|The essential piece of laboratory equipment that has immortalized the name of Robert Wilhelm Bunsen was not invented by him. Bunsen improved the burner's to aid his endeavors in spectroscopy. Ironically, Bunsen will be remembered by generations of chemistry students for a mere improvement in a burner , when his other contributions to the field of chemistry are vastly more significant and diverse, covering such areas as organic chemistry, arsenic compounds, gas measurements and analysis, the galvanic battery, elemental spectroscopy and geology.In Paris and Vienna, Bunsen visited the Sevres porcelain works and met with the outstanding chemists of the times. These travels allowed Bunsen the opportunity to establish a network of contacts that would stay with him throughout his illustrious career.|
While at Marsburg, Bunsen studied blast furnaces and demonstrated that over half the heat was lost in the charcoal-burning German furnaces. In British furnaces, over 80% was lost. Bunsen and a collaborator, Lyon Playfair, suggested techniques that could recycle gases through the furnace and retrieve valuable escaping by-products such as ammonia. Other work during this period concentrated on technological experiments such as the generation of galvanic currents in batteries. In 1841, instead of the expensive platinum electrode used in Grove's battery, Bunsen made a carbon electrode. This led to large scale use of the "Bunsen battery" in the production of arc-light and in electroplating.
One of the more memorable episodes during Bunsen's tenure at Marsburg was a geological trip to Iceland sponsored by the Danish government following the eruption of Mount Hekla in 1845. Indulging his lifelong interest in geology, Bunsen collected gases emitted from volcanic vents and performed extensive chemical analyses of volcanic rock. In addition to sampling lava gases, Bunsen investigated the theory of geyser action. The popular belief of his time was that the water from geysers was volcanic in origin. Bunsen took rocks from the area and boiled them in rain water. He found that the resulting solution was quite similar to geyser water. He conducted temperature studies on the water in the geyser tube at different depths and discovered that the water was indeed hot enough to boil. Due to pressure differentials caused by the moving column of water, boiling occurs in the middle of the tube and throws the mass of water above it into the sky above. In true investigative spirit Bunsen experimented with an artificial geyser in the lab:
"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 andat 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."
A former student of Bunsen's believes that it was this "splendid light" from the combustion of magnesium that led Bunsen to devote considerable attention to photochemical studies. A ten year collaboration with Sir Henry Roscoe began in 1852. They took equal volumes of gaseous hydrogen and chlorine and studied the formation of HCl, which occurs in specific relationship to the amount of light received. Their results showed that the light radiated from the sun per minute was equivalent to the chemical energy of 25 x 1012 mi3 of a hydrogen-chlorine mixture forming HCl. In 1859, Bunsen suddenly discontinued his work with Roscoe, telling him:
At present Kirchhoff and I are engaged in a common work which doesn't let us sleep...Kirchhoff has made a wonderful, entirely unexpected discovery in finding the cause of the dark lines in the solar spectrum....thus a means has been found to determine the composition of the sun and fixed stars with the same accuracy as we determine sulfuric acid, chlorine, etc., with our chemical reagents. Substances on the earth can be determined by this method just as easily as on the sun, so that, for example, I have been able to detect lithium in twenty grams of seawater."
Gustav Kirchhoff, a young Prussian physicist, had the brilliant insight to use a prism to separate the light into its constituent rays, instead of looking through colored glass to distinguish between similarly colored flames. Thus the fledgling science of spectroscopy, which would develop into a vital tool for chemical analysis, was born. In order to study the resultant spectra, however, a high temperature, nonluminous flame was necessary. An article published by Bunsen and Kirchhoff in 1860 states:
"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 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."
In addition to yielding a unique spectrum for each element, the spectroscope had the advantage of definite identification while only using a minimal amount of sample, on the range of nanograms to micrograms for elements like sodium and barium respectively. Using the techniques they devised, Bunsen and Kirchhoff announced the discovery of cesium (Latin caesium, "sky blue") in the following passage:
"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 Srd, 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."
In 1861, only a few months following their cesium discovery, Bunsen and Kirchhoff announced the discovery of yet another new alkali metal. Two hitherto undiscovered violet spectral lines in an alkali of the mineral lepidolite were attributed to a new element, rubidium. Bunsen and Kirchhoff's combined genius quickly paved the way for others to claim elemental discoveries. The spectroscope served as a springboard by which five new elements were discovered. These included thallium (Crookes, 1861), indium (Reich and Richter, 1863), gallium (Lecoq de Boisbaudran, 1875), scandium (Nilson, 1879) and germanium (Winkler, 1886). Fittingly, Bunsen's original vision of analyzing the composition of the stars was realized in 1868 when helium was discovered in the solar spectrum.
"He never said: 'I have discovered,' or 'I found'...He was characterized by extraordinary, distinguished modesty. That does not mean that he was not conscious of his own value. He knew how to use it at the right time and in the right company; he even had a considerable degree of very sound egotism."
Upon his retirement at the age of 78, Bunsen left the chemical work behind, returned to his first love of geology, keeping up with the latest developments in the field and corresponding with his old friends such as Roscoe, Kirchhoff and Helmholtz. Bunsen died August 16, 1899 after a peaceful three day sleep, leaving behind a glowing legacy of discoveries and technological advances that allowed the world of chemistry to burn brightly. (reference: http://step.sdsc.edu/projects95/chem.in.history/essays/bunsen.html)