Phlogiston theory

:Phlogiston is also the name of a substance in the fictional setting Spelljammer.

Challenge and demise

Eventually, experiments revealed problems, including the fact that some metals gained weight when they burned, even though they were supposed to have lost phlogiston. This is not as serious as it sounds; it merely requires phlogiston to be lighter than air. Phlogiston remained the dominant theory until Antoine Laurent Lavoisier showed that combustion requires oxygen, solving the weight paradox and setting the stage for the new caloric theory of combustion, but introducing a new substance, caloric. In fact, the reason for the weight paradox is that these metals, rather than losing oxygen, hydrogen and carbon to the atmosphere as wood does, gained oxygen while keeping all the mass of the original metal.

Related Topics:
Experiment - Antoine Laurent Lavoisier - Oxygen - Caloric theory

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In some respects, the phlogiston theory can be seen as the opposite of the modern "oxygen theory". Whereas the phlogiston theory states that all flammable materials contain phlogiston that is liberated in burning, and the "dephlogisticated" substance was now in its "true" calx form. In fact, flammable materials (or unrusted metals) are "deoxygenated" when in their pure form and become oxygenated when burned.

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