HEINRICH GUSTAV

MAGNUS (1802-1870)  , German chemist and physicist, was born at Berlin on the 2nd of May 1802 . His father was a wealthy merchant; and of his five brothers one, Eduard (1799-1872), became a celebrated painter . After studying at Berlin, he went to Stockholm to work under Berzelius, and later to Paris, where he studied for a while under Gay-Lussac and Thenard . In 1831 he returned to Berlin as lecturer on technology and physics at the university . As a teacher his success was rapid and extraordinary . His lucid style and the perfection of his experimental demonstrations drew to his lectures a crowd of enthusiastic scholars, on whom he impressed the importance of applied science by conducting them round the factories and work-shops of the city; and he further found time to hold weekly " colloquies " on physical questions at his house with a small circle of young students . From 1827 to 1833 he was occupied mainly with chemical researches, which resulted in the discovery of the first of the platino-ammonium compounds (" Magnus's green salt " is Ptll,, 2NHa), of sulphovinic, ethionic and isethionic acids and their salts, and, in conjunction with C . F . Ammermuller, of periodic acid . Among other subjects at which he subsequently worked were the absorption of gases in blood (1837-1845), the expansion of gases by heat (1841-1844), the vapour pressures of water and various solutions (1844-1854), thermo-electricity (1851), electrolysis (1856), induction of currents (1858-1861), conduction of heat in gases (186o), and polarization of heat (1866-1868) . From 1861 onwards he devoted much attention to the question of diathermancy in gases and vapours, especially to the behaviour in this respect of dry and moist air, and to the thermal effects produced by the condensation of moisture on solid surfaces . In 1834 Magnus was elected extraordinary, and in 1845 ordinary professor at Berlin .

He was. three times elected

dean of the faculty, in 1847, 1858 and 1863; and in 1861, rector magnificus . His great reputation led to his being entrusted by the government with several missions; in 1865 he represented Prussia in the conference called at Frankfort to introduce a uniform metric system of weights and measures into Germany . For forty-five years his labour was incessant; his first memoir was published in 1825 when he was yet a student; his last appeared shortly after his death on the 4th of April 1870 . He married in 184o Bertha Humblot, of a French Huguenot family settled in Berlin, by whom he left a son and two daughters . See Allgemeine deutsche Biog . The Royal Society's Catalogue enumerates 84 papers by Magnus, most of which originally appeared in Poggendorff's Annalen .