[en] This research thesis notably addresses the separation of zirconium and hafnium, a crucial but difficult operation. After a presentation of the methods used for the study of solids and of solutions of hafnium and zirconium compounds, and a presentation of the general dosing methods, the author presents the starting compounds (zirconium and hafnium hydrated oxides), the reason for this choice, their preparation and their structures, and reports a comparative study of their behaviour in potassium solutions. In a next chapter, the author addresses the case of zirconium and hafnium iodates by studying the action of aqueous solutions of iodic acid on the zirconium and hafnium hydrated oxides, by determining the charge of complex anions absorbed on Dowex anionic resins, by introducing hexa-iodato-zirconates of monovalent metals, and by studying the IR spectrography of zirconium and hafnium iodates. Then, the author reports the study of sulfamates and sulfamic solutions of zirconium and hafnium, of zirconium and hafnium phosphates and pyro-phosphates, and of hypo-sulphites and hydro-phosphorous solutions of zirconium and hafnium.