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Auguste André Thomas Cahours PARA QUITARLE EL POLVO Educ. quím., 24(4), 451-460, 2013. © Universidad Nacional Autónoma de México, ISSN 0187-893-X Publicado en línea el 15 de septiembre de 2013, ISSNE 1870-8404 Auguste André Thomas Cahours Jaime Wisniak* ABSTRACT To Auguste André Thomas Cahours (1813-1891) we owe the discovery and synthesis of a large number of chemicals, among them, amyl and allyl alcohol, toluene, xylene, cuminic and anisic acids, piperidine, organometallic compounds and radicals, and derivatives of phosphine and arsine, as well as important contributions to the theories of valence, isomerization in the aro- matic series, density of vapors, particularly the abnormal ones, the use of PCl5 as a chlorina- tion agent, and the mechanism of respiration of fruits and flowers. KEYWORDS: Cahours, density of vapors, phosphorus pentachloride, phosphine derivatives, dissociation, essential oils, wintergreen oil, cumene, toluene, xylene, pentanol, allyl alcohol, glycine, radicals, organometallic compounds Resumen 1833 and after graduation (1835) he joined the corps of the A Auguste André Thomas Cahours (1813-1891) le debemos el Army Chief of Staff but promptly abandoned the military ca- descubrimiento y síntesis de un gran número de compues- reer to follow his interests in chemical research. Michel tos, entre ellos, los alcoholes amílico y alílico, tolueno, xile- Eugène Chevreul (1786-1889), his former teacher, appointed no, los ácidos anísico y cumínico, piperidina, compuestos y him préparateur at his laboratory at the Muséum d’Histoire radicales organometálicos, y derivados de la fosfina y la ar- Naturelle, a position Cahours occupied for four years. sina, así como contribuciones importantes a la teoría de la In 1839 he transferred to the private laboratory that Jean- valencia, isomerización en la serie aromática, densidad de Baptiste André Dumas (1800-1884) had on rue Cuvier. In the vapores, en especial los casos anormales, el uso del PCl5 same year (1839) Dumas appointed Cahours as répétiteur at como agente de cloración, así como el mecanismo de respi- the École Centrale des Arts et Manufactures, and afterwards ración de frutas y flores. manager of the students’ laboratories (in those years it was customary for scientists to work at several places simulta- Palabras clave: Cahours, densidad de vapores, pentacloru- neously, in order to improve their financial situation). In ro de fósforo, derivados de fosfina, disociación, aceites 1840 Cahours joined the École Polytechnic as répétiteur ad- esenciales, aceite de gaulteria, cumeno, tolueno, xilenos, joint without salary, and remained in this position until 1851 pentanol, alcohol alílico, glicina, radicales, compuestos or- when he was appointed examinateur de sortie 2 and member ganometálicos. of the Conseil de Perfectionnement, replacing Chevreul who had resigned. In 1870 he replaced Victor Regnault (1810- Life and career (Duchartre, 1891; Etard, 1892; 1878) in the chemistry chair at the École. Cahours became Gautier, 1891; Grimaux, 1892) docteur-ès-sciences at the Faculty of Sciences of Paris in Auguste André Thomas Cahours was born on October 2, 1831 1845 and in the same year he replaced Dumas at the chair of in Paris (Seine), the elder of the two sons of Rose Adelaïde the course on general chemistry that Dumas was giving Cartront and André Cahours, originally employed at the Min- at the École Centrale and stayed in this position until 1870. istry of Finances, and afterwards owner of a modest tailor In 1850 Cahours was appointed professor of chemistry at shop on the rue de Provence.1 After finishing his first educa- the École d’Application de la Manufacture des Tabacs; in tion at the local lycée he entered the École Polytechnique in 1851 Dumas appointed Cahours as suppléant (substitute) to the course he was giving at the Sorbonne and in 1868 Ca- * Department of Chemical Engineering, Ben-Gurion University of the hours substituted him at the chair after Dumas was ap- Negev, Beer-Sheva, Israel 84105. pointed Secrétaire Perpétuel (permanent secretary) of the E-mail: [email protected] Académie des Sciences. In 1888 Cahours resigned his chair Fecha de recepción: Febrero 17, 2013. Fecha de aceptación: Mayo 5, 2013. at the École Polytechnique. 1 The archives of theÉcole Polytechnique contain a statement by Auguste’s father by which he guaranties payment of his son fees in the case he will be admitted to the École: «Je soussigné André Cahours, vérificateur à la 2 The examinateur de sortie is the officer that follows the students’ progress comptabilité générale des receveurs de l’Enregistrement et des Domaines, during their schooling. He sits on the jury, which classifies the pupils in au ministère des Finances, demeurant à Paris rue Buffault n°7, je promets order of merit, at the end of the schooling at the École Polytechnique, and et m’engage envers l’École royale polytechnique, dans le cas que mon fils, before their entrance in engineer and officers’ training schools (École des Auguste André Thomas Cahours, soit admis à la dite École, comme élève, Mines, École des Ponts et Chaussées, School of the artillery and engineer- de payer annuellement la pension de mille francs» (courtesy of Olivier ing) (courtesy of Olivier Azzola, in charge of the archives at the Library of Azzola, in charge of the archives at the Library of the École). the École). octubre de 2013 • EDUCACIÓN QUÍMICA PARA QUITARLE EL POLVO 451 Cahours’s family life was accompanied by tragedy; within showed that cuminic aldehyde, contrary to benzoic alde- a short period of time (1868-1871) he lost his only brother, hyde, pre-existed in the plant (from which it could be sepa- his wife, and his two sons, Georges and André, younger than rated by distillation) and did not originate from fermenta- 23 years. His younger son André, died in 1871 during the tion (enzymatic action). Encouraged by their discovery of Franco-German war. Some years later he married again. Ca- cumene, they distilled cinnamic acid and isolated cinnamene hours passed away in Paris on March 17, 1891. After his death (styrene) and prepared its crystalline bromide. The Aca- Henri Moissan replaced him at the chemistry section of the démie judged their memoir valuable enough to be published Académie des Sciences. in the Recueil des Savants Étrangers (Cahours and Gerhardt, Cahours received many awards and honors for his con- 1841). tributions to science and technology. In 1853 he was ap- Other essential oils studied were those of anis, fennel, pointed assayer (analyst) at the Paris Mint, replacing Au- and wintergreen. Cahours determined the chemical identity guste Laurent (1807-1853) who had recently passed away. of the essences of anis, star anis, and fennel, their centesi- He was elected member of the Société Philomatique (1840); mal composition, their elemental formula, described the of the Académie des Sciences et Belles-Lettres of Rouen preparation and properties of their nitro, chlorine, and bro- (1846); of the Académie des Sciences (chemistry section), mine substitution derivatives, and while looking the action replacing Dumas who had been elected Secrétaire Perpétuel of nitric acid of different concentrations on the essence of (Permanent Secretary) of the same (1868); of the Académie anis, synthesized anisic acid (4-methoxybenzoic acid), and de Cherbourg; of the Académie de Dijon; and of the Chemi- anisol (methyl phenyl ether). He also proved that the es- cal Society of London (1856), replacing Gerhardt who had sence of Gaultheria procumbens (essence of wintergreen) recently passed away. He was also corresponding member was actually methyl salicylate, a compound that was also of the Berlin Academy, replacing Pelouze (1867); of the Ger- simultaneously an acid and a phenol. This was the first ex- man Chemical Society (1870); and of the Académie des Sci- ample of an acid playing a mixed function. Additional work ences of Saint-Pétersbourg (1873). The Académie des Sciences was related to salicylic acid and anisic acids, their methyl awarded him twice (1867 and 1870) the Jecker prize for his and ethyl esters, and the products of their reactions with work on amyl alcohol and on organometallic compounds, a chlorine, bromine, nitric acid and KOH (Cahours, 1841, prize established in 1851 to accelerate the progress in organ- 1843ab, 1844a, 1849, 1857a).3 ic chemistry. He was also nominated commander of the Lé- Another import work done at Dumas’ laboratories was gion d’Honneur. related to the abnormal density of acetic acid. At Cahours’s His research activities encompassed a wide range of sub- time it was accepted that one mole ����������������������of any substance occu- jects. While working for Chevreul at the Muséum, Cahours pied in the vapor state the same volume as one mole of an discovered by accident a bottle containing oil of potatoes, ideal gas. According to Avogadro’s law, relative molecular left from the time his mentor was investigating fatty materi- formulas corresponded to four volumes of vapor. Certain als. After painful work he proved that this oil was an alcohol, molecules, like acetic acid, behaved abnormally and pre- which he named amyl alcohol. Together with spirit of wine sented an equivalent of three volumes. Cahours proved that (ethanol), spirit of wood (ethanol), and éthal (spermaceti these abnormal densities resulted from having been mea- cetyl alcohol, hexadecanol), the new substance was the sured at temperatures a little above the boiling point of the fourth of this new natural family and a discovery that hinted compound. The density of a gas approached
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