Yol. 65.] WITH POEPHYKITIC LABEADOEITE-CEYSTALS. 



93 



In fig. 2 a the perpendicular lines signify the temperature; 



T a , T b , and T c arc 







Fig. 



2«. 









the melting-points 



1 









of a, b, & c. For 



T 1! 









the binary com- 



±a 



r-~^ vl 







-A % 



binations a :b,a:c, 

 and b : c (see fig. 





\">\. 



^\A-&^^ 









2 a) we have the 

 curves of solidifi- 













cation T a Ea-t, 







X s / / 









T h — E a _ b , etc., as 







. Vfl, / 









well as the binary 





\ lc if 









eutectics E a _ b ,E a _ c , 







/>4- c 









and E b _ e . For the 





-^a-c^x^ 









ternary combina- 







"N // 









tion a :b : c we 







Ea-b-c 









have the surfaces 













of solidification, 















T a E a - b Ea-b-c 















— E a _ c , etc., which 













h 



cut each other in 



a 











the'eutectic curves' 











E a .. b — Ea-b-c, etc. 











The point of inter- 











section of the three 











surfaces of solidi- 











fication, namely 



i 



Fig. 2b. 







the ternary eu- 

 tectic point E a - b - c , 

 shows a lower 



a 



Ea-h 





,h 



temperature than 





1 





/O 



the lowest of the 



\ * — 



\ P ~^ 







three binary eutec- 





" 



a 







tics E a . b , E a - C , and 

 E b - C . 



We may now 





V 



Ea-b-c / 







follow the pro- 











cess of crystalliza- 











tion of a ternary 



■va-c\ 



/A b-c 







solution consisting 







of a, b, & c, and 











having a composi- 











tion P. We are 

 assuming that no 

 supersaturation 

 takes place. 





c 







On cooling down 



to the point P 





T a E a -b Ea-b-c — 



E a _ c , a begins 



to separate out. 



By this separating- out of a, 



the 



relative pro 



portion 



between ■ b 



and 



c 



in 



the solution is not 



