September 8, 1923] 



NA TURE 



369 



" chemical contraction " involved in the passage from 

 2CO + O2 (3 vols.) to 2CO2 (2 vols.) was substantially 

 completed at the instant of maximum pressure, the 

 temperature at that instant would have been of the 

 order of 5000° C. In any case the experiment finally 

 disposes of the supposition that carbon monoxide is 

 inherently a " slow-burning " gas. Moreover, the whole 

 character of the pressure-time curve seems inconsistent 

 with the idea, which has sometimes been put forward, 

 that the maximum pressure attained on explosion is 

 materially affected by the dissociation of carbon 

 dioxide ; indeed, there was no sign of any " after 

 burning " or heat evolution after the maximum pres- 

 sure had been attained. 



Concluding Remarks. 



The energy of a gaseous system such as we have 

 considered is of course comprised partly of translational 

 motions of its molecules as a whole, and partly of 

 motions of some kind internal to these molecules. 

 The former causes pressure (temperature), but the latter 

 (which according to circumstances may be 

 partly rotational and partly vibrational) 

 produces no external physical effect other 

 than radiation, which originates in high- 

 frequency vibrations within the molecule. 



Now in each of our experiments a 

 definite amount of energy (thermally 

 equivalent to about 10 K.C.U.) was 

 liberated by the union of carbon mon- 

 oxide and oxygen in the bomb. Presum- 

 ably the greater part of this would appear 

 as increased kinetic energy of the products 

 as a whole {i.e. as pressure). The lesser part of the 

 energy liberated in such explosions would mani- 

 fest itself as " radiation " of wave-lengths char- 

 acteristic of burning carbon monoxide ; i.e. of 



of dissociated nitrogen atoms, and recombination to 

 form ordinary nitrogen caused the characteristic after- 

 glow.^ 



Another view of the " activation " of nitrogen has 

 been suggested which does not necessitate the complete 

 dissociation of nitrogen molecules. According to Lang- 

 muir's statical representation of atomic constitution, 

 there is a great similarity between the configuration 

 of carbon monoxide and nitrogen molecules in the 

 ordinary state, a circumstance to which he has directed 

 special attention. He considers that both molecules 

 are capable of existing in two forms, in one of which 

 (the ordinary and more inert form) the two positive 

 nuclei are both symmetrically located within one and 

 the same outermost shell of eight electrons, whereas 

 in the " active " form they are situated each within 

 one of two separate shells, which have four electrons 

 in common. According to this view not only would 

 the " activation " of each gas be brought about by 

 a reversible transformation from the one configura- 

 tion into the other, as is shown in Fig. 6, but also an 



INACTIVE 



ACTIVE 



Fig. 6. 



I.e. 01 m- 

 cipiently forming carbon dioxide molecules in a highly 

 vibrating state such as would result from CO and : 

 collisions. Now when nitrogen is present as a diluent 

 it is able to intercept part of the " radiation " whereby 

 it acquires energy of a vibrational kind, which may 

 be intense enough even to dissociate the two atoms of its 

 molecule, or in any case to " activate " it chemically. 

 Such an absorption of radiant energy presumably would 

 not affect the ratios P,„/P„ except in so far as any part 

 of the nitrogen primarily " activated " successfully 

 competed with the burning carbon monoxide for the 

 available oxygen, and thus became oxidised to nitric 

 oxide during the combustion period. Indeed further 

 experiments (now proceeding) have shown that such 

 nitrogen " activation " is materially influenced by the 

 initial pressure at which the explosive mixtures are 

 fired ; but this is an aspect of the matter which time 

 does not permit me to develop. 



There is of course nothing new in the idea of an 

 " active " form of nitrogen, for ten years ago the 

 lion. R. J. Strutt (now Lord Rayleigh) discoursed 

 upon it, and showed how ordinary nitrogen is chemi- 

 cally " activated " when subjected at low pressures 

 to a Lcydcn jar discharge, whereby it glows and 

 acquires the ])ower of combining with various sub- 

 stances towards whii li it is normally inert. Such 

 "active" nitroLicii was found to be strongly endo- 

 ' liermic, and Strutt favoured the view that it consists 



NO. 2810, VOL. I 12] 



Models illustrating the reversible transformation of active nitrogen or carbon 

 monoxide into the inactive form. 



inert nitrogen configuration should be capable of 

 being activated through resonance with a carbon mon- 

 oxide molecule of similar configuration undergoing 

 combustion.^ 



It is interesting now to recall the following passage 

 from one of Faraday's letters to Schonbein, which was 

 quoted by the present Lord Rayleigh, when lectur- 

 ing on " Active Nitrogen " ten years ago. " What 

 of nitrogen ? Is not its apparent quiet simplicity 

 of action all a sham ? Not a sham, indeed, but still 

 not the only state in which it can exist. If the com- 

 pounds which a body can form show something of the 

 state and powers it may have when isolated, then 

 what should nitrogen be in its separate state ? " 

 Perhaps the behaviour of nitrogen in our high- 

 pressure carbon monoxide-air explosions will help 

 in realising more fully the deep significance of 

 Faraday's words. 



In the earlier part of my discourse I directed atten- 

 tion to the peculiar influence of a small addition of 

 hydrogen to a carbon monoxide-air mixture under- 

 going combustion whether at atmospheric pressure or 

 when exploded at high pressures in the bomb. We 

 have also found that a similar small addition of 

 hydrogen to a normal carbon monoxide-air mixture 



♦ Proc. Roy. Inst., vol. xx. part 3 (1914), pp. 656-61. 



» It may be noted that support is given to the idea of a similarity between 

 the electronic configurations of nitrogen and carbon monoxide, and their 

 capability of acting in resonance during explosions at high pressures, by a 

 paper appearing in the Proceedings of the Physico-Mathematical Society 

 of Japan for April last (vide Nature, June 23, p. 859). For if the electronic 

 configurations of the two gases are similar, their band spectra should be 

 in close agreement ; and this is shown to be tlie case. The author, however, 

 remarks that the specific heat ratios of the two gases arc incompatible with 

 Langmuir's assumption of the two nuclei being in the same cube ; and he 

 suggests an alternative model, in which two cubes are joined at an edge. 



