Densimetric and ultrasonic characterization of urea and its derivatives in water

Abstract The densities at T  = (288.15, 293.15, 298.15, 303.15, and 308.15) K and sound velocities at T  = 298.15 K have been measured for aqueous solutions of urea, N -methylurea, N , N’ -dimethylurea, N , N , N’N’ -tetramethylurea, N -ethylurea, N , N’ -diethylurea, N -butylurea. From these data the apparent molar volumes, V Φ the apparent molar isentropic compressions, K S ,Φ , and the Passynski solvation numbers of solutes have been determined. The concentration dependencies of the calculated quantities and their limiting values are discussed in terms of solute–solvent and solute–solute interactions.