To elucidate some basic properties in the fundamental antimonide speiss systems, activities of the component elements were determined in the Pb-Fe-Sb and Pb-Cu-Sb ternaries at 1, 200°C by the transportation method.
In the Pb-Fe-Sb system, the activity of antimony exhibits a slightly negative deviation from ideality for the entire composition range. A negative deviation of antimony activity is also seen from the additivity of the Pb-Sb and Fe-Sb binaries. In the two phase region, the activity of antimony ranges from 0.16-0.35, which is relatively large in comparison with arsenide speiss, suggesting a less stable speiss than the arsenic system. Lead activity on the other hand is below 0.77, indicating that gold and silver extraction by lead may be minimal.
In the two phase region of the Pb-Cu-Sb system, antimony activity is below 0.1, displaying a large negative deviation from Raoult's law, while the activity of lead is greater than 0.75, comparatively larger than in the Pb-Fe-Sb system.
Based on the interaction parameters determined in this study, the activity coefficient of antimony in molten lead containing minute amounts of copper and iron may be expressed as follows:
InγSb=-0.422+0.08X_Sb-2.6X_Cu-X_Fe