Cascades to Coast

How do we know what air is made of?

It took scientists centuries to figure out what air is made of. More than 2000 years ago, the ancient Greeks thought that air was an element, not a mixture of gases. People continued to believe the idea that air was an element for a very long time. It was only in the 1700s that experiments by famous chemists such as Lavoisier, Priestley, Cavendish and others showed that air is a mixture of gases. Priestley discovered oxygen in 1770s, and Cavendish showed that air is 21% oxygen. Daniel Rutherford discovered that nitrogen was a part of air in 1772. It was more than a hundred years later, in 1864, that William Ramsay discovered argon.