That is, potassium aluminum sulfate dodecahydrate, also known as alum, alum, potassium alum, potassium aluminum alum and potassium alum, is a double salt of potassium sulfate and aluminum sulfate containing crystal water. Colorless cubic crystals are usually octahedral in appearance, or form polygons with cubes and rhombic dodecahedrons.

The chemical formula kal (SO4) 2. 12h2o, whose aqueous solution is acidic, hydrolyzes in water to generate colloidal precipitates such as aluminum hydroxide. Belonging to mineral Chinese medicine, it can detoxify and kill insects for external use, eliminate dampness and relieve itching, and can stop bleeding, stop diarrhea and resolve phlegm for internal use. Indications: Stroke, epilepsy, laryngitis, scabies, wet sores, carbuncle swelling, fire and water burns.