1. A lustrous, grayish-black, corrosive, poisonous halogen element having radioactive isotopes, especially I 131, used as a medical tracer and in thyroid disease diagnosis and therapy. iodine compounds are used as germicides, antiseptics, and dyes. atomic number 53; atomic weight 126.9045; melting point 113.5°C; boiling point 184.35°C; specific gravity (solid, at 20°C) 4.93; valence 1, 3, 5, 7. see table at element.
2. an antiseptic preparation containing iodine in solution, used to treat wounds.

1. A chemical element (symbol: I) with an atomic number of 53; one of the halogens.
2. an antiseptic incorporating the element.
3. an iodide.

1. A nonmetallic element, of the halogen group of atomic number 53, occurring always in combination, as in the iodides. when isolated it is in the form of dark gray metallic scales, resembling plumbago, soft but brittle, and emitting a chlorinelike odor. symbol I. atomic weight 126.90. If heated, iodine volatilizes in beautiful violet vapors.

1. chemical symbol, I; atomic weight, 126.9. in chem., a peculiar non-metallic elementary solid substance, forming one of the group of halogens.

1. a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)
2. a tincture consisting of a solution of iodine in ethyl alcohol; applied topically to wounds as an antiseptic