The thermal dehydration and decomposition of M(IO3)2·2H2O (M2+=Ni2+ and Zn2+) and their deuterates were investigated by DTA and DSC methods. The data obtained confirm their onestage dehydration and
their decomposition to the respective oxides. Ni(IO3)2·2H2O and Ni(IO3)2·2D2O, were more stable than Zn(IO3)2·2H2O and Zn(IO3)2·2D2O. A considerable isotope effect was observed in relation toTdeh for Ni(IO3)2·2H2O and Ni(IO3)2·2D2O, which was explained by the presence of structural changes well differentiated from the dehydration process for the deuterate.
The data obtained for both pairs of dihydrates were used to determine ΔHfo
for Ni(IO3)2·2H2O and Ni(IO3)2·2D2O.