Potassium aluminium sulfate is otherwise known as potash alum or potassium alum. Chemical formula KAl (SO4)2.12H2O . Naturally occuring mineral potash alum is known as alum - (K). Other potassium aluminium sulfate minerals are alunite and kalinite. It is used as an astringent and antisepsis in various food preparation processes such as a flocculant for water purification among other things.