Abstract: Distribution of iodide and sulphur at the surface of cubic silver bromide microcrystal was studied. The observation and determination of which by the methods of STEM and EDS found that the conversion of AgBr to AgI may form high iodide content island at the crystal surface and sulphur sensitization specks prefer to form at this high iodide region. The principle of hard and soft acid and base is applied to analysis this phenomenon.

Key words: Silver iodide, Sulphur sensitization, principle of Hard and soft acid and base