Sodium hexafluoroaluminate

Sodium aluminium hexafluoride

Names
Other names Sodium fluoroaluminate Cryolite Kryolite Aluminate(3-), hexafluoro-, trisodium, (OC-6-11)-
Identifiers
CAS Number	13775-53-6 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:39289 Y
ChemSpider	11431435 Y
ECHA InfoCard	100.035.575
PubChem CID	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)
Vapor pressure	essentially 0
Hazards
EU classification (DSD) (outdated)	not listed
Lethal dose or concentration (LD, LC):
LDLo (lowest published)	900 mg/kg (rabbit, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 2.5 mg/m3
REL (Recommended)	TWA 2.5 mg/m3
IDLH (Immediate danger)	250 mg/m3 (as F)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (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 (AlF₆³⁻).

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

It was mined as cryolite at Ivigtût on the west coast of Greenland, until the deposit was depleted in 1987.

The main application of synthetic cryolite is as a solvent (or flux) for electrolysis of 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. The LD₅₀ = 600 mg/kg for the comparable compound aluminium trifluoride.