485 
does iiot change appreciabij in presence of the strong negative 
eatalyst hydroqninone. 
cl. The phenomenon of , negative cataljsis is verj cominon in 
oxidation reactions. IjUther’s view whicli emphasises that negative 
catalysis cannot take place in a reaction which is entirelj’ free froni 
positive cataljsts, is not substantiated by experirnental evidence. 
e. The oi'ganic siibstances act as negative cataljsts bj diminishing 
the concentration of the sulpliite ion, which is the active agent in 
this oxidation; the diminution in concentration of sulpliite ion is 
cansed bj the formation of a stable complex of the snlfite and the 
organic substance; this complex is not oxidized as readilj as the 
sulpliite ion. 
c. CataJytic activity of the unclis.sociated acid. 
In recent jears the question of acid cataljsis bas entered into a 
new period; and as a result of the accnmulation of new observati- 
ons and of increased exactitude in the measurement of the velocitj 
of reactions, evidence has been obtained in support of the view that 
the cataljsing power of an acid is not entirelj dne to the hjdrogen 
ion, but that the undissociated acid also contributes to the observed effect. 
This investigation had tbr its object the determination of the 
function of the undissociated parts of oxalic and picric acids in the 
hjdroljsis of methjl acetate. 
The experiments were all conducted at 45°. Drj pure potassium 
oxalate and sodium picrate were added in different quantities to 
dirninish the ionisation of the respective acids. The former salt was 
crjstallised from Merck’s pure sample, and the latter was prepared 
frora pure materials and pnrified bj repeated crjstallisations. 
The following summarj of results is obtained 
Oxalic acid. 
Conc. of acid. 
Conc. of K 2 C 2 O 4 
Acid Conc. 
K, 
Salt. Conc. 
•05 N 
— 
— 
0-00091 
W 
•0038 N 
13-16 
0-00065 
•0114 N 
4-38 
0-00044 
•0174 N 
2-37 
000042 
•0278 N 
1-79 
0-00038 
•0590 N 
1-02 
0-0001 1 
b The experiments described here were finished in 1913. 
