1-"Phlogiston theory states that a substance undergoing combustion mainly contains a mysterious matter called phlogiston and some calx . When a substance burns phlogiston goes into the atmosphere and some calx (also known as dephlogisticated substance ) is left behind as an ash"
eg- when candle burns in a sealed container the air inside becomes saturated with phlogiston and cannot accomodate additional phlogiston.
common air that could hold no more phlogiston is known as "phlogisticated air"
2-this theory was ruled out because Antonie Lavoisier proved that during burning, a component of air is used in chemical reaction which was named as oxygen i.e acid forming