Electrical conductivities of aqueous solutions of an anionic polyelectrolyte sodium carboxymethylcellulose with different degrees of substitution have been reported as a function of concentration and temperature. The conductance-concentration data have been analyzed with the modified Manning counterion-condensation model appropriate for semidilute polyelectrolyte solutions, considering the de Gennes scaling description of the polyion configuration. 36-55% of the counterions were found to remain condensed and the condensation process was shown to be spontaneous. Although the level of counterion-condensation depends appreciably on the degree of substitution, it was found to remain invariant with the polyelectrolyte concentration and the temperature. The free energies of counterion-condensation, the ratios of the mobility of the polyion to that of the counterion, the polyion transference numbers, and the coefficients of monomer-solvent friction have been evaluated. The effects of the polyion charge, its size, and the bulk viscosity of the media on the polyion-counterion interactions have also been discussed. (C) 2016 Elsevier Ltd.