Phlogiston theory: Encyclopedia II - Phlogiston theory - Theory

Phlogiston theory - Theory

The theory holds that all flammable materials contain phlogiston (derived noun form of the Greek phlogistos, meaning flammable), a substance without color, odor, taste, or weight that is liberated in burning. Once burned, the "dephlogisticated" substance was held to be in its "true" form, the calx.

"Phlogisticated" substances are those that contain phlogiston and are "dephlogisticated" when burned. Since any substance could be observed to burn for only a limited time with limited air (for instance in a sealed container), air was thought to have a specific capacity for phlogiston.

Joseph Black's student Daniel Rutherford discovered Nitrogen in 1772 and the pair used the theory to explain his results. The residue of air left after burning, in fact a mixture of nitrogen and carbon dioxide, was sometimes referred to as "phlogisticated air", having taken up all of the phlogiston.

Conversely, when oxygen was first discovered it was thought to be "dephlogisticated air", capable of combining with more phlogiston and thus supporting combustion for longer than ordinary air.

Adapted from the Wikipedia article "Theory", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki