Densities of the binary systems (NaI + H2O) and (NaIO3 + H2O) were measured by an accurate Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K ranging from 283.15 to 353.15 K at ambient pressure and molalities of sodium iodide and sodium iodate ranging from 0.16764 to 2.15208 and 0.02252 to 0.15952 mol kg(-1), respectively. Based on the experimental density data of the binary systems (NaI + H2O) and (NaIO3 + H2O), thermal expansion coefficient (alpha) and apparent molar volume (V-phi) are obtained using an empirical equation calculation, and the diagram for the relationship between temperature and molality was plotted. According to the Pitzer ion-interaction model of the apparent molar volume, Pitzer single salt parameters beta(0)v M.X, beta(1)v M.X, and Cv M.X and their correlation coefficients ai of the temperature-dependent equation f(i, p, T) = a(1) + a(2)ln(T/298.15) + a(3)(T - 298.15) + a(4)/(620 - T) + a(5)/(T - 227) (where T is the temperature in Kelvin and ai values are the correlation coefficients) for NaI and NaIO3 were first obtained by the least-squares method. The obtained apparent molar volumes agree well with the experimental values, and these results indicated that the single salt parameters and the temperature-dependent formula obtained in this work were reliable.