Anhydrous citric acid, molecular formula C6H8O7, is colorless translucent crystal or white particles or white crystalline powder, often containing a molecule of crystalline water, odorless, extremely sour, soluble in water, alcohol and ether. Anhydrous citric acid can be obtained by controlling appropriate temperature during crystallization. The aqueous solution is acidic. Slightly weathered in dry air and deliquescent in moist air. It is mainly used in the food and beverage industry as an acid flavor agent, acidity regulator, flavoring agent, preservative and fresh-keeping agent. It is also used as antioxidant, plasticizer and detergent in chemical industry, cosmetics industry and washing industry.