Apparent Molar Volumes for the Binary Systems (NaI + H₂O) and (NaIO₃ + H₂O) at Temperatures from 283.15 to 353.15 K at Ambient Pressure

Abstract

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 (α) and apparent molar volume (V ϕ) 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 β(0)v M.X, β(1)v M.X, and Cv M.X and their correlation coefficients a i of the temperature-dependent equation f(i, p, T) = a 1 + a 2ln­(T/298.15) + a 3(T – 298.15) + a 4/(620 – T) + a 5/(T – 227) (where T is the temperature in Kelvin and a i 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.