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Bunsen Burner
Brief description
A Bunsen burner is a fundamental laboratory gas burner that mixes combustible gas with regulated amounts of ambient air prior to ignition. Developed by Robert Bunsen and Peter Desaga in 1855, it produces a high-temperature, non-luminous, sootless flame ideal for chemical analysis, glassworking, and laboratory heating.
Use / Function
- Chemical Heating & Reaction Acceleration: Provides clean, controllable heating for boiling liquids, evaporating solvents, and driving endothermic chemical reactions.
- Qualitative Analysis (Flame Tests): Emits minimal background light, allowing characteristic spectral emission colors of metallic elements to be easily observed.
- Sterilization: Rapidly sterilizes metal needles, wire loops, and glass instruments through direct thermal exposure in microbiological procedures.
- Glassworking: Softens glass tubing for bending, drawing capillary tubes, and sealing test tubes or ampoules.
- Scale: Laboratory benchtop apparatus.
Operating principle
- Gas Injection: Pressurized fuel gas (Propane, Biogas, or natural gas) enters through a small orifice (jet) at the base of a vertical metal barrel.
- Venturi Induction: As high-velocity gas shoots upward through the barrel, it creates a localized low-pressure zone (Venturi effect) that draws surrounding air into adjustable collar holes at the base.
- Premixing: The fuel gas and oxygen-rich air thoroughly mix as they flow upward through the hollow tube before reaching the top opening.
- Controlled Combustion: Igniting the gas mixture at the burner orifice creates a stable flame. Adjusting the rotating collar controls air intake: a closed vent yields a cooler yellow safety flame, while an open vent yields a hot, two-zone blue flame reaching up to 1,500°C.
How to create it
- Machining the Metal Base: Cast or lathe-turn a heavy Brass or cast iron base with an internal gas inlet tube to prevent tipping during operation.
- Drill Gas Jet Orifice: Drill a micro-pinhole nozzle in the center of the gas inlet to accelerate fuel gas flow into a high-speed jet.
- Fabricate the Barrel Tube: Cut a hollow Brass cylinder with threads at its base and drill wide air-entry ports near the bottom end.
- Fit the Adjustable Air Collar: Craft a tight-fitting rotating sleeve with matching air ports that fits over the barrel’s lower entry holes to regulate oxygen intake.
- Assemble and Test Seal: Screw the barrel onto the base over the gas jet nozzle, connect a flexible hose to a gas supply (Propane or Biogas), test for leak-free joint seals with soapy water, and ignite.
Materials needed
- Burner Body: Machined Brass tube, threaded collar, and heavy base.
- Fuel Source: Combustible gas supply such as Propane, methane, or Biogas.
- Hose & Valves: Flexible rubber or synthetic hose with needle-valve flow control.
Variants and improvements
- Meker-Fisher Burner: Features a top grid matrix to divide the flame into multiple smaller flamelets, preventing flashback and reaching higher temperatures (~1,700°C).
- Tirrill Burner: Adds an integrated needle valve at the bottom of the gas jet for independent fine-tuning of both gas volume and air intake.
- Micro-Burner: Compact version designed for fine flame operations, micro-scale chemistry, and field work.
Limits and risks
- Flashback Hazard: Excess air flow or reduced gas pressure can cause the flame to burn back down inside the barrel into the gas nozzle, overheating the burner body.
- Fire & Burn Risks: Open high-temperature blue flames are nearly invisible in bright daylight and pose severe fire and skin burn hazards.
- Toxic Gas Accumulation: Unignited fuel gas leakage can lead to explosive vapor accumulation or asphyxiation in poorly ventilated spaces.