Popular Science Monthly/Volume 27/May 1885/Sketch of M. Pierre E. Berthelot
UNTIL a few years ago, investigation in organic chemistry was pursued almost wholly by the road of analysis. As Gerhardt wrote in his treatise: "The chemist did everything in opposition to living Nature. He burned, destroyed, and worked by taking apart, while the vital force operated by synthesis or putting together, to reconstruct the edifice which chemical forces would destroy." The chemist was, in fact, a great destroyer. He could isolate the essence from a flower, and could destroy that essence and determine its chemical composition, but he was powerless to reconstruct the destroyed perfume, and could not even conceive that such a thing was possible. It is the chief title to fame of M. Berthelot that he introduced the synthetic method into organic chemistry, and devised a system of processes by means of which we are able to create organic compounds by the direct combination of their constituent radicals.
Pierre Eugène Marcellin Berthelot was born in Paris, October 25, 1827. He was the son of a physician of some distinction, and while a student in one of the lyceums of Paris showed marked tastes for philosophical studies and chemical research, so that, when the time for the contest came, he easily won the honors in philosophy. Then, following his favorite pursuits, he occupied himself especially with studies of the acids and fatty bodies, and of fermentations. In 1851 he became attached to the de France as preparator in the course of chemistry, in which position he was assistant to Balard. In 1854 he propounded his theory of polyatomic alcohols, and was in the same year made a Doctor in Science. In 1859 he was appointed a Professor in the Superior School of Pharmacy. In 1861 he received the Joecker prize from the Academy of Sciences for his experiments in the artificial production of chemical substances by synthesis. In 1864 he was made a Professor of Organic Chemistry in the College de France in a chair which had been created especially for him, in which he was instructed to advance his own ideas, and to treat in his lectures especially of his own discoveries.
M. Berthelot entered upon the researches in synthesis, which give him his strongest title to fame, in 1854. Berzelius had said that, although we may produce with inorganic bodies a few substances having a composition analogous to that of some organic ones, the imitation is too restricted to justify us in hoping that we shall be able to produce organic bodies in the same sense that we have frequently succeeded in confirming the analysis of inorganic bodies by performing the synthesis of them. Yet, when this was said, Wöhler had already performed the synthesis of urea; and a few other syntheses had been made, but they were so isolated, so insignificant, and so barren of fruit, that all attempts to constitute organic bodies by bringing together the elements of which they are composed were, as a rule, regarded as chimerical. The law and the manner of the formation of the organic matters which enter into the composition of the living being were unknown; the question whether those substances were chemical in their character, or depended for their existence and maintenance upon a peculiar vital force, had been started, but the discussion of it had not been seriously entered upon. M. Berthelot began to give his attention to the solution of this problem very early in his scientific career.
One of the first syntheses he performed was that of formic acid, and this was used as the basis of his further researches. Regarding this substance as formed by the union of water and carbonic oxide, he brought about a compound of that character through the intervention of potash, and secured the result he sought. Other syntheses followed this one, conducted, like it, with very simple compounds, till he was finally led to the artificial composition of the carburets of hydrogen. Among his most important experiments in this line was the artificial production of alcohol from defiant gas. Alcohol once obtained synthetically, he had a station whence he could pursue his investigations in various directions. It was not a long step from this to the composition with the same elements (oxygen, hydrogen, and carbon) of a number of volatile organic substances such as the oils of garlic, mustard, etc—. and then to the formation of glycerine. With these processes he had built up by synthesis what we might perhaps call the first story of organic chemistry. To complete his work it was necessary to produce the saccharine and albuminous substances which constitute what might be called, repeating our figure, the second story of the edifice—a problem of a more difficult character, because those substances are less stable in their nature, and are more completely decomposed under energetic chemical reactions. On this subject M. Berthelot said, several years ago: "The reconstitution of the saccharine and albuminoid principles is the final object of organic chemistry, the most remote one indeed, but also one of the most important, on account of the essential part which these principles play in our economy. When science attains it, it will be able to realize the synthetic problem in its whole extent—that is, to produce, with the elements and by the play of molecular forces alone, all the definite natural compounds and all the changes which matter undergoes in the bodies of living beings."
"The labors of M. Berthelot in this line," says an enthusiastic French biographer, "constitute one of those events which change the aspect of things, not only by the new processes which they have developed, or by the substances, more or less known, which they have given the means of reproducing, but because they have taken hold bodily of one of the strongest intrenched ideas of mankind and overthrown it. We had been taught that all the complex substances constituting plants and animals were produced wholly under the influence of a special vital force peculiar to organized beings. When it came to verifying the facts in the case, it was found that Nature acts in a more simple way than we had thought, and that she employs those chemical affinities that control the metamorphoses of matter equally in executing those immense earth-convulsions that stir the foundations of countries and overthrow cities, and in perfuming a flower by the distillation, molecule by molecule, of its essential oil."
The fruits of M. Berthelot's investigations in this department of research have been given in a number of publications, among which we may name the "Combinaisons de la glycérine avec les acides, et reproduction des corps gras neutres" ("Combinations of Glycerine with the Acids, and Reproduction of Neutral Fatty Bodies"), 1860; various memoirs in the "Annales de physique et de chimie"; "Chimie organique fondée sur la synthèse" ("Organic Chemistry founded on Synthesis") 1860; and "Leçons sur les méthodes générales de synthèse en chimie organique" ("Lessons on the General Methods of Synthesis in Organic Chemistry"), a course of lectures in the Collége de France, 1864.
M. Berthelot has also pursued elaborate researches in specific heat, and in the relations between the heat developed in composition and decomposition, and the force of affinity. On the subject of the relations of specific heat with the composition of bodies he said, in 1873, in a discussion in the French Academy with M. Dumas: "The study of the specific heats established by the most recent researches tends to prove that there is a positive characteristic which, it seems to me, distinguishes the elements of modern chemistry from its compounds, and shows that no known compound body ought to be considered as of the same order as an actually simple one. The importance of such a characteristic can not be doubted, and it becomes greater on account of the mechanical meaning which modern theories attach to specific heat. . . . Nevertheless, exaggerated conclusions must not be drawn from such an opposition between the mechanical and physical characteristics of our simple and compound bodies. If our elements have not as yet been decomposed, and appear not to be decomposable by the forces which are at present at the command of the chemist, nothing compels us to assert that they are not decomposable in another way than our compounds are; as, for instance, as Mr. Lockyer asserts, by means of the forces acting in cosmical space. Nor does anything prevent that such a discovery as that of voltaic electricity would enable the chemists of the future to overpass the limits which are imposed upon us. The possible fundamental identity of the matter constituting our elements, and the possibility of transmuting into one another the so-called elements, can, moreover, be admitted into the category of more or less plausible hypotheses without it necessarily resulting that there is a single really existing matter of which our actual elements represent unequal states of condensation. In fact, nothing compels us to conceive the existence of a final decomposition which shall tend necessarily to reduce our elements either to more simple bodies, from the addition of which they arise, or to multiples of a single elementary ponderable unit."
M. Berthelot's views of the relations between chemical affinity and the intensity of chemical action were presented in his "Essai de mécanique chimique fondée sur la thermo-chimie" ("Essay on Chemical Dynamics based on Thermo-Chemistry"), 1880, of which Mr. M. M. Pattison Muir said, in "Nature," that its publication "marks an important point in the advance of modern chemistry." Among the more recent investigations which M. Berthelot has pursued in the light of his thermo-cbemical theories are those into the properties of explosives and the laws of the propagation of explosions.