If metal ions of group III are precipitated by NH base 4CI and NH base 24OH without prior oxidation by conc. HNO base 3 ……………… is

Fe^3+; Without oxidation with HNO base 3, the Fe^2+ ions present would not be converted into Fe^3+. So Fe(OH) base 2 will not be precipitated as its solubility product is higher than that of Fe(OH) base 3 and as NH base 4CI suppresses the ionization of NH base 4OH, this solubility product is not reached.