Topical Tens: 31st July: Oxygen

Monday 31 July 2017

31st July: Oxygen

On this date in 1774 Joseph Priestley discovered oxygen. Here are ten things you might not know about that stuff you are breathing every minute of the day.

Oxygen's symbol is O and its atomic number is 8.
Joseph Priestly wasn't the first to discover oxygen - he gets the credit because he published his paper first. It was discovered independently the previous year by Carl Wilhelm Scheele, in Uppsala, Sweden. He called the gas "fire air" because it supported combustion and wrote about it in a document titled Treatise on Air and Fire, which was published in 1777. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments even earlier on, but didn't recognise it as a new element.
Oxygen was given its name by Antoine Lavoisier, who was also experimenting with it at around the same time. The name derives from Greek - oxys meaning acid and genes meaning producer - because at the time people thought acids had to have oxygen in them (they don't). Scientists in England didn't like the name at first, possibly because it was a French person naming a substance which had been discovered by an Englishman. However, thanks to Erasmus Darwin, grandfather of Charles Darwin, who wrote a poem in praise of the newly discovered gas and called it Oxygen, the name stuck.
Oxygen melts at 54.36 K (−218.79 °C, −361.82 °F), and boils at 90.188 K (−182.962 °C, −297.332 °F).
Oxygen is colourless when it is a gas, but in its liquid and solid forms it is pale Blue in colour. If the temperature falls and the pressure rises it can turn Orange, Red or Black, and even have a metallic appearance, although it is not a metal.
Liquid oxygen is magnetic, and it can be picked up with a powerful magnet.
Oxygen is the third-most abundant element in the universe, after hydrogen and Helium, and as oxides makes up almost half of the Earth's crust. It's also the most abundant element in the human body since it is a constituent of Water and the human body is mostly water.
Oxygen is essential to life, but it can poison us too, if we get too much. At normal pressure, if there is more than 50% oxygen in the air we breathe. oxygen poisoning occurs. It can also occur at lower levels in divers. Symptoms of oxygen poisoning include vision loss, coughing, muscle twitching, and seizures. Too much oxygen can actually kill you.
When oxygen first became abundant on Earth, it wiped out about 99% of the life on the planet. The Great Oxygenation Event also called the Oxygen Catastrophe, is the name given to the biologically induced appearance of dioxygen (O2), the usual form it takes in Earth's atmosphere. It happened around 2.45 billion years ago during the Siderian period, but nobody knows why. High oxygen levels in the carboniferous period allowed insects to grow absolutely huge - for example, a millipede that was 2.6m long.
As well as O2, the most abundant form of oxygen in the atmosphere, there is also O3, or ozone. When this substance occurs high up in the atmosphere it's a good thing, because it forms the ozone layer which filters out ultraviolet light. Lower down, it's not so good as it is a by product of smog.