The Ternary System, MgO-Al 2 3 -SiO„. 



321 



Table 22 (continued). 



Quenchings showing the characteristics of aggregates of the a- and 

 //-ternary compound. 



Composition Weight Per cent Temp. 



Phases 



MgO 



A1 3 3 



Si0 2 









1100 



a + ? 









1350 



a + MgO.ALA ( ?) 



124 



31-6 



560 



1000 

 1100 

 1425 

 1435 



a 



a + tr. AL0 3 .Si0 2 



15-0 



27-0 



58-0 



950 

 1100 



Not homogeneous 

 Not homogeneous 



100 



300 



600 



1100 

 1170 

 1400 



fj. (a little cloudy) 



a+ 1 



10-4 



26-6 



630 



1100 

 1250 

 1350 • 

 1400 



ti 4- a + AL0 3 .SiO, 

 a + AL0 3 .Si0 2 + ? 

 a + AL0 3 .SiO, + SiO, ( ?) 



110 



23-0 



660 



1400 

 1425 



<x4- ? 



a+ 1 



9- 



240 



67-0 



1400 



a+ ? 



Fig. 4. 



Fig. 4. General relations as in fig. 6. In the area A-A-A-A crystals have 

 composition A' and the crystallization curves are straight lines. In the other 

 parts of the field, because of solid solution, the crystallization curves are not 

 straight lines, and crystals at C, E, etc., have compositions C, E', etc. The 

 maxima are between the arrows. 



Fig. 5. 



fe 



Fig. 5. General relations as in fig. 4 except that solid solution is more 

 extensive. 



