Potassium alum is the white crystalline natural mineral salt (double sulfate) of potassium. Potassium alum is specific chemical compound that is also part of a class of alum chemical compounds. The term alum refers to various double sulfates that have the general formula of (SO4)3•24H2O plus an additional element, such as potassium, which results in potassium alum: KAL(SO4)2•12H2O.
Potassium alum, and alums alike, crystallize in regular octahedral. It is soluble in water, and when heated it liquefies; and if the heating is continued, an unstructured powder will remain. Commonly, potassium alum crystal is colorless and glassy (vitreous), and in its purest form is completely translucent with small fractures.
Potassium alum has been a sought after natural mineral salt for thousands of years due to its abilities to effectively contribute to water purification, pickling, tanning, medical procedures and in cosmetics as an aftershave or deodorant. Additionally, due to its attractive crystal appearance, potassium alum has become a favorite amongst mineral collectors. Potassium alum is antimicrobial and can therefore be used as a natural deodorant by inhibiting the growth of the bacteria responsible for body odor. It is also used in medical procedures as a local astringent and styptic.