152 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



owing to the possible hydrolysis of the salt, as well as to certain reactions 

 which appear to take place in the solutions at the higher temperatures. 11 

 The ionization of hydrochloric and nitric acids falls off much more 

 rapidly than does that of the salts and that of nitric acid falls off more 

 rapidly than that of hydrochloric acid, as may be seen from Table LIV. 

 At 0.08 normal and 306, the ionization of nitric acid is only about one 

 half that of hydrochloric acid. At that temperature .the ionization of 

 hydrochloric acid is approximately the same as that of the typical binary 

 salts, such as potassium and sodium chlorides. The ionization of weak 

 electrolytes, such as ammonium hydroxide and acetic acid, falls off much 

 more rapidly than does that of the strong electrolytes. Correspondingly, 

 at a given concentration, the maximum in the conductance-temperature 

 curves occurs at lower temperatures in the case of weak acids and bases. 

 For acetic acid this maximum lies in the neighborhood of 100. 



The ionization of salts of higher type, as well as that of the more 

 complex acids and bases, such as sulphuric acid and barium hydroxide, 

 falls off very markedly with the temperature, and the decrease is as a 

 rule the greater the higher the type of the salt. This is well illustrated 

 in the case of magnesium sulphate, whose ionization at 0.08 normal and 

 218 is only 7 per cent. Corresponding to this rapid decrease in the 

 ionization of the more complex salts at the higher temperatures, the 

 maximum in the conductance curves lies at relatively low temperatures. 



As the temperature rises, the dielectric constant of water decreases 

 and we should expect the properties of aqueous solutions to approach 

 those of non-aqueous solutions. This is indeed the case. At higher tem- 

 peratures, the ionization values for different electrolytes approach those 

 of the same type of electrolytes in solvents of lower dielectric constants. 

 The low ionization values of the salts of higher type correspond with 

 the relatively low values of the ionization of the same type of salts in 

 nearly all non-aqueous solvents. At 306, many of the properties of 

 electrolytic aqueous solutions, which differentiate these solutions from 

 similar solutions in non-aqueous solvents, have in large measure dis- 

 appeared. So, for example, the great difference in the conductance 

 values of the different ions has almost completely disappeared at 306. 

 Similarly the abnormally high ionization values of hydrochloric and 

 nitric acids, as well as of the strong bases, have disappeared at this 

 temperature. And, finally, the ionization function, for the binary elec- 

 trolytes at any rate, approaches values not very different from those of 

 solutions in many non-aqueous solvents. 



It is evident that, since the ionization decreases with the temperature, 



u Noyes, loc. cit., p. 94. 



