Citric acid is a kind of important organic acid, also known as folic acid, colorless crystals, which often contain a molecular crystal water, odourless, has a strong acid, soluble in water. The calcium salt is easy to dissolve in cold water than hot water. And in the nature of the commonly, it is used to identify and separate citric acid. When crystallization, control the suitable temperature to obtain anhydrous citric acid, which has been widely used in the industry, food, cosmetic etc. Used in chemical and textile industry. Citric acid can be used as the chemical analysis reagent, experimental reagent, chromatographic analysis reagent and biochemical reagent, complexing agent, masking agent and prepare the buffer solution in chemical technology. Adopt citric acid and citrate as the detergent can improve the performance of the washing products, can precipitate the metal ions quickly, prevent the pollutants from re-adhering to the fabric, maintain the necessary alkaline washing, disperse and suspend the dirt and ash, improve the performance of surfactants, which is a good chelating agent. It can used as the reagent to test the acid resistance of the building ceramic tiles.