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  1. #1
    Ian Grant's Avatar
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    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
    __________________
    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #71
    Photo Engineer's Avatar
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    Dimezone-S at Kodak was called HMMP or Hydroxy Methyl Methyl Phenidone. It has the best balance between keeping and being a powerful developing agent.

    The Bisulfite anion HSO3- decomposes rapidly to SO3-- and then scavenges oxygen to form SO4-- or sulfate anion.

    The metabisulfite anion is much more powerful a reducing agent, and one reference I have seen states that it can catch fire during the grinding process to break up lumps. It undergoes exactly the same reactions as above but the initial breakdown from metabisulfite to sulfite or bisulfite (pH dependant) is very quick and strong. This is Na2S2O5 or the S2O5-- anion. The Metabisulfite gives one mole of SO2 and one mole of SO3 upon decomposition in water, both of which end up making HSO3- or the equivalent. It is acidic in water.

    A second reference gives no comment about Sodium Metabisulfite catching fire. However my references do ascribe this to the Potassium salt

    So, I would tend to say take precautions with the Potassium salt.

    PE

  3. #72
    Ian Grant's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Dimezone-S at Kodak was called HMMP or Hydroxy Methyl Methyl Phenidone. It has the best balance between keeping and being a powerful developing agent.

    The Bisulfite anion HSO3- decomposes rapidly to SO3-- and then scavenges oxygen to form SO4-- or sulfate anion.

    The metabisulfite anion is much more powerful a reducing agent, and one reference I have seen states that it can catch fire during the grinding process to break up lumps. It undergoes exactly the same reactions as above but the initial breakdown from metabisulfite to sulfite or bisulfite (pH dependant) is very quick and strong. This is Na2S2O5 or the S2O5-- anion. The Metabisulfite gives one mole of SO2 and one mole of SO3 upon decomposition in water, both of which end up making HSO3- or the equivalent. It is acidic in water.

    A second reference gives no comment about Sodium Metabisulfite catching fire. However my references do ascribe this to the Potassium salt

    So, I would tend to say take precautions with the Potassium salt.

    PE
    Could have done with that Metabisulphite explanation when there was the specific thread, Gainer & I kept back & forth on the subject

    On a safety note, Potassium Metabisulphite is always sold in bulk as a liquid, and that's how Agfa would have used it to make early Rodinal.

    The formulae at the start of the thread use Sulphite, except the early versions Andresen designed, which is widely published.

    Ian

  4. #73
    Photo Engineer's Avatar
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    It seems to me that there is just a tiny need to know some chemistry in order to design new developers and fixes.

    It also seems that this knowledge will explain many early practices and will indeed relate to safety in the modern day photo lab.

    PE

  5. #74
    Ian Grant's Avatar
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    The chemistry was sound that's what I've said before about metabisulphite but others look at the words Kodak Bisuphite and assume simple "Bisulphite" when in fact Kodak's MSDS shows it's mainly Metabisuphite.

    Ian

  6. #75
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    Meanwhile, I AM doing more tests. The trouble is that life tests may require a long time. That would be good. I put a few ounces of the latest all K metolal in my brisker at 104 F to age for a week or so. If it still works, I'll do another test every week until it does not work. The attachments show the first test. The film is EDU 400 Ultra. I also have HP5+ and FP4+ that I will test.
    Attached Thumbnails Attached Thumbnails Metolal K Test 1.jpg   Metolal K Test 1 Detail.jpg  
    Gadget Gainer

  7. #76
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    Ian, Patrick;

    According to my texts, the Sodium Bisulfite available commercially is mostly Sodium Metabisulfite. The same texts do not claim that for the Potassium salt. So, apparently, the Sodium salts are in equillibrium in the solid and liquid state.

    PE

  8. #77

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    Quote Originally Posted by Originally Posted by Photo Engineer
    You would not want to put Ammonium Bisulfite into a developer!
    Quote Originally Posted by Kirk Keyes View Post
    It might get a little stinky...
    And I've been reminded about another reason not to use it.

    The ammonium ion is an excellent silver halide solvent and it will fog the film as a result.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  9. #78

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    Quote Originally Posted by gainer View Post
    Meanwhile, I AM doing more tests.
    Pat - can you do some step wedges or something in addition to your flowers? We might learn a bit more in your tests than how your flowers are aging.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  10. #79

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    Quote Originally Posted by Ian Grant View Post
    It'll be Phenidone-Z, (unless they changed to another derivative
    So all these years I've been using a molecular formula for Phenidone that was short one methyl group! Oh no!!!!
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  11. #80
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    Quote Originally Posted by Kirk Keyes View Post
    Pat - can you do some step wedges or something in addition to your flowers? We might learn a bit more in your tests than how your flowers are aging.
    It would be good to have some reference wedges or photos as well to compare contrast and speed.

    PE



 

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