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 tri-iodide, BI3

Boron tri-iodide, BI3, was first prepared by Moissan in 1891. He obtained it by three different methods: (i.) by acting upon boron trichloride vapour with hydrogen iodide at a high temperature, (ii.) by the action of iodine vapour on "amorphous boron" at 700° to 800°, and (iii.) by the action of hydrogen iodide on " amorphous boron " at a red heat. The third process is the best to employ. The "boron" to be used must be obtained by Wohler and Deville's method, washed with hydrochloric acid, and dried at 200° in a current of hydrogen. It is heated in a Bohemian glass tube in a current of hydrogen iodide (dried over calcium iodide) to a temperature just below that at which the glass softens. The crystalline product is dissolved in carbon disulphide, shaken with mercury to remove iodine, and the boron iodide recovered by allowing the carbon disulphide to evaporate.

Boron tri-iodide crystallises in colourless, transparent, nacreous plates which are very hygroscopic and are easily changed by light. It melts at 43° and boils without decomposition at 210°. It is soluble in carbon disulphide, carbpn tetrachloride, benzene, and other organic media.

Boron tri-iodide is not attacked by hydrogen. It is decomposed by sodium and by magnesium at a red heat, but is unaffected by silver at 500° and by sodium at 210°. The iodine burns in oxygen, is attacked by phosphorus at the ordinary temperature, and by sulphur when gently warmed.

According to Besson, boron tri-iodide forms the compound BI2.5NH3 with ammonia, and also unites with phosphine.

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