Aluminium chloride, or aluminium trichloride, is a chemical compound of aluminium and chlorine, with the formula AlCl3.
Aluminium chloride has a high affinity for water. Hydrated aluminium chloride cannot be turned back anhydrous via heating heating as HCl is lost leaving aluminium hydroxide or alumina (aluminium oxide):
- Al(H2O)6Cl3 → Al(OH)3 + 3 HCl + 3 H2O
Aluminium chloride is a white hygroscopic salt. It melts at 192.4 °C (anhydrous form). The hydrated form, which is much less useful as a reagent, appears as grainy, oily beads which are often yellow due to even the smallest of iron impurities.
Aluminium chloride, both anhydrous and hydrated can be purchased from chemical suppliers.
Hydrated aluminium chloride is available as aqueous solution in may pool stores.
- 2 Al + 3 Cl2 → 2 AlCl3
- 2 Al + 6 HCl → 2 AlCl3 + 3 H2
The resulting AlCl3 vapors are condensed outside the reactor and then collected and stored in anhydrous conditions.
Aqueous AlCl3 can be prepared by reacting hydrochloric acid with aluminium metal. This reaction is very exothermic and the resulting hydrogen may ignite or explode if the reaction is done improperly.
- Friedel–Crafts reactions
- Organoaluminium compounds
Aluminium chloride is irritant to skin, eyes and respiratory system. It is a known neurotoxin.
Anhydrous AlCl3 must be stored in sealed containers, to prevent it from hydrolyzing.
Hydrated aluminium chloride doesn't require special storage.
Aluminium chloride will hydrolyze into aluminium hydroxide and hydrochloric acid. The acid is easy to neutralize and dispose of, but aluminium hydroxide is harmful to environment. Since is insoluble in water, it can easily be separated, purified and recovered.