Ammonium iodide is the inorganic compound with the formula NH4I. A white solid. It is an ionic compound, although impure samples appear yellow. This salt consists of ammonium cation and an iodide anion.[1] It can be prepared by the action of hydroiodic acid on ammonia. It is easily soluble in water, from which it crystallizes in cubes. It is also soluble in ethanol. Ammonium iodide in aqueous solutions are observed as acidic and display elevated vapor pressures at high temperatures[2]