Magnesium oxide

Magnesium oxide
Names
IUPAC name
Magnesium oxide
Other names
Magnesia
Periclase
Identifiers
1309-48-4 YesY
ChEMBL ChEMBL1200572 N
EC Number 215-171-9
PubChem 14792
RTECS number OM3850000
Properties
MgO
Molar mass 40.3044 g/mol
Appearance White powder
Odor Odorless
Density 3.58 g/cm3
Melting point 2,852 °C (5,166 °F; 3,125 K)
Boiling point 3,600 °C (6,510 °F; 3,870 K)
0.00062 g/100 mL (0 °C)
0.0086 g/100 mL (30 °C)
Solubility Soluble in acid, ammonia
insoluble in alcohol
Band gap 7.8 eV[1]
Thermal conductivity 45–60 W·m−1·K−1[2]
1.7355
6.2 ± 0.6 D
Structure
Halite (cubic), cF8
Fm3m, No. 225
a = 4.212Å
Octahedral (Mg2+); octahedral (O2−)
Thermochemistry
37.8 J/mol K
26.9 J·mol−1·K−1[3]
−601.8 kJ·mol−1[3]
-596.6 kJ/mol
Pharmacology
A02AA02 (WHO) A06AD02 (WHO), A12CC10 (WHO)
Hazards
Main hazards Metal fume fever, Irritant
Safety data sheet ICSC 0504
R-phrases R36, R37, R38
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
0
1
0
Flash point Non-flammable
US health exposure limits (NIOSH):
PEL (Permissible)
 TWA 15 mg/m3 (fume)[4]
REL (Recommended)
 None designated[4]
IDLH (Immediate danger)
 750 mg/m3 (fume)[4]
Related compounds
Other anions
 Magnesium sulfide
Other cations
 Beryllium oxide
Calcium oxide
Strontium oxide
Barium oxide
Related compounds
 Magnesium hydroxide
Magnesium nitride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
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 bonding. 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 - other sources give magnesia alba as MgCO3), to differentiate it from magnesia negra, a black mineral containing what is now known as manganese.

While "magnesium oxide" normally refers to MgO, magnesium peroxide MgO2 is also known as a compound. According to evolutionary crystal structure prediction,[5] MgO2 is thermodynamically stable at pressures above 116 GPa (gigapascals), and a totally new semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa. Because of its stability, MgO is used as a model system for investigating vibrational properties of crystals.[6]

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. Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures 1500 - 2000 °C diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory. Calcining temperatures 1000 - 1500 °C produce hard-burned magnesia which has limited reactivity and calcining at lower temperature, (700-1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia. Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, this appears rapidly reversible due to absorption of carbon dioxide from the air.[7]

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."[8]

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.

Desiccant

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.[9]

Environmental

Magnesium oxide is used extensively in the soil and groundwater remediation, wastewater treatment, drinking water treatment, air emissions treatment, and waste treatment industries for its acid buffering capacity and related effectiveness in stabilizing dissolved heavy metal species.

Many heavy metals species, such as lead and cadmium are most soluble in water at acidic pH (below 6) as well as high pH (above 11). Solubility of metals effects bioavailability of the species and mobility soil and groundwater systems. Most metal species are toxic to humans at certain concentrations, therefore it is imperative to minimize metal bioavailability and mobility.

Granular MgO is often blended into metals-contaminated soil or waste material, which is also commonly of a low (acidic) pH, in order to drive the pH into the 8-10 range where most metals are at their lowest solubilities. Metal-hydroxide complexes have a tendency to precipitate out of aqueous solution in the pH range of 8-10. MgO is widely regarded as the most effective metals stabilization compound when compared to Portland cement, lime, kiln dust products, power generation waste products, and various proprietary products due to MgO's superior buffering capacity, cost effectiveness, and ease/safety of handling.

Most, if not all products that are marketed as metals stabilization technologies create very high pH conditions in aquifers whereas MgO creates an ideal aquifer condition with a pH of 8-10. Additionally, magnesium, an essential element to most biological systems, is provided to soil and groundwater microbial populations during MgO-assisted metals remediation as an added benefit.

Medical

In medicine, magnesium oxide is used for relief of heartburn and sour 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.[10] In quantities sufficient to obtain a laxative effect, side effects of long-term use include enteroliths resulting in bowel obstruction.[11]

Other

Unpolished MgO crystal

Precautions

Magnesium oxide is easily made by burning magnesium ribbon, which produces a very bright white light, and a powdery ash. 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.[23] When burned in open air, the magnesium gets hot enough to produce noticeable amounts of yellow magnesium nitride. Burning in a covered crucible that allows enough air in to support combustion will reduce the burning temperature,thus minimizing the production of the nitride.

See also

References

  1. ↑ Taurian, O.E.; Springborg, M.; Christensen, N.E. (1985). "Self-consistent electronic structures of MgO and SrO" (PDF). Solid State Communications 55 (4): 351–5. Bibcode:1985SSCom..55..351T. doi:10.1016/0038-1098(85)90622-2.
  2. ↑ Application of magnesium compounds to insulating heat-conductive fillers. konoshima.co.jp
  3. 1 2 Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
  4. 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0374". National Institute for Occupational Safety and Health (NIOSH).
  5. ↑ Zhu, Qiang; Oganov A.R.; Lyakhov A.O. (2013). "Novel stable compounds in the Mg-O system under high pressure." (PDF). Phys. Chem. Chem. Phys. 15: 7696–7700. doi:10.1039/c3cp50678a.
  6. ↑ Mei, AB; O. Hellman; C. M. Schlepütz; A. Rockett; T.-C. Chiang; L. Hultman; I. Petrov; J. E. Greene (2015). "Reflection Thermal Diffuse X-Ray Scattering for Quantitative Determination of Phonon Dispersion Relations.". Physical Review B 92 (17): 174301.
  7. ↑ R C Ropp Elsevier. Encyclopedia of the alkaline earth compounds. Elsevier. p. 109. ISBN 9780444595508.
  8. ↑ Mark A. Shand (2006). The chemistry and technology of magnesia. John Wiley and Sons. ISBN 978-0-471-65603-6. Retrieved 10 September 2011.
  9. ↑ Ferro, Shaunacy (6 January 2012). "FYI: Why Do Libraries Have That Smell?". Popular Science. Retrieved 19 Jan 2012.
  10. ↑ Magnesium Oxide. MedlinePlus. Last reviewed 02/01/2009
  11. ↑ 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.
  12. ↑ Tellex, Peter A.; Waldron, Jack R. (1955). "Reflectance of Magnesium Oxide". JOSA 45 (1): 19. doi:10.1364/JOSA.45.000019.
  13. ↑ Tan, C.Y.; Yaghoubi, A.; Ramesh, S.; Adzila, S.; Purbolaksono, J.; Hassan, M.A.; Kutty, M.G. (December 2013). "Sintering and mechanical properties of MgO-doped nanocrystalline hydroxyapatite" (PDF). Ceramics International 39 (8): 8979–8983. doi:10.1016/j.ceramint.2013.04.098.
  14. ↑ Stephens, Robert E. and Malitson, Irving H. (1952). "Index of Refraction of Magnesium Oxide" (PDF). Journal of Research of the National Bureau of Standards 49 (4): 249–252. doi:10.6028/jres.049.025.
  15. ↑ wipp.energy.gov Step-By-Step Guide for Waste Handling at WIPP. Waste Isolation Pilot Plant. wipp.energy.gov
  16. ↑
  17. ↑
  18. ↑ "Mass Deacidification: Saving the Written Word". Library of Congress. Retrieved 26 September 2011.
  19. ↑ 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. Bibcode:2004NatMa...3..862P. doi:10.1038/nmat1256. PMID 15516928.
  20. ↑ 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. Bibcode:2000ApPhL..77..720M. doi:10.1063/1.127097.
  21. ↑ Ikeda, S.; Hayakawa, J.; Ashizawa, Y.; Lee, Y. M.; Miura, K.; Hasegawa, H.; Tsunoda, M.; Matsukura, F.; Ohno, H. (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. Bibcode:2008ApPhL..93h2508I. doi:10.1063/1.2976435.
  22. ↑ Wang, D.; Nordman, C.; Daughton, J. M.; Qian, Z.; Fink, J.; Wang, D.; Nordman, C.; Daughton, J. M.; Qian, Z.; Fink, J. (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.
  23. ↑ Magnesium Oxide. National Pollutant Inventory, Government of Australia.

External links

This article is issued from Wikipedia - version of the Friday, April 22, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.