Caloric (calorique) as a weightless conserved fluid

1783-1789 Energy and motion theory theory refuted

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A theory in which heat is a weightless elastic fluid that is neither created nor destroyed and only passes from body to body.

The notion was absorbed into chemistry by the Frenchman Antoine Lavoisier, joining it with the latent heat of the Scot Joseph Black. The term 'calorique' was coined in 1787 by Guyton de Morveau in the Méthode de nomenclature chimique (compiled together with Lavoisier); in the Traité of 1789 caloric is included in the table of simple substances.

All the physics of heat of the first half of the 19th century (Laplace, Poisson, Carnot) was built on this foundation, until the mechanical theory of heat displaced it around 1850.

Why this date

the term 1787, Traité 1789. exact for the term and the Traité; the concept goes back to Black

What grew out of it

• "Réflexions sur la puissance motrice du feu" (Carnot)

  influenced · Confidence: high

  Carnot builds his argument inside the caloric theory, assuming that the quantity of caloric is conserved while the engine works.

  Dispute: Britannica notes that "Carnot himself had doubts about it even while he was writing". The posthumous notes (published by his brother Hippolyte in 1878) show that around 1830 Carnot abandoned caloric in favour of heat as motion (Mason, A History of the Sciences, 1956, quoted via Wikiquote). Chemistry World goes further and writes "He implicitly rejected the idea of caloric", but this is a minority view and contradicts the 1824 text.

  Link sources

  • Mendoza E., «Sadi Carnot», Britannica (2024) Verified 20 Sep 2026

    He worked within the framework of the caloric theory of heat, assuming that heat was a gas that could be neither created nor destroyed.

  • Carnot S. «Reflections on the Motive Power of Heat», R. H. Thurston (New York: Wiley, 1897), archive.org id reflectionsonmot00carnrich (1824)

    The production of motive power is then due ... not to an actual consumption of caloric, but to its transportation from a warm body to a cold body

  • de Oliveira, arXiv:2508.17027 (2025) Verified 20 Sep 2026

    heat is a conserved quantity, which is the fundamental law of heat theories prevalent before the emergence of thermodynamics, called caloric theory, implicit in the Carnot theory.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• The analytical theory of heat and Fourier series

  influenced · Confidence: medium

  Fourier began from a formulation in the spirit of the Laplacian caloric school (Biot's 1804 work on a heated bar), but then replaced the hypothesis about the nature of heat with a law relating measurable heat flux and temperature gradient.

  Link sources

  • T. N. Narasimhan, Fourier's heat conduction equation: history, influence, and connections, Reviews of Geophysics 37 (1), 151-172 (1999) Verified 25 Sep 2026

    Just as Biot before him, Fourier initially formulated the heat conduction problem as an n-body problem, stemming from the Laplacian philosophy of action at a distance.

  • T. N. Narasimhan, Fourier's heat conduction equation: history, influence, and connections, Reviews of Geophysics 37 (1), 151-172 (1999) Verified 25 Sep 2026

    When Fourier commenced his work on heat conduction at the turn of the nineteenth century, the nature of heat was still unresolved. Those of the mechanistic school, including Biot, believed that heat was a permeating fluid.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Other links

• Mechanical equivalent of heat (Joule)

  refuted by · Confidence: high

  A constant mechanical equivalent of heat means that heat is created from work, which denies the conservation of caloric.

  Dispute: A gap between experiment and acceptance: Joule obtained his first value of the equivalent in 1843 and the measurements continued until 1850; the scientific community accepted the mechanical theory of heat in 1850-1851 through the work of Clausius and Thomson, and Thomson himself, according to Mendoza, long found it hard to accept Joule's results because he held to caloric. The historian's judgement that it was Joule's work that overturned caloric is Daub's: Clausius held the first law to have been established by Joule's experiments.

  Link sources

  • Daub E. E. «Clausius, Rudolf», Dictionary of Scientific Biography (via Encyclopedia.com) (1971) Verified 20 Sep 2026

    The denial was based, of course, on what has become the first law of thermodynamics—that whenever work is produced by heat, a quantity of heat equivalent to that amount of work is consumed—a premise that Clausius believed had been firmly established by Joule's experiments.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Links under review

• Rumford: heat from friction in cannon boring

  refuted by · Confidence: medium

  The only sources are Wikipedia articles (citing Fox 1971 and Henry 1802); a verbatim quotation from Fox 1971 or Henry 1802 is needed.

  Rumford's experiment showed unlimited generation of heat by friction, which is incompatible with a conserved fluid; but in Rumford's lifetime this was not taken as a refutation.

  Dispute: Textbooks call Rumford's experiment a "refutation" of caloric; historians (Fox 1971, Cardwell 1971) show that the caloric theory survived comfortably for another half century and that Rumford himself made a "reckless extrapolation" about the inexhaustibility of heat.

  Link sources

  • Wikipedia «An Inquiry Concerning the Source of the Heat...» (2024) Verified 20 Sep 2026

    there was enough uncertainty in the caloric theory to allow its adaptation to account for the new results

  • Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026

    His results were not seen as a 'threat' to caloric theory at the time, as this theory was considered to be equivalent to the alternative kinetic theory.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Three statements on this card (the year and authorship of the term «calorique», the definition of caloric as a weightless conserved fluid, and Carnot's place in the sequence Laplace, Poisson, Carnot) rest on a summary in the Wikipedia article. Verbatim quotations are needed from the works it cites: Fox R., «The Caloric Theory of Gases from Lavoisier to Regnault», 1971, and Best N. W., Foundations of Chemistry, 2016. The card's other statements are supported by the Stanford Encyclopedia and by Best.

Node sources

• Stanford Encyclopedia of Philosophy, «Philosophy of Chemistry», §3.1 (2023) Verified 20 Sep 2026

  Lavoisier incorporated Black’s conception of latent heat into his caloric theory of heat, understanding latent heat transferred to a body without raising its temperature as caloric fluid bound in chemical combination with that body and not contributing to the body’s degree of warmth or temperature.

• Stanford Encyclopedia of Philosophy, «Philosophy of Chemistry», §3.1 (2023) Verified 20 Sep 2026

  Caloric figures in Lavoisier’s list of elements as the “element of heat or fire” (Lavoisier 1789, p. 175), “becom[ing] fixed in bodies” “[and] act[ing] upon them with a repulsive force, from which, or from its accumulation in bodies to a greater or lesser degree, the transformation of solids into fluids, and of fluids to aeriform elasticity, is entirely owing” (1789, p. 183).

• Stanford Encyclopedia of Philosophy, «Philosophy of Chemistry», §3.1 (2023) Verified 20 Sep 2026

  Lavoisier famously rejected phlogiston, but he accepted caloric. It would be another 60 years until the notion of caloric was finally abandoned with the development of thermodynamics.

• Best N. W. «Lavoisier's 'Reflections on phlogiston' II: on the nature of heat», Foundations of Chemistry 18(1), 3-13 (2016) Verified 20 Sep 2026

  He gives a mechanistic account of thermodynamic phenomena in terms of a subtle fluid (not yet named “caloric”) and its ability to penetrate porous bodies. He uses this hypothetical fluid to explain volume changes, heat capacity and latent heat.

• Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026, quotation assembled from fragments

  The term “caloric” was not coined until 1787, when Louis-Bernard Guyton de Morveau used calorique in a work he co-edited with Lavoisier. ... In his influential 1789 textbook Traité élémentaire de Chimie, Lavoisier clarified the concept of caloric and introduced it to a wider audience.

• Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026, quotation assembled from fragments

  Caloric theory held that heat was a conserved, weightless fluid called caloric that flowed from hotter objects to colder ones. ... In [Méthode de nomenclature chimique] we have distinguished the cause of heat, or that exquisitely elastic fluid which produces it, by the term of caloric.

• Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026

  Sadi Carnot, who reasoned purely on the basis of the caloric theory, developed his principle of the Carnot cycle, which still forms the basis of heat engine theory.

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

Further reading

Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.

• Fox R. «The Caloric Theory of Gases from Lavoisier to Regnault», Clarendon Press (1971)

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