34 Mr. W. Sutherland on Ionization in Solutions. 



10. Summary and General Conclusions. 



The ionization of all ordinary solutions at all strengths is 

 complete. This is proved by showing that the fraction 

 currently called the degree of ionization really originates in 

 a resistance which the ions offer to one another's motion 

 because of their forming with the solvent through their 

 electric action on one another a medium w T hich offers a 

 special viscous resistance to the motion of each individual 

 ion. This is one new type of viscosity of electric origin. 

 But the charge of each ion causes electric induction through 

 ihe surrounding solution, and with this is associated a second 

 new type of viscosity also of electric origin. These with the 

 ordinary viscosity of the solution give three resistances to 

 the motion of an ion. When the sum of these is equated to 

 the electric driving force, the formula (10) is obtained for the 

 molecular specific conductivity. This formula is tested by 

 comparison with experimental results of very wide range, 

 especially those of Walden for non-aqueous solutions, those 

 of Kohlrausch for aqueous at ordinary temperatures, and 

 those of Noyes and Coolidge for aqueous at high tempera- 

 tures. Incidentally some insight has been obtained into the 

 properties of the effective force which keeps a solute com- 

 pletely ionized (Section 5). It is shown that the dynamical 

 theory already given for diffusion of non-electrolytes joins on 

 consistently with that developed here for conduction, if the 

 same empirical allowance for slipping is made in each. The 

 equations for conduction and diffusion lead to values of 

 the radius of the hydrogen molecule in good agreement 

 with that yielded by the kinetic theory of gases, namely 

 1 X 10~ 8 cm. There is no need to imagine each conducting 

 ion or diffusing molecule surrounded by an " atmosphere " 

 of solvent. The formulae for conduction and diffusion, 

 enabling the radii of ions and molecules to be found, become 

 means of determining large molecular masses for which the 

 usual methods fail, as I have elsewhere shown in the cases of 

 egg-albumin and globulin. The current theory of solutions 

 will need to be entirely re-written. The idea of partial 

 ionization, while it can give a formal qualitative account of 

 the chief phenomena of solutions, being dynamically wrong, 

 cannot furnish a correct quantitative correlation of their 

 properties. The theories of the raising of the boiling-point 

 and the lowering of the freezing-point of solutions will have 

 to be put upon a sound molecular dynamical basis. With 

 the knowledge that ionization is complete, the neglected 

 theory of the energetics of solutions will become much more 



