Tungstic acid

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Tungstic acid
Yellow tungstic acid
Identifiers
CAS number 7783-03-1 YesY
PubChem 1152
EC number 231-975-2
RTECS number YO7840000
Jmol-3D images Image 1
Properties
Molecular formula 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)
Solubility in water insoluble
Solubility soluble in HF, ammonia
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tungstic acid refers to hydrated forms of tungsten trioxide, WO3. The simplest form, the monohydrate, is WO3·H2O, the dihydrate WO3·2H2O is also known. The solid state structure of WO3·H2O consists of layers of octahedrally coordinated WO5(H2O) units where 4 vertices are shared.[1] The dihydrate has the same layer structure with the extra H2O molecule intercalated between the layers.[1] The monohydrate is a yellow solid and insoluble in water. The classical name for this acid is 'acid of wolfram'.

The acid was discovered for the first time by Carl Wilhelm Scheele in 1781.

Preparation[edit]

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.

Uses[edit]

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

References[edit]

  1. ^ a b Wells, A.F. (1986). Structural inorganic chemistry (5th ed. ed.). Oxford [Oxfordshire]: Clarendon Press. ISBN 0-19-855370-6.