Dilute solutions of sodium in molten bismuth and tin; EMF measurements and interpretation

Results of electromotive force measurements of Na activity in dilute Na-Bi and Na-Sn alloys in the temperature range 573-723 K are reported. The limiting slopes are determined for the logarithm of the activity coefficient of Na as a function of its concentration in the solvent. Using the equations derived by Kirkwood and Buff, the sign and magnitude of the slopes are shown to have structural implications. Data from this study and published literature data on some Na and Li alloys are consistent with a net repulsion between alkali atoms in solution in electronegative metals. (author)