Role: 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 material, clarifying agent, mordant, papermaking, waterproofing agent, etc., often used in people's lives to purify water.

In addition, alum has a flocculating effect, which can make vermicelli and cold noodles become very sinewy and not easy to be cooked in boiling water. Some producers use alum to enhance the 'quality' of their products to make up for poor raw materials and production processes. This is banned.

Expanded:

p>But in the national "hygiene standards for the use of food additives", the use of alum is expressly prohibited in such products. Municipal Food and Drug Administration said consumers who bought the substandard batch of products can return the products to the sales unit with the shopping ticket and the outer packaging.

Alum is a colorless transparent lumpy crystal or crystalline powder, odorless, slightly sweet and sour taste. Weathering in the dry air to lose the water of crystallization, in the humid air dissolved water, heated to 92-5 ° C to lose 9 water of crystallization, 200 ° C to lose all the water of crystallization into a white powder. Easily soluble in water, slowly soluble in glycerol, insoluble in ethanol, acetone.

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