Structural Formula Vector Image
Title: Iodine
CAS Registry Number: 7553-56-2
Literature References: I; at. wt 126.90447; at. no. 53; valences -1, 1, 3, 5, 7. A halogen; Group VIIA (17). Does not occur as elemental state, I2, in nature. Abundance in igneous rocks: 3´10-5% by wt; in seawater: 5´10-8% by wt. Naturally occurring stable isotope (mass number): 127 (100%); known artificial radioactive isotopes: 108 to 141; commonly used radioactive tracer elements: 123 (T½ 13.27 hrs, EC decay), 125 (T½ 59.408 days, EC decay), 129 (T½ 1.57´107 years, b- decay), 131 (T½ 8.02070 days, b- decay). Discovered in 1811 by Courtois. Classed among the rarer elements. Trace element essential to animal and plant life. Extracted commercially from natural subterranean brines, and Chilean nitrate-bearing earth (caliche); formerly from seaweed. Reviews: MTP Int. Rev. Sci.: Inorg. Chem., Ser. One Vol. 3, V. Gutmann, Ed. (Butterworths, London, 1972); A. J. Downs, C. J. Adams, "Chlorine, Bromine, Iodine and Astatine" in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) p 1107-1573; Chemistry of the Elements N. N. Greenwood, A. Earnshaw, Eds. (Pergamin Press, New York, 1984) pp 920-1041; A. Lauterbach, G. Ober in Kirk-Othmer Encyclopedia of Chemical Technology vol. 14 (Wiley-Interscience, New York, 4th ed., 1995) pp 709-737. Review of geochemistry: R. Fuge, C. C. Johnson, Environ. Geochem. Health 8, 31-54 (1986); of human toxicity: Iodine Toxicity (PB89-183016, 1989) 107 pp; of metabolism and nutritional deficiency: J. T. Dunn in Contemporary Endocrinology: Diseases of the Thyroid, L. E. Braverman, Ed. (Humana Press Inc., Totowa, NJ, 1997) pp 349-360; of toxicology and human exposure: Toxicological Profile for Iodine (PB2004-104399, 2004) 580 pp.
Properties: Bluish-black scales or plates; diatomic; metallic luster; characteristic odor; sharp acrid taste. Readily sublimes at rm temp, forming violet corrosive vapor. mp 113.60°. bp 185.24°. d (solid, 25°) 4.93, d (liq 120°) 3.960. Vapor pressure (solid): 0.030 mm (0°); 0.305 mm (25°); 2.154 mm (50°); 26.78 mm (90°). Heat capacity at constant pressure (25°) 13.011 cal/mole/°C: Shirley, Giauque, J. Am. Chem. Soc. 81, 4778 (1959). Total soly in water (25°) 0.0013 moles/l with negligible formation of HOI (6.4´10-6 moles/l); freely sol in aq solns of HI or iodides. Soly in organic solvents (g I2/100 g soln, 25°): benzene 14.09; CS2 16.47; ethanol 21.43; ethyl ether 25.20; cyclohexane 2.719; heptane 1.702; CCl4 (35°) 2.603: Hildebrand, Jenks, J. Am. Chem. Soc. 42, 2180 (1920); Hildebrand et al., ibid. 72, 1017 (1950); sol in chloroform, glacial acetic acid, glycerol oils. Solutions of iodine in aq solns of inorganic iodides are brown or deep brown, depending on the concn of the iodine. Solvents contg nitrogen atoms, such as pyridine, amines, or quinoline form brown solns. Aliphatic hydrocarbons, chloroform, carbon tetrachloride, carbon disulfide, phosphorus trichloride and fluorinated amines give violet solns. Aromatic hydrocarbons give pink or reddish-brown solns. Alcohols and ethers give deep brown solns. Soly in water is increased by alkali bromides, but decreased by sulfates and nitrates. Less reactive than bromine; E° (aq) ½I2/I- 0.535 V dissociation energy (25°): 36.115 kcal. Iodine stains may be removed with sodium thiosulfate soln or ammoniated alc.
Melting point: mp 113.60°
Boiling point: bp 185.24°
Density: d (solid, 25°) 4.93; d (liq 120°) 3.960
Derivative Type: Tamed Iodine see Iodophors
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, and nose; lacrimation; headache; tight chest; skin burns, rash; cutaneous hypersensitivity. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 172. Ingestion of large quantities causes abdominal pain, vomiting and diarrhea due to the highly corrosive action of iodine on the GI tract. See Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Sect. III, pp 213-214.
Use: Manuf of organic and inorganic chemicals, pharmaceuticals, radiopaque contrast agents, animal feed supplements, disinfectants, stabilizers, inks, colorants, photographic chemicals. Catalyst in the alkylation and condensation of aromatic amines; in sulfations and sulfonations; for prodn of synthetic rubber. Microbicide for drinking water and swimming pools. Artificial radioisotopes as tracers in biological, biochemical and chemical research; in medical imaging. Reagent in analytical chemistry.
Therap-Cat: Antihyperthyroid; anti-infective (topical).
Therap-Cat-Vet: Internally for goiter, hypothyroidism, in iodine deficiency. Topically as antiseptic, disinfectant, counterirritant and to promote absorption.
Keywords: Antihyperthyroid; Antiseptic/Disinfectant; Halogens/Halogen Containing Compounds.

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