16 THE THEORY OF IONS 



chemical constitution must be such that ions can 

 be formed from it, its dielectric constant must be 

 high, and it should not contain a large proportion 

 of polymerised molecules.* It is also extremely 

 probable that the degree of dissociation depends 

 considerably upon the capacity of the ions to unite 

 with molecules of the sol vent, f Many substances 

 with large dielectric constants, e.g. water, formic 

 acid, methyl alcohol and ethylalcohol, are bad 

 conductors of electricity because they consist largely 

 of polymerised molecules.} Other substances with 

 large dielectric constants and small polymerisation 

 are unsuitably constituted for electrolytic conduc- 

 tivity, thus : nitrobenzine, ethyl nitrate, and benzo- 

 nitrate contain the groups N0 2 , N0 3 and CN, 

 which readily form ions, but they also contain the 

 groups C 6 H 5 and C 2 H 5 , which have never been ob- 

 served in ions. 



The explanation of dissociation or the formation 

 of ions is not yet complete. Pflaunder and Lemoine 

 explained it by the theory of the Action of Mass, 

 Thompson by the Vortex Atom hypothesis, and 

 others explain it by the kinetic theory of gases and 

 the principles of thermo-dynamics ; but no explana- 

 tion up to the present time has been found satis- 

 factory to all parties. 



The ions are anodic or cathodic, that is they are 

 charged with positive or negative electricity. But 

 their electrical reaction may change or is convertible, 

 and the conversion is demonstrable by experiment. || 



* Abegg : Zeit.fur Electro-Chem., 1899, v., 353. 

 t Ibid. J Ibid. Ibid. 



|j Kiister: Zeit.fur Electro-Chew,., 1897, iv., 105. 



