Volume Properties of Ammonium Halide Solutions in an N-Methyl Pyrrolidone–Water Mixed Solvent at 298.15 K

The densities of solutions of ammonium halides in N-methylpyrrolidone (MP)–water mixtures were studied over the entire range of compositions of the mixed solvent at 298.15 K. The standard partial molar volumes \(\bar {V}_{2}^{0}\) of the electrolytes were calculated. The standard partial molar volume of the ammonium ion \(\bar {V}_{i}^{0}\) in the mixtures was determined. The contributions to \(\bar {V}_{i}^{0}\) due to electrostriction, specific ion–solvent interactions, and structural changes in solution were calculated. The dependence of the obtained values on the composition of the mixture is discussed in connection with the structure of the mixed solvent.