High-speed footage of the iIncomplete combustion of acetylene (ethyne). The test tube contains acetylene gas, which is ignited by a lit splint. In pure oxygen, acetylene burns with an extremely hot flame, producing carbon dioxide and water. In an environment with limited oxygen, however, some of the carbon instead forms invisible carbon monoxide gas, and solid carbon (soot), which is seen as a black deposit on the side of the test tube here.