iCEEDINGS OP Tin: AMKIl! UJEMT. 



tlii- calculation is correct for Bolutiona more dilate than tenth normal, 1 ' 

 at Least we may say that the conductivity data furnish the only mea 



h.tr, at present for calculating the ion concentrations. Every other 

 method which has been employed measures not the concentrations, l>nt the 

 activities qj th ions. 



According to equation XXIII the activities of the undissociated acid 

 and the ions are coimected by the equation, 



fiafa 



ruci 



= K 



If therefore the mass law is false, it must be because the activity is not 

 simply proportional to the concentration for one or more of these three 

 substances. The problem, therefore, is to determine how the activity of 

 the undissociated substance and the activity of the ions vary with the 

 concentrations of both. It seems that all the facts which arc at present 

 known concerning electrolytic dissociation can be explained by the 

 imption that the ions are normal in their behavior; in other words, 

 that the activity of each ion is simply proportional to its concentration, 

 but that the undissociated portion of a strong electrolyte is abnormal in 

 its behavior, the activity being proportional to the concentration of the 

 ondissociated substance multiplied by a quantity which depends solely 

 on the total ion concentration, and increases with the latter. 18 



This simple statement sulhces to explain qualitatively all the known 

 anomalies of strong electrolytes. The exact quantitative formulation 



this principle can hardly be made until still more experimental 

 work has been done. 



However, these considerations illustrate the method of treating 



nica] equilibrium when the ordinary mass law fails ; in other words, 



when for one or more of the reacting substances the activity is not 



proportional to it- concentration. For*a complete analysis of sucha 



e it is necessary to know how the activity of each of the reacting 

 substances changes with its concentration and with the concentration 

 of the other substances present. 



17 The data upon which this paragraph i> based are chiefly those contained 

 in tin- very complete and instructive Bumtnary by A. A. Noyes, entitled, " The 

 Physical Properties of Aqueous Salt Solutions in Relation t<> the Ionic Theory." 

 (Technology Quarterly, 17. 298, 1904). 



18 Probably, strictly Bpeaking, the activity of the ions is likewise a function 



onc< nrration of the undissociated Bubstance, decreasing a- the latter in- 

 creases : lint since the concentration of the undissociated substance always is very 

 11 in dilute solutions of strong electrolyte-, its influence on the activity of the 

 ions is therefore of minor importance. 



