The effect of lead on the activity of sodium in liquid zinc

Thermodynamic properties of liquid binary Zn-Na alloys have been studied by several investigators, but the effect of lead on the activity of sodium in molten zinc has not been determined experimentally. This work was aimed at determining the activities of sodium in zinc-rich Zn-Pb-Na melts and investigating experimentally the thermodyanimc interaction between sodium and lead in liquid zinc at 465 deg C. The electromotive force (emf) method used to determine the activities of sodium in zinc-rich Zn-Na melts was employed. The following conclusions may be drawn. Addition of a small amount of lead to zinc-rich Zn-Na melts lowered the activity of sodium and increased the solubility of sodium in liquid zinc at 465 deg C. The large and negative value of epsilon sub Na exp Pb from this work reveals a strong attraction between sodium and lead atoms in liquid zinc at 465 deg C. Wagner's interaction and Darken's quadratic models can be used to predict the effect of lead on the activity of sodium in zinc-rich Zn-Pb-Na melts at 465 deg C in the compositional range relevant to the zinc-refining processes by the sodium additions.