VOLTAMMETRIC STUDY ON THE REDUCTION OF RARE EARTHS IN ACETONE

The voltammetric and polarographic behaviours of 14 rare earth elements were investigated in anhydrousacetone.The influence of residual oxygen on their waves was examined.At a concentration lower than 6×10~(-4)mol/L,Eu~(3 ),Yb~(3 )and Sm~(3 ) produce two waves and other rare earth ions exhibit only one wave.When the concentration is greater than 8×10~(-4)mol/L,two waves could be observed on the reductionof Yb~(2 ),Sm~(2 )and other RE~(3 )ions except for Eu~(3 ).By adding 0.6% H_2O(or 1×10~(-4)mol/L NH_4ClO_4)one well-defined wave appears instead of two.The phenomenon is explained that a thin deposit film may beformed at electrode surface owing to the interaction of RE~(3 ) with O_2~-,which is the reduction product of traceoxygen in aprotic solvent.In the presence of a proton donor such as H_2O or NH_4~ ,oxygen reduces directly toH_2O_2 and eliminates the appearance of two waves.