200 



favoured inoleciiles. Whether il is necessary for the reaction that 

 tivo active molecules collide, or whether it is sufticient when one o^ 

 them is active, must for the present remain an open question. 



Goi.DSCHMiDT assumed that the velocity of reaction is about pro- 

 portional to the number of molecules the translatory velocity of 

 which exceeds a definite minimum value. Only these molecules, the 

 number of which is given by Maxwell's law of partition, would 

 be active. This restriction to the velocity of translation, is however, 

 entirely unfounded ; it is on the other hand more j)rol)al)le that 

 also the intermolecular and interatomic energies play a part in the 

 reaction, it is, therefore, more plausible to assume a threshold value 

 also for these energies. 



Krijger's theory is of a more exact character; it has, however, 

 only been elaborated for the simplest cases, as e. g. the dissociation 

 Is ^21, in which the reacting substances are already in atomic 

 (active) condition. Trautz gave a more general theory of" velocities 

 of reaction. Starling fiom van 't Hoff's reaction-isochore : 



— r;=r = — — 71-, he substituted for /i r= — and tor 

 dT RT' K 



T 1 



Q=Q, + ^ V, fc', dT - :ErA c"v dT. 







He further assumed that k^ resp. k^ depends only on the proper- 

 ties of the initial resp. resulting substances, and therefore split the 

 reaction isochore into two parts, each referring to this. For this it 

 must also be [)0ssible to split Q^ rationally, for which purpose T. 

 introduces the conception intermediate suhstmices (which have an 

 exceediiigly short period of existence). In the case of the splitting 

 up of 2H1 ^ H, -}- 1, these intermediate substances might be H- and 

 1-atoms. For the decomposition of HI into H- and I-atoms a disso- 

 ciation energy is again required, in the formation of H, and 1^ from 

 these atoms a heat Q^ is liberated. It is clear that Q, = Q, — Q,- 

 Now all the obstacles to the splitting up of the reaction isochore 

 were removed, and the following equation resulted: 



T 

 d In k^ Qj 



dT RT 







- ^ 1', 1 Cv '^^/rT"- 



By integration and further elaboration Trautz obtained a formula 

 which in approximation could be reduced to a considerably simpler 

 form, and from which some important conclusions may be drawn : 



