﻿6 Mr. W. Sutherland on the Molecular 



Suppose an external Jf to approach A from the left. It 

 will repel the J of A and attract \), thus increasing the che- 

 mical cohesion at A by forcing the two oxygen atoms closer 

 together. But Jf on the right of A will lessen the chemical 

 cohesion by repelling the J and attracting the (7 of A. Now 

 I have shown in " The Dielectric Capacity of Atoms " (Phil. 

 Mag. [6] vii. ; Austr. Assoc. Adv. Sci. x. 1904) that all the or- 

 dinary ions have a much smaller dielectric capacity than water; 

 so the electric force between electrons in an ion and electrons 

 in adjacent water molecules will be greater than the forces 

 between electrons in the water molecules at the same distance 

 apart. This shows that an electron can break or strengthen 

 the bonds of (H 2 0) 3 and (H 2 0) 2 according to the relative 

 position of the ion and the bonds. The ions must be con- 

 tinually making and unmaking (H 2 0) 3 and (H 2 0) 2 . The 

 reaction accompanying this action is the process by which 

 water ionizes the solute. 



This theory of Ionization has already been advanced in 

 " Ionization &c." (loc. cit.) . Hence the formula? for the 

 density and ionization of solutions are practically equations 

 for the chemical equilibrium of the complex mixture (H 2 0) 3 , 

 (H 2 0) 2 , solutes and ions. Our present concern is with the 

 rates at which the processes of making and unmaking (H 2 0) 3 

 go on. The chief cause is the electric force at the surface of 

 each ion. The average position for the electron of an ion is 

 at the centre of the ion, although actually the electron may 

 never be there. In the case of a divalent ion we have to 

 assume that each electron acts on the average as though it 

 were at the centre, although the mutual repulsion of the 

 electrons will not allow them both to be at the centre at the 

 same time. If a denote the radius of an ion and K its 

 dielectric capacity, then 1/K« 2 is the chief cause of making 

 and unmaking (H 2 0) 3 . The simplest presentation of the 

 complex reactions is to assume that a positive ion keeps a 

 certain number of (H 2 0) 3 molecules split into three separate 

 groups $H 2 0[? which differ from the H 2 of steam by the 

 large electric moment of Jf and (7 before they have coalesced 

 as in H 2 0. This form of charged molecule or atom I have 

 proposed to call a stion. A positive ion produces from 

 trihydrol a certain number of stions, each of which has a very 

 short separate existence. By their recombination three at a 

 time these form (H 2 0) 3 again. Equilibrium ensues when the 

 number formed in unit time equals the number broken. For 

 simplification w r e have merged the action of a positive ion on 

 (H 2 0) 2 in that on (H 2 0) 3 . Let a positive ion produce x stions, 

 then the number of (H 2 0) 3 molecules formed from these in 



