Ammonium thiosulfate powder to solution?

Discussion in 'Color: Film, Paper, and Chemistry' started by HumbleP, Feb 13, 2013.

  1. HumbleP

    HumbleP Member

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    Hi,

    Seems I've finally found a source down under for Ammonium Thiosulphate in Powder form (98%) but it's not cheap. I can get 500grams for $65

    My understanding to make a 60% solution I would be to mix 600g to 1 litre.

    My question then is if I make a 50% solution (with the available 500g) and my recipe calls for 162ml of a 60% solution can I use a 50% solution and either increase the quantity or perhaps increase the fix time?

    Or should I just bite the bullet and buy more powder to mix my 60% solution?

    Cheers,
    Peter
     
  2. Robert Hall

    Robert Hall Subscriber

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    Thats expensive.

    It's often easier to find ammonium thio in solution.

    60% is just about saturated.

    One would mix it down for a working strength, but yes. 600 grams for a liter.

    You can make your own Am thio with sodium thio and some Ammonium Chloride too.

    If you need a source for Am thio, talk to the folks who make or sell fertilizer. It's who I get it from here.

    55 US Gal is about $300.

    Sounds like you might have reagent grade. Far to pure for what you need.
     
  3. Paul Verizzo

    Paul Verizzo Member

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    I agree with Robert Hall's response. Ammonium Thiosulfate in "powder" form is expensive and very, very difficult to store. I have some. IIRC, it's hugely hygroscopic. You might be best served looking for sources of color fixer, or as Robert said, possibly agricultural. It's used in certain farming practices as a nitrogen source. Hydroponics, I think.

    I did pursue the ag channel a few years ago and found that I was better off buying it as a 60% solution. USA.
     
  4. Gerald C Koch

    Gerald C Koch Member

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    Is there a particular reason you need ammonium thiosulfate? A rapid fixing bath can be made from sodium thiosulfate with the addition of either ammonium chloride or ammonium sulfate. Check the formulas for kodak F-7 or F-9.
     
  5. Paul Verizzo

    Paul Verizzo Member

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  6. Photo Engineer

    Photo Engineer Subscriber

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    Use the liquid form. Don't waste money on the powder. It is way too expensive.

    PE
     
  7. HumbleP

    HumbleP Member

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    Actually I've had good results with sodium thiosulfate so I guess I'll stick with it. It just seems that every time I look into it I keep reading that I should use ammonium thiosulphate instead: much faster etc. So I've just been keeping my eye out for it. I think I'll give up on that idea and do as you suggest and add ammonium chloride or sulphate.

    Thanks,
    Peter
     
  8. Photo Engineer

    Photo Engineer Subscriber

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    Sulfate ion reduces the swelling of gelatin and thus can actually slow fixing and washing. It does work though. I suggest you check fix and wash times carefully, just in case they slow down.

    PE
     
  9. HumbleP

    HumbleP Member

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    That's good to know. Thanks PE
     
  10. Rudeofus

    Rudeofus Subscriber

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    Ammonium Chloride is much easier to get than Ammonium Sulfate and is also used to speed up Sodium Thiosulfate based fixers. At higher concentrations the Chloride forms soluble Silver complexes, which means the Chloride ions don't hurt the fixer as some might expect. Look for Agfa 304 or this recipe for a sample composition. You can add 10 g/l Na[SUB]2[/SUB]CO[SUB]3[/SUB] to Agfa 304 to get its pH up to about 6. Don't go much beyond pH 6 or the Ammonia smell will be obnoxious.

    If you are unsure whether a Sodium Thiosulfate based fixer is strong enough for archival fixing, use retained silver tests to find issues, then use two bath fixing to solve them.
     
  11. Gerald C Koch

    Gerald C Koch Member

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    Kodak specified two different fixers F-7 (using ammonium chloride) and F-9 (using ammonium sulfate). This was done because ammonium chloride can cause corrosion with some forms of stainless steel. Ammonium sulfate does not have this problem. This should not be a problem for the home user since the contact time with the fixer is short.