Apparatus for breathing dephlogisticated air, 1785. Oxygen was originally called dephlogisticated air by Joseph Priestley. From "Nouvelles experiences et observations sur divers objects de physique" by Jan Ingenhousz or Ingen-Housz (1730 - 1799), a Dutch physiologist, biologist and chemist. Ingenhousz is best known for having discovered a key component in photosynthesis, that is, sunlight. Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities.