Inorganic reactions

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I am wanting to investigate the concentration of silver ions in black and white photographic film and see whether there is a correlation between different iso numbers. To extract the silver ions (white part of the paper) I will use thiosulphate ions to form an aqueous complex. However I am unsure how to carry this redox reaction out?
110208

Corrie writes .....
 
The reaction between thiosulphate ions and silver ions is not a redox reaction, it is a complex-forming reaction:
 
Ag⁺ + 2S₂O₃^2- -> [Ag(S₂O₃)₂]⁺
 
[Ag(S₂O₃)₂]⁺ is a colourless complex ion in solution.
 
I would have thought that a sodium thiosulphate solution with a concentration between 0.1 and 0.02 mol dm^-3 would be suitable, depending on how much film your are treating and how you intend to determine the amount of silver you have extracted in the form of the complex.

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updated: 12 February 2008