Phlogiston PHLOGIS'TON, n. [Gr. to burn or inflame.]
The principle of inflammability; the matter of fire in composition with other bodies. Stahl gave this name to an element which he supposed to be pure fire fixed in combustible bodies, in order to distinguish it from fire in action or in a state of liberty. But the theory has been proved to be false and is generally abandoned.

phlogiston n 1: a hypothetical substance once believed to be present in all combustible materials and to be released during burning

phlogiston
n. a substance formerly supposed to exist in all combustible bodies, and to be released in combustion.
Etymology: mod.L f. Gk phlogizo set on fire f. phlox phlogos flame

Phlogiston a name given by the old chemists to an imaginary principle of fire, latent in bodies, and which escaped during combustion.

Phlogiston \Phlo*gis"ton\, n. [NL., fr. Gr. ? burnt, set on fire, fr. ? to set on fire, to burn, fr. ?, ?, a flame, blaze. See Phlox.] (Old Chem.) The hypothetical principle of fire, or inflammability, regarded by Stahl as a chemical element. Note: This was supposed to be united with combustible (phlogisticated) bodies and to be separated from incombustible (dephlogisticated) bodies, the phenomena of flame and burning being the escape of phlogiston. Soot and sulphur were regarded as nearly pure phlogiston. The essential principle of this theory was, that combustion was a decomposition rather than the union and combination which it has since been shown to be.

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