Alum is also known as alum, potassium alum, potassium aluminum alum, potassium alum, potassium aluminum sulfate dodecahydrate. 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 ℃. 64.5 ℃ when the loss of 9 molecules of water of crystallization, 200 ℃ when the 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 past folk method, it is the principle of alum in the water can be ionized out of the two 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 +

Aluminum hydroxide colloidal adsorption capacity is very strong, can adsorb the suspended impurities in the water, and the formation of precipitation, so that water clarification. Therefore, alum is a better water purifier.

Alum Mineral This product is the crystal of the sulfate mineral cholecalciferol, or artificially made aqueous copper sulfate. [Original mineral] Chalcanthite Chalcanthite Synonyms: stone gall, Bi Shi, Jun Shi ("Ben Jing"), black stone, copper le ("Wu Pu Ben Cao"), base stone ("Bie Lu"), standing stone ("Tao Hongjing"), stone liquid, making stone thick ("Shi Yao Er Ya"), duck's mouth chalcanthite ("Jisheng Fong"), Cui chalcanthite ("Materia Medica Meng Chuan"), blue chalcanthite ("Chinese Herbs Handbook"). Morphology: Triclinic crystal system. The crystals are plate-like or short columnar, usually dense massive, stalactitic, pericyclic, reniform, sometimes fibrous. The color is sky blue, blue, sometimes slightly light green. Streaks colorless or light bluish. Glossy glassy. Translucent to transparent. Fracture shell-shaped. Hardness 2.5, specific gravity 2.1-2.3, very brittle. Odorless, astringent, nauseating. [Habitat distribution] Produced in the secondary oxidized zone of copper ore. It is distributed in Yunnan, Shanxi, Jiangxi, Guangdong, Shaanxi, and Gansu. [Harvesting] It can be dug from copper ore, and the blue transparent crystals are selected. Artificial products, can be made by sulfuric acid on copper sheet or copper oxide. [Chemical composition] Usually copper sulfate pentahydrate (CuSO4-5H2O). [Pharmacological effects] can be combined with proteins to produce insoluble protein compounds and precipitation, so its concentrated solution has a corrosive effect on the local mucous membranes, dilute solution has astringent system secretion effect. When taken internally, it can stimulate the perceptual nerve of the stomach wall, and through the reflex to the vomiting center of medulla oblongata, it will cause reflex vomiting. [Sexual flavor and function] Sour, pungent, cold; poisonous. Emetic, expectorant and detoxicant. [Indications and Usage] Treating wind-phlegm congestion, laryngeal paralysis, epilepsy, dental treatment, mouth sores, rotting strings and wind eyes, hemorrhoids, swelling and poisoning. It can be used in pills and powder. Externally, it can be powdered and withdrawn or applied externally, or dissolved in water to wash the eyes. [Dosage] 0.5~1g; Appropriate amount for external use. [Note] Avoid internal use if you are weak.

Paste to join the paste can play a chemical reaction with the principle of paste so that the paste can be more viscous, not easy to deteriorate.