Theory of Electrolytic Dissociation. 289 



conductivity ; if the mobilities are high, it is possible that a 

 small value would be enough. In any case, such obser- 

 vations may be explained by association of the non-ionized 

 solute molecules, or by the existence of complex ions. 



Summing up the results of our inquiry as far as we have 

 gone, we may say that, in those cases for which the theory 

 indicates exact relations, the experimental evidence is in 

 favour of their existence, while all discrepancies are either 

 suggested by the theory itself, or else occur under conditions 

 where the experimental knowledge is too fragmentary for 

 valid conclusions to be drawn. 



We must now turn to other deductions from the theory, 

 towards which considerable criticism has lately been directed. 

 In the first place, the mass law of chemical action, which can 

 be established therm odynamically for dilute systems, has been 

 applied to electrolytic dissociation by Ostwald with complete 

 success in the case of aqueous solutions of weak acids; but 

 the law fails when applied to strong acids and other highly 

 ionized electrolytes, and this failure has been regarded 

 as one of the great objections to the dissociation theory. 

 It is probable, however, that the explanation is to be 

 sought in that difference in the law of the variation of the 

 force with the distance which we have already pointed 

 out must exist between solutions containing non-ionized 

 bipolar molecules and those containing dissociated electrified 

 ions. The thermodynamic basis of the mass law is only 

 valid for dilute systems, and, as we have seen, even at small 

 concentration, the forces between dissociated ions may be 

 quite sensible and produce disturbing effects. 



The dissociation theory has also co-ordinated the electrical 

 ionization of aqueous solutions and the coefficients of chemical 

 activity. There is no such definite theoretical deduction of 

 this relation as of that between the conductivity and osmotic 

 effects ; the connexion of electrical ionization with chemical 

 activity is a matter of observation, and the conclusion that, 

 in the rapid chemical actions characteristic of electrolytes. 

 it is the ions which alone are active, rests on the evidence of 

 this connexion alone. The numerical relations given by 

 Arrhenius, and the many deductions from this hypothesis 

 which have been verified for aqueous solutions, have led to 

 the idea that a similar explanation of the nature of all rapid 

 chemical action might be given, whatever the solvent and 

 whatever the conditions. There seems, however, no valid 

 theoretical reason which necessitates such an extension, and 

 it is possible that, in other solvents and for gaseous systems, 



Phil. Mag. 8. 6. Vol. 5. No. 26. Feb. 1903. U 



