Thorium (IV) oxide
| Crystal structure | ||||||||||||||||
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| __ Th 4+ __ O 2− | ||||||||||||||||
| Crystal system |
cubic |
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| Space group |
Fm 3 m (No. 225) |
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| Coordination numbers |
Th [8], O [4] |
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| General | ||||||||||||||||
| Surname | Thorium (IV) oxide | |||||||||||||||
| other names |
Thorium dioxide |
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| Ratio formula | ThO 2 | |||||||||||||||
| Brief description |
white, crystalline solid |
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| External identifiers / databases | ||||||||||||||||
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| properties | ||||||||||||||||
| Molar mass | 264.04 g mol −1 | |||||||||||||||
| Physical state |
firmly |
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| density |
10 g cm −3 |
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| Melting point |
3390 ° C |
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| boiling point |
4400 ° C |
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| solubility |
almost insoluble in water and acids |
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| Hazard and safety information | ||||||||||||||||
 Radioactive |
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| Toxicological data | ||||||||||||||||
| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Thorium (IV) oxide (thorium dioxide, ThO 2 ) is the only stable oxide of the radioactive element and actinide thorium . In nature the compound occurs as the mineral thorianite .
Manufacturing
Thorium (IV) oxide can be produced by oxidation of thorium and subsequent purification (removal of thorium residues).
It can also be produced by thermal decomposition of thorium (IV) hydroxide , thorium (IV) oxalate , thorium (IV) carbonate or thorium (IV) nitrate . Thorium (IV) sulfate is less suitable as a starting material, since the last traces of sulfate are very difficult to split off.
properties
Thorium (IV) oxide is an odorless white powder. The mineral thorianite crystallizes cubically in the fluorite lattice . It has the highest melting point of all oxides, has a high refraction and a high density of 9.86 g · cm −3 . The water solubility of thorium dioxide is very low. Solubility only increases slightly in the strongly acidic pH range below pH = 4. The thorium contained is an alpha emitter . The activity of one gram of thorium (IV) oxide is 7100 Becquerel .
Applications
Thorium (IV) oxide is used as an additive in optical glasses to increase the refraction of light. It used to be part of incandescent mantles . Furthermore, tungsten electrodes contain between 0.35% and 4.20% thorium dioxide in order to stabilize the electrical spark during tungsten inert gas welding (TIG). Because of the radioactivity of the thorium, civil use is restricted. Thorium dioxide is also used as breeding material in breeder reactors .
Thorium (IV) oxide can be used as a catalyst in the decarboxylation of carboxylic acids .
hazards
Thorium (IV) oxide is irritating to the skin and eyes. If injured, it can get into the body and have a toxic effect; if inhaled, it can be deposited in the lungs and irradiate them. It is also poisonous if swallowed. The extremely durable fabric increases the risk of cancer. The X-ray contrast agent Thorotrast , which was used to highlight details in X-ray images until the late 1940s, was no longer used after the Second World War due to the risk of cancer .
Individual evidence
- ↑ a b Entry on thorium dioxide. In: Römpp Online . Georg Thieme Verlag, accessed on November 30, 2014.
- ↑ a b c thorium dioxide at webelements.com .
- ↑ a b data sheet thorium (IV) oxide from Sigma-Aldrich , accessed on November 5, 2012 ( PDF ).
- ↑ The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling.
- ↑ a b BOC Edwards safety data sheet ( Memento from September 28, 2007 in the Internet Archive ).
- ↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 1145.
- ↑ JF Thorpe and GAR Kon: Cyclopentanone In: Organic Syntheses . 5, 1925, p. 37, doi : 10.15227 / orgsyn.005.0037 ; Coll. Vol. 1, 1941, p. 192 ( PDF ).
literature
- Mathias S. Wickleder, Blandine Fourest, Peter K. Dorhout: Thorium , 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. 52-160; doi : 10.1007 / 1-4020-3598-5_3 .
- AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1972.