Oxidation states and isotopes. Glossary Data for this section been provided by the British Geological Survey. Relative supply risk An integrated supply risk index from 1 very low risk to 10 very high risk. Recycling rate The percentage of a commodity which is recycled. Substitutability The availability of suitable substitutes for a given commodity. Reserve distribution The percentage of the world reserves located in the country with the largest reserves.
Political stability of top producer A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. Political stability of top reserve holder A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. Supply risk. Relative supply risk 6. Young's modulus A measure of the stiffness of a substance. Shear modulus A measure of how difficult it is to deform a material.
Bulk modulus A measure of how difficult it is to compress a substance. Vapour pressure A measure of the propensity of a substance to evaporate. Pressure and temperature data — advanced. Listen to Iodine Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry. Hello, this week cretins, fire crackers and clean water. The story starts in Italy, and here's Andrea Sella. When I was a child, I used spend a couple of weeks each summer high in the Italian Alps in an idyllic little village called Cogne that nestles quietly between high ice-clad peaks.
To most Italians the name is associated with a sensational murder. Others know that in winter the valley has some of the finest ice-climbing in the Alps. But to me, Cogne will always be connected with the element iodine. One afternoon, when I was around 10 years old, returning with my Dad from a long hike, we passed a dull grey building on the edge of the village.
It was surrounded by a tall metal fence and had an institutional look about it. Sitting on the bench all on his own was a strange looking old man - he had rather shaggy hair, a vacant look, and a large, distended pouch of skin where his neck should have been. I was utterly shocked by this strange being. I pestered my father with questions.
Who was he? What was wrong with him? Why did he look so sad? My father, whose patience in the face of a barrage of questions was almost infinite, explained that the poor man had grown up with insufficient iodine in his diet.
Iodine, he went on was essential for the proper development of the thyroid gland in the neck, and that if one didn't eat the right kind of salt, especially as a child, one might develop goitre and one's mental development would also be affected. I would later read of English travellers passing through the Alps referring to The Valleys of the Cretins - travel books of the period often include lurid illustrations of these poor unfortunates. The disease had been known to medical writers for centuries.
Galen for example recommended treatment with marine sponges. In Roger of Salerno recommended seaweed. Similar suggestions were also made in China. Paracelsus, the great renaissance healer, alchemist, and writer was one of the first to spot the connexion between goiter and cretinism, and first suggested that minerals in drinking water might play a role in causing the condition.
But what these mysterious minerals might be was a mystery. In a young French chemist, Bernard Courtois, working in Paris stumbled across a new element. His family's firm produced the saltpetre needed to make gunpowder for Napoleon's wars.
To do this they used wood ash. Wartime shortages of wood forced them instead to burn seaweed, which was plentiful on the coastlines of northern France. Adding concentrated sulphuric acid to the ash, Courtois, obtained an astonishing purple vapour that crystallized onto the sides of the container.
Astonished by this discovery he bottled up the crystals and sent them to one of the foremost chemists of his day Joseph Gay-Lussac who confirmed that this was a new element and named it iode - iodine - after the greek word for purple. Courtois continued to play with the element and was rather shocked to discover that when mixed with ammonia it produced a chocolate-coloured solid that exploded violently at the least provocation.
His contemporary, Pierre Dulong, was less fortunate, losing an eye and part of a hand while studying the material, the first in a long list of casualties from this nasty material.
The toxic qualities of iodine were soon realized, and the tincture, a yellowish brown solution began to be widely used as a disinfectant. Even today, the most common water purification tablets one can buy in travel shops are based on iodine. It was only two years after its discovery, that a doctor in Geneva Francois Coindet began to wonder whether it wasn't the iodine in the seaweed that was the missing mineral responsible for goiter.
He therefore began administering tincture of iodine to his patients by mouth, an unpleasant business, but which, he reported, led to the disappearance of swelling in 6 to 10 weeks.
His colleagues, however, accused him of poisoning his patients, and at one point he was said to be unable to go into the streets for fear of being attacked. But, while elemental iodine clearly was toxic, Coindet was on the right track, and during the 19 th century by a process of one step forward two steps back the hypothesis gradually gained credence as experiments using the more palatable salt, potassium iodide, showed that goitres could be reversed.
By the early 's Swiss cantons began to introduce iodized salt and over the following decades many countries that had been plagued by goitre followed suit, a policy so effective that many of us in the developed world are unaware of how serious a disease this had been and the word cretin has lost much of its meaning. When I returned to Cogne last summer, I tried to remember where the institute had been. All I could find was a summer holiday camp, with children playing happily behind the gates where I had seen the old man.
I phoned my Dad to ask him, and we chatted about the old days - the bad old days of the cretins - and of ghosts banished by that unique purple element, iodine. Ghosts that clearly live on amongst the British aristocracy. Next week we're shining the spotlight on a substance that needs no illuminating at all and that's because it makes its own light.
It was seen as a source of energy and brightness, it was included in toothpastes and patent medicines - it was even rubbed into the scalp as a hair restorer. But the application of radium that would bring it notoriety was its use in glow-in-the-dark paint. Frequently used to provide luminous readouts on clocks and watches, aircraft switches and instrument dials, the eerie blue glow of radium was seen as a harmless, practical source of night time illumination.
It was only when a number of the workers who painted the luminous dials began to suffer from sores, anaemia and cancers around the mouth that it was realized that something was horribly wrong. And you can hear the story of radium from Brian Clegg on next week's Chemistry in its element, I hope you can join us.
I'm Chris Smith, thank you for listening and goodbye. Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists. There's more information and other episodes of Chemistry in its element on our website at chemistryworld. Click here to view videos about Iodine. View videos about. Help Text. Learn Chemistry : Your single route to hundreds of free-to-access chemistry teaching resources.
We hope that you enjoy your visit to this Site. We welcome your feedback. Data W. Haynes, ed. Version 1. Coursey, D. Schwab, J. Tsai, and R. Dragoset, Atomic Weights and Isotopic Compositions version 4. Periodic Table of Videos , accessed December Podcasts Produced by The Naked Scientists. Download our free Periodic Table app for mobile phones and tablets. Explore all elements.
Further saltpetre was produced from sodium nitrate and other nitrates in the mother-liquors, such as calcium and magnesium, by double decomposition using potassium salts from wood ashes:. A shortage of suitable wood ashes for saltpetre production at the time of Courtois' discovery meant that ashes of brown seaweed kelp were being used instead.
The kelp industry began in France in the early 18th century and spread rapidly to places along the Western coasts of Europe, particularly in Scotland, Norway and Ireland. Kelp was a main source of soda Na 2 CO 3 for the growing glass, soap, pottery and textile industries before the Leblanc process provided cheap soda. It was cut and dried on the shore then arranged in hollowed-out pits carpeted with stones. Fires of dry gorse lit over the seaweed slowly fused the masses of kelp, which were then cut into blocks.
After lixiviation aqueous extraction he evaporated the solutions, to yield first a deposit of sodium chloride, then the potassium salts, and finally, crystalline soda. A letter Humphry Davy wrote to the Royal Society on 10 December from Paris provides some details of how Courtois made his discovery:. This substance was accidentally discovered about two years ago by M. In his process for procuring soda from ashes of sea weeds he found the metallic vessels much corroded; and in searching for the cause of this effect, he made the discovery.
The substance is procured from the ashes, after the extraction of carbonate of soda, with great facility, and merely by the action of sulphuric acid: - when the acid is concentrated, so as to produce much heat, the substance appears as a vapour of a beautiful violet colour, which condenses in crystals having the colour and lustre of plumbago. The corrosion in the pots was due to sulfurous and other salts remaining in the mother-liquors.
When the observant Courtois investigated this he used sulfuric acid and noticed the violet vapour of iodine rising from iodides of sodium and potassium in the residue:. Other scientists soon followed Gay-Lussac and Davy's brilliant studies on the new element. Before long the general chemistry of iodine and its compounds was well known. Following research in the s, iodine became valued for its medicinal properties and this led to the French Institute honouring its discoverer, Bernard Courtois, with a prize in There were no immediately obvious uses for this element.
Its applications in photography and dyestuffs date from the later years of the 19th century. However it was soon adopted by some physicians, and in it was being prescribed, hopefully rather than scientifically, for. There were three indications where it was effective, leading to its widespread use in the later 19th century: in killing germs; in treating goitre; and in relieving some symptoms of syphilis. The latter surgeon used phenol solution to sterilize skin, instruments and dressings, significantly reducing post-operative morbidity and mortality caused by infection.
Nevertheless it was used to sterilize surgical sutures silk threads used for stitching wounds from about Its relative expense did not prevent it becoming popular in home medicine chests, where it was poured onto wounds in the hope of preventing infection. The intense stinging pain it caused probably convinced the unhappy patient that good was being done. In truth, cleaning the tissues with soap and water would have served equally well.
Iodine certainly kills bacteria in test tubes. On open wounds it destroys healthy tissues too and probably delays healing overall and increases scar tissue formation. Today the tincture is most frequently used for 'emergency' sterilization of drinking water.
Its successor, Povidone , is a stable complex of polyvinylpyrrolidone and elemental iodine. This releases its iodine very slowly, reducing skin irritation and stinging! It is used in pre- and post-operative skin cleansing, for the treatment and prevention of infection in wounds, ulcers, cuts and burns; and for some eye and gynaecological infections.
However, its benefits are still debated. Goitre is a swelling of the thyroid gland in the neck. It can become very large and rarely causes harm unless it is so big that it obstructs swallowing or breathing, but can be unsightly. It was more common in the Midlands than the coastal regions of the UK and was formerly known as 'Derbyshire neck'.
Writing in , the physician-chemist William Prout recollected that he had used iodine to treat the disease only three years after its discovery was announced. Unlike Prout, he promptly published his findings in , which changed practice across the western world:.
Iodine is required for the synthesis of thyroid hormones thyroxine T 4 and triiodothyronine T 3. T 4 and T 3 contain four and three atoms of iodine per molecule, respectively. These hormones are vital to human health as they control the production and utilization of energy throughout the entire body. In very severe cases of iodine deficiency in pregnant women, babies can be born with congenital hypothyroidism or cretinism, now considered a derogatory term , a condition of severely stunted physical and mental development.
Overall, iodine deficiency affects about 2 billion people worldwide and is the leading preventable cause of mental disability in developing areas of the world, according to Synapse , an Australian brain injury organization. India has the highest prevalence of iodine health conditions, with million people suffering from deficiency, 54 million from goiter and 2 million from full-blown hypothyroidism, according to Synapse.
The U. 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. Since iodine is needed in only trace amounts, getting too much of it can cause health problems as well.
American pathologist David Marine is credited with getting the ball rolling toward putting iodine in salt. On his first day as a new doctor in Cleveland in , Marine was immediately struck with how many people, and even dogs, were walking around with swollen necks, indicative of a widespread goiter problem.
In fact, the condition had become so pervasive that a large stretch of land from the Rockies to the Great Lakes region to western New York was known as the "goiter belt. After exploring a few hypotheses and coming up empty-handed, Marine began experimenting with iodine supplements. He conducted one of the first ever large-scale human experiments by giving miniscule doses of iodine to 2, healthy goiter-free students in Akron, Ohio. A control group of 2, healthy students were not given any iodine but were still closely monitored.
The results were astounding. Of the 2, who received iodine, only five eventually developed a thyroid condition, compared to individuals in the control group. Although there had been some existing research at the time linking iodine to the thyroid gland, Marine conclusively established that iodine was indeed an essential element for life and one in whose absence could result in severe health problems. Marine's important findings led to the first iodized salt being sold in the United States in
0コメント