Regnault, Henri Victor (äNrēˈ vēktôrˈ rənyōˈ) [key], 1810–78, French physicist and chemist. He was professor of chemistry at the École polytechnique, Paris, from 1840 and at the Collège de France from 1841; he became chief engineer of mines (1847) and director of the porcelain manufactory at Sèvres (1854). In chemistry he is known for his work on the halogen and other derivatives of the unsaturated hydrocarbons. In physics he is noted for his careful measurements of the specific heats and expansion coefficients of many gases, liquids, and solids. He showed that Boyle's law is only approximately true for real gases, and he did important research on the operation of steam engines.