VELOCITY OF REACTIONS 41 



is very nearly right till qt reaches the value 08, 

 when about 50 per cent of the end-value of A is 

 reached, as is seen in comparing the last two lines. 



We have here a typical example of two laws 

 of peptic digestion which have long been stated. 

 The second one, that at constant temperature A is 

 dependent only on the value of qt, is in perfect 

 agreement with the general laws of the velocity 

 of reaction. But the first one, which is represented 

 by Schutz's rule, before 50 per cent are transformed, 

 was regarded as absolutely incompatible with those 

 laws. It was said that the organic ferments behave 

 in quite a different manner from common catalytic 

 substances. 



In order to show that this assertion is not true 

 I investigated the case when ammonia acts upon 

 ethyl acetate in great excess. I found that the rule 

 of Schutz is valid also in this case until about 

 50 per cent of the ammonia is used up by the 

 formation of ammonium acetate. (See the fourth 

 column in the following table, which is calculated 

 according to Schutz's rule ; .r-obs. are the observed 

 values.) I had therefore found a case absolutely 

 analogous to that of peptic digestion. The cir- 

 cumstance which causes the deviation from the 

 common law of a monomolecular reaction is that 

 the quantity of OH-ions dissociated from the 

 ammonia is much diminished by the presence of 

 the ammonium acetate. In reality this quantity 

 is nearly inversely proportional to the quantity of 

 ammonium acetate formed, except for the first 



