Lithium fluoride

Cubic

4.026 Å

Li, F

Colorless to white solid

Fixed

2.64 g · cm -3

845 ° C

1680 ° C

2.7 g · l -1 ( H 2 O) at 20 ° C.

1.3921

Risk

2.5 mg · m-3 based on fluorine

  • 200 mg • kg -1 ( LD50, guinea pig, oral)
  • 143 mg • kg -1 ( LD50, rat, oral)

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Lithium fluoride ( LiF), the lithium salt of hydrofluoric acid is colorless, white -looking, little water-soluble crystals. Hydrates of lithium fluoride is not known.

Production

The production of lithium fluoride is carried out by reaction of an aqueous lithium hydroxide or lithium carbonate with hydrogen fluoride and subsequent concentration and drying.

Properties

Lithium fluoride crystallizes in the sodium chloride structure ( CN = ​​6 ) in the space group with the lattice parameters a = 402.6 pm. The solubility in water is only 2.7 g / l Lithium fluoride is only slightly soluble, as the lattice energy is greater than the water of hydration. Aqueous solutions react slightly alkaline (pH 8). Furthermore, it does not form hydrates, such as are known from the other lithium halides.

Due to the small ionic radii of the lithium cation and the fluoride anion lithium fluoride has a very high lattice energy of 1034 kJ / mol. This causes the high melting and boiling points of the salt. The standard enthalpy of formation of lithium fluoride is ΔHf0 = -620 kJ / mol. It has a high transparency to electromagnetic radiation in the infrared, visible light and ultraviolet. An 8 mm thick single crystal of lithium fluoride can be of wavelengths from 140 nm to 6000 nm, more than 60 % of the radiation therethrough.

Lithium fluoride with calcium fluoride forms a eutectic having a composition of 80.5 mole percent and 19.5 mole percent LiF CaF2, which melts at 769 ° C.

Use

Single crystals of lithium fluoride can be used in IR spectrometers as prisms. In the production of aluminum lithium fluoride can be used in the electrolysis bath. Lithium fluoride crystals can be used in radiation detectors for ionizing radiation, especially in thermoluminescence. For this purpose, only the salt is often funded from the 6Li isotope used with copper.

Lattice constant Coordination number CAS registry number Dangerous Substances Directive (67/548/EEC) Base (chemistry) Ionic radius Aluminium Thermoluminescent dosimeter Digital Object Identifier CRC Handbook of Chemistry and Physics Lithium bromide Potassium fluoride Rubidium fluoride Caesium fluoride Integrated Authority File
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