Even CrO3
and V2O5 have low melting points In these higher oxides, the acidic
character is predominant Thus, Mn2O7 gives HMnO4 and CrO3 gives H2CrO4 and H2Cr2O7 V2O5 is, however, amphoteric though mainly acidic and it gives VO4
3– as
well as VO2
+ salts