368 



NATURE 



[September 8, 192 ; 



some constitutional correspondence between CO and N, 

 molecules (the densities of which ere identical) whereby 

 the vibrational energy (radiation) emitted when the 

 one bums is of such a quality as can be readily absorbed 

 by the other, the two thus acting in resonance. The 

 radiant energy so absorbed during the explosion presum- 

 ably would not affect the maximum pressure attained, 

 except in so far as the conditions permitted of any 

 secondary oxidation of the " activated " 

 nitrogen to nitric oxide during the actual 

 combustion period ; but radiant energy so 

 absorbed would be liberated in a kinetic 

 form during the subsequent cooling period, 

 as the " activated " nitrogen slowly re- 

 verted to the ordinary form. Analyses of 

 the pressure-time records obtained have 

 entirely confirmed this supposition. 



The following graphs (Fig. 4) illustrate the strength 

 of the evidence obtained up to this point as to the 

 activation of the nitrogen during a carbon monoxide- 

 air explosion at high pressures. They show the rates 

 of cooling (expressed as pressure fall in atmospheres 

 per second) of the gaseous systems immediately after 

 the attainment of maximum pressure, when each of 

 the four mixtures, 2CO + O2 + 4N2, 2CO + O2 + 4O2, 

 2C04-02 + 4Ar, and 2H2 + O2 + 4N2, were exploded in 

 the bomb at an initial pressure of 50 atmospheres. 



the corresponding carbon monoxide-air mixture. Th) 

 circumstance, combined with the perfect normality « 

 the cooling in the case of the 2CO + 0, + 4Ar mixtur- 

 can scarcely be explained except on the .1 

 that the nitrogen functions differently in a 

 air explosion, where it acts as an inert dil 

 from what it does in a carbon monoxide-air 

 where in addition to its ordinary diluent 



Fig. 



Fig. 



-Rate of cooling .-ifter combustion of carbon monoxide using various diluents. 



It will be seen that, except in the case of the carbon 

 monoxide-air mixture, the cooling was perfectly regular, 

 and presented no abnormal features whatever. In the 

 case of the 2CO + 03-1-4X2 mixture, however, there was 

 no cooling at all during the o*i sec. after the attainment 

 of the maximum pressure ; and it was not until the 

 lapse of the o*6 sec. thereafter that anything like a 

 normal rate of cooling was established. Attention is 

 specially directed to the striking contrast between the 

 perfect normality of the first 0*6 sec. of the cooling 

 period in the case of the hydrogen-air (2H2 + 02-^4X2) 

 mixture, and its complete abnormality in the case of 



NO. 2810, VOL. I 12] 



Tims If Yi*» 

 5.— PrcMure-time record of carbon roonoxide-oxygen'explotUm. 



has a peculiar energy-" absorbing " effect, whereb 

 it becomes chemically "activated." On such a- 

 assumption the meaning of the 2CO + O2 + 4X2 coolin 

 curve is that the radiant energ>' which had been absorbt ■ 

 by the N2 molecule during the previous combustioi, 

 period was being slowly evolved in a kinetic form far 

 into the subsequent cooling period, the "activated " 

 nitrogen not having entirely reverted to its normal 

 condition until at least o"6 sec. after the end of the 

 combustion period. 



Experiments with some Isotherm i 

 Mixtures. 



Much confirmator>' evidence of the 

 radiant energy-absorbing function and 

 consequent "activation " of nitrogen in 

 the combustion of carbon monoxide at 

 high initial pressures has been obtained 

 as the result of experiments in which 

 mixtures of carbon monoxide and ox\ - 

 gen in their combining proportion 

 diluted with successive molecular pr 

 portions (2, 4, or 6) of the four diluent- 

 argon, carbon monoxide, oxygen, or 

 nitrogen, were fired at such initial pres- 

 sures as would always result in the 

 liberation of the same total energv 

 (about 10 K.C.U.) during the subsi 

 quent explosion. For details of the.- 

 experiments the reader is referred to 

 the memoir recently published in con- 

 junction with my co-workers (D. M. 

 Xewitt and D. T. A. Townend) in the 

 Proceedings of the Royal Society, A. 

 103, pp. 205-232. There is, however, 

 a significant feature abou^ the 

 records (Fig. 5) obtained when an 

 mixture was fired in our bomb at 



pressure-time 

 undiluted 2C0-i-0_ 

 an initial pressure of 21*4 atmospheres, to which refer- 

 ence should here be made, because of its bearing on the 

 theory of CO-combustion. 



It will be seen that ihe maximum pressure (245 

 atmospheres) was developed in 0*005 sec, after which 

 the cooling period immediately set in ; the pressure 

 fall during the next 0*5 sec. being 66 atmospheres, or 

 about 27 per cent, of the maximum. It is evident 

 that an exceedingly high temperature was momentarily 

 attained in this experiment ; indeed, assuming that the 



