Potassium dicyanoaurate
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| Names | |
|---|---|
| IUPAC name
Potassium dicyanoaurate(I)
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| Other names | |
| Identifiers | |
3D model (JSmol)
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| 6235525 | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.034.303 |
| EC Number |
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| 37363 | |
PubChem CID
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| UNII | |
| UN number | 1588 |
CompTox Dashboard (EPA)
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| Properties | |
| KAu(CN)2 | |
| Molar mass | 288.101 g/mol |
| Appearance | white crystal[1] |
| Density | 3.45 g/cm3[1] |
| Boiling point | decomposes |
| 140 g/L[1] | |
| Structure | |
| Rhombohedral, hR54, No. 148 | |
| R3 | |
a = 0.728 nm, b = 0.728 nm, c = 2.636 nm
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Lattice volume (V)
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1.2099 nm3 |
Formula units (Z)
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9 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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toxic |
| GHS labelling: | |
  
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| Warning | |
| H290, H300, H310, H315, H317, H318, H330, H410 | |
| P260, P264, P273, P280, P284, P301+P310 | |
| Related compounds | |
Other anions
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Potassium argentocyanide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium dicyanoaurate (or potassium gold cyanide) is an inorganic compound with formula K[Au(CN)2]. It is a colorless to white solid that is soluble in water and slightly soluble in alcohol. The salt itself is often not isolated, but solutions of the dicyanoaurate ion ([Au(CN)2]−) are generated on a large scale in the extraction of gold from its ores.[3]
Production
In mining of gold from dilute sources, gold is selectively extracted by dissolution in aqueous solutions of cyanide, provided by dissolving sodium cyanide, potassium cyanide and/or calcium cyanide. The reaction for the dissolution of gold, the "Elsner Equation", is:
- 4 Au + 8 KCN + O2 + 2 H2O → 4 K[Au(CN)2] + 4 KOH
In this process, oxygen is the oxidant.[4]
It can also be produced by reaction of gold(I) salts with excess potassium cyanide.
- AuCl + 2 KCN → K[Au(CN)2] + KCl
Structure
dicyanoaurate is a rod-shaped anion.
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Potassium dicyanoaurate is a salt. The dicyanoaurate anion is linear according to X-ray crystallography.[3] On the basis of infrared spectroscopy, the dicyanoaurate anion adopts a very similar structure in sodium dicyanoaurate (NaAu(CN)2).[5]
Uses
Dicyanoaurate is the soluble species that is the focus of gold cyanidation, the hydrometallurgical process for winning gold from dilute ores. In fact, sodium cyanide, not the potassium salt, is more widely used in commercial processes.[6]
Aside from its major use as an intermediate in the extraction of gold, potassium dicyanoaurate is often used in gold plating applications.
Related compounds
The compound containing gold(III) cyanide is also known: potassium tetracyanoaurate(III), K[Au(CN)4]. Its use is less common.
The potassium ion can be replaced with quaternary ammonium cations as in tetrabutylammonium dicyanoaurate.[7]
Safety
The ingestion of gram quantities of potassium dicyanoaurate has led to death.[8]
References
- ^ a b c d Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. p. 4.82. ISBN 978-1439855119.
- ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ a b Rosenzweig, A.; Cromer, D. T. (1959). "The Crystal Structure of KAu(CN)2". Acta Crystallographica. 12 (10): 709–712. doi:10.1107/S0365110X59002109.
- ^ Treatment of Ores Containing Reactive Iron Sulphides. Multi Mix Systems
- ^ Chadwick, B.M.; Frankiss, S.G. (1976). "Vibrational Spectra and Structures of Some Dicyanoaurate(I) Complexes". Journal of Molecular Structure. 31 (1): 1–9. Bibcode:1976JMoSt..31....1C. doi:10.1016/0022-2860(76)80113-5.
- ^ Rubo, Andreas; Kellens, Raf; Reddy, Jay; Steier, Norbert; Hasenpusch, Wolfgang (2006). "Alkali Metal Cyanides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.i01_i01. ISBN 978-3527306732.
- ^ Stender, Matthias; Olmstead, Marilyn M.; Balch, Alan L.; Rios, Daniel; Attar, Saeed (2003). "Cation and Hydrogen Bonding Effects on the Self-Association and Luminescence of the Dicyanoaurate Ion, Au(CN)2−". Dalton Transactions (22): 4282. doi:10.1039/b310085e.
- ^ Wright, I. H.; Vesey, C. J. (September 1986). "Acute poisoning with gold cyanide". Anaesthesia. 41 (9): 936–939. doi:10.1111/j.1365-2044.1986.tb12920.x. PMID 3022615.