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  1. #31
    BradS's Avatar
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    Quote Originally Posted by albada View Post
    I remember reading a posting somewhere that tests showed that having too much ascorbate (ascorbic acid?) in a developer is harmless. If so, we can add extra to drop the pH to 8.0. That means we can also delete the boric acid, resulting in this simple formula:

    Water ................................... 750 ml
    Phenidone ............................ 0.15 g developer
    Ascorbic Acid ....................... 14.3 g developer, and adjust pH to 8.00
    Sodium Sulfite (anhydrous) .... 75 g alkali and halide-solvent
    Water to make ...................... 1 L
    Mark Overton
    Is the ascorbic acid going to act as a developing agent at this pH ? I don't think so.

  2. #32
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    Quote Originally Posted by Photo Engineer View Post
    You must remember that there are trade off situations. The developers at Kodak cost millions of dollars to develop. All others were done on a shoestring by comparison.
    (...snip...)
    PE
    I think this is why I keep coming back to plain vanilla D-76. There is a reason that it has been around so long and ther eis a reason that virtually every commercially viable producer of developers fro B&W films has offered an "equivalent" to D-76. Similar ideas apply to XTOL (and maybe even Dektol?).

  3. #33
    Photo Engineer's Avatar
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    There are several variations on Dektol that offer different degrees of similarity and improvement. Same thing as with D76.

    PE

  4. #34

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    Quote Originally Posted by Michael R 1974 View Post
    But if the pH, and therefore activity is low enough the film spends a significantly longer amount of time in contact with the sulfite. I'm thinking here of how D25 works compared to D23, although they both have more sulfite and don't use phenidone.

    Am I wrong in thinking the formula:

    Water ................................... 750 ml
    Phenidone ............................ 0.15 g developer
    Ascorbic Acid ....................... 14.3 g developer, and adjust pH to 8.00
    Sodium Sulfite (anhydrous) .... 75 g alkali and halide-solvent
    Water to make ...................... 1 L

    ...would be a very low energy developer? This seems almost like a POTA variant with lower pH.
    Keep in mind that this formula is an attempt to simplify Ryuji Suzuki's DS-10, which has the above amounts of phenidone and sulfite. It likewise has a pH of 8.00, but it uses different acids/alkalies to achieve 8.00, whereas I increased the ascorbic acid to do so. So with the same pH and sulfite, and equal or greater quantities of same developers present, I'm hoping this formula will behave like DS-10. Although PE warns me (in different words) that things don't always (even usually?) work as expected.

    I got the order with Photo Formulary straightened out, I'll soon have some ascorbic acid for tinkering with this.

    Mark Overton

  5. #35

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    Quote Originally Posted by albada View Post
    Ryuji said in a pure-silver posting, "At this point I do not recommend to store DS-10 for any more than a couple of weeks." Farther down in that posting, Ryuji says, "At this point, I mix DS-10 as I use."

    Here's the link: http://www.freelists.org/post/pure-s...-information,1

    So yes, it makes one question the addition of chemicals for preservation.

    Mark Overton
    I think that Ryuji was being conservative at this point because he hadn't finished testing for the developer's storage life. The Stability Constant for the iron-salicylate complex is 6.55 which I think is adequate.
    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

  6. #36

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    Quote Originally Posted by Alan Johnson View Post
    Solubility of Salicylic acid in water is given here as ~2g/L
    http://en.wikipedia.org/wiki/Salicylic_acid
    In DS-10 you are not dealing with pure water but with an alkaline solution which will increase the solubility.
    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. #37

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    Quote Originally Posted by albada View Post
    I like removing ingredients while only half-knowing what I'm doing.
    Mark Overton
    Saying that a formula has too many ingredients is like saying that Mozart's music has too many notes. In a developer each of the ingredients has a purpose. Remove things at your own peril. You cannot remove the TEA or salicylic acid without changing the developer's pH among with other effects.
    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

  8. #38

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    I wonder what a little bit of EDTA-Na would do for stability.

  9. #39
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    I would like to see the complexation constants for Ferric EDTA and Ferric Salicylate in the same medium and at the same concentration.

    I can't seem to find this information yet.

    PE

  10. #40

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    I came across a list www.coldcure.com/html/stability_constants.html which contained mostly compounds involved in human physiology like amino acids but which also contained the following

    ferric salicylate 16.35 ferrous salicylate 6.55
    ferric EDTA 25.7 ferrous EDTA 14.3
    ferric NTA 15.87 ferrous NTA 8.84

    salicylate constants seems to roughly comparable to those of NTA in stability.
    Last edited by Gerald C Koch; 11-23-2011 at 03:08 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



 

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