Potassium alum

Potassium alum, also known as potash alum or tawas, is a chemical compound commonly used in water purification, leather tanning, and baking powder. It is a double sulfate of potassium and aluminium, with the chemical formula KAl(SO4)2.

History

Potassium alum was known to the ancients and has been used by humans for thousands of years. It was used by the Egyptians for its antiseptic properties and by the Romans as an astringent and for medicinal purposes. In the Middle Ages, it was used in the dyeing process, and in the 19th century, it was used in baking powder.

Production

Potassium alum is produced by dissolving alumina in sulfuric acid and then adding potassium sulfate. The resulting solution is allowed to crystallize, producing large, transparent crystals of potassium alum.

Uses

Potassium alum has a wide range of uses. It is used in water purification, as it causes impurities to coagulate and be easily removed. It is also used in leather tanning, as it helps to stabilize the collagen structure of the leather. In baking powder, it acts as a leavening agent, causing dough to rise. It is also used in cosmetics, as an astringent and antiperspirant, and in medicine, as a styptic to stop bleeding.

Health effects

While potassium alum is generally considered safe for use in food and cosmetics, it can cause skin irritation in some people. Ingesting large amounts can cause gastrointestinal upset, and long-term exposure can lead to kidney damage.

See also

• Alum
• Potassium
• Aluminium sulfate
• Water purification
• Leather tanning
• Baking powder

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  Potassium alum

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  Potassium alum octahedral-like crystal

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  Potassium alum block from India used for shaving aftershave