Conductivity of Organic Acids in Ethyl Alcohol. 121 



with increasing percentage of water, very slowly up to about 12 per 

 cent of water (by weight), and then more rapidly. In every case the 

 molecular conductivity increases slowly with dilution. 



Wakeman 1 measured the conductivity of several organic acids and 

 their sodium salts (as well as of hydrochloric acid, potassium iodide, 

 potassium chloride, and sodium chloride) in alcohol-water mixtures 

 ranging from pure water to 50 per cent alcohol. Using Lenz's values 2 

 for the relative migration velocities of the potassium and iodine ions 

 in solutions of potassium iodide, he was able, by means of his con- 

 ductivity measurements, to calculate the relative migration velocities 

 of the chlorine, hydrogen, and sodium ions in the various mixed solvents 

 which he employed. He then had all the data necessary to apply 

 Ostwald's method 3 for the determination of the /JL^ values of the organic 

 acids from those of their sodium salts. From these values it was a 

 simple matter to calculate percentage dissociation, and, thence, by 

 means of Ostwald's dilution law, affinity constants. 



The results obtained show that, for a given acid at a given dilution, 

 increase in the percentage of alcohol causes a slight decrease in dissoci- 

 ation and a more rapid decrease in the affinity constant (&). For a 

 definite alcohol-water mixture, the value of k decreases regularly with 

 dilution, which seems to point to the action of an unknown influence 

 which decreases the dissociation to such an extent that the formula 



2 



j- r- no longer holds. A very interesting feature of Wakeman' s 



work is his attempt to extrapolate the value of molecular conductivity 

 beyond 50 per cent alcohol, in the direction of 100 per cent alcohol; and 

 he postulates that the conductivity approaches zero as a limit. 



Schall 4 determined the conductivity of oxalic, picric, and dichlor- 

 acetic acids in alcohol and in alcohol-water mixtures. The molecular 

 conductivity of these acids in water is approximately the same, but 

 Schall found that replacement of the water by alcohol decreases 

 the conductivity to quite different extents. This he attributes 

 chiefly to change in the degree of dissociation. In alcohol-water 

 mixtures the acids were found to behave very differently from what 

 they did in the pure solvents. Some appear to behave just the opposite 

 of what might be expected; for example, picric acid gives a much 

 higher, and each of the other acids a much lower conductivity value in 

 water-alcohol mixtures than in pure alcohol. 



In the meantime the conductivity method had been applied to solu- 

 tions of electrolytes in a variety of non-aqueous solvents, with the 

 result that not a single case was on record in which the Ostwald dilution 

 law could be said to apply, even approximately. In order to test the 



t. phys. Chem., 11, 49 (1893). 

 2 Mem. de 1'Acad. de St. Petersb., VII series, 30, 9 (1882). 



3 Zeit. phys. Chem., 2, 270 (1888); 3, 170 (1889). See also Amer. Chem. Journ., 46, 66 (1911). 

 Zeit. phys. Chem., 14, 701 (1894). 



