Nitrogen electrode reaction has been investigated in a LiCl-KCl-CsCl melt containing Li 3 N. The following reaction, N 3 - → ½N 2 + 3e - , is confirmed by quantitative analysis of anodically evolved gas. The Nernst relation holds for the rest potential of Ni electrodes at nitrogen gas pressure, p N 2 , of 0.1-1.0 atm and the anion fraction of N 3 - ion, x N 3-, of 0.003-0.020 (anion fraction). Then the standard formal potential of N 2 /N 3 - , E 0 ' N 2 / N 3-, is evaluated to be 0.193 ′ 0.003 V vs. Li + /Li (p N 2 = 1 atm,x N 3- = 1) at 673 K. The dependence of E 0 ' N 2 / N 3- upon the temperature (605-721 K) gives a linear relation, whose slope is (-0.790 ′ 0.096) X 10 - 3 V K - 1 . Thermodynamic quantities for formation of Li 3 N in the melt are also estimated.