Phlogiston theory

The phlogiston theory, in the 17th and 18th century, postulated the existence of an element called "phlogiston", contained in explosive and burnable objects, and released during combustion. The name comes fom Ancient Greek "phlox" (flame).

The theory states that phlogisticated substances dephlogisticate when burned. Growing plants than absorb this phlogiston, and become phlogisticated themselves.

When the Scottish chemist Daniel Rutherford discovered nitrogen in 1772, he used the phlogiston theory to explain his results. Later, upon the discovery of oxygen, people believed it to be dephlogisticated air, which can support combustion for longer than ordinary air.