Light a Bunsen Burner

You are in a chemistry lab and you have to perform a distillation. Chances are you will use a Bunsen burner to heat the liquid mixture to boiling. As a matter of fact, Bunsen burners are the heat source you will most often use in your introductory chemistry lab, be it inorganic or organic. Lighting and adjusting one need not be nerve-wracking, though, even when you don't have any experience. Bunsen Burners produce different kinds of flames including red yellowish flames and blue flames depending on the amount of oxygen put into the bunsen burner.

Steps

Safety

  1. Ensure that you have a clean and uncluttered work area. It's also a good idea to make sure you are working on a fireproof bench or at least a fireproof mat.
  2. Check to make sure that all of your equipment is clean and is in good working order. And that all materials needed are available.
  3. Know where the safety equipment is located and how to use it. It is best to survey the locations before you start any laboratory procedure. In particular, you should make sure that you have unobstructed access to the following:
    • A fire blanket. Use this as a wrap should your clothing catch fire. The blanket will suffocate the flame by removing the oxygen supply.
    • Fire extinguishers. Know the location of each. It would not hurt to make sure that the inspections are up-to-date. At the same time you can determine the types available and form an action plan in case of emergency. There are several types of extinguishers and each (in the US) should be marked by a colored ring near the top of the extinguisher.
      • Dry powder retardants can be used on every type of fire except for oils. That is, the extinguisher containing dry powders can be used on solids, liquids, gases and on electrical equipment. Extinguishers containing a solid flame retardant (dry powder) are marked with a blue stripe in the US.[1]
      • Foam (yellow stripe, US) or CO2 (black stripe, US) are for oils.
      • CO2 extinguishers can also be used on electrical equipment and on flammable liquids.[1]
      • Foam extinguishers can also be used on flammable liquids and flammable solids (paper, wood, other).[1]
      • Know how to use a fire extinguisher. Use the acronym PASS: Pull the pin and, with the nozzle directed away from you, undo the locking mechanism. Aim low (at the base of the fire). Squeeze the trigger slowly and evenly. Sweep the chemical from side to side.[2]
    • A fire hose. This is for large fires and should be used by trained individuals. Spray the base of the fire to cool the combustible (burning) material. Water should be used on solids-- wood, paper, clothes, furniture, etc., but not on flammable liquids, gases, oils or on electrical equipment. Never use water on liquids less dense than water (1.0 g/cm3). Such liquids float on the surface and spraying with water causes the fire to spread.
    • A safety shower. If your clothes catch on fire and are not saturated with a flammable liquid, this might be a good choice. The safety shower is primarily for rinsing acids from your body, but can come in handy in event of a fire.
  4. Dress for safety. Wear safety goggles and use other protective equipment when dealing with Bunsen burners.
    • Make sure to tie back long hair and tuck in loose clothing (or remove it). Also tuck in your tie and remove jewelry. Think ahead and eliminate hazards before they become a problem. You don't want anything to catch fire.
  5. Make sure there are no cracks in the gas supply line, which is usually a rubber hose/tubing. Gently squeeze the tubing along the entire length and bend it at several places along its length while you look carefully look for visible cracks. If you see cracks, replace the tubing.
  6. Connect the supply hose to the gas main and to the Bunsen burner. Ensure that the hose is pushed well up onto the ribs and that it is secure on both ends. There should be no way for any gas to escape into the air except through the burner.
  7. Get in the habit of only handling the burner at the bottom. Hold the Bunser burner only by the base or by the collar at the bottom of the barrel. After the burner is lit the barrel will be very hot and you will burn yourself if you pick up the burner by the top part of barrel before allowing the burner to cool.

Understanding Burners

  1. Learn the nomenclature for the parts of Bunsen burner.
    • The bottom of the burner that rests on the bench top is called the base. The base provides stability and helps to keep the burner from being tipped over.
    • The upright part of the burner is called the barrel.
    • At the bottom of the barrel is an outer sleeve (the collar) which can be rotated to expose slots in the barrel, called air ports. These allow air to be introduced into the barrel where it is mixed with the gas to produce a highly combustible gaseous mixture.
    • The gas enters the barrel through a needle valve which can be adjusted to control the gas flow.
  2. Learn the parts of the flame. There is really a flame within a flame. The inner flame is the reducing flame and the outer flame is the oxidizing flame. The hottest part of the flame is the tip of the inner, reducing flame.
  3. Learn the specifics of the gas mixing and combustion processes.
    • The air and gas mix within the barrel. If the collar is turned so the air ports are closed, then no air is introduced into the barrel. All of the oxygen (required for combustion) is supplied at the top of the barrel from the surrounding air. This flame burns yellow and is the coolest flame, often called the safety flame. When the burner is not in use the collar should be rotated to close the air ports and produce the cool safety flame.
    • The needle valve and the collar are used in conjunction to control the volume and the the mixture ratio of gas to air. The gas to air ratio determines, in large part, the heat produced. Equimolar amounts of gas and air produce the hottest flame. The total volume of gaseous mixture rising through the barrel determines the flame height.
      • You can slightly open the needle valve and air ports to achieve a hot, small flame or you can increase both flows simultaneously to create a hot taller flame.

Lighting

  1. Make sure that the collar near the bottom of the barrel is positioned so that the air ports are nearly closed. Locate the openings at the base of the chimney and twist the outer metal shell (collar) until the holes are closed. This will ensure that the flame is at its coolest once the gas is ignited (safety flame).
  2. Make sure that your local supply valve is closed and the laboratory gas main is on. The handle should be going across the axis of the gas line, perpendicular to the gas outlet.
  3. Close the needle valve at the bottom of the burner. Make sure that it is closed all the way.
    • You will want to light your match or have your striker ready and then turn the gas on (handle in-line with the gas line) and open the needle valve slightly. This ensures that, initially, the flame will be small.
    • The best way to light a burner is with a striker. This device uses flint on steel to make a spark.
    • Practice making sparks until you can generate a strong spark with each stroke. Push the flint across the "washboard" while pushing up. This will enable you to make a strong spark. Practice until you are able to make a strong spark each time. You are now ready to light the burner.
  4. Open the local gas valve by turning the handle so that it is in line (parallel) to the outlet. You should not hear any gas at this point. If you do, turn the gas off immediately and close the needle valve by turning it clockwise. Open the local gas valve again and make sure your striker is handy.
  5. Open the needle valve at the bottom of the burner until you hear the hiss of gas escaping.
  6. Hold your striker just above (1-2" or 3-5cm) above the top of the barrel and squeeze the striker to create a spark.[3] Once the burner is lit, put the striker away.
    • If you do not have a striker, you can use a match or a (disposable) lighter. Before turning on the gas, light your match/lighter and hold it away from the burner, a bit off to the side. Turn on the gas, then bring the ignition source toward the side of the gas stream/column. Once the flame is lit, put out your match/lighter. Let the match cool completely, then you can put it on the bench out of the way.

Adjustments

  1. The needle valve on the bottom of the Bunser burner adjusts the gas flow rate and, ultimately, determines the height of the flame. Open or close the needle valve to get an appropriately sized flame for the task at hand. Note: The needle valve is the one that is used to increase or decrease the gas flow, not the local shut off valve.
    • To adjust the flame height, throttle the gas flow by opening or closing the needle valve. More gas will give a larger flame; less gas, a smaller flame.
  2. The collar controls the amount of air entering the barrel (mixing chamber) and, ultimately, determines the temperature of the flame. Adjust the collar so that no air enters the barrel for the coolest flame, the safety or "stand by" flame. When you are ready to heat something, open the air ports until the flame is the right color. Yellow is cool, blue and almost invisible is the hottest.
    • For a hotter flame, twist the collar at the bottom until the holes (air ports) are more fully open. Adjust until you have reached the desired heat.
  3. Adjust to achieve the correct operating temperature for your application.
    • At its hottest, the flame is sometimes called a "banana flame" or "working flame". To create a blue flame (the hottest flame), open the collar holes to allow additional oxygen into the combustion chamber. The holes should be completely open, or nearly so.
    • A blue flame is very hot (around 1500 C) and is not easily seen. It can be almost invisible against some backgrounds.
  4. Use different parts of the flame to further adjust the temperature. If you are bending glass tubing, for example, you will try to achieve the hottest flame and, at the same time, get a medium size flame, then position the tubing at or just above the tip of the reducing flame. If it is too hot, raise the tubing a bit into the cooler oxidizing flame.
    • There are many adjustments that you will learn through trial and error, but nothing is too critical other than being safe. Soon you will learn which colors correspond to specific temperatures, at least in a relative, qualitative way.

Clean-up

  1. Never leave a lit Bunsen burner unattended. Keep your eye on it at all times. If you are working on something that does not involve the flame, turn it down to the coolest, most yellow flame (safety flame) by twisting the collar until the holes are completely closed.
  2. Turn off the gas. Turn off the local supply  by positioning the valve handle perpendicular to the gas line.
  3. Wait for the burner to cool. Five minutes will be more than enough, but still handle the burner only from the bottom. Reinforce this habit.
  4. Close the needle valve by turning it clockwise. The valve will then be set for the next use.
  5. Ensure that your burner and hose are clean and in good working order before you put them in the drawer. When your burner is clean and the needle valve is closed, risk of unexpected behavior is reduced. Remember this important step.



Warnings

  • Use the safety flame or turn the burner off when it is not being used.
  • Be aware of anything that may tip the burner over or come into contact with the flame.
  • Make sure to turn the gas off when you are finished with the burner.
  • Never touch the flame or upper portion of the barrel. Serious burns may result.

Things You'll Need

  • Bunsen burner
  • Gas source
  • Ignition source - matches, striker, etc.
  • Fireproof board (optional)
  • Safety goggles

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 1.2 http://www.ulm.edu/police/fire-extinguishers
  2. ↑ https://www.nfpa.org/safety-information/for-consumers/fire-and-safety-equipment/fire-extinguishers
  3. ↑ http://www.wpi.edu/offices/safety/bunsen.html

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