Magnesium oxide

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**Properties**
General
Image:Magnesium oxide crystals (1350x).jpg Magnesium oxide crystals - SEM image (1350x)
Name	Magnesium oxide
Chemical formula	Mg O
Common Reaction	2Mg + O2 ---> 2MgO
Appearance	White, powdery, iron
Physical
Formula weight	40.3044 g/mol
Melting point	3073 K (2800 °C)
Boiling point	3873 K (3600 °C)
Density	3.58 kg/dm³
Crystal structure	Cubic FCC
Solubility	0.00062 g in 100 g water
Thermochemistry
Δ_fH⁰_liquid	? kJ/mol
Δ_fH⁰_solid	-601 kJ/mol
S⁰_solid	32.51 J/(mol·K)
Misc.
Thermal conductivity	42 W m^-1 K^-1 at 0 °C
Coefficient of thermal expansion^[1]	9.84 ×10^-6/K at 0 °C
Specific heat capacity	877 J kg^-1 K^-1
Dielectric constant	9.65 at 1 MHz
Young's modulus	250 GPa
Shear Modulus	155 GPa
Bulk modulus	155 GPa
Poisson's ratio	0.18
Safety
Ingestion	Used as an antacid and/or a laxative. Available over-the-counter.
Inhalation	Causes irritation of upper respiratory tract.
Skin	Causes irritation.
Eyes	Causes irritation.
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

Magnesium oxide

Magnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium. See also oxide. It has an empirical formula of Mg O. It is formed by an ionic bond between one magnesium and one oxygen atom.

1 Applications
2 Precautions
3 See also
4 References
5 External links
6 Suppliers

It is used by many libraries for preserving/deacidifying books, and as an insulator in industrial cables. It is also used as a medication to relieve heartburn, sour stomach, or acid indigestion. Medical uses of magnesium oxide also include using it as a short-term laxative, or used to supplement a diet with magnesium.

Magnesium oxide is used as a basic refractory material for lining crucibles.

Magnesium oxide is a principal ingredient in construction materials used for fireproofing.

It is used as a reference white colour in colorimetry. The emissivity value is about 0.9

Pressed MgO is used as an optical material. It is transparent from 300 nm to 7 µm. The refractive index is 1.72 at 1 µm. It is sometimes known by the Eastman Kodak trademarked name Irtran-5, although this designation is long since obsolete. Crystalline pure MgO is available commercially and has small use in infra-red optics.

Magnesium oxide (electrical grade) is used extensively in electrical heating industry. There are several mesh sizes available and most commonly used ones are 40 and 80 mesh per the American Foundry Society. The extensive use is due to its high di-electric strength and average thermal conductivity. MgO is usually crushed and compacted with minimal airgaps or voids. The electrical heating industry also experimented with Aluminium oxide but is not used now.

Magnesium oxide is also used in animal feeding industry and there are special grades available. MgO is hygroscopic in nature and care must be taken to protect it from moisture. Magnesium hydroxide (Mg(OH)₂) which forms in the presence of water can be reversed by heating to separate moisture.

Inhalation of magnesium oxide fumes can cause metal fume fever.

Related materials calcium oxide, barium oxide, Magnesium sulfide.