GASEOUS COMBUSTION AT HIGH PRESSURES. 289 



will first of all be considered. So far as could be judged from the character of the 

 sound emitted, the explosion at initial pressures up to 16 '5 atmospheres was not very 

 violent; at 21'69 atmospheres the sound was distinctly more audible, and at 31'25 

 atmospheres a sharp metallic click, indicative of detonation, was heard. Carbon was 

 deposited and steam abundantly formed in all experiments ; there was always a 

 permanent increase in pressure (20 to 30 per cent.) on explosion, the ratio, pjpi, 

 increasing regularly with the initial pressure. It is also noteworthy that, although 

 much of the original methane remained unchanged, there was never the slightest 

 trace of either acetylene or ethylene in the products. 

 The principal observations are given in Table I. 



Second Series. (Bomb B.) 



In the next series of experiments (Table II.) the same mixture was exploded, at 

 initial pressures between 10 and 20 atmospheres in the large spherical bomb, B. 



Third Series. (Bomb A.) 



In this series of experiments (Table III.) the effect of gradully increasing the 

 proportion of oxygen between the limits 2CH 4 + O 2 and CH, + 2 was investigated. 

 The initial pressure was nearly the same (12 '6 to 1275 atmospheres) throughout 

 the series. The most noteworthy fact brought to light was the total cessation of any 

 separation of carbon after the proportion of oxygen exceeded the limit 3CH, + 20 2 . 



In interpreting the results given in Tables I. to III. it is important to distinguish 

 between (l) the primary oxidation of the hydrocarbon, which is an exceedingly rapid 

 process, and is probably completed during the short interval between ignition and the 

 attainment of maximum pressure ; and (2) certain probable secondary interactions 

 whose influence may extend far into the subsequent long cooling period. For it is 

 only these latter which would be affected by variations in the rate of cooling down 

 from the maximum temperature. 



With regard to the primary oxidation, the results with the mixture 2CH 4 + 2 are 

 obviously inconsistent with any idea of a preferential burning, whether of carbon 

 or of hydrogen. If, however, it be supposed that the oxygen initially enters 

 the methane molecule, forming unstable " hydroxylated " molecules, which then 

 decompose, it becomes necessary to consider the probabilities of the direct formation 

 of CH 3 .OH and CH 2 (OH) 2 , respectively, and the nature of their respective 

 decomposition products at high temperatures, together with the magnitude of the 

 corresponding heat changes. 



Incidentally, the " hydroxylation " theory, which the author's previous researches 

 has shown to be consistent with all the known chemical data concerning hydrocarbon 

 combustion, is also indirectly supported on the physical side by Prof. W. M. 

 THORNTON'S recent observations on the electrical ignition of the paraffin hydrocarbons in 



