Editing Gold cyanidation (section)

==Chemical reactions==
[[File:Dicyanoaurate(I)-3D-balls.png|thumb|right|[[Ball-and-stick model]] of the aurocyanide or dicyanoaurate(I) complex anion, [Au(CN)<sub>2</sub>]<sup>−</sup><ref>Greenwood, N. N. & Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.), Oxford:Butterworth-Heinemann. {{ISBN|0-7506-3365-4}}.</ref>]]
[[File:Gold heap leaching.jpeg|thumb|Cyanide leaching "heap" at a gold mining operation near [[Elko, Nevada]]]]
The chemical reaction for the dissolution of gold, the "Elsner equation", follows:
: 4{{nbsp}}Au + 8{{nbsp}}NaCN + O<sub>2</sub> + 2{{nbsp}}H<sub>2</sub>O → 4{{nbsp}}Na[Au(CN)<sub>2</sub>] + 4{{nbsp}}NaOH

[[Potassium cyanide]] and [[calcium cyanide]] are sometimes used in place of sodium cyanide.

Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen. The soluble gold species is [[dicyanoaurate]].<ref>{{cite web |title=Technical Bulletin 1 |publisher=Multi Mix Systems |url=http://www.multimix.com.au/DOCUMENTS/Technical%20Bulletin1.PDF |url-status=dead |archive-url=https://web.archive.org/web/20091023235047/http://www.multimix.com.au/DOCUMENTS/Technical%20Bulletin1.PDF |archive-date=2009-10-23}}</ref> from which it can be recovered by adsorption onto activated carbon.<ref>{{cite journal |title=The absorption of gold cyanide onto activated carbon. I. The kinetics of absorption from pulps |journal=Journal of the Southern African Institute of Mining and Metallurgy |date=February 1984 |volume=84 |issue=2 |pages=50–54 |hdl=10520/AJA0038223X_1427 |url=https://journals.co.za/doi/abs/10.10520/AJA0038223X_1427}}</ref>