Lithium fluoride

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Lithium fluoride (LiF) is an inorganic compound with the chemical formula LiF. It is a white, crystalline solid that is highly stable and has a high melting point. Lithium fluoride is notable for its use in specialized optics and as a component in molten salt reactors.

Properties

Lithium fluoride is a crystalline solid with a high melting point of 845 °C. It has a density of 2.635 g/cm³ and is highly stable, making it resistant to decomposition. The compound is soluble in water, with a solubility of 0.27 g/100 mL at 18 °C. It is also slightly soluble in ethanol.

Structure

Lithium fluoride adopts the rock salt structure, which is a common structure for many ionic compounds. In this structure, each lithium ion (Li⁺) is surrounded by six fluoride ions (F⁻), and each fluoride ion is surrounded by six lithium ions. This arrangement results in a highly stable lattice.

Production

Lithium fluoride can be produced by the reaction of lithium hydroxide (LiOH) or lithium carbonate (Li₂CO₃) with hydrofluoric acid (HF): \[ \text{LiOH} + \text{HF} \rightarrow \text{LiF} + \text{H}_2\text{O} \] \[ \text{Li}_2\text{CO}_3 + 2\text{HF} \rightarrow 2\text{LiF} + \text{CO}_2 + \text{H}_2\text{O} \]

Applications

Optics

Lithium fluoride is used in specialized optics due to its transparency to ultraviolet (UV) light. It is used in UV and vacuum ultraviolet (VUV) optics, including lenses and windows. Its low refractive index and high transmission in the UV range make it valuable in these applications.

Nuclear Industry

In the nuclear industry, lithium fluoride is a component of molten salt reactors (MSRs). It is used in the form of LiF-BeF₂ (FLiBe) mixtures, which serve as a coolant and a solvent for nuclear fuel. The high thermal stability and low neutron absorption cross-section of lithium fluoride make it suitable for this purpose.

Other Uses

Lithium fluoride is also used in the production of ceramics, glass, and aluminum. It acts as a flux in the smelting of aluminum and in the production of certain types of glass and ceramics.

Safety

Lithium fluoride is considered to be of low toxicity, but it should be handled with care. Inhalation or ingestion of lithium fluoride can cause irritation to the respiratory and gastrointestinal tracts. Proper safety measures, including the use of personal protective equipment, should be followed when handling this compound.

See Also

• Lithium
• Fluoride
• Molten salt reactor
• Ultraviolet