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Henri, Victor

HENRI, VICTOR

(b. Marseilles, France, 6 June 1872; d. La Rochelle, France, 21 June 1940)

physics.

Henri’s birth record contains the statement “parents unknown.” According to French custom, the child was given an arbitrary surname. In fact, his parents were Russian aristocrats, forbidden to marry by orthodox church law because they were cousins. His uncle was Admiral Alexis Krylov, a famous naval engineer. Krylov’s mother was related to the Lyapunovs, the family of the great mathematician.

Henri studied at the German Gymnasium in St. Petersburg and received the baccalauréat in Paris in October 1889. He studied mathematics, physics, and chemistry in the Classes Préparatoires aux Grandes Écoles, then at the Sorbonne, where he was enrolled from 1893 to 1894. From 1892 to 1894 he worked in the laboratory of physiological psychology at the Sorbonne under Alfred Binet and attended the psychology course of Théodule Ribout at the Collège de France. He contributed chapters on sensation, memory, and psychometry to Binet’s Introduction à la psychologie expérimentale (1894). From 1895 to 1904, he was an editor of the journal Année psychologique.

From October 1894 to March 1896. Henri was a student in the philosophy department of the University of Leipzig, where he worked under Wilhelm Wundt, and from May 1896 to May 1897 at Göttingen, where he worked under Georg Elias Müller. On 5 June 1897, he presented a dissertation at Göttingen that concerned space perception in the sense of touch, a question little studied by psychophysicists. It was published under the title Über die Raumwahrnehmungen des Tastsinnes (1898). At the end of the work, Henri sketched a biological interpretation of the extensional aspects of touch, which in his view should depend on cutaneous physiological structures.

Henri’s physiological orientation to experimental psychology is revealed in his monograph La fatigue intellectuelle (1898), written with Alfred Binet. The work was undertaken to study the mental strain experienced by students. Numerous physiological parameters—cardiac and respiratory rhythm, blood pressure, body temperature, cutaneous sensitivity— were studied during intellectual work. Significant variations were observed, compared with the resting state.

Pursuing his physiological interests, Henri entered the experimental physiology laboratory of the Sorbonne, headed by Albert Dastre, who had been a pupil Henri became technical assistant to Dastre, who encouraged him to study the physicochemical basis of physiology. Henri began to study quantitative aspects of enzymatic action and went to Wilhelm Ostwald’s laboratory of physical chemistry in Leipzig to study catalysis. His science dissertation was presented at the Paris faculty of sciences on 20 February 1903, and published under the title Lois générales de l’ action des diastases. This work laid the theoretical foundations of enzyme kinetics. Relying on Emil Fischer’s concept of a complex between the enzyme and its substrate, Henri treated the formation and dissociation of this complex by the mass action law, thereby deriving fundamental equations. Thus the activity of biological agents was reduced to the basic laws of physical chemistry. Henri opposed vitalist conceptions and the search for laws that would be peculiar to biology. Ten years later, in their classical work on enzyme kinetics, Michaelis and Menten acknowledged Henri’s work.

Henri’s treatment of enzymatic catalysis is based on the concept that the catalyst acting on an equilibrium reaction does not change the equilibrium value. Thus, if a is the total amount of substrate, x the substrate (or product) combined with the enzyme, (a – x)the free substrate, c the total amount of the enzyme, m the amount of enzyme combined with the substrate, (C– m); the free enzyme, then the mass action law allows the following equation: (a – x);(c – m); equals Km, where K is the equilibrium constant for the formation of the complex between the enzyme and its substrate. Henri then assumes that the rate of formation of the product x is proportional to the quantity of combined catalyst m, whose value is given by:

Thus, the rate of formation of the product is given by the following equation: where K1 is a proportionality constant. The value of x given by integrating this equation combines a logarithmic and a linear factor. In their 1913 paper, Michaelis and Menten used the same basic assumptions but introduced some simplifications and gave a simpler expression for the rate equation.

In 1907 Henri was appointed maître de conférences at the Sorbonne, in charge of a course on physical chemistry, and did research in colloid chemistry. He started using absorption spectra of various organic molecules in the infrared, ultraviolet, and X-ray spectra, and he oriented the activity of his research group toward photochemistry, ranging from the basic properties of rays to their chemical and biological actions and their possible technical and industrial applications. The following year Henri went to Jena in order to study new techniques of microscopy at the Carl Zeiss Foundation. For three years he gave a course on photochemistry at the Sorbonne, and worked on a treatise on photochemistry with René Wurmser. During this period he was appointed adjoint director of the physiological laboratory at the École Pratique des Hautes Études (1913–1914). In 1910, Henri married his second wife, Pauline Cernovodeanu, a Romanian bacteriologist at the Pasteur Institute who was part of his research group. They were later divorced.

Many results in the photochemistry and ultraviolet spectra of molecules of organic compounds such as hemoglobin were obtained, and work on photosynthesis was envisaged when World War I broke out. In 1915, Henri collaborated in a research program on gas warfare for national defense. In September of that year, the French government sent him to Russia to inform the Russians of the French work and help them organize their chemical industry for military purposes. After the October Revolution, he was given a chair of physiology at the Choniawski University in Moscow ( 1917–1918) and a laboratory at the Moscow Scientific Institute; he also became the scientific secretary of the Moscow section of the Academy of Sciences Committee for the Study of Natural Resources. Henri resumed his studies on photochemistry, completing calculations, discovering general laws, and formulating hypotheses on the structure of molecules and mechanisms of light absorption. The work, completed in 1918, was published under the title Études de photochimie (1919). While in Moscow, he met a cousin, Vera de Lyapunov, the daughter of Princess Elizabeth Khoviansky and of Vasily Lyapunov. Married in 1923, they had four children.

Henri left Moscow, hoping to resume work at the Sorbonne laboratory. But Dastre had died in 1917 and had been replaced by Louis Lapicque. The laboratory was empty, and the position of adjoint director at Hautes Études was not a steady one. In 1920 Henri left Paris for Zurich, where he held a chair of physical chemistry at the university. Among his colleagues were Hermann Weyl, Erwin Schrödinger, and Peter Debye. While there he made his most important discovery, the predissociation of molecules in an activated state, a significant contribution to molecular physics.

Looking carefully at the absorption spectra of gaseous molecules, Henri discovered narrow and wide bands, depending on the frequency of the light used, for the same molecule. Wide bands were obtained with a higher frequency. Henri was deeply puzzled by this difference in the width of the bands, a phenomenon neglected by other spectroscopists, who were more concerned with the position of the bands. Henri was able to give a theoretical interpretation in terms of the stability of molecular structure. Wide bands are the sign of a “predissociated” chemical reactivity. They were attributed to rotatory states of the whole molecule that were not quantified—as they are in the normal state of the molecule. Electronic activated states and atomic vibratory states also were considered in the explanation of molecular spectra. A basic concept of photochemical action was thus established, and was presented in the monograph Structure des molécules (1925)-Henri continued ot speculate on the relationships between predissociation and photochemistry for the rest of his life.

In Structure des molécules, Henri proposed more controversial ideas on structural chemistry. From the study of absorption spectra and other experimental evidence, and for reasons of symmetry, he deduced unexpected structural models instead of classical ones for molecules such as benzene and its derivatives, In his view, benzene was a distorted octahedron. This was before the Heitler-London concept of the homopolar chemical bond.

In 1927 Henri and René Wurmser published another important contribution to photochemistry, in which they claimed that Einstein’s concept of photochemical equivalence does not hold true for photochemical reactions, since for most of them the quantum yield is not equal to unity. Henri and Wurmser found that Einstein’s law is valid only for elementary photochemical processes, activations. predissociations, and dissociations or ionizations of atoms and molecules. But because other energy exchanges take place within the reaction, the kinetics does not follow Einstein’s law.

In 1930. Henri left the University of Zurich to head a research laboratory to be established by an oil company near Marseilles. He planned to work on the basic mechanisms of oil cracking. Unfortunately, the project never came to fruition, and Henri accepted a chair of physical chemistry at the University of Liége in December 1931.

At Liége, Henri continued his work on spectroscopy. turning to polyatomic molecules, and began to work on thermal activation. In 1934, Peter Debye was invited by the Francqui Foundation to give a series of lectures at the University of Liége. During this year, Debye and Henri organized regular meetings, which were a great source of excitement for those who attended. One of Henri’s pupils, the neuropharmacologist Zénon Bacq, in his book Les transmissions chimiques de l’ influz nerveux (1974). showed that during this period Henri’s interest in biophysics was as strong as ever. Henri helped Bacq, who was searching for the sympathetic neurotransmitter, to use ultraviolet spectroscopy in order to characterize chemically the molecules being investigated. Henri studied the spectra of hormone and vitamin molecules in order to establish structural features as well as to devise measurement and dosing methods. His Liége lectures were published under the title Physique moléculaire; Matière et énergie (1933). He also published numerical tables of molecular spectra and, with William A. Noyes and Fritz London. edited the section on general chemistry of the International Meeting on Physics, Chemistry, and Biology that was held at Paris in 1938.

When World War II broke out. Henri went to Paris to do military research at the French National Center of Scientific Research (CNRS). He left Paris in June 1940, suffering from a lung infection, and died at La Rochelle on the twenty-first of that month.

BIBLIOGRAPHY

I. Original Works. La fatigue intellectuelle (Pais, 1898). Written with Alfred Binet: Über die Raumwahr-nehmungen des Tastsinnes. Ein Beitrag zur experimentellen Psychologie (Berlin, 1898); Lois générales de l’ action des diastases (Paris, 1903): Cours de chimie physique (Paris, 1907); “Absorption des rayons ultra-violets et action photochimique.” in Journal de physique théorique et appliquée, 5th ser., 3 (1913), 305–323, written with René Wurmser: Études de photochimie (Paris, 1919): Structures des molécules. Publications de la Société de Chimie Physique 12 (Paris, 1925), rev, ed by H. Brasseur and C. Corin (Liége. 1934);: Le mecanisme élêmentaire des actions photochimiques, ’ in Journal de physique et le radium. 6th se., 8 (1927), 289–310, written with René Wurmser; “Structure des molécules et spectres de bandes.” in L’ activation et la structure des molécules (Paris. 1928). 96–105; “Experimentelle Grundlagen der Prädissoziation der Moleküle.” in Peter Debye, ed., Leipziger Vorträge 1931 Molekülstrukur (Leipzig, 1933), 131–154; Physique moléculaire. Matiéer et énergie (Paris, 1933);’ étude de l’ adsorption de CO2 par différents cokes et de leur pouvoir réducteur, ’ in Chimie et industrie, 34 (1935), 1485, written with G. Perlmutter and E. GeversOrban: “Étude du spectre de l’ absorption ultraviolet de la vapeur de pyridine: Relation avec le spectre de Raman”, in Journal de chimie physique, 33 (1936), 641–665, written with A. Angenot: Spectres moléculaires. Structure des molecules. nos. 11and 12 of Tables annuelles de constantes et données numériques (Paris, 1937): Chimie Générale (Paris. 1938). edited with William A, Noyes and Fritz London: and “The Ultraviolet Absorption Spectra of 1–3 Cyclohexadiene,” in Journal of Chemical Physics. 7 (1939), 439–440, written with Lucy W. Pickett.

II. Secondary Literature. Léon Brillouin, “Hommage à Victor Henri,” in Volume commémoratif Victor Henri. Contribution à l’ étude de la structure moléculaire (Liège, 1947), vii-ix; Jules Duchesne, “Avant propos,” ibid., xi-xiii, ’ La structure moléculaire.’ in Journal de chimie physique et de physicochimie biologique50 (1953), 608–610 “Victor Henri,” in Robert Demoulin, ed., L’U niversitê de Lieeacurt;ge de1936 á 1966. Liber memorialis, II Notices biographiques (Liége. 1967), 471–477, and “Victor Henri,” in Biographie nationale publié é par l’ Académie royale des sciences, des lettres et des beaux-arts de Bel- gique XLII (Brussels, 1981), 346–354; M. Letort, “La cinétique chimique dans l’oeuvre scientifique de Victor Henri,” in Journal de chimie physique et de physicochimie biologique, 50 (1953), 604–607: B. Rosen, “La prédissociation,” ibid., 601–603; and René Wurmser, “La théorie des enzymes,” ibid., 611–612.

Claude Debru

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