Aluminium fluoride
| Aluminium fluoride | |
|---|---|
| |
| |
| Other names | Aluminium(III) fluoride Aluminum trifluoride |
| Identifiers | |
| CAS number | [], 32287-65-3 (monohydrate) 15098-87-0 (trihydrate) |
| RTECS | BD0725000 |
| PubChem | |
| Properties | |
| Chemical formula | AlF3 |
| Molar mass | 83.9767 g/mol (anhydrous) 101.022 g/mol (monohydrate) 138.023 (trihydrate) |
| Appearance | white, crystalline solid odorless |
| Density | 2.88 g/cm (anhydrous) 2.1 g/cm3 (monohydrate) 1.914 g/cm3 (trihydrate) |
| Melting point |
1291 °C (anhydrous) |
| Solubility in water | 0.56 g/100 mL (0 °C) 0.67 g/100 mL (20 °C) 1.72 g/100 mL (100 °C) |
| Structure | |
| Crystal structure | Rhombohedral, hR24 |
| Space group | R-3c, No. 167 |
| Hazards | |
| EU classification | Harmful (Xn)[1] |
| R-phrases | Template:R22, Template:R36/37/38[1] |
| S-phrases | Template:S26[1] |
| NFPA 704 |
 |
| Template:Tick(what is this?) (verify) 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. This colourless solid can be prepared synthetically but also occurs in nature. It is produced on a substantial scale as a component in the production of aluminium.
Production and occurrence
The majority of aluminium fluoride is produced by heating hexafluorosilicic acid in nitrogen:[2]
- H2SiF6 + Al2O3 → 2 AlF3 + SiO2 + H2O
In the laboratory, AlF3 can be prepared by treating aluminium hydroxide or aluminium metal with HF. Aluminium fluoride trihydrate is found in nature as the rare mineral rosenbergite.
Structure
Its structure resembles that of rhenium trioxide, ReO3, consisting of distorted AlF6 octahedra. Each fluoride is connected to two Al centers. The structure helps explain why AlF3 is refractory, in strong contrast to the other halides of aluminium.[3] 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 D3h symmetry group. The Al-F bond lengths are 163 pm.
Applications
Aluminium fluoride is an important additive that allows the production of aluminium by electrolysis. It lowers the melting point of the alumina feed and, together with cryolite, increases the electrolyte's conductivity of the solution.[2] Together with zirconium fluoride, aluminium fluoride is the basis of fluoroaluminate glasses.
It is also used in ceramics as flux in metallurgy and to inhibit fermentation, and as an evaporation material and sputtering target for preparation of low index films. Should be made into color parts of the atom.
References
- ↑ 1.0 1.1 1.2 BGIA GESTIS (English version)
- ↑ 2.0 2.1 J. Aigueperse, P. Mollard, D. Devilliers, M. Chemla, R. Faron, R. Romano, J. P. Cuer, “Fluorine Compounds, Inorganic” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
External links
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