Bunsen-Kirchhoff and Spectroscopy Theory

Science / Discoveries & Inventions

 

When a chemical element is heated to incandescence, it produces its own characteristic lines in the spectrum of light.

As a chemistry student moons ago, I'll never forget the Bunsen burner as a constant laboratory companion in my numerous "flame test" experiments. Bunsen developed the burner in 1855. The test is used to identify the presence of a particular metal by the colour of the flames produced. The burner's non-luminous flame is basically used as it does not interfere with the coloured flame given off by the sample metal being tested.

Bunsen-Kirchhoff Spectroscopy theory and other Discoveries

Together, Bunsen and Kirchhoff developed the first spectroscope, a device used to produce and observe a spectrum. Using their spectroscope, in 1860, they went on to discover two elements: caesium and rubidium. These discoveries ushered a new era in ways used to find new chemical elements.


The first 50 elements discovered (beyond those known since ancient times) were either the products of chemical reactions or were released by electrolysis. From 1860, however, thanks to Burner and Kirchhoff, the search was on for trace elements detectable only with the help of specialized instruments like the spectroscope. The Bunsen–Kirchhoff Award for spectroscopy is named after Bunsen and Kirchhoff.

Kirchhoff also discovered that when heated to incandescence, each chemical element produced its own characteristic lines in the spectrum. For instance, sodium (Na) has a spectrum with two yellow lines, wavelengths about 588 and 589 nanometres.  Extending experiments beyond Bunsen and Kirchhoff, later scientists were able to determine the presence of elements, for example, in the sun or stars once similar wavelengths were identified in their spectra. 

Robert Bunsen

Robert Wilhelm Eberhard Bunsen (b. 30 March 1811, Göttingen – d. 16 August 1899, Heidelberg) was a German chemist. He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with Gustav Kirchhoff. Bunsen developed several gas-analytical methods, was a pioneer in photochemistry, and did early work in the field of organoarsenic chemistry. With his laboratory assistant, Peter Desaga, he developed the Bunsen burner, an improvement on the laboratory burners then in use. He was awarded the Copley Medal.  The Bunsen burners are still being used in laboratories all over the world.

Gustav R. Kirchhoff

Gustav Robert Kirchhoff (b. 12 March 1824, Kaliningrad – d. 17 October 1887, Berlin) was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. He trained at Königsberg and was a professor of physics at Heidelberg. Kirchhoff coined the term "black body" radiation in 1862. Two sets of independent concepts in both circuit theory and thermal emission are named "Kirchhoff's Laws" after, and a law of thermochemistry.

Bunsen and Kirchhoff Friendship to Scientific Partnership


Bunsen was the son of a professor of modern languages at Göttingen University in Germany. He earned his doctorate from that university in 1830. Through a three-year travel grant, he was able to visit factories, places of geologic interest, and famous laboratories, including Joseph Louis Gay-Lussac’s in Paris. Early in his career he did research in organic chemistry, which cost him the use of his right eye when an arsenic compound, cacodyl cyanide, exploded. He was also deeply interested in geological topics and once made daring temperature measurements of the water in the geyser tube of Iceland’s Great Geyser just before it erupted.

Bunsen and Kirchhoff met and became friends in 1851, when Bunsen spent a year at the University of Breslau, where Kirchhoff was also teaching. Bunsen was called to the University of Heidelberg in 1852, and he soon arranged for Kirchhoff to also teach at Heidelberg.


Resources:

• Bunsen and Kirchhoff at chemheritage.org
• Gustav Kirchhoff Biography at Encyclopaedia Britannica.
• MIT Spectroscopy Lab's History of Spectroscopy at MIT.edu
• Timeline of Spectroscopy Spectroscopy Online
• Robert Wilhelm Bunsen at Woodrow.org

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