The dissolution kinetics of electrochemically grown films and pressed pellets of silver chloride in aqueous potassium nitrate solutions have been investigated using the well-defined, and high, mass transport properties of the scanning electrochemical microscope (SECM). The reaction was found to be diffusion-controlled under all conditions utilized, suggesting that the heterogeneous rate constant controlling the surface process is in excess of 3 cm s(-1). In parallel with the experiments, a theory for SECM-induced dissolution has been developed for the case where dissolution of a binary salt occurs in a solution in which none of the lattice ions are buffered. Under these conditions, theoretical and experimental results demonstrate that when only one of the lattice ions is removed from the tip-substrate gap by electrolysis, the trapping of the electroinactive counterion in the gap between the tip and substrate by hindered diffusion strongly retards the dissolution rate.