German analytical chemist who collaborated with Wöhler in organic chemistry investigations. With Wöhler, he discovered the benzoyl radical (C₇H₅O) in the 1830s, providing seeming support for Berzelius's radical theory. He measured the composition of silver fulminate to be 77.53% silver oxide and 22.47% cyanic acid, which was the same ratio as Wöhler had found for cyanic acid. At first, Liebig thought Wöhler was mistaken, but was eventually forced to agree that the compounds had the same chemical formula. Also with Wöhler, he wrote an article under the pseudonym S. C. H. Windler ("Schwindler" means swindler in German) which made fun of Laurent's substitution reactions. The article related how chlorine had been made to substitute for other compounds, producing substances entirely composed of chlorine atoms, but maintaining their original chemical properties.

Liebig promoted chemistry as the central science, trying to underscore its direct benefit to man in the form of pharmaceuticals. He developed a technique for determining the carbon and hydrogen contained in a sample from the carbon dioxide and water given off when a compound was burned. He also attempted to derive physiological phenomena from physical and chemical laws. In Agricultural Chemistry (1842), he presented organic chemistry in its application to physiology and pathology. He was influenced by Helmholtz in attempting to demonstrate that body heat and muscular action could be derived from the oxidation of foodstuffs. He also sought to establish an elemental balance between ingesta, excreta, and respiratory gases.