Potassium dicyanoaurate

Potassium dicyanoaurate, also potassium dicyanoaurate(I), potassium gold cyanide, potassium gold dicyanide or gold potassium cyanide, is an inorganic compound with formula K[Au(CN)2]. It is a colorless to white crystalline powder, usually prepared by dissolving metallic gold in aqueous solution of potassium cyanide. It is most often used in gold plating applications. It contains 68.2 wt.% of gold. It is soluble in water and slightly soluble in alcohol.

Potassium dicyanoaurate

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)
Identifiers
3D model (JSmol)
6235525
ChEBI
ChemSpider
ECHA InfoCard 100.034.303
EC Number
  • 237-748-4
37363
UNII
UN number 1588
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
Main hazards toxic
GHS pictograms
GHS Signal word Warning
H300, H400, H310, H410, H330, H317, H290, H318, H315
P260, P264, P273, P280, P284, P301+310
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium gold cyanide can be used for photoreduction of gold ions by nanopowder ZnO, preparation of gold-gold junction electrodes in voltammetric glucose detection, and other reactions where metallic gold is prepared.

There is a trivalent compound, potassium tetracyanoaurate(III), K[Au(CN)4], but its use is less common.

The cyanide-gold complex penetrates biological 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.[4]

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

Potassium dicyanoaurate is produced in the cyanide process variant of gold mining. The chemical 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 redox process, oxygen removes, via a two-step reaction, one electron from each gold atom to form the complex Au(CN)−
2 ion.[5]

References
  1. Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  2. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. p. 4.82. ISBN 978-1439855119.
  3. Rosenzweig, A.; Cromer, D. T. (1959). "The crystal structure of KAu(CN)2". Acta Crystallographica. 12 (10): 709–712. doi:10.1107/S0365110X59002109.
  4. 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.
  5. Treatment of Ores Containing Reactive Iron Sulphides. Multi Mix Systems
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