RICHARDS. — SIGNIFICANCE OF CHANGING ATOMIC VOLUME. 13 



Molecular Volumes or Hydroxides. 



order. That is to say, the solution tension of a metal appears to be 

 associated with the excess of affinity of the metal for hydroxyl over its 

 affinity for itself, and intensity of potential seems to be associated with 

 intensity of atomic compression. The inference to be drawn from this 

 comparison is of course that the formation of the metallic ion in water is 

 connected with the affinity of the metal for water, — an affinity 

 which manifests itself even when both of the " bonds" of oxygen are 

 filled.* Similar attraction for nitrogen or sulphur would explain cases 

 in which the solvent does not contain oxygen. 



If this is true, contraction should take place when salts are dissolved 

 in water. This inference is amply verified by facts. In some cases the 

 solution occupies even less space than the water alone, involving a total 

 contraction greater than the volume of the salt itself. The best known 

 of these cases are those of lithic, sodic, and baric hydroxides, and 



* Briihl has suggested that oxygen is the cause of dissociation, but he ascribes 

 it rather to quadrivalence than to a general affinity. 



