USING A GAS BURNER

Laboratory gas burners produce various kinds of flames when different mixtures of gas and air are burned. The most common models are the Bunsen burner and the Tirrell burner. Both have adjustable air vents but the Tirrell burner also has a gas control valve in its base. Our burners use methane gas (CH₄) as the fuel.

Caution: Confine long hair in a scrunchy or rubber band. Remove loose clothing or jewelry. Put on eye goggles.

1. Examine the burner. Turn the gas adjustment wheel and the

barrel that adjusts the air supply.

2. Connect the burner to the gas supply with the rubber tubing.

3. Screw the barrel almost closed, so that a small amount of

air can enter the barrel.

4. Screw the gas adjustment knob almost closed.

5. Hold the butane igniter to the top of the burner tube and

turn on the gas supply. The gas is completely on when the

handle is in line with the nozzle.

6. You should get a blue flame that is about 6-8 inches high. Adjust the air supply and gas supply to achieve the perfect flame.

7. The hottest part of the flame is the top of the inner cone. It should be about 1 -2 inches high and free of yellow color.

Heating liquids

Heating a liquid in a test tube.

Caution: Never point the open end of a test tube you are heating either toward yourself of anyone working nearby. Never heat the bottom of the tube.

1.Always use a Pyrex or Kimax test tube.

2. Adjust your gas burner to produce a gentle blue flame.

3. Fill a test tube one-third full with water from the tap.

4. Grasp the test tube with a test tube holder, near the upper end of the tube.

5. Hold the test tube in a slanting position in the flame with the mouth of the tube facing toward the wall.

6. Gently heat the tube by slowly moving the liquid end in the flame. You do not want to heat just one spot as this will cause the hottest liquid to burst out of the tube.

Heating a liquid in a Beaker

Many experiments require the use of a hot water or boiling water bath. This procedure describes how to assemble a water bath.

Caution: Never heat plastic beakers of graduated cylinders. Never let a boiling water bath boil dry, add water as necessary.

1.Fasten an iron ring securely to a ring stand so that it

is 2-4 cm above the top of a gas burner placed on

the ring stand base.

2. Place a 250 ml beaker one half-filled with water on a wire gauze resting on the iron ring.

3. Light the gas burner and adjust it to produce a hot flame.

4. Place the burner beneath the wire gauze. For slower rate of heating, reduce the intensity of the burner flame.

Glassworking

Cutting and Fire Polishing.

1.Place the glass tubing or glass rod on a flat surface.

2. Hold the glass firmly with one hand close to the area to be cut.

3.Using a firm stroke, make a single deep scratch with

a triangular file.

Caution: Do not use a sawing motion or repeated

scratching.

3. Grasp the glass in both hands, with the scratch facing away from you and both thumbs directly behind the scratch.

4. Push firmly with the thumbs and pull with your fingers. The glass should snap with a clean break.

Caution: Be careful with the cut ends of the glass.

They may be sharp and jagged.

5. The cut ends of the glass tubing should be fire-polished to make the tubing safe to handle. Rotate one end of the glass tube in the hottest part of the burner flame until the sharp edges have softened and become rounded.

Caution: do not hold the tubing in the flame too long.

If you do, the hold in the tube will close.

6. Place the hot glass on a wire gauze square to cool.

Caution: Hot glass and cold glass look alike. Make

sure one end of the piece of glass has cooled before

you attempt to fire-polish the other end.

Bending Glass Tubing

1. Put a wing tip or flame spreader on your gas

burner.

2. Light the burner and adjust the flame to produce an even blue flame across the wing tip.

3. Grasp a length of glass tubing that has been fire-polished at both ends. Hold the center of it lengthwise in the flame, just at the top of the blue region. This is the hottest part of the flame.

4. Rotate the tubing in the flame to heat approximately a 5 cm section uniformly, until it becomes soft and just begins to sag.

5. Remove the rubbing from the flame and bend it to the desired shape in one movement. Examples of good and bad bends are shown below.

6. When it has hardened, put the glass tubing on wire gauze to cool.