BUNSEN, ROBERT WILHELM VON German chemist, was born at Gottingen on March 31, 1811. He was professor of chemistry at Kassel, Marburg, Breslau, and from 1852 to a few months before his death on Aug. 16, 1899, at Heidelberg. His first important research work was concerned with the cacodyl compounds, though he had already, in 1834, discov ered the virtues of freshly precipitated hydrated ferric oxide as an antidote to arsenical poisoning. It was begun in 1837 at Kas sel, and during the six years he spent upon it he not only lost the sight of one eye through an explosion, but nearly killed himself by arsenical poisoning. It represents almost his only excursion into organic chemistry, and is of historical interest as being the forerunner of the fruitful investigations on the organo-metallic compounds subsequently carried out by his English pupil, Edward Frankland. Simultaneously with his work on cacodyl, he was studying the composition of the gases given off from blast fur naces. He showed that in German furnaces nearly half the heat yielded by the fuel was being allowed to escape with the waste gases, and when he came to England, and with Lyon Playfair in vestigated the conditions in English furnaces, he found the waste to amount to over 8o%. These researches led to the elaboration of Bunsen's famous methods of measuring gaseous volumes, etc., which form the subject of the only book he ever published (Gas ometrische Methoden, 1857). In 1841 he invented the carbon zinc electric cell which is known by his name; he first employed it to produce the electric arc, and showed that from 44 cells a light equal to 1,171.3 candles could be obtained with the con sumption of one pound of zinc per hour. To measure this light he designed in 1844 the grease-spot photometer. In 1852 he began to carry out electrolytical decompositions by the aid of the bat tery. He obtained magnesium for the first time in the metallic state, and studied its chemical and physical properties, among other things demonstrating the brilliance and high actinic quali ties of the flame it gives when burnt in air. From 1855 to 1863 he published with Roscoe a series of investigations on photo chemical measurements, which W. Ostwald has called the "classi cal example for all future researches in physical chemistry." He is generally credited with the invention of the Bunsen Burner (q.v.). Other appliances invented by him were the ice-calorimeter (187o), the vapour calorimeter (1887), and the filter pump (1868) . In 1846 he paid a visit to Iceland. There he investigated the phenomena of the geysers.
But the most far-reaching of his many achievements was the elaboration, about 1859, jointly with G. R. Kirchhoff, of spectrum analysis. It led Bunsen himself almost immediately to the isola tion of two new elements of the alkali group, caesium and rubidium. Having noticed some unknown lines in the spectra of certain salts he was examining, he set to work to obtain the substance or substances to which these were due. To this end he evaporated large quantities of the Durkheim mineral water; he dealt with 4o tons of the water to get about 17 grammes of the mixed chlorides of the two substances, and with about one-third of that quantity of caesium chloride was able to prepare the most important compounds of the element and determine their charac teristics, even making goniometrical measurements of their crys tals. He instituted a regular course of practical work at Marburg so far back as 1840.
See Sir Henry Roscoe's "Bunsen Memorial Lecture," Trans. Chem. Soc., 1900, which is reprinted (in German) with other obituary notices in an edition of Bunsen's collected works published by Ostwald and Bodenstein in 3 vols. at Leipzig in 1904.