Thiosulphate Reactions at the Surface of Developed Silver

Abstract

The detection of silver sulphide in processed photographic images has been attributed to the silver adsorbing a monomolecular layer of thiosulphate ions, which react to form silver sulphide when the silver image is bleached in acid dichromate solution. By studying adsorption with thiosulphate having the inner sulphur atom labelled, it has now been shown that most of the thiosulphate ions believed to be adsorbed by the silver image had already suffered rupture at the sulphur-sulphur bond, even before the bleaching step. Treatment of the silver image with a cyanide solution was relatively ineffective in removing the adsorbed sulphur, and it is thus doubtful whether it can be considered to be present in the form of silver sulphide.