the use of polyphosphoric acids for modifying cellulose facilitates the solution of many synthesis problems and leads to production of materials having various new physicochemical properties. despite the importance of the problem of interaction of phosphorus-containing polymers with various sorbates, there are virtually no reports in the literature of systematic studies of sorption effects in such systems. as the equilibrium concentration of a sorbate is sensitive to chemical changes, the purpose of this work was to determine the dependence of this concentration on the amount of polyphosphate groups introduced into the polymer, and on the nature of the sorbate. it is found that changes of thermodynamic functions during sorption, swelling, and dissolution of polymers are functions of their chemical structure. thermodynamic analysis of the sorption data and x-ray structural and ir studies provide evidence of the complex character of changes in the properties of cellulose as the result of phosphorylation. 8 refs