A colorless, gaseous hydrocarbon, C2H4, forming an
   important ingredient of illuminating gas, and also obtained by the
   action of concentrated sulphuric acid in alcohol. It is an unsaturated
   compound and combines directly with chlorine and bromine to form oily
   liquids (Dutch liquid), -- hence called olefiant gas. Called also
   ethene, elayl, and formerly, bicarbureted hydrogen.