Our previous investigation of the kinetics of release of simple particulate solutes of very low (CaSO4 or SrSO4) or very high aqueous solubility (NaCl) from cellulose acetate (CA) matrices (in the form of thin films) in contact with an eluant aqueous phase is here extended to a solute of moderate solubility (CsNO3). Simultaneous measurement of the concurrent variation of the water content of the matrix revealed the occurrence of osmotically induced excess water uptake by the loaded matrix for all loads studied, as previously observed in the case of NaCl at lower loads. The resulting enhancement of solute release rate was considerable but much less than that generated by NaCl. Sorption and diffusion of the solute in the corresponding particle-depleted polymer matrices was also investigated. The results exhibited a pattern qualitatively very similar to that of NaCl but greatly attenuated in quantitative terms. These observations are in keeping with the relatively weak osmotic power of CsNO3. A mechanism for osmotically induced enhancement of solute release rate previously formulated (in terms of the growth of zones of enhanced hydration of the polymer matrix surrounding the embedded solute particles) to account for NaCl release behavior observed at lower particle loads was found to be applicable here at all loads examined. The degree of hydration of the (neat) CA polymer matrix was also varied (by varying the conditions of film preparation or by wet thermal after-treatment of the as-prepared films) and its effect on CsNO3 partition and diffusion coefficients was studied. The results provided the basic information needed for interpretation of the corresponding particle-depleted film data, in comparison with the previous ones for NaCl. It was thus shown that imbibed water was more homogeneously distributed in NaCl-depleted, than in CsNO3-depleted, films. It was also observed that variation of the degree of polymer hydration affected primarily the rate, and only secondarily the kinetics, of particulate CsNO3 release.