The dry powder fire extinguisher contains about 1mol/L alum solution and 1mol/L NaHCO3 (baking soda) solution (and foaming agent), and the volume ratio of the two solutions is about 1 1: 2. Excessive alum is to make the baking soda in the fire extinguisher fully react and release enough carbon dioxide to achieve the purpose of extinguishing the fire.

(2) expansion agent

When frying deep-fried fritters (cakes) or puffed food, if baking soda is added to flour and then alum is added, the production of carbon dioxide will be accelerated and the puffing speed will be greatly accelerated. In this way, you can make the fried dough sticks (cakes) bulge in the hot oil pan at once, and get crispy and delicious fried dough sticks (cakes).

(3) Buffering

It can be used as a buffer in sulfate zinc plating to stabilize the ph value of the plating solution. Potassium aluminum sulfate is used for sulfate zinc plating, brush zinc plating and chemical oxidation of magnesium alloy, and can also be used as coagulant for sewage treatment. If it is used for zinc plating, pay attention to its iron and heavy metal content. ? [5]?

(4) Drug function

Alum is shabby and has a strong astringent effect. Chinese medicine believes that alum has the functions of detoxifying and killing insects, eliminating dampness and relieving itching, stopping bleeding and diarrhea, clearing away heat and resolving phlegm, and resisting trichomonas vaginalis. Some Chinese medicine practitioners use alum to treat hyperlipidemia, duodenal ulcer, tuberculosis and hemoptysis.

(5) Edible function

Alum can also be used to cook mung bean porridge, the main function is to make mung beans easier to cook, but it is not recommended because the dosage is difficult to control and may be poisoned. Edible alkali can be used instead.

Extended data:

In ancient times, there was a bitter child named Bai Fan in Yunnan who lived with his father in a shabby little house. There is a big tree outside their hut. Every summer, this tree will produce yellow flowers, and when the flowers fall, it will bear black fruits. Bai Fan likes this tree very much, and the tree tries its best to protect this shabby hut from the wind, rain and sun with its shade.

One day, Bai Fan dreamed that the big tree became the Prince of Wei Ying. He calls himself Hulile and comes from the far south. I'm leaving. Before I leave, I will give you these things as souvenirs. Remember, give it to your father when necessary. "The white sail woke up with a start, and the tree in front of me disappeared, leaving a package of fruit and a package of colorless, transparent and shiny crystals. Soon, there was an epidemic in the local area, and the old people had diarrhea.

Bai Fan's father is no exception. He simmered two packages of things left by the prince, burned them to ashes, then smashed them carefully, sifted them into powder, and mixed them in porridge to feed his father. Dad's diarrhea stopped, and Bai Fan distributed medicines to other old people and cured their diarrhea. Since then, the method of making drugs with these two things has spread. Therefore, people call this bag of seeds "terminalia chebula" and the crystal is called alum.

References:

Baidu encyclopedia-potassium aluminum sulfate dodecahydrate