General description
Brown powder; decomposes slowly on exposure to sunlight or by heating at 150°C; begins to release oxygen at 110°C; fully decomposes to metallic gold at 250°C; insoluble in water; soluble in hydrochloric and concentrated nitric acids; also soluble in aqueous solutions of sodiumor potassium cyanide.
Preparation
Gold(III) oxide is prepared by heating gold(III) hydroxide, Au(OH)3 at 130 to 140°C:
Chemical Properties
Brownish-black powder, decomposed
by heat.Keep in dark bottle. Soluble in hydrochloric
acid; insoluble in water.
Uses
It is used in aerospace and electrochemical applications such as fuel cells in which they exhibit ionic conductivity. It acts as strong reducing agent in redox reactions.
Purification Methods
The most probable impurities are SO4and Cl-ions. Dissolve it in strong boiling KOH solution (ca 5M) and precipitate (care) with excess of 3N H2SO4. Then shake and centrifuge, resuspend in H2O and repeat the washing several times until free from SO4 and Cl ions. This gives a wet oxide which is dried in air, but decomposes to free gold in sunlight. It is advisable to keep it wet as it decomposes on drying (analyse wet sample). Store it away from light in the presence of H2O vapour. It evolves O2 at 110o. It is insoluble in H2O but soluble in HCl and conc HNO3. [Roseveare & Buehrer J Am Chem Soc 49 1221 1927.]
