ON THE HALOGEN HYDRIDES AS CONDUCTING SOLVENTS. 153 



(2) Combination between the solute and the solvent does not occur, but an ionising 

 polymer of the solute is formed. In this case the equation is 



A B B,,, 

 the active masses are 



a and c, 

 and from the law of mass action 



lea* = k'c and c - Ka", 

 which leads to the same expression as before, namely 



K = KV, p = aKV-', and *V" = K'. 



Now, since the number of molecules always increases with dissociation, must 

 increase with dilution in whatever manner dissociation takes place ; but unless the 

 increase in a is greater than the diminution in a"" 1 which is brought about by 

 dilution, the sum of the effects due to the variation of a and of a"' 1 in the equation 



/,-! 



p = aK'a* 



must produce a diminution in p. with increasing dilution. 



It follows, therefore, that the molecular conductivity may decrease with dilution 

 in the case of any conducting solution in which the electrolyte is a compound of two 

 or more molecules of the dissolved substance, whether it is a simple polymer or a 

 compound containing one or more molecules of the solvent. 



It follows, also, from the equation 



K = aK'a n 



that in the case of a solution in which the ionic dissociation was approaching 

 completion, in which a therefore varied but slightly, the specific conductivity of the 

 solution should be very nearly proportional to the n th power of the concentration of 

 the dissolved substance ; for such solutions we therefore have the relation 



JL = ,cV" = K'. 



Although we have shown that it is not necessary that union with the solvent 

 should occur in order to bring about an abnormal variation of p, we nevertheless 

 consider that the formation of such compounds* affords the best explanation of the 

 behaviour of solutions of organic substances in the halogen hydrides and in 

 sulphuretted hydrogen. 



* See also WALKER, 'J. C. S.,' 1904, vol. 85, p. 1082, and WALKER, MC!NTOSH, and ARCHIBALD, 

 'J. C. S.,' 1904, vol. 85, p. 1098. 



VOL, CCV, A, X 



