Argon

Category: noble gas Atomic number: 18 Colour: colourless Melting point: −189°C (−308°F) Boiling point: −186°C (−302°F) First identified: 1894

These days we are very conscious of the increasing amount of carbon dioxide in the atmosphere; we know all about the environmental problems that this will cause in the future. However, it is not as widely known that the air we breathe every day actually contains more argon (1 per cent) than carbon dioxide (0.4 per cent).

Our first glimpse of argon came in the 1760s during Henry Cavendish’s investigations of the make-up of air. We’ve seen how Cavendish separated ‘phlogisticated air’ from ‘dephlogisticated air’. Each time, Cavendish was puzzled to find that when he went on to extract nitrogen from the phlogisticated air, there was a stubborn residue of about 1 per cent of inert gas.

This was largely forgotten until 1894, when John Strutt (later known as Lord Rayleigh) and William Ramsay established that nitrogen extracted from air was always about 0.5 per cent more dense (and thus ‘heavier’) than nitrogen extracted from ammonia. They identified the heavier gas that remained after oxygen and nitrogen were removed from atmospheric air as a separate element – it was named after the Greek word argos, meaning ‘lazy’, because of its chemical inertness. This inertness is down to the fact that argon has a full outer shell of electrons and is thus one of the ‘noble gases’, which tend not to bond or easily react with other elements.

Discovery Delayed

When Strutt and Ramsay discovered argon in 1894, they didn’t immediately broadcast this to the world, but not because there was any problem with their scientific results. The pair had realized that a major competition for chemical discoveries, being held the following year in America, came with the condition that the discovery had to be made after the start of 1895. Tempted by the money on offer, they sneakily held their discovery back and only announced it the following year. They duly collected $10,000, which would be worth well over $150,000 today.

Argon is an important ingredient in many industrial processes. For instance, in steel production it is combined with oxygen and blown through molten metal during ‘decarburization’: this prevents valuable elements in the steel, such as chromium, from oxidizing in large amounts. It is used in traditional incandescent lightbulbs, again because it doesn’t react easily and prevents the filament from oxidizing at high temperatures. It is often used in double glazing to fill the gap between two panes of glass, because it is heavier than air and conducts less heat, so helps insulate the home. More recently, blue argon lasers have been used in hospitals to destroy cancerous growths and to correct corneal defects in patients’ eyes.

For a substance that we didn’t even know about 125 years ago, argon has turned out to be a very useful gas indeed.