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Minerals in Detail
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
IODINE
Iodine - chemical details
| Symbol | I |
| Atomic number | 53 |
| Atomic mass | 126.9045 g.mol-1 |
| Electronegativity | 2.5 (according to Pauling) |
| Mass volume | 4.93 g.cm-3 at 20°C |
| Melting point | 114 °C |
| Boiling point | 184 °C |
| Vanderwaals radius | 0.177 nm |
| Ionic radius | 0.216 nm (-1) |
| 0.05 nm (+7) |
| Isotopes | 15 |
| Electronic configuration | [ Kr ] 4d10 5s25p5 |
| Energy of first ionisation | 1008.7 kJ.mol-1 |
| Standard potential | + 0.58 V ( I2/ I- ) |
| Discovered | 1811 - Bernard Courtois |
Chemical Details | Description | Industrial Applications |
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Iodine - Description
Iodine is a non-metallic, dark-gray/purple-black, lustrous, solid element. Iodine is the most electropositive halogen and the least reactive of the halogens,
even if it can still form compounds with many elements. Iodine evaporates easily on heating to give a purple vapour. Iodine dissolves in some solvents, such
as carbon tetrachloride, but it is only slightly soluble in water.
Chemical Details | Description | Industrial Applications |
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Iodine - Industrial applications
Iodine is used in medicine, photography, and water purification. For details on
industrial applications and impact on the environment see www.lenntech.com/Periodic-chart-elements/I-en.htm
Chemical Details | Description | Industrial Applications |
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Iodine - In natural form
The most important source of natural iodine is the oceans. Iodine is naturally present in the ocean, and some marine animals and plants will store it in
their tissues. About 400.000 tonnes of iodine escape from the oceans every year as iodide in sea spray or as iodide, hydrichloric acid and methyl iodide,
produced by marine organisms. Much of it is deposited on land where it may become part of the biocycle. Consequently Iodine can be found naturally in air,
water and soil.
There are some iodine-containing minerals, such as
alutarite, found in Chile and iodargyte, found in Colorado, Nevada and New Mexico. World-wide industrial production of iodine is about 13.000 tonnes per
year, mainly in Chile and Japan, plus small amounts in Russia and USA. Iodine is extracted from natural brines and oil brines, which have up to 100 ppm of
the element or form chilean nitrate deposits. Known reserves of easily accessible iodine amount is around 2 million tonnes.
Iodine is added to nearly every kind of salt. It is an ingredient in bread, sea fish and oceanic plants.
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Iodine - Impact on health
Iodine is an essential trace element, the heaviest-known element needed by living organisms. Its main role in animal biology is as constituents of the
thyroid hormones, thyroxine (T4) and triiodothyronine (T3). T4 and T3 contain four and three atoms of iodine per molecule, respectively. The
thyroid gland actively absorbs iodide from the blood to make and release these hormones into the blood, actions which are regulated by a second hormone TSH
from the pituitary. Thyroid hormones are phylogenetically very old molecules which are synthesized by most multicellular organisms, and which even have some
effect on unicellular organisms.
Thyroid hormones play a basic role in biology, acting on gene transcription to regulate the basal metabolic rate. The total deficiency of thyroid hormones
can reduce basal metabolic rate up to 50%, while in excessive production of thyroid hormones the basal metabolic rate can be increased by 100%. T4 acts
largely as a precursor to T3, which is (with minor exceptions) the biologically active hormone.
Iodine accounts for 65% of the molecular weight of T4 and 59% of the T3. 15-20 mg of iodine is concentrated in thyroid tissue and hormones, but 70% of the
body's iodine is distributed in other tissues, including mammary glands, eye, gastric mucosa, cervix, and salivary glands. Its role in mammary tissue is
related to fetal and neonatal development, but its role in the other tissues is unknown.1 It has been shown to act as an
antioxidant in these tissues.1
So to summarise, iodine is a building material of thyroid hormones that are essential for growth, the nervous system and the metabolism. Humans that eat
little to no bread can experience iodine shortages. The function of the thyroid gland will then slow down and the thyroid gland will start swelling up. This
phenomenon is called struma. This condition is rare now as table salt is dosed with a little iodide.
Many medicines and cleansers for skin wounds contain iodine.
Iodine may have a relationship with selenium, and iodine supplementation in selenium-deficient populations may pose risks for thyroid function.1
Large quantities of iodine can be dangerous because the thyroid gland will labour too hastily. This affects the entire body; it causes disturbed heartbeats
and loss of weight.
Chemical Details | Description | Industrial Applications |
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Iodine - Recommended daily & maximum intake
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Risk free |
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intake? |
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Food sources? |
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Result of overdose? |
| Age Group |
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RDA |
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Limit |
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Infants
0-6 mo
7-12 mo
Children
1-3 y
4-8 y
Males
9-13 y
14-18 y
19-30 y
31-50 y
50-70 y
> 70 y
Females
9-13 y
14-18 y
19-30 y
31-50 y
50-70 y
> 70 y
Pregnancy
< 19 y
19-30 y
31+ y
Lactation
< 19 y
19-30 y
31+ y |
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(ug/d)
110.0
130.5
90.0
90.0
120.0
150.0
150.0
150.0
150.0
150.0
120.0
150.0
150.0
150.0
150.0
150.0
220.0
220.0
220.0
290.0
290.0
290.0 |
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(ug/d)
ND
ND
200.0
300.0
600.0
900.0
1,100.0
1,100.0
1,100.0
1,100.0
600.0
900.0
1,100.0
1,100.0
1,100.0
1,100.0
900.0
1,100.0
1,100.0
900.0
1,100.0
1,100.0 |
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Iodised salt
Marine food
Processed food |
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Elevated TSH (thyroid stimulating hormone) concentration |
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Explanations:
ND = Not determinable. There is either insufficient data on adverse effects and/or concern with the body's ability to handle excess amounts. In most
instances it is wise not to supplement for this particular element, but to rely on diet to provide sufficient quantities.
RDA = Recommended Dietary Allowance. May be used as a goal for daily intake. RDAs are set at a level that should meet the needs of 97-98% of all individuals.2, 3, 4, 5
Limit = The maximum level of daily nutrient intake from all sources that is highly likely to pose no risk of adverse effects.2, 3, 4, 5
References:
- Patrick, L. (2008). Iodine: deficiency and therapeutic considerations. Altern Med Rev 13 (2): 116–27.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (1997). Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6,
Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (2000). Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Food and Nutrition Board: Institute of Medicine.
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