Thermodynamics of Fe(II)Fe(III) oxide systems I. Hydrothermal Fe3O4

J.J. Bartel; E.F. Westrum; J.L. Haas

doi:10.1016/0021-9614(76)90031-8

Home/Archive/USGS

USGS · 70011106

Thermodynamics of Fe(II)Fe(III) oxide systems I. Hydrothermal Fe3O4

J.J. Bartel·E.F. Westrum·J.L. Haas

View original source ↗Export metadata ↓

Abstract

The heat capacity of a hydrothermally-prepared polycrystalline sample of Fe3O4 was measured from 53 to 350 K, primarily to study the thermophysics of the Verwey transitions. Although the bifurcation of the transition was confirmed, the sample was found to contain traces of manganese. The observed transition temperatures of 117.0 and 123.0 K are 3.7 and 4.2 K higher respectively than those found in pure Fe3O4. Ancillary analytical results are consistent and indicate a stoichiometry of Mn0.008Fe2.992O4 for this material. Characteristics in the transition region are ascribed to dopant effects. ?? 1976.

Explore related subjects

Journal of Chemical Thermodynamics Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

J.J. Bartel, E.F. Westrum, J.L. Haas. 1976. Thermodynamics of Fe(II)Fe(III) oxide systems I. Hydrothermal Fe3O4. https://doi.org/10.1016/0021-9614(76)90031-8

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS1997

Molar heat capacity and entropy of calcium metal

The heat capacity of calcium has been measured at 85 mean temperatures between T ≈ 8 K and T ≈ 369 K using an adiabatically-shielded calorimeter in an intermittent heating mode. At T = 298.15 K, the recommended values for the molar heat capacity, molar entropy, and molar enthalpy increment referred to T = 0 are (25.77 ± 0.08) J·K −1 ·mol −1 , (42.90 ± 0.11) J·K −1 ·mol −1 , and (5811 ±12)J·mol −1 , respectively. The uncertainties are twice the standard deviation of the mean.

Journal of Chemical Thermodynamics↗

USGS1996

Heat capacity and entropy at the temperatures 5 K to 720 K and thermal expansion from the temperatures 298 K to 573 K of synthetic enargite (Cu3AsS4)

The heat capacity of synthetic Cu3AsS4 (enargite) was measured by quasi-adiabatic calorimetry from the temperatures 5 K to 355 K and by differential scanning calorimetry from T = 339 K to T = 720 K. Heat-capacity anomalies were observed at T = (58.5 ?? 0.5) K (??trsHom = 1.4??R??K; ??trsSom = 0.02??R) and at T = (66.5 ?? 0.5) K (??trsHom = 4.6??R??K; ??trsSom = 0.08??R), where R = 8.31451 J??K-1??mol-1. The causes of the anomalies are unknown. At T = 298.15 K, Cop,m and Som(T) are (190.4 ?? 0.2) J??K-1??mol-1 and (257.6 ?? 0.6) J??K-1??mol-1, respectively. The superambient heat capacities are described from T = 298.15 K to T = 944 K by the least-squares regression equation: Cop,m/(J??K-1??mol-1) = (196.7 ?? 1.2) + (0.0499 ?? 0.0016)??(T/K) -(1918 000 ?? 84 000)??(T/K)-2. The thermal expansion of synthetic enargite was measured from T = 298.15 K to T = 573 K by powder X-ray diffraction. The thermal expansion of the unit-cell volume (Z = 2) is described from T = 298.15 K to T = 573 K by the least-squares equation: V/pm3 = 106??(288.2 ?? 0.2) + 104??(1.49 ?? 0.04)??(T/K). ?? 1996 Academic Press Limited.

Journal of Chemical Thermodynamics↗

USGS1996

Thermodynamic properties of scapolites at temperatures ranging from 10 K to 1000 K

The heat capacities of five mineral samples from the scapolite solid-solution series, Na4Al3Si9O24Cl (marialite) to Ca4Al6Si6O24CO3 (meionite), were measured by the adiabatic method from T=8 K to T=350 K and by the differential scanning calorimetry (d.s.c.) method from T = 300 K to T = 1000 K. The meionite (Me) content in per cent {Me=100 Ca*/(Ca* + Na*)} (where the asterisk indicates that possible substituents are included) and molar heat capacity (Cp,m/R) at T=298.15 K for each sample is: Me28, 82.07; Me44, 82.09; Me55, 83.95; Me69, 85.80; Me88, 84.54. The standard molar entropies, {S,om(298.15 K)-Som(0 K)} R-1 (R=8.31451 J??K-1??mol-1), at T=298.15 K for the respective compositions are: 85.05??0.26, 83.78??0.50, 85.22??0.24, 85.76??0.21, and 84.17??0.59. The calculated standard molar entropies (as above) at T=298.15 K for the end-members marialite and meionite, and for an intermediate composition (mizzonite=Me75) are 84.85, 83.94 and 86.15, respectively. Values of the coefficients in the equation Cp,m/R = a + bT+ cT2 + dT-1/2 + eT-2 (valid from T = 300 K to T =1000 K) are: (Mex, a, b/K, c/K2, d/K-1/2, e/K-2 Me88), 315.580, -0.0795676, 1.52825.10-5, -3954.83, 1808460; Me69, 261.285, -0.0415017, 8.73053.10-7, -3028.28, 1083666; Me55, 232.236, -0.0352222, 6.49875.10-6, 2505.99, 601750; Me44, 276.696, -0.0756614, 2.39722.10-5, -3210.40, 1044363; Me28, 149.917, 0.0229399, -1.23180.10-5, 1208.87, -318470. Smoothed thermodynamic functions for the five samples are also presented. The enthalpies of solution for five natural scapolites were measured in 2PbO??B2O3 melts at T= 973 K by Calvet-type calorimetry. The values of ??solHom/R??K are: Me11, 32.14??0.7; Me28, 32.34??0.4; Me44, 33.66??0.8; Me69, 35.29??0.8; Me88, 32.87??0.3. The calculated enthalpies of formation for stoichiometric scapolites ??fHom/103??R??K at T= 298.15 K are: Me0, -1467.4??1.3; Me11, -1491.2??1.2; Me28, -1527.6??0.9; Me44, -1564.1??1.1; Me55, -1587.4??1.1; Me69, -1619.7??1.1; Me75, -1633.1??1.1; Me88, -1649.1??1.0; Me100, -1664??1.6. The heat capacity, the entropy, and the enthalpy of solution have maximal values near Me75 which may account in part for the relatively common occurrence of that composition in natural assemblages. Earlier measurements on leucite have been extended by the Komada/Westrum phonon dispersion model and corrected to end-member composition. ?? 1996 Academic Press Limited.

Journal of Chemical Thermodynamics↗