SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 175 



It will be observed that the adjustment of the molecular weight does not materially 

 aflfect the relations of the solutions as regards their specific gravities. 



Returning to the consideration of the data obtained from the original experiments, 

 the comparison of the displacements for the same concentrations in the case of solutions 

 of each of the three salts shows a close agreement to exist between the values for 

 rubidium chloride (which are lower in each case) and potassium bromide, while the 

 values for the potassium salts of the mixed halides stand quite apart and are much 

 higher than the corresponding values for the other two salts. 



If we compare the differences of displacements of equivalent solutions of RbCl and 

 KBr for m = 5, thenARbci- Akbi = 0'445, and for m=l it is 0'702. The differences 



of displacements between corresponding solutions of K 



Cl + I 



and KBr are, for m = 5, 



Ag.ci+1- AKBr= 10-318, and form= 1, A^ci+i- AKBr = 2-143. 



The molecular displacement of each of these salts in crystal, as given in 



.01 + 1 



127, is 



RbCl = 44-710, K^ 



46-406, KBr = 44-460, 



and if the sum of the displacements of the constituent materials forming the solution, 

 i.e. 1 gram-molecule and 1000 grams of water, are compared with the displacement of 

 the solution obtained from the constituents, the following results are arrived at : — 





RbCl. 



2 



KBr. 



Sum of displacement of constituents 

 Displacement of solution 



Difference 



1044-710 

 1034-341 



1046-406 

 1037-186 



1044-460 

 1035-043 



10-369 



9-220 



9-417 



Here, with regard to the change in displacement when solution is effected, the 

 potassium salts are quite comparable, while the rubidium chloride shows a much greater 

 change, although in the case of values for the sum of the displacements of the con- 

 stituents, rubidium chloride and potassium bromide are the more comparable. 



§ 95. Difference of Displacement, dA. — c?A gives the increment of displacement 

 of a mass of 1000 grams of water produced by successive additions of 1 gram-molecule 

 of salt to that already in solution. 



The values of v/m represent the mean increment of displacement of 1000 grams of 

 water per gram-molecule of salt when w gram-molecules have been dissolved in it. 



The values of dA from 1 to 4 gram-molecules for each salt show that, with the 

 exception of that for the 1 gram- molecule, they are lowest in the case of potassium 

 bromide, and the values for corresponding concentrations of rubidium chloride very 

 closely approximate to them, while those for the potassium salt of the mixed halides 

 show a considerable divergence. 



