September 8, 1923] 



NA TURE 



367 



data which must be established in such experiments are 

 the following : 



P,- =the initial pressure in atmospheres at which 

 each mixture is fired. 



P„, = the maximum pressure in atmospheres re- 

 corded in the explosion. 



t^n =the time in seconds required for the attain- 

 ment of the maximum pressure after 

 ignition. 



2 =the thermal equivalent in K.C.U. of the 

 energy liberated during the explosion. 



Also the percentage amount by which P,„ falls 

 during (say) 0*5 sec. after /,„. 



1+00 



«0 



These and other similar results led very decidedly 

 to the conclusion that the nitrogen pre- 

 sent in the normal carbon monoxide-air 

 mixture had been exerting a specific in- 

 fluence on the whole course of events, 

 ^ivhich was manifested in a three-fold 

 feet upon the pressure curves — namely, 

 j) a marked retardation of the rate of 

 ttainment of maximum pressure, (2) a 

 )wering of the maximum pressure, and 

 j) a considerable retardation of the sub- 

 Bquent cooling. For whenever such 

 itrogen was wholly replaced by its 

 lolecular equivalent of any one of the 

 |ther three gases, the development of 

 pressure became nearly as rapid as in the 

 explosion of a normal hydrogen-air mix- 

 ture under like conditions. Moreover, 

 comparative analyses of the pressure-time 

 records obtained during the experiments 

 in question have shown that, when nitro- 

 gen was present, much less kinetic (pres- 

 sure) energy was absorbed up to the 

 attainment of maximum pressure than 

 was subsequently liberated during the 

 cooling period. This remarkable circum- 

 stance shows that a considerable part of 

 the radiation emitted by the burning car- 

 bon monoxide (which otherwise would 

 have been absorbed by the walls of the 

 explosion vessel) was intercepted by the 

 nitrogen present. Part of the nitrogen so 

 irradiated would then, in favourable cir- 

 cumstances, be oxidised to nitric oxide, 

 thereby absorbing part of the kinetic 

 energy developed by the explosion and 

 consequently reducing the maximum pressure at- 

 tained. Finally, the radiant energy so absorbed 

 by the nitrogen, plus part of the kinetic energy 

 (if any) absorbed in forming nitric oxide during the 

 combustion, was liberated as kinetic energy during 

 the cooling period, .so delaying the cooling. Thus it 

 was manifest that under our experimental conditions 

 nitro-cn li;i-, the luiwcr (if iihsdrhiiiL'' pnrt of tlic radiant 



NO. 2810, VOL. 112] 



energy developed by the combustion of carbon mon- 

 oxide, and of slowly giving it out again in a kinetic 

 form during the subsequent cooling period. In other 

 words, nitrogen is not inert, but acts as an " energy 

 absorbing " spring in such explosions. Indeed the 

 results set forth in the foregoing table can scarcely be 

 explained on any other supposition. 



Another important conclusion arising out of these 

 experiments is that when nitrogen so absorbs radiant 

 energy developed during a carbon monoxide-air 

 (2CO + O2 + 4N2) explosion under such conditions, it 

 becomes chemically " activated," and capable of com- 

 bining much more readily with oxygen than does 

 nitrogen which has merely been raised to a corre- 

 spondingly high temperature in a similar hydrogen-air 

 (2H2 + O2 + 4N2) explosion. Indeed, when the bomb 

 was rinsed out with distilled water after one of our 

 hydrogen-air explosions at an initial pressure of 50 

 atmospheres, no more than a faint trace of nitric acid 

 could be detected on applying the diphenylamine test 

 to the washings ; whereas, in the case of the cor- 

 responding carbon monoxide-air explosions, a similar 



Tina m /'«» SecOHOi 



TihE m '/loo SectNOt 



Tine IN yioe SECOMOi 



Fi<;, 



TIME /U '/'OO SecOMOi 

 Pressure-time records for the combustion of carbon monoxide using differciit diluents. 



test always showed a considerable formation of nitric 

 acid. 



It would seem as though the nitrogen molecule is 

 able to absorb the particular quality of radiation 

 emitted as the result of the interactions of CO and 

 : during a carbon monoxide-air explosion, which is 

 different from that emitted during a hydrogen-air 

 explosion. In other words, it seems as though there is 



