Potassium tungstate

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Structural formula
Unit cell of potassium tungstate
__ K +      __ W 6+      __ O 2−
Crystal system

monoclinic

Space group

C 2 / m (No. 12)Template: room group / 12

Lattice parameters
  • a = 12.39 Å
  • b = 6.105 Å
  • c = 7.560 Å
  • β = 115.96 °
General
Surname Potassium tungstate
other names
  • Potassium tungsten oxide
  • Dipotassium tungstate
Molecular formula K 2 WO 4
Brief description

colorless and odorless solid

External identifiers / databases
CAS number 7790-60-5
EC number 232-215-2
ECHA InfoCard 100.029.287
PubChem 3084032
Wikidata Q4124794
properties
Molar mass 326.03 g mol −1
Physical state

firmly

density

3.12 g cm −3 (25 ° C)

Melting point

921 ° C

solubility
  • soluble in water
  • almost insoluble in ethanol
safety instructions
GHS labeling of hazardous substances
07 - Warning

Caution

H and P phrases H: 319-335
P: 261-280-305 + 351 + 338-304 + 340-405-501
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium tungstate is an inorganic chemical compound of potassium from the group of tungstates .

Extraction and presentation

Potassium tungstate can be obtained, among other things, by reacting calcium tungstate with potassium fluoride .

It is also formed when potassium pyrosulfate is melted with tungstic acid .

properties

Potassium tungstate is a colorless and odorless solid that is soluble in water. There is also a dihydrate. Under normal conditions, potassium tungstate has a crystal structure with the space group C 2 / m (space group no. 12) . However, there are two other modifications at normal pressure and a high pressure variant. The former are formed at 375 ° C or 455 ° C, the latter having a hexagonal crystal structure with the space group P 6 3 / mmc (space group no. 194) . The high pressure variant has a monoclinic crystal structure. Template: room group / 12 Template: room group / 194

use

Potassium tungstate is used in the use of solar energy and in water treatment . It is also used as a precipitant for alkaloids , in tungsten extraction and as an analytical reagent. It is also added to fuel cells with molten carbonate to retard the corrosion of stainless steel parts and prevent the anode from sintering .

Related links

With K 0.33 WO 3.165 and potassium tungstate K 2 W 2 O 7 , at least two further potassium tungstates besides K 2 WO 4 are known.

Individual evidence

  1. ↑ a b A. S. Koster, FXNM Kools, GD Rieck: The crystal structure of potassium tungstate, K2WO4 . In: Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry . tape 25 , no. 9 , September 15, 1969, p. 1704-1708 , doi : 10.1107 / S0567740869004602 .
  2. ↑ a b c d e data sheet Potassium tungsten oxide, 99.5% (metals basis) from AlfaAesar, accessed on June 6, 2016 ( PDF )(JavaScript required) .
  3. ↑ a b c Data sheet Potassium tungstate, 94% from Sigma-Aldrich , accessed on June 6, 2016 ( PDF ).
  4. ^ A b c Dale L. Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2016, ISBN 978-1-4398-1462-8 ( books.google.com ).
  5. ↑ Advanced Inorganic Chemistry Vol-1 . Krishna Prakashan Media, ISBN 978-81-87224-03-7 ( books.google.com ).
  6. ↑ Pre- samples and separations of cations and anions: Analysis by pre-samples, dissolving and breaking down separation processes . Springer-Verlag, 2013, ISBN 978-3-662-30604-8 ( books.google.com ).
  7. ↑ E. Yu Tonkov: High Pressure Phase Transformations Handbook 3 . CRC Press, 1996, ISBN 978-2-88449-017-7 ( books.google.com ).
  8. ↑ Hajime Wagata, Maki Fujisawa, Yusuke Mizuno, Nobuyuki Zettsu, Shuji Oishi, Katsuya Teshima: Fabrication of Combined One-Dimensional and Three-Dimensional Structure of Potassium Tungstate Crystal Layers by Spray Deposition with Polystyrene Colloidal Crystal Templates . In: Crystal Growth & Design . tape 13 , no. 8 , August 7, 2013, ISSN  1528-7483 , p. 3294-3298 , doi : 10.1021 / cg400714e .
  9. ^ Klaus-Jürgen Range, Wilhelm Hegenbart, Anton M. Heyns, Franz Rau, Ulrich Klement: High-Pressure Synthesis and Crystal Structure of Potassium and Rubidium Diwungstate (VI), K2W2O7 and Rb2W2O7 / High-Pressure Synthesis and Crystal Structure of Potassium and Rubidium Ditungstate (VI ), K2W2O7 and Rb2W2O7 . In: Journal of Nature Research B . tape 45 , no. 2 , February 1, 1990, doi : 10.1515 / znb-1990-0202 .