Decomposition of ammonia on tungsten surface

To interpret the kinetics of the decomposition of ammonia on a hot tungsten wire. 

The heterogeneous decomposition of ammonia on a tungsten wire at 856 °C was studied bj Hinshehvood and Burk (J. Chem. Soc. 1925, 127, 1116) 

In an experiment in which the initial ammonia pressure fi was 200 mm Hg the values of the pressure increase p—pi after a time t aire given in table 1. 

The effect of the addition of hydrogen or nitrogen on the rate is only small and may be neglected. At 1100 °C, Kunsman (J. Amer. Chem. Soc. 1928, 50, 2100) obtained values of the half-time of reaction r, as a function of the initial ammonia pressure, given in table 2. 

We shall tentatively assume that the rate is proportional to the amount of ammonia adsorbed on the surface. 

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