Sodium hexafluoroaluminate

Sodium aluminium hexafluoride

Names
Other names Sodium fluoroaluminate Sodium aluminofluoroaluminate Cryolite Kryolite Aluminate(3-), hexafluoro-, trisodium, (OC-6-11)-
Identifiers
CAS Number	13775-53-6 Y
ChEBI	CHEBI:39289 Y
ChemSpider	11431435 Y
Jmol interactive 3D	Image
PubChem	159692
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
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	0.04% (20°C)[1]
Vapor pressure	essentially 0
Hazards
EU classification (DSD)	not listed
Lethal dose or concentration (LD, LC):
LDLo (Lowest published)	900 mg/kg (rabbit, oral)[2]
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 2.5 mg/m3[1]
REL (Recommended)	TWA 2.5 mg/m3[1]
IDLH (Immediate danger	250 mg/m3 (as F)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Sodium aluminium hexafluoride is the inorganic compound with the formula Na₃AlF₆. This white solid occurs naturally as the mineral cryolite and is used extensively in the industrial production of aluminium metal. The compound consists of the sodium (Na⁺) salt of hexafluoroaluminate (AlF₆^3-).

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. In 1957, sodium aluminium hexafluoride was registered as a pesticide with the United States EPA. Four Sodium hexafluoroaluminate products registered.^[5]

References

1. 1 2 3 4 "NIOSH Pocket Guide to Chemical Hazards #0559". National Institute for Occupational Safety and Health (NIOSH). 
2. ↑ "Fluorides (as F)". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH). 
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
5. ↑ http://www.epa.gov/oppsrrd1/REDs/0087.pdf

External links

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