Alum

Alum - double sulphate one - and trivalent metals. Soluble in water; form of the same form (isomorphic) crystalline. When heated alum lose crystallization water (burnt alum). In medicine used alumina-potassium alum K2SO4·Al2(SO4)3·24H20 rendering astringent, drying and disinfecting action on the mucous membranes and skin.