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  1. #1

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    calcium ascorbate

    Several months ago I bought a bottle of vitamin C at the health-food store to use for developing (E-76, Rodinal, etc.) and haven't opened the bottle yet, (but too late to return it) but I just now noticed on the front it says, "non acidic". Well, of course that made me wonder what is in the bottle. It turns out that it is not sodium ascorbate, but calcium ascorbate.

    I *think* that it's the same type that I've used successfully with E-76 before, but it may explain why my Rodinal w/vitamin C attempts were less than stellar.

    Can calcium ascorbate be subbed for sodium ascorbate? And if so, can it be subbed equally?

    Obviously this changes the ph of any soup to be made, but how much and how to compensate?

    Does it change dev times any?

    Anything else I might need to know???

    All is not lost, however; I can add it to beer and make a health drink out of it!

  2. #2

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    As a general rule, calcium is something that you don't want in photographic solutions, since its presence can lead to deposits on the film.

  3. #3
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    I don't think calcium ascorbate is what you want. Search the apug threads about "Vit C", "Ascorbate" or "Gainer".
    Wilbert
    http://www.photovergne.com
    Cours photo en Auvergne

  4. #4

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    John, where is the lead coming from, my indoor plumbing?



    Quote Originally Posted by john_s
    As a general rule, calcium is something that you don't want in photographic solutions, since its presence can lead to deposits on the film.

  5. #5
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    Quote Originally Posted by jim appleyard

    I *think* that it's the same type that I've used successfully with E-76 before, but it may explain why my Rodinal w/vitamin C attempts were less than stellar.

    Can calcium ascorbate be subbed for sodium ascorbate? And if so, can it be subbed equally?

    Obviously this changes the ph of any soup to be made, but how much and how to compensate?

    Does it change dev times any?

    Anything else I might need to know???

    All is not lost, however; I can add it to beer and make a health drink out of it!
    Jim, as near as I can tell from the little Google research I've done, both sodium and calcium ascorbates are buffered forms of ascorbic acid, mostly used for those people who need Vitamin C supplements, but don't want the acidity.

    They are not strictly interchangeable in a formula with asorbic acid. I'm sure Pat Gainer knows the correct proportions to use for the ascorbate form. But obviously, if it's not acidic, it will affect the pH of the formula. I've never used the ascorbate form, preferring the straight ascorbic acid, but many on this forum have.

    The calcium and sodium varieties appear to be pretty much interchangeable for dietary purposes, but I'm not sure about the calcium variety in a developing formula. I'd tend to agree that it might lead to some deposits on the film, but that's only a guess.

    Larry

  6. #6
    Ole
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    The problem isn't the calcium ascorbate, but how the calcium can react with the other chemicals in the soup. There are many calcium compounds with low solubility - like calcium sulfate (gypsum) and calcium carbonate (lime). I don't know the solubility of calcium sulfite and Ca-borate offhand, but I suspect they are good candidates for low sulubility too...
    -- Ole Tjugen, Luddite Elitist
    Norway

  7. #7
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    Would it be possible to mix the calcium ascorbate solution with sodium sulfate and precipitate out all the calcium first? A guess to the proper ratios?
    Gary Beasley

  8. #8

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    Calcium sulfite is even less soluble in water than calcium sulfate. The two solubility products are 6.8 x 10-8 and 9.1 x 10-6 respectively. Save the calcium sulfite for its intended use and buy some sodium ascorbate.

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    Sorry meant to say "Save the calcium ascorbate ...".

  10. #10
    Ole
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    Quote Originally Posted by Gerald Koch
    Calcium sulfite is even less soluble in water than calcium sulfate. The two solubility products are 6.8 x 10-8 and 9.1 x 10-6 respectively. Save the calcium sulfite for its intended use and buy some sodium ascorbate.
    Great! So you can precipitate out the calcium with sodium sulfite, ending up with sodium ascorbate
    -- Ole Tjugen, Luddite Elitist
    Norway

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