1894.] 



The Action of Heat upon Ethylene. 



103 



These results show how much more stable methane is under the in- 

 fluence of heat than any of the other gaseous hydrocarbons studied. 



It probably decomposes at first into acetylene and hydrogen, 

 according to the equation 



and then the acetylene either polymerises or decomposes to carbon 

 and hydrogen, according to the temperature. 



These results also explain why it is that the flame of methane 

 when burning at an open tube is practically non-luminous, as, under 

 these conditions, the maximum temperature of the flame is below 

 1100 C., and no formation of acetylene takes place ; whilst with 

 increase of temperature the flame becomes rapidly more and more 

 luminous, so that when burnt in a regenerative burner at 1500 C. 

 the light emitted is of considerable illuminating value. 



As a further step in securing factors by which to trace the decom- 

 position, it seemed advisable to attempt to trace the action of heat 

 upon the benzene vapour formed by the polymerisation of the acetyl- 

 ene ; and in order to do this, pure hydrogen was allowed to pass 

 through benzene at a known rate and a constant temperature, the 

 amount of benzene in the gas being determined. 



Table Y. The Action of Heat upon Hydrogen-borne Benzene. 



which shows that the diluted benzene breaks down to acetylene, 

 methane, and carbon, and, finally to carbon and hydrogen. 



Taking the experimental data, it seemed to show that the primary 

 reaction on heating ethylene is the splitting up of 3 mols. into- 

 acetylene and methane, 



and that the acetylene then polymerises into higher bodies as 



i 2 



