Double nitrates of Na and K having the composition 2MINO3·LnIII(NO3)3·2H2O(LnIII=Pr, Nd, Sm, Eu, Gd, Tb and Dy) and of Ni and Cu with the composition 3MII(NO3)2·2LnIII(NO3)3·24H2O (LnIII=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy) have been prepared and their -radiolytic decomposition studied up to 500 kGy. G(NO
) values of K double nitrates at 230 kGy follow the order Dy3+>Pr3+=Nd3+=Sm3+>Tb3+>Eu3+> Gd3+·G(NO
) for NI double nitrates are higher than those of Cu double nitrates. Variation of G(NO
) with cationic radii and the number of f electrons in lanthanide ion show a minimum at Eu. Thermal decomposition studies of double nitrates were also carried out.