114 



BUTLER 



ART. D 



invariable composition, is a maximum or a miaimum, for 

 constant pressure, when the two phases have the same com- 

 position. Examples of this behavior are shown in Figures 



% lodobenzene 

 Fig. 3 



100 



V 10 9 Q 7 6 5 4 3 2 

 Composition of solution ( Hz o/ FeCli) 

 Fig. 4 



3 and 4. Figure 3 shows the compositions of the solutions and 

 mixed crystals of bromobenzene and iodobenzene which are in 

 equilibrium with each other (at constant pressure) at different 

 temperatures. The composition of the two phases is the same 



