Chemistry, — "In-, mono- and divariant equilibria". XVI II. 



By Prof. SCHREINEMAKERS. 



(Communicated in the meeting of October 27, 1917). 



Equilibina of n components in n phases at constant temperature. 



In the considerations of the previous comrniinication XVII we 

 have changed the temperature under constant piessure, now we 

 shall change the pressure, while the temperature remains constant. 

 Then we find similar pi-operties as in the previous communication, e.g. 



"In an equilibrium of n components in n phases at constant T 

 the pressure is maximum or minimum when a phase-reaction may 

 occur between the pliases". 



"Wlien at constant T the pressure on the turning-line is a 

 maximum (minimum), then from this turning-line two leaves of the 

 region go towards lower (higher) pressures and no leaf towards 

 higher (lower) pressures". 



We see that the figs. 2 [XVI], 4 [XVI] and 7 [XVI] are in 

 accordance with this. 



We call the equilibrium E, which occurs under the maximum- 

 or minimumpressure Pf( again E/^ and the equilibria which occur 

 under Pp -\- AP [AP]>0 when Pp is a minimum, AP <^ when 

 Pp is a maximum] again E' and E". The rules a, b, and c. 

 which have been deduced in the previous communication now apply 

 again to the position of those three equilibria with respect to one 

 another. 



In order to examine whether the pressure is a maximum or 

 minimum, we can use again formula 15 [XVII]; this now becomes 



2{XV).AP=^:S{Xd*Z) ...... (1) 



Herein is : 



2{X V) = K \\ -f ;i, F, -f . . . -f i,^ Vn 



consequently the change in volume, which occurs at the reaction: 



A,i^, -f ;.i^. -f . . . -f ;„i^„ = 



Just as in the previous communication also novA^ we may apply 

 this formula (i) to special cases. 



