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

Permolybdic Acid

If a solution of a molybdate be treated in acid solution with hydrogen peroxide, oxidation to permolybdic acid takes place, the solution becoming yellow. The colour remains on warming, and cannot be extracted by ether. Moreover, when molybdic anhydride, MoO3, is dissolved in hydrogen peroxide, a yellow insoluble compound is deposited from the stable, dark yellow solution.

Pechard regarded the compound which he obtained both by double decomposition of the barium salt with sulphuric acid, and by dissolving molybdenum or certain of its oxides in hydrogen peroxide, as HMoO4.2H2O. The compound so obtained, although reasonably stable, is an active oxidising agent; hydrogen chloride is, for instance, oxidised to chlorine, but other strong acids are not attacked. Pechard describes several permolybdates, and assigns to them the formulae KMoO4.2H2O, NH4MoO4.2H2O, etc., thus indicating their analogy to the persulphates of the type R2S2O8; it is not yet certain, however, that compounds of this type (RMoO4) actually exist. In fact, although Cammerer's formula, 2MoO3.H2O2.H2O, is comparable with that of Pechard, Pissarjewsky has prepared, by Pechard's method, a compound to which he assigns the formula H2MoO5.2H2O. By interaction of molybdenum trioxide with 25 per cent, hydrogen peroxide, another hydrate of the acid H2MoO5 - probably 2H2MoO5.3H2O - has been prepared.

From a study of the heat evolution on dissolving molybdic anhydride in varying quantities of hydrogen peroxide, and of the distribution of hydrogen peroxide between ether and aqueous molybdic acid, it is indicated that at least two permolybdic acids exist in acid solutions: (a) H2MoO5 or MoO3.H2O2, and (b) H2MoO6. The constitution of these two compounds is not established. The molybdenum appears to be in the hexavalent state, and the following alternative structural formulae have been suggested:

(a) or ,

(b) or .

As to the permolybdates, potassium, rubidium, caesium, ammonium, and barium salts have been prepared. The formulae ascribed are somewhat complex; for example, for the orange-red ammonium salt (obtained by the action of hydrogen peroxide on a solution of ordinary ammonium molybdate), 3(NH4)2O.7MoO4.12H2O, and for the lemon- yellow ammonium salt (obtained by concentration of the mother-liquor of the orange-red salt), 3(NH4)2O.5MoO3.2MoO4.6H2O. The aqueous solution of these salts contains hydrogen peroxide, and is readily decomposed by small quantities of alkali. Another salt, K2O2.MoO3.H2O2, or K2MoO6.H2O, has been prepared as an unstable solid evolving oxygen on treatment with water, by interaction of cooled solutions of hydrogen peroxide, potassium hydroxide, and Pechard's potassium permolybdate, and precipitation at a low temperature with alcohol.

Fluoropermolybdates, and oxalo- and other organo- salts of the peroxide, have also been described.

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