122 Conductivities and Viscosities in Pure and in Mixed Solvents. 



validity of this law for alcoholic solutions, Wildermann, in 1894, carried 

 out an investigation 1 on the conductivity of certain organic acids 

 (acetic, monochloracetic, dichloracetic, trichloracetic, and succinic) in 

 absolute alcohol at 18. Absolute alcohol was obtained free from 

 aldehyde by treatment with silver nitrate, and from water by heating 

 with lime. Great care was exercised in protecting it from the air, and 

 a special apparatus was constructed, with the aid of which a measured 

 quantity could be drawn out of the supply bottle directly into the 

 conductivity cells. Because of the small values of the conductivities 

 to be measured, the cells were constructed so as to have small constants; 

 but in spite of this the external resistances required were high, and 

 hence a graphite resistance rheostat was employed to make the tone 

 minima more distinct. Before using, the cells were washed with running 

 water for from 8 to 10 days. They could not be dried in the ordinary 

 way by washing with alcohol and then evaporating the alcohol, because it 

 was found that the alcohol which was in contact with the platinized elec- 

 trodes was to some extent oxidized by the air to acetic acid. Therefore, 

 after being washed with water, the cells were allowed to drain com- 

 pletely, after which alcohol was introduced so as to wash the glass walls 

 without coming in contact with the electrodes, and then the alcohol 

 was allowed to cover the electrodes. Some of the alcohol was then 

 drawn off and fresh alcohol added, keeping the electrodes continuously 

 covered, and this process repeated until the conductivity remained 

 constant. This often cost a half day of work and from 300 to 500 c.c. 

 of good absolute alcohol. All the solutions were made up in the cell, 

 the most concentrated by introducing approximately the desired quan- 

 tity of acid, and from this the others by repeated replacement of a 

 portion of the solution with fresh alcohol. The strength of each solu- 

 tion was determined by titration of the portion removed. 



Wildermann found that the conductivity of acetic, monochloracetic, 

 and succinic acids was so small that the values were unreliable, and he 

 was content to make the qualitative statement that between the vol- 

 umes 10 and 160 these substances have a molecular conductivity which 

 increases almost directly proportional to the volume. 



In order to understand fully his conclusions in regard to the stronger 

 acids, it will be necessary to consider briefly a few mathematical rela- 

 tions which Wildermann deduced from the dilution law of Ostwald. 



As Ostwald showed, the dilution law 



T2 v = k (I) 



for weakly dissociated compounds, takes the form 

 rf-tfo (II) 



!Zeit. phys. Chem., 14, 231 (1894). 



