Featured Biography: Robert Wilhelm Bunsen

           Featured Biography: Robert Wilhelm Bunsen

Robert Wilhelm Eberhard Bunsen was born on March 30, 1811, in Göttingen, Germany. He was the youngest of four sons. 

His father was Christian Bunsen, professor of modern languages and Head Librarian at the University of Göttingen. His mother came from a military family. Robert Bunsen once recalled that he had been a wayward child at times, but that his mother kept him in line.

Education and Career

He attended elementary school and high school in Göttingen. When he reached the age of 15 he moved to the grammar school in Holzminden, about 40 miles (60 km) from Göttingen.

In 1828, aged 17, he started work for his degree at the University of Göttingen. He took courses in chemistry, physics, and mathematics, with some geology and botany. He won an award for his work on a humidity meter. When he wrote this work up in 1830, he was awarded a Ph.D. in chemistry – he was just 19 years old. Bunsen stayed at Göttingen until he won a government scholarship to travel around Europe studying chemistry. He spend most of 1832 and 1833 learning chemical techniques in laboratories in Germany, Austria, Switzerland, and France. In France he spent time in Paris working with the famous chemist Joseph Gay-Lussac. Recalling differences between his own time as a university student and many years later, Bunsen said: “In my day, we studied (all) science and not, as now so often happens, only one of them.”

Arsenic – A Triumph and a Disaster

In 1833, aged 22, Bunsen started working as a chemistry lecturer at the University of Göttingen. He had obtained his license to teach, but received no salary from the university. He tutored students and carried out research in the chemistry laboratories.

In the early years of his career, Bunsen researched arsenic compounds, which was a very hazardous work. In 1834 he published his first important work. Working with the physician Arnold Berthold he discovered an antidote to arsenic poisoning. He found that adding iron oxide hydrate to a solution in which arsenic compounds are dissolved causes the arsenic compounds to fall out of the solution as ferrous arsenate, which is an insoluble, harmless solid.

Bunsen developed an ongoing passion for studying the compounds of arsenic. Like the good chemist he was, he tried to take precautions against the toxic effects of these compounds: he devised a face mask with a breathing tube that fed him clean air from outdoors while he worked.

Some arsenic compounds, however, are explosive. Without warning, they explode in dry air. In 1843, nine years after finding the antidote to arsenic poisoning, Bunsen became a victim of such an explosion when a sample of an arsenic compound called cacodyl cyanide exploded, shattering his face mask and permanently blinding his right eye.

The explosion also resulted in Bunsen suffering severe arsenic poisoning. He was saved from death by the iron oxide hydrate antidote he discovered nine years earlier.

Invention of the Zinc-Carbon Battery

In 1841 Bunsen invented the zinc-carbon cell – often called the Bunsen battery. He saw this as an improvement on the expensive Grove cell, which was used, for example, to power telegraph lines. The Grove cell was a zinc-platinum cell. The platinum in it made it very expensive. Bunsen combined his zinc-carbon cells into large batteries, which he used to isolate metals from their ores. He was the first person to produce large scale samples of pure magnesium metal. His replacement of expensive platinum with cheap carbon also allowed other researchers who had been deterred by costs to carry out work in electrochemistry.

The Bunsen Burner

Chemists and alchemists before them were aware that if you sprinkled a sample of a substance into a flame, the color you saw helped you identify chemical elements in the sample. Lithium compounds, for example, burn with a rose- red f lame, while potassium compounds burn with a lilac flame. Bunsen observed that sodium compounds gave an orange- yellow flame. However, the fundamental color of the flame itself, before chemicals were sprinkled into it, could interfere with the test, making it unreliable. Bunsen’s response was his gas burner. By introducing air into the gas in the correct proportion before it burns, a clean, soot-free, almost color less flame is produced. Using his burner, Bunsen used flame tests to analyze substances much more reliably than ever before. The burners he designed were made by Peter Desaga, his laboratory assistant. Bunsen published the design of the burner in 1857, but did not patent his design. He did not wish to make prof its from science; he believed the intellectual rewards were more than enough. His burner is now used not only for flame tests. It is used to heat samples and to sterilize equipment in medical laboratories all over the world.

The Spectrometer and the Discovery of New Elements

Gustav Kirchhoff (Bunsen’s friend and colleague) was interested in the infant science of spectroscopy. Spectroscopy was the science of split ting sunlight into the colors of the rainbow using a prism – much as Isaac Newton did in 1666. Many years later, in 1802, William Hyde Wollaston repeated Newton’s experiment, but looked at the spectrum of sunlight using a magnifying glass. He saw more than the colors of the rainbow: he saw seven dark lines within the colors. In 1812, Josef Fraunhofer looked at a greatly magnified spectrum of colors from sunlight and saw over 500 of these dark lines (we now know there are more than 3,000 such lines.) Kirchhoff was interested in the new science of spectroscopy. He wanted to explain the dark lines in the sun’s spectrum. He made the historic discovery that they were caused by cooler gases in the sun’s atmosphere absorbing particular wavelengths of sunlight. These dark-lined spectra are now called absorption spectra. In 1859, Kirchhoff and Bunsen brought together a spectroscope and a Bunsen burner to study spectra from Bunsen’s flame tests. The two scientists looked at the spectra of a variety of different substances in the hot flame of the Bunsen burner.

The results were stunning. Bright lines appeared in the spectrum: the elements, when strongly heated in the Bunsen burner’s flame, emitted light at particular colors or wavelengths. These bright-lined spectra are now called emission spectra. Lines in the spectrum turned out to be a reliable “fingerprint” for chemical elements. Every element absorbs or emits characteristic wavelengths of light, leading to different “fingerprints” of lines for the different elements. A new science had been born: Chemical Spectroscopy.

Using their newly invented method, Bunsen and Kirchhoff discovered two new elements: cesium in 1860, and rubidium in 1861. The beauty of spectroscopy is that tiny traces of a substance can be detected. This opened up a whole new field of chemical analysis where elements could be detected when their concentrations were exceptionally low.

Bunsen was also credited for explaining how geysers work, after his visit to Iceland in 1846, following an invitation to study volcanic activity.

Bunsen’s research and findings were also crucial in improving efficiency in the British and German steel industries, after identifying large amounts of charcoal not being burnt completely by the furnaces. By recycling the exhaust fumes, Bunsen was able to obtain more energy by converting the carbon monoxide into carbon dioxide.