176 



HYDROGEN ION CONCENTRATION 



correspondingly for the Cl-ions it is = 



osmotic work derived would then be 



V Ci 



— ^ RT In -. 



U + V C2 



U — V Ci 



—-— RT In -. 



U + V C2 



The total 



Since the 



amount of the maximal work to be derived depends only upon the 

 initial and final states of the system, regardless of the way or method 

 of procedure, as long as it functions reversibly, it follows that tt F = 



u — V _ Ci 



--— RT In -. 



U -f V C2 



By transposing F to the right side and bj^ making the numerical 

 transformations shown on page 162, we obtain: 



TT = ^ ~ ^ X 0.0001983 T log - volts 



U + V C2 



This formula agrees quite well with experimental findings. Thus 

 the difference between the migration velocities of the cation and anion 

 is very important in determining the value of tt. Table 25, taken 

 from Kohlrausch, gives the migration velocities of ions at 18 °C. 



TABLE 25 



TABLE 26 



