Bunsen burner, and Bunsen the man
If you mention a science lab and ask people for a common tool used in it, one of the most common replies will be the Bunsen burner. But how much do we know about this simple yet very useful invention and the man it's named after?
It was the 1850s. Natural gas had been piped into England's streets and homes for lights, heat, and cooking since 1812. Gas for city lights reached Germany in 1816-1826. Laboratories often used alcohol burners ("spirit lamps") for low heat experiments, but it was hard to control the size and temperature of flames for hotter work. Coal gas or natural gas from the city provided a better fuel.
a spirit lamp
Fuel gas from the city fed special burners that were topped with a wire mesh and asbestos gauze. As the pictures below show, the flames were quite broad, which caused a low heat. The flame flickered too much for Robert Bunsen, who was investigating the colors that shone from chemicals when they were heated. Particles flying off the gauze were also troublesome when chemists like Bunsen wanted to see as clear an image as possible.
Robert Bunsen (March 30, 1811 – August 16, 1899) was a German chemist. At the University of Gottingen, he studied math under the great Carl Gauss. After he got his doctorate, he traveled under a study grant through Europe including the lab of chemist/physicist Joseph Gay-Lussac. separating, Although he was very interested in geology, his early studies were focused on identifying and measuring various chemical substances.
For example, he researched arsenic compounds and discovered an antidote to arsenic poisoning. This had good and bad results. The good was his invention of a face mask while he worked on the toxic chemical; it had a breathing tube for clean air from outdoors. The bad was that an explosion while working on arsenic blinded him in one eye. His own antidote saved him from death by arsenic poisoning stemming from that event. Shortly afterward, he nearly put out his other eye when he held a flame over platinum from an experiment, and the hydrogen gas above it exploded in his face. It should be no surprise that he soon banned the use of organic chemicals from his lab for safety reasons.
To separate metals from ores, he used a battery in what is called electrochemistry. The battery was expensive because it used platinum, so he improved it and in 1841 invented his own cheaper zinc-carbon cell (sometimes called the Bunsen battery). The electrolysis experiments he conducted produced pure metals, such as chromium, magnesium, aluminum, manganese, sodium, barium, calcium, and lithium.
Bunsen also analyzed gases, not just ores. He improved the efficiency of German steel furnaces from 50% to 80% after showing that they needed to recycle the exhaust gases. His interest in the composition of gases got him invited to study the geochemistry of geysers in Iceland in 1846.
After that, he began working on ways to identify elements by the colors that shone when they were put into flames. Fireworks experts already knew which chemicals to use to create the desired colorful displays, but Bunsen wanted to learn about the unknown composition of chemicals. His gas-powered Bunsen burner created a cleaner flame that didn't interfere with the colors from the burning powders sprinkled into it.
Bunsen worked at many universities over the years. In 1852, he encouraged his friend, the noted physicist Gustav Kirschhoff, to join him at the University of Heidelberg. People already knew that light separated into a rainbow of colors (spectrum) after it was shone through a prism, but Kirschhoff wondered what would happen if flames of different colors were examined that way.
Together, he and Bunsen studied the science of spectroscopy and modified the tool to investigate it: the spectroscope.
They compared spectrum patterns from the prism to the ones they had recorded for elements burning in flames, and this served as a "chemical fingerprint" method to identify elements in chemicals or even sodium from the sun! The light that is missing from the complete spectrum shows up as black lines, and those are the elemental fingerprints. This discovery has been put to use by astronomers who can determine what elements are found in stars.
Bunsen was not only known as a respected chemist, but as an excellent teacher and was very generous towards his students. Emil Erlenmeyer (see earlier blog entry) was a teacher at the same time as Bunsen at the University of Heidelberg, but he was a private lecturer (Privatdozenten), not a professor like Bunsen, so Bunsen did not let him work in his new lab in the 1850s. Unlike Erlenmeyer, who was deeply interested in chemical theories later in life, Bunsen preferred to work on experimental techniques. Nice as he was to his students, Bunsen felt teachers should provide their own funding, so Erlenmeyer never got a chance to work in Bunsen's lab.
But Bunsen was extremely meticulous with his chemical analyses. Case in point, the fly incident. He was analyzing beryllium, and after stepping away for a moment, he returned to his bench to see a fly sucking on the filtered material he wanted to measure. He created such a ruckus chasing the fly that students from the next lab came to see what was happening. Bunsen caught the fly carefully, killed it, cremated it in a platinum dish, then treated it with chemicals to determine how much beryllium the fly had contained (0.1 mg). He added that to the amount from his filter paper for the sake of accuracy.
Although he spent many hours quietly working in his lab, Bunsen was known for his sense of humor. At a dinner party, a woman thought he was the scholar Baron Christian von Bunsen, who had already died earlier. Unaware of that she asked if he (Robert Bunsen) had finished his studies on God and History. Bunsen replied tongue in cheek, “Alas no, madam, my untimely death prevented me from completing my task.”
Bunsen loved cigars, but preferred the ones from Cuba. He knew Cuban soil contained lithium, and he would analyze each box to be sure the tobacconist wasn't selling him something else. Although he enjoyed mountain climbing early in life, it was too hard for him later on. So, he'd start a trek with friends, tell them to go on, and he would sit in the shade until they returned. They would find him with a handkerchief on his face to keep insects off it, and he'd burned a hole in it to allow him to poke and smoke a cigar while he rested!
Bunsen was also proud of the size of his right thumb. He could fill a glass tube with water, seal it with his fat thumb, and tip it upside down into a bowl of water smoothly without spilling a drop. This was important to measure how much gas would displace the water from a test tube reaction (see below). Apparently, he used thumb size to gauge the likelihood of his technician's skills before hiring them. When British chemist, Thomas Thorpe came to work with him in 1867, he learned this the hard way with his much smaller thumb unable to perform that function. Bunsen reportedly said not to worry, "You have to work quite a lot and it will become bigger."
a eudiometer tube inverted to measure volume of gas from a reaction tube
Robert Bunsen's lesser known contributions to science include invention of a filter pump (or modified one by Hermann Sprengel), and two types of calorimeters (ice and vapor) to measure small quantities of heat. With Kirschhoff, he discovered cesium and rubidium using spectroscopy.
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