﻿Molecular Thermodynamics. 617 



Our final " experimental " expression for yjr, in terms o£ 

 " true" concentrations, is 



* = M ' [^K+Rf Idlog (1 + roC)] 



«^c = o 



m 

 f^log(l + mC)J] + Mo'G, (37) 



+ 



0=0 



where G has some form 



G = BSfc'/.O* V ) (38) 



The " general " terms in the original equation (3) were 

 M G'— -that is, M</G"; so that the quantity 



ilv Sl or 2w,i — ; , X-j^-da 8l . . (39) 

 c=o 



in 



*. f SG '' 



has passed from " general " to " linear " terms in yfr ; or, i 



-^ , the quantity 



G 5l "-G,= ( S(V^ S1 (40) 



J c=o 



We may recall at this point equation (22), which is now 

 G„-G, '=f Si^G. ", (41) 



^0 = 



and note that, disregarding (more or less fortuitous) can- 

 cellation, the condition for the vanishing of (40) and (41) is 

 qualitatively the same, viz., that G" shall be independent 

 of the extent of solvation of the solute (s) — an obvious 

 particular case being " Perfect Solution," where G" 

 vanishes. 



The lack of practical significance in such a qualitative 

 statement is illustrated and emphasized when we observe 

 that quantitatively the condition is very different in the two 

 cases. The two differences (40) and (41) are, in fact, 

 complementary parts of the quantity 



S^GVWO/'-G,/), .... (42) 



