Caloric theory
Prior to Lavoisier's caloric theory, published references concerning heat and its existence, outside of being an agent for chemical reactions, were sparse only having been offered by Joseph Black in Rozier's Journal (1772) citing the melting temperature of ice.
[2] In response to Black, Lavoisier's private manuscripts revealed that he had encountered the same phenomena of a fixed melting point for ice and mentioned that he had already formulated an explanation which he had not published as of yet.
On 28 June and 13 July 1783, Lavoisier read his two-part manuscript Reflections on phlogiston (Réflexions sur le phlogistique)[a] at the Royal Academy of Sciences in Paris.
[6]The term “caloric” was not coined until 1787, when Louis-Bernard Guyton de Morveau used calorique in a work he co-edited with Lavoisier.
[8] In his influential 1789 textbook Traité Élémentaire de Chimie, Lavoisier clarified the concept of caloric and introduced it to a wider audience.
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.
[9]According to the caloric theory, the quantity of this substance is constant throughout the universe,[citation needed] and it flows from warmer to colder bodies.
[11] He described a great radiator to be a substance with a rough surface as only a small amount of molecules held caloric in within a given plane allowing for greater escape from within.
[11] Count Rumford would later cite this explanation of caloric movement as insufficient to explain the radiation of cold becoming a point of contention for the theory as a whole.
If we say a little more about what happens to caloric during this absorption phenomenon, we can explain the radiation of heat, the state changes of matter under various temperatures, and deduce nearly all of the gas laws.
Carnot's analysis of energy flow in steam engines (1824) marks the beginning of ideas which led thirty years later to the recognition of the second law of thermodynamics.
[13] Changes of state had gone virtually ignored by previous chemists making the caloric theory the inception point for this class of phenomena as a subject of interest under scientific inquiry.
[2] However, one of the greatest apparent confirmations of the caloric theory was Pierre-Simon Laplace's theoretical correction of Sir Isaac Newton’s calculation of the speed of sound.
In modern thermodynamics, heat is usually a transfer of kinetic energy of particles (atoms, molecules) from a hotter to a colder substance.
