Robert Bunsen’s claims to fame

Thursday 31 March 2011 is the bicentenary of the birth of Robert Wilhelm Bunsen, the German chemist who gave his name to the Bunsen burner, used in laboratories around the world.

But Bunsen has other claims to fame. His early studies of the solubility of arsenic compounds led to the use of metal salts to precipitate arsenic in cases of poisoning. He himself almost died from arsenic poisoning and he lost the sight of one eye when an arsenic compound exploded.

In late 1852, Bunsen became a professor at the University of Heidelberg. The city had just begun to install coal gas street lighting and the university agreed to build Bunsen a new laboratory building that would be both lit and heated by gas.

For laboratory purposes, Bunsen wanted heating apparatus that produced high temperatures with minimal luminosity. He made some suggestions to the university’s instrument maker Peter Desaga, who adapted a principle used earlier by Michael Faraday and designed a burner that produced a hot, soot-free, non-luminous flame. The gas burned at the top of a brass cylinder that had adjustable slits at the base to allow air to enter at a controlled rate.

By the time the new building opened, Desaga had made 50 burners for Bunsen’s students. With Bunsen’s consent, Desaga made burners for sale elsewhere, and his family was to hold the marketing rights for generations.

Bunsen had earlier invented an electrochemical cell that used a carbon electrode rather than the expensive platinum electrodes previously used. He went on to use electrolysis to produce pure metals, and with the help of the new burner began analysing their emission spectra when heated.

With a colleague, Gustav Kirchhoff, he created a prototype spectroscope and was able to show that highly purified metals gave unique spectra. During his work he detected previously unknown blue spectral emission lines in samples of mineral water and was able to isolate two new chemical elements, caesium and rubidium.

Bunsen retired in 1889 at the age of 78 and died 10 years later.