Illustration of Henri Victor Regnault (1810-1878), French physicist and chemist. Regnault is best known for his careful measurements of the thermal properties of gases. He succeeded Gay-Lussac as professor of chemistry at the Ecole Polytechnique in Paris. He 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. Illustration published in 1879.