Thermodynamically stable AgI clusters were studied in the presence of high- and low-molecular-weight additives: polyethyleneiminc (PEI) and dimethylformamide (DMF), respectively. Clusters containing up to 20 silver iodide pairs, roughly twice as many as in the system without PEI or DMF, have been observed. We show that the mechanism stabilizing these clusters is mixed adsorption with iodide ions at the AgI-electrolyte interface. We snake it plausible that more strongly adsorbing additives give rise to ultralow interfacial tensions of the AgI-electrolyte interface, with perspectives for "reversible colloids." (C) 2004 Elsevier Inc. All rights reserved.