A mixture of pure oxygen and acetylene is burnt for welding. Can you explain why a mixture of acetylene and air is not used?

Explanation

i. Ethyne is an unsaturated hydrocarbon. On combustion in air, it produces a yellow flame with lots of black smoke.
ii. Due to this incomplete combustion, heat produced is low and temperature obtained is also low.
iii. For welding purposes, high temperature is required.
iv. When a mixture of acetylene and oxygen is used, complete combustion is achieved and very high temperature required for welding is obtained.
Hence, a mixture if acetylene and oxygen is used for welding instead of a mixture of acetylene and air.