Measurement of chemical activities of rare earths (RE: Ce, Pr, Sm and Eu) in cadmium alloy

• Activities of rare earth (RE) elements such as Ce, Pr, Sm and Eu were measured as a function of temperature in cadmium rich biphasic mixture.
• Partial molar Gibbs energies of these rare earths in liquid cadmium were derived over a temperature range.
• Gibbs energy of formation of CeCd11, PrCd11, SmCd6 and EuCd11 were derived.

Activity of rare earth (RE) elements, Ce, Pr, Sm and Eu is measured in each of the cadmium rich binary alloys of RE, by making use of a molten salt based electrochemical cell. The binary alloy consists of a mixture of cadmium rich intermetallic compound and a liquid phase of known composition. Four independent cells are constructed; one for each of the rare earth elements and electromotive force (EMF) is measured as a function of temperature for each cell, respectively. Partial molar Gibbs energy of these rare earth metals in liquid cadmium is derived from the EMF output over a temperature range. Gibbs energy of formation of CeCd11, PrCd11, SmCd6 and EuCd11 are deduced from the measured EMF values and the reported literature data on the solubility of rare earth elements in liquid cadmium.