A mixture of nitrogen and hydrogen in the ratio of 1 : 3 by volume is passed over heated iron at 450°C in the presence of molybdenum, which acts as catalyst (promoter) under 200 atmospheric pressure. The reaction of nitrogen and hydrogen is a reversible reaction hence ammonia is removed from the reaction vessel from time to time by liquefaction under high pressure, so that the reaction proceeds in the forward direction.
N2 + 3H2 ⇋ 2NH3(Ammonia) + 22 kcal
