Application of Quantum Theory to Chemical Reaction 



s. 



31 



"the rate of absorption o£ radiation would be necessary. 

 Possibly some physicist, better qualified than the writer to 

 deal with the fundamental basis of the quantum theory, 

 might interest himself in this problem, a problem of very 

 great chemical importance. 



In concluding, attention may be very briefly drawn to an 

 empirical expression already employed by the writer in 

 connexion with unimolecular reactions in gases, which seems 

 to account fairly well for the velocity constant in such 

 processes (cf. Lewis, loc. cit.). The expression is : 

 7 ms 2 1-6 X 10 59 _ hv!kT 



where p = c z /87rhn z v d (the definition of Planck), 



and u v has its usual significance. Applying this expression 

 to the case of the decomposition of phosphine at T=9-15, 

 taking v = 8 X 10 14 as before, it is found that 



£ calc. = 1-36 Xl0- 3 , 



whilst k obs. = 10-2 xlO- 3 . 



The observed value is about eight times the calculated. 

 The discrepancy is now small and might even be accounted 

 for by a relatively small change in the value taken for the 

 -characteristic frequency. Whether the above empirical 

 expression has any theoretical significance the writer is 

 unable to decide. 



Summary. 



1. On applying the quantum theory to a unimolecular 

 chemical reaction, it is shown that very different results are 

 obtained according as we assume the continuous or discon- 

 tinuous view of the absorption of radiation. 



2. On comparing the calculated with the observed velocity 

 •constant, it is shown that a very large discrepancy exists 

 between the two values, the discrepancy being much greater, 

 however, on the discontinuous view than it is upon the 

 continuous. 



3. The discrepancy referred to in (2) is always in the 

 sense that the observed velocity constant is many times 

 greater than the calculated. The discrepancy factor (on the 

 continuous view) is of the order 10", and appears to be of 

 the same order of magnitude for different reactions. It also 

 appears to be independent of the temperature. 



4 The explanation of this discrepancy would constitute 

 an exceedingly important contribution to the theory of 

 physico-chemical processes. 



Muspratt Laboratory, 



University of Liverpool. 



