I r elocity of Unimolecular Reactions. 465 



of 0*54: . 10 9 cm. per sec. for the phosphorus electron. Hence 

 the velocity coefficient will certainly not be less tha 



nan 



496{0'29.10 18 



..„«-£ 



= 0-67 . 10" 3 , 



or one-tenth of the observed rate. 

 The agreement is only fair. 

 If the energy of the quantum is electrical in its nature, the 



electrostatic energy of a quantum of diameter A, will be ^ 



\ 

 in a medium of unit S.I.O. This energy can be equated to 



the light energ} 



^ - - = hv = 



2 X "" "' " \ 

 or E 2 = 2hc. 



This relationship is dimension ally correct : [by adopting 

 with Gr. N. Lewis (Phys. Rev. iii. p. 101, 1914) as funda- 

 mental dimensions M mass and I an interval in space or time 

 we find E==M*F,A=MI, c has no dimensions in these units]. 

 In ordinary units, however, E assumes very large values. 

 G. N. Lewis has shown that 



ch = 900 e 2 (approx.), 



where e is the electron charge. The above hypothetical 

 charge would on the same basis be equal to 30 V 2e. The 

 energy can thus not be entirely electrostatic in its nature. 



Summary. 



The reaction velocitv of a unimolecular reaction is given 



dn _ _ 

 by the expression —~ = ve ^, where v the activating radiation 



frequency is identical with the time of molecular relaxation. 

 On the basis of the radiation theory light would appear 

 corpuscular, the size of a quantum being equal to a wave- 

 length of light. If its energy be due to an electrostatic 

 charge E, then W = 2hc. 



University of Illinois, 



Urbana, 111., U.S.A. 



April 24th, 1920. 



