34:0 P. Eskola — Silicates of Strontium and Barium. 



same form of SrO.Si0 2 , as rounded crystal grains and 

 with no euhedral forms. 



To prevent the formation of orthosilicate in the stron- 

 tium chloride melt I finally heated SrO.Si0 2 with SrCl 2 

 and a considerable excess of silica, added in the form of 

 coarse quartz grains, which dissolved rapidly in the melt 

 above a gas burner. This mixture, held over night at 

 about 1000°, gave well-developed crystals of the same 

 form of SrO.Si0 2 . The identity, as in all the other cases, 

 was ascertained by determination of the refractive 

 indices. 



Thus all the experiments failed to show any other form 

 of SrO.Si0 2 than the one similar to the pseudowollas- 

 tonite. 13 



The eutectic SrO.Si0 2 -2SrO.Si0 2 was located at 65.5 

 per cent SrO, as is apparent from the diagram (fig. 1). 

 The steep slope of the liquidus curves at both sides is 

 remarkable. While in the 65 per cent SrO mixture the 

 primary phase is SrO.Si0 2 , it is 2SrO.Si0 2 in the 67 per 

 cent SrO mixture, and the liquidus has risen 60° above 

 the eutectic temperature, 1545°. 



The existence of 3Sr0.2Si0 2 not proved. — The primary 

 phase in all the mixtures between the eutectic at 65.5 per 

 cent SrO and 2SrO.Si0 2 is strontium orthosilicate. The 

 following experiments were carried out in order to es- 

 tablish whether there might be formed the compound 

 3Sr0.2Si0 2 , analogous to 3Ca0.2Si0 2 , known from the 

 studies on the calcium silicates. 



Strontium carbonate and quartz powder in the propor- 

 tion required to form 3Sr0.2Si0 2 (72 per cent SrO), well 

 mixed together, were held 2 hours at 1475° and quenched. 

 The product consisted of SrO.Si0 2 and 2SrO.Si0 2 . 

 Another time the charge was allowed to cool slowly. The 

 result was the same. 



The same mixture was heated 16 hours at 1150°. It 

 was now so fine-grained and poorly individualized, that it 

 could not be decided whether there were one or two 

 phases present. Neither SrO.Si0 2 nor 2SrO.Si0 2 could 

 be identified. 



13 Jaeger and Van Klooster (op. cit., p. 903) heated 0.5 g. of pure SrO.SiOo 

 with 1 or 2 g. of sodium tungstate at 860° during 72 hours and always 

 obtained the same form as by direct crystallization from a melt, whether 

 they had started with crystals or with glass. 



