Tungstic acid refers to hydrated forms of
tungsten trioxide
Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light ...
, WO
3. Both a
monohydrate (WO
3·H
2O) and hemihydrate (WO
3·
1/
2 H
2O) are known. Molecular species akin to sulfuric acid, i.e. (HO)
2WO
2 are not observed.
The solid-state structure of WO
3·H
2O consists of layers of octahedrally coordinated WO
5(H
2O) units where 4 vertices are shared.
The dihydrate has the same layer structure with the extra H
2O molecule
intercalated.
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
tungstate
In chemistry, a tungstate is a compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is , "orthotungstate". Many other tungstates belong to a large group of polyatomic ions that are ...
s.
The acid was discovered by
Carl Wilhelm Scheele
Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish German pharmaceutical chemist.
Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hyd ...
in 1781.
[Scheele, Carl Wilhelm (1781]
"Tungstens bestånds-delar"
(Tungsten's .e.,_Scheelite's.html" ;"title="Scheelite.html" ;"title=".e., Scheelite">.e., Scheelite's">Scheelite.html" ;"title=".e., Scheelite">.e., Scheelite'sconstituents), ''Kungliga Vetenskaps Academiens Nya Handlingar'' (Royal Scientific Academy's New Proceedings), 2: 89–95. (in Swedish)
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.
Uses
It is used as a mordant and a dye in textiles.
References
Tungstates
Tungstic acids
Transition metal oxoacids
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