|Appearance||Vivid, dark orange, opaque crystals|
|insoluble at pH 7|
Solubility product (Ksp)
|2.79×10−39 for Fe(OH)3|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
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.
Iron(III) oxide-hydroxide occurs naturally as four minerals, the polymorphs denoted by the Greek letters α, β, γ and δ: Goethite, α-FeO(OH), has been used as a pigment since prehistoric times. Akaganéite is the β polymorph, formed by weathering and noted for its presence in some meteorhe lunar surface. The γ polymorph lepidocrocite is commonly encountered as rust on the inside of steel water pipes and tanks. Feroxyhyte (δ) is formed under the high pressure conditions of sea and ocean floors, being thermodynamically unstable with respect to the α polymorph (goethite) at surface conditions. It also occurs as siderogel - a colloid - 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.
Yellow iron oxide (CAS
In a solution containing both iron(II) and iron(III), ferric hydroxide precipitates between pH 2 to 4:
- Fe3+ + 3OH− → Fe(OH)3
Ferrous hydroxide precipitates between pH 7 to 9:
- Fe2+ + 2OH− → Fe(OH)2
It is obtained by reacting ferric chloride with sodium hydroxide:
- FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl
Alternately iron(II) may be oxidized to iron(III) by hydrogen peroxide in the presence of an acid:
- Fe2+ → Fe3+ + e−
- H2O2 + 2 e− → 2 OH−
- 2 Fe2+ + H2O2 + 2 H+ → 2 Fe3+ + 2 H2O
- Iron Oxide Hydroxide (GFO) Phosphate Binders
- Rahimi, Safoora, Rozita M
. Moattari, Laleh Rajabi, Ali Ashraf Derakhshan, and Mohammad Keyhani . "Iron Oxide /hydroxide (α, γ-FeOOH) Nanoparticles as High Potential Adsorbents for Lead Removal from Polluted Aquatic Media ." Journal of Industrial and Engineering Chemistry (2014)
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