top of page


Iodine and its derivatives are indispensable in a wide range of nutritional, pharmaceutical and industrial applications.

For optimal development of growth in humans and animals, adequate iodine intake is imperative. Iodine is an essential constituent of the thyroid hormones, and 80 per cent of the iodine in the mammalian body is found in the thyroid gland. Iodine deficiency disorders (IDD) occur when sufficient iodine lacks in the diet. Mild deficiencies can cause mental and physical retardation in humans, and skin-disorders or loss of production in livestock and poultry. More severe effects of IDD include goiter, a swelling at the front of the neck caused by the increase in size of the thyroid gland, abnormal physical development and reproductive loss. The iodine content in diets needs to be balanced. Too much iodine can also compromise thyroid function.

Screenshot 2023-07-18 at 10.13.08.png

Elemental Chemistry

Iodine is the first member of the halogen family to be solid at ordinary temperatures in its elemental state. The most striking property of elemental iodine is its capacity to change states when exposed to heat: from solid dark purple crystals to vivid violet gas. It also has an unusually high specific gravity, and can be rather easily either reduced or oxidized to one of a diversity of ionic states, resulting in a range of positive or negative validities. Iodine is only slightly soluble in water, but dissolves in many organic solvents and the color of the resulting solutions varies with the nature of the solvent from violet to brown color.


The oxidizing properties of iodine containing compounds and their benign environmental character -compared to other halogens- stimulate the development of industrial uses. New uses for the reactivity of iodine and its derivatives in the synthetic and structural chemistry are still being developed.

Screenshot 2023-07-18 at 10.13.08.png

Iodine Diversity

Elemental Iodine is easily reduced or oxidized. The ease of these chemical reactions gives rise to a high diversity of ionic, iodine containing molecules. Ionic iodine can be found in different states of validity, often bound to oxygen or hydrogen. For instance, in the salt Potassium Iodide (KI), iodine is present with a negative validity (1–) in the ion I–. In the salt Potassium Iodiate (KIO3), iodine is molecularly bound to oxygen, and is present with a positive validity (5+) in the ion IO3–. The reducing or oxidative properties of iodine containing molecules make them particularly suitable as catalysts in a wide range of chemical synthesis processes.


In its elemental state, Iodine can be bound to carbon, oxygen or hydrogen in organic molecules. These can be relatively small molecules, such as methyliodide (CH3I), or complex molecules, for instance when Iodine is incorporated in organic matter in the soil to iodo-organic molecules, or in mammalian thyroid hormones.


Iodine Sources

No less than 99.6% of the earth’s mass can be accounted for by thirty-two of the chemical elements. The remaining 0.4% is apportioned among sixty-four elements, all of which are present as traces. Iodine is number 61 on this list, making Iodine one of least abundant non-metallic elements in the total composition of the earth.


Although not abundant in quantity, iodine is distributed almost everywhere. It is present in rocks, soils, waters, plants, animal tissues and foodstuffs. Except for a few rare occasions, elemental iodine is not readily found in nature. Iodine is mostly found combined with other elements, such as oxygen, hydrogen or carbon. Due to the ease with which it can accept or donate electrons in its ionic states, it is readily incorporated in inorganic salts or complex organic compounds such as the mammalian hormone thyroxine.


A few substances characteristically contain iodine in relatively large quantities. Natural accumulating organisms are seaweeds, sponges and corals. For industrial purposes, the main sources of Iodine are deposits of minerals, either as solid ore (Caliche) or in underground brines. The iodine in these deposits is chiefly of oceanic origin, transferred to the atmosphere as iodine-rich organic material and as gaseous iodine formed by photochemical oxidation of iodine at the ocean surface.

Screenshot 2023-07-18 at 10.13.08.png

Iodine Sources

Caliche Ore

Caliche is the name for the deposits of natural saltpeter containing minerals in the Atacama Desert of northern Chile and west of the Andes Mountains. Lautarite [Ca (IO3)2] and Dietzeite [7Ca (IO3)2] * 8CaCrO4], are the two crystalline forms in which iodine naturally occurs in caliche ore with an iodine content of around 0.04% (400 ppm).


To become part of the Caliche deposits, iodine was oxidized to iodate by photochemical reactions in the troposphere and at ground level in the nitrate fields.

Underground Brines

In subsurface brines associated with oil and gas deposits, iodine occurs frequently as sodium iodide with an iodine concentration in the range of 30 to 150 ppm. About 45% of the iodine currently consumed in the world comes from brines processed in Japan, the USA, the Community of Independent States (CIS) and Indonesia.


Before the development of iodine extraction from caliche, seaweed was an important source. Today, no more than 2% of the total iodine consumption comes from this source. Some types of seaweed, particulary brown seaweeds of the Laminaria family, contain significant amounts iodine in the form of sodium and potassium iodide. Iodine concentration is variable, on average around 950 ppm in dried seaweed. Seaweed is grown by companies dedicated to production of this crop.


Iodine is obtained as a by-product in the processing of sodium alginate from seaweed. Yearly output is dependent on the crop and harvest efficiencies which are subject to environmental factors.

Should you wish to receive more detailed information about this topic, or specific applications of iodine within your sector, please feel free to contact the World Iodine Association

Screenshot 2023-07-18 at 10.13.08.png


Rue Belliard 40

1040 Brussels, Belgium



  • Twitter
  • LinkedIn
bottom of page