RE 2 O 3 .Tboxide occursnaturallyasTb 4 O 7 ,andtransformsintoTbO 2 underpositiveoxygenpressure. ThepresentstudyisconcernedwiththevalenciesoftheoxidesofCe,Pr,Nd,Pm,Sm, Eu,Gd,Tb,DyandHo.Undersuitableconditions,alltheREelementsformasesquioxide, 2 andthereisgeneralagreementthat,inthecorresponding...