831 



4. Coexistence of Solid by the Side of Fluid Phases. 



When the curve8 CD and EF in fig. 3 represent projections of 

 binodal lines of a plait on the ifvsurface, the 

 ,; — .I'-plane is divided into six regions by the 

 nodal-lines AB and the tangents to the binodal 

 lines in A and /i. When also a solid phase 

 S coexists with A and B, the point repre- 

 senting the solid phase can lie in each of these 

 regions. Then the rules of § 2 easily give the 

 course of the binodal line through A and B 

 for fluid phases existing by the side of solid 

 for each of these cases. When the solid substance is the second 

 component, the most frequently occurring situations are those of the 

 regions 2 and 1. The first case is represented in fig. 4a, the second 

 in fig. 5a; the plait has been assumed to be stable for both, i.e. 

 to lie on the convex-convex part of the t|?-surface (seen from below). 



Fig. 3. 



Fig. la. Fig. 5a. 



The points A and B are, therefore, elliptical, and the rules of § 2a 

 determine the situation of the binodal line for fluid phases coexisting 

 with solid in the two points, as it has been indicated in figs. 4a 

 and 5a. These situations correspond to the /^-./--figures indicated in 

 figs. 46 and 5/;, in which the three-phase coexistence is again indi- 



m 



Fig. 46. Fig. 5ft. 



cated by ABS, and the two-phase legions are hatched ; the hatching- 

 lines indicate nodal lines. 



64* 



