Silver compounds Sodium thiosulfate

The compound sodium thiosulfate pentahydrate, Na2S203 5H20, is important commercially to the photography business as "hypo," because it has the ability to dissolve unreacted silver salts from photographic film during development. Sodium thiosulfate pentahydrate can be produced by boiling elemental sulfur in an aqueous solution of sodium sulfite. 

Sulfur Complexes. Silver compounds other than sulfide dissolve in excess thiosulfate. Stable silver complexes are also formed with thiourea. Except for the cyanide complexes, these sulfur complexes of silver are the most stable. In photography, solutions of sodium or ammonium thiosulfate fixers are used to solubilize silver hahdes present in processed photographic emulsions. When insoluble silver thiosulfate is dissolved in excess thiosulfate, various silver complexes form. At low thiosulfate concentrations, the principal silver species is Ag2(S203) 2j high thiosulfate concentrations, species such as Ag2(S203) 3 are present. Silver sulfide dissolves in alkaline sulfide solutions to form complex ions such as Ag(S 2 Ag(HS) 4. These ions are... 

Unglazed Berl saddles coated with silver nitrate and operated at 135°C were used at Hanford [Ml] to remove HI and I2 from dissolver off-gases. In 1958, an explosion occurred, which was attributed to an unstable compound of silver and ammonia formed when the reactor was periodically cleaned by washing with ammonium sulfite. After this was replaced by sodium thiosulfate, the reactor operated for 14 years without incident. 

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