Carboxymethylation of cellulosic material (average degree of polymerization 2600) containing 76.5% cellulose and 23.6% xylose isolated from cotton (Gossypium) linters was studied under varying reaction conditions with respect to maximum degree of substitution (DS). The influence of reaction conditions on the apparent viscosity of the prepared derivatives was also studied. The conditions optimized were sodium hydroxide concentration 3.75M, monochloroacetic acid concentration 2.05 mol/AGU, carboxymethylation time 3.5 h, and temperature 55 degrees C, to yield carboxymethyl cellulose of DS 0.77. Rheological studies of I and 2% solutions of the optimized product revealed their non-Newtonian pseudoplastic behavior. Repeating units of the optimized product were also determined by HPLC after complete depolymerization of the polymer. (c) 2005 Wiley Periodicals, Inc.