Johann Joachim Becher was a German physician and alchemist. In 1669, he published his Physica subterranea, where he proposed a theory for combustion (later expanded by Ernest Stahl). The theory stated that any substance that burns loses an invisible, ordorless material called phlogiston. This explained the apparent loss of matter when a candle or stick of fire wood burned. Placing a glass jar over a burning candle soon causes the flame to extinguish. Phlogistionists explained this by saying the air under the jar becomes saturated with phlogiston. When the air can no longer absorb phlogiston, the candle can no longer burn. One problem with phlogiston theory was the observation that metals actually gain mass when they oxidize or burn. Still phlogiston theory had some predictive power and dominated chemistry for 80 years.
Alchemical Symbol for Phlogiston