Hexafluoroaluminates

Aluminium is not found free but its compounds are so widespread that it is the most abundant metal in the earth s crust. Aluminosilicates such as clay, kaolin (or china clay), mica and feldspar are well known and widely distributed. The oxide. AI2O3. occurs (anhydrous) as corundum and emery, and (hydrated) as bauxite. Cryolite. Na,AlF. (sodium hexafluoroaluminate). is found extensively in Greenland. 

Cryolite, see Sodium hexafluoroaluminate Cryptohalite, see Ammonium hexafluorosilicate Cupric and cuprous, see under Copper Cuprite, see Copper(I) oxide... 

Of the fluoroaluminates known, cryoflte, ie, sodium hexafluoroaluminate [15096-52-2], Na AlF, has been an integral part of the process for production of aluminum. Recently, the mixtures of potassium tetrafluoroaluminate [14484-69-6], KAIF, and potassium hexafluoroaluminate [13575-52-5], K AlFg, have been employed as bra2ing fluxes in the manufacture of aluminum parts. 

The common structural element in the crystal lattice of fluoroaluminates is the hexafluoroaluminate octahedron, AIF. The differing stmctural features of the fluoroaluminates confer distinct physical properties to the species as compared to aluminum trifluoride. For example, in A1F. all corners are shared and the crystal becomes a giant molecule of very high melting point (13). In KAIF, all four equatorial atoms of each octahedron are shared and a layer lattice results. When the ratio of fluorine to aluminum is 6, as in cryoHte, Na AlF, the AIFp ions are separate and bound in position by the balancing metal ions. Fluorine atoms may be shared between octahedrons. When opposite corners of each octahedron are shared with a corner of each neighboring octahedron, an infinite chain is formed as, for example, in TI AIF [33897-68-6]. More complex relations exist in chioUte, wherein one-third of the hexafluoroaluminate octahedra share four corners each and two-thirds share only two corners (14). 

Ion transport measurements indicate that Na" ions carry most of the current, yet aluminum is deposited. A charge transfer probably occurs at the cathode interface and hexafluoroaluminate ions are discharged, forming aluminum and F ions to neutralize the charge of the current carrying Na" ... 

Sodium-2,4-dichlorophenoxyethyl sulphate Sodium hexafluoroaluminate Sodium hydroxide Stibine... 

The solution is acidic it reacts with weak bases forming double salts i.e., ammonium hexafluoroaluminate, (NH4)3A1F6 ammonium hexafluorophos-phate, NH4PF6 ammonium hexafluorosihcate, (NH4)2 SiFe ammonium hexa-fluorogallate, (NH4)3GaFe ... 

The most intensively investigated reaction with complex aluminum fluorides has been the reaction of sodium hexafluoroaluminate with tetrachloromethane (1), which does not run with high selectivity.48,49 Compounds 2-6 have been determined but the conversion rate is low.49... 

Thus the complex fluorides of aluminum do not offer any advantages over other fluorinating agents in halogen-exchange reactions and so they have not found application in industry, although sodium hexafluoroaluminate is produced in large quantities. 

Aluminum fluoride is made by heating ammonium hexafluoroaluminate to red heat in a stream of nitrogen by the action of fluorine or hydrogen fluoride gas on aluminum trihydrate at high temperatures, followed by calcining the hydrate formed by fusing cryolite or sodium fluoride with aluminum sulfate or by a reaction of fluosilicic acid on aluminum hydrate (HSDB 1995). 

CRYOLITE ENT 24,984 KRYOLITH (GERMAN) NATRIUMALUMINUMFLUORID (GERiMAN) NATRIUMHEXAFLUOROALUMINATE (GERMAN) SODIUM ALUMINOFLUORIDE SODIUM ALUMINUM FLUORIDE SODIUM HEXAFLUOROALUMINATE VILLIAUMITE... 

SYNS AALMONIUM ALUMINUM FLUORIDE AMMONIUM CRYOLITE AMMONIUM FLUOALUM-INATE AMMONIUM HEXAFLUOROALUMINATE TRIAMMONIUM ALUMINUM HEXAFLUORIDE... 

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