Summary. 



339 



derived from them is not a true measure of the ionization. It has therefore 

 not seemed worth while to make a study of the applicability of these func- 

 tions to all the substances investigated. 



The equivalent conductance and ionization of the slightly ionized sub- 

 stances, acetic acid and ammonium hydroxide, on the other hand, changes 

 with the concentration at all temperatures even up to 306, in accordance 

 with the mass-action law. It is interesting to note that phosphoric acid, 

 an acid of moderate ionization (60 per cent at 18 and 29 per cent at 156 

 at 0.01 normal concentration), has intermediate values of n (1.8-1.9), 

 which, however, approach more nearly the theoretical value (2.0) than 

 the empirical one. 



In order to show the relations between degree of ionization, the charac- 

 ter of the substances, and the temperature, the percentage ionization of all 

 the substances investigated at the different temperatures in 0.08 and 0.01 

 normal solution is shown in table 141. The substances are arranged in the 

 order in which the ionization at 18 decreases. The values in the case of 

 sulphuric acid show the percentage of the total hydrogen which exists in 

 the form of hydrogen-ion, without reference to whether it arises through 

 the primary dissociation into H + and HS0 4 ~ or the secondary one into H + 

 and S0 4 = ; the values are only approximate ones based on an estimate of 

 the relative extent to which these two stages in the dissociation have taken 

 place, as described on page 267. The values for magnesium sulphate are 

 only rough approximations, owing to its being largely hydrolyzed. 



The ionization at 0.08 normal for all of the salts and for hydrochloric 

 and nitric acids is also shown graphically in figure 20. 



Fig. 20. Change of ionization with temperature. 



i-i ICO 



NaC 



c 

 o 



Ba(NCy 2 



c 

 o 



V 

 an 



c 



4> 

 O 



U 







20 40 60 80 100 



120 1*0 160 ISO 200 

 Temperature 



220 240 260 230 300 



