Application of Quantum Theory to Chemical Reactions. 2$ 

 At the temperature 945 abs. the exponential term 



e- A ^ T =4-37xlO- 18 , 

 so that finally 



&o=2'465 x 10" 22 x 64 x 10 2S x 4*37 x lO" 1 *, 



or ^ =6-9xl0- 10 . 



The value of k found by experiment =10'2 X 10~ 3 . 



The observed value is therefore 10 7 times the calculated 

 value. 



It may be mentioned that discrepancies of the same order 

 of m;ionitude are found in other cases, such as the dissociation 



tr> 



of iodine gas, but in these cases the value of k n used fo 



comparison was not directly observed, and consequently, for 

 the purposes of the present argument, less stress, could be 

 laid upon the discrepancy. 



In view of the above results it is necessary to try to 

 account for the experimental velocity constant on the 

 basis of the discontinuous view of absorption, that is, upon 

 the assumption that radiant energy exists in small units or 

 quanta, a view which appears to be indistinguishable from a 

 corpuscular one. Unfortunately, in making this attempt 

 numerical values have to be ascribed to certain quantities 

 about which there is necessarily a very large measure of 

 doubt. The chief of these is the dimensions to be ascribed 

 to the quantum itself. Since an electron is capable of 

 picking up a quantum in the act of absorption, I have 

 assumed that the quantum itself possesses dimensions of the 

 same order of magnitude as an electron, that is, the u radius 

 of a quantum " is 2 x 10~ 13 cm., corresponding to the value of 

 the radius of an electron recently given by Jeans (Trans. 

 Chem. !Soc. cxv. p. 866, 1919). As a matter of fact, the 

 final conclusion arrived at would not be altered by ascribing 

 to a quantum the dimensions of a molecule (10~ 8 cm.). 



When a quantum and a molecule collide with one another, 

 absorption is regarded as occurring and the molecule 

 decomposes. On this basis we treat the problem as we 

 would treat the collisions between molecules in a bimolecular 

 reaction. In the case of a molecular system the number of 

 collisions per second is given by the expression : 



it . er>cr 2 v / ^'i :J + w 2 2 N 1 N 2 , 



in which a l and a 2 are the molecular radii, k x and ?/ 2 the 

 root-mean-square velocities of the molecules of which there 

 are N x and N 2 present per unit volume. In the analogous 

 case we can let a l and N x refer to the molecules and cr 2 and 

 N 2 refer to the quanta. The velocity term becomes simply c } 



