Luminescent study of association of eosin with rare-earth ions in water

Association of the eosin dianion with rare-earth ions is studied in water. It is shown that it is not accompanied by a change in the absorption spectr um of the dye but results in quenching of the dye fluorescence. A statistic al nature of the interaction in the system is established. The composition of associates and their dissociation constants are found for different ion strengths, and thermodynamic parameters of the association are measured. Th e conclusion is made that the interaction between ions in the associates is predominantly of the electrostatic nature.