Abstract: NRTL equation is one of the equations that widely used in chemical engineering thermodynamics. The marked advantage of the NRTL equation is that it can be used for predicting the thermodynamicsproperties of multicomponent systems only with the data of binary systems. However the application of it to molten alloys and the other melts in metallungy has been mrsly reported. In this article, it was used to correlate thermodynamics data of binary molten alloys which are included in the systems-Cd-Bi-Sn, Cd-Bi-Pb, Cd-Sn-Pb. The data of those ternary systems were predicted by NRTL equation. The activities of Cd in quaternary system Cd-Bi-Pb-Sn were also calculated.

Key words: NRTL equation, molten alloy, activity coefficient