Tungstic acid
Dihydroxy-dioxotungsten
Yellow tungstic acid sample
Names
IUPAC name
Tungstic acid
Systematic IUPAC name
Dihydroxydioxotungsten
Other names
Orthotungstic acid
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.068 Edit this at Wikidata
EC Number
  • 231-975-2
RTECS number
  • YO7840000
UNII
  • InChI=1S/2H2O.2O.W/h2*1H2;;;/q;;;;+2/p-2
    Key: CMPGARWFYBADJI-UHFFFAOYSA-L
  • O[W](=O)(=O)O
Properties
H2WO4
Molar mass 249.853 g/mol
Appearance yellow powder
Density 5.59 g/cm3
Melting point 100 °C (212 °F; 373 K) (decomposes)
Boiling point 1,473 °C (2,683 °F; 1,746 K)
insoluble
Solubility soluble in HF, ammonia
slightly soluble in ethanol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Tungstic acid refers to hydrated forms of tungsten trioxide, WO3. Both a monohydrate (WO3·H2O) and hemihydrate (WO3·1/2 H2O)[1] are known. Molecular species akin to sulfuric acid, i.e. (HO)2WO2 are not observed.

The solid-state structure of WO3·H2O consists of layers of octahedrally coordinated WO5(H2O) units where 4 vertices are shared.[2] The dihydrate has the same layer structure with the extra H2O molecule intercalated.[2] The monohydrate is a yellow solid and insoluble in water. The classical name for this acid is 'acid of wolfram'. Salts of tungstic acid are tungstates.

The acid was discovered by Carl Wilhelm Scheele in 1781.[3]

Preparation

Tungstic acid is obtained by the action of strong acids on solutions of alkali metallic tungstates. It may also be prepared from the reaction between hydrogen carbonate and sodium tungstate. It can also be obtained from pure tungsten by reaction with hydrogen peroxide.[4]

Uses

It is used as a mordant and a dye in textiles.

References

  1. ^ Günter, John R.; Amberg, Marcel; Schmalle, Helmut (1989). "Direct synthesis and single crystal structure determination of cubic pyrochlore-type tungsten trioxide hemihydrate, WO3 · 0.5H2O". Materials Research Bulletin. 24 (3): 289–292. doi:10.1016/0025-5408(89)90214-6.
  2. ^ a b Wells, A.F. (1986). Structural inorganic chemistry (5th ed.). Oxford [Oxfordshire]: Clarendon Press. ISBN 0-19-855370-6.
  3. ^ Scheele, Carl Wilhelm (1781) "Tungstens bestånds-delar" (Tungsten's [i.e., Scheelite's] constituents), Kungliga Vetenskaps Academiens Nya Handlingar (Royal Scientific Academy's New Proceedings), 2: 89–95. (in Swedish)
  4. ^ Murau, P. C. (1961). "Dissolution of Tungsten by Hydrogen Peroxide". Analytical Chemistry. 33 (8): 1125–1126. doi:10.1021/ac60176a021.
Category