56 WORK OF C. M. STINE. 



little greater than the difference between the dissociation at 12 and 25 C. (except in 

 some cases in the ammonium chloride), we should expect to find the difference 

 between the columns headed Diff. 12 and Diff. 0, in table 43, the same or slightly 

 greater than the difference between the columns headed Diff. 12 and Diff. 25. The 

 opposite is true, the difference between columns 2 and 3 being from two to four times 

 as great as that between 1 and 2, up to 7= 100. At 7 = 100 the differences are the 

 same, and at 7 = 200 and 7 = 1,000 the column headed Diff. 25 becomes smaller 

 than the other two. 



We must, then, look elsewhere for the cause of at least a part of the change in the 

 conductivities, since it is evidently not due solely to change in dissociation, especially 

 since some of the solutions mixed are nearly isohydric. There are three other factors 

 which might come into play: change in hydration, giving rise to a change in the 

 dimensions of the ionic sphere ; change in the viscosity of the solution with change in 

 temperature; change in the number of the dissolved particles (ions and molecules). 

 Of these three possibilities the first probably does not affect the conductivity appre- 

 ciably, there being little hydration in these cases. The second is probably the prin- 

 cipal factor in causing changes in the conductivity with changes in temperature. The 

 third change in the number of the dissolved particles may also play some part, 

 since the value of a becomes smaller with rise in temperature, and, other things being 

 equal, the fewer the number of ions and molecules with which a moving ion must col- 

 lide, the less the friction it will encounter. The differences in the values of columns 

 1, 2, and 3 are greatest for the most concentrated solutions, and it is in these solutions 

 that the greatest change in the value a with rise in temperature is noted. 



Clearly, values for a which are based upon the conductivity of the completely dis- 

 sociated molecules at high dilution can not be strictly correct, since the conductivity 

 of this completely dissociated solution must be considerably altered by change in vis- 

 cosity and in the number of dissolved ions or molecules, both of which factors enter in 

 increasing the concentration, the number of ions and molecules present undergoing 



especially great alteration. 



SUMMARY. 

 It has been shown: 



1. That the complexity of the hydrates formed by a salt is a function of the amount 

 of water present as solvent. 



2. That when two salts are present in the same solution, the complexity of the 

 hydrates is somewhat less than in separate solutions of these salts, each salt tending 

 to dehydrate the other. 



3. That the ions and the molecules of salts probably have different hydrating power. 



4. That the hydrating power of the molecules is in some cases probably greater 

 than that of the ions into which these molecules dissociate. 



5. Additional proof is furnished for the view that the conductivity method is by no 

 means an accurate measure of dissociation in concentrated solutions. 



6. It has been pointed out that the diminution in conductivity which takes place 

 when two electrolytes of the type potassium chloride-ammonium chloride are mixed is 

 probably not due entirely to suppression of ionization, but also to (a) change in the 

 viscosity of the solvent ; (b) change in the size of the ionic sphere, due to alteration 

 in the amount of water which the ion must drag with it through the solution. 



