Colour of Citrin stop bath?

Discussion in 'B&W: Film, Paper, Chemistry' started by Arctic amateur, Sep 17, 2012.

  1. Arctic amateur

    Arctic amateur Member

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    I bought a soft-pack of Citrin stop bath from Macodirect (http://www.macodirect.de/citrin-citrostopbr330ml-softpack-p-2196.html). According to the label it has an indicator, but which colours it will change from and to was not specified. When I first mixed it it had a clear purple colour. After a three rolls and a week in a plastic bottled-water bottle it has paled noticeably. Surely three rolls can't deplete 1,5 liters of stop bath? The bathroom floor is not particularly warm, a tray of water stored next to the chem bottles with a thermometer in it showed 20-22 C all week.

    Is the stop bath bad? Is this colour change normal even if not depleted, or does stop bath go bad in a week even if barely used?
     
  2. Alessandro Serrao

    Alessandro Serrao Member

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    If you get 1 kg of citric acid you'll spend about 10€ and you'll have a lifetime long supply of stop bath. Used one-shot.
    I'd use one-shot also the Citrin.
     
  3. Arctic amateur

    Arctic amateur Member

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    The stop bath has gone completely transparent, but pH strips say it's more acidic than the fixer, so I'm going to guess it's still good.
     
  4. Smudger

    Smudger Member

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    I would suspect a manufacturing fault. Most indicator stops turn purple when exhausted.
     
  5. Alessandro Serrao

    Alessandro Serrao Member

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    Use plain citric acid at 15g/l one shot. Buy it at your local pharmacy.