266 



Conductivity of Aqueous Solutions. Part VIIL 



between 218 and 260 with 0.08 normal hydrochloric acid. Sulphuric 

 acid shows a very different variation of the conductance with the tempera- 

 ture at different concentrations. This is best seen by reference to 

 figure 18, on which the values for 0.08 normal hydrochloric and nitric 

 acids are also plotted. The most striking feature of this plot is that the 

 conductance values for the most concentrated and the most dilute sul- 

 phuric acid at first diverge rapidly with rising temperature (up to about 



1000 



900 



800 



700 



s 

 -o 

 c 

 o 



~3 



> 

 '3 



cr 

 U] 



600 



500 



400 



3,00 



200 



Temperature 

 Fig. 18. 



100), then approach each other (most closely at 218), and finally again 

 diverge. This behavior can be satisfactorily accounted for by assuming 

 that the dissociation of this acid takes place in two stages according to 

 the reactions : 



H 2 S0 4 = H + + HS0 4 - and HS0 4 " = H + -f- S0 4 = 

 and that the extent to which these two reactions occur is very different 

 at the different temperatures. This matter will be discussed in the fol- 

 lowing section. 



