Which gas is often mixed with oxygen for welding purposes?

Acetylene is frequently mixed with oxygen for welding purposes due to its ability to produce a very high flame temperature. This characteristic makes it ideal for oxy-acetylene welding, where the intense heat is required to melt metals for effective joining. Acetylene's combustion creates a focused and controlled flame, which allows welders to work with precision on a variety of materials, including steel and other ferrous and non-ferrous metals.

In contrast, while propane, hydrogen, and butane can also be used as fuel gases for cutting and heating, they do not achieve the same high flame temperatures as acetylene when mixed with oxygen. This limits their effectiveness for welding applications where the melting of metal is required. Each of these gases has its own specific uses, but in the context of welding, acetylene stands out as the preferred choice due to its efficient combustion properties and suitability for high-temperature applications.