Home Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
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Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)

  • Juraj Majzlan EMAIL logo , Klaus-Dieter Grevel and Alexandra Navrotsky
Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 88 Issue 5-6

Abstract

The enthalpy of formation from the elements at 298.15 K (ΔH0f ) of lepidocrocite (γ-FeOOH) and maghemite (γ-Fe2O3) has been measured by acid-solution calorimetry as -549.4 ± 1.4 and -808.1 ± 2.0 kJ/mol, respectively. The ΔH0f of goethite (α-FeOOH) was measured by high-temperature transposed temperature drop and acid-solution calorimetry as -559.5 ± 1.1 and -560.7 ± 1.2 kJ/mol, respectively.

Mathematical programming analysis (MAP) was used to generate an internally consistent data set for goethite and hematite, using the thermodynamic data presented in this study for goethite, and additional thermodynamic data for hematite and synthesis experiments of Baneyeva and Bendeliani (1973) (BB) and Voigt and Will (1981) (VW). Using BB brackets, the thermodynamic values for goethite were refined to ΔH0f = -561.9 kJ/mol and entropy at standard pressure and temperature (S0) = 59.2 J/K·mol; using VW brackets, we arrived at ΔH0f = -561.4 kJ/mol and S0 = 59.5 J/(K·mol). However, MAP failed to include the magnetic transition in goethite, and the derived data should be used with caution. \

Combined with the entropies for the studied phases, the Gibbs free energies of formation from the elements at 298.15 K are -489.8 ± 1.2, -480.1 ± 1.4, and -727.9 ± 2.0 kJ/mol, for goethite, lepidocrocite, and maghemite, respectively. Only hematite (α-Fe2O3) and goethite have a stability field in the Fe2O3-H2O system at low to moderate pressures; maghemite and lepidocrocite are metastable at all pressures and temperatures. Goethite is 1.0 ± 1.4 kJ/mol metastable in ΔG with respect to hematite and liquid water, and 2.0 ± 1.4 kJ/mol metastable with respect to hematite and water vapor at 298 K and 50% relative humidity.

Received: 2002-7-27
Accepted: 2003-2-3
Published Online: 2015-3-31
Published in Print: 2003-5-1

© 2015 by Walter de Gruyter Berlin/Boston

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  2. The reduction of aqueous Au3+ by sulfide minerals and green rust phases
  3. Manganoan kinoshitalite in Mn-rich marble and skarn from Virginia
  4. Expandability of anchizonal illite and chlorite: Significance for crystallinity development in the transition from diagenesis to metamorphism
  5. X-ray absorption spectroscopy of silicates for in situ, sub-micrometer mineral identification
  6. Radiation damage in zircon
  7. Neutron and temperature-resolved synchrotron X-ray powder diffraction study of akaganéite
  8. Li-rich zincostaurolite and its decompression-related breakdown products in a diaspore-bearing metabauxite from East Samos (Greece): An EMP and SIMS study
  9. Olivine from planetary basalts: Chemical signatures that indicate planetary parentage and those that record igneous setting and process
  10. Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
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  12. New thermochemical evidence on the stability of dickite vs. kaolinite
  13. Thermodynamics of Fe oxides: Part I. Entropy at standard temperature and pressure and heat capacity of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  14. Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  15. An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg2TiO4 at high temperatures
  16. Peristeritic plagioclase in North Sea hydrocarbon reservoir rocks: Implications for diagenesis, provenance and stratigraphic correlation
  17. Incorporation of Ni into natural goethite: An investigation by X-ray absorption spectroscopy
  18. Characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the Erzgebirge, Germany
  19. Gersdorffite (NiAsS) chemical state properties and reactivity toward air and aerated, distilled water
  20. The concentration and speciation of hydrogen in feldspars using FTIR and 1H MAS NMR spectroscopy
  21. The significance of mineral inclusions in large diamonds from Yakutia, Russia
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https://doi.org/10.2138/am-2003-5-614

Articles in the same Issue

  1. TEM study of mullite growth after muscovite breakdown
  2. The reduction of aqueous Au3+ by sulfide minerals and green rust phases
  3. Manganoan kinoshitalite in Mn-rich marble and skarn from Virginia
  4. Expandability of anchizonal illite and chlorite: Significance for crystallinity development in the transition from diagenesis to metamorphism
  5. X-ray absorption spectroscopy of silicates for in situ, sub-micrometer mineral identification
  6. Radiation damage in zircon
  7. Neutron and temperature-resolved synchrotron X-ray powder diffraction study of akaganéite
  8. Li-rich zincostaurolite and its decompression-related breakdown products in a diaspore-bearing metabauxite from East Samos (Greece): An EMP and SIMS study
  9. Olivine from planetary basalts: Chemical signatures that indicate planetary parentage and those that record igneous setting and process
  10. Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
  11. Borocookeite, a new member of the chlorite group from the Malkhan gem tourmaline deposit, Central Transbaikalia, Russia
  12. New thermochemical evidence on the stability of dickite vs. kaolinite
  13. Thermodynamics of Fe oxides: Part I. Entropy at standard temperature and pressure and heat capacity of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  14. Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  15. An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg2TiO4 at high temperatures
  16. Peristeritic plagioclase in North Sea hydrocarbon reservoir rocks: Implications for diagenesis, provenance and stratigraphic correlation
  17. Incorporation of Ni into natural goethite: An investigation by X-ray absorption spectroscopy
  18. Characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the Erzgebirge, Germany
  19. Gersdorffite (NiAsS) chemical state properties and reactivity toward air and aerated, distilled water
  20. The concentration and speciation of hydrogen in feldspars using FTIR and 1H MAS NMR spectroscopy
  21. The significance of mineral inclusions in large diamonds from Yakutia, Russia
  22. Letters. Evidence from surface phonons for the (2 × 1) reconstruction of the (101̄4) surface of calcite from computer simulation
  23. Transformation of SiO2 to the amorphous state by shearing at high pressure
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