( '<»2 ) 



'immediately, after total diiferentiation with respect to .i' (7' constant) : 



du„ da, du. 



■ - -J-" + r, -^' + r, ^^ = . . • . . . (2) 

 d.r d.v dx 



And from (1) and (2) follows, that when n,^-n^z^^\:v^{\.Q. ,r = 0), 

 we ha^■e necessarily 



§^" = (3) 



dx 



So the becoming zero of -f-^ is the priinary moment, on account of 



fdT\ 

 which also — I will have to be in the presence of a solid phase: 

 \dx y„ 



with change of x (with Avhich also « changes) tJie mol. jiotential 



of the unsplit compound does, namely, not change when x:^0. [This 



property will evidently also continue to hold for an arbitrary number 



of splitting products]. 



fdT\ . . .,. . 



That now also | — \^0,io\\o\\&ivom.i\iQ condition of equilibrium: 



— fX + f*o = 0, 

 when fi is the mol. potential of the solid phase. Total differentiation 

 with respect to T yields viz. : 



d d dx 



T;7, {— F + f^o) + -J- (— l^ + f^o) 777, = 0, 



dl dx dl 



d / d è da\ d / d Ö du\ 



in which -T-, IS agam Utt, + ^ 777-, , and —=— + —----. 

 dl \dl Oadljj. dx \ax dadxjT 



But -;;;(— f^ + Mo) =^ — 777. when Q is the total heat of melting, 

 dT J 



hence also : 



T '^ dx dT~ ' 

 because n (in the solid phase) is independent of x. Hence : 



y d[i, 



dT dx 



(4) 



dx Q 



dn^ dT 



So if — = 0, also -— = 0, and in tiiis way the proposition is 

 dx d'V 



proved. When in the liquid phase there is no excess of one of the 



products of dissociation, but instead an indiiferent substance, then 



there are four kinds of molecules, with molecular quantities resp. : 



1 — a , v,a , v„K , X. 



