Tungstic acid

Tungstic acid

Names
IUPAC name dihydroxy-dioxotungsten
Other names Orthotungstic acid
Identifiers
CAS Number	7783-03-1 Y
EC Number	231-975-2
Jmol 3D model	Interactive image
PubChem	1152
RTECS number	YO7840000
InChI InChI=1S/2H2O.2O.W/h2*1H2;;;/q;;;;+2/p-2 Key: CMPGARWFYBADJI-UHFFFAOYSA-L
SMILES O[W](=O)(=O)O
Properties
Chemical 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 slightly soluble in ethanol
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
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. The dihydrate has the same layer structure with the extra H₂O molecule intercalated between the layers. 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

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.