Sodium hexafluoroaluminate

Sodium aluminium hexafluoride

Names
Other names Sodium fluoroaluminate Sodium aluminofluoroaluminate Cryolite Kryolite Aluminate(3-), hexafluoro-, trisodium, (OC-6-11)-
Identifiers
CAS Registry Number	13775-53-6 Y
ChEBI	CHEBI:39289 Y
ChemSpider	11431435 Y
InChI InChI=1S/Al.6FH.3Na/h;6*1H;;;/q+3;;;;;;;3*+1/p-6 Y Key: REHXRBDMVPYGJX-UHFFFAOYSA-H Y InChI=1/Al.6FH.3Na/h;6*1H;;;/q+3;;;;;;;3*+1/p-6/rAlF6.3Na/c2-1(3,4,5,6)7;;;/q-3;3*+1 Key: REHXRBDMVPYGJX-ZWHJLPLDAC
Jmol-3D images	Image
PubChem	159692
SMILES [Na+].[Na+].[Na+].F[Al-3](F)(F)(F)(F)F
Properties
Chemical formula	Na3AlF6
Molar mass	209.94 g/mol
Appearance	white powder
Density	2.9 g/cm3, solid
Melting point	950 °C (1,740 °F; 1,220 K)
Boiling point	decomposes
Solubility in water	insoluble
Vapor pressure	essentially 0
Hazards
EU classification	not listed
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 2.5 mg/m3[1]
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Y verify (what is: Y/N?)
Infobox references

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.

History

In 1957, sodium aluminium hexafluoride was registered as a pesticide with the United States EPA. Today there are four Sodium hexafluoroaluminate products registered.^[2]

Production

Most cryolite is manufactured from aluminium oxides, hydrofluoric acid, and sodium hydroxide or the equivalent reagent hexafluorosilicic acid:^[3]

6 NaOH + Al₂O₃ + 12 HF → 2 Na₃AlF₆ + 9 H₂O

Use

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. ^[4]

Safety

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.

References

1. ↑ "NIOSH Pocket Guide to Chemical Hazards #0559". National Institute for Occupational Safety and Health (NIOSH). 
2. ↑ http://www.epa.gov/oppsrrd1/REDs/0087.pdf
3. ↑ 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
4. ↑ http://www.mineralszone.com/minerals/cryolite.html

External links

• Chemical Land 21
• ESPI Metals
• CDC - NIOSH Pocket Guide to Chemical Hazards