203 



a reaction. Starting from this Scukpfek drew up a simple formula 

 which agrees with a formula derived at about the same time in an 

 entirely different way by Marcklin, viz. : 



w 



lnk= yB, 



in which E represents the difference of energy between the inter- 

 mediate state which is rich in energy, and the mean condition of 

 the reacting substances in the reaction, and 7? is a quantity which 

 does not contain constants dependent on the nature of the substances, 

 except the difference of entropy. This term takes the effective chance 

 of collision into account. It follows from the formula that increase 

 of the energy increment diminishes the velocity of reaction, increase 

 of the difference of entropy on the other hand increases it. In contra- 

 distinction with the formulae discussed before, a catalyst need not 

 necessarily decrease the energy increment; it is even possible that 

 as a result the enei-gy increment is increased, provided the increase 

 of factor B more than neutralizes this unfavourable action. The 

 increase of the energy increment means fewer active molecules, 

 increase of B is equivalent to a more favourable chance of collision. 

 It is, therefore, possible that the action of a catalyst would consist 

 in this that though the threshold of energy should be raised, the 

 number of favourable collisions has been so much increased that 

 the reaction nevertheless proceeds more rapidly. 



In the not catalysed reaction by no means every collision between 

 active molecules would eventuate in a reaction. This is a priori 

 sooner to be expected for complicated than for simple molecules; 

 instances are, therefore, especially to be found in organic chemistry. 



From increase of the energy-increment ensues increase of the 

 temperature coefficient, hence the catalysed reaction can have a 

 greater temperature coefficient than the not catalysed reaction. 

 Entirely in contradiction loith Trautz's and Lewis's conclusions the 

 catalysed reaction can have a temp. coef. and an energy incremen* 

 which are greater than those of tlie same reaction luithout catalyst. 



Measurements of the velocity of one and the same reaction between 

 complicated molecules with and without catalyst and at different tempe- 

 ratures might give a decision in favour of Scheffer's theory, if a 

 reaction could be found which, catalysed, presented a greater tem- 

 perature coefficient than not catalysed. As will be seen in what 

 follows, this appeared to be the case in the acetylation of diphe- 

 nylamin. 



The reaction was carried out at 0°, 20°, 30°, 40^ and 50° C. 



