Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic (absorbs water less readily) than sodium iodide, making it easier to work with. Potassium iodide occurs naturally in kelp. Kelp's iodide content can range from 89 µg/g to 8165 µg/g.Aged and impure samples are yellow because of the slow oxidation of the salt to potassium carbonate and elemental iodine. 4 KI + 2 CO2 + O2 → 2 K2CO3 + 2 I2Potassium iodide is medicinally used for thyroid blockade,thyroid storm and also as an expectorant.