THENARD, LOUIS JACQUES

(b. La Louptiè re [now Louptière–Thenard], Aube, France, 4 May 1777; d, Paris, France, 20 or 21 June 1857)

chemistry.

Thenard was the second son of Étienne Amable Thenard and Cécile Savourat, peasant farmers, who had seven children. He received an elementary education from a local priest, and his obvious intelligence marked him out, so that at the age of eleven he was sent to the collège at Sens. He soon had the ambition to become a pharmacist and went to Paris with two friends to take advantage of the educational resources of the capital. Thenard attended the public courses of Vauquelin and Fourcroy and was taken into the Vauquelin household as a bottle washer and scullery boy. Vauquelin eventually allowed him to deputize for him in his lecture course; Thenard’s first official appointment came in December 1798, when he was named demonstrator at the École Polytechnique.

When Vauquelin retired from his chair at the Collège de France, Thenard was nominated to succeed him (13 April 1804). Upon the founding in 1808 of the faculties of sciences, Thenard was appointed professor of chemistry at the Paris Faculty. With a secure income and a place in the new scientific–teaching community, he could think of marriage; and in 1814, after four years of negotiating with the family, he married the daughter of Arnould Humblot–Conté. Fourcroy’s death in 1809 left a vacancy in the chemistry section of the First Class of the Institute, to which Thenard was elected (29 January 1810). He was a member of the Society of Arcueil and his work in this period (ca. 1807–1814) reveals the influence of his colleagues in that group, not least the physical approach of its leader, Berthollet.

Thenard was a lifelong member of the Société d’Encouragement pour l’Industrie Nationale; and when its founder, Chaptal, died in 1832, he was elected president. His interest in applied chemistry also meant that he played a prominent part in judging the national industrial exhibitions held in 1818 and at five–year intervals thereafter. He was also a member of the governing body of the Conservatoire National des Arts et Métiers.

Thenard was appointed dean of the Paris Faculty of Sciences in 1822. In 1830 he was nominated to the Royal Council of Public Instruction, on which he was especially concerned with the teaching of the physical sciences at the university level. From 1845 to 1852 he was chancellor of the University of France—the highest post in the French educational system.

Thenard was made successively a knight (1814), officer (1828), commander (1837), and grand officer (1842) of the Legion of Honor. In 1825 he was given the title of baron. In 1827 and in 1830 Thenard was elected to the Chamber of Deputies, his politics being to the right of center. On 11 October 1832 he was nominated as a peer; and in the upper chamber, as in the lower, his contributions to debates were usually on technical and scientific matters. He was particularly influential in his support of the sugar beet industry, which had begun in Napoleonic times and under the Restoration was threatened by the importation of cane sugar.

Thenard’s early scientific work, particularly his interest in plant and animal chemistry, betrays the influence of his first patrons, Vauquelin and Fourcroy. In 1801 he obtained a new acid by distilling tallow. He called it sebacic acid and showed that what Guyton de Morveau had called sebacic acid was only impure acetic acid. Three years later he showed that the acid that Berthollet had named “zoonic acid” (obtained by distilling meat) was, again, really impure acetic acid. In his analysis of bile Thenard obtained a resin and another substance that he named “picromel”, which was found to be a good solvent of fats.

His most important organic work was on the esters, then called “ethers”. The name “ether” was given to any neutral product formed by the reaction of an acid with alcohol. The only “ether” that had been prepared and studied with any success prior to this time was “sulfuric ether” but since it was what is now known as diethyl ether and not a true ester, knowledge of this compound tended to hinder rather than help the investigation of other “ethers”. It was part of Thenard’s achievement to distinguish “sulfuric ether” from the true esters. He made a careful study of the action of nitric, hydrochloric, acetic, benzoic, oxalic, citric, malic, and tartaric acids on ethyl alcohol and prepared the respective esters, many for the first time. His preparation of “nitric ether” (ethyl nitrite) is of value for his concern to obtain a pure product and to determine the yield.

Unknown to Thenard, “muriatic ether”(ethyl chloride) had been prepared slightly earlier by Gehlen; but Thenard’s memoir on this ester is notable for its study of the influence of time on chemical reactions involving organic compounds. He studied the reaction at room temperature between ethyl chloride and a concentrated solution of caustic potash over a period of three months, testing for the decomposition of the ester with silver nitrate solution.

Thenard’s quantitative study of “acetic ether” (ethyl acetate) may be regarded as a model for its time. He studied both its preparation (in the presence of concentrated sulfuric acid) and its hydrolysis, always referring quantities of acid to equivalent weights of potash. By distilling the ester with an aqueous solution of caustic potash, he obtained alcohol and potassium acetate. Thenard thus proved conclusively by both analysis and synthesis that the “acetic ether” was a simple compound of acetic acid and alcohol, a valuable datum for organic chemistry. Thenard made the important statement that when alcohol combines with vegetable or mineral acid, the alcohol acts as a “true salifiable base” ¹. Thus he drew an extremely useful analogy between the action of acids on bases to form salts in inorganic chemistry and the action of acids on alcohols to form esters in organic chemistry. This analogy was later extended by Chevreul in his study of saponification.

That Thenard was a worthy heir to the analytical skill of Vauquelin is shown by his early study of nickel (1802). He took particular care to obtain nickel free from traces of cobalt, iron, and arsenic. Typically, he announced the discovery of a new, higher oxide of nickel. It was, however, his study of certain cobalt compounds, published in 1804, that brought him greater fame. There was a particular need in France under the Consulate for a new blue pigment; and Thenard was commissioned by the minister of the interior, Chaptal, to obtain one. At one time lapis lazuli had been used, but it had become extremely rare and expensive. Prussian blue was not an effective substitute, and so Thenard experimented with cobalt arsenate, used in the coloration of Sèvres porcelain. He found that alumina heated in certain proportions with the arsenate or phosphate of cobalt produced the most permanent pigment. His final trials on the pigment included exposure to bright light for two months and exposure to acids, alkalies, and hydrogen sulfide. It became known as “Thenard’s blue”, although a similar color had been obtained earlier by K. F. Wenzel and Gahn. Thenard was helped in his research by the professor of drawing at the École Polytechnique, Léonor Mérimée, who later developed the use of hydrogen peroxide for restoring paintings.

An appreciable part of Thenard’s research was concerned with the combining proportions of elements in certain compounds, particularly metal oxides. One of his earliest pieces of work was a report on the existence of six different oxides of antimony, which Proust reduced to two; the correct number (three) was determined later by Berzelius. Thenard announced the existence of four different oxides of cobalt and investigated the oxides and salts of mercury. He did research on the two sulfides of arsenic, realgar and orpiment, and showed that they contain no oxygen. In 1805 he published a memoir on the oxidation of metals in general. Thenard could not agree with Berthollet that oxidation of metals might take place in an indefinite number of stages, yet he believed that there were more different oxides of each metal than most chemists of the time were prepared to admit. He considered the solubility of different oxides in acids, making a particular study of iron and examining the oxidation of freshly precipitated ferrous hydroxide. Thenard established the existence of the unstable white ferrous oxide and thus helped to throw light on the chemistry of iron salts. He investigated phosphates of soda and ammonia, and analyzed phosphorous acid. His analysis of alloys of antimony and tin are a further reminder of his interest in combining proportions (he considered these alloys as compounds).

In 1812 Thenard obtained crystals of ammonium hydrosulfide by mixing ammonia gas and hydrogen sulfide. The proportions of the elements in another sulfide, hydrogen persulfide, had been studied by Berthollet; and Thenard later reexamined this problem. Believing that oxygen and sulfur were analogous elements and having discovered hydrogen peroxide, he considered that hydrogen persulfide was its analogue. He concluded that it varied in composition between extremes of “four atoms of sulfur and one atom of hydrogen sulfide” and “eight atoms of sulfur and one atom of hydrogen sulfide”. The apparently variable composition helped to convince Thenard that it was a compound with a variable amount of physically dissolved sulfur. In the later editions of his Traité he presented both hydrogen peroxide and hydrogen persulfide as “compounds the elements of which obey forces other than affinity”.

Thenard soon acquired a reputation as an analyst and thereby met Biot. In 1803 Biot was nominated by the First Class of the Institute to examine reports of meteorites; samples were brought back to Paris and a chemical analysis was carried out by Thenard. His most important collaboration with Biot was on a comparison of calcite and aragonite, since the two substances presented one of the earliest examples of dimorphism. Thenard’s chemical analysis showed no difference between the two minerals despite their different crystalline forms. He and Biot concluded: “The same chemical principles combined in the same proportions can give rise to compounds that differ in their physical properties” ².

A considerable amount of research was carried out by Thenard in collaboration with Gay-Lussac in 1818–1811, during which period they published about twenty papers. Thenard probably first met Gay–Lussac either when the latter was a student at the École Polytechnique or when they were both on the junior staff of that institution. The earliest record of their collaboration was on the occasion of Gay–Lussac’s solo balloon ascent on 16 September 1804. Gay–Lussac took the flask of air he had collected at a high altitude to the laboratory of the École Polytechnique and with Thenard analyzed that air in comparison with ordinary Paris air. It was, however, the news of Davy’s isolation of potassium, which reached Paris in the winter of 1807–1808, that prompted them to undertake a sustained collaboration largely in emulation of the English chemist. On 7 March 1808 they announced to the First Class of the Institute that they had prepared potassium by purely chemical means. The method, which involved fusing potash with iron filings in a gun barrel, had the advantage of producing potassium (and similarly sodium) in reasonable quantities, whereas Davy had been able to produce only tiny quantities of the substances. A controversy arose over the nature of potassium and sodium, Davy claiming that they were elements while Gay–Lussac and Thenard gave undue attention to experimental evidence suggesting that they were metal hydrides.

When funds were made available to construct a giant voltaic pile at the École Polytechnique (larger than that used by Davy at the Royal Institution), Gay–Lussac and Thenard were put in charge of the apparatus. Their results, reported in full in their Recherches physico–chimiques, are rather disappointing; Davy had effectively creamed the field. The superiority of the French chemists emerges in their investigations of the reactions of potassium metal. By strongly heating it in hydrogen, they prepared potassium hydride; and by heating the hydride in carefully dried ammonia, they obtained the olive-green solid KNH₂. When the solid was heated, it decomposed and ammonia, hydrogen, and nitrogen were released. The action of water on the solid produced potash and ammonia. Thenard and Gay–Lussac went on to use potassium to decompose boric acid and announced the isolation of a new element, boron, in November 1808. They obtained nearly anhydrous hydrofluoric acid by distilling calcium fluoride with concentrated sulfuric acid in a lead retort; and by heating calcium fluoride with boron trioxide, they obtained the gas boron fluoride, which they collected over mercury.

In their work on chlorine Gay–Lussac and Thenard were surprised to find that when the gas was passed over red–hot charcoal, it was not decomposed. This cast doubt on whether the gas then called “oxymuriatic acid gas” really was a compound containing oxygen. The authority of Berthollet persuaded them that this conclusion was not fully justified, and accordingly they mentioned it as only a possibility. It was left to Davy in 1810, after he had read their memoir, to announce that chlorine was in fact an element. Thenard and Gay–Lussac, however, deserve full credit for their pioneering contributions to photochemistry. They investigated the effect of light on mixtures of chlorine and hydrogen and chlorine and ethylene. The extent of the reaction in darkness or in a diffused light was judged by the change in the greenish–yellow color of the chlorine gas. Bright sunlight was found to bring about combination with explosive violence.

Another fruitful collaboration by Gay–Lussac and Thenard was that carried out in 1810 on the combustion analysis of vegetable and animal substances. Lavoisier’s published organic analysis had made use of oxygen gas; but the two young chemists greatly extended the generality of this method by using an oxidizing agent, potassium chlorate. On the basis of their analysis they divided vegetable compounds into three classes according to the proportion of hydrogen and oxygen they contained. The class (containing starch and sugar) in which hydrogen and oxygen were in the same proportions as in water corresponds to the carbohydrates. Although in this joint research it is impossible to separate the contributions of Thenard from those of Gay–Lussac, one has the impression that Thenard usually came second to his friend in the quality, originality, and precision of his research.

Inspired by the fundamental work of Lavoisier on alcoholic fermentation, the Institute in 1800 and 1802 offered a prize on the subject. Thenard submitted a memoir and, according to a standard source, it “provided many of the facts upon which Liebig subsequently based his views”³. He pointed out that all fermenting liquids deposit a material similar to brewer’s yeast and he demonstrated that it contained nitrogen. His study of yeast used to ferment pure sugar showed that it underwent a gradual change and was finally reduced to a white material that contained no nitrogen and produced no reaction with sugar. Thenard had begun by asking, “How is sugary matter changed into alcohol and carbonic acid by means of an intermediate body? What is the nature of this body? How does it act on sugar?”⁴ The young chemist was not able to solve these complex problems, which a generation later became a subject of vigorous dispute between biological microscopists and chemists. Berzelius, for example, opposed biological explanations with the theory that fermentation was merely an example of contact catalysis due to a nonliving catalyst–a view that may be traced back to Thenard’s work. In 1820, when he was studying the effect of finely divided metals on hydrogen peroxide. Thenard compared this phenomenon to the action of yeast in alcoholic fermentation ⁵.

Thenard’s greatest single discovery was that of hydrogen peroxide. He read his first paper on the subject to the Académie des Sciences on 27 July 1818, and successive volumes of the Annales de chimie contain his researches. The work had its origins in his earlier collaboration with Gay–Lussac, in which they had shown that when potassium or sodium is heated in dry oxygen, a higher oxide is obtained. Heating baryta strongly in oxygen also produced a new higher oxide. In the presence of water all these peroxides decomposed, liberating oxygen. The discovery of hydrogen peroxide seems to have been related to Lavoisier’s theory of chemistry, according to which metals combined with acids to form salts only after an initial oxidation reaction; thus it was the metal oxide rather than the metal that dissolved in the acid. The metal should not be too highly oxidized, however, because it would then have little affinity for acids (acids were considered as extreme products of oxidation). Thenard wished to test this idea by seeing whether barium peroxide would dissolve in acids.

Thenard’s first paper on hydrogen peroxide announced that he had prepared new oxygenated acids by treatment of barium peroxide with mineral acids. Thus, for instance, barium peroxide dissolved in dilute nitric acid to produce a neutral solution. The barium nitrate was precipitated as barium sulfate, leaving what we recognize as hydrogen peroxide. Unfortunately Thenard used sulfuric acid to remove the barium salt and therefore had an acid product. Using this process, he prepared an “oxygenated acid” containing up to eleven times its own volume of oxygen. Since heating caused decomposition, his method of concentration was to use a vacuum pump at room temperature. By September 1818 Thenard had employed this method in preparing a product containing thirty–two times its own volume of oxygen. He recognized that its decomposition was accelerated by light and found that when the concentrated product came into contact with silver oxide, the oxygen was liberated in a violent reaction. By 23 November he had prepared “oxygenated water” and had begun to doubt whether his “oxygenated acids” were true compounds. Thenard had now, therefore, prepared a second compound of hydrogen and oxygen. It was neutral and could be distilled in a vacuum without decomposition. He found that the decomposition occurring when, for example, manganese dioxide was added, was exothermic. He went on to prepare a very concentrated product containing more than four hundred times its own volume of oxygen and found that it attacked the skin.

A major problem throughout this research had been to discover whether oxygen could combine with acids or water indefinitely, thus supporting the largely discredited ideas of Berthollet. This had been one of Thenard’s motives for preparing an increasingly concentrated product. Finally he announced that he had succeeded in reaching the saturation point. This pure “oxygenated water” had a density of 1.455 (modern 1.465) and reacted explosively with various metal oxides. Usually the oxygen evolved consisted of both the “excess” oxygen of the hydrogen peroxide and the oxygen of the metal oxide. In some cases, however, the peroxide acted as an oxidizing agent (for instance, with arsenious oxide). He made the important observation that acids render hydrogen peroxide more stable.

Thenard completed his work on hydrogen peroxide by giving a detailed description of its preparation, starting from pure barium nitrate, which was heated to decompose it: oxygen was passed over the product to convert it into barium peroxide. The latter was then made into a paste in an ice–cooled vessel and just enough sulfuric acid added to precipitate all the barium, which was separated by filtration. Further purification was described to remove alumina, iron, and silica impurities. Thenard’s complete work on hydrogen peroxide was summarized in a long article published in 1820 in the Mémoires of the Academy. In it he concluded that hydrogen peroxide is a true peroxide (peroxide d’hydrogène) and contains twice as much oxygen as water does. He used it to prepare new peroxides and noted its oxidizing action on sulfides. Mérimée, his colleague at the École Polytechnique, suggested applying this reaction to restoration of old paintings.

In Thenard’s final and comprehensive paper on hydrogen peroxide (1820), he devoted several pages to the effect of finely divided metals on hydrogen peroxide, distinguishing, for example, between silver in an extreme state of division, finely divided, filings, and massive. Platinum, gold, osmium, palladium, rhodium, and other metals also were listed according to their state of division. Thenard was particularly concerned how these metals could take part in chemical reactions without apparently being affected.

This earlier work will help to explain Thenard’s particular interest in catalysis in 1823. Indeed, as early as 1813 he had investigated the effect of the presence of metals in promoting the decomposition of ammonia gas passed through a red–hot glazed porcelain tube ⁶. In August 1823 news reached Paris that Döbereiner had shown that spongy platinum at room temperature could bring about the combination of hydrogen and oxygen and that the heat from this reaction was sufficient to make the metal incandescent. Thenard collaborated with Dulong in experiments to confirm this finding. They extended the research by varying the physical state of the metal and by substituting other metals and other gaseous reactions. They demonstrated that the temperatures at which metals showed such effects depended on their state of division. Thenard and Dulong found that palladium, rhodium, and iridium had the same effect as platinum; and they went on to investigate the surface effects of other solids and the conditions under which substances lose their catalytic effect. Thenard, therefore, made significant contributions to knowledge of surface catalysis, although the term “catalyst” was not introduced by Berzelius until 1834.

Thenard was the author of a large and important chemistry textbook that went through six editions and was translated into German, Italian, and Spanish (the section on analysis was translated into English). Through this book he helped restore France to its traditional role as supplier of chemistry textbooks to the rest of the world; his only serious rival was the British chemist Thomas Thomson, who during the first two decades of the nineteenth century produced successive editions of his own textbook. The first edition of Thenard’s Traitéde chimie élémentaire was published in four volumes in 1813–1816. The first two volumes dealt with inorganic chemistry, the third with organic chemistry (divided into vegetable and animal), and the fourth with analytical chemistry. Similar substances were grouped together and discussed in general terms before consideration of their individual properties. In the Lavoisier tradition, oxygen was still considered as a unique element. Besides drawing on previous textbooks–such as those of Lavoisier, Fourcroy, and Thomson–Thenard incorporated the most recent research of his contemporaries. Plates and detailed descriptions of apparatus were provided, and in later editions were published as a separate volume. The detailed index included in each volume makes Thenard’s book a particularly useful reference work for the chemistry of its period.

Thenard took great pains to bring successive editions of his textbook up to date. in the sixth and final edition (1834–1836) there is a major rearrangement of the material. Particularly important is the addition of a fourth part that he described as an “Essai de philosophie chimique”, in which he dealt with the general principles of chemical combination and classification. He continued, however, to show the same reserve about Dalton’s atomic theory that he had expressed in earlier editions.

NOTES

1.Mémoires de la Sociéré d’ Arcueil, 2 (1809), 24.

2.Ibid., 206

3. A. Harden, Alcoholic Fermentation, 4th ed. (London, 1934), 4.

4.Annates de chimie, 46 (1802), 206–207.

5.Mémoires de l’Académie royale des sciences de l’Institut de France, 2nd ser., 3 année 1818 (1820), 487.

6.Annales de chimie, 85 (1813),61.

BIBLIOGRAPHY

I. Original Works. Thenard’s chemistry textbook went through six eds., all published at Paris: Traité de chimie élémentaire, théorique et pratique,, 4 vols. (1813–1816: 2nd ed., 1817–1818; 3rd ed., 1821; 4th ed., 5 vols., 1824; 5th ed., 1827; 6th ed., 1834–1836). With Gay-Lussac he wrote Recherches physico–chimiques, 2 vols. (Paris, 1811).

A selection from Thenard’s research papers is presented below. The order follows that of the text.

“Sur l’acide sébacique”, in Annales de chimie, 39 (1801), 193–202; “Observations sur’acide zoonique”, ibid., 43 (1802), 176–184; “Mémoire sur la bile”;, in Mémoires de la Sociélté d’Arcueil, 1 (1807), 23–45; “Mémoire sur les éthers”, ibid., 73–114; “Deuxième mémoire sur les éthers...”, ibid., 115–134; “Deuxième mémoire sur les éthers . . .,” ibid., 14–160; “De l’action des acides végétaux sur l’alcool . . .”, ibid., 2 (1809), 5–22;“Essai sur la combinaison des acides avec les substances végétales et animales,” ibid., 23–41.

“Sur le nickel” (1802), in Annales de chimie, 50 (1804), 117–133; “Considérations générales sur les couleurs, suivies d’un procédé pour préparer une couleur bleue aussi belle que l’outremer” in Journal des mines, 15 (1804), 128–136; “Différents états de l’oxide d’antimoine...”, in Annales de chimie, 32 (1799), 257–269; “Sur l’oxidation des métaux en général et en particulier du fer”. ibid., 56 (1805), 59–85; “Observations sur les hydro-sulfures”, ibid., 83 (1812), 132–138; “Mémoire sur le soufre hydrogéné ou l’hydrure de soufre”, ibid., 2nd ser., 48 (1831), 79–87; “Mémoire sur l’analyse comparée de l’aragonite et du carbonate de chaux rhomboidal”, in Mémoires de la Société d’ Arcueil, 2 (1809). 176–206, written with Biot.

Five memoirs written with Gay–Lussac: “Sur les métaux de la potasse et de la soude”, in Annales de chimie, 66 (1808), 205–217; “Sur la décomposition et la recomposition de l’acide boracique” ibid., 68 (1808), 169–174; “Sur l’acide fluorique” ibid., 69 (1809), 204–220; “De la nature et des propriétés de l’acide muriatique et de l’acide muriatique oxigéné”, in Mémoires de la Société d’Arcueil, 2 (1809), 339–358; and “Sur l’analyse végétale et animale”, in Annales de chimie, 74 (1810), 47–64.

“Sur la fermentation vineuse” in Annales de chimie, 46 (1803), 294–320; “Observations sur des nouvelles combinaisons entre l’ oxigène et divers acides”, in Annales de chimie et de physique, 2nd ser., 8 (1818), 306–312; “Nouvelles observations sur les acides et les oxides oxigénés”, ibid., 9 (1818), 51–56, 94–98; “Observations sur l’influence de l’eau dans la formation des acided oxigénés”, ibid., 314–317; “Nouvelles recherches sur l’eau oxigée”, ibid., 441–443; “Suite des expériences sur l’eau oxigénée”, ibid., 10 (1819), 114–115, 335; “nouvelles observations sur l’eau oxigénée”, ibid.,11 (1819), 85–87, 208–216; “Mémoire sur la combinaison de l’oxygène avec l’eau, et sur les propriétés extraordinaires que possède l’eau oxigéée”, in Mémoires de l’Académie royale des sciences de l’Instiut de France, année 1818, 3 (1820), 385–488.

With Dulong he wrote “Note sur la propriété que possèdent quelques métaux de faciliter la combinaison des fluides élastiques”, in Annales de chimie et de physique, 2nd ser., 23 (1823), 440–444; and “Nouvelles observations sur la propriété dont jouissent certains corps de favoriser la combinaison des fluides élastiques”, ibid., 24 (1823), 380–387.

II. Secondary Literature. See M.P. Crosland, The Society of Arcueil. A. View of French Science at the Time of Napoleon. I (London, 1967), passim; F. Dubois, éloge de M. Thenard, prononcé dans la séance publique annuelle de l’Académie impériale de médecine du 9 Décember 1862 (Paris, 1863); P. Flourens, “Éloge historique de Louis–Jacques Thenard”, in éloges historeiques, 3rd ser. (Paris, 1862), 201–248; L.R. Le Canu, Souvenirs de M. Thenard (Paris, 1857); J.R. Partington, A history of Chemistry IV (London, 1964), esp. 90–96; and P. Thenard,Un grand français. Le chimiste Thenard 1777–1857 par son fils; avec introduction et notes de Georges Bouchard (Dijon, 1950).

M.P. Crosland