Alum-(K)

Alum-(K), also known as potash alum, potassium alum, or potassium aluminum sulfate, is a chemical compound with the formula KAl(SO₄)₂·12H₂O. It is a double salt of potassium and aluminum sulfate. It is commonly encountered as the dodecahydrate, meaning it has twelve water molecules bound to each formula unit.

Properties:

• It exists as colorless crystals or a white powder.
• It is soluble in water. Solubility increases with temperature.
• It has an astringent and acidic taste.
• Upon heating, it effloresces, losing its water of hydration. At higher temperatures, it melts and eventually decomposes.
• It is a naturally occurring mineral, found in volcanic deposits and in the mineral alunite.

Uses:

• Mordant: Alum-(K) is used as a mordant in dyeing textiles. It helps the dye adhere to the fabric fibers.
• Tanning: It is used in the tanning of leather to improve its durability and suppleness.
• Water Purification: Alum-(K) is used in water treatment plants as a flocculant. It causes small particles to clump together, making them easier to filter out of the water.
• Medicine: It has been used medicinally as an astringent, antiseptic, and styptic (to stop bleeding). It can be found in some styptic pencils used to treat minor cuts.
• Food Industry: It is used in some baking powders and as a firming agent in pickles and other food products.
• Other Uses: It can also be found in deodorants (as an antiperspirant) and in some fireproofing compounds.

Production:

Alum-(K) can be produced through various methods including:

• Extraction from alunite: Alunite is roasted, then leached with sulfuric acid. Potassium sulfate is added to precipitate the alum.
• Reaction of aluminum hydroxide with potassium sulfate and sulfuric acid: This method is used to produce synthetic alum.
• Recovery from bauxite residues: It can be recovered as a byproduct of the Bayer process for producing alumina.

Safety:

While generally considered safe, ingestion of large quantities of Alum-(K) may cause gastrointestinal irritation. Dust inhalation may also cause respiratory irritation.