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The caloric theory is an obsolete scientific theory that heat consists of a self-repellent fluid called caloric that flows from hotter bodies to colder bodies. Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids. The "caloric theory" was superseded by the mid-19th century in favor of the mechanical theory of heat but nevertheless persisted in scientific literature until the end of the 19th century.〔The 1880 edition of A Guide to the Scientific Knowledge of Things Familiar, a 19th century educational science book, explained heat transfer in terms of the flow of caloric〕 ==Early history== In the history of thermodynamics, the initial explanations of heat were thoroughly confused with explanations of combustion. After J. J. Becher and Georg Ernst Stahl introduced the phlogiston theory of combustion in the 17th century, phlogiston was thought to be the ''substance of heat''. There is one version of the caloric theory that was introduced by Antoine Lavoisier. Lavoisier developed the explanation of combustion in terms of oxygen in the 1770s. In his paper "Réflexions sur le phlogistique" (1783), Lavoisier argued that phlogiston theory was inconsistent with his experimental results, and proposed a 'subtle fluid' called caloric as the ''substance of heat''.〔Nicholas W. Best, (Lavoisier's 'Reflections on Phlogiston' II: On the Nature of Heat ), ''Foundations of Chemistry'', 2015, 17. In this early work, Lavoisier calls it “igneous fluid”. The term “caloric” was not coined until 1787, when Louis-Bernard Guyton de Morveau, used ''calorique'' in a work he co-edited with Lavoisier ("Mémoire sur le développement des principes de la nomenclature méthodique" in Guyton de Morveau, L.-B., Lavoisier, A.-L., Bertholet, C.-L., Fourcroy, A.-F. (eds.) ''Méthode de nomenclature chimique'', pp. 26–74. Cuchet, Paris). The word “caloric” was first used in English in a translation of Guyton's essay by James St John ("A memoir to explain the principles of the methodical nomenclature" in ''Method of Chymical Nomenclature'', Kearsley, London (1788), pp. 19–50, at p. 22).〕 According to this 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 changes during chemical reaction. In the 1780s, some believed that cold was a fluid, "frigoric". 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.〔See, for example, Carnot, Sadi (1824). ''Réflexions sur la Puissance Motrice du Feu''.〕 The introduction of the caloric theory was also 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「caloric theory」の詳細全文を読む スポンサード リンク
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