THE ELECTROLYTIC DISSOCIATION THEORY 397 



been said, how the objections might be met. In this connection 

 it will be most instructive to consider some of the points raised 

 by Kahlenberg, 1 as this investigator has collected a wealth of 

 excellent experimental material with the object of showing 

 that the theory in its present form is untenable. Some of the 

 difficulties of the theory are also enumerated by Armstrong 

 in his article on " Chemistr} 7 " in the Encyclopaedia Britannica. 



One point very often made is that the law of mass action 

 does not hold for solutions of strong electrolytes. In the same 

 category is the observation that the values for the coefficient of 

 ionisation of many electrolytes, as calculated from conductivity 

 and from cryoscopic measurements, do not agree within the 

 limits of experimental error. With reference to the latter point 

 it must, in the first place, be borne in mind that cryoscopic and 

 conductivity observations can only be expected to give the same 

 results when ionisation is complete, and no complex ions are 

 present. This is clear from the consideration that, according 

 to the theory, the freezing-point depression depends upon the 

 number of particles present, whilst the conductivity depends 

 upon the number of ions, and if an erroneous assumption be 

 made as to the nature of the ionisation — if, for example, forma- 

 tion of complexes takes place and is not allowed for — the results 

 obtained by the two methods will be different, but that will not 

 be a valid argument against the theory. 



Various suggestions have been made to account for 

 the anomalous results obtained with strong electrolytes. 

 Jahn and Nernst 2 consider that the deviations from the law 

 of mass action are due to the mutual influence of the 

 ions and undissociated molecules, whilst other possible 

 disturbing causes are the formation of complexes and interaction 

 between the undissociated molecules or ions and the solvent. 

 With reference to the last point we have already seen (p. 382) 

 that caesium nitrate, which on other grounds is believed to 

 be only slightly, if at all, hydrated in solution, behaves in 

 complete accordance with the law of mass action. The pre- 

 sence of complexes has been definitely proved in many cases, 

 and as all these effects may play a part, the question becomes 

 a very complicated one. 



Cases where cryoscopic and ebullioscopic measurements 



1 Summary, Trans. Faraday Soc. 1905, 1, 42. 



2 Loc. cit. p. 389. Compare Arrhenius, Zeit. physikal. Chan. 1901, 37, 490. 



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