8CHLUNDT — DIELECTRIC CONSTANTS OP PURE SOLVENTS. 387 



When the exceptions noted are considered collectively it be- 

 comes evident that the Nernst-Thomson rule must relinquish a 

 good share of the prestige it has hitherto enjoyed. While it is 

 true that in these pages a number of new examples supporting 

 the rule have been given, yet the exceptions noted are of a kind 

 not to be underrated. The rule as it now stands is no more gen- 

 eral than the hypothesis of Briihl which attempts to account for 

 the dissociating power of solvents by assuming spare valences 

 to exist, or the parallelism that Dutoit and Aston claim between 

 dissociating power and polymerization of the molecules of the 

 solvent. These theories have been shown to be inadequate by 

 Lincoln, 1 Euler, 2 and Kahlenberg. 3 These investigators cite 

 striking exceptions to these theories and therefore hold them 

 untenable. Hence until we have some experimental evidence 

 in place of the speculative "specific influences" which are said 

 to exist and to account for exceptions to the Nernst-Thomson 

 rule, it must be considered inadequate in accounting for the dis- 

 sociating power of solvents by virtue of their high specific in- 

 ductive capacity. 



Relation behveen the dielectric constant and the latent heat 

 of evaporation. — Since Louguinine 4 and Kahlenberg 5 have re- 

 cently determined the latent heat of evaporation of a number 

 of nitriles it seemed of interest to see how closely Obach's law, 

 that the ratio between the dielectric constant and the latent heat 

 of evaporation is approximately a constant for an homologous 

 series, holds for the nitriles. The following table gives the 

 latent heats of evaporation, the dielectric constants, and in the 

 column headed -57^- the ratio of the heat of evaporation to the 

 dielectric constant : 



1 Jour. Phys. Chem. 3, 457, (1899). 

 a Zeit. phys. Chem. 28, 619, (1899). 

 3 Jour. Phys. Chem. June (1901). 

 * Compt. Rend., 132, 88, (1901). 

 'Jour. Phys. Chem. 5, 215, (1901) 



