I. The Thermal Decomposition of Dimethyl-Triazene. A Homogenous Unimolecular Reaction. II. The Gas Phase Equilibrium between Methyl Nitrite, Hydrogen Chloride, Methyl Alcohol, and Nitrosyl Chloride. The Absorption of Nitrosyl Chloride. III. The Chlor

During the past four years a considerable amount of experimental data has given support to certain theories of unimolecular reaction velocity which postulate that activation occurs by kinetic theory collisions. The rate of production of activated molecules by collisions is a second order process but if only a very small fraction of those molecules which become activated decompose spontaneously the rate of decomposition is first order. At sufficiently low pressures collisions can no longer maintain the Maxwell Boltzmann quota of activated molecules; consequently the rate falls off until finally at still lower pressures the rate approaches the rate of activation and is second order. Now that the rate of decomposition of nitrogen pentoxide has at last also been shown to decrease at very low pressures, every example of a homogeneous unimolecular reaction shows such a decrease or else theory does not require it in the pressure range studied. We have now studied the decomposition of dimethyl-triazene and find that this reaction also is first order at high pressures but falls off in rate at pressures below about one centimeter. Rate measurements have been made at temperatures from 200 to 230° and at pressures from 0.02 to 8.0 cm. of mercury.