Chemical equilibrium in this reaction has been determined experimentally by a static or nonflow method at temperatures of 400° and 450°C. and at pressures of 1,000 to 3,500 atm. Equilibrium was approached from both sides and the two reacting gases were always in the stoichiometric ratio. The results are presented both as mole percentage of ammonia in the equilibrium mixture and as the equilibrium constant Kp. The constant, Kp, which is a function of pressure, was calculated from K, its value at p = 0, by five different methods and from them the corresponding mole percentages of ammonia were derived for comparison with the experimental results. All such calculations involve assumptions of varying degrees of validity, and no calculated value can be considered accurate. However two of the calculation methods give values which agree reasonably well with the experimental values.