Instantaneous rates of dissolution of polydisperse solids in a batch dissolver depend on the aggregate surface area for mass transfer and the concentration driving force both of which can change with time. By generalizing the fluid-solid reaction framework to include the particle size distribution, a model is presented for evaluation of the integral dissolution rates under widely applicable process and operating conditions without questionable assumptions made in mono-size particles based analysis. Experimental dissolution rate data published by various researchers in a number of problems involving mass transfer controlled solid dissolution in reactive media could be successfully interpreted by the model in a consistent manner irrespective of the poly-dispersity of the charge, complex composition of the solutes and the underlying chemistry. While in most cases the estimated mass transfer coefficient is in the range of those computed by the available correlations in the literature, both the value and the trend of its dependence on key variables like particle size and agitation speed could be somewhat different in some cases. The discrepancy may be partly due to imperfect design and conduct of the dissolution experiments. But this may also be an indication of the inadequacy of the empirical correlations under reactive and/or high mass flux conditions. The model. proved useful in estimating and correlating the transport coefficient. (c) 2006 Elsevier B.V. All rights reserved.