Henri Victor Regnault (July 21, 1810 - January 19, 1878) was a French chemist and physicist best known for his careful measurements of the thermal properties of gases. In 1830, he was admitted to the ?cole Polytechnique, and in 1832 he graduated from the ?cole des mines. Working under Justus von Liebig, he distinguished himself in the new field of organic chemistry by synthesizing several chlorinated hydrocarbons (vinyl chloride, polyvinyl chloride, dichloromethane). Beginning in 1843, he began compiling extensive numerical tables on the properties of steam. These were published in 1847, and led to his receiving the Rumford Medal of the Royal Society of London. he continued work on the thermal properties of matter. He designed sensitive thermometers, hygrometers, hypsometers and calorimeters, and measured the specific heats of many substances and the coefficient of thermal expansion of gases. He was an avid amateur photographer. He introduced the use of pyrogallic acid as a developing agent, and was one of the first photographers to use paper negatives. In 1871, his laboratory at S癡vres was destroyed and his son Alex-Georges-Henri Regnault killed, both as a result of the Franco-Prussian War. He retired from science the next year, never recovering from these losses. He died in 1878 at the age of 67.