Copper(I) iodide
Copper(I) iodide is a white solid. It does not dissolve in water. It easily turns tan or brown. It is a reducing agent. The iodide easily oxidizes to iodine. Copper does not form a stable copper(II) iodide; copper(II) iodide breaks down right away to make copper(I) iodide and iodine. It dissolves in concentrated iodides like potassium iodide. When it is diluted, it makes copper(I) iodide again.