The thiosulfate ion does not freely diffuse out of a hardened photographic gelatin emulsion. Salts in the washing water displaces the adsorbed thiosulfate ions and allows them to freely diffuse out of the emulsion. The effect of temperature upon the diffusion of the thiosulfate ion is on the order of other diffusion processes. The type and amount of hardening also affects the diffusion of thiosulfate. The diffusion of thiosulfate out of the emulsion is fastest when a non-hardening fixer is used. The use of an alum hardening fixer results in slower diffusion than with formaldehyde prehardening.
Library of Congress Subject Headings
Photography--Developing and developers
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Haring, Kenneth, "Diffusion of the thiosulfate ion out of photographic film during washing" (1970). Thesis. Rochester Institute of Technology. Accessed from
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