Volumetric properties of disodium dihydrogen pyrophosphate aqueous solution from 283.15 to 363.15 K at 101.325 kPa.

The purpose of this exploration was to determine the density and volumetric properties of the aqueous solution of NaHPO with the molality varied from 0.08706 to 0.88402 mol·kg measured at temperature intervals of 5 K from 283.15 to 363.15 K at 101.325 kPa using Anton Paar Digital vibrating-tube densimeter. The thermal expansion coefficient (α), apparent molar volume (V), expansibility (ϕ), and partial molar volume (V) of NaHPO (aq) against temperature and molality have been evaluated from density data. On the basis of Pitzer ion-interaction apparent molar volume theory, the Pitzer single-salt parameters (β, β, β and C, MX = NaHPO), and their correlation coefficients a of the temperature-dependence formula f (i, p, T) = a + aln(T/298.15) + a(T - 298.15) + a/(620 - T) + a/(T - 227) for NaHPO were obtained for the first time. It was revealed that predicted apparent molar volumes agreed well with the experimental values indicating the single salt parameters and the temperature-dependent formula are reliable.