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Self-mixing fixer 24, gone milky. Help!

Shakti V.

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I mixed a non-hardening fixer recommended for prints, F-24 fixer. Here is the formula I used:

Water (125F/52C) 500 ml
Sodium thiosulfate (anhy) 152 g
Sodium sulfite (anhy) 10 g
Citric Acid 22 g
Cold water to make 1000 ml


I multiplied all values (except for temperature, of course) by 3.8 to make 3.8 litres/1 gallon.


The mixture remained clear until I added citric acid. When I poured citric acid, the mixture turned milky. I researched that too much acid does this.
My questions are:


1. Can I just add sodium sulfite again to remove the resulting sulfur precipitate?
2. Is there another reason why the mixture turned milky?
3. Can I still use the fixer even if the mixture turned out to be milky?
4. What should be the final color of the fixer after mixing?


I let the solution stand for hours and now it is not as milky as when freshly mixed. What's the reason for this? The solution is yellowish, though. Should this be the final color of fixer 24? Can I still use this fixer?



I hope for replies soon. Thanks.
 
The fixer should continue to clear with time. You can check it for efficacy using a piece of un-exposed film.
 
It looks like you are using a version of Kodak's F-24 fixer with about 90g less hypo than the formula I have used and where citric acid is substituted for sodium bisulfite, often done to help control the odor of fixer solutions.

I think why the cloudiness happens with citric acid vs. using sodium bisulfite is that hypo has very little buffering ability with the citric acid.

It should be fine. You can try adding some sodium bisulfite to help clear the solution. Not sure how you mixed it, but always make sure to mix in order of the formula and that each addition is completely dissolved before moving on to the next. So, no, do not add any more sulfite it is there mostly as a preservative. Also, when you multiply out formulas for larger quantities often some of the components need to be adjusted.

There is also a F-24 variant that consists of only Hypo, sodium sulfite and bisulfite.
 
I realized that my sodium thiosulfate is pentahydrate, as I have received replies from another forum that the crystalline form is penta and the powder form is anhydrous. I have the colourless, big, crystalline form, so it must be penta. I should have put 240 grams instead of 152grams (all multiplied by 3.8 ).

The solution cleared overnight without any precipitate, but as I realized that I should have added more sodium thiosulfate, I experimented. I added the lacking amount
[(240grams*3.8 )-(152grams*3.8 )] of sodium thiosulfate. Then I added a teaspoon of sodium sulfite. It produced a precipitate, no matter how I mix. This precipitate, I've researched, is sulfur. Then that means my fixer is busted. Lesson learned: know your chemical first, and mix in the proper order.

I will try to mix another one, then try other formulae as I prefer a rapid fixer. Hope you will contribute to the next post.

Thanks for your replies.
 

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