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Iodine is a rare nonmetallic element found in seawater, algae, and some minerals. It is essential for human nutrition and has useful applications in medicine and chemistry. Iodine deficiency can cause health problems, but the element is toxic in its elemental form. It is used as a laboratory reagent, in the production of acetic acid and iodized salt, and as a tracer in medicine. The element was first prepared in 1811 and is mostly obtained from brine or sodium iodate.
Iodine is a nonmetallic chemical element with the symbol I and atomic number 53. It is part of a group of elements known as halogens, which also include fluorine, chlorine, and bromine. Like most of the heavier elements, it is quite rare in the universe, but is found in seawater, algae and some minerals. It is an essential trace element required for proper human nutrition, but is toxic in its elemental form. Iodine has a number of useful applications, especially in medicine, and is a common reagent used in chemistry laboratories.
Property
Iodine is a dark gray, lustrous solid with a slightly bluish tinge. When heated, some fusion occurs, but much of the substance turns directly into vapor, which has a deep purple color. The vapor, once cooled, condenses directly into small solid crystals. The element is only slightly soluble in water, but dissolves easily in many organic solvents, such as ethanol, acetone, and chloroform.
Like the other halogens, this element is an oxidizing agent, meaning it will accept electrons to form compounds, but it is a less potent oxidizer than fluorine, chlorine, or bromine. In common with these elements, it will form ionic compounds with metals by accepting an electron, giving a positively charged metal ion and a negatively charged iodide ion; an example is potassium iodide. It will also form covalent compounds with other nonmetals, including hydrogen and many organics.
Salute
Iodine is required by the thyroid gland, which produces a number of important hormones that contain the element. It is also essential for proper brain development in unborn babies and young children. The recommended daily intake of iodine is usually measured in micrograms (mcg) or thousandths of a gram and varies based on age and a few other factors. For example, children between one and eight years of age should get about 90 mcg a day and breastfeeding women about 290. Good dietary sources of this nutrient are fish and other seafood, seaweed, breads, grains, and dairy products.
Iodine deficiency can be a problem in some parts of the world. It can present as goiter – a condition of the thyroid gland – and in retarded growth and poor intellectual development. People living in regions with a deficiency of this element can take a suitable supplement. The element, however, should not be ingested in its uncombined form, as it is toxic and corrosive; instead, it is usually given in the form of nontoxic iodide salts, such as potassium iodide. These are sometimes added to table salt to make iodized salt.
it is used
Many people are familiar with tincture of iodine, a brown solution of the element in alcohol, used medicinally as a germicide or antiseptic. Its oxidizing properties make it effective in killing harmful microorganisms. A solution of the element in water, together with potassium iodide, which increases its solubility, is sometimes used as a disinfectant and for emergency drinking water purification. In industry, one of the major uses of iodine is in the production of acetic acid from methanol. Other industrial uses include the production of iodized salt and the red dye, erythrosine, which is used as a food colorant and in some colored inks.
In medicine, small amounts of a radioactive isotope of the element can be used as a tracer to check the functioning of the thyroid gland. It can also be used to treat thyroid cancer in such a way that it is taken up by the cancerous cells and not the healthy ones. Radioactive iodine is also produced by nuclear tests and accidents and, if inhaled or ingested, tends to accumulate in the thyroid gland, where it can cause damage or cancer. For this reason, in the event of an accident at a nuclear power plant, people in the immediate vicinity may be given potassium iodide tablets: these provide a safe way to absorb the non-radioactive form of the element, in order to stop the buildup of potassium. radioactive form in the thyroid.
As a laboratory reagent, the element is often used in analytical chemistry. For example, it is used in a very sensitive chemical test for starch, as the two react to form a compound with a deep dark blue color. This test can be used to detect very small amounts of starch. Unsaturated fats can combine with amounts of iodine that are proportional to the degree of unsaturation: the less the fat is saturated, the more element it will consume. This forms the basis of the iodine value that can be given to fats.
Production
The element was first prepared in 1811 by Bernard Courtois, when he treated seaweed ash with sulfuric acid. He got a purple vapor, which condensed into crystals. Today, most iodine comes from brine, which contains iodides, or from sodium iodate, which is present in a type of calcium carbonate rock called caliche.
