Chemical elements
  Aluminium
    Isotopes
    Energy
    Preparation
    Physical properties
    Chemical properties
      Aluminium subfluoride
      Aluminium trifluoride
      Aluminium trichloride
      Aluminium tribromide
      Aluminium iodide
      Aluminium chlorate
      Aluminium perchlorate
      Aluminium bromate
      Aluminium periodate
      Aluminium suboxide
      Alumina
      Aluminium sesqui-oxide
      Aluminium peroxide
      Aluminium hydroxides
      Aluminates
      Tricalcium aluminate
      Sodilim aluminate
      Aluminium sesqui-sulphide
      Aluminium selenide
      Aluminium telluride
      Aluminium sulphite
      Aluminium sulphate
      Alums
      Sodium alum
      Potassium alum
      Ammonium alum
      Hydroxylamine alum
      Silver alum
      Pseudo-alums
      Aluminium dithionate
      Aluminium selenite
      Aluminium selenate
      Aluminium chromate
      Aluminium molybdate
      Aluminium silicomolybdate
      Aluminium tungstate
      Aluminium silicotungstate
      Aluminium phosphotungstate
      Aluminium nitride
      Aluminium phosphide
      Aluminium arsenide
      Aluminium nitrate
      Aluminium Phosphates
      Basic aluminium arsenite
      Aluminium carbide
      Aluminium carbonate
      Aluminium thiocyanate
      Aluminium oxalate
      Aluminium alkyls
      Aluminium Hydrocarbon
      Aluminium acetylacetonate
      Aluminium silicide
      Aluminium silicates
      Leucite
      Nephelite
      Spodumene
      Topaz
      Beryl
      Tourmaline
      Axinite
      Sodalite
      Hauynite
      Kaolinite
      Aluminosilicic acids aluminosilicates
      Aluminium Borides
      Aluminium Boride
      Aluminium Boride
      Aluminium borocarbides
      Aluminium borate
      Aluminium sodium perborate
    Applications
    PDB 1a6e-1zca
    PDB 2b8w-3i62
    PDB 3kql-5ukd

Aluminium tribromide, AlBr3






Aluminium tribromide, AlBr3, is most readily prepared by adding aluminium carefully, in small quantities at a time, to bromine, the reaction being extremely vigorous. Other methods of preparation are to pass bromine vapour over heated aluminium or an intimate mixture of alumina and carbon heated to redness. The product should be rectified over metallic aluminium.

Aluminium tribromide forms colourless, transparent rhombohedra of density 2.54. It melts at 93° and boils at 263.3° under 747 mm. pressure (Mallet); its critical temperature is 772° C. At 444° and 1 atmosphere the vapour density is 18.62, the formula Al2Br6 corresponding to the value 18.42. The specific heat of aluminium bromide (22° to 76°) is 0.08912, and the latent heat of fusion 10.47 cals. per gram.; as a cryoscopic solvent the molecular depression of the freezing-point is 262. The bromide is a non-electrolyte, but dissolves numerous halogen salts with the production of conducting solutions. Aluminium bromide dissolves in alcohol and many organic liquids. The molecular weight corresponds to the double formula Al2Br6 in carbon disulphide and in bromine, but in nitrobenzene it corresponds to the single formula AlBr3. From a solution of aluminium bromide in ethyl bromide, aluminium can be deposited by electrolysis, but the deposited metal readily attacks the solvent, butane being produced.

Aluminium bromide is decomposed when heated in oxygen. It is extremely deliquescent and dissolves in water with the evolution of much heat. The aqueous solution, which may be prepared from aluminium or its hydroxide and hydrobromic acid, reacts acid and becomes basic when boiled. The hexahydrate AlBr3.6H2O can be prepared by methods corresponding to those given for the hexahydrate of aluminium chloride; a dilute aqueous solution when cooled is said to deposit the hydrate 2AlBr3.15H2O.

Aluminium bromide forms double salts with the alkali bromides, of which AlBr3.KBr and AlBr3.NaBr have been described. With the tribromides of antimony and bismuth it forms solid solutions. It combines with hydrogen sulphide, forming a white, crystalline compound, AlBr3.H2S, which melts at 84°; and with phosphorus oxychloride, forming a compound of the molecular formula Al2Br6.2POCl3 in carbon disulphide solution. The compounds AlBr3.2Br2.CS2 and 2AlBr3.2Br2.CS2 have also been described. Like the chloride, it combines with many organic compounds. The following are the molecular formula in carbon disulphide solution, of a few such compounds: - Al2Br6.2C6H5SO2Cl, Al2Br6.2(C6H5)2CO, Al2Br6.2C6H5COCl, Al2Br6.2C6H5NO2.


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