Aluminum iodide is a salt with the molecular formula AlI3. Its molar mass is 407.695 grams per mole for the anhydrous form and 515.786 grams per mole for a hexahydrate. Pure samples appear as a white powder, with a density of 3.98 grams per cubic centimeter for the anhydrous form.
Aluminum iodide is a strong Lewis acid, and it absorbs water from the air. The reactions between aluminum metal or aluminum hydroxide, and hydrogen iodide or hydroiodic acid, produce aluminum iodide hexahydrate. Solid AlI3 exists as a dimer, Al2I6. It is used as a reagent in several organic chemistry processes, such as the cleavage of aryl ethers or the deoxygenation of epoxides.