Formation of silver sulfide in the photographic image during fixation.

Abstract

A photographic Ag image is made permanent after development by bathing it in a soln. contg. thiosulfate, which forms a sol. complex with the residual Ag halide. Some of the Ag in the image is sulfided by the thiosulfate during fixation. The purpose of this study was to det. the amt. of sulfiding of the Ag in the image during fixation of film and paper. The amt. of Ag reacting depends on the type of light-sensitive layer. Also, during bleaching, the residual thiosulfate in the film or paper reacts with Ag in a K2Cr2O7-H2SO4 bleach bath to form Ag2S. For one paper, it was shown that the amt. of Ag2S which was formed in the bleach bath increased with the increase of the concn. of the residual thiosulfate in the paper. A procedure was developed for the reduction of Ag2S in all emulsion layer to Ag so that the Ag2S could be detd. in terms of the optical d. of the Ag deposit. The use of hypo eliminators was investigated and a test procedure was found for testing their effectiveness. A small amt. of KI added to the fixing bath was effective in preventing most of the sulfiding of the Ag image during fixation. [on SciFinder(R)]