Alum Alternative names: white alum , snow alum, mica alum, withered alum, alum stone, raw alum, Shi Nie, Fei Nie, Fei Zee, Nie Shi, Li Shi, Bai Jun, alum essence, willow alum.

Alum is a compound salt of potassium sulfate and aluminum sulfate containing crystalline water, chemical formula KAl(SO4)2-12H2O, its aqueous solution is acidic, hydrolyzed in water to produce aluminum hydroxide colloidal precipitate and so on.

The product is in the form of irregular crystalline block. Colorless or white. Transparent or translucent, glass-like luster. The surface is slightly smooth or uneven, with fine longitudinal ribs, and with white powder. Hard and brittle, easy to smash. Slightly sweet and astringent flavor. Large, colorless, transparent and unadulterated pieces are preferred.

Alum is alkaline aluminum potassium sulfate [KAl3(SO4)2(OH)6], of which potassium oxide (K2O) 11.4%, aluminum oxide (Al2O3) 37.0%, sulfur trioxide (SO3) 38.6%, water (H2O) 13.O%. Alum is aqueous aluminum potassium sulfate [KAl(SO4)2-12H2O].

Aluminum potassium sulfate dodecahydrate is an inorganic substance, also known as alum, with the chemical formula KAl(SO4)2-12H2O, is a compound salt of potassium sulfate and aluminum sulfate containing water of crystallization . It is soluble in water and insoluble in ethanol.

Alum is sour and astringent, cold; antibacterial effect, astringent effect, etc., can be used to do traditional Chinese medicine, but also can be used for the preparation of aluminum salts, baking powder, paint, tanning, clarifying agent, mordant, papermaking, waterproofing agent, etc., life is often used for water purification. Because long-term consumption of aluminum-containing food additives on the human body is very harmful, especially for children's growth and development and intelligence will be affected, the country has banned its use in food additives.