Toning Photographic Prints

1921 Scientific American  
The active constituent of these papers consists of an emul sion of silver chloride in gelatin, albumen or colloidon in the presence of citric acid and an excess of a soluble silver salt (citrate or nitrate). The latter absorbs the chlorine, disen gaged in the decomposition of the silver chloride by exposure to light. The soluble silver salts are removed by washing and the undecomposed chloride of silver by means of a "hypo" bath. At the same time the subchloride of silver (Ag.Cl), which forms
more » ... .Cl), which forms the image, is converted into the chloride of silver and the metal itself: Ag.Cl = AgCl + Ag.
doi:10.1038/scientificamerican05011921-431supp fatcat:dp323njyiraxppde37stppvy3a