CATALYSIS. 



55 



If the theoretical considerations upon which this formula is based 

 are correct, then the x values determined by the polariscope after various 

 times must give the same figure for k. This is indeed the case. 1 k is 

 called the velocity coefficient (also velocity constant or specific reaction 

 velocity). If in the equation (1) C x or the concentration of the still 



undecomposed cane-sugar =1, then the equation becomes -r- = k, from 



which it follows that A; indicates the reaction velocity if the concen- 

 tration of the substrate could be kept the entire time at=l. 



In these experiments k retains the same value. If in different 

 experiments the quantity of catalyst (acid) varies, then the obtained 

 value for k is proportional to the concentration of the H ions. This 

 is so prominent that the catalytic action of acids is due to the H ions 

 (ARRHENIUS 2 ) . Still irregularities occur as the anions of acids as well as 

 of salts present can under certain circumstances influence the action 

 of H ions (see page 73). 



FRANKEL 3 has recently studied the decomposition of diazoacetic ether 

 under the influence of different acids. The reaction is as follows : 



N 2 : HC.CO.O.C 2 H 3 + H 2 O = HO.CH 2 .CO.O.C 2 H 5 4- N 2 . 



The progress of the reaction can be determined by measuring the nitrogen 

 set free. The following figures explain the results: 



Jtr 



As -^ for the different acids and different quantities of acid is the same, then 

 the velocity coefficient is here also proportional to the concentration of the H ions. 



As the catalytic action of acids is caused by the H ions, so are the 

 catalytic properties of bases due to the OH ions. The first determined 

 case of this kind was the transformation of hyoscyamine into the stable 

 at ro pine. 4 



1 See Poggend. Ann., 81, 413 and 499, 1850. 



2 Zeitschr. f. physik. Chem., 4, 226, 1889. 



3 Ibid., 60, 202, 1907. 



4 Ber. d. d. chem. Gesellsch., 21, 2777, 1888. 



