DISSOCIATION IN NON-AQUEOUS SOLUTIONS 149 



is very much more difficult when appUed to hpoids. This is because 

 the conductivity of the hpoids themselves is so extraordinarily small, 

 and electrolytes dissolved in them are so poorly dissociated that the 

 total conductivity in all such cases remains very small. Besides, 

 it is generally quite impossible to obtain the value of Aa, by extra- 

 polation. The other method which led to further results was that 

 of the concentration chains. The measurement of the electromotive 

 force in these chains is easily carried out in aqueous solutions. These 

 methods are all based upon the measurements of electric currents, 

 or more specially, upon compensation of currents by oppositely 

 directed currents. The hpoids offer such tremendous resistance to 

 the electric current that measurable current intensity is not generally 

 obtainable. It is chiefly electrostatic tension that can be measured 

 in these cases. Special instruments have been devized for this 

 purpose, such as the quadrant electrometer by Thomsen and its 

 newer modification, the binant electrometer, by Dolezalek. These 

 methods were successfully appUed by Cremer,^ Haber and Klemen- 

 siewicz,^ Loeb,^ and Beutner^ to determine the degree of dissociation 

 of electrolytes, covering, to be sure, only a part of the above de- 

 veloped general purpose. Only a few points of support are available 

 for attacking our problem. First, a certain regularity discovered 

 by P. Walden^ must be mentioned. As was stated earlier (page 14), 

 Walden found that on comparing those concentrations (c) of a given 

 electrolyte which have the same degree of dissociation in different 

 solvents, it appeared that the cubic roots of the concentrations were 

 directly proportional to the dielectric constants D of the correspond- 

 ing solvents, or, 



Di : D2 = a/c*! : V^Cj 



Let us find, for instance, that concentration c of an electrolyte in 

 different solvents at which the degree of dissociation, a = 0.5. Now 



1 Cremer, Zeitschr. f. Biol. 47, 1 (1906). 



2 Haber and Klemensiewicz, Ann. d. Physik [4] 26, 927 (1908). 

 2 Jacques Loeb, Journ. of Gen. Physiol. 3, 667 (1921). 



* R. Beutner, Die Entstehung elektrischer Strome in lebenden Geweben. 

 Stuttgart 1920. 



5 P. Walden, Zeitschr. f. physik. Chem. 54, 228 (1905) ; 94, 263 and 372 (1920). 



