Section 56. I onization-values. 



141 



somewhat decreases. Hydrochloric acid, on the contrary, exhibits a con- 

 stantly decreasing temperature-coefficient.* 



It is also worthy of note that the migration velocities of the ions of 

 these three substances differ by a less percentage amount the higher the 

 temperature. Thus the ratio of the equivalent conductance of sodium ace- 

 tate and of hydrochloric acid at zero concentration to that of potassium 

 chloride has the following values at the various temperatures : 



18 100 156 218 



NaC2Hs02 : KC1 0.60 0.69 0.72 0.80 



HC1 : KC1 2.91 2.05 1.73 1.53 



The effect of temperature on the conductivity at the higher concentra- 

 tions does not require special discussion, since the phenomenon is better 

 analyzed through the consideration, presented in the following section, of 

 the relation of ionization to temperature. It is, however, of some interest 

 to note that acetic acid, owing to the decrease in its ionization overcom- 

 pensating the increase in the migration velocity of its ions, has a maxi- 

 mum value of the equivalent conductance at some temperature between 

 18 and 156. 



56. ION1ZATION-VALUES AND THEIR CHANGE WITH THE 

 CONCENTRATION AND TEMPERATURE. 



Table 41 shows the percentage degree of ionization of the various sub- 

 stances. These values were obtained merely by dividing the conductances 

 at the different concentrations by the conductance at zero concentration, 

 all of which are given in table 36. The values corrected for hydrolysis 

 were used in the case of sodium acetate, and those corrected for the con- 

 ductance of the water in the case of acetic acid. 



Table 41. Percentage ionization. 



*Its value for the interval 10-30 is 6.30 (computed from the data of Noyes and 

 Sammet [Ztschr. phys. Chem., 43, 70, 1903] and our value of A at 18). 



