Joseph Priestley (1733-1804).
Priestley was an English chemist and a radical clergyman.
Prior to his experiments and during most of the 18th century, the overwhelming theory in relation to combustion was the Phlogiston Theory.
It was advanced by Johann Joachim Becher (1635-1682) and Georg Ernst Stahl (1660-1734).
The theory was incorrect but Priestley believed in it and it became the basis of chemical investigations up to the 18th century.
The experimental results ultimately lead to the theory’s demise which in turn paved the way to the present concepts of photosynthesis.