 Occurrence
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| Iodine naturally occurs in the environment chiefly as dissolved iodide in seawater, although it is also found in some minerals
and soils. The element may be prepared in an ultrapure form through the reaction of potassium iodide with copper(II) sulfate. There are also a few other methods of isolating this element. Although the element is actually quite rare, kelp
and certain other plants have the ability to concentrate iodine, which helps introduce the element into the food chain as
well as keeping its cost down.
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| Iodine is found in the mineral Caliche, found in Chile, between the Andes and the sea. It can also be found in some seaweeds as well as extracted from seawater, however extracting
Iodine from the mineral is the only economical way to extract the substance.
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| Extraction from seawater involves electrolysis, the brine is first purified and acidified using sulphuric acid and is then
reacted with chlorine. An iodine solution is produced but it is yet too dilute and has to be concentrated. To do this air is blown into the solution
which causes the iodine to evaporate, then it is passed into an absorbing tower containing acid where sulfur dioxide (SO2) is added to reduce the iodine, the solution is then added to chlorine again to concentrate the solution more, the final solution is the iodine at a level of about 99%.
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| Another source is from kelp. This source was used in the 18th and 19th centuries but is no longer economically viable. |
| In 2005, Chile was the top producer of iodine with almost two-thirds world share followed by Japan and the USA reports the British Geological Survey.
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