Einstein’s Theory of Viscosity – Applicability to Amino Acid Solutions with Urea (Aq)

To determine the effective hydrodynamic radii of small uncharged molecules in dilute aqueous solution, Einstein's classical theory of viscosity can be employed. The radii thus obtained are considered as hypothetical sphere whose hydrodynamic behavior is the same as that of the solute molecule along with that solvent which is too firmly bound to the solute in viscous shearing process. Einstein's formula is recuperated as a first-order asymptotic extension of the effective viscosity in the volume fraction. The formula is applied to molecules having comparable size to that of water.Determining the viscometric radii of Glycine in solution with Urea(aq) from Einstein's equation, an attempt has been carried out to obtain empirical correction for Stokes-Einstein diffusion equation.