352 P. Eskola — Silicates of Strontium and Barium. 



The density at 4° was determined to be 4,399. 



The melting point of BaO.SKX is, according to Jaeger 

 and Van Klooster, 1604 ±0.5°. 



To find ont whether the barinm metasilicate conld be 

 inverted into some other form I heated a sample of the 

 crystallized compound, first alone and a second time with 

 one-fifth of its weight Ba(V0 3 ) 2 , over night at about 

 1100°. No change took place. 19 



Eutectic BaO.Si0 2 -2BaO.Si0 2 . — A mixture of these 

 compounds, containing 75 per cent BaO, gave at 1546° 

 crystals of both kinds, but at 1556° only crystals of 2BaO. 

 Si0 2 and glass. From this it may be concluded that 

 there is a eutectic at about 74.5 per cent BaO with a melt- 

 ing point of 1551 ±6°. 



No other compounds except the two named above occur 

 in this part of the system. 



Barium ortho silicate, 2BaO.Si0 2 . — Barium orthosili- 

 cate appears as a granular mass of rounded grains and 

 does not show any cleavages or twinning. The melting 

 point is higher than that of platinum. 



a (D) = 1.810 ± 0.005; y(D) =1.830 ± 0.005. 



Barium oxide, BaO. — Mixtures of barium orthosilicate 

 and barium oxide were not studied more closely. The 

 fact that all the mixtures containing an excess of BaO 

 over the orthosilicate ratio attack platinum, seems to 

 prove that they contain free BaO. 20 



Coarsely crystalline barium oxide was prepared from 

 barium nitrate by heating slowly in a graphite crucible. 

 It was obtained in clear translucent crystals showing 

 cubic cleavage. 



The refractive index is very high, but difficult to deter- 

 mine; the substance absorbs moisture from the air 

 almost immediately when exposed and also attacks the 

 high-refractive media (in this case mixtures of sulphur 

 and selenium). I found (in red light) : 



n = 2.16 ± 0.05. 



Briigelmann has determined the specific gravity of 

 barium oxide as 5.722. 



19 Jaeger and Van Klooster (loc. cit.) were not more successful in their 

 attempt to effect a change by heating 0.5 g. barium metasilicate with 1 g. 

 sodium tungstate at 860° for 72 hours. 



20 Barium oxide attacks the platinum in the same way as strontium oxide, 

 but still more strongly. 



