Magnesium fluoride is an ionically bonded inorganic compound with the formula MgF2. It is a white, crystalline solid that is often used for its optical and electrical properties. The compound is a colorless to 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.
It is a highly stable and useful material, particularly valued for its optical properties and its ability to transmit ultraviolet and infrared light. It occurs naturally in limited quantities but is mostly produced synthetically for use in various technological applications.
Properties
- Chemical formula: MgF2
- Molar mass: 62.3018 g/mol
- Appearance: Colorless to 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)
- Solubility in water: 0.013 g/(100 mL)
- Solubility product (Ksp): 5.16⋅10−11
- Solubility: Soluble in nitric acid, Slightly soluble in acetone, Insoluble in ethanol
Production
Magnesium fluoride is prepared from magnesium oxide with sources of hydrogen fluoride such as ammonium bifluoride, by the breakdown of it:
MgO + [NH4]HF2 → MgF2 + NH3 + H2O
Related metathesis reactions are also feasible:
Mg(OH)2 + CuF2 → MgF2 + Cu(OH)2
Occurrences
Magnesium fluoride occurs naturally as the mineral sellaite, though it is relatively rare. Sellaite is found in evaporite deposits, which are formed through the evaporation of seawater or other bodies of water. It can also occur in some areas with volcanic activity.
In addition to its natural occurrence, magnesium fluoride is widely produced synthetically for industrial applications. Some common methods of synthesizing MgF₂ include:
- Reaction of magnesium oxide (MgO) with hydrofluoric acid (HF).
- Direct fluorination of magnesium metal in the presence of fluorine gas.
Uses
- Optical Applications: Magnesium fluoride is widely used in the production of optical coatings, particularly in lenses, windows, and other optical components. It has a low refractive index and is transparent to ultraviolet light, making it ideal for use in UV optics.
- Laser Technology: MgF₂ is used in high-power laser applications due to its ability to withstand high energy levels and its transparency in the ultraviolet spectrum.
- Fluoride Sources: It is sometimes used as a source of fluoride in various industrial processes.
- Electronics: It is used in the manufacture of semiconductors and as an insulator in certain electrical components.
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.
