Chloroauric acid

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Chloroauric acid
Identifiers
CAS number 16903-35-8 YesY
PubChem 28133
ChemSpider 26171 YesY
Jmol-3D images Image 1
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
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Contents

[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 is in equilibrium with 2 HAuCl4

In 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

  1. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1057.
  2. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  3. ^ 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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