Jean Baptiste Andre Dumas (1800-1884), French chemist. Dumas was born at Ales in the south of France, and in his youth was apprenticed to an apothecary. At the age of just 16 he moved to Geneva to study and in 1822 he was appointed professor of chemistry at the Lyceum. In 1826 he described a method for determining vapour densities and thus the atomic weights of many elements. In 1830 he published his concept of 'type theory', a chemical structure unlike the orthodox model of Berzelius. Dumas maintained that there are certain types of compound that remain essentially the same when hydrogen is substituted by a halogen - e.g. chlorine substituted into acetic acid. He developed a method for determining the nitrogen content of organic compounds and showed that the kidneys remove urea from the blood. After 1848 he turned to politics and took ministerial posts under Napoleon III.