Abstract: An aqueous colloidal dispersion of at least one lanthanide compound and a complexing agent with a pK (cologarithm of the dissociation constant of the complex formed by the complexing agent and the lanthanide cation) or more than 2.5. The dispersion can also include a compound of at least one other element selected from groups IVa, Va, VIIa, VIIa, VIII, Ib and IIb of the periodic table. A process for preparing the dispersion starts by forming an aqueous mixture comprising at least one lanthanide salt, optionally a salt of one of the elements mentioned, and the complexing agent. A base is added to the mixture, which is heated to obtain the dispersion. Methods that use the dispersion are also disclosed.

Abstract: The invention relates to an aqueous colloidal dispersion of a compound of cerium and at least one other element M chosen from among the rare earths other than cerium; titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminium, gallium and zirconium. This dispersion is characterized in that it displays a conductivity of at most 5 mS/cm. It is obtained by a process in which there is reacted with a base a mixture of at least one salt of cerium with at least one salt of an element M mentioned above and in the presence of an acid in a quantity such that the atomic ratio H+/(Ce+M) is greater than 0.1, then the precipitate from the preceding reaction is re-dispersed in water. The dispersions of this type cane be used in catalysis, in lubrication, in ceramics, in the manufacture of luminophorous compounds, in cosmetics and as anticorrosion agents.