Aluminum chloride kitchen reaction (personal anecdote)

Used to illustrate aluminum chloride's instability relative to magnesium chloride; pure aluminum's protective oxide skin is the corollary.

Magnesium oxide is more stable, but when it forms with a chloride it pits, it delaminates, it just corrodes. It prefers the chloride. Magnesium chloride is much more stable than aluminum chloride. Aluminum chloride isn't really that stable. In fact, if you react aluminum chloride with water, it generates hydrogen — it creates HCl and aluminum oxide. I learned this when my oldest son was doing a high school chemistry project. I brought back all the chlorides I could think of, and he was going to look at their solubility. I was sitting at the kitchen table and put a little bit of aluminum chloride in water, and there was a little fire — generated hydrogen. I didn't realize it was that reactive.