Lavoisier’s “Reflections on phlogiston” II: on the nature of heat

Abstract

Having refuted the phlogiston theory, Lavoisier uses this second portion of his essay to expound his new theory of combustion, based on the oxygen principle. 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. Beyond the three types of combustion that he distinguishes and defines, Lavoisier also explains other chemical sources of heat, such as the heat of solution.