630 Mr. Bernard Cavanagh on 



and for solvent-separation data \_cf. (35) and (34-)] 

 P _LAT_/i_ 1\ Ap _ _ 



(82) 



Now in the nomenclature of G. N. Leu is, as will be clear 

 from (42), we could write 



P^ = 2{ (const.) -R log c 7 } . . . (83) 

 on 



for a completely ionized electrolyte, this being simply the 

 equivalent of LewisVdefinition of 7 in this case, and 7 being 

 what Bronsted calls the " stoichiometric activity coefficient " 

 of an ion. 



Comparing (81) and (83) we find 



logy- |f «* (84) 



But Lewis and Linhart * have recently shown as a purely 

 empirical fact derived from the most accurate data then 

 available, that this form B<^ is actually the limiting form of 

 log 7 for uni-univalent strong electrolytes in very dilute 



solution I below T^n). This seems to be rather striking 



confirmation both for Milner's calculation of %%r<j)(r) and 

 for the "complete ionization" theory. 



It will be very interesting to test Milner's calculation 

 more closely by obtaining the experimental value for u' 

 itself. 



If (and only if), as we have assumed, the general terms in 

 the expression for Y can be neglected in comparison with 

 those in U t> then, as we have seen [equation (69)] 



that is, at a given concentration (c) by (82) 



.a. 





g^ W — 2 6 ' 3 * J2 ' ("^ 



and by (84) 



oT 



log 7 = 1^.^; (86) 



* Journ. Amer. Ohem. Soc. xli. p. 1951 (1919). 



t This assumption requires that the pressure coefficient of log y, when 



P 

 multiplied by ^, be negligible in comparison with the temperature 



coefficient of log y, and of this there can be little doubt. 



