The retention mechanisms of silver ions were studied on some nickel and zinc ferrocyanides Which represent several types of structures. This was performed through the study of the influence of the ferrocyanide composition and structure, a determination of the kinetics and capacity, a study of the modification of the solid at each step of the fixation. All the studied ferrocyanides are able of removing silver from aqueous solutions with a high efficiency. The kinetics is always very fast. It could be interpreted by an intracrystalline diffusion for acid-nickel ferrocyanide, but was too fast for Interpretation in other cases. The main feature is a substitution of all ferrocyanide cations leading to a composition tending to Ag4Fe(CN)6. However, the stability of this compound is questionable. The capacity of fixation exceeds the predicted value and may reach 6 silver atoms per iron atom in the initial product. A possible interpretation is the formation of silver cyanide. The fixation is a complex phenomenon involving structural changes in the crystal lattice.