Forces between Atoms and Chemical Affinity. 769 



the chemical properties of molecules corresponds to the 

 difference between OH acting as an acid or as a base, and 



+ 

 that the acid OH in the molecule is represented by — H, 



+ 

 while the basic is represented by — H. 



+ 

 Consider a molecule R — H in a solution and surrounded 

 + = + 



by H and — H ions arising from the dissociation of the 



water ; the H of the jnolecule would combine with the 



+ 

 — H ion from the water, and leave therefore an excess 



+ 

 of H ions in the water, and the molecule would therefore 

 have acid properties. 



+ = + , 



Next consider a molecule R — — H in which the hydroxyl 



- + 

 radicle was of the second type : the — H in the molecule 

 would combine with the H + ion from the dissociation of the 



= + 

 water, would leave therefore an excess of — H ions in the 

 water, and therefore the molecule would have a basic character. 



The more electropositive the element R in the molecule 

 ROH, the more likely would there be a transference of 

 a corpuscle from R to and therefore of acquiring a 

 second charge, and OH on this view showing basic pro- 

 perties : this is quite in accordance with ordinary chemical 

 experience. 



Let us now consider what conditions would have an 

 influence on the process of molecular ionization. We may 

 regard the atoms in the molecules as analogous to an 

 electrical condenser such as a Leyden jar : the work re- 

 quired to charge up such a condenser is, for a given charge, 

 inversely proportional to the capacity of the condenser ; 

 hence anything which increases the " capacity " of the 

 molecule will make it easier for the atoms in it to acquire 

 opposite electrical charges. It is by an effect analogous to 

 this that I think the electric field round the molecule can 

 come into play and set at work a mechanism by which the 

 transference of corpuscles from one atom to another in the 

 molecule may be facilitated. Suppose, for example, that 

 A, B represent the atoms in a molecule which when by 

 themselves have so small an electrical capacity that the work 

 required to charge up the one positively, the other negatively, 

 is more than than the energy available from their difference 

 in the electro-chemical series. Suppose that there are other 

 molecules in the neighbourhood, and that the electric force 



