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Magnesium oxide
Archivo:Magnesium oxide.jpg
IUPAC name Magnesium oxide
Other names Magnesia
CAS number 1309-48-4
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 0.0086 g / 100 mL[1]
Solubility soluble in acid, ammonia
insoluble in alcohol
Refractive index (nD) 1.736
Crystal structure Halite (cubic), cF8
Space group Fm3m, No. 225
Octahedral (Mg2+); octahedral (O2–)
EU Index Not listed
Main hazards Metal fume fever, irritant
NFPA 704
NFPA 704
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
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 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 forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to separate moisture.

The crystal structure of MgO matches the crystal structure of NaCl.[2]


  • 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.[3] In quantities sufficient to obtain a laxative effect, side effects of long-term use include enteroliths resulting in bowel obstruction.[4]
  • It is used by many libraries for preserving books by reacting with ambient moisture to dry the book storage areas.
  • It is used as one of the raw materials for making cement in dry process plants; specifically Portland cement. If too much is added, the cement may be expansive.
  • It is used as an insulator in industrial cables.
  • It is used as a principal ingredient in construction materials used for fireproofing.
  • It is used by rock climbers as a way to reduce sweat and moisture on hands and holds.
  • It is used as a reference white color in colorimetry, owing to its good diffusing and reflectivity properties.[5] It may be smoked onto the surface of an opaque material to form an integrating sphere.
  • It is used as an insulator in devices that exhibit the tunnel magnetoresistance effect.
  • It is used extensively in electrical 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.
  • It is used in feeding animals and there are special grades available.
  • An industrial use of magnesium oxide is in leather processing, as a basifying agent on chrome tanning process.[clarify]
  • 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 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.[6]
  • It is packed around transuranic waste at the Waste Isolation Pilot Plant, to control the solubility of radionuclides.[7]
  • As a construction material, magnesium oxide wallboards have several attractive characteristics: fire resistance, moisture resistance, mold and mildew resistance, and strength.[8]


Inhalation of magnesium oxide fumes can cause metal fume fever.[9]

See also[]


  1. https://fscimage.fishersci.com/msds/13450.htm
  2. WebElements. Chemistry : Periodic Table : compound data [magnesium (II) oxide. Retrieved on 2008-12-06.
  3. MedlinePlus medicinal use
  4. 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.
  5. Tellex, Peter A.; Waldron, Jack R. (January 1955). "Reflectance of Magnesium Oxide". JOSA 45: 19. DOI:10.1364/JOSA.45.000019.
  6. Index of Refraction of Magnesium Oxide Robert E. Stephens and Irving H. Malitson
  7. wipp.energy.gov Waste-handling guide for WIPP
  8. http://www.concretecottage.com/Magnesium-oxide-boards.htm
  9. National Pollutant Inventory - Magnesium Oxide Fume Fact Sheet

External links[]

Plantilla:Magnesium compounds Plantilla:Antacids

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