Courtois, Bernard

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Courtois, Bernard

(b. Dijon, France, 8 February 1777; d. Paris, France, 27 September 1838)


The son of a Dijon saltpeter manufacturer, Courtois studied under Fourcroy at the École Polytechnique and worked as a pharmacist in military hospitals before becoming an assistant to Thénard in 1801. The following year he was assistant to Armand Séguin.

Courtois then returned to Dijon to take over his father’s business. The firm used seaweed ash as a source of valuable potassium and sodium salts. By leaching the ashes with water and evaporating the mother liquor, these salts could be precipitated. However, Courtois first had to add strong acid in order to remove the undesirable sulfur-containing compounds. One day late in 1811 he added sulfuric acid in excess and observed clouds of violet vapor evolving from the solution. The vapor, condensing on cold objects, formed dark lustrous crystals. For about six months he investigated the properties of this new substance, preparing its compounds of hydrogen, phosphorus, ammonia, and several metals. Barely able to eke out a living in the saltpeter business, Courtois then decided that he did not have the means to continue work on the substance and abandoned his research.

Sometime in July 1812, Courtois told two Dijon chemists, Charles-Bernard Désormes and Nicolas Clément, of his discovery and urged them to continue the research. With his permission they announced his work to the Institut de France on 29 November 1813. Before the end of the year both Gay-Lussac and Humphry Davy had examined the substance and independently established it as an element. Gay-Lussac named the new element “iode” because of its violet color.

All of these men acknowledged Courtois as the discoverer of iodine, and in 1831 the Institute awarded him a prize of 6,000 francs for the discovery. By this time Courtois had given up the saltpeter business and, from the 1820’s, attempted to make a living by preparing and selling iodine and iodine compounds. This enterprise also failed, and he died in poverty.


The first publications on iodine are somewhat confusing. Courtois’s research is found in a paper attributed to him but actually the work of Clément: “Découverte d’une substance nouvelle dans le Vareck,” in Annales de chimie, 88 (1813), 304–310. It was followed by an anonymous article, “Sur un nouvel acide forme avec la substance découverte par M. Courtois,” ibid., 311–318. Gay-Lussac, who repeated and extended Courtois’s work, was responsible for this paper. Courtois himself published nothing. These two articles were immediately followed by short contributions of Gay-Lussac and Humphry Davy on the new element: “Note sur la combinaison de l’iode avec l’oxigéne,” ibid., 319–321; and “Lettre de M. Humphry Davy sur la nouvelle substance découverte par M. Courtois, dans le sel de Vareck,” ibid., 322–329. Gay-Lussac’s views (none too flattering to Davy) on the history of the discovery of iodine appeared in his “Mémoire sur l’iode,” ibid., 91 (1814), 5–160.

There is a biography of Courtois by L. G. Toraude, Bernard Courtois, 1777–1838, et la découverte de l’iode, 1811 (Paris, 1921). Among the brief notices on Courtois, the most informative are Paul-Antoine Cap, “Notes historiques sur Bernard Courtois et sur la découverte de I’iode,” in Journal de pharmacie et de chimie, 20 (1851), 131–138; Paul Richter, “Über die Entdeckung des Jod and ihre Vorgeschichte,” in Archiv fur die Geschichte der Naturwissenschaften and der Technik, 4 (1907), 1–7; and Mary Elvira Weeks, in Discovery of the Elements, 7th ed., rev., new material added by Henry M. Leicester (Easton, Pa., 1968), pp. 708–712.

Albert B. Costa