| 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.
Contents |
Production [edit]
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 [edit]
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 [edit]
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 [edit]
MgO is a 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 [edit]
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 [edit]
- 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 obsolete. Crystalline pure MgO is available commercially and has a small use in infrared optics.[10]
- MgO 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]
- MgO is also used as a protective coating in plasma displays.
- Magnesium oxide is used as an oxide barrier in spin-tunneling devices. Owing to the crystalline structure of its thin films, which can be deposited by magnetron sputtering, for example, it shows characteristics superior to those of the commonly used amorphous Al2O3. In particular, spin polarization of about 85% has been achieved with MgO[13] versus 40–60% with alluminium oxide.[14] The value of tunnel magnetoresistance is also significantly higher for MgO (600% at room temperature and 1100% at 4.2 K[15]) than Al2O3 (ca. 70% at room temperature[16]). MgO is thermally stable up to about 700 K, vs. 600 K for Al2O3.
Precautions [edit]
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.[17]
See also [edit]
References [edit]
- ^ 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.
- ^ Application of magnesium compounds to insulating heat-conductive fillers. konoshima.co.jp
- ^ 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. 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. Retrieved 4 Oct 2010.
- ^ Ferro, Shaunacy (6 January 2012). FYI: Why Do Libraries Have That Smell?. Popular Science. 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.
- ^ Stephens, Robert E. and Malitson, Irving H. (1952). "Index of Refraction of Magnesium Oxide". Journal of Research of the National Bureau of Standards 49 (4): 249–252. doi:10.6028/jres.049.025.
- ^ 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. Retrieved 26 September 2011.
- ^ Parkin, S. S. P.; Kaiser, C.; Panchula, A.; Rice, P. M.; Hughes, B.; Samant, M.; Yang, S. H. (2004). "Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers". Nature Materials 3 (12): 862–867. doi:10.1038/nmat1256. PMID 15516928.
- ^ Monsma, D. J.; Parkin, S. S. P. (2000). "Spin polarization of tunneling current from ferromagnet/Al2O3 interfaces using copper-doped aluminum superconducting films". Applied Physics Letters 77 (5): 720. doi:10.1063/1.127097.
- ^ Ikeda, S.; Hayakawa, J.; Ashizawa, Y.; Lee, Y. M.; Miura, K.; Hasegawa, H.; Tsunoda, M.; Matsukura, F. et al. (2008). "Tunnel magnetoresistance of 604% at 300 K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature". Applied Physics Letters 93 (8): 082508. doi:10.1063/1.2976435.
- ^ Wang, D.; Nordman, C.; Daughton, J. M.; Qian, Z.; Fink, J.; Wang, D.; Nordman, C.; Daughton, J. M. et al. (2004). "70% TMR at Room Temperature for SDT Sandwich Junctions with CoFeB as Free and Reference Layers". IEEE Transactions on Magnetics 40 (4): 2269. doi:10.1109/TMAG.2004.830219.
- ^ Magnesium Oxide. National Pollutant Inventory, Government of Australia.
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