Enthalpies of formation of pyrrhotite Fe1-0.125xS (0 ≤ x ≤ 1) solid solutions

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8 Scopus citations


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 languageEnglish (US)
Pages (from-to)717-723
Number of pages7
JournalAmerican Mineralogist
Issue number5-6
StatePublished - 2010
Externally publishedYes


  • Enthalpy of formation
  • Iron sulfides
  • Oxidative high-temperature oxide melt solution calorimetry
  • Pyrrhotite
  • Thermodynamics

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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