Iodine (I), chemical element, a member of the halogen elements, or Group 17 (Group VIIa) of the periodic table. Iodine is never found in nature uncombined, and it is not concentrated sufficiently to form independent minerals. It is present in seawater, but sparingly, as the iodide ion, I−, to the extent of approximately 50 mg per metric ton (0.0016 ounce per ton) of seawater. It is also formed in seaweeds, oysters, and cod livers. Continue reading from Encyclopedia Britannica
In 1811 the French chemist Bernard Courtois obtained a violet vapour by heating seaweed ashes with sulfuric acid as a by-product of the manufacture of saltpetre. This vapour condensed to a black crystalline substance, which he called “substance X.” In 1813 British chemist Sir Humphry Davy, who was passing through Paris on his way to Italy, recognized substance X as an element analogous to chlorine; he suggested the name iodine from the Greek word ioeides, “violet coloured.” Continue reading from Encyclopedia Britannica
Iodine is an essential element needed for life. It is best known for the vital role it plays in thyroid hormone production in humans as well as in all vertebrates. Iodine deficiency can lead to serious health problems, including goiter (enlarged thyroid gland), intellectual disability and cretinism.
The U.S. recommended daily intake of iodine is 150 micrograms (mcg) per day for adults and approximately double that amount for pregnant and nursing women. Sea vegetables and animals — particularly seaweeds (wakame and kelp), scallops, shrimp and cod — have the highest concentrations of iodine, but iodine also comes from land-based food sources, such as plants that grow in iodine-rich soil or from dairy products and eggs as long as the cows and chickens had enough iodine in their diets. Iodine is a component of nuclear fallout, the residual radioactive material that falls from the sky after a nuclear blast. Photography was the first commercial use for iodine. Continue reading from LiveScience
