THE ELECTROLYTIC DISSOCIATION THEORY 391 



by Bousfield, is very improbable. In very concentrated solu- 

 tions, on the other hand, the complexity of the hydrates will 

 probably increase up to a point with dilution. 



(4) If ions are associated with water molecules, the latter must 

 also be transported through the solution during electrolysis, 

 and if the positive and negative ions are hydrated to a different 

 extent, changes of concentration might be expected to occur 

 at the electrodes, and could be detected by adding a neutral 

 substance to the electrolyte. On Nernst's initiative, this sug- 

 gestion has been tested by Garrard and Oppermann, 1 who 

 submitted to electrolysis solutions of strong acids and bases 

 with boric acid as the non-electrolyte. On the assumption 

 that the hydrogen ion is not hydrated, the authors find that 

 SO4", CI', Br', and N0 3 ' ions are associated with 9, 5, 4, and 2-5 

 molecules of water respectively. Similar experiments have 

 been made by Buckbock, 2 who used mannite and resorcin as 

 non-electrolytes and hydrochloric acid as the electrolyte. 

 Assuming that the hydrogen ion is associated with one 

 molecule of the solvent, he finds that in very dilute solution 

 four molecules of water are transported with the chlorine ion. 

 As the experimental error in such observations is large, the 

 results must be regarded as of a preliminary nature, but it is 

 significant that the hydration found is by no means large, 

 and, as we have already seen, this is a priori much more 

 probable than the high values found by Jones and others. 



(5) Additional confirmation of the presence of hydrates in 

 solution is obtained from the results of solubility determina- 

 tions in solutions of electrolytes. 3 In general, inactive gases 

 are less soluble in solutions of electrolytes than in water, as 

 would be expected if, owing to hydrate formation, only part 

 of the solvent is free, and the solubility is most depressed by 

 the salts which, from other considerations, are regarded as being 

 most highly hydrated in solution. 



Further, the fact that so many hydrates have been obtained 

 in crystalline form may be considered as proving that there is 

 such an affinity between solvent and solute as might conceivably 

 lead to the formation of hydrates in solution. We may 



1 Gottinger Nachrichten, 1900, p. 86. 



* Zeit. physikal. Chcm. 1906,55, 563. Compare also Lobry de Bruyn, Receuil. 

 Trav. Chim. 1904, 22, 430. Morgan and Kanolt, J. Am. Ch. Soc. 1904, 26, 1635. 

 3 Results summarised by Baur, Ahrens' Sammlung, 1903, 8, 466. 



