Acetylene

Acetylene (C₂H₂) is a hydrocarbon gas that, when burned with pure oxygen, produces an extremely high-temperature flame (over 3,000°C), making it ideal for welding and cutting steel. Historically, it was also very important for portable lighting (miner’s lamps).

Description of what it is like

It is a colorless gas. In its pure state it is odorless, but commercial grade has a strong and distinct garlic-like odor due to impurities. It is highly flammable and can be explosive if not handled correctly.

Origin and where to find it

• Manufactured: Generated by the reaction of calcium carbide with water.
• Stored: In industrial cylinders, dissolved in acetone within a porous mass to keep it stable.

Minimum processing required

1. Obtaining Carbide: Calcium Carbide is needed.
2. Generation: In a gas generator (such as a carbide lamp or a gasogene), water drips onto the calcium carbide.
3. Reaction: $CaC_2 + 2H_2O \rightarrow C_2H_2 + Ca(OH)_2$ (Acetylene + Slaked Lime).

Tools needed to work on it

• Gas Generator: Airtight container with water drip control.
• Hoses and Valves: To direct the gas to the torch.

Common forms of use

• Oxy-acetylene Welding: Mixed with oxygen for welding.
• Lighting: In carbide lamps for caving or old mining.

Possible substitutes

• Propane/Butane: Safer and easier to store fuel gases, but with lower flame temperature (good for brazing, bad for fusion welding of steel).
• Hydrogen: Used in oxy-hydrogen welding, clean flame but difficult to see.

Limitations and common failures

• Instability: Acetylene can decompose explosively if compressed to more than 15 PSI (approx. 1 bar) in a free state.
• Reaction with Metals: Forms explosive acetylides if it comes into contact with pure copper, silver, or mercury. Alloys like Brass should be used.

Risks and safety

• Explosion: Extremely dangerous if there are leaks in closed spaces.
• Asphyxiation: Displaces oxygen in confined spaces.

Related Materials

• Calcium Carbide
• Oxygen
• Water