|Sodium aluminium hexafluoride|
|Jmol-3D images||Image 1|
|Molar mass||209.94 g/mol|
|Density||2.9 g/cm³, solid|
|Melting point||950 °C|
|Solubility in water||insoluble|
|Vapor pressure||essentially 0|
|EU classification||not listed|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Sodium aluminium hexafluoride is the inorganic compound with the formula Na3AlF6. This colourless solid, which occurs naturally as the mineral cryolite, is used extensively in the industrial production of aluminium.
In 1957, sodium aluminium hexafluoride was registered as a pesticide with the United States EPA. Today there are four Sodium hexafluoroaluminate products registered.
- 6 NaOH + Al2O3 + 12 HF → 2 Na3AlF6 + 9 H2O
The main application of synthetic cryolite is as a solvent (or flux) for electrolysis aluminium oxides such as bauxite. The conversion of aluminium oxides into metallic aluminium requires that the metal ions be dissolved so that they can accept the electrons provided in the electrolysis cell. A mixture of cryolite and some aluminium trifluoride is that solvent. Unlike typical solutions, this one requires temperatures approaching 1000 °C to melt. Sodium aluminium hexafluoride is also used as a pesticide. Other uses include a whitener for enamels and an opacifier for glass. 
Cryolite is poorly soluble in water which mitigates problems. Upon ingestion, however, the acids in the stomach increases this solubility. The LD50 = 200 mg/kg, comparable to that for soluble fluoride salts.
- 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.doi:10.1002/14356007.a11_307
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