JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. VIII MAY 4, 1918 No. 9 



CHEAIISTRY. — Crystals of harium disilicate in optical glass. 

 X. L. BowEN, Geophysical Laboratory. (Communicated by 

 J. C. Hostetter.) 



In optical glass of the variety known as ''barium crown," 

 and especially in those types rich in barium, there frequently 

 form in the melting furnace numerous six-sided crystal plates 





-.,4 



"■■^-^ 



P'iG. 1. Fragment of barium crown glass showing crystals of BaSi205 with 

 "frayed" edges. (Natural size.) 



upwards of 3 mm. in diameter. These crystals are colorless and 

 transparent in their central portions but are surrounded by white 

 opaque rims that render them verj^ conspicuous (see photograph, 

 fig. 1). A piece of glass containing these crystals, with their 



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