Alum is a chemical compound that typically appears as a white crystalline solid. It is often used in various applications, including water purification, food processing, and as a mordant in dyeing fabrics. The most common type of alum is potassium aluminum sulfate, which is known for its ability to help clarify water and improve the quality of certain foods. In addition to its practical uses, alum has historical significance. It has been utilized since ancient times for its astringent properties and as a preservative. Today, alum can be found in many household products, such as baking powder and aftershave, highlighting its versatility in everyday life.