Parodinal with ascorbate in place of sulfite

Discussion in 'B&W: Film, Paper, Chemistry' started by MichaelMadio, Sep 27, 2011.

  1. MichaelMadio

    MichaelMadio Member

    Messages:
    49
    Joined:
    Sep 6, 2006
    Location:
    Ontario, Can
    Shooter:
    Multi Format
    I've been using parodinal + vit-c + borax to make a low pH p-aminophenol + vit-c developer that works well. I tried making a version that replaces the sulfite with ascorbate in an effort to not use sulfite. It's not that I have anything against sulfite, it's something I stock anyway as I use it in my fix, but I wanted to see if it could be replaced. It works well but the problem I find is that I need to use twice as much of the ascorbate version to get the same level of activity as the sulfite version.

    Besides the activity level, the major visible difference is in the formation of long needle-like crystals. The sulfite version does this but the ascorbate version does not. I don't know what the crystals are but if they are p-aminophenol that means that the sulfite-parodinal is super-saturated and ascorbate-parodinal is not ... is this correct? It could be that the acetaminophen to p-aminophenol conversion does not complete in the ascorbate version which would explain the reduced activity. Does the conversion to p-aminophenol need sulfite?

    Hopefully others with more knowledge about this can reply as I am a non-chemist hack and really appreciate learning from others.
     
  2. daveandiputra

    daveandiputra Member

    Messages:
    192
    Joined:
    Jul 10, 2010
    Location:
    Jakarta, Ind
    Shooter:
    35mm RF
    Hi,
    this interest me as i've been fiddling around using parodinal as my main developer, what will the advantages of using ascorbate instead of sulfite?

    no expert but i'm getting the suggestion that the hydroxide-paracetamol is the one doing the conversion.

    dave
     
  3. MichaelMadio

    MichaelMadio Member

    Messages:
    49
    Joined:
    Sep 6, 2006
    Location:
    Ontario, Can
    Shooter:
    Multi Format
    The advantage of using ascorbate in place of sulfite is simpler preparation. I don't see much pictorial difference when using the ascorbate and sulfite versions. This may turn out to be more of an academic exercise than anything else.

    About the conversion, my understanding, as yours, is that it's the hydroxide that does the conversion and this is what has me confused. The only change I made was using ascorbate instead of sulfite and I confirmed that the pH was the same so I expected similar results. I wonder why the sulfite version has crystals and is more active than the ascorbate version.
     
  4. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,340
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    You are not really replacing sodium sulfite with ascorbic acid. The two chemicals are not equivalent. Ascorbic acid is a developing agent and adding it to parodinal changes the whole nature of the developer.

    I fail to see the need for experiments such as this. Just because you can do something doesn't mean that you should do it.
     
  5. Alan Johnson

    Alan Johnson Subscriber

    Messages:
    1,536
    Joined:
    Nov 16, 2004
    Are you referring to the following with sulfite and with 100g sodium ascorbate instead of sulfite?
    http://www.digitaltruth.com/data/parodinal.php
    (The sulfite version contains an excess of sodium sulfite which produces crystals on cooling.I use only 25g sulfite ,it seems to keep just as well.This may explain your crystals)
    When you compare the activity of the sulfite and ascorbate versions is that both without borax?
     
  6. MichaelMadio

    MichaelMadio Member

    Messages:
    49
    Joined:
    Sep 6, 2006
    Location:
    Ontario, Can
    Shooter:
    Multi Format
    @Gerald: I completely agree that this may not be a good thing and concur with "because you can do something doesn't mean that you should do it". I also realize that I am not chemically replacing sulfite with ascorbate but I am replacing it in the context of the recipe. I realize ascorbate changes the nature of the developer because what caused me to look at this is that I had good results by using parodinal + vit-c + borax to make a p-aminophenol-c developer at pH 9.2 that gave good speed and fine grain. I'm trying to better understand the mechanisms involved to help diagnose the problem.

    @Alan: I am referring to the digitaltruth rodinal formula but I add 5g of ascorbate instead of sulfite. I then use a borax + ascorbate solution to dilute the developer. I use this same solution to dilute sulfite-parodinal. When I compare the two diluted with the same borax-ascorbate solution, they have the same pH but the ascorbate-parodinal one needs twice as much concentrate to get the same level of activity. It could be that the crystals in the sulfite version mean something or they could mean nothing ... I don't know. I'm trying to find an explanation for my observations.
     
  7. Alan Johnson

    Alan Johnson Subscriber

    Messages:
    1,536
    Joined:
    Nov 16, 2004
    Like p-aminophenol,metol is an aminophenol.
    It is known that metol & ascorbate are superadditive.
    Metol-sulfite is different, sulfite speeds up development by reacting with metol oxidation product.
    If your observation is correct it might be there is a reaction between p-aminophenol oxidation product and sulfite as well as superadditivity between p-aminophenol and ascorbate.
    Sodium hydroxide is hazardous,see msds.
     
  8. MichaelMadio

    MichaelMadio Member

    Messages:
    49
    Joined:
    Sep 6, 2006
    Location:
    Ontario, Can
    Shooter:
    Multi Format
    Interesting theory. Something else to add is there is a noticable difference in the colour of the two versions. They both start the same by turning pink/orange, the original sulfite keeps getting darker, looking more brown while the ascorbate one looks more yellow and doesn't get much darker. Is this any indication of what is or is not happening in the ascorbate version?
     
  9. Alan Johnson

    Alan Johnson Subscriber

    Messages:
    1,536
    Joined:
    Nov 16, 2004
    See"The Theory of the Photographic Process" Mees & James p367.
    They dont find any difference in the rates with sulfite and ascorbate for the aminophenol metol but they note it forms a sulfonate with sulfite but is reduced back to metol by ascorbate.The sulfonate may be the cause of the color you see.
    It would be interesting if you could give your ascorbate formula when the experiments are finished.