Aurous iodide, AuI

The iodide is produced by decomposition of auric iodide at ordinary temperature; by the interaction of auric oxide and hydriodic acid; by precipitation of auric chloride with potassium iodide, hydrogen iodide, or ferrous iodide; by the interaction of gold and iodine in ether solution or in a sealed tube at 50° C., or ferric iodide, or manganese tetraiodide; by boiling powdered gold with hydriodic acid and nitric acid, filtering, and pouring the hot filtrate into aqueous hydriodic acid; and by the interaction of aurous chloride and potassium iodide.

Aurous iodide is a lemon-yellow powder, and is very difficult to prepare in the pure state, as it is decomposed by moist air at ordinary temperatures. The excess of iodine is best eliminated by sublimation at 30° C. It is decomposed by heating with water, dilute sulphuric acid, and nitric acid, although not so readily as the corresponding chloride and bromide. Chlorine and bromine exert an oxidizing action, liberating iodine and forming auric compounds. Potassium hydroxide precipitates metallic gold, producing potassium iodide and iodate. Alcohol, ether, and other organic compounds cause precipitation of metallic gold. The iodide dissolves readily in potassium-iodide solution, probably with formation of complex anions.