396 EXPLOSIVE GASES AND DETONATING GASEOUS MIXTURES. 



The heating of the elements, excepting oxygen, consumes, 

 moreover, a portion of this work, and this limits the elevation of 

 the temperature and pressure, as has just been said. Moreover, 

 let us note that the storage of oxygen in its compounds is always 

 very costly. 



Hence it can scarcely be expected that economical engines 

 can be invented which will derive their motive power from solid 

 explosive substances, such as ordnance powder, as Papin once 

 imagined. Nevertheless, such machines, if they could be con- 

 trolled, would perhaps be applicable to special conditions, where 

 the reduction of the volume of the apparatus would be of 

 paramount consideration. 



19. From these facts and considerations it results that the 

 employment of gaseous mixtures appears more economical in 

 machines than that of other explosive mixtures, solid or liquid. 

 In fact, gas engines are based on the combustion of coal gas by 

 air. However, in this case, the combustible and the combustive 

 are introduced from without and the products are gradually 

 discharged, and this limits the volume of the apparatus. 



20. The gaseous mixtures we have under consideration have 

 been supposed to be produced under atmospheric pressure ; the 

 theoretical pressures which they then develop, being comprised 

 between 18 atm. and 51 atm., are far removed from the pressures 

 developed by most explosives, whether solid or liquid. The 

 effective pressures are even far less, since they do not exceed 

 20 atm. (p. 389), a result which differs from the opinions enter- 

 tained by most persons during the siege of Paris. 



21. It would be advantageous to compress gaseous explosive 

 mixtures beforehand, but the pressures developed would become 

 comparable to those of solid or liquid mixtures only by employ- 

 ing enormous compressions capable of reducing the initial 

 volume of the mixture to one-hundredth, or a still smaller 

 fraction, that is by bringing it to a density equal to that of solids 

 or liquids. Apart from the practical difficulties attending such 

 a compression, it would result in liquefying most of the hydro- 

 carbon gases without liquefying the oxygen at the same time, 

 which would destroy the homogeneity of the explosive mixture 

 and the possibility of its immediate ignition. 



4. MIXTURE OF LIQUEFIED GASES AND ANALOGOUS LIQUIDS. 



In this case certain advantages could be obtained by the 

 employment of nitrogen monoxide in the liquid state or of liquid 

 nitric peroxide, a compound which may be likened to a liquefied 

 gas owing to its great volatility. 



The oxides of chlorine, whose combustive properties would be 

 extremely valuable if they were not too dangerous to manipulate, 



