Potassium Ferricyanide Keeping Properties

Discussion in 'B&W: Film, Paper, Chemistry' started by dancqu, Apr 22, 2008.

  1. dancqu

    dancqu Member

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    Both as a powder and in solution, may I expect
    long life from the two? Dan
     
  2. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    In solution it doesn't last long. I mix it up just before use. Dry it lasts.
     
  3. Photo Engineer

    Photo Engineer Subscriber

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    The powder lasts almost forever in a closed bottle.

    The solution of the compound alone lasts a rather long time as well. At least a minimum of 8 weeks to 16 weeks in my experience. If you add stuff it goes down.

    PE
     
  4. jamusu

    jamusu Member

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    How is it mixed?

    What are the dilution ratios for a strong solution and a weak solution. I attempted to use some for the first time this weekend and it did not go well at all.

    Jamusu.
     
  5. Erik L

    Erik L Subscriber

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    someone may correct if I'm wrong, but Jamusu I believe a stock solution of say 100 grams/1000 milliliters can be made and you can use a 10% solution of this stock solution as a starting point.
    regards
    Erik
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I put a few grains in a glass container and add water to make a pale yellow solution for local bleaching with a brush.
     
  7. Photo Engineer

    Photo Engineer Subscriber

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    Erik;

    That solution is a 10% solution. 10% of that would be 1% total. So, your answer could be a bit ambiguous.

    I should have been more specific above. If anything else is present it can be oxidized, and so typical rehal bleaches go bad because the bromide can be oxidized to bromate while the ferri can b reduced to ferro.

    PE
     
  8. Erik L

    Erik L Subscriber

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    Yes PE, I guess my reply was a little ambiguous. I just meant to use the 10% stock solution and cut it by varying %'s to experiment with as a starting point to play with.
    regards
    Erik
     
  9. Kirk Keyes

    Kirk Keyes Member

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    Store soultions of ferricyanide in dark glass or opaque bottles, and away from light. Light, UV in particular, will break down the complex that holds the cyanide to the iron.
     
  10. Ian Grant

    Ian Grant Subscriber

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    Well to add to the confusion a 10% solution of Potassium Ferricyanide can last well over 2 years, stored well. I used some to make up a re-halogenating bleach last week. It's probable the solution was much older but it worked perfectly, and showed no signs at all of decomposition.

    As for the powder I have some that's at least 30 years old, and it's still fine.

    Ian
     
  11. Photo Engineer

    Photo Engineer Subscriber

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    Well, I'm conservative in this, but Kirk and Ian are both right. It can keep a very long time as both a solid and in solution, especially stored well in dark bottles.

    PE
     
  12. Snapshot

    Snapshot Member

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    How does one know if potassium ferricyanide goes bad if it is in solid form? Does the colour change? I have stockpiled a fair bit of it because of the difficulty of acquiring it.
     
  13. Ian Grant

    Ian Grant Subscriber

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    It goes blue when it decomposes.

    Ian
     
  14. panastasia

    panastasia Member

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    Thank's Ian, I was also wondering about that. I also have a half full 1 lb brown glass jar from Kodak that's more than 30 years old and the crystals are still bright red/orange color - always kept it in a dark place.

    Paul
     
  15. Snapshot

    Snapshot Member

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    Yes, thank you Ian.
     
  16. dancqu

    dancqu Member

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    From the other current thread dealing with ferricyanide
    I see it's longevity at working strength when EXTREMELY
    dilute is an issue. As an oxidizer any organic or other
    oxidizable matter will kill it. So for post exposure
    pre-development use I'd suggest distilled. Dan