Nitrogen electrode reaction has been investigated in a LiCl-KCl-CsCl melt containing Li3N. The following reaction, N3--> 1/2N(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(N2), of 0.1-1.0 atm and the anion fraction of N3- ion, x(N)(3-), of 0.003-0.020 (anion fraction). Then the standard formal potential of N-2/N3-, E-N2/N3-(0'), is evaluated to be 0.193 +/-0.003 V vs. Li+/Li (p(N2)=1 atm,x(N3-)=1) at 673 K. The dependence of E-N2/N3-0' upon the temperature (605-721 K) gives a linear relation, whose slope is (-0.790 +/- 0.096)x10(-3) V K-1. Thermodynamic quantities for formation of Li3N in the melt are also estimated. (c) 2005 The Electrochemical Society. All rights reserved.