Iron(III) oxide

Iron(III) oxide
	; Fe O
Names
	IUPAC name Iron(III) oxide
	Other names ferric oxide, haematite, ferric iron, red iron oxide, rouge, maghemite, colcothar, iron sesquioxide, rust, ochre
Identifiers
CAS Number	1309-37-1 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:50819 ;
ChemSpider	14147 ;
ECHA InfoCard	100.013.790
EC Number	215-168-2;
E number	E172(ii) (colours)
Gmelin Reference	11092
KEGG	C19424 ;
PubChem CID	518696;
RTECS number	NO7400000;
UNII	1K09F3G675 ;
CompTox Dashboard (EPA)	DTXSID0029632 ;
	InChI InChI=1S/2Fe.3O [inchi] Key: JEIPFZHSYJVQDO-UHFFFAOYSA-N [inchi]; InChI=1/2Fe.3O/rFe2O3/c3-1-4-2(3)5-1 Key: JEIPFZHSYJVQDO-ZVGCCQCPAC;
	SMILES O1[Fe]2O[Fe]1O2;
Properties
Chemical formula	Fe2O3
Molar mass	159.687 g·mol−1
Appearance	Red-brown solid
Odor	Odorless
Density	5.25 g/cm3[1]
Melting point	1,539 °C (2,802 °F; 1,812 K)[1]; decomposes; 105 °C (221 °F; 378 K); β-dihydrate, decomposes; 150 °C (302 °F; 423 K); β-monohydrate, decomposes; 50 °C (122 °F; 323 K); α-dihydrate, decomposes; 92 °C (198 °F; 365 K); α-monohydrate, decomposes[2]
Solubility in water	Insoluble
Solubility	Soluble in diluted acids,[1] barely soluble in sugar solution[3]; Trihydrate slightly soluble in aq. tartaric acid, citric acid, CH3COOH[2]
Magnetic susceptibility (χ)	+3586.0x10−6 cm3/mol
Refractive index (nD)	n1 = 2.91, n2 = 3.19 (α, hematite)[4]
Structure
Crystal structure	Rhombohedral, hR30 (α-form)[5]; Cubic bixbyite, cI80 (β-form); Cubic spinel (γ-form); Orthorhombic (ε-form)[6]
Space group	R3c, No. 161 (α-form)[5]; Ia3, No. 206 (β-form); Pna21, No. 33 (ε-form)[6]
Point group	3m (α-form)[5]; 2/m 3 (β-form); mm2 (ε-form)[6]
Coordination geometry	Octahedral (Fe3+, α-form, β-form)[5]
Thermochemistry[7]
Heat capacity (C)	103.9 J/mol·K[7]
Std molar; entropy (S⦵298)	87.4 J/mol·K[7]
Std enthalpy of; formation (ΔfH⦵298)	−824.2 kJ/mol[7]
Gibbs free energy (ΔfG⦵)	−742.2 kJ/mol[7]
Hazards
	GHS labelling:
Pictograms	[8]
Signal word	Warning
Hazard statements	H315, H319, H335[8]
Precautionary statements	P261, P305+P351+P338[8]
NFPA 704 (fire diamond)	[9] 0 0 0
Threshold limit value (TLV)	5 mg/m3[1] (TWA)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	10 g/kg (rats, oral)[9]
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 10 mg/m3[10]
REL (Recommended)	TWA 5 mg/m3[10]
IDLH (Immediate danger)	2500 mg/m3[10]
Related compounds
Other anions	Iron(III) fluoride
Other cations	Manganese(III) oxide; Cobalt(III) oxide
Related iron oxides	Iron(II) oxide; Iron(II,III) oxide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Quick facts: Names, Identifiers, Properties, Structure, Th... ▼

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe₂O₃. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe₃O₄), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe₂O₃ is the main source of iron for the steel industry. Fe₂O₃ is readily attacked by acids. Iron(III) oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as Hydrous ferric oxide.[11]

Iron(III) oxide

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Names
Fe O


IUPAC name Iron(III) oxide
Other names ferric oxide, haematite, ferric iron, red iron oxide, rouge, maghemite, colcothar, iron sesquioxide, rust, ochre
Identifiers
CAS Number	1309-37-1^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:50819^Y
ChemSpider	14147^N
ECHA InfoCard	100.013.790
EC Number	215-168-2
E number	E172(ii) (colours)
Gmelin Reference	11092
KEGG	C19424^N
PubChem CID	518696
RTECS number	NO7400000
UNII	1K09F3G675^Y
CompTox Dashboard (EPA)	DTXSID0029632
InChI InChI=1S/2Fe.3O^Y[inchi] Key: JEIPFZHSYJVQDO-UHFFFAOYSA-N^Y[inchi] InChI=1/2Fe.3O/rFe2O3/c3-1-4-2(3)5-1 Key: JEIPFZHSYJVQDO-ZVGCCQCPAC
SMILES O1[Fe]2O[Fe]1O2
Properties
Chemical formula	Fe₂O₃
Molar mass	159.687 g·mol⁻¹
Appearance	Red-brown solid
Odor	Odorless
Density	5.25 g/cm³[1]
Melting point	1,539 °C (2,802 °F; 1,812 K)[1] decomposes 105 °C (221 °F; 378 K) β-dihydrate, decomposes 150 °C (302 °F; 423 K) β-monohydrate, decomposes 50 °C (122 °F; 323 K) α-dihydrate, decomposes 92 °C (198 °F; 365 K) α-monohydrate, decomposes[2]
Solubility in water	Insoluble
Solubility	Soluble in diluted acids,[1] barely soluble in sugar solution[3] Trihydrate slightly soluble in aq. tartaric acid, citric acid, CH₃COOH[2]
Magnetic susceptibility (χ)	+3586.0x10⁻⁶ cm³/mol
Refractive index (n_D)	n₁ = 2.91, n₂ = 3.19 (α, hematite)[4]
Structure
Crystal structure	Rhombohedral, hR30 (α-form)[5] Cubic bixbyite, cI80 (β-form) Cubic spinel (γ-form) Orthorhombic (ε-form)[6]
Space group	R3c, No. 161 (α-form)[5] Ia3, No. 206 (β-form) Pna2₁, No. 33 (ε-form)[6]
Point group	3m (α-form)[5] 2/m 3 (β-form) mm2 (ε-form)[6]
Coordination geometry	Octahedral (Fe³⁺, α-form, β-form)[5]
Thermochemistry[7]
Heat capacity (C)	103.9 J/mol·K[7]
Std molar entropy (S^⦵₂₉₈)	87.4 J/mol·K[7]
Std enthalpy of formation (Δ_fH^⦵₂₉₈)	−824.2 kJ/mol[7]
Gibbs free energy (Δ_fG^⦵)	−742.2 kJ/mol[7]
Hazards
GHS labelling:
Pictograms	[8]
Signal word	Warning
Hazard statements	H315, H319, H335[8]
Precautionary statements	P261, P305+P351+P338[8]
NFPA 704 (fire diamond)	[9] 0 0 0
Threshold limit value (TLV)	5 mg/m³[1] (TWA)
Lethal dose or concentration (LD, LC):
LD₅₀ (median dose)	10 g/kg (rats, oral)[9]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 10 mg/m³[10]
REL (Recommended)	TWA 5 mg/m³[10]
IDLH (Immediate danger)	2500 mg/m³[10]
Related compounds
Other anions	Iron(III) fluoride
Other cations	Manganese(III) oxide Cobalt(III) oxide
Related iron oxides	Iron(II) oxide Iron(II,III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is ^YN ?) Infobox references