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  1. #1

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    Citric acid stop bath crystals

    I think I've got gremlins in my cellar...
    Now I've got a problem with stop bath: I just mix Kodak Sb-8, that is 15g citric acid in 1lt of plain water. The day after I got many crystals of citric acid floating freely in the bottle and there's not any conceivable way of getting them back into solution...

    What the hell is this?

    It happens with distilled water and tap water with edta alike...

  2. #2

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    make the water warmer.

  3. #3

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    Quote Originally Posted by amuderick View Post
    make the water warmer.
    It's at 22°C

  4. #4

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    Heat it 50C and stir vigorously. How pure is your citric acid?

    Nate Potter, Austin TX.

  5. #5

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    Quote Originally Posted by Nathan Potter View Post
    Heat it 50C and stir vigorously. How pure is your citric acid?

    Nate Potter, Austin TX.
    It's reagent grade.

  6. #6

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    A google search showed a couple of sites that say that approx 600g of citric acid is soluble in 1 Litre of water at 20degC.

    Something else is happening if 15g doesn't seem to be dissolving.

  7. #7

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    The weird thing is that those crystals keep coming back after all the citric acid is dissolved.
    It's like citric acid re-precipitates.

    However, to cut a long story short, I'll mix stop bath on a per session basis (3g/250ml)...

  8. #8

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    I regularly mix a 3% citric acid (30 g/1 Liter) clearing bath for Kallitype prints in room temperature (~20°C) distilled water and never had a problem. It dissolves fast and easily. I have never seen any crystals or precipitation.

    According to Wikipedia, the solubility of citric acid in water is 133 g/100 ml (22°C)

    What is the quality of you water?

  9. #9
    Ole
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    It can't be citric acid crystals, so it must be something else. I can't remember if there are any likely candidates among the citrates, but my guess is that something carried over from the developer is insoluble in acid solutions. Or something in your bottle...

    In other words, you're not giving us enough information.
    -- Ole Tjugen, Luddite Elitist
    Norway

  10. #10
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    15g/1 ltr is a quite normal (1,5%) stop bath. And indeed the solubility of Citric Acid in a liter water is very high so that can not be any problem at all.
    Somewhere there must be a contamination.
    Put those Gremlins back in the box where they can not disturb you.

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