:;os 



Rankin and Merwin — 



Part of the melting temperatures of all the other fields, 

 except the field of MgO, may be thus determined. Tables 

 8-13 show these ascertained melting temperatures for 

 various compositions within each field. From these 

 temperatures and others referred to later the iso- 

 therms of fig. 6 were drawn. 



Table 8. 



Quenchings which determine melting temperatures of various compositions 



within field A-6-4-3-7-B; Primary phase is (MgO.AL0 3 ) spinel. 



npositio 

 MgO 



u Weight 

 ALO, 



Per cent 

 Si0 2 



Temp. 



Time in 

 hours 



Phases present 



17-5 



42-5 



400 



1600 



■25 



Glass -|- tr. spinel 



25-0 



320 



43-0 



1583 



•5 



Glass 



290 



23-0 



48-0 



1570 

 1450 



■5 

 .5 



Glass -j- spinel 

 Glass 



20-0 



30-0 



500 



1430 

 1450 



•5 

 ■5 



Glass -4- spinel 

 Glass 



250 



250 



50-0 



1435 

 1410 



•5 

 •5 



Glass -4- spinel 

 Glass 



26-0 



23-0 



510 



1390 

 1380 



•5 



10 



Glass -4- spinel 

 Glass 









1376 



1-0 



Glass -f- spinel 



Table 9. 



Quenchings which determine melting temperatures of various compositions 



within the field G-6-4-5-F; Primary phase is 2MgO.Si0 2 . 



npositio 



n Weight 



Per cent 



Temp. 



Time in 



Phases present 



MgO 



AL0 3 



Si0 2 





hours 





350 



200 



450 



1555 



•5 



Glass 









1550 



■5 



Glass + tr. 2MgO.Si0 2 



350 



15-0 



50.0 



1560 

 1530 



•5 



Glass -f tr. 2MgO.Si0 2 



260 



210 



53.0 



1375 



•5 



Glass 









1365 



■5 



Glass + 2MgO.Si0 2 



27-0 



180 



550 



1415 



•5 



Glass 









1390 



•5 



Glass + 2MgO.SiOo 



Table 10. 

 Quenchings which determine melting temperatures of various compositions 

 within field is F-5-1-E; Primary phase is MgO.SiO... 



Composition 

 MgO 



Weight 

 A1 2 0, 



Per cent 

 Si0 2 



Temp. 



Time in 

 hours 



Phases present 



25-0 



200 



550 



1375 



•5 



Glass 



24-0 



170 



590 



1365 

 1383 



•5 

 1-5 



Glass -f MgO.SiO, 

 Glass 



350 



50 



600 



1370 

 1515 



10 

 •5 



Glass 4- MgO.SiO. 

 Glass 









1510 



•5 



Glass 4- MgO.SiO, 



210 



180 



61-0 



1370 



•5 



Glass 









1360 



•5 



Glass 4- MgO.SiO,. 



25 



120 



630 



1440 



•5 



Glass 



300 



60 



640 



1420 

 1500 



10 

 ■5 



Glass 4- MgO.SiO, 

 Glass 



250 



110 



640 



1498 

 1450 



.5 

 10 



Glass 4- MgO.SiO, 

 Glass 









1425 



•5 



Glass 4- MgO.SiO, 



