Density, sound velocity and viscosity properties of aqueous sodium metatungstate solutions and an application of these solutions in heavy mineral separations

Densities, sound velocities and viscosities of aqueous sodium metatungstate (SMT) solutions, medium for heavy mineral separations, have been measured accurately in a concentration range from 0.0055 mol kg− 1 to 1.73 mol kg− 1 at 288.15, 293.15, 298.15, 303.15 and 308.15 K at 1 atm. The data were used in evaluating thermodynamic properties as apparent molar volumes, apparent molar isentropic compressibilities and apparent molar expansivities. Infinite dilution values of these properties were determined using appropriate extrapolation procedures utilizing Debye-Hückel limiting law for electrolyte solutions. Apparent molar volumes were found to decrease with concentration and increase with temperature. The data of apparent molar volumes at infinite dilution as a function of temperature were found to fit excellently to a quadratic equation. Apparent molar expansivities at various temperatures were determined from the derivative of this equation. Apparent molar isentropic compressibilities were found to be negative and to increase with temperature. The results were interpreted in term of solute–solvent interactions. Heavy mineral separation process using SMT at a density of 2.89 g cm− 3 was applied on fine grained sand samples taken from Goynuk region of southwest Turkey.