Born May 4, 1777, in La Loupti-ére, near the city of Nogent-sur-Seine; died June 20, 1857, in Paris. French chemist. Member of the Paris Academy of Sciences (1810).
Thénard was a professor at the College de France from 1804 to 1840, and in 1810 he also became a professor at the University of Paris and the Ecole Poly technique. Together with J. Gay-Lussac, he developed a method of obtaining potassium and sodium through the reduction of their hydroxides with iron while heating, obtained boron in impure form through the action of potassium on boric anhydride (1808), and discovered the effect of light on the reaction of chlorine with hydrogen (1809). Also in collaboration with Gay-Lussac, Thénard proposed a method of analyzing organic substances and, in 1810, proved that sodium, potassium, and chlorine are chemical elements. In 1818 he discovered hydrogen peroxide. Thénard was the author of numerous works on chemistry and chemical engineering. He became an honorary member of the St. Petersburg Academy of Sciences in 1826.