34:2 P. Eskola — Silicates of Strontium and Ba 



num. 



Strontium oxide, SrO 1 *. — All the mixtures which 

 contained more SrO than 2SrO.Si0 2 , resulted in two 

 phases, 2SrO.Si0 2 and SrO, when heated at high 

 temperatures. In these mixtures the strontium oxide 

 could always be identified from its isotropic character 

 and high index of refraction. 





Fig. 5, 



P 



ex. 



a 



Fig. 5.— Crystals of 2SrO.Si0 2 . 



Pure SrO was prepared in two ways, from strontium 

 carbonate and from strontium nitrate. In the first case 

 it forms minute rounded, though clear grains. When 

 these were held 4 hours at 1580° they reacted slowly with 

 water and even with HC1. From nitrate the oxide may 

 be obtained as large clear crystals showing a perfect 

 cubic cleavage. 15 



The determination of the index of refraction was very 

 difficult, because the oxide instantly reacts with the high 

 refractive liquids containing iodine. It was found to be 

 somewhat higher than 1.86 for all the colors and may be 

 very roughly estimated at 1.87. 



15 See also G. Briigelmann, Z. anorg. Chem., 10, 415, 1895. 



