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Chemist and physicist, b. at Lessines, Belgium, 11 May, 1798; d. at Paris, 11 May, 1863. He was appointed early in life master of studies in the lyceum of Bruges, and later went to Paris to complete his studies. Here he attracted the attention of Gay-Lusac, who had him appointed tutor of the chemical course which the former was then giving at the Ecole Polytechnique. In 1824 Despretz was made adjunct and the titular professor of physics at the College Henri IV, and in 1837 received the chair of physics at the Sorbonne. He was naturalized as a Frenchman in 1838, and in 1841 he was elected to the Academy of Sciences in the division of general physics, being the successor of Savart. The researches of Despretz did much to establish the foundation of modern physics, notably in the domain of heat. In 1818 he investigated latent heat and the elasticity of vapours. In 1821, following the same line, he studied the heat-conductivity of solids, vapour density, and the latent heat of steam at different pressures; his memoir of 1822 on the causes animal heat was crowned by the Academy. In 1823 the results of his investigation of the compressibility of liquids were published, and in 1827 his researches on the density of gases at different pressures; the latter investigation proved that Mariotte's law was not exactly followed by gases. The titles of some of his leading memoirs and their dates of publication are as follows: "The Heat of Combustion" (1828); "Investigation of the Mercurial Thermometer" (1837); "The Laws of Conductivity of Heat in Liquids" (1838); "The limit of Appreciable Sound" (1845).
After this he turned his attention the voltaic cell and voltaic arc. By uniting the heat from a very large burning glass with the heat of the voltaic arc and with the oxy-hydrogen flame, he experimented on the diffusion and volatilization of refractory solids, performing some experiments of remarkable interest in those days when electricity was not so highly developed as at the present time. Under the discharge of the Ruhmkorff coil he approximated the formation of diamonds. Among his books may be cited "Recherches expérimentales su les causes de la chaleur animale" (Paris, 1824); "Traité élémentaire de physique" (Paris, 1825, and many later editions); "Eléments de chimie théorique et pratique" (Paris, 1828-30); in addition to these some fifty memoirs were published by him between 1817 and 1863, the list of which is given in the "Catalogue of Scientific Papers of the Royal Society" (London, 1868), VII. Despretz was a true Catholic; he constantly resisted assaults upon the Church and the clerical body, was always ready to lead in their defence, and died a devout member of the Church.
Dictionnaire Larousse, s. v.; Moigno in Les Mondes (Paris, 1863), I.
T. O'CONOR SLOANE