1893-94.] 
Dr Walker on Hydrolysis. 
255 
Hydrolysis in Some Aqueous Salt Solutions. By James 
Walker, D.Sc., Ph.D. 
(Read May 28, 1894.) 
Some years ago, in an investigation on the affinity of organic 
bases,* I was led to study the amount of decomposition suffered by 
various salts when dissolved in water, for a knowledge of this 
amount gives us a method of comparing the relative strengths of 
weak bases. When these bases are made to unite with a given 
acid, the extent to which the resulting salts are decomposed, in 
equivalent aqueous solutions, into acid and base, depends directly 
on the strength of the various bases. The same process of decom- 
position by water, or hydrolysis, can also be made use of to deter- 
mine the strengths of weak acids, and experiments in this direction 
have been executed by Lellmann and his pupils, f and by Shields.! 
As the amount of free acid or free base in a hydrolysed solution 
cannot he determined directly by neutralisation, on account of the 
progressive disturbance of the chemical equilibrium involved in the 
process, it must he determined by taking advantage of some pro- 
perty of the acid or base which is susceptible of accurate measure- 
ment, and does not destroy the chemical equilibrium, or else does 
so in a manner amenable to calculation. 
The properties I employed were the electrolytic conductivity of 
the solutions and the catalysis of methyl acetate effected by the acid, 
the speed of this reaction giving a measure of the free acid present. 
Lellmann, working in aqueo-alcoholic solution, used a colorimetric 
method, and Shields has employed the saponification of ethyl 
acetate by the free alkali. In the present paper I communicate the 
results of a few experiments by Shields' method, made with solu- 
tions regarding whose constitution there was some doubt. 
Solutions of Alhaline Sulphides. 
We very often find it stated in text-books and elsewhere that 
sodium and potassium hydrosulphides, when mixed in equivalent 
* Zeitschrift filr pJiysiTcalisdie Chemie, iv. p. 319. 
t Liebig’s Annalen, cclx. p. 262 ; cclxxiv. p. 121. 
t Zeit. physikal. Chem., xii. p. 167 ; also Phil. Mag. [5] xxxv. p. 365. 
