Uranium (VI) oxide
| Crystal structure | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||||||
| γ-uranium (VI) oxide | ||||||||||||||||
| General | ||||||||||||||||
| Surname | Uranium (VI) oxide | |||||||||||||||
| other names |
Uranium trioxide |
|||||||||||||||
| Ratio formula | UO 3 | |||||||||||||||
| Brief description |
yellow-orange crystals |
|||||||||||||||
| External identifiers / databases | ||||||||||||||||
|
||||||||||||||||
| properties | ||||||||||||||||
| Molar mass | 286.03 g mol −1 | |||||||||||||||
| Physical state |
firmly |
|||||||||||||||
| density |
7.3 g cm −3 |
|||||||||||||||
| Hazard and safety information | ||||||||||||||||
 Radioactive |
||||||||||||||||
|
||||||||||||||||
| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Uranium (VI) oxide (also called uranium trioxide , UO 3 ) is a chemical compound of uranium that, depending on the modification, forms yellow or orange crystals and belongs to the heavy metal oxides.
presentation
Uranium (VI) oxide is prepared by heating uranyl compounds such as uranyl nitrate hexahydrate in an oxygen atmosphere at 600 ° C.
It can also be represented by the reaction of uranium (V, VI) oxide with oxygen at high pressure, with various modifications occurring depending on the pressure and temperature.
properties
Physical Properties
Uranium (VI) oxide is radioactive due to its uranium content. There is one amorphous and six different crystalline modifications in which uranium has the coordination number 6 or 7.
- α-UO 3 can be obtained from amorphous uranium (VI) oxide by heating to 500 ° C. at an oxygen partial pressure of 40 bar as a beige crystalline powder. It has an orthorhombic structure with the space group C 2 mm (space group no. 38, position 4) .
- β-UO 3 is obtained as an orange or red powder from α-UO 3 at 550 ° C. and an oxygen partial pressure of 40 bar. It is also formed when ammonium diuranate is heated to 500 ° C in air. β-UO 3 crystallizes in the monoclinic space group P 2 1 (space group no. 4) .
- γ-UO 3 is produced as a yellow powder when uranyl nitrate hexahydrate is heated in air to 400–600 ° C. It crystallizes in the tetragonal space group I 4 1 / amd (space group no. 141) . At 50 ° C it changes into an orthorhombic structure with the space group Fddd (space group no. 70) .
- δ-UO 3 is formed as a deep red powder when β-UO 3 · H 2 O is dehydrated at 375 ° C in air. The crystal structure is cubic with the space group Pm 3 m (space group no. 221) .
- ε-UO 3 forms from U 3 O 8 in NO 2 at 250–375 ° C as a red powder.
- ζ-UO 3 is a high pressure modification that forms at 30 kbar and 1100 ° C. It crystallizes in the orthorhombic space group P 2 1 2 1 2 1 (space group no. 19) .
Freshly produced uranium (VI) oxide from earthly natural uranium has a specific activity of 21050 Bq / g.
Chemical properties
Uranium (VI) oxide is amphoteric . In acidic solutions it forms uranyl ions UO 2 2+ . Oxouranates are formed in an alkaline environment . At 700–900 ° C it breaks down into triurane octoxide .
use
Most of it is processed into uranium dioxide , otherwise there is no important use.
toxicology
The chemical toxicity of this metal oxide is much more dangerous than its radioactivity . So, above all, precautions against poisoning must be taken.
Individual evidence
- ↑ a b David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Properties of the Elements and Inorganic Compounds, pp. 4-97.
- ↑ Entry on uranium compounds in the GESTIS substance database of the IFA , accessed on February 1, 2016 (JavaScript required)
- ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry uranium compounds with the exception of those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA) , accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling.
- ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1971.
- ↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1225.
- ↑ B. O. Loopstra, E. H. P. Cordfunke: On the structure of alpha UO 3 . In: Recueil des Travaux Chimiques des Pays-Bas et de la Belgique 85, pp. 135-142.
- ↑ PC Debets: The Structure of β-UO 3 . In: Acta Crystallographica , 1966, 21, pp. 589-593 ( doi : 10.1107 / S0365110X66003505 )
- ↑ B. O. Loopstra, J. C. Taylor, A. B. Waugh: Neutron Powder Profile Studies of the Gamma Uranium Trioxide Phases . In: Journal of Solid State Chemistry , 1977, 20, pp. 9-19 ( doi : 10.1016 / 0022-4596 (77) 90046-9 )
- ↑ M. T. Weller, P. G. Dickens, D. J. Penny: The Structure of δ-UO 3 . In: Polyhedron , 1988, 7 (3), pp. 243-244 ( doi : 10.1016 / S0277-5387 (00) 80559-8 )
- ^ S. Siegel, H. Hoekstra, E. Sherry: The Crystal Structure of High-Pressure UO 3 . In: Acta Crystallographica , 1966, 20, pp. 292-295 ( doi : 10.1107 / S0365110X66000562 )
literature
- Ingmar Grenthe, Janusz Drożdżynński, Takeo Fujino, Edgar C. Buck, Thomas E. Albrecht-Schmitt, Stephen F. Wolf: Uranium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (eds.): The Chemistry of the Actinide and Transactinide Elements , Springer, Dordrecht 2006; ISBN 1-4020-3555-1 , pp. 253-698 ( doi : 10.1007 / 1-4020-3598-5_5 ).