Chloroauric acid
| Chloroauric acid | |
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Other names
Hydrogen tetrachloroaurate, |
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| Identifiers | |
| CAS number | 16903-35-8  |
| PubChem | 28133 |
| ChemSpider | 26171 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | HAuCl4 |
| Molar mass | 339.785 g/mol (anhydrous) 393.833 g/mol (trihydrate) 411.85 g/mol (tetrahydrate) |
| Appearance | golden yellow crystals hygroscopic |
| Density | 3.9 g/cm3 (tetrahydrate) |
| Melting point |
254°C |
| Solubility in water | soluble |
| Solubility | soluble in alcohol, ether |
| Related compounds | |
| Other anions | Tetrabromoauric acid |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Chloroauric acid is a inorganic compound with the formula HAuCl4. This pale yellow compound is a common precursor to gold (Au) in a variety of purposes. The term chloroauric acid is also sometimes used to describe other gold chlorides.
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[edit] Preparation and structure
Chloroauric acid is obtained by dissolving gold in aqua regia followed by evaporation of these solutions.[1] Upon heating, chloroauric acid liberates hydrogen chloride, giving gold(III) chloride. This reaction is reversible: dissolving gold(III) chloride in hydrochloric acid:
- Au2Cl6 + 2 HCl
2 HAuCl4
2 HAuCl4In aqueous solution, chloroauric acid consists of the square planar [AuCl4]− ion. It is a common precursor to other gold coordination complexes.[2]
[edit] Reactions
Chloroauric acid is readily reduced by most metals to precipitate elemental gold.
This compound is reduced by dimethyl sulfide to give chloro(dimethyl sulfide)gold(I), which is also useful as a precursor to other gold complexes.[3]
[edit] Applications
Chloroauric acid is used as the electrolyte in the Wohlwill process for refining gold.
Generally, colloidal gold and gold nanoparticles are produced in a solution ("liquid chemical methods") by reduction of chloroauric acid with trisodium citrate, although alternative methods exist, such as the Norrish reaction and the aldehyde reduction used in Angel gilding.
[edit] References
- ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1057.
- ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ Marie-Claude Brandys , Michael C. Jennings and Richard J. Puddephatt (2000). "Luminescent gold(I) macrocycles with diphosphine and 4,4-bipyridyl ligands". J. Chem. Soc., Dalton Trans. (24): 4601–4606. doi:10.1039/b005251p.
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