Equations of State / Mixed Solvents / Solutions / Thermodynamics / Volume Densities of solutions of NaCl, NaI, KCl, KBr and CsCI in three mixtures containing 10 wt% (3.22 mol%), 20 wt% (6.98 mol%) and 30 wt% (11.39 mol %) urea in water have been measured at 298.15 K using the magnetic float densitometer. The apparent molal· volumes of the electrolytes calculated from the experimental data were extrapolated to infinite dilution by means of the Masson equation. The ionic partial molal volumes of alkali-metal and halide ions have been estimated. The disordered and electrostriction partial molal volumes of investigated ions were calculated and the effect of urea on these functions is discussed.