Apparent molar volumes of sodium arsenate aqueous solution from 283.15 K to 363.15 K at ambient pressure: an experimental and thermodynamic modeling study

Abstract

Abstract Densities of the sodium arsenate aqueous solution with the molality varied from (0.04165 to 0.37306) mol · kg−1 were determined experimentally at temperature intervals of 5 K from 283.15 K to 363.15 K and ambient pressure using a precise Anton Paar Digital vibrating-tube densimeter. The apparent molar volumes (V ϕ ), thermal expansion coefficient (α) and partial molar volume ( V ¯ B ) $({\bar V_{\rm{B}}})$ were obtained based on the results of density measurement. The 3D diagram of apparent molar volume against temperature and molality as well as the diagram of thermal expansion coefficient and partial molar volume against molality were plotted, respectively. On the basis of the Pitzer ion-interaction equation of apparent molar volume model, the Pitzer single-salt parameters ( ( β M,X ( 0 ) v , β M,X ( 1 ) v , β M,X ( 2 ) v and C M,X v , M X = N a 3 A s O 4 ) $(\beta _{{\rm{M,X}}}^{(0)v},\beta _{{\rm{M,X}}}^{(1)v},{\rm{ }}\beta _{{\rm{M,X}}}^{(2)v}{\rm{ and }}C_{{\rm{M,X}}}^v,MX = N{a_3}As{O_4})$ and their temperature-dependent correlation 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 temperature in Kelvin, a i is the correlation coefficient) for Na3AsO4 were obtained on account of the least-squares method. Predictive apparent molar volumes agree well with the experimental values, and those results indicate that the single-salt parameters and their relational coefficients of temperature-dependence for Na3AsO4 obtained are reliable.