LEE knows the following paper: We know that the main component of salt is sodium chloride, which is the most commonly used condiment in people's lives. But its function is not only to increase the taste of food, it is the basic component of human tissue and plays an important role in ensuring normal physiological and biochemical activities and functions in the body. The functions of Na+ and Cl- in vivo are closely related to K+ and other elements. Its main function is to control the electrolyte balance in cells, tissue fluid and blood, so as to maintain the normal circulation of body fluids and control the acid-base balance in the body. Na+, K+, Ca2+ and Mg2+ are also helpful to maintain the appropriate stress level of nerves and muscles. NaCl and KCl play a role in regulating the proper viscosity or consistency of blood; The acids that begin to digest certain foods in the stomach and other digestive compounds in gastric juice, pancreatic juice and bile are also formed by sodium and potassium salts in the blood. In addition, appropriate concentrations of Na+, K+ and Cl- also play an important role in the physiological process of retinal response to light. In addition, gargling with light salt water can not only treat and prevent oral diseases such as sore throat and swollen gums, but also prevent colds. Iodine-containing compounds such as potassium iodide, sodium iodide and iodate are important reagents in the laboratory. In food and medical treatment, they are also important nutrients and drugs, which play an important role in maintaining human health. Iodine is an essential trace element for human body and an important component of thyroid hormone. In normal people, * * * contains iodine 15 mg ~ 20 mg, of which 70% ~ 80% is concentrated in the thyroid gland. Iodine in human body exists in the form of compound, and its main physiological function occurs through the formation of thyroid hormone. Therefore, the physiological function and important role of thyroxine are directly related to iodine. Iodine deficiency in human body can lead to a series of biochemical disorders and physiological dysfunction, such as endemic goiter, infant growth and development stagnation, mental retardation and so on. China is a serious iodine deficiency area in the world, and there are about 400 million people in China who are iodine deficient. The government has also taken some measures, such as providing iodized salt and other foods (such as eggs with high iodine content), iodizing well water and eating iodine-rich seafood, among which iodized salt is the most convenient and effective. 1991March, our government solemnly promised the international community that iodine deficiency disorders would be eliminated in Chinese mainland in 2000.