Use of a Bunsen Burner
A Bunsen burner is a gas-fueled device used for heating or burning materials in laboratories. It produces an open flame which can be very hot. Bunsen burners provide safe,
efficient heat when used properly.
The key to proper operation of a Bunsen burner is controlling the gas and air supply to
the burner. The Bunsen burner is connected to a gas supply on the bench by means of a
rubber tube. As shown in Figure 1, the valve on the bench is open if the handle aligns
with the gas nozzle, and closed when the handle is perpendicular to the nozzle. It should
be fully open when operating the Bunsen Burner. IF THE BURNER IS NOT LIT, THE
BENCH VALVE SHOULD BE CLOSED. The gas supply to the burner is regulated by a
needle valve, which is opened and closed by a dial below the base of the burner, as
shown in Figure 2. This should be open about a full turn when you intend to light the
burner. For efficient combustion, oxygen is combined with gas in the burner. This is done
by opening holes in the barrel sleeve of the burner (Figure 2) by unscrewing the cylinder
to allow air into the gas stream. The holes should be closed when you light the burner,
and opened afterward.
FIGURE 1. Gas valve at bench.
Figure 2. Bunsen burner, showing valves
Hottest part
of flame
Tube to bench
gas valve
On
Air inlet holes
Off
Off
Gas flow regulator
Bench Gas Valve
To light the burner, follow the steps below:
1.
2.
3.
4.
5.
6.
7.
8.
Clear the area over and around the burner of flammable materials (paper,
organic solvents, human body parts such as your face or hand).
Connect the burner to the lab bench gas valve using rubber tubing.
Open the gas flow regulator dial at the base of the burner about one full turn.
Rotate the barrel sleeve to close the air supply holes completely.
Have a striker or lit match ready, and open the gas valve on the bench.
Light the burner. A striker may take two or three tries. IF YOU CANNOT
LIGHT THE BURNER, TURN OFF THE GAS! Then request help from your
instructor. You can light the burner with a match or lighter if you have one.
Once lit, the burner flame will be yellow.
Rotate the barrel sleeve to open the air holes. The flame will become bluer
and more intense.
Adjust the gas and air flow to produce a flame of the desired size (1-2 inches)
that has two distinct blue zones, the inner of which is a bright blue cone.
The hottest part of the flame is just above the tip of the inner bright blue cone. Set up
any apparatus to be heated so it contacts this hot zone. No combustion occurs within the
bright blue cone. If your instructions call for gentle heat, do not open the barrel sleeve;
work with the yellow flame. You can also move the burner away from the item being
heated for a few minutes, then move it back, to control a temperature. The burner will
not get too hot to touch except near the flame.
If the burner flows loudly, blows itself out, or burns with a detached flame, reduce the
gas flow and readjust the air flow.
To extinguish the flame, turn the lab bench gas valve to the off position.
ANY TIME YOU ARE UNSURE OF WHAT YOU ARE DOING WITH THE BURNER,
CLOSE THE VALVE AT THE BENCH AND ASK FOR ASSISTANCE.
Setting up apparatus to be heated with a Bunsen burner:
Often, a ring stand and metal ring are used to support a container contents that are to be
heated with a burner. Before lighting the burner, set up the ring stand. The ring should
be about 3 cm (1.25”) above the top of the (unlit!) burner. This distance approximately
the width of your index and middle fingers held together.
A clay triangle or wire gauze is placed on the ring to support the container. Wire gauze
is used with glassware, usually a beaker or flask. A clay triangle is used with a crucible.
When using a ring stand, wait till the burner is lit and adjusted to move it into position.
Test tubes are hand-held in a test-tube holder for heating. The bottom of the tube is exposed to the flame. Often, the tube is held at a slant; if this is required, do not point the
top of the tube toward yourself, another student or the instructor! Do not use your utility
clamp to hold a test tube for heating; you’ll melt the plastic padding on the grips.
Safety precautions:
1.
Never leave a lighted burner unattended. Drafts (including those created by a
hood) may extinguish the flame, but the gas will still be on. This could result
in an explosion.
2.
Never face the vessel (test tube, beaker, etc.) being used to heat a material
toward yourself or others near the burner.
3.
In some experiments, a hot plate may be used in place of the Bunsen burner.
A hot plate or heating mantle must be used when flammable liquids are to be
heated.
4.
Anything that has been heated with a Bunsen burner is likely to be very hot.
Do not touch apparatus with your bare hands unless the air near it feels cool.
If you have to handle hot apparatus, use crucible tongs. Do not set hot apparatus on paper, you might set it on fire. Let the apparatus cool in place, with
the burner removed or extinguished.