306 Shepherd, Rankin, Wright— Binary Systems of 



eutectics with the exception of 3Ca0.5Al 2 3 — A1 2 3 can be 

 precisely located by means of the thermoelement. The study 

 of this system with the microscope shows seven phases in 

 addition to the two components. The phases are CaO.Al 2 3 , 

 5Ca0.3Al 2 3 , 3CaO.Al 2 3 and an unstable form of both 

 3Ca0.5Al 2 3 and 5Ca0.3Al 2 3 . The equilibrium diagram 

 is shown in fig. 6. 



Fig. 6. 



1700 c 



1600 c 



1500 c 



1400° 



\.A 



\ 



\ 

 \ 



\ 



\ t 



1 

 1 • 



/ 



/ 



/ 

 / 



/ 



- _ 



P R 



1 



6 n » » 



\ / 



^ / 



' ' 







1 1 1 







s » . • 



M 





•1 



c 



E 1 ' 



CaO 



iCaO.Al 2 Os 



CaO.Al 2 3 



A1 2 £ 



5Ca0.3Al 2 : 



3Ca0.5Al 2 3 



The approximate melting temperature of lime is not known, 

 except that it melts in the arc. The optical and other prop- 

 erties were given in the lima-silica paper to which reference 

 has been made. 



There is no eutectic between lime and the first compound, 

 3CaO.Al 2 3 , at 37*78 per cent of alumina. The compound 

 being unstable at its melting point, the liquidus must show a 



