ON THE PHENOMENA AND THEORIES OF SOLUTION. 



461 



difficulty. Such are the hydrated oxides or hydroxides of the metals ; 

 hut these are generally infusible : — 



Al203.3H20\ 



FejOs.SHaO 



CraOa.SHaO 



MgO.HaO 



CaO.HaO 



- infusible, very slightly soluble. 



Those which are easily fusible are also easily soluble, as the following : — 



Ba02H208H20 m.p. 100° 

 Sr02H208H20 m.p. ? 

 K2OH2O 

 NaaOHaO 



I take such examples as these as aflFording an argument for the hypo- 

 thesis that such compounds retain their water when they pass into solu- 



FiG. 5. 



tion, else how can we account for the immense difference of solubility 

 between baryta and strontia on the one hand, and lime and magnesia on 

 the other ? 



Take the converse of easy fusibility associated with no connection of 

 composition between solvent and solid, or in a series a diminishing con- 

 pection. 



The lower terms of the various series of alcohols and acids show con- 

 siderable similarity to water in their general behaviour, the higher terms 



