Henri Regnault. Portrait of Henri Victor Regnault, French physicist and chemist (1810-78). Regnault worked with Liebig and succeeded Gay-Lussac as professor of chemistry at the Ecole Polytechnique in Paris. In 1841, he became professor of physics in the College de France. Regnault studied aliphatic chloro-compounds and discovered vinyl chloride and other industrially important materials. He published a chemistry treatise in 1847. In physics, Regnault improved techniques for determining the specific heats of solids, liquids, and devised a method for gases. He was able to show how real gases deviate from the ideal gas laws and he measured the velocity of sound.