It reacts with chlorine to make iodine and potassium chloride. It turns yellow when in air. This is because it reacts with oxygen and carbon dioxide to make iodine and potassium carbonate. ... That is why a solution of potassium iodide dissolves iodine.

Application

Potassium iodide is a chemical compound, medication, and dietary supplement. As a medication it is used to treat hyperthyroidism, in radiation emergencies, and to protect the thyroid gland when certain types of radiopharmaceuticals are used.