Molecular formula: KAl (SO4)2-12H2O
Also known as: alum, alum, potassium alum, potassium alum, potassium alum
It is a compound salt of potassium sulfate and aluminum sulfate containing water of crystallization. Chemical formula KAl(SO4)2-12H2O, formula 474.39, colorless cubic, monoclinic or hexagonal crystals, glassy, density 1.757g/cm3, melting point 92.5 ° C. Loss of 9 molecules of water of crystallization at 64.5 ° C, 200 ° C, loss of 12 molecules of water of crystallization, soluble in water, insoluble in ethanol. Alum is sour and astringent, cold and toxic. Therefore, it has antibacterial effect, astringent effect, etc., can be used as traditional Chinese medicine. Alum can also be used in the preparation of aluminum salt, baking powder, paint, tanning, clarifying agent, mordant, papermaking, waterproofing agent. Alum water purification is often used in the folk in the past, it is the principle of alum in the water can be ionized out of two kinds of metal ions:
KAl (SO4)2 = K+ + Al3+ + 2SO42-
And Al3 + easily hydrolyzed, born into a colloidal aluminum hydroxide Al (OH) 3:
Al3 + 3H2O = Al (OH) 3 (colloidal) + 3H+
Al (OH) 3 (colloidal). Colloid) + 3H+
Aluminum hydroxide colloid adsorption capacity is very strong, can be adsorbed in the water suspended impurities, and the formation of precipitation, so that the water clarification. Therefore, alum is a better water purifier.
Alum can be made from alum stone by calcination, extraction, crystallization. China's origin is Lujiang alum mine in Anhui Province
China's largest alum producer should be the alum mine in Alum Hill Town, Cangnan County, Zhejiang Province (accounting for 67% of the world's total reserves).
Alum, also known as alum, is a refined product of alum stone. Alum is cold, sour and astringent, with a strong astringent effect, Chinese medicine believes that alum has the effect of detoxifying and killing insects, drying dampness and relieving itching, stopping bleeding and stopping diarrhea, and clearing heat and eliminating phlegm. Recent studies have confirmed that alum also has antibacterial, anti-vaginal trichomonas and other effects. Some Chinese medicine practitioners use alum to treat hyperlipidemia, duodenal ulcer, tuberculosis hemoptysis and other diseases.
In addition, alum is also a traditional food improver and bulking agent, commonly used as an additive in the production of doughnuts, vermicelli, rice noodles and other foods. But because the chemical composition of alum is potassium aluminum sulfate, containing aluminum ions, so excessive intake will affect the body's absorption of iron, calcium and other ingredients, leading to osteoporosis, anemia, and even affect the development of nerve cells. Therefore, some nutrition experts suggest that we should try to eat less food containing alum.
Alum is a traditional water purification agent, has been widely used by people