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

Molybdenum Dioxide, MoO2

Molybdenum Dioxide, MoO2, is produced by a number of reactions involving either the reduction of the trioxide or the oxidation of the sesquioxide. Thus it may be prepared by the action of hydrogen, or of a mixture of carbon monoxide and carbon dioxide, upon molybdic acid or mercurous molybdate; by heating sodium or potassium trimolybdate to redness in hydrogen and washing the residue with water; by heating sodium trimolybdate with zinc and washing the residue with potassium hydroxide solution and then hydrochloric acid; by reduction of ammonium molybdate with colloidal palladium at ordinary temperatures; by heating ammonium molybdate, a mixture of sodium molybdate and ammonium chloride, or a mixture of molybdenum trioxide and ammonium molybdate, and suitably washing the residue with ammonia and then hydrochloric acid; and by electrolysis of fused molybdic anhydride.

Molybdenum dioxide forms violet-blue monoclinic crystals, pseudo-tetragonal,

a:b:c = 0.9869:1:0.5765; β = 91° 34',

of density 6.34. It is more strongly magnetic than the metal. The dioxide is insoluble in water, in hydrochloric acid, and in caustic potash solution, but is attacked by nitric acid and by fused potash. It reduces ammoniacal solutions of salts of silver, but not those of mercury or copper.

Reduction of a solution of molybdic acid by means of long digestion with the powdered metal causes the dark blue solution to assume a reddish colour; on addition of ammonia a reddish-brown precipitate is obtained, originally thought to be the hydrate of molybdenum dioxide, but more recently considered to be a hydrate of the oxide Mo2O5. The red solution before precipitation contains a salt of this oxide; it is considered probable (Guichard) that the dioxide does not form salts. A similar red solution may be obtained by electrolysis of a sulphuric acid or oxalic acid solution of molybdic acid, or by heating a hydrochloric acid solution of an alkali molybdate with potassium iodide. The hydrate MoO2.H2O, obtained in each case by precipitation with ammonia, is soluble in water, but is reprecipitated by the addition of salts, thus behaving as a colloid; the aqueous solution upon evaporation yields first a gel, and finally a dark brown insoluble hydrate. Though soluble in ammonium carbonate solution, the hydrate in question is insoluble in aqueous caustic potash; in the air it is readily oxidised, giving the blue oxide. The salts obtained by dissolving the freshly precipitated hydroxide in acids (the anhydrous oxide being insoluble) are, when anhydrous, black in colour; when hydrated they are reddish brown; several of these salts are known.

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