Co-precipitation of francium and caesium with heteropolyacids

Tests on the precipitation of very small quantities of Fr and Cs with di- heteropolyacids (di-HPA) under various reaction conditions and the determination of the degree of coprecipitation with some tri- and tetra-HPA with various central atoms and ligands were made. The highest coprecipitation yields were obtaimed with di- and tri-HPA where W and Mo ligands were bouded to a central P or As atom. The lowest yields occurred with HPA with central B, Ge, or Se atoms. In most cases the presence of V in the HPA molecule led to lower yields. Francium was better precipitated that Cs, but this was probably due to the small difference between Fr and Cs ionic radii. Coprecipitation with carrier was also investigated.