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

Iron Phosphides






Cast-iron which has been made from phosphatic ores contains phosphides which seriously affect the properties of the metal. Various compounds rich in phosphorus have been prepared by heating iron in phosphorus vapour, or iron with phosphoric acid, bone-ash, sand and carbon (Pelletier, Wohler, loc. cit., Berzelius; also Hatchett). The freezing-point diagram of the system iron- phosphorus shows several maxima and minima. The melting-point of iron was lowered from 1510° C. to about 1400° C. by the addition of 1.7 per cent, of phosphorus, but this was not an end-point of crystallisation. The first eutectic was found at 1003° C. with 10.2 per cent, of phosphorus, the solid phases being Fe and Fe3P. The maximum freezing-point corresponding to Fe3P was about 1100° C. There was a halt-point of crystallisation, or another eutectic, between this compound and Fe2P, which melted at 1350° C. Solid solutions of these compounds, which may be recognised microscopically, increase the hardness of pure iron from 3.5 to 5.0 or 5.5, but above about 1 per cent, of phosphorus render it brittle. Other phosphides which have been reported are FeP, Fe3P4 and Fe2P3. The lower phosphides FeP and Fe2P retain their phosphorus up to a red heat. The former has also been prepared at a red heat by the action of phosphine, thus:—

2FeS + 2PH3 = 2FeP + 2H2S + H2
FeCl3 + PH3 = FeP + 3HCl

Most of the phosphides are insoluble or only slowly soluble in single acids, but are attacked by aqua regia and chlorine. Fe3P dissolves in hydrochloric acid, thus:—

2Fe3P + 12HCl + 8H2O = 6FeCl2 + 2H3PO4 + 11H2

When iron containing phosphides is dissolved in acids one of the products is phosphine, which is formed in greater proportion (i.e. more of the phosphorus is present as phosphine) as the amount of phosphorus diminishes, i.e. between 0.1 and 0.03 per cent.


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