Use
Alum is a double sulphate of a monovalent and trivalent
salt.
Alum acts as a flocculating agent. It is used in sewage
treatment and in purification of drinking water. Alum is
also used in the preparation of mordant and as a
fireproofing agent.
Aluminum sulphate is sometimes erroneously called
alum in some industries (such as in the paper industry).