The thermal decomposition of nitrous oxide I. Secondary catalytic and surface effects

In the region of pressure 0 to 500 mm the thermal decomposition of nitrous oxide conforms approximately to the equation k = $\frac{an}{1+a^{\prime}n}$ + bn, where k is the formal first-order rate constant, - (1/n) dn/dt, n the initial concentration and a, a$^{\prime}$ and b are nearly constant. Above about 100 mm this expression approximates to k = A + bn, which holds up to several atmospheres. Fresh and more detailed experiments have once again disproved the suggestion that the first term in these expressions is due to a surface reaction. (In certain states of reaction vessels, made of a particular brand of silica, a surface reaction may appear but is immediately recognizable by special criteria, and can be eliminated.) Detailed study of the formation of nitric oxide in the course of the decomposition, and of the effect of inert gas upon this process, shows that side reactions involving oxygen atoms, chain reactions and catalysis by nitric oxide play only minor parts in determining the shape of the k-n curve. The form of this curve, which is an inherent character of the reaction N$_{2}$O = N$_{2}$ + O, raises theoretical questions of considerable interest.