The system Fe-Os-S at 1180°, 1100°and 900°C

Phase relations in the condensed system Fe-Os-S were investigated by means of dry syntheses from the elements at 1180degrees, 1100degrees and 900degreesC. The Fe-rich sulfide melt dissolves only traces of Os. Fe1-xS dissolves up to 0.7 at.% Os at 1180degreesC; Os solubility decreases to 0.3 at.% at 900degreesC. The S-rich sulfide melt dissolves up to 0.5 at.%. Os at 1180degreesC. The principal Fe-Os alloys at all temperatures studied are cubic gamma (Fe,Os), rhombohedral (Os,Fe) and nearly pure Os. The bulk of Fe-Os alloys coexist with Fe-rich sulfide melt and S-poor Fe1-xS; we provide Nernst partition coefficients for Os. The three-phase association alloy-FeS1-xS-OsS2 involves alloys with less than 1 at.% Fe. The solubility of Fe in OsS2 increases with decreasing temperature and increasing fugacity of sulfur, possibly making analyses of erlichmanite for trace quantities of Fe important.