Ferguson and Merwin — The Ternary System. 167 



the fact that the low temperature forms readily invert to 

 the higher temperature forms but the reverse operation 

 does not take place in a reasonable time. The microsco- 

 pic determination of inhomogeneity was at times impos- 

 sible because of the similar optical properties of the crys- 

 talline phases present. In these cases the changes in the 



Fig. l. 



CrislobalLbt. 



BCaOSzOc 







aCa.O-SxX)^ \ 





1340i^ 



5CaO£MgO6Si0T^ 





1 . 



GxO-SiOt / 

 1540 .F% 



\g 



<^2. 



3(hDZSi0tlm5 { 



s? 





ZCaX)-5iO a / 



~V587 fsoo - 



<JiZ0 



7400- 



Pj /roxe nes\^_J "~\ ffqO-5jjO e 



'' >890 



GxOfljO- 



2570 



■Boundaries , Isotherms determined, Isotherms by eytrapo/atic 



-t— 1--4.,|^ Solid solutions 



O Compounds 



Vfro 



Tig. 1. The triangular concentration diagram of the system CaO-MgO- 

 Si0 2 showing the location of the fields, the fixed points and their temperature 

 relations. 



inversion temperatures of the low-temperature forms 

 were assumed to indicate the extent of the solid solutions. 



Solid Solutions of CaO.Si0 2 with Silica. — The follow- 

 ing observations were made to determine the extent of 

 these solid solutions: 



(1) A charge with composition CaO 45, Si0 2 55, which 



