Chemical elements
  Uranium
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
    Compounds
      Uranium Difluoride
      Uranium Tetrafluoride
      Uranous Oxyfluoride
      Uranium Hexafluoride
      Uranyl Fluoride
      Uranium Trichloride
      Uranium Tetrachloride
      Uranium Pentachloride
      Uranyl Chloride
      Uranyl Chlorate
      Uranyl Perchlorate
      Uranium Tetrabromide
      Uranyl Bromide
      Uranium Tetra-iodide
      Uranyl Iodide
      Uranyl Iodate
      Uranous Oxide
      Uranous Hydroxide
      Uranium Pentoxide
      Urano-uranic Oxide
      Uranium Trioxide
      Ammonium Diuranate
      Ammonium Hexa-uranate
      Hydroxylamine Uranate
      Hydroxylamine Potassio-uranate
      Barium Uranate
      Barium Diuranate
      Bismuth Uranate
      Iron Uranate
      Lithium Uranate
      Potassium Uranate
      Potassium Diuranate
      Potassium Tetra-uranate
      Potassium Hexa-uranate
      Rubidium Uranate
      Silver Diuranate
      Sodium Uranate
      Sodium Diuranate
      Sodium Triuranate
      Sodium Penta-uranate
      Strontium Uranate
      Zinc Uranate
      Peruranic acid
      Ammonium Peruranate
      Barium Peruranates
      Lithium Peruranate
      Nickel Peruranate
      Potassium Peruranate
      Sodium Peruranates
      Uranium Monosulphide
      Uranium Sesquisulphide
      Uranium Disulphide
      Uranium Oxysulphide
      Uranyl Sulphide
      Uranium Sulphite
      Uranyl Sulphite
      Complex Uranyl Sulphites
      Uranium Sulphate
      Uranium Dithionates
      Uranyl Sulphate
      Uranyl Pyrosulphate
      Uranyl Thiosulphate
      Uranyl Dithionate
      Uranium Sesquiselenide
      Uranium Diselenide
      Uranyl Selenide
      Uranyl Selenite
      Uranyl Selenate
      Uranium Telluride
      Uranium Nitrides
      Uranous Nitrate
      Uranyl Nitrate
      Uranium Monophosphide
      Uranous Phosphide
      Uranyl Hypophosphite
      Uranyl Phosphite
      Uranous Phosphates
      Uranyl Phosphates
      Complex Uranyl Phosphates
      Uranyl Aminophosphates
      Uranous Arsenide
      Uranyl Metarsenite
      Uranous Arsenate
      Uranyl Arsenates
      Complex Uranyl Arsenates
      Uranous Antimonide
      Uranous Antimonate
      Uranium Carbide
      Complex Uranyl Carbonates
      Ammonium Uranyl Carbonate
      Calcium Uranyl Carbonate
      Potassium Uranyl Carbonate
      Sodium Uranyl Carbonate
      Thallium Uranyl Carbonate
      Potassium Uranyl Ferrocyanide
      Uranyl Platinocyanide
      Uranyl Cyanate
      Uranyl Thiocyanate
      Uranium Silicide
      Uranium Boride
      Uranyl Perborate
    PDB 1anv-3pu4

Peruranic acid, H4UO6






The existence of uranium tetroxide, or uranium peroxide, UO4, in the anhydrous condition, has not been established, although Fairley claimed to have obtained it as a heavy crystalline precipitate by adding hydrogen peroxide to a solution of uranyl nitrate in presence of a large excess of sulphuric acid, and allowing the mixture to stand for a few days. The product, when carefully dried, did not lose moisture on heating. It decolorised potassium permanganate solution on warming, and when heated with hydrochloric acid, liberated chlorine.

The hydrate, peruranic acid, UO4.2H2O, is obtained as a yellowish-white precipitate by the addition of dilute hydrogen peroxide to a solution of uranyl nitrate or acetate, excess of the uranyl salt being allowed to remain unacted upon. The precipitate may be dried at 100° C. without loss of oxygen. The precipitation has been investigated by Mazzucchelli. It is hindered by the presence of chlorides, sulphates, acetates, oxalates, or tartrates, owing to the tendency to form soluble complexes. In presence of alkali or alkaline earth metals no precipitation occurs owing to the formation of soluble peruranates. The precipitate is very slightly soluble in water and in a solution of ammonium chloride. In the former the solubility, expressed in grams of UO3 per litre of solution, is 0.0061 at 20° C. and 0.0084 at 90° C. When strongly ignited, the hydrate loses water and oxygen, leaving a residue of urano-uranic oxide. It decolorises permanganate in dilute sulphuric acid solution, the ratio of active oxygen to uranium being 1:1.

Peruranates of the alkali metals are obtained by acting on alkaline solutions of uranyl nitrate with hydrogen peroxide. They are soluble in water, but may be precipitated by the addition of alcohol. Corresponding peruranates of the heavier metals may be obtained by double decomposition with solutions of the sodium salt.

The constitution of peruranic acid and of the peruranates is not yet completely understood. Fairley, from a study of the decomposition of the acid by means of alkalies, suggested the formula (UO3)2UO6. It was shown, however, by Melikoff and Pissarjewsky that, by means of aluminium hydroxide, the alkali peruranates could be quantitatively resolved into the alkali peroxides and uranium tetroxide. This reaction is more in accordance with the constitution, for example, for the sodium salt, (Na2O2)2UO4. Moreover, carbon dioxide, which has no action on uranic acid, converts insoluble peruranates into metallic hydrogen carbonates, hydrogen peroxide, and free peruranic acid, again supporting the formula (R'O2)2UO4. The action of alkali on the peracid, the latter being partially reduced to uranium trioxide, whilst the alkali peroxide is formed, is also in agreement with such formulation. These considerations lead to the suggestion that the tetroxide is a peroxide of the hydrogen peroxide type, probably



and that the peruranates, instead of being salts of a peruranic acid, are probably additive compounds of the tetroxide with metallic peroxides.

The following value for the heat of formation of peruranic acid has been obtained:

UO3.H2O + H2O2 = UO4.2H2O - 6151 calories.

By drying the precipitate of the dihydrate at ordinary temperatures Fairley obtained a product which he considered to be a tetrahydrate, UO4.4H2O, but it has not been established that this is a definite chemical compound. Huttig and von Schroeder also describe a bright yellow hygroscopic trihydrate, UO4.3H2O, which, when heated, loses oxygen before all the water is expelled. If heated in a vacuum, it yields the trioxide, not the tetroxide. By means of the Hlittig tensi-eudiometer these investigators also obtained indications of the following hydrates: UO3.H2O2.3.5H2O; 2UO3.H2O2.5H2O; 2UO3.H2O2.3H2O.


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