In order to simulate the precipitation of silver bromide octahedral crystals, a model is developed, which encompasses the main kinetic and thermodynamic features of crystallization including primary nucleation, as well as equilibria in solution. The model is then validated during three steps (nucleation, ripening and growth) of experimental precipitations, which are supposed to be performed under well mixed conditions. The unknown kinetic parameters of the primary nucleation process are fitted to experimental data through the precipitation model. These investigations will contribute to a better understanding of the nucleation process, which is shown to be the most critical moment for the shape of the final crystal size distribution (CSD). Nevertheless, the duration of nucleation step is so short and the nuclei are so small that no quantitative results can be expected. Finally, mixing effects were observed and seemed to play a major role during the nucleation step.