The Distribution of Iodide Within the Double Structure Grain

A method of etching silver halide crystals combined with electronic micrography and X-ray fluorescence analysis was used to study the iodide distribution in the double structure grain. A double structure grain emulsion was prepared by double precipitation. The mole ratio of the core to the shell was 3:4. The designed composition of the double structure grain was 25 mol% iodide in the core and 0 mol% iodide in the shell. Two models of iodide distribution were discussed. In one model iodide was assumed to be concentrated in the core and the shell was pure silver bromide, and in the other model some iodide was assumed to diffuse from the core to the shell. Two relations between iodide content and the ratio of diameter after t