Rapid fixers - chloride X sulphate

Discussion in 'B&W: Film, Paper, Chemistry' started by Jorge Oliveira, Feb 4, 2004.

  1. Jorge Oliveira

    Jorge Oliveira Member

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    Hello,

    Thre are rapid fixers made by mixing hypo with ammonium chloride or sulphate (Kodak's F-7 and F-9).

    It just happens that Kodak F-7 uses 50g of chloride, F-9 uses 60g of sulphate.

    The molecular weight of chloride is 53.49g and of sulphate is 132,14g.

    Doesn't it looks like there is too little sulphate in F-9?

    Thanks,

    Jorge
     
  2. Ole

    Ole Moderator Staff Member

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    Not really. There's roughly twice as much ammonium in the F-7, but the only thing it does is assist in mobilizing the silver ions. It's almost a catalyst. so it doesn't matter (much) how much there is, as long as it's sufficient.
    I have no idea how much is sufficient.
    My own recipe uses chloride, since I have an idea that the chloride will help in dissolving silver iodide. But I could be completely wrong. At least it works...
     
  3. Jorge Oliveira

    Jorge Oliveira Member

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    Thanks, Ole

    Jorge O