194 



solvent breaking up the molecule HC1 in some way, but not being 

 itself directly concerned in the reaction. 



This view, although sufficient for many purposes, will not 

 stand strict investigation. Thus we know by experiment that 

 the ions, when they migrate with the electric current in elec- 

 trolysis, carry water with them. This indicates that ions are 

 hydrated. The solvent is therefore chemically active in ioniza- 

 tion. 



Recent work, indeed, suggests that the distinction drawn 

 between solvent and solute in explaining ionization phenomena 

 is entirely misleading. Pure liquefied hydrogen chloride is prac- 

 tically a non-conductor, just like pure water. It is quite an 

 arbitrary procedure, therefore, to ascribe all of the conducting 

 power of a mixture of hydrogen chloride and water to the former 

 substance, and to regard the latter as quite inert. It would be 

 more logical to consider both components of the solution as equally 

 concerned in ionization. Now experiment shows that extensive 

 ionization in solution always accompanies extensive compound 

 formation on admixture. When no interaction at all between 

 the components occurs, the solution is non-conducting. All 

 strong acids, for example, give hydrates with water which are 

 sufficiently stable to be isolated in the solid state. No very weak 

 acids give isolable hydrates. Those mercuric salts which are 

 highly ionized, as mercuric nitrate Hg(N0 3 )2, all yield hydrates, 

 such as Hg(N0 3 )2,8H 2 0. Those which are only slightly ionized 

 are all non-hydrated. It is possible, therefore, to regard ion- 

 ization as due to the formation of solvent-solute complexes. The 

 attractive forces between the constituent groups in such complexes 

 would be considerably weaker than in the simpler molecules of 

 the two components, and disintegration into oppositely-charged 

 radicals could occur much more readily. 



It should be added that ionization is not restricted to solu- 

 tions of electrolytes in water. Many other solvents, such as liquid 

 ammonia NH 3 , formic acid H.COOH, ethyl alcohol C 2 H 5 OH, 



