The silicates of strontium and barium

Abstract

Considering the wide occurrence of isomorphous sulfates and carbonates of Ca, Sr and Ba, the question rises: Do Sr and Ba under exptl. conditions form such silicates as are known in the case of Ca? For this study the purest SiO2, Ca, Sr and Ba carbonates obtainable were used. These substances were dried at 150°, weighed, mixed, melted if possible, chilled and crushed, then reheated and ground twice more. The equil. relations were ascertained by the quenching method. Heating curves were run in some cases for the purpose of checking the temp. measurements. Temps. were detd. by a potentiometer and a thermoelement calibrated against the m. p. of diopside and anorthite. Refractive indices were detd. by the improved immersion method of Merwin. The systems SrO.SiO2, BaO.SiO2, CaO.SiO2-SrO.SiO2 and CaO.SiO2-BaO.SiO2 were worked out and the results collected in 12 tables and 12 charts of curves. Crystallographic features are shown in 5 illustrations. Sr and Ba feldspars were found to be analogous to anorthite.