Temperature Dependence of Chloride Complexation for the Trivalent f-Elements

The influence of elevated temperatures on the formation of 1:1 chloro complexes for Eu³⁺ and Am³⁺ are reported. Using a solvent extraction technique, stability constants for the equilibrium M_(aq) ³⁺+Cl_(aq) ^– MCl_(aq) ²⁺ have been measured in the temperature range of 25–75 °C. Modest increases in ₁ are observed, and small positive enthalpies for these reactions are reported. These data are discussed in the context of previous reports for the trivalent lanthanide and actinide chloro systems.