Wednesday, March 30, 2011

Robert Bunsen - 200 years of science

 "As an investigator he was great, as a teacher he was greater, as a man and friend he was greatest."

- so said Sir Henry Roscoe about his colleague Robert Bunsen, the 200th anniversary of whose birthday we celebrate this Thursday 31st March.

Bunsen was one of the most influential chemistry teachers of his time - some of his students included the noted Irish scientist John Tyndall and Dmitri Mendeleev, the creator of the Periodic Table.

Bunsen was born in Germany in 1811 and is probably best remembered for inventing (or at least refining the design of) the Bunsen Burner. His father was a professor of modern languages at Gottingen and he received his doctorate from that university at the age of 19.

Bunsen-Kirchoff spectroscope

As well as being a noted chemist, Bunsen had a lifelong interest in geology and took a trip to Iceland, sponsored by the Danish government to study the eruption of Mount Hekla in 1845.

The chemist collected gases from the erupting volcano and analysed the volcanic rock. He also investigated the theory of geyser action and showed that the water from geysers was not volcanic in origin and that the boiling of water below the surface caused the water above to move upwards:

"To confirm his theory, Bunsen made an artificial geyser, consisting of a basin of water having a long tube extending below it. He heated the tube at the bottom and at about the middlepoint. As the water at the middle reached its boiling point, all of the phenomena of geyser action were beautifully shown, including the preliminary thundering. That was in 1846. From that day to this Bunsen's theory of geyser action has been generally accepted by geologists." (Darrow, 1923)

Bunsen's statue in Heidelberg faces the building where he and Kirchoff worked.

Kirchoff (left) and Bunsen (right)
He also discovered the elements cesium and rubidium with his colleague Gustav Kirchhoff.

Announcing their discovery of cesium (Latin caesium, "sky blue"), the scientists wrote:

"Supported by unambiguous results of the spectral-analytical method, we believe we can state right now that there is a fourth metal in the alkali group besides potassium, sodium, and lithium, and it has a simple characteristic spectrum like lithium; a metal that shows only two lines in our apparatus: a faint blue one, almost coinciding with Sr, and another blue one a little further to the violet end of the spectrum and as strong and as clearly defined as the lithium line."

The apparatus referred to here is the Bunsen-Kirchoff spectroscope, developed around 1865, which had its origins  in a "prism, a cigar box and two ends of otherwise unusable old telescopes". The pair discovered rubidium (Latin rubidus, "darkest red") a few after cesium using the same apparatus.

Bunsen never married and devoted much of his time to his work in the laboratory and his teaching. he received many honours for his work but once remarked: "Such things had value for me only because they pleased my mother; she is now dead." He died in 1899 after a ten-year retirement which he spent indulging his first love of geology.

Google are celebrating Bunsen's 200th birthday with a specially comissioned logo on their homepage:


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