Function: Alum tastes sour, cold and toxic. Therefore, it has antibacterial and astringent effects and can be used as traditional Chinese medicine. Alum can also be used to prepare aluminum salt, baking powder, paint, tanning material, clarifier, mordant, papermaking, waterproof agent and so on. It is often used to purify water in people's lives.

In addition, alum has flocculation effect, which can make vermicelli and bean jelly hard and difficult to scald with boiling water. Some manufacturers use alum to improve the quality of their products to make up for the shortcomings of poor raw materials and production technology. This is forbidden.

Extended data:

However, in the national hygienic standard for the use of food additives, alum is clearly prohibited in this kind of products. According to the US Food and Drug Administration, consumers who buy unqualified batches of products can request a return from the sales unit with the shopping receipt and outer packaging.

Alum is a colorless and transparent block crystal or crystalline powder, odorless, slightly sweet and sour. Weathering in dry air loses crystal water, melting water in humid air, heating to 92.5℃ loses nine crystal water, and losing all crystal water at 200℃ becomes white powder. Soluble in water, slowly soluble in glycerol, insoluble in ethanol and acetone.

Baidu encyclopedia-potassium aluminum sulfate dodecahydrate

Phoenix Net-Fans use alum to "tendon" but it hurts people.