Chemist and physicist, b. at Aachen, 21 July, 1810; d. in Paris, 19 Jan., 1878. Being left an orphan at the age of eight he was soon obliged to work in order to provide for himself and his sister. Up to the age of eighteen he worked as a clerk in a drapery establishment in Paris, but made use of all his spare time in studying, until he was received at the Ecole Polytechnique in 1830. In 1832 he entered the School of Mines, was graduated, and in 1835 he was attached to the chemical laboratory of the school, becoming professor and adjunct director in 1838, and remaining until his call to the chair of physics at the Collège de France. Up till then he had been working in the comparatively new field of organic chemistry, chiefly in producing new compounds by the method of substituting chlorine for hydrogen equivalents in hydro-carbons. The results were published in eighteen memoirs in the "Annales de Chimie et de Physique" and earned for him the election as member of the Chemical Section of the Academy of Sciences. In 1843 he was commissioned by the Government to investigate the properties of steam and to obtain numerical data that should be of value to the steam engineer. The results were published in 1847, as vol. XXI of the "Mémoires" of the Academy of Sciences. They obtained for him the Rumford Medal of the Royal Society of London, and the exceptional appointment as Chief Engineer of Mines. In 1852 he became the Director of the porcelain manufactory at Sèvres, where he continued his experiments until his laboratory, instruments and papers were destroyed during the Franco-German War, in 1871. This, together with the loss of his talented son, a well-known painter, broke his spirit, and a stroke of apoplexy in 1873 was followed by years of long, slow agony. Daubrée says of him, that "only his religious faith could console him, and this consolation was not wanting".

His invaluable work was done as a skilful, thorough, patient experimenter in determining the specific heat of solids, liquids, gases, and the vapour-tensions of water and other volatile liquids, as well as their latent heat at different temperatures. He corrected Mariotte's law of gases concerning the variation of the density with the pressure, determined the coefficients of expansion of air and other gases, devised new methods of investigation and invented accurate instruments. Two laws governing the specific heat of gases are named after him. This mass of numerical data are recognized as standards by the engineer as well as by the physical chemist.

He was a foreign member of the Royal Society of London, received its highest honour, the Copley Medal, in 1869, and in 1863 was made Commander of the Legion of Honour.

"Cours élémentaire de Chimie" was published in 1849 at Paris, and received several later editions. "Premiers éléments de Chimie", Paris, 1850, 6th ed., 1874, is a shorter work. "Relations des expériences", etc., 1847-70, were collected in 3 vols., Paris, 1870.

J. H. NORTON in Nature, XVII (London, 1878), 263; VOGT, Pop. Sc. My. 13, 20 (New York, 1878); DUMAS, Eloge historique de H. V. Regnault (Paris, 1881); DEBRAY, JAMIN, DAUBRÉE, AND LABOULAYE, Discours, etc., in Comptes Rendus, LXXXVI, 131-43 (Paris, 1878); BERTHELOT, Science et philos. (Paris, 1886), 218.

WILLIAM FOX