Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and three ethylene glycol-water mixtures containing 10, 20, and 30 mass % of ethylene glycol have been reported at 35 degrees C. Isoionic dilutions were performed at total ionic strengths in the range of 0.0002-0.0008 eqv L-1 using sodium chloride to obtain the intrinsic viscosities along with the Huggins constants. The influence of the medium and the ionic strength on the intrinsic viscosities have been interpreted from the points of view of the counterion condensation and expansion/contraction of the polyion chains in solution. The variations of Huggins constants, on the other hand, provided information on the intermolecular interactions in these solutions. A convenient method has been proposed to decompose the reduced viscosity of a polyelectrolyte solution into its conformational and electrostatic components. The electrostatic reduced viscosities obtained in the present study, purely from experimental considerations, quantitatively corroborates the conclusions derived from the Huggins constants. Using the Hess and Klein theoretical approach, an expression for the reduced viscosity due to the electrostatic interactions as a function of polyelectrolyte concentration could be obtained and the reported experimental electrostatic contributions could be nicely described with the help of this approach. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1196-1202, 2010