GENERAL DISCUSSION OF RESULTS. 201 



centration; while the number of molecules of water combined with one molecule 

 of the dissolved substance increases with the dilution of the solution. 



The difference between the amount of water combined with the calcium chloride 

 when alone, and when in the presence of potassium chloride, increases with the con- 

 centration of the two salts present. 



The next system studied was a pair of salts both having large hydrating power 

 and also approximately the same hydrating power. The salts chosen were calcium 

 chloride and magnesium chloride. It was soon found, as would be expected from 

 the effect of mass action, that each of these salts exerted a hydrating action upon 

 the other, and that each was combined with less water when the two were mixed 

 than when they were separate. The magnitude of the hydrating effect of each of 

 these salts on the other was worked out quantitatively. 



The following ternary systems were also studied in the above connection: Mag- 

 nesium chloride and strontium chloride, magnesium nitrate and strontium nitrate, 

 and magnesium nitrate and calcium nitrate. Results of the same general character 

 were obtained with these substances as with those already mentioned. Each salt 

 diminishes the hydration of the other, and the magnitude of this effect was worked 

 out approximately. 



A pair of binary electrolytes (sodium bromide -f- lithium bromide) and a pair of 

 quaternary electrolytes (aluminium chloride + ferric chloride) were studied in this 

 connection. Results of the same general character were obtained as with the ternary 

 electrolytes. The results with the quaternary electrolytes are somewhat compli- 

 cated by the hydrolysis of these substances, especially in the more dilute solutions. 

 Nevertheless, the effect of each salt in dehydrating the other is clearly shown from 

 the freezing-point determinations. 



The work was then extended from pairs of salts with a common anion to pairs 

 with a common cation. The salts used were calcium chloride and calcium nitrate, 

 and the results are similar to those obtained when the anion was kept constant. 



Another problem that was studied by Stine was the effect of temperature on the 

 conductivities of solutions of electrolytes and of mixtures of these solutions. For 

 this purpose it was necessary to select salts that do not form double salts with one 

 another, and which have little or no power to combine with water. The salts chosen 

 were potassium chloride and ammonium chloride. 



The conductivities of potassium chloride and of ammonium chloride were deter- 

 mined separately, and then the conductivities of the mixtures taken. The conduc- 

 tivities of the mixtures are less than the sum of the conductivities of the individual 

 salts, as would be expected from the fact that each of the two salts with a common 

 ion suppresses the ionization of the other. 



If this were the only cause of the difference, then this difference should be greatest 

 when the most strongly dissociated solutions are mixed. This difference should, 

 therefore, be greater at than at 12, and greater at 12 than at 25. Exactly the 

 opposite is true. 



Again, if this difference is dependent only upon the amount of the dissociation, 

 and the driving back of the dissociation of one salt by another salt with a common 

 ion, then, since the change in dissociation from to 12 is a little greater than 



