Sodium Aluminum Hexafluoride Cryolite

Cryolite is utilized in the manufacture of aluminum, in the processing of aluminum waste (as a flux in the electrochemical removal of magnesium), as a flux in the aluminization of steel and in welding technology, in the manufacture of glass and enamel, as an additive in the manufacture of abrasives and as an auxiliary product in the remelting of light metals. 

There are a number of processes for manufacturing cryolite, starting from aqueous hydrogen fluoride solutions of hexafluorosilicic acid. In the latter case hexafluorosilicic acid is first converted into an ammonium fluoride solution, which is then reacted with sodium aluminate. 

In variants of this process, the ammonium fluoride is first reacted with sodium hydroxide to ammonia and sodium fluoride and then with aluminum fluoride to cryolite. After separation, the cryolite is calcined at 500 to 700°C. In the 

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Sodium fluoroaluminate CAS 15096-52-3 EINECS/ELINCS 215-560-3 Synonyms Aluminum sodium fluoride Cryolite Sodium aluminofluoride Sodium aluminum fluoride Sodium aluminum hexafluoride Sodium fluoaluminate Sodium hexafluoroaluminate... 

Electrowinning of Aluminum. Aluminum, the most abundant metal in the Earth s crust, did not become readily available commercially until the development of the Hall-Heroult process. This process involves electrolysis of dry aluminum oxide (alumina) dissolved in cryolite (sodium aluminum hexafluoride). Additional calcium fluoride is used to lower the melting point of the cryolite. The process runs at about 960 degrees Celsius and uses carbon electrodes. The alumina for the Hall-Heroult process is obtained from an ore called bauxite, an impure aluminum oxide with varying amounts of compounds such as iron oxide and silica. The preparation of pure alumina follows the Bayer process The alumina is extracted from the bauxite as a solution in sodium hydroxide (caustic soda), reprecipitated by acidification, filtered, and dried. The electrolysis cell has a carbon coating at the bottom that forms a cathode. 

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