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Sodium hexafluoroaluminate
Sodium aluminium hexafluoride unit cell
Sodium aluminium hexafluoride unit cell
Other names

Sodium fluoroaluminate
Aluminate(3-), hexafluoro-, trisodium, (OC-6-11)-


CAS Number

  • 13775-53-6 check

3D model (JSmol)

  • Interactive image
  • CHEBI:39289 check
  • 11431435 check

PubChem CID

  • 159692
  • 5ZIS914RQ9 check

CompTox Dashboard (EPA)

  • DTXSID90872955 Edit this at Wikidata


  • InChI=1S/Al.6FH.3Na/h;6*1H;;;/q+3;;;;;;;3*+1/p-6 check


  • 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



  • [Na+].[Na+].[Na+].F[Al-3](F)(F)(F)(F)F


Chemical formula

Molar mass 209.94 g/mol
Appearance white solid
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
GHS labelling:[3]


GHS08: Health hazardGHS07: Exclamation markGHS09: Environmental hazard

Signal word


Hazard statements

H332, H372, H411
Lethal dose or concentration (LD, LC):

LDLo (lowest published)

600 mg/kg (guinea pigs, oral)[2]
NIOSH (US health exposure limits):

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).

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Infobox references

Sodium hexafluoroaluminate is an inorganic compound with formula Na3AlF6. This white solid, discovered in 1799 by Peder Christian Abildgaard (1740–1801),[4][5] occurs naturally as the mineral cryolite and is used extensively in the industrial production of aluminium metal. The compound is the sodium (Na+) salt of the hexafluoroaluminate (AlF63−) ion.


Most cryolite is manufactured by a variety of related pathways. One route entails combining sodium aluminate and hydrofluoric acid:[2]

Na3Al(OH)6 + 6 HF → Na3AlF6 + 6 H2O

Other routes include:[6]

6 HF + 3 NaAlO2 → Na3AlF6 + Al2O3 + 3 H2O
4 AlF3 + 3 Na2O → 2 Na3AlF6 + Al2O3

Often the hexafluoroaluminic acid, which is recovered from phosphate mining, is the precursor in a two-step process beginning with neutralization with ammonia to tát give ammonium hexafluoroaluminate:

H3AlF6 + 3 NH3 → (NH4)3AlF6
(NH4)3AlF6 + 3 NaOH → Na3AlF6 + 3 NH3 + 3 H2O

The mineral size of sodium hexafluoroaluminate, which is called cryolite, was mined at Ivigtût on the west coast of Greenland until the deposit was depleted in 1987.


The dominant 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 sánh that they can accept the electrons provided in the electrolysis cell. A mixture of cryolite and some aluminium trifluoride is used as that solvent. Unlike typical solutions, this one requires temperatures approaching 1000 °C to tát melt. Other uses include a whitener for enamels and an opacifier for glass.[2]


It adopts a perovskite-like structure. The AlF3−6 centers are nearly idealized octahedra. Na+ occupy both six- and distorted 8-coordinate sites.[7]


The LD50 is 600 mg/kg for the comparable compound aluminium trifluoride.[2] Cryolite is poorly soluble in water.

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  • Chiolite ( Na5Al3F14), another sodium fluoroaluminate.


  1. ^ a b c d NIOSH Pocket Guide to tát Chemical Hazards. "#0559". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b c d Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307.
  3. ^ GHS: GESTIS 001900
  4. ^ (Staff) (1799). "Norwegische Titanerze und andre neue Fossilien" [Norwegian titanium ores and other new minerals]. Allgemeine Journal der Chemie (in German). 2: 502. "Zugleich theilte er … wie gefrorne Salzlauge schmilzt." (At the same time he also communicated a report on an especially white, spar-like mineral [that had been] brought a few years ago from Greenland to tát Denmark. According to tát one of the investigations undertaken regarding it, it consisted of alumina and hydrofluoric acid. A compound of which no similar example has yet occurred in the mineral realm. It has received the name "cryolite" because it melts lượt thích frozen brine before the [flame of a] blowpipe.)
  5. ^ Abildgaard, P.. C. (1800). "Om Norske Titanertser og om en nye Steenart fra Grönland, som bestaaer af Flusspatsyre og Alunjord" [On Norwegian titanium ores and on a new mineral from Greenland, which consists of hydrofluoric acid and alumina]. Det Kongelige Danske Videnskabers-Selskabs (The Royal Danish Scientific Society). 3rd series (in Danish). 1: 305–316. [From p. 312] Han har kaldt denne grönlandske Steen Kryolith eller Iissteen formedelst dens Udseende, og fordi den smelter saa meget let for Blæsröret. (He has named this Greenlandic stone cryolite or ice stone on trương mục of its appearance, and because it melts sánh easily under a blowpipe.)
  6. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 209. ISBN 978-0-08-037941-8.
  7. ^ F. C. Hawthorne; R. B. Ferguson (1975). "Refinement of the crystal structure of cryolite". The Canadian Mineralogist. 13: 377–382.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links[edit]

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