What is alum?

Alum, also known as alum, is a double sulfate salt of potassium and aluminum, with the chemical formula KAl(SO 4 ) 2 , also known as Potassium alum. Alum is in the form of large and small irregular crystals, colorless or white, can also be clear or slightly opaque. Alum is soluble in water, insoluble in alcohol.

Alum is non-toxic, has a sour taste, slightly soluble in cold water but very soluble in hot water, so it is easy to refine by recrystallization in water. Also due to the precipitation of Al(OH) 3 , when stirred into the water, the small soil particles suspended in the turbid water became larger, heavier soil particles and sank, making the water clear. So alum is often used to filter water.

What is alum?
Alum has a sour taste, helps detoxification, low apples, antiseptic skin, cures stomach diseases, enteritis…

Alum is an inorganic compound, prepared from the main raw materials of clay (the composition contains Al 2 O 3 ), sulfuric acid and K 2 SO 4 . Alum has a sour taste, helps in detoxification, low apple, antiseptic skin, cures stomach diseases, enteritis, rheumatism, is used to make medicines for toothache, eye pain, hemostasis, hemoptysis (types of hemorrhage). Besides, alum also has the effect of beautifying the skin, treating acne, cleaning yellow stains on clothes… Alum is also widely used for water purification, tanning, fireproof fabrics and baking powder.

Alum also has many different names in Sino-Vietnamese such as: Vu Nhat, Vu Trach, Crushed Thach, Minh Thach, Tran Phong Thach, Tat Phan, Minh Phan, Phan Thach…

In addition to its use in water treatment and medical applications, alum is also used in many culinary applications. Alum has the effect of increasing the whiteness and crispiness of foods such as jams and pickles. If the use of alum is limited, it can be replaced with lime water in soaking food, which also helps food to be more crispy. These two types are allowed to be used but need to ensure that the residue is not too large.

Alum also keeps eggs fresh longer. The way to do it is to soak the eggs in 5% alum solution, 15 minutes after taking them out, the eggs will keep fresh longer. Alum is also used to eliminate the bad smell of pig’s intestines, by using a spoon to grind alum into powder, rub it on the pig’s intestines, then wash it, the pig’s intestine will be completely reduced.

Alum is used to make water in wells. Boiled de-alumated water can be used for drinking and cooking. This is also the substance used by the water plant as a coagulant to make in the water source.

Alum is also used to soak with vegetables and fruits to increase the whiteness and crispiness of the product, so it is used in the processing of coconut jam, pumpkin jam to create toughness and transparency for ingredients. When cooking grapefruit tea, alum is also favored to reduce the bitter taste in grapefruit peel. With the dosage of alum according to the usual recipe, the dish or product will not affect health.

Alum is weakly acidic, so it stimulates baking soda to release carbon dioxide, so it is used as a baking powder in baked goods. The weak acidity of the aluminum alum makes the cake swell when it is in the oven, but not in a hurry when kneading the dough.

What is alum?
Alum is also used to soak with vegetables and fruits to increase the whiteness and crispiness of the product.

The amount of aluminum contained in alum is about 10% (or 0.5g aluminum/liter of water). At this level, alum is not a concern. The amount of alum used to filter water is about 20mg/liter, but aluminum is precipitated in the water purification process. Therefore, the aluminum residue left in the water is negligible. Aluminum alum used in baking powder, must comply with the maximum permissible level of use of the safety agency depending on the type of cake.

Alum has the chemical formula: K 2 SO 4 .Al 2 (SO 4 )3.24H 2 O

When we look at the chemical formula we also realize that it is a sulphate salt that combines aluminum and potassium.

Alum contains 24 water molecules and is crystalline

Why can alum filter water in our family, now perhaps there is no longer a situation where families take alum to filter water, here I am talking in the past, usually put alum into the water and a little while later the water will be clear ===> the reason is that when alum is added to the water, the reaction will occur:

Al 3 + + 3H 2 O → Al(OH) 3 + 3H+

=> Al(OH) 3 is a precipitate, perhaps in chemistry everyone knows, this precipitate is in the form of a colloid, this glue will attach sand and dust particles in the water, causing them to sink into the urine.

Alum is not toxic because alum contains only about 10% aluminum at this level, it is not a problem at all, has a sour taste, is slightly soluble in cold water and dissolves quickly in hot water.

Alum is used for water treatment and disinfection.