Phlogiston Theory
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Basic Information

The phlogiston theory (from the Ancient Greek φλογιστόν phlŏgistón "burning up," from φλόξ phlóx "fire"), first stated in 1667 by Johann Joachim Becher, is an obsolete scientific theory that posited the existence of, in addition to the classical four elements of the Greeks, an additional fire-like element called “phlogiston” that was contained within combustible bodies, and released during combustion. The theory holds that all flammable materials contain phlogiston, a substance without colour, odour, taste, or mass 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; "in general, substances that burned in air were said to be rich in phlogiston; the fact that combustion soon ceased in an enclosed space was taken as clear-cut evidence that air had the capacity to absorb only a definite amount of phlogiston. When air had become completely phlogisticated it would no longer serve to support combustion of any material, nor would a metal heated in it yield a calx; nor could phlogisticated air support life, for the role of air in respiration was to remove the phlogiston from the body."[2] Thus, phlogiston as first conceived was a sort of anti-oxygen.

Origin and etymology

In 1667, Johann Joachim Becher published his Physical Education, which was the first mention of what would become the phlogiston theory. Traditionally, alchemists considered that there were four classical elements: fire, water, air, and earth. In his book, Becher eliminated fire and air from the classical element model and replaced them with three forms of earth: terra lapidea, terra fluida, and terra pinguis. Terra pinguis was the element which imparted oily, sulphurous, or combustible properties. Becher believed that terra pinguis was a key feature of combustion and was released when combustible substances were burned.

Georg Ernst Stahl, a German chemist, was a student of Becher's who expanded on his theories with several publications in the period between 1703 and 1731. In a 1718 work, Stahl was the first to rename terra pinguis as phlogiston from the Ancient Greek phlogios for "fiery". Stahl's work analyzed the role of phlogiston in combustion and calcination, the 17th century term for oxidation.


2. James Bryan Conant, ed. The Overthrow of Phlogiston Theory: The Chemical Revolution of 1775–1789. Cambridge: Harvard University Press (1950), 14.

Game and Story Use

  • In a fantasy or steampunk world, phlogiston theory may be true and pure phlogiston may have some interesting uses.
    • Phlogiston would behave much like elemental fire.
    • Alternatively, alchemists and wizards may use "phlogiston" or "terra pinguis" as a name for elemental fire.
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