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Last updated on April 19, 2014 at 21:20 EDT

Bunsen Burner

A Bunsen burner produces a single open gas flame; it is commonly found in labs – used for heating, sterilization, and combustion. Robert Bunsen, in 1852, was hired at the University of Heidelberg and promised a new laboratory building. Heidelberg had just started installing coal-gas street lighting which provided light but not necessarily heat.

Laboratory lamps, at the time, left much to be desired regarding economy and simplicity. The desire was to maximize the temperature and minimize the luminosity. In 1854, Bunsen and Peter Desaga created a burner design that generated a hot, sootless, non-luminous flame by mixing gas with air in a controlled fashion before combustion.

In 1855, Desaga had made fifty of the burners by the time the building had opened. Desaga created slits for air at the bottom of the first cylindrical burner. Two years later many of his colleagues had adopted the design and today they are used around the world in laboratories. The burners used today safely burn a continuous stream of flammable gas such as natural gas, propane, butane or a mixture.

The hose barb is connected to a gas nozzle on the lab bench with rubber tubing. The gas flows up through the base to the burner. There are slots in the side of the tube bottom to admit air into the stream via the Venturi effect. Usually the burner is lit with a match or spark lighter. The amount of air in the gas stream affects the completeness of the combustion reaction. The more air the hotter the reaction. The air can be controlled by opening or closing the slots at the base.

A hot flame will appear blue as a result of more air mixing with the gas. If the holes are closed then gas only mixes with ambient air and produces a cooler but brighter yellow flame, or a safety flame. This yellow flame is considered dirty since it leaves a layer of carbon on whatever it is heating. Increasing the amount of fuel flow through the tube by opening the valve will increase the flame. This will only increase the heat of the flame if the airflow is adjusted as well; otherwise, the gas is mixed with the same amount of air which starves the flame of oxygen. The hottest part of the blue flame on the Bunsen burner is just above the unburnt gas. The hottest part of the yellow flame is the chimney.

Bunsen Burner