Potash alum (aluminium potassium sulfate dodecahydrate) is a white, crystalline, water-soluble salt valued for its strong coagulating, astringent, and stabilizing properties. It is commonly used in water and wastewater clarification, paper sizing, dyeing and tanning, fire-retardant formulations, and as a key functional ingredient in cosmetics and personal-care products.

It also serves as a laboratory reagent, a mordant in textiles, and a processing aid in various chemical syntheses. Product grade and impurity limits should be chosen according to the specific application, especially for cosmetic and pharmaceutical uses where higher purity is required.