Alum

Application

1.Industrial application

(1)Extinguishing agent

The foam extinguisher contains about 1mol/L of alum solution and about 1mol/L of NaHCO3 (baking soda) solution (and froth). 

The volume ratio of the two solutions is about 11:2. Alum excess is to make the baking soda in the fire extinguisher fully react and release enough carbon dioxide to achieve the purpose of fire extinguishing.

(2)Expanding agent

When frying fries (cakes) or puffed foods, adding baking soda to flour and alum will accelerate the production of carbon dioxide and greatly accelerate the puffing speed, but it is not good for human body. 

In this way, the fried dough sticks (cakes) can be bulged up in a hot oil pan, and the crisp and delicious fried dough sticks (cakes) can be obtained.

(3)Buffer

Alum can be used as a buffer in sulfate zinc plating to stabilize the pH value of the bath. 

Potassium aluminium sulfate is used for chemical oxidation of sulphate galvanizing, brush galvanizing and magnesium alloys. 

Alum can also be used as a coagulant for sewage treatment. 

If alum is used for galvanizing, attention should be paid to the content of iron and heavy metals. 

2.Drug function

Alum is cold, sour and astringent, and has a strong convergence effect. 

Chinese medicine believes that alum has the functions of detoxification and insecticide, dampness explosion and itching relief, hemostasis and diarrhea, heat clearance and phlegm elimination, and anti-trichomonas vaginalis. 

Some Chinese medicine uses alum to treat hyperlipidemia, duodenal ulcer, tuberculosis hemoptysis and other diseases.

3.Edible function

Alum can also be used to cook mung bean porridge, the main role is to make mung beans more easily boiled.
Alum can also be used to prepare aluminium salts, paints, tannins, mordants, papermaking, waterproofing agents, etc.

4.Water purifying agent

Aluminum dissolves in water and ionizes to produce Al3+. Al3+ combines with OH - produced by water ionization to produce aluminium hydroxide. 

Aluminum hydroxide colloidal particles have positive charges and meet with negatively charged sediment colloidal particles, and their charges are neutralized. 

When the charged colloidal particles are lost, they will soon coalesce together. 

The larger the coalescence, the more they sink to the bottom of the water. 

In this way, the water becomes clear and clean.

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