, Volume 134, Issue 4, pp 475-487

Volumetric and Viscometric Studies on Sodium Nitrate and Potassium Nitrate in Aqueous and H2 O-urea Solutions

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 Density and viscosity of NaNO3 and KNO3 in aqueous and in H2O-urea solutions were determined as a function of electrolyte concentrations at 308, 313, 318, 323, and 328 K, respectively. The apparent molal volume (φ v ) of the electrolytes were found to be linear functions of the square root of the solute molality (b). The φ v and \(\) data were fitted to the Masson equation [1] by the least square method to obtain the apparent molar volume at infinite dilution (φ v ^), which is practically equal to the partial molar volume \(\). The viscosity coefficients A and B were calculated on the basis of the viscosity of the solutions and the solvent concerned using the JonesDole [2] equation. The activation parameters for viscous flow (ΔG , ΔS , and ΔH ) were calculated according to Eyring [3]. The values of \(\) for the two systems were also calculated from B-coefficient data. The results were found to be of opposite nature in the two electrolyte systems. Where sodium nitrate showed structure making behaviour both in aqueous and in H2O-urea solutions, KNO3 showed structure breaking behaviour in aqueous solutions and structure making behaviour in 5 molal H2O-urea solutions in the studied temperature range. The behaviour of these two electrolytes in aqueous binary and in aqueous-urea ternary systems are discussed in terms of charge, size, and hydrogen bonding effects.