305 
does not change appreciably in presence of the strong negative 
catalyst hydroquinone. 
d. The phenomenon of negative catalysis is very common in 
oxidation reactions. LutuEr’s view which emphasises that negative 
catalysis cannot take place in a reaction which is entirely free from 
positive catalysts, is not substantiated by experimental evidence. 
e. The organic substances act as negative catalysts by diminishing 
the concentration of the sulphite ion, which is the active agent in 
this oxidation; the diminution in concentration of sulphite ion is 
caused by the formation of a stable complex of the sulfite and the 
organic substance; this complex is not oxidized as readily as the 
sulphite ion. 
c. Catalytic activity of the undissociated acid. 
In recent years the question of acid catalysis has entered into a 
new period; and as a result of the accumulation of new observa- 
tions and of increased exactitude in the measurement of the velocity 
of reactions, evidence has been obtained in support of the view that 
the catalysing power of an acid is not entirely due to the hydrogen 
ion, but that the undissociated acid also contributes to the observed effect. 
This investigation had for its object the determination of the 
function of the undissociated parts of oxalie and pierie acids in the 
hydrolysis of methyl acetate. 
The experiments were all conducted at 45°. Dry pure potassium 
oxalate and sodium picrate were added in different quantities to 
diminish the ionisation of the respective acids. The former salt was 
crystallised from Merck’s pure sample, and the latter was prepared 
from pure materials and purified by repeated crystallisations. 
The following summary of results is obtained *) 
Oxalic acid. 
Conc. of acid. | Conc. of KgC,0, ao K, 
05 N | ~- - 0:00091 
5 ‘0038 N 13°16 0:00065 
5 ‘0114 N 4:38 0:00044 
i ‘0174 N 2-37 0:00042 
” ‘0278 N 1:79 0:00038 
ï 0590 N | 1°02 0:00011 
1) The experiments described here were finished in 1913. 
