Thermodynamic Investigation of Sodium Nitrate in N,N-dimethylformamide Aqueous Mixtures Based on Potentiometric Measurements at T = (298.2, 303.2, and 308.2) K

Abstract

In this work, thermodynamic properties of ternary (NaNO₃ + DMF + water) system were reported using the potentiometric method. The electromotive force measurements were performed on the galvanic cell of the type: \({\text{NO}}_{{3}} {\text{ - ISE}}\left| {{\text{NaNO}}_{{3}} \left( m \right),{\text{DMF}}\left( {w\% } \right),{\text{H}}_{{2}} {\text{O }}({1} - w)\% } \right|{\text{Na - ISE}}\), in various mixed solvent systems containing 0, 5, 10, 15 and 20% mass fractions of DMF over total ionic strengths from 0.0100 to 2.500 mol·kg⁻¹ at T =  (298.2, 303.2 and 308.2) K and P = 0.1 MPa. The experimental activity coefficients of NaNO₃ were analysed using extended Debye–Hückel equation, Pitzer ion interaction model and Scatchard equation. The Pitzer adjustable parameters were used to calculate \(\gamma_{ \pm } ,\varphi , \, {{G^{{\text{E}}} } \mathord{\left/ {\vphantom {{G^{{\text{E}}} } {n{\text{R}}T}}} \right. \kern-0pt} {n{{R}}T}}, \, {{H^{{\text{E}}} } \mathord{\left/ {\vphantom {{H^{{\text{E}}} } {n{{R}}T}}} \right. \kern-0pt} {n{{R}}T}}\,{\text{and}}\,{{S^{{\text{E}}} } \mathord{\left/ {\vphantom {{S^{{\text{E}}} } {n{\text{R}}}}} \right. \kern-0pt} {n{{R}}}}\). Also, Scatchard parameters were used to calculate \({{{\gamma_{N}^{{\left( {2} \right)}} } \mathord{\left/ {\vphantom {{\gamma_{N}^{{\left( {2} \right)}} } {\gamma_{N}^{{\left( {1} \right)}} }}} \right. \kern-0pt} {\gamma_{N}^{{\left( {1} \right)}} }}}\) for the whole series of under investigation system.