SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
Henri Victor Regnault French physicist and chemist (1810-78). He 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. In physics he improved techniques for determining the specific heats and thermal properties of solids, liquids, and gases. In organic chemistry he synthesized several chlorinated hydrocarbons such as vinyl chloride and dichloromethane. His extensive numerical tables on the properties of steam brought him the Rumford Medal of the Royal Society in 1847, and he was elected a Foreign Member in 1852. Following his interest in photography and the chemistry of the photographic process, he introduced in 1851 the use of pyrogallic acid as a developing agent. Known as 'pyro', it formed the basis of most photographic developers in use for the next 50 years.
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