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Braconnot, Henri

Braconnot, Henri

(b. Commercy, France, 29 May 1780; d. Nancy, France, 13 January 1855)

chemistry.

Braconnot, a pioneer in the study of plant and animal chemistry, was the son of Gabriel Braconnot, a lawyer. His father died in 1787, leaving to his widow’s care not only Henri but also a younger brother, André. His mother enrolled Henri in the Collège de Commercy, a Benedictine school, but he rebelled against its strict discipline and she was forced to remove him and find private means of education. Meanwhile, Mme. Braconnot remarried. This compounded Henri’s unhappiness, for his stepfather, a physician named Huvet, disliked him from the start and did all he could to come between the boy and his mother.

Braconnot was apprenticed to an apothecary in Nancy at the age of thirteen; two years later he went to Strasbourg as a pharmacist in a military hospital. He remained in Strasbourg until 1801, studying scientific and medical subjects at a number of institutions, the most important being the École Centrale du Département du Bas-Rhin. In 1801 he went to Paris to complete his scientific education, attending courses in chemistry, biology, and geology given by such luminaries as Fourcroy and Étienne Geoffroy Saint-Hilaire. He made a good impression on his teachers, and reinforced it by his first major paper, “Recherches sur la force assimilatrice dans les végétaux” (1807). Through the influence of Fourcroy, Braconnot secured the directorship of the Jardin Botanique de Nancy, a position he held for the rest of his career. In 1823 he was elected a corresponding member of the Institut de France. After the death of his stepfather, Braconnot lived with his mother, to whom he was very much attached, until her death in 1843. He was highly skeptical of physicians and suffered greatly from an untreated cancer of the stomach, which caused his death.

Braconnot lived a life of great simplicity; his only amusements were literature and the ater. In adult life, in contrast to his childhood, he was retiring and painfully shy. He never married.

Braconnot’s research was conditioned by his double interest in botany and chemistry. What made it original and fruitful was not any novelty of theory or experimental method but, rather, the scope and detail of his investigations, carried out over thirty years. Added to this were his experimental facility and his sensitivity to the presence of previously unknown substances. A guiding theme, exhibited in his first major paper in bizarre, romantic chemical terms and in a number of subsequent important papers, was the attempt to elucidate the steps by which the complex organic constituents of plants were synthesized from simple inorganic substances.

Braconnot’s methods of analysis remained conservative—similar, for example, to those outlined by Fourcroy in 1801 for organic substances. Although he made careful gravimetric determinations of the initial and final products collectively, he almost never attempted quantitative analysis of the individual products that he had discovered. He was generally content to describe such substances as new “vegetable acids” or “animal substances” and to give some idea of their chemical properties.

From 1807 to 1819, Braconnot analyzed a variety of plant and animal substances. One of his first discoveries was a cellulose substance in mushrooms, which he named fungine. He began a study of fatty substances, which he analyzed physically into combinations of a solid tallow and a liquid oil, but his work was superseded by that of Chevreul. In 1817 he published a paper in which he disproved the idea, enunciated by Fourcroy and held by Berzelius, among others, that there existed a unitary “extractive principle” in vegetable substances. The following year, he published his discovery of ellagic acid in nutgalls.

Beginning in 1819, Braconnot embarked upon a series of researches on the effects of sulfuric acid on wood and ligneous fibers. He discovered that sawdust, when treated with concentrated sulfuric acid, was converted into a gum that, in turn, was convertible into sugar and what he called a “vegeto-sulfuric” ulmin—a substance discovered by Vauquelin in 1797. He went on to study the effects of sulfuric acid on animal substances: gelatin, muscle fibers, and wool. In the case of gelatin, he discovered a sugar-like substance which he called sucre de gélatine, later named glycocoll (glycine). Sulfuric acid converted wool and muscle fiber to a white substance he called leucine.

In the 1820’s and 1830’s Braconnot’s discoveries included pectic acid; legumin, a substance discovered in beans that he thought was analogous to albumin; populin (benzoylsalicin), discovered in the bark of the aspen; pyrogallic acid, produced from the heating of gallic acid; and xyloïdine (nitrocellulose), produced by the action of concentrated nitric acid on potato starch or wood. Various substances he thought he had discovered turned out subsequently to be identical with known ones; these included aposépédine, a product obtained from the distillation of the liquid of petrified cheese, later shown to be leucine, and equisetic acid, shown to be maleic acid.

BIBLIOGRAPHY

I. Original Works. For a listing of Braconnot’s many articles, see the Royal Society of London’s Catalogue of Scientific Papers, I (1867), 557–561. The biography by M. J. Nicklès (see below) contains a bibliography taken from Braconnot’s own catalog of his works. He published no large monographs or textbooks. His papers include: “Recherche sur la force assimilatrice dans les végétaux”, in Annales de chimie, 1st ser., 61 (1807), 187–246; “Mémoire sur le principe extractif et sur les extraits en général”, in Journal de physique, de chimie, d’histoire naturelle et des arts, 84 (1817), 267–296, 325–349; “Observations sur la préparation et la purification de l’acide gallique, et sur l’existence d’un acide nouveau dans la noix de galle”, in Annales de chimie et de physique, 2nd ser., 9 (1818), 181–189; “Mémoire sur la conversion du corps ligneux en gomme, en sucre, et en un acide d’une nature particulière, par le moyen de l’acide sulfurique; conversion de la méme substance ligneuse en ulmine par la potasse”, ibid., 12 (1819), 172–195; “Mémoire sur la conversion des matières animales en nouvelles substances par le moyen de l’acide sulfurique”, ibid., 13 (1820), 113–125; “Recherches sur un nouvel acide universellement répandu dans tous les vég;étaux”, ibid., 28 (1825), 173–178; “Nouvelles observations sur l’ acide pectique” ibid.,30 (1825), 96–102.

II. Secondary Literature. M. J. Nickès, “Braconnot sa vie et ses travaux”, in Mémoires de l’Académie Stanislaus (1855), xxiii–cxlix, is the only extensive biography of Braconnot. Although a bit melodramatic about his personal life, it is very thorough in its account of his scientific career. See also E. Frémy, Encyclopédie chimique, I (Paris, 1882), fasc. 1, 101–103; M. J. Nicklès, “Correspondence of J. Nicklès”, in American Journal of Science, 2nd ser., 21 (1856), 118–119; and J. R. Partingon, A History of Chemistry, IV (London, 1964), 251.

Seymour H. Mauskopf

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