1891.] on the Bate of Explosions in Gases. 449 



9 



extra oxygen is inert in propagating the explosion-wave, then the 

 addition of this inert oxygen would diminish the rate of explosion : — 



Marsh Gas. Ethylene, Cyanogen. 



Calculated rate of explosion when burnt 1 q2 88 87 



to CO with inert oxygen present . . J 



The experiments show that if 100 be taken as the rate of explosion 

 when the oxygen is only sufficient to burn the carbon to carbonic 

 oxide, the following are the rates found when oxygen is added 

 sufficient to burn the carbon to carbonic acid: — 



Marsh Gas. Ethylene. Cyanogen. 



Bates found 94 92 84 



The results are, therefore, in favour of the view that, in the explosion 

 of these gases, the carbon is first burnt to carbonic oxide. 



But stronger evidence on this point is obtained by comparing the 

 explosion rate of these gases (1) when fired with oxygen sufficient to 

 burn the carbon in them to carbonic acid, and (2) when nitrogen is 

 substituted for the oxygen in excess of that required to burn the 

 carbon to carbonic oxide. We have seen that oxygen added to 

 electrolytic gas hinders the explosion more than nitrogen. In pre- 

 cisely the same way oxygen added to a mixture of equal volumes of 

 cyanogen and oxygen hinders the explosion more than the same 

 volume of nitrogen. The conclusion we must come to is that the 

 oxygen added to the mixture expressed by the formula C2 N2 -|- O2 is 

 as inert (so far as the propagation of the explosion- wave is concerned) 

 as oxygen added to the mixture expressed by the formula H2 + 0. 

 The same phenomena occur in the explosion of marsh gas, ethylene, 

 and acetylene. In all these cases the substitution of nitrogen for the 

 oxygen required to burn the carbon from carbonic oxide to carbonic 

 acid increases the velocity of the explosion. These facts seem only 

 consistent with the view that the carbon burns directly to carbonic 

 oxide, and the formation of carbonic acid is an after-occurrence. 



Finally, the rates of explosion of cyanogen and the hydro- 

 carbons, when their carbon is burnt to carbonic oxide, have been 

 found greater than the velocities calculated from Berthelot's formula. 

 This accords with the observation previously made that the rate of 

 explosion of electrolytic gas with excess either of hydrogen or 

 oxygen is far higher than the calculated rate. It would seem 

 probable that the theoretical rates as calculated by Berthelot should 

 be modified, in spite of the close agreement which his numbers show. 

 I think the low rates found, when hydrogen, marsh gas, cyanogen, 

 &c., are exploded with equivalent proportions of oxygen, depend 

 partly on the carbon burning to carbonic oxide and partly on the 

 dissociation of the steam at the high temperature. If the formula is 

 modified in these respects, velocities can be calculated which agree 

 with the experimental results where dissociation does not occur. 



