hy Displacement in their own Mother-liquor. 37 



pair respectively are very different. The lowest solubilities 

 are on the diagonal KCl-CsI and the highest solubilities on 

 the diagonal IQ-CsCl. RbBr, which occupies the middle 

 place on both these diagonals, is also in the middle of the 

 middle column and of the middle line, and is the center of 

 the ennead. Its solubility, besides being nearly the average 

 of the group, has a symmetrical position with respect to those 

 of the other salts. On one diagonal the solubility of its neigh- 

 bors is lower, on the other higher than its own. In its column 

 the solubility of its neighbors is higher, in its line it is lower 

 than its own. 



In compartment (b) of Table "V we have the values of S, the 

 specific gravity of the mother-liquor at T, referred to that of 

 distilled water of the same temperature as unity. These num- 

 bers cannot, as they stand, be compared with each other 

 because they refer to solutions of such different concentrations. 

 They enable us, however, to arrive at the average apparent 

 displacement of one gram molecule of salt in the saturated 

 solution which contains 1000 grams of water at T. Thus, tak- 

 ing again caesium chloride as an example, we have for the 

 weight of salt dissolved in 1000 grams of water 



to = m. CsCl = 2048-34 grams. 



Adding 1000 grams to this we have for the weight of the 

 solution 



W = 1000 + 20 = 3048-34 grams. 



The specific gravity (S) being 1-9101, the displacement of the 

 solution is 



W 



V-=-jt- = 1595*92 grams of water, 



whence the gross apparent displacement of the salt in solution 

 is 



v — V — 1000 = 595-92 grams, 



and the mean apparent displacement per molecule is 



v 



— = 49-021 2-rams. 



m 



v 

 In compartment (c) we have the value of -- for each mem- 



m 



ber of the enneacl. This expresses, in grams of water, the 

 average apparent displacement of one gram molecule of salt in 

 its saturated solution at T. In compartment (d) the same con- 

 stant is expressed in terms of gram molecules of water ( — -\. 



Before commenting on the numbers in the table, it is impor- 

 tant to form a clear conception of their physical meaning. 



