Potassium aluminium sulphate dodecahydrate.
Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the double sulfate of potassium and aluminium, with chemical formula KAl(SO4)2. It is commonly encountered as the dodecahydrate, KAl(SO4)2·12H2O.
Used in printing, fabrics, dyeing, manufacturing of paper, vegetable glue, baking powder, purifying water, clarifying sugar, as catalyst in ammonia synthesis, hardening agent in microscopy