Potassium Ferricyanide Keeping Properties

dancqu · Apr 22, 2008

Both as a powder and in solution, may I expect
long life from the two? Dan

David A. Goldfarb · Apr 22, 2008

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

Photo Engineer · Apr 22, 2008

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

jamusu · Apr 22, 2008

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.

Erik L · Apr 22, 2008

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

David A. Goldfarb · Apr 22, 2008

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

Photo Engineer · Apr 22, 2008

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

Erik L · Apr 22, 2008

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

Kirk Keyes · Apr 23, 2008

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.

Ian Grant · Apr 23, 2008

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

Photo Engineer · Apr 23, 2008

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

Snapshot · Apr 23, 2008

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.

Ian Grant · Apr 23, 2008

It goes blue when it decomposes.

Ian

panastasia · Apr 23, 2008

Ian Grant said:
It goes blue when it decomposes.

Ian

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

Snapshot · Apr 23, 2008

Ian Grant said:
It goes blue when it decomposes.

Ian

Yes, thank you Ian.

dancqu · Apr 23, 2008

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

Potassium Ferricyanide Keeping Properties

dancqu

David A. Goldfarb

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Photo Engineer

jamusu

Erik L

David A. Goldfarb

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Photo Engineer

Erik L

Kirk Keyes

Ian Grant

Photo Engineer

Snapshot

Ian Grant

panastasia

Snapshot

dancqu

Potassium Ferricyanide Keeping Properties

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