322 



Rankin and Merwia — 



The Concentration-Temperature Solid Model. 



By interpolation from the foregoing melting tempera- 

 tures together with those for the binary systems MgO- 

 Al 2 O s , Al a 3 -Si0 2 , and MgO-Si0 2 which were obtained 

 from studies previously published, constant-temperature 

 lines or isotherms may be drawn. This has been done 

 for every 100° from 1400° to 1900° and the resulting 



Fig. 6. 

 Si0 2 



MgO-Si02 



2MgO-Si0 2 



1890 / 



•2MgO2Al203-5S02 



& 



Ai 2 03-SiO^ 



1816 



Mg6-Xl203 



-U 



MgO 

 2800 



AI2O3 

 2050 



diagram is given in fig. 6, which shows moreover the 

 melting temperature of each compound, component, 8 

 quadruple and quintuple point. Those isotherms repre- 

 sented by full lines (isotherms 1400°-1600°) are based on 

 accurate data, those represented by dotted lines (iso- 

 therms 1700° -1900°) are approximations based on data 

 largely obtained from extrapolation on the high melting 



8 The melting point of Si0 2 (cristobalitc) is taken from recent unpub- 

 lished determinations by J. B. Ferguson and H. E. Merwin. 



