Action of Hydrated and Nonhydrated Salts on Saponification. 89 



The hydrocyanic acid would dissociate very slightly, while the potas- 

 sium hydroxide would be almost entirely dissociated, giving a large 



excess of OH ions, and therefore an alkaline reaction. The hydroxyl 

 ions, being in large numbers as compared with the hydroxyl ions from 

 the water, would vitiate the results. In the case of a salt of a weak 

 base we would find an acid reaction. 



The hydrolysis of salts can be calculated from the formula of 

 Arrhenius, 1 



(Salt) Kacid 



(Acid) X (Base) HKOH 



in which the salt, acid, and base represent the total concentrations, 

 ionized, and non-ionized, at the point of equilibrium; and the K's are 

 the ionization constants. Similar formulse were worked out by Walker 2 

 for a salt of a weak base and a strong acid, and by Arrhenius for a salt 

 of a weak acid and a weak base. 



Where the ionization constant can not be determined by conduc- 

 tivity measurements, other methods must be used. 



Shields 3 employed the saponification of ethyl acetate and showed 

 that with increasing dilution the hydrolysis increased. 



Ley 4 used the saponification of methyl acetate, the inversion of 

 cane sugar, and the conductivity methods; he found that these three 

 methods gave results which agreed very well with one another. These 

 being the most general methods, are the only ones that need to be 

 considered. 



Since the reaction of the saponification of an ester has been used to 

 measure the hydrolysis of salts such as potassium cyanide and aluminum 

 chloride, which react basic and acidic with indicators, it is of primary 

 importance that neutral salts be used. 



Salts which give no reaction with litmus, according to Salm, 5 have 



+ 

 a concentration of H or OH ions less than 0.000001, which is so small 



that it is practically negligible. 



We found that the salts of potassium, sodium, lithium, magnesium, 

 calcium, barium, and strontium, with chlorine, bromine, iodine and the 

 nitric and sulphuric acid anions, gave no reaction with litmus. The 

 acids have an ionization constant which is very nearly unity; and the 

 weakest of the bases has so large a constant that if substituted in 

 Walker's formula the hydrolysis would be negligible. 



Finally, Bruner 6 showed that the hydrolysis of solutions of the 

 chlorides of potassium, lithium, barium, strontium, calcium, and mag- 

 nesium was too small to be measured. He also pointed out that, in general, 

 chlorides were most hydrolyzed, then nitrates, and least of all sulphates. 



Therefore, in the solutions to be studied the effect due to hydrolysis 

 may be neglected. 



it. phys. Chem., 5, 16 (1890). Ubid., 12, 167 (1893). 6 /6id.,57,471 (1907). 



*Ibid., 4, 319 (1889). *Ibid., 30, 193 (1899). *Ibid., 32, 133 (1900). 



