Chemistry. — ''The Influence of a Catali/st on the IVierm adynamic 

 Quantities Regulating the Velocity of a Reaction.''' Bj E. van 

 Thiel. (Communicated by Prof. J. Böeseken.) 



(Communicated at the meeting of May 27, 1922). 



According to GufiDBERG and Waage's hypothesis the velocity of 

 reaction in a homogeneous system of constant temperature is equal 

 to the product of the active masses of the converted substances 

 multiplied by the velocity constant. This constant is, of course, 

 variable with the temperature, and dependent on the nature of the 

 reacting molecules. The differential equations of G. and W. only 

 indicate the number of molecules decomposed in tiie time unit ; they 

 do not indicate precisely how the reaction(s) takes place; hence they 

 do not show either how the reaction constant depends on the 

 nature of the substances and on the temperature. 



Disregarding Nernst's formulation, in which the velocity of reac- 



chemical force n ^ -, ^ 



tion IS put = — , a formula that proved untenable, 



chem. resistance 



Goldschmidt's attempt ^) to give an explanation of the nature of the 



reaction constant may be called the first. Starting-point for these 



and following theories were especially two considerations referring 



to bi-molecular gas reactions : 



1. the reaction constant (velocity for concentration = 1) is doubled 

 about per 10° of increase of temperature, so long as the obsei-vations 

 are not too far from room temperature. The number of collisions 

 of the molecules is proportional to the translatory velocity, hence 

 proportional to l/J". The increase of this kinetic energy can, there- 

 fore, contribute to a maximum of 2"/^ to the increase of the velocity 

 of the reaction found. Hence a deeper insight into the nature of 

 the reaction than is given by G. and W.'s theoi'y is necessary. 



2. if all the molecules of the decomposed gas were in the same 

 state, every collision would be followed by a reaction. Every reaction 

 would then take place with the same explosive velocity. This not 

 being the case, all molecules are not equally reactive. A fraction of 

 them is in a more favourable condition. It is, therefore, possible 

 that the velocity of reaction is proportional to the number of these 



') Diss. Breslau, 1907. Cf. also Todd and Owen, Phil. Mag. 37, 224. 



13 

 Proceedings Royal Acad. Amsterdam. Vol. XXV- 



