CHEMICAL THEORY OF SOLUTIONS. PART T. 



25 



of the pure compound, and it is quite clear that 



K 



>o- 



s. 



For example, for the binary compound «SiSo K is less 



and for the compound 3i„S2 



4 

 K is less than -^. 



When the solid is a com- 

 ponent, we have by (14), 



C, = K. 



In a binary system this is 

 represented by a point on 

 the line of composition (Fig. 

 5, A). In a ternary system 

 the equation is represented 

 by a straight line parallel to 

 one of the axes of composi- 

 tion (Fig. 5, Bj ; while in a 

 quaternary system, by a plane 

 parallel to one of the planes 

 of the tetrahedron of com- 

 position (Fig. 5, C). 



When the solid is a 

 binary compound, then we 

 have 



c;'^ a^"- = K. 



In the case of a binary system 

 this becomes 



than 



Ö, 



