Auric iodide, AuI₃

Gradual addition of a solution of auric chloride to one of potassium iodide yields complex AuI₄-ions, converted by further addition of auric chloride into auric iodide:

3AuI₄' + Au^••• = 4Aul₃.

On drying, the dark-green product decomposes into aurous iodide and iodine. It is soluble with difficulty in water to an unstable solution.

A complex iodide having the formula CsI,AuI₃ is produced in glistening, black crystals by the interaction of gold dichloride and caesium iodide.