Abstract: Impure liquid media containing contaminating amounts of metallic impurities, e.g., alkaline earth metals, heavy metals and/or radioactive elements, for example industrial effluents from the nitric acidulation of rare earth concentrates, are purified by separately introducing a source of phosphorus and a source of barium into the impure medium, whereby precipitating a solid residue which comprises a barium phosphate having such contaminating metallic impurities distributed therein, and thence separating the solid residue from the liquid medium thus purified.

Abstract: Very finely divided ammonium rare earth double oxalates, readily converted into corresponding rare earth oxides by calcination, such oxides being well adopted, e.g., for the production of luminescent compounds therefrom, are prepared by (a) admixing a second solution of a rare earth compound, e.g., a salt, with a first solution containing oxalate and ammonium ions, (b) then separating the precipitate thus obtained from such mixed solution of reaction, and (c) optionally, drying the separated precipitate.

Abstract: Morphologically improved, aggregated, monodispersed rare earth trifluoride particulates having a controlled and narrow grain size distribution, and a mean diameter of less than 1 .mu.m, are prepared by (i) reacting an aqueous solution of a rare earth salt with a solution of ammonium fluoride, (ii) separating the precipitate thus formed, and (iii) heat treating the separated precipitate.