Polarographic studies on Eu(III), Yb(III), and Er(III) ions in the molten salts of KNO3-LiNO3-NaNO3

The DC and AC polarographic studies on Eu(III), Yb(III), and Er(III) ions in the molten salts of KNO3-LiNO3-NaNO3 (53+30+17 mol%, mp 1200C) were carried out with DME and Ag/AgNO3 reference electrode, at 1800C in an argon atmosphere. All the salts were used after drying them at 1000C in an argon atmosphere under a reduced pressure. And the values of slope of E against log ) 7i/(isub(d)-i){ are 82.5, 96.0, and 97.5 mV for the reduction of Eu(III), Yb(III), and Er(III), respectively. The limiting currents of the metal ions are proportional to the square root of the mercury heights. On the basis of the linear dependence of limiting current on metal ion concentration, in the range of 0--4.0 mmol/kg for Eu(III), 0--1.0 mmol/kg for Yb(III), and 0--1.0 mmol/kg for Er(III), it was confirmed that such limiting currents are diffusion controlled. The polarographic reductions of these metal ions are one-electron reversible reactions and the half-wave potentials Eu(III), Yb(III), and Er(III) ions are -0.54, -1.10, and -1.21 V vs. Ag/AgNO3 electrode, respectively. The AC polarogram of Eu(III) ion showed that the potential is -0.45 V vs. Hg counter electrode and the relation of peak current vs. metal ion concentration is linear in the range from 0 to 4.0 mmol/kg. (auth.). )]