Last Updated : Dec 02,2020
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Also known as:
Phitkari, rock alum
Alum is any of various double sulphates of a trivalent metal such as chromium, aluminum, or iron and a univalent metal such as potassium or sodium, especially aluminum potassium sulphates. It is translucent in appearance and is available both as loose crystals and small solid blocks. They are soluble in water and have a primary nature to crystallize. They have an astringent, sweetish and acid taste. When heated, the crystals liquefy and on continued heating, they lose all the crystalline form and turn to a amorphous powder. Alums are useful for a range of industrial processes.
Types of alum
Sodium alum mainly occurs in nature as the mineral "Mendozite". It is commonly called Soda Alum.It is very soluble in water, and is extremely difficult to purify. It is used in the manufacture of baking powder as well as a acidulant in food.
It is a white crystalline double sulphate of aluminium and is used for water purification. It also finds place in vegetable glues, tanning and dyeing. It is one of the ingredients in making of natural deodorants also.
It is chemically the potassium double sulphate of aluminium. It is commonly called as Potash Alum. It is commonly used in a similar manner like Ammonium Alum. It is also used as an effective aftershave treatment.
How to select
Ensure that the alum is in solid crystal form and translucent in appearance. Powdered alum should be in a sealed air- tight container and in proper packaged condition.
1. It is used as a water purifier since it makes solid impurities settle at the bottom of the container.
2. Alum is used as the acidic component of some commercial baking powders.
3. Alum powder, found in the spice section of grocery stores, may be used in pickling recipes and as a preservative to maintain fruit and vegetable crispness.
4. It can also be used to curdle milk for recipes like "Milk Cake" where the milk, sugar and alum mixture is cooked till it thickens and resembles khoya. Use ¼ tsp alum for 2 litres full fat milk when preparing Milk Cake.
How to Store
Store the alum in crystal form/ powder form in a air-tight container in a cool, dark and dry place.
1. Alum, in its various forms, is commonly used as an astringent and antiseptic. This is the main reason why it is used to inhibit body odour when used as natural deodorant.
2. The astringent and antiseptic properties in Potash Alum also help in reducing bleeding in minor abrasions and cuts, nosebleeds etc.
3. Alum in powder or crystal form, or in styptic pencils, is sometimes applied to cuts to prevent or treat infection.
4. Alum is used in vaccines as an adjuvant to enhance the body's response to immunogens.
5. Powdered alum is commonly cited as a home remedy for ulcers.
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