(b. Châtillon-sur-Loing, Loiret, France, 7 March 1788; d. Paris, France, 18 January 1878)
Becquerel’s father was the royal lieutenant at Châtillon-sur-Loing. Becquerel himself entered the École Polytechnique in 1806, and on graduation embarked on a military career in the Corps of Engineers, being promoted to captain in 1812. The following year he was appointed sous inspecteur of the École Polytechnique; he returned to active service in 1814, but after the fall of Napoleon in 1815 devoted himself entirely to science. Becquerel was elected to the Académie des Sciences in 1829; was awarded the Copley Medal of the Royal Society of London in 1837; and, when the chair of physics at the Muséum d’s Histoire Naturelle was founded in 1838, became its first occupant. In 1813 he married Aimée-Cécile Darlui, a relative of the due de Feltre, and became the founder of a dynasty of distinguished scientists. His son Alexandre Edmond succeeded him at the Museum, and his grandson Antoine Henri was the discoverer of radioactivity. Becquerel lived to a ripe old age, and his vivacity amazed his younger colleagues in the Academy, in the proceedings of which he took a lively and regular part to the end of his life.
Becquerel’s first studies were in mineralogy, and in association with Alexandre Brongniart, whose disciple he was, he discovered in 1819 a collection of important recent deposits at Auteuil that contained previously unknown crystalline forms of calcium phosphate. The study of minerals led easily to electrical experiments. Following up Haüy’s observation that Iceland spar became electrified when compressed, Becquerel showed that this phenomenon was general, provided that the crystals under investigation were insulated; his studies on tourmaline became classics. This effect is called the piezoelectric effect, and obtains only in crystals which possess no center of symmetry. From studying the electrical effects of compression, Becquerel moved on to thermoelectricity, investigating the electrical effects of heating minerals. He discovered various definite transition temperatures, at which the electrical state of a substance changes discontinuously. These researches led to experiments on the electrical measurement of temperature.
Of perhaps greater interest was Becquerel’s work on the voltaic cell. In the early decades of the nineteenth century, it was not clear whether the production of electricity in the cell was due to the mere contact of dissimilar bodies, or whether it depended upon a chemical reaction. The principle of conservation of energy had not yet been clearly enunciated; but Becquerel believed that there was a close relationship between electricity on the one hand, and heat, light, and chemical forces on the other. In a series of careful experiments, he put it beyond doubt that electricity could be generated only by the contact of dissimilar bodies when they reacted together chemically, or differed in temperature, or were rubbed together. Conversely, he established that all chemical reactions can generate electricity. This was related to earlier work, notably by Humphry Davy, and in 1829 Becquerel employed Davy’s discovery that a battery could be made of two liquids separated by a solid barrier in the construction of the first battery that, not being polarized, could supply current at a reasonably constant EMF.
Using these cells, Becquerel performed elegant small-scale experiments on the synthesis of mineral substances. Since he was able to control his EMF’s, through secondary electrolysis he succeeded in obtaining crystals of various substances—notably sulfides—that had previously been produced only in an amorphous condition. He suggested that the presence of crystalline substances in mineral veins might be accounted for by their having been deposited by electric currents operating over a very long period of time. Becquerel remarked that chemical synthesis had lagged behind analysis, and hoped that through his techniques many naturally occurring crystals would be synthesized and the balance thus redressed. It was for this work that he received the Copley Medal. These researches found industrial applications in the treatment of silver-bearing ores and the extraction of potassium chloride from the sea.
Becquerel wrote a great number of papers; of his joint papers, the majority were written in collaboration with his son, but his co-workers also included Ampère and Biot. He corresponded with Michael Faraday over diamagnetism; he had noticed examples of it before Faraday but had failed to generalize from them. He also invented an electromagnetic balance and a differential galvanometer.
I. Original Works. Becquerel’s papers are listed in the Royal Society Catalogue of Scientific Papers, I (1867), 233–239; VII (1877), 118–121; IX (1891), 164–166. See also Analyse succient des travaux de M. Becquerel (Paris, 1829), published by the Académie des Sciences. His most important books are Traité expérimental de l’électricité et du magnétisme, et de leur rapports aves les phénomènes naturels, 7 vols. (Paris, 1834–1840); Traité de physique considérée dans ses rapports avec la chimie et les sciences naturelles, 2 vols. (Paris, 1842–1844); Élements d’électro-chimie appliquée aux sciences naturelles et aux arts (Pairs, 1843; 1864), also translated into German (Erfurt, 1845; 1848; 1857); and Résumé de l’histoire de l’électicité et du magnétisme, et des applications de ces sciences à la chimie., aux sciences naturelles et aux arts (Paris, 1858), written with Alexandre Edmond Becquerel. There is an extensive collection of MSS of A. C. Becquerel at the Académie des Sciences in Paris.
II. Secondary Literature. Obituaries of Becquerel are in Comptes rendus de l’Académie des sciences, 86 (1878), 125–131. See also Abstracts of the Philosophical Transactions, 4 (1843), 22–23; and T. Cooper, ed., Men of the Time, 9th ed. (London, 1875), p. 87.
David M. Knight