Robert Wilhelm Von Bunsen (1811-1899), German chemist, was born at Göttingen on the 31st of March 1811, his father, Christian Bunsen, being chief librarian and professor of modern philology at the university. He himself entered the university in 1828, and in 1834 became Privat-docent. In 1836 he became teacher of chemistry at the Polytechnic School of Cassel, and in 1839 took up the appointment of professor of chemistry at Marburg, where he remained till 1851. In 1852, after a brief period in Breslau, he was appointed to the chair of chemistry at Heidelberg, where he spent the rest of his life, in spite of an urgent invitation to migrate to Berlin as successor to E. Mitscherlich. He retired from active work in 1889, and died at Heidelberg on the 16th of August 1899. The first research by which attention was drawn to Bunsen's abilities was concerned with the cacodyl compounds (see Arsenic), though he had already, in 1834, discovered the virtues of freshly precipitated hydrated ferric oxide as an antidote to arsenical poisoning. It was begun in 1837 at Cassel, 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 apart from its accuracy and completeness it is of historical interest in the development of that branch of the science 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 furnaces. 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 in conjunction with Lyon Playfair investigated the conditions obtaining in English furnaces, he found the waste to amount to over 80%. These researches marked a stage in the application of scientific principles to the manufacture of iron, and they led also to the elaboration of Bunsen's famous methods of measuring gaseous volumes, etc., which form the subject of the only book he ever published (Gasometrische Methoden, 1857). In 1841 he invented the carbon-zinc electric cell which is known by his name, and which conducted him to several important achievements.
He first employed it to produce the electric arc, and showed that from 44 cells a light equal to 1171.3 candles could be obtained with the consumption of one pound of zinc per hour. To measure this light he designed in 1844 another instrument, which in various modifications has come into extensive use - the grease-spot photometer. In 1852 he began to carry out electrolytical decompositions by the aid of the battery. By means of a very ingenious arrangement 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 qualities of the flame it gives when burnt in air. From 1855 to 1863 he published with Roscoe a series of investigations on photochemical measurements, which W. Ostwald has called the "classical example for all future researches in physical chemistry." Perhaps the best known of the contrivances which the world owes to him is the "Bunsen burner" which he devised in 1855 when a simple means of burning ordinary coal gas with a hot smokeless flame was required for the new laboratory at Heidelberg. Other appliances invented by him were the ice-calorimeter (1870), the vapour calorimeter (1887), and the filter pump (1868), which was worked out in the course of a research on the separation of the platinum metals.
Mention must also be made of another piece of work of a rather different character. Travelling was one of his favourite relaxations, and in 1846 he paid a visit to Iceland. There he investigated the phenomena of the geysers, the composition of the gases coming off from the fumaroles, their action on the rocks with which they came into contact, etc., and on his observations was founded a noteworthy contribution to geological theory. But the most far-reaching of his achievements was the elaboration, about 1859, jointly with G.R. Kirchhoff, of spectrum analysis, which has put a new weapon of extraordinary power into the hands both of chemists and astronomers. It led Bunsen himself almost immediately to the isolation 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 Dürkheim mineral water, and it says much both for his perseverance and powers of manipulation that he dealt with 40 tons of the water to get about 17 grammes of the mixed chlorides of the two substances, and that with about one-third of that quantity of caesium chloride was able to prepare the most important compounds of the element and determine their characteristics, even making goniometrical measurements of their crystals.
Bunsen founded no school of chemistry; that is to say, no body of chemical doctrine is associated with his name. Indeed, he took little or no part in discussions of points of theory, and, although he was conversant with the trend of the chemical thought of his day, he preferred to spend his energies in the collection of experimental data. One fact, he used to say, properly proved is worth all the theories that can be invented. But as a teacher of chemistry he was almost without rival, and his success is sufficiently attested by the scores of pupils who flocked from every part of the globe to study under him, and by the number of those pupils who afterwards made their mark in the chemical world. The secret of this success lay largely in the fact that he never delegated his work to assistants, but was constantly present with his pupils in the laboratory, assisting each with personal direction and advice. He was also one of the first to appreciate the value of practical work to the student, and he instituted a regular practical course at Marburg so far back as 1840. Though alive to the importance of applied science, he considered truth alone to be the end of scientific research, and the example he set his pupils was one of single-hearted devotion to the advancement of knowledge.
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.