Phlogiston Theory

Phlogiston Theory

This theory tryed to find the diffrent elements on earth.

There people belived that there are four elements: earth, air, fire, and water. In the heavens was the fifth element (the quintessence), the ether. Eventually, early chemists decided that combustion was the most important chemical reaction,and that if they could understand combustion they would actually revolutionize chemistry.

One early theory was that sulphur caused combustion (After all, sulphur itself burned completely). It was reasonable to think that any combustible substance contained sulphur. When wood burned, then sulphur was given off, into the air. But, the sulphur given off by wood was certainly different from the sulphur given off by solid sulphur. At least the smell was different.

As you can see above, phlogiston theory made some sense. But, the experiments which, more and more, convinced chemists that phlogiston was incorrect. The Antiphlogistians measured the weight of every substance involved in the experiment, even the gasses. When iron rusts away completely, the rust actually weighs more than the original iron. When charcoal burns, the resultant carbon dioxide (fixed air) weighs more than the original charcoal. So, in every case, phlogiston would have to have a negative weight. This disturbing attribute convinced most of the last Phlogistians to abandon their theory.

You and I know that various substances combine with oxygen during combustion. But, please suspend your righteous contempt for this phlogiston theory, and try to ignore what you know, and look at the theory as a somewhat skeptical 18th century chemist would. I will continue to use some 18th century terminology, to keep your mind from leaping ahead to 20th century chemistry.

Phlogiston theory evolved throughout the 18th century, because many experiments were being performed which needed to be explained. Most of these experiments were being performed by Antoine Lavoisier (the father of modern chemistry) and his followers (the Antiphlogistians). They would come up with an objection to phlogiston theory, and the Phlogistians (usually Priestley) would modify the theory to fit the new experiment. As the years went on, more and more Phlogistians became Antiphlogistians, until only Priestley was left.

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