What does phlogistic mean?
Phlogistic is chiefly a historical adjective meaning connected with phlogiston, the supposed universal substance that eighteenth-century chemists believed was released when matter burned. The phlogiston theory treated fire as the result of this substance escaping from combustible material, but it could not explain convincingly why substances sometimes gained weight while burning. Experiments by chemists including Robert Boyle, Joseph Priestley, and especially Antoine Lavoisier eventually displaced the theory with an explanation based on oxygen and oxidation. In older medical writing, phlogistic could also describe heat, redness, swelling, or inflammation. Today, the word survives mainly in histories of chemistry and in the names of the theory and its doctrine. Its familiar sound can be misleading: despite the resemblance between phlogistic and words such as phlegmatic, they have different origins and meanings.
adjectiveRelating to phlogiston, the hypothetical fire-like substance once believed to be present in all combustible matter. In historical or medical contexts, the term can also mean inflammatory or heat-producing.
- Relating to phlogiston or the historical theory of combustion based on it.
- In medicine, relating to or characterized by inflammation or the production of heat.
"Lavoisier's experiments helped overturn the phlogiston explanation of combustion."
"The phlogiston model could not adequately account for the role of oxygen in combustion."
"The physician described the affected area as phlogistic because it was hot, red, and swollen."
Phlogiston was once treated as the secret ingredient of fire until careful weighing revealed that something was missing: oxygen.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does phlogistic come from?
Phlogistic comes through English from the Greek phlogistēs, meaning heat-giving, which was derived from phlogizein, 'to set on fire.' The related Greek noun phlogos denotes flame, and phlogosis was used for inflammation or a burning condition. The scientific doctrine took its name from phlogiston, the supposed substance associated with fire, and became prominent in eighteenth-century chemistry before oxygen-based accounts of combustion replaced it.
Related word forms
How phlogistic is actually used
The principal modern use is historical, referring to the obsolete phlogiston theory. The medical sense is archaic or specialist. The word is more often encountered in discussions of the history of chemistry than in ordinary contemporary prose.
Easily confused with phlogistic
Phlogiston was the hypothetical substance that the phlogiston theory proposed was released during combustion.
Phlegmatic means characterized by calmness or an absence of emotion, whereas phlogistic relates to the old theory of combustion or, archaically, to heat and inflammation.