242 Conductivity of Aqueous Solutions. Part XII. 



trie constant. The above ratio is evidently equivalent, since C 2 y 2 = C x y 1} 

 to the ratio 4- , , , where, however, y 1 and y., refer to the slightly 



different concentrations C x and C 2 (C 2 being equal to C 1 y 1 /y 2 ). 



Now for the four uni-univalent salts given in table 141 the mean values 

 of the percentage ionization at 0.08 normal is 84.4 at 18 and 80.9 at 100, 

 or by interpolation, 80.6 at 100 at 0.08 X 1.042 normal (that is, at 

 C-fl^/y?) ; whence the value of the ratio just referred to is found to be 1.30. 

 The value of the corresponding ratio for the two tri-ionic salts at 0.08 nor- 

 mal is in the same way found to be 1.38.* While the former of these 

 values differs considerably from the ratio (1.40) of the dielectric constants, 

 yet all the values lie in the same neighborhood. Indeed, the agreement is 

 as close as could be expected considering the character of the data involved. 



Finally, even though it seems theoretically to correspond to a less com- 

 parable condition in the solution, yet, in view of the valence principle dis- 

 cussed just below, it is of interest to note the values of the simpler ratio, 



-^7 {, of the concentrations of the un-ionized substance at two tem- 



^(1 yj 



peratures at the same total concentration, instead of the same ion-concen- 

 tration. At 0.08 the value of this ratio for 100/18 is 1.22 for the four 

 uni-univalent, and 1.21 for the two uni-bivalent salts, thus considerably 

 less than the ratio of the dielectric-constants. 



The degree of ionization of the different substances may be next con- 

 sidered in relation to the ionic type to which they belong and to their chem- 

 ical nature. It has already been pointed out that even up to the highest 

 temperatures neutral salts of the same ionic type have roughly the same 

 percentage ionization, the differences not exceeding 8 per cent in any case 

 investigated. The strong acids, hydrochloric acid and (up to 156) nitric 

 acid, and the strong bases, sodium and barium hydroxides, also conform in 

 a general way to this principle, though their ionization seems to be several 

 per cent greater than that of the corresponding salts ; it is worthy of men- 

 tion, however, that this greater value may be due to an increase in the 

 equivalent conductance of the hydrogen-ion or hydroxide-ion with the 

 concentration of the solute, as is indicated to be the case by the transfer- 

 ence results with these acids presented in Part XI and again referred to 

 below. 



It is also remarkable that the rough proportionality which had previ- 

 ously been shown to exist at ordinary temperaturesf between the un-ion- 



*The mean values of the percentage ionization for these two salts at 0.08 normal 

 are 71.7 at 18 and 65.8 at 100, or by interpolation 64.8 at 100 at 0.08 X 109 normal. 



fFor a discussion of this principle, see the author's article on The Physical Prop- 

 erties of Aqueous Salt Solutions...., loc. cit. 



