[en] From a set of critically selected literary data on the emf's of concentration cells consisting of sodium metal and sodium amalgam in a sodium salt non-aqueous electrolyte a value of E⁰sub(Na(Hg)/Na+) = -1.9558₄ V was calculated for the standard equilibrium potential of diluted liquid sodium amalgam at 25⁰C. The standard state of the amalgam was derived from an amalgam at infinite dilution where fsub(Na)→ 1.0 for xsub(Na)→ 0. The activity coefficient of sodium in the amalgam at an arbitrary composition, corresponding to this standard state, is obtained from the expression 1g fsub(Na(Hg)) = 16.393 xsub(Na). (author)