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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Caloric theory | 2/3 | https://en.wikipedia.org/wiki/Caloric_theory | reference | science, encyclopedia | 2026-05-05T16:14:11.452778+00:00 | kb-cron |
==== Caloric theory ==== According to the caloric theory, the quantity of this substance is constant throughout the universe, and it flows from warmer to colder bodies. Indeed, Lavoisier was one of the first to use a calorimeter to measure the heat released during chemical reaction. Lavoisier presented the idea that caloric was a subtle fluid, obeying the common laws of matter, but attenuated to such a degree that it is capable of passing through dense matter without restraint; caloric's own material nature is evident when it is in abundance such as in the case of an explosion. In the 1780s, Count Rumford believed that cold was a fluid, "frigoric", after the results of Pictet's experiment. Pierre Prévost argued that cold was simply a lack of caloric. Since heat was a material substance in caloric theory, and therefore could neither be created nor destroyed, conservation of heat was a central assumption. Heat conduction was believed to have occurred as a result of the affinity between caloric and matter thus the less caloric a substance possessed, thereby being colder, attracted excess caloric from nearby atoms until a caloric, and temperature, equilibrium was reached. Chemists of the time believed in the self-repulsion of heat particles as a fundamental force thereby making the great fluid elasticity of caloric, which does not create a repulsive force, an anomalous property which Lavoisier could not explain to his detractors. Radiation of heat was explained by Lavoisier to be concerned with the condition of the surface of a physical body rather than the material of which it was composed. Lavoisier described a poor radiator to be a substance with a polished or smooth surface as it possessed its molecules lying in a plane closely bound together thus creating a surface layer of caloric which insulated the release of the rest within. 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. 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. The introduction of the caloric theory was influenced by the experiments of Joseph Black related to the thermal properties of materials. Besides the caloric theory, another theory existed in the late eighteenth century that could explain the phenomenon of heat: the kinetic theory. The two theories were considered to be equivalent at the time, but kinetic theory was the more modern one, as it used a few ideas from atomic theory and could explain both combustion and calorimetry. Caloric theory's inability to explain evaporation and sublimation further led to the rise of kinetic theory through the work of Count Rumford. Count Rumford observed solid mercury's tendency to melt under atmospheric conditions and thus proposed that the intensity of heat itself must stem from particle motion for such an event to occur where great heat was not expected to be.
== Successes == Quite a number of successful explanations can be, and were, made from these hypotheses alone. We can explain the cooling of a cup of tea in room temperature: caloric is self-repelling, and thus slowly flows from regions dense in caloric (the hot water) to regions less dense in caloric (the cooler air in the room). We can explain the expansion of air under heat: caloric is absorbed into the air, which increases its volume. 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. 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. 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. Caloric was believed to be capable of entering chemical reactions as a substituent inciting corresponding changes in the matter states of other substances. Lavoisier explained that the caloric quantity of a substance, and by extent the fluid elasticity of caloric, directly determined the state of the substance. Thus, changes in state were a central aspect of a chemical process and essential for a reaction where the substituents undergo changes in temperature. 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. 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. Newton had assumed an isothermal process, while Laplace, a calorist, treated it as adiabatic. This addition not only substantially corrected the theoretical prediction of the speed of sound, but also continued to make even more accurate predictions for almost a century afterward, even as measurements became more precise.
== Later developments == In 1798, Count Rumford published "An Inquiry Concerning the Source of the Heat Which Is Excited by Friction", a report on his investigation of the heat produced while manufacturing cannons. He had found that boring a cannon repeatedly does not result in a loss of its ability to produce heat, and therefore no loss of caloric. This suggested that caloric could not be a conserved "substance", though the experimental uncertainties in his experiment were widely debated. 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. In fact, to some of his contemporaries, the results added to the understanding of caloric theory.