Substitute chemical for reversal process

Discussion in 'B&W: Film, Paper, Chemistry' started by Marc Leest, Jun 13, 2005.

  1. Marc Leest

    Marc Leest Member

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    Can, in the bleaching stage (Ilford B+W reversal process) , hydrochloric acid used in place of sulfuric acid and when yes, at what dilution ?

    thx, Marc
     
  2. Ian Grant

    Ian Grant Subscriber

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    No definately not !

    The last thing you want is a halide, like chloride present as the bleach would form Silver Chloride.

    The bleach needs to form a very soluble silver salt which is removed by washing and won't be redeveloped.

    BTW pure concentrated Sulpuric Acid is sold as drain cleaner.

    Ian
     
  3. Gerald Koch

    Gerald Koch Member

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    pH Minus (used to lower swimming pool alkalinity) is 92.3% sodium bisulfate and 6.5% sodium sulfate. This product and others like it can be used in place of sulfuric acid in photographic solutions. 5 grams is roughly equivalent to 1 ml of concentrated sulfuric acid. When dissolved in water it acts like a mixture of sulfuric acid and sodium sulfate.
     
  4. Jordan

    Jordan Member

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    Gerald is right on with the sodium bisulfate idea (NOT bisulfite, which is totally different). I have used it with success. Generally sulfuric acid (and salts that dissolve to give sulfuric acid solutions) is one of the only commonly available acids suitable for acidifying the reversal bleach.