Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and in two acetonitrile-water mixtures containing 10 and 20 vol % of acetonitrile have been reported at 35, 40 and 50 degrees C. Isoionic dilutions were performed with the total ionic strengths of the solutions maintained with sodium chloride at similar to 4.20 x 10(-4) and 1.45 x 10(-3) mol dm(-3) of NaCl to obtain the intrinsic viscosities. The Huggins constants were also obtained from the experimental results. The influences of the medium, the temperature, and the total ionic strength on the intrinsic viscosities as well as on the Huggins constants have been interpreted from the points of view of the solvodynamic and thermodynamic interactions prevailing in the polyelectrolyte solution under investigation. (c) 2007 Wiley Periodicals, Inc.