What is the chemical name for laughing gas?

Nitrous oxide, and it spent about half a century as a party drug before anyone used it in surgery. Humphry Davy inhaled it in the 1790s, noted that it removed the pain of a wisdom tooth, and suggested it might be used in operations - and then nobody acted on it. Laughing gas parties and public demonstrations became a fashionable entertainment instead.

The gap is one of the more painful delays in medical history. Surgery continued without anaesthesia for another fifty years, with speed as the main mercy, while a substance known to abolish pain was being used for amusement. It took a dentist, Horace Wells, seeing a demonstration in 1844 in which a man gashed his leg and felt nothing, to make the connection. His first public demonstration went badly, the patient cried out, he was ridiculed, and he later took his own life.

It is still used, and it is also a serious greenhouse gas - around 270 times more potent than carbon dioxide per molecule and long-lived, with the great majority of emissions coming from agricultural fertiliser rather than medicine. Several health services have started capturing or scrubbing it for that reason. Recreational use has risen sharply and is not harmless: it inactivates vitamin B12, and heavy users turn up with nerve damage.