486 
Picric acid. 
Conc. of acid. 
Conc. of 
Sodiurn picrate. 
Acid Conc. 
Salt. Conc. 
K, 
•03 N 
— 
0-00135 
0-0031 N 
9-67 
0-00139 
„ 
0-0050 N 
6.00 
0.00141 
0-0513 N 
0-58 
0-00173 
0-0778 N 
0-38 
0-00160 
» 
0-1161 N 
0-25 
0-00153 
0-1597 N 
0-18 
0.00134 
0-3066 N 
0-09 
0-00122 
!l vvili be evident trom Ibe tbregoing tables lliat the velocitj 
coeffieients do not deerease proportionallj witli the decrease in the 
(‘oncentration of tlie hydrogen ions. In the case of oxalic acid tl)e 
velocily coefficietits fall off with the concentration of potassiuin 
oxalate ; whilst in the case of picric acid the addition of sodiuin 
picrate prodnces at tirst an increase in tlie velocity coëfficiënt and 
then when tlie concentration of sodiurn picrate reaches the value of 
0-159 N, the velocity coeffieients begin to fall off. This is explicable 
on the assnmption ihat even iindissociated acids are catalytically 
active in the hydrolysis of esters. Bnt in view of' the work of 
Wai.dkn (Jour. Amer. Cheni. Soc. 1912, 35, 1649) on the measni-e- 
inent of the di-electric constants of Solutions, a different interpretation 
of these results is possible. W ai, den has shown with non-aqueons 
Solutions thal the di-electric constant and the ionising power of a 
solvent are enonnonsly increased when electrolyts ai-e dissolved in 
it. Natiirally the degree of ionisation of the dissolved acid and along 
ivith it the concentration of hydrogen ions are also increased. Thus 
by the addition of salts of the same acids, there are two effecis: 
1. The diminution of hydrogen ions dne to the increase of the 
connnon negative ion. 
2. The increase in the concentration of the hydrogen ions dne to 
the greater ionisation of the acid cansed by the increase in the 
di-electric constant of the solvent. 
it is evident that these two etïects counteract each other. 
In the case of potassium oxalate the first effect preponderates 
over the second and hence the xelocity coëfficiënt falls otf with the 
concenti-atioii of potassium oxalate, whilst in the case of [licric acid 
