Iron(III) oxide-hydroxide
| Iron(III) oxide-hydroxide | |
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Iron(III) oxide-hydroxide |
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Other names
Ferric acid |
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| Identifiers | |
| CAS number | 1310-14-1  , 20344-49-4 |
| PubChem | 91502 |
| ChemSpider | 82623 |
| EC number | 215-176-6 |
| MeSH | Goethite |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | HFeO2 |
| Molar mass | 88.85 g mol−1 |
| Appearance | Vivid, dark orange, opaque crystals |
| Odor | odorless |
| Density | 4.25 g/cm3 |
| Solubility in water | 0.115 g/100 mL (20 °C) |
| Solubility product, Ksp | 2.79×10-39 for Fe(OH)3[1] |
| Hazards | |
| NFPA 704 |
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 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
A number of chemicals are dubbed iron(III) oxide-hydroxide. These chemicals are oxide-hydroxides of iron, and may occur in anhydrous (FeO(OH)) or hydrated (FeO(OH)·nH2O) forms. The monohydrate (FeO(OH)·H2O) might otherwise be described as iron(III) hydroxide (Fe(OH)3), and is also known as hydrated iron oxide or yellow iron oxide.
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Natural occurrences [edit]
Iron(III) oxide-hydroxide occurs naturally as the minerals goethite (CAS number[]), akaganéite (rarely found in weathered meteorites), lepidocrocite and feroxyhyte, as well as siderogel and limonite, which is a commonly found mixture of mainly goethite, lepidocrocite, quartz and clay minerals. Goethite and lepidocrocite, both crystallizing in orthorhombic system, are the most common forms of iron(III) oxide-hydroxide and the most important mineral carriers of iron in soils. The mineral ferrihydrite, also a soil constituent, is a related compound.
Uses [edit]
Yellow iron oxide (CAS []) is used as a pigment, e.g. Pigment Yellow 42 or C.I. 77492. Pigment Yellow 42 is Food and Drug Administration (FDA) approved for use in cosmetics and is used in some tattoo inks. Solid material color ranges from yellow through dark-brown to black. Iron oxide-hydroxide is also used in aquarium water treatment as a phosphate binder.[2]
Chemistry [edit]
Ferric oxide precipitates between pH 2 to 4:[citation needed]
- Fe3+ + 3OH- → Fe(OH)3
Ferrous oxide precipitates between pH 7 to 9:[citation needed]
- Fe3+ + 3OH- → Fe(OH)3
Production [edit]
It is obtained by reacting ferric chloride with sodium hydroxide:
- FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl
Safety [edit]
The risk and safety phrases for iron oxides are R36, R37, R38, S26, and S36.
See also [edit]
References [edit]
External links [edit]
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