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  1. #11
    PerfesserKev's Avatar
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    A reply on an old thread, tossed mainly to Photo Engineer:

    I recently mixed a batch of FX-10 using CD-2. The newly purchased CD-2 was brown, and when added to the sulfite solution produced a nasty brown oily tar that ruined a PVC graduate and stir rod. I assume the CD-2 has oxidized, though the vendor says it's good and fresh. Knowing little about this chemical I was wondering if you could verify. I read elsewhere online that the solid should be white.

    If there is some other caution on mixing that I should know, send it my way -- temperature, pH, etc.

    Thanks!
    "Photography has flourished for a century and a half with only two real subjects: beauty, and bad news." -- Larry McMurtry

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  2. #12
    Athiril's Avatar
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    How much oil did it produce? Can you take a pic? Mine is pretty good, though I do get a small oil spot on the top of solution, but I filter it out. Nothing that sticks to plastic or glass though.

    You could potentially recrystalise it too, to keep whatever left of it that's good.

  3. #13
    Photo Engineer's Avatar
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    Good CD2 is hard to dissolve, and bad CD2 gives an oily tar. Your description says that the CD2 was likely bad. It should not ruin your stirring rod or cylinder.

    In sulfite it should be straw colored to tea colored. A small tad of oil might be expected due to the formula you are using.

    Best go bck to the dealer.

    PE

  4. #14

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    Para-phenylenediamine is a weak developing agent that causes severe loss of speed when used alone. Its presence in a developer is more for its silver halide solvency than for its developing capability. This is why it is usually used in combination with one or more other developing agents. According to the Kendall-Peltz rule it should be super-additive with developing agents like hydroquinone and catechol.
    Last edited by Gerald C Koch; 04-04-2014 at 03:50 PM. Click to view previous post history.
    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

  5. #15
    Ian Grant's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    According to the Kendall-Peltz rule it should be super-additive with developing agents like hydroquinone and catechol.
    And so back to Meritol the combination product with Pyrocatechin

    These developer combinations are under explored but the commercial products lived up to their hype.

    Ian

  6. #16
    Photo Engineer's Avatar
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    But, CD2 is not PPD, it is N, N-Diethyl p-Phenylene Diamine which has many different properties including much lower solvency of silver Halide. Although PPD would not win any pize for being a silver halide solvent itself.

    CD2 is a true color developing agent with a much higher ability to reduce silver and thus it can be oxidized in air rather easily. It is usually sold as the HCl or H2SO4 salt, but I have seen the p-Tosyl salt as well.

    PE

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