THERMAL-DECOMPOSITION OF NITROUREA

The thermal decomposition of nitrourea in the solid phase proceeds wit h a pronounced self-acceleration, the maximum reaction rate being reac hed at extremely high extents of conversion. A significant increase in the specific surface is simultaneously observed: the specific surface increases 33-fold by the time when the maximum reaction rate is reach ed, and the mean particle size becomes equal to 230 angstrom. In a clo sed system an increase in the pressure of the gas evolved is followed by an abrupt decrease. A mechanism for the process, in which an interm ediate, isocyanic acid, and the heterogeneous character of the reactio n play the key role is proposed on the basis of kinetic measurements a nd data on the composition of the decomposition products.