ii8 PHYSICAL SCIENCE 



salts of univalent, divalent, and trivalent metals 

 were found to be proportional to the numbers 

 1:35: 1023 respectively. Most properties which 

 depend on the valency vary in the ratios i : 2 : 3, 

 and the great difference in the numbers now 

 under consideration is very striking. An attempt 

 at a preliminary explanation of these unusual 

 relations has been made by the present writer. 



Let us frame a mental picture of a solution as 

 it is represented by the dissociation theory. A 

 certain number of the dissolved molecules are 

 regarded as dissociated into charged ions, which 

 wander, free from each other, through the liquid, 

 perhaps by successive combinations with solvent 

 molecules in their path. When an electric force 

 is applied, though still moving sometimes in one 

 direction and sometimes in another, the ions, on 

 the whole, drift in the direction indicated by the 

 force, and we may imagine, therefore, that two pro- 

 cessions of oppositely charged ions pass each other, 

 drifting in opposite directions through the solution. 



When there is no electric force, the ions are 

 subject to no steady drift, and must move some- 

 times in one direction, sometimes in another, as 

 the chances of their life direct. Any one ion will 

 be passing sometimes from one solvent molecule 

 to another, carrying its electric charge with it ; 

 sometimes it will come across an ion of the opposite 

 kind in such a way that combination occurs, and, 

 for a time, an electrically neutral molecule is formed. 

 By collisions of unusual violence, or by other 

 means, soon this molecule will be dissociated, and 

 its ions again set free from each other, to be handed 

 backwards and forwards by the solvent molecules 

 as already described. 



