Iron Oxide Iii
| Iron oxide (III) | ||
|---|---|---|
-oxide-sample.jpg)  Appearance and structure of hematite , -Fe 2 O 3 | ||
| General | ||
| Thesaurus | Diiron trioxide, Ferric oxide, Yellow iron oxide Iron oxide red CI 77491 CI Pigment Red 101 and 102 | |
| CAS No. | 1309-37-1 | |
| EINECS No. | 215-168-2 | |
| PubChem | 518696 | |
| N o E | E172 (ii) | |
| Chemical Properties | ||
| Empirical formula | Fe 2O 3 | 159.688 0.005 g mol -1 Fe 69.94%, 30.06% O, |
| Physical Properties | ||
| Melting temp | 1565 C (decomposition) | |
| Solubility | in water: none | |
| Density | 5240 kg m -3 | |
| Thermochemistry | ||
| f H 0solid | -198.5 Kcal mol -1your theme (25 C) | |
| C p | 103.9 J K -1 mol -1 (crystal at 25 C) | |
| Precautions | ||
Powder form :
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Not Controlled | ||
The oxide of iron (III), also called ferric oxide is the chemical compound of formula Fe 2 O 3. It is an oxide paramagnetic stable iron , which form hydrated is the rust. It is light tan to rust as powder - which gives particular color to Mars - but gray to black as crystallized. He is one of the three main oxides of iron, the other two being the oxide of iron (II) FeO, rare, and iron oxide (II, III) Fe 3 O 4 (sometimes spelled Fe FeO 2 O 3), found naturally in the magnetite.
Summary |
Structure
There are five phases separate iron oxide (III):
- -Fe 2 O 3 structure rhombohedral of corundum -Al 2 O 3 and is the most common form of iron oxide (III), that of the hematite , the main ore of iron. It is antiferromagnetic below about 260 K, and slightly ferromagnetic between this temperature (the transition from Morin) and about 960 K, the Neel temperature . It can be easily prepared by thermolysis and liquid phase precipitation. Its magnetic properties depend on several factors, primarily the pressure, particle size and intensity of magnetic field applied.
- -Fe 2 O 3 has a structure fcc. It is metastable, and restores the phase above about 500 C. It can be produced by reduction of hematite in carbon , pyrolysis of a solution of ferric chloride or thermolysis of ferric sulphate.
- -Fe 2 O 3 has a cubic structure. It is metastable, and restores the phase at high temperature. Its shape is the natural mineral maghemite. Its particles with diameters below 10 nm are superparamagnetic. It may be prepared by dehydration of an iron oxyhydroxide (III) -FeOOH or by oxidation of iron oxide (II, III) FeO Fe 2 O 3). Ultrafine particles can be produced by thermolysis of oxalate iron (III).
- -Fe 2 O 3 structure has a rhombohedral. The properties of this phase are intermediate between those of and phases. It has never been prepared in pure form so far, and has always been obtained mixed with a phase or. It can be prepared by oxidation of iron in electric arc furnace or pcipitation sol-gel of iron nitrate (III). A material with high phase can however be obtained by heat treatment of phase. The phase is metastable, restoring the phase above 500 C to 750 C..
- Fe 2 O 3 is amorphous at high pressure.
Chemical properties and applications
Iron oxide (III) dissolves readily in strong acids such as the hydrochloric acid and sulfuric acid. It also dissolves very well in the agents of chelation as the EDTA and oxalic acid.
It is often used in the composition of thermite , which burns very exothermic :
This reaction is used to weld large metal parts such as rails for railroads in guiding the molten iron between the workpieces by means of a ceramic funnel.
The mineral oxide of iron (III) is the main source of iron for the steel industry.
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