The Quantity of Silver Sulphide Produced During Sulphur Senitization

Abstract

An iodobromide emulsion prepared with an inert gelatin was sensitized with various quantities of thiourea. Analytical tests involving both potentiometric measurements and direct sulphide analyses show that the quanity of silver sulphide present on the emulsion grains at selected speed and fog values depends on the amount of added sulphur sensitizer and increases with the sensitizer concentration. It is suggested that two forms of silver sulphide (fogging and non-fogging) can be present on the surface of a silver halide crystal. Fog is produced by three-dimensional nuclei (specks) whereas a mono-molecular layer of silver sulphide can optically sensitize but does not fog.