Ultrasonic velocity (u), density (ρ), and viscosity (η) have been measured for glycylglycine and CoCl 2 in aqueous and aqueous ethanol systems at T=(288.15 to 318.15)K. Using the experimental values, the adiabatic compressibility (κ s ), molar hydration number (n H ), apparent molar compressibility (K S Φ ), apparent molar volume (V Φ ), limiting apparent molar compressibility (KSϕ0), limiting apparent molar volume (Vϕ0), their constants (S K ,S V ), viscosity coefficients of A and B parameters of Jones–Dole equation, relative viscosity (η r ), and excess Gibbs free energy of activation (ΔG∗E) were calculated and the results of all these parameters have been discussed in terms of solute–solvent and solute–solute interactions.