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Discussion in 'B&W: Film, Paper, Chemistry' started by dancqu, Apr 22, 2008.
Both as a powder and in solution, may I expect
long life from the two? Dan
In solution it doesn't last long. I mix it up just before use. Dry it lasts.
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.
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.
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.
I put a few grains in a glass container and add water to make a pale yellow solution for local bleaching with a brush.
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.
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.
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.
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.
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.
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.
It goes blue when it decomposes.
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.
Yes, thank you Ian.
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