Uranium compounds: triuranium octaoxide

uranium symbol icon

The uranium in triuranium octaoxide formally is in the oxidation state 5, 6.

Crystal structure of triuranium octaoxide

Triuranium octaoxide

  • Formula as often written: U3O8
  • Hill system formula: O8U3
  • CAS registry number: [1344-59-8]
  • Formula weight: 842.082
  • Class: oxide


  • triuranium octaoxide
  • uranium (V, VI) oxide
  • pitchblende
  • uranium oxide

Physical properties

  • Colour: very dark green-black
  • Appearance:
  • Melting point: 1150°C; 1300°C (decomposes to UO2)
  • Boiling point:
  • Density: 8380 kg m-3


Coming soon...

Element analysis

Element percentages for the elements in triuranium octaoxide
Element %
O 15.20
U 84.80


Not available

Solid state structure

  • Geometry of uranium: 7 coordinate: pentagonal bipyramidal
  • Prototypical structure:

Crystal structure of triuranium octaoxide

Isotope pattern

What follows is the calculated isotope pattern for the U3O8 unit with the most intense ion set to 100%.

Formula: U3O8

mass  %
836   0.0 
837 0.0
838 0.0
839 2.2 _
840 0.0
841 0.0
842 100.0 __________________________________________________
843 0.3
844 1.6 _
845 0.0
846 0.0


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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uranium atomic number