His research did not yield the desired results. But it did lead to the discovery of iodine as a brand new element when Courtois observed an attractive violet vapour arising from his flasks. Iodine is part of thyroxin, a hormone produced by the thyroid gland that controls the body's rate of physical and mental development. A lack of iodine can also cause a goiter, a swelling of the thyroid gland.
Iodine is added to salt iodized salt to prevent these diseases. Iodine is used as a test for starch and turns a deep blue when it comes in contact with it. Potassium iodide KI is used to make photographic film and, when mixed with iodine in alcohol, as an antiseptic for external wounds. A radioactive isotope of iodine, iodine, is used to treat some diseases of the thyroid gland.
Although it neither rid the body of the spirochetes that cause the disease nor achieved a 'cure', it had some effect on the distressing syphilitic ulcers and pustules. In we read:. Multiplied experiments establish that the preparations of iodine possess valuable properties in the treatment of syphilitic diseases. The iodide of potassium is to be preferred to all other preparations.
It is more particularly applicable to the pustular form of the disease and is specific in the tertiary forms This medicine supplies a want which was long felt by the profession but it is doubtful whether it is advisable to combine the iodine and mercury treatment. Although Salvarsan seemed to have a curative effect, particularly on the early stages of the disease, potassium iodide was still being used as late as against the 'tertiary lesions of syphilis'.
Treatment of the disease was revolutionised by the introduction of penicillin in the mids. This killed the spirochetes, curing all stages of the condition although without reversing the significant damage caused to the body during the illness. Nevertheless, venereologists were initially reluctant to give up using KI as an adjunct therapy.
Whilst acknowledging the effectiveness of penicillin and 'the arsenicals', in Dr Walsh MacDermott of New York claimed that potassium iodide was still of value in 'relieving the pain caused by diminished coronary arterial circulation secondary to syphilitic atresia of the coronary orifices'. The pressures of warfare often drive technological advances.
This was not so with iodine. While the urgent need for gunpowder led to kelp being used instead of wood ash, it was work by respected English and French chemists which led to its discovery and identification as a new element. It was the rapid transmission of this information in the scientific literature that led to its early effective medical use.
We cannot forget that iodine is one of the body's essential elements and a constituent of the hormones thyroxine a tetra-iodo compound and tri-iodothyronine.
These regulate the rate of metabolism, affect growth, and influence many other body systems. They are produced in the thyroid, one of the largest endocrine glands in the body. Iodine is absorbed as the iodide ion from foods such as fish, milk and table salt to which iodine is routinely added and is preferentially absorbed into the thyroid gland. The developing thyroid of children is thought to be more sensitive than those of adults.
Potassium iodide tablets, given in some fold usual dietary amounts, can reduce this risk by saturating all the absorptive capacity of the thyroid. If the individual is then exposed to I, very little of this can be absorbed and it is rapidly excreted, protecting against the risk of later thyroid cancer. Alan Dronsfield is emeritus professor of the history of science at the University of Derby. Pat Swain is a retired research scientist and school teacher.
How chemists at Queen Mary University of London are helping secondary school science teachers include the contributions of BAME scientists in their teaching. Site powered by Webvision Cloud. Skip to main content Skip to navigation. No comments. Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K. A measure of the stiffness of a substance.
It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain. A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain. A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.
A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system. This Site has been carefully prepared for your visit, and we ask you to honour and agree to the following terms and conditions when using this Site. Copyright of and ownership in the Images reside with Murray Robertson.
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Discovery date Discovered by Bernard Courtois Origin of the name The name is derived from the Greek 'iodes' meaning violet. Allotropes I 2. Glossary Group A vertical column in the periodic table. Fact box. Group 17 Melting point Glossary Image explanation Murray Robertson is the artist behind the images which make up Visual Elements.
Appearance The description of the element in its natural form. Biological role The role of the element in humans, animals and plants. Natural abundance Where the element is most commonly found in nature, and how it is sourced commercially. Uses and properties.
Image explanation. The image is of seaweed. Many species of seaweed contain iodine. A black, shiny, crystalline solid. When heated, iodine sublimes to form a purple vapour. Photography was the first commercial use for iodine after Louis Daguerre, in , invented a technique for producing images on a piece of metal.
These images were called daguerreotypes. Today, iodine has many commercial uses. Iodide salts are used in pharmaceuticals and disinfectants, printing inks and dyes, catalysts, animal feed supplements and photographic chemicals. Iodine is also used to make polarising filters for LCD displays. Iodide is added in small amounts to table salt, in order to avoid iodine deficiency affecting the thyroid gland. The radioactive isotope iodine is sometimes used to treat cancerous thyroid glands.
Biological role. Iodine is an essential element for humans, who need a daily intake of about 0. Our bodies contain up to 20 milligrams, mainly in the thyroid gland.
This gland helps to regulate growth and body temperature. Normally we get enough iodine from the food we eat. A deficiency of iodine can cause the thyroid gland to swell up known as goitre. Natural abundance. Iodine is found in seawater, as iodide. It is only present in trace amounts 0. In the past iodine was obtained from seaweed. Now the main sources of iodine are iodate minerals, natural brine deposits left by the evaporation of ancient seas and brackish briny waters from oil and salt wells.
Iodine is obtained commercially by releasing iodine from the iodate obtained from nitrate ores or extracting iodine vapour from the processed brine. Help text not available for this section currently. Elements and Periodic Table History.
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