Patent ID: 7495033

Claim:
An aqueous colloidal dispersion comprising an aqueous liquid phase and particles of a size of at most 100 nm, wherein said particles consist of: (1) an oxide and/or hydrated oxide of at least two elements selected from the group consisting of lanthanides; or an oxide and/or hydrated oxide of at least two elements selected from the group consisting of the lanthanides, in combination with an oxide and/or hydrated oxide of at least one other element selected from the group consisting of iron and palladium; (2) a complexing agent with a pK (cologarithm of the dissociation constant of the complex formed by the complexing agent and the lanthanide cation) of more than 2.5, wherein the complexing agent is selected from the group consisting of acid- or polyacid-alcohols, polyacrylic acids and salts thereof; and (3) optionally, residual quantities of bound or adsorbed ions; wherein said aqueous liquid phase comprises water, and optionally, residual quantities of ions or the complexing agent in ionized form.