ALUMINIUM SULFATE OR ALUM IS USED AS A FLOCCULANT TO REMOVE UNWANTED COLOUR AND TURBIDITY FROM WATER SUPPLIES. IT HAS BEEN USED SINCE ANCIENT TIMES FOR THIS PURPOSE AND ITS USE TOGETHER WITH FILTRATION IS STANDARD PRACTICE IN CONVENTIONAL WATER TREATMENT PROCESSES AROUND THE WORLD.
When used as a mordant (binder) in dyeing, it fixes dye to cotton and other fabrics, rendering the dye insoluble. Alums are also used in pickling, in baking powder, in fire extinguishers, and as astringents in medicine.
Alum is used in depilatory waxes that are used for the removal of body hair or applied to freshly waxed skin as a demulcent (relieves inflammation or skin irritation).