If a disposable alkaline battery leaks inside a piece of personal electronics, the leakage can ruin the device. Most cylindrical batteries, including AAA, AA, C and D cells, are alkaline, as are many button-type batteries that fit in watches and hearing aids. The alkaline chemical in these batteries is potassium hydroxide. This chemical is toxic and corrosive, but you can neutralize it with an acid and clean it without much trouble. Be warned: You use a different agent on alkaline battery leaks than you use on acid battery leaks. There is a chance your leaking battery contains an acid electrolyte. If so, the casing will indicate that, and you shouldn't use an acid to neutralize it.