Aluminium sulfate is a chemical compound with the formula Al₂(SO₄)₃. It is soluble in water and is mainly used as a coagulating agent in the purification of drinking water and waste water treatment plants, and also in paper manufacturing.  This compound is also known as papermaker’s alum or Non Ferric Alum. However, it is not technically an alum. Aluminium sulfate is used in water purification and as a mordant in dyeing and printing textiles. In water purification, it causes suspended impurities to coagulate into larger particles and then settle to the bottom of the container (or be filtered out) more easily. This process is called coagulation or flocculation.