ACETYLENE is a colourless gaseous compound of 7.75% of hydrogen and 92.25% of carbon, used as a fuel, both in the oxyacetylene process for the welding and cutting of metals, and also for isolated or inde pendent lights. It is of great in terest to the chemist, being the simplest of all the unsaturated or ganic compounds with the com position CH CH (see CHEMIS