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

Uranyl Chloride, UO2Cl2






Uranyl Chloride, UO2Cl2, is obtained in the anhydrous condition by the action of chlorine on heated uranous oxide. It yields a yellow crystalline mass, stable in dry air but very hygroscopic and readily soluble in water. It is also soluble in alcohol or ether. When heated in air, uranyl chloride loses chlorine and leaves uranous oxide which is oxidised to higher oxides. If heated to redness in hydrogen, it is reduced to uranous oxide. Fusion with excess of caustic potash in an open tube produces a red peruranate, K2UO5, which gradually changes to the yellow uranate, K2UO4, with loss of oxygen.

It is formed in solution by oxidising uranous chloride with nitric acid; by dissolving uranic oxide in concentrated hydrochloric acid; or by adding barium chloride to a concentrated solution of uranyl sulphate until precipitation is complete. Its aqueous solution on evaporation yields the monohydrate, UO2Cl2.H2O. The solution is unstable at ordinary temperatures and slowly deposits uranic hydroxide, which after a time partly redissolves. The uranyl chloride may be reduced in solution to black uranous oxide by the action of magnesium or aluminium powder. The densities of aqueous solutions of uranyl chloride have been determined as follows:

Temperature, ° C.Concentration, UO2Cl2 per cent.Density.
14.611.0056
16.321.0112
13.731.0161
13.141.0215
14.251.0260
15.261.0313
14.371.0366
14.581.0418
15.091.0469
14.8101.0517


The equivalent conductivities of aqueous solutions containing ½UO2Cl2 in v litres at 25° C. are as follows:

v481632641282565121024
Λ79.889.396.6104.3111.3118.5127.4136.4147.0


From the solution in hydrochloric acid, the trihydrate, UO2Cl2.3H2O, possibly H4UO5.2HCl, separates in yellowish-green hygroscopic prisms, which when heated above 100° C. decompose, losing water, hydrogen chloride, and chlorine. The trihydrate dissolves in water, 1 part in 0.134 part of water at 18° C., yielding a viscous solution of density 2.74.

A saturated solution of uranyl chloride in hydrochloric acid when cooled to -10° C. yields yellow crystals of an unstable hydrochloride, UO2Cl2.HCl.2H2O. The compound may also be obtained by the action of hydrochloric acid on uranyl nitrate.

Compounds of uranyl chloride with ammonia, of composition UO2Cl2.2NH3 and UO2Cl2.3NH3, and with organic compounds, for example UO2Cl2.2NH3.(C2H5)2O and UO2Cl2.2(C2H5)2O, have been described. Well crystallised compounds with organic bases have also been prepared.

Uranyl chloride reacts with the chlorides of the alkali metals to form a series of complex salts of the type R2(UO2)Cl4. Uranyl potassium chloride, K2(UO2)Cl4, is prepared in the anhydrous condition by passing dry chlorine first over heated uranous oxide and then over heated potassium chloride. It is obtained as a golden-yellow powder which when heated to redness melts without decomposition. It is very soluble in water. The dihydrate, K2(UO2)Cl4.2H2O, separates on evaporation of a solution containing potassium chloride and uranyl chloride; or of a hydrochloric acid solution of potassium uranate. It yields greenish-yellow, triclinic pinacoidal plates. The double salt can only be obtained pure from the aqueous solution above 60° C., as below this temperature it undergoes partial decomposition with separation of potassium chloride. The ammonium salt, (NH4)2(UO2)Cl4.2H2O, prepared by crystallisation from a solution of ammonium and uranyl chlorides in concentrated hydrochloric acid, is isomorphous with the potassium salt, and behaves similarly with water. The sodium salt, Na2(UO2)Cl4, obtained in the dry way by passing chlorine successively over heated uranous oxide and sodium chloride, is a golden-yellow substance with properties similar to the anhydrous potassium salt. The rubidium salt, Rb2(UO2)Cl4.2H2O, is isomorphous with the potassium and ammonium salts, but differs from them in being undecomposed by water both at high and low temperatures. The caesium compound, Cs2(UO2)Cl4, is obtained in yellow rhombic leaflets from an aqueous solution of the mixed chlorides containing hydrochloric acid. Like the rubidium salt, it is stable towards water.


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