Displacement in their own Mother -liquor 215 



bv increased pressure, while that of the caesium salts must be 

 helped by the same agency. 



Conclusion. The method of determining the specific 

 gravity of a soluble salt in its own mother-liquor, as described 

 in the first part of the paper, involves manipulations of too 

 delicate a character to permit it to pass into general practice 

 in competition with other methods for the same primary 

 purpose. When, however, the specific gravity of the salt has 

 been ascertained in this way, the relation between its apparent 

 displacement in the state of crystal and in that of saturated 

 solution have been ascertained at the same time. In the 

 second part of the paper the observations are discussed from 

 this point of view, but owing to exigencies of space the discussion 

 has been limited to the accentuation of the salient features. 

 One of the most important of these is the connection which 

 ils itself between the molecular weight of the salts and 

 their specific gravity and displacement in crystal and in 

 saturated solution, in definite conditions. The authority of 

 the periodic law makes itself as clearly felt in the limited area 

 of the ennead as it does in the realm of the elements. It is 

 true that the caesium salts introduce some irregularity into the 

 periodicity, but this is not to be looked on as an exception, but 

 as an interference, the nature of which it will be interesting 



to trace 1 . 



1 See Contents, p. xxxiii. 



