Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound of potassium, with chemical formula KAl(SO4)2. It is commonly encountered as the dodecahydrate , KAl(SO4)2·12H2O. It crystallizes in an octahedral structure in neutral solution and cubic structure in an alkali solution with space group P a -3 and lattice parameter of 12.18 Å. The compound is the most important member of the generic class of compounds called alums , and is often called simply alum.
Potassium alum is commonly used in water purification , leather , and baking powder E522. It also has cosmetic uses as a deodorant, as an aftershave treatment and as a styptic for minor bleeding from shaving.