The kinetics of the nitrogen reaction with liquid Fe-C alloys was investigated by using the isotope exchange technique. The effect of small amounts of S, P, Pb, Sn, Bi and Te in Fe-Csat, alloys on the rate constant of the interfacial nitrogen reaction was studied at 1450°C The rate constant for Fe-Csat.-S alloys was in agreement with the previous results for Fe-S alloys. It was also confirmed that the influence of carbon in Fe-C-S alloys on the rate of the nitrogen reaction is negligible. The effect of tin on the rate constant is small even when the tin content is as high as 0.8wt%. However Pb, Bi and Te have significant effects on the rate constant and the addition of small amounts of these elements decreases the rate significantly. Phosphorus also decreased the rate constant. According to the adsorption model, the interfacial reaction rate should approach zero at high concentration of surface active elements, but in the case of Fe-Csat.-P, Fe-Csat.-Pb and Fe-Csat.-Te alloys, there was evidence of a residual rate at high concentrations of P, Pb and Fe.