Just Ask Antoine!
Atoms & ions
Energy & change
The quantum theory
Electrons in atoms
The periodic table
Acids & bases
History of chemistry
How does photographer's hypo work?
- Is AgCl solid soluble in Na2S2O3 aqueous?, if so why? If Ag solid is present will a developer coninue to reduce to Ag ions? if so why?
Elizabeth Brown firstname.lastname@example.org
Converting Ag into Ag+ is oxidation, not reduction.
An emulsion of sodium thiosulfate (called hypo by
photographers) is used to stop development of exposed film. Thiosulfate converts
undeveloped silver bromide grains in the film into water-soluble silver thiosulfate
complexes that can be removed when the film is washed.
S2O32-+ AgBr(s) AgS2O3- + Br-
S2O32-+ AgS2O3- Ag(S2O3)3-
Silver chloride behaves as silver bromide does.
See these Web sites for more detail on the chemistry of photography:
Chemistry in Black and White Photography (Shane Phillips, California State University)Components of Photographic Materials (George L. Smyth)
Author: Fred Senese email@example.com