Pierre Eug癡ne Marcellin Berthelot (1827-1907) was a French chemist and politician noted for the Thomsen-Berthelot principle of thermochemistry 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. He synthesized many organic compounds from inorganic substances and disproved the theory of vitalism. He is considered as one of the greatest chemists of all time. The fundamental conception that underlay all Berthelot's chemical work was that all chemical phenomena depend on the action of physical forces which can be determined and measured. He proved that organic compounds can be formed by ordinary methods of chemical manipulation and obey the same principles as inorganic substances. He died suddenly, immediately after the death of his wife .