Ferguson and Merwin — The Ternary System. 103 



Table XI. 

 Quenches which determine the temperature relations at point 9. 

 Time 

 Composition wt. % Temp. in Phases present 



CaO MgO Si0 2 °C. min. 



33 24 43 1439 20 Glass + 2MgO.Si0 2 + CaO.MgO.Si0 2 



+ No 2CaO.Mg0.2Si0 2 

 1434 20 Glass + 2CaO.Mg0.2Si0 2 -f- 2MgO.Si0 2 



34 22 44 1439 30 Glass + 2CaO.Mg0.2Si0 2 + 



CaO.MgO.Si0 2 

 1434 35 Glass -f 2CaO.Mg0.2Si0 2 + 2MgO.Si0 2 



Point 10 is a quintuple point between periclase, a mon- 

 ticellite solid solution and a2CaO.Si0 2 . It has a compo- 

 sition CaO 37-3, MgO 22-3, Si0 2 40-3, and a temperature 

 1498 ± 5°C. 



Table XII. 

 Quenches which determine the temperature relations at point 10 



Time 

 Composition wt. % Temp. in Phases present 



CaO MgO SiO a °C. min. 



37 23 40 1494 20 Glass + 2CaO.Si0 2 + CaO.MgO.Si0 2 



1500 25 Glass -j- trace MgO + CaO.MgO.Si0 2 



38 22 40 1503 10 Glass -f MgO 4- 2CaO.Si0 2 



1498 20 Glass + 2CaO.Si0 2 -f CaO.MgO.Si0 2 



Point 11 is a quintuple point between periclase, f orster- 

 ite and a monticellite solid solution. Its composition is 

 CaO 32-1, MgO 26-4, Si0 2 41-5, and its temperature 

 1502 ± 5°C. 



Table XIII. 

 Quenches which determine the temperature relations at point 11. 

 Time 



Phases present 



Glass + 2MgO.SiO, + CaO.MgO.SiO, 



+ No MgO 

 Glass 4- MgO + 2MgO.Si0 2 

 Glass + 2MgO.Si0 2 -f CaO.MgO.SiO> 



No MgO 4- ? 

 MgO 4- ? 



Point 12 is a eutectic 40 between periclase, lime and 

 a2CaO.Si0 2 . Its composition and temperature are uncer- 

 tain since the latter lies above the working temperatures 

 of either of our furnaces and the rapidity with which 

 a2CaO.Si0 2 and periclase both crystallize precluded the 



40 See the discussion of the lime field following Table I. 



Composition 

 CaO MgO 



iwt. % 

 Si0 2 



Temp. 

 °C. 



in 

 min 



31-5 27 



41-5 



1499 



25 



32 26 



30 28 



42 

 42 



1507 

 1496 

 1500 

 1508 



25 

 15 

 25 

 15 



