Chemical elements
    Physical properties
    Chemical properties
      Boron Hydrides
      Boron trihydride
      Boron halogen
      Boron trifluoride
      Hydrofluoboric acid
      Potassium borofluoride
      Fluoboric acid
      Perfluoboric acid
      Boron subchloride
      Boron trichloride
      Boron tribromide
      Boron tri-iodide
      Oxides of Boron
      Tetraboron trioxide
      Boron dioxide
      Tetraboron pentoxide
      Boron sesqui-oxide
      Boron trioxide
      Boric anhydride
      Boric Acids
      Orthoboric acid
      Boric acid
      Boracic acid
      Complex Boric Acids
      Perboric Acid and Perborates
      Sodium perborate
      Sodium hyperborate
      Potassium perborate
      Rubidium perborate
      Ammonium perborate
      Barium perborate
      Boron sesquisulphide
      Boron trisulphide
      Boron pentasulphide
      Boron selenide
      Boron nitride
      Boron amide
      Boron imide
      Boron phosphide
      Boron phospho-iodides
      Boron carbide
      Boron thiocyanate
      Boron Alkyls
      Boron trimethyl
      Boron Silicides and

Boron halogen

Boron forms halogen compounds of the type BX3. The fluoride, chloride, and bromide can be prepared by the direct union of their elements, but not the iodide. The chloride and bromide can also be prepared by heating to redness in a stream of either chlorine or bromine an intimate mixture of boron sesqui-oxide and carbon: -

B2O3 + 3C + 3X2 = 2BX3 + 3CO.

The boron halides have none of the properties of salts. At the ordinary temperature the fluoride is a gas; the liquid chloride boils at 12.5° C.; the bromide is a volatile liquid, and the iodide a solid of low melting-point. Each is rapidly decomposed by water, the change being expressed, except for the fluoride, by the (irreversible) equation: -

BX3 + 3H2O = H3BO3 + 3HX.

Besson has described the bromo-iodides of boron, BBr2I and BBrI2. They are colourless liquids which boil at 125° and 180° respectively. A mixture of these compounds and boron tri-iodide is obtained when hydrogen iodide acts upon boron tribromide at a high temperature.

Two oxychlorides of boron, BOCl and BOCl3, have been described, but it is doubtful whether they really exist. The first is stated by Gustavson to be obtained as a white, gelatinous solid when boron sesqui-oxide and boron trichloride are heated together at 150° in a sealed tube.

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