A slag-metal equilibrium study of the system SnO-FeO-(Si02+Al2O3)/Sn-Fe was carried out at 1250C. The distribution coefficient, k =(Sn/Fe)metal X (Fe/Sn)slag was found to range from 246 for an iron contentof 053 per cenrt in the metal to 82 for an iron content of 64 per cent. The value of the ratio SnO/FeO was calculated and found to be approximately a function of per cent SnO in slag alone in the region (Si02+Al2O3)/ FeO = 04 to 12. Comparison with other published work suggests that the addition of CaO to slags having (SiO2+Al203)/FeO ratios of about 11 raises the value of SnO/FeO...