440 Andersen — System Anorthite-For sterile-Silica. 



eutectic composition, therefore, gave only approximate results. 

 Breaks were recorded at about 1230°, in two of the mix- 

 tures. The exact determination of the eutectic temperature 

 was based on quenchings of mixtures which also were used for 



Fig. 10. 



SiO 



the location of the eutectic composition, 

 are listed in Table 4. The results were : 



These quenchings 



Eutectic temperature : 1222° db 2°. 



Eutectic composition : An 50-5 ; En 23'6 ; SiO a 25-9.* 



The boundary curves. — The general slope of the boundary 

 curves (saturation curves) could, of course, be roughly inferred 

 from the determined quadruple points and quintuple points. 

 The more accurate determination was based on quenchings of 



* An 50-5: Fo 16'5 ; SiO a 33. 

 Si0 2 61-90 ; A1 2 3 18-51 ; CaO 10-15 



MgO 9-44. 



