration are attributed to the difficulty in measuring the quenched water content.

Observations, Water, Thermal properties, Phase rule and equilibrium, Phase equilibrium

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Phase equilibria in the systems Fe2O3-MgO-TiO2 and FeO-MgO-TiO2 between 1173 and 1473 K, and Fe2+-Mg mixing properties of ilmenite, ferrous-pseudobrookite and ulvospinel solid solutions

Article Abstract:

The phase relations in the systems Fe2O3-MgO-TiO2 and FeO-MgO-TiO2 over the temperature ranges from 1173 K and 1473 K were investigated using a combined of optical microscope, X-ray diffraction and EMP examination. Results showed that the Mg2TiO4 end-member breaks down to MgO and MgTiO3 at temperatures below 1273 K. A continuous solid solution along the M3O4 binary of the FeO-MgO-TiO2 system was observed over 1273 K. Fe2+-Mg partitioning data were also obtained for coexisting M2O3-M3O5 and M2O3-M3O4 pairs in the FeO-MgO-TiO2 ternary.

Rocks, Metamorphic, Metamorphic rocks, Rocks, Igneous, Igneous rocks, Minerals, Minerals (Geology), Titanates

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Thermodynamic data from redox reactions at high temperatures: v. thermodynamic properties of Nio-MnO solid solutions from emf measurements

Article Abstract:

The calibration of the (Ni,Mn)O/Ni redox sensor is described. In this system, the familiar univariant oxygen buffer NiO is diluted through the addition of MnO to achieve the displacement of the nickel-nickel oxide buffer equilibrium to lower oxygen fugacity. This sensor was found to exhibit excellent stability across different pressures and yielded highly accurate measurements when used to generate measurements on different types of (Ni,Mn)O solid solutions.

Calibration, Oxidation-reduction reaction, Oxidation-reduction reactions, Chemistry, Analytic, Analytical chemistry

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