108 Conductivities and Viscosities in Pure and in Mixed Solvents. 



The position of the curve for a salt, then, seems to be a function of its 

 water of crystallization supplemented by an effect due to the ions it 

 forms, e. g., water of crystallization would place the curve above the 



curves of salts that do not have water of crystallization; the anion Cl 



would place it above a salt with an anion N0 3 or Br; and the cation 



++ ++ ++ f+ 



Mg would place it above a salt with a cation Ca, Sr, or Ba. This 

 general relation appears to hold among the salts that have no water of 

 crystallization. On figures 8 and 9 the lithium salts do not seem to fit 

 in with the sodium and potassium salts, but what has been said about 

 calcium bromide and barium bromide applies also to these salts, as is 

 shown by figures 9, 10, and 11. 



How can we explain this increase in the velocity of the reaction 

 caused by salts that have water of crystallization, and the decrease in 

 their effect on dilution. 



Getman and Bassett 1 showed that the salts having water of crystal- 

 lization are in solution the most hydrated. Assuming that the effect 

 of the salts with water of crystallization is due to their being hydrated, 

 let us see what we should expect. 



(1) According to Getman and Bassett, the chlorides, nitrates, etc., 

 of such salts as magnesium, calcium, strontium, and barium would 

 increase the velocity of the reaction to very nearly the same extent, 

 and this is much greater than with the non-hydrated salts. 



(2) As the concentration decreases the effect would be lessened, 

 since the total combined water would be less, the decrease being far 

 more rapid than in the case of non-hydrated salts. 



(3) From the work of Pearce, 2 who showed that the hydrating power 

 of a cation is inversely proportional to its atomic volume, we should 

 expect the curves for the salts of magnesium, calcium, barium, and 

 strontium with a common anion, to be similar to those found by him, 

 i. e., magnesium salts have the greatest effect, then calcium, strontium, 

 and barium. 



Let us see if the experimental data confirm these conclusions, based 

 on the assumption that between salts that have water of crystallization 

 and salts that do not, the difference in action is due largely to the 

 hydrates formed by the salts with water of crystallization. 



Taking into consideration the facts brought out earlier, that the 

 dilution of maximum saponification for the apparent exceptions had 

 not been reached, and that larger percentages of ester saponified would 

 also tend to make the apparent exceptions not real, we can draw from 

 the curves the following conclusions: 



(1) Salts with water of crystallization increase the velocity of the 

 reaction much more than salts without water of crystallization. 



Carnegie Inst. Wash. Pub. No. 60, 15 (1907). *Ibid., 180, 57 (1913). 



