Uranyl hydroxide

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Crystal structure
Crystal structure of uranyl hydroxide
__ U 6+      __ O 2−
General
Surname Uranyl hydroxide
other names

Dihydroxydioxiurane

Ratio formula UO 2 (OH) 2
External identifiers / databases
CAS number 211573-15-8
PubChem 5465112
ChemSpider 4576989
Wikidata Q415222
properties
Molar mass 304.04 g mol −1
Physical state

firmly

Hazard and safety information
Radioactive
Radioactive
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
06 - Toxic or very toxic 08 - Dangerous to health 09 - Dangerous for the environment

danger

H and P phrases H: 330-300-373-411
P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Uranyl hydroxide is a hydroxide of uranium with the chemical formula UO 2 (OH) 2 in the monomeric and (UO 2 ) 2 (OH) 4 in the dimeric form. Both isomers can exist in normal aqueous medium. Uranyl hydroxide hydrate is precipitated as a gelatinous yellow cake from oxidized uranium lye at approximately neutral pH .

properties

Uranyl hydroxide is derived as the uranates from the hypothetical uranium acid from which can react as well as the acid, both as the base. The uranyl compounds are formed as the base and the uraniumates as the acid . The latter, however, are not stable and convert into the di-uranates (U 2 O 7 2− ). The corresponding reaction equations are as follows:

Due to these reactions, uranyl salts and uranyl salts can easily be converted into the other form.

Modifications

The modifications were described with the following properties:

modification colour Space group Crystal system Lattice constants Density
/ g cm −3
a / Å b / Å c / Å β / ° Z
α ‐ UO 2 (OH) 2 greenish yellow Cmce (No. 64)Template: room group / 64 Orthorhombic 4,242 10.302 6.868 4th 6.73
β ‐ UO 2 (OH) 2 yellow-green Pbca (No. 61)Template: room group / 61 Orthorhombic 5.6438 6.2867 9.9372 4th 5.73
γ ‐ UO 2 (OH) 2 gray chamois P 2 1 / c (No. 14)Template: room group / 14 Monoclinic 6.419 5.518 5.561 112.77 2 5.56
UO 2 (OH) 2 · H 2 O light yellow Pbna (No. 60, position 5)Template: room group / 60.5 Orthorhombic 13.977 16,696 14.672 32 5

use

Uranyl hydroxide used to be used in glass and ceramic production to color the glass phases and to produce pigments for high temperature firing. Introducing alkaline diuranates into glass creates a yellow tone in the glass and a green reflection. In addition, this glass emits cold light under ultraviolet light and fluoresces . The uranyl hydroxide conducts protons when it is steadily compressed and then slowly relaxed again; and it is used as a component in fuel cells .

Health effects

Uranyl hydroxide damages the genetic material , leads to malformations and is radioactive ; therefore, it should be handled with extreme caution.

Individual evidence

  1. Entry on uranium compounds in the GESTIS substance database of the IFA , accessed on February 1, 2016 (JavaScript required)
  2. 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 .
  3. The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling.
  4. ^ AF Holleman , E. Wiberg : Textbook of Inorganic Chemistry . 37-39 Edition. Walter de Gruyter, Berlin 1956, p. 519.
  5. 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 .
  6. The former name of this group of rooms was Ccma .
  7. United States Patent 4179491: Electrical device with separator as conductor for hydrogen cations .

literature