Kinetics of Decomposition of Titanium Tetraiodide

����� The rate of growth of an incandescent filament exposed to a steady stream of titanium tetraiodide vapour was determined from changes in the electrical conductance of the filament, and used to calculate the rate of decomposition of titanium tetraiodide at 1100-1500�C and at various vapour pressures. The method used eliminates the effects of titanium evaporation, counter-current gaseous diffusion, and the iodide synthesis reaction, which have influenced previous work.�The results show that the rate of decomposition is proportional to the vapour concentration but independent of the surface area for a given length of filament. The decomposition rate varies with temperature according to an Arrhenius-type relationship, leading to a provisional estimate for the energy of activation of 28.6 kcal/mole. Under suitable conditions high deposition rates are obtained. The decomposition appears to proceed as a first-order, homogeneous, gas-phase reaction in a hot reaction zone around the filament, rather than heterogeneously on the surface.