potassium iodide is slightly hygroscopic in humid air, which precipitates free iodine and turns yellow, and forms trace iodate, which can be accelerated by light and humidity. Potassium iodide is a kind of iodine supplement medicine, which can be used in the prevention and treatment of endemic goiter, preoperative preparation for hyperthyroidism and hyperthyroidism crisis. Take potassium iodide according to the doctor's advice, and don't blindly take it yourself to avoid adverse reactions.