P. Eskola — Silicates of Strontium and Barium. 339 



p 



<f> 



Observed 



Calculated 



Observed 



Calculated 



Limits Average 



0° 0' 

 49° 32' 

 55° 41' 

 66° 55' 



80° 20' 



30° 10' 





c (0001) 



p(10ll) 49° 10' - 49° 55' 49° 32' 

 o (4945) 55° 50' — 56° 2' 55° 56' 

 n (2021) 66° 32° - 66° 55' 66° 44' 

 t (5051) 78° 20' - 80° 50' 79° 17' 



30° - 



Axial ratio a : c = 0. 



symmetry that, judging only from the characters of the 

 rather poor crystals available, it should belong to this 

 class. 



Another question that arose from the similarity to 

 a-CaO.Si0 2 was whether SrO.Si0 2 would also appear in 

 more than one form. Several experiments were made to 

 settle this question. 



SrO.Si0 2 -glass was held one hour at 1020°. The result 

 was a crystallized mass showing radiating scaly crystals, 

 uniaxial, positive, o = 1.600 ± 0.003, e == 1.640 ± 0.003. 

 It is consequently identical with the crystals separating 

 from the melt. 



The same result was achieved when the glass was held 

 4 hours at 950°. 



SrO.Si0 2 was melted together with SrCl 2 in a Fletcher 

 furnace and allowed to cool very slowly. After dissolv- 

 ing the chloride in water to which finally was added a 

 little HC1 to decompose the chloro-silicate that had 

 formed, the result was the same form of SrO.Si0 2 as 

 before. 



The last-named experiment was modified so that the 

 SrO.Si0 2 -SrCl 2 -melt was left in the platinum resistance 

 furnace over night at about 1000°. The product was not 

 metasilicate at all, but strontium orthosilicate, which was 

 identified by its refringence and characteristic twinning. 



Now, imitating the method that Allen and White 12 

 found most effective in changing pseudowollastonite into 

 wollastonite, I prepared strontium vanadate, Sr(V0 8 ) 2 , 

 and melted one gram of this with two grams of SrO.Si0 2 . 

 The mixture was held over night at about 900°. After 

 washing away the vanadate, the mass consisted of the 



12 E. T. Allen and W. P. White, this Journal, 21, 89, 1906. 



