400 



Prof. V. B. Lewes. 



[Mar. 7, 



points to its being radiant heat, and not contact with the heated sides 

 of the tube, which is responsible for the largest proportion of the 

 decomposition ; since, had contact been the active factor, dilution, by 

 reducing the number of impacts of the hydrocarbon molecules with 

 the heated surface, would have shown a considerable decrease in 

 decomposition. 



Some information can be obtained as to the secondary reactions 

 which accompany the main decomposition, by studying the propor- 

 tions in which the products, other than ethylene, are present in the 

 gases after heating. 



Taking the experiments made upon the effect of length of heated 

 tube and rate of flow, and tabulating the percentages of saturated 

 hydrocarbons and hydrogen corrected for change of volume, we 

 obtain the following results : 



Saturated Hydrocarbons. 



The temperature employed in these experiments is not sufficiently 

 high to cause any large amount of the methane to decompose, so that 

 the volume should, according to theory, approximate to two-thirds of 

 the ethylene decomposed. 



