Viscosities and Densities of Mixed Aqueous Alkali Metal Nitrate Solutions at T = (293.15–333.15) K

In order to study the physical properties of aqueous solutions containing mixed alkali metal nitrate compositions used in the field of concentrated solar power, the densities (ρ) and viscosities (η) of five nitrate solutions were measured, and apparent molar volumes (Vϕ), viscosity B-coefficients of the Jones–Dole equation, variation of B with temperature (dB/dT), and the Gibbs free energy of activation per mole of the solvent (Δμ10#) and solute (Δμ20#) were evaluated. The experimental measurements were carried out by the Anton Paar’s oscillation-type (DMA 4500) density measuring instrument combined with a rolling ball viscosimeter module (Lovis 2000 M/ME). Five different composition series of nitrate solutions were measured at atmospheric pressure, and each composition series contained five concentration gradients. The concentration gradient was divided according to the solubility at room temperature, and the temperature range (293.15–333.15) K was selected according to the temperature changes of the atomized droplets and the accuracy of the viscosity test. Finally, the physical properties of the mixed nitrate solutions were estimated based on the readily available sodium nitrate and potassium nitrate data. Also, the extended Jones–Dole equation containing the square term, polynomial equation, and extended semiempirical exponential model was used to predict the viscosities of nitrate solutions.