Sodium metabisulfite in glycol - problem with dissolving

Discussion in 'B&W: Film, Paper, Chemistry' started by skljocnulbumte, Jan 20, 2018.

  1. skljocnulbumte

    skljocnulbumte Member

    Messages:
    22
    Joined:
    Mar 8, 2017
    Location:
    Croatia
    Shooter:
    Medium Format
    Hello!
    I started to dissolve a powder chemistry for pyrocat-hd in glycol. From the start I had a problem with sodium metabisulfite. I couldn't dissolve it. Temperature was 65C. After 30min of mixing it is the same like on the start. Is there any trick to dissolve it? I didn't add any other chemistry yet. Thanks a lot for any advise.
     
  2. Alan Johnson

    Alan Johnson Subscriber

    Messages:
    1,942
    Joined:
    Nov 16, 2004
    http://www.pyrocat-hd.com/html/mixing.html
    The metabisulfite and bromide are meant to be dissolved separately in water before adding to the glycol.
    If you let the undissolved metabisulfite settle out overnight it may be possible to pour off the clear glycol and dissolve the residue metabisulfite-glycol slurry in water as per the instructions.
     
    Last edited: Jan 20, 2018
  3. ritternathan

    ritternathan Member

    Messages:
    164
    Joined:
    Sep 10, 2010
    Location:
    Jersey City,
    Shooter:
    Multi Format
    If you are mixing in glycol, I recommend Pyrocat-HDC. Here is the recipe from the website, pyrocat-hd.com:

    B. Pyrocat-HDC (Solution A mixed in glycol)
    Stock A
    Propylene Glycol at 150F 750ml
    Pyrocatechin 50 g
    Phenidone 2.5g
    Ascorbic Acid 4.0g
    Propylene Glycol to 1000ml

    Pyrocat-HDC gives almost identical results as Pyrocat-HD with most films and development methods.
     
  4. Gerald C Koch

    Gerald C Koch Member

    Messages:
    8,262
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    There is a saying in chemistry, "Like dissolves like." What it means is that organic solvents like a glycol dissolve organic substances while water being ionic dissolves ionic substances like sodium chloride. The solubility of sodium metabisufite in glycols is very low.
     
  5. Alan9940

    Alan9940 Subscriber

    Messages:
    917
    Joined:
    Jun 17, 2006
    Location:
    Arizona
    Shooter:
    Multi Format
    FWIW, this is how I've mixed Pyrocat-HD in glycol for years:

    1. Weigh out all the dry chemicals for Stock A.

    2. Pre-heat the glycol to about 150F in a water bath or hot plate stirrer.

    3. Add the pyrocatechin to the warm glycol and stir until dissolved. Should take no more than about a minute.

    4. Add the phenidone and stir. Should dissolve completely in about a minute.

    5. Add the bromide and sodium metabisulfite to about 50-75ml (for 1L final volume) of hot distilled water at about 120F. Stir until completely dissolved, and then add this solution to the glycol solution.

    6. Top off the solution with glycol to final volume.

    I've never had any issues with any of the dry chemicals dissolving completely using this method. Hope it helps.
     
  6. Gerald C Koch

    Gerald C Koch Member

    Messages:
    8,262
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    However you are dissolving the bromide and metabisulfite in water so this really doesn't really help the OP's problem.
     
  7. john_s

    john_s Member

    Messages:
    1,227
    Joined:
    Nov 19, 2002
    Location:
    Melbourne, A
    Shooter:
    Medium Format
    Sodium metabisulfite is soluble in glycerol, which might be preferable to water to add to the Pyrocat.
     
  8. dario

    dario Member

    Messages:
    69
    Joined:
    Jan 15, 2006
    Shooter:
    Large Format
    Does that mean that glycerol could be used instead of the propylene glycol?
     
  9. John Wiegerink

    John Wiegerink Member

    Messages:
    1,495
    Joined:
    May 29, 2009
    Location:
    Lake Station, MI
    Shooter:
    Multi Format
    I think what he's hinting to is to mix the glycerol and sodium metabisulfite together first and then add to the propylene glycol. JohnW
     
  10. dario

    dario Member

    Messages:
    69
    Joined:
    Jan 15, 2006
    Shooter:
    Large Format
    Yes, agreed. It just occurred to me that maybe one could perhaps replace the glycol with glycerol, and if so would there be any advantage?
     
  11. Murray Kelly

    Murray Kelly Subscriber

    Messages:
    524
    Joined:
    Jan 31, 2007
    Location:
    Brisbane, QLD
    Shooter:
    Multi Format
    IIRC Pat Gainer suggested exactly that. Glycerol is easier to get for some people.
     
  12. Raghu Kuvempunagar

    Raghu Kuvempunagar Member

    Messages:
    95
    Joined:
    Jul 28, 2016
    Location:
    Seattle/Bangalore
    Shooter:
    Multi Format
    Isn’t glycerol hygroscopic? It’s probably impossible to get water free Pyrocat developer Part A that has Metabisulphite in it.
     
  13. John Wiegerink

    John Wiegerink Member

    Messages:
    1,495
    Joined:
    May 29, 2009
    Location:
    Lake Station, MI
    Shooter:
    Multi Format
    It's my belief that you use just enough "glycerol" to get the Sodium Metasulfite into solution. You could do the same with a small amount of H2O also. These tiny amounts of water have very little or maybe even "NO" effects on shelf life. I have finally settled on Pyrocat-HDC and see no reason to try the other forms of Pyrocat after using HDC version for a while. I've used the PC version, HD version and the MC version and they are all good. That's just me of course. JohnW
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies. If you have a Photrio account, please log in (and select 'stay logged in') to prevent recurrence of this notice.