*** Welcome to piglix ***

Iron(III) oxide-hydroxide

Iron(III) oxide-hydroxide
Samples of iron(III) oxide-hydroxide monohydrate in a vial, and a spoon
Names
IUPAC name
Iron(III) oxide-hydroxide
Other names
Ferric acid
Identifiers
1310-14-1 YesY
20344-49-4 YesY
3D model (Jmol) Interactive image
ChemSpider 82623 YesY
ECHA InfoCard 100.039.754
EC Number 215-176-6
MeSH Goethite
PubChem 91502
Properties
Appearance Vivid, dark orange, opaque crystals
Odor odorless
Density 4.25 g/cm3
insoluble at pH 7
2.79×10−39 for Fe(OH)3
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
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.

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 meteorites and the 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.


...
Wikipedia

...