Magnesium fluoride
| |
| Names | |
|---|---|
| Other names
Sellaite
Irtran-1 | |
| Identifiers | |
3D model (JSmol)
|
|
| ChemSpider | |
| ECHA InfoCard | 100.029.086 |
| EC Number |
|
PubChem CID
|
|
| RTECS number |
|
| UNII | |
CompTox Dashboard (EPA)
|
|
| |
| |
| Properties | |
| MgF2 | |
| Molar mass | 62.3018 g/mol |
| Appearance | White tetragonal crystals |
| Density | 3.148 g/cm3 |
| Melting point | 1,263 °C (2,305 °F; 1,536 K) |
| Boiling point | 2,260 °C (4,100 °F; 2,530 K) |
| 0.013 g/100 mL | |
Solubility product (Ksp)
|
5.16⋅10−11 |
| Solubility | Insoluble in ethanol |
| −22.7⋅10−6 cm3/mol | |
Refractive index (nD)
|
1.37397 |
| Structure | |
| Rutile (tetragonal), tP6 | |
| P42/mnm, No. 136 | |
| Thermochemistry | |
Heat capacity (C)
|
61.6 J⋅mol−1⋅K−1 |
Std molar
entropy (S⦵298) |
57.2 J⋅mol−1⋅K−1 |
Std enthalpy of
formation (ΔfH⦵298) |
−1124.2 kJ⋅mol−1 |
Gibbs free energy (ΔfG⦵)
|
−1071 kJ/mol |
| Hazards[2][3] | |
| GHS labelling: | |
| |
| Warning | |
| H303, H315, H319, H335 | |
| P261, P304+P340, P305+P351+P338, P405 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
|
2330 (rat, oral) |
| Safety data sheet (SDS) | ChemicalBook |
| Related compounds | |
Other anions
|
Magnesium chloride Magnesium bromide Magnesium iodide |
Other cations
|
Beryllium fluoride Calcium fluoride Strontium fluoride Barium fluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Magnesium fluoride is an inorganic compound with the formula MgF2. The compound is a white crystalline salt and is transparent over a wide range of wavelengths, with commercial uses in optics that are also used in space telescopes. It occurs naturally as the rare mineral sellaite.
Production and structure
Magnesium fluoride is prepared from magnesium oxide with sources of hydrogen fluoride such as ammonium bifluoride:
- MgO + (NH4)HF2 → MgF2 + NH3 + H2O
Related metathesis reactions are also feasible.
The compound crystallizes as tetragonal birefringent crystals. The structure of the compound is similar to that in rutile, featuring octahedral Mg2+ centers and 3-coordinate fluoride centres.[4]
Uses
Optics
Magnesium fluoride is transparent over an extremely wide range of wavelengths. Windows, lenses, and prisms made of this material can be used over the entire range of wavelengths from 0.120 μm (vacuum ultraviolet) to 8.0 μm (infrared). High quality synthetic VUV grade MgF2 is quite expensive, in the region of $3/kg (2007) but the real cost of optics in this material is due to relatively low volume manufacture. However, with lithium fluoride it is one of the two materials that will transmit in the vacuum ultraviolet range at 121 nm (Lyman alpha) and this is where it finds its application. Lower grade MgF2 is sometimes used in the infrared but here it is inferior to calcium fluoride. MgF2 is tough and works and polishes well, but it is slightly birefringent and should be cut with the optic axis perpendicular to the plane of the window or lens.[4]
Due to its having a suitable refractive index of 1.37, thin layers of MgF2 are very commonly used on the surfaces of optical elements as inexpensive anti-reflective coatings.
The Verdet constant of (MgF2) at 632.8 nm is 0.00810 arcmin/G⋅cm.[5]
Safety
Chronic exposure to magnesium fluoride may affect the skeleton, kidneys, central nervous system, respiratory system, eyes and skin, and may cause or aggravate attacks of asthma.[6]
References
- ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 4–67, 1363, ISBN 0-8493-0594-2
- ^ "Magnesium Fluoride Material Safety Data Sheet". Science Labs. May 21, 2013. Retrieved October 13, 2017.
- ^ "Magnesium fluoride". CAS DataBase List. ChemicalBook. Retrieved October 13, 2017.
- ^ a b Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, Renée; Cuer, Jean Pierre (2005), "Fluorine Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a11_307
- ^ J. Chem. Soc., Faraday Trans., 1996, 92, 2753 - 2757. doi:10.1039/FT9969202753
- ^ "Magnesium Fluoride Material Safety Data Sheet". ESPI Metals. August 2004. Retrieved October 13, 2017.[dead link]