Magnesium oxide

Magnesium oxide
Magnesium oxide
CAS number 1309-48-4 YesY
PubChem 14792
RTECS number OM3850000
ATC code A02AA02
Molecular formula MgO
Molar mass 40.3044 g/mol
Appearance White powder
Odor Odorless
Density 3.58 g/cm3
Melting point

2852 °C, 3125 K, 5166 °F

Boiling point

3600 °C, 3873 K, 6512 °F

Solubility in water 0.086 g/L[2]
Solubility Soluble in acid, ammonia
insoluble in alcohol
Band gap 7.8 eV [1]
Refractive index (nD) 1.736
Crystal structure Halite (cubic), cF8
Space group Fm3m, No. 225
Octahedral (Mg2+); octahedral (O2–)
Std enthalpy of
-601.24 kJ·mol−1
EU Index Not listed
R-phrases R36, R37, R38
Main hazards Metal fume fever, Irritant
NFPA 704
NFPA 704.svg
Flash point Non-flammable
Related compounds
Other anions Magnesium sulfide
Other cations Beryllium oxide
Calcium oxide
Strontium oxide
Barium oxide
Related compounds Magnesium hydroxide
Magnesium nitride
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Magnesium oxide, or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to separate moisture.

Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from magnesia negra, a black mineral containing what is now known as manganese.



A refractory material is one that is physically and chemically stable at high temperatures. "By far the largest consumer of magnesia worldwide is the refractory industry, which consumed about 56% of the magnesia in the United States in 2004, the remaining 44% being used in agricultural, chemical, construction, environmental, and other industrial applications."[3]


MgO is one of the raw materials for making Portland cement in dry process plants. If too much MgO is added, the cement may become expansive. Production of MgO-based cement using serpentinite and waste CO2 (as opposed to conventional CaO-based cement using fossil fuels) may reduce anthropogenic emissions of CO2.[4]


MgO is relatively poor dessicant, but because it neutralizes sulfur oxide acids created by oxidation of Kraft-processed papers, it is used by many libraries for preserving books.[citation needed]


In medicine, magnesium oxide is used for relief of 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.[5] In quantities sufficient to obtain a laxative effect, side effects of long-term use include enteroliths resulting in bowel obstruction.[6]


  • MgO is used as an insulator in industrial cables, as a basic refractory material for crucibles and as a principal fireproofing ingredient in construction materials. As a construction material, magnesium oxide wallboards have several attractive characteristics: fire resistance, moisture resistance, mold and mildew resistance, and strength.
  • It is used extensively in heating as a component of "CalRod"-styled heating elements. 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 dielectric 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.
Unpolished MgO crystal
  • Pressed MgO is used as an optical material. It is transparent from 0.3 to 7 µm. The refractive index is 1.72 at 1 µm and the Abbe number is 53.58. 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.[8]
  • An aerosolized solution of MgO is used in library science and collections management for the deacidification of at-risk paper items. In this process, the alkalinity of MgO (and similar compounds) neutralizes the relatively high acidity characteristic of low-quality paper, thus slowing the rate of deterioration.[10]
  • It is also used as a protective coating in plasma displays.


Magnesium oxide is easily made by burning magnesium ribbon which oxidizes in a bright white light, resulting in a powder. However, the bright flame is very hard to extinguish and it emits a harmful intensity of UV light. Inhalation of magnesium oxide fumes can cause metal fume fever.[11]

See also


  1. ^ O. E. Taurian et al. (1985). "Self-consistent electronic structures of MgO and SrO". Solid State Communications 55 (4): 351. doi:10.1016/0038-1098(85)90622-2. 
  2. ^ Material Safety Data Sheet. Magnesium oxide
  3. ^ Mark A. Shand (2006). The chemistry and technology of magnesia. John Wiley and Sons. ISBN 978-0-471-65603-6. Retrieved 10 September 2011. 
  4. ^ McKenna, Phil (25 September 2010 (updated 1 October 2010)). "Emission control: Turning carbon trash into treasure". New Scientist 2779: 48–51. Retrieved 4 Oct 2010. 
  5. ^ Magnesium Oxide. MedlinePlus. Last reviewed 02/01/2009
  6. ^ Tatekawa Y, Nakatani K, Ishii H et al. (1996). "Small bowel obstruction caused by a medication bezoar: report of a case". Surgery today 26 (1): 68–70. doi:10.1007/BF00311997. PMID 8680127. 
  7. ^ Tellex, Peter A.; Waldron, Jack R. (1955). "Reflectance of Magnesium Oxide". JOSA 45 (1): 19. doi:10.1364/JOSA.45.000019. 
  8. ^ Index of Refraction of Magnesium Oxide Robert E. Stephens and Irving H. Malitson
  9. ^ Step-By-Step Guide for Waste Handling at WIPP. Waste Isolation Pilot Plant.
  10. ^ "Mass Deacidification: Saving the Written Word". Library of Congress. Retrieved 26 September 2011. 
  11. ^ National Pollutant Inventory – Magnesium Oxide Fume Fact Sheet

External links

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Look at other dictionaries:

  • magnesium oxide — n. (Chem.) Magnesia. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • magnesium oxide — n a white highly infusible compound MgO used esp. in refractories, cements, insulation, and fertilizers, in rubber manufacture, and in medicine as an antacid and mild laxative * * * [USP] a bulky (light m. oxide) or relatively dense (heavy m.… …   Medical dictionary

  • magnesium oxide — noun a white solid mineral that occurs naturally as periclase; a source of magnesium • Syn: ↑periclase, ↑magnesia • Hypernyms: ↑mineral • Substance Meronyms: ↑magnesium, ↑Mg, ↑atomic numbe …   Useful english dictionary

  • magnesium oxide — magnio oksidas statusas T sritis chemija formulė MgO atitikmenys: angl. magnesia; magnesium oxide rus. магнезия; магния оксид ryšiai: sinonimas – magnezija …   Chemijos terminų aiškinamasis žodynas

  • magnesium oxide — noun A white powder (MgO) with a high melting point; it occurs naturally as periclase, an ore of magnesium. Syn: magnesia …   Wiktionary

  • magnesium oxide — noun Date: 1866 a white highly infusible compound MgO used especially in refractories, cements, insulation, and fertilizers, in rubber manufacture, and in medicine as an antacid and mild laxative …   New Collegiate Dictionary

  • magnesium oxide — Chem. magnesia. [1905 10] * * * …   Universalium

  • magnesium oxide — magne′sium ox′ide n. chem. magnesia • Etymology: 1905–10 …   From formal English to slang

  • magnesium oxide — /mægˌniziəm ˈɒksaɪd/ (say mag.neezeeuhm oksuyd) noun → magnesia …   Australian-English dictionary

  • Magnesium oxide wallboard — (10 mm thickness) Magnesium oxide more commonly called magnesia is a versatile mineral that when used as part of a cement mixture and cast into thin cement panels under proper curing procedures and practices can be used in residential and… …   Wikipedia

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