The literature on kinetics of the urea decomposition reaction was reviewed for the 333-373 K range of temperature. Possible reactions in the pH range of 5-9 were identified. Kinetic simulations indicated significant accumulation of the cyanate intermediate in the pH-time-temperature range that was studied. The effects of Ni2+ hydrolysis and complexation with the urea decomposition products were incorporated into the simulations. The kinetic simulation of the rate of Ni2+ removal from the solutions was compared against the experimental data. The experimental results indicated an agglomerative growth mechanism for the precipitation process. Chemical analyses showed that the composition of the precipitate varies with digestion time, in agreement with the predictions of the kinetic simulation.