Sodium hexafluoroaluminate is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

Na₃ Al F₆. This white solid, discovered in 1799 by Peder Christian Abildgaard (1740–1801), occurs naturally as the mineral

cryolite Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is a rare mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987. It is used in the reduction ("smelting") of aluminium, in pest ...

and is used extensively in the industrial production of aluminium. The compound is the sodium (Na⁺) salt of the hexafluoroaluminate (AlF₆³⁻) ion.

Production

Most cryolite is manufactured by a variety of related pathways. One route entails combining

sodium aluminate Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as ...

and

hydrofluoric acid Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive. A common concentration is 49% (48–52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling p ...

: :Na₃Al(OH)₆ + 6 HF → Na₃AlF₆ + 6 H₂O Other routes include: : : Often the hexafluoroaluminic acid, which is recovered from phosphate mining, is the precursor in a two-step process beginning with neutralization with ammonia to give ammonium hexafluoroaluminate: :H₃AlF₆ + 3NH₃ → (NH₄)₃AlF₆ :(NH₄)₃AlF₆ + 3NaOH → Na₃AlF₆ + 3NH₃ + 3H₂O The mineral form of sodium hexafluoroaluminate, which is called

, was mined at

Ivigtût Ivittuut (formerly, Ivigtût) ( Kalaallisut: "Grassy Place") is an abandoned mining town near Cape Desolation in southwestern Greenland, in the modern Sermersooq municipality on the ruins of the former Norse Middle Settlement. Ivittuut is one ...

on the west coast of Greenland until the deposit was depleted in 1987.

Use

The dominant application of synthetic

is as a

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

(or

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

) for electrolysis of aluminium oxides such as

bauxite Bauxite () is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH) ...

. 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 Aluminium fluoride is an inorganic compound with the formula . It forms hydrates . Anhydrous and its hydrates are all colorless solids. Anhydrous is used in the production of aluminium. Several occur as minerals. Occurrence and production Aside ...

is used as that solvent. Unlike typical solutions, this one requires temperatures approaching 1000 °C to melt. Other uses include a whitener for enamels and an opacifier for glass.

Structure

It adopts a

perovskite Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as , known as the perovskite (stru ...

-like structure. The centers are nearly idealized

octahedra In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

. Na⁺ occupy both six- and distorted 8-coordinate sites.

Safety

The is 600 mg/kg for the comparable compound

. Cryolite is poorly soluble in water.

Related compounds

* Chiolite ( ), another sodium fluoroaluminate.

References

External links

Chemical Land 21
{{fluorine compounds Sodium compounds Hexafluoroaluminates