Chemical elements
    Physical Properties
    Chemical Properties
      Silicon Tetrahydride
      Silicon Tetrafluoride
      Hydrofluosilicic Acid
      Silicon Subfluoride
      Silicon Tetrachloride
      Silicon Tetrabromide
      Silicon Tetra-iodide
      Mixed Halides of Silicon
      Halogen Derivatives of Silico-ethane
      Halogen Derivatives of Silicopropane
      Halogen Derivatives of Silicobutane
      Halogen Derivatives of Silicopentane and Silicohexane
      Silicon Oxychlorides
      Silicon Dioxide
      Silicoformic Anhydride
      Silico-oxalic Acid
      Silicomes-oxalic Acid
      Silicon Disulphide
      Silicon Monosulphide
      Silicon Oxysulphide
      Silicon Thiochloride
      Silicon Thiobromide
      Silicon Chloroitydrosulphide
      Silicon Selenide
      Silicon Tetramide
      Silicon Di-imide
      Silicon Nitrimide
      Siliconitrogen Hydride
      Silicon Nitrides
      Crystalline Silicon Monocarbide
      Silicon Dicarbide
      Silicon Carboxide
      Borides of Silicon
    PDB 1fuq-4ehr

Borides of Silicon

Two borides of silicon are known: SiB3 and SiB6. They are formed together when boron is heated with excess of crystallised silicon in an electric furnace. Uncombined silicon is removed from the cooled mass by treatment with a cold mixture of nitric and hydrofluoric acids, and the crystals are further purified by heating them with moist potash for half an hour, washing with nitric acid and hot water, and drying at 130° C.

Each compound may be separated from the mixture by suitable treatment. Boiling nitric acid oxidises the hexaboride, leaving the triboride in black, rhombic plates, of density 2.52; whilst fused anhydrous potash decomposes the triboride and leaves the hexaboride in black, opaque crystals of density 2.47, which are intermediate in hardness between ruby and diamond.

Both borides are good conductors of electricity; fluorine acts vigorously upon them, and chlorine at a red heat; they are stable when heated in the air, but must not be heated in platinum, with which the silicon would combine; concentrated sulphuric acid attacks them slowly at 330° C.

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