Ferguson and Merwin — The Ternary System. 97 



difficulty if solid solutions do not exist and the crystalli- 

 zation lines are straight lines, but if solid solutions exist 

 these lines which represent the changes in the composi- 

 tion of the liquid in a charge during crystallization are 

 curved, and since their curvature is often difficult to 

 determine, in this case the method may be quite uncertain. 

 In the ternary system under investigation there is much 

 solid solution and for this reason most of the charges 

 which were used for this part of the study lay close to 

 the boundary lines in composition. The experimental 

 results of this study are given in Table II. 



Table II. 



Quenches which determine the melting temperatures along the boundary lines. 



Time 

 Composition wt. t Temp. in Phases present Boundary 



CaO MgO Si0 2 °C. min. 



32 6 62 1361 15 Glass + aCaO.SiO, + Si0 2 1, 16, 15, E 



1370 15 Glass + aCaO.SiO, 



1339 15 Glass + aCaO.SiO, + SiO, 



1334 20 Glass -f /3CaO.SiO, + SiO, 



32 7 61 1331 20 Glass -j- /3CaO.SiO, + Si0 2 



1337 20 Glass -+- a CaO.Si0 2 

 31 7 62 1343 20 Glass -j- Si0 2 



1338 20 Glass + SiO., + aCaO.SiO, 



23 14-5 62-5 1370 20 Glass -j- trace Si0 2 1, 2 



1365 25 Glass + trace Si0 2 + 



CaO.MgO.2SiO, 



25-25 12-5 62-5 1352 20 Glass -f CaO.MgO.SiO, 



1350 20 Glass + CaO.MgO.2Si6, + Si0 2 



28 10 62 1349 30 Glass 



1338 20 Glass -f SiO, + CaO.MgO.2SiO, 



31 9 60 1326 15 Glass + CaO~.MgO.2SiO, 1, 3 



1321 15 Glass + CaO.Mg0.2Si0 2 + 



5Ca0.2Mg0.6Si0 2 



32 8 60 1340 20 Glass -f trace CaO.MgO.2SiO, 



+ trace 5CaO.2MgO.6SiO, 



33 10 57 1352 30 Glass 



1350 20 Glass -f 5CaO. 2Mg0.6SiO, -f 



CaO.MgO.2SiO, 



35 11 54 1353 20 Glass -f 5CaO.2MgO.6SiO, -f- 



CaO.Mg0.2Si0 2 

 1356 25 Glass + 5CaO.2MgO.6SiO, 

 38 11 51 1361 30 Glass + (trace aCaO.SiO,)* 



+ 5Ca0.2Mg0.6Si0 2 

 + trace CaO.Mg0.2Si0 2 1, 3 



36 12 52 1368 25 Glass + aCaO.SiO, 13, 14, 15 



1363 25 Glass + aCaO.SiO, + 



5Ca0.2Mg0.6Si0 2 

 32 8 60 1344 Glass + aCaO.SiO, 



36 12 52 1368 Glass -f aCaO.SiO, 



(See also quenches 1, 3 above) 



* aCaO.Si0 2 is here unstable. 



Am. Jour. Sci.— Fourth Series, Vol. XLVI1T, No. 284.— August, 1919. 



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