

1894.] The Action of Heat upon Ethylene. 93 



acetylene series, whilst samples of the gases escaping absorption were 

 finally collected over water. Carbon was deposited in the decomposi- 

 tion tube, and at the end of one month 15 c.c. of liquid had been 

 slowly condensed in the \J -tubes, and in this liquid they detected 

 benzene, naphthalene, anthracene,' and some other aromatic hydro- 

 carbons, present in quantities too small for determination. Faint 

 traces only of precipitate were found in the ammoniacal cuprous 

 chloride solution, whilst among the bodies absorbed by bromine they 

 identified crotonylene tetrabromide, and the gas collected over water 

 proved to be a mixture of methane and ethane. The absence of 

 acetylene from the products obtained led them to the view that these 

 products are formed directly by the action of heat upon ethylene. 



From the work of the earlier observers, the text-books have 

 accepted the equation 



1. C 2 H 4 = C 3 +2H 2 



as representing the decomposition which takes place at a very high 

 temperature, whilst, on the evidence of the work done by Marchand, 

 and Buff and Hofmann, they represent the change taking place at a 

 lower temperature by the equation 



2. C 2 H 4 =C + CH4. 



During my attempts to trace the actions taking place in the inner 

 zone of luminous flames, I was struck by the complexity of the 

 changes, and the absence of any evidence which would tend to con- 

 firm the second equation, and I have made the experiments detailed 

 in the following paper in the hope of being able to trace the decom- 

 position effected by heat in such simple hydrocarbons as ethylene, 

 ethane, and methane. 



The first step was to make experiments to corroborate the state- 

 ment made by Day that, if ethylene is heated at 400 C. for a sufficient 

 length of time, it is entirely decomposed, with formation of methane, 

 ethane, and liquid products. 



In order to do this an apparatus of the form used by Day in his 

 experiments was employed, the only difference being that instead of 

 using an air thermometer, the temperature was taken by means of a 

 platinum and platinum-rhodium couple as introduced by Le Chatelier, 

 and fully described by Mr. C. Roberts- Austen which had been pre- 

 viously carefully calibrated, employing salts of known fusing points. 

 The ethylene was prepared for this and for all the following experi- 

 ments by making a mixture of 25 parts by weight of rectified methyl- 

 ated spirit and 150 parts of strong sulphuric acid. The mixture was 

 heated in a flask containing a layer of sand, and the gas evolved was 

 washed by contact with strong sulphuric acid, and by passage 

 through several bottles containing a strong solution of caustic soda. 

 The gas was stored in a glass gas-holder for several days over water 



