The standard potentials of the silver/silver azide electrode in four different compositions of urea + water mixtures at seven different temperatures from 5 to 35°C have been determined from the electromotive force measurements of cells of the type: Ag(s)|AgCl(s)|NaCl(c)‖NaN 3(c)|AgN 3(s)|Ag(s) These values have been used to evaluate the transfer thermodynamic quantities accompanying the transfer of 1 gram-ion of the N 3 − ion from the standard state in water to the standard state in urea + water mixtures.