182 Ferguson and Merwin — The Ternary System. 



2Mg0.6Si0 2 solid solution F ; the final glass has the com- 

 position of point 14. 



(8) Compositions represented by the area BSY will go 

 solid along the line 14, 16 and form mixtures of the wol- 

 lastonite solid solution B, and solid solutions of 5CaO. 

 2Mg0.6Si0 2 ranging from F to M. 



(9) Compositions lying within the region BBiMsMjY 

 will form mixtures of the wollastonite solid solution B. 

 silica, and the 5Ca0.2Mg0.6Si0 2 solid solution M; the 

 final glass has the composition of the point 16. 



(10) Compositions lying in the area MjM^lSNgNi will 

 crystallize along the line 16, 1 to form mixtures of silica 

 with solid solutions of 5Ca0.2Mg0.6Si0 2 ranging from 

 M to N. 



(11) Compositions represented by the area NjN^MR 

 will crystallize to mixtures of silica, diopside, and the 

 5Ca0.2Mg0.6Si0 2 solid solution N; the final glass has 

 the composition represented by point 1. 



(12) Compositions lying within the region NjRlSTC 

 will go solid along 1, 3 to form mixtures of solid solutions 

 of 5Ca0.2Mg0.6Si0 2 and diopside. 16 



Enough evidence to indicate the general character of 

 the solidus relations has been presented. The inversion 

 of pure wollastonite to pseudowollastonite has been 

 found by previous investigators to take place at 1200 °C 

 and we have confirmed this figure upon the pure sub- 

 stances. The reverse reaction, i. e., the inversion of 

 pseudowollastonite to wollastonite, we have never- 

 observed in the solid state except possibly in some 

 charges which had been crystallized at 900° C and in 

 which pseudowollastonite has first formed as an unstable 

 phase and later partly inverted to wollastonite at some- 

 what higher temperature. Wollastonite solid solutions 

 of the various kinds found by us in this system inverted 

 with slight lags, but in none of these compositions could 

 the reverse operation be induced to take place even by 

 heat treatments of 16 or more hours. Perhaps the pres- 

 ence of large crystals of pseudowollastonite which form 

 readily even in undercooled glasses is responsible for this 

 sluggishness. 



The melting interval of solid solutions is so well known 



16 Not strictly true as the area includes a small area which would crystal- 

 lize at 13 to form mixtures of akermanite, 5Ca0.2Mg0.6Si0 2 , and solid 

 solution R x of pseudowollastonite but which lying near T is too small to 

 show. 



