36 J. Y. Buchanan — Specific Gravity of Soluble Salts 



lowest equivalents. The average difference between the volu- 

 metric equivalents of the iodides and bromides is 0*563 H 2 0, 

 and that between the bromides and chlorides is 0*343 H„0. 



The Mother-liquor. — The values of T are the same for the 

 mother-liquor as for the crystals, and are presented in Table 

 IV («■). In Table "V {a) we have the values of m or the molec- 

 ular concentration of the mother-liquor. This is expressed in 

 gram molecules salt per 1000 grams water. It represents also 

 with great exactness the solubility of the salt in water at T, 

 and we shall consider it for a moment from this point of view. 







Table V 











The Salt in Mother-liquor. 







K 



Eb 



Cs 





(a) 





Values of 



m. 







4-7619 



7-7670 



12-1563 



CI 





5-7250 



6-7229 



5-3057 



Br 





8-9344 



8-2307 



3-5454 



I 



(6) 





Values of 



S. ' 







1-1798 



1-4971 



1-9101 



CI 





1-3746 



1-6292 



1-6968 



Br 





1-7222 



1-8548 



1-5488 



I 



(<0 





Values of 



V 



m 







31-223 



38-069 



49-021 



CI 





39-038 



44-131 



48-137 



Br 





49-506 



58-575 



67-907 



I 



(d) 





Values of 



V 



18m 







1-735 



2-115 



2-723 



CI 





2-169 



2-452 



2-674 



Br 



2-750 3-257 3-773 I 



The least soluble of the nine is caesium iodide, which has 

 the highest molecular weight, and potassium chloride, which 

 has the lowest molecular weight, comes next to it. Next to 

 caesium iodide, in molecular weight and in solubility, we have 

 caesium bromide ; and, similarly, next to potassium chloride, 

 in molecular weight and in solubility, we have potassium bro- 

 mide. In the latter case the solubility increases with the 

 molecular weight while in the former it decreases with it. 

 But, if Table III be referred to, it will be observed that, as 

 regards molecular weight, KC1 and Csl occupy singular posi- 

 tions in the ennead. On the other hand, KBr (119"1) and 

 RbCl (121) have almost identical molecular weights, as have 

 also CsBr (213) and Ebl (212-5), yet the solubilities in each 



