Regnault made extensive contributions to 19th-century chemistry (he was the first to synthesise PVC, albeit accidentally) and physics (showing Boyle’s law to be only approximate), as well as contributing to the development of photography. He worked under Liebig, and was Gay-Lussac’s demonstrator at the École Polytechnique. He collaborated with Foucault on research into binocular vision, was a colleague of Biot’s, and wrote a comprehensive chemistry textbook, influential in both its French and German editions. Bunsen, Herschel and Airy were correspondents.