392 EXPLOSIVE GASES AND DETONATING GASEOUS MIXTURES. 



atm. 



8-2 



7-4 



9-5 



7.7 



8-0 

 15-6 



11. Mixture of detonating gases with an inert gas. 



H 2 + + N 2 

 H 2 + + N 4 

 H 2 + N 2 + N 2 

 CO + + N 2 

 CO + + N 

 CN + 2 + N 



From these various measurements very important results 

 may be deduced for the theoretical study of the temperatures 

 of combustion, specific heat and dissociation ; but this discussion 

 would lead us too far, and it suffices to cite the above-mentioned 

 figures as terms of comparison. 



12. The temperature may be lowered to a limit at which the 

 inflammation ceases to propagate itself, and this limit is interest- 

 ing, since it is the same as that which commences to produce 

 the inflammation of the mixture in an adverse sense. 



We have here two distinct notions to define : the composition 

 limit, 1 and the temperature limit. 



13. Composition limit of inflammability. An explosive gaseous 

 mixture ceases to burn when the relative proportion of one 

 of its components falls below a certain proportion. For instance, 

 3 vols. of electrolytic gas, formed by 1 vol. of oxygen and 2 vols. 

 of hydrogen, cease to ignite when mixed with 27 vols. of oxygen 

 or with 24 vols. of hydrogen. 



A similar volume of water vapour, above 100, also prevents 

 ignition. It is the same at the ordinary temperature with 

 18 vols. of nitrogen, 12 vols. of carbonic oxide, 9 vols. of 

 carbonic acid, 6 vols. of ammonia gas, hydrochloric acid or 

 sulphurous acid, etc. 



Three vols. of gas, formed by 1 vol. of oxygen and 2 vols. of 

 carbonic oxide, ceases to ignite when mixed with 10 vols. of 

 carbonic oxide or 29 vols. of oxygen. 



The mixture of methane with air only gives rise to an exact 

 combustion when it is formed by 9*5 vols. of air for 1 vol. of 

 methane. It ceases to burn where the proportion of air exceeds 

 17 vols. to 20 vols. These are very important data, owing to 

 the presence of fire-damp in mines. 



The combustion is incomplete near the limits of inflamma- 

 bility. 



These limits, however, vary considerably according to the 

 process of inflammation, and, above all, with the temperature 

 and mass of the body in ignition, which serves to produce the 

 combustion. 



They also vary according to the nature of the electric spark, 

 when the latter is employed to produce ignition, the spark pro- 

 duced with the aid of a condenser being much more efficacious 



1 See " Essai de M<?canique Chimique," torn. ii. pp. 73 et 343. 



