magnesium oxide
American Heritage Dictionary:
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magnesium oxide
n.
A white powdery compound, MgO, having a high melting point (2,800°C), used in high-temperature refractories, electrical insulation, food packaging, cosmetics, and pharmaceuticals.
Oxford Dictionary of Chemistry:
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magnesium oxide
Variant: magnesia
A white compound, MgO; cubic; r.d. 3.58; m.p. 2800°C. It occurs naturally as the mineral periclase and is prepared commercially by thermally decomposing the mineral magnesite:
MgCO3(s) → MgO(s)+CO2(g)
It has a wide range of uses, including reflective coatings on optical instruments and aircraft windscreens and in semiconductors. Its high melting point makes it useful as a refractory lining in metal and glass furnaces.
Oxford A-Z of Medicinal Drugs:
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magnesium oxide
A salt of magnesium that has laxative properties and is therefore included as an ingredient in aluminium-containing antacids, such as aluminium hydroxide, to reduce their constipating effect. Antacid preparations containing magnesium oxide are freely available over the counter.
Side effects and precautions:
see magnesium salts.
Interactions with other drugs:
see antacids.
Proprietary preparations:
Asilone Suspension (combined with aluminium hydroxide and dimeticone); Kolanticon Gel (combined with aluminium hydroxide, dimeticone, and dicycloverine hydrochloride).
| magnesium hydroxide, magnesium citrate, magnesium carbonate | |
| magnesium salts, magnesium sulphate, magnesium trisilicate |
American Heritage Stedman's Medical Dictionary:
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magnesium oxide
Wikipedia on Answers.com:
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Magnesium oxide
| Magnesium oxide | |
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Magnesium oxide |
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Other names
Magnesia |
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| Identifiers | |
| CAS number | 1309-48-4  |
| PubChem | 14792 |
| ChEMBL | CHEMBL1200572  |
| RTECS number | OM3850000 |
| ATC code | A02,A06AD02, A12CC10 |
| Properties | |
| 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 (30 °C) |
| Solubility | Soluble in acid, ammonia insoluble in alcohol |
| Acidity (pKa) | 10.3 |
| Band gap | 7.8 eV[1] |
| Thermal conductivity | 45–60 W·m−1·K−1[2] |
| Refractive index (nD) | 1.736 |
| Structure | |
| Crystal structure | Halite (cubic), cF8 |
| Space group | Fm3m, No. 225 |
| Coordination geometry |
Octahedral (Mg2+); octahedral (O2–) |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−602 kJ·mol−1[3] |
| Standard molar entropy S |
27 J·mol−1·K−1[3] |
| Hazards | |
| MSDS | ICSC 0504 |
| EU Index | Not listed |
| R-phrases | R36, R37, R38 |
| Main hazards | Metal fume fever, Irritant |
| NFPA 704 |
 0
1
0
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| 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 |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Magnesium oxide (MgO), 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.
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Production
Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide or by the treatment of magnesium chloride with lime followed by heat.
Applications
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."[4]
Cement
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.[5]
Desiccant
MgO is relatively poor desiccant, but because it neutralizes sulfur oxide acids created by oxidation of Kraft-processed papers, it is used by many libraries for preserving books.[6]
Medical
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.[7] In quantities sufficient to obtain a laxative effect, side effects of long-term use include enteroliths resulting in bowel obstruction.[8]
Other
- 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 as a reference white color in colorimetry, owing to its good diffusing and reflectivity properties.[9] It may be smoked onto the surface of an opaque material to form an integrating sphere.
- 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.
- 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.[10]
- It is packed around transuranic waste at the Waste Isolation Pilot Plant, to control the solubility of radionuclides.[11]
- 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.[12]
- It is also used as a protective coating in plasma displays.
Precautions
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.[13]
See also
References
- ^ Taurian, O.E.; Springborg, M.; Christensen, N.E. (1985). "Self-consistent electronic structures of MgO and SrO". Solid State Communications 55 (4): 351–5. doi:10.1016/0038-1098(85)90622-2. http://users-phys.au.dk/nec/Papers/necSSC/SSC55351.pdf.
- ^ Application of magnesium compounds to insulating heat-conductive fillers
- ^ a b Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
- ^ Mark A. Shand (2006). The chemistry and technology of magnesia. John Wiley and Sons. ISBN 978-0-471-65603-6. http://books.google.com/books?id=0ShuV4W0V2gC. Retrieved 10 September 2011.
- ^ McKenna, Phil (25 September 2010 (updated 1 October 2010)). "Emission control: Turning carbon trash into treasure". New Scientist 2779: 48–51. http://www.newscientist.com/article/mg20727791.100-emission-control-turning-carbon-trash-into-treasure.html?full=true. Retrieved 4 Oct 2010.
- ^ Ferro, Shaunacy (6 January 2012). FYI: Why Do Libraries Have That Smell?. Popular Science. http://www.popsci.com/science/article/2011-12/fyi-why-do-libraries-have-smell. Retrieved 19 Jan 2012.
- ^ Magnesium Oxide. MedlinePlus. Last reviewed 02/01/2009
- ^ 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.
- ^ Tellex, Peter A.; Waldron, Jack R. (1955). "Reflectance of Magnesium Oxide". JOSA 45 (1): 19. doi:10.1364/JOSA.45.000019. http://www.opticsinfobase.org/abstract.cfm?URI=josa-45-1-19.
- ^ Index of Refraction of Magnesium Oxide Robert E. Stephens and Irving H. Malitson
- ^ wipp.energy.gov Step-By-Step Guide for Waste Handling at WIPP. Waste Isolation Pilot Plant. wipp.energy.gov
- ^ "Mass Deacidification: Saving the Written Word". Library of Congress. http://www.loc.gov/preservation/scientists/projects/mass_deacid.html. Retrieved 26 September 2011.
- ^ National Pollutant Inventory – Magnesium Oxide Fume Fact Sheet
External links
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Dictionary of Chemistry
A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved.
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Oxford A-Z of Medicinal Drugs
Market University Press. © 2000, 2003, 2010 An A-Z of Medicinal Drugs. All rights reserved.
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American Heritage Stedman's Medical Dictionary
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company.
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