Acetylene is a fuel gas used in welding. It comes dissolved in acetone in cylinders and is very common in workshops, garages and maintenance facilities. Being a highly flammable gas, its storage and use is therefore subject to stringent safety precautions.



Approximately 80% of the acetylene produced is used in chemical synthesis. The remaining 20% is used primarily for oxy-acetylene gas welding and cutting due to the high temperature of the flame. Combustion of acetylene with oxygen produces a flame of over 3300 C (6000 F) -- Oxy-acetylene is the hottest burning fuel gas.

Physical Properties

Acetylene, symbol C2H2, is a gas similar in density to air with an odour of sweet garlic. It is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. Because it contains a triple bond, acetylene is an unsaturated chemical compound.

Gas Acetylene
Chemical formula C2H2
Molecular weight 26.0
Gas density 1.097 Kg/m3
SG vapour 0.91
Boiling point -81°C
Critical temperature 35.6°C
Critical pressure 61.9 bar


Acetylene is produced by mixing calcium carbide with water. The resultant reaction is highly exothermic and must be cooled by adding extra water. Acetylene effervesces and calcium hydroxide (hydrated lime) is a further product. It is then purified and dried and dissolved into acetone soaked in a porous mass under pressure in steel cylinders. Acetylene is also produced in chemical plants but normally the gas produced in such plants is used as feedstock in the same plant for further chemical synthesis.


Acetylene is highly flammable and in high enough concentrations may also cause asphyxiation and death. Acetylene flames cannot be extinguished with water and are normally kept cool until the source of acetylene is exhausted. For more detail on the hazards associated with acetylene check the Safety Data sheet.

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