Electromigration of trivalent lanthanide ions in aqueous solution

The migration velocities of lanthanide aquo-ions (Ce3+, Nd3+, Eu3+, Gd3+, Tb3+, Tm3+ and Yb3+) have been measured as a function of ionic strength and temperature. The relationship between the mobility and the conductibility data has been checked for each lanthanide. A discontinuity near the middle of the series is infered from the plot of the migration velocities as a function of the crystallographic radius. The magnitude of the activation energy of the mobility u is derived from the measurements performed at various temperatures between 9 and 300C. It confirms the large variation of u with T. From the known temperature dependence of the viscosity, variations of the size of the aquo-ion with T are deduced. No change in the structure of the hydrated species can be detected in the temperature range investigated. (orig.)