Bunsen Burner: Parts, Principle, and Application

Bunsen burner is a gas burner that produces smokeless, nonluminous flame used for heating, sterilizing, and combustion purposes in laboratory experiments. It was named after Robert Bunsen, a German scientist who designed it in 1857. A.D.

Bunsen burner ignites by the fusion of fuel and air (oxygen). There are two primary fuel sources for bunsen burner: natural gas (methane) and liquified petroleum gas (propane, butane, or a mixture of both).

Parts of a Bunsen Burner

The Bunsen burner is an essential part of laboratory equipment used for heating materials in the laboratory. It consists of seven major components: the base, barrel (chimney), air regulator (collar), air holes, gas valve, gas nozzle, and gas intake tube.

1. Base: It is a wide and weighty part, present in the bottom of the Bunsen burner, available in variable shapes. It helps to provide support to the burner. It also helps to provide direct contact of the burner with the work surface. 
2. Barrel: It is also known as a chimney. It is a 5 inches long metal tube that rests on the base of the burner. It consists of two holes near the bottom end, known as an air intake opening that allows passage of air into the barrel. When natural gas passes through the air intake opening, the gas and air mixture ignites at its upper end.
3. The air regulator (collar): It is a short metallic cylindrical structure around the air holes at the bottom end of the barrel. The primary function of the collar is to control the amount of air entering the barrel. It works on the screw mechanism; a clockwise turn increases air intake, whereas anticlockwise rotation decreases air intake.
4. Air holes: Two air holes are present near the bottom end of the barrel. It allows air to enter the burner to make a mixture of air or any other liquid fluid and gas.
5. Gas valve:  It is connected internally with the gas nozzle, the gas receiving part. The gas supply to the burner can be controlled by rotating the gas valve right or left.
6. Gas nozzle: A plastic or rubber pipe is connected to the gas source. It helps to allow natural gas to enter the burner.
7. Gas intake tube: Ruber tubes transfer gas into a bunsen burner.

Principle

Bunsen burner is generally fitted with spiky fittings at the base of the barrel that helps to connect the rubber tube, which is responsible for feeding gas to the burner. The gas passing through the rubber tube goes up the barrel from the bottom of the burner.

The principle of the bunsen burner is based on its ability to mix gases with oxygen by venturi effect before the mixture is ignited. The venturi effect states that the pressure decreases due to an increase in the velocity of the fluid that flows through the constricted pipe or hole. Likewise, in the case of a bunsen burner, gas flowing through the chimney has low pressure than the steady air surrounding it. This variation in pressure causes air to be drawn into the air hole as the gas flowing passes through it with the help of the venturi effect. As a result, the flame burning at the top of the barrel occurs on the mixing of gas and oxygen.

Thus, the amount of air supplied, which can be regulated by the collar (adjustable valve), is directly proportional to the strength and color of the flame. With a closed valve, a minimal amount of air (oxygen) passes, and a smoky yellow (low temperature) flame is produced. Whereas, with opened valve, a sufficient amount of air enters, and the roaring flame is produced hot, nearly colorless.

Types of Flame on a Bunsen Burner

Generally, the flame produced by the burner can be controlled by two factors; fuel to air ratio 

and amount of energy. 

Fuel-to-air ratio: It determines the intensity and type of flame produced. The amount of air is controlled by an air valve.

Amount of fuel: The amount of fuel is controlled by a gas valve.

Based on the above two factors, the burner produces different flames. These include; safety flame, medium flame, and roaring flame. 

Safety flame

• It is one of the coolest flames that are orange or yellow.
• It can be easily seen in a well-lit room and helps to remind the burner is on.
• Reaches temperature of approximately 300℃; not used for heating any materials in the laboratory.
• It is produced when the air valve is closed, but the air needed for combustion comes from the area near the top of the burner.

Medium blue flame

• They are also known as standard, blue, or invisible.
• Difficult to see in a bright room.
• It is mainly used to heat materials in laboratories.
• Reaches a temperature of approximately 500℃.
• It is produced when the air gap is partially opened.

Roaring flame

• It is the only type that makes noise.
• It reaches a temperature of up to 1400℃ and provides the highest possible temperature of the burner.
• It is the hottest flame, characterized by the light blue triangle in the middle.
• It is produced when the air gap is fully opened. Gas and air ignite at the top of the barrel on increasing airflow, resulting in a noisy, bluish-colored three-cone flame.

In summary,

Air hole	Types of flame	Inference
Air hole closed	yellow safety flame	when we are not using it.
Air hole half-open	blue flame	to gently heat things up.
Air holes open	roaring flame	to heat things fast.

Types of Bunsen Burner

There are different types of Bunsen burners to choose from, depending on the gas source and experimental conditions, which include; the tirrill burner, teclu burner, and meker burner.

Tirrill burner

• It consists of a wing nut at the bottom of the tube that supplies gas oxygen.
• Temperature can rise to 1560-1575℃ along with the production of a blue flame.

Teclu burner

• It consists of a screw nut at the bottom of the chimney that helps to regulate the gas input.
• The barrel tube is longer than other types of bunsen burner. As a result, gas and oxygen mix well.
• The combustion power of the flame is stronger.

Maker burner

• The diameter of the barrel tube is larger than other burners. Therefore, the mixing of gas and air is more.
• The chimney is flared and equipped with an extra grid that covers the top of the barrel, separating the flame into shorter, quieter, and more powerful (up to +1180 ℃).
• The gas supply is controlled by a gas valve present below the barrel tube.

Application/Uses of Bunsen Burner

In the chemical laboratories

• Drying salts
• Analysis of moisture content.
• Dehydration of complexes
• Determination of solvent flash point.
• Determination of compound’s flammability.

Within microbiology laboratories

• The burner helps in achieving a contamination-free area for research laboratory purposes.
• It also helps with sterilizing inoculating loop and spreader used in microbiological experiments.
• The Bunsen burner is used in the fixation of the smear while staining.
• It is also used in sterilizing neck tubes and flask to maintain the aseptic condition.

In zoology and botany laboratories

• Preparation of permanent slides.
• Heating purpose

Advantages of Bunsen Burner

• Easy to set up and operate.
• Cost-effective
• It can be used not only for heating purposes but can also be used for simple glass-blowing work.
• Available in different sizes and types for the operator’s convenience and requirements.

Limitations of Bunsen Burner

1. Using Bunsen burners inside a biological safety cabinet (BSC) is not recommended because it disrupts airflow, compromising the protection of the workers and the product. Bunsen burner causes excessive heat build-up within the cabinet and may damage the HEPA filter, or melt the adhesive holding, thus compromising the cabinet’s integrity. It also presents a potential fire or explosion within the cabinet. Disposable sterile loops or micro-incinerators are suitable alternatives for using bunsen burners in safety cabinets.
2. Temperature control at the required amount is impossible.
3. Risk of fire accidents.

References

1. Jensen W.B. The origin of Bunsen Burner. J.Chem.Edu. 2005 82:518. DOI: https://doi.org/10.1021/ed082p518
2. Bykowski T, Verma A, Brissette CA, Stevenson. Aseptic technique. Research gate 2012. Available on https://www.researchgate.net/publication/280947477_Aseptic_techniques
3. Bunsen burner, Meker burners, and Tirrill burner: what’s the difference? Grainger Know How. Retrieved on 10th September 2022. Retrieved from https://www.grainger.com/know-how/equipment-information/kh-bunsen-burners-meker-burners-tirrill-burners