ALUMINIUM FLUORIDE

Aluminium fluoride
Aluminium trifluoride crystal structure
General
Geometry	Octahedral
Other names	Aluminium(III) fluoride Aluminium trifluoride
Molecular formula	AlF3
Molar mass	83.977 g mol−1
Appearance	white, crystalline solid odorless
CAS number
Properties
Density and phase	2.91 g cm−3, solid
Solubility in water	insoluble
Melting point	1290 °C
Sublimation point	1272 °C (at 1 atm pressure)
'Hazards'
EU classification	not listed
NFPA 704
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

'Aluminium fluoride' is the inorganic compound with the formula AlF₃. It can be prepared by treating aluminium hydroxide or aluminium metal with HF. As a solid, its structure resembles that of rhenium trioxide, ReO₃, consisting of distorted AlF₆ octahedra.
AlF₃ is refractory, in strong contrast to the other halides of aluminium.^[1] AlCl₃, AlBr₃, and AlI₃ are dimeric in the liquid and evaporate as dimers as well. In the gas phase, at ca. 1000 °C, aluminium fluoride exists as trigonal molecules of ''D_3h'' symmetry group. The Al-F bond lengths are 163 pm.

Aluminum fluoride in the gas phase at 1000°C

Aluminum fluoride in the gas phase at 1000°C

Aluminium fluoride is an important additive during electrolyte aluminium production because it lowers the melting point of the alumina feed and increase the electrolyte's conductivity.

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References

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References

1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

External links