14 HYDROGEN ION CONCENTRATION 



between any two oppositely charged particles found in ifc. Water 

 has almost the largest dielectric constant of all substances as shown 

 in the table 1 (the figures given*^ are mostly for 17 to 18°C.). 



Only polyhydric alcohols (glycerin) and perhaps the acid amides 

 and the nitriles approach the magnitude of the dielectric constant 

 of water, and formamide and hydrocyanic acid alone surpass it. 



Because of this factor all electrostatic forces of attraction are 

 greatly diminished in water and the dissociation of electrolytes 

 dissolved in it is powerfully enhanced. This interdependence 

 between the dielectric constant of the solvent and the degree of 



TABLE I 

 Table of dielectric constants 



Hydrogen-gas 1.000500 Aniline 7.32 



Air 1.000576 Amyl alcohol 16.0 



Hexane l.SS Diamond 16.47 



Petroleum 2.0 Ammonia 22. 



Wood, paper 2.0-7.0 Ethyl alcohol 25.4 



Benzene 2. 26 Methyl alcohol 35. 4 



Olive oil 3.0 Nitrobenzene 36.45 



Ice (at -18°) 3.16 Acetonitrile 38.8 



Bromine 3.2 Glycol 41. 2 



Octyl alcohol 3.4 Glycerol 56 



Urea (solid) 3.5 Acetamide (fused) 59.2 



Ethyl ether 4.3 Glycollic acid nitrile 68 



Chloroform 4. 95 Water 81. 7 



Sodium chloride (solid) 6.12 Formamide 94 



Acetic acid 6.3 Hydrocyanic acid 95 



dissociation of solute electrolytes is universally applicable, and it 

 was simultaneously discovered in 1893 by Nernst'' and J. J. Thom- 

 son.^ 



The quantitative relationship between the degree of dissociation 

 of the solute and the dielectric constant D of the solvent was worked 

 out by P. Walden.^ He compared the behavior of solutions of a 



' The figures were taken chiefly from Landolbt-Bornstein, Physikalisch- 

 chemische Tabellen. Berlin, 1912. 



7 W. Nernst, Gottinger Nachr. No. 12 (1893); Zeitschr. f. physikal. Chem. 

 13,531 (1894). 



8 J. J. Thomson, Phil. Mag. 36, 320 (1893). 



9 P. Walden, Zeitschr. f. physikal. Chem. 54, 228 (1905), also 94, 263 and 374 

 (1920). 



