Chemical elements
  Molybdenum
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
    Alloys
    Compounds
      Molybdenum Hexafluoride
      Fluoroxypermolybdates
      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
      Molybdates
      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
      Thiomolybdates
      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
      Molybdohypophosphates
      Molybdophosphites
      Molybdohypophosphites
      12-Molybdo-arsenates
      9-Molybdo-arsenates
      3-Molybdo-arsenates
      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

Molybdenum Oxide (Blue), Mo3O8






Molybdenum Oxide (Blue), Mo3O8 (?) or Mo5O14 (?), if a suspension of molybdenum trioxide in water be heated on a water-bath with a large excess of powdered molybdenum, a blue solution is obtained, containing, it is supposed, unpolymerised molecules of the compound Mo3O8; but it is by no means certain either that this formula represents the actual composition of the substance, or that there is but one blue oxide of molybdenum. On addition of certain salts polymerisation is considered (Dumanski) to take place, and the oxide passes to the colloid form.

The blue oxide may be prepared by double decomposition of ammonium dimolybdate and molybdenum chloride, and washing the precipitate first with ammonium chloride solution and then with water; Berzelius accorded the substance the formula MoO2.4MoO3. Rammelsberg's blue oxide, obtained by interaction of solutions in hydrochloric acid of molybdenum dioxide and trioxide, was given the formula MoO2.MoO3.3H2O, while Muthmann's formula was MoO2.2MoO3, i.e. Mo3O8. The blue oxide may also be obtained by reduction of ammonium molybdate by means of hydriodic acid, by heating in nitrogen the oxysulphate Mo2O(SO4)2, or the oxyoxalate Mo2O(C2O4)2, or by electrolysis. Guichard considered the blue oxide to be a compound of the formula MoO2.4MoO3.6H2O, while Junius' formula is Mo7O20.

The blue oxide is best obtained by allowing powdered molybdenum to remain for a long time at ordinary temperatures in contact with an aqueous suspension of the trioxide, filtering, and then digesting with a further quantity of molybdenum. The solution is evaporated in vacuo. Cold water used for washing the solid should previously be rendered air-free. Another good method of preparation consists in precipitating in the cold, by means of excess of a solution of hydrated molybdenum tetrachloride, a solution of ammonium molybdate in hydrochloric acid; the precipitate is washed with air-free water in an atmosphere of carbon dioxide, and is dried in vacuo.

It is evident, therefore, that the blue oxide may be obtained in a solid state either by precipitation or by evaporation of a solution.

The blue oxide of molybdenum, which can be regarded as a molybdate of molybdenum, is a dark blue substance, of density 3.6 at 18° C., which consists, when obtained by evaporation of a solution, of brilliant vitreous particles, giving the substance a crystalline appearance.

It is a colloid, and is extremely soluble in water, solution taking place slowly in the cold but rapidly at 50° C. A number of salts, e.g. sodium or ammonium chloride, without reacting with the blue oxide, considerably reduce its solubility; other salts, e.g. sodium or magnesium sulphate, do not exhibit this effect. It is readily dissociated by heat into a mixture of the dioxide and trioxide, and for this reason cannot be dried by heat even in vacuo. Oxidation to the trioxide takes place with the dry substance or in solutions slowly at ordinary temperatures but much more rapidly on heating. Its reactions with acids and alkalies point to its formula being probably MoO2.4MoO3; with hydrochloric acid the tetrachloride and trioxide are obtained, while with caustic alkali an alkali molybdate and molybdenum dioxide are produced.


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