404 Mr Bevan, On the Temperature Effect in the combination 



And dividing the rates of combination obtained from the 

 smoothed curve we obtain for k the following values : 



The value of k, therefore, diminishes rapidly with rise of 

 temperature. If the action take place first between chlorine 

 molecules and aggregates of water molecules or with individual 

 water molecules in a special state, as seems probable from the 

 character of the induction period and from the fact that. damp 

 chlorine which has been illuminated combines more readily with 

 Hydrogen than unilluminated Chlorine, then k will depend on 

 the number of such aggregates or special molecules. And further, 

 the number of these special molecules or aggregates will depend 

 on the temperature of the water vapour. We have then to 

 consider the equilibrium condition of water vapour with regard 

 to the number of these special systems present. And as such 

 a state must evidently be a state of dynamical equilibrium, we 

 can apply thermodynamical results to find the variation in con- 

 centration of such molecules. Considering the case of molecules 

 in a special condition, their concentration, as far as pressure is 

 concerned, is proportional to the concentration of the ordinary 

 water molecules present. This is expressed in our values of 

 kp (c — p) by the factor p. 



k, therefore, must be assumed to be of the form KK' where K' 

 is the constant for the water molecules, and K is the velocity 

 constant for the action between the CI molecules and these special 

 molecules. The constant K' being an equilibrium constant is 

 subject to the thermodynamical relation 



dhgK _A' 

 dT T*' 



And for K the velocity constant we have the equation of 

 van 't Hoff, 



dlogK A" 

 dT T* ' 



d log KK A D 

 so that Jrm = 7 j f2 + ±>, 



d log k A n 

 or -—jm- =m, + B; 



dT T> 



log k _ A 

 dT~ ~T* 



