30 Rankin and Wright — Ternary System CaO-Al.fi \-SiO^ 



VI. The field of 2CaO.Alfi z .SiO, {6-5-7-1 1-12-13-$.— 

 This field, whose boundaries lie wholly within the triangle, 

 possesses a maximum which is the melting point for the com- 

 position of the primary phase 2CaO.Al 2 3 .Si0 2 1590° ± 2°. 

 The melting temperatures of various compositions within this 

 field are given in Table IV. 



Table IV. 



Melting temperature of various compositions within field 6-5-7-11-12 13-4. 



Primary phase is 2CaO.Al 2 3 .Si0 2 (M. P. 1590° ±2°). 



I - + . CaO 



Composition ai ^ 



Wt. per cent ^ » « 

 klU 2 



of m^ltfog™ 1475 1430 1554 1558 1503 1394 1450 1515 1537 



Table IV — Continued. 



40 



35 



45 



40 



35 



30 



31 45 



35 



25 



30 



25 



30 



35 



40 



41-5 30 



40 



35 



35 



30 



30 



30 



30 



27*5 25 



25 



46*3 

 33-7 

 20- 



45 



35 

 20 



36 

 46 



18 



48*8 

 356 

 15-6 



45 

 40 

 15 



40 

 45 

 15 



47'6 



38' 



14-4 



47' 



39-4 



136 



40 

 50 

 10 



1548 



1569 



1571 



1490 



1529 



1564 



1495 



1490 



1537 



VII. The field of alumina (Alfi 3 ) (7-I-Alfi 5 -B-ll).—IJi 

 the preliminary report, a field was given between this field 

 and that for Al 2 Si0 5 for a compound of unknown composition 

 and properties. More careful study lias shown this supposed 

 new compound to be alumina. Most of the melting tempera- 

 tures within this field are too high for determination ; those of 

 certain compositions are given in Table V. 



Table V. 



Melting temperature of various compositions within field 7-I-Al 2 03-i3 r -ll. 



Primary phase is A1 2 3 (M. P. 2050°).* 



Composition 

 Wt. per cent 



CaO 



A1 2 3 



Si0 2 



14 



38-5 



47*5 



18-5 



39' 

 42-5 



20 

 40 

 40 



23-5 

 41*5 

 35- 



28-5 

 39-5 

 32- 



29 30- 

 40 42-5 

 31 27-5 



29 



50-5 



20-5 



Temperature 

 of melting 





1575 



1550 



1560 



1530 



1395 



1430 1475 



1550 



VIII. The field of calcium orthosilicate (Ca^SiO^) (B'-Jb.— 

 H-15-16-C). — Ca 2 Si0 4 occurs in 3 forms, two stable (a and ./?) 

 and one unstable ($') ; all 3 are found within the field. The 



* According to Kanolt, J. Wash. Acad. Sci., iii, 315, 1913. 



