34& 



Conductivity of Aqueous Solutions. Part XII. 



ion in pure water in equivalents per liter. (The value for ammonium 

 acetate at 18 is not based on direct measurements, but is calculated from 

 the results of Kanolt with the ammonium salt of diketotetrahydrothiazole.) 



Table 144. Hydrolysis of ammonium acetate and ionization of water. 



It will be seen that the hydrogen-ion concentration in pure water 

 increases with extraordinary rapidity between and 100 ; namely, by 

 about 3 fold between and 25 and 7y 2 fold between 25 and 100. 

 Between the latter temperature and 218 the ionization increases more 

 slowly, afterwards passes through a maximum (which appears to lie 

 between 250 and 275), and finally decreases. When it is considered 

 that the ionization of weak acids and bases, as shown by the data for 

 ammonium hydroxide, acetic acid, and phosphoric acid, decreases rapidly 

 with rising temperature, and that this acts in the same direction in 

 increasing the hydrolysis of salts as does an increase in the ionization of 

 water, it will be evident that the tendency of salts to hydrolyze is enor- 

 mously greater at high temperatures, as is well illustrated by the values 

 given for ammonium acetate. 



The great increase in hydrolysis is also exemplified by the hydrolysis 

 values for sodium acetate and ammonium chloride in 0.01 normal solution 

 that can be calculated from the preceding data; these salts, which at 18 

 are 0.02 per cent hydrolyzed, are found to be 1.6 per cent at 218 and 

 3.4 to 1.1 per cent hydrolyzed at 306. 



The fact also deserves mention that the values of the concentration of 

 the hydrogen-ion in water at 0, 18, and 25 as derived from these 

 hydrolysis experiments are only 16 to 20 per cent lower than those obtained 

 directly by Kohlrausch and Heydweiller* from the conductance of their 

 purest water ; thus proving that the ionization-constant of water is at 

 any rate roughly the same when it is pure as when an ionized salt is 

 present in it at a concentration of 0.02 to 0.05 normal. 



*Z. phys. Chem., 14, 330 (1894). 



