Reactions
On contact with water, AuCl3 forms a series of species, sometimes described as AuCl3·H2O and its conjugate base −. Reaction with reducing agents such as hydrogen peroxide or Fe2+ causes elemental gold to be precipitated from solution.
Anhydrous AuCl3 begins to decompose to AuCl at around 160 °C; however, this in turn undergoes disproportionation at higher temperatures to give gold metal and AuCl3.
- AuCl3 → AuCl + Cl2 (>160 °C)
- 3 AuCl → AuCl3 + 2 Au (>420 °C)
AuCl3 is Lewis acidic and readily forms complexes. For example, it reacts with hydrochloric acid to form chloroauric acid (HAuCl4):
- HCl + AuCl3 (aq) → H+ + −
Other chloride sources, such as KCl, also convert AuCl3 into AuCl−
4. Aqueous solutions of AuCl3 react with aqueous base such as sodium hydroxide to form a precipitate of Au(OH)3, which will dissolve in excess NaOH to form sodium aurate (NaAuO2). If gently heated, Au(OH)3 decomposes to gold(III) oxide, Au2O3, and then to gold metal.
Gold(III) chloride is the starting point for the synthesis of many other gold compounds. For example, reaction with potassium cyanide produces the water-soluble complex, K:
- AuCl3 + 4 KCN → K + 3 KCl
Read more about this topic: Gold(III) Chloride
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