The New Student's Reference Work/Iodine

I′odine, one of the nonmetallic elements, is a black crystalline solid. It is never found in the free state, but occurs in combination, particularly in the ashes of seaweeds and in Chilean saltpeter. It forms a beautiful violet vapor when heated; hence its name comes from a Greek word which signifies this color. Iodine and its compounds, the most important of which is potassium iodide, are used in medicine and photography and by chemists.