Phlogiston – The Forgotten Theory of Combustion

Marko July 14, 2025 1 minute read

Introduction

The theory of phlogiston was an early scientific explanation for combustion, oxidation, and rust. It was proposed in the 17th century by German chemist Johann Becher and further developed by Georg Ernst Stahl. Despite being a cornerstone of chemistry for over a century, phlogiston was ultimately replaced by modern theories of combustion and oxygen.

Origins

Phlogiston was believed to be a fire-like element contained within combustible materials, released during burning. This idea dominated the scientific community until the late 18th century when Antoine Lavoisier’s discovery of oxygen rendered it obsolete.

Theories and Evidence

Combustion and Phlogiston: According to the theory, substances containing phlogiston would burn, releasing it and leaving behind a substance with a “negative weight” (i.e., ash).
Lavoisier’s Oxygen Theory: Lavoisier’s work disproved the phlogiston theory, showing that combustion was the result of a reaction with oxygen, not the release of a mystical substance.

Critical Analysis

Phlogiston theory, though scientifically flawed, was an important step in the development of modern chemistry. The rise and fall of phlogiston highlight the evolving nature of scientific understanding, where theories are discarded as new evidence becomes available.