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Iodine


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For disinfectant
Atomic Number:53Atomic Symbol:I
Atomic Weight:126.9045Electron Configuration:2-8-18-18-7
Shells:2,8,18,18,7Filling Orbital:5p5
Melting Point:113.5oCBoiling Point:184oC
Description:Shiny grayish-black flakes. It is a halogen.
Uses:Required in small amounts by humans. Once used as an antiseptic, no longer due to its poisonous nature.

History

(Gr. iodes, violet) Discovered by Courtois in 1811, Iodine, a halogen.

Occurence

occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, in Chilean saltpeter and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and salt wells. Ultrapure iodine can be obtained from the reaction of potassium iodide with copper sulfate. Several other methods of isolating the element are known.

Properties

  • Iodine is a bluish-black, lustrous solid, volatizing at ordinary temperatures into a blue-violet gas with an irritating odor;
  • it forms compounds with many elements, but is less active than the other halogens, which displace it from iodides.
  • Iodine exhibits some metallic-like properties.
  • It dissolves readily in chloroform, carbon tetrachloride, or carbon disulfide to form beautiful purple solutions.
  • It is only slightly soluble in water.

    Uses

  • Iodine compounds are important in organic chemistry and very useful in medicine.
  • Thirty isotopes are recognized. Only one stable isotope, 127I is found in nature.
  • The artificial radioisotope 131I, with a half-life of 8 days, has been used in treating the thyroid gland.
  • The most common compounds are the iodides of sodium and potassium (KI) and the iodates (KIO3).
  • Lack of iodine is the cause of goiter.
  • Iodides, and thyroxin which contains iodine, are used internally in medicine, and as a solution of KI and iodine in alcohol is used for external wounds.
  • Potassium iodide finds use in photography.
  • The deep blue color with starch solution is characteristic of the free element.

    Handling

  • Care should be taken in handling and using iodine, as contact with the skin can cause lesions;
  • iodine vapor is intensely irritating to the eyes and mucous membranes.
  • The maximum allowable concentration of iodine in air should not exceed 1 mg/m^3 (8-hour time-weighted average - 40-hour).

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