Iodine

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

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. It has an atomic number of 53 and forms one of the halogen group of elements, of which it is the least reactive.

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 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

Applications Source: SQM

Sources

Iodine is primarily obtained as a by-product with nitrate minerals that are associated with caliche deposits in places such as the Atacama Desert of Chile. It is present in seawater, which contains about 0.05 ppm iodine, meaning that there are approximately 35 million metric tons of iodine in the world’s oceans, but extraction is impractical at these low concentrations. Iodine was first isolated from seaweed, and dried seaweeds, (particularly those of the Liminaria family) contain as much as 0.45 per cent. iodine. Prior to 1959, seaweed was a major source of iodine and it remains a significant source for iodine in the diets of many people around the world.

Iodine is also retrieved from underground brines (formation waters containing many dissolved salts and ions) which are associated with natural gas and oil deposits as in Japan and the USA. However, production from caliche, as in Chile, is currently the most important and lowest cost source of the element.

Iodine is currently produced in nine countries, with output concentrated in Chile, Japan and the USA. Chilean companies currently control about half of the world’s nominal capacity and account for around 58 per cent. of global production while Japan produces 21 per cent. of the current global supply of iodine. In the USA, which only accounts for 5 per cent of global production, three producers of crude iodine, all Japanese owned operating in Oklahoma, supply about 28 per cent. of domestic demand, with the remainder having to be imported. The supply for iodine has been and continues to be extremely limited. Worldwide Estimated Consumption of Iodine by Region and Country

Iodine Worldwide Production Source: SQM

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, with a recommended daily allowance of 150µg. It 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.

Some of the pharmaceuticals and crop protecting agents have iodine as the substituent. 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. The iodine derivatives market is $5-6.5 billion per year annum with substantial profit margins.

Prices

Iodine is a rare element with a large and diverse range of commercial uses. The current world market is approximately 32,100 metric tons per year, showing a growth rate of 6 per cent. per year between 2000 and 2011 driven by strong growth in existing markets, increased demand from developing countries and the continual development of new uses. Strong growth combined with a tightly controlled supply from just a few countries has resulted in a long term bullish uptrend for iodine prices which have increased over 500 per cent since 2002.

Iodine Substitutes and Alternative Sources

For many of iodine’s uses, there is no comparable substitute. For example, other substances cannot replace its applications in pharmaceuticals, and human and animal nutrition. There are some chemical applications for iodine that can be accomplished using other chemicals. For example, bromine and chlorine can be used in place of iodine for ink and colorant purposes, and for disinfectant purposes.

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

isoNAhalf-lifeDMDE (MeV)DP
127I100%I is stable with 74 neutrons
129Isyn15.7×106yβ-0.194129Xe
131Isyn8.02070 dβ-0.971131Xe
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