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A Bunsen burner, named after Robert Bunsen, is a kind of ambient air gas burner used as laboratory equipment; it produces a single open gas flame, and is used for heating, sterilization, and combustion.[1][2][3][4][5]
The gas can be natural gas (which is mainly methane) or a liquefied petroleum gas, such as propane, butane, or a mixture. Combustion temperature achieved depends in part on the adiabatic flame temperature of the chosen fuel mixture.
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Transcription
In this video, you're going to learn how to use a bunsen burner saftly and properly. This is a bunsen burner. It allows you to heat materials in the lab both quickly and efficiantly. Because you will be working with an open flame it can be dangerous, so I will start by going over some safety rules. All long hair should be tied back and you should not wear any loose or bulky clothing. You should never heat inflammable materials on the bunsen burner. Volatile and inflammable materials like ethers and alcohols can combust in heat, so it is defiantly to dangerous for the bunsen burner . When handling the barrel of the bunsen burner it is important to hold it at the bottom. When the flame is lit it can get very hot any higher up, so doing this regularly will help your remember to do it . You should never leave your bunsen burner unattended when it is lit. You should make sure your are aware where all emergency exit and emergency gas shut offs are as well as all safety equipment before you start using your bunsen burner. Now that you know all the safety percautions you can begin to light your bunsen burner. The first step is to attach the hose to both the bunsen burner and the gas line. Make sure that you attach it to the gas line and not an air or water line. You will now want to turn the barrel clock wise to completely close the air inlet, do this until there is resistance. Now turn it back slightly so that just a small amount of air is let through You will also want to close the gas needle valve located underneath the bunsen burner. Do this by turning it completely counter clockwise. Leave this closed for now and turn on the gas You will know the gas tap is open when the the handle lines up with the tap. You will now want to turn the gas needle valve clockwise slightly to open it. This lets a small amount of gas through you should be able to hear faint hissing which lets you know that the gas is coming out of the burner. The next step is to take your flint and generate sparks over your bunsen burner. You may want to practice this a few times just before you turn the gas on like I am doing. To do this you want to push up and across Hold the flame just above the bunsen burner and generate the sparks. You should now have a flame that is yellow and orange colour. To get a taller flame turn the gas needle valve clockwise. and likewise to get a shorter flame turn it counter clockwise. and like wise to get a short flame turn it counter clockwise. Once you have your flame at a sufficient height you will want to adjust the heat to make a hotter flame you will want to turn the barrel, do this by holding it at the base. To increase the heat you will want to turn the barrel counter clockwise. This should change the colour of your flame from yellow-orange to blue. Be careful when handling the barrel at this point because it can get very hot only handle it at the bottom. You will also want to make sure not to let too much air in because this can blow out your flame. You will know your flame is ready to use when it is dark blue in colour with a darker inner core. You will want to hold your item just above the inner core to be in the hottest location. When you have finished using the bunsen burner there is a correct proceedure for turning it off safely. First you will want to turn your flame back to yellow by letting more air in. Do this by turning the barrel, holding the bottom, in the clockwise direction now you will want to turn your gas needle valve off by turning it counter clockwise. at this point the flame should go out. Lastly, turn off the gas tap. You have now finished turning off your bunsen burner, but make sure to let it cool before putting it away. Using a bunsen burner can be intimidating to even some of the most experienced chemists but if you follow the instructions and safety protocols that I have taught you, you can always make sure that you proceed with the utmost safety precautions.
History
In 1852, the University of Heidelberg hired Bunsen and promised him a new laboratory building. The city of Heidelberg had begun to install coal-gas street lighting, and the university laid gas lines to the new laboratory.
The designers of the building intended to use the gas not just for lighting, but also as fuel for burners for laboratory operations. For any burner lamp, it was desirable to maximize the temperature of its flame, and minimize its luminosity (which represented lost heating energy). Bunsen sought to improve existing laboratory burner lamps as regards economy, simplicity, and flame temperature, and adapt them to coal-gas fuel.
While the building was under construction in late 1854, Bunsen suggested certain design principles to the university's mechanic, Peter Desaga, and asked him to construct a prototype. Similar principles had been used in an earlier burner design by Michael Faraday, and in a device patented in 1856 by gas engineer R. W. Elsner. The Bunsen/Desaga design generated a hot, sootless, non-luminous flame by mixing the gas with air in a controlled fashion before combustion. Desaga created adjustable slits for air at the bottom of the cylindrical burner, with the flame issuing at the top. When the building opened early in 1855, Desaga had made 50 burners for Bunsen's students. Two years later Bunsen published a description, and many of his colleagues soon adopted the design. Bunsen burners are now used in laboratories around the world.[6]
Operation
The device in use today safely burns a continuous stream of a flammable gas such as natural gas (which is principally methane) or a liquefied petroleum gas such as propane, butane, or a mixture of both.
The hose barb is connected to a gas nozzle on the laboratory bench with rubber tubing. Most laboratory benches are equipped with multiple gas nozzles connected to a central gas source, as well as vacuum, nitrogen, and steam nozzles. The gas then flows up through the base through a small hole at the bottom of the barrel and is directed upward. There are open slots in the side of the tube bottom to admit air into the stream using the Venturi effect, and the gas burns at the top of the tube once ignited by a flame or spark. The most common methods of lighting the burner are using a match or a spark lighter.
The amount of air mixed with the gas stream affects the completeness of the combustion reaction. Less air yields an incomplete and thus cooler reaction, while a gas stream well mixed with air provides oxygen in a stoichiometric amount and thus a complete and hotter reaction. The air flow can be controlled by opening or closing the slot openings at the base of the barrel, similar in function to the choke in a carburettor.
If the collar at the bottom of the tube is adjusted so more air can mix with the gas before combustion, the flame will burn hotter, appearing blue as a result. If the holes are closed, the gas will only mix with ambient air at the point of combustion, that is, only after it has exited the tube at the top. This reduced mixing produces an incomplete reaction, producing a cooler but brighter yellow, which is often called the "safety flame" or "luminous flame". The yellow flame is luminous due to small soot particles in the flame, which are heated to incandescence. The yellow flame is considered "dirty" because it leaves a layer of carbon on whatever it is heating. When the burner is regulated to produce a hot, blue flame, it can be nearly invisible against some backgrounds. The hottest part of the flame is the tip of the inner flame, while the coolest is the whole inner flame. Increasing the amount of fuel gas flow through the tube by opening the needle valve will increase the size of the flame. However, unless the airflow is adjusted as well, the flame temperature will decrease because an increased amount of gas is now mixed with the same amount of air, starving the flame of oxygen.
Generally, the burner is placed underneath a laboratory tripod, which supports a beaker or other container. The burner will often be placed on a suitable heatproof mat to protect the laboratory bench surface.
A Bunsen burner is also used in microbiology laboratories to sterilise pieces of equipment[7] and to produce an updraft that forces airborne contaminants away from the working area.[8]
Variants
Other burners based on the same principle exist. The most important alternatives to the Bunsen burner are:
- Teclu burner – The lower part of its tube is conical, with a round screw nut below its base. The gap, set by the distance between the nut and the end of the tube, regulates the influx of the air in a way similar to the open slots of the Bunsen burner. The Teclu burner provides better mixing of air and fuel and can achieve higher flame temperatures than the Bunsen burner.[9][10]
- Meker burner – The lower part of its tube has more openings with larger total cross-section, admitting more air and facilitating better mixing of air and gas. The tube is wider and its top is covered with a wire grid. The grid separates the flame into an array of smaller flames with a common external envelope, and also prevents flashback to the bottom of the tube, which is a risk at high air-to-fuel ratios and limits the maximum rate of air intake in a conventional Bunsen burner. Flame temperatures of up to 1,100–1,200 °C (2,000–2,200 °F) are achievable if properly used. The flame also burns without noise, unlike the Bunsen or Teclu burners.[11]
- Tirrill burner – The base of the burner has a needle valve which allows the regulation of gas intake directly from the burner, rather than from the gas source. Maximum temperature of flame can reach 1560 °C.[12]
See also
References
- ^ Lockemann, G. (1956). "The Centenary of the Bunsen Burner". Journal of Chemical Education. 33 (1): 20–21. Bibcode:1956JChEd..33...20L. doi:10.1021/ed033p20.
- ^ Rocke, A. J. (2002). "Bunsen Burner". Oxford Companion to the History of Modern Science. p. 114.
- ^ Jensen, William B. (2005). "The Origin of the Bunsen Burner" (PDF). Journal of Chemical Education. 82 (4): 518. Bibcode:2005JChEd..82..518J. doi:10.1021/ed082p518. Archived from the original (PDF) on November 9, 2006.
- ^ Griffith, J. J. (1838). Chemical Reactions – A compendium of experimental chemistry (8th ed.). Glasgow: R Griffin and Co.
- ^ Kohn, Moritz (1950). "Remarks on the history of laboratory burners". Journal of Chemical Education. 27 (9): 514. Bibcode:1950JChEd..27..514K. doi:10.1021/ed027p514.
- ^ Ihde, Aaron John (1984). The development of modern chemistry. Courier Dover Publications. pp. 233–236. ISBN 978-0-486-64235-2.
- ^ "Spreading Liquid Cultures of Bacteria on Agar-Media Plates" (PDF). chemistry.ucla.edu. Archived (PDF) from the original on 2022-10-09. Retrieved 4 November 2018.
- ^ Sanders, Erin R. (2012). "Aseptic Laboratory Techniques: Volume Transfers with Serological Pipettes and Micropipettors". Journal of Visualized Experiments (63): 2754. doi:10.3791/2754. PMC 3941987. PMID 22688118.
- ^ Teclu, Nicolae (1892). "Ein neuer Laboratoriums-Brenner". J. Prakt. Chem. 45 (1): 281–286. doi:10.1002/prac.18920450127.
- ^ Partha, Mandal Pratim & Mandal, B. (2002-01-01). A Text Book of Homoeopathic Pharmacy. Kolkata, India: New Central Book Agency. p. 46. ISBN 978-81-7381-009-1.
- ^ Hale, Charles W. (1915). Domestic Science, Volume 2. London: Cambridge University Press. p. 38.
- ^ Cruzan, Jeff (2012). "The lab burner- Anatomy of a Tirrill burner". xaktly.com.
External links
- Sella, Andrea (2007). "Bunsen's Burner". Classic Kit, Chemistry World. Royal Society of Chemistry.
- Poliakoff, Martyn (2011). "Robert Bunsen and his Burner". The Periodic Table of Videos. University of Nottingham.
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This page was last edited on 10 April 2024, at 05:21