Abstract: The podium activity and its composition and temperature dependences can be satisfactorily accounted for by a structural model of the melt for the compositions of x=0.00002-0.02568 in Na_xHg_1-x and in the temperature interval 303. 15 K-383. 15 K. The calculation of tentative equilibria suggests that the structural species in the liquid amalgam of low sodium content may possibly be dominated by the following chemical equilibrium.