Potassium aluminum sulfate, also known as potassium alum or potash alum, is the potassium double sulfate of aluminum with chemical formula KAl(SO4)2. Usually potassium alum appears in the hydrated form and thus has the chemical formula KAl(SO4)2·12H2O. This compound is commonly used in cosmetics as a deodorant, aftershave treatment, and as an astringent and styptic for minor bleeding. It can also be found in baking powder and sees use in water purification, tanning and dyeing, and in the manufacture of textiles and flame retardants.