Science Fair Project Encyclopedia
A Bunsen burner is a device used in scientific laboratories for heating, sterilization, and many other uses.
The device safely burns a continuous stream of gas without the risk that the flame will travel back down the tube to the gas supply. It is most common for the burner today to run on natural gas, or alternatively Liquified petroleum gas such as propane or butane or a mixture of both. (Natural gas is composed of methane and small amounts of propane and butane). At the time of its invention it would have mostly burnt coal gas.
The burner has a weighted base, where the gas supply tube plugs into, and a vertical tube rising from it. The gas flows from the gas supply connection to the base. The stream of gas then passes through a small hole at the bottom of the tube and is directed upward through the tube. There are perforations in the side of the tube at the bottom to admit air into the stream (via the venturi effect and the gas burns at the top of the tube, once it is ignited.
The in-flow of gas and thus the heat of the flame can be controlled by adjusting the size of the holes at the base of the tube. 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 mix with oxygen in the atmosphere at the point of combustion (that is, only after it has exited the tube at the top), and so it will burn less efficiently, producing a cooler flame (appearing yellow). The yellow flame is luminous due to small soot particles in the flame which are heated to incandescence.
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