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 Oxytrifluoride, POF3






The production of this compound by the partial hydrolysis of PF5 or PF3Cl2 has already been mentioned. It may also be made by passing electric sparks through a mixture of PF3 and oxygen. The first method of preparation consisted in heating phosphorus pentoxide with a fluoride, such as cryolite. It is also produced by the action of hydrogen fluoride on phosphorus pentoxide.

It is best prepared by the action of silver, zinc or lead fluoride on POCl3. The oxychloride is allowed to drop gradually on to anhydrous zinc fluoride in a brass tube at 40° to 50° C. The gas passes out through a lead tube, then through a condenser at -20° C. to retain POCl3, through a tube of zinc chloride to absorb the last traces of oxychloride, and finally is collected over mercury.

It is colourless, with a pungent odour, and fumes slightly in the air. The vapour density is 3.68 to 3.71 (air = 1) and 52.0 (H = l), the theoretical densities for POF3 being 3.69 and 52.0 respectively. The gas condenses to a colourless liquid which boils at -40° C. and freezes to a white solid at -68° C. When dry it does not attack glass in the cold, but does so when heated, although not so strongly as phosphorus trifluoride. On the other hand, whilst the trifluoride was absorbed very slowly by water, the oxyfluoride was absorbed very quickly. Neither gas is completely hydrolysed, appearing to form fluooxyacids.


Fluophosphoric Acids

Fluorine is pre-eminent among the halogens in its power of replacing oxygen of oxyacids to form fluoacids, as is exemplified by such well-known compounds as H2SiF6. Examples of fluoacids are also found among the more strongly electronegative elements of Group VI B, i.e. sulphur and its congeners.

In the case of phosphorus such compounds as P(OH)3OK.KF may perhaps be regarded as belonging to this type.

It has already been noted that the hydrolysis of phosphoryl fluoride is not at first complete. It reaches a stage at which the addition of "nitron" gives a salt, C20H16N4HPO2F2 (m.pt. 230.5—232.5° C.), of difiuophosphoric acid, POF2(OH). The ammonium salt of this acid has been prepared. The acid is also produced when phosphorus pentoxide is fused with ammonium fluoride, or when the pentoxide is dissolved in aqueous hydrofluoric acid. The last-mentioned solution, when kept at the ordinary temperature, undergoes hydrolysis, and with "nitron" yields the "nitron" salt of hexafluo phosphoric acid, HPF6, the ions of which have also been prepared by dissolving phosphorus pentafluoride in cold water. The ions, PF6-, are stable towards boiling water. Solutions of the potassium salt do not give precipitates with salts of the alkaline earth metals.
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