Sodium metabisulfite is a white to pale-yellow crystalline powder (Na₂S₂O₅) with a strong sulfur odor, functioning as a versatile preservative, antioxidant, and antimicrobial agent across food, beverage, pharmaceutical, and cosmetic industries. It forms a mildly acidic aqueous solution (pH ~3.5–5), releasing sulfur dioxide that inhibits microbial growth and oxidation. Widely used in dried fruits, wines, medications, and photography, it requires cautious handling due to potential allergenic and respiratory effects