In
thermochemistry, the
Thomsen–Berthelot principle is a hypothesis in the
history of chemistry which argued that all
chemical changes are accompanied by the production of
heat and that processes which occur will be ones in which the most heat is produced. This principle was formulated in slightly different versions by the Danish chemist
Julius Thomsen in 1854 and by the French chemist
Marcellin Berthelot in 1864. This early postulate in classical thermochemistry became the controversial foundation of a research program that would last three decades.