Chemical elements
    Physical Properties
    Chemical Properties
    Slow Oxidation
    Phosphatic Fertilisers
      Sources of Phosphates
      Composition of Phosphorites
      Distribution of Phosphatic Rocks
      Oceanic Deposits and Guanos
      System Lime
      Changes during Neutralisation
      Acid Phosphates
      Manufacture of Superphosphate
      Potassium Phosphates
      Ammonium Phosphates

Composition of Phosphorites

Phosphoric anhydride, in the form of tribasic calcium phosphate, forms about 65 to 79 per cent, of a rock suitable for use in the fertiliser industry. There is present, in addition, an excess of calcium carbonate, also ferric oxide and alumina, silica (2 to 8 per cent.), organic matter and moisture (2 to 3 per cent.). The following analyses furnish a comparison between the principal constituents of the raw materials. Complete analyses are given in three typical cases of the most important classes.

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