Saline oxides are the oxides which are capable of forming salts either through the function of acid or through the function of base.
Chemical formulae of higher saline oxides given in Mendeleev's Periodic Table
R2O3 = Al2O3 , Fe2O3
R2O4 = SnO2
R2O5 = N2O5, P2O5, Cl2O5
R2O7 = Cl2O7