1894] 



The Action of Heat upon Ethylene. 



99 



rapidly diminished, and at 1200 C. methane is the only member of 

 the series present. 



In the same way a small trace of some unsaturated hydrocarbon, 

 probably benzene, is present at the lower temperatures, but disappears 

 when 1200 C. is reached. 



The next step was to see if the action of heat upon ethane under 

 the same conditions as those existing in the previous set of experi- 

 ments bore out the results arrived at. 



Ethane was prepared by acting on ethyl iodide with a copper-zinc 

 couple in presence of water, and passing the evolved gas through 

 fuming sulphuric acid to purify it. 



Table III. The Action of Heat upon flowing Ethane. 



These results show that, even below 900 C., ethane decomposes 

 with liberation of hydrogen and formation of unsaturated hydro- 

 carbons, which on examination prove to consist of ethylene with 

 small quantities of acetylene, rise of temperature completing this 

 decomposition, and also causing the ethylene to decompose as before. 



It is evident that, if ethane had been a primary product in the 

 decomposition of ethylene, it would in turn have decomposed with 

 liberation of hydrogen at or below 900 C., and hydrogen would have 

 been found at that temperature as a product of the decomposition of 

 the ethylene instead of its appearance being coincident with the 

 deposition of carbon at 1200 C. 



The fact that with a rapid flow I was unable to detect a trace of 

 free hydrogen until carbon has begun to deposit, or vice versa, shows 

 the fallacy of the text-book equation 



and on examining the evidence upon which the statement is based we 

 find that Marchaiid,* who originated it, passed ethylene through glass 

 and earthenware tubes heated to redness, and analysed the resulting 

 * ' Journal fur prakt. Chemie,' vol. 26, p. 478. 



