Nitrous oxide: are you having a laugh?

Nitrous oxide (N₂O), also known as laughing gas, was first discovered in 1772 by Joseph Priestley. A key step towards this was the design of experimental apparatus to collect gas over water, by Stephen Hales in the early 1700s. But Hales' concept of what constituted a gas was quite different from what we know today. He thought that all gases were forms of air. If they wouldn't support life, he believed that the air was loaded with toxic particles. And if they caught fire, the air was contaminated by invisible, flammable particles. That gases are substances in their own right was first recognised by Joseph Black in his classic 1750s investigations into the nature of magnesium oxide, carbonate and their connection with car