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  1. #301
    Photo Engineer's Avatar
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    I note in your experiment Mark that there is no roll with no added PG. So, what if that one differed in the same way in time? Do we know that?

    PE

  2. #302

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    Quote Originally Posted by Photo Engineer View Post
    I note in your experiment Mark that there is no roll with no added PG. So, what if that one differed in the same way in time? Do we know that? PE
    Hmm, I haven't tested that case. I'll try to run an experiment tomorrow night (on All Hallows' Eve) to see what no PG does for a roll.

    Alan: A strip has more flow over it than an entire roll, so I'd expect strips to be denser than a roll. But for this dev, strips were thinner. Strange indeed! An odd thing is that the more concentrated formula that crystallized back in July (here) didn't have this time-issue.

    Mark Overton

    EDIT: It's been a while, so I figured I'd repost the formula for the concentrate we're talking about:

    Propylene glycol .................... 17 ml (hot; a little below 100C)
    Sodium metaborate 4 mol ..... 2.7 g
    Ascorbic acid ......................... 4.5 g
    Phenidone ............................. 0.05 g
    Propylene glycol to make ...... 22 ml

    One litre of working solution contains 45 g of sodium sulfite and 25 g (22 ml) of concentrate.
    Target pH = 8.18-8.19.
    Last edited by albada; 10-31-2012 at 01:54 AM. Click to view previous post history.

  3. #303
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    You know that if you don't test that new alternative, it will haunt you!

    PE

  4. #304

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    Quote Originally Posted by Photo Engineer View Post
    You know that if you don't test that new alternative, it will haunt you!
    PE
    I got spooky test-results! I mixed the formula again, but omitting the PG and decreasing the sodium metaborate by .1 g/L to maintain the same pH. Here are the curves with/without PG:

    Click image for larger version. 

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    They are eerily identical! At least you can't claim that my process lacks consistency. It makes one wonder if I actually added PG before. My log says so, and I remember measuring the PG. And if I didn't, the lower pH should have gotten my attention.

    To summarize what I've seen: Adding 16 ml/L of propylene glycol (that's 1.6% of volume) causes dev-time to increase by 7% for test-strips. But it has no effect on complete rolls. I doubt this is a problem for typical users, but it's something that's haunting me.

    Mark Overton

    PS: The title on the graph is wrong. I forgot to change that part of the gnuplot script-file.

  5. #305

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    Fenton test results

    Quote Originally Posted by Alan Johnson View Post
    In the UK the maximum limit for copper in drinking water is 2mg/L and for iron 0.2mg/L.I don't know the US values.
    http://dwi.defra.gov.uk/about/annual...ir09thames.pdf
    I daresay there may be high copper concentations in the UK which has mostly copper pipes and high iron concentrations in the US (which has mainly iron pipes?).
    The Fenton test consisted of adding Fe and Cu ions (iron and copper) to the developer to simulate iron and copper pipes, and impurities in chemicals. I added 1 mg/L each of Fe(II) and Fe(III) ions using ferrous sulfate heptahydrate and ferric ammonium sulfate, and 2 mg/L of Cu(II) ions by adding copper sulfate pentahydrate. Jerry: I used ferrous sulfate because PhotoFormulary doesn't carry ferrous ammonium sulfate. Was this change a mistake? The separate beaker of these ions at 100x concentration was a cloudy light-yellow. Surprise: When adding 1 ml of it to the developer, the developer turned light purple. I'll guess the ammonia is reacting with something.

    I waited 50 minutes before developing, to simulate easy-going one-shot usage. Here are density-curves with and without these added ions:

    Click image for larger version. 

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    The curves match well, so the Fenton reaction had no measurable effect. Nor did the purple, fortunately.
    Earlier tests show that hard water causes cloudiness starting at 30-45 minutes after mixing. So all should go well if this one-shot is used within 30 minutes of mixing.
    I guess my next step is to mix the concentrate and test its longevity and compatibility with various films. Comments are welcome as always.

    Mark Overton

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    Hi Mark,

    Iron forms a lavender/purple complex with salicylate ions. So it appears that the chelating agents are working. To answer your other question ferrous sulfate oxidizes fairly rapidly particularly in moist air. Ferrous ammonium sulfate is more stable but either should be OK.

    I would be interested in what would happen without the chelating agents. Would be ascorbate ion be rapidly destroyed at the concentrations you used. Also the longevity of your developer with the chelating agents and iron and copper present.

    Jerry
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  7. #307

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    Quote Originally Posted by Gerald C Koch View Post
    Hi Mark,

    Iron forms a lavender/purple complex with salicylate ions. So it appears that the chelating agents are working. To answer your other question ferrous sulfate oxidizes fairly rapidly particularly in moist air. Ferrous ammonium sulfate is more stable but either should be OK.

    I would be interested in what would happen without the chelating agents. Would be ascorbate ion be rapidly destroyed at the concentrations you used. Also the longevity of your developer with the chelating agents and iron and copper present.

    Jerry
    Hi Jerry, here's a surprise: Yesterday's brew had no chelating agents! I guess I didn't make that clear, but I wanted to see whether it would die quickly with no protection against Fe/Cu ions. Thanks for the note about oxidation of ferrous sulfate. I transferred it to a little amber glass bottle last night, so hopefully it'll keep a while. Anyway, do you know of anything else that would cause the purple? I used distilled water, so there should be no unknown chemicals in there.

    Mark Overton

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    One of oxidation products of phenidone is magenta in color. But this product shouldn't form in the presence of a reducing agent like ascorbate ion. So I really don't know what caused the color. All the oxidation products of ascorbate are colorless.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  9. #309

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    Quote Originally Posted by Gerald C Koch View Post
    One of oxidation products of phenidone is magenta in color. But this product shouldn't form in the presence of a reducing agent like ascorbate ion. So I really don't know what caused the color. All the oxidation products of ascorbate are colorless.
    Jerry, thanks for the help. Here are a few more tidbits I just got:

    * The purple coloration of the used developer was gone this afternoon; it was water-clear.

    * A clip-test from 20 minutes ago with normal temp/time/agitation/stop/fix/wash gave identical results to yesterday, so the dev did not degrade noticeably over 22 hours.

    * I divided the used dev into three parts, and put the three ion-producing chemicals into each. This was not measured; just a little bit in each, which was undoubtedly far too much. The Ferrous sulfate gave light purple, and the Ferric ammonium sulfate (FAS) produced a dense purple. Copper sulfate gave no color. So I suspect the colour is due to the FAS.

    * I put a little FAS into a beaker and added unmeasured quantities of each chemical in the dev. Nothing produced a purple, so maybe pH matters and I should measure quantities correctly.

    A caution:
    The FAS from the Formulary was labelled "Ferric Ammonium Sulfate", but the CAS-number on the packet is for Ferric Ammonium EDTA. It came as large crystals covered with white powder. When broken up, their internal colour is slightly pink as is pictured in Wikipedia here, so I think I have the correct stuff.

    Well, assuming I don't have the erroneous EDTA in there, it looks like the Fenton reaction is not an issue over the time-frame of one day.

    Mark Overton

  10. #310

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    Crystallization

    I've been experimenting with more concentrates using propylene glycol as the solvent, and characterizing the issue of crystallization. By way of review:

    * Paul Verizzo and I independently discovered that sodium metaborate dissolves in propylene glycol (PG).

    * I discovered that having some metaborate dissolved in PG increases the solubility-limit of ascorbic acid.

    * And I discovered that if one isn't careful, the solution of PG+metaborate+ascorbic can crystallize, causing the solution to separate into a cream and a liquid. It starts as smoke-like wisps, or cloudiness, or a few crystals appearing on the bottom. This can happen while mixing the concentrate hot, or it can start after a few days of sitting at room-temperature.

    Here's a smattering of observations about crystallization:

    1. It is not solely or even primarily a function of concentration-ratio (weight of powders in grams divided by final volume in ml). One solution with a ratio of 0.33 failed, and another with a ratio of 0.40 succeeded.

    2. All solutions with a metaborate-ratio (weight of metaborate in grams divided by final volume in ml) exceeding 0.12 failed. None with less than 0.12 failed. Of two with ratios of exactly 0.12, one passed and one failed.

    3. All solutions with a metaborate/ascorbic ratio of at least 0.533 failed. This ratio determines the alkalinity of the concentrate, and it appears that it dislikes alkalinity.

    4. Phenidone and perhaps especially Dimezone S make the crystallization problem worse.

    5. Higher temperatures while mixing ascorbic acid and Phenidone encourage crystallization during the mixing process.

    6. Metaborate alone in PG will not crystallize. You need ascorbic acid in there.

    That's what I know. Numbers 2 and 3 encourage one to reduce the metaborate, but if you do, you can't dissolve all the ascorbic acid in a reasonable time (or at all?). So there's a trade-off. In fact, it seems that there's a narrow zone where one can dissolve all the ascorbic acid while avoiding crystallization. And the developer D316 that I created back in January just happened to hit that zone. Alan Johnson, who named that developer after its posting-number, mixed the concentrate back then and has been testing it. I have a similar developer that's been sitting since then as a longevity-test. D316 is:

    Propylene glycol .................... 16 ml (hot)
    Sodium metaborate 4 mol ..... 2.2 g
    Ascorbic acid ......................... 4.5 g
    Phenidone ............................. 0.05 g
    The result is almost exactly 20 ml of concentrate.
    A litre of developer contains 20 ml of concentrate and 45 grams of sodium sulfite (but I'm thinking of boosting the sulfite).

    I tried changing the amount of metaborate. At 2.0 g, I could not dissolve all the ascorbic acid. At 2.4 g, the solution crystallized while hot. That tells you how narrow the workable zone is. Also, D316 showed the beginning of crystallization when I mixed it too hot (around 90C), consistent with observation 5. Alan mixed his at 70C with no problem.

    I posted this information so other home-brewers won't have to re-discover these things. I hope it helps somebody.

    Mark Overton



 

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