Léon Péan de Saint-Gilles
Léon Péan de Saint-Gilles (January 4, 1832 – March 22, 1862) was a French chemist who studied how fast reactions happen and how they settle into balance. He worked with Marcellin Berthelot on chemical kinetics and equilibria and even tried to put the ideas into math.
Born into a wealthy Paris family, he was educated at home before earning a degree. He started his own analytical laboratory with Théophile-Jules Pelouze and carried out experiments. His notable work used potassium permanganate as an indicator in titrations, especially in ester formation from acids and alcohols.
Together with Berthelot, he showed that reactions often reach an equilibrium that depends on the amounts of the reactants, not a fixed end composition.
In 1861 he moved to Cannes because he was ill with tuberculosis. He had married Pauline Thion de la Chaume, and they had two children. He died of tuberculosis in Cannes at the age of 30.
This page was last edited on 2 February 2026, at 15:09 (CET).