ETHYLENE, or ETHENE, C2H4  , or H2C:CH2, the first representative of the series of olefine hydrocarbons, is found in coal gas . It is usually prepared by heating a mixture of ethyl alcohol and sulphuric acid . G . S . Newth (Jour . Chen . Soc., 1901, 79, p . 915) obtains a purer product by dropping ethyl alcohol into syrupy phosphoric acid (sp. gr . 1.75) warmed to 200° C., subsequently raising the temperature to 220° C . It can also be obtained by the action of sodium on ethylidene chloride (B . Tollens, Ann., 1866, 137, p . 311); by the reduction of copper acetylide with zinc dust and ammonia; by heating ethyl bromide with an alcoholic solution of caustic potash; by passing a mixture of carbon bisulphide and sulphuretted hydrogen over red-hot copper; and by the electrolysis of a concentrated solution of potassium succinate, (CH2 .

CO2K) 2+2H20 = C2H4+2CO2+2KOH +H2 . It is a colourless gas of somewhat sweetish

taste; it is slightly soluble in water, but more so in alcohol and ether . It can be liquefied at-1.1° C., under a pressure of 42i atmos, It solidifies at-181° C. and melts at-169° C . (K . Olszewski); it boils at -105° C . (L . P . Cailletet), or-102° to-103° C . (K . Olszewski) . Its critical temperature is 13° C., and its specific gravity is o•9784 (air =1) . The specific gravity of liquid ethylene is o•386 (3° C.) .

Ethylene

burns with a bright luminous flame, and forms a very explosive mixture with oxygen . For the combustion of ethylene see FLAME . On strong heating it decomposes, giving, among other products, carbon, methane and acetylene (M . Berthelot, Ann., 1866, 139, p . 277) .