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Dassonville T5 - Disposal

Xícara

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Hi,

I'll shortly start experimenting with Dassonville T5 copper toner. In "The Darkroom Cookbook" Dassonville T5 is cited as a "replacement toner", "replacing silver with another metal", which in this case I assume is copper.
I imagine then that silver is released into the toning liquid. Is this correct? In which case I'll dispose of it together with spent fixer - there's a fellow that collects it to extract the silver.

Cheers,
 

John Wiegerink

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Or maybe the copper coats the silver?
 
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Xícara

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Reading a bit more, the component of Dassonville T5, potassium ferricyanide, is used in bleaching solutions to remove silver from negatives. So I'm inclined to think it will go into solution.

The formula for Dassonville T5 given in the Darkroom Cookbook is as follows:

Solution A
Copper sulfate 6.5g
Potassium citrate, neutral, 24.8g
Water to make 1 litre

Solution B
Potassium ferricyanide, 5.5g
Potassium citrate, neutral, 24.8g
Water to make 1 litre
 

Donald Qualls

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Based on that formula, I expect your understanding is correct. Thiosulfate makes the silver accessible to the sulfate ions in solution, and the copper plates onto each silver grain even as the silver dissolves, leaving either copper grains or copper plated silver grains (likely depending on the length of toning), and silver sulfate in solution.
 
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