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Transcript :
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You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.
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Chris Smith
Hello and this week to the story of the element that's named after a rooster although the man here to tell us about it actually chickened out when it came to eating some of this chemical, although he did confess to giving it a quick lick. And to tell us how it tasted and why Gallium could hold the key to the next generation of LEDs, here's Andrea Sella.
Andrea Sella
When I was a child growing up in New York, some of the sweets most sort after by my classmates and me, with yellow and brown packs of highly coloured sugar coated chocolate pills bearing the characters M & M. You could pop them into your mouth one by one and suck them gently until the smooth surface became crumbling to reveal the smooth milk chocolate beneath; alternatively you cold cram your mouth with as many as you could and crunch them greedily to cause an explosion of sound, texture and flavour in your head. A secret pleasure that was hard to beat. I was reminded of all this when a colleague of mine who was having a lab clear out, knocked on my door and asked me knowing full well what my answer would be, 'Hi Andrea, would you like a lump of Gallium?', 'of course I would love some Gallium', I gurgled. The M & M of the elements; the one which reputedly melts in your mouth but not in your hand, he handed me a small plastic bag badly stained with black smudges. I undid the knot eagerly and there it was, a gleaming silvery lump bearing all the hallmarks of a metal that had been repeatedly melted and then refrozen.
Gallium, you see, melts at 30oC, which means that on a hot day, you hold it in your pocket at your peril. Surprisingly however it's not very volatile. In fact Gallium has the largest liquid range of any material known to man. Its boiling point is just over 2400oC. So unlike other liquid metals, there is no toxic vapour to worry about. Bizarrely as well, the metal contracts as it melts, rather like water. So solid Gallium floats on its liquid, a property shared only by a couple of other elements, Bismuth and Antimony. The reason for this weird melting behaviour has been a matter of argument and speculation for about 50 years. It's now fairly well established that Gallium surrounds itself with more of its neighbours when in the liquid than in the solid, although the reasons for this still remains obscure.
Yet for all its strangeness the discovery of this odd element was no accident. Dmitri Mendeleev, the bearded Russian chemist who constructed the periodic table as we know it today, spotted a number of gaps and discrepancies in his arrangement. One of these was the absence of an element which he expected to fit below Aluminum. So confident was he in the correctness of his framework that he named the as yet undiscovered element ekaaluminium. Six years later in 1875, an ambitious French element hunter François Lecoq de Boisbaudran one of the earliest proponents of the new-fangled technique of spectroscopy spotted a line in the violet part of the visible spectrum at 417nm in a sample of zinc sulphide, he realized that this must come from a new element. Working in his home laboratory in spite of starting from some 52 kilos of an ore from the Pyrenees, it took three weeks for him to accumulate a couple of milligrams of the mysterious material. He then scaled up his extraction and took the product of his labours to Paris where he studied it further in Adolphe Wurtz's lab. Just before Christmas in 1875, Lecoq presented his results to the French academy proudly displaying a sample of almost 600mg, less than a gram of material harvested from 450 kilos of ore. And the name Lecoq patriotically chose to base it on the Latin name for France, Gallia; Gaul in English. But it was immediately pointed out that there might be something more to the name than met the eye. The Latin word for a rooster is Gallus, Lecoq, rooster, Gallium, get it. It seems he may have been a rather cunning linguist as well as a chemist. Either way, Lecoq could look back with some satisfaction at having helped to cement Mendeleev's table, was the foundation stone of chemistry. He then moved on to the intriguing mystery of the 'rare earths', ultimately isolating two more elements and conforming the existence of several more.
Gallium soon moved into the main stream of chemistry. Nowadays the metal itself finds few uses, but its compound with arsenic, gallium arsenide has for several years been touted as a possible replacement for Silicon. Since not only is it a semiconductor but it is one with a direct band gap, in other words it can be made to emit light, a property which is particularly useful for infrared but also visible LEDs. Gallium arsenide solar cells are also much more efficient than those made of conventional Silicon and are being used in solar powered cars and in space probes.
But I'm sure you really want to know is, if this really is the M & M element, what does it taste like? I knew you would ask. So I had a quick lick a couple of days back and the answer is it doesn't actually taste very much to be honest. There's a faintly astringent, metallic taste which lingers on your tongue for few hours. And when it is molten, sorry I'll leave that experiment for someone more intrepid than I.
Chris Smith
UCL chemist Andrea Sella with the story of gallium, the element that Lecoq allegedly named after himself. Next week we are meeting the metal that powers nuclear rectors but can also be lethal for another reason.
Polly Arnold
Because it is so dense DU is also used in shielding in the keels of boats and more controversially in the noses of armour piercing weapons. The metal has the desirable ability to self sharpen as it pierces a target rather than mushrooming upon impact, the way conventional tungsten carbide tipped weapons do.
Chris Smith
DU being Depleted Uranium of course and Edinburgh chemist Polly Arnold will be here to tell us its story as well as revealing why it actually makes very beautiful glass on next week's Chemistry in its element. I hope you can join us. I'm Chris Smith, thank you for listening and good bye.
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Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com . There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements
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Ever since the Bronze age, people have been seeking novel ways to develop, refine, and utilize metal. Thousands of types of metal and just as many grades allow for applications and uses that are bound only by the limits of our creativity. As a foundation of many industries and at the very root of the Industrial Revolution itself, metals have supported the development and growth of not just our society but civilization as a whole. From buildings and infrastructure to household appliances, each day we're surrounded by at least eighty different types of metal. The following five types of metal are some of the most popularly used worldwide. We have explored some of their infinite uses and provided a few insights about each specific metal type.
Steel is an iron alloy enriched with around 1% carbon and it is generally free of the impurities and residues that can otherwise be found in iron. While iron itself is stronger than other metals, it is remarkably heavy, dense, and prone to corrosion. For these reasons, purely iron structures can be difficult to build and maintain. Not only does adding carbon to iron mitigate these vulnerabilities, but it also makes the material stronger. Additionally, steel has a rather high strength to weight ratio compared to other types of metals, which enables the manufacturing of small yet strong steel parts. With over 3500 different grades and almost 2 billion tons of steel manufactured globally each year, steel is the most commonly used metal in the world. With the number of different elements and varying qualities of those elements being added to create steel alloys there are a multitude of different types of steel. Without further ado, let's dig deeper into the world of steel!
Alloy steel is made by combining elements such as chromium, manganese, nickel, tungsten, or vanadium with iron. Each of the alloying elements brings different properties to the mix, thus making the alloy steel highly customizable. Depending on the needs of the project, the specific alloy can be modified to produce many desired qualities, a couple of which might be a higher material strength or a product that is more resistant to wear and corrosion. Alloy steel can be relatively inexpensive to produce, making it very widely used.
Stainless steel is a highly corrosion-resistant alloy steel that consists of iron, carbon, significant amounts of chromium and residues of other metals. It is a versatile material widely applied in many households. From kitchen utensils to tables, sinks, and other furniture, stainless steel is perfect for the manufacturing of anything that comes into contact with food because it doesn't rust easily.
Carbon steel is an alloy made of iron and carbon, sometimes with residues of other elements. It is commonly categorized into three groups (low, medium, and high carbon steel) based on the amount of carbon the alloy contains. The more carbon is used to manufacture steel, the harder the alloy will be. On the other hand, small amounts of carbon make for an alloy that is easier and cheaper to manufacture. Carbon steel is often used to produce tools and mechanical elements but is best known as a structural building material.
Due to its hardness, tool steel is used for the manufacturing of cutting, drilling, and other shock-resistant tools. The hardness comes from alloying iron with elements such as cobalt, molybdenum, tungsten, or vanadium. Tool steel has a wide variety of applications, including construction, shipbuilding and automotive industries. It is primarily used to machine and make changes to different kinds of steel.
With around 5% of the Earth's crust and as the 6th most common element in the universe, iron is a highly abundant and immensely popular metal. Unalloyed iron is an unstable element that easily reacts with the oxygen from the air and forms iron oxide. In order to make it more stable, it is commonly alloyed with other elements to create steel. Iron finds its application in cookware because its porous surface combined with hot oil prevents sticking. Due to its remarkably high melting point, cast iron is used for the production of wood stoves. Being a heavy metal, iron provides rigidity and reduces vibrations, which is why it is often used for the manufacturing of heavy machinery frames and bases.
Aluminum is a highly durable, light-weight and corrosion-resistant metal derived from its ore bauxite. First made in the 19th century, aluminum found wide-spread use due to its machinability, electrical conductivity, and inability to magnetize. It is the most common non-ferrous metal on Earth, known for its malleability and ability to form alloys with almost all other metals. Aluminum has an impressive strength-to-weight ratio, and even though it doesn't rust, it oxidizes and corrodes when it is exposed to salt. Its applications are wide: from cans and household appliances to airplanes.
Zinc is a common metal with a low melting point. Because it flows smoothly in its melted form, it is easy to cast and recycle. The end product is quite strong and has low electrochemical potential. Zinc is used to coat and protect other metals, as well as to prevent rusting in galvanized steel. Its applications include the industrial, marine, and medical sectors, as well as hardware, electrical and automotive industries.
Bronze is made by alloying copper and tin, and often small amounts of elements such as aluminum, manganese, silicon or phosphorus. As the first human-made alloy, bronze is incredibly historically significant - thus the “Bronze Age.” Even though it is brittle, bronze is a hard element known to resist fatigue that doesn't bend or crack. Due to its high corrosion resistance and solid thermal and electrical conductivity, it is used for the manufacturing of electrical connectors, church bells, ship parts and reflectors. In addition to the five most popular metals outlined above, Texas Iron & Metal offers a large inventory of materials that may be suitable for your next project. Call us at 800.839.4766 or request a quote here and one of our knowledgeable representatives will gladly help you find the perfect type of metal.
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