Acetylene, C₂H₂

Acetylene or Ethine was discovered by Edmund Davy in 1836, but was first investigated by Berthelot, to whom the name Acetylene is due. Berthelot produced this gas synthetically by striking the electric arc between carbon poles in an atmosphere of hydrogen:

2C + H₂ = HC≡CH.

Bone and Jerdan have investigated this action and find that methane and ethane are also produced, so that when equilibrium is attained the issuing gas has the following approximate composition:

Hydrogen	90-91 %
Acetylene	7-8 %
Methane	1.25 %
Ethane	0.75 %

They are of opinion that these hydrocarbons are produced synthetically and independently, so that the acetylene does not result from the thermal decomposition of the other hydrocarbons.

It was further shown by Berthelot that acetylene is produced when ethylene or the vapour of alcohol is passed through a red-hot tube, and also by the action of electric sparks on methane, ethylene, or a mixture of cyanogen and hydrogen. The formation of acetylene from ethylene by the action of heat has been confirmed by Bone and Coward, but the same observers have shown that methane does not produce acetylene by thermal decomposition.