The sulfur partitions between carbon-saturated iron melt and Na₂O-SiO₂ slags with the Na₂O/SiO₂ molar ratio of 3/2, 1/1, 2/3 and 1/3 have been measured at 1 250 and 1 350°C. The sulfide capacities C'_S [=(wt%S)•(a_O/a_S)] calculated from the sulfur partitions were found to be in the range 10^-2 to 10^-4 and their temperature dependence was not observed. These values were lower than the previous measurements obtained from the gas-slag equilibrium studies above Na₂O/SiO₂=0.5-0.7, but were higher than the previous measurements at the slag composition below this ratio. The sulfur partitions between carbon-saturated iron melt and Na₂O-CaO-SiO₂ melts at the constant silica content were also measured at 1 250°C. The effect of lime on the sulfur distribution was compared with that of Na₂O in the plot of log (S)/[S] vs. (Na₂O+mCaO)/SiO₂ ratio, thus resulting m=0.3. The significant amount of iron was observed in the slag phase after equilibration and the ratio of sulfur as FeS against total sulfur in slag was found to be maximum at the composition with the Na₂O/SiO₂ molar ratio of 0.9. Desulfurization and dephosphorization of the carbon-saturated iron melts (0.1% P, 0.05% S) by the sodium vapor produced by the reaction of NaCl with CaC2 investigated at 1 300°C. Desulfurization was found to occur, but no dephosphorization was found.