8 KCN + 4 Au + O2 + 2 H2O → 4 K[Au(CN)2] + 4 KOH

This is a complexation reaction: K[Au(CN)2] is the formed complex.

This is an oxidation-reduction (redox) reaction:

8 CII + 8 e- → 8 CI (reduction)

4 Au0 - 12 e- → 4 AuIII (oxidation)

2 O0 + 4 e- → 2 O-II (reduction)

KCN is an oxidizing agent, Au is a reducing agent, O2 is an oxidizing agent.

Reactants:

  • KCN – Potassium cyanide source: wikipedia, accessed: 2019-09-27source: ICSC, accessed: 2019-09-04
    • Other names: Potassium cyanide (as CN) source: NIOSH NPG, accessed: 2019-09-02, Hydrocyanic acid, potassium salt source: ICSC, accessed: 2019-09-04, Potassium salt of hydrocyanic acid source: NIOSH NPG, accessed: 2019-09-02
    • Appearance: White crystalline solid | deliquescent source: wikipedia, accessed: 2019-09-27; Hygroscopic crystals or solid in various forms with characteristic odour. odourless when dry source: ICSC, accessed: 2019-09-04; White, granular or crystalline solid with a faint, almond-like odor. source: NIOSH NPG, accessed: 2019-09-02
  • Au
    • Names: Gold source: wikidata, accessed: 2019-09-07, Au source: wikidata, accessed: 2019-09-07, Element 79 source: wikidata, accessed: 2019-09-07, Aurum source: wikidata, accessed: 2019-09-07
  • O2
    • Names: Dioxygen source: wikidata, accessed: 2019-09-07, Oxygen source: ICSC, accessed: 2019-09-04source: wikidata, accessed: 2019-09-07, Oxygen (liquefied) source: ICSC, accessed: 2019-09-04
    • Appearance: Odourless compressed gas source: ICSC, accessed: 2019-09-04; Liquefied gas. colourless-to-blue extremely cold liquid source: ICSC, accessed: 2019-09-04
  • H2O – Water, oxidane source: wikipedia, accessed: 2019-09-27
    • Other names: Water (H2O) source: wikipedia, accessed: 2019-09-27, Hydrogen hydroxide (HH or HOH) source: wikipedia, accessed: 2019-09-27, Hydrogen oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas source: wikipedia, accessed: 2019-09-27

Products:

  • K[Au(CN)2]
  • KOH – Potassium hydroxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02
    • Other names: Caustic potash source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Lye source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02, Potash lye source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Appearance: White solid, deliquescent source: wikipedia, accessed: 2019-09-27; White hygroscopic solid in various forms source: ICSC, accessed: 2019-09-04; Odorless, white or slightly yellow lumps, rods, flakes, sticks, or pellets. [Note: May be used as an aqueous solution.] source: NIOSH NPG, accessed: 2019-09-02