Alum

Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate (potassium alum) with the formula KAl(SO 4 ) 2 ·12H 2 O. The wider class of compounds known as alums have the related empirical formula, AB(SO 4 ) 2 ·12H 2 O.



Alums are useful for a range of industrial processes. They are soluble in water; have an astringent, acid, and sweetish taste; react acid to litmus; and crystallize in regular octahedra. When heated they liquefy; and if the heating is continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains. Alum is a chemical compound. It is used for many processes involving industry.

Alum is used in many subunit vaccines as an adjuvant to enhance the body's response to immunogens. Such vaccines include hepatitis A, hepatitis B, and DTaP.
 * __Medical Uses__**

Alum in powder or crystal form, or in styptic pencils, is sometimes applied to cuts to prevent or treat infection.

Powdered alum is commonly cited as a home remedy for canker sores.

Preparations containing alum are used by pet owners to stem bleeding associated with animal injuries caused by improper nail clipping.

Alum is listed as an ingredient of some brands of toothpaste or toothpowder.

Alum powder dissolved in five parts water has been used to shrink hemorrhoids and stop them from bleeding.

__**Culinary Uses**__ Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness.

Alum is used as the acidic component of some commercial baking powders.

Alum was used by bakers in England during the 1800s to make bread whiter. The Sale of Food and Drugs Act 1875 prevented this and other adulterations.