Péan De Saint-Gilles, L
PéAN DE SAINT-GILLES, LéON
(b. Paris, France, 4 January 1832; d. Cannes, France, 22 March 1862)
Péan de Saint-Gilles was born into an old and very rich family. His father, like his ancestors, was a notary. Sickly and weak, he never attended public schools but received private tutoring instead. At the age of seventeen he earned his bachelor of letters degree. Departing from family tradition, he chose scientific research as a profession, but his poor health made it impossible for his to pursue university studies on a regular basis. Thus, he gained his knowledge of chemistry by himself and acquired paratical laboratory experience under the guidance of Pelouze, a student and successor of Gay-Lussac at the École Polytechnique. Independently wealthy, péan de Saint-Gilles later had a laboratory built for himself in which he carried out chemical investigations. He had already achieved some success when death ended his very promising career. The sysmptoms of consumption appeared at the beginning of 1861; he moved to Cannes to aid hs cure, but it was no longer of any help. He was survived by his window and two children.
Péan de Saint-Gilles’s fmost important work was in the field of titrimetry. In 1846 Frédéric Marguerite introduced the standard solution of potassium permanganate (then called chameleon solution) into the volumetric analysis employed in the determination of iron. Pelouze applied this method to other determinations. Péan de Saint-Gilles extended the use of potassium permanganate as a titrimetric solution for the quantitative determination of nitrite and iodide, as well as of oxalic acid and other organic substances. All of these procedures are still used. He also worked on lthe identification of the oxidatin products of organic substances. His investigations in the area lof inorganic chemistry are of no particular importance.
In physical chemistry he examined, in collaboration with Berthelot, the esterification of alcohols with acids. They found that the reaction was never complete but reached a state of equilibrium. This state was independent of the quality of the alcohol and aicd. Finding that “the amount of ester formed in each moment is proportional to the product of the reacting substances,” they attempted to give a mathematical formulation of the phenomenon. It was the crucial reaction to which Guldberg and Waage referred in their enunciation of the law of mass action in 1864.
There is a bibliography of Péan de Saint-Gilles’s works in Poggendorff, III, 1010–1011. See also the Royal Society Catalogue of Scientific Papers, which lists eighteen works, seven of them written with Berthelot. The latter include the important “Recherches sur les affinités,” in Annales de chimie et de physique, 3rd ser., 65 (1862), 385–422; 66 (1862), 5–110; 68 (1863), 225–359.
On his life and work, see M. Berthelot, “Nécrologie,” in Bulletin. Société chimique de France, A5 (1863), 226–227; J. R. Partington, A History of Chemistry, IV (London, 1964), 584–585; and F. Szabadvary, History of Analytical Chemistry (Oxford, 1966), 251.