Bunsen--Without his Burner

Colin Russell*

This year marks the centennary of the death of Robert Wilhelm Bunsen (1811-1899). He is famed chiefly for the burner named after him, though others had already invented rather similar apparatus for using coal-gas as a laboratory heating agent. However, Bunsen had the services of a technician suffciently enterprising to make such burners in large quantities and associate with them the name of the famous professor at Heidelberg: an early case of chemical sponsorship? As with much named apparatus (Leibig condenser, Dewar flask, Crookes tube, etc.), this device did not represent the main contribution of its presumed inventor.

Bunsen obtained his doctorate in 1830 from the University of Göttingen. Thereafter his chief work was done as professor at Marburg (1839-1851) and Heidelberg (1852-1889). His first sustained research programme concerned the substance cacodyl (now named tetra-methyldiarsine), which seemed to persist in a number of its compounds (oxide, chloride, cyanide) and thus offered the beleaguered followers of Berzelius new "evidence" for the existence of the radicals he had proposed as part of his dualistic system. It stimulated Bunsen's students Kolbe and Frankland to further important work with the same quest. After this, Bunsen had little to do with organic chemistry, partly because he had little patience with detailed theoretical schemes which were inevitably a part of this growing new subject.

His next research, still at Marburg, was on gas analysis. This seems to have begun with early (1838) work on the gases present in the blast furnaces used for making iron. Accompanied by Lyon Playfair, he visited England and their results were taken up by iron-masters with huge savings of fuel that would otherwise have been needlessly wasted. From this work he went on to show how to determine the specific gravity of gases, to measure their absorption by liquids, and their rates of diffusion. Above all, he perfected the technique of eudiometry, where known volumes of gas are exploded with oxygen and the amounts of the products measured. His pioneering studies of gas analysis laid the foundation of techniques still in use 100 years later.

At Heidelberg, Bunsen pioneered studies in photochemsitry (with H. E. Roscoe), working with hydrogen/chlorine mixtures exposed to sunlight. Shortly afterwards he launched into spectroscopy with his colleague in physics, G.R. Kirchoff. Using simple prisms they devised the first chemical spectrometer, determining the position of the spectral lines emitted from highly purified samples of alkali and alkaline earth compounds. In this way they discovered two new alkali elements: cesium and rubidium. Investigations of solar spectra convinced them that here was a method of chemical anlaysis applicable to luminescent material millions of miles away. In electricity, Bunsen invented the "Bunsen battery," where the expensive platinum of the Grove cell was replaced by carbon, with zinc as the other electrode. This device assisted Kolbe in his early research on electrolysis, and led its inventor to many important experiments in electrochemistry.

For teachers it seems that the life and work of Bunsen have three obvious lessons. First, was the importance of technique. No great theoretician, Bunsen nevertheless made possible the development of future chemcal theory by providing a sound empirical basis for the subject. "His" burner, and still more, his analytical and spectroscopic methods proved indispensable to future generations of chemistry students. Do we, perhaps, underplay the importance of experimental technique in reducing chemistry to a science of "black boxes," or abstruse results from higher mathematics?

Second, Bunsen deplored the demarcation lines between related sciences and would today be a hero for those who worship at the shrine of interdisciplinarity (assuming they had ever heard of him). He held strongly to the view that "a chemist who is not also a physicist is a mere nobody." One of his earliest researches was on the volcanic phenomena of Iceland, and through this work he became one of the founders of petrology. An integrated approach to science does not need complex ideological justification. As Bunsen found, it simply works!

Third, Bunsen illustrates the supreme importance of dedicated teaching. At Göttingen he attended the first teaching chemistry laboratory in Germany, and that may have inspired his later efforts. A lecture from 8 to 9 every day of the week (or 9 to 10 in the winter) was followed by a full day in the laboratory alongside the students, teaching by example and advice throughout the day. His superb technique could never have been passed on by mere exhortation.

So it was that the students or co-workers of Bunsen represent a roll call of chemical distinction in the 19th century and beyond, persons who passed on to their successors thevalued aspects of the Bunsen tradition: Playfair, Frankland, Crum Brown, Ludwig, Mond, Roscoe, Kolbe, Lothar Meyer, Victor Meyer, Baeyer, Ladenburg and many more. All had an immense respect for the grand old man living out in bachelor loneliness his last decade in Heidelberg. He would be remembered by them for much more than a mere burner.

*Reprinted from the BSHS Education Forum, with our appreciation.

Further Resources on Bunsen: