ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET
The free energy of the reaction (GISQ): 2 Fe + 2 3 Al2SiO5 + 4 3 SiO2 + O2 = 2 3 Fe3Al2Si3O12 metal sillimanite quartz almandine has been measured electrochemically between 1073 and 1173 K at 1 atmosphere pressure. Relative to quartz-fayalite-iron (QFI) equilibrium we obtain: log f{hook}O2GISQ - log...
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| Format: | Journal article |
| Language: | English |
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1989
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| _version_ | 1797070674537218048 |
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| author | Woodland, A Wood, B |
| author_facet | Woodland, A Wood, B |
| author_sort | Woodland, A |
| collection | OXFORD |
| description | The free energy of the reaction (GISQ): 2 Fe + 2 3 Al2SiO5 + 4 3 SiO2 + O2 = 2 3 Fe3Al2Si3O12 metal sillimanite quartz almandine has been measured electrochemically between 1073 and 1173 K at 1 atmosphere pressure. Relative to quartz-fayalite-iron (QFI) equilibrium we obtain: log f{hook}O2GISQ - log f{hook}O2QFI (± 0.1) = -2.23 + 2400 T (1073-1173 K). In the experimental temperature range this result is in excellent agreement with data obtained from studies of garnet-rutile-sillimanite-ilmenite-quartz (GRAIL) equilibrium and for Fe-Mg partitioning between garnet and olivine. It is also in good agreement with recently published estimates based on other phase equilibrium data (Berman, 1988; Anovitz and Essene, 1987). The measured f{hook}O2 for GISQ equilibrium was found to increase with increasing cell edge of the synthetic almandine. The above value is for almandine with ao = 11.527 (±0.001) A ̊. Almandine with a cell edge of 11.534 Å gave f{hook}o2 values about 0.3 log units more oxidized. This increase in f{hook}O2 correlates with increasing Fe+3 of the synthetic garnet. 57Fe Mössbauer spectroscopy indicates that between 3 and 6 percent of the iron is Fe+3 in the high cell-edge material, whereas almandine with ao = 11.527 A ̊ is essentially ferric-free. © 1989. |
| first_indexed | 2024-03-06T22:42:19Z |
| format | Journal article |
| id | oxford-uuid:5c001969-57a7-4c65-a7e1-ac67410510f7 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T22:42:19Z |
| publishDate | 1989 |
| record_format | dspace |
| spelling | oxford-uuid:5c001969-57a7-4c65-a7e1-ac67410510f72022-03-26T17:25:30ZELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNETJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:5c001969-57a7-4c65-a7e1-ac67410510f7EnglishSymplectic Elements at Oxford1989Woodland, AWood, BThe free energy of the reaction (GISQ): 2 Fe + 2 3 Al2SiO5 + 4 3 SiO2 + O2 = 2 3 Fe3Al2Si3O12 metal sillimanite quartz almandine has been measured electrochemically between 1073 and 1173 K at 1 atmosphere pressure. Relative to quartz-fayalite-iron (QFI) equilibrium we obtain: log f{hook}O2GISQ - log f{hook}O2QFI (± 0.1) = -2.23 + 2400 T (1073-1173 K). In the experimental temperature range this result is in excellent agreement with data obtained from studies of garnet-rutile-sillimanite-ilmenite-quartz (GRAIL) equilibrium and for Fe-Mg partitioning between garnet and olivine. It is also in good agreement with recently published estimates based on other phase equilibrium data (Berman, 1988; Anovitz and Essene, 1987). The measured f{hook}O2 for GISQ equilibrium was found to increase with increasing cell edge of the synthetic almandine. The above value is for almandine with ao = 11.527 (±0.001) A ̊. Almandine with a cell edge of 11.534 Å gave f{hook}o2 values about 0.3 log units more oxidized. This increase in f{hook}O2 correlates with increasing Fe+3 of the synthetic garnet. 57Fe Mössbauer spectroscopy indicates that between 3 and 6 percent of the iron is Fe+3 in the high cell-edge material, whereas almandine with ao = 11.527 A ̊ is essentially ferric-free. © 1989. |
| spellingShingle | Woodland, A Wood, B ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title | ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title_full | ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title_fullStr | ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title_full_unstemmed | ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title_short | ELECTROCHEMICAL MEASUREMENT OF THE FREE-ENERGY OF ALMANDINE (FE3AL2SI3O12) GARNET |
| title_sort | electrochemical measurement of the free energy of almandine fe3al2si3o12 garnet |
| work_keys_str_mv | AT woodlanda electrochemicalmeasurementofthefreeenergyofalmandinefe3al2si3o12garnet AT woodb electrochemicalmeasurementofthefreeenergyofalmandinefe3al2si3o12garnet |