Potassium dicyanoaurate

Summary

Potassium dicyanoaurate 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.

Potassium dicyanoaurate
Ball-and-stick model of the aurocyanide or dicyanoaurate(I) complex anion
Ball-and-stick model of the aurocyanide or dicyanoaurate(I) complex anion, [Au(CN)2].[1]
Names
Other names
potassium cyanoaurate[2]
potassium dicyanoaurate(I)
potassium gold cyanide
potassium gold dicyanide
Identifiers
  • 13967-50-5
3D model (JSmol)
  • ionic form: Interactive image
  • coordination form: Interactive image
6235525
ChEBI
  • CHEBI:30057
ChemSpider
  • 19988798
ECHA InfoCard 100.034.303 Edit this at Wikidata
EC Number
  • 237-748-4
37363
  • 159710
UNII
  • 54L0T2BQF5
UN number 1588
  • DTXSID8044549 Edit this at Wikidata
  • InChI=1S/2CN.Au.K/c2*1-2;;/q2*-1;2*+1
    Key: XTFKWYDMKGAZKK-UHFFFAOYSA-N
  • ionic form: [C-]#N.[C-]#N.[K+].[Au+]
  • coordination form: N#C[Au-]C#N.[K+]
Properties
C2AuKN2
Molar mass 288.101 g·mol−1
Appearance white powder[2]
Density 3.45 g/cm3[2]
Boiling point decomposes
140 g/L[2]
Structure[3]
Rhombohedral, hR54, No. 148
R3
a = 0.728 nm, b = 0.728 nm, c = 2.636 nm
1.2099 nm3
9
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS09: Environmental hazard
Warning
H290, H300, H310, H315, H317, H318, H330, H410
P260, P264, P273, P280, P284, P301+P310
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

ProductionEdit

 
Cyanide leaching "heap" at a gold mining operation near Elko, Nevada

In mining of gold from dilute sources, gold is selectively extracted by dissolution in aqueous potassium 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

StructureEdit

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]

UsesEdit

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 compoundsEdit

Thet 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]

SafetyEdit

The cyanide-gold complex penetrates cells much more easily than gold ions alone, facilitating gold toxicity. Gold inhibits activity of many enzymes, hindering detoxification of the cyanide ion to thiocyanate, potentiating the cyanide toxicity.[8]

ReferencesEdit

  1. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  2. ^ 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.
  3. ^ 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.
  4. ^ Treatment of Ores Containing Reactive Iron Sulphides. Multi Mix Systems
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.