Abstract
Binary iron sulfides are of major interest and importance in environmental, geological, and planetary science. Oxidative high-temperature oxide melt drop-solution calorimetry in molten sodium molybdate (3Na2O· 4MoO3) solvent at 975 K was applied to determine the energetics of formation of the binary iron monosulfide solid solution (pyrrhotite) (Fe 1-0.125xS, 0 ≤ x ≤ 1). The enthalpies of formation from elements are consistent with earlier data in the literature, available for a few compositions. Within the experimental errors, the enthalpies of formation of the solid solution from the end-members Fe0.875S and FeS (ΔH mix, kJ/mol) at 25 °C equal to zero. Under the assumption of random distribution of Fe vacancies, the Gibbs free energies of mixing of Fe1-0.125xS (0 ≤ x ≤ 1) are estimated. Our data support the two-sublattice model proposed by Waldner and Pelton (2005).
Original language | English (US) |
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Pages (from-to) | 717-723 |
Number of pages | 7 |
Journal | American Mineralogist |
Volume | 95 |
Issue number | 5-6 |
DOIs | |
State | Published - 2010 |
Externally published | Yes |
Keywords
- Enthalpy of formation
- Iron sulfides
- Oxidative high-temperature oxide melt solution calorimetry
- Pyrrhotite
- Thermodynamics
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology