344 P. Eshola — Silicates of Strontium and Barium. 



Solidus of the solid solutions Ba0.2Si0 2 -2Ba0.3Si0 2 



58 42 71 29 1418 60 Crystals 



58 42 71 29 1424 60 Mix crystals with little gls 



60 40 42 58 1435 60 Mix crystals and glass 



60 40 42 58 1431 60 Mix crystals 



61.25 38.75 23.9 76.1 1443 60 Mix crystals and glass 



61.25 38.75 23.9 76.1 1440 60 Mix crystals and glass 



61.25 38.75 23.9 76.1 1438 60 Mix crystals 



Melting point of 2Ba0.3Si0 2 . 

 62.90 37.10& 1451 60 . Glass 



62.90 37.10 1451 30 Glass 



62.90 37.10 1448 30 Glass and 2Ba0.3Si0 2 



Eutectic 2Ba0.3SiO,-BaO.Si0 2 

 65 35 1439 15 Glass 



BaO.SiOo and 2Ba0.3Si0 2 

 30 with a little glass. 



30 BaO.SiO, and 2Ba0.3SiO,. 



15 2BaO.SiO, and glass. 

 15 2BaO.Si0 2 and BaO.SiO, 



From these determinations results the equilibrium 

 diagram tig. 6. A part of it is given on a larger scale in 



The liquidus curves of cristobalite and tridymite in 

 this binary system were, by means of a few quenchings, 

 shown to have the same general character as in the 

 system SrO-Si0 2 , and were not investigated any more 

 closely. 



The eutectic tridymite-BaO .2SiO 2 . — The mixture con- 

 taining 47.5 per cent BaO was found to be very close 

 to the eutectic composition, and on the tridymite side of 

 it. The eutectic composition was placed at 47 per cent 

 BaO, 53 per cent Si0 2 and the temperature at 1374°. 



Barium disilicate, Ba0.2Si0 2 , has previously been 

 studied by N. L. Bowen. 18 Crystals of this composition 

 were found in optical glass of the variety known as 

 "barium crown." They had the shape of platy elon- 

 gated hexagons (fig. 8a), about 3 mm long, 2 mm wide, 



65 



35 



1435 



65 



35 



1431 

 Eutectic Ba( 



75 



25 



1556 



75 



25 



1546 





a — Ba0.2Si0 2 



b — 2Ba0.3SiO 



1S N. L. Bowen: Crystals of barium disilicate in optical glass. J. Wash. 

 Acad. Sci., 8, 265, 1918. Cf. also N. L. Bowen: Devitrification of glass, 

 J. Am. Ceram. Soc, 2, 261, 1919. 



