My watch list  

Magnesium oxide

Magnesium oxide
IUPAC name Magnesium oxide
Other names Magnesia
Molecular formula MgO
Molar mass 40.3044 g
Appearance white powder
Density 3.58 g/cm3
Melting point

3073 K (2800 C)

Boiling point

3873 K (3600 C)

Solubility in water 0.0086 g / 100 mL[1]
Main hazards Metal fume fever; May cause irritation in eyes or respiratory tract
NFPA 704
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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 MgO. It is formed by an ionic bond between one magnesium and one oxygen atom. Magnesium oxide is easily made by burning magnesium ribbon which oxidizes in a bright white light, resulting in a powder. It is hygroscopic in nature and care must be taken to protect it from moisture. Magnesium hydroxide (Mg(OH)2), forms in the presence of water, but it can be reversed by heating it to separate moisture.



In medicine, magnesium oxide is used for relief for heartburn and sore stomach, as an antacid, magnesium supplement, and as a short-term laxative. It is also used to improve symptoms of indigestion. Side effects of magnesium oxide may include nausea and cramping.

It is used by many libraries for preserving books. It is used as an insulator in industrial cables.

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

It is also used as 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 infrared optics.

Magnesium oxide is used extensively in electrical heating . 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 it is not used anymore.

Magnesium oxide is also used in feeding animals and there are special grades available.

Magnesium oxide is also a promising insulator for use in devices that exhibit the Tunnel magnetoresistance effect. The crystal structure of MgO matches the crystal structure of iron and cobalt.


Inhalation of magnesium oxide fumes can cause metal fume fever.

See also

Related materials calcium oxide, barium oxide, Magnesium sulfide.


  1. ^
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Magnesium_oxide". A list of authors is available in Wikipedia.
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE