Change of Oxygen into Ozone. 205 



make the dissociation less rapid than the combination, and 

 thus both on account of diminution of volume and com- 

 bination N 2 /B increases, so that the collisions of 3 with 3 

 cease to occur at the destructive periodicity, and the special 

 cause of destruction or dissociation being removed, we have 

 now to do with a more ordinary case, where the dissociation 

 which takes place arises out of accidentally favourable col- 

 lisions of 3 with 3 or with 2 , and combination out of 

 accidentally favourable collisions of 2 with 2 ; now the 

 number of collisions per second of an 3 with an 3 is 



2 v 2 = 2 (N 2 /B) (a 2 + a 2 ) V(« 2 2 + * a 8 )*, 



where a 2 is radius and 3/c 2 /2 mean squared velocity of mole- 

 cule of 3 ; and the number of collisions per second of an O s 

 with an 2 is 



« = 2(N,/B) («! + a 2 )V(K, 2 + « 2 2 ) j ; 

 and as 



<? 2 3 = 2a 1 3 and te 1 2 /fc 2 2 = m 2 /m l = 2, 



the coefficients of N 2 /B and Nj/B in the two expressions are 

 nearly identical, and 2 v 2 + iV 2 is proportional to (Ng + N^/B; 

 but according to Bohr's discovery (Ng + NJ/B is constant 

 after the discontinuity occurs, so that it appears that on 

 diminishing volume after the discontinuity, combination and 

 dissociation are in equilibrium when the total number of 

 collisions of an 3 per second has a certain constant value. 

 Thus a periodicity in which the 2 molecules play as im- 

 portant a part as the 3 molecules gets established as the one 

 which the 3 molecules can just stand, and diminution of 

 volume goes on so as to keep (N 2 + JNi)/B constant. But 

 when the diminution of volume has gone a certain length 

 another discontinuity appears which leads into the region of 

 Bohr's equation (p + a)B = k, to which the same explanation 

 must apply as to his other equation, so that a new periodicity, 

 which is to the former one as a to a', suddenly appears 

 amongst the collisions of 3 with 3? as specially destructive 

 to the 3 molecules. 



But one consequence of our theory is that k ought to be 

 the same in the two equations of the form (p + a)B = k, 

 whereas Bohr's values make k! = 1'045&, because in the 

 theory k in both cases stands for (N/B)wv 2 /3 : accordingly 

 we must revert to Bohr's experimental data to ascertain 

 whether k is necessarily different from k'. These are 

 arranged in two series, the first at 14° C, and the second at 

 11°*5, Bohr giving the preference for reliability to the first ; 

 but if we plot them both with B as abscissa and pB as 



