Iodine

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Iofina iodine is marketed under the brand names IOflo® and IOprill® based on the form desired.

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Iodine is a shiny, blue-black, solid element, which derives its name from the Greek word ‘iodes’ which means ‘violet’ in reference to its colour observed in the gaseous state. It has an atomic number of 53 and forms one of the halogen group of elements.  Iodine is essential to many forms of life, including human, and is found in thyroid hormones. A lack of iodine in the human body results in a condition known as ‘goitre’ in which the thyroid gland in the neck becomes enlarged. In order to assure an adequate amount of iodine in the diet, table salt in many countries is routinely iodized. Iodine is also used as the core commodity in a wide variety of products and in many cases there is no substitute

 

Science of Iodine

Iodine is included in the element list of the lesser 1/3 in abundance and is therefore classified as a rare element. It is classified as a non metallic element – showing that it has little of the characteristics of metallic elements. Its appearance however is metallic, dark bluish black in color. It is a solid, not a liquid or gas like the halogens above it in the periodic table. It is however volatile and therefore when heated it sublimes to a purple vapor. It is included in the seventh column of the periodic table, fourth in this halogen column. It has a characteristic odor and a sharp acrid taste. Like the other halogen elements it is diatomic, meaning that in its atomic state there are two atoms bound together to give one entity referred to as I2. Elemental Iodine can easily be reduced chemically or electrochemically to iodide ion by the addition of an electron, and can easily be oxidized chemically or electrochemically, yes by removal of from 1 to 7 electrons. It is quite interesting that both the addition of one electron and the removal of from 1 to 7 electrons eliminate the color of elemental Iodine. This interesting fact is extremely useful and used extensively for a number of analytical procedures for Iodine analysis. It is also interesting to note that Iodine is slightly soluble in water; however the addition of iodide ion increases the solubility in water substantially. Iodine’s atomic diameter is quite large and heavy. Its size and weight and physicochemical parameters significantly affect its chemistry when compared to other halogens and make it a most unique and interesting state of elemental matter to work with and include in the development of useful value added products.

In addition to the inorganic chemistry of elemental Iodine there is another class of quite different and interesting chemistry involving bound or organic Iodine chemistry. Iodine combines with other elements such as carbon to produce what is referred to as organo Iodine compounds or organic iodides.

 

A partial list of iodine derivatives includes:

  • 2.3.3 Triiodo allylalcohol
  • 1,4-Diiododurene
  • 2.2.2 Trifluoro-1-iodo ethane
  • 2,3,5 Triiodo sodium benzoate
  • 3,5-Diiodosalicyclic acid
  • 4,4’-Diiododiphenyl
  • Ammonium iodide
  • Barium Iodide
  • Butyl Iodide
  • Cesium Iodide
  • Copper Iodide
  • Cetyl iodide
  • Diacetoamido-triiodobenzoic acid
  • Difluordiiodomethane
  • Diiodobenzoic Acid
  • Diiododiphenyl
  • Ethyl iodide
  • Ethylene iodide
  • Ethylene diamine dihydrooiodide (EDDI)
  • Ethyltriphenyl phosphonium iodide
  • Hydroiodic acid solution (HI)
  • Iodic acid
  • Iodic acid (aqueous solution)
  • Iodine monocholoride
  • Iodine pentafluoride
  • Iodo acetic acid
  • Iodobenzene
  • Iodoxybenzene
  • Iodoform
  • IPBC
  • Iodine disinfectant
  • Iodine Tincture
  • Iron Iodide
  • Isobutyl Iodide
  • Isopropyl iodide
  • Isoquinoline butyliodide
  • Lithium iodide
  • o-Iodotoluene
  • p-Iodotoluene
  • m-Iodotoluene
  • Methyl iodide
  • Methylene iodide
  • Methyltributyl phosphonium iodide
  • n-Butyl iodide
  • n-Hexyl iodide
  • n-Octyl iodide
  • n-Propyl iodide
  • o-Iodotoluene
  • o-Iodonitrobenzene
  • o-Iodobenzoic acid
  • p-Iodobenzoic acid
  • p-Iodotoluene
  • Potassium Iodide
  • p-Tolydiiodo methyl sulfonium
  • Silver iodide
  • Sodium iodate
  • Sodium iodide
  • Tetramethyl oxosulfonium iodide
  • Tetraethyl ammonium iodide
  • Tetramethyl ammonium iodide
  • Tetrabutyl ammonium iodide
  • Thymol iodide
  • Titanium iodide
  • Tin iodide
  • Triiodobenzoic acid
  • Triiodo pheno

Uses

Due to its high reactivity, iodine forms numerous compounds which have a wide variety of medical and industrial uses. Iodine is also considered to be an essential element to human growth. The Institute of Medicine has set the Recommended Dietary Allowance (RDA) for iodine in adult men and women at 150 μg per day. Iodine also has an excellent ability to absorb X-rays and as such is frequently used as a substitute in the production of various diagnostic contrast-media.

Iodine, being a simple substance and having an anti-biotic function by nature, is used as a raw material for the production of various bactericides or disinfectants. Iodine compounds are added to table salt and feed to treat and prevent “iodine deficiency symptom”. Iodine also has a wide range of other uses, for example, in photo-sensitisers, catalysts, stabilisers and polarising films on the liquid crystal display.

 

Iodine General Information

Name, Symbol, Number iodine, I, 53
Chemical series halogens
Group, Period, Block 17, 5, p
Appearance violet-dark gray, lustrous
Standard atomic weight 126.90447(3)  g·mol−1
Electron configuration [Kr] 4d10 5s2 5p5
Electrons per shell 2, 8, 18, 18, 7

Physical properties

Phase solid
Density (near r.t.) 4.933  g·cm−3
Melting point 386.85 K (113.7 °C, 236.66 °F)
Boiling point 457.4 K (184.3 °C, 363.7 °F)
Critical point 819 K, 11.7 MPa
Heat of fusion (I2) 15.52  kJ·mol−1
Heat of vaporization (I2) 41.57  kJ·mol−1
Heat capacity (25 °C) (I2) 54.44  J·mol−1·K−1

Vapor pressure (rhombic)

P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 260 282 309 342 381 457

Atomic properties

Crystal structure Orthorhombic
Oxidation states ±1, 5, 7 (strongly acidic oxide)
Electronegativity 2.66 (Pauling scale)
Ionization energies 1st: 1008.4 kJ/mol
2nd: 1845.9 kJ/mol
3rd: 3180 kJ/mol
Atomic radius 140  pm
Atomic radius (calc.) 115  pm
Covalent radius 133  pm
Van der Waals radius 198 pm

Miscellaneous

Magnetic ordering Nonmagnetic
Electrical resistivity (0 °C) 1.3×107 Ω·m
Thermal conductivity (300 K) 0.449  W·m−1·K−1
Bulk modulus 7.7  GPa
CAS registry number 7553-56-2

 

Selected isotopes

 

iso NA half-life DM DE (MeV) DP
127I 100% I is stable with 74 neutrons
129I syn 15.7×106y β- 0.194 129Xe
131I syn 8.02070 d β- 0.971 131Xe

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