Aurous chloride, AuCl

Partial elimination of chlorine from auric chloride by means of heat yields aurous chloride, but it is difficult to prepare it free from gold and auric chloride, and there is much divergence in the temperatures cited by various experimenters, the values ranging between 120° and 300° C. The auric chloride can be washed out of it by means of ether, but it is difficult to prevent decomposition of the aurous chloride into auric chloride and gold under the influence of traces of water:

3AuCl=AuCl₃+2Au.

The decomposition by water is accelerated by rise of temperature.

The chloride is a yellowish-white substance, soluble in aqueous alkali-metal chlorides with formation of complex anions, the solutions soon decomposing with precipitation of metallic gold and the formation of complex auric derivatives. The transformation is more rapid in bromide solutions. At 110° to 120° C. aurous chloride and excess of phosphorus trichloride combine to form a double compound of the formula AuCl,PCl₃, colourless prisms insoluble in water.