Tungstic acid
| Tungstic acid | ||
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| IUPAC name dihydroxy-dioxotungsten | ||
| Other names Orthotungstic acid | ||
| Identifiers | ||
| CAS number | 7783-03-1  | |
| PubChem | 1152 | |
| EC number | 231-975-2 | |
| RTECS number | YO7840000 | |
| Jmol-3D images | {{#if:O[W](=O)(=O)O|Image 1 | |
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| Properties | ||
| Molecular formula | H2WO4 | |
| Molar mass | 249.853 g/mol | |
| Appearance | yellow powder | |
| Density | 5.59 g/cm3 | |
| Melting point | 100 °C (decomp) | |
| Boiling point | 1,473 °C; 2,683 °F; 1,746 K | |
| Solubility in water | insoluble | |
| Solubility | soluble in HF, ammonia | |
| Hazards | ||
| NFPA 704 |
 0
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(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | ||
| 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
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
It is used as a mordant and a dye in textiles.
References
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