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  1. #531

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    Quote Originally Posted by Rafal Lukawiecki View Post
    Congratulations, Mark! Next time you visit Ireland, let me know and I'd love to buy you a drink—thank you for your impressive work.
    Thanks for the encouragement! It's nice to know that others value this effort.

    Quote Originally Posted by Alan Johnson View Post
    Sodium ascorbate was from ebay, it is a food supplement.
    I just did a search on both ebay and amazon, and sodium ascorbate is plentiful. Where have I been hiding? Photographer's Formulary doesn't carry it, and apug postings from 5-8 years ago made it sound like it was hard to find (it's used in Mytol), so I assumed it's hard to find. Not so.

    Quote Originally Posted by Alan Johnson View Post
    Conclusion- some of the phenidone survived 34 days oxidation and was regenerated.
    It seems likely all the ascorbate is oxidized first, before the phenidone.
    Alan, these are valuable results. It means we could do the following:

    1. Mix Mytol or something similar.
    2. Store it recklessly, letting it sit a long time in a partly filled bottle. It'll go off.
    3. Each time it's used, drop 1/8 or 1/4 or 1/2-teaspoon of sodium ascorbate into the beaker. Then the dev will work fine.

    This idea relies on the original ascorbate in the developer acting as a preservative, preserving the sulfite and Phenidone/Dimezone. Normally, we would want the sulfite to preserve the ascorbate, but that's not what happens. Instead, the ascorbate preserves the sulfite, which was (until now) considered a problem. We are taking advantage of that fact by adding ascorbate just before use, knowing that the other chemicals will be fine. We have turned a problem into an advantage.

    This idea also relies on the observation that having excess ascorbate in a dev is harmless. This is what Gainer found, and my tests confirm it. But we'd need to run more tests before relying on this. If true, it means that the ascorbate added at time-of-use does not need to be measured accurately; hence the use of teaspoons.

    These findings also suggest that one could revive dead XTOL by adding ascorbate to it. More experiments to try...

    Mark Overton

  2. #532

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    I published the article about Mocon (aka 214D). Here it is:

    http://www.apug.org/forums/forum223/...ml#post1483496

  3. #533
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    Quote Originally Posted by Alan Johnson View Post
    Attachments show that the solution containing sodium ascorbate alone went orange, strongly suggesting the orange color is due to the formation of an ascorbate oxidation product, it does not come from phenidone.
    Phenidone turns orange quickly at pH>7. Your test with Phenidone alone may not be conclusive.
    Trying to be the best of whatever I am, even if what I am is no good.

  4. #534

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    I do think the colors shown in the attachments I posted are relevant to the chemical changes and color changes likely to occur in the concentrate,mainly because the pH of the concentrate (with a little water) ,the sodium ascorbate solution and the phenidone solution are all very similar, just over pH=5.
    The phenidone doesn't see higher pH in the concentrate.

  5. #535

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    Quote Originally Posted by Rudeofus View Post
    Phenidone turns orange quickly at pH>7. Your test with Phenidone alone may not be conclusive.
    True, this is observed after mixing POTA (1.5g Phenidone + 30g Sodium Sulfite)/L.

  6. #536
    MattKing's Avatar
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    At the risk of making all of the excellent efforts of all of the contributors to this thread superfluous, wouldn't it be even better to have developed some kind of an easy to use test for the activity of stored, working strength X-Tol?

    Something like the retained silver tests or something as easy to use as litmus paper.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  7. #537
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    Matt, there was a thread on this a while back. There is a good test that relies on the time of development o achieve a given density of fresh and kept developer. Small clips of film are used.

    PE

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    Quote Originally Posted by Photo Engineer View Post
    Matt, there was a thread on this a while back. There is a good test that relies on the time of development o achieve a given density of fresh and kept developer. Small clips of film are used.

    PE
    PE:

    That is a "good" test, but not necessarily an "easy" test.

    The need for the test is most pronounced for those of us who have inconsistent film use needs, and temporary darkrooms - so something that just requires us to put a couple of drops of a solution into a few millilitres of developer and check for precipitate would be wonderful.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  9. #539
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    Matt;

    That is the problem.... There is no "easy" test.

    PE

  10. #540
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    Quote Originally Posted by Photo Engineer View Post
    Matt;

    That is the problem.... There is no "easy" test.

    PE
    PE:

    Are aware whether any research work has been done with a goal of developing such tests? Not just for X-Tol, but for other chemicals as well (e.g. E6 and C41). It seems to me that in the current circumstances, such tests would be much more likely to be commercially valuable than when volumes were higher.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2



 

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