Category: noble gas
Atomic number: 36
Colour: colourless
Melting point: −157°C (−251°F)
Boiling point: −153°C (−244°F)
First identified: 1898
|
Category: noble gas Atomic number: 36 Colour: colourless Melting point: −157°C (−251°F) Boiling point: −153°C (−244°F) First identified: 1898 |
Before William Ramsay and Morris Travers discovered neon in 1898, they had in the same year already identified the fourth member of the group of noble gases, krypton. In this case, they liquefied and evaporated argon, to see if it would leave a heavier component behind. From 15 litres of argon they managed to produce 25 cm3 of a gas: when they tested it with a spectrometer, it was clear that this was indeed a new element, which they named after the Greek word kryptos, meaning ‘concealed’, as it had been hidden in the argon.
Krypton is a gas without smell or colour and doesn’t tend to react with any other element (apart from fluorine gas). It makes up only one part in a million of the Earth’s atmosphere (by volume). It has been used to fill energy-saving fluorescent lightbulbs as well as in ‘neon’ lighting to expand the range of colours produced, and krypton fluoride has been used in the production of lasers.
In the 2006 movie Superman Returns, the chemical formula for kryptonite (Superman’s nemesis) is given as ‘sodium lithium boron silicate hydroxide with fluorine’. This is remarkably close to the mineral jadarite, which was discovered a year later – although those scientists who whipped up mass media attention by claiming that kryptonite had been found to be ‘real’ should have noted that the new mineral didn’t contain fluorine, and it certainly didn’t glow with an eerie green light. So, close, but no cigar.
In the Cold War, the radioactive isotope Kr-85 was used by Western scientists to spy on their counterparts behind the Iron Curtain – the isotope is produced at a fairly constant rate by nuclear reactors, and they realized that by estimating the amount of this isotope that was being produced by Western nuclear plants and subtracting this from the measurable total in the atmosphere, they could come up with a pretty good estimate of the level of nuclear activity in those countries that were in the Russian sphere of influence.
And, of course, krypton was the inspiration behind the planet Krypton, fictional home to Superman (not to mention Supergirl and ‘Krypto the Dog’) in the original DC Comics stories and the many films and comics that followed in its footsteps.