Chloroauric acid
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| Names | |
|---|---|
| Other names
Hydrogen tetrachloroaurate,
Aurochloric acid, Aurate(1-), tetrachloro-, hydrogen, (SP-4-1)- | |
| Identifiers | |
| ECHA InfoCard | 100.037.211 |
CompTox Dashboard (EPA)
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| Properties | |
| HAuCl4 | |
| Molar mass | 339.785 g/mol (anhydrous) 393.83 g/mol (trihydrate) 411.85 g/mol (tetrahydrate) |
| Appearance | golden yellow crystals hygroscopic |
| Density | 3.9 g/cm3 (tetrahydrate) |
| Melting point | 254°C |
| soluble | |
| Solubility | soluble in alcohol, ether |
| Hazards | |
| NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chloroauric acid is a inorganic compound with the formula HAuCl4. It is commonly used as a precursor to gold (Au) in a variety of purposes. The term chloroauric acid is also sometimes used to describe other gold chlorides.
Preparation and structure
Chloroauric acid is obtained by dissolving gold in aqua regia followed by evaporation of these solutions. 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
In aqueous solution, chloroauric acid consists of the square planar [AuCl
4]−
ion and the proton is associated with water. It is a common precursor to other gold coordination complexes.[1]
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 sodium sulfide, although alternative methods exist, such as the Norrish reaction.
External links
References
- ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
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