The Caloric Theory and its Problems

We come, hence,to the last quarter of the 18th century. The caloric theory of heat, whose origin lies - as we have seen - with Descartes subtle fluid, is fairly well accepted but there is some strong opposition to it. Hatsopoulos and Keenan describe the situation as follows  

Caloric is an elastic fluid, the particles of which repel one another strongly. 

Particles of caloric are attracted by particles of ordinary matter in different degrees for different substances and different states of aggregation. 

1t is either sensible or latent. Latent caloric is caloric which has combined chemically with particles of solid to form liquid or of liquid to form vapor. 

These postulates were ingeniously contrived to account for certain observed phenomena. Postulate  

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