Chemical elements
  Phosphorus
    Isotopes
    Energy
    Preparation
    Applications
    Physical Properties
    Chemical Properties
      Alkali Phosphides
      Alkaline Earth Phosphides
      Copper Silver and Gold Phosphides
      Zinc Group Phosphides
      Aluminium Phosphide
      Titanium Group Phosphides
      Tin Phosphides
      Lead Phosphides
      Arsenic Phosphides
      Antimony Phosphides
      Bismuth Phosphides
      Chromium Phosphides
      Molybdenum and Tungsten Phosphides
      Manganese Phosphides
      Iron Phosphides
      Cobalt Phosphides
      Phosphonium Chloride
      Phosphonium Bromide
      Phosphonium Iodide
      Hydrogen Phosphides
      Alkylphosphines
      Phosphorus Trifluoride
      Phosphorus Pentafluoride
      Phosphorus Trifluorodichloride
      Phosphorus Trifluorodibromide
      Fluophosphoric Acid
      Phosphorus Dichloride
      Phosphorus Trichloride
      Phosphorus Pentachloride
      Phosphorus Chlorobromides
      Phosphorus Chloroiodides
      Phosphorus Tribromide
      Phosphorus Pentabromide
      Phosphorus Diiodide
      Phosphorus Triiodide
      Phosphorus Oxytrifluoride
      Phosphorus Oxychloride
      Pyrophosphoryl Chloride
      Metaphosphoryl Chloride
      Phosphoryl Monochloride
      Phosphoryl Dichlorobromide
      Phosphoryl Chlorodibromide
      Phosphoryl Tribromide
      Metaphosphoryl Bromide
      Phosphoryl Oxyiodides
      Phosphorus Thiotrifluoride
      Phosphorus Thiotrichloride
      Phosphorus Thiotribromide
      Mixed Phosphorus Thiotrihalides
      Phosphorus Suboxides
      Phosphorus Trioxide
      Phosphorus Dioxide
      Phosphorus Pentoxide
      Hypophosphorous Acid
      Phosphorous Acid
      Meta- and Pyro-phosphorous Acids
      Hypophosphoric Acid
      Tetraphosphorus Trisulphide
      Diphosphorus Trisulphide
      Tetraphosphorus Heptasulphide
      Phosphorus Pentasulphide
      Phosphorus Oxysulphides
      Phosphorus Thiophosphites
      Phosphorus Thiophosphates
      Phosphorus Selenophosphates
      Phosphorus Sulphoselenides
      Diamidophosphorous Acid
      Phosphorus Triamide
      Monamidophosphoric Acid
      Diamidophosphoric Acid
      Triamidophosphoric Acid
      Dimetaphosphimic Acid ≡P=
      Trimetaphosphimic Acid
      Tetrametaphosphimic Acid
      Penta- and Hexametaphosphimic Acid
      Monamidodiphosphoric Acid
      Diamidodiphosphoric Acid
      Triamidodiphosphoric Acid
      Nitrilotrimetaphosphoric acid
      Monothioamidophosphoric Acids
      Thiophosphoryl Nitride
      Di- Tri-imido- and -amido-thiophosphates
      Imidotrithiophosphoric Acid =
      Phosphorus Chloronitrides
      Triphosphonitrilic Chloride
      Tetraphosphonitrilic Chloride
      Pentaphosphonitrilic Chloride
      Hexaphosphonitrilic Chloride
      Heptaphosphonitrilic Chloride
      Triphosphonitrilic Bromide
      Phosphorus Halonitrides
      Phosphorus Nitride
      Phosphine
      Pyrophosphoric Acid
      Phosphoric acids
    Slow Oxidation
    Phosphatic Fertilisers

Phosphorus Pentafluoride, PF5






This compound was discovered by Thorpe, who prepared it by the reaction between AsF3 and PCl5:—

5AsF3 + 3PCl5 = 3PF5 + 5AsCl3

The same method and precautions may be adopted as already described for the trifluoride. The first condenser is, however, kept at about -60° C. The pentafluoride can also be made by heating PCl5 with PbF2, or by combining PF3 with Br2 and warming the product:—

5PF3Br2 = 3PF5 + 2PBr5

The pentabromide being a solid is easily separated, and it only remains to free the gas from a small quantity of bromine by allowing it to stand over mercury. It can be made similarly from PF3Cl2. It is produced, together with some PF3, by the action of fluorine upon phosphorus.

Phosphorus pentafluoride is a heavy colourless gas with an unpleasant smell; it strongly attacks the skin and respiratory tract. Unlike the trifluoride it fumes strongly in air and is rapidly absorbed by water. It neither burns nor supports combustion. It does not attack dry glass at room temperatures. The density is 4.5 (air = l) according to Thorpe and Moissan, and the formula is established from this and the analysis. It condenses to a colourless liquid at -75° C. and freezes to a white solid at -83° C.

This compound is by far the most stable pentahalide of phosphorus. It is not dissociated by moderate heat or weak sparks from an induction coil, but on strong sparking it gives PF3 and F2, the latter attacking the glass. The small extent of the dissociation is shown by the fact that the pentafluoride does not react with isoamyl alcohol at the boiling-point of the latter. It is not attacked by oxygen, fluorine or iodine. With dry ammonia it forms an ammine, PF5.5NH3, and with N2O4 an addition compound PF5.N2O4. It is completely hydrolysed by water (or alkalies) giving phosphoric and hydrofluoric acids (or their salts). It is not reduced by heating with phosphorus or sulphur.


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