Phlogiston theory

Quick Facts: Who was Phlogiston theory?

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Phlogiston theory

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Superseded theory of combustion positing a fire-like element released during burning.

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Origins & Early Life

The phlogiston theory, a superseded scientific theory, postulated the existence of a fire-like element dubbed phlogiston () contained within combustible bodies and released during combustion. The name comes from the Ancient Greek φλογιστόν phlogistón (burning up), from φλόξ phlóx (flame). The idea of a phlogistic substance was first proposed in 1669 by Johann Joachim Becher and later put together more formally in 1697 by Georg Ernst Stahl. Phlogiston theory attempted to explain chemical processes such as combustion and rusting, now collectively known as oxidation. The theory was challenged by the concomitant mass increase and was abandoned before the end of the 18th century following experiments by Antoine Lavoisier in the 1770s and by other scientists.

Career & Major Achievements

Phlogiston theory led to experiments that ultimately resulted in the identification (c. 1771), and naming (1777), of oxygen by Joseph Priestley and Antoine Lavoisier, respectively. Phlogiston theory states that phlogisticated substances contain phlogiston and that they dephlogisticate when burned, releasing stored phlogiston, which is absorbed by the air. Growing plants then absorb this phlogiston, which is why air does not spontaneously combust and also why plant matter burns. This method of accounting for combustion was inverse to the oxygen theory by Antoine Lavoisier. In general, substances that burned in the 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 finite amount of phlogiston.

Enduring Legacy & Impact

When the air had become completely phlogisticated it would no longer serve to support the combustion of any material, nor would a metal heated in it yield a calx; nor could phlogisticated air support life. Breathing was thought to take phlogiston out of the body. Joseph Black's Scottish student Daniel Rutherford discovered nitrogen in 1772, and the pair used the theory to explain his results. The residue of air left after burning, a mixture of nitrogen and carbon dioxide, was sometimes referred to as phlogisticated air, having taken up all of the phlogiston. Conversely, when Joseph Priestley discovered oxygen, he believed it to be dephlogisticated air, capable of combining with more phlogiston and thus supporting combustion for longer than ordinary air.

Chronological Milestones & Life Events

1. 1669: 1669 Milestone — The idea of a phlogistic substance was first proposed in 1669 by Johann Joachim Becher and later put together more formally in 1697 by Georg Ernst Stahl.
2. 1771: 1771 Milestone — 1771), and naming (1777), of oxygen by Joseph Priestley and Antoine Lavoisier, respectively.
3. 1772: 1772 Milestone — Joseph Black's Scottish student Daniel Rutherford discovered nitrogen in 1772, and the pair used the theory to explain his results.

Notable Quotes by Phlogiston theory

“To him, wood was just a combination of ash and phlogiston, and making a metal was as simple as getting a metal calx and adding phlogiston.” (1723)

Historical Fact-Check Quiz: Phlogiston theory

True or False: “The primary reason the Phlogiston theory failed was its inability to account for the measurable increase in mass during combustion reactions.”

Answer (TRUE ⭕): The theory struggled because it predicted a loss of material (phlogiston) during burning, contradicting empirical observations of mass gain.

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Frequently Asked Questions about Phlogiston theory