Chemical elements
    Physical Properties
    Chemical Properties
      Molybdenum Hexafluoride
      Molybdenum Dichloride
      Molybdenum Trichloride
      Molybdenum Tetrachloride
      Molybdenum Pentachloride
      Molybdenum Oxychlorides
      Chlormolybdic Acids
      Molybdenum Dibromide
      Molybdenum Tribromide
      Molybdenum Tetrabromide
      Molybdenum Oxybromide
      Molybdenum Di-iodide
      Molybdenum Oxyiodide
      Iodomolybdic Acid
      Molybdenum Sesquioxide
      Molybdenum Dioxide
      Molybdenum Oxide Blue
      Molybdenum Trioxide
      Aluminium Molybdates
      Ammonium Molybdate
      Ammonium Dimolybdate
      Ammonium Paramolybdate
      Ammonium Trimolybdate
      Ammonium Tetramolybdate
      Ammonium Octamolybdate
      Barium Molybdates
      Barium Paramolybdate
      Barium Trimolybdate
      Barium Tetramolybdate
      Barium Octamolybdate
      Barium Nonamolybdate
      Beryllium Molybdate
      Bismuth Molybdates
      Cadmium Molybdates
      Caesium Molybdates
      Calcium Molybdate
      Calcium Trimolybdate
      Calcium Tetramolybdate
      Calcium Octamolybdate
      Chromium Molybdates
      Cobalt Molybdates
      Cobalt Dimolybdate
      Cobalt Trimolybdate
      Copper Molybdates
      Ferrous Molybdate
      Ferric Molybdate
      Indium Molybdate
      Lead Molybdates
      Lithium Molybdate
      Lithium Dimolybdate
      Lithium Paramolybdate
      Lithium Trimolybdate
      Lithium Tetramolybdate
      Magnesium Molybdates
      Magnesium Paramolybdate
      Magnesium Trimolybdate
      Manganese Molybdate
      Mercurous Molybdates
      Nickel Molybdates
      Potassium Molybdate
      Potassium Dimolybdate
      Potassium Paramolybdate
      Potassium Trimolybdate
      Potassium Tetramolybdate
      Potassium Octamolybdate
      Potassium Decamolybdate
      Rhodium Molybdates
      Rubidium Molybdate
      Rubidium Dimolybdate
      Rubidium Paramolybdate
      Rubidium Trimolybdate
      Rubidium Tetramolybdates
      Silver Molybdates
      Normal Silver Molybdate
      Sodium Molybdate
      Sodium Dimolybdate
      Sodium Paramolybdate
      Sodium Trimolybdate
      Sodium Tetramolybdate
      Sodium Iodomolybdate
      Strontium Molybdate
      Thallous Molybdate
      Thallous Paramolybdate
      Thallous Tetramolybdate
      Thorium Molybdate
      Uranium Molybdates
      Uranyl Octamolybdate
      Zinc Molybdates
      Zinc Trimolybdate
      Zinc Tetramolybdate
      Zinc Octamolybdate
      Zirconium Molybdate
      Permolybdic Acid
      Molybdenum Sesquisulphide
      Molybdenum Disulphide
      Dimolybdenum Pentasulphide
      Molybdenum Trisulphide
      Molybdenum Tetrasulphide
      Ammonium Thiomolybdates
      Ammonium Molybdosulphites
      Potassium Thiomolybdate
      Potassium Thiodimolybdate
      Potassium Dithiodioxymolybdate
      Potassium Molybdosulphite
      Sodium Thiomolybdates
      Sodium Molybdosulphites
      Molybdenum Sulphates
      Molybdenum Selenide
      Complex Molybdoselenites
      Chromates of Molybdenum
      Molybdenum Phosphide
      Molybdic Metaphosphate
      Heteropoly-compounds with Phosphorus
      12-Molybdophosphoric Acid
      9-Molybdophosphoric Acid
      172-Molybdophosphoric Acid
      Molybdenum Carbides
      Molybdenum Carbonyl
      Reddish-violet Salts
      Yellow Salts
      Thiocyanates of Molybdenum
      Molybdenum Monosilicide
      Molybdenum Sesquisilicide
      Molybdenum Disilicide
      Molybdosilicic Acid and Molybdosilicates
      12-Molybdosilicic Acid
    PDB 1aa6-1qh8
    PDB 1r27-2jir
    PDB 2min-3unc
    PDB 3uni-4f6t

Heteropoly-compounds with Phosphorus

Heteropoly-compounds of Molybdenum and Phosphorus include those acids and salts which contain acid anhydrides of one or more elements combined with a hydrate or salt of the acid of another element. Compounds which contain the acid anhydride and the acid hydrate or salt of the same element - for example, polychromates, polytungstates, etc. - are distinguished as isopoly- compounds.

Perhaps the most characteristic group of heteropoly-compounds is that of the phosphomolybdic acids which have hitherto been considered as complex acids. Much early work was directed towards the action of phosphoric acid on molybdic acid and the alkali molybdates with the object of explaining the nature of the products obtained. It was shown that when molybdic anhydride dissolved in orthophosphoric acid a yellow solution was obtained, which on evaporation gave a viscous uncrystallisable liquid. On adding ammonia to the yellow solution a yellow precipitate was obtained in the presence of acid. The precipitation was impeded by the presence of certain organic salts, e.g. ammonium oxalate or citrate, and the meta- and pyro-phosphoric acids only gave the reaction after being converted to the ortho-acid. The yellow precipitate was shown to be the ammonium salt of a definite phosphomolybdic acid, which was isolated from it by Debray by gently heating with excess of aqua regia, when the ammonia was expelled and a yellow solution remained which by spontaneous evaporation gave crystals of the acid, to which he assigned the formula P2O5.20MoO3.25H2O. It forms yellow salts, those of potassium, ammonium, rubidium, caesium, and thallium being insoluble in water.

The yellow phosphomolybdates are decomposed by excess of alkali, giving neutral molybdates and other white phosphomolybdates, soluble in alkaline solution and richer in phosphoric acid. These white salts are reconverted to yellow phosphomolybdates with liberation of phosphoric acid by the action of acids.

The composition of phosphomolybdic acid given by Debray was contested by Rammelsberg, who found the ratio P2O5:MoO3 to be 1:22, while other workers found 1:24. Numerous other combinations in which the proportion of the two oxides varied considerably have been described.

The study of these complex compounds was simplified by the application of the electrical conductivity as an indicator in the neutralisation of acids, and it was found that the phosphomolybdates and other heteropoly-compounds could be satisfactorily formulated by the application of a modification of Werner's co-ordination theory suggested by Miolati and extended by Rosenheim. According to this theory, the complex phosphomolybdic compounds may be divided into two groups, the members of the first group possessing a heptavalent complex anion with phosphorus as the central atom, surrounded by six divalent atoms or groups of atoms. The anion is derived from [PO6]''', the oxygen atoms being replaced, wholly or in part, by the dimolybdate ion (Mo2O7)''. These complex anions are of a deep yellow colour, which is imparted to their salts in the absence of coloured cations. The members of the second group contain colourless anions derived from [PO4]''', the oxygen being replaced by the ion (MoO4)''. Compounds are said to be saturated when all the oxygen atoms of the parent anion are replaced by metallic acid anions, unsaturated compounds containing some replaceable oxygen.

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