Manchester Memoirs, Vol 7n. (igoS), No. 10. 35 



in a solvent is perhaps a more fundamental change than 

 the ordinary dissociation of a gas : yet the ions may 

 accumulate notwithstanding, for the obstacles to recombi- 

 nation presented by the dense molecular aggregation of 

 the liquid in which they are entangled are also enormous 

 in comparison with any that are present in the gas. Thus 

 the circumstance that self-ionisation is hardly detectable 

 in a gas is not conclusive evidence that it never occurs 

 without the assistance of a liquid solvent medium. 



It seems worth while 16 follow up these relations 

 somewhat further in the light of Faraday's conclusion, so 

 emphatically enforced by Helmholtz in i88i, that the 

 strongest forces of chemical affinity are of electric type. 

 It would almost seem as if we must adopt the view that 

 the active atom in ordinary chemical change is the ion, with 

 its large intrinsic electric charge as an essential feature. No 

 permanent state such as we associate with a simple dense 

 material substance can be reached until these enormously 

 active positive and negative bodies have become paired ; 

 until, in fact, their domains of activity, in place of being 

 the widely ramifying fields of force of free ions, are 

 changed to the more concentrated and individualised 

 fields of molecules,* in which the lines of force instead of 

 spreading out far into space simply pass across in more 

 or less curved lines from one ion to its adjacent conjugate. 

 No substance could exist completely ionised in free 

 space for a moment, nor with any considerable excess of 

 ions of one sign : ionisation is, however, continually 

 occurring in substances to a small extent, spontaneously 

 and so to speak by accident, i.e., in a manner not con- 



* In the molecular groups of solvent media, which have abnormally 

 high dielectric capacities, the two conjugate ionic poles are so far apart that 

 these groups may be held to occupy a position intermediate between 

 ordinary molecules and active ions. Cf. p. 37. 



