128 Studies on Solution. 



A tentative explanation based upon these somewhat limited observa- 

 tions is offered which is by no means final. When a salt is added to 

 water or to the solution of another added salt, the added salt is dis- 

 sociated by the water present. It is believed that combined water 

 i. e., water of hydratlon in the solution of hydrated salts possesses less 

 ionizing power than the uncombined water, in which case the salts 

 added would be less dissociated. And further, this effect would be 

 greater the greater the concentration, since more combined water 

 would then be present. The hydrated salts used as added salts are less 

 dissociated than the other added salts because water of hydration now 

 exists in both of any pair of solutions. However, the dissociation 

 is always less in the case of the hydrated salt of any pair because of 

 the less dissociating power of the water of hydration already present 

 in that solution. 



These results and conclusions which follow are to be regarded as 

 preliminary. The nitrates and chlorides have been used and not the 

 sulphates, principally because they are less liable to form double salts. 

 But in the concentrated solutions it can not be said with certainty 

 that no complexes were present. 



Values for the degree of dissociation based upon the equation 



M 

 a = - are somewhat open to doubt. 1 The conductivity of a solution 



(apart from experimental errors) is dependent to a greater or less 

 extent upon the viscosity of the medium and the migration velocity 

 of the ions. The latest relation between viscosity and conductivity 

 has been deduced by Washburn and Clark. 2 Unfortunately this is of 

 little value in applying a viscosity correction, since one of the factors 

 is dependent upon the nature of the medium and there is at present no 

 means of evaluating it for solutions of strong electrolytes. 



Considering the speed of the ions, no quantitative correction can 

 be made. It will be noticed that normal solutions of sodium and potas- 

 sium nitrates have been paired with calcium nitrate solutions. The 

 migration velocity of potassium is greater, while that of sodium is less 

 than the migration velocity of | calcium, yet this fact hardly affects 

 the results. Lewis 3 has recently held that the speed of ions actually 

 increases rather than decreases with increasing concentration, and so 

 the degree of dissociation based upon the conductance ratio is always 

 too high. The evidence either way, however, is not conclusive. 



From his extensive work upon dielectric properties of solutions, 

 Walden 4 concludes that the presence of salts in solutions increases the 

 ionizing power of the solvent. With this granted, the hydrated salts 

 may be said to alter the dielectric constant differently from the non- 



^ourn. Amer. Chem. Soc., 38, 788 (1916). *Ibid., 37, 1043 (1915). 



*Ibid., 38 (1916). 4 Zeit. physik. Chem., 55, 683 (1906). 



