Dumas , Jean Baptiste André

(1800–1884) French chemist

Dumas was educated in classics at the college in his native city of Alais and intended to serve in the navy. However, after Napoleon's final defeat he changed his mind and became apprenticed to an apothecary. In 1816 he went to Geneva, again to work for an apothecary. His first research was in physiological chemistry, investigating the use of iodine in goiter (1818). He also studied chemistry in Geneva and was encouraged by Friedrich von Humboldt to go to Paris, where he became assistant lecturer to Louis Thenard at the Ecole Polytechnique (1823). He subsequently worked in many of the Parisian institutes, becoming professor at the Ecole Polytechnique (1835) and at the Sorbonne (1841).

Dumas's early work included a method for measuring vapor density (1826), the synthesis of oxamide (1830), and the discoveries of the terpene cymene (1832), anthracene in coal tar (1832), and urethane (1833). In 1834 Dumas and Eugène Peligot discovered methyl alcohol (methanol) and Dumas recognized that it differed from ethyl alcohol (ethanol) by one –CH₂ group. The subsequent discovery that Chevreul's ‘ethal’ was cetyl alcohol (1836) led Dumas to conceive the idea of a series of compounds of the same type (this was formalized into the concept of homologous series by Charles Gerhardt).

Dumas was both a prolific experimentalist and a leading theorist and he took a vigorous part in the many controversies that bedeviled organic chemistry at the time. He was originally an exponent of the ‘etherin’ theory (in which ethyl alcohol (ethanol) and diethyl ether were considered to be compounds of etherin (ethene) with one and two molecules of water, respectively). However, he was converted to the radical theory (an attempt to formulate organic chemistry along the dualistic lines familiar in inorganic chemistry) by Justus von Liebig in 1837. He then introduced his own theory – the substitution theory – which was his greatest work. It had been noticed that candles bleached with chlorine gave off fumes of hydrogen chloride when they burned. Dumas discovered that during bleaching the hydrogen in the hydrocarbon oil of turpentine became replaced by chlorine. This seemed to contradict Jöns Berzelius's electrochemical theory and the latter was bitterly opposed to the substitution theory. Liebig, too, was hostile at first. Dumas then prepared trichloroacetic acid (1838) and showed that its properties were similar to those of the parent acetic acid. This convinced Liebig but not Berzelius. Further work on this series of acids, combined with the substitution theory, led him to a theory of types (1840), essentially similar to the modern concept of functional groups, although the credit for this theory was disputed between Dumas and Auguste Laurent.

Dumas also carried out important work on atomic weights. He had been an early supporter of Amedeo Avogadro but he never properly distinguished between atoms and molecules and the problems this raised caused him to abandon the theory. He also supported William Prout's hypothesis that atomic weights were whole-number multiples of that of hydrogen. In 1840, working with Jean Stas, he obtained the figure 12.000 for carbon instead of the figure 12.24 in use at that time.

Following the revolution of 1848 Dumas became involved in administration, becoming minister of agriculture and commerce (1849–51), minister of education, and permanent secretary of the Academy of Sciences (1868).