Phase relations in the zinc-iron-sulfur ternary system at 1100 and 1200 K have been determined by electron probe X-ray microanalysis and X-ray diffraction studies of the quenched samples. The results are summarized as follows:
(1) Phase relations in the Fe-Zn-ZnS-FeS system at 1100 and 1200 K consist of two-condensed-phase fields and three-condensed-phase fields. The most characteristic observation is that the solubility of sulfur in metal coexisting with sulfide is negligibly small, while the sulfur content in sulfide coexisting with metal is less than 50 mol%. Concerning the mutual solid solubilities between FeS and ZnS, the solubility of FeS in ZnS is considerably larger than that of ZnS in FeS, both at 1100 and 1200 K.
(2) The effect of temperature on the phase relations of Fe-Zn-ZnS-FeS system was studied. The three-condensed-phase field of alpha ZnS s.s. + beta-ZnS s.s. + Fe was observed at 1200 K, which was not found at the lower temperature 1100 K. The mutual solid solubilities between FeS and ZnS at 1200 K are larger than those at 1100 K.
(3) Zinc content in the FeS which will form in the new zinc distillation process with environmental consciousness proposed by the authors, is expected to be negligibly small, since the FeS in the FeS + ZnS s.s. + Fe three-condensed-phase field has an almost stoichiometric composition. This is one of the advantages of the process.