Field of Science

Bunsen and quantum mechanics

Today's Google doodle honors the 200th birthday of Robert Bunsen, the inventor (or not?)of the eponymous burner. The doodle is great, click on it and it bubbles and whirs.

"It is known that several substances have the property of producing certain bright lines when brought into the flame. A method of qualitative analysis can be based on these lines, whereby the field of chemical reactions is greatly widened and hitherto inaccessible problems are solved. We limit ourselves here to developing the method for alkali and earth-alkali metals and demonstrating its value by some examples.

The lines show up the more distinctly the higher the temperature and the lower the luminescence of the flame itself. The gas burner described by one of us (Bunsen, these Ann. 100, p. 85) has a flame of very high temperature and little luminescence and is, therefore, particularly suitable for experiments on the bright lines that are characteristic for these substances." Opening to Gustav Kirchhoff and Robert Bunsen, Annalen der Physik und der Chemie 110 (1860), 161-189.

Bunsen is not a name typically associated with the development of quantum mechanics, yet I might argue he is one of the key figures. The observation of line spectra and the realization that the lines are characteristic of particular elements is a significant step toward the development of quantum mechanics. It's one of the observations that Bohr was trying to explain in his model of the atom. General chemistry texts boast figures of line spectra to demonstrate the point - I showed several in my lecture last week. This apparatus developed by Kirchoff and Bunsen made possible the routine observation of such lines. I have a beautiful brass example in my office.

This paper goes on to note that sodium, even at very low concentrations produces quite bright lines. It reminds me of the many happy hours I spent playing with my mom's gas stove and making flame tests on anything I could scrounge up (most of which contained sodium). Is this the formative experience that impelled me toward quantum mechanics? Who knows! I do still think of sodium and line spectra every time the pasta boils over and the flame on my stove flares that characteristic sodium yellow-orange.

Happy birthday, Bunsen, I might not have a job without you!

There is more on Bunsen beyond the burner at The Sceptical Chymist.

1 comment:

  1. My favorite lesson of the year is when I show the bright-line spectra followed by a flame-test lab. In my classroom this year, I do not have bunsen burners (sad but true for students theoretically studying Regents chemistry). I do the flame tests with aspirator bottles (the kind sold for saline solution) and candles. It works and my students are amazed both by the fact that they can identify an unknown AND gain some understanding of pyrotechnics.

    I love teaching atomic theory! Both for the Nature of Science story of the scientists involved and the WOW lab. I also much enjoyed Google's logo that day.


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