New results regarding the synthesis and characterization of water-soluble phosphorylated cellulose by reaction of microcrystalline cellulose with phosphorous acid in molten urea are presented. The maximal value of DS attained by this method was about 1. By elemental analysis of phosphorous, titration of acidic groups and IR spectra the structure of monobasic cellulose phosphate was demonstrated. The results of elemental analysis are in agreement with those obtained by potentiometric or conductometric titration so that the potentiometric titration is proposed as a convenient and rapid method for the evaluation of the substitution degree. The thermal behavior and the ability to influence the separation of sparingly soluble salts were examined in view of the use of phosphorylated cellulose in the control of biomineralization processes or as additive in the preparation of hydroxyapatite or other inorganic salts by hydrothermal method. (c) 2006 Elsevier B.V. All rights reserved.