Iodine is the least reactive of the halogens. It consists of heavy, grayish-black granules or solid plates, readily sublimed to a violet vapor. Iodine is insoluble in water and soluble in alcohol, carbon disulfide, chloroform, ether, carbon tetrachloride, and glycerol. It is toxic by ingestion and inhalation, strong irritant to eyes and skin. TLV: ceiling 0.1 ppm in air. Iodine is use as an antiseptic, germicide, X-ray, water treatment, medicinal soaps, and food and feed additive. Fluorine, chlorine, bromine, and iodine will be discussed further in chapter 8.