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Bunsen, Robert Wilhelm

analysis devised theory compounds

(1811–99) German chemist: wide-ranging experimenter, and pioneer of chemical spectroscopy.

Bunsen’s father was librarian and professor of linguistics in Göttingen, and Robert studied chemistry there before travelling and studying also in Paris, Berlin and Vienna. He became professor at Heidelberg in 1852 and remained there until retirement, 10 years before his death.

Bunsen was pre-eminently an experimentalist with little interest in theory. His first major research did much to support the radical theory, due largely to and which held that organic groups (‘compound radicals’) correspond, in part, to the simple atoms of inorganic compounds. He prepared a series of compounds all containing the cacodyl group (CH3 )2 As–; and did so despite their remarkably offensive character. They combine a repulsive and persistent odour with toxicity and flammability. The presence in all of them of the same cacodyl group effectively established the theory. During this work Bunsen lost the sight of an eye and nearly died of arsenic poisoning; he excluded organic chemistry from his laboratory thereafter.

With his fellow-professor he discovered the use of spectroscopy in chemical analysis (1859) and within 2 years they had discovered the new elements caesium and rubidium with its aid. He devised the Bunsen cell, a zinc-carbon primary cell which he used to obtain metals (Cr and Mn) by electrodeposition from solution, and others (Mg, Al, Na, Ba, Ca, Li) by electrolysis of the fused chlorides. To find the relative atomic mass of these metals he measured their specific heat capacity (to apply Law) and for this he designed an ice calorimeter. He was a master of gas analysis, and used it in many ways, eg his study of Icelandic volcanoes and the improvement of English blast-furnaces. He was a pioneer, working with , in photochemistry, and for this devised a photometer and an actinometer. His great interest in analysis led him to invent many laboratory devices, including the filter pump. The Bunsen gas burner was probably devised and sold by his technician, Peter Desaga, and based on one due.

Bunsen was a great teacher and his lecture courses were famous; his researches continued until he was 80. Like he admitted that he never found time to marry (although this may have been because he worked with odorous compounds). wife said of him, ‘First, I would like to wash Bunsen and then I would like to kiss him because he is such a charming man.’


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