Storage life of Sodium Sulfite solution?

Discussion in 'Darkroom Developing and Printing' started by Stephan Goldstein, Jan 1, 2004.

  1. Polaroid Type 55 PN film negatives require a clearing solution that
    is sodium sulfite in water. How long can I expect a properly stored
    mixture to last? And does anyone know the capacity of, say, 1 liter
    of solution?

    Thanks, and Happy New Year!
    Stephan Goldstein, Jan 1, 2004
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  2. I fail to understand why sodium sulfite, a simple salt solution, wouldn't have
    essentially an infinite storage life. After all, what's the life of a sodium
    chloride solution?
    David Nebenzahl, Jan 2, 2004
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  3. The life of a sulfite solution depends partly on its
    concentration. About a 10% concentration will last a couple
    of months at least in a filled, closed container. More
    diluted solutions will have a shorter life. Solutions
    exposed to the air will not last more than about 12 to 24
    Sulfite is a podigeous absorber of oxygen. It is oxidized
    to sulfate. In some applications the form in important, for
    instance, as a wash aid sulfate does no harm but is much
    less effective than sulfite. Sulfite in developers also must
    be capable of absorbing oxygen, that's one of its main jobs.
    I'm not quite sure of what function it has when clearing
    Polaroid negatives, it may be that sulfate would work as
    well, in which case the solution would have very long life
    but wouldn't be sulfite any more.
    Sulifte solution life is extended if mixed with deareated
    water. The easiest way to do this is to boil the water for a
    few minutes and let it stand and cool. Boiling will drive
    off the dissolved air.
    Richard Knoppow, Jan 2, 2004
  4. Stephan Goldstein

    fbo Guest

    Many thanks for the information...

    fbo, Jan 2, 2004
  5. Stephan Goldstein

    Dan Quinn Guest

    There is something very elementry you should know about sulfites.
    If oxygen is present they are on their way to becoming sulfates.
    Sulfites are used for, amoung other things, preserving developing
    agents in most developers and are used in some other
    photographic solutions.
    Copper in particular, in extremly minute amounts, will speed greatly
    the conversion of sulfite to sulfate. As little as one part copper per
    trillion of water will speed the conversion.
    Now and then someone reports the short life of some solution. Then
    again there are reports of very long lived solutions. Dan
    Dan Quinn, Jan 2, 2004
  6. I think I'll take Richard K's suggestion and boil the water I use to make my
    sulfite solution to deaerate it.
    David Nebenzahl, Jan 2, 2004
  7. Stephan Goldstein

    Dan Quinn Guest

    I use distilled water and have considered boiling it. I'll need
    something extremly clean to come out ahead. Dan
    Dan Quinn, Jan 3, 2004
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