Displacement in their own Mother-liquor 213 



iturated solution at _\;-i is equal to that of 2-723 gram- 

 molecules of water, and therefore, that, in these conditions, 

 CsCl is ro!n metrically equivalent to 2723 H 2 0. 



If we study Table V (d), we see that the average molecular 

 displacement of the salts increases with their molecular weight, 

 whether we follow the columns or the lines. The only exception 

 is furnished by caesium bromide, the displacement of which 

 i- very slightly lower than that of caesium chloride. The 

 greatest molecular displacement is that of caesium iodide, 

 which has the highest molecular weight ; and the least molecular 

 displacement is that of potassium chloride, which has the 

 lowest molecular weight. The pair, potassium bromide and 

 rubidium chloride, which have almost equal molecular weights, 

 have also almost equal molecular displacements. The same is 

 true of the pair, potassium iodide and caesium chloride, but 

 rubidium bromide has a markedly lower displacement. Finally, 

 th-- pair, rubidium iodide and caesium bromide, which have 

 almost identical molecular weights, present no resemblance in 

 tin ir apparent molecular displacements. 



Comparison of the Displacement of the Salt in Crystal and in 



Kjf J? 



cr-liquor. The molecular displacement =- of the salts 

 in crystal is ^ivi-n in Table IV (c) in terms of grammes of water ; 



that of the salts in mother-liquor - is similarly jjivcn in 



1.- V(c). 



If we compare these two tables, we find the remarkable 

 result that while in the case of the potassium and the rubidium 

 salts the figures for the displacement in crystal are greater than 

 those for the displacement in mothrr-liquor. in the case of the 

 caesium salt- tin- reverse i- the case. 



In T-.ble VI (a) we have the difference -- of the 



\ LJ tti 



molecular di-pla. rim-nt <>l tin- s.dt in crystal Inun its mean 

 molecular displacement in mother-liquor. In Compartment (b) 



we ha\< th- ratio ( ' x . m i i tin--.- quantii 



Taking th. i , nmpaitmrnt (</) we see that in tin- 



