Alum

Alum is a common name for a class of chemical compounds, typically referring to potassium aluminum sulfate (KAl(SO₄)₂·12H₂O), a white crystalline substance widely used for purification, preservation, and various industrial and household applications. Known for its astringent and antibacterial properties, alum is most commonly used in water purification, where it acts as a coagulant—clumping together fine particles and impurities for easier removal. Alum is also used in the cosmetic industry as a natural deodorant, in aftershaves for its skin-tightening effects, and in traditional medicine for treating minor cuts and wounds. In the food industry, it serves as a food additive and preservative, especially in pickling. Additionally, alum finds application in dyeing and tanning processes due to its ability to fix dyes and stabilize colors.

Available in powder, crystal, or block form, alum is non-toxic in small quantities and easy to store, making it a widely accessible and versatile compound. However, it should be used in moderation, particularly in food and skin applications, to avoid irritation or adverse reactions.