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 Na₂H₂P₂O₇ with the molality varied from 0.08706 to 0.88402 mol·kg^-1 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_Φ), expansibility (ϕ_E), and partial molar volume (V_B) of Na₂H₂P₂O₇ (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_M,X^0v, β_M,X^1v, β_M,X^2v and C_M,X^v, MX = Na₂H₂P₂O₇), and their correlation coefficients a_i of the temperature-dependence formula f (i, p, T) = a₁ + a₂ln(T/298.15) + a₃(T - 298.15) + a₄/(620 - T) + a₅/(T - 227) for Na₂H₂P₂O₇ 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.