Beryllium

Chris Smith

Hello, this week to the element that the big bang forgot but which has bounced back as the stuff that the world's best springs are made from. It's also given us gorgeous gemstones, spark proof tools for the oil industry and a deadly lung condition.  

Richard Van Noorden

Only hydrogen, helium and lithium were formed during the big bang itself. The next element, beryllium, is relatively rare in the universe because it is also not formed in the nuclear furnaces of stars. It takes a supernova, in which heavier nuclei disintegrate, to make this metal. 

Earlier plans to use beryllium on a large scale in the aerospace industries did not materialise even though it lightness and strength made it seem an ideal metal for such purposes. At one time it was even thought that beryllium powder would be used as a fuel for rockets on account of the colossal amount of heat which it releases when it is burnt. Now less than 500 tons of metal are refined each year because it is dangerously toxic.

Beryllium has no known biological role, and its dust causes chronic inflammation of the lungs and shortage of breath. Brief exposure to a lot of beryllium, or long exposure to a little, will bring on this lung condition which is known as berylliosis. The disease may take up to five years to manifest itself and about a third of those who are affected by it die prematurely and the rest are permanently disabled. Workers in industries using beryllium alloys were most at risk, such as those making early types of fluorescent lamps which were coated inside with an oxide film containing beryllium. In 1950 the manufacture of this type of lamp ceased. 

The minerals beryl and emerald are beryllium silicates and were known to the ancient world; the emperor Nero used a large emerald the better to view gladiatorial fights in the area. Their beautiful green colour is due to traces of chromium. Analysis of the oxygen in these gems enables their source to be identified because the isotope ratio of oxygen-18 to oxygen-16 varies according to where the mineral is found. The Romans got their emeralds mainly from Austria, although some came from as far away as Pakistan. More surprising was the discovery that the Mogul rulers of India got some of theirs from Colombia in South America probably via trade across the Pacific. The chief ores of beryllium are beryl and bertrandite, which is also a silicate. Sometimes truly enormous crystals of bertranide turn up, one specimen found in Maine in the USA was over 5 metres in length and weighed almost 20 tonnes. 

That beryl and emerald might harbour a new element was suspected by the 18th century and Nicholas Louis Vauquelin analysed them, and on 15 February 1798 he announced that they contained a new element – but he was unable to separate it from its oxide. Beryllium metal was isolated in 1828 from beryllium chloride (BeCl₂) by reacting this with potassium.

Beryllium was to play a historic role in advancing our knowledge of atomic theory since it helped uncover the fundamental particle, the neutron. This was discovered in 1932 by James Chadwick who bombarded a sample of beryllium with the alpha-rays (which are helium nuclei) emanating from radium. He observed that it then emitted a new kind of subatomic particle which had mass but no charge. The combination of radium and beryllium is still used to generate neutrons for research purposes, although a million alpha-particles only manage to produce 30 neutrons. 

Beryllium is a silvery-white, lustrous, relatively soft metal of group 2 of the periodic table. The metal is unaffected by air or water, even at red heat. When copper and nickel are alloyed with beryllium they not only become much better at conducting electricity and heat, but they display remarkable elasticity. For this reason their alloys make good springs and the copper alloy is used to make spark-proof tools, which are the only ones allowed in sensitive areas such as oil refineries.

Beryllium has but a single isotope, beryllium-9 which is not radioactive but beryllium-10, which cosmic rays produce in the upper atmosphere, is radioactive with a half-life of 1.5 million years. Radioactive beryllium-10 has been detected in Greenland ice cores and marine sediments and the amount that has been measured in ice cores deposited over the past 200 years increases and decreases in line with the Sun's activity, as shown by the frequency of sun-spots. The amount of this isotope in marine sediments laid down in the last ice age was 25% higher than that in post-glacial deposits. That tells us that the Earth's magnetic field was much weaker then than it is now.

Chris Smith

Richard Van Noorden with the story of beryllium. Next time we're telling the tale of a pair of twins that can make a glass blower's life a lot safer. 

Andrea Sella

One day, as he stood at his lathe with an orange inferno raging before him I asked him about the glasses he was wearing. 'Didymium' he answered cryptically, and then noticing my blank look, he added 'cuts out the light. Try them.' He passed me his specs, the lenses of a curious greeny-grey colour. I slipped them on and suddenly the flame was gone. All I could see was a red-hot piece of spinning glass unobscured by the glare. I gawped in wonder until Geoff pulled the specs off my face saying 'give 'em back ya fool' and went back to his work. 

Chris Smith

And you can catch up on the story of didymium and its mysterious light controlling chemistry with Andrea Sella on next week's Chemistry in its Element, I do hope you can join us. I'm Chris Smith, thank you for listening and goodbye.